Abstract:
A wrapping connector driving device for transmitting a rotational motion from a driving shaft to a driven shaft comprises a driving wheel operatively connected to the driving shaft, a driven wheel operatively connected to the driven shaft, a wrapping connector wound around the driving wheel and the driven wheel in a stretched state therebetween, and a bracket which is mounted to an electric motor provided with the driving shaft and a drive device provided with the driven shaft.  
     The driving wheel is supported to be rotatable to the bracket. The wrapping connector driving device may further comprises a projection member provided for the bracket so as to project inside the driving wheel and a bearing disposed between the driving wheel and the projection member and adopted to support the driving wheel during rotating motion. The bearing is arranged on substantially a central line in a width direction of the wrapping connector. This wrapping connector driving device is effectively mounted to a drive unit such as linear motion guide.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a wrapping connector driving device and a drive unit provided with this wrapping connector driving device.  
           [0002]    Usually, when a rotation (rotational motion) of a driving shaft is transmitted to a driven shaft, there has been used a wrapping connector driving device having a structure that wheels are mounted to both the shafts and a wrapping connector such as belt or rope having a flexible structure, capable of being bent, is stretched around (wound round) both the driving and driven wheels to thereby transmit the rotation of the driving shaft to the driven shaft. As the wrapping connector, there has also been known, for example, V-belt, timing belt, chain or the like.  
           [0003]    In a case where a belt, V-belt or rope is utilized as such wrapping connector, the rotation of the driving shaft is transmitted to the driven shaft through frictional force between the driving wheel and the belt, and in such structure, as the belt is pressed around the outer periphery of the wheel, it is required for the belt to have an initial tension to some extent.  
           [0004]    Further, in a case where a timing belt or chain is utilized as such wrapping connector, the rotation of the driving shaft is transmitted to the driven shaft through engagement of teeth of a timing pulley with teeth of the timing belt in place of the transmission through the frictional force. In this structure, the rotation can be surely transmitted with no slipping, and since the frictional force is not utilized, it is not required for the timing belt to have the initial tension. However, in such structure, in a case where a rotational angle of the driven shaft is controlled, in order to more surely transmit the rotation of the driving shaft to the driven shaft, it is still required for the timing belt to have a tension to some extent.  
           [0005]    As mentioned above, in the conventional wrapping connector driving device, it is basically required for the wrapping connector to have a tension. With this viewpoint, in a prior art, in order to provide the tension to the wrapping connector, a distance between the driving wheel and the driven wheel is made large by moving the driving wheel together with a motor (prime mover). However, the movement of the driving wheel together with the motor involves a difficult working for adjusting the tension, which results in application of excessive tension or less tension.  
           [0006]    Furthermore, since a driving (output) shaft of the motor is connected to the driving wheel, a lateral load will be applied to the driving shaft of the motor by the tension of the wrapping connector. Such lateral load will disturb the rotation of the driving shaft, which may cause shaft failures of the motor.  
         SUMMARY OF THE INVENTION  
         [0007]    An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide a wrapping connector driving device capable of not giving a lateral load to the driving shaft of a motor (prime mover) by a tension of the wrapping connector and suitably adjusting the tension of the wrapping connector and also provide a drive unit provided with such wrapping connector driving device.  
           [0008]    This and other objects can be achieved according to the present invention by providing, in one aspect, a wrapping connector driving device for transmitting a rotational motion from a driving shaft to a driven shaft, comprising:  
           [0009]    a driving wheel operatively connected to the driving shaft;  
           [0010]    a driven wheel operatively connected to the driven shaft;  
           [0011]    a wrapping connector wound around the driving wheel and the driven wheel in a stretched state therebetween; and  
           [0012]    a bracket which is to be mounted to a motor provided with the driving shaft and to a drive device provided with the driven shaft,  
           [0013]    wherein the driving wheel is supported to be rotatable by the bracket.  
           [0014]    According to this aspect, since the driving wheel is supported by the bracket, the load due to the tension of the wrapping connector is received by the bracket, and hence, no load due to the tension is applied to the driving shaft. Accordingly, no lateral load is applied to the driving shaft of the motor, and thus, the motor can be effectively and smoothly operated.  
           [0015]    Moreover, since the driving wheel is supported by the bracket, the tension adjustment can be done before the connection of the driving shaft to the driving wheel. Accordingly, a user can freely mount any type of motor after the tension has been adjusted at the manufacturing firm or the like. Furthermore, since the tension of the wrapping connector is received by the bearing, any lateral load due to the tension is not applied to the driving shaft of the motor. Therefore, a user can use any type of electric motor and mount it easily.  
           [0016]    In preferred embodiments of the above aspect, the bracket has a structure movable relative to drive device to thereby adjust a tension of the wrapping connector. That is, for example, the bracket may be formed with a slot to which the drive device is mounted to be movable.  
           [0017]    The wrapping connector driving device may further comprises a projection member provided for the bracket so as to project inside the driving wheel and a bearing disposed between the driving wheel and the projection member and adopted to support the driving wheel during rotating motion, and the bearing is arranged on substantially a central line in a width direction of the wrapping connector.  
           [0018]    According to the present invention, since the bearing is arranged on substantially a central line in a width direction of the wrapping connector, the load due to the tension of the wrapping connector can be surely received by the bearing.  
           [0019]    Furthermore, the projection member is a cylindrical member, the driving wheel is provided with an outer ring contacting the wrapping connector and an input shaft disposed inside the outer ring of the driving wheel so that central axes thereof are coincident with each other, the outer ring is disposed outside the cylindrical projection member, the input shaft is disposed inside the cylindrical projection member, and the bearing is arranged between an outer periphery of the input shaft and an inner periphery of the projection member.  
           [0020]    According to the present invention, since the bearing and the projection member holding the bearing are stored inside the driving wheel, the space for arranging the bearing and the projection member is reduced.  
           [0021]    The bearing may be a radial bearing.  
           [0022]    Accordingly, since the tension of the wrapping connector is received by the bearing, any lateral load due to the tension is not applied to the driving shaft of the electric motor.  
           [0023]    The driving wheel is connected to the driving shaft of the motor through a flexible coupling. The wrapping connector is a timing belt and the driven wheel is a timing pulley.  
           [0024]    According to this structure, the flexible coupling can absorb eccentricity or deviation, to some extent, between driving and driven axes, so that the lateral load to be applied to the driving shaft can be further reduced, and a user can easily mount the electric motor.  
           [0025]    In another aspect of the present invention, there is provided a drive unit including a motor provided with a driving shaft, a drive device provided with a driven shaft and a wrapping connector driving device for transmitting a rotational motion from the driving shaft to the driven shaft, the wrapping connector driving device comprising:  
           [0026]    a driving wheel operatively connected to the driving shaft;  
           [0027]    a driven wheel operatively connected to the driven shaft;  
           [0028]    a wrapping connector wound around the driving wheel and the driven wheel in a stretched state therebetween; and  
           [0029]    a bracket which is to be mounted to the motor and the drive device;  
           [0030]    wherein the driving wheel is supported to be rotatable by the bracket.  
           [0031]    In a preferred embodiment, the wrapping connector driving device further comprises a projection member provided for the bracket so as to project inside the driving wheel and a bearing disposed between the driving wheel and the projection member and adopted to support the driving wheel during rotating motion, and the bearing is arranged on substantially a central line in a width direction of the wrapping connector.  
           [0032]    The drive device comprises a track rail having a linear structure, a slide member mounted to the track rail to be linearly movable and a nut member provided for the slide member and screw-engaged with the driven shaft, the nut member and the driven shaft constituting a feed screw mechanism in combination.  
           [0033]    According to the drive unit of the structure mentioned above, in addition to the effective merits mentioned above in connection with the wrapping connector driving device, the slide member can be positioned in accordance with a rotational angle of the driven shaft by the location of the feed screw to the drive device.  
           [0034]    The nature and further characteristic features of the present invention will be made more clear from the following descriptions made with reference to the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0035]    In the accompanying drawings:  
         [0036]    [0036]FIG. 1 is a plan view, partially in section, of a driving unit according to one embodiment of the present invention;  
         [0037]    [0037]FIG. 2 shows a bracket of the driving unit and includes  
         [0038]    [0038]FIG. 2A being a front view of the bracket,  
         [0039]    [0039]FIG. 2B being a plan view thereof and  
         [0040]    [0040]FIG. 2C being a sectional view taken along the line II-II in FIG. 2A;  
         [0041]    [0041]FIG. 3 is a sectional view of a driving wheel;  
         [0042]    [0042]FIG. 4 is a plan view of the driving wheel; and  
         [0043]    [0043]FIG. 5 is a perspective view of a drive device. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0044]    A preferred embodiment of the present invention will be described hereunder with reference to the accompanying drawings.  
         [0045]    With reference to FIG. 1, showing a drive unit provided with a wrapping connector driving device according to one embodiment of the present invention, a drive unit comprises an electric motor  2  as a prime mover having a driving (output) shaft  1 , a drive device  4  provided with a driven shaft  3  and a wrapping connector driving device  5  which transmits a rotation (rotational motion) of the driving shaft  1  to the driven shaft  3 .  
         [0046]    The wrapping connector driving device  5  comprises a driving wheel  6  mounted to the driving shaft  1 , a driven wheel  7  mounted to the driven shaft  3  and a wrapping connector  8  wound round (stretched around) both the driving and driven wheels  6  and  7 . In the illustrated embodiment, a timing belt is utilized as such wrapping connector  8 , and timing pulleys are utilized as driving and driven wheels  6  and  7 . The driving wheel  6  has a structure capable of being coupled to the driving shaft  1  through a flexible coupling  9 , and the driven wheel  7  also has a structure capable of being coupled to the driven shaft  3  through a joint  10 .  
         [0047]    A bracket  11  is secured to the electric motor  2  and the driving device  4  by fastening means such as bolts, and the bracket  11  is shown in FIG. 2.  
         [0048]    With reference to FIG. 2 (FIGS. 2A, 2B and  2 C), the bracket  11  is formed from a base plate  12  having a rectangular shape to which through holes  13  and  14  are formed for insertion of the driving and driven shafts  1  and  2 . The base plate  12  is provided with reinforcing members  15 , - - - , 15  for reinforcing the base plate  12  itself at its peripheral and central portions. Furthermore, a cylindrical projection (projecting member)  16  projecting inside the driving wheel  6  is formed to the peripheral portion of the through hole  13  for the driving shaft  1 , and a stepped portion  17  and a ring fitting groove  18  are formed to the inner peripheral portion of the projection  16  so that an outer ring of a bearing is fitted thereto as described hereinlater.  
         [0049]    As shown in FIG. 2A, holes  19 , - - - ,  19  for mounting and fixing the electric motor  2  to the bracket  11  are formed to the peripheral portions of the through hole  13  formed to the base plate  1 . And holes  20 , - - - ,  20  for mounting and fixing the driving device  4  to the bracket  11  also formed to the base plate  1 . Further, the mounting holes  20 , - - - ,  20  are formed as long holes (slots) so that the driving device  4  is relatively movable with respect to the bracket  11 .  
         [0050]    [0050]FIG. 3 shows the driving wheel  6 , which comprises an outer ring  6   a  contacting the wrapping connector  8  and an input shaft  6   b  which is disposed inside the outer ring  6   a  and to which the flexible coupling  9  is connected. The outer ring  6   a  and the input shaft  6   b  have a common central line (axis). The outer ring  6   a  is formed, at its outer peripheral surface, with teeth meshed with the timing belt. The input shaft  6   b  is formed with a stepped portion  22  and a ring groove  23  for the mounting of an inner ring of a bearing which will be described hereinlater.  
         [0051]    [0051]FIG. 4 shows the driven wheel  7  having an approximately cylindrical appearance and formed, at its outer peripheral surface, with teeth meshed with the timing belt. An insertion hole  24 , where the joint  10  for coupling the driven wheel  7  to the driven shaft  3  is inserted, is formed to the inner peripheral surface of the driven wheel  7 .  
         [0052]    With reference to FIG. 1, a bearing  25  composed of a radial bearing is disposed between the driving wheel  6  and the projection of the bracket  11  so as to serve as a member for supporting the input shaft  6   b  of the driving wheel  6  carrying out rotational motion. The bearing  25  has an axial central line C 1  coincident with a central line C 2  of the wrapping connector  8  in the width direction thereof. According to such arrangement, a force F due to the tension of the wrapping connector  8  is applied as a load to the bearing  25 . Further, in this arrangement, the outer ring  6   a  of the driving wheel  6  is positioned outside the projection  16  and the input shaft  6   b  thereof is positioned inside the projection  16 . The bearing  25  is arranged between the outer periphery of the input shaft  6   b  of the driving wheel  6  and the inner periphery of the projection  16  in a manner such that the bearing  25  is clamped between an inner retainer ring  26  mounted to the input shaft  6   b  and an outer retainer ring  27  mounted to the projection  16 .  
         [0053]    The electric motor  2  is mounted to the bracket  11  through a motor adapter  28  and a motor adapter flange  29 . The driving shaft  1  of the electric motor  2  and the input shaft  6   b  of the driving wheel  6  are aligned on the same straight line and coupled together through the flexible coupling  9  disposed inside the motor adapter  28 .  
         [0054]    The driving device  4  is also attached to the bracket  11  so that the central line (axis) of the driven shaft  3  of the driving device  4  and that of the driven wheel  7  are aligned on the same line and the driven shaft  3  and the driven wheel  7  are operatively connected through the joint  10 .  
         [0055]    [0055]FIG. 5 shows the driving device  4 , which comprises a track rail  31  secured to the bracket  11 , a slide member  32  guided along the track rail  1  to be linearly freely movable and a nut member  33  provided for the slide member  32  and screwed with the driven shaft  3 . The driven shaft  3  has an outer peripheral surface on which a screw groove is formed, which constitutes a feed screw mechanism in combination of the nut member  33 .  
         [0056]    The track rail  31  has a box-shaped section having an upper opening (recessed side)  31   a  such as shown in FIG. 5. That is, the upper opening  31   a  of the track rail  31  is defined by a pair of ridges  34 ,  34  extending in parallel to each other at both longitudinal ends of the opening  31   a . Recessed grooves  35 ,  35  are formed to both the inner side surfaces of the ridges  34 ,  34 , respectively. Furthermore, two rows of ball rolling grooves  36 ,  36  are formed to upper and lower corner portions of each of the recessed grooves  35 ,  35 . Both the longitudinal end portions of the track rail  31  are closed by end plates or end covers  37 ,  37 , one of which is secured to the bracket  11 .  
         [0057]    The slide member  32  comprises a block body  32   a  and end plates  32   b  attached to both longitudinal end portions of the block body  32   a . The slide member  32  is inserted into the upper opening  31   a  of the track rail  31  and supported between both the ridges  34 ,  34  so as to be clamped therebetween through balls  38 , —,  38  as rolling members.  
         [0058]    Loaded rolling grooves are formed to both side surfaces of the block body  32   a  so as to oppose to the ball rolling grooves  36  of the track rail  11 , respectively, and a number of balls  38  are accommodated between the opposed ball rolling grooves  36  and loaded rolling grooves to be rollable therebetween. Furthermore, the block body  32   a  is formed with ball escape holes  39 ,  39  for returning the balls  38  rolling in the loaded area so as to extend in parallel to the loaded rolling grooves. The end plates  32   b ,  32   b  disposed both end portions of the block body  32   a  are formed with ball return passages, respectively, so as to scoop up and then return the balls in the loaded area to thereby circulate the balls  8  again in the loaded area.  
         [0059]    As mentioned hereinbefore, the nut member  33  screw-engaged with the driven shaft  3  is provided at the central portion of the block body  32   a , and a loaded rolling groove in a spiral shape is formed to the nut member  33  so as to face the spiral ball rolling groove formed to the driven shaft  3 . A number of balls  40 , - - - ,  40  as rolling members are also arranged between these spiral ball rolling groove and the spiral loaded rolling groove to freely roll and move therebetween. The nut member  33  is further provided with a return tube  41  through which the balls rolling in the loaded area circulate.  
         [0060]    The driven shaft  3  is supported at its both ends by the end plates  37 ,  37  so as to allow the driven shaft  3  performs only rotational motion by means of bearing  42 . As mentioned before, one end of the driven shaft  3  is operatively coupled to the driven wheel  7  through the joint  10 .  
         [0061]    The driving unit of the structure mentioned above will operate in the following manner.  
         [0062]    When the electric motor  2  is driven, the driving shaft  1  is rotated, and this rotational motion is transmitted to the driving wheel  6  coupled to the driving shaft  1  through the flexible coupling  9 , thus rotating the driving wheel  6 . The rotation of the driving wheel  6  is then transmitted to the driven wheel  7  through the wrapping connector  8 , and when the driven wheel  7  is rotated, the slide member  32  is moved linearly along the track rail  31  through the engagement with the feed screw.  
         [0063]    The rotating driving wheel  6  is supported by the bearing  25 , which is disposed on the central line in the width direction of the wrapping connector  8 . For this reason, a load caused by the tension of the wrapping connector  8  is received by the bearing  25 , and hence, a load due to the tension of the driving shaft  1  is not applied. Accordingly, the driving shaft  1  of the electric motor  2  is not applied with a lateral load due to the tension, and the driving shaft  1  can be hence smoothly driven and rotated.  
         [0064]    Next, the tension adjusting method or manner of the tension of the wrapping controller driving device  5  will be described.  
         [0065]    Only the drive device  4  is first mounted to the bracket  11  before the mounting of the electric motor  2  to the bracket  11 . Next, the bracket  11  is moved relatively to the drive device  4 . Since the driven wheel  7  is connected to the drive device  4 , the driven wheel  7  is also moved relatively to the bracket  11  through the relative movement between the bracket  11  and the drive device  4 . On the other hand, since the driving wheel  6  is supported by the bracket  11 , the position thereof is not changed. Accordingly, the distance between the driving wheel  6  and the driven wheel  7  changes, whereby the tension of the wrapping connector  8  can be adjusted.  
         [0066]    Since the driving wheel  6  is supported by the bracket  11 , such tension adjustment can be done before the connection of the driving shaft  1  of the electric motor  2  to the driving wheel  6 . Accordingly, a user can freely mount any type of electric motor  2  after the tension has been adjusted at the manufacturing firm or the like. Furthermore, since the tension of the wrapping connector  8  is received by the bearing  25 , any moment load due to the tension is not applied to the driving shaft  1  of the electric motor  2 . Accordingly, a user can use any type of electric motor and mount it easily.  
         [0067]    It is to be noted that the present invention is not limited to the described embodiment and many other changes or modifications may be made without departing from the scopes of the appended claims.  
         [0068]    For example, in the described embodiment, the belt connector (transmission) driving device is utilized, another device such as chain or rope connector (transmission) driving device may be instead utilized.