DE4339931C1 - Locator (position sensor, position encoder), in particular for the selector lever of a vehicle gear (transmission, gearbox) - Google Patents

Abstract

The invention relates to a locator for the selector lever of a vehicle gear, which is intended to sense the gear mode selected. According to the invention, the locator is a film pressure sensor consisting of two interlaminated polymer layers. One layer is coated with a semiconductor material and the other with comb-like, interdigitised electrodes which branch off, on the one hand, from a conductor track and, on the other hand, from a resistance track. These pressure-sensitive regions are locally confined to the defined positions of the selector lever, the position of which is transmitted to the film pressure sensor by means of a slider.

Description

The invention relates to a position transmitter, in particular for the gear selector lever of a vehicle transmission, according to the preamble of the main claim.

In motor vehicles, the position of a gear selector lever is abge asks to control units and the driver via the turned on put gearbox to inform. There are many orders known in which to generate a position signal for the Selector lever of a vehicle transmission a potentiometer, the Grinder is mechanically coupled to the selector lever, as a positi onsender is used. To control the vehicle transmission is the electrical resistance in an evaluation circuit the respective selector lever position evaluated according to the program. A Such evaluation circuit is for example from DE 38 36 145 A1 known. The evaluation circuit disclosed therein also delivers an information signal that indicates whether a is on by then is left.

Using a potentiometer to tap individual exactly However, defined position points have the disadvantage that the intermediate positions read during a change of position by programming the downstream evaluation circuit must be suppressed. The limit information required for this due to the inevitable installation tolerances in be programmed into a teach-in process.

To avoid this effort, DE 40 39 842 C1 Potentiometer combined with a push button switch, which by the  Snap a spring-loaded rolling element into the notches on the defined selector lever positions is operated. Through a switch signal of the push button switch, the evaluation circuit is triggered, the selector lever position from the present measured potentiometer value to investigate. Since the measured values for the dis  Critical positions are sufficiently far apart is one clear assignment based on value ranges is possible without any problems Lich. The tolerance range when installing the potentiometer and for the game of the selector lever is thereby increased, so that a Teaching process is omitted. However, the known arrangement has the Disadvantage that they are due to the many mechanical components is agile and also highly susceptible to environmental influences.

Furthermore, the film pressure sensors from the DE magazine: Feinwerktechnik & Meßtechnik 99 (1991) 7-8, pp. 339-341 known, their electrical resistance with increasing, in normal direction force on the sensor surface decreases. These Push button sensors have no moving parts and are inexpensive stig, robust and due to their thick film design thin profile. They can be in almost any geometry shapes and dimensions very easily by seri screen printing Manufacture en and are in various designs also used in the automotive industry.

A simple film pressure sensor consists of two laminated together Polymer layers built up, the one layer with a half lead term material and the other with two separate conductor tracks is layered. The conductor tracks have a main strand, from which thin branch lines branch off vertically and one came Form like electrode that came with an opposite one m-like electrode is arranged. Will the Foil pressure sensor loaded with pressure, the semiconductor switches material the contact fingers of the electrodes more or less parallel, whereupon the electrical resistance between the elec treading decreases. Between the two connection points of the conductor there is resistance (FSR), which increases with increasing Compressive force decreases and depending on it in a range of unsung varied by three powers of ten. Furthermore, with a suitable Neten training of the carrier and cover material a distinctive Switching characteristics of the film pressure sensors can be achieved.  

One application of film pressure sensors as position sensors is for example in the form of a membrane keyboard for an electro African musical instrument known from EP 489 344 A1. In this the resistances of the individual keys are assigned pressure-sensitive areas contacted individually and after a be selected special procedures. The process is complex because buttons pressed at the same time must also be recognized.

Potentiometric are also from the above-mentioned DE magazine Foil pressure sensors are known, through which in a certain type finally a linear position along a resistance path can be measured. They are different from the normal ones Foil pressure sensors in their structure essentially in that the main strand of one of the two conductor tracks by a counter is replaced and connection points at the beginning and at the end the resistance track are present.

Furthermore, from the generic DE 42 22 878 A1 order for detecting the switching position of a motor vehicle drive known, which a potentiometric foil printing sor used to switch the axial position of a Sensing gearshift stage shaft. One with the Switching shaft mechanically coupled grinder exercises on the Foil pressure sensor a local pressure at a linear positi on, which corresponds to the axial position of the selector shaft. The allocation to discrete switching stages is again one quasi stepless determination of the position of the grinder with all the disadvantageous requirements for a subsequent evaluation circuit.

From the quite extensive state of the art for gear selector detection The general background is still printed on ten DE 41 35 362 A1 and DE 37 10 286 A1 referenced.

The invention has for its object a generic To implement position sensors that are simple, reliable,  detection of position change insensitive to tolerances and allocation of discrete positions guaranteed.

This task is characterized by the characteristic features of Pa claim 1 solved.

By expanding the pressure-sensitive areas accordingly installation and position tolerances can be compensated. A pre precision when installing the film pressure sensor or even teaching process is therefore not necessary. Another advantage is that the position signals are sharp at different positions differentiated from one another and therefore easily distinguishable. To In addition, this is zero in the intermediate positions of the selector lever  declining position signal to detect a general Position change can be evaluated.

Further advantages and configurations result from the subclaims Chen and the description. The invention is as follows described in more detail with reference to a drawing. Show it

Fig. 1, the mechanical transmission of the lever position to the film formed as a pressure sensor position sensor,

Fig. 2 shows the position sensor according to the invention in a training for gangue detection in an automatic transmission.

To detect the selector lever position by means of a film pressure sensor, a local pressure must be exerted on the sensor surface at the location which is assigned to a respective selector lever position. This function fulfills the arrangement shown in FIG. 1: a contactless grinder 2 protrudes from the selector lever 1 , at the end of which a scanning tip 6 is fastened, which is prestressed by means of a spring 5 . The scanning tip 6 can be ball-shaped, hemispherical or designed as a roller. The scanning 6 exerts a constant pressure on a narrowly limited! Th region of the surface of the film pressure sensor 3 from where the film pressure sensor 3 is glued to a carrier board 4 up plan.

FIG. 2 shows an exemplary embodiment the top view of the invention in the form of a film pressure sensor 3 and the bib Positi onsgeber arranged shifting gate 7 of a au matic transmission. The representation of the film pressure sensor 3 is limited to the routing of the resistance and the conductor track, without dispensing with a reproduction of the polymer layer forming the carrier substrate and the semiconductor layer in the area of the electrodes. The contactless grinder is also not shown in FIG. 2. Positions 8.1-8.6 of the selector lever are shown as circles (P, R, N, D, 3 , 2 ) within the shifting gate 7 . The film pressure sensor 3 with the resistance track 9 and the parallel main strand of the conductor track 10 is adapted to the outer shape of the shift gate 7 .

In contrast to the known potentiometric film pressure sensors, the resistance track 9 is divided into different sections which follow one another, a first section type a and a second section type b decreasing according to the sequence. . . alternate a. The first section type a forms a fixed resistance z. B. 9 a.1, the dimensioning of which is calculated from the product of the length of the track section with its specific resistance related to a unit length. The second section type b represents a potentiometric section z. B. 9 b.1 and consequently consists of a resistance track branch off from the vertically thin stub lines made of conductor material, which form a comb structure and protrude into the space between the resistance track 9 and the conductor track 10 . There they intermesh with the comb structure of the electronic stub lines that emanate from the conductor track 10 . This area, where stub lines emanating from the resistance track 9 and stub lines emanating from the conductor track 10 are closely adjacent, forms the pressure-sensitive area. The framing 11 indicates such an area in which a pressure on the surface of the film pressure sensor 3 causes the semiconductor material neighbored stub lines more or less short depending on the pressure and a current from the resistance path 9 to the Lei line 10 can flow.

The distribution of the pressure-sensitive areas and consequently the distribution of the sections a and b on the resistance path 9 is selected in function of the positions to be sensed 8.1-8.6 so that the pressure-sensitive area assigned to a specific position is rich from the scanning tip 6 of the contactless grinder 2 ( FIG . 1) is pressurized when the selector lever 1 ( Fig. 1) assumes the position. The size of the pressure sensitive area z. B. 11 is dimensioned so that a safe pressure load is ensured by the scanning tip and Einbauto leranzen and game of the selector lever are absorbed.

Three connections 3.1-3.3 are provided for contacting the film pressure sensor 3 . The first terminal 3.1 contacts the beginning of the resistance path 9 and is connected to a voltage V, the second terminal 3.2 contacts the end of the resistance path 9 and is connected to ground, the third terminal 3.3 contacts the conductor path 10 and gives the position signal 12 to an evaluation circuit 13 . This connection method speaks ent of the usual voltage divider circuit, as is known from potentiometers.

The voltage of the position signal 12 for a specific position results from the voltage V and the resistances involved using the known voltage divider formula. The selector lever is, for example, in the position of 8.2 (R), the resistance path 9 is divided stands by short-circuiting the comb-like electrodes in the corresponding pressure-sensitive area 11 into two part abutment, the first to 9 a.1, b of the series connection of the fixed resistors. 9 1 and 9 a.2 and the second result from the series connection of the resistors of the remaining sections ent along the resistance track 9 . Furthermore, the tapped voltage depends on the exact y-position of the probe tip within the pressure-sensitive region 11 , since it divides the resistance of the corresponding potentiometric section of the resistance track 9 - in position 8.2 (R) it is section 9 b.2 . Furthermore, the tapped voltage also depends on the pressure of the scanning tip on the pressure-sensitive area, which, however, is the same for all positions due to the preload by the spring.

How the position signal 12 changes when changing from one position to the other depends on the particular dimensioning of the resistances in the individual sections of the resistance track 9 applied by screen printing. Some advantageous versions are set out below:

In a first embodiment, the resistance path 9 is dimensioned with a constant resistance per unit length. This corresponds most closely to the known potentiometric film pressure sensor. In contrast to the latter, the areas which correspond to intermediate positions of the selector lever are not tapped, since there are no interdigitating electrodes there. In these intermediate positions, the position signal 12 therefore drops to zero. Thus, in addition to the voltage assigned to a specific position, there is also a steep signal edge for evaluating a change in the selector lever position, which can be evaluated to detect a general change in position. As a further advantage, the different positions corresponding voltages are clearly graded, which allows a sharp delimitation and separation of the different selector lever positions.

In a further development, the fixed resistances in the non-passive sections 9 a.1, 9 a.2,. . . chosen so that the voltage difference from one position to an adjacent one is the same for all positions. The position signals of closely adjacent selector lever positions are thus well delimited in the same way as the position signals of further adjacent selector lever positions.

In the previously illustrated embodiments both of the position encoder a selected position is changed to a small extent, the position signal 12 also continuously within the tolerance range with a small change in position in the y-direction of the print point of the stylus. This can be used to know the direction of a change in position of the selector lever based on the slight increase or decrease in the voltage level. The early detection of the direction of a change in position of the gear selector lever can be useful, for example, to initiate an electrical synchronization process in the vehicle transmission.

In the third embodiment, a simple and reliable detection of the discrete positions 8.1-8.6 is in the foreground, so that within the tolerance range of a selected position a change in the position of the imprint point of the scanning tip leads to little or no change in the position signal 12 . For this purpose, sensitive sections 9 b.1, 9 b.2,. . . the resistance per unit length was chosen much lower than for the non-sensitive sections 9 a.1, 9 a.2,. . . the resistance track 9 . In the borderline case of a conductor material for the sensitive sections 9 b.1, 9 b.2,. . . The position signal 12 remains unchanged within the tolerance range of a position. The position signal is therefore stable and only changes abruptly when leaving a selector lever position. In addition, a combination with the features of the second exemplary embodiment is readily possible.

In view of the fact that there is a lot of space around the gear selector lever re controls such as switches and indicator lights - z. B. for the Seat heating - are arranged and this increasingly can be networked with each other, everyone can be integrated electromechanical and electronic components on the Carrier board of the film pressure sensor. The assembly includes then the sensors, the signal processing, the mechanical Inclusion of additional switches and the lamps (LED) for the Function and location lighting of the other switches elements. This results in advantages in relation to one rational assembly and easy contacting. Of the Effort can be reduced even more, even if the scarf ter realized on the basis of the known film pressure sensors are, so that a common but multi-component films pressure sensor for gangue detection and the neighboring ones Switch can be used. Furthermore, if the different switching states through voltage coding are queried, the resistors for voltage division as Resistance tracks can be integrated in the film pressure sensor.

Claims (11)

1. position transmitter, in particular for the gear selector lever of a vehicle transmission, for detecting defined, discrete positions of a contactless grinder arranged along a path,

• - The position transmitter is a on a carrier board angeord Neten film pressure sensor, which has a track of the grinder arranged in accordance with the resistance track and a parallel ver running conductor track, with thin, closely adjacent stub lines protrude from the resistor track and the opposite conductor track, which engage like a comb and form a pressure sensitive area,
• the grinder exerts a local pressure on the surface of the film pressure sensor, as a result of which a current-conducting connection can be established between adjacent branch lines, so that a voltage is tapped from the resistance track in a voltage divider ratio which is characteristic of the position of the grinder, characterized in that
• - That the resistance track ( 9 ) is divided into several alternately arranged non-sensitive sections ( 9 a.1, 9 a.2,...) and sensitive sections ( 9 b.1, 9 b.2,...), so that a sensitive section ( 9 b.1) is always preceded by a non-sensitive section ( 9 a.1) and another non-sensitive section ( 9 a.2), whereby only the sensitive sections ( 9 b.1, 9 b.2,...) project vertical stub lines and form a spatially delimited pressure-sensitive area ( 11 ) with stub lines engaging like a comb of the opposite conductor track section,
• - That the defined discrete positions ( 8.1-8.6 ) of the grinder ( 2 ) each have a pressure-sensitive area ( 11 ) and the undefined intermediate positions are assigned to the non-pressure-sensitive areas.

2. Position encoder according to claim 1, characterized in that the electrical resistance of the resistance track ( 9 ) in the various non-sensitive sections ( 9 a.1, 9 a.2,...) Is selected so that when changing from a discrete position to the next one, the resistance increment along the resistance track ( 9 ) is almost the same for all starting positions. 3. Position sensor according to claim 1, characterized in that the electrical resistance of the resistance track ( 9 ) related to a unit length in sensitive sections ( 9 b.1, 9 b.2,...) Is very much smaller than in the non-sensitive sections ( 9 a.1, 9 a.2,...). 4. Position sensor according to claim 1, characterized in that in the sensitive sections ( 9 b.1, 9 b.2,...) The resistance track is replaced by a piece of conductor track. 5. Position transmitter according to claim 1, characterized in that the resistance track ( 9 ) at one end ( 3.1 ) to a voltage source, connected at its other end ( 3.2 ) to ground and at a connection point ( 3.3 ) of the conductor track ( 10 ) a position signal ( 12 ) can be tapped. 6. Position transmitter according to claim 5, characterized in that an evaluation circuit ( 13 ) compares the voltage of the position signal ( 12 ) with stored voltage values , each assigned to a defined position ( 8.1-3.6 ) and detects a defined position when the voltage within a Tolerance range around the corresponding stored voltage value. 7. Position transmitter according to claim 6, characterized in that the evaluation circuit ( 13 ) recognizes a general change of position when the position signal ( 12 ) drops to zero. 8. Position sensor according to claim 6, characterized in that the evaluation circuit ( 13 ) for detecting the direction of a change in position be a small voltage change of the position signal ( 12 ) evaluates within the tolerance range of a stored voltage value. 9. Position transmitter according to claim 1, characterized in that the position transmitter for detecting the position of a gear selector lever ( 1 ) of a vehicle transmission is formed by the grinder ( 2 ) with the gear selector lever ( 1 ) is mechanically coupled and the defined positions ( 8.1- 8.6 ) of the grinder correspond to the positions of the gear selector lever ( 1 ) in which a gear is engaged. 10. Position transmitter according to claim 1, characterized in that on the carrier board ( 4 ) further electronic or mechanical components, in particular an evaluation circuit ( 13 ) for evaluating the position signal ( 12 ) are arranged. 11. Position transmitter according to claim 10, characterized in that on the carrier board ( 4 ) arranged switches in a manner known per se use film pressure sensors as switching elements which form a coherent but more component film pressure sensor with the position transmitter.