1. Field of the Invention
The present invention pertains to a pressure plate assembly for a friction clutch, which assembly includes a housing; a pressure plate connected to the housing for rotation in common around an axis of rotation which is free to move axially with respect to the housing; a stored-energy device which pretensions the pressure plate in the axial direction with respect to the housing; a wear-compensating device which acts in the path of support between the stored-energy device and at least one of the housing and the pressure plate and comprises at least one wear-compensating element, which is free to move when wear occurs and/or when wear is compensated; an indicator arrangement comprising at least one indicator opening in the housing and at least one indicator element on a wear-compensating element, where information concerning the amount of wear which has occurred can be derived from the position of the indicator element relative to the minimum of one indicator opening.
2. Description of the Related Art
U.S. Pat. No. 5,531,308 discloses a friction clutch in which a wear-compensating device can be used to ensure that the wear which occurs during the operation of the clutch, such as the wear of the friction linings of a clutch disk, for example, is compensated. For this purpose, two adjusting rings are provided, one of which is held nonrotatably with respect to a housing, whereas the other adjusting ring is free to rotate to compensate for wear. The two rings have corresponding ramp surfaces, so that, upon rotation of the second adjusting ring, the total axial length of the wear-compensating device consisting essentially of the two adjusting rings changes. On the adjusting ring which can rotate relative to the housing, an axial projection is provided, which engages in a curved, slot-like opening in the housing, i.e., in a bottom area of the housing. When the adjusting ring turns, this projection moves in the opening through which it passes. From the position which this projection occupies in the opening, it can be determined how far the rotatable adjusting ring has rotated up to that point, which is an indication in turn of the extent to which wear compensation has occurred and thus also of the amount of wear which has occurred.
It is the task of the present invention to improve a pressure plate assembly of the general type in question in such a way that, by the use of a simple design, the amount of wear which has occurred can be detected more easily.
According to the invention, the indicator element at least partially fills at least one indicator opening in at least one state of wear.
With the design of a pressure plate assembly according to the invention, the geometry of the indicator element can be made essentially independent of the geometry of the indicator opening. This facilitates the design and also makes it possible for both the indicator element and the indicator opening to be designed with respect to their shape and/or configuration in such a way that, through the cooperation of these two assemblies, a very precise indication of the actual amount of wear which has occurred or of the degree of wear compensation which has occurred can be obtained.
It is possible, for example, for the width of the indicator element, i.e., the dimension essentially transverse to the direction of its movement with respect to the minimum of one indicator opening, to change over the length of the indicator element in the direction of movement. It is thus achieved that the width of the indicator element visible in the minimum of one indicator opening changes as the element moves past, so that, as the indicator element moves, the area of the indicator opening which it fills also changes, from which information can be derived concerning different states of wear.
For this purpose, it is possible, for example, for the width of the indicator element to change continuously, at least in certain of its areas. Alternatively or in addition, it is possible for the width of the indicator element to change in step-like increments. Although a step-like change in width produces a very clear-cut discontinuity in the indicator characteristic, an indicator element with a continuous change in width provides information of higher resolution concerning the state of wear.
It is also possible to provide a plurality of indicator openings in succession in the direction of the movement of the indicator element. In another, preferred embodiment of the pressure plate assembly according to the invention, it is possible, in conjunction with the provision of a plurality of indicator openings, for the indicator element to have an indicator section which fills essentially all of the indicator openings in one wear state and at least partially fills one indicator opening or essentially no indicator opening in at least one other wear state. It can therefore be provided, for example, that the indicator fills all of the indicator openings when the clutch is new and has not yet been affected by wear, and that, as the amount of wear increases, the indicator element moves successively along the indicator openings and thus opens various indicator openings one after the other.
As an alternative, it is also possible for the indicator element to have an indicator section which does not fill all of the indicator openings in any wear state. It can be provided in this case, for example, that, as a function of the amount of wear which has occurred, the indicator section completely fills one of the indicator openings or partially fills two of the indicator openings.
In a design of the pressure plate assembly which is very simple to realize, it is possible for the wear-compensating device to comprise an adjusting ring, which can rotate around the axis of rotation for the purpose of wear compensation, and for the indicator element to be free to move along with the adjusting ring constituting the wear-compensating element.
An alternative embodiment of the pressure plate assembly according to the invention can be designed in such a way that the wear-compensating device comprises: an arresting element which, upon the occurrence of wear, is able to move with respect to the pressure plate assembly in correspondence with the amount of wear which has occurred; an essentially wedge-shaped slider element, which is installed between the pressure plate assembly and the arresting element and which, upon movement of the arresting element with respect to the pressure plate assembly, is free to move under the pretensioning effect in correspondence with the extent of the movement of the arresting element with respect to the pressure plate assembly in order to keep the arresting element in the position relative to the pressure plate assembly to which it has moved as a result of wear; and an adjusting ring, which is able to rotate around the axis of rotation to perform a wear-compensating movement, where the adjusting rotation of the adjusting ring is limited by the slider element and/or by the arresting element, where the indicator element is able to move along with the slider element forming the wear-compensating element.
In addition, the pressure plate assembly according to the invention can be designed so that the stored-energy device is located in an area between the indicator element and the minimum of one indicator opening and has a see-through opening associated with the minimum of one indicator opening. To avoid the introduction of additional openings in the stored-energy device, it is possible, for example, for the see-through opening to be formed by an area between two of the spring tongues of the stored-energy device.
It is also possible, according to the invention, for the indicator element to be connected to the wear-compensating element by connecting sections provided on the indicator element. It is also possible for the indicator element to have a contact area, by means of which it is supported on a surface of the wear-compensating element facing the axis of rotation. It is possible in this way to prevent the indicator element from shifting position as a result of centrifugal force during rotational operation.
The present invention also pertains to a friction clutch which contains a pressure plate assembly according to the invention.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.