JPH05302649A - Worm speed reducer - Google Patents

Abstract

PURPOSE:To reduce friction between a worm gear and a worm wheel, and restrain to the minimum level energy loss of rotating power to be transmitted from the worm gear to the worm wheel and a backlash. CONSTITUTION:In a worm speed reducer 1, a worm gear 4 fixed to an input shaft 2 and a worm wheel 5 secured to an output shaft 3 reduce an input engine speed. Coil-like ball grooves 6 formed on the hourglass-shaped worm gear 4 are engaged with balls 8 contained inside numerous recesses 7 formed on the worm wheel 5. Consequently, rotating power of the worm gear 4 can be transmitted to the worm wheel 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a worm speed reducer for reducing the rotation transmitted to a worm gear and transmitting it to a worm wheel.

[0002]

2. Description of the Related Art A worm speed reducer is composed of a worm gear having a spiral tooth trace and a worm wheel that meshes with the worm gear. The number of teeth of the worm wheel is set larger than the number of teeth of the worm gear. .. For this reason, when the worm gear is rotationally driven, the worm wheel decelerates and rotates.

[0003]

Since the conventional worm speed reducer has a structure in which power is transmitted with friction between tooth surfaces, the mechanical loss due to friction is large and the efficiency is low. .. In addition, a reduction gear using a drum-shaped worm that reduces backlash by slightly changing the lead angles of the front and back of the tooth surface by using a worm gear as a drum to increase the transmission torque is also used. The point that friction of the tooth surface with the wheel is not improved.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce friction between a worm gear and a worm wheel, to prevent backlash by constantly contacting tooth contact, and to reduce manufacturing cost. The purpose is to provide a worm reducer that suppresses this.

[0005]

The worm speed reducer of the present invention employs the following technical means. The worm speed reducer includes a worm gear having a spiral tooth trace and a worm wheel that meshes with the worm gear, and decelerates the rotation transmitted to the worm gear and transmits the decelerated rotation to the worm wheel. The worm wheel has a large number of depressions on its periphery, and balls are arranged in the depressions. Further, the tooth trace of the worm gear is a ball groove that receives the power transmission of the worm gear via the ball.

[0006]

When the worm gear is rotationally driven, the ball groove of the tooth trace spirally rotates. The balls arranged in the ball groove move as the ball groove rotates, and the worm wheel rotates by the movement of the ball.

[0007]

As described above, in the worm reducer of the present invention, when the rotation of the worm gear is transmitted to the worm wheel, it is transmitted through the balls. Therefore, due to the rotation of the ball, the friction between the worm gear and the worm wheel becomes much smaller than in the conventional case. As a result, the energy loss transmitted from the worm gear to the worm wheel can be suppressed to a low level. Further, since the tooth of the worm wheel is replaced by a rotatable ball, the worm gear reducer with high transmission efficiency can be provided at low cost.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a worm speed reducer of the present invention will be described based on an embodiment shown in the drawings. [Structure of Embodiment] FIGS. 1 to 3 show a first embodiment of the present invention. FIG. 1 is a sectional view of a worm speed reducer, and FIG. 2 is a sectional view taken along line AA of FIG. 3 is a sectional view of a meshing portion of a worm gear and a worm wheel. The worm reducer 1 of the present embodiment is used for a mechanical device that requires high efficiency, high accuracy, long life, and high torque transmission, such as a joint of an industrial robot or a transfer device of a precision machine. The rotational power transmitted to the shaft 2 is decelerated and transmitted to the output shaft 3. The rotation power is decelerated by the worm gear 4 fixed to the input shaft 2 and the worm wheel 5 fixed to the output shaft 3, and the ball groove 6 provided as a spiral tooth trace of the worm gear 4 is The power of the worm gear 4 is transmitted to the worm wheel 5 by meshing with the balls 8 arranged in the depressions 7 around the wheel 5.

The input shaft 2 and the output shaft 3 intersect vertically without intersecting each other, and are rotatably supported by the case 10 via bearings 9.

The worm gear 4 of the present embodiment has a drum shape in which both ends have a large diameter so as to mesh with the worm wheel 5 over a wide range (for example, 1/4 of the outer diameter of the worm wheel 5).

Further, the ball groove 6 of this embodiment is composed of the balls 8
It is provided in a Gothic arch shape with a V-shaped cross section having a curvature slightly larger than the curvature of the curved surface (see FIG. 3). In particular,
Assuming that the diameter of the ball 8 is d, the curvature R of the ball groove 6 is
For example, it is provided in the range of R = 0.52 to 0.6 d. Since the ball groove 6 is provided in a Gothic arch shape, the ball 8 has a line of action of approximately 45 ° with two-point contact as shown in FIG. Thus, the rolling resistance of the ball 8 is slightly increased because of the two-point contact, but the backlash is eliminated, and the load capacity is high, and it is possible to face a load in two directions of forward rotation and reverse rotation. Further, since the ball groove 6 is in two-point contact with the ball 8 and has a line of action of approximately 45 °, the meshing angle θ between the worm gear 4 and the worm wheel 5 is 9
It can be 0 ° or 90 ° or more. For comparison, in the meshing of the teeth of the worm gear of the prior art and the teeth of the worm wheel, even if the worm gear is shaped like a drum, the contact area of the teeth is increased, and the oil retention is also high (drum shaped worm), When the end of the tooth surface of is at a right angle,
The tooth length of the worm gear cannot be increased any longer. Therefore, conventionally, the meshing angle between the worm gear and the worm wheel has been limited to about 40 °. In this way, the worm gear reducer 1 according to the present embodiment transmits a very large torque by achieving a meshing ratio that has not been achieved in the past.

The worm wheel 5 of this embodiment is provided with a large number of depressions 7 at equal intervals on the outer circumference. This many depressions 7
It is a spherical hole into which a part of a large number of balls 8 are fitted and which holds the balls 8 rotatably, and its shape matches the curvature of the balls 8. Further, an oil sump 11 for accumulating lubricating oil is formed at the bottom of each recess 7.

The balls 8 are hard spheres arranged in the depressions 7 of the worm wheel 5 and having excellent wear resistance.
It is held by the inner wall 12 of the case 10 in a state where it does not mesh with the worm gear 4 so as not to fall off from it.

[Operation of Embodiment] Next, the operation of the above embodiment will be briefly described. Input shaft 2 depending on the output of the motor
Is driven to rotate, the worm gear 4 together with the input shaft 2 is driven.
Rotates. The spirally wound ball groove 6 is rotated by the rotation of the worm gear 4, and the ball 8 fitted in the ball groove 6 is driven. When the ball 8 is driven by the worm gear 4, the worm wheel 5 that arranges the ball 8 in the recess 7 rotates, and the output shaft 3 rotates. As a result, the rotational power transmitted to the input shaft 2 is decelerated and transmitted to the output shaft 3.

[Effects of the Embodiment] In the worm gear reducer 1 of this embodiment, the rotation of the worm gear 4 causes the worm wheel 5 to rotate.
When transmitted to the worm gear 4, it is transmitted via the balls 8 held around the worm gear 4. That is, since the worm gear 4 and the ball 8 are in rolling contact with each other and the ball 8 and the worm wheel 5 are in sliding contact with each other, friction when power is transmitted from the worm gear 4 to the worm wheel 5 is much smaller than in the conventional case. As a result, the energy loss transmitted from the worm gear 4 to the worm wheel 5 can be suppressed low. Since the worm wheel 5 is in spherical spherical sliding contact with the ball 8, the friction is small and the contact area is wide, so that a large load can be carried. Although the worm gear 4 and the ball 8 are in rolling contact with each other, the meshing angle between the worm gear 4 and the worm wheel 5 is 90 °, which is a very high meshing ratio as compared with the conventional art, and thus a large torque can be transmitted. By reducing the distance between the input shaft 2 and the output shaft 3, that is, by applying a preload to the input shaft 2 and the output shaft 3, the rigidity can be increased, and
Backlash can be kept very low. Since the tooth of the worm wheel 5 is replaced by the rotatable ball 8, the structure is simple and the number of parts and the number of processing steps are low.
It can be manufactured at a low price. The ball groove 6 of the worm gear 4 is
The worm gear 4 can easily be formed into a drum shape because the accuracy is lower than that of the teeth of the conventional drum-shaped worm.

[Second Embodiment] FIG. 4 is a sectional view of a worm gear reducer 1 according to a second embodiment. In the present embodiment, the balls 8 arranged on the outer periphery of the worm wheel 5 are arranged in two rows to increase the transmission torque capacity of the worm speed reducer 1.

[Modification] In the above embodiment, the ball groove is formed as a V-shaped groove having a Gothic arch shape, but a flat V-shaped groove or a ball groove adapted to the curvature of the ball may be used. Other shapes are acceptable. Further, although an example is shown in which the depression is matched with the curvature of the ball, the shape of the depression may be formed in a V-shaped cross section or may be provided as a groove. Although the ball is prevented from falling along the inner wall of the case, it may be held by another member (for example, a guide).

[Brief description of drawings]

FIG. 1 is a sectional view of a worm speed reducer (first embodiment).

FIG. 2 is a sectional view taken along line AA of FIG. 1 (first embodiment).

FIG. 3 is a cross-sectional view of a meshing portion (first embodiment).

FIG. 4 is a sectional view of a worm reducer (second embodiment).

[Explanation of symbols]

 1 Worm reducer 4 Worm gear 5 Worm wheel 6 Ball groove (tooth line) 7 Dimple 8 Ball

Claims (2)

[Claims] 1. A worm wheel reducer comprising: a worm gear having toothed spirals; and a worm wheel meshing with the worm gear, wherein the rotation transmitted to the worm gear is decelerated and transmitted to the worm wheel. Is provided with a large number of depressions in the periphery and balls are arranged in the plurality of depressions, and the tooth trace of the worm gear is a ball groove that receives transmission of the power of the worm gear via the balls. Worm reducer. 2. The worm reducer according to claim 1, wherein the ball groove has a curvature slightly larger than a curved surface of the ball and has a V-shaped cross section.