Patent Publication Number: US-6901704-B2

Title: Vehicle rear gate opening and closing apparatus

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a vehicular rear gate opening and closing apparatus whose upper end is pivotally connected with a vehicle body so as to swing up and down and more particularly to a rear gate capable of opening and closing in two ways by an actuator or by hand. 
   2. Discussion of Prior Art 
   As shown in  FIG. 11 , generally a rear gate  102  disposed in the rear of a vehicle is a lid swinging up and down for opening and closing an opening  101 . The rear gate  102  is at the upper end thereof secured to a hinge arm  103  rotatably supported by an upper edge of the opening  101  of a vehicle body  100 . 
   A gas stay  105  is connected between a side edge of the rear gate  102  and a side edge  104   a  of the opening  101  formed along a rear pillar  104 . The gas stay  105  has a piston rod  105   a  biased in an axial (longitudinal) direction by sealed gas pressure. When the rear gate  102  opens or closes, the gas stay  105  expands or contracts according to an opening or closing angle of the rear gate  102  and the biasing force applies an assist force to the piston rod  105   a , thereby an opening or closing effort of the rear gate  102  can be reduced. 
   According to a rear gate opening and closing mechanism disclosed in Japanese Patent Application Laid-open No. Toku-Kai-Hei 5-280242 and also shown in  FIG. 12 , the rear gate  112  has a hinge arm  113  at the upper end thereof and the hinge arm  113  is pivotally supported by a vehicle body  110 . The hinge arm  113  has a curved section  114  formed in such a manner as extending forwardly from a pivoting point P of the hinge arm  113 , making a U-turn and then extending backwardly. The curved section  114  communicates with a rear gate fitting section  115  to which the rear gate  112  is secured. A rod  116  is pivotally connected at a boss section  117  provided at the rear end thereof with a slightly lower part of the curved section  114  than the pivoting point P. A front end of the rod  116  is slidably fitted to a supporting hole  118  and a coil spring  119  is interposed between a rear spacer  120  and the boss section  117 . 
   According to the rear gate structure shown in  FIG. 11 , the gas stay  105  laid between the rear gate  102  and the side edge  104   a  provides an assist force when the rear gate  102  operates to open or closed and as a result the operating effort of the rear gate  102  can be reduced. 
   Referring to  FIG. 12 , when the rear gate  112  is wings upward, the hinge arm  113  rotates integrally with the rear gate  112  around the pivoting point P. Then, since the coil spring  119  pushes the curved section  114 , a rotating force is applied to the hinge arm  113 , thereby the operating effort when opening the rear gate  112  can be reduced. 
   However, there is a fear that the gas stay  105  which is provided between the rear gate  102  and the side edge  104   a  hinders loading or unloading works through the opening  101 . Further, since the gas stay  105  is exposed to the compartment, there is a problem that the interior space is limited as much and also there is an aethetic problem. To solve these problems, one idea is to accommodate the gas stay between the rear gate  102  and the side edge  104   a  of the opening  101 . Since the diameter of the gas stay is determined by gas pressure for supporting the weight of the rear gate, the thickness of the pillar in which the gas stay is housed is dependant upon the rear gate. Further, since the stroke of the gas stay is determined by the specification of the rear gate, the straight portion of the rear pillar for accommodating the gas stay has an effect on the styling of the rear pillar itself. That is, the freedom of the rear design of the vehicle is restricted. 
   According to the rear gate structure disclosed by Toku-Kai-Hei 5-280242, when the rear gate  112  swings upward to open, the curved section  114  of the hinge arm  113  is pushed by the coil spring  119 . As a result, the hinge arm  113  has a rotating force to reduce the operating effort of an operator. Further, since the gas stay is not disposed between the side edge of the opening and the rear gate  112 , the freedom of designing of the rear pillar, the rear gate  112  and the like is enlarged. 
   On the other hand, the rear gate structure according to Toku-Kai-Hei 5-280242 is designed so as to open and close by lifting up or pushing down an outer handle of the rear gate by hand from outside of the vehicle. The opening and closing effort of the rear gate is generally troublesome to the operator and particularly, when it rains heavily and his or her hands are full with baggage, it is desirable that an opening and closing apparatus for automatically opening and closing the rear gate can be operated by the operator while he or she stays in the passenger compartment. 
   SUMMARY OF THE INVENTION 
   It is a first object of the present invention to provide a compact rear gate opening and closing apparatus capable of automatically opening and closing a rear gate without hindering an interior space of the passenger compartment. It is a second object of the present invention to provide a rear gate opening and closing apparatus capable of opening and closing the rear gate not only automatically but also by hand. It is a third object of the present invention to provide a rear gate opening and closing apparatus capable of properly regulating the opening and closing speed. 
   In order to achieve the first object, the rear gate opening and closing apparatus comprises a power source means for producing a power to actuate the rear gate, a slider for transforming the power into a reciprocating motion and traveling in the longitudinal direction of a vehicle, a hinge arm provided at the upper end of the rear gate for pivotally connected with the vehicle body, a connecting rod for interlocking between the slider and the hinge arm and for transmitting the reciprocating motion to the hinge arm, a mounting base for supporting the power source means and the slider, a mounting base installing means for detachably installing the mounting base in a space formed by a rear rail, a side rail and an under roof of the vehicle, and a gas stay extending in the longitudinal direction of the vehicle, provided between the side rail and the hinge arm and disposed at approximately the same height as and in parallel with the connecting rod for biasing the rear gate in an opening direction. 
   To attain the second object of the present invention, The rear gate opening and closing apparatus comprise a clutch means for disconnecting the power source means with the slider so as to enable an operator to open or close the rear gate by hand. 
   Further, to attain the third object, the rear gate opening and closing apparatus comprises a position detecting means for detecting a position of the rear gate and for outputting a detection signal thereof, an operating means for operating an opening and closing motion of the rear gate and a control means for automatically opening and closing the rear gate based on an operating signal from the operating means and the detection signal from the position detecting means. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective rear view showing a vehicle having a rear gate opening and closing apparatus according to the present invention; 
       FIG. 2  is a plan view showing a drive unit of a rear gate opening and closing mechanism according to a first embodiment of the present invention; 
       FIG. 3  is a side view showing a drive unit of a rear gate opening and closing mechanism according to the present invention; 
       FIG. 4  is an exploded view of a drive unit of a rear gate opening and closing apparatus according to the present invention; 
       FIG. 5  is a sectional view taken along a line V—V of  FIG. 2 ; 
       FIG. 6  is a sectional view taken along a line VI—VI of  FIG. 2 ; 
       FIG. 7  is a sectional view taken along a line VII—VII of  FIG. 2 ; 
       FIG. 8  is a plan view showing a drive unit of a rear gate opening and closing mechanism according to a second embodiment of the present invention; 
       FIG. 9  is a block diagram of a control apparatus of a rear gate opening and closing apparatus according to a second embodiment of the present invention; 
       FIG. 10  is an explanatory view showing a control strategy of a rear gate opening and closing apparatus; 
       FIG. 11  is a perspective rear view of a vehicle having a rear gate structure according to a prior art; and 
       FIG. 12  is a side view showing a rear gate structure according to a prior art. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention will be described more in detail by reference to the accompanying drawings. 
   Referring now to  FIG. 1 , a vehicle body  10  is provided with a rear opening  13  having a side edge  13   a  at each side of the body  10  and an upper edge  13   b . A roof  12  is connected at the rear end thereof with a rear gate  20  for pivotally opening and closing the opening  13  through a hinge arm  23 . The rear gate  20  is rotatably swung up and down by an opening and closing apparatus  30 . 
   The opening and closing apparatus  30 , especially the hinge arm  23  and the drive unit  31 , will be described by reference to  FIGS. 2  to  7 . In the drawings, an arrow-marked “F” denotes a front direction of the vehicle, an arrow-marked “IN” denotes an inner direction of the vehicle and an arrow-marked “OUT” denotes an outer direction of the vehicle. 
     FIG. 2  shows a drive unit of a rear gate opening and closing mechanism according to a first embodiment of the present invention and  FIG. 3  shows a drive unit of the rear gate opening and closing mechanism. In  FIGS. 2 and 3 , the vehicle body  10  and the rear gate  20  are shown by two-dots chain lines. 
   The hinge arm  23  is rotatably supported at the end boss  23   a  thereof by a pivot  22  secured to an hinge base  21  which is attached to the neighborhood of the rear end of a roof  12 . Describing the state where the rear gate  20  is closed, the hinge arm  23  extending downwardly and forwardly from the end boss  23   a , forms a bent section  24 . The bent section  24  extends backwardly being bent in a circle around the pivot  22 , penetrates through a hinge arm penetrating hole  23 A provided in a rear rail  14  and projects the rear end thereof outside. The rear end has a rear gate mounting bracket  25  for mounting the rear gate  20  and the front end of the bent section  24  has a connecting rod connection section  26  and a gas stay connection section  27 . 
   The opening and closing apparatus  30  has the drive unit  31  and a gas stay apparatus  50  for assisting the operation of the drive unit  31 . As shown in  FIGS. 2 and 4 , the drive unit  31  is provided with a mounting base  32  having a base plate  32 A with a slot  32   a  longitudinally spaced, a rear flange  32   b  and a side flange  32   c  for reinforcing the base plate  32 A. 
   Further, a power unit module  40  as shown in  FIG. 4  is mounted on the top surface of the base plate  32 A of the mounting base  32 . 
   The power unit module  40  includes a motor  41  operative forwardly and reversely and a gear box (not shown) for converting the rotating motion of the motor into the reciprocating motion, through which a slider  45  disposed under the base plate  32 A is reciprocatingly moved in the longitudinal direction along the slot  32   a.    
   The slider  45  is roughly rectangular in configuration and has a U-shaped cross section. The slider  45  is rotatably connected at the side face thereof with a connecting rod  46  by a bolt and nut  47 . Further, the connecting rod  46  is rotatably connected at the rear end thereof with the connecting rod connection section  26  of the hinge arm  23  through a ball joint  48 . 
   When the motor  41  in the power unit module  40  operates, the slider  45  travels backwardly along the base plate  32 A to push backwardly the connecting rod connection section  26  of the hinge arm  23  through the connecting rod  46  and as a result the hinge arm  23  rotates around the pivot  22  outwardly through the hinge arm penetrating hole  23 A. As a result, the rear gate  20  supported by the rear gate mounting bracket  25  swings in a direction of opening the opening  13 . On the other hand, when the slider  45  travels forwardly along the base plate  32 A, the hinge arm  23  rotates around the pivot  22  inwardly to swing the rear gate  20  in a direction closing the opening  13 . 
   The mounting base  32  on which the power unit module  40 , the slider  45  and the like are disposed, is secured to roof members, rear rail  14 , brace  15  and side rail  16 , respectively so as to hold the base plate  32 A horizontally. 
   The connecting section of the mounting base  32  and the rear rail  14  will be described by reference to  FIG. 5  showing a cross section taken by the line I—I. 
   The rear rail  14  has a hollow cross section formed by an outer rear rail  14 A extending in the widthwise direction of the vehicle and having a L-shaped cross section and an inner rear rail  14 B disposed opposite to the outer rear rail  14 A. The inner rear rail  14 B is reinforced by a reinforcement  14 C covering the upper surface of the inner rear rail  14 B. The rear rail  14  is connected at left and right ends thereof with the rear end of left and right side rails  16  and is connected at the upper surface of the outer rear rail  14 A with the rear end of a roof panel  17 , respectively. 
   Further, a plate-shaped rear bracket  34  is spot-welded to the under surface of the inner rear rail  14 B, extending therefrom forwardly. The rear section of the base plate  32 A of the mounting base  32  is mounted on the upper surface of the front end of the rear bracket  34  and detachably connected by a bolt  14   a  and a nut  14   b.    
   The mounting base  32  is connected at the middle section thereof with the brace  15  through a first inner bracket  35  and a second inner bracket  36 , respectively. The brace  15  is, as shown in  FIG. 6 , a belt like reinforcement member provided under the roof panel  17  across left and right side rails  16  (in the drawing, only left side is shown). The side rail  16  has a hollow cross section extending in the longitudinal direction of the vehicle and formed by L-shaped or C-shaped outer side rail  16 A and inner side rail  16 B reinforced by a reinforcement  16   c.    
   The first inner bracket  35 , as shown in  FIGS. 4 and 6 , has plate-like configuration and mounting surfaces  35   b ,  35   c  are bent at the upper end of a connecting surface  35   a  of the first inner bracket  35  and project in the outer and inner directions, respectively so as to form a T-shaped cross section. These mounting surfaces  35   b  and  35   c  are connected to the under surface of the brace  15  by welding. 
   On the other hand, as shown in  FIG. 4 , the second inner bracket  36  having a L-shaped cross section includes a connecting surface  36   a  and a mounting surface  36   b . The mounting surface  36   b  is connected with the base plate  32 A of the mounting base  32 . By connecting the connecting surface  36   a  with the connecting surface  35   a  of the first inner bracket  35  by means of bolts  15   a  and nuts  15   b , the mounting base  32  can be detachably connected with the brace  15 . 
   Describing the front portion of the mounting base  32 , the mounting base  32  is connected with the side rail  16  through an outer bracket  37 . The outer bracket  37  is connected at the rear edge thereof with the front edge of the base plate  32 A of the mounting base  32  and at the same time its outer edge extends in the forward direction along the side rail. Further, the outer bracket  37  forms a triangular configuration with a base lying along the front edge of the base plate  32 A and has a reinforcement flange  37   b  bent upward along the oblique side of the triangle and a mounting flange  37   c  bent downward along the other base of the triangle. 
   The connecting section of the mounting base  32  and the side rail  16  is shown in FIG.  7 . The mounting flange  37   c  of the outer bracket  37  is connected by a bolt  16   a  and a nut  16   b  with an inner side rail  16 B of the side rail  16 . That is, the front portion of the mounting base  32  is detachably connected with the side rail  16 . Thus, an accommodation space for the power module unit  40  is formed at the corner enclosed by the rear rail  14  and the side rail  16  under the roof. 
   A gas stay apparatus  50  is disposed between the mounting base  32  and the side rail  16  at almost the same height as and approximately in parallel with the connecting rod  46  and has a gas spring  51  jointing the side rail  16  and the hinge arm  23 . 
   The gas spring  51  is rotatably connected at one end thereof with a bracket  53  secured to the side rail  16  through a ball joint  54  and is also rotatably connected with at the other end thereof, that is, an end of a position rod  51   a , with the gas stay connection section  27  of the hinge arm  23  through a ball joint  55 . 
   Accordingly, when a switch provided on an instrument panel is turned on to open the rear gate  20 , the slider  45  is driven by the motor  41  to travel backward. Then, the connecting rod connection section  26  of the hinge arm  23  is pushed backward through the connecting rod  46  and the hinge arm  23  rotates about the pivot  22  together with the rear gate  20 . As a result, the end of the piston rod  51   a  of the gas spring  51  rotates about the pivot  22  to draw a circle. The piston rod  51   a  is biased in the projecting direction by the pressure of sealed gas. 
   When the rear gate  20  is fully closed, the downward force due to the weight of the rear gate  20  is designed so as to be larger than the force pushing the rear gate  20  upward due to the biasing force of the gas spring  51 . 
   Further, as shown in  FIG. 10 , when the rear gate  20  starts to open from the fully closing position, a dead point where the weight of the rear gate  20  balances with the biasing force of the gas spring  51  is found. A self closing zone where the weight of the rear gate  20  is larger than the biasing force of the gas spring  51  and the rear gate closes without any operating force applied is formed between the fully closing position and the dead point. On the other hand, a self opening zone where the biasing force of the gas spring  51  is larger than the weight of the rear gate  20  is formed between the dead point and the fully opening position. 
   Accordingly, since the power unit module  40  and the slider  45  which have relatively large weight and are subjected to the reaction force from the rear gate  20 , is mounted on the mounting base  32  and the mounting base  32  is secured to the steady roof members such as the rear rail  14 , the brace  15 , the side rail and the like, the power unit module  40 , the slider  45 , the connecting rod  46  interlocking the slider  45  and the hinge arm  23  can be supported in a stable condition. 
   Further, since the mounting base  32  is detachably connected with the rear rail  14 , the brace  15  and the side rail  16  by the bolts and nuts, it is possible first to attach the power unit module  40 , the slider  45  and the like to the mounting base  32  and then to mount this subassembly to the rear rail  14 , the brace  15  and the side rail  16 , thereby the installation work of the rear gate opening and closing apparatus  30  is simplified. As a result, the productivity at the production stage or the workability at the repairing stage is can be enhanced. 
   Further, since the gas spring  51  is longitudinally disposed at approximately the same height as and in parallel with the connecting rod  46 , the opening and closing apparatus  30  comprising the drive unit  31  and the gas stay apparatus  50  can be formed compactly within a limited vertical space. Further, since the opening and closing apparatus  30  is efficiently accommodated in a space enclosed by the rear rail  14 , the side rail  16  and the roof, the passenger compartment space can be utilized effectively. 
   Further, since the gas spring  51  is not disposed between the side edge  13   a  and the rear gate  20 , the rear pillar, the rear gate  20  and the like can be freely styled and designed. 
     FIG. 8  shows a rear gate opening and closing mechanism according to a second embodiment. The power unit module  40  includes the motor  41  described before, a clutch  42  and an encoder  43 . Further, an electronic control unit (hereinafter, referred to as ECU)  60  is disposed in the vehicle and makes an automatic opening and closing control of the rear gate  20 . 
   The clutch  42  connects the motor  41  with the slider  45  when it is energized and the connection is released when it is deenergized. When an operator wants to open or close the rear gate  20  manually, a handle switch  62  which will be described hereinafter is operated and the ECU  60  detects this to deenergize the clutch  42 . When the clutch is deenergized, the motor  41  is disengaged with the slider  45  and the rear gate  20  can be operated to open or close manually. On the other hand, when the operator wants to open or close the rear gate  20  automatically, the clutch  42  is energized to engage the motor  41  with the slider  45 . As a result, the rear gate can be opened or closed automatically. 
   The encoder  43  provided in the power unit module  40  detects the position of the slider  45  and outputs the positional signal to the ECU  60 . 
   As shown in  FIG. 9 , the ECU  60  is connected with a warning buzzer  44 , a latch switch  61 , a handle switch  62 , an operating switch  63  and an auto closure  65 . The operating switch  63  is provided with an opening switch (not shown), a closing switch (not shown) and a stop switch (not shown). When an operator operates these switches, an opening signal, a closing signal and a stop signal are outputted to the ECU  60 , respectively. The handle switch  62  provided in an outer handle (not shown) for operating the rear gate  20  manually, is for detecting the operating condition of the outer handle. 
   The auto closure switch  65  is for holding or releasing a striker provided at the lower end of the rear gate  20  by actuating an electrically operated latch thereof. 
   The latch switch  61  acts as detecting whether or not the striker exists in a guide groove of the auto closure  65 . When the latch switch  61  detects the striker, the latch rotates to engage the striker in an engaging groove of the latch. 
   The warning buzzer  44  raises warnings intermittently when the rear gate  20  is in an automatic opening or closing mode. The interval of intermittent warning is established so as to change according to the opening mode or closing mode. 
   Accordingly, the operator can recognize whether the rear gate  20  is opening or closing without seeing the movement of the rear gate. Further, the buzzer can warn surrounding persons of the moving rear gate  20 . The warning buzzer  44  may be accompanied by a hazard lamp and the like. 
   Signals from the operating switch  63 , encoder  43 , handle switch  62  and latch switch  61  are inputted to the ECU  60  and the clutch  42 , motor  41  and auto closure  65  are controlled by the output from the ECU  60  to automatically open or close the rear gate  20 . 
   Hereinafter, the automatic opening and closing operation will be described. First, in case where the rear gate  20  is fully closed, when the opening switch of the operating switch  63  is operated, the latch of the auto closure  65  rotates in the opening direction to release the striker from the hold position. 
   When the striker is released, the rear gate  20  is pushed in the opening direction by the reaction force of weather strips and the like and the striker comes out of the guide groove. At this moment, the latch switch  61  detects the release of the striker. 
   Then, the ECU  60  receives a release signal from the latch switch  61  and energizes the clutch  42  to connect the motor  41  with the slider  45 . At the same time, the ECU  60  energizes the motor  41  and the motor  41  rotates in the forward (opening) direction. 
   When the motor  41  rotates in the forward direction, the slider  45  travels in the opening direction of the rear gate  20 , that is, in the backward direction, through the gear box. When the slider  45  travels in such a way, the rear gate  20  rotates in the opening direction through the connecting rod  46  and hinge arm  23 . The ECU  60  detects a position where the rear gate is based on signals from the encoder  43  and controls the driving force of the motor  41  according to the position of the rear gate  20 . 
   For example, as shown in  FIG. 10 , when the rear gate  20  is in the self closing zone as described before, the driving force of the motor  41  is controlled so as to assist the biasing force of the gas spring  51  in the opening direction of the rear gate  20 . On the other hand, when the rear gate  20  in the self opening zone, the driving force of the motor  41  is controlled so as to restrict the movement of the rear gate  20  in the opening direction. 
   Thus, when the rear gate  20  is in the self closing zone, the biasing force of the gas spring  51  is reduced and, when in the self opening zone, the rear gate  20  is prevented from rotating in the opening direction at a speed higher than a specified speed. Particularly, since the biasing force of the gas spring  51  tends to become large in accordance with an increase of outside temperature and as a result the opening speed of the rear gate  20  tends to become high, the opening speed can be controlled to be constant. 
   When the encoder  43  detects the rear gate  20  fully opened, the opening motion is finished. In case where the output of the encoder  43  does not change in spite of driving the motor  41 , it is judged that the rotation of the rear gate  20  in the opening direction is inhibited by an obstacle and the like, and the opening motion is stopped. 
   Further, when an operator operates the outer handle to stop the opening motion and an input signal is received from the handle switch  62 , the opening motion stops. In order to stop the opening motion, the motor  41  stops its rotation. The operating switch  63 , according to the input from the operating switch  63  or the handle switch  62 , selects condition of continuing the opening operation, condition of continuing the closing operation and condition of enabling the manual operation. 
   The above control is initialized when the rear gate  20  is closed by the manual or automatic operation and comes into a fully closing condition. The ECU  60  sets the position of the rear gate to the fully closing position based on the detection signal of the latch switch  61 . 
   Accordingly, in case where the rear gate  20  stops its motion on the way of opening or closing and as a result the encoder is unable to detects the current position of the rear gate  20 , the position of the rear gate  20  can be initialized by once manually bringing the rear gate  20  into the fully closing condition. 
   On the other hand, in case where the rear gate  20  is in a fully opening condition, when the closing switch of the operating switch  63  is operated, the ECU  60  energizes the clutch  42  to engage the motor  41  with the slider  45  and the motor  41  is driven in the closing direction. 
   When the motor  41  is driven in the closing direction, the slider  45  travels in the direction of closing the rear gate  20 , that is, in the forward direction through the gear box, and rotates the rear gate  20  in the closing direction through the connecting rod  46  and the hinge arm  23 . The ECU  60  detects the position of the rear gate  20  based on a detection signal of the encoder  43  and controls the driving force of the motor  41  according to the position of the rear gate. 
   For example, when the rear gate  20  is in the self opening zone, the rear gate  20  is controlled against the biasing force of the gas spring  51  so as to rotate in the closing direction and when the rear gate  20  is in the self closing zone, the rear gate  20  is controlled so as to restrict the rotation in the closing direction. Through this control, the rear gate  20  can be prevented from rotating in the closing direction at a speed higher than established beforehand. 
   When the rear gate  20  rotates in the closing direction and the entrance of the striker into the guide groove is detected, the clutch  42  is deenergized and the engagement of the clutch  42  is released. At the same time, the latch is rotated by the auto closure  65  and the striker is engaged with the engagement groove of the latch, thereby the rear gate  20  comes in a fully closing condition. 
   Thus, a series of the opening and closing motion through the operating switch  63  finishes. With respect to the stop of closing operation due to an obstacle or by the operation of the outer handle and the initialization of the control, since these are the same as the above described controls from the fully closing condition to the fully opened condition, descriptions in more detail will be omitted. 
   Next, the automatic opening and closing motion by other operations than the operating switch  63  will be described. 
   For example, in case where the rear gate  20  is in a fully closing condition, an operator operates the outer handle to release the engagement between the latch and the striker. As a result, the rear gate can be opened manually. 
   The ECU  60  calculates the rotation speed in the opening direction of the rear gate  20  based on a detection signal of the encoder  43  and judges whether or not the speed is within an established speed range. When it is within a specified speed range, the motor  41  is controlled to rotate at a speed corresponding to the specified opening speed and then the clutch  42  is engaged. As a result, the rear gate  20  rotates automatically in the opening direction. On the other hand, when it is not within a specified speed range, the automatic opening motion of the rear gate  20  stops. 
   Further, in case where the rear gate  20  is fully opened, when the operator rotates the rear gate  20  by hand in the closing direction, the ECU  60  calculates the traveling speed in the closing direction of the rear gate  20  based on a detection signal from the encoder  43 . Further, the ECU  60  judges whether or not the traveling speed is within a specified speed range. If it is within a specified speed, the motor  41  rotates in the closing direction at a speed corresponding to the traveling speed and the clutch  42  is engaged. The rear gate  20  rotates in the closing direction automatically. If it is not within a specified speed, the automatic closing motion stops. 
   Thus, since the rear gate  20  can be opened or closed without using the operating switch  63 , it is convenient and easy to use, for example, baggage can be carried into or out of the compartment easily. 
   The present invention is not limited to the embodiment described above. For example, according to the embodiment of the present invention, the encoder  43  serves as detecting the fully opening or closing position of the rear gate  20  or the encounter of an obstacle during traveling of the rear gate, however alternatively, an electric current passing through the motor  41  may be used. 
   That is, the fully opening or closing position or an obstacle during opening and closing operation may be detected based on an increase or decrease of electric current passing through an ampere detection circuit according to the load of the motor. 
   According to a rear gate automatic opening and closing apparatus for a vehicle disclosed in the second embodiment, the clutch and actuator is controlled based on the operation of the operating means to automatically open or close the rear gate. At this moment, the traveling speed of the rear gate is calculated based on a detection signal of the encoder and the actuator is controlled so as to open or close at a specified speed. 
   Accordingly, the traveling speed of the rear gate can be controlled properly. Particularly, the rear gate opening speed tends to increase due to an increase of the biasing force according to outside temperature rise and the control means according to the present invention enables the rear gate to open irrespective of outside temperature at a constant speed. 
   Further, since the clutch is provided between the actuator and the rear gate, by disengaging the clutch the rear gate can be operated to open or close by hand. 
   While the presently preferred embodiments of the present invention have been shown and described, it is to be understood that these disclosures are for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims.