Patent Application
20130118285
The present disclosure relates to a shift tower for a manual transmission and more particularly to a shift tower for a manual transmission having a decoupled inertial mass.
The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Notwithstanding myriad improvements to the operation and performance of automatic transmissions, there remain vehicle purchasers who prefer the control and enhanced driving experience provided by manual transmissions. Manual transmission aficionados praise their visceral connection and throughput from the vehicle to the driver.
It is not surprising then that efforts to improve the operation of manual transmissions continue. One of the areas of continued development relates to the shift tower and shift lever which are, ultimately, the interface between the driver and the transmission.
For example, in order to provide a more positive, defined and distinct feel to the shift lever, it has been suggested that a mass of dense material, such as lead, be added to the base of the shift lever. Once accelerated, the momentum of the mass assists positive engagement of a gear by providing additional energy to move the shift lever to the end of a shift pattern slot. This approach is not without a drawback, however, the drawback being the amount of energy that must be expended by the driver to initiate motion of the shift lever from its center or neutral position. More specifically, the energy expended by the driver and absorbed by the mass during lateral motion of the shift lever, referred to as “selection,” has little impact on and does not significantly contribute to improved shift feel. That is, only mass assisted longitudinal motion of the shift lever, referred to as “shift,” improves the feel and positiveness of the overall shift. A corollary to this drawback is the energy that must be expended by the driver to negotiate complex, e.g., U-shaped, shift patterns with a mass loaded shift lever. Again, the energy expended and absorbed to move the shift laterally does not provide any appreciable improvement of shift feel.
It is therefore apparent that improvements to the shift lever art directed to improving shift feel are desirable.
The present invention provides a shift assembly for a manual transmission that includes a decoupled inertial mass. The decoupled mass is active only for engagement and to assist and drive home the shift (longitudinal motion of the shift lever) rather than to require additional operator effort during the selection (lateral motion) portion of the shift process. The shift tower includes a shaft or stub shaft which is translated axially by a first shift cable through a first linkage. This motion is generated by and corresponds to lateral motion of the shift lever (selection). A mass of material such as metal or other dense material is mounted on an outer end of an arm which rotates about the axis of the stub shaft. A second shift cable is connected through a second linkage to the arm and rotates the arm in response to longitudinal motion (gear engagement) of the shift lever (shift). The stub shaft and the arm are connected by an offset member or extension coupled to the stub shaft which is received in a slot in the arm. Thus the mass moves (pivots about the stub shaft axis) during motion of the second shift cable and gear engagement (shift) but does not move during motion of the first shift cable, axial motion of the stub and gear selection. In this way, the added gear shifting or engaging force provided by the mass only affects (is coupled to) rotation of the stub shaft and thus gear engagement (shifting), not gear selection.
Thus it is an aspect of the present invention to provide a shift tower having improved gear shifting feel.
It is a further aspect of the present invention to provide a shift tower having a mass which is coupled to the shift lever for gear engagement (shifting) action but is uncoupled from the shift lever for gear selection action.
It is a still further aspect of the present invention to provide a shift tower having a mass which is active during gear engagement (shifting) action but is inactive during gear selection action.
It is a still further aspect of the present invention to provide a shift tower having a stub shaft which translated axially for gear selection and rotates for gear shifting.
It is a still further aspect of the present invention to provide a shift tower having a shaft and an arm with a mass at one end which is attached to the shaft by means which couple the arm for rotation with the shaft but decouple the arm from the shaft upon axial motion of the shaft.
It is a still further aspect of the present invention to provide a shift tower having a shift assisting mass which is coupled to a shift lever by a pair of cables.
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.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
With reference now to
Referring now to
At the top of the stub shaft 40 resides a bobbin, collar or hub 44 that defines a circumferential channel or groove 46. The collar or hub 44 is secured to and retained on the stub shaft 40 by a nut 48 or similar fastener and rotates therewith. The upper portion of the collar or hub 44 defines or includes a right angle member, extension or lever arm 50 that extends first radially outwardly and then parallel to the stub shaft 40. Residing within the channel or groove 46 is a follower block 52 that is coupled through a ball and socket joint 54 to one end of a crank arm assembly 60. At the center of the crank arm assembly 60 is secured a shaft 62 which is received within a pair of bearings 64. Thus, the crank arm assembly 60 is free to pivot about the axis of the shaft 62 while supported and retained within the bearings 64. At the other end of the crank arm assembly 60 is disposed another ball and socket joint 66. The first, selection cable 22 (illustrated in
Disposed within the tubular tower 38, between the tower 38 and the stub shaft 40 is a quill or tubular member 70. The quill or tubular member 70 is preferably rotationally supported both on its inner and outer surfaces by a suitable plurality of anti-friction bearings 72 such as ball or roller bearing assemblies. To the upper end of the quill or tubular member 70 is secured a radial arm 76. The radial arm 76 extends outwardly from the quill or tubular member 70 and, at its end most distant therefrom, resides an inertial mass or weight 80. The mass or weight 80 is preferably fabricated of a dense material such as a metal and preferably weighs several ounces. Between the quill or tubular member 70 and the mass 80, and preferably closer to the mass 80 is a ball 82 of a ball and socket joint 84 through which the second, shift cable 24 is coupled to the radial arm 76. The radial arm 76 also includes an opening or slot 86, preferably located between the quill or member 70 and the ball 82 which is complementary to and receives the end of the right angle shift lever member, extension or arm 50. Thus, motion of the second, shift cable 24 is transferred through the right angle shift lever arm 50 and rotates the stub shaft 40 about its axis in response to longitudinal (shift) motion of the shift lever 18.
A bellows 88, preferably fabricated of an elastomeric material, extends between the lower portion of the bobbin, collar or hub 40 and the upper surface of the radial arm 76 and provides a seal therebetween that prevents foreign material from entering and fouling the shift tower assembly 30. A spring biased detent assembly 92 engages suitable recesses (not illustrated) in the stub shaft 40 and provides both tactile feedback to the operator of the vehicle when a gear has been positively and fully engaged and assists retention of the entire shift linkage in the selected gear as those familiar with detent assemblies will readily understand.
From the foregoing, it will be appreciated that whereas axial motion of the stub shaft 40 will not translate the radial arm 76 and the mass or weight 80 due to the freedom of the right angle shift lever arm 50 within the opening or slot 86, rotational motion of the radial arm 76 which is directly affected and controlled by motion of the second shift cable 24 will translate the mass or weight 80 and will thus affect the action of shifting, that is, actual gear engagement.
Thus, the mass or weight 80 is de-coupled from lateral (selection) motion of the shift lever 18 transferred to the shift tower assembly 30 but is coupled to longitudinal (shift) motion of the shift lever 18. Accordingly, the term “de-coupled” as utilized herein with regard to the overall invention and specifically the mass or weight 80 has this definition: de-coupled or unaffected by lateral (selection) movement of the shift lever 18 by coupled to and translated by longitudinal (shift) movement of the shift lever 18. From the foregoing definition, it should be apparent that “decoupled” does not mean totally or completely decoupled as this interpretation is manifestly illogical.
Referring now to
Attached to each of the shift rails 102A, 102B and 102C is a respective shift fork 104A, 104B and 104C. Each of the shift forks 104A, 104B and 104C are secured to a respective one of the shift rails 102A, 102B and 102C at a location where it aligns with, engages and translates a synchronizer clutch (not illustrated) which is associated with at least one, and typically, two gears. Also associated with each of the shift rails 102A, 102B and 102C, in a location proximate the shift tower assembly 30, such that they can be selectively engaged by one or more arms, lugs or fingers 108 on the stub shaft 40 is a respective channel, recess or slot 106A, 106B and 106C. The channels, recesses or slots 106A, 106B and 106C are arranged such that only one channel, recess or slot 106A, 106B and 106C associated with one of the shift rails 102A, 102B and 102C will be engaged in any one of the (typically) three axial positions of the stub shaft 40.
Stated somewhat differently, in any one axial position of the stub shaft 40, which corresponds to a defined lateral position of the shift lever 18, only one of the channels, recesses or slots 106A, 106B and 106C may be engaged with or by one of the arms, lugs or fingers 108 on the stub shaft 40. When the stub shaft 40 has been moved into an axial position which engages a specific channel, recess or slot 106A, 106B and 106C, longitudinal motion of the shift lever 18 which is carried through the second, shift cable 24 and the radial arm 76, rotates the stub shaft 40 and axially translates the selected one of the shift rails 102A, 102B and 102C to synchronize and engage a gear. During this action, the inertial mass or weight 80 is momentarily accelerated and moved angularly about the axis of the quill 70 and the stub shaft 40. The energy absorbed by the mass or weight 80 during the initial portion of the gear shifting and engaging activity is then released to assist and positively and completely engage the desired gear.
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.
