Servo booster for vehicle braking systems

PATENT ATTORNEYS

WUESTHOFF - ν. PECHMANN - BEHRENS · GCETZ

PROFESSIONAL REPRESENTATIVE BEF ORE THE EUROPEAN PATENT OFFICE MANDATAiREs agrees pres l'office européen des brevets

1A-52 277 May 18, 1979

I / R. ING. FRANZ VUESTHOFF

ΓΡ. PHIL. FREDA WUESTHOFF (1927-I956)

£ iIPL.-ING. GERHARD PULS (1952-I971)

DIPL.-CHEM. DR. E. FREIEHERR VON FECHMANN

DR. DIETER BEHRENS

DIPL.-ING .; GRADUATE ECONOMY ING. RUPERT GOETZ

Ό-8ϋΟϋΟ9 M SWEEPER ROAD

telephone: (089) 6610 telegram: protectpatent telex: 524070

applicant:

Girling Limited Kings Road, Tyseley, Birmingham 11, West Midlands

Great Britain

title

Brake booster for vehicle door ems systems

"09847/0933

PATENT ATTORNEYS

WUESTHOFF - ν. PECHMANN - BEHRENS - GOETZ

PROFESSIONAL REPRESENTATIVE BEFORE THE EUROPEAN PATENT OFFICE MANDATAIRES AGREES PRES l'OFFICE EOROPEEN DES BREVETS

DR-ING. FRANZWUESTHOFF

JI PHIL. FREDA WUESTHOFF

DIPL.-ING. GERHARD PULS (19J-I971)

DIPL.-CHEM. DR. E. FREIEHERR VON PECHMANN

DR. DIETER BEHRENS

DIPL.-ING .; GRADUATE WIRTSCH.-ING. RUPERT GOETZ

D-8000 MUNICH SCHWEIGERSTRASSE phone: (089) 66 zo telegram: protectpatent telex: j 24070

1A-52 277

18th May 1979

description

Brake booster for vehicle brake systems Addendum to P 28 45 794.5

A known brake booster for a vehicle brake system has a housing, a movable wall which divides the housing interior into two chambers and transmits a force to an output element when, depending on a force acting on an input element, the chambers are exposed to a pressure difference, at least one stationary arranged force transmission element, extending through a movable wall from a housing wall to a housing wall located on the opposite side of the movable wall, and means for sealing the movable wall directly or indirectly against the power transmission element.

According to the invention, in a brake booster of this type, the power transmission element with a passage

/ 2

909847/0933

provided, which is able to establish a fluid connection.

The passage may establish fluid communication between components located outside and at opposite ends of the housing, for example, between a reservoir for brake fluid on the one hand and a master brake cylinder on the other hand. However, the passage preferably provides fluid communication of one of the chambers with another chamber or with a component disposed outside the housing.

The power transmission element is usually a stud.

The passage is operable to establish fluid communication between said one chamber and an external vacuum or pressurized air line or between said one chamber and a control valve disposed in the housing.

However, the brake booster preferably has a further movable wall which is arranged in tandem arrangement of said movable wall in the housing and is capable of applying an axial force to the output element, and means which seal the further movable wall against the power transmission element, the housing being a transversely extending partition which lies axially between the movable walls, whereby four axially spaced apart chambers are formed by means of the partition wall and the movable walls in the housing and the passage is capable of establishing fluid communication between two of the chambers bypassing an intermediate third chamber.

Thus, the invention makes it possible in a tandem brake booster to connect a pressure chamber with the next but one pressure chamber in a simple manner, without formerly needed auxiliary links are kept ready. To avoid connecting pipes outside the housing, it has hitherto been customary to provide the dividing wall with axially extending edges or collars which form channels connecting the pressure spaces in alternating sequence. The invention makes such collars unnecessary, which leads to a weight reduction and savings in the manufacturing cost of the partition.

909847/0933 /³

- 52 277

In one embodiment two force transmission elements are present, each having a tube, and the tubes are provided with axially spaced radial openings communicating with the associated pressure chambers, ie with every other pressure chamber. Directly.

It is advantageous if the two tubes of the same design, but with respect to each other in opposite directions are arranged so that the openings of one tube are arranged offset with respect to the openings of the other tube.

In order to keep the weight as low as possible, however, in such an embodiment restrictions are placed on the cross-sectional dimensions of the tubes, which can lead to unacceptable resistance to fluid flow between the respective chambers, resulting in an undesirable time delay between the operation of the brake booster and the brake booster Achieving the full output force of the brake booster corresponding to a given input force.

In a preferred embodiment, a tube is secured to one of the moveable walls, extends axially through an opening in the dividing wall and is sealed against the dividing wall, and the interior of the tube is adapted to provide continuous fluid communication between the other two chambers ,

Preferably, in the preferred embodiment, there are two stationarily arranged force transmitting members, each of which has a passage which provides fluid communication between the same two chambers. The use of two power transmission elements in this manner enables a substantial reduction in the time delay mentioned above.

/ 4 909847/0933

- / - 52

Preferably, the tube is coaxially arranged with the central axis of the power brake booster. When using two power transmission elements, these are preferably arranged at diametrically opposite positions with respect to the brake booster axis.

The means which seals the tube against the dividing wall may be a sliding seal or a flexible membrane.

When the movable walls each comprise a diaphragm assembly, the tube may be formed as a one-piece molding integral with the diaphragm support plate of the diaphragm assembly, or as a separate component sealed to the support plate.

The tube is preferably connected to the front movable wall and extends rearwardly through the partition, with the front of the brake booster facing away from the input member of the brake booster.

Preferably, the tube is coaxially disposed with the output member and the force applied in operation from the front movable wall to the output member is transmitted via the tube.

It has previously been proposed to rigidly interconnect the two movable walls of a tandem brake booster using a coaxial tube with the output rod and to use the tube to make a fluid connection between two alternating chambers of the brake booster. However, in the previously proposed embodiment, a cylindrical rim or collar had to be formed on the outer circumference of the partition, which formed with the housing wall of the brake booster an annular chamber, which is a connection between the anden α both chambers of the brake booster

Γ109847 / 0933/5

52 277

It was necessary to provide a seal between the diaphragm of the rear movable wall and the rear end of the collar.

A disadvantage of this embodiment is that through the space in the brake booster housing, which occupy the collar and the annular chamber, the diameter of the movable walls is reduced, which can be accommodated in the housing, and thus the available output power is reduced, and that the membranes must be made with different dimensions to account for the fact that that the one against the housing wall and the other is sealed against the collar.

Since the invention avoids the need for a collar and the movable walls can be sealed in the same way against the housing, it is possible to choose the diameters of the movable walls as large as possible. If necessary, the membranes of the movable walls can be of equal design to save costs. Avoiding a collar can also lead to weight savings.

When the power transmission element comprises a pipe, at least one end of the pipe is preferably provided with a closure piece in the form of a bolt capable of connecting the pipe to the housing of a master cylinder or vehicle bulkhead and being sealed in the end of the pipe by any convenient means , such as by Scherstauchnieten, by the use of an annular elastic sealing member or by means of a corresponding adhesive.

The opposite end of the tube may be provided with a similar threaded bolt or with a fitting which connects the passage of the tube with a vacuum or compressed air line and may be equipped with a check valve if required.

909847/0933 ^{/ 6}

ORIGINAL INSPECTED-

-40-

52

Preferably, the ends of the tubes abut the inner surfaces of the housing walls when the walls are of substantially uniform thickness.

The means by which each movable wall is sealed against each tube is preferably a diaphragm which is secured to the tube so as not to close the openings in the tube, which could occur if a sliding seal carried by the movable wall is used for sealing would become.

The two housing shells of a tandem brake booster are preferably held at their enclosure by a cylindrical member provided with a partition at a distance from each other. The peripheries of the housing shells are directly connectable with each other so that the same housing shells can be used to form the housing of a brake booster with a single bwweglichen wall, in which case the cylindrical member is omitted.

In a brake booster having two movable walls, movement of the partition wall in one direction with respect to a tubular force transmitting member may be prevented by a spring ring received in an outer annular groove in the pipe.

Exemplary embodiments of various vacuum-operated tandem brake booster according to the invention are explained in more detail below with reference to schematic drawings. It shows:

1 a longitudinal section through a brake booster, the rod-shaped input element and movable walls are drawn in their withdrawn ü LLungen

ORIGINAL INSPECTED

/ 7 909847/0933

- At -

52

Fig. 2 is a longitudinal section through a tandem brake booster according to the invention, which is connected to a hydraulic tandem master cylinder and its parts are drawn in their retracted positions, wherein the upper power transmission element assembly drawn for the purpose of clarity in the vertical plane is

3 and 4 are similar longitudinal sections through modified embodiments of the brake booster according to FIG. 2.

The brake booster shown in Fig. 1 has a housing 1, which is formed by housing shells 2 and 3, a cylindrical housing part 4 and a partition wall 5, which are all compacts of thin sheet steel. The opposite housing shells 2 and 3 are connected to each other at their Außenurafängen by the cylindrical housing part 4, and the outer peripheries of the housing shells and 3 are connected to the housing part 4 in a known manner by corresponding, arranged with circumferential spacing interlocking mold elements 6. The partition wall 5 is arranged at the same distance between the housing shells 2 and 3.

A first movable wall 7 and a second movable wall 8 each have a cup-shaped membrane-otützplatte or 10, which supports an associated flexible membrane 11 and 12 respectively. The Außenumfangswulst 13 of the diaphragm 11 is between the Gehäusechale 3 and the housing part A._f and the corresponding bead 14 of the membrane 12 is between the

/ 8 9098 47/09 33

- * "- Λη 52 277

G-ehäuseschale 2 and the outer periphery of the partition 5 is clamped. To the diaphragm support plate 10, a rearwardly facing pressed cup 15 made of steel is welded against which an inner peripheral bead 16 of the diaphragm 12 seals. The membrane support plate 9 supports a corresponding bead 17 of the membrane 11 at a centrally located, rearwardly extending tubular extension 18, which engages over the head piece 19 of a substantially cylindrical valve housing 20. The bead 17 is held by a pressed onto the neck 18 conical washer 21 in position.

Between the housing shell 3 and the first movable wall is a first chamber 22, between the wall 7 and the partition 5, a second chamber 23, between the partition 5 and the second movable wall 8, a third chamber 24 and between the wall 8 and the housing shell 2, a fourth chamber 25 is formed. In the unactuated state of the brake booster, all pressure chambers formed by the chambers 22 to 25 are connected to a vacuum source; however, upon actuation of the brake booster, the alternating chambers 22 and 24 adjacent the rear sides of the associated movable walls 7 and 8 are connected to the atmosphere.

Two diametrically opposed, in the example shown as a connecting pieces formed Kraftübertragungselement assemblies 26 and 27 extend axially through the entire housing 1 and enforce both movable walls 7 and 8 and the fixed partition 5 · each transmission element assembly 26 and 27 has a same trained Tube 28 up, which extends between the opposite inner surfaces of the housing shells 2 and 3 and is provided with two axially spaced groups of radial passages 29 and 30. The openings 29 and 30 of the power transmission element 26 are in direct communication with the chamber 23 or 25, and the bore of the tube 28 forms together with the openings 29 and 30th

909847/0933 /₉

a passage which establishes a permanent connection between these two chambers 23 and 25. The tubes 28 of the two power transmission elements 26 and 27 extend in opposite directions to each other so that the openings 29 and 30 of the power transmission element 27 are offset from the openings 29 and 30 of the power transmission element 26 to provide a permanent connection between the chambers 22 and 24 *

Each of the diaphragms 11 and 12 of the two movable walls 7 and 8 is integrally formed with two tubular rolling diaphragm portions 31 having annular ridges 32 received in respective annular recesses 33 in the associated tubes 28 to face the movable walls 7 and 8 to seal both force-over-elements 26 and 27. The partition wall 5 is sealed against each of the tubes 28 by an annular sealing member 34 which is held by an associated, rearwardly directed circular flange 35 of the partition wall 5.

Rearward movement of the partition wall 5 with respect to the tubes 28 as a result of the prevailing during actuation of the partition 5 pressure difference is prevented by spring rings 36 against which abut the back surfaces of the sealing members 34 and held in annular grooves 37 in the tubes 28 are. By the force transmission elements 26 and 27, it is thus possible to carry out the partition wall 5 less vigorously and consequently with a lower weight than would otherwise be necessary.

Each of the tubes 28 is closed at its rear end by a bolt 38, the rear portion is provided with an external thread on which, for attaching the housing 1 to a vehicle partition wall, a nut is screwed. The middle section of each bolt 38 has been subjected to a shear-neck riveting operation.

909847/0933 / 10

52 277

to clamp the housing shell 3 with sealing engagement with the rear ends of the tubes 28.

The front end of the drawing corresponding to the lower tube 28 is closed in the example shown by a modified bolt arrangement in which a bolt 39 is formed with an elastic annular sealing member 40 which seals the housing 1 reliably as soon as the bolt 39 at a flange 41 of a master cylinder is attached.

The front end of the drawing according to the upper tube 28 is provided with a tubular connecting piece 42 which is connectable to a vacuum supply line not shown. The fitting 42 has a hexagonal portion 43 "on which the connector 42 can pack and rotate to clamp the flange 41 of the master cylinder between the hexagonal part 43 and the housing shell 2, wherein a sealing member 44 performs the same task as the sealing member 40.

In a rearwardly extending tubular portion 47 of the valve housing 20, an air filter 46 is held, through which a formed in the example shown as an actuating rod input member 45 extends, which engages an input piston 48 of a known reaction assembly 49, to which an elastic reaction disc 50 and the head 51 of a rod-shaped output member assembly 52 in the example shown. The output member assembly 52 has two rods 53 and 54 which are interconnected by a spring pin 55, wherein the support plate 10 of the second movable wall 8 is clamped between them and with washers 56, the total length of the output member assembly 52 is variable. Between the front housing shell 2 and the support plate 10, a compression spring 57 is clamped, which generates a restoring force for both movable walls 7 and 8.

909847/0933

52

A seat valve 58 of known type has

axially movable valve closure member 59, which is able to apply to a first annular seat 60 at the rear end of the input piston 48 and a second annular seat 61 on the head piece 19 of the valve housing 20. In the retracted position of the input member 45, the valve closure member 59 abuts the first seat 60 to separate an atmospheric pressure inlet 62 from a chamber 22 leading to the radial opening 63 in the head piece 19, and has sufficient distance from the second seat 61, whereby between the Chambers 23 and 22 a Fluxdverbindung on the openings 64 and 63 may exist. Since the chamber 22 is constantly connected via the bore of the lower tube 28 and the openings 29 and 30 with the chamber 24 and the chambers 23 and 25 are connected by the upper tube 28 in a similar manner, all chambers 22, 23, 24th and 25 exposed to a vacuum, because the connector 42 is connected in operation with a vacuum supply line. As the input member 45 moves forward, the valve closure member 59 abuts against the second seat 61 and disengages from the first seat 60 to flow atmospheric air into the chamber 22 and thus into the chamber 24 from the inlet 62 via the orifice 63 allow.

A held in the interior of the rear end of the housing shell 3 seal 65 seals between the housing shell 3 and the valve housing 20. The partition wall 5 is sealed against the rod 53 by a further rolling diaphragm 66.

In operation, the power transmission members 26 and reaction forces from the flange 41 of the master cylinder housing to the vehicle bulkhead and prevent the housing shells 2 and 3 move apart. This makes it possible to make the housing shells 2 and 3 less strong and therefore lighter in weight than before.

009847/0 933

52 277

2 shows a hydraulic tandem master cylinder 81, the rear half of which is arranged in the housing 82 of a pedal-operated vacuum tandem brake booster 83. The housing 82 of the brake booster 83 has front and rear housing shells 84 and 85 and an intermediate shell 86, with which a transverse to the brake booster axis extending partition wall 87 is integrally formed. The molded as plastic moldings housing shells 84 and 85 and the intermediate shell 86 are connected to snap connection points 88 and 89 with each other; between them, the circumferential beads 90 of flexible membranes 91 and 92 of a front and a rear movable wall 93 and 94 are clamped. The peripheries of the housing shells 84 and 85 are designed so that mutually identical housing shells are used in a brake booster with a single movable wall, in which case the Gehäuseschalenumfänge are connected directly to each other by means of the corresponding mold elements and the intermediate shell 86 is omitted.

The movable walls 93 and 94 further comprise annular diaphragm support plates 95 and 96 formed as plastic moldings, the support plate 95 of the front movable wall 93 being integrally connected at its radially inner edge to a forwardly extending axial sleeve 97 and the rear support plate 96 forms a one-piece molding with a substantially cylindrical valve housing 98, which has a rearwardly extending tubular extension piece 99 in which a poppet valve 100 is disposed. The valve housing 98 is sealed against the rear housing shell 85 with an annular sealing member 101 which slidably abuts the outer surface of the extension piece 99 and is integrally formed with a collar 102. The design of the sealing member 101 and the sleeve 102 is the subject of the main application P 28 45 794.

The housing 82 of the brake booster 83 is divided by the movable walls 93 and 94 and the fixed partition wall 87 into four chambers 103, 104, 105 and 106. The housing shells 84 and 85, the intermediate shell 86 and both movable walls 93 and 94 are stationary of two in the example shown as connecting pieces

/ 13

80 9847/0933

At

arranged force transmission elements 107, of which only one is drawn, passes through axially. The two power transmission elements 107 are disposed diametrically opposite each other with respect to the center axis of the brake power amplifier 85 tern. Each power transmission element 107 has as a central portion a tube 108, which is screwed at opposite ends with bolts 109 and 110, the

protrude out of dep housing 82 of the brake booster 83 to the outside and can be connected to a flange 113 of the master cylinder .Gehäuses 114 or with a not shown vehicle partition.

The flexible membranes 91 and 92 are made equal to each other and integrally formed with an associated rolling diaphragm portion 115 and 116, which are provided with annular beads 117 and 118, which are received in annular recesses in the outer surface of the force transmission elements 107. The bead 117 is sealingly attached to the rear end of a ribbed sleeve 119 integrally formed with the front housing shell 84, and seals both between the forward end of the power transmission element 107 and the housing shell 84 and between the chambers 103 and 104. The bead 118 seals only between the chambers 105 and 106, while the seal between the rear end of the Kraftübertragungseiementes 107 and the rear housing shell 85 is concerned by a separate annular sealing member 120 which is disposed on the bolt 110. The rib sleeve 119 supports the rolling diaphragm sections 115 in forward movement of the front movable wall 93, while the rolling diaphragm sections 116 of the rear movable wall 94 are supported by a group of louvers or ribs 121 extending circumferentially from the partition wall 87 of the intermediate shell 86 extend behind and are integrally connected to the partition 87. Each of the power transmission elements 107 is sealed against the partition wall 87 with a circular annular sealing member 122.

909847/0933. /H

■ - / f ο -

52

To provide a continuous fluid communication between the chambers 104 and 106, the mutually equal force transmission elements .107 each have axially spaced interspaces 123 and 124, which in the example shown are continuous transverse bores, and the force transmission elements 107 are different in the embodiment according to Pig. 1, arranged in the same direction.

The master cylinder 81 has a primary piston 125 integrally connected to a rod-shaped output member 126 of the brake booster 83 in the example shown, and a secondary piston 127 connected to the primary piston 125 via a backlash link 128. The primary piston 125 and the secondary piston are forced apart by a coil spring 129. In a bore extension in the rear end of the master cylinder housing 114 an annular seal 130 is held with a U-shaped bracket 131 made of wire and acts as a stop member, which determines the retracted position of. Primary piston 125 and thus of the secondary piston 127. The force to reset the primary piston 125th is generated by a coil spring 132 which abuts with its front end at a diameter transition 133 on the master cylinder housing 114 and is supported with its rear end to a flange 134 of a head 135 which by means of caulking 136 at the rear end of the output member 126th is attached.

A stepped tube 137 has sections 138 and 139 of larger and smaller diameter, respectively. The larger diameter portion 138 is coaxially disposed with the output member 126 and. is at its front end by means of a radially outwardly directed end flange 140 and an outwardly compressed portion 141 with the sleeve 97 rigidly connected, wherein the portion 141 is received in a bore extension 142 of the bore of the sleeve 97. A 0-ring 143 seals between the sleeve 97 and the

/ 15 909847/0933

Pipe 137 from to separate the chambers 103 and 104 from each other, and the portion 138 of the tube 137 is sealed against the partition wall 87 with a formed as a sliding seal annular sealing member 144 which is arranged in a one-piece with the partition wall 87 annular groove collar 145.

The smaller diameter portion 139 of the tube 137 is slidably disposed in a bore portion 146 at the forward end of the valve housing 98 and slidably receives the end portion of the head 135. An inner flange 147 of section 139 forms a bore in which the front end 148 of a valve control member 149 is displaceable bar, which is connected to the head of a rod-shaped in the example shown input member 150 which is actuated by a pedal. At the rear end of the valve control member 149 and the valve housing 98 co-axial valve seats 151 and 152 are formed in a conventional manner, to which the annular head or plate of the poppet valve 100 is able to create.

A continuous flux connection between the chambers 103 and 105 exists over the interior of the portion 138 of the tube 137 and a group of axially directed holes 154 circumferentially spaced in the diameter transition between the portions 138 and 139 of the tube 137. Since the interior of the portion 138 is of relatively large diameter, pressure equilibrium arises between the chambers 103 and 105 in a short time when a passage 155 in the valve housing 98 by means of the poppet valve 100, the pressure in the chamber 105 is changed.

The movable walls 93 and 94 are not rigidly connected to each other. If the rear movable wall 94 were to settle in the housing 82, the front movable wall 93 may still be able to provide an amplifying force

909847/0933 ^{/ 16}

because it is able to move axially with respect to the rear wall 94. In an annular recess in the outer surface of portion 139 of the tube, an O-ring 156 is arranged, which acts as a sliding seal between the portion 139 and the valve housing 98 to accommodate relative movement between the movable walls 93 and 94 and at the same time the chambers 105 and 106 seal against each other.

In addition to the primary piston 125 and the secondary piston 127, the coil spring 132 also returns both movable walls 93 and their retracted positions.

When in Pig. 3 illustrated modified embodiment of a brake booster are components that the embodiment according to Pig. 2, designated by like reference numerals.

The main differences between the embodiments according to Pig. Figures 2 and 3 are, firstly, that the tube 137 is integrally formed with the sleeve of the front movable wall 9 3, the portion 138 having inside longitudinally spaced circumferentially spaced reinforcing ribs 160; second, that the circumferentially spaced holes 154 are machined into the portion 138 of the tube 137, and third, the manner in which the reaction disc 153 is held in position. In the example shown, the smaller diameter portion 139 of the tube 137 has a closed rear end wall 161 slidably disposed directly in the bore portion 146 of the valve housing 98 and the elastic reaction disc 153 is disposed from the end wall 161 from the forward end of the bore portion 146 Sleeve 162 and held by the front end of the valve control member 149 in position. The output member 126 has at its rear end a with it integrally or firmly connected head piece 135 · which is received in the bore of the portion 139 of the tube 137 and abuts on the end wall 161 via an intermediate disc 163 made of metal.

909847/0933. / 17

The force generated by the front movable wall 93 is transmitted via the end wall 161 directly to the output member 126 and does not act on the reaction disc 153 »which is subject only to the force generated by the movable wall 94, the output member 126 via the sleeve 162nd , the reaction disk 153 and the end wall 161 is transferred.

The pressure generated in the elastic reaction disc 153 in operation and acting on the front end 148 of the valve control member 149 to apply a reaction force to the input member 150 is thus entirely due to the force generated by the rear movable wall 94 and is independent of the force which generates the front movable wall 93. This makes it possible to use in a brake booster with only a single movable wall, the same embodiments of the housing shell 85, the rear movable wall 94, the valve housing 98, the reaction disk 153t aer sleeve 162 and the valve control member 149.

The embodiment shown in FIG. 3 does not have a sealing member equivalent to the O-ring 156 according to FIG. 2, since the reaction disk 153 seals between the chambers 105 and 106.

In the modified embodiment shown in FIG. 4, components which correspond to those of the embodiments according to FIGS. 3 and 3 are designated by the same reference numerals. The embodiment shown in Fig. 4 is similar to the embodiment of FIG. 3 in that the tube 137 is integrally formed with the sleeve 97 of the front movable wall 93, but has with the embodiment of FIG. the feature in common that the reaction disc 153 is designed so that it transmits the sum of the forces generated by both movable walls 93 and 94.

S09847 / 093