DE1081789B - Hydraulic actuation system for a disc brake especially intended for motor vehicles - Google Patents

Description

GERMAN

kl. 63c 54/03

INTERNAT. KL. B 62 d

PATENT OFFICE

G961911 / 63c

REGISTRATION DATE: AUGUST 21, 1952

B EKANNTMACHÜNG
THE REGISTRATION
AND ISSUE OF THE
SUPPLY: MAY 12, 1960

The invention relates to a hydraulic actuation system for a particularly for road and other motor vehicles provided disc brake, "in which in one or more places brake pads are brought into contact on both sides of the brake disc and the remaining part of the Disc is exposed for the purpose of cooling. The brake pads are provided on pistons that are in the open inner ends of opposing equiaxed hydraulic cylinders operate. The fluid spaces in the brake cylinders between the pistons and the closed outer ones Pressurized fluid is supplied to the ends of the cylinder from a master cylinder at the same time, so that the brake pads are brought into contact with the disc with the same force. When solved Brake remains in the hydraulic actuation system, a residual pressure that the brake pads on the Keeps the brake disc in slightly rubbing contact. The brake pads are not supported by a return spring brought into a release position.

Tests on a vehicle equipped with such a disc brake have shown that when changing the direction of travel one of the brake pads together with the associated piston An effort shows to move axially away from the disc in its cylinder and liquid from the cylinder to push back into the pressure chamber of the master cylinder. The same effect can be caused by others Influences are caused, for example by impact of the brake disc and by wear on the Wheel bearings or their associated parts. The next time the brake is applied, therefore, before the brake takes effect, enough fluid will be displaced from the master cylinder in order to to bring the brake pad into contact with the brake disc. But that means a considerable increase of the pedal travel.

To overcome this difficulty, the hydraulic actuation system according to the invention is shown in FIG designed in such a way that a connection between the opposing brake cylinders is provided, which allows an unimpeded exchange of fluid, and in the line, which is extends from this connecting line to the master cylinder, a control device is arranged in the A piston works in a cylinder bore and has limited axial freedom of movement in the cylinder owns. When the brake pedal is depressed, the piston is displaced by the one from the master cylinder Liquid displaced and thereby in turn displaces the liquid at the other end of the cylinder flows to the two brake cylinders and these with equal pressures on both sides against the brake hydraulic Actuation system

for a disc brake intended in particular for motor vehicles

Applicant:

Girling Limited,

Tyseley, Birmingham, Warwickshire (UK)

Representative: Dr.-Ing. F. Wuesthoff, Dipl.-Ing. G. Pulse and Dipl.-Chem. Dr. rer. nat. E. Frhr. v. Pechmann, patent attorneys, Munich 9, Schweigerstr. 2

Claimed priority: Great Britain August 21, 1951 and January 2, 1952

Joseph Warwick Kinchin,

Tyseley, Birmingham, Warwickshire (Great Britain), has been named as the inventor

Disc presses. In the control device, a spring-loaded valve is also provided that the piston bridged and directs fluid from the master cylinder side to the brake cylinder side of the piston, when the pressure in the master cylinder exceeds the pressure in the brake cylinders by a predetermined amount. This valve has the task of the part of the hydraulic system between the piston and the Refill brake cylinders if the brake pads have to be pushed further forward due to abrasion to achieve the necessary contact pressure on the brake discs. Finally in the control device is still a spring-loaded valve is provided which pushes the piston in the other direction from the. Brake cylinder side bridged to the master cylinder side and opens when the pressure in the brake cylinders is released when the brake is released and when the piston rests against the rear stop in the control device when it is very hot exceeds predetermined limit pressure. So this valve is a safety valve that prevents that the pressure in the plant part behind the piston of the control device a predetermined limit pressure can exceed.

To limit the free travel or air travel of Brake members that are withdrawn by springs in the release position, it is already known in the Line to the brake cylinders to connect a piston

0O9 509/243

who have limited freedom of movement and bypassed by a valve that opens under the pressure of the pressure source when the piston rests against its stop on the brake cylinder side, as well as providing a spring-loaded safety valve, p that opens when the pressure in the brake cylinders exceeds the pressure in the master cylinder when the brake is released exceeds by a predetermined amount.

The arrangement of the same means provided according to the invention is used in the hydraulic Control system for the opposing brake pads of a disc brake, in which the Brake pads are not pulled into a release position by springs, but by the fluid pressure to remain in slightly rubbing contact with the brake disc, another object is achieved, namely which prevent the backflow of liquid into the master cylinder when the Brake disc, e.g. B. when changing the direction of rotation, od with road bumps released position, the brake pushes back, and at the same time ensure that the one Brake pad displaced fluid gets behind the other brake pad and this in corresponding Way so that both are constantly in contact with the brake disc under equal pressure stay.

The invention is illustrated below with reference to schematic drawings of several exemplary embodiments explained in more detail.

Fig. 1 shows the hydraulic actuation system of a disc brake;

Fig. 2 is a sectional view of a back pressure valve inserted into a conduit connecting a master cylinder to the Brake cylinders connects, can be switched on;

Fig. 3 is a schematic section through a back pressure valve of another embodiment;

Fig. 4 is a section through an embodiment of the valve shown schematically in Fig. 3;

Fig. 5 is a section through another embodiment of the valve;

Figures 6 and 7 are cross-sections taken along lines 6-6 and 7-7, respectively, in Figure 5;

Figure 8 is a section through a simplified embodiment of the valve.

In the arrangement shown schematically according to FIG. 1, 10 is a part of a rotatable brake disc, which is attached to the wheel of a vehicle or is located together with the wheel of a vehicle turns, designated. The pressure pieces are placed on the opposite sides of the brake disc 11, which are attached to pistons 12, which are arranged in opposite and coaxially Cylinders 13 are located. These cylinders are provided in a fixed bracket 14 which is around grips around the edge of the brake disc. The liquid spaces of the cylinder 13 are by means of a pipe 16 connected to each other; the pipe 16 in turn is connected by a pipe 17 to a master cylinder 18, the piston of which is actuated by a pedal 19. In the tube 17 is located near his Connection to the pipe 16 is a regulating device which is generally provided with the reference numeral 20 and which is shown in FIG the following is also referred to as a back pressure valve. If one of the pressure pieces 11 and the associated Piston 12 strives to move away from the brake disc in the axial direction in the associated cylinder, the displaced liquid simply flows over from this cylinder to the other cylinder; the path of movement of the piston in the master cylinder when the brake is actuated is not affected.

One possible embodiment of the control device or the counter-pressure valve is shown in FIG. The valve comprises a cylinder 30 which is closed at its front end; the front end is designed so that it can be connected at 31 to a line or duct that the brake cylinder connects with each other. The rear end of the cylinder, the one at 32 with one to the master cylinder leading pipeline is closed with the aid of a screw plug 33. A hollow one Piston 34 works in the cylinder between stops made by one with cylinder 30 integral shoulder 35 near the closed end of the cylinder and through a annular flange 36 can be formed on the screw plug 33.

At the front end of a valve spool 37, which operates within the piston 34, is an annular one a protruding head is provided which is normally in contact with the front end of the piston is held, namely by a spring 39, which is in a recess at the rear end of the piston is arranged on the circumference of the slide, a ring 40 being attached to the rear end of the slide is to provide support for the spring. Are in the outer surface of the valve spool Longitudinal grooves 41 formed, which are used for the passage of liquid when the head of the slide of its seat at the end of the piston has been lifted, which is caused by excess fluid pressure at the rear end of the cylinder sufficient to overcome the bias of the valve will.

The passage of liquid through the piston in the reverse direction is through a valve disc 42 failed; this valve disk rests on a seat at the rear end of the axial bore 43 in the front end of the valve slide, and the plate is normally held by a strong spring 44, which is supported between the valve disk and a plug 45 provided with an opening, in held in its closed position; the plug45 is screwed into the valve slide or onto another Wisely fastened in it,

Normally, the piston 34 is in its rearmost position, i. E. at the end of its cylinder to which the master cylinder is connected. When the brake pedal is depressed, the initial displacement of fluid from the master cylinder causes the piston 34 to move to its front stop 35, the piston displacing the fluid from the front end of the valve cylinder and introducing it into the brake cylinders for attraction to effect the brake. If, with a further increase in pressure in the master cylinder, the difference in the pressures in front of and behind the piston 34 is sufficient to overcome the force of the spring 39, the valve slide 37 will open the valve. This pressure difference can be on the order of about 0.175 kg / cm ² . The fluid then flows through the valve and the brake is operated in the normal manner with a force proportional to the force exerted on the brake pedal and the valve 37 closes when the pressure in front of the piston decreases no longer changed.

When the brake pedal is released, the pressure behind the piston 34 is reduced and a l) determined The amount of liquid returns due to the ela-

5 6

static return movement of the pressure pieces and other end of the cylinder flows. The mentioned channel 53

Non-rigid parts of the arrangement made up of the brake is available via a spring-loaded check valve 56

cylinders back, this liquid in communication with a chamber 57, which in turn

Liquid space at the front end of the valve via another check valve 58 with the channel The cylinder enters and causes the valve S 50 to be connected. In the chamber 57 opens a

piston moved backwards. Bore 59, the upper end of which has a non-return

If one of the pressure pieces from some valve 60, connected to a fluid container, tends to move away from the brake disc, while the lower end of the bore is moving towards the, it can only do this by opening into the cylinder 51 with further graduations in diameter. Displaced fluid from the brake cylinder. The * _Q immediately behind the gradation of the piston is of total movement, however, an annular groove 61 is formed by the return of the circumference of the piston. Valve piston to its rearmost position, which is limited to the valve 56 is set to a smaller opening increase in the volume of the liquid space at the pressure than the valve 55 in the piston, front end of the cylinder. and the valves 58 and 60 are only very slightly

This prevents further liquid 15 from being stretched.

is displaced from a brake cylinder and as a result of When the brake pedal is depressed

Centrifugal forces, deformation of the brake disc or fluid from the master cylinder through the channel

due to some other cause in the 50 through into the rear end of the cylinder

Master cylinder is transferred. Liquid is also fed to the rear end of the cylinder

speed, the pressure exerted by the brake cylinder behind one of the _ae pushes the piston forward so that

Pressure piece is displaced, causes this liquid from the front end of the cylinder

to flow over the opposite cylinder. ders displaced and leads to the brake cylinder

The valve 42 in the valve slide 37 enables the brakes to be applied.

it's the liquid, from the space at the front end Since the rear end of the piston is a smaller one

of the valve cylinder through the piston - 35 has a diameter than the front end

flow when the pressure in this space results from a comparatively smaller shift of the

for some reason rises so far that it needs exiting in the master cylinder to achieve a given

is enough to override the spring load on the valve - shifting the pressure pieces in the brake cylinders

squirm. This value can be between about 7 and cause, and the loading provided for the piston

70 kg / cm ³ can be selected, 30 travel distances are sufficient for normal braking processes

The pressure in the brake cylinders can be reduced as a result, without any fluid flowing through the valve 55 into the a temperature rise occurring on sustained or piston. When the pressure in the front end repeated braking is based, up to such a level of the cylinder to a value which the Be value increase, and the valve limits the maximum load of the valve 56 exceeds, a liquid level that can be reached flows and allows 35 speed through the valve 56 into the chamber 57 that fluid from the brake cylinders to the loading and into the bore 59, so that a pressure on the ring holder for the master cylinder returns when the shaped surface is applied to the, stage of the piston mentioned pressure is reached. This increases the differential effect

The piston of the counter pressure valve can be lifted as a dif-

be formed differential piston, which can be applied _{a greater 40 force.}

Has diameter at the front end, so that a If the brake pedal is released, then the

minor displacement of the piston in the master cylinder relaxes pressure in the rear end of the cylinder, and

is required to be able to return from the brake cylinders and on at low pressures

correct shifting of the pressure pieces - the front end of the piston acting fluid

respectively. 45 returns the piston to its normal position.

The distance of movement of the brake pedal can be simultaneously closed, the valve 56, and the

Reduce to a minimum by moving the ring into the annular space behind the step of the piston

load of the valve slide 37 adjusts accordingly, displaced liquid flows through the valve 58 in

ttnd the arrangement can be made so that the channel 50 and on to the master cylinder

this valve is returned with normal brake actuation.

remains closed, whereby the forward movement of the brake is not applied and exists

Valve piston when actuating the master cylinder from negative pressure in the leading to the master cylinder

the front end of the valve cylinder has an out-line, liquid can flow out of the container through the

sufficient amount of liquid displaced to reach the valves 60 and 58 through into the channel 50.

Let the brake take full effect before the 55 When the pressure exerted by the master cylinder

Piston reaches its stop while the brake is being applied and after the

In the valve piston 52 shown schematically in FIG. 3, the front end of its movement path

when the channel 50 is connected to the master cylinder, it continues to rise until the pressure

and leads into the rear end of a graduated or load of the valve 55 in the piston exceeds can

cylinder 51 designed as a differential cylinder. 60 fluid through valve 55 into the front

A stepped piston 52 works in this cylinder, flowing in and onto the end of the cylinder

the one, the front end of which pass through a channel 53 with a way into the brake cylinder in order to

a pipe or a channel is connected to increase the effect. All excess liquid

a pair of opposing braking speeds which are passed through valve 55 in this way.

cylinders is in communication. Flows through an axial bore 65, is returned by the valve 58.

54 through the piston is guided by means of a spring- when the brake is released,

loaded ball check valve 55 controlled, whereby the valve remains when the brake is released

at this valve allows liquid below 56 to be normally closed, and during liquid

Maintaining a predetermined pressure difference from the speed unimpeded between the liquid spaces

rear (right in the drawing) can flow over to the front 70 two brake cylinders, no-

Claims (6)

1 Ö81 789 -%, .. y 7 ^^ 8 Let the liquid return to the master cylinder. see two opposing brake cylinders If, however, the pressure in the brake cylinders builds up from the. for any reason, for example as a result of the valve of Fig. 8 is cylindrical Overheating of the brake, due to the load on the valve body 90, on its front (in the drawing tils 56 also rises, this valve opens and 5 right) end a connection 91 for connection allows fluid from the brake cylinders to be located with the ^ brake cylinders. A small axial one cylinder escapes to the master cylinder. BohrJfh this end of the cylinder leads to a The valve shown in Fig. 4 is a practical cylindrical bore 93 of comparatively large size Embodiment of the in Fig. 3 schematically dar- diameter, which is posed from the rear end of the body Valve. In FIG. 4, the same bees have been extended into this. The outer end Marks used as in Fig. 3, so that none of the bore 93 is through a plug 94 with further explanation is required. a connection 95 for connection to the main The valve shown in Fig. 5, 6 and 7 corresponds to cylinder is provided, closed. An axial drilling in terms of structure and mode of operation, the in Fig. 3 tion 96 in this plug forks at its inner- ünd 4 illustrated valve; only the components are 15 rem end and can be a protruding between them arranged differently. axial pin 97 stand. Works in bore 93 A connection 70 at one end of the body 71 is a piston 98, which is designed as a hollow socket, of the valve is designed so that it can be passed through a pipe - this bushing at both ends, apart from Line connected to a master cylinder are small axial openings that are closed. The open can; Furthermore, the connection 70 is normalized by an oblique ao at the rear end of the piston Channel 72 with the rear end of a deflected by an internal ball valve 99, the stepped or designed as a differential cylinder by one between the ball and the front Cylinder 73 connected in the valve body. Spring 100 located in the end of the piston is loaded Cylinder works a stepped piston 74, which is kept closed with. an axial bore 75 which is depressed by a spring-loaded pedal, which is controlled to operate the master cylinder, fluid is seen in FIG. The front end of the cylinder is conveyed through the rear (left) end of the bore 93, a screw plug 77, the inner end of which is one and this fluid moves the piston 98 forward, limiting stop for the forward movement of the so that it flows out of the front end of the piston forms, closed. The fluid space 30 is displaced by a bore and is lowered into the brake cylinder at the front end of the cylinder in order to apply the brake. When the piston connects the right channel 78 to a port 79; has reached the front end of the bore and when this connection can receive a tube that continues to rise to pressure behind the piston, a pipeline opens or leads to a channel leading to the valve 99, and fluid can pass through the piston two opposite one another Flow through the brake cylinder in order to connect the braking effect to one another. A transverse channel 80, which by a like. When the brake is released, which is controlled by the spring-loaded ball valve 81, fluid returning to the brake cylinders leads the KoI-binds the channel 78 with a longitudinal bore 82, which ben back to the rear end of the bore,
Via a spring-loaded ball valve 83 to the connection. When the brake is released, the piston connection 70 is located. The bore 82 is also at 40 times in the position shown in FIG a connection 85 in connection, the brake cylinder can flow over, but can generally be connected to a storage tank _NEN no liquid can back into the master cylinder. 45 flows. If the pressure in the brake cylinders but If that is to actuate the piston in the main for any reason, for example as a result of an over-cylinder Depressing the serving pedal will overheat the brake, above a predetermined value If liquid rises into the rear end of the cylinder 73, the piston will move toward promotes so that the piston 74 pushed forward "pushed back against the projection 97 so that the Venwird and opening fluid from the front end of the 50 valve. The cylinder is displaced and through the channel 78. In the event of a slightly dragging contact, it leads through to the brake cylinder in order to apply the brake. If the pressure in the front end of the piston in the master cylinder is required to exceed the load on valve 81, the pressure pieces to rest on the brake disc can bring fluid through this valve and through the 55 can channel between the pedal and the brake 82 through to the step or the shoulder to a very large leverage will get applied to the piston, and additional liquid. Even a small increase in the amount of liquid can flow through the piston if the amount of pressure exerted by the master cylinder in a brake cylinder must be greater when a pressure piece from the braking load of the ball valve 76 exceeds it. When releasing 60 the disk has moved away, a considerable spoilage of the brake would make excess fluid behind.
that flow back. If supplemental fluid is required, the required amount of fluid can be claimed:
from the reservoir through the valves 84 and 83 to the 65
Master cylinder arrive. 1. Hydraulic actuation system for a The valve shown in Fig. 8 is designed, in particular intended for motor vehicles that it can be switched into a pipeline, disc brake, in which the a master cylinder with a channel or a kung of return springs standing brake pads Pipe connects, which in turn normally makes the connection between 70 on both sides of the brake disc are in slight dragging contact with this and by opposing hydraulic ones Brake cylinders, those from a master cylinder or some other source of pressurized fluid Hydraulic fluid is supplied at the same time, is pressed against the disc, characterized in that that between the opposing brake cylinders (13) a connection (16) exists, which allows an unimpeded exchange of fluid, and that between this connecting line and the master cylinder (18) one in the case of brakes with return springs for the brake pads known control device with a limited axial movement in one Cylinder (30) working piston (34) is provided, the piston when the brake pedal is pressed (19) is moved by the fluid displaced by the master cylinder and thereby displaces fluid into the two brake cylinders, that also a known spring-loaded bypass valve (37), the liquid on the other side of the piston relays when the master cylinder pressure increases the pressure in the brake cylinders exceeds by a predetermined amount, and a spring-loaded, also known per se Safety valve (42, 43, 44) or means (pin 97, Fig. 8) for opening the bypass valve (99) are provided, which opens or acts when the pressure in the brake cylinders is at released brake exceeds the pressure in the master cylinder by a predetermined amount. 2. Hydraulic actuation system according to claim 1, characterized in that the closing body (37) of the bypass valve is formed by a sleeve mounted in the piston (34) and that the safety valve (37) is located within the bypass valve body. 3. Hydraulic actuation system according to claim 1, characterized in that the bridging valve (55) is arranged in a known manner within the piston (52) and that the safety valve (56) in a special the ends of the cylinder (51) interconnecting the flow path. 4. Hydraulic actuation system according to claim 1, characterized in that the piston (52) is graduated in a manner known per se in control devices, the piston end with the smaller diameter is exposed to the pressure in the master cylinder (18). 5. Hydraulic actuation system according to claim 4, characterized in that the safety valve (56) in a channel between the brake cylinder side of the cylinder (51) and a Chamber (59, 61) is located, which is in communication with the stage of the piston, and that another Check valve (58) in a channel between this chamber and the main cylinder side of the cylinder is attached. 6. Hydraulic actuation system according to claim 1, characterized in that the piston (98 in Fig. 8) is designed as a sleeve in which the bypass valve (99) is arranged, and that the means for lifting the closure body of the bypass valve from its Seat is formed in a manner known per se from a fixed pin (97) on the main cylinder side of the cylinder (93) protrudes into this. Considered publications:
German Patent Nos. 726 761, 726 863;
Austrian Patent No. 157 887;
French Patent No. 891 176;
British Patent No. 643,106;
U.S. Patent Nos. 2,281,538, 2,345,811. 1 sheet of drawings ® 009 5 »/» 3 5.60