Abstract:
A detent mechanism for a dual mode shift lever unit having a shift lever inserted into a housing through a guide groove formed on an indicator panel as an upper part of the housing, and a cable bracket pivotally supported by the housing and connected to a transmission manual valve which is responsively operated by shift lever manipulation, wherein the detent mechanism interposed between the shift lever and a pivot shaft of the cable bracket includes a bracket fixedly connected to a lower end of the shift lever that is pivotally connected to a rotational member which is rotationally mounted on the pivot shaft supported by a shift lever housing, a support member integrally formed on one end portion of the rotational member and extended in an upward direction, and a turnover spring installed onto one open side of the bracket for contacting the support member.

Description:
BACKGROUND OF THE INVENTION 
     (a). Field of the Invention 
     The present invention relates to a dual mode shift lever unit for an automatic transmission, and in particular, to a detent mechanism for a dual mode shift lever unit having automatic and manual modes capable of enhancing detent quality while in mode conversion. 
     (b). Description of the Related Art 
     Recently, high class automobiles have tended to be equipped with a dual mode transmission shift mechanism for satisfying driver&#39;s whimsical tastes to sometimes take the pleasure of manually shifting the transmission like a sports car, and sometimes to enjoy ride quality of an automatic operation of a high class sedan. 
     This kind of dual mode shift mechanism provides two shift modes, i.e., an automatic mode and a manual mode, such that an indicator panel is formed having a guide groove separating respective mode portions. 
     FIG. 1 is a top plane view showing a presently used indicator panel. FIG.  2  and FIG. 3 are respective side elevation and internal perspective views of a dual mode shift lever unit which is presently used, and FIG. 4 is a perspective view of a shift lever of the dual mode shift lever unit as presently used. 
     As shown in FIG. 2, the dual mode shift lever unit comprises a shift lever  2  inserted into a housing  1  through a guide groove formed on an indicator panel at an upper part of the housing  1 , and a cable bracket  3  which is pivotally supported by the housing  1  and connected to a transmission manual valve (not shown) by a cable (not shown) such that the transmission manual valve is responsively operated by shift lever manipulation. 
     In terms of mode conversion, the shift lever  2  moves in widthwise directions in relation to the vehicle&#39;s direction of travel at a D range. Normally, the shift lever  2  is located in automatic mode in which the shift lever is connected to the cable bracket  3  by engaging a pin  4  formed on the shift lever  2  with a pinhole  5  formed on the cable bracket  3  such that the shift lever can move to and fro along an automatic mode groove by driver&#39;s manipulation. 
     To convert the mode to the manual mode, the shift lever  2  moves in an opposite side direction at the range D in order for the pin of the shift lever to be disengaged from the pinhole of the cable bracket  3 . 
     FIG. 3 shows that under the indicator panel a guide rail  6  is fixedly mounted along the automatic mode portion and has a guide groove  7  such that a guide projection  9  having an L-shape, downwardly bent on one side of the shift lever  2 , is guided along the guide groove  7  of the guide rail  6  during range shifting in automatic mode. 
     Also, the shift lever  2  is provided with a detent mechanism (see FIG. 4) at it lower end portion so as to provide detent quality when changing the mode from automatic mode to the manual mode or vice versa. 
     As shown in FIG. 4, the detent mechanism comprises a bracket  240  having a pair of parallel arms  251  formed in a middle portion thereof and fixedly mounted to the lower end of the shift lever  2  at its upper end and pivotally connected to a rotation member  250 , which also pivots on a pivot shaft  245  such that the shift lever can pivot in front, rear, left, and right directions; and a detent block  253  pivotally connected to the bracket  240  at it&#39;s lower portions by a pin  254  crossing between two opposite walls of the bracket  240  and biased to a bar  252  installed between the parallel arms  251  of the bracket  240  by a coil spring  256  which is supported by a support  260  integrally formed with the rotation member  250  such that the detent block  253  is hooked to the bar  252  at one of two recesses  255  formed on the detent block vertically arranged with respect to the pivot shaft  245 . 
     Practically, while the shift mode is converted from the automatic mode to the manual mode, i.e., the bracket  240  pivots to push the detent block  253 , the detent block  253  moves to overcome a biasing force of the coil spring  256  such that the bar  252  slides down to engage with a lower recess. 
     However, this dual mode shift lever unit has drawbacks in that the coil spring for elastically biasing the detent block is unstable so as to be easily deviated from its place resulting in degraded detent quality. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in an effort to solve the above problems of the prior art. 
     It is an object of the present invention to provide a dual mode shift lever unit capable of providing a reliable detent quality during a mode conversion operation, and to provide durability by simplifying the structure of a detent mechanism. 
     To achieve the above object, the detent mechanism for a dual mode shift lever unit comprises a bracket fixedly connected to a lower end of the shift lever and pivotally connected to a rotational member which is rotationally mounted on a pivot shaft supported by a shift lever housing, a support member integrally formed on one end portion of the rotational member and extended in an upward direction, and a turnover spring installed onto one open side of the bracket for contacting the support member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and together with the description, serve to explain the principles of the invention. 
     FIG. 1 shows an indicator panel of a presently used dual mode shift lever unit; 
     FIG. 2 is a side elevation view of a conventional dual mode shift lever unit; 
     FIG. 3 is a perspective view of the conventional dual mode shift lever unit of FIG. 2; 
     FIG. 4 is a perspective view of a detent mechanism of the conventional dual mode shift lever unit of FIG. 2; 
     FIG. 5 is a perspective view of a detent mechanism according to a first preferred embodiment of the present invention; 
     FIG. 6 is an operational view showing behavior of the detent mechanism of FIG. 5 while the shift lever moves from an automatic mode position to a manual mode position; 
     FIG. 7 is an operational view showing the behaviors of a detent block and a turnover spring of the detent mechanism of FIG. 5 while the shift lever moves from the automatic mode position to the manual mode position; 
     FIG. 8 is an operational view showing the behavior of the detent mechanism of FIG. 5 while the shift lever moves from the manual mode position to the automatic mode position; 
     FIG. 9 is a graph showing characteristics of a turnover spring of the detent mechanism of FIG. 5; 
     FIG. 10 is a perspective view showing a detent mechanism according to a second preferred embodiment of the present invention; 
     FIG. 11 is an operational view showing behavior of the detent mechanism of FIG. 10 while the shift lever moves from the automatic mode position to the manual mode position. 
     FIG. 12 is an operational view showing behavior of the detent mechanism of FIG. 10 at a turnover point. 
     FIG. 13 is a graph showing characteristics of a turnover spring of the detent mechanism of FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In this specification, not all the feature of a dual mode shift lever unit of the present invention will be explained but rather it will focus on the detent mechanism thereof, and the reference numerals in FIG. 1, FIG. 2, and FIG. 3 will be used to explain the present invention because the features in these drawings are common with the present invention. 
     A detent mechanism for a dual mode shift lever unit according to a first preferred embodiment of the present invention will be described hereinafter with reference to the accompanying drawings. 
     FIG. 5 is a perspective view of a detent mechanism according to a first preferred embodiment of the present invention. 
     As shown in FIG. 5, the detent mechanism comprises a bracket  24  fixedly connected to a lower end of a shift lever  2  and pivotally connected, via a pivot pin  5 , to a rotational member  30  which is rotationally mounted on a shaft  28  that is supported by a shift lever housing  1  (see FIG.  1 ), a support member  33  integrally formed on one end portion of the rotational member  30  so as to be extended in an upward direction, and a detent block  39  pivotally connected to an upper end of the support member  33  by a hinge pin  35 . 
     The bracket  24  is formed having a pair of arms  23  and  23 ′ that are formed on an open side of the bracket  24  approximately in the middle in a longitudinal direction of the bracket  24  such that a turnover spring  25  is installed between the arms  23  and  23 ′. The turnover spring  25  is a double torsion spring having offset ends and a flat portion  31  formed between two coiled portions  27  and  29 . The turnover spring  25  is mounted to the arms  23  and  23 ′ of the bracket  24  at its offset ends of the turnover spring  25  in order for the flat portion  31  to contact the detent block  39  such that the detent block  39  is biased. 
     The support member  33  is provided with a pair of pin supports  34  at ends of side walls thereof and two stoppers  37  and  37 ′ at ends of front and rear walls in relation to the moving direction of the detent block  39 , such that the detent block  39  is pivotally installed between the pin supports  34  by a pin  35  and its movement range is limited and defined by the front and rear stoppers  37  and  37 ′. 
     The detent block  39  is provided with a recess on its upper portion facing the turnover spring  25  such that the flat portion  31  of the turnover spring  25  is secured therein. 
     The operation of the detent mechanism according to the first preferred embodiment of the present invention will be described hereinafter with reference to FIG. 6, FIG.  7  and FIG.  8 . 
     Reference numerals S 1  and S 2  refer to axes of the shift lever  2  when the shift lever  2  is positioned at the initially normal automatic mode and at the manual mode respectively. 
     If the shift lever  2  moves from the initial automatic mode position S 1  to the manual mode position S 2 , the turnover spring  25  rotates on an axis of it&#39;s offset ends in a clockwise direction as well as revolves wholly along an arc RH 1 , which has a radius R 1  extended from a point P 3 , from an initial point P 1  to a point P 2  by as much as an angle a in relation to the point P 3 , in the clockwise direction. At the same time, the flat portion  31  of the turnover spring  25  revolves along an arc RH 2 , which has a radius R 2 , from a point P 5  to a point P 6  in relation to a point P 4  where the pin  35  is inserted, in a counter-clockwise direction, by overcoming an elastic force of the turnover spring  25 . 
     When the shift lever  2  moves from the manual mode position to the automatic mode position, the turnover spring  25  is operated in an inverse order of the above automatic to manual shift mode conversion. 
     The points P 5  and P 6  on the arc RH 2  along which the flat portion  31  of the turnover spring  25  passes is defined by the front and rear stoppers  37  and  37 ′, which limit the pivot range of the detent block  39 . 
     Now, the operation of the turnover spring and the detent block will be more precisely explained with reference to FIG.  7 . 
     As shown in FIG. 7, while the shift lever  2  moves from the initial automatic mode position Si to the manual mode position S 2 , initially the flat portion  31  of the turnover spring  25  secured to the recess  41  of the detent block  39  revolves from its initial point P 5  to the point P 6  along the arc RH 2  having a radius R 2  in relation to a pivot point P 4  so as to contact the front stopper  37 . Also, while the shift lever  2  moves by as much as an angle α/2, the turnover spring  25  increases it&#39;s potential energy by winding upon itself as the axis of the offset ends of the turnover spring  25  moves from the point P 1  to a turnover point P 7 . That is, the turnover spring  25  secures a torsion displacement T between the turnover point P 7  and a point P 8  which are on an arc RH 3  having a radius R 3 , along which the axis of the offset ends of the turnover spring  25  passes unless the turnover spring  25  is held by the detent block  39 . 
     In this case, if the shift lever  2  moves over more than an angle α/2, the detent block  39  is pushed in the opposite direction so as to be blocked by the rear stopper  37 ′, and the turnover spring is relaxed (see FIG.  8 ). 
     On the other hand, while the shift lever  2  moves from the manual mode position S 2  to the automatic mode position S 1 , the flat portion  31  of the turnover spring  25  revolves from the point P 6  to the point P 5  along the arc RH 2  in relation to the pivot point P 4 . Also, while the shift lever  2  moves as much as the angle α/2, the turnover spring  25  increases it&#39;s potential energy by winding upon itself as the axis of the offset ends of the turnover spring  25  moves from the point P 1 ′ to a turnover point P 7 ′. That is, the turnover spring  25  secures a displacement T between the turnover point P 7 ′ and a point P 8 ′, having the radius R 3 ′ in relation to a pivot point P 6 , along which the axis of the offset ends of the turnover spring  25  passes if the turnover spring  25  is not held by the detent block  39 . 
     FIG. 9 is a graph showing characteristics of the turnover spring of the detent mechanism. 
     As shown in FIG. 9, the turnover spring  25  is wound and relaxed whenever the shift lever  2  passes over the turnover point P 7  and P 7 ′. Since the turnover spring  25  and the detent block  39  cooperate in this way, the dual mode shift lever unit provides a driver with good detent quality when the shift lever  2  is manipulated in order to convert a present mode to the other mode. 
     A detent mechanism for a dual mode shift lever unit according to a second preferred embodiment of the present invention will be described hereinafter. 
     FIG. 10 is a perspective view showing a detent mechanism according to a second preferred embodiment of the present invention. 
     As shown in FIG. 10, the detent mechanism has the same configuration as the first preferred embodiment except that there is no detent block, but rather the support member  33  acts like the detent block. 
     The support member  33  is provided with a recess  26  at its upper end so as to receive the flat portion  31  of the turnover spring  25 . 
     The operation of the detent mechanism according to the second preferred embodiment of the present invention will be described hereinafter with reference to FIG.  11  and FIG.  12 . 
     If the shift lever  2  moves from the initial automatic mode position to the manual mode position, the turnover spring  25  rotates on an axis of the offset ends in a clockwise direction as well as wholly rolls over, forming an exterior arc RH 101  which has a radius R 101  in relation to the point P 101 . 
     At the same time, the axis of the offset ends moves from a point P 102  to a point P 103  by as much as an angle α along an arc RH 102 , having a radius R 102  in relation to a pivot point P 104  of the shift lever  2 , in a clockwise direction. 
     As shown in FIG. 12, while the shift lever  2  moves as much as angle α/2, the turnover spring  25  increases it&#39;s potential energy by winding upon itself, and the axis of the offset ends of the turnover spring  25  moves from the point P 102  to a turnover point P 105 . That is, the turnover spring  25  secures a torsion displacement T between the turnover point P 105  and a point P 104  which are on an arc RH 103  having a radius R 3 , along which the axis of the offset ends of the turnover spring  25  passes if the turnover spring  25  is not held by its offset ends. Consequently, if the shift lever  2  moves over more than an angle α/2, the turnover spring  25  flops so as to be relaxed. 
     As shown in FIG. 13, the turnover spring  25  is wound and relaxed whenever the shift lever  2  passes over the turnover point P 105 . Since the turnover spring  25  operates in this way, the dual mode lever unit according to the second preferred embodiment of the present invention provides a driver with a good detent quality when the shift lever  2  is manipulated in order to convert a present mode to the other mode. 
     As described above, the dual mode shift lever unit of the present invention is provided with a detent mechanism using the turnover spring which gets wound and then relaxed while passing over a turnover point such that the detent mechanism provides an improved detent quality during mode conversion operation. 
     While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.