JP2006184040A - Torque detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized and power-thrifty torque detector, easily attached to a motor shaft, a transmission output shaft, etc. and also applied to real time monitoring of torque acting on these shafts. <P>SOLUTION: This torque detector is equipped with a shaft and a magnetic sensor. The shaft 1 has a groove forming zone 2 where a plurality of helical grooves 2a inclined about 45 degrees in the direction of the axis are formed so as to have a prescribed width A. A magnetized part 3 circumferentially magnetized is formed in the forming zone 2 so as to have a width B. The magnetic sensor 4, such as a hall sensor, is disposed so as to confront the forming zone 2 on the shaft 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a torque detection device used to detect shaft torque in a motor shaft, an output shaft of a transmission, and the like in a non-contact manner.

For example, if the output shaft torque of an automobile transmission can be monitored in real time, it will be possible to alleviate a shift shock in an AT car without performing difficult control that is currently performed. .
In addition, since comprehensive control of the vehicle becomes possible and it can be connected to the realization of a fuel-saving vehicle, there are not a few potential demands for a small and inexpensive torque sensor, and research and development are being carried out in various institutions.

As such a torque sensor, various types are known. For example, as shown in FIG. 7, a belt-like portion having a spiral groove is provided on a shaft (measurement shaft) that is a torque detection target. A sensor is proposed that detects torque by forming two coils on the left and right sides, and by providing coils that surround these band-shaped parts, exciting them with the coils, and detecting changes in the permeability of the left and right grooved band-shaped parts. (For example, refer to Patent Document 1 and Non-Patent Document 1).
Here, the grooves are inclined at 45 degrees in opposite directions on the left and right sides, and when torque acts on the shaft as shown in the figure, the permeability increases in the band on the left side in the figure, and the band on the right side Then, the magnetic permeability decreases. When torque is applied, tensile and compressive stresses are applied in the 45-degree direction, and the grooves form shape anisotropy. This is a description of a material having a positive magnetostriction, and the same applies to the following description.
Japanese Patent No. 2677066 R. Ishino et al. : IEEE trans. on Magnetics, vol. 38, no. 5,3306, Sep. 2002

In addition, as shown in FIG. 8, a magnetostrictive torque sensor of a type in which a magnetostrictive ring is fitted to the shaft, that is, the magnetostrictive ring is magnetized in the circumferential direction, and is generated in the axial direction when torque is applied to the shaft. A device that detects a magnetic field component to be detected by a small magnetic sensor such as a Hall element has also been proposed (for example, see Non-Patent Documents 2 and 3).
In this type of sensor, since a ring having magnetostriction is fitted to the shaft, tensile stress is exerted on the ring in the circumferential direction. When magnetized in the circumferential direction, the magnetization is oriented in the circumferential direction. When torque is applied to the shaft, stress acts in the direction of 45 degrees, so that the magnetization is tilted in the axial direction and the magnetization appears in the axial direction. By arranging a sensor such as a hall element, a signal correlated with torque is detected.
I. J. et al. Garshelis: IEEE trans. on Magnetics, vol. 28, no. 5, 2202, Sep. 1992 I. J. et al. Garshelis and C.M. R. Conto: JAP, Vol. 79, no. 8,4756,1996

Furthermore, as shown in FIG. 9, a method of magnetizing a part of a shaft member having magnetostriction in a band shape in the circumferential direction has been proposed (for example, see Non-Patent Document 4).
The principle of torque detection in such a device is the same as that of the magnetostrictive ring method described above. A material having magnetostriction is used for the shaft, and the torque is applied to the shaft by magnetizing it in the circumferential direction in a band shape. In this case, since the magnetization directed in the circumferential direction is inclined in the axial direction, a signal corresponding to the torque can be detected by arranging a magnetic sensor such as a Hall element in the vicinity of the end of the band.
I. J. et al. Garshelis and C.M. A. Jones: JAP, Vol. 85, no. 8,5468, 1999

However, in the magnetostrictive torque sensor of the spiral groove type shown in FIG. 7, in addition to the fact that there are two belt-like portions provided with the groove portions in the axial direction, a coil that respectively covers these belt-like portions is used. There is a problem in that it requires space, and it is difficult to reduce the size of the sensor.
In addition, an alternating current of the order of 10 kHz is passed through the coil, and since it is several tens of mA and several volts, there is a problem that it requires about 1 W of power and consumes a large amount of power.

  Further, in the magnetostrictive torque sensor of the magnetostrictive ring fitting type shown in FIG. 8, the axial length is shorter and the detection sensor is smaller than that shown in FIG. It can be downsized, and Hall sensors such as Hall elements or Hall ICs are also power-saving, so they meet the requirements for small size and power saving. As expected, the shaft is preferably non-magnetic (eg, austenitic stainless steel) or a material that is difficult to magnetize. In addition, since the shaft and the ring are an interference fit, there is a problem that if a little large torque is applied, a slip occurs between the shaft and the ring. In addition, it is necessary to develop a method for attaching the ring to an actual motor shaft. At this time, it is considered that a design review in consideration of setup or the like is also involved in fitting the ring to the mounting position of the torque detection device.

  In the case of the band-shaped magnetism type torque sensor shown in FIG. 9, it is necessary to change the shaft material to a special material, although there is no problem of slip that was a problem in the ring fitting method. There is a problem in that it cannot be magnetized in the form of a band which is local and clearly separated in the axial direction as shown in the figure.

  The present invention has been made in view of the above problems in the conventional magnetostrictive torque sensor, and its object is to reduce the size and power consumption, such as a motor shaft and an output shaft of a transmission. A torque detection device that can be attached to various shafts and can be applied to monitor the torque applied to these shafts in real time, and further includes a rotation detection unit that detects the rotation of the shaft simultaneously with the torque detection. An object of the present invention is to provide a torque detection device that can correct not only the rotation detection signal but also the fluctuation of the torque detection signal that occurs with rotation based on the rotation detection signal.

  As a result of intensive studies aimed at solving the above-mentioned problems, the present inventors have utilized only one of the groove forming portions in the conventional torque sensor using the spiral groove method, magnetized the center of the portion in the circumferential direction, As a result of attempts to detect torque using a sensor, it was found that a sufficient detection signal was obtained, and the present invention was completed.

The present invention is based on the above knowledge, and the torque detection device of the present invention includes a shaft and a magnetic sensor, and the shaft includes a plurality of spiral grooves inclined at 45 degrees with respect to the axial direction. The groove forming band is formed with a circumferentially magnetized portion, and the magnetic sensor is disposed to face the groove forming band of the shaft.
Moreover, the suitable form of the torque detection apparatus of this invention is further provided with the rotation detection part which detects rotation of the said axis | shaft.

According to the present invention, a plurality of spiral grooves inclined at 45 degrees in the axial direction are formed in a band shape around the shaft, and circumferential magnetization is performed in a region where the spiral grooves of the shaft are formed (groove forming band). Part is formed, and the groove bottom is uniformly magnetized in the circumferential direction. By using a small magnetic sensor such as a Hall element, a power-saving small torque detection device can be realized. Such a torque detection device can be suitably used as a device for monitoring in real time the torque applied to the motor shaft, the output shaft of the transmission, and the like.
Further, in the above preferred embodiment of the present invention, since the rotation detection unit for detecting the rotation of the shaft is provided, the rotation of the shaft can be detected simultaneously with the torque detection, and further the rotation from the rotation detection unit. Based on the detection signal, the variation in the torque detection signal based on the rotation of the shaft can be corrected.

  Hereinafter, the torque detection device of the present invention will be described in more detail together with embodiments thereof.

The torque detection device of the present invention has a structure as shown in FIG. 1, for example. As a basic structure, a shaft 1 for detecting torque, such as a motor shaft or an output shaft of a transmission, and a Hall element or Hall IC, for example. The shaft 1 is provided with a groove forming band 2 formed with a plurality of spiral grooves 2a inclined at approximately 45 degrees with respect to the axial direction. In the center of the groove forming band 2, a magnetized portion 3 magnetized in the circumferential direction is formed in the width B dimension. On the other hand, the magnetic sensor 4 is disposed at a position facing the groove forming band 2.
In the figure, since the spiral groove 2a has a spiral shape, it should be represented in an S shape as shown in FIG. 7, but it is schematically represented as a straight line for convenience of drawing. .

As the inclination direction of the spiral groove 2a, the effect of the present invention is exhibited not only in the range of just 45 degrees but also in the range of about ± 5 degrees. However, it is desirable that the parallelism of the grooves to be formed be within about ± 0.5 degrees.
In addition, the magnetic sensor for torque detection needs to be an analog output. The same applies to the Hall IC. However, the Hall IC for rotation detection is preferably a pulse output type (digital output type).

At this time, the size of the spiral groove 2a is not particularly limited, but from the viewpoint of ensuring ease of manufacture and mechanical strength, the groove width is 1 mm to 3 mm, and the depth is 0. A range of 5 mm to 2.0 mm is desirable respectively. Further, if the formation area of the spiral groove 2a, that is, the width A of the groove formation band 2 is too large, it is against the downsizing of the sensor, and it is difficult to ensure the sensor performance. From 5 mm to 20 mm is desirable.
The number of spiral grooves 2a is determined according to the diameter D of the shaft 1 to be measured. However, if the amount is too small, the effect of forming the groove cannot be obtained. The formation effect cannot be obtained. In view of the balance with the remaining ridges, it is desirable to select the number so that the ridge: groove ratio is in the range of approximately 1: 1 to 3: 1.

As shown in the drawing, it is desirable that the magnetized portion 3 is magnetized in a band shape that is locally separated in the axial direction, thereby improving detection sensitivity.
The width B of the magnetized portion 3 is preferably in the range of 1/2 to 1/1 of the width A of the groove forming band 2 because it is preferable that the band is accommodated in the width A.

  In addition to the Hall element and Hall IC described above, an MI sensor or the like can be used as the magnetic sensor 4, but from the viewpoint of obtaining sufficiently large sensitivity, the width A is set as shown in the figure. It is desirable to arrange in the position near the end of the groove forming band 2 formed.

In the torque detecting device of the present invention having such a structure, the groove forming band 2 as a torque detecting portion is one place and does not use a coil, so that it is compared with a groove type torque sensor (see FIG. 7). Thus, power saving and downsizing are possible, and the shaft 1 is directly magnetized, so that no ring slip occurs as in the ring fitting torque sensor (see FIG. 8), and the spiral groove 2a. Is magnetized in the circumferential direction, so that the detection sensitivity can be improved, and a conventional band-shaped magnetization type torque sensor (FIG. 9) is obtained. Compared to the reference), the magnetized portion can be formed in a band shape that is divided in the axial direction locally in the inter-groove portion.
Further, it is not necessary to use a special material for the material of the shaft 1, and it can be easily attached to an output shaft of a motor or transmission, and these output shafts can be used as the shaft 1 as they are.

The shaft 1 is preferably subjected to heat treatment such as induction hardening or aging treatment depending on the shaft material, for example, with the spiral groove 2a formed.
That is, the structure at the bottom of the groove becomes uniform by performing the heat treatment after providing the groove. In addition, it is considered that the distortion caused by the processing leads to the refinement of the structure and the uniformity of the structure. Furthermore, since there is a groove, the residual stress distribution at the bottom of the groove becomes uniform, the distribution of magnetization in the circumferential direction becomes almost uniform, and it is assumed that good sensor characteristics are obtained.

Further, as shown in FIGS. 2A and 2B, the magnetic sensor 4 is provided with a yoke 5 made of a soft (soft) magnetic material having a small coercive force, such as a silicon steel plate, electromagnetic soft iron, or permalloy. It is desirable to collect magnetism, which makes it possible to nearly double the sensor sensitivity. Furthermore, by using the yoke 5, in addition to the above-described increase in sensitivity, it is possible to provide resistance to electromagnetic noise from the outside, and against variations in the gap (distance between the surface of the shaft 1 and the magnetic sensor 4). Can be insensitive. The axial length of the yoke 5 is suitably set to a length that covers the groove forming band 2 of the shaft 1.
In the example shown in the figure (diameter D = 19 mm of the shaft 1), PB permalloy (40 to 50% Ni—Fe) having a thickness of about 0.5 mm is used for the yoke 5, and the surface of the shaft 1 of the yoke 5 is used. As shown in the figure, it is appropriate to arrange the magnetic sensor 4 at a position such that the magnetic sensor 4 is in the center with the yoke 5 as shown in the figure.

Further, it is desirable to use two magnetic sensors. As shown in FIG. 3, in addition to the magnetic sensor 4, the second magnetic sensor 6 is arranged in the axial direction, and these are positioned in the vicinity of both ends of the groove forming band 2. It is desirable to arrange them respectively. In this case, since the sense of the sensor sensitivity is reversed for the second magnetic sensor 6, it is preferable to subtract, whereby the two sensor signals can be added and doubled.
By arranging the two sensors 4 and 6 in this way, the influence can be canceled with respect to a substantially uniform magnetic field from the outside, and the resistance to disturbance is further increased.

In the torque detection device of the present invention, a rotation detection unit can be arranged adjacent to the torque detection unit including the groove forming band 2 and the magnetic sensor 4 opposed to the groove formation band 2.
As shown in FIGS. 4A to 4C, such a rotation detection unit is composed of, for example, a bond magnet, and a ring magnet 7 attached to a position near the groove forming band 2 on the shaft 1 to be measured, For example, the magnetic sensor 8 (second magnetic sensor) made of a Hall IC can be configured to face the ring magnet 7. This Hall IC is preferably a pulse output type (digital output type).

As shown in FIG. 4C, the ring magnet 7 is magnetized in multiple poles (repetition of N and S), and the magnetization direction in this example is the radial direction.
The detection signal from the Hall IC 8 is a signal as shown in FIG. 5A, and the rotation position and the rotation speed of the shaft 1 can be detected. Thus, the rotation detection unit is provided adjacent to the torque detection unit. By providing, it is possible to realize a torque detection device that can take a rotation signal together with the torque loaded on the shaft 1.

  As described above, in the torque detection device including the rotation detection unit together with the torque detection unit, the torque from the magnetic sensor 4 for torque detection is based on the rotation detection signal from the Hall IC (second magnetic sensor) 8. Variations (waviness variation) accompanying rotation of the shaft 1 included in the detection signal can be corrected.

That is, FIG. 5B shows a torque signal accompanying the rotation of the shaft 1 by the torque detection device shown in FIG. Here, T = 0 is a torque signal when no torque is applied, and + T and -T indicate torque signals when a + and -torque is applied, respectively. In this figure, for convenience of explanation, the fluctuation range is emphasized, but such fluctuation of the torque signal accompanying rotation is not preferable.
The cause of this rotational fluctuation is that the magnetic characteristics of the shaft material are not uniform in the circumferential direction and that the gap between the torque detecting magnetic sensor 4 and the shaft surface is not uniform (the shaft center is eccentric).

In the torque detection device shown in FIG. 4, since the rotation signal is obtained from the second magnetic sensor 8, the rotation position of the shaft 1 can be known by this, and the torque detection signal is processed based on the rotation detection signal. By doing so, the fluctuation | variation (a sensitivity fluctuation | variation is included) accompanying rotation of the said axis | shaft 1 can be correct | amended.
With the current signal processing technology, signal processing can be performed in real time, and a correction torque signal as shown in FIG. 5C can be obtained.

  Hereinafter, the present invention will be specifically described based on examples. In addition, this invention is not limited only to these Examples.

(Invention Example 1)
Using maraging steel (trade name YAG300, manufactured by Hitachi Metals, Ltd., 18% Ni-9% Co-5% Mo-Fe), as shown in FIG. Fabricated by machining, using an end mill with a diameter of 1 mm, 20 spiral grooves 2 a inclined in the direction of 45 degrees in the axial direction were formed in the circumferential direction to a width of 1 mm and a depth of 1.5 mm. In addition, the width A of the groove forming band 2 in which the 20 spiral grooves 2a were formed was 11 mm (the distance between the centers of the end mills was 10 mm).
After these machining processes, solution treatment and aging heat treatment were performed. The solid solution was 820 ° C. × 1 h, and the aging was 490 ° C. × 5 h in vacuum. After solid solution, it was cooled in a furnace with nitrogen (air cooling is possible), and after aging it was air cooled.

Next, the magnetized portion 3 was formed in a band shape in the circumferential direction using a NdFeB sintered magnet at the center of the groove forming band 2 having a width of 11 mm where the spiral groove 2a was formed. At this time, the target width B of the magnetized portion 3 was set to 6 mm.
In addition, about the magnetization method, based on the method described in the nonpatent literature 3, 6 mm in width, 12 mm in depth, NdFeB sintered magnet of 3 mm in thickness (magnetization is thickness direction), and the side of width 6 mm (Aimed at a target width of 6 mm) was held parallel to the rotating shaft (rotation speed: about 260 rpm) (the surface including the shaft core was centered on the thickness of the magnet) to be magnetized in a band shape. First, the shaft surface was approached, then held at 1 mm position (3 minutes), and then the magnet was slowly moved away in the radial direction. The total magnetizing time was about 5 minutes.

And while arrange | positioning the Hall sensor 4 as a magnetic sensor in the position shown in a figure, the torque was applied to the to-be-measured axis | shaft 1, and the output of the Hall sensor 4 was investigated.
The Hall sensor 4 detected a magnetic field in the radial direction, the magnetically sensitive area was about 2 mm ² , and the center of the area was at a position about 0.5 mm from the surface of the shaft 1.

  FIG. 6 shows the result, and it has been found that a characteristic having almost no hysteresis is shown for a torque of ± 50 Nm.

(Invention Example 2)
Permendule (trade name YEP-2V, 49% Co-2% V-Fe, manufactured by Hitachi Metals, Ltd.) was used as the material of the shaft 1, and heat treatment was performed to ensure the magnetic properties of the permendur. (In a vacuum, preferably in an H ₂ atmosphere, held at 850 ° C. for 3 hours and then cooled in the furnace as it is), using the shaft obtained by repeating the same operation as in the above invention example 1, Based on this, the output characteristics of the Hall sensor 4 were similarly investigated.
As a result, although the sensitivity was slightly inferior, a characteristic with almost no hysteresis was obtained.

(Invention Example 3)
As the material of the shaft 1, the carbon steel for mechanical structure S40C specified in JIS G4051 is used, induction hardening is performed as heat treatment, and then tempering treatment is performed at 170 ° C. × 2 hours. Using the shaft obtained by repeating the same operation, the output characteristics of the Hall sensor 4 were similarly investigated under the same conditions. The purpose of the heat treatment is that the surface hardness is HRC50 or more, the effective hardened layer depth of HRC45 or more is 0.8 mm or more, and the surface hardness and hardened layer depth after tempering satisfy the target conditions. It was.
As a result, although the sensitivity was slightly inferior, a characteristic with almost no hysteresis was obtained as in the case of the invention example 2.

(Comparative example)
The above invention example, except that carbon steel S40C for mechanical structure is used as the shaft material to be measured, and the induction hardening and tempering treatment is performed as heat treatment in the same manner as in the above invention example 3, and the spiral groove 2a is not formed on the shaft. Using the shaft obtained by repeating the same operation as 1, the output characteristics of the Hall sensor were similarly investigated under the same conditions.
As a result, the sensitivity was somewhat low, but the characteristic showed a lens-like hysteresis (level of 20% or more).

It is explanatory drawing which shows an example of embodiment of the torque detection apparatus of this invention. (A) It is a front view which shows the example of a form of the torque detection apparatus which provided the yoke in the magnetic sensor shown in FIG. (B) It is a top view of the torque detection apparatus shown to Fig.2 (a). It is explanatory drawing which shows the example which added the magnetic sensor to the torque detection apparatus shown in FIG. (A) It is a front view which shows the example of a form of the torque detection apparatus which added the rotation detection part to the apparatus of FIG. (B) It is a top view of the torque detection apparatus shown to Fig.4 (a). (C) It is expansion explanatory drawing which shows the shape of the ring magnet shown to Fig.4 (a) and (b). (A) It is a graph which shows the rotation detection signal in the torque detection apparatus shown in FIG. (B) It is a graph which shows the torque detection signal in the torque detection apparatus shown in FIG. (C) It is a graph which shows the torque detection signal after correction | amendment in the torque detection apparatus shown in FIG. It is a graph which shows an example of the sensor output characteristic data in the torque detection apparatus shown in FIG. It is a schematic explanatory drawing which shows the structure of the conventional groove type torque sensor. It is a schematic explanatory drawing which shows the structure of the conventional ring fitting system torque sensor. It is a schematic explanatory drawing which shows the structure of the conventional band-shaped magnetization type torque sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Axis 2 Groove formation zone 2a Spiral groove 3 Magnetized part 4, 6 Hall sensor (magnetic sensor)
5 Yoke 7 Ring magnet 8 Hall IC (second magnetic sensor)

Claims (14)

  An axis having a groove forming band having a plurality of spiral grooves inclined in a direction of about 45 degrees with respect to the axis, and having a magnetized portion magnetized in the circumferential direction on the groove forming band; A torque detection device comprising a magnetic sensor disposed to face the groove forming band portion.   The torque detection device according to claim 1, wherein the magnetized portion is formed in a band shape.   3. The torque detection device according to claim 1, wherein the magnetic sensor is disposed at a position near an end of the shaft groove forming band.   2. The magnetic sensor according to claim 1, wherein two of the magnetic sensors are arranged side by side in the axial direction, and are arranged at positions near both ends of the groove-forming band of the shaft, respectively. The torque detection device described in 1.   The torque detection device according to any one of claims 1 to 4, wherein a yoke is disposed on a side opposite to the axis of the magnetic sensor.   6. The torque detector according to claim 5, wherein the yoke is made of a soft magnetic material.   The torque detection device according to claim 5 or 6, wherein the yoke has a size substantially equal to a groove forming band width of the shaft.   The torque detection apparatus according to claim 1, further comprising a rotation detection unit that detects rotation of the shaft.   The rotation detection unit includes a ring magnet attached to a portion near the groove forming band of the shaft, and a second magnetic sensor for detecting rotation arranged to face the ring magnet. The torque detection device according to claim 8.   The torque detection device according to claim 9, wherein the ring magnet is multipolarly magnetized.   The torque detection device according to claim 9 or 10, wherein a signal of the magnetic sensor for torque detection and a signal of the second magnetic sensor for rotation detection are synchronized.   13. The torque detection device according to claim 12, wherein signal processing is performed based on a signal of the second magnetic sensor for detecting rotation, and fluctuation of the signal accompanying rotation of the magnetic sensor for detecting torque is corrected and output. .   The torque detection device according to any one of claims 1 to 12, wherein the shaft is heat-treated steel.   The torque detection device according to any one of claims 1 to 13, wherein the magnetic sensor is a Hall element or a Hall IC.

Images