JPH08159241A - Gear device capable of regulating backlash and regulation method - Google Patents

Abstract

PURPOSE: To provide a gear device which is constituted to be capable of regulating a backlash. CONSTITUTION: In a gear device wherein a rotational drive force is transmitted from an input gear 28 to an output gear 20 through two intermediate gears 24a and 24b arranged rotatably around one and the same rotary shaft, the rotary shafts of the two intermediate gears 24a and 24b are movably arranged in a direction paralleling a straight line, through which the rotation center of the input gear 28 and the rotation center of the output gear 20 are interconnected and a direction vertical to the straight line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear device capable of adjusting backlash, a backlash adjusting device and method therefor.

[0002]

2. Description of the Related Art Conventionally, there are various types of devices for transmitting a rotational driving force, but a gear device is widely used as a device for reliably transmitting a rotational driving force. For example, in an industrial robot, various driving force transmission devices are well known for rotating a wrist rotatably attached to a tip end portion of a robot arm. Due to the miniaturization, a wrist casing driving motor is arranged near the wrist of the robot, and a device for transmitting the rotational driving force from the motor through a gear device having a plurality of gears has been adopted.

However, in a power transmission device using a gear device, backlash is inevitably generated between the gears. The backlash is necessary to rotate the gear, but since it affects the positioning accuracy of the driven body driven by the gear, it is necessary to adjust the backlash as small as possible within the allowable limit. For example, in the above-described robot wrist, the backlash of the gear train that transmits the rotational driving force from the wrist casing drive motor to the wrist is
It directly affects the motion accuracy of the wrist of the robot. Therefore, in order to improve the positioning accuracy of the end effector attached to the tip of the wrist of the robot, it is necessary to adjust the backlash as small as possible.

Needless to say, backlash can be reduced by strictly controlling the processing accuracy of the gear itself and the accuracy of the distance between the axes of the gears in the manufacturing and assembling steps of the product using the gears. However, in order to reduce the backlash by strictly controlling the machining accuracy of the gear itself and the accuracy of the axial distance between the gears, very strict dimensional tolerance is required, and the manufacturing and assembling costs of the product increase. Also, the gears wear out over extended periods of time, which increases backlash over time. Therefore, the adjustment of the backlash is necessary even in the maintenance after the product is delivered to the user, and it is not enough to simply control the manufacturing accuracy of the gear.

Conventionally, various gear devices having an adjustable backlash have been proposed. For example, Japanese Patent Application No. 5-22788 and Japanese Patent Application No. 5-170548.
The Japanese Patent Application discloses a wrist device of a robot including a gear device in which a rotating shaft of a gear is rotated about an shaft that is eccentric from the rotating shaft to adjust an axial distance between two meshing gears. ing. Further, JP-A-62-29
Japanese Patent No. 2389 discloses an apparatus that is configured to adjust the axial distance of a gear that drives a wrist of a robot to reduce backlash as much as possible.

[0006]

However, the gear device of the prior art, which is constructed so as to be able to adjust the backlash, generally has a complicated structure and, in addition, is a device which can easily perform sufficient backlash adjustment. is not. Japanese Patent Application 5
In the devices of the No. 22788 application and the Japanese Patent Application No. 5-170548, it is difficult to form an eccentric shaft with a predetermined length from the central axis of the rotating shaft of the gear, which not only increases the manufacturing cost but also causes backlash. Fine adjustment is difficult. Further, in the device disclosed in the publication, only the backlash between the output gear and the intermediate gear engaged with the gear can be adjusted, and the backlash between the input gear and the intermediate gear can be sufficiently adjusted. There is a problem that cannot be done.

Further, the complicated structure may cause another problem. For example, JP-A-6
Since the apparatus disclosed in Japanese Patent Laid-Open No. 2-292389 has a complicated structure, the weight of the tip of the robot arm increases, resulting in an increase in the load on the motor for driving the robot arm and a decrease in the positioning accuracy of the robot arm. To do. Further, there is a problem that the manufacturing cost increases.

In view of the above-mentioned problems, an object of the present invention is to provide a gear device having a simple structure which is capable of displacing the axial distance of gears and adjusting the backlash.

[0009]

According to a first aspect of the present invention, a rotational driving force is transmitted from an input gear to an output gear via two intermediate gears that are rotatable about the same rotation shaft. In the gear device, the rotation shafts of the two intermediate gears are provided so as to be movable in a direction parallel to a straight line connecting a rotation center of the input gear and a rotation center of the output gear and a direction perpendicular to the straight line. The gist is a gear device characterized by the fact that

According to a second aspect of the present invention, a backlash of a gear device for transmitting a rotational driving force from an input gear to an output gear via two intermediate gears rotatably provided around the same rotary shaft is provided. In the adjusting device, a support plate disposed on a plane substantially perpendicular to the rotation axis, and a coupling means for engaging one of two intermediate gears provided on the support plate to couple the intermediate gear and the support plate And a moving means for moving the support plate in a direction parallel to a straight line connecting the rotation center of the input gear and the rotation center of the output gear.

According to a third aspect of the present invention, there is provided a backlash of a gear device for transmitting a rotational driving force from an input gear to an output gear via two intermediate gears rotatably provided around the same rotation shaft. In the method of adjusting, each of the two intermediate gears is in full engagement with the input gear and the output gear, moving the rotary shaft of the intermediate gear to a reference point where the backlash between the gears is zero; From the point to the target point to obtain the desired backlash, the step of moving the rotary shaft of the intermediate gear in the direction perpendicular to the straight line connecting the rotation center of the input gear and the rotation center of the output gear, and the desired backlash And a step of moving the rotation axis of the intermediate gear in a direction parallel to a straight line connecting the rotation center of the input gear and the rotation center of the output gear toward the target point to be obtained. .

[0012]

According to the first aspect of the invention, the rotation shaft of the intermediate gear moves in a direction parallel to a straight line connecting the rotation center of the input gear and the rotation center of the output gear and in a direction perpendicular to the straight line. Therefore, the two backlashes can be adjusted at the same time so that the backlash between the input gear and the intermediate gear and the backlash between the output gear and the intermediate gear are optimal backlashes.

According to a second aspect of the present invention, the connecting means engages with the intermediate gear to fix the intermediate gear, and the moving means integrates the support plate, the connecting means, the intermediate gear, and the rotary shaft thereof. Move to a position where the desired backlash is obtained.

According to a third aspect of the present invention, the step of moving the rotary shaft of the intermediate gear in a direction perpendicular to the straight line connecting the center of rotation of the input gear and the center of rotation of the output gear, and parallel to the straight line. By separating the step of moving in the direction, the adjustment of the backlash becomes clear and easy.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an industrial robot as shown in FIG. 6 as a gear device requiring precise backlash adjustment to which the present invention is applied, a motor for rotating a wrist at the tip of a robot arm to a wrist casing will have a rotational driving force. A preferred embodiment of the present invention will be described by taking as an example the case where the present invention is applied to a gear device that transmits power.

Referring to FIG. 6, the industrial robot shown as an example includes a fixed base 10 and a swivel base 12 mounted on the fixed base 10 so as to be rotatable about a vertical swivel axis. A robot arm 16 is attached to the swivel base 12 via a joint 14 so as to be swivelable about a horizontal swivel axis. The robot arm 16 is composed of a first robot arm 16a and a second robot arm 16b.
b is the joint part 15 at the tip of the first robot arm 16a.
Can be swiveled around a generally horizontal swivel axis,
Further, it is attached so as to be rotatable around the central axis in the longitudinal direction.

At the tip of the second robot arm 16b,
The robot wrist 18 is attached via the joint portion 18a so as to be rotatable about a rotation axis perpendicular to the center axis of the second robot arm. The wrist 18 is provided with a wrist flange 18b provided at the tip thereof so as to be rotatable around a rotation axis perpendicular to the rotation axis of the wrist. That is, the industrial robot shown in FIG. 5 constitutes a 6-axis industrial robot. An end effector (not shown) such as a robot hand is attached to the wrist flange 18
It is attached to b.

Next, the structure of the joint portion 18a for the wrist 18 provided at the tip of the second robot arm 16b will be described with reference to FIG. FIG. 1 is a partial cross-sectional view showing a part of the joint portion 18a by fracture. In the following description, for convenience of explanation, as shown in FIG. 1, the X axis is set in the longitudinal direction of the second robot arm 16b and is perpendicular to both the X axis and the rotation axis of the wrist 18. Define the Y axis in the direction.

In FIG. 1, the wrist 18 is attached to the tip of the second robot arm 16b so as to be rotatable within a predetermined angle range by the rotation shaft 20b of the output gear 20 as a turning shaft. More specifically, the casing of the wrist 18 is fixed to the rotary shaft 20b of the output gear 20.
0b is rotatably supported by a casing 16c of the second robot arm 16b via a bearing 22. The output shaft 20 is connected to the input gear 28 via an intermediate gear 24. The rotation shaft 28b of the input gear 28 is rotatably supported by the casing 16c of the second robot arm 16b via a bearing 32, and rotation of a servomotor (not shown) as a rotation drive source for the wrist 18 is performed. It is connected to the shaft. The casing 16b is closed by a cover 16c.

The intermediate gear 24 has a first integrally formed first gear.
Of the intermediate gear 24a and the second intermediate gear.
The first intermediate gear 24a is engaged with the input gear 28, and the second intermediate gear 24b is engaged with the output gear 20. Also,
The intermediate gear 24 is rotatably supported on the inner surface of the casing 16c by a mounting member 26 via a bearing 27. With such a configuration, the rotational driving force of the servo motor is transmitted from the input gear 28 to the first intermediate gear 24a, and then from the second intermediate gear 24b integrally formed with the first intermediate gear 24a to the output gear. Transmitted to 20,
It is transmitted to the casing of the wrist 18 attached to the rotary shaft 20a of the output gear 20.

Referring to FIG. 2, the mounting member 26 is provided with a flat plate-like flange portion 26a and a shaft portion 24b as a rotating shaft of the intermediate gear 24. In order to attach the attachment member 26 to the inner surface of the casing 16c of the second robot arm 16b, the flange portion 26a has a plurality of attachment holes 26c.
Are formed. As a preferred embodiment of the present invention, the mounting hole 26c is a long hole extending in the Y-axis direction and is a flange portion 26.
It is formed at the four corners of a. Then, the mounting member 26 is
The bolt 30 is passed through the mounting hole 26c, and the bolt 30 is fastened to a bolt hole (not shown) formed in the casing 16c, whereby the bolt 16 is attached to the inner surface of the casing 16c. More specifically, the mounting hole 26c is formed with a width slightly longer than the diameter of the bolt 30 in the Y-axis direction.

Next, the operation of this embodiment will be described with reference to FIGS. The figure is a schematic view of the gear train of the joint portion 18a shown in FIG. In order to adjust the backlash between the input gear 28, the intermediate gears 24a and 24b, and the output gear 20, first, the bolt 30 is loosely fitted so that the mounting member 26 can freely move in the X-axis and Y-axis directions. To Then, the first intermediate gear 24a is connected to the input gear 28.
The mounting member is appropriately moved in the X-axis and Y-axis directions so that the second intermediate gear 24b completely meshes with the output gear 20. At this time, the backlash between all the gears becomes zero, and all the gears cannot operate. This position of the mounting member 26 is defined as a reference point.

In order to obtain the above-mentioned reference point, preferably
The distance L between the rotation center of the input gear 28 and the rotation center of the output gear 20 is determined so as to satisfy the following formula. L <(di + d1 + d2 + do) / 2 where di is the pitch circle diameter of the input gear d1 is the pitch circle diameter of the first intermediate gear d2 is the pitch circle diameter of the first intermediate gear do is the pitch circle of the output gear Is the diameter.

Next, a target point for moving the mounting member 26 from the reference point so as to obtain a desired backlash is obtained. Now, in FIG. 3, the rotation center of the output gear 20 is the origin a1 (0, 0), and the rotation center of the input gear 28 is a3 (L, L,
0), and the rotation center of the intermediate gear 24 at the reference point is a2 (x, y). In the coordinate system defined in this way, a target point for moving the mounting member 26, that is, a target point for moving the rotation center of the intermediate gear 24 is a
2 '(x', y ').

Output gear 20 and intermediate gear 2 at the reference point
If the distance between the respective rotation centers of 4 is L1, then L1 ² = x ² + y ² (1). Similarly, if the distance between the rotation centers of the input gear 28 and the intermediate gear 24 at the reference point is L2, then L2 ² = (x−L) ² + y ² (2) Solving equations (1) and (2) for x and y, x = (L ² + L 1 ² −L ^{2 2} ) / 2L (3) y = (L 1 ² −x ² ) ^1/2 (4)

Generally, when the central distance increment from the central distance of no backlash is δ, the Kamiai pressure angle is α, and the backlash on the pitch circumference corresponding to δ is C, C = 2 · δ · tan α (5 ) Is represented by. From equation (5), the increment of the center-to-center distance is determined so as to obtain the desired backlash.

Now, when the center of rotation of the intermediate gear 24 is moved to the target point, the increment of the center distance between the output gear 20 and the intermediate gear 24 is δ1, and the center distance between the input gear 28 and the intermediate gear 24 is If the increment is δ2, then (L1 + δ1) ² = x ' ² + y' ² (6) (L2 + δ2) ² = (x'-L) ² + y ' ² (7). When equations (6) and (7) are solved for x ′ and y ′, the coordinates of the target point to be moved are x ′ = ((L ² + (L 1 + δ 1) ² − (L ² + δ ² ))
² ) / 2L y '= ((L1 + δ1) ² -x' ² ) ^1/2 .

In order to move the mounting member to the target point obtained as described above, first, the mounting member 26 is moved in the Y-axis direction, and then in the X-axis direction using a pickup meter as will be described later. Move precisely. Means that
As will be understood from the above, since the angle formed by the straight line a1 a3 and the straight line a1 a2 and the angle formed by the straight line a1 a3 and the straight line a3 a2 are small, the center distance a1 a2 and the center distance a
This is because the increment of 3a2 is more affected by the displacement amount in the X-axis direction than the displacement amount in the Y-axis direction.

In order to move the mounting member 26 in the Y-axis direction, the output gear 20 is fixed so as not to rotate by a pin (not shown) or the like. Since the second intermediate gear 24b meshes with the fixed output gear 20, it cannot rotate. Therefore, the first intermediate gear 24a formed integrally with the second intermediate gear 24b cannot rotate either. When the input gear 28 is rotated in this state, the mounting member 26 is centered on the meshing point between the output gear 20 and the second intermediate gear 24b, and is on the circumference with the radius of the pitch circle of the second intermediate gear 24b as the radius. To move. The movement of the mounting member 26 is large in the Y-axis direction and small in the X-axis direction. Therefore, the displacement in the X-axis direction is adjusted later, and the input gear 28 is rotated at an appropriate angle so that a desired displacement can be obtained in the Y-axis direction.

Next, in order to precisely adjust the mounting member 26 in the X-axis direction, a jig as a backlash adjusting device shown in FIGS. 4 and 5 is attached to the end surface of the casing 16c.
This jig includes a support plate 36, a fixed block 38, an adjusting screw 38a provided as an adjusting means for connecting the support plate 36 and the fixed block 38, and a first intermediate gear 24a. 36 and a pair of connecting gears 40 as connecting means.

The support plate 36 has a plurality of elongated holes 36c as mounting holes. The long hole 36c is formed so as to extend in the X-axis direction. The support plate 36 is attached to the casing 16c by inserting a bolt 36b (see FIG. 5) into the elongated hole 36c and fastening the cover 16d to the bolt hole for attaching the cover 16d to the casing 16c. More specifically, the slot 36c is the center of rotation of the input gear 28,
The support plate 36 is formed so as to extend in a linear direction connecting the center of rotation of the output gear 20, and the support plate 36 is guided by the engagement of the elongated hole 36c and the bolt 36b to be movable in the linear direction in the casing 16c. It is attached.

At the end of the support plate 36 on the joint 15 side of the second robot arm 16b, an arcuate recess 36 is provided so as to escape the first intermediate gear 24a from the steel plate.
d is formed, and a pair of support branch portions 36e is formed on both sides of the support plate 36 by the recess 36d. In each of the pair of support branch portions 36e, a pair of connecting gears 40 as connecting means can be engaged with the first intermediate gear 24a,
The second intermediate gears 24a are arranged side by side on a straight line in the Y-axis direction that passes through the center of the second intermediate gear 24a. In the support plate 36,
A substantially L-shaped connecting portion 3 is provided at the opposite end of the connecting gear 36.
6a is provided, and the tip of the adjusting screw 38a is attached to the vertical portion of the connecting portion 36a.

The adjusting screw 38a is provided so as to bridge the fixing block 38 fixed to the casing 16c of the second robot arm with the bolt 38b (see FIG. 5) and the connecting portion 36a. By rotating the screw 38a, the support plate 36 moves in the X-axis direction together with the first intermediate gear 24a connected to the support plate 36 by the connection gear 40. At this time, with the detection needle of the pickup meter 34 in contact with the pitch circumference of the output gear 20, a force in the circumferential direction is applied to the wrist casing attached to the rotary shaft 20a of the output gear 20, and the pickup meter Is read, and the first intermediate gear 24a is moved in the X-axis direction so that a desired backlash can be obtained. Thereby, the backlash between the output gear 20 and the second intermediate gear 24b can be adjusted. The backlash between the output gear 20 and the second intermediate gear 24b at this time is indicated by Co1.

Next, the connecting gear 40 is moved to the first intermediate gear 2
4a to release the first and second intermediate gears 24a, 2
4b can be freely rotated. In this state, as described above, the detection needle of the pickup meter 34 is connected to the output gear 20.
Then, the backlash of the entire gear train is measured by applying the force in the circumferential direction to the wrist casing to read the fluctuation of the pickup meter. Thus, the output gear 2
0 and the backlash Co1 between the second intermediate gear 24b
And the distribution of backlash Ci between the input gear 28 and the first intermediate gear 24a.

The backlash between the input gear 28 and the first intermediate gear 24a is controlled by the output gear 20 in consideration of the influence of Ci.
And the backlash Cot between the second intermediate gear 24b and
It is expressed by the following formula. Cot = Co1 + Ci * (do / d2) where do is the pitch circle diameter of the output gear 20 and d2 is the pitch circle diameter of the second intermediate gear 24b.

Considering the above equation, the influence of the backlash between the input gear 28 and the first intermediate gear 24a on the positioning accuracy of the wrist 18 is influenced by the output gear 20 and the second intermediate gear 2.
It can be seen that it is smaller than the backlash between 4b and 4b.
With this in mind, it is important to determine the distribution of the two backlashes. Further, in the description of the above-mentioned embodiment,
The case where the present invention is applied to the joint portion that rotationally drives the wrist of the industrial robot has been described as an example, but the present invention can be applied to all gear devices other than the robot.

[0037]

In the gear device according to the present invention, the rotary shaft of the intermediate gear that transmits the rotational driving force from the input gear to the output gear is
The simple structure of the mounting member allows it to move in the direction parallel to the line connecting the center of rotation of the input gear and the center of rotation of the output gear and in the direction perpendicular to the line, increasing the weight of the gear unit. It is possible to adjust the backlash without doing this. Further, the mounting member as the backlash adjusting means of the present invention can be manufactured more easily than the conventional structure in which the rotating shaft of the gear is rotated about an eccentric shaft.

In the gear device of the present invention, the reference point at which the backlash between the input gear and the first intermediate gear and the backlash between the output gear and the second intermediate gear are zero is determined, and then, By moving the rotary shaft of the intermediate gear first in the Y-axis direction and then more precisely in the X-axis direction,
The backlash adjustment procedure is clear and simplified.

Further, in the gear device of the present invention, the first intermediate gear that engages with the input gear and the second intermediate gear that engages with the output gear are configured to rotate about the same rotary shaft. At the same time, by configuring the rotary shaft so that it can move in the X-axis and Y-axis directions as described above, it is possible to adjust the backlash only in the circumferential direction around the predetermined rotary shaft. In contrast, the backlash between the input gear and the first intermediate gear and the backlash between the output gear and the second intermediate gear can be adjusted to be optimal at the same time.

[Brief description of drawings]

FIG. 1 is a partial sectional view of a joint portion of a wrist of an industrial robot equipped with a gear device according to the present invention.

FIG. 2 is a front view of a mounting member.

FIG. 3 is a schematic view showing meshing of gears.

FIG. 4 is a schematic plan view showing a state in which a backlash adjusting jig is attached to a robot casing.

5 is a cross-sectional view taken along a straight line connecting the rotation centers of the input gear and the output gear in FIG.

FIG. 6 is an elevation view showing an example of an industrial robot.

[Explanation of symbols]

 20 ... Output gear 24 ... Intermediate gear 26 ... Mounting member for rotating shaft of intermediate gear 26a ... Rotating shaft of intermediate gear 36 ... Backlash adjusting jig

Claims (3)

[Claims] 1. A gear device for transmitting rotational driving force from an input gear to an output gear via two intermediate gears rotatably provided around the same rotation shaft, wherein the rotary shafts of the two intermediate gears are provided. Is provided so as to be movable in a direction parallel to a straight line connecting the rotation center of the input gear and the rotation center of the output gear and in a direction perpendicular to the straight line. 2. A device for adjusting the backlash of a gear device for transmitting a rotational drive force from an input gear to an output gear via two intermediate gears rotatably provided about the same rotary shaft, wherein A support plate arranged on a plane substantially perpendicular to the axis, a connecting means provided on the support plate for engaging one of the two intermediate gears to connect the intermediate gear and the support plate, and a rotation center of the input gear. And a moving means for moving the support plate in a direction parallel to a straight line connecting the rotation center of the output gear and the rotation center of the output gear. 3. A method for adjusting the backlash of a gear device for transmitting a rotational driving force from an input gear to an output gear via two intermediate gears rotatably provided about the same rotary shaft, comprising: Obtaining the desired backlash from the reference point by moving the rotary shaft of the intermediate gear to a reference point where each of the intermediate gears completely engages with the input gear and the output gear and the backlash between the gears becomes zero. A step of moving the rotation axis of the intermediate gear toward the target point in a direction perpendicular to the straight line connecting the rotation center of the input gear and the rotation center of the output gear, and inputting toward the target point to obtain the desired backlash. Moving the axis of rotation of the intermediate gear in a direction parallel to a straight line connecting the center of rotation of the gear and the center of rotation of the output gear.