JP2856495B2 - External magnetic field compensator for magnetostrictive torque sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an external magnetic field compensating device for a magnetostrictive torque sensor.

2. Description of the Related Art A magnetostrictive torque sensor that forms a magnetically anisotropic part on a power transmission shaft and measures the magnitude of a transmission torque based on a change in the magnetic permeability of the magnetically anisotropic part during torque transmission is known. Is conventionally known. Such a magnetostrictive torque sensor is often provided on a power transmission shaft driven by a motor or braked by an eddy current type dynamometer or an electromagnetic powder brake.

For example, in FIG. 8, reference numeral 1 denotes a DC motor, and its coil 2 is connected to a DC power supply 3. A power transmission shaft 4 from the DC motor 1 is connected to a load 5, and the power transmission shaft 4 is provided with a magnetostrictive torque sensor 6.

FIG. 9 shows an AC motor 7 driven by a three-phase AC.
A torque transmitting sensor 4 is attached to a power transmission shaft 4 from
Is provided as an example. The coil 8 of the motor 7 is connected to a three-phase AC power supply 9.

Problems to be Solved by the Invention By the way, in the case of being driven or braked electromagnetically, the power transmission shaft 4 directly connected to the electromagnetic equipment is not required.
Then, an external magnetic field substantially proportional to the driving current or the braking current is generated. When the magnetostrictive torque sensor 6 is installed in the power transmission unit where such an external magnetic field is generated, the leakage magnetic flux Φ
Therefore, there is a problem that a zero shift of the sensor, a change in sensitivity, and an increase in hysteresis occur.

Accordingly, it is an object of the present invention to solve such a problem and prevent an adverse effect on a magnetostrictive torque sensor due to an external magnetic field.

Means for Solving the Problems To achieve the above object, the present invention provides a magnetostrictive torque sensor for measuring the torque of an electromagnetic device such as a motor or an electromagnetic brake, wherein the torque is proportional to a current flowing through the electromagnetic device, and A compensating coil for flowing a compensating current capable of canceling out a leakage magnetic flux from an electromagnetic device is provided on a power transmission shaft connecting the electromagnetic device and a magnetostrictive torque sensor.

According to such a configuration, a magnetic field that adversely affects the magnetostrictive torque sensor can be effectively reduced to zero by flowing a compensation current through the compensation coil. It is not affected by the state or the braking state of the electromagnetic brake.

Embodiment FIG. 1 shows a first embodiment of the present invention. In FIG. 1, 1 is a DC motor similar to that shown in FIG.
It has a coil 2 and is connected to a DC power supply 3. A compensating coil 12 whose winding number is adjusted is connected in series with the coil 2. The compensation coil 12 is wound around the power transmission shaft 4 between the DC motor 1 and the magnetostrictive torque sensor 6 so as to be concentric with the power transmission shaft 4.

An exciting current flowing through the exciting coil 2 of the DC motor 1 flows through the compensating coil 12, and a compensating magnetic flux Φ _C proportional to the intensity of this current is generated on the power transmission shaft 4. it is possible to generate a compensation magnetic flux [Phi _C of leakage flux [Phi _M opposite direction and the same intensity from the DC motor 1 by adjusting.

According to such a configuration, since the compensation coil 12 is connected in series with the coil 2 of the motor 1,
In 12, a compensation current flows in proportion to the current flowing in the DC motor 1. When the magnitude of the magnetic flux Φ _C is adjusted to be equal to the magnitude of the leakage magnetic flux Φ _M by adjusting the number of turns of the compensating coil 12, the two magnetic fluxes Φ _M and Φ _C cancel each other because they are in opposite directions. Act like so. Therefore, the magnetic field that adversely affects the magnetostrictive torque sensor 6 is effectively reduced to zero, and the torque sensor 6 can be prevented from being affected by the driving state of the motor 1.

FIG. 2 shows a second embodiment of the present invention, in which the mechanism for passing a current through the compensation coil shown in FIG. 1 is changed.

That, which put the current sense resistor 10 for excitation current detection in the excitation circuit of the DC motor 1, the voltage across the current sense resistor 10 is amplified by the amplifier 24 adjusts the variable resistor 11, and [Phi _M Compensation magnetic flux Φ _C in the opposite direction and of the same magnitude
Is generated.

According to this configuration, even if the number of turns of the compensating coil 12 is not strictly adjusted, the leakage flux Φ
_{Since M} can be compensated, it is convenient in terms of the device configuration.

FIG. 3 shows a third embodiment of the present invention. Here the ninth
A three-phase AC motor 7 similar to that in the figure is shown.
A compensation coil 12 whose winding number is adjusted is connected in series to the coil 8 of the motor 7, and the compensation coil 12 is provided on the power transmission shaft 4 connecting the motor 7 and the torque sensor 6.

Also in this case, similarly to the motor shown in FIG.
A magnetic flux Φ _C that cancels out a leakage magnetic flux Φ _M from the magnetic field Φ _M can effectively reduce the magnetic field that adversely affects the torque sensor 6 to zero.

FIG. 4 shows a fourth embodiment of the present invention, in which the mechanism for flowing a current through the compensation coil shown in FIG. 3 is changed to the same mechanism as that shown in FIG.

That is, a current sense resistor 10 for exciting current detection is inserted in one phase of the exciting circuit of the three-phase AC motor 7,
The voltage across the current sense resistor 10 is amplified by the amplifier 25,
The variable resistor 11 is adjusted to generate a compensating magnetic flux Φ _C in the opposite direction and the same magnitude as Φ _M. Hereinafter will be described the fifth to seventh embodiment of the present invention, in these embodiments, will be described to follow a mechanism for generating a compensating magnetic flux [Phi _C to the embodiment of Figure 1 and Figure 3.

FIG. 5 shows a fifth embodiment of the present invention. Here, the motor 13 is connected by a power transmission shaft 4 to an electromagnetic brake 14 such as an eddy current brake or an electromagnetic powder brake. Coil 1 of motor 13 and electromagnetic brake 14
5 and 16 are connected to AC power supplies 17 and 18, respectively. 19
Is a variable resistor for adjusting the braking force. The magnetostrictive torque sensor 6 is provided on the power transmission shaft 4 between the motor 13 and the electromagnetic brake 14.

When it such, the torque sensor 6, a leakage flux [Phi _M from the motor 13, and it Oyoboso both the influence of the leakage magnetic flux [Phi _B from the electromagnetic brake 14 to. Therefore, a compensation coil 12 connected to the coil 15 of the motor 13 and having an adjusted number of windings is provided on the power transmission shaft 4 between the motor 13 and the torque sensor 6 and connected to the coil 16 of the electromagnetic brake 14. Another compensating coil 12 whose number of turns is adjusted is provided on a portion of the power transmission shaft 4 between the electromagnetic brake 14 and the torque sensor 6.

In this way, both the leakage magnetic fluxes Φ _M and Φ _B are canceled by the magnetic fluxes Φ _CM and Φ _CB generated in the respective compensation coils 12 and 12, respectively. Therefore, also in this case, the torque sensor 6 is not affected by the leakage magnetic flux.

FIG. 6 shows a sixth embodiment of the present invention. Here, a generator 20 is connected to the power transmission shaft 4 from the motor 13 instead of the electromagnetic brake 14 in FIG. 21 is a coil, 22
Is a variable load resistance. In such a case, the leakage magnetic flux Φ _G from the generator 20 is compensated by the compensation coil 12 provided between the generator 20 and the torque sensor 6 on the power transmission shaft 4 and having an adjusted number of turns. Is canceled out by the magnetic flux Φ _CG generated at.

FIG. 7 shows a seventh embodiment of the present invention. In the first and third embodiments, the compensation coil 12 is connected in series to the coil 2 of the motor 1 and the like.
Instead of the series connection of the first embodiment, the coil 2 of the motor 1 and the compensation coil 12 are connected in parallel. By doing so, the current flowing through the compensation coil 12 can be made proportional to the current flowing through the motor 1. Similarly, in each of the above embodiments, the series connection can be changed to the parallel connection.

Although detailed description is omitted, FIGS. 2 and 4 also show in the fifth to seventh embodiments shown in FIGS. 5 to 7.
Similar to the embodiment shown in FIG, it is possible to adjust the compensation magnetic flux [Phi _C by the current sense resistor and the amplifier and the current adjustment knob.

Effect of the Invention As described above, according to the present invention, by providing a compensation coil on the power transmission shaft connecting the electromagnetic device and the magnetostrictive torque sensor, the magnetic field exerted on the magnetostrictive torque sensor can be effectively reduced to zero. Thus, it is possible to prevent the magnetostrictive torque sensor from being adversely affected by the leakage magnetic flux of the electromagnetic device and causing an error in the sensor output.

[Brief description of the drawings]

1 to 7 are circuit diagrams of first to seventh embodiments of the present invention,
8 and 9 are circuit diagrams of a conventional example. 1 DC motor, 4 power transmission shaft, 6 Magnetostrictive torque sensor, 7 AC motor, 12 Compensating coil, Φ
_M , Φ _C magnetic flux, 13 motor, 14 electromagnetic brake,
20 ... Generator.

Claims (1)

(57) [Claims] 1. A magnetostrictive torque sensor for measuring torque of an electromagnetic device such as a motor or an electromagnetic brake, wherein the compensation is proportional to a current flowing through the electromagnetic device and can cancel a leakage magnetic flux from the electromagnetic device. An external magnetic field compensating device for a magnetostrictive torque sensor, wherein a compensating coil for flowing a current is provided on a power transmission shaft connecting the electromagnetic device and the magnetostrictive torque sensor.