JPH06272740A - Epicyclic gear type speed changer - Google Patents

Abstract

PURPOSE:To eliminate backlash by using tapered gears as an inner gear, a sun gear and an epicyclic gear, forming the epicyclic gear movable in the axial direction, energizing to the small-diameter end side from the large-diameter end side, and increasing elastic deformation ability in the radial direction with rigidity degradation in the circumferential direction avoided for the epicyclic gear. CONSTITUTION:Tapered parts corresponding to an epicyclic gear 36 is given to a sun gear 30 and an internal gear 50. Three epicyclic gears 36 are mounted in a housing part 46 to fit the internal gear 50 onto its outside. When a predetermined fixed axial load is given to it, a carrier 34 equipped with the three epicyclic gears 36 and the internal gear 50 are positioned coaxially to each other, preset load is given by 1/3 of the axial load to a belleville spring 90, and an engaging part with the internal gear 50 of the epicyclic gear 36 is elastically- deformed by the amount which meets the preset load in the radial direction. If the respective gears 30, 36, 50 are worn, the epicyclic gear 36 is moved to the small-diameter end side from the large-diameter end side, so it is possible to prevent backlash from being generated and increased by the wear.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planetary gear type transmission, and more particularly to reduction of its backlash.

[0002]

2. Description of the Related Art A planetary gear type transmission is widely used because its input shaft and output shaft are coaxial, which is convenient for use, and it is compact and has a large reduction ratio and high transmission efficiency. . However, as with other gear type transmissions, there is a problem that backlash cannot be eliminated. Backlash is a play between tooth surfaces when a pair of gears are engaged with each other, and is considered to be indispensable for smooth rotation of the pair of gears.

However, backlash not only causes noise and vibration during operation of machinery, but also
A load torque exceeding the calculated value is generated in the entire system including the transmission, which adversely affects each component. For example, the control accuracy of the servo motor is reduced. Servo motors are widely used for positioning members that frequently move and stop, but generally have high speed and low torque, and the influence of load disturbance on the servo motor is the square of the reduction ratio. Since the size is reduced in proportion, a speed reducer is often provided between the servo motor and the driven device. A planetary gear type speed reducer is used as the speed reducer, and the backlash of the speed reducer reduces the control accuracy of the servomotor. Although the control accuracy of the servo motor itself has been significantly improved by the recent advances in power electronics and its control technology, the backlash of the planetary gear type transmission connected to the servo motor improves the control accuracy of the entire mechanical device. The fact is that is being hindered.

[0004]

Therefore, the present invention has been made to reduce the backlash of a planetary gear type transmission, or to eliminate it substantially.

[0005]

The summary of the present invention is as follows.
In a planetary gear type transmission including a sun gear, a planetary gear and an internal gear, the planetary gear is a taper gear and the internal gear and the sun gear are taper gears corresponding to the planetary gear, and the planetary gear is movable in the axial direction. And urges from the large diameter end side toward the small diameter end side by the urging means,
In addition, the planetary gear is provided with a selective deformation capacity increasing portion that increases the elastic deformation capacity in the radial direction while avoiding a decrease in the circumferential rigidity of the planetary gear. The selective deformation capability increasing portion can be provided, for example, by concentrically forming an annular groove that does not reach the opposite end surface from each end surface on both sides of the planetary gear.

[0006]

In the conventional planetary gear type transmission, the sun gear,
If the planetary gears and the internal gears are taper gears corresponding to each other and the planetary gears are moved from the large diameter end side toward the small diameter end side, the planetary gears and the sun gears, and the planetary gears and the internal gears The backlash between them can be reduced. However, backlash cannot be completely eliminated. This is because the sun gear, the planetary gear, the internal gear, and the members that hold them have processing errors and thermal expansion.

The planetary gear meshes with the sun gear,
Since it also meshes with the internal gear, if the backlash between the planetary gear and the sun gear disappears when the planetary gear, which is a taper gear, is moved to the smaller diameter end side, move the planetary gear further toward the smaller diameter end. However, backlash between the planetary gear and the internal gear remains. The same applies to the opposite case. In order to completely eliminate the backlash, the thermal expansion state of each component is the largest backlash, and the backlash between the sun gear and the internal gear is the largest in the backlash due to machining error. It is necessary to move the planetary gear to the small diameter end side until
When each gear rotates to a position where the backlash is originally small, or when the thermal expansion state of each gear changes, the tooth flanks are pressed against each other with an extremely large force, and it becomes impossible to rotate. The taper of the planetary gear is relatively small,
This is because when the tooth flanks are strongly pressed against each other, the frictional force between the tooth flanks becomes larger than the force to push the planetary gear back to the large diameter end side due to the effect of the slope.

Therefore, in the present invention, the elastic deformation capacity of the planetary gear is made larger than that of a normal planetary gear, and the tooth surfaces are prevented from being pressed by an excessive force. However, if the elastic deformation capacity of the planetary gears is simply increased, the rotational torque that can be transmitted is limited due to the elastic deformation of the planetary gears, or the rotational speed becomes uneven. It was decided to provide a selective deformation capacity increasing part that increases the elastic deformation capacity of.
In this way, since it is possible to easily elastically deform in the radial direction while avoiding an increase in the elastic deformation in the circumferential direction, it is possible to avoid the problems of the limitation of the transmittable rotational torque and the occurrence of the rotational speed unevenness of the planetary gear. The elastic deformation ability can be increased.

By the elastic deformation of the planetary gear in the radial direction, it is possible to simultaneously solve the above-mentioned problem that it is difficult to eliminate the backlash in both the planetary gear and the sun gear, and in both the planetary gear and the internal gear. . For example, when the backlash between the planetary gear and the sun gear disappears first, the planetary gear is moved to the smaller diameter end side with the elastic deformation in the radial direction, and the planetary gear and the internal gear are separated. Backlash can also be eliminated.

From the above explanation, it is easy to think that the backlash of the planetary gear type transmission can be sufficiently reduced only by increasing the elastic deformation capacity of the planetary gear in the radial direction. Absent. Certainly, it is possible to reduce the backlash by increasing the elastic deformation capacity of the planetary gear in the radial direction. However, there is a limit in that it is possible to prevent a decrease in rigidity in the circumferential direction by increasing the elastic deformation capability of the planetary gear in the radial direction by forming the annular groove. If the size of the planetary gear is determined, the amount by which the planetary gear can be elastically deformed in the radial direction is naturally determined within a range that does not adversely affect the operation.

In the planetary gear type transmission, as described above, it is necessary to reduce the backlash between both the planetary gear and the sun gear and between the planetary gear and the internal gear. It is difficult to eliminate by only the elastic deformation of the planetary gears. In addition, the gears always make sliding contact at points other than the pitch point, and wear cannot be eliminated.Therefore, in order to prevent an increase in backlash due to this wear, the elastic deformation capacity of the planetary gears must be increased. , This is practically difficult.

Therefore, the planetary gear, the sun gear, and the internal gear are tapered gears, and the planetary gear is urged toward the small diameter end side by the urging means and the radial elastic deformation capability of the planetary gear is increased. It is especially effective to use them together.

[0013]

As described above, according to the present invention, the input shaft and the output shaft are coaxial, which is convenient for use, and the planetary gear is excellent in that it has a small size, a large reduction ratio, and a high transmission efficiency. In the gear type transmission, the backlash is remarkably reduced and, in some cases, substantially eliminated. Moreover, the means therefor is extremely simple, and the object can be achieved with almost no increase in device size or manufacturing cost. Machine tools, industrial robots, conveyors, FA (flexible manufacturing) related Equipment, printing machines, packaging machines, textile machines,
It has the effect of enhancing the performance of an extremely wide range of mechanical equipment such as semiconductor manufacturing equipment, medical equipment, assembly machines, paper making machines, and general industrial machines.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings by taking as an example the case where the present invention is applied to a planetary gear type speed reducer for reducing the rotation of a servo motor. In FIG. 1, 10 is a servo motor. The rotation of the servomotor 10 is reduced by a planetary gear type speed reducer (hereinafter, abbreviated as a speed reducer) 12. The rotation of the rotary shaft 14 of the servo motor 10 is decelerated and transmitted to the output shaft 16 of the speed reducer 12.

A housing 22 of the speed reducer 12 is fixed to a casing 20 of the servomotor 10 with bolts 23. An input shaft 24 is rotatably supported by a housing 26 in the housing 22, and the input shaft 24 is connected to the rotary shaft 14 of the servomotor 10 by a connecting device 28. A sun gear 30 is integrally provided at an end of the input shaft 24 opposite to the servo motor 10 side.

On the other hand, a carrier 34 is integrally provided at an end portion of the output shaft 16 near the sun gear 30, and three planet gears 36 are equiangularly spaced on the carrier 34 as shown in FIG. Is held. Three support shafts 38 are fixed to the carrier 34 in parallel with the output shaft 16 and non-rotatably. The planetary gears 36 are rotatably supported by the support shafts 38 via radial bearings 40. is there.

The housing 22 of the speed reducer 12 is provided with a first housing part 44 on the side closer to the servomotor 10 and a second housing part 46 on the far side. 50 are sandwiched. By fixing the internal gear 50 to the first housing portion 44 with the plurality of bolts 54 via the spacer 52 and the second housing portion 46 with the plurality of bolts 58 via the spacer 56, The first housing portion 44, the internal gear 50, and the second housing portion 46 are fixed to each other to form the integral housing 22. Therefore, the internal gear 50 has the housing 22
It is also a component of.

In the housing 22, as shown in FIG.
A lubricating oil supply port 62 and a lubricating oil discharge port 64 are provided to lubricate and cool the inside of the housing 22. The lubricating oil supplied from the lubricating oil supply port 62 is discharged from the lubricating oil discharge port 64, the meshing portion of the sun gear 30, the planetary gear 36, and the internal gear 50 and the output shaft 1
The bearing 66 of No. 6 is lubricated, and each gear 30, 36,
50, the carrier 34, the output shaft 16, the bearing 66, etc. are cooled. However, when the rotation speed and load of the speed reducer 12 are small and the amount of heat generation is not so large, it is possible to employ grease-filled lubrication instead of forced lubrication.

As shown in the enlarged view of FIGS. 4 and 5, each planetary gear 36 has a tapered toothed portion to form a tapered gear, and one annular groove 7 is provided from each end face on both sides.
0, 72 are formed. The annular groove 70 is the planetary gear 36.
Is formed from the end surface on the large diameter end side toward the end surface on the small diameter end side, and the annular groove 72 is formed on the inner peripheral side of the annular groove 70 from the end surface on the small diameter end side to the end surface on the large diameter end side. Has been done. Both of the annular grooves 70, 72 are cut from one end face toward the other end face, but their depth is smaller than the thickness of the planetary gear 36 and does not reach the other end face. However, the two annular grooves 70, 72 are overlapped with each other in the intermediate portion in the axial direction of the planetary gear 36, and if a radially inward force indicated by the arrow F is applied to the planetary gear 36, the periphery of the both annular grooves 70, 72 is increased. The planetary gear 36 is allowed to elastically deform in the radial direction with a decrease in the width of the annular grooves 70, 72 due to elastic deformation mainly due to bending of the portion.

The formation of the annular grooves 70, 72 also reduces the rigidity of the planetary gear 36 against the circumferential force. This is because the portions where the annular grooves 70, 72 are formed are annular grooves 70, 72.
This is because elastic deformation due to shearing is more likely to occur than before the formation of. However, since the widths of the annular grooves 70 and 72 are made small, the increase in the elastic deformation amount due to the shearing of this portion is insignificant and can be ignored. However, in order to make the planetary gear 36 have sufficient deformability in the radial direction and negligible elastic deformability in the circumferential direction, the dimensions of the annular grooves 70, 72 can be appropriately determined. In particular, it is necessary to make the width of the annular grooves 70, 72 as small as possible and secure the wall thickness of the portion between the bottom surface of the annular grooves 70, 72 and the end surface of the planetary gear 36.

As the planetary gear 36 is tapered as described above, the sun gear 30 and the internal gear 50
A tooth corresponding to the taper of the planetary gear 36 is also attached to the tooth portion of these, and these are also tapered gears. As shown in FIG. 1, the planetary gear 36 is fitted in a generally annular gap formed between the sun gear 30 and the internal gear 50, but the diameter of the tooth portion of the planetary gear 36 is a servo. Motor 1
Since the portion closer to 0 is made smaller, the sun gear 30
The annular gear gap formed between the sun gear 3 and the internal gear 50 is narrower toward the portion closer to the servomotor 10.
0 and the teeth of the internal gear 50 are tapered.

Each planetary gear 36 is movable in the axial direction of each support shaft 38. As shown in FIG. 6, the radial bearing 40 provided between the planetary gear 36 and the support shaft 38 is a needle bearing, and the retainer 7 thereof is provided.
8 is sandwiched between a retaining ring 80 attached to the support shaft 38 and a retainer 84 of the thrust bearing 82, and its axial movement is restricted within a certain range. However, the movement of the planetary gear 36 in the axial direction with respect to the bearing 40 is not restricted, and the movement in the axial direction is allowed.

The planetary gear 36 is biased toward the servomotor 10 by a disc spring 90 via the thrust bearing 82. The disc spring 90 has a relatively small elastic force, and the planetary gear 36 is elastically pushed into the tapered gap between the sun gear 30 and the internal gear 50 by this elastic force. is there. The inner peripheral surface of the planetary gear 36 is in direct contact with the needle of the radial bearing 40, and the end surface on the thrust bearing 82 side is in direct contact with the needle of the thrust bearing 82. Therefore, these inner peripheral surface and end surface are It is hardened by heat treatment.

In FIG. 2, reference numeral 94 denotes a servo motor mounting surface of the housing 22, and female screw hole 96 denotes the bolt 2 described above.
It is for 3. Further, 98 is a bearing retainer of the bearing 26, and the bolt hole 100 is for fixing the housing 22 to the target device. In FIG. 3, the female screw hole 10
Reference numeral 2 denotes a bolt 54 for fixing the first housing portion 44 to the internal gear 50, and is provided between bolts 58 for fixing the internal gear 50 to the second housing portion 46.

As is apparent from FIG. 1, the first housing portion 44 and the second housing portion 46 have annular fitting projections 1 which fit into the counterbore holes 110 and 112 of the internal gear 50.
14 and 116 are formed, but these are provided for rough positioning. That is, the inner diameters of the counterbore holes 110, 112 are made larger than the outer diameters of the fitting protrusions 114, 116 by a certain dimension, and the first and second housing parts 44, 46 and the internal gear 50 are radially arranged. It is possible to move relative to a certain amount.

Next, a method of assembling the speed reducer 12 of this embodiment will be described. First, in the second housing portion 46, the output shaft 16,
The planetary gears 36 and the like are assembled, and the internal gear 50 is fitted to the outside of the three planetary gears 36. If a predetermined constant axial load is applied to the internal gear 50, the three planetary gears 36
And the internal gear 50 are concentrically positioned, each disc spring 90 is given a set load of 1/3 of the axial load, and the planetary gear 36 is
The meshing portion with the internal gear 50 is elastically deformed in the radial direction by an amount corresponding to the set load.

The gap between the second housing portion 46 and the internal gear 50 in this state is measured by a thickness gauge or a depth micrometer, and the thickness of the spacer 56 is finished to the same dimension as the gap. The internal gear 50 is once removed, the finished spacer 56 is placed on the second housing portion 46, and then the internal gear 50 is fitted again to the outer sides of the three planetary gears 36 and the internal gear 50. And the carrier 34 are concentric, and the internal gear 5 is
0 is fixed to the second housing part 46.

The second housing portion 46 and the internal gear 50
The first housing portion 44 with the input shaft 24 assembled thereon is placed on the assembly of the above, and the sun gear 30 is attached to the three planetary gears 3.
Fit inside 6 and apply a constant predetermined axial load. As a result, the carrier 34 having the three planetary gears 36 and the sun gear 30 are positioned concentrically, and the meshing portion of each planetary gear 36 with the sun gear 30 is elastically deformed by an appropriate amount in the radial direction. To be

In this state, the gap between the first housing portion 44 and the internal gear 50 is measured, and the thickness of the spacer 52 is finished to the same dimension as the gap. Then, the finished spacer 52 is used as the first housing portion 44 and the internal gear 50.
It is sandwiched between and and fixed by bolts 54.

As described above, the assembly of the speed reducer 12 is completed, and the sun gear 30, the planetary gear 36 and the internal gear 50 are brought into the meshing state without backlash. However, if the speed reducer 12 is rotated from this state, the gears 30, 36,
The gear 50 meshes at a position different from that when it is assembled, and the meshing state changes due to a machining error of these gears 30, 36, 50. When the change in the meshing state can be absorbed by the elastic deformation of the planetary gear 36 in the radial direction, the speed reducer 12 operates substantially without backlash. Even if it cannot be absorbed, backlash is generated in the reduction gear 12 to the extent that it cannot be absorbed, which is significantly smaller than that of a conventional planetary gear type reduction gear.

Further, due to the heat generated by the operation, the sun gear 3
0, the planetary gear 36, the internal gear 50, and the like have different amounts of thermal expansion, and conventionally, the amount of backlash had to be determined in consideration of the amount of thermal expansion as well, so the backlash was further increased. However, in the speed reducer 12 of the present embodiment, the change in the thermal expansion amount is absorbed by the elastic deformation of the planetary gear 36 in the radial direction, which is also advantageous from this point.

Further, if the sun gear 30, the planetary gear 36 and the internal gear 50 wear due to use, the disc spring 9
The planetary gear 36 is moved from the large-diameter end side toward the small-diameter end side by the biasing force of 0, and the occurrence or increase of backlash due to wear is prevented.

Therefore, the rotation of the servo motor 10 is accurately transmitted to the output shaft 16, and the driven member connected to the output shaft is accurately positioned. In the conventional planetary gear type speed reducer, the substantial rigidity of the speed reducer is reduced due to the presence of backlash, the positioning accuracy of the driven member is poor when the servo motor is repeatedly started and stopped, and in some cases, vibration is generated. Although it sometimes occurred that the positioning could not be performed, the speed reducer 12 of the present embodiment can position the driven member with high precision, and the occurrence of vibration or the like hardly occurs.

As is clear from the above description, in this embodiment, the portion of the planetary gear 36 in which the annular grooves 70 and 72 are formed constitutes the selective deformation capacity increasing portion, and the disc spring 90 is provided.
Constitutes the biasing means.

In this embodiment, the speed reducer 12 is attached to the high speed, low torque servomotor 10,
Although the rotation thereof is decelerated, the present invention may be applied to a planetary gear type transmission that decelerates the rotation of a low-speed, high-torque DD motor (direct drive motor), or vice versa. It is possible. Further, the effect can be obtained even when applied to a transmission of a general drive motor, not for positioning. For example, when the load fluctuation is large, the backlash of the transmission may cause the vibration of the entire system. In such a case, if the planetary gear type transmission according to the present invention is used, the vibration will be reduced. It can be reduced or prevented.

Further, in the present embodiment, the internal gear is made non-rotatable, but the carrier or the sun gear may be made non-rotatable depending on the purpose of the planetary gear type transmission. It is also possible to increase the number of annular grooves formed in the planetary gear or change the structure of the selective deformation increasing portion. Further, the planetary gear is held by the support shaft so as to be rotatable and immovable in the axial direction, and the support shaft is held by the carrier so as not to be rotatable and movable in the axial direction, or vice versa. It is also possible to change the holding mechanism of the planetary gear, for example, by holding the planetary gear so as to be movable in the axial direction. In addition, the present invention can be implemented in various modified and improved modes based on the knowledge of those skilled in the art, such as changing the urging means for urging the planetary gear in the axial direction.

[Brief description of drawings]

FIG. 1 is a front sectional view showing a state in which a planetary gear type speed reducer according to an embodiment of the present invention is attached to a servo motor.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is a sectional view taken along line BB in FIG.

FIG. 4 is a front sectional view of a planetary gear used in the speed reducer.

FIG. 5 is a left side view of the planetary gear.

6 is an enlarged view showing the periphery of the planetary gear of FIG. 1. FIG.

[Explanation of symbols]

 16 Output shaft 22 Housing 24 Input shaft 30 Sun gear 34 Carrier 36 Planetary gear 38 Support shaft 40 Radial bearing 44 First housing part 46 Second housing part 50 Internal gear 52,56 Spacer 70,72 Annular groove 82 Thrust bearing 90 Disc Spring

Claims (1)

[Claims] 1. A planetary gear type transmission comprising a sun gear, a planetary gear and an internal gear, wherein the planetary gear is a tapered gear, the internal gear and the sun gear are tapered gears corresponding to the planetary gear, and the planetary gear is a shaft. Direction and the biasing means urges from the large diameter end side to the small diameter end side, and increases the elastic deformation capacity in the radial direction while avoiding a decrease in the circumferential rigidity of the planetary gear. A planetary gear type transmission characterized in that a selective deformation capacity increasing portion is provided.