GB1594168A

GB1594168A - Vacuum booster device

Info

Publication number: GB1594168A
Application number: GB765578A
Authority: GB
Original assignee: Tokico Ltd
Current assignee: Tokico Ltd
Priority date: 1977-02-28
Filing date: 1978-02-27
Publication date: 1981-07-30
Also published as: JPS53118984U; ES467407A1; FR2381927A1; CS213337B2; JPS5814135Y2; DE2808622A1; BR7801198A; FR2381927B1

Description

(54) VACUUM BOOSTER DEVICE (71) We, TOKICO LTD., a Japanese body corporate of 6-3, Fujimi l-chome, Kawasaki-ku, Kawasaki-shi, Kanagawa-ken, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a vacuum booster device for use in such as a vehicle hydraulic braking system or the like.

In vacuum booster devices of the type wherein a power piston of the booster device consists of a valve body disposed in a generally central portion of a main body of the vacuum booster device and a piston plate surrounding the valve body to receive differential pressure force acting across a diaphragm, it is usual to secure the piston plate to the valve body by a plurality of bolts interposing the inner circumference of the diaphragm therebetween. For this end, the bolts are usually threaded into screw-threaded holes formed in the piston plate passing through respective through holes formed in the piston plate, but, since an air passage is formed in the valve body to communicate opposite sides of the diaphragm in the inactuated condition of the device, it is necessary to locate the screw-threaded holes outside of the air passage thereby increasing the diameter of the valve body.Further, the depth or the length of the screw-threaded holes must be sufficiently large to afford a predetermined tightening force, thus, the thickness of the valve body will increase. The screw-threaded holes will receive tightening stress, and thermal stress when the valve body is formed of a synthetic resin, thus there arises problems in strength. Further, since the head of the bolts project from the surface of the piston plate there is problems in reducing the size of the device.

To overcome the problems mentioned as above, there has already been proposed a vacuum booster device comprising a piston plate receiving differential pressure force acting between two chambers defined in a main body of the vacuum booster device, a cylindrical valve body incorporating valve means therein for connecting or intercepting communication between the two chambers and between one of chambers and the atmosphere, an opening and a head portion being formed in the central portion of the piston plate and one end of the valve body respectively with specified configuration such that the head portion can be fitted in the opening only at a specified positional relationship therebetween, and a neck portion formed contiguous to the head portion being received rotatably in the opening of the piston plate, thereby, the piston plate, the diaphragm and the valve body are clamped together by passing the head portion of the valve body through the opening in the piston plate with the diaphragm interposing between the valve body and the piston plate and, thereafter, rotating the piston plate relatively around the neck portion of the valve body by a predetermined angle. However, the relative rotation between the valve body and the piston plate after the clamping operation is prevented only by the interference of the diaphragm in the direction of the thickness thereof. After a long period of use, problems have occurred in that the valve body and the piston plate rotate relatively according to the vibrations and decrease in the interference due to the permanent strain of the diaphragm, thus, in the worst case, the piston plate will be released from the valve body.

According to the present invention, there is provided a vacuum booster device comprising a main body, a piston plate dividing the main body into a pair of chambers and adapted to be subjected, in use, to differential pressure thereacross, and a generally cylindrical valve body incorporating therein valve means for selectably connecting and disconnecting communication between the two chambers and between one of the chambers and the atmosphere for developing said differential pressure across the piston plate, said piston plate and said valve body being connected to one another by providing an opening of noncircular configuration in the central portion of the piston plate and a correspondingly shaped head portion on one end of the valve body, passing the head portion through the opening and rotating the valve body relative to the piston plate by a predetermined angle, a rotation control member being attached to the piston plate with a portion thereof disposed adjacent to the outer periphery of the head portion and adapted to engage therewith to control the relative rotation between the piston plate and the valve body within said predetermined angle.

The present invention will be explained in detail with reference to the attached drawings exemplifying some embodiments of the present invention, in which: Figure 1 is a longitudinal cross-sectional view of a vacuum booster device according to the present invention Figure 2 is an enlarged side view showing one portion of device of Figure 1; Figure 3 is a cross-sectional view taken along line III - Ill in Figure 2; Figures 4 and 5 are views similar to Figures 2 and 3 but showing another embodiment of the present invention, and Figure 6 is a view showing a further modified form of the present invention.

In Figure 1, the vacuum booster device comprises a main body 1, a valve body 2 slidably supported in a seal member 2' secured to the main body 1, a piston plate 3, a diaphragm 4 dividing the interior of the main body 1 into two chambers A and B and coacting with the piston plate 3 in receiving differential pressure force. On the inner end of the valve body 2, there provided a head portion 2a having a noncircular cross-section as shown in Figure 2, and an opening 3a having a configuration corresponding to the head portion 2a is formed in the central portion of the piston plate 3, so that the head portion 2a of the valve body 2 can be inserted into the opening 3a of the piston plate 3 at a specified positional relationship.The configuration of the head portion 2a of the valve body 2 and the opening 3a of the piston plate 3 may be defined by any desired noncircular form having an inscribed circle of a suitable dimension, such as a square, a hexagon, an octagon, or a circle with a cutout or projecting portion on a portion of its periphery so as to be fitted one into the other at a specified positional relationship. A neck portion 2b is formed contiguous to the head portion 2a of the valve body 2 so as to allow rotation of the piston plate 3 thereon when the head portion 2a of the valve body 2 has passed through the opening 3a of the piston plate 3.The crosssectional configuration of the next portion 2b may have any suitable form so as to allow relative rotation of the valve plate 3 when the neck portion 2b is located in the opening 3a but, preferably, is determined as the inscribed circle of the head portion 2a in view of the strength. An annular projection or shoulder 2c is formed contiguous to the neck portion 2b for cooperating with the piston plate 3 in clamping the inner circumference of the diaphragm 4 therebetween. An annular projection 4a is formed on the inner circumference of the diaphragm 4 which projects, as shown in Figure 3, in the direction of the thickness of the diaphragm when compressive force is not applied.

Accordingly, a power piston according to the invention is constituted by locating the inner circumference of the diaphragm 4 on the annular projection 2c of the valve body 2, fitting the head portion 2a of the valve body 2 in the opening 3a of the piston plate 3 with a specified angular positional relationship being maintained therebetween, pressing the piston plate 3 toward the axis of the valve body 2 against resilient force of the inner circumferential portion of the diaphragm 4 so that the head portion 2a of the valve body 2 pass completely through the opening 3a of the piston plate 2, and rotating the piston plate 3 around the neck portion 2b relatively by a predetermined angle.In the embodiment shown in Figure 2, it is possible to clamp the diaphragm 4 between the piston plate 3 and the valve body 2 by rotating the piston plate 3 by a suitable angle smaller than 90" (preferably, 450) securely by the resiliency of the inner circumferential portion, particularly, of the annular projection 4a of the diaphragm 4. The annular projection 4a in the embodiment may be omitted by providing an annular projection formed on the inner circumference of the piston plate 3 on the side of the diaphragm 4. Thus, the power piston according to the present invention comprises the valve body 2, the diaphragm 4 and the piston plate 3 secured integrally, without utilizing bolts or the like, by rotating the piston plate 3 relative to the valve body 2 by the predetermined angle (socalled bayonet type connection).Thereafter, the outer circumferential portion of the diaphragm 4 is clamped between main body portions la and ib.

In the drawing, shown at 4' is a ring fitted in an annular groove formed in the diaphragm 4 for preventing flow of the material of the inner circumferential portion of the diaphragm 4 in the radially outward direction under a compressive stress given from the piston plate and the valve body and a tension stress acting on the radially outer portion of the diaphragm during usage of the vacuum booster device.

The vacuum booster device further comprises reaction levers 7 and pins 8 interposed between a cover plate 9 and a plate 10. Pawls 9a formed on the cover plate 9 are inserted into holes 10a formed in the plate 10 so as to connect them integrally. The plate 10 further includes a flange 10b inserted into an annular groove 2d of the valve body 2, and a pawl portion 10d being adapted to abut with the outer peripheral surface portion 2e of the head portion 2a of the valve body 2 so as to control relative rotation between the valve body 2 and the piston plate 3. Namely, the plate 10 is pressed on the leftside surface of the valve body 2 and the piston plate 3 as viewed in Figure 1 after the power piston has been assembled as described heretofore so that the flange 10b of the plate 10 is fitted in the groove 2d of the valve body 2 to control the relative positional relationship of the piston plate 3 and the plate 10 in the radial direction and that the pawl portion 10d of the plate 10 is inserted into one of spaces 11 formed between the piston plate 3 and the valve body 2 in connecting them one to another such that the pawl portion 1 0d of the plate 10 is disposed adjacent to a generally planar outer peripheral portion 2e of the head portion 2a of the valve body 2.At that condition, the pawl portion 10d extends, as shown clearly in Figure 3, to the position adjacent to the inner periphery of the opening 3a in the piston plate 3, whereby, the plate 10 cannot rotate relative to the piston plate 3 when the pawl portion 1 0d engages with the inner periphery of the opening 3a. Therefore, when the piston plate 3 is rotated relative to the valve body 2, the pawl portion 10d will engage with the inner periphery of the opening 3a of the piston plate 3 and also with the outer periphery 2e of the head portion 2a of the valve body 2, thereby restricting the amount of relative rotation to an angle smaller than the aforementioned predetermined angle in the assembling operation.

Figures 4 and 5 show another embodiment wherein a pawl portion 3b is formed on the piston plate 3 for engaging with corresponding hole 10c formed in the plate 10 so as to control relative rotation between the piston plate 3 and the plate 10. in the embodiment, the pawl portion 10d of the plate 10 can act only to restrict the relative rotation between the plate 10 and the valve body 2. Since the relative rotation between the plate 10 and the piston plate 3 can be controlled within a very small range (as defined by dimensional tolerance) the relative rotation between the piston plate 3 and the valve body 2 can be restricted within a small range.Further, it will be understood that a plurality of equally spaced pawl portions 3b may, as shown in Figure 6, be provided to engage respectively with correspondingly shaped holes 10c formed in the plate 10 for simplifying assembling operation. In the embodiment of Figure 6, the pawl portion 10d of the plate 10 abuts normally with the generally flat surface 2e of the head portion 2a of the valve body 2, but in the embodiments of Figures 2 and 4 there can be observed a space between the radially inner surface of the pawl portion 10d and the outer peripheral surface 2e of the head portion 2a of the valve body 2.

In the embodiments, the plate 10 acts to support reaction levers 7 and has pins 8 which serves as fulcrums of the rocking movement of the reaction levers 7, therefore, the relative rotation between the valve body 2 and the piston plate 3 is effectively controlled within a desired range without increasing the number of parts.

However, it is possible to provide a member being separate from the essential components of the booster device and being attached nonrotatably to the piston plate and engageable to the outer peripheral surface of the head portion 2a of the valve body 2.

The construction and the action of the vacuum booster device shown in Figure 1 will be explained briefly. When an input rod 5 associated with a brake pedal or the like (not shown) is not pressed, the valve body 2 and the piston plate 3 is pressed rightward in the draw ing by a return spring 6 so that stops 4" formed on the diaphragm 4 engage with the side wall of the main body portion lb.At that condition, the chamber A connected permanently with a source of vacuum pressure such as intake mani fold of an engine not shown) is communicated with the chamber S through a spacing between a fulcrum plate 23 and cover plate 9, spacings be tween reaction levers 7, a passage 2f formed in the valve body 2, a spacing between a valve seat 12 and a poppet valve 13, an annular space 14 formed in the valve body 2 and a radial passage 15, and the input rod 5 is maintained at re tracted position shown in the drawing by a re turn spring 16.When the input rod 5 is moved leftward against the force of the return spring 16 by such as depressing the brake pedal, the poppet valve 13 moves leftward with respect to the valve body 2 which is stationary at that time so as to engage with the valve seat 12 thereby intercepting the communication between chambers A and B. When the input rod 5 further moves leftwards a valve seat 17 formed on a plunger 17 slidably disposed in the valve body 2 and associated with the input rod 5 will separate from the poppet valve 13, whereby a chamber 18 communicating permanently with atmosphere through a filter 20 and an atmos pheric air introducing opening 19' formed in a dust preventing boot 19 will be communicated with the chamber B through the space 14 and the passage 15.The pressure in the chamber B will increase toward the atmospheric pressure, and a differential pressure will be generated between the chambers A and B, thus, the dia phragm 4, the piston plate 3 and the valve body 2 move leftward in the drawing. The differential pressure force is transmitted to a piston of a master cylinder or the like (not shown) through the piston plate 3, the reaction levers 7, the fulcrum plate 23 and an output rod 21.

A reaction force acts on the input rod 5, namely, since the outer end portion of reaction levers 7 are confined between the piston plate 3 and an annular projecting portion 23a of the fulcrum plate 23 and the inner ends of the levers 7 engage with and being supported by a shoulder 1 7a formed on the plunger 17, reac tion force of the force acting on the output rod 21 is transmitted through the fulcrum plate 23 and reaction levers 7 to the plunger 17 and the input rod 5.

According to the reaction force counter acting with the pressing force applied on the input rod 5 and the leftward movement of the valve body 2, the poppet valve 13 engages with the valve seat 17' again to disconnect the communication between the chamber B and the atmosphere, whereby an equilibrium con dition of the vacuum booster device is attained.

When the pressing force applied on the input rod 5 is decreased a clearance is formed between the valve seat 12 and the poppet valve 13 thereby decreasing the pressure in the chamber B and the booster device takes a new equilibrium condition which is determined by the position of the input rod, the output force or the reaction force thereof in the output rod 21, the force of each of the springs, the differential pressure force acting across the diaphragm, and the pressing force in the input rod 5. When the pressing force applied on the input rod 5 is reduced to zero, the vacuum booster device returns to the condition shown in Figure 1.

It will be understood that the present invention is not limited to the vacuum booster device having the construction and function described as above, and the present invention may be applied to power pistons of vacuum booster devices of any other types provided that the power piston is formed of a valve body and a piston plate connected one to another by the use of a so-called bayonet type connection.

As described heretofore, the vacuum booster device comprises a rotation control member mounted substantially non-rotatably on a piston plate with one end of the rotation control member being disposed adjacent to a head portion of a valve body so as to control the rotation of the valve body with respect to the piston plate within a predetermined amount, so that the relative rotation between the valve body and the piston plate can be prevented effectively under the influence of vibrations or the like during long period of usage and the disengagement of the valve body from the piston plate can be avoided. Further, by mounting the rotation control member on the piston plate nonrotatably it is possible to restrict the amount of relative rotation between the piston plate and the valve body to such an extent that disengagement therebetween can reliably be prevented.

It is possible to assemble the power piston by connecting the piston plate, the diaphragm and the valve body by the use of a so-called bayonet type connection wherein the piston plate and the valve body are rotated relatively at a small angle, whereby the assembling operation is very easy and efficient as compared with prior art devices utilizing a plurality of clamping bolts and, further, it is not necessary to arrange any special means for attaining sealing between the diaphragm and the valve body. Further, it is possible to reduce the outer diameter and the thickness of the valve body since the threaded holes in the prior art devices can be omitted, thus, the size of the vacuum booster device can be reduced. Further, it is possible to avoid stress concentration which has been observed around the threaded holes in the prior art devices.The invention, moreover, is particularly adapted for use in vacuum booster devices of the type utilizing reaction levers since there are no bolt heads projecting on the side surface of the valve body as compared with prior art devices, thereby providing sufficient space in the main body of the vacuum booster device.

WHAT WE CLAIM IS: 1. A vacuum booster device comprising a main body, a piston plate dividing the main body into a pair of chambers and adapted to be subjected, in use, to differential pressure thereacross, and a generally cylindrical valve body incorporating therein valve means for selectively connecting and disconnecting communication between the two chambers and between one of the chambers and the atmosphere for developing said differential pressure across the piston plate, said piston plate and said valve body being connected to one another by providing an opening of non-circular configuration in the central portion of the piston plate and a correspondingly shaped head portion on one end of the valve body, passing the head portion through the opening and rotating the valve body relative to the piston plate by a predetermined angle, a rotation control member being attached to the piston plate with a portion thereof disposed adjacent to the outer periphery of the head portion and adapted to engage therewith to control the relative rotation between the piston plate and the valve body within said predetermined angle.

2. A vacuum booster device as claimed in claim 1 wherein the rotation control member is formed by a plate-like member disposed contiguous to the piston plate and engaging therewith by means of a pawl and recess arrangement.

3. A vacuum booster device as claimed in claim 1 wherein the rotation control member is attached to thc piston platc in a substantially non-rotatable manner.

4. A vacuum booster device substantially as hereinbefore particularly described with reference to and as illustrated in Figures 1, 2 and 3; or in Figures 1,4 and 5; or in Figures 1, 4 and 5 as modified by Figure 6 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. dition of the vacuum booster device is attained. When the pressing force applied on the input rod 5 is decreased a clearance is formed between the valve seat 12 and the poppet valve 13 thereby decreasing the pressure in the chamber B and the booster device takes a new equilibrium condition which is determined by the position of the input rod, the output force or the reaction force thereof in the output rod 21, the force of each of the springs, the differential pressure force acting across the diaphragm, and the pressing force in the input rod 5. When the pressing force applied on the input rod 5 is reduced to zero, the vacuum booster device returns to the condition shown in Figure 1. It will be understood that the present invention is not limited to the vacuum booster device having the construction and function described as above, and the present invention may be applied to power pistons of vacuum booster devices of any other types provided that the power piston is formed of a valve body and a piston plate connected one to another by the use of a so-called bayonet type connection. As described heretofore, the vacuum booster device comprises a rotation control member mounted substantially non-rotatably on a piston plate with one end of the rotation control member being disposed adjacent to a head portion of a valve body so as to control the rotation of the valve body with respect to the piston plate within a predetermined amount, so that the relative rotation between the valve body and the piston plate can be prevented effectively under the influence of vibrations or the like during long period of usage and the disengagement of the valve body from the piston plate can be avoided. Further, by mounting the rotation control member on the piston plate nonrotatably it is possible to restrict the amount of relative rotation between the piston plate and the valve body to such an extent that disengagement therebetween can reliably be prevented. It is possible to assemble the power piston by connecting the piston plate, the diaphragm and the valve body by the use of a so-called bayonet type connection wherein the piston plate and the valve body are rotated relatively at a small angle, whereby the assembling operation is very easy and efficient as compared with prior art devices utilizing a plurality of clamping bolts and, further, it is not necessary to arrange any special means for attaining sealing between the diaphragm and the valve body. Further, it is possible to reduce the outer diameter and the thickness of the valve body since the threaded holes in the prior art devices can be omitted, thus, the size of the vacuum booster device can be reduced. Further, it is possible to avoid stress concentration which has been observed around the threaded holes in the prior art devices.The invention, moreover, is particularly adapted for use in vacuum booster devices of the type utilizing reaction levers since there are no bolt heads projecting on the side surface of the valve body as compared with prior art devices, thereby providing sufficient space in the main body of the vacuum booster device. WHAT WE CLAIM IS:

1. A vacuum booster device comprising a main body, a piston plate dividing the main body into a pair of chambers and adapted to be subjected, in use, to differential pressure thereacross, and a generally cylindrical valve body incorporating therein valve means for selectively connecting and disconnecting communication between the two chambers and between one of the chambers and the atmosphere for developing said differential pressure across the piston plate, said piston plate and said valve body being connected to one another by providing an opening of non-circular configuration in the central portion of the piston plate and a correspondingly shaped head portion on one end of the valve body, passing the head portion through the opening and rotating the valve body relative to the piston plate by a predetermined angle, a rotation control member being attached to the piston plate with a portion thereof disposed adjacent to the outer periphery of the head portion and adapted to engage therewith to control the relative rotation between the piston plate and the valve body within said predetermined angle.