Link system for transmission of gear-change movements between a vehicle's gear lever and gearbox

Abstract: Link system for movement transmission between a gear lever and a gearbox in a vehicle, whereby the link system is coupled between a shift rod (2) and a gearchange shaft (4) which extends into the gearbox and whose bearing therein is arranged to absorb bending moments. The end of the shift rod (2) adjacent to the link system is supported by a journal bearing (32) mounted on the gearbox, and the link system includes a rigid planar link element (8), which at its opposing ends has parallel rotary articulations (14,30; 16,24) whereby the link element is coupled at one end to a crank (6) connected to the shift rod, and at the other end to a crank (10) fixed to the gearchange shaft (4).

Description: The present invention refers to a link system for transmission of gearchange movements between a gear lever and a gearbox in a vehicle whereby the link system is coupled between a shift rod which constitutes the system's movement-transmission input part and a gearchange shaft which constitutes the system's movement-transmission output part and extends into the gearbox. Various types of systems and mechanisms are previously known for transmitting gearchange movements between a vehicle's gear lever and gearbox. They involve the driver operating the gear lever, which is coupled to and controls the movement of a shift rod which then in its turn operates, via a mechanism or a link system, a gearchange shaft which extends into the gearbox. In modern cars with five-speed gearboxes the gearchange movement which can thus be transmitted from the shift rod to the gearchange shaft is a composite movement consisting partly of a pure axial displacement movement in the shift rod's longitudinal direction and partly of a rotary movement of the shift rod. In many vehicle designs it is impossible, inter alia for space reasons and because of the placing of the parts involved, for this movement transmission to take place in a direct and straight manner between shift rod and gearbox and it has to take place via a special link mechanism between the shift rod and the gearbox's gearchange shaft. A common feature of these known designs with such intermediate link mechanisms is that they are complicated in structure and expensive to manufacture because of their many constituent parts. The object of the present invention is to achieve a new and constructionally simpler type of such link system between shift rod and gearchange shaft. This involves endeavouring to have as few constituent parts and articulation points as possible in the link system. It is also desirable for the link system to be functionally simple and capable of being assembled quickly and for it to be so designed as to make it easy to install the engine unit with associated gearbox and link system from beneath the vehicle and up into the intended mounting position and in connection with the shift rod already prefitted to the vehicle. The aforesaid object is achieved according to the invention in that the bearing of the gearchange shaft (4) in the gearbox is arranged to absorb bending moments, preferably by being a two-point bearing, that the end of the shift rod (2) adjacent to the link system is supported by a journal bearing (32) mounted on the drive unit, that the link system comprises a link mechanism with a rigid and at least substantially planar link element (8) which is provided at a pair of opposite ends with rotary articulations (14, 30; 16, 24) with mutually parallel rotation spindles (30; 24), articulations by which the link element (8) is coupled at one end to a crank (6) which is connected, preferably elastically, to the shift rod (2), and at the other end to a crank (10) fixed to the gearchange shaft (4). A link system of this kind has only three articulation points, namely one at the crank of the gearchange shaft and two at the crank which is placed at the end of the shift rod. The fact that the bearing of the gearchange shaft in the gearbox absorbs bending moments (by being a two-point bearing) means that the link system can be controlled by spindles which are parallel to the gearchange shaft. No problems arise in this way with tolerances or insufficient parallelism, since only the gearchange shaft is directionally determinant. The particular unique feature of the link system according to the invention is that just one link mechanism part, namely the planar link element, is required and is sufficient to transmit both the axial movement and the radial movement (rotary movement) from the shift rod to the gearchange shaft which is aligned parallel with it. As the two rotary joints of the link element, i.e. the crank connections, have only one degree of movement freedom, namely rotation, and as the rotation spindles are parallel, both axial movement and rotary movement can be transmitted. The rigid link element is designed for maximum rigidity in both of the directions of displacement which apply to it (i.e. in its planar plane), either because of the crank movement or because of the axial displacement movement caused by the shift rod. The link system according to the invention thus has few constituent parts and is functionally simple and also easy to assemble, which makes it particularly advantageous in today's constructionally "tightly packed" cars in which the gearshift has to pass the accelerator rack, which obstructs a direct straight movement transmission between gear lever (shift rod) and gearbox (gearchange shaft). The use of cranks for rotary movement transmission between the shift rod and the gearchange shaft makes it easy, by suitable choice of respective crank lengths, to achieve desired "step-down" from the shift rod's rotary movement to a smaller rotary movement of the gearchange shaft. This is advantageous, since it is desirable for there to be relatively large gear lever movements (shift paths) clearly perceptible to the driver (and correspondingly relatively great rotary movements of the shift rod), whereas significantly smaller rotary movements are sufficient and desirable for the gearchange shaft in the gearbox. The dependent claims indicate further developments and the preferred form of the link system and its constituent parts. Claim 2 indicates a preferred form of the link element and claim 3 indicates an embodiment of the crank coupled to the shift rod, an embodiment which allows the installing of an elastic element which damps (absorbs) vibration and to some extent allows obliqueness, e.g. a rubber pad between the shift rod end situated there and the crank. Claim 4 indicates a preferred form of journal bearing which prevents the bearing from absorbing bending moments (bending forces), which instead are transmitted via the link element to the gearchange shaft and are absorbed by the fact that the latter's bearing in the gearbox is arranged to absorb bending moments. Claim 5 indicates a form of end connection for the shift rod which is preferred from the assembly viewpoint and facilitates the coupling together of the link system and the shift rod. Claim 6 indicates finally a vibration-damping form of connection between the shift rod end and the crank which is connected to it. The invention will now be explained below and described in greater detail with reference to an embodiment example, shown in the accompanying drawings, of the link system according to the invention. The drawings show the following: Fig. 1 shows schematically and in perspective a link system according to the invention which is operative between input shift rod and output gearchange shaft; Figs. 2A, 2B and 2C respectively show a side view, an end view and a plan view of the link system's crank connected to the end of the shift rod; Figs. 3A and 3B respectively show a plan view and an end view of the link system's planar link element; Figs. 4A and 4B respectively show a side view and an end view of the crank fixed to the gearchange shaft; and Fig. 5 finally shows a plan view of the link system according to the invention viewed at right angles to the planar link element's own plane. Fig. 1 shows schematically a link system according to the invention which is intended to transmit gearchange movements (in the form of axial displacement movements and/or rotary movements) from a shift rod 2 operated by the driver (by means of a gear lever not shown) to a gearchange shaft entering the vehicle's gearbox. The link system's main components for movement transmission between the shift rod 2 and the gearchange shaft 4 comprise the primary crank 6 connected elastically to the shift rod 2, the planar link element 8 which is articulatedly connected to this crank, and the secondary crank 10 which is articulatedly connected to the link element and is non rotatably attached to the end of the gearchange shaft 4. The planar link element 8 is shown in more detail in Figs. 3A and 3B, from which it can be seen that the link element is an even-thickness plane 12 in the shape of a parallelogram which on two of its parallel side edges is provided with mutually parallel articulation sockets 14, 16. The crank 10 rigidly attached to the gearchange shaft 4 is shown in more detail in Figs. 4A, 4B, from which it can be seen that the crank has in its lower part a socket-like portion 18 in whose hole 20 the gearchange shaft's end 4′ is non rotatably fitted. The crank 10 has in its upper part a socket-like portion 22 in which is fixed an articulation pin 24, which is rotatably borne in the articulation socket 16 of the link element 8. The crank 6 connected elastically to the shift rod 2 is shown in more detail in Figs. 2A, 2B and 2C. As can be seen from these diagrams, the crank 6 includes a planar link part 26 with an articulation pin 28 projecting from its lower portion and an articulation pin 30 projecting from its upper portion. The lower articulation pin 28, which is non rotatably fixed in the crank 6, is borne rotatably and displaceably in the socket-like journal bearing 32, which is rigidly mounted on the gearbox or the engine. The upper articulation pin 30 of the crank 6, which is also non-rotatably fixed in the crank, is borne rotatably in the articulation socket 14 of the link element 8. On the opposite side to the pins 28, 30, the crank 6 has a projecting bracket 34 which is provided at its outer edge with two laterally separated flange members 36, 38. The link element 8 with the articulation sockets 14, 16 may for example take the form of an integral piece of polymer material, which has the advantage of not requiring any special bearing bushes in the articulation sockets 14, 16 for the articulation pins 24, 30, which may be made of, for example, steel. Regarding the socket-like journal bearing 32 mounted on the gearbox or the engine, for the indirect support of the end of the shift rod 2, it should be noted that this bearing is so designed as to create only line contact with the crank 6's articulation pin 28, which is borne therein displaceably and rotatably and thus constitutes a supporting spindle for the extension of the end of the shift rod 2. The fact that the bearing 32 thus only creates line contact with the supporting spindle or the crank pin 28 means that only radial forces can be absorbed by this journal bearing, thus permitting a certain obliqueness in this bearing. As already indicated above, the primary crank 6 is not directly coupled to the end of the shift rod 2, and the connection comprises a to some extent non-rigid, elastic connection which will now be described. Reference is made here to Fig. 5, which shows the shift rod 2 ending in a cylindrical end portion 2′ clamped within a socket 40 which embraces the shift rod end. The socket is clamped by means of a clamp 42 which is lockable by means of a removable screw 44. The socket 40 is rigidly connected at its forward end to a plate 46 placed in the intermediate space 47 between the two flange members 36, 38 of the bracket 34. The lower edge (see Fig. 1) of the plate 46 is rigidly secured to, or manufactured integral with, a horizontal planar carrier 48 which pushes in beneath and parallel with the bracket 34 and is provided at its forward free edge with two upwardly angled flange members 50 and 52. The bracket 34 with its two flange members 36, 38 and the plate 46 and the planar carrier 48 with its two flange members 50, 52 thus delineate between them an inner space in which is installed an elastic element 54 which may, for example, consist of a rubber pad with the shape 56 of a "waisted" 8 suggested in Fig. 5. This rubber element 54 is anchored in the bracket 34 by means of a pair of bolts 58, 60 fitted in holes 62 and 64 in the bracket 34. The rubber element 54 is thus clamped between the bracket 34 with associated flange members 36, 38, which is rigidly connected to the crank 6, and the planar follower 48 with its respective flange members 50, 52 which is secured to the plate 46. Owing to the rubber element 54, compressive and tensile loads can thus be transmitted elastically between the shift rod 2 and the crank 6. This means in its turn that the rubber element 54 will act as a vibration damper which counteracts transmission of vibration arising from the engine or the gearbox (via the gearchange shaft 4, the crank 10, the link element 8 and the crank 6) to the shift rod 2 and therefrom on to the gear lever (not here shown) operated by the driver. The rubber element 54 thus has capacity for absorbing vibration coming from the engine, but it can also absorb such obliqueness movements as are transmitted to the crank 6 or the journal bearing 32 because of the engine tilt which occurs on acceleration. The rubber element 54 will also be able to absorb a minor obliqueness between the shift rod 2 and the crank pin 28 which is located in the extension of the latter and forms a supporting spindle for the end bearing of the shift rod 2. At its right end in Fig. 5, the socket 40 is provided at its lower part (in the region below the shift rod 2 in Fig. 5) with a wing-like flange portion 66 which forms an upwardly concave "cradle" to accommodate the shift rod 2 prefitted to the vehicle at the time of the installation in the vehicle from beneath of the drive unit consisting of engine, gearbox and link system, for connection to the shift rod 2. As an alternative to the flange portion 66 to accomodate the shift rod 2 at the time of installing the drive unit, an embodiment is conceivable whereby the right end of the socket 40 ends in or merges with an end portion widened in a funnel shape wherein the end 2′ of the shift rod can be accommodated and be inserted in the socket 40 during said installation.

Claims: Link system for transmission of gearchange movements between a gear lever and a gearbox in a vehicle whereby the link system is coupled between a shift rod (2), which constitutes the system's movement-transmission input part, and a gearchange shaft (4), which constitutes the system's movement-transmission output part and extends into the gearbox, characterised in that the bearing of the gearchange shaft (4) in the gearbox is arranged to absorb bending moments, preferably by being a two-point bearing, that the end of the shift rod (2) adjacent to the link system is supported by a journal bearing (32) mounted on the drive unit, that the link system comprises a link mechanism with a rigid and at least substantially planar link element (8) which is provided at a pair of opposite ends with rotary articulations (14, 30; 16, 24) with mutually parallel rotation spindles (30; 24), articulations by which the link element (8) is coupled at one end to a crank (6) which is connected, preferably elastically, to the shift rod (2), and at the other end to a crank (10) fixed to the gearchange shaft (4). Link system according to claim 1, characterised in that the link element (8) is a parallelogram-shaped plane (12) of essentially even thickness and the rotary articulations include articulation sockets (14, 16) fixed to two of the plane's parallel side edges. Link system according to claim 1 or 2, characterised in that the crank (6) connected to the shift rod (2) includes a planar link part (26) with two pins (28, 30) projecting from a side surface of that part, one of which (30) constitutes part of the articulated connection to the link element (8), while the other (28) constitutes part of the journal bearing (28, 32) for the end of the shift rod (2), and that at the opposite other side of the link part (26) there is a projecting bracket (34) with flange members (36, 38) at the outer edge. Link system according to any one of the foregoing claims, characterised in that the journal bearing (32) for the shift rod (2) is designed with only line contact for the supporting spindle (28) borne therein as the crank pin, resulting in the journal bearing (32) being only able to absorb radial forces. Link system according to any one of the foregoing claims, characterised in that the end (2′) of the shift rod (2) which is connected to the crank has an end connection with a clampable end socket (40) provided with a projecting flange portion (66) which when the link system is connected to the shift rod provides accommodation for the end of the shift rod (2) for the purpose of setting the position thereof. Link system according to claim 3 in combination with claim 4 or 5, characterised in that the end (2′) of the shift rod (2) which is connected to the link system is fixed in an end socket (4) provided with an end plate (46) which is placed on one side of a carrier (48) which is parallel to the bracket (34) and which has at its other side a pair of raised flange members (50, 52), and that a vibration-absorbing elastic element (54) is placed in the space between the bracket (34) with associated flange members (36, 38) and the carrier (48) with associated flange members (50, 52).

Inventors: LYCKBERG MATS, LYCKBERG, MATS
Applicants: SAAB AUTOMOBILE, SAAB AUTOMOBILE AKTIEBOLAG
Application year: 1992
Main classification: B60K20
IPC codes: F16H59, F16H61