JP2008013041A - Stop controller for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely stop the revolution of an engine at a target stop position without being affected by the change of the cylinder pressure of the engine in a system for controlling the revolution stop position of the engine by the torque of an MG(motor generator). <P>SOLUTION: In stopping the revolution of an engine 11 by stopping the fuel injection and ignition of the engine 11, cylinder change coefficients on which a cylinder pressure in controlling the stop of the engine 11 is reflected are calculated based on the revolution speed of the engine when the load operation of the engine 11 ends and a time (or crank angle) from the end of the load operation till the start of the stop control of the engine 11. Then, basic command torque corresponding to the crank angle position of the engine 11 is corrected with the cylinder pressure change coefficients to calculate final command torque, and the torque of a MG12 is controlled like feed-forward to generate the command torque, so that the revolution of the engine 11 is stopped at the target stop position. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a stop control device for an internal combustion engine that controls the rotation stop position of the internal combustion engine with the torque of a motor generator when stopping the rotation of the internal combustion engine.

  In recent years, the demand for hybrid vehicles is rapidly expanding due to the social demand for low fuel consumption and low exhaust emissions. A hybrid vehicle currently on the market includes an engine (internal combustion engine), a first motor generator mainly used as a generator, and a second motor generator mainly driving a wheel via a power split mechanism. Many of them are linked together.

  In this type of hybrid vehicle, when the engine is cranked by the first motor generator and the engine is started, if the engine rotational speed is rapidly increased and the resonance frequency band is quickly passed, Although vibration can be reduced, it is desirable to stop the rotation of the engine at the target stop position in advance when the engine is stopped in order to quickly increase the engine rotation speed by the motor generator when starting the engine. In general, the target stop position is set to a position where the torque required for the piston to overcome the compression top dead center at the time of starting the engine is approximately near the minimum (slightly before top dead center).

  Conventionally, for the purpose of controlling the engine rotation stop position to the target stop position, as described in Patent Document 1 (Japanese Patent Laid-Open No. 9-264235), the engine is stopped when the engine rotation is stopped. The torque of the motor generator is controlled based on the crank angle position, and the engine rotation is stopped at a target stop position (within a specific crank angle range).

Further, as described in Patent Document 2 (Japanese Patent Application Laid-Open No. 2005-16505), when stopping the rotation of the engine, the target engine rotation speed required to stop the rotation of the engine at the target stop position is set. The motor generator is set so as to correct the target engine speed based on the deviation between the actual crank angle displacement from the reference timing for starting the engine stop control and the target displacement, and to realize the target engine speed. In some cases, the engine rotation is stopped at a target stop position by controlling the torque of the engine.
JP-A-9-264235 (second page, etc.) Japanese Patent Laying-Open No. 2005-16505 (pages 2 to 3 etc.)

  By the way, if the in-cylinder pressure at the time of engine stop control (for example, the in-cylinder pressure in the compression stroke) changes due to a difference in the operating state before starting the engine stop control, etc., the motor required to stop the engine rotation at the target stop position The generator torque also changes.

  However, in the technique of Patent Document 1 described above, the change in the in-cylinder pressure during engine stop control is not taken into consideration at all, and the torque of the motor generator is simply controlled based on the crank angle position of the engine. If the in-cylinder pressure during the stop control changes, the engine rotation may not be stopped at the target stop position due to the influence.

  Further, in the technique of Patent Document 2, when the in-cylinder pressure at the time of engine stop control changes, the motor generator is controlled based on the deviation between the actual displacement amount of the crank angle generated by the change in the in-cylinder pressure and the target displacement amount. In this case, feedback control for controlling the torque is performed. In this case, since the change in the in-cylinder pressure during the engine stop control changes in the engine rotation stop behavior, the torque of the engine is controlled in order to control the torque of the motor generator. The rotation stop behavior may be disturbed and unpleasant vibration may occur.

  The present invention has been made in consideration of these circumstances. Therefore, the object of the present invention is to rotate the internal combustion engine at the target stop position without being affected by the change in the in-cylinder pressure during the stop control of the internal combustion engine. It is an object of the present invention to provide a stop control device for an internal combustion engine that can be stopped with high accuracy and can suppress vibration when the rotation of the internal combustion engine is stopped.

  In order to achieve the above object, an invention according to claim 1 is directed to an internal combustion engine comprising stop position control means for controlling the rotation stop position of the internal combustion engine with the torque of the motor generator when the rotation of the internal combustion engine is stopped. In the stop control device, the in-cylinder pressure at the time of stop control of the internal combustion engine or information correlated therewith (hereinafter collectively referred to as “in-cylinder pressure information”) is detected by the in-cylinder pressure information detection means. The torque of the motor generator is controlled based on the crank angle position to control the rotation stop position of the internal combustion engine.

  In this configuration, when the rotation of the internal combustion engine is stopped, the torque of the motor generator is controlled based on the in-cylinder pressure information of the internal combustion engine and the crank angle position. Thus, even if the in-cylinder pressure at the time of stop control of the internal combustion engine changes, the rotation of the internal combustion engine can be accurately stopped at the target stop position without being affected by the change. In addition, the torque of the motor generator is fed forward based on the in-cylinder pressure information and the crank angle position of the internal combustion engine before the change in the rotation stop behavior of the internal combustion engine due to the change in the in-cylinder pressure during the stop control of the internal combustion engine. Since it becomes possible to control, the disturbance of the rotation stop behavior of the internal combustion engine can be prevented, and the rotation of the internal combustion engine can be accurately stopped at the target stop position with a stable rotation stop behavior with less vibration.

  In this case, as in claim 2, the rotational speed at the end of the load operation of the internal combustion engine (operation that opens the throttle opening more than that during idle operation) and the period from the end of the load operation of the internal combustion engine to the start of stop control The in-cylinder pressure information may be calculated based on this. As shown in FIG. 4, there is a characteristic that the intake pressure at the start of the stop control of the internal combustion engine changes according to the rotation speed at the end of the load operation of the internal combustion engine and the time from the end of the load operation of the internal combustion engine to the start of stop control. In addition, since the in-cylinder pressure at the time of stop control changes according to the intake pressure at the time of stop control of the internal combustion engine, the rotation speed at the end of load operation of the internal combustion engine and from the end of load operation of the internal combustion engine to the start of stop control If the in-cylinder pressure information is calculated based on the period, the in-cylinder pressure information that accurately reflects the in-cylinder pressure during the stop control of the internal combustion engine can be obtained.

  In the case of a system having an in-cylinder pressure sensor for detecting the in-cylinder pressure of the internal combustion engine as in claim 3, the in-cylinder pressure at the specific crank angle position detected by the in-cylinder pressure sensor during stop control of the internal combustion engine is You may make it detect as internal pressure information. In this way, the torque of the motor generator can be controlled using the highly accurate in-cylinder pressure detected by the in-cylinder pressure sensor during stop control of the internal combustion engine, and the control accuracy of the rotation stop position of the internal combustion engine is further improved. be able to.

  In the case of a system having an intake pipe pressure sensor for detecting the intake pipe pressure of the internal combustion engine as in claim 4, based on the intake pipe pressure detected by the intake pipe pressure sensor during stop control of the internal combustion engine. In-cylinder pressure information may be calculated. Since the in-cylinder pressure at the time of stop control changes according to the intake pipe pressure (intake pressure) at the time of stop control of the internal combustion engine, if the in-cylinder pressure information is calculated based on the intake pipe pressure at the time of stop control of the internal combustion engine, the internal combustion engine In-cylinder pressure information that accurately reflects the in-cylinder pressure at the time of engine stop control can be obtained.

  Hereinafter, an embodiment in which the present invention is applied to a series / parallel hybrid vehicle will be described with reference to the drawings. First, a schematic configuration of a hybrid vehicle drive system will be described with reference to FIG. The hybrid vehicle includes an engine 11 that is an internal combustion engine, a first motor generator (hereinafter referred to as “first MG”) 12, and a second motor generator (hereinafter referred to as “second MG”) 13. The engine 11 and the second MG 13 are mounted as a power source for driving the wheels 14. The power of the crankshaft 15 of the engine 11 is divided into two systems by a planetary gear mechanism 16 which is a power split mechanism. The planetary gear mechanism 16 includes a sun gear 17 that rotates at the center, a planetary gear 18 that revolves while rotating on the outer periphery of the sun gear 17, and a ring gear 19 that rotates on the outer periphery of the planetary gear 18. The crankshaft 15 of the engine 11 is connected through a non-carrier, the rotation shaft of the second MG 13 and the drive shaft 20 of the wheel 14 are connected to the ring gear 19, and the sun gear 17 is used mainly as a generator. The rotating shaft of 1 MG12 is connected.

  The first MG 12 and the second MG 13 exchange power with the battery 29 via inverters 27 and 28, respectively. The first MG 12 and the second MG 13 are provided with rotational position sensors 32 and 33 for detecting the rotational position of the rotor, respectively, and the first MG 12 is based on the output signals of these rotational position sensors 32 and 33. And the rotation speed of the second MG 13 are detected.

  As shown in FIG. 2, an air cleaner 35 is provided at the most upstream portion of the intake pipe 34 of the engine 11, and an air flow meter 36 for detecting the intake air amount is provided downstream of the air cleaner 35. . On the downstream side of the air flow meter 36, a throttle valve 38 whose opening is adjusted by a motor 37 and a throttle opening sensor 39 for detecting the opening (throttle opening) of the throttle valve 38 are provided.

  Further, the surge tank 40 provided on the downstream side of the throttle valve 38 is provided with an intake manifold 41 for introducing air into each cylinder of the engine 11, and fuel is supplied to the vicinity of the intake port of the intake manifold 41 of each cylinder. A fuel injection valve 42 for injection is attached. A spark plug 43 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by the spark discharge of each spark plug 43.

  On the other hand, the exhaust pipe 44 of the engine 11 is provided with an exhaust gas sensor 45 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting the air-fuel ratio or rich / lean of the exhaust gas. A catalyst 46 such as a three-way catalyst for purifying gas is provided. A cooling water temperature sensor 47 that detects the cooling water temperature and a crank angle sensor 31 that outputs a pulse signal each time the crankshaft 15 of the engine 11 rotates by a predetermined crank angle are attached to the cylinder block of the engine 11. Based on the output signal of the crank angle sensor 31, the crank angle and the engine speed are detected.

  As shown in FIG. 1, the hybrid ECU 30 is a computer that comprehensively controls the entire hybrid vehicle, and includes an accelerator sensor 21 that detects an accelerator opening, a shift switch 22 that detects a shift range of an automatic transmission, and a brake operation. Various sensors such as the brake switch 23 to be detected and output signals of the switches are read to detect the driving state of the vehicle and determine the required travel mode. The hybrid ECU 30 includes an engine ECU 24 that controls the operation of the engine 11, a first MG-ECU 25 that controls the operation of the first MG 12, and a second MG-ECU 26 that controls the operation of the second MG 13. Control signals are transmitted and received between the ECUs 24 to 26, and the operations of the engine 11, the first MG 12, and the second MG 13 are controlled according to the required travel mode.

  For example, when starting or at low to medium speed (when the fuel efficiency of the engine 11 is poor), the engine 11 is kept stopped and the vehicle travels only with the power of the second MG 13. Further, when starting the engine 11, torque is generated in the first MG 12, and torque is applied to the sun gear 17 of the planetary gear mechanism 16, whereby the revolution speed of the planetary gear 18 is increased along the outer periphery of the sun gear 17. By changing, the crankshaft 15 of the engine 11 is rotationally driven to start the engine 11.

  During normal driving, the power of the crankshaft 15 of the engine 11 is driven by the planetary gear mechanism 16 so that the fuel efficiency of the engine 11 is maximized and the drive shaft 20 side (rotation shaft side of the second MG13). ), The drive shaft 20 is driven by the output of one of the systems to drive the wheels 14, the first MG 12 is driven by the output of the other system, and the power generated thereby is supplied to the second system. The wheel 14 is also driven by the power of the second MG 13 supplied to the MG 13.

  At the time of sudden acceleration, the most torque is required. Therefore, in addition to the generated power during normal driving, the direct current power of the battery 29 is added and converted into alternating current power by the inverter 28 and supplied to the second MG 13. The MG 13 is operated. Further, at the time of deceleration or braking, the wheel 14 drives the second MG 13 to act as a generator, and converts the deceleration energy and braking energy of the vehicle into electric power to charge the battery 29.

  By the way, when the engine 11 is cranked by the first MG 12 and the engine 11 is started, if the engine rotation speed is rapidly increased and a resonance frequency band (for example, a region near 300 rpm) is quickly passed, Although the vibration at the time of engine start can be reduced, in order to quickly increase the engine rotation speed by the first MG 12 at the time of engine start, the rotation of the engine 11 is stopped in advance at the target stop position when the engine is stopped. Is desirable. In general, the target stop position may be set to a position (a little before top dead center) where the torque necessary for the piston to overcome the compression top dead center at the time of starting is approximately near the minimum.

  Therefore, the hybrid ECU 30 executes an engine stop control program shown in FIG. 3 to be described later, thereby stopping the fuel injection and ignition of the engine 11 and stopping the rotation of the engine 11. In-cylinder pressure change reflecting the in-cylinder pressure at the time of stop control of the engine 11 based on the rotation speed at the end) and the period from the end of load operation of the engine 11 to the start of stop control A coefficient (in-cylinder pressure information) is calculated, the basic command torque corresponding to the crank angle position of the engine 11 is corrected with the in-cylinder pressure change coefficient to obtain a final command torque, and the first command torque is generated so as to generate this command torque. The rotation of the engine 11 is stopped at the target stop position by performing feedforward control of the torque of the MG 12. The target stop position is set, for example, in a range from BTDC 30 ° C. to TDC (30 ° C. before top dead center to top dead center).

  Hereinafter, the processing content of the engine stop control program of FIG. 3 executed by the hybrid ECU 30 will be described.

[Engine stop control program]
The engine stop control program shown in FIG. 3 is executed in a predetermined cycle after the hybrid ECU 30 is turned on, and plays a role as stop position control means in the claims. When this program is started, first, in step 101, it is determined whether or not the load operation of the engine 11 is completed based on, for example, required power or required torque for the engine 11, and the load operation of the engine 11 is completed. If not, the program is terminated without performing the processing related to engine stop control in step 102 and thereafter.

  Thereafter, when it is determined in step 101 that the load operation of the engine 11 has been completed, the processing relating to the engine stop control after step 102 is executed as follows. First, in step 102, the engine speed at the end of load operation of the engine 11 is stored in the RAM of the ECU 30 or the like.

  Thereafter, the process proceeds to step 103, where it is determined whether an engine stop command has been issued. If no engine stop command has been issued, the process proceeds to step 104, from the end of load operation of the engine 11 to the start of stop control (engine stop). The counter that measures the time until the command is issued is counted up.

  Thereafter, when it is determined in step 103 that an engine stop command (that is, a fuel injection and ignition stop command) has been issued, the routine proceeds to step 105, where the engine pressure change coefficient map of FIG. 11 calculates the in-cylinder pressure change coefficient according to the engine speed at the end of the load operation 11 and the time from the end of the load operation of the engine 11 to the start of the stop control.

  As shown in FIG. 4, the lower the engine speed at the end of load operation of the engine 11, the higher the intake pressure at the start of stop control, and the shorter the time from the end of load operation of the engine 11 to the start of stop control. There is a characteristic that the intake pressure at the start of the stop control becomes higher, and further, the in-cylinder pressure at the time of stop control becomes higher as the intake pressure at the start of the stop control of the engine 11 becomes higher.

  In consideration of such characteristics, the in-cylinder pressure change coefficient map of FIG. 5 has a larger in-cylinder pressure change coefficient as the engine speed at the end of the load operation of the engine 11 becomes lower, and stops after the end of the load operation of the engine 11. The in-cylinder pressure change coefficient is set to increase as the time until the start of control becomes shorter. Note that the crank angle from the end of the load operation to the start of the stop control may be used instead of the time from the end of the load operation to the start of the stop control. The processing in step 105 serves as in-cylinder pressure information detecting means in the claims.

  Thereafter, the routine proceeds to step 106, where the basic command torque of the first MG 12 corresponding to the current crank angle position of the engine 11 is calculated with reference to the basic command torque map of FIG.

  The map of the basic command torque in FIG. 6A is a direction in which the basic command torque stops the rotation of the engine 11 for a while after the start of the engine stop control (for example, a period in which the engine speed is higher than a predetermined value). The torque is set to act in the negative direction. Further, the basic command torque map of FIG. 6B shows that the direction of the basic command torque is reversed immediately before the rotation of the engine 11 stops (for example, when the engine rotation speed becomes a predetermined value or less). The command torque is set so as to be a torque that acts in the direction of rotating the engine 11 (plus direction). Thus, the basic command torque is set so that the rotation of the engine 11 is prevented from stopping before reaching the target stop position, and the engine 11 is rotated to the target stop position and stopped.

  Thereafter, the routine proceeds to step 107, where the basic command torque is multiplied by the in-cylinder pressure change coefficient to correct the basic command torque according to the crank angle position with the in-cylinder pressure change coefficient, and the final command torque of the first MG 12 is reached. And the feedforward control of the torque of the first MG 12 so as to generate this command torque.

  Thereafter, the process proceeds to step 108, where it is determined whether or not the rotation of the engine 11 has stopped, for example, based on whether or not the engine rotation speed has become equal to or less than a stop determination value. If the rotation of the engine 11 has not stopped, the process returns to step 106, and the process (steps 106 and 107) for correcting the basic command torque according to the crank angle position with the in-cylinder pressure change coefficient and obtaining the final command torque is repeated. . Thereafter, when it is determined in step 108 that the rotation of the engine 11 has stopped, this program is terminated.

  Although the command torque may be obtained by correcting the basic command torque with the in-cylinder pressure change coefficient from the start of the engine stop control, a period immediately before the engine 11 stops rotating (for example, the engine speed is a predetermined value). The command torque may be obtained by correcting the basic command torque with the in-cylinder pressure change coefficient only during the following period).

  If the in-cylinder pressure during the stop control of the engine 11 (for example, the in-cylinder pressure in the compression stroke) changes due to a difference in the operating state before the stop control of the engine 11 is started, it is necessary to stop the rotation of the engine 11 at the target stop position. The torque of the first MG 12 also changes.

  However, conventionally, as shown in FIG. 8, when the rotation of the engine 11 is stopped, the change in the in-cylinder pressure during the stop control of the engine 11 is not taken into consideration, and the first change is simply based on the crank angle position of the engine 11. In order to control the torque of one MG 12, if the in-cylinder pressure at the time of stop control of the engine 11 changes, there is a possibility that the rotation of the engine 11 cannot be stopped at the target stop position due to the influence.

  On the other hand, in the present embodiment, as shown in FIG. 7, when the rotation of the engine 11 is stopped, based on the in-cylinder pressure change coefficient reflecting the in-cylinder pressure at the stop control of the engine 11 and the crank angle position. In order to control the torque of the first MG 12, even if the in-cylinder pressure during the stop control of the engine 11 changes due to a difference in the operating state before the stop control of the engine 11 starts, the engine 11 The rotation can be accurately stopped at the target stop position. As a result, when the engine 11 is cranked by the first MG 12 and the engine 11 is started, it is possible to quickly increase the engine rotation speed and quickly pass the resonance frequency band. Can be reduced.

  In addition, before the change in the rotation stop behavior of the engine 11 due to the change in the in-cylinder pressure during the stop control of the engine 11, the torque of the first MG 12 is fed based on the in-cylinder pressure change coefficient of the engine 11 and the crank angle position. Since the control can be performed in a forward manner, the rotation stop behavior of the engine 11 can be prevented from being disturbed, and the rotation of the engine 11 can be accurately stopped at the target stop position with a stable rotation stop behavior with little vibration.

  Further, in this embodiment, the in-cylinder pressure at the time of stop control is changed by changing the intake pressure at the start of stop control according to the engine rotation speed at the end of load operation of the engine 11 and the time from the end of load operation to the start of stop control. Since the engine pressure change coefficient is calculated according to the engine rotation speed at the end of the load operation of the engine 11 and the time from the end of the load operation to the start of the stop control, The in-cylinder pressure change coefficient that accurately reflects the in-cylinder pressure during the stop control can be obtained.

  In the system including the intake pipe pressure sensor, the in-cylinder pressure change coefficient may be calculated based on the intake pipe pressure (intake pressure) detected by the intake pipe pressure sensor during the stop control of the engine 11. In a system including an in-cylinder pressure sensor, the in-cylinder pressure change coefficient is calculated based on the in-cylinder pressure at a specific crank angle position (for example, at or near the top dead center) detected by the in-cylinder pressure sensor during engine stop control. Also good.

  In the above embodiment, the basic command torque is corrected by the in-cylinder pressure change coefficient. However, the intake pipe pressure (intake pressure) detected by the intake pipe pressure sensor or the cylinder at the specific crank angle position detected by the in-cylinder pressure sensor. The basic command torque may be corrected based on the internal pressure.

  In the above embodiment, the present invention is applied to a series-parallel type hybrid vehicle in which the engine 11, the first MG 12, and the second MG 13 are connected via the planetary gear mechanism 16. The present invention may be applied to other types of hybrid vehicles such as a series / parallel type hybrid vehicle, a series type hybrid vehicle, and a parallel type hybrid vehicle, and the present invention can rotate the engine 11 with MG torque. It can be widely applied to a system for controlling the stop position.

1 is a schematic configuration diagram of a hybrid vehicle drive system according to an embodiment of the present invention. It is a schematic block diagram of an engine control system. It is a flowchart which shows the flow of a process of an engine stop control program. FIG. 6 is a characteristic diagram showing the relationship between the engine speed at the end of load operation, the time from the end of load operation to the start of stop control, and the intake pressure at the start of stop control. It is a figure which shows notionally an example of the map of a cylinder pressure change coefficient. (A) is a figure which shows notionally an example of the map of the basic command torque in the period when an engine speed is higher than a predetermined value, (b) is the map of the basic command torque in the period when an engine speed is below a predetermined value. It is a figure which shows an example of no. It is a time chart which shows the execution example of the engine stop control of a present Example. It is a time chart which shows the example of execution of the conventional engine stop control.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... 1st MG, 13 ... 2nd MG, 16 ... Planetary gear mechanism, 24 ... Engine ECU, 25 ... 1st MG-ECU, 26 ... 2nd MG-ECU 30 ... Hybrid ECU (stop position control means, in-cylinder pressure information detection means) 31 ... Crank angle sensor

Claims (4)

An internal combustion engine stop control device comprising stop position control means for controlling the rotational stop position of the internal combustion engine with the torque of the motor generator when stopping the rotation of the internal combustion engine.
In-cylinder pressure information detecting means for detecting in-cylinder pressure at the time of stop control of the internal combustion engine or information correlated therewith (hereinafter collectively referred to as “in-cylinder pressure information”),
The stop position control means controls the rotation stop position of the internal combustion engine by controlling the torque of the motor generator based on the in-cylinder pressure information detected by the in-cylinder pressure information detection means and the crank angle position of the internal combustion engine. An internal combustion engine stop control device.   The in-cylinder pressure information detecting means calculates the in-cylinder pressure information based on a rotation speed at the end of load operation of the internal combustion engine and a period from the end of load operation of the internal combustion engine to the start of stop control. Item 2. The stop control device for an internal combustion engine according to Item 1. An in-cylinder pressure sensor for detecting the in-cylinder pressure of the internal combustion engine;
2. The internal combustion engine according to claim 1, wherein the in-cylinder pressure information detecting unit detects an in-cylinder pressure at a specific crank angle position detected by the in-cylinder pressure sensor during stop control of the internal combustion engine as the in-cylinder pressure information. Stop control device. An intake pipe pressure sensor for detecting the intake pipe pressure of the internal combustion engine;
2. The internal combustion engine stop according to claim 1, wherein the in-cylinder pressure information detecting means calculates the in-cylinder pressure information based on an intake pipe pressure detected by the intake pipe pressure sensor during stop control of the internal combustion engine. Control device.

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