JPH06336160A - Negative pressure type booster device - Google Patents

Abstract

PURPOSE:To provide a negative pressure type booster device having a small operation start input and good operational feeling by providing a relief valve keeping the negative pressure in the negative pressure chamber of a power piston provided with the negative pressure chamber on the front side in the operating direction in a shell and a pressure chamber on the rear side at a predetermined value or below, and setting the bouncing force of an exciting spring small. CONSTITUTION:A cylindrical valve body 6 connected with power pistons 9, 10 is airtightly and slidably inserted into the shaft section of a center plate 3 at the center section in a shell 2, and negative pressure chambers A, C and pressure chambers B, D having a fluid circuit selector valve 13 are formed by diaphragms 11, 12 behind the power pistons 9, 10. The valve mechanism is provided with the circular first and second valve seats 14, 16, a spring 17, and a valve element 18. Negative pressure is introduced into the negative pressure chambers A, C from a negative pressure source 21 via a guide pipe 20. A relief valve 35 keeping the negative pressure of the negative pressure chambers A, C at a predetermined value is provided in the middle, and the bouncing force of a spring 32 is set small not to cause a problem when the differential pressure is applied to the valve element 18.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative pressure type booster used in an automobile or the like, and more particularly to a negative pressure type booster having a negative pressure chamber into which a negative pressure is introduced.

2. Description of the Related Art Conventionally, a negative pressure type brake booster generally includes a power piston provided in a shell so as to be reciprocally movable,
A negative pressure chamber formed on the front side in the operating direction of the power piston to introduce a negative pressure, a pressure chamber formed on the rear side to introduce the atmospheric pressure, and a first chamber formed on the valve body of the power piston shaft portion. A valve seat, a second valve seat formed on a valve plunger slidably mounted on the valve body, a valve body seated on the first valve seat and the second valve seat from the rear side, and the first valve seat A negative pressure passage for communicating a space on the outer peripheral side of the seat portion of the valve body with the negative pressure chamber, and an atmosphere passage for communicating a space on the inner peripheral side of the seat portion of the second valve seat and the valve body with the atmosphere. And a pressure passage that connects a space between the two seat portions to the pressure chamber, an input shaft that interlocks with the valve plunger, and a spring that biases the input shaft rearward. In the brake booster of this type, in the non-actuated state, the input shaft and the valve plunger are urged rearward by the spring, whereby the second valve seat of the valve plunger is seated on the valve body to open the atmosphere passage. It's closed. Further, the valve body is integrally retracted by the valve plunger, and thereby the valve body is separated from the first valve seat of the valve body, so that the negative pressure passage communicates with the pressure passage and the negative pressure introduced into the negative pressure chamber is reached. Are introduced into the pressure chamber via the negative pressure passage and the pressure passage. As a result, the pressure difference across the power piston is practically kept at zero. When the brake pedal is stepped on from this state and the input shaft and the valve plunger are advanced, the valve body is seated on the first valve seat to block the communication between the negative pressure chamber and the pressure chamber, and the valve plunger of the subsequent valve plunger is closed. Since the valve body and the second valve seat are separated by the forward movement, the atmospheric pressure is introduced into the pressure chamber through the atmosphere passage and the pressure passage. This causes a pressure difference before and after the power piston, so that the power piston moves forward. Further, when the braking action is released, the input shaft and the valve plunger are retracted by the spring, so that the second valve seat of the valve plunger and the valve element come into contact with each other to interrupt the communication between the pressure chamber and the atmosphere, and continue. Since the valve body is separated from the first valve seat formed in the valve body by the integral retraction of the valve plunger and the valve body, the pressure chamber communicates with the negative pressure chamber. As a result, the atmospheric pressure introduced into the pressure chamber escapes to the negative pressure chamber, so that the pressure difference between the pressure chamber and the negative pressure chamber becomes small and the power piston retracts. By the way, when the brake action is released or not activated, atmospheric pressure acts on the rear side of the valve body seated on the second valve seat of the valve plunger, and the valve body is separated from the first valve seat of the valve body. Since a negative pressure acts on the front side of, the forward force due to the differential pressure acts on the valve body. Therefore, the spring for urging the input shaft to the rear side is required to have a strength enough to retreat the valve body against the forward force acting on the valve body. The magnitude of the repulsive force of the spring was determined in consideration of the maximum value of the negative pressure introduced.

However, the magnitude of the negative pressure introduced into the negative pressure chamber does not always reach the maximum value, and if the spring force of the spring can be reduced, the operation of the input shaft starts. Input can be reduced. In other words, conventionally, the elastic force of the spring is set relatively large in consideration of the maximum negative pressure value introduced into the negative pressure chamber, which increases the operation start input on the input shaft. It was a cause of worsening the operation feeling. In view of the above-mentioned circumstances, the present invention provides a negative pressure type booster capable of reducing the operation start input in the input shaft and improving the operation feeling by setting the elastic repulsive force of the spring to be small. It is provided.

That is, the present invention provides a power piston reciprocally provided in a shell, a negative pressure chamber formed at the front side in the operating direction of the power piston, and a negative pressure chamber into which a negative pressure is introduced. A pressure chamber formed on the side to introduce atmospheric pressure, a first valve seat formed on the valve body of the power piston shaft portion, and a second valve seat formed on a valve plunger slidably provided on the valve body. A valve body seated on the first valve seat and the second valve seat from the rear side, and a negative pressure passage for connecting a space on the outer peripheral side of the seat portion of the first valve seat and the valve body to the negative pressure chamber. An atmosphere passage for communicating a space on the inner peripheral side of the seat portion between the second valve seat and the valve body with the atmosphere, and a pressure passage for communicating an intermediate space between the two seat portions with the pressure chamber, The input shaft that works with the valve plunger and the input shaft on the rear side. In the vacuum booster comprising a spring biasing and it is characterized in that a relief valve to keep below a predetermined value determined in advance a negative pressure in the negative pressure chamber.

According to the above construction, since the negative pressure in the shell can be kept below a predetermined value by the relief valve, the elastic force of the spring can be set in accordance with the predetermined value. Therefore, the elastic force of the spring can be set to be relatively small as compared with the conventional one, whereby the operation start input on the input shaft can be reduced and the operation feeling can be improved.

EXAMPLES The present invention will be described below with reference to the illustrated examples. In FIG. 1, the inside of a sealed container constituted by a front shell 1 and a rear shell 2 is divided into a front chamber 4 and a front chamber 4 by a center plate 3 provided at the center thereof. The valve body 6 is divided into two chambers, a rear chamber 5 and a substantially cylindrical valve body 6 which penetrates the shaft portions of the rear shell 2 and the center plate 3 slidably while being kept airtight by annular seal members 7 and 8, respectively. I am letting you. A front power piston 9 and a rear power piston 10 housed in the front chamber 4 and the rear chamber 5 are connected to the valve body 6, respectively, and a front diaphragm 11 and a rear diaphragm 12 are provided on the rear surfaces of the power pistons 9 and 10. And the negative pressure chamber A in front of and behind the front diaphragm 11, respectively.
And a pressure chamber B, and a negative pressure chamber C and a pressure chamber D are formed in front of and behind the rear diaphragm 12. A valve mechanism 13 for switching a fluid circuit between the two negative pressure chambers A and C and the pressure chambers B and D is provided in the valve body 6, and the valve mechanism 13 has a first annular shape formed in the valve body 6. Valve seat 14
An annular second valve seat 16 formed at the right end of a valve plunger 15 slidably provided on the valve body 6 inside the annular first valve seat 14;
6, the valve body 1 seated by the spring 17 from the right side of FIG.
8 and. The space on the outer peripheral side of the annular seat portion where the first valve seat 14 and the valve body 18 are in contact with each other is a negative pressure chamber C and a negative pressure chamber A via an axial negative pressure passage 19 formed in the valve body 6. And a negative pressure is introduced into the negative pressure chamber A from a negative pressure source (intake manifold) 21 via a negative pressure introducing pipe 20. The negative pressure source 21
And the negative pressure introducing pipe 20 are connected to each other, a check valve 2 is provided in the middle of the negative pressure pipe.
2 is provided so that the air can flow only from the negative pressure chamber A toward the negative pressure source 21. Further, on the inner peripheral side of the annular seat portion where the first valve seat 14 and the valve body 18 are in contact with each other, the outer peripheral portion, that is, inside and outside of the annular seat portion where the second valve seat and the valve body 18 are in contact with each other. The space in the middle portion of the annular seat portion is communicated with the pressure chamber D through a radial pressure passage 23 formed in the valve body 6, and the pressure chamber D is further connected to another pressure passage 2 formed in the valve body 6.
4 to communicate with the pressure chamber B. Further, the space on the inner peripheral side of the inner annular seat portion where the second valve seat 16 and the valve body 18 contact each other communicates with the atmosphere passage 25 that communicates with the atmosphere. Terminal cylindrical portion 6a of the valve body 6
A right end portion of the input shaft 26 slidably inserted into is connected to a brake pedal (not shown), and a left end portion thereof is connected to a valve plunger 15 slidably accommodated in the valve body 6. A plunger plate 27 and a reaction disc 28 are provided on the left end side of the valve plunger 15.
Are sequentially arranged. The reaction disk 28 is housed in the right end portion of the push rod 29, and the left end portion of the push rod is slidably projected from the shaft portion of the front shell 1 to the outside through a seal member 30 and is not shown. It is linked to the piston of the master cylinder. Further, the valve body 6 has a return spring 3
1 normally holds it in the inoperative position shown. A spring 32 for retracting the input shaft 26 and the valve plunger 15 with respect to the valve body 6 is disposed between the valve body 6 and the input shaft 26, and the valve plunger 15
The key member 33 is fitted around the outer periphery of the valve body and is slidable within a predetermined range with respect to each of the valve plunger and the valve body 6, and is prevented from coming out of the valve body 6. The terminal tubular portion 6a of the valve body 6 protruding from the shell is covered with a rubber bellows-like dust cover 34. However, in this embodiment,
A relief valve 35 for keeping the negative pressure in the negative pressure chambers A and C below a predetermined value is provided in the middle of the negative pressure pipe that connects the negative pressure source 21 and the negative pressure introduction pipe 20. The relief valve 35 has, for example, a negative pressure in the negative pressure chambers A and C of 550 mmHg.
The elastic force of the spring 32 is set so as not to become larger than that of the valve body 18 even if the differential pressure generated when a negative pressure of 550 mmHg is introduced into the negative pressure chambers A and C acts on the valve element 18. It has a size that is not problematic and is set as small as possible. In the above-described configuration, in the non-operating state shown in the drawing, the atmospheric pressure is acting on the right side of the valve body 18 and the negative pressure is acting on the left side, so that the valve body 18 tries to move forward to the left due to the pressure difference. The spring 32 overcomes its forward force and holds the input shaft 26 and the valve plunger 15 in the right inoperative position shown. In this state, when the negative pressure introduced into the negative pressure chambers A and C becomes large, the differential pressure acting on the valve body 18 becomes large, so that the forward force of the valve body 18 to the left increases. Pressure source 21
When the negative pressure of exceeds 550 mmHg, the relief valve 35 is opened to reduce the negative pressure in the negative pressure chambers A and C to 550 mm.
It comes to keep below Hg. Therefore, the increase of the advancing force to the left of the valve element 18 is limited to a constant value, and the size of the spring 32 is such that the valve element 18 moves forward even if the maximum differential pressure at that time acts on the valve element 18. Since the size is set so that the brake booster is not released, the valve body 18 is not advanced due to the above-mentioned pressure difference, and the return failure of the brake or the dragging does not occur. Moreover, since the spring 32 is set as small as possible in such a size that the valve body 18 does not move forward even if the maximum differential pressure acts on the valve body 18, the conventional maximum negative pressure of 760 mmHg is set. Compared with the case where the spring force of the spring 32 is determined in consideration, the spring force of the spring 32 can be made smaller. Therefore, the operation start input of the input shaft 26 can be made smaller and the brake operation feeling can be improved. Can be one. FIG. 3 shows another embodiment of the present invention. In the above embodiment, the relief valve 35 is provided in the negative pressure pipe. In this embodiment, the front shell 101 has an opening 101a and the opening 101a. A relief valve 135 is attached to the. The relief valve 135 is the first
It is provided with a tubular member 135A and a second tubular member 135B, and the second tubular member 135B is attached to the opening 101a of the front shell 1 via a seal member 136 while maintaining airtightness. Then, the left end portion of the second tubular member 135B is press-fitted into the right end portion of the first tubular member 135A to integrally connect the two, and the valve body 1 is inserted into the first tubular member 135A.
37 is accommodated and the valve body 137 is normally seated on the valve seat 139 of the first tubular member 135A by the spring 138. The magnitude of the elastic force of the spring 138 is such that, when the negative pressure in the negative pressure chamber A becomes larger than 550 mmHg, the valve body 137 separates from the valve seat 139 and the atmosphere enters the negative pressure chamber A. It is set to a size that can be introduced. Other configurations are the same as those of the above-described embodiment, and it is obvious that the same effects as those of the above-described embodiment can be obtained in this embodiment as well.

As described above, according to the present invention, it is possible to obtain the effect that the operation start input on the input shaft can be reduced and the operation feeling can be improved.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view of a main part showing another embodiment of the present invention.

[Explanation of sign]

 1, 2, 101 ... Shell 6 ... Valve body 9, 10 ... Power piston 13 ... Valve mechanism 14 ... First valve seat 15 ... Valve plunger 16 ... Second valve seat 18 ... Valve body 19 ... Negative pressure passage 21 ... Negative pressure source 23, 24 ... Pressure passage 25 ... Atmosphere passage 26 ... Input shaft 32 ... Spring 35, 135 ... Relief valve A, C ... Negative pressure chamber B, D ... Pressure chamber

Claims (1)

[Claims] 1. A power piston reciprocally provided in a shell, a negative pressure chamber formed on the front side in the operating direction of the power piston to introduce negative pressure, and an atmospheric pressure formed on the rear side. Pressure chamber, a first valve seat formed on the valve body of the power piston shaft portion, a second valve seat formed on a valve plunger slidably mounted on the valve body, and a first valve seat from the rear side. And a second valve seat, a negative pressure passage for communicating a space on the outer peripheral side of the seat portion between the first valve seat and the valve body with the negative pressure chamber, the second valve seat and the valve. An atmosphere passage for communicating the space on the inner peripheral side of the seat portion with the body to the atmosphere, a pressure passage for communicating an intermediate space between the two seat portions with the pressure chamber, and an input shaft which is further interlocked with the valve plunger. , Negative pressure type booster equipped with a spring that biases this input shaft to the rear side A negative pressure type booster comprising: a relief valve for keeping the negative pressure in the negative pressure chamber at a predetermined value or less.