JP2008026210A - Magnetostrictive ring-type torque sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetostrictive ring-type torque sensor excelling in sensor sensitivity. <P>SOLUTION: This magnetostrictive ring-type torque sensor is equipped with a turning shaft, a magnetostrictive ring-shaped member, and a magnetic detection part. The ring-shaped member is fitted to the turning shaft with the ring-shaped member circumferentially magnetized. The detection part is disposed close to the ring-shaped member. In this torque sensor of a non-contact type, the intensity of magnetic flux leakage from the ring-shaped member is detected by the detection part when torque is exerted on the turning shaft. The ring-shaped member has a nonmagnetic part in its interior. The nonmagnetic part is a space. The cross-sectional shape of the ring-shaped member along its central axis direction is a rotated U-shape while the space of the nonmagnetic part substantially has a rectangular shape. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnetostrictive torque sensor, and more particularly, to a magnetostrictive ring type torque sensor among magnetostrictive torque sensors that detect a torque acting on a rotating shaft in a non-contact manner.

Conventionally, although a sensor using magnetostriction has been proposed as a torque sensor, there seems to be no practical use for a vehicle.
If it becomes possible to monitor the output shaft torque of the vehicle's mission, it is not necessary to perform difficult control as is currently performed for the AT shift shock. In addition, there is a potential demand for an inexpensive and small torque sensor, which has been researched and developed in order to enable comprehensive control of the vehicle and contribute to the realization of a fuel-saving vehicle.

As a magnetostrictive torque sensor according to a conventional proposal, there is one in which two belt-like grooves provided on a rotating shaft and a coil surrounding them are provided (see, for example, Patent Document 1 and Non-Patent Document 1). In the sensor, torque is detected by exciting with a coil and detecting a change in permeability of the left and right grooves.
Japanese Patent No. 2677066 R. Ishino et al. : IEEE Trans. on Magnetics, vol. 38, no. 5, 3306, September 2002.

On the other hand, a magnetostrictive torque sensor of a type in which a magnetostrictive ring is fitted to a rotating shaft has also been proposed (for example, see Non-Patent Documents 2 and 3). This magnetostrictive ring type torque sensor magnetizes the magnetostrictive ring in the circumferential direction and detects the magnetic field component generated in the rotational axis direction with a small magnetic sensor such as a Hall element when torque is applied to the rotational axis. To do.
I. J. et al. Garshelis: IEEE Trans. on Magnetics, vol. 28, no. 5, 2202, September 1992. I. J. et al. Garshelis and C.M. R. Conto: JAP, vol. 79, no. 8, 4756, 1996.

However, among the conventional magnetostrictive torque sensors, a sensor using a coil has a problem that a space is required because the coil is used.
In addition, it is necessary to pass an alternating current of the order of 10 kHz to the coil, and in terms of electrical power, power of about 1 W or less is necessary, and there is a problem in terms of power.

On the other hand, the magnetostrictive torque sensor that fits the magnetostrictive ring to the rotating shaft satisfies the requirements of small size and power saving, but since the rotating shaft and the magnetostrictive ring are tightly fitted, a little large torque is applied. In this case, there is a problem that slip occurs between the rotating shaft and the ring.
In addition, a tensile stress in the circumferential direction (Hoop stress) acts on the magnetostrictive ring, and this ensures uniaxial magnetic anisotropy in the circumferential direction. This portion is essential for good sensor characteristics. It has become a part.

  However, in such a magnetostrictive ring type torque sensor, when the rotating shaft is a magnetic body, a considerable part of the leakage magnetic flux passes through the rotating shaft, so that there is a problem that the sensitivity is remarkably deteriorated. When the dynamic shaft is an output shaft such as a motor, the output shaft is made of steel and is not made of a non-magnetic material except for special purposes, and this problem is remarkable.

  The present invention has been made in view of such problems of the prior art, and an object thereof is to provide a magnetostrictive ring type torque sensor excellent in sensor sensitivity.

  As a result of intensive studies to achieve the above object, the present inventors have found that the above object can be achieved by forming a space in the magnetostrictive ring and separating the magnetostrictive ring and the rotating shaft that is a magnetic body. The headline and the present invention were completed.

That is, the magnetostrictive ring type torque sensor of the present invention includes a rotating shaft, a ring-shaped member having magnetostriction, and a magnetic detection unit, and the ring-shaped member having the magnetostriction is fitted to the rotating shaft,
The magnetostrictive ring-shaped member is magnetized in the circumferential direction, and the magnetism detecting portion is disposed close to the magnetostrictive ring-shaped member, and when torque is applied to the rotating shaft, the magnetostrictive ring-shaped member is separated from the magnetostrictive ring-shaped member. In the non-contact type magnetostrictive ring type torque sensor that detects the magnitude of the magnetic flux leakage of the magnetic detection unit,
The magnetostrictive ring-shaped member has a nonmagnetic portion therein.

According to the present invention, since the space portion is formed in the magnetostrictive ring and the magnetostrictive ring and the rotating shaft as the magnetic body are separated from each other, a magnetostrictive ring type torque sensor having excellent sensor sensitivity can be provided.
Since the magnetostrictive ring type torque sensor of the present invention can target a steel rotating shaft, its usefulness is dramatically improved.

Hereinafter, the present invention will be described in detail with reference to the drawings.
In order to clarify the contents of the present invention, first, the prior art will be described again.
FIG. 13 is a configuration diagram showing an AC permeability differential type magnetostrictive torque sensor as disclosed in Patent Document 1 and Non-Patent Document 1.
On the other hand, FIG. 14 is a side view showing a magnetostrictive ring type torque detection device proposed by Galcheris, which is disclosed in Non-Patent Document 2 and Non-Patent Document 3.

  In FIG. 13, the grooves 1g provided on the rotation shafts 1L and 1R are inclined at 45 degrees in different directions on the left (1L) and the right (1R). When torque acts on the rotation shafts 1L and 1R as shown in the figure, the magnetic permeability increases at the groove band (mountain portion) of the rotation shaft 1L and decreases at the rotation shaft 1R. When torque is applied, tensile and compressive stresses are applied in the 45-degree direction, and the grooves form shape anisotropy, which is more likely due to the inverse effect of magnetostriction (explaining materials with a positive magnetostriction value) The same applies to the following).

  In the sensor shown in FIG. 13, since there are two groove portions 1g in the axial direction and the coil 2 that covers the groove 1g needs to be installed, it is difficult to reduce the size of the sensor. Further, an alternating current of the order of 10 kHz is passed through the coil 2. Since it is several volts at several tens of mA, it requires a little less than 1 W of power, and there is a problem that power consumption is large.

On the other hand, in the magnetostrictive ring type torque sensor shown in FIG. 14, a ring 3 having magnetostriction is fitted to the rotating shaft 1. As a result, tensile stress (Hoop stress) acts on the ring 3 in the circumferential direction. When magnetized in the circumferential direction, the magnetization is oriented in the circumferential direction.
When torque is applied to the rotating shaft 1, tensile stress (compressive stress orthogonal to it) acts in the 45 ° direction, so that magnetization is tilted in the axial direction due to the inverse effect of magnetostriction. Accordingly, a magnetic pole appears at the end of the ring, and a leakage magnetic flux is generated. Therefore, if a sensor 4 such as a Hall element is arranged, a signal having a correlation with torque is detected.

Such a magnetostrictive ring type torque sensor may be shorter in the rotational axis direction than the torque sensor of FIG. 13, and the detection sensor is also small, so that it can be miniaturized in the radial direction. Further, since the Hall element also saves power, there is an advantage that power saving and downsizing can be achieved.
However, since the ring 3 is tightly fitted to the rotating shaft 1, there is a problem that slip occurs between the two, and unless the size of the tightening margin is secured to some extent, good sensor characteristics cannot be obtained, There is a difficulty in the ease of.

  In addition, such a magnetostrictive ring type torque sensor has a problem that sensitivity is remarkably reduced when the rotating shaft is made of steel.

The inventors of the present invention have studied the structure of the magnetostrictive ring in view of such a background. As a result, they have found that the sensor sensitivity can be ensured by adopting a predetermined structure, and have completed the present invention.
Therefore, the magnetostrictive ring type torque sensor of the present invention basically has a structure as shown in FIG.

  The magnetostrictive ring type torque sensor of the present invention can be fastened by fastening means so that the magnetostrictive ring and the rotating shaft do not slip when torque is applied.

  EXAMPLES Hereinafter, although an Example and a reference example demonstrate this invention further in detail, this invention is not limited to these Examples.

(Reference Example 1)
FIG. 1 is a schematic view showing an example of a magnetostrictive ring type torque sensor in which a maraging steel ring 20 having a length of 13 mm and a thickness of 0.76 mm is fitted to a rotating shaft 10 having a diameter of 12.64 mm by cold fitting. It is sectional drawing.
The tightening margin was 55 μm. The ring 20 is manufactured by machining YAG300, which is a maraging steel made by Hitachi Metals, solidified at 820 ° C. for 1 hour, and then heat-treated by aging at 490 ° C. for 5 hours. The moving shaft 10 was fitted with cooling. The rotating shaft 10 used was made of SUS303 and S45C induction-hardened.

The ring 20 was magnetized in the circumferential direction by energizing in the axial direction. The energization magnetization was performed with a pulse current having a peak current value of about 10,000 A.
Thus, the magnetostrictive ring type torque sensor of this example was produced.

  In this torque sensor, the leakage magnetic field at a position 1 mm from the end of the ring 20 was measured with a gauss meter while applying torque to the rotating shaft 10. The detection part of the gauss meter was at a position of about 0.5 mm from the ring surface, and a magnetic field having a component perpendicular to the ring surface was measured. The measurement results are shown in FIG.

As shown in FIG. 2, even if the material of the rotating shaft 10 is different, a good linearity characteristic without hysteresis is obtained in both cases.
However, in the case of SUS303, it is 9 G when a torque of 15 Nm is applied, whereas in the case of S45C, it is 1.5 G, and it can be seen that the sensitivity is reduced to 1/6.
Thus, even if the conditions such as the structure of the ring are the same, the sensitivity is lowered due to the difference in the material of the rotating shaft. The reason for this is as described above.

(Reference Example 2)
An aging ring 20 made of YAG300 (having the same specifications as in Reference Example 1) is refrigerated and fitted to the rotating shaft 10 made of SUS303 at 20 μm, and the ring 20 and the rotating shaft 10 are electron beamed as shown in FIG. Welded. As shown in the figure, the entire circumference was welded with a penetration of about 0.5 mm to obtain a torque sensor of this example.
Moreover, what was cooled and fitted at 50 μm was welded with an electron beam. The magnetizing method and the sensor characteristic measuring method are the same as those in Reference Example 1.

FIG. 4 shows a measurement result at ± 15 Nm in a torque sensor having a cooling fit tightening allowance of 20 μm. There is a big hysteresis.
The ring and shaft do not slip because they are joined by electron beam welding. (On the other hand, if the shaft and ring slip due to application of torque, the torque-sensor output characteristics show hysteresis. End up.) Therefore, the hysteresis in this case can be interpreted as not having good sensor characteristics because the circumferential tensile stress (Hoop stress) due to cold fitting is small.

In a torque sensor with a cold fitting interference of 50 μm, the torque-sensor output characteristics at ± 15 Nm are as shown in FIG. It has been experimentally found that when the torque is further increased, slipping occurs and hysteresis is drawn.
In the case of bonding with an electron beam, as shown in FIG. 5, good sensor characteristics, that is, the characteristics are straight and do not draw hysteresis.

(Example 1)
A ring 21 whose cross section in the central axis direction has a U-shape rotated 90 degrees was manufactured using YAG300, which is maraging steel. A specific shape is shown in FIG.
The length of the ring 21 is 13 mm, the outer diameter is 16.7 mm, the inner diameter is 14.7 mm, and the legs (in the axial direction) have a length of 2 mm. Further, both corners inside the U-shaped ring 21 were processed with 1R.

  After machining, solution treatment and aging heat treatment were performed. The rotating shaft 10 was made into S45C (phi) 12.64mm, and it produced by induction hardening. And the ring 21 and the axis | shaft 10 were fitted by cold fitting at 50 micrometers, and the torque sensor of this example was obtained.

FIG. 7 shows sensor characteristics when torque is applied and ± 15 Nm. Good sensor characteristics with good linearity without hysteresis are obtained. The magnetization method and the sensor characteristic measurement method were the same as in Reference Example 1.
As shown in FIG. 7, the sensor output at 15 Nm is 1.7 G, which does not appear to be much improved with respect to the result shown in FIG. 2, but in this case the diameter of the sensor part is 16.7 mm. Therefore, the actual improvement is 2.3 times or more.

Therefore, it can be seen that a significant improvement in sensitivity is achieved by employing the ring structure shown in FIG.
In FIG. 6, a substantially rectangular space is provided in the ring 21 g. The thickness of the space is thicker than 1 mm. That is, it is thicker than the ring 21. Such a thickness relationship is suitable for ensuring the sensitivity.
On the other hand, it seems that the more the ring 21 is separated from the shaft 10, the better. However, since the stress against the torque is reduced by the cube of the diameter, it is not a good idea to separate the ring 21 so much. However, if it is too close, an improvement in sensitivity cannot be expected.

(Example 2)
Except that the ring and the rotating shaft were joined by an electron beam, the same configuration as in Example 1 was adopted to obtain a torque sensor of this example.
When the torque sensor characteristics were examined in the same manner as described above, the characteristics at ± 15 Nm were the same as the results shown in FIG. Furthermore, the characteristics excellent in linearity without hysteresis were obtained up to the high torque range.

(Example 3)
In Example 1, it fitted by the cold fitting of 50 micrometers of interference. In Example 2, the ring and the rotating shaft were joined by an electron beam in the state of Example 1. In this example, the ring and the rotating shaft were fitted to each other, and the ring and the rotating shaft were joined by electron beam welding in a state where the ring was compressed in the axial direction, thereby obtaining a torque sensor. The compression allowance in the axial direction of the ring was 10 μm. Other than that was the same as in Examples 1 and 2.

When the torque sensor characteristics were examined in the same manner as described above, the torque-sensor output characteristics were also similar to the results shown in FIG.
Therefore, it is judged that applying the compression in the axial direction is equivalent to applying a tensile stress in the circumferential direction for the (sensor) ring.
The construction method employed in this example is useful as a construction method that can ensure sensor characteristics when cold fitting or shrink fitting cannot be employed.

Example 4
FIG. 8A is a cross-sectional view showing another embodiment of the magnetostrictive ring type torque sensor of the present invention, and shows a torque sensor having a detecting portion provided with two Hall elements 30 and a yoke 40.
The flow of magnetic flux is as shown in FIG. Therefore, the right Hall element and the left Hall element in the drawing have sensor characteristics with opposite polarities. By making the outputs of both differential, double sensitivity can be obtained. Further, the sensitivity is further doubled by providing the yoke 40.

The sensor characteristics are shown in FIG. The sensitivity is 4 times. Employing the arrangement of the Hall elements as described above is advantageous because the common-mode input is canceled and the SN ratio is improved.
Further, when the yoke is provided, it has resistance against electromagnetic noise from the outside. Furthermore, there is an effect that it becomes insensitive to fluctuations in the gap (distance between the magnetostrictive ring surface and the detection sensor).

The yoke 40 is made of PB (Permalloy B type) permalloy and has a thickness of 1.0 mm. The yoke 40 may have a size that can cover the Hall element 30 and the ring 20 as illustrated. Moreover, the circumferential direction length should just have the width | variety about 3 times the magnitude | size (size of a resin package) of the Hall element 30. FIG.
The element package and the yoke are attached in contact with each other. The Hall element 30 is close to the ring 20. The magnetic sensitive part is positioned at a distance of about 0.5 mm from the ring surface.

(Example 5)
FIG. 10 is a cross-sectional view showing still another embodiment of the magnetostrictive ring type torque sensor of the present invention, and the rotating shaft 11 can be a reduced diameter shaft as shown.
When the same configuration as in Example 1 was adopted except for the rotating shaft 11, the sensor sensitivity was improved by about 40%. This is because the ring stress with respect to the torque increases.

(Example 6)
FIG. 11 is a cross-sectional view showing another embodiment of the magnetostrictive ring type torque sensor of the present invention, and shows an example in which a SUS ring 50 is arranged in a space in the ring 20.
In this example, a ring 50 having an inner diameter that is the axis diameter of the rotating shaft 10 and an outer diameter that is the inner diameter of the ring 20 is made of SUS303. Then, the ring 50 was divided into three as shown in FIG. The gap was about the blade thickness.
And this ring 50 was put inside the U-shaped ring 20, and it was cold-fitted with the allowance of 50 micrometers with respect to the rotating shaft 10, and the torque sensor of this example was obtained.

The sensor characteristics were the same as in Example 1. If SUS is inserted in the ring 20, the temperature characteristics of the sensor can be improved. The sensitivity of the sensor tended to decrease with respect to the temperature in the test in the range from room temperature to 120 ° C., but was almost flat in the present example.
The linear expansion coefficient of maraging steel is 11.3 × 10 ⁻⁶ / ° C. SUS303 is 14.7 × 10 ⁻⁶ / ° C., and S45C is 10.7 × 10 ⁻⁶ / ° C.
Since the linear expansion of SUS is larger than that of maraging steel, the ring 20 is pressed from the inside when the temperature rises, so there is a function to increase the circumferential stress of the ring 20, and the temperature dependence of sensitivity is improved flat. It is guessed that he / she does.

As mentioned above, although this invention was demonstrated in detail by the suitable Example, this invention is not limited to these Examples, A various deformation | transformation is possible within the range of the summary of this invention.
For example, although only the Hall sensor is illustrated as the torque detection magnetic sensor, the invention is not limited to this, and it goes without saying that Hall IC and MI sensors can be used which are power-saving and compact. Yes.

It is a typical sectional view showing an example of a magnetostriction ring type torque sensor. It is a graph which shows a torque sensor characteristic. It is sectional drawing which shows the torque sensor which carried out the electron beam welding. It is a graph which shows a torque sensor characteristic. It is a graph which shows a torque sensor characteristic. It is sectional drawing which shows one Example of the magnetostriction ring type torque sensor of this invention. It is a graph which shows a torque sensor characteristic. It is sectional drawing which shows the other Example of the magnetostriction ring type torque sensor of this invention. It is a graph which shows a torque sensor characteristic. It is sectional drawing which shows other Example of the magnetostriction ring type torque sensor of this invention. It is sectional drawing which shows the other Example of the magnetostriction ring type torque sensor of this invention. It is a top view which shows a division | segmentation ring. It is sectional drawing which shows an example of the conventional magnetostrictive torque sensor (groove system). It is sectional drawing which shows an example of the conventional magnetostrictive ring type torque sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotating shaft 1L, 1R Rotating shaft 1g Groove 2 Coil 3 Ring 10, 11 Rotating shaft 20, 21 Ring 30 Hall element 40 Yoke 50 Split ring

Claims (12)

A ring-shaped member having a rotating shaft and magnetostriction, and a magnetic detection unit, and the ring-shaped member having the magnetostriction is fitted to the rotating shaft;
The magnetostrictive ring-shaped member is magnetized in the circumferential direction, and the magnetism detecting portion is disposed close to the magnetostrictive ring-shaped member, and when torque is applied to the rotating shaft, the magnetostrictive ring-shaped member is separated from the magnetostrictive ring-shaped member. In the non-contact type magnetostrictive ring type torque sensor that detects the magnitude of the magnetic flux leakage of the magnetic detection unit,
The magnetostrictive ring type torque sensor, wherein the magnetostrictive ring-shaped member has a non-magnetic portion therein.   The magnetostrictive ring torque sensor according to claim 1, wherein the nonmagnetic portion is a space.   3. The magnetostrictive ring type torque sensor according to claim 1, wherein a thickness of the nonmagnetic space portion is larger than a thickness of the link-like member in a cross section perpendicular to the rotation axis at the center of the sensor portion.   4. The magnetostrictive ring-shaped member according to claim 1, wherein a cross-sectional shape along a central axis direction of the magnetostrictive ring-shaped member is a U-shaped rotating shape, and the nonmagnetic part space has a substantially rectangular shape. The magnetostrictive ring type torque sensor as described in one term. 5. The magnetostrictive ring torque sensor according to claim 4, wherein a leg portion of the U-shaped magnetostrictive ring member and the rotating shaft are fastened.   6. The magnetostrictive ring torque sensor according to claim 5, wherein the leg portion of the U-shaped magnetostrictive ring-shaped member and the rotating shaft are fastened by electron beam welding.   A ring-shaped nonmagnetic material having a linear expansion coefficient larger than that of the magnetostrictive ring member is inserted into the space of the nonmagnetic portion while being in contact with the rotating shaft and the inner surface of the U-shaped magnetostrictive ring member. The magnetostrictive ring type torque sensor according to any one of claims 2 to 6, wherein the magnetostrictive ring type torque sensor is provided.   8. The magnetostrictive ring torque sensor according to claim 7, wherein the ring-shaped nonmagnetic material is made of austenitic stainless steel.   The magnetostrictive ring type torque sensor according to any one of claims 1 to 8, wherein the rotation shaft is made of steel.   The magnetostrictive ring torque sensor according to any one of claims 1 to 9, wherein the magnetostrictive ring member is made of maraging steel.   The magnetostrictive ring type torque sensor according to claim 1, wherein the magnetic detection unit includes a Hall sensor and a yoke.   The said U-shaped ring member is fastened with the said rotating shaft in the state in which the compressive stress was applied to the central-axis direction, The statement of any one of Claims 4-11 characterized by the above-mentioned. Magnetostrictive ring type torque sensor.

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