Control device for internal combustion engine

Abstract

To provide a control device for an internal combustion engine capable of suppressing a wrong determination of opening fixation caused by execution of fuel cut processing for temporarily stopping fuel injection during an operation of the internal combustion engine.SOLUTION: A control device is a control device for an internal combustion engine mounted on a vehicle. The internal combustion engine includes a fuel tank, a fuel injection valve, a fuel passage, a shutoff valve disposed in the fuel passage, and a pressure sensor for detecting passage fuel pressure that is fuel pressure at a portion between the shutoff valve and the fuel injection valve in the fuel passage. The control device outputs a valve closing signal to the shutoff valve and executes determination processing for determining opening fixation of the shutoff valve on the basis of a reduction amount of the passage fuel pressure generated until a lapse period after the valve closing signal is output reaches a predetermined specified period. In the control device, the lapse period does not include a period of execution of fuel cut processing for stopping fuel injection by using the fuel injection valve during an operation of the internal combustion engine (S200 to S230).SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Patent Document 1 discloses an internal combustion engine that uses gaseous fuel. A shutoff valve is arranged in a fuel passage of the internal combustion engine. When the internal combustion engine is stopped, the shutoff valve closes, thereby stopping the supply of fuel from the fuel tank to the fuel injection valve. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-041106 Summary of the Invention [Problem to be solved by the invention]

[0004] One method for determining whether a shutoff valve is stuck open is to determine from a change in the fuel pressure in the fuel passage between the shutoff valve and the fuel injection valve (hereinafter referred to as "passage fuel pressure") after a valve close command is output to the shutoff valve during fuel injection. If the shutoff valve is closed, the fuel in the fuel passage decreases as fuel injection is performed, and the passage fuel pressure drops. If the shutoff valve is stuck open, fuel continues to be supplied from the fuel tank to the fuel injection valve, so the passage fuel pressure is unlikely to drop even when fuel injection is performed. Therefore, it can be determined that the shutoff valve is stuck open based on a small drop in the passage fuel pressure.

[0005] However, a fuel cut process may be executed to temporarily stop fuel injection during operation of the internal combustion engine. During the fuel cut process, the passage fuel pressure does not decrease due to fuel injection. Therefore, if the above-described stuck open valve determination is executed during the fuel cut process, there is a risk of erroneously determining that the valve is stuck open. [Means for solving the problem]

[0006] A control device for an internal combustion engine that solves the above problem is a control device for an internal combustion engine mounted on a vehicle. The internal combustion engine includes a fuel tank that stores gaseous fuel, a fuel injection valve that supplies the fuel into a cylinder, a fuel passage connecting the fuel tank and the fuel injection valve, a shutoff valve disposed in the fuel passage, and a pressure sensor disposed in a portion of the fuel passage between the shutoff valve and the fuel injection valve to detect a passage fuel pressure, which is the pressure of the fuel in that portion. The control device outputs a valve closing signal to the shutoff valve, and executes a determination process to determine whether the shutoff valve is stuck open based on an amount of decrease in the passage fuel pressure that occurs during a predetermined period of time that has elapsed since the output of the valve closing signal. The control device excludes, within the elapsed period, a period during which a fuel cut process is executed to stop fuel injection by the fuel injection valve while the internal combustion engine is operating. [Effects of the Invention]

[0007] The control device for an internal combustion engine described above can suppress erroneous determination of a stuck-open valve caused by the execution of a fuel cut process that temporarily stops fuel injection while the internal combustion engine is in operation. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an internal combustion engine and a control device for the internal combustion engine according to an embodiment. [Figure 2] FIG. 2 is a flowchart illustrating a procedure of a determination process executed by the control device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Embodiment> An embodiment of a control device for an internal combustion engine will be described below with reference to FIGS. <Configuration of Internal Combustion Engine and Control Device for Internal Combustion Engine> 1 is mounted on a vehicle. The fuel for the internal combustion engine 10 is gaseous fuel. An example of the gaseous fuel is hydrogen gas.

[0010] The internal combustion engine 10 includes an engine body 11. The engine body 11 generates power for propelling a vehicle by combusting fuel injected from fuel injection valves 13 inside each cylinder. In Fig. 1, illustrations of cylinders, spark plugs, etc. are omitted.

[0011] The internal combustion engine 10 includes a fuel tank 12, a fuel injection valve 13, a fuel passage 14, a shutoff valve 15, and a pressure sensor 16. The fuel tank 12 stores gaseous fuel. The gaseous fuel is stored in the fuel tank 12 in a compressed state. The gaseous fuel is supplied from the fuel tank 12 to the fuel injection valve 13. The fuel injection valve 13 supplies fuel into a cylinder.

[0012] Fuel passage 14 connects fuel tank 12 and fuel injection valve 13. Fuel passage 14 is composed of fuel piping 17 connected to fuel tank 12 and delivery pipe 18 connecting fuel piping 17 and fuel injection valve 13. Fuel stored in fuel tank 12 is supplied to fuel injection valve 13 via fuel piping 17 and delivery pipe 18.

[0013] The shutoff valve 15 is disposed in the fuel passage 14. The shutoff valve 15 is, for example, a solenoid valve. The shutoff valve 15 is switched between an open state and a closed state by the control device 100. The shutoff valve 15 enters an open state when it receives a valve open command from the control device 100. The shutoff valve 15 enters a closed state when it receives a valve close command from the control device 100. Specifically, when the control device 100 inputs a valve open command to a drive circuit of the shutoff valve 15, the drive circuit supplies power to the shutoff valve 15. As a result, the shutoff valve 15 enters an open state. When the control device 100 inputs a valve close command to a drive circuit of the shutoff valve 15, the drive circuit stops supplying power to the shutoff valve 15. As a result, the shutoff valve 15 enters a closed state. The shutoff valve 15 is maintained in an open state while the internal combustion engine 10 is operating. The shutoff valve 15 is maintained in a closed state while the internal combustion engine 10 is stopped. The shutoff valve 15 includes a first shutoff valve 19 and a second shutoff valve 20 .

[0014] The first shutoff valve 19 is disposed in the fuel passage 14 near the outlet of the fuel tank 12. The first shutoff valve 19 is disposed at the end of the fuel pipe 17 on the fuel tank 12 side. When the first shutoff valve 19 is in an open state, fuel is supplied from the fuel tank 12 to the fuel pipe 17. When the first shutoff valve 19 is in a closed state, fuel supply from the fuel tank 12 to the fuel pipe 17 is stopped.

[0015] The second shutoff valve 20 is disposed downstream of the first shutoff valve 19 in the fuel passage 14. The second shutoff valve 20 is disposed near the delivery pipe 18. The second shutoff valve 20 is disposed between the fuel pipe 17 and the delivery pipe 18. When the second shutoff valve 20 is in an open state, fuel is supplied from the fuel pipe 17 to the delivery pipe 18. When the second shutoff valve 20 is in a closed state, fuel supply from the fuel pipe 17 to the delivery pipe 18 is stopped.

[0016] A pressure reducing valve 21 is disposed in the fuel passage 14 between the first shutoff valve 19 and the second shutoff valve 20. The pressure reducing valve 21 adjusts the pressure of the fuel flowing into the delivery pipe 18 from the high-pressure fuel tank 12.

[0017] The pressure sensor 16 is disposed in a portion of the fuel passage 14 between the shutoff valve 15 and the fuel injection valve 13. The pressure sensor 16 detects the passage fuel pressure, which is the pressure of the fuel in the portion between the shutoff valve 15 and the fuel injection valve 13. The pressure sensor 16 outputs a detection signal relating to the detected passage fuel pressure to the control device 100.

[0018] The pressure sensor 16 includes a first pressure sensor 23 and a second pressure sensor 24. The first pressure sensor 23 is disposed in the fuel passage 14 between the first shutoff valve 19 and the fuel injection valve 13. The first pressure sensor 23 is disposed in the fuel passage 14 between the first shutoff valve 19 and the second shutoff valve 20. The first pressure sensor 23 detects a first passage fuel pressure that indicates the passage fuel pressure between the first shutoff valve 19 and the fuel injection valve 13. The second pressure sensor 24 is disposed between the second shutoff valve 20 and the fuel injection valve 13. The second pressure sensor 24 detects a second passage fuel pressure that indicates the passage fuel pressure between the second shutoff valve 20 and the fuel injection valve 13.

[0019] The internal combustion engine 10 is equipped with a temperature sensor 25. The temperature sensor 25 is disposed in a portion of the fuel passage 14 between the shutoff valve 15 and the fuel injection valve 13. The temperature sensor 25 detects the passage fuel temperature, which is the temperature of the fuel in the portion between the shutoff valve 15 and the fuel injection valve 13. The temperature sensor 25 outputs a detection signal related to the detected passage fuel temperature to the control device 100.

[0020] The temperature sensors 25 include a first temperature sensor 26 and a second temperature sensor 27. The first temperature sensor 26 is disposed between the first shutoff valve 19 and the fuel injector 13. The first temperature sensor 26 is disposed between the first shutoff valve 19 and the second shutoff valve 20. The second temperature sensor 27 is disposed between the second shutoff valve 20 and the fuel injector 13.

[0021] The control device 100 performs various controls of the internal combustion engine 10 by controlling various control objects such as the fuel injection valve 13, the first shutoff valve 19, the second shutoff valve 20, and the pressure reducing valve 21. For example, the control device 100 drives the shutoff valve 15 to open by sending a valve open signal to the shutoff valve 15, and drives the shutoff valve 15 to close by sending a valve close signal to the shutoff valve 15.

[0022] The control device 100 includes a CPU 110 and a memory 120 configured from a ROM, a RAM, etc. The CPU 110 executes a program stored in the memory 120, whereby the control device 100 performs various controls.

[0023] The control device 100 acquires various values ​​necessary for controlling the internal combustion engine 10. For example, the control device 100 acquires detection signals from the pressure sensor 16 and the temperature sensor 25. The control device 100 also acquires detection signals from various other sensors, such as an accelerator opening sensor 200, a vehicle speed sensor 300, and an ignition sensor 400. The accelerator opening sensor 200 detects the accelerator opening, which is the amount of operation of the accelerator pedal operated by the user of the vehicle equipped with the internal combustion engine 10. The vehicle speed sensor 300 detects the vehicle speed of the vehicle equipped with the internal combustion engine 10. The control device 100 acquires detection signals from the internal combustion engine 10 for calculating the engine rotation speed of the internal combustion engine 10, a detection signal of the intake air amount, and the like.

[0024] <About the judgment process> The control device 100 outputs a valve closing signal to the shutoff valve 15 and determines whether the shutoff valve 15 is stuck open based on the amount of decrease in passage fuel pressure that occurs during the period from when the valve closing signal was output until a predetermined period has elapsed. During the determination process, the fuel injection valve 13 performs fuel injection. During the determination process, fuel is continuously supplied into the cylinder from the fuel injection valve 13. The control device 100 stores in the memory 120 a determination result indicating that the shutoff valve 15 is stuck open if the amount of decrease in passage fuel pressure that occurs during the period from when the valve closing signal was output until the predetermined period has elapsed is smaller than a predetermined threshold. The predetermined threshold is set, for example, based on the amount of fuel consumed during idling of the internal combustion engine 10. The amount of fuel consumed during idling of the internal combustion engine 10 is calculated based on the number of fuel injections performed during idling, the injection time, and the passage fuel temperature.

[0025] The control device 100 may set the predetermined threshold value according to the passage fuel pressure, the passage fuel temperature, etc. at the start of the determination process. The control device 100 sets a larger predetermined threshold value as the passage fuel temperature at the start of the determination process is higher.

[0026] The determination process includes a first determination process for determining whether the first shutoff valve 19 is stuck open, and a second determination process for determining whether the second shutoff valve 20 is stuck open. The first determination process will now be described. During the execution of the first determination process, the second shutoff valve 20 is in an open state.

[0027] When the first shutoff valve 19 is in a closed state, the supply of fuel from the fuel tank 12 to the fuel passage 14 is stopped. Fuel is supplied from the fuel injection valve 13 into the cylinder when the fuel is injected from the fuel injection valve 13, but the supply of fuel from the fuel tank 12 to the fuel passage 14 is stopped, so the first passage fuel pressure drops. On the other hand, when the first shutoff valve 19 is stuck open, fuel continues to be supplied from the fuel tank 12 to the fuel passage 14, so the first passage fuel pressure does not drop, or the amount of drop in the first passage fuel pressure is smaller than when the first shutoff valve 19 is in a closed state. For this reason, it can be determined that the first shutoff valve 19 is stuck open based on the amount of drop in the first passage fuel pressure.

[0028] The second determination process will now be described. During the execution of the second determination process, the first shutoff valve 19 is preferably in a closed state. When second shutoff valve 20 is in the closed state, fuel supply from fuel pipe 17 to delivery pipe 18 is stopped. Fuel is supplied into the cylinders from fuel injection valve 13 when fuel is injected from fuel injection valve 13, but the second passage fuel pressure drops because the fuel supply from fuel pipe 17 to delivery pipe 18 is stopped. On the other hand, when second shutoff valve 20 is stuck open, fuel continues to be supplied from fuel pipe 17 to delivery pipe 18, so the second passage fuel pressure does not drop, or the drop in the second passage fuel pressure is smaller than when second shutoff valve 20 is in the closed state. Therefore, it can be determined that second shutoff valve 20 is stuck open based on the drop in the second passage fuel pressure.

[0029] The control device 100 executes a determination process when a stop operation of the internal combustion engine 10 is performed. The stop operation of the internal combustion engine 10 is, for example, when a user of the vehicle turns off the ignition switch. When a stop operation of the internal combustion engine 10 is performed, the control device 100 starts the determination process and continues operating the internal combustion engine 10 until the determination process ends. When a stop operation of the internal combustion engine 10 is performed, the control device 100 executes the determination process and then stops the internal combustion engine 10.

[0030] <Determination process during fuel cut processing> The control device 100 executes a fuel cut process to stop fuel injection by the fuel injection valve 13 while the internal combustion engine 10 is operating. The fuel cut process is executed when the accelerator pedal is not depressed and the engine speed of the internal combustion engine 10 is equal to or greater than a predetermined value while the internal combustion engine 10 is operating. The fuel cut process ends when the accelerator pedal is depressed or when the engine speed of the internal combustion engine 10 falls below a predetermined value. By executing such a fuel cut process, the fuel efficiency of the internal combustion engine 10 can be improved.

[0031] During the fuel cut process, fuel injection by the fuel injection valve 13 is stopped, and therefore no drop in the passage fuel pressure due to fuel injection occurs. Therefore, if the determination process is executed while the fuel cut process is being executed, the passage fuel pressure does not drop even if the shutoff valve 15 is not stuck open. Therefore, if the determination process is executed while the fuel cut process is being executed, there is a risk of erroneously determining that the shutoff valve 15 is stuck open even though the shutoff valve 15 is not stuck open.

[0032] In the determination process, the control device 100 does not refer to changes in passage fuel pressure that occur while the fuel cut process is being executed. Specifically, the control device 100 does not include the period during which the fuel cut process is being executed in the elapsed period after the valve close signal is output in the determination process. If the fuel cut process is being executed while the determination process is being executed, the control device 100 starts measuring the elapsed period from the end of the fuel cut process. If the determination process is started while the fuel cut process is being executed, the control device 100 starts measuring the elapsed period from the end of the fuel cut process.

[0033] <Determination process flow> FIG. 2 shows a series of processing flows related to the determination processing executed by the control device 100. The control device 100 repeatedly executes the processing of FIG. 2. Both the first determination processing and the second determination processing are executed according to the processing procedure shown in FIG. 2. Below, the processing procedure when the first determination processing is executed as the determination processing according to the processing procedure shown in FIG. 2 will be described. In the following processing, the shutoff valve 15 is the first shutoff valve 19.

[0034] The control device 100 determines whether or not a stop operation of the internal combustion engine 10 has been performed (S100). If a stop operation of the internal combustion engine 10 has been performed (S100: YES), the control device 100 outputs a valve close command to the shutoff valve 15, acquires the passage fuel pressure (S110), and proceeds to the processing of S200. If a stop operation of the internal combustion engine 10 has not been performed (S100: NO), the control device 100 ends the processing of FIG. 2.

[0035] The control device 100 determines whether or not a fuel cut process is being executed in the internal combustion engine 10 (S200). If a fuel cut process is being executed in the internal combustion engine 10 (S200: YES), the control device 100 clears a counter (S210) and proceeds to the processing of S230. If a fuel cut process is not being executed in the internal combustion engine 10 (S200: NO), the control device 100 counts up the counter (S220) and proceeds to the processing of S230. The counter is a counter that measures the elapsed time after the valve close signal was output in S110. The counter is stored in the memory 120 of the control device 100 in an updatable manner.

[0036] The control device 100 determines whether the counter is equal to or greater than a predetermined value (S230). The predetermined value of the counter is set to a period corresponding to a specified period. If the counter is equal to or greater than the predetermined value (S230: YES), the control device 100 proceeds to the processing of S300. If the counter is not equal to or greater than the predetermined value (S230: NO), the control device 100 repeats the series of processing from S200.

[0037] The control device 100 acquires the passage fuel pressure (S300) and determines whether the amount of decrease in the passage fuel pressure is equal to or greater than a predetermined threshold (S310). The amount of decrease in the passage fuel pressure is the difference between the passage fuel pressure acquired in S110 and the passage fuel pressure acquired in S300. If the amount of decrease in the passage fuel pressure is equal to or greater than the predetermined threshold (S310: YES), the control device 100 stores in the memory 120 a determination result indicating that the shutoff valve 15 is normal and not stuck open (S320), and ends the processing of FIG. 2. If the amount of decrease in the passage fuel pressure is not equal to or greater than the predetermined threshold (S310: NO), the control device 100 stores in the memory 120 a determination result indicating that the shutoff valve 15 is abnormal and stuck open (S330), and ends the processing of FIG. 2. The control device 100 may output the determination result of whether the shutoff valve 15 is stuck open to a vehicle user or the like.

[0038] After the first determination process is executed as part of the series of processes in Fig. 2, the second determination process is executed in the same procedure as the series of processes in Fig. 2. When the second determination process is executed following the first determination process, the process of S100 is omitted from the series of processes in Fig. 2 in the second determination process.

[0039] <Actions and Effects of This Embodiment> (1) In the determination process, the control device 100 does not include the period during which the fuel cut process is being executed when measuring the elapsed period after the valve close signal is output to the shutoff valve 15. This makes it possible to suppress erroneous determination of a stuck-open valve due to the execution of the fuel cut process.

[0040] (2) As an example, racing may be performed for scavenging when the internal combustion engine 10 is stopped. If racing is performed immediately before or after the internal combustion engine 10 is stopped, a fuel cut process may be performed while the determination process is being executed. When the internal combustion engine 10 is stopped, the control device 100 executes the determination process while continuing to operate the internal combustion engine 10. Therefore, even if the determination process is started due to the internal combustion engine 10 being stopped while the fuel cut process is being executed, an erroneous determination is unlikely to occur in the determination process.

[0041] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0042] The internal combustion engine 10 may be configured to have only one of the first shutoff valve 19 and the second shutoff valve 20 as the shutoff valve. When the control device 100 executes the determination process, only one of the first determination process and the second determination process may be executed as the determination process.

[0043] The determination process may be executed in a case other than when an operation to stop the internal combustion engine is performed. For example, the determination process may be executed while the vehicle is stopped. The fuel cut process of the internal combustion engine 10 may be executed by a control device other than the control device 100. In this case, the control device 100 is configured to receive a signal indicating that the fuel cut process is being executed from the other control device.

[0044] If a fuel cut process is started while the determination process is being executed, the control device 100 may start measuring the elapsed period from the end of the fuel cut process. For example, if a fuel cut process is started while the determination process is being executed, the control device 100 clears the measurement result of the elapsed period up to that point and starts measuring the elapsed period anew from the end of the fuel cut process. In the determination process of this modified example, the decrease amount of the passage fuel pressure may be the decrease amount from the time when the internal combustion engine 10 is stopped, or may be the decrease amount from when measurement of the elapsed period is started anew from the end of the fuel cut process. In the latter case, for example, in S210 of FIG. 2, the counter may be cleared and the passage fuel pressure may be acquired.

[0045] When a fuel cut process is initiated during execution of the determination process, the control device 100 may temporarily suspend measurement of the elapsed period and resume measurement of the elapsed period when the fuel cut process ends.

[0046] 2 illustrates a method for measuring the elapsed time using a counter, but any method other than a counter may be used as long as it can measure the elapsed time. For example, instead of a counter, the control device 100 may have a timer function for measuring the elapsed time. [Explanation of symbols]

[0047] 10...Internal combustion engine 11...Engine body 12...Fuel tank 13...Fuel injection valve 14…Fuel passage 15...Shut-off valve 16...Pressure sensor 17…Fuel piping 18...Delivery pipe 19...First shutoff valve 20...Second shutoff valve 21...Reducing valve 23...First pressure sensor 24...Second pressure sensor 25...Temperature sensor 26...First temperature sensor 27...Second temperature sensor 100...Control device 110...CPU 120...Memory 200...Accelerator opening sensor 300...Vehicle speed sensor 400...Ignition sensor

Claims

1. A control device for an internal combustion engine mounted on a vehicle, The internal combustion engine includes: a fuel tank for storing gaseous fuel; a fuel injection valve that supplies the fuel into a cylinder; a fuel passage connecting the fuel tank and the fuel injection valve; a shutoff valve disposed in the fuel passage; a pressure sensor disposed in a portion of the fuel passage between the shutoff valve and the fuel injection valve, for detecting a passage fuel pressure that is the pressure of the fuel in that portion, The control device outputting a valve close signal to the shutoff valve, and executing a determination process to determine whether the shutoff valve is stuck open based on an amount of decrease in the passage fuel pressure that occurs during a period of time that has elapsed since the output of the valve close signal until the time when the valve close signal reaches a predetermined specified period; The elapsed period does not include a period during which a fuel cut process is being executed to stop fuel injection by the fuel injection valve while the internal combustion engine is in operation. Control device for internal combustion engines.

2. When the determination process is started while the fuel cut process is being executed, the control device starts measuring the elapsed period from the end of the fuel cut process. The control device for an internal combustion engine according to claim 1.

3. When the fuel cut process is started during the execution of the determination process, the control device starts measuring the elapsed period from the end of the fuel cut process. The control device for an internal combustion engine according to claim 1.

4. The control device starts the determination process when a stop operation of the internal combustion engine is performed, and continues operation of the internal combustion engine until the determination process is completed. The control device for an internal combustion engine according to any one of claims 1 to 3.

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