Abstract:
Improvements in one way clutches include a first embodiment directed to a one way clutch having two sets of helical teeth arranged about the axis of rotation of a drive and driven member that translate axially into and out of engagement. The one way clutch is biased into engagement by a wave washer or similar device. As the speed of rotation of the clutch increases, hydraulic fluid which is directed axially against the drive member by a dam urges the drive member away from the driven member and opens the clutch. In a second embodiment, a pair of one way clutches having oppositely arranged sets of helical teeth selectively provide one way or overrunning operation in both directions. In this embodiment, each of the drive members may be selectively engaged with the driven member by a hydraulic piston. Respective return springs bias the pistons and drive members toward disengaged positions.

Description:
FIELD 
     The present disclosure relates to clutches for use in motor vehicle powertrains and more particularly to one way or overrunning helical clutches for use in motor vehicle powertrains. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
     A one way or overrunning clutch is an ingenious mechanical device typically associated with two co-axial or concentric components in a power or torque transmitting assembly or machine. The unique feature or capability of a one way clutch is its action in response to opposite relative rotational motion between its two or more components. When, in one direction, a first component attempts to drive or rotate faster than a second component, a one way clutch releases, allows the faster first component to freewheel and transfers essentially no torque. In the opposite rotational direction, unless the second component is rotating faster than the first component, the one way clutch locks and transfers or reacts torque from the first component to the second component up to the torque carrying limit of the clutch. When the second component is the torque input or drive member, the one way clutch operates in the reverse manner. 
     Because of their unique function and capability, one way or overrunning clutches have found broad application in mechanical power transfer devices such as multiple speed transmissions utilized in motor vehicles. For example, a one way clutch may restrain, i.e., ground, a transmission component in reverse and allow it to freely rotate in a forward gear or the one way clutch may restrain a component in one speed range or gear ratio and release it in another speed range or gear ratio. 
     There are several common one way clutch configurations. A sprag one way clutch utilizes a pair of concentric rings that nominally function as the input and output members and a plurality of oblique bars or sprags disposed between the rings. In one direction of relative rotation, the sprags are urged to tilt or relax such that one ring readily rotates (freewheels) relative to the other. With the opposite direction of relative rotation, the sprags move toward a more radial position and lock the inner and outer rings together. Ball ramp one way clutches utilize a plurality of ball bearings between the rings and corresponding ramps on the inner surface of one of the rings. Again, in one direction of relative rotation, the balls are urged to the bottom of the ramps and the rings freewheel. Relative rotation in the opposite direction causes the ball bearings to ride up the ramps, engage the other ring and lock them together. 
     While these and other, similar one way clutch configurations function well when the device has a relatively small diameter such as would be utilized with a shaft, engineering complications arise as the diameter of the controlled mechanical element becomes large. For example, in a transmission having a plurality of planetary gear assemblies, it may be unavoidable that a one way clutch must be installed about the ring gear of a planetary gear assembly. A one way clutch so mounted will require a large number of sprags or ball bearings in addition to much larger races. The device will thus weigh significantly more than a smaller, shaft mounted clutch. 
     SUMMARY 
     The present invention provides improvements in one way clutches. A first embodiment is directed to a one way clutch having two sets of helical teeth arranged about the axis of rotation of a drive and driven member that translate axially into and out of engagement. The one way clutch is biased into engagement by a wave washer or similar device. As the speed of rotation of the clutch increases, hydraulic fluid which is directed axially against the drive member by a dam urges the drive member away from the driven member and opens the clutch. In a second embodiment, a pair of one way clutches having sets of oppositely arranged helical teeth selectively provide one way or overrunning operation in both directions. In this embodiment, each of the drive members may be selectively engaged with the driven member by a control piston. Respective return springs bias the pistons and drive members toward disengaged positions. In both embodiments, the angle of the helical teeth, the magnitude of the hydraulic force and the magnitude of the spring force primarily determine the one way lock and release thresholds. 
     Thus it is an aspect of the present invention to provide one way or overrunning clutches. 
     It is a further aspect of the present invention to provide one way or overrunning clutches having mating, opposed helical teeth. 
     It is a still further aspect of the present invention to provide one way or overrunning clutches having mating, helical teeth on opposed drive and driven members. 
     It is a still further aspect of the present invention to provide one way or overrunning clutches having hydraulically translated drive and driven members. 
     It is a still further aspect of the present invention to provide one way or overrunning clutches having spring biased drive and driven members. 
     It is a still further aspect of the present invention to provide one way or overrunning clutches having spring biased, opposed drive and driven members. 
     It is a still further aspect of the present invention to provide one way or overrunning clutches having spring biased, opposed drive and driven members having helical teeth. 
     It is a still further aspect of the present invention to provide one way or overrunning clutches having spring biased, hydraulically translated, opposed drive and driven members having helical teeth. 
     Further aspects, advantages and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a sectional view of a first embodiment of a one way or overrunning clutch having opposed sets of helical teeth according to the present invention in a fully engaged position; 
         FIG. 2  is a sectional view of a first embodiment of a one way or overrunning clutch having opposed sets of helical teeth according to the present invention in a fully disengaged position; 
         FIG. 3  is a fragmentary sectional view of the sets of opposed teeth in a one way or overrunning clutch according to the present invention taken along line  3 - 3  of  FIG. 2 ; and 
         FIG. 4  is a sectional view of a second embodiment of a one way or overrunning clutch having two pairs of opposed sets of helical teeth according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
     At the outset, it should be understood that the inventor is aware of a certain preference to describe or refer to a selectable coupling device between two rotating members as a “clutch” whereas the same device between a rotating member and a stationary member is described or referred to as a “brake.” With regard to one way or overrunning clutches, the inventor, however, does not subscribe to this convention and prefers to and herein has referred to such devices, whether they are disposed between two rotating members or one rotating and one stationary member as one way, freewheeling or overrunning clutches. This preference is consistent with his long experience in industry wherein only the term “clutch” is utilized with “one way,” “overrunning” or “freewheeling” to describe and refer to such a device utilized either as a clutch (between two rotating elements) or a brake (between a rotating and a stationary element). He has, however, in certain locations in the text, inserted the parenthetical “(brake)” to clarify the description of a one way or overrunning clutch disposed between rotating and stationary members and acknowledge the above-noted alternate naming convention. 
     Referring now to  FIG. 1 , a portion of a transmission incorporating the present invention is illustrated and generally designated by the reference number  10 . The transmission  10  which may by a component of a motor vehicle powertrain (not illustrated) or other torque transferring assembly includes a stationary housing  12  which locates, supports and protects various components of the transmission  10  and a rotating element  14  such as a shaft, collar, quill or component of, for example, a planetary gear assembly. If the rotating element  14  is a component of a planetary gear assembly, it may typically be a ring gear or a planetary gear carrier  16  as illustrated in  FIG. 1 . 
     Operably disposed between the planet gear carrier  16  and the stationary housing  12  is a first embodiment of a one way or overrunning clutch (brake) assembly  20  according to the present invention. The one way clutch assembly  20  includes an axially translatable collar or annular inner first or input member  22  having a smooth outer circumferential pilot journal surface  24  which is adjacent and slides along a complementary inner annular pilot surface  26 . The inner surface  22  of the collar or member  22  includes female splines  28  that mate with and engage complementary male splines  32  on the outer periphery of the planet gear carrier  16 . Thus, the collar or member  22  always rotates with the planet gear carrier  16  or other rotating member  14  and independently rotates and translates with regard to the housing  12 . 
     The collar or inner member  22  defines an annular re-entrant region or fluid chamber  34  which receives a flat, circular, outer portion  38  of a circular lubrication dam  40 . The lubrication dam  40  includes an O-ring or similar seal  42  about the circumference of the flat, circular portion  38  which provides a fluid tight seal against an inner wall  44  of the collar or member  22  and defines an annular passageway or orifice  45  at the inner end of the flat, circular portion  38 . An inner edge  46  of the lubrication dam  40  seats against a hub  48  of the rotating member  14  and is retained in this location by a snap ring  50  or similar mechanical component. 
     The collar or inner member  22  includes a radially inwardly directed lip or stop  52  which is engaged by and retains an engagement spring  54  such as a wave washer, Belleville spring, coil packs or similar component or components. The engagement spring  54  biases the collar or member  22  to the left in  FIG. 1 . 
     Referring now to  FIGS. 1, 2 and 3 , the one way or overrunning clutch assembly  20  also includes an outer or second member  60  which may be an insert in the housing  12  or may be integrally formed therewith. The outer member  60  includes an inwardly extending flange or stop  62  against which the collar or inner member  22  abuts when it is in the fully engaged position as illustrated in  FIG. 1 . The outer member  60  includes a first plurality of helical teeth  64  adjacent the stop  62  and the inner surface  26 . Aligned with and opposing the first plurality of helical teeth  64  are a complementary, second plurality of helical teeth  66  formed on the collar or inner member  22 . As illustrated in  FIG. 3 , the adjacent (opposing) ends of the helical teeth  64  and  66  define tapered terminal portions  68 , i.e., have reduced height and width, to facilitate engagement. Also, it should be appreciated, that the sense of the helical teeth  64  and  66  is determined by the nominal direction of relative rotation between the inner member  22  and the outer member  60 . If the inner member  22  rotates clockwise (as viewed from the right in  FIGS. 1 and 2 ), the helical threads  64  and  66  are of right hand sense and if the inner member  22  rotates counter-clockwise, the helical threads  64  and  66  are of left hand sense. 
     As  FIGS. 1 and 2  illustrate, when the collar or inner member  22  translates to the left, the first and second pluralities of helical teeth  64  and  66  engage and when the collar or inner member  22  translates to the right, the first and second pluralities of helical teeth  64  and  66  disengage. The engagement spring  54  biases the collar or inner member  22  to the left, into engagement. As the rotational speed of the rotating member  14  increases, radially outwardly flowing hydraulic fluid (transmission oil) from the transmission  10  is collected and directed by the circular lubrication dam  40  into the fluid chamber  34 . As fluid pressure within the chamber  34  increases, the force of the engagement spring  54  will be overcome, the collar or inner member  22  translates to the right in  FIGS. 1 and 2  and the helical teeth  64  and  66  disengage completely. As noted above, the angle of the helical teeth  64  and  66 , the magnitude of the hydraulic force and the force of the engagement spring  54  primarily determine the one way lock and release thresholds of the one way or overrunning clutch (brake) assembly  20  according to the present invention. It should also be appreciated that the volume of the chamber  34  and the size of the annular orifice  45  will affect the speed, i.e., the elapsed time, for the chamber  34  to fill and disengage the helical teeth  64  and  66 , with a larger chamber  34  and smaller annular orifice  45  increasing the time to disengagement and vice versa. 
     Referring now to  FIG. 4 , a second embodiment of a one way or overrunning clutch assembly is illustrated and generally designated by the reference number  80 . The second embodiment one way clutch assembly  80  is bi-directional and selectively functions as a one way clutch (brake) to react torque or overrun in both forward and reverse directions, freewheel and react torque in both directions. The second embodiment one way clutch  80  may also be disposed in a motor vehicle transmission or other torque or power transmission device which includes a stationary housing  82 . The transmission includes a shaft, quill or other rotating member  86  which provides drive or input torque to the one way clutch assembly  80 . The shaft, quill or rotating member  86  includes an annular, re-entrant region  88  which receives a first set of helical teeth  90  of a first sense (either right hand or left hand) which are secured to or integrally formed with the rotating member  86  and a second set of helical teeth  130  of a second, opposite sense (either left hand or right hand) which are also secured to or integrally formed with the rotating member  86 . 
     Disposed opposite and in axial alignment with the first set of helical teeth  90  of the first sense are a complementary second set of helical teeth  92  of the first sense. The sets of helical teeth of the first sense  90  and  92  are like those illustrated in  FIG. 3  and include tapered terminal or end regions  94  of reduced width and height which facilitate smooth engagement. The second set of teeth  92  of the first sense are secured to or integrally formed with a first non-rotating piston assembly  96 . The first piston assembly  96  includes a radially extending flange or web  98 . An interengaging spline set  100  or similar rotation inhibiting connection operably disposed between the periphery of the web or flange  98  and the housing  82  inhibits rotation of the first piston assembly  96  but allows axial motion of the first piston assembly  96  relative to the housing  82 . 
     The first piston assembly  96  includes a first pair of annular walls  104  which include a suitable first pair of O-ring seals  106  on their outer surfaces which provide a fluid tight seal against a complementary first pair of annular walls  108  carried by a stationary hub  110 . The stationary hub  110  is secured to the stationary housing  82 . The complementary pair of annular walls  108  define a first cylinder  112  which receives the first pair of annular walls  104  which thus function as a first piston  114  albeit a hollow piston. The stationary hub  110  includes a first fluid passageway  116  which communicates between a first controlled source  118  of pressurized hydraulic fluid (transmission oil) and the first cylinder  112 . A first compression spring pack  122  which may be a plurality of compression springs or a plurality of wave washers, for example, is disposed between a first lip or flange  124  in the first piston assembly  96  and a circular stop or washer  126  restrained by a snap ring  128  or similar device and biases the first piston assembly  96  to the right in  FIG. 4 , to a disengaged, freewheeling position. 
     As noted above, a second set of helical teeth  130  of a second sense (either left hand or right hand) are also secured to or integrally formed with the rotating member  86 . Disposed opposite and in axial alignment with the second set of helical teeth  130  of the second sense are a complementary second set of helical teeth  132  of the second sense. The sets of helical teeth of the second sense  130  and  132  are like those illustrated in  FIG. 3  and include terminal regions  134  of reduced width and height which facilitate smooth engagement. The second set of teeth  132  of the second sense are secured to or integrally formed with a second non-rotating piston assembly  136 . The second piston assembly  136  includes a radially inwardly extending flange or web  138 . An interengaging spline set  140  or similar rotation inhibiting connection operably disposed between the periphery of the web or flange  138  and the stationary hub  110  inhibits rotation of the second piston assembly  136  but allows axial motion of the second piston assembly  136  relative to the stationary hub  110 . Disposed between the end of the stationary hub  110  and the adjacent, inner end of the shaft, quill or rotating member  86  is a roller, needle or similar bearing assembly  142 . 
     The second piston assembly  136  includes a second pair of annular walls  144  which include a suitable second pair of O-ring seals  146  on their outer surfaces which provide a fluid tight seal against a complementary second pair of annular walls  148  in the stationary hub  110 . The complementary pair of annular walls  148  define a second cylinder  152  which receives the second pair of annular walls  144  of the second piston assembly  136  which thus function as a second piston  154  albeit a hollow piston. The stationary hub  110  includes a second fluid passageway  156  which communicates between a second controlled source  158  of pressurized hydraulic fluid (transmission oil) and the second cylinder  152 . A second compression spring pack  162  which may be a plurality of compression springs or a plurality of wave washers, for example, is disposed between a second lip or flange  164  in the second piston assembly  136  and the circular stop or washer  126  restrained by the snap ring  128  or similar device and biases the second piston assembly  136  to the right in  FIG. 4 , to a disengaged, freewheeling position. 
     In operation, the second embodiment one way clutch  80 , as noted above, is bi-directional and selectively functions as a one way clutch to transmit or react torque or overrun in both forward and reverse directions or freewheel depending upon whether the first piston assembly  96  or the second piston assembly  136  is activated. With regard to the first piston assembly  96 , the first set of helical teeth  90  and the second set of helical teeth  92  of the first sense, the first compression spring pack  122  biases the second set of helical teeth  92  to the right in  FIG. 4 , out of engagement. 
     Assuming the first and second sets of helical teeth  130  and  132  of the opposite (second) sense are disengaged, no torque transfer or torque reaction occurs through the one way clutch  80  and it freewheels in both directions. When pressurized hydraulic fluid is supplied to the first cylinder  112  from the controlled source  118  through the first fluid passageway  116 , the first piston assembly  96  translates to the left in  FIG. 4  and the first set of helical teeth  90  and the second set of helical teeth  92  of the first sense engage. Depending upon the force generated by the first piston  114 , the angle of the first and second sets of helical teeth  90  and  92  and the torque and the direction of torque applied thereto, the helical teeth  90  and  92  may remain engaged and transmit or react torque or they may overrun. 
     Operation of the second piston assembly  136 , the first set of helical teeth  130  and the second set of helical teeth  132  of the second, opposite sense is essentially the same except that all directional (rotational) actions are the reverse of that occurring with the regard to the first piston assembly described directly above. When both the first piston assembly  96  and the second piston assembly  136  are activated, both the sets of helical teeth  90  and  92 , and  130  and  132  engage and the shaft, quill or other rotating member  86  is inhibited from rotation in either direction. 
     The description of the invention is merely exemplary in nature and 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.