Abstract:
A transmission device includes an output shaft, first and second input shafts, a first gear mechanism, a selective fixing device and a connecting and disconnecting device. The second input shaft is coaxially arranged on an outside periphery of the first input shaft. The first gear mechanism couples the first input shaft and the output shaft with a first gear ratio. The first gear mechanism includes an idle gear mounted on one of the first input shaft and the output shaft. The selective fixing device selectively fixes the idle gear to one of the first input shaft and the output shaft. The second gear mechanism couples the second input shaft and the output shaft with a second gear ratio. The connecting and disconnecting device selectively connects and disconnects the second input shaft to the rotating shaft.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Stage of International Application No. PCT/JP2011/078503, filed Feb. 12, 2011. 
     BACKGROUND 
     Field of the Invention 
     The present invention relates to a transmission device for achieving a two-speed transmission for low-speed and high-speed, and an electric vehicle comprising same. 
     Background Information 
     A conventional transmission device is disclosed in Japanese Laid-Open Utility Model Publication No. 1-146044. In this patent publication, the transmission device, is provided with a low gear supported on an output shaft via a one-way clutch and a high gear that is freely rotatable on the output shaft. The high gear is arranged so as to be selectively fixed to the output shaft by a synchro mechanism. The transmission device automatically achieves a low-speed stage on the basis of the relative rotation between the low gear and the output shaft, and achieves a high-speed stage by fixation of the higher gear to the output shaft by the synchro mechanism. 
     In the transmission device of such description, a switching operation between the high-speed stage and the low-speed stage can be carried out merely by an operation of the synchro mechanism for fixing or releasing fixation of the high gear to the output shaft, and therefore the number of components can be reduced and the transmission operation can be simplified. 
     SUMMARY 
     In recent years, electric-operated vehicles driven by a motor have also seen a heightened need for such transmission devices capable of two-stage transmission as disclosed in Japanese Laid-Open Utility Model Publication No. 1-146044, in order to combine both driving force and maximum vehicle speed. 
     However, the transmission device disclosed in Japanese Laid-Open Utility Model Publication No. 1-146044 suffers from shortcomings such as the inability to fully ensure the speed reduction ratio needed for reverse travel, because reverse travel is possible only in the high-speed stage, as well as the low efficiency of when kinetic energy during speed reduction is recovered as electric energy. 
     An object of the present invention is to provide a transmission device of simple configuration with which the necessary power can be outputted irrespective of the direction of rotation of a motor, and with which energy can be efficiently recovered, and the present invention adopts the following means in order to at least partially achieve this object. 
     A transmission device of the present invention transmits power coming from an electric motor, the transmission device comprising: an output shaft; a first input shaft configured to be coaxial with a rotating shaft of the electric motor and rotate integrally with the rotating shaft; a second input shaft coaxially arranged on an outside periphery of the first input shaft; a first gear mechanism coupling the first input shaft and the output shaft with a first gear ratio, the first gear mechanism including an idle gear mounted on one of the first input shaft and the output shaft; a selective fixing device configured to selectively fix the idle gear to one of the first input shaft and the output shaft; a second gear mechanism coupling the second input shaft and the output shaft with a second gear ratio that is different from the first gear ratio; and a connecting and disconnecting device configured to selectively connect and disconnect the second input shaft to the rotating shaft. 
     In the transmission device of the present invention, an idle gear which, of the gears of the first gear mechanism by which the first input shaft that is coaxial with the rotating shaft of the electric motor and rotates integrally with the rotating shaft and the output shaft connected to the axle side can be connected, is arranged so as to be able to idle on either the first input shaft or the output shaft is selectively fixed to the first input shaft or to the output shaft by the selective fixing device, thereby making it possible to transmit the power coming from the electric motor to the output shaft with the first gear ratio. Connecting the second input shaft, arranged so as to be externally fitted coaxially onto the first input shaft, to the rotating shaft of the electric motor by the connecting and disconnecting device makes it possible to transmit the power coming from the electric motor to the output shaft with the second gear ratio different from the first gear ratio. Therefore, it is possible to transmit power by selecting whichever gear mechanism is able to output the required power to the output shaft from among the first gear mechanism and the second gear mechanism. As a result, the requisite power can be outputted irrespective of the direction of rotation of the electric motor. 
     Also, when energy is being recovered as well, selecting the gear mechanism having better energy recovery efficiency from among the first gear mechanism and the second gear mechanism makes it possible to efficiently recover energy. The effects described above can be obtained with a simple configuration because, simply, the switch for power transmission by the first gear mechanism is carried out using the selective fixing device and the switch for power transmission by the second gear mechanism is carried out using the connecting and disconnecting device. It shall be readily understood that when the selective fixing device and the connecting and disconnecting device are actuated at the same time, there will not occur any interruption of power transmission during the switch between the power transmission by the first gear mechanism and the power transmission by the second gear mechanism. 
     The transmission device of the present invention may be configured so that the first and second gear mechanisms are configured such that the first gear ratio is set to a greater gear ratio than that of the second gear ratio, the idle gear is rotatably arranged on the output shaft, and the selective fixing device is arranged on the output shaft at a position adjacent to the idle gear. 
     In so doing, the gear diameter of the idle gear can be set to be smaller compared to a case where the idle gear is arranged on the input shaft side with the same gear ratio is being achieved. As a consequence thereof, the device can be rendered more compact. 
     The present invention may also be configured so that the first and second gear mechanisms are configured such that the first gear ratio is set to a greater gear ratio than that of the second gear ratio, the idle gear is rotatably arranged on the input shaft, and the selective fixing device is arranged on the input shaft at a position adjacent to the idle gear. 
     In so doing, it is possible to minimize the load of inertia applied to the selective fixing device in comparison to a case where the selective fixing device is arranged on the output shaft. As a consequence thereof, the durability of the selective fixing device can be improved. 
     The transmission device of the present invention may also be configured so that the selective fixing device is a synchro mechanism, and the connecting and disconnecting device is a friction clutch. 
     In so doing, costs can be minimized because of the utilization of merely a synchro mechanism and a friction clutch, which are used in conventional manual transmissions. 
     The essence of an electric vehicle of the present invention resides in the inclusion of the transmission device as set forth in claim  1 , and in which the electric vehicle comprises an axle that is mechanically connected to the output shaft. 
     With the electric vehicle of the present invention, including the transmission device of the present invention of the mode described above, it is possible to exhibit the effects exhibited by the transmission device of the present invention, e.g., the ability to output the requisite power irrespective of the direction of rotation of the electric motor and the ability to obtain, with a simple configuration, a transmission device by which energy can be efficiently recovered. As a consequence thereof, the power consumption of the vehicle can be improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an arrangement and configuration schematic view of an electric vehicle provided with a transmission device of a first embodiment; and 
         FIG. 2  is an arrangement and configuration schematic view of an electric vehicle provided with a transmission device of a second embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Modes for carrying out the present invention shall next be described with reference to the embodiments. 
     Embodiment 1 
       FIG. 1  is an arrangement and configuration schematic view of an electric vehicle provided with a gear transmission device for achieving a two-stage transmission for low speed and high speed. 
     An electric vehicle  1  is provided with: a motor  2 , which is a power source; a transmission device  3  for shifting the power coming from the motor  2  to two stages for low speed and high speed; a differential device  5  that is connected to the transmission device  3  and transmits the power coming from the transmission device  3  to an axle  6 ; and wheels  7  that are rotated by the power sent to the axle  6 . 
     The transmission device  3  has input shafts  9 ,  10  and an output shaft  11  that are rotatably arranged in parallel within a case  8 , and a ring gear  4  of the differential device  4  is in meshed engagement with an output gear  21  fixed to the output shaft  11 . 
     The input shafts are constituted of a low-side input shaft  9  and a high-side input shaft  10  that is arranged coaxially with the low-side input shaft  9  and on the outside of the low-side input shaft  9 ; the low-side input shaft  9  is directly connected to a motor shaft  2   a  of the motor  2 , and the high-side input shaft  10  is coupled to the motor shaft  2   a  of the motor  2  via a dry clutch  12 . 
     The dry clutch  12  is provided with a flywheel  12   a  that is rotated by the motor shaft  2   a , a clutch disc  12   b  fixedly mounted by spline fitting or the like to an outer peripheral surface of the motor  2  side of the high-side input shaft  10 , a pressure plate  12   c  that is arranged so as to sandwich the clutch disc  12   b  with the flywheel  12   a  on the other side, and a diaphragm spring  12   d  for urging a spring force in a direction by which the pressure plate  12   c  is separated from the clutch disc  12   b ; the motor shaft  2   a  and the high-side input shaft  10  are connected and disconnected by axially directed movement of the pressure plate  12   c  by a clutch switch device  30  coupled to the diaphragm spring  12   d  via a release bearing RB. 
     The dry clutch  12  is formed so as to be a so-called normally-open type with which the state where the motor shaft  2   a  and the high-side input shaft  10  are disconnected from each other is normally maintained. 
     The clutch switch device  30  is constituted of a motor  30   a , and a slider  30   b  that has threaded engagement with a thread section provided to a rotating shaft of the motor  30   a  and is connected to the release bearing RB, and the rotation of the rotating shaft of the motor  30   a  is converted to axially directed movement of the slider  30   b , thereby moving the pressure plate  12   c  in the axial direction via the diaphragm spring  12   d.    
     A driving low gear  14  is fixedly provided to the low-side input shaft  9 , and a driven low gear  15  constituted of an idle gear capable of idling via a needle bearing with respect to the output shaft  11  is provided to the output shaft  11 ; the driven low gear  15  is in meshed engagement with the driving low gear  14 . 
     Herein, the driving low gear  15  is of greater diameter than the driving low gear  14  and thus can more readily serve as an idle gear without sizing up, and therefore a more compact device can be achieved in comparison to a case where the driving low gear  14  serves as the idle gear. 
     A synchro mechanism  16  is arranged at a position adjacent to the driven low gear  15  on the output shaft  11 . The synchro mechanism  16  is constituted of a hub  16   a  fixed by spline fitting to the output shaft  11 , and a sleeve  16   b  that is spline-fitted to a spline formed on an outer peripheral part of the hub  16   a  and is slidable in the right-hand direction depicted in relation to the hub  16   a ; the sleeve  16   b  is configured so as to enable meshed engagement with a clutch gear  15   a  fixed to the driven low gear  15 . 
     A low-side gear mechanism  17  is constituted of the driving low gear  14  and the driven low gear  15 , and fixation of the driven low gear  15  to the output shaft  11  by the synchro mechanism  16  makes it possible to achieve power transmission of the low-speed stage. 
     A driving high gear  18  is fixedly provided to the high-side input shaft  10 , and a driven high gear  19  is fixedly provided to the output shaft  11  side; meshed engagement between the driving high gear  18  and the driven high gear  19  constitutes a high-side gear mechanism  20 , which is configured so as to achieve power transmission of the high-speed stage. 
     The gear ratio of the low-side gear mechanism  17  is set to a greater gear ratio than the gear ratio of the high-side gear mechanism  20 . 
     The operation of the electric vehicle  1  of the embodiment thus configured shall next be described, in particular regarding the shift operation of the transmission device  3 . 
     First, the shift operation of the transmission device  3  at the time of the starting of the electric vehicle  1  shall be described. 
     During starting, the synchro mechanism  16  is actuated by an actuator (not shown) so that the power of the motor  2  is transmitted to the output shaft  11  via the low-side gear mechanism  17 . 
     That is to say, the sleeve  16   b  of the synchro mechanism  16  is moved to the right-hand direction depicted from the state illustrated in  FIG. 1 , the clutch gear  15   a  and the hub  16   a  are engaged together via the sleeve  16   b , and the driven low gear  15  is fixed to the output shaft  11  via the hub  16   a . This achieves the low-speed stage serving as starting. At this time, the clutch switch device  30  is not driven, and thus the dry clutch  12  maintains the disconnected state. 
     Next, the shift operation for when shifting from the low-speed stage to the high-speed stage shall be described. 
     When there is an increase in the vehicle speed of the electric vehicle  1  of the embodiment, during travel at the low-speed stage, then a command is issued to the transmission device  3  from a control device (not shown) to shift to the high-speed stage. When the transmission device  3  is commanded to shift to the high-speed stage, the dry clutch  12  is actuated by the clutch switch device  30  so that the power of the motor  2  is transmitted to the output shaft  11  via the high-side gear mechanism  20 , and also the synchro mechanism  16  is actuated by the actuator (not shown) so as to release the engagement between the clutch gear  15   a  and the hub  16   a.    
     That is to say, the slider  30   b  of the clutch switch device  30  is moved to the left-hand direction depicted to cause the dry clutch  12  to become connected, and the sleeve  16   b  of the synchro mechanism  16  is moved to the left-hand direction depicted to release the engagement, via the sleeve  16   b , between the hub  16   a  and the clutch gear  15   a . This achieves the high-speed stage. 
     Herein, an interruption of the power transmission is prevented from taking place during the switch from the low-speed stage to the high-speed stage by simultaneously carrying out (while overlapping) the operation to connect the dry clutch  12  by the clutch switch device  30  and the release operation of the synchro mechanism  16  by the actuator (not shown). 
     Finally, the shift operation for when shifting from the high-speed stage to the low-speed stage shall be described. 
     A command is issued from the control device (not shown) to the transmission device ( 3 ) to shift to the low-speed stage when the vehicle speed of the electric vehicle  1  of the embodiment during travel at the high-speed stage is being reduced or when a need to re-accelerate arises. When a command to shift to the low-speed stage is issued to the transmission device  3 , the transmission device  3  is controlled to as to begin operating opposite to during the previously described switch from the low-speed stage to the high-speed stage. 
     That is to say, the slider  30   b  of the clutch switch device  30  is moved to the right-hand direction depicted to cause the dry clutch  12  to become disconnected, and the sleeve  16   b  of the synchro mechanism  16  is moved to the right-hand direction depicted to engage the hub  16   a  and the clutch gear  15   a  together via the sleeve  16   b . This achieves the low-speed stage. 
     Herein, similarly with respect to during the shift from the low-speed stage to the high-speed stage, an interruption of the power transmission is prevented from taking place during the switch from the high-speed stage to the low-speed stage by simultaneously carrying out (while overlapping) the operation to disconnect the dry clutch  12  by the clutch switch device  30  and the engagement operation of the synchro mechanism  16  by the actuator (not shown). 
     According to the transmission device of the embodiment described above, the low-speed stage is constituted of the low-side input shaft  9  that is directly connected to the motor shaft  2   a , the driving low gear  14  fixed to the low-side input shaft  9 , the driven low gear  15  idly arranged on the output shaft  11 , and the synchro mechanism  16  for selectively fixing the driven low gear  15  to the output shaft  11 , and the high-speed stage is constituted of the high-side input shaft  10  arranged by being externally fitted to the low-side input shaft  9 , the dry clutch  12  for selecting connecting the high-side input shaft  10  and the motor shaft  2   a  of the motor  2  together, the driving high gear  18  fixed to the high-side input shaft  10 , and the driven high gear  19  fixed to the output shaft  11 . 
     That is to say, having the shift to the low-speed stage be the switch by the synchro mechanism  16  and having the shift to the high-speed stage be the switch by the dry clutch  12  means that it is readily possible to ensure a configuration by which the power required can be transmitted to the output shaft  11  irrespective of the direction of rotation of the motor shaft  2   a  of the motor  2 . It is moreover possible to efficiently recover energy, by selecting the low-speed stage for during energy recovery. It shall also be readily understood that simultaneously carrying out the switch of the synchro mechanism  16  and the switch of the dry clutch  12  prevents any interruption of power transmission during shifting from taking place. 
     Embodiment 2 
     An electric vehicle  100  equipped with a transmission device  103  of a second embodiment of the present invention shall next be described. 
       FIG. 2  is a schematic configuration diagram of the electric vehicle equipped with the transmission device  103  of the second embodiment. 
     The electric vehicle  100  of the transmission device  103  of the second embodiment is given the same configuration as that of the electric vehicle  1  provided with the transmission device  3  of the first embodiment, except in that the low-side gear mechanism  17  is changed to a low-side gear mechanism  117 , and in that the synchro mechanism  16  is changed to a synchro mechanism  116 . As such, like reference numerals are assigned to parts of the electric vehicle  100  of the second embodiment that are of like configuration to that of the electric vehicle  1  of the first embodiment, and a description thereof is omitted. 
     In the transmission device  103  of the second embodiment, as is depicted, a driving low gear  114  is idly arranged on the low-side input shaft  9  and a driven low gear  115  is fixed onto the output shaft  11 ; on the low-side input shaft  9 , the synchro mechanism  116  is disposed adjacently on the left-hand side depicted of the driving low gear  114 . 
     A clutch gear  114   a  is fixedly provided to the driving low gear  114 , and moving a sleeve  116   b  of the synchro mechanism  16  to the right-hand side depicted causes the clutch gear  114   a  and a hub  116   a  of the synchro mechanism  116  to become engaged with each other via the sleeve  116   b . This fixes the driving low gear  114  to the low-side input shaft  9  and achieves the low-speed stage. 
     According to the transmission device  103  of the second embodiment described above, the effects are similar to those of the transmission device  3  of the first embodiment, i.e., it is readily possible to ensure a configuration by which the power required can be transmitted to the output shaft  11  irrespective of the direction of rotation of the motor shaft  2   a  of the motor  2 , and also possible to efficiently recover energy, by selecting the low-speed stage for during energy recovery. It shall also be readily understood that the effect where simultaneously carrying out the switch of the synchro mechanism  116  and the switch of the dry clutch  12  prevents any interruption of power transmission during shifting from taking place is also exhibited. 
     It is also possible to minimize the load of inertia applied to the synchro mechanism  116 , because the synchro mechanism is arranged not only the output shaft  11  but rather on the low-side input shaft  9 . As a consequence thereof, it is possible to improve the durability of the synchro mechanism  116 . 
     With the transmission devices  3  and  103  of the embodiments described above, the switch to the low-speed stage was made by actuating the synchro mechanisms  16  and  116  and the switch to the high-speed stage was made by actuating the dry clutch  12 , but, conversely, the configuration may be such that the switch to the low-speed stage is made by actuating the dry clutch and the switch to the high-speed stage is made by actuating the synchro mechanism.