Patent Publication Number: US-8117937-B2

Title: Automobile door-lock drive device

Description:
TECHNICAL FIELD 
     The present invention relates to an automobile door-lock drive device housing within a case a worm gear provided on an output shaft of an electric motor and a wheel gear engaging with this worm gear and performing a switching operation of a lock mechanism using a torque of this wheel gear. 
     BACKGROUND ART 
     Conventionally, automobile door-lock drive devices have been as specified in patent document 1. In this patent document 1, a worm-gear type drive gear driven by a motor (electric motor) is engaged with a reduction gear in the form of a wheel gear, a torque from this reduction gear is further engaged with a sector gear, and a torque of this sector gear is transmitted to an output gear.
     Patent document 1: JP H05-33541   

     DISCLOSURE OF INVENTION 
     Problem to be Solved by the Invention 
     In devices provided with a reducing mechanism transmitting a torque of an electric motor from a worm gear to a wheel gear such as specified in patent document 1, an output shaft of the electric motor and the worm gear are often fixed by connection. 
     To give one such example, as shown in  FIG. 6 , a fixing-by-fitting configuration wherein an output shaft  02  of an electric motor  01  is inserted to a position whereat contact is made with an inner end of a fitting hole  011 C of a worm gear  011  has been used. 
     To explain in more detail, freely transmitting torque is made possible by, for example, D-cutting the output shaft  02  or forming a spline fitting section on the output shaft  02  and forming the fitting hole  011 C of the worm gear  011  so as to have a shape corresponding thereto. For example, this output shaft  02  is fixed by driving into the worm gear  011 , or the output shaft  02  and the worm gear  011  are each completely fixed using a pin, etc. passing through both thereof. Many configurations reliably transmitting a torque of the output shaft  02  to the worm gear  011  in this way have been used. 
     Furthermore, in configurations wherein the output shaft  02  and the worm gear  011  are fixed by connection in this way, the relative positioning of the worm gear  011  and the wheel gear  012  must be properly maintained. For this reason, configurations wherein, as shown in the same figure, an end section  04  of the electric motor  01  at a side opposite to that of the worm gear  011  and an end section of a shaft section  011 A of the worm gear  011  at a side opposite to that of the electric motor  01  are supported so as to come into contact with a case  020  are also used. 
     In this type of automobile door-lock drive device, locking is carried out and locking is released using an operation of the electric motor. However, when this operation of the electric motor has been stopped, a dynamic inertial force of the wheel gear acts powerfully on the worm gear in a direction of thrust immediately after this stopping. For this reason, the electric motor connected to the worm gear makes powerful contact with the case, and in some cases, an impact sound has been transmitted to a door. 
     A cushioning member may be used in order to curb this impact sound. However, when rubber-type material is used in the support system for the motor and worm gear, the number of parts increases and cost rises. Furthermore, it becomes impossible to maintain a high degree of accuracy of the relative positions of the worm gear and the wheel gear, and practical usage is difficult. 
     The object of the present invention is to provide a reasonable configuration of a device capable of reducing the impact sound generated upon stopping of the electric motor while maintaining high relative positioning of the worm gear and the wheel gear. 
     Means for Solving Problems 
     The characteristic feature of the present invention is that, in an automobile door-lock drive device housing a worm gear provided on an output shaft of an electric motor and a wheel gear engaging with this worm gear in a case and performing a switching operation of a lock mechanism using a torque of this wheel gear, a support member making contact while interposed between the worm gear and the electric motor is provided, a transmission section including the output shaft of the electric motor and the worm gear pivotally supported on the output shaft is provided, and the transmission section allows relative motion of the output shaft and the worm gear. 
     When the electric motor stops and a force resulting from dynamic inertia of the wheel gear acts on the worm gear in a direction of thrust, this configuration makes it possible for the support member to bear the force in the direction of thrust of the worm gear. Furthermore, this force in the direction of thrust is not transmitted to the output shaft. In addition, provision of a support member makes it possible for a position of the worm gear in a direction of an axis of the output shaft to be maintained. As a result, the relative positioning of the worm gear and the wheel gear can be maintained high. Furthermore, despite the fact that no cushioning member is used, a reasonable configuration of a device capable of reducing impact sound generated when the electric motor stops is realized. 
     In accordance with the present invention, the transmission section may be configured such that the output shaft is fitted into a fitting hole formed in the worm gear so as to be capable of freely transmitting torque and of freely moving relatively in a direction of an axis, and a tip of the output shaft and an inner end of the fitting hole may be separated in a direction of the axis. 
     As a result of this configuration, for example, a gap is formed by D-cutting the output shaft, forming the fitting hole of the worm gear with a shape fitting the D-cut, and separating a tip of the output shaft and an inner end of the fitting hole in a direction of the axis. When using a relatively-simple configuration of this kind, there is no need to use a complicated configuration and costs can be reduced. 
     In accordance with the present invention, the support member may include a two-pronged section forming a recess wherein the output shaft is inserted. 
     This configuration makes it possible for deflection of the output shaft in a radial direction to be reduced since the output shaft is inserted into the recess of the two-pronged section. 
     In accordance with the present invention, the support member may include a fitting section wherein an end section of the electric motor on the output-shaft side thereof is fitted and a receiving section receiving an end section of the worm gear on the electric-motor side thereof so as to be capable of rotating freely, formed as one with the two-pronged section. 
     This configuration makes it possible for a degree of accuracy of the relative positions of the electric motor and the worm gear to be increased since an end section of the electric motor is fitted into one of the fitting sections formed in the support section and the worm gear is supported so as to be capable of rotating freely by the receiving section formed in the support section. 
     In accordance with the present invention, a support member configured as a separate member to the case may be mounted on an inner section of the case. 
     For example, when the case is manufactured using a resin or metal mold, this configuration eliminates the need for a complicated configuration to be employed in order to integrally form the support member. Even changes of the specification of the electric motor or the worm gear can be supported simply by changing the configuration of the support member. 
     In accordance with the present invention, the support member may be formed inside the case as one with the case. 
     For example, when the case is manufactured using a resin or metal mold, this configuration makes it possible for only integral forming of the support member to be required. 
     In accordance with the present invention, a gear support section receiving an end section of the worm gear on a side opposite to that of the electric motor so as to be capable of rotating freely may be provided in the case, and a cushioning member making contact with the end section of the worm gear supported by this gear support section from a direction parallel to the axis may be provided in the gear support section. 
     This configuration makes it possible not only for the accuracy of support of this worm gear to be increased by supporting the worm gear in the support section, but even in cases where the worm gear moves in a direction of approach to the gear support section due to an action of a force from the wheel gear upon stopping of the electric motor, for this motion to be reduced and stopped by the cushioning member and the occurrence of impact sound to be curbed. 
     In accordance with the present invention, a cushioning member making contact with the end section of the worm gear supported by the receiving section from a direction parallel to the axis may be provided in this receiving section. 
     Even in cases where the worm gear moves in a direction of approach to the electric motor upon stopping of the electric motor, this configuration makes it possible for this motion to be reduced and stopped by the cushioning member and the occurrence of impact sound to be curbed. 
     In accordance with the present invention, a cushioning member may be provided between a tip of the output shaft and an inner end of the fitting hole. 
     Even in cases where the output shaft and the worm gear move in a direction so as to approach relatively due to an external force acting on the worm gear, this configuration makes it possible for this motion to be reduced and stopped by the cushioning member and the occurrence of impact to be curbed. 
     In accordance with the present invention, a bearing section may be formed as a protrusion on the electric motor at an end thereof opposite to that of the output shaft, a motor support section wherein this bearing section is supported by fitting may be provided in the case, and a cushioning member making contact with the bearing section supported by this motor support section from a direction parallel to the axis may be provided in this motor support section. 
     Even in cases where the electric motor moves so as to become separated from the worm gear, this configuration makes it possible for this motion to be reduced and stopped by the cushioning member and the occurrence of impact to be curbed. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     The following is a description of the preferred embodiments of the present invention, with reference to the drawings. 
     Overall Configuration 
     As shown in  FIG. 1  to  FIG. 4 , a reduction mechanism including a worm gear  11  pivotally supported on an output shaft  2  of an electric motor  1  and a wheel gear  12  engaging with this worm gear  11  is housed in a case  20 . The wheel gear  12  is supported by the case  20  via a support shaft  13 . An arm  15  having a recess  15 A operated by a pin  14  formed on this wheel gear  12  as a protrusion parallel to the support shaft  13  is housed in the case  20 . An operation shaft  16  rotating as one with this arm  15  is pivotally supported by the case  20 , and an operation system transmitting an operation force from an arm (not shown) provided in this protrusion section to a lock mechanism (not shown) is formed. An automobile door-lock drive device operating the lock mechanism is formed from these. 
     This door-lock drive device is provided inside the door of a vehicle such as an automobile, and operations switching the lock mechanism between a locked condition and an unlocked condition can be achieved through reduction of a torque of the electric motor  1  and transmission thereof to the operation shaft  16 . 
     The electric motor  1  is provided with bearing sections  3 ,  4  at a front-end side and a rear-end side of the motor body as a bearing means for the output shaft  2  rotating as one with an internal rotor (not shown). This output shaft  2  passes through the bearing section  3  of the front-end side. A protrusion section of this output shaft  2  is formed by D-cut machining so as to have a D-shaped cross section. 
     The output shaft  2  and the worm gear  11  are disposed on the same axis X. This worm gear  11  includes a shaft section  11 A and a gear section  11 B formed at a central position in the direction of the axis X on this shaft section  11 A. A fitting hole  11 C wherein the output shaft  2  is fitted so as to be capable of freely transmitting torque is formed at one end-section side. 
     The output shaft  2  having been D-cut in this way and the fitting hole  11 C form a transmission section wherein a torque of the output shaft  2  is transmitted to the worm gear  11 , and in addition, the output shaft  2  and the worm gear  11  are capable of freely moving relatively in the direction of the axis X. Furthermore, with the electric motor  1  and the worm gear  11  supported by the case  20 , as shown in  FIG. 3  and  FIG. 4 , a tip of the output shaft  2  and an inner end of the fitting hole  11 C are separated in the direction of the axis X and a gap therebetween of a distance D is formed. 
     This transmission section may be configured by, for example, forming a spline section on an outer surface of the output shaft  2  and a structure fitting with the spline section in the fitting hole  11 C, or by embedding a key in a channel formed parallel to a direction of an axis of the output shaft  2  and forming a channel into which this key enters in a hole section of the worm gear  11 . 
     Support Structure 
     A motor support section  21  into which the bearing section  4  at the rear-end side of the electric motor  1  is fitted and a gear support section  22  into which the shaft section  11 A of the worm gear  11  at an end thereof opposite to that of the electric motor is fitted are formed on an inner surface of the case  20 . Furthermore, a support member  30  touching (making contact with) the shaft section  11 A of the worm gear  11  at an end section thereof on the side of the electric motor is mounted on an inner surface of the case  20 . 
     The support member  30  has a two-pronged member  31  including a recess  31 A wherein the output shaft  2  is fitted, and a receiving section  32  supporting the shaft section  11 A of the worm gear  11  so as to be capable of freely rotating and a fitting section  33  into which the bearing section  3  at the front-end side of the electric motor  1  (example of an end section at the output-shaft side of the electric motor  1 ) has been fitted, formed as one. 
     As shown in  FIG. 5 , a mounting section  34  is provided on this support member  30 , and this mounting section  34  is fixed by fitting into a channel-shaped section  23  formed in the case  20 . Although a configuration whereby this support member  30  is fixed by fitting thereof into the channel-shaped section  23  is used, a means of fixing through bonding by melting the plastic at a contact point using a laser beam or a fixing configuration using adhesive or a screw, etc. may be used. 
     In particular, the support member  30  may, upon formation of the case  20 , be formed as one with the case  20  using the same material. By forming as one with the case  20  in this way, the strength of this supporting member  30  can be raised. 
     Function of Support Structure 
     As the electric motor  1  and the worm gear  11  are supported by the case  20  in this way, upon driving of the electric motor  1 , the torque from the output shaft  2  is transmitted from the worm gear  11  to the wheel gear  12 , and the pin  14  of this wheel gear  12  drives the arm  15  via the recess  15 A. In this way, the lock mechanism can be locked and unlocked using the rotation of the arm  15 . After operation of this electric motor  1 , the dynamic inertia of the wheel gear  12  acts on the worm gear  11  in a direction of thrust when the electric motor  1  has been stopped. However, as force from the worm gear  11  is borne by the support member  30 , the phenomenon of the electric motor  1  making powerful contact with the case  20  is prevented and impact sound is not generated. 
     In particular, by supporting an end section of the shaft section  11 A of the worm gear  11  in the receiving section  32  formed in the support member  30  so as to be capable of rotating freely and supporting the bearing section  3  at the front-end side of the electric motor  1  in a fitting condition in the fitting section  33  formed in this support member  30 , a high degree of accuracy of the relative positions of the worm gear  11  and the electric motor  1  can be maintained. 
     Other Embodiments 
     In addition to the above-explained embodiment, the present invention may be configured as follows. 
     (a) A configuration wherein an end section of the output shaft  2  has a member of a large diameter, a fitting hole is formed parallel to the direction of the axis X on this, and the worm gear  11  has a shaft-shaped member inserted into this fitting hole so as to be capable of freely transmitting torque may be provided as a transmission section transmitting torque from the output shaft  2  of the electric motor  1  to the worm gear  11 . 
     (b) A mechanism assembling a simple gear and crank mechanism to a transmission system transmitting torque from the worm gear  11  to the operation shaft  16  may be used, or a non-circular gear may be used to convert rotation motion from the electric motor  1  into intermittent motion. 
     (c) As shown in  FIG. 7 , a cushioning member  41  of rubber, etc. may be provided to stop the motion of the worm gear  11  in a direction of approach to the gear support section  22 . In the event that such a configuration is used, even if the worm gear  11  moves in a direction of the gear support section  22  upon stopping of the wheel gear  12 , this motion is reduced and stopped by the cushioning member  41 , and the occurrence of impact is curbed. 
     (d) As shown in  FIG. 8 , a cushioning member  42  of rubber, etc. may be provided to stop the motion of the worm gear  11  in a direction of approach to the receiving section  32  (a direction of approach to the electric motor  1 ). In the event that such a configuration is used, even if the worm gear  11  moves in a direction of the receiving section  32  upon stopping of the wheel gear  12 , this motion is reduced and stopped by the cushioning member  42 , and the occurrence of impact is curbed. 
     (e) As shown in  FIG. 9 , a cushioning member  43  of rubber, etc. may be provided in a gap between a tip of the output shaft  2  of the electric motor  1  and an inner end of the fitting hole  11 C of the worm gear  11 . In the event that such a configuration is used, when either of the electric motor  1  or the worm gear  11  moves in a direction of approach to the other thereof, this motion is reduced and stopped by the cushioning member  43 , and the occurrence of impact is curbed. 
     (f) As shown in  FIG. 10 , a cushioning member  44  of rubber, etc. may be provided in the motor support section  21  supporting the bearing section  4  at the rear-end side of the electric motor  1  to stop the motion of the electric motor  1  towards this motor support section  21 . In the event that such a configuration is used, even when force acts so as to move the electric motor  1  in the direction of the motor support section  21 , this motion is reduced and stopped by the cushioning member  44 , and the occurrence of impact is curbed. 
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1 : Partial cut-out front elevation view of a drive device. 
       FIG. 2 : Perspective view of an electric motor and a worm gear separated from a case. 
       FIG. 3 : Cross-sectional view showing a support condition of an electric motor and a worm gear. 
       FIG. 4 : Cross-sectional view showing a support condition of a support section. 
       FIG. 5 : Cross-sectional view of an electric motor and a worm gear separated from a case. 
       FIG. 6 : Cross-sectional view showing a conventional support mechanism of an electric motor and a worm gear. 
       FIG. 7 : Cross-sectional view showing a support condition of an electric motor and a worm gear, with a cushioning member in the gear support section. 
       FIG. 8 : Cross-sectional view showing a support condition of an electric motor and a worm gear, with a cushioning member in the receiving section. 
       FIG. 9 : Cross-sectional view showing a support condition of an electric motor and a worm gear, with a cushioning member between a tip of the output shaft and an inner end of the fitting hole. 
       FIG. 10 : Cross-sectional view showing a support condition of an electric motor and a worm gear, with a cushioning member in the motor support section. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           1 . Electric motor 
           2 . Output shaft 
           4 . Bearing section 
           11 . Worm gear 
           11 C. Fitting hole 
           12 . Wheel gear 
           20 . Case 
           21 . Motor support section 
           22 . Gear support section 
           30 . Support section 
           31 . Two-pronged member 
           31 A. Recess 
           32 . Receiving section 
           33 . Fitting section 
         X. Axis