JP5131000B2 - Brake device for vehicles with front wheel anti-skid control adapted to brake force front / rear wheel distribution control - Google Patents

Description

  The present invention relates to a vehicle braking device, and more particularly, to better adapt braking force front / rear wheel distribution control to front wheel anti-skid control in the operation of a vehicle braking device.

When the running of the vehicle is braked, the ground contact load of the wheel moves from the rear wheel to the front wheel, so as the braking force increases, the distribution of the braking force between the front and rear wheels is changed to the front, In particular, EBD (Electronic
Known as Braking Force Distribution. On the other hand, if the braking force applied to the wheel is too strong compared to the frictional force obtained between the wheel and the road surface, the rolling trajectory maintaining ability of the wheel will be reduced due to the increase in wheel slip, and the vehicle will become unstable. In this case, the control system for performing the control to release the brake once and then apply it again is an anti-skid control device or ABS (Anti-lock).
Braking System).

Various proposals have been made for associating EBD control and ABS control, and as one of them, the following Patent Document 1 regulates an increase in the braking pressure of the rear wheel by EBD control. When executing rear wheel ABS control, it has been proposed to alleviate the degree of restriction of increase in rear wheel braking pressure by EBD control in order to prevent the braking distance from being extended by the execution of ABS control. Patent Document 2 listed below prohibits EBD control when ABS control is started for at least one rear wheel, delays start of EBD control when ABS control is started for at least one front wheel, It has been proposed not to delay or prohibit EBD control when control cannot be performed normally. In Patent Document 3 below, an upper limit is set for an increase in the braking force of the rear wheel, and when the ABS control is started on any of the wheels during the execution of the control performed by the front wheel, It has been proposed to gradually reduce the amount of increase in the braking force of the front wheels.
JP-A-11-192930 JP 2001-39283 A JP 2004-306784 A

  The anti-skid control for the front wheels starts during execution of the braking force front / rear wheel distribution control. This means that the braking force front / rear wheel distribution control in which the braking force is biased from the rear wheel side to the front wheel side is restored. Means desirable. In this case, the return of the braking force front / rear wheel distribution control is gradually performed as described in Patent Document 3 from the viewpoint of preventing the ride comfort of the vehicle from being impaired by a sudden change in the braking force front / rear wheel distribution. However, the start of anti-skid control for the front wheels indicates that the distribution of the braking force between the front and rear wheels is considerably large and is biased toward the front wheels. The ratio of the braking force lost by the vehicle to the total braking force is quite large. Therefore, it is considered that the influence of the anti-skid control of the front wheels on the braking effect of the vehicle should be particularly noted.

  From the above viewpoint, the present invention provides a vehicle braking apparatus having braking force front-rear wheel distribution control means, and particularly anti-skid control means for front wheels, corresponding to the operation of anti-skid control for front wheels. In correcting the braking force front / rear wheel distribution control, an object is to achieve a more appropriate harmony between the quick braking performance of the vehicle and the ride comfort.

In order to solve the above-described problems, the present invention provides a vehicle braking device having braking force front-rear wheel distribution control means and anti-skid control means for front wheels, and the braking force front-rear wheel distribution control means is in operation. Further, when the anti-skid control means is activated, the braking force front-rear wheel distribution control means is terminated more quickly as the braking operation by the driver is steeper. A vehicle braking device is proposed.

It is, regulation of the braking operation by the driver is steeper than a predetermined degree to end the operation of fast braking force front and rear wheels between distribution control means than enough pace of the braking operation by the driver as described above is steeper In some cases, it may include immediately ending the operation of the braking force front / rear wheel distribution control means.

To end the operation of fast braking force front and rear wheels between distribution control means than enough pace of the braking operation by the driver as described above is steeper, regulation of the braking operation by the driver is not steep than the predetermined degree Sometimes, the braking force front-rear wheel distribution control is gradually decreased with time to finish the operation of the braking force front-rear wheel distribution control means.

As described above, in the vehicle braking apparatus having the braking force front-rear wheel distribution control means and the anti-skid control means for the front wheels, the anti-skid control means is operated during the operation of the braking force front-rear wheel distribution control means. When activated , the more rapid the braking operation performed by the driver, the faster the braking force front / rear wheel distribution control means is terminated. When the front wheels are anti-skid controlled while being biased toward the front wheels, the quicker the braking performance of the driver, the more rapid the vehicle's braking performance, the more comfortable the ride is. From the standpoint that the degree of priority to do is large, it is possible to achieve a balance between ensuring the quick braking performance of the vehicle and ensuring the riding comfort.

In this case, to end the operation of fast braking force front and rear wheels between distribution control means than enough pace of the braking operation by the driver as described above is steep, pace of the braking operation by the driver is greater than a predetermined degree If the operation of the brake force front / rear wheel distribution control means is immediately terminated when the vehicle is sudden, it is possible to ensure the vehicle's rapid braking performance to a certain extent by appropriately determining the predetermined degree. When this is important, it is possible to give the highest priority to securing the vehicle's prompt braking performance to ensuring the ride comfort.

Also in this case, to end the operation of fast braking force front and rear wheels between distribution control means than enough pace of the braking operation by the driver as described above is steep, the degree pace of the braking operation by the driver is given If the braking force includes a gradual decrease in the braking force front / rear wheel distribution control over time and the operation of the braking force front / rear wheel distribution control means is terminated when it is not steep , the predetermined degree is appropriately determined. Thus, when the importance of the quick braking performance of the vehicle is not so important, it is possible to secure the quick braking performance while paying sufficient attention to ensuring the riding comfort of the vehicle.

  FIG. 1 is a schematic view showing an example in which the vehicle braking device according to the present invention is implemented as an electrohydraulic braking device. However, the present invention is not limited to the electrohydraulic braking device. Since the present invention has the gist of a software configuration relating to the operation of the vehicle braking device, the hardware configuration shown in FIG. 1 is known.

  The hydraulic circuit portion of the braking device generally indicated at 10 has a master cylinder 14 that pumps brake oil in response to a depression operation of the brake pedal 12 by the driver. A dry stroke simulator 16 is provided between the brake pedal 12 and the master cylinder 14. The master cylinder 14 has a first master cylinder chamber 14A and a second master cylinder chamber 14B. One end of a hydraulic conduit 18A for the left front wheel and one end of a hydraulic conduit 18B for the right front wheel are respectively provided in these master cylinder chambers. It is connected. Wheel cylinders 20FL and 20FR for generating braking forces for the left front wheel and the right front wheel are connected to the other ends of the hydraulic conduits 18A and 18B, respectively. 20RL and 20RR are wheel cylinders for the left rear wheel and the right rear wheel. During normal braking, these four wheel wheel cylinders receive hydraulic pressure from the oil pump under the opening / closing control of the electromagnetic opening / closing valve described below. It comes to be supplied.

  Normally open electromagnetic open / close valves (master cut valves) 22L and 22R are provided in the middle of the hydraulic conduits 18A and 18B, respectively. These electromagnetic on-off valves 22L and 22R function as shut-off valves that selectively block communication between the first master cylinder chamber 14A and the second master cylinder chamber 14B and the corresponding wheel cylinders 20FL and 20FR, respectively. A wet stroke simulator 26 is connected to a brake hydraulic pressure supply conduit 18A between the master cylinder 14 and the electromagnetic on-off valve 22FL via a normally-closed electromagnetic on-off valve 24.

  A reservoir 28 is connected to the master cylinder 14, and one end of an oil feeding conduit 30 is connected to the reservoir 28. An oil pump 34 driven by an electric motor 32 is connected to the oil feeding conduit 30, and an accumulator 38 for accumulating pressurized oil pressure is connected to a hydraulic pressure supply conduit 36 on the discharge side of the oil pump 34. One end of an oil return conduit 40 is connected to the oil supply conduit 30. The reservoir 28, the oil pump 34, the accumulator 38, etc. function as a hydraulic pressure source for increasing the pressure in the wheel cylinders 20FL, 20FR, 20RL, 20RR.

  Although not shown in FIG. 1, a conduit is provided to connect the oil supply conduit 30 on the suction side of the oil pump 34 and the hydraulic supply conduit 36 on the discharge side, and an accumulator 38 is provided in the middle of the conduit. When the pressure exceeds the reference value, there is provided a relief valve that opens and returns oil from the discharge-side hydraulic supply conduit 36 to the suction-side oil supply conduit 30.

  The hydraulic supply conduit 36 on the discharge side of the oil pump 34 is connected to the wheel cylinder 20FL via a normally closed electromagnetic on-off valve 42FL and a hydraulic conduit 44FL. Similarly, the hydraulic supply conduit 36 on the discharge side of the oil pump 34 is connected to the wheel cylinder 20FR via a normally closed electromagnetic on / off valve 42FR and a hydraulic conduit 44FR, and the normally closed electromagnetic on / off valve 42RL and the hydraulic conduit 44RL are connected. Then, it is connected to the wheel cylinder 20RL, and is connected to the wheel cylinder 20RR via a normally closed electromagnetic on-off valve 42RR and a hydraulic conduit 44RR.

  The wheel cylinders 20FL, 20FR, 20RL, and 20RR are also connected to the oil return conduit 40 through hydraulic conduits 44FL, 44FR, 44RL, and 44RR and normally closed solenoid valves 46FL, 46FR, 46RL, and 46RR, respectively.

  The electromagnetic on-off valves 42FL, 42FR, 42RL, and 42RR function as pressure-increasing valves (or hydraulic holding valves) for the wheel cylinders 20FL, 20FR, 20RL, and 20RR, respectively. The electromagnetic on-off valves 46FL, 46FR, 46RL, and 46RR are respectively wheel cylinders 20FL, It functions as a pressure reducing valve (or hydraulic pressure holding valve) for 20FR, 20RL, and 20RR. Therefore, these electromagnetic on-off valves cooperate with each other to increase / decrease the hydraulic pressure supplied to each wheel cylinder based on the hydraulic pressure source in the accumulator 38. The hydraulic control valve is configured.

  The normally open type electromagnetic on / off valves 22L and 22R are maintained in the open state in the non-control mode where no drive current is supplied, and the normally closed type electromagnetic on / off valves 42FL, 42FR, 42RL, 42RR and 46FL, 46FR, 46RL, 46RR are maintained. Is kept in the closed state in the non-control mode in which no drive current is supplied. If any of the solenoid valves 42FL, 42FR, 42RL, 42RR and 46FL, 46FR, 46RL, 46RR breaks down and the pressure in the corresponding wheel cylinder cannot be controlled normally, these solenoid valves The non-control mode is set, whereby the pressure in the wheel cylinders of the left and right front wheels is directly controlled by the master cylinder 14.

  The hydraulic conduit 18A between the first master cylinder chamber 14A and the electromagnetic on-off valve 22L is provided with a first hydraulic sensor 48A that detects the pressure in the hydraulic conduit as the first master cylinder pressure Pma. Similarly, a second hydraulic sensor 48B that detects the pressure in the hydraulic conduit as the second master cylinder pressure Pmb is provided in the hydraulic conduit 18B between the second master cylinder chamber 14B and the electromagnetic on-off valve 22R. Yes. The brake pedal 12 is provided with a stroke sensor 50 that detects the depression stroke St of the brake pedal by the driver. The hydraulic pressure supply conduit 36 on the discharge side of the oil pump 34 is provided with a hydraulic sensor 52 that detects the pressure in the conduit as an accumulator pressure. Pressures in the wheel cylinders 20FL, 20FR, 20RL, and 20RR are detected as pressures Pbfl, Pbfr, Pbrl, and Pbrr by hydraulic sensors 54FL, 54FR, 54RL, and 54RR, respectively. The rotational speeds of the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel are detected as rotational speeds Vwfl, Vwfr, Vwrl, and Vwrr by wheel speed sensors 56FL, 56FR, 56RL, and 56RR, respectively.

  The electromagnetic on / off valves 22L and 22R, the electromagnetic on / off valve 24, the electric motor 32, the electromagnetic on / off valves 42FL to 42RR, and the electromagnetic on / off valves 46FL to 46RR are controlled by an electronic control unit 58. The electronic control unit 58 includes a microcomputer 60 and a drive circuit 62. The microcomputer 60 includes a signal indicating the vehicle speed from the vehicle speed sensor, a signal indicating the first master cylinder pressure Pma and the second master cylinder pressure Pmb from the hydraulic sensors 48A and 48B, and a depression stroke of the brake pedal 12 from the stroke sensor 50, respectively. A signal indicating Sm, a signal indicating the accumulator pressure from the hydraulic pressure sensor 52, a signal indicating the pressure Pbi (i = fl, fr, rl, rr) in the wheel cylinders 20FL to 20RR from the hydraulic pressure sensors 54FL to 54RR, and a wheel speed sensor 56FL , 56FR, 56RL, and 56RR are input signals indicating the rotational speed Vwi (i = fl, fr, rl, rr) of each wheel.

  The microcomputer 60 stores a braking control routine. When the brake pedal 12 is depressed, the microcomputer 60 opens the electromagnetic on-off valve 24 and closes the electromagnetic on-off valves 22L and 22R. In this state, the hydraulic sensor 48A, Based on the master cylinder pressures Pma and Pmb detected by 48B and the depression stroke Sm detected by the stroke sensor 50, the required braking force is calculated as a target value, and the distribution ratio for distributing it to the front, rear, left and right wheels is calculated. A target wheel cylinder pressure Pbti (i = fl, fr, rl, rr) is calculated for each of the wheel cylinders 20FL to 20RR, and the electromagnetic on-off valve 42FL is set so that the pressure Pbi of each wheel cylinder becomes the target wheel cylinder pressure Pbti. -42RR and 46FL-46RR are controlled.

  The microcomputer 60 includes a signal indicating the yaw rate of the vehicle body from a yaw rate sensor (not shown), a signal indicating the longitudinal acceleration of the vehicle body from the longitudinal acceleration sensor, and a signal indicating the lateral acceleration of the vehicle body from the lateral acceleration sensor. Etc., and the black computer 60 refers to these signals at the same time and performs braking control for each wheel for vehicle travel control in various control modes proposed in the field of vehicle travel control technology. As part of this, the distribution control of the braking force between the front and rear wheels according to the present invention is performed.

  FIG. 2 is a flowchart showing one embodiment of the braking force distribution control between the front and rear wheels in the vehicle braking apparatus according to the present invention. Calculations, determinations, and commands in accordance with the flowchart are performed by the microcomputer 60 in FIG. 1 while sewing the vehicle, that is, when the brake pedal is depressed, between other driving support controls.

  When the control is started, a difference ΔVw between the sum of the rotational speeds Vwfl and Vwfr of the left and right front wheels and the sum of the rotational speeds Vwrl and Vwrr of the left and right rear wheels is calculated in step (S) 10. This corresponds to the difference between the average value of the rotational speeds of the left and right front wheels and the average value of the rotational speeds of the left and right rear wheels, and this ΔVw is positive because of the forward inertial force acting on the vehicle body due to braking. When the load is deviated from the rear wheel side to the front wheel side, it indicates that the slip of the rear wheel with respect to the road surface is increased as compared with the slip of the front wheel, and the magnitude of the value of ΔVw indicates the degree. Therefore, the magnitude of the value of ΔVw is a parameter that represents the degree to which it is preferable to bias the braking force distribution between the front and rear wheels toward the front wheels in accordance with an increase in the braking force.

  Control then proceeds to step 20 where it is determined whether flag F is 1. The flag F is reset to 0 at the start of each control, and is set to 1 when the control reaches Step 50 described later. Accordingly, the first answer is no (N), and the control proceeds to step 30.

  In step 30, it is determined whether or not ΔVw is equal to or greater than a predetermined threshold value ΔVw1. This threshold value ΔVw1 is a value of ΔVw that should start braking force front-rear wheel distribution control (EBD) if ΔVw is more than that. Here, the braking force front / rear wheel distribution control (EBD) is a control for reducing the braking force of the rear wheels in comparison with the braking force of the front wheels, and the total braking force of the front wheels and the rear wheels is made constant. Control to transfer a part of the braking force of the rear wheel to the front wheel, control to keep the braking force of the rear wheel constant while increasing the braking force of the front wheel, increase both the braking force of the rear wheel and front wheel, Various aspects, such as control for making the increase rate of the braking force smaller than the increase rate of the braking force of the front wheels, may be included.

  If the answer to step 30 is yes (Y), control proceeds to step 40, where braking force front-rear wheel distribution control (EBD) is started and executed in any control manner. When EBD is started, control proceeds to step 50 where flag F is set to one. If the answer to step 30 is no, the control at this time is finished.

  When the control reaches step 40 and the braking force front / rear wheel distribution control is started, the flag F is set to 1. Therefore, in the subsequent flow, the answer to step 20 is yes, and the control is step. From step 20, the process proceeds to step 60.

  In step 60, it is determined whether or not ΔVw is equal to or larger than a predetermined threshold value ΔVw2 smaller than ΔVw1. This threshold value ΔVw2 is a value of ΔVw that stops the braking force front-rear wheel distribution control when ΔVw falls below that (that is, when ΔVw becomes no more). Once the braking force front / rear wheel distribution control is started, the answer in step 60 is no. This means that the deceleration caused by the deceleration of the vehicle is reduced or the braking force applied to the wheels is reduced. This means that the forward bias of the wheel contact load has been reduced due to the release, etc., and the braking force front / rear wheel distribution control is no longer necessary. At this time, the control proceeds directly to step 90 described later. Thus, the braking force front / rear wheel distribution control is canceled. This release is a normal release, that is, an immediate release. Until such a state is reached, the answer to step 60 is yes and control proceeds to step 70.

  In step 70, it is determined whether or not anti-skid control (ABS control) has been started or is being executed on at least one of the front wheels. If the answer is no, the control advances from this to step 40, and the braking force front / rear wheel distribution control is continued as it is. On the other hand, if the answer is yes, control proceeds to step 80.

  In step 80, it is determined whether or not the driver's braking operation is steeper than a predetermined degree. This is because, in the illustrated example, the temporal change rate dPm / dt of the master cylinder pressure or the temporal change rate dSm / dt of the brake pedal stroke is equal to or higher than a predetermined threshold Vpo or Vso set for each. It is made by something. The threshold value Vpo or Vso is used to grasp that the driver is stepping on the brake pedal at an increasing speed that should give priority to ensuring the braking performance of the vehicle as much as possible over ensuring the riding comfort. This is a threshold for the time change rate dPm / dt of the master cylinder pressure or the time change rate dSm / dt of the brake pedal stroke. However, whether or not dPm / dt or dSm / dt is equal to or higher than Vpo or Vso is a basic concept for determining the degree of abruptness of braking operation by the driver, and dPm / dt at each moment of time. Or it does not ask only the magnitude of the dSm / dt value itself. That is, in many cases, the brake pedal is depressed in the braking of the vehicle, except in the case of a sudden braking. In many cases, the pedal is depressed at a stroke to a certain depth regardless of the braking speed. Since the braking force is adjusted according to the magnitude of the pedal reaction force at the driver, the speed of braking operation by the driver is determined by the depth of the pedal depression, that is, the stroke of the brake pedal. It may be determined by the stepping depth of the stepping, and it may be determined that the increase speed of the braking force is larger as the depth is larger. In any case, when it is determined that the driver's braking operation is steeper than a predetermined degree and the answer to step 80 is yes, the control proceeds to step 90, and the braking force front / rear wheel distribution control is performed. It is released immediately.

On the other hand, when the answer to step 80 is no, the control proceeds to step 100 where control for gradually reducing the braking force front-rear wheel distribution control is performed. The gradual reduction of the braking force distribution control between the front and rear wheels here is a gradual reduction of at least two steps, a gradual reduction by a constant gradient, a gradual reduction by combining multiple gradients, and any other control that is not a simple one-time distribution change Reduction change of power front and rear wheel distribution control may be included. At this time, the control repeats steps 100 and 110, and while the answer to step 110 is NO, the control proceeds to step 40 while gradually decreasing the braking force front-rear wheel distribution control, and continues the braking force front-rear wheel distribution control. When the answer to step 110 becomes yes, the routine proceeds to step 90 where the braking force front-rear wheel distribution control is released. When the braking force front / rear wheel distribution control is released, the flag F is reset to 0 in step 120.
While the present invention has been described in detail with respect to one embodiment thereof, it will be apparent to those skilled in the art that various modifications can be made within the scope of the present invention.

Schematic which shows an example at the time of implementing the vehicle braking device by this invention as an electrohydraulic braking device. The flowchart which shows distribution control between the front and rear wheels of the braking force in one embodiment of the braking device for a vehicle according to the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Brake device, 12 ... Brake pedal, 14 ... Master cylinder, 16 ... Dry stroke simulator, 18A, 18B ... Hydraulic conduit, 20FL, 20FR, 20RL, 20RR ... Wheel cylinder, 22L, 22R ... Electromagnetic on-off valve, 24 ... Electromagnetic On-off valve, 26 ... wet stroke simulator, 28 ... reservoir, 30 ... oil supply conduit, 32 ... electric motor, 34 ... oil pump, 36 ... hydraulic supply conduit, 38 ... accumulator, 40 ... oil return conduit, 42FL, 42FR, 42RL, 42RR ... electromagnetic on-off valve, 44FL, 44FR, 44RL, 44RR ... hydraulic conduit, 46FL, 46FR, 46RL, 46RR ... electromagnetic on-off valve, 48A, 48B ... hydraulic sensor 48, 50 ... stroke sensor, 52 ... hydraulic sensor, 54FL, 54FR , 54RL, 54RR ... hydraulic pressure sensor, 56FL, 56FR, 56RL, 56RR ... wheel speed sensor, 8 ... electronic control unit, 60 ... microcomputer, 62 ... drive circuit

Claims (3)

A braking force the front and rear wheels between distribution control means, in the vehicle braking system and a anti-skid control means for the front wheel, when the anti-skid control means during operation of the braking force the front and rear wheels between distribution control means is actuated, the operation The braking device for a vehicle is characterized in that the more rapid the braking operation by the user, the faster the braking force front / rear wheel distribution control means is finished. 2. The vehicle according to claim 1, wherein the operation of the braking force front-rear wheel distribution control means is immediately terminated when a driver's braking operation is steeper than a predetermined degree. 3. Braking device. When the driver's braking operation is not as steep as the predetermined degree, the braking force front / rear wheel distribution control is gradually reduced with time to finish the operation of the braking force front / rear wheel distribution control means. The vehicle braking device according to claim 1, wherein the vehicle braking device is a vehicle braking device.

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