Control device for internal combustion engine

Abstract

To enable a diagnosis of leakage of blow-by gas including leakage of blow-by gas from a body of an internal combustion engine.SOLUTION: Blow-by gas flowing into a crank case 12c recirculates to an intake passage 22 upstream of a compressor 34 via a communication passage 60, an internal space of a head cover 19 and an oil separator 62. Internal pressure Pc of the crank case 12c is detected by a pressure sensor 250 provided in an oil level gauge guide 100. A memory 202 of a control device 200 stores a reference value Ps of the internal pressure corresponding to an operating state of an engine 1. The control device 200 diagnoses leakage of the blow-by gas by comparing the internal pressure Pc detected by the pressure sensor 250 with the reference value Ps.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In an internal combustion engine, blow-by gas (an unburned mixture containing combustion gas) passes through the gap between the piston and the cylinder and flows from the combustion chamber into the crankcase. A blow-by gas recirculation device (also called a PCV (Positive Crankcase Ventilation) system) recirculates (returns) the blow-by gas that has flowed into the crankcase to the intake passage. In Japanese Patent Laid-Open Publication No. 10-184336 (Patent Document 1), a pressure sensor is provided in a blow-by gas passage that returns the blow-by gas introduced into the head cover to the intake passage, and an abnormality in the blow-by gas passage is determined based on the blow-by gas pressure value, which is the pressure in the blow-by gas passage that connects the inside of the head cover with the intake passage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-184336 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, an abnormality (leak or blockage) in the blow-by gas passage that connects the inside of the head cover to the intake passage is determined based on the pressure in the blow-by gas passage. Therefore, when blow-by gas leaks from the main body of the internal combustion engine (for example, the seal between the head cover and the cylinder head), the pressure change in the blow-by gas passage is small, making it difficult to determine whether or not there is a blow-by gas leak.

[0005] An object of the present disclosure is to make it possible to diagnose blow-by gas leaks, including blow-by gas leaks from the body of an internal combustion engine. [Means for solving the problem]

[0006] The present disclosure relates to a control device for an internal combustion engine having a blow-by gas passage that recirculates blow-by gas in a crankcase to an intake passage. The internal combustion engine has a pressure sensor that detects the internal pressure of the crankcase. The control device includes a memory unit that stores a reference value of the internal pressure corresponding to the operating state of the internal combustion engine, and a diagnosis unit that compares the internal pressure detected by the pressure sensor with the reference value and diagnoses a blow-by gas leak.

[0007] According to this configuration, the pressure sensor detects the internal pressure of the crankcase. The memory unit of the control device stores a reference value for the internal pressure corresponding to the operating state of the internal combustion engine. The reference value is the value of the internal pressure of the crankcase when no blow-by gas leakage occurs. The diagnosis unit compares the internal pressure detected by the pressure sensor with the reference value to diagnose blow-by gas leakage. When no blow-by gas leakage occurs, the internal pressure detected by the pressure sensor and the reference value are nearly identical. When blow-by gas leakage occurs, the internal pressure detected by the pressure sensor deviates from the reference value, so it is possible to diagnose blow-by gas leakage from the main body of the internal combustion engine as well.

[0008] Preferably, the internal combustion engine includes an oil level gauge guide into which an oil level gauge for checking the oil level of the engine oil is inserted. The pressure sensor may be provided in the oil level gauge guide.

[0009] The oil level gauge guide guides the oil level gauge inserted into the oil level gauge guide so that it reaches the engine oil level. The oil level gauge guide opens inside the crankcase, and the internal pressure of the crankcase can be detected by a pressure sensor provided in the oil level gauge guide. With this configuration, the pressure sensor is provided in the oil level gauge guide, so the pressure sensor can be installed relatively easily without changing the configuration of the internal combustion engine body. In addition, the space near the oil level gauge guide can be effectively used as installation space for the pressure sensor.

[0010] Preferably, the internal combustion engine includes a head cover. The blow-by gas passage may be connected to the intake passage via a space in the head cover, and the pressure sensor may be provided in the head cover.

[0011] With this configuration, blow-by gas flows back into the intake passage via the space inside the head cover, so the pressure inside the head cover is approximately equal to the internal pressure of the crankcase.The internal pressure of the crankcase can be detected by a pressure sensor installed in the head cover, making it possible to utilize the space around the head cover.

[0012] Preferably, the diagnosing unit may diagnose that a blow-by gas leak has occurred when the internal pressure detected by the pressure sensor is lower than a reference value by a predetermined value or more.

[0013] If blow-by gas is leaking from any location, including the internal combustion engine body, the crankcase internal pressure will be lower than a reference value. If the detected internal pressure is lower than the reference value by a predetermined value or more, it is diagnosed as a blow-by leakage, thereby reducing the possibility of a misdiagnosis.

[0014] Preferably, the internal combustion engine may further include a supercharger, wherein the blow-by gas passage is connected to an intake passage upstream of a compressor of the supercharger.

[0015] In an internal combustion engine equipped with a turbocharger, the intake air upstream of the compressor is at approximately atmospheric pressure and has a stable pressure. According to this configuration, the blow-by gas passage is connected to the intake air passage upstream of the compressor, so the reference value corresponding to the operating state of the internal combustion engine and the internal pressure detected by the pressure sensor are highly robust, and blow-by gas leakage can be effectively diagnosed. [Effects of the Invention]

[0016] According to the present disclosure, it is possible to diagnose blow-by gas leakage, including leakage of blow-by gas from the main body of an internal combustion engine. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram showing a schematic configuration of an engine according to an embodiment of the present invention; [Figure 2] 4 is a flowchart of a leakage diagnosis process executed by the control device. [Figure 3] 10 is a reference value Pa map stored (memorized) in the memory of the control device. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, the same or corresponding parts in the drawings will be denoted by the same reference numerals, and description thereof may not be repeated.

[0019] FIG. 1 is a diagram showing a schematic configuration of an engine 1 according to this embodiment. In FIG. 1, the engine 1 is a compression autoignition internal combustion engine (diesel engine) and corresponds to the "internal combustion engine" of the present disclosure. The engine 1 may be mounted on a vehicle and serve as a drive source for the vehicle. The engine 1 may also be used as a drive source for a hydraulic pump of an industrial vehicle such as a forklift, and as a drive source for traveling. The engine 1 includes an engine body 10, an air cleaner 20, an intake passage 22, an intercooler 26, a turbocharger 30, an exhaust passage 52, and a control device 200.

[0020] The engine body 10 includes a cylinder head 11, a cylinder block 12, a piston 13, and a head cover 19. The piston 13 is reciprocally mounted in a cylinder formed in the cylinder block 12. A combustion chamber 14 is formed by the space surrounded by the top of the piston 13, the cylinder head 11, and the cylinder, and a fuel injection valve (injector) 15 is mounted in the cylinder head 11 so as to face the combustion chamber 14. In this embodiment, the engine 1 has four cylinders, and FIG. 1 shows one cylinder. The number of cylinders is not limited to four, and may be three, six, or the like.

[0021] The reciprocating motion of the pistons 13 is converted into rotational motion by connecting rods 16 and crankshaft 17. A crankcase 12c that houses the crankshaft 17 is formed below the cylinder block 12. In this embodiment, the crankcase 12c is formed integrally with the cylinder block 12, but a separate crankcase may be attached to the cylinder block 12. An oil pan 18 is fastened to the crankcase 12c, and engine oil (lubricating oil) EO is stored therein. The upper part of the cylinder head 11 is covered by a head cover 19.

[0022] Air (atmosphere) outside the engine 1 is drawn into an intake passage (intake pipe) 22 via an air cleaner 20. A compressor 32 of a supercharger (turbocharger) 30 is provided in the intake passage 22 downstream of the air cleaner 20. The compressor 32 supercharges the air (intake air). The supercharged air is cooled by an intercooler 26. The intercooler 26 may be water-cooled or air-cooled.

[0023] A diesel throttle valve (intake throttle valve) 25 is disposed in the intake passage 22 downstream of the intercooler 26. The intake passage 22 is connected to an intake port 21 formed in the engine body 10 (cylinder head 11) via an intake manifold, and intake air flows into the combustion chamber 14.

[0024] The combustion gas (exhaust) burned in the combustion chamber passes through an exhaust port 51 and is collected in an exhaust manifold, and the exhaust (combustion gas) collected in the exhaust manifold passes through an exhaust passage (exhaust pipe) 52 and flows into the turbine 36 of the turbocharger 30. An exhaust purification device is provided in the exhaust passage 52 downstream of the turbine 36. The exhaust purification device may be, for example, an oxidation catalyst, a DPF (Diesel Particulate Filter), and a selective reduction catalyst, and a silencer (exhaust muffler) is arranged in the exhaust passage 52 downstream of the selective reduction catalyst, and the exhaust is silenced by the silencer before being released into the atmosphere.

[0025] The turbocharger 30 includes a compressor 32 and a turbine 36. A compressor wheel 34 is housed in the housing of the compressor 32, and a turbine wheel 38 is housed in the housing of the turbine 36. The compressor wheel 34 is rotationally driven by the energy of the exhaust gas supplied to the turbine wheel 38, compressing the intake air (air) and supercharging it.

[0026] When the air-fuel mixture burns in the combustion chamber 14, blow-by gas (unburned mixture including combustion gas) passes through the gap between the piston 13 and the cylinder and flows from the combustion chamber 14 into the crankcase 12c. The blow-by gas that has flowed into the crankcase 12c is returned to the intake passage 22, thereby ventilating the interior of the crankcase 12c. The space between the cylinder head 11 and the head cover 19 is connected to the interior of the crankcase 12c by a communication passage 60 formed in the cylinder head 11 and the cylinder block 12. The space between the cylinder head 11 and the head cover 19 is connected to the intake passage 22 between the air cleaner 20 and the compressor 32 by a blow-by gas passage 61 via an oil separator 62. The blow-by gas passage 61 is connected to the intake passage 22 upstream of the compressor 32.

[0027] In this embodiment, when the engine 1 is operating, the intake passage 22 between the air cleaner 20 and the compressor 32 is maintained at a relatively stable negative pressure close to atmospheric pressure due to pressure loss in the air cleaner 20. The pressure (internal pressure) inside the crankcase 12c and the head cover 19 becomes positive due to the inflow of blow-by gas. This generates a pressure difference between the inlet (connection with the head cover 19) and outlet (connection with the intake passage 22) of the blow-by gas passage 61. This pressure difference causes the blow-by gas in the crankcase 12c to return to the intake passage 22 between the air cleaner 20 and the compressor 32 via the communication passage 60, the space inside the head cover 19, the oil separator 62, and the blow-by gas passage 61 (see the dashed arrow in the figure). The oil component contained in the blow-by gas is separated by the oil separator 62 and returned to the oil pan 18.

[0028] The control device 200 controls the operation of the engine 1. The control device 200 includes a CPU (Central Processing Unit) 201 that performs various processes, memory 202 including a ROM (Read Only Memory) that stores programs and data and a RAM (Random Access Memory) that stores CPU processing results, etc., and an input / output port (not shown) for exchanging information with the outside. Various sensors are connected to the input port, and devices to be controlled (for example, fuel injection valve 15, diesel throttle valve 25, etc.) are connected to the output port.

[0029] The control device 200 executes predetermined calculation processing based on signals from various sensors and devices, and maps and programs stored in the memory 202. Then, the control device 200 controls the fuel injection valve 15, the diesel throttle valve 25, etc. based on the results of the calculation processing.

[0030] In this embodiment, the various sensors include an intake air amount sensor 210, an engine rotation speed sensor 220, an accelerator opening sensor 230, a coolant temperature sensor 240, a pressure sensor 250, and the like.

[0031] The intake air amount sensor 210 detects the intake air amount Ga. The engine rotation speed sensor 220 detects the rotation speed NE of the engine 1. The accelerator opening sensor 230 detects the accelerator opening AP, which is the amount of depression of the accelerator pedal. The coolant temperature sensor 240 detects the coolant temperature THW of the engine 1.

[0032] The control device 200 calculates the fuel injection amount Qf and the fuel injection timing based on, for example, the accelerator opening AP and the rotation speed NE, and when the crank angle of the engine 1 reaches the fuel injection timing, opens the fuel injection valve 15 for a time corresponding to the fuel injection amount Qf and performs fuel injection.

[0033] If a leak occurs in the path where the blow-by gas that has flowed into the crankcase 12c returns (recirculates) to the intake passage 22, the blow-by gas may be released into the atmosphere. For example, the blow-by gas may leak from the seal between the head cover 19 and the cylinder head 11, the connection between the blow-by gas passage 61 and the head cover 19 (oil separator 42), the seal between the crankcase 12c and the oil pan 18, etc. Also, the blow-by gas passage 61 may be damaged, causing the blow-by gas to leak. In this embodiment, the detection value of the pressure sensor 250 provided in the oil level gauge guide 100 is used to diagnose the leakage of blow-by gas.

[0034] The oil level gauge guide 100 is formed in a pipe shape (cylindrical shape), is inserted into a mounting hole 12h provided in the cylinder block 12 (crankcase 12c), and is fixed to the engine body 10 by a bracket or the like (not shown). One end of the oil level gauge guide 100 opens to the interior of the crankcase 12c, and the other end opens to the atmosphere. An oil level gauge 101 is inserted into the oil level gauge guide 100. The oil level gauge 101 is used to check the oil level (position of the oil level) of the engine oil EO, and the tip of the oil level gauge 101 is placed in the engine oil EO stored in the oil pan 18. A grip portion is formed at the base end of the oil level gauge 101, which closes the opening at the other end of the oil level gauge guide 100 and also serves as a handle. The oil level gauge guide 100 guides (guides) the tip of the oil level gauge 101 inserted into the oil level gauge guide 100 so that it reaches the liquid level (oil level) of the engine oil EO.

[0035] A pressure sensor 250 that detects the internal pressure of the crankcase 12c is provided in the oil level gauge guide 100. The inside of the pipe-shaped oil level gauge guide 100 is in communication with the space inside the crankcase 12c, so the pressure sensor 250 can detect the internal pressure of the crankcase 12c.

[0036] FIG. 2 is a flowchart of the leakage diagnosis process executed by the control device 200. This flowchart is repeatedly executed at predetermined intervals while the engine 1 is operating (when the ignition switch is ON). In step (hereinafter, step will be abbreviated as "S") 10, it is determined whether or not the diagnosis conditions are met. In this embodiment, it is determined that the diagnosis conditions are met when the operating state of the engine 1 is stable. For example, it is determined that the diagnosis conditions are met when the change amount ΔAP in the accelerator opening AP is equal to or less than a predetermined value S, the cooling water temperature THW is equal to or greater than the warm-up completion temperature, and the engine is not in a fuel cut state (the fuel injection amount Qf is not 0). If the diagnosis conditions are not met, a negative determination is made, and the current routine is terminated. If the diagnosis conditions are met, the routine proceeds to S12.

[0037] In S12, the internal pressure Pc of the crankcase 12c is detected based on the detection signal of the pressure sensor 250, and then the process proceeds to S14.

[0038] In S14, a reference value Ps is read from memory 202 based on the engine operating state when the internal pressure Pc was detected in S12. FIG. 3 shows a reference value Ps map stored (memorized) in memory 202 of control device 200. The reference value Ps map is a map with the fuel injection amount Qf and the rotation speed NE as parameters. The internal pressure Pc when no blow-by gas leakage occurs is obtained in advance through experiments, simulations, etc., corresponding to the operating state of engine 1 (combination of fuel injection amount Qf and rotation speed NE), and a reference value Pa map is created. The created reference value Ps map is then stored in memory 202.

[0039] In S14, the reference value Pa is read from the reference value Ps map based on the fuel injection amount Qf and the rotation speed NE when the internal pressure Pc was detected in S12. At this time, the reference value Ps may be determined by interpolation.

[0040] In the following S16, the internal pressure Pc detected in S12 is compared with the reference value Ps read out in S14 to diagnose a blow-by gas leak. In this embodiment, when the internal pressure Pc is lower than the reference value Ps by a predetermined value α or more, it is determined that a blow-by gas leak has occurred. If the internal pressure Pc is lower than the reference value Ps by the predetermined value α or more (Ps-Pc≧α), a positive determination is made and the process proceeds to S18. If the internal pressure Pc is not lower than the reference value Ps by the predetermined value or more (Ps-Pc<α), a negative determination is made and the current routine is terminated.

[0041] In S18, it is diagnosed that a blow-by gas leak has occurred, and the MIL (Malfunction Indicator Lamp) 300 is illuminated, and a diagnostic code (DTC: Diagnostic Trouble Code) is written to the memory 202. The DTC is written as a code indicating that a blow-by gas leak has occurred. After that, the current routine is terminated. After S18 is processed, execution of this routine (leak diagnosis processing) may be postponed until the measures (repairs, etc.) are completed. The processing of S16 corresponds to an example of a "diagnostic unit" in the present disclosure.

[0042] According to this embodiment, the leakage of blow-by gas is diagnosed by comparing the internal pressure Pc of the crankcase 12c detected by the pressure sensor 250 with the reference value Ps. Therefore, the leakage of blow-by gas, including the leakage of blow-by gas from the engine body 10, can be diagnosed.

[0043] According to this embodiment, the pressure sensor 250 is provided in the oil level gauge guide 100. There is often a relatively large space around the oil level gauge guide 100, so the pressure sensor 250 can be provided without interfering with other components of the vehicle. The oil level gauge guide 100 is attached to a mounting hole 12h provided in the cylinder block 12, and is configured separately from the engine body 10. Therefore, by changing the oil level gauge guide in an existing engine to the oil level gauge guide 100 equipped with the pressure sensor 250, it becomes possible to diagnose blow-by gas leaks without requiring major modifications to the engine body.

[0044] According to this embodiment, the blow-by gas passage 61 is connected to the intake passage 22 upstream of the compressor 32 of the turbocharger 30. When the engine 1 is operating, the intake passage 22 between the air cleaner 20 and the compressor 32 is at a relatively stable negative pressure close to atmospheric pressure due to a slight pressure loss caused by the air cleaner 20, and is approximately at atmospheric pressure. Therefore, the reference value Ps and the internal pressure Pc corresponding to the operating state of the engine 1 are highly robust, and blow-by gas leakage can be properly diagnosed.

[0045] (Variation) The internal pressure of the crankcase 12c may be detected using a pressure sensor 250A provided in the head cover 19, as shown by the dashed line in Fig. 1. Since the blow-by gas returns to the intake passage 22 via the space inside the head cover 19, the pressure inside the head cover 19 is approximately equal to the internal pressure of the crankcase 12c, and the pressure detected by the pressure sensor 250A can also be used to diagnose a blow-by gas leak, as in the above embodiment.

[0046] According to this modification, the pressure inside the crankcase can be detected by the pressure sensor provided in the head cover 19, and the space around the head cover can be utilized. Also, since the head cover 19 is thinner than the cylinder block 12, etc., the pressure sensor 250A can be provided relatively easily.

[0047] In the above embodiment, the oil level gauge guide 100 is provided in the cylinder block 12 (crankcase 12c). However, the oil level gauge guide 100 may be provided in an engine component such as the engine front cover.

[0048] In the above embodiment, the engine 1 is a diesel engine, but it may also be a spark-ignition internal combustion engine (gasoline engine). A turbocharger is used as the supercharger 30, but the supercharger may also be an electric turbo driven by an electric motor, a supercharger driven by the output shaft of the engine 1, or the like. Also, a supercharger need not be provided.

[0049] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0050] 1 engine, 10 engine body, 11 cylinder head, 12 cylinder block, 12c crankcase, 13 piston, 14 combustion chamber, 15 fuel injection valve, 16 connecting rod, 17 crankshaft, 18 oil pan, 19 head cover, 20 air cleaner, 21 intake port, 22 intake passage, 25 diesel throttle valve, 26 intercooler, 30 turbocharger, 32 compressor, 34 compressor wheel, 36 turbine, 38 turbine wheel, 51 exhaust port, 52 exhaust passage, 60 connecting passage, 61 blow-by gas passage, 62 oil separator, 100 oil level gauge guide, 101 oil level gauge, 200 control device, 201 CPU, 202 memory, 210 intake air amount sensor, 220 engine rotation speed sensor, 230 throttle opening sensor, 240 Coolant temperature sensor, 250,250A pressure sensor, MIL 300.

Claims

1. A control device for an internal combustion engine having a blow-by gas passage that returns blow-by gas in a crankcase to an intake passage, the internal combustion engine has a pressure sensor that detects the internal pressure of the crankcase, The control device a storage unit that stores a reference value of the internal pressure corresponding to an operating state of the internal combustion engine; a diagnosis unit that compares the internal pressure detected by the pressure sensor with the reference value and diagnoses leakage of the blow-by gas.

2. the internal combustion engine is provided with an oil level gauge guide into which an oil level gauge for checking the position of the engine oil level is inserted; 2. The control device for an internal combustion engine according to claim 1, wherein the pressure sensor is provided on the oil level gauge guide.

3. the internal combustion engine includes a head cover, the blow-by gas passage is connected to the intake passage via a space within the head cover, 2. The control device for an internal combustion engine according to claim 1, wherein the pressure sensor is provided in the head cover.

4. 4. The control device for an internal combustion engine according to claim 1, wherein the diagnosing unit diagnoses that a leak of the blow-by gas has occurred when the internal pressure detected by the pressure sensor is lower than the reference value by a predetermined value or more.

5. The internal combustion engine further includes a supercharger, 5. The control device for an internal combustion engine according to claim 4, wherein the blow-by gas passage is connected to the intake passage upstream of a compressor of the supercharger.

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