JP2014059050A - Planetary gear mechanism of high transmission gear ratio type speed reducer with removed backlash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate backlash so as to perform an accurate operation of a speed reducer having two planetary gear mechanisms with a stationary ring gear and a rotary ring gear having different number of teeth to each other.SOLUTION: A first planetary gear mechanism in which a sun gear shaft 2 formed with a sun gear SG is mounted at the center of a housing 1, comprising a sun gear SG and a stationary ring gear RGf and a second planetary gear mechanism comprising the sun gear SG and a rotary ring gear RGr are combined to each other to constitute a speed reducer. The rotary ring gear RGr at a low speed side of the speed reducer is axially divided into two parts, one inner teeth part is arranged at a sub-gear body 3B and the sub-gear body 3B is rotatably fitted to the rotary ring gear body 3A. Further, a thin plate 3C is inserted between both gear bodies and a thickness of the plate is set equally to an amount of backlash of the second planetary gear mechanism. The teeth of the sub-gear body 3B and the teeth of the rotary ring gear main body 3A have a phase displacement, so that the backlash between the planetary gear and the rotary ring gear RGr is removed.

Description

  The present invention relates to a reduction gear having a large gear ratio, which is configured by combining a plurality of planetary gear mechanisms in which a planetary gear is arranged between a sun gear and a ring gear, and in particular, eliminates such backlash of the reduction gear and performs accurate operation. The purpose is to make it happen.

  In a power transmission system that rotationally drives mechanical parts or work equipment, a transmission for changing the rotational speed and torque is conventionally used so as to match the characteristics of the driven equipment. Recently, automatic operation using power has been developed in various fields, and in OA equipment such as a copying machine, various devices are often driven using a very small motor as a drive source. Since a small motor has high speed rotation and low torque, in such a case, a small speed reducer that adjusts the rotation speed and the like is often interposed in the power transmission system. Further, in parts assembly robots, semiconductor inspection devices, etc., a reduction gear with a high reduction ratio is used for the purpose of determining a highly accurate position.

As a transmission, there is a friction transmission type such as a belt transmission device using pulleys of different diameters, but generally a gear type transmission device is used, and among them, a planetary gear using a planetary gear mechanism is used. There is a type transmission. The planetary gear mechanism has a sun gear (sun gear) at the center and a ring gear (ring gear) that is an internal gear around the sun gear, and a plurality of planetary gears that mesh with both gears between the sun gear and the ring gear. A gear (planetary gear) is arranged. The plurality of planetary gears are attached to and supported by a carrier (also called a retainer) that carries the planetary gears. The carrier is configured to be rotatable about a rotation axis that is concentric with the sun gear and the ring gear. When the carrier rotates, the planetary gear performs a planetary motion that rotates while revolving inside the ring gear.
In this planetary gear type transmission, each gear and carrier can be freely selected as input / output elements, and the input shaft and the output shaft are arranged concentrically, so the arrangement design of the power transmission device is easy. In addition, a large gear ratio can be obtained by using planetary motion. For example, a large-speed-ratio reducer generally called a cyclo reducer ("Cyclo" is a registered trademark) disclosed in JP-A-5-296301 is a reducer that uses the planetary motion of an internal gear. Used in robot arm drive devices.

Two planetary gear mechanisms each having a fixed ring gear and a rotating ring gear are combined to constitute a reduction gear having a very large gear ratio using the planetary gear mechanism, and the number of teeth of both ring gears is adjusted. A speed reducer having a slight difference (hereinafter referred to as “differential planetary gear speed reducer”) is known, and is disclosed in Japanese Patent Application Laid-Open No. 55-100445 as an example.
In the differential planetary gear speed reducer of this publication, as shown in FIG. 8, a plurality of planetary gears PG meshing with the sun gear SG fixed to the input shaft IS are arranged. As shown in the longitudinal sectional view of FIG. 8A, the planetary gear PG is a relatively long gear in the axial direction, and meshes with both the fixed ring gear RGf and the rotating ring gear RGr arranged on the outer periphery thereof. A first planetary gear mechanism having a fixed ring gear RGf and a second planetary gear mechanism having a rotating ring gear RGr are configured. The rotating ring gear RGr is fixed to the output shaft OS and is rotatable, and the planetary gear PG is fitted into the support shaft SS, and both ends of the support shaft SS are supported rotatably with respect to the input / output shaft. The two carriers CR are fitted through ball bearings.

  When the sun gear SG of the input shaft IS rotates, the planetary gear PG rotates in the opposite direction, and at the same time receives the reaction force from the fixed ring gear RGf, and its center is along the fixed ring gear RGf of the first planetary gear mechanism. Revolve. The carrier CR that pivotally supports the planetary gear PG rotates in the same direction as the sun gear SG while being rotated. The planetary gear PG of the differential planetary gear reducer meshes with the rotating ring gear RGr of the second planetary gear mechanism fixed to the output shaft OS, and there is a slight difference in the number of teeth of both ring gears. Therefore, when the planetary gear PG revolves around the sun gear SG once (the carrier CR rotates once), the rotating ring gear RGr is rotationally driven by the difference in the number of teeth. In such a differential planetary gear speed reducer, a sun gear and a rotating ring gear constitute a transmission that serves as an input / output unit for power transmission.

  In the differential planetary gear speed reducer of FIG. 8, the planetary gears in the first and second planetary gear mechanisms are shared, and the fixed ring gear RGf and the rotating ring gear RGr that are ring gears of the first and second planetary gear mechanisms. Set the number of teeth difference between. On the other hand, the present applicant has improved a differential planetary gear speed reducer in which a planetary gear is separately provided for each planetary gear mechanism in a transmission that combines two planetary gear mechanisms. Devised. This improved transmission is not limited to the ring gears in the first and second planetary gear mechanisms, and can be operated as a transmission by providing a difference in the number of teeth in the sun gear. It is also generalized in principle.

JP-A-5-296301 JP-A-55-100445

  As described above, with the differential planetary gear reducer, a reduction gear with a very large reduction ratio can be realized by a relatively simple structure, but backlash between meshing teeth is accompanied by the use of the gear. The problem of inevitably occurs. In particular, in parts assembly robots, etc., when the rotational speed of the sun gear is greatly reduced and transmitted to the rotating ring gear to perform high-accuracy positioning with improved resolution, the sun gear rotates in reverse. When returning the angular position of the ring gear, the rotating ring gear does not immediately rotate in the reverse direction due to backlash between the rotating ring gear and the planetary gear. Therefore, even if a differential planetary gear speed reducer is interposed in the control system of the positioning device, if backlash occurs, the positioning accuracy cannot be improved as expected, and the responsiveness may be lowered.

  To eliminate backlash not only with differential planetary gear reducers but also with gear reducers, etc., the gear is divided into two parts in the axial direction and the teeth are slightly shifted in phase and screwed together. There is a way to conclude. This is to prevent a gap from being generated by pinching the gear teeth meshing between the teeth of the divided gears whose phases are shifted. Further, in the reduction gear disclosed in Patent Document 1, the internal gear and the fixed internal gear that meshes with the internal gear are combined into two in the axial direction so as to have opposite phases, and the backlash is adjusted.

However, such a backlash adjustment method requires time and labor for an operator because the operator adjusts the gap corresponding to each product when assembling the reduction gear. It is easy to finish and the amount of backlash is often not constant. When screwing a divided gear or the like is not fastened symmetrically at two or more locations, “floating” occurs on one side, so that the work becomes complicated from this surface as well, and the fastening portion is caused by vibration during operation of the speed reducer. There is also a risk of loosening.
An object of the present invention is to solve the above-mentioned problems by removing backlash between gears by a simple and reliable means in a reduction gear combining two planetary gear mechanisms such as a differential planetary gear reduction gear. There is.

In view of the above problems, the present invention is a reduction gear that combines a first planetary gear mechanism and a second planetary gear mechanism each provided with a fixed ring gear and a rotating ring gear, and the rotating ring gear is divided into two in the axial direction. A shim (thin plate) having a predetermined thickness is inserted between both of the rotating ring gears so that both teeth have a slight phase shift. That is, the present invention
A first planetary gear mechanism having a sun gear shaft installed at the center of a fixed housing and formed with a sun gear, and a sun gear of the sun gear shaft and a non-rotatable fixed ring gear provided around the sun gear shaft; And a second planetary gear mechanism having a sun gear of the sun gear shaft and a rotatable rotating ring gear provided around the sun gear,
In the first planetary gear mechanism and the second planetary gear mechanism, a planetary gear meshing with a ring gear and a sun gear is disposed, and at least one of the ring gear and the sun gear is provided with a tooth number difference, The sun gear shaft and the rotating ring gear are reduction gears that serve as input / output portions for power transmission,
The rotating ring gear includes a rotating ring gear main body in which one internal tooth portion divided in the axial direction is formed, and a secondary gear body in which the other internal tooth portion is formed, and the rotating ring gear main body; A fitting portion that fits relatively rotatably with the auxiliary gear body is provided,
A thin plate that contacts the radial surface of the rotating ring gear body and the radial surface of the auxiliary gear body is interposed in the fitting portion, and the thickness of the thin plate is the same as that of the first planetary gear mechanism. It is equal to the backlash between the rotating ring gear of the second planetary gear mechanism and the planetary gear that occurs when the second planetary gear mechanism is assembled. "
It is a reduction gear characterized by this.

  According to a second aspect of the present invention, the thin plate is preferably provided with elasticity in a direction in which a radial surface of the rotating ring gear body and a radial surface of the auxiliary gear body are separated from each other.

  As described in claim 3, while forming a peripheral wall portion provided with a notch portion in the rotating ring gear main body, the auxiliary gear body is fitted to the peripheral wall portion, and on the outer periphery of the auxiliary gear body. The protrusion part which fits into the notch part of the said surrounding wall part and comprises a joint part can be provided.

  According to a fourth aspect of the present invention, the fixed ring gear in the first planetary gear mechanism includes a fixed ring gear main body in which one internal tooth portion divided in the axial direction is formed, and the other internal tooth portion. A second fitting portion that is divided into a second auxiliary gear body and that the second auxiliary gear body is fitted to the fixed ring gear main body so as to be rotatable relative to the fixed ring gear body; Includes a second thin plate in contact with a radial surface of the fixed ring gear body and a radial surface of the second auxiliary gear body, and the thickness of the second thin plate is determined by the thickness of the first planetary gear. The backlash between the fixed ring gear of the first planetary gear mechanism and the planetary gear can be made equal when the mechanism and the second planetary gear mechanism are assembled.

According to a fifth aspect of the present invention, a plurality of first planetary gears meshing with the gears are disposed between the sun gear of the first planetary gear mechanism and the fixed ring gear, and the second planetary gears. Between the sun gear of the planetary gear mechanism and the rotating ring gear, a plurality of second planetary gears meshing with these gears are installed, and between the first planetary gear mechanism and the second planetary gear mechanism. The disk-shaped carrier provided with support shafts on both sides is installed, the first planetary gear is rotatably fitted on the support shaft on one side of the carrier, and the second planetary gear is mounted on the other side of the carrier. It is preferable that the support shaft on the side is rotatably fitted.
In this case, as described in claim 6, the first planetary gear and the second planetary gear can be fitted to the support shaft of the carrier via a rolling bearing.

  The speed reducer of the present invention is a combination of two planetary gear mechanisms each having a fixed ring gear and a rotating ring gear, and the rotating ring gear of the planetary gear mechanism on the reduction side is divided in the axial direction. The rotating ring gear main body in which the inner tooth portion is formed and the auxiliary gear body in which the other inner tooth portion is formed. The rotating ring gear body and the sub-gear body are fitted so as to be relatively rotatable, and opposing radial surfaces are formed in the fitting portion, and a thin plate is interposed therebetween. The thickness of the thin plate is set to be equal to the amount of backlash generated when two planetary gear mechanisms are assembled.

Specifically, the setting of the thickness of the thin plate and the insertion into the gap between the rotating ring gear main body and the sub-gear body are performed in the following procedure.
A first planetary gear mechanism having a fixed ring gear and a second planetary gear mechanism having a rotating ring gear are assembled, and the sun gear of the sun gear shaft is meshed with the planetary gear in each planetary gear mechanism, and then the rotating ring gear. A rotational force in one direction is applied to the sun gear shaft in a state where the rotation of the sun gear is blocked. At this time, the teeth of the planetary gear meshing with the rotating ring gear are in contact with one surface pressed against the teeth of the internal teeth of the rotating ring gear (both the rotating ring gear main body and the auxiliary gear body) Backlash occurs between the teeth of the teeth. In this state, when the sub-gear body is rotated in a direction that separates the opposing radial surfaces, when the sub-gear body is slightly rotated by the amount of backlash, the sub-gear body has its teeth different from the other surface of the planetary gear teeth. Stop in contact. The gap between the opposing radial surfaces at the position where the auxiliary gear body is stopped is measured using, for example, a gap gauge, and a thin plate having the same thickness is inserted between the opposing radial surfaces.

  In the speed reducer of the present invention in which the thin plate is interposed, the teeth of the rotating ring gear main body and the sub gear body are slightly out of phase in the circumferential direction. When the sun gear shaft rotates in one direction, the planetary gear of the second planetary gear mechanism comes into contact with the internal tooth portion of the rotating ring gear main body and rotates the rotating ring gear main body in one direction. Further, when the sun gear shaft rotates in the opposite direction, the planetary gear is in contact with the internal gear portion of the auxiliary gear body, so that the auxiliary gear body rotates the rotating ring gear main body in the opposite direction via the thin plate. Since this switching is performed without backlash, for example, when the speed reducer according to the present invention is interposed as a speed reducer for controlling the positioning device, the positioning accuracy can be improved reliably and the rotation is performed in the reverse direction. The responsiveness will not be deteriorated. Generation of noise due to backlash and occurrence of looseness associated with vibration during use of power transmission or screws can be prevented.

  As in the second aspect of the invention, when the thin plate between the rotating ring gear main body and the sub-gear body is given elasticity in the direction of separating both radial surfaces, the rotation ring gear main body and the sub-gear body Backlash removal can be achieved by reliably bringing the teeth of the inner teeth into contact with the teeth of the planetary gear. Further, even when a slight dimensional difference occurs in the gap between the rotating ring gear main body and the auxiliary gear body due to variations among individual products, the difference can be absorbed by the elasticity of the thin plate.

  According to a third aspect of the present invention, a peripheral wall portion is formed on the rotating ring gear main body, a notch portion is provided in a part of the peripheral wall portion, the auxiliary gear body is fitted to the peripheral wall portion, and the peripheral wall is provided on the outer periphery of the auxiliary gear body. The protrusion part which fits into the notch part of a part and comprises a joint part is provided. According to this, the auxiliary gear body can be fitted into the peripheral wall portion of the rotating ring gear main body and can be easily rotated, and the thin plate can be easily inserted into the mating portion.

  In the invention of claim 4, the method of removing the backlash in which the rotating ring gear of the second planetary gear mechanism is divided in the axial direction and a thin plate is interposed therebetween is also applied to the fixed ring gear of the first planetary gear mechanism. To do. In the speed reducer of the present invention, the sun gear shaft and the rotating ring gear are input / output portions of the speed reducer, and the rotating ring gear rotates at a much lower speed than the sun gear shaft. For this reason, applying the backlash removal method to the rotating ring gear is effective for high-precision positioning and the like, but it is also essential between the fixed ring gear and the planetary gear in the first planetary gear mechanism. There is a backlash. When the fixed ring gear is divided into the fixed ring gear main body and the second auxiliary gear body and the second thin plate is interposed between the two gear bodies as in the invention of claim 4, the first planetary gear mechanism This eliminates the backlash and enables more accurate positioning.

According to a fifth aspect of the present invention, in the speed reducer of the present invention, the planetary gears of the first and second planetary gear mechanisms are provided separately, and support shafts are provided on both sides between the planetary gear mechanisms. A disc-shaped carrier is installed, and each planetary gear is rotatably fitted to the support shafts on both sides of the carrier. According to this configuration, the speed reducer can be configured not only by the ring gears in the first and second planetary gear mechanisms but also by setting the number of teeth difference in the sun gear. Furthermore, since the first planetary gear and the second planetary gear supported on both sides of the carrier are separate gears, gears that can rotate at different rotational speeds and have different numbers of teeth and pitch circle diameters. It is possible to adopt.
When the planetary gear is fitted on the support shaft of the carrier via the rolling bearing as in the invention of claim 6, the frictional resistance is reduced and the planetary gear can be rotated smoothly.

It is a figure which shows the whole structure of 1st Example of the reduction gear of this invention. It is a figure which shows stationary components, such as a housing in the reduction gear of FIG. It is a figure which shows the planetary gear, the carrier, etc. in the reduction gear of FIG. It is a figure which shows the part of the rotating ring gearwheel in the reduction gear of FIG. It is a figure explaining the action | operation of the reduction gear of FIG. It is a figure which shows the modification of the reduction gear of FIG. It is a figure which shows the whole structure of 2nd Example of the reduction gear of this invention. It is a figure which shows the structure of the conventional differential type planetary gear reducer.

The speed reducer of the present invention will be described below based on the drawings. FIG. 1 shows the overall structure of the speed reducer according to the first embodiment of the present invention for the purpose of removing backlash, and FIGS. 2 to 4 show the components as single items. First, a basic operation of a reduction gear having a high gear ratio combining two planetary gear mechanisms that are the premise of the present invention and a calculation method of the gear ratio will be described with reference to these drawings.
As shown in the longitudinal sectional view in the center of FIG. 1, the speed reducer of the first embodiment includes a first planetary gear mechanism M <b> 1 (cross-sectional view BB) arranged on the right side in the fixed housing 1. The second planetary gear mechanism M2 (cross-sectional arrow AA) disposed on the left is combined. A sun gear shaft 2 is installed at the center of the housing 1, and a sun gear SG formed on the sun gear shaft is a single gear that is long in the axial direction, and is a sun gear common to the first and second planetary gear mechanisms. It has become.

  As shown in the cross sectional view BB, in the first planetary gear mechanism M1, four first planetary gears PG1 are arranged around the sun gear SG, and the first planetary gears PG1 are fixed on the housing 1. Engages with ring gear RGf. Further, as shown in the sectional view AA, in the second planetary gear mechanism M2, three second planetary gears PG2 are arranged around the sun gear SG, and the second planetary gear PG2 has a housing. 1 is meshed with a rotating ring gear RGr formed on the inner surface of the rotating member 3 accommodated in 1 (as will be described later, the rotating member 3 is divided into a rotating ring gear main body 3A and a sub gear body 3B. In the basic operation of the reduction gear and the calculation of the gear ratio, there is no problem assuming that the rotating member 3 and the rotating ring gear RGr are integrated). A rotating ring gear connecting shaft 31 for power transmission is fixed to the central portion of the rotating member 3, and the connecting shaft 31 passes through the cover plate 5 fitted in the end of the housing 1 for shielding. ing.

  Between the fixed ring gear RGf and the rotating ring gear RGr, a disk-shaped carrier 4 in which the support shafts of the planetary gears are erected on both sides is disposed. As shown in FIG. 3, a center hole 41 through which the sun gear shaft 2 passes is provided in the center of the carrier 4, and four supports in which the first planetary gear PG <b> 1 is erected on one surface of the carrier 4. The second planetary gear PG <b> 2 is rotatably fitted on the three support shafts 4 </ b> P <b> 2 erected on the other surface of the carrier 4. The axial length of the second planetary gear PG2 meshing with the rotating ring gear RGr is longer than that of the first planetary gear PG1 meshing with the fixed ring gear RGf. Each gear is a cycloid gear having a tooth profile curve based on cycloid.

  2, the housing 1 is a cup-shaped fixing member that includes a circumferential wall 11 and an end plate 12, and a fixing ring gear RGf is provided inside the circumferential wall 11. And a large diameter portion 11B that accommodates the rotating ring gear RGr. The end plate 12 is formed with a central hole so as to support the sun gear shaft 2 penetrating the end plate 12, and a step portion 21 (FIG. 3) of the sun gear shaft 2 is formed on the inner surface of the end plate 12. Axial positioning is performed by contact.

  As shown in FIG. 3, a small-diameter shaft portion 22 is provided at the tip of the sun gear shaft 2, and the small-diameter shaft portion 22 is in contact with the inner surface of the rotating member 3 as shown in the longitudinal sectional view of FIG. 1. Yes. Since the step portion 21 of the sun gear shaft 2 is in contact with the housing 1 and is positioned in the axial direction, when the tip of the sun gear shaft 2 is brought into contact with the rotating member 3, the positioning of the rotating member 3 with respect to the housing 1 is performed. Is called. As a result, an axial space for the first and second planetary gears and the carrier 4 interposed in the middle is secured, and an increase in frictional resistance due to pressure contact between the rotating gear and the housing 1 is prevented. The Further, the rotating member 3 and the sun gear shaft 2 are in contact with each other by the small diameter shaft portion 22 having a small cross-sectional area provided at the tip of the sun gear shaft 2, and therefore exist between the sun gear SG and the rotating ring gear RGr. Regardless of a large rotational speed difference, the frictional resistance of the contact portion can be suppressed to an extremely small amount.

  When the speed reducer of the first embodiment is operated in the power transmission system, the sun gear shaft 2 is rotated in one direction, for example, by a motor using the sun gear shaft 2 as an input shaft. The sun gear SG, like a general planetary gear mechanism, causes the first planetary gear PG1 to rotate in the opposite direction to cause planetary movement along the fixed ring gear RGf, and causes the carrier 4 to revolve around the sun gear SG. (See the operational diagram in FIG. 5). The sun gear SG is also meshed with the second planetary gear PG2 of the second planetary gear mechanism. In the second planetary gear mechanism M2, the rotation of the sun gear SG is canceled by the revolution of the carrier 4, but the rotation Since the number of teeth of ring gear RGr is slightly different from the number of teeth of fixed ring gear RGf, rotating ring gear RGr rotates at a low speed based on the difference in the number of teeth. This low-speed rotation is output by the rotating ring gear connecting shaft 31 to drive the driven device and the like.

The gear ratio of the reduction gear can be calculated as follows.
Generally, in the planetary gear mechanism, the following relationship exists among the rotational speed nSG of the sun gear, the rotational speed nRG of the ring gear, and the rotational speed nCR of the carrier.
nRG + γ · nSG = (1 + γ) nCR
γ = ZSG / ZRG ZSG: number of teeth of sun gear, ZRG: number of teeth of ring gear The gear ratio is the ratio between the number of rotations nSG of the sun gear and the number of rotations nRGr of the rotating ring gear of the second planetary gear mechanism. In general, the number of teeth of the sun gear may be different between the first planetary gear mechanism and the second planetary gear mechanism of the reduction gear (however, the rotation speed is the same), and the rotation speed nCR of the common carrier is a fixed ring. It is determined by the first planetary gear mechanism provided with the gear RGf. Therefore, the gear ratio of the reduction gear is expressed by the following equation.
nSG / nRGr = (1 + γ1) / (γ1-γ2)
γ1 = ZSG1 / ZRGf ZSG1: Number of teeth of the sun gear of the first planetary gear mechanism γ2 = ZSG2 / ZRGr ZSG2: Number of teeth of the sun gear of the second planetary gear mechanism In other words, if the value of (γ1-γ2) is decreased, the gear ratio The number of teeth and the number of rotations of the planetary gear do not affect the overall gear ratio. The speed ratio i of the differential planetary gear speed reducer in FIG. 8 is the same as that in the above speed ratio equation when the number of teeth of the sun gears of the first and second planetary gear mechanisms is equal (ZSG1 = ZSG2). This is the gear ratio and is given by
i = (1+ (ZRGf / ZSG)) / (1- (ZRGf / ZRGr))
ZSG: Number of teeth of sun gear SG

  In the first embodiment of FIG. 1, the number of teeth of each gear constituting the planetary gear mechanism is 12 for the sun gear SG, 44 and 42 for the fixed ring gear RGf and the rotating ring gear RGr, respectively. The difference in the number of teeth is set to 2. The transmission ratio, which is the ratio between the rotational speed of the sun gear SG and the rotational speed of the rotating ring gear RGr, is −98 according to the above-described equation. That is, in the speed reducer having this number of teeth, the rotating ring gear RGr and its connecting shaft 31 are decelerated to 1/98 of the rotational speed of the sun gear SG and rotate in the opposite direction, and the torque increases in inverse proportion to this. To do.

Here, the configuration for removing the backlash in the speed reducer according to the first embodiment of the present invention will be described.
As shown in FIGS. 1 and 4, the rotating member 3 of the first embodiment is divided into a rotating ring gear main body 3A and a sub gear body 3B so as to divide the rotating ring gear RGr in the axial direction. The rotating ring gear main body 3A is a cup-shaped member including an end plate 32 to which the rotating ring gear connecting shaft 31 is attached and an outer edge wall 33. The outer ring wall 33 has a divided rotating ring gear on the end plate 32 side. An internal tooth portion that is one of RGr is formed. The outer edge wall 33 adjacent to the inner tooth portion is a peripheral wall portion 34 having a reduced thickness. A recess having a circular cross section is formed inside the peripheral wall portion 34, and a part of the peripheral wall portion 34 is formed. A notch 35 is formed in the.

  The auxiliary gear body 3B is an annular component in which an inner tooth portion that is the other of the divided rotary ring gear RGr is formed, and a protrusion 36 is provided on the outer periphery thereof. The auxiliary gear body 3B is fitted into a recess having a circular cross section inside the peripheral wall portion 34 of the rotating ring gear main body 3A. At this time, the protrusion 36 is fitted into the cutout portion 35 of the peripheral wall portion 34 cut out. And the surface of the radial direction which opposes between both is formed, and a joint part is comprised here. Although the circumferential length of the notch 35 is longer than that of the protrusion 36, the internal teeth of the rotating ring gear main body 3A and the auxiliary gear body 3B mesh with the same second planetary gear PG2. In addition, the protrusion 36 does not move freely in the notch 35.

A thin plate (shim) 3C is inserted between the rotating ring gear main body 3A and the auxiliary gear body 3B, that is, between the opposing surfaces of the protrusion 36 and the notch 35. As shown in FIG. 4, the thin plate 3 </ b> C is a plate material having a rectangular shape that is curved in the longitudinal direction so that elasticity is imparted, and the plate thickness t is an assembly of the first planetary gear mechanism M <b> 1 and the second planetary gear mechanism M <b> 2. Is equivalent to the backlash between the rotating ring gear RGr and the second planetary gear PG2 in the second planetary gear mechanism M2.
The thin plate 3C having a plate thickness appropriate for each speed reducer is selected by the above-described procedure, and is inserted between the opposing surfaces of the mating portion. When the rotating ring gear main body 3A, the sub-gear body 3B, etc. are manufactured by pressing using a mold, within the same production lot, a certain amount is sampled to measure the amount of backlash, and the average You may make it insert the thin plate 3C of the board thickness corresponding to quantity into all the reduction gears. At this time, the backlash variation among the individual products can be absorbed by the elasticity imparted to the thin plate 3C.

The operation of the speed reducer configured as described above will be described with reference to FIG. The upper diagram of FIG. 5 shows the rotation state of each gear when the sun gear shaft 2 is rotated in one direction, and the lower diagram shows the rotation state when rotated in the opposite direction.
When the sun gear shaft 2 is rotated in the direction of the arrow in the center diagram of the upper figure, the sun gear SG first rotates the first planetary gear PG1 of the first planetary gear mechanism M1 in the opposite direction, and the carrier 4 is moved to the sun gear SG. Revolve around. In the second planetary gear mechanism M2, the rotating ring gear RGr is rotationally driven at a low speed in the direction opposite to the sun gear shaft 2 by the second planetary gear PG2. At this time, the tooth of the meshing portion of the second planetary gear PG2 has its front surface in the rotational direction in contact with the internal tooth portion of the rotating ring gear main body 3A to rotate the rotating ring gear main body 3A (cross-sectional arrow C -C). The internal gear portion of the secondary gear body 3B does not contact the front surface in the rotational direction of the teeth of the second planetary gear PG2, but contacts the rear surface in the rotational direction.

  When the sun gear shaft 2 is rotated in the direction opposite to the upper diagram as shown in the lower diagram of FIG. 5, all the rotation directions of the gears and the like in the first planetary gear mechanism M1 and the second planetary gear mechanism M2 are all illustrated in the upper diagram. The reverse of. In the second planetary gear PG2, the tooth surface which is the rear surface in the rotation direction in the above figure becomes the front surface in the rotation direction. For this reason, the internal gear portion of the auxiliary gear body 3B that is in contact with the second planetary gear PG2 is pushed and rotated, and this rotational force is transmitted to the radial surface of the notch 35 via the thin plate 3C. Then, the rotating ring gear main body 3A reverses at a low speed (cross-sectional arrow AA). Since the internal gear portion of the secondary gear body 3B is always in contact with the tooth surface of the second planetary gear PG2 (no backlash), the rotation ring gear is not delayed from the start of rotation in the opposite direction of the sun gear shaft 2. The main body 3A is reversed.

  A modification of the first embodiment of the present invention is shown in FIG. In the speed reducer of this modified example, a rolling bearing is interposed between the planetary gear and the support shaft in order to reduce the frictional resistance between the first and second planetary gears and the support shaft of the carrier 4 in which they are fitted. It has been made. As the rolling bearing, a needle bearing using a cylindrical roller long in the axial direction may be arranged outside the ball bearing BR shown in the figure. When the rolling bearing is interposed, the inclination and swinging of the support shaft of the carrier 4 generated during the operation of the speed reducer are absorbed by the rolling bearing, and the frictional resistance between the planetary gear, the sun gear, and the ring gear also from this surface. Can be prevented from increasing.

FIG. 7 shows a reduction gear according to a second embodiment in which the backlash removal method of the present invention is applied to the fixed ring gear of the first planetary gear mechanism.
In the second embodiment of FIG. 7, the rotating ring gear RGr of the second planetary gear mechanism M2 is divided in the axial direction, and a thin plate 3C is interposed between the two divided (cross sectional view AA). Similarly, the fixed ring gear RGf of the first planetary gear mechanism M1 is also divided into a fixed ring gear main body 1A and a second auxiliary gear body 1B formed in the housing 1, and a combined portion (first) A thin plate 1C (second thin plate) is inserted between the opposing radial surfaces of the housing 1 and the second auxiliary gear body 1B, which are two meshing portions) (cross-sectional arrow BB). Further, the end surface of the housing 1 on the fixed ring gear RGf side is an open surface that is shielded by the lid 5 so as to enable such a configuration.

  The thickness of the thin plate 1C is the back between the fixed ring gear RGf of the first planetary gear mechanism M1 and the first planetary gear PG1, which is generated when the first planetary gear mechanism M1 and the second planetary gear mechanism M2 are assembled. Set to be equal to rush. As a result, not only the second planetary gear mechanism M2 but also the backlash of the first planetary gear mechanism M1 is removed. For example, when this reduction gear is interposed in the positioning control system, the positioning accuracy can be further improved. It becomes.

As described above in detail, the present invention is a transmission that combines two planetary gear mechanisms each having a fixed ring gear and a rotating ring gear having different numbers of teeth, and the rotating ring gear is divided into two in the axial direction. A thin plate having a predetermined thickness is inserted between both of the divided rotating ring gears so that both teeth have a slight phase shift, thereby eliminating backlash in the rotating ring gear portion.
In the above embodiment, the sun gears of the first planetary gear mechanism and the second planetary gear mechanism are made common and the number of teeth is the same. However, a sun gear having a different number of teeth is adopted for the two planetary gear mechanisms. The rotation direction of the sun gear and the rotating ring gear can be set to the same direction by setting the number of teeth of the sun gear and the ring gear. In addition, as the tooth profile curve of each gear, the shape of the mating part of the rotating ring gear body and the sub gear body is changed, the internal teeth of the fixed ring gear and rotating ring gear are manufactured separately and assembled to the parts. It is obvious that various modifications can be made to the above-described embodiment, such as adopting an involute tooth profile or other specially shaped tooth profile.

DESCRIPTION OF SYMBOLS 1 Housing 2 Sun gear shaft 3 Rotating member 3A Rotating ring gear main body 3B Sub gear body 3C Thin plate 31 Rotating ring gear connecting shaft 34 Peripheral wall portion 35 Notch portion 36 Protruding portion 4 Carrier 4P1, 4P2 Support shaft (planetary gear)
SG Sun gear PG1, PG2 First planetary gear, Second planetary gear RGf Fixed ring gear RGr Rotating ring gear

Claims (6)

A first planetary gear mechanism having a sun gear shaft installed at the center of a fixed housing and formed with a sun gear; a sun gear of the sun gear shaft; and a non-rotatable fixed ring gear provided around the sun gear shaft; A second planetary gear mechanism having a sun gear of the sun gear shaft and a rotatable rotating ring gear provided around the sun gear;
In the first planetary gear mechanism and the second planetary gear mechanism, a planetary gear meshing with a ring gear and a sun gear is disposed, and at least one of the ring gear and the sun gear is provided with a tooth number difference, The sun gear shaft and the rotating ring gear are reduction gears that serve as input / output portions for power transmission,
The rotating ring gear includes a rotating ring gear main body in which one internal tooth portion divided in the axial direction is formed, and a secondary gear body in which the other internal tooth portion is formed, and the rotating ring gear main body; A fitting portion that fits relatively rotatably with the auxiliary gear body is provided,
A thin plate that contacts the radial surface of the rotating ring gear body and the radial surface of the auxiliary gear body is interposed in the fitting portion, and the thickness of the thin plate is the same as that of the first planetary gear mechanism. A reduction gear characterized by being equivalent to a backlash between a rotating ring gear and a planetary gear of the second planetary gear mechanism, which is generated when the second planetary gear mechanism is assembled. The reduction gear according to claim 1, wherein the thin plate is provided with elasticity in a direction separating a radial surface of the rotating ring gear main body and a radial surface of the auxiliary gear body. The rotating ring gear main body has a peripheral wall portion provided with a notch portion, the auxiliary gear body is fitted to the peripheral wall portion, and an outer periphery of the auxiliary gear body is provided with a notch of the peripheral wall portion. The speed reducer according to claim 1 or 2, further comprising a protrusion that is fitted to the portion and forms a mating portion. The fixed ring gear in the first planetary gear mechanism includes a fixed ring gear body in which one internal tooth portion divided in the axial direction is formed, and a second auxiliary gear body in which the other internal tooth portion is formed. In addition, a second fitting portion is provided in which the second auxiliary gear body is fitted so as to be rotatable relative to the fixed ring gear body,
A second thin plate that contacts the radial surface of the fixed ring gear body and the radial surface of the second auxiliary gear body is interposed in the second fitting portion, and the thickness of the second thin plate is 4. A backlash between a fixed ring gear and a planetary gear of the first planetary gear mechanism, which is generated when the first planetary gear mechanism and the second planetary gear mechanism are assembled. A reduction gear according to any one of the above. Between the sun gear of the first planetary gear mechanism and the fixed ring gear, a plurality of first planetary gears meshing with these gears are installed, and the sun gear of the second planetary gear mechanism and the rotating ring A plurality of second planetary gears that mesh with the gears are installed between the gears, and
Between the first planetary gear mechanism and the second planetary gear mechanism, a disk-shaped carrier provided with support shafts on both sides is installed, and the first planetary gear is a support shaft on one side of the carrier. The speed reducer according to any one of claims 1 to 4, wherein the second planetary gear is rotatably fitted to a support shaft on the other side of the carrier. The speed reducer according to claim 5, wherein the first planetary gear and the second planetary gear are fitted to a support shaft of the carrier via a rolling bearing.

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