GB1583901A

GB1583901A - Gearwheel changespeed gear comprising a main gearbox and a two-range auxiliary gearbox

Info

Publication number: GB1583901A
Application number: GB3972577A
Authority: GB
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1976-09-25
Filing date: 1977-09-23
Publication date: 1981-02-04
Also published as: FR2365841A1; IT1079837B

Description

(54) A GEARWHEEL CHANGE-SPEED GEAR COMPRISING A MAIN GEARBOX AND A TWO-RANGE AUXILIARY GEARBOX (71) We, ZAHNRADFABRIK FRIEDRICH SHAFEN AKTIENGESELLSCHAFT, 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 gearwheel change-speed gear comprising a main gear and an auxiliary range gearbox with detent devices for axial shift positions corresponding to speed gate positions of a manual gearshift lever, the movements of which are transmitted by shift means to positive clutches in the main gearbox, parts of this shift means being of multiple construction so that, in spite of the shifts in the main gearbox occuring in a higher range in the same way as in the lower range, a particular position of the manual gearshift lever can be associated with each speed of the change-speed gear. A changespeed gear of this type is known, for example, from German Patent Specification 1130 300. These change-speed gears are in general constructed with two ranges, for example with a four-speed main gearbox which in the two ranges allows a total of eight forward speeds, of which in this case the speeds 1 to 4 lie in the lower range and speeds 5 to 8 in the upper range the gearshifts for the four speeds of the main gearbox and thus of one range being carried out according to the usual H-type gearshift motion pattern. It is possible, for example by means of a second shift finger engaging in gearshift bars in the main gearbox, to effect the changes of the four speeds of the higher range according to the same H-type shift motion pattern as in the lower range, but offset laterally and adjacent to the latter, so that the overall pattern assumes the form of a double "H" (HHshift diagram). If the gearshift arrangement concerned has an automatic changeover of the auxiliary range gearbox which takes effect on transition of the manual shift lever from an "H"-shift pattern section into the neighbouring one, then the shifting process in an auxiliary gearbox of this type takes place as simply and consistently as in a simple gearbox within this example-eight forward speeds in four associated gates so that false gearshifts can be avoided to a great extent.

In spite of these advantages the known gear changing arrangements have the disadvantage that the space required by the manual gearshift lever to move through the numerous gates has to be unusually large so as to permit reliable orientation as to the existing position of the shift lever.

In practice, however, so much space is rarely available.

The invention aims at providing a change-speed gear in which the space required for movement of the manual gearshift lever can be reduced. Accordingly, the present invention consists in a gearwheel change-speed gear, comprising a main gearbox and an auxiliary range gearbox, with detent devices for axial shift positions corresponding to speed gate positions of a manual gearshift lever, the movements of which are transmitted by way of shift means to positive clutches in the main gearbox, parts of these shift means being of multiple construction so that, in spite of the gearshifts of the main gearbox which take place in a higher range in the same way as in the lower range, it is possible to associate with each speed of the change-speed gear a particular position of the manual gearshift lever, characterised in that the detent devices are so designed and combined with spring elements that, as the manual gearshift lever is moved in the gate selection direction, at the level of the gate positions (speeds 1-2, 3-4, 5-6, 7-8) clearly perceptible, abrupt changes occur in the detent forces.

In a gearshift arrangement of such a change-speed gear the usual principle of " space orientation ", that is to say orienta- tion regarding the speed which has been engaged by reference to the position in space of the gearshift lever, is replaced substantially by the principle of "force orientation". The person operating the mechanism obtains, through the different forces, or force-free zones, additional clear information concerning the gear-change gate which has been selected at any given time, so that the distance between the gates can be shortened while at the same time there is improved orientation regarding the gate which has been selected at any time. The space orientation which is still posible here contributes further to an increased dependability of gear changing and in any case it helps to distinguish the speeds within a gate.

As a constructional means of generating forces which vary in relation to distance on an abrupt and clearly perceptible manner it is possible, in a further development of the invention, to employ a compression spring fixed between movable abutments (anchored spring).

To keep the frictional influences acting on the gearshift arrangement to a minimum it is advantageous if the measures described in claims 3 and 4 are employed. In this way the force differences in the detent device remain clearly perceptible since the frictional forces which superimpose themselves remain slight. The measure in claim 3 obviates unilateral transverse forces on the gearshift shaft so that little frictional resistance appears in the gearshift shaft guides, while with the rollers described in claim 4 the detent devices themselves become free of action and so the detent forces are approximately equal in both directions of movement.

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 one embodiment thereof, and in which: Figure 1 is an overall representaiton of a gearwheel change-speed gear with a gearshift arrangement for a motor vehicle, shown in perspective view; Fig. 2 shows a gearshift diagram looking from above on the manual gearshift lever of the change-speed gear; Fig. 3 illustrates detent forces of the manual gearshift lever, plotted against the travel s in the direction of selection (transverse to the longitudinal axis of the vehicle, selection of gate) and associated with the gear shift diagram in Fig. 2, with arrows showing the direction of the restoring force; Figs. 4 and 5 show a section on the line IV-IV of Fig. 1, made in two parts to permit a larger scale for the Figure. Fig.

5 represents the axial continuation of Fig.

4 at the dash-dot line and in this section a gear-shift shaft can be seen with the shift finger and the detent devices; and Fig. 6 is a section on the line VI-VI of Fig. 4.

The gearwheel change-speed gear 10 comprises a main gearbox 11 having four forward speeds and an auxiliary range gearbox 12 with two ranges (speeds). The auxiliary gearbox 12 has the end effect of doubling the four speeds of the main gearbov 11 so that as a result there are available 8 forward speds in all which are passed through in succession in two ranges of gear ratio. The input shaft 13 of the change-speed gear leads into the main gearbox 11, which has the auxiliary gearbox connected directly after it, so that the output shaft 14 of the change-speed gear leads out of the auxiliary gearbox 12. However, it is of no importance to the invention whether the auxiliary gearbox is situated in front of the main gearbox or behind it in the direction of power flow.

The gearshift arrangement of this change-speed gear consists of a manual gearshift lever 9, mounted on a support bracket 9a so as to pivot in several directions, the movements of said lever according to the diagram in Fig. 2 are transmitted by pulling/pushing or rotation on a gearshift bar 15 by way of a crank 16 and with the co-operation of a joint support 17, to a gearshift shaft 18, at which the selection motions (transverse to the gates 1-2, 3-4, etc.) of the manual gearshift lever appear in the form of the corresponding axial movements.

As is shown in Figs. 4 and 5, the gearshift shaft 18 is rotatable in rolling bearings 19 and 20 and is also guided for axial movement. Onward transmission of the shift movement takes place by way of one of two shift fingers 21 and 22 respectively, each of which is associated with a transmission ratio range of the auxiliary gearbox 12, to one of the gearshift bars 23, 24 or 25 which are associated respectively with the speeds, 3, 4/7, 8 or 1, 2/5, 6, or the reverse speed R, and to this end act on the appropriate shift clutches (not shown in the drawing). In speeds 1 to 4 the shift finger 21, and in speeds 5 to 8 the shift finger 22, comes into engagement with the corresponding gearshift bar 23 or 24. The gearshift shaft 18 is coupled to an automatic changeover device 26,27 which, when a predetermined position of the gearshift shaft 18 is reached or crossed, between the gates 3,4 and 5,6 or in the position in which the intermediate space between the shift fingers 21 and 22 lies in the region of both gearshift bars 23 and 24, changes the auxiliary gearbox 12 over into the other range, which may be effected, for example, by way of an electrically controlled servomechanism.

The gearshift arrangement is provided with detent devices for each gearshift position, of which the stop devices for the selection motion (gate selection) is described below with reference to Figs. 5 to 6 in further detail. The detent devices act on the gearshift shaft 18, whereby the detent forces are superimposed by spring forces generated by pre-stressed compression springs 28 and 29, the compression spring 29 being used almost exclusively for compensating the dead weight of the gearshift shaft 18.

For the gate selection motion a total of three detent devices 30, 31 and 32 are provided to which there are respectively assigned recesses 33, 34 and 35 on the gearshift shaft 18. Each of the recesses respectively has inclined flanks 33b, 34a, 34b and 35a, 35b as well as an axially parallel region 35c, 34c, and 35c. The recesses 33, 34 and the associated detent elements 36, 37 of the detent devices 30 and 31 are respectively of dual construction and disposed radially diametrically opposite with respect to the gearshift shaft 18 so that the forces exerted by detent springs 39 or 40 on the detent element 36 or 37 respectively are compensated in the radial direction in order to keep the radial loading of the bearings 19, 20 to a minimum. The twinned detent devices 30 and 31 are each disposed in a common axial plane at right angles to one another. In the case of the detent devices 30 and 31, rollers 36 or 37 respectively are provided as the detent elements and these are carried on holders 42 or 43, which are mounted for radial movement and are urged by the springs 39 or 40 radially toward the gearshift shaft 18, in such a way that said rollers can roll along on the gearshift shaft moved in the longitudinal direction.

The detent device 32, which is brought into action only when reverse speed is engaged, is a single construction only as is usual per se-with the single recess 35 and a single associated detent element 38 which has no rollers but has a conical engagement zone 44 which co-operates with the flanks 35a, 35b, of the recess 35.

Of considerable importance in the production of the sudden course, along the sliding path, of the axial forces acting on the gearshift shaft 18 is the compression spring 28 which is fixed between two discs 45 and 46. The discs 45 and 46 are supported by abutment faces 47 and 48 on the gearshift shaft or faces 49 and 50 on the casing portion surrounding the gearshift shaft 18 in such a way that the effect of the pre-stressing of the spring 28 in a predetermined sliding region of the gearshift shaft 18 is completely neutralised (fixed) and does not take effect on the gearshift shaft 18 until the outward movement of the abutment 47 via the abutment 49 or of the abutment 48 via the stop 50, which becomes apparent in a sudden rise in the axial force of the gearshift shaft.

The course of the axial forces P acting on the gearshift shaft 18, shown schematically in Fig. 3, plotted against the (axial) sliding path s of the gearshift shaft, or the gearshift path of the manual gearshift lever proportional thereto, is produced in the following manner. In the position of the gearshift shaft 18 represented in Figs. 4 to 6, which corresponds to position R in Fig.

3, the detent elements 36 are located on the axially parallel region 33c of the recess 33 and that the detent elements 37 and 38 outside the recesses on the likewise axially parallel directed outer surface of the gearshift shaft 18. Thus the detent devices exert no restoring force. However, in consequence of the application of the discs 45 and 46 to the abutment 47 of the gearshift shaft or the abutment 50 on the casing, the compression spring 28 exerts a force on the gearshift shaft 18 which in respect of the representation in Fig. 4 tends to move the gearshift shaft to the left towards the gate 3, 4 (curve section 51 in Fig. 3). If the gearshift shaft 18 is displaced slightly to the left the conical engagement zone 44 of the r adially spring-loaded detent element 38 comes into engagement with the inclined face 35 a of the recess 35, thus producing a sudden rise in the restoring force, since to the force of the spring 28 there is also added the relatively strong force of the detent device 32 (curve section 52). This strong restoring force persists as the gearshift shaft is moved further so long as the detent element 38 is in contact with the face 35a alone (curve section 53). Once the detent element 38, in a position of the gearshift shaft 18 close to the gate 1, 2, impinges on the axially parallel section 35c, the detent device 32 no longer exerts any axial force. Hence the restoring force at the gearshift shaft decreases suddenly (curve section 54) to the value of the force of the spring 28 (curve section 55) which, as the gearshift shaft moves further towards the left may extend so that the force thereby decreases to a certain extent (curve section 55).

When, on moving further to the left, the gearshift shaft 18 reaches a predetermined position close to the gate 3 4 the abutment 48 of the gearshift shaft makes contact with the disc 46 instead of the abutment 50, as a result of which the force of the spring 28 is supported within the gearshift shaft and thus is no longer effective outwardly. This leads to a sudden disappearance of the gearshift shaft restoring force (curve section 56). In a narrow area at the level of the gate 3, 4 all the forces are neutralised since the detent devices, too, are no longer exerting any axial forces (curve section 57). As the gearshift shaft 18 moves further to the left (Fig. 4 to 6), the sloping faces 33b come into engagement with the rollers 36 of the detent device 30. A suddenly increasing resistance to the movement takes place (curve sections 58 and 59). Just behind the centre of the distance between gate positions 3, 4 and 5, 6 the faces 34a come into engagement with the rollers 37 of the detent device 31 (Fig. 6), after the rollers 36 of the detent device 30 have reached the axially parallel directed outer surface of the gearshift shaft 18. As a result (after a very narrow path section with instable equilibrium), there is a reversal in the direction of the force acting on the gearshift shaft (curve section 60). On the further movement the rollers 37 come on to the axially parallel section 34 c, which brings about a sudden drop to zero of the axial force exerted by the detent device 31 on the gearshift shaft 18 (curve sections 61 and 62). This region coincides with the gate position 5, 6.

If the gearshift shaft 18 is moved further to the left towards gate position 7, 8 then after only a very short distance there is a suddenly increasing resistance to the movement which is generated by the pre-stressed spring 28 which comes into contact by way of the disc 45, while the casing abutment 49 (curve section 63). As the gearshift shaft 18 is moved further, into gate position 7, 8, the spring 28 is compressed still more and so the spring force increases slightly (curve section 64). Between the gate positions 5, 6 and 7, 8 the detent devices 30, 31 and 32 have a neutral action in respect of axial force influencing the gearshift shaft 18.

The force pattern shown schematically in Fig. 3, holds good in both directions of movement because in order to simplify the illustration the frictional influences have been left out of account. The functional progress in a movement from gate position 7, 8 towards R therefor applies analogously in the reverse sequence. The arrows shown in Fig. 3 here indicate the direction of action of the respective overall axial force.

As is shown, further, in Fig. 3, as a consequence of these forces the gearshift arrangement always tends towards one of the two gate positions 3, 4 or 5, 6 so long as the lever is not in one of the gearspeed positions R or 1 to 8. By means of these detent positions it becomes possible to obtain perfect orientation.

Moreover the forces in the detent positions are clearly distinguishable in all directions (curve section 55 to 59 or 64 to 60) so that as a result the detent positions 3, 4 and 5, 6 can also be distinguished from one another by force orientation (in detent position 3, 4 the high resistance is to the right, in detent position 5, 6 on the other hand it is towards the left.

WHAT WE CLAIM IS: - 1. A gearwheel change-speed gear, comprising a main gearbox and an auxiliary range gearbox, with detent devices for axial shift positions corresponding to speed gate positions of a manual gearshift lever, the movements of which are transmitted by way of shift means to positive clutches in the main gearbox, parts of these shift means being of multiple construction so that, in spite of the gearshifts of the main gearbox which take place in a higher range in the same way as in the lower range, it is possible to associate with each speed of the change-speed gear a particular position of the manual gearshift lever, characterised in that the detent devices are so designed and combined with spring elements that, as the manual gearshift lever is moved in the gate selection direction, at the level of the gate positions (speeds 1-2, 3-4, 5-6, 7-8) clearly perceptible, abrupt changes occur in the detent forces.

2. A change-speed gear according to claim 1, wherein in those gate positions (3-4, 5-6) from which a direct transition into another range can take place the detent forces return to zero so that the manual gearshift lever tends towards one of these gate positions (apart from the gearshift positions).

3. A change-speed gear according to claim 1, wherein production of the detent forces which change abruptly in the gate positions is effected with the co-operation of a compression spring, which is fixed between movable abutments.

4. A change-speed gear according to claim 1 or 2, with a gearshift shaft,

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. at the level of the gate 3, 4 all the forces are neutralised since the detent devices, too, are no longer exerting any axial forces (curve section 57). As the gearshift shaft 18 moves further to the left (Fig. 4 to 6), the sloping faces 33b come into engagement with the rollers 36 of the detent device 30. A suddenly increasing resistance to the movement takes place (curve sections 58 and 59). Just behind the centre of the distance between gate positions 3, 4 and 5, 6 the faces 34a come into engagement with the rollers 37 of the detent device 31 (Fig. 6), after the rollers 36 of the detent device 30 have reached the axially parallel directed outer surface of the gearshift shaft 18. As a result (after a very narrow path section with instable equilibrium), there is a reversal in the direction of the force acting on the gearshift shaft (curve section 60). On the further movement the rollers 37 come on to the axially parallel section 34 c, which brings about a sudden drop to zero of the axial force exerted by the detent device 31 on the gearshift shaft 18 (curve sections 61 and 62). This region coincides with the gate position 5, 6. If the gearshift shaft 18 is moved further to the left towards gate position 7, 8 then after only a very short distance there is a suddenly increasing resistance to the movement which is generated by the pre-stressed spring 28 which comes into contact by way of the disc 45, while the casing abutment 49 (curve section 63). As the gearshift shaft 18 is moved further, into gate position 7, 8, the spring 28 is compressed still more and so the spring force increases slightly (curve section 64). Between the gate positions 5, 6 and 7, 8 the detent devices 30, 31 and 32 have a neutral action in respect of axial force influencing the gearshift shaft 18. The force pattern shown schematically in Fig. 3, holds good in both directions of movement because in order to simplify the illustration the frictional influences have been left out of account. The functional progress in a movement from gate position 7, 8 towards R therefor applies analogously in the reverse sequence. The arrows shown in Fig. 3 here indicate the direction of action of the respective overall axial force. As is shown, further, in Fig. 3, as a consequence of these forces the gearshift arrangement always tends towards one of the two gate positions 3, 4 or 5, 6 so long as the lever is not in one of the gearspeed positions R or 1 to 8. By means of these detent positions it becomes possible to obtain perfect orientation. Moreover the forces in the detent positions are clearly distinguishable in all directions (curve section 55 to 59 or 64 to 60) so that as a result the detent positions 3, 4 and 5, 6 can also be distinguished from one another by force orientation (in detent position 3, 4 the high resistance is to the right, in detent position 5, 6 on the other hand it is towards the left. WHAT WE CLAIM IS: -

1. A gearwheel change-speed gear, comprising a main gearbox and an auxiliary range gearbox, with detent devices for axial shift positions corresponding to speed gate positions of a manual gearshift lever, the movements of which are transmitted by way of shift means to positive clutches in the main gearbox, parts of these shift means being of multiple construction so that, in spite of the gearshifts of the main gearbox which take place in a higher range in the same way as in the lower range, it is possible to associate with each speed of the change-speed gear a particular position of the manual gearshift lever, characterised in that the detent devices are so designed and combined with spring elements that, as the manual gearshift lever is moved in the gate selection direction, at the level of the gate positions (speeds 1-2, 3-4, 5-6, 7-8) clearly perceptible, abrupt changes occur in the detent forces.

4. A change-speed gear according to claim 1 or 2, with a gearshift shaft,

mounted for axial and rotary motion in a casing of the change-speed gear and provided with detent recesses, which is slid axially for the purpose of gate selection, wherein the detent recesses and the detent elements associated therewith are of dual construction and are disposed radially diametrically opposite in respect of the gearshift shaft.

5. A change-speed gear according to claim 4, wherein in part at least of the detent devices rollers, are provided as detent elements which can roll along the gearshift shaft and are carried on radially movable and radially spring-loaded holders.

6. A gearwheel change-speed gear, substantially as herein described with reference to and as shown in the accompanying drawings.