Abstract:
For actuating a manual transmission in an automated manner, an actuator comprises a gate selection actuating cylinder for selecting a shift gate, a gear selection actuating cylinder for engaging a gear in the shift gate, and a catch device configured to releasably fix one of the gate selection actuating cylinder and a component moveable by the gate selection actuating cylinder in at least one predetermined catch position.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to a gearbox actuator for automatic operation of a manual gearbox. 
     BACKGROUND OF THE INVENTION 
     Gearbox actuators of the general type under consideration are used to automate gearboxes in manual transmissions. In such manual transmissions, it is proposed that a gear selector element, which would be operated with a gear stick on manual operation, is guided along a selection gate to a desired shift gate and then moved into a gear position in order to engage a gear. Usually several shift gates are provided along the selection gate, transverse to the selection gate. These shift gates end in positions in which a gear is engaged.  FIG. 1  is a high level schematic showing, as an example, a gearbox with six forward gears and one reverse gear. Three shift gates  9 ,  10 ,  11  are provided along a selection gate  7  for forward gears and a further shift gate  8  for reverse gear. 
     A gearbox actuator for gearbox automation usually has an actuating cylinder via which the gear selector element is guided along the selection gate and can be positioned at an intersection point of a desired shift gate. Such an actuating cylinder is called a gate selection actuating cylinder. To engage a gear in the selected shift gate, a gear selection actuating cylinder is provided that guides the gear selection element accordingly into the selected shift gate and positions it so that the desired gear is engaged. 
     For precise positioning of the gear selection element in the selection gate, conventional gearbox actuators use a gate selection actuating cylinder with a number of defined shift positions corresponding to the number of shift gates, which positions can be set by activation of a pressure medium. To approach three positions, for example, a three-position cylinder is used. Such a three-position cylinder is in itself already relatively complex. For precise positioning with a higher number of shift positions, the design complexity for a corresponding multiposition cylinder would be even greater. 
     SUMMARY OF THE INVENTION 
     Generally speaking, it is an object of the present invention to provide a gear actuator for automated operation of a manual gearbox in which a multiplicity of defined positions can be approached with low constructional complexity. 
     According to an embodiment of the present invention, a gate selection actuating cylinder, or a component that can be moved by the gate selection actuating cylinder, can be fixed automatically via a catch device in at least one predetermined catch position. Such a catch device can be provided with relatively little constructional complexity and favorable production costs. A catch device can also be implemented in existing gear actuator constructions at reasonable cost. Embodiments of the invention make it advantageously possible to use a relatively simple actuating cylinder as a gate selection actuating cylinder, such as, e.g., a double-action actuating cylinder with only two defined positions, namely a front and a rear end position. On activation of such an actuating cylinder with pressure medium, in particular compressed air, it would not be possible simply to approach defined intermediate positions between the end positions. The use of the catch device, however, allows fixing in one or more additionally desired intermediate positions corresponding to the catch positions between the end positions to be possible at low cost. 
     In relation to other constructional solutions such as, e.g., the provision of an additional piston in a multi-position actuating cylinder, the solution provided by embodiments of the present invention can be achieved economically, and because little construction space is required, the various embodiments can be easily integrated in existing devices. In comparison with spring centering, the necessary shift force of the actuating cylinder is advantageously not or only insignificantly increased. 
     The device also provides the possibility of forming one or both end positions of the actuating cylinder as catch positions. According to an advantageous embodiment of the invention, the catch position is different from the end positions of the gate selection actuating cylinder. As a result, an additional shift position that can be approached in a defined manner for gate selection can easily be created. 
     According to an embodiment of the invention, the fixing achieved by the catch device can be overcome by activation of the gate selection actuating cylinder. This has the advantage that no additional components are required for unlocking the catch device, such as a piston activated by compressed air. Fixing can be overcome by activation of the pressure medium of the gate selection actuating cylinder if this is activated with sufficiently high pressure. 
     According to a further embodiment of the invention, the gate selection actuating cylinder is designed to move a shift finger into a selection gate. The shift finger serves advantageously as a gear selection element with which the corresponding gear parts can be activated to engage a gear. 
     According to another embodiment of the invention, the gate selection actuating cylinder is formed as a multi-position cylinder, which has end positions as well as at least one predetermined intermediate position that can be approached by activation of the pressure medium. The gate selection actuating cylinder can, in particular, be formed as a three-position cylinder. The catch position here differs from the end positions and the intermediate position. As a result, a further shift position, which can be approached in a defined manner, is created at low cost and without the need to further complicate the design of the gate selection actuating cylinder. Thus, with a three-position cylinder and an additional catch position, a gearbox with four shift gates can be operated automatically by the gearbox actuator. 
     It is contemplated that further catch positions can be provided. As a result, the number of shift positions that can be approached in a defined manner can be increased further with little cost. 
     According to another embodiment of the invention, the catch device has a locking element, which in the catch position, engages in an allocated locking recess. The locking element is under spring force in the direction of the locking recess. This allows a constructionally simple and low cost production of an automatically acting catch device. 
     According to a still further embodiment the invention, the locking recess has sloping side walls. With corresponding dimensioning of the spring force of the catch device, this advantageously allows the angle of the side walls and the profile of the locking element engaging in the locking recess to be matched to the catch device such that, firstly, secure fixing in the catch position is achieved, and, secondly, by activating the pressure medium, the fixing achieved by the catch device can be overcome by activating the pressure medium of the gate selection actuating cylinder. 
     According to a further embodiment of the invention, the locking element is integrated in the shift finger. This allows a favourable design and space-saving arrangement of the locking element. 
     According to another embodiment of the invention, the gear actuator has a distance sensor for detecting the activation stroke of the gate selection actuating cylinder. By means of the distance sensor, the activation of the gate selection actuating cylinder and the reaching of the desired shift positions can be advantageously monitored. 
     According to a further embodiment of the invention, the distance sensor is connected to an electronic control device. The electronic control device is designed to evaluate the distance signal of the distance sensor and output an actuating signal to the gate selection actuating cylinder. The electronic control device is furthermore designed for automatic learning of the catch position and the actuating time necessary for actuation of the gate selection activating cylinder from an end position or from the intermediate position into the catch position. This allows an advantageous self-learning function of the electronic controller of the gearbox actuator. The learning function can be provided, for example, in the form of a function in the software of the electronic control device. Via the learning function, e.g., under modified friction conditions in operation of the gearbox actuator, automatic adjustment of the necessary actuation time of the gate selection actuating cylinder required to approach a particular position can be learned and then applied. This allows, as a whole, low-maintenance operation of the gearbox actuator. 
     Still other objects and advantages of the present invention will in part be obvious and will in part be apparent from the specification. 
     The present invention accordingly comprises the features of construction, combination of elements, and arrangement of parts, all as exemplified in the constructions herein set forth, and the scope of the invention will be indicated in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the invention will be described in greater detail below with reference to the appended drawings, in which: 
         FIG. 1  is a schematic view of a gearbox actuator with a manual gearbox in accordance with an embodiment of the present invention; 
         FIG. 2  is a schematic view of a gate selection actuating cylinder with activating elements in accordance with an embodiment of the present invention; and 
         FIG. 3  is a cross-sectional view of a gearbox actuator in accordance with an embodiment of the present invention. 
     
    
    
     In the figures, the same reference numerals are used for corresponding elements. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a high level schematic illustration of a manual gearbox with four shift gates  8 ,  9 ,  10 ,  11  and one selection gate  7 . A gear selection element  6  can be moved along the selection gate  7  and, on reaching a shift gate  8 ,  9 ,  10 ,  11 , can be moved in the orthogonal direction into one of the positions  12 ,  13 ,  14 ,  15 ,  16 ,  17 ,  18 . In these positions, a desired gear of the manual gearbox shown can be engaged. To activate the gear selection element  6  along the selection gate, a gate selection actuating cylinder  1  is provided. To activate the gate selection element  6  along a shift gate, a gear selection actuating cylinder is provided. 
     The gate selection actuating cylinder  1  is formed, e.g., as a double-action actuating cylinder with a piston  3  and a piston rod  2 . The piston rod  2  is connected with the gear selection element  6 . By corresponding application of the pressure medium of the pressure medium chamber to the left or right of piston  3 , the piston  3  can be moved in the actuating cylinder  1  either into the left end position  4  or into the right end position  5 . In particular, compressed air can be used as the pressure medium. 
       FIG. 2  shows an embodiment of the gate selection actuating cylinder  1  as a three-position cylinder. The gate selection actuating cylinder  1  in this case has a further piston  20  as well as the piston  3  shown in  FIG. 1  that is connected with piston rod  2 . The piston  3  can be moved in relation to the further piston  20 . The gate selection actuating cylinder  1  at position  21  also has a shoulder that serves as a stop for the further piston  20 . Between the piston  3 , the further piston  20  and the housing of the gate selection actuating cylinder  1  are formed pressure medium chambers  22 ,  23 ,  24 . By corresponding control of the application of the pressure medium of pressure medium chambers  22 ,  24 , the piston rod  2  can be moved into three positions, namely into the positions corresponding to shift gates  8 ,  9 ,  11 . To approach the shift gate  8 , pressure medium chamber  24  is pressurized. To approach shift gate  9 , pressure medium chambers  22  and  24  are pressurized. To approach shift gate  11 , only pressure medium chamber  22  is pressurized. The positions corresponding to shift gates  8 ,  9 ,  10 ,  11  are shown in  FIG. 2  in relation to the end of the piston rod  2 . The pressure medium chamber  23  (middle chamber) is connected with atmospheric pressure and is not pressurized. 
     In order to also be able to approach shift gate  10 , a catch device is provided that has a locking element  28 , which is supported via a spring  30  on a housing component or other fixed component of the gearbox actuator. A catch recess is provided on the piston rod  2  that can be formed as a dip  29 . When the gate selection actuating cylinder  1  is moved, for example, from shift gate  9  towards shift gate  11 , the locking element  28  at a particular time meets the locking recess  29  and engages therein. If the pressure in the pressure medium chamber  22  remains sufficiently high, the piston rod is moved further in the direction towards shift gate  11  and the fixing at the catch position is then overcome again. If the pressure medium chamber  22  is pressurized with a correspondingly short pressure pulse, which is reduced to a sufficiently low level on reaching catch position  19 , an automatic fixing in catch position  19  takes place. The level to which the pressure pulse must be reduced on reaching catch position  19  to guarantee fixing is determined by the spring force of the spring  30  and by the respective contouring of the intermeshing surfaces of the locking element  28  and locking recess  29 . 
     The gate selection actuating cylinder  1  is moved from catch position  19  into another shift position by pressurizing the corresponding pressure medium chambers  22 ,  24 . This overcomes the fixing at the catch position. 
     The gate selection actuating cylinder  1  has an electrically controllable actuating unit  25 , which can be implemented, for example, by solenoid valves. Via actuating unit  25 , the pressure medium is introduced into pressure medium chambers  22 ,  24  or dissipated therefrom according to the setting of an electronic control unit  27 . 
     The actuating cylinder  1  also has a distance sensor  26  via which the stroke covered by the piston  3  or piston rod  2  can be detected. The distance sensor  26  can be formed, for example, as an inductive sensor, in particular a PLCD sensor. 
     The distance sensor  26  and actuating unit  25  are connected via electrical lines with the electronic control device  27 . The electronic control device  27  serves to control the gearbox actuator and has a corresponding control program. 
       FIG. 3  is a sectional view showing the design elements of the gearbox actuator. The piston rod  2  with which the gear selector element  6  is connected can be seen in  FIG. 3 . The gear selection element  6  has a blocking piece  31 , a shift finger  32 , a gate shift piece  35 , and a gear shift piece  34 . The blocking piece  31  constitutes the connection of the piston rod  2  with the gear selection element  6 . The shift finger  32  is arranged inside the blocking piece  31 . The gate shift piece  35  is firmly screwed to the blocking piece  31 . The gate shift piece  35  serves for gate selection and is therefore movable in the selection gate direction. The gate shift piece  35  simultaneously serves as a guide element for the shift finger  32  in the shift gate direction. The gear shift piece  34  can be shifted in the direction of the shift gates. It serves simultaneously as a guide in the selector gate direction. 
     The locking element  28  is arranged within the shift finger  32  in the form of a catch bolt with spring  30 . The locking recess  29  is arranged in the gear shift piece  34  below the shift finger  32  in the form of a dip. The dip  29  has a peripheral wall  33 , which has a predetermined slope. The slope of the wall  33  is matched to the tip of the locking bolt  28  such that, further taking into account the force of the spring  30 , catch position  19  can be overcome by pressurization of the actuating cylinder  1 . 
     As evident from the exemplary embodiments shown in  FIGS. 2 and 3 , various advantageous arrangements of the components of the catch device in the gearbox actuator are provided.  FIG. 2  shows an example in which the locking element  28  and spring  30  are firmly arranged at a position fixed in relation to the housing, while the locking recess  29  is arranged on a movable component in relation thereto.  FIG. 3  shows an example in which the locking recess  29  is arranged at a position fixed in relation to the housing while the locking element  28  and spring  30  are arranged on a movable component in relation thereto. It will be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since certain changes may be made without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention that, as a matter of language, might be said to fall therebetween.