Switch system for motor vehicle transmissions
FIELD OF THE INVENTION 
     This invention relates generally to vehicular transmissions and more particularly to electrical switches for providing an electrical signal responsive to the position of the manual shaft and detent lever associated with such transmissions. 
     BACKGROUND OF THE INVENTION 
     It is conventional to mount a rotary switch on the transmission housing externally thereof to receive mechanical gear selection inputs from the operator of a vehicle through various linkages and output gear selections to appropriate output means such as a decoder module and the transmission electronic control unit via electronic signals. The switch includes a quadrant with a selected number of electrical switch segments disposed thereon with each segment providing an output to the output means. The manual valve controlling hydraulic operation of the transmission is mechanically coupled to a plate having indexing detents, called a detent lever, mounted on a shaft and pivotably movable therewith. The shaft extends through the transmission housing wall and a switch bar is fixedly attached to the shaft externally of the transmission housing so that when a vehicle operator selects a gear the switch bar within the rotary switch moves across the quadrant to a predetermined position to engage one or more of the electrical contact segments. In certain systems the electronic control monitors the gear position along with other inputs relative to such things as throttle position, output shaft speed, engine speed, engine load and so on. 
     In U.S. Pat. No. 5,338,907, assigned to the assignee of the present invention, a switch system is disclosed which is mounted within the transmission housing in order to avoid placing the switches in a hostile environment subject to water splash and the like as well as to avoid tolerance stack-up problems associated with linkages employed when mounting the switches externally of the transmission housing. In that patent a switch housing is shown mounted on the manual lever shaft. The housing is coupled to a roller attached to the detent spring which biases the roller into engagement with the outer edge of the detent lever to maintain the housing stationary relative to the transmission housing. A switch arm fixedly mounted on the manual lever shaft mounts a plurality of first electrical contacts and extends into the switch housing. The switch arm, movable with the detent lever, moves into and out of engagement with respective second electrical contacts mounted on the switch housing. Although transmission fluid can enter and leave the switch housing, suitable seals are provided to prevent ingress of metal particles and other debris into the switch housing. Flexible electrical leads have one end connected to terminals of the electrical contact segments and an opposite end connected to terminals of a connector mounted in a bore provided in the wall of the transmission housing. 
     Although the switch operates effectively mounted within the transmission housing, a problem can occur during assembly of the transmission in that the electrical leads sometimes are chaffed, pinched or run over a sharp edge thereby causing a short circuit. This problem becomes exacerbated in many newly designed transmissions which tend to be smaller in size. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an electric switch assembly responsive to gear selection free of the limitations of the above noted prior art. Another object is the provision of a switch assembly which can be accommodated within available space of existing, as well as smaller, newly designed vehicle transmission housings and which do not have wiring harnesses of flexible wires disposed within the housing. Yet another object is the provision of an electric switch assembly responsive to gear selection which is easily assembled in a vehicle transmission having improved reliability yet with sufficient accuracy to accurately track gear selection. 
     Other objects, advantages and details of the switch system of this invention appear in the following detailed description of the preferred embodiment of the invention. 
     Briefly, in accordance with the invention, a switch housing is mounted within a transmission housing of a vehicle on the manual lever shaft between the wall of the transmission housing and the detent lever. The switch housing is formed with an integral connector portion which is receivable in a bore formed in the wall of the transmission housing so that the manual lever shaft and the connector portion, respectively received through first and second bores in the transmission housing wall, fix the orientation of the housing. An actuator or switch arm is fixedly mounted on the manual lever shaft within the housing and is movable within the housing as the manual lever shaft is turned. Movable electrical contacts are mounted on the actuator arm and are biased into engagement with a circuit board disposed in the housing so that they move into and out of electrical engagement with stationary contact segments on the circuit board as the actuator arm pivots with the manual lever shaft. The contact segments are coupled to terminal pins mounted in the connector portion of the housing. The connector portion is provided with a threaded female insert used to mechanically couple a mating connector outside of the transmission housing. According to a feature of the invention, first and second annular spring seal elements are disposed on opposite sides of the actuator arm around the manual lever shaft on respective seal seats formed between the actuator arm and the housing. The seal elements are effective to prevent entry into the housing of debris which could otherwise interfere with the electrical switching operation. The seal elements are curved in the radial direction and have a selected crown height between at least one of the inner and outer edges lying in a plane to that portion of the elements furthest removed from the plane. A particularly advantageous seal element has a load vs. deflection curve which has a portion decreasing in load as the element is deflected as it approaches a flat configuration. The seal seats are formed having opposed surface portions spaced from one another a distance selected so that the seal elements are collapsed to an extent that the spring force exerted by the elements is relatively low to thereby minimize drag as the actuator arm pivots within the housing. According to a feature of the invention the seal elements are able to move laterally sufficiently to accommodate slight misalignment caused by manufacturing tolerances in machining the two bores in the transmission housing wall. According to another feature of the invention, the housing is formed of thermoplastic material, such as nylon, having first and second portions which are fixed to one another by vibration welding made possible by the ability of the seal elements to accommodate the lateral component of the vibration movement. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a switch assembly made in accordance with the invention; 
     FIG. 2 is a side elevational view of the FIG, 1 switch assembly mounted within a transmission housing with the connector portion 16 facing downwardly and with the housing wall shown in cross section; 
     FIG. 3 is an exploded view of the FIG. 1 switch assembly; 
     FIG. 4 is a cross sectional view of the FIG. 1 switch assembly taken prior to welding the housing and lid together and with the housing and lid separated from one another and from the actuator arm for purpose of illustration; FIG. 5 is a perspective view of a movable contact assembly used in the FIG. 1 assembly; 
     FIG. 6 is a perspective view of an actuator arm used in the FIG. 1 assembly; 
     FIG. 7 is a cross sectional view of a spring sealing element used in the FIG. 1 switch assembly; and 
     FIG. 8 is a graph of load vs. deflection of the FIG. 7 spring sealing element. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, numeral 10 represents a switch system made in accordance with the invention comprising a first housing member 12 formed with a recess 14 therein and closed by a second housing member or lid 13. With particular reference to FIGS. 1 and 2, switch system 10 is provided with a connector portion 16 having a connector shroud 16a, generally cylindrical in configuration, and having a longitudinal axis 18 and a manual lever shaft receiving bore 32b having a longitudinal axis 22. Axes 18 and 22 are generally parallel with one another and are spaced from one another a precise distance a selected to be essentially the same as the distance a&#39; between the longitudinal axes of bores 2, 4 respectively of wall 6 of a vehicle transmission housing, as will be explained below. 
     As best seen in FIGS. 3 and 4, a high current circuit board 24 and a low current circuit board 26 are mounted in cavity 14 of housing member 12. The circuit boards have arcuate shaped contact segments 24a, 26a respectively disposed on the bottom surface thereof as viewed in the figures, which in turn are connected to terminal pads 24b, 26b respectively. Preferably, the circuit boards are each formed from a single lead frame insert molded in a suitable electrically insulative polymer with individual circuit segments separated after molding by severing bridging runners in a known manner. Terminal pins 28 are mounted in connector portion 16, preferably by insert molding, and have lower distal end portions 28a extending into a connector recess 16b of connector portion 16. Distal end portions 28a are received in apertures formed in circuit boards 24, 26 in alignment with terminal pads 24b, 26b respectively and are connected thereto by suitable means, such as soldering. A generally tubular insert 30 having a closed end and formed of suitable material such as brass is also insert molded in connector 16 and is provided with a threaded bore to cooperate with a mating connector 16d shown in dashed lines in FIG. 2 received outside the transmission housing. A suitable annular groove 16c is preferably provided about the outer periphery of connector 16 to serve as an O-ring seat for a suitable O-ring 17. 
     An actuator arm 32 has a hub 32a formed with a bore 32b having suitable key means to maintain a selected angular orientation with a shaft received in the bore. As shown, bore 32b is provided with a pair of opposed flat surfaces 32c to serve this function so that the actuator arm will maintain a given angular orientation relative to a manual lever shaft having corresponding flat surfaces received in the bore. 
     As best seen in FIG. 4, a first annular seat of opposed surfaces, being spaced apart by a selected distance when assembled, is formed between annular surface portion 32d of actuator arm 32 around the periphery of hub 32a and the bottom annular surface 12a of housing member 12 about the periphery of bore 12b which receives the top portion of hub 32a. A second annular seat of opposed surfaces, being spaced apart by a selected distance when assembled, is formed on the opposite side of actuator arm 32 between surface portion 32e around the periphery of hub 32a and the top surface 13a of lid member 13 about the periphery of bore 13b which receives the bottom portion of hub 32a. 
     First and second annular spring sealing elements 34 are disposed at the respective first and second seats. Seal elements 34 are sloped or curved in the radial direction and have a crown height between at least one of the inner and outer edges lying in a plane to that portion of the elements furthest removed from the plane, i.e., distance ch in FIG. 7. Sealing elements of this type are also disclosed in pending application Ser. No. 176,753, assigned to the assignee of the present invention. 
     While any spring sealing element curved in the radial direction can be used to effectively prevent ingress of debris a particularly suitable element has a load deflection curve in which load decreases as the spring is collapsed as it approaches a flat configuration. An example of this type of spring is one type of a so-called Belleville spring washer. By way of example, as seen in FIG. 8, deflection of the spring element having a thickness t of 0.003 inches and a crown height ch of 0.015, by placing a load on the element, results in increasing force as the deflection commences and then after a zenith at slightly less than half of the total deflection to a flat configuration, the force decreases with increasing deflection. By forming a seal element seat in which the opposed surfaces are spaced apart by a vertical dimension selected so that the seal element will be deflected between the zenith of the force vs. deflection curve and the flat configuration, preferably, slightly prior to the flat configuration, a system results in which the sealing function is provided yet which produces very little drag when moving actuator arm 32. For example, for a sealing element 34 having a thickness t of 0.076 inches and a crown height ch of 0.432/0.482, a vertical gap for the seat of 0.150 would provide a suitable low drag seal. 
     As seen in FIG. 6, actuator arm 32 is provided with alignment and staking protrusions 32d on which is received low current spring contact member 36 (FIG. 5) which comprises a base portion 36a having a plurality of apertures 36b which receive protrusions 32d and a plurality of contact fingers 36c each of which having a distal end portion adapted to be biased against circuit board 26 so that the free distal end portions will slide into and out of engagement with respective contact segments 26a as actuator arm 32 is pivoted. 
     Actuator 32 is also provided with high current contact seats 32f which received generally U-shaped contact elements 38 (FIG. 3) which are each biased by a respective coil spring 38a into engagement with circuit board 24 so that the contacts will slide into and out of engagement with respective contact segments 24a as actuator arm 32 is pivoted. 
     Housing member 12 and lid 13 are preferably composed of suitable electrically insulative material such as a moldable polymer. According to a feature of the invention, the housing and cover are preferably formed of thermoplastic material such as nylon and are vibration welded together. Seal elements 34 accommodate the lateral vibratory motion of the vibration welding process which would not be possible if conventional gasket type seals were used. Bore 13b of lid 13 is made sufficiently large so that during vibration welding approximately 1 mm of lateral motion can be accommodated without bore 13b contacting the actuator hub diameter 32a on the lid side. Housing member 12 is provided with a circumferential channel 12c along its outer perimeter opening downwardly as seen in FIG. 4 while cover 13 is provided with a circumferential lip 13c along its outer perimeter extending upwardly as seen in the figures. The volume of channel 12c is selected to be at least as large as the volume occupied by lip 13c so that as the lip liquefies due to the vibratory energy the material will be contained within the channel and lid 3 will be flush with surfaces 12d of housing member 12 around the periphery of the housing to provide known selected dimensional relationships within recess 14, e.g., to provide the selected distance between the respective seal element seating surfaces. 
     The provision of spring seal elements 34 not only make it possible to weld the parts together using vibratory energy, it also makes it possible to accommodate the switch assembly to two fixed bores in the wall of the transmission housing and still provide a sealing function to prevent ingress of debris and the like. That is, bores 2 and 4 can be machined in sidewall 6 a selected distance a&#39; from each other within a manufacturing tolerance within which seal elements can adjust due to their ability to be moved sideways in the seating area. 
     The center lines of bore 2 and manual shaft 8 are determined by transmission and vehicle design requirements. The switch assembly is then designed to be mounted on the manual lever shaft 8 with connector portion 16 located such that it is receivable in bore 2 with the electrical contacts placed in the correct relative angular position. The ability to adjust the switch dimension a to the transmission bores dimension a&#39;, or more properly to the dimension between the longitudinal axes of bore 2 and manual shaft 8, by having the actuator hub 32a move within bore 12b of housing 12 allows the switch assembly to be installed in the transmission. 
     Improved angular control of the orientation of the housing with respect to relevant transmission datums, i.e., the center lines of manual shaft 8 and bore 2, can be obtained by making the diameter of bore 12b slightly smaller relative to hub 32a while at the same time, as seen in dashed lines in FIG. 1, elongating the bore to form a slot along a line extending between axes 18 and 22 so that the seal elements can adjust to a position along a line established between the centers of bore 2 and manual lever shaft 8. The outer diameter of sealing member 34 determines the amount of adjustment along that line which can be accommodated without adversely affecting the sealing function. 
     It should be understood that although the preferred embodiment of the invention has been described in order to illustrate the invention, the invention includes various modifications and equivalents to the disclosed embodiment. For example, in certain applications it may not be necessary to employ seal elements 34 in switch assembly 10. Further, although the connector portion 16 in the disclosed embodiments has a longitudinal axis parallel with that of manual shaft 8, it is within the purview of the invention to relate manual shaft 8 to some other reference in the switch housing and the manual valve position, for example, where the connector portion extends from the housing at some angle wherein the longitudinal axes are not parallel with one another. The slot extending along a line established between the selected reference in the switch housing and the designed position of the longitudinal axis of the manual lever shaft can still be utilized in fitting the switch to the transmission housing bores without having to rely on the detent roller to establish the proper alignment. It is intended that the invention include all modifications and equivalents falling within the scope of the appended claims.