JP2007083960A - Vehicle braking force control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle braking force control device reducing increase of sound oscillation at hill decent control and fade by heat generation by suppressing interference of front and rear wheels with each other in control by appropriately changing a drive force distribution amount, based on deviation of a wheel speed and a target wheel speed. <P>SOLUTION: The vehicle braking force control device obtains desired braking force by controlling a liquid pressure of a wheel cylinders provided on each wheel in a four-wheel drive vehicle, and is provided with: a liquid pressure control unit for controlling a liquid pressure of the wheel cylinder; a drive force distribution means for distributing drive forces of the front wheel and the rear wheel; and a drive force distribution control unit for controlling a distribution amount in the drive force distribution means. The liquid pressure control unit controls the liquid pressures of the respective wheel cylinders, and the drive force distribution control unit operates the distribution amount in the drive force distribution means, based on the deviation of the wheel speed and the target wheel speed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle braking force control device including a hill decent (HDC) system that realizes stable running by controlling the braking force of each wheel on a downhill.

  Conventionally, in a vehicle braking force control device equipped with a hill decent (HDC) system, the hydraulic pressure command value is calculated by PID control so that the actual wheel speed follows the target vehicle speed according to the accelerator opening. Yes. Here, in the case of the so-called X piping system that connects the diagonal wheels of each wheel, when the rear wheel is depressurized when the front wheel is pressurized, the hydraulic oil returned from the rear wheel to the reservoir is pumped out to increase the front wheel pressure. Therefore, the control of the front and rear wheels interferes with each other, and independent control of the front and rear wheels is difficult. On the other hand, when the front and rear wheels are simultaneously pressurized, the responsiveness is deteriorated.

Therefore, in the technique described in Patent Document 1, accurate control is performed by maintaining the target hydraulic pressure of the rear wheel at zero and performing hydraulic pressure control only on the front wheel.
Japanese National Patent Publication No. 10-507145

  However, the above-described prior art has a problem in that since the braking is performed only with the front wheels, a fading phenomenon is likely to occur due to an increase in operating noise and heat generation. In addition, when the vehicle is going downhill, the braking force of the rear wheel, which requires a large part of the weight, is not generated, resulting in insufficient braking force.

  The present invention has been made paying attention to the above-mentioned problems, and the purpose of the present invention is to install a hill decent system that suppresses interference between front and rear wheels during control and reduces fade due to increased operating noise and heat generation. An object of the present invention is to provide a vehicle braking force control device.

  In order to achieve the above object, the present invention has wheel speed detection means for detecting the wheel speed of each wheel in a four-wheel drive vehicle, and controls the hydraulic pressure of a wheel cylinder provided in each wheel. A vehicle braking force control device that obtains a desired braking force in the vehicle, wherein the vehicle braking force control device is a fluid pressure control unit that controls the fluid pressure of the wheel cylinder, and a drive that distributes the driving force of the front and rear wheels. Force distribution means and a driving force distribution control unit for controlling the amount of distribution in the driving force distribution means, the hydraulic pressure control unit controls the hydraulic pressure of each wheel cylinder, the driving force distribution control unit is The distribution amount in the driving force distribution means is calculated based on the deviation between the wheel speed and the target wheel speed.

  Therefore, the driving force distribution amount is calculated based on the deviation between the wheel speed and the target wheel speed, and by appropriately changing the driving force distribution amount, the interference between the front and rear wheels during control is suppressed, and the sound during hill decent control is controlled. It is possible to provide a vehicle braking force control device in which fade due to increased vibration or heat generation is reduced.

  Hereinafter, the best mode for realizing a vehicle braking force control device of the present invention will be described based on an embodiment shown in the drawings.

[System configuration of vehicle braking force control device]
(Brake system)
The first embodiment will be described with reference to FIGS. FIG. 1 is a configuration diagram of a brake system in a four-wheel drive vehicle equipped with the vehicle braking force control device of the present application. The brake system of the vehicle braking force control device includes a brake ECU 1 (hydraulic pressure control unit), a hydraulic pressure unit 2, a G sensor 3a, and a wheel speed sensor 4.

  The brake ECU 1 performs PID control on the basis of the wheel speed VW (FL to RR) detected by the wheel speed sensor 4 and the vehicle longitudinal acceleration Gy detected by the G sensor 3, and causes the hydraulic unit 2 to move the front and rear wheels FL. Output braking force command to ~ RR. Based on this command, the hydraulic unit 2 optimally controls the braking force of the wheels FL to RR.

  Further, the PID control amounts P_HDC (proportional component), I_HDC (integral component), and D_HDC (differential component) of the wheel speed VW (FL to RR) are output to the driving force distribution ECU 5 (see FIG. 2) that calculates the front and rear wheel driving force. Is done. The longitudinal acceleration Gy may be a differential value of the vehicle speed and is not particularly limited.

(Front and rear wheel drive force distribution system)
FIG. 2 is a configuration diagram of a front and rear wheel driving force distribution system in a four-wheel drive vehicle equipped with the vehicle braking force control device of the present application. The front and rear wheel driving force distribution system includes a driving force distribution ECU 5 (driving force distribution control unit), a transmission 6, a transfer 7, a driving force distribution device 8, front and rear and lateral G sensors 3a and 3b, and a wheel speed sensor 4.

  The driving force of the engine is increased or decreased by the transmission 6 and transmitted to the front differential 9F and the rear differential 9R via the transfer 7 and the center shaft 9. Further, a driving force distribution device 8 is provided between the center shaft 9 and the rear differential 9R, and by changing the fastening force T (driving force distribution amount) between the center shaft 9 and the rear differential 9R, the front wheels FL, FR The driving force distribution of the rear wheels RL and RR is changed.

  The driving force distribution ECU 5 calculates the driving force distribution amount of the front and rear wheels based on the PID control amounts P_HDC, I_HDC, and D_HDC of the wheel speed VW (FL to RR), the longitudinal acceleration Gy, the lateral acceleration Gx, and the wheel speed deviation VWSA. To the driving force distribution device 8. Based on this, the driving force distribution device 8 changes the fastening force T. If the fastening force T is increased, the driving force transmission between the front wheels FL, FR and the rear wheels RL, RR is increased, and if the fastening force T is decreased, the driving force transmission between the front and rear wheels is decreased.

[Hydraulic circuit]
FIG. 3 is a hydraulic circuit diagram of the hydraulic unit 2. The hydraulic unit 2 is a tandem hydraulic circuit having P and S systems. The pump P is a one-way pump and is driven by a motor M. The suction side of the pump P is connected to the master cylinder 20 through oil passages 51 and 52 and in-side gate valves 21 and 22, and the discharge side is connected to each wheel cylinder W / through oil passages 53 to 56 and in-valves 25 to 28. Connect to C (FL to RR).

  The oil passages 53 to 56 are connected to the reservoirs 41 and 42 through the out valves 29 to 32 and the oil passages 57 and 58, respectively, and are connected to the suction side of the pump P together with the oil passages 51 and 52. Further, the pump P side of the in valves 25 to 28 is connected to the master cylinder 20 via the oil passages 61 and 62 and the out side gate valves 23 and 24.

  The out-side gate valves 23 and 24 are provided in parallel with check valves 33 and 34 that prevent backflow to the master cylinder 20. Further, check valves 35 to 38 for preventing backflow to the respective wheel cylinders W / C (FL to RR) are provided in parallel to the in valves 25 to 28, respectively. Further, diaphragms 43 and 44 are provided between the in-side gate valves 21 and 22 and the pump P in the oil passages 51 and 52.

(When pressure is increased)
When the pressure is increased, the in-side gate valves 21 and 22 and the in-valves 25 to 28 are opened, the out valves 29 to 32 are closed, and the pump P is driven. The hydraulic oil is pumped out from the master cylinder 20 by the pump drive, and is introduced into the wheel cylinders W / C (FL to RR) via the oil passages 51 and 52 and the oil passages 53 to 56 to increase the pressure.

(At reduced pressure)
At the time of depressurization, the in valves 25 to 28 are closed, the out valves 29 to 32 are opened, and the working oil of each wheel cylinder W / C (FL to RR) is returned to the reservoirs 41 and 42 to reduce the pressure.

[HDC (Hill Decent System) control basic control processing]
FIG. 4 is a flowchart showing a flow of basic control processing of HDC control. Hereinafter, each step will be described.

  In step S1, it is determined whether the HDC control switch is ON. If YES, the process proceeds to step S100, and if NO, the process proceeds to step S700.

  In step S100, the target wheel speed VMOKU at the time of HDC control is calculated, and the process proceeds to step S200.

  In step S200, a deviation VWSA between the target value VMOKU of the wheel speed VW (FL to RR) used for PID control and the actual value, a differential value VWSAD of this deviation, and an integral value VWSAI are calculated, and the process proceeds to step S300. .

  In step S300, the control amount for the front wheels FL and FR is calculated by PID control, and the process proceeds to step S2. The control amount for the rear wheels RL and RR is determined based on the front and rear G signals from the G sensor 3 instead of the PID control. Further, the driving force distribution of the front and rear wheels is performed by changing the fastening force T of the driving force distribution device 8 (see FIG. 2). The fastening force T is determined based on the PID control amount (PBS_HDC) obtained in step S200.

  In step S2, the magnitude relationship between the control amount (hydraulic pressure) (PBS_HDC) for the front wheels FL and FR obtained in step S300 and the actual hydraulic pressure Pr of the FL and FR wheels is determined. If (PBS_HDC)> Pr, the actual value is satisfied. If the hydraulic pressure is insufficient, the process proceeds to step S4. Otherwise, the process proceeds to step S3.

  In step S3, if (PBS_HDC) <Pr, the actual hydraulic pressure is excessive and the process proceeds to step S600. Otherwise (PBS_HDC) = Pr, the process proceeds to step S700 and the holding control is executed.

  In step S4, the motor M is turned on to prepare for pressure increase, and the process proceeds to step S400.

  In step S400, pressure increase control of the front wheels FL and FR is executed based on the control hydraulic pressure calculated in the PID control, and the process proceeds to step S5.

  In step S500, the pressure reduction control of the front wheels FL and FR is executed based on the control hydraulic pressure calculated in the PID control, and the process proceeds to step S5.

  In step S600, holding control is executed, and the process proceeds to step S5.

  In step S5, it is determined whether the time from the start of control has passed 10 ms. If YES, the process returns to step S1, and if NO, the time measurement is continued.

  In step S6, the motor M is turned off and the control is terminated.

[Target wheel speed calculation control processing]
FIG. 5 is a flowchart showing the flow of target wheel speed calculation control processing. This corresponds to step S100 in the basic control flow of FIG.
In step S101, the target wheel speed VMOKU based on the accelerator opening is calculated from the map, and the process proceeds to step S200 in FIG.

[PID control signal calculation control processing]
FIG. 6 is a flowchart showing the flow of the PID control signal calculation control process. This corresponds to step S200 in the basic control flow of FIG.
In step S201, signals of the initial value VWSA0, the deviation VWSA, the differential value VWSAD of the deviation VWSA and the integral value VWSAI of the deviation between the target value and the actual value of the wheel speed used for PID control are calculated, and the process proceeds to step S300.

Here, each control signal has an initial deviation value VWSA0 = actual wheel speed VW−target wheel speed VMOKU.
Deviation VWSA = VWSA + 1/4 (VW-VWSA)
Deviation differential value VWSAD = (VWSA−30 ms before VWSA) / 30 ms
Deviation integral value VWSAI = VWSA + VWSA before 10 ms
As described above, it is calculated by each formula.

[Control amount calculation control processing]
FIG. 7 is a flowchart showing the flow of control amount calculation control processing. This corresponds to step S300 in the basic control flow of FIG. FIG. 8 is a control amount calculation flow in the conventional example.
(Front wheel control)
In step S301, the control amounts of the front wheels FL and FR are calculated based on the following formulas by PID control, and the final control amount PBSf_HDC is calculated by adding each of them, and the front wheel speeds VW (FL, FR ) Is converged to the target wheel speed VMOKU. The components of the PID control amount are defined as a deviation (proportional) control amount P_HDC, a differential control amount D_HDC, and an integral control amount I_HDC.

Each control amount is calculated by the following formula using gains KP, KD, and KI.
Deviation (proportional) control amount P_HDC = deviation VWSA × KP
Differential control amount D_HDC = deviation differential value VWSAD × KD
Integral control amount I_HDC = deviation integral value VWSAI × KI
Control amount PBSf_HDC = P_HDC + D_HDC + I_HDC

(Rear wheel control)
In the case of a so-called X pipe that connects the FL wheel and the RR wheel and connects the FR wheel and the RL wheel, if the front and rear wheels have different pressure increasing / decreasing commands, such as front wheel pressure increase and rear wheel pressure reduction, The hydraulic oil pumped up from the master cylinder 20 is increased in pressure, but the hydraulic oil in the rear wheel cylinder W / C (RL, RR) is recirculated to the reservoirs 41, 42. Pumped out and used to increase the pressure on the front wheels FL and FR. As a result, the front wheels FL and FR are increased more than necessary, and their braking forces interfere with each other.

  Therefore, in the conventional example, only the front wheel is increased and the target hydraulic pressure of the rear wheel is maintained at a zero value to suppress the interference between the front wheel and the rear wheel (see FIG. 8). Since this does not occur, the burden on the front wheels is large, and sound vibration and fading are likely to occur.

  On the other hand, in the embodiment of the present invention, the rear wheel hydraulic pressure control at the time of HDC control is only pressure increase or holding, and pressure reduction control is not performed. Further, a step-like control mode (XGF) is set according to the vehicle front-rear G value detected by the G sensor 3 (see FIG. 9), and multiplied by the gain KG, the rear wheel pressure increase control amount for each mode. Determine PBSr_HDC. Therefore, the rear wheel control amount PBSr_FDC changes stepwise according to the front and rear G (see FIG. 10).

  In this way, the front wheel FL, FR and the rear wheels RL, RR are caused to generate a braking force by an independent control law, and the rear wheel is only increased in pressure or held, so that the rear wheel wheel cylinder W / C (RL, RR) reduces the burden on the front wheels FL and FR while eliminating hydraulic interference between the front wheels FL and FR and the rear wheels RL and RR.

  Furthermore, if the mode transition is frequently performed in the control of the rear wheel, the control amount and the change frequency increase, and the controllability deteriorates. Therefore, hysteresis is provided at the time of transition to each mode, and controllability is improved by suppressing frequent changes in the control amount. The front wheels FL and FR may be controlled based on the front and rear G, and the rear wheels RL and RR may be braked as hydraulic pressure control using PID control without any particular limitation.

[Fastening force calculation control based on wheel speed deviation]
When the fastening force T of the driving force distribution device 8 is small and the driving forces of the front wheels FL, FR and the rear wheels RL, RR are independent of each other, the wheel speed VW (FL, FR) and the target wheel speed of the front wheels FL, FR are independent. If the deviation VWSA from the VMOKU is large, the front wheels FL and FR rotate independently. Therefore, it becomes difficult for the front wheel speed VW (FL, FR) to converge to the target value VMOKU.

Therefore, in this embodiment, when the front wheel deviation VWSA_f exceeds the range of the predetermined value ± γ, the proportional proportion VWSA, the differential portion VWSAD, and the integral portion VWSAI calculated based on the front wheel deviation VWSA (see FIG. 6: step S600). The fastening force T is calculated by multiplying the gains KTP, KTD, and KTI and multiplying them. That is, the fastening force T is expressed by an equation using gains KTP, KTD, and KTI.
T = | VWSA × KTP + VWSAD × KTD + VWSAI × KTI |
In addition, since the PID component of each deviation may take a negative value, when calculating the fastening force T, the absolute value of the sum of each component is taken.

  As a result, the fastening force T is increased as the front wheel deviation VWSA increases, and the driving reaction force of the front wheels FL and FR is transmitted to the rear wheels RL and RR so that the deviation VWSA of the front wheels FL and FR is quickly set to the target value VMOKU. Converge. Similarly, even when the rear wheel speed deviation VWSA_r exceeds the range of the predetermined value ± γ, the fastening force T of the driving force distribution device 8 is increased to converge the deviation early.

[Solenoid pressure increase control processing]
FIG. 11 is a flowchart showing a flow of solenoid pressure increase control processing. This corresponds to step S400 in the basic control flow of FIG.
In step S401, the normally closed in-side gate valves 21 and 22 are turned on (opened), and the normally opened out-side gate valves 23 and 24 are turned on (closed), and the process proceeds to step S5.

[Solenoid pressure reduction control processing]
FIG. 12 is a flowchart showing the flow of the solenoid pressure reduction control process. This corresponds to step S500 in the basic control flow of FIG.
In step S501, the normally closed in-side gate valves 21 and 22 are turned off (closed), and the normally opened out-side gate valves 23 and 24 are turned off (opened), and the process proceeds to step S5 or step S6.

[Solenoid holding control processing]
FIG. 13 is a flowchart showing the flow of the solenoid holding control process. This corresponds to step S600 in the basic control flow of FIG.
In step S601, the normally closed in-side gate valves 21 and 22 are turned off (closed), and the normally opened out-side gate valves 23 and 24 are turned on (closed), and the process proceeds to step S5.

[Change over time in HDC control]
FIG. 14 is a comparison of time charts of HDC control in the conventional example and this embodiment. Since the present embodiment and the conventional example are the same except for the control amounts for the rear wheels RL and RR, the conventional example shows only the R_LH and R_RH hydraulic pressures with broken lines. For rear wheels RL and RR, wheel speed average value {VW (RL) + VW (RR)} / 2 is used for control.

(Time t0)
At time t0, a pressure increase request is output, and the hydraulic pressure of each front wheel starts increasing. In the embodiment of the present application, the hydraulic pressure of each rear wheel also starts to increase according to the control law in step S301 (see FIG. 7), but in the conventional example, the zero value is maintained.

(Time t1)
At time t1, the actual wheel speed VW (FL, FR) of the front wheels falls below the target wheel speed VMOKU, and hydraulic pressure holding control is started for the front wheels FL, FR. Until the actual wheel speed VW (FL, FR) exceeds the target wheel speed VMOKU, the hydraulic pressure holding / reducing control is repeated for the FL and FR wheels.

(Time t2)
At time t2, the FL wheel speed VW (FL) falls below VMOKU-γ, and the FL wheel deviation VWSA_fl exceeds the range of the predetermined value ± γ. Accordingly, the fastening force T is calculated in step S300. The driving force distribution device 8 distributes the driving force based on this T.

(Time t3)
At time t3, the actual wheel speed VW (FR) of the FR wheel exceeds the target wheel speed VMOKU, and the pressure reduction control for the FR wheel is released. Thereafter, the pressure increasing / holding command is output until the value of the actual wheel speed VW (FR) of the FR wheel again falls below the target wheel speed VMOKU, and after the actual wheel speed VW falls below the target wheel speed VMOKU, increases and decreases again. The pressure reduction / holding and pressure increase / holding are repeated with the period up to one cycle.

(Time t4)
At time t4, the FL wheel deviation VWSA_fl falls within the range of the predetermined value ± γ, and the fastening force T becomes zero.

(Time t5)
At time t5, the average value {VW (RL) + VW (RR)} / 2 of the rear wheel speed VW (RL, RR) exceeds the target wheel speed VMOKU, and the pressure reduction control for the rear wheels RL, RR is released.

(Time t6)
At time t4, the FL wheel actual wheel speed VW (FL) exceeds the target wheel speed VMOKU, and the pressure reduction control for the FL wheel is released. As with the FR wheel, pressure reduction / holding and pressure increase / holding are repeated every cycle.

(Time t7)
At time t7, the FR wheel speed VW (FR) exceeds VMOKU-γ, the FR wheel deviation VWSA_fr exceeds the range of the fixed value ± γ, and the fastening force T is calculated and output in step S300.

(Time t8)
At time t8, the deviation VWSA_fr is within the range of the constant value ± γ, and the fastening force T is zero.

(Time t9)
At time t9, the FL wheel deviation VWSA_fl exceeds the range of the predetermined value ± γ, and the fastening force T is calculated and output in step S300.

(Time t10)
At time t10, the FL wheel deviation VWSA_fl falls within the range of the predetermined value ± γ, and the fastening force T becomes zero.

  Thus, when the front wheel deviation VWSA_f exceeds the range of the predetermined value ± γ, the fastening force T is increased as the front wheel deviation VWSA increases. As a result, the driving reaction force of the front wheels FL, FR is transmitted to the rear wheels RL, RR, and the deviation VWSA of the front wheels FL, FR is quickly converged to the target value VMOKU. Even when the rear wheel speed deviation is large, the fastening force T of the driving force distribution device 8 is increased to converge the deviation early.

  Further, the control hydraulic pressure for the rear wheels RL and RR continues to be zero in the conventional example, but in the present application, a constant hydraulic pressure (> 0) is maintained according to the control law in step S301 (see FIG. 7). Is done. The braking force is also generated on the rear wheels to reduce the load on the front wheels and suppress the sound vibration and the fade phenomenon.

[Effect of the embodiment of the present application]
In the present embodiment, when the deviation VWSA_f between the actual front wheel speed VW (FL, FR) and the target wheel speed VMOKU in the four-wheel drive vehicle exceeds the range of a predetermined value ± γ, the fastening force in the driving force distribution device 8 is obtained. It was decided to increase T. The fastening force T is also increased when the rear wheel deviation VWSA_r exceeds the predetermined value ± γ.

  Accordingly, when the front wheel deviation VWSA_f is large, the front wheel driving force Ff is transmitted to the rear wheels RL and RR, and when the rear wheel deviation VWSA_r is large, the rear wheel driving force Fr is transmitted to the front wheels FL and FR. This makes it possible to quickly converge the front wheel deviation VWSA_f or the rear wheel deviation VWSA_r to the target value VMOKU, thereby reducing the load on the brake system.

  In addition, when the independent hydraulic pressure control law is applied to the front wheels and the rear wheels, and the front wheels are controlled to follow the target wheel speed VMOKU, the control amount is determined for the rear wheels based on the front and rear G values of the vehicle. When the control based on the value of the front and rear G is performed on the front wheel, the rear wheel is controlled to follow the target wheel speed VMOKU.

  This makes it possible to avoid interference between the braking forces of the front and rear wheels even when the control amounts for the front and rear wheels are different in a so-called X piping system. Therefore, it is possible to reduce the load on the front wheels by generating a braking force on the rear wheels, and to suppress the vibration and fading phenomenon of the front wheels.

  Further, the fastening force T is calculated based on a proportional component VWSA, a differential component VWSAD, and an integral component VWSAI (see FIG. 6: step S600) calculated based on the front wheel deviation VWSA. Accordingly, the calculation load can be reduced by using the PID control amount calculated in the hydraulic pressure control for calculating the fastening force T.

[Other embodiments]
As described above, the best mode for carrying out the present invention has been described based on the first embodiment. However, the specific configuration of the present invention is not limited to each embodiment and does not depart from the gist of the present invention. Such design changes are included in the present invention.

(Fastening force adjustment control when locked)
If the fastening force T of the driving force distribution device 8 is large when the front wheels FL and FR have a locking tendency, the locking tendency is transmitted to the rear wheels RL and RR via the center shaft 9 and the driving force distribution device 8. The vehicle stability is impaired. The same applies when the rear wheels RL and RR have a locking tendency.

Therefore, when the locking tendency of any one of the front wheels FL, FR and the rear wheels RL, RR is detected, the fastening force T of the driving force distribution device 8 is set to 0 to prevent the locking tendency from propagating to other wheels. Good. Multiply T by the lock coefficient α and calculate the fastening force T by the following equation. In this case, when the lock tendency of any of the wheels FL to RR is detected, the lock coefficient α = 0. By normally setting α = 1, the above-described locking-time fastening force control is executed.
T = | VWSA × KTP + VWSAD × KTD + VWSAI × KTI | × α

(Fastening force adjustment control by deviation)
FIG. 15 is a diagram illustrating a correlation of the fastening force T with respect to the values of the front wheel deviation VWSA_f and the rear wheel deviation VWSA_r. The fastening force T may be calculated by the following equation by multiplying T by the fastening force adjustment gain K shown in FIG. The fastening force T can be changed according to the deviation to realize an optimal vehicle behavior.
T = | VWSA × KTP + VWSAD × KTD + VWSAI × KTI | × K
When either one of the front wheel deviation VWSA_f and the rear wheel deviation VWSA_r is large and the other is small (mode a or mode d), the gain K multiplied by the fastening force T in order to release the driving force on the larger deviation side of the front and rear wheels to the other The value of is medium. When the deviation is large for both the front and rear wheels (mode b), the gain K may be increased to increase the fastening force T, and the braking force may be increased by transmitting the road surface reaction force to the four-wheel front wheels.

  Further, when the deviation is small for both the front and rear wheels (mode c), since the wheel speed is lower than the target value, K is arbitrarily set according to the desired vehicle behavior, and the fastening force T is controlled. When importance is attached to the stability, the fastening force T is decreased in order to avoid the front wheel locking tendency from propagating to the rear wheels, and when the vehicle speed is increased, the fastening force T is increased to prevent the front wheel locking tendency.

(Combination of locking control and fastening force control based on deviation)
The fastening force T may be calculated by the following equation by multiplying T calculated based on the wheel speed deviation by the lock coefficient α and the fastening force adjustment gain +.
T = | VWSA × KTP + VWSAD × KTD + VWSAI × KTI | × α × K

(Continuous change of rear wheel control mode)
In the embodiment of the present application, the control amount is determined in a stepwise manner using a step-like control mode based on the front and rear G of the vehicle for the rear wheel control law (see step S301), but continuously changes based on the front and rear G. Also good.

  Further, technical ideas other than the claims that can be grasped from the above embodiments will be described below together with the effects thereof.

(A) In the vehicle braking force control device according to claim 1,
The wheel cylinders of each vehicle wheel are connected to each other diagonally.

  In the so-called X piping system in which it is difficult to independently control the braking force of the front and rear wheels, the effect of the vehicle braking force control device of the present application becomes more remarkable.

(B) In the vehicle braking force control device according to (a) above,
The second control side is only pressure increasing control or holding control.

  For example, if the rear wheel is depressurized when the front wheel is increased, the hydraulic oil is returned from the rear wheel to the reservoir and pumped out by the pump, and used to increase the front wheel, the front wheel is unnecessarily increased, and the rear wheel control is performed. Interfering with control. By using only the pressure increase control or the holding control on the second control side, it is possible to avoid interference between the hydraulic pressure control of the front and rear wheels.

(C) In the vehicle braking force control device according to claim 2,
The second control side is provided with hysteresis when switching between the pressure increase control and the pressure reduction control.

  A stepwise (step-like) control mode (XGF) is set according to the vehicle front and rear G values detected by the G sensor 3 (see FIG. 9), and multiplied by the gain KG, the rear wheel control amount for each mode. PBS_HDC is determined. At that time, by providing hysteresis at the time of transition to each mode, it is possible to suppress frequent changes in the control amount and improve controllability.

(D) In the vehicle braking force control device according to claim 1,
The driving force distribution control unit sets the driving force distribution amount to the rear wheels to zero when detecting the locking tendency of any of the wheels.

  Propagation of the locking tendency to other wheels can be avoided.

(E) In the vehicle braking force control device according to claim 1,
The driving force distribution control unit changes a driving force distribution amount to the rear wheel based on the deviation of the front wheel and the deviation of the rear wheel.

  The fastening force T can be changed according to the deviation to realize an optimal vehicle behavior.

It is a block diagram of this-application brake system. It is a block diagram of this application front-and-rear wheel driving force distribution system. It is a hydraulic circuit diagram of a brake unit. It is a flowchart which shows the flow of the basic control process in HDC control. It is a flowchart which shows the flow of target wheel speed calculation control processing. It is a flowchart which shows the flow of a PID control signal calculation control process. It is a flowchart which shows the flow of control amount calculation control processing. It is a control amount calculation flow in the conventional example. It is a control mode-control amount map. It is a figure which shows the control amount corresponding to front-back G and each control mode. It is a flowchart which shows the flow of a solenoid pressure increase control process. It is a flowchart which shows the flow of a solenoid pressure reduction control process. It is a flowchart which shows the flow of a solenoid holding | maintenance control process. It is contrast of the time chart in a prior art example and this-application Example. It is a figure which shows the correlation of the fastening force with respect to a front-wheel deviation and a rear-wheel deviation.

Explanation of symbols

1 Brake ECU
2 Hydraulic unit 3a, 3b G sensor 4 Wheel speed sensor 5 Driving force distribution ECU
6 Transmission 7 Transfer 8 Driving force distribution device 9 Center shaft 9F, 9R Differential 20 Master cylinder 21, 22 In side gate valve 23, 24 Out side gate valve 25-28 In valve 29-32 Out valve 33, 34 Check valve 35 38 Check valve 41, 42 Reservoir 43, 44 Diaphragm 51-58 Oil path 61, 62 Oil path P_HDC Proportional control amount I_HDC Integral control amount D_HDC Differential control amount PBS_HDC PID control amount VMOKU Target wheel speed VWSA Wheel speed deviation VWSAD deviation Differential value VWSAI Deviation integral value

Claims (3)

A vehicle braking force control device having wheel speed detecting means for detecting the wheel speed of each wheel in a four-wheel drive vehicle and obtaining a desired braking force by controlling a hydraulic pressure of a wheel cylinder provided in each wheel. Because
The vehicle braking force control device includes:
A hydraulic control unit for controlling the hydraulic pressure of the wheel cylinder;
Driving force distribution means for distributing the driving force of the front wheels and the rear wheels;
A driving force distribution control unit for controlling the amount of distribution in the driving force distribution means,
The hydraulic pressure control unit controls the hydraulic pressure of each wheel cylinder,
The driving force distribution control unit calculates a distribution amount in the driving force distribution means based on a deviation between the wheel speed and a target wheel speed. In the vehicle braking force control device according to claim 1,
Further comprising a slope detection means for detecting the slope of the vehicle;
The hydraulic control unit is
A first hydraulic pressure control law for controlling the hydraulic pressure of the wheel cylinder so as to converge the wheel speed to a target wheel speed;
A second hydraulic pressure control law for controlling the hydraulic pressure of the wheel cylinder based on the actual gradient detected by the gradient detecting means;
Of the front and rear wheels of each wheel, when the first hydraulic pressure control law is applied to the front wheels, the second hydraulic pressure control law is applied to the rear wheels, and the second hydraulic pressure control is applied to the front wheels. When the law is applied, the first hydraulic pressure control law is applied to the rear wheel. In the vehicle braking force control device according to claim 1,
The hydraulic pressure control unit executes PID control for converging a deviation between the wheel speed and a target wheel speed,
The driving force distribution control unit calculates the driving force distribution amount based on the control amounts of the proportional control amount, integral control amount, and differential control amount of the PID control calculated by the hydraulic pressure control unit. A vehicle braking force control device characterized by the above.

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