JP2015051734A - Control device of hybrid vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve emission while suppressing deterioration of drivability when warming up a catalyst.SOLUTION: A catalyst warming-up control section 53 executes catalyst warming-up control for warming up a catalyst. A travel control section 51 can execute travel control of controlling an engine and a motor generator to travel while keeping the operation point of the engine at a predetermined operation point during execution of the catalyst warming-up control. The catalyst warming-up control section 53, when braking of a hybrid vehicle is demanded, makes the catalyst warming-up control non-execution on the basis of the output of the engine. The output of the engine for making the catalyst warming-up control non-execution during execution of the travel control is larger than the output of the engine for making the catalyst warming-up control non-execution during non-execution of the travel control.

Description

  The present invention relates to a control device for a hybrid vehicle, and more particularly to warming up a catalyst mounted in a hybrid vehicle.

  Japanese Patent Laying-Open No. 2012-040915 (Patent Document 1) discloses a hybrid vehicle that performs catalyst warm-up control. In this warm-up control, when warming-up of the catalyst is required, the ignition timing is retarded and the exhaust gas temperature rises to warm the catalyst. Thereafter, when the temperature of the catalyst rises to a predetermined value, the ignition timing is advanced, and the catalyst is warmed up by running while keeping the engine output constant. This stabilizes combustion during warm-up of the catalyst and improves fuel efficiency (see Patent Document 1).

JP 2012-040915 A JP 2010-000998 A JP 2012-111408 A JP 2013-067297 A

  When the ignition timing is retarded in the warm-up control as described above, the engine torque tends to fluctuate, and the engine torque fluctuations become more prominent as the engine output increases. In particular, when the brake is operated, the driver can easily feel the vibration due to the engine torque fluctuation, and thus the drivability may be deteriorated by the warm-up control. On the other hand, if the warm-up control is uniformly limited to suppress the deterioration of drivability, the warm-up of the catalyst is hardly promoted. As a result, emissions will deteriorate.

  Therefore, an object of the present invention is to improve emission while suppressing deterioration of drivability when warming up the catalyst.

  According to this invention, the hybrid vehicle includes an internal combustion engine, an exhaust purification catalyst, and a rotating electrical machine. The exhaust purification catalyst is provided in the exhaust passage of the internal combustion engine. The rotating electrical machine generates a traveling driving force. The control apparatus for a hybrid vehicle includes a catalyst warm-up control unit and a travel control unit. The catalyst warm-up control unit executes catalyst warm-up control for warming up the exhaust purification catalyst. The travel control unit can execute travel control for controlling the internal combustion engine and the rotating electrical machine so as to travel while maintaining the operating point of the internal combustion engine at a predetermined operating point during execution of the catalyst warm-up control. The catalyst warm-up control unit does not execute the catalyst warm-up control based on the output of the internal combustion engine when braking of the hybrid vehicle is requested. The output of the internal combustion engine for not executing the catalyst warm-up control when the travel control is executed is larger than the output of the internal combustion engine for not executing the catalyst warm-up control when the travel control is not executed.

  In the present invention, when the catalyst warm-up control is executed, the travel control of the internal combustion engine is performed when the operation point of the internal combustion engine is maintained at a predetermined operation point, compared to when the travel control is not performed. Since the torque fluctuation is small, it is possible to continue the catalyst warm-up control without deteriorating drivability to a region where the output of the internal combustion engine is higher. Therefore, according to the present invention, it is possible to improve emission while suppressing deterioration of drivability when warming up the catalyst.

1 is a block diagram showing an overall configuration of a hybrid vehicle to which a control device according to an embodiment of the present invention is applied. It is a functional block diagram regarding the warming-up process which the control apparatus shown in FIG. 1 performs. It is a flowchart which shows the control structure of the warming-up process which the control apparatus shown in FIG. 1 performs.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a block diagram showing an overall configuration of a hybrid vehicle to which a control device according to an embodiment of the present invention is applied. Referring to FIG. 1, hybrid vehicle 100 includes an engine 2, motor generators MG <b> 1 and MG <b> 2, power split device 4, speed reducer 5, drive wheel 6, brake pedal sensor 300, power storage device B, A PCU (Power Control Unit) 20 and a control device (hereinafter also referred to as an ECU (Electronic Control Unit)) 50 are included.

  The engine 2 is an internal combustion engine that generates a driving force for rotating a crankshaft by combustion energy generated when an air-fuel mixture sucked into a combustion chamber is combusted. Motor generators MG1 and MG2 are AC motors, for example, three-phase AC synchronous motors.

  Hybrid vehicle 100 travels by driving force output from at least one of engine 2 and motor generator MG2. The driving force generated by the engine 2 is divided into two paths by the power split device 4. That is, one is a path through which driving force is transmitted to the drive wheels 6 via the speed reducer 5, and the other is a path through which driving power is transmitted to the motor generator MG1.

  Power split device 4 includes a planetary gear constituted by a sun gear, a pinion gear, a carrier, and a ring gear. The pinion gear engages with the sun gear and the ring gear. The carrier supports the pinion gear so as to be capable of rotating, and is connected to the crankshaft of the engine 2. The sun gear is coupled to the rotation shaft of motor generator MG1. The ring gear is connected to the rotation shaft of motor generator MG2 and speed reducer 5.

  The brake pedal sensor 300 detects the operation amount of the brake pedal, and outputs a signal indicating the operation amount of the brake pedal to the ECU 50. ECU 50 determines whether braking is requested by the driver based on a signal received from brake pedal sensor 300.

  The power storage device B is a power storage element configured to be chargeable / dischargeable. The power storage device B includes, for example, a secondary battery such as a lithium ion battery, a nickel metal hydride battery, or a lead storage battery, or a cell of a power storage element such as an electric double layer capacitor.

  Power storage device B is connected to PCU 20 for driving motor generators MG1, MG2. Then, power storage device B supplies power for generating driving force of hybrid vehicle 100 to PCU 20. Power storage device B stores the electric power generated by motor generators MG1 and MG2. The output of power storage device B is, for example, 200V.

  PCU 20 includes a converter 21, inverters 22 and 23, and a capacitor C1. Converter 21 performs voltage conversion between power lines PL1, NL1 and power lines PL2, NL1 based on control signal S1 from ECU 50.

Inverters 22 and 23 are connected in parallel to power lines PL2 and NL1. Inverters 22 and 23 convert DC power supplied from converter 21 to AC power based on control signals S2 and S3 from ECU 50, and drive motor generators MG1 and MG2, respectively.

  Capacitor C1 is provided between power lines PL2 and NL1, and reduces voltage fluctuation between power lines PL2 and NL1.

  The operating state of the engine 2 is controlled based on a control signal S4 from the ECU 50. The engine 2 is provided with a temperature sensor 202 for detecting an engine water temperature Tw indicating the temperature of the cooling water of the engine 2. The temperature sensor 202 outputs the detected value of the engine water temperature Tw to the ECU 50.

  Air is introduced into the engine 2 through the intake passage 210. A throttle 212 is provided in the intake passage 210. The throttle 212 changes the passage resistance of the intake passage 210 based on the control signal S5 from the ECU 50. The ECU 50 controls the amount of air introduced into the engine 2 by changing the passage resistance of the intake passage 210 by the throttle 212.

  Exhaust gas discharged from the engine 2 passes through the exhaust passage 220 and is discharged outside the vehicle. A catalyst 222 is provided in the exhaust passage 220. The catalyst 222 is provided to purify the exhaust gas. The catalyst 222 is, for example, a three-way catalyst, and purifies carbon monoxide (CO), hydrocarbon (HC), NOx and PM contained in the exhaust gas.

  The catalyst 222 is provided with a temperature sensor 226 for detecting a catalyst temperature Tc indicating the temperature of the catalyst 222. Temperature sensor 226 outputs a detected value of catalyst temperature Tc to ECU 50. Note that the ECU 50 may estimate the catalyst temperature Tc based on parameters for controlling the engine 2 instead of the output of the temperature sensor 226.

  In the configuration as described above, the catalyst 222 has a characteristic that the purification rate becomes high when the catalyst 222 is warmed up to a predetermined temperature. For this reason, in order to improve the emission of the hybrid vehicle 100, it is necessary to warm up the catalyst 222 to a predetermined temperature when the operation of the engine 2 is started.

  In general, in order to warm up the catalyst 222, a method of increasing the exhaust gas temperature by retarding the ignition timing of the engine 2 is known. However, when the ignition timing is retarded, there is a problem that the operating efficiency of the engine 2 is deteriorated and the combustion becomes unstable, so that the torque fluctuation increases.

  In particular, when the brake of the hybrid vehicle 100 is operated, the driver tends to feel torque fluctuations of the engine 2, and thus drivability deteriorates when the catalyst 222 is warmed up.

  In the present embodiment, after the temperature of catalyst 222 rises to a predetermined value, engine 2 and motor generator MG2 are advanced so that the ignition timing is advanced and the operating point of engine 2 is maintained at the predetermined operating point. The traveling control for controlling the vehicle is executed. As a result, the operating efficiency of the engine 2 can be increased to improve fuel efficiency and stabilize combustion so that the catalyst 222 can be warmed up while reducing torque fluctuations. The predetermined operating point is an operating point at which the output of the engine 2 is larger than when the ignition timing is retarded and the catalyst 222 is warmed up.

  In the present embodiment, when warming up of the catalyst 222 is requested during the operation of the brake, and the output of the engine 2 is equal to or lower than the threshold value, the warming up of the catalyst 222 for warming up the catalyst 222 is performed. When the control is executed and the output of the engine 2 is larger than the threshold value, a process for not executing the catalyst warm-up control is executed. Here, when the braking of the hybrid vehicle 100 is requested, the threshold value is set higher when the traveling control is executed than when the traveling control is not executed.

  As a result, when the travel control is executed, the torque fluctuation of the engine 2 is smaller than when the travel control is not executed, so that the catalyst warm-up control is continued without deteriorating the drivability to a region where the output of the engine 2 is higher. Can do. Therefore, emission can be improved while suppressing deterioration of drivability when the catalyst is warmed up. Hereinafter, the contents of this warm-up process will be described in detail.

  FIG. 2 is a functional block diagram related to warm-up processing executed by the ECU 50 shown in FIG. Each functional block described in the functional block diagram of FIG. 2 is realized by hardware or software processing by the ECU 50.

  Referring to FIG. 1 together with FIG. 2, ECU 50 includes a travel control unit 51, a threshold setting unit 52, and a catalyst warm-up control unit 53.

  Travel controller 51 receives a detected value of catalyst temperature Tc from temperature sensor 226. The travel control unit 51 receives a signal indicating the execution state of the catalyst warm-up control from the catalyst warm-up control unit 53. The traveling control unit 51 controls the engine 2 so that the ignition timing is retarded when the catalyst temperature Tc is lower than a predetermined value when the catalyst warm-up control is being performed. The predetermined value is a value for determining that the catalyst 222 has been partially warmed up, and is, for example, 300 ° C.

  On the other hand, when the catalyst warm-up control is being executed and the catalyst temperature Tc is equal to or higher than the predetermined value, the traveling control unit 51 advances the ignition timing and sets the operating point of the engine 2 for the predetermined catalyst warm-up. Travel control is performed to control engine 2 and motor generator MG2 so as to travel while maintaining the operating point. Travel control unit 51 outputs a signal indicating the execution state of the travel control to threshold setting unit 52.

  The threshold setting unit 52 receives a signal indicating the amount of operation of the brake pedal from the brake pedal sensor 300. The threshold setting unit 52 sets a threshold for determining whether or not to perform catalyst warm-up control. When braking of hybrid vehicle 100 is requested, threshold setting unit 52 sets the threshold higher when running control is being executed than when running control is not executed. Threshold value setting unit 52 outputs the set threshold value to catalyst warm-up control unit 53.

  The catalyst warm-up control unit 53 performs catalyst warm-up control for warming up the catalyst 222 when the output of the internal combustion engine is equal to or lower than the threshold when warming-up of the catalyst 222 is requested. When the engine output is larger than the threshold value, the catalyst warm-up control is not executed. The catalyst warm-up control unit 53 outputs a signal indicating the execution state of the catalyst warm-up control to the travel control unit 51.

  FIG. 3 is a flowchart showing a control structure of warm-up processing executed by ECU 50 shown in FIG. The flowchart shown in FIG. 3 is realized by executing a program stored in advance in the ECU 50 at a predetermined cycle. Alternatively, for some steps, it is also possible to construct dedicated hardware (electronic circuit) and realize processing.

  Referring to FIG. 1 together with FIG. 3, ECU 50 determines in step (hereinafter, step is abbreviated as S) 100 whether or not catalyst warm-up control is being executed. If it is determined that the catalyst warm-up control is not being executed (NO in S100), the subsequent processing is skipped and the processing is returned to the main routine.

  When it is determined that catalyst warm-up control is being executed (YES in S100), ECU 50 determines whether braking of hybrid vehicle 100 is requested (S110). If it is determined that braking of hybrid vehicle 100 is not requested (NO in S110), the subsequent processing is skipped and the processing returns to the main routine.

  If it is determined that braking of hybrid vehicle 100 is requested (YES in S110), ECU 50 determines whether traveling control is being executed (S120). That is, ECU 50 determines whether or not hybrid vehicle 100 is traveling while maintaining the operating point of engine 2 at a predetermined operating point (engine output Pe is constant).

  If it is determined that traveling control is being executed (YES in S120), ECU 50 sets a threshold value for determining whether to prohibit warm-up control to X (S130). On the other hand, when it is determined that traveling control is not being executed (NO in S120), ECU 50 sets the threshold value to Y (S140). X is a value higher than Y.

  Subsequently, in S150, the ECU 50 determines whether or not the engine output Pe is larger than a set threshold value. If it is determined that engine output Pe is greater than the set threshold value (YES in S150), ECU 50 prohibits warm-up operation (S160). Thereby, the vibration by engine torque fluctuation is suppressed.

  On the other hand, when it is determined that engine output Pe is equal to or less than the set threshold value (NO in S150), ECU 50 permits warm-up operation (S170). Thereby, the deterioration of emission is suppressed. Here, during running control, the threshold value is set higher because the engine torque fluctuation is smaller than when running control is not being executed. For this reason, catalyst warm-up continues for a longer time.

  As described above, in this embodiment, the torque fluctuation of the engine 2 is smaller when executing the traveling control in which the operating point of the engine 2 is maintained at a predetermined operating point than when the traveling control is not performed. The catalyst warm-up control can be continued without deteriorating drivability up to a region where the output of 2 is higher. Therefore, according to this embodiment, it is possible to improve emission while suppressing deterioration of drivability when warming up the catalyst.

  In the above embodiment, the series / parallel type hybrid vehicle has been described in which the power split device 4 can split and transmit the power of the engine 2 to the drive wheels 6 and the motor generators MG1, MG2. The invention is also applicable to other types of hybrid vehicles. That is, for example, the present invention can be applied to a so-called series type hybrid vehicle in which engine 2 is used only for driving motor generator MG1 and vehicle driving force is generated only by motor generator MG2.

  In the above, engine 2 corresponds to an embodiment of “internal combustion engine” in the present invention, and motor generator MG2 corresponds to an embodiment of “rotating electric machine” in the present invention.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  2 engine, 4 power split device, 5 speed reducer, 6 drive wheel, 21 converter, 22, 23 inverter, 51 travel control unit, 52 threshold setting unit, 53 catalyst warm-up control unit, 100 hybrid vehicle, 202, 226 Temperature sensor, 210 intake passage, 212 throttle, 220 exhaust passage, 222 catalyst, 300 brake pedal sensor, B power storage device, C1 condenser, MG1, MG2 motor generator, PL1, PL2, NL1 power line.

Claims (1)

A control device for a hybrid vehicle,
The hybrid vehicle
An internal combustion engine;
An exhaust purification catalyst provided in an exhaust passage of the internal combustion engine;
Including a rotating electrical machine that generates travel driving force,
The controller is
A catalyst warm-up control unit for performing catalyst warm-up control for warming up the exhaust purification catalyst;
A travel control unit capable of executing travel control for controlling the internal combustion engine and the rotating electrical machine so as to travel while maintaining the operating point of the internal combustion engine at a predetermined operating point during execution of the catalyst warm-up control. ,
The catalyst warm-up control unit, when braking of the hybrid vehicle is requested, disables the catalyst warm-up control based on the output of the internal combustion engine,
The output of the internal combustion engine for not executing the catalyst warm-up control when the travel control is executed is more than the output of the internal combustion engine for not executing the catalyst warm-up control when the travel control is not executed. Large, hybrid vehicle control system.

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