Magnetostrictive torque sensor

Abstract

The present invention addresses the problem of satisfactorily ensuring the coaxiality between a bobbin and a magnetic ring and sufficiently ensuring the bonding strength between the bobbin and the magnetic ring regardless of temperature changes. [Solution] A magnetostrictive torque sensor (1) is provided with: a bobbin (3) having a bobbin-side cylindrical section (7) disposed around a rotating shaft (2), a cylindrical-surface-shaped bobbin-side fitting surface (8), and a bobbin-side locking hole (9); a detection unit (4) having a detection coil disposed around the bobbin-side cylindrical unit (7); a magnetic ring (5) having a ring-side cylindrical section (13) disposed around the detection section (4), a ring-side fitting surface (14) fitted to the bobbin-side fitting surface (8), and a ring-side locking hole (15); and a positioning member (6) bridged between the bobbin-side locking hole (9) and the ring-side locking hole (15).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a magnetostrictive torque sensor that measures a torque applied to a rotating shaft. BACKGROUND

[0002] As a sensor that measures a torque applied to a rotating shaft, a magnetostrictive torque sensor that measures a torque applied to a rotating shaft using a reverse magnetostrictive effect generated in the rotating shaft when a torque is applied to the rotating shaft has been known conventionally, as described in Japanese Patent Application Publication No. 2020-085814, for example.

[0003] The torque sensor described in Japanese Patent Application Publication No. 2020-085814 is configured by injection molding and combining an epoxy resin in a manner of covering a detection portion and a magnetic body ring of a strong magnetic body. The detection portion has a resin-made bobbin and a plurality of detection coils formed by winding an insulated wire on the bobbin. The magnetic body ring of the strong magnetic body is disposed in a manner of covering around the detection coils of the detection portion in order to suppress leakage of magnetic flux to the outside.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENTS

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-085814 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] In the magnetostrictive torque sensor, a magnetic circuit is formed in a manner of passing through the rotating shaft, the bobbin of the detection portion in which the detection coils are disposed on the outer periphery, and the magnetic body ring. Therefore, it is necessary to ensure the coaxiality of these rotating shaft, bobbin, and magnetic body ring well. In addition, the bobbin and the magnetic body ring need to be combined and fixed without relative displacement in the axial direction and the circumferential direction regardless of temperature changes.

[0009] The torque sensor described in Japanese Patent Application Publication No. 2020-085814 has room for improvement in terms of sufficiently ensuring the bonding strength of the bobbin and the magnetic body ring.

[0010] That is, the difference in linear expansion coefficient between the resin material that constitutes the bobbin and the metal material that constitutes the magnetic body ring is large. Therefore, with temperature changes, the tightness of the bobbin and the magnetic body ring decreases, and relative sliding (creep), i.e., relative rotation and / or relative displacement in the axial direction, is likely to occur between these bobbin and magnetic body ring.

[0011] It is also conceivable to bond the bobbin to the magnetic body ring with an adhesive, but in this case, there is a problem that the tightness of the bobbin to the magnetic body ring decreases in accordance with temperature changes.

[0012] On the other hand, it is also conceivable to ensure the axial coupling strength of the bobbin to the magnetic body ring by snap-fitting the claw portion to the locking recess after the bobbin with the claw portion and the magnetic body ring with the locking recess are combined in a state where the bobbin is elastically deformed. However, in this case, the following problem arises.

[0013] In order to well ensure the coaxiality of the bobbin to the magnetic body ring, it is necessary to fit without play in the radial direction by inside fitting or the like. That is, it is necessary to make the diameter (inner diameter or outer diameter) of the fitting portion of the bobbin with respect to the magnetic body ring and the diameter (outer diameter or inner diameter) of the magnetic body ring with respect to the bobbin substantially the same. Therefore, when the bobbin and the magnetic body ring are combined, even if the bobbin is elastically deformed, the claw portion becomes an obstacle, and thus the bobbin and the magnetic body ring cannot be fitted.

[0014] An object of the present disclosure is to achieve a magnetostrictive torque sensor structure capable of well ensuring the coaxiality of a bobbin to a magnetic body ring and sufficiently ensuring the coupling strength of the bobbin to the magnetic body ring regardless of temperature changes.

[0015] Solution to the problem

[0016] A magnetostrictive torque sensor of one embodiment of the present disclosure is a sensor that measures a torque applied to a rotating shaft having a magnetostrictive property, and includes a bobbin, a detection portion, a magnetic body ring, and a positioning member.

[0017] The bobbin includes a bobbin-side cylindrical portion arranged around the rotating shaft, a bobbin-side fitting surface that is a cylindrical surface, and a bobbin-side locking hole.

[0018] The detection portion includes a detection coil arranged around the bobbin-side cylindrical portion.

[0019] The magnetic body ring includes a ring-side cylindrical portion arranged around the detection portion, a ring-side fitting surface that fits with the bobbin-side fitting surface, and a ring-side locking hole.

[0020] The positioning member is provided in the bobbin-side locking hole and the ring-side locking hole.

[0021] In the magnetostrictive torque sensor of one embodiment of the present disclosure, the bobbin-side fitting surface and the ring-side fitting surface can be fitted without play in the radial direction. More preferably, the bobbin-side fitting surface and the ring-side fitting surface can be gap fitted without play in the radial direction, i.e., inside fitted.

[0022] In the magnetostrictive torque sensor of one embodiment of the present disclosure, the bobbin-side fitting hole can be formed to pass through the bobbin in the radial direction, and the positioning member can project in the radial direction from the opening portion on the side opposite to the magnetic body ring in the openings on both sides in the radial direction of the bobbin-side fitting hole.

[0023] The magnetostrictive torque sensor of one embodiment of the present disclosure can include a plurality of the above-described combinations of the bobbin-side fitting hole, the ring-side fitting hole, and the positioning member. Alternatively, the magnetostrictive torque sensor of one embodiment of the present disclosure can include one of the above-described combinations of the bobbin-side fitting hole, the ring-side fitting hole, and the positioning member.

[0024] In the magnetostrictive torque sensor of one embodiment of the present disclosure, the positioning member can be formed of a spring pin. Alternatively, the positioning member can be formed of a cylindrical or tubular pin, a screw, or the like.

[0025] In the magnetostrictive torque sensor of one embodiment of the present disclosure, the bobbin-side fitting surface can be provided on the inner circumferential surface of the bobbin, and the ring-side fitting surface can be provided on the outer circumferential surface of the magnetic body ring.

[0026] In this case, the bobbin can include a connection plate portion extending outward in the radial direction from an end portion on one side in the axial direction of the bobbin-side cylindrical portion and an outer diameter side cylindrical portion extending in the axial direction from an end portion on the other side in the radial direction of the connection plate portion. The inner circumferential surface of the bobbin can be formed by the inner circumferential surface of the outer diameter side cylindrical portion. The bobbin-side fitting hole can pass through the outer diameter side cylindrical portion in the radial direction. The ring-side fitting surface can be provided on an end portion on one side in the axial direction of the outer circumferential surface of the magnetic body ring. The ring-side fitting hole can be open at the ring-side fitting surface.

[0027] The present disclosure can be implemented by appropriately combining the above-described various embodiments as long as there is no contradiction.

[0028] Effects of Invention

[0029] According to the magnetostrictive torque sensor of one embodiment of the present disclosure, the coaxiality of the bobbin and the magnetic body ring can be favorably ensured, and the strength of the coupling of the bobbin and the magnetic body ring can be sufficiently ensured regardless of temperature change. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 FIG. 1 is a perspective view of a magnetostrictive torque sensor of a first example illustrating an embodiment of the present disclosure.

[0031] Figure 2 FIG. 2 is a cross-sectional view of the magnetostrictive torque sensor of the first example.

[0032] Figure 3 is an exploded perspective view of the magnetostrictive torque sensor of the first example, omitting the detection section.

[0033] Figure 4 is a cross-sectional schematic view showing one example of the detection section.

[0034] Figure 5 (A) and Figure 5 (B) are another example of the detection section, a development view of the detection coil viewed from the radial outer side, Figure 5 (A) is a view showing the first detection coil and the fourth detection coil, Figure 5 (B) is a view showing the second detection coil and the third detection coil.

[0035] Figure 6 is a view showing a detection circuit configured to include four detection coils.

[0036] Figure 7 is a perspective view of the magnetostrictive torque sensor of the second example of the embodiment of the present disclosure.

[0037] Figure 8 is a main part enlarged cross-sectional view of the magnetostrictive torque sensor of the second example.

[0038] Figure 9 is a view for explaining a method of stopping rotation of the magnetostrictive torque sensor of the second example with respect to the housing.

[0039] Figure 10 is a perspective view of the magnetostrictive torque sensor of the third example of the embodiment of the present disclosure.

[0040] Figure 11 is a view for explaining a method of stopping rotation of the magnetostrictive torque sensor of the third example with respect to the housing. DETAILED DESCRIPTION

[0041] [First Example]

[0042] Using Figures 1 to 3 The first example of the embodiment of the present disclosure is explained.

[0043] The magnetostrictive torque sensor 1 of the present example is a sensor that measures a torque applied to a rotating shaft 2 (refer to Figure 2 ) having a magnetostrictive property, and has a bobbin 3, a detection section 4, a magnetic body ring 5, and a positioning member 6.

[0044] In the following description, the axial direction, the radial direction, and the circumferential direction of the magnetostrictive torque sensor 1 refer to the axial direction, the radial direction, and the circumferential direction of the rotating shaft 2, unless otherwise specified. The axial direction, the radial direction, and the circumferential direction of the rotating shaft 2 coincide with the axial direction, the radial direction, and the circumferential direction of the bobbin 3, with the axial direction, the radial direction, and the circumferential direction of the detection unit 4, and with the axial direction, the radial direction, and the circumferential direction of the magnetic body ring 5.

[0045] The bobbin 3 has a bobbin-side cylindrical portion 7 disposed around the rotating shaft 2, a cylindrical surface-shaped bobbin-side fitting surface 8, and a bobbin-side locking hole 9.

[0046] The bobbin 3 is composed of a synthetic resin as a material having non-magnetic and non-conductive (insulating) properties. In this example, the bobbin 3 is integrally formed by injection molding of the synthetic resin. However, in the case of implementing the magnetostrictive torque sensor of one embodiment of the present disclosure, the bobbin 3 can also be composed by combining a plurality of components.

[0047] The bobbin-side cylindrical portion 7 has a portion in which the detection coil 28 of the detection unit 4 is disposed around the bobbin-side cylindrical portion 7, specifically, around the outer periphery or the inner periphery thereof. The bobbin-side cylindrical portion 7 has a cylindrical shape. That is, the bobbin-side cylindrical portion 7 has an inner peripheral surface whose inner diameter does not change in the axial direction and an outer peripheral surface whose outer diameter does not change in the axial direction. In addition, the bobbin-side cylindrical portion 7 is disposed coaxially with the rotating shaft 2 in a state in which the magnetostrictive torque sensor 1 is supported and fixed to the non-rotating member 20. In this state, the peripheral surface of the bobbin-side cylindrical portion 7 opposes the peripheral surface of the rotating shaft 2. In this example, in the state in which the magnetostrictive torque sensor 1 is supported and fixed to the non-rotating member 20, the inner peripheral surface of the bobbin-side cylindrical portion 7 is close to and opposes the outer peripheral surface of the rotating shaft 2 with a slight gap therebetween.

[0048] The bobbin-side fitting surface 8 is provided to the peripheral surface of any portion in the bobbin 3. Specifically, the bobbin-side fitting surface 8 is provided to the entirety or a portion of the bobbin-side cylindrical portion 7 or a cylindrical portion separate from the bobbin-side cylindrical portion 7, such as an outer diameter-side cylindrical portion 11 provided on the outer diameter side thereof or an inner diameter-side cylindrical portion provided on the inner diameter side thereof, but is not limited thereto. In this case, the bobbin-side fitting surface 8 is preferably composed of a single cylindrical surface whose diameter does not change in the axial direction.

[0049] The winding tube side locking hole 9 is provided in any part of the winding tube 3. The winding tube side locking hole 9 has the function of preventing relative displacement (creep), especially axial relative displacement, between the winding tube 3 and the magnetic ring 5 by combining with the positioning member 6 and the annular side locking hole 15 of the magnetic ring 5. The configuration of the winding tube side locking hole 9 is not particularly limited, and it can be appropriately set at any position in the winding tube 3 according to the ease of assembly, etc. In addition, the winding tube side locking hole 9 can be formed in any direction including the radial direction or the axial direction of the winding tube 3 as long as it can fulfill its function, but it is preferred to form it in the radial direction of the winding tube 3.

[0050] The winding tube side locking hole 9 can be formed as a through hole or a bottom hole, depending on its relationship with the annular side locking hole 15, as long as the positioning member 6 can be positioned (inserted) inside the winding tube side locking hole 9 and inside the annular side locking hole 15. In addition, the opening shape of the winding tube side locking hole 9 can be arbitrarily set according to the shape of the positioning member.

[0051] Although not limited to the following structure, in this example, the winding tube 3 has an axial side from the winding tube side cylinder 7 ( Figure 2 The connecting plate portion 10 extends radially outward from the right end of the connecting plate portion 10, and the outer diameter side cylinder portion 11 extends axially to the other side from the radially outward end of the connecting plate portion 10. The winding tube side fitting surface 8 is integrally formed by the inner circumferential surface of the outer diameter side cylinder portion 11. The winding tube side locking hole 9 penetrates the outer diameter side cylinder portion 11 radially.

[0052] The connecting plate portion 10 has a hollow circular end face shape when viewed from the axial direction. That is, the connecting plate portion 10 extends radially outward from one end of the winding tube side cylinder portion 7. The radially outward end of the connecting plate portion 10 is connected to one end of the outer diameter side cylinder portion 11 from the axial direction. In other words, the connecting plate portion 10 connects the one end of the winding tube side cylinder portion 7 from the one end of the outer diameter side cylinder portion 11 in the radial direction.

[0053] In this example, the winding tube 3 has a connector receiving portion, therefore the outer diameter side cylindrical portion 11 is provided on the portion of the winding tube 3 other than the portion having the connector receiving portion 12, extending from the radially outer end of the connecting plate portion 10 toward the axial side ( Figure 2 The outer diameter side cylinder 11 extends to the left side. That is, in this example, the outer diameter side cylinder 11 has an overall notched cylindrical shape. However, in a structure without the connector receiving portion 12, the outer diameter side cylinder 11 extends to the axial side from the radially outer end of the connecting plate portion 10. The outer diameter side cylinder 11 is coaxially arranged with the winding tube side cylinder 7 and the winding tube side mating surface 8.

[0054] In the present example, the outer diameter side tubular portion 11 has an axial length shorter than that of the bobbin side tubular portion 7. Therefore, the axial other side portion of the bobbin side tubular portion 7 protrudes more to the axial other side than the end portion of the axial other side of the outer diameter side tubular portion 11.

[0055] Note that the axial length of the outer diameter side tubular portion 11 is not particularly limited, and can be set to three times or more, preferably four times or more, the diameter of the bobbin side locking hole 9. In the example illustrated, the axial length of the outer diameter side tubular portion 11 is about three times the diameter of the bobbin side locking hole 9.

[0056] In the present example, the bobbin side fitting surface 8 is provided to the inner peripheral surface of the outer diameter side tubular portion 11. The bobbin side fitting surface 8 is provided to the entire inner peripheral surface of the outer diameter side tubular portion 11.

[0057] In the present example, the bobbin side locking hole 9 penetrates the outer diameter side tubular portion 11 in the radial direction. The bobbin side locking hole 9 is open at both the bobbin side fitting surface 8 provided to the inner peripheral surface of the outer diameter side tubular portion 11 and the outer peripheral surface of the outer diameter side tubular portion 11. In the present example, the bobbin side locking hole 9 is constituted by a circular hole having a circular opening shape.

[0058] In the present example, the bobbin side locking hole 9 is provided at an arbitrary position in the circumferential direction of the outer diameter side tubular portion 11. In particular, since the bobbin 3 is provided with the connector housing portion 12, the bobbin side locking hole 9 is provided to a portion of the outer diameter side tubular portion 11 slightly offset in the circumferential direction from the end portion on the radially inner side of the portion to which the connector housing portion 12 is connected, specifically, to a portion deviated by about 45 degrees from the circumferential direction central position of the connector housing portion 12.

[0059] In the present example, the bobbin 3 also has a connector housing portion 12. The connector housing portion 12 houses a connector for electrically connecting a cable extending from a detection circuit present outside the magnetostrictive torque sensor 1 to the detection portion 4.

[0060] In the present example, the connector housing portion 12 has a rectangular tubular shape elongated in the radial direction of the bobbin 3. The end portion on the radially inner side of the connector housing portion 12 is open at the bobbin side fitting surface 8 provided to the inner peripheral surface of the outer diameter side tubular portion 11.

[0061] Note that in the case of implementing the magnetostrictive torque sensor of one embodiment of the present disclosure, the shape of the connector housing portion can be appropriately changed depending on the shape of the connector housed therein. Alternatively, the connector housing portion can be omitted.

[0062] The detection unit 4 has a detection coil 28 disposed around the bobbin-side cylindrical portion 7. In this example, the detection coil 28 is disposed around the outer periphery of the bobbin-side cylindrical portion 7. The detection unit 4 varies the output signal in accordance with the magnitude and direction of the torque applied to the rotating shaft 2. The output signal of the detection unit 4 is sent to the detection circuit via a connector housed in the connector housing portion 12 and a cable.

[0063] The shape, number, arrangement, and the like of the detection coil are not particularly limited.

[0064] For example, as in the example shown in FIG. 8, the detection unit 4 can be configured by arranging two detection coils 23a, 23b in the axial direction, each of which is wound around the periphery of the bobbin 3 in a circular or spiral shape. Figure 4

[0065] In this case, two magnetic change units 26a, 26b are provided on the outer peripheral surface of the rotating shaft 2, each of which is configured by alternately arranging a plurality of magnetic portions 24a, 24b having magnetic anisotropy and a plurality of non-magnetic portions 25a, 25b having no magnetic anisotropy. The magnetic portions 24a and the non-magnetic portions 25a that configure the first magnetic change unit 26a of the two magnetic change units 26a, 26b are elongated in a direction that is inclined by a predetermined angle (for example, +45 degrees) with respect to the axial direction of the rotating shaft 2. In contrast, the magnetic portions 24b and the non-magnetic portions 25b that configure the second magnetic change unit 26b are elongated in a direction that is inclined by a predetermined angle (for example, -45 degrees) with respect to the axial direction of the rotating shaft 2 in a direction opposite to the inclination direction of the magnetic portions 24a and the non-magnetic portions 25a of the first magnetic change unit 26a.

[0066] Then, the first detection coil 23a of the two detection coils 23a, 23b is disposed around the first magnetic change unit 26a, and the second detection coil 23b is disposed around the second magnetic change unit 26b.

[0067] When a torque is applied to the rotating shaft 2, the magnetic portions 24a, 24b provided on the outer peripheral surface of the rotating shaft 2 are deformed to exert a tensile stress on one of the magnetic portions 24a (or 24b) and a compressive stress on the other of the magnetic portions 24b (or 24a). The permeability of the portion on which the tensile stress is exerted increases, and in contrast, the permeability of the portion on which the compressive stress is exerted decreases. Then, the difference in the voltage (induced electromotive force) of the detection coils 23a, 23b is found by the detection circuit described above, and from this difference, the direction and magnitude of the torque applied to the rotating shaft 2 are found.

[0068] Alternatively, as in (A) and (B) of FIG. 9, the detection unit 4 can be configured by arranging two detection coils 23a, 23b in the axial direction, each of which is wound around the periphery of the bobbin 3 in a circular or spiral shape. Figure 5 (A) and (B) of FIG. 9, the detection unit 4 can be configured by arranging two detection coils 23a, 23b in the axial direction, each of which is wound around the periphery of the bobbin 3 in a circular or spiral shape. Figure 5 ​As shown in another example (B), the detection section 4 can also be constructed by stacking four detection coils 28a-28d, which are arranged in parallelogram shape when viewed from the radial direction, in the radial direction.

[0069] Each detection coil 28a to 28d is constructed by winding an insulated wire around a winding tube 3. The outer circumferential surface of the winding tube 3 has a first inclined groove 29a inclined at a predetermined angle (e.g., +45 degrees) relative to the axial direction of the winding tube 3, and a second inclined groove 29b inclined at a predetermined angle (e.g., -45 degrees) relative to the axial direction of the winding tube 3 in the direction opposite to the first inclined groove 29a. Furthermore, the coil sheet 27a constituting the first detection coil 28a and the coil sheet 27d constituting the fourth detection coil 28d are constructed by winding an insulated wire along the first inclined groove 29a. Conversely, the coil sheet 27b constituting the second detection coil 28b and the coil sheet 27c constituting the third detection coil 28c are constructed by winding an insulated wire along the second inclined groove 29b.

[0070] like Figure 6 As shown, the detection coils 28a to 28d are connected in a loop to form the detection circuit 30. To measure the torque applied to the rotating shaft 2, an AC voltage is applied between the junction A of the first detection coil 28a and the second detection coil 28b, and between the junction C of the third detection coil 28c and the fourth detection coil 28d. Then, the voltage between the junction B of the second detection coil 28b and the third detection coil 28c, and between the junction D of the first detection coil 28a and the fourth detection coil 28d, is measured. Based on these voltages, the direction and magnitude of the torque transmitted by the rotating shaft 2 are determined.

[0071] Furthermore, when the detection unit 4 is constructed by stacking four detection coils 28a to 28d radially, the rotating shaft 2 is made of an iron-based alloy with magnetostrictive properties and is cylindrical or cylindrical in shape. It is also possible to perform shot peening on the portion of the outer circumferential surface of the rotating shaft 2 that exists radially inside the detection unit 4 to form a modified layer that improves the magnetostrictive properties.

[0072] However, in the case of implementing a magnetostrictive torque sensor according to one aspect of the present disclosure, the detection unit is not limited to the two examples mentioned above. Any structure can be adopted as long as it can detect the change in the magnetic field existing around the rotating shaft as torque is applied to the rotating shaft.

[0073] Furthermore, the detection coil constituting the detection unit 4 is not limited to a coil made by winding insulated wires on the winding tube 3, but can also be composed of a pattern printed on a flexible substrate (FPC).

[0074] The magnetic body ring 5, also referred to as a back yoke, has a function of suppressing leakage of magnetic flux generated by the detection coil 28 constituting the detection unit 4 to the outside. The magnetic body ring 5 has a ring-side cylindrical portion 13 disposed around the detection unit 4, a ring-side fitting surface 14 fitted with the bobbin-side fitting surface 8, and a ring-side locking hole 15.

[0075] The magnetic body ring 5 is integrally formed of a magnetic material. As the magnetic material constituting the magnetic body ring 5, for example, an iron-based alloy such as a mechanical construction alloy steel or stainless steel can be used.

[0076] In this example, the magnetic body ring 5 is constituted only by the ring-side cylindrical portion 13, and the entire body is formed in a substantially cylindrical shape. The shape of the ring-side cylindrical portion 13 is arbitrary as long as the entire body is substantially cylindrical, and for example, the outer diameter and the inner diameter can be constant in the axial direction, but at least one of the outer diameter and the inner diameter can be constituted by a stepped cylindrical surface.

[0077] In this example, the ring-side cylindrical portion 13 has a small-diameter portion 16 on the other-axial-side portion (a portion other than the end portion on the one-axial-side), and has a large-diameter portion 17 having a larger outer diameter than the small-diameter portion 16 on the end portion on the one-axial-side. That is, the ring-side cylindrical portion 13 has an outer peripheral surface in the shape of a stepped cylindrical surface in which the outer peripheral surface of the small-diameter portion 16 and the outer peripheral surface of the large-diameter portion 17 are connected by a step surface 18 toward the other-axial-side. In contrast, the inner peripheral surface of the small-diameter portion 16 and the inner peripheral surface of the large-diameter portion 17 are on the same cylindrical surface. Therefore, the radial thickness of the large-diameter portion 17 is thicker than the radial thickness of the small-diameter portion 16.

[0078] In addition, the ring-side cylindrical portion 13 has a notch 19 at a position in the circumferential direction of the end portion on the one-axial-side of the large-diameter portion 17, the notch 19 penetrating the large-diameter portion 17 from the inner peripheral surface to the outer peripheral surface and opening at the end surface on the one-axial-side of the large-diameter portion 17. The notch 19 is disposed at a portion in the circumferential direction where the phase coincides with the connector housing portion 12 in a state in which the magnetostrictive torque sensor 1 is assembled. Inside the notch 19, a cable extending from the detection unit 4 and / or a connector provided at the front end portion of the cable are disposed.

[0079] The ring-side fitting surface 14 is provided to the peripheral surface of an arbitrary portion in the magnetic body ring 5. Specifically, the ring-side fitting surface 14 is provided to the entire body or a portion of the ring-side cylindrical portion 13 or a cylindrical portion provided separately from the ring-side cylindrical portion 13, for example, an outer-diameter-side cylindrical portion provided on the outer diameter side thereof or an inner-diameter-side cylindrical portion provided on the inner diameter side thereof, but is not limited thereto. In this case, the ring-side fitting surface 14 is preferably constituted by a single cylindrical surface whose diameter does not change in the axial direction.

[0080] In this example, the ring-side fitting surface 14 is provided to the outer peripheral surface of the large-diameter portion 17, and more specifically, to the entire outer peripheral surface thereof.

[0081] The fitting state of the bobbin-side fitting surface 8 and the ring-side fitting surface 14 is arbitrary, and any one of clearance fit, interference fit, transition fit can be adopted, but from the viewpoint of favorably ensuring the coaxiality of the bobbin 3 and the magnetic body ring 5, it is preferable to fit the bobbin-side fitting surface 8 and the ring-side fitting surface 14 without wobbling in the radial direction. As the fitting in this case, fitting by inside fitting, press-in (including light press-in) can be adopted. From this viewpoint, the radial direction dimension of the ring-side fitting surface 14 is determined by the relation with the radial direction dimension of the bobbin-side fitting surface 8.

[0082] In the present example, the ring-side fitting surface 14 has an outer diameter dimension slightly smaller than the inner diameter dimension of the bobbin-side fitting surface 8. Therefore, in the state where the magnetostrictive torque sensor 1 is assembled, the bobbin-side fitting surface 8 and the ring-side fitting surface 14 are fitted by clearance fit without wobbling in the radial direction, that is, inside fitting.

[0083] The relation of the axial length of the bobbin-side fitting surface 8 and the axial length of the ring-side fitting surface 14 is arbitrary, and they can be made the same length or different lengths. In the present example, the axial length of the bobbin-side fitting surface 8 and the axial length of the ring-side fitting surface 14 are substantially the same. In other words, the axial length of the outer diameter side cylindrical portion 11 and the axial length of the large diameter portion 17 are substantially the same. Therefore, in the state where the magnetostrictive torque sensor 1 is assembled, the axial position of the step surface 18 and the axial position of the end surface of the other side of the outer diameter side cylindrical portion 11 are substantially the same. That is, the step surface 18 and the end surface of the other side of the outer diameter side cylindrical portion 11 are located on substantially the same plane.

[0084] The ring-side locking hole 15 is provided at an arbitrary portion of the magnetic body ring 5. The ring-side locking hole 15 has a function of preventing the relative displacement (creep) of the bobbin 3 and the magnetic body ring 5, particularly the axial relative displacement, by the combination with the positioning member 6 and the bobbin-side locking hole 9 of the bobbin 3. The arrangement of the bobbin-side locking hole 9 is not particularly limited, but in the state where the magnetostrictive torque sensor 1 is assembled, it is provided at a portion matching the bobbin-side locking hole 9. Also the orientation of the ring-side locking hole 15 is determined by the relation with the orientation of the bobbin-side locking hole 9, and it can be formed in any direction of the radial direction of the magnetic body ring 5 or the axial direction or the like, but it is preferable that, in cooperation with the case where the bobbin-side locking hole 9 is formed in the radial direction, the ring-side locking hole is also formed in the radial direction of the magnetic body ring 5. In this case, the ring-side locking hole 15 is provided at a portion matching the bobbin-side locking hole 9, that is, a portion where the axial position and the phase in the circumferential direction are coincident, in the state where the magnetostrictive torque sensor 1 is assembled.

[0085] The ring-side engaging hole 15 can be configured by a through hole or a bottomed hole, as long as the positioning member 6 can be disposed (inserted) inside the bobbin-side engaging hole 9 and inside the ring-side engaging hole 15, according to the relationship with the bobbin-side engaging hole 9. Further, the opening shape of the ring-side engaging hole 15 can be arbitrarily set according to the shape of the positioning member.

[0086] In the present example, the ring-side engaging hole 15 is provided in the large-diameter portion 17. The ring-side engaging hole 15 is opened in the ring-side fitting surface 14 provided in the outer circumferential surface of the large-diameter portion 17. In the present example, instead, the ring-side engaging hole can be formed so as to pass through the magnetic body ring in the radial direction. In the present example, the ring-side engaging hole 15 is configured by a bottomed hole having a circular opening shape and opened only on the radial outer side.

[0087] The positioning member 6 is erected in the bobbin-side engaging hole 9 of the bobbin 3 and the ring-side engaging hole 15 of the magnetic body ring 5, thereby having a function of preventing the relative displacement of the bobbin 3 and the magnetic body ring 5.

[0088] The material configuring the positioning member 6 is not particularly limited, as long as it can sufficiently ensure the bonding strength of the bobbin 3 and the magnetic body ring 5, and in addition to metal materials such as iron-based alloys, light alloys, etc., synthetic resins, etc. can also be used.

[0089] The structure of the positioning member 6 is not particularly limited, as long as it can achieve its function. For example, the positioning member 6 can be configured by a cylindrical or cylindrical pin, in addition to a split cylindrical spring pin having a slit in a linear shape or a wave shape at one position in the circumferential direction thereof. In these cases, the cross-sectional shape of the positioning member 6 is not limited to a circular shape, and can be set to a split circular shape, a polygonal shape, or the like. It is preferable to determine the opening shape of the bobbin-side engaging hole 9 provided in the bobbin 3 and the ring-side engaging hole 15 provided in the magnetic body ring 5 according to the cross-sectional shape of the positioning member 6.

[0090] Alternatively, the positioning member 6 can be configured by a screw. In this case, one of the bobbin-side engaging hole 9 and the ring-side engaging hole 15 is provided as a threaded hole. In this case, even in the case where the bobbin-side engaging hole 9, the ring-side engaging hole 15, and the positioning member 6 are disposed in the axial direction of the magnetostrictive torque sensor 1, the relative displacement of the bobbin 3 and the magnetic body ring 5 in the axial direction and the circumferential direction can be reliably prevented.

[0091] The positioning member 6 has a length that is such that, when the magnetostrictive torque sensor 1 is used, even if the bobbin 3 and / or the magnetic body ring 5 thermally expand, the state of being erected in the bobbin-side hole 9 and the ring-side hole 15 can be maintained. The positioning member 6 can be provided with a length in which the entirety thereof is disposed inside the bobbin-side hole 9 and the ring-side hole 15. Alternatively, the positioning member 6 can project radially from the opening of at least one of the bobbin-side hole 9 and the ring-side hole 15, as long as the function of the magnetostrictive torque sensor 1 is not hindered.

[0092] In this example, the radially outer portion of the positioning member 6 is disposed (inserted) inside the bobbin-side hole 9, and the radially inner portion of the positioning member 6 is disposed (inserted) inside the ring-side hole 15.

[0093] In this example, the positioning member 6 is composed of a split cylindrical spring pin having a slit in a straight line shape or a wavy shape at one position in the circumferential direction thereof. The positioning member 6 is inserted into the bobbin-side hole 9 and the ring-side hole 15 in a state in which the outer diameter thereof is reduced by elastically narrowing the width of the slit, and is then elastically restored. Thereby, the positioning member 6 is embedded in an interference fit in at least one of the bobbin-side hole 9 and the ring-side hole 15, and is erected in the bobbin-side hole 9 and the ring-side hole 15.

[0094] In this example, the end portion of the radially outer portion of the positioning member 6 does not project radially outward from the end portion of the radially outer portion of the bobbin-side hole 9. In addition, the positioning member 6 is composed of a metal material such as a ferrous alloy or a light alloy.

[0095] In the magnetostrictive torque sensor 1, the function of preventing the relative displacement (creep) of the bobbin 3 and the magnetic body ring 5, particularly the relative displacement in the axial direction, is realized by the combination of the bobbin-side hole 9, the ring-side hole 15, and the positioning member 6. The number of combinations of the bobbin-side hole 9, the ring-side hole 15, and the positioning member 6 can be arbitrarily set according to the use, the installation site, and the like of the magnetostrictive torque sensor 1. That is, the magnetostrictive torque sensor 1 can be provided with one combination of the bobbin-side hole 9, the ring-side hole 15, and the positioning member 6. Alternatively, a plurality of combinations of the bobbin-side hole 9, the ring-side hole 15, and the positioning member 6 can also be provided.

[0096] In this example, only one combination of the positioning member 6, the bobbin-side hole 9, and the ring-side hole 15 is provided. Therefore, the magnetostrictive torque sensor 1 of this example is provided with only one positioning member 6.

[0097] The magnetostrictive torque sensor 1 is supported and fixed to the non-rotating member 20 in a state in which the small-diameter portion 16 of the ring-side cylindrical portion 13 of the magnetic body ring 5 is fitted to the inner peripheral surface of the non-rotating member 20 without play in the radial direction, and the side surfaces of the connector housing portion 12 on both sides in the circumferential direction thereof are opposed to the stop surfaces provided on the non-rotating member 20. Figure 2 ) without play in the radial direction, and the side surfaces of the connector housing portion 12 on both sides in the circumferential direction thereof are opposed to the stop surfaces provided on the non-rotating member 20.

[0098] Further, the magnetostrictive torque sensor 1 is positioned in the axial direction by abutting the fixing-side step surface 32 provided on the non-rotating member 20 toward one side in the axial direction against the step surface 18 of the magnetic body ring 5 and the end surface of the outer-diameter-side cylindrical portion 11 on the other side in the axial direction, and abutting the anti-disengagement member 33 such as a retainer ring provided on the inner peripheral surface of the non-rotating member 20 against the side surface of the connecting plate portion 10 on one side in the axial direction.

[0099] Thus, in a state in which the magnetostrictive torque sensor 1 is supported and fixed to the non-rotating member 20, the magnetostrictive torque sensor 1 is disposed around the rotating shaft 2. In other words, the magnetostrictive torque sensor 1 is supported and fixed to the non-rotating member 20 in a state in which the rotating shaft 2 is inserted into the inside of the bobbin-side cylindrical portion 7. Note that the method of supporting and fixing the magnetostrictive torque sensor to the non-rotating member that does not rotate during use is not limited to the above-described method, and can be performed by any method.

[0100] In a state in which the magnetostrictive torque sensor 1 of the present example is supported and fixed to the non-rotating member 20, a portion of the non-rotating member 20 can also abut against or be in close proximity to and opposed to the peripheral portion of the opening portion on the radial outer side of the bobbin-side retainer hole 9 in the outer peripheral surface of the bobbin 3 in a manner of covering the opening portion provided on the radial outer side of the bobbin-side retainer hole 9 of the bobbin 3. Thus, it is possible to reliably prevent the positioning member 6 from disengaging from the bobbin-side retainer hole 9 and the ring-side retainer hole 15.

[0101] When a torque is applied to the rotating shaft 2 and the rotating shaft 2 is elastically twisted and deformed, the magnetic permeability of the rotating shaft 2 changes based on the inverse magnetostrictive effect. Thus, when the magnetic field existing around the rotating shaft 2 changes, the voltage (induced electromotive force) of the detection coil constituting the detection portion 4 changes. Based on the change in the voltage, the torque applied to the rotating shaft 2 is calculated by the detection circuit.

[0102] In the magnetostrictive torque sensor 1 of the present example, the bobbin-side fitting surface 8 provided on the bobbin 3 is fitted to the ring-side fitting surface 14 provided on the magnetic body ring 5 without play. Thus, it is possible to favorably ensure the coaxiality of the bobbin 3 and the magnetic body ring 5, and thus it is possible to stably constitute the magnetic path passing through the rotating shaft 2, the bobbin 3, and the magnetic body ring 5.

[0103] In the magnetostrictive torque sensor 1 of the present example, the positioning member 6 is fitted on the bobbin side fitting hole 9 provided in the bobbin 3 and the ring side fitting hole 15 provided in the magnetic body ring 5. Therefore, even in the case where the bobbin 3 and / or the magnetic body ring 5 expand or contract due to a change in temperature, the relative displacement of the bobbin 3 and the magnetic body ring 5 in the axial direction and the circumferential direction can be reliably prevented. That is, according to the magnetostrictive torque sensor 1 of the present example, the strength of the coupling of the bobbin 3 and the magnetic body ring 5, specifically, the strength of the coupling in the axial direction and the circumferential direction, can be sufficiently ensured.

[0104] In the magnetostrictive torque sensor 1 of the present example, the bobbin side fitting surface 8 is provided on the inner peripheral surface of the bobbin 3, and the ring side fitting surface 14 is provided on the outer peripheral surface of the magnetic body ring 5. That is, in the magnetostrictive torque sensor 1 of the present example, the bobbin side fitting surface 8 facing the radially inner side is fitted with the ring side fitting surface 14 facing the radially outer side without play, and the positioning member 6 is inserted into the bobbin side fitting hole 9 of the bobbin 3 and the ring side fitting hole 15 of the magnetic body ring 5 from the radially outer side. By adopting such a structure, it is possible to form the bobbin side fitting hole 9 in the outer diameter side cylindrical portion 11 rather than the bobbin side cylindrical portion 7, to arrange the detection coil 28 of the detection portion 4 around (in the present example, the outer periphery), and to more appropriately ensure the roundness of the bobbin side cylindrical portion 7 in which the peripheral surface (in the present example, the inner peripheral surface) and the peripheral surface (in the present example, the outer peripheral surface) of the rotation shaft 2 are opposed.

[0105] In the case of implementing the magnetostrictive torque sensor of one embodiment of the present disclosure, as an alternative, a bobbin side fitting surface can be provided on the outer peripheral surface of the bobbin, and a ring side fitting surface can be provided on the inner peripheral surface of the magnetic body ring. That is, the bobbin side fitting surface facing the radially outer side can be fitted with the ring side fitting surface facing the radially inner side (preferably, without play), and the positioning member can be inserted into the bobbin side fitting hole provided in the bobbin and opening in the bobbin side fitting surface and the ring side fitting hole provided in the magnetic body ring and passing through the magnetic body ring in the radial direction from the radially outer side.

[0106] More specifically, the bobbin side cylindrical portion of the bobbin and the ring side cylindrical portion of the magnetic body ring are each integrally configured in a substantially cylindrical shape, and a protruding portion (bobbin side protruding portion or ring side protruding portion) protruding to one or both of the radially outer side and the radially inner side from an end portion on one side in the axial direction of at least either of the bobbin side cylindrical portion and the ring side cylindrical portion is provided. In this case, the bobbin side fitting surface is constituted by the outer peripheral surface of the end portion on one side in the axial direction of the bobbin side cylindrical portion or the outer peripheral surface of the bobbin side protruding portion, and the ring side fitting surface is constituted by the inner peripheral surface of the end portion on one side in the axial direction of the ring side cylindrical portion or the inner peripheral surface of the ring side protruding portion.

[0107] [Second Example]

[0108] Using Figures 7 to 9 A second example of an embodiment of the present disclosure will be described.

[0109] The magnetostrictive torque sensor 1a of the present example differs from the structure of the first example in that the bobbin-side retaining hole 9 penetrates the bobbin 3 in the radial direction, and the positioning member 6a protrudes in the radial direction from the opening portion on the side opposite the magnetic body ring 5 side among the opening portions on both sides in the radial direction of the bobbin-side retaining hole 9 of the bobbin 3.

[0110] Specifically, in the magnetostrictive torque sensor 1a of the present example, the positioning member 6a is composed of a metal material. In addition, the length of the positioning member 6a is made longer than the sum of the radial depth of the bobbin-side retaining hole 9 provided to the bobbin 3 and the radial depth of the ring-side retaining hole 15 provided to the magnetic body ring 5. Therefore, the end portion on the radial outer side of the positioning member 6a protrudes to the radial outer side from the opening portion on the radial outer side of the bobbin-side retaining hole 9 provided to the bobbin 3.

[0111] In the present example, in a state in which the magnetostrictive torque sensor 1a is supported and fixed to the non-rotating member 20a, the radial outer side portion of the positioning member 6a that protrudes from the opening portion on the radial outer side of the bobbin-side retaining hole 9 is disposed inside the engagement recess 21 provided to the inner circumferential surface of the non-rotating member 20a. Also, the radial outer side portion of the positioning member 6a is disposed between the side surfaces that face each other in the circumferential direction among the inner surfaces of the engagement recess 21. That is, the radial outer side portion of the positioning member 6a is made to approach and oppose the side surfaces provided to the non-rotating member 20a and facing in the circumferential direction. Thereby, rotation stop of the magnetostrictive torque sensor 1a with respect to the non-rotating member 20a is achieved.

[0112] According to the magnetostrictive torque sensor 1a of the present example, it is easy to miniaturize or omit the connector housing portion 12 provided to the bobbin 3.

[0113] In order to achieve rotation stop of the magnetostrictive torque sensor 1 of the first example with respect to the non-rotating member 20, it is considered to make the side surfaces on both sides in the circumferential direction of the connector housing portion 12 provided to the bobbin 3 oppose the stop surface provided to the non-rotating member 20. Here, the bobbin 3 is composed of synthetic resin, so it is easy for fretting wear to occur between the circumferential direction side surfaces of the connector housing portion 12 and the above-mentioned stop surface due to vibration and the like during use, and it is difficult to achieve miniaturization of the connector housing portion 12.

[0114] In contrast, in the present example, rotation stop of the magnetostrictive torque sensor 1a with respect to the non-rotating member 20a is achieved by disposing the radial outer side portion of the positioning member 6a inside the engagement recess 21 provided to the inner circumferential surface of the non-rotating member 20a. Therefore, it is easy to miniaturize or omit the connector housing portion 12.

[0115] As a modification of the second example, in a structure in which the outer peripheral surface of the bobbin is provided with a bobbin-side fitting surface and the inner peripheral surface of the magnetic body ring is provided with a ring-side fitting surface, the ring-side locking hole penetrates the magnetic body ring in the radial direction, the bobbin-side fitting surface facing the radial outer side is fitted with the ring-side fitting surface facing the radial inner side, and the positioning member protrudes in the radial direction from the opening portion on the side opposite to the bobbin 3 side in the radial direction among the opening portions on both sides of the ring-side locking hole in the radial direction.

[0116] The structure and the effects of the other parts of the second example are the same as those of the first example.

[0117] [Third Example]

[0118] Use Figure 10 and Figure 11 A third example of an embodiment of the present disclosure will be described.

[0119] The magnetostrictive torque sensor 1b of the present example differs from the structures of the first and second examples in that it is provided with a plurality of bobbin-side locking holes, the above-described ring-side locking hole, and the above-described positioning member.

[0120] Specifically, the magnetostrictive torque sensor 1b of the present example is provided with a combination of two bobbin-side locking holes provided in the bobbin 3, the ring-side locking hole provided in the magnetic body ring 5, and the positioning member 6a.

[0121] In the present example, as in the structure of the second example, the radial outer side portion of each positioning member 6a protrudes to the radial outer side from the opening portion on the radial outer side of the bobbin-side locking hole provided in the bobbin 3.

[0122] In the present example, in a state in which the magnetostrictive torque sensor 1b is supported and fixed to the non-rotating member 20b, the radial outer side portion of one positioning member 6a is opposed to the stop surface 22a provided in the non-rotating member 20b and facing one side in the circumferential direction, and the radial outer side portion of the other positioning member 6a is opposed to the stop surface 22b provided in the non-rotating member 20b and facing the other side in the circumferential direction. Thus, rotation stop of the magnetostrictive torque sensor 1b with respect to the non-rotating member 20b is achieved.

[0123] The structure and the effects of the other parts of the third example are the same as those of the first and second examples.

[0124] Explanation of Symbols

[0125] 1, 1a, 1b Magnetostrictive torque sensor

[0126] 2 Rotational axis

[0127] 3 Bobbin

[0128] 4 detection section

[0129] 5 magnetic body ring

[0130] 6, 6a positioning member

[0131] 7 bobbin side cylindrical portion

[0132] 8 bobbin side fitting surface

[0133] 9 bobbin side locking hole

[0134] 10 connecting plate portion

[0135] 11 outer diameter side cylindrical portion

[0136] 12 connector housing portion

[0137] 13 ring side cylindrical portion

[0138] 14 ring side fitting surface

[0139] 15 ring side locking hole

[0140] 16 small diameter portion

[0141] 17 large diameter portion

[0142] 18 step surface

[0143] 19 notch

[0144] 20, 20a, 20b non-rotating member

[0145] 21 engagement recess

[0146] 22a, 22b stop surface

[0147] 23a first detection coil

[0148] 23b second detection coil

[0149] 24a, 24b magnetic portion

[0150] 25a, 25b non-magnetic portion

[0151] 26a first magnetic change portion

[0152] 26b second magnetic change portion

[0153] 27a, 27b, 27c, 27d coil piece

[0154] 28 detection coil

[0155] 28a first detection coil

[0156] 28b second detection coil

[0157] 28c third detection coil

[0158] 28d fourth detection coil

[0159] 29a first inclined groove

[0160] 29b second inclined groove

[0161] 30 detection circuit

[0162] 31 fixed side fitting surface

[0163] 32 fixed side step surface

[0164] 33 anti-disengagement member

Claims

1. A magnetostrictive torque sensor that measures a torque applied to a rotating shaft having a magnetostrictive property, The magnetostrictive torque sensor is characterized by comprising: a bobbin having a bobbin-side cylindrical portion disposed around the rotating shaft, a bobbin-side cylindrical surface, and a bobbin-side locking hole; a detection portion having a detection coil disposed around an outer periphery of the bobbin-side cylindrical portion; a magnetic body ring having a ring-side cylindrical portion disposed around the detection portion, a ring-side cylindrical surface fitted to the bobbin-side cylindrical surface, and a ring-side locking hole; and a positioning member erected in the bobbin-side locking hole and the ring-side locking hole.

2. The magnetostrictive torque sensor according to claim 1, wherein the bobbin-side cylindrical surface and the ring-side cylindrical surface are fitted without play in a radial direction.

3. The magnetostrictive torque sensor according to claim 1 or 2, wherein the bobbin-side locking hole penetrates the bobbin in the radial direction, the positioning member protrudes in the radial direction from an opening portion on a side opposite to the magnetic body ring in the radial direction among opening portions on both sides in the radial direction of the bobbin-side locking hole.

4. The magnetostrictive torque sensor according to any one of claims 1 to 3, wherein a plurality of the bobbin-side locking holes, the ring-side locking hole, and the positioning member are provided.

5. The magnetostrictive torque sensor according to any one of claims 1 to 4, wherein the positioning member is composed of a spring pin.

6. The magnetostrictive torque sensor according to any one of claims 1 to 5, wherein the bobbin-side cylindrical surface is provided to an inner peripheral surface of the bobbin, and the ring-side cylindrical surface is provided to an outer peripheral surface of the magnetic body ring.

7. The magnetostrictive torque sensor according to claim 6, wherein the bobbin has a connection plate portion elongated toward the radial direction from an end portion on one side in the axial direction of the bobbin-side cylindrical portion, and an outer diameter side cylindrical portion elongated toward the other side in the axial direction from an end portion on the radial direction outer side of the connection plate portion, the inner peripheral surface of the bobbin is composed of an inner peripheral surface of the outer diameter side cylindrical portion, the bobbin-side locking hole penetrates the outer diameter side cylindrical portion in the radial direction, the ring-side cylindrical surface is provided to an end portion on one side in the axial direction of the outer peripheral surface of the magnetic body ring, the ring-side locking hole is opened at the ring-side cylindrical surface. ​ ​ ​ ​ ​ ​

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