Abstract:
A device for sensing the input shaft speed of an automotive automatic transmission that is driven by the engine through the fluid coupling of a torque converter. The speed sensor device includes circumferentially spaced markings about the transmission input shaft and a speed sensor that is placed at close proximity to the circumferentially spaced markings through a hole in the torque converter stator shaft. An electronic control unit (ECU) analyzes the sensor output signal and in the case of an active speed sensor it also functions as its power source. During vehicle operation, the transmission input shaft rotates the target wheel in front of the speed sensor causing modulation of its output signal. The electronic control unit analyzes the signal modulation and calculates the input shaft rotational speed. A variety of sensor/target-wheel options and sensor mounting techniques could be used depending on the application constraints.

Description:
This application claims the benefit of U.S. Provisional Patent Application No. 60/490,377 filed on Jul. 25, 2003. 

   BACKGROUND 
   Knowledge of input and output shaft speeds for an automatic transmission would enable its control unit to execute smooth transmission shifts leading to enhanced vehicle performance. Although output-shaft speed measurement of an automatic transmission is easily accomplished, speed measurement of its input shaft is difficult due to the transmission complexity and its input shaft inaccessibility. Current methods for input-shaft speed measurement, such as the ones described in U.S. Pat. Nos. 6,522,133B1, 4,586,401 and 3,845,671, require a magnetic sensor that senses either the rotation of a large magnetic target wheel through a non-ferromagnetic reaction shell or the rotation of a transmission output gear. These solutions require sensors that are bulky and expensive for sensing rotating target wheels at great distances, expensive magnetic target wheels due to their large size, the use of an expensive non-ferromagnetic reaction shell, and placement of sensors through a hole on the transmission housing that requires robust sealing methods. Also, in certain designs where the large air-gap between the sensor and the target wheel requires the choice of a VR speed sensor, the resulting output signal does not allow low speed measurements. 
   SUMMARY 
   The present invention relates to a device for sensing the speed of an automotive automatic transmission input shaft that is part of a transmission input assembly. The transmission input assembly comprises a transmission input shaft, the associated transmission torque converter stator shaft, and the corresponding transmission pump housing. The device comprises a sensor positioned adjacent the input shaft and configured to sense a plurality of markers circumferentially spaced about the input shaft. The circumferentially spaced markers may be formed directly in the input shaft or may be provided by a target wheel attached onto the transmission input shaft having a plurality of markers circumferentially spaced about the wheel. For example, the markers may be metallic teeth or a series of alternating magnetic poles around the wheel&#39;s outer diameter (“OD”) surface. The speed sensor is placed at close proximity to the circumferential markers through a hole in the torque converter stator shaft. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevation view in partial section of a transmission input assembly incorporating a speed sensing device according to a first embodiment of the present invention; 
       FIG. 2  is a top plan view of a transmission input shaft having a plurality of circumferential markings formed thereon; 
       FIG. 3  is a cross sectional view along the line  3 - 3  in  FIG. 2 ; 
       FIG. 4  is a top plan view of the transmission input shaft and the associated transmission torque converter stator shaft of  FIG. 1 ; 
       FIG. 5  is an isometric view of the transmission input shaft and the associated transmission torque converter stator shaft of  FIG. 1  with the speed sensor device according to the first embodiment positioned therewith; 
       FIG. 6  is an isometric view of the transmission input shaft assembly of  FIG. 1  with the speed sensor device according to the first embodiment positioned therewith; 
       FIG. 7  is a side elevation view of a gear ring useable as a target wheel in the present invention; 
       FIG. 8   a  is a side elevation view and  FIG. 8   b  is a front elevation view of a cage ring useable as a target wheel in the present invention; 
       FIG. 8   c  is a side elevation view of a cage ring similar to that of  FIGS. 8   a  and  8   b;    
       FIGS. 9-13  are side elevation views of various molded rings useable as a target wheel in the present invention; 
       FIG. 14   a  is a side elevation view and  FIG. 14   b  is a front elevation view of a molded ring with side ribs useable as a target wheel in the present invention; 
       FIG. 15  is a side elevation view in partial section of a transmission input assembly incorporating a speed sensing device according to a second embodiment of the present invention; 
       FIG. 16  is a side elevation view in partial section of a transmission input assembly incorporating a speed sensing device according to a third embodiment of the present invention; 
       FIG. 17  is a side elevation view in partial section of a transmission input assembly incorporating a speed sensing device according to a fourth embodiment of the present invention; 
       FIG. 18  is a side elevation view in partial section of a transmission input assembly incorporating a speed sensing device according to a fifth embodiment of the present invention; 
       FIG. 19  is a side elevation view in partial section of a transmission input assembly incorporating a speed sensing device according to a sixth embodiment of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   While the invention is susceptible of embodiment in many different forms, there is shown in the drawings and described in detailed preferred embodiments of the invention. It is understood that the present disclosure is to be considered only as an example of the principles of the invention. This disclosure is not intended to limit the broad aspect of the invention to the illustrated embodiments. The scope of the protection should only be limited by the accompanying claims. 
   A first embodiment of the invention will be described with reference to  FIG. 1-14 . Referring to  FIG. 1 , the transmission input shaft assembly  10  generally comprises an input shaft  12 , a torque converter stator shaft  14  positioned about the input shaft  12  and the transmission pump housing  18  positioned about the input shaft  12  and the torque converter stator shaft  14 . The torque converter stator shaft  14  typically includes a radial flange  16  extending adjacent the side wall of the pump housing  18 . The speed sensing device  20  generally includes a plurality of circumferentially spaced markings  22  about the input shaft  12  and a sensor  24  extending through the torque converter stator shaft  14  in close proximity to the circumferentially spaced markings  22 . 
   Referring to  FIGS. 1-6 , the torque converter stator shaft  14  includes a hole  17  therethrough configured to receive the sensor  24 . As seen in  FIG. 4 , the hole  17  is aligned with the circumferentially spaced markings  22  such that the sensor  24 , positioned in the hole  17 , will be aligned with and in close proximity to the circumferentially spaced markings  22 . The sensor  24  has a body  27  configured to plug and seal the hole  17 . To accommodate the cable  25  extending from the sensor  24 , an axial groove  19  extends along the torque converter stator shaft  14  from the hole  17  to a radial groove  21  extending along the torque converter stator shaft flange  16 . As can be seen in  FIGS. 5 and 6 , the cable  25  can be run through the grooves  19  and  21  and then along the wall of the pump housing  18  and out of the transmission assembly  10  without providing substantial obstruction. A seal member  23  may be used to fill the groove  19  to further ensure sealing of the hole  17 . 
   The speed sensor cable  25  exits the transmission assembly  10  radially and is connected to an electronic control unit (ECU) that analyzes its output signal. In the case of an active speed sensor, the ECU provides power to the sensor. As the circumferentially spaced markings  22  rotate with the input shaft  12  in front of the speed sensor  24 , the sensor output signal is modulated and the ECU calculates the input shaft  12  rotational speed. The sensor  24  preferably has dual sensing elements which can, for example, be utilized for noise cancellation. In certain applications where direction of rotation is also desired, the dual sensing elements may be configured to determine the direction of rotation. In addition, the sensor  24  may be configured to provide a temperature measurement within the torque converter stator shaft  14 . Commonly owned PCT Application No. PCT/US03/32692, herein incorporated by reference, describes a system of obtaining a temperature measurement with a VR sensor. Alternatively, a separate temperature sensor may be integrated with the active speed sensor in order to provide temperature measurement at a location deep inside the transmission interior. Depending on the design configuration, various hardware and software, for example, a specially designed ASIC, can be used. 
   Depending on the application constraints, the circumferentially spaced markings  22  can be provided in a variety of ways. For example, as illustrated in  FIGS. 2 and 3 , the circumferentially spaced markings  22  can be defined around the input shaft  12  by machining, forming or otherwise providing splines into OD surface of the input shaft  12 . Alternatively, the circumferentially spaced markings  22  can be provided by attaching a target wheel incorporating the markings  22  to the input shaft  22 . A variety of target wheels are illustrated in  FIGS. 7-14 . The target wheel can be attached to the input shaft  12  in a variety of ways, for example, but not limited to, press-fitting, welding, or bolting of the target wheel onto the input shaft  12  OD surface. 
   The variety of illustrated target wheels will be described with reference to  FIGS. 7-14 .  FIG. 7  illustrates a gear ring  30  with a plurality of teeth  31  that define the circumferentially spaced markings. The gear ring may be manufactured in various ways, for example, from powdered metal or may be a stamped metal gear ring.  FIGS. 8   a  and  8   b  illustrate a stamped metal cage ring  32  made from one or more sections and having a plurality of openings  33  that define the circumferentially spaced markings  22 .  FIG. 8   c  illustrates a stamped metal cage ring  32 ′ similar to that shown in  FIGS. 8   a  and  8   b , with the cage ring  32 ′ being formed in to halves  32   a  and  32   b  to facilitate positioning about the input shaft  12 . Each halve  32   a ,  32   b  has a projecting tab  39  and a retaining slot  41  for interconnection of the two halves  32   a ,  32   b  about the input shaft  12 . Other interconnection means may also be utilized. Additionally, the multi-piece configuration may be utilized for other target wheel types other than the stamped metal cage. For example, the split pair of magnetic rings  46  illustrated in  FIG. 12  and described hereinafter may be formed with interconnecting ends. 
     FIG. 9  illustrates a molded ring  34  with a plurality of spaced apart metallic inserts  36  that define the circumferentially spaced markings  22 .  FIG. 11  illustrates a target wheel similar to  FIG. 9  but further including a protective rim  38  positioned thereabout.  FIGS. 11-13  illustrate molded multi-pole magnetic rings  40 ,  44  and  50  for use as the target wheel. The multi-pole magnetic ring  40  of  FIG. 11  includes a split  42  for facilitating positioning about the input shaft  12 . The multi-pole magnetic ring  44  of  FIG. 12  includes a split pair of magnetic rings  46  with a retaining band  48  thereabout. The multi-pole magnetic ring  50  of  FIG. 11  is configured as an elastic member configured to be slipped over the input shaft  12 .  FIGS. 14   a  and  14   b  illustrates a multi-pole magnetic ring similar to that shown in  FIGS. 11 ,  12  and  13 , with protective ribs  52  positioned about the ring  50 . 
   The sensor  24  can be any one of the available speed sensors such as a VR sensor, a Hall-Effect sensor, a Magnetoresistive sensor, a GMR sensor, or an Eddy Current sensor. The type of sensor  24  is selected to be compatible with the chosen circumferentially spaced markings  22 . For example, if the circumferentially spaced markings  22  are defined by teeth formed around the normally ferromagnetic input shaft by machining its OD surface, or a ferromagnetic gear-ring  30  target wheel is placed around the input shaft  12 , a VR sensor, a Hall sensor, a Magnetoresistive sensor, or a GMR sensor with a back-biased magnet can be used. A multi-pole magnetic target wheel placed around the input shaft  12  preferably utilizes a magnetic sensor without the back-biased magnet. Alternatively, an Eddy Current sensor is preferably utilized with circumferentially spaced markings  22  defined by a ferromagnetic material or a non-ferromagnetic conductive material. 
   Referring to  FIG. 15 , an alternate embodiment of the invention is illustrated. The circumferentially spaced markings  22  are provided around the transmission input shaft  12  at a point along its axial length so that, in the final transmission assembly, the markings  22  are directly underneath the pump housing  18 . The chosen sensor  24  is mounted over the circumferentially spaced markings  22  after the pump housing  18  placement over the torque converter stator shaft  14  through an angled hole  17  from the pump housing sidewall to the stator  14  ID surface. The sensor body  27  forms a sealed cylindrical plug inside the sensor hole  17  and extends beyond the pump housing  18  sidewall. In the illustrated embodiment, the sensor body  27  is mounted to the stator radial flange  16  by a clip  29  or the like. Alternatively, the sensor body  27  may be secured to the pump housing  18  or otherwise secured within the angled hole  17 , for example, by an interference fit. Beyond the pump housing  18 , the sensor cable  25  exits the transmission assembly  10  radially routed along the sidewall of the transmission pump housing  18 . 
   Referring to  FIG. 16 , an alternate embodiment of the invention is illustrated. The circumferentially spaced markings  22  are provided around the transmission input shaft  12  inside a slot  35  next to a fluid channel  37 . This may cause axial displacement of existing oil channels for certain applications. The chosen sensor  24  is mounted over the circumferentially spaced markings  22  through a radial hole  17  on the body of the torque converter stator shaft  14 . The sensor body  27  forms a sealed cylindrical plug inside the sensor hole  17  and extends beyond the stator OD surface in a way that allows its mounting onto the stator radial flange  16  or any other available mounting surface by a clip  29  or the like. Beyond the stator flange  16 , the sensor cable  25  exits the transmission assembly  10  radially routed along the sidewall of the transmission pump housing  18 . 
   Referring to  FIG. 17 , an alternate embodiment of the invention is illustrated. The circumferentially spaced markings  22  are provided around the transmission input shaft  12  inside a slot  35  next to a fluid channel  37 . This may cause axial displacement of existing oil channels for certain applications. The chosen sensor  24  is mounted over the circumferentially spaced markings  22  through a radial hole  17  inside the torque converter stator shaft flange  16 . The sensor body  27  forms a sealed cylindrical plug inside the sensor hole  17  and extends beyond the stator flange  16  in a way that allows its mounting onto the flange body. Beyond the stator flange  16 , the sensor cable  25  exits the transmission assembly  10  radially routed along the sidewall of the transmission pump housing  18 . 
   Referring to  FIG. 18 , an alternate embodiment of the invention is illustrated. The circumferentially spaced markings  22  are provided around the transmission input shaft  12  at a point along its axial length so that, in the final transmission assembly, the markings  22  are directly underneath the pump housing  18 . The pump housing  18  is formed with a radial hole  43  extending from the pump housing  18  inner diameter to the pump housing  18  outer diameter. The hole  43  may be formed in the pump housing  18  or may be drilled in to a previously manufactured pump housing  18 . The pump housing radial hole  43  is aligned with a radial hole  17  in the torque converter stator shaft  14 . The body  27  of the chosen sensor  24  is extended through the aligned radial holes  17  and  43  such that a forward end of the sensor is mounted in close proximity to the circumferentially spaced markings  22 . The sensor body  27  forms a sealed cylindrical plug inside the sensor hole  17 . The other end of the sensor body  27  extends beyond the pump housing  18 . In the illustrated embodiment, the sensor body  27  extends through a hole  62  of an oil pan  60  positioned at the outer diameter of the pump housing  18 . The oil pan  60  has a removable cover  64  that can be removed to access the sensor  24 . The sensor body  27  is removable from the radial holes  17  and  43  through the oil pan  60  to allow service or the like of the sensor  24 . The sensor cable  25  extends from the sensor body  27  and exits oil pan  60  through a sealed hole  66 . 
   Referring to  FIG. 19 , an alternate embodiment of the invention is illustrated. The circumferentially spaced markings  22  are provided around the transmission input shaft  12  at a point along its axial length so that, in the final transmission assembly, the markings  22  are directly underneath the pump housing  18 , however, the markings  22  may be alternatively positioned. The chosen sensor  24  is mounted over the circumferentially spaced markings  22  after the pump housing  18  placement over the torque converter stator shaft  14  through an angled hole  17  from the pump housing sidewall to the stator  14  ID surface. The sensor body  27  forms a sealed cylindrical plug inside the sensor hole  17  and extends beyond the pump housing  18  sidewall. In the present embodiment, the sensor body  27  has an extended axial length configured to pass through open space in the transmission assembly  10 . The extended sensor body  27  is configured to extend to an easily accessible portion of the transmission assembly  10 , for example, a sealed hole  72  through the transmission bell housing  70 , or alternatively, through the removal of the oil pan or the like accessible component. A clip  29  or the like can be provided to support a midsection of the sensor  24 . The sensor cable  25  extends from the sensor body  27  outside of the bell housing  70  from where it routed to the ECU. If the sensor  24  requires servicing, it can be easily withdrawn through the hole  72 .