JPH0617383U - Stepping motor - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce torque attenuation and noise generation when the stepping motor rotates. [Structure] A recess 21 having a mortar-shaped bottom surface 21a at a position facing the tip of the lead screw 5 of the bearing member 10.
Are formed on the bottom surface 21a, and projections 21b are formed on the bottom surface 21a so as to radially protrude from the center of the bottom surface 21a toward the distal end side of the lead screw 5. Then, the ball 11 is sandwiched between the taper portion 21c of the protrusion 21b and the recess 5a formed in the end face of the lead screw 5, and the ball 11 is pressed from the recess 5a to the taper portion 21c. The screw 5 is rotatably supported by the bearing member 10. The ball 11 and the bottom surface 21a have a tapered portion 21.
Since there is no contact in parts other than c, the contact area between the bottom surface 21a and the ball 11 is reduced.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a small stepping motor, and more particularly to a stepping motor in which torque attenuation and noise generation during motor rotation are reduced.

[0002]

[Prior art]

 A so-called stepping motor is often used for a lens driving mechanism of an autofocus camera. As this type of stepping motor, the one shown in FIG. 4 or FIG. 5 is conventionally known.

The structure of a standard stepping motor is shown in FIG. Reference numeral 1 denotes a stator composed of a pair of cylindrical yokes and a coil wound around these yokes. In the space formed in the center of the stator 1, there is a rotating shaft 2 and a rotor 3 fixed around the rotating shaft 2. The rotor assay product 4 consisting of is inserted. Further, one end side of the rotary shaft 2 is extended along the axial direction and is threaded at the periphery to form a lead screw 5. On the other hand, a leaf spring 6 for applying a preload to the other end of the rotating shaft 2 in the direction toward one end of the rotating shaft 2 is fixed to the end surface of the stator 1 on the other end side of the rotating shaft 2 by resistance welding or the like.

Further, one end of a flat plate annular plate 7 is abutted and fixed to the end surface of the stator 1 on the side of the lead screw 5, and the central portion of the plate 7 has an intermediate portion between the rotary shaft 2 and the lead screen 5. A metal bearing 8 that rotatably supports is installed, and one end of a bracket 9 extending in the tip direction of the lead screw 5 is fixed to the other end of the plate 7 by screwing or the like.

A bearing member 10 is fixed to the tip end side of the lead screw 5 of the bracket 9, and a mortar-shaped recess 10 a is formed at a position facing the tip end of the lead screw 5 of the bearing member 10. Then, the ball 11 is sandwiched between the recess 10a and the recess 5a, which is also formed in the end face of the lead screw 5, and the ball 11 is pressed from the recess 5a to the recess 10a by the action of the leaf spring 6. By doing so, the lead screw 5 is rotatably supported.

Further, in FIG. 5, the recess 10 a formed in the bearing member 10 has a U-shaped cross-section, and the recess 10 a is provided between the bottom surface of the recess 10 a and the recess 5 a on the end face of the lead screw 5. This is an example in which the lead screw 5 is rotatably supported via the ball 11.

In each of the above stepping motors, when the coil is energized, a magnetic pole is formed in the stator 1, and the action of this magnetic pole and the magnetic pole formed on the rotor 3 causes the rotor assay product 4 to rotate around the rotating shaft 2. Rotate. In this case, the ball 11 rotates together with the recess 5a by the contact pressure received from the recess 5a.

[0008]

[Problems to be solved by the device]

 In recent years, resin is often used as the material of the ball 11 from the viewpoint of preventing noise generated between the recess 10a and the ball 11 when the motor rotates. However, when the resin ball 11 is used, for example, in the stepping motor having the structure shown in FIG. 4, due to the wear of the ball 11 at the contact portion with the recess 10a and the deformation of the ball 11 due to the contact pressure from the recess 5a. As a result, the contact area between the ball 11 and the recess 10a increases, and the frictional resistance between the ball 11 and the recess 10a increases, and this increase in resistance sometimes attenuates the torque during motor rotation.

Further, the volume of the space S formed between the recess 10a and the ball 11 decreases with an increase in the contact area between the ball 11 and the recess 10a, and the space S has a negative pressure relative to the external pressure. As a result, the ball 11 may be sucked into the recess 10a and the rotation of the ball 11 may stop. In this case, new noise was generated at the contact portion between the non-rotating ball 11 and the rotating concave portion 5a.

On the other hand, in the stepping motor having the structure shown in FIG. 5, since the space S is not formed, the ball 11 is not sucked into the recess 10a. However, the positioning of the ball 11 with respect to the recess 10a is performed only by pressing the ball 11 from the recess 5a. Therefore, depending on the axial accuracy of the lead screw 5 and the like, the ball 11 may be moved in the motor rotation direction between the recess 10a and the ball 11. There was a problem that vibration occurred, and that caused noise and vibration. Especially when used in a device having a recording function such as a video camera, the influence of these noises was remarkable.

[0011]

[Means for Solving the Problems]

 The present invention has been made in view of the above problems, and includes a rotating shaft, a cylindrical yoke provided around the rotating shaft, and around which a coil is wound, and one end of the rotating shaft. In a stepping motor having a bearing member rotatably supported at its end face, a slender bowl-shaped recess facing the end face at the one end is formed in the bearing member, and the bottom face is provided in the recess. A plurality of concavities and convexities radially extending from the center of the is formed.

In this case, a mortar-shaped recess is formed on the end face of the one end, and the rotary shaft is rotatably supported via a ball rotatably held between the recess and the recess of the bearing member. It may be configured to be held.

[0013]

[Action]

 In the stepping motor of the present invention, the bearing member is formed with a recessed portion in the shape of a mortar facing the end face of the rotary shaft of the motor, and the recessed portion has a plurality of radially extending radially from the center of the recessed portion. Since the unevenness is formed, the contact area between the bearing member and the end face or the ball held between the end face and the bearing member is reduced. Therefore, the frictional resistance generated between the bearing member and the end surface or the ball when the motor rotates is reduced.

[0014]

Embodiments Next, embodiments of the present invention will be described in more detail with reference to the drawings. FIG. 1 is a vertical sectional view of a bearing portion of a standard stepping motor showing an embodiment of the present invention. Since the present invention relates to the improvement of the bearing portion that rotatably supports the end surface of the lead screw in the conventional stepping motor, the description of the other portions of the stepping motor will be omitted.

In FIG. 1, reference numeral 20 is a bearing member fixed to the tip side of the lead screw 5 of the bracket 9, and has a mortar-shaped bottom surface 21 a at a position facing the tip of the lead screw 5 of the bearing member 20. A recess 21 is formed. Here, the diameter of the recess 21 is slightly larger than the diameter of the lead screw 5.

As shown in FIGS. 2 and 3, the bottom surface 21a is formed with a plurality of projections 21b that are radially extending from the center of the bottom surface 21a and project toward the tip side of the lead screw 5. There is. In the case of the present embodiment, the projection 21b gradually increases its projection amount radially outward from the center of the bottom surface 21a to form the tapered portion 21c, but does not project from the plane formed by the circumference of the bottom portion 21a. The plane portion 21d is formed on the plane. Further, six protrusions 21b are formed, the angle α formed by the adjacent protrusions 21b is 30 °, and the angle β formed by the opposing protrusions 21b and the bottom surface 21a is 90 °.

Then, the ball 11 is sandwiched between the taper portion 21c and the same recess 5a formed in the end surface of the lead screw 5, and the ball 11 is tapered from the recess 5a by the action of a leaf spring (not shown). The lead screw 5 is rotatably supported by the bearing member 10 by pressing against the portion 21c. As the material of the ball 11, for example, a hard sphere such as SUJ2 or SUS, or a sintered product of a powder made of resin or ceramic is used.

By energizing a coil (not shown), the lead screw 5 rotates about its axis. In this case, the ball 11 rotates together with the recess 5a by the contact pressure received from the recess 5a.

By the way, in the stepping motor of the present embodiment, the ball 11 is held between the taper portion 21c of the bottom surface 21a and the recess 5a of the lead screw 5. That is, since the ball 11 and the bottom surface 21a do not contact with each other except the tapered portion 21c, the contact area between the bottom surface 21a and the ball 11 is reduced. In the case of this embodiment, six protrusions 21b are formed and the angle α formed by the adjacent protrusions 21b is 30 °. Therefore, the contact area between the bottom surface 21a and the ball 11 is larger than that in the case without the protrusion 21b. It becomes 1/2.

Therefore, the frictional resistance generated between the bottom surface 21a and the ball 11 during the rotation of the motor is reduced, and the attenuation of the torque due to the frictional resistance during the rotation of the motor is suppressed and the wear of the ball 11 is suppressed. Also decreases.

Further, since the space S formed between the bottom surface 21a and the ball 11 is open to the outside air through the space formed between the adjacent protrusions 21b, the resin ball 11 Even when the contact area between the ball 11 and the taper portion 21c is increased by using, the pressure in the space S is equal to the external pressure. Therefore, it is possible to prevent the rotation of the ball 11 from being stopped by the suction of the ball 11 to the bottom surface 21a and the accompanying generation of noise at the contact portion between the ball 11 and the recess 5a.

Further, since the lubricant such as grease is evenly distributed around the bottom surface 21a through the space formed between the adjacent protrusions 21b, the ball 11 can be smoothly rotated and the bottom surface 21a and the ball 21a can be smoothly rotated. Even if a foreign matter enters the space between the ball 11 and the ball 11, the foreign matter falls into the space, so that the smooth rotation of the ball 11 is not hindered.

[0023]

【effect】

 As described above, in the stepping motor having the above structure, the bearing member that rotatably supports the end surface of the rotating shaft, and the end surface of the rotating shaft or the ball held between the end surface and the bearing member described above. Since the contact area of the bearing is reduced, the frictional resistance generated between the bearing member and the end surface or the ball when the motor is rotated is reduced, the damping of the torque due to this frictional resistance is suppressed, and the frictional resistance is increased. It prevents the generation of noise.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a bearing portion of a stepping motor showing a first embodiment of the present invention.

FIG. 2 is a front view from the II direction of the recess in the first embodiment of the present invention.

FIG. 3 is a view showing a structure of a bottom surface in the first embodiment of the present invention.

FIG. 4 is a vertical sectional view of a conventional stepping motor.

FIG. 5 is a vertical sectional view of a bearing portion of a conventional stepping motor.

[Explanation of symbols]

 1 stator 2 rotating shaft 3 rotor 4 rotor assay product 5 lead screw 5a, 10a, 21 recess 6 leaf spring 7 plate 8 metal bearing 9 bracket 10, 20 bearing member 11 ball 21a bottom face 21b protrusion 21c taper portion 21d plane portion α adjacent Angle formed by the protrusion β Angle formed by the opposite protrusion and the center of the bottom surface

Claims (2)

[Scope of utility model registration request] 1. A rotary shaft, a rotor provided around the rotary shaft, a cylindrical yoke provided around the rotor and spaced from the rotor, and having a coil wound around the rotor.
In a stepping motor comprising a bearing member that rotatably supports one end of the rotary shaft at its end face, a slender pot-shaped recess facing the end face of the one end is formed in the bearing member, and the recess is A stepping motor having a plurality of irregularities radially extending from the center of the recess along the radial direction. 2. A mortar-shaped recess is formed on the end face of the one end, and the rotary shaft is rotatable through a ball rotatably held between the recess and the recess formed in the bearing member. A stepping motor that is supported by.