JP2006101605A - Motor with parallel gear reducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for absorbing accuracy errors and cutting the accuracy errors of gears by an elastic body in a gear device, having a backlash reduction mechanism utilizing a spur gear, a helical gear, and conical gears, and to provide a gear device that can be used without replacing gears or bearings for a long time. <P>SOLUTION: The parallel gear device has the spur gear, the helical gear, and a pair of the conical gears whose cone angles are substantially equal. The spacer formed of an elastic body is used to fasten a motor and the spacer together, and to fasten the spacer and a speed reducer. When the spacer and the motor and the spacer and a gear case are fastened together, the planes for fastening the motor and the spacer together and for fastening the spacer and the gear case are two planes that are parallel. They are fixed on lines that pass through the center of the motor in the two planes and intersect with each other substantially at a right angle. They are fixed at equal distances from the center of the motor at two points, respectively so that backlash required in the accuracy errors and the cutting accuracy errors of the gears is absorbed by the elastic bodies. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a structure of a gear device with small backlash, and more particularly to a mechanism of an actuator gear device that requires positioning accuracy.

For example, since an actuator for driving a robot arm and the like requires a particularly high arm positioning accuracy, position control is often performed using a rotation angle of a shaft obtained by a rotary encoder or the like.
On the other hand, in order to reduce the size of the drive motor, the actuator is generally equipped with a gear reducer. However, the backlash that extends to the clearance on the anti-loading tooth surface side is indispensable for the gear device to absorb errors and deformations. The rotation angle of the shaft becomes indefinite due to the clearance due to. Since this is difficult to eliminate by control, the presence of backlash is one of the factors that degrade actuator positioning accuracy.

  On the other hand, a mechanism for adjusting the backlash using a conical gear or the like has been proposed. A conical gear is a gear in which the shift coefficient of a cylindrical gear is linearly changed in the axial direction, and is also called a conical gear or a conical gear. Since the tooth thickness also changes in the axial direction according to the change of the dislocation coefficient, the backlash can be adjusted by moving the gear in the axial direction. However, such a gear position adjusting mechanism is generally difficult to apply to a gear device that is small and manufactured in large quantities because the adjustment procedure is complicated. Another problem is that if the tooth surface is worn as a result of long-term use, the backlash will increase.

For this problem, for example, a structure as in Patent Document 1 has been proposed. In other words, one of the gears is movable in the axial direction, and a spring for biasing the movable gear in the axial direction is provided so that both tooth surfaces are brought into close contact with each other so that the backlash is zero. According to this structure, both tooth surfaces are automatically brought into close contact with each other by the biasing spring, so that precise adjustment work for reducing backlash becomes unnecessary. In addition, even if the tooth surfaces wear due to long-term use, both tooth surfaces remain in close contact by the biasing spring, so that backlash does not increase.
Further, in Patent Document 2, adjustment is made so that backlash is eliminated through the through hole of the gear case, and the amount of deflection of the output shaft of the motor is related to the meshing run-out of the gear of the reduction-side output shaft and the output shaft of the motor. Proposals have been made, for example, in which a small gear that is directly geared or single geared is assembled so as to be equal to the total value of the meshing runout of the gear fixed to the output shaft.

JP-A-6-257660 JP2003-257207A

The cone angle of a conical gear is generally small and often a few degrees. This is based on the fact that the dislocation coefficient of the conical gear is large at one end of the tooth and small at the other, as shown in FIG. That is, in a small gear with a small number of teeth, the tip of the tooth may be sharp at the end portion where the dislocation coefficient is large, and an undercut may occur on the tooth root side at the end portion where the dislocation coefficient is small. This restriction becomes more severe as the cone angle and tooth width increase or the number of teeth decreases. Therefore, in a parallel shaft gear device using a conical gear having a realistic reduction ratio, the cone angle of the gear is generally small.
By the way, when the conical gear is urged in the axial direction, the reaction force generated on the tooth surface is larger than the thrust in the axial direction, like that of the wedge. Similarly to the wedge, the smaller the cone angle, the larger the reaction force generated on the tooth surface by the axial thrust. For this reason, when one of the conical gear pairs having a small cone angle as described above is urged in the axial direction, the reaction force generated on the tooth surface becomes extremely large and not only significantly shortens the service life of the gear and bearing. ， In many cases, noise and vibration are increased.
The present invention relates to a gear device having a backlash reduction mechanism using a spur gear, a helical gear, and a conical gear, and a low backlash reduction mechanism or a reduction mechanism without a backlash is used to reduce the amount of deflection caused by an accuracy error of a single gear. Provides a method of absorbing, and can be used without replacing gears and bearings over a long period of time. Between the spacer and the motor, and between the spacer and the reduction gear case. It was made to provide an electric motor with a machine.

1. The gear device according to the present invention is a spur gear, a helical gear, and a conical gear, in which the conical gear is a parallel shaft type gear device having a pair of conical gears having substantially the same conical angle, between the motor and the pacer. The spacer for fastening the spacer and the reduction gear case is made of an elastic body.
2. Furthermore, when fastening between the spacer and the motor, and between the spacer and the gear box, the surfaces for mounting the motor and the spacer and between the spacer and the gear box are two parallel surfaces, and the motor center on the two surfaces. , Cross at a substantially right angle, are fixed at equal intervals from the center of the motor, and fixed at two points each.
Above 1.2. With this configuration, the rigidity of the elastic spacer and the rigidity force generated by fixing at two points that intersect almost perpendicularly act flexibly, absorb the stress caused by gear accuracy errors, and reduce the low back Provided is an electric motor with a parallel shaft type gear reducer that can operate in a rush and quiet manner.

  By configuring the gear device as described above, both tooth surfaces of the gear are maintained in close contact with each other, and backlash is minimized, so that highly accurate positioning is possible. In addition, there are two parallel surfaces between the motor and the spacer, and between the spacer and the gear box. The two surfaces pass through the motor center, intersect substantially at right angles, and are equidistant from the motor center. In addition, by fixing at two points each, a part of the thrust due to the meshing error is borne by the spacer, which is an elastic body, so that the thrust due to the meshing error is absorbed and the reaction force generated on the tooth surface is small. And the bearing can be used continuously for a long time without damage.

  Either the gear is cut directly on the output shaft of the motor, or a small gear cut at the tip of the output shaft is press-fitted or fixed with a pin, and the front cover of the motor is fitted with the cover of the reduction mechanism. A one-stage reduction mechanism that has a possible inlay portion and is constituted by a large gear that directly meshes with the small gear at the tip of the motor output shaft is desirable. The single-stage reduction mechanism makes it easy to measure backlash, and backlash management by adjustment is easy.

  An embodiment according to the present invention is shown in FIG. The drive motor 1 is fitted to the rotor core 2, the small gear shaft 3 and the small gear shaft integrated with the rotor core, and the small gear bearings 4a and 4b for rotatably supporting the small gear shaft and the small gear bearing. A control motor such as a stepping motor, for example, comprising a stator core 6 sandwiched between the housings 5a and 5b and the motor housing. A small gear 7a is formed at one end of the small gear shaft, the small gear bearing 4a is provided between the small gear and the rotor core, and the small gear bearing 4b is provided in the vicinity of the small gear shaft end opposite to the small gear. It has been.

The motor and the spacer pass through the center of the motor and are fastened at two points at equal intervals from the center. The other surface in the spacer thickness direction passes through the motor center and is fastened to the speed reducer at two points at equal intervals from the center. The two points fastened by each of them are perpendicular to the motor center.
The small gear 7a and the large gear 7b meshing with the small gear 7a are both conical gears having substantially the same conical angle, and are arranged so that their axes are parallel to each other. The large gear bearings 8a and 8b are also rolling bearings, which are fitted simultaneously with the large gear shaft 9 and the gear box 10 integrated with the large gear, and support the large gear shaft rotatably with respect to the gear box. is doing.

  The spacer, which is an elastic body, has a degree of freedom in the range of Young's modulus from 800 MPa to 3000 MPa, and an optimum Young's modulus is selected using the thickness of the spacer as a parameter.

Incidentally, gears, gear shafts, and gear boxes have unavoidable shape errors, and deformation occurs due to the process of transmitting power and temperature changes. In this case, if there is no backlash, the gear meshing proceeds while deforming each part of the speed reducer, and an internal force corresponding to the spring constant of each part is generated as a reaction force. The spacer made of an elastic body absorbs the internal force, and the degree of freedom of absorption is increased by fastening at two points on each of the two orthogonal surfaces passing through the center of the motor.
In the present invention, the small gear is provided in the small gear shaft between the small gear and the rotor core and in the vicinity of the small gear shaft end on the opposite side to the small gear, so that the small gear has a cantilever structure. descend. Further, a portion having a small shaft diameter is provided between the small gear and the small gear bearing 4a, and the load support at the end of the small gear shaft shaft is a convex spherical surface so as not to constrain the small gear in the radial direction. By adopting the shape, the bending rigidity of the small gear shaft is further reduced. As a result, the internal force generated by the shape error is small, and the burden on the gears and bearings is small. By reducing the Young's modulus of the spacer made of an elastic body, it is possible to keep the internal force due to errors and deformation small.

When the gear device is configured as described above and the drive motor is energized, the rotor core rotates and power is transmitted from the small gear to the large gear. By providing an eccentric adjustment ring (not shown) between the motor and the spacer, and adjusting the inter-shaft distance between the large gear and the small gear, the backlash can be adjusted. Therefore, the rotation of the small gear is accurately transmitted to the large gear.
Since the motor housing and the gear box are coupled via a spacer made of an elastic body, the generated internal force can be released by the relative displacement of the motor housing and the gear box. For this reason, the burden on the gears and bearings is small, and operation is possible for a long time without exchanging them.

  Robot arm driving actuators and the like are required to have particularly high arm positioning accuracy, and therefore position control is often performed using the rotation angle of the shaft obtained by a rotary encoder or the like. On the other hand, in order to reduce the size of the drive motor, the actuator is generally equipped with a gear reducer. However, the backlash that extends to the clearance on the anti-loading tooth surface side is indispensable for the gear device to absorb errors and deformations. The rotation angle of the shaft becomes indefinite due to the clearance due to. Since this is difficult to eliminate by control, the presence of backlash is one of the factors that degrade actuator positioning accuracy. The presence of such backlash determines the actuator positioning accuracy and has industrial applicability in applications that require improvement.

It is the front view and side sectional drawing explaining embodiment by this invention. It is the front view and side view of the spacer which consist of elastic bodies by this invention. It is explanatory drawing which shows the assembly | attachment form of a gear box, an electric motor, and a spacer.

Explanation of symbols

1 ... Electric motor,
2 ... Rotor core,
3 ... small gear shaft,
4 ... small gear bearing,
5 ... Motor housing,
6 ... stator core,
7 ... gear pairs,
8 ... Large gear bearing,
9: Large gear shaft,
10 ... gearbox,
DESCRIPTION OF SYMBOLS 11 ... Spacer 12 ... Gear box, spacer mounting hole 13 ... Spacer, motor mounting hole 14 ... Gear box, spacer mounting screw 15 ... Spacer, motor mounting screw

Claims (4)

  A parallel shaft type gear device having a pair of gears, and there are two parallel surfaces for mounting the motor and the spacer, the spacer and the gear box, and the two surfaces pass through the motor center and intersect at almost right angles. And an electric motor with a parallel shaft type gear reducer, which is fixed at two points from the center of the motor at two points, and the spacer is made of an elastic body.   2. An electric motor with a parallel shaft type gear reducer according to claim 1, wherein said gear pair is a parallel shaft type gear device having a conical gear pair having substantially the same cone angle, comprising a motor, a spacer, a spacer, a gear box, There are two parallel planes that pass through the motor center on the two planes, intersect substantially at right angles, are substantially equidistant from the motor center, and are fixed at two points, respectively. An electric motor with a parallel shaft type gear reducer made of an elastic material.   2. The electric motor with a reduction gear according to claim 1, wherein the spacer has a thickness in a range of 1 mm to 12 mm and a Young's modulus of an elastic body is in a range of 800 MPa to 3000 MPa. An electric motor with a parallel shaft type gear reducer consisting of a body.   The electric motor with a reduction gear according to claim 1, wherein the electric motor is a hybrid stepping motor, and the parallel shaft type gear reduction motor with a spacer made of an elastic body.