JPS624651B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a coil spring type rotating body torque measuring device that corrects errors in detected torque values depending on rotational speed and measures accurate torque over the entire rotational speed. The present invention relates to a torque measuring device capable of measuring torque.

An induction motor with a built-in torque meter has been developed as a drive machine for monitoring the machining of machine tools, etc., but its method was originally published in Japanese Patent Application No. 53-65223.
The system using a torsion bar as disclosed in No. 1996 has been replaced by a coil spring system (disclosed in Japanese Patent Application No. 145364-1982) which is advantageous in terms of appearance. In the latter coil spring method, the centrifugal force applied to the coil spring changes depending on the rotation speed, which causes torsional displacement of the coil spring and changes in the zero point of torque output, so high-precision torque detection is performed at variable speed. Some measures are required for this.

The present invention aims to solve the conventional problems with such a coil spring type torque measuring device, correct the detected torque value according to the rotation speed, and perform highly accurate torque measurement. .

FIGS. 1, 2, 3, and 4 are cross-sectional views of a pulley device and an induction motor each having a coil spring type torque measuring device, and each coil spring.

First, to explain the pulley device shown in FIGS. 1 and 2, the drive side or load side shaft 1
A boss 2 is fixed to the boss 2 by a key and a keyway, a fixed ring 3a of a coil spring 3 as shown in FIG. Possibly installed. A belt mounting ring 5 in which a pulley belt groove is formed is fixed to the movable ring 3b, and the other end of the ring 5 is connected to a fixed ring 3 of the coil spring 3.
It is rotatably supported on the outer periphery of a by a needle bearing 6. The fixed ring 3a has a first salient pole 11a formed on the circumference at an index angle that equally divides the circumference.
A detection plate 11 is fixed to the belt mounting ring 5, and salient poles 12a are also mounted on the belt mounting ring 5 at index angles that equally divide the circumference.
A second detection plate 12 having a periphery formed thereon is fixed. The number of salient poles on both detection plates is set to be equal. First and second detection elements 14 and 15 are attached to the detection element mounting frame 13 in proximity to the respective salient poles of the first and second detection plates 11 and 12, and the mounting frame 13 Board 11,
In order to maintain a constant gap between the salient poles 12 and the detection elements 14 and 15, the ring 5 is supported by a ball bearing 16 on the outer periphery of the end of the belt device ring 5.

7 in the figure is overtorque and coil spring 3
This is a protective stopper provided on the boss 2 to prevent permanent deformation.

The detection elements 14 and 15 are configured to generate one pulse each time the salient poles 11a and 12a pass, and as is already known, they may be of the type that detects changes in magnetic flux or of the electromagnetic induction type. , an electrostatic induction type, a photoelectric type, etc. can be used.

3 and 4 show an example of an induction motor in which a coil spring type torque detection device is built in. The main shaft 21 is supported by bearings 23, 23 in a motor casing 22, and A fixed ring 3a' of the coil spring 3' is fitted onto the main shaft 21. The main shaft 21 also includes a rotor shaft 2.
4 is rotatably supported by needle bearings 25, 25, and a movable ring 3b' of the coil spring 3' is attached to one end of the rotor shaft 24. The fixed ring 3a' is provided with a first detection plate 11 similar to the above-mentioned embodiment, and the movable ring 3a' is
A second detection plate 12 is attached to b', and a salient pole 11 of each detection plate 11, 12 is attached to a detection element mounting frame 13 fixed to the motor casing 22.
Detection elements 14 and 15 are provided adjacent to a and 12a. In the figure, 26 is a rotor attached to the rotor shaft 24, and 27 is a stator fixed to the motor casing.

Coil spring 3 or 3' in such a configuration
The error due to the rotation speed will be explained below.

The centrifugal force F that acts on the unit length of the coil spring wire when the coil spring rotates around its central axis.
is, F=ρSγω ² ... (however; density of coil wire [Kg/m ³ ], S;
It is expressed as follows: cross-sectional area of the coil wire [m ² ], γ: radius of the coil [m], ω: rotational speed [γad/sec]. This centrifugal force causes the radius of the coil to
As the value of γ increases, the energy per unit length of the wire received by the coil spring is as follows: U=1/2Sγω ² Δγ . Now, as shown in Fig. 6, the spring wire with a length of 2πγ increases from the radius γ to the radius (γ + △γ), so the angle of the spring wire viewed from the central axis changes from 2π to (2π−△ θ), the length of the spring wire is constant, so 2πγ=(2π
-△θ)(γ+△γ) holds true. From this, △γ≒γ△θ/2π Also, if the twist angle per unit length of the wire is △φ, then △φ=△θ/2πγ, so from these two relational expressions, △γ=γ ² △φ... holds true, and the following equation is derived from this equation and the above equation.

U=1/2ρSγ ³ ω ² △φ ... On the other hand, when the wire is bent by △φ, the energy U' stored in the wire is expressed by the following formula.

U'=1/2EI△ ^φ2 ... However, E is the longitudinal elastic modulus of the coil wire, and I is the second moment of area of the coil wire.

Since the above two energies U and U' are equal, △φ=ρSγ ³ ω ² /EI... holds true. From this, the torsion angle Δθ per revolution of the coil spring is as follows: Δθ=2πγ ⁴ ρS/EIω ² . This Δθ is proportional to the correction torque ΔT. For example, if the coil spring wire has a rectangular cross section, and the radial side is h and the axial side is b, then Δθ=24πγ ⁴ ρ/Eh ² ω ² .

When trying to measure torque when the rotational speed changes using a coil spring in this way, the coil itself is twisted by centrifugal force, causing a zero point fluctuation error in the torque meter.

Estimating the size of △θ for one example, γ = 35 × 10 ^-3 m, h = 11 × 10 ^-3 m, ρ = 7.8 × 10 ³
Kg/m ³ , E=200×10 ⁹ N/m ² , ω=2π×30γ
When ad/sec (=1800rpm), △θ=1.3×
10 ^-3 γad (=0.074 degree).

Changes in the radial direction of the coil spring at both ends are restrained by the fixed ring and the movable ring, so this angular change is small, but if the torsion of the spring due to the torque to be measured is about 1 degree per revolution, the above example This will result in a speed error of several percent. In the present invention,
By correcting this speed error, highly accurate torque measurement is performed using the coil spring method.

FIG. 5 is a block diagram showing the configuration of a torque measuring device that performs speed correction according to the present invention. In this figure, pulses or sine waves with a frequency corresponding to the rotational speed of the first detection plate 11 and the second detection plate 12 are output from the first detection element 14 and the second detection element 15, and are shaped into waveforms. After being shaped into a rectangular wave by the circuits 31 and 32, the time difference detection circuit 33
It is configured to output an output according to the phase difference between the two detected waveforms. That is, when the load torque becomes large, the second detection plate 1 on the load side becomes more sensitive than the first detection plate 11 on the drive side due to the twist of the coil spring.
On the other hand, when the rotation phase of the second detection plate 12 lags behind, and conversely during deceleration, the rotation phase of the second detection plate 12 advances due to the moment of inertia on the load side, and an electric signal corresponding to the phase time difference is sent from this time difference detection circuit 33. It is output together with the lead/lag sign. Then, the output is amplified by the next amplifier 34, and the torque output before correction is obtained by selecting the degree of amplification to a required value. This torque output is corrected by the following configuration. That is,
A rectangular wave with a frequency proportional to the rotation speed obtained by the waveform shaping circuit 32 (or 31 may be used),
It is applied to a monostable multivibrator 35, and its output pulse is inputted to a smoothing circuit 36 to obtain a DC voltage proportional to the rotation speed. This output is input to the next correction value setting circuit 37 to create the correction value of the above formula. The correction amount is an amount proportional to the square of the speed, but may be a first-order approximation value of the speed depending on the width of speed change. This correction value is applied to the subtraction circuit 38 together with the output of the amplifier 34.
The true value of torque is output from this. 39 in the figure is a forward/reverse changeover switch, which makes a correction by subtracting when the winding direction of the coil spring matches the rotation direction when viewed from the drive side, and by adding when the coil spring rotates in the opposite direction. It is something that can be switched. This changeover switch 39 can also be operated automatically by detecting the rotational direction of the rotating body.

As described above, the present invention provides an apparatus in which the driving side and the driven side of a rotating body are connected via a coil spring, and the transmitted torque is detected based on the rotational phase difference between the driving side and the driven side and the constant of the coil spring. ,
means for detecting the rotational speed of the rotating body; means for calculating a correction torque determined from the mechanical constant and rotational speed of the coil spring based on the detected rotational speed; Since the configuration includes means for correcting the detected transmission torque value based on the rotational speed, the error in the detected torque caused by the change in the zero point of the coil spring due to the rotational speed is eliminated, and accurate torque measurement is achieved. This has the effect that it is possible to obtain the same accuracy as the torsion bar method, and to take advantage of the advantages of the coil spring method in terms of external shape.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the main parts of a pulley device equipped with a coil spring type torque measuring device, Figure 2 is a side view showing an example of the coil spring used therein, and Figure 3 is a pulley device equipped with a coil spring type torque measuring device. FIG. 4 is a partially cutaway side view showing an embodiment of the coil spring used in the induction motor; FIG. 5 is a block diagram showing the configuration of the torque measuring device according to the present invention; FIG. It is an explanatory view explaining twist of a coil spring and a change in diameter.

Claims (1)

[Scope of Claims] 1. A device that connects a driving side and a driven side of a rotating body via a coil spring and detects transmitted torque based on a rotational phase difference between the driving side and the driven side and a constant of the coil spring, means for detecting the rotational speed of the rotating body; means for calculating a correction torque determined from the mechanical constant and rotational speed of the coil spring based on the detected rotational speed; A torque measuring device comprising: means for correcting the detected transmission torque value based on the detected transmission torque value. 2. The torque measuring device according to claim 1, wherein the amount of correction of the transmitted torque is an amount proportional to the square of the rotational speed. 3. The torque measuring device according to claim 1, wherein the transmission torque correction amount is a first-order approximation value of the rotation speed in a certain rotation speed range.