Electrical switch system for use with vehicular transmissions |
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申请号 | US12228988 | 申请日 | 2008-08-19 | 公开(公告)号 | US20090107811A1 | 公开(公告)日 | 2009-04-30 |
申请人 | David J. DiPaola; George P. Krajewski; Bonnie L. Moore; Denis J. Villard; | 发明人 | David J. DiPaola; George P. Krajewski; Bonnie L. Moore; Denis J. Villard; | ||||
摘要 | A linear vehicle transmission switch (10) has first and second interfitting housing members (12, 14) each having an electrically conductive lead frame (12m) insert molded in electrically insulative material and formed with exposed segments (12f) of lead frame material along linear tracks. An elongated actuator (16) is slidably received in a channel of one of the housing members and is disposed along a side of the tracks. A paddle (16b) extends transversely across the tracks. Ribs are disposed between tracks and dimensioned to limit rotational movement of the paddle. A pair of stabilized contact switches is disposed on the paddle for each track. The housing members have a selected camber to lower the force required to move the actuator. The lead frames are plated to reduce contact resistance and improve wear. | ||||||
权利要求 | What is claimed: |
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说明书全文 | This invention relates generally to vehicular transmissions and more particularly to apparatus for sensing the position of the shifter of the automatic transmission of a vehicle thereby indicating the mode of the transmission by means of providing an input to the electronic control module (ECM). It is conventional to provide a switch assembly that changes position based on mechanical linkages connected to the shifter of a transmission of the vehicle to provide an output display signal. Such switch assemblies generally comprise either a rotary movable contact mechanism such as those shown in U.S. Pat. Nos. 5,525,768 and 5,440,087, or a straight linear movable contact mechanism such as shown in U.S. Pat. No. 5,902,975. The present invention relates to the latter type in which an actuator carrying a set of movable contacts is caused to slide back and forth in a straight line. According to the present invention, the shifter changes the position of the internal mode switch and the internal mode switch's electrical bit pattern may trigger a change in electronically controlled valves. According to the latter noted patent, the movable contacts are spring cantilever arms biased into engagement with respective stationary electrically conductive segments along tracks in locations selected to provide a selected pattern so that output signals are obtained based on the longitudinal position of the internal mode switch to identify the switching position of the gear shift selector of the vehicle transmission. According to the present invention the spring contact arms were changed to include dual bends however, testing has shown that over time the contact force of these spring contact arms decrease and eventually become less reliable. For example, if the contact force is insufficient the spring contact arm can lose contact with the stationary conductive segment during periods of high vibration. Another limitation in the system is that over time the contact resistance can increase sufficiently to cause a problem due to oxidation of wear particles and the surface of the mating stainless steel conductive surfaces. The electrical switch system operates by applying a voltage to the stationary conductive segments with one of those segments being grounded. All the spring arms are connected electrically and one particular spring arm and the stationary conductive segment that is grounded are in continual contact. When a grounded spring contact arm makes contact with a stationary conductive segment at high voltage, it grounds that segment causing the voltage to drop below a specific threshold. When the spring contact arm rides on the plastic for that segment, the stationary conductive segment remains at high voltage. Since the spring contact arms and the stationary conductive segments are stainless steel, exposure to oxygen, time and heat cause them to oxidize and the subsequent oxidized wear particles also causing the contact resistance to increase thereby increasing Vout until there is insufficient deferential between the switching level for the electronic module to determine whether or not the spring contact arms are in engagement with a stationary conductive segment. It is an object of the invention to provide a vehicular transmission electrical switch system that has an extended expected life expectancy relative to prior art systems. Another object of the invention is the provision of a switch system that has lower contact resistance. Another object of the invention is the provision of such a system that requires less force to move the switch actuator along its operational linear path. Yet another object of the invention is to improve switch functionality during severe vibration. Briefly, in accordance with the preferred embodiment of the invention, a plurality of parallel extending tracks are provided in each of two mating housing. The tracks are formed by a lead frame having parallel extending strips insert molded in electrically insulating plastic and exposed at selected locations along each track to provide a unique binary electrical input indicative of the particular location of an actuator. The actuator comprises a plurality of leaf springs with a pair of respective leaf springs aligned with each track. The leaf springs are all simultaneously grounded through a grounding trace in the actuator. When electrical contact is made between an exposed conductive segment and a leaf spring, Vout is shorted to ground. When the leaf spring is on plastic Vout is above a voltage threshold because current can not flow. The actuator comprises an elongated slidable member received in a channel that extends parallel to the tracks on one side of a housing member. The slidable member has an electrically insulative paddle adapted to extend transversely across the several tracks. An electrically conductive sheet of suitable conductive material, such as stainless steel, is disposed about the two face surfaces of the paddle facing the tracks and attached to the paddle. For each track a pair of aligned cantilever contact arms are struck from the sheet, the arms generally extending toward each other but slightly offset from one another so that both arms of a pair are elongated extending away from the surface of the paddle and are engageable with a single strip of the lead frame forming the track. One of the housing members is provided with a suitable mounting means such as a pair of bored bosses provided with bushings and an electrical harness having electrical wires for connections with the lead frames. One housing member is received on the other housing member and a plurality of clip members are used to pinch the two housing members together. According to a feature of the invention, a selected camber is provided for each housing member so that the distance between each track of a housing member and its respective aligned track in the other housing member varies along the length of the track with the distance between the tracks at the center of a respective track length being greater than at it is at the extremities of the respective track length. This feature lowers the force required to move the actuator along its path. The tracks of each housing member are separated from one another by a rib member extending from a base wall of a housing member to a selected height to provide a certain gap between a rib of one housing and a respective aligned rib of the other housing member. According to another feature of the invention, the rib in the housing member containing the actuator channel furthest from the actuator channel extends slightly higher from the base wall than the remaining ribs of the bottom housing member to provide a limit to rotational movement of the actuator paddle about the longitudinal axis of the elongated actuator and thereby provide enhanced vibration insensitivity of the switch system. According to another feature of the invention, the lead frames are formed of stainless steel and are provided with a bright nickel plating to reduce contact resistance and reduce fretting corrosion and oxidized wear particles. According to yet another feature of the invention, the cantilever leaf springs arms are formed so that the free distal ends of the arms have a selected free height relative to their fixed end that is greater than the designed operational free height. A force is then applied to the free end of each arm deflecting the free end down to a level of approximately 2 mm above the plane in which the fixed end of the arm lies, and then the force is removed. This cycle is repeated at least once resulting in a stabilized free height of somewhat below the height as formed thereby providing the operational height that maintains a preselected level of contact force that is greatly extended. With particular reference to As best seen in Housing member 14, preferably formed of the same material as housing 12, has a base wall that is also formed with three parallel, straight tracks or strips two of which, 14b, 14c, are shown, and a third track not seen in With reference to Stainless steel is used for the lead frames and in order to lower the contact resistance between the lead frames and the spring contact arms and minimize the production of severely oxidized wear particles the lead frames are plated with bright nickel. This is particularly advantageous in the preferred embodiment described herein in which the lead frames form conductive tracks in both the top and bottom housings and debris can collect on the lower tracks and cause changes in switching distances. A nickel flash is first deposited followed by a sulfamate electrolytic bath (Rohm and Haas Electronic Materials Sulfamate Concentrate) with 1.25%±0.75% Nikal PC-3 additive (Rohm and Haas Electronic Materials. A layer of approximately 100 to 300 microinches is deposited to provide sufficient hardness for extended wear resistance and lower contact resistance while still permitting the lead frames to be cambered. The camber flattens out somewhat during the molding process to provide a differential gap that varies from 0 at the extremities to a maximum of 6.8+0.25/−0.30 mm at the center of the housing members between the top and bottom housing ribs when all the ribs are formed having the same height. As will be discussed in greater detail below, according to a preferred feature of the invention, one rib is formed with a height extended an extra 0.15 mm so that in a switch made having that feature the maximum gap is 6.65+0.25/−0.30 mm. Actuator assembly 16 comprises an elongated sliding member 16a formed of suitable material, such as Nylon, that is adapted to be received in channel 14m of housing 14. A transversely extending paddle 16b extends from elongated member 16a. A sheet 20 of suitable electrically conductive material, such as stainless steel (see A selected space or gap is provided between corresponding ribs of housing members 12 and 14 to allow paddle 16b of the actuator assembly 16 to slide back and forth along the several tracks. In the preferred embodiment there are three separate tracks in each housing member. In housing member 12 two identical ribs 12k separate tracks 12b from 12c and 12c from 12d. In housing member 14 rib 14k1 separates tracks 14b and 14c and rib 14k2 separates tracks 14c and 14d (hidden). In order to make the switching system less sensitive to vibration, the rotational movement of paddle 16b along the longitudinal axis of sliding member 16a is limited by providing a slightly greater height to the rib of bottom housing member 14 furthest from channel 14m in which the actuator slide member 16a is received, that is rib 14k1. The differential between the extended height rib and the normal rib is approximately 0.15 mm. The closer rib, 14k2 has a height of 2.65 mm from the conductive track while the furthest rib has a height of 2.80 mm. The location of the top surface of the ribs is measured from a datum on the mating surfaces of the housings, i.e., the bottom surface of notches 14j. When Amodel is used for the housing member the camber for the top housing 12 is 0.150-0.168 inches and for bottom housing 14 the camber is 0.405-0.422 inches. The measurement from the datum to rib 14k1 is 4.75±0.1 mm. The lead frame camber is 0.670-0.730 inches. Housing member 14 is provided with a pair of mounting bosses 14n that are bored to receive bushings 14p for mounting the switch system. Wiring harness 18 is provided with a connector 18a and a cable containing six wires that are welded to the lead frame strips. Housing member 12 is received on housing member 14 with actuator sliding member 16a received in channel 14m and tabs 14h of housing member 14 disposed in mating notches 12h of housing member 12 with the housing members held together by stainless steel clips 22. It should be understood that although the preferred embodiment of the invention has been described to illustrate the invention, the invention includes various modifications and equivalents to the disclosed embodiment. It is intended that the invention include all such modifications and equivalents falling within the scope of the appended claims. |