JP2017203444A - Engine control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve estimation accuracy for exhaust pressure, in relation to an engine control system.SOLUTION: An engine control system includes: an acquisition unit 2 that acquires a flow rate Q of an exhaust gas of an engine 10, an opening degree S of a supercharging control valve 17 and a downstream pressure Pof a turbine 14; and an estimation unit 3 that estimates an upstream pressure Pof the turbine 14 that is equivalent to exhaust pressure of the engine 10 based on the flow rate Q, the opening degree S and the downstream pressure P.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an engine control device that estimates a turbine upstream pressure of a supercharger.

  2. Description of the Related Art Conventionally, a technology for controlling an operating state of a supercharger in accordance with an exhaust pressure (engine back pressure, exhaust port pressure) of an engine, which is a turbine upstream pressure, is known in a control device for a supercharged engine. For example, a technique is known in which an exhaust port pressure sensor is attached to an exhaust manifold of an engine and control is performed to increase the turbine capacity of a supercharger based on the exhaust pressure detected by the sensor (see Patent Document 1). . By controlling the operating state of the supercharger while referring to the exhaust pressure, the supercharging response and controllability can be improved.

JP 2015-135079

  However, since the temperature of the exhaust gas passing through the exhaust manifold is very high, there is a problem that an exhaust port pressure sensor with high heat resistance must be used, or cooling is required, which tends to increase costs. In addition, since the engine manifold and exhaust vibration can act on the exhaust manifold, a situation in which deformation or breakage of the sensor mounting location may occur. Therefore, even if an exhaust port pressure sensor is used, it is desirable to prepare another method capable of accurately estimating the exhaust pressure of the engine in preparation for the occurrence of a sensor failure.

  One of the objects of the present case was invented in view of the above-described problems, and is to provide an engine control device with improved estimation accuracy of exhaust pressure. It should be noted that the present invention is not limited to this purpose, and is an operational effect that is derived from each configuration shown in “Mode for Carrying Out the Invention” to be described later. Can be positioned as a purpose.

  (1) The present specification discloses an engine control device in which a turbine of a supercharger is interposed in an exhaust passage, and a supercharge control valve is interposed in a bypass passage of the turbine. The engine control device includes an acquisition unit and an estimation unit. The acquisition unit acquires an exhaust flow rate of the engine, an opening degree of the supercharging control valve, and a downstream pressure of the turbine. The estimation unit estimates an upstream pressure of the turbine based on the flow rate, the opening degree, and the downstream pressure.

  The supercharging control valve is preferably an electromagnetic control valve (for example, an electrically controlled waste gate valve). In this case, it is preferable that the acquisition unit acquires the opening degree based on a drive signal transmitted to the supercharging control valve. The flow rate of the exhaust gas is preferably a volume flow rate. The volume flow rate can be calculated by dividing the exhaust mass flow rate by its density. The mass flow rate can be calculated as the sum of the mass flow rate of intake air and the mass flow rate of fuel. The mass flow rate of the intake air can be detected by a thermal air flow sensor. The mass flow rate of the intake air can also be calculated by multiplying the volume flow rate of the intake air detected by a flap airflow sensor or a sonic airflow sensor by the density of the intake air.

(2) It is preferable that the estimation unit estimates an upstream pressure of the turbine using a map in which a relationship among the flow rate, the opening degree, and the turbine pressure ratio is defined.
(3) In the map, it is preferable that the increasing gradient of the pressure ratio with respect to the flow rate is set to be larger as the opening degree is smaller.
(4) In the map, the square root of the difference obtained by subtracting the first soot from the square of the first soot with the value obtained by subtracting the reciprocal of the specific heat ratio of the exhaust from 1 as an index is the flow rate. It is preferable that a relationship proportional to a value obtained by dividing the above by a flow path cross-sectional area of the turbine is defined.
(5) It is preferable that the acquisition unit acquires the downstream pressure based on atmospheric pressure.

(6) It is preferable to provide a downstream pressure sensor for measuring the downstream pressure of the turbine.
(7) It is preferable to provide an exhaust treatment device interposed in the exhaust passage on the downstream side of the turbine. In this case, the estimation unit uses the second map in which the relationship between the flow rate and the pressure ratio of the exhaust treatment device is defined, and the upstream pressure of the exhaust treatment device is based on the flow rate and the atmospheric pressure. It is preferable to estimate the downstream pressure of the turbine.

  The upstream pressure of the turbine (engine exhaust pressure) can be estimated with high accuracy.

It is a schematic diagram which shows the structure of an engine control apparatus and an engine. It is a schematic diagram for demonstrating the control content by an engine control apparatus. (A) is a first map example that defines the relationship between the pressure ratio, flow rate, and opening of the turbine, and (B) is a second map example that defines the relationship between the pressure ratio and flow rate of the exhaust treatment device. . It is a flowchart which illustrates the control procedure by an engine control apparatus.

  An engine control apparatus as an embodiment will be described with reference to the drawings. Note that the embodiment described below is merely an example, and there is no intention to exclude various modifications and technical applications that are not explicitly described in the following embodiment. Each configuration of the present embodiment can be implemented with various modifications without departing from the spirit thereof. Further, they can be selected as necessary, or can be appropriately combined.

[1. Device configuration]
The engine control device 30 of the present embodiment is applied to an engine 10 of a vehicle provided with a supercharger 13 (turbocharger) shown in FIG. The turbine 14 of the supercharger 13 is interposed on the exhaust passage 12, and the compressor 15 is interposed upstream of the throttle valve on the intake passage 11. An airflow sensor 21 (for example, a thermal airflow sensor) that detects the mass flow rate C of intake air is provided on the upstream side of the compressor 15.

  The exhaust passage 12 is provided with a bypass passage 16 for communicating between the upstream side and the downstream side of the turbine 14, and a supercharging control valve 17 for controlling the flow rate of the exhaust gas passing through the bypass passage 16 is provided in the bypass passage 16. Is done. The supercharging control valve 17 is a flow rate control valve (for example, an electromagnetically controlled waste gate valve) whose opening degree S is electrically controlled by the engine control device 30. An exhaust gas treatment device 18 such as an exhaust gas purification device, a catalyst device, or a sound absorbing buffer device is interposed in the exhaust passage 12 downstream of the turbine 14.

  The engine control device 30 is an electronic device (electronic control device) including a processor 31, a memory 32, and an interface device 33 that are connected to each other via an internal bus 34. Connected to. The processor 31 is a processing device (processor) including, for example, a control unit (control circuit), an arithmetic unit (arithmetic circuit), a cache memory (register), and the like. The memory 32 is a memory device that stores a program and working data, and includes a ROM (Read Only Memory), a RAM (Random Access Memory), a nonvolatile memory, and the like. The contents of the control performed by the engine control device 30 are recorded and stored in the memory 32 as firmware or an application program. When the program is executed, the contents of the program are expanded in the memory space and executed by the processor 31.

The engine control device 30 of this embodiment is connected to the supercharging control valve 17, the air flow sensor 21, and the atmospheric pressure sensor 22. The engine control device 30 has a function of detecting or calculating the degree of opening S based on the drive signal transmitted to the supercharging control valve 17 and acquiring it. Further, information on the mass flow rate C of the intake air detected by the air flow sensor 21 and information on the atmospheric pressure BP detected by the atmospheric pressure sensor 22 are input to the engine control device 30 as needed. The engine control device 30 performs control for estimating the upstream pressure P ₁ of the turbine 14 corresponding to the exhaust pressure of the engine 10 based on such information.

The estimation program 1 for estimating the upstream pressure P ₁ is recorded and stored in the memory 32, for example. Alternatively, it is recorded and stored in a computer-readable recording medium, and is read and executed by the engine control device 30 via a reading device connected to the interface device 33. The estimation program 1 includes an acquisition unit 2, an estimation unit 3, and a control unit 4. These elements indicate some functions of a program executed by the engine control device 30 and are implemented by software. However, part or all of each function may be realized by hardware (electronic circuit), or may be realized by using software and hardware together.

[2. Control configuration]
Acquisition unit 2 is for acquiring the flow rate Q of the exhaust gas of the engine 10, the opening degree S of the boost pressure control valve 17, the respective information to the downstream pressure P ₂ of the turbine 14. The flow rate Q is the volumetric flow rate of the exhaust gas and can be calculated by dividing the exhaust mass flow rate G by its density (for example, the ratio of the downstream pressure P ₂ to the standard atmospheric pressure multiplied by the standard condition air density). . The exhaust mass flow rate G can be calculated as the sum of the intake mass flow rate C detected by the airflow sensor 21 and the fuel mass flow rate. As the method of acquiring the downstream pressure P _2, for example, it is mentioned three kinds of techniques.

In the first method, a pressure sensor (downstream pressure sensor) is provided downstream of the turbine 14 in the exhaust passage 12 (for example, between the turbine 14 and the exhaust processor 18), and the detection value of this pressure sensor is set downstream. it is an pressure P _2. The second approach is the preferred method when the pressure loss of the exhaust processor 18 is relatively small, those regarded atmospheric pressure BP detected by the atmospheric pressure sensor 22 and downstream pressure P _2. The third method is a method that uses the downstream pressure P ₂ estimated based on the atmospheric pressure BP in consideration of the pressure characteristics of the exhaust treatment device 18. The third method will be described later.

As shown in FIG. 2, the estimating unit 3 estimates the upstream pressure P ₁ of the turbine 14 based on the flow rate Q, the opening degree S, and the downstream pressure P ₂ . The upstream pressure P ₁ is accurately estimated using the pressure characteristics of the turbine 14. Further, the estimating unit 3 of this embodiment, both the flow rate Q, the ability to estimate the downstream pressure P ₂ of the turbine 14 based on the atmospheric pressure BP. However, this function is not essential and can be omitted when a pressure sensor is provided between the turbine 14 and the exhaust treatment device 18. It can also be omitted when the atmospheric pressure BP is regarded as the downstream pressure P ₂ (that is, when the actual downstream pressure P ₂ is not referred to).

Respect estimating function of upstream pressure P _1, the value of the upstream pressure P ₁ is estimated using the first map the relationship between the pressure ratio R ₁ of the flow rate Q and the opening S the turbine 14 is defined. The pressure ratio R ₁ is the ratio of the upstream pressure P ₁ to the downstream pressure P ₂ of the turbine 14. First map, as shown in FIG. 3 (A), a map defining the flow rate Q, the opening degree S, the tripartite relationship of the pressure ratio R _1. In the first map, a pressure ratio characteristic is set such that as the flow rate Q increases, the pressure ratio R ₁ increases in a range of 1 or more. The relationship of increasing gradient of the pressure ratio R ₁ is greater as the angle S is smaller for the flow rate Q is set. When the three-way relationship here is defined by a mathematical expression (function), it can be considered that the following Expression 1 is used. Here, the power of the pressure ratio R ₁ (= P ₁ / P ₂ ) as a radix and the power obtained by subtracting the reciprocal of the exhaust specific heat ratio κ from 1 as an index is defined as the first power. In the present embodiment, the relationship in which the square root of the difference obtained by subtracting the first power from the square of the first power is proportional to the value obtained by dividing the flow rate Q by the flow path cross-sectional area A of the turbine 14 is set in the first map.

(P₁/P₂)：タービン１４の圧力比，κ：比熱比，Q：流量（体積流量）
A：タービン１４の流路断面積，a₀：よどみ点音速，T₀：標準温度，T₁：上流温度

(P ₁ / P ₂ ): Pressure ratio of turbine 14, κ: Specific heat ratio, Q: Flow rate (volumetric flow rate)
A: Cross-sectional area of the flow path of the turbine 14, a ₀ : stagnation point sound velocity, T ₀ : standard temperature, T ₁ : upstream temperature

Respect estimating function of the downstream pressure P _2, the value of the downstream pressure P ₂ is estimated using the second map the relationship between the flow rate Q and the pressure ratio R ₂ of the exhaust processor 18 is defined. The pressure ratio R ₂ is the ratio of the upstream pressure (eg, downstream pressure P ₂ ) of the exhaust treatment device 18 to the downstream pressure (eg, atmospheric pressure BP) of the exhaust treatment device 18. Second map, as shown in FIG. 3 (B), the flow rate Q, is a map that defines the dyads of the pressure ratio R _2. In the second map, a pressure ratio characteristic is set such that as the flow rate Q increases, the pressure ratio R ₂ increases in a range of 1 or more. When the second map is expressed by a mathematical expression, it is conceivable to use the following Expression 2. Here, the power of the pressure ratio R ₂ (= P ₂ / BP) as a radix and the power obtained by subtracting the reciprocal of the specific heat ratio κ of exhaust gas from 1 as an index is set as the second power. In the present embodiment, a relationship in which the square root of the difference obtained by subtracting the second soot from the square of the second soot is proportional to the value obtained by dividing the flow rate Q by the flow path cross-sectional area B of the exhaust treatment device 18 is set in the second map. The

(P₂/BP)：排気処理器１８の圧力比，B：排気処理器１８の流路断面積

(P ₂ / BP): Pressure ratio of the exhaust treatment device 18, B: Cross-sectional area of the flow path of the exhaust treatment device 18

The control unit 4 controls the engine 10 based on the upstream pressure P ₁ estimated by the estimation unit 3. The information on the upstream pressure P ₁ is used, for example, when calculating the friction (pumping loss) of the engine 10 and is reflected in the control content of the target intake air amount, fuel injection amount, and ignition timing of the engine 10. The information on the upstream pressure P ₁ can be used when calculating the target opening degree of the supercharging control valve 17 and can be reflected in the control content of the supercharger 13.

[3. flowchart]
The flow of the estimation program 1 is illustrated in FIG. When estimating the upstream pressure P ₁ of the turbine 14, various sensor information is read into the engine control device 30 (A 1), information on the exhaust gas flow rate Q calculated in the previous calculation cycle is acquired, and the supercharging control valve is acquired. Information on the opening degree S of 17 and information on the atmospheric pressure BP are acquired by the acquisition unit 2 (A2). Subsequently, with the flow rate Q as an argument, the pressure ratio R ₂ of the exhaust gas processor 18 is estimated by the estimation unit 3 using the second map (A3), and the turbine 14 corresponding to the product of the pressure ratio R ₂ and the atmospheric pressure BP. downstream pressure P ₂ is estimated in (A4).

Further, the calculated mass flow rate G of exhaust gas corresponding to the sum of the mass flow rate of the mass flow rate C and the fuel detected by the air flow sensor, the exhaust based on and the downstream pressure P ₂ mass flow rate G flow Q (in this The volume flow rate in the calculation cycle) is estimated (A5). Thereafter, the pressure ratio R ₁ of the turbine 14 is estimated by the estimation unit 3 using the first map with the latest flow rate Q and the opening degree S as arguments (A6), and the pressure ratio R ₁ and the downstream pressure P ₂ are The upstream pressure P ₁ of the turbine 14 corresponding to the product is estimated (A7). Information on the upstream pressure P ₁ is transmitted to the control unit 4 and used for intake control of the engine 10, fuel amount control, ignition control, supercharger 13 control, and the like.

[4. effect]
(1) As described above, by referring to the opening S and the downstream pressure P ₂ of the exhaust gas flow rate Q and supercharge control valve 17, to estimate the pressure conditions resulting from the pressure characteristics of the turbine 14 accurately Thus, the upstream pressure P ₁ of the turbine 14 can be estimated with high accuracy.
(2) Also, by preparing a first map based on the pressure ratio R ₁ of the turbine 14, the pressure characteristics of the turbine 14 with respect to the opening degree S of the supercharging control valve 17 and the flow rate Q of the exhaust gas can be expressed in a simple format. Can be identified. For example, when the pressure ratio R ₁ is not used and the upstream pressure P ₁ is obtained from the relationship between the upstream pressure P ₁ , downstream pressure P ₂ , opening degree S, and flow rate Q of the turbine 14, a four-dimensional map ( Map) representing the interrelationship of the four variables must be prepared, and the amount of map data becomes enormous. On the other hand, if the pressure ratio R ₁ is used, the map dimension becomes three-dimensional, and the amount of map data can be reduced. In addition, the calculation load can be reduced by estimating the upstream pressure P ₁ using the first map. Furthermore, since the pressure characteristic defined in the first map does not change depending on the atmospheric pressure BP, the upstream pressure P ₁ can be estimated with high accuracy without being influenced by the altitude of the place where the vehicle is traveling.

Further, according to the engine control device 30 described above, the upstream pressure P ₁ corresponding to the exhaust pressure of the engine 10 can be accurately grasped even when there is no exhaust pressure sensor upstream of the turbine 14 in the exhaust passage 12. It becomes possible to do. Therefore, the controllability of the operating state of the engine 10 and the supercharging state of the supercharger 13 can be improved. Further, when such an exhaust pressure sensor is also provided, the information on the upstream pressure P ₁ estimated by the estimation unit 3 can be used as the calibration data (or alternative data) of the exhaust pressure sensor. Reliability can be improved.

(3) In the first map, since the pressure characteristic of the turbine 14 is set such that the increasing gradient of the pressure ratio R ₁ with respect to the flow rate Q increases as the opening degree S decreases, the upstream pressure P ₁ corresponding to the pressure characteristic is set. Thus, the estimation accuracy of the upstream pressure P ₁ can be improved.
(4) As shown in Equation 1, the first map shows a relationship in which the square root (left side) of the difference obtained by subtracting the first square from the square of the first square is proportional to the value obtained by dividing the flow rate Q by the channel cross-sectional area A. By setting, the pressure ratio R ₁ that matches the theoretical pressure ratio characteristic can be obtained, and the upstream pressure P ₁ can be estimated with extremely high accuracy.

(5) The upstream pressure P ₁ of the turbine 14 is calculated by multiplying the pressure ratio R ₁ (= P ₁ / P ₂ ) by the downstream pressure P ₂ . If the atmospheric pressure BP is used as the downstream pressure P ₂ multiplied by the pressure ratio R ₁ , it is not necessary to provide a pressure sensor on the downstream side of the turbine 14, and the apparatus configuration and calculation configuration can be simplified. The method of regarding the atmospheric pressure BP as the downstream pressure P ₂ is preferably applied when the pressure loss of the exhaust treatment device 18 is relatively small.

(6) On the other hand, a pressure sensor disposed downstream of the turbine 14, if the detected value at the pressure sensor and the downstream pressure P _2, the estimation accuracy of the upstream pressure P ₁ than with the atmospheric pressure BP Can be improved. Such a method using a pressure sensor is preferably applied when the pressure loss of the exhaust treatment device 18 is relatively high. If the downstream pressure P ₂ is calculated by using the detected value of the pressure sensor and the atmospheric pressure BP, further improvement of the estimation accuracy of the upstream pressure P ₁ can be expected.

(7) In the above estimation unit 3, the downstream pressure P ₂ are estimated using the second map. As a result, the downstream pressure P ₂ in consideration of the pressure loss in the exhaust treatment device 18 can be grasped with high accuracy, and as a result, the estimation accuracy of the upstream pressure P ₁ can be improved. Also, the pressure ratio R ₂ of the exhaust processor 18 by creating a second map as a reference, it is possible to specify the pressure characteristics of the exhaust processor 18 in a simple format. Thereby, the calculation load can be reduced and the data amount of the second map can be reduced. Furthermore, since the pressure characteristics defined in the second map are not changed by the atmospheric pressure BP, the upstream pressure P ₁ and the downstream pressure P ₂ of the turbine 14 are accurately determined without being influenced by the altitude of the place where the vehicle is traveling. Can be estimated well.

[5. Modified example]
In the above embodiment, both the first map and the second map is used, in the case of using a pressure sensor for detecting the case or downstream pressure P ₂ regarded atmospheric pressure BP and the downstream pressure P ₂ are The second map is not necessary. Further, if the mutual relationship among the flow rate Q, the opening degree S, the upstream pressure P ₁ , and the downstream pressure P ₂ is defined by mathematical formulas and functions, the first map is also unnecessary. It is possible to carry out computations having the same operations and effects as those of the above-described embodiment by adopting a computation configuration that estimates the upstream pressure P ₁ based on at least the flow rate Q, the opening degree S, and the downstream pressure P _2. it can.

In addition, since the flow rate Q whose characteristics are set in the first map and the second map is a volume flow rate, in the above-described embodiment, after converting the mass flow rate G of the exhaust gas to the volume flow rate Q, the first map, Used as an argument for the second map. However, when a flow rate sensor capable of detecting the volume flow rate Q of the exhaust gas is provided on the exhaust passage, the value may be used as an argument. The upstream pressure P ₁ can be accurately estimated by defining at least the three-way relationship of the flow rate Q, the opening degree S, and the pressure ratio R ₁ in the first map. The same applies to the second map, and the downstream pressure P ₂ can be accurately estimated by prescribing at least a binary relationship between the flow rate Q and the pressure ratio R ₂ in the second map.

DESCRIPTION OF SYMBOLS 1 Estimation program 2 Acquisition part 3 Estimation part 14 Turbine 17 Supercharging control valve (electric control wastegate valve)
18 Exhaust processor 21 Air flow sensor 22 Atmospheric pressure sensor 30 Engine control device

Claims (7)

In an engine control device in which a turbine of a supercharger is interposed in an exhaust passage, and a supercharge control valve is interposed in a bypass passage of the turbine,
An acquisition unit for acquiring an exhaust flow rate of the engine, an opening degree of the supercharging control valve, and a downstream pressure of the turbine;
An engine control device comprising: an estimation unit configured to estimate an upstream pressure of the turbine based on the flow rate, the opening degree, and the downstream pressure. The engine control according to claim 1, wherein the estimation unit estimates an upstream pressure of the turbine using a map in which a relationship among the flow rate, the opening degree, and the pressure ratio of the turbine is defined. apparatus. The engine control apparatus according to claim 2, wherein, in the map, an increasing gradient of the pressure ratio with respect to the flow rate is set to be larger as the opening degree is smaller. In the map, the square root of the difference obtained by subtracting the first soot from the square of the first soot, where the pressure ratio is a radix and the reciprocal of the specific heat ratio of the exhaust gas is subtracted from 1, is the flow rate as the turbine. The engine control device according to claim 2 or 3, wherein a relationship proportional to a value divided by the flow path cross-sectional area is defined. The engine control device according to claim 1, wherein the acquisition unit acquires the downstream pressure based on atmospheric pressure. The engine control apparatus according to claim 1, further comprising a downstream pressure sensor that measures a downstream pressure of the turbine. An exhaust treatment device interposed in the exhaust passage on the downstream side of the turbine,
The estimation unit uses a second map in which the relationship between the flow rate and the pressure ratio of the exhaust treatment device is defined, and the downstream of the turbine that is the upstream pressure of the exhaust treatment device based on the flow rate and the atmospheric pressure. The engine control device according to claim 1, wherein the pressure is estimated.

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