JP2018100859A - Absolute encoder of geared motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an absolute encoder capable of accurately detecting an absolute rotational position of an output shaft of a geared motor.SOLUTION: An absolute encoder 8 detects an absolute rotational position of an output shaft 5 in a geared motor 1 in which the rotation of a motor shaft 3 is decelerated through a reduction gear 4 and is output from the output shaft 5. The absolute encoder has a wave gear device 13 for decelerating the rotation of the motor shaft 3 and a detection unit 14 for detecting the absolute rotational position of a driving side internal gear 17 which is a reduced rotation output member of the wave gear device 13. The operating range of the output shaft 5 is, for example, one revolution, and the speed ratio R(13) of the wave gear device 13 is set equal to the speed ratio R(4) of the reduction gear 4.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a geared motor, and more particularly to an absolute encoder that detects an absolute rotational position of an output shaft thereof.

  A geared motor configured to output the output rotation of a motor via a reduction gear with high transmission accuracy is used in a drive portion that requires high positioning accuracy in an industrial robot, a machine tool, or the like. The geared motor includes a motor and a reduction gear connected to the motor shaft. The load side device is rotationally driven by the output shaft of the reduction gear.

  In a geared motor, it is necessary to control the rotational position of the output shaft of the speed reducer with high accuracy in order to accurately position the load side device. For this purpose, a motor shaft encoder is attached to the motor shaft, and a rotational position sensor is also attached to the output shaft.

  The rotational position sensor is disposed, for example, at the tip end portion (the shaft end portion on the load side) of the output shaft. When the rotational position sensor cannot be disposed at the tip portion of the output shaft, the rear end portion of the output shaft extends to the rear side of the motor through the hollow portion of the hollow motor shaft, and the rotational position sensor is disposed at the rear side of the motor. As the battery-less rotational position sensor, an origin sensor that detects the origin position of the output shaft or an absolute sensor that detects the absolute rotational position of the output shaft is used. When an absolute sensor is used, it is not necessary to find the origin of the output shaft when starting the motor.

  Patent Document 1 proposes a multi-rotation absolute rotation angle detection device that detects an absolute rotation position of an output shaft based on rotation of a motor shaft. In this device, the absolute rotation position within one rotation of the output shaft can be detected by decelerating and taking out the rotation of the motor shaft through a reduction gear composed of a plurality of spur gears.

Japanese Patent No. 5420624

  In order to detect the absolute rotational position of the output shaft based on the rotation of the motor shaft, it is difficult to accurately manufacture and assemble each spur gear accurately when using a reduction mechanism composed of a plurality of spur gears. There are many cases. If the production accuracy of each spur gear is low and the assembly accuracy thereof is low, the absolute rotational position of the output shaft cannot be detected with high accuracy. Further, if a reduction gear train made of spur gears is arranged in the radial direction on the outer peripheral side of the motor shaft, the outer diameter of the portion where the absolute sensor in the geared motor is incorporated becomes large.

  In view of the above, an object of the present invention is to provide an absolute encoder capable of accurately detecting the absolute rotational position of an output shaft of a geared motor with a compact configuration.

  In order to solve the above problems, an absolute encoder for detecting an absolute rotation position of an output shaft in a geared motor in which rotation of a motor shaft is decelerated via a reduction gear and output from an output shaft according to the present invention is a motor. A wave gear device that decelerates the rotation of the shaft and a detection unit that detects the absolute rotation position of the reduced rotation output member of the wave gear device. The speed ratio of the wave gear device is set to the same or larger value as the speed ratio of the speed reducer.

  Since the wave gear device has no backlash and less rotation transmission error, it is more accurate than when the absolute rotation position of the output shaft is detected by decelerating the motor shaft using a speed reduction mechanism consisting of a gear train such as a spur gear. Detection is possible. Further, since the wave gear device is a reduction mechanism having a compact configuration in which three parts of an internal gear, an external gear, and a wave generator are arranged concentrically, the installation space is smaller than when other reduction mechanisms are used. Less is enough.

  As the wave gear device, a flat wave gear device having a short axial length can be used. The flat type wave gear device can mesh with both a stationary stationary internal gear fixed so as not to rotate, a rotatable driving internal gear, a stationary internal gear, and a driving internal gear. A flexible external gear and a wave generator that flexes the external gear into a non-circular shape and partially meshes with both the stationary internal gear and the drive internal gear are provided. The wave generator is a rotation input member fixed to the motor shaft, and the drive-side internal gear is a reduction rotation output member.

  For example, if the speed ratio of the wave gear device is set to be the same as the speed ratio of the speed reducer, the drive-side internal gear rotates at the same rotational speed as the output shaft. Each rotation position within one rotation of the drive-side internal gear corresponds to each rotation position within one rotation of the output shaft. Therefore, if the absolute rotation position within one rotation of the drive side internal gear is detected by the detection unit, the absolute rotation position within one rotation of the output shaft can be obtained.

  For example, a magnetic detection mechanism can be used as the detection unit. In this case, for example, a detection surface in which magnetic poles are formed at a constant pitch along the circumferential direction is formed on the circular outer peripheral surface or the annular end surface of the drive-side internal gear. Or a to-be-detected surface in which the uneven | corrugated | grooved part was formed with a fixed pitch, for example, an external tooth is formed with a fixed pitch. What is necessary is just to arrange | position the magnetic sensor comprised from the position fixed in the circumferential direction, MR element, etc. with respect to a to-be-detected surface.

  Next, the geared motor of the present invention is characterized by including the absolute encoder having the above-described configuration. For example, the absolute encoder is arranged next to the motor shaft encoder that detects the rotational position of the motor shaft at a position opposite to the speed reducer (opposite output side) in the motor.

  In the geared motor of the present invention, a wave gear device is used as a reduction mechanism for reducing the rotation of the motor shaft in order to detect the absolute rotation position of the output shaft. The wave gear device can transmit rotation with higher accuracy than when a reduction gear train made of a spur gear or the like is used. Therefore, the absolute rotational position of the output shaft can be detected with high accuracy, and based on this, positioning control of the geared motor can be performed with high accuracy.

It is explanatory drawing which shows an example of the motor with a gear provided with the absolute encoder to which this invention is applied.

  Hereinafter, an example of a geared motor including an absolute encoder to which the present invention is applied will be described with reference to FIG.

  A geared motor 1 equipped with an absolute encoder (hereinafter simply referred to as “geared motor 1”) includes a motor 2 and a speed reducer 4 connected to the output side of the motor shaft 3. A load-side device 6 is connected to the output shaft 5 of the speed reducer 4 and is driven to rotate by the output shaft 5. For example, one rotation of the output shaft 5 is installed as an operating range of the load-side device 6.

  In order to perform positioning control of the load side device 6, that is, positioning control within one rotation of the output shaft 5 of the speed reducer 4, a motor shaft encoder 7 that detects the rotational position of the motor shaft 3, and an output shaft 5 And an absolute encoder 8 for detecting an absolute position within one rotation of the encoder.

  The motor shaft encoder 7 and the absolute encoder 8 are arranged on the outer peripheral portion of the shaft end portion 3a on the rear side (opposite output side) of the motor shaft 3. The absolute encoder 8 is disposed adjacent to the rear side of the motor shaft encoder 7.

  The detection signal of the motor shaft encoder 7 and the detection signal of the absolute encoder 8 are subjected to signal processing such as waveform shaping in a common signal processing circuit 11 in the control unit 10, and the rotation of the motor shaft 3 is performed based on the processed signal waveform. The position and the absolute rotational position within one rotation of the output shaft 5 are calculated. Based on the calculation result, the control unit 10 drives the motor 2 via the motor driver 12 to perform positioning control of the load-side device 6.

  For example, the motor shaft encoder 7 is a magnetic encoder, and the detection unit thereof is a multipolar magnetized rotating disk 7a fixed coaxially to the shaft end 3a of the motor shaft 3 and a two-pole magnetized rotating disk. 7b, and magnetic sensors 7c and 7d composed of a Hall element, an MR element, and the like opposed to the outer peripheral surface of each rotating disk. As the motor shaft encoder 7, for example, a magnetic or optical rotary encoder can be used.

  The absolute encoder 8 includes a wave gear device 13 that decelerates the rotation of the motor shaft 3 and a detection unit 14 that detects the absolute rotation position of the reduced rotation output member of the wave gear device 13. The speed ratio R (13) of the wave gear device 13 is set to be the same as the speed ratio R (4) of the speed reducer 4 in this example.

  The wave gear device 13 is a flat type wave gear device, which is a rigid stationary internal gear 16 fixed so as not to rotate, a rotatable ring-shaped drive side internal gear 17, and a stationary internal gear. A flexible external gear 18 having a cylindrical shape that can mesh with the gear 16 and the drive-side internal gear 17, and the external gear 18 bend in a non-circular shape, for example, an ellipse, so that the stationary-side internal gear 16 and the drive are driven. And a wave generator 19 partially meshed with both of the side internal gears 17. The drive-side internal gear 17 and the external gear 18 have the same number of teeth, and the stationary-side internal gear 16 has more teeth than these gears. For example, when the external gear 18 is bent into an elliptical shape and meshes with both internal gears at two locations in the circumferential direction, the difference in the number of teeth is 2n (n = 1, 2, 3,...・).

  The stationary internal gear 16 is fixed to an encoder cover 21 fixed to the motor case 2a. The wave generator 19 is a rotation input member that is fixed to the motor shaft 3 and rotates integrally with the motor shaft 3. The drive-side internal gear 17 is a reduced speed rotation output member, and is rotatably supported by the encoder cover 21 via a bearing 22.

  The absolute encoder 8 is, for example, a magnetic encoder. The detection unit 14 has an external tooth 23 formed at a constant pitch over the entire circumference in the circular outer peripheral surface of the drive-side internal gear 17 of the wave gear device 13, and the external tooth 23. One or a plurality of magnetic sensors 24 facing each other at a fixed position on the outer peripheral side are provided. The magnetic sensor 24 includes a magnetic detection element such as a Hall element or MR.

  Instead of forming the external teeth 23 on the circular outer peripheral surface of the drive-side internal gear 17 made of a magnetic material, the external teeth 23 can be formed on the annular end surface 17a. Further, instead of the external teeth 23, a magnet ring in which magnetic poles are formed at a constant pitch along the circumferential direction can be used. The magnetized surface can be formed on the circular outer peripheral surface or the annular end surface of the drive-side internal gear 17. An optical rotary encoder can also be used.

  In the absolute encoder 8, the speed ratio R (13) of the wave gear device 13 that decelerates the rotation of the motor shaft 3 is reduced to transmit the rotation of the motor shaft 3 from the output shaft 5 to the load-side device 6. Is the same as the speed ratio R (4). The drive-side internal gear 17 of the wave gear device 13 rotates within the range of one rotation at the same speed as the output shaft 5 (load-side device 6). Therefore, the absolute position within one rotation of the output shaft 5 is detected by detecting the absolute position within one rotation of the drive side internal gear 17. The absolute encoder 8 functions as an output shaft 1-rotation battery-less absolute encoder.

  Here, in the absolute encoder 8 of this example, it is desirable that the wave gear device 13 does not use grease. No load is applied to the wave gear device 13 and no torque is transmitted. For this reason, a non-lubricated drive type wave gear device can be easily obtained by changing the components of the wave gear device 13 to a material suitable for the non-lubricated drive. In this way, there is an advantage that a seal mechanism for preventing the grease supplied to the meshing part and the sliding part of the wave gear device 13 from leaking out to the magnetic sensor 24 side or the outside becomes unnecessary. .

(Other embodiments)
In order to detect the absolute position of the output shaft within the operating range when the operating range of the load-side device 6 is equal to the number of rotations of the output shaft, the output shaft rotation amount is usually detected using an internal counter. It is necessary to count and store count data. In the absolute encoder 8 of the present invention, for example, when the operating range of the load-side device 6 is equivalent to two rotations of the output shaft, the drive-side internal gear 17 of the wave gear device 13 makes one rotation for every two rotations of the output shaft. Thus, the speed ratio R (13) of the wave gear device 13 may be set to twice the speed ratio R (4) of the speed reducer 4. That is, the speed ratio R (13) is set to a value larger than the speed ratio R (4) according to the operating range on the load side, and the rotation angle of the output shaft 5 corresponding to the operating range on the load side is driven. The side internal gear 17 may be rotated once. Therefore, according to the present invention, there is no need for an internal counter for counting the rotation amount (rotation speed) of the output shaft, no counting error occurs, and further no storage of counter data is required. A batteryless absolute encoder capable of detecting an absolute position within the range of several revolutions can be obtained.

  In the above example, a flat wave gear device is used as the wave gear device 13. The flat-type wave gear device has a short shaft length and can suppress an increase in the shaft length of the geared motor. When the increase in the axial length is not a problem, other types of wave gear devices can be used. A cup type wave gear device and a top hat type wave gear device can be used.

  As the speed reducer 4, various types of speed reducers can be used. For example, a wave gear device can be used as the speed reducer 4. In this case as well, a flat type, cup type, and top hat type wave gear device can be used. Of course, a reduction gear such as a general planetary gear device can be used.

DESCRIPTION OF SYMBOLS 1 Motor with gear 2 Motor 2a Motor case 3 Motor shaft 3a Shaft end 4 Reduction gear 5 Output shaft 6 Load side device 7 Motor shaft encoder 7a, 7b Rotary disk 7c, 7d Magnetic sensor 8 Absolute encoder 10 Control section 11 Signal processing Circuit 12 Motor driver 13 Wave gear device 14 Detector 16 Stationary side internal gear 17 Drive side internal gear 17a End face 18 External gear 19 Wave generator 21 Encoder cover 22 Bearing 23 External tooth 24 Magnetic sensor R (4) Speed ratio R (13) Speed ratio

Claims (5)

An absolute encoder that detects the absolute rotational position of the output shaft in a geared motor in which the rotation of the motor shaft is decelerated via a reduction gear and output from the output shaft,
A wave gear device that decelerates rotation of the motor shaft;
A detection unit that detects an absolute rotation position of the reduction rotation output member of the wave gear device;
An absolute encoder for a geared motor, wherein a speed ratio of the wave gear device is equal to or greater than a speed ratio of the speed reducer. In claim 1,
The wave gear device is
A rigid stationary internal gear fixed so as not to rotate;
A drive-side internal gear with rotatable rigidity,
A flexible external gear that can mesh with the stationary-side internal gear and the drive-side internal gear;
A wave generator that bends the external gear into a non-circular shape and partially meshes with both the stationary-side internal gear and the drive-side internal gear;
The wave generator is fixed to the motor shaft;
The drive-side internal gear is an absolute encoder of a geared motor, which is the reduction rotation output member. In claim 1,
The wave gear device is a gearless motor absolute encoder which is a non-lubricated drive type wave gear device. In claim 2,
The detector is
On the circular outer peripheral surface or annular end surface of the drive-side internal gear, a detected surface in which magnetic poles are formed at a constant pitch along the circumferential direction, or a detected surface on which irregularities are formed at a constant pitch. Surface,
An absolute encoder of a geared motor, comprising: a magnetic sensor facing the detected surface at a fixed position in the circumferential direction. A motor,
A reduction gear connected coaxially to one first shaft end of the motor shaft of the motor;
5. The absolute device according to claim 1, wherein the absolute rotation position of the reduction rotation output member of the reduction gear is detected on the other second shaft end side of the motor shaft. A geared motor having an encoder.

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