Patent Application
20140083813
1. Field of the Invention
This invention relates generally to a clutch wherein a reinforcement mechanism is provided in a force flow zone between a pressure element and a second clutch part, which mechanism has ramps to generate an axial servo force for pressing the pressure element against the second clutch part.
2. Description of the Prior Art
Such clutches with reinforcement mechanisms are described in EP 1 882 862 A2 and EP 1 801 441 B1. The ramps can here be described as force transmission surfaces which are arranged at an angle of greater than zero to the drive shaft and at which a circumferential force is partly deflected into an axial servo force. A problem with such clutches is that on a load change, i.e. on a change from an acceleration of the output shaft to a braking of the output shaft, metallic knocking noises known as clonking noises can occur due to the mutual impacts of the ramps. As well as the noise nuisance, this leads to increased wear on the clutch. The pressure element and the second clutch part usually each have a flat friction surface for their mutual friction connection, so the pressure element is also often called a pressure plate and the second clutch part a friction disc.
A clutch includes a first clutch part connected to a drive shaft, a second clutch part connected to an output shaft and a pressure element arranged between the clutch parts, wherein a reinforcement mechanism is provided in a force flow zone between the pressure element and the second clutch part, which mechanism has ramps to generate an axial servo force for pressing the pressure element against the first clutch part.
To avoid clonking noises on load change, the ramps are arranged permanently lying against each other. A generic clutch is provided in which the clonking noises from the mutual impact of the ramps can be avoided.
The ramps are arranged permanently guided against each other. The ramps lie against each other without interruption. This permanent contact between the ramps means that in all operating states of the clutch, the ramps do not separate from each other but remain arranged lying against each other. Thus on correct operation of the clutch, there is no separation of the ramps from each other, so that on a load change in which the direction of the torque to be transmitted to the clutch changes, the ramps can no longer impact on each other, causing the clonking noise.
This permanent contact between the ramps can be achieved by a form fit of the components constituting the ramps. For this for example, the ramps can be arranged on claw-like components which are arranged to intermesh with each other by form fit such that the ramps are arranged lying against each other. To achieve this permanent contact of the ramps in practice however, constructionally complex, tight form tolerances are required.
Structurally, it is simpler to provide a force-fit connection, as permanent as possible, of the ramps. This can be achieved under the permanent action of a force with a force component perpendicular to the ramps. For this it can be provided that the mutually associated ramps are held lying against each other by a magnetic force or an electromagnetic force. For this at least one of the ramps lying against each other can be formed as a permanent magnet, for example magnetized or made from magnetic material.
Advantageously, a measure acting purely mechanically, in a manner which is structurally simple and reliable for example on vibrations of the clutch, can be provided for axial pressurization of the ramps. In a structurally simple manner, the ramps can lie against each other under spring pretension.
To generate the servo force, the ramps can each have a surface normal with a direction component which is axial to the shaft and a direction component which is circumferential to the shaft. Thus the amount of the self-reinforcement or the axial servo force can be set by adjustment of the ramps i.e. via the size of the axial direction component of the surface normals of the ramp or the force transmission surfaces. Preferably a so-called ramp angle between the axial direction of the surface normals of the respective ramps or force transmission surfaces is more than 45°, preferably more than 60°, or is around 70°. On torque transmission, a normal force, the axial direction component of which is the servo force, can be applied in the direction of the surface normal. The greater this ramp angle, the higher the proportion of the axial force component of the normal force, i.e. the greater the servo force.
The ramps can form first and second ramp pairs, in each of which a first ramp and a second ramp cooperate. The direction component, which is circumferential to the shafts, of the ramps of the first ramp pair can point in a first circumferential direction and the direction component, which is circumferential to the shafts, of the ramps of the second ramp pair can point in a second circumferential direction opposite the first circumferential direction. Thus the ramps of first ramp pair can be set in the opposite direction to the ramps of the second ramp pair. Thus the direction component, which is circumferential to the shafts, of the ramps of the first ramp pair can point clockwise and the direction component, which is circumferential to the shafts, of the ramps of the second ramp pair can point counter-clockwise.
On clutch engagement i.e. when the two clutch parts begin to rub against each other, torque is transmitted because of the rotation speed differences of the shafts relative to each other. Via the ramps of the first ramp pair which are lying against each other and have a circumferential direction component pointing in a first circumferential direction, torques acting in the first circumferential direction can be transmitted. Similarly via the ramps of the second ramp pair which are lying against each other and have a circumferential direction component pointing in the second circumferential direction, torques acting in the second circumferential direction can be transmitted. Thus torques can be transmitted in both circumferential directions via the first and second ramp pairs. Since the ramps of both ramp pairs lie permanently against each other, on a load change, i.e. on a change of circumferential direction, there is no mutual impacting of the ramps of the ramp pairs which are subjected to the torque during and after the change.
In a manner favorable for force mechanics, the ramp pairs can be distributed circumferentially in relation to the shafts, in particular at equal circumferential distances, and arranged on the same circumferential circle. Preferably the first ramp pairs and the second ramp pairs are arranged in a mutually alternating sequence circumferentially.
In a structurally simple manner it can be provided that the reinforcement mechanism has a ramp piece pair, a first ramp piece having first ramps and a second ramp piece having second ramps. Here the ramp pieces in relation to the shafts can lie against each other axially on the faces via mutually associated ramps. The ramp pieces can lie against each other exclusively via mutually associated ramps. For torque transmission, the first ramp piece can be mounted torque-resistantly on the first clutch part and the second ramp piece can be mounted torque-resistantly on the pressure element. Since the two clutch parts and hence the pressure element, for function reasons, are moved axially relative to each other on release or engagement of the clutch, for example corresponding to the first axial relative movement of the clutch parts, the first ramp piece can be mounted axially movably on the first clutch part and/or the second ramp piece can be mounted axially movably on the pressure element. However as will be explained in more detail below, the latter is less favorable because of the jerking of the pressure element away from the second clutch part on release of the clutch.
At least one ramp of the ramp pair, or one ramp piece of the ramp piece pair, can lie under spring pretension on the associated ramp or on the other ramp piece. The first ramp piece can be arranged pressed against the second ramp piece by means of a first spring in a pressure application direction away from the first ramp piece towards the second ramp piece, and/or the second ramp piece can be arranged pressed against the first ramp piece by means of a second spring against the pressure application direction. Thus the two springs can act on the ramp pieces in mutually opposing directions.
To release the pressure disc from the second clutch part, tangential leaf springs can be provided for example, as in a conventional clutch. Such a clutch can comprise a drive-side clutch component such as a flywheel or clutch basket as a first clutch part, and a clutch cover attached to the clutch component and cranked axially away, wherein the output-side second clutch part, such as the friction disc, and the pressure element such as the pressure plate, are arranged axially between the clutch component and clutch cover. Here the tangential leaf springs rest with the effect of spring force between the pressure disc and the clutch cover. The pressure plate can be pressed mechanically against the second clutch element via a so-called plate spring in the pressure application direction, wherein the plate spring is formed substantially stronger than the tangential springs. On release of the plate spring from the pressure disc on clutch release, the pressure plate is pressed away from the second clutch part directly via the tangential springs against the pressure application direction, in order thus to prevent slippage between the pressure plate and the first clutch part which would increase the wear and extend the coupling process. Thus an undesirable drag moment acting on the gearbox input shaft is avoided. Thus the second spring can exert a force against the pressure application direction on the second ramp piece and hence on the ramps lying against each other and at the same time on the pressure plate in order to release the pressure plate from the second clutch part.
In a preferred embodiment of the clutch according to the invention, it is provided that the second spring performs this function of the tangential springs conventionally used in the prior art. Consequently on opening of the clutch, i.e. on release of the pressure element from the second clutch part, the second spring can exert a force on the pressure element against the pressure application direction, in order to release the pressure element from the second clutch part in an accelerated manner. The second ramp piece can lie on the pressure element at the back in the pressure application direction. When the clutch is in a closed position, the pressure element lies on the plate springs at the back in the pressure application direction. The second spring can itself rest on the pressure element at the front in the pressure application direction and on the clutch component at the back in the pressure application direction.
The first ramp piece and/or the second ramp piece can each have a head portion with the respective associated ramps on the face, wherein the ramp pieces are arranged lying against each other on their faces via the ramps. The first ramp piece and/or the second ramp piece can each have a head portion and a foot portion, wherein the foot portion is arranged in a first guide channel on the first clutch part or in a second guide channel on the pressure element. The foot portion can connect directly to the head portion. In a structurally simple manner, the first spring can be arranged guided on the outside on the foot portion of the first ramp piece and/or the second spring can be arranged guided on the outside on the foot portion of the second ramp piece. The springs can have a spring axis, in the direction of which they act as springs. In a manner favorable for force mechanics, the spring axes of the springs, in the installation position thereof, can lie at least approximately on a common line. Also in a manner favorable for force mechanics, the ramp pieces can have a common longitudinal axis in the installation position. The longitudinal axes of the ramp pieces and the spring axes of the springs can coincide in the installation position. The ramp pieces can each be formed integrally. Furthermore in relation to their longitudinal axis they can have two middle longitudinal sections arranged vertically to each other as mirror-symmetrical planes, wherein one of the mirror-symmetrical planes is arranged perpendicular to the pressure application direction in the installation position.
The foot portion of the first ramp piece and/or the foot portion of the second ramp piece can be arranged guided axially movably in the first guide channel and/or in the second guide channel respectively. Despite the contact between the ramps or ramp parts, a movement of the pressure element relative to the clutch parts can take place in that at least one of the clutch parts is guided in an axially moveable manner.
The spring constant of the second spring can have a value which amounts to a multiple of the value of the spring constant of the first spring. This is structurally favorable since the two springs act opposite each other on the ramps, and have the same spring travels on axial movement of the ramps. The first spring can rest on the first clutch element at the front in the pressure application direction and on the first ramp piece at the back in the pressure application direction. If the first ramp piece is guided in an axially movable manner on the first clutch element, on the axial movement of the ramp pieces described above, the first spring is compressed against the pressure application direction to open the clutch. In this case the second spring “works” against the first spring and can consequently advantageously, at least to support the movement of the pressure element against the pressure application direction, have a correspondingly higher spring force than the first spring for the same spring travel. The value of the spring constant of the second spring can be five times higher, preferably fifteen times higher and ideally twenty times higher than the value of the spring constant of the first spring. The higher the spring constant of the second spring in relation to the spring constant of the first spring, the more quickly the pressure element can be separated from the second clutch part, and the slip which would otherwise occur can be avoided. On the occurrence of slip, a tilt moment described below and the axial servo force can be generated at the ramps, which would counter a separation of the pressure plate from the second clutch element. The spring constant of the first spring must merely be so high that the ramps or ramp pieces can be reliably held against each other by the first spring when the clutch is in the open position, and so low that it does not have a disadvantageous effect on separation of the clutch element from the second clutch part on opening of the clutch.
In a preferred refinement of the clutch, the cross section of the foot portion of the first ramp piece and/or the cross section of the foot portion of the second ramp piece can have a smaller dimension than the cross section of the first guide channel and/or the cross section of the second guide channel respectively. Since, as in a preferred embodiment of the clutch described above, the ramps are arranged in the head portion of the respective ramp piece and its foot portion can be guided axially in the allocated guide channel, on transmission of a torque to the ramps a tilt moment can occur in relation to the foot portion, by means of which the foot portion can tilt into a tilt position on the inside in the guide channel and seize axially. Thus the axial servo force generated at the ramps by the torque can act on the pressure element in the pressure direction. As a result the clutch force applied externally can be reduced accordingly and/or the necessary clutch engagement time shortened. Advantageously the smaller dimension and/or the surface areas of the foot portion and guide channel can be designed constructionally or by material such that they are suitable for self-inhibition of the axial displaceability of the respective foot portion by tilting it in the guide channel. In material terms, it is advantageous if at least the regions in which the foot portion and guide channel can lie against each other by friction fit in the tilt position, in this pairing have as high a coefficient of friction as possible in order to achieve the maximum degree of self-inhibition.
For improved self-inhibition of the first ramp piece, it can be provided that the foot portion in the region in which it is guided in the first guide channel has outwardly pointing protrusions which are spaced axially by an amount and on which the first ramp piece rests in the tilt position. In particular the protrusions are arranged on the outsides of the foot portion pointing in the circumferential direction. Two protrusions running in the cross section plane of the foot portion or vertically to the pressure application direction can be provided. These can be arranged spaced from each other by an amount. Via these protrusions, the foot portion of the respective ramp piece on torque transmission can lie axially friction-resistantly on the inside in the guide channel in a locally defined manner. The smaller the axial spacing of the two protrusions from each other, the greater can be the self-inhibition force generated by the resulting tilt moment.
In a mechanically favorable manner, at least one of the ramp pieces can be arranged twist-resistantly in the associated guide channel. In a manner favorable for spring mechanics, at least one of the springs can be arranged guided twist-resistantly on the associated ramp piece, in particular on the foot portion of the associated ramp segment. For this the foot portion and spring can have a rectangular cross section.
To generate an axial servo force which is equal over the circumference, and for tilt-safe separation of the pressure disc from the second clutch element, the reinforcement mechanism can have a series of ramp piece pairs which in relation to the shafts are arranged radially on a circumferential circle and evenly spaced from each other circumferentially. Preferably the ramp piece pairs are formed identically.
The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art.
The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which:
a is an extract enlargement III according to
b is an extract enlargement III according to
a and 4b are an extract enlargement III slightly enlarged in comparison with
a and 5b are an extract enlargement III slightly enlarged in comparison with
The clutch 1, 1′ has a first clutch part 2.1, 2.1′ connected to a drive shaft A, a second clutch part 2.2, 2,2′ connected to an output shaft B, and a pressure element formed as a pressure plate 3, 3′ between the clutch parts 2.1, 2.1′; 2.2, 2.2′. The clutch 1 according to the invention to a great extent has a similar structure to the clutch 1′ shown in
The embodiment shown here of the clutch 1 according to the invention in regions has a structure similar to the conventional clutch 1′ shown in
The ramps 5.1, 5.2 are arranged permanently lying against each other. The ramps 5.1, 5.2 are arranged lying against each other in all operating states of the clutch 1. In the embodiment of the clutch 1 shown here, the ramps 5.1, 5.2 always lie against each other by force fit. This is particularly clear from
The ramps 5.1, 5.2 each have a surface normal f with a direction component fa which is axial to the shafts A, B, and a direction component fu which is circumferential to the shafts A, B (
When clutch 1 transmits a torque with the resulting circumferential force U to the reinforcement mechanism, a normal force N is built up between the ramps 5.1, 5.2. (
The reinforcement mechanism 4 has a series of ramp piece pairs 14, which in relation to shafts A, B, are arranged equally spaced about the circumference and on a circumferential circle (not shown). The ramp piece pairs 14 each have a first ramp piece 15.1 with first ramps 5.1 and a second ramp piece 15.2 with second ramps 5.2, wherein the ramp pieces 15.1, 15.2 lie against each other on the face via the ramps 5.1, 5.2. Each ramp piece pair 14 has a first ramp pair 13.1 and a second ramp pair 13.2. The normal force N, and hence the servo force V as its axial force component, is built up as a reaction to a circumferential force U in the first circumferential direction u1 at the first ramp pair 13.1 (
The ramp pieces 15.1, 15.2 each have a head portion 16 and a foot portion 17. The first ramp piece 15.1 with its foot portion 17 is mounted torque-resistantly and moveably in the axial direction r in a first guide channel 18.1 at the first clutch part 2.1. The second ramp piece 15.2 with its foot portion 17 is mounted torque-resistantly in a second guide channel 18.2 on the pressure plate 3, wherein the foot portion 17 protrudes through the pressure plate 3, and on its back side guides the tangential leaf springs 12. On the flywheel side, this spring is guided by the pin 18.3. The second ramp piece 15.2 lies with its head portion 16 on the pressure plate 3 at the front in the pressure application direction a from the first ramp piece 15.1 towards the second ramp piece 15.2.
The ramp pieces 15.1, 15.2 lie permanently on each other under spring pretension. For this a first spring 19.1 associated with the first ramp piece 15.1 is provided, which rests on the head portion 16 of the first ramp piece 15.1 and on the first clutch part 2.1, on the outer edge side of the first guide channel 18.1. This first spring 19.1 presses the first ramp piece 15.1 in the pressure application direction a against the second ramp piece 15.2. Also a second spring 19.2 is provided which rests between the pressure plate 3 and the flywheel 6 and lifts the pressure plate 3 away from the second clutch part 2.2 when the clutch is released. The two springs 19.1, 19.2 each have a spring axis fe, which lies on a line with the longitudinal axes 1 of the ramp pieces 15.1, 15.2. Springs 19.1, 19.2 and ramp pieces 15.1, 15.2 are formed mirror-symmetrically in relation to the drawing plane in
For the relative angular positioning of the ramp pieces 15.1, 15.2 to each other, at the head portion 16 of the second ramp piece 15.2, side guide cheeks 20 are provided which extend laterally over the head portion 16 of the first ramp piece 15.1 (
To tilt the first ramp piece 15.1 in the first guide channel 18.1, the foot portion 17 has a smaller dimension than the guide channel 18.1. This is designed relatively slight and therefore difficult to see on the drawing. If the tilt moment exerted is high enough, a seizing or self-inhibition of the first ramp piece 15.1 in the first guide channel 18.1 occurs and thus acts as an abutment, allowing the servo force V acting on the ramps 5.1, 5.2 to increase and act in the pressure application direction a.
As evident from
To create defined contact points 21.1, 21.2 and minimize the possible wear due to the tilt process for self-inhibition against axial displaceability, two protrusions 23.1, 23.2 with rounded profile are provided at the same height on the two short sides 22 of the foot portion 17. The protrusions 23.1, 23.2 on the respective short side 22 are spaced apart by a distance b. Here the two rear protrusions 23.1 in the pressure application direction b each have a first contact point 21.1, and the two front protrusions 23.2 in the pressure application direction a each have a second contact point 21.2. As illustrated in
For better guidance of the first ramp piece 15.1 on the clutch cover 7, a guide sleeve 24 is established thereon with the first guide channel 18.1.
In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that the alternate embodiments can be practiced otherwise than as specifically illustrated and described.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102012217508.3 | Sep 2012 | DE | national |
