Fluid operated friction device

Abstract: A friction device, such as a clutch assembly, has a hub (12) and a piston (14) interlaced to provide an operating chamber (58) for the piston. A plurality of friction plates (18,20) are in alternate drive connection with the hub and a housing (16) surrounding the hub, and are engaged by the piston when the chamber is pressurised to establish a friction torque transmitting connection between the hub and the housing.

Description: This invention relates to fluid operated friction devices, and more particularly, to such torque transmitting devices having an axially moving piston for engaging a plurality of friction plates. Fluid operated, multi-disc type, torque transmitting friction devices have a piston slidably disposed in a housing and cooperating therewith to form a chamber. The chamber is generally axially aligned with a multi-plate disc pack and therefore additive to the overall axial length requirement of the torque transmitting device. While the performance of the torque transmitting device is not affected by this structure, the overall axial length may prevent the use of some transmission structures in vehicles where space is limited. An example of the prior art is shown in US Patent No. 3,016,121. The present invention aims to reduce the axial space requirement of multi-plate fluid operated torque transmitting friction devices by providing an interlaced hub and piston, wherein the fluid chamber is disposed radially inward of and radially aligned with the friction plates. It is therefore an object of the present invention to provide an improved fluid operated friction device having a minimum axial spaced requirement. To this end, a fluid operated friction device in accordance with the present invention is characterised by the features specified in the characterising portion of claim 1. The present invention provides an improved fluid operated friction device having an interlaced piston and hub structure for providing a device operating chamber radially inward of the friction plates. The present invention also provides an improved fluid operated friction device having an apertured piston interlaced with a hub having fingers extending through the apertures and providing a drive connection in the space between the adjacent apertures for a plurality of friction plates which are alternately spaced with friction plates having a drive connection with a housing, and wherein the piston has an annular apply surface intermediate the housing and the hub for enforcing frictional engagement of the friction plates in response to fluid pressure admitted to the chamber formed through cooperating portions of the hub and the piston. The present invention will now be described, by way of example, with reference to the following description, and the accompanying drawings, in which:- Figure 1 is a cross-sectional elevational view of a torque transmitting friction device, such as a clutch assembly, incorporating the present invention; and Figure 2 is an exploded view of the piston and hub incorporated in the present invention. Referring to the drawings, wherein like characters represent the same or corresponding parts throughout the several views, there is seen in Figure 1 a clutch assembly, generally designated 10, which includes an annular hub 12 (inner hub member), an annular piston 14, an annular housing 16, a plurality of friction plates 18 drivingly connected with the hub 12 and alternately spaced with a plurality of friction plates 20 drivingly connected with the housing 16. The hub 12 is secured, as by welding at 22, to a rotatable shaft 24 which may provide a rotary input for a transmission. The hub 12 has, as best seen in Figure 2, an annular end wall 26 from which axially extends a plurality of fingers 28. The fingers 28 are separated by slots 30 which extend radially, as at 32, into the annular end wall 26. The slots 30 separate adjacent finger portions, as for example, slot 30A separates finger portions 28A and 28B (Figure 2). In the detailed description which follows, and as previewed in the previous paragraph, a particular structural member, component or arrangement, may be employed in more than one location. When referring generally to that type of structural member, component or arrangement, a common numerical designation shall be employed. However, when one structural member, component or arrangement so identified, is to be individually identified, it shall be referred to as a letter suffix in combination with the numerical designation employed for general identification of that structural member, component or arrangement. Thus, there are at least four laterally spaced fingers which are generally identified by the numeral 28. But the specific individual fingers are therefore identified as 28A, 28B, etc., in the specification and on the drawings. This same suffix convention will be employed throughout the specification. The piston 14 has an outer end wall 34 and an axially extending annular sealing surface 36. The outer end wall 34 has a plurality of apertures or fenestrae 38. An inner end wall 40 is formed between the annular sealing surface 36 and an inner support surface 42. The outer end wall 34 terminates in an axially extending lip or presser plate portion 44, which has an annular end face 46 which defines a presser plate surface for engaging the friction plate 18A. The fingers 28, during assembly of the clutch assembly 10, are inserted through the apertures 38, such that finger 28A passes through aperture 38A, finger 28B passes through aperture 38B, finger 28C passes through aperture 38C and finger 28D passes through aperture 38D. The fingers 28, after passing through the respective apertures, will present slots 30, formed between adjacent fingers 28, for engagement by spline members 48 formed on the inner periphery of the friction plates 18. The friction plates 18 are limited in movement in the slots 30 in one direction by a backing plate 50, which is also splined in the slots 30. The backing plate 50 is maintained in position in one direction by a locking ring 52 which is disposed in a locking groove 54 which, except for the slots 30, forms an annular slot in the fingers 28. The locking ring 52 also serves as an outer stop member for a conventional Belleville or diaphragm spring 56. The inner portion of the diaphragm spring 56 is in abutment with the outer end wall 40 of the piston 14 to urge the piston toward the hub 12. Intermediate the outer end wall 40 of the piston 14 and the annular end wall 26 of the hub 12 is formed a chamber 58. Disposed within the chamber 58 is a seal assembly 60 comprised of an annular sheet metal stamping 62, which presents an outwardly opening seal groove 64 in which is disposed a conventional lip seal 66. The lip seal 66 abuts the seal surface 36 of the piston 14 so as to provide a substantially leak proof interface therebetween. The support surface 42 also cooperates with a lip seal 68 which is disposed in a groove 70 formed in the shaft 24. Thus, the chamber 58 is substantially leak proof such that the only pathway for fluid to enter or leave the chamber 58 is via a passage 72 formed in the shaft 24. The passage 72 is communicated with a radial passage 74 formed in a support sleeve 76. The radial passage 74 receives fluid through an annular chamber 78 formed between the support sleeve 76 and a sleeve 80. This is a conventional assembly for supplying fluid to or exhausting fluid from the rotating clutch assembly. The housing 16 is preferably a sheet metal component, however, other materials can be utilised. The housing 16 has an annular outer structure 82 (outer housing member) in which is rolled or otherwise formed a spline 84 (splined inner periphery). The spline 84 is adapted to engage splines or toothed components 86 which are formed on the outer periphery of the friction plates 20. Thus, a drive connection is provided between the housing 16 and the friction plates 20. The housing 16 has an output or annular hub 88 which is drivingly connected to a gear member 90 which forms part of a gear structure within a transmission. When fluid pressure is admitted to the chamber 58, the piston 14 will be urged rightward, as viewed in Figure 1, against the force of Belleville spring 56, such that the end face 46 will cause the friction plates 18 to frictionally engage the friction plates 20, since rightward movement thereof is limited by the backing plate 50. When sufficient pressure is present in the chamber 58, the frictional engagement between the friction plates 18 and 20 will result in substantially unitary rotation between the shaft 24 and the housing 16. This will provide a conventional rotary type or rotating type clutch mechanism. In the alternative, it should be appreciated that the housing 16 and/or the shaft 24 can be connected to a stationary member, such as a transmission housing, in which case, the engagement of the piston 14 with the friction plates 18 and 20 would result in holding the gear member or shaft stationary, thereby providing a brake structure within a transmission. As best seen in Figure 1, the chamber 58 is radially aligned with the friction plates 18 and 20, such that the overall axial length of the clutch assembly 10 is maintained at a minimum when compared to fluid operated friction torque transmitting assemblies wherein the engagement or control chamber is substantially axially aligned but radially offset from the respective friction plates. Typical friction devices incorporating the axially aligned structure can be seen in US Patent No. 5,009,116, or US Patent No. 4,635,778. US 4,635,778 discloses both a clutch and a brake utilising the axially aligned chamber and friction plates.

Claims: A fluid operated friction device comprising an outer housing member (82) having a splined inner periphery (84); an inner hub member (12) having an annular end wall (26); a piston (14) having an inner end wall (40) cooperating with the annular end wall to define a fluid chamber (58), an outer end wall (34), and a continuous presser plate surface (46); and a plurality of friction plates (18,20); characterised in that the inner hub member (12) has a plurality of axially extending, equiangularly spaced, fingers presented axially from the annular end wall (26); in that the outer end wall (34) of the piston (14) includes a plurality of apertures (38) aligned with the respective ones of the spaced fingers, whereby the inner end wall (40) is radially inward of the fingers and the presser plate surface (46) is radially outward of the fingers; and in that the friction plates (18,20) are disposed between the fingers and the splined inner periphery (84) with alternate ones of the friction plates being drivingly connected between the fingers and to the splined inner periphery. A fluid operated friction device as claimed in Claim 1, wherein the fluid chamber (58) is disposed substantially radially inward of the friction plates (18,20). A fluid operated friction device as claimed in Claim 1 or Claim 2, wherein the piston (14) includes an axially extending sealing wall (36) interconnecting the inner end wall (40) and the outer end wall (34); and wherein a seal assembly (60) provides a seal (66) cooperating with the axially extending sealing wall to define the fluid chamber (58) at a location radially inward of and substantially axially aligned with the friction plates (18,20).

Inventors: GROCHOWSKI EDWIN THOMAS, GROCHOWSKI, EDWIN THOMAS
Applicants: GEN MOTORS CORP, GENERAL MOTORS CORPORATION
Application year: 1993
Main classification: F16D25
IPC codes: F16D43, F16D25, F16D48