fuel injection control device

Abstract

To suppress the control accuracy worsening of a fuel injection amount due to thermal distortion of an injector resulting from a temperature difference between a cylinder head and a delivery pipe.SOLUTION: An electronic control unit 20 controlling the fuel injection of an injector 16 mounted to a cylinder head 12 of an internal combustion engine 10 and connected to a delivery pipe 17 while computing an injection period for the injector 16, required to inject the required amount of fuel, Furthermore, during computing the injection period when there is a great temperature difference between the cylinder head 12 and the delivery pipe 17, the electronic control unit 20 executes injection period computing processing for computing the injection period to be a longer time than when there is a small temperature difference.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fuel injection control device for controlling fuel injection in an internal combustion engine. [Background technology]

[0002] There is known an internal combustion engine equipped with an injector attached to a cylinder head and a delivery pipe installed outside the cylinder head. The injector of this type of internal combustion engine is fixed at one end to the cylinder head and the other end to the delivery pipe. Therefore, when the temperature difference between the cylinder head and the delivery pipe becomes large, the difference in thermal expansion between the two causes thermal distortion in the injector. Patent Document 1 describes a technology for suppressing thermal distortion of the injector caused by the difference in thermal expansion between the cylinder head and the delivery pipe. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-217354 Summary of the Invention [Problem to be solved by the invention]

[0004] When thermal distortion occurs, the sliding resistance of the injector's sliding parts, such as the needle, increases, which in turn changes the injection characteristics of the injector. As a result, if the temperature difference between the cylinder head and the delivery pipe becomes large, the accuracy of fuel injection quantity control may deteriorate. [Means for solving the problem]

[0005] A fuel injection control device that solves the above problem calculates the injection period of an injector required to inject a required amount of fuel when controlling fuel injection of the injector attached to the cylinder head of an internal combustion engine and connected to a delivery pipe. Furthermore, the fuel injection control device performs an injection period calculation process that calculates a longer injection period when the temperature difference between the cylinder head and the delivery pipe is large than when the temperature difference is small.

[0006] When the temperature difference between the cylinder head and the delivery pipe increases and thermal strain in the injector increases, the sliding resistance of the injector's sliding parts increases. The increased sliding resistance then reduces the injector's fuel injection rate. In response to this, the fuel injection control device calculates a longer injection period than normal when such a reduction in injection rate due to thermal strain occurs. Therefore, the reduction in injection quantity caused by the reduction in injection rate due to thermal strain is compensated for by extending the injection period. Therefore, the fuel injection control device has the effect of suppressing deterioration in the control accuracy of the fuel injection quantity due to thermal strain in the injector caused by the temperature difference between the cylinder head and the delivery pipe. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram schematically illustrating a configuration of an embodiment of a fuel injection control device. [Figure 2] 3 is a flowchart of an injection period calculation routine executed by the fuel injection control device. [Figure 3] 10 is a graph showing the relationship between the temperature difference between the cylinder head and the delivery pipe and the injection rate of the injector. [Figure 4] 10 is a graph showing the relationship between the temperature difference between the cylinder head and the delivery pipe and the correction factor of the injection period. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of a fuel injection control device will be described in detail below with reference to FIGS. <Configuration of fuel injection control device> First, the configuration of the fuel injection control device of this embodiment will be described with reference to Fig. 1. The fuel injection control device of this embodiment is applied to a direct-injection internal combustion engine 10 that uses hydrogen gas as fuel. The internal combustion engine 10 is mounted on a vehicle.

[0009] The internal combustion engine 10 includes a cylinder block 11 and a cylinder head 12. The cylinder block 11 includes cylinders 14 each housing a piston 13. A combustion chamber 15 for burning hydrogen gas is formed inside the cylinder 14. The internal combustion engine 10 also includes an injector 16 for injecting hydrogen gas into the cylinder 14. The cylinder head 12 includes a mounting hole 12A for mounting the injector 16. The injector 16 is mounted to the cylinder head 12 with its nozzle end inserted into the mounting hole 12A. A delivery pipe 17 is installed on the outside of the cylinder head 12 of the internal combustion engine 10. A hydrogen tank 18 is connected to the delivery pipe 17 via a pressure regulator 19. The pressure regulator 19 reduces the pressure of high-pressure hydrogen stored in the hydrogen tank 18 to a predetermined supply pressure and supplies the hydrogen to the delivery pipe 17. The end of the injector 16 opposite the nozzle end is connected to the delivery pipe 17.

[0010] The fuel injection control device of this embodiment controls fuel injection from the injector 16 in the internal combustion engine 10. The fuel injection control device includes an electronic control unit 20. The electronic control unit 20 includes a processor 21 and a memory 22. The memory 22 stores programs and data for controlling fuel injection from the injector 16. The processor 21 reads and executes the programs from the memory 22, thereby causing the electronic control unit 20 to perform various processes for controlling fuel injection. The electronic control unit 20 receives detection signals from various sensors 23 installed in various parts of the vehicle. The sensors 23 include sensors for detecting the temperatures of the cooling water for the internal combustion engine 10, the lubricating oil for the internal combustion engine 10, the outside air, the hydrogen gas in the delivery pipe 17, and the like. The sensors 23 also include sensors for detecting the operating conditions of the internal combustion engine 10, such as the pressure of the hydrogen gas in the delivery pipe 17, the crank angle of the internal combustion engine 10, and the intake air amount. The sensors 23 also include sensors for detecting the driving conditions of the vehicle, such as the accelerator pedal operation amount and vehicle speed. The electronic control unit 20 determines the engine speed, which is the rotation speed of the internal combustion engine 10, based on the crank angle detection signal.

[0011] The electronic control unit 20 determines a required value for the amount of hydrogen gas injection based on the detection results of each sensor 23. The electronic control unit 20 also calculates the injection period of the injector 16 required to inject an amount of hydrogen gas equal to the determined required value. The electronic control unit 20 then commands the injector 16 to inject hydrogen gas according to the calculation result of the injection period. The electronic control unit 20 controls the amount of hydrogen gas injection into the internal combustion engine 10 through the above processing. In other words, the electronic control unit 20 calculates the injection period of the injector 16 required to inject the required amount of fuel, and controls the fuel injection of the injector 16.

[0012] <Injection period calculation routine> 2 to 4, the processing of the electronic control unit 20 for calculating the injection period in controlling the fuel injection amount will be described. Fig. 2 shows a flowchart of an injection period calculation routine executed by the electronic control unit 20 to calculate the injection period. The electronic control unit 20 executes this routine at predetermined control intervals while the internal combustion engine 10 is operating.

[0013] When this routine starts, the electronic control unit 20 first reads the required injection amount, which is the required value of the hydrogen gas injection amount, in step S100. In a separate routine, the electronic control unit 20 determines the required output of the internal combustion engine 10 based on the accelerator pedal operation amount, vehicle speed, etc. Then, based on the required output, engine speed, etc., the electronic control unit 20 calculates the injection amount of hydrogen gas required to generate the required output as the value of the required injection amount.

[0014] Next, in step S110, the electronic control unit 20 calculates a basic injection period TAUb. The basic injection period TAUb represents the injection period of hydrogen gas from the injector 16 required to inject the required injection amount of hydrogen gas in a rated state where no thermal strain occurs in the injector 16. The electronic control unit 20 calculates the basic injection period TAUb based on the required injection amount, the pressure and temperature of the hydrogen gas in the delivery pipe 17, etc.

[0015] In the next step S120, the electronic control unit 20 calculates a head temperature Th and a pipe temperature Tp. The head temperature Th represents an estimated temperature of the cylinder head 12. More specifically, the head temperature Th represents an estimated temperature of a portion of the cylinder head 12 around the mounting hole 12A of the injector 16. The pipe temperature Tp represents an estimated temperature of the delivery pipe 17. The electronic control unit 20 calculates the head temperature Th based on the respective temperatures of the lubricating oil and cooling water of the internal combustion engine 10, the engine speed, and the required output. The electronic control unit 20 also calculates the pipe temperature Tp based on the temperatures of the outside air and the hydrogen gas in the delivery pipe 17.

[0016] Next, in step S130, the electronic control unit 20 determines whether the difference between the head temperature Th and the pipe temperature Tp (=Th-Tp) is equal to or greater than a predetermined threshold value X. Hereinafter, the difference between the head temperature Th and the pipe temperature Tp will be referred to as the temperature difference ΔT.

[0017] If the temperature difference ΔT is less than the threshold value X (S130: NO), the electronic control unit 20 sets the value of the basic injection period TAUb as the value of the command injection period TAU in step S140. The command injection period TAU represents a command value for the injection period of hydrogen gas for the injector 16.

[0018] On the other hand, if the temperature difference ΔT is equal to or greater than the threshold value X (S130: YES), the electronic control unit 20 proceeds to step S150. In step S150, the electronic control unit 20 calculates a correction factor K based on the temperature difference ΔT. Furthermore, in the following step S160, the electronic control unit 20 multiplies the basic injection period TAUb by the correction factor K. Then, in step S160, the electronic control unit 20 sets the multiplied value (=TAUb×K) as the value of the command injection period TAU.

[0019] After setting the command injection period TAU in step S140 or step S160, the electronic control unit 20 ends the processing of this routine for the current control cycle. Thereafter, the electronic control unit 20 commands the injector 16 to inject hydrogen gas for a period corresponding to the command injection period TAU.

[0020] <Actions and Effects of the Embodiment> The operation and effects of this embodiment will be described. During operation of the internal combustion engine 10, the cylinder head 12 is subjected to heat generated by the combustion of hydrogen gas in the combustion chamber 15. As a result, a temperature difference ΔT between the externally installed delivery pipe 17 and the cylinder head 12 may increase during operation of the internal combustion engine 10. As the temperature difference ΔT increases, the difference in the amount of thermal expansion between the cylinder head 12 and the delivery pipe 17 increases. Meanwhile, the injector 16 is installed in the internal combustion engine 10 with its nozzle-side end attached to the cylinder head 12 and its end opposite the nozzle-side connected to the delivery pipe 17. As a result, as the temperature difference ΔT increases, the thermal strain of the injector 16 increases. As the thermal strain increases, the sliding resistance of the sliding parts inside the injector 16 increases. As a result, the injection rate of hydrogen gas from the injector 16 decreases.

[0021] The injection rate is the amount of hydrogen gas injected by the injector 16 per unit time. As described above, the electronic control unit 20 calculates the injection period required to inject the required injection amount of hydrogen gas as the value of the basic injection period TAUb. The basic injection period TAUb is calculated on the assumption that no thermal strain occurs in the injector 16. Therefore, if the injection rate decreases due to thermal strain, the amount of hydrogen gas that can be injected during the basic injection period TAUb will fall short of the required injection amount.

[0022] In the case of an injector that injects liquid fuel, the sliding surfaces of the sliding parts are lubricated by the fuel. In contrast, in the case of an injector that injects gaseous fuel such as hydrogen gas, the sliding surfaces of the sliding parts are not lubricated by the fuel. Therefore, in an injector that injects gaseous fuel, the effect of thermal distortion on the injection rate is more likely to be greater than in an injector that injects liquid fuel.

[0023] Injectors mounted in the cylinder head include port-injection injectors that inject fuel into the intake port. Direct-injection injectors are mounted closer to the combustion chamber than port-injection injectors. Therefore, the temperature of the area around the injector in the cylinder head tends to be higher with direct-injection injectors than with port-injection injectors. Therefore, direct-injection injectors are more likely to experience thermal distortion than port-injection injectors.

[0024] In contrast, the injector 16 employed in this embodiment is configured to inject hydrogen gas, which is a gaseous fuel, into the cylinder 14. Therefore, in the injector 16, the change in injection rate due to thermal strain becomes large.

[0025] 3 shows the relationship between the temperature difference ΔT between the cylinder head 12 and the delivery pipe 17 and the injection rate of the injector 16. The injection rate of the injector 16 varies depending on the temperature and pressure of the hydrogen gas supplied from the delivery pipe 17. For simplicity of explanation, it is assumed here that the temperature and pressure of the hydrogen gas supplied from the delivery pipe 17 to the injector 16 are maintained constant.

[0026] The injector 16 is designed to operate as specified even if there are some variations in the shapes and dimensions of its components. Therefore, the injection characteristics of the injector 16 are maintained at rated characteristics until thermal distortion exceeds a certain level. Therefore, when the temperature difference ΔT is less than a certain value, the injection rate of the injector 16 is maintained approximately constant. On the other hand, when the temperature difference ΔT is in a range equal to or greater than a certain value, thermal distortion increases to the point where it affects the injection characteristics of the injector 16. Therefore, when the temperature difference ΔT is in a range equal to or greater than a certain value, the injection rate of the injector 16 gradually decreases as the temperature difference ΔT increases. In this embodiment, the upper limit of the temperature difference ΔT at which the rated injection rate can be maintained is set as the above-mentioned threshold value X.

[0027] FIG. 4 shows the relationship between the correction factor K calculated by the electronic control unit 20 in step S150 of FIG. 2 and the temperature difference ΔT. Note that step S150 is a process that is executed only when the temperature difference ΔT is equal to or greater than the threshold value X. When the temperature difference ΔT is equal to the threshold value X, the electronic control unit 20 calculates a value of "1" as the value of the correction factor K. Then, when the temperature difference ΔT gradually increases from a value equal to the threshold value X, the electronic control unit 20 calculates values ​​that gradually increase from "1" as the value of the correction factor K. Here, the injection rate of the injector 16 when the temperature difference ΔT is less than the threshold value X is defined as the rated injection rate. The ratio of the injection rate of the injector 16 at each temperature difference ΔT to the rated injection rate is defined as the rate of change C of the injection rate due to thermal strain. The electronic control unit 20 calculates a value that is the reciprocal of the rate of change C at each temperature difference ΔT as the value of the correction factor K at each temperature difference ΔT.

[0028] In the injection period calculation routine of FIG. 2, if the temperature difference ΔT is less than the threshold value X (S130: NO), the electronic control unit 20 sets the value of the basic injection period TAUb as the value of the command injection period TAU (S140). On the other hand, if the temperature difference ΔT is equal to or greater than the threshold value X (S130: YES), the electronic control unit 20 calculates a correction factor K based on the temperature difference ΔT (S150). The electronic control unit 20 then multiplies the basic injection period TAUb by the correction factor K and calculates the value as the command injection period TAU (S160). In step S150, the electronic control unit 20 calculates a value of the correction factor K that is greater than or equal to 1 when the temperature difference ΔT is large than when it is small. Thus, in the injection period calculation routine, the electronic control unit 20 executes injection period calculation processing to calculate a longer injection period when the temperature difference ΔT between the cylinder head 12 and the delivery pipe 17 is large than when the temperature difference ΔT is small. Therefore, deterioration in the accuracy of control of the fuel injection amount due to thermal distortion of the injector 16 caused by the difference in thermal expansion between the cylinder head 12 and the delivery pipe 17 can be suppressed.

[0029] In this embodiment, the injection period calculation process is a process for increasing the command injection period TAU when the temperature difference ΔT is equal to or greater than the threshold value X. Therefore, the injection period calculation process can increase the command injection period TAU in a manner that reflects the relationship between the temperature difference ΔT and the injection rate of the injector 16 as shown in FIG.

[0030] <Other embodiments> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0031] The temperature of the hydrogen gas in the delivery pipe 17 may be determined indirectly based on a detection signal of the internal pressure of the hydrogen tank 18 . 2, the temperature difference ΔT may be calculated directly based on the parameters used in the calculation of the head temperature Th and the pipe temperature Tp, rather than calculating them separately. Also, temperature sensors may be installed in the cylinder head 12 or the delivery pipe 17 to directly detect the head temperature Th and the pipe temperature Tp.

[0032] The fuel injection control of the above embodiment can also be applied to injectors that inject gaseous fuels other than hydrogen gas, such as CNG and LPG, and injectors that inject liquid fuels such as gasoline and diesel. Injectors that inject gaseous fuels other than hydrogen gas have sliding surfaces that are not lubricated by the fuel, so thermal distortion of the injector is likely to have a significant effect on the injection characteristics, similar to the injector 16 that injects hydrogen gas. On the other hand, injectors that inject liquid fuels have sliding surfaces that are lubricated by the fuel, but if thermal distortion exceeds a certain level, the injection characteristics will change. Therefore, the fuel injection control device of the above embodiment can achieve the same effect even when controlling an injector that injects gaseous fuels other than hydrogen gas or liquid fuels.

[0033] The fuel injection control of the above embodiment can also be applied to an internal combustion engine equipped with a port injection injector. Even in an internal combustion engine equipped with a port injection injector, the temperature difference between the cylinder head and the delivery pipe may be large, causing thermal distortion of the injector. Therefore, the fuel injection control device of the above embodiment can achieve the same effect even when a port injection injector is the control target. [Explanation of symbols]

[0034] 10...internal combustion engine, 11...cylinder block, 12...cylinder head, 12A...mounting hole, 13...piston, 14...cylinder, 15...combustion chamber, 16...injector, 17...delivery pipe, 18...hydrogen tank, 19...pressure regulator, 20...electronic control unit, 21...processor, 22...memory, 23...sensor

Claims

1. 1. A fuel injection control device that controls fuel injection of an injector attached to a cylinder head of an internal combustion engine and connected to a delivery pipe by calculating an injection period of the injector required to inject a required amount of fuel, comprising: The injector injects gaseous fuel, calculating a basic injection duration based on a requested fuel injection amount, a pressure of the gaseous fuel, and a temperature of the gaseous fuel; an injection period calculation process for calculating the basic injection period as the injection period when the temperature difference between the cylinder head and the delivery pipe is less than a predetermined threshold value, and calculating a value obtained by multiplying the basic injection period by one or more correction factors as the injection period when the temperature difference is equal to or greater than the threshold value; In the injection period calculation process, the correction factor is calculated as a value that gradually increases from 1 as the temperature difference gradually increases from a value equal to the threshold value. Fuel injection control device.

2. 2. The fuel injection control device according to claim 1, wherein the injector injects fuel into a cylinder.

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