JP6487791B2 - Control device for internal combustion engine - Google Patents

Description

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

  Conventionally, there is a control device described in Patent Document 1 as a control device for reducing the pumping loss of an internal combustion engine. The control device described in Patent Literature 1 stops supplying fuel to the internal combustion engine when the fuel cut condition is satisfied. Then, during the fuel cut, the closing timing of the intake valve is changed to the retard side from the intake bottom dead center, and the opening timing of the intake valve is changed to the advance side from the closing timing of the exhaust valve. . As a result, the amount of fresh air remaining in the combustion chamber after the intake valve is closed can be reduced, and the pumping loss can be reduced.

JP 2010-203279 A

  However, in the control device described in Patent Document 1, valve overlap occurs between the intake valve and the exhaust valve while the fuel supply is stopped. When returning from the stop of the fuel supply in this state, the EGR gas remaining in the combustion chamber becomes excessive until the valve timing before the fuel cut is changed, and there is a risk of causing a misfire when returning from the stop of the fuel supply.

  The present invention has been made in order to solve the above-described problems, and a main object of the present invention is an internal combustion engine that can suppress misfire even if EGR gas remaining in the combustion chamber increases. It is to provide an engine control device.

The present application is a control device that is applied to an internal combustion engine that includes a fuel injection unit that injects fuel to be used for combustion, and a valve timing adjustment mechanism that adjusts the opening / closing timing of an intake valve or an exhaust valve. And an EGR rate calculation unit that calculates an EGR rate of the gas used for combustion based on the current opening / closing timing of the exhaust valve, and between the combustion cycle in which the fuel is burned, and the combustion cycle, an intermittent combustion execution unit for executing an intermittent combustion mode to insert a non-combustion cycle to stop the injection of fuel by the fuel injection unit, the EGR rate calculated by the EGR rate calculating unit, the combustion of the fuel takes place the combustion beyond the continuous combustion limit EGR rate set as the risk-free limit of misfire in the practice of continuous combustion mode to execute the cycle continuously If large, discloses a control apparatus characterized by comprising an execution control unit for executing the intermittent combustion mode by the intermittent combustion execution unit.
The present invention further includes a fuel injection stop unit that stops fuel injection by the fuel injection unit when a predetermined condition is satisfied, a period during which the fuel injection stop unit stops the fuel injection, and the valve timing. A valve timing control unit that controls the opening / closing timing of the intake valve or the exhaust valve so that a pumping loss is reduced by an adjustment mechanism; and a request torque calculation unit that calculates a request torque required by a driver. When the required torque calculated by the torque calculation unit is greater than zero and smaller than a specified torque that is a torque value that needs to be output, the control by the valve timing control unit is stopped, and in that state, The EGR rate calculated by the EGR rate calculating unit is smaller than the continuous combustion limit EGR rate. The fuel injection by the fuel injection stop unit is continued until the EGR rate calculated by the EGR rate calculation unit becomes smaller than the continuous combustion limit EGR rate. The control for stopping the injection is terminated.

  According to the above configuration, the internal combustion engine includes the fuel injection unit and the valve timing adjustment mechanism. The opening / closing timing of the intake valve or the exhaust valve is adjusted by the valve timing adjusting mechanism. At this time, EGR gas may remain in the cylinder depending on the opening / closing timing adjusted by the valve timing adjusting mechanism. Since there is little oxygen contained in this EGR gas, if the ratio of EGR gas becomes high in a cylinder, there is a possibility of misfire.

Therefore, the control device applied to the internal combustion engine includes an EGR rate calculation unit. The EGR rate calculation unit calculates the EGR rate of the gas used for combustion based on the current opening / closing timing of the intake valve and the exhaust valve. In addition, an intermittent combustion execution unit is provided, and an intermittent combustion mode is executed in which a non-combustion cycle for stopping fuel injection by the fuel injection unit is inserted between the combustion cycle in which fuel combustion is performed. . Therefore, when the EGR rate calculated by the EGR rate calculating unit is larger than the continuous combustion limit EGR rate and may cause misfire, the execution control unit executes the intermittent combustion mode . As a result, during the execution of the intermittent combustion mode , a non-combustion cycle is inserted between the combustion cycles, and the EGR gas remaining in the internal combustion engine during the execution of the non-combustion cycle can be discharged. Therefore, even if the EGR gas remaining in the internal combustion engine increases, it is possible to suppress the occurrence of misfire.

1 is a schematic diagram illustrating a system configuration of a vehicle according to an embodiment. FIG. 2 is a schematic diagram of the internal combustion engine of FIG. 1 and its control device. It is a diagram of valve timing. It is a flowchart of the control performed by ECU which concerns on this embodiment. It is a timing chart which shows the transition of the EGR rate which concerns on this embodiment, and the relationship of operation mode switching. It is a flowchart of the control performed by ECU which concerns on another example. It is a timing chart which shows the transition of the EGR rate which concerns on another example, and the relationship of operation mode switching. It is a timing chart which shows the transition of the EGR rate which concerns on another example, and the relationship of operation mode switching. It is a flowchart of the control performed by ECU which concerns on another example.

  FIG. 1 is a schematic diagram showing a system configuration of a vehicle equipped with an internal combustion engine 17. As shown in FIG. 1, the vehicle includes an internal combustion engine 17 that obtains kinetic energy by burning fuel, and a rotating machine (corresponding to an electric motor) 13 that applies torque to the internal combustion engine 17. An output shaft of the rotating machine 13 is drivingly connected to an output shaft (crankshaft) (not shown) of the internal combustion engine 17 by an auxiliary machine belt 15. For this reason, the rotating shaft of the rotating machine 13 is rotated by the rotation of the output shaft of the internal combustion engine 17. On the other hand, the output shaft of the internal combustion engine 17 is rotated by the rotation of the rotating shaft of the rotating machine 13. In this case, the rotating machine 13 includes a power generation function for generating power (regenerative power generation) by rotation of the output shaft and axle of the internal combustion engine 17 and a power output function for applying a rotational force to the output shaft of the internal combustion engine 17. (Integrated Starter Generator).

  The vehicle includes a battery 11 that stores electric power generated by the rotating machine 13 or supplies electric power to the rotating machine 13, and an inverter 12 that converts AC power and DC power between the rotating machine 13 and the battery 11. It has. The rotating machine 13 and the inverter 12 can regenerate kinetic energy as electric energy when the vehicle is decelerated, for example.

  The vehicle includes an ECU (corresponding to a control device) 10 that controls the operation of the internal combustion engine 17 and the rotating machine 13. The ECU 10 is connected to the sensors 20 to 23 and has a function of acquiring information by receiving signals output from these sensors. The ECU 10 controls the driving state of the internal combustion engine 17 and the driving state of the rotating machine 13, whereby the engine running in which the rotational power of the internal combustion engine 17 is transmitted to the wheels via a transmission or the like and the rotation of the rotating machine 13. EV traveling that travels by driving the internal combustion engine 17 with power and HV traveling that uses both driving forces are realized.

  FIG. 2 is a schematic diagram showing the internal combustion engine 17 and the ECU 10. FIG. 2 illustrates only one cylinder among the plurality of cylinders included in the internal combustion engine 17.

  A cylinder 43 is formed in the cylinder block 41, and a piston 44 that reciprocates in the vertical direction with respect to the cylinder 43 is disposed in the cylinder 43. The piston 44 is connected to a crankshaft (not shown) via a connecting rod 45. A combustion chamber 42 defined by a cylinder 43 and a cylinder head 38 is provided above the piston 44, and the combustion chamber 42 is provided with an intake port and an exhaust port, respectively. A spark plug 35 is disposed on the cylinder head 38. The spark plug 35 is ignited by an ignition high voltage supplied from an igniter (not shown).

  An intake pipe 31 that sucks intake air into the combustion chamber 42 is connected to the intake port, and an exhaust pipe 34 that discharges exhaust gas from the cylinder is connected to the exhaust port. The intake pipe 31 includes a throttle valve 32 that is electronically controlled based on an operation amount of an accelerator pedal (not shown), and an electromagnetically driven injector that is supplied with high-pressure fuel from a fuel supply system (corresponding to a fuel injection unit) 33 is provided. The injector 33 injects fuel into the intake pipe 31 when energized. Although the injector 33 is provided in the intake pipe 31, the injector 33 may be provided in the cylinder head 38 to directly inject fuel into the combustion chamber 42. The intake port is provided with an intake valve (corresponding to an intake valve) 18 that opens and closes the port. On the other hand, the exhaust pipe 34 is provided with an exhaust purification device 39, and the exhaust port is provided with an exhaust valve (corresponding to an exhaust valve) 19 for opening and closing the port with respect to the inside of the cylinder.

  The opening degree of the throttle valve 32 is detected by a throttle opening degree sensor 23, and the throttle opening degree sensor 23 also detects the fully closed state of the throttle. The throttle opening is represented by an angle with respect to the direction perpendicular to the intake pipe 31. That is, 0 degrees indicates fully closed and 90 degrees indicates fully open.

  The exhaust purification device 39 includes an exhaust purification catalyst inside, and purifies the exhaust by oxidizing and / or reducing the exhaust discharged through the exhaust pipe 34 after the combustion of the fuel. In addition, when the catalyst temperature is lower than an appropriate temperature, the exhaust purification catalyst has a reduced exhaust oxidation efficiency and / or reduction efficiency. That is, when the catalyst temperature is lower than the appropriate temperature, exhaust gas purification is not sufficiently performed.

  An intake side camshaft 36 for opening and closing the intake valve 18 at a predetermined timing and an exhaust side camshaft 37 for opening and closing the exhaust valve 19 at a predetermined timing are connected to a crankshaft via a timing belt (not shown). Has been. The crankshaft is provided with a crank angle sensor 22 that detects the rotational position of the crankshaft.

  The intake camshaft 36 is provided with an intake cam angle sensor 20 that detects the cam angle of the intake camshaft 36, and the exhaust camshaft 37 detects the cam angle of the exhaust camshaft 37. An exhaust side cam angle sensor 21 is provided.

  The intake side camshaft 36 is provided with an intake side variable valve mechanism (intake side VCT) 46, and the exhaust side camshaft 37 is provided with an exhaust side variable valve mechanism (exhaust side VCT) 47. The intake side VCT 46 (corresponding to the valve timing adjusting mechanism) and the exhaust side VCT 47 (corresponding to the valve timing adjusting mechanism) respectively have relative rotational phases between the intake side cam shaft 36, the exhaust side cam shaft 37 and the crankshaft. Then, it is changed by adjusting the center phases of the intake side camshaft 36 and the exhaust side camshaft 37. The intake side camshaft 36 and the exhaust side camshaft 37 are rotated to the retard side or the advance side with respect to the crankshaft according to the control amounts of the intake side VCT 46 and the exhaust side VCT 47, and the intake side is adjusted in accordance with the operation. The opening / closing timing of the valve 18 and the exhaust valve 19 is changed to the retard side or the advance side.

  In the control system of the internal combustion engine 17 having the above-described configuration, the ECU 10 inputs detection signals of the various sensors described above, and based on the detection signals, the internal combustion engine such as the intake air amount, the throttle opening degree, the rotational speed of the internal combustion engine 17 and the like. The operating state of the engine 17 is detected. Further, the ECU 10 controls the fuel injection by the injector 33, the opening degree control of the throttle valve 32, the ignition timing control by the spark plug 35, the intake side VCT 46 based on the operating states of the various internal combustion engines 17 detected as described above. The control of the opening / closing timing of the intake valve 18 by means of, the control of the opening / closing timing of the exhaust valve 19 by the exhaust side VCT 47, etc. are carried out.

  In the present embodiment, when a fuel cut condition (corresponding to a predetermined condition) is satisfied, the ECU 10 causes the injector 33 to temporarily stop fuel injection and perform fuel cut. The fuel cut condition corresponds to, for example, that the accelerator operation amount is 0 and the rotational speed of the internal combustion engine 17 is higher than a predetermined value (for example, 1000 rpm). The ECU 10 corresponds to a valve timing control unit and a fuel injection stop unit. In addition, the ECU 10 corresponds to an EGR rate calculation unit, an intermittent combustion execution unit, an execution control unit, and a first drive assist unit.

  When the fuel cut is performed, the vehicle shifts to the inertial running state, so that the internal combustion engine 17 continues to idle due to the driving force transmitted from the driving wheels. At this time, if the valve timing is kept at the valve timing at the time of fuel injection, a pumping loss occurs during the idling of the internal combustion engine 17, and a strong deceleration force acts on the vehicle, which may cause a deterioration in fuel consumption. Therefore, the ECU 10 controls the valve timing so that the pumping loss is reduced when the fuel cut is performed.

  In the present embodiment, as shown in FIG. 3, the valve opening timing of the intake valve 18 is controlled to be retarded from the piston top dead center (TDC) of the intake stroke. In the intake stroke, the timing at which fresh air flows from the intake valve 18 is delayed by the retarded angle, negative pressure is generated in the piston 44, and pumping loss occurs. With respect to this, the valve closing timing of the exhaust valve 19 is controlled to the advance side with respect to the TDC, and is controlled to be the advance side with respect to the state in which the fuel injection is performed. By this control, fresh air (because the fuel is cut) remains in the combustion chamber 42 during the exhaust stroke. As a result, the expansion action occurs until the fresh air compressed during the exhaust stroke returns to its original volume, and therefore it is possible to reduce the pumping loss during the intake stroke. Furthermore, it is possible to reduce the amount of fresh air flowing to the exhaust purification device 39 through the exhaust port during fuel cut.

  Further, the closing timing of the intake valve 18 is controlled to be retarded from the piston bottom dead center (BDC) of the intake stroke, and is retarded from the state in which fuel is being injected. Control as follows. In this case, the return of fresh air to the intake port can be increased, and the amount of fresh air flowing to the exhaust purification device 39 during the fuel cut can be reduced. For this reason, it can suppress that the temperature of the exhaust gas purification catalyst of the exhaust gas purification device 39 falls.

  However, when returning from the fuel cut in this state, the EGR gas remaining in the combustion chamber 42 increases because the exhaust valve 19 is closed during the exhaust stroke until the valve timing before the fuel cut is changed. . This may cause misfire when returning from the fuel cut. In the present embodiment, in order to suppress such misfire induction, the two operation modes (continuous combustion mode and intermittent combustion mode) of the internal combustion engine 17 are switched according to the EGR rate in the combustion chamber 42.

  In the continuous combustion mode, a combustion cycle in which fuel combustion is performed is continuously performed. In the intermittent combustion mode, a scavenging cycle (non-combustion cycle) in which intake and exhaust are performed without performing fuel injection by the injector 33 is provided between the combustion cycles. In the scavenging cycle, the following four cycles are performed without performing fuel injection by the injector 33. The intake stroke for taking air from the intake pipe 31 into the combustion chamber 42, the compression stroke for compressing the mixture of the taken-in air and the EGR gas remaining in the combustion chamber 42 by the piston 44, and rotating the crankshaft by inertia traveling, thereby burning An expansion stroke in which the piston 44 moves in the direction in which the air-fuel mixture in the chamber 42 expands, and an exhaust stroke in which the exhaust valve 19 is opened to exhaust the air-fuel mixture. By performing these four cycles, the EGR gas remaining in the combustion chamber 42 is discharged. In the present embodiment, in the intermittent combustion mode, the combustion cycle and the non-combustion cycle are alternately performed.

  The control contents of the internal combustion engine 17 of FIG. 4 performed by the ECU 10 will be described below.

  First, in step S100, it is determined whether or not a fuel cut condition is satisfied. When it is determined that the fuel cut condition is not satisfied (S100: NO), this control is terminated as it is. When it is determined that the fuel cut condition is satisfied (S100: YES), the process proceeds to step S105, and the fuel cut is performed.

  In step S110, the valve timing is controlled to the valve timing shown in FIG. And it progresses to step S115 and it is determined whether the fuel cut cancellation conditions are satisfied. The fuel cut cancellation condition is satisfied, for example, when the accelerator operation amount is larger than a predetermined operation amount. When it is determined that the fuel cut cancellation condition is not satisfied (S115: NO), the fuel cut is continued and the process returns to step S110. When the fuel cut cancellation condition is satisfied (S115: YES), the process proceeds to step S120, the valve timing control performed in step S110 is canceled, and the valve timing at the time of fuel injection is controlled.

  In step S125, based on the current opening / closing timing of the intake valve 18 and the exhaust valve 19, an EGR rate that is a ratio of EGR gas to the entire gas in the combustion chamber 42 (that is, gas used for combustion) is calculated. Then, it is determined whether or not the calculated estimated EGR rate is smaller than a combustion limit EGR rate (corresponding to a threshold value) set as an upper limit value that does not cause misfire in carrying out the continuous combustion mode. The EGR rate of the gas in the combustion chamber 42 can be calculated by calculating according to the following equation (1). At this time, Vn is the volume of the combustion chamber 42 at the crank position n in FIG. For example, V0 is the volume of the combustion chamber 42 at the crank position 0. Further, v'1 is the amount of fresh air in the combustion chamber 42 at the previous intake cycle position 1, and v'2 is the amount of fresh air in the combustion chamber 42 at the previous intake cycle position 2. Vtotal is the volume of the combustion chamber 42 when the piston 44 is positioned at the BDC.

... (1)

  When it is determined that the estimated EGR rate is larger than the combustion limit EGR rate (S125: NO), it is determined that there is a risk of misfire if the continuous combustion mode is performed, and the process proceeds to step S135, and the intermittent combustion mode is performed. In step S140, it is determined whether or not the current cycle of the cylinder 43 in the internal combustion engine 17 is a combustion cycle. When it is determined that the current cycle of the cylinder 43 in the internal combustion engine 17 is a non-combustion cycle (S140: NO), torque is applied to the internal combustion engine 17 by the rotating machine 13. Then, the process returns to step S125. If it is determined that the current cycle performed by the cylinder 43 in the internal combustion engine 17 is a combustion cycle (S140: YES), the process proceeds to step S145, where it is assumed that torque is generated in the vehicle, and the rotating machine 13 Implement regenerative power generation. Then, the process returns to step S125.

  When it is determined that the estimated EGR rate is smaller than the combustion limit EGR rate (S125: YES), the continuous combustion mode is executed because the possibility of misfire is low even if the continuous combustion mode is executed.

  Next, the operation of this control system will be described with reference to FIG.

  In FIG. 5, “accelerator opening” represents the accelerator operation amount operated by the driver. “Vehicle speed” represents the traveling speed of the vehicle, and “Engine rotational speed” represents the rotational speed of the internal combustion engine 17. The “IN-VCT operating angle” indicates whether the intake side VCT 46 controls the intake side camshaft 36 to the advance side or the retard side as compared with the valve timing at the time of fuel injection. The “EX-VCT working angle” represents whether the exhaust side VCT 47 controls the exhaust side camshaft 37 to the advance side or the retard side as compared with the valve timing at the time of fuel injection. The “F / C flag” indicates whether the fuel cut condition is satisfied by ON / OFF. The “calculated EGR rate” represents the ratio of EGR gas to the entire gas in the combustion chamber 42. The “combustion mode” represents an operation mode that the internal combustion engine 17 is implementing.

  From the normal running in which the continuous combustion mode is implemented, the F / C flag is turned on and the fuel cut is performed on condition that the accelerator operation amount is 0 and the rotational speed of the internal combustion engine 17 is higher than a predetermined value. (See time t1). In the present embodiment, during the fuel cut, the EGR rate is not calculated because no EGR gas remains in the combustion chamber 42. Therefore, in FIG. 5, the EGR rate is represented as 0 during the fuel cut period.

  When the fuel cut is performed, the intake-side VCT 46 controls the intake-side camshaft 36 to the retard side with respect to the valve timing at the time of fuel injection, and the exhaust-side VCT47 is controlled to the exhaust-side camshaft from the valve timing at the time of fuel injection. 37 is controlled to the advance side. Specifically, control is performed so that the valve timing shown in FIG. 3 is obtained.

  During the fuel cut period (see times t1 to t2), no torque is generated in the vehicle, so the rotational speed of the internal combustion engine 17 decreases and the vehicle speed also decreases. Thereafter, when the accelerator operation amount operated by the driver becomes larger than the predetermined operation amount, the ECU 10 satisfies the fuel cut cancellation condition (see time t2). As a result, the fuel cut is released, and the fuel injection by the injector 33 is resumed. As the fuel injection is restarted, the calculation of the EGR gas ratio is restarted.

  When the fuel cut is released, the valve timing of the intake valve 18 and the exhaust valve 19 is controlled to the valve timing at the time of fuel injection. However, immediately after canceling the fuel cut, the valve timing of the intake valve 18 and the exhaust valve 19 is still the valve timing at the time of fuel cut, so the EGR rate calculated by the equation (1) is calculated to be larger than the combustion limit EGR rate. The Therefore, the intermittent combustion mode is performed on the assumption that misfire may occur when the continuous combustion mode is performed. In the intermittent combustion mode, since a non-combustion cycle is inserted between the combustion cycle, the EGR rate is accurately calculated in the equation (1) used in the continuous combustion mode in which the combustion cycle is continuously performed. I can't. Therefore, during the intermittent combustion mode execution period, the EGR rate is calculated using the following equation (2). At this time, v′7 is the amount of fresh air in the combustion chamber 42 at the previous intake cycle position 7, and v′8 is the amount of fresh air in the combustion chamber 42 at the previous intake cycle position 8.

... (2)

  When the intermittent combustion mode is performed and the valve timing of the intake valve 18 and the exhaust valve 19 shifts to the valve timing at the time of fuel injection, the calculated EGR rate decreases. On the other hand, when the intermittent combustion mode is performed, torque is generated in the vehicle, and the rotational speed and the vehicle speed of the internal combustion engine 17 that have decreased during the fuel cut period start to increase. Then, when the calculated EGR rate becomes lower than the combustion limit EGR rate, the continuous combustion mode is performed (see time t3), assuming that the possibility of misfire is low even if the continuous combustion mode is performed.

  With the above configuration, the ECU 10 according to the present embodiment has the following effects.

  During the fuel cut period, the opening / closing timing of the intake valve 18 and the exhaust valve 19 is controlled by the intake side VCT 46 and the exhaust side VCT 47 so that the pumping loss is reduced. By performing this control, the pumping loss is reduced during the fuel cut period, and deterioration of fuel consumption can be suppressed. However, if this control is performed, EGR gas may remain at the time of return from the fuel cut, and misfire may occur. Regarding the excessive EGR gas remaining, the EGR rate is calculated as a value larger than the combustion limit EGR rate. Therefore, when the EGR rate calculated based on the current valve timing is larger than the combustion limit EGR rate, an intermittent combustion cycle is performed. Thereby, during the execution of the intermittent combustion cycle, a non-combustion cycle is inserted between the combustion cycles, so that the EGR gas remaining in the internal combustion engine 17 during the non-combustion cycle can be discharged. it can. Therefore, even if the EGR gas remaining in the combustion chamber 42 increases, it is possible to suppress the occurrence of misfire.

  -During the implementation period of the intermittent combustion cycle, torque is applied to the output shaft of the internal combustion engine 17 by the rotating machine 13 in the non-combustion cycle. For this reason, it is possible to suppress a decrease in the output of the vehicle in a non-combustion cycle in which no fuel is burned.

  During the fuel cut period, control is performed by the intake side VCT 46 and the exhaust side VCT 47 so that the valve timing shown in FIG. 3 is obtained, so that the pumping loss can be reduced. Further, during the fuel cut period, the exhaust valve 19 closes in the middle of the exhaust stroke, so it is possible to reduce the low temperature fresh air that flows out to the exhaust pipe 34. For this reason, it is possible to suppress the temperature drop of the catalyst provided in the exhaust pipe 34 and to suppress the deterioration of the exhaust performance.

  The above embodiment can also be implemented with the following modifications.

  In the above embodiment, the intake side VCT 46 and the exhaust side VCT 47 are provided to control the valve timing of the intake valve 18 and the exhaust valve 19. For this, for example, a variable valve lift mechanism such as a VTEC that makes the lift amount variable may be provided.

  In the above embodiment, when the intermittent combustion mode is performed, the combustion mode and the non-combustion mode are alternately performed. About this, you may set the ratio of a non-combustion cycle high with respect to the ratio of a combustion cycle. As a result, the remaining EGR gas and the EGR gas accumulated in the combustion cycle can be scavenged more quickly.

  In the above embodiment, when the fuel cut condition is satisfied, the valve timing shown in FIG. 3 is controlled by the intake side VCT 46 and the exhaust side VCT 47. In this regard, the valve overlap may be controlled to occur. Specifically, the closing timing of the exhaust valve 19 is controlled to be retarded from the TDC of the exhaust stroke, and the opening timing of the intake valve 18 is controlled to be advanced from the closing timing of the exhaust valve. Such control also makes it possible to reduce the pumping loss when the fuel is cut.

  In the above embodiment, it is assumed that the valve timing is controlled so as to reduce the pumping loss when the fuel is cut, and then the EGR gas increases when the fuel cut is restored. In this example, it is assumed that an abnormality in which EGR gas remains due to a failure of the intake side VCT 46 or the exhaust side VCT 47 or the like.

  FIG. 6 shows the control contents of the internal combustion engine 17 performed by the ECU (corresponding to the failure detection unit) 10 according to this example, and is a partial modification of FIG. That is, step S100, step S105, step S110, step S115, and step S120 are deleted. And step S255, step S260, and step S265 are newly provided.

  Specifically, the control is terminated when the continuous combustion mode is performed in step S130, but in step S230 corresponding to step S130, the process proceeds to step S255 when the continuous combustion mode is performed. In step S145, when the cycle currently performed by the cylinder 43 during the intermittent combustion mode is a combustion cycle, regenerative power generation is performed by the rotating machine 13, and the process returns to step S125. Similarly, in step S150, when the cycle currently performed by the cylinder 43 during the intermittent combustion mode is a non-combustion cycle, torque is applied to the internal combustion engine 17 by the rotating machine 13, and the process returns to step S125. It was. In step S245 corresponding to step S145 and step S250 corresponding to step S150, when the control in the step is finished, the process proceeds to step S255.

  In step S255, it is determined whether or not the control deviations of the intake side VCT 46 and the exhaust side VCT 47 are smaller than the upper limit value (control deviation limit value) of the control deviation including an error when normally controlled. For example, the control deviation of the intake side VCT 46 is obtained as follows. Based on the detection values of the crank angle sensor 22 and the intake side cam angle sensor 20, the ECU 10 calculates the actual relative rotational phase (actual phase). Then, the target phase is calculated by the ECU 10 based on the operating conditions (rotational speed, load, etc. of the internal combustion engine 17). Then, a control deviation is calculated from the calculated actual phase and target phase.

  If it is determined that the calculated control deviation is larger than the control deviation limit value (S255: NO), it is determined that the corresponding intake side VCT 46 or exhaust side VCT 47 has failed, and the process proceeds to step S265. In step S265, the failure flag is set to ON, and the process returns to step S225. When it is determined that the calculated control deviation is smaller than the control deviation limit value (S255: YES), it is determined that the intake side VCT 46 and the exhaust side VCT 47 have not failed, and the failure flag is set to OFF to perform this control. finish.

  For the other steps, the processes in steps S225, S235, and S240 in FIG. 6 are the same as the processes in steps S125, S135, and S140 in FIG. 4, respectively.

  Next, the operation of the control system according to this another example will be described with reference to FIGS.

  First, FIG. 7 will be described. Since the control during the fuel cut period is the same as that in the above embodiment, the description thereof is omitted. When the fuel cut cancellation condition is satisfied (see time t12), the fuel injection by the injector 33 is resumed. In addition, the calculation of the EGR rate is resumed with the establishment of the fuel cut cancellation condition. Since the valve timing at this time is the valve timing at the time of fuel cut, the calculated EGR rate is higher than the combustion limit EGR rate. Therefore, the intermittent combustion mode is performed by the ECU 10.

  At this time, the intake side VCT 46 and the exhaust side VCT 47 are controlled by the valve timing at the time of fuel injection. Here, for example, the intake side VCT 46 is out of order and the intake side camshaft 36 can be controlled to the retard side. Is assumed. In this case, since the exhaust side camshaft 37 is controlled by the valve timing at the time of fuel injection by the exhaust side VCT 47 (see time t13), the calculated EGR rate decreases accordingly. However, since the intake camshaft 36 is controlled to the retard side, the calculated EGR rate is not lower than the combustion limit EGR rate, and the intermittent combustion mode is continued (see time t14).

  FIG. 8 shows a case in which when the fuel cut is released, the intake side VCT 46 is fixed when it is advanced from the valve timing of FIG. 7 and is controlled to be retarded from the valve timing at the time of fuel injection. (See time t23). In this case, the EGR rate calculated from FIG. 7 is reduced by the amount that the intake side VCT 46 controls the intake side camshaft 36 to the retard side. As a result, if the calculated EGR rate becomes smaller than the combustion limit EGR rate, the continuous combustion mode can be executed even if the intake side VCT 46 is abnormal, and the continuous combustion mode is executed (see time t24). ).

  As described above, when a failure of the intake side VCT 46 or the exhaust side VCT 47 is detected, if the calculated EGR rate is larger than the combustion limit EGR rate, an intermittent combustion cycle is performed. On the other hand, when the calculated EGR rate is smaller than the combustion limit EGR rate, even if the intake side VCT 46 or the exhaust side VCT 47 has failed, the possibility of misfire is low and the continuous combustion mode is performed. . Therefore, even if the intake side VCT 46 or the exhaust side VCT 47 fails, it is possible to switch to a suitable combustion mode according to the calculated EGR rate.

  FIG. 9 is a partial modification of FIG. That is, step S140 and step S145 are deleted. Instead of determining whether or not the fuel cut release condition corresponding to step S115 is satisfied, it is determined in step S315 whether or not there is an acceleration request. In this other example, for example, when the accelerator operation amount operated by the driver becomes larger than 0, it is considered that the acceleration request has occurred. In addition, when the cycle currently performed by the cylinder 43 during the intermittent combustion mode corresponding to step S150 is a non-combustion cycle, torque is applied to the output shaft of the internal combustion engine 17 by the rotating machine 13, In step S450, torque is applied to the output shaft of the internal combustion engine 17 by the rotating machine 13 during the implementation period of the intermittent combustion mode.

  Further, step S316 and step S318 are newly inserted between step S315 corresponding to step S115 and step S420 corresponding to step S120. In addition, step S317, step S320, step S325, and step S330 are newly provided.

  Specifically, when it is determined in step S315 that there is no acceleration request (S315: NO), the fuel cut is continued and the process returns to step S310. If it is determined that there is an acceleration request (S315: YES), the process proceeds to step S316. In step S316, it is determined whether or not the required torque calculated based on the operated accelerator operation amount is smaller than an output torque value (ISG output torque value) that can be applied by the rotating machine 13. When it is determined that the required torque is smaller than the ISG output torque value (S316: YES), the process proceeds to step S317, the fuel cut is continued, and the valve timing is set to the valve timing at the time of fuel cut. Torque is applied to the output shaft of the internal combustion engine 17 by the machine 13. And this control is complete | finished. Therefore, the ECU 10 according to this different example corresponds to the second drive assist unit and the required torque calculation unit.

  On the other hand, if it is determined that the required torque is greater than the ISG output torque value (corresponding to the auxiliary threshold value) (S316: NO), the process proceeds to step S318, where it is determined whether the required torque is smaller than the specified torque value. Is done. The specified torque value is set as a value at which torque needs to be output immediately.

  When it is determined that the required torque is smaller than the specified torque value (S318: YES), the process proceeds to step S320, and the valve timing is controlled to the valve timing at the time of fuel injection by the intake side VCT 46 and the exhaust side VCT 47. Then, the process proceeds to step S325. In step S325, it is determined whether or not the calculated EGR rate is smaller than the combustion limit EGR rate. If it is determined that the calculated EGR rate is greater than the combustion limit EGR rate (S325: NO), there is a risk of misfire if the continuous combustion mode is performed in this state, but the required torque is smaller than the specified torque. There is no need to output torque immediately. For this reason, the intermittent combustion mode is not performed, and step S325 is performed again while continuing the fuel cut. If it is determined that the calculated EGR rate is smaller than the combustion limit EGR rate (S325: YES), the process proceeds to step S330, and the continuous combustion mode is executed because the possibility of misfire is low even if the continuous combustion mode is executed. . And this control is complete | finished.

  On the other hand, if it is determined that the required torque is greater than the specified torque value (S318: NO), the process proceeds to step S420.

  Regarding the other steps, the processes in steps S300, S305, S310, S420, S425, S430, and S435 in FIG. 9 are respectively performed in steps S100, S105, S110, S120, S125, S130, and S135 in FIG. It is the same as the process.

  According to the above configuration, if the required torque is low and the required torque can be satisfied by applying torque to the output shaft of the internal combustion engine 17 by the rotating machine 13, the fuel cut is continued and the valve timing is also the same as that at the time of the fuel cut. Maintain valve timing. This makes it possible to continue improving fuel efficiency.

  Further, when the required torque is higher than the ISG output torque value and lower than the predetermined torque, it is assumed that there is little need to output torque immediately, and fuel injection is performed by the intake side VCT 46 and the exhaust side VCT 47 in a state where fuel cut is continued. Return to the valve timing set at the time. Thereby, even if the calculated EGR rate is higher than the combustion limit EGR rate, the EGR rate decreases in the process of returning to the valve timing set at the time of fuel injection. When the EGR rate decreases below the combustion limit EGR rate, the possibility of misfire due to excessive EGR gas remaining can be suppressed by resuming fuel injection by the injector 33.

  When the required torque is higher than the predetermined torque, it is necessary to output the torque immediately, and the intermittent combustion mode is performed when the calculated EGR rate is higher than the combustion limit EGR rate. Further, during the intermittent combustion mode, torque is applied by the rotating machine 13. As a result, it is possible to output torque even when the EGR rate is higher than the combustion limit EGR rate, and it is possible to respond to a required torque larger than a predetermined torque.

  About this example, you may delete step S316 and step S317. In this case, when it is determined that there is an acceleration request in the determination of whether there is an acceleration request corresponding to step S315 (S315: YES), the process proceeds to step S318. Even with such a configuration, the required torque can be satisfied and misfire can be suppressed.

  About this example, you may delete step S318, step S320, step S325, and step S330. In this case, when it is determined in the determination of whether the required torque corresponding to step S316 is smaller than the ISG output torque value (S316: NO), the process proceeds to step S420. . Even with such a configuration, if the required torque can be satisfied by applying torque to the output shaft of the internal combustion engine 17 by the rotating machine 13, the fuel cut is continued and the valve timing is also maintained at the time of the fuel cut. Can be made. Further, when the required torque is larger than the ISG output torque, it is possible to output the torque to satisfy the required torque while suppressing misfire by switching to an appropriate operation mode based on the current EGR rate. Become.

  DESCRIPTION OF SYMBOLS 17 ... Internal combustion engine, 18 ... Intake valve, 33 ... Injector, 44 ... Piston, 46 ... Intake side VCT, 47 ... Exhaust side VCT

Claims (5)

An internal combustion engine (17) including a fuel injection section (33) for injecting fuel to be used for combustion and a valve timing adjustment mechanism (46, 47) for adjusting the opening / closing timing of the intake valve (18) or the exhaust valve (19). A control device (10) applied to
An EGR rate calculating unit that calculates an EGR rate of the gas supplied to the combustion based on the current opening / closing timing of the intake valve and the exhaust valve;
An intermittent combustion execution unit that executes an intermittent combustion mode in which a non-combustion cycle for stopping fuel injection by the fuel injection unit is inserted between a combustion cycle in which combustion of the fuel is performed and a combustion cycle;
Continuous combustion in which the EGR rate calculated by the EGR rate calculating unit is set as an upper limit value that does not cause misfire in the continuous combustion mode in which the combustion cycle in which the fuel is burned is continuously executed. An execution control unit that causes the intermittent combustion execution unit to execute the intermittent combustion mode when it exceeds a limit EGR rate , and
A fuel injection stop unit that stops fuel injection by the fuel injection unit when a predetermined condition is satisfied;
A valve timing control unit for controlling the opening / closing timing of the intake valve or the exhaust valve by the valve timing adjustment mechanism so that a pumping loss is reduced during a period when the fuel injection is stopped by the fuel injection stop unit;
A request torque calculation unit that calculates the request torque requested by the driver,
When the required torque calculated by the required torque calculation unit is greater than zero and smaller than a specified torque value that is a torque value for which torque needs to be output, control by the valve timing control unit is stopped, The control for stopping the fuel injection by the fuel injection stop unit is continued until the EGR rate calculated by the EGR rate calculation unit becomes smaller than the continuous combustion limit EGR rate in a state, and the EGR rate calculation unit calculates A control device for an internal combustion engine, wherein control for stopping fuel injection by the fuel injection stop unit is ended after the EGR rate to be performed becomes smaller than the continuous combustion limit EGR rate . A control device for an internal combustion engine applied to a vehicle including an electric motor (13) connected to an output shaft of the internal combustion engine and increasing a rotational speed of the internal combustion engine by applying torque to the output shaft,
A first drive assisting unit is provided that performs torque application as output compensation to the output shaft by the electric motor in the non-combustion cycle during an execution period of the intermittent combustion mode by the intermittent combustion execution unit. Item 2. A control device for an internal combustion engine according to Item 1. The valve timing control unit controls the valve opening timing of the intake valve to be retarded from the piston top dead center of the intake stroke during the period in which the fuel injection stop unit stops the fuel injection. Controlling the closing timing of the intake valve to be retarded from the state in which the fuel injection is being performed, and controlling the intake valve to be retarded from the bottom dead center of the piston in the intake stroke, and The valve closing timing of the exhaust valve is controlled to an advance side with respect to a state where the fuel injection is performed, and is controlled to an advance side with respect to the top dead center of the exhaust stroke. The control apparatus for an internal combustion engine according to any one of 1 and 2 . A failure detection unit for detecting a failure of the valve timing adjustment mechanism;
The execution control unit, when the failure detection unit detects a failure of the valve timing adjustment mechanism, the EGR rate calculated by the EGR rate calculation unit is larger than the continuous combustion limit EGR rate The intermittent combustion mode is executed by the intermittent combustion execution unit, and when the EGR rate calculated by the EGR rate calculation unit is smaller than the continuous combustion limit EGR rate , switching to the continuous combustion mode is performed. The control device for an internal combustion engine according to any one of claims 1 to 3 , wherein the control device is an internal combustion engine. The intermittent combustion execution unit, an internal combustion engine according to any one of claims 1 to 4, characterized in that said set higher proportion of non-combustion cycle in the intermittent combustion mode for the proportion of the combustion cycle Control device.