Control method for internal combustion engine and control device for internal combustion engine

Abstract

To enable continuous operation of an internal combustion engine even when a crank angle sensor has failed.SOLUTION: When a crank angle sensor 3 has failed, an internal combustion engine 1 estimates timing when a piston of any cylinder reaches a top dead center position by using a detection signal of an intake pressure sensor 12 which is a signal indicating that a piston of any cylinder reaches the top dead center position, and performs a crank angle sensor failure time operation on the basis of the estimated timing when the piston of any cylinder reaches the top dead center position. During the crank angle sensor failure time operation, a first fuel injection amount obtained by dividing a fuel injection amount during a normal operation in which the crank angle sensor 3 is not failed by the number of cylinders is simultaneously injected to each of the cylinders as many as the number of the cylinders in one combustion cycle.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] For example, Patent Document 1 discloses a technology in which, in the event of a crank angle sensor failure in a four-stroke inline two-cylinder spark ignition engine, the fuel injection start timing and ignition timing are set to the time when the intake pressure detected by the intake pressure sensor reaches its peak or when a predetermined delay time has elapsed since that detection value, thereby enabling the engine to continue operating even if the crank angle sensor fails. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-209846 Summary of the Invention [Problem to be solved by the invention]

[0004] However, Patent Document 1 is based on the premise of a two-cylinder engine and cannot be applied to a multi-cylinder engine with three or more cylinders. Furthermore, Patent Document 1 has a configuration in which one injector is used for two cylinders, and therefore, during normal operation, so-called sequential injection, in which fuel is injected when each cylinder is on its exhaust stroke, cannot be performed.

[0005] In other words, there is room for further improvement in the internal combustion engine so that the internal combustion engine can continue to operate even if the crank angle sensor fails. [Means for solving the problem]

[0006] The internal combustion engine of the present invention is a port injection, four-stroke internal combustion engine that, when a crank angle sensor fails, estimates the timing at which the piston of one of the cylinders will reach top dead center using a first signal that indicates that the piston of one of the cylinders will reach top dead center, and performs operation for when the crank angle sensor fails based on the estimated timing at which the piston of one of the cylinders will reach top dead center.In operation for when the crank angle sensor fails, a first fuel injection amount, obtained by dividing the fuel injection amount during normal operation when the crank angle sensor is not malfunctioning by the number of cylinders, is injected into each cylinder simultaneously, and the number of times during one combustion cycle is the same as the number of cylinders. [Effects of the Invention]

[0007] The internal combustion engine of the present invention can reliably supply fuel for combustion to each cylinder and continue stable operation even when it is not possible to determine which cylinder will undergo the next combustion stroke due to a failure of the crank angle sensor. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is an explanatory diagram that schematically shows an example of a system configuration of a vehicle equipped with an internal combustion engine to which the present invention is applied; [Figure 2] FIG. 2 is an explanatory diagram illustrating the operating cycles of the cylinders of the internal combustion engine under normal conditions. [Figure 3] FIG. 4 is an explanatory diagram showing a change in intake pressure detected by an intake pressure sensor. [Figure 4] FIG. 4 is an explanatory diagram illustrating the operating cycles of the cylinders of the internal combustion engine when the crank angle sensor fails. [Figure 5] 3 is a flowchart showing the flow of control of the internal combustion engine in the first embodiment. [Figure 6] FIG. 4 is an explanatory diagram showing changes in the rotation speed of the motor / generator detected by a resolver. [Figure 7] 10 is a flowchart showing the flow of control of an internal combustion engine in a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described in detail below with reference to the drawings.

[0010] FIG. 1 is an explanatory diagram that schematically shows an example of the system configuration of a vehicle equipped with an internal combustion engine 1 to which the present invention is applied.

[0011] The vehicle of this embodiment equipped with the internal combustion engine 1 is a so-called series hybrid vehicle that does not use the internal combustion engine 1 as a direct power source. In other words, the internal combustion engine 1 is installed on the vehicle for generating electricity.

[0012] The internal combustion engine 1 is mounted on a vehicle to drive a motor / generator 2, which is an electric power generator, and is connected to the motor / generator 2.

[0013] For example, the output shaft of the internal combustion engine 1 is connected to the rotating shaft (motor rotating shaft) of the motor / generator 2 via a gear train (not shown). Therefore, the rotation speed of the rotating shaft of the motor / generator 2 is uniquely determined once the engine rotation speed of the internal combustion engine 1 is determined. Similarly, the engine rotation speed of the internal combustion engine 1 is uniquely determined once the rotation speed of the rotating shaft of the motor / generator 2 is determined. Note that the internal combustion engine 1 may be directly connected to the motor / generator 2 without a gear train.

[0014] A crank angle sensor 3 is attached to the rear end of the crankshaft of the internal combustion engine 1 to detect the crank angle of the crankshaft.

[0015] A resolver 4 is attached to the rotating shaft of the motor / generator 2 to detect the rotation speed of the rotating shaft.

[0016] The internal combustion engine 1 is a four-stroke spark ignition internal combustion engine, and a fuel injection valve 6 is disposed in the intake port 5 of each cylinder. The internal combustion engine 1 is a port injection type internal combustion engine that injects fuel into the intake port 5.

[0017] A first intake port 5a equipped with a first fuel injection valve 6a is connected to a first cylinder #1 of the internal combustion engine 1. A second intake port 5b equipped with a second fuel injection valve 6b is connected to a second cylinder #2 of the internal combustion engine 1. A third intake port 5c equipped with a third fuel injection valve 6c is connected to a third cylinder #3 of the internal combustion engine 1. Each intake port 5 is connected to an intake collector 7. The intake ports 5 are located downstream of the intake collector 7 in the intake air flow direction. The intake collector 7 constitutes an intake passage and is a collective part of an intake manifold located downstream of a throttle valve (not shown) in the intake air flow direction.

[0018] The fuel injection valve 6 is capable of changing (controlling) the fuel injection amount and fuel injection timing in response to a control signal from a control unit 11.

[0019] The control unit 11 corresponds to a control section and is a well-known digital computer equipped with a CPU, ROM, RAM and an input / output interface, and controls the internal combustion engine 1 based on detection signals from various sensors.

[0020] The control unit 11 can calculate the rotation speed of the crankshaft (engine rotation speed) based on the detection signal of the crank angle sensor 3. The control unit 11 can also calculate the rotation speed of the motor / generator 2 (electric motor rotation speed) based on the detection signal of the resolver 4.

[0021] In addition to the detection signals from the crank angle sensor 3 and resolver 4 described above, the control unit 11 also receives a detection signal from an intake pressure sensor 12 that detects the pressure inside the intake collector 7, and a detection signal from a cam angle sensor 13 that detects the cam angle of a camshaft (not shown) of the internal combustion engine 1.

[0022] The control unit 11 is capable of determining which cylinder will undergo the next combustion stroke using the detection signal from the crank angle sensor 3. That is, the control unit 11 is capable of determining whether the operating cycle of cylinders #1 to #3 is currently in the intake stroke, compression stroke, expansion (combustion) stroke, or exhaust stroke, as shown in FIG. 2, using the detection signal from the crank angle sensor 3, and is capable of controlling the fuel injection valve 6 so that fuel is injected at the timing of the latter half of the exhaust stroke. In other words, during normal operation when the crank angle sensor 3 is not malfunctioning, the internal combustion engine 1 performs so-called sequential injection, in which fuel is injected from the fuel injection valve 6 into the intake port 5 of the cylinder that is currently in the exhaust stroke. FIG. 2 is an explanatory diagram showing the operating cycles of each cylinder of the internal combustion engine 1 during normal operation (normal operation) when the crank angle sensor 3 is not malfunctioning.

[0023] Then, the control unit 11 uses the detection signal from the crank angle sensor 3 to identify a cylinder that is near the top dead center of the compression stroke, and generates a spark from the spark plug of that cylinder to ignite that cylinder. In other words, the control unit 11 controls the ignition timing of each cylinder. The control unit 11 also controls the fuel injection timing of each cylinder so that fuel is injected into the corresponding intake port 5 at the timing of the latter half of the exhaust stroke.

[0024] If the crank angle sensor 3 fails, the control unit 11 will be unable to determine whether each cylinder is in the intake stroke, compression stroke, expansion (combustion) stroke, or exhaust stroke.

[0025] Therefore, in the internal combustion engine 1 of the first embodiment, when the control unit 11 detects a malfunction of the crank angle sensor 3, the control unit 11 uses the detection signal of the intake pressure sensor 12, which corresponds to the first signal, to estimate the timing at which the piston of one of the cylinders (cylinders #1 to #3) reaches the top dead center position of the compression stroke. A malfunction of the crank angle sensor 3 can be detected by using a well-known method, for example, when the signal sent from the crank angle sensor 3 is not a normal value.

[0026] 3 is an explanatory diagram showing the change (fluctuation) in the intake pressure in the intake collector 7 detected by the intake pressure sensor 12. In the internal combustion engine 1, one of the cylinders is at compression top dead center at the timing when the intake pressure in the intake collector 7 reaches a trough (extreme value) of the pressure change (fluctuation). In other words, if the engine has three cylinders, the period including three troughs of the pressure change corresponds to the period during which combustion occurs once in each of the cylinders.

[0027] In FIG. 3, one of the cylinders reaches compression top dead center at the timing indicated by the arrow at the valley of the pressure change.

[0028] In this way, the control unit 11 can accurately estimate (determine) the timing at which the piston of any cylinder reaches the compression top dead center by finding the peak value of the intake pressure change (intake pressure fluctuation) from the detection signal of the intake pressure sensor 12.

[0029] Furthermore, the control unit 11 performs operation for when the crank angle sensor fails based on the timing at which the piston of one of the cylinders (cylinders #1 to #3) reaches the compression top dead center position, which is estimated using the detection signal of the intake pressure sensor 12.

[0030] FIG. 4 is an explanatory diagram showing an arrangement of the operating cycles of the cylinders of the internal combustion engine 1 when the crank angle sensor 3 fails (operation for when the crank angle sensor fails).

[0031] In the operation for when the crank angle sensor 3 has failed, a first fuel injection amount for when the crank angle sensor has failed is calculated by dividing the fuel injection amount per cylinder during normal operation when the crank angle sensor 3 is not malfunctioning by the number of cylinders, and the first fuel injection amount is injected into each cylinder simultaneously and the number of times equal to the number of cylinders during one combustion cycle.

[0032] In the operation for when the crank angle sensor has failed, the first fuel injection amount of fuel is injected from all fuel injection valves 6 at the timing of the latter half of the exhaust stroke of any cylinder, based on the timing when the piston of any cylinder reaches the compression top dead center position estimated using the detection signal of the intake pressure sensor 12. In other words, in the operation for when the crank angle sensor has failed, the first fuel injection amount of fuel is injected simultaneously into all intake ports 5.

[0033] In the operation mode for when the crank angle sensor has failed, ignition sparks are simultaneously generated in the spark plugs of the cylinders at the timing of ignition of any of the cylinders, based on the timing when the piston of any of the cylinders will reach the compression top dead center position estimated using the detection signal of the intake pressure sensor 12. In other words, in the operation mode for when the crank angle sensor has failed, ignition sparks are simultaneously generated in the spark plugs of the cylinders at the timing when the piston of any of the cylinders will reach the compression top dead center position based on the timing when the piston of any of the cylinders will reach the compression top dead center position estimated using the detection signal of the intake pressure sensor 12.

[0034] In operation when the crank angle sensor is faulty, sparks are generated from the spark plugs in all cylinders at the same time. In operation when the crank angle sensor is faulty, the cylinder that ignites when a spark is generated from the spark plug is the cylinder in which the fuel gas inside the cylinder is compressed and under high pressure, so only one cylinder is ignited at any one time.

[0035] 5 is a flowchart showing the flow of control of the internal combustion engine 1 in the first embodiment described above. In step S11, it is determined whether or not there is a malfunction in the crank angle sensor 3. If it is determined in step S11 that there is a malfunction in the crank angle sensor 3, the process proceeds to step S12.

[0036] In step S12, the timing at which the piston of any cylinder reaches the compression top dead center is estimated from the detection signal of the intake pressure sensor 12.

[0037] In step S13, the fuel injection timing for each cylinder is set to a timing when one of the cylinders is in the latter half of the exhaust stroke, based on the timing when the piston of one of the cylinders reaches the compression top dead center estimated using the detection signal from the intake pressure sensor 12.

[0038] In step S14, the ignition timing of each cylinder is set to the timing when the piston of one of the cylinders reaches the compression top dead center position, based on the timing when the piston of one of the cylinders reaches the compression top dead center position estimated using the detection signal of the intake pressure sensor 12.

[0039] In the internal combustion engine 1 of the first embodiment described above, even if it is not possible to determine which cylinder will undergo the next combustion stroke due to a malfunction of the crank angle sensor 3, fuel for combustion can be reliably supplied to each cylinder and each cylinder can be reliably ignited, allowing stable continued operation.

[0040] Another embodiment of the present invention will be described below, in which the same components as those in the above-described embodiment are designated by the same reference numerals and redundant description will be omitted.

[0041] The internal combustion engine 1 of the second embodiment has substantially the same configuration as the internal combustion engine 1 of the first embodiment described above, but employs a detection signal of the resolver 4 as the first signal.

[0042] The rotation speed of the crankshaft of the internal combustion engine 1 is uniquely determined once the rotation speed of the rotating shaft of the motor / generator 2 is determined, and therefore can be calculated using the detection signal of the resolver 4. Therefore, even if the crank angle sensor 3 fails, it can be determined that one of the cylinders is at top dead center from the rotation speed of the crankshaft estimated using the detection signal of the resolver 4.

[0043] 6 is an explanatory diagram showing the change (fluctuation) in the rotation speed of the rotating shaft of the motor / generator 2 detected by the resolver 4. In the internal combustion engine 1, one of the cylinders is at compression top dead center at the timing of a valley (extreme value) in the rotation speed change (rotation speed fluctuation) of the rotating shaft of the motor / generator 2. In other words, if the engine has three cylinders, the period that includes three valleys in the rotation speed change corresponds to the period during which combustion occurs once in all the cylinders.

[0044] In FIG. 6, one of the cylinders reaches compression top dead center at the timing indicated by the arrow in the valley of the rotational speed change.

[0045] In this way, the control unit 11 can accurately estimate (determine) the timing at which the piston of any cylinder reaches the compression top dead center by finding the peak value of the rotational speed change (rotational speed fluctuation) of the rotating shaft of the motor / generator 2 from the detection signal of the resolver 4.

[0046] 7 is a flowchart showing the flow of control of the internal combustion engine 1 in the second embodiment. In step S21, it is determined whether or not there is a malfunction in the crank angle sensor 3. If it is determined in step S11 that there is a malfunction in the crank angle sensor 3, the process proceeds to step S22.

[0047] In step S22, the timing at which the piston of any cylinder reaches the compression top dead center is estimated from the detection signal of resolver 4.

[0048] In step S23, the fuel injection timing for each cylinder is set to a timing when one of the cylinders is in the latter half of the exhaust stroke, based on the timing when the piston of one of the cylinders reaches the compression top dead center estimated using the detection signal of resolver 4.

[0049] In step S24, the ignition timing of each cylinder is set to the timing when the piston of one of the cylinders reaches the compression top dead center position, based on the timing when the piston of one of the cylinders reaches the compression top dead center position estimated using the detection signal of resolver 4.

[0050] The internal combustion engine 1 of the second embodiment can also achieve substantially the same effects as the internal combustion engine 1 of the first embodiment described above.

[0051] Although specific embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention.

[0052] The internal combustion engine 1 of the first embodiment described above is mounted on a series hybrid vehicle, but the internal combustion engine 1 of the first embodiment can also be mounted on, for example, a parallel hybrid vehicle or a non-hybrid vehicle that drives the wheels by transmitting the rotation of the crankshaft of the internal combustion engine.

[0053] Although the internal combustion engine 1 of the second embodiment described above is mounted on a series hybrid vehicle, the internal combustion engine 1 of the second embodiment can also be mounted on, for example, a parallel hybrid vehicle.

[0054] The internal combustion engine 1 of the first and second embodiments described above is an in-line three-cylinder internal combustion engine, but the present invention is also applicable to, for example, a multi-cylinder internal combustion engine with three or more cylinders, a V-type internal combustion engine with six or more cylinders, etc.

[0055] When the internal combustion engine 1 of the first and second embodiments described above performs the operation for when the crank angle sensor has failed, for example, when starting the internal combustion engine 1, the motor / generator 2 may increase the engine speed of the internal combustion engine 1 to a predetermined power generation rotation speed set at an operating point for power generation, and then the first signal may be used to perform the operation for when the crank angle sensor has failed. The operating point of the internal combustion engine 1 is an operating point determined by, for example, the engine speed and torque of the internal combustion engine 1.

[0056] If the first signal is used to estimate the timing at which the piston in one of the cylinders will reach the top dead center position during a transient period in which the engine speed of the internal combustion engine 1 is changing, the accuracy of estimating the timing at which the piston in one of the cylinders will reach the top dead center position may decrease compared to a steady state that is not in a transient period, and there is a risk that the timing at which the piston will reach the top dead center position may not be accurately estimated.

[0057] While the engine speed of the internal combustion engine 1 is increasing until it reaches the power-generation speed, the timing at which the piston of any cylinder will reach the top dead center position may not be estimated using the first signal. In other words, the internal combustion engine 1 may not use the first signal to estimate the timing at which the piston of any cylinder will reach the top dead center position during a transition in which the engine speed is changing.

[0058] In this case, the estimation of the timing when the piston of any cylinder will reach the top dead center position using the first signal is performed when the engine speed of the internal combustion engine 1 is constant, and the estimation of the timing when the piston of any cylinder will reach the top dead center position can be performed with even greater accuracy.

[0059] In this way, the internal combustion engine 1 in which the engine rotation speed is increased by the motor / generator 2 prior to performing the operation for when the crank angle sensor fails can also be applied to an internal combustion engine 1 mounted on a parallel hybrid vehicle, for example.

[0060] In the internal combustion engine 1 of the first and second embodiments described above, the operation for when the crank angle sensor fails may be performed, for example, by injecting the first fuel injection amount at a timing that is retarded by a predetermined time from the fuel injection timing that is determined depending on the timing at which the piston of one of the cylinders, estimated from the first signal, reaches the top dead center position.

[0061] This allows the internal combustion engine 1 to perform fuel injection during operation in the event of a crank angle sensor failure at an appropriate fuel injection timing that avoids, for example, a period in which the opening periods of the intake valve and the exhaust valve in the same cylinder overlap (a valve overlap engine).

[0062] In the internal combustion engine 1 of the first and second embodiments described above, the operation for when the crank angle sensor fails may be performed by, for example, simultaneously generating ignition sparks in the spark plugs of the cylinders at a timing that is retarded by a predetermined time from the timing at which the piston of one of the cylinders, estimated from the first signal, reaches the top dead center position.

[0063] This allows the internal combustion engine 1 to perform spark ignition during operation in the event of a crank angle sensor failure, for example, at an appropriate ignition timing that avoids the period in which the intake valve opening period and the exhaust valve opening period in the same cylinder overlap (a valve overlap engine).

[0064] In the internal combustion engine 1 of the first and second embodiments described above, when the crank angle sensor 3 fails, the operating cycle of each cylinder can be estimated without using the detection signal of the cam angle sensor 13. That is, in the internal combustion engine 1 of the first and second embodiments described above, for example, the cam angle sensor 13 can be omitted. In other words, the present invention is a technology that can be applied to internal combustion engines that do not have a cam angle sensor 13.

[0065] The above-described embodiments relate to a control method for an internal combustion engine and a control device for an internal combustion engine. [Explanation of symbols]

[0066] 1...Internal combustion engine 2...Motor / generator 3...Crank angle sensor 4...Resolver 5...Intake port 6...Fuel injection valve 7...Intake collector 11...Control unit 12...Intake pressure sensor 13...Cam angle sensor

Claims

1. A control method for a multi-cylinder port injection four-stroke internal combustion engine capable of injecting fuel into the intake port of each cylinder when each cylinder is on its exhaust stroke, comprising: When a crank angle sensor that detects the crank angle of the crankshaft fails, a timing at which the piston of one of the cylinders will reach the top dead center position is estimated using a first signal that indicates that the piston of one of the cylinders will reach the top dead center position, and an operation for use when the crank angle sensor fails is performed based on the estimated timing at which the piston of one of the cylinders will reach the top dead center position; a control method for an internal combustion engine, wherein the operation for when the crank angle sensor has failed is performed by injecting a first fuel injection amount, which is obtained by dividing the fuel injection amount during normal operation when the crank angle sensor is not faulty, by the number of cylinders, into each cylinder simultaneously and a number of times equal to the number of cylinders during one combustion cycle.

2. 2. The method for controlling an internal combustion engine according to claim 1, wherein the first signal is a detection signal of an intake pressure in an intake passage of the internal combustion engine.

3. 2. The method for controlling an internal combustion engine according to claim 1, wherein the internal combustion engine is connected directly or via a gear to a motor / generator to drive the motor / generator to generate electric power, and the first signal is a detection signal of a resolver that detects the rotational speed of a rotary shaft of the motor / generator.

4. The internal combustion engine is capable of driving a motor / generator to generate electric power, 2. The control method for an internal combustion engine according to claim 1, wherein, if a crank angle sensor that detects the crank angle of the crankshaft fails, at start of the internal combustion engine, the motor / generator increases the engine speed of the internal combustion engine up to a predetermined power-generation rotation speed that is set at an operating point for power generation, and then the first signal is used to implement operation for when the crank angle sensor fails.

5. 2. The control method for an internal combustion engine according to claim 1, wherein the operation for when the crank angle sensor fails uses the first signal to simultaneously generate ignition sparks in the spark plugs of each cylinder at the timing of igniting any one of the cylinders.

6. 6. The control method for an internal combustion engine according to claim 5, wherein the operation for use when the crank angle sensor fails comprises injecting the first fuel injection amount at a timing retarded by a predetermined time from a fuel injection timing determined based on a timing at which a piston of any one of the cylinders reaches a top dead center position estimated from the first signal.

7. 6. The control method for an internal combustion engine according to claim 5, wherein the operation for when the crank angle sensor fails comprises simultaneously generating ignition sparks in the spark plugs of each cylinder at a timing retarded by a predetermined time from the timing at which the piston of any of the cylinders, estimated from the first signal, reaches the top dead center position.

8. A control device for a multi-cylinder port injection type four-stroke internal combustion engine capable of injecting fuel into the intake port of each cylinder when each cylinder is on its exhaust stroke, a control unit that, when a crank angle sensor that detects the crank angle of the crankshaft fails, estimates the timing at which the piston of one of the cylinders will reach the top dead center position using a first signal that indicates that the piston of one of the cylinders will reach the top dead center position, and performs operation for use when the crank angle sensor fails based on the estimated timing at which the piston of one of the cylinders will reach the top dead center position; The operation for when the crank angle sensor has failed is characterized in that a first fuel injection amount, which is obtained by dividing the fuel injection amount during normal operation when the crank angle sensor is not faulty, by the number of cylinders, is injected into each cylinder simultaneously and the number of times during one combustion cycle is equal to the number of cylinders.

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