JPH0197826A - Detecting device of torque - Google Patents

Abstract

PURPOSE:To detect a torque from the time of stop to the time of high speed, by obtaining sine wave outputs from magnetoresistance effect elements disposed opposite to magnetic rotary encoders which are provided on the drive side and the load side of a rotating shaft, and by detecting an angular difference between these outputs. CONSTITUTION:Drums 2 and 2' having N and S poles 3 and 3' recorded thereon are provided on a rotating shaft 1 at a prescribed gap between them, and sensors 4 and 4' consisting of magnetoresistance effect (MR) elements R1 and R2 are disposed opposite to these drums at a small gap therefrom. The MR elements R1 and R2 are disposed in separation by lambda/2 from each other when an interval between the N and S poles is lambda. The resistances of the elements R1 and R2 are varied due to changes in intensities of the N and S poles. The shaft 1 is distorted when a torque is applied thereto, and causes a phase difference proportional to the torque between outputs due to variations in the resistances of the sensors 4 and 4'. By taking out only a fundamental wave by offsetting a third harmonic component by means of bridge connection, on the occasion, the torque is detected as a phase difference between outputs of sine waves. By this method, the torque is detected highly precisely from the time of stop to the time of high speed.

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]

Conventional devices include, for example, Mitsubishi Electric Technical Report Vofl, 58°N
As shown in Figure 1 of α7 1984, the torsion of the shaft was detected as a phase difference between gears A and B attached to the shaft using an electromagnetic pickup. However, the magnitude of the output signal of an electromagnetic pickup depends on the rotation speed of the gear,
Since the output signal becomes smaller at low speeds, it is used only for torque detection during high-speed rotation, and no consideration has been given to torque detection at very low speeds or when stopped.

[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 vehicle is stopped.

There was a problem in that it was not possible to measure the torque when the motor etc. was stopped.

An object of the present invention is to provide a high-precision, high-resolution torque detection device that utilizes magnetic rotary encoder technology using a magnetoresistive element and can be used from a standstill 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, by making the output waveform a sine wave, even torque at a stop can be detected by measuring the angle from the magnitude of each sine wave.

〔Example〕

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

FIG. 1 is a diagram showing a shaft bearing configuration of a torque detection device according to an embodiment of the present invention. FIG. 2 is a diagram showing the structure of a bearing showing the relationship between one of the magnetic drums and the magnetic sensor in FIG. 1'. Figure 3 is a partially expanded view of (A), (B), and Figure 2.
FIGS. 4 and 5 are explanatory diagrams of the 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 have been recorded are fixedly attached to the shaft 1 with only a spacing between them. 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, the rotating drum 2 and the magnetic sensor 4 are taken out to explain the operation. As mentioned above, the rotating drum 2
N and S magnetic signals are recorded over the entire circumference of the magnetic body 3, and a magnetic sensor 4 composed of MR elements R1 and R2 is placed facing each other with a gap a interposed therebetween.

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 FIG. 3, MR element R
t*Rz is arranged at a distance of λ/2 from the recording wavelength (interval 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 element R1
, Rz have a characteristic that the resistance value decreases when either the N pole or S pole magnetic flux change signal of the magnetic signal is applied, so when the magnetic body 3 moves as shown by the arrow, the MR element R1
, Rx corresponds to the recording wavelength λ, and each (R1, R2) has 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 FIG. 5(A) and a voltage V is applied to both ends, the voltage obtained from the output terminal FAI is as shown in FIG. 6(A). The output E^1 corresponding to the magnetic signal recorded on the magnetic material 3 is obtained. On the other hand, similarly, the first
A waveform E^2 shown in FIG. 6(B) is obtained from the rotating drum 2' and the magnetic sensor 4' shown in the figure by a similar effect.

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

Here, θ: Torsion angle (rad), G: Shaft shear coefficient (kg/cd), L distance between Ni drums i!
! 1 (CIll), D: shaft diameter (1). The shear coefficient G is determined by the material of the shaft, and once the distance between the drums and the shaft diameter are determined, the torque T relative to the torsion angle θ can be determined. Therefore, by detecting the torsion angle θ of the shaft 1, torque can be measured. 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 of the shaft 1 is 0 by measuring the phase difference θ2-θl 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'. Figure 7 (A)
As shown in , when the load torque is small, the amount of twist of the shaft 1 is also small, so the phase difference O1 at the zero cross between the output E^1 and EAII 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 θ1 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 θ was actually measured.

On the other hand, as mentioned above, the resistance value of the MR element wire changes depending on the magnitude of the magnetic field, so even if axis 1 is stopped,
Since the MS element is always applied with a magnetic field of a predetermined strength due to the north and south poles from the magnetic bodies 3, 3' of the rotating drums 2, 2', it is possible to detect the torque when the shaft 1 is stopped. 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 that drive machine tools and the like are rapidly changing from DC motors to AC motors with the development of inverters and the like. On the other hand, detection of the shaft torque of the electric motor that drives machine tools, etc. is important for determining the processing accuracy of the workpiece.
It is indispensable for feedback for control of machining speed, etc. 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 difficult. Therefore, a torque detection device such as the one according to 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 MR element, the output of the magnetic sensor can be made into a two-phase output by simply changing the specifications of the MRR element pattern, since it is made by vapor-depositing permalloy or the like on a glass substrate, as mentioned above. 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, two-phase outputs EAL, EBI, and EAz that are approximately 90 degrees out of phase from the magnetic sensors 2 and 2'
and Eat, and each output is a comparator 51.52.5
2' and 53' provide a square wave At.

Bt, Az and B2 are obtained. This two-phase square wave A h
.

B1 is used to divide the output E^1 of the magnetic sensor 4 into four modes as shown in FIG. , B
The relationship between t is HA and LO, and in the range of 90° to 180°, Hl and Hl. 'Similarly, in the range of 180' to 270@, LQ and Hz, and in the range of 270' to 360@, L
o, Lo. Furthermore, the square wave Az+ 13z is used to divide the output E^2 of the magnetic sensor 4' into four modes. In addition, the output FAI of the magnetic sensors 4, 4',
E^2 is for the above person.

As shown in (B) of FIG. 10(A), each is compared with the carrier wave PM of the triangular wave to obtain the sine wave outputs A H1 and AM2.
For example, the output AAI of the magnetic sensors 4, 4'.

Since AAz is a sine wave as shown in (a) of Fig. 10(A), the output is E^1. The angle θ can be determined using an analog value of EAt. Furthermore, the output E^1. There are points where the analog value of EAz becomes the same voltage in one cycle, but the mode discriminator 8 or 8' determines whether it is 0 to 90 degrees or 90 to 1 degree.
It is possible to judge 80 degrees, 180 to 270 degrees, and 270 to 360 degrees. Furthermore, position detection units 9 and 9' provide position detection 12, 12' and speed detection 13 in addition to torque detection 14.
．． 13' information can be obtained. Regarding the position and speed detection, in order to accurately detect the position and speed of the load 7, the rotary drum 2' and the magnetic sensor 4' on the load side are used.
By using this information, detection accuracy can be improved. 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 rotating drums 2, 2' are shown in (a) of Fig. 10 (a).
Considering the case where the carrier wave PM stops at a point, the time tax until the carrier wave PM reaches the point (a) of the output E^1 of the magnetic sensor 4 is
A pulse AMl 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 EA2. has a waveform as shown by the broken line in (a) of FIG. 10(A), and a pulse Axz having a width of time tlIz is obtained. These pulses AMI and AM2 are proportional to the analog amounts of sensor output E^1 and EAt, so
The values of time iml and tlI2 are input to the torque measuring section 1 and are determined as the angular difference between the drums 2 and 2', making it possible to detect the torque.

Next, FIG. 11 shows an example in which a microcomputer is used to obtain the angle of each rotating drum from the sine wave output and calculate the torque based on the angle difference.

This will be explained with reference to FIG. Magnetic sensor 4 shown in Figure 9
2-phase output E al, E Al and magnetic sensor 4'
The two-phase outputs of EAt and EBB are input into FIG. 11, respectively. This output is amplified by amplifiers A M i to A M 4 to form Azsinθ1t Btcosθ*Az
sin θ.

g z cos θ. These are input to the microcomputer MC through analog-to-digital (A/D) converters AD1 to AD4, respectively. The microcomputer MC performs arithmetic processing according to the flowchart shown in FIG. 12, and outputs an output proportional to the torque to the terminal 14.

The flowchart in Figure 12 begins with the magnetic sensor 4.4'
Digital value A after amplifying and A/D converting the output of
t, Bt, and Aay Hz are read, and then the angle θl of the rotating drum 2 is obtained by calculating the following equation from A1 and 81.

Here, the mode is determined by determining the sign of A1 and B1, and B
Determine the value of 1.

Similarly, the angle θ2 of the rotating drum 2' is calculated using the following equation based on the inputs Ax and Bz.

Next, the angular difference between the rotating drums 2 and 2', that is, the torsion angle θ0, is calculated from the difference between the angles θ1 and 02, and the torque T is calculated using the following equation modified from the equation (1).

Next, torque T is output and the state returns to the beginning. Here (2
) The operation of 01 in equation (5) is A1 or 0 x=
sin-”Ax=cos-IB t
-(5) Calculations can be made using only B1. However, due to changes in the small gap (spacing) between the rotating drum 2 or 2' and the magnetic sensor 4 or 4', the magnetic sensor 4,
If the output of 4' changes, the output is A 1 .

Since B2 changes at the same time, A1 and Bi
The accuracy can be increased by dividing.

FIG. 13 shows a flowchart of rotational position and rotational speed. First, the digital input A 1 of a sine wave.

Take in B1, read the time t of the timer for speed measurement, store it for 1 o'clock, then start the timer both times.
Obtain the fine angle θl within the cycle.

Next, read the previous fine angle on-1 from the memory, calculate the difference from the current angle θ1, and calculate the angle change (θ.-1-
Calculate the speed V by calculating θl) and dividing this by the time difference t between the previous time and this time when the vehicle was stored for 1 hour.

Output to output terminal 13. Further, the position is calculated by adding the accumulated angle θΣ-1 up to the previous time to the difference between the current minute angle θ1 and the previous minute angle θ1-1 to calculate the current angle θΣ, and outputs the result to the output terminal 12. Next, the current fine position θ1 is stored in the memory θ□−1, the current angle θΣ is stored in the previous degree θΣ−1 memory, and the process returns to the original state. The above is an example in which the minute angle θ1 and the previous minute angle 0n-1 are within one cycle, but when they change for more than one cycle, calculation is performed using angle accumulation.

The above has described the case where a sinusoidal output can be obtained from the magnetic sensors 4, 4', but a method for actually obtaining a sinusoidal output will be explained with reference to FIG. The magnetoresistive element of the magnetic sensor 4 (
MR element) Ran and Raw and Rbi and Rbz are arranged at a distance of λ/2 from the recording wave λ, and R&1 and Rb 1 and Rat and Rbz are arranged at a distance of λ/6XIIL, respectively. With this arrangement, each MR element is connected as shown in the figure, so when the rotating drum 2 rotates, each MR element Rat
The output ea from RaZ and RaZ is as shown by the solid line ea shown in the figure. This waveform distortion occurs because the resistance change of the MR element is saturated with respect to the magnetic field. Therefore, the main component of this distorted wave is the third harmonic, and it can be divided into the fundamental wave eat and the third harmonic eJ18 as shown by the broken line in the figure. Also, MR element Rbx
Similarly, the output 8 from Rbx and Rbx has a fundamental wave 8bl and a third harmonic eb8. The bridge output shown in the connection diagram (
tm+e-), that is, considering E^1, the third harmonic ea
A and ebs are struck in opposite phases and only the fundamental wave is obtained.

In this embodiment, the rotating drums 2, 2' and the magnetic sensors 4, 4
Although the structure has been described in which the rotary drums 2, 2' and the magnetic sensors 4, 4' are externally attached to the shaft 1 of the motor 6, the rotating drums 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 also have a structure in which magnetic bodies 3, 3' are attached to the flat surface (one or both sides) of a disk for detection, as shown in FIG. 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, a sine wave output can be obtained by configuring the torque detection device with 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 with precision. 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 the drawing]

Fig. 1 is a diagram of the shaft bearing configuration 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 exploded view of the magnetic body. , FIG. 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 block diagram of an embodiment of the method. FIG. 12 is a flowchart of torque calculation in another embodiment. FIG. 13 is a flowchart of speed detection and position detection in another embodiment. FIG. 14 shows an embodiment of the means for obtaining a sine wave output according to the present invention. FIG. 15 is a diagram of the shaft bearing configuration of another embodiment. l...shaft, 2,2'...rotating drum, 3,3'...
・Magnetic material, 4, 4'... Magnetic sensor, 6... Motor, 7... Load, 8, 8'... Mode discriminator, 9, 9
'...Position detection section, 10.10'...Selector switch, 11...Torque measurement section, 12.12'...Position output section, 13゜13'...Speed output section, 14 ...Torque output section, 51°52.53, 51', 52',
53'... Comparator. R...MS element, EAR, EAt...magnetic sensor output, A1. Bl...2-phase output for mode discrimination, AMII
AM2...Pulse output when stopped. \QNo.1 1st $40 Z I AZ thing'7I2Il (A') Figure 11 Figure 170 13th Fixed $140

Claims (1)

[Claims] 1. A plurality of angle detectors installed at predetermined intervals on a rotating shaft connecting a drive source and a load, and the relative angles of the angles detected by the plurality of angle detectors. A device for detecting load torque based on a difference includes a plurality of rotating drums or rotating disks that are attached at a predetermined distance to the drive side and load side of the rotating shaft and have a plurality of magnetic poles on their surfaces that generate magnetic signals. , a magnetic sensor provided with a magnetoresistive element disposed opposite to the surface of each of these rotating drums or rotating disks, and whose internal resistance changes in response to the magnetic field of the magnetic pole; Alternatively, a torque detection device is characterized in that the load torque is detected by calculating the angular difference between the two sets of sinusoidal outputs obtained from two sets of substantially sinusoidal output magnetic sensors corresponding to the angle of the rotating disk. A torque device that is characterized by 2. The torque detection device according to claim 1, wherein each set of sine wave outputs is a multiphase output having a different phase. 3. The torque detection device according to claim 2, characterized in that the angle is calculated using the multiphase output. 4. The torque detection device according to claim 1, wherein the angular difference between the plurality of rotating drums or rotating disks when maximum torque is applied is within one cycle of the sine wave output. 5. The torque detection device according to claim 1, characterized in that angle calculation is performed by dividing one cycle of the sine wave output into a plurality of modes. 6. A torque detection device according to claim 1, characterized in that the output signal of the magnetic sensor is not only used to detect torque, but also calculates and outputs the position or speed of a rotating shaft.