JPS6226156A - Braking force servo unit - Google Patents

Abstract

PURPOSE:To enable servo ratios of relatively many kinds to be obtained by allowing an effective diameter of a diaphragm, on which a fluid pressure inducted into each of pressure chambers acts, to be made different between both sides of the diaphragm. CONSTITUTION:An effective diameter D1 of a diaphragm on a pressure chamber (45) side is designed to be capable of being increased to be larger by far than an effective diameter D2 of the diaphragm which energizes the said diaphragm to the opposite direction. No.1 turned edge 42a is formed on the inner circumference of the diaphragm 42 which is connected with an auxiliary piston 40, a turn-over preventing section 40a which is located on the inner side of No.1 turned edge 42a preventing the turned edge from being turned over, is provided for the auxiliary piston 40 while being integrally formed simultaneously. On the other hand, No.2 turned edge 42b is formed on the outer circumference of the diaphragm 42 which is connected with a valve body 6, and a turn-over preventing section 6d which prevents No.2 turned edge 42b from being turned over, is integrally formed in a similar manner.

Description

[Detailed description of the invention] "Industrial application field" The present invention relates to a brake booster used in a vehicle.

"Prior Art" In general, a brake booster consists of a power piston slidably disposed within a shell, a valve mechanism housed in a valve body of the power piston shaft, and a front side of the power piston in the operating direction. a constant pressure chamber formed in the rear side, a variable pressure chamber formed in the rear side, an input shaft that operates a valve plunger constituting the valve mechanism to switch the wave path and supply pressure fluid to the variable pressure chamber to advance the power piston. It is equipped with

However, in conventional brake boosters of this type, the servo ratio is substantially constant and cannot be changed. Therefore, for example, when a brake booster is used as a brake booster for a truck, there will be a difference in the driver's braking sensation when the vehicle is empty and when the vehicle is loaded, and the braking force will be perceived to be smaller when the vehicle is loaded. There were many things.

Furthermore, even under the same braking condition, some drivers may perceive the braking force to be too large or too small, and there are individual differences in preferred braking sensations.

For this reason, the applicant provided an auxiliary piston in a space formed in the valve body, connected it to the valve plunger, and applied fluid pressure to the auxiliary piston to move the valve plunger in the operating direction. We have proposed a brake booster that can adjust the servo ratio by applying force to the front or rear side and exerting force in the same or opposite direction for the same pedal force (Japanese Patent Application No. 130-198). No. 24807,
(Japanese Patent Application No. Sho H-53984).

[Problems to be Solved by the Invention] However, when a sliding seal member is provided on the auxiliary piston and pressure chambers are formed on both sides of the sliding seal member, a problem arises in that hysteresis occurs due to the sliding resistance of the sliding seal member. Therefore, it is desirable to form the pressure chamber with a diaphragm that does not cause such problems.

However, when pressure chambers are formed by diaphragms, 1, generally speaking, the fluid pressure introduced into one pressure chamber is always kept greater than the fluid pressure introduced into the other pressure chamber, so that the diaphragm is separated from the auxiliary piston, or Because it is necessary to prevent part of the fluid from getting caught during re-contact, there are certain restrictions on the size of the pressure fluid introduced into the pressure chambers on both sides of the diaphragm, and therefore a wide variety of servo ratios can be obtained. There were restrictions on that.

In order to obtain other types of servo ratios, it is possible to supply fluid pressure of any size to the pressure chambers on both sides of the diaphragm regardless of the above-mentioned size relationship, but it is possible to prevent the above-mentioned jamming etc. If this configuration is adopted, the effective diameter of the diaphragm on both sides of the diaphragm, on which fluid pressure acts, is usually the same. When selecting the above servo ratio,
It is desirable to select several types of optimal servo ratios that correspond to various conditions, but if the effective diameters on both sides of the diaphragm are the same, it will be difficult to freely select the value of the servo ratio. It was hoped that they would be able to freely vary the

In particular, the brake booster equipped with the above-mentioned auxiliary piston detects a certain condition such as when the vehicle is stopped, and energizes the auxiliary piston to forcibly switch the above-mentioned valve mechanism to create atmospheric pressure in the variable pressure chamber. It is possible to use this as a parking brake device that can perform braking even when the brake pedal is not depressed. However, in order to switch the valve mechanism, the pressure receiving area of the auxiliary piston must be If it is made considerably large, the servo ratio becomes too large, making it difficult to perform fine servo ratio control.

"Means for Solving the Problems" In view of such circumstances, the present invention provides a diaphragm stretched between the auxiliary piston and the valve body to form pressure chambers on both sides of the diaphragm. A supply device is provided for supplying pressure fluid to the pressure chambers, and when the pressure fluid is supplied to one of the pressure chambers, at least one of the auxiliary piston and the housing receives pressure by coming into close contact with the diaphragm. , forming a radially extending support part that allows separation from the diaphragm when pressure fluid is supplied to the other pressure chamber, and increasing the effective diameter of the diaphragm on which the pressure fluid introduced into each pressure chamber acts. Both sides of the diaphragm are different.

``Operation'' With such a configuration, not only will hysteresis not occur as in the case of using the above-mentioned sliding seal member, but also a relatively wide variety of servo ratios can be achieved since the effective diameters on both sides of the diaphragm are different. In particular, it is possible to obtain the required small servo ratio change with a small pressure receiving area on the effective diameter side, while ensuring a good ja of the above-mentioned parking brake device due to the large pressure receiving area on the effective diameter side. Become.

``Embodiment'' The present invention will be described below with reference to an illustrated embodiment. In FIG. 1, a power piston 2 is slidably provided in a shell 1 of a brake booster, and a diaphragm 3 is installed on the back surface of the power piston 2. The power piston 2 and the diaphragm 3 partition the inside of the shell 1 into a constant pressure chamber 4 at the front and a variable pressure chamber 5 at the rear. A valve body 6 is integrally attached to the shaft of the power piston 2.
A valve mechanism 7 for switching the flow path is housed within the valve body 6.

The valve mechanism 7 has a first valve seat 10 formed on the valve body 6.
, the rear side of the power piston 2, that is, the first valve seat 12 and both valve seats 10.
Valve body 1 is seated from the right side of the figure by the elastic force of spring 13
It is equipped with 4. Then, the first valve seat 10 and the valve body 14
The constant pressure chamber 4 is connected to the constant pressure chamber 4 through the passage 15 on the outside of the seat part.
Further, the constant pressure chamber 4 is communicated with a negative pressure source such as an engine intake manifold (not shown) via a negative pressure introduction pipe 16 provided in the shell 1.

On the other hand, the first valve seat 10 and the valve body 14. and second valve seat 1
2 and the valve body 14, the valve body 6
It communicates with the variable pressure chamber 5 through a passage 17 formed in the same direction, and further communicates with the atmosphere through a filter 18 inside the seat portion between the second valve seat 12 and the valve body 14. The variable pressure chamber 5 is kept airtight from the outside by a seal member 19 that slidably passes through the valve body 6.

The valve plunger 11 constituting the valve mechanism 7 is connected to an input shaft 25 that is linked to a brake pedal (not shown), and the tip surface of the valve plunger 11 is connected to a reaction disk 27 housed in a recess formed at the base of the output shaft 26. is facing. The output shaft 26 is connected to a sealing member 28.
It penetrates and projects to the outside of the shell 1, and is linked to a piston of a master cylinder (not shown).

The power piston 2, valve body 6, etc. are normally held in the non-operating position shown in the figure by a return spring 29, and in this non-operating state, the valve plunger 11 is prevented from being pulled out from the valve body 6. The key member 30 is attached to the inner surface of the shell l':! ! 3 in contact with each other to restrict the free movement of the valve plunger 11 to the right with respect to the valve body 6;
Next, when the input shaft 25 and the valve plunger 11 are actuated, the valve mechanism 7 can immediately switch the fluid circuit.

The above configuration is basically the same as a conventionally known negative pressure type brake booster, and when the brake pedal (not shown) is depressed and the input shaft 25 and valve plunger 11 are moved to the left, the valve body 14 is First valve seat 1 of valve body 6
0 to cut off communication between the variable pressure chamber 5 and the constant pressure chamber 4, and the valve body 14 is seated on the second valve seat 1 of the valve plunger 11.
2 and communicates the atmosphere with the variable pressure chamber 5, thereby supplying the atmosphere into the variable pressure chamber 5. When a pressure difference is generated before and after the power piston 2 and the power piston 2 is moved forward against the repulsive force of the return spring 29, a braking action is performed.

When the force on the brake pedal is released from this brake operating state, the second valve seat 12 of the valve plunger 11 seats on the valve body 14, cutting off communication between the variable pressure chamber 5 and the atmosphere.
Since the valve body 14 is separated from the first valve seat 10 and communicates the variable pressure chamber 5 with the constant pressure chamber 4, the power piston 2 is returned to its original non-operating position by the return spring 29.

Then, due to the retraction of the power piston 2, the key member 3
0 comes into contact with the inner surface of the shell 1, the associated retreat of the valve plunger 11 stops, but the power piston 2 and the valve body 6 continue to retreat, and the valve body 6
The first valve seat 10 of the valve body 6 is moved back to the valve body 1 by the retraction of the
When the valve body 6 approaches the key member 4 and the gap between them becomes almost zero, the valve body 6 comes into contact with the key member 30 and stops. Therefore, the next time the input shaft 25 is moved forward again, the wave path of the valve mechanism 7 is immediately switched.

However, in this embodiment, the valve body 6 is comprised of a stepped cylindrical body 6a, an intermediate plate 6b fitted into the large diameter portion of the left end of the stepped cylindrical body 6d, and a stepped cylindrical body 6a. and a fixed plate 6c attached to the left end surface of the intermediate plate 6b and the fixed plate 6c.
It forms a space between.

A generally dish-shaped auxiliary piston 40 is slidably fitted into this space, and the auxiliary piston 40 is connected to the valve by the stepped portion formed on the valve plunger 11 and the snap ring 41 attached to the valve plunger 11. Plunger 1
1, and two diaphragms 42, 43 are stretched between the auxiliary piston 40 and the valve body 6 to partition the space into three pressure chambers 44, 45, 46.

The pressure chamber 44 located behind the auxiliary piston 40 is
A passage 47 formed in the valve body 6, a flexible conduit 48 spirally arranged in the constant pressure chamber 4 and connected to the valve body 6, and the conduit 48 formed outside the shell 1.
It is connected to a flow path switching mechanism 51 of a supply device i50 that supplies pressure fluid to the pressure chamber 44 through a conduit 48 connected to the pressure chamber 44. Similarly, the pressure chamber 45 located in front and outside of the auxiliary piston 40 also has a passage 52 formed in the valve body 6.
, a flexible conduit 5 spirally arranged in the constant pressure chamber 4
3, and is connected to the flow path switching mechanism 51 of the supply device 50 via a conduit 54 outside the shell 1. On the other hand, the pressure chamber 4 located in front and inside of the auxiliary piston 40
B is always communicated with the constant pressure chamber 4 through a passage 55 formed in the valve body 6.

The flow path switching mechanism 51 is connected to the constant pressure chamber 4 via a conduit 60.
It communicates with a negative pressure source (not shown) that communicates with the variable pressure chamber 5 through a conduit 61, and is further provided with an atmospheric boat 62 for introducing atmospheric pressure. Further, the supply device 50 is equipped with a control device 63 including a microcomputer, and this control device 83 receives a detection signal from a vehicle weight sensor 64 that detects the loading state of the vehicle and a signal from a stoppage sensor 65. Accordingly, the flow path of the flow path switching mechanism 51 is switched, and atmospheric pressure, the pressure inside the variable pressure chamber 5, or negative pressure is selectively introduced into the pressure chamber 44 on the rear side, and the pressure inside the variable pressure chamber 5 is introduced into the pressure chamber 45 on the front and outside side. It is possible to switch between internal pressure or negative pressure (see Figure 2).

The stop brake device 65 listed in L includes a vehicle speed sensor 66, a brake lamp switch 67, an accelerator switch 68, and so on. Parking brake release switch 69, parking brake switch 70. The vehicle weight sensor 64 includes one that detects the load from the suspension stroke between the vehicle body and the axle, and one that detects the load from a load switch installed on the seat. A device with an appropriate configuration, such as one that detects the amount, can be used.

Next, as mentioned above, atmospheric pressure is applied to the pressure chamber 44 on the rear side.
The pressure or negative pressure within the variable pressure chamber 5 is introduced into the front and outer pressure chamber 45, and the pressure or negative pressure within the variable pressure chamber 5 is introduced into the front and inner pressure chamber 46. The negative pressure in the constant pressure chamber 4 is always introduced into the chamber. As a result, the pressure in the pressure chamber 46 never becomes greater than the pressure in the pressure chamber 45, so the front diaphragm 43 that partitions the pressure chamber 45 (II is the high pressure side and the pressure chamber 46 side is the low pressure side) It is only necessary to install it by considering that it will be on the side.

Therefore, the inner circumferential side of this diaphragm 43 is connected to the auxiliary piston 40, and the outer circumferential side is connected to the valve body 6, and a folded part 43a is formed in the middle thereof by bulging toward the pressure chamber 45 side, which is the low pressure side. is forming.

On the other hand, the diaphragm 42 that partitions the pressure chambers 44, 45 is urged both toward the pressure chambers 44 and 45 by the combination of pressures introduced into each pressure chamber 44, 45, so both It is necessary to consider the direction of biasing. In this embodiment, such a state is effectively utilized to change the diaphragm effective diameter D1 when urging the pressure chamber 45 side, that is, the front side, to the diaphragm effective diameter D2 when urging the diaphragm to the opposite side.
We are trying to make it much bigger than that.

That is, the diaphragm 42 connected to the auxiliary piston 40 is provided with a first folded portion 42a that bulges rearward in the axial direction on the inner circumference thereof, and the auxiliary piston 40 is provided with a first folded portion 42a on the inside of the first folded portion 42a. A reversal prevention portion 40a that is positioned to prevent the first folded portion 42a from reversing.
are integrally formed. On the other hand, on the outer circumference of the diaphragm 42 connected to the valve body 6, there is a second folded part that bulges forward in the axial direction, is located radially outward from the first folded part 42a, and extends in the opposite direction. Section 42
b, and an inversion prevention part 6d that is located inside the second folded part 42b and prevents the second folded part 42b from being reversed is integrally formed on the intermediate plate 6b constituting the valve body 6. is forming.

The outer peripheral portion of the auxiliary piston 40 located between the two folded portions 42a and 42b is formed as a conical support portion 40b with the front side being the larger diameter side.
A support portion 6e parallel to the support portion 40b is also formed on the intermediate plate 6b opposite to b, so that no matter which direction the diaphragm 42 is biased, one of the support portions 40b,
6e makes it possible to support the diaphragm 42 between the folded portions 42a and 42b.

Furthermore, in order to effectively apply pressure to the diaphragm 42 when the biasing direction of the diaphragm 42 is changed, a part of the diaphragm 42 is provided with pressure on the portion forming the support portion 40b of the auxiliary piston 40. A through hole 75 is formed to prevent the fluid from being sealed, and for the same purpose, a groove 76 is formed along the axial and radial directions from the inversion prevention part 6d to the support part 6e of the intermediate plate 6b. . Note that it goes without saying that a groove may be formed instead of the through hole 75, or a groove, a rib, etc. may be provided on the diaphragm 42. Further, the effective diameter D3 of the diaphragm 43 on the front side is set to be smaller than the effective diameter D2 on the small diameter side of the diaphragm 42 on the rear side by a required amount.

In the brake booster having the above configuration, when this is used as a stop brake device, the control device 6
3 detects a stopped state of the vehicle with the vehicle speed sensor 66 and detects that the brake pedal has been continuously depressed for a predetermined period of time by continuous operation of the brake lamp switch 67, switches the flow path of the flow path switching mechanism 51. The conduit 49.
Atmospheric pressure is introduced into the pressure chamber 44 on the rear side of the auxiliary piston 40 through the passage 48 and the passage 47, and the flow path switching mechanism 51 and the conduit 54 are introduced from the conduit 60 communicating with the negative pressure source.
．． Negative pressure is introduced into the pressure chamber 45 on the front outer side of the auxiliary piston 4o through the passage 53 and the passage 52 (see FIG. 2).

Then, as shown in the upper half of the center line in FIG. 40a prevents the folded portion 42a from being reversed and is brought into close contact with the support portion 40b of the auxiliary piston 40, thereby advancing the auxiliary piston 4°. This allows the booster to act and continue the braking action. At this time, the support portion 6e of the valve body 6
Of course, this allows the diaphragm 42 to be separated.

This parking brake device 65 is provided with a parking brake switch 70 and a door switch 71 on the driver's seat side so that the driver does not leave the driver's seat in this state when the vehicle is stopped. If the door is opened without pulling the brake, the controller 83 can activate the alarm 77.

On the other hand, when the control device 63 detects that the accelerator switch that detects depression of the accelerator pedal or the manual stop brake release switch 69 is operated, the control device 63 is introduced into the rear pressure chamber 44. This causes the input shaft 25 to return to its original non-operating position and release the braking action by the brake booster.

Next, the operation of the brake booster when the vehicle has a large load capacity will be explained. The flow path is switched, and the pressure chamber 44 on the rear side of the auxiliary piston 40 is connected to the flow path switching mechanism 51 and the conduit 61.
The inside of the pressure chamber 45 on the front outer side of the auxiliary piston 40 is also communicated with the inside of the variable pressure chamber 5 through the auxiliary piston 40 .

In this state, the pressure in the variable pressure chamber 5 is introduced into both the pressure chambers 44 and 45, so that no pressure difference occurs between them, but the pressure chamber 46 on the front inner side of the auxiliary piston 40 is constantly Since negative pressure is introduced, the auxiliary piston 4
0 is a variable pressure chamber 5 that acts on the effective diameter D3 of the diaphragm 43
Since the pressure inside applies forward force to the valve plunger 11 and the input shaft 25, the driver can obtain strong braking force with a light pedal effort. Therefore, in this state, the servo ratio becomes large.

Next, when the loading capacity of the vehicle becomes medium, the above-mentioned supply device 5
0 detects this state with the vehicle weight sensor 64, and introduces negative pressure into the two pressure chambers 44 and 45, which have been in communication with the variable pressure chamber 5. In this state, negative pressure is introduced into all the pressure chambers 44, 45, 46 and no pressure difference occurs before and after the auxiliary piston 40. The reaction force is transmitted at an intermediate servo ratio determined by the

Furthermore, when the loading capacity of the vehicle becomes small, the supply device 50
While introducing negative pressure into the pressure chamber 44 on the rear side of the auxiliary piston 40, the pressure chamber 45 on the front outer side is communicated with the inside of the variable pressure chamber 5. Then, as shown in the lower half of the center line in FIG. 1, the diaphragm 42 is deformed by the biasing force in the backward direction from the pressure introduced into the pressure chamber 45, and the inversion prevention portion 6d provided on the intermediate plate 6b deforms. folded part 4
Since the diaphragm 2b is tightly attached to the support portion 6e on the valve body 6 side while being prevented from being reversed, the effective diameter D2 of the diaphragm when urging the auxiliary piston 40 in the backward direction is smaller than the effective diameter D1 in the forward direction. Become.

As a result, the auxiliary piston 40 is moved by the pressure within the variable pressure chamber 5 that acts on the pressure receiving area corresponding to the difference between the effective diameter D2 of the rear diaphragm 42 and the effective diameter n3 (D2 > 03) of the front diaphragm 43. Since the input shaft 25 is energized in the opposite direction to the forward direction, a relatively heavy pedal force is required for a 1M rider to obtain a constant output, resulting in excessive braking force. This will prevent skids and the like from occurring. It is clear that in this state, the servo ratio becomes small.

Next, FIG. 3 shows another embodiment of the present invention. In this embodiment, 100 is added to the reference numerals in the above embodiment for the main parts of the same or equivalent parts as in the above embodiment. It is shown with a numeral.

In this embodiment, a third
A diaphragm 180 is disposed, and this diaphragm 18
A pressure chamber 144 into which pressure fluid is introduced during stop braking is formed between the diaphragm 142 and the diaphragm 142, and at the same time a negative pressure chamber 181 is formed between the rear of the diaphragm 180 and the valve body 6. And this negative pressure chamber 1
A passage 182 formed at 81 in the shaft portion of the auxiliary piston 140
By communicating with the front and inner pressure chamber 146 through the negative pressure chamber 181, the inside of the negative positive chamber 181 is always communicated with the constant pressure chamber 104, and the passage 115 is communicated with the negative pressure chamber 181.

Therefore, in this embodiment, unlike the previous embodiment, the intermediate plate 6b is not required to form the passage 115, so that the structure of the valve body 10B is simplified.

Further, in this embodiment, inversion prevention parts 8d and 40a are formed on each of the support parts 6e and 40b to prevent the folded parts 42a and 42b of the diaphragm 42 from being inverted. , 40a are omitted.

"Effects of the Invention" As described in E below, according to the present invention, one diaphragm that partitions the pressure chambers can be biased in both directions, so there is no restriction on the magnitude of the pressure introduced into each pressure chamber. Furthermore, since the effective diameters on both sides of the diaphragm are different, it is possible to obtain a wide variety of servo ratios with appropriate values without causing hysteresis, unlike when using a sliding seal member. It becomes possible.

In particular, when used as a parking brake device, the large pressure receiving area on the effective diameter side ensures the function of the parking brake device, while the required small servo ratio change can be obtained with the small pressure receiving area on the effective diameter side. This effect can be obtained.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, and is a systematic cross-sectional view in which the upper half and lower half of the center line are shown with different operating directions;
FIG. 2 is a diagram showing the conditions for changing the servo ratio in the brake booster shown in FIG. 1, and FIG. 3 shows another embodiment of the present invention. It is a sectional view showing the operating direction different from the lower half. 1.101...Shell 4,104...Constant pressure chamber 2.102...Power piston 5.105...
・Transformer chamber 6.106...Valve body ee, 40
b...Support part 11.111...Valve plunger 7
, 107...Valve mechanism 40.140...Auxiliary piston 25,125...Input shaft 42.142...Diaphragm 50...Supply device B4...Stop brake device 51...Flow path switching Mechanism 44.45,4Ei
, 144, 145, 146... Pressure base cylinder 3 Figure

Claims (1)

[Claims] A power piston slidably disposed within the shell, a valve mechanism housed within the valve body of the power piston shaft, a constant pressure chamber formed on the front side in the operating direction of the power piston, and a variable pressure chamber formed on the rear side. In the brake booster, the brake booster includes a chamber and an input shaft that operates a valve plunger constituting the valve mechanism to switch a flow path and supply pressure fluid to the variable pressure chamber to advance the power piston. An auxiliary piston is disposed in a space formed in the body and connected to the valve plunger, a diaphragm is stretched between the auxiliary piston and the valve body, and pressure chambers are defined on both sides of the diaphragm. A supply device is provided for supplying pressure fluid to the pressure chambers, and the auxiliary piston and the housing are provided with a supply device that is in close contact with the diaphragm when pressure fluid is supplied to one of the pressure chambers. Forming a support portion extending in the radial direction that receives pressure and allows separation from the diaphragm when pressure fluid is supplied to the other pressure chamber,
A brake booster characterized in that the effective diameter of a diaphragm on which pressure fluid introduced into each pressure chamber acts is different on both sides of the diaphragm.