JP2016113946A - Control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promptly raise an exhaust temperature to early raise a temperature of a catalyst for activation during catalyst warming-up and thus suppress deterioration of exhaust emission.SOLUTION: A control device for a vehicle includes: a spark ignition type internal combustion engine; a variable compression ratio mechanism that can change an engine compression ratio; and a catalyst provided in an exhaust passage to purify exhaust gas. During catalyst warming-up in which the temperature of the catalyst is lower than an activating temperature, such as at cold start or at restart of the engine after idle stop, an operation is performed in a catalyst warming-up mode in which an engine compression ratio is lowered while ignition timing is retarded.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a control device for a vehicle including a spark ignition type internal combustion engine capable of changing an engine compression ratio, and more particularly to control during warm-up of a catalyst provided in an exhaust passage.

  Patent Document 1 includes a variable compression ratio mechanism capable of changing the engine compression ratio of a spark ignition type internal combustion engine as a technique for quickly raising the temperature of the catalyst and activating it when the internal combustion engine is cold started. A technique is described in which an expansion ratio is lowered by lowering an engine compression ratio sometimes to suppress a decrease in the temperature of exhaust gas discharged from the cylinder.

WO09 / 091077 pamphlet

  However, simply lowering the engine compression ratio during catalyst warm-up raises the temperature in the cylinder to some extent, but it cannot be said that it is sufficient to quickly raise the temperature of the catalyst provided in the exhaust passage. Improvement was desired.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a novel vehicle control device that can suppress deterioration of exhaust emission by quickly raising the temperature of a catalyst. Yes.

  Accordingly, the present invention provides a spark ignition type internal combustion engine, variable compression ratio means capable of changing the engine compression ratio of the spark ignition type internal combustion engine, and an exhaust passage of the spark ignition type internal combustion engine for purifying exhaust gas. In a vehicle control device equipped with a catalyst, when the catalyst temperature is lower than the activation temperature, operation is performed in a catalyst warm-up mode in which the engine compression ratio is lowered while retarding the ignition timing. It is characterized by.

  According to the present invention, when the catalyst is warmed up, it is possible to reduce the expansion ratio by lowering the engine compression ratio to suppress the rise in the exhaust temperature, and to reduce the ignition timing while ensuring the combustion stability by lowering the compression ratio. Can be greatly retarded, and the exhaust gas temperature can be increased more rapidly by retarding the ignition timing.

  As a result, the exhaust gas temperature can be quickly raised when the catalyst is warmed up so that the catalyst can be warmed up and activated early, and deterioration of exhaust emission can be suppressed.

The block diagram which shows the power train of the hybrid vehicle which concerns on one Example of this invention. Sectional drawing which shows the variable compression ratio mechanism of the said Example. The flowchart which shows the flow of control at the time of catalyst warming-up of a present Example. The timing chart which shows an example of the control content at the time of catalyst warming-up. The timing chart which similarly shows the other example of the control content at the time of catalyst warm-up. The timing chart which similarly shows the other example of the control content at the time of catalyst warm-up. The timing chart which similarly shows the other example of the control content at the time of catalyst warm-up. The timing chart which similarly shows the other example of the control content at the time of catalyst warm-up.

 Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. First, a basic configuration of a hybrid vehicle to which the present invention is applied will be described. FIG. 1 shows a power train of a hybrid vehicle having a front engine / rear wheel drive (FR) configuration as an example of a hybrid vehicle to which the present invention is applied.

  The power train of the hybrid vehicle shown in FIG. 1 is a rear wheel drive vehicle whose rear wheels are drive wheels 2, and is behind a spark ignition type internal combustion engine (hereinafter simply referred to as “internal combustion engine”) 1 in the vehicle front-rear direction. The automatic transmission 3 is arranged in tandem. A motor generator 5 that constitutes a vehicle drive source together with the internal combustion engine 1 is integrally provided on the shaft 4 that transmits the rotation of the internal combustion engine 1 from the crankshaft 1 a to the input shaft 3 a of the automatic transmission 3.

  The motor generator 5 is composed of a synchronous motor using a permanent magnet as a rotor, and acts as a motor (so-called “powering”) and also acts as a generator (so-called “regeneration”). Thus, the engine is located between the internal combustion engine 1 and the automatic transmission 3. A battery 9 is electrically connected to the motor generator 5. The battery 9 supplies electric power to the motor generator 5 during the power running operation of the motor generator 5, and charges the electric power supplied from the motor generator 5 during the regenerative operation of the motor generator 5.

  A first clutch 6 is inserted between the motor generator 5 and the internal combustion engine 1, more specifically, between the shaft 4 and the crankshaft 1a. The first clutch 6 is connected to the internal combustion engine 1 and the motor. The generator 5 is detachably coupled.

  Further, a second clutch 7 is interposed between the motor generator 5 and the drive wheel 2, more specifically, between the shaft 4 and the transmission input shaft 3a. The second clutch 7 is connected to the motor generator. 5 and the automatic transmission 3 are detachably coupled.

  The automatic transmission 3 shifts the rotation input from the input shaft 3a at a gear ratio corresponding to the selected shift speed and outputs it to the output shaft 3b. This output rotation is distributed and transmitted to the left and right drive wheels (rear wheels) 2 via the differential gear device 8. The automatic transmission 3 has a P (parking) range and N (neutral) range which are non-traveling ranges, and a D (drive) range and R which are traveling ranges as ranges selected by the driver via a select lever or the like. (Reverse) range at least.

  In the power train described above, an electric vehicle traveling mode (EV mode) that travels using only the power of the motor generator 5 as a power source, and a hybrid traveling mode (HEV mode) that travels while the internal combustion engine 1 is included in the power source together with the motor generator 5. ) Is possible.

  In the EV mode, since the power from the internal combustion engine 1 is unnecessary, it is stopped, the first clutch 6 is released, the second clutch 7 is engaged, and the automatic transmission 3 is in the power transmission state. To. In this state, the vehicle is driven only by the motor generator 5.

  In the HEV mode, both the first clutch 6 and the second clutch 7 are engaged, and the automatic transmission 3 is set in the power transmission state. In this state, both the output rotation from the internal combustion engine 1 and the output rotation from the motor generator 5 are input to the transmission input shaft 3a, and hybrid traveling by both is performed.

  In the HEV mode, when a predetermined idle stop condition is satisfied, an idle stop for stopping the internal combustion engine 1 is performed. For example, the idle stop condition is satisfied when the coolant temperature is equal to or higher than the predetermined temperature, the brake hydraulic pressure is equal to or higher than the predetermined pressure, the vehicle speed is equal to or lower than the predetermined speed, the accelerator opening is equal to or lower than the predetermined opening, and the engine speed is equal to the idle speed. As an idle stop. Then, when a predetermined idle stop cancellation condition is satisfied during the idle stop, the internal combustion engine is restarted. For example, the accelerator is ON, the brake is OFF, the battery charge is a predetermined amount or less, the brake hydraulic pressure is a predetermined pressure or less, the oil temperature in the automatic transmission 3 is a predetermined temperature or less, the oil temperature in the automatic transmission 3 is a predetermined pressure or less, If any of the above conditions is satisfied during idle stop, the internal combustion engine 1 is automatically restarted assuming that the idle stop cancellation condition is satisfied.

  The motor generator 5 can recover and recover braking energy when the vehicle decelerates, and can recover surplus energy of the internal combustion engine 1 as electric power in the HEV mode.

  Here, when transitioning from the EV mode to the HEV mode, the first clutch 6 is engaged, and the internal combustion engine 1 is started using the torque of the motor generator 5. Further, when restarting the internal combustion engine 1 during idling stop, the first clutch 6 is engaged and the motor generator 5 is started using the torque.

  Note that the second clutch 7 functions as a so-called starting clutch, and by variably controlling the transmission torque capacity at the time of starting the vehicle and slip-engaging, the second clutch 7 absorbs torque fluctuations smoothly even in a power train that does not include a torque converter. It is possible to start.

  A three-way catalyst 10 (hereinafter simply referred to as “catalyst”) for purifying exhaust gas is provided in the exhaust passage 10A of the internal combustion engine 1.

  FIG. 2 is a cross-sectional view showing a variable compression ratio mechanism 11 provided in the internal combustion engine 1 as an example of the variable compression ratio means. This variable compression ratio mechanism 11 uses a multi-link type piston-crank mechanism in which the piston 1B and the crank pin 13 of the crankshaft 1a are connected by a plurality of link parts, and the basic structure is the above-mentioned special structure. Since it is publicly known as described in Japanese Unexamined Patent Application Publication No. 2012-67758, etc., it will be briefly described here.

  The variable compression ratio mechanism 11 is rotatably supported by a lower link 14 rotatably attached to the crankpin 13, an upper link 15 connecting the lower link 14 and the piston 1B, and a cylinder block 1C as an engine body. And a control link 17 that connects the control shaft 16 and the lower link 14 to each other.

  The piston 1B and the upper end of the upper link 15 are connected to each other by a piston pin 18 so as to be relatively rotatable, and the lower end of the upper link 15 and the lower link 14 are connected to each other by a first connecting pin 19 so as to be relatively rotatable. The upper end of the link 17 and the lower link 14 are connected to each other by a second connecting pin 20 so as to be relatively rotatable, and the lower end of the control link 17 is attached to an eccentric shaft portion 16A provided eccentric to the control shaft 16. It has been.

  Further, the control shaft 16 is connected to a variable compression ratio motor 21 whose rotation position can be changed. By changing the rotation position of the control shaft 16 by the variable compression ratio motor 21, the top dead center of the piston 1B is reached. The stroke characteristics of the piston 1B including the point position and the bottom dead center position are changed, and consequently the engine compression ratio is changed. The operation of the actuator is controlled by the control unit 22 according to the engine operating state.

  The control unit 22 has a function of storing and executing catalyst warm-up control, as will be described later, in addition to ignition timing control and fuel injection control.

  FIG. 3 is a flowchart showing a control flow when the catalyst warms up, which is a main part of the present embodiment. This routine is repeatedly executed by the control unit 22 every predetermined period (for example, every 10 ms).

  In step S11, it is determined whether or not the temperature of the catalyst 10 has not reached the activation temperature, and the catalyst warm-up operation is performed to raise the temperature of the catalyst 10 and activate it. That is, it is determined whether or not the temperature of the catalyst 10 is lower than the activation temperature, such as when the engine is cold and when the engine is restarted after a long idle stop. If the catalyst is not warmed up, the determination in step S11 is negative, and this routine ends.

  If it is determined in step S11 that the catalyst is warming up, the process proceeds to step S12, and the operation is performed in the catalyst warming-up mode in which the engine compression ratio is lowered while retarding the ignition timing with respect to the normal setting according to the engine operating state. To do. At this time, if the throttle opening is 0, for example, the throttle opening is close to full closure.

  In continuing step S13, based on SOC (charge condition) of the battery 9, it is determined whether the battery 9 is in a chargeable state. If the battery 9 is in the vicinity of full charge, in order to prevent overcharging of the battery 9, it is determined that the battery 9 cannot be charged, and this routine is terminated.

  On the other hand, if the state of charge (SOC) of the battery 9 is small and chargeable, the process proceeds from step S13 to step S14, the throttle opening is increased to increase the driving torque of the internal combustion engine 1, and the motor generator 5 is turned on. Regenerative operation. The throttle opening (corresponding to the driving torque of the internal combustion engine) and the regenerative torque of the motor generator 5 at this time are set according to the state of charge of the battery 9 as will be described later.

  In step S15, it is determined whether or not there is a required torque of the internal combustion engine 1 during the catalyst warm-up operation. For example, when the driver depresses the accelerator pedal during the catalyst warm-up operation, the required torque of the internal combustion engine becomes valid. In this case, the ignition timing is advanced and the throttle opening (driving torque of the internal combustion engine) is increased while the engine compression ratio is fixed and maintained at a low compression ratio with respect to the setting in the catalyst warm-up mode.

  4 to 8 are timing charts showing some examples of control contents during catalyst warm-up when the control of this embodiment is applied. With reference to these FIGS. 4-8, the effect of a present Example is demonstrated.

  [1] As shown in FIG. 4, at the time of catalyst warm-up when the temperature of the catalyst 10 is less than the activation temperature, the catalyst warm-up request is turned on, the engine compression ratio is lowered, and the catalyst warm-up that retards the ignition timing The operation is performed in the mode (see step S12 in FIG. 3).

  By reducing the engine compression ratio in this way, it is possible to suppress an increase in the exhaust temperature due to a decrease in the expansion ratio, and to send a large amount of high-temperature exhaust gas with less HC into the exhaust passage 10A, thereby promoting an increase in the exhaust temperature. Is done. Further, since the amount of combustion gas increases due to the low compression ratio, the combustion is stabilized, and accordingly, a large amount of ignition timing retardation can be secured while ensuring combustion stability, and the ignition timing is greatly retarded. The exhaust gas temperature can be increased more rapidly by the keratinization, and the catalyst 10 can be activated early.

  [2] Further, in this embodiment, the above-described operation is performed not only when starting the engine cooler but also when the catalyst temperature falls below the activation temperature during operation, such as when the engine is restarted after idling stop for a long time. Since the operation in the catalyst warm-up mode is performed, the catalyst 10 can be activated quickly.

  [3] As shown in FIGS. 5 and 6, when the catalyst 9 is warmed up, if the charge amount (SOC) of the battery 9 is in a low chargeable ON state, the throttle opening is increased and the motor generator 5 is increased. Perform regenerative operation. In this way, surplus drive torque due to the increase in throttle opening is absorbed and offset by the regenerative operation of the motor generator 5, so that the increase in throttle opening (drive torque), in-cylinder temperature, without causing torque fluctuations. As a result, the rise in the exhaust temperature can be promoted, and the catalyst 10 can be further activated earlier. Further, while the amount of charge of the battery 9 is increased by the power generation of the motor generator 5, the temperature rise of the battery 9 can be promoted by the power input to the battery 9 by the power generation.

  [4] The throttle opening (driving torque of the internal combustion engine) and the regenerative torque of the motor generator 5 at this time are set according to the SOC of the battery 9. In other words, when the SOC (charge amount) of the battery 9 is small, as shown in FIG. 6, the throttle opening and the regenerative torque are increased, and the ignition timing is advanced to actively generate power. Thus, early activation of the catalyst 10 can be promoted while the battery 9 is brought close to full charge at an early stage, and the temperature rise of the battery 9 can be promoted by power input to the battery 9 by power generation. On the other hand, when the SOC of the battery 9 is near full charge, the battery 9 can be protected from overcharging by prohibiting the regenerative operation of the motor generator 5 or suppressing the regenerative torque (power generation amount).

  [5] As shown in FIG. 7, during the catalyst warm-up operation, for example, when the required torque of the internal combustion engine is generated by the driver's operation of the accelerator pedal, the setting in the catalyst warm-up mode is as follows. While maintaining the engine compression ratio at a low compression ratio, the ignition timing is advanced and the driving torque of the internal combustion engine is increased. In other words, in the above-mentioned catalyst warm-up mode, the ignition timing is greatly retarded so as to give priority to early activation of the catalyst, but when required torque occurs, ignition is performed so as to ensure vehicle driving force. The timing is returned to the advance side to improve the thermal efficiency, and the driving torque of the internal combustion engine is increased. Although an increase in the exhaust temperature is suppressed by the advancement of the ignition timing by improving the thermal efficiency, the increase in the exhaust temperature is not hindered because the driving torque of the internal combustion engine is increasing.

  [6] As shown in FIG. 8, during the catalyst warm-up operation, for example, when the driver suddenly depresses the accelerator pedal, a large required torque of the internal combustion engine greater than a predetermined value is abruptly generated. In such a case, in contrast to the setting in the catalyst warm-up mode described above, as in the case of FIG. 7, the ignition timing is advanced while the engine compression ratio is maintained at a low compression ratio, and the internal combustion engine Increase the drive torque. In addition, the ignition timing is controlled so that a driving force corresponding to the required torque can be obtained. In other words, during the catalyst warm-up operation, the ignition timing is greatly retarded, and there is a sufficient margin for changing the ignition timing to the advance side, so by controlling the ignition timing with high responsiveness, The driving force commensurate with the required torque can be quickly secured.

  As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes. For example, although the present invention is applied to a hybrid vehicle in the above-described embodiment, the present invention can be similarly applied to a vehicle capable of performing an idle stop having only an internal combustion engine as a vehicle drive source.

DESCRIPTION OF SYMBOLS 1 ... Spark ignition internal combustion engine 5 ... Motor generator 9 ... Battery 10 ... Catalyst 11 ... Variable compression ratio mechanism 22 ... Control part

Claims (6)

A spark ignition internal combustion engine,
Variable compression ratio means capable of changing the engine compression ratio of the spark ignition type internal combustion engine;
In a control device for a vehicle, comprising a catalyst for purifying exhaust gas, provided in an exhaust passage of the spark ignition internal combustion engine,
A control apparatus for a vehicle, characterized in that when the catalyst temperature is lower than the activation temperature, the operation is performed in a catalyst warm-up mode in which the engine compression ratio is lowered while retarding the ignition timing. It is possible to realize an idle stop that temporarily stops the spark ignition internal combustion engine during vehicle operation,
2. The vehicle control device according to claim 1, wherein the operation in the catalyst warm-up mode is performed when the cold engine is started and when the engine is restarted after an idle stop. 3. A motor generator provided with the internal combustion engine as a vehicle drive source;
A battery electrically connected to the motor generator,
3. The regenerative operation of the motor generator is performed while increasing the driving torque of the internal combustion engine and when the battery is in a chargeable state in the catalyst warm-up mode. Vehicle control device.   In the catalyst warm-up mode and when the battery is in a chargeable state, the drive torque of the internal combustion engine and the regenerative torque of the motor generator are set according to the charge state of the battery. The vehicle control device according to claim 3.   When the catalyst is warmed up and there is a required torque of the internal combustion engine, the ignition timing is advanced while maintaining the engine compression ratio at a low compression ratio with respect to the setting in the catalyst warmup mode. The vehicle control device according to claim 1, wherein the driving torque of the internal combustion engine is increased.   If the required torque of the internal combustion engine suddenly exceeds a predetermined value during the catalyst warm-up, the engine compression ratio is maintained at a low compression ratio with respect to the setting in the catalyst warm-up mode, and the internal combustion engine 6. The vehicle control device according to claim 1, wherein the driving torque is increased and the ignition timing is controlled in accordance with the required torque.

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