GB2145782A

GB2145782A - Gearshift mechanism for a change-speed gearing of a motor vehicle

Info

Publication number: GB2145782A
Application number: GB08417186A
Authority: GB
Inventors: Walter Guss; Herwig Leinfellner; Kiyokazu Okubo
Original assignee: Steyr Daimler Puch AG
Current assignee: Steyr Daimler Puch AG
Priority date: 1983-07-05
Filing date: 1984-07-05
Publication date: 1985-04-03
Also published as: ATA245583A; GB8417186D0; DE3424793C2; GB2145782B; FR2548800A1; FR2548800B1; AT390038B; DE3424793A1

Abstract

The gearshift mechanism for a change-speed gearing of a motor vehicle includes four gearshift rods (1,2,3,4) which are arranged in two pairs with a gearshift finger (12,13) associated with each pair (1,2) (3,4) of the gearshift rods. One pair (3,4) of the gearshift rods includes the gearshift rod (3) for the gears of the three highest speeds, whilst the other pair (1,2) of the gearshift rods includes the gearshift rod (2) for an extremely low-speed gear and the gearshift rod (1) for the two lower- speed gears. The gearshift rod (3) for the three highest speeds carries two gearshift forks (6,6' (not shown, Fig. 2)), one (6') of which is fixedly secured to the gearshift rod (3) whereas the other gearshift fork (6) is longitudinally displaceably mounted and provided with a separate coupling member (5). <IMAGE>

Description

SPECIFICATION Gearshift mechanism for a change-speed gearing of a motor vehicle This invention relates to a gearshift mechanism for a change-speed gearing of a motor vehicle, comprising a plurality of parallel, longitudinally displaceable gearshift rods having coupling members and gearshift forks mounted thereon, and further comprising a longitudinally displaceable gearshift crossshaft positioned normal to the gearshift rods and provided with two axially spaced gearshift fingers which cooperate with the coupling members and are engageable with the latter by a longitudinal displacement of the gearshift shaft, whereas a rotation of the gearshift shaft effects a displacement of the gearshift rods.

Such gearshift mechanism are well known and in such mechanisms, the parallel gearshift rods are juxtaposed and closely spaced in order to reduce the displacements and angular movements to be performed by the gearshift shaft. Nevertheless, relatively large distances from the gearshift shaft to the coupling members on the gearshift rods and from the gearshift rods to the synchromesh clutches must be bridged in these known designs so that the gearshift fingers and coupling members as well as the gearshift forks are long and must be properly reinforced for a satisfactory transmission of force. As a result, relatively heavy components must be used for the gearshift fingers, coupling members and gearshift forks.

Whereas it is also known to provide two spaced coupling members on the gearshift shaft, which is longitudinally displaceable and rotatable and is positioned across the parallel gearshift rods (German Patent Specification 2506570), that publication relates only to a four-speed transmission in which the second gearshift finger serves to facilitate the engagement of a synchronizing clutch and the arrangement of the gearshift rods is unchanged in other respects.

It is an object of the invention to eliminate these disadvantages and to provide a gearshift mechanism of the kind referred to above and suitable for gearing for a larger number of speeds and distinguishes from known arrangements by comprising gearshift elements which are comparatively simple and light in weight.

The present invention consists in a gearshift mechanism for a change-speed gearing of a motor vehicle, comprising a plurality of parallel, longitudinally displaceable gearshift rods having coupling members and gearshift forks mounted thereon for actuating the synchromesh clutches, a longitudinally displaceable gearshift cross-shaft positioned normal to the gearshift rods and provided with two axially spaced gearshift fingers with cooperate with the coupling members and are engageable with the latter by a longitudinal displacement of the gearshift shaft, whereas a rotation of the gearshift shaft effects a displacement of the gearshift rods, wherein four gearshift rods are provided, arranged in two pairs, a gearshift finger is associated with each pair of gearshift rods, one pair of the gearshift rods including the gearshift rod for engaging reverse gear and the gearshift rod for the gears of the three highest speeds, the other pair of gearshift rods including the gearshift rod for an extremely low-speed gear and the gearshift rod for the two lower-speed gears, the gearshift rod for the three highest speeds carrying two gearshift forks, one of which is fixedly secured to the gearshift rod whereas the other gearshift fork is longitudinally displaceable on the rod and provided with a separate coupling member.

Because the four gearshift rods are arranged in pairs and the two pairs of gearshift rods are spaced apart with a gearshift finger associated with each pair, the distance between the gearshift shaft, the gearshift rods and the synchromesh clutches is reduced as desired and the shafts of the gearing can be arranged as desired. This results in a simpler structure and of lighter weight so that the shorter gearshiftelements may be lighter in weight. The gearing comprises six gears for forward speeds, one of which is an extremely low speed, e.g. for cross-country travel. In spite of its large number of gears, the gearshift mechanism is of simple construction.A further simplification is due to the fact that a common gearshift rod is provided for the gears for the three highest speeds but this requires the provision of a gearshift fork which is freely displaceable on the gearshift rod and carries a separate coupling member so that one speed can be selected by a displacement of the gearshift rod and of the gearshift fork which is fixedly secured to the gearshift rod and the other speed can be selected by a displacement of the other gearshift fork while the gearshift rod remains in position.

According to a further feature of the invention the distance from the coupling member of the reverse gearshift rod to the coupling member of the gearshift rod for the extremely low-speed gear, measured in the longitudinal direction of the gearshift shaft, equals the distance between the two gearshift fingers, the reverse gearshift rod being coupled by a pin-slot connection to the associated gearshift fork, the displacement required for the disengagement of the extremely low-speed gear being increased at least by the displacement required to engage the reverse gear. By this arrangement, the structure and operation are further simplified because the same gate slot is associated with the extremely low-speed gear and the reverse gear although different gearshift fingers are used to shift these two gears.In order to prevent engagement of the extremely low-speed gear during engagement of the reverse gear, the displacement required for the disengagement of the extremely lowspeed gear is correspondingly increased. On the other hand, the reverse gear is not affected by the engagement of the extremely low-speed gear because the gearshift rod for the reverse gear is coupled to the associated gearshift fork by means of the pin-slot connection and the slot allows for lost motion of the corresponding gearshift rod.

Also in accordance with a still further feature of the invention, a spring is provided which urges the gearshift shaft against a stop to define for the gearshift shaft that position in which one gearshift finger engages the coupling member of the gears for the speeds preceding top speed, the stop is resiliently yieldable so that the gearshift finger can reach the coupling member for the top speed gear, and an oblique ramp and a ball or the like is provided resiliently urged against said ramp in order to increase the axial force which has to be exerted on the gearshift shaft shortly before it reaches the position which is respectively associated with the engagement of the reverse gear and the extremely low-speed gear.Whenever a gear has been disengaged, the first spring returns the gearshift shaft to its neutral position, which is disposed in conventional manner between the third and fourth gears. For engaging the top speed gear, the force of the spring acting on the stop must be overcome so that the first spring is no longer effective. Finally, the ramp and the ball which is resiliently urged against the ramp ensure that the axial force to be exerted on the gearshift shaft is appreciably increased shortly before the extremely low-speed gear is engaged so that a highly sensitive shifting of the gears is permitted and a selection of a wrong gate slot will be avoided as far as possible.

In the accompanying drawings: Figure 1 is a vertical cross-section of a gearshift mechanism for the change-speed gearing of a motor vehicle according to the present invention, Figure 2 is a transverse cross-section taken on the line ll-ll of Figure Figure 3 is a view similar to Figure 2 taken adjacent the gearshift rod for the reverse gear, and Figure 4 is a vertical cross-section taken on the line IV-IV of Figure 1.

Referring now to the drawings, the changespeed gearing comprises six forward gears and a reverse gear.

The arrangement includes four parallel gearshift rods 1, 2, 3, 4, which are longitudinally displaceable and carry coupling members 5, 5a and gearshift forks 6, 6', 6a for actuating the synchromesh clutches, which are not shown. The gearshift mechanism also comprises a gearshift cross shaft 7, which lies normal to the gearshift rods 1, 2, 3, 4 and can be partially rotated by a crank arm 8. The gearshift shaft 7 is longitudinally reciprocatable by means of a striker or lifting arm 10, which is secured to a shaft 9 and engages with a coupling member 11.

The gearshift rods are arranged in two pairs 1, 2 and 3, 4 and gearfingers 1 2 and 1 3,fixedly secured to the gearshift shaft 7, are associated with the respective pairs. A slotted U-shaped member 1 4 is associated with each of the gearshift fingers 1 2, 1 3 and these Ushaped members follow the axial movement of the gearshift shaft 7, but are held against rotation by a rod 1 5 (Figure 4), positioned parallel to the gearshift shaft 7. When one of the coupling members 5, 5a engages one of the gearshift fingers 1 2, 1 3, the slotted Ushaped members 14 lock the remaining coupling members 5, 5a.In the position shown in Figure 1, the upper gearshift finger 1 3 is interengaged with the coupling member 5 of the gearshift rod 3 and it is apparent that the remaining coupling elements are locked and that the lower gearshift finger 1 2 is disposed outside the region in which it can interengage with the coupling members 5 of the gearshift rods 1, 2. A longitudinal displacement can be imparted to the gearshift shaft 7 by means of the lifting arm 10 in order to select a gate slot so that the gearshift finger 1 2 or the gearshift finger 1 3 is caused to engage one of the coupling members 5, 5a of the gearshift rods 1 to 4.The gearshift shaft 7 can then be rotated by the crank arm 8 so as to shift the associated gearshift rod and gearshift fork in order to engage or disengage a selected gear The gearshift rod 1 carries the gearshift forks for the first-speed and second-speed gears (not shown). The gearshift rod 2 is associated with an extremely low-speed gear, i.e. a cross-country gear. The gearshift rod 3 is associated with the gears for the three highest speeds, i.e., for the third, fourth and fifth gears. The gearshift rod 4 serves to engage the reverse gear. To permit any of the three (higher) gears to be selectively engaged by means of only one gearshift rod 3, as shown in Figure 2, that rod 3 carries two gearshift forks 6, 6'. The gearshift fork 6' is fixedly secured to the gearshift rod 3 and is associated with the top speed gear. The other gearshift fork 6 is slidably mounted on the gearshift rod 3 and has a separate coupling member 5, whilst the coupling member 5a is fixedly connected to the gearshift rod 3. The gearshift rod 6 is reciprocated on the gearshift rod 3 in order to engage and disengage the third-speed and fourth-speed gears.

The distance between the two gearshift fingers 12, 1 3 is equal to the distance from the coupling member 5 of the reverse gearshift rod 4 to the coupling member 5 of the gearshift rod 2 for the extremely low-speed gear or cross-country gear. For this reasons, the two gearshift fingers 12, 1 3 engage with respective coupling members 5 when the gearshift shaft 7 is in its lowermost position.

In order to prevent engagement of the reverse gear during the engagement of the crosscountry gear, the reverse gearshift rod 4 is not directly connected to the associated gearshift fork 6a, as is apparent from Figure 3. The gearshift fork 6a is pivoted on the pivot 1 6 and has an angled slot 17, which receives a pin 1 8 carried by a transverse arm 1 9 that is fixedly secured to the gearshift rod 4.

When the gearshift rod 4 is lowered from the position shown in Figure 3, in order to engage the cross-country gear, the gearshift fork 6a will not be carried along because the pin 1 8 is capable of a lost motion in that portion of the slot 1 7 which is parallel to the gearshift rod 4. During raising of the gearshift rod 4, the pin 1 8 carries the gearshift fork 6a along in the clockwise sense so that the reverse gear will be engaged. In that case the extremely low-speed gear or cross-country gear will remain disengaged because the displacement required for its disengagement is longer by the displacement required for the engagement of the reverse gear.

It is apparently from Figure 1 that the lifting arm 10 is biassed by a coiled torsion spring 20, which urges the lifting arm against a stop 21 in a position which corresponds to the gate slot for the third-speed and fourth-speed gears so that the coupling element 5 of the gearshift rod 3 engages the gearshift finger 13. But in this position the coupling element 11 also engages a pot-shaped stop 23, which is biased downwardly by a spring 22. When it is desired to engage the fifth-speed gear (coupling member 5a), the gearshift shaft 7 must be lifted against the force of the spring 22.

The coupling member 11 is provided with a ramp 24 (Figure 4) and spring 26 urges a ball 25 against the ramp 24. The ramp becomes effective shortly before the gearshift shaft 7 assumes the position associated with the reverse gear and the cross-country gear and in which the gearshift fingers 12, 1 3 interengage with the coupling members 5 of the gearshift rods 2 and 4. As the ball 25 moves up the ramp 24, a stronger force must be exerted against the action of the spring 20 in order to depress the gearshift rod 7 so that the driver becomes aware he is leaving the usual gate slots.

Claims

1. A gearshift mechanism for a changespeed gearing of a motor vehicle,comprising a plurality of parallel, longitudinally displaceable gearshift rods having coupling members and gearshift forks mounted thereon for actuating the synchromesh clutches, a longitudinally displaceable gearshift cross-shaft positioned normal to the gearshift rods and provided with two axially spaced gearshift fingers with cooperate with the coupling members and are engageable with the latter by a longitudinal displacement of the gearshift shaft, whereas a rotation of the gearshift shaft effects a displacement of the gearshift rods, wherein four gearshift rods are provided, arranged in two pairs, a gearshift finger is associated with each pair of gearshift rods, one pair of the gearshift rods including the gearshift rod for engaging reverse gear and the gearshift rod for the gears of the three highest speeds, the other pair of gearshift rods including the gearshift rod for an extremely low-speed gear and the gearshift rod for the two lower-speed gears, the gearshift rod for the three highest speeds carrying, two gearshift forks, one of which is fixedly secured to the gearshift rod whereas the other gearshift fork is longitudinally displaceable on the rod and provided with a separate coupling member.

2. A mechanism according to claim 1, wherein the distance from the coupling member of the reverse gearshift rod to the coupling member of the gearshift rod for the extremely low-speed gear, measured in the longitudinal direction of the gearshift shaft, equals the distance between the two gearshift fingers, the reverse gearshift rod being coupled by a pin-slot connection to the associated gearshift fork, the displacement required for the disengagement of the extremely low-speed gear being increased at least by the displacement required to engage the reverse gear.

3. A mechanism according to claim 1 or 2, wherein a spring urges the gearshift shaft against a stop to define for the gearshift shaft that position in which one gearshift finger engages the coupling member of the gears for the speeds preceding top speed, the stop is resiliently yieldable so that the gearshift finger can reach the coupling member for the top speed gear, an oblique ramp and a ball or the like being provided which latter is resiliently urged against said ramp in order to increase the axial force which has to be exerted on the gearshift shaft shortly before it reaches the position which is respectively associated with the engagement of the reverse gear and the extremely low-speed gear.

4. A gearshift mechanism for a changespeed gearing of a motorvehicle substantially as described with reference to, and as illustrated in, the accompanying drawings.