Abstract:
A manually shiftable transmission includes a blocking mechanism to prevent unintended engagement of a first forward gear set. An electronic controller is provided for moving the blocking mechanism into an unblocking position. A manually operable release switch is provided to generate a signal to an electronic controller to move the blocking mechanism into the unblocking position when an intentional engagement of the first gear set is desired. The transmission may also include a mechanism to inhibit engagement of a reverse gear set. The electronic controller and manually operable release switch may be used to move the reverse gear inhibiting mechanism to an uninhibited position.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/900,950 filed Nov. 6, 2013, the disclosure of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to transmissions, and more particularly to shift controls for manually shifted transmissions. 
       BACKGROUND OF THE INVENTION 
       [0003]    Transmissions, such as those widely used in vehicles, are well know in the art. Transmissions, also known as gearboxes, typically include a case or housing containing an input shaft, an output shaft, and a plurality of meshing gears. The meshing gears contained within the transmission case are of varying size to provide a plurality of gear ratios. By appropriately shifting among these various gear ratios, acceleration and deceleration of the vehicle can be accomplished in a smooth and efficient manner. 
         [0004]    Manually shifted vehicle transmissions, that is, those in which gear engagement is shifted in response to some physical exertion by an operator, are well known and are often preferred various types of vehicles, such as heavy duty trucks and racing or competition vehicles. Many transmission structures are known for manually shifting among the various gear ratios. In a conventional manual transmission, the driver moves an upper portion of a pivotable shift lever to effect shifting of the gears. In response thereto, a lower portion of the shift lever engages and moves one or more shift rails provided within the transmission. Shift rails are typically supported within the transmission case for sliding movement from a central or neutral position forward to one gear set engaging position or rearward to another gear set engaging position. Shift forks attached to a shift rail engage collars connected to various clutches to connect and disconnect the gear sets with various shafts. The initial selection and subsequent movement of a shift rail causes certain sets of gears to be connected between the input shaft and the output shaft to provide a desired output gear ratio. 
         [0005]    Typically, manually shifted transmission gear ratio positions are arranged in pairs of shift rail movement paths, with movement of the shift rail forward or backward out of a neutral position effective to engage one set of gears. For example, in a typical six speed transmission, the first and second gear ratios are located in a first path, the third and fourth gear ratios are located in a second path, and the fifth and sixth gear ratios are located in a third path. A reverse gear may be located on a separate path or on a path along with another forward ratio. For example, in a five forward speed transmission, the reverse gear may be located on the same path as that used to engage the first or fifth gear sets. 
         [0006]    Human error may be introduced during manual shifting of the shift lever. A common problem is shifting a transmission to an unintended gear, such as shifting into a reverse gear when a forward gear is intended. This could lead to disastrous results. Several types of reverse gear lockout safety systems have been developed to alleviate such problems. 
         [0007]    Another problem is downshifting into an unintended gear. Downshifting is common in racing or competition vehicles to maximize vehicle performance. For example, downshifting from fourth gear to third gear would be common to slow the vehicle for a turn and put the vehicle in a better gear for acceleration when the vehicle comes out of the turn. However, it is possible that the driver may mistakenly downshift the transmission by moving the shift lever into an undesired path of movement. This is not uncommon in racing or competition vehicles because of the intensity of the racing event. Such inadvertent downshifting may result in undesirable consequences. For example, downshifting from fourth gear to first gear (instead of third gear) would cause the vehicle engine to unacceptably increase engine speed, possibly causing damage to the engine and to the vehicle&#39;s main friction clutch. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention is a manually operable transmission, such as a transmission for racing or competition vehicles. The transmission includes standard components such as a housing, input and output shafts, and one or more shift rails that selectively clutch various gear sets having various gear ratios for driving engagement of the input and output shafts. A manually operable shift lever is pivotally mounted to drivingly engage a shift rail assembly to selectively effect engagement of the various gear sets. 
         [0009]    The transmission includes a blocking mechanism selectively movable between a blocked position wherein the shift lever is prevented from drivingly connecting a first forward gear set between the input shaft and the output shaft, and an unblocked position in which the shift lever is free to cause the first forward gear set to drivingly connect the input shaft and the output shaft. An electronic controller is provided for moving the blocking mechanism into the unblocked position. A manually operable release switch is provided to generate a signal to the electronic controller to move the blocking mechanism into the unblocked position when an intentional engagement of the first gear set is desired. Preferably, the release switch is a momentary release switch that operates a solenoid to allow the blocking mechanism to move into the unblocked position only for so long as the switch is activated. 
         [0010]    The transmission may also include a reverse gear inhibiting mechanism selectively movable between an inhibiting position inhibiting the shift lever from engaging a reverse gear set and an uninhibited position wherein the inhibiting mechanism allows the shift lever to engage the reverse gear set. A second solenoid may be provided to control, within limits, the reverse gear inhibiting mechanism. The same signal generated by the manually operable release switch may be used to simultaneously move the reverse gear inhibiting mechanism to an uninhibited position. 
         [0011]    Various aspects of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIGS. 1A and 1B  together are a cross-sectional view of a transmission in accordance with the present invention. 
           [0013]      FIG. 2  is a cross-sectional view of a portion of the transmission of  FIGS. 1A and 1B  taken along line  2 - 2 . 
           [0014]      FIG. 3  is a perspective view of the gate control of  FIG. 2 . 
           [0015]      FIG. 4  is plan view of the guide plate of  FIG. 2 . 
           [0016]      FIG. 5  is a partial cross-sectional view of the transmission of  FIGS. 1A and 1B  taken along line  5 - 5 . 
           [0017]      FIG. 6  is a view of the reverse shift rail of the transmission of  FIGS. 1A and 1B . 
           [0018]      FIG. 7  is a partial cross-sectional view of the transmission of  FIGS. 1A and 1B  taken along line  7 - 7 . 
           [0019]      FIG. 8  is a schematic view of controls for the transmission of  FIGS. 1A and 1B . 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0020]    Referring to  FIG. 1A and 1B , a transmission  10  is, in large measure, a conventional manually shifted vehicular transmission adapted to provide several forward gear ratios between an input shaft  12  at the forward end of the transmission and an output shaft  14 , as is well known in the art. The transmission  10  has a single countershaft  16 , six forward gear ratios and one reverse gear ratio, although the present invention may be applied to multi-countershaft transmissions, range boxes and nearly any number of gear ratios. Transmission housing  18  encases the various components of the transmission  10 . 
         [0021]    As is well known in the art, various gears may be selectively clutched to the output shaft  14  to drive the output shaft at various speed ratios relative to the input shaft speed. For example, first gear set  22 ,  22 ′ and second gear set  24 ,  24 ′ may be selectively clutched to output shaft  14  by clutch  26 . Third gear set  32 ,  32 ′ and fourth gear set  34 ,  34 ′ may be selectively clutched to output shaft  14  by clutch  36 . Fifth gear set  42 ,  42 ′ and sixth gear set  44 ,  44 ′ may be selectively clutched to output shaft  14  by clutch  46 . Reverse gear set  52 ,  52 ′,  52 ″ (idler gear  52 ″ shown out of position for illustrative purposes) may be selectively clutched to output shaft  14  by clutch  56 . The various clutches are drivingly connected to the shift rail assembly  70  by shift forks, as is well known in the art. 
         [0022]    Transmission  10  may be manually shifted among the various gear ratios through manual shift lever  60  mounted on shift lever housing  62 . The shift lever  60  may pivot forward  60   a  and backward  60   b  (as viewed in  FIGS. 1A and 1B ) as well as transversely about a pivot pin  64 . The lower end of the shift lever  60  is formed with a finger  66  that drivingly engages a shift rail assembly  70 . The shift rail assembly  70  includes a rear shift rail  72  having an aperture  74  for receiving the shift lever finger  66 . The shift rail assembly  70  also includes a forward shift rail  76  drivingly connected to the rear shift rail  72  by pins  78  which extend through a gate member  80 . Shift rail  72  includes a reverse paddle  75 , the purpose of which will be explained later. 
         [0023]    As is well known in the art, transverse movement of the shift lever  60  about the pivot pin  64  causes rotation of the shift rail assembly  70  about rotational axis  71  to select pairs of gear sets that can be engaged. Forward and backward pivoting of the shift lever  60  moves the shift rail assembly  70  axially along axis  71  to cause engagement of one of the pairs of selected gear sets with the output shaft  14 . A spring and detent system  82  provides operator feel for the forward, neutral and rearward positions of the shift rail assembly  70 . 
         [0024]    Selection of pairs of gear sets to engage the output shaft  14  is made through the gate  80 . Referring to  FIGS. 2 ,  3  and  4 , the gate  80  includes a selector finger  82  that travels within a guide plate  90 . The gate  80  may be cast, machined or formed from powdered metal. Guide plate  90  is secured to the transmission housing  18  by bolts (not shown). A cover plate  84  is bolted to the housing  18  for assembly purposes and to provide access to the gate  80 . When the shift lever  60  is in a neutral position in which no gear set is engaged with the output shaft, selector finger  82  is in the neutral track  92  of the guide plate  90 . In this position, transverse movement of the shift lever  60  causes the selector finger  82  to pivot between various guide plate tracks  91 ,  93 ,  95 ,  97 . 
         [0025]    The guide plate tracks limit rotation of the shift rail assembly  70  when the shift lever  60  is in a forward or backward position corresponding to engagement of a gear set. The guide plate tracks correspond to rotational positions of the shift rail assembly  70 . Guide plate track  97  corresponds to forward gear set pairs for first and second gears (i.e. gear ratios); guide plate track  95  corresponds to forward gear set pairs for third and fourth gears; guide plate track  93  corresponds to forward gear set pairs for fifth and sixth gears; guide plate track  91  corresponds to the reverse gear set. 
         [0026]    Referring to  FIGS. 1 and 5 , a selector finger  100  is rigidly attached to the forward shift rail  76 . Rotation of the shift rail  76  causes the finger  100  to select a forward gear set pair lever  102 ,  104  or  106  or reverse gear lever  108  for driving engagement with the shift lever assembly  70 . When a forward gear pair lever  102 ,  104 , or  106  is selected, the shift rail assembly  70  will be drivingly engaged with the clutch collars and shift forks of the respective forward gear sets. Forward and backward pivotal movement of the shift lever  60  will force backward and forward movement of the shift rail assembly  70  causing clutching of one of the forward gears sets of the selected pair with the output shaft  14 . 
         [0027]    Referring also to  FIG. 6 , a separate shift rail assembly  110  is provided to engage the fifth and sixth gear sets and the reverse gear set. When selector finger  100  is engaged with the lever  106 , axial movement of the shift lever  60  causes axial movement of the shift rail  105  and shift fork  116 , and engagement of the fifth or sixth gear sets with output shaft  14 . When selector finger  100  engages the reverse lever  108 , axial movement of the shift lever  60  causes axial movement of the shift rail  110  and shift fork  118 , and engagement of the reverse gear set with output shaft  14 . 
       Forward Gate Control 
       [0028]    Referring again to  FIGS. 2 and 3 , gate  80  is rigidly connected to shift rail assembly rails  72  and  76  by pins  78  for rotational and axial movement in response to shift lever  60  movements. Rotational movement of the gate  80  aligns the shift finger  82  for axial travel in one of the gear guide tracks  91 ,  93 ,  95 , or  97 . Gate  80  includes an integral cam track  86 . A centering mechanism in the form of a ball and spring detent mechanism  88  is threaded into the housing  18 , with the ball  89  engaging the cam track  86  under a spring load. The cam track  86  has a neutral position  87  that provides feel to the shift lever  60  at the neutral track  92  of the guide plate  90 . 
         [0029]    A track block extension  130  is integrally formed on the gate  80  opposite the cam track  86 . A twelve volt gate control solenoid  120  is threaded into housing  18  opposite the detent mechanism  88 . The solenoid includes a pin  122  that is retractable when power is applied to the solenoid, as is well known in the art. A spring  124  forces the pin  122  to its fully extended position as shown in  FIG. 2  when power is not applied to the solenoid. 
         [0030]    The track block  130  includes a blocking surface  132  for selective engagement with the solenoid pin  122 . The solenoid pin  122  and blocking surface  132  are oriented such that the selector finger  80  cannot be rotated to the first and second gear set track  97  unless the pin  122  is retracted, that is, unless power is applied to the solenoid. The blocking extension  130  has an undercut surface  136  adjacent to blocking surface  132 . The pin  122  cannot engage the undercut surface  136  when fully extended, thereby permitting free movement of the selector finger among track guide tracks  91 ,  93 , and  95 . The solenoid  120  is designed such that the pin  122  has sufficient strength to carry the side load which will be applied by the selector  80  through the blocking surface  132 . A twelve volt solenoid can be used, but other sizes and voltages may be used. 
         [0031]    In operation of the transmission, the operator must apply power to the solenoid  120  in order to access the first pair of gear sets. The first pair of gear sets includes the first gear set  22 ,  22 ′ and the second gear set  24 ,  24 ′, which provide the lowest output shaft speed ratios. This pair of gear sets is typically engaged for the initial launch of a vehicle. If the first forward gear set  22 ,  22 ′ is engaged, a shift to the second forward gear set  24 ,  24 ′ will be possible without powering the solenoid because the solenoid pin  122  will be restricted from extending by slide surface  134  on the track block extension. 
         [0032]    When the transmission is shifted from the second forward gear set  24 ,  24 ′ to the third forward gear set  32 ,  32 ′ or fourth forward gear set  34 ,  34 ′, the selector finger  82  will move to gate track  95  with minimal resistance from the solenoid pin  122  as it slides along the slide surface  134 . However, when the selector finger  82  reaches the gear set track  95 , the blocking surface  132  will have already passed the pin  122 , allowing the pin to extend fully under the force of solenoid spring  124 . 
         [0033]    After the selector finger  82  is moved from the guide track  97 , the gate  80  will prevent the transmission operator from returning the selector finger  82  to guide track  97  because the gate  80  will be blocked by the pin  122  engaging the blocking surface  132 . Of course, activating the solenoid will retract the pin  122 , thereby allowing the selector finger  82  access to the track  97  ultimately access to the associated forward gear sets. 
       Reverse Inhibiting Mechanism 
       [0034]    As previously explained, reverse gear set  52  can be clutched to the output shaft  18  through the output clutch  56 . To position the shift lever  60  so that the gate control  80  is in the reverse guide track  91  ( FIG. 2 ), selector finger  100  must engage the reverse lever  108 . A reverse inhibiting mechanism  140  prevents inadvertent access to the reverse gear guide track  97 . 
         [0035]    Referring to  FIG. 7 , mechanism  140  includes a plunger  142  seated in a cylindrical opening  19  in the housing  18 . The plunger has a forward surface  141  and an integral annular flange  150  which is sized to allow a close fit in the opening  19 . When the plunger  142  is in an extended position, the forward surface  141  will engage the reverse paddle  75  and block the reverse paddle  75  from rotating to an extreme position, thereby blocking the selector finger  80  from entering guide track  91 . Plunger  142  is biased into the blocking position shown in  FIG. 7  by biasing spring  144 . 
         [0036]    A collar  146  surrounds the plunger  142 . A spring  150  is positioned to react against the collar  146  and the plunger flange  150 . The spring  150  biases the collar  148  axially away from the plunger flange  150 . When the plunger  140  is in an uninhibited position, the spring  144  will bias the plunger to block the reverse paddle from a position for engaging the reverse gear set. In this configuration, the shift lever  60  easily will be able to overcome the force of spring  144  to move the plunger from the blocking position to allow access the reverse shift rail  110 . 
         [0037]    A reverse inhibitor solenoid  160  is threaded into the housing  18 . Reverse inhibitor solenoid  160  has an extendible pin  162 . Reverse inhibitor solenoid  160  is a twelve volt solenoid identical to the gate control solenoid  120 ; however, the two solenoids do not have to be identical. The pin  162  is retractable when power is applied to the solenoid  160 . A solenoid spring  164  forces the pin  162  to its fully extended position as shown in  FIG. 7  when no power is applied to the solenoid. When the reverse paddle  75  is not engaged with the plunger  142 , solenoid pin  162  is extended by the solenoid spring into the path of collar  146 . If the collar  146  is moved away from the reverse paddle  75 , the collar flange surface  147  will engage the pin  162 , thereby blocking the plunger from retracting unless the force of spring  148  is overcome. 
         [0038]    The intent of this design is that the spring force  148  will be sufficient to prevent an unintentional shift engaging the reverse gear set, but not an absolute restriction. For safety reasons, it is preferred that the transmission operator be capable of engaging the reverse gear set manually if this is truly intended by the operator, but such intention must be demonstrated by overcoming the force of spring  148 . The reverse inhibitor mechanism merely inhibits engagement of the reverse gear set, but does not absolutely prevent engagement. 
       Controls 
       [0039]    The gate control solenoid  120  and reverse lockout solenoid  160  may be controlled simultaneously. For example, a switch may be used by a vehicle operator to momentary engage both solenoids simultaneously, thereby allowing engagement of the first pair of gear sets as well as the reverse gear set. The solenoids  102  and  160  are identical, but solenoids of different voltages or types may be used provided the controller  170  is adapted accordingly. Solenoids are commonly known and used and are readily available, such as Fema Corp. solenoid 51160. 
         [0040]    Referring to  FIG. 8 , a thumb button switch  50  on a shift lever knob  61  may be used to send a signal to an electronic controller  170  to provide a simultaneous momentary signal to each of the solenoids  120  and  160  through appropriate wiring  162 ,  164  connected to and powered by a vehicle electrical system. Of course, alternatively, separate switches also may be use to power the separate solenoids. 
         [0041]    This invention relates is particularly applicable to transmissions for completion or racing vehicles. The gate  80  limits the ability of a vehicle driver to downshift into the lower gear ratios without activating solenoid  120  which controls the blocking mechanism  80 . As such, the shift gate control between the first and second gear ratios is referred to a competition gate. The momentary release switch moves the solenoid pin  122  to its retracted position for a relatively short period of time, thereby allowing a driver to manually override the downshift limiting structure in a quick and easy manner for a relatively short period of time. 
         [0042]    The descriptions of specific embodiments of the invention herein are intended to be illustrative and not restrictive. The invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope as defined by the appended claims.