JP2020169581A - Control device of internal combustion engine - Google Patents

Abstract

To provide a control device of an internal combustion engine which can surely set a valve at valve timing appropriate to a succeeding start time at a stop of the internal combustion engine.SOLUTION: In a control device of an internal combustion engine having a variable valve timing device (40) for changing the valve timing of an intake valve (22) or an exhaust valve (23) by using an electric motor (41), the control device performs a first operation (Q1) for mostly retarding the valve timing of the intake valve by carrying electricity to the electric motor according to an engine stop requirement of the internal combustion engine, or mostly advancing the valve timing of the exhaust valve, and a second operation (Q2) for mostly retarding the valve timing of the intake valve which is operated by the first operation by carrying electricity to the electric motor after the rotation of the internal has been completely stopped, or mostly advancing the valve timing of the exhaust valve which is operated by the first operation.SELECTED DRAWING: Figure 3

Description

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

In recent years, in internal combustion engines such as vehicle engines, variable valve timing devices that control the valve timing of intake valves and exhaust valves according to the operating state of the internal combustion engine have been installed for the purpose of high output, low fuel consumption, and low exhaust gas. ing. As the variable valve timing device, a device that hydraulically operates a valve using an oil pump driven by an internal combustion engine and a device that operates a valve by the power of an electric motor are known.

For example, as a technology using an electric variable valve timing device, a technology is proposed in which the valve timing of the intake valve is set to the slowest angle (the timing at which the opening and closing of the intake valve is the latest) by the power of the electric motor after the internal combustion engine is stopped. (For example, Patent Document 1). By setting the valve timing of the intake valve to the latest angle, it is possible to suppress the shock at the next start of the internal combustion engine. In the hydraulic variable valve timing device, the driving force is reduced as the engine rotation speed of the internal combustion engine decreases. Unlike this, in the electric variable valve timing device, when the internal combustion engine is stopped, the intake valve can be reliably set to the maximum retardation timing at an appropriate timing without being affected by the driving state of the internal combustion engine. it can.

Japanese Unexamined Patent Publication No. 2006-144567

In an internal combustion engine, when the fuel injection is stopped and the engine rotation is stopped, the rotation speed does not gradually decrease linearly to reach a complete stop, but the rotation speed fluctuates or reverse rotation due to the influence of the internal pressure fluctuation of the cylinder or the like. Behavior in the direction (movement such as swinging back) may occur. Due to such rotation fluctuation before complete stop, the set valve timing may shift.

For example, when the internal combustion engine is stopped, after the valve timing of the intake valve is set to the latest angle by the variable valve timing device, the intake valve may move to the advance side due to the rotation fluctuation remaining on the engine side. It was. Some hydraulic variable valve timing devices have a mechanism to hold them at the most retarded angle position, but electric variable valve timing devices have a deviation from the most retarded angle to the advance angle side as described above. It can occur. If such a valve timing shift occurs, the effects of shock suppression and improvement of startability at the next internal combustion engine start are impaired.

There is a similar problem when an electric variable valve timing device is provided on the exhaust valve side. For example, when the internal combustion engine is stopped, the valve timing of the exhaust valve is controlled to be the maximum angle, but the valve timing of the exhaust valve is on the retard side due to the rotation fluctuation before the engine is completely stopped. There is a risk of shifting to.

The present invention has been made in view of the above points, and an object of the present invention is to provide a control device for an internal combustion engine capable of reliably setting a valve at a valve timing suitable for the next start when the internal combustion engine is stopped.

The present invention is an internal combustion engine control device including a variable valve timing device that changes the valve timing of an intake valve or an exhaust valve by an electric motor, and energizes the electric motor to take in air in response to an engine stop request of the internal combustion engine. In the first operation of setting the valve timing of the valve to the latest or the valve timing of the exhaust valve to the maximum angle, and after the rotation of the internal combustion engine is completely stopped, the electric motor is energized and the first operation is performed. It is characterized by performing a second operation of setting the valve timing of the operated intake valve to the latest angle or setting the valve timing of the exhaust valve operated in the first operation to the maximum angle.

According to the present invention, it is possible to obtain an internal combustion engine control device that ensures that the intake valve and the exhaust valve are set to the valve timing suitable for the next start when the internal combustion engine is stopped.

It is a peripheral schematic diagram of the internal combustion engine of this embodiment. It is a control block diagram of the control device of the internal combustion engine of this embodiment. It is a figure which shows the relationship between the engine rotation when the internal combustion engine is stopped, and the intake valve control. It is a flowchart which shows the control operation when the internal combustion engine is stopped.

Hereinafter, the present embodiment will be described in detail with reference to the accompanying drawings. First, the components of the internal combustion engine of the present embodiment will be described with reference to FIGS. 1 and 2. In the following description, the configuration in which the technology of the present disclosure is applied to a vehicle will be described, but it can be applied to other vehicles in which an internal combustion engine is installed. Further, FIGS. 1 and 2 are simplified for convenience of explanation to explain the technique of the present disclosure, and it is assumed that the configuration normally provided by the vehicle is provided even if it is not shown.

As shown in FIG. 1, the internal combustion engine 1 mixes fuel with the air taken in through the intake passage 11 and burns it in the combustion chamber 12 to generate power, and exhaust gas after combustion is discharged through the exhaust passage 13. It is configured to be discharged to the outside. A throttle valve 15 is installed in the intake passage 11 to change the opening degree according to the amount of depression of the accelerator pedal 14. The amount of air sent into the combustion chamber 12 is adjusted according to the valve opening degree of the throttle valve 15. The amount of depression of the accelerator pedal 14 is detected by the accelerator position sensor 16.

The combustion chamber 12 is formed in a cylinder block 2 in which a cylinder and a crankcase are integrated. The cylinder head 3 provided on the upper part of the cylinder block 2 is formed with an intake port 20 communicating with the intake passage 11 and the combustion chamber 12 and an exhaust port 21 communicating with the exhaust passage 13 and the combustion chamber 12. As movable valves involved in intake and exhaust, an intake valve 22 that opens and closes between the intake port 20 and the combustion chamber 12 and an exhaust valve 23 that opens and closes between the exhaust port 21 and the combustion chamber 12 are installed.

The cylinder head 3 is provided with a port injector 17 that injects fuel into the intake port 20. The port injector 17 injects fuel according to the amount of depression of the accelerator pedal 14 in the intake stroke of the internal combustion engine 1. Although the port injector 17 is illustrated here, an in-cylinder injector may be installed in the cylinder to inject fuel in the compression stroke of the internal combustion engine 1. Further, the cylinder head 3 is provided with a spark plug 18 projecting from the upper part of the combustion chamber 12, and an ignition coil 19 is connected to the spark plug 18.

By opening the intake valve 22, the air-fuel mixture is sent to the combustion chamber 12 through the intake passage 11, the spark plug 18 is discharged by the high-voltage current of the ignition coil 19, and the air-fuel mixture in the combustion chamber 12 is ignited. The combustion of fuel pushes down the piston 25 in the cylinder block 2 at once, and the downward movement of the piston 25 is transmitted to the crankshaft 27 via the connecting rod 26. Then, the exhaust gas is discharged from the exhaust port 21 by opening the exhaust valve 23, and the air pollutants contained in the exhaust gas are purified by the catalyst device 28 installed in the exhaust passage 13.

An intake camshaft 30 and an exhaust camshaft 31 are provided corresponding to the intake valve 22 and the exhaust valve 23. The rotation of the crankshaft 27 is transmitted to the camshafts 30 and 31 via a cam chain (not shown). The rotation of the intake camshaft 30 causes the intake valve 22 to reciprocate toward the combustion chamber 12, and the rotation of the exhaust camshaft 31 causes the exhaust valve 23 to reciprocate toward the combustion chamber 12. .. In this way, the opening / closing operation of each of the intake valve 22 and the exhaust valve 23 is controlled.

A crank angle sensor 33 that measures the rotational state of the crankshaft 27 is installed in the cylinder block 2. Further, an intake cam angle sensor 34 for detecting the rotation angle of the intake camshaft 30 and an exhaust cam angle sensor 35 for detecting the rotation angle of the exhaust camshaft 31 are provided.

The internal combustion engine 1 includes a variable valve timing device 40 that changes the relative rotation phase of the intake camshaft 30 with respect to the crankshaft 27 to change the timing (valve timing) of the opening / closing operation of the intake valve 22. The variable valve timing device 40 uses an electric motor 41 (see FIG. 2) as a drive source, and the valve timing can be changed without relying on the power of an oil pump or the like provided in the internal combustion engine 1.

A signal is input to the ECU (Electrical Control Unit) 50 from each of the above sensors, and the ECU 50 controls the internal combustion engine 1 in an integrated manner. The ECU 50 is composed of a processor, a memory, and the like that execute various processes. The memory is composed of a storage medium such as a ROM (Read Only Memory) or a RAM (Random Access Memory) depending on the application. In addition to various parameters and various map information, the memory stores a program for causing the variable valve timing device 40 to execute the valve timing control operation of the intake valve 22.

As shown in FIG. 2, various sensors such as an accelerator position sensor 16, a crank angle sensor 33, an intake cam angle sensor 34, and an exhaust cam angle sensor 35 are connected to the input port of the ECU 50. Further, a brake pedal sensor 36 that detects the depressed state of the brake pedal (not shown), a vehicle speed sensor 37 that detects the speed of the vehicle, and an ignition switch 38 are connected to the input port of the ECU 50. The ignition switch 38 can select each of the off, on, and start states by the operation of the occupant of the vehicle.

In addition to the port injector 17 and the ignition coil 19 described above, the output port of the ECU 50 is connected to a control circuit of a starter 42 that forcibly rotates the crankshaft 27 when the internal combustion engine 1 is started. Further, the ECU 50 includes an energization control unit 51 that controls energization of the variable valve timing device 40 to the electric motor 41, and a current detection unit 52 that detects the amount of energization to the electric motor 41.

The start and stop of the internal combustion engine 1 are performed in response to the engine start request and the engine stop request to the ECU 50. When the ignition switch 38 is switched from off to on by the operation of the occupant, the power of the electrical system is turned on, and when the ignition switch 38 is switched to start, an engine start request is input. When the ignition switch 38 is switched from on to off while the internal combustion engine 1 is operating independently, an engine stop request is input. Further, when the ignition switch 38 is turned from on to off, a request for turning off the power of the electrical system is input.

The internal combustion engine 1 of the present embodiment can be automatically stopped and restarted according to the presence or absence of an output request, in addition to the above operation via the ignition switch 38. Whether or not there is an output request is determined based on the detected values of the accelerator position sensor 16, the brake pedal sensor 36, the vehicle speed sensor 37, and the like. When the internal combustion engine 1 is operating independently and the conditions such as no depression of the accelerator pedal 14, the brake pedal being depressed, and the vehicle speed being below a predetermined value (stopped) are satisfied, the vehicle is stopped. It is determined that it is in a state and it is not necessary to continue the engine drive (there is no output request), and an engine stop request is input. If the above conditions are not satisfied while the internal combustion engine 1 is stopped, it is determined that the engine needs to be driven (there is an output request), and an engine start request is input. Whether or not there is an output request is determined by the start / stop determination unit included in the ECU 50.

When the engine start request is input, the ECU 50 executes cranking by driving the starter 42, fuel injection from the port injector 17, and ignition of the spark plug 18 by energizing the ignition coil 19, and the internal combustion engine 1 becomes independent. Start operation. When the engine stop request is input, the ECU 50 ends the fuel injection from the port injector 17 and the energization of the ignition coil 19 (ignition of the spark plug 18), and stops the self-sustaining operation of the internal combustion engine 1.

When the internal combustion engine 1 is stopped by the engine stop request, the ECU 50 energizes the electric motor 41 via the energization control unit 51 to operate the variable valve timing device 40, and causes the valve timing of the intake valve 22 to be the latest. Control to make it. FIG. 3 shows the relationship between the engine rotation when the internal combustion engine 1 is stopped and the control of the intake valve 22.

FIG. 3A is a time chart showing changes in the rotation speed of the crankshaft 27 of the internal combustion engine 1, and the horizontal axis shows the passage of time. The vertical axis shows the rotation speed of the crankshaft 27, and the rotation speed decreases from the upper side to the lower side. At or immediately before the start of the time chart of FIG. 3A, an engine stop request is input and the above-mentioned engine stop control (stop of fuel injection from the port injector 17, stop of ignition of the spark plug 18) is executed. Has been done. In the present embodiment, the control stop stage in which the fuel injection is stopped by the engine stop request is set as the engine stop, the rotation of the crankshaft 27 is completely stopped, and the rotating portion of the internal combustion engine 1 is mechanically stopped. The stage is completely stopped.

In section T1 of FIG. 3A, the crankshaft 27, which is no longer supplied with power due to combustion in the combustion chamber 12 due to engine stop control, gradually reduces the number of revolutions per unit time while coasting. (Decelerate rotation). Although the deceleration of the crankshaft 27 in the inertial rotation is completed at the end of the section T1, the crankshaft 27 may further operate due to various mechanical factors, and this state is shown as the rotation fluctuation in the section T2.

When the rotation direction of the crankshaft 27 when the internal combustion engine 1 is driven is set to the forward rotation direction, in the section T2, a so-called swing-back operation occurs in which the crankshaft 27 rotates in the reverse direction and then returns to the normal rotation direction repeatedly. Causes of causing rotational fluctuations such as the swing-back operation include the influence of the weight of the piston 25, connecting rod 26, and the like, fluctuations in the internal pressure of the cylinder, and the like. When the rotational fluctuation converges, the crankshaft 27 is completely stopped (end of section T2). The operation of the crankshaft 27 in both the section T1 and the section T2 is detected by the crank angle sensor 33. That is, the ECU 50 can detect a complete stop of the internal combustion engine 1.

FIG. 3B is a time chart showing the position control of the intake valve 22 by the variable valve timing device 40 when the internal combustion engine 1 is stopped. Similar to FIG. 3 (A), the horizontal axis of FIG. 3 (B) shows the passage of time. The vertical axis in FIG. 3B shows the position of the intake valve 22, the lower end is the slowest angle, and the upper side is the advance angle side.

When the engine stop request is input, the ECU 50 energizes the electric motor 41 after a lapse of a predetermined time to operate the valve timing of the intake valve 22 to the retard side. This operation is referred to as the first retard angle operation Q1. The first retard angle operation Q1 causes the valve timing of the intake valve 22 to be the latest retard angle, and is the difference from the current position of the intake valve 22 detected by the intake cam angle sensor 34 to the latest retard angle. Is set as the target amount of retardation. Then, the amount of movement per unit time is increased so as to quickly change to the latest retard angle within the section T1 (the tilt angle of the first retard angle operation Q1 in FIG. 3B is made steep). The variable valve timing device 40 is made to operate to the retard side. In the first retard angle operation Q1, since the target retard angle amount is recognized, damage due to mechanical collision or electric motor when the most retard angle position is reached while performing high-speed operation to the retard angle side. Appropriate stop control of the electric motor 41 can be performed so that an excessive load of the 41 is not generated.

When the rotation fluctuation (swing back operation) of the crankshaft 27 occurs in the section T2, this rotation fluctuation is transmitted to the intake camshaft 30, and the intake valve 22 set to the latest retard angle in the first retard operation Q1 above. May shift to the advance side. The case where the deviation amount V occurs on the advance angle side is shown in FIG. 3 (B). The deviation amount V schematically shows the deviation amount toward the final advance angle side, and the actual behavior of the displacement of the intake valve 22 is a straight line in the section T2 of FIG. 3 (B). It may appear as a complicated position change different from that shown by the broken line. In this case, the position of the intake valve 22 at the end of the section T2 in which the internal combustion engine 1 is completely stopped is the final amount of deviation toward the advance angle side.

The control device for the internal combustion engine of the present embodiment ensures that the valve timing of the intake valve 22 is finally set to the latest angle even if the valve timing shifts to the advance angle side occurs in the section T2. .. That is, after the rotation of the internal combustion engine 1 is completely stopped, the variable valve timing device 40 causes the second retard angle operation Q2 to be performed.

Specifically, when the crank angle sensor 33 detects a complete stop of the crankshaft 27 (the end of the section T2), the ECU 50 energizes the electric motor 41 and causes the variable valve timing device 40 to operate to the retard side. The second retard angle operation Q2 is executed. At this time, if the deviation amount V is unknown, there is a problem that an accurate target retard angle amount for eliminating the deviation cannot be set. Therefore, in the second retard angle operation Q2, the movement amount per unit time is reduced (the inclination angle of the second retard angle operation Q2 in FIG. 3B is loosened), and the first retard angle operation is performed. Gradually move to the retard side at a slower operating speed than Q1. As a result, it is possible to prevent an excessive load from acting on the electric motor 41 when the most retarded angle position is reached and the mechanical moving end is reached.

If the electric motor 41 is continuously energized while the maximum retard angle is reached by the second retard angle operation Q2, the variable valve timing device 40 cannot perform any further operation due to mechanical restrictions. The amount of energization of is increased. The ECU 50 detects the amount of energization by the current detection unit 52, and when the drive current of the electric motor 41 is equal to or higher than a predetermined value, determines that the maximum retardation state of the intake valve 22 has been reached, and energizes the electric motor 41. Stop. As a result, the valve timing can be reliably set to the latest angle without providing a separate sensor or the like.

Subsequently, the control flow of the present embodiment will be described with reference to FIG. The flowchart of FIG. 4 shows an example and can be changed as appropriate. The control flow of FIG. 4 is started in a state where the internal combustion engine 1 is operating independently and the power of the electrical system such as the ECU 50 is turned on.

In step S1, it is determined whether or not an engine stop request for the internal combustion engine 1 is input. When the engine stop request is input (Yes in step S1), stop control is performed (step S2). This stop control includes stopping the fuel injection from the port injector 17, stopping the ignition of the spark plug 18 (energization of the ignition coil 19), and controlling the operation of the intake valve 22 to the latest angle by the variable valve timing device 40 ( The first retard angle operation Q1) shown in FIG. 3B is included. If the engine stop request is input by turning off the ignition switch 38 in step S1, the power off signal is also input. In this case, after setting the flag of "power off request", the process proceeds to step S2 without executing the power off.

In step S3, it is determined whether or not the rotation of the crankshaft 27 has stopped and the internal combustion engine 1 has been completely stopped by referring to the detection result of the crank angle sensor 33. The complete stop here is a state in which rotational fluctuations such as the swing-back operation in the section T2 of FIG. 3A are contained.

When the complete stop of the internal combustion engine 1 is detected (Yes in step S3), valve correction control for the intake valve 22 is performed (step S4). The valve correction control is performed by the variable valve timing device 40 in order to eliminate the deviation of the valve timing to the advance angle side (for example, the deviation amount V shown in FIG. 3B) that occurs before the internal combustion engine 1 is completely stopped. This is a control for re-operating to the retard angle position (second retard angle operation Q2 shown in FIG. 3B).

In step S5, in the valve correction control, it is determined whether or not the amount of energization of the variable valve timing device 40 to the electric motor 41 is equal to or greater than a predetermined value. When the amount of energization exceeds a predetermined value (Yes in step S5), it is determined that the latest retard angle has been reached, the energization of the electric motor 41 is stopped, and the control flow is exited.

Further, until the correction control is completed, it is continuously determined whether or not a power off signal due to the ignition switch 38 being turned off or the like is input (step S6). When the power off signal is input (Yes in step S6), the power of the electrical system is not turned off immediately, and the operation to the latest retard angle in the variable valve timing device 40 in the valve correction control (second retard angle operation Q2). ) Is continued, and the power is turned off after reaching the most retarded angle position (step S7). Although not clearly shown in FIG. 4, when the process proceeds to step S7, the maximum retard angle is determined by referring to the amount of electricity supplied to the electric motor 41 as in step S5. In this way, since the power is always turned off after the correction control is completed, it is possible to prevent the electric motor 41 from stopping when the valve timing of the intake valve 22 is not the most retarded angle. If the "power off request" flag is set when proceeding from step S1 to step S2, it is treated as if the power off signal was input in step S6.

As described above, according to the control device of the internal combustion engine of the present embodiment, even if the intake valve timing shifts to an unintended timing due to the rotation fluctuation immediately before the complete stop of the internal combustion engine 1, the latest retard angle is thereafter. Operate so that As a result, the valve timing can be always optimized at the next start of the internal combustion engine 1, and shock suppression at the next start can be surely realized.

The above embodiment is applied to the control for operating the intake valve at the latest angle when the internal combustion engine is stopped, but the present invention can also be applied to the operation control of the exhaust valve. Although detailed description of the control of the exhaust valve is omitted based on the illustration, the exhaust valve is controlled so that the relationship between the retard angle and the advance angle is opposite to that of the intake valve described above. That is, when the internal combustion engine is stopped, the exhaust valve is controlled so that the valve timing of the maximum advance angle is reached by the first advance operation, and the deviation to the retard side that occurs immediately before the complete stop of the rotation of the internal combustion engine is prevented. The exhaust valve is stopped in the state where it is surely set to the maximum advance angle by correcting it by the second advance angle operation.

Both the control of the intake valve to the retard side and the control of the exhaust valve to the advance side are common in that the valve overlap is reduced and the startability at the next start is improved. Therefore, in the present invention, after the rotation of the internal combustion engine is completely stopped, the valve timing (the most retarded angle for the intake valve and the most retarded angle for the exhaust valve) is suitable for the next start of the predetermined valve by the second (retard or advance) operation. It is covered by the technical idea of guaranteeing that the valve is at the most advanced angle.

The present invention is not limited to the above embodiment, and can be modified in various ways. In the above embodiment, the configuration, control, and the like shown in the accompanying drawings are not limited to this, and can be appropriately changed within the range in which the effects of the present invention are exhibited. In addition, it can be appropriately modified and implemented as long as it does not deviate from the scope of the object of the present invention.

In the above embodiment, the rotation detection of the internal combustion engine 1 is performed by the crank angle sensor 33, but the rotation detection may be performed by a means different from this. For example, since the rotation of the crankshaft 27 is transmitted to the intake camshaft 30 and the exhaust camshaft 31, it is possible to detect the rotation state of the internal combustion engine 1 by using the intake cam angle sensor 34 and the exhaust cam angle sensor 35. is there.

As described above, the present invention has an effect that the intake valve and the exhaust valve can be surely set to the valve timing suitable for the next start when the internal combustion engine is stopped, and in particular, highly accurate valve timing control is required. It is useful for internal combustion engines.

1: Internal combustion engine 12: Combustion chamber 14: Accelerator pedal 17: Port injector 18: Ignition plug 22: Intake valve 23: Exhaust valve 25: Piston 27: Crankshaft 30: Intake camshaft 31: Exhaust camshaft 33: Crank angle sensor 34: Intake cam angle sensor 35: Exhaust cam angle sensor 40: Variable valve timing device 41: Electric motor 50: ECU
51: Energization control unit 52: Current detection unit Q1: First retard angle operation (first operation)
Q2: Second retard angle operation (second operation)

Claims (4)

A control device for an internal combustion engine equipped with a variable valve timing device that changes the valve timing of the intake valve or exhaust valve by an electric motor.
The first operation of energizing the electric motor to set the valve timing of the intake valve to the latest angle or the valve timing of the exhaust valve to the maximum angle in response to the engine stop request of the internal combustion engine.
After the rotation of the internal combustion engine was completely stopped, the electric motor was energized to set the valve timing of the intake valve operated in the first operation to the latest angle, or to operate in the first operation. The second operation of setting the valve timing of the exhaust valve to the maximum angle and
A control device for an internal combustion engine, which is characterized by performing. The control device for an internal combustion engine according to claim 1, wherein in the second operation, the energization is stopped when the drive current of the electric motor is equal to or higher than a predetermined value. The control device for an internal combustion engine according to claim 1 or 2, wherein the operation speed of the second operation is slower than that of the first operation. The internal combustion engine according to any one of claims 1 to 3, wherein when a power-off signal is input during the second operation, the power-off is executed after the second operation is completed. Engine control device.

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