JPH0545538U - Magnetostrictive torque sensor - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent the magnetic flux that has entered the magnetostrictive shaft from leaking out and becoming a leakage magnetic flux, and improve the torque detection sensitivity. [Structure] On the outer peripheral side of the magnetostrictive shaft 2, each core member 6,
7 is located between the leg portions 6B and 7B, and the slit grooves 4,
5, cylindrical coating layers 21 and 21 are provided to cover the respective coating layers 2
No. 1 has a configuration in which it is made of a non-magnetic material having a magnetic permeability lower than that of air and having conductivity. Therefore, since each coating layer 21 is non-magnetic, the magnetic flux penetrating into the magnetostrictive shaft 2 from each leg 6B, 7B is exposed to the outside (air gap δ).
To prevent you from jumping in). Further, since each coating layer 21 has conductivity, even when the magnetic flux inside the magnetostrictive shaft 2 enters into each coating layer 21, this magnetic flux is reduced by the eddy current loss. Further, as the conductivity increases, the thickness dimension S1 from the surface, which is the range where the skin effect occurs, decreases, and the density of the magnetic flux flowing in the magnetostrictive shaft 2 increases.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a magnetostrictive torque sensor suitable for use in detecting torque generated in an output shaft of an automobile engine, for example.

[0002]

[Prior Art]

 FIGS. 3 to 5 show examples in which the magnetostrictive torque sensor according to the related art is used for torque detection of an automobile engine.

In the figure, 1 is a cylindrical casing fixed to a vehicle body (not shown) of an automobile, 2 is rotatably disposed in the casing 1 via bearings 3 and 3, and a propeller shaft, Magnetostrictive shafts forming an output shaft and a drive shaft are respectively shown. The magnetostrictive shaft 2 is formed of a magnetostrictive material such as chrome molybdenum steel into a cylindrical shape, and a sensor portion 2A is integrally formed at an axially intermediate portion thereof. .. Further, on the outer peripheral surface of the sensor portion 2A, a large number of one-side slit grooves 4, 4, ... Engraved at an angle of 45 ° downward, and facing the respective one-side slit grooves 4 are provided. A large number of other side slit grooves 5, 5, ... Engraved at an angle of 45 ° are provided.

Reference numeral 6 denotes a one-side core member that is located on the outer peripheral side of each one-side slit groove 4 and is provided on the inner peripheral surface of the casing 1. The one-side core member 6 is a ferrite member as shown in FIG. Is formed into a cylindrical shape by abutting a pair of core pieces 6A, 6A formed in a bottomed stepped cylindrical shape from a magnetic material such as The annular leg portions 6B extending in the respective directions are formed. Reference numeral 7 denotes the other side core member provided on the outer peripheral side of each of the other side slit grooves 5 so as to face the one side core member 6, and the other side core member 7 also has a ferrite core similar to the one side core member 6. It is formed of a pair of core pieces 7A, 7A made of magnetic material such as, and each of the core pieces 7A is formed with an annular leg portion 7B. A small air gap δ of, for example, about 1 mm is formed between the core members 6 and 7 and the magnetostrictive shaft 2. The core members 6 and 7 form the magnetic circuit shown in FIG. 5 together with the magnetostrictive shaft 2 and the like.

Reference numerals 8 and 9 denote one side coil bobbin and the other side coil bobbin provided on the inner peripheral side of the core members 6 and 7, and 10 and 11 denote excitation and detection coils wound around the coil bobbins 8 and 9. One coil and the other coil are shown, respectively, and each of the coils 10 and 11 is formed in a bridge circuit together with an adjusting resistor, and is connected to a detection circuit (not shown) including an oscillator and a differential amplifier. ing. Here, each of the coils 10 and 11 is configured as an exciting coil that is excited by a high frequency voltage from the oscillator to generate a magnetic flux and a detecting coil that detects a magnetic flux flowing in a magnetic circuit 15 described later. Has been.

Reference numerals 12 and 12 denote outer spacers provided at the ends of the core members 6 and 7, and 13 denotes inner spacers disposed between the core members 6 and 7, respectively. Is to engage and position the core pieces 6A and 7A of the core members 6 and 7, respectively. The core members 6, 7 and the like integrated by the spacers 12, 13 are fixed to the inner peripheral surface of the casing 1 by the C rings 14, 14.

Further, reference numeral 15 denotes a magnetic circuit formed from the core members 6, 7 to the magnetostrictive shaft 2 by the magnetic flux generated by the coils 10, 11, and the magnetic circuit 15 is as shown in FIG. An in-core magnetic path 15A formed in each core member 6, 7 and having a magnetic resistance R1 is formed between each leg 6B, 7B of each core member 6, 7 and the magnetostrictive shaft 2, and a magnetic resistance R2 is formed. And a pair of core-shaft magnetic paths 15B and 15B having a magnetic resistance R3 between the legs 6B and 7B via the coil bobbins 8 and 9, respectively, and an air gap. It is formed in δ by bypassing the magnetic paths 15B between the core and the shaft, and is formed along the slit grooves 4 and 5 in the magnetostrictive shaft 2 and the shaft outer magnetic path 15D having the magnetic resistance R4. And has a magnetic resistance R5 And a shaft within the magnetic path 15E. Here, each of the magnetic resistances R1, R2, R3, R4, R5 is

[0008]

[Equation 1] S: magnetic path cross-sectional area μ: magnetic permeability

Reference numerals 16 and 16 are C rings for fixing the magnetostrictive shaft 2 to the casing 1.

The magnetostrictive torque sensor according to the prior art has the above-described configuration. When an AC voltage is applied to the coils 10 and 11 from the oscillator of the detection circuit, for example, as shown by a chain double-dashed line in FIG. Magnetic flux is generated from each of the coils 10 and 11. Then, this magnetic flux enters the magnetostrictive shaft 2 from the core members 6 and 7 through the air gap δ and flows along the slit grooves 4 and 5 on the surface of the magnetostrictive shaft 2, while the magnetostrictive shaft 2 is being moved. It flows back into the core members 6 and 7 from 2 through the air gap δ, whereby the magnetic circuit 15 shown in FIG. 5 is formed. Here, the self-inductance L of each coil 10, 11 is Rt and the number of coil turns is N, where Rt is the total magnetic resistance obtained by combining the magnetic resistances R1 to R5.

[0011]

## EQU00002 ## It can be obtained as L = N2 / Rt.

Further, when the oscillation frequency of the oscillator becomes high, a so-called skin effect occurs, and the magnetic flux in the magnetostrictive shaft 2 falls within a predetermined thickness dimension S range obtained from the surface of the magnetostrictive shaft 2 by the following mathematical formula 3. It will flow intensively.

[0013]

[Equation 3] Where α: conductivity ω: angular frequency

When a counterclockwise torque T is applied to one end side of the magnetostrictive shaft 2 as shown in FIG. 3, tensile stress + σ is generated along the one side slit groove 4 and the other side slit groove 5 is generated. A compressive stress −σ is generated along the line. As a result, the magnetic permeability μ of the magnetostrictive shaft 2 on the one side slit 4 side increases due to the tensile stress + σ, and the magnetic resistance R5 of the in-shutter magnetic path 15E decreases, while the magnetic permeability μ on the other side slit 5 side decreases. It becomes smaller due to the compressive stress −σ, and the magnetic resistance R5 becomes larger. As a result, the total magnetic resistance Rt of the one-side coil 10 decreases and the self-inductance L increases, while the other side coil 11 increases the total magnetic resistance Rt and the self-inductance L of the other coil 11 decreases. The balance is lost and an output voltage corresponding to the torque T appears in the differential amplifier.

On the contrary, when a clockwise torque is applied to the one end side of the magnetostrictive shaft 2, a compressive stress −σ is generated along the one side slit groove 4 to reduce the magnetic permeability μ, Since tensile stress + σ is generated along the other side slit groove 5 and the magnetic permeability μ increases, the self-inductance L of the one side coil 10 decreases and the self-inductance L of the other side coil 11 increases, resulting in a differential A voltage corresponding to this reverse torque is output from the amplifier.

[0016]

[Problems to be solved by the device]

 By the way, in the above-described conventional magnetostrictive torque sensor, an AC voltage is applied to each coil 10 and 11 to generate a magnetic flux, and the magnetic circuit 15 extending over each core member 6 and 7, the air gap δ, and the magnetostrictive shaft 2 is generated. This torque is detected by utilizing the fact that the magnetic resistance R5 of the in-shaft magnetic path 15E changes due to the torque generated and transmitted from the outside. However, the magnetic flux that has entered the magnetostrictive shaft 2 from the legs 6B and 7B of the core members 6 and 7 via the air gap δ does not all flow in the magnetic path 15E in the shaft. As shown by the dotted line in FIG. 3, a part of the magnetic flux does not flow along the slit grooves 4 and 5 but jumps out of the magnetostrictive shaft 2 into the air gap δ to form a leakage magnetic flux, which bypasses the internal magnetic path 15E of the shaft. 15D will be formed.

Therefore, according to the above-described conventional technique, the magnetic flux flowing through the in-shaft magnetic path 15E is reduced, which not only significantly reduces the torque detection sensitivity but also reduces the torque detection signal. There is a problem in that it is easily affected by noise generated by vehicle vibrations, etc., and detection accuracy and reliability are greatly reduced.

The present invention has been made in view of the above-described problems of the prior art, and prevents the magnetic flux that has entered the magnetostrictive shaft from leaking out and becoming a leakage magnetic flux, so that the torque detection sensitivity can be improved. An object of the present invention is to provide a magnetostrictive torque sensor.

[0019]

[Means for Solving the Problems]

 In order to solve the above problems, the feature of the configuration adopted by the first invention is that a coating layer is provided on the outer peripheral side of the magnetostrictive shaft between each leg of the core member, and the coating layer is It is made of a non-magnetic material.

The feature of the configuration adopted by the second invention is that a coating layer is provided on the outer peripheral side of the magnetostrictive shaft between each leg of the core member, and the coating layer is made of a conductive material. It has been formed.

[0021]

[Action]

 With the configuration of the first invention, the coating layer made of a non-magnetic material prevents the magnetic flux that has entered the magnetostrictive shaft from each leg of the core member from jumping out and prevents the generation of leakage magnetic flux. it can.

According to the structure of the second invention, when the magnetic flux that has entered the magnetostrictive shaft from each leg of the core member jumps out of the magnetostrictive shaft and enters the coating layer made of a conductive material, the coating film is formed. Eddy currents are generated in the layers, which can reduce this magnetic flux and prevent the generation of leakage flux.

[0023]

【Example】

 An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. In the embodiments, the same components as those of the above-described conventional technique are designated by the same reference numerals, and the description thereof will be omitted.

In the figure, reference numerals 21 and 21 are located between the leg portions 6 B and 7 B of the core members 6 and 7, respectively, and are provided on the outer peripheral side of the magnetostrictive shaft 2 so as to cover the slit grooves 4 and 5. A cylindrical coating layer is shown, and each coating layer 21 is a non-magnetic material having a magnetic permeability μ lower than that of air and a conductive material such as copper, aluminum, gold, silver, etc. It is formed with L and a thickness t.

Here, the length dimension L is set to allow the magnetic flux to enter the magnetostrictive shaft 2 from the legs 6B and 7B of the core members 6 and 7 via the air gap δ. The air gap is formed so as to be substantially equal to the length between the portions 6B and 7B, and the thickness t is set so as to prevent the film layers 21 from slidingly contacting the coil bobbins 8 and 9. It is formed to be smaller than δ.

The magnetostrictive torque sensor according to the present embodiment has the above-described configuration, and its basic operation is not significantly different from that of the conventional art.

However, in the magnetostrictive torque sensor according to the present embodiment, the slit grooves 4 and 5 are located on the outer peripheral side of the magnetostrictive shaft 2 between the leg portions 6B and 7B of the core members 6 and 7, respectively. The cylindrical coating layers 21 and 21 are provided, and each coating layer 21 is formed of a material such as copper, aluminum, gold, or silver which has a magnetic permeability μ lower than that of air and is nonmagnetic and has conductivity. Therefore, the following effects are achieved.

First, since each coating layer 21 is non-magnetic, the magnetic flux that has entered the magnetostrictive shaft 2 from each leg 6B, 7B is ejected to the outside (in the air gap δ) by each coating layer 21. Can be effectively shielded by preventing the magnetic flux from leaking, the leakage magnetic flux from being generated in the air gap δ, and the magnetic flux flowing in the shaft outer magnetic path 15D of the magnetic circuit 15 can be greatly reduced. As a result, it is possible to prevent the magnetic flux flowing in the magnetostrictive shaft 2 from decreasing, greatly improve the torque detection sensitivity, and improve the detection accuracy and reliability.

Secondly, since each coating layer 21 has conductivity, even if the magnetic flux inside the magnetostrictive shaft 2 penetrates into each coating layer 21, this magnetic flux can be effectively reduced by eddy current loss. As a result, leakage magnetic flux can be prevented from being generated, and torque detection sensitivity can be greatly improved. Further, as shown in the above mathematical expression 3, when the conductivity α becomes higher, the range in which the skin effect occurs, that is, the thickness dimension S from the surface becomes smaller. A thickness dimension S1 (S1 <S) smaller than the dimension S can be effectively obtained. As a result, the density of magnetic flux flowing in the magnetostrictive shaft 2 can be improved, and the torque detection sensitivity can be further improved.

In the above-mentioned embodiment, each coating layer 21 is described as being formed in a cylindrical shape so as to cover each slit groove 4 and 5, but the present invention is not limited to this, and for example, FIG. As shown in the modified example, each film layer 31 is formed with a projection 31A corresponding to each slit groove 4 and 5, and each projection 31A is fitted into each slit groove 4 and 5. It may be provided. In this case, it is possible to effectively prevent the magnetic flux flowing in the magnetostrictive shaft 2 from entering the slit grooves 4 and 5 and shortening the magnetic path length. The accuracy can be improved.

In addition, in the above-mentioned embodiments, each coating layer 21 is described as being formed from a material such as copper, aluminum, gold, and silver which is non-magnetic and has conductivity lower than that of air and which is electrically conductive. However, instead of this, for example, when only the magnetic shielding effect due to non-magnetism is required, it may be formed from a non-magnetic material having no conductivity such as quartz glass.

Further, in the above-described embodiment, the two-coil type magnetostrictive torque sensor has been described as an example, but the present invention is not limited to this, and may be used, for example, in a four-coil type magnetostrictive torque sensor. ..

Further, in the above-described embodiment, the case where it is used for the torque detection of the automobile engine has been described as an example, but it can be used for other torque detection such as the torque of the rotating shaft of the electric motor.

[0034]

[Effect of the device]

 As described in detail above, according to the first invention, the coating layer made of the non-magnetic material can prevent the magnetic flux that has entered the magnetostrictive shaft from each leg of the core member from jumping out. As a result, it is possible to effectively prevent the magnetic flux in the magnetostrictive shaft from leaking out and becoming a leakage magnetic flux, prevent the magnetic flux flowing in the magnetostrictive shaft from decreasing, enhance the torque detection sensitivity, and improve the detection accuracy. And reliability can be improved.

According to the second invention, when the magnetic flux that has entered the magnetostrictive shaft from each leg of the core member jumps out of the magnetostrictive shaft and enters the coating layer made of a conductive material, the inside of the coating layer An eddy current is generated, which reduces this magnetic flux and prevents the generation of leakage magnetic flux. As a result, it is possible to improve the torque detection sensitivity, the torque detection accuracy, and the like, as in the first device. Further, as the conductivity increases, the range in which the skin effect occurs is reduced, so that the density of the magnetic flux flowing in the magnetostrictive shaft can be improved, and the torque detection sensitivity can be further improved.

[Brief description of drawings]

FIG. 1 is an enlarged longitudinal sectional view showing a main part of a magnetostrictive torque sensor according to an embodiment of the present invention.

FIG. 2 is an enlarged vertical cross-sectional view showing an essential part of a magnetostrictive torque sensor according to a modified example of the present invention.

FIG. 3 is a vertical sectional view showing a magnetostrictive torque sensor according to a conventional technique.

FIG. 4 is a longitudinal sectional view showing an enlarged main part in FIG.

FIG. 5 is a circuit diagram showing a magnetic circuit formed on a core member, a magnetostrictive shaft, and the like.

[Explanation of symbols]

 1 Casing 2 Magnetostrictive shaft 6 One side core member 6B, 7B Leg part 7 Other side core member 8 One side coil bobbin 9 Other side coil bobbin 10 One side coil (excitation and detection coil) 11 Other side coil (excitation and detection coil) 21 Coating layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideki Kano Inventor Hideki Kanogawa, Isesaki-shi, Gunma 1167-1 Nippon Electric Equipment Co., Ltd. Incorporated (72) Inventor Nobuaki Kobayashi 1671, Kasukawa-cho, Isesaki-shi, Gunma Nippon Electric Equipment Co., Ltd. (72) Inventor Atsumi Hoshina 1671, Kasukawa-cho, Isesaki-shi, Gunma Prefecture (72) Yoichi Katahira, Inventor Yoichi Katahira 167-1 Kasukawa-cho, Isesaki-shi, Gunma Nippon Electric Equipment Co., Ltd.

Claims (2)

[Scope of utility model registration request] 1. A cylindrical casing, a magnetostrictive shaft rotatably arranged in the casing, a magnetostrictive shaft provided in the casing so as to surround an outer peripheral side of the magnetostrictive shaft, and radially inward facing both ends. In order to detect a torque acting on the magnetostrictive shaft as an electric signal, a core member formed with an annular leg portion extending in the direction of the core member, a coil bobbin provided on the inner peripheral side of the core member, and wound around the coil bobbin. In a magnetostrictive torque sensor including at least a pair of excitation and detection coils, a coating layer is provided on the outer peripheral side of the magnetostrictive shaft between the legs of the core member, and the coating layer is nonmagnetic. A magnetostrictive torque sensor characterized by being formed of a material. 2. A tubular casing, a magnetostrictive shaft rotatably disposed in the casing, a magnetostrictive shaft provided in the casing so as to surround an outer peripheral side of the magnetostrictive shaft, and radially inward facing both ends. In order to detect a torque acting on the magnetostrictive shaft as an electric signal, a core member formed with an annular leg portion extending in the direction of the core member, a coil bobbin provided on the inner peripheral side of the core member, and wound around the coil bobbin. In a magnetostrictive torque sensor consisting of at least a pair of excitation and detection coils, a coating layer is provided on the outer peripheral side of the magnetostrictive shaft between the leg portions of the core member, and the coating layer is conductive. A magnetostrictive torque sensor characterized by being formed of a material.