Normally open clutch assembly device

A normally open clutch assembly includes a device holding a centrifugal weight in a position causing axial movement of pressure plates and thereby a clamping force between pressure plates and the friction disks. The clamping force holds the friction disks in a desired aligned position during assembly.

BACKGROUND OF THE INVENTION

This invention relates to a normally open clutch assembly, and specifically to a device for maintaining alignment of a normally open clutch during assembly.

Typically, a normally open clutch assembly includes a rotating input member such as a flywheel, that engages one or more friction disks. The frictions disks are forced against the flywheel by one or more pressure plates. An output shaft is driven by rotation of the friction disks. A plurality of centrifugal weights are pivotally mounted to rotate radially outward in response to rotation of the clutch assembly. As the rotational speed of the clutch assembly increases rollers on the centrifugal weights are forced up a ramped surface to force engagement of the pressure plates with the friction disks and transmit rotational movement to the output shaft.

Assembly of a clutch assembly requires proper alignment between the friction disks and the flywheel. Normally closed clutch assemblies use the biasing force normally clamping the pressure plates against the friction disks to maintain proper alignment during assembly. Disadvantageously, a normally open clutch assembly does not clamp the friction disks unless the centrifugal weights are driven outward by rotation of the clutch assembly. Therefore the friction disks are not held in a desired aligned position during assembly.

Alignment devices for normally open clutch assemblies include cammed sleeves inserted within the clutch assembly to hold the centrifugal weights in a position where the pressure plates hold the friction plates in proper alignment with the flywheel. Such cammed sleeves are costly and time consuming to install and produce.

Accordingly, it is desirable to develop a simple and cost effective device for maintaining alignment of friction disks of a normally open clutch assembly during assembly.

SUMMARY OF THE INVENTION

The present invention is a device for holding centrifugal weights of a normally open clutch in a position causing application of clamping forces to maintain friction disk alignment.

The clutch assembly of this invention includes a plurality of holding members holding a corresponding plurality of centrifugal weights in a position causing engagement between pressure plates and the friction disks. Each of the holding members holds a corresponding centrifugal weight in a position causing application of a clamping force on the friction disks. The clamping force holds the friction disks in the desired aligned position during assembly.

Another device according to this invention includes a sleeve movable between an engaged position with at least some of the centrifugal weights, and a released position. The engaged position holds the centrifugal weights in a position causing the application of clamping forces on the friction disks. The clamping force maintains the desired alignment of the friction disks relative to the clutch cover and flywheel during assembly. After assembly, the sleeve is movable to selectively engage the clutch assembly during circumstances where full clutch clamping force is desired, although sufficient centrifugal force is not available.

Accordingly, the devices of this invention provide simple and cost effective alignment of friction disks within a normally open clutch during assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring toFIG. 1, a clutch assembly10includes a clutch cover12attached to a flywheel14. A plurality of centrifugal weights16are pivotally mounted within the clutch cover12and rotate radially outward in response to rotation of the clutch cover12. Each centrifugal weight16is biased toward a central axis18by a biasing spring20. Rollers21are mounted to each centrifugal weight16and ride along surfaces of a ramp plate22and an inner surface of the clutch cover12. The ramp plate22includes a ramped surface24on which the roller21moves to cause axial movement of the ramp plate22. Axial movement of the ramp plate22is transmitted through a clamp spring26to pressure plates28. Friction disks30are disposed between the pressure plates28such that axial movements of the pressure plates28clamp the friction disks30therebetween.

The biasing member20biases the centrifugal weight16toward the axis18such that the pressure plates28are not engaged to the friction disks30. An alignment tool (not shown) such as a splined shaft is used to align the position of the friction disks30relative to the clutch cover12and flywheel14. However, once the alignment tool is removed and prior to an output shaft32being installed into the clutch assembly10, the friction plates30are not restrained and are free to move out of the set alignment.

The clutch assembly10of this invention includes a plurality of pins34holding a corresponding plurality of centrifugal weights16in a position causing axial movement and thereby engagement between the pressure plates28and the friction disks30. Each of the pins34hold a corresponding centrifugal weight16in a position causing application of a clamping force on the friction disks30that holds the friction disks30in the desired aligned position.

Referring toFIG. 2, each pin34extends through an opening36in the clutch cover12and into a cavity38defined within the centrifugal weight16. The biasing spring20exerts a force holding the pin34against one side of the opening36. The opening36for the clutch cover12may extend through the entire thickness of the clutch cover12or may be configured as a blind hole not extending entirely through the clutch cover12. Preferably, all the centrifugal weights16are held, however, it may only be required to hold selected centrifugal weights16to retain the friction disks30in a desired aligned position.

The pin34temporarily holds the centrifugal weights16during assembly, and prior to installation of the output shaft32. The pin34is fabricated from a frangible material that shears in response to centrifugal force driving the centrifugal weights16radially outward.

Referring toFIG. 3, assembly of the output shaft32to the clutch assembly10fixes the friction disks30in the desired aligned position. Accordingly, the pins34are no longer required to maintain friction disk30alignment. The pin34maintains position of the centrifugal weights16until the clutch assembly10is rotated to a speed that creates sufficient centrifugal force to shear the pin34. The pin34shears along a shear plane40in response to the centrifugal force from the centrifugal weights16. Once the pin34has sheared, the centrifugal weights16rotate freely responsive to rotation of the clutch assembly10.

Residue from the pin34is simply dropped into the clutch assembly10. As appreciated, the environment within the clutch assembly10includes residue from the friction disks30. Additional residue and material from the pin34is substantially insignificant in comparison to the residue and debris found within the clutch assembly10and does not affect operation of the clutch assembly10. The sheared remains of the pin34may contact one another sporadically during clutch operation. Such sporadic contact will shear and wear additional material from the sheared ends until such contact no longer occurs.

Referring toFIG. 4, another alignment device10′ according to this invention includes a retractable pin54disposed within a cavity52defined within the centrifugal weight16. A retraction spring56biases the pin54coward a retracted position within the cavity52. During assembly, the pin54is pulled from the cavity52and inserted into a corresponding opening50within the clutch cover12. The pin54may be fabricated from any material, including steel or plastic.

Referring toFIG. 5, the biasing spring20exerts a biasing force in the direction indicated at58. The biasing force pushes the pin54against a surface60of the opening50. Friction between the pin54created by the force58normal to the surface60maintains the pin54in the extended position and holds the centrifugal weights16in a position clamping the friction disks30in the aligned position. The friction force prevents the pin54from being pulled back into the cavity52by the retraction spring56. The pin54therefore remains within the cavity50during assembly.

Referring toFIG. 6, the pin54retracts into the cavity52once centrifugal forces drive the centrifugal weights16outward away from the axis18and against the biasing force58. Rotation of the clutch cover12lifts the pin54of the surface60. Once the pin54lifts off the surface60, the frictional force previously holding the pin54is reduced to a point below that of the force exerted by the retracting spring56. The pin54is pulled out of the opening50and into the cavity52of the centrifugal weight16. The centrifugal weight16may then move freely between engaged and disengaged positions without interference from the pin54. Further, the retraction spring56holds the pin54within the cavity52of the centrifugal weight16during operation such that the pin54does not interfere with operation and movement of the centrifugal weights16.

Referring toFIG. 7another alignment device according to this invention includes a hook70that rotates about pivot axis76and that engages a stepped surface74incorporated on the centrifugal weights16. The hook70is biased away from the centrifugal weights16by a retraction spring72. The biasing spring20pushes each of the centrifugal weights16about pivot axis80toward a stop pin78. The fully open position of the clutch assembly10″ includes each of the centrifugal weights16being positioned against the stop pins78. In this position, the pressure plates28do not apply clamping force against the friction disks30.

Referring toFIG. 8, the hook70holds each of the centrifugal weights16in a position causing application of clamping force by the pressure plates28on the friction disks30in a desired aligned position. The hooks70are held in place by a friction force generated by the biasing force exerted by the biasing springs20on each of the centrifugal weights16. The biasing spring20pushes on the centrifugal weight16and against the hook70such that a frictional force is created between the hook70and the hook surface74. The frictional force prevents the biasing spring72from pulling the hook70free of the hook surface74.

Referring toFIG. 9, after completed assembly of the output shaft32to the clutch assembly10″, the clutch assembly is rotated. Initial operation of the clutch assembly10″ generates a centrifugal force that overcomes the biasing spring20. Rotation of the centrifugal weights16outwardly toward the clutch cover12removes the forces holding the hook70such that the biasing spring72pulls the hook70clear of the hook surface74.

Referring toFIG. 10, with hook70pulled clear, and held clear of the centrifugal weight16, normal operation can occur allowing the centrifugal weight16to move freely against the stop pins78to provide the fully open clutch position.

Referring toFIG. 11, another clutch assembly10′″ according to this invention includes a movable sleeve90that engages and moves each centrifugal weight16′ into a position causing clamping engagement between the pressure plates28and the friction disks30. The sleeve90includes an engagement surface96acting on a corresponding surface98of the centrifugal weight16′. The sleeve90is biased axially by springs100. The sleeve90is preferably biased toward a retracted position corresponding to an open position of the centrifugal weight16′.

A drive102controls movement of the sleeve90between the retracted position, and an engaged position. In the engaged position the ramped surface96of the sleeve90moves along the axis18to engage the ramped surface98of the centrifugal weight16′. Engagement between the ramped surfaces96,98translates axial movement of the sleeve90into radial movement of the centrifugal weights16′. The radial movement outward of the centrifugal weights16′ moves the rollers21along the ramped surface24of the ramp plate22. Movement of the rollers21along the ramped surface24results in axial movement of the ramp plate and clamping of the friction disks30between the pressure plates28.

The sleeve90is moved to the engaged position to move the centrifugal weights16′ to a position that causes clamping of the friction disks30. Once the friction disks30are aligned, the sleeve90is moved to the engaged position causing application of a clamping force on the friction disks30. The clamping force on the friction disks30maintains the desired alignment until assembly is completed by installation of the output shaft32.

Referring toFIG. 12, once installation of the output shaft32is complete the sleeve90is movable to the retracted position to release the friction disks30. The sleeve90is biased axially, outward of the clutch assembly10to allow free radial pivoting of the centrifugal weights16′. The sleeve90remains within the clutch assembly10′″ after completed assembly.

The drive102can be actuated to hold the sleeve90in during the assembly process and can be connected for actuation during clutch assembly operation. The drive102may be any kind of controllable drive known in the art. For example, the drive102maybe a hydraulically or pneumatically controlled cylinder, or an electromechanical device such as an electric motor or a solenoid. Further, a controller104is in communication with the drive102to control engagement of the sleeve90with the centrifugal weights16.

The sleeve90may be actuated to engage the centrifugal weights16and cause full clamping pressure to be applied to the friction disks30under conditions were there is normally insufficient centrifugal force to cause full engagement of the clutch assembly10. For, example, it may be desirable in some driving conditions to fully engaged the clutch assembly10before sufficient centrifugal force is created to fully drive the centrifugal weights16outward to cause full clamping force against the friction disks30.

The foregoing description is exemplary and not just a material specification. The invention has been described in an illustrative manner, and should be understood that the terminology used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications are within the scope of this invention. It is understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.