CENTRIFUGAL CLUTCH FOR A DRIVETRAIN OF A MOTOR VEHICLE, HAVING BRAKED CENTRIFUGAL MASSES

Abstract

A centrifugal clutch includes an input part, an output part, a centrifugally engageable and disengageable friction unit, and a shifting apparatus. The friction unit has first frictional elements connected to the input part, and second frictional elements connected to the output part and layered alternately with the first frictional elements. The shifting apparatus is for frictionally engaging the first frictional elements and the second frictional elements to engage the clutch. The shifting apparatus has a centrifugal mass and a brake spring. When the centrifugal mass moves from a disengaged position to an engaged position, the brake spring is arranged to apply a first braking force contrary to a first direction of motion of the centrifugal mass. The brake spring is also arranged to apply a second braking force contrary to a second direction of motion of the centrifugal mass. The first braking force is greater than the second braking force.

Claims

1.-10. (canceled)

11. A centrifugal clutch for a drivetrain of a motor vehicle comprising: an input part; an output part positioned coaxially and rotatably in relation to the input part; a centrifugally engageable and disengageable friction unit comprising: first frictional elements connected non-rotatingly to the input part; and, second frictional elements connected non-rotatingly to the output part and layered alternately with the first frictional elements in an axial direction; and, a shifting apparatus for frictionally engaging the first frictional elements and the second frictional elements to engage the centrifugal clutch, comprising: a centrifugal mass movable from a disengaged position to an engaged position by a centrifugal force that occurs when the shifting apparatus rotates; and, a brake spring, wherein: when the centrifugal mass moves from the disengaged position to the engaged position, the brake spring is arranged to apply a first braking force to the centrifugal mass in a direction contrary to a first direction of motion of the centrifugal mass; the brake spring is arranged to apply a second braking force to the centrifugal mass, contrary to a second direction of motion of the centrifugal mass; and, the first braking force is greater than the second braking force.

12. The centrifugal clutch of claim 11, wherein the brake spring is a diaphragm spring.

13. The centrifugal clutch of claim 11, wherein the brake spring comprises a spring arm.

14. The centrifugal clutch of claim 13, wherein the brake spring comprises a plurality of spring arms arranged in V-shaped pairs.

15. The centrifugal clutch of claim 11, wherein: the centrifugal mass comprises a first contact surface; and, the brake spring for contacting the first contact surface to apply the first braking force.

16. The centrifugal clutch of claim 15, wherein: the centrifugal mass comprises a second contact surface; and, the brake spring is arranged to contact the second contact surface to apply the second braking force.

17. The centrifugal clutch of claim 16, wherein the first contact surface and the second contact surface are not parallel.

18. The centrifugal clutch of claim 11, wherein: the shifting apparatus comprises an angle plate; and, the centrifugal mass comprises a third contact surface for moving the angle plate.

19. The centrifugal clutch of claim 18, wherein: the angle plate comprises an opening; and, the brake spring extends at least partway through the opening.

20. The centrifugal clutch of claim 11, further comprising: a leaf spring core; and, a pivot bearing positioned between the shifting apparatus and the leaf spring core.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The disclosure as well as the technical environment will be explained in greater detail below on the basis of the figures. It must be pointed out that the figures show an example variant of the invention, but the disclosure is not limited thereto. Like components in the figures are provided with the same reference labels. The figures show the following, by way of example and schematically:

[0027] FIG. 1 shows a centrifugal clutch in longitudinal section;

[0028] FIG. 2 shows a centrifugally engageable and disengageable shifting apparatus of the centrifugal clutch in top view;

[0029] FIG. 3 shows a centrifugally engageable and disengageable shifting apparatus without an angle plate in top view;

[0030] FIG. 4 shows a partial view of FIG. 3 in a perspective view;

[0031] FIG. 5 shows a sectional view of a centrifugal mass of the centrifugal clutch in a disengaged position;

[0032] FIG. 6 shows a sectional view of the centrifugal mass of the centrifugal clutch in an engaged position;

[0033] FIG. 7 shows a brake spring of the centrifugal clutch in a perspective view; and

[0034] FIG. 8 shows a diagram of the clamping force of a friction unit of the centrifugal clutch depending on the speed of rotation of an input part of the centrifugal clutch.

DETAILED DESCRIPTION

[0035] FIG. 1 shows a sectional view of a centrifugal clutch 1 in longitudinal section. The centrifugal clutch 1 has an input part 2 having an input plate 23 that is rotatable around an axis of rotation 26 by a drive unit (not shown here), and an outer plate carrier 24 attached non-rotatingly to the input plate 23. Connected non-rotatingly to the outer plate carrier 24 of the input part 2 are first frictional elements 5 of a friction unit 4. The friction unit 4 has, in addition, second frictional elements 6, which are attached non-rotatingly to a hub 27 and a contact plate 29 of a leaf spring core 21. The hub 27 has toothing 28, by means of which the hub 27 is connectable non-rotatingly to a transmission shaft of a transmission (not shown here). The contact plate 29 is attached non-rotatingly to the hub 27 by means of leaf springs 44, and is movable to a limited extent in an axial direction 7 parallel to the axis of rotation 26. The leaf spring core 21 is part of an output part 3 of the centrifugal clutch 1. When the centrifugal clutch 1 is in a disengaged state, the output part 3 is (essentially) freely rotatable around the axis of rotation 26 relative to the input part 2.

[0036] The input part 2 has a centrifugally engaging and disengaging shifting apparatus which is rotatable with the input part 2. The shifting apparatus 8 is fastened non-rotatingly to the input plate 23 of the input part 2 by means of bolts 32. The shifting device 8 includes centrifugal masses 9, which here are in a disengaged position 10, that is, maximally to the inside in a radial direction 25. When the input part 2 rotates, the centrifugal masses 9 are moved outward in the radial direction 25 by centrifugal force. As this occurs, an oblique third contact surface 18 of the centrifugal masses 9 contacts ramps 31 of an angle plate 19 of the shifting apparatus 8, which causes the angle plate 19 to be moved in the axial direction 7 in the direction of the leaf spring core 21. The angle plate 19 thereby moves the contact plate 29, so that the first frictional elements 5 and the second frictional elements 6 are clamped between the contact plate 29 and a counter-pressure plate 30 and brought into frictional engagement, so that torque is transmissible from the input part 2 to the output part 3. To this end, a pivot bearing 22, which is formed here in the nature of a needle bearing, is positioned between the angle plate 19 and a support 45 of the leaf spring core 21. Furthermore, a brake spring 13 is positioned between the angle plate 19 and the centrifugal masses 9 in the axial direction 7.

[0037] FIG. 2 shows the shifting apparatus 8 of the centrifugal clutch 1 shown in FIG. 1, from above in the direction of the axis of rotation 26. The angle plate 19 in the variant shown here has six openings 20, through each of which a spring arm 15 of the brake spring 13 extends at least partway. Also evident in FIG. 2 is that the angle plate 19 in the variant shown here has three ramps for the centrifugal masses 9 shown in FIG. 1. Furthermore, the input plate 23 has external toothing 33 on its outer circumferential surface, by means of which the input plate 23 is rotatable around the axis of rotation 26 by a drive unit (not shown here).

[0038] FIG. 3 shows the shifting apparatus 8 without the angle plate 19 shown in FIG. 2. Particularly evident here is the brake spring 13, which has six spring arms 15 arranged in V-shaped pairs on an outer circumferential surface. In addition, the brake spring 13 has three plate-links 34, by means of which the brake spring 13 is fastened non-rotatingly on the input plate 23 with the bolts 32. The three centrifugal masses 9 are in the disengaged position 10 here. In the disengaged position 10, the spring arms 15 contact the centrifugal masses 9 on an oblique first contact surface 16. When the shifting apparatus 8 rotates, the centrifugal masses 9 are moved outward in the radial direction 25 by the centrifugal force, so that the spring arms 15 slide over the first oblique contact surfaces 16 in the direction of a second contact surface 17 of the centrifugal masses 9. As this occurs, the spring arms 15 of the brake spring 13 introduce a first braking force through the oblique first contact surface 16 into the centrifugal masses 9 against the movement direction of the centrifugal masses 9. After the second contact surface 17 has been reached, the spring arms 15 of the brake spring 13 introduce a second braking force that is smaller than the first braking force into the centrifugal masses 9, against the movement direction of the centrifugal masses 9.

[0039] FIG. 4 shows a detail of the shifting apparatus 8 shown in FIG. 3 in a perspective view. Recognizable here are, in particular, the first contact surfaces 16 of the centrifugal mass 9, which is in the disengaged position. The first contact surfaces 16 here are in the form of recesses 35, and run obliquely or at an angle to the radial direction 25. Additionally, the first two contact surfaces 16 are formed at a radially outer end 26 of the centrifugal masses 9. Also formed on this radially outer end 26 is the third contact surface 18, by means of which the centrifugal masses 9 move the angle plate 19. It must be clarified here that the first contact surfaces 16 and the third contact surfaces 18 may also be formed as a single contiguous oblique contact surface. In the area of the first contact surface 16, the spring arms 15 are bent in a U-shape or V-shape. When the centrifugal masses 9 are moved outward in the radial direction 25 as a result of the centrifugal force, the U-shaped or V-shaped areas of the spring arms 15 of the brake spring 13 contact the centrifugal masses 9 (only) on the second contact surface 17, which is oriented orthogonally to the axis of rotation 26 shown in FIG. 2.

[0040] FIG. 5 shows a schematic sectional view along the cutting line V shown in FIG. 3, through one of the centrifugal masses 9. Here, the centrifugal mass 9 is in the disengaged position 10 and in the first motion range 12. In the first motion range 12 the spring arms 15 of the brake spring 13 contact the centrifugal masses 9 (only) on the first contact surface 16, so that the brake spring 13 introduces a first braking force inward in the direction of the radial direction 25. The first motion range 12 of the centrifugal masses 9 extends outward in the radial direction 25 from the disengaged position 10 shown here, until the brake spring 13 no longer contacts the centrifugal masses 9 on the oblique contact surface 16, but now only in the area of a boundary 37 between the first contact surface 16 and the second contact surface 17.

[0041] FIG. 6 shows the sectional view shown in FIG. 5, after the centrifugal mass 9 has been moved outward maximally in the radial direction 25. Here, the centrifugal mass 9 is thus in the engaged position 11 or in the second motion range 14. In the second motion range 14, the spring arms 15 of the brake spring 13 no longer contact the centrifugal mass 9 in the area of the first contact surface 16, but rather now only on the second contact surface 17. In the second motion range 14, the brake spring 13 introduces a normal force into the centrifugal mass 9 in the longitudinal direction 38, which, contrary to the direction of motion of the centrifugal mass 9 in the radial direction 25 in the form of a friction force resulting from the normal force, causes a second braking force which is smaller than the first braking force.

[0042] FIG. 7 shows a perspective view of the brake spring 13.

[0043] FIG. 8 shows the pattern of a clamping force 46 of the friction unit 4 shown in FIG. 1, between a driving-off process of a motor vehicle (not shown here) and a subsequent standstill of the motor vehicle. A speed in revolutions per minute [rpm] of a drive unit of the motor vehicle (not shown here) is plotted on an x-axis 39, and the level in Newtons [N] of the clamping force 46 acting on the friction unit 4 is plotted on a y-axis. At a first point 41, before the vehicle begins to move, the clamping force is essentially 0 N. At the second point 42, the rotational speed of the drive unit or of the input part is increased to a driving-off speed. Because of the first braking force then introduced by the brake spring 13 onto the centrifugal masses 9 contrary to the direction of motion of the centrifugal masses 9, the clamping force 46 essentially does not increase between the first point 41 and the second point 42. Only when the rotational speed of the drive or of the input part increases further is the clamping force 46 increased, until a maximum value of the clamping force 46 is reached at a third point 43.

[0044] At the third point 43, the centrifugal masses 9 are in the engaged position 11 or in the second motion range 14, so that the brake spring 13 now acts on the centrifugal masses 9 contrary to the movement direction of the centrifugal masses only with a smaller braking force, compared to the first braking force. When the rotational speed of the drive is reduced starting from the third point 43, the clamping force 46 is always greater than 0 N, so that until the first point 41 is reached, that is, the idle speed of the drive, torque is transmissible from the input part 2 to the output part 3.

[0045] The present disclosure is distinguished by a smaller construction space requirement, a lower weight and a lower assembly and installation cost.

REFERENCE NUMERALS

[0046] 1 centrifugal clutch

[0047] 2 input part

[0048] 3 output part

[0049] 4 friction unit

[0050] 5 first frictional elements

[0051] 6 second frictional elements

[0052] 7 axial direction

[0053] 8 shifting apparatus

[0054] 9 centrifugal mass

[0055] 10 disengaged position

[0056] 11 engaged position

[0057] 12 first motion range

[0058] 13 brake spring

[0059] 14 second motion range

[0060] 15 spring arm

[0061] 16 first contact surface

[0062] 17 second contact surface

[0063] 18 third contact surface

[0064] 19 angle plate

[0065] 20 opening

[0066] 21 leaf spring core

[0067] 22 pivot bearing

[0068] 23 input plate

[0069] 24 outer plate carrier

[0070] 25 radial direction

[0071] 26 axis of rotation

[0072] 27 hub

[0073] 28 toothing

[0074] 29 contact plate

[0075] 30 counter-pressure plate

[0076] 31 ramp

[0077] 32 bolt

[0078] 33 external toothing

[0079] 34 strap

[0080] 35 recess

[0081] 36 end

[0082] 37 boundary

[0083] 38 longitudinal direction

[0084] 39 x-axis

[0085] 40 y-axis

[0086] 41 first point

[0087] 42 second point

[0088] 43 third point

[0089] 44 leaf spring

[0090] 45 support

[0091] 46 clamping force