JPH0747712Y2 - Magnetostrictive torque sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a magnetostrictive torque sensor for detecting torque generated in an output shaft of an automobile engine, for example.

[Conventional technology]

Generally, in an automatic vehicle equipped with an automatic transmission mechanism, a torque sensor is attached to a propeller shaft to optimize the shift timing of the automatic transmission mechanism.

As such a torque sensor, as shown in FIG. 3 and FIG.
A bridge circuit type magnetostrictive torque sensor shown in the figure is known.

In FIG. 3, reference numeral 1 denotes a cylindrical casing. The casing 1 is made of non-magnetic stainless steel or the like in a stepped cylindrical shape as shown in the figure, and is fixedly mounted on a vehicle body (not shown) or the like. It has become. Reference numeral 2 denotes a magnetostrictive shaft as a rotary shaft formed of a magnetostrictive material such as chrome molybdenum steel. The magnetostrictive shaft 2 is provided, for example, in the middle of a propeller shaft, and both ends thereof are an input side mounting portion 2A and an output side mounting portion. 2B, and the middle of these is the slit forming part 2C.
Thus, the outer circumference of the slit forming portion 2C has a first slit 3 engraved downward 45 ° and a second slit 3 engraved upward 45 °.
The slits 4 are provided so as to face each other. The magnetostrictive shaft 2 is rotatably arranged in the casing 1 via bearings 5, 5.

Reference numeral 6 denotes a core cylinder as a core member which is located between the magnetostrictive shaft 2 and the casing 1 and fixed to the inner peripheral surface of the casing 1. The core cylinder 6 is a PB permalloy made of, for example, an alloy of nickel and iron. It is formed into a stepped cylindrical shape by a magnetic material such as, and has a semi-longitudinal sectional shape of E shape as shown in the drawing. The core tube 6 includes a first core portion 6A of the slits 3 and 4 of the magnetostrictive shaft 2 that faces the slit 3 in the radial direction and a second core portion 6B that faces the slit 4 in the radial direction. The core portions 6A and 6B are integrally formed.

Reference numerals 7 and 7 denote a pair of coil bobbins respectively provided in the core portions 6A and 6B of the core tube 6, and each coil bobbin 7 is formed in a tubular shape using a non-magnetic material and a high magnetic permeability, for example, a resin material or the like. , Its half-section is U-shaped. Reference numerals 8 and 9 denote a pair of detection coils wound around the coil bobbins 7, and the detection coils 8 and 9 are arranged in the core portions 6A and 6B of the core cylinder together with the coil bobbins 7, and the slits of the magnetostrictive shaft 2 are provided. It is arranged to face 3, 4 in the radial direction. The self-inductance of the detection coils 8 and 9 is L ₁ L ₂
And the iron loss and the direct current resistance are shown as r and r, respectively.

Further, FIG. 4 shows a detection circuit, which is composed of a bridge circuit 10, an AC power supply 11, a differential amplifier 12, and the like. Here, the bridge circuit 10 includes detection coils 8 and 9, iron loss and DC resistance r of each detection coil 8 and 9, fixed resistances R and R.
And a voltage adjusting resistor R ₀ are connected as a bridge as shown in the figure. Between the connection points a and b, an AC power supply 1 of frequency f and voltage V
It is connected to 1, and the connection points c and d are the output voltage of the detection coils 8 and 9.
It serves as an output terminal for deriving V ₁ and V ₂ , the connection points c and d are connected to the input side of the differential amplifier 12, and the sensor output voltage E corresponding to the detected torque is output from the output terminal 13 of the differential amplifier 12. It is designed to output ₀ . The voltage adjusting resistor R ₀ is adjusted so that the output voltage E ₀ becomes zero when the torque acting on the magnetostrictive shaft 2 is zero.

In the bridge circuit type magnetostrictive torque sensor configured as described above, when an AC voltage V of the AC power supply 11 is applied to the detection coils 8 and 9, a magnetic path is formed on the surface of the magnetostrictive shaft 2, but a slit is formed. Since the slits 3 and 4 in the 45 ° direction are provided on the surface of the portion 2C, the magnetic path due to the surface magnetic field is formed along the slits 3 and 4.

On the other hand, if a torque T in the direction of the arrow in the drawing is applied to the input side mounting portion 2A of the magnetostrictive shaft 2, a tensile stress + σ is generated in the slit 3 and a compressive stress −σ is generated in the slit 4. When a positive magnetostrictive material is used for the magnetostrictive shaft 2, it is known that the tensile stress + σ increases the magnetic permeability μ and the compressive stress −σ decreases the magnetic permeability μ.

Therefore, the self-inductance of the detection coils 8 and 9 L ₁ and L
₂ is However, μ: permeability N: number of coil windings S: magnetic path cross-sectional area l: average magnetic path length, and in bridge circuit 10, L ₁ and R and L ₂ and R are connected in series, so Current flowing through coils 8 and 9
i ₁ and i ₂ are Becomes

Further, the output voltages V ₁ and V _{2 at} the connection points c and d are V ₁ = i ₁ R, V ₂ = i ₂ R (3), and the sensor output from the output terminal 13 of the differential amplifier 12 The voltage E ₀ is given by the following equation (4) when the amplification factor is α.

E ₀ = α × (V ₂ −V ₁ ) ... (4) Thus, when the torque T is applied to the magnetostrictive shaft 2, the permeability μ increases due to the tensile stress + σ on the slit 3 side. The inductance L ₁ increases, the current i ₁ decreases, and the output voltage V ₁ decreases. On the slit 4 side, the magnetic permeability μ decreases due to the compressive stress −σ, and as a result, the self-inductance L ₂ of the detection coil 9 decreases.
The current i ₂ increases and the output voltage V ₂ increases. This allows
The sensor output voltage E ₀ of the equation (4) is E ₀ > 0, and a detection signal proportional to the torque T can be output as the sensor output voltage E ₀ .

[Problems to be solved by the device]

By the way, in the above-mentioned conventional technique, since the core portion 6A on the detection coil 8 side and the core portion 6B on the detection coil 9 side are integrally formed by the core tube 6, the magnetic fluxes of the core portions 6A and 6B are mutually different. Due to the interference, the mutual inductance L _M of the detection coils 8 and 9 increases, and the output voltage V ₁ shown in the equation (3),
V ₂ is affected by mutual inductance L _M , and output voltage V ₂ , V ₁
There is a problem that the difference between the two becomes small and the initial characteristic output decreases.

That is, assuming that the degree of electromagnetic coupling between the detection coils 8 and 9 is the coil coupling coefficient K ₀ (K ₀ ≦ 1), the mutual inductance L _M
Is Therefore, in the conventional technique, since the core portions 6A and 6B are integrally formed, the coupling coefficient K _{0 of the} coil is substantially increased to K ₀ = 1 and the initial characteristic output cannot be improved. .

The present invention has been made in view of the above-mentioned problems of the prior art. The present invention provides a magnetostrictive torque sensor that can reduce the mutual inductance of a pair of detection coils and effectively improve the initial characteristic output. It is provided.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, the present invention provides a tubular casing, a magnetostrictive shaft rotatably disposed in the casing, and a magnetostrictive shaft provided in the casing so as to surround an outer peripheral side thereof. A single and cylindrical bobbin member made of a non-magnetic material in which a pair of coil bobbin portions are formed on both sides in the axial direction, and a fixed portion of the bobbin member. A pair of detection coils wound around the coil bobbin portions located on both sides in the axial direction with sandwiching them, and the bobbin member in a state of being spaced apart on both sides in the axial direction of the bobbin member in order to cover each coil bobbin portion together with the detection coil from the outside. It is composed of a pair of core cylinders each made of a magnetic material.

[Action]

With the above structure, a single tubular bobbin material made of a non-magnetic material is integrally formed with a pair of coil bobbin portions on both sides in the axial direction with an axially fixed portion sandwiched therebetween, and then each of the coil bobbins is formed. Since a separate core cylinder is provided in each part along with each detection coil, the coupling coefficient indicating the degree of electromagnetic coupling between these detection coils can be significantly reduced, and the mutual inductance between the detection coils can be significantly reduced. Can be reduced.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. In the embodiment, the same components as those of the prior art shown in FIG. 3 and FIG. 4 described above are designated by the same reference numerals and the description thereof will be omitted.

Thus, FIG. 1 shows a first embodiment of the present invention.

In the figure, reference numeral 21 designates a magnetostrictive shaft rotatably arranged in the casing 1. The magnetostrictive shaft 21 is formed in substantially the same manner as the magnetostrictive shaft 2 described in the prior art, and its slit forming portion 21C has an axial direction. First slit 2 with a predetermined distance
2 and a second slit 23 are provided.

Reference numeral 24 denotes a bobbin member provided in the casing 1 so as to surround the outer peripheral surface of the magnetostrictive shaft 21 with a small gap, and the bobbin member 24 is a stepped cylinder made of a nonmagnetic material such as a resin material. Shaped like a slit, with both ends slit
It extends in the axial direction of the magnetostrictive shaft 21 to a position facing 22,23. Here, the bobbin member 24 is located at an intermediate portion in the axial direction and has a fixing portion 24A formed in a thick-walled cylindrical shape with an outer diameter corresponding to the inner diameter of the casing 1, and is located at both axial end portions, and has a semi-longitudinal section. A pair of coil bobbin portions 24B, 24B formed in a stepped cylindrical shape so that the surface has a two-character shape, and thin-walled cylindrical connecting portions 24C, 24C connecting the coil bobbin portions 24B and the fixing portion 24A. It consists of and.

Further, conical recesses 24D, 24, ... Are formed on the outer periphery of the fixed portion 24A of the bobbin member 24 at predetermined intervals in the circumferential direction,
The bobbin member 24 is fitted and inserted into the casing 1 through the fixing portions 24A together with the core cylinders 28 and the like, which will be described later, and when assembled, the tips of the fixing screws 25, 25, ... As a result, the casing 1 is positioned with high accuracy.

Reference numerals 26 and 27 denote a pair of detection coils wound around each coil bobbin portion 24B of the bobbin member 24. The detection coils 26 and 27 are formed in the same manner as the detection coils 8 and 9 described in the prior art, and the magnetostrictive shaft 21 The slits 22 and 23 are opposed to each other in the radial direction. Reference numerals 28 and 29 denote a pair of core cylinders provided in each coil bobbin portion 24B of the bobbin member 24 so as to cover the detection coils 26 and 27 from the outside, and each core cylinder 28 is, for example, PB made of an alloy of nickel and iron. A core member 29 made of a magnetic material such as permalloy and having a semi-longitudinal section of a substantially L shape.
And a pair of half rings are fitted to the outer periphery of the connecting portion 24C of the bobbin member 24 from the outside in the radial direction, thereby connecting the connecting portion 24C.
It is composed of a core ring 30 provided on the outer periphery.

Here, each core cylinder 28 is fixed to each coil bobbin portion 24B of the bobbin member 24 by crimping the crimping portion 29A formed on the tip side of each core member 29 to the outer periphery of each core ring 30, and each core member 29 is adapted to sandwich each coil bobbin portion 24B together with each core ring 30 in the axial direction.
Then, each core cylinder 28 surrounds the slits 22, 23 of the magnetostrictive shaft 21 together with the detection coils 26, 27, etc.
A magnetic path based on the magnetic field generated at 6, 27 is formed on the surface of the magnetostrictive shaft 21. Further, the core cylinders 28 are arranged in the casing 1 so as to be axially separated from each other via the bobbin member 24. Harness outlets 29B and 29B for taking out harnesses for the detection coils 26 and 27 are axially formed on the bottom side of each core member 29.

The magnetostrictive torque sensor according to the present embodiment has the above-mentioned configuration, and the basic detecting operation is not different from that according to the prior art.

Therefore, in this embodiment, the detection coils 26 and 27 are wound around the coil bobbin portions 24B formed on both axial sides of the bobbin member 24, and the coil bobbin portions 24B are separately provided so as to cover the outer sides of the detection coils 26 and 27. Core barrels 28, 28 are provided, the bobbin member 24 is inserted between the casing 1 and the magnetostrictive shaft 21 together with the core barrels 28, and these are fixed by the fixing portion 24A of the bobbin member 24 via the fixing screws 25 to the casing. Since it is configured to be fixedly mounted inside 1, the separate core cylinders 28, 28 can be largely separated in the axial direction of the magnetostrictive shaft 21 by the bobbin member pump 24 made of a non-magnetic material, and the detection coils 26, 27
Thus, the magnetic fluxes generated in the core cylinders 28 can be prevented from interfering with each other, and the mutual inductance L _M can be effectively reduced. That is, according to the present embodiment, the core cylinders 28 are axially separated from each other with the fixed portions 24A of the bobbin member 24 sandwiched between the detection coils 26 and 27, which indicates the electromagnetic coupling degree between the detection coils 26 and 27. The coupling coefficient K ₀ in the equation (5) can be significantly reduced to reduce the mutual inductance L _M, and the difference between the output voltages V ₂ and V ₁ shown in the equation (3) can be minimized. Therefore, the initial characteristic output can be improved.

Further, since each coil bobbin portion 24B is integrally formed on both axial ends of the bobbin member 24B and the core barrels 28, 28 which are separate bodies are attached to the respective coil bobbin portions 24B, the bobbin member 2
It is possible to improve the assembling accuracy in the radial direction and the thrust direction of each core cylinder 28 with respect to 4. Then, conical recesses 24D are formed on the outer periphery of the fixed portion 24A of the bobbin member 24, and the tips of the fixing screws 25 screwed into the casing 1 are fitted into the recesses 24D. The bobbin member can be positioned with high accuracy together with the core cylinder 28, etc., and the eccentricity error in the radial direction with respect to the magnetostrictive shaft 21 and the thrust direction (slit
It is possible to effectively reduce errors and the like (with respect to 22,23) and improve the assembling accuracy, so that various effects can be obtained.

Next, FIG. 2 shows a second embodiment of the present invention. In this embodiment, the same components as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted. The feature of this embodiment is that each core cylinder 31 is formed by a pair of core halves 32, 32, and the core halves 32, 32 can be abutted against each other at the abutting surfaces 32A, 32A and can be divided. There is that. Here, the core tube 31
Is assembled by splitting the core halves 32, 32 into the coil bobbin portion 24B of the bobbin member 24 from the outside in the radial direction, and abutting the outer periphery of the coil bobbin portion 24B as shown in FIG. It is firmly bonded with an adhesive or the like. And, semicircular collar parts 32B, 32B, 32C, 32C are integrally formed on the core half-split bodies 32, 32 of the core cylinder 31 at both axial ends, and each of the collar parts 32C is the first one. It constitutes a portion corresponding to the core ring 30 of the core cylinder 28 described in the embodiment. Reference numerals 33 and 33 denote harness outlets for the coils 26 and 27.

Thus, in this embodiment configured as described above, substantially the same operation and effect as in the first embodiment can be obtained. In particular, in this embodiment, the core cylinder 31 is composed of the core halves 32. However, since the collar portions 32B and 32C are integrally formed on these, a core member like the core cylinder 28 used in the first embodiment is formed.
It is possible to eliminate the possibility that the magnetic path is divided between the 29 and the core ring 30.

[Effect of device]

As described above in detail, according to the present invention, the coil bobbin portions are integrally formed on both sides in the axial direction with the fixed portion of the single and cylindrical bobbin member made of a non-magnetic material sandwiched between the coil bobbin portions. Since a core tube made of a magnetic material separate from the bobbin member is provided on both sides in the axial direction so as to cover the rotated detection coils, the magnetic field is generated in each detection coil. At this time, the magnetic fluxes formed in the core cylinders are prevented from interfering with each other, and the mutual inductance between the detection coils can be reduced by reducing the coupling coefficient of the mutual inductance, and the initial characteristic output can be reduced. In addition to the improvement, the accuracy of assembling each core cylinder with respect to the bobbin member can be improved, and these can be positioned in the casing with high accuracy.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a magnetostrictive torque sensor showing a first embodiment of the present invention, FIG. 2 is a perspective view of a core cylinder showing a second embodiment, and FIGS. 3 and 4 are prior arts. FIG. 3 is a longitudinal sectional view of the magnetostrictive torque sensor, and FIG. 4 is a circuit configuration diagram of the detection circuit. 1 ... Casing, 21 ... Magnetostrictive shaft, 22,23 ... Slit, 24 ... Bobbin member, 24A ... Fixed part, 24B ... Coil bobbin part, 26, 27 ... Detection coil, 28, 31 ... Core cylinder.

Claims (1)

[Scope of utility model registration request] 1. A tubular casing, a magnetostrictive shaft rotatably disposed in the casing, and a magnetostrictive shaft provided in the casing so as to surround an outer peripheral side thereof.
A single and cylindrical bobbin member made of a non-magnetic material having a pair of coil bobbin portions formed on both sides in the axial direction serves as a fixing portion fixed to the casing, and the fixing portion of the bobbin member is sandwiched. A pair of detection coils respectively wound around the coil bobbin portions located on both sides in the axial direction, and the bobbin member in a state of being spaced apart on both axial directions of the bobbin member in order to cover each coil bobbin portion together with the respective detection coils from the outside. A magnetostrictive torque sensor including a pair of core cylinders each made of a magnetic material.