JP2013177024A - Brake control device for electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve increase in regenerative energy in an operation region in which a reservoir port is closed, while suppressing a deceleration change in an operation region in which the reservoir port is open, when performing brake operation.SOLUTION: A brake control device for FF (front engine front drive) hybrid vehicle includes a VDC (vehicle dynamic control) brake hydraulic unit 2 in a hydraulic system that connects a master cylinder 13 with wheel cylinders 4FL, 4FR, 4RL, 4RR. In this brake control device for FF hybrid vehicle, there is provided a regenerative and cooperative brake means (Fig.3) for, during brake operation, depending upon an operation region, varying: a vehicle velocity at which the substitution where a regenerative torque is reduced and an increase of a friction torque by a pump hydraulic pressure is started; and a substitution slope of the regenerative torque. The regenerative and cooperative brake means, when determined that it is in an operation region in which a reservoir port is closed, sets: a substitution start vehicle velocity to be lower than that when the reservoir port is open; and a substitution slope to be larger than that when the reservoir port is open.

Description

  The present invention relates to a brake control device for an electric vehicle that generates wheel cylinder hydraulic pressure by pump hydraulic pressure and master cylinder hydraulic pressure.

  During the brake operation, at the initial stage of depression of the brake pedal before the piston of the master cylinder closes the reservoir port, the braking torque is controlled by cooperative control of the friction torque by the VDC pump operation and the regenerative torque. On the other hand, in the brake pedal depression area after the piston of the master cylinder closes the reservoir port, a vehicle brake device that controls the braking torque by increasing the wheel cylinder hydraulic pressure by the master cylinder hydraulic pressure is known (for example, , See Patent Document 1).

JP 2006-96218 A

  However, in the conventional vehicle brake device, when the master cylinder hydraulic pressure is generated and when the master cylinder hydraulic pressure is not generated, the latter increases the hydraulic pressure due to the operation of the VDC pump. slow. On the other hand, there is a demand for the change gradient of regeneration → friction replacement to be as steep as possible within a range in which there is no deceleration fluctuation or pedaling force fluctuation caused by a hydraulic pressure response delay. This is because the regenerative torque generation region increases.

In other words, depending on whether or not the master cylinder hydraulic pressure is generated, there is a difference in the speed of hydraulic pressure response due to VDC pump operation
(a) Based on the assumption that master cylinder hydraulic pressure is generated, if the regeneration → friction displacement gradient is determined to be steep, if there is no master cylinder hydraulic pressure, the slow response cannot be taken into account and the deceleration decreases. To do.
(b) Regeneration on the assumption that master cylinder hydraulic pressure is not generated → If the friction displacement gradient is determined to be a gentle gradient, the response speed cannot be taken into account when the master cylinder hydraulic pressure is generated, and the regenerative torque that can be recovered is Less.
There was a problem.

  The present invention has been made paying attention to the above-mentioned problems. During braking, the fluctuation of the deceleration is suppressed when the reservoir port is open, and the regeneration is performed when the reservoir port is closed. It is an object of the present invention to provide a brake control device for an electric vehicle that can achieve an increase in energy.

In order to achieve the above object, the brake control device for an electric vehicle according to the present invention is configured such that a part of the hydraulic fluid in the master cylinder is sucked into a hydraulic system connecting the master cylinder and the wheel cylinder to obtain a pump hydraulic pressure. It is assumed that a hydraulic fluid supply means for supplying to
In this brake control device for an electric vehicle, during the brake operation, the regenerative torque is reduced depending on whether the reservoir port of the master cylinder is a closed operation region or an open operation region. There is provided regenerative cooperative brake control means for making the change start vehicle speed at which the friction torque starts to increase and the change gradient, which is the decrease gradient of the regenerative torque due to change, differ.
When the regenerative cooperative brake control means determines that the reservoir port is in the closed operation region, the regenerative start brake vehicle speed is lower than the replacement start vehicle speed when the reservoir port is open, and The replacement gradient is made larger than the replacement gradient when the reservoir port is open.

Therefore, during the brake operation, when the master cylinder reservoir port is in the closed operation region, the re-starting vehicle speed at which the regenerative torque is reduced and the friction torque starts increasing is the operation region where the master cylinder reservoir port is open. It will be lower than the vehicle speed at the start of replacement. At the same time, the switching gradient, which is the decreasing gradient of the regenerative torque, is made larger than the switching gradient in the operation region where the reservoir port of the master cylinder is open.
That is, in the operation region where the reservoir port is open in the brake operation region, the response speed of the friction torque due to the pump hydraulic fluid pressure is slow. However, in the operation region where the reservoir port is closed, the response speed of the friction torque due to the pump hydraulic pressure is fast.
Paying attention to this point, in the operation area where the reservoir port of the master cylinder is open, the speed at which the hydraulic fluid supply means catches up with the slow response speed of the friction torque by increasing the vehicle speed at which replacement is performed and decreasing the gradient of replacement. The change in deceleration is suppressed, and fluctuations in deceleration are suppressed. On the other hand, in the operation region where the reservoir port of the master cylinder is closed, the regenerative energy that can be recovered during the brake operation is increased by lowering the replacement start vehicle speed and increasing the replacement gradient.
As a result, at the time of brake operation, it is possible to achieve an increase in regenerative energy when the reservoir port is closed while suppressing fluctuations in deceleration when the reservoir port is open.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a brake system diagram illustrating a configuration of a hybrid vehicle by front wheel drive to which a brake control device according to a first embodiment is applied. It is a brake fluid pressure circuit diagram showing the VDC brake fluid pressure unit in the brake control device of Example 1. It is a flowchart which shows the flow of the regeneration cooperation brake control process performed with the integrated controller of the brake control apparatus of Example 1. FIG. It is a figure which shows the low vehicle speed area regenerative torque limitation map used by the regeneration cooperative brake control process performed with the integrated controller of the brake control apparatus of Example 1. FIG. It is a wheel cylinder hydraulic pressure characteristic figure which shows the basic share characteristic of the wheel cylinder hydraulic pressure (pump working hydraulic pressure + master cylinder hydraulic pressure) with respect to a pedal stroke. FIG. 6 is a braking torque sharing diagram showing basic sharing of a friction torque component (VDC PU component), a regenerative torque component, and a friction torque component (M / Cyl component) with respect to a total braking torque during brake operation. It is the schematic which shows the brake system provided with the master cylinder and the VDC brake hydraulic pressure unit. FIG. 8 is a low hydraulic pressure reservoir operation explanatory view showing the operation of the low hydraulic pressure reservoir when the brake fluid pushed out by the primary piston in the brake system shown in FIG. 4 is a time chart showing characteristics of vehicle speed and braking torque sharing during a slow braking operation equivalent to or less than a stroke for closing a reservoir port in the first embodiment. 6 is a time chart showing characteristics of vehicle speed / braking torque sharing during a sudden braking operation exceeding the stroke equivalent to closing the reservoir port in the first embodiment. It is a flowchart which shows the flow of the regeneration cooperation brake control process performed with the integrated controller of the brake control apparatus of Example 2. FIG. It is a figure which shows the low vehicle speed area regenerative torque limitation map used by the regeneration cooperation brake control process performed with the integrated controller of the brake control apparatus of Example 2. FIG.

  Hereinafter, the best mode for realizing a brake control device for an electric vehicle according to the present invention will be described based on Example 1 and Example 2 shown in the drawings.

First, the configuration will be described.
The configuration of the brake control device for an electric vehicle according to the first embodiment will be described by dividing it into an “overall system configuration”, a “VDC brake hydraulic unit configuration”, and a “regenerative cooperative brake control configuration”.

[Overall system configuration]
FIG. 1 shows the configuration of a front-wheel drive FF hybrid vehicle (an example of an electric vehicle) to which the brake control device of the first embodiment is applied. Hereinafter, based on FIG. 1, the whole structure of the brake system using VDC is demonstrated.

  As shown in FIG. 1, the brake torque generating system of the brake system includes a brake fluid pressure generating device 1, a VDC brake fluid pressure unit 2 (working fluid supply means), a stroke sensor 3, and a left front wheel wheel cylinder 4FL. A right front wheel wheel cylinder 4FR, a left rear wheel wheel cylinder 4RL, a right rear wheel wheel cylinder 4RR, and an electric motor 5 for traveling.

  In other words, the brake system uses an existing VDC system (VDC is an abbreviation of “Vehicle Dynamics Control”). The VDC system is a system that performs vehicle behavior control (= VDC control) that prevents skidding and ensures excellent running stability when the vehicle posture is disturbed due to high-speed corner approach or sudden steering operation. is there.

  The brake fluid pressure generating device 1 is a master cylinder fluid pressure generating unit that generates a master cylinder fluid pressure component to be applied to each of the front and rear wheels in accordance with a brake operation by a driver. As shown in FIG. 1, the brake fluid pressure generating device 1 includes a brake pedal 11, a negative fluid pressure booster 12, a master cylinder 13, and a reservoir 14. That is, the driver's brake pedal force applied to the brake pedal 11 is boosted by the negative hydraulic pressure booster 12, and the master cylinder hydraulic pressure (primary hydraulic pressure and secondary hydraulic pressure) is generated by the primary piston and the secondary piston of the master cylinder 13. . At this time, the brake fluid pressure generator 1 is statically mastered regardless of the pedal depression operation by the driver so that the deceleration generated by the master cylinder fluid pressure is smaller than the target deceleration (= the driver requested deceleration). It has a loss stroke area where cylinder hydraulic pressure is not generated. That is, the master cylinder 13 has a design in which the loss stroke area is expanded in advance.

  The VDC brake fluid pressure unit 2 is disposed in a fluid pressure system that connects the brake fluid pressure generator 1 and the wheel cylinders 4FL, 4FR, 4RL, 4RR of each wheel. This VDC brake fluid pressure unit 2 has fluid pressure pumps 22 and 22 driven by a VDC motor 21 and controls the increase / hold / reduction pressure of the master cylinder fluid pressure and applies it to the master cylinder fluid pressure. A hydraulic fluid supply means for generating pump hydraulic fluid pressure. The VDC brake fluid pressure unit 2 and the brake fluid pressure generator 1 are connected by a primary fluid pressure pipe 61 and a secondary fluid pressure pipe 62. The VDC brake hydraulic unit 2 and the wheel cylinders 4FL, 4FR, 4RL, 4RR of each wheel are connected by a left front wheel hydraulic pipe 63, a right front wheel hydraulic pipe 64, a left rear wheel hydraulic pipe 65, and a right rear wheel hydraulic pipe 66. ing. That is, when the master cylinder hydraulic pressure generated by the brake hydraulic pressure generator 1 is insufficient during brake operation, the VDC brake hydraulic pressure unit 2 applies pressure to each wheel cylinder 4FL, 4FR, 4RL, 4RR. A hydraulic braking torque is obtained.

  The stroke sensor 3 is means for detecting a brake pedal operation amount by a driver with a potentiometer or the like. The stroke sensor 3 is a component added to an existing VDC system as a configuration for detecting a target deceleration (= driver-requested deceleration), which is necessary information when performing regenerative cooperative brake control, for example.

  The wheel cylinders 4FL, 4FR, 4RL, 4RR are set on the brake discs of the front and rear wheels, and the hydraulic pressure from the VDC brake hydraulic pressure unit 2 is applied. Then, when hydraulic pressure is applied to each wheel cylinder 4FL, 4FR, 4RL, 4RR, hydraulic braking torque is applied to the front and rear wheels by clamping the brake disc with the brake pads.

  The travel electric motor 5 is provided as a travel drive source for the left and right front wheels (drive wheels) and has a drive motor function and a power generator function. The electric motor 5 for traveling transmits driving force to the left and right front wheels by driving the motor while consuming battery power during power running. During regeneration, the load is applied to the rotational drive of the left and right front wheels to convert it into electrical energy, and the generated power is charged to the battery. That is, the load applied to the rotational drive of the left and right front wheels is the regenerative braking torque. The driving system for the left and right front wheels (drive wheels) provided with the traveling electric motor 5 is provided with an engine 10 as a traveling drive source in addition to the traveling electric motor 5, and is driven to the left and right front wheels via the transmission 11. Transmit power.

  As shown in FIG. 1, the braking torque control system of the brake system includes a brake controller 7, a motor controller 8, an integrated controller 9, and an engine controller 12.

  The brake controller 7 inputs a command from the integrated controller 9 and hydraulic pressure information from the master cylinder hydraulic pressure sensor 24 of the VDC brake hydraulic pressure unit 2. Then, a drive command is output to the VDC motor 21 and solenoid valves 25, 26, 27, 28 of the VDC brake hydraulic unit 2 according to a predetermined control law.

  The motor controller 8 is connected to a traveling electric motor 5 connected to left and right front wheels, which are drive wheels, via an inverter 13. When a regenerative command is input from the integrated controller 9 during brake control, the regenerative braking torque generated by the traveling electric motor 5 is controlled according to the input regenerative command. The motor controller 8 also has a function of controlling the motor torque and the motor rotation speed generated by the traveling electric motor 5 according to the traveling state and the vehicle state during traveling.

  The integrated controller 9 is means for controlling the brake controller 7 and the motor controller 8 in an integrated manner so as to obtain a target deceleration (= target braking torque) during regenerative cooperative brake control or the like. The integrated controller 9 includes battery charge capacity information from the battery controller 91, vehicle speed information from the vehicle speed sensor 92, brake operation information from the brake switch 93, pedal stroke information from the stroke sensor 3, and from the master cylinder hydraulic pressure sensor 24. The master cylinder hydraulic pressure information, etc. are input. As the vehicle speed sensor 92, a wheel speed rotation number sensor capable of detecting a vehicle speed up to an extremely low vehicle speed range is used. And real deceleration is calculated | required by carrying out time differentiation calculation processing of the wheel speed rotation speed.

[VDC brake hydraulic unit configuration]
FIG. 2 shows a VDC brake hydraulic unit that is an example of the hydraulic fluid supply means. Hereinafter, a specific configuration of the VDC brake hydraulic unit 2 will be described with reference to FIG.

  The VDC brake fluid pressure unit 2 performs control to generate pump working fluid pressure based on a command from the brake controller 7. As shown in FIG. 2, the VDC brake hydraulic unit 2 includes a VDC motor 21, hydraulic pumps 22 and 22 driven by the VDC motor 21, low hydraulic reservoirs 23 and 23, and a master cylinder hydraulic sensor 24. And having. Solenoid valves include a first M / C cut solenoid valve 25, a second M / C cut solenoid valve 26, holding solenoid valves 27, 27, 27, 27, and reduced pressure solenoid valves 28, 28, 28, 28. Have.

The first M / C cut solenoid valve 25 and the second M / C cut solenoid valve 26 are differential pressure valves. When the VDC motor 21 drives the pump, the wheel cylinder hydraulic pressure (downstream hydraulic pressure) and the master cylinder hydraulic pressure (upstream) Control the differential pressure (= pump hydraulic pressure).
That is, when a pump operation hydraulic pressure command is output from the brake controller 7 during braking torque control, the pump operation hydraulic pressure by the VDC motor 21 and the first M / C cut solenoid valve 25 and the second M / C cut solenoid valve 26 are output. The hydraulic pressure of the pump is controlled by the differential pressure control based on the operating current value.

  The holding solenoid valves 27, 27, 27, 27 (IN valve) and the pressure reducing solenoid valves 28, 28, 28, 28 (OUT valve) are wheel cylinder hydraulic pressures to the wheel cylinders 4FL, 4FR, 4RL, 4RR. Are controlled independently for each wheel. The VDC brake hydraulic pressure unit 2 performs VDC control, TCS control, ABS control, regenerative cooperative brake control, front and rear wheel braking torque distribution control, and the like in addition to the pump hydraulic pressure control.

[Regenerative cooperative brake control configuration]
FIG. 3 shows a flow of regenerative cooperative brake control processing executed by the integrated controller 9 in the brake control device of Embodiment 1 (regenerative cooperative brake control means). Hereinafter, each step of FIG. 3 showing the regenerative cooperative brake control configuration will be described. This process is started when a brake operation start is input from the brake switch 93.

In step S1, it is determined whether or not the brake pedal stroke S from the stroke sensor 3 is less than the pedal stroke threshold value S _RES that reaches the position where the reservoir port of the master cylinder 13 is closed. If YES (S <S _RES ), the process proceeds to step S2, and if NO (S ≧ S _RES ), the process proceeds to step S3.
Here, the pedal stroke threshold value S _RES reaching the position where the reservoir port of the master cylinder 13 is closed is measured in advance.

At step S2, subsequent to the judgment of the S <S _RES in step S1, the low vehicle speed region regenerative torque restriction map that defines the regenerative torque limit value Tlmt (4), a reservoir port of the master cylinder 13 is opened The basic map in the state is maintained without being updated, and the process proceeds to step S4.
Here, the basic map when the reservoir port of the master cylinder 13 is opened matches the slow response of the VDC pump operating fluid pressure when there is no master cylinder fluid pressure, as shown by the thick line characteristics in FIG. , The replacement start vehicle speed and replacement gradient are set. In other words, the basic map increases the switching start vehicle speed (drive wheel speed Vdr) at which the regenerative torque is decreased and the friction torque due to the pump hydraulic pressure starts to increase, and the renewal gradient, which is the regenerative torque decreasing gradient due to the replacement, is set. It is low. As the drive wheel speed Vdr, the average wheel speed of the left and right front wheels that are drive wheels is used.

In step S 3, following the determination that S ≧ S _RES in step S 2, a low vehicle speed range regenerative torque limit map (FIG. 4) that defines the regenerative torque limit value Tlmt is displayed on the brake pedal stroke S from the stroke sensor 3. Is updated according to the size of, and the process proceeds to step S4.
Here, the map updated when the reservoir port of the master cylinder 13 is closed is, as shown in FIG. 4, the switching start vehicle speed (drive wheel speed Vdr) is larger than the basic map as the brake pedal stroke S is larger. It is low and the replacement gradient is high compared to the basic map.

  In step S4, following the maintenance of the low vehicle speed range regenerative torque limit map in step S2 or the update of the low vehicle speed range regenerative torque limit map in step S3, the low vehicle speed range regenerative torque limit map selected at that time is updated. Then, the brake pedal stroke S and the drive wheel speed Vdr from the stroke sensor 3 are input, the regenerative torque limit value Tlmt is calculated, and the process proceeds to the end.

Next, the operation will be described.
First, “the problem in the regenerative cooperative brake control of the comparative example” will be described. Next, the operation of the brake control device for the FF hybrid vehicle of the first embodiment will be described separately for “regenerative cooperative brake control operation during slow brake operation” and “regenerative cooperative brake control operation during sudden brake operation”.

[Problems in regenerative cooperative brake control of comparative example]
In the case of an existing conventional VDC, a target deceleration requested by the driver is obtained by a basic hydraulic pressure component by a negative pressure booster during brake operation. On the other hand, in the regenerative cooperative brake system using VDC, the basic hydraulic pressure component by the negative pressure booster is offset from the target deceleration requested by the driver as shown in FIG. That is, the regenerative gap is set by enlarging the loss stroke region, which is a stroke in which the master cylinder hydraulic pressure is not generated, and the regenerative gap can be used with the regenerative torque. However, for example, when the maximum regenerative torque cannot be generated due to vehicle speed conditions, battery charge capacity conditions, or the like, it is insufficient to fill the regenerative gap with only the regenerative torque.

  Therefore, the target deceleration requested by the driver is basically achieved by the sum of negative pressure booster (basic hydraulic pressure) and regenerative brake (regenerative), and the shortage is determined by the VDC brake hydraulic actuator (brake operating hydraulic pressure). To compensate). A regenerative cooperative brake system using this VDC is used as a comparative example.

  In the regenerative cooperative brake control of the comparative example, the friction torque component (VDC PU component), regenerative torque component and friction torque component (M / Cyl component) with respect to the total braking torque when the wheel cylinder hydraulic pressure at the time of braking is replaced with the braking torque The basic assignment is as shown in FIG. That is, from the break operation start time t0 to the time t1 at which the stroke for closing the reservoir port is reached, it is shared by (regenerative torque) + (VDC PU). From time t1 to time t2 when the maximum regenerative torque is reached, it is shared by (regenerative torque) + (VDC PU) + (M / Cyl). From time t2 to time t3 when the restriction of regenerative torque is started, it is shared by (regenerative torque) + (M / Cyl). From time t3 to time t4 when the regenerative torque reaches zero, it is shared by (regenerative torque) + (VDC PU min) + (M / Cyl min). From time t4 to vehicle stop time t5, it is shared by (VDC PU minutes) + (M / Cyl minutes).

  In this way, from (regenerative torque limit start time t3) to (regenerative torque) + (VDC PU component), the (regenerative torque component) is decreased from the time t3 when the regenerative torque reaches zero until time t4. , (VDC PU component) is increased, and torque switching is performed.

  In this torque change, there is a difference in the speed of the hydraulic pressure response due to the operation of the VDC pump depending on whether or not the brake stroke exceeds the stroke for closing the reservoir port, that is, whether or not the master cylinder hydraulic pressure is generated. The reason will be described below.

  First, in the stroke region where the brake port remains open in the reservoir port, as shown in FIG. 7, the hydraulic pump flows in and discharges the hydraulic fluid from the low pressure reservoir and the reservoir of the master cylinder. That is, when the piston moves in a direction in which the low-pressure reservoir chamber is narrowed by the pump operation (upward direction in FIG. 7), the piston rod pushes up the check ball, and the liquid path blocked by the check ball is slightly opened. However, even if the liquid passage is opened, the low pressure reservoir chamber corresponding to the atmospheric pressure and the reservoir chamber of the master cylinder are merely communicated.

  On the other hand, in the stroke area where the brake stroke closes the reservoir port, as shown in FIG. 8, the hydraulic pump flows in and discharges the master cylinder hydraulic pressure from the low pressure reservoir and the master cylinder. That is, when the piston moves in a direction in which the low-pressure reservoir chamber is narrowed by the pump operation (upward direction in FIG. 8), the piston rod pushes up the check ball, and the liquid path blocked by the check ball is slightly opened. Therefore, when the fluid passage is opened, the master cylinder fluid pressure acts on the suction side of the fluid pressure pump, and the fluid pressure response due to the VDC pump operation is accelerated. And this hydraulic pressure responsiveness has the relationship that the hydraulic pressure response by the VDC pump operation becomes faster as the master cylinder hydraulic pressure increases.

For this reason,
(a) Based on the assumption that master cylinder hydraulic pressure is generated, if the regeneration → friction displacement gradient is determined to be steep, if there is no master cylinder hydraulic pressure, the slow response cannot be taken into account and the deceleration decreases. To do.
(b) Regeneration on the assumption that master cylinder hydraulic pressure is not generated → If the friction displacement gradient is determined to be a gentle gradient, the response speed cannot be taken into account when the master cylinder hydraulic pressure is generated, and the regenerative torque that can be recovered is Less.
There was a problem.

[Regenerative cooperative brake control action during slow brake operation]
In response to the problem of the comparative example described above, it is necessary to devise a technique for suppressing the decrease in deceleration in consideration of the slow response of the hydraulic pressure due to the operation of the VDC pump when the brake operation is performed before the pedal stroke closes the reservoir port. Hereinafter, based on FIG. 3, FIG. 4, and FIG. 9, the regenerative cooperative brake control action at the time of the gentle brake operation reflecting this will be described.

When the brake pedal stroke S is less than the pedal stroke threshold value S _RES that reaches the position where the reservoir port of the master cylinder 13 is closed, the flow of steps S1 → step S2 → step S4 → end is repeated in the flowchart of FIG. It is.
Therefore, in step S2, the basic map in a state where the reservoir port of the master cylinder 13 is opened is maintained as the low vehicle speed range regenerative torque limit map (FIG. 4) that defines the regenerative torque limit value Tlmt without being updated. . In the next step S4, the brake pedal stroke S and the drive wheel speed Vdr from the stroke sensor 3 are input to the selected basic map, and the regenerative torque limit value Tlmt is calculated.

  Here, the basic map before the reservoir port of the master cylinder 13 is closed, that is, in the opened state, shows the VDC pump operating hydraulic pressure when the master cylinder hydraulic pressure is not generated, as shown by the thick line characteristics in FIG. In accordance with the slow response, the replacement start vehicle speed and replacement gradient are set. In other words, the basic map increases the switching start vehicle speed (drive wheel speed Vdr) at which the regenerative torque is decreased and the friction torque due to the pump hydraulic pressure starts to increase, and the renewal gradient, which is the regenerative torque decreasing gradient due to the replacement, is set. It is low.

  Then, based on the calculated regenerative torque limit value Tlmt, the regenerative command for the traveling electric motor 5 is decreased. At the same time, the differential pressure control command to the VDC brake hydraulic pressure unit 2 is increased so as to compensate for the braking torque limit amount based on the regenerative torque limit value Tlmt, and pressure increase control of the pump operating hydraulic pressure (= PU hydraulic pressure) is performed. .

  Therefore, in the operation region where the reservoir port of the master cylinder 13 is open, as shown by the arrow A in FIG. 9, the replacement start vehicle speed Vdr1 at the regenerative torque limit start time t3 is increased and from time t3 to time t4. The replacement gradient α becomes smaller. For this reason, it is replaced at a speed that catches up with the slow response speed of the friction torque due to the pump hydraulic pressure, and the deceleration fluctuation (deceleration reduction) as shown by the dotted line characteristic B in FIG. 9 is suppressed.

[Regenerative cooperative brake control action during sudden braking]
In contrast to the problem of the comparative example described above, it is necessary to devise a technique for increasing the recoverable regenerative torque in consideration of the speed of the hydraulic pressure response due to the operation of the VDC pump at the time of sudden braking operation after the pedal stroke is closed after the reservoir port is closed. Hereinafter, based on FIG. 3, FIG. 4, and FIG. 10, the regenerative cooperative brake control action at the time of sudden braking operation reflecting this will be described.

When the brake pedal stroke S exceeds the pedal stroke threshold value S _RES for reaching the position where the reservoir port of the master cylinder 13 is closed, the flow from step S 1 → step S 3 → step S 4 → end is repeated in the flowchart of FIG. It is.
Therefore, in step S3, the low vehicle speed range regenerative torque limit map (FIG. 4) that defines the regenerative torque limit value Tlmt is updated according to the magnitude of the brake pedal stroke S from the stroke sensor 3. In the next step S4, the brake pedal stroke S and the drive wheel speed Vdr from the stroke sensor 3 are input to the selected basic map, and the regenerative torque limit value Tlmt is calculated.

  Here, the map updated when the reservoir port of the master cylinder 13 is closed is, as shown in FIG. 4, the switching start vehicle speed (drive wheel speed Vdr) is larger than the basic map as the brake pedal stroke S is larger. It is low and the replacement gradient is high compared to the basic map.

  Then, based on the calculated regenerative torque limit value Tlmt, the regenerative command for the traveling electric motor 5 is decreased. At the same time, the differential pressure control command to the VDC brake hydraulic pressure unit 2 is increased so as to compensate for the braking torque limit amount based on the regenerative torque limit value Tlmt, and pressure increase control of the pump operating hydraulic pressure (= PU hydraulic pressure) is performed. .

  Therefore, in the operation region where the reservoir port of the master cylinder 13 is closed, as shown by an arrow C in FIG. 10, the replacement start vehicle speed is changed at time t3 ′ delayed from the regenerative torque limit start time t3 according to the basic map. The starting vehicle speed is Vdr3 (<Vdr2). Then, the replacement gradient β from the time t3 ′ to the time t4 is made larger than the replacement gradient α in the operation region where the reservoir port is closed so as to match the time t4 at which the regenerative torque according to the basic map becomes zero. That is, in the operation region in which the reservoir port is closed, replacement at a speed corresponding to the fast response speed of the friction torque due to the pump hydraulic pressure is possible, so that the regenerative torque limit start can be caught up.

  For this reason, by setting the control to delay the start of limiting the regenerative torque and increase the substitution gradient β, the regenerative energy is increased by the recovery amount E at the time Δt (= t3′−t3) indicated by the arrow D in FIG. To do. Further, in the operation region in which the reservoir port of the master cylinder 13 is closed, the response speed of the pump hydraulic fluid pressure increases as the brake pedal stroke S increases. Therefore, the regenerative energy amount increases as the brake operation increases. Larger amounts can be recovered. As a result, it is possible to increase the amount of charge to the in-vehicle battery, extend the cruising distance by EV traveling that stops the engine 10, and improve fuel efficiency.

Next, the effect will be described.
In the brake control device for the FF hybrid vehicle of the first embodiment, the effects listed below can be obtained.

(1) A part of the hydraulic fluid in the master cylinder 13 is sucked into the hydraulic system connecting the master cylinder 13 and the wheel cylinders 4FL, 4FR, 4RL, 4RR to make the pump hydraulic fluid pressure, and the wheel cylinders 4FL, 4FR, 4RL, In a brake control device for an electric vehicle (FF hybrid vehicle) provided with hydraulic fluid supply means (VDC brake hydraulic unit 2) for supplying to 4RR,
During the brake operation, depending on whether the reservoir port of the master cylinder 13 is the closed operation region or the open operation region, the regenerative torque is decreased and the increase of the friction torque due to the pump hydraulic pressure is started. A regenerative cooperative brake control means (FIG. 3) is provided that makes the change start vehicle speed different from the change gradient that is the decrease gradient of the regenerative torque due to change,
The regenerative cooperative brake control means (FIG. 3) determines that the replacement start vehicle speed is lower than the replacement start vehicle speed when the reservoir port is open when it is determined that the operation region is closed. And the replacement gradient is made larger than the replacement gradient when the reservoir port is open.
For this reason, at the time of brake operation, an increase in regenerative energy can be achieved in the operation region where the reservoir port is closed while suppressing the fluctuation of the deceleration in the operation region where the reservoir port is open.

(2) When it is determined that the regenerative cooperative brake control means (FIG. 3) is an operation region in which the reservoir port of the master cylinder 13 is closed, the pedal stroke is large or the master cylinder hydraulic pressure is generated. The larger the value, the lower the replacement start vehicle speed and the steeper gradient (FIG. 4).
For this reason, in addition to the effect of (1), in the operation region where the reservoir port is closed, the response speed of the pump hydraulic pressure increases as the pedal stroke increases or the master cylinder hydraulic pressure increases. And regenerative energy to be recovered can be further increased. In the operation region where the reservoir port is closed, the magnitude of the pedal stroke is proportional to the magnitude of the master cylinder hydraulic pressure.

(3) A pedal stroke detecting means (stroke sensor 3) for detecting the stroke of the brake pedal 11 is provided.
The regenerative cooperative brake control means (FIG. 3) determines that the reservoir port of the master cylinder 13 is closed when the brake pedal stroke S is _{equal to} or greater than the pedal stroke threshold S _RES when the reservoir port of the master cylinder 13 is closed. To do.
For this reason, in addition to the effect of (1) or (2), whether or not the reservoir port of the master cylinder 13 is closed by the piston is accurately determined by the stroke of the brake pedal 11 representing the positional relationship between the reservoir port and the piston. be able to.

  The second embodiment is an example in which it is determined by the master cylinder hydraulic pressure whether or not the reservoir port of the master cylinder is closed.

First, the configuration will be described.
FIG. 11 shows a flow of regenerative cooperative brake control processing executed by the integrated controller 9 in the brake control device of Embodiment 2 (regenerative cooperative brake control means). Hereinafter, each step of FIG. 11 representing the regenerative cooperative brake control configuration will be described. This process is started when a brake operation start is input from the brake switch 93.

In step S21, it is determined whether or not the master cylinder hydraulic pressure Pm from the master cylinder hydraulic pressure sensor 24 is less than the master cylinder hydraulic pressure threshold Pm _RES that reaches the position where the reservoir port of the master cylinder 13 is closed. If YES (Pm <Pm _RES ), the process proceeds to step S22. If NO (Pm ≧ Pm _RES ), the process proceeds to step S23.
Here, the master cylinder hydraulic pressure threshold value Pm _RES reaching the position where the reservoir port of the master cylinder 13 is closed is measured in advance. The master cylinder hydraulic pressure threshold Pm _RES is theoretically zero, but in reality, a slight pressure is generated due to the flow resistance received by the hydraulic fluid flowing until the piston reaches the position where the reservoir port closes. .

In step S22, following the determination in step S21 that Pm <Pm _RES , the reservoir port of the master cylinder 13 is opened as a low vehicle speed range regenerative torque limit map (FIG. 12) that defines the regenerative torque limit value Tlmt. The basic map in the state is maintained without being updated, and the process proceeds to step S24.
Here, the basic map in the state where the reservoir port of the master cylinder 13 is opened matches the slow response of the VDC pump operating fluid pressure when the master cylinder fluid pressure is not generated, as shown by the thick line characteristics in FIG. , The replacement start vehicle speed and replacement gradient are set. In other words, the basic map increases the switching start vehicle speed (drive wheel speed Vdr) at which the regenerative torque is decreased and the friction torque due to the pump hydraulic pressure starts to increase, and the renewal gradient, which is the regenerative torque decreasing gradient due to the replacement, is set. It is low.

In step S23, following the determination that Pm ≧ Pm _RES in step S22, a low vehicle speed range regenerative torque limit map (FIG. 12) that defines the regenerative torque limit value Tlmt is displayed on the brake pedal stroke S from the stroke sensor 3. Is updated according to the size of, and the process proceeds to step S4.
Here, the map updated when the reservoir port of the master cylinder 13 is closed is, as shown in FIG. 12, the replacement start vehicle speed (drive wheel speed Vdr) as compared with the basic map as the master cylinder hydraulic pressure Pm increases. , And the replacement gradient is higher than that of the basic map.

In step S24, following the maintenance of the low vehicle speed range regenerative torque limit map in step S22 or the update of the low vehicle speed range regenerative torque limit map in step S23, the low vehicle speed range regenerative torque limit map selected at that time is updated. Then, the master cylinder hydraulic pressure Pm and the drive wheel speed Vdr from the master cylinder hydraulic pressure sensor 24 are input, the regenerative torque limit value Tlmt is calculated, and the process proceeds to the end.
The system configuration and the VDC brake hydraulic unit are the same as those in the first embodiment shown in FIGS.

  Next, regarding the operation, whether or not the reservoir port of the master cylinder 13 is closed is determined by the master cylinder hydraulic pressure Pm instead of the brake pedal stroke information of the first embodiment. Furthermore, the low vehicle speed range regenerative torque limit map is updated in accordance with the magnitude of the master cylinder hydraulic pressure Pm instead of the brake pedal stroke information of the first embodiment. Since other operations are the same as those of the first embodiment, the description thereof is omitted.

Next, the effect will be described.
In the brake control device for the FF hybrid vehicle of the second embodiment, in addition to the effects (1) and (2) of the first embodiment, the following effects can be obtained.

(4) A master cylinder hydraulic pressure detecting means (master cylinder hydraulic pressure sensor 24) for detecting the master cylinder hydraulic pressure Pm is provided,
The regenerative cooperative brake control means (FIG. 11) closes the reservoir port of the master cylinder 13 when the master cylinder hydraulic pressure Pm exceeds the master cylinder hydraulic pressure threshold Pm _RES when the reservoir port of the master cylinder 13 is closed. It is determined that
For this reason, whether or not the reservoir port of the master cylinder 13 is closed by the piston can be accurately determined from the generation state of the master cylinder hydraulic pressure Pm related to the response speed of the pump hydraulic pressure.

  As mentioned above, although the brake control apparatus of the electric vehicle of this invention has been demonstrated based on Example 1 and Example 2, it is not restricted to these Examples about a concrete structure, Each of Claims Design changes and additions are permitted without departing from the scope of the claimed invention.

  In the first and second embodiments, an example in which the VDC brake hydraulic unit 2 is used as the hydraulic fluid supply unit has been described. However, the hydraulic fluid supply means is a means that generates a pump hydraulic pressure by a hydraulic pump that is arranged in a hydraulic system that connects the master cylinder and the wheel cylinder and that sucks and discharges a part of the hydraulic fluid in the master cylinder. If there is, it is not limited to the VDC brake hydraulic unit 2 of the first embodiment.

  In the first embodiment, an example in which the stroke sensor 3 is used to determine whether or not the reservoir port of the master cylinder 13 is closed has been described. In the second embodiment, the master cylinder hydraulic pressure sensor 24 is used to determine whether or not the reservoir port of the master cylinder 13 is closed. However, whether or not the reservoir port of the master cylinder is closed may be determined based on detection of the stroke position of the piston, or may be determined by combining stroke information, master cylinder hydraulic pressure information, or the like. .

  In the first embodiment, the brake control device of the present invention is applied to an FF hybrid vehicle. However, the brake control device of the present invention can be applied to other hybrid vehicles, electric vehicles, fuel cell vehicles, etc. as long as it is an electric vehicle that performs regenerative cooperative brake control.

1 Brake fluid pressure generator 13 Master cylinder 2 VDC brake fluid pressure unit (working fluid supply means)
21 VDC motor 22 Hydraulic pump 24 Master cylinder hydraulic pressure sensor (master cylinder hydraulic pressure detection means)
25 1st M / C cut solenoid valve 26 2nd M / C cut solenoid valve 3 Stroke sensor (pedal stroke detection means)
4FL Left front wheel wheel cylinder 4FR Right front wheel wheel cylinder 4RL Left rear wheel wheel cylinder 4RR Right rear wheel wheel cylinder 5 Driving electric motor 61 Primary hydraulic pipe 62 Secondary hydraulic pipe 63 Left front wheel hydraulic pipe 64 Right front wheel hydraulic pipe 65 Left rear wheel liquid Pressure tube 66 Right rear wheel hydraulic tube 7 Brake controller 8 Motor controller 9 Integrated controller 91 Battery controller 92 Vehicle speed sensor 93 Brake switch

Claims (4)

In a brake control device for an electric vehicle provided with hydraulic fluid supply means for sucking a part of hydraulic fluid in the master cylinder and supplying it to the hydraulic cylinder as a pump hydraulic fluid pressure to a hydraulic system that connects the master cylinder and the wheel cylinder,
During the brake operation, depending on whether the reservoir port of the master cylinder is a closed operation region or an open operation region, the regenerative torque is decreased and the friction torque due to the pump hydraulic fluid pressure starts to be increased. A regenerative cooperative brake control means is provided for differentiating the starting vehicle speed and the changing gradient, which is the decreasing gradient of the regenerative torque due to changing,
When the regenerative cooperative brake control means determines that the reservoir port is in the closed operation region, the regenerative start brake vehicle speed is lower than the replacement start vehicle speed when the reservoir port is open, and The brake control device for an electric vehicle, wherein the replacement gradient is made larger than a replacement gradient when the reservoir port is open. In the brake control device for an electric vehicle according to claim 1,
When it is determined that the regenerative cooperative brake control means is an operation region where the reservoir port of the master cylinder is closed, the regenerative start brake vehicle speed is increased as the pedal stroke is larger or the master cylinder hydraulic pressure is larger. A brake control device for an electric vehicle, characterized by further lowering and making the replacement gradient steeper. In the brake control device for an electric vehicle according to claim 1 or 2,
Pedal stroke detection means for detecting the stroke of the brake pedal is provided,
The regenerative cooperative brake control means determines that the reservoir port of the master cylinder is closed when a brake pedal stroke becomes equal to or greater than a pedal stroke threshold when the reservoir port of the master cylinder is closed. Brake control device. In the brake control device for an electric vehicle according to claim 1 or 2,
A master cylinder hydraulic pressure detecting means for detecting the master cylinder hydraulic pressure is provided,
The regenerative cooperative brake control means determines that the reservoir port of the master cylinder is closed when the master cylinder hydraulic pressure is equal to or higher than a master cylinder hydraulic pressure threshold when the reservoir port of the master cylinder is closed. Brake control device for electric vehicles.