Abstract:
A transmission shift position sensor that is adapted to provide an indication of the position of a transmission shift lever. The transmission shift position sensor includes a rotary position sensor and a rooster comb formed as an assembly. The direct coupling of the sensor to the rooster comb provides a positive indication of the automatic transmission shift sensor without the need for compensating for tolerances in mechanical linkages.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a transmission shift position sensor and more particularly to a transmission shift position sensor configured to be disposed within an automatic transmission housing and directly coupled to a so-called rooster comb. The transmission shift position sensor includes a rotary position sensor, optionally configured to be electronically calibrated to the detent positions of the rooster comb, to compensate for mechanical tolerances in the assembly and generate an electrical signal, for example, a linear signal pulse width modulated signal, representative of the position of the transmission shift position. 
     2. Description of the Prior Art 
     Various transmission shift position sensors for sensing the position of a transmission shifter assembly or an automatic transmission are known in the art. Examples of such shift position sensors are disclosed in U.S. Pat. Nos. 4,683,768; 4,907,475; 4,936,166; 5,247,279; 5,468,197; 5,651,293; 5,673,596; 5,775,166; 5,846,160; 5,847,344; 5,867,092; 5,934,436; 6,018,294; 6,027,026; 6,072,390; 6,124,789 and 6,209,408. These patents disclose various techniques for sensing the position of the transmission shift used to shift gears of an automatic transmission. For example, U.S. Pat. Nos. 5,847,344; 6,027,426 and 6,209,408 disclose transmission shift position sensors which sense the position of the transmission shift lever within the passenger compartment of the vehicle. However, the signals from such transmission shift position sensors are known to be not inherently accurate due to the tolerances in the mechanical linkages between the transmission shift lever and the automatic transmission. In particular, such automatic transmissions are hydraulic mechanisms which rely primarily on the position of manual control valves within the automatic transmission housings to direct fluid flow to change the shift positions, for example, as disclosed in U.S. Pat. Nos. 4,683,768; 4,936,166; 5,651,293 and 5,846,160, all hereby incorporated by reference. In general mechanical linkages are used to position hydraulic control valves which, in turn, control the automatic transmission. In general, these mechanisms include a so-called “rooster comb” that is mechanically coupled on one end to a transmission shift lever within the vehicle passenger compartment and is mechanically coupled to the hydraulic control valves within the automatic transmission housing. Such rooster combs are normally disposed within the automatic transmission housing and are formed with a cam surface having a number of detent positions which cooperate with a biasing member for latching each of the shift positions of the automatic transmission. Often times, tolerances or play in the mechanical linkages can result in relatively inaccurate signals being generated by transmission shift position sensors which rely on the position of the transmission shift lever within the vehicle passenger compartment such as disclosed in U.S. Pat. Nos. 5,847,344; 6,027,426 and 6,209,408. Such inaccurate transmission shift position sensor signals are highly undesirable for several reasons. First, such signals are known to be applied to a powertrain control module which prevents cranking of the engine unless the transmission is in the park or neutral positions. In addition, such position signals are also used to provide the vehicle operator with a visual indication of the shift position of the automatic transmission. Lastly, such signals are used to control operation of the reverse back-up lamps in an automobile. Accordingly, it is necessary to have a relatively accurate indication of the transmission shift position. 
     In an effort to improve the accuracy of such transmission shift position sensors, new sensors have been developed. For example, U.S. Pat. No. 4,907,475 discloses a shift position sensor which relies on pressure switches within the automatic transmission housing. With this sensor, the pressure at various points within the automatic transmission is sensed to provide a signal representative of the shift position of the automatic transmission. Such sensors are also subject to various inaccuracies which can result in an incorrect indication of the shift position of the automatic transmission. For example, such sensors are subject to changes in pressure within the automatic transmission; as well as tolerances in drifting of the set point of the pressure switches. 
     Still other systems have been developed which incorporate sensors within the transmission housing in an attempt to provide more accurate sensing of the position of the transmission shift lever. For example, U.S. Pat. No. 6,018,294 discloses a shift position sensor which includes a rooster comb which includes a cam surface which corresponds to the detent positions of the rooster comb. An electronic contact-type switch rides along the cam surface to provide an indication of the rooster comb and thus the shift position of the automatic transmission. Such a sensor as disclosed in the &#39;294 patent, incorporates a contact-type switch, which, unfortunately, is subject to wear and failure. Moreover, replacement of the worn switch would be rather difficult and expensive for a consumer since the switch is disposed within the transmission housing. 
     In order to avoid the problems associated with contact-type switches, sensors have been developed which incorporate non contact-type sensors. For example, U.S. Pat. No. 5,867,092 discloses a position sensor for a transfer case for a four wheel drive vehicle. The transfer case includes an input shaft which drives a planetary gear assembly which provides various speed reduction ratios to provide two-wheel or four-wheel operation. Various gear reduction ratios are selected by a shift control rod. 
     This includes a plurality of Hall effect sensors disposed within the transfer case housing. The Hall effect sensors are disposed to detect the position of a metal plate coupled to a transmission shift control rod. While the shift position sensor utilizes non-contact Hall effect sensors for sensing the position of a shift control rod in a transfer case, the sensor disclosed in the &#39;092 patent is based upon utilizing three Hall effect sensors and a metal plate attached to the shift control rod within the transfer case housing. Unfortunately, there is insufficient room in automatic transmission housing for such a configuration. Thus, there is a need for a non-contact sensor for sensing the position of a transmission shift lever which provides an accurate indication of the position of the transmission shift lever. 
     SUMMARY OF THE INVENTION 
     Briefly, the present invention relates to a transmission shift position sensor that is adapted to provide an indication of the position of a transmission shift lever. The transmission shift position sensor includes a rotary position sensor and a rooster comb formed as an assembly. The direct coupling of the sensor to the rooster comb provides a positive indication of the automatic transmission shift sensor without the need for compensating for tolerances in mechanical linkages. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     These and other advantages of the present invention will be readily understood with reference to the following specification and attached drawing wherein: 
     FIG. 1 is a exploded perspective view of a transmission shift position sensor assembly in accordance with the present invention. 
     FIG. 2A is a partial plan view of a transmission housing shown with a hydraulic control valve. 
     FIG. 2B is a partial perspective view illustrating the transmission shift sensor in accordance with the present invention installed within a cavity of a transmission housing. 
     FIG. 3A is a plan view of a rotary position sensor for use with the present invention illustrating the rotary drive for receiving one end of the drive arm. 
     FIG. 3B is a plan view of one end of the drive arm in accordance with the present invention. 
     FIG. 4A is a plan view of a transmission shift sensor assembly in a parked position. 
     FIG. 4B is a elevational view of a transmission shift sensor in accordance with the present invention in a parked position. 
     FIGS. 5A and 5B are similar to FIGS. 4A and 4B but in a reverse position. 
     FIGS. 6A and 6B are similar to FIGS. 4A and 4B but in a neutral position. 
     FIGS. 7A and 7B are similar to FIGS. 4A and 4B but in a drive position. 
     FIGS. 8A and 8B are similar to FIGS. 4A and 4B but in a manual three position. 
     FIGS. 9A and 9B are similar to FIGS. 4A and 4B but in a manual two position. 
     FIGS. 10A and 10B are similar to FIGS. 4A and 4B but in a manual one position. 
    
    
     DETAILED DESCRIPTION 
     The present invention relates to a transmission shift position sensor which provides a positive indication of the transmission shift position. The transmission shift position sensor in accordance with the present invention, generally identified with the reference numeral  20 , is directly coupled to a rooster comb and is disposed within the automatic transmission housing. By providing direct coupling of the transmission position sensor to the rooster comb, a positive indication of the shift position of the automatic transmission is provided. 
     The shift position sensor includes a rotary position sensor which, in turn, includes a Hall effect IC to provide non-contact-type sensing of the position of the rooster comb. A drive arm is directly coupled to the rooster comb and to the rotary position sensor. The rotary position sensor is calibrated to the various detent positions corresponding the automatic transmission shift positions on the rooster comb. The rotary position sensor may optionally be provided with a electronic calibration circuit which enables the rotary position sensor to be electronically calibrated. 
     Referring to FIG. 1, the transmission shift position sensor  20  in accordance with the present invention is illustrated. The transmission shift position sensor  20  includes a rotary position sensor  22 , a bracket assembly  24 , a drive arm or adapter  26 , a rooster comb  28  and a detent spring assembly  30 . The rooster comb  28  is formed with a number of detent positions, generally identified with the reference numeral  32 , for latching the automatic transmission in a selected shift position. The detent positions  32  are adapted to receive the detent spring assembly  30  to latch the rooster comb  32  and thus the automatic transmission in the selected automatic transmission shift position. 
     The bracket assembly  24  is adapted to be secured within an automatic transmission housing by way of a pair of slotted flanges  34  and  36 . The bracket assembly  34  is provided with a third flange  38  which includes a pair of spaced apart apertures  40  and  42  for receiving and securing the detent spring assembly  30 , for example, by way of a fastener  41  and a tab  43 . The position of the flange assembly  24  is selected such that a roller  44  disposed on one end of the detent spring assembly  30  is in communication with the detent positions  32  on the rooster comb  28 . The configuration of the bracket assembly  24  as well as the entire assembly is selected to fit within a cavity, generally identified with the reference numeral  46  (FIGS. 2A and 2B) in an automatic transmission housing  48 . 
     The bracket assembly  24  includes an aperture  50  for receiving an extending end  52  of the adapter  26  that is adapted to be coupled to the rotary position sensor  22  by way of central aperture  54 . The other end  56  of the adapter  26  is formed with in irregular shape or keyed to be received within a corresponding aperture  60  in the rooster comb  28 , such that rotation of the drive arm  26  will cause rotation of the rooster comb  28 . 
     As shown, the bracket  24  assembly includes two spaced apart apertures  62  and  64 , adjacent opposing ends of the aperture  50 , which are aligned with a pair of opposing flanges  66  and  68  on the rotary position sensor  20 . The flanges  66  and  68  on the rotary position sensor  20  are provided with through holes  70  and  72  to enable the rotary position sensor  22  to be rigidly secured to the bracket assembly  24  with suitable fasteners  74  and  76 . 
     The rooster comb  28  is provided with a cam slot with cooperates with a rotatable linkage  80  rotatably, attached to one end of the bracket assembly  24 . The rotatable linkage  80  is formed from a lever  81  which includes a pair of oppositely facing studs  82  and  84  on opposing ends. The stud  82  functions as a cam and is adapted to be received in a cam slot  78 , formed in the rooster comb  28 . The other stud  84  is adapted to be mechanically coupled to a manual valve  86  (FIG.  2 A), which controls the shift position of the automatic transmission  48 . 
     The adapter  26  is provided with an increased diameter portion  88  which enables the drive arm to be sandwiched between the bracket assembly  24  and the rooster comb  28  and provide bearing surfaces relative thereto. The rooster comb  28 , in turn, may be rigidly secured to the adapter  26  by various conventional methods including brazing or by way of a c-clamp  87  (FIG.  4 B). After assembly into the automatic transmission  48  (FIG.  2 A), the extending portion  56  (FIG. 1) of the adapter  26  is disposed adjacent a sidewall  91  (FIGS. 2A and 2B) of the automatic transmission  48 . The extending portion  56  (FIG. 1) is directly coupled to a shaft  93  (FIGS. 2A and 2B) which extends through the sidewall  91 . The shaft  93  is rotatable relative to the sidewall  91  and is hermetically sealed thereto in a known manner. One end (not shown) of the shaft  93  is configured to be received within a central aperture  95  (FIG. 1) of the adapter  56  such that rotation of the shaft  93  (FIGS. 2A and 2B) causes rotation of the adapter  26  (FIG.  1 ). 
     The rotary position sensor may be a rotary position sensor, for example, as disclosed in U.S. Pat. Nos. 5,757,181 and 6,198,275 assigned to American Electronic Components, Inc. or alternatively as disclosed in copending application Ser. No. 09/653,507, filed on Sep. 1, 2000 and may be formed with various types of circular magnets including both diametric and radially magnetized magnets. A compensation circuit may optionally be provided, for example, as disclosed in aforementioned American Electronic Components, Inc. U.S. Patents. The compensation circuit may be used to electronically calibrate the rotary position sensor  22 . 
     With reference to FIG. 3A, the rotary position sensor  22  includes a rotor drive cavity  90 , formed with two opposing tabs  92  and  94 . These tabs  92  and  94  are adapted to be received in axial slots  96  and  98 , formed on the end  52  the adapter  26  such that rotation of the adapter  26  causes a corresponding rotation of rotary drive cavity  90 . Other configurations are possible and are well within the ordinary skill in the art. 
     FIGS. 4A through 10B illustrate the various positions of the assembly in a park, reverse, neutral, drive, manual  3 , manual  2  and manual  1  (FIG. 3B) position of the transmission shift sensor  20  in accordance with the present invention. As shown in FIGS. 4B-10B, as the position of the cam  82  within the cam slot  78  in the rooster comb  28 , changes the position of the adapter  26  changes relative to an axis  100 . As mentioned above, the rotary position sensor  22  is directly coupled to the adapter  26 . Thus, incremental changes in the position of the adapter  26  result in corresponding rotational changes in the rooster comb  28 . These rotational changes are used to generate an electrical signal representative of the angular position of the adapter  26  as well as the rooster comb  28 . These signals, in turn, may be applied to a power train control module, for example, by way of cable  102  (FIG. 2B) to provide a cranking enable to allow the engine in the vehicle to be started only when the vehicle is in the park or neutral position. The signals from the sensor may also be used in applications, for example, hybrid hydraulic/electronic transmission in which one or more transmission shift positions are hydraulically controlled by a manual hydraulic control valve and one or more of the transmission positions are electronically controlled by an electronic solenoid. Lastly, these signals may be used to control the reverse back-up lamps as well as provide a position indication on the dashboard to the driver of vehicle of the selected shift position. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. For example, thus, it is to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described above. 
     What is claimed and desired to be secured by Letters Patent of the United States is: