JPH0521784B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brake booster in which a housing supports a pair of pistons and a valve arrangement is operative to control fluid pressure communication to a pair of working chambers. More particularly, the present invention relates to a full power brake booster in which fluid pressure from an accumulator is selectively communicated to the working chamber.

U.S. Pat. No. 3,979,153 discloses a pair of parallel holes housing a pair of pistons and a valve arrangement actuated by an input device to control fluid pressure communication to the holes to move the pair of pistons. A master cylinder is disclosed that is actuated by a booster that includes a booster. When the brake is applied, the reaction force resisting movement of the input device is determined by a pair of springs that engage the input device and fluid pressure acting on the input device. The pair of pistons includes an extension member that is mechanically coupled to the input device in the event of a failure of the fluid pressure source used to move the pistons.
However, the extension member does not exert a reaction force on the input device during normal operation. Therefore, the extension member performs only a single function within the master cylinder operated by the booster.

It is an object of the present invention that during the initial application of the brakes, the input device is moved against the spring associated with it, so that the driver of the vehicle requires a light pedal effort, and after the initial application of the brakes, the input device is moved against the spring associated with it, and after the initial brake application, the input device is moved against the spring associated with it. The object of the present invention is to improve brake boosters known in the art in such a way that they require a strong pedal force which is directly related to the fluid pressure acting on the piston, ie the brake pressure generated by the booster.

According to the invention, this object is achieved by providing a housing comprising a first hole for accommodating the first piston, a second hole parallel to the hole for accommodating the second piston, and a third hole for accommodating the valve device. and an input device extending within the housing and cooperating with the valve device to control fluid pressure communication to the first and second holes when the brake is applied.
The input device and both pistons are arranged between the input device and the first and second pistons when the fluid communicating with the first and second holes cannot move the first and second pistons, respectively. and a coupling device for mechanically coupling between the input device and the pistons, wherein the coupling device forms a gap between the input device and the pistons in a rest position so as to provide a free movement coupling portion between the input device and the pistons. , the input device engages the valve device after the initial movement;
The valve device is opened to allow fluid pressure to communicate with the first and second holes, and the communication device is connected to the first and second holes.
This is accomplished by transmitting a reaction force to the input device that resists its movement in response to fluid pressure communicated with the aperture.

The present invention not only achieves the above objectives, but also
It has the advantage that the set point or "knee point" at which the output pressure acts to resist input by the vehicle operator can be determined by the gap provided in the coupling device.

These and other features and advantages of the invention will become apparent from the following description of preferred embodiments, taken in conjunction with the accompanying drawings.

In the drawings, brake system 10 includes a brake pedal 12 connected to a brake booster 16 via an input rod 14. Brake booster 16 communicates with first brake circuit 18 and second brake circuit 20 . These brake circuits are shown as front and rear axle piping types, as in the prior art. However, the brake booster 16 can also be used in an X-shaped piping type two-system brake circuit.
The accumulator 22 is charged with fluid pressure by a pump 24 driven by an electric motor or engine driven belt and pulley.

Brake booster 16 includes a housing 26 consisting of a first part 28 and a second part 30 secured together by a bolt and nut arrangement 31. First portion 28 includes a stepped aperture 32 extending from open end 34 into chamber 36 . The second portion 30 includes the first hole 3
8, a second hole 40 and a third hole 42 located between the first and second holes. Holes 38, 40 and 4
2 are provided parallel to each other, and each bottom wall 44, 4
6 and 48 into chamber 36. The bore 38 houses a first piston 50 that sealingly engages the wall of the bore 38 to define a first working chamber 52 and a first pressure chamber 54 . Similarly, the bore 40 houses a second piston 56 which sealingly engages the wall of the bore 40 to form a second working chamber 58 and a second pressure chamber 60.
and limits. A first plug 62 is fitted into the hole 38 to limit the rest position of the piston 50, and a second plug 64 is fitted into the hole 40 to limit the rest position of the piston 50.
6 rest positions are limited. Springs 66 and 68 are disposed within pressure chambers 54 and 60, respectively, to urge pistons 50 and 56 to a rest position in which they engage plugs 62 and 64, respectively.

The third hole 42 is stepped to form shoulders 70 and 72. A valve device 74 is disposed within this third hole. The valve device 74 includes a valve seat 76 that abuts the shoulder 72 and a valve member 78 that is biased by a spring 80 into engagement with the valve seat 76 . It is interposed between. Valve seat 76 has a hole 82 communicating with opening 84 . Valve member 78 extends to engage the wall of aperture 84 and interrupts communication between the portion of aperture 42 between shoulders 70 and 72 and aperture 82 . This portion of the hole 42 between the shoulders communicates with the accumulator 22 via an inlet 86.

An input device 90 is connected to the input rod 14. Input device 90 includes a piston 92 that sealingly and movably engages the wall of bore 32 adjacent open end 34 . Piston 92 includes a radially extending flange 94 disposed within chamber 36 and a recess 96 for receiving a spring 98. Input device 90 also includes a plunger 100 extending within bore 82 of valve seat 76 and opposing valve member 78 . A cap 102 is fitted within the piston recess 96 and engages the end of the plunger 100, with a snap ring 104 defining the rest position of the cap 102. Housing part 30 and snap spring 10
A spring 106 is interposed between the piston 92 and the flange 94 to resist movement of the piston 92.
is brought into contact with the housing portion 28.

Housing portion 30 includes outlets 108 and 110, outlet 108 communicating first pressure chamber 54 with brake circuit 18, and outlet 110 communicating second pressure chamber 60 with brake circuit 20. A pair of fill ports 112 and 114 in housing portion 30 communicate pressure chambers 54 and 60 with reservoir 116 in the rest position. Housing portion 30 extends from hole 42 to hole 3.
8 and 40 to connect the working chambers 52 and 58 to the valve device 74.
a pair of passages 118 and 120 communicating with the
Valve seat 76 of the valve arrangement connects its hole 82 to passage 118 and 1
20 is provided with a restriction orifice 122 communicating therewith. Plunger 100 includes an axially extending bore 1 that communicates working chambers 52 and 58 with chamber 36 through a radial opening 126 adjacent cap 102.
It has 24. Chamber 36 is in constant communication with reservoir 116 via outlet 128.

A pair of pins 130 and 132 are movably supported within openings 134 and 136 of plugs 62 and 64, respectively. In the rest position shown, pin 130
and 132 are the piston flange 94 and the piston 5
It is far from 0 and 56. Pins movably disposed within openings 134 and 136 are responsive to fluid pressure in communication with the corresponding working chambers. These pairs of pins 130 and 132 are connected to piston flange 94 and pistons 50, 56 in the event of a fluid pressure system failure.
It constitutes a connecting device that connects the

Brake booster 16 is shown in a rest position in which pistons 50 and 56 abut corresponding plugs 62 and 64, piston flange 94 abuts housing portion 28, and pins 130 and 132 abut flange 94. Alternatively, a gap is formed between the pistons 50, 56, or both. Fluid pressure from the accumulator 22 communicates with the portion of the bore 42 between the shoulders 70 and 72.
Because the diameter of valve member 78 at opening 84 is approximately equal to the diameter at its left end, valve member 78 is pressure balanced;
Spring 80 holds the valve member in engagement with valve seat 76, thus blocking fluid passage between accumulator 22 and working chambers 52, 58. Plunger 100 is isolated from valve member 78 to open aperture 124 into working chambers 52 and 58, so that the working chambers are in communication with reservoir 116.

When applying the brake, the brake pedal 12 is rotated clockwise in the figure, causing the input rod 14 and piston 9 to
Move 2 to the left. Snap spring 104 moves with piston 92 to compress spring 106. Initially, spring 98 moves in an extended state with piston 92 to move plunger 100 to the left.

If the clearance at pins 130 and 132 is greater than the clearance between plunger 100 and valve member 78 that corresponds to the initial amount of movement of input device 90 from the rest position, then upon initial brake application, pin 130
The gap between flange 94 and piston 5 is
0.56, the valve member opens before absorption. That is, plunger 100 engages and isolates valve member 78 from valve seat 76, and fluid pressure is communicated to bore 82 and through restriction orifice 122 and passages 118 and 120 to working chambers 52 and 58. Ru. Valve member 78 includes a passageway 79 that communicates fluid pressure to its left end so that the valve member remains pressure balanced during brake application. Fluid pressure within bore 82 acts on plunger 100 to bias it to the right against spring 98.
Also, the fluid pressure in the working chambers 52 and 58 is
0 and 56 to move the piston to the left and pressurize the fluid confined within the first and second pressure chambers 54 and 60. Fluid pressure within the working chamber also acts on pins 130 and 132, resisting leftward movement of the pins while causing them to engage flange 94. Pins 130 and 132 are plunger 1
00 to generate a reaction force that resists leftward movement of the piston 92. This reaction force is provided by fluid pressure acting on the plunger and pin. Accordingly, during initial braking application, the fluid pressure communicating with the working chambers 52 and 58 will act on the three reaction sections described above, gradually producing a reaction force proportional to the power acting on the pistons 50 and 56. . In this case, by varying the clearance at pins 130 and 132, a set point or You can change the knee point.

Further brake application causes spring 98 to contract slightly while valve member 78 modulates between open and closed positions to increase fluid pressure in communication with working chambers 52 and 58. At this point, piston flange 94 forces pins 130 and 132 into the working chamber, reducing the gap between them and pistons 50,56. Therefore, pistons 50 and 56
moves further to the left and contracts springs 66 and 68, causing pressure chambers 54 and 60 and brake circuit 18 to contract.
and 20.

Upon still further application of the brakes, the input device 90 is moved to the left and the plunger 100 pushes the valve member 78 leftward toward the end of the hole 42 proximate the bottom wall 48. Alternatively, springs 98 and 80
Depending on the selection of the spring constant, the input device 90 will move relative to the plunger 100 and the plunger will be absorbed into the recess 96 causing the spring 98 to contract further. In addition, input device 90 moves leftward to communicate pins 130 and 132 with pistons 50 and 56, so that further leftward movement of input device 90 causes fluid pressure in pressure chambers 54 and 60 to increase. will be increased.

If the clearance between pins 130 and 132 is less than the clearance between plunger 100 and valve member 78, the vehicle operator will first resist the force of springs 106, 66, and 68 during initial braking application. to move the input device 90, and then move the plunger 100.
will move the valve member 78 to the open position.
Therefore, plunger 100 and pins 130 and 13
The reaction force due to the fluid pressure acting on pins 130 and 132 occurs with a delay, but even in this case, the forces of springs 66 and 68 act on pins 130 and 132, so pin 13
By varying the gap at 0 and 132, the set point or knee point at which springs 66 and 68 create a reaction force that resists the input of input device 90 can be varied.

Pedal 12 by the driver of the vehicle when releasing the brake
As the force on is released, spring 106 causes piston 92 to move to the right. Plunger 1
00 and the valve member 78 are moved to the right,
The valve member is engaged with the valve seat 76 and the plunger is isolated from the valve member. Thus, fluid pressure within actuating chambers 52 and 58 is vented to chamber 36 via passageways 118 and 120 and restriction orifice 122, causing springs 66 and 68 to force pistons 50 and 56 into plug 62.
and move it towards 64.

During brake release, pins 130 and 132 are moved to the right with piston flange 94 by fluid pressure within working chambers 52 and 58 after leaving pistons 50 and 56. When the fluid pressure in the working chamber is vented to chamber 36 and the pressures in these chambers are equalized, pins 130 and 132 are no longer engaged with pistons 50 and 56, so pins 130 and 132 are removed from plugs 62 and 64 as shown. While remaining substantially stationary, piston 92 continues to move to the right due to spring 106 until flange 94 abuts housing portion 28 . piston 50 and 5
6 is moved to the right by springs 66 and 68 into contact with plugs 62 and 64, but is kept away from pins 130 and 132 because of the recesses formed in its opposite ends. Therefore, the gap between the pin and flange 94 and/or the gap between the pin and the piston is set again.

In the event of a failure of one of the pumps, accumulators, valve gear, or brake circuit, a heavy brake application will cause the input piston 92 to be moved to the left by the pedal 12 and the pistons 50 and 56 via pins 130 and 132. mechanically push the
The mechanical connection between input piston 92 and pistons 50 and 56 therefore applies the other brake at the input. During fault braking, valve member 78 is moved to the left to retract spring 80 and plunger 100 is moved into recess 96 to retract spring 98.

If a sliding fit between the plug and the pin does not provide a sufficient seal of the working chamber, it is within the skill of the person skilled in the art to provide a sealing ring between them. It is also possible to provide a sealing ring between the plunger and the valve seat.

[Brief explanation of the drawing]

The drawing is a schematic representation of a brake system with a brake booster according to the invention, with the booster shown in cross section. 16... Brake booster, 26... Housing, 38, 40, 42... Hole, 50, 56... Piston, 52, 58... Working chamber, 74... Valve device, 76... Valve seat, 78... Valve member, 90...Input device, 92...Piston, 100...Plunger, 102...Cap, 130, 132...Pin (coupling device).

Claims (1)

[Claims] 1. A first hole 38 that accommodates the first piston 50, a second hole 40 that is provided parallel to the hole and that accommodates the second piston 56, and a third hole 4 that accommodates the valve device 74.
2, an input device 90 extending within the housing and cooperating with the valve arrangement 74 to control fluid pressure communication to the first and second holes during brake application; and the first and second pistons 50, 56, when the fluid communicating with the first and second holes cannot move the first and second pistons, respectively, the input device and both pistons. In the brake booster, the coupling devices 130, 132 mechanically connect the input device 90 and both pistons 5 in the rest position.
A gap is formed between the input device 0 and 56 to provide a lost movement connection, and the input device, after the initial movement,
The connecting device 130, 132 is engaged with the valve device 74 to open the valve device and communicate fluid pressure to the first and second holes 38, 40, and the connecting device 130, 132 is connected to the first and second holes. A brake booster characterized in that, in response to fluid pressure, a reaction force is transmitted to the input device 90 to resist its movement. 2 The gap is formed between the coupling devices 130 and 132 after the input device 90 engages with the valve device 74.
2. The brake booster of claim 1, wherein the brake booster is greater than an initial travel amount of the input device so as to engage the pistons 50, 56 through the input device. 3 The gap is such that the coupling devices 130 and 13 are connected to each other before the input device 90 engages the valve device 74
2. The brake booster of claim 1, wherein the brake booster is smaller than an initial travel amount of the input device so as to engage the pistons 50, 56 via the input device.