Control device for internal combustion engines

Abstract

This can suppress the occurrence of water hammer within the cylinder. [Solution] The control device 90 of the internal combustion engine 1 controls the internal combustion engine 1, which includes a fuel pump 16 that pressurizes fuel and an injector 15 that supplies fuel into the cylinder 4 by injecting the fuel pressurized from the fuel pump 16. The control device 90 is configured to stop the operation of the fuel pump 16 when the degree of discrepancy between the output timing of a signal output from a knocking sensor 48, which is a sensor that detects the vibration state of the internal combustion engine 1, and the output timing of an injection command signal that drives the injector 15, is greater than a predetermined degree.

Description

Technical Field

[0006] ,

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

Background Art

[0002] Patent Document 1 discloses a control device for controlling an internal combustion engine including a fuel pump that pumps fuel and an injector that supplies the fuel pumped from the fuel pump into a cylinder by injection.

[0003] The injector is opened and closed based on an injection command signal output from the control device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When a mechanical or electrical defect occurs in the injector, fuel may be injected at a timing different from the normal timing. In this case, as a result of injecting more fuel than necessary into the cylinder of the internal combustion engine, there is a risk of causing a water hammer phenomenon.

Means for Solving the Problems

[0006] A control device for an internal combustion engine that solves the above problems is a control device for controlling an internal combustion engine comprising a fuel pump that pressurizes fuel and an injector that supplies the fuel pressurized from the fuel pump into the cylinder by injecting it, wherein the operation of the fuel pump is stopped when the degree of discrepancy between the output timing of a signal output from a sensor that detects the vibration state of the internal combustion engine and which fluctuates in accordance with the opening or closing of the injector, and the output timing of an injection command signal that drives the injector is greater than a predetermined degree.

[0007] According to this configuration, if the degree of deviation is greater than a predetermined degree, the fuel pump is stopped because it is highly likely that there is some kind of malfunction in the injector. This prevents the injector from injecting more fuel than necessary into the cylinder. [Effects of the Invention]

[0008] This internal combustion engine control system can suppress the occurrence of water hammer within the cylinder. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram of an internal combustion engine in one embodiment. [Figure 2] Figure 2 is a flowchart showing the steps of the process performed by the control device. [Figure 3] Figure 3 is a timing chart showing an example of the time progression of the outputs of (a) the injection command signal, (b) the knocking sensor signal, and (c) the fuel pressure sensor signal. [Modes for carrying out the invention]

[0010] Below, one embodiment of a control device for an internal combustion engine will be described with reference to Figures 1 to 3. <Configuration of an internal combustion engine> As shown in Figure 1, the cylinder block 2 of the internal combustion engine 1 is provided with cylinders 4. A piston 5 is provided inside each cylinder 4, and the piston 5 is connected to the crankshaft 7 via a connecting rod 6. Note that the cylinder block 2 is provided with multiple cylinders 4.

[0011] A cylinder head 3 is assembled to the top of the cylinder block 2. In cylinder 4, a combustion chamber 8 is formed between the top surface of the piston 5 and the cylinder head 3. The cylinder head 3 is also equipped with an injector 15 for directly injecting fuel from the internal combustion engine 1 into the cylinder 4, and a spark plug 11 for igniting the fuel-air mixture in the combustion chamber 8, for each cylinder 4 of the internal combustion engine 1.

[0012] Furthermore, the cylinder head 3 is provided with an intake port 9 and an exhaust port 10 connected to the combustion chamber 8. The intake port 9 constitutes part of the intake passage through which intake air flows. The intake port 9 is connected to an intake passage 20, which is equipped with a throttle valve 14 for adjusting the amount of intake air. The intake port 9 is also provided with an intake valve 12 for opening and closing the intake port 9.

[0013] The exhaust port 10 is provided with an exhaust valve 13 that opens and closes the exhaust port 10. The exhaust port 10 is connected to the exhaust passage 30. Furthermore, a fuel pump 16 is connected to the fuel line to which the injector 15 is connected, for pressurizing and supplying fuel to the same fuel line.

[0014] <Control device> The control device 90 includes a CPU 91, a memory 92 that stores control programs and data, and the like. The CPU 91 executes the programs stored in the memory 92 to perform various engine control functions.

[0015] The control device 90 is connected to various sensors for detecting the operating state of the internal combustion engine. Examples of the various sensors include a crank angle sensor 41 for detecting the rotation angle of the crankshaft 7, an air flow meter 44 for detecting the intake air amount GA, a water temperature sensor 45 for detecting the cooling water temperature TW which is the temperature of the cooling water of the internal combustion engine 1, a fuel pressure sensor 46 for detecting the fuel pressure PF which is the pressure of the fuel supplied to the injector 15, a knocking sensor 48 which is a vibration sensor that outputs an output signal S corresponding to the magnitude of the vibration of the cylinder 4, an accelerator sensor 49 for detecting the accelerator operation amount ACCP which is the operation amount of the accelerator pedal, and the like.

[0016] Based on the signals output from the above various sensors, the programs and data stored in the memory 92, and the calculation results, etc., the control device 90 executes ignition timing control for the ignition plug 11 and control of the fuel injection amount and injection timing by the valve opening control of the injector 15.

[0017] Specifically, the control device 90 outputs an injection command signal which is a signal for driving the injector 15 to the injector 15. When the injection command signal is turned ON, the injector 15 is driven to open the valve. Also, when the injection command signal is turned OFF, the injector 15 is driven to close the valve.

[0018] When the degree of deviation between the output timing of the signal output from the knocking sensor 48, which is a signal that varies with the opening or closing of the injector 15, and the output timing of the injection command signal for driving the injector 15 is greater than a predetermined degree, the control device 90 is configured to stop the operation of the fuel pump 16.

[0019] Next, referring to FIG. 2, the procedure of the process executed by the control device 90 will be described. This process is repeatedly executed at regular intervals during the operation of the internal combustion engine 1. As shown in FIG. 2, first, the control device 90 acquires the ON timing T1 of the injection command signal (step S10).

[0020] Next, the control device 90 determines whether or not the output S of the knocking sensor 48 is equal to or greater than the first threshold value S1 (step S11). When the control device 90 determines that the output S of the knocking sensor 48 is not equal to or greater than the first threshold value S1 (step S11: NO), it assumes that the injector 15 is not open and repeatedly executes the determination process of step S11.

[0021] On the other hand, when the control device 90 determines that the output S of the knocking sensor 48 is equal to or greater than the first threshold value S1 (step S11: YES), it assumes that the injector 15 is open. Next, it acquires the output timing t1 of the knocking sensor 48 (step S12).

[0022] Next, the control device 90 determines whether or not the difference t1 - T1 between the output timing t1 and the ON timing T1 is equal to or less than the threshold value ΔT (step S13). When the control device 90 determines that the difference t1 - T1 is not equal to or less than the threshold value (step S13: NO), it assumes that some abnormality has occurred in the injector 15, stops the operation of the fuel pump 16, and ends this series of processes (step S14).

[0023] On the other hand, when the control device 90 determines that the difference t1 - T1 is equal to or less than the threshold value (step S13: YES), next, it acquires the OFF timing T2 of the injection command signal (step S15).

[0024] Next, the control device 90 determines whether or not the output S of the knocking sensor 48 is equal to or greater than the second threshold value S2 (step S16). When the control device 90 determines that the output S of the knocking sensor 48 is not equal to or greater than the second threshold value S2 (step S16: NO), it assumes that the injector 15 is not closed and repeatedly executes the determination process of step S16.

[0025] On the other hand, when the control device 90 determines that the output S of the knocking sensor 48 is equal to or greater than the second threshold value S2 (step S16: YES), it assumes that the injector 15 is closed. Next, it acquires the output timing t2 of the knocking sensor 48 (step S17).

[0026] Next, the control device 90 determines whether the difference t2-T2 between the output timing t2 and the OFF timing T2 is less than or equal to the threshold ΔT (step S18). If the control device 90 determines that the difference t2-T2 is not less than or equal to the threshold ΔT (step S18: NO), it determines that some kind of abnormality has occurred in the injector 15, stops the operation of the fuel pump 16, and terminates this series of processes (step S14).

[0027] On the other hand, if the control device 90 determines that the above difference t2-T2 is less than or equal to the threshold ΔT (step S18: YES), it determines that there is no abnormality in the injector 15 and continues to operate the fuel pump 16 (step S19), thus ending this series of processes.

[0028] <Operation and Effects of This Embodiment> Next, with reference to Figure 3, an example of the time progression of (a) the injection command signal and (b) the knocking sensor signal will be described, along with an explanation of the operation and effects of this embodiment.

[0029] When fuel is injected by the injector 15, the fuel pressure in the injector 15 and the fuel piping connected to the injector 15 fluctuates, causing the internal combustion engine 1, or more specifically, the cylinder 4 in which the injector 15 is installed, to vibrate.

[0030] When the injector 15 is functioning normally, as shown in Figure 3(a), when the control device 90 outputs an injection command signal (ON) to drive the injector 15 to open at timing T1, the injector 15 is driven to open immediately thereafter. Therefore, as shown by the solid line in Figure 3(b), the difference t1-T1 between the output timing T1 of the injection command signal (ON) and the output timing t1 of the signal output from the knocking sensor 48, which fluctuates with the opening of the injector 15, is small.

[0031] Furthermore, as shown in Figure 3(a), when the control device 90 outputs an injection command signal (OFF) that drives the injector 15 to close at timing T2, the injector 15 is driven to close immediately thereafter. For this reason, as shown by the solid line in Figure 3(b), the difference t2-T2 between the output timing T2 of the injection command signal (OFF) and the output timing t2 of the signal output from the knocking sensor 48, which fluctuates in conjunction with the closing of the injector 15, is small.

[0032] On the other hand, if a mechanical or electrical malfunction occurs in the injector 15, it takes more time than usual from the time the injection command signal is output from the control device 90 until the injector 15 is driven. As a result, as shown by the dashed line in Figure 3(b), the difference t1-T1 between the output timing T1 of the injection command signal (ON) and the output timing t1 of the signal output from the knocking sensor 48, which fluctuates with the opening of the injector 15, becomes larger than under normal conditions.

[0033] Furthermore, as shown by the dashed line in Figure 3(b), the difference t2-T2 between the output timing T2 of the injection command signal (OFF) and the output timing t2 of the signal output from the knocking sensor 48, which fluctuates with the closing of the injector 15, becomes larger than under normal conditions.

[0034] According to this embodiment, when the difference t1-T1 is greater than a predetermined threshold ΔT, and the difference t2-T2 is also greater than a predetermined threshold ΔT, the operation of the fuel pump 16 is stopped. This prevents the injection of more fuel than necessary into the cylinder 4 from the injector 15. Therefore, the occurrence of water hammer in the cylinder 4 can be suppressed.

[0035] <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0036] The internal combustion engine 1 is not limited to one equipped with an injector 15 that directly injects fuel into the cylinder 4, but may also be equipped with an injector that injects fuel into the intake port 9 instead of, or in addition to, the injector 15.

[0037] The sensor used to detect the vibration state of the internal combustion engine 1 is not limited to the knocking sensor 48; other sensors, such as a fuel pressure sensor 46, can also be used. If a mechanical or electrical malfunction occurs in the injector 15, it will take longer than normal time from the time the injection command signal is output from the control device 90 until the injector 15 is driven. As a result, as shown by the dashed line in Figure 3(c), the difference t1-T1 between the output timing T1 of the injection command signal (ON) and the output timing t1 of the signal output from the fuel pressure sensor 46, which fluctuates with the opening of the injector 15, becomes larger than under normal conditions.

[0038] Furthermore, as shown by the dashed line in Figure 3(c), the difference t2-T2 between the output timing T2 of the injection command signal (OFF) and the output timing t2 of the signal output from the fuel pressure sensor 46, which fluctuates with the closing of the injector 15, becomes larger than under normal conditions.

[0039] Therefore, similar to the above embodiment, if the difference t1-T1 is greater than a predetermined threshold ΔT, and the difference t2-T2 is also greater than a predetermined threshold ΔT, it is highly likely that there is some kind of malfunction in the injector 15, and the operation of the fuel pump 16 should be stopped.

[0040] In the above embodiment and its modifications, the operation of the fuel pump 16 is stopped when both the difference t1-T1 and the difference t2-T2 are greater than the threshold ΔT. Alternatively, the operation of the fuel pump 16 may be stopped when either t1-T1 or the difference t2-T2 is greater than the threshold ΔT. [Explanation of symbols]

[0041] 1...Internal combustion engine 4...Cylinder 15...Injector 16...Fuel pump 48...Knocking sensor 90...Control unit

Claims

[Claim 1] A control device for controlling an internal combustion engine comprising a fuel pump for pressurizing fuel and an injector for supplying the fuel pressurized from the fuel pump into a cylinder by injecting it, The system is configured to stop the operation of the fuel pump when the degree of discrepancy between the output timing of the signal, which fluctuates in conjunction with the opening or closing of the injector, and the output timing of the injection command signal that drives the injector, is greater than a predetermined degree. Control device for internal combustion engines.

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