Friction clutch

Abstract

A friction clutch for a motor vehicle for frictional coupling a first shaft and a second shaft, comprising a plurality of clutch discs articulated interactively on a clutch basket and a clutch hub, wherein the first shaft is connected to the clutch basket and the second shaft is connected to the clutch hub and the clutch discs are selectively coupled by an associated actuation unit. Associated with the clutch basket is an oil-collection and guiding arrangement through which oil spun off the clutch basket is collected and delivered into a collection region outside the clutch basket. A switching device coupled to the actuation unit controls the backflow of the oil from the collection region outside the clutch basket (KK) in the direction of the clutch discs.

Claims

1. A friction clutch for a motor vehicle comprising a first shaft, a second shaft, a plurality of clutch plates articulated alternately on a clutch cage and a clutch hub, wherein the first shaft is connected to the clutch cage and the second shaft is connected to the clutch hub, the clutch plates are selectively coupled by means of an associated actuation unit, wherein the clutch cage is surrounded by an oil-collection and guiding arrangement such that oil flung off the clutch cage is collected and delivered into a collection region outside of the clutch cage, and wherein a switching device coupled to the actuation unit controls the return of the oil from the collection region outside of the clutch cage in the direction of the clutch plates.

2. The friction clutch as claimed in claim 1, wherein the clutch, together with the actuation unit are arranged in a housing, and wherein the collection region is an oil tank designed as part of the housing.

3. The friction clutch as claimed in claim 2, wherein the oil tank is capable of holding the entire quantity of oil allocated to the clutch.

4. The friction clutch as claimed in claim 1, wherein the actuation unit comprises a fixed actuation ring and a rotationally and axially movable actuation ring, between which balls run in ramp-shaped structures.

5. The friction clutch as claimed in claim 4, wherein the switching device is actuated by the rotationally and axially movable actuation ring.

6. The friction clutch as claimed in claim 2, wherein the oil-collection and guiding arrangement surrounding the clutch cage is designed as a sheet-metal part which extends outward in the direction of the oil tank.

7. The friction clutch as claimed in claim 1, wherein the clutch cage has openings in the outer region to allow oil to exit.

8. The friction clutch as claimed in claim 2, wherein the housing has at least one of special machined features, surface properties, and sealing elements for separating the oil tank.

9. A friction clutch assembly for use in a motor vehicle, comprising: a housing defining a coupling region and an oil collecting region; first and second rotary members disposed in the coupling region of the housing and supported for relative rotation; a clutch disposed in the coupling region of the housing and including a clutch cage fixed for rotation with the first rotary member, a clutch hub fixed for rotation with the second rotary member, and a set of clutch plates alternately coupled for cojoint rotation with the clutch cage and the clutch hub; an actuation unit disposed in the coupling region of the housing and having an actuator ring moveable relative to the clutch plates in a first direction to frictionally engage the clutch plates and place the clutch in an engaged state and in a second direction to release engagement of the clutch plates and place the clutch in a released state; a power-operated actuator for selectively moving the actuator ring to shift the clutch between its engaged and released states; an oil collecting and guiding device surrounding the clutch cage and disposed within the housing to delineate the oil collection region from the coupling region, the oil collecting and guiding device configured to collect oil centrifugally flung from the clutch cage and to deliver the collected oil to the oil collection region of the housing; and a switching device coupled to the actuator ring and operable in an opened mode when the clutch is in its engaged state and further operable in a closed mode when the clutch is in its released state, wherein the switching device operates in its opened mode to permit oil in the oil collection region to flow into the coupling region and further operates in its closed mode to prevent the transfer of oil from the collection region to the coupling region.

10. The friction clutch assembly of claim 9, wherein the oil collection region of the housing is configured as an annular ring-shaped oil tank.

11. The friction clutch assembly of claim 10, wherein the oil tank is capable of holding the entire quantity of oil allocated to the clutch.

12. The friction clutch assembly of claim 10, wherein the switching device is shifted into its opened mode when the actuator ring moves axially in the first direction and is shifted into its closed mode when the actuator ring moves axially in the second direction.

13. The friction clutch assembly of claim 9, wherein the clutch cage includes openings permitting oil within the clutch plates to be discharged out of the clutch cage for collection by the oil collecting and guiding device.

14. The friction clutch assembly of claim 13, wherein the oil collecting and guiding device is configured such that the coupling region becomes free from oil and the clutch plates do not dip into an oil bath upon rotation of the clutch cage following shifting the switching device into its closed mode.

Description

DRAWINGS

(1) The drawings described herein are for illustrative purposes only of selected embodiments and not all implementations and are not intended to limit the present disclosure to only that actually shown. With this in mind, various features and advantages of example embodiments of the present disclosure will become apparent from the written description when considered in combination with the appended drawings, wherein:

(2) FIG. 1 shows a sectional view of an embodiment of a friction clutch according to the invention; and

(3) FIG. 2 shows a perspective view of the friction clutch according to the invention, more specifically without the housing.

DETAILED DESCRIPTION

(4) An illustrative embodiment of the invention is furthermore explained by means of the drawings.

(5) FIG. 1 shows an embodiment of a friction clutch assembly according to the invention in section. The friction clutch assembly includes a clutch K which connects a first shaft W1 to a second shaft W2, wherein the first shaft W1 is coupled to the rear axle/final drive or the main transmission of the vehicle, and wherein the second shaft W2 is connected to a wheel or the cardan shaft of the motor vehicle. The two shafts W1, W2 extend coaxially and can move in rotation relative to one another.

(6) A clutch cage KK is connected for conjoint rotation to shaft W1. A clutch hub KN is connected for conjoint rotation to shaft W2. The two shafts W1, W2 are held in a housing GH by means of a rolling bearing in a manner which allows them to move in rotation relative to one another.

(7) Arranged in the clutch cage KK are clutch plates KL, which are alternately coupled for conjoint rotation and axial movement to the clutch cage KK via corresponding external toothing and to the clutch hub KN via corresponding internal toothing. The actuation unit associated with the plates KL comprises two actuator rings A1, A2, between which are arranged balls (not shown), which run in ramp-shaped structures on the rings A1, A2 and form a ball ramp mechanism. The actuator ring A2 is fixed in relation to the housing, i.e. said ring is arranged in a fixed manner in the housing GH of the clutch K and is press-fitted in a corresponding seat. Shaft W2 is supported relative to the housing GH by means of a rolling bearing WL, while a small axial needle bearing AL is provided for axial support, said needle bearing being arranged between the housing GH and a supporting disk on shaft W2.

(8) The rotatable actuator ring A1 acts on the clutch plates KL via a large axial bearing AL1 and brings about the contact pressure required for torque transmission on the plate system. Here, the contact pressure movement of the actuator ring A1 is counteracted by the force of springs F which are arranged within the clutch hub and bring about release of the clutch, of the clutch plates KL.

(9) The rotatable actuation ring A1 is moved axially in the direction of the clutch plates KL by the ball ramp principle using balls (not shown) guided in a cage. For this purpose, the actuation ring A1 has toothing on part of its outer circumference engaged with the thread on a rotatable spindle driven by an electric motor.

(10) The front part of the housing GH, which lies radially substantially at the level of the clutch plates KL, forms an oil tank T, in which the oil for the clutch K can be held. The size of the oil tank T, which, in the form of an annular ring, surrounds the part of the housing GH shaped as an indentation, is such that the entire quantity of oil for the clutch K can be held.

(11) If the entire quantity of oil for the clutch K is in the oil tank T, the oil flow in the direction of the clutch plates KL is enabled by an oil switching unit SE that is opened through rotation of the actuator ring A1. When the clutch K is closed, the actuator ring A1 closes the clutch plates KL in the rotated and axially advanced state, i.e. when there is torque transmission, such that the oil switching unit SE is opened and the oil flow in the direction of the clutch plates KL is enabled. When the clutch K is opened, the clutch plates KL are released by rotating the actuator ring A1 back with an axial reverse movement, such that the oil switching unit SE is closed and oil flow is stopped.

(12) FIG. 2 shows a perspective view of the clutch according to the invention, more specifically without the housing GH. In its outer region, the clutch cage KK hasin addition to the visible openings on the end, which serve, in particular, for oil inflowopenings through which oil can flow outward out of the region of the clutch plates KL owing to the centrifugal force. An oil-collection and guiding arrangement F configured as a formed sheet, a sheet-metal strip, receives some of the oil flung off the clutch cage KK and guides it in accordance with the slope in the direction of the oil tank T, which is situated at the rear in the depiction shown in FIG. 2. During this process, the flinging effect drives the oil on the sheet extending outward in the direction of the oil tank T.

(13) When the clutch K is closedthe clutch plates KL being pressed together by the actuator ring A1 for torque transmissionthe oil switching unit SE is opened and the oil from the tank space T can flow into the clutch space, from where it is delivered back in the direction of the oil tank T via the oil-collection and guiding arrangement F. It thus forms an equilibrium of the oil quantity in the clutch space KL and oil tank T.

(14) Once the clutch K has been released by appropriate rotation of the actuator ring A1, with the clutch plates KL separated, the oil switching unit SE is closed. The oil flung off the rotating clutch cage KK is delivered in the direction of the oil tank T by means of the oil-collection and guiding arrangement F and is prevented from flowing back in the direction of the clutch space KL by the closed oil switching unit SE. The clutch plates KL thus run dry in the released state, and therefore operation very largely without residual torque is possible.

(15) The drive for the rotatable and axially movable actuator ring A1 is shown in FIG. 2. An actuating spindle SP, which is fixedly mounted in the axial direction, interacts with toothing formed on the outer circumference of the actuator ring A1. The actuating spindle SP is driven by an actuator drive AA, an electric motor, to which an electronic control unit in a housing is assigned.

(16) The toothing of the actuator ring A1 is of a width in the axial direction such that it remains in engagement with the actuating spindle SP over the axial movement path.

(17) In one embodiment, the oil-collection device F and the element for separating the oil spaces can be embodied as a single component.

(18) The oil-collection and oil-separating arrangement F is embodied in such a way that the clutch space remains free from oil and the plates no longer dip into an oil bath (apart from wetting of the surfaces).

(19) Thus, not only the switching off of the oil supply but also the emptying of the clutch space (dry sump) is ensured. In addition, the lubrication concept is switched from dip lubrication or splash lubrication which means that the cage KK dips into the oil when stationary and at low and medium speeds, to dry operation when the clutch is completely open.

(20) For clean separation of the tank space and the clutch space, there are, on the oil-collection device F, separating and guiding elements which also perform the separating function, or on the housings there are special machined features and/or surface properties, and/or sealing elements which serve for sealing and preventing or reducing leaks into the clutch region in dry operation. Only by this means is it ensured that the clutch space does not refill with oil and the flinging out of oil does not have to begin again when the vehicle is stationary for a brief period, for example.

(21) The dry sump system is used together with an enlarged release travel to lower the residual torques in the clutch.

(22) The dry sump system can assist at two operating points of the clutch: 1. Reduction of splash losses. This works for connect and disconnect operation. Connect operation means that, although the clutch is open, the drive train to the secondary axle is not decoupled by a second unit. 2. Reduction of the residual torque. Here, residual torque is the torque which is transmitted via the clutch even when it is actually open. This works or makes sense especially in a disconnect mode, in which very high differential speeds of rotation occur since the secondary axle is completely decoupled and comes to a halt.

(23) The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

LIST OF REFERENCE SIGNS

(24) W1 first shaft

(25) W2 second shaft

(26) K clutch

(27) KK clutch cage

(28) KN clutch hub

(29) WL rolling bearing

(30) AL axial bearing, axial needle bearing

(31) GH housing

(32) A1 first actuator ring, actuation ring

(33) A2 second actuator ring, actuation ring

(34) F spring element

(35) AL1 axial bearing, axial needle bearing

(36) T collection region for oil, oil tank

(37) SE oil switching unit

(38) F oil-collection and guiding arrangement

(39) opening in clutch cage

(40) SP actuating spindle

(41) AA actuation drive