CN102076938B - Gaseous fuel injection systems for engines - Google Patents

Abstract

A gaseous-fuel direct injection system (10), comprising: a main tank (13) for containing a gaseous fuel such as LPG and a secondary tank for containing a reserve fuel supply. Gaseous fuel is delivered to a fuel injector (23) connected to the fuel rail (15). The operation of the fuel injector (23) is controlled by an Electronic Control Unit (ECU). As the gaseous fuel available in the main fuel tank (13) is depleted, the vapour pressure in the fuel rail (15) decreases. The ECU is able to compensate for the reduced vapour pressure in the fuel rail (15) by increasing the duration of opening of the fuel injector (23) as required to maintain delivery of the necessary mass of gaseous fuel by the fuel injector (23). However, at some stage the ECU can no longer compensate for the reduced fuel pressure, at which point it is necessary to switch the fuel supply from the main tank (13) to the secondary tank. That phase is identified and a switch of fuel supply to the secondary fuel tank is initiated using the decaying pressure characteristic of the gaseous fuel being depleted in the primary fuel tank (13).

Description

Gaseous fuel injection systems for engines

technical field

The present invention relates to gaseous fuel injection for internal combustion engines.

The term "gaseous fuel" as used herein refers to compressed gaseous fuels such as compressed natural gas (CNG) and hydrogen ( _H2 ), and liquefied gaseous fuels such as liquefied petroleum gas (LPG) and liquefied natural gas (LNG).

The term "direct injection" refers to the delivery of fuel directly into the combustion chamber of the internal combustion engine, usually by means of fuel injectors.

Background technique

The following discussion of the background art is intended only to aid in the understanding of the present invention. This discussion is not an acknowledgment or admission that any of the referenced material was common knowledge before the priority date of the application.

Gaseous fuels are known to have certain advantages for internal combustion engines over liquid fuels such as petrol and diesel, notably with regard to cost and exhaust emissions. Because of these advantages, there is a growing trend to use this fuel in engines.

One example of such use involves two-stroke direct injection gas fueled engines for vehicles. Typically, the vehicle is fitted with a main fuel tank and a reserve fuel tank for gaseous fuel, arranged so that the fuel supply can be switched from the main fuel tank to the reserve fuel tank when the main fuel tank is depleted to an almost empty state. However, there is a need to detect when there is no longer adequate gaseous fuel available in the main tank to continue to run the engine well. While this can be achieved by using a fuel level sensor in the fuel tank, it is not necessarily a cost-effective solution for some applications.

It is against this background, problem and associated difficulties that the present invention has been developed.

Contents of the invention

According to a first aspect of the present invention there is provided a method of controlling a gaseous fuel injection system for an engine, the method comprising: monitoring the supply pressure of gaseous fuel from a fuel source (source), monitoring the pressure of gaseous fuel to a fuel injector Delivery pressure, operating the fuel injector as a function of delivery pressure to compensate for any decrease in delivery pressure, and detecting whether changes in supply pressure or in delivery pressure decrease at a rate greater than a prescribed rate.

Due to this arrangement, the amount of gaseous fuel delivered is a function of the duration of operation of the fuel injector.

Preferably, the operation of the fuel injectors is controlled by control means such as an Electronic Control Unit (ECU). Specifically, the ECU determines the parameters by which the fuel injectors operate. The operating parameters may, for example, include duration of opening of the fuel injector, time the fuel injector opens corresponding to the beginning of the engine operating cycle, time the fuel injector closes corresponding to the beginning of the engine operating cycle, or any combination thereof.

Preferably, the ECU monitors the supply pressure and delivery pressure of the gaseous fuel.

Preferably, the ECU refers to a "look-up" map or table" to determine the desired operating parameters of the fuel injector.

Preferably, the delivery of gaseous fuel to the fuel injector is terminated in the event the ECU identifies a change in supply pressure or delivery pressure involving a decrease greater than a specified rate.

Normally, the ECU will switch the engine to reserve fuel supply. The reserve fuel supply may be a gaseous fuel supply or another form of fuel including liquid fuel (such as gasoline or diesel fuel).

Preferably, a signal is sent indicating that the fuel source is about to run out of gaseous fuel in the event the ECU identifies that a change in supply pressure or delivery pressure involves a greater than specified rate of decrease.

This signal sent by the ECU can initiate a switch to reserve fuel supply.

In fact, the ECU recognizes changes in the operating characteristics while the engine is running, and initiates actions in response thereto, which may involve switching the fuel supply to a reserve fuel supply.

Thus, the present invention seeks to exploit the decaying pressure characteristics of a depleting gaseous fuel source (which is typically a gas container being emptied) while the engine is running to recognize this event and initiate subsequent actions. This subsequent action may take any suitable form, such as sending a signal indicating that the gaseous fuel source has been depleted to a predetermined level and/or switching engine operation to a reserve fuel supply, thereby avoiding undesirable engine performance.

According to a second aspect of the present invention there is provided a gaseous fuel injection system for an engine, the fuel injection system comprising: means for monitoring the supply pressure of gaseous fuel from a fuel source, for monitoring the supply pressure of gaseous fuel to a fuel injector and means for operating the fuel injector as a function of the delivery pressure to compensate for any decrease in delivery pressure and to detect a reduction in supply pressure or delivery pressure at a rate greater than a specified rate.

According to a third aspect of the present invention there is provided an engine having a fuel injection system comprising: a first fuel supply for gaseous fuel, a second fuel supply for monitoring the supply pressure of the gaseous fuel from the first fuel supply means for monitoring the delivery pressure of the gaseous fuel to the fuel injector means for operating the fuel injector as a function of the delivery pressure to compensate for any decrease in delivery pressure and to detect a rate in the delivery pressure or delivery pressure greater than specified means for reducing the rate, and means for switching the engine from the first fuel supply to the second fuel supply when a decrease in supply pressure or delivery pressure at a rate greater than a specified rate is detected.

According to a fourth aspect of the invention there is provided a vehicle having an engine according to the third aspect of the invention.

Description of drawings

The present invention will be better understood by reference to the following description of a specific embodiment of the invention, as shown in the accompanying drawings, in which:

FIG. 1 is a schematic view of a gaseous fuel direct injection system according to this embodiment; and

FIG. 2 illustrates the emptying of the fuel tank in the fuel system according to this embodiment.

Detailed ways

The embodiment shown in the drawings is directed to a gaseous fuel direct injection system 10 for an internal combustion engine (not shown) of a vehicle. This arrangement is suitable for vehicles ranging from smaller vehicles such as auto-rickshaws of the type commonly used in India to heavy trucks.

The gaseous fuel direct injection system 10 includes a gas container providing a main fuel tank 13 for containing a gaseous fuel such as LPG. The fuel system 10 also includes a secondary fuel tank (not shown) for containing a reserve fuel supply, which may include gaseous fuel or conventional liquid fuel (such as gasoline or diesel, depending on the fuel cycle in which the engine is operating).

If the gas fuel includes liquefied gas fuel such as liquefied petroleum gas (LPG) or liquefied natural gas (LNG), it is stored in the fuel tank 13 in a liquefied state.

The gaseous fuel is delivered to a fuel rail 15 along a fuel line 17 . A pressure regulator 19 is incorporated in the fuel supply pipe 17 to adjust the supply pressure of the gaseous fuel supplied to the fuel rail 15 . A heat exchanger 21 is also incorporated in the fuel supply pipe 17 for vaporizing the liquefied gaseous fuel so that the gaseous fuel is delivered to the fuel rail 15 in a gaseous state. In the illustrated arrangement, the regulator 19 and the heat exchanger 21 are configured as an integral unit. The fuel supply line also incorporates a filter 25 and a solenoid lock-off valve 27 .

In this embodiment, the engine is a multi-cylinder engine, and gaseous fuel is injected directly into the combustion chamber defined by each cylinder through fuel injectors 23 connected to the fuel rail 15 .

Operation of fuel injector 23 is controlled by an electronic control unit (not shown). The electronic control unit (ECU) can control the operating parameters of each fuel injector 23, in particular the duration of opening of the injector, and the points of time during the engine cycle when the injector opens and closes.

The ECU receives input signals from various sensors that provide information about the engine's operating conditions and driver commands. The ECU outputs various control signals including control signals regarding the operation of the fuel injector 23 .

As the gaseous fuel available in the main fuel tank 13 is depleted, the vapor pressure in the fuel rail 15 decreases. The ECU is able to compensate for the reduced vapor pressure in the fuel rail 15 by controlling the amount of gaseous fuel delivered by the fuel injector 23 by virtue of changes in the operating parameters of the fuel injector. By controlling the duration of the opening of the fuel injectors, the time the fuel injectors open corresponding to the start of the engine cylinder cycle, the time the fuel injectors close corresponding to the start of the engine cylinder cycle, or any combination thereof, the ECU changes each fuel injector 23 operating parameters. Specifically, the ECU increases the duration of opening of the fuel injector 23 as needed to maintain the delivery of the requisite mass of gaseous fuel into the combustion chamber as required by prevailing engine operating conditions.

At a certain stage when the ECU is no longer able to compensate for the reduced fuel pressure, it is necessary to switch the fuel supply from the main tank 13 containing gaseous fuel to a secondary tank (not shown). This is necessary because it is undesirable to continue running the engine without sufficient fuel available, which would result in reduced engine power, a lean air-fuel ratio, and poor drivability. However, it is also desirable to optimize the use of the gaseous fuel available in the main fuel tank 13 . Therefore, there is a need to detect when it is imminent that there is no longer enough gaseous fuel available in the main fuel tank 13 to continue to run the engine well, and only then to switch to the reserve fuel supply. To this end, the gaseous fuel vapor pressure in the main fuel tank 13 and the gaseous fuel vapor pressure in the fuel rail 15 are continuously monitored, any decrease over a short period of time indicating an imminent shortage of available fuel.

For this purpose, the sensors for providing information to the ECU include: a first sensor 31 for sensing the vapor pressure of the gaseous fuel contained in the fuel tank 13; and a second sensor 32 for sensing the gaseous fuel in the fuel rail 15 vapor pressure. The first sensor 31 also senses the temperature of the gaseous fuel contained in the fuel tank 13 and the second sensor 32 also senses the temperature of the gaseous fuel in the fuel rail 15 . The temperature sensing capability provides additional benefits for certain gaseous fuels, which will be explained later.

The collected data regarding the gaseous fuel vapor pressure in the main fuel tank 13 and the gaseous fuel vapor pressure in the fuel rail 15 is temporarily stored in the ECU memory for a given engine speed and engine load. Typically, this is performed every engine cycle, but other timing arrangements are possible. New pressure data is compared, although typically performed multiple times per second on a continuous basis, other timing arrangements are possible. If the change in the gaseous fuel vapor pressure in the main tank 13 and/or the gaseous fuel vapor pressure in the fuel rail 15 decreases faster than a calibrated rate, the main tank 13 is considered to be empty.

This monitoring strategy will be better understood with reference to Figure 2, which is a graph representing the emptying of the fuel tank showing: (1) the gaseous fuel vapor pressure (indicated as TANK) in the main fuel tank 13; gaseous fuel vapor pressure in rail 15 (indicated in RAIL); (3) duration of opening of each fuel injector 23 (indicated in FPW, fuel pulse width); and (4) air-fuel ratio (indicated in AFR). Referring to FIG. 2 , the stage indicated at A represents the moment at which the gaseous fuel vapor pressure in the main fuel tank 13 begins to decrease, and due to the characteristics of the pressure regulator 19 the gaseous fuel vapor pressure in the fuel rail 15 also begins to decrease. . During this phase, the duration of opening of the fuel injector 23 begins to increase to maintain delivery of the necessary mass of gaseous fuel into the combustion chamber, thereby compensating for lost fuel supply due to the reduced gaseous fuel vapor pressure in the fuel rail 15 ( fueling). The phase indicated with B represents the moment at which the duration of opening of the fuel injector 23 reaches the maximum compensation limit. After this point, more compensation during the opening of the fuel injectors is ineffective to address the reduced fuel rail pressure, and the mass of gaseous fuel required for the engine operating cycle cannot be delivered into the combustion chamber, resulting in AFR Grows to unacceptable levels and becomes lean. The stage indicated by C represents the limit of combustion stability, at which stage the engine handling performance is not good. The stage indicated by D represents the moment when the engine will stall due to lack of fuel.

From the monitoring performed by the ECU, the ECU recognizes the slope of TANK and the RAIL plot line before reaching phase B and initiates a switch to reserve fuel supply.

In other words, the ECU recognizes a change in operating characteristics while the engine is running, and initiates action in response thereto, which in this embodiment involves switching fuel supply from the primary tank 13 to the secondary tank.

The ECU may also initiate any suitable form of signal (eg visual and/or audio signal) for engine operation, instructing the switching of fuel supply from the main tank 13 to the secondary tank.

As mentioned above, the temperature sensing performed by the first sensor 31 and the second sensor 32 provides additional benefits for certain gaseous fuels because it, along with the pressure sensing, takes into account the composition of this fuel to be evaluated and the potential for significant changes in the fuel supply to compensate. This is advantageous because the composition of some gaseous fuel mixtures varies depending on the source as well as the season of the year. Changes in the composition of gaseous fuels can affect the fuel's mass flow rate, calorific value, and stoichiometric ratio. This in turn affects the performance of the engine, in particular, where the engine is used in a vehicle, with respect to emission levels, torque, combustion stability and handling performance. Variations of LPG that may be used include, for example, mixtures that are primarily propane, mixtures that are primarily butane, and more generally mixtures that include propane and butane. Similarly, the composition of natural gas (which is primarily methane) will vary, as will the composition of blended gaseous fuels (typically hydrogen and natural gas). The ECU refers to a "look-up" map or table to determine the composition of the gaseous fuel based on the temperature and vapor pressure of the gaseous fuel stored in the fuel tank 13.

From the foregoing, it is evident that the present invention provides a simple but very effective method of determining the phase at which it is necessary to switch the fuel supply from the main tank containing the gaseous fuel to the secondary tank. The ECU recognizes changes in operating characteristics while the engine is running, and initiates actions in response thereto, switching fuel supply from a primary tank containing gaseous fuel to a secondary tank. In particular, the decaying pressure characteristic of the depleting gaseous fuel in the main tank 13 is used to identify that the ECU is no longer able to compensate for the reduced gaseous fuel pressure and that it is necessary to switch the fuel supply to the secondary tank stage.

It should be appreciated that the scope of the present invention is not limited to the scope of the described embodiments.

For example, the invention is not limited to direct injection systems. The invention is applicable to systems relying on port injection or fumigation (whether fuel is metered by injectors or other metering devices such as servoid metering valves).

The invention is applicable to gaseous fuel delivery systems that may be used on heavy-duty on-road diesel engines and associated vehicles. Furthermore, although the present embodiment has been described with respect to an arrangement using one fuel injector per engine cylinder, the present invention is not limited thereto. For example, the invention is applicable to arrangements where the number of injectors is not equal to the number of cylinders.

Furthermore, the invention may not be limited to arrangements in which injection operation is synchronized with engine timing.

The invention is applicable to engines operating on two-stroke or four-stroke cycles.

Furthermore, the invention is applicable to both compression-ignition and spark-ignition engines.

Furthermore, the present invention may be used in fuel injection systems involving two-fluid, where fuel is delivered to the combustion chamber as a compressed gas, such as air.

Throughout the specification and claims, unless the context requires otherwise, the word "comprise" and variations thereof, such as "comprises" or "comprising", will be understood to mean the entirety of the statement. (integer) or group of complete things (group), not the exclusion of any other complete thing or group of complete things.

Claims (20)

1. control is for a method for the gaseous fuel injection system of motor, and the method comprises: monitoring is from the supply pressure of the gaseous fuel of fuel source; Monitoring is delivered to the discharge pressure of the gaseous fuel of fuel injector; Moving fuel injector by the function of described discharge pressure reduces to compensate any of described discharge pressure; Whether reduce with the speed that is greater than assigned rate with the variation that detects described supply pressure or described discharge pressure.

2. method according to claim 1, wherein, the operation of fuel injector is by control member control, and, described supply pressure and the described discharge pressure of this control member gas-monitoring fuel.

3. method according to claim 2, wherein, control member is determined the Operational Limits of required fuel injector with reference to " Cha Tu or table ".

4. according to the method in claim 2 or 3, wherein, the speed that the variation that identifies described supply pressure or described discharge pressure relates to being greater than assigned rate reduces, stop the conveying of gaseous fuel to fuel injector at control member.

5. method according to claim 4, wherein, in the time that described situation occurs, motor is switched to the supply of deposit fuel by control member.

6. for a gaseous fuel injection system for motor, this fuel injection system comprises: for monitoring the member from the supply pressure of the gaseous fuel of fuel source, the member for gas-monitoring fuel to the discharge pressure of fuel injector; With anyly reduce and detect the member that described supply pressure or discharge pressure reduce to be greater than the speed of assigned rate with what compensate described discharge pressure for move fuel injector by the function of described discharge pressure.

7. gaseous fuel injection system according to claim 6, wherein, the described supply pressure of a kind of control member for gas-monitoring fuel and the described discharge pressure of gaseous fuel are provided, and, this control member is exercisable to control the operation of fuel injector by the function of described discharge pressure, reduces to compensate any of discharge pressure.

8. gaseous fuel injection system according to claim 7, wherein, this control member is suitable for monitoring supplies with the variation of pressure or discharge pressure, and in the time that pressure reduces to be greater than the speed of assigned rate, initiates action.

9. according to the gaseous fuel injection system described in claim 6,7 or 8, wherein, also comprise gas container for holding gaseous fuel and for responding to the first sensor of vapor tension of gas container gaseous fuel, this gas container provides the fuel source of gaseous fuel.

10. gaseous fuel injection system according to claim 9, wherein, first sensor is also responded to the temperature of the gaseous fuel holding in gas container.

11. gaseous fuel injection systems according to claim 9, wherein, also comprise the second sensor of the vapor tension for responding to the gaseous fuel that is delivered to fuel injector.

12. gaseous fuel injection systems according to claim 11, wherein, the second sensor is also responded to the temperature of the gaseous fuel that is delivered to fuel injector.

13. gaseous fuel injection systems according to claim 11, wherein, fuel injector is connected to fuel rail, and wherein, the vapor tension of the gaseous fuel in this second sensor sensing fuel rail.

14. gaseous fuel injection systems according to claim 12, wherein, fuel injector is connected to fuel rail, and wherein, the vapor tension of the gaseous fuel in this second sensor sensing fuel rail.

15. gaseous fuel injection systems according to claim 9, wherein, this gas container provides main fuel tank, is provided with in addition the secondary fuel tank of supplying with for holding deposit fuel.

16. gaseous fuel injection systems according to claim 15, also comprise the member that switches to secondary fuel tank and operate in response to the action of control member initiation from main fuel tank for the fuel to fuel injector is supplied with.

17. 1 kinds of motors, have according to the gaseous fuel injection system described in any one in claim 6 to 16.

18. 1 kinds of motors, have fuel injection system, and this fuel injection system comprises: the first fuel for gaseous fuelled is supplied with; The second fuel is supplied with; Be used for the member of the supply pressure of monitoring the gaseous fuel of supplying with from the first fuel; Member for from gas-monitoring fuel to the discharge pressure of fuel injector; Anyly reduce and detect the member that described supply pressure or discharge pressure reduce to be greater than the speed of assigned rate with what compensate described discharge pressure for move fuel injector by the function of described discharge pressure; With the member for motor is switched to the second fuel supply in the time detecting that described supply pressure or discharge pressure reduce to be greater than the speed of assigned rate from the first fuel supply.

19. 1 kinds have the vehicle of motor according to claim 17.

20. 1 kinds have the vehicle of motor according to claim 18.