JP3004709U - Car door mirror - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a clutch mechanism that has the same engaging force both during the retracting operation and the returning operation of the door mirror. [Structure] A trapezoidal recess 34 provided on the upper surface of a hollowed out portion of a center gear 31 made of a worm wheel that is rotatably supported by a center shaft and to which drive from a motor is transmitted, and non-rotatably supported by a center shaft. The inclined surface of the trapezoidal convex portion 30 of the engaged clutch 28 is changed. That is, when the center gear receives a downward force due to its rotation direction, the slope of the trapezoidal concavo-convex portion that contacts is formed gently, and when the center gear receives an upward force, the slope of the trapezoidal concavo-convex portion that contacts is formed steep. . [Effect] Even if a force is applied to the center gear in an upward or downward direction depending on the rotation direction, the engagement force between the center gear and the clutch can be made constant regardless of the rotation direction.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an electric retractable door mirror mounted on a front door of an automobile, and more particularly to a door mirror having a shock absorbing function, which allows the door mirror to be folded forward or backward of a vehicle body when colliding with an obstacle.

[0002]

[Prior art]

 Conventionally, this type of electric retractable door mirror has a possibility of colliding with an obstacle during traveling because it protrudes to the outside of the vehicle body. In the event of such a collision, the electric system is released to mitigate the impact, and the door mirror only is suddenly moved forward and backward with respect to the mirror base without applying a rotational force due to an external force to the drive motor. It has a structure that allows it to be overturned.

FIG. 6 shows a conventional example, 1 is a mirror base plate fixed to a front door of a vehicle body, 2 is a hollow center shaft fixed to the base plate 1, and 3 is a center plate on the base plate 1. It is a mirror holder rotatably supported on the shaft 2. Reference numeral 4 denotes a ball bearing for smoothly rotating the mirror holder 3 with respect to the base plate 1. A mirror (not shown) and an actuator (not shown) for tilting the mirror are attached to the mirror holder 3. A pair of flat surfaces 5 is formed on the center shaft 2 at a portion located above the mirror holder 3. Reference numeral 6 denotes a ring-shaped clutch, which is axially movably supported on the shaft 2 via a washer 7 on the mirror holder 3, and has four convex portions 8 and 8. This clutch 6 is formed with a flat surface 9 which corresponds to the flat surface 5 of the shaft 2 and therefore the clutch 6 cannot rotate relative to the shaft 2. Reference numeral 10 denotes a center gear rotatably supported on the shaft 2, the lower surface of which is hollowed out, and the clutch 6 is housed in the hollowed-out portion 11. On the upper surface of the cut-out portion 11, there are formed recesses 12 and 12-to which the protrusions 8 and 8-of the clutch 6 mesh. Reference numeral 13 is a coil spring that penetrates the shaft 2 and elastically presses the center gear 10 via a washer 14. Reference numeral 15 is a fixing ring that fixes the upper end of the coil spring 13 near the upper end of the center shaft 2. A worm gear 16 meshes with the center gear 10 and is connected to the forward / reverse rotation motor 18 via a reduction gear group 17. The motor 18, the gear group 17, and the worm gear 16 are fixed to the mirror holder 3.

The trapezoidal concave portion 12 of the center gear 10 and the trapezoidal convex portion 8 of the clutch 6 have the same inclination angle A as shown in FIG.

In the above-mentioned structure, the center gear 10 and the clutch 6 are normally in a state in which the convex portions 8 and 8 − and the concave portions 12 and 12 − are engaged with each other by the force of the coil spring 13, and the both are mechanically coupled. It is in. Therefore, when the motor 18 rotates, the driving force is transmitted to the center gear 10, and the center gear 10 is rotated to actuate the force to rotate the clutch 6. However, since the clutch 6 is supported so as not to rotate with respect to the center shaft 2, the mirror holder 3 itself rotates with respect to the shaft 2. By rotating the motor 17 forward and backward, the mirror holder 3 is rotated to the normal position or the storage position.

When an external force is suddenly applied to the door mirror from the front or the rear due to a collision of an obstacle or the like, the meshing portion of the center gear 10 and the clutch 6 is disengaged against the spring force of the coil spring 13. The mirror holder 3 becomes rotatable with respect to the center shaft 2 and rapidly rotates rearward or forward of the vehicle body. This is because the magnitude of the rotational force of the center gear 10 due to the impact force exceeds the meshing force between the center gear 10 and the clutch 6 due to the coil spring 13.

[0007]

[Problems to be solved by the device]

 According to the above structure, when the right side door mirror is driven from the use position to the storage position, the worm gear 16 rotates in the direction of arrow a (counterclockwise) by the drive of the motor 18 as shown in FIG. The force that tries to rotate in the a direction is released. At this time, the center gear 10 receives a downward force c, a rightward force d in the drawing, and a center gear centering force e. On the contrary, when the door mirror is driven from the retracted position to the use position, the worm gear 16 is rotated in the direction of arrow b (clockwise) by the drive of the motor 18 as shown in FIG. The force that tries to rotate in the direction works. At this time, a force c in the upward direction, a force d in the leftward direction in the figure, and a force e in the center gear center direction are applied to the center gear 10. That is, the center gear 10 reverses the vertical force applied to the center gear 10 in the clockwise direction and the counterclockwise direction, and acts to strengthen the engaging force with the clutch 6 in the counterclockwise direction, and in the clockwise direction, the engaging force is increased. Acts to weaken the resultant force. The forces c, d, and e in the above directions are generated when the center gear 10 has teeth in the right-hand twist direction as shown in the drawing.

The fact that the engaging force between the center gear 10 and the clutch 6 differs depending on the tilting direction of the door mirror causes the following problems. I. When the spring pressure of the coil spring 13 is set to match the operation (large engagement force) from the normal use position to the retracted position, the spring pressure can be small. The pressure becomes even weaker. In this way, when the normal use position is reached, for example, if the motor is stopped by stopping with a stopper and detecting the overcurrent flowing in the motor at that time, the overcurrent cannot be detected so small that the motor is stopped. There are things you can't do. B. If the spring pressure of the coil spring 13 is set to match the operation (small engagement force) from the retracted position to the normal position, it is necessary to increase the spring pressure. This will cause the clutch 6 to disengage from the center gear 10 during the retracting operation. It may become difficult, and it may not move backward when external force is applied.

As described above, the center gear and the clutch are disengaged when a constant external impact is applied, but the spring pressure of the coil spring must be adjusted so that they are not disengaged by the rotational force of the motor. It is extremely difficult to adjust because the size is narrow and the size varies depending on the driving direction.

The present invention has been made to solve such a problem, and provides an automobile door mirror in which the engagement force between the center gear and the clutch can be the same both when the door mirror is tilted backward and when it is tilted forward. It is provided.

[0011]

[Means for Solving the Problems]

 The present invention includes a mirror base plate that projects outward from the front door and is fixed substantially horizontally, a center shaft fixed substantially vertically to the mirror base plate, and a rotatably supported center shaft on the mirror base plate. The supported mirror holder, which is rotatably supported by the center shaft with respect to the center shaft, has a circular hollow portion on the lower surface, and has a plurality of trapezoidal recesses on the upper surface of the hollow portion ( Or a center gear consisting of a worm wheel having a convex portion), a trapezoidal convex portion (or concave portion) which is housed in the above-mentioned hollow portion of the center gear and which engages with the above trapezoidal concave portion (or convex portion). It has it on its upper surface, it is in a state where it cannot rotate on the center shaft, and it can only move in the axial direction of the center shaft. Ring-shaped clutch supported in a stationary state, a reversible motor in which the driving force is fixed to the mirror holder and transmitted to the center gear via a worm gear, and the engaging force on both sides of the center gear and the clutch is increased. And a trapezoidal recess (or a protrusion) of the center gear that makes contact with the center gear with a downward force applied thereto, and the clutch. Of the trapezoidal convex portion (or concave portion) of the trapezoidal concave portion (or convex portion) of the center gear and the trapezoidal convex portion of the clutch that come into contact with the center gear with an upward force applied. It is formed more gently than the angle of the other slope of the part (or recess).

Further, the present invention provides a mirror base plate which is fixed to the front door outside the vehicle body and is fixed substantially horizontally, a center shaft which is fixed substantially vertically to the mirror base plate, and the center shaft is rotatable on the mirror base plate. The center shaft is rotatably inserted through the mirror holder supported on the mirror holder, and the center shaft has an opening having a diameter larger than the outer diameter of the center shaft. On the mirror holder, the conical concave member has a conical concave member, which is positioned in the open portion and is movable in the radial direction of the conical concave member, and the tip of the conical concave member is substantially on the conical inclined surface of the conical concave member. A slide body having a matching wedge shape, and a coil for elastically urging the slide body in the direction of the center shaft. The lower spring is supported by the center shaft under the conical concave body in a rotatable state and in a movable state in the axial direction of the center shaft, and on the concave inclined surface of the conical concave body. A conical convex body having a convex inclined surface which substantially coincides with the convex inclined surface facing the concave inclined surface, supported by the center shaft so as to be rotatable with respect to the center shaft and circular on the lower surface. A center gear including a home wheel having a hollow portion and a plurality of trapezoidal concave portions (or convex portions) formed on the upper surface of the hollow portion, and the trapezoid that is housed in the hollow portion of the center gear. It has a trapezoidal convex portion (or concave portion) that engages with the concave portion (or convex portion) on its upper surface, and is in a state in which it cannot rotate on the center shaft and the axial direction of the center shaft. A door mirror for an automobile including a ring-shaped clutch supported only in a movable state, a reversible motor fixed to the mirror holder and having its driving force transmitted to the center gear via a worm gear, The angle of the slopes of the trapezoidal concave portion (or convex portion) of the center gear and the trapezoidal convex portion (or concave portion) of the clutch that come into contact with the center gear in a state where force is applied downward is set to the center gear upward. The trapezoidal concave portion (or convex portion) of the center gear and the other trapezoidal convex portion (or concave portion) of the clutch, which come into contact with each other under the force of, are formed more gently than the angle.

[0013]

[Action]

 As shown in FIG. 4, when the force to rotate the center gear 10 in the direction of the arrow a acts, the gentle slope (the left slope in the figure) of the trapezoidal recess 12 on the center gear 10 side and the trapezoid on the clutch 6 side. The gentle slope of the convex portion 8 comes into contact with the clutch 6, and a rotational force in the a direction from the center gear 10 is applied to the clutch 6. At this time, a downward force c is applied to the center gear 10. The reaction force f that the center gear 10 receives from the clutch 6 generates an upward component force g, and subtracts the difference (g−c) between the force g and the force c from the spring pressure F generated by the spring 44 (FIG. 1). The obtained value is obtained as the engagement force between the center gear 10 and the clutch 6.

FIG. 5 shows the case of reverse rotation, and when the center gear 10 rotates in the direction of arrow b, the steep slope (the right slope in the figure) of the trapezoidal recess 12 on the center gear 10 side and the trapezoidal projection on the clutch 6 side. The steep slope of the portion 8 comes into contact with the clutch 6, and a rotational force from the center gear 10 in the direction b is applied to the clutch 6. At this time, an upward force c is applied to the center gear 10. The reaction force f received from the clutch 6 by the center gear 10 generates a component force g in the upward direction, and is a value obtained by subtracting the sum (g + c) of the force g and the force c from the spring pressure F generated by the spring 44 (FIG. 1). Is obtained as the engagement force between the center gear 10 and the clutch 6. The angle B of the gentle slope and the angle C of the steep slope are set so that the force (g-c) obtained when rotating in the a direction and the force (g + c) obtained when rotating in the b direction are the same.

[0015]

【Example】

 1 to 5, reference numeral 20 designates a plastic, ceramic or metal mirror base plate which is fixed to the front door of the automobile outwardly of the vehicle body and is fixed substantially horizontally. Reference numeral 21 is formed substantially vertically in the center of the plate 20. A hollow plastic or metal center shaft is fixed to the plate 20 either integrally with the plate 20 or by screws or the like. A pair of flat surfaces 22 is formed on the center shaft 21. Reference numerals 23, 23, and 23 are arc-shaped first grooves provided on the upper surface of the mirror base plate 20 with the center shaft 21 as a center.

Reference numeral 24 denotes a plastic mirror holder that is supported by the center shaft 21 on the base plate 20. The circular opening 25 is located at the base of the center shaft 21 and is rotatable about the shaft 21. Reference numeral 26 denotes a circular arc-shaped second groove formed around the center shaft 21 on the lower surface of the mirror holder 24, that is, the surface contacting the base plate 20, and is formed on the same circumference as the radius of the first groove 23. ing. Reference numeral 27 is a ball bearing housed in a space formed by overlapping the first and second grooves 23 and 26, and regulates the rotation angle of the mirror holder 24 with respect to the mirror base plate 20.

Reference numeral 28 denotes a ring-shaped clutch that is inserted through the center shaft 21, and has a flat surface 29 a formed in the center opening 29, and is therefore supported by the center shaft 21 so that it cannot rotate. Reference numerals 30 and 30- are four trapezoidal convex portions formed on the upper surface of the clutch 28.

Reference numeral 31 is a center gear composed of a worm wheel disposed above the clutch 28, and the center shaft 21 penetrates a circular opening 32 formed in the center. The center gear 31 is rotatable with respect to the shaft 21. Reference numeral 33 denotes a circular hollow portion formed on the lower surface of the center gear 31, and four trapezoidal recesses 34 are formed on the upper surface of the hollow portion 33. A clutch 28 is housed in the hollowed-out portion 33, and a trapezoidal convex portion 30 of the clutch 28 is engaged with a trapezoidal concave portion 34 to mechanically couple the two.

Reference numerals 35 and 36 denote conical convex bodies that are inserted through the center shaft 21. The inclination angle of the conical inclined surface with respect to the horizontal plane can be set to about 26.6 °, and the inclined surfaces face each other. Has been. Numeral 37 is a conical concave body rotatably supported on the mirror holder 24 with respect to the center shaft 21, and has a circular opening 38 through which the center shaft 21 penetrates, and upper and lower surfaces centering on the opening 38. It has a conical inclined surface 39. The inclination angle of these inclined surfaces 39 with respect to the horizontal plane is equal to the inclination angle of the conical convex bodies 35 and 36, and can be set to about 26.6 °. The conical concave body 37 is positioned between the pair of conical convex bodies 35 and 36. The diameter of the opening 38 is designed to be slightly larger than the outer diameter of the shaft 21, so that the conical recess 37 can move horizontally on the mirror holder 24. Here, as an example of the dimensions, the diameter of the opening 38 can be 16 mm, and the outer diameter of the center shaft 21 in this portion can be 14 mm. Further, the conical concave body 38 is formed with an opening 40 in its radial direction. Reference numeral 41 denotes a guide portion surrounding the open portion 40, which is integrally formed with the conical concave body 37. The tilt angle must be 10 ° or more and less than 45 °. If the angle is smaller than 10 °, the slide body, which will be described later, becomes too thick, and accordingly, the outer diameter must be increased, resulting in an unreasonable structure. If the angle is 45 ° or more, the coil spring penetrating the shaft 21 will be formed. 13 (FIG. 6) requires a stronger spring. The conical concave body 37 and the guide portion 41 are arranged in a support frame 42 formed to project on the surface of the mirror holder 24, and are prevented from rotating with respect to the mirror holder 24.

Reference numeral 43 denotes a slide body that slides in the open portion 40 and the guide portion 41, and the tip located on the center shaft 21 side has an inclination that matches the conical inclined surface 39 of the conical concave body 37. It has a wedge-shaped cross section. Reference numeral 44 is a coil spring that is housed in the guide portion 41 and has a tip end that constantly elastically biases the slide body 43 toward the center shaft 21. The coil spring 44 has a steel wire diameter (diameter) of 1.6 mm, a winding outer diameter of 10 mm, and a mounting length of 15 mm. Due to the elasticity of the coil spring 44, the slide body 43 is elastically pressed in the right direction in FIG. 1 and the conical concave body 37 is elastically pressed in the left direction, and a force is applied toward the center shaft 21 center.

The trapezoidal concave portion 34 of the center gear 31 and the trapezoidal convex portion 30 of the clutch 28 are formed asymmetrically as shown in FIGS. 4 and 5, and contact each other when a downward force c is applied to the center gear 31 during rotation. The inclined surfaces of the concave portion 34 and the convex portion 30 are formed gently, and the inclined surface of the concave portion 34 and the convex portion 30 which come into contact when the upward force c is applied to the center gear 31 are formed steeply. As an example, a gentle slope angle B = 67 ° and a steep slope angle C = 71 ° can be set. In this embodiment, the trapezoidal concave portion 34 is formed on the center gear 31 side and the trapezoidal convex portion 30 is formed on the clutch 28 side, but conversely, the trapezoidal convex portion 30 is formed on the center gear 31 side and the clutch 28 side is formed. The trapezoidal recess 34 may be formed.

Reference numeral 45 denotes a C ring that prevents the center gear 31 from coming off upward, and is locked to the upper end of the center shaft 21.

Reference numeral 46 is a worm gear that transmits a rotational force to the center gear 31, 47 is a reduction gear group, and 48 is a reversible motor, which are supported by the mirror holder 24. A cord (not shown) for supplying power to the motor 48 passes through the hollow portion of the center shaft 21 and is led out below the base plate 20 to be connected to the vehicle body side.

In such a structure, the slide body 43 and the conical concave body 37 are elastically pressed toward the center shaft 21 by the elastic force of the coil spring 44, and the tip of the slide body 43 and the conical concave body 37, especially the right inclined surface. The conical protrusions 35 and 36 are pressed upward and downward by (in FIG. 1), and the clutch 28 is engaged with the center gear 31 by this pressing force.

Next, the operation of the above structure will be described. In a normal use state, the driving force is reduced by the rotation of the motor 48 via the reduction gear group 47 and transmitted to the center gear 31 via the worm gear 46. Since the center gear 31 is engaged with the clutch 28, the rotational force is also applied to the clutch 28 at the same time. Since the clutch 28 is non-rotatably supported by the center shaft 21, the clutch 28 tries to rotate the center shaft 21. However, since the center shaft 21 is fixed to the vehicle body via the base plate 20, the clutch 28 side, that is, the entire mirror holder 24 rotates about the center shaft 21.

In the operation from the normal use position to the retracted position, the center gear 31 and the clutch 28 are in contact with each other by the gentle slopes of the trapezoidal concave portion 34 and the trapezoidal convex portion 30, respectively. The force g is reduced to the pressing force c and becomes a predetermined engagement force. Further, in the operation from the retracted position to the normal use position, the center gear 31 and the clutch 28 are in contact with each other on the steep slopes of the trapezoidal concave portions 34 and the trapezoidal convex portions 30, and the upward direction obtained from the slopes. The force g is added with the push-up force c and becomes a predetermined engagement force which is substantially equal to the above-mentioned engagement force. Due to this engaging force, the center gear 31 and the clutch 28 maintain the engaged state, and the normal storing operation and the returning operation are performed.

Next, when an obstacle collides with the door mirror and a strong force that pushes the door mirror backward suddenly acts, a large turning force (clockwise in FIG. 1) is applied to the center gear 31, and therefore The concave portion 34 of the center gear 31 is disengaged from the convex portion 30 of the clutch 28. The rotational force of the center gear 31 pushes the center gear 31 upward. At this time, when the center gear 31 is pushed up, the conical convex body 35 is also pushed up, the slide body 43 moves slightly outward (to the left in the figure), and the conical concave body 37 also slightly moves to the right in the figure. Then, the coil spring 44 is compressed. Thus, the mirror holder 24 becomes rotatable with respect to the center shaft 21, rapidly rotates in the storage direction, and the ball bearing 27 abuts on the ends of the first and second grooves 23, 26 and stops at the storage position. After returning to the normal position after stopping at the storage position, the motor 48 may be rotated toward the normal position. Immediately, the center gear 31 is rotated by the drive of the motor 48, and the recessed portion 34 of the hollowed portion 33 idles until it matches the convex portion 30 of the clutch 28, and after the concave portion 34 matches the convex portion 30, The driving force is transmitted to the shaft 21 by rotating the clutch 28, and the mirror holder 24 rotates in the normal position direction.

Conversely, when an obstacle collides with the door mirror from the rear and a strong force that pushes the door mirror forward suddenly acts, a large turning force (counterclockwise) is applied to the center gear 31, and therefore the center gear 31 is rotated. The concave portion 34 of the gear 31 is disengaged from the convex portion 30 of the clutch 28. As in the case described above, the center gear 31 is pushed upward by the rotational force of the center gear 31. In order to return the door mirror to the use position after tilting it forward, the motor 48 may be rotated in the retracted direction, that is, the center gear 31 is rotated by the rotational driving of the motor 48, and the hollow portion 33 of the center gear 31 is first rotated. The concave portion 34 of the gear meshes with the convex portion 30 of the clutch 28 to rotate the mirror holder 24 with respect to the shaft 21.

[0029]

[Effect of device]

 According to the present invention, the angle of the two slopes is made different for each of the trapezoidal concave portion (or the convex portion) of the center gear and the cutout portion and the trapezoidal convex portion (or the concave portion) of the clutch that engages with the center gear, and the center gear has the different angles. By canceling or adding the upward or downward force applied depending on the rotation direction, a constant engagement force can be obtained in either rotation direction.Therefore, when the settable range of spring pressure by the coil spring is narrow. Even so, it can be easily adjusted within that range. Therefore, it is possible to obtain an appropriate spring pressure necessary for performing a normal storing / returning operation and, at the same time, surely perform a forward or backward tilting operation even when an external impact force is applied.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of an embodiment of the present invention.

FIG. 2 is a cross-sectional perspective view of a main part of the embodiment.

FIG. 3 is a perspective view of a main part of the embodiment.

FIG. 4 is a cross-sectional view of main parts for explaining the embodiment.

FIG. 5 is a cross-sectional view of essential parts for explaining the embodiment.

FIG. 6 is a perspective view of a field for explaining a conventional example.

FIG. 7 is a cross-sectional view of an essential part for explaining a conventional example.

FIG. 8 is a perspective view of a main part for explaining an operation of a conventional example and one embodiment of the present invention.

FIG. 9 is a perspective view of a main part for explaining an operation of a conventional example and one embodiment of the present invention.

[Explanation of symbols]

 1, 20 Base plate 2, 21 Center shaft 3, 24 Mirror holder 6, 28 Clutch 10, 31 Center gear 30 Trapezoidal convex portion 33 Hollowout portion 34 Trapezoidal concave portion 37 Conical concave body 43 Sliding body 44 Coil spring 46 Worm gear 48 Motor

Claims (2)

[Scope of utility model registration request] 1. A mirror base plate that projects outward from a vehicle body of a front door and is fixed substantially horizontally, a center shaft fixed substantially vertically to the mirror base plate, and rotatably supported by the center shaft on the mirror base plate. Mirror holder, the center shaft, to the center shaft,
A center gear composed of a worm wheel which is rotatably supported and has a plurality of trapezoidal recesses (or protrusions) on its one main surface, and which is in contact with the center gear and has the trapezoidal recesses (or protrusions). ) Having a trapezoidal convex portion (or concave portion) which is engaged with the main shaft, and is supported by the center shaft in a non-rotatable state and in a state in which only the axial movement of the center shaft is possible. -Shaped clutch, a reversible motor that is fixed to the mirror holder and the driving force of which is transmitted to the center gear via a worm gear, and elastic force is applied to the center gear and the clutch in the direction in which the engagement force between the two increases. And a trapezoidal recess of the center gear, which is in contact with the center gear with a downward force applied thereto. (Or a convex portion) and the angle of the slope of the trapezoidal convex portion (or concave portion) of the clutch, the trapezoidal concave portion (or convex portion) of the center gear that contacts the center gear with an upward force applied, The vehicle door mirror is characterized in that it is formed more gently than the angle of the other slope of the trapezoidal convex portion (or concave portion) of the clutch. 2. A mirror base plate which projects outward from the vehicle body of the front door and is fixed substantially horizontally, a center shaft fixed substantially vertically to the mirror base plate, and rotatably supported by the center shaft on the mirror base plate. A center holder having the opening larger than the outer diameter of the center shaft and having an opening at the center thereof. Body, on the mirror holder, has a wedge shape which is positioned in the open portion and is movable in the radial direction of the conical concave body, and whose tip is substantially coincident with the conical inclined surface of the conical concave body. A slide body having, a coil spring for elastically biasing the slide body in the direction of the center shaft, Under the conical concave body, a protrusion that is supported by the center shaft in a rotatable state and movable in the axial direction of the center shaft, and that is substantially coincident with the concave inclined surface of the conical concave body. A conical convex body having a curved inclined surface, the convex inclined surface facing the concave inclined surface, and a plurality of trapezoids supported on the center shaft in a rotatable state with respect to the center shaft. A center gear composed of a worm wheel having a concave portion (or a convex portion), and a trapezoidal convex portion (or a concave portion) which is in contact with the center gear and engages with the trapezoidal concave portion (or the convex portion) on one main surface thereof. A ring-shaped clutch supported on the center shaft in a non-rotatable state and in a state where only the axial movement of the center shaft is possible, fixed to the mirror holder, Is a door mirror for an automobile including a reversible motor whose driving force is transmitted to the center gear via a worm gear, wherein the trapezoidal recess of the center gear that comes into contact with the center gear under a downward force ( (Or a convex portion) and the angle of the slope of the trapezoidal convex portion (or concave portion) of the clutch, the trapezoidal concave portion (or convex portion) of the center gear that contacts the center gear with an upward force applied, The vehicle door mirror is characterized in that it is formed more gently than the angle of the other slope of the trapezoidal convex portion (or concave portion) of the clutch.