JP2009121263A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably feed intake negative pressure adequate for a brake device while favorably keeping an operating condition of an internal combustion engine. <P>SOLUTION: This internal combustion engine 1 is provided with an intake pressure sensor 26 detecting the intake negative pressure P, and VVTs 40, 42 setting valve timing variably. In an ECU 50, a brake request negative pressure P0, which is the minimum negative pressure value necessary for the brake device 44 to exert its function adequately, is stored in advance. The ECU 50 executes blow back amount reducing control when the internal combustion engine 10 is in a decelerating condition, and the intake negative pressure P is insufficient in comparison with the brake request negative pressure P0. In this blow back amount reducing control, a minus overlap interval α of each of valves 36, 38 is shortened by at least one of the VVTs 40, 42. This can reduce the amount of blow back of exhaust gas blown back to an air inlet system, and raise the intake negative pressure by the amount. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine suitable for use in, for example, a vehicle equipped with an internal combustion engine and a brake device, and more particularly, to a control device for an internal combustion engine having a variable valve mechanism that variably sets valve timing. About.

  2. Description of the Related Art Conventionally, as disclosed in, for example, Patent Document 1 (Japanese Utility Model Publication No. 5-66237), an internal combustion engine control device that can change the overlap period of an intake valve and an exhaust valve is known. In this prior art, exhaust emission is improved by shortening the overlap period when the internal combustion engine is decelerated.

  For example, as disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 11-270371), when the driver performs a driving operation to decelerate the vehicle, the valve overlap period is shortened. It is also known. In this conventional technique, when the driver's deceleration request is detected, the overlap period is shortened, thereby increasing the pumping loss in the cylinder and improving the effectiveness of the engine brake.

Japanese Utility Model Publication No. 5-66237 JP 11-270371 A

  By the way, vehicles, such as a motor vehicle, are equipped with the brake device with the internal combustion engine. This type of brake device is provided with a booster (booster) for assisting the driver in braking. This booster uses an intake negative pressure of the internal combustion engine to generate an assisting force for a brake operation, and reduces the stepping force when the driver steps on the brake pedal.

  However, in the conventional techniques described in Patent Documents 1 and 2, the intake negative pressure changes according to the operating state of the internal combustion engine. As a result, depending on the operating state, the actual intake negative pressure may be insufficient with respect to the intake negative pressure required by the booster.

  For this reason, in the prior art, when the driver performs a brake operation, the intake negative pressure necessary for the booster device is not supplied, and the booster device may not function sufficiently. As a result, it is necessary for the driver to depress the brake pedal more strongly than usual, and there is a problem that the operational feeling of the brake is deteriorated.

  The present invention has been made to solve the above-described problems, and is an internal combustion engine that can stably supply an intake negative pressure sufficient for a brake device while maintaining a good operating state of the internal combustion engine. The object is to provide an engine control device.

According to a first aspect of the present invention, there is provided a variable valve mechanism that variably sets a valve timing of at least one of an intake valve and an exhaust valve of an internal combustion engine,
Negative pressure acquisition means for acquiring the intake negative pressure of the internal combustion engine;
Negative pressure determination means for determining whether or not intake negative pressure sufficient for the brake device is generated when the internal combustion engine is decelerated;
A standard timing setting means for setting the valve timing to a standard timing at the time of deceleration by the variable valve mechanism when the negative pressure determination means determines that the intake negative pressure is sufficient;
When the negative pressure determining means determines that the intake negative pressure is insufficient, the valve timing is changed by the variable valve mechanism, and the amount of exhaust gas blown back to the intake system is changed to the amount of blowback at the standard timing. Blowing weight loss means to reduce more than,
It is characterized by providing.

  According to the second invention, the standard timing is an initial timing used as an initial setting of the valve timing when the variable valve mechanism is started.

According to a third invention, the standard timing includes a minus overlap period in which both the intake valve and the exhaust valve are closed,
The blowback reduction means is configured to reduce the exhaust gas blowback amount by shortening the minus overlap period.

  According to a fourth aspect of the present invention, the blow back reducing means is configured to shorten the minus overlap period by retarding the valve timing of the exhaust valve.

  According to a fifth aspect of the present invention, the blow back reducing means is configured to shorten the minus overlap period by advancing the valve timing of the intake valve.

6th invention is provided with the memory | storage means by which the valve timing which minimizes the amount of blowbacks of the said exhaust gas was previously memorize | stored as target timing,
The blowback reduction means is configured to set the valve timing to the target timing when reducing the exhaust gas blowback amount.

  According to a seventh aspect of the present invention, there is provided a returning means for returning the valve timing to the standard timing when a sufficient intake negative pressure is generated during the operation of the blow back reducing means.

  According to the first invention, when the internal combustion engine is decelerated, the negative pressure determining means can determine whether or not intake negative pressure sufficient for the brake device is generated. When it is determined that the intake negative pressure is sufficient, the standard timing setting means can set the valve timing to the standard timing during deceleration. Further, when it is determined that the intake negative pressure is insufficient, the exhaust gas blow back amount can be reduced by the blow back reducing means, thereby increasing the intake negative pressure.

  For this reason, at the time of deceleration at which the brake operation is easily performed, it is possible to stably ensure a sufficient intake negative pressure for the brake device. Therefore, it can be avoided that the operating force of the brake is increased or the operational feeling is deteriorated due to the lack of the intake negative pressure, and the brake device can be operated satisfactorily.

  According to the second aspect of the invention, when starting the internal combustion engine, it is necessary to keep the valve at a predetermined initial timing even when hydraulic pressure or electric power is not supplied to the variable valve mechanism. For this reason, the variable valve mechanism includes a lock mechanism for mechanically locking the valve at the initial timing. The lock mechanism can perform a lock operation when the valve is operating at the initial timing.

  Therefore, the standard timing setting means uses the initial timing as the standard timing at the time of deceleration. As a result, when the internal combustion engine is decelerated, the valve can be operated at the initial timing except when the blowback reduction means is operated. For this reason, even if the internal combustion engine stops from the deceleration state, the valve can be returned to the initial timing prior to the stop. Therefore, when the internal combustion engine is stopped, the lock mechanism can be quickly operated with the valve at the initial timing, and preparation for restart can be made.

  According to the third invention, the blowback reduction means can shorten the minus overlap period between the intake valve and the exhaust valve. Thus, the exhaust gas in the combustion chamber is not extremely compressed during the minus overlap period. As a result, the exhaust gas blow-back amount can be reduced, and the intake negative pressure can be increased.

  According to the fourth aspect of the present invention, the blow back reducing means can retard the valve timing of the exhaust valve by the variable valve mechanism. As a result, the minus overlap period can be shortened, and the exhaust gas blowback amount can be reduced.

  According to the fifth aspect of the present invention, the blow back reducing means can advance the valve timing of the intake valve by the variable valve mechanism. As a result, the minus overlap period can be shortened to reduce the exhaust gas blowback amount.

  Here, when the internal combustion engine stops, it is necessary to prepare for restart by holding the valve at a predetermined initial timing by the variable valve mechanism. In the variable valve mechanism on the intake side, the operation direction when returning the advanced intake valve to the initial timing is the forward direction with respect to the rotation direction of the output shaft of the internal combustion engine. For this reason, the variable valve mechanism on the intake side has a higher speed when the intake valve is returned to the initial timing than the variable valve mechanism on the exhaust side.

  That is, the variable valve mechanism on the intake side can return the valve timing to the initial timing at high speed until the internal combustion engine stops even if the valve timing is advanced while the engine speed is low. Therefore, by increasing the valve timing of the intake valve, the blowback reduction means can be operated at a lower engine speed. As a result, the intake negative pressure sufficient for the brake device can be stably secured in a wide range from high rotation to low rotation.

  According to the sixth aspect of the invention, the optimum valve timing at which the exhaust gas blowback amount is minimized can be obtained in advance by experiments or the like. The optimum valve timing can be stored in advance in the storage means as the target timing. Then, the blowback reduction means can set the valve timing to the target timing. As a result, exhaust gas blow-back can be reduced to a minimum amount, and intake negative pressure can be maximized.

  According to the seventh aspect of the present invention, when the intake negative pressure has sufficiently increased due to the operation of the blowback reduction means, the return reduction means can be stopped by the return means. As a result, the valve timing can be returned to the standard timing, and appropriate control can be performed according to the situation.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
The first embodiment of the present invention will be described below with reference to FIGS. First, FIG. 1 shows an overall configuration diagram for explaining the system configuration of the first embodiment. The system of this embodiment includes, for example, a multi-cylinder internal combustion engine 10, and a combustion chamber 14 is provided between each piston and the piston 12. Further, the piston 12 of each cylinder is connected to the crankshaft 16 of the internal combustion engine 10. The internal combustion engine 10 is provided with a crank angle sensor 18 for detecting the rotation angle (crank angle) of the crankshaft 16.

  An intake passage 20 through which intake air of the internal combustion engine 10 flows toward the combustion chamber 14 and an exhaust passage 22 through which exhaust gas flows out from the combustion chamber 14 are connected to the combustion chamber 14 of each cylinder. An air flow meter 24 for detecting the flow rate (intake air amount) of intake air flowing through the intake passage 20 is provided in the vicinity of the inlet of the intake passage 20 and negative pressure acquisition for detecting the intake negative pressure P in the intake passage 20 is provided. An intake pressure sensor 26 is provided as means. The intake passage 20 is provided with an electronically controlled throttle valve 28 for adjusting the intake air amount. The throttle valve 28 is driven by a throttle motor 30 based on the accelerator opening and the like.

  The internal combustion engine 10 includes a fuel injection valve 32 that injects fuel toward the combustion chamber 14 of each cylinder, and an ignition plug 34 that ignites the air-fuel mixture in the combustion chamber 14. The combustion chamber 14 of each cylinder is provided with an intake valve 36 that opens and closes the intake passage 20 with respect to the combustion chamber 14 and an exhaust valve 38 that opens and closes the exhaust passage 22 with respect to the combustion chamber 14. It has been.

  The valve timings of the intake valve 36 and the exhaust valve 38 are variably set by VVT (Variable Valve Timing system) 40 and 42 as variable valve mechanisms. Here, the VVT 40 on the intake side is configured using a known technique as described in, for example, Japanese Patent Application Laid-Open No. 2003-293711.

  The VVT 40 advances or retards the phase (opening timing and closing timing) of the intake valve 36 in accordance with a command signal input from the ECU 50 described later. Similarly, the exhaust-side VVT 42 advances or retards the phase of the exhaust valve 38 in accordance with a command signal from the ECU 50.

  On the other hand, the system of the present embodiment is provided with a brake device 44 for stopping the vehicle on which the internal combustion engine 10 is mounted. The brake device 44 includes a booster (not shown) for assisting the stepping force when the driver of the vehicle steps on the brake pedal. This booster device uses the intake negative pressure of the internal combustion engine 10 introduced through the negative pressure passage 46 to generate an assisting force for the driver's brake operation and reduce the depression force of the brake pedal. is there.

  Further, the system of the present embodiment includes an ECU (Electronic Control Unit) 50 for controlling the operating state of the internal combustion engine 10. The ECU 50 is configured by a microcomputer including a storage circuit 52 such as a ROM or a RAM as storage means. On the input side of the ECU 50, in addition to the crank angle sensor 18, the air flow meter 24, the intake pressure sensor 26, and the like, a water temperature sensor that detects the cooling water temperature of the internal combustion engine 10, and an accelerator opening that detects the accelerator opening degree. A sensor system including a degree sensor, an air-fuel ratio sensor for detecting the air-fuel ratio of the exhaust gas, and the like are connected.

  Various actuators including a throttle motor 30, a fuel injection valve 32, a spark plug 34, VVTs 40, 42, and the like are connected to the output side of the ECU 50. The ECU 50 controls the operation by driving the actuators while detecting the operation state of the internal combustion engine 10 using the sensor system. In addition, the ECU 50 performs the following controls using the VVTs 40 and 42.

(Exhaust valve early closing control)
When the internal combustion engine 10 is started, the ECU 50 executes control for operating the valves 36 and 38 at a predetermined initial timing (hereinafter referred to as exhaust valve early closing control). Here, the initial timing is used, for example, as an initial setting of the valve timing when the VVTs 40 and 42 are started. FIG. 2 shows the open and closed states of the valves 36 and 38 at the initial timing. Note that the initial timing shown in FIG. 2 is merely an example, and does not limit the present invention.

  At the initial timing, for example, the intake valve 36 is held at the most retarded position that can be realized by the VVT 40, and the exhaust valve 38 is held at the most advanced position that can be realized by the VVT 42. Further, at the initial timing, for example, at a timing slightly advanced from the intake top dead center (TDC), a negative overlap period α in which both the valves 36 and 38 are closed is provided. The minus overlap period α has a length of about 10 to 15 CA ° (crank angle), for example.

  Thus, when the valves 36 and 38 are operated at the initial timing, the intake valve 36 is opened after the minus overlap period α has elapsed since the exhaust valve 38 was closed early. As a result, the exhaust gas left in the combustion chamber 14 at the end of the exhaust stroke is compressed in the combustion chamber 14 during the minus overlap period α. The exhaust gas blows back to the intake system (intake passage 20 side) when the intake valve 36 is opened.

  For this reason, when the internal combustion engine 10 is started, the valves 36 and 38 are operated at the initial timing, whereby the amount of exhaust gas blown back can be increased, and the emission at the time of starting can be improved by this blowback.

(Standard control during deceleration)
When the internal combustion engine 10 is started, it is necessary to keep the valves 36 and 38 at the initial timing even when no hydraulic pressure or electric power is supplied to the VVTs 40 and 42. For this reason, the VVTs 40 and 42 include a lock mechanism (not shown) for mechanically locking the valves 36 and 38 at the initial timing. The lock mechanism can perform a lock operation when the valves 36 and 38 are operating at the initial timing.

  For this reason, when the internal combustion engine 10 is decelerated, standard control at the time of deceleration in which the valves 36 and 38 are actuated at the initial timing is executed, except in the case of performing blowback reduction control described later. That is, in the present embodiment, the standard valve timing (standard timing) at the time of deceleration is the initial timing.

  Thereby, even if the internal combustion engine 10 is stopped from the deceleration state, the valves 36 and 38 can be returned to the initial timing prior to the stop. For this reason, when the internal combustion engine 10 is stopped, the lock mechanism can be quickly operated in a state where the valves 36 and 38 are at the initial timing, and preparation for restart can be made.

(Blow-back weight loss control)
On the other hand, in a vehicle such as an automobile, a brake operation is often performed by the driver when the internal combustion engine 10 is decelerated. In this case, in order to operate the brake device 44 smoothly, it is necessary to supply a sufficiently large intake negative pressure from the intake passage 20 to the brake device 44 (a booster device).

  For this reason, when the internal combustion engine 10 is in a decelerating state and the start condition of the blowback reduction control is satisfied, the ECU 50 does not perform the deceleration standard control but performs the blowback reduction control instead. In the present embodiment, the start condition of the blowback reduction control is set as, for example, when the absolute value of the intake negative pressure P is less than the brake request negative pressure P0. Here, the brake required negative pressure P0 is a minimum negative pressure value necessary for the above-described booster to sufficiently function, and is stored in advance in the storage circuit 52 of the ECU 50.

  When the above-described start condition is satisfied, even if a brake operation is performed, the actual intake negative pressure P is insufficient with respect to the required negative pressure P0 of the brake device 44. Therefore, the ECU 50 retards the valve timing of the exhaust valve 38 and reduces the exhaust gas blowback amount as will be described later. As a result, the intake negative pressure can be increased by the amount by which the exhaust gas blow-back amount has decreased.

  In addition, when the absolute value of the intake negative pressure P becomes equal to or higher than the brake request negative pressure P0, the ECU 50 stops the blowback reduction control and restarts the deceleration standard control. That is, the valves 36 and 38 are returned to the standard timing (initial timing) at the time of deceleration.

  Further, the intake negative pressure P is particularly likely to be insufficient when the internal combustion engine 10 is operated at a low speed. Therefore, the blowback reduction control may be executed when the above-described start condition is satisfied or when the engine speed of the internal combustion engine 10 is lower than a predetermined determination value.

  On the other hand, when the internal combustion engine 10 starts to decelerate from a high rotation speed, the exhaust gas blows back into the intake system, so that vibration noise is likely to be generated from the intake passage 20 and the like. For this reason, the blowback reduction control is also executed when deceleration is started in a state where the engine speed exceeds a certain determination value. Thereby, it is possible to suppress the generation of the vibration noise of the intake system due to the exhaust gas blowing back, and to reduce the noise level of the internal combustion engine 10.

(Valve timing for blowback weight loss control)
FIG. 3 shows a change in the valve timing by the blowback reduction control. In the blowback reduction control, the valve timing of the exhaust valve 38 is retarded from the aforementioned initial timing (illustrated by a virtual line) by the VVT 42 on the exhaust side.

  Due to this retardation, the valve timing of the exhaust valve 38 is set to a target timing at which the exhaust gas blowback amount is minimized. This target timing is obtained in advance by experiments or the like, and is stored in the storage circuit 52 of the ECU 50. In other words, in the blowback reduction control, the valve timing of the exhaust valve 38 is set so that the minus overlap period α is shortened or becomes zero.

  FIG. 4 shows the relationship between the valve timing of the exhaust valve 38 and the exhaust gas blowback amount. The vertical axis in FIG. 4 represents the gas flow rate in the combustion chamber 14, and increasing this gas flow rate on the negative side means that the exhaust gas blowback amount increases.

  Also, the solid line in FIG. 4 indicates the exhaust gas blowback amount at the initial timing, and the dotted line indicates the exhaust gas blowback amount at the base timing. Here, the base timing is a general valve timing at which a slight overlap occurs in the vicinity of the intake top dead center. That is, in the negative overlap period α of the valve, the base timing is shorter than the initial timing.

  As can be seen from FIG. 4, the amount of exhaust gas blown back is smaller at the base timing than at the initial timing. Therefore, in the blowback reduction control, the exhaust gas blowback amount can be reduced by reducing the minus overlap period α or setting the valve timing so as to be zero.

[Specific Processing for Realizing Embodiment 1]
FIG. 5 is a flowchart of a routine executed by the ECU 50 in order to realize the system operation of the present embodiment. The routine shown in FIG. 5 is started when the internal combustion engine is started, and is repeatedly executed at regular intervals.

  First, in step 100, it is determined whether or not the internal combustion engine 10 is in a deceleration state. If “YES” is determined here, the process proceeds to step 104 described later. When it is determined “NO” in step 100, the valve timing control during acceleration is executed in step 102, and the process returns.

  Next, at step 104, the intake negative pressure P is detected by the intake pressure sensor 26. In step 106, the brake request negative pressure P0 is calculated. In this case, for the brake required negative pressure P0, for example, the stored data of the required negative pressure stored in advance in the ECU 50 based on the specifications of the brake device 44 or the like is read, or the stored data is corrected in accordance with the operating state. It is calculated by doing.

  Next, in step 108, it is determined whether or not the blowback reduction control is being executed. If “YES” is determined here, the process proceeds to step 116 described later. If “NO” is determined in the step 108, it is determined whether or not a start condition for the blowback reduction control is satisfied in a step 110. More specifically, in step 110, it is determined whether or not the intake negative pressure P is less than the brake required negative pressure P0.

  When it is determined “YES” in step 110, it is determined that the intake negative pressure is insufficient for the brake device 44. Therefore, in this case, blowback reduction control is performed in step 112. That is, in step 112, the exhaust-side VVT 42 is operated, and as shown in FIG. 3, the valve timing of the exhaust valve 38 is retarded from the initial timing. As a result, the exhaust gas blowback amount is smaller than the blowback amount at the initial timing, so that the intake negative pressure P can be increased.

  In addition, when the valve timing of the exhaust valve 38 is retarded, the valve timing of the intake valve 36 may be held at the initial timing, but as described in the second embodiment described later, it is advanced from the initial timing. It is good also as a structure to make it horn.

  On the other hand, when it is determined “NO” in step 110, it is determined that the intake negative pressure sufficient for the brake device 44 is generated. In this case, therefore, standard control at the time of deceleration is performed in step 114. That is, in step 114, the valves 36 and 38 are set to the initial timing, and the process returns.

  Further, in step 116, it is determined whether or not the intake negative pressure P has risen above the brake request negative pressure P0 when the blowback reduction control is being executed. Here, when it is determined as “YES”, it is determined that sufficient intake negative pressure is generated by the blowback reduction control. Therefore, in this case, standard control at the time of deceleration is performed in step 114, and the valve timing of each valve 36, 38 is returned to the initial timing. If “NO” is determined in the step 116, the process returns to the step 110 to continue the blowback reduction control.

[Effect of Embodiment 1]
According to the present embodiment, the ECU 50 can determine whether or not the intake negative pressure sufficient for the brake device 44 is generated when the internal combustion engine 10 is decelerated. When it is determined that the intake negative pressure is sufficient, the valve timing can be set to the standard timing during deceleration to prepare for the stop or restart of the internal combustion engine 10.

  When it is determined that the intake negative pressure is insufficient, the valve timing of the exhaust valve 38 can be retarded by the blowback reduction control. As a result, the exhaust gas blow-back amount can be reduced, and the intake negative pressure can be increased.

  For this reason, it is possible to stably ensure a sufficient intake negative pressure for the brake device 44 at the time of deceleration at which braking is easily performed. Therefore, it is possible to avoid an increase in the operating force of the brake due to a lack of intake negative pressure or a deterioration in the operational feeling, and the brake device 44 can be operated satisfactorily.

  In the blowback reduction control, the valve timing of the exhaust valve 38 can be retarded by the exhaust-side VVT 42. Thereby, the minus overlap period (alpha) of each valve | bulb 36 and 38 can be shortened. As a result, the exhaust gas in the combustion chamber 14 is not extremely compressed during the minus overlap period. Therefore, the exhaust gas blow-back amount can be reduced, and the intake negative pressure can be increased.

  In this case, in the blowback reduction control, an optimum valve timing at which the exhaust gas blowback amount is minimized can be obtained in advance by experiments or the like. The optimum valve timing can be stored in advance in the storage circuit 52 of the ECU 50 as the target timing. In the blowback reduction control, the valve timing of the exhaust valve 38 can be delayed to the target timing. As a result, exhaust gas blow-back can be reduced to a minimum amount, and intake negative pressure can be maximized.

  On the other hand, by performing the blowback reduction control, the ECU 50 can stop the blowback reduction control when the intake negative pressure has sufficiently increased. Thereby, the valve timing of the exhaust valve 38 can be returned to the standard timing, and appropriate control can be performed according to the situation.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Characteristics of Embodiment 2]
The system of the present embodiment has the same configuration as that of the first embodiment (see FIG. 1). When it is determined that the intake negative pressure is insufficient for the brake device 44, the blowback reduction control is performed. However, in the blowback reduction control, the valve timing of the intake valve 36 is advanced from the initial timing, and this embodiment is different from the first embodiment in this respect.

  FIG. 7 shows a change in the valve timing by the blowback reduction control. In the blowback reduction control of the present embodiment, the valve timing of the intake valve 36 is advanced from the initial timing (illustrated by phantom lines) by the VVT 40 on the intake side. With this advance angle, the valve timing of the intake valve 36 is set to a target timing at which the exhaust gas blowback amount is minimized. This target timing is obtained in advance by experiments or the like, and is stored in the storage circuit 52 of the ECU 50.

  In other words, in the blowback reduction control, the valve timing of the intake valve 36 is set so that the minus overlap period α is shortened or becomes zero. Therefore, even with the blowback reduction control of the present embodiment, the exhaust gas blowback amount can be reduced from the initial timing.

[Specific Processing for Realizing Embodiment 2]
FIG. 8 is a flowchart of a routine executed by the ECU 50 in order to realize the system operation of the present embodiment. In the description of FIG. 8, the same processes as those in the first embodiment (FIG. 5) are denoted by the same step numbers, and the description thereof is omitted. As shown in FIG. 8, in the present embodiment, when the blowback reduction control is performed in step 200, the valve timing of the intake valve 36 is advanced.

[Effect of Embodiment 2]
In the present embodiment configured as described above, it is possible to obtain substantially the same operational effects as in the first embodiment. In particular, in the present embodiment, when the blowback reduction control is performed, the valve timing of the intake valve 36 is advanced by the VVT 40 on the intake side. Even in this configuration, the minus overlap period α of the valves 36 and 38 can be shortened, and the exhaust gas blowback amount can be reduced.

  Moreover, in the present embodiment, the following effects can be further obtained by advancing the intake valve 36.

  First, when the internal combustion engine 10 stops, as described in the first embodiment, the valves 36 and 38 need to be held at the initial timing by the VVTs 40 and 42 to prepare for restart. In the VVT 40 on the intake side, the operating direction when the advanced intake valve 36 is returned to the initial timing is the forward direction with respect to the rotation direction of the crankshaft 16. For this reason, the VVT 40 on the intake side has a higher speed when returning the intake valve 36 to the initial timing than the VVT 42 on the exhaust side.

  That is, the intake-side VVT 40 can return the valve timing to the initial timing at high speed until the internal combustion engine 10 stops even if the valve timing is advanced while the engine speed is low. Therefore, by increasing the valve timing of the intake valve 36, the blowback reduction control can be performed at a lower engine speed. As a result, it is possible to stably ensure a sufficient intake negative pressure for the brake device 44 in a wide range from high rotation to low rotation.

  In each of the above embodiments, step 110 in FIGS. 5 and 7 shows a specific example of the negative pressure determination means, and step 114 shows a specific example of the standard timing setting means. Further, steps 112 and 200 in FIGS. 5 and 7 show a specific example of the blowback reduction means, and step 116 shows a specific example of the return means.

  In the first and second embodiments, the intake pressure sensor 26 is used as the negative pressure acquisition means. However, the present invention is not limited to this. For example, the intake negative pressure may be estimated and calculated according to the engine speed, the load state, and the like of the internal combustion engine 10.

  In the first embodiment, the valve timing of the exhaust valve 38 is retarded to execute the blowback reduction control, and in the second embodiment, the valve timing of the intake valve 36 is advanced. However, the present invention is not limited to this. For example, by combining the first and second embodiments, in the blowback reduction control, the retard angle of the exhaust valve 38 and the advance angle of the intake valve 36 may be executed together. Good.

  In the embodiment, both the intake-side VVT 40 and the exhaust-side VVT 42 are mounted on the internal combustion engine 10. However, the present invention is not limited to this, and may be applied to an internal combustion engine equipped with only one of VVTs 40 and 42. In other words, the first embodiment may be configured to have only the exhaust-side VVT 42 instead of the intake-side VVT 40. In the second embodiment, the exhaust-side VVT 42 may not be provided, and only the intake-side VVT 40 may be mounted.

  In the embodiment, the case where the brake request negative pressure P0 is set to a constant value has been described as an example. However, the present invention is not limited to this. For example, the brake request negative pressure P0 may be changed according to the operating state of the internal combustion engine 10, the operating state of the brake device 44, and the like.

  Further, in the embodiment, the case where the intake negative pressure P is less than the brake request negative pressure P0 has been described as an example as the start condition of the blowback reduction control. However, the start condition of the present invention is not limited to this. For example, the intake negative pressure P may be less than the brake request negative pressure P0, and the engine speed may be lower than the determination value.

  Furthermore, in the embodiment, the initial timing having the minus overlap period α has been described as an example of the standard timing at the time of deceleration. However, the present invention is not limited to this, and any timing suitable for the requirements of the internal combustion engine can be used as the standard timing at the time of deceleration. For this reason, in the present invention, the standard timing does not necessarily have the minus overlap period α.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall view for explaining a system configuration according to a first embodiment of the present invention. It is explanatory drawing which shows the initial timing of an intake valve and an exhaust valve. It is explanatory drawing which shows the state which retards the valve timing of an exhaust valve by blowback reduction control. It is explanatory drawing which shows the relationship between the amount of blowbacks to an intake system, and valve timing. It is a flowchart of the routine performed in Embodiment 1 of the present invention. In Embodiment 2 of this invention, it is explanatory drawing which shows the state which advances the valve timing of an intake valve by blowback reduction control. It is a flowchart of the routine performed in Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Piston 14 Combustion chamber 16 Crankshaft 18 Crank angle sensor 20 Intake passage 22 Exhaust passage 24 Air flow meter 26 Intake pressure sensor (negative pressure acquisition means)
28 Throttle valve 30 Throttle motor 32 Fuel injection valve 34 Spark plug 36 Intake valve 38 Exhaust valve 40, 42 VVT (variable valve mechanism)
44 Brake device 46 Negative pressure passage 50 ECU
52 Memory circuit (memory means)
P Intake negative pressure P0 Brake required negative pressure α Minus overlap period

Claims (7)

A variable valve mechanism that variably sets at least one of the intake valve and the exhaust valve of the internal combustion engine;
Negative pressure acquisition means for acquiring the intake negative pressure of the internal combustion engine;
Negative pressure determination means for determining whether or not intake negative pressure sufficient for the brake device is generated when the internal combustion engine is decelerated;
A standard timing setting means for setting the valve timing to a standard timing at the time of deceleration by the variable valve mechanism when the negative pressure determination means determines that the intake negative pressure is sufficient;
When the negative pressure determining means determines that the intake negative pressure is insufficient, the valve timing is changed by the variable valve mechanism, and the amount of exhaust gas blown back to the intake system is changed to the amount of blowback at the standard timing. Blowing weight loss means to reduce more than,
A control device for an internal combustion engine, comprising:   The control apparatus for an internal combustion engine according to claim 1, wherein the standard timing is an initial timing used as an initial setting of the valve timing when the variable valve mechanism is started. The standard timing includes a minus overlap period in which both the intake valve and the exhaust valve are closed,
The control device for an internal combustion engine according to claim 1 or 2, wherein the blowback reduction means is configured to reduce the exhaust gas blowback amount by shortening the minus overlap period.   The control apparatus for an internal combustion engine according to claim 3, wherein the blowback reduction means is configured to shorten the minus overlap period by retarding a valve timing of the exhaust valve.   The control apparatus for an internal combustion engine according to claim 3, wherein the blowback reduction means is configured to shorten the minus overlap period by advancing the valve timing of the intake valve. Comprising a storage means in which the valve timing for minimizing the exhaust gas blow-back amount is stored in advance as a target timing;
The control device for an internal combustion engine according to any one of claims 1 to 5, wherein the blowback reduction means is configured to set the valve timing to the target timing when reducing the blowback amount of the exhaust gas. .   The internal combustion engine according to any one of claims 1 to 6, further comprising return means for returning the valve timing to the standard timing when a sufficient intake negative pressure is generated during the operation of the blowback reduction means. Engine control device.

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