Patent Publication Number: US-2005128035-A1

Title: Electric actuator

Description:
TECHNICAL FIELD  
      The present invention relates to an electric type actuator for a transmission.  
     BACKGROUND ART  
      As a transmission for an automobile, there have been widely used a manual transmission in which a driver changes gears by operating a shift lever along with a clutch pedal and an automatic transmission in which a gear ratio is automatically changed in accordance with a driving situation. Further, there is known an automatic transmission there among combined with a torque converter and a planetary gear mechanism, combined with a variable type pulley and an endless belt or the like. Further, in recent years, there has been used a transmission for an automobile for automatically switching a gear change unit which has been used as a manual transmission in a background art and automatically connecting and disconnecting a clutch since operation thereof is easy and a transmission efficiency is higher than that of a general automatic transmission.  
      International Publication WO 01/31234 A1 discloses a structure for switching gears constituting a gear change unit in such a transmission for an automobile. An explanation will be given of an electric driving apparatus for a transmission according to the international publication in reference to  FIGS. 18 through 24 .  
      First, an explanation will be given of a first example shown in  FIGS. 18 through 21 . A transmission case  1  is a case including a gear change unit similar to that of a manual transmission. A front end portion  3  of a switch shaft  2  for switching a gear ratio of the gear change unit is projected from a side face of the transmission case  1 . A middle portion of the front end portion  3  is formed with a male spline portion  4 . The male spline portion  4  is engaged by a spline with a spline cylinder  5  formed with a female spline at an inner peripheral face thereof. A further end portion of the front end portion  3  projected from the spline cylinder  5  is coupled with an engaging claw  7  formed with an engaging groove  6  at an outer peripheral face thereof.  
      The switch shaft  2  is displaced in an axial direction (head and tail direction of  FIG. 18 , up and down direction of  FIG. 19 ) in selecting operation and rotated in shifting operation. Here, the selecting operation is operation of displacing a shift lever in a width direction of a vehicle in a general manual type floor shift vehicle to thereby select a gear for changing speed. Meanwhile, the shifting operation is operation of displacing the shift lever in a front and rear direction of the vehicle to thereby couple a synchromesh mechanism in correspondence with the selected gear to make the gear capable of transmitting power.  
      A detailed explanation will be given of the selecting operation and the shifting operation as follows. Consider here a gear change unit realizing six kinds of gear change states of forward 5 stages (1 speed through 5 speed) and rearward  1  stage (R).  
      In the selecting operation, one of three kinds of both end positions in a left and right direction and a center position in the left and right direction of  FIG. 22  is selected. In the selecting operation, the synchromesh mechanism is maintained in a free state and therefore, a neutral state is brought about and any gear change state is not brought about. In the shifting operation, the shift lever is displaced from any position of the three kinds brought into the neutral state in either direction (upper direction or lower direction of  FIG. 22 ). Thereby, any synchromesh mechanism is brought into a connected state to bring about any gear change state. Here, according to International Publication WO 01/31234 A1, a selecting type actuator  8  which is a pivoting type actuator is provided between an outer face of the transmission case  1  and the engaging claw  7  to displace the switch shaft  2  in the axial direction in the selecting operation.  
      As shown by  FIG. 20 , the selecting actuator  8  includes a selecting electric motor  9  and a multistreak worm gear  10  driven to rotate by an output shaft of the selecting electric motor  9 . The multistreak worm gear  10  is brought in mesh with a worm wheel  11 . An output shaft  12  of the worm wheel  11  constituting a rotational center thereof is coupled to fix to a base end portion of a pivoting arm  13  and the pivoting arm  13  is rotated along with the worm wheel  11 . An engaging projected portion  14  formed at one side face of a front end portion (an upper face of a left end portion of  FIG. 18 ) of the pivoting arm  13  is engaged with an engaging groove  6  of an engaging claw  7  to thereby enable to displace the switch shaft  2  in the axial direction.  
      Meanwhile, a shifting actuator  16  for rotating the switch shaft  2  to carry out the shifting operation is provided between the outer face of the transmission case  1  and a front end portion of a driving arm  15  fixedly provided to an outer peripheral face of the spline cylinder  5 . The shifting actuator  16  is fixedly supported by a shifting electric motor  18  capable of rotating regularly and reversely via a motor housing  19  in a shape of a stepped cylinder at one end portion (left end portion of  FIG. 21 ) of a shifting case  17  substantially in a cylindrical shape.  
      A portion of a ball screw shaft  20  proximate to a base end portion thereof is rotatably supported by a rolling bearing  21  of a deep groove type ball bearing or the like (in a state of being hampered from being displaced in an axial direction) at inside of the motor housing  19 . A portion of the base end portion of the ball screw shaft  20  projected from the rolling bearing  21  is coupled to an output shaft  22  of the shifting electric motor  18  to enable to transmit a rotational force.  
      A ball nut  23  is arranged at a surrounding of the ball screw shaft  20 . A plurality of balls  26  are arranged between a male ball screw groove  24  formed at an outer peripheral face of the ball screw shaft  20  and a female ball screw groove  25  formed at an inner peripheral face of the ball nut  23  to constitute a ball screw apparatus  27 . The ball nut  23  is displaced in an axial direction of the ball screw shaft  20  in accordance with rotation of the ball screw shaft  20  since the ball nut  23  is hampered from being rotated by itself as mentioned later. A base end portion of an output member  28  in a cylindrical shape is coupled to one end face (right end face of the drawing) of the ball nut  23 .  
      A sliding bearing  29  locked by an inner peripheral face of a front end portion (right end portion of  FIG. 21 ) of the shifting case  17  is brought into sliding contact with an outer peripheral face of a middle portion of the output member  28 . Further, a front end portion of the output member  28  is coupled with a front end portion of the driving arm  15  via a coupling bracket  30  and a coupling pin  31  ( FIG. 18  through  FIG. 19 ). Further, an outer peripheral face of a middle portion of the output member  28  is formed with a guide groove  32  in an axial direction of the output member  28 . The guide groove  32  is engaged with a guide pin  33  fixed to the front end portion of the shifting case  17  to prevent the output member  28  and the ball nut  23  from being rotated.  
      Further, there is provided a detent mechanism  34  engaged with the output member  28  at a middle position of a stroke of the ball nut  23  for producing a resistance against a displacement of the ball nut  23  in the axial direction between the output member  28  and the shifting case  17 . In order to constitute the detent mechanism  34 , a recess hole  35  in a conical shape is formed at an outer peripheral face of a middle portion of the output member  28  and a ball  37  is held at inside of a cylinder portion  36  provided at the shifting case  17  to be able to displace in a diameter direction of the shifting case  17 . Further, the ball  37  is elastically pressed to an outer peripheral face of the output member  28  by a spring  38 .  
      The electric driving apparatus for a transmission of the background art constituted as described above changes the gear of the gear change unit included in the transmission case  1  as follows. First, the selecting electric motor  9  constituting the selecting actuator  8  is rotated in a predetermined direction to thereby displace to pivot the pivoting arm  13  in an up and down direction of  FIG. 19 . Further, the switch shaft  2  is displaced in the axial direction in a predetermined direction via the engaging claw  7  by the engaging recess portion  14  provided at the front end portion of the pivoting arm  13  to thereby carry out the selecting operation.  
      After carrying out the selecting operation in this way, the switch shaft  2  is rotated in a predetermined direction via the driving arm  15  by extracting and retracting the shifting actuator  16  in order to carry out the shifting operation. When the shifting operation is carried out in this way, the ball screw shaft  20  is rotated in a predetermined direction by the shifting electric motor  18 . Further, the ball nut  23  and the output member  28  are displaced in the axial direction by the ball screw apparatus  27  to push and pull the driving arm  15 .  
      Next,  FIGS. 23 through 24  show a second example of the background art according to the above-described international publication. In the case of the example, a driving bracket  140  is fixed to a portion of a front end portion (upper end portion of  FIG. 24 ) of the switch shaft  2  rotatably supported on an inner side of a supporting plate  139  fixed to an opening portion of the transmission case  1  which is projected from the transmission case  1 . Further, the engaging projected portion  14  provided at the front end portion of the pivoting arm  13  of the selecting actuator  8  (refer to  FIGS. 18 through 20 ) is engaged with an engaging groove  6   a  formed on one face of the driving bracket  140 . Further, a sliding pin  141  is supported between front end portions of a pair of driving arms  15   a ,  15   a  formed at both end portions in an axial direction of other side of the portion of the outer peripheral face of the driving bracket  140  in parallel with the switch shaft  2 . Further, the sliding pin  141  is inserted into a circular hole  142  formed at a front end portion of the output member  28   a  of the shifting actuator  16  (refer to  FIGS. 18, 20  and  22 ).  
      Also in the case of the second example constituted as described above, similar to the above-described case of the first example, the selecting operation can be carried out by displacing the switch shaft  2  in the axial direction by pivoting the pivoting arm  13 . Further, the shifting operation can be carried out by displacing the output member  28   a  in the axial direction.  
      However, when the above-described electric driving apparatus for a transmission is reduced into practice, it is necessary in view of carrying out swift gear change operation to increase an output of the shifting electric motor  18  constituting the shifting actuator  16 . That is, in the above-described selecting operation and switching operation, a force required for the selecting operation is small, however, a force required for the shifting operation is large and therefore, it is necessary to swiftly and firmly carry out the shifting operation. For that purpose, it is necessary to use the shifting electric motor  18  having a large output (torque×rotational speed). Here, in order to firmly carry out the shifting operation by using a motor having a small output, it is necessary to ensure a force of pushing and pulling the output shaft member  28  by increasing a speed reduction ratio of the ball screw mechanism  28 , however, in that case, a speed of moving the output shaft member  28  is retarded and shift shifting operation cannot be carried out.  
      However, in the case of the structure of the background art, it is difficult to use the shifting electric motor  18  having the large output. An explanation will be given in this regard in reference to  FIGS. 25 and 26  showing an electric actuator.  FIGS. 25 and 26  show a structure in which a shifting actuator  16   a  is attached to an outer face of a transmission case  1   a  containing a gear change unit constituting a driven portion at inside thereof and a switch shaft  2   a  projected from an outer face of the transmission case  1   a  is made to be able to drive to rotate by the shifting actuator  16   a . In the case of the example, a driving arm  15   a  is provided at an outer peripheral face of a spline cylinder  5   a  engaged by spline with an outer peripheral face of the switch shaft  2   a , and a long hole  39  prolonged in a diameter direction of the switch shaft  2   a  is formed at a middle portion of the driving arm  15   a . Further, the long hole  38  is coupled with a coupling pin  31   a  supported by a front end portion of an output shaft member  28   a  of the shifting actuator  16   a . According to the constitution, the switch shaft  2   a  is displaced in a rotational direction based on displacement of the output shaft member  28   a  in an axial direction. Therefore, it is not necessary to pivot to displace a center shaft of the output shaft member  28   a  as in the structure of the background art shown in  FIGS. 18 and 19  and the shifting actuator  16   a  is fixed to the outer face of the transmission case  1   a  by an attaching flange  40 .  
      In the case of the structure shown in  FIGS. 25 and 26 , a center axis α of the shifting actuator  16   a  is in parallel with the outer face of the transmission case  1   a . Therefore, an outer diameter d 18  of a shifting electric motor  18   a  constituting the shifting actuator  16   a  is restricted by a distance L 5  between the outer face of the transmission case  1   a  and a center of the spline cylinder  5   a . Specifically, the outer diameter d 18  of the shifting electric motor  18   a  is to be twice as much as or smaller than the distance L 5  (d 18 ≦2 L 5 ). Further, the distance L 5  cannot be increased so much since it is necessary to ensure bending rigidity of the switch shaft  2   a  and prevent a damage of crack, bending or the like from being brought about at the switch shaft  2   a . Therefore, the outer diameter d 18  of the shifting electric motor  18   a  cannot be increased according to the structure shown in  FIGS. 25, 26 .  
      On the other hand, in order to increase the output of the shifting electric motor  18   a  to carry out swift gear change operation, it is effective to increase the outer diameter d 18  of the shifting electric motor  18   a . It is desired to realize a structure to be able to increase an outer diameter of a shifting electric motor constituting a shifting actuator while ensuring the bending rigidity of the switch shaft  2   a  in consideration of these facts. In the case of the electric driving apparatus for the transmission according to the international publication, shown in  FIG. 19 , the switch shaft  2  is supported by an inner diameter side of the bracket in the cylindrical shape fixed to the outer face of the transmission case  1  and therefore, it is possible in one respect to increase a diameter of the selecting electric motor  9  while ensuring the rigidity of the switch shaft  2 . However, according to the invention of the electric driving apparatus for a transmission according to the above-described international publication, a consideration is given to supporting the selecting actuator  8  by the transmission case  1  to be able to displace to pivot and a consideration is not given to increasing the diameter of the selecting electric motor  9 . Further, integrating operation is complicated by providing the above-described bracket.  
     DISCLOSURE OF THE INVENTION  
      It is an object of the invention to provide an electric type actuator capable of swiftly and firmly carrying out shifting operation in view of the above-described problem.  
      An electric type actuator of the invention is an electric type actuator fixed to an outer face of a case containing a driven portion at inside thereof for driving a transmitting member projected from the outer face for driving the driven portion, the electric type actuator including: 
          an electric motor; and     an output member for transmitting a displacement based on rotation of the electric motor to the transmitting member;     wherein a radius of the electric motor is larger than a distance from an axis center of the output member disposed at an axis center portion of the transmitting member to the outer face of the case.        

      Further, the outer face of the case of provided with a recess portion and a portion of a housing of the electric motor is made to advance into the recess portion.  
      Further, the outer face of the case is an inclined face formed with a portion of projecting the transmitting member and a portion of attaching a housing of the electric motor continuously to each other.  
      Further, the electric type actuator includes an actuator case, a ball screw shaft provided at inside of the actuator case, and a ball nut reciprocated along the ball crew shaft, an inner peripheral face of the actuator case is provided with a stopper for preventing an end face in an axial direction of the ball nut from being butted to a portion fixed to the ball screw shaft.  
      According to the electric type actuator of the invention constituted as described above, the output of the electric motor can be increased by increasing the outer diameter of the electric motor while ensuring the rigidity of the transmitting member without excessively increasing the amount of projecting the transmitting member from the outer face of the case. Therefore, when the electric type actuator is integrated, for example, an electric driving apparatus for a transmission, gear change operation can swiftly and firmly be carried out. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a side view showing a first embodiment of the invention.  
       FIG. 2  is a side view showing a modified example of the first embodiment of the invention.  
       FIG. 3  is an outline plane view showing a total constitution of a second embodiment of the invention.  
       FIG. 4  is a front view of a selecting actuator.  
       FIG. 5  is a plane view of the selecting actuator.  
       FIG. 6  is a rear view of the selecting actuator.  
       FIG. 7  is a left side view of the selecting actuator.  
       FIG. 8  is a sectional view taken along a line A-A of  FIG. 4 .  
       FIG. 9  is a plane view of a shifting actuator.  
       FIG. 10  is a front view of the shifting actuator.  
       FIG. 11  is a right side view of the shifting actuator.  
       FIG. 12  is a sectional view taken along a line B-B of  FIG. 8 .  
       FIG. 13  is a view enlarging a central portion of  FIG. 12  showing a state of moving a ball nut to an end portion.  
       FIG. 14  is a front view showing a state of connecting the shifting actuator and a driving arm.  
       FIG. 15  is a sectional view taken along a line C-C of  FIG. 14 .  
       FIG. 16  is a sectional view showing other example of a detent structure of a ball nut.  
       FIG. 17  is a plane view showing an example of a structure of integrating a selecting actuator and a shifting actuator.  
       FIG. 18  is a plane view showing a first example of an electric driving apparatus for a transmission of a background art.  
       FIG. 19  is a sectional view taken along a line D-D of  FIG. 18 .  
       FIG. 20  is a sectional view taken along a line E-E of the same.  
       FIG. 21  is a sectional view taken along a line F-F of the same.  
       FIG. 22  is an outline plane view showing an example of a shift pattern of a transmission.  
       FIG. 23  is a partial plane view showing a second example of an electric driving apparatus for a transmission of a background art.  
       FIG. 24  is a sectional view taken along a line G-G of  FIG. 23 .  
       FIG. 25  is a plane view showing an example of an electric actuator of a background art.  
       FIG. 16  is a side view of the electric actuator of  FIG. 25 . 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION  
      An explanation will be given in details of Embodiments of the invention in reference to the drawings as follows.  
      (First Embodiment)  
      An explanation will be given of an electric actuator according to First Embodiment of the invention as follows.  FIG. 1  shows a case of applying to attach a shifting actuator  16   b  integrated to an electric driving apparatus for a transmission for carrying out shifting operation to an outer face of a transmission case  1   b  according to First Embodiment of the invention. According to the embodiment, the shifting actuator  16   b  is attached to an outer face  41  of the transmission case  1   b  containing a gear change unit which is a driven portion at inside thereof. The shifting actuator  16   b  is made to be able to drive to rotate a switch shaft  2   a  projected from the outer face of the transmission case  1   b  per se (a portion integrated with the transmission case  1   b ). Also in the case of the embodiment, similar to the structure shown in  FIGS. 25 and 26 , the driving arm  15   a  is provided at the outer peripheral face of the spline cylinder  5   a  engaged with the outer peripheral face of the switch shaft  2   a  by a spline and the middle portion of the driving arm  15   a  is formed with a long hole  39  (refer to  FIG. 25 ) prolonged in the diameter direction of the switch shaft  2   a . Further, the long hole  39  is engaged with a coupling pin  31   a  supported by a front end portion of an output shaft member  28   a  of the shifting actuator  16   b.    
      According to the embodiment, the shifting actuator  16   b  is fixed to the outer face  41  of the transmission case  1   b  by an attaching flange  39   a . The shifting actuator  16   b  is provided in a state of being inclined to the outer face  41 . In other words, a center axis β of the shifting actuator  16   b  and the outer face  41  are not in parallel with each other. Further, the switch shaft is projected from the outer face  41  in an inclined state. Further, the center axis β of the shifting actuator  16   b  is present on an imaginary plane orthogonal to a center axis γ of the switch shaft  2   a . Therefore, a butting face  42  of the attaching flange  40   a  brought into contact with the outer face  41  is inclined in accordance with inclination of the center shaft γ of the switch shaft  2   a  relative to the outer face  41 . Further, inside of a portion of a middle portion of the shifting actuator  16   b  installed with the attaching flange  40   a  contains the ball screw mechanism  27  (refer to  FIG. 21 ) for converting a rotational movement of the shifting electric motor  18   b , mentioned later, into linear movement to transmit to the output shaft member  28   a.    
      In the case of the embodiment, the outer diameter D 18  of the shifting electric motor  18   b  constituting the shifting actuator  16   b  can be made to be larger than twice of the distance between the outer face  41  of the transmission case  1   b  and the center of the spline cylinder  5   a  (distance from an axis center of the output shaft member  28  to the outer face  41  at an axis center portion of the switch shaft  2   a ) L 5  (D 18 &gt;2 L 5 ). That is, the output of the shifting electric motor  18   b  can be increased by increasing the outer diameter D 18  of the shifting electric motor  18   b  while ensuring rigidity of the switch shaft  2   a  without excessively increasing an amount of projecting the switch shaft  2   a  from the outer face  41  of the transmission case  1   b . Therefore, when integrated to, for example, an electric driving apparatus for a transmission, gear change operation can swiftly and firmly be carried out. These effects can be achieved by utilizing the transmission case  1   b  of the prior art as it is depending on a shape of the outer face of the transmission case  1   b.    
      Next,  FIG. 2  shows a modified example of Embodiment 1 of the invention. In the case of the example, by constituting an outer face  41   a  of a transmission case  1   c  by a stepped shape, the outer diameter D 18  of the shifting electric motor  18   b  constituting the shifting actuator  16   b  is increased without excessively increasing an amount of projecting the switch shaft  2   a  from the outer face  41   a . That is, a portion of installing the shifting electric motor  18   b  is recessed in comparison with a portion of the outer face  41   a  of the transmission case  1   c  projecting the switch shaft  2   a  and to be brought into contact with a butting face  42   a  of an attaching flange  40 . Further, the outer diameter D 18  of the shifting electric motor  18   b  is increased by an amount of recessing the portion. In accordance therewith, in the case of the example, the butting face  42   a  of the attaching flange  40  is not inclined as in the above-described first example.  
      Constitutions and operation of other portions are similar to those of First Embodiment and therefore, equivalent portions are attached with the same notations and a duplicated explanation thereof will be omitted.  
      (Second Embodiment)  
      An explanation will be given of Second Embodiment of the invention as follows. An electric driving apparatus for a transmission according to the embodiment is applicable to the electric driving apparatus for a transmission according to Embodiment 1. An explanation will be given in details in reference to the drawings as follows.  
       FIG. 3  shows a transmission apparatus for an automobile integrated with the electric driving apparatus of a transmission according to Second Embodiment of the invention. Rotation of a crankshaft  44  of an engine  43  is transmitted to an input shaft  47  of a gear change unit  46  via a clutch apparatus  45 . Further, an output of the gear change unit  46  is transmitted to drive wheels  49 ,  49  via a propeller shaft  48 . In the case of a structure shown in  FIG. 3 , the clutch apparatus  45  is a dry type single plate clutch combined with a general manual transmission and is connected and disconnected by a clutch actuator  50  of a hydraulic type or an electric type.  
      A gear ratio of the gear change unit  46  is changed by the electric driving apparatus for a transmission constituting an object of the invention. The switch shaft  2   a  projected from an outer face of a transmission case  1   a  containing the speed change unit  46  is driven freely by a selecting actuator  8   a  and a shifting actuator  16   a . The selecting actuator  8   a  in the actuators displaces the switch shaft  2   a  in an axial direction (up and down direction of  FIG. 3 ). Meanwhile, the shifting actuator  16   a  rotates the switch shaft  2   a  in a twisting direction.  
      The selecting actuator  8   a  is constituted as shown by  FIGS. 4 through 8 . The selecting actuator  8   a  is constituted by integrating a selecting electric motor  9   a , a pinion gear  52 , an output shaft  12   a , and a displacement sensor  53  which is a position sensor to a selecting case  51 . The pinion gear  52  is formed at an outer peripheral face of a middle portion of a transmitting shaft  55  integrally with the transmitting shaft  55 . The transmitting shaft  55  is rotatably supported by a pair of ball bearings at inside of the selecting case  51  in a state of being arranged concentrically with a rotating drive shaft  54  of the selecting electric motor  9   a . A front end portion of the rotating drive shaft  54  and a base end portion of the transmitting shaft  55  are engaged with each other by serration engagement (including spline engagement) to thereby transmit rotation of the rotating drive shaft  54  to the transmitting shaft  55 . By the constitution, a rotation transmitting portion having inconsiderable rattling can be provided at low cost. Further, male and female of the serration engagement in this case may be reversed from those in the illustrated case.  
      The selecting electric motor  9   a  is coupled to fix to one side face of a main body  57  constituting the selecting case  51  by bolts  65 ,  65  inserted through an attaching flange  64 . Under the state, a front end portion of the selecting electric motor  9   a  is fit into a recess hole  66  formed at one side face of the main body  57  without play. An O ring  67  is locked by the front end portion of the selecting electric motor  91  to seal a fit portion. By the constitution, a foreign matter of rain water or the like is prevented from invading the selecting case  51  installed with the transmitting shaft  55  and the like and grease sealed in the selecting case  51  is prevented from being leaked.  
      The output shaft  12   a  is rotatably supported similarly by a pair of ball bearings at inside of the selecting case  51  in a state of being arranged in parallel with the transmitting shaft  55 . A sector gear (fan-like gear)  56  is provided at an outer peripheral face of a middle portion of the output shaft  12   a  integrally with the output shaft  12   a . The sector gear  56  and the pinion gear  52  are brought in mesh with each other to be able to drive to rotate the output shaft  12   a  in two directions by an amount of a predetermined angle. By the constitution, there is compactly realized a structure capable of driving the output shaft  12   a  by the amount of the predetermined angle by a torque needed for selecting operation. In order to be able to contain the sector gear  56  and the pinion gear  52  at inside of the selecting case  51 , the selecting case  51  is constituted by attaching a cover  58  to the main body  57 . By constituting the grease sealed into the selecting case  51  by kinds the same as each other at the respective ball bearings and the two gears  52  and  56 , a deterioration accompanied by mixing grease used for lubrication of respective portions is prevented and low cost formation is achieved by simplifying control and filling operation of grease.  
      A front end face (right end face of  FIG. 8 ) of the output shaft  12   a  is formed with a recess portion  59  in a diameter direction of the front face. A portion of a center portion of the front face of the output shaft  12   a  disposed at the recess portion  59  is formed with a screw hole  60  to fit a base end portion of the pivoting arm  13   a  into the recess portion  59  without play. Further, a coupling screw  62  inserted through a through hole  61  formed at a base end portion of the pivoting arm  13   a  is screwed to the screw hole  60  to fasten. Under the state, the base end portion of the pivoting arm  13   a  is coupled to fix to the front end portion of the output shaft  12   a  and is made to be rotatable along with the output shaft  12   a . There is constituted an engaging projected portion  14   a  fit to fix with a pin and engageable with the engaging claw  7  (refer to  FIG. 3 ) fixed to the switch shaft  2   a  at a front end portion of the pivoting arm  13   a . A front half portion (right half portion of  FIGS. 7 through 8 ) to constitute the engaging projected portion  14   a  is subjected to a high frequency heat treatment and an outer peripheral face of the engaging projected portion  14   a  is quenched to harden. By the treatments, there is restrained wear of the outer peripheral face of the engaging projected portion  10   a  accompanied by engaging the engaging claw  7  fixed to the end portion of the switch shaft  2   a  with an engaging groove  6   b  (refer to  FIG. 3 ).  
      The displacement sensor  53  is supported by the selecting case  51  concentrically with the output shaft  12   a . Therefore, an attaching hole  63  formed at the front end portion of the main body  57  for mounting the output shaft  12   a  is opened to two side faces of the main body  57 . An engaging projection  69  projected at a detecting portion  68  of the displacement sensor  53  is engaged with an engaging recess portion  70  to transmit rotation of the output shaft  12   a  to the detecting portion  68 . The displacement sensor  53  is like a potentiometer changing an electric property thereof of a resistance value or the like in accordance with an rotational angle of the detecting portion  68  to detect a pivoting angle of the output shaft  12   a  based on a measured value thereof.  
      Further, a structure of fixing the pin to constitute the engaging projected portion  14   a  to the front end portion of the pivoting arm  13   a  can be constituted by calking other than press-fitting, screwing or the like. Even in the case of constituting the structure by calking, a portion of the pin quenched to harden by the high frequency heat treatment is disposed only at the outer peripheral face of the front half portion of the engaging projected portion  14   a  and therefore, calking operation can easily be carried out. The base end portion of the pin is inserted into the attaching hole formed at the front end portion of the pivoting arm  13   a  when fixed by calking. Further, a flange portion in a shape of an outward flange formed at the middle portion in the axial direction of the pin or one face of the stopper ring stopped by the middle portion in the axial direction is butted to one face of the locking arm  13   a  (right face of  FIGS. 7 through 8 ). Further, a portion of an end face of the pin projected from other face (left face of  FIGS. 7 through 8 ) of the pivoting arm  13   a  is calked to widen outwardly in the diameter direction and the front end portion of the pivoting arm  13   a  is pinched between the portion and the flange portion or the stopper ring. The base end portion of the pin stays to be untreated without being quenched to harden and therefore, the calking and widening operation can easily be carried out.  
      The selecting actuator  8   a  having the above-described constitution is coupled to fix to the outer face of the transmission case  1   a  (refer to  FIG. 3 ) by an attaching bolt, (not illustrated) inserted through an attaching flange  71  fixedly provided at a base end portion of the main body  57  of the selecting case  51 . Among the respective members mounted to the selecting case  51 , the selecting electric motor  9   a  having a large weight is attached proximately to the base end of the main body  57 , that is, a portion thereof proximate to the attaching flange  71 . In contrast thereto, the displacement sensor  53  having a light weight is attached proximately to the front end of the main body  57 , that is, a side thereof being remote from the attaching flange  71 . By the constitution, growth of vibration transmitted from the transmission case  1   a  to the selecting case  51  is prevented in operation to prevent an error brought about in the detected value of the displacement sensor  53  and damage of the displacement sensor  53 .  
      When the switch shaft  2   a  is displaced in the axial direction by the selecting actuator  8   a , the pinion gear  52  is rotated in a predetermined direction based on electricity conduction to the selecting motor  9   a . As a result, the output shaft  12   a  fixedly provided with the sector gear  56  brought in mesh with the pinion gear  52  is pivoted to pivot to displace the pivoting arm  13   a . Further, the engaging projected portion  14   a  provided at the front end portion of the pivoting arm  13   a  displaces the switch shaft  2   a  in the axial direction. An amount of the displacement is detected by the displacement sensor  53  as the rotational angle of the output shaft  12   a . By transmitting a detecting signal of the displacement sensor  53  to a controller for controlling electricity conduction to the selecting electric motor  9   a , the switch shaft  2   a  can be displaced to a predetermined position in the axial direction.  
      According to the embodiment, fine adjustment of a position of attaching the displacement sensor  53  relative to the main body  57  of the selecting case  51  is made to be able to carry out easily. That is, in the case of the example, in order to attach a holder  72  containing the displacement sensor  53  to the main body  57  of the selecting case  51 , the holder  72  is provided with flange portions  73 ,  73  as shown by  FIG. 6 . Further, attaching screws  75 ,  75  inserted into through holes  74 ,  74  formed at the two flange portions  73 ,  73  are screwed to screw holes formed at the main body  57  to fasten. In the case of the embodiment, the respective through holes  74 ,  74  are long holes in a shape of a circular arc centering on a point on a center line of the output shaft  12   a  constituting the center of pivoting the pivoting arm  13   a . By the constitution, a position of pivoting the pivoting arm  13   a  is made to be able to properly detect by easily carrying out fine adjustment of the position of attaching the displacement sensor  53  relative to the main body  57 .  
      According to the embodiment, by making directions of attaching the selecting electric motor  9   a  and the displacement sensor  53  relative to the main body  57  the same as each other, the two members  9   a  and  53  are facilitated to integrate. That is, both of the selecting electric motor  9   a  and the displacement sensor  53  are integrated to the main body  57  from a left-side of  FIG. 8 . Therefore, the integrating operation can be facilitated by facilitating to arrange harnesses belonging to the selecting electric motor  9   a  and the displacement sensor  53  or the like.  
      Although according to the embodiment, the displacement sensor  53  of a contact type is used, as the displacement sensor  53 , a noncontact type sensor of a proximity sensor or the like can also be used. When the noncontact type sensor is used, a problem of wearing a contact portion of the engaging projection  69  and the engaging recess portion  70  by vibration applied in operation can be restrained from being posed. As a detecting mechanism of the noncontact type sensor, various mechanisms which have been known in background arts of an optical type, an electromagnetic type, a type of using a hall IC and the like can be used. In this case, it is not necessary that the noncontact type sensor (similarly also in the case of the contact type) can detect the position in the all the range of vibration of the pivoting arm  13   a . The sensor will do so far as positions necessary for carrying out selecting operation, that is, three portion positions of both end positions and a central position of pivoting can be detected.  
      Further, regardless of whether the displacement sensor  53  is of the contact type or the noncontact type, the displacement sensor  53  can also be constituted such that the detecting signal of the displacement sensor  53  is transmitted to the side of the controller by wireless communication. By transmitting the detecting signal by wireless, a harness belonging to the displacement sensor  53  can be omitted. Further, in this case, the displacement sensor  53  can include a battery, or power can also be supplied from the side of the selecting electric motor  9   a  in which a harness is indispensable. The selecting electric motor  9   a  and the displacement sensor  53  are contiguous to each other and therefore, it is easy to provide the harness for supplying power from the selecting electric motor  9   a  to the displacement sensor  53 .  
       FIGS. 9 through 12  are views showing the shifting actuator  16   a . According to the shifting actuator  16   a , a shifting electric motor  18   a  capable of being rotated regularly and rotated reversely is fixedly supported by one end portion (left end portion of  FIGS. 9, 10 ,  12 ) of a shifting case  17   a  made of a nonferrous metal of a light metal or the like such as an aluminum alloy and having substantially a cylindrical shape. According to the case of the embodiment, an outer diameter side fitting portion  76  in a shape of a stepped cylinder is provided at the one end portion of the shifting case  17   a  and an inner diameter side fitting portion  77  formed at a front end portion (right end portion of  FIGS. 9, 10 ,  12 ) of the shifting electric motor  18   a  is inwardly fit to the outer diameter side fitting portion  76 . An O ring  78  is mounted to a locking groove formed at an outer peripheral face of the inner diameter side fitting portion  77  and the O ring  87  is compressed elastically between a bottom portion of the locking groove and an inner peripheral face of the outer diameter side fitting portion  76 . Under the state, coupling flanges formed at the outer peripheral face of the front end portion of the shifting electric motor  18   a  and formed at an outer peripheral face of the base end portion of the shifting case  17   a  are butted to each other to couple the two coupling flanges by coupling bolts  79 ,  79 .  
      Further, when the shifting case  17   a  and the shifting electric motor  18   a  are integrated while pressing the O ring  78  to the outer diameter side fitting portion  76 , pressure at inside of the shifting electric motor  18   a  is increased. In order to prevent a seal ring  93  provided between an inner peripheral face of a front end portion of the shifting case  17   a  and an outer peripheral face of an output member  28   a , mentioned later, from being turned out by restraining such a pressure increase, a small hole for air vent can also be formed at a portion of the shifting case  17   a . Such a hole is closed by a resin (adhering agent) after integration is finished. However, when the seal ring  93  is finally integrated, or the pressure increase is limited, such a consideration is not necessary.  
      The O ring  78  prevents a foreign matter of rain water or the like from invading inside of the shifting case  17   a  and prevents grease sealed in the shifting case  17   a  from being leaked. The grease lubricates respective rolling contact portions provided in the shifting case  17   a  and lubricates sliding contact portion between an outer peripheral face of the output member  28   a , mentioned later and an inner peripheral face of a sliding bearing  29 . Also with regard to the grease lubricating the respective portions in this way, grease of the same kind is used for a total of the shifting actuator  16   a  to prevent a deterioration accompanied by mixing grease and achieves low cost formation by simplifying control and operation of filling the grease. Further, with regard to the shifting electric motor  18   a , it is preferable to use the shifting electric motor  18   a  having a specification the same as that of the selecting electric motor  9   a  ( FIGS. 5 through 8 ) (the same kind) in view of achieving a reduction in cost. That is, by making the specifications of the two motors  18   a  and  9   a  the same as each other, other than a reduction in cost by a mass production effect, the cost is reduced by making portions of control circuits common and a consideration or the like for preventing erroneous integration is dispensed with. Further, it is preferable in view of making small-sized formation of the two motors  18   a  and  9   a  and swift formation of gear change operation compatible with each other to use the two motors  18   a  and  9   a  driven by power source voltage higher than that of a battery for an automobile of a background art.  
      Further, a portion of a middle portion of a ball screw shaft  20   a  proximate to a base end thereof is supported to be able to only rotate by a rolling bearing  21  of a deep groove type ball bearing or the like (in a state of hampering displacement in a axial direction) at a portion of a middle portion on an inner side of the shifting case  17   a  proximate to the base end. Further, rotation of an output shaft  22  is made to be able to transmit to the ball screw shaft  20   a  by subjecting a portion of a base end portion of the ball screw shaft  20   a  projected from the rolling bearing  21  and the output shaft  22  of the shifting electric motor  18   a  to serration engagement (including spline engagement) similar to the above-described case of the selecting actuator  8   a . Further, also with regard to male and female of the serration engagement in this case, the male and female may be reverse to that in the illustrated case. Further, male and female of the serration coupling in this case maybe reversed from that of the illustrated case. Further, the ball screw shaft  20   a  may be integrated to the output shaft  22  of the shifting electric motor  18   a . By integrating the ball screw shaft  20   a  with the output shaft  22 , operation of coupling the ball screw shaft  20   a  and the output shaft  22  can be omitted and coupling at the coupling portion can completely be eliminated.  
      Further, in an outer ring  80  and an inner ring  81  of the rolling bear  21 , in a state of being butted to a steppe portion  82  formed at the inner peripheral face of the shifting case  17   a  via an outer ring interposing seat  83 , the outer ring  80  is pressed to the stepped portion  82  by a press nut  84  in a cylindrical shape to fix to the inner peripheral face of the shifting case  17   a . Further, an inner diameter of the outer ring interposing seat  83  is made to be smaller than an outer diameter of a ball nut  23   a  to make the outer ring interposing seat  83  serve as a stopper. Meanwhile, the inner ring  81  is pinched between a stopper ring  85  (or a flange portion integral with the ball screw shaft  20   a ) locked by the outer peripheral face of the middle portion of the ball screw shaft  20   a  and a press nut  86  screwed to a male screw portion formed at the outer peripheral face of the base end portion of the ball screw shaft  20   a  to fix to the outer peripheral face of the ball screw shaft  20   a . Further, in order to make the outer ring interposing seat  83  serve as a stopper, a face of two side faces of the stop ring  85  opposed to the ball nut  23   a  is recessed more than a face of two side faces of the outer ring interposing seat  83  opposed to the ball nut  23   a  in an axial direction (direction of  FIG. 12 ).  
      Therefore, when the ball nut  23   a  is moved in the left direction from the state of  FIG. 12 , as shown by  FIG. 13 , the end face of the ball nut  23   a  is butted to the outer ring interposing seat  83  and is not butted to the stop ring  85 . The reason of constituting in this way is for preventing the end face in the axial direction of the ball nut  23   a  from being butted to a portion fixed to the ball screw shaft  20   a  to thereby prevent occurrence of operational failure accompanied by misalignment of a ball arranged between the ball nut  23   a  and the ball screw shaft  20   a.    
      Further, a ball screw apparatus  27   a  is constituted by arranging the ball nut  23   a  at a surrounding of the ball screw shaft  20   a  and arranging a plurality of balls between a male ball screw groove formed at the outer peripheral face of the ball screw shaft  20   a  and a female ball screw groove formed at the inner peripheral face of the ball nut  23   a . Further, all of the ball screw shaft  20   a  and the ball nut  23   a  and the respective balls are made by a ferrous metal of bearing steel or the like to prevent play accompanied a change in temperature of use from being brought about by reducing differences in thermal expansion amounts. Further, at least portions brought into rolling contact with each other are formed with layers hardened by a heat treatment to ensure rolling fatigue life of the portions. As the heat treatment which is carried out in this case, a pertinent heat treatment in accordance with a material is selected from quenching tempering, carbonizing, carbo-nitriding, high frequency heat treatment and the like. Further, it is preferable to constitute a surface hardness of the hardened layer by about HRc55 or higher and constitute a thickness thereof by about 0.1 through 1.5 mm. Further, with regard to the plurality of balls, balls made by ceramic of silicon nitride or the like can also be used. When the ball made of ceramic is used, occurrence of metal contact at rolling contact portion can firmly be prevented and even when a failure in lubrication is assumedly brought about, the failure can be made to be difficult to amount to other important damage of seizure or the like.  
      Further, although a method of working the male ball screw groove at the outer peripheral face of the ball screw shaft  2   a  and a method of working the female ball screw groove at the inner peripheral face of the ball nut  23   a , various method which have been known in background arts of cutting and the like can be adopted, when the ball screw grooves are produced by plastic deformation, the screw grooves of high quality having excellent durability can be produced at low cost. As the plastic deformation used in this case, forming of rod is pertinent with regard to the male ball screw groove and cold forging is pertinent with regard to the female ball screw groove, respectively.  
      In any of the cases, it is preferable to provide a positive clearance of about 1 through 250 μm as a clearance in the axial direction in view of reducing consumption energy and promoting durability. That is, when the ball screw apparatus  27   s  is provided with a negative clearance (applied with prepressure), the consumption energy of the shifting electric motor  18   a  is increased. Further, by vibrating to displace the ball under no load state by vibration of about 200 through 300 Hz incessantly applied from the engine in operation, fretting wear is liable to be brought about at the respective ball screw grooves. In contrast thereto, when the clearance in the axial direction is constituted by a positive value of about 1 through 250 μm, not only the consumption energy of the shifting electric motor  18   a  can be reduced but also the fretting wear can be restrained. Further, when the value of the axial direction clearance is made to be equal to or larger than 300 μm, the fretting wear is liable to be brought about similarly.  
      The ball nut  23   a  is displaced in the axial direction of the ball screw shaft  20   a  in accordance with rotation of the ball screw shaft  20   a  since rotation of the ball nut  23   a  per se is hampered as mentioned later. Further, one end face (right end face of  FIG. 12 ) of the ball nut  23   a  is coupled with a base end portion of the output member  28   a  in a shape of a circular cylinder. In the case of the embodiment, a large diameter portion  87  formed at an inner peripheral face of the base end portion of the output member  28   a  is outwardly fit to a coupling projected portion  88  in a shape of a circular cylinder projected at a central portion of a front end face (right end face of  FIG. 12 ) of the ball nut  23   a  without play. Further, by calking a base end edge of the output member  28   a  to a locking groove  89  formed at the outer peripheral face of the base end portion of the coupling projected portion  88 , the output member  28   a  and the ball nut  23   a  are coupled to fix. By the constitution, a structure capable of transmitting a thrust force in two directions between the output member  28   a  and the ball nut  23   a  without play is realized at the low cost. Further, a base half portion (left half portion of  FIG. 12 ) of the output member  28   a  is constituted by a shape of a hollow circular cylinder to prevent interference with the ball screw shaft  20   a . By the constitution, a necessary stroke is ensured while preventing a length in the axial direction of the ball nut  23   a  from being prolonged more than necessary.  
      Further, it is preferable to constitute the output member  28   a  by a material in consideration of rust prevention since the output member  28   a  is exposed to outside air when used. For that purpose, a total of the output member  28   a  is made of stainless steel, or at least a portion of the outer peripheral face of the output member  28   a  exposed from the shifting case  17   a  when used is formed with a corrosion preventing skin film of a plating layer, a resin skin film or the like. By the constitution, the outer peripheral face of the output member  28   a  is prevented from being corroded and the sliding resistance between the outer peripheral face of the output member  28   a  and an inner peripheral face of the sliding bearing  29 , mentioned later is prevented from being increased base on corrosion.  
      The outer peripheral face of the middle portion of the output member  28   a  is brought into sliding contact with the sliding bearing  29  locked by the inner peripheral face of the front end portion (right end portion of  FIGS. 9, 10 ,  12 ) of the shifting case  17   a . A dimension in the axial direction of the sliding bearing  29  is sufficiently ensured to ensure a rigidity against a moment load applied to the output member  28   a . Further, the front end portion of the output member  28   a  is formed by a bifurcated shape to couple to the middle portion of a driving arm  16   b  engaged by a spline with the end portion of the switch shaft  2   a  as shown by  FIGS. 14 through 16 . That is, a middle portion of the driving arm  16   b  is formed with a long hole  90  prolonged in the diameter direction of the switch shaft  2   a  and the middle portion is inserted into a recess portion  91  formed at a front end face of the output member  28   a  in a diameter direction. Further, a pin  92  fixed to the front end portion of the output member  28   a  is engaged with the long hole  90  in a state of traversing the recess portion  91 . By constituting the electric driving apparatus for a transmission of the example in this way, the switch shaft  2   a  is made to be able to pivot to displace in a state of fixing the shifting case  17   a  to the outer face of the transmission case  1   a.    
      Here, the shifting case  17   a  is provided with a flange  17   c  for attaching to the transmission case  1   a . A contact fact  17   d  of the attaching flange  17   c  in contact with the transmission case  1   a  is made to be unparallel with a center axis of the output member  28   a , that is, a center axis of the shifting actuator  16   a  and the shifting electric motor  18   a  is attached to be remote from the transmission case  1   a . Therefore, also in the embodiment, similar to the first embodiment, a diameter of the shifting electric motor  18   a  can be made to be larger than twice of a distance between the outer face of the transmission case  1   a  and the center of the spline cylinder (distance from an axis center of the output shaft member  28   a  to the outer face of the transmission case  1   a  at an axis center portion of the switch shaft) L 5  (D 18 &gt;2 L 5 )  
      Further, as described above, the shifting case  17  is made by a nonferrous metal of an aluminum alloy or the like and is produced by a material of a species the same as that of the transmission case  1   a . Therefore, light-weighted formation of the shifting case  17   a  is achieved and occurrence of rattling accompanied by a change in a temperature of use is prevented by reducing a difference between thermal expansion coefficients of the shifting case  17   a  and the transmission case  1   a.    
      Further, in the case of the example, as shown by  FIG. 10 , the output member  28   a  and the ball nut  23   a  are prevented from being rotated by engaging a guide pin  33   a  fixed to the front end portion of the shifting case  17   a  to a guide groove  32   a  formed at the outer peripheral face of the ball nut  23   a  in the axial direction. However, it is not necessarily needed to provide such a detent structure by the guide groove  32   a  and the guide pin  33   a . That is, in the case of the example, as described above, the output member  28   a  and the ball nut  23   a  fixed with the output member  28   a  are prevented from being rotated based on engagement between the driving arm  15   a  and the recess portion  91 . Therefore, the detent structure by the guide groove  32   a  and the guide pin  33   a  may be omitted. Further, even when the detent structure by the guide pin is provided, the detent structure is not limited to the structure of fixing the guide pin  33   a  to the shifting case  17   a  by stopping by screw as shown by  FIG. 10  but as shown by  FIG. 16 , a structure of simply fitting to fix a guide pin  33   b  in a shape of a circular cylinder to the shifting case  17   a  can also be adopted.  
      As described above, the electric driving apparatus according to the embodiment changes gears of the gear change unit included in the transmission case  1   a  as follows. First, the pivoting arm  13   a  is pivoted to displace in an up and down direction of  FIGS. 3, 4 ,  8  by rotating the selecting electric motor  9   a  constituting the selecting actuator  8   a  in a predetermined direction. Further, selecting operation is carried out by displacing the switch shaft  2   a  in the axial direction in a predetermined direction via the locking claw  7  by the engaging projected portion  14   a  provided at the front end portion of the locking arm  13   a . In this case, a position of the switch shaft  2   a  in the axial direction is detected by the displacement sensor  53 .  
      After carrying out the selecting operation in this way, the switch shaft  2   a  is rotated in a predetermined direction via the driving arm  15   b  by extracting and retracting the shifting actuator  16   a  in order to carry out shifting operation. In carrying out shifting operation in this way, the ball screw shaft  20   a  is rotated in a predetermined direction by the shifting electric motor  18   a . Further, the ball nut  23   a  and the output member  28   a  are displaced in the axial direction by the ball screw apparatus  27   a  to push and pull the driving arm  15   b.    
      At this occasion, the shifting actuator  16   a  is displaced from a neutral state in correspondence with the state of neutral (a state of middle of the length dimension) to a fully elongated state or a fully contracted state. Gear change operation for successively carrying out the selecting operation and the shifting operation in this way are carried out by an electric control from a controller while relating the displacement in the selecting direction (X direction) and the displacement in the shifting direction (Y direction).  
      Next,  FIG. 17  shows a modified example of the second embodiment of the invention. In the case of the example, a selecting case  51   a  for containing the selecting actuator  8   a  and a shifting case  17   b  for containing the shifting actuator  16   a  are integrally formed. Further, by coupling an attaching flange  71   a  common to the two cases  51   a  and  17   b  to the outer face of the transmission case  1   a  ( FIG. 3 ), the two actuators  8   a  and  6   a  are made to be able to fix to the outer face. In the case of the example, by adopting such a constitution, a space of attaching the two actuators  8   a  and  16   a  is made to be able to reduce and attaching operation is facilitated.  
      Further, although in the above-described respective examples, as the shifting actuator, there is shown the structure of rotating the ball screw shaft without moving the ball screw shaft in the axial direction and moving the ball nut in the axial direction without rotating the ball nut, the ball screw apparatus constituting the shifting actuator constituting the electric driving apparatus for a transmission of the invention is not limited to such a structure but following three kinds of structure can also be adopted. A first structure is a structure of engaging a ball screw shaft to a ball nut which is not rotated and moved in an axial direction to be able to rotate and move in the axial direction. A second structure is a structure of engaging a ball screw shaft to a ball nut which is only rotated and is not moved in the axial direction movably in the axial direction in a state of being hampered to rotate. A third structure is a structure of engaging a ball nut to a ball screw shaft which is not rotated and moved in the axial direction to be able to rotate and move in the axial direction.  
      Although an explanation has been given of the invention in details and in reference to the specific embodiments as described above, it is apparent for a skilled person that the invention can variously be changed or modified without deviating from the spirit and the range of the invention.  
      The application is based on Japanese Patent Application (Japanese Patent Application No. 2002-016500) filed on Jan. 25, 2002 and Japanese Patent Application (Japanese Patent Application No. 2002-028542) filed on Feb. 5, 2002 and contents thereof are incorporated here by reference.  
     Industrial Applicability  
      According to the invention, the electric type actuator capable of swiftly and firmly carrying out shift operation can be provided. Therefore, when the electric type actuator is applied to, for example, the electric driving apparatus for a transmission, a strange feeling given to a driver in gear change can be reduced or resolved by realizing swift gear change operation.