GB1594664A

GB1594664A - Gear-shift device for fridtion clutches

Info

Publication number: GB1594664A
Application number: GB20707/78A
Authority: GB
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1977-06-27
Filing date: 1978-05-19
Publication date: 1981-08-05
Also published as: IT1105211B; ES471050A1; DE2728832C3; DE2728832B2; DE2728832A1; IT7849833A0

Description

(54) GEAR-SHIFT DEVICE FOR FRICTION CLUTCHES (71) We, ZAHNRADFABRIK FRIEDRICH- SHAFEN AKTIENGESELLSHAFT, of Friedrichshafen-on-the-Bodensee, Federal Republic of Germany, a Joint-Stock Company organised under the laws of the Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a gear-shift device for a friction clutch which is operable by means of an axially slidable gear-shift sleeve adapted to act on a clutch friction ring bearing against inclined surfaces.

In gear-shift devices of this kind the gearshift fork serving for the axial displacement of the gear-shift sleeve is mounted on a shaft and held by means of sliding blocks in the gearshift sleeve. In order in this case to permit automatic engagement of the clutches by means of the friction rings provided with inclined surfaces, a determined play is provided between the sliding blocks and the associated bearing surfaces on the gear-shift sleeve, so that on completion of the shift angle and also in the event of any shift shocks occurring the clutches can still tighten up. Centre locking is effected by stops by which the pivoting movement of the gear-shift fork is limited.

Although this arrangement has been successful, its adjustment is nevertheless very expensive. In order to prevent the sliding blocks from making contact prematurely and thus causing increased wear, the remote control shift stroke must in fact coincide very accurately with the shift stroke of the gearbox in which the shift is to be made. Despite the stops provided, the sliding blocks are easily damaged because the adjustment of strokes and stops is frequently not made with the necessary accuracy, so that on occasion undesirable breakdowns occur.

In addition, a shift device for a friction clutch of the kind described above is known (German Specification No. 2,045,383), in which the shift sleeve is provided with an engagement member with shift surfaces which face one another in U-shape and between which is mounted an eccentric gear-shift cam which is of special shape and provided with a plurality of gear-shift surfaces. When a gear-shift device of this kind is used for a servo clutch, it is true that after engagement the latter can tighten up and also be disengaged again without limiting the adjustment path, but the production of the gear-shift cam is very expensive because special tools are required for the purpose. Apart from the fact that in the event of it becoming necessary to change the gear-shift stroke or angle the gear-shift cam must be replaced, the cam is subject to considerable wear because its shift surfaces rub against the shift surfaces of the engagement member and efficiency is therefore also poor. The shift forces available are therefore often insufficient to disengage the clutch, because of the high losses.

The invention aims at providing a shift device for a friction clutch of the kind first mentioned, which does not have these disadvantages. At the same time, it should above all be ensured that tolerances in the shift stroke and gearbox stroke can be compensated in a simple manner, so that no deformation or damage will be caused to the transmission elements. The shift forces required for the operation of a clutch should be kept uniformly low, while wear should be practically eliminated. In addition, inexpensive production and assembly of the shift device should be ensured without accurate adjustment of the shift stroke in the shift apparatus being necessary.

To this end, the present invention consists in a gear-shift device for a friction clutch which is operable by means of an axially slidable gearshift sleeve adapted to act on a clutch friction ring bearing against inclined surfaces, wherein for the axial displacement of the gear-shift sleeve there is provided a pivotally mounted gear-shift lever one end of which is connected to the gear-shift sleeve, or to a gear-shift fork acting on the latter, by way of a shift guide and a shift pin engaging in the guide, by means of which guide and pin the gear-shift sleeve is positively guided by an engaging surface of said guide until the friction ring of the clutch comes into contact with said inclined surfaces, said shift guide having a lateral clearance portion for the purpose of engaging the clutch.

The lateral clearance portion can in a simple manner be formed by a cutout or recess, extending in the direction of displacement of the shift sleeve, in the shift guide receiving the shift pin, while the transition from the shift guide to the cutout or recess of the lateral clearance portion should be in the form of a preferably hardened disengaging edge.

It is also advantageous for the engaging surface to be in the form of a flat surface which extends in the direction of the pivoting axis of the shift lever and which may extend perpendicularly or at an angle to a shift rod carrying a shift fork. It is, however, also immediately possible for the engaging surface to be in the form of a curved path. In that case, however, it must be ensured that this path does not extend concentrically to the pivoting axis, so that a shift stroke is also obtained.

In order to reduce friction it is in addition appropriate to provide on the shift pin engaging in the shift guide a rolling body or a frictionreducing covering, for example of molybdenum.

For the alternate operation of a double clutch the shift lever may in an extremely simple manner be provided with two lever ends disposed in a mirror-image arrangement, cooperating with the shift sleeve through shift guides and pins, and constructed as a gear-shift gate.

In this case it is advantageous for the pivoting axis of the shift lever to be disposed centrally between the shift pins, co-planar with the axes of the said shift pins or offset perpendicularly to the plane of the shift pin axes.

A shift device, constructed in accordance with the invention, for a firction clutch is not only simple in respect of construction and capable of inexpensive production without difficulty because the shift guides can be milled without problems, but is also very reliable in operation and requires only small forces for engagement and disengagement. If in fact the shift sleeve is operated by means of a lever connected to it by a shift gate which for engagement purposes ensures guidance by constraint but which also has a clearance, the shift stroke and also the disengagement angle can be freely selected for a given shift angle. In addition, the shift stroke or shift angle or the disengaging forces can be varied by a simple adjustment of the machine. Moreover, since the shift pins can be equipped with rolling bodies, the frictional forces and consequently the shift forces which have to be applied are extremely small.

In the construction according to the invention the shift angle can without difficulty be made larger than would be necessary per se. A reserve for wear is thus provided. Moreover, the construction of the shift gate ensures great reliability of adjustment, so that operational breakdowns are avoided in a simple manner.

By changing the positions of the shift guides it is also possible to achieve adaptation to different circumstances in an extremely simple manner and with simple production methods, without special tools being required for the purpose. In contrast to comparable previously known arrangements, the shift device according to the invention thus provides considerable advantages of an economic nature and also in respect of the mode of operation.

In order that the invention may be more readily understood, reference is made to the accompanying drawings which illustrate diagrammatically and by way of example several embodiments thereof, and in which: Figure 1 is a partial section of a gearbox provided with a shift device; Figure 2 shows the shift device in a section on the line II-II of Figure 1; Figures 3 and 4 show different constructions of the shift gate similarly to Figure 2; Figure 5 shows a different construction of the shift device according to Figure 1; and Figures 6 to 8 show diagramatically a shift device in various shift positions.

Referring to Figure 1, the shift device 1 serves for the axial displacement of a shift sleeve 8 by which in turn, friction clutches 6 and 7 can be operated. Gears 4 or 5 disposed in a casing 2 can alternately be coupled to a gear unit shaft 3 by means of the clutches 6 and 7, each of which is in the form of a servo clutch with a friction ring supported on inclined surfaces.

As can be seen in detail in Figures 2 to 4, the shift device 1 consists of an angled shift lever 11 which is mounted for rotation by means of a pin 15 in the casing 12, and whose end cooperating with a shift fork 9 embracing the shift sleeve 8 and held slidably on a guide rod 10, is in the form of a shift gate 14. The gear-shift linkage is articulated on the other end 13 of the shift lever 11, so that by a swivelling movement about the swivelling axis 28 of the pin 15 an axial displacement of the shift fork 9 and hence of the shift sleeve 8 to the right or left is effected.

In order to make a connection to the shift fork 9, inclined shift guides 16 and 17 constructed as grooves are formed in the shift gate 14, which may be regarded as being in the form of a two-armed lever bent over at both ends, while shift pins 22 and 23, which engage in the shift guides 16 and 17 are inserted in the shift fork 9. The outer walls of the shift guides 16 and 17 form the engaging surfaces 18 and 19 for the clutches 7 and 6 respectively. In addition, each of the shift pins 22 and 23 has associated with it a clearance 20 and 21 respectively, whose transition from the shift guides 16 and 17 is in the form of a disengaging edge 26 and 27 respectively. In order to reduce friction, rolling bodies 24 and 25 are mounted on the shift pins 16 and 17 in the example of embodiment shown in Figure 2. However, a friction-reducing coating may also be applied to these pins.

If, for example, the clutch 7 is to be engaged, the shift lever 11, on whose lever end 13 (shown offset by 90 in Figure 1) the gearshift linkage is articulated, should be pivoted to the left (as viewed in Figure 2). The engaging surface 18 thus moves the shift pin 22 to the left, so that the shift fork 9 and the shift sleeve 8 connected to it are also moved to the left.

Thus a friction ring (not shown) of the servo clutch 7 runs up on an inclined surface and the clutch 7 is automatically engaged.

During the engagement of the clutch 7 the shift pin 22 is no longer guided by constraint in the shift guide 16, but on the contrary it is pushed by the shift sleeve 8 to a greater or lesser extent into the clearance 20. During the shifting operation the clutch 7 can thus tighten up unhindered and for a short time can even take overloads.

During the return movement of the shift lever 11 for the purpose of disengaging the clutch 7, the disengaging edge 26 comes to bear against the shift pin 22. Thus through the action of the shift fork 9 and the shift sleeve 8 the friction ring of the clutch 7 is applied against a coacting surface and the clutch is automatically disengaged. Particularly as the shift pins 22 and 23 are provided with rolling bodies 24 and 25, the shift forces which have to be applied for the engagement and disengagement of the shift device 1 are extremely small. Moreover, great shift accuracy is always achieved without special adjustments and adaptation being required.

In the embodiment shown in Figure 3 the shift guides 16' and 17' of the shift gate 14 extend perpendicularly to the axis in relation to the guide rod 10 by means of the engaging surfaces 18' and 19' and also the disengaging surfaces 26' and 27' the shift pins 22 and 23, which on the engagement of the clutches 6 or 7 are guided into the clearances 20' and 21' formed by recesses, can be moved axially in the same way.

In the embodiment of Figure 4, the shift guides 16" and 17" of the shift gate 13 are once again inclined in relation to the longitudinal axis of the shift lever 11, whose pivoting axis 28" is, however, offset in relation to the shift pins 22 and 23. In this way, it is readily possible to influence the inclination of the engaging surfaces 18" and 19", and consequently the shift path and the position of the clearances 20" and 21" aiid of the disengaging edges 26" arid 27".

As shown in Figure 5, the shift guides 1 6a and 1 7a are formed in the shift fork 9 and the shift pins 22a and 23a are mounted on the shift gate 14. The mode of operation of this embodiment is, however, similar to that of the embodiment shown in Figure 1.

Figures 6, 7 and 8 illustrate diagrammatically the mode of operation of the shift device 61 associated with a servo clutch. The angled shift lever 62, which is swivellable about an axis 70 and whose one. end 63 is acted on by the shift linkage, is provided at the other end 64 with a shift guide 65 into which a shift pin 66 projects.

If the shift lever 62 is swivelled out of the neutral position shown in Figure 6 into the engaging position shown in Figure 7, making the stroke a, the shift pin 66 will come to bear against the engaging surface 67 and will thus be moved to the left to the extent of the shift stroke c of the shift sleeve. A further swivelling movement to the maximum stroke b has no effect on the shift pin 66. Since the shift guide 67 is provided with a clearance 68 formed by a recess, the shift pin 66 can moreover automatically yield to the left to the extend of the distance d on engagement of the clutch or if shift shocks occur. The shift sleeve thus likewise has a clearance.

When the shift lever 63 is moved back, the disconnecting edge 69 comes to bear against the shift pin 66 as shown in Figure 8, and the pin 66 is thereby moved to the right. Because a friction ring in the clutch which is to be disengaged runs up on a coacting surface, the said clutch is automatically disengaged. The engaging surface 67 in this case limits the return movement of the shift pin 66.

WHAT WE CLAIM IS: 1. A gear-shift device for a friction clutch which is operable by means of an axially slidable gear-shift sleeve adapted to act on a clutch friction ring bearing against inclined surfaces, wherein for the axial displacement of the gearshift sleeve there is provided a pivotally mounted gear-shift lever one end of which is connected to the gear-shift sleeve, or to a gearshift fork acting on the latter, by way of a shift guide and a shift pin engaging in the guide, by means of which guide and pin the gear-shift sleeve is positively guided by an engaging surface of said guide until the friction ring of the clutch comes into contact with said inclined surfaces, said shift guide having a lateral clearance portion for the purpose of engaging the clutch.

2. A gear-shift device according to claim 1, wherein the lateral clearance portion is formed by a cutout or recess, extending in the direction of displacement of the gear-shift sleeve, in the shift guide receiving the shift pin.

3. A gear-shift device according to claim 2, wherein the transition from the shift guide to the cutout or recess of the clearance portion is in the form of a hardened disengaging edge.

4. A gear-shift device according to claims 1 to 3, wherein the engaging surface is in the form of a flat surface extending in the direction of the pivoting axis of the gear-shift lever.

5. A gear-shift device according to claims 1 and 4, wherein the gear-shift fork is carried by a guide rod and the engaging surface extends perpendicularly or at an angle to the gear-shift rod.

6. A gear-shift device according to claims 1 to 5, wherein rolling bodies or a friction-reducing coating, for example molybdenum, are disposed on the shift pin engaging in the shift guide.

7. A gear-shift device according to claims 1 to 6, wherein for the purpose of the alternate

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. left, so that the shift fork 9 and the shift sleeve 8 connected to it are also moved to the left. Thus a friction ring (not shown) of the servo clutch 7 runs up on an inclined surface and the clutch 7 is automatically engaged. During the engagement of the clutch 7 the shift pin 22 is no longer guided by constraint in the shift guide 16, but on the contrary it is pushed by the shift sleeve 8 to a greater or lesser extent into the clearance 20. During the shifting operation the clutch 7 can thus tighten up unhindered and for a short time can even take overloads. During the return movement of the shift lever 11 for the purpose of disengaging the clutch 7, the disengaging edge 26 comes to bear against the shift pin 22. Thus through the action of the shift fork 9 and the shift sleeve 8 the friction ring of the clutch 7 is applied against a coacting surface and the clutch is automatically disengaged. Particularly as the shift pins 22 and 23 are provided with rolling bodies 24 and 25, the shift forces which have to be applied for the engagement and disengagement of the shift device 1 are extremely small. Moreover, great shift accuracy is always achieved without special adjustments and adaptation being required. In the embodiment shown in Figure 3 the shift guides 16' and 17' of the shift gate 14 extend perpendicularly to the axis in relation to the guide rod 10 by means of the engaging surfaces 18' and 19' and also the disengaging surfaces 26' and 27' the shift pins 22 and 23, which on the engagement of the clutches 6 or 7 are guided into the clearances 20' and 21' formed by recesses, can be moved axially in the same way. In the embodiment of Figure 4, the shift guides 16" and 17" of the shift gate 13 are once again inclined in relation to the longitudinal axis of the shift lever 11, whose pivoting axis 28" is, however, offset in relation to the shift pins 22 and 23. In this way, it is readily possible to influence the inclination of the engaging surfaces 18" and 19", and consequently the shift path and the position of the clearances 20" and 21" aiid of the disengaging edges 26" arid 27". As shown in Figure 5, the shift guides 1 6a and 1 7a are formed in the shift fork 9 and the shift pins 22a and 23a are mounted on the shift gate 14. The mode of operation of this embodiment is, however, similar to that of the embodiment shown in Figure 1. Figures 6, 7 and 8 illustrate diagrammatically the mode of operation of the shift device 61 associated with a servo clutch. The angled shift lever 62, which is swivellable about an axis 70 and whose one. end 63 is acted on by the shift linkage, is provided at the other end 64 with a shift guide 65 into which a shift pin 66 projects. If the shift lever 62 is swivelled out of the neutral position shown in Figure 6 into the engaging position shown in Figure 7, making the stroke a, the shift pin 66 will come to bear against the engaging surface 67 and will thus be moved to the left to the extent of the shift stroke c of the shift sleeve. A further swivelling movement to the maximum stroke b has no effect on the shift pin 66. Since the shift guide 67 is provided with a clearance 68 formed by a recess, the shift pin 66 can moreover automatically yield to the left to the extend of the distance d on engagement of the clutch or if shift shocks occur. The shift sleeve thus likewise has a clearance. When the shift lever 63 is moved back, the disconnecting edge 69 comes to bear against the shift pin 66 as shown in Figure 8, and the pin 66 is thereby moved to the right. Because a friction ring in the clutch which is to be disengaged runs up on a coacting surface, the said clutch is automatically disengaged. The engaging surface 67 in this case limits the return movement of the shift pin 66. WHAT WE CLAIM IS:

1. A gear-shift device for a friction clutch which is operable by means of an axially slidable gear-shift sleeve adapted to act on a clutch friction ring bearing against inclined surfaces, wherein for the axial displacement of the gearshift sleeve there is provided a pivotally mounted gear-shift lever one end of which is connected to the gear-shift sleeve, or to a gearshift fork acting on the latter, by way of a shift guide and a shift pin engaging in the guide, by means of which guide and pin the gear-shift sleeve is positively guided by an engaging surface of said guide until the friction ring of the clutch comes into contact with said inclined surfaces, said shift guide having a lateral clearance portion for the purpose of engaging the clutch.

operation of a double clutch, the gear-shift lever is provided with two lever ends disposed in a mirror-image arrangement, cooperating with the gear-shift sleeve through shift guides and pins, and constructed as a gear-shift gate.

8. A gear-shift device according to claim 7, wherein the pivoting axis of the gear-shift lever is disposed centrally between the shift pins coplanar with their axes or offset perpendicularly to the plane of the shift pin axes.

9. A gear-shift device, substantially as herein described with reference to and as shown in any of the accompanying drawings.