The disclosure relates to a friction clutch for a drivetrain of a motor vehicle, having an input part on the engine side, disposed rotatably around an axis of rotation, and an output part on the transmission side, connectible frictionally to the former by means of friction elements while forming a frictional engagement, the friction elements being designed to be clampable axially against one another by means of at least one actuating device controlled by centrifugal force.
Friction clutches according to this species known as centrifugal clutches are known, which are disengaged when the centrifugal force of the friction clutch rotating around the axis of rotation is low, for example when an engine of the drivetrain is at idle speed, and which engage as the speed of rotation increases, and hence the centrifugal force increases. Such friction clutches are known, for example, from two-wheeled vehicles. Here, the friction clutch functions as a starting clutch, having an actuating device which engages and disengages depending on centrifugal force, positioned between the input part of the friction clutch and the friction elements, in that the friction elements are acted upon axially by means of centrifugal masses which are displaced radially along a ramp device. Such friction clutches may be combined with an automated transmission, for example a continuously variable transmission (CVT). Alternatively, a friction clutch according to this species—as known for example from WO 2015/135540 A1—may be employed, where the actuating device in the friction clutch, which operates depending on centrifugal force, serves as a moving-off element, and in addition a release mechanism operated by the driver is provided as an engaging and disengaging clutch, which disengages and engages the engaged frictional clutch against the centrifugal force.
In this case, the friction clutch, which is engaged by the actuating device operating dependent on centrifugal force, engages under centrifugal force at comparatively high speeds of the engine, so as to enable the provision of an appropriate start-up torque. As rotational speeds decrease, the friction clutch disengages at appropriately high speeds, so that at low rotational speeds above idle speed there is no longer any torque available from the engine while the motor vehicle is still moving.
The proposed friction clutch is intended for a drivetrain of a motor vehicle. The friction clutch contains an input part on the engine side, disposed so that it can rotate about an axis of rotation, and an output part on the transmission side, connectible thereto frictionally by means of friction elements, forming a frictional engagement. To form a frictional engagement depending on the effect of centrifugal force, friction elements are assigned to the input part and the output part, which are designed so that they are clamp able axially against one another by means of at least one actuating device controlled by centrifugal force.
In particular to make it possible for the motor vehicle, for example two-wheel vehicles, to move off at a high rotational speed, and nevertheless to postpone disengagement due to centrifugal force at low rotational speeds, and thus, for example, to be able to drive in partial-load mode at low rotational speeds, an actuating device is provided on the engine side between the input part and the friction elements in an inherently normal manner, and in addition an actuating device on the transmission side between the output part and the friction elements. Both actuating devices apply an axial force to the friction elements to form a frictional engagement, depending on centrifugal force. This means that as the rotational speed of the input part increases and as the rotational speed of the output part increases, that is, with the vehicle moving, the friction clutch is engaged or remains engaged depending on centrifugal force, that is, depending on the rotational speeds of the engine and the transmission, and by derivation, of the drive wheel or wheels, until the friction clutch is disengaged again, for example at idle speed and with the motor vehicle essentially stopped. With the motor vehicle stopped, the friction clutch can therefore only be engaged at comparatively high rotational speeds, and thus when there is sufficient power for a rapid start. Because of the additional load on the friction elements by means of the actuating device on the transmission side with the motor vehicle in motion, the friction clutch remains engaged during the moving-off process until speeds below the clutch speed are reached, or it still transmits torque at least with slippage.
According to an example embodiment, the actuating devices may be connected parallel to one another. This means that the actuating devices are nested in one another, and exert a mutual axial force on the friction elements. In this case, one of the actuating devices, for example the actuating device on the transmission side, may act directly on the friction elements, while the other actuating device, for example the actuating device on the engine side, acts on the actuating device having the direct effect. In an alternative embodiment, the actuating devices may be connected in series with one another. This means that each of the actuating devices acts directly on the friction elements.
According to an example embodiment, an additional release mechanism operable by a driver may be provided to operate the clutch which is engaged under the effect of centrifugal force. This means that the actuating devices press the friction clutch closed under the effect of centrifugal force, and during the closed process, by means of the release mechanism, the torque transmitted by means of the friction clutch is interrupted, for example in order to undertake a shift procedure in the transmission. It goes without saying that the release mechanism may be actuated automatically, as an alternative to actuation by a driver, or may be provided with power-assist to assist the driver.
The proposed friction clutch may have the form of a dry-operated friction clutch, having a counter-pressure plate in an axially fixed position and a contact plate which is movable axially in relation thereto, which constitute the input-side friction elements, constituting the input part. The output-side friction elements are designed as friction linings of a clutch disk, which constitutes the output part of the friction clutch. The actuating devices, under the influence of centrifugal force, pre-stress the contact plate, forming a frictional engagement between the friction elements against the counter-pressure plate.
Alternatively, the proposed friction clutch may be operated wet, in which case the friction elements are made of alternately stacked laminae, which are pre-stressed against an axial stop by the actuating device, under the influence of centrifugal force. In this case, steel plates may be stacked alternately with friction plates and form a corresponding plate pack. For example, the friction plates may be joined non-rotatingly with an input-side plate carrier and the steel plates with an output-side plate carrier, such as hooked into them, which are pre-stressable axially by means of the actuating devices, depending on the centrifugal force.
According to an example embodiment, the plate pack of the friction clutch may be designed so that it can be pre-stressed by the actuating devices by means of a plate carrier which is movable axially relative to an axially fixed base plate, and rotary-coupled, depending on centrifugal force. In this case, each of the actuating devices may include two plate parts containing axially between them radially movable centrifugal masses, which form a ramp device, one of which plate parts is axially fixed and the other plate part axially movable, and the axially movable plate parts press the plate carrier axially against the base plate. To form a friction clutch which is forcibly engaged by the actuating clutch under the influence of centrifugal force, the axially movable plate parts of the ramp devices may be firmly connected axially in both directions to a plate carrier. The axially movable plate parts may however act on the plate carrier against the effect of at least one spring element, so that an equilibrium is operative between the pre-stressing of the spring element and the centrifugal force, so that the plate part engages the friction clutch against the effect of the spring element, under the influence of frictional force.
In a serial arrangement of the actuating devices, the axially movable plate parts may be arranged so that they are rotary-uncoupled against one another, with one of the plate parts, e.g., the plate part of the actuating device on the transmission side, acting axially on the plate carrier. In this case, the axially movable plate part of the actuating device on the engine side presses under the influence of centrifugal force, axially and rotary-uncoupled, for example by means of a needle bearing or the like, against the axially movable plate part of the actuating device on the transmission side, with an axial force which is redirected axially by the radially displaced centrifugal masses and the ramp device.
In an alternative embodiment, the two axially movable plate parts may act on the plate carrier directly, that is, axially in series.
The ramp devices may be formed by pre-stamped plate pieces having ramps running outward toward one another in a radial direction, between which centrifugal masses are provided, distributed axially around the circumference. The ramps may have a radial guideway along their extension. The centrifugal masses may be designed as rolling elements, such as balls, cylinders, sliding elements or the like.
The disclosure will be explained in further detail on the basis of the exemplary embodiment depicted in
The plate carrier 5 receives the friction elements 18 in the form of friction plates 17, rotationally fixed and axially movable to a limited extent. These, stacked alternating with the output-side friction elements 20 in the form of steel plates 19, form the plate pack 21.
The output part 3 is constructed as follows: The steel plates 19 are received radially inside on the plate carrier 22, for example hooked in, non-rotating and axially movable to a limited extent. The plate pack 21 is supported axially on the output-side base plate 24, and is acted on axially by the cup-shaped load transfer plate 23 connected to the plate carrier 22.
The base plate 24 receives the hub plate 26 firmly at an axial distance by means of the bolts 25 distributed around the circumference. The hub plate 26 is received firmly on the hub piece 4 by means of the thrust ring 27, and forms a rotationally locked connection with the transmission input shaft 28. The plate piece 29 is connected firmly to the hub plate 26 at an axial distance by means of the bolts 30 distributed around the circumference.
The plate carrier 22 is connected non-rotatingly and axially movably to the hub plate 26 by means of the leaf springs 31 distributed around the circumference, so that when a frictional engagement of the friction elements 18, 20 is formed, a torque introduced into the input part 2 is transmitted via the plate carrier 22 and the cup-shaped load transfer plate 23 to the hub plate 26, and thus to the transmission input shaft 28. The plate piece 32 is axially pre-stressed relative to the cup-shaped load transfer plate 23 by means of the bolts 33 distributed around the circumference and the spring elements 34—in this case helical compression springs. The axially fixed plate piece 29 and the plate piece 32, which is movable axially contrary to the effect of the spring elements 34, receive axially between them the centrifugal masses 35, which are distributed around the circumference and are radially movable. Radially outside, the plate piece 32 has the ramps 36 which run toward the plate piece 29. The plate piece 29 has stampings 40, which guide the centrifugal masses 35 fixedly in the circumferential direction and radially movably. These components form the ramp device 37, and the actuating device 38 on the transmission side. When the centrifugal force increases due to the speed of rotation, the centrifugal masses 35 are displaced radially outward, so that when the spring elements 34 and the leaf springs 31 are pre-stressed the cup-shaped load transfer plate 23 is moved axially and the frictional engagement of the friction elements 18, 20 is produced.
The coupling of the input-side actuating device 11 to the cup-shaped load transfer plate 23 occurs by means of the actuating device 38. The bolts 39 on the axially movable plate piece 32, distributed around the circumference and extending in the direction of the thrust ring 16, are provided for this purpose. When the actuating device 11 is actuated on the input side, the plate piece 8 moves the thrust ring 16 by means of the roller bearing 15, and thus the bolts 39. This moves the plate piece 32 axially, and the cup-shaped load transfer plate 23 acts on the plate pack 21.
During a driving-off process, in this way the actuating device 11 takes over pressing the plate pack against the base plate 24. As soon as the transmission input shaft 28 has reached a sufficient speed, the centrifugal masses 35 are accelerated radially outward, so that the contact pressure is intensified. A limitation of the contact pressure can be achieved through appropriate design of the spring elements 34, which give way under a specified overpressure. If the engine speed is reduced while the vehicle is moving, the pressing of the plate piece 8 decreases; however, the pressing and pre-stressing of the plate pack 21 is maintained as a result of the axial movement of the plate piece 32 and pre-stressing of the cup-shaped load transfer plate 23, until the motor vehicle has slowed below an appropriate velocity corresponding to a specified rotational speed of the transmission input shaft 28.
In addition to the actuating devices 11, 38, which press the friction clutch 1 into engagement depending on centrifugal force, the friction clutch 1 has the release mechanism 41, which enables disengagement of the friction clutch 1, which is engaged under centrifugal force. To this end, the release mechanism 41 has the release bearing 42, actuated in the axial direction by the driver or automatically, which moves the collar 43 of the cup-shaped load transfer plate 23 against the effect of the spring elements 34 and thereby breaks the frictional engagement between the friction elements 18, 20 brought about by the actuating devices 11, 38.
The ramp device 10a of the actuating device 11 a includes the plate piece 44a, firmly connected to the hub piece 4a, which firmly braces the plate piece 45a of the ramp device 10a axially by means of the roller bearing 6a. The plate piece 8a with the ramp 13a is designed to be axially movable, and acts on the plate piece 46a, rotationally uncoupled, by means of the roller bearing 15a. Positioned between the plate pieces 8a, 45a are the radially movable centrifugal masses 9a, which are distributed around the circumference. The plate piece 46a is pre-stressed axially against the plate piece 32a by means of the spring element 47a—here a diaphragm spring. The plate piece 46a is slide-supported on the plate piece 44a by means of the axial extension 48a, and has arms 49a on its end which come to a stop against the hub plate 26a after the plate piece 46a has moved a specified distance. This limits the travel of the actuating device 11a, and brings about a pressure on the plate pack 21a due to centrifugal force, by means of an axially rigid connection through the plate piece 36a and the centrifugal masses 35a. If the output part 3a reaches a specified rotational speed, the centrifugal masses 35a move radially outward and pre-stress the plate pack 21a further. When the rotational speed at the input part 2a is reduced, for example by letting up on the gas to the engine, the plate piece moves back from the hub plate 26a, for example when the engine is idling; the plate pack 21a is pre-stressed by the actuating device 32a when the motor vehicle is moving, however.
Number | Date | Country | Kind |
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10 2016 204 111.8 | Mar 2016 | DE | national |
This application is the U.S. National Phase of PCT Appln. No. PCT/DE2017/100197 filed Mar. 13, 2017, which claims priority to German Application No. DE102016204111.8 filed Mar. 14, 2016, the entire disclosures of which are incorporated by reference herein.
Filing Document | Filing Date | Country | Kind |
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PCT/DE2017/100197 | 3/13/2017 | WO | 00 |