JP5163000B2 - Regenerative control device for hybrid vehicle - Google Patents

Description

  The present invention relates to a control technique for increasing the regeneration efficiency of a motor functioning as a generator during deceleration in a hybrid vehicle including a prime mover in which an internal combustion engine having a mechanism for changing an effective compression ratio for each cylinder and an electric motor are connected. .

In Patent Document 1, in a vehicle equipped with the above hybrid prime mover, at the time of deceleration, the motor functions as a generator to reduce the compression ratio of the internal combustion engine when regenerating by converting braking force into electric power. A technique for improving the regeneration efficiency is disclosed.
JP 2004-270679 A

  In Patent Document 1, the compression ratio is always reduced during regeneration. However, in practice, it may be difficult to reduce the compression ratio during deceleration.

  Further, no special correction is made to increase the regenerative efficiency with respect to the change in the compression ratio until the predetermined amount is reduced from the state before the compression ratio is reduced at the initial stage of deceleration, and the regenerative efficiency can be sufficiently increased. It wasn't.

  The present invention has been made paying attention to such a conventional problem, and an object thereof is to maintain a high regeneration efficiency with respect to regeneration at different compression ratios during deceleration.

For this reason, the present invention enables regeneration by causing the motor to function as a generator during deceleration of a hybrid vehicle equipped with a prime mover in which an internal combustion engine having a mechanism for changing the effective compression ratio for each cylinder and an electric motor are connected. In the regenerative control device for a hybrid vehicle, the target rotational speed of the motor at the time of regeneration is set to a larger value when the effective compression ratio of the internal combustion engine is low than when the effective compression ratio is high, and the rotational speed of the motor is The electric motor is driven by the power generation torque calculated based on the target power generation amount and the target rotation speed while controlling the speed ratio of the continuously variable transmission so as to converge to the target rotation speed.

  In this way, when the effective compression ratio is low, the rotational resistance of the internal combustion engine decreases. Therefore, the target rotational speed at the time of regeneration of the motor linked to the internal combustion engine is set to a larger value when the effective compression ratio is high. As a result, the power generation torque required to obtain the target power generation amount when the motor functioning as the generator is rotated at the target rotation speed is reduced, thereby reducing the energy loss and improving the regeneration efficiency. be able to.

  FIG. 1 schematically shows a drive system of a hybrid vehicle according to an embodiment of the present invention.

  The output shaft of the engine (internal combustion engine) 1 and one end portion of the output shaft of the motor (electric motor) 2 are connected, and the other end portion of the motor 2 has a gear ratio by changing the input / output pulley diameter ratio. A continuously variable transmission 3 that is variably controlled continuously is connected, and an output shaft (output pulley shaft) of the continuously variable transmission 2 is connected to one end of a gear shaft 5 via a clutch 4.

  The gear 5a fixed to the gear shaft 5 meshes with a gear 7a fixed to an axle (drive shaft) 7 having wheels 6 connected to both ends, and the driving force of the engine 1 and the motor 2 is used for the continuously variable transmission. 3, and transmitted to the wheel 6 through the clutch 4, the gear 5 a, the gear 7 a, and the axle 7.

  In addition, a battery (power storage device) 9 is connected to the motor 2 via an inverter 8. When the motor 2 functions as an electric motor, electric power is supplied from the battery 9, and when the motor 2 functions as a generator, The generated power is charged in the battery 9.

  FIG. 2 shows an example of the engine 1.

  The engine 1 is a diesel engine, and intake air is drawn into the cylinder 28 from an air cleaner 22 through an intake passage 23, a collector 24, an intake manifold 25, and an intake valve 26 that is driven to open and close by an intake cam 26.

  A piston 29 is fitted into the cylinder 28 and fuel is injected and supplied by a fuel injection valve 30. The combustion exhaust is discharged to the exhaust passage 33 through an exhaust valve 32 that is opened and closed by an exhaust cam 31.

  A part of the exhaust is introduced into the EGR passage 34 as EGR gas, and is returned to the intake manifold 25 while the EGR amount is controlled by the EGR valve 35.

  In addition, as a mechanism for changing the effective compression ratio of the engine 1, a variable valve timing mechanism 36 for changing the valve timing of the intake valve 27 is provided, and in the late closing system in which the intake valve is closed after intake bottom dead center, the intake valve 27 The effective compression ratio decreases by retarding the closing timing IVC. It should be noted that an early closing method in which the intake valve is closed before intake bottom dead center may be employed, and in this method, the effective compression ratio is reduced by advancing the closing timing IVC.

  Changing the effective compression ratio is substantially equivalent to changing the compression pressure at the compression top dead center, that is, changing the charging efficiency of the intake air. In addition to the variable valve timing mechanism, a variable valve lift mechanism that changes the operating angle or lift amount of the intake valve, an intake throttle mechanism using an intake throttle valve, or the like may be used.

  Of course, the engine 1 may be a gasoline engine.

  In the hybrid vehicle configured as described above, the regeneration control according to the present invention will be described according to the flowchart of FIG.

  In step S1, it is determined whether or not a regeneration request has occurred. If so, the process proceeds to step S2.

  In step S2, the target power generation amount tP by regeneration, the effective compression ratio by the variable valve timing mechanism, and the like are set based on the operation information of the driver, specifically, the brake pedal depression amount BPS and the accelerator pedal depression amount APS.

  Specifically, in a state where the required braking amount is small, such as when braking is performed only by the engine brake when the accelerator pedal is released and the brake pedal is not depressed, regeneration is not performed or even if it is performed, the target power generation amount Is set to be small, and control for reducing the effective compression ratio (retarding IVC) is not performed.

  On the other hand, when the required braking amount for depressing the brake pedal is large, the target power generation amount is set to a large value, and control for reducing the effective compression ratio is performed.

  Subsequently, in step S3, the state of charge SOC of the battery 9 is equal to or lower than a predetermined value Cb. In step S4, the motor coil temperature MTEMP is equal to or lower than a predetermined value Ts. In step S5, the variable valve timing mechanism is used. It is determined whether control for reducing the compression ratio is being performed.

  If it is determined in steps S3 to S5 that the SOC is Cb or less, the TEMP is equal to or less than the predetermined value Ts, and the control is performed to reduce the effective compression ratio, the process proceeds to step S6, and the electric motor 2 The target rotational speed (= target rotational speed of the engine 1) tN is calculated as a value N2 corresponding to the reduced effective compression ratio EPR based on the characteristics shown in FIG.

  Here, the characteristic shown in FIG. 4 is a characteristic that the target rotational speed tN increases as the effective compression ratio EPR is smaller. Hereinafter, the reason for such characteristics will be described.

  FIG. 5 shows efficiency characteristics with respect to the rotational speed of the motor and the generated torque. In order to obtain the same power generation output (power generation amount), the power generation torque (= field coil current), that is, the power consumption amount can be reduced as the rotational speed is increased, so that the motor efficiency can be increased.

  FIG. 6 shows the characteristic of the energy loss rate when the effective compression ratio is high (when it is not reduced), and FIG. 7 shows the characteristic of the energy loss rate when the effective compression ratio is reduced.

  As described above, since the efficiency of the motor 2 increases as the rotational speed increases, the energy loss rate of the motor 2 alone decreases as the rotational speed increases.

  On the other hand, for the engine 1, since the friction increases as the rotational speed increases, the energy loss rate also increases as the rotational speed increases. However, when the effective compression ratio is high, the friction is lower than when it is low. As it increases, the energy loss rate also increases.

  The target rotational speed N is set to the rotational speed of the motor 2 (and the engine 1) when the total energy loss that is the sum of the energy losses of the engine 1 and the motor 2 is minimized, that is, the regeneration efficiency is maximized. As shown in FIGS. 6 and 7, this rotational speed increases to N2 when the effective compression ratio is low, as compared to N1 when the effective compression ratio is high.

  Returning to FIG. 3, in step S7, based on the target power generation amount tP and the target rotation speed tN (= tN2), the target power generation torque tTM (= tTM2) of the electric motor 2 is calculated based on the characteristics shown in FIG. Set. The power generation torque is a negative torque because it is a resistance to the driving force.

  In step S8, regeneration control is performed by controlling the electric motor 2 to an operating point determined by the target rotational speed tN (= tN2) and the target power generation torque tTM (= tTM2). Specifically, the speed ratio of the continuously variable transmission 3 is controlled so that the rotational speed N of the electric motor 2 (and the engine 1) converges to the target rotational speed tN, and the power generation torque of the electric motor 2 is set to the target power generation. The field coil current is controlled so as to obtain the torque tTM.

  On the other hand, when it is determined at step S3 that the state of charge SOC of the battery 9 is greater than the predetermined value Cb, when it is determined at step S4 that the motor coil temperature TEMP is greater than the predetermined value Ts, the effective compression ratio is set at step S. If it is determined that the control to be reduced is not performed, the process proceeds to step S9, and the target rotational speed (= target rotational speed of the engine 1) tN of the electric motor 2 is determined based on the characteristics of FIG. Then, it is calculated as a value N1 (<N2) corresponding to the effective compression ratio EPR that has not been reduced (see FIG. 6).

  Next, the process proceeds to step S7, where the target power generation torque tTM (= tTM1) of the electric motor 2 is set based on the characteristics shown in FIG. 6 based on the target power generation amount tP and the target rotation speed tN (= tN1). In step S8, the electric motor 2 is controlled to an operating point determined by the target rotational speed tN (= tN1) and the target power generation torque tTM (= tTM2) to perform regenerative control.

  In this way, as basic regenerative control, the target rotational speed N corresponding to the effective compression ratio is set, and from N1 when the effective compression ratio is reduced to when the compression ratio is not high. By increasing to N2, the regeneration efficiency can be maximized, and the fuel consumption can be improved.

  Further, when it is determined that the state of charge SOC of the battery 9 is larger than the predetermined value Cb during regeneration, even if the effective compression ratio is reduced, the low target rotational speed tN1 in a high state that is not reduced is maintained, and regeneration is performed. By reducing the efficiency, overcharging of the battery 9 can be prevented.

  Similarly, at the time of regeneration, even when the motor coil temperature TEMP is larger than the predetermined value Ts, by maintaining the target rotational speed tN1 in a high state where the effective compression ratio is not reduced, the temperature rise is suppressed, Performance degradation due to demagnetization can be suppressed.

  In the above, for the sake of simplicity, it has been described that the effective compression ratio at the time of regeneration is switched stepwise between the case where the effective compression ratio is not reduced and the case where the effective compression ratio is not reduced. If the ratio can be varied continuously, the effective compression ratio at the time of regeneration can be arbitrarily controlled by the required braking amount. Even when the target value of the effective compression ratio is switched in stages, the effective compression ratio gradually changes during the switching due to a response delay of the variable valve timing mechanism.

  As described above, when the effective compression ratio at the time of regeneration is continuously varied or gradually changes during switching, the basic control is to continuously reach the target rotational speed N according to the changing effective compression ratio. By changing, the regeneration efficiency can be sufficiently increased. In this case, the regenerative efficiency can be improved to the maximum if the actual rotational speed is made to follow the target rotational speed as responsively as possible by performing advance correction in consideration of the operation delay of the continuously variable transmission.

  FIG. 9 shows how various state quantities change when control during regeneration according to the present invention is performed.

  At time t0, a coast deceleration state is achieved by braking only with the engine brake, and at t1, a deceleration regeneration state is achieved in which the brake pedal is depressed and braking by the brake is applied.

  Simultaneously with the start of the deceleration regeneration, the closing timing IVC of the intake valve 27 is gradually operated after the intake bottom dead center until t2 by the variable valve timing mechanism 36 of the engine 1. As a result, the effective compression ratio is reduced, and a command to change the power generation operation point (rotation speed, power generation torque) of the motor 2 is issued in accordance with a decrease in the effective compression ratio.

  The actual value of the power generation torque follows the target value with good response, but the rotational speed is delayed from the target value and converges at t3. That is, the actual operation point follows the power generation operation point command.

  The brake depression amount changes until t4, and the power generation operating point changes accordingly. Here, the operation of performing the correction processing shown in FIGS. 4 and 8 by changing the command value at the time of regeneration is included in addition to the operation of shifting the regeneration amount to the low output side.

  At t4, the brake is turned off, and the power generation amount is reduced to the setting for coast deceleration.

  At t5, the accelerator is depressed, the engine torque becomes positive and the vehicle accelerates.

  When the state of charge SOC of the battery 9 is greater than the predetermined value Cb, or when the motor coil temperature TEMP is greater than the predetermined value Ts, N1 when the effective compression ratio of the target rotational speed is high as in the above embodiment. Instead of maintaining, the reduction control of the effective compression ratio may be prohibited, or the reduction amount may be limited, or the target power generation amount may be reduced.

The figure which shows the outline of the drive system of the hybrid vehicle which concerns on one Embodiment of this invention. The figure which shows an example of the engine of embodiment same as the above. The flowchart which shows the regeneration control of embodiment same as the above. The figure which shows the characteristic of the target rotational speed with respect to an effective compression ratio in embodiment same as the above. The figure which shows the characteristic of the efficiency with respect to the rotational speed of a motor, and electric power generation torque in embodiment same as the above. The figure which shows the characteristic of the energy loss rate when an effective compression ratio is high (when not reducing) in embodiment same as the above. The figure which shows the characteristic of the energy loss rate when reducing an effective compression ratio in embodiment same as the above. The characteristic view which shows the relationship of the target electric power generation amount with respect to target electric power generation amount and target rotational speed in embodiment same as the above. The figure which shows the mode of the change of various state quantities at the time of performing control at the time of the regeneration which concerns on this invention.

Explanation of symbols

1 engine (internal combustion engine)
2 Motor (electric motor)
3 Continuously variable transmission 9 Battery

Claims (6)

A regenerative control device for a hybrid vehicle that performs regeneration by causing the motor to function as a generator during deceleration of a hybrid vehicle equipped with a prime mover in which an internal combustion engine having a mechanism that changes the effective compression ratio for each cylinder and a motor is connected. In
When the effective compression ratio of the internal combustion engine is low, the target rotational speed of the motor at the time of regeneration is set to a larger value than when the effective compression ratio is high,
The motor is driven by the power generation torque calculated based on the target power generation amount and the target rotation speed while controlling the gear ratio of the continuously variable transmission so that the rotation speed of the motor converges to the target rotation speed. A regenerative control device for a hybrid vehicle. The mechanism for changing the effective compression ratio can continuously change the effective compression ratio,
The regenerative control device for a hybrid vehicle according to claim 1, wherein the target rotational speed setting means sets the target rotational speed of the electric motor to a higher value as the effective compression ratio of the internal combustion engine is lower. The operating point determined by the rotational speed of the motor and the power generation torque is set in or near the operating region where the sum of the energy loss rate of the motor and the energy loss rate of the internal combustion engine with respect to the target power generation amount is minimum. The regeneration control device for a hybrid vehicle according to claim 2, wherein a target rotation speed is set. When electric power is supplied to the electric motor and the electric motor functions as a generator, when the amount of charge of the power storage device that charges the generated electric power is larger than a predetermined value, the target rotational speed at the time of regeneration is set when the effective compression ratio is low. The regenerative control device for a hybrid vehicle according to any one of claims 1 to 3, wherein a setting to be larger than when it is high is limited or a reduction amount of the effective compression ratio is limited. When the temperature of the electric motor or a parameter conforming to the temperature is higher than a predetermined value, the target rotational speed at the time of regeneration is limited to a higher setting when the effective compression ratio is low, or the effective compression ratio The regenerative control device for a hybrid vehicle according to any one of claims 1 to 3, wherein a reduction amount is limited. The regenerative control device for a hybrid vehicle according to any one of claims 1 to 5, wherein the effective compression ratio at the time of regeneration is lowered as the required braking amount at the time of deceleration is larger.

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