JP5453752B2 - Braking force control device - Google Patents

Description

The present invention relates to the technical field of the braking force control equipment for performing brake assist.

In the vehicle brake control device described in Patent Document 1, so-called build-up is performed in which the ratio of the target deceleration to the driver's required deceleration is increased with the passage of time in order to obtain a feeling of increase in braking in the latter half of braking. Control is implemented.
JP 2000-233733 A

  However, in the above prior art, since the wheel cylinder pressure increasing amount is always set at a constant ratio corresponding to the stroke amount of the brake pedal, the wheel is unnecessarily necessary when the driver's required braking force is high. The cylinder pressure is increased, resulting in excessive braking force.

The present invention has been made in view of the above problems, and an object is to provide a braking force control equipment which can suppress the braking force excessive when high demand deceleration of the driver.

In order to achieve the above object, in the present invention , the first gain is reduced as the operating speed of the brake pedal is lower.

Therefore, in the present invention, when the required deceleration is high, the second gain is corrected to be small, so that excessive braking force when the driver's required deceleration is high can be suppressed.
Further, since the first gain is decreased as the operation speed of the brake pedal is lower, it is possible to prevent deterioration of the braking feeling when the depression speed of the brake pedal is slow.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to each embodiment based on the drawings.

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 controller W / C (FL) for the left front wheel FL and a right rear wheel RR based on a command from a brake controller (braking force control means, hereinafter referred to as a brake ECU) 32. The hydraulic pressure of wheel cylinder W / C (RR), wheel cylinder W / C (FR) of right front wheel FR, and wheel cylinder W / C (RL) of left rear wheel RL is maintained, increased or reduced. The HU 31 and each wheel cylinder W / C constitute a braking force generating means for generating a braking force.

  The brake ECU 32 includes a yaw rate / lateral G sensor (lateral acceleration detection means) 33 for detecting the yaw rate and lateral acceleration of the vehicle, a wheel speed sensor (vehicle speed detection means) 34 for detecting the wheel speed of each wheel, and an engine controller (hereinafter referred to as the engine controller). , ENGCU) 35, information obtained from the automatic transmission controller (hereinafter referred to as ATCU) 36 through CAN communication, and information from the steering angle sensor (steering angle detection means) 39, the execution of braking control is determined. . 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 at a boost ratio set in advance by the electric booster 41. The input boosted by the electric booster 41 is converted into a brake fluid pressure by the master cylinder M / C and supplied from the HU 31 to each wheel cylinder W / C. Each wheel cylinder W / C brakes the corresponding wheel.

  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 4FL and 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 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.

  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.

  In the oil passage between the master cylinder M / C and the gate-in valve 2 and the gate-out valve 3, master cylinder pressure sensors 42P and 42S (hereinafter referred to as “hydraulic pressure sensors”) that output an output signal corresponding to the master cylinder pressure. A master cylinder pressure sensor 42) is provided.

  The brake ECU 32 is used to control vehicle behavior such as calculation of normal brake control according to the driver's braking operation based on the input signal of each sensor, anti-skid brake control (ABS), vehicle behavior stabilization control (VDC), etc. An arithmetic operation is performed to calculate a target braking force necessary for the vehicle, and each wheel cylinder pressure is controlled.

  The brake ECU 32 executes build-up control that simulates the build-up characteristics of the brake pad as brake assist control that generates a larger braking force with respect to the braking force corresponding to the braking operation of the driver. Hereinafter, the build-up control will be described.

  Brake pads are used to brake the wheels of automobiles. In general, when the brake pedal depression force (operation amount, depression pressure) is constant, the brake pads are continuously braked to reduce the brake pads. As the temperature rises, the coefficient of friction rises, thereby having a build-up characteristic that the braking pressure gradually increases. This build-up characteristic greatly depends on the material characteristics of the brake pad.

  For this reason, in the conventional braking device, a brake pad having a desired material characteristic is selected, and a build-up characteristic is generated by this material characteristic. Recently, attempts have been made to produce desired build-up characteristics without being affected by the material characteristics of the brake pad and by controlling the braking force in addition to the material characteristics of the brake pad.

  Thus, in the first embodiment, the wheel cylinder pressure is gradually increased with the passage of time to increase the target deceleration, thereby ensuring a feeling of increase in braking in the latter half of braking. This build-up control ends when the vehicle speed reaches a preset low vehicle speed threshold (≈0).

FIG. 3 is a build-up control block diagram of the brake ECU 32.
The estimated master pressure calculation unit 32 a estimates the change amount of the master cylinder pressure based on the pressure increase amount of the pump P, and based on the estimated change amount of the master cylinder pressure and the master pressure that is an output signal of the master cylinder pressure sensor 42. Thus, an estimated master pressure that is an estimated value of the master cylinder pressure is calculated.

Based on the master pressure at the start of the brake assist control and the amount of change in the estimated master pressure calculated by the estimated master pressure calculating unit 32a, the base pressure calculating unit (required deceleration detecting means) 32b An estimated value of the quantity, that is, a base pressure as an estimated value of the driver's required deceleration is calculated.
The target pressure calculation unit (gain calculation unit, target deceleration calculation unit, gain correction unit) 32c calculates the target pressure of the wheel cylinder pressure based on the base pressure calculated by the base pressure calculation unit 32b.

  The drive control unit 32d outputs a drive command to the pump P based on the target pressure calculated by the target pressure calculation unit 32c and controls the drive amount of the pump P. At the same time, a valve opening command or a valve closing command is output to the gate-in valve 2 and the gate-out valve 3 to control the opening and closing of the valves 2 and 3.

  When the wheel cylinder pressure is increased by driving the pump P during the execution of the brake assist (build-up) control, the gate-in valve 2 is opened from the normal control state shown in FIG. C brake fluid is sucked up by the pump P from the pipe line 11 and supplied from the pipe line 12 to the wheel cylinder W / C. At the same time, the gate-out valve 3 is closed to prevent the brake fluid from returning from the wheel cylinder W / C to the master cylinder M / C via the conduit 13. On the other hand, when reducing the wheel cylinder pressure during the execution of the build-up control, the pump cylinder P is stopped, the gate-in valve 2 is closed, and the gate-out valve 3 is opened at the same time. The brake fluid is returned to the master cylinder M / C through the conduit 13.

[Brake assist control processing]
FIG. 4 is a flowchart showing a flow of a brake assist control process executed by the brake ECU 32 of the first embodiment. Each step will be described below. This calculation process is repeatedly executed every predetermined calculation cycle.

  In step S1, the estimated master pressure calculation unit 32a determines whether the driver is stepping on the brake pedal BP based on the master pressure from the master cylinder pressure sensor. If yes, then go to step S2, if no, go to return.

  In step S2, the estimated master pressure calculation unit 32a determines whether or not the brake assist execution condition is satisfied. If yes, then go to step S3, if no, go to return. Here, when the master pressure is within a predetermined range, the brake assist execution condition is determined to be a brake assist execution condition by determining that the driver is making a constant stepping.

  In step S3, the estimated master pressure calculation unit 32a and the base pressure calculation unit 32b perform the base pressure calculation process shown in FIG. 5, and the process proceeds to step S4. The base pressure calculation process will be described later.

  In step S4, the base pressure calculation unit 32b performs an end process shown in FIG. 7, and the process proceeds to step S5. The termination process will be described later.

  In step S5, the target pressure calculation unit 32c performs a gain calculation process shown in FIG. 8, and the process proceeds to step S6. The gain calculation process will be described later.

  In step S6, the target pressure calculation unit 32c performs the target pressure calculation process shown in FIG. 9 and proceeds to return. The target pressure calculation process will be described later.

[Base pressure calculation processing]
FIG. 5 is a flowchart illustrating the flow of the base pressure calculation process executed by the estimated master pressure calculation unit 32a and the base pressure calculation unit 32b according to the first embodiment. Each step will be described below.

  In step S31, it is determined whether or not an end process is currently being performed based on whether or not an end flag is set. If YES, this control is terminated, and if NO, the process proceeds to step S32.

  In step S32, the estimated master pressure calculation unit 32a calculates the estimated master pressure, and the base pressure calculation unit 32b calculates the absolute value of the deviation between the calculated master pressure and the base pressure calculated in the previous calculation cycle. It is determined whether or not it is smaller than a preset base pressure fluctuation threshold. If YES, the process moves to step S34, and if NO, the process moves to step S33. The “base pressure fluctuation threshold value” is set to a value larger than the fluctuation amount of the estimated master pressure accompanying the pulsation of the pump P.

Here, the estimated master pressure is calculated by calculating the pressure increase amount of the pump P from the drive command output to the pump P from the drive control unit 32d and referring to the map shown in FIG. 6 from the calculated pump pressure increase amount. A master pressure change amount that is a cylinder pressure change amount is calculated. Then, the estimated master pressure is calculated by adding the master pressure and the master pressure change amount.
Estimated master pressure = master pressure + master pressure change (pump increase)

  In step S33, the base pressure calculation unit 32b determines whether the value obtained by subtracting the estimated master pressure from the base pressure is negative. If YES, the process proceeds to step S35, and if NO, the process proceeds to step S36.

  In step S34, the base pressure calculation unit 32b holds the base pressure at the previous value calculated in the previous control cycle, and the process proceeds to step S37.

In step S35, the base pressure calculation unit 32b calculates the amount of change (increase) in the estimated master pressure from the difference between the estimated master pressure calculated in step S32 and the previous value of the estimated master pressure calculated in the previous control cycle. Then, the base pressure is calculated by adding the base pressure calculated in the previous control cycle and the estimated master pressure change amount.
Base pressure = base pressure previous value + estimated master pressure change amount Here, the initial value of the base pressure previous value is the master pressure detected at the start of the brake assist control.

  In step S36, the base pressure calculation unit 32b sets an end control flag, and the process proceeds to step S37.

In step S37, the master pressure is compared with the base pressure to determine whether the master pressure is smaller than the base pressure. If YES, this control is terminated, and if NO, the process proceeds to step S38.
In step S38, the master pressure is set to the base pressure, and this control is terminated.

  In the base pressure calculation process, even if the base pressure deviates from the value corresponding to the actual master pressure due to sensor noise or the like, the base pressure is The target pressure is selected by selecting high of the calculated target pressure and master pressure.

[End processing]
FIG. 7 is a flowchart showing a flow of termination processing executed by the base pressure calculation unit 32b according to the first embodiment. Each step will be described below.

  In step S41, it is determined whether an end process flag is set. If YES, the process proceeds to step S42, and if NO, this control is terminated.

  In step S42, it is determined whether or not the master pressure change amount is larger than the estimated master pressure change amount due to the pump pressure increase / decrease change. If YES, the process proceeds to step S43, and if NO, the process proceeds to step S44.

In step S43, the base pressure is obtained from the added value of the previous base pressure value and the change in master pressure due to the driver's operation, and the process proceeds to step S45. Here, the “master pressure fluctuation due to the driver's operation” can be obtained by subtracting the fluctuation due to the pump pressure increase change (or the pressure reduction change) from the master pressure fluctuation.
Base pressure = Base pressure previous value + Master pressure fluctuation due to driver's operation

In step S44, the base pressure is set to a value obtained by subtracting the maximum value of the estimated master pressure change amount from the previous base pressure value, and the process proceeds to step S45.
Base pressure = Base pressure previous value−Maximum value of estimated master pressure change amount Here, the “maximum value of estimated master pressure change amount” is the maximum decrease amount of the estimated master pressure calculated during execution of the end control. .
In step S45, the end flag is reset and this control is ended.

[Gain calculation process]
FIG. 8 is a flowchart showing the flow of gain calculation processing executed by the target pressure calculation unit 32c of the first embodiment, and each step will be described below.

  In step S51, it is determined whether an end flag is set. If YES, the process proceeds to step S52, and if NO, this control is terminated.

  In step S52, a first gain UP_GAIN1 for calculating the target pressure is calculated, and the process proceeds to step S53. Here, as shown in the frame of step S52 in FIG. 8, the first gain UP_GAIN1 sets a counter that starts counting from the start of the brake assist control, and the counter value of this counter reaches a predetermined value (predetermined time). Until the counter value is set, the higher the counter value, the larger the value. When the counter value exceeds a predetermined value, the higher the counter value, the lower the value. Here, the predetermined value is a time slightly shorter than the continuous driving time allowed by the motor M of the HU 31.

  In step S53, the second gain UP_GAIN2 for calculating the target pressure is calculated, and this control is terminated. Here, as shown in the frame of step S53 in FIG. 8, the second gain UP_GAIN2 is constant until the driver's required deceleration exceeds a predetermined value, and when the required deceleration exceeds the predetermined value, Set so that the higher the required deceleration, the lower the value. In the first embodiment, the driver's requested deceleration is calculated by multiplying a base pressure, which is an estimated value of the driver's brake operation amount, by a predetermined gain.

[Target pressure calculation processing]
FIG. 9 is a flowchart showing the flow of the target pressure calculation process executed by the target pressure calculation unit 32c of the first embodiment, and each step will be described below.

In step S61, the base pressure calculated in step S3 or step S4 is multiplied by the value obtained by multiplying the first gain UP_GAIN1 and the second gain UP_GAIN2 calculated in step S5 as a final gain, thereby obtaining the target pressure. Calculate and move to step S62.
Target pressure = base pressure x gain

  In step S62, the target pressure calculated in step S61 is compared with the master pressure to determine whether or not the target pressure is smaller than the master pressure. In the case of YES, this control is finished, and in the case of NO, the master pressure is set to the target pressure, and this control is finished.

[Second gain calculation logic]
(Calculation Example 1)
PUP1 indicated by a broken line in FIG. 10 is a pressure increase amount when the pressure is increased with a constant gain with respect to the required deceleration. On the other hand, the maximum pressure increase amount (PUP_Max2) based on the allowable pressure increase amount of HU31 or the amount of brake pedal BP sucked in (the brake pedal BP stroke increase amount accompanying the brake assist) is indicated by the solid line PUP2 It is.

  Therefore, when setting the second gain UP_GAIN2 such as GAIN2 in FIG. 11, the sign (±) of the slope of the final deceleration (deceleration corresponding to the target pressure and target deceleration) from PUP2 is not reversed. (FIG. 12) GAIN2 is calculated.

(Calculation example 2)
The case where the second gain UP_GAIN2 is set to PUP3 indicated by a one-dot chain line in FIG. 10 will be described. In FIG. 13, the maximum final deceleration is limited based on the allowable pressure increase amount of the HU 31 or the suction amount of the brake pedal BP (G_max3). To do.

  Next, when setting the second gain UP_GAIN2 like GAIN3 in FIG. 11, GAIN3 is calculated so that the sign (±) of the slope of the final deceleration does not reverse from P3 to G_max3 in FIG. 13 (FIG. 12).

Using the method of calculation example 1 or 2 above, by setting the second gain UP_GAIN2 so that the slope of the final deceleration does not reverse ±, the final deceleration increases when the driver's required deceleration increases. When the required deceleration decreases, the final deceleration decreases. For this reason, it is possible to prevent a mismatch between the direction of change in the required deceleration and the direction of change in the deceleration of the vehicle, so that the driver does not feel uncomfortable.
By setting the second gain UP_GAIN2 obtained above, the change over time in the pressure increase ratio is as shown in FIG.

Next, the operation will be described.
[Pressure increase ratio suppression when required deceleration is high]
In the hydraulic circuit of the HU 31 according to the first embodiment, when the target pressure is increased by the brake assist control, the gate-out valve 3 is closed and the gate-in valve 2 is opened, and the pump P is driven according to the target pressure. As a result, the brake fluid in the master cylinder M / C is sucked and pressurized by the pump P via the conduit 11, and the brake fluid is supplied from the conduit 12 to the wheel cylinder W / C.

  Here, in the above-mentioned Patent Document 1, as a build-up control for obtaining a feeling of increase in braking in the latter half of braking, the pressure increase amount of the brake assist is set at a constant ratio (a constant gain) corresponding to the brake pedal stroke amount with time. It is increasing. For this reason, when the driver's required braking force is high, the wheel cylinder pressure is unnecessarily increased and the braking force becomes excessive, and the wheel tends to be locked and the durability of the HU 31 may be lowered.

  Further, in the closed hydraulic circuit such as the HU 31 of the first embodiment, when the driver's required deceleration is high, the amount of brake fluid that is discharged by the pump P from the master cylinder M / C to the wheel cylinder W / C becomes excessive. As a result, the stroke amount of the brake pedal BP greatly fluctuates, so-called pedal suction amount increases, which gives the driver a sense of incongruity.

  Here, the “closed hydraulic circuit” means that the brake fluid is drained from the master cylinder M / C and supplied to the wheel cylinder W / C during brake assist, and the brake fluid supplied to the wheel cylinder W / C is supplied to the master cylinder M / C. A hydraulic circuit that returns to the reservoir 16 via C. For this closed hydraulic circuit, the brake fluid can be drained from the reservoir and supplied to the wheel cylinder during brake assist, and the brake fluid supplied to the wheel cylinder can be returned directly to the reservoir without going through the master cylinder. The circuit is called “open hydraulic circuit”.

  On the other hand, in the first embodiment, when the driver's required deceleration is high (exceeding a predetermined value), the second gain UP_GAIN2 is decreased as the required deceleration is higher, so that the target pressure for the required deceleration is reduced. Increase rate, that is, the pressure increase rate of the target deceleration with respect to the required deceleration can be suppressed.

  For this reason, it is possible to suppress an excessive braking force and a pedal suction amount when the required deceleration is high. Even when the increase in the target pressure is suppressed in a state where the required braking force is high, a sufficient deceleration can be obtained according to the required braking force, so that there is no possibility that the vehicle deceleration will be insufficient.

  In the first embodiment, the pressure increase amount of the pump P is set so as not to exceed the allowable pressure increase amount of the HU 31. In the above prior art, if the master cylinder pressure sensor fails and it is erroneously determined that the master cylinder pressure has become high, a pressure increase command exceeding the permissible pressure of the hydraulic unit is output, which reduces the durability of the hydraulic unit. Accompany. On the other hand, in the first embodiment, even when the master cylinder pressure sensor 42 has failed or when the detected value of the master cylinder pressure sensor 42 is a value indicating high pressure, the pressure increase beyond the tolerance of the HU 31 is achieved. Since no command is output, the durability of the HU 31 can be improved.

Next, the effect will be described.
In the braking force control apparatus according to the first embodiment, the following effects can be obtained.

  (1) Base pressure calculation unit 32a that detects the driver's required deceleration, HU31 and wheel cylinder W / C that generate braking force, and large first gain UP_GAIN1 and second gain UP_GAIN2 over time A target pressure calculation unit 32c that calculates and calculates a target deceleration based on the requested deceleration and the first gain UP_GAIN1 and the second gain UP_GAIN2, and a brake controller 32 that controls the HU 31 based on the target deceleration In the braking force control apparatus, the target pressure calculation unit 32c decreases the second gain UP_GAIN2 as the required deceleration increases. Thereby, it is possible to suppress excessive braking force when the driver's required deceleration is high.

  (2) When the braking time exceeds the predetermined time, the target pressure calculation unit 32c drives the motor M within the continuous driving time allowed by the HU 31 in order to decrease the first gain UP_GAIN1 as the braking time increases. Unit protection can be achieved.

  (3) The target deceleration is set based on the driver's required deceleration and the gain (first gain UP_GAIN1 x second gain UP_GAIN2) that increases with the passage of time, and the vehicle is based on the set target deceleration. In the braking force control method for controlling the braking force, the second gain UP_GAIN2 is corrected to be smaller as the required deceleration is higher. Thereby, it is possible to suppress excessive braking force when the driver's required deceleration is high.

The second embodiment is an example in which the ratio of the target deceleration to the required deceleration is changed according to the vehicle speed.
[Gain calculation processing]
FIG. 15 is a first gain setting map of the second embodiment. In the second embodiment, the map of FIG. 15 is used in step S52 of the gain calculation process shown in FIG. 8, and the lower the vehicle speed, the first gain UP_GAIN1. Make it smaller.

Next, the operation will be described.
Since the deceleration control is severe in the low vehicle speed range, if the ratio of the pressure increase amount is large, the deceleration greatly varies due to a slight difference in the brake operation amount, and the controllability of the vehicle deteriorates. Therefore, in the second embodiment, the controllability of the vehicle in the low vehicle speed range can be improved by decreasing the ratio of the pressure increase amount as the vehicle speed is lower.

  Further, since the quietness in the passenger compartment is higher in the low vehicle speed range than in the high vehicle speed range, the operating sound and vibration of the pump P and each valve of the HU 31 are easily noticed by the driver. Therefore, in the second embodiment, it is possible to reduce the sound vibration in the low vehicle speed range by reducing the ratio of the pressure increase amount as the vehicle speed is lower.

Next, the effect will be described.
The braking force control apparatus according to the second embodiment has the following effects in addition to the effects (1) and (3) of the first embodiment.

  (4) A wheel speed sensor 34 for detecting the vehicle speed is provided, and the target pressure calculation unit 32c reduces the first gain UP_GAIN1 as the vehicle speed decreases. Can be planned.

The third embodiment is an example in which the ratio of the target deceleration to the required deceleration is set according to the lateral acceleration.
[Gain calculation process]
FIG. 16 is a first gain setting map of the third embodiment. In the third embodiment, the map of FIG. 16 is used in step S52 of the gain calculation process shown in FIG. Decrease UP_GAIN1.

Next, the operation will be described.
During turning, the driver loosens the brake to drive the vehicle on the target driving line according to the turning state (lateral acceleration, etc.). Getting worse. In the third embodiment, therefore, the controllability of the vehicle during turning can be improved by decreasing the ratio of the pressure increase amount as the lateral acceleration is higher.

Next, the effect will be described.
The braking force control apparatus according to the third embodiment has the following effects in addition to the effects (1) and (3) of the first embodiment.

  (5) The yaw rate / lateral G sensor 32 that detects the lateral acceleration acting on the vehicle is provided, and the target pressure calculation unit 32c decreases the first gain UP_GAIN1 as the lateral acceleration increases. Improvements can be made.

The fourth embodiment is an example in which the ratio of the target deceleration to the required deceleration is set according to the lateral force.
[Gain calculation process]
FIG. 17 is a first gain setting map of the fourth embodiment. In the fourth embodiment, the steering wheel (front wheels FL, FR) is used in step S52 of the gain calculation process shown in FIG. 8 using the map of FIG. The first gain UP_GAIN1 is decreased as the tire lateral force acting on is increased.
Here, the tire lateral force acting on the front wheels FL and FR can be estimated according to the vehicle speed obtained from the steering angle detected by the steering angle sensor 39 and the respective wheel speeds detected by the wheel speed sensor 34. That is, the tire lateral force acting on the front wheels FL, FR usually has a characteristic that it increases as the steering angle increases and increases as the vehicle speed decreases.

Next, the operation will be described.
During turning, the driver loosens the brake to drive the vehicle on the target driving line according to the turning state (lateral acceleration, etc.). Getting worse. Therefore, in Example 4, the controllability of the vehicle during turning can be improved by decreasing the ratio of the pressure increase amount as the tire lateral force increases.

  Further, if the tire longitudinal force (braking force) is increased when the tire lateral force is large, the tire resultant force jumps out of the friction circle and the tire enters a non-linear region, so that the tire grip force decreases. Here, the “friction circle” refers to a circle having a tire lateral force on the horizontal axis, a tire longitudinal force on the vertical axis, and a radius obtained by multiplying the wheel load by the road surface μ. The non-linear region refers to a region of the tire slip angle where the magnitude of the response of the tire lateral force to the tire slip angle has a non-linear relationship.

  In contrast, the greater the tire lateral force, the smaller the rate of pressure increase, so that the tire longitudinal force can be kept small, so the tire resultant force can be prevented from jumping out of the friction circle, and the tire grip force can be maintained. it can.

Next, the effect will be described.
The braking force control apparatus according to the fourth embodiment has the following effects in addition to the effects (1) and (3) of the first embodiment.

  (6) The target pressure calculation unit 32c reduces the first gain UP_GAIN1 as the lateral force acting on the front wheels FL and FR increases, so that both control of the vehicle during turning and maintenance of tire grip force are to be achieved. Can do.

The fifth embodiment is an example in which the ratio of the target deceleration to the required deceleration is set according to the steering angle.
[Gain calculation process]
FIG. 18 is a first gain setting map of the fifth embodiment. In the fifth embodiment, in step S52 of the gain calculation process shown in FIG. 8, the map of FIG. 18 is used, and the first gain UP_GAIN1 increases as the steering angle increases. Make it smaller.

Next, the operation will be described.
During turning, the driver loosens the brake to drive the vehicle on the target driving line according to the turning state (lateral acceleration, etc.). Getting worse. Therefore, in the fifth embodiment, the controllability of the vehicle at the time of turning can be improved by decreasing the ratio of the pressure increase amount as the steering angle is higher.

Next, the effect will be described.
The braking force control apparatus according to the fifth embodiment has the following effects in addition to the effects (1) and (3) of the first embodiment.

  (7) The steering angle sensor 39 that detects the steering angle of the steering wheel is provided, and the target pressure calculation unit 32c decreases the first gain UP_GAIN1 as the steering angle increases, so that the controllability of the vehicle during turning is improved. Can do.

The sixth embodiment is an example in which the ratio of the target deceleration to the required deceleration is set according to the road surface μ.
[Gain calculation process]
FIG. 19 is a first gain setting map of the sixth embodiment. In the sixth embodiment, the map of FIG. 19 is used in step S52 of the gain calculation process shown in FIG. Decrease UP_GAIN1.

  Here, the brake controller 32 calculates the slip ratio of the drive wheel from the drive wheel speed detected by the wheel speed sensor 34 and the pseudo vehicle speed (average value of the driven wheel speed), and estimates the road surface μ based on the slip ratio. (Corresponding to road surface μ estimation means).

Next, the operation will be described.
Since the friction circle of the tire is small on the low μ road, if the ratio of the pressure increase amount is increased, the tire resultant force tends to jump out of the friction circle. Therefore, in Example 6, the smaller the road surface μ is, the smaller the ratio of the pressure increase amount is, so that the tire longitudinal force can be kept small. Therefore, the tire resultant force can be prevented from jumping out of the friction circle, and the tire grip force Can be maintained. Furthermore, since it can suppress that tire resultant force jumps out of a friction circle, the operating frequency of ABS reduces, Therefore The durability of HU31 can be improved.

Next, the effect will be described.
In addition to the effects (1) and (3) of the first embodiment, the braking force control device of the sixth embodiment has the following effects.

  (8) A road surface μ estimation means (brake controller 32) for estimating the road surface μ is provided, and the target pressure calculation unit 32c decreases the first gain UP_GAIN1 as the road surface μ is lower. Improvements can be made. Moreover, durability improvement of HU31 can be aimed at by the operating frequency of ABS falling.

Example 7 is an example in which the ratio of the target deceleration to the required deceleration is set according to the relationship between the resultant force of the steering wheel and the friction circle.
[Gain calculation process]
FIG. 20 is a first gain setting map of the seventh embodiment. In the seventh embodiment, the map of FIG. 20 is used in step S52 of the gain calculation process shown in FIG. The first gain UP_GAIN1 is decreased as the resultant force and lateral force are closer to the circumference of the friction circle.
Here, the road surface μ can be estimated by the method shown in the sixth embodiment. The wheel load can be estimated from vehicle specifications, vehicle deceleration, yaw rate, and the like.

Next, the operation will be described.
Since the friction circle of the tire is small on the low μ road, if the ratio of the pressure increase amount is increased, the tire resultant force tends to jump out of the friction circle. Therefore, in Example 7, by reducing the ratio of the pressure increase amount as the tire resultant force is closer to the circumference of the friction circle, the tire resultant force can be prevented from jumping out of the friction circle, and the tire grip force can be maintained. . Furthermore, since it can suppress that tire resultant force jumps out of a friction circle, the operating frequency of ABS reduces, Therefore The durability of HU31 can be improved.

Next, the effect will be described.
In addition to the effects (1) and (3) of the first embodiment, the braking force control device of the seventh embodiment has the following effects.

  (9) The target pressure calculation unit 32c takes the tire lateral force on the horizontal axis, the tire longitudinal force on the vertical axis, and the road surface μ as the wheel load. The closer to the circumference of the friction circle whose radius is the multiplied value, the smaller the first gain UP_GAIN1 is. For this reason, it is possible to improve the controllability of the vehicle when the tire resultant force is close to the circumference of the friction circle. Moreover, durability improvement of HU31 can be aimed at by the operating frequency of ABS falling.

The eighth embodiment is an example in which the ratio of the target deceleration to the required deceleration is set according to the operation speed of the brake pedal.
[Gain calculation process]
FIG. 21 is a first gain setting map of the eighth embodiment. In the eighth embodiment, the map of FIG. 21 is used in step S52 of the gain calculation process shown in FIG. The first gain UP_GAIN1 is decreased.
The brake controller 32 calculates the operation speed of the brake pedal BP from the amount of change in the required deceleration per time (corresponding to the operation speed detection means).

Next, the operation will be described.
If the ratio of the pressure increase amount is increased while the driver slowly depresses the brake pedal BP, the driver feels uncomfortable. Therefore, in the eighth embodiment, when the driver's brake pedal BP is depressed at a slow speed, the ratio of the pressure increase amount is kept small so that the pedaling speed and the vehicle deceleration change coincide with each other. Can be prevented.

Next, the effect will be described.
The braking force control apparatus according to the eighth embodiment has the following effects in addition to the effects (1) and (3) of the first embodiment.

  (10) An operation speed detecting means (brake controller 32) for detecting the operation speed of the brake pedal BP is provided, and the target pressure calculation unit 32c is configured to reduce the first gain UP_GAIN1 as the operation speed is lower. It is possible to prevent the braking feeling from deteriorating when the stepping speed is slow.

(Other examples)
The best mode for carrying out the present invention has been described with reference to the respective embodiments based on the drawings. However, the specific configuration of the present invention is not limited to the respective embodiments, and departs from the gist of the present invention. Even if there is a design change or the like within a range not to be included, it is included in the present invention.

For example, a configuration in which two or more first gain setting methods shown in each embodiment are combined may be adopted. In that case, a value obtained by multiplying the first gains calculated by the respective methods may be used as the final first gain.
Further, the present invention is not limited to the hydraulic brake shown in the embodiment but can be applied to a vehicle having a configuration in which brake assist is performed using a regenerative brake by an electric motor.

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. It is a buildup control block diagram of brake ECU32. 3 is a flowchart showing a flow of a brake assist control process executed by the brake ECU 32 of the first embodiment. It is a flowchart which shows the flow of the base pressure calculation process performed by the estimation master pressure calculating part 32a and the base pressure calculating part 32b of Example 1. FIG. It is a setting map of the master pressure change amount with respect to the pump pressure increase amount. It is a flowchart which shows the flow of the completion | finish process performed in the base pressure calculating part 32b of Example 1. FIG. It is a flowchart which shows the flow of the gain calculation process performed in the target pressure calculating part 32c of Example 1. FIG. It is a flowchart which shows the flow of the target pressure calculation process performed in the target pressure calculating part 32c of Example 1. FIG. FIG. 6 is a relationship diagram between a requested deceleration and a pressure increase amount showing a second gain setting method according to the first embodiment. 6 is a second gain setting map according to the required deceleration of the first embodiment. FIG. 6 is a relationship diagram between a requested deceleration and a final deceleration in Calculation Example 1; FIG. 10 is a relationship diagram between a requested deceleration and a final deceleration in Calculation Example 2. It is a figure which shows the time-dependent change of the pressure increase ratio of Example 1. FIG. 6 is a first gain setting map according to the second embodiment. 10 is a first gain setting map of Example 3. FIG. 10 is a first gain setting map of Embodiment 4. FIG. 10 is a first gain setting map of Embodiment 5. FIG. 18 is a first gain setting map of Embodiment 6. FIG. 18 is a first gain setting map of Example 7. FIG. 18 is a first gain setting map according to an eighth embodiment.

Explanation of symbols

AP accelerator pedal
BP brake pedal
P pump
M / C master cylinder
W / C Wheel cylinder 2 Gate-in valve 3 Gate-out valve 4 Solenoid-in valve 5 Solenoid-out valve 6-10 Check valves 11-18 Pipe line 31 Hydraulic unit (braking force generating means)
32 Brake controller (braking force control means, road surface μ estimation means, operation speed detection means)
32a Estimated master pressure calculation unit 32b Base pressure calculation unit (required deceleration detection means)
32c Target pressure calculation unit (gain calculation means, target deceleration calculation means, gain correction means)
32d Drive control unit 33 Yaw rate / lateral G sensor (lateral acceleration detecting means)
34 Wheel speed sensor (vehicle speed detection means)
37 Engine 38 Automatic transmission 39 Steering angle sensor (steering angle detection means)
41 Electric booster 42 Master cylinder pressure sensor

Claims (8)

A braking force control device that performs brake assist control to increase the braking force with the passage of time when it is determined that the driver is depressing the brake pedal at a certain level,
Requested deceleration detection means for detecting the requested deceleration of the driver;
Braking force generating means for generating braking force;
First gain calculating means for calculating a first gain that increases with the passage of time;
Lateral acceleration detection means for detecting lateral acceleration acting on the vehicle;
A first gain correction means for the lateral acceleration corrected A higher, the first gain small,
Second gain calculating means for calculating a second gain that decreases as the required deceleration increases when the required deceleration exceeds a predetermined value;
Target deceleration calculation means for calculating a target deceleration by multiplying the required deceleration by the first gain corrected by the first gain correction means and the second gain;
Braking force control means for controlling the braking force generation means based on the target deceleration;
A braking force control device comprising: A braking force control device that performs brake assist control to increase the braking force with the passage of time when it is determined that the driver is depressing the brake pedal at a certain level,
Requested deceleration detection means for detecting the requested deceleration of the driver;
Braking force generating means for generating braking force;
First gain calculating means for calculating a first gain that increases with the passage of time;
A first gain correction means for correcting small lateral force create greater, the first gain acting on the steering wheel,
Second gain calculating means for calculating a second gain that decreases as the required deceleration increases when the required deceleration exceeds a predetermined value;
Target deceleration calculation means for calculating a target deceleration by multiplying the required deceleration by the first gain corrected by the first gain correction means and the second gain;
Braking force control means for controlling the braking force generation means based on the target deceleration;
A braking force control device comprising: A braking force control device that performs brake assist control to increase the braking force with the passage of time when it is determined that the driver is depressing the brake pedal at a certain level,
Requested deceleration detection means for detecting the requested deceleration of the driver;
Braking force generating means for generating braking force;
First gain calculating means for calculating a first gain that increases with the passage of time;
Steering angle detection means for detecting the steering angle of the steering wheel;
First gain correction means for correcting the first gain to be smaller as the steering angle is larger;
Second gain calculating means for calculating a second gain that decreases as the required deceleration increases when the required deceleration exceeds a predetermined value;
Target deceleration calculation means for calculating a target deceleration by multiplying the required deceleration by the first gain corrected by the first gain correction means and the second gain;
Braking force control means for controlling the braking force generation means based on the target deceleration;
A braking force control device comprising: A braking force control device that performs brake assist control to increase the braking force with the passage of time when it is determined that the driver is depressing the brake pedal at a certain level,
Requested deceleration detection means for detecting the requested deceleration of the driver;
Braking force generating means for generating braking force;
First gain calculating means for calculating a first gain that increases with the passage of time;
A circle of friction circles, where the resultant force of the longitudinal force and lateral force that can be generated by the steered wheel is the tire lateral force on the horizontal axis, the tire longitudinal force on the vertical axis, and the wheel load multiplied by the road surface μ as the radius A first gain correction means for correcting the first gain to be smaller as the circumference is closer;
Second gain calculating means for calculating a second gain that decreases as the required deceleration increases when the required deceleration exceeds a predetermined value;
Target deceleration calculation means for calculating a target deceleration by multiplying the required deceleration by the first gain corrected by the first gain correction means and the second gain;
Braking force control means for controlling the braking force generation means based on the target deceleration;
A braking force control device comprising: In the braking force control device according to any one of claims 1 to 4,
Vehicle speed detection means for detecting the vehicle speed,
The braking force control apparatus according to claim 1, wherein the first gain correction means corrects the first gain to be smaller as the vehicle speed detected by the vehicle speed detection means is lower. The braking force control apparatus according to any one of claims 1 to 5,
A road surface μ estimation means for estimating the road surface μ is provided,
The braking force control apparatus according to claim 1, wherein the first gain correction unit decreases the first gain as the road surface μ estimated by the road surface μ estimation unit decreases. The braking force control apparatus according to any one of claims 1 to 6,
The braking force generating means includes an actuator for generating a braking force,
When the braking time exceeds the continuous drive time allowed by the actuator, the first gain correction means reduces the first gain as the braking time becomes longer. The braking force control apparatus according to any one of claims 1 to 7,
The braking force generating means includes a master cylinder that generates a master cylinder pressure corresponding to a driver's brake operation amount, a hydraulic pressure sensor that generates an output signal corresponding to the master cylinder pressure, and a master cylinder pressure provided in each wheel. A wheel cylinder that generates a braking force in accordance with the pump, and a pump that sucks in the brake fluid of the master cylinder from a fluid pressure passage that connects the master cylinder and the wheel cylinder;
The braking force control means supplies the pump discharge pressure to the wheel cylinder according to the output signal as the brake assist control, and supplies brake fluid of the wheel cylinder from the hydraulic pressure passage to the master cylinder. Implement the return control,
Estimated master pressure calculating means for calculating an estimated master pressure that is an estimated value of the master cylinder pressure from the output signal and the pressure increase amount of the pump,
The required deceleration detecting means calculates the required deceleration based on the output signal at the start of the brake assist control and the amount of change in the estimated master pressure.

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