JPS5947945A - Motor with torque detecting means - Google Patents

Abstract

PURPOSE:To improve the detecting accuracy of torque detecting means by arranging a strain sensor at the stator side of a motor, detecting the strain affected at the stator side as a reaction to the generated torque of the motor, thereby detecting the generated torque. CONSTITUTION:A slender section 18 is formed between a frame 17 for fixing a stator 16 of a motor and a part 11 to be fixed for fixing the frame, and strain sensors 1A-1D are respectively bonded to left and right, upper and lower mounts 18A, 18B. The sensors 1A-1D are provided to be connected in bridge shape to generate detected outputs only for the rotary force at the Z-shaft as a center and not to generate an output for any other force, thereby detecting the strain affected by the frame 17 as a reaction to the generated torque of the motor to detect the torque. In this manner, sensors are arranged on the stationary unit to simplify the structure, thereby accurately detecting the torque.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motor equipped with a motor torque detection means that can detect the torque generated by the motor at high speed and with high precision by providing a sensor on the stator side of the motor.

FIG. 1 is a diagram showing an embodiment of a conventional motor torque detection method. In this embodiment, a strain sensor such as the strain gauge 1 shown in FIG. The strain gauge 1 that detects torque normally has a resistance value of about 12 on between the leads, and when a force is applied in the direction shown in the figure, the resistance value between the leads changes l - Strain can be detected. However, even if a force other than the direction A is applied, the resistance value does not change. In this embodiment, since the strain sensor is provided on the rotor side of the motor, there is a drawback that the torque generated during infinite rotation, that is, continuous rotation of the motor cannot be detected as it is. If a sliding part, that is, a slip ring and brushes, are installed on the rotor side to detect the torque generated during infinite rotation of the motor, continuous rotation is possible, but long-term stability is not achieved, and detection accuracy and reliability are reduced. However, there are also drawbacks such as noise generation due to the presence of sliding parts.

FIG. 2 is a diagram showing another embodiment of the conventional motor torque detection method. If the armature current flowing through the armature winding 4 of the motor is ``2'' and the field magnetic flux density generated by the field magnet is assumed to be the field magnetic flux density, the generated torque T of the motor can be obtained from the magnetic flux density BX armature current ``2''. In this embodiment, the armature current ■ is detected by the detection resistor 6 and amplified by the amplifier 8, and then inputted to one input terminal of the arithmetic circuit 9, and the field magnetic flux density B is stopped as a voltage by the Hall element 5. After being detected and amplified by the amplifier 7, it is similarly input to the other input terminal of the arithmetic circuit 9. The arithmetic circuit 9 calculates B×■ and converts it into generated torque. In this embodiment, the Hall element 5 and the detection resistor 6, which are sensors, are provided on the stationary side or only detect the local magnetic flux density, and do not detect the effective magnetic flux density that contributes to the torque of the motor. This has the disadvantage of poor torque detection accuracy. Historically, it has had the disadvantage that it requires time for arithmetic processing and causes a time delay from detection to control, making it unsuitable for applications that require control by forming a closed feedback loop.

Servo motors that use this conventional method of detecting torque generated by a motor are mainly used to control the displacement of the motor rotor, such as in servo motors for robots and NC machines, or to control the displacement of the motor's rotor, such as in servo motors for constant speed operation, etc. Previously, the rotational speed of the rotor was controlled as in the case of a motor, or the current was controlled as in a servo motor, such as with a torque limiter or motor protection circuit. K was not achieved until the rotor acceleration was controlled. Since these servo motors cannot control the acceleration of the rotor when starting and stopping, they perform a stepping operation in which they suddenly start and stop suddenly in steps, making smooth positioning impossible. In other words, if we look at this step-like operation in detail, it is a transient vibration state in which the rotor rotates more than the expected amount and then returns, making smooth positioning of the rotor impossible. Looking at this from the side controlled by the servo motor, impact force is applied when starting and stopping, so conventional servo motors are not used as servo motors for moving soft or fragile objects such as tofu. is inappropriate.

The object of the present invention has been made in view of the various circumstances mentioned above, and it is an object of the present invention to improve the reliability of detecting the torque generated by the motor by the reaction of the stator to the rotational force of the motor by providing a strain sensor on the stator side of the motor. It is an object of the present invention to provide a motor equipped with a torque detection means having high torque and a fast detection speed. Specifically, the stator of the motor is connected to a frame that is configured to have a shape that easily generates strain and surrounds the stator, and strain sensors are arranged in the shape that easily generates strain. The purpose of the present invention is to detect a motor equipped with a highly accurate and high-speed torque detection means that detects the reaction force exerted on the stator against the rotational force of the motor as distortion of the frame.

Embodiments of the present invention will be described in detail below with reference to FIGS. 3 to 6. Incidentally, the same parts as those in the conventional example are given the same reference numerals and the explanation thereof will be omitted.

FIG. 3 is a diagram showing an embodiment of a motor equipped with a torque detection means of the present invention. Assume that the coordinate axes, that is, x, y, and z axes are taken as shown in FIG. 3, and that the center of the rotation axis 12 of the motor coincides with the z-axis. Although the strain sensor may be a strain gauge shown in FIG. 1(b), a piezoelectric element configured in a bridge, or the like, the description will be made by taking the strain gauge 1 as an example, as in the conventional example. A rotor 14 of the motor is connected at both ends to a rotating shaft 12 supported by ball bearings 13, and a stator 16 of the motor is fixed to a frame 17 surrounding the stator 16. Frame 17 and fixed part 11
The frame 17 is either integrally constructed or fixed to the fixed part 11, and the fixed part 11 is attached to the base with bolts or the like. In particular, the frame 17 has a thin portion that is likely to generate strain and improve strain detection sensitivity.The shape and material of this portion that is likely to generate strain can be selected as appropriate. .

The four strain sensors IA to ID are arranged in a bridge shape as shown in Figure 5 so that they generate detection outputs only for rotational forces around two axes and do not generate outputs for any other forces. Connected. Therefore, strain caused by forces other than rotational force around the rotating shaft becomes in phase and does not appear in the output. In the embodiment, the four strain sensors IA to ID are bonded to the thin (shaped) portion 18 for detecting strain at 1702 locations on the frame in FIG. Since each sensor has well-matched characteristics in terms of temperature fluctuations, humidity m' fluctuations, aging changes, etc., by connecting as shown in Figure 5, stable motor torque detection that is unaffected by ambient conditions is possible.Figure 3 In the embodiment, four strain sensors IA to I
Although D is used, the same function as in this embodiment may be obtained even if the shape of the frame 17 is changed and an even number of strain sensors other than four are used.

The operation of the embodiment will be briefly explained. Drive load -V
When the motor is energized and torque is applied to rotate the rotary shaft 12 in the direction of arrow B around the Z-axis, the frame 17 is rotated against the stator 16 because the fixed part 11 is fixed.
The force that tries to rotate this frame 17 via
The load is received in the direction of arrow C as a reaction to the rotational force that drives the load. Due to this reaction force, strain due to torsional stress concentrates on the portions of the frame 17 to which the strain gauges IA to 1D are attached, and the resistance values of the strain gauges change.

By detecting this change in resistance value, the torque generated by the motor can be detected. What should be noted here is that action and reaction always have a one-to-one correspondence in magnitude and direction, and there is no time delay.Therefore, the present invention directly and continuously applies the torque generated by the motor. can be detected in real time, and torque control can be performed based on the generated torque.
can become. This is an epoch-making method of detecting the torque generated by the rotor that cannot be realized using the conventional detection method of installing a strain sensor on the rotor side or the conventional method of detecting the generated torque as the product of current and magnetic flux. .

FIG. 4 is a diagram illustrating the force F and rotational force T applied to the sensor mounting portion 18 of the frame 17 in FIG. 3. The sensor mounting part 18 is attached to the frame as a reaction to the torque generation of the motor.
The explanation will be broken down into an X axis perpendicular to , a Z axis which is the center of the rotation axis 12 of the motor, and a Y axis perpendicular to these X and Z axes. It is assumed that the four strain gauges IA to ID are arranged on the virtual strain sensor mounting portions 18A and 18B with their detection directions aligned in the Z-axis direction.

First, as shown in FIG. 4(b), when the frame 17 receives a force Fx in the X-axis direction, the strain gauges IA and I
Since B, IC and ID each show exactly the same change in resistance value, no torque is detected according to the connections shown in FIG. Even when the frame 17 receives a force Fy in the Y-axis direction shown in FIG. 4 (C1), no torque is detected because the strain gauges IA and IC and IB and ID each show the same change in resistance value.

Next, the strain gauges IA to ID show the same change in resistance value with respect to the force Fz in the Z-axis direction shown in FIG. 4(C). 4(
a) In response to a rotational force Tz centered on the Z-axis in the figure, strain gauges IB and IC and IA and ID generate positive and negative resistance changes, respectively. That is, one strain gauge increases its resistance value and the other strain gauge decreases its resistance value. Thereby, the torque generated by the motor can be detected from the strain caused by the reaction received by the frame 17 as a potential difference across the bridge of the strain gauge.

FIG. 5 shows a torque detection electric circuit incorporating the strain sensor shown in FIG. Strain gauges IA to ID are connected in such a way that, for example, strain gauges IA and ID receive a compressive force and reduce the resistance value, while strain gauges IB and IC receive a tensile force. Since the resistors are connected to increase their resistance values, the voltage applied to them changes. A voltage change due to a change in resistance of the strain gauges IA to ID is amplified by an amplifier 20 and then outputted as a control input for a high precision servo motor or the like.

As described above, according to the present invention, it is possible to control the motor torque with high precision and high speed response using a simple feedback loop as shown in FIG. Furthermore, by incorporating a microprocessor in which the necessary generation torque case of the control servo motor is stored in advance in a feedback loose manner, the present invention can be applied to fields that require acceleration control in addition to position and speed control. For example, it can be applied to low-vibration robot actuators, video rotation unevenness control, high-precision servo motors, beam scanners for laser printers, etc. Furthermore, in the field of robots, it can be applied to robots that handle living things, precision machinery assembly robots, and medical equipment control. There are mechanisms etc.

[Brief explanation of the drawing]

1 and 2 are diagrams showing an example of a conventional motor torque detection method, respectively. FIG. 3 is a diagram showing an example of a motor equipped with the torque detection means of the present invention. FIG. 4 is a diagram showing a strain sensor. Figure 5 is an electric circuit for torque detection incorporating the strain sensor shown in Figure 3;
The figure shows a field pack loop of the electrical circuit of FIG. 5. 1, IA-II...Strain sensor, 2... Rotating shaft 3...
Field magnet, 4.Armature winding, 5.Hall resistor, 6.
Fist detection resistor, 7.8.20.21 Amplifier, 9. Arithmetic circuit, 10.19-. DC power supply, 11. Fixed part,
12...Rotating shaft, 13...Ball bearing, 14-...
Rotor, 15... Stator coil, 16... Stator, 17
...Frame, 18...Sensor mounting surface, 21...Motor patent applicant Shinano Electric Co., Ltd. a Agent Patent attorney Miyao Ichinose 13- Procedural amendment (voluntary) 57. ! '), 17 Showa Date, Month, Day Kazuo Wakasugi, Commissioner of the Japan Patent Office 2 Name of the invention Motor with torque detection means 3 Relationship to the case of the person making the amendment Patent applicant Address 1-chome Sengoku, Bunkyo-ku, Tokyo 23-11 Name: Shinano Electric Co., Ltd. 4, Agent address: Matsuoka Kudan Building, 2-2-8 Kudanminami, Chiyoda-ku, Tokyo Telephone: 2.63-9524 Name (76]4)
Patent Attorney Ichinose Miyao 5, Cleaning the drawing as shown in the attached drawing 6 attached to the application subject to amendment, the details of the amendment

Claims (1)

[Claims] (1) A strain sensor is provided on the stator side of the motor,
A motor equipped with a torque detecting means, wherein the strain sensor detects the strain received by the stator as a reaction to the torque generated by the motor, thereby detecting the torque generated by the motor. (2. In the motor according to claim 1,
The stator of the motor is fixed to the base via a member that is likely to generate strain, and a strain sensor is disposed on the member that is likely to generate strain, and the strain is detected to detect the torque generated by the motor. Motor equipped with a torque detection means characterized by (3) The motor according to claim 1,
Torque detection characterized in that several members that are likely to generate strain are connected and arranged on the members such that several strain sensors are connected so as to cancel each other except for the torque generated by the motor. Motor with means. (4) In the motor according to claim 2,
A motor equipped with a torque detection means, wherein the member that is likely to generate strain has a rod-like or plate-like shape.