Patent Application
20130270057
The present invention relates to hydraulic clutches, and more particularly to hydraulic clutches comprising hydraulic balance chambers, as well as a method of providing hydraulic fluid to hydraulic balance chambers.
High-speed, hydraulically actuated clutches generate large centrifugal pressures. The centrifugal pressure, operating on a clamping piston, generates clamp loads in excess of forces provided by most mechanical springs designed to release a clutch. Therefore, these clamp loads must be overcome to effectively release an applied clutch. Typically, such clutches implement a costly mechanical dump valve to circumvent the clamp loads and allow springs to retract an applied clutch. This results in additional time and fluid necessary to refill a hydraulic clutch application chamber and an associated hydraulic circuit for subsequent clutch application. For clutch assemblies employing multiple hydraulic chambers in an effort to counteract the centrifugal forces generated, hydraulic fluid is directed from a reservoir to the multiple hydraulic chambers, but the order of filling is typically not controlled and one or more of the hydraulic chambers may require a separate and unique filling system.
According to one embodiment, a hydraulic clutch assembly includes a plurality of frictional clutch discs moveable between an engaged condition and a disengaged condition, wherein the engaged condition provides a transfer of rotational energy. Also included is a first toroidal hydraulic chamber configured to depress the plurality of frictional clutch discs into the engaged condition. Further included is a second toroidal hydraulic chamber opposing the first toroidal hydraulic chamber, wherein the second toroidal hydraulic chamber is configured to balance centrifugal expansion forces of the first toroidal hydraulic chamber. Yet further included is a lubrication circuit for supplying a hydraulic fluid from a fluid reservoir to the second toroidal hydraulic chamber and the plurality of frictional clutch discs, wherein the second toroidal hydraulic chamber is substantially filled prior to delivery of the hydraulic fluid to the plurality of frictional clutch discs.
According to another embodiment, a method of providing hydraulic fluid to a hydraulic clutch assembly is provided. The method includes supplying a hydraulic balance chamber and a plurality of frictional clutch discs with a hydraulic fluid, wherein the hydraulic fluid is directed from a fluid reservoir through a lubrication circuit. Also included is directing the hydraulic fluid to the hydraulic balance chamber to a relatively filled state prior to directing the hydraulic fluid to the plurality of frictional clutch discs.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
Referring to
The second hub 22 may be configured to depress the plurality of clutch discs 16 arranged within the first hub 20 so as to engage the clutch 10, resulting in an engaged condition. The clutch 10 may include a plurality of hydraulic circuits arranged therein to enable depressing the plurality of clutch discs 16. The plurality of clutch discs 16 may be annular, frictional clutch discs of any suitable material and form. The plurality of clutch discs 16 may be wet clutch discs configured to receive oil or fluid for cooling through a lubrication circuit 24 supplied from a fluid reservoir 26, where the lubrication circuit 24 is disposed within the clutch 10.
The clutch 10 includes a first toroidal hydraulic chamber (“application chamber”) 28 within the second hub 22, and that is defined by interior space of the second hub 22 and a first annular wall 32. The first annular wall 32 is a protrusion from a main body 34 of the clutch 10, and provides support for the second hub 22. The clutch 10 further includes a clutch application fluid circuit 36 in fluid communication with the application chamber 28. The clutch application fluid circuit 36 may transfer hydraulic fluid through the main body 34 to fill the application chamber 28. Upon receiving hydraulic fluid, increase in pressure within the application chamber 28 causes the second hub 22 to slide upon the first annular wall 32, thereby depressing the plurality of clutch discs 16 against the interior of the first hub 20. Thus, a combination of the clutch application fluid circuit 36 and the application chamber 28 allows application of the clutch 10 and produces the engaged condition.
It is to be appreciated that as the clutch 10 rotates, hydrostatic pressure builds within the application chamber 28, thereby increasing expansive forces within the application chamber 28 which would otherwise increase the force applied on the plurality of clutch discs 16 and increase a required force to disengage the clutch 10. However, in order to balance and mitigate negative effects from rotation, an opposing balance chamber 40 is provided.
The balance chamber 40 is a second toroidal hydraulic chamber within the second hub 22 and is defined by interior space of the second hub 22, the first annular wall 32 and a second annular wall 44. The second annular wall 44 is fixedly attached to the second hub 22 and the balance chamber 40 is configured to slide upon the second annular wall 44. The balance chamber 40 is configured to receive hydraulic fluid through the lubrication circuit 24 from the fluid reservoir 26, as is the case with the plurality of clutch discs 16. In order to ensure that the balance chamber 40 fills first, the hydraulic fluid is directed to the balance chamber 40 immediately upon operation of the clutch 10 (i.e., when a gearbox is started). Once the balance chamber 40 is substantially full, the lubrication circuit 24 directs hydraulic fluid to the plurality of clutch discs 16. This alleviates the need for a separate fluid circuit and ensures failure of the clutch 10 in a disengaged condition. Upon receiving the hydraulic fluid, an increase in pressure within the balance chamber 40 restricts the expansive forces of the balance chamber 40, thereby serving to mechanically “balance” the hydraulic system.
For example, as the clutch 10 rotates, hydrostatic pressure building within the application chamber 28 is mitigated through hydrostatic pressure building within the balance chamber 40, which produces expansive forces against the second annular wall 44. Therefore, overall forces between the second annular wall 44 and the second hub 22 are balanced. It should be appreciated that a relative size and radial position of each of the application chamber 28 and the balance chamber 40 determine an overall balance to centrifugal forces within the clutch 10. Further, a central axis of the main body 38 is co-linear with the central axis 18 of the first hub 20 and the second hub 22.
Referring now to
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while the various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
