CLUTCH ACTUATION MECHANISM

Abstract

A clutch actuation mechanism for actuating a clutch operator of a spring loaded friction clutch having at least a motor driven rotary disc for being connected to the clutch operator enables to operate the motor with an essentially constant and reduced torque, if a pin is attached to the disc with an offset from the disc's rotary axis, and if a lever has a curved contacting surface and if a spring forces the lever with its contacting surface against the pin to thereby provide an additional torque to the disc. Thus, the pin travels over the contacting surface when the disc rotates to open or close the spring loaded clutch via the clutch operator and the curvature enables to adapt the torque provided by the spring to the torque required to compensate for the clutch spring.

Claims

1. A clutch actuation mechanism for actuating a clutch operator of a spring loaded friction clutch, the clutch actuation mechanism comprising: at least one a rotary disc connectable to the clutch operator, the at least one rotary disc being supported by a radial bearing defining the at least one rotary disc's rotary axis and being coupled to a motor to provide a first torque to the at least one rotary disc; a pin attached to the at least one rotary disc with an offset from the disc's rotary axis; a lever having a contacting surface and being pivotally supported to pivot around a lever's pivot axis, wherein the pivot axis and the rotary axis are substantially parallel; and a spring that forces the lever with a contacting surface against the pin to thereby provide an additional torque to the at least one rotary disc, wherein the pin travels over the contacting surface when the at least one rotary disc rotates to open or close the spring loaded clutch via the clutch operator.

2. The clutch actuation mechanism of claim 1, wherein the contacting surface is curved.

3. The clutch actuation mechanism of claim 1, wherein the pin contacts the contacting surface at a first position, said first position defining a first tangent of the contacting surface, wherein the path of the pin when rotating the at least one rotary disc defines a second tangent at said first position, wherein said first and second tangents intersect at an angle , wherein the contacting surface is curved to provide an angle with $=\mathrm{Arcsin}\left(\frac{-M_C.Math.\sqrt{r^2.Math.\sin \left(\right)+{\left(d_{\min }+r\left(1-\cos \left(\right)\right)\right)}^2}}{r\left(F_0+k.Math..Math..Math.l\right).Math.d_S}\right).Math..Math.,$ wherein M.sub.C is the torque required to compensate the clutch spring, is the angle between the radial direction ({right arrow over (r)}) pointing from the rotary axis to the pin's center and the ray starting at the rotary axis through the pivot axis and, d.sub.min is the minimum distance between the pin's center and the pivot axis, F.sub.0 is the force provided by the spring with at a length l.sub.0 to the lever at a distance d.sub.S from the pivot axis, k the spring's constant and l the deflection of the spring relative to l.sub.0, where it is assumed that {right arrow over (F.sub.0)} and {right arrow over (k)} are substantially orthogonal to {right arrow over (d.sub.S)} and 10.

4. The clutch actuation mechanism of claim 1, wherein: $=\mathrm{Arcsin}\left(\frac{-M_C.Math.\sqrt{r^2.Math.\sin \left(\right)+{\left(d_{\min }+r\left(1-\cos \left(\right)\right)\right)}^2}}{r\left(F_0+k.Math..Math..Math.l\right).Math.d_S.Math.\sin \left(\right)}\right),$ wherein is the angle between the {right arrow over (F.sub.0)} and {right arrow over (k)} with {right arrow over (d.sub.S)}, and wherein the restriction of orthogonality between {right arrow over (F.sub.0)}, {right arrow over (k)} and {right arrow over (d.sub.S)} is omitted.

5. The clutch actuation mechanism of claim 1, wherein the pin is rotatably supported by the at least one rotary disc.

6. The clutch actuation mechanism of claim 1, further comprising a support structure supporting the radial bearing of the disc and the pivotable support mechanism of the lever and the motor.

7. The clutch actuation mechanism of claim 1, wherein the motor is an electro motor being coupled to the disc via a reduction gear.

8. The clutch actuation mechanism of claim 1, wherein the contacting surface has at least a first segment, and wherein the angle is substantially zero.

9. The clutch actuation mechanism of claim 8, wherein the first segment contacts the pin when M.sub.C<M.sub.min, wherein M.sub.min is smaller than 10% of the maximum torque required to compensate the clutch spring when opening or closing the clutch.

10. The clutch operating mechanism of claim 1, wherein the at least one rotary disc is a disc segment or a shaft.

11. The clutch operating mechanism of claim 1, wherein the pin is rotatably supported relative to the at least one rotary disc.

12. The clutch operating mechanism of claim 1, wherein the pin comprises a core attached to the rotary disc, wherein the core supports a radial bearing, and wherein the radial bearing comprises or supports a ring or a ring segment that is in contact with the lever's contact surface.

13. The clutch operating mechanism of claim 1, wherein the lever's contacting surface has a number of adjacent first protrusions with first recesses in between, wherein the pin has a number of adjacent second protrusions with second recesses in between, and wherein at least one of the first protrusions engage/s into at least one of the second recesses and at least one of the second protrusions engage/s into at least one the first recesses.

14. The clutch operating mechanism of claim 1, wherein a radial bearing supports a ring having the second protrusions and the second recesses.

15. The clutch operating mechanism of claim 1, wherein the pin comprises a gear wheel being rotatably supported relative to the at least one rotary disc by at least one radial bearing, and wherein the lever is a teethed rack, which teethed rack gears with the gear wheel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0029] FIG. 1 shows an example of a clutch actuation mechanism;

[0030] FIG. 2 shows a simplified representation of the lever mechanism of FIG. 1;

[0031] FIG. 3 shows a simplified representation of further lever mechanism; and

[0032] FIG. 4 shows a further example of a clutch actuation mechanism.

DETAILED DESCRIPTION

[0033] In FIG. 1 an exemplary embodiment of a clutch actuation mechanism is shown. The clutch operating mechanism has a support 80, being symbolized by a frame. The support 80 supports a motor 30 driving a disc 10 via a symbolized reduction gear 40. The motor 30 could as well drive the disc 10 via a shaft or directly, but the reduction gear 40 is a preferred alternative. The motor is preferably an electric motor.

[0034] Only for completeness, it is noted that the disc 10 is rotatably supported relative to the support, enabling a rotation of the disc 10 around its rotary axis 11. In the depicted example, the disc 10 is represented by a disc segment 10 with a disc extension 19. The disc extension 19 and the disc 10 can be made of a single piece, i.e. form a unitary piece. A clutch operator 3, here in the form of a push rod is connected to the disc 10 at a distance d.sub.o, thus the lever arm is {right arrow over (d.sub.S)}. Advancing or retracting the clutch operator 3 enables to open or close the clutch 90. The clutch operator 3 transmits a force {right arrow over (F.sub.C )} required to open the clutch.

[0035] As usual, the clutch 90 has an input shaft 91 and an output shaft 92 which can be connected enabling a torque transmission between said two shafts 91, 92. Spring loaded friction clutches 90 are known in the prior art and thus it is symbolized by a dashed box, only. To summarize: a rotation of the motor 30 is transmitted via the reduction gear into a rotation of the disc 10, and thus in principle enables to advance or retract the clutch operator 3, if the torque provided by the motor via the reduction gear is sufficient to compensate the force {right arrow over (F.sub.C)} or more precisely the torque {right arrow over (M.sub.C)}={right arrow over (F.sub.C)}{right arrow over (d.sub.0)}.

[0036] To keep the motor torque low, an additional torque is provided by a spring 4 via a lever 20. The lever 20 is pivotable supported by the support 80. The lever's pivot axis 21 is at least essentially parallel (5) to the rotary axis 11 of the disc 10. The spring 4 presses a curved contacting surface 22 of the lever 20 against a pin 12 being connected to the disc 10 at distance r from the rotary axis 11. Thus the lever 20 provides an additional torque {right arrow over (M.sub.l)} to the disc, thereby supporting the motor 30. The additional torque {right arrow over (M.sub.l)} provided to the disc 10 depends on the force {right arrow over (F)}.sub.S provided by the spring to the lever 20 at the lever arm {right arrow over (d)}.sub.S, the angle of attack of the lever 20 to the pin 12 and the lever arm {right arrow over (d)}.sub.l of the lever 20 relative to the pin 12.

[0037] To simplify an understanding of the clutch actuation mechanism, FIG. 2 shows a simplified picture of a similar clutch actuation mechanism making use of the same principle. A lever 20 with a first lever arm {right arrow over (d)}.sub.S is forced by a spring force {right arrow over (F)}.sub.S against a pin 12, being rotatable relative to a rotary axis 11. The pin 12 may thus travel along a circular path 13. The vector {right arrow over (r)} indicates the lever arm of the pin 12. The vector {right arrow over (r)} thus rotates around the rotary axis 11 and forms an angle with a ray from the rotary axis 11 through the pivot axis 21 ({right arrow over (r)}(=0)). As can be seen, the pin 12 travels over the contacting surface 22 when the disc 10 and thus the vector {right arrow over (r)} rotates. Thus, the lever arm is a function of the angle , the length r of the vector {right arrow over (r)} and the distance between the pin 12 at =0 and the pivot axis 21. Said distance is referred to as d.sub.min. When the pin 12 travels over the contacting surface 22, the angle between the normal of the contacting surface at the position where the pin 12 contacts the contacting surface varies as a function of . This angle can be reflected by the angle of the tangents t.sub.1 and t.sub.2, wherein t.sub.1 is the tangent of the contacting surface 22 at the position of the pin 12, and t.sub.2 the tangent of the circular path 13 at the pin's 12 corresponding position. It is thus possible, to compensate the torque M.sub.C provided via the clutch operator 3 to the disc 10 by adjusting the angle of the lever as function of , d.sub.min, r and {right arrow over (F)}.sub.S, wherein {right arrow over (F)}.sub.S={right arrow over (F)}.sub.0+{right arrow over (k)}.Math.l. {right arrow over (F)}.sub.0 is the force of the spring 4 at an initial length l.sub.0, {right arrow over (k)} the spring constant and l a change in length of the spring 4 relative to l.sub.0. A compensation of the torque {right arrow over (M)}.sub.C can be obtained by setting :

[00005]$=\mathrm{Arcsin}\left(\frac{-M_C.Math.\sqrt{r^2.Math.\sin \left(\right)+{\left(d_{\min }+r\left(1-\cos \left(\right)\right)\right)}^2}}{r\left(F_0+k.Math..Math..Math.l\right).Math.d_S}\right).Math..Math.,$

[0038] provided that {right arrow over (F)}.sub.S is essentially orthogonal to the lever arm {right arrow over (d)}.sub.S. If the orthogonality is not provided this can be accounted for by selecting :

[00006]$=\mathrm{Arcsin}\left(\frac{-M_C.Math.\sqrt{r^2.Math.\sin \left(\right)+{\left(d_{\min }+r\left(1-\cos \left(\right)\right)\right)}^2}}{r\left(F_0+k.Math..Math..Math.l\right).Math.d_S.Math.\sin \left(\right)}\right).Math..Math.,$

[0039] wherein is the angle between {right arrow over (F.sub.S)} and {right arrow over (d.sub.S)}.

[0040] The above formulas can be understood easily starting from the demand that the additional torque M.sub.l provided via the lever 20 to disc 10 compensates for the torque M.sub.C, i.e. M.sub.l=M.sub.C. M.sub.l equals the torque M.sub.S provided by spring 4, i.e. M.sub.l=M.sub.S. This enables to calculate the force F.sub.l provided by the lever at the contacting point via the contacting surface 22 to the pin 12:

[00007]$F_l=\frac{F_S.Math.d_S.Math..Math.\sin \left(\right)}{d_l}.$

[0041] d.sub.l can be expressed as a function of , as

[00008]$d_l={\left(r^2.Math..Math.{\sin }^2\left(\right)+{\left(d_{\min }+r\left(1-\cos \left(\right)\right)\right)}^2\right)}^{\frac{1}{2}}.$

[0042] As the torque M.sub.l is given as M.sub.l=F.sub.l.Math.r sin(), M.sub.C reads:

[00009]$-M_C=\sin \left(\right).Math.\frac{r.Math.F_S.Math.d_S.Math.\sin \left(\right)}{d_l},$

[0043] the equation can be solved as:

[00010]$=\mathrm{Arcsin}\left(\frac{-M_C.Math.d_l}{r.Math.F_S.Math.d_S.Math.\sin \left(\right)}\right)$

[0044] Expressing d.sub.1 as function of and F.sub.S as a function of l yields:

[00011]$=\mathrm{Arcsin}\left(\frac{-M_C.Math.\sqrt{r^2.Math.\sin \left(\right)+{\left(d_{\min }+r\left(1-\cos \left(\right)\right)\right)}^2}}{r\left(F_0+k.Math..Math..Math.l\right).Math.d_S.Math.\sin \left(\right)}\right)$

[0045] The description of FIG. 2 can be read equally with respect to FIG. 3, but the angles have been selected differently. Further the curvature of the lever arm is different to account for a different torque {right arrow over (M)}.sub.C to be compensated.

[0046] FIG. 4 shows a clutch actuating mechanism. The mechanism is similar to the mechanism as shown in FIG. 1 and generally the description of FIG. 1 can be read on FIG. 4 as well. The difference is that the pin 12 comprises a core 14 being attached to the disc 10. The core rotatably supports a toothed ring 15, i.e. a gear wheel 15. In turn the lever 20 is a toothed rack and the gear wheel 15 is geared with the lever 20. This gearing ensures that the ring 15 rotates on the core 14 and friction and wear is reduced when the pin travels over the lever's contacting surface 22. The core 14 and the ring 15 provide plain bearing surfaces, but other bearings can be used as well. Beyond the description of FIG. 1 can be read on FIG. 4 as well.

[0047] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.