JPH0241890A - Fitting structure for encoder of industrial robot - Google Patents

Abstract

PURPOSE:To fit an encoder with sufficient rigidity and to increase the position detecting accuracy and control stability by fitting an encoder shaft integrally with an arm after adjusting it so as to conform to an arm revolving shaft. CONSTITUTION:An encoder shaft 22 is fitted by adjusting it by centering with an adjusting screw 18 to the encoder shaft fitting part 15 which is rotated integrally with an arm 3. Then, an encoder main body 21 is rigidly fitted in the radial direction to a non-rotation part(robot shaft of rigid body) 8 via an encoder fitting plate 9. Consequently, no distortion stress is generated on an encoder 2 with the rotation of a motor 1 and the position detecting accuracy and control stability of the encoder 2 can be improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a structure in which an encoder for detecting position is directly attached to the robot arm of an articulated robot [Prior Art] In an articulated robot driven by a motor. In this type, the position detection of the rotation angle is performed by an optical encoder attached to the motor, but in the type where the robot arm is driven by the motor via a deceleration mechanism, backlash of the deceleration mechanism etc. , the rotation angle indicated by the encoder and the rotation angle of the arm do not correspond one-to-one.

To solve this problem, the shaft of the encoder is attached so as to rotate together with the arm, without using a transmission means such as a timing belt, so as to directly detect the rotation angle of the arm. Furthermore, in a direct drive robot in which a motor directly drives an arm, due to its structure, a position detection encoder is attached so that the shaft of the encoder rotates together with the arm.

FIG. 6 shows a conventional encoder mounting structure, in which an arm 3 is fixed to a hollow shaft 7 driven by a motor, and an encoder shirt is fixed to the rotating arm 3 with a screw S0!・The encoder shaft 22 is precisely fitted into the fitting hole 11□ of the protruding sleeve 16 of the mounting member 15, and the mounting member 15 and shaft 22 are fixed with screws S3 so that the encoder shaft 22 rotates together with the arm 3. It is installed on.

On the other hand, the encoder main body 21 has a non-rotating fixed shaft 8.
It is attached via the encoder mounting plate 9' with screws S+ and Sz.

FIG. 7 is a plan view of the encoder mounting plate 9', which has an annular shape with holes punched out for cables to pass through, and has four protruding holes on the outer periphery. Mounting piece 91'
The mounting piece 91' has two cut grooves 94 and 95 cut in parallel and from different side edges to provide elasticity in the radial direction.

Bolt holes 93' on the main body of the mounting plate 9' are for mounting to the encoder main body 21, and bolt holes 92' on the mounting piece 91' are for mounting to the encoder main body 21.
' is for attachment to the shaft 8.

In the case where the encoder is mounted as shown in Fig. 6, the mounting plate 9' has cut grooves 94 and 95, so the encoder shaft (detector shaft) is not perfectly centered. Even if the shaft rotates, the eccentric action can be absorbed by the radial expansion and contraction by the cut grooves 94 and 95 of each mounting piece 91'.

[Problem to be solved by the invention]

a motor shaft of an encoder (detector) shaft 22;
That is, the centering with respect to the rotating hollow shaft 7 is performed by the arm 3
It depends on the mounting precision of the mounting member 15 to the mounting member and the processing precision of the sleeve 16 of the mounting member, and it is impossible to completely center the encoder shaft and the motor shaft due to the processing precision.In the end, the lower end of the encoder shaft is supported by the bearing R2. It was necessary to absorb the rotational eccentricity of the encoder shaft by the radial elasticity of the mounting plate 9' of the encoder body 21.

Since the encoder is supported by the elastic mounting plate 9', the rigidity between the motor and the encoder is reduced.
The motor causes oscillation and control becomes unstable.

The present invention solves the above-mentioned deficiencies by establishing a rigid relationship between the motor and the encoder shaft and achieving centering between the two.

[Means and effects for solving the problem] For example, as shown in FIG. 1, the encoder shaft 22 is loosely fitted into the fitting hole H in the sleeve 16 of the encoder shaft mounting member 15 that rotates together with the arm. The encoder body 21 is mounted in a non-rotating manner in the radial direction via a rigid encoder mounting plate 9. It was rigidly attached to the robot shaft 8.

Therefore, the encoder shaft 22 is the rotation axis of the motor,
In other words, the arm can be fixed in a centered state with respect to the rotational axis This eliminates the flexibility required to remove distortion, which was the cause of oscillation in conventional motors.

〔Example〕

The present invention was applied to a direct drive robot. Second
The figure is an overall perspective view of a robot to which the present invention is applied, and FIG. 3 is a schematic cross-sectional view showing only the drive mechanism of the first arm 3.

As is clear from FIGS. 2 and 3, direct drive motors 1 and 4 each include a stator 12 and a rotor 11.
are arranged to drive the first arm 3 and the second arm 6, respectively, and encoders 2 and 5 are respectively attached to rotate together with the arms to detect the rotational position of each arm. For convenience, only the encoder of the first arm will be illustrated, but the installation of the encoder of the second arm is basically the same.

A hollow shaft 7 fixed to a rotor 11 of a motor 1 is attached to rotate around a non-rotating robot shaft 8 by a bearing B1, and a first arm 3 is integrally fixed to the hollow shaft.

As shown in FIG. 1, the encoder body 21 has a bearing B.
The encoder shaft 22 is rotatably supported via the shaft 2.

As shown in FIG. 5, the encoder mounting plate 9 is made of a steel plate having a diameter hole in the center, four mounting pieces equally spaced around the outer periphery, and bolt holes 93 and 92. It was formed by punching out. The bolt hole 92 has a diameter larger than the shaft diameter of the threaded bolt so that the position can be adjusted.

The encoder shaft mounting member 15 has a hole H1 having a diameter larger than the shaft diameter in the sleeve 16 that protrudes downward.
Four equally spaced screw holes were provided.

That is, as shown in FIG.
2 and the hole H1 of the sleeve 16, the distance d was maintained, and the sleeve 16 was provided with four screw holes 17.

To assemble the encoder, the encoder mounting plate 9 is fixed to the encoder body 21 via screws S2, and the mounting plate 9 is temporarily fixed onto the robot shaft 8 via bolt holes 92 with screws S1 loosened. Encoder shaft mounting member 15
, the sleeve hole H1 is fitted to the upper end of the encoder shaft 22 and fixed to the arm 3 with the screw S0, then each adjustment screw 18 is screwed into the screw hole 17 of the sleeve 16, and the dial gauge G is applied to the After centering the rotation axis XX of the first arm and the encoder shaft 22, set each adjustment screw 18, fix the encoder shaft mounting member 15 and the shaft 22 with the screw S, and fix the encoder mounting plate 9 with the screw S. and the robot shaft 8 were fixed, and the cover 19 was put on.

In the obtained mounting structure, the encoder shaft 22
is centered with the arm rotation axis, that is, the motor axis Since the motor 1 is fixed to the rigid robot shaft 8 via the rigid mounting plate 9 in the radial direction, the rotation of the motor 1 does not cause any strain stress on the encoder 2;
Rotation is equivalent to 800,000 pulses, 7.8×1O-6rad
Regardless of whether a device with a resolution of 1. No oscillation occurred in the motor.

〔Effect of the invention〕

Since the encoder shaft is adjusted to match the arm rotation axis and then installed integrally with the arm, rotation of the arm does not apply excessive force to the detector (encoder), and therefore the encoder has sufficient rigidity. The position detection accuracy and control stability are improved.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of the encoder mounting portion of the present invention. FIG. 2 is an overall perspective view of a robot according to the present invention, and FIG. 3 is a vertical sectional view of its first shaft portion. FIG. 4 is a plan view of the adjusting screw portion of the present invention, and FIG. 5 is a plan view of the encoder mounting plate used in the present invention. FIG. 6 is a longitudinal cross-sectional view of a conventional encoder mounting part.
FIG. 7 is a plan view of a conventional encoder mounting plate. 1.4: Direct drive motor, 2.5: Encoder, 3: First arm, 6: Second arm, 7: Hollow shaft, 8: Shaft,
9: Encoder mounting plate, ll: Rotor, 12
: Stator, 15: Encoder shaft mounting member, 16: Sleeve, 17: Screw hole, 18: Adjustment screw, 19: Cover 21: Encoder body, 22: Encoder shaft. 1.4... Direct drive motor 2, 5... Encoder 3... First arm 6... Second arm 7... Hollow shaft 8... Yaft 9... Encoder mounting plate 11° ° Rotor 12... Stator 15... Encoder shaft mounting member 16... Sleeve 17... Screw hole 18... Adjustment screw 19... Cover 21... Encoder body 22... Encoder installation Board x No. 4

Claims (1)

[Claims] 1. An encoder shaft (22) is attached to an encoder shaft mounting member (15) that rotates together with the arm (3).
Adjust the centering with the adjustment screw (18) and install the encoder body (21) on the non-rotating part of the encoder mounting plate (
9) Encoder mounting structure for an industrial robot rigidly mounted in the radial direction. 2. Sleeve 1 of encoder shaft mounting member (15)
2. The industrial robot encoder mounting structure according to claim 1, wherein the encoder shaft (22) is loosely fitted into the sleeve (16) and centered with a plurality of adjustment screws (18) from the outside of the sleeve (16).