GB2269431A

GB2269431A - Arrangement for detecting the shift position of a vehicle transmission system comprises parallel resistance elements

Info

Publication number: GB2269431A
Application number: GB9314025A
Authority: GB
Inventors: Ingo Franz; Reiner Voss
Original assignee: Fichtel and Sachs AG
Current assignee: ZF Sachs AG
Priority date: 1992-07-11
Filing date: 1993-07-07
Publication date: 1994-02-09
Anticipated expiration: 2013-07-07
Also published as: SE9302145D0; FR2693532A1; FR2693532B1; SE9302145L; GB2269431B; SE505926C2; DE4222878A1; GB9314025D0

Description

2269431 ARRANGEMENT FOR DETECTING THE SHIFT POSITION OF A MOTOR VEHICLE

TRANSMISSION SYSTEM The invention relates to an arrangement for detecting the operative shift position of a motor vehicle transmission system.

Conventional motor vehicle transmission systems generally have several selector shafts which are displaceably guided in their longitudinal axis and are allocated one or more respective speeds to be shifted. The axial position of the selector shaft determines the shift position of the speed. Whereas the selector shafts allocated directly to the speeds are normally shifted exclusively in their longitudinal axis for the changeover movement, these selector shafts are in turn moved by a central selector shaft which is mounted in the gearbox so as to be not only displaceable in the direction of their longitudinal axis but rotatable round their longitudinal axis. The central selector shaft is normally actuated via a manually operable selector lever, 2 the selector shafts are moved by actuators for automation of the transmission system.

For a plurality of applications, in particular for controlling an automatic clutch or for controlling the actuators during automation of the transmission system, knowledge of the actual shift position of the transmission system is required. It is known from DE-U-91 09 855 to arrange, on the central selector shaft of the transmission system which is both displaceable in the direction of its longitudinal axis and rotatable round the longitudinal axis, a magnet which is opposed by several Reed contacts combined to form a unit at the positions of the magnet defined by the shift positions of the gear. One of the respective Reed contacts is closed in each case without being touched as a function of the shift position of the central selector shaft and therefore signals the instantaneous shift position of the gear. With the known arrangement, the Reed contacts are arranged substantially radially to the central selector shaft and are uncoupled from one another by magnetic screens. The unit is inserted from the exterior through an orifice in the wall of the gearbox and closes the orifice in the manner of a cover. However, the disposition of the Reed contacts necessitates a comparatively large amount of space which is very limited in mass produced transmission systems. Furthermore, the accuracy of positional detection with which the Reed contacts detect the position of the selector shaft is comparatively low zo the accuracy of shifting is not sufficient for a plurality of applications, in particular with automatic clutches, particularly if intermediate positions of the selector shafts also have to be recognised.

A similar arrangement for detecting the shift position of a motor vehicle transmission system is known from FR-A-2 581 002, in which, instead of the detection of the position of the central selector shaft in the direction of its 3 longitudinal axis and in its circumferential direction, only the movement of the selector shafts which are allocated directly to the speeds and are only longitudinally moveable is monitored. Each of the selector shafts issues from the gearbox with one of its ends and enters an orifice in a sensor casing attached to the gearbox. A plurality of light barriers which are interrupted or cleared as a function of the position of the selector shaft is arranged in succession in the displacement direction of the selector shaft in the sensor casing. The light barrier signals are linked to one another and are evaluated. With this arrangement also, apart from the comparatively great space requirement, only a comparatively small number of discriminatable positions of the individual selector shafts may be achieved outside the gearbox. An arrangement is known from DE-A-38 36 145 (GB-A-2 224 791) which allows analog detection of the position of the central selector shaft. The central selector shaft is connected to the wiper of a planar potentiometer which rests resiliently on a resistance face of the planar potentiometer and moves along the resistance face in two control directions extending transversely to one another according to the movement of the central selector shaft. The resistance face which may be curved cylindrically round the longitudinal axis of the selector shaft is operated alternately in the two control directions in potentiometer circuits lying transversely to one another, one evaluation circuit deriving position signals corresponding to the co-ordinates of the wiper from the resistance conditions. An arrangement of this type allows comparatively precise determination of the position co-ordinates even for intermediate positions between the individual shift positions of the gear, and virtually no mechanical adjustment of the planar potentiometer is required as the information required to identify the shift positions may be stored in a memory in which they may be input electronically according to the current situation of the planar potentiometer. Such an arrangement may therefore be 4 adapted without difficulty to different situations and different shift paths.

The planar potentiometer used in the known arrangement for determining the position co-ordinates is comparatively sensitive to soiling, so it has to be arranged outside the lubricant-filled gearbox. Although the planar potentiometer is flat in shape, additional space has to be available at a point of the gearbox which may be coupled to the central shaft. This may cause problems of installation in individual cases. Furthermore, the planar potentiometer has to be protected from the rough operating conditions on the motor vehicle, and measures have to be taken to adapt the planar potentiometer to the comparatively high changing temperatures in the region of the transmission system. The abovementioned operating conditions entail comparatively high expenditure for protection of the planar potentiometer.

Design and Elektronik 20, September 1991, pages 106-108 and Feinwerktechnik and Messtechnik 99 (1991), 7-8, pages 339-341 disclose membrane keyboards comprising two meshing comb-like conductor arrangements with a plurality of conductor portions arranged next to one another in parallel in each case between a supporting plate and a covering film over it. The conductor portions of one conductor arrangement are connected to one another by identical resistors in each case whereas the conductor portions of the other conductor arrangement which are insulated from this conductor arrangement are connected to one another. A foil coated with a semiconductor polymer material is applied to the conductor arrangements. The semiconductor polymer material has the property that its specific resistance diminishes as soon as it is loaded with pressure. When the membrane keyboard is loded with prdssure, the conductor portions of the two conductor arrangements are electrically conductively connected by the semiconductor polymer material at the pressure-loaded point. The position of the pressure loading may therefore be determined by measuring the resistance conditions of the arrangement forming a potentiometer circuit. It is also known from Feinwerktechnik and Messtechnik 99 (1991) 7-8, pages 339341, to use sensors of the described type f or position determination and also to determine surf ace co-ordinates by using two sensors with transversely extending conductor portions. It is also known to determine the contact pressure from the value of the change in resistance.

An object of the invention is to provide an arrangement for detecting the shift position of a motor vehicle transmission system which may be arranged compactly and simply on the transmission system, can withstand the rough operating conditions of the motor vehicle and allows exact detection of the shift position of the gear. According to the invention there is provided arrangement for detecting the shift position of a motor vehicle transmission system with a gearbox containing at least one selector shaft controlling the changeover of speeds the shaft being mounted for displacement in the direction of its longitudinal axis and/or rotatably Around its longitudinal axis, said arrangement comprising 6 at least one planar sensor element associated with a control element which is connected to the selector shaft to follow the movement thereof and rests resiliently and displaceably in the control direction on the sensor element and, according to its rest position, defines a specific resistance value of the sensor element and an evaluating circuit which is connected to the sensor element and, depending on the resistance value, produces a signal which corresponds to the position of the selector shaft to represent the shift position of the transmission system, wherein the sensor element is arranged inside the gearbox and for at least one control direction of the control element, comprises a conductor layout or network with a plurality of mutually parallel conductor portions which are arranged next to one another at equal intervals, extend transversely to the control direction and are connected to one another by equal electrical resistances and a contacting or connecting means which extends transversely over the conductor portions is substantially electrically insulated from the conductor portions in the rest condition and, by exertion of a pressing force transversely to the face of the conductor network may be conductively connected to the conductor portions, the conductor network and the 7 contacting means being surrounded in a sealed manner by a sheath which is designed, at least on one of its flat sides, as a sheet, with the control element in the form of a pusher element resting on the exterior of the flat side of the sheet.

The contacting or connecting means may include another conductor layout or network with conductor portions interdigitated between the conductor portions of the first network and a plastics coating which changes resistance as a function of pressure overlying the networks.

A sensor element of this type can take the form of a flat, for example sheet-form body, and requires extremely little space. In contrast to the resistance face, exposed for contact with the wiper, of the planar potentiometer from DE-A-3836145, the conductor portions defining the resistance value including the conductor networks are arranged within the sheath and are therefore protected, whereas the pusher element producing the contact merely mechanically connects the contacting means to one or optionally more adjacent conductor portions at the point determined by its position. The flat, protected construction of the sensor element allows the sensor element to be arranged in the interior of the 8 gearbox' in the immediate vicinity of the selector shaft to be monitored without significant constructional changes to. the wall of the gearbox. As the conductor portions may be arranged comparatively closely to one another, substantially continuous discrimination of the position of the pusher element may be achieved. For evaluating the resistance value, determined by the position of the pusher element, between the terminal conductor portions and the contacting arrangement forming an interposed pick-off similar to a potentiometer circuit, it is possible to follow DE-A-3836145, to which explicit reference is made.

In a preferred embodiment, the sensor element rests in a planar manner on the internal face of a cover removably sealing an orifice in the gearbox. It therefore forms part of the wall of the gearbox without the shape of the gearbox, in particular toward the exterior, having to be changed. As the sensor element is very thin, for example has a thickness of only 0.5 to 1 mm, the installation site may be selected substantially freely and defined exclusively by the position of the selector shaft.

It goes without saying that the sensor element monitors the position either only in one control direction or in two control directions extending transversely to one 9 another, depending on the number of control directions in which the selector shaft to be monitored can be moved. An embodiment is preferred for the last-mentioned variation in which the sensor element surrounds the selector shaft over an arcuate or cylindrical face equidistant to its longitudinal axis, the sensor element within the sheath comprising two pairs, insulated from one another by an insulating foil, of one respective conductor network and one respective contacting means with its conductor network. The conductor portions of the two interdigitated conductor networks extend substantially perpendicularly to one another. By means of such an arrangement, the position, for example of the central selector shaft of the transmission system, may be discriminated directly according to longitudinal position and rotational angle.

However, two-dimensional direction recognition may alternatively be achieved with a reduced number of necessary conductor networks or contacting networks in that the contacting means has a planar resistance path which is made of a plastics resistance material changing its specific electric resistance as a function of pressure and which rests jointly on all conductor portions of the first-mentioned conductor arrangement and on a second conductor networks extending along the f irst conductor arrangement in the control direction. In a first control direction extending transversely to the conductor portions, the evaluating circuit evaluates the resistance of the arrangement forming a potentiometer circuit in this direction. For determining the position of the pusher element in a second control direction extending along the conductor portions, the sensor element or the pusher element are allocated oblique faces which, in the second control direction, change the pressing force as a function of the position of the pusher element relative to the sensor element. In contrast to the embodiment described hereinbefore, a single set of conductor networks is sufficient for detecting the two- dimensional position co-ordinates.

For determining the position of a central selector shaft which is displaceable in the direction of its longitudinal axis and also rotatable about its longitudinal axis, the sensor element may be arranged on a carrier face which surrounds the selector shaft in the form of an arc at a radial distance f rom the selector shaft which increases or decreases either in the direction of the longitudinal axis of the selector shaft or in the circumferential direction of the selector shaft. For the sake of simplicity, the carrier face may be a cylindrical face arranged parallel to the axis but eccentrically to the selector shaft. However, the carrier face may also be an arcuate face with an axis which intersects the longitudinal axis of the selector shaft at an acute angle.

The second conductor network of the contacting means described hereinbefore may be a planar conductor path which is coated with the resistance path in a planar manner. In such an embodiment, the resistance path is therefore located between the two conductor networks. However, the device may be arranged such that the second conductor networks has a plurality of conductor portions which are parallel to one another and to the conductor portions of the first conductor networks and are arranged at a distance from one another and next to one another in a common surface to the conductor portions of the first conductor networks the conductor portions being 12 conductively connected by a connecting line, and in that the resistance path rests on,all conductor portions of the first and secon - d conductor networks Such an arrangement allows all conductor portions to be produced together in the manner of a "printed circuit".

Regardless of whether the resistance value of the resistance path which is dependent on the pressure force is utilised for determining the position, the evaluating circuit can comprise a signal store for at least- one desired value of the signal representing the contact resistance and can produce a signal respresenting the readiness for operation of the sensor element as a function of the contact resistance and the desired value. The fact that the pressure force changes when the sensor element or the pusher element is depleted is utilised so that the state of wear may be monitored by comparison with a desired value representing the new state.

Although the spacing of the conductor portions may be selected comparatively closely, it may happen that for specific applications the resolution of the sensor element is not sufficiently small. In an advantageous embodiment, therefore, the sensor element for at least one control direction.comprises two pairs of one respective.conductor networks and one respective contacting networ.kswhich are insulated from one another by an insulating foil, the conductor portions of the two conductor networks being arranged parallel to one another in the control direction but staggered from one another. In this way. it is possible not only to double the resolution but to achieve properties of redundancy as, during the failure of a pair of conductor and contacting networks only the resolution is impaired and the sensor element does not fail entirelv.

13 Embodiments of the invention are described in detail hereinafter with reference to the accompanying drawings, wherein:

Figure 1 is a perspective, partially sectional view of a sensor arrangement for detecting the shaft position of several linearly displaceable selector shafts of a motor vehicle transmission system.

Figure 2 is a schematic exploded view of a sensor element of the sensor arrangement according to Figure 1.

Figure 3 is a sectional view of the sensor element, as viewed along a line III-III in Figure 1.

Figure 4 is a perspective, partially sectional view of a sensor arrangement for detecting the shift position of a central selector shaft of a motor vehicle transmission system which is movable in two control directions.

Figure 5 is a schematic exploded view of a sensor element of the sensor arrangement according to Figure 4.

Figures 6 and 7 show variations of sensor elements for a sensor arrangement according to Figure 4.

Figures 8 and 9 may be used or embodied in the sensor arrangements according to Figures 1 to 7.

Figure 1 shows three selector shafts 5 which are arranged next to one another with parallel axes. the shafts 5 are 14 displaceably guided in the direction of their longitudinal axes 1 in a gearbox 3 of a motor vehicle transmission system (not shown in detail) with several selectable speeds, and the shafts 5 are longitudinally displaced in a known manner by a central selector shaft or by respective separately allocated actuators for engaging and changing speed. The selector shafts can be essentially non-rotatably guided and, by their position relative to the gearbox 3, define the shift position and the selected speed. It is necessary to know the exact shift position of the transmission system and whether in what direction the shift position is being changed, or a variety of applications such as, in particular, for controlling an automatic friction clutch arranged between the internal combustion engine and the transmission system. For detecting its instantaneous position, each of the selector shafts 5 is provided with an almost continuously smoothly operating analogue sensor element 7 which detects the instantaneous position of a pusher element 9 connected to the selector shaft 5 with respect to its longitudinal axis 1. The sensor elements 7 take the form of a f lat sheet and are disposed so as to rest in a planar manner on the interior of a cover 13 sealing an orifice 11 in the gearbox 3.

As shown most clearly in Figures 2 and 3, the sensor elements 7 which are identical in design each comprise two foil portions of insulating material 15, 17 which are sealed at their edges 18 (Figure 3) and are rigidly connected to one another so that together they form a sheath for two comb-like conductor networks 19, 21 applied to one of the foil portions, the portion 15 in this case, is the manner of a printed circuit. The two conductor networks 19, 21 each have a plurality of conductor portions 23 and 25 which extend transversely to the longitudinal axis 1 of the selector shaft 5 along the surface of the foil portion 15, are arranged parallel to one another and at a distance from one another and alternate in the direction of the longitudinal axis 1. the spacing between the conductor portions 23, 25 is exaggerated in Figure 2 but, in practice, is comparatively small. The conductor portions 23 of the conductor network 19 are connected to a resistance path 27 extending transversely to them, more specifically such that the resistance of the resistance path 27 is equally great between successive conductor portions 23. The ponductor portions 25 opposite the resistance path 27 are 16 connected to one another by a common connecting line 29.

Within the sheath formed by the portions 15, 17, the foil portion 17 carries a coating 31 of a plastics resistance material, for example a material of the type mentioned at the I- -- 1 17 outset, which changes its specific electric resistance as a function of pressure. The coating 31 lies with electrical contact o'n the conductor portions 23, 25 of the two conductor networks 19, 21, but it has a comparatively high specific resistance when not stressed by the pusher element 9. At the point where the pusher element 9 rests on the exterior of the sensor element 7, the specific resistance of the coating 31 diminishes by several orders of magnitude so that, at the site of the pusher element 9, the conductor portions 23, 25 located there are connected to one another with a comparatively low contact resistance. The resistance path 27 therefore forms a potentiometer circuit of which the resistance ratio is determined by the position of the pusher element 9 without the pusher element 9 having to make electrical contact with the arrangement which is sheathed completely by the foil portions 15, 17. The pusher element 9 rests solely on the exterior of the sensor element 7 and comprises a pressure part 37, for example in the form of a ball or a press pin, which is biased against the sensor element 7 by a spring 33 (Fig. 3) and is displaceably guided in a guide 35.

The ends of the resistance path 27 as well as the connectingline 29 are connected to an evaluating circuit 39 which, in turn, may be allocated a data memory 41. The evaluating circuit 39 determines the position information as a function of the divider ratio of the potentiometer circuit formed by the resistance path 27. For allocation of the shift position of the transmission system to the position information, the evaluating circuit 39 compares voltage potentials with potential limit value information supplied from the memory 41, as described in detail in DE-A-38 36 145 described at the outset. Reference is made to this document for explanation.

Beyond the determination of the position, the evaluating circuit 39 allows monitoring of the operability and, in 18 particular, of the state of wear of the sensor element 7, as the absolute value of the resistance occurring between the terminal.s of the resistance path 27 on the one hand and the connecting line 29 on the other hand is a measure of the pressing force of the pusher element 9 with respect to the supporting face of the cover 13 and can change during the service life of the sensor arrangement when the mechanical conditions are changed, for example owing to depletion of the sensor element 7 and of the pusher element 9. The wear and the readiness for operation of the sensor element 7 may be monitored and optionally displayed by comparison with desired resistance information stored in the memory 41.

Fig. 4 shows a variation of a sensor arrangement in which the shift position of a central selector shaft 43 is monitored rather than the position of the selector shafts 5allocated to the individual speeds. The selector shaft 43 is guided in a displaceable manner in the direction of its longitudinal axis 47 and also rotatably around the longitudinal axis 47 in a gearbox 45 of the transmission system. The displacement position and the rotational position of the central selector shaft 43 coupled, for example, to selector shafts 5 according to Fig. 1 determines the shift position of the gearing and is controlled, for example, manually by means of a shift lever or the like. The position of the selector shaft 43 is detected in two co-ordinate directions by a planar sensor element 49 arranged on the interior of a cover 53 sealing an orif ice 51 in the gearbox 45. On its interior the cover 53 has an arcuate - shaped supporting face which is concentric to the longitudinal axis 47 and on which a sheet-form sensor element 49 is fastened so as to lie in a planar manner. A pusher element 55 arranged on the supporting shaft 43 exerts a pressure force on the sensor element 49 at a position corresponding to the position of the selector shaft 43.

19 Fig. 5 shows details of the sensor element 49 consisting, in principle, of two sensor elements of-the type described with reference-to Fig. 2 and 3 which are arranged above one another in the pressure direction of the pusher element 55 but with conductor portions extending perpendicularly to one another. For explanation, reference is made to the description of Fig. 2 and 3, identically acting components being provided with the reference numerals from Fig. 2 and 3 with the letter a for distinction. The illustration in Fig. 5 shows the sensor arrangement 49 which is distinguished from Fig. 4 in the development of the supporting face of the cover 53.

In particular, the sensor element 49 comprises two foil portions 1 5a which each carry conductor networks 19a, 21a with conductor portions 23a and 25a parallel to one another on the mutually facing sides. The conductor portions 23a, 25a of one of the two foil portions 15a, the foil portion 15a adjacent to the cover 53 in this case, extend in the direction of the longitudinal axis 47 and therefore detect the position of the pusher element 55 in the circumferential direction of the selector shaft 43. The conductor portions 23a, 25a of the other foil portion 15a extend transversely to the longitudinal axis 47 and therefore detect the position of the pusher element 55 in the direction of the longitudinal axis. The conductor portions 23a are in turn connected to resistance paths 27a while the conductor portions 25a are connected to one another by connecting lines 29a.

The coatings 31a with plastics resistance material changing its specific electrical resistance as a function of pressure are provided on the flat sides of a common foil portion 17a arranged between the foil portions 15a.

The edge regions of the foil portions 15a, 17a, but at least of the two external foil portions 15a, are connected tightly to one another so that these portions form a tightly protective sheath. It will be appreciated that separate foil portions---may be provided as a carrier for the coating 31a instead of a common foil portion 17a for the two control directions.

The evaluating circuit 39a which, in turn, may comprise a memory 41a evaluates the divider ratios, produced for the two control directions, of the resistance paths 27a forming respective potentiometer circuits for the two control directions separately and delivers switch position information both for the position of the selector shaft 43 in the direction of its longitudinal axis 47 and for its rotational position. Wear may be monitored for both control directions, as explained with reference to Fig. 1 to 3.

Fig. 6 and 7 show variations of the sensor arrangement of Fig. 4 of which the sensor element requires only a single sensor element instead of two sensor elements of the type described with reference to Fig. 2 and 3. Identically acting parts are provided with the reference numerals from Fig. 1 to 4 with a letter for distinction. Reference is made to the description of Fig. 1 to 4 for explanation.

In the embodiment in Fig. 6, a sensor element 7b of the design of which a development is shown in Fig. 2 and 3 is held so as to lie in a planar manner on the arcuate shaped supporting fade of the cover 53b. On thesupporting shaft 47b there is in turn arranged a pusher element 55b which rests movably in the direction of the longitudinal axis 47b of the central selector shaft 43b and in the circumferential direction thereof with bias on the sensor element 7b. The position of the pusher element 55b in the direction of the longitudinal axis 47b is determined in the manner described with re-JEerence to Fig. 2 and 3, the 21 conductor portions of the sensor element 47b not shown in detail extending in the circumferential direction of the selector shaft 43b.

The pressure dependency of the coating 31 of the sensor element from Fig. 2 is used for determining the position of the pusher element 55b in the circumferential direction. For this purpose, the cylinder axis 57 of the aylindrical or arcuate shaped supporting face of the cover 53b extends parallel to the axis but eccentrically to the longitudinal axis 47b, the pressure force exerted by the spring 33b of the pusher element 55b on the pressure part 37b thereof changing as a function of the rotational position of the selector shaft 43b. The evaluating circuit not shown in detail therefore evaluates the change of resistance of the potentiometer circuit of the sensor element for the rotational position of the selector shaft 43.

Fig. 7 shows a variation in which the sensor element 7c described with reference to Fig. 2 and 3 is arranged with the conductor portions of its conductor networks in the direction of the longitudinal axis 47c of the'central selector shaft 43c. The sensor element 7c therefore detects the angular position of the selector shaft 43c in the manner described with reference to Fig. 2 and 3. The value of the pressure with which the pusher element 55c rests on the sensor element 7c is in turn evaluated for detecting the position in the direction of the longitudinal axis 47c. To achieve a change in the force exerted by the spring 33c of the pusher element 55c on the pressure part 37c thereof in the direction of the longitudinal axis 47c, the cylinder axis indicated at 57c of the cylindrical or arcuate shaped supporting face of the cover 53c extends at an inclination to the longitudinal axis 47c. An evaluating circuit not shown in ditail is in tdrn provided for evaluation in both control directions.

22 It will be appreciated that the value of the resistance of the potentiometer circuit can in turn be utilised for monitoring wear in the two embodiments in Fig. 6 and 7.

Fig. 8 and 9 show variations of sensor elements which may be used in accordance with the sensor element 7, 7b and 7c and of which the components deviating from these sensor elements may also be used in each of the two corresponding sensor components of the sensor element 49. Identically acting components are therefore designated with the reference numerals in Fig. 2 and 3 and are provided with a letter for distinction. Reference is made to the description of

Fig. 1 to 5 for explanation of these components. Fig. 8 shows an embodiment which, despite the comparatively high resolution of-the already described sensor elements, allows the resolution thereof to be further increased and at the same time allows the reliability of operation to be improved by redundancy. Similarly to the sensor element 49 in Fig.

5, the sensor element 7d shown in Fig. 8 comprises two foil portions 15d which are both in turn provided with two respective conductor networks 19d and 21d on their mutually facing flat sides. The conductor networks 19d, 21d of each of the two foil portions in turn consist of mutually parallel conductor portions 23d and 25d which are arranged equidistantly from one another and of which the conductor portions 23d are each connected to a resistance path 27d and the conductor portions 25d to a connecting line 29d. Between the two foil portions 15d there is provided a foil portion 17d which is coated on its two surfaces facing the foil portions 15d with a coating 31d of plastics material which changes its specific electric resistance as a function of pressure. At least the foil portions 15d are tightly connected to one another along their edges. For supporting -thd pressure element 9d, the sensor element 7d rests in a planar manner on a supporting face of a cover part 13d or the like.

23 As described hereinbefore, the sensor element 7d corresponds to the sensor element 49 described in conjunction with Fig. 5. In contrast to this sensor element, however, all conductor portions 23d, 25d extend parallel to one another on the two foil portions 15d and transversely to the control direction of the pusher element 9d indicated at ld. However, as viewed in a projection, the conductor portions are staggered relative to one another on the supporting face of the part 13d, as indicated by a dot-dash line at 59 for the projection of a conductor portion of the lower foil portion 15d in the plane of the upper foil portion 15d. The offset may be selected such that the projection of each conductor portion of one foil portion comes to rest between adjacent conductor portions 23d, 25d of the other foil portion. However, it may also be selected such that the projection of each conductor portion 23d of one respective foil portion is overlapped by the projection of the conductor portion 25d of the other respective foil portion. The evaluating circuit not shown in detail in Fig. 8 evaluates the potentiometer circuits of the two resistance paths 27d separately, increasing the accuracy of resolution. When one of the two sensor components fails, the position of the pusher element 9d may still be determined, although with lower resolution. It will be appreciated that two of the sensor elements 7d shown in Fig. 8 are required for a sensor element according to Fig. 5.

In the sensor elements described hereinbefore, the conductor networks connected to the resistance path, as for example the arrangement 19 in Fig. 2, as well as the conductor networks - forming a contacting arrangement, for example 21 in Fig. 2, is provided on the same side of the pressure sensitive resistance material coating. Fig. 9 shows a variation which may be used in all sensor elements described hereinbefore and in which the conductor networks forming a 24 contacting arrangement as well as the conductor networks connected to the resistance path are arranged on mutually opposed sIdes of the pressure sensitive resistance path. A plurality of mutually parallel conductor portions 23e of a conductor networks. 19e arranged at a distance from one another is in turn provided on a foil portion 15e consisting of insulating material. The conductor portions 23e extend transversely to the control direction of a pusher element 9e indicated at le and are connected at equal intervals to a resistance path 27e. As a carrier of the coating 31e of a plastics resistance material changing its electric specific resistance as a function of pressure, a metal foil portion 61 which is coated without gaps in a planar manner and makes electrical contact with the pressure-sensitive resistance material is used-instead of a foil portion of an insulating material in contrast to the above-described embodiments.

Furthermore, the coating 31e in turn lies directly on the conductor networks 19e. The foil portions 61, 15e are tightly connected to one another along their edges. The sensor element 7e in turn rests in a planar manner on a supporting face of a carrier part, for example a cover part 13d of the gearbox.

In the unloaded state, the contact resistance between the conductor portions 23e and the metal foil portion 61 is comparatively high. Under pressure loading, the contact resistance is reduced until the metal foil portion 61 is It contacted" by at least one of the conductor portions 23e forming the respective pick offs of the resistance path 27e.

Claims

Arrangement for detecting the shift position of a motor vehicle transmission system with a gearbox containing at least one selector shaft controlling the changeover of speeds the shaft being mounted for displacement in the direction of its longitudinal axis and/or rotatably around its longitudinal axis, said arrangement comprising at least one planar sensor element associated with a control element which is connected to the selector shaft to follow the movement thereof and rests resiliently and displaceably in the control direction on the sensor element and, according to its rest position, defines a specific resistance value of the sensor element and an evaluating circuit which is connected to the sensor element and, depending on the resistance value, produces a signal which corresponds to the position of the selector shaft to represent the shift position of the transmission system, wherein the sensor element is arranged inside the gearbox and for at least one control direction of the control element, comprises a conductor network with a plurality of mutually parallel conductor portions which are arranged next to one another at equal intervals, extends 26 transversely to the control direction and are connected to one another by equal electrical resistances and, means which extends transversely over the conductor portions, is substantially electrically insulated from the conductor portions in the rest condition and, by exertion of a pressing force transversely to the face of the conductor network, may be conductively connected to the conductor portions, the conductor network and the connecting means being surrounded in a sealed manner by a sheath which is designed, at least on one of its flat sides, as a sheet, with the control element in the form of a pusher element resting on the exterior of the flat side of the sheet.
2. Arrangement according to Claim 1, wherein the sensor element lies in a planar manner on the internal face of a cover which removably closes an orifice of the gearbox.
3. Arrangement according to Claim 1, wherein the sensor element surrounds the selector shaft over an arcuate region parallel to or coaxial with the shaft and the sensor element within the sheath comprises two pairs, insulated from one another by an insulating foil of one respective conductor network and one respective 27 contacting means the conductor portions of thetwo conductor networks extending substantially perpendicularly to one another.
4. Arrangement according to one of Claims 1 to 3, wherein the contacting means has a planar resistance path of a plastics resistance material which changes its specific electric resistance as a function of pressure, the resistance path resting jointly on all conductor portions of the first mentioned conductor network and also resting on a second conductor network extending in the control direction along the first conductor network.
5. Arrangement according to Claim 4, wherein the evaluating circuit produces a signal representing the contact resistance between the first and the second conductor networks.
6. Arrangement according to Claim 5, wherein the conductor portions of the first conductor network are arranged next to one another in a first control direction and the sensor element and/or the pusher element have oblique faces which, in a second control direction extending transversely to the first control direction, as a function of the position of the pusher element relative to the sensor element change the pressing power thereof.
7. Arrangement according to Claim 6, wherein the 1 28 sensor element is arranged on a carrier f ace which is rigid with the gearbox and surrounds the selector shaf t in the manner of an arc at a radial distance from the selector shaft which increases or decreases either in the direction of the longitudinal axis of the selector shaft or in the circumferential direction of the selector shaft.
8. Arrangement according to Claim 7, wherein the carrier face is an arcuate or cylindrical face which is arranged parallel with but eccentric to the selector shaft.
9. Arrangement according to Claim 7, wherein the carrier face is an arcuate or cylindrical face of which the axis intersects the longitudinal axis of the selector shaft at an acute angle.
10. Arrangement according to one of Claims 4 to 9, wherein the second conductor network forms a planar conductor path which totally overlaps the conductor of the first conductor network and the resistance path is arranged between this conductor path and the face of the first conductor.
11. Arrangement according to one of Claims 4 to 9, wherein the second conductor network has a plurality of conductor portions which are parallel to one another and to the conductor portions of the f irst conductor network and are arranged next to one another with spacing f rom one another and in a common face to the conductor portions of the first conductor network and the conductor portions are conductively connected to one another by a connecting line with the resistance path resting on all conductor portions of both the f irst and the second conductor.
12. Arrangement according to Claim 1, wherein the conductor portions of the or each conductor network follow one another alternately in the control direction.
13. Arrangement according to any one of Claims 4 to 12, wherein the evaluating circuit comprises means for storing at least one desired value of the signal representing the electrical resistance and produces a signal representing the. readiness for operating of the sensor element as a function of the electrical resistance signal and the desired value.
14. Arrangement according to any one of Claims 1 to 13, wherein the sensor element comprises for at least one control direction, two pairs of one respective conductor network and one respective contacting means insulated from one another by an insulating fail with the conductor portions corresponding to one another, of the two conductor arrangements being arranged parallel to one another in the control direction but staggered from one another. is. An arrangement for detecting the shift position of a motor vehicle transmission substantially as described with reference to, and as illustrated in Figures 1 to 3 or Figures 4 and 5 of the accompanying drawings or Figures 4 and 5 as modified by Figures 6 and 7 of the accompanying drawings or Figures 1 to 3 or 4 and 5 as modified by Figures 8 and 9 of the accompanying drawings.