JPS62239031A - Torque detecting device - Google Patents

Abstract

PURPOSE:To improve reliability by providing rotary drums having magnetic bodies where magnetic signals are recorded and a magnetoresistance effect element. CONSTITUTION:The rotary drums 2 and 2' having the magnetic bodies 3 and 3' where magnetic signals are recorded are fixed on a shaft 1 at an interval L and the magnetoresistance effect element R is arranged opposite the drums 2 and 2' at small intervals. For example, a motor is fitted on, for example, the driving side of the shaft 1 and a load is fitted on the load side, so that the shaft 1 is twisted by an angle theta=32/piGXL/D<4>XT in proportion to load torque. Here, theta is the angle of the twisting, G is the shearing coefficient (kg/cm<2>), L is the distance (cm) between the drums 2 and 2', and D is the diameter (cm) of the shaft 1. Further, the coefficient G is determined by the material of the shaft 1 and when the distance L and shaft diameter D are determined, the torque T to the angle theta of the twisting is found. This angle theta is obtained by measuring the zero-cross phase difference theta2-theta1 between outputs EA1 and EA2 obtained by the drum 2 and sensor 4, and drum 2' and sensor 4'. Thus, the torque is detected with high reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a torque detection device, and particularly to a torque detection device suitable for detecting relative positional displacement caused by twisting of a shaft.

[Conventional technology]

The conventional device is, for example, Wangling Electric Technical Report Vol. 1.58°Nα.
7 in 1984, the torsion of the shaft was detected by an electromagnetic pickup as a phase difference between gears A and B attached to the shaft. However, the magnitude of the output signal of an electromagnetic pickup depends on the rotation speed of the gear, and the output signal becomes smaller at low speeds, so it is only used to detect torque during high-speed rotation, and it is used only for detecting torque at very low speeds or when stopped. No consideration was given to detection.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not take into consideration torque detection at very low speeds or when the motor is stopped, and there is a problem in that it is not possible to measure torque when the motor or the like is stopped.

An object of the present invention is to provide a torque detection device that utilizes magnetic rotary encoder technology using a magnetoresistive element and can be used from a stop to a high speed range.

[Means for solving problems]

The above object is achieved by detecting the torsion of the shaft by using a magnetic sensor consisting of a magnetic drum having a signal track on the surface of which a magnetic signal is recorded, and a magnetoresistive element placed opposite the magnetic drum.

[Effect]

A magnetoresistive element is made by depositing permalloy or the like on a glass substrate, and its resistance value changes depending on the strength of the magnetic field, regardless of polarity. Therefore, N all around.

When the magnetoresistive element is placed opposite the magnetic drum on which the S magnetic signal is recorded, a magnetic field corresponding to the N and S signals of the magnetic drum is applied to the magnetoresistive element, and the magnetic drum is moved regardless of the speed. The relative position of can be extracted as a resistance change of the magnetoresistive element. Thereby, even torque at a stop can be detected by measuring the magnitude of each resistance change.

〔Example〕

An embodiment of the torque detection device according to the present invention will be described.

FIG. 1 is a schematic configuration diagram of a torque detection device that is an embodiment of the present invention. FIG. 2 is a schematic configuration diagram showing the relationship between one of the magnetic drums and the magnetic sensor in FIG. 1. Third
The figures are partially expanded views of (A), (R), and Figure 2, and Figure 4.
FIG. 5 is an explanatory diagram of its operating waveforms.

In FIG. 1, 1 is a rotating shaft, and 2°2' is a rotating drum. Rotary drums 2, 2' having magnetic bodies 3, 3' on which magnetic signals are recorded are fixed to the shaft 1 at a distance. Reference numeral 4 denotes a magnetic sensor composed of magnetoresistive elements (hereinafter referred to as MR elements) R, which are arranged opposite to the rotating drums 2 and 2' with a small gap therebetween.

Here, the operation of the rotating drums 2, 2' and the magnetic sensors 4, 4' will be explained using FIG. 2.

In FIG. 2, operation explanation - L rotating drum 2 and magnetic sensor 4
This is what was extracted. As mentioned above, N and S magnetic signals are recorded on the magnetic body 3 of the rotating drum 2 over the entire circumference, and a magnetic sensor 4 composed of MR elements Rz and Rx is arranged facing each other with a gap Q interposed therebetween. ing.

3(A) and 3(B) are enlarged development views showing the arrangement relationship between the magnetic body 3 and the magnetic sensor 4 in the rotating drum 2 shown in FIG. 2. FIG. In Figure 3, the MR element'
Rs and Rx are spaced apart from each other by λ/2 with respect to the recording wavelength (the distance between the north pole and the south pole) λ. Figure 4 shows this operating waveform.

In FIG. 4, the magnetic body 3 of the rotary drum 2 moves as indicated by the arrows as the rotary drum 2 rotates. On the other hand, as is well known, the MR elements R, R2 have a characteristic that the resistance value decreases when a magnetic flux change signal of either the N pole or the S pole of the magnetic signal is applied.
moves in the direction of the arrow, the resistance changes of the MR elements R, , R, correspond to the recording wavelength λ, and each (R
1°R2) results in a waveform with a phase shift of λ/2. here,
When the MR elements RL and Rz are connected to three terminals as shown in Figure 5 (A) and a voltage V is applied to both ends, the voltage obtained from the output terminal E^1 is as shown in Figure 6 (A). Output E^1 corresponding to the waveform and magnetic signal recorded on the magnetic material 3
is obtained. On the other hand, similarly, the rotating drum 2' and magnetic sensor 4' shown in FIG.
A waveform EAt shown in Figure (B) is obtained.

Here, in the torque detection device shown in FIG. 1, for example, the shaft 1
When a motor is attached to the drive side and a load is attached to the load side, the shaft 1 twists by an angle O in proportion to the load torque. Expressing this as a formula, it becomes as follows.

πXG D' where θ: torsion angle (rad) + G: shearing coefficient of the "shaft (kg/am"), L: distance between two drums (cm), D: shaft diameter (cm). new coefficient G
is determined by the material of the shaft, and if the distance between the drums (■) and the shaft diameter are determined, the torque T for the torsion angle O can be determined. Therefore, by detecting the torsion angle O of the shaft 1, torque measurement becomes possible. An example of a method for measuring the torsion angle θ of the shaft 1 is shown in FIGS. 7(A) and 7(B). Figure 7 (A
, ), the torsion θ of the shaft 1 is the phase difference 0x-Ox at the zero cross between the output FAI obtained from the rotating drum 2 and the magnetic sensor 4 and the output E^2 obtained from the rotating drum 2' and the magnetic sensor 4'. Measure and do it. In other words, Fig. 7 (A
), when the load torque is small, the amount of twist of the shaft 1 is also small, so the phase difference 0 at the zero cross of the output E^ and EAR becomes small. Conversely, when the load torque is large as shown in FIG. 7(B), the amount of twist of the shaft 1 also increases, so the phase difference θ2 at the zero cross becomes large. Therefore, by measuring this phase difference 01 or θ2, the magnitude of the torque can be detected. FIG. 8 shows one characteristic of the torque detection device according to the present invention, in which the relationship between the torque T and the phase angle O was actually measured.

On the other hand, as mentioned above, the resistance value of the MR element R changes depending on the magnitude of the magnetic field, so even if the axis 1 is stopped,
The MS element has a rotating drum 2.2'.

Since a magnetic field of a predetermined strength due to the north and south poles from the magnetic body 3.3' is always applied, the torque when the shaft 1 is stopped can be detected. FIGS. 9 and 10 show an example of torque detection when the vehicle is stopped.

In FIG. 9, the torque detection device of the present invention is
This is an example of how it is incorporated into. Rotating drum 2.2'
are fixed to the shaft 1 of the motor 6 at arbitrary intervals. The magnetic sensors 4゜4' are connected to the rotating drums 2, 2, respectively.
' are placed opposite each other with a small gap between them. or,
A load such as a machine tool is connected to one end of the shaft on the rotating drum 2.2' side. In general, electric motors for driving machine tools and the like are rapidly changing from DC motors to AC motors due to the development of inverters and the like. On the other hand, detection of shaft torque of an electric motor that drives a machine tool or the like is indispensable for feedback control of processing accuracy, processing speed, etc. of a workpiece. In the case of a DC motor, the shaft torque of an electric motor can be easily detected by detecting the current because the current and torque are proportional, but in the case of an AC motor, the torque is not proportional to the current, so the torque can be easily detected by the current. Torque detection is
Have difficulty. Therefore, a torque detection device such as the present invention is required.

The difference between the torque detection device in Fig. 9 and that in Fig. 1 is as follows.
Since the output of the magnetic sensor is used for position detection and speed detection in addition to torque detection, the outputs of the magnetic sensors 4 and 4' are each made into two-phase outputs. Here, in the case of an MS element, the output of the magnetic sensor can be made into a two-phase output by simply changing the specifications of the MR element pattern, since as mentioned above, permalloy or the like is vapor-deposited on the glass substrate. Magnetic sensor 4.4
′ does not increase, and the size of the sensor itself remains almost the same, so the structure of the entire system becomes simpler.

Now, in Fig. 9, the two-phase outputs E^, EBt and EAx, which are approximately 90 degrees out of phase from the magnetic sensors 2 and 2',
and EBt, and each output is sent to comparators 51, 52, 5
3. Square wave A1 by 51', 52' and 53',
Obtain Bz, Ax and Bz. This two-phase square wave Ax,
B-type is used to divide the output E^1 of the magnetic sensor 4 into four modes as shown in FIG. 10(B). For example, in the range of O'' to 90'' of output E^1, AI,
The relationship of B1 is Hi and Lo, and in the range of 90'' to 180m, it is Hi and Hs.Similarly, in the range of 180' to 27
0″, L(1*Hs* In the range of 270° to 360＠, I(+, Hl. Furthermore, square wave Ag,
Bl is used to divide the output E^2 of the magnetic sensor 4' into four modes. In addition, the outputs FAI and E^2 of the magnetic sensors 4 and 4' are directed to the above-mentioned direction (in FIG. 10(A)).
As shown in (b), each is compared with the triangular carrier wave PM to obtain outputs AM1 and All. For example, magnetic sensors 4, 4'
Assuming that the outputs E^s and E^2 are sine waves as shown in (a) of Fig. 10(A), the output FAI.

The angle θ can be determined using the analog value of Ehx.

Furthermore, the output E^1. There is a point in each analog quantity of E^2 where the voltage becomes the same in one cycle, but the mode discriminator 8
Or 0 to 90 degrees, 90 to 180 degrees, 18 by 8'
It is possible to judge from 0 to 270 degrees and from 270 to 360 degrees. Furthermore, in addition to the torque detection 14, information on position detection 12.12' and speed detection 13.13' can be obtained from the position detection units 9 and 9'. Regarding the position and speed detection, when detecting the position and speed of the load 7 with high accuracy, the detection accuracy can be improved by using information from the rotary drum 2' and the magnetic sensor 4' on the load side. Alternatively, if smooth motor control is desired, it is better to use the position and speed information of the rotating drum 2 and magnetic sensor 4 on the motor side (drive side). Further, depending on the operating state of the load, the load side and the drive side may be switched by switches 10 and 10'.

Here, the one-rotation drums 2, 2' are (,) in Fig. 10 (A).
Considering the case where the carrier wave PM stops at a point, it takes time tmz for the carrier wave PM to reach the point (a) of the output E^ of the magnetic sensor 4.
A pulse A H1 having a width of is obtained.

At this time, if torque T is applied to the shaft 1 of the motor 6 in Fig. 9, the output EAa obtained from the rotating drum 2' and the magnetic sensor 4' will be indicated by the broken line (A) in Fig. 10 (A). The waveform becomes as shown, and the pulse As with a width of time t1
s is obtained. These pulses AM1 and Asz are proportional to the analog amounts of sensor outputs E^1 and EA4, so the time t
ax and t, 2. Input the value into the torque measuring section 1 and
, 2', which enables torque detection.

In this embodiment, rotating drums 2, 2' and magnetic sensors 4, 4 are used.
Although the structure has been described in which the rotary drum 2, 2' and the magnetic sensors 4, 4' are externally attached to the shaft 1 of the motor 6, the rotating drum 2, 2' and the magnetic sensors 4, 4' may be built inside the motor 6.

Furthermore, although the rotary drums 2, 2' are of drum type, they may have a structure in which magnetic bodies 3, 3' are attached to the flat surface (one or both sides) of a disc as shown in FIG. 11 for detection. When the magnetic bodies 3, 3' are mounted on both sides of the disc, it is necessary to arrange the required number of magnetic sensors.

Furthermore, in this embodiment, in addition to torque detection, position detection and speed detection information can be obtained from the same sensor, so that highly reliable and accurate motor control etc. can be achieved.

〔Effect of the invention〕

According to the present invention, the torque detection device is constituted by a rotating drum having a magnetic material on which magnetic signals are recorded and a magnetic sensor having an MR element.

Torque can be detected even when stopped. Furthermore, the magnitude of the output of the magnetic sensor is constant regardless of the rotation speed, and the processing circuit can be configured easily. Further, since it utilizes magnetism, it has excellent resistance to environments such as dust and dew condensation, so a highly reliable torque detection device can be provided.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of a torque detection device according to an embodiment of the present invention, Fig. 2 is a detailed view of the rotating drum and magnetic sensor that constitute the torque detection device, and Fig. 3 (A) is an expanded view of the magnetic material. Figure 3 (B) is a plan view of a magnetic sensor for this magnetic material,
Figure 4 is a diagram showing the magnetic poles recorded on the magnetic material and the output of the sensor, Figure 5 is a three-terminal connection diagram of the MR element, and Figures 6 (A) and 6 (B) are the midpoints of the three terminals. 7(A) and 7(B) are also explanatory diagrams of the method of detecting load torque based on the output waveform obtained from the magnetic sensor, and FIG. 8 is a torque detection device according to the present invention. 9 is a configuration diagram of a torque detection device showing an example of torque detection at a stop, FIG. 10 (A) is a diagram showing the relationship between the sensor output waveform and carrier wave, and FIG. 10 (B ) is an explanatory diagram of the modes from the two magnetic sensor output signals,
FIG. 11 is a schematic configuration diagram of another embodiment. 1...Axis, 2,2'...Rotating drum, 3,3'...
・Magnetic material, 4.4'...Magnetic sensor, 51, 52, 5
3゜51', 52', 53'... Comparator, 6...
- Motor, 7... Load, 8, 8'... Mode discrimination section, 9, 9'... Position detection section, 10.10'... Changeover switch, 11... Torque measurement section, 12.12'・
...Position output section, 13.13'...Speed output section, 14
...Torque output section, R...MS element, E^1. E
^2...Magnetic sensor output, At, Bt-2 phase output for mode discrimination, AMI, AHz = pulse output when stopped.

Claims (1)

[Claims] 1. An angle detector mounted on a shaft rotated by a drive source at predetermined intervals and a relative angular difference between the angles detected by the angle detector to determine the load torque. The detection device includes two rotating drums or rotating disks that are mounted at a predetermined distance on the drive side and load side of the shaft and have a plurality of magnetic poles on their surfaces that generate magnetic signals, and each of these rotating drums. Alternatively, a magnetic sensor provided with a magnetoresistive effect element disposed opposite to the surface of the rotating disk and whose internal resistance changes in response to the magnetism of the magnetic pole, A torque detection device characterized in that a difference in angular position is extracted as a resistance change of a magnetoresistive element. 2. In the device described in claim 1, the amount of twist of the rotating shaft caused by the load on the rotating shaft load side is
A torque detection device characterized in that the torque is detected by measuring the phase difference between the outputs of the magnetic sensor, converting it into an angular difference between both magnetic drums or magnetic disks, and detecting the torque based on this. 3. In the device described in claim 1, the output of the magnetic sensor obtained from at least one magnetic drum or magnetic disk is a multiphase output, and the output is divided into multiple modes, and the output of the magnetic sensor is divided into multiple modes. How to measure phase difference,
A torque detection device characterized by switching according to each of the modes. 4. The torque detection device according to claim 1, characterized in that the phase difference between the outputs of the magnetic sensor is extracted as a special interval. 5. The torque detection device according to claim 1, wherein the output signal of the magnetic sensor on the load side is used not only for torque detection but also for position detection. 6. The torque detection device according to claim 1, wherein the output signal of the drive-side magnetic sensor is used not only for torque detection but also for position detection. 7. The torque detection device according to claim 1, characterized in that position detection of the output signal of the magnetic sensor is switched between the load side and the drive side depending on the operating state. 8. The torque detection device according to claim 1, wherein the sum or difference of the output signals of the magnetic sensors on the load side and the drive side is used as a position detection signal.