JP2010159650A - Engine stop control device for hybrid vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit deterioration of exhaust emission at engine stop of a hybrid vehicle. <P>SOLUTION: This device is an engine stop control device for the hybrid vehicle travelling with driving force of one or both of an engine 1 and a motor 3, and includes an engine stop demand detection means (S1) detecting engine stop demand, an in-stop engine demand torque calculation means (S5) calculating engine demand torque so as to slowly reducing engine torque after engine stop demand is detected until the engine 1 is stopped, and an in-stop throttle valve control means (S6) controlling opening of a throttle valve 722 based on engine demand torque. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an engine stop control device for a hybrid vehicle.

  Conventionally, a hybrid vehicle that travels with driving force of either one or both of an engine and a motor is known (see, for example, Patent Document 1).

JP 2008-265577 A

  However, the conventional system quickly stops the engine when switching from hybrid traveling that travels using the driving force of the engine and motor to motor traveling that travels using only the driving force of the motor. Therefore, when the engine is stopped from a high load state, the throttle valve is closed at the same time, so the pressure in the intake collector suddenly becomes negative and the wall flow vaporization amount increases and exhaust emission deteriorates. There was a problem.

  The present invention has been made paying attention to such conventional problems, and an object thereof is to suppress deterioration of exhaust emission when the engine is stopped.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention includes a port injection engine (1) having a throttle valve (722) that opens and closes an intake passage (72), and injects fuel into an intake passage (72) downstream of the throttle valve (722). , And a motor (3) driven by electric power supplied from the battery (4), and an engine stop control device for a hybrid vehicle that travels with driving force of either one or both of the engine (1) and the motor (3) An engine stop request detecting means (S1) for detecting an engine stop request, and an engine request torque so that the engine torque from when the engine stop request is detected until the engine (1) is stopped gradually decreases. Based on the engine request torque calculation means (S5, S21) for calculating the engine torque during stop, the opening degree of the throttle valve (722) is controlled based on the engine request torque. Characterized in that it comprises a stop when the throttle valve control means (S6), the.

  According to the present invention, when the engine is stopped, the engine torque is gradually reduced and the throttle valve is closed gently, so that the pressure in the intake collector can be suppressed from suddenly becoming negative. Thereby, since the vaporization of the wall flow can be suppressed, it is possible to suppress the exhaust emission from deteriorating due to the air / fuel ratio becoming richer than the target air / fuel ratio.

It is a system diagram showing an outline of an engine stop control device of a hybrid vehicle. It is a schematic block diagram of an engine. It is a flowchart explaining the engine stop control by 1st Embodiment. It is a time chart explaining the operation | movement of the engine stop control by 1st Embodiment. It is a flowchart explaining the engine stop control by 2nd Embodiment. It is a table which calculates the reduction rate of engine torque. It is a figure explaining operation of engine engine stop control by other embodiments. It is a figure explaining operation of engine engine stop control by other embodiments.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a system diagram schematically illustrating an engine stop control device for a hybrid vehicle according to a first embodiment of the present invention.

  The hybrid vehicle includes an engine 1, a clutch 2, a motor generator 3, a battery 4, and a transmission 5.

  The engine 1 generates a driving force for the hybrid vehicle. The configuration of the engine 1 will be described later with reference to FIG.

  The clutch 2 connects and disconnects the output shaft 11 of the engine 1 and the input shaft 31 of the motor generator 3. By connecting the clutch 2, the driving force of the engine 1 can be transmitted to the input shaft 31 of the motor generator 3.

  The motor generator 3 has a function as a generator that is driven by the engine 1 to generate electric power and a function as a motor that generates a driving force of the hybrid vehicle by the electric power of the battery 4.

  The battery 4 stores the electric power generated by the motor generator 3, while driving the motor generator 3 by supplying electric power. Electric power is stored and supplied via an inverter 41, respectively.

  The transmission 5 outputs the driving force of the engine 1 and the motor generator 3 to the propeller shaft 51 by changing the driving force according to the vehicle traveling state. The driving force output to the propeller shaft 51 is transmitted to the left and right drive wheels 54 via the differential gear 52 and the drive shaft 53 to drive the vehicle.

  The hybrid vehicle is configured as described above and can travel using the power of either one or both of the engine 1 and the motor generator 3. That is, it is possible to travel by selecting an optimal travel mode from the three travel modes of engine travel, motor travel, and hybrid (engine + motor) travel according to the driving state.

  FIG. 2 is a schematic configuration diagram of the engine 1.

  The engine 1 includes a cylinder block 6 and a cylinder head 7 that covers the top of the cylinder block 6.

  A plurality of cylinders 61 are formed in the cylinder block 6. A piston 62 is slidably fitted into the cylinder 61. The piston 62 is connected to the crankshaft 64 by a connecting rod 63.

  The cylinder head 7 is formed with an intake passage 72 and an exhaust passage 73 that open to the top wall of the combustion chamber 71, and an ignition plug 74 is provided at the center of the top wall of the combustion chamber 71. The cylinder head 7 is provided with a pair of intake valves 75 that open and close the opening of the intake passage 72 and a pair of exhaust valves 76 that open and close the opening of the exhaust passage 73. In FIG. 2, only one intake valve and exhaust valve are shown to prevent the drawing from being complicated. Further, the cylinder head 7 is provided with an intake valve variable valve mechanism 77 that can open and close the intake valve 75 and set the opening and closing timing to an arbitrary timing, and an exhaust camshaft 78 that drives the exhaust valve 76 to open and close. .

  In the intake passage 72, an air flow sensor 721, a throttle valve 722, an intake collector 723, a boost sensor 724, and a fuel injection valve 725 are provided in order from the upstream.

  The air flow sensor 721 detects the volume of fresh air drawn into the engine 1.

  The throttle valve 722 is an electronically controlled throttle valve that can change its opening degree independently of the accelerator operation, and adjusts the intake air amount of the engine 1. The target opening of the throttle valve 722 changes according to the engine required torque, and increases as the engine required torque increases.

  The intake collector 723 stores the air sucked into the cylinder.

  Boost sensor 724 detects the internal pressure of intake collector 723 (hereinafter referred to as “collector pressure”).

  The fuel injection valve 725 injects fuel according to the operating state.

  The exhaust passage 73 is provided with an air-fuel ratio sensor 731 that detects the air-fuel ratio.

  The controller 8 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface).

  In addition to the sensor signals described above, the controller 8 includes signals from various sensors such as an engine speed sensor 81 that detects the engine speed based on the crank angle and an accelerator stroke sensor 82 that detects the amount of depression of the accelerator pedal. Is entered.

  The controller 8 calculates a required torque based on the detected engine rotation speed and the accelerator depression amount, and controls the torque of the engine 1 and the motor generator 3 so that the required torque is realized. At this time, when the required torque can be realized only by the torque of the motor generator 3 (hereinafter referred to as “motor torque”), the engine required torque is set to 0, the engine 1 is stopped, and the vehicle runs only by the motor torque (motor running). .

  Here, when the required engine torque is suddenly reduced to 0 when switching from hybrid travel to motor travel, the throttle valve 722 is simultaneously closed to the fully closed state. If it does so, collector pressure will become a negative pressure rapidly and wall flow evaporation will increase. Therefore, there is a problem that the air-fuel ratio temporarily becomes rich by the amount of wall flow vaporization, the amount of hydrocarbon (HC) emission increases, and exhaust emission deteriorates.

  Therefore, in the present embodiment, when switching from hybrid travel to motor travel, the engine torque is not suddenly reduced to 0, but the engine torque is gradually decreased to 0. Thereby, since the throttle valve 722 is gently closed, it is possible to suppress the collector pressure from rapidly becoming negative pressure and to suppress an increase in the amount of vaporization of the wall flow. Hereinafter, engine stop control according to the present embodiment will be described.

  FIG. 3 is a flowchart illustrating the engine stop control according to the present embodiment. The controller 8 repeatedly executes this routine at a predetermined calculation cycle (for example, 10 milliseconds).

  In step S1, the controller 8 determines whether or not there is an engine stop request. Specifically, an engine stop request is issued when the engine torque is unnecessary, such as when the accelerator pedal depression amount is zero. If there is an engine stop request, the controller 8 proceeds to step S2. On the other hand, if there is no engine stop request, the current process is terminated.

  In step S2, the controller 8 determines whether or not the operation state of the engine 1 when the engine stop request is issued is a high load operation. Specifically, it is determined whether the engine torque when the engine stop request is issued is greater than a predetermined high load determination torque. If the controller 8 is a high load operation, the process proceeds to step S3. On the other hand, if it is a low / medium load operation, the process proceeds to step S4.

  In step S3, the controller 8 determines whether the wall flow rate is large. Specifically, it is determined whether the engine water temperature is lower than a predetermined water temperature or whether the elapsed time after starting the engine 1 is shorter than a predetermined time. In any case, it can be estimated that the temperature of the intake passage is low while the engine is warming up and the wall flow rate is increased. When the controller 8 determines that the wall flow rate is large, the controller 8 proceeds to step S5. On the other hand, when it is determined that the wall flow rate is small, the process proceeds to step S4.

  In step S4, the controller 8 sets the required engine torque to 0 and stops the engine 1. As described above, when the operation state when the engine stop request is issued is a low / medium load operation and when the wall flow rate is small even if the operation state when the engine stop request is issued is a high load operation. Then, the engine required torque is suddenly set to 0 and the engine 1 is stopped. This is because if the operation state immediately before the engine stop request is issued is a low / medium load operation, the engine request torque is suddenly reduced to 0 and the throttle valve 722 is fully closed at a stroke. This is because the collector pressure does not suddenly become negative. Further, even if the operation state immediately before the engine stop request is issued is a high load operation, if the wall flow rate is small, the amount of vaporization is small and the exhaust emission is not deteriorated.

  In step S5, the controller 8 calculates the engine required torque so that the engine torque decreases at a predetermined reduction rate.

  In step S6, the controller 8 controls the throttle opening based on the engine required torque.

  FIG. 4 is a time chart for explaining the operation of the engine stop control according to the present embodiment. In order to facilitate understanding of the invention, as a comparative example, the operation when the engine required torque is set to 0 and the engine 1 is stopped regardless of the operation state when the engine stop request is issued is indicated by a broken line. Further, in order to clarify the correspondence with the flowchart, the step numbers of the flowchart will be described together.

  At time t1, the engine 1 is started or restarted.

  When the engine torque becomes unnecessary at time t2 and an engine stop request is issued (Yes in S1), it is determined whether the engine torque at the time of the engine stop request is larger than the high load determination torque (S2). In this time chart, since it is assumed that the engine torque is higher than the high load determination torque (Yes in S2), it is determined whether or not the wall flow rate is greater than a predetermined amount (S3). In this time chart, since the wall flow rate is larger than the predetermined amount (FIG. 4F; Yes in S3), the engine required torque is calculated so that the engine torque decreases at a constant reduction rate (FIG. 4B). S5).

  As a result, the throttle valve 722 is gradually closed as compared with the case where the engine required torque is suddenly reduced to 0 (broken line) (FIG. 4 (C); S6), so that the collector pressure suddenly becomes negative. It can be suppressed (FIG. 4D). Therefore, the amount of wall flow vaporization can be suppressed (FIG. 4 (F)), and it can be suppressed that the air-fuel ratio becomes rich and exhaust emission deteriorates (FIG. 4 (E)).

  According to the present embodiment described above, when it can be estimated that the operating state before the engine stop request is a high load and the wall flow rate is large, the engine torque is gradually decreased to 0 at a constant reduction rate. The engine 1 is stopped.

  As a result, the throttle valve 722 is also gradually closed, so that it is possible to suppress the collector pressure from suddenly becoming a negative pressure and increasing the amount of vaporization of the wall flow. Therefore, it can be suppressed that the air-fuel ratio temporarily becomes rich when the engine is stopped and the exhaust emission deteriorates.

  Further, when the wall flow rate is small, the engine 1 can be quickly stopped. Therefore, deterioration of fuel consumption can be suppressed.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. The present embodiment is different from the first embodiment in that the reduction rate of the engine required torque is calculated according to the engine torque at the time of the engine stop request. Hereinafter, the difference will be mainly described. In each of the following embodiments, the same reference numerals are used for portions that perform the same functions as those of the first embodiment described above, and repeated descriptions are omitted as appropriate.

  FIG. 5 is a flowchart illustrating engine stop control according to the present embodiment. The controller 8 repeatedly executes this routine at a predetermined calculation cycle (for example, 10 milliseconds).

  In step S21, the controller 8 refers to a table shown in FIG. 6 to be described later, and calculates an engine torque reduction rate according to the engine torque at the time of the engine stop request.

  In step S22, the controller 8 calculates the engine required torque so that the engine torque decreases at the reduction rate calculated in step S21.

  FIG. 6 is a table for calculating the engine torque reduction rate.

  As shown in FIG. 6, the engine torque reduction rate decreases as the engine torque at the time of engine stop request increases. This is because the throttle opening increases as the engine torque at the time of the engine stop request increases. Therefore, as the engine torque at the time of the engine stop request is larger, it is necessary to reduce the reduction rate of the engine torque and gradually reduce the throttle opening to suppress the collector pressure from suddenly becoming negative pressure. .

  According to the present embodiment described above, the engine torque reduction rate corresponding to the engine torque at the time of engine stop request is calculated, so that the same effect as the first embodiment can be obtained and the deterioration of fuel consumption can be further suppressed. can do.

  Note that the present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  For example, in the first embodiment, the engine torque is gradually decreased to 0 at a constant reduction rate, but may be gradually decreased to 0 as shown in FIG. 7, or as shown in FIG. After gradually decreasing to a predetermined engine torque at a constant reduction rate, it may be reduced to 0 at once.

  Further, the amount of the wall flow rate in the intake passage 72 is estimated based on the water temperature and the elapsed time since the start, but when the detected value of the exhaust air / fuel ratio is leaner than the target air / fuel ratio, the wall flow of the injected fuel Since it can be judged that the ratio of the obtained fuel is large, it can be estimated that the wall flow rate is large.

1 Engine 3 Motor 4 Battery (Accumulator)
72 Intake passage 722 Throttle valve 731 Air-fuel ratio sensor (air-fuel ratio detection means)
S1 Engine stop request detection means S3 Wall flow rate estimation means S5 Stop engine request torque calculation means S6 Stop throttle valve control means S22 Stop engine request torque calculation means

Claims (10)

A port injection type engine having a throttle valve for opening and closing an intake passage, and injecting fuel into the intake passage downstream of the throttle valve;
A motor driven by electric power supplied from the capacitor;
With
An engine stop control device for a hybrid vehicle that travels with driving force of one or both of the engine and the motor,
Engine stop request detecting means for detecting an engine stop request;
A stop-time engine request torque calculation means for calculating the engine request torque so that the engine torque from when the engine stop request is detected until the engine is stopped is gently reduced;
A throttle valve control means for stopping when controlling the opening of the throttle valve based on the engine required torque;
An engine stop control device for a hybrid vehicle, comprising: The engine demand torque calculation means at the time of stop is
The engine required torque is calculated so that the engine torque decreases at a predetermined reduction rate if the engine operating state when the engine stop request is detected is a high load state. Engine stop control device for hybrid vehicles. The engine demand torque calculation means at the time of stop is
2. The engine torque reduction rate is calculated based on an engine torque when the engine stop request is detected, and the engine required torque is calculated so that the engine torque decreases at the reduction rate. An engine stop control device for a hybrid vehicle as described in 1. 4. The engine stop control device for a hybrid vehicle according to claim 3, wherein the reduction rate decreases as the engine torque increases when the engine stop request is detected. 5. A wall flow rate estimating means for estimating a wall flow rate of the intake passage;
5. The engine torque is reduced at the reduction rate when it is estimated that the wall flow rate of the intake passage when the engine stop request is detected is larger than that during normal operation. The engine stop control device for a hybrid vehicle according to any one of the above. The wall flow rate estimating means includes
6. The engine stop control device for a hybrid vehicle according to claim 5, wherein when the engine water temperature is lower than a predetermined water temperature, it is estimated that the wall flow rate of the intake passage is larger than that during normal operation. The wall flow rate estimating means includes
6. The engine stop of a hybrid vehicle according to claim 5, wherein when the elapsed time after starting the engine is shorter than a predetermined time, it is estimated that the wall flow rate of the intake passage is larger than that during normal operation. Control device. An air-fuel ratio detecting means provided in the exhaust passage of the engine for detecting the air-fuel ratio;
The wall flow rate estimating means includes
6. The engine stop control device for a hybrid vehicle according to claim 5, wherein when the air-fuel ratio is leaner than a target air-fuel ratio, it is estimated that the wall flow rate of the intake passage is larger than that during normal operation. The engine stop request detecting means includes
The engine stop control device for a hybrid vehicle according to any one of claims 1 to 8, wherein the engine stop request is detected when traveling is possible only with the torque of the motor. The stop time throttle valve control means includes:
The engine stop control device for a hybrid vehicle according to any one of claims 1 to 9, wherein the throttle valve opening is made smaller as the engine required torque is smaller.

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