JP6286203B2 - Brake control device for vehicle - Google Patents

Description

  The present invention relates to a vehicle braking control device applied to a vehicle including a regenerative braking device and a hydraulic braking device.

  Patent Document 1 describes an example of a braking control device that controls a braking force of the entire vehicle by coordinating a regenerative braking device and a hydraulic braking device. In this device, the regenerative braking device is controlled so that a change speed, which is a change amount per unit time, of the regenerative braking force applied to the vehicle by the regenerative braking device does not exceed a preset limit value.

  The response speed of the hydraulic braking force based on the operation of the hydraulic braking device is smaller than the response speed of the regenerative braking force based on the operation of the regenerative braking device. Therefore, the limit value is set so that the hydraulic braking force can sufficiently follow the change in the regenerative braking force.

JP 11-115744 A

  By the way, the regenerative braking device generates electric power according to the regenerative braking force applied to the vehicle and stores the electric power in the battery. Further, in a vehicle equipped with such a regenerative braking device, further improvement in energy (electric power) recovery efficiency during vehicle braking is required.

  An object of the present invention is to provide a vehicle braking control device that can improve energy recovery efficiency during vehicle braking.

  A vehicle braking control device for solving the above-described problems is provided with a regenerative braking device that applies a regenerative braking force to a vehicle, and a hydraulic pressure in a wheel cylinder that is provided for a wheel, thereby adjusting the fluid pressure to the vehicle. The present invention is applied to a vehicle including a hydraulic braking device that applies a pressure braking force, and is based on a device that controls the regenerative braking device and the hydraulic braking device based on a required braking force required for the vehicle. When the regenerative braking device changes the regenerative braking force that the regenerative braking device applies to the vehicle, the braking control device sets the limit value of the change gradient that is the amount of change per unit time of the regenerative braking force to the operation of the hydraulic braking device. A limit value setting unit for setting a value according to the state is provided.

  The response speed of the hydraulic braking force based on the operation of the hydraulic braking device may be small or large. The response speed of the hydraulic braking force can be predicted from the operating state of the hydraulic braking device. Therefore, in the above configuration, when the regenerative braking force is changed, if it can be predicted that the response speed of the hydraulic braking force is likely to increase, the limit value of the change gradient of the regenerative braking force is increased, and the response speed of the hydraulic braking force is decreased. When it can be predicted that it will be easy, the limit value of the regenerative braking force change gradient is reduced. As a result, the opportunity for rapidly increasing the regenerative braking force is increased as compared with the case where the limit value of the change gradient of the regenerative braking force is fixed to a value adjusted when the response speed of the hydraulic braking force is small. . Therefore, the energy recovery efficiency during vehicle braking can be improved.

  In the vehicle braking control device, the limit value setting unit may increase the limit value of the change gradient of the regenerative braking force as the required braking force correlated with the operating state of the hydraulic braking device increases. . According to this configuration, the change gradient of the regenerative braking force can be changed according to the magnitude of the required braking force. Therefore, compared with the case where the limit value of the change gradient of the regenerative braking force is fixed at a value when the required braking force is small, the chance of increasing the regenerative braking force quickly increases, so that energy is recovered during vehicle braking. Efficiency can be improved.

  Also, for example, the inflow amount (or outflow amount) of liquid necessary for increasing (or reducing) the hydraulic pressure in the wheel cylinder by a specified pressure is smaller as the reference hydraulic pressure that is the current hydraulic pressure is higher. . That is, when the liquid flows into (or flows out) into the wheel cylinder at a constant speed, the response speed of the hydraulic braking force corresponding to the hydraulic pressure in the wheel cylinder tends to increase as the reference hydraulic pressure increases. Therefore, it is preferable that the limit value setting unit increases the limit value of the change gradient of the regenerative braking force as the hydraulic pressure in the wheel cylinder is higher. According to this configuration, the regenerative braking force changes more rapidly as the hydraulic pressure in the wheel cylinder is higher and the response speed of the hydraulic braking force is higher. Therefore, when increasing the regenerative braking force, the regenerative braking force can be increased more quickly as the hydraulic pressure in the wheel cylinder is higher. Therefore, since the limit value of the change gradient of the regenerative braking force is fixed at a value when the hydraulic pressure in the wheel cylinder is low, the opportunity to increase the regenerative braking force quickly increases. Energy recovery efficiency can be improved.

  The vehicle braking control device is configured such that a difference between a required hydraulic braking force, which is a required value for the hydraulic braking device, and a hydraulic braking force applied to the vehicle by the hydraulic braking device exceeds a dead band equivalent value. In addition, a hydraulic pressure control unit that controls the hydraulic braking device to bring the hydraulic braking force closer to the target hydraulic braking force may be provided. In this case, when the required hydraulic braking force is changed and the above difference becomes larger than the dead zone equivalent value, the hydraulic braking force approaches the target hydraulic braking force by the operation of the hydraulic braking device.

  Further, the mode for maintaining the required braking force is referred to as the holding mode, the mode for increasing the required braking force is set to the increasing mode, and the mode for decreasing the required braking force is set to the decreasing mode. When the mode is the holding mode and the hydraulic braking force applied to the vehicle by the hydraulic braking device is held, the difference between the hydraulic braking force and the required hydraulic braking force is equal to or less than the dead band equivalent value. When the hydraulic braking force is increased by shifting from the holding mode to the increasing mode, the required hydraulic braking force increases, the required hydraulic braking force is greater than the hydraulic braking force, and the above difference is a dead zone. After exceeding the equivalent value, the hydraulic braking force starts to increase by the operation of the hydraulic braking device.

  Further, when the mode is the decrease mode and the hydraulic braking force applied to the vehicle by the hydraulic braking device is reduced, the hydraulic braking force is larger than the required hydraulic braking force. Therefore, when the hydraulic braking force is increased by shifting from the decrease mode to the increasing mode, the required hydraulic braking force becomes larger and the required hydraulic braking force becomes larger than the hydraulic braking force. After exceeding the dead band equivalent value, the hydraulic braking force starts to increase by the operation of the hydraulic braking device.

  That is, when the hydraulic braking force is increased by switching the mode, there is a time lag between the time when the mode is shifted to the increasing mode and the time when the increase of the hydraulic braking force is actually started by the operation of the hydraulic braking device.

  As a method of increasing the braking force of the entire vehicle, a method of increasing only the hydraulic braking force (first method), a method of increasing only the regenerative braking force (second method), a hydraulic braking force and a regenerative braking There is a method (third method) for increasing both of the powers. Then, an increase mode when the braking force of the entire vehicle is increased by the first method not including an increase of the regenerative braking force, and a control of the entire vehicle by the second method or the third method including an increase of the regenerative braking force. If the increase mode in the case of increasing the power is different, the deceleration mode of the vehicle will vary depending on the method selected. In this case, the vehicle occupant may feel uncomfortable. In order to make it difficult for the vehicle occupant to feel such a sense of incongruity, regardless of which of the first to third methods is selected as a method of increasing the braking force of the entire vehicle, the mode of increasing the braking force of the entire vehicle is uniform. Preferably there is.

  Therefore, in the braking control device for a vehicle described above, the limit value setting unit, when shifting from the hold mode or the decrease mode to the increase mode, is within a specified period that is a period from when the mode is switched to when the specified time elapses. It is preferable that the limit value of the change gradient of the regenerative braking force is made smaller than the limit value of the change gradient of the regenerative braking force after the specified period.

  According to the above configuration, when the regenerative braking force is increased by shifting to the increase mode, the regenerative braking force is gradually increased within the specified period than after the specified period. In this way, by changing the increasing gradient of the regenerative braking force depending on whether it is within the specified period or after the specified period, the entire vehicle is controlled regardless of which method is selected from the first to third methods. Differences in the increase in braking force are less likely to occur. That is, even if the selected increase method is different, the difference in the deceleration mode of the vehicle is unlikely to occur. For this reason, it is possible to make it difficult for the vehicle occupant to feel uncomfortable due to the difference in the deceleration mode of the vehicle.

  The length of the time lag varies depending on the time. For example, when the mode is shifted to the increase mode in a state where the hydraulic braking force applied to the vehicle by the hydraulic braking device is less than the required hydraulic braking force, the above-described time lag causes the hydraulic braking force to exceed the required hydraulic braking force. In this state, the mode becomes shorter than when the mode is shifted to the increase mode. Therefore, the vehicle braking control apparatus may further include a period length setting unit that sets the length of the specified period. Then, when the period length setting unit shifts from the holding mode or the decrease mode to the increase mode, when the hydraulic braking force applied to the vehicle by the hydraulic braking device at the time of mode switching is less than the required hydraulic braking force, The specified period is preferably shorter than when the hydraulic braking force applied to the vehicle by the hydraulic braking device at the time of switching the mode is equal to or greater than the required hydraulic braking force.

  According to the above configuration, when shifting to the increase mode, when the time lag is predicted to be short, the specified period during which the regenerative braking force is gradually increased is shortened. As a result, the braking mode of the entire vehicle when the regenerative braking force is increased by the second method or the third method is different from the braking mode of the entire vehicle when the hydraulic braking force is increased by the first method. You can get closer. That is, even if the selected increase method is different, a difference in the deceleration mode of the vehicle is unlikely to occur, so that it is possible to make it difficult for the vehicle occupant to feel uncomfortable due to the difference in the deceleration mode of the vehicle.

  In addition, when the hydraulic braking force is increased in the increase mode, the difference between the required hydraulic braking force and the hydraulic braking force applied to the vehicle by the hydraulic braking device becomes earlier as the increase gradient of the required hydraulic braking force increases. It tends to be more than the equivalent value. That is, the time lag becomes shorter as the increase gradient of the required hydraulic braking force in the increase mode is larger. Therefore, in the braking control device for a vehicle described above, the period length setting unit shortens the specified period as the increase gradient of the required braking force in the increase mode increases when shifting from the holding mode or the decrease mode to the increase mode. Is preferred. According to this configuration, when the time lag is predicted to be short, the specified period during which the regenerative braking force is gradually increased is shortened. In this way, by optimizing the length of the specified time, it becomes possible to make it more difficult for the vehicle occupant to feel uncomfortable due to the difference in the increase mode.

  In addition, compared with the case where the specified period is fixed at a value corresponding to the situation where the time lag is the longest, the increase gradient of the regenerative braking force can be increased earlier, so that energy is recovered during vehicle braking. Efficiency can be improved.

  The vehicle braking control device preferably includes a required braking force calculation unit that increases the required braking force as the amount of operation of the brake operation member increases. According to this configuration, when the driver is operating the brake operation member, the required braking force for the vehicle can be calculated according to the operation amount of the brake operation member by the driver.

The block diagram which shows schematic structure of a hybrid vehicle provided with the control apparatus which is one Embodiment of the braking control apparatus of a vehicle. FIG. 5 is a timing chart when a brake operation is performed, where (a) shows a change in vehicle body speed, (b) shows a change in effective braking force and effective regenerative braking force, and (c) shows effective hydraulic pressure control. Shows the transition of power. The graph which shows the relationship between the amount of brake fluid required in order to change a wheel cylinder pressure and a wheel cylinder pressure. The timing chart which shows transition of the wheel cylinder pressure when the increase gradient changes in the middle of increasing hydraulic braking force. The timing chart which shows transition of the wheel cylinder pressure at the time of transfering from a decreasing state to an increasing state. (A)-(c) is a timing chart which shows transition of the wheel cylinder pressure at the time of transfering from a hold | maintenance state to an increase state. The flowchart explaining the processing routine performed when brake operation is performed. The flowchart explaining the process routine performed in order to calculate a request | requirement regenerative braking force. The flowchart explaining the processing routine performed in order to determine the limiting value of the increase gradient of regenerative braking force. It is a timing chart at the time of vehicle braking, (a) shows change of demand braking force, (b) shows change of effective regenerative braking force, and (c) shows change of effective hydraulic braking force.

Hereinafter, an embodiment embodying a vehicle braking control device will be described with reference to FIGS.
FIG. 1 illustrates a hybrid vehicle including a control device 100 that is a vehicle braking control device of the present embodiment. As shown in FIG. 1, the hybrid vehicle includes a two-motor hybrid system 10 and a hydraulic braking device 20 that applies a braking force (hydraulic braking force) to all wheels FL, FR, RL, and RR. Is provided.

  The hybrid system 10 includes an engine 11 that is operated by supplying fuel such as gasoline. A first motor 13 and a second motor 14 are connected to the crankshaft 11a of the engine 11 through a power transmission mechanism 12 having a planetary gear mechanism and the like. The power transmission mechanism 12 divides and transmits the power from the engine 11 to the first motor 13 and the front wheels FL and FR which are driving wheels. Further, when the second motor 14 is driven, the power transmission mechanism 12 transmits the power from the second motor 14 to the front wheels FL and FR.

  The first motor 13 generates power using the power transmitted via the power transmission mechanism 12. Then, the electric power generated by the first motor 13 is supplied to the battery 16 through the inverter 15 and stored.

  The second motor 14 functions as a vehicle drive source when the driver operates the accelerator pedal 18. At this time, power is supplied from the battery 16 to the second motor 14 via the inverter 15. Then, the power generated by the second motor 14 is transmitted to the front wheels FL and FR via the power transmission mechanism 12 and the differential 17. In the vicinity of the accelerator pedal 18, an accelerator opening sensor SE <b> 1 that outputs a signal corresponding to an accelerator operation amount that is an operation amount of the accelerator pedal 18 to the control device 100 is provided.

  On the other hand, the power accompanying the rotation of the front wheels FL and FR is transmitted to the second motor 14 through the differential 17 and the power transmission mechanism 12 when the driver operates the brake pedal 21 as a brake operation member. At this time, the second motor 14 functions as a generator, and the electric power generated by the second motor 14 is supplied to the battery 16 via the inverter 15 and stored. Then, the second motor 14 that generates power in this way applies a regenerative braking force corresponding to the amount of power generated by the second motor 14 to the vehicle. Therefore, in the present embodiment, the second motor 14 constitutes an example of a “regenerative braking device”.

  The hydraulic braking device 20 includes a hydraulic pressure supply device 22 to which a brake pedal 21 is drivingly connected, and a brake actuator 23 that can automatically adjust the hydraulic braking force for the wheels FL, FR, RL, and RR. Further, the hydraulic braking device 20 is provided with a brake operation amount detection sensor SE2 that detects the operation amount of the brake pedal 21.

  Such a hydraulic braking device 20 has a supply pump that operates to supply brake fluid into the wheel cylinders 24a, 24b, 24c, 24d of the brake mechanism provided for each of the wheels FL, FR, RL, RR. Yes. The hydraulic braking device 20 includes a valve for adjusting the inflow speed of the brake fluid into the wheel cylinders 24a to 24d, a valve for adjusting the outflow speed of the brake fluid from the wheel cylinders 24a to 24d, and the like. Have.

  The brake mechanism includes a rotating body (for example, a disk) that rotates integrally with the wheels FL, FR, RL, and RR, and a friction material (for example, a brake pad) supported by the vehicle body. The friction material is pressed against the rotating body with a force corresponding to a wheel cylinder pressure (hereinafter also referred to as “WC pressure”) which is a hydraulic pressure in the wheel cylinders 24 a to 24 d. That is, the brake mechanism applies a hydraulic braking force corresponding to the WC pressure to the wheels FL, FR, RL, RR. In the present embodiment, when the hydraulic braking force is applied to the vehicle during the braking operation by the driver, the WC pressures in the wheel cylinders 24a to 24d are substantially the same.

Next, the control device 100 will be described.
As shown in FIG. 1, in addition to the accelerator opening sensor SE1 and the brake operation amount detection sensor SE2, a vehicle speed sensor SE3 for detecting a vehicle body speed VS is electrically connected to the control device 100. And the control apparatus 100 performs vehicle control comprehensively based on the detection signal from various detection systems, such as each sensor SE1-SE3.

  The control device 100 controls the power management computer 101, the engine control unit 102 that controls the engine 11, the motor control unit 103 that controls the first and second motors 13 and 14, and the hydraulic braking device 20. And a brake control unit 104.

  When the driver performs an accelerator operation, the power management computer 101 calculates the required power required for the engine 11 and the required power required for the second motor 14 based on the traveling state of the vehicle. The power management computer 101 individually transmits a control command based on the calculated required power to the engine control unit 102 and the motor control unit 103.

  Further, the power management computer 101 transmits information on the requested regenerative braking force received from the brake control unit 104 to the motor control unit 103 when the driver performs a brake operation. In addition, the power management computer 101 receives information on the effective regenerative braking force, which is a regenerative braking force applied to the vehicle by the second motor 14, from the motor control unit 103, and performs brake control on the information on the effective regenerative braking force. Transmit to unit 104.

  The motor control unit 103 receives information related to the required regenerative braking force from the power management computer 101 when the vehicle is decelerated due to a brake operation by the driver. Further, the motor control unit 103 regenerative braking force that can be applied to the front wheels FL and FR based on the charged amount of the battery 16 and the wheel speeds of the front wheels FL and FR (that is, the vehicle body speed VS of the vehicle) at that time. The maximum value of is calculated. Then, when the maximum value of the regenerative braking force at that time is equal to or greater than the required regenerative braking force, the motor control unit 103 sets the second regenerative braking force equal to the required regenerative braking force to the front wheels FL and FR. The motor 14 generates power. On the other hand, when the maximum value of the regenerative braking force at that time is less than the required regenerative braking force, the motor control unit 103 applies an effective regenerative braking force equal to the maximum value of the regenerative braking force to the front wheels FL and FR. The second motor 14 generates power. Further, the motor control unit 103 transmits information related to the effective regenerative braking force to the power management computer 101.

  When the driver performs a brake operation, the brake control unit 104 calculates a required braking force for the vehicle based on a signal from the brake operation amount detection sensor SE2. At this time, the required braking force is increased as the brake operation amount is increased. The brake control unit 104 calculates a required regenerative braking force based on the calculated required braking force on the vehicle and transmits information related to the required regenerative braking force to the power management computer 101.

  At this time, if the brake control unit 104 determines that the required braking force for the vehicle can be covered only by the regenerative braking force, that is, if the required braking force and the effective regenerative braking force are equal, the hydraulic braking device 20 is activated. I won't let you. That is, the brake control unit 104 does not apply the hydraulic braking force from the hydraulic braking device 20 to the vehicle. On the other hand, the brake control unit 104 gives a hydraulic braking force to the vehicle when the required braking force for the vehicle cannot be covered only by the regenerative braking force, that is, when the effective regenerative braking force is less than the required braking force. The hydraulic braking force applied to the vehicle by the hydraulic braking device 20 is also referred to as “effective hydraulic braking force”.

  Next, an example of cooperative control between the regenerative braking force and the hydraulic braking force during vehicle braking accompanying a brake operation will be described with reference to the timing chart shown in FIG. In the description here, the sum of the effective regenerative braking force BPR and the effective hydraulic braking force BPP is referred to as an “effective braking force BPA”.

  As shown in FIGS. 2A, 2B, and 2C, when the brake operation is started at the first timing t11, the required braking force BPT gradually increases as the brake operation amount increases. The effective braking force BPA increases as the braking force BPT increases. In the period from the first timing t11 to the second timing t12, since the effective hydraulic braking force BPP is not applied to the vehicle, the effective braking force BPA is equal to the effective regenerative braking force BPR.

  Then, after the second timing t12, a deviation occurs between the required braking force BPT and the effective regenerative braking force BPR. Therefore, after the second timing t12, the hydraulic braking device 20 operates to bring the effective hydraulic braking force BPP closer to the difference obtained by subtracting the effective regenerative braking force BPR from the required braking force BPT. That is, the effective hydraulic braking force BPP corresponding to the WC pressure in the wheel cylinders 24a to 24d is applied to the vehicle. Therefore, during the period from the second timing t12 to the third timing t13, the effective braking force BPA is equal to the sum of the effective regenerative braking force BPR and the effective hydraulic braking force BPP. When the third timing t13 is reached, it is considered that the effective regenerative braking force BPR has reached the required braking force BPT, and the effective hydraulic braking force BPP becomes “0 (zero)”. That is, after the third timing t13, the effective braking force BPA is equal to the effective hydraulic braking force BPP.

  Although details will be described later, the effective hydraulic braking force BPP is executed from the required braking force BPT during the period from the second timing t12 to the third timing t13 due to the control characteristics of the hydraulic braking device 20. It is not necessarily the same value as the difference obtained by reducing the regenerative braking force BPR. In other words, the effective braking force BPA is slightly different from the required braking force BPT.

  Incidentally, the response speed of the hydraulic braking force applied to the vehicle by the hydraulic braking device 20 is smaller than the response speed of the regenerative braking force applied to the vehicle by the second motor 14 which is a regenerative braking device. Therefore, in a vehicle that can apply both the regenerative braking force and the hydraulic braking force, it is preferable to set the response speed of the regenerative braking force to a speed according to the response speed of the hydraulic braking force. That is, when the regenerative braking force is fluctuated (increased or decreased) under a situation where the response speed of the hydraulic braking force is assumed to be high, it is preferable to increase the response speed of the regenerative braking force. On the other hand, when changing the regenerative braking force under a situation where the response speed of the hydraulic braking force is assumed to be low, it is preferable to reduce the response speed of the regenerative braking force. As a result, when adjusting only the hydraulic braking force, adjusting only the regenerative braking force, or adjusting both the hydraulic braking force and the regenerative braking force, the variation of the braking force of the entire vehicle Variation can be suppressed. That is, when the required braking force varies due to the brake operation by the driver, it is possible to make it difficult for the driver who operates the brake pedal 21 to feel uncomfortable.

  It should be noted that the response speed of the hydraulic braking force applied to the vehicle by the hydraulic braking device 20 may vary depending on the magnitude of the WC pressure in the wheel cylinders 24a to 24d and the state before the increase of the hydraulic braking force is started. .

With reference to FIG. 3, the change in the response speed of the hydraulic braking force according to the WC pressure Pwc in the wheel cylinders 24a to 24d will be described.
FIG. 3 shows the relationship between the WC pressure Pwc and the amount Y of brake fluid required to change (increase or decrease pressure) the WC pressure Pwc. As shown in FIG. 3, the amount Y of brake fluid required to increase the WC pressure Pwc increases as the WC pressure Pwc decreases. For example, the fluid amount for increasing the WC pressure Pwc from the eleventh fluid pressure Pwc11 to the twelfth fluid pressure Pwc12 that is higher than the eleventh fluid pressure Pwc11 by a predetermined amount ΔPwc1 is the first fluid amount ΔY1. It is. In contrast, when the WC pressure Pwc is increased from the 21st hydraulic pressure Pwc21 higher than the 12th hydraulic pressure Pwc12 to the 22nd hydraulic pressure Pwc22 higher than the 21st hydraulic pressure Pwc21 by a predetermined amount ΔPwc1. The liquid amount required for the second liquid amount ΔY2 is smaller than the first liquid amount ΔY1.

  That is, when the WC pressure Pwc is increased or decreased while the WC pressure Pwc is low, the wheel is larger than when the WC pressure Pwc is increased or decreased while the WC pressure Pwc is high. The amount of brake fluid flowing into the cylinders 24a to 24d or the amount of brake fluid flowing from the wheel cylinders 24a to 24d increases. Therefore, the higher the WC pressure Pwc, the higher the response speed of the hydraulic braking force because the change gradient of the WC pressure Pwc tends to be steep.

With reference to FIGS. 4 to 6, changes in the response speed of the hydraulic braking force according to the state before the hydraulic braking force is increased by the operation of the hydraulic braking device 20 will be described.
First, control of the effective hydraulic braking force BPP in accordance with the variation of the target hydraulic braking force BPPT as the required hydraulic braking force will be described. That is, when the difference ΔBPP (= | BPPT−BPP |) between the target hydraulic braking force BPPT and the effective hydraulic braking force BPP is equal to or less than a predetermined dead band equivalent value D1, the target hydraulic braking force BPPT fluctuates (increases or decreases). Even so, the effective hydraulic braking force BPP is maintained. That is, the control dead zone DZ is set between the sum of the target hydraulic braking force BPPT and the dead zone equivalent value D1 and the difference obtained by subtracting the dead zone equivalent value D1 from the target hydraulic braking force BPPT. When the difference ΔBPP is larger than the dead band equivalent value D1, the hydraulic braking device 20 is operated to bring the effective hydraulic braking force BPP closer to the target hydraulic braking force BPPT.

  Next, with reference to FIG. 4, the case where the increase speed changes during the increase of the target hydraulic braking force BPPT will be described. As shown in FIG. 4, before the timing t21 when the increase speed is switched, the effective hydraulic braking force BPP is increased in accordance with the increase in the target hydraulic braking force BPPT within the range where the difference ΔBPP does not become the dead band equivalent value D1 or less. Will be increased. The increasing speed of the effective hydraulic braking force BPP at this time is substantially equal to the increasing speed of the target hydraulic braking force BPPT. Then, the timing t21 is reached, and the increasing speed of the target hydraulic braking force BPPT is increased. At this time, the difference ΔBPP is larger than the dead band equivalent value D1. Therefore, even if the increase speed of the target hydraulic braking force BPPT increases at the timing t21, the effective hydraulic braking force BPP is increased at a speed substantially equal to the increased speed of the target hydraulic braking force BPPT after the change.

That is, when the increase speed is changed during the increase of the target hydraulic braking force BPPT, the response speed of the effective hydraulic braking force BPP is relatively high.
Next, with reference to FIG. 5, a case will be described in which a transition is made from a decreasing state in which the target hydraulic braking force BPPT is decreased to an increasing state in which the target hydraulic braking force BPPT is increased. As shown in FIG. 5, in the reduced state until the first timing t31, the effective hydraulic braking force BPP is slightly larger than the sum of the target hydraulic braking force BPPT and the dead zone equivalent value D1, and the target hydraulic pressure control is performed. It is reduced in accordance with the decrease in power BPPT.

  Then, when the state is shifted to the increase state at the first timing t31, the target hydraulic braking force BPPT is increased, so that the difference ΔBPP between the target hydraulic braking force BPPT and the effective hydraulic braking force BPP is equal to or less than the dead zone equivalent value D1. Become. Therefore, the effective hydraulic braking force BPP is maintained from the first timing t31. Then, at the second timing t32, the effective hydraulic braking force BPP becomes equal to the target hydraulic braking force BPPT, and at the subsequent third timing t33, the above difference is obtained in a state where the effective hydraulic braking force BPP is smaller than the target hydraulic braking force BPPT. ΔBPP becomes equal to the dead band equivalent value D1. Then, the increase of the effective hydraulic braking force BPP is started with the passage of the third timing t33.

  That is, a time lag TL is generated between the start of increase of the target hydraulic braking force BPPT (first timing t31) and the start of increase of the effective hydraulic braking force BPP (third timing t33). The response speed of the hydraulic braking force is reduced by the amount of time lag TL.

Next, with reference to FIGS. 6A, 6 </ b> B, and 6 </ b> C, description will be given of a case where the holding state in which the target hydraulic braking force BPPT is held is shifted to the increasing state.
FIG. 6A shows the case where the target hydraulic braking force BPPT and the effective hydraulic braking force BPP are substantially equal in the holding state, that is, the case where the difference ΔBPP is substantially “0 (zero)”. In this case, even if the holding state is increased from the holding state at the first timing t41, the execution hydraulic pressure braking force BPP is held from the first timing t41 to the second timing t42 where the difference ΔBPP is equal to the dead zone equivalent value D1. Will continue. That is, the period from the first timing t41 to the second timing t42 is the time lag TL. Then, when the second timing t42 elapses, the effective hydraulic braking force BPP starts to increase.

  In this case, at the start of the increase of the target hydraulic braking force BPPT, the difference ΔBPP is small compared to the case where the decrease state shown in FIG. 5 is shifted to the increase state. Therefore, the response speed of the hydraulic braking force is greater than when shifting from the decreasing state to the increasing state.

  However, the length of the time lag TL that occurs when shifting from the holding state to the increasing state also varies depending on the magnitude relationship between the target hydraulic braking force BPPT and the effective hydraulic braking force BPP in the holding state. That is, as shown in FIG. 6B, when the execution hydraulic pressure braking force BPP is shifted from the reduced state to the holding state at the first timing t51, the effective hydraulic pressure braking force BPP is larger than the target hydraulic pressure braking force BPPT. Held in a state. Thereafter, when the holding state is shifted to the increasing state at the second timing t52, the target hydraulic braking force BPPT starts to increase, but the difference ΔBPP becomes equal to or less than the dead zone equivalent value D1, so that the effective hydraulic braking force is increased. BPP retention is continued. Then, when the difference ΔBPP becomes larger than the dead band equivalent value D1 at the third timing t53, an increase in the effective hydraulic braking force BPP is started.

  In this case, the period from the second timing t52 to the third timing t53 is the time lag TL. In this case, the time lag TL is longer than the time lag TL shown in FIG. That is, the response speed of the hydraulic braking force is smaller than that shown in FIG.

  Further, as shown in FIG. 6C, when the state is shifted from the increasing state to the holding state at the first timing t61, the effective hydraulic braking force BPP is held in a state smaller than the target hydraulic braking force BPPT. After the transition from the holding state to the increasing state at the second timing t62 thereafter, when the increase in the target hydraulic braking force BPPT is started, the difference ΔBPP is calculated from the dead band equivalent value D1 at the third timing t63 immediately after that. Also grows. Therefore, the increase in the effective hydraulic braking force BPP is started at the third timing t63.

  In this case, the period from the second timing t62 to the third timing t63 is the time lag TL. In this case, the time lag TL is more than that in the case shown in FIG. 6A and the case shown in FIG. Shorter. That is, the response speed of the hydraulic braking force is greater than in the case shown in FIG. 6A and the case shown in FIG.

  Next, a processing routine executed by the brake control unit 104 when the driver operates the brake will be described with reference to flowcharts shown in FIGS. This processing routine is executed every preset control cycle during the driver's braking operation.

  As shown in FIG. 7, in the present processing routine, the brake control unit 104 calculates a required braking force BPT based on the brake operation amount detected by the brake operation amount detection sensor SE2 (step S11). In this respect, the brake control unit 104 constitutes an example of a “required braking force calculation unit”. Subsequently, the brake control unit 104 calculates a required regenerative braking force BPRT and transmits information related to the required regenerative braking force BPRT to the motor control unit 103 (step S12). The process of step S12 will be described later.

  Then, the brake control unit 104 acquires an effective regenerative braking force BPR, which is a regenerative braking force that the second motor 14 is currently applying to the vehicle, from the motor control unit 103 (step S13). Subsequently, the brake control unit 104 sets the difference (= BPT−BPR) obtained by subtracting the execution regenerative braking force BPR acquired in step S13 from the required braking force BPT calculated in step S11 as the target hydraulic braking force BPPT (step S14). ). Then, the brake control unit 104 controls the hydraulic braking device 20 so that the effective hydraulic braking force BPP approaches the calculated target hydraulic braking force BPPT (step S15). In this respect, in the present embodiment, the brake control unit 104 constitutes an example of a “hydraulic pressure control unit”. Thereafter, the brake control unit 104 once ends this processing routine.

Next, a processing routine for calculating the required regenerative braking force BPRT in step S12 will be described with reference to the flowchart shown in FIG.
As shown in FIG. 8, in this processing routine, the brake control unit 104 calculates a provisional required regenerative braking force BPRT1 (step S21). The temporary required regenerative braking force BPRT1 is a regenerative braking force requested to the motor control unit 103 regardless of the response speed of the hydraulic braking force. Then, the brake control unit 104 sets a difference (= BPRT1−BPR) obtained by subtracting the execution regenerative braking force BPR acquired in step S13 from the provisional required regenerative braking force BPRT1 calculated in step S21 as a regenerative gradient ΔBPR ( Step S22).

  Subsequently, the brake control unit 104 determines whether or not there is a request for increasing the regenerative braking force (step S23). For example, in step S23, when the regenerative gradient ΔBPR calculated in step S22 is a positive value, it may be determined that there is a request for increasing the regenerative braking force. If there is no request for increasing the regenerative braking force (step S23: NO), the brake control unit 104 determines the required regenerative braking force BPRT as the provisional required regenerative braking force BPRT1 calculated in step S21 (step S24). The process proceeds to step S27 described later.

  On the other hand, when there is a request to increase the regenerative braking force (step S23: YES), the brake control unit 104 calculates a limit value ΔLim of the regenerative braking force increase gradient (an example of a change gradient) (step S25). This limit value ΔLim is determined to be larger as the response speed of the hydraulic braking force at that time increases. In this regard, in the present embodiment, the brake control unit 104 constitutes an example of a “limit value setting unit”. A method for calculating the limit value ΔLim will be described later.

  Subsequently, the brake control unit 104 calculates the required regenerative braking force BPRT based on the regenerative gradient ΔBPR calculated in step S22 or the limit value ΔLim calculated in step S25 (step S26). That is, the smaller value of the regenerative gradient ΔBPR and the limit value ΔLim is added to the effective regenerative braking force BPR acquired in step S13, and the sum is used as the required regenerative braking force BPRT. For example, when the limit value ΔLim is smaller than the regenerative gradient ΔBPR, the sum of the effective regenerative braking force BPR and the limit value ΔLim is set as the required regenerative braking force BPRT. Then, the brake control unit 104 proceeds to the next step S27.

  In step S27, the brake control unit 104 transmits information regarding the required regenerative braking force BPRT calculated in step S24 or step S26 to the power management computer 101. Thereafter, the brake control unit 104 ends this processing routine. The power management computer 101 that has received the information from the brake control unit 104 transmits the information to the motor control unit 103.

Next, a processing routine for calculating the limit value ΔLim of the increasing gradient of the regenerative braking force in step S25 will be described with reference to the flowchart shown in FIG.
As shown in FIG. 9, in this processing routine, the brake control unit 104 acquires the current WC pressure Pwc in the wheel cylinders 24a to 24d (step S31). The WC pressure Pwc acquired in step S31 may be the sensor value detected by the sensor when the sensor for detecting the WC pressure is provided in the vehicle, or the operation mode of the hydraulic braking device 20 It may be an estimated value calculated based on.

  Then, the brake control unit 104 determines the WC pressure correction value K1 based on the acquired WC pressure Pwc (step S32). The WC pressure correction value K1 is a correction value used when determining the limit value ΔLim of the regenerative braking force increase gradient based on the current WC pressure Pwc. As described above, the response speed of the hydraulic braking force based on the operation of the hydraulic braking device 20 increases as the WC pressure Pwc increases (see FIG. 3). Therefore, the WC pressure correction value K1 is determined to be larger as the current WC pressure Pwc is higher.

  Subsequently, the brake control unit 104 determines whether or not the mode for controlling the braking force on the vehicle has been shifted to the increasing mode for increasing the required braking force BPT (step S33). That is, in this step S33, when the previous main processing routine is executed, the holding mode for holding the required braking force BPT or the decreasing mode for decreasing the required braking force BPT, and when the current main processing routine is executed, the increase mode is set. Is affirmative (YES). On the other hand, if the current mode is not the increase mode, a negative determination (NO) is made if the previous mode of execution of this processing routine is the increase mode even if the current mode is the increase mode.

  If it is not during the transition from the holding mode or the decrease mode to the increase mode (step S33: NO), the brake control unit 104 turns on the increase mode flag FLG for determining whether or not it can be regarded immediately after the shift to the increase mode. It is determined whether or not (step S34). When the increase mode flag FLG is on, it can be regarded as immediately after the transition to the increase mode, whereas when the increase mode flag FLG is off, it is not immediately after the transition to the increase mode (ie, In the case of the hold mode or the decrease mode, it can be considered that a certain amount of time has passed since the shift to the increase mode.

  If the increase mode flag FLG is on (step S34: YES), the brake control unit 104 proceeds to step S43 to be described later. On the other hand, when the increase mode flag FLG is off (step S34: NO), the brake control unit 104 proceeds to step S47 described later.

  On the other hand, when it is the time of transition from the hold mode or the decrease mode to the increase mode (step S33: YES), the brake control unit 104 turns on the increase mode flag FLG (step S35). Subsequently, the brake control unit 104 acquires the current target hydraulic braking force BPPT (step S36), and acquires the effective hydraulic braking force BPP applied to the vehicle by the hydraulic braking device 20 (step S37). The effective hydraulic pressure braking force BPP acquired here is a value corresponding to the WC pressure Pwc acquired in step S31.

  Then, the brake control unit 104 determines whether or not the target hydraulic braking force BPPT acquired in step S36 is substantially equal to the effective hydraulic braking force BPP acquired in step S37 (step S38). For example, when the difference ΔBPP between the target hydraulic braking force BPPT and the effective hydraulic braking force BPP is equal to or less than the error judgment value smaller than the dead zone equivalent value D1, the target hydraulic braking force BPPT and the effective hydraulic braking force BPP are substantially equal. It may be determined that they are equal.

  When the target hydraulic braking force BPPT and the effective hydraulic braking force BPP are substantially equal (step S38: YES), the brake control unit 104 determines the specified period X as a first time X1, which is an example of a specified time (step). S39). In this regard, in the present embodiment, the brake control unit 104 constitutes an example of a “period length setting unit” that sets the length of the specified period. Thereafter, the brake control unit 104 proceeds to step S43, which will be described later. The specified period X is a period corresponding to the above-described time lag TL (see FIGS. 5 and 6). As a case where the target hydraulic braking force BPPT and the effective hydraulic braking force BPP are substantially equal, for example, the state shown in FIG. The first time X1 is set to a time corresponding to the length of the time lag TL in the state shown in FIG.

  Returning to FIG. 9, when the difference ΔBPP between the target hydraulic braking force BPPT and the effective hydraulic braking force BPP is large (step S38: NO), the brake control unit 104 determines that the target hydraulic braking force BPPT is smaller than the effective hydraulic braking force BPP. Is determined (step S40). When the target hydraulic braking force BPPT is smaller than the effective hydraulic braking force BPP (step S40: YES), the brake control unit 104 determines the specified period X as a second time X2, which is an example of the specified time (step S41). ). Thereafter, the brake control unit 104 proceeds to step S43, which will be described later. An example of the case where the target hydraulic braking force BPPT is smaller than the effective hydraulic braking force BPP is the state shown in FIG. 6B. The second time X2 is longer than the first time X1, and is set to a time according to the length of the time lag TL in the state shown in FIG. 6B.

  Returning to FIG. 9, when the target hydraulic braking force BPPT is larger than the effective hydraulic braking force BPP (step S40: NO), the brake control unit 104 sets the specified period X to a third time X3, which is an example of a specified time. Determine (step S42). Thereafter, the brake control unit 104 proceeds to step S43, which will be described later. As a case where the target hydraulic braking force BPPT is larger than the effective hydraulic braking force BPP, for example, the state shown in FIG. The third time X3 is shorter than the first time X1, and is set to a time according to the length of the time lag TL in the state shown in FIG.

  In step S43, the brake control unit 104 determines whether or not the current time is included in the specified period X. If it is within the specified period X (step S43: YES), the brake control unit 104 determines the mode correction value K2 as the first correction candidate value K21 (step S44), and the process proceeds to step S47 described later. To do. This mode correction value K2 is a correction value used when determining the limit value ΔLim of the regenerative braking force increase gradient in consideration of the response delay of the hydraulic braking force. For example, the first correction candidate value K21 may be a value close to “0 (zero)” or “0 (zero)”.

  On the other hand, when the specified period X has elapsed (step S43: NO), the brake control unit 104 sets the increase mode flag FLG to OFF (step S45). Subsequently, the brake control unit 104 determines the mode correction value K2 as the second correction candidate value K22 that is larger than the first correction candidate value K21 (step S46), and the process proceeds to the next step S47.

  In step S47, the brake control unit 104 sets the sum (= ΔLimB + K1 + K2) obtained by adding the determined WC pressure correction value K1 and the mode correction value K2 to the limit reference value ΔLimB as the limit value ΔLim of the regenerative braking force increase gradient. . Then, the brake control unit 104 ends this processing routine. The limit reference value ΔLimB is determined to be a limit value when the response speed of the hydraulic braking force is minimum or a value corresponding to the limit value.

Next, with reference to FIG. 10, the operation during the driver's braking operation will be described.
As shown in FIGS. 10A, 10B, and 10C, the regenerative braking force can be increased in a state where the required braking force BPT is constant because the amount of brake operation by the driver is constant. Suppose that In this case, the effective hydraulic braking force BPP is decreased in conjunction with the increase of the effective regenerative braking force BPR as in the first timing t71 and thereafter.

  At the first timing t71, it is assumed that the WC pressure Pwc in the wheel cylinders 24a to 24d is relatively high and the effective hydraulic braking force BPP is relatively large. In this case, when the WC pressure correction value K1 is determined to be a large value (step S32), the response speed of the effective hydraulic braking force BPP is relatively large. Therefore, the limit value ΔLim of the increase gradient of the regenerative braking force is increased, and the effective regenerative braking force BPR is increased early as shown by the solid line in FIG. That is, at the second timing t72, the effective regenerative braking force BPR becomes a value BPR_Max corresponding to the maximum value of the regenerative braking force that can be applied to the vehicle at that time.

  Here, FIG. 10B shows the limit value ΔLim according to the state in which the WC pressure Pwc is low, regardless of the magnitude of the WC pressure Pwc at the first timing t71 when the regenerative braking force starts to increase. A comparative example fixed in FIG. For example, in this comparative example, the limit value ΔLim is assumed to be the limit reference value ΔLimB. In this case, in the comparative example, as shown by a broken line in FIG. 10B, the effective regenerative braking force BPR is gradually increased. Therefore, at the third timing t73 after the second timing t72, the effective regenerative braking force BPR becomes a value BPR_Max corresponding to the maximum value of the regenerative braking force that can be applied to the vehicle at that time.

  On the other hand, in the present embodiment, the effective regenerative braking force BPR increases earlier as the response speed of the effective hydraulic braking force BPP at that time increases. Therefore, in this embodiment, the increase gradient of the effective regenerative braking force BPR becomes larger than in the comparative example, and the time when the effective regenerative braking force BPR starts to be held at the value BPR_Max is earlier. Therefore, the power recovery efficiency during vehicle braking increases. Moreover, since the increasing gradient of the effective regenerative braking force BPR is a gradient corresponding to the response speed of the effective hydraulic pressure braking force BPP at that time, the sum of the effective regenerative braking force BPR and the effective hydraulic pressure braking force BPP and the required braking force BPT It is difficult for the deviation to occur.

  Further, at the fourth timing t74, the amount of brake operation by the driver increases, and the required braking force BPT increases. At this time, for example, only the effective hydraulic braking force BPP is increased based on the increase in the required braking force BPT. Then, since it is a transition from the holding state to the increasing state, as shown by a broken line in FIG. 10C, in the period from the fourth timing t74 to the fifth timing t75, the target hydraulic braking force BPPT and the execution fluid Since the difference ΔBPP with the pressure braking force BPP is equal to or less than the dead band equivalent value D1, the effective hydraulic braking force BPP is not increased. Then, at the fifth timing t75, the difference ΔBPP becomes equal to the dead zone equivalent value D1, so that the effective hydraulic braking force BPP starts to increase.

  On the other hand, when the effective regenerative braking force BPR is increased based on the increase in the required braking force BPT, the period from the fourth timing t74 to the fifth timing t75 is set as the specified period X. Then, within the specified period X (step S43: YES), the mode correction value K2 is determined to be the first correction candidate value K21 (step S44), so that the limit value ΔLim is reduced (step S47). As a result, within the specified period X, the effective regenerative braking force BPR is increased very slowly.

  Thereafter, after the lapse of the specified period X (step S43: NO), the mode correction value K2 is determined to be the second correction candidate value K22 (> K21) (step S46), so that the limit value ΔLim increases (step S46). S47). Then, at the fifth timing t75, the increasing gradient of the effective regenerative braking force BPR is changed to a steep gradient. As a result, the increase mode of the braking force of the entire vehicle approaches the case where only the hydraulic braking force is increased (that is, the increase mode indicated by the broken line in FIG. 10C).

As mentioned above, according to the said structure and effect | action, the effect shown below can be acquired.
(1) When the effective regenerative braking force BPR is increased, if it can be predicted that the response speed of the hydraulic braking force is likely to increase, the limit value ΔLim of the increase gradient of the regenerative braking force is increased, and the response speed of the hydraulic braking force is decreased. When it can be predicted that it is easy, the limit value ΔLim is reduced. As a result, as compared with the case where the limit value ΔLim is fixed to a value adjusted when the response speed of the hydraulic braking force is small, the opportunity to increase the effective regenerative braking force BPR quickly increases. Therefore, the energy (electric power) recovery efficiency during vehicle braking can be improved.

  (2) The response speed of the hydraulic braking force increases as the WC pressure Pwc in the wheel cylinders 24a to 24d increases. Therefore, in the present embodiment, when the effective regenerative braking force BPR is increased, the limit value ΔLim of the increase gradient of the regenerative braking force is increased as the WC pressure Pwc is higher. Thereby, the effective regenerative braking force BPR is rapidly increased as the WC pressure Pwc is higher. As a result, the effective regenerative braking force BPR is likely to increase compared to the case where the limit value ΔLim is fixed to a value adjusted when the response speed of the hydraulic braking force is small. Recovery efficiency can be improved.

  (3) Moreover, the increase aspect of the braking force of the whole vehicle accompanying the increase of the effective regenerative braking force BPR can be brought close to the increase aspect of the braking force of the entire vehicle when only the effective hydraulic braking force BPP is increased. As a result, the difference in the deceleration mode of the vehicle due to the difference in the method of increasing the braking force of the entire vehicle is less likely to occur. Therefore, it is possible to make it difficult for the vehicle occupant (particularly, the driver) to feel uncomfortable due to the difference in the method of increasing the braking force of the entire vehicle.

  (4) When shifting from the hold mode or the decrease mode to the increase mode, the time lag TL is likely to occur. Therefore, in the present embodiment, a specified period X is provided as a period correlated with the time lag TL, and the effective regenerative braking force BPR is gradually increased in the specified period X than after the specified period X has passed. That is, the increasing gradient of the effective regenerative braking force BPR is changed depending on whether it is within the specified period X or has passed the specified period X. Thereby, the increase aspect of the braking force of the whole vehicle accompanied by the increase of the effective regenerative braking force BPR can be brought close to the increase aspect of the braking force of the entire vehicle when only the effective hydraulic braking force BPP is increased. As a result, the difference in the deceleration mode of the vehicle due to the difference in the method of increasing the braking force of the entire vehicle is less likely to occur. Therefore, it is possible to make it difficult for the vehicle occupant (particularly, the driver) to feel uncomfortable due to the difference in the method of increasing the braking force of the entire vehicle.

  (5) In the present embodiment, when shifting to the increase mode, the specified period X is shortened when the time lag TL is predicted to be short. As a result, the mode of increase in the braking force of the entire vehicle accompanying the increase in the effective regenerative braking force BPR can be made closer to the mode of increase in the braking force of the entire vehicle when only the effective hydraulic braking force BPP is increased. As a result, the difference in the deceleration mode of the vehicle due to the difference in the method of increasing the braking force of the entire vehicle is less likely to occur, and the vehicle occupant (especially the driver) feels uncomfortable due to the difference in the method of increasing the braking force of the entire vehicle. Can be difficult to give.

The above embodiment may be changed to another embodiment as described below.
When shifting to the increase mode, the difference ΔBPP (= | BPPT−BPP |) tends to increase earlier than the dead band equivalent value D1 as the increase gradient of the target hydraulic braking force BPPT increases. That is, the time lag TL tends to be shortened. Therefore, the specified period X correlated with the time lag TL may be shortened as the increase gradient of the required braking force BPT in the increase mode increases. For example, a gain that increases as the increase gradient of the target hydraulic braking force BPPT in the increase mode increases is set. Then, the specified period X set in the processes of steps S39, S41, and S42 may be multiplied by a gain, and the product may be used as the corrected specified period. In this case, within the specified period after correction, the effective regenerative braking force BPR may be increased more slowly than after the specified period after correction. According to this, the aspect of increasing the braking force of the entire vehicle accompanied by the increase of the effective regenerative braking force BPR can be brought close to the aspect of increasing the braking force of the entire vehicle when only the effective hydraulic braking force BPP is increased. As a result, the difference in the deceleration mode of the vehicle due to the difference in the method of increasing the braking force of the entire vehicle is less likely to occur. Therefore, it is possible to make it difficult for the vehicle occupant (particularly, the driver) to feel uncomfortable due to the difference in the method of increasing the braking force of the entire vehicle.

  If the length of the specified period X set when shifting from the hold mode or the decrease mode to the increase mode is longer than “0 (zero)”, the length of the specified period X may be a fixed value. Even in this case, the same effect as the above (4) can be obtained.

  If the limit value ΔLim is determined according to the WC pressure Pwc in the wheel cylinders 24a to 24d, the specified period X may not be set. In this case, the limit value ΔLim is the sum of the limit reference value ΔLimB and the WC pressure correction value K1. Even if such a control configuration is adopted, the same effect as the above (2) can be obtained.

  A time lag TL may occur even when shifting from the hold mode or the increase mode to the decrease mode. Therefore, when shifting to the decrease mode, a specified period X that correlates with the time lag TL is provided, and the limit value of the regenerative braking force decrease gradient is reduced within the specified period X and increased after the specified period X has elapsed. May be. According to this, the mode of reducing the braking force of the entire vehicle accompanying the decrease of the effective regenerative braking force BPR can be brought close to the mode of decreasing the braking force of the entire vehicle when only the effective hydraulic braking force BPP is decreased. As a result, the difference in the deceleration mode of the vehicle due to the difference in the method of reducing the braking force of the entire vehicle is less likely to occur. Therefore, it is possible to make it difficult for the vehicle occupant (particularly, the driver) to feel uncomfortable due to the difference in the braking force reduction method of the entire vehicle.

  In this case, the specified period X may be made longer as the time lag TL is predicted to be longer. According to this, the reduction mode of the braking force of the entire vehicle accompanied by the decrease of the effective regenerative braking force BPR can be made closer to the reduction mode of the braking force of the entire vehicle when only the effective hydraulic braking force BPP is reduced.

  Further, the specified period X may be shortened as the decrease gradient of the required braking force BPT in the decrease mode increases. According to this, the reduction mode of the braking force of the entire vehicle accompanied by the decrease of the effective regenerative braking force BPR can be made closer to the reduction mode of the braking force of the entire vehicle when only the effective hydraulic braking force BPP is reduced.

  When reducing the effective regenerative braking force BPR, the limit value of the regenerative braking force decrease gradient (an example of a change gradient) may be increased as the WC pressure Pwc in the wheel cylinders 24a to 24d increases. In this case, the higher the WC pressure Pwc, the earlier the effective regenerative braking force BPR is reduced. Even in this case, the same effect as the above (3) can be obtained.

  When shifting to the increase mode, if the specified period X is provided and the limit value ΔLim is changed depending on whether it is within the specified period X or after the specified period X has elapsed, the limit value ΔLim is changed to the wheel cylinder 24a. You may make it not change according to WC pressure Pwc in -24d. Even with such a control configuration, the same effect as in the above (4) can be obtained.

  The WC pressure correction value K1 may be increased as the required braking force that correlates with the operating state of the hydraulic braking device 20 increases, instead of the WC pressure Pwc. Even in this case, the limit value ΔLim increases as the required braking force increases. For this reason, compared to the case where the limit value ΔLim is fixed at a value when the required braking force is small, an opportunity to rapidly increase the effective regenerative braking force BPR is increased, so that energy recovery efficiency during vehicle braking is improved. be able to.

  -As a vehicle, there is a vehicle having a function of automatically applying a braking force without a vehicle operation by a driver. In such a vehicle, the second motor 14 and the hydraulic braking device 20 are controlled based on the required braking force BPT set by automatic braking. Therefore, even during such automatic braking, the limit value ΔLim of the change gradient of the regenerative braking force may be made variable according to the operating state of the hydraulic braking device 20.

  The regenerative braking device may be an actuator other than the motor as long as the regenerative braking force applied to the vehicle can be adjusted. For example, the regenerative braking device may be a simple generator that does not function as a drive source.

  The vehicle may be a one-motor hybrid vehicle as well as a two-motor hybrid vehicle as long as the vehicle includes the engine 11. Further, when the generator is provided as the regenerative braking device, the vehicle may be provided with only the engine 11 as a drive source.

The vehicle may be a vehicle that does not include the engine 11. For example, the vehicle may be an electric vehicle.
The brake operation member may be an arbitrary member (for example, a brake lever) other than the brake pedal 21 as long as it is operated by the driver.

Next, the technical idea that can be grasped from the above embodiment and another embodiment will be added below.
(B) When the limit value setting unit shifts from the holding mode or the increase mode to the decrease mode, the limit value setting unit regenerates within a specified period, which is a period from when the mode is switched to when the specified time elapses. The limit value of the power decrease gradient may be made smaller than the limit value of the decrease gradient after the specified period.

  According to the above configuration, the regenerative braking force is gradually reduced within the specified period than after the specified period. Thus, by changing the decrease gradient of the regenerative braking force depending on whether it is within the specified period or after the specified period, the reduction mode of the braking force of the entire vehicle accompanying the decrease of the regenerative braking force is changed to only the hydraulic braking force. It is possible to approach a mode of reducing the braking force of the entire vehicle in the case of reducing. That is, even if the selected reduction method is different, the difference in the deceleration mode of the vehicle is unlikely to occur. For this reason, it is possible to make it difficult for the vehicle occupant to feel uncomfortable due to the difference in the deceleration mode of the vehicle.

  (B) When the period length setting unit shifts from the holding mode or the increase mode to the decrease mode, the hydraulic braking force applied to the vehicle by the hydraulic braking device at the time of mode switching is the request. When the hydraulic braking force is equal to or greater than the hydraulic braking force, the specified period is made shorter than when the hydraulic braking force applied to the vehicle by the hydraulic braking device is less than the required hydraulic braking force when the mode is switched. Also good.

  According to the above configuration, when shifting to the decrease mode, if the time lag is predicted to be short, the specified period during which the regenerative braking force is gradually decreased is shortened. As a result, the mode of reducing the braking force of the entire vehicle accompanying the decrease of the regenerative braking force can be made closer to the mode of reducing the braking force of the entire vehicle when only the hydraulic braking force is reduced. That is, even if the selected reduction method is different, the difference in the deceleration mode of the vehicle is unlikely to occur, so that it is possible to make it difficult for the vehicle occupant to feel uncomfortable due to the difference in the deceleration mode of the vehicle.

  (C) When the period length setting unit shifts from the holding mode or the increase mode to the decrease mode, the period length setting unit shortens the specified period as the decrease gradient of the required braking force in the decrease mode increases. It may be.

  According to the above configuration, when the time lag is predicted to be short, the specified period during which the regenerative braking force is gently reduced is shortened. By optimizing the length of the specified time in this way, it becomes possible to make it more difficult for the vehicle occupant to feel uncomfortable due to the difference in the reduction mode.

  DESCRIPTION OF SYMBOLS 14 ... The 2nd motor which is an example of a regenerative braking device, 20 ... Hydraulic pressure braking device, 21 ... Brake pedal which is an example of a brake operation member, 22a-22d ... Wheel cylinder, 100 ... Control device as a braking control device, 104: Brake control unit (an example of a limit value setting unit, an example of a hydraulic pressure control unit, an example of a period length setting unit, an example of a required braking force calculation unit), FL, FR, RL, RR ... wheels, BPP ... execution fluid Pressure braking force, BPPT ... target hydraulic braking force as required hydraulic braking force, BPR ... execution regenerative braking force, BPT ... required braking force, D1 ... dead zone equivalent value, X ... specified period, X1 ... first example of specified time , X2... Second time which is an example of the specified time, X3... Third time which is an example of the specified time, ΔBPP... Difference, ΔLim.

Claims (6)

A regenerative braking device that applies regenerative braking force to the vehicle;
Applied to a vehicle including a hydraulic braking device that applies a hydraulic braking force to the vehicle by adjusting a hydraulic pressure in a wheel cylinder provided for the wheel,
In a vehicle braking control device for controlling the regenerative braking device and the hydraulic braking device based on a required braking force required for the vehicle,
When changing the regenerative braking force applied to the vehicle by the regenerative braking device, the limit value of the change gradient which is the amount of change per unit time of the regenerative braking force is set to a value corresponding to the operating state of the hydraulic braking device. A limit value setting section to be set ;
When the difference between the required hydraulic braking force, which is a required value for the hydraulic braking device, and the hydraulic braking force applied to the vehicle by the hydraulic braking device exceeds the dead band equivalent value, the hydraulic braking device is A hydraulic pressure control unit that controls the hydraulic braking force to approach the required hydraulic braking force, and
When the mode for maintaining the required braking force is a holding mode, the mode for increasing the required braking force is an increasing mode, and the mode for decreasing the required braking force is a decreasing mode,
When the limit value setting unit shifts from the holding mode or the decrease mode to the increase mode, the limit value of the change gradient within a specified period, which is a period from when the mode is switched to when the specified time elapses. Is made smaller than the limit value of the change gradient after the specified period has elapsed . The vehicle brake control device according to claim 1, wherein the limit value setting unit increases the limit value of the change gradient as the required braking force that correlates with an operating state of the hydraulic brake device increases. The vehicle braking control device according to claim 1, wherein the limit value setting unit increases the limit value of the change gradient as the hydraulic pressure in the wheel cylinder increases. A period length setting unit for setting the length of the specified period;
The period length setting unit
When shifting from the holding mode or the decreasing mode to the increasing mode, when the hydraulic braking force applied to the vehicle by the hydraulic braking device at the time of mode switching is less than the required hydraulic braking force, the specified period Is made shorter than when the hydraulic braking force applied to the vehicle by the hydraulic braking device is greater than or equal to the required hydraulic braking force when the mode is switched.
The braking control device for a vehicle according to any one of claims 1 to 3 . The period length setting unit, when the transition from the holding mode or the reduction mode to the increase mode, according to claim 4 to shorten the prescribed period as increase gradient of the braking force demand in the increase mode is large Vehicle braking control device. The vehicle braking control apparatus according to any one of claims 1 to 5 , further comprising a required braking force calculation unit that increases the required braking force as the amount of operation of the brake operation member increases.