GB2224791A

GB2224791A - Arrangement for the detection of the position of a machine part, especially of a gear change lever using a surface potentiometer

Info

Publication number: GB2224791A
Application number: GB8921673A
Authority: GB
Inventors: Erich Peter; Franz Nagler; Hans Fliege
Original assignee: Fichtel and Sachs AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1988-10-22
Filing date: 1989-09-26
Publication date: 1990-05-16
Anticipated expiration: 2009-09-26
Also published as: FR2638230B1; GB8921673D0; DE3836145C2; DE3836145A1; FR2638230A1; GB2224791B

Description

2224791 Arrangement for the detection of the position of a machine part,

especially of a gear-change lever The invention relates to an arrangement for the detection of the position of a machine part movable in two co-ordinate directions which is settable in the two coordinate directions according to choice to several predetermined positions, especially for detecti.ng the position of a gear- change lever of a motor vehicle change-speed gear.

The detection of the momentary position of a machine part which is movable in two co-ordinate directions, for example a selector lever or the like, requires relatively high expenditure, if both co-ordinate directions are to be monitored. Thus in motor vehicles for several controlling tasks the gear engaged manually on the change-speed gear must be capable of being detected, for example in order to be able to pre-determine the coupling characteristics of an automatically controlled friction clutch in dependence upon the gear position. In this connection it is known to detect the position of the gear-change lever by limit switches in the change-speed gear. However it is also known to monitor, with the aid of several sensors, pre-determined positions of a gear-change shaft coupling the gear-change lever with the gear. By way of example Hall sensors were arranged in the pre-determined positions, and respond to a magnet moved with the gear-change shaft. Furthermore it was attempted to couple the gear-change shaft with separate path sensors and angle sensors which supply information, independently of one another, for position determination. All known - 2 arrangements for detection of the position of the gearchange lever are however comparatively expensive and/or require high assembly expenditure.

It is the problem of the invention to indicate an arrangement for the detection of the position of a machine part, especially the position of a gear-change lever of a motor vehicle change-speed gear, which makes comparatively low design expenditure suffice for the exact detection of the position and can be fitted with low fitting expense.

This problem is solved in accordance with the invention in that the machine part is coupled mechanically with a surface potentiometer and sets its slider, resting on a resistance-path, in dependence upon setting movements of the machine part in two resistance path co-ordinate directions allocated to the machine part co-ordinate directions, to slider positions associated with the pre-determined positions of the machine part, in relation to the resistance path in that the surface potentiometer is connected to a voltage source in a voltage divider circuit arrangement each, for the two resistance path co-ordinate directions, and in that to the surface potentiometer there is connected an evaluator circuit responding in both resistance path coordinate directions to voltage potentials on the slider, which evaluator circuit compares the voltage potentials of the two resistance path co-ordinate directions with ideal itemspotential information stored in a store and allocated to the pre-determined positions of the machine part.

In contrast to conventional arrangements for position A detection, it is sufficient to couple the surface potentiometer as sole sensor with the machine part to be monitored as regards its position. For the connection of the surface potentiometer it is necessary only to lay a few signal leads. Almost no mechanical adjustment of the surface potentiometer is necessary, since the information necessary for the identifiation of the pre-determined positions of the machine part is stored in a store into which it can be read electronically according to the installation situation of the moment. The arrangement according to the invention can therefore be adapted without problem to different installation situations and different shift movements of the machine part.

The ideal potential information stored in the store can be written into the store as early as in the production of the circuit arrangement, according to the intended purpose. In order however to be able to take account of installation tolerances a store programming device is expediently associated with the evaluator circuit, and writes ideal potential information into the store in dependence upon the voltage potential of the slider, in a learner operation style. Thus the store can be programmed in accordance with the voltage potentials resulting in the current situation of installation on the slider.

The store expediently forms a tabular store in which potential limit value information items are stored for both resistance path co-ordinate directions, which items are each allocated to limit positions between adjacent pre-determined positions of the machine part. In this way the storage space requirement is comparatively slight, and the evaluation is facilitated, since the evaluator circuit merely has to respond to the exceeding or falling short of the potential limit value information items by voltage potential information items of the slider, that is must only monitor whether the voltage potential information items of the slider are greater or smaller than the stored potential limit value information.

Especially in the detection of the position of a gear change lever for the control of automatically actuated motor vehicle clutches it is advantageous to be able to recognise as early as during the movement of the gear-change lever in which direction the gear-change lever is being moved. that is for example whether a driving gear is being engaged from the neutral gear position or whether a change is being made from the gear engaged at the moment into the neutral position. The direction of movement can be additionally detected if pairs of potential limit value information items are stored in the store for at least one of the two resistance path co-ordinate directions, which items are allocated by pairs in each case to the limit positions, and if the evaluator circuit responds to the chronological sequence in which the pairs of information items are exceeded or fallen short of by the voltage potential information items.

Surface potentiometers are known per se and were hitherto utilised in the form of graphic panels for the IF 1 ascertaining of the setting position with which a pencil is set upon the panel. The graphic panel comprises a substantially rectangular resistance path, to the edges of which several diodes in each case are connected through attachment points distributed along the edges, which diodes connect the attachment points of each edge with a connection point allocated to the edge. The diodes of the edges, lying opposite to one another by pairs, are in each case polarised in the same direction and connected through a two-pole change-over switch with a voltage source in such a way- that the two pairs of mutually opposite edges are connected alternately with the voltage source. The pencil has in its point a contact which, when set upon the resistance path, supplies voltage potential information which is a measure for the momentary position of the pencil on the resistance path. - The arrangement according to the invention is especially suitable for detecting the position of a gearchange lever of a motor vehicle change- speed gear. Such a gear is frequently coupled through a rotatable and axially movable change shaft with the gear-change lever. The position in rotation ahd the axial position of the change shaft are here an indication of the gear engaged. In a preferred development of the invention the slider of the surface potentiometer is held on a rotatable and axially displaceable shaft which is coupled with the change shaft of the change-speed gear. The resistance path is here made as a cylindrical face coaxial with the shaft axis and can be - 6 secured, especially stuck, on a wall inner surface of cylinder segment form of the potentiometer housing. Especially for the controlling by way of change-speed slideways however forms of embodiment of the surface potentiometer with flat resistance path are also suitable.

Examples of embodiment of the invention will be explained in greater detail hereinafter by reference to a drawing, wherein:

FIGURE 1 shows a block circuit diagram of an arrangement for detecting the position of a gear-change lever of a motor vehicle change-speed gear; FIGURE 2 shows a diagram for the explanation of the manner of function of the arrangement according to Figure 1, which shows the situation of the pre-determined positions to which the gear-change lever is settable; FIGURE 3 shows a partially broken-away diagrammatic representation of a first form of embodiment of a surface potentiometer usable in the arrangement according to Figure 1 and FIGURE 4 shows a diagrammatic representation of a second form of embodiment of a surface potentiometer usable in the arrangement according to Figure 1.

Figure 1 shows a circuit arrangement for detecting the position of a gearchange lever 1 of a change-speed gear, indicated diagrammatically at 3, of a motor vehicle. As indicated by arrows 5, the gear-change lever 1 is settable in two mutually perpendicular co-ordinate directions to a plurality of pre-determined positions allocated in the usual way to the individual gears and the neutral position of the gear. With the gear-change lever 1 there is mechanically coupled a slider 7 of a surface potentiometer 9 which rests on a resistance path 11 of the surface potentiometer and is movable in two co-ordinate directions allocated to the coordinate directions 5 of the gear-change lever 1 and indicated by arrows 13. The co-ordinate directions 13 extend parallel to edges 15 and 17, lying opposite by pairs, of the resistance path 11, each of which comprises a plurality of attachment points 19, distributed along the edge, for diodes 21. The diodes 21 of each edge 15 or 17 are polarised in the same direction, the diodes 21 of adjacent edges 15, 17, polarised in opposite directions, being connected with a connection point 23 or 25 common to the pair of adjacent. edges 15, 17. It is self-evident that the connection points 23, 25 can in practice be made as collecting lines. lying oppositely The diodes 21 of the edges 15 and 17 by pairs are polarised in the same direction in relation to the current path 11 including the resistance path. The connection points 23, 25 are connected to two change-over switches 29, 31 which can be switched over periodically by a control system 27, which switches in common form a pole-changing circuit and connect the connection points 23,. 25, with periodically changing polarity, with a direct current voltage source (not shown further) connected between earth 33 and a voltage supply terminal 35.

The diodes 21 ensure that at every moment only one of 8 the pairs of mutually opposite edges 15 or 17 is connected with the voltage source, while the other pair is uncoupled from the vcoltage source. The distribution of the attachment points 17 along the edges 15, 17 is so selected that a constant _hstribution of the voltage potential results parallel with the pairs of opposite edges. The voltage potential varies linearly between the opposite edges. so that the potential present on the slider 7 is a measure for the relative position between the two opposite edges. By reason of the periodic switch-over of the change over switches 29, 31, periiodically changing voltage potentials are present on the slider 7 which represent the position of the slider in the two co-ordinate directions 13 and accordingly in the two co-ordinate directions 5 of the gear-change lever 1.

Figure 2 shows, in a co-ordinate system x, y related by way of example to a hand knob of the gear-change lever 1, the positional regions of the gear-change lever 1 allocated to the gear ratios of the change-speed gear 3. The numbers 1 to 5 designate the zones in which the gear-change lever is situated in the forward gears. R designates the region of the reverse gear and N the neutral zone (empty lane). An active zone 37, indicated by a chjain line in Figure 1, of the resistance track 11 in a co-ordinate system x', y', corresponds to the zone represented in Figure 2. For the detection of the momentary position of the slider 7 within the active zone 37 the slider 7 is connected to an analogdigital converter 39 which delivers digital voltage 4 potential information proportional to the voltage potential on the slider 7 and thus to its position. A comparator 41 of an evaluator circuit designated generally by 43 compares the potential information with potential limit value information items fed from a digital store 45, which information items designate the limit positions between the individual gears separately for the two co-ordinate directions. As example in Figure 2 limit positions 47, 49 are entered which separate the region of the first gear from the neutral zone N and the third gear. According to the coordinate system x', y' as represented in Figure 2, the first gear is engaged when the potential information of the slider 7 falls short of the potential limit value 49 and exceeds the potential limit value 47. Logic circuits (not further illustrated) of the comparator 41 allocate at least one predetermined pair of comparison results to each of the gears, for identification. The comparator 41 delivers at its output a digital signal designating the gear, for further processing, for example in an automatic clutch control system.

The store 45 expediently stores not only a single potential limit value information item but in each case a pair of information items for two closely adjacent position limit values, at least for some of the limit positions, as represented in Figure 2 by chain lines 51 for the transition of the gears to the neutral region N. In the case of a gear change the position limits are overstepped successively in dependence upon the direction of movement of the gear-change lever 1. The comparator 41 detects the chronological sequence with which the pairs of information items follow one another, and delivers an information signal which indicates whether the gear- change lever 1 is being moved into the neutral zone N, that is the former gear is being left, or whether the gear change lever I is being moved out of the neutral region, that is a new gear is being engaged.

For the programming of the potential limit value information items stored in the store 45 aprogramming device 53 is provided which, in a learning type of operation of the store, ascertains from the potential information delivered from the analog-digital converter 39 in the individual gear positions potential limit value information items lying therebetween and writes these into the store 45.

In this way a mechanical adjustment the surface potentiometer 9 in relation to the gear 3 becomes superfluous. However it is understood that the potential limit value information stored in the store 45 can also already be written into the store 45 in inalterable form in the production.

The active zone 37 of the surface potentiometer 9 covers only a partial region of the resistance path 11. Thus potential limit value information items likewise stored in the store 45 can be allocated to the limits of the active zone 37, within which items the slider potential must lie in the case of correct operation of the surface potentiometer 9. By monitoring of the limit value information, allocated to the limits of the active region 37, by means of the 7 J comparator 41, it is possible to test the functional capacity of the arrangement.

Examples of embodiment of surface potentiometers for use in an arrangement according to Figure 1 will be explained below. Parts of like effect are designated with the reference numerals from Figure 1 and provided with an additional letter for distinction. Reference is made to the description of Figures 1 and 2 for more detailed explanation.

Figure 3 shows a surface potentiometer 9a for direct coupling with a shif t shaft 55 of the gear, which is displaced in the axial direction x' and rotated about its axis in the co-ordinate direction y', by the gearchange lever la, mounted for pivoting in all directions in a joint 57,, in the movement of the lever la in the co-ordinate directions x, y. The surface potentiometer 9a comprises a housing 59 for attachment for example to the gear, in which housing a shaft 61 coupled with the shift shaft 55 is rotatably and axially displaceably guided. The shaf t 61 issues from the housing 59, being sealed by seals (not illustrated further). The resistance path 11a is formed by a resistance foil which is secured, for example by sticking, on an inner wall face 63 of cylinder segment form, coaxial with the shaft 61, of a housing part 65 of the housing 59. The shaft 61 carries a radially resilient slider 7a, which rests on the resistance foil.

Figure 4 shows a flat variant of a surface potentiometer 9b with a flat resistance path 11b on which the slider 7b displacement in the resistance longitudinal guides slideway guide is coupled with the gear-change lever lb, which is movable in the co-ordinate directions x and y, and can be formed especially by components of the slideway guide of the gear-change lever.

rests. The slider 7b is guidedfor the co-ordinate directions x' and y' along path 11b by a slideway guide formed from 67 and transverse guides 69. The i 13

Claims

CLAIMS:

1. Arrangement for detecting the position of a machine part (1) movable in two co-ordinate directions which is adjustable selectably in both coordinate directions to several predetermined positions, especially for detecting the position of a gear-change lever of a motor vcehicle changespeed gear, characterised in that the machine part (1) is coupled mechanically with a surface potentiometer (9) and sets its slider (7), resting on a resistance path (11), in dependence upon the setting movement of the machine part (1),in two resistance path coordinate directions allocated to the machine part coordinate directions, to slider positions associated with the pre-determined positions of the machine part (1), in relation to the resistance path (11), in that the surface potentiometer (9) is connected to a voltage source (33, 35) in a voltage divider circuit arrangement each, for the two resistance path co-ordinate directions, and in that to the surface potentiometer (9) there is connected an evaluator circuit (43) responding in both resistance path co-ordinate directions to voltage potentials on the slider (7), which evaluator circuit compares the voltage potentials of the two resistance path co-ordinate directions with ideal potential information stored in a store (45) and allocated to the pre-determined positions of the machine part.

2. Arrangement according to Claim 1, characterised in that a storeprogramming device (53) is provided which, - 14 a learning type of operation, in dependence upon the voltage potentials of the slider (7), writes ideal potential information items into the store (45).

3. Arrangement according to Claim 1 or 2, characterised in that potential limit value information items are stored in the store (45) for both resistance path coordinate directions, which items are in each case allocated to limit positions between adjacent pre-determined positions of the machine part (1), and in that the evaluator circuit (43) responds to the exceeding or shortfall of the potential limit value information by the voltage potential information items corresponding to the voltage potentials on the slider (7).

4. Arrangement according to Claim 3, characterised in that for at least one of the two resistance path coordinate directions pairs of potential limit value information items are stored in the store (45), which items are allocated in each case as pairs to the limit positions, and in that the evaluator circuit (43) responds to the chronological sequence in which the information pairs are exceeded or shortfallen by the voltage potential information items.

5. Arrangement according to one of Claims 1 to 4, characterised in that the slider (7a) is held on a rotatably and axially displaceable shaft (61) and the resistance path (11a) is formed as cylindrical face (63) coaxial with the shaft axis, and in that the shaft (61) is coupled with a shift shaft (55) of the change-speed gear.

1 4 -

6. Arrangement according to Claim 5, characterised in that the surface potentiometer (9a) has a housing (59) with a wall inner surface (63) forming a cylinder segment, against which surface a resistance foil rests, especially is stuck.

7. Arrangement according to one of Claims I to 4, characterised in that the resistance path (11b) is flat and the slider (7b) is coupled with a slidewey (67, 69) of the change-speed gear..

8. Arrangement for detecting the position of a machine part substantially is described with reference to Figures 1 and 3 (or Figures 1- and 4) of the accompanying drawings.

Published 1990 at The Patent Office. State House 66 71 High Holborn. LondonWClR4TP. Further copies maybeobt-ained from The Patent Office. Sa:, es Branch. St Ma-y Cray. Orpington. Kent ER5 3RD Printed by Multiplex technques ltd. St Ma.7 Cray. Kent. Con. 1 87