JP2003274679A - Thin servo motor - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a thin servomotor capable of realizing low capacity, low weight, compactness, and space saving of a control motor. SOLUTION: An ultrasonic motor unit (1) including an oscillator (2), a stator (3), a rotor (4), and a shaft (10); a shaft (10) as a shaft; (8
A), a substrate (8B), and a capacitive encoder section (6) provided with a disk (7). The ultrasonic motor section (1) and the capacitive encoder section (6) are both It is structured to be stored in the case (5).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servomotor using an ultrasonic motor, and more particularly to a thin servomotor capable of realizing space saving.

[0002]

2. Description of the Related Art An ultrasonic motor is a vibrating body (stator) made of a piezoelectric element such as piezoelectric ceramics and an elastic body such as metal.
It is a motor that is activated by pressing a moving body (rotor) on the surface of and contacting it. The operating principle is that a traveling wave is generated in the vibrating body by applying a high frequency voltage to the piezoelectric element,
As a result, vibration is generated in the drive unit, and the vibration is transmitted to the moving body (rotor) contacting the drive unit as frictional force. Due to such an operating principle, the ultrasonic motor can be easily configured as a linear motor in addition to the rotary motor.

The ultrasonic motor can obtain a low speed and a high torque without using a reduction mechanism such as a gear, can be directly driven, has a quiet operation sound, is easy in speed control, has a large holding torque, and does not require consideration of braking. It has many excellent features such as high responsiveness, simple structure, easy device compaction, hollow structure, almost no magnetic field. Taking advantage of these characteristics, ultrasonic motors are used in robot drive joints, medical equipment, camera autofocus, optical equipment lens mirror drive, roll screen hoisting, automobile handle position / headrest, component transfer, high magnetic field actuators. It is used as a control motor for position control of satellite receivers, and its applications are expected to further expand in the future.

In the feedback control of the ultrasonic motor,
A rotation detector such as an encoder that detects the rotation of the shaft is used, but conventionally, an optical encoder or the like is used.

FIG. 4 is an explanatory side view showing one of the basic constructions of the optical encoder. In the figure, an optical encoder has a rotary plate 4 in which a large number of slits 41 are arranged.
A light emitting portion 43 such as a light emitting diode (hereinafter, referred to as "LED") for projecting light on the rotary plate 42 with the two in between,
And a light receiving portion 44 (two groups are provided) such as a photodiode for receiving the light processed by the fixed slit 46 through the slit 41 on the rotary plate 42, and the rotary plate 42 is a motor. The basic structure is that it is provided at the end of the shaft 45. In the optical encoder having such a configuration, the light L emitted from the light emitting unit 43 is applied to the rotary plate 42 that reveals the rotation of the motor, and the displacement information of the rotation angle is generated by the action of the slit on the rotary plate 42. And pulsed as two types of pulse signals having different phases in the two light receiving portions 44 provided through the fixed slit 46, and the two types of pulse signals are arithmetically processed to obtain the motor. It is possible to detect the displacement amount and direction of rotation of the.

[0006]

However, the optical encoder has to occupy a certain space due to its structure, and when this is used as an ultrasonic motor and used as a servo motor, the ultrasonic motor has it. There was a limit to fully utilize the ease of making the structure compact. In particular, when it is necessary to reduce the thickness in the axial direction, or when it is desired to reduce the thickness, the limit of downsizing the optical encoder is directly limited to the reduction of the servomotor. FA), office automation (OA), medical fields, and other industrial fields require low capacity, low weight, and compact equipment, and solutions for thinner servo motors are required. It was

FIG. 3 is a sectional view showing the structure of a servo motor using a conventional ultrasonic motor. In the figure, the conventional servomotor includes an oscillator 32, a stator 33, and a rotor 3.
4, an ultrasonic motor unit 31 having a shaft 30 and substrates 38A, 38B, a rotary plate (hereinafter,
Also called a "disk". ) 37 and an optical encoder section 36, and the ultrasonic motor section 31 is housed in a case 35, while the optical encoder section 36 is housed in a case 39.
39 are fixed to each other.

As shown in the figure, in the servo motor using the optical encoder, the encoder portion 36 has a thickness in the axial direction which is almost the same as that of the ultrasonic motor portion 31 due to the structure of the encoder. There are limits to how thin the motor can be made. Moreover, the encoder unit 36 includes the above-mentioned disc 37.
In addition, since it is necessary to provide a light emitting unit, a light receiving unit, a fixed slit, and the like (not shown), the shape and structure of the case 39 is complicated, the number of parts is large, the number of assembling steps is large, and considerable manufacturing cost is required. Has become.

Further, in the optical encoder, LE
Since it is necessary to constantly supply a current to the light-emitting part such as D, and the auxiliary power supply to cover this requires a considerable amount of power consumption, there is a limit to the reduction of the power cost, and the extra power consumption is also in terms of protecting the global environment. It was something I wanted to avoid, and there was a need for improvement.

The object of the present invention is to eliminate the drawbacks of the prior art described above, and to reduce the capacity and weight of control motors in various industrial fields such as factory automation (FA), office automation (OA) and medical fields. It is an object of the present invention to provide a thin servo motor capable of realizing compactness and space saving.

Another object of the present invention is to provide a servo motor which can reduce the number of parts and the number of steps to reduce the manufacturing cost by improving the shape and structure of the rotation detector portion. .

Still another object of the present invention is to provide a thin servomotor which can reduce the power consumption of the rotation detector portion and can be made thin in its overall structure.

[0013]

Means for Solving the Problems As a result of extensive studies on the above problems, the present inventor can solve the above problems by using a capacitance type rotation detector instead of the conventional optical rotation detector. Found. That is, the invention claimed in the present application as means for solving the above problems is as follows.

(1) In a servomotor having an ultrasonic motor and a rotation detector attached to the ultrasonic motor for detecting the rotation angle of the ultrasonic motor, the rotation detector is rotated by a capacitance type. A thin servomotor characterized by being used as a detector.

(2) The thin servomotor according to (1), wherein the capacitance type rotation detector is a capacitance type encoder.

(3) The ultrasonic motor is a rotary ultrasonic motor, and the electrostatic capacitance type rotation detector is a rotary electrostatic capacitance type encoder. (1)
Thin servo motor.

(4) The ultrasonic motor is a linear ultrasonic motor, and the electrostatic capacitance type rotation detector is a linear electrostatic capacitance type encoder.
The thin servomotor of (1).

That is, in the present invention, in a servomotor using an ultrasonic motor, as a rotation detector responsible for its feedback control, a conventional optical rotation detector which has no choice but to occupy a certain space due to its structure is replaced. The servo motor is thinned by using a capacitance type rotation detector which has a thin structure, occupies less space, saves space, and consumes less power. The object of the present invention is to provide a solution to the above problems by making it compact and saving space.

An example of the electrostatic capacitance type rotation detector is an electrostatic capacitance type encoder. FIG. 2 is an explanatory diagram illustrating the principle of the capacitance type encoder. In the capacitance type encoder shown in the figure, a rotor 20 is provided on a rotating shaft 22 for rotation, and a rotor electrode 27 is provided on the rotor 20. The stator 21 is fixed to the housing of the rotor 20 and the like, and the stator 21 is provided with a transmission electrode 26 and a reception electrode 28. The stator 21 and the rotor 20 are provided with a small gap (hereinafter referred to as “gap”) 23 between them, and the transmitter electrode 26 and the receiver electrode 28 are provided through the gap 23.
And the rotor electrode 27 are electrostatically coupled to each other. When an AC voltage is applied from the AC power supply 29 to the transmitting electrode 26, signals are (a) transmitting electrode 26 and (b) rotor electrode 2
7, (c) the receiving electrode 28 is transmitted along the path.
Based on the signal received by the receiving electrode 28, the capacitance calculator 24 detects the capacitance at each time point. In the capacitance type encoder, the electrodes 26, 2 are arranged so that the capacitance changes according to the rotation angle of the rotor 20.
Since 7, 28 are arranged, from the detected capacitance,
The rotation angle of the rotor 20 can be obtained.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings. The present invention is not limited to the examples below. Hereinafter, in the drawings, the same components will be denoted by the same reference numerals for description.

[0021]

[Structure] FIG. 1 shows a thin servo motor of the present invention.
FIG. 4 is a side sectional view showing an example in which the capacitance type rotation detector is a capacitance type encoder. In the figure, the thin servo motor is an ultrasonic motor unit 1 including an oscillator 2, a stator 3, a rotor 4, and a shaft 10.
And an electrostatic capacity type encoder section 6 having the shaft 10 as an axis and provided with substrates 8A, 8B and a disk 7, and the ultrasonic motor section 1 and the electrostatic capacity type encoder section 6 are Both have a structure housed in the case 5.

[0022]

In the figure, in the thin servomotor of the present invention using an electrostatic capacity type encoder, the electrostatic capacity encoder section 6 has a considerably small axial thickness as compared with the ultrasonic motor section 1. , About 50% of the thickness of the motor unit 1
It can be thinned to a moderate thickness or even less.

Further, in the prior art, a case is required for each of the motor section and the encoder section, and the thickness of the case affects the axial thickness of the entire servo motor.
In the servo motor of the present invention, the motor unit 1 and the encoder unit 6
The case can be shared by (5), and since no boundary is provided between the two parts by the case, the case thickness can be reduced correspondingly, which is effective in reducing the thickness of the servomotor.

As a result, the axial thickness of the entire servo motor can be reduced by about 25%, and can be reduced to about 75% (see FIGS. 1 and 3). Alternatively,
As a result of thinning the encoder unit 6 and the like, the axial thickness of the entire servo motor can be reduced by about 25% or more, and can be reduced to about 75% or less.

As shown in FIG. 1, in the thin servomotor of the present invention, when a rotary ultrasonic motor is used as the ultrasonic motor unit 1, a rotary electrostatic motor is used as the electrostatic capacity encoder unit 6. Although a capacitive encoder is used, when a linear ultrasonic motor is used as the ultrasonic motor unit 1, a linear electrostatic encoder can be used as the electrostatic encoder unit 6. . In any case, by using a capacitance type encoder for the encoder unit, the thickness of the encoder unit can be reduced and the case of the motor unit and the encoder unit can be shared, so that the servo motor can be made thinner. .

[0026]

Since the thin servo motor of the present invention is configured as described above, it can be used as a control motor in various industrial fields such as factory automation (FA), office automation (OA) and medical fields. It is possible to realize capacity, low weight, compactness, and space saving.

Further, according to the present invention, since the shape and structure of the rotation detector portion can be improved and the case can be made common, the number of parts and the number of steps can be further reduced to reduce the manufacturing cost. .

Furthermore, according to the present invention, the power consumption of the rotation detector portion can be reduced and the overall structure can be made thin.

[Brief description of drawings]

FIG. 1 is a side sectional view of an example in which a capacitance type rotation detector is a capacitance type encoder in a thin servomotor of the present invention.

FIG. 2 is an explanatory diagram illustrating the principle of a capacitive encoder.

FIG. 3 is a cross-sectional view showing a configuration of a servo motor using a conventional ultrasonic motor.

FIG. 4 is an explanatory side view showing one of basic configurations of an optical encoder used in a conventional servo motor.

[Explanation of symbols]

1, 31 ... Ultrasonic motor section, 2, 32 ... Oscillator,
3, 33 ... Stator, 4, 34 ... Rotor (ultrasonic motor), 5, 35, 39 ... Case, 6, 36 ... Encoder section, 7 ... Rotor (capacitance type encoder), 8
A, 8B, 38A, 38B ... Substrate, 10, 30 ... Axis,
37 ... Rotating plate <Fig. 2: Capacitance encoder> 20 ... Rotor, 21 ... Stator, 22 ... Rotating shaft,
23 ... Gap, 24 ... Capacitance calculator, 26 ... Transmission electrode, 27 ... Rotor electrode, 28 ... Reception electrode, 2
9 ... AC power supply <Fig. 4: Optical encoder> 41 ... Slit, 42 ... Rotating plate, 43 ... Light emitting part,
44 ... Light receiving part, 45 ... Shaft, 46 ... Fixed slit,
L ... light

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2F077 AA49 NN02 NN14 PP01 QQ03                       RR02                 5H680 AA19 BB01 BB12 BB15 BB17                       BC01 BC08 BC10 CC01 DD01                       DD11 DD23 DD27 DD35 DD65                       DD87 DD88 EE22 FF24 GG01

Claims (4)

[Claims] 1. A servo motor comprising an ultrasonic motor and a rotation detector attached to the ultrasonic motor for detecting a rotation angle of the ultrasonic motor, wherein the rotation detector is a capacitance type rotation detector. A thin servo motor characterized by being used as a container. 2. The thin servomotor according to claim 1, wherein the capacitance type rotation detector is a capacitance type encoder. 3. The ultrasonic motor according to claim 1, wherein the ultrasonic motor is a rotary ultrasonic motor, and the electrostatic capacitance type rotation detector is a rotational electrostatic capacitance type encoder. Thin servo motor. 4. The ultrasonic motor according to claim 1, wherein the ultrasonic motor is a linear ultrasonic motor, and the electrostatic capacitance type rotation detector is a linear electrostatic capacitance type encoder. Thin servo motor.