Magnetostrictive torque sensor

Abstract

[Problem] To sufficiently ensure a coupling strength between a bobbin and a magnetic ring regardless of temperature changes, while satisfactorily ensuring coaxiality between the bobbin and the magnetic ring. [Solution] A magnetostrictive torque sensor 1 comprises: a bobbin 3 having a bobbin-side cylindrical portion 7 disposed around a rotating shaft 2, a cylindrical-surface-shaped bobbin-side mating surface 8, and a bobbin-side locking hole 9; a detecting portion 4 having a detection coil disposed around the bobbin-side cylindrical portion 7; a magnetic ring 5 including a ring-side cylindrical portion 13 disposed around the detecting portion 4, a ring-side mating surface 14 which mates with the bobbin-side mating surface 8, and a ring-side locking hole 15; and a positioning member 6 spanning the bobbin-side locking hole 9 and the ring-side locking hole 15.

Description

Magnetostrictive torque sensor

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

[0002] As a sensor for measuring torque applied to a rotating shaft, a magnetostrictive torque sensor that measures torque applied to a rotating shaft by utilizing the inverse magnetostriction effect that occurs in the rotating shaft when torque is applied to the rotating shaft has been known for some time, as described in JP 2020-085814 A, for example.

[0003] The torque sensor described in JP 2020-085814 A is constructed by injection molding epoxy resin to cover and bond a detection unit having a resin bobbin, a plurality of detection coils formed by wrapping insulated wire around the bobbin, and a magnetic ring made of a ferromagnetic material that is arranged to surround the detection coils of the detection unit in order to suppress magnetic flux leakage to the outside.

[0004] Japanese Patent Application Laid-Open No. 2020-085814

[0005] In a magnetostrictive torque sensor, a magnetic circuit is formed through the rotating shaft, the bobbin on which the detection coil of the detection unit is arranged, and the magnetic ring, so it is necessary to ensure good coaxiality between the rotating shaft, the bobbin, and the magnetic ring.Furthermore, the bobbin and the magnetic ring must be joined and fixed so that they cannot move relative to each other in the axial and circumferential directions, regardless of temperature changes.

[0006] The torque sensor described in JP 2020-085814 A has room for improvement in terms of ensuring sufficient bonding strength between the bobbin and the magnetic ring.

[0007] That is, the resin material constituting the bobbin has a linear expansion coefficient that is significantly different from that of the metal material constituting the magnetic ring, and therefore, as the temperature changes, the adhesion between the bobbin and the magnetic ring decreases, which may cause relative slippage (creep) between the bobbin and the magnetic ring, i.e., relative rotation and / or relative axial displacement.

[0008] It is also conceivable to use an adhesive to bond the bobbin and the magnetic ring together, but in this case too, there arises the problem of a decrease in adhesion between the bobbin and the magnetic ring due to temperature changes.

[0009] In response to this, it is also possible to secure the axial connection strength between the bobbin and the magnetic ring by combining a bobbin having a claw portion and a magnetic ring having a locking recess while the bobbin is in an elastically deformed state, and then allowing the bobbin to return to its original shape, thereby locking the claw portion into the locking recess, in a snap-fit ​​manner. However, in this case, the following problems arise.

[0010] To ensure good coaxiality between the bobbin and the magnetic ring, they must be fitted together without any radial play, for example by spigot fitting. That is, the diameter (inner or outer diameter) of the fitting portion of the bobbin relative to the magnetic ring and the diameter (outer or inner diameter) of the magnetic ring relative to the bobbin must be approximately the same. Therefore, even if the bobbin is elastically deformed when combining the bobbin and the magnetic ring, the claws get in the way and the bobbin and the magnetic ring cannot be fitted together.

[0011] The present disclosure aims to realize a magnetostrictive torque sensor structure that can ensure good coaxiality between a bobbin and a magnetic ring while also ensuring sufficient bonding strength between the bobbin and the magnetic ring regardless of temperature changes.

[0012] A magnetostrictive torque sensor according to one aspect of the present disclosure is a sensor that measures torque applied to a rotating shaft having magnetostrictive properties, and includes a bobbin, a detection unit, a magnetic ring, and a positioning member.

[0013] The bobbin has a bobbin side cylindrical portion disposed around the rotation shaft, a cylindrical bobbin side fitting surface, and a bobbin side locking hole.

[0014] The detection section has a detection coil disposed around the bobbin side cylinder section.

[0015] The magnetic ring has a ring-side cylindrical portion disposed around the detection portion, a ring-side fitting surface that fits with the bobbin-side fitting surface, and a ring-side locking hole.

[0016] The positioning member is bridged between the bobbin-side locking hole and the ring-side locking hole.

[0017] In the magnetostrictive torque sensor according to one aspect of the present disclosure, the bobbin-side fitting surface and the ring-side fitting surface can be fitted together without any play in the radial direction. More preferably, the bobbin-side fitting surface and the ring-side fitting surface can be fitted together in a spigot-joint manner, which is a clearance fit without any play in the radial direction.

[0018] In one embodiment of the magnetostrictive torque sensor of the present disclosure, the bobbin side locking hole can be made to penetrate radially through the bobbin, and the positioning member can be made to protrude radially from the opening on either radial side of the bobbin side locking hole that is radially opposite the magnetic ring side.

[0019] The magnetostrictive torque sensor according to an aspect of the present disclosure may include a plurality of combinations of the bobbin-side locking hole, the ring-side locking hole, and the positioning member, or may include one combination of the bobbin-side locking hole, the ring-side locking hole, and the positioning member.

[0020] In the magnetostrictive torque sensor according to one aspect of the present disclosure, the positioning member may be a spring pin, or may be a columnar or cylindrical pin, screw, or the like.

[0021] In the magnetostrictive torque sensor according to one aspect of the present disclosure, the bobbin-side fitting surface may be provided on the inner peripheral surface of the bobbin, and the ring-side fitting surface may be provided on the outer peripheral surface of the magnetic ring.

[0022] In this case, the bobbin may have a connecting plate portion extending radially outward from one axial end of the bobbin side cylindrical portion, and an outer diameter side cylindrical portion extending radially outward from the radially outer end of the connecting plate portion toward the other axial side. The inner peripheral surface of the bobbin is formed by the 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 fitting surface is provided at one axial end of the outer peripheral surface of the magnetic ring. The ring side locking hole opens into the ring side fitting surface.

[0023] The present disclosure can be implemented by appropriately combining the above-described aspects as long as no contradiction occurs.

[0024] According to the magnetostrictive torque sensor of one aspect of the present disclosure, it is possible to ensure good coaxiality between the bobbin and the magnetic ring, while also ensuring sufficient bonding strength between the bobbin and the magnetic ring regardless of temperature changes.

[0025] FIG. 1 is a perspective view of a magnetostrictive torque sensor according to a first embodiment of the present disclosure. FIG. 2 is a cross-sectional view of the magnetostrictive torque sensor according to the first embodiment. FIG. 3 is an exploded perspective view of the magnetostrictive torque sensor according to the first embodiment, with the detection unit omitted. FIG. 4 is a cross-sectional schematic view of an example of the detection unit. FIGS. 5A and 5B are development views of another example of the detection unit, with the detection coils viewed from the radially outer side, where FIG. 5A shows the first and fourth detection coils, and FIG. 5B shows the second and third detection coils. FIG. 6 is a diagram showing a detection circuit including four detection coils. FIG. 7 is a perspective view of a magnetostrictive torque sensor according to a second embodiment of the present disclosure. FIG. 8 is an enlarged cross-sectional view of a main portion of the magnetostrictive torque sensor according to the second embodiment. FIG. 9 is a diagram for explaining a method of preventing the magnetostrictive torque sensor according to the second embodiment from rotating relative to the housing. FIG. 10 is a perspective view of a magnetostrictive torque sensor according to a third embodiment of the present disclosure. FIG. 11 is a diagram illustrating a method for preventing the magnetostrictive torque sensor of the third example from rotating relative to the housing.

[0026] First Example A first example of an embodiment of the present disclosure will be described with reference to FIGS. 1 to 3. FIG.

[0027] The magnetostrictive torque sensor 1 of this example is a sensor that measures the torque applied to a rotating shaft 2 (see Figure 2) that has magnetostrictive properties, and includes a bobbin 3, a detection unit 4, a magnetic ring 5, and a positioning member 6.

[0028] In the following description, unless otherwise specified, the axial, radial, and circumferential directions of the magnetostrictive torque sensor 1 refer to the axial, radial, and circumferential directions of the rotating shaft 2. The axial, radial, and circumferential directions of the rotating shaft 2 coincide with the axial, radial, and circumferential directions of the bobbin 3, the axial, radial, and circumferential directions of the detection unit 4, and the axial, radial, and circumferential directions of the magnetic ring 5.

[0029] The bobbin 3 has a bobbin side cylindrical portion 7 arranged around the rotary shaft 2 , a cylindrical bobbin side fitting surface 8 , and a bobbin side locking hole 9 .

[0030] The bobbin 3 is made of synthetic resin, which is a non-magnetic and non-conductive (insulating) material. In this example, the bobbin 3 is integrally formed by injection molding of the synthetic resin. However, when implementing the magnetostrictive torque sensor according to one aspect of the present disclosure, the bobbin 3 can also be formed by combining multiple parts.

[0031] The bobbin side cylinder portion 7 has a portion around its periphery, specifically its outer or inner periphery, where the detection coil 28 of the detection unit 4 is disposed. The bobbin side cylinder portion 7 has a cylindrical shape. That is, the bobbin side cylinder portion 7 has an inner circumferential surface whose inner diameter does not change along the axial direction and an outer circumferential surface whose outer diameter does not change along the axial direction. Furthermore, the bobbin side cylinder portion 7 is disposed coaxially with the rotating shaft 2 when the magnetostrictive torque sensor 1 is supported and fixed to the non-rotating member 20. In this state, the circumferential surface of the bobbin side cylinder portion 7 faces the circumferential surface of the rotating shaft 2. In this example, when the magnetostrictive torque sensor 1 is supported and fixed to the non-rotating member 20, the inner circumferential surface of the bobbin side cylinder portion 7 faces closely to the outer circumferential surface of the rotating shaft 2 with a small gap between them.

[0032] The bobbin side fitting surface 8 is provided on the peripheral surface of any portion of the bobbin 3. Specifically, the bobbin side fitting surface 8 is provided on the entire or part of the bobbin side cylinder portion 7 or a cylinder portion provided separately from the bobbin side cylinder portion 7, for example, but not limited to, the outer diameter side cylinder portion 11 provided on the outer diameter side of the bobbin side cylinder portion 7 or the inner diameter side cylinder portion provided on the inner diameter side of the bobbin side cylinder portion 7. In this case, the bobbin side fitting surface 8 is preferably configured as a single cylindrical surface whose diameter does not change in the axial direction.

[0033] The bobbin side locking hole 9 is provided in any part of the bobbin 3. The bobbin side locking hole 9, in combination with the positioning member 6 and the ring side locking hole 15 of the magnetic ring 5, has the function of preventing relative displacement (creep), particularly relative displacement in the axial direction, between the bobbin 3 and the magnetic ring 5. The arrangement of the bobbin side locking hole 9 is not particularly limited, and it can be appropriately set at any position on the bobbin 3 depending on factors such as ease of assembly. Furthermore, as long as the bobbin side locking hole 9 can be formed in any direction, including the radial direction or axial direction, of the bobbin 3, as long as it can achieve its function, but it is preferable to form it in the radial direction of the bobbin 3.

[0034] The bobbin side locking hole 9 can be configured as a through hole or a bottomed hole in relation to the ring side locking hole 15, as long as it is possible to place (insert) the positioning member 6 inside the bobbin side locking hole 9 and inside the ring side locking hole 15. Furthermore, the opening shape of the bobbin side locking hole 9 can be set as desired depending on the shape of the positioning member.

[0035] Although not limited to the following configuration, in this example, the bobbin 3 has a connecting plate portion 10 extending radially outward from an end portion on one axial side (the right side in FIG. 2 ) of the bobbin side cylindrical portion 7, and an outer diameter side cylindrical portion 11 extending radially outward from the radially outer end portion of the connecting plate portion 10. The bobbin side fitting surface 8 is formed by the entire inner circumferential surface of the outer diameter side cylindrical portion 11. The bobbin side locking hole 9 penetrates the outer diameter side cylindrical portion 11 in the radial direction.

[0036] The connecting plate 10 has a hollow circular end face shape when viewed from the axial direction. That is, the connecting plate 10 extends from one axial end of the bobbin side tube portion 7 toward the radially outward direction around the entire circumference. The radially outer end of the connecting plate 10 is connected to one axial end of the outer diameter side tube portion 11. In other words, the connecting plate 10 radially connects one axial end of the bobbin side tube portion 7 and one axial end of the outer diameter side tube portion 11.

[0037] In this example, since the bobbin 3 is provided with a connector accommodating portion, the outer diameter side cylinder portion 11 is provided in a portion of the bobbin 3 excluding the portion where the connector accommodating portion 12 is provided, and extends from the radially outer end of the connecting plate portion 10 toward the other axial side (left side in FIG. 2 ). That is, in this example, the outer diameter side cylinder portion 11 has an asymmetrical cylindrical shape. However, in a structure where the connector accommodating portion 12 is not provided, the outer diameter side cylinder portion 11 extends from the entire radially outer end of the connecting plate portion 10 toward the other axial side. The outer diameter side cylinder portion 11 is arranged coaxially with the bobbin side cylinder portion 7 and the bobbin side fitting surface 8.

[0038] In this example, the outer diameter side cylinder portion 11 has an axial length that is shorter than the axial length of the bobbin side cylinder portion 7. Therefore, the other axial side portion of the bobbin side cylinder portion 7 protrudes further in the axial direction than the other axial side end portion of the outer diameter side cylinder portion 11.

[0039] The axial length of the outer cylindrical portion 11 is not particularly limited, but can be at least three times, and preferably at least four times, the diameter of the bobbin-side locking hole 9. In the illustrated example, the axial length of the outer cylindrical portion 11 is approximately three times the diameter of the bobbin-side locking hole 9.

[0040] In this example, the bobbin side fitting surface 8 is provided on the inner circumferential surface of the outer diameter side cylindrical portion 11. The bobbin side fitting surface 8 is provided on the entire inner circumferential surface of the outer diameter side cylindrical portion 11.

[0041] In this example, the bobbin side locking hole 9 penetrates radially through the outer diameter side tubular portion 11. The bobbin side locking hole 9 opens to both the bobbin side fitting surface 8 provided on 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 this example, the bobbin side locking hole 9 is configured as a circular hole having a circular opening shape.

[0042] In this example, the bobbin side locking hole 9 is provided at any position in the circumferential direction of the outer diameter side cylindrical portion 11. In particular, since the bobbin 3 includes the connector accommodating portion 12, the bobbin side locking hole 9 is provided at a portion of the outer diameter side cylindrical portion 11 that is slightly shifted in the circumferential direction from a portion where the radially inner end of the connector accommodating portion 12 is connected, specifically, at a portion that is shifted about 45 degrees from the circumferential center position of the connector accommodating portion 12.

[0043] In this example, the bobbin 3 further includes a connector accommodating portion 12. The connector accommodating portion 12 accommodates a connector for electrically connecting a cable extending from a detection circuit located outside the magnetostrictive torque sensor 1 to the detection portion 4.

[0044] In this example, the connector accommodating portion 12 has a rectangular cylindrical shape that extends in the radial direction of the bobbin 3. The radially inner end of the connector accommodating portion 12 opens to the bobbin side fitting surface 8 provided on the inner peripheral surface of the outer diameter side cylindrical portion 11.

[0045] When implementing the magnetostrictive torque sensor according to one aspect of the present disclosure, the shape of the connector housing can be changed as appropriate depending on the shape of the connector to be housed therein. Alternatively, the connector housing can be omitted.

[0046] The detection unit 4 has a detection coil 28 arranged around the bobbin side cylinder portion 7. In this example, the detection coil 28 is arranged on the outer periphery of the bobbin side cylinder portion 7. The detection unit 4 changes its output signal depending on the magnitude and direction of the torque applied to the rotating shaft 2. The output signal of the detection unit 4 is transmitted to the detection circuit via a connector and a cable housed in the connector housing portion 12.

[0047] The configuration of the detection coils, such as their shape, number, and arrangement, is not particularly limited.

[0048] For example, as shown in the example of FIG. 4, the detection unit 4 can be configured by arranging two detection coils 23a, 23b, each of which is formed by winding an insulated electric wire around a bobbin 3 in a circular or spiral shape, side by side in the axial direction.

[0049] In this case, two magnetic change portions 26a, 26b are provided on the outer peripheral surface of the rotating shaft 2, each of which is composed of a plurality of magnetic portions 24a, 24b having magnetic anisotropy and a plurality of non-magnetic portions 25a, 25b not having magnetic anisotropy, arranged alternately. Of the two magnetic change portions 26a, 26b, the magnetic portions 24a and non-magnetic portions 25a constituting the first magnetic change portion 26a extend in a direction 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 non-magnetic portions 25b constituting the second magnetic change portion 26b extend in a direction inclined by a predetermined angle (for example, −45 degrees) with respect to the axial direction of the rotating shaft 2, in the opposite direction to the inclination direction of the magnetic portions 24a and non-magnetic portions 25a of the first magnetic change portion 26a.

[0050] Of the two detection coils 23a, 23b, the first detection coil 23a is arranged around the first magnetic change portion 26a, and the second detection coil 23b is arranged around the second magnetic change portion 26b.

[0051] When torque is applied to the rotating shaft 2, distortion occurs in the magnetic portions 24a, 24b provided on the outer peripheral surface of the rotating shaft 2, causing tensile stress to act on one of the magnetic portions 24a (or 24b) and compressive stress to act on the other magnetic portion 24b (or 24a). The magnetic permeability increases in the portion where tensile stress acts, while it decreases in the portion where compressive stress acts. The detection circuit then calculates the difference in voltage (induced electromotive force) between the detection coils 23a, 23b, and based on this difference, the direction and magnitude of the torque applied to the rotating shaft 2 are determined.

[0052] Alternatively, as shown in another example in Figures 5(A) and 5(B), the detection unit 4 can be constructed by stacking four detection coils 28a to 28d in the radial direction, each of which is made up of multiple parallelogram coil pieces 27a to 27d arranged around the entire circumference when viewed from the radial direction.

[0053] Each of the detection coils 28a to 28d is formed by winding an insulated electric wire around a bobbin 3. The outer peripheral surface of the bobbin 3 is provided with a first inclined groove 29a inclined at a predetermined angle (e.g., +45 degrees) with respect to the axial direction of the bobbin 3, and a second inclined groove 29b inclined at a predetermined angle (e.g., −45 degrees) with respect to the axial direction of the bobbin 3 in the opposite direction to the first inclined groove 29a. Of the four detection coils 28a to 28d, the coil pieces 27a constituting the first detection coil 28a and the coil pieces 27d constituting the fourth detection coil 28d are formed by winding an insulated electric wire along the first inclined groove 29a. In contrast, the coil pieces 27b constituting the second detection coil 28b and the coil pieces 27c constituting the third detection coil 28c are formed by winding an insulated electric wire along the second inclined groove 29b.

[0054] 6, the detection coils 28a to 28d are connected in a ring shape to form a detection circuit 30. To measure the torque applied to the rotating shaft 2, an AC voltage is applied between a contact point A between the first detection coil 28a and the second detection coil 28b and a contact point C between the third detection coil 28c and the fourth detection coil 28d. Then, the voltages between a contact point B between the second detection coil 28b and the third detection coil 28c and a contact point D between the first detection coil 28a and the fourth detection coil 28d are detected, and the direction and magnitude of the torque transmitted by the rotating shaft 2 are determined based on these voltages.

[0055] When the detection unit 4 is configured by stacking the four detection coils 28a to 28d in the radial direction, the rotating shaft 2 is configured in a columnar or cylindrical shape using an iron-based alloy having magnetostrictive properties. A shot peening treatment can be performed on the outer peripheral surface of the rotating shaft 2 in a portion located radially inside the detection unit 4 to form a modified layer with improved magnetostrictive properties.

[0056] However, when implementing a magnetostrictive torque sensor according to one aspect of the present disclosure, the detection unit is not limited to the two examples described above, and any configuration can be adopted as long as it can detect changes in the magnetic field existing around the rotating shaft as torque is applied to the rotating shaft.

[0057] Furthermore, the detection coil that constitutes the detection unit 4 is not limited to a coil formed by winding an insulated wire around the bobbin 3, but can also be formed by a pattern printed on a flexible printed circuit (FPC).

[0058] The magnetic ring 5 is also called a back yoke, and has the function of preventing external leakage of magnetic flux generated by the detection coil 28 that constitutes the detection unit 4. The magnetic ring 5 has a ring-side cylindrical portion 13 that is arranged around the detection unit 4, a ring-side mating surface 14 that mates with the bobbin-side mating surface 8, and a ring-side locking hole 15.

[0059] The magnetic ring 5 is integrally formed from a magnetic material. Examples of the magnetic material that can be used for the magnetic ring 5 include iron-based alloys such as alloy steel for mechanical structures and stainless steel.

[0060] In this example, the magnetic ring 5 is made up of only the ring side cylindrical portion 13 and is configured to have a substantially cylindrical shape as a whole. The shape of the ring side cylindrical portion 13 is arbitrary as long as it is substantially cylindrical as a whole. For example, the outer diameter and inner diameter can be constant along the axial direction, or at least one of the outer diameter and inner diameter can be configured with a stepped cylindrical surface.

[0061] In this example, the ring side cylindrical portion 13 has a small diameter portion 16 in the other axial side portion (excluding the end portion on one axial side), and a large diameter portion 17 at the end portion on one axial side, the large diameter portion 17 having an outer diameter larger than that of the small diameter portion 16. That is, the ring side cylindrical portion 13 has a stepped cylindrical outer peripheral surface in which the outer peripheral surfaces of the small diameter portion 16 and the large diameter portion 17 are connected by a step surface 18 facing the other axial side. In contrast, the inner peripheral surfaces of the small diameter portion 16 and the large diameter portion 17 are located 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.

[0062] The ring side cylindrical portion 13 also has a notch 19 at one circumferential position on one axial end of the large diameter portion 17. The notch 19 penetrates the large diameter portion 17 from the inner peripheral surface to the outer peripheral surface and opens onto the end face on one axial side of the large diameter portion 17. When the magnetostrictive torque sensor 1 is assembled, the notch 19 is located at a portion whose phase in the circumferential direction coincides with that of the connector accommodating portion 12. A cable extending from the detecting unit 4 and / or a connector provided at the tip of the cable are located inside the notch 19.

[0063] The ring side fitting surface 14 is provided on the circumferential surface of any portion of the magnetic ring 5. Specifically, the ring side fitting surface 14 is provided on the entire or part of the ring side cylindrical portion 13 or a cylindrical portion provided separately from the ring side cylindrical portion 13, for example, but not limited to, an outer diameter side cylindrical portion provided on the outer diameter side of the ring side cylindrical portion 13 or an inner diameter side cylindrical portion provided on the inner diameter side of the ring side cylindrical portion 13. In this case, the ring side fitting surface 14 is preferably configured as a single cylindrical surface whose diameter does not change in the axial direction.

[0064] In this example, the ring-side fitting surface 14 is provided on the outer peripheral surface of the large diameter portion 17, more specifically, on the entire outer peripheral surface.

[0065] The fitting state between the bobbin-side fitting surface 8 and the ring-side fitting surface 14 is arbitrary, and any of a clearance fit, an interference fit, and an intermediate fit can be used. However, from the viewpoint of ensuring good coaxiality between the bobbin 3 and the magnetic ring 5, it is preferable to fit the bobbin-side fitting surface 8 and the ring-side fitting surface 14 without any play in the radial direction. In this case, fitting by spigot fitting or press-fitting (including light press-fitting) can be used. From this viewpoint, the radial dimension of the ring-side fitting surface 14 is determined in relation to the radial dimension of the bobbin-side fitting surface 8.

[0066] In this example, the ring-side mating surface 14 has an outer diameter dimension that is slightly smaller than the inner diameter dimension of the bobbin-side mating surface 8. Therefore, when the magnetostrictive torque sensor 1 is assembled, the bobbin-side mating surface 8 and the ring-side mating surface 14 are fitted together by a spigot fit, which is a clearance fit with no play in the radial direction.

[0067] The relationship between the axial length of the bobbin-side fitting surface 8 and the axial length of the ring-side fitting surface 14 is arbitrary, and these lengths can be the same or different. In this example, the axial length of the bobbin-side fitting surface 8 and the axial length of the ring-side fitting surface 14 are approximately 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 approximately the same. Therefore, when the magnetostrictive torque sensor 1 is assembled, the axial position of the stepped surface 18 and the axial position of the end face on the other axial side of the outer-diameter side cylindrical portion 11 are approximately the same. In other words, the stepped surface 18 and the end face on the other axial side of the outer-diameter side cylindrical portion 11 are located on approximately the same plane.

[0068] The ring-side locking hole 15 is provided in any desired portion of the magnetic ring 5. The ring-side locking hole 15, in combination with the positioning member 6 and the bobbin-side locking hole 9 of the bobbin 3, functions to prevent relative displacement (creep), particularly axial relative displacement, between the bobbin 3 and the magnetic ring 5. The arrangement of the bobbin-side locking hole 9 is not particularly limited, but the bobbin-side locking hole 9 is provided in a portion that aligns with the bobbin-side locking hole 9 when the magnetostrictive torque sensor 1 is assembled. The orientation of the ring-side locking hole 15 is also determined in relation to the orientation of the bobbin-side locking hole 9, and the ring-side locking hole 15 can be formed in any direction, including the radial or axial direction, of the magnetic ring 5. However, it is preferable that the ring-side locking hole 15 be formed in the radial direction of the magnetic ring 5 in accordance with the radial formation of the bobbin-side locking hole 9. In this case, the ring-side locking hole 15 is provided in a portion that aligns with the bobbin-side locking hole 9 when the magnetostrictive torque sensor 1 is assembled, i.e., a portion that is in phase with the bobbin-side locking hole 9 in the axial position and circumferential direction.

[0069] The ring-side locking hole 15 can be configured as a through hole or a bottomed hole in relation to the bobbin-side locking hole 9, as long as it is possible to place (insert) the positioning member 6 inside the bobbin-side locking hole 9 and inside the ring-side locking hole 15. Furthermore, the opening shape of the ring-side locking hole 15 can be set as desired depending on the shape of the positioning member.

[0070] In this example, the ring-side locking hole 15 is provided in the large diameter portion 17. The ring-side locking hole 15 opens to the ring-side fitting surface 14 provided on the outer peripheral surface of the large diameter portion 17. Alternatively, in this example, the ring-side locking hole can be formed so as to penetrate the magnetic ring in the radial direction. In this example, the ring-side locking hole 15 has a circular opening shape and is configured as a bottomed hole that opens only radially outward.

[0071] The positioning member 6 is fitted between the bobbin-side locking hole 9 of the bobbin 3 and the ring-side locking hole 15 of the magnetic ring 5 , thereby preventing relative displacement between the bobbin 3 and the magnetic ring 5 .

[0072] The material constituting the positioning member 6 is not particularly limited as long as it can ensure sufficient bonding strength between the bobbin 3 and the magnetic ring 5, and metal materials such as iron-based alloys and light alloys, as well as synthetic resins, can be used.

[0073] The structure of the positioning member 6 is not particularly limited as long as it can perform its function. For example, the positioning member 6 can be configured as a segmented cylindrical spring pin with a linear or wavy slit at one circumferential position, or as a columnar or cylindrical pin. In these cases, the cross-sectional shape of the positioning member 6 is not limited to a circle, but can also be a non-circular shape such as a segmented circle or polygon. It is preferable that the opening shapes of the bobbin-side locking hole 9 provided in the bobbin 3 and the ring-side locking hole 15 provided in the magnetic ring 5 be determined according to the cross-sectional shape of the positioning member 6.

[0074] Alternatively, the positioning member 6 can be formed of a screw. In this case, one of the bobbin side locking hole 9 and the ring side locking hole 15 is a threaded hole. In this case, even if the bobbin side locking hole 9, the ring side locking hole 15, and the positioning member 6 are arranged in the axial direction of the magnetostrictive torque sensor 1, it is possible to reliably prevent relative displacement between the bobbin 3 and the magnetic ring 5 in the axial and circumferential directions.

[0075] The positioning member 6 has a length sufficient to maintain its position spanning the bobbin-side locking hole 9 and the ring-side locking hole 15 even if the bobbin 3 and / or the magnetic ring 5 thermally expands during use of the magnetostrictive torque sensor 1. The positioning member 6 may be long enough to be positioned entirely inside the bobbin-side locking hole 9 and the ring-side locking hole 15. Alternatively, the positioning member 6 may protrude radially from the opening of at least one of the bobbin-side locking hole 9 and the ring-side locking hole 15, as long as this does not impede the function of the magnetostrictive torque sensor 1.

[0076] In this example, the radially outer portion of the positioning member 6 is positioned (inserted) inside the bobbin side locking hole 9, and the radially inner portion of the positioning member 6 is positioned (inserted) inside the ring side locking hole 15.

[0077] In this example, the positioning member 6 is a notched cylindrical spring pin with a linear or wavy slit at one circumferential location. The positioning member 6 is inserted into the bobbin-side locking hole 9 and the ring-side locking hole 15 with its outer diameter reduced by elastically narrowing the width of the slit, and then elastically restored to its original shape. As a result, the positioning member 6 is tightly fitted into at least one of the bobbin-side locking hole 9 and the ring-side locking hole 15 and spans between the bobbin-side locking hole 9 and the ring-side locking hole 15.

[0078] In this example, the radially outer end of the positioning member 6 does not protrude radially outward from the radially outer end of the bobbin-side locking hole 9. The positioning member 6 is made of a metal material such as an iron-based alloy or a light alloy.

[0079] In the magnetostrictive torque sensor 1, the combination of the bobbin-side locking hole 9, the ring-side locking hole 15, and the positioning member 6 serves to prevent relative displacement (creep), particularly relative displacement in the axial direction, between the bobbin 3 and the magnetic ring 5. The number of combinations of the bobbin-side locking hole 9, the ring-side locking hole 15, and the positioning member 6 can be set as desired depending on the application and installation location of the magnetostrictive torque sensor 1. That is, the magnetostrictive torque sensor 1 can have one combination of the bobbin-side locking hole 9, the ring-side locking hole 15, and the positioning member 6. Alternatively, the magnetostrictive torque sensor 1 can have multiple combinations of the bobbin-side locking hole 9, the ring-side locking hole 15, and the positioning member 6.

[0080] In this example, there is only one combination of a positioning member 6, a bobbin-side locking hole 9, and a ring-side locking hole 15. Therefore, the magnetostrictive torque sensor 1 of this example has only one positioning member 6.

[0081] The magnetostrictive torque sensor 1 is prevented from rotating relative to the non-rotating member 20 by fitting the outer surface of the small diameter portion 16 that constitutes the ring side cylindrical portion 13 of the magnetic ring 5 without any radial play into the fixed side fitting surface 31 provided on the inner surface of the non-rotating member 20 (see Figure 2) that does not rotate even when the housing or frame is in use, and by arranging the side surfaces on both circumferential sides of the connector accommodating portion 12 to face the stopper surfaces provided on the non-rotating member 20.

[0082] Furthermore, the magnetostrictive torque sensor 1 is positioned in the axial direction by abutting the fixed-side step surface 32 facing one axial side of the non-rotating member 20 against the step surface 18 of the magnetic ring 5 and the end face on the other axial side of the outer diameter side cylindrical portion 11, and by abutting a retaining member 33 such as a retaining ring engaged with the inner surface of the non-rotating member 20 against the side surface on one axial side of the connecting plate portion 10.

[0083] In this way, the magnetostrictive torque sensor 1 is disposed around the rotating shaft 2 with the magnetostrictive torque sensor 1 supported and fixed to the non-rotating member 20. In other words, the magnetostrictive torque sensor 1 is supported and fixed to the non-rotating member 20 with the rotating shaft 2 inserted inside the bobbin side cylindrical portion 7. Note that the method of supporting and fixing the magnetostrictive torque sensor to a non-rotating member that does not rotate during use is not limited to the above-described method, and any method can be used.

[0084] With the magnetostrictive torque sensor 1 of this example supported and fixed to the non-rotating member 20, a portion of the non-rotating member 20 can be brought into contact with or closely facing the peripheral portion of the outer circumferential surface of the bobbin 3 around the radially outer opening of the bobbin-side locking hole 9 so as to cover the radially outer opening of the bobbin-side locking hole 9 provided in the bobbin 3. This reliably prevents the positioning member 6 from falling off from the bobbin-side locking hole 9 and the ring-side locking hole 15.

[0085] When torque is applied to the rotating shaft 2 and the rotating shaft 2 undergoes elastic torsional deformation, the magnetic permeability of the rotating shaft 2 changes due to the inverse magnetostriction effect. As a result, when the magnetic field existing around the rotating shaft 2 changes, the voltage (induced electromotive force) of the detection coil that constitutes the detection unit 4 changes. Based on this change in voltage, the detection circuit determines the torque applied to the rotating shaft 2.

[0086] In the magnetostrictive torque sensor 1 of this example, the bobbin-side mating surface 8 of the bobbin 3 and the ring-side mating surface 14 of the magnetic ring 5 are mated without any rattle. This ensures good coaxiality between the bobbin 3 and the magnetic ring 5, and allows a stable magnetic circuit to be formed that passes through the rotating shaft 2, bobbin 3, and magnetic ring 5.

[0087] In the magnetostrictive torque sensor 1 of this example, the positioning member 6 is fitted over the bobbin-side locking hole 9 provided in the bobbin 3 and the ring-side locking hole 15 provided in the magnetic ring 5. Therefore, even if the bobbin 3 and / or the magnetic ring 5 expand or contract due to temperature changes, it is possible to reliably prevent relative displacement in the axial and circumferential directions between the bobbin 3 and the magnetic ring 5. In other words, the magnetostrictive torque sensor 1 of this example can ensure sufficient bonding strength between the bobbin 3 and the magnetic ring 5, specifically, bonding strength in the axial and circumferential directions.

[0088] In the magnetostrictive torque sensor 1 of this example, the bobbin-side mating surface 8 is provided on the inner peripheral surface of the bobbin 3, and the ring-side mating surface 14 is provided on the outer peripheral surface of the magnetic ring 5. That is, in the magnetostrictive torque sensor 1 of this example, the bobbin-side mating surface 8 facing radially inward and the ring-side mating surface 14 facing radially outward are mated without any rattle, and the positioning member 6 is inserted from the radially outer side into the bobbin-side locking hole 9 of the bobbin 3 and the ring-side locking hole 15 of the magnetic ring 5. By adopting this configuration, the bobbin-side locking hole 9 can be formed in the outer diameter side cylinder portion 11 rather than the bobbin side cylinder portion 7, so that the detection coil 28 of the detection unit 4 is arranged around the periphery (outer circumference in this example), and the roundness of the bobbin side cylinder portion 7, whose peripheral surface (inner peripheral surface in this example) faces the peripheral surface (outer circumference surface in this example) of the rotating shaft 2, is more appropriately ensured.

[0089] Alternatively, in the magnetostrictive torque sensor according to one aspect of the present disclosure, the bobbin-side mating surface may be provided on the outer peripheral surface of the bobbin, and the ring-side mating surface may be provided on the inner peripheral surface of the magnetic ring. That is, the bobbin-side mating surface facing radially outward may be mated with the ring-side mating surface facing radially inward (preferably without rattle), and positioning members may be inserted from the radially outer side into the bobbin-side locking holes that are provided in the bobbin and open to the bobbin-side mating surface, and the ring-side locking holes that are provided in the magnetic ring and pass radially through the magnetic ring.

[0090] More specifically, both the bobbin side cylindrical portion of the bobbin and the ring side cylindrical portion of the magnetic ring are configured to be approximately cylindrical overall, and a protrusion (bobbin side protrusion or ring side protrusion) is provided that protrudes radially outward and / or inward from one axial end of at least one of the bobbin side cylindrical portion and the ring side cylindrical portion. In this case, the bobbin side fitting surface is formed by the outer circumferential surface of the one axial end of the bobbin side cylindrical portion or the outer circumferential surface of the bobbin side protrusion, and the ring side fitting surface is formed by the inner circumferential surface of the one axial end of the ring side cylindrical portion or the inner circumferential surface of the ring side protrusion.

[0091] Second Example A second example of the embodiment of the present disclosure will be described with reference to FIGS.

[0092] The magnetostrictive torque sensor 1a of this example differs from the structure of the first example in that the bobbin side locking hole 9 penetrates the bobbin 3 in the radial direction, and the positioning member 6a protrudes radially from the opening on the radial side of the bobbin side locking hole 9, which is on the opposite side to the magnetic ring 5 in the radial direction.

[0093] Specifically, in the magnetostrictive torque sensor 1a of this example, the positioning member 6a is made of a metal material, and the length of the positioning member 6a is longer than the sum of the radial depth of the bobbin-side locking hole 9 in the bobbin 3 and the radial depth of the ring-side locking hole 15 in the magnetic ring 5. Therefore, the radially outer end of the positioning member 6a protrudes radially outward from the radially outer opening of the bobbin-side locking hole 9 in the bobbin 3.

[0094] In this example, with the magnetostrictive torque sensor 1a supported and fixed to the non-rotating member 20a, the radially outer portion of the positioning member 6a that protrudes from the radially outer opening of the bobbin-side locking hole 9 is positioned inside the engagement recess 21 provided on the inner circumferential surface of the non-rotating member 20a. The radially outer portion of the positioning member 6a is then positioned between the circumferentially opposing side surfaces of the inner surface of the engagement recess 21. In other words, the radially outer portion of the positioning member 6a is closely opposed to the circumferentially facing side surface provided on the non-rotating member 20a. This prevents the magnetostrictive torque sensor 1a from rotating relative to the non-rotating member 20a.

[0095] According to the magnetostrictive torque sensor 1a of this embodiment, the connector accommodating portion 12 provided in the bobbin 3 can be easily reduced in size or omitted.

[0096] In order to prevent the magnetostrictive torque sensor 1 of the first example from rotating relative to the non-rotating member 20, it is conceivable to make both circumferential side surfaces of the connector accommodating portion 12 provided on the bobbin 3 face stopper surfaces provided on the non-rotating member 20. Here, because the bobbin 3 is made of synthetic resin, fretting wear is likely to occur between the circumferential side surfaces of the connector accommodating portion 12 and the stopper surfaces due to vibrations during use, etc., making it difficult to reduce the size of the connector accommodating portion 12.

[0097] In contrast, in this example, the radially outer portion of the positioning member 6a is positioned inside the engaging recess 21 provided on the inner circumferential surface of the non-rotating member 20a, thereby preventing the magnetostrictive torque sensor 1a from rotating relative to the non-rotating member 20a. This makes it easy to reduce the size of the connector housing 12 or to omit it.

[0098] As an alternative to the second example, in a structure in which the bobbin side mating surface is provided on the outer peripheral surface of the bobbin and the ring side mating surface is provided on the inner peripheral surface of the magnetic ring, the ring side locking hole penetrates radially through the magnetic ring, the bobbin side mating surface facing radially outward and the ring side mating surface facing radially inward are mated, and the positioning member protrudes radially from the opening on the radially opposite side of the bobbin 3 in the radial direction, of the openings on both radial sides of the ring side locking hole.

[0099] The other configurations and effects of the second example are the same as those of the first example.

[0100] Third Example A third example of the embodiment of the present disclosure will be described with reference to FIGS. 10 and 11. FIG.

[0101] The magnetostrictive torque sensor 1b of this example differs from the structures of the first and second examples in that it includes a plurality of bobbin-side locking holes, the ring-side locking holes, and the positioning members.

[0102] Specifically, the magnetostrictive torque sensor 1b of this example has two combinations of a bobbin-side locking hole provided in the bobbin 3, a ring-side locking hole provided in the magnetic ring 5, and a positioning member 6a.

[0103] In this example, similar to the structure of the second example, the radially outer portions of the positioning members 6 a protrude radially outward from the radially outer openings of the bobbin-side locking holes provided in the bobbin 3 .

[0104] In this example, with the magnetostrictive torque sensor 1b supported and fixed to the non-rotating member 20b, the radially outer portion of one positioning member 6a faces a stopper surface 22a provided on the non-rotating member 20b and facing one circumferential side, and the radially outer portion of the other positioning member 6a faces a stopper surface 22b provided on the non-rotating member 20b and facing the other circumferential side, thereby preventing rotation of the magnetostrictive torque sensor 1b relative to the non-rotating member 20b.

[0105] The configuration and effects of the other parts of the third example are similar to those of the first and second examples.

[0106] DESCRIPTION OF SYMBOLS 1, 1a, 1b Magnetostrictive torque sensor 2 Rotating shaft 3 Bobbin 4 Detection section 5 Magnetic ring 6, 6a Positioning member 7 Bobbin side cylindrical section 8 Bobbin side fitting surface 9 Bobbin side locking hole 10 Connection plate section 11 Outer diameter side cylindrical section 12 Connector accommodating section 13 Ring side cylindrical section 14 Ring side fitting surface 15 Ring side locking hole 16 Small diameter section 17 Large diameter section 18 Step surface 19 Notch 20, 20a, 20b Non-rotating member 21 Engaging recess 22a, 22b Stopper surface 23a First detection coil 23b Second detection coil 24a, 24b Magnetic section 25a, 25b Non-magnetic section 26a First magnetic change section 26b Second magnetic change section 27a, 27b, 27c, 27d Coil pieces 28 Detection coil 28a First detection coil 28b Second detection coil 28c Third detection coil 28d Fourth detection coil 29a First inclined groove 29b Second inclined groove 30 Detection circuit 31 Fixed side fitting surface 32 Fixed side stepped surface 33 Anti-disconnection member

Claims

1. A magnetostrictive torque sensor that measures torque applied to a rotating shaft having magnetostrictive properties, a bobbin having a bobbin side tubular portion disposed around the rotation shaft, a cylindrical bobbin side fitting surface, and a bobbin side locking hole; a detection unit having a detection coil disposed on the outer periphery of the bobbin side cylinder portion; a magnetic ring having a ring-side cylindrical portion disposed around the detection portion, a ring-side fitting surface that fits with the bobbin-side fitting surface, and a ring-side locking hole; a positioning member that is bridged between the bobbin-side locking hole and the ring-side locking hole; A magnetostrictive torque sensor comprising:

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

3. The bobbin side locking hole penetrates the bobbin in a radial direction, the positioning member protrudes radially from one of the openings on both radial sides of the bobbin-side locking hole, the opening being on the opposite side to the magnetic ring in the radial direction; 2. The magnetostrictive torque sensor according to claim 1.

4. 2. The magnetostrictive torque sensor according to claim 1, comprising a plurality of the bobbin-side locking holes, the ring-side locking holes, and the positioning members.

5. 2. The magnetostrictive torque sensor according to claim 1, wherein the positioning member is a spring pin.

6. 2. The magnetostrictive torque sensor according to claim 1, wherein the bobbin-side fitting surface is provided on an inner peripheral surface of the bobbin, and the ring-side fitting surface is provided on an outer peripheral surface of the magnetic ring.

7. the bobbin has a connecting plate portion extending radially outward from one axial end of the bobbin side cylindrical portion, and an outer diameter side cylindrical portion extending radially outward from the radially outer end of the connecting plate portion toward the other axial end, the inner peripheral surface of the bobbin is formed by the 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 fitting surface is provided at one axial end of the outer peripheral surface of the magnetic ring, The ring-side locking hole opens onto the ring-side fitting surface.

7. The magnetostrictive torque sensor according to claim 6.