JP2008215303A - Control system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control system of an internal combustion engine for effectively cooling an exhaust valve in the case where temperature of the exhaust valve is high. <P>SOLUTION: The control system of the internal combustion engine includes: a catalyst provided in an exhaust duct 14 of the internal combustion engine 10; a valve control means which under metering of the internal combustion engine 10, holds both of an intake valve 36 and an exhaust valve 38 in a closed state; a temperature-obtaining means which measures or estimates temperature at a specified part of the internal combustion engine; and an exhaust-valve-cooling means which, in the case where under the motoring of the internal combustion engine, the temperature measured or estimated by the temperature-obtaining means has reached a specified value or higher, holds the intake valve 36 temporarily in an open state, and thereby makes fresh air flow in/out the cylinders over and over to cool the exhaust valve 38. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  Japanese Patent No. 3209046 discloses that in a hybrid vehicle in which an internal combustion engine and an electric motor (rotary electric machine) are mechanically connected, when the operation of the internal combustion engine is stopped and the vehicle runs only with the electric motor, that is, the internal combustion engine is in a motoring state. Therefore, in order to reduce drag loss of the internal combustion engine, a system is disclosed in which the pump loss of the internal combustion engine is reduced by fixing the intake valve in the closed state and the exhaust valve in the open state.

Japanese Patent No. 3209046

  When the internal combustion engine is operated at a high rotation and high load, the exhaust valve becomes hot. In the above-described conventional system, if the operation of the internal combustion engine is stopped when the exhaust valve is hot, fresh air is not drawn into the cylinder, so that the temperature of the exhaust valve does not decrease easily. When the operation of the internal combustion engine is resumed before the temperature of the exhaust valve is lowered, there is a problem that the high-temperature exhaust valve easily induces knocking.

  The above situation is the same for a hybrid vehicle of the type that can stop the rotation of the internal combustion engine when traveling with only the electric motor.

  Further, even in a normal vehicle that uses only an internal combustion engine as a drive source, in order to suppress deterioration of the exhaust purification catalyst, a vehicle that performs control to stop the intake valve or exhaust valve in a closed state during fuel cut during deceleration However, there is a problem similar to the above because the temperature of the exhaust valve is unlikely to decrease during fuel cut.

  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 that can effectively cool the exhaust valve when the exhaust valve is hot.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
Valve control means for holding both the intake valve and the exhaust valve closed during motoring of the internal combustion engine;
Temperature acquisition means for measuring or estimating the temperature of a predetermined portion of the internal combustion engine;
When the temperature measured or estimated by the temperature acquisition means at the time of the motoring is equal to or higher than a predetermined value, the intake valve is temporarily kept open so that fresh air is repeatedly entered and exited into the cylinder. An exhaust valve cooling means for cooling the exhaust valve;
It is characterized by providing.

The second invention is the first invention, wherein
The exhaust valve cooling means closes the intake valve near top dead center after temporarily holding the intake valve in an open state.

The third invention is the first or second invention, wherein
The motoring is during engine braking,
It further comprises engine brake control means for controlling the lift amount of the intake valve when the exhaust valve cooling means holds the intake valve temporarily in an open state in accordance with the degree of engine brake demand. To do.

The fourth invention is a control device for an internal combustion engine,
A hybrid system of an internal combustion engine and an electric motor, the hybrid system capable of stopping the rotation of the internal combustion engine when operating the electric motor and stopping the combustion of the internal combustion engine;
Temperature acquisition means for measuring or estimating the temperature of a predetermined portion of the internal combustion engine;
When the temperature measured or estimated by the temperature acquisition means is equal to or higher than a predetermined value when the combustion of the internal combustion engine is stopped, the intake valve, the exhaust valve, and the piston are expanded so that the air confined in the cylinder expands. An exhaust valve cooling means for cooling the exhaust valve by controlling a movement and utilizing a temperature decrease when the air in the cylinder expands;
It is characterized by providing.

The fifth invention is the fourth invention, wherein
The exhaust valve cooling means includes
Exhaust valve control means for holding the exhaust valve in a closed state;
An intake valve control means for opening the intake valve once and closing it near the top dead center, and holding the closed state;
Piston position control means for holding for a predetermined time in a state where the piston is moved to near the bottom dead center after the intake valve is closed near the top dead center;
It is characterized by including.

The sixth invention is the fifth invention, wherein
The exhaust valve cooling means repeatedly executes a control operation by the intake valve control means and the piston position control means for a plurality of cycles with a predetermined time interval.

According to a seventh invention, in any one of the first to sixth inventions,
The predetermined portion is the exhaust valve.

Further, an eighth invention is any one of the first to seventh inventions,
A catalyst is provided in the exhaust passage of the internal combustion engine.

  According to the first aspect of the present invention, it is possible to reliably prevent leakage of fresh air into the exhaust passage during motoring of the internal combustion engine, and the temperature of the predetermined portion measured or estimated during motoring is equal to or higher than a predetermined value. In this case, by temporarily holding the intake valve in the open state, the fresh air can repeatedly enter and exit the cylinder to cool the exhaust valve. For this reason, when the exhaust valve is hot, the temperature of the exhaust valve can be effectively lowered while preventing leakage of fresh air into the exhaust passage. As a result, after the combustion of the internal combustion engine is resumed, knocking can be reliably prevented from being induced by the exhaust valve.

  According to the second invention, when the exhaust valve is cooled, the intake valve can be closed near the top dead center after the intake valve is temporarily kept open. As a result, it is possible to reliably prevent high-pressure air from being blown back from the inside of the cylinder to the intake manifold when the intake valve is opened next time, so that generation of abnormal noise and vibration can be prevented.

  According to the third aspect of the invention, when the exhaust valve is cooled during engine braking, the lift amount of the intake valve when the intake valve is temporarily kept open is controlled according to the engine brake request level. be able to. As a result, the engine braking force in accordance with the driver's expectation can be generated, and excellent drivability can be obtained.

  According to the fourth invention, when the temperature of the predetermined portion measured or estimated at the time of stopping the combustion of the internal combustion engine in the hybrid system is equal to or higher than a predetermined value, the air confined in the cylinder expands. By controlling the movements of the intake valve, the exhaust valve, and the piston, the exhaust valve can be cooled by utilizing the temperature drop when the in-cylinder air expands. For this reason, when the exhaust valve is hot, the temperature of the exhaust valve can be effectively lowered while preventing leakage of fresh air into the exhaust passage. As a result, after the combustion of the internal combustion engine is resumed, knocking can be reliably prevented from being induced by the exhaust valve. In particular, according to the fourth aspect of the invention, the in-cylinder air temperature can be made significantly lower than the outside air temperature, so that the exhaust valve can be cooled with high efficiency.

  According to the fifth aspect of the invention, when cooling the exhaust valve, the exhaust valve is held in a closed state, and the intake valve is temporarily opened, closed near the top dead center, and then held closed, while the piston is bottom dead. The piston position can be held for a predetermined time while being moved to the vicinity of the point. Thereby, the temperature drop due to the expansion of the in-cylinder air can be utilized with higher efficiency, and the temperature of the exhaust valve can be lowered quickly.

  According to the sixth aspect of the invention, the control operation during cooling of the exhaust valve can be repeatedly executed for a plurality of cycles with a predetermined time interval. Thereby, the temperature of the exhaust valve can be sufficiently lowered.

  According to the seventh aspect, the temperature of the exhaust valve is estimated or detected, and when the estimated or detected exhaust valve temperature is equal to or higher than a predetermined temperature, the control for cooling the exhaust valve can be executed. According to the seventh aspect, since it is possible to determine whether or not the exhaust valve cooling control needs to be executed according to the temperature of the exhaust valve itself, the exhaust valve cooling control can be executed without excess or deficiency.

  According to the eighth invention, it is possible to reliably prevent fresh air from flowing into the exhaust passage and flowing into the catalyst during motoring of the internal combustion engine. For this reason, deterioration of a catalyst can be suppressed reliably.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram showing a system configuration according to Embodiment 1 of the present invention. The system shown in FIG. 1 includes an internal combustion engine 10. It is assumed that the internal combustion engine 10 is mounted on a vehicle. The internal combustion engine 10 of this embodiment is of an in-line four cylinder type, and FIG. 1 shows a cross section of one of the cylinders.

  An intake passage 12 and an exhaust passage 14 communicate with the internal combustion engine 10. The intake passage 12 includes an air filter 16 at an upstream end. An air flow meter 20 that detects the amount of air flowing through the intake passage 12 is disposed on the downstream side of the air filter 16.

  A throttle valve 22 is provided on the downstream side of the air flow meter 20. In the vicinity of the throttle valve 22, a throttle position sensor 24 for detecting the throttle opening degree TA is disposed. A surge tank 28 is provided downstream of the throttle valve 22. Downstream of the surge tank 28, the intake passage 12 is divided into the number of cylinders and connected to each cylinder.

  Each cylinder of the internal combustion engine 10 is provided with a fuel injector 30 that injects fuel into the combustion chamber (inside the cylinder). The fuel injector 30 may be arranged so as to inject fuel into the intake port. On the other hand, a catalyst 32 for purifying exhaust gas is installed in the middle of the exhaust passage 14.

  Each cylinder is provided with an intake valve 36 and an exhaust valve 38. The internal combustion engine 10 includes an intake variable valve operating device 48 that drives the intake valve 36 and an exhaust variable valve operating device 50 that drives the exhaust valve 38.

  Each cylinder is provided with a spark plug (not shown) for igniting the air-fuel mixture in the combustion chamber. Further, a piston 44 that reciprocates inside the cylinder is provided in the cylinder.

  The system of this embodiment further includes an ECU (Electronic Control Unit) 40. In addition to the various sensors described above, the ECU 40 is connected to a crank angle sensor 70 that detects the rotation angle of the crankshaft, and the actuators such as the fuel injector 30, the intake variable valve operating device 48, and the exhaust variable valve operating device 50 described above. Has been.

  FIG. 2 is a diagram showing a configuration of the intake variable valve operating apparatus 48 included in the system shown in FIG. Hereinafter, the intake variable valve operating device 48 will be further described with reference to FIG.

  As shown in FIG. 2, the internal combustion engine 10 includes two intake valves 36 per cylinder. The internal combustion engine 10 includes four cylinders (# 1 to # 4) as described above, and combustion is performed in the order of # 1 → # 3 → # 4 → # 2. The intake variable valve operating device 48 includes two devices, that is, an intake variable valve operating device 48A and an intake variable valve operating device 48B. The intake variable valve operating device 48A drives the intake valves 36 of the # 2 cylinder and # 3 cylinder, and the intake variable valve operating device 48B drives the intake valves 36 of the # 1 cylinder and # 4 cylinder.

  The intake variable valve operating device 48A includes a motor 54A, a gear train 56A for transmitting the rotational motion of the motor 54A, and a cam shaft 58A having a cam 62 for lifting the intake valve 36. Similarly, the intake variable valve operating device 48B includes a motor 54B, a gear train 56B, and a camshaft 58B.

  The motors 54A and 54B are servo motors capable of controlling the rotation speed and the rotation angle, respectively. For example, a DC brushless motor or the like is preferably used as the motors 54A and 54B. The motors 54A and 54B incorporate rotation angle detection sensors such as a resolver and a rotary encoder for detecting the rotation position (rotation angle). The ECU 40 feedback-controls the operation of the motors 54A and 54B so that the rotation speed and rotation angle of the motors 54A and 54B detected by the rotation angle detection sensor coincide with the target value.

  The camshaft 58A is disposed above the intake valves 36 of the # 2 and # 3 cylinders. The cam shaft 58A has a hollow shape. On the other hand, the camshaft 58B is arranged in the upper part of the intake valves 36 of the # 1 and # 4 cylinders in a state of being divided into two. The camshaft 58B divided into two is connected via a connecting shaft inserted through the hollow portion of the camshaft 58A, and is configured to rotate integrally. Cam drive gears 60A and 60B are installed on the camshafts 58A and 58B, respectively.

  The gear train 56A transmits the rotation of the motor gear 64A attached to the output shaft of the motor 54A to the cam drive gear 60A via the intermediate gear 66A, thereby rotating the cam shaft 58A. Similarly, the gear train 56B transmits the rotation of the motor gear 64B attached to the output shaft of the motor 54B to the cam drive gear 60, thereby rotating the cam shaft 58B.

  FIG. 3 is a schematic diagram showing how the intake valve 36 is driven by the cam 62. The cam 62 is opposed to a tappet 68 installed at the valve shaft end of the intake valve 36. The intake valve 36 is biased toward the cam 62 by a valve spring (not shown). When the base circle portion 62b of the cam 62 faces the tappet 68, the intake valve 36 is brought into close contact with the valve seat formed in the intake port by the biasing force of the valve spring, and the intake valve 36 is closed. On the other hand, when the vicinity of the nose 62a of the cam 62 faces the tappet 68 and depresses the tappet 68, the intake valve 36 is lifted and opened.

  3A and 3B show two drive modes of the cam 62. FIG. FIG. 3A shows a normal rotation drive mode in which the cam 62 is rotated in one direction. FIG. 3B shows a swing drive mode in which the cam 62 swings. In the swing drive mode, the intake valve 36 is closed by reversely rotating the cam 62 before the intake valve 36 reaches the maximum lift.

  In such an intake variable valve operating device 48, the rotational speed and rotational angle of the motors 54A and 54B are controlled in relation to the crank angle, so that the opening timing and closing timing of the intake valve 36 of each cylinder are set to arbitrary timings. Can be controlled. Further, in the swing drive mode, the maximum lift amount of the intake valve 36 can be arbitrarily controlled by the cam 62 controlling the swing angle.

  Therefore, according to the intake variable valve operating device 48, it is possible to drive the intake valve 36 with the optimum operating angle and lift amount according to the operating state. FIG. 4 is a schematic diagram showing the relationship between the engine speed and load (torque) of the internal combustion engine 10 and the drive mode of the cam 62. As shown in FIG. 4, the drive mode of the cam 62 is selectively used in association with the engine speed and the load. Basically, the swing drive mode is selected in the low rotation range, and the normal rotation drive mode is selected in the high rotation range. The operating angle and lift amount of the intake valve 36 are reduced in the low rotation range, and the operating angle and lift amount of the intake valve 36 are increased in the high rotation range. As a result, it is possible to send an optimal amount of air corresponding to the engine speed and load into the cylinder.

  Further, according to the intake variable valve operating device 48, the rotation of the motors 54A and 54B is stopped, and the rotation of the camshafts 58A and 58B is stopped, thereby stopping (pausing) the operation of the intake valves 36 of the respective cylinders. be able to.

  FIG. 5 is a view showing two cams 62 provided on the camshaft 58A. As shown in FIG. 5, the cam shaft 58A has a cam 62 for driving the intake valve 36 for the # 2 cylinder and a cam 62 for driving the intake valve 36 for the # 3 cylinder at an angle of 180 °. The positions are separated from each other. Therefore, when the rotation of the camshaft 58A is stopped in a state where the straight line connecting the nose 62a of the cam 62 for the # 2 cylinder and the nose 62a of the cam 62 for the # 3 cylinder is substantially parallel to the upper surface of the tappet 68. The # 2 cylinder intake valve 36 and the # 3 cylinder intake valve 36 can be stopped in a closed state.

  On the other hand, although not shown, the cam 62 for driving the intake valve 36 of the # 1 cylinder and the cam 62 for driving the intake valve 36 of the # 4 cylinder are also 180 °, not shown. They are spaced apart by an angular position. Therefore, when the rotation of the camshaft 58B is stopped in a state where the straight line connecting the nose 62a of the cam 62 for the # 1 cylinder and the nose 62a of the cam 62 for the # 4 cylinder is substantially parallel to the upper surface of the tappet 68. The # 1 cylinder intake valve 36 and the # 4 cylinder intake valve 36 can be stopped in a closed state. Therefore, according to the intake variable valve operating device 48, the intake valves 36 of all the cylinders can be stopped in the closed state.

  Although the intake variable valve operating device 48 has been described above, the exhaust variable valve operating device 50 also has substantially the same configuration as the intake variable valve operating device 48. For this reason, detailed illustration and description of the variable exhaust valve operating device 50 are omitted. Further, according to the variable exhaust valve operating device 50, the exhaust valves 38 of all the cylinders can be stopped in the closed state in the same manner as the variable intake valve operating device 48.

[Features of Embodiment 1]
(Intake and exhaust valve stop control when fuel is cut)
In the system of the present embodiment, a fuel cut that stops fuel injection from the fuel injector 30 is executed during engine braking, that is, when the internal combustion engine 10 is decelerated. When the intake valve 36 and the exhaust valve 38 are operated normally during the fuel cut, fresh air (air) flows through the exhaust passage 14 as it is. The catalyst 32 has a property that the deterioration proceeds when exposed to air at a high temperature. For this reason, when the intake valve 36 and the exhaust valve 38 are operated normally during fuel cut, there is a problem that fresh air flows into the catalyst 32 and the catalyst 32 is likely to deteriorate.

  Therefore, in the present embodiment, when the fuel is cut, the operations of the intake variable valve operating device 48 and the exhaust variable valve operating device 50 are controlled so that both the intake valve 36 and the exhaust valve 38 are stopped in a closed state. . Thereby, since both the intake valve 36 and the exhaust valve 38 are kept closed when the fuel is cut, it is possible to prevent fresh air from flowing into the exhaust passage 14. For this reason, deterioration of the catalyst 32 can be sufficiently suppressed.

  In particular, in this embodiment, since both the intake valve 36 and the exhaust valve 38 are kept closed when the fuel is cut, it is possible to reliably prevent fresh air from flowing into the catalyst 32. That is, when only one of the intake valve 36 and the exhaust valve 38 is kept closed and the operation of the other is not stopped, it is difficult to completely prevent leakage of fresh air into the exhaust passage 14. . On the other hand, in the present embodiment, since both the intake valve 36 and the exhaust valve 38 are kept closed when the fuel is cut, leakage of fresh air to the exhaust passage 14 can be extremely reliably prevented. Therefore, deterioration of the catalyst 32 can be reliably suppressed.

  Further, according to the present embodiment, it is possible to prevent leakage of fresh air to the exhaust passage 14 without closing the throttle valve 22 when the fuel is cut. For this reason, since a large negative pressure does not act in the cylinder, it is possible to reliably prevent the oil from rising or falling. Therefore, the oil consumption of the internal combustion engine 10 does not increase.

(Exhaust valve cooling control during fuel cut)
When the internal combustion engine 10 is operated at a high rotation and high load, the exhaust valve 38 becomes high temperature. If the exhaust valve 38 is hot, knocking is likely to be induced. In the present embodiment, as described above, since the intake valve 36 and the exhaust valve 38 are kept closed during the fuel cut, the exhaust valve 38 does not come into contact with fresh air, and the exhaust valve 38 is not easily cooled. For this reason, when the exhaust valve 38 is hot, knocking is likely to occur when the fuel injection is resumed after the fuel cut is resumed.

  In order to prevent the occurrence of knocking as described above, in the present embodiment, when it is estimated that the exhaust valve 38 is hot during fuel cut, the intake valve 36 is temporarily kept open to newly The exhaust valve cooling control for cooling the exhaust valve 38 by repeatedly letting the gas in and out of the cylinder is performed.

  FIG. 6 is a diagram schematically showing the internal combustion engine 10 during execution of the exhaust valve cooling control in the present embodiment. As shown in FIG. 6, when the exhaust valve cooling control is executed, the intake valve 36 is temporarily kept open, so that fresh air in the intake passage 12 repeatedly enters the cylinder as the piston 44 moves up and down. Go out. As a result, the exhaust valve 38 is efficiently cooled by fresh air, and the temperature of the exhaust valve 38 can be quickly reduced. For this reason, it is possible to reliably prevent knocking from being induced by the exhaust valve 38 when returning from the fuel cut and restarting the fuel injection.

  Further, since the exhaust valve 38 is always kept closed when the exhaust valve cooling control is executed, the leakage of fresh air into the exhaust passage 14 can be sufficiently prevented even if the intake valve 36 is temporarily opened. it can. Further, since the exhaust valve cooling control is executed only when the exhaust valve 38 is estimated to be at a high temperature, leakage of fresh air to the exhaust passage 14 can be minimized. For this reason, according to the present embodiment, the deterioration of the catalyst 32 can be reliably suppressed.

  FIG. 7 is a view showing a valve opening period of the intake valve 36 of each cylinder when the exhaust valve cooling control is executed in the present embodiment. As shown in FIG. 7, in the present embodiment, the intake valve 36 is temporarily held open for each cylinder of the internal combustion engine 10 when the exhaust valve cooling control is executed. Therefore, the exhaust valve 38 of each cylinder can be cooled without variation.

  In the example shown in FIG. 7, the exhaust valve cooling control of each cylinder is performed in the order of # 1 → # 3 → # 4 → # 2 as in the explosion order. However, because of the structure of the intake variable valve operating device 48, the # 1 and # 4 cylinder intake valves 36 sharing the camshaft 58B cannot be opened at the same time. Therefore, after the # 1 cylinder intake valve 36 is closed, # The four-cylinder intake valve 36 is opened. Similarly, the # 3 and # 2 cylinder intake valves 36 sharing the camshaft 58A cannot be opened at the same time, so the # 2 cylinder intake valve 36 is opened after the # 3 cylinder intake valve 36 is closed. ing. As shown in FIG. 7, it is possible to simultaneously open the intake valve 36 of the # 1 or # 4 cylinder and the intake valve 36 of the # 3 or # 2 cylinder.

  Further, in the exhaust valve cooling control shown in FIG. 7, the intake valve 36 of each cylinder is kept open over a period of 720 ° in crank angle, but this period may be longer.

  Further, in the exhaust valve cooling control shown in FIG. 7, when the intake valve 36 that is temporarily kept open is closed, the intake valve 36 is closed near the top dead center (TDC). Thereby, when the intake valve 36 is opened next (when returning to normal operation), it is possible to reliably prevent high-pressure air from being injected back into the intake manifold (intake passage 12) from the inside of the cylinder.

  On the other hand, unlike the present embodiment, if the intake valve 36 is closed near the bottom dead center (BDC) in the exhaust valve cooling control as usual, the exhaust valve 38 is held in the closed state. The air trapped in is repeatedly compressed, and then when the intake valve 36 is opened, high-pressure air is jetted back from the cylinder to the intake manifold. At that time, there is a risk that abnormal noise or vibration may occur.

[Specific Processing in Embodiment 1]
FIG. 8 is a flowchart of a routine executed by the ECU 40 in the present embodiment in order to realize the above function. This routine is repeatedly executed every predetermined time.

  According to the routine shown in FIG. 8, when the accelerator pedal is turned off, the fuel cut is executed, and the valve stop control for stopping both the intake valve 36 and the exhaust valve 38 in the closed state is executed (step 100).

  Subsequently, processing for estimating the temperature of the exhaust valve 38 from the operation history of the internal combustion engine 10 is executed (step 102). Specifically, the estimated temperature of the exhaust valve 38 is calculated according to a predetermined calculation method stored in advance based on the history of the fuel injection amount, the accelerator opening, the engine speed NE, etc. in the past predetermined time.

  Next, it is determined whether or not the temperature of the exhaust valve 38 calculated in step 102 is equal to or higher than a reference value (step 104). As a result of the determination, if the temperature of the exhaust valve 38 does not exceed the reference value, it can be determined that there is no possibility that the exhaust valve 38 will induce knocking. Therefore, in this case, the routine processing is immediately terminated without executing the exhaust valve cooling control.

  On the other hand, if it is determined in step 104 that the temperature of the exhaust valve 38 is equal to or higher than the reference value, it can be determined that the exhaust valve 38 may induce knocking. Therefore, in this case, exhaust valve cooling control is executed to reduce the temperature of the exhaust valve 38 (step 106). Since the contents of the exhaust valve cooling control are as described above, the description thereof is omitted here.

  Subsequently, it is determined whether or not the valve stop control is still continued (step 108). As a result of the determination, when the valve stop control is continued, the processing from step 102 onward is executed again. In this case, in step 102, the estimated temperature of the exhaust valve 38 is calculated again in consideration of the number of executions of the exhaust valve cooling control.

  As described above, according to the routine processing shown in FIG. 8, the exhaust valve cooling control can be repeatedly executed until the temperature of the exhaust valve 38 falls below the reference value. For this reason, it is possible to reliably prevent the exhaust valve 38 from inducing knocking after returning from the fuel cut and restarting the fuel injection.

  By the way, when the exhaust valve cooling control is executed, the strength of the engine brake changes according to the lift amount of the intake valve 36 that is temporarily kept open. That is, as the lift amount of the intake valve 36 is smaller, the ventilation resistance in the vicinity of the intake valve 36 is increased and the pumping loss is increased, so that the engine brake is strongly applied. Therefore, in the present embodiment, control is performed so that the lift amount of the intake valve 36 when the exhaust valve cooling control is executed is smaller as the required level is higher in accordance with the required engine brake level from the driver. Also good. As a result, the engine braking force in accordance with the driver's expectation can be generated, and excellent drivability can be obtained. The engine brake request level can be determined based on the shift position of the transmission.

  In the first embodiment described above, the temperature of the exhaust valve 38 is estimated from the operation history, but the temperature of the exhaust valve 38 may be detected by a temperature sensor. Further, the temperature of a part other than the exhaust valve 38, which has a correlation with the temperature of the exhaust valve 38, is estimated or detected, and the necessity of executing the exhaust valve cooling control is determined based on the temperature. May be.

  Further, in the first embodiment described above, the case where the exhaust valve cooling control is performed at the time of the deceleration fuel cut of the internal combustion engine 10 has been described. However, in the present invention, the internal combustion engine 10 is in the motoring state even when the deceleration fuel cut is not performed. In such a situation, the same exhaust valve cooling control can be performed. For example, in a hybrid vehicle having an electric motor that is mechanically connected to the internal combustion engine 10, exhaust valve cooling control is performed during motoring of the internal combustion engine 10 when the operation of the internal combustion engine 10 is stopped and only the electric motor is running. You may do it.

  In addition, the variable valve apparatus in the first embodiment described above is configured to drive the camshaft with a motor, but the variable valve apparatus in the present invention is not limited to this, for example, It can also be set as the structure using an electromagnetically driven valve.

  In the first embodiment described above, the ECU 40 executes the process of step 100, so that the “valve control means” in the first invention executes the process of step 102. The “temperature acquisition means” in the present invention executes the processing of step 106, so that the “exhaust valve cooling means” in the first invention determines the lift amount of the intake valve 36 during the exhaust valve cooling control as an engine brake request. The “engine brake control means” in the third aspect of the present invention is realized by controlling according to the degree.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. 9. The description will focus on the differences from the first embodiment described above, and the same matters will be simplified or described. Omitted.

[Description of system configuration]
FIG. 9 is a diagram for explaining a system configuration according to the second embodiment of the present invention. In FIG. 9, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  The system of this embodiment shown in FIG. 9 is a hybrid system that can drive the drive shaft 82 of the vehicle by combining the output of the internal combustion engine 10 and the output of the first motor generator 80. This hybrid system further includes a first motor generator 80, a power distribution and integration mechanism 84, a second motor generator 86, an inverter 88, and a battery 90 in addition to the system shown in FIG.

  Each of the first motor generator 80 and the second motor generator 86 is configured as a known synchronous generator motor that can be driven as a generator and can be driven as an electric motor. The power distribution and integration mechanism 84 is composed of a planetary gear mechanism. The sun gear of the power distribution and integration mechanism 84 is connected to the second motor generator 86. The planetary carrier of the power distribution and integration mechanism 84 is connected to the crankshaft of the internal combustion engine 10. The ring gear of the power distribution and integration mechanism 84 is connected to the first motor generator 80 and is also connected to the drive shaft 82 of the vehicle via the transfer 92.

  During operation of the internal combustion engine 10, the power of the internal combustion engine 10 is divided into two by the power distribution and integration mechanism 84 and transmitted to the drive shaft 82 and the second motor generator 86, respectively. Further, the power of the first motor generator 80 is also transmitted to the drive shaft 82.

  In the present hybrid system, the internal combustion engine 10 drives the second motor generator 86 to generate electric power, and the generated electric power can be charged to the battery 90 via the inverter 88. Further, by supplying the electric energy stored in the battery 90 to the first motor generator 80 via the inverter 88, the first motor generator 80 can be operated as an electric motor. The first motor generator 80 can also be operated as an electric motor by supplying the electric power generated by the second motor generator 86 to the first motor generator 80 via the inverter 88. Further, when the vehicle is decelerated, the first motor generator 80 is operated as a generator by the power transmitted from the drive shaft 82, and the generated electric power is charged into the battery 90 via the inverter 88 to recover braking energy. be able to.

  In the present hybrid system, it is possible to stop the combustion of the internal combustion engine 10 and travel only with the power of the first motor generator 80. When the combustion of the internal combustion engine 10 is stopped during traveling, the rotation of the internal combustion engine 10 can be stopped. When the internal combustion engine 10 is restarted, the internal combustion engine 10 can be cranked and started by operating the second motor generator 86 as an electric motor.

[Features of Embodiment 2]
In the system of the present embodiment, when the accelerator of the vehicle is turned off, the combustion of the internal combustion engine 10 is stopped and the rotation of the internal combustion engine 10 is stopped. In the present embodiment, when the temperature of the exhaust valve 38 is equal to or higher than a reference value while the internal combustion engine 10 is stopped, the second motor generator 86 is operated as an electric motor and the internal combustion engine 10 is motored. The intake valve 36 and the exhaust valve 38 are controlled in the same manner as in the first embodiment, and the same exhaust valve cooling control is performed. Thereby, it is possible to reliably prevent knocking from being induced by the exhaust valve 38 after the internal combustion engine 10 is restarted.

  Since the second embodiment is the same as the first embodiment except for the above points, further description is omitted here.

Embodiment 3 FIG.
Next, the third embodiment of the present invention will be described with reference to FIG. 10 and FIG. 11. The difference from the above-described embodiment will be mainly described, and the description of the same matters will be simplified. Or omit.

  The system configuration of this embodiment is the same as that of the hybrid system of the second embodiment described above. In the present embodiment, as in the second embodiment, when the accelerator of the vehicle is turned off, the combustion of the internal combustion engine 10 is stopped and the rotation of the internal combustion engine 10 is stopped. When the temperature of the exhaust valve 38 is equal to or higher than a reference value while the internal combustion engine 10 is stopped, exhaust valve cooling control as described below is executed.

  FIG. 10 is a diagram schematically showing the internal combustion engine 10 during execution of the exhaust valve cooling control in the present embodiment. In the exhaust valve cooling control of the present embodiment, after the intake valve 36 is opened once and the air in the cylinder is exhausted, the piston 44 is raised with both the intake valve 36 and the exhaust valve 38 closed as shown in FIG. Move from dead center to bottom dead center. Thereby, the air confined in the cylinder is adiabatically expanded.

  When the air in the cylinder is adiabatically expanded in this manner, the temperature of the air greatly decreases. For example, when the compression ratio of the internal combustion engine 10 is ε = 12.5 and the initial temperature of the in-cylinder air is 20 ° C., the in-cylinder air temperature after adiabatic expansion is theoretically −166 ° C. Thus, in this embodiment, since the in-cylinder air temperature can be set to a temperature that is significantly lower than the outside air temperature, the exhaust valve 38 can be cooled with high efficiency.

  FIG. 11 is a diagram showing a valve opening period of the intake valve 36 of each cylinder when the exhaust valve cooling control is executed in the present embodiment. Hereinafter, the exhaust valve cooling control of the present embodiment will be described in more detail with reference to FIG. In the exhaust valve cooling control of the present embodiment, the ECU 40 controls the position of the piston 44 of each cylinder by controlling the rotation angle of the second motor generator 86.

  During execution of the exhaust valve cooling control, the exhaust valve 38 is always kept closed. On the other hand, as shown in FIG. 11, the intake valve 36 of the # 1 cylinder is first opened, and at the timing when the pistons 44 of the # 1 and # 4 cylinders are near top dead center, the intake valve 36 of the # 1 cylinder is Closed. As a result, most of the air in the # 1 cylinder is discharged to the intake passage 12, and only an amount of air that corresponds to the volume of the combustion chamber under atmospheric pressure remains in the # 1 cylinder. Subsequently, after the intake valve 36 of the # 4 cylinder is once opened, the crankshaft rotates once and the piston 44 of the # 1 and # 4 cylinders again returns to the vicinity of the top dead center. Valve 36 is closed. As a result, most of the air in the # 4 cylinder is discharged to the intake passage 12, and only an amount of air that corresponds to the volume of the combustion chamber under atmospheric pressure remains in the # 1 cylinder. While the crankshaft makes one rotation as described above, the air in the # 1 cylinder is once expanded and then compressed and returned to the original state.

  As described above, most of the air in the # 1 and # 4 cylinders is discharged to the intake passage 12, and a slight amount of air remains in the # 1 and # 4 cylinders. From this state, the pistons 44 of the # 1 and # 4 cylinders are moved to near the bottom dead center to adiabatically expand the air in both cylinders, and then the rotation of the crankshaft is stopped and held for a predetermined time. During this time, the exhaust valves 38 of the # 1 and # 4 cylinders are cooled by the in-cylinder air that has become low temperature due to expansion.

  If the piston 44 is stopped in a state where the in-cylinder air has a large negative pressure due to adiabatic expansion, gas leaks into the cylinder through the gaps between the parts, and the negative pressure in the cylinder is, for example, about 10 to 15 seconds. Decrease. For this reason, the predetermined time, that is, the time for holding the piston 44 in the vicinity of the bottom dead center after adiabatic expansion, is suitably about several seconds, for example.

  After the elapse of the predetermined time, as shown in FIG. 11, the exhaust valve cooling control is similarly executed for the # 2 and # 3 cylinders, and the exhaust valves 38 of the # 2 and # 3 cylinders are cooled.

  In the exhaust valve cooling control of the present embodiment, the operation shown in FIG. 11 may be set as one cycle, and this cycle may be repeated a plurality of cycles as necessary.

  As described above, according to the exhaust valve cooling control of the present embodiment, the in-cylinder air temperature can be made significantly lower than the outside air temperature, so that the exhaust valve 38 can be cooled with high efficiency. For this reason, it is possible to reliably prevent the exhaust valve 38 from inducing knocking after the internal combustion engine 10 is restarted. Further, the exhaust valve 38 is always kept closed during execution of the exhaust valve cooling control, so that fresh air can be reliably prevented from flowing into the catalyst 32. For this reason, deterioration of the catalyst 32 can be reliably suppressed.

  Furthermore, in the present embodiment, as described above, the exhaust valve 38 can be cooled together for each of the two cylinders, which is efficient. Further, according to this embodiment, the periphery of the intake system (intake passage 12) is also cooled at the same time. For this reason, since the intake air can be cooled after the internal combustion engine 10 is restarted, the charging efficiency can be improved.

  In the third embodiment described above, the ECU 40 executes the exhaust valve cooling control as described above, whereby the “exhaust valve cooling means” in the fourth aspect of the present invention performs the exhaust valve 38 during the exhaust valve cooling control. Is maintained in the closed state, the "exhaust valve control means" in the fifth invention is controlled, and the "intake valve control means" in the fifth invention is controlled by controlling the intake valve 36 as shown in FIG. The “piston position means” according to the fifth aspect of the present invention is realized by controlling the position of the piston 44 of each cylinder by controlling the rotation angle of the second motor generator 86.

It is a figure which shows the system configuration | structure of Embodiment 1 of this invention. It is a figure which shows the structure of the intake variable valve operating apparatus with which the system of Embodiment 1 is provided. It is a schematic diagram which shows a mode that an intake valve is driven with a cam. It is a schematic diagram which shows the relationship between the engine speed of an internal combustion engine, output torque, and the drive mode of a cam. It is a schematic diagram which shows two types of cams provided in the cam shaft. It is a figure which shows typically the internal combustion engine at the time of exhaust valve cooling control execution in Embodiment 1 of this invention. It is a figure which shows the valve opening period of the intake valve of each cylinder at the time of exhaust valve cooling control execution in Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure for demonstrating the system configuration | structure of Embodiment 2 of this invention. It is a figure which shows typically the internal combustion engine at the time of exhaust valve cooling control execution in Embodiment 3 of this invention. It is a figure which shows the valve opening period of the intake valve of each cylinder at the time of exhaust valve cooling control execution in Embodiment 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 20 Air flow meter 30 Fuel injector 36 Intake valve 38 Exhaust valve 40 ECU
48 Intake variable valve operating device 50 Exhaust variable valve operating device 54A, 54B Motor 56A, 56B Gear train 58A, 58B Camshaft 62 Cam 62a Nose 62b Base circular portion 80 First motor generator 82 Drive shaft 84 Power distribution and integration mechanism 86 Second Motor generator

Claims (8)

Valve control means for holding both the intake valve and the exhaust valve closed during motoring of the internal combustion engine;
Temperature acquisition means for measuring or estimating the temperature of a predetermined portion of the internal combustion engine;
When the temperature measured or estimated by the temperature acquisition means at the time of the motoring is equal to or higher than a predetermined value, the intake valve is temporarily kept open so that fresh air is repeatedly entered and exited into the cylinder. An exhaust valve cooling means for cooling the exhaust valve;
A control device for an internal combustion engine, comprising:   2. The control apparatus for an internal combustion engine according to claim 1, wherein the exhaust valve cooling means closes the intake valve near a top dead center after the intake valve is temporarily kept open. The motoring is during engine braking,
It further comprises engine brake control means for controlling the lift amount of the intake valve when the exhaust valve cooling means holds the intake valve temporarily in an open state in accordance with the degree of engine brake demand. The control apparatus for an internal combustion engine according to claim 1 or 2. A hybrid system of an internal combustion engine and an electric motor, the hybrid system capable of stopping the rotation of the internal combustion engine when operating the electric motor and stopping the combustion of the internal combustion engine;
Temperature acquisition means for measuring or estimating the temperature of a predetermined portion of the internal combustion engine;
When the temperature measured or estimated by the temperature acquisition means is equal to or higher than a predetermined value when the combustion of the internal combustion engine is stopped, the intake valve, the exhaust valve, and the piston are expanded so that the air confined in the cylinder expands. An exhaust valve cooling means for cooling the exhaust valve by controlling a movement and utilizing a temperature decrease when the air in the cylinder expands;
A control device for an internal combustion engine, comprising: The exhaust valve cooling means includes
Exhaust valve control means for holding the exhaust valve in a closed state;
An intake valve control means for opening the intake valve once and closing it near the top dead center, and holding the closed state;
Piston position control means for holding for a predetermined time in a state where the piston is moved to near the bottom dead center after the intake valve is closed near the top dead center;
The control device for an internal combustion engine according to claim 4, comprising:   6. The control of an internal combustion engine according to claim 5, wherein the exhaust valve cooling means repeatedly executes a control operation by the intake valve control means and the piston position control means at a predetermined time interval for a plurality of cycles. apparatus.   The control device for an internal combustion engine according to claim 1, wherein the predetermined portion is the exhaust valve.   The control apparatus for an internal combustion engine according to any one of claims 1 to 7, further comprising a catalyst in an exhaust passage of the internal combustion engine.

Images