Patent Publication Number: US-7707775-B2

Title: Power slide device for controlling sliding speed of vehicle sliding door

Description:
FIELD OF THE INVENTION 
     This invention relates to a method to control a speed of a vehicle slide door configured to be slidably moved by a power slide device. 
     DESCRIPTION OF THE RELATED ART 
     Various types of power slide devices having a motor, a wire drum to be rotated by the motor for winding and paying out a wire cable, and a clutch mechanism disposed between the motor and the wire drum, and are constructed so as to cause a vehicle slide door slide toward an opening direction or a closing direction through rotating the wire drum have been proposed so far. 
     The sliding speed of a door slidingly moved by the power slide device is feedback controlled for matching it with a predetermined reference speed. For example, when the sliding speed is “80” against a reference speed of “100” the door is accelerated and when the sliding speed is “120” against the reference speed of “100” the door is decelerated. 
     Under such conventional feedback control, a “motor speed” obtained based on a rotational speed of the motor or a “drum speed” obtained based on a rotational speed of the wire drum has been utilized as a sliding speed of the slide door. 
     A motor speed or a drum speed are not always the same with an actual speed of the slide door (door speed, hereinafter). It is common to assume that the drum speed corresponds to that of the door, however, as the slide door can move independently with respect to the wire drum due to the effect of a tension mechanism for the wire cable, the door speed may be faster or slower than the drum speed. Similarly, as the motor moves the slide door by way of the wire drum, the door speed of the slide door varies recording a faster speed or slower speed than that of the motor due to similar reasons. In addition, as the clutch mechanism is interposed between the motor and the wire drum, a difference between the motor speed and the door speed may be amplified further depending on looseness present in the clutch mechanism. A factor which effects such difference between the motor speed or the drum speed and the door speed will be called as “connection looseness”, hereinafter. 
       FIG. 22  shows a result of measurements of a motor speed and a door speed of a slide door when the slide door was opened through feedback control based on the motor speed in a nose-up inclined state of the vehicle. When a motor was accelerated toward a reference speed the door speed also was accelerated. In this case, however, the door speed was faster than the motor speed. This result indicates that the slide door accelerated its speed preceding acceleration of the motor because of an external force toward a direction of acceleration due to the nose-up inclined state acted on the slide door through the connection looseness. 
     After the motor speed reached the reference speed the motor was kept at a constant aped to match the reference speed, however, the slide door continuously increased its speed by a rate corresponding to the connection looseness and then turned to reduce its speed due to a braking effect of the motor brought about by the removal of the connection looseness. At the same time, as the connection looseness had been absorbed the motor advanced its speed because of a pulling effected by the slide door. When such acceleration in the motor speed was detected, the motor speed was reduced in accordance with the feedback control. In that case, however, the speed difference resulting from the connection looseness brought about repeated acceleration and deceleration of the motor speed recording alternately large ridges and troughs in the door speed. 
     Such a repetition of large ridges and troughs in the door speed appears larger number of times and lasts longer proportionately to the speed difference between the door speed and the motor speed effected when the motor speed is accelerated toward the reference speed. In other words, as no preceding acceleration of the door speed resulting from the connection looseness occurs in opening the door of a vehicle placed in a nose-down inclined state where an external force acts to decelerate the slide door, the variation in the door speed may be confined within a negligible range resulting in a smooth and stable movement of the slide door. 
     Such undesirable change in the door speed as shown in  FIG. 22  is possible to be suppressed through effective control of the motor speed (and drum speed). In this case, accurate measurements of the motor speed (and drum speed) become an important factor to implement appropriate control over the door speed. However, under the conventional PWM (pulse width modulation) control and the DUTY control the motor speed has been measured by detecting motor pulses, and its accuracy has been inadequate to restrain the undesirable variation shown in  FIG. 22 . 
     SUMMARY OF THE INVENTION 
     Therefore, the object of this invention is to provide a method to restrain such a difference between the door speed and the motor speed as observed in accelerating the motor speed and to move the slide door smoothly at a stable speed. 
     Furthermore, the object of this invention is to provide a power slide device constructed into a rational structure comprising a mechanism to detect an actual rotational speed of the motor and also a mechanism to detect an actual rotational speed of the wire drum. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view showing a rearward side face of a vehicle equipped with a slide door; 
         FIG. 2  is a view showing the relationship between the slide door and the vehicle body, in which the slide door closed; 
         FIG. 3  is a view showing the relationship between the slide door and the vehicle body, in which the slide door opened; 
         FIG. 4  is a conceptual view showing a case where a power unit is to be installed within an interior space of a quarter panel; 
         FIG. 5  is a side view of the power unit for the slide door; 
         FIG. 6  is a sectional view of the power unit; 
         FIG. 7  is a sectional view of the power unit; 
         FIG. 8  is a plan view of a tension mechanism of the power unit; 
         FIG. 9  is a perspective view of a cam member of the power unit; 
         FIG. 10  is a perspective view of a moving gear member of the power unit; 
         FIG. 11  is a detailed view of a cam face of the cam member; 
         FIG. 12  is a sectional view showing an engaging state between an engaging groove of a first worm wheel and a leg portion of the moving gear member; 
         FIG. 13  is an illustration showing a gap between the engaging groove and the leg portion; 
         FIG. 14  is a side view showing a cam surface of the cam member and the cam surface of the moving gear member at a clutch disconnecting state; 
         FIG. 15  is a schematic view showing the moving gear member and a fixed gear member at the clutch disconnecting state corresponding to  FIG. 14 ; 
         FIG. 16  is a side view showing the cam surface of the cam member and the cam surface of the moving gear member at the clutch connecting state; 
         FIG. 17  is a schematic view showing the moving gear member and the fixed gear member at the clutch connecting state corresponding to  FIG. 16 ; 
         FIG. 18  is a side view showing the cam surface of the cam member and the cam surface of the moving gear member at a brake-clutch connecting state in an off state of an electromagnetic coil unit; 
         FIG. 19  is a schematic view showing the moving gear member and the fixed gear member of the brake-clutch connecting state corresponding to  FIG. 18 ; 
         FIG. 20  is a side view showing the cam surface of the cam member and the cam surface of the moving gear member in the midst of releasing the brake-clutch connecting state; 
         FIG. 21  is a schematic view showing the moving gear member and the fixed gear member in the midst of releasing the clutch connecting state corresponding to  FIG. 20 ; and 
         FIG. 22  shows the results of measurements of a motor speed and a door speed of a slide door when the slide door was opened under the conventional feedback control based on the motor speed in a nose-up inclined state of the vehicle in accordance with the conventional technology. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Embodiment of the present invention will be described with reference to the drawings.  FIGS. 1 to 3  shows a vehicle body  10 , a slide door  11  slidably attached to the vehicle body  10 , and a door aperture  12  which can be closed by the sliding door  11 . The vehicle  10  in the vicinity of the upper portion of the door aperture  12  is fixed with an upper rail  13 , and the vehicle body  10  in the vicinity of the lower portion of the door aperture  12  is fixed with a lower rail  14 . @A quarter panel  15  which is a rear side surface of the vehicle body  10  is fixed with a center rail  16 . The slide door  11  is provided with an upper roller bracket  17  slidably engaged with the upper rail  13 , a lower roller bracket  18  slidably engaged with the lower rail  14 , and a center roller bracket  19  slidably engaged with the center rail  16 . Each of the roller brackets  17 ,  18  and  19  is suitably swingably journaled to the slide door  11 . 
     A power unit  20  of the power slide device in accordance with this invention may be arranged in an inner space  50  ( FIG. 2 ) of the slide door  11  or in an interior space of the quarter panel  15 . However, the location of the power unit  20  is irrelevant to the essence of this invention. 
     The power unit  20 , as shown in  5  through  7 , is provided with a wire drum  30  for winding and paying out wire cables, and the wire drum  30  is connected with base ends of two wire cables, that is, a door-opening cable  21 A and a door-closing cable  21 B. When the wire drum  30  rotates in a door-opening direction, the door-opening cable  21 A is wound up, and the door-closing cable  21 B is paid out, and when the wire drum  30  rotates in a door-closing direction, the door-opening cable  21 A is paid out, and the door-closing cable  21 B is wound up. 
     The opening cable  21 A is pulled out from a front lower position of the slide door  11 , namely the vicinity of the lower bracket  18 , toward a vehicle body side (on the side of the lower bracket  18 ) out of the slide door  11  as shown in  FIGS. 2 ,  3 . The opening cable  21 A pulled out from the slide door  11  is extended backward inside the lower rail  14  after passing on a pulley (not shown) of the lower bracket  18 , and is then fixed to the rear end portion of the lower rail  14  or the vehicle body  10  in the vicinity of the rear end portion of the lower rail. With this arrangement, when the opening cable  21 A is wound under the door-closed state the slide door  11  slides rearward (toward the door-opening direction) by way of lower bracket  18 . 
     The closing cable  21 B is pulled out from a rearward, middle height position of the slide door  11 , namely the vicinity of the center bracket  19  toward a vehicle body side (on the side of the center bracket  19 ) out of the slide door  11 . The closing cable  21 B pulled out from the slide door  11  is extended frontward inside the center rail  16  after passing on a pulley (not shown) of the center bracket  19 , and is then fixed to the front side of the center rail  16  or the vehicle body  10  in the vicinity of the front side portion of the center rail. With this arrangement, when the closing cable  21 B is wound under a door-open state the slide door  11  slides forward (toward the door-closing direction) by way of the center bracket  19 . 
     In case where the power unit  20  is installed in the interior space of the quarter panel  15 , the free end of the opening cable  21 A is connected to the center bracket  19  of the slide door  11  by way of a front pulley  22  pivoted at the front part of the center rail  16  as shown in  FIG. 4 , and similarly the free end of the closing cable  21 B is connected to the center bracket  19  by way of a rear pulley  23  pivoted at the rear part of the center rail  16 . 
       FIG. 8  shows a tension mechanism  100  to maintain tension of the wire cable  30  at an appropriate level, the tension mechanism  100  being preferable to be installed inside the power unit  20 . Within a case  101  of the tension mechanism  100  a pair of tension rollers  102 ,  103  on which the cables  21 A,  21 B abut are provided. The tension rollers  102 ,  103  are pivoted by tension shafts  104 ,  105  and are biased so as to draw each other by elasticity of a tension spring  106 . 
     As shown in  FIGS. 5 ,  6 , a cylindrical worm  25  is mounted on an output shaft of a motor  24  of the power unit  20 , and a worm wheel  26  is meshed with the cylindrical worm  25 . The worm wheel  26  is pivoted in a housing  29  of the power unit  20  by a support shaft  28 , on which the wire drum  30  is also pivoted. Between the worm wheel  26  and the wire drum  30  a clutch mechanism  31  is disposed. When the clutch mechanism  31  is on, the rotation of the worm wheel  26  is transmitted to the wire drum  30 , and when turned off, the wire drum  30  is rendered free with respect to the worm wheel  26 . Hence, in  FIG. 5 , when the clutch mechanism  31  is turned on during clockwise rotation of the worm wheel  26  by forward rotation of the motor  24 , the wire drum  30  also makes a clockwise rotation, so that the door-opening cable  21 A is paid out, and the door-closing cable  21 B is wound up. On the contrary, when the clutch mechanism  31  is turned on during counter-clockwise rotation of the worm wheel  26  by reverse rotation of the motor  24 , the wire drum  30  also makes a counter-clockwise rotation, so that the door-opening cable  21 A is wound up, and the door-closing cable  21 B is pulled out. 
     The clutch mechanism  31  is irrelevant to the essence of the application of this invention and any type of clutch mechanism may be used. However, for the present application the clutch mechanism described in detail in the U.S. patent application Ser. No. 10/971,707, now U.S. Pat. No. 7,434,354, has been applied. The clutch mechanism  31  is such a type of clutch provided with an electromagnetic coil  60  which can be turned on or off through an electric control. Briefly, the clutch mechanism  31  shifts to a clutch connecting state when the electromagnetic coil  60  is turned on and to a clutch disconnecting state when the coil  60  is turned off. Furthermore, as will be described later, the clutch mechanism  31  has a characteristic that a clutch disconnecting state (a brake-clutch connecting state) can be maintained even if the electromagnetic coil  60  has been turned off. 
     The electromagnetic coil  60  is formed in cylindrical shape and disposed around the support shaft  28 . The electromagnetic coil  60  is fixed onto the housing  29  and the support shaft  28  being rotatable with respect to the electromagnetic coil  60 . The worm wheel  26  is rotatably supported by the outer periphery of the electromagnetic coil unit  60 . As shown in  FIG. 6 , close to the left of the electromagnetic coil unit  60 , there is disposed a circular armature  61 . The circular armature  61  is rotatably journaled by the support shaft  28 , and moreover, is movable in the shaft direction. The armature  61  is biased toward left away from the electromagnetic coil  60  by a small elastic force of a brake release spring  62  and abuts against a shoulder of the support shaft  28 . The right surface of the armature  61  is attracted toward the electromagnetic coil  60  against the elasticity of the brake release spring  62  when the electromagnetic coil  60  is turned on and closely contacts the left surface of the electromagnetic coil  60 . Frictional resistance generated through this close contact is caused to be the braking resistance required for clutch connection. 
     A cam member  63  ( FIG. 9 ) is secured on the left surface of the armature  61 . As the armature  61  and the cam member  63  move together, they may be formed into an integral component. A cam surface  64  of the cam member  63 , as shown in  FIG. 9 , is a disciplined circularly rugged surface which has a top portions  64 A protruding leftward in a direction to the shaft center of the support shaft  28 , bottom portions  64 B formed by notching, and inclined surfaces  64 C connecting these portions. The inclined surface  64 C is a two step inclined surface comprising a clutch holding surface  64 D halfway across its surface. The clutch holding surface  64 D halfway across the inclined surface  64 C comprises a function to maintain the clutch mechanism  31  in the brake-clutch connecting state when the electromagnetic coil unit  60  is turned off.  FIG. 11  shows a detailed shape of the cam surface  64 . The cam surface  64 C is preferably an inclined surface having about 30 degrees for a shaft center X of the first supply shaft  28 , and further, the clutch holding surface  64 D is preferably formed in a sweep-back surface having about 10 degrees, though it may be formed in a flat surface orthogonal to the shaft center X. 
     In  FIG. 6 , to the left of the cam member  63 , there is provided a moving gear member  65  ( FIG. 10 ). The moving gear member  65  is rotatably and movably journaled to the support shaft  28  in the shaft direction, and its outer periphery is formed with a plurality of leg portions  66  extending toward the right side worm wheel  26 . The right side top end portion of the leg portion  66 , as shown in  FIGS. 6 and 12 , is engaged with an engaging groove  67  of the worm wheel  26 , and by the rotation of the worm wheel  26 , the moving gear member  65  is also rotated in association. While the leg portion  66  is slidable for the engaging groove  67  in the shaft direction of the support shaft  28 , even when the moving gear member  65  moves leftward maximum, the engagement between the leg portion  66  and the engaging groove  67  is not released, and consequently, the moving gear member  65  and the worm wheel  26  always integrally rotate. Further, between the leg portion  66  and the engaging groove  67 , as shown in  FIG. 13 , there is formed a gap Y in the rotational direction, and the leg portion  66  (moving gear member  65 ) is set to be able to freely rotate by approximately six degrees for the engaging groove  67  (worm wheel  26 ). The left surface of the moving gear member  65  is provided with a moving circular gear portion  68  with the support shaft  28  as a center. 
     A fixed gear member  69  is provided on left side of the moving gear member  65 , and between the moving gear member  65  and the fixed gear member  69 , there is provided a clutch releasing spring  70  which presses the moving gear member  65  to the right side. The left surface of the fixed gear member  69  is fixed to the wire drum  30 , and both of them integrally rotate. The wire drum  30  is fixed to the left end of the support shaft  28  so as to integrally rotate with the support shaft  28 . 
     A fixed circular gear portion  71  is provided on the right surface of the fixed gear member  69 . When the moving gear member  65  slides leftward along the support shaft  28  against the elastic force of the clutch releasing spring  70 , the moving circular gear portion  68  engages with the fixed circular gear portion  71 . A state in which the gear portion  68  and the gear portion  71  are engaged each other is a normal clutch connecting state of the clutch mechanism  31 , and the rotation of the worm wheel  26  is transmitted to the wire drum  30 . In contrast to this, when the moving gear member  65  slides rightward for the support shaft  28  by the elastic force of the clutch releasing spring  70 , the moving circular gear portion  68  breaks away from the fixed circular gear portion  71 , and the clutch is put into a clutch disconnecting state, and the rotation of the worm wheel  26  is not transmitted to the wire drum  30 . 
     As shown in  FIG. 10 , the moving gear member  65  is formed with a cam surface  72 , which slides the moving gear member  65  leftward in cooperation with the cam surface  64  of the cam member  63  against the elastic force of the clutch releasing spring  70 . The cam surface  72  is a disciplined circular rugged surface comprising top portions  72 A protruding rightward in the shaft center direction of the support shaft  28 , bottom portions  72 B, and inclined surfaces  72 C connecting these portions. The cam surface  72  has a configuration substantially symmetrical to the cam surface  64 , however, no clutch holding portion is provided on the cam surface  72  in this embodiment. If provided on either of the cam faces  64 ,  72 , the clutch holding portion causes the effect pursued. 
     When the moving gear member  65  slides rightward by elastic force of the clutch releasing spring  70 , normally as shown in  FIGS. 14 and 15 , the top portion  72 A of the cam surface  72  exactly matches the bottom portion  64 B of the cam surface  64 , and the moving circular gear portion  68  breaks away from the fixed circular gear portion  71 , and the clutch mechanism is put into a clutch disconnecting state. In this clutch disconnecting state, when the electromagnetic coil unit  60  is turned on, the armature  61  is pulled and the right surface of the armature  61  is adhered to the left surface (friction surface) of the electromagnetic coil unit  60  by magnetic force against the elastic force of the brake release spring  62 , so that the armature  61  and the cam member  63  are given a brake resistance. Subsequently, when the moving gear member  65  (cam surface  72 ) is rotated by motive power of the motor  24 , since the cam member  63  is in a state in which the rotation is controlled by the break resistance, as shown in  FIG. 16 , the phase between the cam surface  64  of the cam member  63  and the cam surface  72  are shifted due to a wedge effect brought about by the cam surfaces, and the moving gear member  65  is pushed leftward against the elastic force of the clutch releasing spring  70 , and as shown in  FIG. 17 , the moving circular gear portion  68  engages with the fixed circular gear portion  71  so as to be put into a normal clutch connecting state. 
     When the motor  24  and the electromagnetic coil unit  60  are both turned off in the normal clutch connecting state of  FIGS. 16 and 17 , the armature  61  and the cam member  63  are released from the brake resistance. Then, by the elastic force of the clutch releasing spring  70 , the moving gear member  65  is moved rightward, while rotating the cam member  63  in a flank direction (downward in  FIG. 16 ), and before the moving gear member  65  is disengaged from the fixed gear member  69 , as shown in  FIGS. 18 and 19 , the top portion  72 A of the moving gear member  65  abuts against the clutch holding surface  64 D of the cam member  63 , and in this manner, the moving gear member  65  is unable to rotate the cam member  63 , and at the same time, is controlled also in the rightward movement. Hence, even when the electromagnetic coil unit  60  is in an off state, the engagement between the moving gear member  65  and the fixed gear member  69  is maintained, and the clutch mechanism  31  is put into a brake-clutch connecting state. 
     In the brake-clutch connecting state of  FIGS. 18 and 19 , due to resistance by the abutment between the top portion  72 A and the clutch holding surface  64 D, the moving gear member  65  and the armature  61  as well as the cam member  63  are maintained in a state in which they rotate integrally. Consequently, even when the fixed gear member  69  is rotated upward to move the moving gear member  65  upward in  FIG. 19 , since the armature  61  and the cam member  63  are also associatingly moved upward, the brake-clutch connecting state is not released. Additionally, the frictional force between the top portions  72 A and the clutch holding portions  64 D to hold the moving gear member  65  and the cam member  63  in an integral state can be secured through forming the clutch holding portions  64 D with flat surfaces disposed normal to the axis X of the support shaft  28 , however, in case where the clutch holding portions  64 D are configured by slant surfaces retarding approximately 10 degrees, preferable magnitude of friction may be ensured. 
     The abutment of the top portion  72 A against the clutch holding portions  64 D can be released through moving the moving gear member  65  upward as shown in  FIGS. 18 ,  19  relative to the armature  61  and the cam member  63  after turning on the electromagnetic coil  60  as will be described later in association with a manual operation to release the brake-clutch connecting state. In this case, the rotational angle required for the moving gear member  65  is approximately 5 degrees, which is set to be smaller than the free-rotation angle (approximately 6 degrees) for the moving gear member  65  enabled by the gap Y formed between each pair of leg portions  66  and the engaging grooves  67 . 
     The housing  29  comprises a metal base plate  120 , a metal or plastic cover plate  121 , and a plastic housing body  122  disposed between the plates  120 ,  121 . A first space  123  is defined between the base plate  120  and the body  122 , and a second space  124  between the cover plate  121  and the body  122 . Within the first space  123  the wire drum  30  and the clutch mechanism  31  are housed. 
     As shown in  FIGS. 6 ,  7 , one end of the support shaft  28  passes through the housing body  122  and extends into the second space  124 , with a large gear  125  being secured to the extended end. A small gear  127  of the drum rotor  126  is meshed with the large gear  125 . The drum rotor  126  is pivoted by a shaft  128  disposed in parallel with the support shaft  28  in the second space  124  and rotates together with the rotation of the support shaft  28  rotated by the wire drum  30 . 
     As shown in  FIG. 6 , a parallel gear  129  is meshed with the worm wheel  26 . The parallel gear  129  is disposed on the same plane with the worm wheel  26  in the first space  123 . A shaft  130  of the parallel gear  129  is parallel with the supporting shaft  28 , and one end of the shaft  130  passes through the housing body  122  and extends into the second space  124 , with a motor rotor  131  being fixed to the extended end. The motor rotor  131  is connected to the motor  24  for rotation by way of the worm wheel  26 . The motor rotor  131  is disposed so as not to overlap with the drum rotor  126  in the axial direction of the support shaft  28 . 
     A drum rotor element  132  and a motor rotor element  133  both of which are made of a magnetic body are disposed on the drum rotor  126  and the motor rotor  131 , respectively. 
     On an outer surface of the cover plate  121  a control unit  134  is mounted. On a control board  135  of the control unit  134  a control unit  136  is provided, and also a drum speed sensor  137  to detect a rotational speed of the wire drum  30  in cooperation with the drum rotor element  132  and a motor speed sensor  138  to detect a rotational speed of the motor  24  in cooperation with the motor rotor element  133  are disposed. The sensors  137 ,  138  are Hall effect IC, and are disposed so as to be able to detect the rotational elements  132 ,  133  through windows  139 ,  140  formed on the cover plate  121 . Also, if the sensors  137 ,  138  extending toward the control board  135  are disposed within the windows  139 ,  140 , the control board  135  may snuggly fit on the cover plate  121  and distances between the sensors  137 ,  138  and the rotational elements  132 ,  133  may be reduced. 
     (Operation of Clutch) 
     Now, operation of the clutch mechanism  31  will be explained. When the electromagnetic coil  60  is off substantially no frictional resistance may be generated between the armature  61  and the electromagnetic coil  60 . Under this state, if the cylindrical worm  25  is rotated by the motor  24  rotating in a forward direction the worm wheel  26  rotates clockwise in  FIG. 5 , and the moving gear member  65  also rotates clockwise due to the engagement of the leg portions  66  with the engaging grooves  67 . In this case, the moving gear member  65  is shifted to the right by the elasticity of the clutch releasing spring  70 , and the moving circular gear portion  68  of the moving gear member  65  is disengaged from the fixed circular gear portion  71  of the fixed gear member  69  (in the clutch disconnecting state) as shown in  FIGS. 6 ,  15 , and further the cam surface  72  of the moving gear member  65  is in contact with the cam surface  64  of the cam member  63  as shown in  FIG. 14 . As a result, if the motor  24  is rotated in the forward direction under this state, the moving gear member  65 , the cam member  63 , and the armature  61  attached to the cam member  63  simply rotate integrally resulting in no displacement of the moving gear member  65  toward the fixed gear member  69 . 
     Under the above state ( FIGS. 14 ,  15 ), if the electromagnetic coil  60  is turned on, the armature  61  is attracted by a generated magnetic force toward the electromagnetic coil  60  against the resilience of the brake release spring  62  and a predetermined magnitude of braking resistance is generated between the electromagnetic coil  60  and the armature  61 . As a result, the integral rotation of the armature  61  and the cam member  63  against the moving gear member  65  is restricted, and the moving gear member  65  rotates about the support shaft  28  relative to the cam member  63 . Then, the phase between the cam surfaces  64 ,  72  shifts as shown in  FIG. 16 , and the moving gear member  65  is pushed out toward the fixed gear member  69  against the resilience of the clutch releasing spring  70 , and then the moving circular gear portion  68  of the moving gear member  65  engages the fixed circular gear portion  71  of the fixed gear member  69  to bring about the normal clutch connecting state. Consequently, the rotation of the motor  24  may be transmitted to the wire drum  30  by way of the fixed gear member  69  for winding the closing cable  21 B to move the slide door  11  toward the door-closing direction. After the clutch engagement, both the armature  61  and the cam member  63  rotate integrally with the moving gear member  65 . 
     If both the motor  24  and the electromagnetic coil  60  are turned off while the slide door  11  is moving in the door-closing direction, the moving gear member  65  engaged with the worm wheel  26  stops its rotation, and the armature  61  and the cam member  63  are released from the braking resistance, and the moving gear member  65  is returned toward the right by the elastic force of the clutch releasing spring  70  while rotating the cam member  63  in the release direction (downward in  FIGS. 16 ,  17 ). Then, prior to the disengagement of the moving gear member  65  from the fixed gear member  69 , the top portion  72 A of the moving gear member  65  abuts against the clutch holding portions  64 D of the cam member  63  as shown in  FIGS. 18 ,  19 , whereby the moving gear member  65  is unable to rotate the cam member  63 , and at the same time, the rightward movement of gear member  65  is restricted. As a result, even if the electromagnetic coil  60  is off, the engagement of the moving gear member  65  with the fixed gear member  69  is maintained and the clutch mechanism  31  is brought into the brake-clutch connecting state. Under the brake-clutch connecting state, being directly connected to a speed reduction mechanism on the side of the motor  24 , the slide door  11  is maintained in a state substantially of no move. Consequently, if a user turns the motor  24  and the electromagnetic coil  60  off intentionally, the slide door  11  can be held at a desired semi-door-open position. Also, if this intermediate stopping is devised to be performed by the control unit  136 , a semi-door-open state of the slide door  11  may be attained easily and automatically. 
     When the slide door  11  has moved to the door-closed position with normal closing control executed by the control unit  136  (in this case the clutch mechanism  31  is in the normal clutch connecting state as shown in  FIGS. 16 ,  17 ), the motor  24  is rotated in a reverse direction for a predetermined time (predetermined rotation). Then, as the electromagnetic coil  60  is kept in the activated state the moving gear member  65  alone moves upward in  FIG. 17  by a predetermined distance leaving the armature  61  and the cam member  63  behind, and further the top portion  72 A of the moving gear member  65  shifts upward away from the clutch holding portions  64 D of the cam member  63 . When this state is attained, the electromagnetic coil  60  and the motor  24  are turned off. By this operation, the top portion  72 A of the moving gear member  65  moves rightward by the elastic force of the clutch releasing spring  70  without contacting the clutch holding portions  64 D of the cam member  63  to resume the clutch disconnecting state of  FIGS. 14 and 15 . 
     Now, a method to release the brake-clutch connecting state ( FIGS. 18 ,  19 ) of the clutch mechanism  31  will be explained. For changing the brake-clutch connecting state to the clutch disconnecting state, the electromagnetic coil  60  is turned on at first. Then, the armature  61  and the cam member  63  are attracted toward the electromagnetic coil  60  for generation of braking resistance. At this stage, though the moving gear member  65  also slightly moves rightward by the elastic force of the clutch releasing spring  70 , the engagement with the fixed gear member  69  still continues. Next, in the case of the motive power, the motor  24  is rotated, and the moving gear member  65  is rotated upward in the case of  FIG. 19 , and when the top portion  72 A of the moving gear member  65  moves upper than the clutch holding surface  64 D of the cam member  63 , the electromagnetic coil unit  60  and the motor  24  are turned off. As a result, the top portions  72 A of the moving gear member  65  move rightward without contacting the clutch holding portions  64 D of the cam member  63  by the resilience of the clutch releasing spring  70 , and the clutch returns to the clutch disconnecting state as shown in  FIGS. 14 ,  15 . 
     In case the brake-clutch connecting state is to be released manually instead of the motive power of the motor  24 , after the electromagnetic coil unit  60  is turned on, the slide door  11  is manually moved. Then, the wire drum  30  is rotated, and the moving gear member  65  is also rotated through the fixed gear member  69 . At this time, in the brake-clutch connecting state, though the wire drum  30  is connected to the motor  24  side, since the gap Y formed between the leg portion  66  and the engaging groove  67  allows the moving gear member  65  to freely rotate approximately six degrees for the worm wheel  26 , the slide door  11  moves by slight operational force without rotating the worm wheel  26 , and can rotate the moving gear member  65 . Subsequently, by the rotation of the moving gear member  65 , when the top portion  72 A of the moving gear member  65  comes off from the clutch holding surface  64 D of the cam member  63 , the moving gear member  65  moves rightward by the elastic force of the clutch releasing spring  70 , and the clutch returns to the clutch disconnecting state of  FIGS. 14 and 15 . 
     Under the manual release of the brake-clutch connecting state as described above, the control unit  136  outputs a signal for turning on the electromagnetic coil  60  for a give time when it detects a manual operation for clutch disengagement. Various kinds of operations may be employed for determining the manual operation for clutch disengagement; for example, a movement of a door open handle of the slide door  11  by a manual door opening operation can be a typical signal of the manual operation for clutch disengagement. 
     (Operation for Speed Control by the Control Unit  136 ) 
     A travel distance of the slide door  11  driven by the power unit  20  is divided roughly into three sections, i.e., an initial section from the start to a completion of acceleration, an intermediate section of substantially a constant speed, and a deceleration section as a final section. Also, in the initial section a slow speed section extending for a given time may be provided, if required. 
     When the slide door  11  is opened from the closed position (or closed from the open position) by the power unit  20 , the motor  24  is rotated at a slow speed for a given time as may be desired, and after that the motor  24  is accelerated for a predetermined reference speed. The control unit  136  monitors the movement of the slide door  11  in this initial section to detect abnormal accelerations. Preferably, the sliding door  11  is determined to be under abnormal acceleration, when a rotational speed of the wire drum  30  measured by the drum speed sensor  137  is above a given value (of and above 120 mm/sec. on sliding speed equivalent), a difference between the rotational speed of the wire drum  30  and a rotational speed of the motor  24  measured by the motor speed sensor  138  is above a given value (of and above 400 mm/sec. on sliding speed equivalent), and acceleration of the wire drum  30  is above a given value. Also, it is preferable to determine that the sliding door  11  is under abnormal acceleration, when a rotational speed of the wire drum  30  is above a given value (of and above 120 mm/sec. on sliding speed equivalent), a difference between the rotational speed of the wire drum  30  and a rotational speed of the motor  24  is above a given value (of and above 180 mm/sec. on sliding speed equivalent), and the difference of and above a given value has been detected consecutively. 
     Such abnormal acceleration as described above may be caused when the sliding door  11  is in a state to receive an external force for accelerating the door. For example, the vehicle body  10  is in an inclined state, or the slide door  11  is received a manual operating force by the user. In other words, according to this invention the inclination of the vehicle body  10  can be estimated based on the results of comparison of the motor speed and the drum speed. 
     When the abnormal acceleration has been detected, the control unit  136  lowers a rotational speed of the motor  24  to stabilize a sliding speed of the slide door  11 , and then accelerate the motor  24  again toward the reference speed. This re-acceleration of the motor  24  is preferable to be performed at a lower rate of acceleration than the initial rate. 
     When the control over the slide door  11  is implemented through detecting the abnormal acceleration as described above, the difference between the motor speed and the door speed of the slide door  11  in the initial section will substantially be reduced in comparison with the prior art, and as result, the slide door  11  may be traveled smoothly at a stable speed. 
     (Advantages) 
     In accordance with this invention, when the slide door  11  is slid by the power unit  20 , the abnormal accelerations in the initial section from the start to the completion of acceleration can be detected by utilizing the drum speed and the motor speed. And the control unit  136  lowers a rotational speed of the motor  24  to stabilize the actual door speed of the slide door  11  when the abnormal acceleration is detected, and then the motor  24  is accelerated (preferably at a smaller rate of acceleration) again toward the reference speed. Thus, the difference between the motor speed and the door speed of the slide door  11  at the end of the initial section can be reduced substantially relative to the prior art, whereby the difference between the door speed and the motor speed brought about by the connection looseness can be reduced to enable the slide door  11  travel smoothly at a stable speed. 
     Also, in accordance with this invention, the wire drum  30 , the clutch mechanism  31 , the drum rotor  126 , and the motor rotor  131  are installed within the housing  29 , and the shaft  128  of the drum rotor  126  and the shaft  130  of the motor rotor  131  are disposed in parallel to the support shaft  28  of the wire drum  30 . Accordingly, the drum rotor  126  and the motor rotor  131  can be mounted rationally within the housing. In addition, as the control board  135  having the control unit  136  which performs control of the motor  24  is attached to the outer surface of the cover plate  121  of the housing  29 , and the drum speed sensor  137  and the motor speed sensor  138  are disposed on the control board  135 , rational placing of the sensors  137 ,  138  can be materialized. 
     Furthermore, as the drum speed sensor  137  and the motor speed sensor  138  are disposed in the windows  139 ,  140  formed on the cover plate  121 , the control board  135  can be fit snuggly to the cover plate  121  and also distances between the sensors  137 ,  138  and the rotational elements  132 ,  133  can be reduced. 
     In addition, as the drum rotor  126  is configured to rotate together with the wire drum  30  by way of the support shaft  28 , and the motor rotor  131  is configured to rotate together with the motor  24  by way of the worm wheel  26  rotated by the motor  24 , the drum rotor  126  can accurately reflect rotation of the wire drum  30  and similarly the motor rotor  131  can accurately reflect rotation of the motor  24 , whereby accuracy of measurements can be expected to enhance. 
     Finally, as the drum rotor  126  and the motor rotor  131  can be disposed so as to avoid overlap in an axial direction of the support shaft  28 , any enlargement of the housing  29  can be restrained.