Patent Publication Number: US-7721867-B2

Title: Rotation output device

Description:
TECHNICAL FIELD 
     The present invention relates to a rotation output device usable in, for example, an electric tool such as an electric driver or the like and capable of locking an output shaft of a motor when the motor is controlled to stop and thus the output shaft is stopped. 
     BACKGROUND ART 
     Conventionally, electric tools having a function of automatically locking an output shaft (spindle) when the motor is controlled to stop as described above are known (for example, see Patent Document 1 mentioned below). 
     The automatic lock mechanism of the electric tool described in Patent Document 1 is structured as follows. A projection formed on a circumference of an input shaft for inputting a rotation driving force and a projection formed on a circumference of an output shaft for outputting a rotation driving force are coupled with each other with a predetermined play angle. A pair of rollers are located between these projections within the play angle. One of the rollers is operable in correspondence with a rotation in a forward direction, and the other roller is operable in correspondence with a rotation in a reverse direction. On the side of the output shaft, a pair of wedge effect slopes are provided for providing a locking function with a wedge effect using one roller in the case of a rotation in the forward direction and the other roller in the case of a rotation in the reverse rotation. Thus, the lock mechanism is realized. 
     This electric tool operates as follows. The motor is controlled to stop, and the input shaft stops rotating. In this state, the operator pivots the output shaft by the play angle. Then, one of the pair of rollers bites into one of the wedge effect slopes corresponding to the rotation direction. Thus, the output shaft is locked by the wedge effect. 
     Such a lock mechanism using the rollers requires the rollers to rotate freely. Therefore, it is difficult to define the position at which each roller bites into the wedge effect slope. As a result, a problem may occur that the roller does not bite or bites insufficiently. 
     Instead of the rollers, a lock mechanism disclosed in Patent Document 2 is employable. 
     The lock mechanism described in Patent Document 2 operates as follows. A movable lock member (referred to as a “brake shoe” in Patent Document 2) movable in a radial direction is provided between an inner circumferential surface of a fixed ring which is fixed to a casing and an outer circumferential surface of a lock ring which is fixed to an output shaft. The movable lock member is pressed toward the fixed ring using a cam face formed on the outer circumferential surface of the lock ring. Thus, the output shaft is locked. 
     With a lock mechanism formed by such a movable lock member, when the relative rotation angle between the lock ring and the movable lock member is changed (when the relative rotation direction is changed), the movable lock member is pressed toward the fixed ring with certainty by the cam face. Therefore, the locking position is defined, which solves the above-mentioned problem of the lock mechanism using the rollers. 
     Patent document 1: Japanese Publication for Opposition No. 6-53350 
     Patent document 2: Japanese Laid-Open Patent Publication No. 2002-337062 
     DISCLOSURE OF INVENTION 
     Problems to be Solved by the Invention 
     However, the lock mechanism using the movable lock member described in Patent Document 2 has the following problem. 
     In order to lock the movable lock member, this lock mechanism requires the relative rotation direction between the lock ring and the movable lock member to be changed as described above. When such a change does not occur, no locking function is provided. 
     When the operator stops the rotation of the motor and rotates the output shaft in the same direction as the rotation driving direction, there is a play angle between the input shaft and the output shaft. The relative rotation direction between the lock ring fixed to the output shaft and the movable lock member is changed by an angle corresponding to the play angle. Thus, a locking function is provided. 
     By contrast, when the operator stops the rotation of the motor and rotates the output shaft in the opposite driving direction, there is no play angle between the input shaft and the output shaft. Therefore, when the operator pivots the output shaft, the input shaft and elements related thereto pivot and the movable lock member also pivots. Even if the output shaft is pivoted much, the relative rotation direction between the lock ring and the movable lock member is not changed, and the movable lock member rotates concomitantly with the input shaft and elements related thereto. 
     When the movable lock member concomitantly rotates, the locking function is not provided and the lock mechanism does not act as intended. In addition, because the locking function is not provided, the operator needs to pivot the output shaft having a load imposed by the stoppage of the motor for an extended period of time. This lowers the operability. 
     This problem also occurs when the output shaft is first pivoted in the same direction as the driving direction to provide a locking function and then is pivoted in the opposite direction. 
     The present invention has an object of providing a rotation output device, including a lock mechanism using a movable lock member for defining a locking position, which is capable of, when the operator operates an output shaft to pivot, providing a locking function with certainty by preventing the movable lock member from concomitantly rotating with the output shaft. 
     Means for Solving the Problems 
     A rotation output device according to the present invention comprises an output conveyance mechanism including a rotation driving member for outputting a rotation driving force and a rotation output member for outputting a rotation force in response to the driving of the rotation driving member, which are coaxially connected to each other so as to convey the rotation force, with a predetermined play angle to which the rotation force is not conveyed being formed in a relative rotation direction; and a lock mechanism including a movable lock member for locking a rotation conveyed from the rotation output member by being pressed toward a fixing member by the rotation output member, wherein the rotation output member and the fixing member located on an outer circumferential surface of the rotation output member and rotational-fixed are provided to face each other while being separated by a predetermined distance in a radial direction; a lock operation member operable to press the movable lock member toward the fixing member by the rotation conveyed from the rotation output member; and a release member capable of releasing the pressed state of the movable lock member by the rotation conveyed from the rotation driving member and thus capable of releasing the locked state. Retaining means is provided, between the movable lock member and the fixing member, for retaining the position of the movable lock member in the rotation direction when receiving the rotation from the rotation output member. 
     Namely, the retaining means, for retaining the position of the movable lock member in the rotation direction when receiving the rotation from the rotation output member, is provided between the movable lock member and the fixing member. Thus, the fixing member which is rotational-fixed is used as a member for preventing a concomitant rotation of the movable lock member. 
     According to the above-described structure, the fixing member which is rotational-fixed is used as a member for preventing a concomitant rotation of the movable lock member. Therefore, the position of the movable lock member in the rotation direction is constantly retained under the influence of the fixed state of the fixing member by the retaining means. Namely, the position of the movable lock member in the rotation direction is retained with certainty regardless of the pivoting direction of the output shaft. 
     In one embodiment of the present invention, the retaining means is formed of a contact member integrally rotatable with the movable lock member and partially contacting the fixing member. 
     Namely, the contact member integrally rotatable with the movable lock member is provided on the side of the movable lock member, among the movable lock member and the fixing member, and the contact member is used as the retaining means. 
     According to the above-described structure, the relative rotation direction between the contact member as the retaining means and the movable lock member is not changed in the state of being driven to rotate by the motor or the like. Rather, the relative rotation direction between the contact member and the fixing member is changed. By causing the relative rotation direction between the contact member and the fixing member to be changed, the undesirable possibility that the routine operations for locking or releasing the movable lock member are disturbed by the influence of such a change with respect to the contact member as the retaining means can be eliminated. 
     In one embodiment of the present invention, a plurality of the movable lock members are provided, and the plurality of movable lock members are integrally rotatable with one another by one contact member. 
     According to the above-described structure, the lock torque can be increased by providing a plurality of movable lock members. Since the plurality of movable lock members are integrally rotatable with one another by one contact member, the positions of the plurality of movable lock members in the rotation direction are retained in the state of being matched with one another. 
     In one embodiment of the present invention, sliding resistance increasing means for increasing a sliding resistance is provided at a position where the contact member contacts the fixing member. 
     According to the above-described structure, the contact member contacts the fixing member while having a high sliding resistance. Therefore, the contact member is easily influenced by the rotational-fixed state of the fixing member. As a result, the position of the contact member in the rotation direction is retained with higher certainty, and the contact member retains the position of the movable lock member in the rotation direction with higher certainty. 
     In one embodiment of the present invention, the sliding resistance increasing means is formed of an elastic member. 
     According to the above-described structure, the elastic member acts as sliding resistance means. Therefore, the contact member can be in constant contact with the fixing member. Namely, since the offset of the relative positions of the contact member and the fixing member in the axial direction is absorbed by the elastic member, the contact member can be in constant contact with the fixing member. 
     As a result, the contact member can constantly retain the position of the movable lock member in the rotation direction with higher certainty. 
     The rotation output device according to the present invention can be provided in an output system of an electric tool, and is also applicable to an apparatus requiring rotation output. 
     EFFECT OF THE INVENTION 
     According to the present invention, retaining means for retaining the position of the movable lock member in the rotation direction when receiving the rotation from the rotation output member is provided between the movable lock member and the fixing member. Thus, the fixing member which is rotational-fixed is used as a member for preventing a concomitant rotation of the movable lock member. Therefore, the position of the movable lock member in the rotation direction is retained with certainty regardless of the pivoting direction of the output shaft. 
     Accordingly, a rotation output device, including a lock mechanism employing a movable lock member, which is capable of, when the operator operates an output shaft to pivot, preventing the movable lock member from being concomitantly rotated with the output shaft and thus providing a locking function with certainty can be provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view of the entirety of an electric tool employing a rotation output device according to the present invention. 
         FIG. 2  is a cross-sectional view of the rotation output device. 
         FIG. 3  is an exploded view showing elements of a lock mechanism section of the rotation output device together with a side view thereof. 
         FIG. 4  is a front view of the lock mechanism section. 
         FIG. 5  is a rear view of the lock mechanism section. 
         FIG. 6  is a cross-sectional view of the lock mechanism section taken along line A-A in  FIG. 4 . 
         FIG. 7  is a front view of the lock mechanism section illustrating a locking function. 
         FIG. 8  is a rear view of the lock mechanism section illustrating the locking function. 
         FIG. 9  is a front view of the lock mechanism section illustrating the locking function. 
         FIG. 10  is a rear view of the lock mechanism section illustrating the locking function. 
         FIG. 11  is a rear view of the lock mechanism section without an input carrier. 
     
    
    
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
         
           
               31  . . . input carrier (rotation driving member) 
               31   d  . . . release guide hole (release member) 
               32  . . . center ring (rotation output member) 
               32   b  . . . lock guide cam face (lock operation member) 
               33  . . . lock ring (fixing member) 
               35  . . . lock gear (movable lock member) 
               37  . . . carry plate (retaining member) 
           
         
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     One embodiment of the present invention will be described in detail with reference to the drawings. 
       FIG. 1  shows an electric tool employing a rotation output device according to the present invention. As shown in  FIG. 1 , the electric tool includes a housing  1  having a handle  1   a  to be held by an operator when the operator uses the electric tool, a power source pack  2  provided below the housing  1 , a spindle  3  provided forward to the housing  1 , a chuck  4  attached to the spindle  3 , and a drill bit  5  supported by the chuck  4 . 
     The housing  1  accommodates a motor M selectably rotatable in a forward direction or a reverse direction and a rotation output device  10  (see  FIG. 2 ) describe below. A rotation driving force of the motor M is conveyed to the spindle  3  via the rotation output device  10 . 
     The housing  1  includes a switch handle  6  used for inputting a driving signal for the motor  2 , a clutch handle  7  for adjusting a tightening torque of the spindle  3 , and a gearshift switch  8  for shifting the rotation speed of the spindle  3 . 
     This embodiment is described with a hand-held electric tool. The present invention is not limited to such a hand-held electric tool and is applicable to a general electric tool with a cord. The present invention is not limited to being used in an electric tool and is also applicable to a driver, grinder, router or the like. The present invention is not limited to being used in an appliance driven by electricity, and is applicable to a hydraulic appliance or the like. 
     Next, with reference to  FIG. 2 , the rotation output device  10  provided in the electric tool will be described. The rotation output device  10  roughly includes a gearshift mechanism section  10 A for shifting the rotation speed of an output shaft M 1  of the motor M, a torque limiter mechanism section  10 B for adjusting the tightening torque of the spindle, and a lock mechanism section  10 C for automatically locking or automatically releasing the spindle. 
     The gearshift mechanism section  10 A includes a first planetary gear set  12  having a sun gear  11  fixed to the output shaft M 1  of the motor, and a second planetary gear set  13  provided parallel to the above-mentioned gear set. The gear shifting is performed in accordance with whether the second planetary gear set  13  decelerates or not. 
     The specific gearshift mechanism is well known and will not be described here. 
     The torque limiter mechanism section  10 B includes a sun gear  20   a  provided on a small-radius portion of an output carrier member  20  of the gearshift mechanism section  10 A, a planetary gear  22  engageable with the sun gear  20   a  for outputting a rotation driving force to a spindle-side carrier member  21 , an internal gear  23  engageable with the planetary gear  22  and pivotable, and a clutch mechanism  24  for providing a pressing force to the internal gear  23  and rotational-fixing the internal gear  23  when the rotation driving torque is equal to or less than a predetermined level. The torque limiter mechanism section  10 B limits the conveyance of a tightening torque equal to or greater than a set value of torque in order to protect the tightening nut and the like. 
     The structure of the torque limiter mechanism section  10 B is also well known and will not be specifically described here. 
     The lock mechanism section  10 C mainly includes an input carrier  31  for receiving the rotation driving force from the spindle-side carrier member  21  of the torque limiter mechanism section  10 B, a center ring  32  fixedly engageable with the spindle  3  for outputting a rotation driving force to the spindle  3 , and a lock ring  33  located at an outer periphery of the lock mechanism section  10 C for fixing the lock mechanism section  10 C to a clutch casing  25 . The lock mechanism section  10 C automatically locks the spindle  3  in response to the rotation conveyed from the spindle  3 , and automatically releases the spindle  3  in response to the rotation conveyed from the motor M. 
     A structure of the lock mechanism section  10 C will be described in detail with reference to  FIG. 3  through  FIG. 6 .  FIG. 3  is an exploded view showing elements of the lock mechanism section together with a side view thereof.  FIG. 4  is a front view of the lock mechanism section.  FIG. 5  is a rear view of the lock mechanism section.  FIG. 6  is a cross-sectional view of the lock mechanism section taken along line A-A in  FIG. 4 . 
     As shown in  FIG. 3 , the lock mechanism section  10 C includes, from the side of the spindle  3 , a click spring  34 , the center ring  32 , four lock gears  35 , the lock ring  33 , an O-ring  36 , a carry plate  37 , and an input carrier  31 . The elements, except for the center ring  32  and the four lock gears  34 , are ring-shaped and coaxially located. 
     The input carrier  31  includes projections  31   a  at positions facing each other on a rear surface thereof while interposing the axis of the spindle  3 . The projections  31   a  are engaged with coupling holes  21   a  (see  FIG. 2 ) which are formed at corresponding positions of the spindle-side carrier member  21  mentioned above. Thus, the projections  31   a  receive a rotation driving force from the spindle-side carrier member  21  and is rotated in synchronization with the spindle-side carrier member  21 . 
     The input carrier  31  has a hole-shaped coupling section  31   b  at the center thereof, which is loosely engageable with a shaft-shaped coupling portion  3   a  of the spindle with a play angle α (see  FIG. 5 ). The input carrier  31  also has arms  31   c  extending in the axial direction at both of two side positions thereof. The click spring  34  is caulked to be fixed by tips of the arms  31   c . On both sides of each projection  31   a , release guides holes  31   d  are formed for releasing the lock gears  35 . 
     The center ring  32  has a hole-shaped coupling portion  32   a  at the center thereof, which is fixedly engageable with the shaft-shaped coupling portion  3   a  of the spindle with no play. The center ring  32  also has lock guide cam faces  32   b  at four positions on an outer circumferential surface thereof (at an interval of 60 degrees and 120 degrees). The lock guide cam faces  32   b  are respectively in contact with inner surfaces of the four lock gears  35 . When the relative rotation direction between the center ring  32  and the lock gears  35  is changed, the lock guide cam faces  32   b  press the lock gears  35  toward the lock ring  33 . The center ring  32  has receiving sections  32   c  (see  FIG. 3 ) for receiving a steel ball  39  engageable with the click spring  34 . 
     The lock gears  35  each have a sloping cam face  35   a  on an inner side thereof, which is slightly projected at the center so as to correspond to the lock guide cam face  32   b . Each lock gear  35  has an outer circumferential gear  35   b  on an outer side thereof, which is engaged with the inner circumferential surface of the lock ring  33  when being pressed by the lock ring  33 . Each lock gear  35  has a projecting pin  35   c  extending in the axial direction on a side wall thereof. The projecting pin  35   c  is loosely engageable with the release guides hole  31   d  of the input carrier and a fixing guide hole  37   c  of the carry plate described later. 
     Four lock gears  35  are provided in correspondence with the four lock guide cam faces  32   b  of the center ring. The sloping cam face  35   a  on the inner side thereof is sloping both rightward and leftward. Therefore, whether the relative rotation direction between the lock gears  35  and the center ring  32  is changed in a forward direction or n a reverse direction, the lock gears  35  are pressed toward the lock ring  33  and the rotation of the spindle  3  is locked by all the four lock gears  35 . 
     The lock ring  33  is located at the outer periphery of the lock mechanism section  10 C. The lock ring  33  has an inner circumferential gear  33   a  which is engaged with the outer circumferential gears  35   a  of the lock gears  35  when the lock gears  35  are pressed. The lock ring has three engageable pins  33   b , on a side wall thereof, which extend in the axial direction to be fixedly engaged with a clutch housing  25  (see  FIG. 2 ). By being fixedly engaged with the engageable pins  33   b , the lock ring  33  acts as a rotational-fixed member. The lock ring  33  has a guide groove  33   e  on the other side wall thereof for guiding the O-ring  36  to a contact position. 
     The carry plate  37  has an engageable hole  37   a  at the center thereof, which is loosely engageable with the shaft-shaped coupling portion  3   a  of the spindle. On both sides of the engageable hole  37   a , the carry plate  37  has insertion holes  37   b  through which the arms  31   c  are insertable. The carry plate  37  has the four fixing guide holes  37   c  at an interval of 60 degrees and 120 degrees. The fixing guide holes  37   c  are respectively loosely engageable with the projecting pins  35   c  of the four lock gears  35  in the radial direction. Between each two fixing guide holes  37   c  located at an interval of 60 degrees, a bearing portion  37   d  is formed for positioning a steel ball  38  which is provided between two lock gears  35  for supporting the side surfaces thereof. 
     The carry plate  37  has an engageable groove  37   e , along an outer periphery on the side of the lock ring, for supporting the O-ring  36  through engagement therewith. 
     The O-ring  36  is engaged with, and supported by, the engageable groove  37   e  and thus contacts the side wall of the lock ring  33 . Therefore, the O-ring  36  is inconstant contact with the side wall of the lock ring  33 , more specifically, with the guide groove  33   e.    
     The O-ring  36  is formed of an elastic rubber material and contacts the side wall of the lock ring  33  with a sliding resistance. The O-ring  36  is formed of a rubber material, and therefore constantly exerts an influence of the rotational-fixed state of the lock ring  33  on the carry plate  37  even at the time of rotation driving. 
     The click spring  34  acts to prevent an impact noise from being generated by the rotation of the spindle and elements related thereto caused by inertia while the motor M is at a stop, and thus to reduce the impact load imposed on the rotation output device  10 . The click spring  34  has an engageable hole  34   a  at the center thereof, which is loosely engageable with the shaft-shaped coupling portion  3   a  of the spindle. The click spring  34  also has an elastically deformable portion  34   b  projecting in a brim shape at two positions along an outer periphery facing each other while interposing the axis of the spindle  3 . The two elastically deformable portions  34   b  each have two steel ball stopping holes  34   c , which are separated from each other by a distance approximately corresponding to the play angle α. Owing to this structure, the stainless ball  39  provided on the center ring  32  is stopped by one of the steel ball stopping holes  34   c  (see the click spring  34  represented with the dashed line in  FIG. 4 ). The click spring  34  also has fixing holes  34   d  along the outer periphery thereof for caulking and fixing the tips of the arms  31   c  extending from the input carrier  31 . The arms  31   c  are caulked and thus fixed by the fixing holes  34   d , and thus the click spring  34  is rotated integrally with the input carrier  31 . 
     Owing to such a structure of the click spring  34 , the rotation of the center ring  32  which is integral with the spindle  3  and elements related thereto is limited by an urging force of the elastically deformable portions  34   b  of the click spring  34  rotating integrally with the input carrier  31 . 
     Accordingly, when the spindle  3  and elements related thereto are rotated with an inertial force smaller than the urging force of the elastically deformable portions  34   b , the spindle  3  and elements related thereto do not freely rotate and thus no impact noise is generated. When the spindle  3  and elements related thereto are rotated with an inertial force greater than the urging force of the elastically deformable portions  34   b , the elastically deformable portions  34   b  are deformed and the spindle  3  and elements related thereto are rotated by the play angle α. However, while the steel ball  39  provided on the center ring  32  moves between the two steel ball stopping holes  34   c , the elastically deformable portions  34   b  give the steel ball  39  a sliding resistance. Therefore, the rotation force of the spindle  3  and elements related thereto is reduced and the generation of the impact noise is alleviated. 
     The elastically deformable portions of the click spring  34  are deformed in the axial direction to reduce the rotation force. Therefore, the space required due to the deformation can be smaller than in the case where the deformation occurs in the radial direction. This makes the click spring compact. 
     The click spring also acts as a member for fixing the assembly of the entire lock mechanism section  10 C, which can reduce the number of elements. 
     The locking function of the lock mechanism section  10 C having such a structure will be described with reference to  FIG. 7  through  FIG. 10  illustrating the function.  FIG. 7  and  FIG. 8  are respectively a front view and a rear view of the lock mechanism section  10 C when the spindle  3  is rotated in a direction with the play angle, i.e., in a forward rotation direction.  FIG. 9  and  FIG. 10  are respectively a front view and a rear view of the lock mechanism section  10 C when the spindle  3  is rotated in a direction with no play angle, i.e., in a reverse rotation direction. 
     As shown in  FIG. 7 , the center ring  32  is fixedly engaged with the shaft-shaped coupling portion  3   a  of the spindle and thus is rotated integrally with the spindle  3 . The four lock gears  35  respectively put the sloping cam faces  35   a  into contact with the lock guide cam faces  32   b  of the center ring  32 . The lock ring  33  located at the outermost position is fixed to the clutch casing (not shown in  FIG. 7 ) and therefore is constantly fixed. 
     The state represented with the solid line in  FIG. 7  is a normal state, i.e., a state where the locking function is not provided. In this state, the center ring  32  and the four lock gears  35  are freely rotatable concomitantly with the spindle  3  by the rotation driving force of the motor M. 
     Next, a locked state will be described. 
     First, the locking function when the relevant elements are rotated in the forward direction will be described. After the motor is stopped, the operator rotates the spindle  3  in the direction of the arrow (the forward rotation direction). Then, as represented with the one-dot chain line, the center ring  32  is pivoted by the play angle α. When the center ring  32  is pivoted in this manner, the four lock gears  35  are pressed toward the lock ring  33  by the lock guide cam faces  32   b  (represented with the arrow). When the lock gears  35  are pressed in this manner, the outer circumferential gears  35   b  of the lock gears  35  are engaged with the inner circumferential gear  33   a  of the lock ring, and thus the motion of the lock gears  35  in the rotation direction is locked. By the lock gears  35  being locked, the center ring  32  is also locked. 
     As also shown in  FIG. 8 , the input carrier  31  is not rotated in the locked state. Therefore, the projecting pins  35   c  extending from the lock gears  35  are moved to a locked position L 2  from a normal position L 1 . 
     In other words, when the spindle  3  is rotated in the forward direction, the center ring  32  is pivoted and the four lock gears  35  and the carry plate  37  supporting the four lock gears  35  are also pivoted by the influence of the center ring  32 . The other elements, i.e., the input carrier  31  and the click spring  34  are fixed at this point. Therefore, the relative rotation direction between the center ring  32  and the lock gears  35  is changed. Thus, the lock mechanism section  10 C acts as intended. 
     By the center ring  32  being locked, the spindle  3  is locked. As a result, the attachment/detachment operation of the chuck  4  and the manual operation of the electric tool can be easily performed. 
     Next, the locking function when the relevant elements are rotated in the reverse direction will be described. As shown in  FIG. 9  and  FIG. 10 , after the motor is stopped, the operator rotates the spindle  3  in the direction of the arrow (the reverse rotation direction). Then, the center ring  32  is also pivoted in the reverse rotation direction. Since there is no play angle α in the reverse rotation direction, the input carrier  31  and the click spring  34  are also rotated, unlike the case of the forward rotation direction. 
     Without the carry plate  37 , the lock gears  35  would concomitantly rotate with the other elements and the locking function would not be provided. 
     However, in this embodiment, the carry plate  37  is influenced by the fixed state of the lock ring  33  and retains the positions of the lock gears  35  in the rotation direction. Therefore, the lock gears  35  are not concomitantly rotated with the other elements and retain the positions thereof in the rotation direction. As a result, the relative rotation direction of the lock gears  35  is changed with respect to the center ring  32 . 
     Owing to such a change in the relative rotation direction, as shown in  FIG. 9 , the lock gears  35  are pressed toward the lock ring  33  by the lock guide cam faces  32   b , and the outer circumferential gears  35   b  of the lock gears are engaged with the inner circumferential gear  33   a  of the lock ring. Thus, the motion of the lock gears  35  in the rotation direction is locked. 
     By the lock gears  35  being locked in this manner, the center ring  32  is also locked. Thus, the lock mechanism section  10 C acts as intended. 
     In other words, since the carry plate  37  retains the positions of the lock gears  35  in the rotation direction, the lock gears  35  can be locked even in response to the rotation in the reverse direction with no play angle. 
     For releasing these elements from the locked state, a rotation driving force from the motor M is input to the lock mechanism section  10 C. In the locked state, when the rotation driving force from the motor M is input to the input carrier  31  as described above, only the input carrier  31  is rotated among the elements of the lock mechanism section  10 C. Then, as shown in  FIG. 8 , the projecting pins  35   c  of the lock gears  35  are guided from the locked position L 2  to the normal release position L 1  by the release guides holes  31   d  formed in the input carrier  31 . By the projecting pins  35   c  of the lock gears  35  being guided to the release position, the lock gears  35  and the lock ring  33  are disengaged from each other, and the relevant elements are released from the locked state. 
     Since the release from the locked state is automatically conducted by the rotation driving force of the motor M, the usual output of the rotation driving force from the motor M is resumed easily. Thus, the normal operation using the electric tool can be performed. 
     Next, the carry plate will be described in detail with reference to  FIG. 6  and  FIG. 11 .  FIG. 11  is a rear view of the lock mechanism section  10 C without the input carrier  31 . 
     The carry plate  37  has the four fixing guide holes  37   c  respectively loosely engageable with the projecting pins  35   c  of the four lock gears  35  as described above. Owing to this, the carry plate  37  is integrally rotatable with the lock gears  35 . The carry plate  37  has the engageable groove  37   e  for supporting the O-ring  36  along the outer periphery through engagement therewith, so that the outer periphery is in contact with the lock ring  33  via the O-ring  36 . The carry plate  37  is also structured to give the lock ring  33  a slight urging force such that the carry plate  37  contacts the lock ring  33  with a certain degree of pressure. 
     Owing to such a structure, the lock gears  35  are always influenced by the rotational fixation of the lock ring  33  via the carry plate  37 . Especially because one carry plate  37  defines the positions of the four lock gears  35 , the rotational fixation can influence all the four lock gears  35 . In addition, the one carry plate  37  can maintain the rotational phase of the four lock gears  35 . 
     The provision of the carry plate  37  allows the lock gears  35  to be influenced by the rotational fixation of the lock ring  33  as described above. Therefore, even when the operator pivots the spindle  3  in the reverse rotation direction with no play angle after the motor M is stopped, the relative rotation direction between the lock gears  35  and the center ring  32  is changed with certainty. 
     In this embodiment, the O-ring  36  is provided on the carry plate  37  to increase the sliding resistance and thus to put the O-ring  36  in contact with the lock ring. In another embodiment, an outer edge of the carry plate  37  can be put into direct contact with the lock ring. 
     In this embodiment, the O-ring is constantly in contact with the lock ring. Alternatively, the O-ring is designed to be separated from the lock ring when the rotation speed of the spindle becomes sufficiently high, so that the O-ring  36  is protected against deterioration. 
     Next, the function and effect of the rotation output device  10  including the lock mechanism section  10 C having such a structure will be described. 
     The rotation output device in this embodiment has the following structure. The rotation output device includes an output conveyance mechanism including an input carrier  31  for outputting a rotation driving force of the motor and the center ring  32  for outputting a rotation driving force in response to the driving of the input carrier  31 , which are coaxially connected to each other so as to convey the rotation driving force, with a predetermined play angle α to which the rotation force is not conveyed being formed in a relative rotation direction. The rotation output device also includes a lock mechanism section  10 C including a lock gear  35  for locking a rotation conveyed from the center ring  32  by being pressed toward a lock ring  33  by the center ring  32 , wherein the center ring  32  and the lock ring  33  located on an outer circumferential surface of the center ring  32  and rotational-fixed are provided to face each other while being separated by a predetermined distance in a radial direction; a lock guide cam face  32   b  operable to press the lock gear  35  toward the lock ring  33  by the rotation conveyed from the center ring  32 ; and a release guide hole  31   d  capable of releasing the pressed state of the lock gear  35  by the rotation conveyed from the input carrier  31  and thus capable of releasing the locked state. A carry plate  37  is provided, between the lock gear  35  and the lock ring  33 , for retaining the position of the lock gear  35  in the rotation direction when receiving the rotation from the center ring  32 . 
     Namely, the carry plate  37 , for retaining the position of the lock gear  35  in the rotation direction when receiving the rotation from the center ring  32 , is provided between the lock gear  35  and the lock ring  33 . Thus, the lock ring  33  which is rotational-fixed is used as a member for preventing a concomitant rotation of the lock gear  35 . 
     According to the above-described structure, the lock ring  33  which is rotational-fixed is used as a member for preventing a concomitant rotation of the lock gear  35 . Therefore, the position of the lock gear  35  in the rotation direction is constantly retained under the influence of the fixed state of the lock ring  33  by the carry plate  37 . Namely, the position of the lock gear  35  in the rotation direction is retained with certainty regardless of the pivoting direction of the spindle. 
     Since the position of the lock gear  35  in the rotation direction is constantly retained by the carry plate  37 , the lock gear  35  is prevented from being concomitantly rotated with the spindle  3  even when the operator pivots the spindle  3 . Thus, the rotation output device for realizing a locking function with certainty can be provided. 
     In this embodiment, the carry plate  37  is formed of a contact member rotatable integrally with the lock gear  35  and having an outer periphery contacting the lock ring  33 . 
     Namely, the carry plate  37  integrally rotatable with the lock gear  35  is provided on the side of the lock gear  35 , among the lock gear  35  and the lock ring  33 . 
     According to the above-described structure, the relative rotation direction between the carry plate  37  and the lock gear  35  is not changed at the time of rotation driving. Rather, the relative rotation direction between the carry plate  37  and the lock ring  33  is changed. By causing the relative rotation direction between the carry plate  37  and the lock ring  33  to be changed, the undesirable possibility that the routine operations for locking or releasing the lock gear  35  are disturbed by the influence of such a change with respect to the carry plate  37  can be eliminated. 
     In this embodiment, a plurality of lock gears  35  are provided, and the plurality of lock gears  35  are integrally rotatable with one another by one carry plate  37 . Namely, the plurality of lock gears  35  are structured to be integrally rotatable with one another by one carry plate  37 . 
     According to the above-described structure, the lock torque can be increased by providing a plurality of lock gears  35 . Since the plurality of lock gears  35  are integrally rotatable with one another by one carry plate  37 , the positions of the plurality of lock gears  35  in the rotation direction are retained in the state of being matched with one another. 
     In this embodiment, the O-ring  36  for increasing a sliding resistance is provided at a position where the carry plat  37  contacts the lock ring  33 . 
     According to the above-described structure, the carry plate  37  contacts the lock ring  33  while having a high sliding resistance. Therefore, the carry plate  37  is easily influenced by the rotational-fixed state of the lock ring  33 . As a result, the position of the carry plate  37  in the rotation direction is retained with higher certainty, and the carry plate  37  retains the position of the lock gear  35  in the rotation direction with higher certainty. 
     In this embodiment, the O-ring  36  is formed of an elastic member. 
     According to the above-described structure, the O-ring is formed of an elastic rubber member. Therefore, the carry plate  37  can be in constant contact with the lock ring  33 . Namely, since the offset of the relative positions of the carry plate  37  and the lock ring  33  in the axial direction is absorbed by the elasticity of rubber, the carry plate  37  can be in constant contact with the lock ring  33 . 
     As a result, the carry plate  37  can retain the position of the lock gear  35  in the rotation direction with higher certainty. 
     In this embodiment, the rotation output device  10  is included in an output system of an electric tool. The rotation output device  10  in this embodiment is also applicable to other apparatuses requiring a rotation output. 
     In another embodiment, a member extending from the lock ring  33  to the side surfaces of the lock gears  35  may be provided so as to exert an influence of rotational fixation on the lock gears  35 , as long as the member is capable of retaining the positions of the lock gears  35  in the rotation direction while the motor is at a stop. 
     The elements of the present invention and the elements in the above-described embodiment correspond as follows. 
     The rotation driving member of the present invention corresponds to the input carrier  31  in the embodiment; 
     the rotation output member corresponds to the center ring  32 ; 
     the fixing member corresponds to the lock ring  33 ; 
     the movable lock member corresponds to the lock gear  35 ; 
     the lock operation member corresponds to the lock guide cam face  32   b;    
     the release member corresponds to the release guide hole  31   d ; and 
     the retaining means corresponds to the carry plate  37 . 
     However, the present invention is not limited to the above-described embodiment.