JPH0637284Y2 - Motor rotation position detector - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention is a device for detecting the absolute rotational position of a direct drive motor (hereinafter referred to as DD motor) that directly drives an object to be driven without passing through a speed reducer. It is about.

[Prior Art] As a conventional DD motor, for example, there is an outer rotor type shown in FIG.

In this motor, the driven object is fixed to the portion a and the position of the portion b is fixed, and in this state, rotational power is applied to the driven object.

An optical rotary encoder as a rotation angle sensor incorporated in this motor is a high resolution one that generates 160,000 to 1,000,000 pulses when the motor makes one revolution, but measures the increment of the pulse. Since it is an incremental type that detects the rotation angle of the motor, a reference origin that is a reference position for one rotation is required.

A mechanical or optical limit switch is used as the reference origin, and when the robot is powered on, the motor is rotated in a predetermined direction, and the limit origin is detected by the limit switch described above with coarse accuracy, and then the The position where the origin pulse is generated is used as an accurate reference position. This origin pulse is output to the code plate of the encoder by using a slit provided separately from the incremental position output. When the motor makes one rotation, 60 to 100 pulses are output.

When a motor using such a position detection device is applied to a robot, particularly in the case of an articulated robot arm, when the power of the robot is turned on, the motor is rotated until the reference origin is detected. Then, the robot arm may hit an obstacle to perform the origin detection operation. Therefore, it is desirable that the rotation detecting device for the articulated robot arm be capable of detecting the absolute rotation position of the motor as soon as the robot is powered on.

In order to meet such demands, as shown in FIG.
In the outer rotor type DD motor, a gear 2 is fixed to the outer peripheral surface of the rotor 1, a small gear 4 meshing with the gear 2 is attached to the rotary shaft of a small potentiometer 3, and the absolute rotational position of the rotor 1 is detected by the potentiometer 3. Conceivable.

[Problems to be Solved by the Invention] However, in this device, the potentiometer 3 rotates more than the rotation speed of the rotor 1 due to the gear ratio of the gears 2 and 4, so the potentiometer is expensive and the high-speed rotation is possible. There was a problem that it would wear out quickly.

If the number of teeth of the gear 4 is increased to prevent wear, the gear 4
The diameter becomes larger and the device becomes larger.

The present invention solves the above problems at the same time,
An object of the present invention is to realize a motor rotation position detection device that can detect the absolute rotation position of a motor without making the structure large.

[Means for Solving the Problems] The present invention provides a ring gear fixed to the rotor circumferential surface of an outer rotor type direct drive motor and a ring gear that meshes with the ring gear and changes the amount of dislocations so that the number of teeth is different. Rotational position detection of a motor comprising two concentric gears and a rotation detection means for detecting an absolute rotational position of the rotor based on a difference in rotation angle between the two concentric gears caused by rotation of the rotor. It is a device.

[Embodiment] The present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an embodiment of a motor rotational position detecting device according to the present invention.

In the figure, 10 is an outer rotor type DD motor. DD motor
Reference numeral 10 denotes a rotor, 12 denotes a stator, and 13 denotes a ring gear that is fitted on the outer peripheral surface of the rotor 11. The ring gear 13
May be cut on the outer peripheral surface of the rotor 11.

Reference numeral 20 is a potentiometer having a gear that meshes with the ring gear 13. FIG. 2 is an enlarged configuration diagram of this potentiometer.

In FIG. 2, 21 is a gear that meshes with the ring gear 13 and is fixed to the rotary shaft 22 of the potentiometer, and 23 is a ring gear.
A gear that meshes with 13 and is fixed to the main body 25 of the potentiometer by a bush 24.

The gears 21 and 23 have the same outer diameter and mesh with the ring gear 13 at the same time, but the number of teeth is different by changing the dislocation amount.

Next, the operation of such a device will be described.

The numbers of teeth of gears 13, 21, and 23 are N ₀ , N ₁ , and N ₂ , respectively.

When the rotor 11 makes one revolution, the rotation speeds of the gears 21 and 23 become N ₀ / N ₁ and N ₀ / N ₂ , respectively. This allows the potentiometer 20 to Rotate. For example, if N ₀ = 100, N ₁ = 20, N ₂ = 21, the relative rotation number of the potentiometer becomes 0.238. Therefore, the potentiometer may be a single rotation, small size, and inexpensive. Further, since the rotation speed is also lower than N ₀ , even the contact type potentiometer is less worn.

FIG. 3 is an enlarged block diagram of another embodiment of the device according to the present invention.

3 (a) is a longitudinal sectional view, and FIG. 3 (b) is a plan view of a main part.

In these figures, 31 and 32 are gears meshing with the ring gear 13, 33 and 34 are polarizing plates incorporated inside the gears 31 and 32,
35 is the shaft fixed to the fixed part, 36 and 37 are the gears 31 and 32
It is a bearing that is rotatably attached to. The gears 31 and 32 have the same outer diameter as in the embodiment of FIG. 1, but differ in the number of teeth by changing the amount of dislocation.

Reference numeral 38 is a light source, 39 is a lens that converges the light of the light source 38 onto the polarizing plates 33 and 34, and 40 is a light receiving element that detects the light that has passed through the polarizing plates 33 and 34.

In such a device, the polarization planes of the polarizing plates 33 and 34 are aligned at the absolute rotation position of 0 °.

From this state, when the rotation angles of the gears 31 and 32 when the ring gear 13 rotates by a predetermined angle are θ ₁ and θ ₂ , respectively, the light quantity I that has passed through the two polarizing plates 33 and 34 is I = It becomes cos (θ ₁ −θ ₂ ). Therefore, if θ ₁ −θ ₂ = cos ⁻¹ I is adjacent and I is measured, θ ₁ −θ _2, that is, the rotation angle of the rotor 11 can be obtained.

In the detection device using the potentiometer as shown in FIG. 1, the potentiometer rotates and swings the detection signal output cable, but in the device of FIG. 3, the light receiving element 40 is fixed, which is not the case. There is.

[Effect] According to the present invention, the following effects can be obtained.

By using an outer rotor type motor having many rotating parts, one gear is fixed to the rotor, and the absolute rotational position of the motor can be detected by a simple configuration in which two concentric gears that mesh with the gear are added.

In the embodiment of FIG. 1, the potentiometer shaft rotates, but the body also rotates. This reduces the effective rotation angle of the potentiometer. As a result, a single-rotation small potentiometer and a concentric gear having a small diameter can be used, the configuration can be downsized, and the restriction on the rotational speed of the potentiometer can be relaxed.

In the embodiment shown in FIG. 3, since the difference between the two rotation angles is optically detected, it is possible to achieve non-contact. As a result, the position of the light receiving element that detects the angular difference between the two gears is fixed, and the detection signal output line is not swung.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a motor rotation position detecting device according to the present invention, FIG. 2 is an enlarged configuration diagram of the device of FIG. 1, and FIG. 3 is a motor rotation position detecting device according to the present invention. FIG. 4 is a diagram showing a configuration example of a main part of another embodiment of the device, FIG. 4 is a diagram showing a configuration example of a direct drive motor, and FIG. 5 is a diagram showing a configuration example of a conventional motor rotation position detecting device. . 10 ... DD motor, 11 ... Rotor, 12 ... Stator, 13 ... Ring gear, 20 ... Potentiometer, 21,23 ... Gear, 22 ... Rotating shaft, 25 ... Main body, 31,32 ... Gear, 33, 34 ... Polarizing plate, 35 ... fixed shaft, 36,37 ... bearing, 38 ... light source, 40 ... light receiving element.

Claims (1)

[Scope of utility model registration request] 1. An outer rotor type direct drive
A ring gear fixed to the rotor peripheral surface of the motor, two concentric gears that mesh with the ring gear and have different numbers of teeth by changing the dislocation amount, and the two concentric gears by rotation of the rotor. A rotation position detection device for a motor, comprising rotation detection means for detecting the absolute rotation position of the rotor based on the difference in the rotation angle of the motor.