JPH04121262A - Hydraulic booster for vehicle - Google Patents

Abstract

PURPOSE:To facilitate the use of a pedal by disposing an elastic member between an input piston and a power piston for the input piston to come closer and less apart according to the increase and decrease quantities of brake operational power by the elasticity. CONSTITUTION:A rubber ring 136 is attached to a face of a rower piston 106 side for a spring retainer 122 and faced to the rear end face of the power piston 106 through an annular support member 138 slidably fitted on the periphery of a communication member 121. Such a design is made that there is a prescribed positive shaft directional clearance between the rubber ring 136 and the support member 138 in state where an input piston 116 and the power piston 106 are both in their receding end positions. After a brake is pedaled and the shaft directional clearance is closed, compression of the rubber ring 136 is required. The rubber ring 136 is provided with proper elasticity to enhance a feeling of rigidity toward the brake pedal because of increased change in pedaling force.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a hydraulic booster for a vehicle that boosts the brake operating force applied to a brake operating member by hydraulic actuation, and particularly improves the usability of the hydraulic booster. It is related to the technology to

BACKGROUND OF THE INVENTION The above-mentioned hydraulic pressure booster generally includes (a) an input piston that cooperates with a brake operating member such as a brake pedal, as described in Japanese Patent Application Laid-open No. 149547/1983 to which the present applicant is the applicant; , (b) a power piston that cooperates with the pressurizing piston of the brake master cylinder and is actuated by Nihower hydraulic pressure, and (C) when the brake operating force increases, the power hydraulic pressure is increased as the input piston approaches the power piston. and power hydraulic pressure control means for decreasing the power hydraulic pressure as the input piston moves away from the power piston when the brake operating force decreases.

Problem to be Solved by the Invention During vehicle braking, the hydraulic pressure generated in the brake master cylinder (
It may be desirable to keep the power hydraulic pressure constant in order to keep the mask cylinder hydraulic pressure (hereinafter simply referred to as mask cylinder hydraulic pressure) constant. In such cases, the driver only needs to keep the brake operating force constant, but it is not that easy for humans to do so, and in reality, the brake operating force may increase or decrease slightly. It's normal. In a hydraulic booster, there is generally hysteresis in the relationship between the brake operating force and the power hydraulic pressure due to sliding resistance of the power hydraulic pressure control means and the power piston sliding portion. However, in conventional hydraulic boosters, no special measures have been taken to appropriately widen the hysteresis width, so the hysteresis width is relatively narrow, and the power hydraulic pressure is relatively small in response to changes in brake operating force. It changes sensitively, and even though the driver is trying to keep the power fluid pressure constant, the power fluid pressure actually changes.

Furthermore, in the conventional hydraulic booster, the brake operating force increases in the hysteresis region.

The amount of approach and separation of the input piston relative to the amount of reduction was relatively large, making it possible to easily make small changes in the brake operating force, resulting in a lack of rigidity of the brake operating member.

In summary, the conventional hydraulic booster has a problem in that it is not easy to use, and the present invention has been made to solve this problem.

Means for Solving the Problems And the gist of the present invention is that in a hydraulic booster including the input piston power piston and power hydraulic pressure control means, a brake operation is performed between the input piston and the power piston by its own elasticity. This is because elastic members are arranged to reduce the amount of approach and separation of the input piston in response to the increase and decrease in force.

Note that the r input piston j in the above expression j between the r input piston and the power piston means not only the input piston but also a member that moves integrally with it, and
``Like the input piston, the power piston j refers not only to the power piston but also to a member that moves integrally with it.

Operation In the device of the present invention, since the elastic member reduces the amount of approach of the input piston by 1M with respect to the increase and decrease of the brake operating force, the elastic member is applied to the brake operating member in order to move the input piston closer or farther apart by a certain amount. The amount of increase and decrease in the required operating force is greater than in the conventional device. The approach and separation of the input piston causes movement of the movable member (for example, the pulp spool in the embodiment described later) of the control valve of the power hydraulic pressure control means, so in order to move the movable member by a certain amount, the brake operating member is eventually forced to move. The amount of increase or decrease in the operating force to be applied is also greater than in the conventional device.

Effects of the Invention Therefore, according to the present invention, the width of the hysteresis region is appropriately expanded, the rigidity of the brake operating member in the hysteresis region is improved, and the amount of movement of the brake operating member relative to the amount of change in brake operating force is improved. In other words, the amount of approach and separation of the input piston relative to the amount of change in brake operating force is slightly reduced.As a result, the usability of the hydraulic pressure booster is improved.

Furthermore, according to the present invention, the kinetic energy of the input piston is absorbed by the elastic member, so that the input piston hits the stopper that defines the limit of its approach to the power piston because the brake operating member is operated fairly quickly. Even if they come into contact, a very large reaction force is not generated, and there is also the effect that the deterioration in the flake operation feeling caused by the reaction force is suppressed to a small level.

Furthermore, since a relatively rapid change in the input piston due to the driver's operation is absorbed by the elastic member, the effect that the movement of the input piston, that is, the change in the power hydraulic pressure, is smoothly performed is also obtained.

EXAMPLE Hereinafter, a brake system with a hydraulic pressure booster capable of anti-skid/traction control for a rear-wheel drive four-wheel vehicle, which is an example of the present invention, will be described in detail with reference to the drawings. Anti-skid control is performed to prevent excessive slip from occurring on the driving wheels (rear wheels) or non-driving wheels (front wheels) when the vehicle is braking, while traction control is performed on the driving wheels when the vehicle is accelerating. This is done to prevent excessive slip from occurring in the rear wheels.

In FIG. 1, 10 is a hydraulic booster (hereinafter simply referred to as a booster), and 12 is a tandem brake master cylinder (hereinafter simply referred to as a mask cylinder).

The mask cylinder 12 includes a housing 14 . The housing 14 is formed with a cylinder bore 16 into which a first pressure piston 18 and a second pressure piston 20 are fluid-tightly and slidably fitted, whereby each piston 1
8.20 (to the left in the figure) are the first pressurizing chambers 22. A second pressurizing chamber 24 is formed.

The first pressurizing chamber 22 is a provisioning/bypass valve (hereinafter simply referred to as the P/B valve. The same applies in the figure).
26 to the left rear wheel 30. The second pressurizing chamber 24 is connected to each brake wheel cylinder 34.36 of the right rear wheel 32, while the second pressurizing chamber 24 is connected to the left front wheel 42.36 through the P/B valve 26. Front wheel cylinder 46.4 for each brake of the right front wheel 44
8 is connected. The P/B valve 26 proportionally reduces the brake fluid pressure in the rear system when the front system is normal, but when the front system fails, the brake fluid pressure generated in the mask cylinder 12 is directly transferred to the rear wheel cylinder. 34.36.

An electromagnetic directional control valve 54 and an electromagnetic hydraulic pressure control valve 56 are provided between the P/B valve 26 and the rear wheel cylinder 3436.
58 are provided. The electromagnetic directional switching valve 54 is connected to the power pressure chamber 62 of the booster 10 and the accumulator 63 via the electromagnetic directional switching valve 60, and the mask cylinder pressure (mask cylinder 1
2), power pressure (hydraulic pressure generated in power pressure chamber 62), and accumulator pressure (hydraulic pressure generated in accumulator 63). The electromagnetic directional control valve 54.60 is always in a state of supplying mask cylinder pressure to the rear wheel cylinder 34.36, but when performing anti-skid control, it supplies power pressure, and when performing traction control, it supplies accumulator pressure. It is in a state of supply.

On the other hand, the P/B valve 26 and the front wheel cylinder 4
An electromagnetic directional control valve 6466 is provided between the directional control valve 6.48 and the directional control valve 6466. The electromagnetic directional control valves 64, 66 are each connected to the power pressure chamber 62 via an electromagnetic hydraulic pressure control valve 68, 70, and either mask cylinder pressure or power pressure is supplied to the front wheel cylinders 46, 48. It has become so. The electromagnetic directional control valves 64, 66 are always in a state of supplying mask cylinder pressure to the front wheel cylinders 46, 48, but are in a state of supplying power pressure when performing anti-skid control. Note that the left 5th and right front wheels 42 and 44 are not drive wheels, so traction control is not performed on them.

These electromagnetic directional valves 54. Switching between '60, 64 and 66 is performed by an electronic control unit (hereinafter simply referred to as ECtJ, the same applies in the figure) 72.

In addition, the electromagnetic hydraulic pressure control valves 56, 58, 68 and 70 can each be switched to the third position chamber, and each wheel 3
0, 32, 42.44 are subjected to anti-skid control, and the left and right rear wheels 30.32, which are drive wheels, are subjected to traction control. That is, by increasing, maintaining, and decreasing the hydraulic pressure in the wheel cylinders 3436, 46, and 48 by these electromagnetic hydraulic pressure control valves 5658, 68, and 70, the slip ratios of the wheels 30, 32, 42, and 44 are maintained within an appropriate range. This switching is also performed by each wheel speed sensor 74.
This is done by the ECU 72 while detecting the rotational speed of the
Since this is a well-known control, a detailed explanation will be omitted.

Note that an ignition switch is connected to the ECU 72 and starts operating when the engine is started.

The P/B valve 26 and the electromagnetic directional control valve 64.66
A pressure increase cylinder 8o is provided between the pressure increase cylinder 80 and the power pressure chamber 62, and a pilot-controlled on-off valve 82 is provided between the pressure increase cylinder 80 and the power pressure chamber 62. Further, a differential pressure switch 84 is provided between the pressure increasing cylinder 80 and the pyro-controlled on-off valve 82. The pressure increasing cylinder 80 and the like are described in detail in Japanese Patent Application No. 2-5736 filed by the present applicant, and will therefore be briefly described here. The pressure increase cylinder 80 can be switched between a state in which the output hydraulic pressure from the P/B valve 26 is transmitted to the electromagnetic directional control valves 64, 66 without increasing the pressure, and a state in which the pressure is increased and transmitted. Switching is controlled by a pilot-controlled on-off valve 82 that operates based on power pressure. Specifically, when the power pressure is normal, the pilot-controlled on-off valve 82 does not operate, so the pressure increase cylinder 80 cannot increase the pressure, but when the power pressure fails, Since the pilot-controlled on-off valve 82 operates, the pressure increase cylinder 80 can perform a pressure increase action. Further, when the power pressure is normal, the differential pressure switch 84 sends a signal to that effect to the E.
If the power pressure fails, a signal to that effect is supplied.

The housing 14j is the housing 1 of the booster 10.
00 is fitted in a liquid-tight manner. This housing 100
Inside is a cylinder bore 1 communicating with the cylinder bore 16.
04, into which the power piston 106 is liquid-tightly and slidably fitted, whereby the housing 100
The space inside is divided into the power pressure chamber 62 and the low pressure chamber 108.

Small diameter portion 112 from the center of the rear end of the power piston 106
The housing 100 extends through the end wall of the housing 100 in a fluid-tight and slidable manner and is exposed to the atmosphere. A large-diameter hole 114 and a small-diameter hole 115 are formed in this small-diameter portion 112 in this order from its rear end surface, and an input piston 116 is fitted into the small-diameter hole 115 in a liquid-tight and slidable manner. As a result, a liquid chamber 118 is formed between the input piston 116 and the small-diameter hole 115, and this liquid chamber 118 is constantly in communication with the power pressure chamber 62 via the communication passage 120.

Power pressure is applied to the input piston 116 in the backward direction.

A cylindrical transmission member 121 is slidably fitted into the large diameter hole 114 of the power piston 106 .

The rear end portion of the input piston 116 is fitted inside the transmission member 121 in such a manner that it cannot be removed from the transmission member 121. An annular spring retainer 122 is fitted into the outer peripheral surface of the rear end of the transmission member 121 and is prevented from detaching by an annular detachment prevention member 123 fixed to the rear end of the transmission member 121. A return spring 124 is disposed coaxially with the input piston 116 between the spring retainer 122 and the housing 100. An input rod 125 is caulked to the rear end of the input piston 116. Therefore, a reaction force proportional to the power pressure is applied to the input rod 25, and the biasing force of the return spring 124 is transmitted to the input rod 125 via the spring retainer 122, the transmission member 121, and the input piston 116. As a result, the input rod 125 is urged in the backward direction by the return spring 124. Input piston 11
6 is engaged with a pin 130 attached to the power piston 106 at its length 128, thereby regulating the relative retraction limit with respect to the power piston 106. Therefore, the return spring 124 also functions as a spring for the power piston 106. It will work.

The retreating end position of the power piston 106 is located at the stopper protrusion 13
2, and the actuation force of the power piston 106 is transmitted to the second pressurizing piston 20 by the relay rod 134. Note that a brake pedal (not shown) serving as a brake operation member is connected to the rear end of the manual rotor 125.

Power piston 106 of the spring retainer 122
A rubber ring 136 (this is one aspect of the elastic member in the present invention) is adhered to the surface of the example, and a member 138 is an annular receiver that is slidably fitted on the outer peripheral surface of the transmission member 121.
The rear end surface of the power piston 106 is opposed to the rear end surface of the power piston 106 via. The rubber ring 136 and the bearing member 138 are designed so that a certain positive axial clearance D exists when both the input piston 116 and the power piston 106 are at the retreat end position (original position as shown). ing.

The feeder 10 is equipped with a control valve 140. The control valve 140 includes a valve hole 141 and a valve spool 142 slidably fitted therein in a fluid-tight manner. A communication hole 144 is formed in the valve spool 142, and a low pressure boat 146 and a high pressure boat 148 are opened in the valve hole 141.

Relative movement of the valve spool 142 with respect to the valve hole 141 is conceptually shown in FIGS. 2 to 5. Valve spool 142
is the normal position P shown in FIG.

In this case, the low pressure boat 146 is communicated with the power pressure chamber 62 through the communication hole 144, and the high pressure port 148 is blocked. By moving the valve spool 142 forward (to the left in the figure) a certain distance from this position P0,
As shown in FIG. 3, the position P where the high pressure boat 148 is shut off and the low pressure boat 146 begins to shut off (this is also the end position of power pressure reduction and the start position of pressure holding) ↓ this position L, and further this position P1 By moving forward a certain distance L2 from the point P2, as shown in FIG. (which is also the starting position). When the valve spool 142 moves further forward, it reaches the forward end position P shown in FIG.
Reach 3. This position Pff is such that the front end surface of the transmission member 121 is connected to the large diameter hole 1 of the small diameter portion 112 of the power piston 106.
14 and the small-diameter hole 115 are defined by abutment against a shoulder surface connecting them to each other. That is, this shoulder surface is a stopper 149 that defines the relative forward limit of the input piston 116 toward the power piston 106.

Further, the valve spool 142 is located at position P2 shown in FIG.
By retreating a certain distance L2 from the point P2, as shown in FIG.
(This is also the power pressure holding end position and depressurization start position).

Therefore, when the valve spool 142 is located between the position P1 shown in FIG. 3 and the position P2 shown in FIG. 4, the power pressure is kept constant regardless of the movement of the valve spool 142. Become.

The fixed distance L2 of the valve spool 142 is an invalid stroke, and this is generally about 0.5 to 1.0.

Note that the length of the axial clearance D is determined at the position P of the valve spool 142 shown in FIG. It is determined that it disappears when it moves forward from the normal position and reaches the position P (pressure holding start position) shown in FIG.

The valve spool 142 is a link machine tlI shown in FIG.
150, the power piston 106 and the input piston 11
6 such that movement of the valve spool 142 is caused by movement of the input piston 116 relative to the power piston 106. The link mechanism 150 includes a first link 154 and a second link 156 which are rotatably connected to each other by a pin 152, which is described in the above-mentioned Japanese Patent Laid-Open No. 62
Since it is described in Japanese Patent No. 149547, detailed explanation will be omitted. As is clear from the above description, in this embodiment, the control valve 14o, the link mechanism 150, etc. constitute the power hydraulic pressure control means 158.

The control valve 140 is connected to the reservoir 16 in the low pressure boat 146.
0 and pump 162 in high pressure boat 148
and a hydraulic pressure source 163 including the accumulator 63. Note that the low pressure chamber 108 is also connected to the reservoir 160. Brake fluid in a reservoir 160 is supplied to the accumulator 63 by a pump 162 .

The accumulator pressure is maintained within a certain range by controlling the start and stop of the motor 166 by the ECU 72 based on the output signal of the pressure switch 164. A check valve 1 is used to prevent the brake fluid stored in the accumulator 63 from flowing back into the pump 162.
68 is provided, and a relief valve 170 is also provided to prevent the accumulator pressure from becoming abnormally high. The accumulator 63 also includes a pressure sensor 1.
72 is also provided.

In the brake system with a hydraulic pressure booster configured as described above, the initial setting of the computer that constitutes the main body of the ECtJ 72 is performed at the same time as the engine is started. Also,
The electromagnetic directional control valves 54, 60, 64, 66 and the electromagnetic hydraulic control valves 56, 58, 68'70 are always kept in the original position shown.

If the brake pedal is depressed from this state, the input piston 116 attempts to approach the power piston 106. Since there is an axial clearance D between the rubber ring 136 and the bearing member 138, the input pistons 11 and 6 are not attached to the return spring 124 until it disappears, as in a conventional booster. The power piston 106 can be approached only by overcoming the force. Therefore, in this case, the relationship between the axial position of the valve spool 142 and the depression force applied to the brake pedal is the sixth
This is represented by area A of the graph in the figure.

However, after the axial clearance D disappears, that is, after the valve spool 142 reaches the position P,
In order for the input piston 116 to approach the power piston 106, it is necessary to compress the rubber ring 136 to reduce its axial dimension. Also, rubber ring 13
6 is provided with appropriate elasticity (spring characteristics). Therefore, the input piston 116 cannot approach the power piston 106 unless it overcomes both the repulsive force of the rubber ring 136 and the biasing force of the return spring 124. Therefore, in this case, the relationship between the axial position of the valve spool 142 and the pedal force is represented by region B of the graph. Of this area B, area C is the valve spool 14.
This is the invalid stroke area of No. 2. In the conventional booster, the change in pedal force N (hereinafter simply referred to as the amount of change in pedal force) while the valve spool 142 moves throughout the invalid stroke region is indicated by F in the figure, whereas the present booster 10 In this case, it is shown as 8 and F2 in the figure. Since F2 is larger than Fl, this booster 10
This increases the amount of change in pedal force compared to the conventional booster, and as a result, the stiffness of the brake pedal improves when the valve spool 142 is in the invalid stroke region.

When the brake pedal is pressed down to maintain the mask cylinder pressure and the brake pedal is pumped slightly, an appropriate feeling of rigidity of the brake pedal can be obtained.

In addition, when the brake pedal is pressed fairly quickly (in the conventional booster), the input piston 116 comes into contact with the stopper 149 of the power piston 106, and the reaction force is transmitted to the driver via the brake pedal. However, in this booster 1°, the rubber ring 136 is considerably deformed and the kinetic energy of the input piston 116 is absorbed by the time the input piston 116 comes into contact with the stopper 149. , when the input piston 126 makes contact, a very large reaction force is not generated, and the operation feeling is improved.In addition, in this embodiment, 1. As shown in FIG.
Since the design is such that the larger the amount of compression 6, the greater the amount of change in the repulsive force with respect to the amount of compression 6, the reaction force due to contact is effectively reduced.

In addition, when releasing the brake pedal, the process is reversed to the above case, but in this case, 4.
While the valve spool 142 moves from position WPz to position P, both the power pressure and the mask cylinder pressure are kept constant. In other words, the mask cylinder pressure remains constant regardless of the decrease in pedal effort, and this is hysteresis. FIG. 7 is a graph showing an example of the relationship between the pedal force and the mask cylinder pressure when the brake pedal is depressed from a non-active state and then released from the brake pedal to return to the non-active state. The width of the hysteresis in FIG. 6 is determined by the sum of F2 in FIG. 6 and the sliding resistance present in the booster 10 and mask cylinder 12, and F2
Since F is larger than Fl, this booster 10 has a wider hysteresis width than the conventional booster, and the brake operation to keep the mask cylinder pressure constant is easier.

When the slip rate of the rear wheels 30.32 becomes high when the vehicle starts, the electromagnetic directional control valves 54.60 are switched and the accumulator pressure is supplied to the electromagnetic hydraulic pressure control valves 5658, and these control valves 56.58 control the rear wheel cylinders. 34.
Traction control is performed in which the hydraulic pressure of 36 is controlled.

Furthermore, when the vehicle brakes, if the slip ratio of the wheels 30, 32, 42° 44 becomes high, the electromagnetic directional valves 54, 60, 6
4.66 is switched and the power pressure is changed to the electromagnetic hydraulic control valve 5.
6, 58, 68, and 70, and these control valves 56.
Wheel cylinder 34, 36 by 58, 68.70
, 46. Anti-skid control is performed in which the hydraulic pressure of 48 is controlled.

Although one embodiment of the present invention has been described above in detail based on the drawings, the present invention can be implemented in other embodiments.

For example, in the above embodiment, the power piston 106
and a transmission member 1 that moves integrally with the input piston 116.
Although the elastic member is disposed between the power piston 106 and the input piston 116, the elastic member may be disposed between the power piston 106 and the input rod 125, which moves integrally with the input piston 116, for example.

Further, in the embodiment described above, a positive axial clearance D was provided between the rubber ring 136 and the bearing member 138, but the axial clearance can be changed appropriately. For example, it can be set to 0 or a negative value (minus clearance).

In addition to these, it is possible to implement the present invention with various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an anti-skid/traction control brake system with a hydraulic booster for a four-wheel vehicle, which is an embodiment of the present invention. FIGS. 2 to 5 are diagrams each conceptually showing how the valve spool moves in the hydraulic booster. FIG. 6 is a graph showing an example of the relationship between the axial position of the valve spool and the pedal force. FIG. 7 is a graph showing an example of the relationship between the pedal force and the mask cylinder pressure in the brake system. 10: Hydraulic pressure booster 12: Tandem type brake master cylinder 34.367
Rear wheel cylinder 46.48: Front wheel cylinder 136: Rubber ring 158: Power hydraulic pressure control means

Claims (1)

[Claims] an input piston that cooperates with a brake operating member; a power piston that cooperates with a pressurizing piston of a brake master cylinder and is actuated by power hydraulic pressure; and when the brake operating force increases, the input piston approaches the power piston. and power hydraulic pressure control means for increasing the power hydraulic pressure when the brake operating force decreases, and decreasing the power hydraulic pressure as the input piston moves away from the power piston. and the power piston, an elastic member is disposed between the power piston and the power piston to reduce the approach and separation of the input piston in response to the increase and decrease in brake operating force, respectively.