JPS6213894Y2 - - Google Patents

Description

[Detailed description of the invention] The invention relates to a tandem brake booster.
This is an improvement in the connection structure between the valve body containing the valve mechanism and the case supporting the output shaft.

Conventionally, a tandem brake booster having the following configuration has been used. That is, the rear power piston is connected to the valve body, while the front power piston is held between the valve body and a case that fits and supports the output shaft. It is designed to be supported by this valve body by inserting it into the valve body. Therefore, its action is as usual when the valve mechanism housed in the valve body operates to generate a fluid pressure difference across the diaphragm provided on the back of each power piston, thereby moving each power piston forward. This boosts the braking force, but because of the configuration described above, the fluid force acting on the rear power piston is transmitted to the output shaft via the valve body and case, while the fluid force acting on the front power piston is transmitted to the output shaft via the valve body and case. Physical strength is transmitted to the output shaft via the case,
It has virtually no effect on the valve body.

In this conventional device, when operating normally, the fluid passage between the valve mechanism and the front power piston is through the rear power piston, so after the valve mechanism starts operating, fluid force is first applied to the rear power piston. Since fluid force acts on the front power piston with a slight time delay, each power piston begins to move forward as one with the rear power piston pushing the front power piston from behind. Furthermore, when reversing, the return spring pushes the front power piston rearward, and also pushes the rear power piston rearward via the front power piston, causing both pistons to retreat together. That is, each power piston moves forward and backward as one, and the front power piston does not relatively precede the rear power piston and these two power pistons do not separate from each other.

However, if a sliding failure occurs between the valve body and the shell, for example, and fluid force acts on each power piston, the valve body will not move forward due to frictional resistance with the shell, while the front power piston will not move forward due to the fluid force. The valve moves forward with the case and attempts to separate the case from the valve body. However, the return operation of the brake pedal is delayed when the brake pedal is operated before such a sliding failure occurs, so the driver notices this and does not drive such a vehicle, and the case should be removed from the valve body in advance. In most cases, this can be avoided, but for safety reasons, it is preferable to take measures to prevent the case from separating from the valve body.
It is desirable that this means be constructed as simply as possible in consideration of the assembly or disassembly of the case and the valve body.

In view of the above points, the present invention provides a tandem type brake booster which has a simple structure and a coupling structure of a case and a valve body that is easy to assemble and disassemble. a valve mechanism that controls the opening and closing of a flow path, a valve body that houses this valve mechanism, a case disposed on the front end surface of this valve body, an output shaft whose end is fitted into this case, and the above valve mechanism. The power piston is connected to the case and the valve body in order to operate in response to fluid pressure from the engine and transmit thrust to the output shaft, and includes a front power piston that supports the fluid pressure on the case side and a rear power piston that supports the valve body side. In the tandem brake booster, a cylindrical protrusion protruding from the case is inserted into a hole in the shaft core of the valve body, and a step part formed by expanding the diameter in the hole is inserted. Correspondingly, an annular groove is carved in the protruding portion, and a locking member having elasticity that is locked to the stepped portion is installed in the groove to form a portion for preventing the case from coming off from the valve body. It is characterized by

The present invention will be explained below based on the illustrated embodiments. In Fig. 1, 1 is a front shell, 2 is a rear shell, and inside the container composed of both shells 1 and 2, there is a front power piston 3 and a rear power piston 4.
are arranged in series. Reference numeral 5 denotes a center plate that divides the inside of the container into a front chamber on the front power piston 3 side and a rear chamber on the rear power piston 4 side. The rear chamber is partitioned into pressure chambers C and D by a rear diaphragm 7 attached to the rear surface of the rear power piston 4.

The center plate 5 consists of a cylindrical member 5A and an annular member 5B, and the outer diameter of the outer periphery of the cylindrical member 5A is set smaller than the inner diameter of the rear shell 2, so that the outer circumferential surface and the inner circumferential surface of the shell 2 are A passage 8 is formed therebetween, and a thick outer peripheral portion 7A of the rear diaphragm 7 is attached to the end portion of the passage 8. A plurality of grooves are cut into this outer peripheral thick portion 7A, and these grooves serve as a communication path 9 between the passage 8 and the chamber D. The cylindrical member 5A and the annular member 5B, which supports the thick outer peripheral portion of the front diaphragm 6 at the outer peripheral edge thereof, are integrally formed by, for example, spot welding, with their respective partition walls 5a and 5b in contact with each other. However, a plurality of reinforcing ribs 5C bulged toward the chamber B are formed on the partition wall 5b of the annular member 5B, and a plurality of reinforcing ribs 5C are formed between this and the partition wall 5a of the cylindrical member 5A. The gap between the chamber B and the passage 8 is defined as a communication passage 10 between the chamber B and the passage 8.

On the other hand, the front power piston 3 has a cylindrical portion 3A whose shaft portion protrudes toward the rear power piston 4 side and slides into contact with the inner circumferential edge 5D of the center plate 5, and the end of the cylindrical portion 3A extends inward. It is bent to form a bent part 3B, and a communication hole 11 is bored in the cylindrical part 3A, thereby communicating between the chambers A and C. As mentioned above, chambers A and C are connected to the communication hole 11.
Accordingly, chambers B and D are connected to communication passages 9 and 10 and passage 8.
The chamber A is connected to a negative pressure source (not shown) via an operating pressure inlet 24.

The valve body 12 has a substantially cylindrical shape, and includes a cylindrical main body portion 12A and a large diameter portion 12B integrally provided therewith, and an annular groove portion 12D carved on the outer periphery of the large diameter portion 12B. The rear power piston 4 is fitted into the rear diaphragm 7 via the inner peripheral thick walled portion 7B. In front of this large diameter portion 12B, that is, on the opposite side from the cylindrical main body portion 12A,
A cylindrical front protrusion 12C having approximately the same diameter as this cylindrical main body 12A is protrudingly provided, and the front protrusion 12C has the following features:
A case 15 that supports an output shaft 17, which will be described later, is fitted therein. Further, a hole 13 provided inside the front protrusion 12C and the large diameter portion 12B is formed in the front protrusion 12.
It has a small diameter at C, and a slightly large diameter at the large diameter section 12B, thereby forming a stepped section 14, and furthermore, the hole entrance section 13A is enlarged in a tapered shape.

Therefore, the case 15 has the above-mentioned front protrusion 12C.
A large-diameter cylindrical portion 15A that fits on the outer periphery of the cylindrical portion 15A, and a cylindrical protrusion portion 15B that is located inside the large-diameter cylindrical portion 15A and that can be inserted into the hole 13. When the case 15 is inserted into the front protrusion 12C, the large diameter cylindrical part 15A holds the bent part 3B of the front power piston 3 between it and the front end surface of the large diameter part 12A of the valve body 12. It supports the power piston 3. In this state, the tip of the protruding portion 15B extends beyond the stepped portion 14 toward the larger diameter side,
The annular spring 30 attached to the annular groove 15C on the outer periphery of the tip of the protruding portion 15B is engaged with the stepped portion 14,
This prevents the case 15 from being removed from the valve body 12. This spring 30 is formed by cutting a part of a metal ring, and the illustrated position where it is engaged with the stepped portion 14 is the neutral position of the spring. In addition, 31
is an airtight O-ring.

Also, in front of this case 15 is the large diameter cylindrical portion 1.
A cylindrical shaft support part 15D having a slightly smaller diameter than 5A is provided, and the disk 16 is fitted into this shaft support part 15D, and the end part of the output shaft 17 is fitted and abutted thereon. A sealing material 18 provided in a concave portion 14 whose tip end is formed in the front shell 1.
It protrudes outward through the. This concave portion 1A
A spring seat 1B is formed at the end of the case 15, and a return spring 19 is elastically mounted between the spring seat 1B and the large diameter cylindrical portion 15A of the case 15. It is constantly biased toward the non-operating position shown in the figure.

Furthermore, the tip of the output shaft 17 is linked to a master cylinder (not shown), while the operating rod 20 inserted from behind the rear power piston 4 into the valve body 12 is linked to a brake pedal (not shown). Note that 21 is a valve plunger provided at the tip of the operating rod 20 and inserted into the protrusion 15B of the case 15;
A well-known valve mechanism 22 including 1 performs communication cutoff control between a passage 23 communicating with the pressure chamber C and a passage 25 communicating with the pressure chamber D in accordance with the displacement of the operating rod 20. Also,
A key 26 is provided on the valve body 12 and is used to prevent the valve plunger 21 from coming off.

With the above configuration, in the non-operating state shown in the figure in which no pedal force is applied to the brake pedal and the operating rod 20 is not displaced, the valve mechanism 22 is connected to the passage 23 and the passage 2.
5, the pressure chambers C and D are communicated with each other, so that the pressure chambers A, B, C, and D are all maintained at the same pressure, and the power pistons 3 and 4 are not displaced. In contrast, the operating lever 20
During a brake operation in which C is displaced to the left in the figure, the valve mechanism 22 acts to cut off communication between pressure chambers C and D and introduce atmospheric air into pressure chamber D. As mentioned above, since the pressure chamber C communicates with the pressure chamber A through the communication hole 11, and the pressure chamber D communicates with the pressure chamber B through the passage 8, the communication passage 9, etc., the valve mechanism 22 Due to the operation of Front and rear power pistons 3,
As a result of the displacement of 4, the output shaft 17 operates the master cylinder to perform a braking action. At this time, the valve plunger 21 is in contact with the disc 16, and the brake reaction force is transmitted to the brake pedal via the output shaft 17, the disc 16, the valve plunger 21, and the operating rod 20.

However, in the above embodiment, the annular spring 3 is provided in the annular groove 15C of the protrusion 15B formed on the back surface of the case 15.
0 is attached, and this spring 30 is locked to the stepped portion 14 of the hole 13 of the valve body 12. Therefore, even if a force is applied to the case 15 to separate it from the valve body 12, the case 15 will not fall out from the valve body 12. When the case 15 is assembled into the valve body 12, the spring 30 is first guided by the hole entrance portion 13A and bent inward, and the case 15 comes into contact with the front end surface of the valve body 12, and the spring 30 is inserted into the hole 13A. reaches the stepped portion 14, returns outward, and is locked to the stepped portion 14. On the other hand, in order to remove this case 15 from the valve body 12, it is necessary to remove the hole 13 and the protrusion 1.
A thin cylindrical member matching this shape is inserted into the gap between the spring 30 and the spring 30, and the spring 30 is deflected inward.
What is necessary is to release the locking relationship between the spring 30 and the stepped portion 14 and move the case 15 in the axial direction.

FIG. 2 shows a second embodiment of the present invention, in which the cross-sectional shape of the annular spring 30 is different from that of the first embodiment, and is approximately U-shaped and has a groove on its inner periphery. The outer peripheral side is brought into contact with the wall surface side of the hole 13. The material of this spring 30 may be metal, rubber, or plastic as long as it has flexibility; however, in the case of rubber, it should have a cross-sectional shape as in the second embodiment and its inner peripheral edge. It is preferable to fit it into the annular groove 15C and to make the outer peripheral part bulge out from the outer peripheral surface of the protruding part 15B and to lock it to the stepped part 14. Further, in this second embodiment, the stepped portion 14 is tilted so that the case 15 can be removed from the valve body 12 by applying an external force above a certain level. That is, during disassembly, there is no need to use a thin cylindrical member as in the case of the first embodiment, and the work is extremely easy.

As described above, according to the present invention, the combination structure of the case and the valve body can be made simple, and the assembly and disassembly operations thereof can be facilitated.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of a tandem brake booster according to the present invention, and FIG. 2 is a cross-sectional view of a main part of a second embodiment of the present invention. 3: Front power piston, 4: Rear power piston, 12: Valve body, 13: Hole, 1
4: Stepped portion, 15: Case, 15B: Projection, 1
5C: Groove, 17: Output shaft, 20: Input shaft, 2
2: Valve mechanism, 30: Locking member (spring).

Claims (1)

[Scope of utility model registration request] A valve mechanism that controls the opening and closing of a pressure fluid flow path in response to forward and backward movement of an input shaft, a valve body that houses this valve mechanism, a case disposed on the front end surface of this valve body, and an end fitted into this case. A front power piston is connected to the case and the valve body to operate in response to fluid pressure from the valve mechanism and transmit thrust to the output shaft, and supports the fluid pressure on the case side. In a tandem brake booster equipped with a rear power piston supported on the valve body side,
A cylindrical protrusion protruding from the case is inserted into the hole in the shaft core of the valve body, and an annular groove is formed in the protrusion in correspondence with the stepped part formed in the hole with an enlarged diameter. A tandem type brake booster, characterized in that a locking member having elasticity is installed in the groove to prevent the case from coming off from the valve body. .