GB2247502A

GB2247502A - Vacuum brake power booster

Info

Publication number: GB2247502A
Application number: GB9117817A
Authority: GB
Inventors: Ralf Jakobi; Juergen Bauer; Rolf Fellinger
Original assignee: Alfred Teves GmbH
Current assignee: Continental Teves AG and Co oHG
Priority date: 1990-08-31
Filing date: 1991-08-16
Publication date: 1992-03-04
Also published as: JPH04254245A; DE4027562A1; DE4027562C2; FR2666289B1; JP3626209B2; FR2666289A1; GB9117817D0

Abstract

In order to simplify the assembly in a vacuum brake power booster, actuation of which causes the air in the vicinity of a splashboard carrying it to be sucked in, whilst accomplishing a reduction of the mounting space requirement, a boot (19) protecting the control housing (5) includes radial air intake apertures (13) in the area of its attachment to the booster housing (1). The apertures (13) may be covered internally by an annular filter (11). The end of the housing (5) may have a noise damper (24) with passages (25). <IMAGE>

Description

0 1 1 VACUUM BRAKE POWER BOOSTER The present invention relates to a vacuum

brake power booster.

More specifically, the invention relates to a vacuum brake power booster comprising a booster housing providing a vacuum chamber of constant pressure and a working chamber of variable pressure and comprising a control valve incorporated in a control valve housing located partially within the booster housing but with part of the control housing protruding out of the booster housing protected by a boot which, on the one hand, is sealingly secured to the booster housing and, on the other hand, is sealingly secured to a piston rod serving to actuate the control valve.

A vacuum brake power booster of the above construction i s know n from Applicant's prior-filed German Patent Application P3923843.1. When this known brake power booster is actuated, air is taken in close to the splashboard of the automotive vehicle which carries the brake power booster and flows in parallel to the longitudinal axis of the brake power booster through a spacer which attaches the boot to the booster housing as well as through an air filter into the interior of the boot. This construction provides for the propagation of air to a large-diameter opening designed at the end of the control housing and permitting air supply to the control valve. It is thereby accomplished that the level of the disturbing noises caused by the inflowing air is very low in the passenger cabin and that almost no noise r 2 will reach the passengers of the automotive vehicle.

Primarily, the complicated assembly of the spacer is to be regarded as less favourable in the known vacuum brake power booster which involves considerable manufacturing costs. Another shortcoming results from the increased mounting space requirement which is due to the installation dimensions of the booster (that is to say the diameter of the booster neck projecting through the splashboard wall opening) being augmented in the radial direction because of the employment of the spacer. Still another disadvantage ultimately resides in the unfavourable flow of the entering air which, due to the spacer's design, is caused to follow several changes in direction which have unfavourable response times as a result.

The present invention has for an object thereof to improve upon a vacuum brake power booster of the foregoing construction so that the assembly is simplified and the mounting space requirement is minimised simultaneously. To this effect. the particular area where the air required for the actuation enters is configured such as to be favourable in respect of flow so that the response time is shortened.

This object is achieved by the present invention which provides a vacuum power booster comprising a booster housing providing a vacuum chamber of constant pressure and a working chamber of variable pressure and comprising a control valve accommodated in a control valve housing located partially within the booster housing but with part of the control housing protruding out of the booster housing protected by a boot which. on the one hand, is sealingly secured to the booster housing and, on the other hand, is sealingly secured to a piston rod serving to actuate the control valve, characterised in that the boot comprises radial air intake apertures in the region of its securement to the booster housing.

A brake power booster according to the invention af fords a compact form of construction facilitating ease of assembly.

3 In a preferred embodiment of the invention an annular f ilter element is provided which covers the air intake apertures of the boot and which may be arranged either radially inwardly on the boot or lying radially outwardly on 5 it. As a result, all pollutants are removed f rom. the inflowing air which pollutants on ingress into the interior of the vacuum brake power booster might otherwise impair its reliability in operation. The filter element can be retained in a f avourable manner by beads shaped on the boot.

Lowering of the noise level is accomplished in another advantageous improvement upon the subject matter of this invention by arranging that the f ilter element is made of sound-absorbing material.

Further lowering of the noise level is achieved by another inventive f eature in that a noise damper is arranged in the end of the control housing projecting from the booster housing, which noise damper preferably is formed by a ring made of foam material for example, and comprising air ducts extending in parallel to the longitudinal axis of the vacuum brake power booster.

By way of example the present invention will now be described with reference to the single figure accompanying drawing showing a simplified enlarged view of a vacuum brake power booster according to the invention in axial cross- section.

Referring to the drawing, the booster housing 1 of the brake power booster shown therein is subdivided by an axially movable wall 2 into a working chamber 3 and a vacuum chamber 4. The axially movable wall 2 is composed of a diaphragm plate 8 deep-drawn from sheet metal and a flexible diaphragm 18 abutting thereon which although not illustrated forms a rolling diaphragm to provide sealing between the external periphery of the diaphragm plate 8 and the booster 1.

A control valve 12 operable by an actuating rod 7 is incorporated in a control housing 5 sealingly guided in the booster housing 1 and carrying the movable wall 2. The 4 valve 12 is composed of a first sealing seat 15 designed on the control housing 5, and a second sealing seat 16 designed on a valve piston 9 coupled to the actuating rod 7, and a poppet valve member 10 which cooperates with both sealing 5 seats 15,16 and which is pressed against the valve seats 15,16 by means of a compression spring 22 supported on a poppet valve mounting structure 21. In the illustrated nonactuated position of the booster, the working chamber 3 is connected to the vacuum chamber 4 through a channel 28 extending laterally in the control housing 5.

via a rubber-elastic reaction disc 6 abutting against the front end of control housing 5 and via a push rod 14 comprising a head flange 23, the brake force is transmitted to an actuating piston of a non-illustrated master cylinder of the brake system which is fitted on the vacuum-side of the power booster. The input force introduced at the actuating rod 7 is transmitted to the reaction disc 6 by means of a ratio variation cylinder or disc 20 interposed between the valve piston 9 and the reaction disc 6.

A resetting spring 26 illustrated schematically in the drawing takes support on a flange on the vacuum-side end wall of the booster housing 1 and maintains the movable wall 2 in its initial position, as shown. A second compression spring 27 is arranged between the valve piston 9 and a-supporting surface provided on the control housing 5 the force of this spring 27 providing biasing of the valve piston 9 and its valve seat 16 in relation to the poppet vale member 10.

In order to be able to connect the working chamber 3 to atmosphere when the control valve 12 is actuated a channel 29 is formed in the control housing 5 and extends generally in the radial direction of the housing.

As can readily be seen from the drawing, the part of the control housing 5 projecting from the booster housing 1 is protected against contamination and moisture by means of an elastic boot 19 which at one end, is buttoned into a circumferential groove in the actuating rod 7 and at the t other end is attached to the booster housing 1. In the area of its securement to the booster housing 1, the boot 19 is provided with a number of radial air intake apertures 13 which are evenly distributed around its periphery and permit the ingress of air into its interior of the boot. Arranged radially inwardly opposite to the air intake apertures 13 is an annular filter element 11 which is preferably kept in axial abutment with the booster housing 1 by way of a bead 17 f ormed on the boot 19 and which can be made of any suitable sound-absorbing material. However, other designs would also be possible wherein the filter element 11 is located radially outwardly of the boot 19 and is retained thereto by two axially opposed filter retaining beads.

Finally, in order to accomplish additional noise attenuation, the control housing 5 accommodates at its end projecting from the booster housing 1 a noise damper 24 which is formed of a ring or annulus made of foam material, for instance, and which is provided with a number of air ducts 25 extending in parallel to the longitudinal axis of the vacuum brake power booster and permitting unhindered inflow of air into the interior of the booster housing 1.

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Claims

CLAIMS:

1. A vacuum brake power booster comprising a booster housing providing a vacuum chamber of constant pressure and a working chamber of variable pressure and comprising a control valve accommodated in a control valve housing located partially within the booster housing but with part of the control housing protruding out of the booster housing protected by a boot which, on the one hand, is sealingly secured to the booster housing and, on the other hand, is sealingly secured to a piston rod serving to actuate the control valve, characterised in that the boot (19) comprises radial air intake apertures (13) in the region of its securement to the booster housing (1).

2. A vacuum brake power booster as claimed in claim 1, characterised in that an annular filter element (11) is provided which covers the air intake apertures (13).

3. A vacuum brake power booster as claimed in claim 2, characterised in that the filter element (11) is located radially inwardly on the boot (19). 20

4. A vacuum brake power booster as claimed in claim 2, characterised in that the filter element (11) is located radially outwardly on the boot (19).

5. A vacuum brake power booster as claimed in claim 3 or 4, characterised in that the filter element (11) is retained by beads (17) formed on the boot (19).

6. A vacuum brake power booster as claimed in any one of claims 2 to 5, characterised in that the filter element (11) is made of a soundabsorbing material.

7. A vacuum brake power booster as claimed in any one of the preceding claims, characterised in that a noise damper (24) is arranged in the control housing (5) at the end thereof protruding from the booster housing (1).

8. A vacuum brake power booster as claimed in claim 7. characterised in that the noise damper is formed by a ring or annulus (24) which comprises air ducts (25) extending in parallel to the longitudinal axis of the vacuum brake power booster.

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9. A vacuum brake power booster as claimed in claim 8, characterised in that the ring (24) is made of foam material.

10. A vacuum brake power booster substantially as hereinbefore described with reference to the accompanying drawing.

Published 1992 at The Patent Office. Concept House. Cardiff Road. Newport. Gwent NP9 I RH- Further copies mav be obtained floni 5ales Branch, Unit 6. Nine Mile Point. Cumifelinfach. Cross Keys. Newport. NPI 7HZ. Printed by Mult'plex techniques ltd- St Mary Cray. Kent-