JP2010032006A - Worm gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a worm gear that causes less chatter during motor operation. <P>SOLUTION: A resin worm 4 used in the worm gear 1 includes ribs 13 extending longitudinally toward a tip of a body part 11 from the middle of a shaft insertion hole 10. When a shaft 3 is pressed in as collapsing each rib 13, the worm 4 is secured on the shaft 3 under a predetermined press-in force. In this state, the ribs 13 collapsed by the shaft 3 form resin beads 15 on the tip of the shaft 3. The resin beads 15 appearing on the tip of the shaft 3 gradually increase as the shaft 3 is pressed into the worm 4, and the resin beads 15 substantially resist a backward movement of the worm 4 on drop impact. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a small worm gear used for small electronic devices such as disk drives and digital cameras.

  Conventionally, as a technique in such a field, there is JP-A-2005-7930. The worm gear described in this publication includes a worm fixed to a motor shaft and a worm wheel meshing with the worm, and a small diameter portion is integrally formed at the tip of the worm. In order to suppress the occurrence of a hitting sound inside the motor, the small diameter portion is disposed to face the standing surface (stopper portion), and a leaf spring is installed between the small diameter portion and the standing surface. The small-diameter portion of the worm is biased by a leaf spring, and the movement of the worm in the thrust direction is restricted by the leaf spring.

JP 2005-7930 A

When an electronic device including the worm gear having such a configuration is subjected to a strong impact such as dropping, the tip of the worm is strongly pressed against the standing surface. As a result, the worm retreats to the motor side from the initial position, and the shaft of the motor is pressed deeply into the worm. In particular, such a situation is likely to occur when the worm is made of a resin for reducing the size and weight. When such a situation occurs, the distance between the tip of the worm and the rising surface becomes larger than the originally planned dimension, so that the stroke amount of the worm becomes large, so that when the motor is driven, The tapping sound when the tip of the sword periodically hits the rising surface is increased. In particular, in order to reduce costs and simplify the structure, the hitting sound appears very prominently in the case where no leaf spring is provided.
In order to suppress the occurrence of squealing noise, reducing the diameter of the shaft insertion hole of the worm or increasing the shaft diameter of the shaft of the motor increases the worm removal force and increases impact resistance. In this method, since the force when the shaft is press-fitted into the worm increases, the shaft and the motor bearing are likely to be deformed.
In addition, by pushing the tip of the shaft against the bottom of the worm shaft insertion hole in advance, the worm can be prevented from retreating during a drop impact, but strict dimensional control is required when forming the worm. Therefore, it is difficult to cope with variations due to individual differences of motors.

  It is an object of the present invention to provide a worm gear that hardly generates a hitting sound during motor operation.

The present invention has a main body portion having a shaft insertion hole into which a shaft of a motor is inserted, and a gear portion spirally provided around the main body portion, and the front end of the main body portion is disposed to face the stopper portion. In the worm gear with a resin worm to be
On the wall surface forming the shaft insertion hole, a rib extending in the longitudinal direction from the middle of the shaft insertion hole toward the tip of the main body is projected, and the rib crushed by the shaft is resin on the tip side of the shaft. It becomes a reservoir part.

The resin worm applied to this worm gear is provided with ribs in the middle of the shaft insertion hole, and the shaft is pressed into the shaft insertion hole to some extent, so that the shaft is stabilized against the worm. Can be press-fitted, and the shaft is less likely to be bent during press-fitting. In particular, the smaller the diameter of the shaft due to the miniaturization of the motor, the more effective. Furthermore, the rib of the worm extends in the longitudinal direction from the middle of the shaft toward the tip of the main body, so that the worm is fixed to the shaft with a predetermined pressure input by pressing the shaft while crushing the rib. Is done. At this time, the rib is not crushed by the shaft, but the shaft is pushed into the worm while gradually increasing the resin reservoir that appears on the tip side of the shaft. At the time of occurrence, the worm becomes very difficult to retreat, so that the distance between the tip of the worm and the stopper portion is less likely to expand than originally planned, and the stroke amount of the worm is difficult to change. Therefore, the hitting sound generated when the tip of the worm periodically hits the stopper portion when the motor is driven does not increase. In the present invention, it goes without saying that a resin material (for example, PBT (polybutylene terephthalate), POM (polyoxymethylene), etc.) capable of forming such a resin reservoir is selected. Furthermore, even if they are made of the same material, the pressure input can be easily adjusted only by changing the height and number of ribs, so that it can be easily applied to motors having various torques.

Further, it is preferable that a plurality of ribs are provided and arranged at equal intervals in the circumferential direction of the shaft insertion hole.
By adopting such a configuration, a uniform pressure input can be generated in the circumferential direction of the shaft, so that the worm can be further prevented from coming off the shaft.

  Further, the rib has a reduced diameter surface located on the inner side, and this reduced diameter surface preferably has an arc shape centered on the axis of the worm and is formed with a diameter smaller than that of the shaft insertion hole.

  By adopting such a reduced diameter surface, the pressure-bonding property to the shaft is improved, and the rib can be uniformly crushed by the shaft. The rib having such a shape is optimal for producing a resin reservoir uniformly. The generation of a uniform resin reservoir is extremely effective in preventing the shaft from retreating.

  According to the present invention, it is difficult for a hitting sound to occur during motor operation.

  Hereinafter, preferred embodiments of a worm gear according to the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, the worm gear 1 includes a resin worm 4 fixed to the shaft 3 of the motor 2 and a resin worm wheel 5 meshed with the worm 4. It is used in many electronic devices such as digital cameras. Moreover, the weight reduction and cost reduction are enabled by using the worm gear 1 as resin.

  The motor 2 is small and is mounted on an electronic device in a state of being fixed to the bracket 6. A worm 4 is fixed to the shaft 3 of the motor, and a worm wheel 5 meshed with the worm 4 rotates around a support shaft 7 provided on a bracket 6 that can be attached to a device.

  The worm gear 1 can obtain a very high reduction ratio in a compact size and has relatively low noise. However, because of the structure of the small motor 2 itself, the shaft 3 has a backlash in the thrust direction, and the worm 4 always generates a force in the thrust direction while the motor 2 is driven, so that the backlash of the worm 4 is prevented. There is a need to.

  In order to prevent rattling, when the worm 4 is rotating forward, the hemispherical abutting portion 4a provided at the tip of the worm 4 comes into contact with the planar stopper portion 8 provided in the bracket 6, and the worm 4 When 4 is reversed, the rear end of the shaft 3 is supported by the preload bearing portion 9 disposed on the rear end side inside the motor 2.

  However, if the distance H between the abutting portion 4a of the worm 4 and the stopper portion 8 becomes larger than necessary, it occurs when the tip of the abutting portion 4a periodically contacts the stopper portion 8 when the motor 2 is driven. The beating sound becomes louder than necessary. Therefore, the worm gear 1 according to the present invention employs the worm 4 to which this measure is applied.

  As shown in FIGS. 2 and 3, the worm 4 includes a main body 11 having a shaft insertion hole 10 having a diameter substantially the same as the diameter of the shaft 3 and a periphery of the main body 11. A gear portion 12 provided in a spiral shape, and an abutting portion 4 a disposed at the tip of the main body portion 11 so as to face the stopper portion 8. The diameter of the shaft insertion hole 10 may be slightly smaller than that of the shaft 3.

  On the wall surface 10 a that forms the shaft insertion hole 10, two ribs 13 that extend in the longitudinal direction from the middle of the shaft insertion hole 10 toward the tip of the main body 11 are provided. Each rib 13 has a reduced diameter surface 13 a located on the inner side, and this reduced diameter surface 13 a has an arc shape centered on the axis L of the worm 4 and is formed with a smaller diameter than the shaft insertion hole 10. .

  By adopting such a reduced diameter surface 13a, the press-bonding property to the shaft 3 is improved, and the rib 13 can be uniformly crushed by the shaft 3. The rib 13 having such a shape is optimal for uniformly creating a resin reservoir portion 15 to be described later. The generation of the uniform resin reservoir portion 15 is extremely effective in preventing the shaft 3 from retreating.

  Further, a plurality of ribs 13 (two in the present embodiment) are provided and are arranged at equal intervals in the circumferential direction of the shaft insertion hole 10. By adopting such a configuration, it is possible to generate a uniform pressure input in the circumferential direction of the shaft 3, so that the worm 4 can be more easily removed from the shaft 3. Further, it is possible to prevent the axis L of the worm 4 and the axis of the shaft 3 from deviating.

The resin worm 4 applied to the worm gear 1 is provided with a rib 13 extending in the longitudinal direction from the middle of the shaft insertion hole 10 toward the tip of the main body 11. Since it is press-fitted from the holding state inserted into the insertion hole 10 to some extent, the shaft 3 can be pressed into the worm 4 in a stable state, so that the bending of the shaft 3 hardly occurs during the press-fitting. In particular, the smaller the diameter of the shaft 3 due to the miniaturization of the motor 2, the more effective when the diameter of the shaft 3 is 1 mm or less.

  Further, as shown in FIG. 4, the worm 4 is fixed to the shaft 3 by a predetermined pressure input by press-fitting the shaft 3 while crushing each rib 13. At this time, the rib 13 is not crushed so as to be buried by the shaft 3, but the rib 13 crushed by the shaft 3 becomes a resin reservoir 15 on the distal end side of the shaft 3 and appears on the distal end side of the shaft 3. The shaft 3 is pushed into the worm 4 while gradually increasing the pressure input and the pressure input is gradually increased, so that when the drop impact occurs, the worm 4 is moved backward by the resin reservoir 15. It becomes difficult to press-fit the shaft 3 deeply.

  Accordingly, the distance H between the tip of the worm 4 and the stopper portion 8 is less likely to be larger than the originally planned dimension (about 0.1 to 0.2 mm), and the stroke amount of the worm 4 is difficult to change. Therefore, a tapping sound generated when the tip of the worm 4 periodically hits the stopper portion 8 when the motor 2 is driven does not increase. Incidentally, the worm 4 is hardly retracted by the resin reservoir 15, but the forward movement of the worm 4 due to impact does not cause the hitting sound because the interval H is narrowed.

  There are various types of resin materials from which such a resin reservoir portion 15 is created. For example, PBT (polybutylene terephthalate), POM (polyoxymethylene), and the like are suitable. Furthermore, even if the same material is used, the pressure input can be easily adjusted only by changing the height and number of the ribs 13, so that it can be easily applied to motors having various torques.

  The number and shape of the ribs 13 of the worm 4 applied to the present invention are not limited to the above embodiment.

It is a top view which shows one Embodiment of the worm gear which concerns on this invention. It is a longitudinal cross-sectional view of a worm applied to the worm gear according to the present invention. It is sectional drawing which follows the III-III line of FIG. It is a longitudinal cross-sectional view which shows the state which press-fitted the shaft into the worm.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Worm gear, 2 ... Motor, 3 ... Shaft, 4 ... Worm, 4a ... Tip of worm (tip of abutting part), 5 ... Worm wheel, 8 ... Stopper part, 10 ... Shaft insertion hole, 10a ... Shaft insertion hole 11 ... Main body part, 12 ... Gear part, 13 ... Rib, 13a ... Reduced diameter surface, 15 ... Resin reservoir part, L ... Axis.

Claims (3)

A main body having a shaft insertion hole into which a shaft of the motor is inserted; and a gear provided spirally around the main body, the tip of the main body being disposed opposite the stopper In a worm gear with a resin worm,
On the wall surface forming the shaft insertion hole, a rib extending in the longitudinal direction from the middle of the shaft insertion hole toward the tip of the main body portion is provided to protrude, and the rib crushed by the shaft is Worm gear characterized by a resin reservoir at the tip end of the shaft.   The worm gear according to claim 1, wherein a plurality of the ribs are provided and are arranged at equal intervals in a circumferential direction of the shaft insertion hole.   The rib has a reduced-diameter surface located on the inner side, and the reduced-diameter surface has an arc shape centered on the axis of the worm and is formed with a smaller diameter than the shaft insertion hole. Item 3. The worm gear according to item 1 or 2.

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