CN120007457A - System and method for diagnosing a compression brake system - Google Patents

Abstract

A method for diagnosing a compression brake system of an engine is provided. The method includes determining a value of a parameter associated with operation of the compression brake system of the engine; retrieving a baseline value of the parameter associated with the compression brake system of the engine operating as intended, comparing the value of the parameter to the baseline value of the parameter; retrieving a diagnostic threshold value indicative of a healthy compression brake system; and providing an alert in response to determining that a result of the comparison does not match the diagnostic threshold value.

Description

System and method for diagnosing compression brake system

The present application is a divisional application of the application application with the application number 202110587684.X, the application name "system and method for diagnosing compression brake system" of the application day 2021, 5, 27.

Cross-reference to other applications

The present application claims priority from the indian patent application filed 5/27/2020 entitled "system and method for diagnosing compression brake systems" with application number 202041022134, which is incorporated herein by reference in its entirety for all purposes.

Technical Field

The present disclosure relates to systems and methods for diagnosing a compression braking system.

Background

The internal combustion engine may be equipped with a compression braking system that helps to slow the vehicle, which may or may not be used with an external braking system. In operation, the compression braking system changes the timing of engine valves during operation of the internal combustion engine. For example, during a compression stroke, the exhaust valve may be opened rather than held closed, thereby releasing a quantity of compressed air that would otherwise be used to output power from the engine. In this way, the expansion stroke is driven by much less compressed air than during normal operation, thereby generating negative power.

Disclosure of Invention

One embodiment relates to a system that includes a controller coupled to a compression braking system associated with an engine. The controller includes at least one processor coupled to a memory storing instructions that when executed by the at least one processor cause the controller to perform operations including activating compression braking by a compression braking system associated with an engine, determining a value of a parameter associated with operation of the compression braking system associated with the engine, retrieving a reference value of the parameter associated with a compression braking system of an engine operating as intended, comparing the value of the parameter to the reference value of the parameter, retrieving a diagnostic threshold value of the compression braking system indicative of health, and providing an alert in response to determining that the comparison does not match the diagnostic threshold value.

Another embodiment relates to a method for diagnosing a compression braking system of an engine. The method includes determining a value of a parameter associated with operation of a compression braking system of an engine, retrieving a reference value of the parameter associated with the compression braking system of the engine operating as expected, comparing the value of the parameter to the reference value of the parameter, retrieving a diagnostic threshold value of the compression braking system indicative of health, and providing an alert in response to determining that the result of the comparison does not match the diagnostic threshold value.

Yet another embodiment relates to a system. The system includes a compression braking system associated with an engine, and a controller coupled to the compression braking system, the controller configured to provide a command to activate compression braking by the compression braking system associated with the engine, determine a value of a parameter associated with operation of the compression braking system of the engine, retrieve a reference value of the parameter associated with the compression braking system of the engine operating as intended, compare the value of the parameter to the reference value of the parameter, retrieve a diagnostic threshold value of the compression braking system indicative of health, and provide an alert in response to determining that the comparison does not match the diagnostic threshold value.

This summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the devices or processes described herein, as well as the inventive features, will become apparent in the detailed description set forth herein when taken in conjunction with the drawings, wherein like reference numerals refer to like elements.

Drawings

FIG. 1 is a schematic diagram of an engine system according to an example embodiment.

FIG. 2 is a schematic diagram of a controller of the engine system of FIG. 1, according to an example embodiment.

Fig. 3A is a graph of experimental values of engine speed versus charge pressure and experimental values of charge flow rate for an engine with a functional compression brake system and an engine with a non-functional compression brake system according to an example embodiment.

FIG. 3B is a graph of a difference in engine speed versus charge pressure value and a difference in charge flow rate value for an engine having an active compression brake system and an engine having an inactive compression brake system according to an example embodiment.

FIG. 4 is a graph of engine speed versus exhaust pressure experimental values, and differences between these values, for an engine with an active compression brake system and an engine with an inactive compression brake system according to an example embodiment.

FIG. 5A is a graph of experimental values of engine speed versus torque and experimental values of power output for an engine with an active compression brake system and an engine with an inactive compression brake system according to an example embodiment.

FIG. 5B is a graph of a difference in engine speed versus torque values and a difference in power output values for an engine with an active compression brake system and an engine with an inactive compression brake system according to an example embodiment.

FIG. 6A is a graph of engine speed versus charge pressure reference for an engine having an active compression brake system, an experimental charge pressure value for an engine having an inactive compression brake system, and an integral of the difference between the two values over time, according to an example embodiment.

FIG. 6B is a graph of engine speed versus charge pressure reference value for an engine having an active compression brake system, charge pressure experimental values for an engine having an active compression brake system, and the integral of the difference between the two values over time, according to an example embodiment.

FIG. 7 is a flowchart of a method for diagnosing a compression braking system according to an example embodiment.

Detailed Description

The following is a more detailed description of various concepts related to methods, devices, and systems for diagnosing the function of a compression braking system of an engine and implementations thereof. Before turning to the drawings, which illustrate certain example embodiments in detail, it is to be understood that the disclosure is not limited to the details or methodology set forth in the specification or illustrated in the drawings. It is also to be understood that the terminology used herein is for the purpose of description only and should not be regarded as limiting.

Referring generally to the drawings, various embodiments disclosed herein relate to systems, devices, and methods for diagnosing a compression braking system of an engine system. Compression braking is an important feature in engines because the use of compression braking reduces maintenance costs associated with maintaining a service brake system. However, current diagnostic systems lack a means for diagnosing compression braking systems on newly manufactured engines because they rely on inaccurate manual measurements and standards of inconsistency between engine type and test unit. Furthermore, current testing methods for compression brake systems typically require the labor of a skilled tester. In this regard, the end of line testing (i.e., checking the test unit of the engine prior to exiting the manufacturing facility) does not produce a flag or other indication that the compression brake system is inoperable. This results in the need for an engineer to investigate the operation of the compression brake system to identify faults or potential faults. When the engine is used after being installed for various applications (e.g., in a vehicle, as part of a stationary genset, etc.), the operator is lacking in conclusive signs (e.g., fault codes, dashboard indications, etc.). Thus, it takes more time to solve the compression brake failure in the field. Technically, the ability to identify and potentially address fault conditions in a compression braking system would be advantageous in reducing engine downtime and reducing the resource expenditure required for typical troubleshooting exercises, as well as other potential benefits.

The present disclosure relates to systems and methods for diagnosing a compression braking system of an internal combustion engine. The controller is coupled to an engine that is coupled to the plurality of sensors. If the sensor is authentic, the sensor is located throughout the engine and related components. Real or virtual sensors acquire data indicative of the operation of the compression braking system, including monitoring the "breathing" capability of the engine (i.e., the flow of air and exhaust through the combustion chamber). As a result, the controller is constructed or configured to determine a value of a parameter associated with the compression braking system of the engine (such as the pressure or flow of the charge, the pressure of the exhaust, etc.), retrieve a reference value of the parameter associated with the compression braking system of the engine operating as intended, compare the value of the parameter to the reference value of the parameter, retrieve a diagnostic threshold value of the compression braking system that indicates health, and provide an alert in response to determining that the comparison does not match the diagnostic threshold value. These and other features and advantages are more fully described below.

Referring now to FIG. 1, an engine system 10 is shown having an engine 12, a turbocharger, shown as a compressor 22 and a turbine 23, and a controller 26, according to an example embodiment. According to one embodiment, engine system 10 is implemented within a vehicle. The vehicle may include an on-road vehicle or an off-road vehicle including, but not limited to, long haul trucks, medium duty trucks (e.g., pick-up trucks, etc.), cars, coupes, tanks, aircraft, watercraft, and any other type of vehicle. Based on these configurations, various additional types of components may also be included in the system, such as a transmission, one or more gearboxes, pumps, actuators, or any component powered by an engine.

The engine 12 may be any type of engine capable of operating in conjunction with a compression braking system. Thus, as shown herein, the engine 12 may be an internal combustion engine (e.g., a gasoline, natural gas, or diesel engine), a hybrid engine (e.g., a combination of an internal combustion engine and an electric motor), and/or any other suitable engine. In the example shown, the engine 12 is configured as a diesel powered compression ignition engine. The engine 12 has cylinders 14, with the cylinders 14 receiving fuel (e.g., from fuel injectors, from a fuel supply, etc.) and air (e.g., from a turbocharger). The cylinder 14 includes an intake valve 15 that selectively opens to receive air into the cylinder 14 and an exhaust valve 16 that selectively opens to exhaust gases from the cylinder 14. The internal combustion engine 12 also has a piston positioned in the cylinder 14. Combustion of fuel within cylinders 14 causes movement of the pistons, and internal combustion engine 12 is configured to selectively convert the movement of the pistons into mechanical energy that may be harvested for use in, for example, rotationally driving a drive shaft housing wheels of a vehicle of engine system 10.

Although only one cylinder is shown, it should be appreciated that the engine 12 may include a second cylinder, a third cylinder, a fourth cylinder, and additional other cylinders such that the engine 12 has a target number of cylinders and is tailored to the target application. For example, the engine 12 may include six, eight, ten, twelve, sixteen, twenty, or other numbers of cylinders and an equal number of pistons. The arrangement of the cylinders may be any of a variety of arrangements, such as an in-line configuration, a V-configuration, a W-configuration, and the like. Further, in addition to intake valve 15 and exhaust valve 16, cylinder 14 may include a second intake valve, a second exhaust valve, a third intake valve, a third exhaust valve, and any other valves such that cylinder 14 has a target number of intake and exhaust valves and may be customized for a target application.

The engine 12 operates in a cyclical manner. In an example embodiment, the cycle is a four-stroke cycle that includes an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke in that order. It should be appreciated that while the cycle of the engine 12 is a four-stroke cycle in the exemplary embodiment, the present disclosure should not be construed as limited to a four-stroke cycle, but rather as applicable to a two-stroke or other cycle.

The illustrated engine system 10 also includes a compression braking system 11. Compression brake system 11 is configured to be engaged or disengaged by an operator of engine system 10, or according to a control scheme implemented by controller 26. When the compression brake system 11 is disengaged, the engine 12 does not apply compression braking. When the compression braking system 11 is engaged, the exhaust valve 16 opens during the compression stroke of the four-stroke cycle, releasing some of the compressed or to be compressed air. In this way, the movement of the piston resulting from the expansion stroke is reduced, and therefore the energy collected for rotating the drive shaft is reduced, which in turn slows down the vehicle.

Compression braking system 11 may use any number of cylinders such that the exhaust valve(s) open during the compression stroke of some cylinders, but remain closed for other cylinders. If more cylinders are used by the compression brake system 11, more negative power (i.e., braking capacity) is generated as more compressed air or air to be compressed is released. The number of cylinders utilized by the compression brake system 11 may be determined by an operator when engaging the compression brake system 11 or by the controller 26 according to a control scheme. In some embodiments, the number of cylinders utilized remains the same throughout the length of time that the compression brake system 11 is utilized. In other embodiments, the number of cylinders utilized is changed based on the demand for the compression braking system 11 (e.g., if more braking is required, the number of cylinders utilized is increased).

Products of the combustion process, i.e., exhaust gases from compression braking and exhaust air (exhaust GAS AND DISCHARGED AIR), are exhausted from the cylinders 14 via the exhaust valves 16 and into the turbine 23 through exhaust passages. The turbine 23 is mechanically coupled to the compressor 22, for example by a shaft, thereby forming a turbocharger. Exhaust gas and air discharged from the cylinders 14 may drive a turbine 23 in rotation, which may in turn drive a compressor 22 to compress air supplied to the engine 12. Wastegate 24 may bypass a portion of the exhaust and exhaust air around turbine 23 such that less energy is available for the turbine, which in turn reduces the power delivered to compressor 22 and reduces the pressure of the air supplied to engine 12. However, in some embodiments, the turbocharger may be omitted from engine system 10. In these embodiments, the engine is naturally aspirated, meaning that the air/fuel mixture is drawn into the cylinder 14 by the atmospheric pressure and the slight vacuum created by the downward movement of the piston during the intake stroke.

When the compression brake system 11 is engaged and operating as intended, the increased amount of exhaust gas and air is discharged into the turbine 23 as the exhaust valve 16 is opened twice in the four-stroke cycle (rather than once in the four-stroke cycle when the compression brake system 11 is disengaged). This increased emissions increases the volumetric efficiency of the engine system 10, resulting in an increase in flow through the turbine 23. This increased flow through turbine 23 results in a higher expansion ratio of turbine 23, which in turn results in a greater exhaust pressure at the inlet of turbine 23. The increased flow through turbine 23 also increases the amount of power transferred to compressor 22, thereby increasing the boost pressure from compressor 22. The increase in boost pressure from the compressor 22 means that the pressure and flow rate of the charge air at the intake valve 15 is greater.

In some embodiments, the engine may be coupled to an aftertreatment system configured to treat exhaust gas emitted from the engine. The aftertreatment system is configured to receive the exhaust gas and reduce components of the exhaust gas to less harmful compounds prior to discharging the exhaust gas into the atmosphere. The aftertreatment system may include one or more other components of a diesel oxidation catalyst, a diesel particulate filter, a selective catalytic reduction system, a reductant dosing system, and one or more sensors.

As also shown, various sensors 30 are included in the engine system 10. The sensor 30 is coupled (and in particular communicatively coupled) to the controller 26 such that the controller 26 can monitor and acquire data indicative of the operation of the system 10. As shown, the system 10 includes a flow rate sensor 2, a pressure sensor 4, a torque sensor 6, and an engine sensor 8. The flow rate sensor 2 acquires data indicating the flow rate of the exhaust gas and/or the charge air at or about its arrangement position, or if virtual determines an approximate flow rate of the exhaust gas and/or the charge air at or about its arrangement position. The pressure sensor 4 acquires data indicative of the pressure of the exhaust and/or charge air at or about its location of arrangement, or if virtual determines an approximate pressure of the exhaust and/or charge air at or about its location of arrangement. The torque sensor 6 acquires data indicating the torque of the internal combustion engine 12 or, if virtual, determines an approximate torque of the internal combustion engine 12. If the torque sensor 6 is virtual, the torque sensor 6 may determine the torque of the engine 12 based on the speed of the engine 12, the exhaust pressure at the intake valve 15, and the exhaust pressure at the exhaust valve 16. The engine sensor 8 acquires data indicating the operation of the engine 12, or if virtual, determines approximate data indicating the operation of the engine 12. Operational data about the engine 12 may include, but is not limited to, engine speed, power output, load, and the like. It should be understood that the depicted locations, numbers, and types of sensors are merely exemplary. In other embodiments, the sensor 30 may be positioned in other locations, there may be more or fewer sensors than shown, and/or different/additional sensors may also be included in the system 10 (e.g., ambient air sensors, temperature sensors, etc.). Those of ordinary skill in the art will understand and appreciate the high configurability of the sensors 30 in the system 10.

Because there are various sensed values (e.g., charge pressure, charge flow, exhaust pressure, etc.) that are directly responsive to the operation of the compression brake system 11, the controller 26 may determine and monitor the health and operating condition of the compression brake system 11 through analysis of these sensed values. The health of the compression brake system 11 refers to the ability of the compression brake system 11 to operate as intended. A healthy compression brake system indicates that the compression brake system is working properly. Conversely, if the compression brake system is in poor health, it is indicated that the compression brake system is not operating properly. For example, if the compression braking system 11 is engaged, but the charge pressure of the air at the intake valve 15 is not increased or is increased to a lesser extent than expected, the health of the compression braking system 11 may be problematic such that the compression braking system may not be able to properly slow down the engine 12). As described herein, the controller 26 may monitor various parameters of the engine system to determine whether the compression brake system is healthy (operating as intended) or unhealthy or possibly unhealthy.

The health determination may be based on one data point (e.g., a comparison of inflation pressure) relative to an associated data point of a healthy compression brake system. In other embodiments, the health determination may be based on two or more data points (e.g., a comparison of charge pressure and a comparison of exhaust pressure) relative to associated data points of a healthy compression braking system. The data point(s) may be specified by a number of factors including, but not limited to, the number of cylinders utilized by the compression braking system 11, the air density at the inlet of the compressor 22, and the like.

As described herein, the controller 26 utilizes one or more values to diagnose a compression braking system. Examples of sensed values of compression brake system 11 that are directly responsive to operation include, but are not limited to, charge flow rate of air at intake valve 15, exhaust pressure at exhaust valve 16, and engine torque. Furthermore, timely monitoring on only a single instance will result in an unreasonable number of false faults (or alternatively, missing true faults (positives)). Thus, a cumulative summing (Cusum) function or integration is incorporated for absorbing transient noise and monitoring the value over a period of time.

Another sensed value of the compression brake system 11 in response to operation is the torque of the engine 12. Because the operating compression brake system 11 decelerates the engine 12 by reducing the amount of power delivered to the rotating camshaft, the operating compression brake system 11 may be considered to increase the negative torque provided by the engine. In this way, by monitoring the torque produced by the engine 12 while the compression brake system 11 is engaged, the controller 26 may determine whether the compression brake system 11 is operating (also referred to as operating as intended or designed). In some embodiments, torque is sensed by a real sensor. In other embodiments, torque is determined or estimated by virtual sensors that are determined based in part on exhaust pressure, charge pressure, and engine speed. Engine power output (defined as the product of engine speed and engine torque) is similarly responsive to an operating compression braking system and may be similarly monitored.

Because the components of fig. 1 are shown as being embodied in the system 10, the controller 26 may be configured as one or more Electronic Control Units (ECUs). The controller 26 may be separate from or included in at least one of a transmission control unit, an exhaust aftertreatment control unit, a powertrain control module, an engine control module, and the like. The function and structure of the controller 26 is described in more detail in fig. 2.

The components of the vehicle may communicate with each other or with external components (e.g., a remote operator) using any type and number of wired or wireless connections. Communication between and among the controller 26 and components of the vehicle may be through any number of wired or wireless connections (e.g., any standard under IEEE). For example, the wired connection may include a serial cable, a fiber optic cable, a CAT5 cable, or any other form of wired connection. The wireless connection may include the Internet, wi-Fi, cellular, radio, bluetooth, zigBee, and the like. In some embodiments, a Controller Area Network (CAN) bus provides for the exchange of signals, information, and/or data. The CAN bus includes any number of wired and wireless connections that provide for the exchange of signals, information, and/or data. The CAN bus may include a Local Area Network (LAN) or a Wide Area Network (WAN), or may establish a connection with an external computer (e.g., through the internet using an internet service provider).

Referring now to FIG. 2, a schematic diagram of a controller 26 of the engine system of FIG. 1 is shown, according to an example embodiment. As shown in fig. 2, the controller 26 includes a processing circuit 51 having a processor 52 and a memory 53, a dosing circuit 55, a threshold circuit 56, and a communication interface 54. The controller 26 is configured to diagnose the compression brake system 11. By determining differences (if any) between sensed values of various compression brake parameters and predetermined and preset operating thresholds and comparing these differences to predefined or preset diagnostic thresholds. Based on this comparison, the controller 26 determines whether the compression brake system 11 is operating as intended, or whether the compression brake system is malfunctioning, and acts in response.

In one configuration, the dosing circuit 55 and the threshold circuit 56 are implemented as a machine or computer readable medium executable by a processor (e.g., the processor 52). As described herein, among other uses, a machine-readable medium facilitates performance of certain operations to enable reception and transmission of data. For example, a machine-readable medium may provide instructions (e.g., commands, etc.) to, for example, obtain data. In this regard, a machine-readable medium may include programmable logic defining a data acquisition frequency (or data transmission). The computer-readable medium may include code that may be written in any programming language, including, but not limited to, java or the like, and any conventional procedural programming language, such as the "C" programming language or similar programming languages. The computer readable program code may be executed on a processor or multiple remote processors. In the latter case, the remote processors may be connected to each other through any type of network (e.g., CAN bus, etc.).

In another configuration, the dosing circuit 55 and the threshold circuit 56 are implemented as hardware units, such as an electronic control unit. As such, the dosing circuitry 55 and threshold circuitry 56 may be implemented as one or more circuit components including, but not limited to, processing circuitry, network interfaces, peripherals, input devices, output devices, sensors, and the like. In some embodiments, the dosing circuit 55 and the threshold circuit 56 may take the form of one or more analog circuits, electronic circuits (e.g., integrated Circuits (ICs), discrete circuits, system on a chip (SOC) circuits, microcontrollers, etc.), telecommunications circuits, hybrid circuits, and any other type of "circuit. In this regard, the dosing circuit 55 and the threshold circuit 56 may include any type of components for accomplishing or facilitating the operations described herein. For example, the circuitry described herein may include one or more transistors, logic gates (e.g., NAND, AND, NOR, OR, XOR, NOT, XNOR, etc.), resistors, multiplexers, registers, capacitors, inductors, diodes, wiring, and so forth. The dosing circuit 55 and the threshold circuit 56 may also include programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices, and the like. The dosing circuit 55 and the threshold circuit 56 may include one or more memory devices for storing instructions executable by the processor(s) of the dosing circuit 55 and the threshold circuit 56. The memory device(s) and processor(s) may have the same definition as provided below with respect to memory 53 and processor 52. In some hardware unit configurations, the dosing circuit 55 and the threshold circuit 56 may be geographically dispersed in separate locations in the vehicle. Alternatively, and as shown, the dosing circuit 55 and the threshold circuit 56 may be implemented in or within a single unit/housing (shown as controller 26).

In the example shown, the controller 26 includes a processing circuit 51 having a processor 52 and a memory 53. The processing circuitry 51 may be constructed or configured to perform or implement the instructions, commands, and/or control processes described herein with respect to the dosing circuitry 55 and the threshold circuitry 56. The depicted configuration represents the dosing circuit 55 and the threshold circuit 56 as machine or computer readable media. However, as noted above, this illustration is not meant to be limiting, as the present disclosure contemplates other embodiments in which the dosing circuit 55 and the threshold circuit 56 or at least one of the dosing circuit 55 and the threshold circuit 56 is configured as a hardware unit. All such combinations and variations are intended to be within the scope of the present disclosure.

Processor 52 may be implemented as a single or multi-chip processor, digital Signal Processor (DSP), application Specific Integrated Circuit (ASIC), field Programmable Gate Array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The processor may be a microprocessor, or any conventional processor or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some embodiments, one or more processors may be shared by multiple circuits (e.g., the dosing circuit 55 and the threshold circuit 56 may include or otherwise share the same processor, which in some example embodiments may execute instructions stored or otherwise accessed via different regions of memory). Alternatively or additionally, one or more processors may be configured to perform or otherwise perform certain operations independently of one or more co-processors. In other example embodiments, two or more processors may be coupled by a bus to enable independent, parallel, pipelined, or multi-threaded instruction execution. All such variations are intended to fall within the scope of the present disclosure.

Memory 53 (e.g., memory device, memory unit, storage device) may include one or more devices (e.g., RAM, ROM, flash memory, hard disk storage) for storing data and/or computer code to complete or facilitate the various processes, layers, and modules described in this disclosure. The memory 53 may be communicatively connected to the processor 52 to provide computer code or instructions to the processor 52 to perform at least some of the processes described herein. Further, the memory 53 may be or include a tangible non-transitory volatile memory or a non-volatile memory. Accordingly, memory 53 may include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described herein.

The dosing circuit 55 is configured or structured to communicate with the sensor 30 via the communication interface 54, receive information regarding various operating parameters of the system 10, and determine differences between sensed values of the operating parameters and associated expected values (or references) of the operating parameters. The resulting difference is referred to as the compression braking function (functionality) value. The compression brake function value generally represents the amount by which the compression brake system 11 deviates from the intended performance. These operating parameters are related to the operation of compression braking system 11 and include, but are not limited to, exhaust pressure (e.g., at or near exhaust valve 16), charge pressure (e.g., at or near intake valve 15), charge flow rate, engine torque, and/or engine power output. The desired value for each of these parameters may be set according to the engine speed for the current operating conditions, such as a given ambient air density and engine type (e.g., number of cylinders, engine design characteristics such as swept volume (SWEPT CYLINDER volume), etc.). Then, by determining the actual value of the parameter at the specific engine speed, the quantifying circuit 55 compares the actual value of the parameter with the expected value of the parameter, and determines the difference between the two (i.e., the compression brake function value). Example graphs illustrating parameter tracking performed by the dosing circuit 55 are shown in fig. 3A, 4 and 5A, which are described in more detail below. Diagrams illustrating the determined compression brake function values for these same parameters are shown in fig. 3B, 4 and 5B, which are described in more detail below.

Thus, referring now to FIG. 3A, an example chart 300 is shown in which the dosing circuit 55 tracks two parameters, inflation flow rate and inflation pressure. The X-axis of the chart 300 reflects the speed of the engine 12 and is given in Revolutions Per Minute (RPM), with values increasing from left to right. The left Y-axis of the graph 300 reflects the charge flow rate (e.g., when charge enters the intake valve 15) and is given in kilograms per minute (kg/min), with values increasing from bottom to top. The right Y-axis of the graph 300 reflects the charge pressure of the air (e.g., as the charge air enters the intake valve 15) and is given in kilopascals (kPa (abs)) with values increasing from bottom to top. Line 310 plots the value of the charge flow rate as a function of engine speed when the compression brake system 11 is operating normally, and generally shows that the charge flow rate increases with increasing engine speed with normal operation of the compression brake system. Line 315 plots the value of the charge flow rate as a function of engine speed when the compression brake system 11 is not operating properly and generally shows that in the event of a compression brake system failure the charge flow rate will also increase with increasing engine speed, but the charge flow rate of the failed compression brake system is generally at a lower level. The dashed line 320 plots the value of the charge pressure according to the engine speed when the compression brake system 11 is operating normally, and generally shows that in the case of the compression brake system operating normally, the charge pressure increases rapidly to a certain point as the engine speed increases and then gradually decreases. The dashed line 325 plots the value of the charge pressure of air according to the engine speed when the compression brake system 11 is not operating properly, and generally shows that the charge pressure steadily increases with increasing engine speed, but the charge pressure of the failed compression brake system is generally at a lower level. As shown, at each engine speed tracked on graph 300, the values of the charge flow rate and charge pressure when compression brake system 11 is operating normally are greater than the values of the charge flow rate and charge pressure when compression brake system 11 is not operating normally. Alternatively, if the engine 12 is a naturally aspirated engine (i.e., the engine 12 does not have a turbocharger), the charge pressure will be substantially the same for a normally operating compression brake system 11 and a malfunctioning compression brake system 11. In addition, the charge pressure will be substantially equal to the ambient pressure due to the inherent function of the naturally aspirated engine.

In some embodiments, lines 310 and 320 may show reference values for the inflation flow rate and inflation pressure (respectively) that the quantifying circuit uses to determine the compression brake function values associated with those parameters. In these embodiments, the reference value represents an actual sensed value of the relevant parameter in a system having a compression brake system operating as intended (i.e., a "healthy" system). For proper comparison, the characteristics of the health system may be the same or about the same as the system under test (e.g., the same engine type, same number of cylinders, etc. used by the compression brake system, turbocharger system, aftertreatment system components). Thus, the health benchmark is directly analogous to the system being tested/diagnosed. In operation, various engine systems may be tested to obtain a chart of health values, allowing for rapid diagnosis of the various engine systems.

Although in this example lines 315 and 325 (respectively) plot the inflation flow rate and inflation pressure when the compression brake system 11 is not operating properly (unhealthy) (i.e., operating at 0% capacity), the tracking performed by the dosing circuit 55 is not limited to those extremes, so that the dosing circuit may track those parameters when the compression brake system 11 is operating but at less than 100% capacity. As such, lines 315 and 325 may be considered to illustrate sensed values (received from sensor 30) of system 10 diagnosed by comparison to reference values of 310 and 320.

Fig. 3B shows an example chart 350 of the quantitative circuit 55 determining the compression brake function values of the same two parameters depicted in fig. 3A. The X-axis of the graph 350 reflects the speed of the engine and is given in Revolutions Per Minute (RPM), with values increasing from left to right. The left Y-axis of the graph 350 reflects the charge flow rate of air (e.g., when charged air enters the intake valve 15) and is given in kilograms per minute (kg/min), with values increasing from bottom to top. The right Y-axis of the graph 350 reflects the charge pressure of the air (e.g., as the charge air enters the intake valve 15) and is given in kilopascals (kPa (abs)) with values increasing from bottom to top. Line 360 plots the difference between lines 310 and 315 as a function of engine speed, and generally shows that the difference between lines 310 and 315 increases to a point as engine speed increases, then decreases, but never becomes negative (i.e., at each value of engine speed, the charge flow rate of a system having a normally operating compression brake system is greater than the charge flow rate of a system having a failed compression brake system). Line 370 plots the difference between lines 320 and 325 as a function of engine speed, and generally shows that the difference between lines 320 and 325 increases to a point as engine speed increases and then decreases, but never to a negative value (i.e., at each value of engine speed, the charge pressure of a system having a normally operating compression brake system is greater than the charge pressure of a system having a failed compression brake system). In those embodiments where lines 310 and 320 show reference values and lines 315 and 325 show sensed values, lines 360 and 370 thus show compression brake function values for the associated parameters.

FIG. 4 illustrates an example chart 400 of the dosing circuit 55 tracking the pressure of exhaust gas (e.g., at the exhaust valve 16) and determining an associated compression brake function value. The X-axis of graph 400 reflects the speed of the engine and is given in Revolutions Per Minute (RPM), with values increasing from left to right. The Y-axis of graph 400 reflects the pressure of the exhaust gas (e.g., as the exhaust gas exits the exhaust valve 16) and is given in kilopascals (kPa (abs)) with values increasing from bottom to top. Line 410 plots the value of exhaust pressure as a function of engine speed when compression brake system 11 is operating normally, and generally shows that for a normally operating compression brake system, exhaust pressure increases with increasing engine speed. Line 420 plots the value of exhaust pressure as a function of engine speed when compression brake system 11 is not operating properly (e.g., when exhaust gas leaves exhaust valve 16), and generally shows that in the event of a compression brake system failure, exhaust pressure will also increase with increasing engine speed, but the exhaust pressure of the failed compression brake system will generally be at a lower level. The dashed line 430 plots the difference between lines 410 and 420 as a function of engine speed, and generally shows that the difference between lines 410 and 420 increases as engine speed increases and is almost completely positive (i.e., at each value of engine speed, but at relatively lower values, the exhaust pressure of a system with a normally operating compression brake system is greater than the exhaust pressure of a system with a malfunctioning compression brake system). Similar to fig. 3A and 3B, in some embodiments, line 410 shows a baseline value of the exhaust pressure, line 420 shows a sensed value of the exhaust pressure, and line 430 shows a compression brake function value of the exhaust pressure.

FIG. 5A shows an example chart 500 in which the dosing circuit 55 tracks two parameters (engine torque and engine power output). The X-axis of graph 500 reflects the speed of the engine and is given in Revolutions Per Minute (RPM), with values increasing from left to right. The left Y-axis of graph 500 reflects the torque of the engine and is given in newton meters (Nm), with values increasing from bottom to top. The right Y-axis of graph 500 reflects the power output of the engine and is given in Kilowatts (KW), with values increasing from bottom to top. Line 510 plots the sensed value of the torque of the engine as a function of engine speed when the compression brake system 11 is not operating properly, and generally shows that the sensed torque steadily increases with increasing engine speed. Line 520 plots an estimate of the torque of the engine as a function of engine speed when the compression brake system 11 is not operating properly, and generally shows that for a failed compression brake system, the estimated torque steadily increases with increasing engine speed. The estimation is made based on sensed values of engine speed, charge pressure (e.g., at intake valve 15), exhaust pressure (e.g., at exhaust valve 16), and cam profile of the engine. Line 530 plots an estimate of the torque of the engine as a function of engine speed when the compression brake system 11 is operating normally, and generally shows that for a normally operating compression brake system, the estimated torque steadily increases with increasing engine speed. Similarly, the estimation is made based on sensed values of engine speed, charge pressure (e.g., at the intake valve), exhaust pressure (e.g., at the exhaust valve), and cam profile of the engine 12.

Still referring to fig. 5A, line 515 plots the sensed value of the power output of the engine as a function of engine speed when the compression brake system 11 is not operating properly, and generally shows that the sensed power output steadily increases with increasing engine speed. Line 525 plots an estimate of the power output of the engine as a function of engine speed when the compression brake system 11 is not operating properly, and generally shows that for a failed compression brake system, the estimated power output steadily increases with increasing engine speed. The estimation is made based on sensed values of engine speed, charge pressure (e.g., at intake valve 15), exhaust pressure (e.g., at exhaust valve 16), and cam profile of the engine. Line 535 plots an estimate of the power output of the engine as a function of engine speed when the compression brake system 11 is operating normally, and generally shows that for a normally operating compression brake system, the estimated power output steadily increases with increasing engine speed. Similarly, the estimation is made based on sensed values of engine speed, charge pressure (e.g., at intake valve 15), exhaust pressure (e.g., at exhaust valve 16), and cam profile of the engine.

Fig. 5B shows an example chart of the quantitative circuit 55 determining the compression brake function values of the same two parameters depicted in fig. 5A. The X-axis of the graph 550 reflects the speed of the engine and is given in Revolutions Per Minute (RPM), with values increasing from left to right. The left Y-axis of graph 550 reflects the torque of the engine and is given in newton meters (Nm), with values increasing from bottom to top. The right Y-axis of graph 550 reflects the power output of the engine and is given in Kilowatts (KW), with values increasing from bottom to top. Line 560 plots the difference between line 530 and line 520 such that in some embodiments line 560 plots the difference between a reference value of the estimated torque of the engine when compression brake system 11 is operating normally (i.e., line 530) and an estimated value of the torque of the engine when compression brake system 11 is not operating normally (based on the current sensed value) (i.e., line 520). Thus, similar to lines 360 and 370 of FIG. 3B, in these embodiments, line 560 plots the compression braking function values for estimated engine torque, and generally shows that the difference between lines 520 and 530 increases as engine speed increases, and is completely positive (i.e., at each value of engine speed, the estimated torque for a system with a normally operating compression braking system is greater than the estimated torque for a system with a malfunctioning compression braking system). Line 570 plots the difference between line 535 and line 525 such that in some embodiments, line 570 plots the difference between a reference value of the estimated power output of the engine when compression brake system 11 is operating normally (i.e., line 535) and an estimated value of the power output of the engine when compression brake system 11 is not operating normally (based on the currently sensed value) (i.e., line 525). Thus, in these embodiments, line 570 plots the compression brake function value of the estimated power output of the engine, and generally shows that the difference between lines 525 and 535 increases as the engine speed increases, and is entirely positive (i.e., at each value of engine speed, the estimated power output of a system with a normally operating compression brake system is greater than the estimated power output of a system with a malfunctioning compression brake system).

The threshold circuit 56 is constructed or arranged to receive the compression brake function value from the dosing circuit 55 and to determine the health of the compression brake system 11 (i.e., whether the compression brake system 11 is operating properly). The threshold circuit is constructed or configured to retrieve a diagnostic threshold indicative of a "healthy" compression brake system, which may be based on the age of the compression brake system 11, the status of other components within the engine system 10, or the operator's preference.

In some embodiments, the threshold circuit 56 reacts to each condition that the compression brake function value exceeds or does not match the diagnostic threshold and alerts whenever the diagnostic threshold is exceeded. In other embodiments, the threshold circuit 56 feeds the compression brake function value into an accumulated sum, i.e., the "CUSUM" function, for absorbing noise. The Cusum function sums the compression brake function values over a predefined period of time and triggers an alarm if the sum of the compression brake function values over the predefined period of time exceeds a predefined or preset threshold value of the sum of the compression brake function values over the period of time. The function operates like a bucket (bucket) that overflows and triggers an alarm if the bucket fills and exceeds a threshold value within a certain period of time. By utilizing the Cusum function in these embodiments, the threshold circuit 56 ignores small compression brake function values that last for short time frames, thereby avoiding false failures and operator signal fatigue. For example, when compression brake system 11 is first engaged (i.e., activated), there may be some hysteresis in the parameter response due to inertia from moving components (e.g., turbine 23) in system 10, which may not immediately react to engagement of compression brake system 11.

In other embodiments, the threshold circuit 56 calculates an integral of the compression brake system value, examples of which are shown in fig. 6A and 6B. The utility of the integral calculation is similar to that of the Cusum function, since the integral allows real-time monitoring of the compression brake function value over time. When the integrated value reaches the established threshold, the threshold circuit 56 triggers an alarm.

While in some embodiments the threshold circuit 56 triggers an alarm when the diagnostic threshold is exceeded, in other embodiments the threshold circuit 56 triggers an alarm when the compression brake function value does not match the diagnostic threshold (e.g., the compression brake function value is within a range of, for example, 5% of the diagnostic threshold). By triggering an alarm in situations other than those where the diagnostic threshold is fully exceeded, the threshold circuit 56 is adaptive and may be more sensitive to possible problems in the compression brake system 11. Thus, the threshold circuit 56 may also trigger an alarm if the compression brake system 11 is active but operating below 100% such that the compression brake function value is approaching the diagnostic threshold but has not exceeded the diagnostic threshold, which may indicate a possible problem with the compression brake system but not a completely inactive compression brake system. Furthermore, in some of these embodiments, the threshold circuit triggers a secondary alarm that indicates that the compression braking function is within 5% of the diagnostic threshold but has not exceeded the diagnostic threshold so that the user can expect an upcoming problem with the compression braking system 11.

In some embodiments, the diagnostic threshold is determined based on the type of engine (e.g., number of cylinders, engine design features such as swept volume, type of turbocharger, etc.), and/or based on those engine operating conditions that affect the "breathing" ability of the engine (e.g., ambient air density, etc.).

Referring now to FIG. 6A, an example chart 600 of a system 10 featuring a malfunctioning compression brake system 11 is shown. The X-axis of graph 600 reflects the time since the compression brake system was engaged and is given in seconds(s), with values increasing from left to right. The left Y-axis of the graph 600 reflects the charge pressure of the engine (e.g., at the intake valve 15) and is given in kilopascals (kPa), with values increasing from bottom to top. The right Y-axis of graph 600 reflects the integral value of the compression brake function value and is given in units of kilopascal seconds (kPa s), with the value increasing from bottom to top. Line 610 plots a baseline value of charge pressure over time for the given engine and at the ambient air density, and shows that for this particular set of external operating conditions (e.g., road grade, tire pressure, external wind, etc.) and braking power applied by compression brakes, the baseline charge pressure decreases over time after engaging a normally operating compression brake system. Line 620 plots sensed values of inflation pressure over time and shows that for this particular set of external operating conditions and braking power applied by the compression brake, the inflation pressure remains flat over time after engagement of the failed compression brake system. Line 630 plots the integral of the difference (i.e., "line 610" - "line 620") over time and generally shows that the integral increases continuously over time (i.e., the baseline inflation pressure in a system with a normally operating compression brake system is greater than the inflation pressure in a system with a malfunctioning compression brake system such that the difference is positive throughout the time after the compression brake system is engaged). In some cases, such as when the vehicle is driving down a particularly steep hill, the speed of the engine 12 may increase even with the compression brake system 11 engaged and operating properly. Thus, in this case, the inflation pressure will increase over time, although the compression brake system 11 is operating normally. In this case, however, the inflation pressure will still be greater for a normally operating compression brake system 11 than for a malfunctioning compression brake system 11, meaning that the poor integral (e.g., line 630) will still capture an indication of the operation of the compression brake system 11.

Referring now to FIG. 6B, an example chart 650 of the system 10 featuring a normally functioning compression brake system 11 is shown. The units of the axes of graph 650 are the same as the units of the axes in graph 600. However, the ratio of the X-axis and the right Y-axis of graph 650 is significantly less than the ratio of graph 600, such that less time passes from left to right, and the line of integration (line 635) is plotted less than 1/10 of the ratio of line 630. Line 615 similarly plots a baseline value over time for the given engine and the charge pressure at the ambient air density (e.g., at intake valve 15), and shows that for this particular set of external operating conditions and braking power applied by compression braking, the charge pressure decreases over time after engaging a normally operating compression braking system. The sensed value of the charge pressure at the intake valve 15 over time is plotted like ground line 625 and generally shows the decrease in charge pressure over time after engagement of a normally operating compression brake system. Similar ground 635 plots the integral of the difference (i.e., "line 615" - "line 625") over time and shows that the integral is moving in one direction or the other non-uniformly (i.e., the difference between the baseline value and the sensed value is not uniformly different over time) for the particular set of external operating conditions and braking power applied by the compression brake. As is clear from the comparison of the compression braking function values of the inactive compression braking system 11 and the active compression braking system 11 plotted by lines 630 and 635, respectively, monitoring the integral of these values over time is an effective method of identifying an inactive compression braking system, as the integral of the compression braking system monitoring for failure (line 630) continues to increase, while the integral of the compression braking system monitoring for normal operation (line 635) is not as consistent.

In response to the threshold circuit 56 determining that the diagnostic threshold has been exceeded (in some cases or as a result of Cusum/integration), the threshold circuit 56 issues an alarm regarding the health of the compression brake system 11. In some embodiments, the alert is a raised flag that a technician can read during a maintenance event. In other embodiments, the alert is a fault code, which is accessible, for example, through a service diagnostic tool. In other embodiments, the alarm is a light (e.g., an indicator light) on the dashboard or other display area of the vehicle that is illuminated to indicate a fault. In some embodiments, the alert may be sent to a remote operator via a network. In this case, remote monitoring and inspection diagnostics are provided.

Referring now to FIG. 7, a method 700 for diagnosing the function of a compression braking system is shown, according to an example embodiment. The method 700 may be performed at least in part by the controller 26. Accordingly, reference may be made to the controller 26 and components of the system 10 to aid in the explanation of the method 700.

Method 700 begins with process 702. At process 704, the compression braking system 11 is activated. Controller 26 may provide commands to initiate compression braking to control valves and other components of the engine to effect compression braking (e.g., to cause the exhaust valve(s) to open during a compression stroke). The activation may be based on explicit user input for compression braking (e.g., flipping a switch on the vehicle dashboard, pressing a button, pressing an icon on a touch screen, etc.). The activation may be based on programming in the controller 26.

At process 706, a value of a parameter indicative of the performance of the compression brake system 11 is determined or obtained. Based on the parameter, the value may be sensed directly, or the value may be estimated based on other sensed values. Possible parameters are shown at process 707. After this determination, reference values for the parameters are retrieved at process 708 based on the factors given at process 709. After this, the sensed value and the reference value are compared at process 710. The result of the comparison is then either fed into a cumulative summing (Cusum) function or calculated as an integral at process 712. If the result of the comparison is fed into Cusum functions, the results of the comparison over a predetermined period of time are added together. The result (accumulated sum or integral) is then compared to a diagnostic threshold at decision step 714, and if the result matches the threshold (714: yes), then process 706 is returned, or if the result does not match the threshold (714: no), then an alarm is triggered at process 716.

As used herein, the terms "about," "substantially," and similar terms are intended to have a broad meaning, consistent with the ordinary and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. Those skilled in the art who review this disclosure will appreciate that these terms are intended to allow the description and claims of certain features without limiting the scope of such features to the precise numerical ranges provided. Accordingly, these terms should be construed to mean that insubstantial or insignificant modifications or variations of the described and claimed subject matter are considered to be within the scope of the disclosure as set forth in the appended claims.

It should be noted that the term "example" and variations thereof as used herein to describe various embodiments are intended to represent possible examples, representations, or illustrations of such embodiments as possible (and such term is not intended to imply that such embodiments must be extraordinary or optimal examples).

As used herein, the term "coupled" and variations thereof refer to two members being connected to one another either directly or indirectly. Such a connection may be stationary (e.g., permanent or fixed) or movable (e.g., movable or releasable). Such connection may be achieved by coupling two members directly to each other, coupling two members to each other using one or more separate intermediate members, or coupling two members to each other using an intermediate member integrally formed as a single unitary body with one of the two members. If a modification is made to "couple" or a variant thereof by an additional term (e.g., direct coupling), the generic definition of "couple" provided above will be modified by the plain language meaning of the additional term (e.g., direct coupling refers to the connection of two members without any separate intermediate member), with the resulting definition being narrower than the generic definition of "couple" provided above. Such coupling may be mechanical, electronic or fluid. For example, circuit a may be communicatively "coupled" to circuit B, which may mean that circuit a communicates directly with circuit B (i.e., without intermediaries) or communicates indirectly with circuit B (e.g., through one or more intermediaries).

Although various circuits having particular functions are shown in fig. 2, it should be understood that controller 26 may include any number of circuits for accomplishing the functions described herein. For example, the activities and functions of the dosing circuit 55 and the threshold circuit 56 may be combined in multiple circuits or as a single circuit. Additional circuitry with additional functionality may also be included. In addition, the controller 26 may also control other activities beyond the scope of the present disclosure.

As described above, in one configuration, the "circuitry" may be implemented in a machine-readable medium for execution by various types of processors (e.g., processor 52 of FIG. 2). For example, circuitry of the identified executable code may comprise one or more physical or logical blocks of computer instructions which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified circuit need not be physically located together, but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the circuit and achieve the stated purpose for the circuit. Indeed, the circuitry of the computer readable program code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within circuits, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices.

Although the term "processor" is briefly defined above, the terms "processor" and "processing circuitry" are intended to be interpreted broadly. In this regard and as described above, a "processor" may be implemented as one or more general purpose processors, application Specific Integrated Circuits (ASICs), field Programmable Gate Arrays (FPGAs), digital Signal Processors (DSPs), or other suitable electronic data processing components configured to execute instructions provided by a memory. The one or more processors may take the form of a single-core processor, a multi-core processor (e.g., dual-core processor, tri-core processor, quad-core processor, etc.), a microprocessor, or the like. In some embodiments, one or more processors may be external to the device, e.g., one or more processors may be remote processors (e.g., cloud-based processors). Preferably or additionally, the one or more processors may be internal and/or local to the apparatus. In this regard, a given circuit or component thereof may be disposed locally (e.g., as part of a local server, local computing system, etc.) or remotely (e.g., as part of a remote server, such as a cloud-based server). To this end, a "circuit" as described herein may include components distributed over one or more locations.

Embodiments within the scope of the present disclosure include program products comprising machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media can be any available media that can be accessed by a general purpose or special purpose computer or other machine with a processor. By way of example, such machine-readable media can comprise RAM, ROM, EPROM, EEPROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of machine-executable instructions or data structures and that can be accessed by a general purpose or special purpose computer or other machine with a processor. Combinations of the above are also included within the scope of machine-readable media. For example, machine-executable instructions comprise instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing machine to perform a certain function or group of functions.

Although the figures and descriptions may show a particular order of method steps, the order of the steps may differ from what is depicted and described unless otherwise specified above. In addition, two or more steps may be performed concurrently or with partial concurrence, unless otherwise indicated above. Such variations may depend, for example, on the software and hardware system selected and the designer's choice. All such variations are within the scope of the present disclosure. Likewise, software implementations of the described methods can be accomplished using standard programming techniques with rule based logic and other logic to accomplish the various connecting steps, processing steps, comparison steps and decision steps.

Claims (20)

1. A system for diagnosing a compression braking system of an engine, comprising:

A controller coupled to a compression braking system associated with an engine, the controller comprising at least one processor coupled to a memory, the memory storing instructions that when executed by at least one of the processors cause the controller to perform operations comprising:

Compression braking is activated via a compression braking system associated with the engine by opening at least one exhaust valve during a compression stroke of the engine to release compressed or to-be-compressed air to thereby slow a vehicle having the compression braking system;

Determining a plurality of values of a parameter associated with operation of the compression braking system associated with the engine over a period of time at different speeds of the engine during activation of the compression braking, wherein the parameter associated with operation of the compression braking system is at least one of an exhaust pressure exiting at least one cylinder of the engine, a pressure of charge air entering at least one cylinder of the engine, a flow rate of charge air entering at least one cylinder of the engine;

retrieving a plurality of reference values for said parameters associated with a compression braking system of the engine operating as intended and different engine speeds;

comparing each of a plurality of values of the parameter with a corresponding reference value of the plurality of reference values of the parameter according to a respective speed of the engine;

Generating a comparison value representing a comparison of each of a plurality of values with the corresponding reference value over a period of time at a respective speed of the engine;

retrieving diagnostic thresholds indicative of a healthy compression braking system, and

An alert is provided in response to determining that the comparison value does not match the diagnostic threshold.

2. The system of claim 1, wherein the parameter associated with operation of the compression braking system is also at least one of an estimated torque of the engine or an estimated power output of the engine.

3. The system of claim 1, wherein the diagnostic threshold is based on an age of the compression braking system.

4. The system of claim 1, wherein the determination that the comparison value does not match the diagnostic threshold is based on a cumulative summation function that sums the results of the comparison of each of the plurality of values of the parameter with the corresponding reference value over the period of time.

5. The system of claim 4, wherein the instructions, when executed by at least one of the processors, further cause the controller to perform operations comprising:

providing the alert in response to the result of the comparison not matching the diagnostic threshold for the period of time.

6. The system of claim 4, wherein the instructions, when executed by at least one of the processors, further cause the controller to perform operations comprising:

In response to at least one of the results of the comparison matching the diagnostic threshold for the period of time, triggering the alarm is avoided.

7. The system of claim 1, wherein the instructions, when executed by at least one of the processors, further cause the controller to perform operations comprising providing a secondary alert in response to determining that the comparison value is within a predefined amount of the diagnostic threshold but does not exceed the diagnostic threshold.

8. The system of claim 1, wherein the alert provided is at least one of a fault code or a light.

9. A method for diagnosing a compression braking system of an engine, the method comprising:

Determining a plurality of values of a parameter associated with operation of a compression braking system of an engine at different speeds of the engine over a period of time during activation of the compression braking system, wherein the compression braking system is activated by decelerating a vehicle having the compression braking system by opening at least one exhaust valve to release compressed or about to compress air during a compression stroke of the engine, wherein the parameter associated with operation of the compression braking system is at least one of an exhaust pressure exiting at least one cylinder of the engine, a pressure of charge air entering at least one cylinder of the engine, a flow rate of charge air entering at least one cylinder of the engine;

retrieving a plurality of reference values for said parameters associated with a compression braking system of the engine operating as intended and different engine speeds;

comparing each of a plurality of values of the parameter with a corresponding reference value of the plurality of reference values of the parameter according to a respective speed of the engine;

Generating a comparison value representing a comparison of each of a plurality of values with the corresponding reference value over a period of time at a respective speed of the engine;

retrieving diagnostic thresholds indicative of a healthy compression braking system, and

An alert is provided in response to determining that the comparison value does not match the diagnostic threshold.

10. The method of claim 9, wherein the parameter associated with operation of the compression braking system is also at least one of an estimated torque of the engine or an estimated power output of the engine.

11. The method of claim 9, wherein the diagnostic threshold is based on an age of the compression braking system.

12. The method of claim 9, wherein the determination that the comparison value does not match the diagnostic threshold is based on a cumulative summation function that sums the results of the comparison of each of the plurality of values of the parameter with the corresponding reference value over the period of time.

13. The method as recited in claim 12, further comprising:

providing the alert in response to the result of the comparison not matching the diagnostic threshold for the period of time, or

In response to at least one of the results of the comparison matching the diagnostic threshold for the period of time, triggering the alarm is prevented.

14. The method of claim 9, further comprising providing a secondary alert in response to determining that the comparison value is within a predefined amount of the diagnostic threshold but does not exceed the diagnostic threshold.

15. The method of claim 9, wherein the alert provided is at least one of a fault code or a light.

16. A system for diagnosing a compression braking system of an engine, comprising:

Compression braking system associated with an engine, and

A controller coupled to the compression braking system, the controller configured to:

Providing a command to activate compression braking via the compression braking system associated with the engine by opening at least one exhaust valve to release compressed or impending compressed air during a compression stroke of the engine to thereby slow a vehicle having the compression braking system;

Determining a plurality of values of a parameter associated with operation of the compression braking system of the engine at different speeds of the engine over a period of time during activation of the compression braking, wherein the parameter associated with operation of the compression braking system is at least one of an exhaust pressure exiting at least one cylinder of the engine, a pressure of charge air entering at least one cylinder of the engine, a flow rate of charge air entering at least one cylinder of the engine;

Retrieving a plurality of reference values for the parameter associated with a compression braking system of an engine operating as expected and a speed of a different engine, wherein the plurality of reference values are associated with at least one of an exhaust pressure exiting at least one cylinder of the engine, a pressure of charge air entering at least one cylinder of the engine, a flow rate of charge air entering the at least one cylinder of the engine;

comparing each of a plurality of values of the parameter with a corresponding reference value of the plurality of reference values of the parameter according to a respective speed of the engine;

Generating a comparison value representing a comparison of each of a plurality of values with the corresponding reference value over a period of time at a respective speed of the engine;

retrieving diagnostic thresholds indicative of a healthy compression braking system, and

An alert is provided in response to determining that the comparison value does not match the diagnostic threshold.

17. The system of claim 16, wherein the diagnostic threshold is based on an age of the compression braking system.

18. The system of claim 16, wherein the determination that the comparison value does not match the diagnostic threshold is based on a cumulative summation function that sums the results of the comparison of each of the plurality of values of the parameter with the corresponding reference value over the period of time.

19. The system of claim 16, wherein in response to determining that the comparison value is within a predefined amount of the diagnostic threshold but does not exceed the diagnostic threshold, the controller is further configured to provide a secondary alert.

20. The system of claim 16, wherein the alert provided is at least one of a fault code or a light.