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BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a door opening/closing device for controlling opening and closing of a door.  
         [0003]     2. Description of the Related Art  
         [0004]     Generally, a door opening/closing device for controlling opening and closing of a door of a vehicle is provided with a door driving mechanism that includes a door opening/closing motor that drives the door to be open or closed. The door opening/closing device also includes a latch for holding the door to be closed. The latch includes a closer mechanism having a closer motor that drives the latch so that the latch in a half-latch state is brought to a full-latch state, and a release mechanism including a solenoid that drives the latch so that the latch in the full-latch state is released. In other words, in the above door opening/closing device, the door-closing operation is succeeded from the door driving mechanism to the closer mechanism when the door has brought to the half-latch state. Moreover, a door-opening operation is succeeded from the release mechanism to the door driving mechanism when the door has brought to a position at which the latch is released.  
         [0005]     In the door-closing operation, a reaction force of a weatherstrip occurs. Due to the reaction force, transition from the door driving mechanism to the closer mechanism may not be conducted properly. In a conventional technology, for example, such a region that the door driving mechanism and the closer mechanism are simultaneously driven after the latch has brought to the half-latch state. Accordingly, the door is securely moved to a position to be the half-latch state by the door driving mechanism against the reaction force so that the closer mechanism can succeed the door-closing operation to bring the latch to the full-latch state (for example, Japanese Patent No. 2715747).  
         [0006]     Another conventional door opening/closing device that includes reels and cables for controlling opening and closing of the door. The door opening/closing device rotates the reels connected with respective ends of the cables fixed to the door in forward and reverse directions with a motor to cause the reels to wind the cables therearound. In this apparatus, each of the reels includes a large diameter portion that winds the cable so as to provide a relatively high speed and a low power operation of the door, and a small diameter portion that winds the cable so as to provide a relatively low speed and a high power operation. Thus, the door is first moved at a high speed in a door-closing direction, and then, with a high power so that the door is closed against the reaction force (for example, Japanese Patent No. 2554786).  
         [0007]     However, in the conventional door opening/closing device disclosed in Japanese Patent No. 2715747, if a load occurs at the transition between the door driving mechanism and the closer mechanism while the door driving mechanism and the closer mechanism are simultaneously driven, a catching detector (arranged separately) can erroneously determine that something is caught in the door. In this case, the door is controlled to be reversely moved to the door opening direction. Therefore, a specific control must be conducted to perform the transition from the door driving mechanism to the closer mechanism.  
         [0008]     In the conventional door opening and closing device disclosed in Japanese Patent No. 2554786, if the cable is stretched or shrunk, or if the cable slides on the reel, power can be provided at positions deviated from desired positions.  
       SUMMARY OF THE INVENTION  
       [0009]     It is an object of the present invention to at least solve the problems in the conventional technology.  
         [0010]     A device according to one aspect of the present invention is for controlling a door operated by a motor and includes an opening/closing mechanism configured to open and close the door; and a gear mechanism including a plurality of tooth units each of which has different mesh, and configured to convey a torque of the motor to the opening/closing mechanism. The torque conveyed to the opening/closing mechanism is changed by selecting a tooth unit based on a position of the door at the time of starting an opening or closing operation of the door.  
         [0011]     A device according to another aspect of the present invention is for controlling a door operated by a motor and includes an opening/closing mechanism configured to open and close the door; a gear mechanism including a plurality of tooth units each of which has different mesh, and configured to convey a torque of the motor to the opening/closing mechanism; and a controller configured to control the motor in such a manner that a rotation speed of the motor gradually changes while the tooth units are being switched. The torque conveyed is changed by selecting a tooth unit based on a position of the door at the time of starting an opening or closing operation of the door.  
         [0012]     The other objects, features, and advantages of the present invention are specifically set forth in or will become apparent from the following detailed description of the invention when read in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a schematic of a vehicle to which a door opening/closing device according to an embodiment of the present invention is applied;  
         [0014]      FIG. 2  is a front view of the door opening/closing device;  
         [0015]      FIG. 3  is a rear view of the door opening/closing device;  
         [0016]      FIG. 4  is a side view of the door opening/closing device;  
         [0017]      FIG. 5  is a cross-section of the door opening/closing device;  
         [0018]      FIG. 6  is a perspective view of a driving gear group;  
         [0019]      FIG. 7  depicts a transmission speed and a transmission torque obtained by a variable-speed-gear mechanism;  
         [0020]      FIG. 8  is a schematic of the door opening/closing device in a fully-open state;  
         [0021]      FIG. 9  is a schematic of the door opening/closing device in a fully-closed state;  
         [0022]      FIG. 10  is a block diagram of a control system for the door opening/closing device; and  
         [0023]      FIG. 11  is a schematic for illustrating a door speed control by an opening/closing control unit when the door is positioned near a door closing position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]     Exemplary embodiments of the present invention will be explained below in detail with reference to the accompanying drawings. Note that the invention is not limited by the embodiments.  
         [0025]      FIG. 1  is a schematic of a vehicle to which a door opening/closing device according to an embodiment of the present invention is applied,  FIG. 2  is a front view of the door opening/closing device,  FIG. 3  is a rear view of the door opening/closing device,  FIG. 4  is a side view of the door opening/closing device,  FIG. 5  is a cross-section of the door opening/closing device, and  FIG. 6  is a perspective view of a driving gear group.  
         [0026]     As shown in  FIG. 1 , a door opening/closing device according to the embodiment is provided between body  1  of a vehicle and a door (for example, a spring-up type back door)  2  for closing an opening  1   a  that is formed in the vehicle body  1 . The door opening/closing device moves the door  2  to be open and closed. The door opening/closing device includes a driving unit  3 , and a transmission rod  4  arranged between the driving unit  3  and the door  2 . The transmission rod  4  constitutes a door opening and closing mechanism. The door opening/closing device transmits power of the driving unit  3  to the door  2  via the transmission rod  4 , thereby moving the door  2 . The door  3  is moved in a region between a full open position at which the door is fully open and a full closed position at which the door is completely closed. A latch R that engages with a striker S arranged at an edge of the opening  1   a  is arranged on at an end of the door  2  to hold the door  2  at the full closed position. The latch R can be a known member, and it takes a half-latch state, in which the latch R temporarily holds the door  2  positioned just before the full closed position, and a full-latch state, in which the latch R holds the door  2  at the full closed position. The latch R includes a release mechanism (not shown) including a solenoid for releasing the door  2  from a full-latch state. The release mechanism can be also a conventional one.  
         [0027]     As shown in FIGS.  2  to  5 , the driving unit  3  is arranged in a casing  3 A constituting a base member of the door opening/closing device, and has a driving motor  31 , a clutch  32 , a driving gear group  33 , an arm  34  constituting the door opening and closing mechanism, and a rotation sensor  35 . The casing  3 A is formed by combining a front cover  3 Aa and a back cover  3 Ab that are obtained by bending metal plates.  
         [0028]     As shown in FIGS.  3  to  5 , the driving motor  31  is attached to an outer face of the casing  3 A, specifically, the back cover  3 Ab. The driving motor  31  is disposed such that an output shaft (not shown) thereof extends downward. The driving motor  31  has a motor base  36  made from metal (for example, aluminum alloy) that houses a worm gear  31 A including the output shaft. The driving motor  31  is fixed on the back cover  3 Ab of the casing  3 A by bolts  36 A inserted into though-holes formed in the motor base  36 .  
         [0029]     As shown in  FIG. 5 , the clutch  32  is constituted as an electromagnetic clutch. The clutch  32  is housed in a clutch case  37  made from synthetic resin. The clutch case  37  is interposed between the motor base  36  and the back cover  3 Ab, and it is fixed to the back cover  3 Ab by the bolts  36 A.  
         [0030]     The clutch  32  includes a clutch shaft  32 A, a worm wheel  32 B, an armature  32 C, a rotor  32 D, and a coil unit  32 E. One end of the clutch shaft  32 A is rotatably supported to the motor base  36  in a state that the clutch shaft  32 A is orthogonal to the output shaft of the driving motor  31 , while the other end thereof is rotatably supported to the back cover  3 Ab of the casing  3 A. The worm wheel  32 B is rotatably fit on the clutch shaft  32 A to mesh with a worm gear  31 A of the driving motor  31 . The armature  32 C is formed in a disc shape from magnetic substance and it is rotatably fit on the clutch shaft  32 A. The armature  32 C is provided to engage with the worm wheel  32 B so as to move in an axial direction of the clutch shaft  32 A and rotate together with the worm wheel  32 B. The rotor  32 D is fixed on the clutch shaft  32 A so as to be opposed to the armature  32 C. The coil unit  32 E is arranged around the clutch shaft  32 A. The rotor  32 D is arranged between the coil unit  32 E and the armature  32 C. One end of the clutch shaft  32 A extends through the motor base  36 , while the other end thereof extends inside the casing  3 A.  
         [0031]     In the clutch  32 , when the coil unit  32 E is energized, the armature  32 C is attracted toward the coil unit  32 E to frictionally engage with the rotor  32 D. Thereby, a driving force of the driving motor  31  via the worm gear  31 A and the worm wheel  32 B is transmitted to the clutch shaft  32 A via the rotor  32 D so that the clutch shaft  32 A is rotated. On the other hand, when the coil unit  32 E is not energized, the armature  32 C and the rotor  32 D separate from each other. Thereby, mutual transmission of power between the driving motor  31  and the clutch shaft  32 A is released.  
         [0032]     As shown in  FIG. 5 , the rotation sensor  35  is housed in a sensor case  39  fixed on a rear face of the motor base  36 . The rotation sensor  35  includes a sensor gear  35 A, a magnet disc  35 B, and a sensor unit  35 C. The sensor gear  35 A is fixed at one end of the clutch shaft  32 A extending through the motor base  36 . The magnet disc  35 B is obtained by forming a permanent magnet in a disc shape, and it is rotatably supported to the sensor case  39 . The magnet disc  35 B meshes with the sensor gear  35 A. The sensor unit  35 C is fixed on an inner face of the sensor case  39  and it has two hall integrated circuits (ICs)  35 Ca for detecting rotation of the magnet disc  35 B.  
         [0033]     In the rotation sensor  35 , when a driving force of the driving motor  31  is transmitted to the clutch shaft  32 A via connection of the clutch  32 , the sensor gear  35 A is rotated according to rotation of the clutch shaft  32 A. The magnet disc  35 B is rotated according to rotation of the sensor gear  35 A and the rotation is detected by the respective hall ICs  35 Ca of the sensor unit  35 C. The respective hall ICs  35 Ca output pulse signals with different phases according to driving of the driving motor  31 .  
         [0034]     As shown in  FIGS. 3 and 6 , the driving gear group  33  includes an output gear  33 A, an intermediate gear  33 B, and a driving gear  33 C.  
         [0035]     The output gear  33 A is fixed to the other end of the clutch shaft  32 A inside the casing  3 A. That is, the output gear  33 A is rotated via the clutch  32  according to rotation of the driving motor  31 .  
         [0036]     The intermediate gear  33 B is fixed to an intermediate gear shaft  33 Ba supported inside the casing  3 A so as to be parallel to the clutch shaft  32 A. The intermediate gear  33 B is constituted by concentrically stacking and unitizing a large diameter gear  33 Bb and a small diameter gear  33 Bc having a diameter smaller than that of the large diameter gear  33 Bb. The large diameter gear  33 Bb of the intermediate gear  33 B meshes with the output gear  33 A and a small diameter sector gear  33 Cc of the driving gear  33 C described later. The small diameter gear  33 Bc of the intermediate gear  33 B meshes with a large diameter sector gear  33 Cb of the driving gear  33 C.  
         [0037]     The driving gear  33 C is fixed to the driving shaft  33 Ca supported in the casing  3 A so as to be parallel to the clutch shaft  32 A and the intermediate gear shaft  33 Ba. The driving shaft  33 Ca extends toward a front face of the casing  3 A. The driving gear  33 C is constituted by concentrically stacking and unitizing the large diameter sector gear  33 Cb and the small diameter sector gear  33 Cc having a diameter smaller than that of the large diameter sector gear  33 Cb. The large diameter sector gear  33 Cb of the driving gear  33 C is formed in a fan shape having teeth on an arc face and meshes with the small diameter gear  33 Bc of the intermediate gear  33 B. The small diameter sector gear  33 Cc of the driving gear  33 C is formed in a fan shape having teeth on an arc face and meshes with the large diameter gear  33 Bb of the intermediate gear  33 B.  
         [0038]     The driving gear  33 C includes the large diameter sector gear  33 Cb and the small diameter sector gear  33 Cc so as to satisfy the following relationship. When the large diameter sector gear  33 Cb meshes with the small diameter gear  33 Bc of the intermediate gear  33 B, the small diameter sector gear  33 Cc is released from the meshing state with the large diameter gear  33 Bb of the intermediate gear  33 B. On the other hand, when the small diameter sector gear  33 Cc mainly meshes with the large diameter gear  33 Bb of the intermediate gear  33 B, the large diameter sector gear  33 Cb is released from the small diameter gear  33 Bc of the intermediate gear  33 B. Thus, the driving gear  33 C is constituted such that the large diameter sector gear  33 Cb and the small diameter sector gear  33 Cc correspond to the intermediate gear  33 B independently of each other.  
         [0039]     In the driving gear group  33 , when a driving force of the driving motor  31  is transmitted to the clutch shaft  32 A via the clutch  32 , the output gear  33 A is rotated according to rotation of the clutch shaft  32 A. At that time, the intermediate gear  33 B with which the large diameter gear  33 Bb meshes rotates around the intermediate gear shaft  33 Ba according to the rotation of the output gear  33 A. The driving shaft  33 Ca is rotated via the driving gear  33 C with the large diameter sector gear  33 Cb or the small diameter sector gear  33 Cc meshes according to the rotation of the intermediate gear  33 B. When the small diameter sector gear  33 Cc meshes with the large diameter gear  33 Bb, rotation of the intermediate gear  33 B is transmitted from the large diameter gear  33 Bb to the small diameter sector gear  33 Cc, so that rotation speed of the driving shaft  33 Ca is made relatively high. On the other hand, when the large diameter sector gear  33 Cb meshes with the small diameter gear  33 Bc, rotation of the intermediate gear  33 B is transmitted from the small diameter gear  33 Bc to the large diameter sector gear  33 Cb, so that rotation speed of the driving shaft  33 Ca is made relatively low.  
         [0040]     The arm  34  together with the transmission rod  4  constitutes the door opening and closing mechanism, and a proximal end  34 A thereof is fixed to the driving shaft  33 Ca extending toward the front face of the casing  3 A, as shown in  FIGS. 2, 4 , and  5 . That is, the arm  34  is rotated according to rotation of the driving shaft  33 Ca. The transmission rod  4  is attached to a rotating end  34 B of the arm  34 . As shown in  FIGS. 1, 2 , and  4 , the transmission rod  4  is formed in an elongated rod shape, and one end  4 A thereof is attached to a rotating end  34 B of the arm  34 , while another end  4 B thereof is attached to the door  2 . The transmission rod  4  moves the door  2  in an opening direction or a closing direction thereof according to rotation of the arm  34  of the driving unit  3 . Thus, the door opening/closing device transmits rotation of the driving motor  31  to the door opening and closing mechanism via the driving gear group  33  to move the door  2  to the vehicle body  1  for opening and closing.  
         [0041]     That is, the intermediate gear  33 B and the driving gear  33 C in the driving gear group  33  constitute a variable-speed gear mechanism having different meshing teeth for changing a rotational speed to be transmitted to the door opening and closing mechanism in a state that rotation speed of the driving motor  31  is kept constant during opening or closing operation of the door  2 . The variable-speed gear mechanism has high speed meshing teeth constituted to transmit relatively high speed rotation to the driving shaft  33 Ca by meshing between the large diameter gear  33 Bb of the intermediate gear  33 B and the small diameter sector gear  33 Cc of the driving gear  33 . Furthermore, the variable-speed gear mechanism also has low speed meshing teeth constituted to transmit relatively low speed rotation to the driving shaft  33 Ca by meshing between the small diameter gear  33 Bc of the intermediate gear  33 B and the large diameter sector gear  33 Cb of the driving gear  33 C. The high speed meshing teeth and the low speed meshing teeth may be arranged to partially overlap with each other in a transition section between the high speed meshing teeth and the low speed meshing teeth, and may be arranged not to overlap with each other at all. When a transition between the high speed meshing teeth and the low speed meshing teeth cannot be performed smoothly due to meshing between both the high speed meshing teeth and the low speed meshing teeth caused by the partial overlapping therebetween, for example, such a constitution can be employed that both or one of the large diameter sector gear  33 Cb and the small diameter sector gear  33 Cc is provided independently of the driving shaft  33 Ca, and an independent gear is provided for the driving shaft such that a relative position between the large diameter sector gear  33 Cb and the small diameter sector gear  33 Cc can be restored.  
         [0042]     In the variable-speed gear mechanism, as shown in  FIG. 7 , a meshing state between the high speed meshing teeth (the large diameter gear  33 Bb and the small diameter sector gear  33 Cc) means that the door  2  is positioned in a door opening and closing section between a door open position (see  FIG. 8 ) that is the full open position and a pre-closed position that is a position just before the full closed position at which the door  2  becomes almost completely closed. On the other hand, in the variable-speed gear mechanism, as shown in  FIG. 7 , a meshing state between the low speed meshing teeth (the small diameter gear  33 Bc and the large diameter sector gear  33 Cb) means that the door  2  is positioned in a region between the pre-closed position and the full closed position (see  FIG. 9 ) at which the latch R becomes in the full-latch state. The pre-closed position means a position just before the latch R is transferred to the half-latch state while the door  2  is moved from the full open position to the full closed position. The pre-closed position corresponds to such a position of the door  2  that leaves the opening  1  open for, for example, about 30 centimeters, which likely to catch a part of human body.  
         [0043]     That is, when the door  2  is moved from the full open position to the full closed position, a rotation speed to be transmitted toward the door opening and closing mechanism is made relatively high in the section from the full open position to the pre-closed position by the high speed meshing teeth in the variable-speed gear mechanism, while the rotation speed of the driving motor  31  is kept constant, so that the door  2  is rapidly moved for closing in that section. Since rotation speed to be transmitted to the door opening/closing device is made relatively low in the section from the pre-closed position to the full closed position by the low speed meshing teeth in the variable-speed gear mechanism, the door  2  is moved slowly in that section. Therefore, it is possible to reduce such a concern that a part of body is caught by the door  2  even when the door  2  moves to the pre-closed position. Furthermore, since the torque for closing the door  2  becomes large in the section from the pre-closed position to the full closed position due to a low rotation speed of the driving motor, a closing force for transferring the latch R from the half-latch state to the full-latch state against the reaction force of the weatherstrip can be obtained. Accordingly, the closer mechanism for transferring the latch R from the half-latch state to the full-latch state is unnecessary, thereby reducing a weight and manufacturing cost of the door  2 .  
         [0044]     When the door  2  is moved from the full closed position to the full open position after releasing the latch R, since rotation speed to be transmitted to the door opening and closing mechanism is made relatively low in the full closed position to the pre-closed position by the low speed meshing teeth in the variable-speed gear mechanism, while rotation of the driving motor  31  is kept constant, the door  2  is opened slowly in that section. Since rotation speed to be transmitted to the door opening and closing mechanism is made relatively high in the section from the pre-closed position to the full open position by the high speed meshing teeth, the door  2  is opened rapidly in that section. Accordingly, it is possible to ease uncomfortable feeling due to rapid movement of the door  2  from the full closed position.  
         [0045]     In the door opening/closing device, therefore, since the rotation speed to be transmitted to the door opening/closing device is made variable by different meshing states in the variable-speed gear mechanism according to a position of the door  2 , a moving speed and a torque of the door  2  can be made variable without performing a special control on the driving unit  3  unlike the conventional technology.  
         [0046]     In addition to the above embodiment, for example, such a constitution can be adopted that low speed meshing teeth are additionally arranged in the region between the full open position and a pre-open position that is a position just before the full open position at which the door  2  becomes almost fully open. With such a constitution, the door can be opened or closed slowly at the full open position, and when a latch is arranged at the full open position, a torque for engagement with the latch can be obtained. In the door opening/closing device, therefore, a speed in which the door  2  is moved can be changed depending on a position of the door  2 .  
         [0047]     In the above embodiment, the constitution including the large diameter gear  33 Bb and the small diameter sector gear  33 Cc constituting the high speed meshing teeth, and the small diameter gear  33 Bc and the large diameter sector gear  33 Cb constituting the low speed meshing teeth has been explained as the variable-speed gear mechanism. However, the variable-speed gear mechanism is not limited to such a constitution. Though not shown, another embodiment including a rack and pinion mechanism can be constituted by providing racks with different tooth heights in parallel and combining the racks with pinions having different diameters meshing with the respective racks. In addition, various gear structure where rotation speed can be changed or made variable through a series of meshing states can be adopted as the variable-speed gear mechanism.  
         [0048]      FIG. 10  is a block diagram of a control system for the door opening/closing device. A controller  100  shown in  FIG. 10  integrally controls the door opening/closing device according to data or a program(s) stored in advance. The controller  100  is connected with the rotation sensor  35 , a pulse width modulation (PWM) control circuit  51 , an actuation switch  52 , the driving motor  31 , and the clutch  32 .  
         [0049]     The rotation sensor  35  outputs pulses having different phases according to driving of the driving motor  31 , as described above. The controller  100  receives different pulse signals according to the pulses with the different phases, thereby detecting a rotation speed and a rotation direction of the driving motor  31 , that is, an opening or closing position and an opening direction or closing direction of the door  2 .  
         [0050]     The PWM control circuit  51  is for controlling a voltage to be supplied to the driving motor  31 , where the rotation speed of the driving motor  31 , namely, moving speed of the door  2  can be changed by changing a time duration of voltage application.  
         [0051]     The actuation switch  52  is for an opening or closing actuation of the door  2 . The actuation switch includes a main switch, a driver seat switch, a rear seat switch, an inner handle switch, an outer handle switch, and a keyless switch. The main switch is for making opening or closing control of the door opening/closing device effective, and the door opening/closing device can be controlled for opening and closing, only when the main switch is on. Accordingly, when the main switch is off, the door  2  must be opened or closed manually. Each of the other switches outputs an instruction signal for moving or stopping the door  2 .  
         [0052]     The controller  100  adjusts rotation of the driving motor  31  such that rotation speed to be transmitted to the door opening/closing device gradually changes in the section where switching between meshing states of the meshing teeth in the variable-speed gear mechanism. Specifically, as shown in  FIG. 11 , when the high speed meshing teeth (the large diameter gear  33 Bb and the small diameter sector gear  33 Cc) are in a meshing state, and the low speed meshing teeth (the small diameter gear  33 Bc and the large diameter sector gear  33 Cb) are in a meshing state, the door  2  is moved, while rotation of the driving motor  31  is kept constant. As regards the pre-closed position where switching between meshing states of respective meshing teeth occurs, the controller  100  reduces rotation speed of the driving motor  31  to make moving speed of the door  2  slow at a position where the high speed meshing teeth are in the meshing state. Furthermore, the controller  100  increases rotation speed of the driving motor  31  to make moving speed of the door fast at a position where the low speed meshing teeth are in a meshing state. Accordingly, as shown in  FIG. 11 , the moving speed of the door  2  can be changed smoothly in the section (near door closed position that is the pre-closed position) where switching between the high speed meshing teeth and the low speed meshing teeth occurs. The controller  100  can control the driving motor  31  during door-closing or door-opening actuation such that the motor rotation speed (door moving speed) gradually changes from a low speed to a high speed at a starting time of actuation, and the motor rotation speed (door moving speed) gradually changes from a high speed to a low speed at a terminating time of actuation. Thus, the whole actuation can be performed smoothly.  
         [0053]     While in the embodiment described above, the example where the door  2  is the back door has been explained, the present invention is not limited to the example. The invention is applicable to a trunk lid, a side hinge door or the like. Furthermore, the invention can be similarly adopted for a sliding door of a gear type.  
         [0054]     According to the embodiments described above, a moving speed and a torque of a door can be changed without a special control of a driving motor.  
         [0055]     Moreover, according to the embodiments described above, the moving speed is smoothly changed.  
         [0056]     Furthermore, according to the embodiments described above, it is possible to ease fear that a part of body of a user can be caught in the door.  
         [0057]     Moreover, according to the embodiments described above, a force against a reaction force of the weatherstrip can be obtained. Accordingly, a closer mechanism for transferring a latch from the half-latch state to the full-latch state is unnecessary, thereby reducing a weight and manufacturing cost of the door.  
         [0058]     Furthermore, according to the embodiments described above, a rotational speed is relatively high in the section from the full open position to the pre-closed position, thereby closing the door rapidly.  
         [0059]     Although the invention has been described with respect to a specific embodiment for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art which fairly fall within the basic teaching herein set forth.

Summary:
A device for controlling a door operated by a motor includes an opening/closing mechanism that opens and closes the door, and a gear mechanism that includes a plurality of tooth units each of which has different mesh and that conveys a torque of the motor to the opening/closing mechanism. The tooth units include a low-torque tooth unit that convey a relatively low torque, and a high-torque-tooth unit that conveys a relatively high torque. The torque conveyed to the opening/closing mechanism is changed by selecting a tooth unit based on a position of the door at the time of starting an opening or closing operation of the door.