JP2009149195A - Controller for hybrid system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology for stabilizing combustion at the start-up of an internal combustion engine, while generating requirement output at restoration to normal fuel injection control from fuel cut control, in a hybrid system having an EGR device. <P>SOLUTION: This controller for the hybrid system has: the EGR device making a part of exhaust emission from the internal combustion engine flow into an intake system of the internal combustion engine as EGR gas; a means for performing the fuel cut control to stop fuel injection in the internal combustion engine; a decision means deciding whether an EGR rate of gas took into the internal combustion engine is not more than a prescribed limit EGR rate at which a misfire does not occur in the internal combustion engine; and a means for continuing the fuel cut control without restoring the internal combustion engine to the normal fuel injection control during a period, until it is decided by the decision means that the EGR rate becomes not larger than the limit EGR rate, after a condition to be restored is satisfied, when the condition to be restored to the normal fuel injection control from the fuel cut control is satisfied during execution of the fuel cut control, and performing control, such that the required output is generated by only an electric motor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for a hybrid system.

  There is known a hybrid system that includes an internal combustion engine and an electric motor as a power source, and generates a required output by the internal combustion engine and / or the electric motor according to operating conditions. In a hybrid system, a technique for improving fuel efficiency by performing fuel cut control for stopping fuel supply to an internal combustion engine when decelerating or stopping a vehicle and stopping the internal combustion engine is known.

  As a technique for reducing exhaust emission and improving fuel efficiency of an internal combustion engine, an EGR device that returns part of the exhaust from the internal combustion engine to the intake system as EGR gas is known.

In a hybrid system equipped with an EGR device, if fuel cut control is performed while EGR gas is being introduced into the intake system by the EGR device, EGR gas remains in the intake system and the exhaust system during fuel cut control. In some cases, the remaining EGR gas is discharged outside the vehicle without being sufficiently purified by the exhaust purification catalyst when returning from the fuel cut control. On the other hand, at the time of deceleration, the clutch between the electric motor and the internal combustion engine is engaged to perform motoring, and the throttle valve is fully opened to send the residual EGR gas to the exhaust purification catalyst, thereby purifying the residual EGR gas. A technique to be performed is described in Patent Document 1.
JP 2002-256919 A JP-A-6-257518

  In a hybrid system equipped with an EGR device, if fuel cut control is performed while EGR gas is being introduced into the intake system by the EGR device, EGR gas remains in the intake system during the fuel cut control, and this residual The EGR gas is sucked into the cylinder when returning from the fuel cut control. If the amount of EGR gas at this time is excessively large, combustion instability such as misfire may occur when the internal combustion engine is started when returning from the fuel cut control.

  The present invention has been made in view of such problems, and in a hybrid system equipped with an EGR device, the internal combustion engine is started while generating a required output when returning from fuel cut control to normal fuel injection control. It aims at providing the technique which stabilizes the combustion of time.

In order to achieve the above object, a control device for a hybrid system of the present invention provides:
An EGR device that causes a part of the exhaust from the internal combustion engine to flow into the intake system of the internal combustion engine as EGR gas;
Means for performing fuel cut control for stopping fuel injection in the internal combustion engine;
Determining means for determining whether an EGR rate of gas sucked into the internal combustion engine is equal to or less than a predetermined limit EGR rate at which misfire does not occur in the internal combustion engine;
When the condition for returning from the fuel cut control to the normal fuel injection control is satisfied during the execution of the fuel cut control, the determination unit performs the determination from the time when the condition for returning to the normal fuel injection control is satisfied. During the period until it is determined that the EGR rate is equal to or less than the limit EGR rate, the internal combustion engine continues the fuel cut control without returning to the normal fuel injection control, and the electric motor Control means for controlling to generate the required output only by the electric motor;
It is characterized by providing.

  In the configuration of the present invention, the “limit EGR rate” is determined in advance based on the upper limit value of the EGR rate at which misfire does not occur in the internal combustion engine. The upper limit value of the EGR rate at which misfire does not occur in the internal combustion engine varies depending on the operating conditions of the internal combustion engine. Therefore, the “limit EGR rate” in the above configuration may also be a variable value according to the operating condition of the internal combustion engine when the condition for returning to normal fuel injection control is satisfied. Generally, when the operating condition of the internal combustion engine is low load, the combustion resistance against EGR gas is low, and when the operation condition is high load, the combustion resistance against EGR gas is high. Therefore, the limit EGR rate may be set to a lower concentration as the operating condition of the internal combustion engine when the condition for returning to normal fuel injection control is satisfied is lower. Further, a constant value that can suppress the occurrence of misfire regardless of the operating condition of the internal combustion engine when the condition for returning to the normal fuel injection control is satisfied may be set as the “limit EGR rate”.

  The “determination means” may be any means as long as it can determine whether or not the EGR rate of the intake gas of the internal combustion engine is equal to or less than the limit EGR rate. For example, a gas concentration sensor can be installed in the intake manifold or the intake passage, and determination can be made based on a comparison between the output of the gas concentration sensor and the limit EGR rate. In addition, the control state of the EGR device (EGR gas amount, EGR valve opening, EGR gas temperature, etc.) immediately before the fuel cut control is started, the control state of the internal combustion engine (rotation speed, load, fuel injection amount, exhaust gas) Internal combustion engine by model calculation based on data such as inert component concentration, exhaust temperature, throttle opening, etc., and time from when fuel cut control is started until the conditions for returning to normal fuel injection control are satisfied The EGR rate of the intake gas may be estimated, and the determination may be made based on a comparison between the estimated EGR rate and the limit EGR rate. In addition, a correspondence relationship between these physical quantities, the elapsed time since the condition for returning to normal fuel injection control, and the EGR rate of the intake gas of the internal combustion engine is obtained in advance, and normal fuel injection is performed. It is also possible to make a determination based on the measured value of the elapsed time since the condition for returning to control is established. When the operating condition of the internal combustion engine immediately before the fuel cut control is started is an operating condition in which the EGR gas is not introduced by the EGR device, it is considered that there is no EGR gas remaining in the intake system. Therefore, it may be determined that the EGR rate has become equal to or less than the limit EGR rate when the condition for returning to the normal fuel injection control is satisfied.

  “Normal fuel injection control” means that the required output is distributed at a predetermined distribution ratio between the internal combustion engine and the electric motor, and a predetermined amount determined so as to be able to generate the required output distributed to the internal combustion engine. In this control, fuel is injected and supplied to the internal combustion engine. Further, the fuel cut control is executed under an operating condition in which a required output such as a deceleration state or a vehicle stop state is 0, for example. Accordingly, the “condition for returning to normal fuel injection control” is established when the operating condition of the internal combustion engine changes from the operating condition in which the fuel cut control is performed to another operating condition. For example, it is possible to exemplify when re-acceleration from a deceleration state or when starting running from an idling stop state.

  According to the present invention, during the period from when the condition for returning from the fuel cut control to the normal fuel injection control is satisfied, until the EGR rate of the intake gas of the internal combustion engine is determined to be equal to or lower than the limit EGR rate, Is delayed to return to normal fuel injection control, and fuel cut control is continued. That is, fuel injection is not performed when the EGR rate of the intake gas of the internal combustion engine is in a high concentration state that may cause a misfire. Therefore, it is possible to suppress the occurrence of combustion instability such as misfire caused by the excessively high EGR rate of the intake gas.

And, by delaying the return to the normal fuel injection control of the internal combustion engine during the period, an output that is assumed to be generated by the internal combustion engine under the operating conditions under which the normal fuel injection control should be performed, It cannot be generated by the internal combustion engine. In this regard, in the present invention, the electric motor is controlled by the control means so that the electric motor generates all the required outputs including the output that should be originally generated by the internal combustion engine. Thereby, it is possible to suppress the output generated by the hybrid system from being less than the required output during the period in which the return of the internal combustion engine to the normal fuel injection control is delayed. Therefore, combustion instability at the time of return from the fuel cut control to the normal fuel injection control can be suppressed, and problems such as insufficient acceleration feeling, torque fluctuation, and drivability deterioration can be suppressed. .

  In the present invention, the control means may control the electric motor to further crank the internal combustion engine during a period in which the return to the normal fuel injection control of the internal combustion engine is delayed. This cranking is naturally performed when the fuel cut control is performed. Thereby, scavenging of the EGR gas remaining in the intake system can be promoted. Accordingly, it is possible to shorten the time required until the EGR rate of the intake gas of the internal combustion engine becomes equal to or lower than the limit EGR rate, in other words, the delay time until the internal combustion engine is returned to the normal fuel injection control.

  In the present invention, when it is determined that the EGR rate of the intake gas of the internal combustion engine has become equal to or less than the limit EGR rate, the internal combustion engine is returned to normal fuel injection control, and the electric motor is also returned to normal control. Can do.

  Here, “returning the electric motor to normal control” means that, as described above, the required output can be distributed between the internal combustion engine and the electric motor at a predetermined ratio, and the required output distributed to the electric motor can be generated. It means that predetermined control determined in such a manner is performed on the electric motor.

  According to the present invention, in a hybrid system equipped with an EGR device, it is possible to stabilize combustion at the time of starting an internal combustion engine while generating a required output when returning from fuel cut control to normal fuel injection control. become.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention only to those unless otherwise specified.

  FIG. 1 is a conceptual diagram illustrating a schematic configuration of a hybrid system according to the present embodiment. In FIG. 1, the hybrid system 1 includes an internal combustion engine 10, a transaxle 30, an inverter 40, and a battery 50. The hybrid system 1 is provided with an ECU 60 that is a computer that controls the hybrid system 1.

  The internal combustion engine 10 generates a driving force of the hybrid vehicle using fuel combustion energy as a source. The transaxle 30 is configured with a transmission and an axle (axle) as an integral structure. Inside the transaxle 30, a power split mechanism (for example, a planetary gear mechanism) 31, a speed reducer 32, an electric motor 33, a generator 34, A power control unit 35 for controlling the electric motor 33 and the generator 34 is accommodated. Further, lubricating oil is stored in the transaxle 30, and the electric motor 33, the generator 34, the power split mechanism 31, the speed reducer 32, and the like are lubricated.

The generator 34 generates power using the output generated by the internal combustion engine 10. The electric motor 33 generates the driving force of the hybrid vehicle by the electric power supplied from the battery 50 or the generator 34 that charges the electric power for driving the electric motor 33. The output from the internal combustion engine 10 and the output from the electric motor 33 are transmitted to the wheels via the power distribution mechanism 31 and the speed reducer 32.

  The power distribution mechanism 31 performs power transmission between the internal combustion engine 10 and the generator 34, power transmission between the internal combustion engine 10 and the speed reducer 32, and power transmission between the electric motor 33 and the speed reducer 32. Further, the inverter 40 converts the direct current of the battery 50 and the alternating current of the electric motor 33 and the generator 34.

  Next, a schematic configuration of the internal combustion engine 10 and its intake / exhaust system will be described. An intake manifold 11 is connected to the internal combustion engine 10, and each branch pipe of the intake manifold 11 communicates with a combustion chamber of each cylinder 2 through an intake port. The intake manifold 11 is connected to an intake passage 13, and a compressor 14 a of a turbocharger 14 that operates using exhaust energy as a drive source is provided in the intake passage 13. An intercooler 15 that cools the gas flowing through the intake passage 13 is provided downstream of the compressor 14 a in the intake passage 13. The intake air flowing into the compressor 14a is compressed by the rotation of a compressor wheel (not shown) provided in the compressor 14a. The compressed intake air having a high temperature is cooled by the intercooler 15 and then flows into the intake manifold 11. The intake air flowing into the intake manifold 11 is distributed to each cylinder 2 via the intake port. The intake air distributed to each cylinder 2 is combusted together with the fuel injected from the fuel injection valve 6 provided in each cylinder 2. The intake manifold 11 is provided with a gas concentration sensor 5 that measures the concentration of carbon dioxide in the intake air.

  An exhaust manifold 18 is connected to the internal combustion engine 10, and each branch pipe of the exhaust manifold 18 is connected to the combustion chamber of each cylinder 2 via an exhaust port (not shown). The exhaust manifold 18 is connected to an exhaust passage 19, and a turbine 14 b of the turbocharger 14 is provided in the exhaust passage 19. An exhaust purification catalyst 20 is provided downstream of the turbine 14 b in the exhaust passage 19, and the exhaust passage 19 is connected to a muffler (not shown) downstream of the exhaust purification catalyst 20. The burnt gas in each cylinder 2 is discharged to the exhaust manifold 18 through the exhaust port. This exhaust gas flows through the exhaust passage 19 and flows into the turbine 14b, and rotationally drives a turbine wheel (not shown) rotatably supported in the turbine 14b. The rotational torque of the turbine wheel (not shown) is transmitted to the compressor wheel (not shown) in the compressor 14a. Exhaust gas flowing out from the turbine 14b is discharged into the atmosphere through a muffler after harmful substances (for example, NOx, HC, CO, etc.) are purified by the exhaust purification catalyst 20.

  The exhaust passage 19 upstream from the turbine 14 b and the intake passage 13 downstream from the compressor 14 a are connected by the EGR passage 3. A part of the exhaust gas flowing through the exhaust passage 19 flows into the intake passage 13 as EGR gas via the EGR passage 3. An EGR valve 4 for adjusting the amount of EGR gas flowing through the EGR passage 3 is provided in the middle of the EGR passage 3.

  In the hybrid system 1, in addition to the gas concentration sensor 5 described above, a crank position sensor 23 that outputs a signal corresponding to the rotation angle of the crankshaft, and an accelerator that outputs a signal corresponding to the amount of depression of the accelerator pedal (accelerator opening). Various sensors such as a position sensor 21, a vehicle speed sensor 22 that outputs a signal corresponding to the traveling speed of the vehicle, and an SOC sensor 51 that acquires the state of charge (SOC) of the battery 50 are provided, and signals from each sensor are input to the ECU 60. It has come to be. The ECU 60 calculates the EGR rate of the intake gas existing in the intake manifold 11 based on the signal input from the gas concentration sensor 5.

In addition, the ECU 60 is connected to various devices other than the fuel injection valve 6 and the EGR valve 4 described above.
The operations of these devices are controlled in accordance with signals input from the various sensors. For example, a required output to be generated by the hybrid system 1 is calculated based on signals input from the accelerator position sensor 21 and the crank position sensor 23, and the required output is calculated based on operating conditions and a signal input from the SOC sensor 51. The distribution ratio between the internal combustion engine 10 and the electric motor 33 is determined, and the fuel injection amount to the internal combustion engine 10 and the power supply to the electric motor 33 are controlled so that the output according to the distribution can be generated.

  By opening the EGR valve 4, EGR gas flows into the intake passage 13. By introducing the EGR gas into the intake system of the internal combustion engine 10 in this way, the cooling loss and the pumping loss are reduced, so that the fuel consumption can be improved. Moreover, since the amount of harmful substances such as NOx contained in the exhaust gas is reduced, the exhaust performance can be improved. However, if the EGR rate of intake air becomes excessively high, combustion may become unstable, and problems such as misfire and torque fluctuation may occur. In general, when the operating condition of the internal combustion engine 10 is low load and low rotation, since the amount of fresh air and the amount of fuel injection are small, combustion instability is likely to occur when EGR gas is introduced. On the other hand, when the operating condition of the internal combustion engine 10 is a high load and high rotation, stable combustion is performed, so that even if a large amount of EGR gas is introduced, combustion instability is unlikely to occur. FIG. 2 shows the relationship between the EGR rate of intake air and torque fluctuation in each of the cases where the operating condition of the internal combustion engine 10 is low load and low speed and high load and high speed. As shown in FIG. 2, when the operating condition of the internal combustion engine 10 is high load and high rotation, even when the EGR rate is less likely to cause torque fluctuation, Large torque fluctuations may occur.

  Thus, in view of the fact that the upper limit (limit EGR rate) of the intake EGR rate at which combustion does not become unstable varies depending on the operating conditions of the internal combustion engine 10, the hybrid system of the present embodiment operates the internal combustion engine 10. The EGR control is performed so that the EGR rate of the intake air increases as the condition becomes a high load and high speed. FIG. 3 shows the relationship between the operating conditions of the internal combustion engine 10 and the EGR rate. As shown in FIG. 3, the EGR rate increases as the rotational speed and / or load of the internal combustion engine 10 increases. Further, the introduction of EGR gas is stopped in a predetermined low-load low-rotation region indicated by diagonal lines in FIG.

  In the hybrid system of the present embodiment, fuel cut control for stopping fuel injection by the fuel injection valve 6 is performed under predetermined operating conditions such that the required output to the internal combustion engine 10 is zero. The predetermined driving conditions are a deceleration state, a time when the vehicle is stopped, and the like. By performing fuel cut control, unnecessary fuel consumption can be suppressed and fuel consumption can be improved. During fuel cut control, the EGR valve 4 is closed and the introduction of EGR gas is also stopped.

  Here, when the fuel cut control is started when the internal combustion engine 10 is operated under the operation condition in which the EGR gas is introduced, during the fuel cut control, the EGR passage 3 and the EGR passage 3 on the downstream side of the EGR valve 4 are operated. EGR gas remains in the intake system region including the intake passage 13 and the intake manifold 11 on the downstream side of the connection location. A part of the EGR gas remaining in the intake system region is sucked into the cylinder 2 and scavenged before the rotation of the internal combustion engine 10 completely stops after the fuel cut control is started. There may be a case where the air is not sufficiently scavenged from the intake system region due to the operating condition of the internal combustion engine 10 immediately before the start. In such a case, the internal combustion engine 10 is stopped with EGR gas remaining in the intake system region. In this state, when a condition (return condition) for returning from the fuel cut control to the normal fuel injection control (normal control) is satisfied for the internal combustion engine 10, first, the EGR gas remaining in the intake system region is the cylinder 2 Will be inhaled.

In particular, when fuel cut control is started from an operating condition belonging to a high-load, high-rotation region where a large amount of EGR gas is introduced, a large amount of EGR gas remains in the intake system region when the return condition to normal control is satisfied. There is a possibility. In such a case, if the return to normal control is performed immediately when the return condition to normal control is satisfied, the residual gas having a high EGR rate in the intake system region is sucked into the cylinder 2 of the internal combustion engine 10. Then, the fuel is supplied to the internal combustion engine 10 by the fuel injection valve 6. Therefore, the EGR rate of the cylinder intake gas exceeds the limit EGR rate corresponding to the operating condition of the internal combustion engine 10 when the return condition is satisfied, and there is a possibility that combustion instability such as misfire may occur.

  Therefore, in the hybrid system 1 of the present embodiment, when the return condition from the fuel cut control to the normal control is satisfied during execution of the fuel cut control, the gas in the intake manifold 11 is determined based on the output of the gas concentration sensor 5. When the EGR rate is calculated and the calculated EGR rate exceeds the limit EGR rate corresponding to the operating condition of the internal combustion engine 10 when the return condition is satisfied, the internal combustion engine 10 is not returned from the fuel cut control to the normal control. The fuel cut control was continued. Then, when the EGR rate of the gas in the intake manifold 11 calculated based on the output of the gas concentration sensor 5 becomes equal to or lower than the limit EGR rate, the fuel cut control is terminated and returned to the normal control. Further, the output originally assumed to be generated by the internal combustion engine 10 during a delay period from when the return condition from the fuel cut control to the normal control is satisfied until the actual return to the normal control is executed. The electric motor 33 is controlled so as to be output by the electric motor 33. Furthermore, the electric motor 33 is controlled so that the internal combustion engine 10 is cranked by the electric motor 33 during this delay period.

  By performing such control, when the internal combustion engine 10 is returned from the fuel cut control to the normal control, the EGR rate of the gas sucked into the cylinder 2 of the internal combustion engine 10 becomes equal to or less than the limit EGR rate. Therefore, combustion instability such as misfire is suppressed when returning to normal control, and problems such as torque fluctuation and drivability deterioration can be suppressed. Further, during the delay period, the return of the internal combustion engine 10 to the normal control is delayed even though the internal combustion engine 10 originally returns from the fuel cut control to the normal control and the output from the internal combustion engine 10 is assumed. Since the output that cannot be generated by the internal combustion engine 10 is compensated by the electric motor 33, the required output during the delay period can be generated without excess or deficiency, and drivability such as lack of acceleration. Can be prevented from occurring. Further, during the delay period, the electric motor 33 is further controlled to perform cranking of the internal combustion engine 10, so that scavenging of the gas remaining in the intake system region can be completed earlier. Therefore, the delay period can be shortened and the internal combustion engine 10 can be returned to the normal control earlier.

  FIG. 4 shows the vehicle speed, the required output, and the inside of the intake manifold 11 when the control of the present embodiment described above is applied when the internal combustion engine 10 is decelerated from the high-load operation state and reaccelerated. It is the time chart which showed an example of the time change of the EGR rate of this gas. 4A shows the vehicle speed of a vehicle equipped with the hybrid system 1 of this embodiment as a power source, FIG. 4B shows the required output for the hybrid system 1, and FIG. 4C shows the gas concentration sensor 5 Represents the EGR rate of the gas in the intake manifold 11 calculated by the ECU 60 based on the signal from.

In the example shown in FIG. 4, before the time t ₁ , all the required outputs for the hybrid system 1 are distributed to the internal combustion engine 10, and the hybrid system 1 is controlled by the ECU 60 so that all the required outputs are generated by the internal combustion engine 10. Is called. At this time, the internal combustion engine 10 is operated at a high load, and a large amount of EGR gas is introduced into the intake system as described above.

When a condition to be decelerated is satisfied by the driver's request at time t ₁ , the required output to the hybrid system 1 becomes 0 and the required output to the internal combustion engine 10 also becomes 0. Accordingly, the fuel cut in the internal combustion engine 10 occurs. Control is implemented. At the same time, the target EGR gas rate becomes 0, and the EGR valve 4 is closed accordingly.

During the fuel cut control of the time t ₁ and later, the internal combustion engine 10 will continue to rotate in inertia, gradually speed decreases. Due to the inertia rotation after the start of the fuel cut control, the gas in the intake system region is scavenged, and the EGR valve 4 is closed and the introduction of new EGR gas is also stopped. The EGR rate gradually decreases.

In time t _2, the re-acceleration request is made. As a result, a condition for returning from the fuel cut control to the normal control is established. At this time, the EGR rate of the gas in the intake manifold 11 is calculated based on the signal from the gas concentration sensor 5, and the calculated EGR rate is compared with the limit EGR rate Rc. In the example shown in FIG. 4, since the EGR rate of the intake manifold 11 in the gas at time t ₂ is higher than the limit EGR rate Rc, not performed return to the normal control of the internal combustion engine 10, the fuel cut control is continued, All the required outputs for the hybrid system 1 at this time are distributed to the electric motor 33, and the electric motor 33 is controlled so that the electric motor 33 generates the required output. Furthermore, the control of the electric motor 33 to perform the cranking of the internal combustion engine 10 is performed by the electric motor 33, thereby since the scavenging gas in the intake system area is promoted, the time t ₂ later, the intake manifold 11 The rate of decrease in the EGR rate of gas increases. The cranking of the internal combustion engine 10 at this time is executed together with the fuel cut control, and is cranking that does not involve fuel injection.

At time t _3, when the EGR rate calculated on the basis of the signal from the gas concentration sensor 5 becomes less than the limit EGR rate Rc, it is returned to the normal controlling an internal combustion engine 10 from the fuel cut control. That is, all the required outputs for the hybrid system 1 are distributed to the internal combustion engine 10 and the electric motor 33 at a distribution ratio determined in advance according to the operating conditions, and the fuel in the internal combustion engine 10 is generated so that the distributed output can be generated. Injection control and power supply control in the electric motor 33 are performed.

  FIG. 5 is a flowchart showing a routine for executing the control of the present embodiment described above. This routine is executed during fuel cut control of the internal combustion engine 10.

  In step S101, the ECU 60 determines whether or not a condition for returning the internal combustion engine 10 to the normal control is satisfied. For example, this condition is satisfied when there is an acceleration request. If an affirmative determination is made in step S101, the ECU 60 proceeds to step S102. If a negative determination is made in step S101, the ECU 60 once ends the execution of this routine.

  In step S102, the ECU 60 calculates the EGR rate of the gas in the intake manifold 11 based on the signal from the gas concentration sensor 5, and determines whether or not the calculated EGR rate R is higher than the limit EGR rate Rc. If an affirmative determination is made in step S102 (R> Rc), the ECU 60 proceeds to step S103. If a negative determination is made in step S102 (R ≦ Rc), the ECU 60 proceeds to step S104.

  In step S <b> 103, the ECU 60 continues the fuel cut control for the internal combustion engine 10 and performs power supply control to the electric motor 33 so that the electric motor 33 generates the required output distributed to the internal combustion engine 10. Further, cranking of the internal combustion engine 10 by the electric motor 33 is started.

  In step S104, the ECU 60 returns the internal combustion engine 10 to normal control. That is, fuel injection is performed so that the required output distributed to the internal combustion engine 10 is generated by the internal combustion engine 10, and power supply control is performed so that the required output distributed to the electric motor 33 is generated by the electric motor 33.

In the above example, the EGR rate of the intake manifold 11 in the gas at time t ₂ which was re-acceleration request has been described control performed in the case above a critical EGR rate Rc, the inertia of the internal combustion engine 10 in the deceleration state If there is a request for re-acceleration when the remaining gas in the intake system region is sufficiently scavenged by rotation, the EGR rate of the gas in the intake manifold 11 at that time may be less than or equal to the limit EGR rate. . In such a case, the return to the normal control of the internal combustion period 10 may be executed immediately without performing the control for delaying the return to the normal control of the internal combustion engine 10 according to the present embodiment. In addition, it is not essential to perform fuel cut cranking of the internal combustion engine 10 by the electric motor 33 during the delay period for returning the internal combustion engine 10 to normal control.

  FIG. 6 shows the time change of the vehicle speed, the required output, and the EGR rate of the gas in the intake manifold 11 when the control of the present embodiment described above is applied at the time of acceleration from the vehicle stop state accompanied by the stop of the internal combustion engine 10. It is the time chart which showed an example. 6A shows the vehicle speed of a vehicle equipped with the hybrid system 1 of this embodiment as a power source, FIG. 6B shows the required output for the hybrid system 1, and FIG. 6C shows the gas concentration sensor 5 Represents the EGR rate of the gas in the intake manifold 11 calculated by the ECU 60 based on the signal from.

Time t ₁ Previously, the vehicle is stopped, this time the fuel cut control is performed for the internal combustion engine 10, the engine 10 is stopped, the idling stop control is performed. In the example shown in FIG. 6, it is assumed that a high concentration EGR gas remains in the intake system region in the idling stop state. For example, such a situation can be assumed when control for introducing a large amount of EGR gas is performed immediately before the idling stop state is started.

At time t _1, re-acceleration request is made. As a result, a condition for returning from the fuel cut control to the normal control is established. At this time, the EGR rate of the gas in the intake manifold 11 is calculated based on the signal from the gas concentration sensor 5, and the calculated EGR rate is compared with the limit EGR rate. In the example shown in FIG. 6, the EGR rate of the intake manifold 11 in the gas at time t ₁ is higher than the limit EGR rate Rc, the return to normal control of the internal combustion engine 10 is not performed, the fuel cut control is continued, All the required outputs for the hybrid system 1 at this time are distributed to the electric motor 33, and the electric motor 33 is controlled so that the electric motor 33 generates the required output. Furthermore, the control of the electric motor 33 to perform the cranking of the internal combustion engine 10 is performed by the electric motor 33, thereby since the scavenging gas in the intake system area is promoted, after time t _1, the intake manifold 11 The EGR rate of gas gradually decreases. The cranking of the internal combustion engine 10 at this time is executed together with the fuel cut control, and is cranking that does not involve fuel injection.

In time t _2, the the EGR rate calculated on the basis of the signal from the gas concentration sensor 5 becomes less than the limit EGR rate Rc, is returned to the normal controlling an internal combustion engine 10 from the fuel cut control. That is, all the required outputs for the hybrid system 1 are distributed to the internal combustion engine 10 and the electric motor 33 at a distribution ratio determined in advance according to the operating conditions, and the fuel in the internal combustion engine 10 is generated so that the distributed output can be generated. Injection control and power supply control in the electric motor 33 are performed.

  FIG. 7 is a flowchart showing a routine for executing the control of this embodiment described above. This routine is executed in the idling stop state.

In step S201, the ECU 60 determines whether a condition for returning the internal combustion engine 10 to the normal control is satisfied. For example, this condition is satisfied when there is an acceleration request.
If an affirmative determination is made in step S201, the ECU 60 proceeds to step S202. If a negative determination is made in step S201, the ECU 60 once ends the execution of this routine.

  In step S202, the ECU 60 calculates the EGR rate of the gas in the intake manifold 11 based on the signal from the gas concentration sensor 5, and determines whether or not the calculated EGR rate R is higher than the limit EGR rate Rc. If an affirmative determination is made in step S202 (R> Rc), the ECU 60 proceeds to step S203. If a negative determination is made in step S202 (R ≦ Rc), the ECU 60 proceeds to step S204.

  In step S <b> 203, the ECU 60 continues the fuel cut control for the internal combustion engine 10 and performs power supply control to the electric motor 33 so that the electric motor 33 generates the required output distributed to the internal combustion engine 10. Further, cranking of the internal combustion engine 10 by the electric motor 33 is started.

  In step S204, the ECU 60 returns the internal combustion engine 10 to normal control. That is, fuel injection is performed so that the required output distributed to the internal combustion engine 10 is generated by the internal combustion engine 10, and power supply control is performed so that the required output distributed to the electric motor 33 is generated by the electric motor 33.

  In the above embodiment, the EGR passage 3, the EGR valve 4, and the ECU 60 that controls the EGR valve 4 correspond to the EGR device in the present invention. Moreover, ECU60 which performs determination of step S102 and step S202 is equivalent to the determination means in this invention. Further, the ECU 60 that delays the return to the normal control of the internal combustion engine 10 in step S103 according to the determination result of step S102, and the ECU 60 that delays the return to the normal control of the internal combustion engine 10 in step S203 according to the determination result of step S202. This corresponds to the control means in the present invention.

  Various modifications can be made to the above-described embodiment within the scope of the present invention. For example, it is possible to determine whether or not the EGR rate of the gas sucked into the internal combustion engine is equal to or lower than the limit EGR rate by a method different from the above embodiment. For example, as shown in FIG. 8, the EGR rate of the gas in the intake manifold 11 after the internal combustion engine 10 shifts from the normal control state to the fuel cut control state is the operating condition of the internal combustion engine 10 immediately before the start of the fuel cut control ( For example, the rotation speed, the load, the intake air amount, the fuel injection amount, the target EGR rate, the carbon dioxide concentration in the exhaust gas, etc.) and the elapsed time since the start of the fuel cut control can be obtained. The relationship between the operating conditions immediately before the start of the fuel cut control, the elapsed time from the start of the fuel cut control, and the EGR rate of the gas in the intake manifold 11 is obtained in advance, and the internal combustion engine 10 is changed from the fuel cut control to the normal control. The EGR rate of the gas in the intake manifold 11 when the condition is satisfied may be estimated based on the elapsed time from the start of the fuel cut control when the condition to be restored is satisfied. Further, the EGR passage in the above embodiment may be a passage connecting the exhaust passage 19 downstream of the turbine 14b or the exhaust purification catalyst 20 and the intake passage 13 upstream of the compressor 14a. Further, as the limit EGR rate, a predetermined constant may be used, or a variable value may be set according to the operating condition when the return condition from the fuel cut control to the normal control is established.

It is a figure which shows schematic structure of the hybrid system in a present Example. It is the figure which showed the relationship between the EGR rate of intake gas, and a torque fluctuation according to the driving | running state of an internal combustion engine. It is the figure which showed the target value of the EGR rate defined for every operating condition of an internal combustion engine. When the internal combustion engine is decelerated from the high-load operation state and re-accelerated, the vehicle speed, the required output, and the EGR rate of the gas in the intake manifold when the control for delaying the return to the normal control of the internal combustion engine of this embodiment is applied. It is a figure which shows an example of a time change. 7 is a flowchart showing a control routine when applying a control for delaying the return to normal control of the internal combustion engine of the present embodiment when the internal combustion engine is decelerated from the high load operation state to re-accelerate. The figure which shows an example of the time change of the vehicle speed, request | requirement output, and the EGR rate of the gas in an intake manifold when the control which delays the return to the normal control of the internal combustion engine of a present Example is applied when reaccelerating from an idling stop state. It is. It is a flowchart which shows a control routine when the control which delays the return to normal control of the internal combustion engine of a present Example is applied when reaccelerating from an idling stop state. It is a figure which shows an example of the time change of the EGR rate of the gas in an intake manifold when an internal combustion engine transfers to fuel cut control from a normal control state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hybrid system 2 Cylinder 3 EGR passage 4 EGR valve 5 Gas concentration sensor 6 Fuel injection valve 10 Internal combustion engine 11 Intake manifold 13 Intake passage 14 Turbocharger 14a Compressor 14b Turbine 15 Intercooler 18 Exhaust manifold 19 Exhaust passage 20 Exhaust purification catalyst 21 Accelerator Position sensor 22 Vehicle speed sensor 23 Crank position sensor 30 Transaxle 31 Power split mechanism 32 Reducer 33 Electric motor 34 Generator 35 Power control unit 40 Inverter 50 Battery 51 SOC sensor 60 ECU

Claims (5)

A hybrid system including an internal combustion engine and an electric motor as a power source, and generating and outputting a required output by the internal combustion engine and / or the electric motor;
An EGR device that causes a part of the exhaust from the internal combustion engine to flow into the intake system of the internal combustion engine as EGR gas;
Means for performing fuel cut control for stopping fuel injection in the internal combustion engine;
Determining means for determining whether an EGR rate of gas sucked into the internal combustion engine is equal to or less than a predetermined limit EGR rate at which misfire does not occur in the internal combustion engine;
When the condition for returning from the fuel cut control to the normal fuel injection control is satisfied during the execution of the fuel cut control, the determination unit performs the determination from the time when the condition for returning to the normal fuel injection control is satisfied. During the period until it is determined that the EGR rate is equal to or less than the limit EGR rate, the internal combustion engine continues the fuel cut control without returning to the normal fuel injection control, and the electric motor Control means for controlling to generate the required output only by the electric motor;
A control apparatus for a hybrid system, comprising: In claim 1,
The control device of the hybrid system, wherein the control means controls the electric motor to further crank the internal combustion engine during the period. In claim 1 or 2,
The control means returns to the normal fuel injection control from the fuel cut control for the internal combustion engine when the determination means determines that the EGR rate is equal to or less than the limit EGR rate, and the electric motor About the control apparatus of a hybrid system characterized by returning to normal control. In claim 1 or 2,
The fuel cut control is executed in a deceleration state or a vehicle stop state. In any one of Claim 1 to 3,
The condition for returning to the normal fuel injection control is a condition that is satisfied at the time of re-acceleration from a deceleration state or a vehicle stop state.

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