LIQUID-IMMERSED DISC BRAKE

Abstract: A liquid-immersed disc brake has a housing (1) containing friction elements (7) rotatable with a member (2) to be braked and providing rotary braking surfaces. Fixed braking surfaces (12, 13) are provided for resisting torque arising on the elements (7) and actuator means (10, 11) is provided for bringing the rotary and fixed surfaces into braking engagement. The member (2) has a fluid passage (24, 25) serving to direct liquid which has been introduced into the housing towards a region from which the introduced liquid is applied to the braking surfaces. A sleeve (4) surrounding the shaft may provide further passages (25) forming a further part of the path.

Description: 1 - LIQUID-IMMERSED DISC BRAKE This invention relates to a liquid-immersed disc brake, primarily for a vehicle, the brake having a housing which contains at least one friction element rotatable with a rotary member to be braked and providing a first braking surface, a torque-resisting member providing a second braking surface which is relatively fixed, actuator means operable to bring the first and second surfaces into braking engagement, and means for supplying cooling liquid to the housing in cooling relationship with said surfaces. It can be advantageous in some liquid-immersed disc brakes to supply cooling oil into the housing along a rotary member to be braked, such as a shaft, but it can then be difficult to direct the oil from the interior of the member to a required location in the brake, or distribute the oil evenly within the brake in adequate quantities. Difficulties can also arise in providing an adequate rotary seal between the rotary member and the exterior and/or the interior of the brake housing. An object of the invention is to provide an improved liquid-immersed disc brake in which the aforesaid difficulties are alleviated or avoided. According to a first aspect of the invention, a liquid-immersed disc brake comprises a housing containing at least one friction element rotatable with a member to be braked and providing a first braking surface, a torque- resisting member providing a second braking surface which is relatively fixed, actuator means operable to bring the first and second surfaces into braking engagement, and means for supplying cooling liquid to the housing in cooling relationship with said surfaces, the rotary member providing at least a part of a path serving to direct liquid which has been introduced into the housing towards a region from which the introduced liquid is applied to said braking surfaces. Preferably the rotary member to be braked is drivingly connected to said at least one friction element via an intermediate member which provides a further part of said path serving to direct the introduced liquid towards said region. In one typical arrangement, the rotary member is a shaft and the intermediate member is a sleeve surrounding and keyed to the shaft, preferably by one or more interengaged splines respectively on the shaft and sleeve, the sleeve being also keyed to said at least one friction element so as to be fast for rotation with the element and to permit axial movement of the at least one element along the shaft, the sleeve having one or more passages therein forming part of said path, and preferably extending radially through the sleeve peripheral wall. According to a further aspect of the invention, a liquid-immersed disc brake comprises a housing containing at least one friction element rotatable with a member to be braked and providing a first braking surface, a torque-resisting member providing a second braking surface which is relatively fixed, actuator means operable to bring the first and second surfaces into braking engagement, the actuator means including at least one annular pressure plate operable to move the friction element axially to cause engagement of the braking surfaces, the pressure plate surrounding a core member which is supported for longitudinal movement relative to the rotary member and substantially fills the annular - 3 - space formed between the exterior of the rotary member and the internal extremity of the or each plate. Preferably, the core member is supported by the pressure plates and, in one convenient arrangement in which a pair of separable pressure plates is provided, the core member is fast for axial movement with one plate and axially slidable relative to the other plate. The core member may conveniently be formed integrally with said one pressure plate. The invention will now be described, by way of example, with reference to the single accompanying drawing which is a longitudinal cross-section of one form of the liquid-immersed disc brake of the invention. The illustrated oil immersed disc brake has a housing 1 , through which extends a rotary member to be braked, illustrated as a shaft 2 rotatably mounted in the housing. The shaft is externally splined at 3 and surrounded by a sleeve 4 which has complementary internal splines 5 engaged with those of the shaft so that the sleeve is rotatably keyed to the shaft. The sleeve is also externally splined at 6 and carries a plurality of rotary friction discs 7 which are arranged in two axially spaced groups and keyed to the external splines 6 of the sleeve by way of projecting lugs 8 so as to be fast for rotation with the sleeve but axially movable relative thereto, when required. Interleaved with the rotary discs 7 are further friction discs 9 which freely surround the shaft and are keyed against rotation in the housing by way of one or more abutment pins 9A. Disposed between the groups of discs is a pair of actuator plates 10, 1 1 , which are separable by a convenient form of primary actuator, such as a ball and ramp, wedge or other mechanism, to compress the groups of friction discs between opposed pairs of braking surfaces 12, 13 formed respectively on the internal surface of the housing and on the actuator plates 10 and 1 1 , braking torque arising on the actuator plates being resisted by the housing, in known manner. The invention is particularly concerned with the manner in which cooling liquid is supplied to the friction discs at least during braking. Liquid enters the brake via a pipe 15 connected to an external boss 16, of which a smaller diameter portion 17 is screwed into the housing. A sealing device, indicated generally at 18 includes an annular collar 19 mounted in the housing by way of pins 20 and being urged by at least one spring 21 against the adjacent end of the shaft 2. The collar 19 carries a seal element 22, which largely precludes the flow of oil around the outside of the collar and ensures that oil flows predominantly from the boss 16 along a central axial passage 23 of the shaft and into radial passages 24 which direct the liquid into the interior of the sleeve 4. The seal element 22 seals against the end face of the shaft around the entrance to the passage 23. The sleeve 4 is provided, at locations conveniently adjacent the groups of disc 7, 9, with radial through holes 25 providing communication between the interior of the sleeve and optimum locations within the housing for distribution of liquid to the plates. Liquid entering the interior of the sleeve via the radial passages 24 is able to pass along axial passages formed by the shaft splines and those of the surrounding sleeve and thence through the holes 25 to the aforesaid locations. Appropriate internal splines of the sleeve 4, or splines of the shaft 3, or both such splines, may be omitted to provide a flow path of increased volume. A further feature of the described embodiment resides in the provision of an annular core member 26, of metal or plastics material for example, which lies in the space defined in part by each of the radially innermost surfaces of the actuator plates 10, 1 1 , the inner surfaces of the innermost plates 7 and the external surface of the shaft 2. The core member 26 is mounted securely on the actuator plate 1 1 , as by press fitting for example, the plate 1 1 having an annular recess within which is received a small annular shoulder 27 of the core member. The other actuator plate 10 is slidably mounted around the core member, a seal 28 being provided between the plate 10 and core member. The seal 28 prevents oil escaping through the actuation plates 10 and 1 1 when they are moved apart for brake actuation. In certain instances, it may be convenient to manufacture the core 26 and pressure plate 11 as a unitary component. It will be seen that, upon separation of the plates 10 and 1 1 for brake actuation, the core member 26 moves with the plate 1 1 , whilst performing a sliding movement relative to the plate 10. The function of the core member is to minimise the liquid capacity of the brake by filling a redundant area which would otherwise fill with cooling liquid during brake actuation. In order to accommodate the core member, return springs 29 for the actuator plates 10 and 1 1 , one of which springs can be seen in the drawing, are accommodated in a radially outer region of the housing rather than, in conventional manner, in the central region of the brake. It would be possible to dispense with the sleeve 4 and provide radial passages within the shaft, opening at locations adjacent the friction plates. - 6 - or at other appropriate locations, the numbers and locations of such passages, whether in a sleeve 4 or in the shaft, being variable as required. It would also be possible to dispense with the sealing collar 19 and to arrange, for example, for an extension of the shaft 2 to protrude through the adjacent wall of the housing 1 into the boss 16, in which an appropriate sealing arrangement may be incorporated.

Claims: CLAIMS 1 . A liquid-immersed disc brake comprising a housing containing at least one friction element rotatable with a member to be braked and providing a first braking surface, a torque-resisting member providing a second braking surface which is relatively fixed, actuator means operable to bring the first and second surfaces into braking engagement, and means for supplying cooling liquid to the housing in cooling relationship with said surfaces, the rotary member providing at least a part of a path serving to direct liquid which has been introduced into the housing towards a region from which the introduced liquid is applied to said braking surfaces. 2. A brake according to Claim 1 , wherein the rotary member to be braked is drivingly connected to said at least one friction element via an intermediate member which provides a further part of said path serving to direct introduced liquid towards said region. 3. A brake according to Claim 2, wherein the rotary member is a shaft and the intermediate member is a sleeve surrounding and keyed to the shaft, the sleeve being also keyed to said at least one friction element so as to be fast for rotation with the element and to permit movement of the at least one element along the shaft, the sleeve having one or more passages therein forming part of said path. 4. A brake according to Claim 3, wherein the sleeve passages extend generally radially through the sleeve peripheral wall. 5. A brake according to Claim 3 or Claim 4, wherein the shaft has an axially extending passage forming a part of said path. 6. A brake according to Claim 5, wherein cooling liquid is delivered through an end of the shaft to said axially extending passage by way of a sealing device which includes a sealing element urged against said shaft end and surrounding the adjacent end of the passage. 7. A brake according to any one of Claims 3 to 6, wherein the sleeve is keyed to the shaft by splines respectively on the sleeve and shaft, at least one interengaging pair of said splines forming a passage serving as part of said path. 8. A liquid-immersed disc brake comprising a housing containing at least one friction element rotatable with a member to be braked and providing a first braking surface, a torque-resisting member providing a second braking surface which is relatively fixed, actuator means operable to bring the first and second surfaces into braking engagement, the actuator means including at least one annular pressure plate operable to move the friction element axially to cause engagement of the braking surfaces, the pressure plate surrounding a core member which is supported for longitudinal movement relative to the rotary member and substantially fills the annular space formed between the exterior of the rotary member and the internal extremity of the or each plate. 9. A brake according to Claim 8, wherein the core member is supported by the pressure plate. 10. A brake according to Claim 9, wherein a pair of separable pressure plates is provided and the core member is fast for axial movement with one plate and axially slidable relative to the other plate. 1 1. A brake according to Claim 10, wherein the core member is formed integrally with said one pressure plate.

Inventors: MUELLER JAN-PETER, MUELLER, JAN-PETER
Applicants: MERITOR HEAVY VEHICLE BRAKING, MUELLER JAN PETER, MERITOR HEAVY VEHICLE BRAKING SYSTEMS (UK) LIMITED, MUELLER, JAN-PETER
Application year: 1999
Main classification: F16D65
IPC codes: F16D55, F16D65