JP2009096239A - Braking control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a braking control device capable of suppressing rising of a liquid pressure of a low pressure side wheel cylinder when a driver reduces an amount of braking operation in such a state that different braking force is imparted in left and right wheels or front and rear wheels. <P>SOLUTION: When the amount of braking operation of the driver is reduced in such a state that difference of braking force is given to the left and right wheels, control instruction for only reducing the brake liquid pressure of the high pressure side wheel cylinder is outputted to a solenoid in-valve 4 while retaining the brake liquid pressure of the low pressure side wheel cylinder of the left and right wheel cylinders until difference of braking force of the left and right wheels becomes a predetermined value or lower. When difference of braking force becomes a predetermined value or lower, control instruction for also reducing the brake liquid pressure of both wheel cylinders is outputted to the solenoid in-valve 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technical field of a braking control device that applies a braking force difference to left and right wheels or front and rear wheels.

In a hydraulic circuit of a conventional braking control device, a pressure increasing valve that opens and closes the branch path is provided in each branch path that branches the braking hydraulic pressure generated in the master cylinder to the front and rear or left and right wheel cylinders. In this hydraulic circuit, it is possible to apply a braking force difference to the front and rear wheels or the left and right wheels by opening one of the pressure increasing valves and closing the other (for example, see Patent Document 1).
Japanese Patent Laid-Open No. 2001-18776

  In the conventional hydraulic circuit, when the driver reduces the braking operation amount, the braking hydraulic pressure supplied to each wheel cylinder is merged from the branch path and directly returned to the master cylinder. At this time, if the pressure increasing valve is opened at the same time, the brake fluid pressure discharged from the high-pressure side wheel cylinder flows back to the low-pressure side wheel cylinder, which causes an increase in the low-pressure side wheel cylinder pressure.

  The present invention has been made paying attention to the above-mentioned problem, and the object of the present invention is to reduce the pressure when the driver reduces the braking operation amount while the braking force difference between the left and right wheels or the front and rear wheels is applied. An object of the present invention is to provide a braking control device capable of suppressing an increase in hydraulic pressure of the side braking force applying means (low pressure side wheel cylinder).

  In order to achieve the above-described object, in the present invention, when the braking operation amount of the driver decreases while the braking force difference is applied to the left and right wheels or the front and rear wheels, the braking force difference between the left and right wheels and the front and rear wheels is a predetermined value. Until the following, the braking fluid pressure difference of the high pressure side braking force applying means is decreased while maintaining the braking fluid pressure of the low pressure side braking force applying means among the left and right or front and rear braking force applying means. When the value becomes equal to or less than the predetermined value, both the braking hydraulic pressures of both braking force applying means are reduced.

  In the present invention, after the braking hydraulic pressure difference between the high pressure side braking force applying means and the low pressure side braking force applying means becomes equal to or less than a predetermined value, both the braking hydraulic pressures of both braking force applying means are reduced. The amount of braking hydraulic pressure that flows back from the means to the low pressure side braking force applying means can be kept small, and an increase in the hydraulic pressure of the low pressure side braking force applying means can be suppressed.

  Hereinafter, the best mode for carrying out the present invention will be described based on the first embodiment.

FIG. 1 is a system configuration diagram of a vehicle to which the braking force control apparatus according to the first embodiment is applied.
The hydraulic unit (hereinafter referred to as HU) 31 is a wheel cylinder W / C (FL) for the left front wheel FL and a wheel for the right rear wheel RR based on commands from a brake controller (braking control means, hereinafter referred to as brake ECU) 32. The cylinder W / C (RR), the wheel cylinder W / C (FR) of the right front wheel FR, and the wheel cylinder W / C (RL) of the left rear wheel RL are maintained, increased or reduced in pressure. Each wheel cylinder W / C corresponds to a braking force applying means for applying a braking force to the wheel in accordance with the supplied brake fluid pressure (braking fluid pressure).

  The brake ECU 32 includes a yaw rate / lateral G sensor (running state detecting means) 33 that detects the yaw rate and lateral acceleration of the vehicle, a wheel speed sensor (running state detecting means) 34 that detects the wheel speed of each wheel, and an engine controller ( Hereinafter, based on the information obtained from the ENGCU) 35, the automatic transmission controller (hereinafter referred to as ATCU) 36 through CAN communication, the information from the steering angle sensor 39, and the brake pedal stroke sensor 40, it is determined whether to execute the braking control. I do. During the execution of the control, the wheel cylinder hydraulic pressure is maintained and an increase / decrease command is generated.

  The brake pedal BP is operated when the driver performs braking. The brake pedal operation amount of the driver is boosted by the electric booster 41. The input boosted by the electric booster 41 is converted into brake hydraulic pressure by a master cylinder (hydraulic pressure generating means) M / C and supplied from the HU 31 to each wheel cylinder W / C. Each wheel cylinder W / C brakes the corresponding wheel.

  The brake ECU 32 determines a boost ratio according to the brake pedal stroke amount (braking operation amount) detected by the brake pedal stroke sensor 40, and drives a motor (not shown) of the electric booster 41 based on the boost ratio. To do. Here, the master cylinder M / C is configured to generate a certain amount of brake fluid pressure when the driver depresses the brake pedal BP even when the electric booster 41 is stopped due to an electric system failure. Yes.

  The accelerator pedal AP performs vehicle acceleration / deceleration control by the driver's operation. The ENGCU 35 controls the engine 37 from the driver's accelerator pedal operation. In addition, the generated torque of the engine 37 and information on the accelerator pedal operation amount are output by communication (CAN). The ATCU 36 controls the automatic transmission 38. Further, a gear position signal (range position of the automatic transmission 38) is output by communication (CAN).

FIG. 2 is a hydraulic circuit diagram of the HU 31 according to the first embodiment. The HU 31 according to the first embodiment has a piping structure called a so-called X piping, which includes two systems of a P system and an S system.
The P system is connected to the wheel cylinder W / C (FL) for the left front wheel and the wheel cylinder W / C (RR) for the right rear wheel. The wheel cylinder W / C (FR) for the right front wheel is connected to the S system. The wheel cylinder W / C (RL) on the left rear wheel is connected. Each of the P system and the S system is provided with a pump PP and a pump PS, and the pump PP and the pump PS are driven by one motor M. In addition, a plunger pump, a gear pump, etc. are suitably mounted as a pump. In terms of cost, a plunger pump is desirable, and in terms of smoothness (controllability), a gear pump is desirable.

  Master cylinder M / C and the suction side of pumps PP and PS (hereinafter referred to as pump P) are connected by pipelines 11P and 11S (hereinafter referred to as pipeline 11). On each pipeline 11, gate-in valves 2P and 2S, which are normally closed solenoid valves, are provided.

  Further, check valves 6P and 6S (hereinafter referred to as check valves 6) are provided on the pipeline 11 between the gate-in valves 2P and 2S (hereinafter referred to as gate-in valves 2) and the pump P. The check valve 6 allows the flow of brake fluid in the direction from the gate-in valve 2 toward the pump P, and prohibits the flow in the opposite direction.

  The discharge side of each pump P and each wheel cylinder W / C are connected by pipes 12P and 12S (hereinafter, pipe 12). Pipe line 12P is branched into two pipe lines (branch paths) 12FL and 12RR, and the pipe lines 12FL and 12RR are solenoids that are normally open solenoid valves corresponding to the wheel cylinder W / C (FL, RR). In valves (hydraulic pressure adjusting means) 4FL, 4RR are provided. Pipe line 12S is branched into two pipe lines (branch paths) 12FR and 12RL. Pipe lines 12FR and 12RL are normally open solenoid valves corresponding to wheel cylinders W / C (FR and RL). Certain solenoid-in valves (hydraulic pressure adjusting means) 4FR and 4RL are provided. Hereinafter, the solenoid valves 4FL, 4RR, 4FR, and 4RL are referred to as solenoid-in valves 4.

  In addition, check valves 7P and 7S (hereinafter referred to as check valves 7) are provided on the pipe lines 12 and between the solenoid-in valves 4 and the pumps P. The check valves 7 are connected to the pumps P. The brake fluid is allowed to flow in the direction from the valve to the solenoid-in valve 4, and the flow in the opposite direction is prohibited.

  Furthermore, each pipeline 12 is provided with pipelines 17FL, 17RR, 17FR, 17RL (hereinafter referred to as pipeline 17) that bypass each solenoid-in valve 4. The pipeline 17 includes check valves 10FL, 10RR, 10FR, 10RL (hereinafter, check valve 10) is provided. Each check valve 10 allows the flow of brake fluid in the direction from the wheel cylinder W / C toward the pump P, and prohibits the flow in the opposite direction.

  Master cylinder M / C and conduit 12 are connected by conduits 13P and 13S (hereinafter referred to as conduit 13), and conduit 12 and conduit 13 merge between pump P and solenoid-in valve 4. On each pipeline 13, gate-out valves 3P and 3S (hereinafter referred to as gate-out valves 3), which are normally open solenoid valves, are provided.

The brake fluid pressure from the master cylinder M / C is controlled by the left and right wheel cylinders W / C (FL) and W / C (RR). ) Is formed.
Also, the brake fluid pressure from the master cylinder M / C is branched to the right front wheel wheel cylinder W / C (FR) and the left rear wheel wheel cylinder W / C (RL) by the pipeline 13S pipeline 12S branch passage 12FR2RL. A hydraulic pressure supply circuit is configured.

  Each pipe line 13 is provided with pipe lines 18P and 18S (hereinafter referred to as pipe lines 18) that bypass each gate-out valve 3. The pipe line 18 includes check valves 9P and 9S (hereinafter referred to as check valves 9). ) Is provided. Each check valve 9 permits the flow of brake fluid in the direction from the master cylinder M / C side toward the wheel cylinder W / C, and prohibits the flow in the opposite direction.

  Reservoirs 16P and 16S (hereinafter referred to as reservoir 16) are provided on the suction side of the pump P, and the reservoir 16 and the pump P are connected by pipe lines 15P and 15S (hereinafter referred to as pipe line 15). Check valves 8P and 8S (hereinafter referred to as check valves 8) are provided between the reservoir 16 and the pump P, and each check valve 8 allows the flow of brake fluid in the direction from the reservoir 16 to the pump P. , Prohibit flow in the opposite direction.

The wheel cylinder W / C and the pipeline 15 are connected by pipelines 14P and 14S (hereinafter, pipeline 14), and the pipeline 14 and the pipeline 15 merge between the check valve 8 and the reservoir 16. Each pipeline 14 is provided with a solenoid-out valve (pressure reduction control valve) 5FL, 5RR, 5FR, 5RL (hereinafter, solenoid-out valve 5), which is a normally closed solenoid valve.
The conduit 14, the conduit 15, the portion of the conduit 12 upstream of the branch passages 12FL, 12RR, 12FR, and 12RL, and the conduit 13 constitute a reflux circuit.

  Master cylinder pressure sensors 42P and 42S (hereinafter referred to as master cylinder pressure sensor 42) for detecting the master cylinder pressure are provided in the oil passage between the master cylinder M / C and the gate-in valve 2 and the gate-out valve 3. Yes.

  Further, in the oil passage between the solenoid-in valve 4 and the solenoid-out valve 5 and the oil passage between each wheel cylinder W / C, wheel cylinder pressure sensors 43FL, 43FR, 43RL, which detect wheel cylinder pressures are provided. 43RR (hereinafter referred to as wheel cylinder pressure sensor 43) is provided.

  The brake ECU 32 calculates the normal brake control according to the driver's braking operation based on the input signal of each sensor, the brake pedal operation amount, etc., and the vehicle behavior such as anti-skid brake control (ABS) and vehicle behavior stabilization control (VDC). Is calculated, a target braking force required for the vehicle is calculated, and each wheel cylinder pressure is controlled.

  The brake ECU 32 distributes the braking force so that the braking force of the front outer wheel is large and the braking force of the rear rear wheel is small during braking turning of the vehicle, and the braking force of the other two wheels is when traveling straight ahead. The turning behavior is stabilized by making it the same size as. The brake ECU 32 first calculates the target deceleration of the vehicle according to the brake pedal operation amount of the driver, estimates the dynamic wheel load of each wheel based on the deceleration and yaw rate of the vehicle, and sets the target deceleration. And the wheel load, the braking force required for each wheel is calculated.

  Subsequently, the boost ratio of the electric booster 41 is changed with reference to the master cylinder pressure and the wheel cylinder pressure of the turning outer front wheel so that the calculated braking force of the turning outer front wheel is obtained. As a result, the brake fluid pressure required for the front outer wheel is supplied to the P system and S system of the HU 31. Here, with respect to the wheel cylinders of the other wheels excluding the turning outer front wheel, the brake fluid pressure is excessively supplied with respect to the required wheel cylinder pressure. Therefore, the brake ECU 32 requires the wheel cylinder pressure of each wheel. When pressure is reached, the corresponding solenoid-in valve is closed to ensure the necessary braking force.

  If the driver loosens the brake during the turning, the solenoid valves 4FL, 4RR, 4FR, 4RL are opened to return the brake fluid to the master cylinder M / C. At this time, until the hydraulic pressure difference between the wheel cylinder of the turning outer front wheel and the wheel cylinder of the turning inner rear wheel becomes a predetermined value or less, only the solenoid-in valve of the turning outer front wheel opens, and the solenoid-in valve of the turning inner rear wheel Keep closed. Thereafter, when the hydraulic pressure difference becomes equal to or less than a predetermined value, the solenoid-in valve of the rear inner wheel is opened.

[Braking force distribution control processing]
FIG. 3 is a flowchart showing the flow of the braking force distribution control process executed by the brake ECU 32 of the first embodiment. Each step will be described below. This control process is repeatedly executed every predetermined calculation cycle.

  In step S1, the brake pedal stroke amount of the driver detected by the brake pedal stroke sensor 40 is read to detect whether or not there is a brake request from the driver. If yes, then go to step S2, if no, go to return.

  In step S2, the target deceleration of the vehicle is calculated based on the brake pedal stroke amount read in step S1, and the process proceeds to step S3.

  In step S3, each wheel is determined based on the time variation (deceleration) of the vehicle speed calculated from each wheel speed detected by the wheel speed sensor 34 and the vehicle yaw rate detected by the yaw rate / lateral G sensor 33. The dynamic wheel load is estimated, and the process proceeds to step S4.

In step S4, the target braking force of each wheel is calculated based on the wheel load estimated in step S3, and the process proceeds to step S5. Here, the target braking force of each wheel is set so as to satisfy the following relationship in order to stabilize the turning behavior.
Turning front wheel> Turning inside front wheel = Turning outside rear wheel> Turning inside rear wheel

  In step S5, the brake pedal stroke amount detected by the brake pedal stroke sensor 40 is read, and it is determined from the difference from the brake pedal stroke amount read in step S1 whether or not the brake release by the driver has been performed. If YES, the process proceeds to step S6. If NO, the process proceeds to step S11.

  In step S6, it is determined whether or not the hydraulic pressure difference between the wheel cylinder of the turning outer front wheel (hereinafter referred to as the high pressure side wheel cylinder) and the wheel cylinder of the turning inner rear wheel (high pressure side wheel cylinder) is equal to or greater than a predetermined value. If YES, the process proceeds to step S7. If NO, the process proceeds to step S10.

  Here, the “predetermined value” is when the brake fluid discharged from the high pressure side wheel cylinder flows back to the low pressure side wheel cylinder when the solenoid in valve (hereinafter referred to as the low pressure side solenoid in valve) of the low pressure side wheel cylinder is opened. Even in this case, the hydraulic pressure difference is such that the wheels do not tend to lock, but the predetermined value may be zero.

  In step S7, each solenoid-in valve is opened according to the brake release amount calculated in step S5, and the braking force of each wheel is reduced, but the low-pressure side solenoid valve remains closed, and the process proceeds to step S8. To do.

  In step S8, while maintaining the low pressure side wheel cylinder pressure in step S7, in order to compensate the target deceleration corresponding to the brake pedal stroke amount read in step S5, the solenoid valve of the high pressure side wheel cylinder is used. The valve opening amount of the high pressure side solenoid-in valve (hereinafter referred to as “high pressure side solenoid-in valve”) is made larger than the valve opening amount at the normal time (during straight traveling) to increase the pressure reduction speed, and the process proceeds to step S9.

  In step S9, it is determined whether or not the high-pressure wheel cylinder pressure and the low-pressure wheel cylinder pressure are zero (≈0). If YES, the process proceeds to step S10, and if NO, the process proceeds to step S7. Here, the predetermined value described in step S6 may be used instead of zero.

  In step S10, the low pressure side solenoid valve is opened, the opening amount of the high pressure side solenoid valve is returned to normal, and the process proceeds to return.

  In step S11, the boost ratio of the electric booster 41 is changed and the opening and closing of each solenoid-in valve is controlled to apply the braking force to each wheel so that the target braking force calculated in step S4 is obtained. Migrate to

Next, the operation will be described.
[Increase in low-pressure wheel cylinder pressure during decompression]
During braking turning, a larger load is applied to the turning outer wheel than to the turning inner wheel and to the front wheel rather than the rear wheel, so that the turning inner rear wheel (for example, the left rear wheel when turning left) is easily locked. Therefore, the turning behavior can be stabilized by distributing the braking force so that the braking force of the front outer wheel is large and the braking force of the rear rear wheel is small.

  Here, the pedal force applied by the driver to the brake pedal is converted into an electrical signal, and the wheel cylinder is operated with the brake hydraulic pressure generated by the electric braking device based on this electrical signal. A so-called BBB (brake-by-wire) system that generates a reaction force is also known. In this BBW system, the brake pressure distribution after the brake force distribution is configured such that the brake fluid is returned to the reservoir tank by opening the solenoid out valves of the four wheels. There is no (see FIGS. 4 and 5).

  However, in the hydraulic circuit in which the master cylinder and each wheel cylinder are configured as a closed circuit as in the HU 31 (see FIG. 2) employed in the first embodiment, when the four-wheel braking force distribution is performed, When the pressure is released from the solenoid-out valve, the pump for pumping up the fluid must be operated, and pedal kickback occurs as in ABS operation.

  For this reason, a method of draining the brake fluid from the solenoid-in valve instead of the solenoid-out valve can be considered. However, since a hydraulic pressure difference is generated in the left and right wheel cylinders due to the braking force distribution that makes the left and right wheels different in braking force, when the left and right solenoid-in valves are simultaneously opened, as shown in FIG. Is affected by the high pressure side wheel cylinder pressure (outer ring hydraulic pressure), and the low pressure side wheel cylinder pressure (inner ring hydraulic pressure) increases rapidly. Therefore, the turning inner rear wheel having a small wheel load has an excessive braking force, and the wheel tends to be locked, so that the turning behavior may be disturbed.

[Low wheel cylinder pressure rise suppression effect]
On the other hand, in the braking control device of the first embodiment, when distributing the braking force, the high-pressure wheel cylinder pressure is generated by the upstream electric booster 41, and the upstream pressure is supplied to the wheel cylinder by operating the solenoid-in valve on the low-pressure side. By not reaching, the hydraulic pressure is prevented from increasing and a differential pressure from the high pressure side is generated (“pressure increase” in FIG. 6).

  In the subsequent pressure reduction, until the high pressure side wheel cylinder pressure becomes equal to the low pressure side wheel cylinder pressure, the brake ECU 32 repeats the flow of step S7 → step S8 → step S9 in the flowchart of FIG. The cylinder pressure is maintained, and only the high-pressure wheel cylinder pressure is reduced ("decompression" in FIG. 6).

  That is, as shown in the inner ring hydraulic pressure graph of FIG. 7, the brake ECU 32 holds the low pressure side solenoid-in valve in a closed state, opens the high pressure side solenoid in valve, and the high pressure side wheel cylinder pressure decreases together with the upstream pressure. Until it is done, do not open the low-pressure side solenoid-in valve. For this reason, the low pressure side wheel cylinder pressure is not affected by the hydraulic pressure discharged from the high pressure side wheel cylinder, and a sudden increase in brake hydraulic pressure can be prevented.

  Moreover, since the brake fluid is discharged from the solenoid-in valve to the master cylinder M / C, it is not necessary to operate the pump P for pumping up the fluid, and pedal kickback does not occur as in ABS operation. While a certain amount of pedal kickback is required as feedback to the driver during ABS operation, pedal kick kick-up occurs every time the brake is released from the braking turn, resulting in a deterioration of the operational feeling. In addition, the pedal kickback is a significant problem because there are so many driving scenes in which a braking turn is performed compared to a driving scene in which ABS operates.

  On the other hand, in the first embodiment, the brake fluid is returned to the master cylinder M / C without operating the pump P at the time of pressure reduction after distributing the braking force while adopting the normal ABS (+ VDC) hydraulic circuit configuration. Therefore, the occurrence of pedal kickback can be avoided, and the deterioration of the operation feeling can be prevented. Furthermore, since the number of operations of the pump P can be kept small, the durability of the pump P can be improved as compared with the case where the brake fluid is returned from the solenoid out valve to the master cylinder M / C.

[Total braking force compensation]
In the first embodiment, while the low pressure side wheel cylinder pressure is maintained, in order to maintain the total braking force corresponding to the target deceleration required by the driver, in step S8 in FIG. Increase the amount of decompression.

  After the braking force is distributed, the hydraulic pressure on the low pressure side is maintained during decompression, so that the decompression speed becomes slow although the driver releases the brake pedal and requests decompression. The total braking force is determined based on the target deceleration calculated by the driver's braking request (pedal displacement, master cylinder pressure, etc.), but only the high-pressure wheel cylinder pressure is reduced and the low-pressure wheel cylinder pressure is maintained. This is because the total braking force changes.

  Therefore, in the first embodiment, as shown in the outer ring hydraulic pressure graph of FIG. 6, the total braking force is requested to the driver by reducing the hydraulic pressure held by the low pressure side wheel cylinder without reducing the pressure on the high pressure side. It can be set to a value that matches. For this reason, it does not give a sense of incongruity to the decompression after the braking force distribution compared to the decompression in the normal time.

Next, the effect will be described.
In the braking control device of the first embodiment, the effects listed below can be obtained.

  (1) When the brake pedal stroke amount is reduced while the braking force difference is being applied to the left and right wheels, the brake ECU 32 moves the left and right wheel cylinders until the braking force difference between the left and right wheels becomes a predetermined value or less. A control command for reducing only the brake fluid pressure of the high-pressure side wheel cylinder while maintaining the brake fluid pressure of the low-pressure side wheel cylinder is output to the solenoid-in valve 4, and when the difference in braking force falls below a predetermined value, both wheels A control command for decreasing the brake fluid pressure of the cylinder is output to the solenoid-in valve 4. As a result, the amount of brake fluid pressure that flows back from the high-pressure side wheel cylinder to the low-pressure side wheel cylinder can be kept small, and an increase in the low-pressure side wheel cylinder pressure is suppressed. Therefore, it is possible to suppress the wheels from becoming locked due to the excessive braking force of the turning inner rear wheel, and it is possible to minimize the disturbance of the vehicle behavior.

  (2) The brake ECU 32 maintains the brake fluid pressure of the low-pressure wheel cylinder until the braking force difference between the left and right wheels becomes zero, so that the low-pressure wheel cylinder pressure when the low-pressure solenoid-in valve is opened is maintained. Fluctuation (rise) is almost eliminated, and disturbance of vehicle behavior can be reliably prevented.

  (3) While the brake ECU 32 is reducing only the brake fluid pressure of the high-pressure wheel cylinder, the brake ECU 32 reduces the decrease rate of the high-pressure wheel cylinder pressure so that the target deceleration of the vehicle according to the brake pedal stroke amount can be obtained. A control command to be increased is output to the solenoid-in valve 4. As a result, the total braking force of the vehicle can be matched with the driver's required braking force, so that it is possible to prevent a sense of incongruity caused by a deviation between the driver's required braking force and the vehicle's braking force.

  (4) A reflux circuit (pipe line 14 →) provided on the branch path 12FL, 12RR, 12FR, 12RL, between the solenoid-in valve 4 and the wheel cylinder W / C, and between the master cylinder M / C. Pipe 15 → pipe 12 → pipe 13), a normally-closed solenoid-out valve 5 that opens and closes the reflux circuit, and is on the reflux circuit and is a master on the reflux circuit than the solenoid-out valve 5. A reservoir 16 provided on the cylinder M / C side for temporarily storing brake fluid discharged from the master cylinder M / C, and provided on the recirculation circuit between the reservoir 16 and the master cylinder M / C; A pump P that recirculates the brake fluid stored in the reservoir 16 to the master cylinder M / C. In other words, the brake fluid can be returned to the master cylinder M / C without causing a pedal kickback while adopting a normal ABS hydraulic circuit configuration as the HU 31, thereby improving the operational feeling.

  (5) Since the master cylinder M / C includes the electric booster 41 that boosts the brake hydraulic pressure according to the brake pedal stroke amount with electric power, the electric booster 41 generates the brake hydraulic pressure necessary for the high-pressure wheel cylinder. In addition, the brake fluid pressure required for the other wheel cylinders can obtain the braking force required for the four wheels by simple control of closing the corresponding solenoid-in valve 4. Furthermore, compared to the case where the pump P is driven to generate the high-pressure side wheel cylinder pressure as in VDC, it is advantageous in terms of quietness and durability of the pump P.

(Other examples)
Although the best mode for carrying out the present invention has been described with reference to the first embodiment based on the drawings, the specific configuration of the present invention is not limited to that shown in the first embodiment. Any design changes that do not change the gist of the present invention are included in the present invention.

  For example, in the first embodiment, an example is shown in which the hydraulic piping is X piping, and a braking force difference is generated between the turning outer front wheel and the turning inner rear wheel. However, the front and rear wheels are controlled according to the center of gravity movement accompanying the deceleration of the vehicle. It may be configured to generate a power difference. Also in this case, by performing the control at the time of pressure reduction as shown in the first embodiment, the same effect as that of the first embodiment can be obtained.

  In the first embodiment, the target braking force of each wheel is set so as to satisfy the relationship of the turning outer front wheel> the turning inner front wheel = the turning outer rear wheel> the turning inner rear wheel. You may set so that it may become larger than the braking force of a turning outer rear wheel.

1 is a system configuration diagram of a vehicle to which a braking force control device according to a first embodiment is applied. FIG. 3 is a hydraulic circuit diagram of the HU 31 according to the first embodiment. 3 is a flowchart illustrating a flow of a braking force distribution control process executed by the brake ECU 32 according to the first embodiment. It is a hydraulic-braking G characteristic figure at the time of braking force distribution in a BBW system. It is a time chart which shows the brake fluid pressure of the turning outside front wheel and the turning inside rear wheel at the time of pressure reduction after distribution of the conventional braking force. FIG. 6 is a hydraulic pressure-braking G characteristic diagram at the time of braking force distribution according to the first embodiment. 6 is a time chart showing brake hydraulic pressures of a turning outer front wheel and a turning inner rear wheel during pressure reduction after the braking force distribution of the first embodiment.

Explanation of symbols

M / C master cylinder
W / C Wheel cylinder 2 Gate in valve 3 Gate out valve 4 Solenoid in valve (hydraulic pressure adjusting means)
5 Solenoid out valve (pressure reduction control valve)
6 Check valve 7 Check valve 8 Check valve 9 Check valve 10 Check valve 11 Pipe line 12 Pipe line
12FL, 12FR, 12RL, 12RR pipe (branch)
13 Pipe line 14 Pipe line 15 Pipe line 16 Reservoir 17 Pipe line 18 Pipe line 31 Hydraulic unit 32 Brake controller (braking control means)
33 Yaw rate / lateral G sensor (running state detection means)
34 Wheel speed sensor (traveling state detection means)
37 Engine 38 Automatic transmission 39 Steering angle sensor 40 Brake pedal stroke sensor 41 Electric booster 42 Master cylinder pressure sensor 43 Wheel cylinder pressure sensor

Claims (5)

Hydraulic pressure generating means for generating a braking hydraulic pressure according to the amount of braking operation of the driver;
A braking force applying means provided on each wheel for applying a braking force to the wheel according to the supplied braking fluid pressure;
A hydraulic pressure supply circuit provided between the hydraulic pressure generating means and the braking force applying means, and having a branch path for branching the braking hydraulic pressure from the hydraulic pressure generating means to the front and rear or left and right braking force applying means;
A hydraulic pressure adjusting means for adjusting a braking hydraulic pressure provided on the branch path and supplied to the braking force applying means;
Traveling state detecting means for detecting the traveling state of the vehicle;
Braking control means for outputting a control command for giving a braking force difference to the left and right wheels or the front and rear wheels in accordance with the detected traveling state;
With
When the braking operation amount of the driver is reduced in a state where the braking force difference is applied to the left and right wheels or the front and rear wheels, the braking control unit is configured to wait until the braking force difference between the left and right wheels or the front and rear wheels becomes a predetermined value or less. The control command for reducing only the braking fluid pressure of the high pressure side braking force applying means while maintaining the braking fluid pressure of the low pressure side braking force applying means among the left and right or front and rear braking force applying means is output to the fluid pressure adjusting means. When the braking force difference becomes equal to or less than the predetermined value, the braking control device outputs a control command for reducing both the braking hydraulic pressures of both braking force applying means to the hydraulic pressure adjusting means. The braking control device according to claim 1, wherein
The braking control device according to claim 1, wherein the predetermined value is zero. In the braking control device according to claim 1 or 2,
The braking control means applies the high-pressure braking force so that a target deceleration of the vehicle corresponding to the amount of braking operation of the driver can be obtained while only the braking hydraulic pressure of the high-pressure braking force applying means is reduced. A braking control device for outputting a control command for increasing the rate of decrease in braking fluid pressure of the means to the fluid pressure adjusting means. The braking control device according to any one of claims 1 to 3,
A reflux circuit provided on the branch path, between the hydraulic pressure adjusting means and the braking force applying means, and between the hydraulic pressure generating means;
A normally closed pressure-reducing control valve provided on the reflux circuit for opening and closing the reflux circuit;
A reservoir on the reflux circuit and provided closer to the hydraulic pressure generating means than the pressure reducing valve, and temporarily stores braking fluid discharged from the braking force applying means;
A pump provided on the reflux circuit and between the reservoir and the hydraulic pressure generating means, and configured to return the braking fluid stored in the reservoir to the hydraulic pressure generating means;
A braking control device comprising: In the braking control device according to any one of claims 1 to 4,
The brake control device according to claim 1, wherein the hydraulic pressure generating means includes an electric booster that boosts with a power a braking hydraulic pressure corresponding to a braking operation amount of the driver.

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