Patent Abstract:
A solenoid assembly for implementation with an electronic transmission range selection (ETRS) system that shifts a transmission range between a park position and an out-of-park position. The solenoid assembly includes an extension arm biased against a member of the ETRS system. The extension arm is movable to an extended position to maintain the member in the out-of-park position. A solenoid is interconnected with the extension arm. The solenoid is operable to selectively move the extension arm between the extended position and a retracted position to selectively retain the member in the out-of-park position.

Full Description:
FIELD OF THE INVENTION 
     The present invention relates to automatic transmissions and more particularly to an internal transmission range selection system using electronic controls. 
     BACKGROUND OF THE INVENTION 
     Motorized vehicles include a power plant (e.g., engine or electric motor) that produces driving power. The driving power is transferred through a transmission to a driveline for driving a set of wheels at selected gear ratios. As is well known, automatic transmissions shift automatically to the appropriate gear ratio based on various vehicle operating conditions including speed and torque. Typically, a desired transmission operating mode or range is selected by the vehicle operator. The ranges provided by most automatic transmissions generally include Park, Neutral, Reverse and Drive. In Drive, the automatic transmission automatically shifts between three, four, five or even six different forward gear ratios based on the vehicle operating conditions. 
     Traditionally, a driver interface device is provided which the vehicle operator shifts to select the desired transmission range. The driver interface device is linked to the automatic transmission by a range shift mechanism which typically includes a series of interconnected mechanical devices such as levers, push/pull rods, cables and the like. The number and size of such mechanical components make it difficult to package the range shift mechanism between the driver interface device and the transmission and can add significant frictional resistance to the overall system. As a result, the overall cost for design, manufacture and assembly of the vehicle is increased. 
     In an attempt to address such issues related to mechanically-shifted transmission range shift mechanisms, several “shift-by-wire” range shift mechanisms have been developed. Typically, a shift-by-wire range shift mechanism is based on an external system having an electric motor for controlling movement of the transmission&#39;s manual shaft to the desired range select position. Switches associated with the driver interface device send a mode signal to a transmission controller that is indicative of the selected transmission range. Thereafter, the controller actuates the electric motor to move the transmission manual shaft to the corresponding range select position. Drawbacks of conventional shift-by-wire systems include the size and weight of the external motor, the associated packaging issues related to the motor, the cost of the motor and the controller and the undesirable failure modes associated with such a device. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention provides a solenoid assembly for implementation with an electronic transmission range selection (ETRS) system that shifts a transmission range between a park position and an out-of-park position. The solenoid assembly includes an extension arm biased against a member of the ETRS system. The extension arm is movable to an extended position to maintain the member in the out-of-park position. A solenoid is interconnected with the extension arm. The solenoid is operable to selectively move the extension arm between the extended position and a retracted position to selectively retain the member in the out-of-park position. 
     In one feature, the solenoid assembly further includes a plunger interconnecting the extension arm and the solenoid to pull the extension arm to the retracted position when the solenoid is de-energized. 
     In another feature, the solenoid assembly further includes a locking mechanism to selectively lock the extension arm in the extended position when the member is in the out-of-park position and the solenoid is energized. The locking mechanism includes an inner sleeve selectively actuated by the solenoid and bearings disposed between the inner sleeve and the extension arm. When the extension arm is in the extended position and the solenoid is energized the inner sleeve biases the bearings against the extension arm to prohibit movement of the extension arm to the retracted position. When the solenoid is de-energized a bias force of the inner sleeve against the bearings is relieved to enable movement of the extension arm to the retracted position. The extension arm and the inner sleeve each include respective conical faces in between which the bearings are wedged to retain the extension arm in the extended position when the solenoid is energized. 
     In still another feature, the solenoid assembly further includes a spring that biases the extension arm toward the member. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a schematic illustration of a vehicle system incorporating an electronic transmission range selection (ETRS) system according to the principles of the present invention; 
         FIG. 2  is a side view of the ETRS system in a Park mode; 
         FIG. 3  is a side view of the ETRS system in an Out-of-Park mode; 
         FIG. 4  is a detailed view of a portion of the ETRS system detailing pressurized fluid flow therethrough in the Out-of-Park mode; 
         FIG. 5  is an exploded view of a detent lever assembly associated with the ETRS system of the present invention; 
         FIG. 6  is a cross-sectional view of a park solenoid assembly associated with the ETRS system shown in a Park position; and 
         FIG. 7  is a cross-sectional view of the park solenoid assembly shown in an Out-of-Park position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     Referring now to  FIG. 1 , a schematic illustration of a vehicle  10  is shown. The vehicle  10  includes an engine  12  and an automatic transmission  14 . The engine  12  produces driving torque that is transferred through the transmission  14  at varying gear ratios to drive at least one pair of wheels (not shown). A driver interface device  16  enables a vehicle operator to select various transmission range positions. The driver interface device  16  can include a lever, switches, dials, push-buttons or any other type of input interface desired. The normal transmission range positions, including Park, Reverse, Neutral, and Drive (PRND) are selectable, as well as manual downshifts and tap-up, tap-down capabilities via actuation of the driver interface device  16 . In operation, the driver interface device  16  sends an electric mode signal to a controller  18  based on the selected transmission range. 
     The controller  18  signals an electronic transmission range selection (ETRS) system  20  to shift the transmission  14  to the corresponding range in response to the electric mode signal. For purposes of clarity, the ETRS system  20  is considered to be operating in a “Park” mode when the transmission  14  is in its Park range and to be operating in an “Out-of-Park” mode when the transmission  14  is in any other of the available ranges. 
     Referring now to  FIG. 2 , the ETRS system  20  is an integral part of the transmission  14  and is operable to manipulate the flow of pressurized fluid to shift the transmission  14  between its available transmission ranges. The ETRS system  20  includes a park servo valve  22 , a park servo valve solenoid  24 , a forward-reverse enable (FRE) valve  26 , a hydraulic servo assembly  28  and a two-position detent lever assembly  30 . The ETRS system  20  also includes a park solenoid  32  that prevents shifting from the Out-of-Park mode into the Park mode in the event of a loss of pressurized fluid under specific circumstances. 
     Referring now to  FIGS. 2 through 4 , the ETRS components are shown supported within a housing  34  associated with the transmission  14  and which defines a valve body having a series of fluid flow passages.  FIG. 2  illustrates the position of the various components when the ETRS system  20  is shifted into its Park mode. In contrast,  FIGS. 3 and 4  illustrate the same components moved to positions corresponding to the ETRS system  20  operating in its Out-of-Park mode. In particular, the park servo valve  22  is slidably supported within the housing  34  for movement between a first position ( FIG. 2 ) and a second position ( FIG. 3 ). The park servo valve  22  is biased to its first position by a spring  36 . The spring  36  is disposed between a fixed spring seat  38  and the park servo valve  22 . In its first position, the park servo valve  22  prohibits the flow of pressurized fluid to the hydraulic servo assembly  28 . As discussed in further detail below, the park servo valve solenoid  24  can be selectively actuated to control the supply of fluid required for moving the park servo valve  22  between its first and second positions. 
     Referring still to  FIGS. 2 through 4 , the hydraulic servo assembly  28  is shown to include a servo pin  40  having a servo piston  42  fixed to one end. The servo piston  42  is slidably supported within a cylinder  44  formed in the housing  34  and includes a piston seal  46  disposed therearound. A port  47  formed in the housing  34  provides a fluid communication path to a pressure chamber  48  formed within the cylinder  44 . The servo piston  42  and servo pin  40  are biased to a first position (see  FIG. 2 ) by a spring  50  and the detent lever assembly  30 . The spring  50  seats between the servo piston  42  and a servo cap  52  that is fixed to the housing  34  by a retainer ring  54 . An opposite end of the servo pin  40  abuts one end of the FRE valve  26  and is also fixed to a first end of an elongated servo link rod  56 . The servo link rod  56  operably connects servo pin  40  to the detent lever assembly  30 . As described in further detail below, the flow of pressurized fluid through the port  47  into the pressure chamber  48  induces movement of the servo piston  42  and servo pin  40  to a second position (see  FIGS. 3 and 4 ) against the biasing force exerted thereon by the spring  50  and the detent lever assembly  30 . Movement of the servo pin  40  from its first position to its second position causes the servo link rod  56  to likewise move from a first position ( FIG. 2 ) to a second position ( FIG. 3 ). Furthermore, such movement of the servo pin  40  to its second position acts to release it from engagement with the FRE valve  26 . 
     The FRE valve  26  is slidably disposed within a valve chamber formed in the housing  34  for movement between a first position and a second position. When the servo pin  40  of the hydraulic servo assembly  28  is in its first position, the spring  50  and the detent lever assembly  30  hold FRE valve  26  in its first position ( FIG. 2 ) in opposition to the biasing force exerted thereon by a spring  58 . As seen, the spring  58  is seated between the FRE valve  26  and a wall portion of the housing  34 . In its first position, the FRE valve  26  blocks the flow of pressurized fluid to the shifting components of the transmission  14 . However, upon movement of the servo pin  40  of the hydraulic servo assembly  28  to its second position, the biasing force of the spring  58  forcibly moves the FRE valve  26  to its second position ( FIGS. 3 and 4 ). With the FRE valve  26  in its second position, the flow of pressurized fluid from port  60  is permitted to the shifting components of transmission  14  through ports  60  and  63  at a desired line pressure. 
     Referring primarily to  FIG. 5 , the detent lever assembly  30  is shown to include a detent lever  62 , a bushing  64  and a manual shaft  66 . The manual shaft  66  is rotatably supported in one or more aligned apertures in the transmission case and extends through the bushing  64 . The bushing  64  is retained in an aperture  68  formed in the detent lever  62 , whereby the detent lever  62  is rotatably supported by the bushing  64 . 
     The manual shaft  66  includes a flat  70  formed along a portion thereof. The manual shaft  66  is received through a keyed aperture  72  of the bushing  64 . In particular, the flat  70  of the manual shaft  66  engages a key  74  in the bushing  64 , thereby fixing the manual shaft  66  and bushing  64  for concurrent rotation. However, the detent lever  62  is free to rotate about the bushing  64 . As a result, during normal operation, the manual shaft  66  does not rotate as the ETRS system  20  is moved from the Park position to the Out-of-Park position, thereby eliminating any drag associated with a manual release mechanism external to the transmission  14 . 
     The bushing  64  includes a raised circumferential flange  59  having a slot  61  which forms a pair of laterally-spaced engagement faces  63 . A pin  65  extends from an aperture  67  in the detent lever  62  and into the slot  61  in the bushing  64 . When the manual shaft  66  and the bushing  64  are induced to rotate, as discussed in further detail below, one of the engagement faces  63  eventually contacts the pin  65  to induce rotation of the detent lever  62 . The open space provided by the arc length of the slot  61  defines a range of free-motion for the detent lever  62 . That is to say, during normal operation, the detent lever  62  is rotatable relative to the bushing  64  with the pin  65  traveling within the slot  61  without contacting one of the engagement faces  63 . 
     The detent lever  62  further includes a J-shaped slot  76  with a pin  77  fixed to the second end of the servo link rod  56  engaging the slot  76 . As such, servo link rod  56  connects detent lever  62  to the servo pin  40  of hydraulic servo assembly  28 . A park solenoid pin  78  extends from an aperture  79  in the detent lever  62  and, as will be detailed, interfaces with moveable components of the park solenoid  32 . An aperture  80  formed through the detent lever  62  facilitates attachment of a first end of an actuator rod  82  to the detent lever  62 . A torsion spring  84  is disposed about the bushing  64  and functions to bias the detent lever  62  to rotate to a park position ( FIG. 2 ). A first end  86  of the torsion spring  84  rests against a stationary anchor portion  88  of the transmission case while a second end  90  of the torsion spring  84  engages a flange segment  92  of the detent lever  62 . 
     The second end of the actuator arm  82  is coupled to, or engages, an actuator assembly  94  that is operable to selectively move a park lug  96  between a Park range position and the Out-of-Park range position. As will be detailed, movement of servo pin  40  from its first position to its second position causes the servo link rod  56  to pull on the detent lever  62 . In response, the detent lever  62  is induced to rotate from its park position to an out-of-park position ( FIG. 3 ) against the biasing force of the torsion spring  84 . Such rotary movement of the detent lever  62  causes the actuator rod to move from a first position ( FIG. 2 ) to a second position ( FIG. 3 ) for moving park lug  96  to its Out-of-Park range position. 
     Referring now to  FIGS. 6 and 7 , the components associated with the park solenoid assembly  32  will be discussed in greater detail. The park solenoid assembly  32  includes an exterior body  100  that is attached to a portion of housing  34 . The park solenoid assembly  32  also includes a solenoid body  102  which has a solenoid plunger  104 , an extension arm rod  106  that is slidably disposed within the solenoid plunger  104 , and an extension arm  108  that is slidably disposed on the solenoid body  102  and the exterior body  100 . The extension arm rod  106  is fixed to slide with the extension arm  108 . A front face  110  of the extension arm  108  is biased against the park solenoid pin  78  by a spring  111 . As shown in  FIG. 7 , when the detent lever  62  is rotated to its out-of-park position, the extension arm  108  and extension arm rod  106  move toward an extended position under the biasing force exerted by the spring  111 . Movement of the extension arm  108  to the fully extended position is limited by a flange  113  formed by the exterior body  100 . 
     When the ETRS system  20  is in the Out-of-Park position, the extension arm  108  is able to move to the fully extended position under the biasing force of the spring  111  and is stopped by the flange  113 . Under certain circumstances, for example when the vehicle  10  is traveling above a threshold speed, the controller  18  energizes the park solenoid assembly  32  to prevent movement of the solenoid plunger  104  by locking it in the previously staged Out-of-Park position. More specifically, bearings  112  are supported in apertures  114  of the solenoid body  102 . As the solenoid plunger  104  is induced to extend, the bearings  112  ride up a conical face  116  of the solenoid plunger  104  and engage a conical face  118  of the extension arm  108 . The interface between the bearings  112  and the conical faces  116 , 118  prohibit the extension arm  108  from moving back from its extended position. As such, the detent lever  62  is prohibited from rotating back as a result of the contact between the park solenoid pin  78  and the face  110  of the extension arm  108 . 
     When the vehicle  10  is operating at or below the threshold speed, the park solenoid assembly  32  is de-energized to enable the ETRS system  20  to shift into the Park mode if so desired. More specifically, to enable rotation of the detent lever  62  back to its park position, the park solenoid assembly  32  is de-energized to enable the solenoid plunger  104  to return to the retracted position under the biasing force of a spring  119  to disengage the bearings  12 . As the solenoid plunger  104  retracts, the extension arm  108  is pushed by the detent lever  62  against the bias of the spring  111  enabling rotation of the detent lever  62  to its park position if so indicated. 
     In operation, the vehicle operator selects a desired transmission range through manipulation of the driver interface device  16 . The driver interface device  16  sends an electronic signal to the controller  18 . The controller  18  commands a transmission range shift by sending an appropriate mode signal to the ETRS system  20 . The transmission range shift includes shifting the transmission range from Park to an Out-of-Park range and enabling the flow of pressurized fluid at a desired transmission line pressure to shift components (not shown) of the transmission  14 . 
     The signal sent from the controller  18  to the ETRS system  20  actuates the park servo valve solenoid  24  to enable flow of pressurized fluid to the park servo valve  22  through a port  120  (see  FIG. 2 ). This flow of pressurized fluid causes movement of the park servo valve  22  from its first position to its second position. With of the park servo valve  22  located in its second position, pressurized fluid is supplied from the park servo valve  22  to the hydraulic servo assembly  28 . More specifically, the pressurized fluid flows into an inlet port  124  of the park servo valve  22  and through an outlet port  122  and the port  47  into pressure chamber  48  of the hydraulic servo assembly  28 . This flow of pressurized fluid into the pressure chamber  48  causes movement of the servo pin  40  from its first position to its second position, in opposition to the biasing of spring  50 . Such sliding movement of servo pin  40  causes corresponding movement of the servo link rod from its first position to its second position which, in turn, causes rotation of the detent lever  62  from its park position to its out-of-park position. Such rotation of the detent lever  62  induces a pulling force on the actuator rod  82 , thereby shifting the transmission range to the Out-of-Park position. 
     Concurrently, movement of the servo pin  40  of the hydraulic servo assembly  28  to its second position enables movement of the FRE valve  26  from its first position to its second position due to the biasing force of the spring  58 . Movement of the FRE valve  26  to its second position permits flow of pressurized fluid from port  60  to port  63 . This flow of pressurized fluid is provided to the shifting components of the transmission  14  at the desired line pressure, enabling the transmission  14  to shift to the desired range. 
     Following actuation of the ETRS system  20  into its Out-of-Park mode (see  FIGS. 3 and 4 ), the park solenoid assembly  32  is actuated. In particular, the extension arm  108  contacts the park solenoid pin  78 , thereby prohibiting the detent lever  62  from rotating back to its park position. The park solenoid assembly  32  maintains the extension arm  108  in its extended position while the vehicle  10  is traveling above the threshold speed. In the event of a loss of fluid pressure, the actuator assembly  94  is prevented from shifting the transmission range into Park while the vehicle is moving. Once the vehicle  10  is below the threshold speed, and assuming there is no fluid pressure holding the ETRS system  20  in the Out-of-Park mode, the park solenoid assembly  32  is de-energized to retract the extension arm  108  and permit the torsion spring  84  to rotate the detent lever  62  to shift the transmission range into the Park position. 
     The ETRS system  20  can be manually actuated in the event of a loss of electrical power and fluid pressure within the vehicle  10 . An accessible handle or cable (not shown) is connected for rotation with the manual shaft  66 . A vehicle operator or maintenance personnel can manually rotate the manual shaft  66  using the handle or cable to induce rotation of the detent lever  62  from its park position to its out-of-park position. As described above, rotation of the detent lever  62  enables shifting of the transmission range to the Out-of-Park position. In this manner, the vehicle  10  is free to roll without the transmission prohibiting rolling motion. 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

Technology Classification (CPC): 5