JPH10194110A - Brake power assist - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the outside diameters of springs to be enlarged to obtain an adequate set load and enable the servo ratio to be freely set through the contact areas of a reaction disc with a holder and a plate plunger. SOLUTION: This brake power assist is provided with reaction force transmitting means 33 having springs 43, 44 which are compressed when brake reaction force from a reaction disc 35 exceeds a set load. A holder 36 is mounted to a valve body 6 so that the brake reaction force transmitted to the reaction disc can be received by the valve body through the holder. Further, a plate plunger 34 is slidably fitted in the holder to transmit the brake reaction force transmitted to the reaction disc to the reaction force transmitting means, a valve plunger 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake booster for use in a vehicle brake system.

[0002]

2. Description of the Related Art Conventionally, a brake booster generally includes a valve body provided slidably in a shell, a valve mechanism provided in the valve body, and a valve plunger which constitutes the valve mechanism is advanced and retracted. An input shaft for switching the flow path, an output shaft slidably provided on the valve body, and a reaction disk interposed between the base of the output shaft and the valve plunger. In a brake booster of this type, a brake reaction force applied to an output shaft is transmitted from a reaction disk to a brake pedal via a valve plunger and an input shaft. At this time, if the servo ratio of the brake booster is set large,
That is, when the reaction force transmitted to the brake pedal is set to be small, the brake booster can be operated with a light pedaling force, but the operability is deteriorated in a range where a small braking force is required. Conversely, if the servo ratio of the brake booster is set to a small value, the ratio of the reaction force transmitted to the brake pedal increases, so that operability in a range where a small brake force is required should be improved. On the other hand, a large pedal force is required to obtain a large output, and it has been particularly difficult for a woman or an old man to obtain a large braking force. For this reason, conventionally, a reaction force transmitting means having a spring that is compressed when the brake reaction force exceeds a set load is interposed between the reaction disc and the valve plunger, and a small servo ratio is used in the initial stage of braking of the brake booster. However, a brake booster has been proposed in which a large servo ratio can be obtained in the latter period of braking (Japanese Patent Laid-Open No. 59-92242, Japanese Utility Model Laid-Open No. 61-205).
858, JP-A-8-85442). According to such a brake booster, the servo ratio of the brake booster can be reduced in the initial stage of braking, so that operability in a range where a small brake force is required can be improved, and braking can be improved. Since the servo ratio increases in the latter period, a large braking force can be obtained with a light pedaling force.

[0003]

By the way, generally, when an optimum set load is to be obtained, the outer diameter of the spring increases, and when the outer diameter of the spring increases, the hole of the valve body for accommodating the spring increases. It is necessary to increase the inside diameter of The brake reaction force from the reaction disk is transmitted to the reaction force transmission mechanism having the spring and the valve body, but when the outer diameter of the spring is increased, that is, the contact area between the reaction disk and the reaction force transmission mechanism is reduced. If it has increased, it is necessary to increase the outer diameter of the reaction disk to increase the contact area between the reaction disk and the valve body in order to keep the servo ratio constant. However, when the outer diameter of the reaction disk is increased, problems such as difficulty in forming the constant pressure passage and enlargement of the valve body arise. On the other hand, if the outer diameter of the reaction disk is not increased, the servo ratio at the initial stage of braking increases, and the intention to provide the reaction force transmitting means is lost, and the contact area between the reaction disk and the valve body decreases, and the valve body decreases. There is also a drawback that the strength of the steel is reduced. In view of such circumstances, the present invention provides a brake booster capable of obtaining a required servo ratio without increasing the outer diameter of the reaction disk even if the outer diameter of the spring of the reaction force transmitting means is increased. An apparatus is provided.

[0004]

That is, the present invention provides a valve mechanism which is slidably provided in a shell, a valve mechanism provided in the valve body, and a valve plunger which constitutes the valve mechanism is advanced and retracted. An input shaft for switching the flow path of the valve body, an output shaft slidably provided on the valve body, a reaction disk interposed between a base of the output shaft and the valve plunger, and a reaction disk between the reaction disk and the valve plunger. And a reaction force transmitting means having a spring that is interposed between the reaction disk and transmits a brake reaction force from the reaction disk to the valve plunger and is compressed when the brake reaction force exceeds a set load. , A holder is mounted on the valve body, and the reaction disk is disposed on the front side of the holder to dispose the reaction disk. The brake reaction forces transmitted to the disk along with undergo in the valve body through the holder,
A brake booster, wherein a plate plunger is slidably fitted to the holder, and the brake reaction force transmitted to the reaction disk is transmitted to the reaction force transmission means via the plate plunger.

[0005]

According to the above construction, the brake reaction force transmitted to the reaction disk is received by the valve body via the holder, and the reaction force via the plate plunger slidably fitted to the holder. It is transmitted to the transmission means and further transmitted to the valve plunger. The servo ratio at this time is obtained from the contact area between the reaction disk and the holder and the contact area between the reaction disk and the plate plunger. Therefore, even if the outer diameter of the spring of the reaction force transmitting means is increased in order to obtain a suitable set load, the contact area between the reaction disc, the holder and the plate plunger is set to be optimal regardless of the outer diameter. Thus, a suitable servo ratio can be set freely.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiment. In FIG. 1, a shell 2 of a tandem brake booster 1 defines a front chamber 4 and a rear chamber 5 in front and rear by a center plate 3. . Then, the cylindrical valve body 6 is connected to the rear side of the shell 2 and the center plate 3.
The airtightness is maintained by sealing means 7 and 8, respectively, so as to be slidably penetrated. A front power piston 10 and a rear power piston 11 are provided on the outer periphery of the valve body 6 located in the front chamber 4 and the rear chamber 5, respectively.
And a front diaphragm 12 and a rear diaphragm 1 on the back of each power piston 10, 11.
3 are stretched respectively. A constant pressure chamber A and a variable pressure chamber B are formed before and after the front diaphragm 12 in the front chamber 4, and a constant pressure chamber C and a variable pressure chamber D are formed before and after the rear diaphragm 13 in the rear chamber 5. . In the valve body 6, a valve mechanism 15 for switching a communication state between the constant pressure chambers A and C and the variable pressure chambers B and D is provided. The valve mechanism 15 includes an annular first valve seat 16 formed on the valve body 6, and a valve plunger 17 slidably provided on the valve body 6 inside the first valve seat 16.
An annular second valve seat 18 formed on the rear side of the valve seat and a valve body 20 further seated on both valve seats 16 and 18 by a poppet return spring 19. The first valve seat 1
The space on the outer peripheral side of the annular seat portion of the valve body 20 that comes into contact with and separates from the valve body 6 communicates with the constant pressure chamber A through a first constant pressure passage 21 formed in the valve body 6, and the inside of the constant pressure chamber A is a second constant pressure passage. It communicates with the constant pressure chamber C via 22. Above constant pressure chamber A
Is connected to a negative pressure source (not shown) via a negative pressure introducing pipe 23, whereby a constant negative pressure is introduced into the constant pressure chambers A and C. Further, a space inside the annular seat portion of the valve body 20 that comes into contact with and separates from the first valve seat 16 and on the outer peripheral side of the seat portion of the valve body 20 that comes into contact with and separates from the second valve seat 18 is formed in the valve body 6. The variable pressure chamber D communicates with a variable pressure chamber D via a first radial variable pressure passage 24 in the radial direction, and the variable voltage chamber D communicates with a variable pressure chamber B via a second variable pressure passage 25 formed in the valve body 6. Further, a space on the inner peripheral side of the annular seat portion of the valve body 20 that is in contact with the second valve seat 18 communicates with the atmosphere via a pressure passage 26 formed in the valve body 6 and a filter 27 provided therein. .

The right end of the valve plunger 17 has an input shaft 3
A valve return spring 31 having an elasticity greater than the elasticity of the poppet return spring 19 is elastically mounted between the input shaft 30 and the valve body 6. , Usually valve plunger 17
The valve body 20 is seated on the second valve seat 18 and the valve body 20 is separated from the first valve seat 16 of the valve body 6. The end of the input shaft 30 is linked to a brake pedal (not shown). Further, the valve plunger 17 is prevented from coming out of the valve body 6 by the key member 32. The key member 32 can move forward and backward in the axial direction of the valve body 6, and abuts on the inner surface of the shell 2 when the brake booster 1 is not operated to hold the valve plunger 17 in the forward position with respect to the valve body 6. The loss stroke of the input shaft 30 at the start of the operation of the brake booster 1 can be reduced. Further, on the front side of the valve plunger 17, a reaction force transmitting means 33, which will be described in detail later, a plate plunger 34 and a reaction disk 35 are sequentially arranged. The plate plunger 34 is
The valve body 6 is slidably fitted in a holder 36 which is fixed to the front end surface of the valve body 6 while maintaining airtightness. The reaction disk 35 is housed in a concave portion formed at the base of the output shaft 37. The recess formed in the base of the output shaft 37 is slidably fitted on the outer peripheral surface of the holder 36,
The distal end of the output shaft 37 is kept airtight by a seal member 38 and protrudes out of the shell 2, and is linked to a piston of a master cylinder (not shown). Therefore,
The brake reaction force transmitted from the piston of the master cylinder is applied to the reaction disk 3 via the output shaft 37.
5 and received by the valve body 6 from the reaction disk 35 via the holder 36 and transmitted to a brake pedal (not shown) via the plate plunger 34, the reaction force transmitting means 33, the valve plunger 17 and the input shaft 30. It has become so. The valve body 6 and the power pistons 10 and 11 are normally held at a non-operating position by a return spring 39 mounted between the shell 2 and the valve body 6.

Next, the reaction force transmitting means 33 includes a first retainer 41 and a second retainer 4 as shown in an enlarged view in FIG.
2 and two coil springs 43 and 44 which are concentrically arranged and mounted between the two retainers 41 and 42. The first retainer 41 is slidably fitted in a large-diameter hole 6A formed in the valve body 6, and extends radially inward from a front end of the outer cylindrical portion 41a. And a radial portion 41b abutting on the rear end surface of the plate plunger 34;
Inner cylindrical portion 41 extending from the inner peripheral side to the axial front side
c. On the other hand, the second retainer 42 has an outer tubular portion 42a slidably fitted in the outer tubular portion 41a of the first retainer 41 and a radially inner portion from the rear end of the outer tubular portion 42a. Radial portion 42b extending toward the front side and abutting against the front end surface of the valve plunger 17.
And a protruding portion 42c protruding from the center of the radial portion 42b to the front side and slidably fitted in the inner cylindrical portion 41c of the first retainer 41. The coil springs 43 and 44 are elastically mounted between the radial portion 41b of the first retainer 41 and the radial portion 42b of the second retainer 42, and the coil springs 43 and 44 are compressed by a predetermined amount. In this state, the retaining portion 41d provided at the rear end of the outer cylindrical portion 41a of the first retainer 41 is brought into contact with the radial portion 42b of the second retainer 42, so that both the retainers 41, 42 and Coil spring 4
3, 44 are integrally assembled.

Further, when the brake booster 1 is not operated, the locking portion 41d of the first retainer 41 is in contact with the radial portion 42b of the second retainer 42 in contact with the front end surface of the valve plunger 17. A gap L1 is formed between the valve body 6 and the abutting portion of the valve body 6, and in this state, the radial portion 4 of the first retainer 41 is formed.
A gap L2 is formed between the plate plunger 34 abutting on 1b and the protrusion 42c of the second retainer 42. By setting the gap L2 larger than the gap L1, the locking portion 41d of the first retainer 41 is brought into contact with the valve body 6 before the plate plunger 34 comes into contact with the projection 42c of the second retainer 42. So that it can abut the part.

In the above arrangement, when the brake pedal is depressed to advance the input shaft 30 and the valve plunger 17, the reaction force transmitting means 33 is operated until the depression force exceeds the set load of the two coil springs 43 and 44. 2 is integrally advanced while maintaining the state of FIG. 2, whereby the plate plunger 34 is also advanced. And the valve plunger 17
Is advanced, the air flow is introduced into the variable pressure chamber B by switching the flow path of the valve mechanism 15 in the same manner as the conventionally known brake booster, so that the pressure difference between the constant pressure chamber A and the variable pressure chamber B Since the power pistons 10, 11 and the valve body 6 are advanced, whereby the output shaft 37 is advanced, a brake fluid pressure is generated in the master cylinder. The brake reaction force due to the brake fluid pressure is transmitted to the reaction disk 35 via the output shaft 37, and further from the reaction disk 35 to the plate plunger 34 and the reaction force transmission means 33.
Is transmitted to the brake pedal via the first retainer 41, the two coil springs 43 and 44, the second retainer 42, the valve plunger 17 and the input shaft 30. FIG. 3 shows the relationship between the pedal effort (input) and the output of the brake booster 1 at this time.
Is indicated by a straight line A.

When the depressing force of the brake pedal increases from the above-mentioned state and the output of the brake booster 1 increases, the brake reaction force also increases accordingly, and the reaction force is
When the set load of the two coil springs 43, 44 is exceeded, both coil springs 43, 44 are compressed, and the second retainer 42 is advanced relative to the first retainer 41 (point B in FIG. 3). ). When the coil springs 43 and 44 are compressed, the second retainer 42 and the valve plunger 17 are advanced accordingly, so that the output of the brake booster 1 is larger than the servo ratio indicated by the slope of the straight line A. It increases with the servo ratio (straight line C in FIG. 3). The inclination (servo ratio) of the straight line C is determined by the two coil springs 4.
By setting the spring constants of 3, 44 as appropriate, they can be set freely. At this time, the second retainer 4
2 and the valve plunger 17 are advanced relatively to the first retainer 41, but the position of the valve plunger 17 in the servo balance state, that is, the valve body 20 is positioned between the first valve seat 16 and the second valve seat 18 Since the position for simultaneous seating is substantially constant with respect to the valve body 6, in practice, the first retainer 42 and the valve plunger 17 are in the first position.
The retainer 41 is relatively retracted.

As the compression of the coil springs 43 and 44 continues, the engaging portion 41d of the first retainer 41 comes into contact with the valve body 6 (point D in FIG. 3). Then, all of the brake reaction force transmitted from the plate plunger 34 to the valve plunger 17 via the reaction force transmission means 33 can be received by the valve body 6.
Thereafter, the brake reaction force transmitted to the valve plunger 17 does not increase. As a result, even if the brake pedal is further depressed, the brake reaction force cannot exceed a certain value.
Cannot be pushed back, and the air is continuously introduced into the transformer chamber B, so that the output increases without increasing the pedaling force (the straight line E in FIG. 3), and the brake booster 1 Becomes a full load state (point F in FIG. 3). When the brake pedal is depressed, the plate plunger 34
When the gap L2 between the plate plunger 34 and the protruding portion 42c abuts and the plate plunger 34 abuts on the protruding portion 42c, the depression force of the brake pedal is applied from the valve plunger 17 to the protruding portion 42c of the second retainer 42, the plate. Output shaft 3 via plunger 34 and reaction disk 35
7, the output of the brake booster 1 increases in a 1: 1 relationship with the increase in the depression force of the brake pedal (straight line G in FIG. 3).

In the above embodiment, the point B in FIG. 3 can be freely set by changing the set load of the two coil springs 43 and 44. Further, since the reaction force transmitting means 33 can be assembled in advance as an assembly, it is only necessary to arrange the reaction force transmitting means 33 at a predetermined position when assembling the brake booster. Properties can be improved.

FIG. 4 shows a second embodiment of the present invention. In this embodiment, two coil springs are provided in the first embodiment. In this embodiment, the large-diameter hole 10 of the valve body 106 is provided at the rear end of the holder 136.
A cylindrical portion 136a projecting into 6A is formed, and the distal end portion of the outer peripheral side cylindrical portion 141a of the first retainer 141 is loosely fitted into the cylindrical portion 136a. The first retainer 141 includes a stepped outer cylindrical portion 141a having a small diameter on the front side, and a radial portion 141b extending radially inward from a front end of the stepped outer cylindrical portion 141a.
And an inner cylindrical portion 141c extending rearward from the inner peripheral portion of the radial portion 141b. The protruding portion 117B of the valve plunger 117 is slidably fitted in the inner cylindrical portion 141c. ing. On the other hand, the second retainer 142
The outer cylindrical portion 1 slidably fitted in the rear-side large-diameter portion of the outer cylindrical portion 141a of the first retainer 141.
42a, a radial portion 142b extending radially inward from the rear end of the outer cylindrical portion 142a, and an inner cylindrical portion 142c extending frontward from the inner peripheral portion of the radial portion 142b. In addition, the projecting portion 117B of the valve plunger 117 is slidably fitted in the inner cylindrical portion 142c. Further, a ring-shaped stopper 140 is attached by caulking to a rear side portion of the outer cylindrical portion 141a of the first retainer 141, and the stopper 140
This prevents the second retainer 142 from dropping out of the first retainer 141. And the first retainer 1
A coil spring 143 is elastically mounted between the radial portion 141b of the second retainer 141 and the radial direction 142b of the second retainer 142, and the radial portion 142b of the second retainer 142 is normally provided on the first retainer 141 by the coil spring 143. Abutted against the stopper 140. The other configuration is the same as that of the first embodiment, except for the gaps L1 and L2.
The same parts as those in the first embodiment are denoted by “100” in the first embodiment.
Is added. And according to this embodiment,
Even if the valve plunger 117 is tilted and operated with respect to the valve body 106 during operation of the brake booster, the first retainer 141 and the second retainer 142 do not allow the valve body 106 to operate.
Since there is no sliding or contact between them and the holder 136, there is no danger of generating abnormal noise.

[0015]

As described above, according to the present invention, the outer diameter of the spring of the reaction force transmitting means can be increased in order to obtain a suitable set load, and at the same time, the reaction disk, the holder and the plate plunger can be used. By setting the contact area to be optimal, an effect that a suitable servo ratio can be set freely can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a main part of the present invention.

FIG. 3 is a characteristic diagram of the embodiment.

FIG. 4 is a sectional view showing a second embodiment of the present invention.

[Explanation of symbols]

6, 106… Valve body 6A, 106A
... large-diameter holes 15, 115 ... input shafts 17, 117 ...
Valve plunger 117B ... projecting part 30, 130 ...
Input shafts 33, 133 ... reaction force transmitting means 34, 134 ...
Plate plunger 35, 135 ... Reaction disk 36, 136 ...
Holders 37, 137 ... Output shafts 41, 141 ...
First retainers 42, 142... Second retainers 43, 44, 1
43 ... Coil spring

Claims (3)

[Claims] 1. A valve body slidably provided in a shell, a valve mechanism provided in the valve body, and an input shaft for switching a flow path of the valve mechanism by moving a valve plunger constituting the valve mechanism forward and backward. An output shaft slidably provided on the valve body, a reaction disk interposed between the base of the output shaft and the valve plunger, and an output shaft interposed between the reaction disk and the valve plunger, A brake booster that transmits a brake reaction force to a valve plunger and a reaction force transmission means having a spring that is compressed when the brake reaction force exceeds a set load, wherein a holder is attached to the valve body; The above reaction disk is arranged on the front side of the holder, and the brake reaction force transmitted to the reaction disk is reduced. Receiving the valve body via the holder and slidably fitting a plate plunger to the holder, and transmitting the brake reaction force transmitted to the reaction disk to the reaction force transmission means via the plate plunger. A brake booster characterized by the following. 2. The reaction force transmitting means is elastically mounted with a predetermined set load between a first retainer and a second retainer which are respectively displaceably provided on the valve body, and between the first retainer and the second retainer. And a spring that normally holds the two retainers in a separated state, and transmits a brake reaction force transmitted from the reaction disk to the valve plunger via the first retainer, the spring, and the second retainer. The brake booster according to claim 1. 3. The reaction disk is housed in a recess formed in a base of an output shaft, and the recess of the output shaft is slidably fitted on an outer peripheral surface of the holder. The brake booster according to claim 1 or 2.