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

Abstract

In the present invention, when a fully closed position learning condition is satisfied, an electric motor (6) for driving a throttle valve (3) disposed in an intake passage (2) is driven so that the valve opening degree of the throttle valve (3) will be in a fully closed state. When a predetermined valve opening degree determination condition is satisfied and it is determined that the valve opening degree of the throttle valve (3) has reached the fully closed position, and a predetermined learning value update condition is also satisfied, an output value outputted from a throttle sensor (10) at that time is learned as an output value corresponding to the fully closed position of the throttle valve (3). Due to this configuration, it is possible to accurately determine the fully closed position of the throttle valve (3) even if deposits are accumulated.

Description

Control method and control device for internal combustion engine

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

[0002] For example, in Patent Document 1, the throttle valve of an internal combustion engine is forcibly controlled to a fully closed position, and it is determined that the throttle valve is in the fully closed position when there is a small change in the output voltage of a throttle sensor that detects the opening degree of the throttle valve.

[0003] In Patent Document 1, the throttle valve's fully closed position learning value is updated if, after a predetermined time has elapsed since it was determined that the throttle valve was in the fully closed position, the current flowing through the motor that drives the throttle valve is equal to or greater than the fully closed position determination current value.

[0004] However, in Patent Document 1, if deposits have accumulated around the throttle valve, controlling the throttle valve toward the fully closed position may cause the deposits to interfere with the throttle valve, reducing the rate of change in the throttle valve opening. In other words, in Patent Document 1, if deposits interfere with the throttle valve, the rate of change in the throttle valve opening decreases, resulting in a smaller change in the output voltage of the throttle sensor, which may result in the throttle valve being erroneously determined to be in the fully closed position before it actually reaches the fully closed state.

[0005] Therefore, there is room for further improvement in determining the fully closed position of the throttle valve of an internal combustion engine.

[0006] Japanese Patent Application Laid-Open No. 2000-73784

[0007] When the current supplied to the electric motor becomes equal to or greater than a predetermined current threshold and predetermined learning value update conditions are met, the internal combustion engine of the present invention learns the output value output from the throttle sensor that detects the opening degree of the throttle valve as an output value corresponding to the fully closed position of the throttle valve.

[0008] According to the present invention, even if deposits have accumulated, it is possible to accurately determine the fully closed position of the throttle valve, and the opening of the throttle valve is accurately controlled based on the fully closed position of the throttle valve, thereby suppressing a deterioration in fuel efficiency.

[0009] The present invention is directed to an internal combustion engine, and is also directed to a timing chart showing an example of a change in the current supplied to the electric motor and the output value of the throttle sensor after a fully closed position learning condition is satisfied.

[0010] An embodiment of the present invention will be described in detail below with reference to the drawings.

[0011] FIG. 1 is an explanatory diagram that schematically shows the system configuration of an internal combustion engine 1 to which the present invention is applied.

[0012] A throttle valve 3 is disposed in an intake passage 2 of an internal combustion engine 1. The throttle valve 3 has a valve element 4 disposed in the intake passage 2 and a valve shaft 5 which serves as a rotation axis of the valve element 4, and adjusts the intake air flow rate according to the opening degree of the valve element 4. One end of the valve shaft 5 of the throttle valve 3 is connected to an electric motor 6.

[0013] The electric motor 6 is driven by a current from a motor drive circuit 7. The current supplied from the motor drive circuit 7 to the electric motor 6 is controlled by a control unit 8.

[0014] The control unit 8 is a well-known digital computer equipped with a CPU, ROM, RAM, and an input / output interface.

[0015] The control unit 8 receives detection signals from various sensors such as a current sensor 9, a throttle sensor 10, and an accelerator opening sensor 11.

[0016] The current sensor 9 detects the current supplied from the motor drive circuit 7 to the electric motor 6. In other words, the current sensor 9 detects the current flowing through the electric motor 6 when the electric motor 6 is being driven. The throttle sensor 10 is provided on the other end of the valve shaft 5 and detects the valve opening (throttle opening) of the throttle valve 3. The accelerator opening sensor 11 detects the amount of depression of an accelerator pedal (not shown) of the vehicle in which the internal combustion engine 1 is mounted.

[0017] The control unit 8 determines a target valve opening (target throttle opening) of the throttle valve 3 based on an output signal from an accelerator opening sensor 11 and the like.

[0018] When a fully closed position learning condition, which is a condition for learning the fully closed position of the throttle valve 3, is met, the control unit 8 as a control section controls the opening of the throttle valve 3 so that the opening of the throttle valve 3 is at the fully closed position. The fully closed position learning condition is met, for example, when the ignition switch of the vehicle is turned off.

[0019] If deposits have accumulated in the intake passage 2, the fully closed position of the throttle valve 3 will be changed from that in a brand new state (a state in which no deposits have accumulated). Therefore, if the current fully closed position of the throttle valve 3 is not correctly determined, the opening of the throttle valve 3 will be controlled based on the fully closed position of the throttle valve 3 in a brand new state. In this case, the controlled opening of the throttle valve 3 in the internal combustion engine 1 is not opened to the originally required opening, so the fuel injection amount is greater than the actual air amount, resulting in poor fuel economy.

[0020] When the throttle valve 3 is new and has no deposits, it rotates to the initial fully closed position when driven in the fully closed direction.

[0021] On the other hand, if deposits have accumulated, when the throttle valve 3 is driven in the fully closed direction, the valve element 4 may interfere with the deposits before reaching the initial fully closed position, and may not be able to rotate to the initial fully closed position. Also, depending on the strength of the accumulated deposits, it is possible that after the valve element 4 of the throttle valve 3 hits the deposits, it may crush the deposits and rotate in the fully closed direction.

[0022] The electric motor 6 that drives the throttle valve 3 receives a large load and a lock current flows when the throttle valve 3 is driven in the fully closed direction and the valve element 4 of the throttle valve 3 reaches the initial fully closed position, or when the throttle valve 3 is driven in the fully closed direction and the valve element 4 of the throttle valve 3 hits a deposit and becomes stuck. The lock current is a current that flows when the load becomes large and the electric motor 6 stops moving.

[0023] When the fully closed position learning condition is satisfied, the control unit 8 drives the electric motor 6 so that the opening of the throttle valve 3 is brought to the fully closed state. Then, when the current supplied to the electric motor 6 reaches a predetermined lock current value or more in a state in which the throttle valve 3 does not rotate in the closing direction even when current is supplied to the electric motor 6, the control unit 8 determines that the opening of the throttle valve 3 has reached the fully closed position because the throttle valve 3 is sufficiently pressed in the closing direction and reaches a stable state. In other words, when the current supplied to the electric motor 6 reaches a predetermined current threshold Thi in a state in which the throttle valve 3 does not rotate in the closing direction even when current is supplied to the electric motor 6, the control unit 8 determines that the opening of the throttle valve 3 has reached the fully closed position because the throttle valve 3 is sufficiently pressed in the closing direction and reaches a stable state.

[0024] When the control unit 8 is able to determine that the valve opening of the throttle valve 3 has reached the fully closed position and a predetermined valve opening determination condition (first condition) is satisfied, the control unit 8 determines that the valve opening of the throttle valve 3 has reached the fully closed position.

[0025] The valve opening degree determination condition is met, for example, when the state in which the current supplied to the electric motor 6 is equal to or greater than the current threshold Thi (lock current value) continues for a predetermined time T1. The predetermined time T1 is set, for example, to be longer than the pulse width of the inrush current flowing through the electric motor 6. In other words, the predetermined time T1 is set to be longer than the time it takes for the inrush current flowing through the electric motor 6 to converge to a steady current.

[0026] After the fully closed position learning condition is met, if the current supplied to the electric motor 6 remains above the current threshold Thi for a predetermined time T1, it is determined that the throttle valve 3 has reached the fully closed position. This further reduces erroneous determinations and enables more accurate determination of the fully closed position of the throttle valve 3.

[0027] Furthermore, if the predetermined time T1 is set to be longer than the pulse width of the inrush current flowing through the electric motor 6, it is possible to prevent the throttle valve 3 from being erroneously determined to have reached the fully closed position when an inrush current flows through the electric motor 6.

[0028] When the control unit 8 is able to determine that the valve opening of the throttle valve 3 has reached the fully closed position and a predetermined valve opening determination condition is met, it determines that the throttle valve 3 has reached the fully closed position where it will not move any further in the closing direction (fully closed position determination).

[0029] Then, when the control unit 8 determines that the throttle valve 3 has reached the fully closed position and a predetermined learning value update condition (second condition) is met, it learns the output value output from the throttle sensor 10 at that time as a learning value corresponding to the fully closed position of the throttle valve 3.

[0030] The learning value update condition is met, for example, when the output value of the throttle sensor 10 remains constant for a second predetermined time T2 set in advance from the timing when the valve opening degree determination condition is met. Note that it is also possible to use the valve opening degree determination condition (first condition) as the learning value update condition and omit checking the second condition.

[0031] 2 is a timing chart showing an example of changes in the current supplied to the electric motor 6 and the output value of the throttle sensor 10 after the fully closed position learning condition is satisfied. In Fig. 2, the solid line indicates the case where deposits have accumulated in the intake passage 2, and the dashed line indicates the case where no deposits have accumulated in the intake passage 2 (when the intake passage 2 is new). Note that Fig. 2 illustrates the case where no deposits have accumulated in the intake passage 2 and the case where deposits have accumulated in the intake passage 2, with the fully closed position learning condition being satisfied at the same time, so that the cases where no deposits have accumulated in the intake passage 2 and where deposits have accumulated in the intake passage 2 can be compared.

[0032] First, a case where no deposits have accumulated in the intake passage 2 will be described.

[0033] At time t1, the fully closed position learning condition is met. The output value of the throttle sensor 10 starts to change at a predetermined rate from time t1. This is because current is supplied to the electric motor 6 from time t1 so that the opening of the throttle valve 3 changes toward the fully closed position at a predetermined constant rate.

[0034] Time t3 is the timing when the output value of the throttle sensor 10 becomes constant and stops changing. This is because the opening of the throttle valve 3 no longer moves in the closing direction, even when the electric motor 6 drives the throttle valve 3 in the closing direction. The current supplied to the electric motor 6 increases rapidly from time t3, as the opening of the throttle valve 3 no longer moves in the closing direction. If no deposits have accumulated in the intake passage 2, the current supplied to the electric motor 6 after time t3 is a lock current.

[0035] At time t4, the current supplied to the electric motor 6 increases to the current threshold Thi (lock current value).

[0036] Time t5 is the timing when the current supplied to the electric motor 6 reaches the predetermined maximum value of the lock current. When the fully closed position learning condition is met and the throttle valve 3 is controlled to be in the fully closed position, a current up to the predetermined maximum value of the lock current is supplied to the electric motor 6. Therefore, if no deposits have accumulated in the intake passage 2, after time t5, a current exceeding the maximum value of the lock current will not be supplied to the electric motor 6 once the fully closed position learning condition is met.

[0037] At time t6, the predetermined time T1 has elapsed since time t4, and the valve opening determination condition is met. If no deposits have accumulated in the intake passage 2, the control unit 8 determines that the throttle valve 3 is in the fully closed position at time t6.

[0038] If no deposits have accumulated in the intake passage 2, the learning value update condition is met if the output value from the throttle sensor 10 is constant for a second predetermined time T2 from time t6, when it is determined that the throttle valve 3 is in the fully closed position, and the output value of the throttle sensor 10 at the point when the second predetermined time T2 has elapsed from time t6 is learned as the learning value corresponding to the fully closed position of the throttle valve 3.

[0039] Next, a case where deposits have accumulated in the intake passage 2 will be described.

[0040] The output value of the throttle sensor 10 starts to change at a predetermined rate from the timing t1 when the fully closed position learning condition is met.

[0041] Time t2 is the timing when the throttle valve 3 comes into contact with a deposit accumulated in the intake passage 2. The rate of change of the output value of the throttle sensor 10 is slower from time t2 than before the contact with the deposit (before time t2). This is because the valve element 4 of the throttle valve 3 comes into contact with the deposit, increasing the rotational load on the valve element 4, and the rate of change of the valve opening of the throttle valve 3 in the closing direction is slower than before time t2. Time t2 is earlier than time t3, at which the output value of the throttle sensor 10 stops changing if no deposits have accumulated in the intake passage 2. In conventional technology, the output value of the throttle sensor 10 at time t2, when the rate of change of the output value of the throttle sensor 10 slows, may be erroneously determined to be the output value at the fully closed position.

[0042] Time t7 is the timing at which the output value of the throttle sensor 10 becomes constant and stops changing. This is because the opening of the throttle valve 3 no longer moves in the closing direction, even when the electric motor 6 drives the throttle valve 3 in the closing direction. The current supplied to the electric motor 6 increases rapidly from time t7, as the opening of the throttle valve 3 no longer moves in the closing direction. If deposits have accumulated in the intake passage 2, the current supplied to the electric motor 6 from time t7 onwards is a lock current. Time t7 is later than time t3, at which the output value of the throttle sensor 10 stops changing if no deposits have accumulated in the intake passage 2.

[0043] Time t8 is the timing when the current supplied to the electric motor 6 rises to the current threshold value Thi (lock current value). Time t8 is later than time t4, at which the current supplied to the electric motor 6 rises to the current threshold value Thi when no deposits have accumulated in the intake passage 2.

[0044] Time t9 is the timing when the current supplied to the electric motor 6 reaches a predetermined maximum value of the lock current. If deposits have accumulated in the intake passage 2, after time t9, if the fully closed position learning condition is met, a current exceeding the maximum value of the lock current will not be supplied to the electric motor 6. Time t9 is later than time t5, at which the current supplied to the electric motor 6 reaches the lock current value when no deposits have accumulated in the intake passage 2.

[0045] Time t10 is the timing when the valve opening degree determination condition is met after a predetermined time T1 has elapsed since time t8. If deposits have accumulated in the intake passage 2, the control unit 8 determines that the throttle valve 3 is in the fully closed position at time t10. Time t10 is later than time t6, at which the control unit 8 determines that the throttle valve 3 is in the fully closed position if no deposits have accumulated in the intake passage 2.

[0046] When deposits have accumulated in the intake passage 2, if the output value from the throttle sensor 10 is constant for a second predetermined time T2 from time t10 when it is determined that the throttle valve 3 is in the fully closed position, the learning value update condition is met, and the output value of the throttle sensor 10 at the point when the second predetermined time T2 has elapsed from time t10 is learned as the learning value corresponding to the fully closed position of the throttle valve 3.

[0047] In this way, even if deposits have accumulated, the internal combustion engine 1 of the above-described embodiment can accurately determine the fully closed position of the throttle valve 3. Therefore, the internal combustion engine 1 can accurately learn the fully closed position of the throttle valve 3, and accurately control the opening of the throttle valve 3 based on the fully closed position of the throttle valve 3, thereby suppressing deterioration of fuel economy.

[0048] 3 is a flowchart showing the control flow of the embodiment described above. In step S1, it is determined whether or not the fully closed position learning conditions for the throttle valve 3 are met. If the fully closed position learning conditions for the throttle valve 3 are met in step S1, the routine proceeds to step S2. If the fully closed position learning conditions for the throttle valve 3 are not met in step S1, the current routine is terminated.

[0049] In step S2, the electric motor 6 is driven so that the throttle valve 3 is closed.

[0050] In step S3, it is determined whether the current supplied to the electric motor 6 has reached the current threshold value Thi. If it is determined in step S3 that the current supplied to the electric motor 6 has reached the current threshold value Thi, the process proceeds to step S4. If it is determined in step S3 that the current supplied to the electric motor 6 has not reached the current threshold value Thi, the process proceeds to step S2.

[0051] In step S4, it is determined whether a predetermined time T1 has elapsed since the current supplied to the electric motor 6 reached the current threshold value Thi. If in step S4 the predetermined time T1 has elapsed since the current supplied to the electric motor 6 reached the current threshold value Thi, the process proceeds to step S5. In step S5, it is determined that the opening of the throttle valve 3 has reached the fully closed position. In step S6, it is determined whether the output value of the throttle sensor 10 has not changed for a predetermined second predetermined time T2 since it was determined that the opening of the throttle valve 3 had reached the fully closed position. If in step S6 the output value of the throttle sensor 10 has not changed for the second predetermined time T2, the process proceeds to step S7. If in step S6 a change has been detected in the output value of the throttle sensor 10 for the second predetermined time T2, the process proceeds to step S8.

[0052] In step S7, learning of the fully closed position of the throttle valve 3 is performed. That is, in step S7, the current output value of the throttle sensor 10 is learned as a value corresponding to the fully closed position, and the current routine is terminated.

[0053] In step S8, the fully closed position learning of the throttle valve 3 is not performed. That is, in step S8, the fully closed position learning of the throttle valve 3 is not performed and the current routine is ended.

[0054] 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.

[0055] For example, the valve opening degree determination condition may be satisfied when the current supplied to the electric motor 6 becomes equal to or greater than a current threshold Thi (lock current value).

[0056] For example, the learning value update condition may be satisfied when the fluctuation range of the output value of the throttle sensor 10 is equal to or less than a predetermined value during a second predetermined time T2 after the valve opening degree determination condition is satisfied. Also, the learning value update condition may be satisfied when the current supplied to the electric motor 6 is equal to or greater than a current threshold Thi (lock current value).

[0057] The above-described embodiment relates to a control method for the internal combustion engine 1 and a control device for the internal combustion engine 1 .

Claims

1. A method for controlling an internal combustion engine, comprising: driving an electric motor that drives a throttle valve arranged in an intake passage so that the opening degree of the throttle valve is fully closed; and, when a current supplied to the electric motor becomes equal to or exceeds a predetermined current threshold and predetermined learning value update conditions are satisfied, learning an output value output from a throttle sensor that detects the opening degree of the throttle valve as an output value corresponding to the fully closed position of the throttle valve.

2. The method for controlling an internal combustion engine according to claim 1, wherein the learning value update condition is met when a preset predetermined time has elapsed since the current supplied to the electric motor became equal to or greater than the current threshold value.

3. The method for controlling an internal combustion engine according to claim 2, wherein the predetermined time is set to be longer than the pulse width of an inrush current flowing through the electric motor.

4. A control device for an internal combustion engine comprising: a throttle valve arranged in an intake passage; an electric motor for driving the throttle valve; a throttle sensor for detecting the opening degree of the throttle valve; and a control unit for controlling the electric motor, wherein the control unit learns the output value output from the throttle sensor as an output value corresponding to the fully closed position of the throttle valve when a current supplied to the electric motor becomes equal to or exceeds a predetermined current threshold value and predetermined learning value update conditions are satisfied.

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