Load detection device

Abstract

To provide a load detection device capable of improving detection accuracy. [Solution] The magnetic circuit 10 has a magnetic flux generating unit 13 and magnetostrictive materials 11, 12, and 100, and is configured in a ring shape so that the magnetic flux generated by the magnetic flux generating unit 13 flows through the magnetic flux generating unit 13 and the magnetostrictive materials 11, 12, and 100. The first transmission member 31 transmits a load applied from the outside on one side in the axial direction of the magnetic circuit 10 to the magnetostrictive materials 11, 12, and 100. The second transmission member 32 transmits a load applied from the outside on the other side in the axial direction to the magnetostrictive materials 11, 12, and 100. The magnetic detection element 20 is located opposite to or inside a gap 14 provided between a plurality of magnetostrictive materials 11, 12, or opposite to or inside a gap 141 provided between the magnetic flux generating unit 13 and the magnetostrictive material 100, and outputs a signal corresponding to the magnetic flux flowing through the magnetic circuit 10. The magnetic shield 40 covers at least a portion of the first transmission member 31 and the second transmission member 32, as well as the magnetic circuit 10 and the magnetic detection element 20.

Description

Technical Field

[0001] The present invention relates to a load detection device using the magnetostrictive effect.

Background Art

[0002] Conventionally, a load detection device using the magnetostrictive effect has been known.

[0003] The load detection device described in Patent Document 1 includes a magnetic circuit configured such that magnetic flux flows annularly by a magnet, a magnetostrictive material, and a yoke, a load transmission member that transmits a load applied from the outside to the magnetostrictive material, and a magnetic detection element that outputs a signal corresponding to a change in the magnetic flux flowing through the magnetic circuit. In this load detection device, when a load applied from the outside is transmitted to the magnetostrictive material via the load transmission member, the magnetic permeability of the magnetostrictive material changes, and the amount of magnetic flux generated by the magnet passing through the magnetic circuit changes. Therefore, the load applied from the outside can be measured based on the output signal of the magnetic detection element. In Patent Document 1, the load transmission member is referred to as a stress transmission member.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the load detection device described in Patent Document 1, the magnetic circuit and the magnetic detection element are exposed to a magnetic field existing outside the device (hereinafter referred to as "external disturbance magnetic field"). Therefore, the magnetic flux flowing through the magnetic circuit may be affected by the external disturbance magnetic field. Accordingly, this load detection device has a problem that the magnetic detection element cannot correctly detect the change in the magnetic flux of the magnetic circuit corresponding to the load applied from the outside, and the detection accuracy deteriorates.

[0006] In view of the above points, the present invention aims to provide a load detection device capable of improving detection accuracy. [Means for solving the problem]

[0007] To achieve the above objective, according to the invention of claim 1, a load detection device for detecting an externally applied load is: A magnetic circuit (10) is configured in a ring shape such that the magnetic flux generated by the magnetic flux generating unit (13) generates magnetic flux, and magnetostrictive materials (11, 12, 100) whose permeability changes according to an external force, and the magnetic flux generated by the magnetic flux generating unit flows through the magnetic flux generating unit and the magnetostrictive materials. A first transmission member (31) made of a non-magnetic material transmits a load applied from the outside on one side in the direction in which the axis (CL) of the annular magnetic circuit extends to a magnetostrictive material, A second transmission member (32) made of a non-magnetic material transmits a load applied from the outside on the other side in the direction in which the axis extends to the magnetostrictive material, A magnetic detection element (20) is provided at a position opposite to or within a gap (14) provided between multiple magnetostrictive materials, or at a position opposite to or within a gap (141) provided between a magnetic flux generating unit and a magnetostrictive material, and outputs a signal corresponding to the magnetic flux flowing through the magnetic circuit. It is made of a magnetic material and comprises a magnetic shield (40) that covers at least a portion of the first transmission member and the second transmission member, a magnetic circuit and a magnetic detection element.

[0008] According to this, when an externally applied load is transmitted to the magnetostrictive material via the first or second transmission member, the permeability of the magnetostrictive material changes, and the amount of magnetic flux generated in the magnetic flux generation section that passes through the magnetostrictive material changes. As a result, the magnetic flux density detected by the magnetic detection element changes, making it possible to measure the externally applied load. In this configuration, the magnetic shield prevents at least a portion of the first and second transmission members, the magnetic circuit, and the magnetic detection element from being exposed to the external magnetic field. Therefore, the magnetic flux flowing through the magnetic circuit is prevented from being affected by the external magnetic field, and the magnetic detection element can correctly detect the change in magnetic flux in the magnetic circuit in response to the externally applied load. Thus, this load detection device can prevent the influence of the external magnetic field and improve detection accuracy.

[0009] In this specification, "ring-shaped" is not limited to circular shapes, but includes various shapes such as elliptical, polygonal, and curved shapes, in which the magnetic path from the magnetic flux generated at the magnetic flux generating part to the magnetic flux generating part does not intersect along the way.

[0010] The reference numerals in parentheses attached to each component indicate an example of the correspondence between that component and the specific components described in the embodiments described later. [Brief explanation of the drawing]

[0011] [Figure 1] This is a perspective view of the load detection device according to the first embodiment. [Figure 2] This is a plan view of the load detection device according to the first embodiment. [Figure 3] This is a side view in direction III of Figure 2. [Figure 4] This is a bottom view of the IV direction in Figure 3. [Figure 5] This is an exploded perspective view of the load detection device according to the first embodiment. [Figure 6] This is a perspective view showing the magnetic circuit, the first transmission member, and the second transmission member. [Figure 7]It is a cross-sectional view excluding the mold member at the VII-VII line of FIG. 3 (i.e., the boundary between the first transmission member and the magnetic circuit). [Figure 8] It is a cross-sectional view of the VIII-VIII line of FIG. 7. [Figure 9] It is a cross-sectional view of the IX-IX line of FIG. 7. [Figure 10] In FIG. 7, it is a cross-sectional view including the resin mold. [Figure 11] It is a cross-sectional view of the XI-XI line of FIG. 10. [Figure 12] It is a cross-sectional view of the XII-XII line of FIG. 10. [Figure 13] In the load detection device according to the second embodiment, it is a cross-sectional view along the X plane showing the magnetic shield and the internal structure. [Figure 14] It is a cross-sectional view of the XIV-XIV line of FIG. 13. [Figure 15] In the load detection device according to the third embodiment, it is a cross-sectional view along the X plane showing the magnetic shield and the internal structure. [Figure 16] It is a cross-sectional view of the XVI-XVI line of FIG. 15. [Figure 17] In the load detection device according to the fourth embodiment, it is a cross-sectional view along the X plane showing the magnetic shield and the internal structure. [Figure 18] It is a cross-sectional view of the XVIII-XVIII line of FIG. 17. [Figure 19] In the load detection device according to the fifth embodiment, it is a cross-sectional view along the X plane showing the magnetic shield and the internal structure. [Figure 20] It is a cross-sectional view of the XX-XX line of FIG. 19. [Figure 21] In the load detection device according to the sixth embodiment, it is a cross-sectional view along the X plane showing the magnetic shield and the internal structure. [Figure 22] It is a cross-sectional view of the XXII-XXII line of FIG. 21. [Figure 23] In the load detection device according to the seventh embodiment, it is a cross-sectional view along the X plane showing the magnetic shield and the internal structure. [Figure 24]Figure 23 shows a cross-sectional view of the line XXIV-XXIV. [Figure 25] This is a cross-sectional view along the X-plane showing the magnetic shield and internal structure in the load detection device according to the eighth embodiment. [Figure 26] Figure 25 shows a cross-sectional view of the line XXVI-XXVI. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals, and their descriptions are omitted.

[0013] (First Embodiment) The first embodiment will be described with reference to Figures 1 to 12. The load detection device 1 of the first embodiment is a load sensor that detects an externally applied load using the inverse magnetostrictive effect.

[0014] As shown in Figures 5 to 12, the load detection device 1 includes a magnetic circuit 10, a magnetic detection element 20, a first transmission member 31, a second transmission member 32, a magnetic shield 40, a molded member 50, and the like. Figures 7 to 9 show cross-sectional views excluding the molded member 50, while Figures 10 to 12 show cross-sectional views including the molded member 50.

[0015] As shown in Figures 6, 7, and 10, the magnetic circuit 10 includes a magnet 13 as a magnetic flux generating part, and a first magnetostrictive material 11 and a second magnetostrictive material 12 through which the magnetic flux generated by the magnet 13 passes. The magnet 13 is a permanent magnet that generates magnetic flux and is made of, for example, a samarium-cobalt magnet, a neodymium magnet, or the like.

[0016] The first magnetostrictive material 11 and the second magnetostrictive material 12 are made of a magnetic material whose permeability changes in response to an external force. The first magnetostrictive material 11 and the second magnetostrictive material 12 are made of, for example, electromagnetic stainless steel. The first magnetostrictive material 11 and the second magnetostrictive material 12 are each formed in a substantially arc shape.

[0017] One end of the first magnetostrictive material 11 is connected to the north pole side of the magnet 13, and one end of the second magnetostrictive material 12 is connected to the south pole side of the magnet 13. A gap 14 is provided between the other end of the first magnetostrictive material 11 (i.e., the end of the first magnetostrictive material 11 opposite to the magnet 13) and the other end of the second magnetostrictive material 12 (i.e., the end of the second magnetostrictive material 12 opposite to the magnet 13). The magnetic circuit 10 is configured in a ring shape so that the magnetic flux generated by the magnet 13 flows in the order of north pole of the magnet 13, first magnetostrictive material 11, gap 14, second magnetostrictive material 12, and south pole of the magnet 13.

[0018] In this specification, "ring-shaped" is not limited to circular shapes, but includes various shapes such as elliptical, polygonal, and curved shapes, in which the magnetic path from the magnetic flux generated by the magnet 13 through each component to the magnet 13 does not intersect along the way.

[0019] In the following explanation, the direction in which the axis CL of the magnetic circuit 10 extends is referred to as the "axial direction." The circumferential direction of a virtual circle perpendicular to the axis CL of the magnetic circuit 10 and centered on the axis CL is simply referred to as the "circumferential direction." The radial direction of that virtual circle is simply referred to as the "radial direction," with the side of the virtual circle farther from the axis CL being called the "radial outer side" and the side closer to the axis CL being called the "radial inner side." Furthermore, the first magnetostrictive material 11 and the second magnetostrictive material 12 are sometimes collectively referred to as "sensor magnetostrictive materials 11 and 12".

[0020] As shown in Figures 5, 8, and 11, the magnetic detection element 20 is mounted on the substrate 21 and provided on the gap 14 side of the magnetic circuit 10. The magnetic detection element 20 is provided at a position facing the gap 14 in the axial direction (i.e., a position facing the gap 14 in the axial direction) and outputs an electrical signal corresponding to the magnetic flux flowing through the magnetic circuit 10. The magnetic detection element 20 may also be provided at a position facing the gap 14 on one or the other side in the axial direction of the gap 14. The electrical signal output by the magnetic detection element 20 is output to the outside from terminal 22. The magnetic detection element 20 is composed of, for example, a TMR-IC or a Hall IC, and may or may not have a substrate 21. TMR stands for Tunnel Magneto Resistance. IC stands for Integrated Circuit. The substrate 21 is sealed with potting material 23.

[0021] As shown in Figures 6, 8, and 9, the first transmission member 31 is provided on one side in the axial direction relative to the sensor magnetostrictive materials 11 and 12. The first transmission member 31 is a load transmission member that transmits a load applied from the outside on one side in the axial direction to the sensor magnetostrictive materials 11 and 12. The second transmission member 32 is provided on the other side in the axial direction relative to the sensor magnetostrictive materials 11 and 12. The second transmission member 32 is a load transmission member that transmits a load applied from the outside on the other side in the axial direction to the sensor magnetostrictive materials 11 and 12. The first transmission member 31 and the second transmission member 32 are formed from non-magnetic materials such as SUS316L, SUSXM7, SUH660, A6061, and ADC12.

[0022] The first transmission member 31 and the second transmission member 32 transmit the load applied from the outside to a portion of the sensor magnetostrictive materials 11 and 12. In the following description, the portion of the first magnetostrictive material 11 to which the load is transmitted from the first transmission member 31 and the second transmission member 32 (i.e., the portion of the first magnetostrictive material 11 that is in contact with the first transmission member 31 and the second transmission member 32) is referred to as the first pressed portion 15. The portion of the second magnetostrictive material 12 to which the load is transmitted from the first transmission member 31 and the second transmission member 32 (i.e., the portion of the second magnetostrictive material 12 that is in contact with the first transmission member 31 and the second transmission member 32) is referred to as the second pressed portion 16. In Figures 7 and 10, the first pressed portion 15 and the second pressed portion 16 are shown with dashed hatching, although this does not represent a cross-section. The second transmission member 32 presses the first pressed portion 15 and the second pressed portion 16 against the first transmission member 31 from the other side in the axial direction.

[0023] The radial width of the first transmission member 31 and the second transmission member 32 is greater than or equal to the width of the first pressed portion 15 and the second pressed portion 16. The first transmission member 31 and the second transmission member 32 press over the entire radial width range of the first pressed portion 15 and the second pressed portion 16. In addition, the first transmission member 31 and the second transmission member 32 press over the first pressed portion 15 and the second pressed portion 16, but do not press over the end of the first magnetostrictive material 11 on the gap 14 side or the end of the second magnetostrictive material 12 on the gap 14 side.

[0024] In the following explanation, the side of the first transmission member 31 opposite to the sensor magnetostrictive materials 11 and 12 will be referred to as the "interface surface 34 of the first transmission member 31". Similarly, the side of the second transmission member 32 opposite to the sensor magnetostrictive materials 11 and 12 will be referred to as the "interface surface 36 of the second transmission member 32".

[0025] In the following description, the line connecting the center of the magnet 13 and the axis CL, and the plane containing the axis CL, are referred to as the X-plane, and the line perpendicular to the X-plane and containing the axis CL is referred to as the Y-plane. In the first embodiment, the interface surface 34 of the first transmission member 31 and the interface surface 36 of the second transmission member 32 are symmetrical with respect to the X-plane.

[0026] Furthermore, as shown in Figures 7 and 10, in the first embodiment, the first pressed portion 15 and the second pressed portion 16 are symmetrical with respect to the X-plane. In addition, in the first embodiment, the first magnetostrictive material 11 and the second magnetostrictive material 12 are symmetrical with respect to the X-plane.

[0027] Furthermore, the first pressed portion 15 and the second pressed portion 16 have a shape in which the radial width gradually changes from the magnet 13 towards the gap 14. Specifically, the first pressed portion 15 and the second pressed portion 16 have a shape in which the radial width gradually decreases from the magnet 13 side towards the gap 14 side. Also, the first magnetostrictive material 11 has a shape in which the radial width gradually increases from the part of the first pressed portion 15 opposite to the magnet 13 towards the end on the gap 14 side. Similarly, the second magnetostrictive material 12 also has a shape in which the radial width gradually increases from the part of the second pressed portion 16 opposite to the magnet 13 towards the end on the gap 14 side. Therefore, the first pressed portion 15 is the part of the first magnetostrictive material 11 where the magnetic flux density is greater than that of the end on the gap 14 side. In other words, the first pressed portion 15 is a portion within the first magnetostrictive material 11 where the change in permeability in response to the application of a load is greater than that at the end on the gap 14 side. Similarly, the second pressed portion 16 is a portion within the second magnetostrictive material 12 where the magnetic flux density is greater than that at the end on the gap 14 side. In other words, the second pressed portion 16 is also a portion within the second magnetostrictive material 12 where the change in permeability in response to the application of a load is greater than that at the end on the gap 14 side.

[0028] Here, the detection accuracy of the magnetic detection element 20 is expressed by the following equation 1. Detection accuracy = {(Sensitivity drift / 100) × B0 + Offset} / ΔB ... (Equation 1) B0 is the magnetic flux density detected by the magnetic detection element 20 when no load is applied to the first transmission member 31 and the second transmission member 32 from the outside (hereinafter referred to as "no-load magnetic flux density B0"). ΔB is the amount of change in magnetic flux density that the magnetic detection element 20 detects in response to a change in the load applied from the outside (hereinafter referred to as "magnetic flux density gain ΔB").

[0029] According to Equation 1 above, the larger the magnetic flux density gain ΔB and the smaller the no-load magnetic flux density B0, the better the detection accuracy of the magnetic detection element 20. In the load detection device 1 of the first embodiment, the magnetic flux density gain ΔB can be increased and the detection accuracy improved by setting the magnetic flux density of the first pressed portion 15 and the second pressed portion 16 of the sensor magnetostrictive materials 11 and 12 to an appropriate range with a large magnetostrictive coefficient (for example, a range near 1T).

[0030] Next, as shown in Figures 1 to 5 and Figures 7 to 12, the magnetic shield 40 is a housing formed from a magnetic material that covers the first transmission member 31, part of the second transmission member 32, the magnetic circuit 10, and the magnetic detection element 20. In the following description, the first transmission member 31, the second transmission member 32, the magnetic circuit 10, and the magnetic detection element 20 will be collectively referred to as the internal structure.

[0031] The magnetic shield 40 is formed from, for example, electromagnetic pure iron such as SUY-0 equivalent to JISC2504. Preferably, the magnetic shield 40 is made of a material with a maximum magnetic permeability of 10,000 or more. That is, the magnetic permeability of the material used for the magnetic shield 40 is higher than that of general-purpose steel. This makes it possible to suppress the influence of the magnetic field generated by a magnetic foreign object (for example, general-purpose steel) when it approaches the load detection device 1 from the outside. Furthermore, it is possible to suppress magnetic flux leakage from the magnetic circuit 10 to the outside.

[0032] The magnetic shield 40 has an outer cylinder portion 43, an inner cylinder portion 44, a top plate portion 45, and a bottom plate portion 46. The outer cylinder portion 43 is formed in a cylindrical shape with an axis extending parallel to the axis CL of the magnetic circuit 10 and is provided radially outward relative to the internal structure. The inner cylinder portion 44 is formed in a cylindrical shape with an axis extending parallel to the axis CL of the magnetic circuit 10 and is provided radially inward relative to the internal structure. The top plate portion 45 is provided on one side in the axial direction of the internal structure. The bottom plate portion 46 is provided on the other side in the axial direction of the internal structure. In this specification, "cylindrical" is not limited to cylindrical shapes, but includes, for example, rectangular cylinders, elliptical shapes, etc.

[0033] The magnetic shield 40 of the first embodiment is composed of two parts. Specifically, the outer cylinder portion 43, the inner cylinder portion 44, and the bottom plate portion 46 are composed of the first shield member 41, and the top plate portion 45 is composed of the second shield member 42. As shown in Figures 1, 2, and 5, the first shield member 41 has a plurality of claw portions 47 that protrude from the outer edge on one side in the axial direction of the outer cylinder portion 43. These plurality of claw portions 47 are bent and the outer edge of the second shield member 42 (i.e., the top plate portion 45) is crimped and fixed.

[0034] The top plate portion 45 has a first insertion hole 48 through which the interface surface 34 side end of the first transmission member 31 is inserted. Therefore, the interface surface 34 side end of the first transmission member 31 protrudes to the outside from the magnetic shield 40 through the first insertion hole 48. Also, as shown in Figure 4, the bottom plate portion 46 also has a second insertion hole 49 through which the interface surface 36 side end of the second transmission member 32 is inserted. Therefore, the interface surface 36 side end of the second transmission member 32 also protrudes to the outside from the magnetic shield 40 through the second insertion hole 49. As a result, load transmission occurs between the first transmission member 31, the sensor magnetostrictive materials 11 and 12, and the second transmission member 32 without passing through the magnetic shield 40. Therefore, loads applied from the outside to the interface surface 34 of the first transmission member 31 or the interface surface 36 of the second transmission member 32 are transmitted to the sensor magnetostrictive materials 11 and 12 via only the first transmission member 31 or the second transmission member 32, without passing through the magnetic shield 40. Consequently, loads applied from the outside can be applied perpendicularly (i.e., parallel to the axis CL) to the first pressed portion 15 and the second pressed portion 16 of the sensor magnetostrictive materials 11 and 12, without being affected by the shape or rigidity of the magnetic shield 40. As a result, the change in the magnetic permeability of the sensor magnetostrictive materials 11 and 12 in response to the external force becomes stable, and detection accuracy can be improved.

[0035] The portion of the magnetic shield 40 where the top plate 45 and bottom plate 46 cover the internal structure includes the portion on one side and the portion on the other side in the axial direction relative to the magnet 13 and the magnetic detection element 20. Therefore, the first insertion hole 48 and the second insertion hole 49 are provided in the portion of the magnetic shield 40 that excludes the portions on one side and the other side in the axial direction relative to the magnet 13 and the magnetic detection element 20. In Figure 2, the portion of the top plate 45 corresponding to the axial direction of the magnet 13 is shown by a dashed line 131, and the portion of the top plate 45 corresponding to the axial direction of the magnetic detection element 20 is shown by a dashed line 201. In Figure 4, the portion of the bottom plate 46 corresponding to the axial direction of the magnet 13 is shown by a dashed line 132, and the portion of the bottom plate 46 corresponding to the axial direction of the magnetic detection element 20 is shown by a dashed line 202.

[0036] As shown in Figures 7 to 9, the distance D1 between the end of the first magnetostrictive material 11 on the gap 14 side and the inner cylinder portion 44 is closer than the distance D2 between the first pressed portion 15 and the inner cylinder portion 44. Also, the distance D1 between the end of the first magnetostrictive material 11 on the gap 14 side and the inner cylinder portion 44 is closer than the distance D3 between the first pressed portion 15 and the outer cylinder portion 43. Similarly, the distance D4 between the end of the second magnetostrictive material 12 on the gap 14 side and the inner cylinder portion 44 is closer than the distance D5 between the second pressed portion 16 and the inner cylinder portion 44. Also, the distance D4 between the end of the second magnetostrictive material 12 on the gap 14 side and the inner cylinder portion 44 is closer than the distance D6 between the second pressed portion 16 and the outer cylinder portion 43. Therefore, the amount of magnetic flux leakage from the end of the first magnetostrictive material 11 on the gap 14 side and the end of the second magnetostrictive material 12 on the gap 14 side to the inner cylinder 44 increases, resulting in a decrease in the no-load magnetic flux density B0. On the other hand, the distances D2 and D5 between the first pressed portion 15 and the second pressed portion 16 and the inner cylinder 44, and the distances D3 and D6 between the first pressed portion 15 and the second pressed portion 16 and the outer cylinder 43 are spaced apart so as to reduce the amount of magnetic flux leakage from the first pressed portion 15 and the second pressed portion 16 to the magnetic shield 40. Thus, as explained with reference to Equation 1 above, by reducing the no-load magnetic flux density B0 and suppressing the decrease in magnetic flux density gain ΔB, the detection accuracy of the magnetic detection element 20 can be improved.

[0037] As shown in Figures 5, 8, 9, 11, and 12, the gaps between the first insertion hole 48 and the first transmission member 31, the gap between the second insertion hole 49 and the second transmission member 32, and the gap between the first shield member 41 and the second shield member 42 are sealed with a sealing material 60. As the sealing material 60, for example, a silicone-based moisture-curing liquid gasket (FIPG: Formed In Place Gasket) is used.

[0038] As shown in Figures 5, 10 to 12, the molded member 50 is resin-molded with the magnet 13, the first magnetostrictive material 11, the second magnetostrictive material 12, the first transmission member 31, the second transmission member 32, and the terminal 22, etc. In the first embodiment, the internal structure is resin-molded, excluding the magnetic detection element 20 and the substrate 21, etc. The molded member 50 is formed of a fiber-reinforced resin, for example, a resin material such as polyphenylene sulfide (PPS) resin, epoxy resin, or phenolic resin, which is composited with glass fibers, etc. The molded member 50 has material-reducing portions 51 on the radially outer and radially inner sides relative to the sensor magnetostrictive materials 11 and 12. Therefore, the radial thickness of the molded member 50 can be reduced in the areas where the material-reducing portions 51 are formed. Consequently, thermal stress from the molded member 50 can be reduced on the sensor magnetostrictive materials 11 and 12, thereby improving detection accuracy.

[0039] Furthermore, the material-reducing portion 51 of the molded member 50 is provided in the portion of the magnetic shield 40 that does not correspond to the axial direction of the multiple claw portions 47. Therefore, the columnar portion 52 of the molded member 50 is positioned in the portion of the multiple claw portions 47 that is axial. This prevents deformation of the second shield member 42 (i.e., the top plate portion 45) and the molded member 50 when the multiple claw portions 47 are bent.

[0040] An example of a manufacturing method for the load detection device 1 described above will be explained. First, the magnet 13, the first magnetostrictive material 11, the second magnetostrictive material 12, the first transmission member 31, the second transmission member 32, and the terminal 22 are placed in a mold (not shown), and molten resin is injected into the mold. This forms a molded member 50 (i.e., a sub-assembly) in which these components are integrally molded in resin. Next, the substrate 21 on which the magnetic detection element 20 is mounted is fixed to the molded member 50 with adhesive or the like, and the substrate 21 is sealed with potting material 23. Subsequently, the internal structure is inserted into the first shield member 41 together with the molded member 50, and then the first shield member 41 and the second shield member 42 are crimped and fixed together. Finally, sealing material 60 is applied to the gap between the first insertion hole 48 and the first transmission member 31, the gap between the second insertion hole 49 and the second transmission member 32, and the gap between the first shield member 41 and the second shield member 42, etc., and the load detection device 1 is completed.

[0041] (Effects of the first embodiment) The load detection device 1 of the first embodiment described above provides the following effects.

[0042] (1) In the first embodiment, the magnetic shield 40 is configured to cover at least a portion of the first transmission member 31 and the second transmission member 32, the magnetic circuit 10 and the magnetic detection element 20. According to this, the magnetic shield 40 prevents the internal structure of the load detection device 1 from being exposed to disturbing magnetic fields. Therefore, the magnetic flux flowing through the magnetic circuit 10 is prevented from being affected by the disturbing magnetic field, and the magnetic detection element 20 can correctly detect the change in magnetic flux in the magnetic circuit 10 in response to the externally applied load. Thus, this load detection device 1 can prevent the influence of disturbing magnetic fields and improve detection accuracy.

[0043] (2) In the first embodiment, the magnetic shield 40 has a first through hole 48 through which a part of the first transmission member 31 passes, and a second through hole 49 through which a part of the second transmission member 32 passes. The interface surface 34 of the first transmission member 31 protrudes from the magnetic shield 40 through the first through hole 48. The interface surface 36 of the second transmission member 32 protrudes from the magnetic shield 40 through the second through hole 49. According to this, load transmission occurs between the first transmission member 31, the sensor magnetostrictive materials 11 and 12, and the second transmission member 32 without passing through the magnetic shield 40. Therefore, a load applied from the outside to the interface surface 34 of the first transmission member 31 or the interface surface 36 of the second transmission member 32 is transmitted to the sensor magnetostrictive materials 11 and 12 only via the first transmission member 31 or the second transmission member 32, without passing through the magnetic shield 40. Consequently, the load applied from the outside can be applied perpendicularly (i.e., parallel to the axis CL) to the first pressed portion 15 and the second pressed portion 16 of the sensor magnetostrictive materials 11 and 12, without being affected by the shape or rigidity of the magnetic shield 40. As a result, the change in the magnetic permeability of the sensor magnetostrictive materials 11 and 12 in response to the external force becomes stable, and the detection accuracy can be improved.

[0044] Furthermore, the first transmission member 31 and the second transmission member 32 are made of a non-magnetic material, with only a portion of them protruding from the first insertion hole 48 and the second insertion hole 49, while the other portion is located inside the magnetic shield 40. As a result, the axial distance between the first insertion hole 48 and the second insertion hole 49 and the magnetic circuit 10 is increased, which suppresses the influence of external disturbance magnetic fields from the axial direction on the magnetic circuit 10 and improves detection accuracy.

[0045] (3) In the first embodiment, the first insertion hole 48 and the second insertion hole 49 are provided in locations that exclude the portion on one side and the portion on the other side in the axial direction relative to the magnet 13 and the magnetic detection element 20. Therefore, the portion covered by the magnetic shield 40 includes the portion on one side and the portion on the other side in the axial direction relative to the magnet 13 and the magnetic detection element 20. According to this, the magnetic shield 40 covers one side and the other side of the magnet 13 in the axial direction, preventing the magnetic flux generated by the magnet 13 from leaking outside the magnetic shield 40. Also, the magnetic shield 40 covers one side and the other side of the magnetic detection element 20 in the axial direction, preventing the magnetic detection element 20 from being affected by disturbing magnetic fields. Therefore, the detection accuracy of the magnetic detection device 1 can be improved.

[0046] (4) In the first embodiment, the magnetic shield 40 has an outer cylinder portion 43, an inner cylinder portion 44, a top plate portion 45, and a bottom plate portion 46. According to this, because the magnetic shield 40 has an outer cylinder portion 43 and an inner cylinder portion 44, the magnetic flux flowing through the magnetic circuit 10 leaks into the magnetic shield 40, and the no-load magnetic flux density B0 becomes smaller. The magnetic flux density gain ΔB also becomes smaller, but the rate of decrease in the magnetic flux density gain ΔB is smaller than the rate of decrease in the no-load magnetic flux density B0. Therefore, as explained with reference to Equation 1 above, the detection accuracy of the magnetic detection element 20 can be improved.

[0047] (5) In the first embodiment, the magnetic shield 40 comprises a first shielding member 41 and a second shielding member 42. The first shielding member 41 consists of an outer cylinder portion 43, an inner cylinder portion 44, and a bottom plate portion 46, and the second shielding member 42 consists of a top plate portion 45. According to this, by constructing the magnetic shield 40 with multiple components, the internal structure can be reliably isolated from external magnetic fields, improving detection accuracy. Furthermore, by using the first shielding member 41 to constitute the outer cylinder portion 43, the inner cylinder portion 44, and the bottom plate portion 46, and the second shielding member 42 to constitute the top plate portion 45, the number of components can be reduced, and the assembly of the magnetic shield 40 can be made easier, thereby reducing manufacturing man-hours and manufacturing costs.

[0048] (6) In the first embodiment, the first shield member 41 has a claw portion 47 that protrudes from one of the outer edges of the outer cylinder portion 43 in the axial direction. The outer edge of the second shield member 42 is fixed to the first shield member 41 by bending and crimping the claw portion 47. According to this, the number of parts can be reduced, and the assembly of the magnetic shield 40 can be made easier, thereby reducing manufacturing man-hours and manufacturing costs.

[0049] (7) In the first embodiment, the magnetic shield 40 has a maximum magnetic permeability of 10,000 or more. According to this, by using a material with higher magnetic permeability than general-purpose steel, when a magnetic foreign object (e.g., general-purpose steel) approaches the load detection device 1 from the outside, the influence of the magnetic field generated by that magnetic foreign object can be suppressed. Furthermore, magnetic flux leakage from the magnetic circuit 10 to the outside can be suppressed. Therefore, the detection accuracy of the magnetic detection device can be improved.

[0050] (8) In the first embodiment, the magnetic circuit 10 is configured in a ring shape so that the magnetic flux generated by the magnet 13 flows in the order of magnet 13, first magnetostrictive material 11, gap 14, second magnetostrictive material 12, and magnet 13. The magnetic detection element 20 is located opposite the gap 14 provided between the end of the first magnetostrictive material 11 opposite to the magnet 13 and the end of the second magnetostrictive material 12 opposite to the magnet 13, or within the gap 14, and outputs a signal corresponding to the magnetic flux flowing through the magnetic circuit 10. Incidentally, the load detection device described in Patent Document 1 has a configuration in which there is a gap or a layer with lower magnetic permeability than the magnetostrictive material between the magnet and the magnetostrictive material, and between the magnetostrictive material and the yoke within the magnetic circuit. As a result, in this magnetic circuit, magnetic flux leakage increases at the gap-side end of the magnetostrictive material, the magnetic flux density distribution of the magnetostrictive material becomes larger, and low-density regions exist in the magnetostrictive material. Consequently, the load detection device described in Patent Document 1 has the problem that the magnetic flux density gain ΔB becomes small and the detection accuracy deteriorates.

[0051] Furthermore, the load detection device described in Patent Document 1 is configured such that a load is applied only to the magnetostrictive material constituting the magnetic circuit, and no load is applied to the yoke. As a result, in this load detection device, the length of the magnetostrictive material is relatively shorter by the length of the yoke within the magnetic circuit, which leads to a decrease in the magnetic flux density gain ΔB and a deterioration in detection accuracy. In contrast, the load detection device 1 of the first embodiment does not require a gap between the magnetostrictive material and the yoke, or a layer with lower permeability than the magnetostrictive material, to be provided in the middle of the magnetic circuit 10, except for the gap 14 where the magnetic detection element 20 is provided, as described in Patent Document 1. Therefore, it is possible to increase the magnetic flux density of the first pressed portion 15 and the second pressed portion 16. Consequently, this load detection device 1 can increase the magnetic flux density gain ΔB and improve detection accuracy.

[0052] Furthermore, in the load detection device 1 of the first embodiment, since the first transmission member 31 and the second transmission member 32 transmit the load to both the first magnetostrictive material 11 and the second magnetostrictive material 12, the first pressed portion 15 and the second pressed portion 16 can be made longer compared to the configuration with a yoke to which no load is applied, as described in Patent Document 1. Therefore, assuming the same area conditions as the device described in Patent Document 1, the width of the magnetic paths of the first pressed portion 15 and the second pressed portion 16 can be reduced, and the magnetic flux density of those pressed portions can be increased accordingly. Consequently, this load detection device 1 can increase the magnetic flux density gain and improve detection accuracy.

[0053] Furthermore, in the load detection device 1 of the first embodiment, the magnetic circuit 10 is configured in a ring shape so that the magnetic flux flows in the order of magnet 13, first magnetostrictive material 11, gap 14, second magnetostrictive material 12, and magnet 13. Therefore, a gap 14 can be provided at the position furthest from the magnet 13, and the magnetic detection element 20 can be placed between or near the gap 14. As a result, the magnetic flux density of the first pressed portion 15 and the second pressed portion 16 can be increased, and the length of these pressed portions can be secured. Consequently, this load detection device 1 can increase the magnetic flux density gain ΔB and improve detection accuracy.

[0054] (9) In the first embodiment, the distance D1 between the end of the first magnetostrictive material 11 on the gap 14 side and the inner cylinder portion 44 is closer than the distance D2 between the first pressed portion 15 and the inner cylinder portion 44, and also closer than the distance D3 between the first pressed portion 15 and the outer cylinder portion 43. Similarly, the distance D4 between the end of the second magnetostrictive material 12 on the gap 14 side and the inner cylinder portion 44 is closer than the distance D5 between the second pressed portion 16 and the inner cylinder portion 44, and also closer than the distance D6 between the second pressed portion 16 and the inner cylinder portion 44. According to this, the amount of magnetic flux leakage from the end of the first magnetostrictive material 11 on the gap 14 side and the end of the second magnetostrictive material 12 on the gap 14 side to the magnetic shield 40 increases, so the no-load magnetic flux density B0 decreases. On the other hand, the distances D2 and D5 between the first pressed portion 15 and the second pressed portion 16 and the inner cylinder portion 44, and the distances D3 and D6 between the first pressed portion 15 and the second pressed portion 16 and the outer cylinder portion 43 are spaced apart so that the amount of magnetic flux leakage from the first pressed portion 15 and the second pressed portion 16 to the magnetic shield 40 is reduced. Therefore, by reducing the no-load magnetic flux density B0 and suppressing the decrease in magnetic flux density gain ΔB, the detection accuracy of the magnetic detection element 20 can be improved.

[0055] (Second Embodiment) A second embodiment will now be described. The second embodiment is a modification of the configuration of the magnetic shield 40 compared to the first embodiment, and is otherwise the same as the first embodiment. Therefore, only the parts that differ from the first embodiment will be described.

[0056] As shown in Figures 13 and 14, the magnetic shield 40 of the load detection device 1 of the second embodiment does not have a first insertion hole 48 and a second insertion hole 49. Therefore, the magnetic shield 40 covers the entirety of the first transmission member 31 and the second transmission member 32, as well as the magnetic circuit 10 and the magnetic detection element 20. This makes it possible to more reliably prevent the magnetic circuit 10 from being affected by disturbance magnetic fields.

[0057] In this case, load transmission occurs between the top plate portion 45 of the magnetic shield 40, the first transmission member 31, the sensor magnetostrictive materials 11 and 12, the second transmission member 32, and the bottom plate portion 46 of the magnetic shield 40. Therefore, a load applied from the outside on one side in the axial direction is transmitted from the top plate portion 45 of the magnetic shield 40 to the sensor magnetostrictive materials 11 and 12 via the first transmission member 31. Similarly, a load applied from the outside on the other side in the axial direction is transmitted from the bottom plate portion 46 of the magnetic shield 40 to the sensor magnetostrictive materials 11 and 12 via the second transmission member 32.

[0058] The load detection device 1 of the second embodiment described above can more reliably prevent the magnetic circuit 10 from being affected by disturbing magnetic fields. Therefore, the magnetic detection element 20 can correctly detect the change in magnetic flux of the magnetic circuit 10 in response to the load applied from the outside. Thus, this load detection device 1 can prevent the influence of disturbing magnetic fields and improve detection accuracy.

[0059] (Implementations 3 to 8) The third to eighth embodiments will now be described. The third to eighth embodiments are modified versions of the first embodiment, etc., in which the configuration of the magnetic circuit 10 and the magnetic detection element 20 is changed, but otherwise the configuration is the same as the first embodiment, etc. In the description of the third to eighth embodiments, the left side of the paper in the figure will be referred to as one side in the X direction, and the right side of the paper will be referred to as the other side in the X direction.

[0060] (Third embodiment) As shown in Figures 15 and 16, in the third embodiment, a magnet 13 is arranged on one side in the X direction of the annular magnetic circuit 10, and a magnetic detection element 20 is arranged on the other side in the X direction. The magnetic detection element 20 is provided within a gap 14. More specifically, the magnetic detection element 20 is provided within a gap 14 formed between the end 11a of the first magnetostrictive material 11 opposite to the magnet 13 and the end 12a of the second magnetostrictive material 12 opposite to the magnet 13. The magnetic detection element 20 is capable of outputting a signal corresponding to the magnetic flux flowing through the magnetic circuit 10.

[0061] (Fourth embodiment) As shown in Figures 17 and 18, in the fourth embodiment, the annular magnetic circuit 10 is formed in a substantially rectangular shape when viewed from the axis CL side. In the annular magnetic circuit 10, a magnet 13 is arranged on one side in the X direction, and a magnetic detection element 20 is arranged on the other side in the X direction. The magnetic detection element 20 is provided in a gap 14. In detail, the magnetic detection element 20 is provided in a gap 14 formed between the end 11a of the first magnetostrictive material 11 opposite to the magnet 13 and the end 12a of the second magnetostrictive material 12 opposite to the magnet 13. The magnetic detection element 20 is capable of outputting a signal corresponding to the magnetic flux flowing through the magnetic circuit 10.

[0062] In the fourth embodiment, the magnetic shield 40 is also formed in a roughly rectangular shape when viewed from the axis CL side. Specifically, the outer cylinder portion 43 and the inner cylinder portion 44 are formed in a roughly rectangular shape, and their corners are curved. The top plate portion 45 and the bottom plate portion 46 are formed in a roughly rectangular shape (specifically, a rectangular shape with rounded corners) to match the shapes of the outer cylinder portion 43 and the inner cylinder portion 44.

[0063] (Fifth embodiment) As shown in Figures 19 and 20, in the fifth embodiment, the magnetic detection element 20 is mounted offset to one side in the axial direction relative to the sensor magnetostrictive materials 11 and 12. The magnetic circuit 10 and magnetic detection element 20 in the fifth embodiment are arranged substantially the same as in the third embodiment. In this configuration as well, the magnetic detection element 20 is capable of outputting a signal corresponding to the magnetic flux flowing through the magnetic circuit 10.

[0064] (Sixth Embodiment) As shown in Figures 21 and 22, in the sixth embodiment, the magnet 13 and the magnetic detection element 20 are arranged side by side on one side in the X direction in an annular magnetic circuit 10. One magnetostrictive material 100 is formed in a continuous annular shape except for the areas where the magnet 13 and the magnetic detection element 20 are provided. The magnetic circuit 10 is configured in an annular shape so that the magnetic flux generated by the magnet 13 flows in the order of the N pole of the magnet 13, through the magnetostrictive material 100, and then through the S pole of the magnet 13. The magnetic detection element 20 outputs a signal corresponding to the magnetic flux passing through the gap 141 provided between one end 101 of the magnetostrictive material 100 and the magnet 13.

[0065] (Seventh Embodiment) As shown in Figures 23 and 24, in the seventh embodiment, a magnet 13 is provided on one side in the X direction of the annular magnetic circuit 10, and a magnetic detection element 20 is provided on the other side in the X direction. The magnetic detection element 20 is provided at a position facing the gap 14 (i.e., a position opposite the gap 14). In detail, the magnetic detection element 20 is provided at a position facing the gap 14 on the side closer to the axis CL of the gap 14. The magnetic detection element 20 is capable of outputting a signal corresponding to the magnetic flux flowing through the magnetic circuit 10.

[0066] (Eighth embodiment) As shown in Figures 25 and 26, the eighth embodiment is an annular magnetic circuit 10 in which a magnet 13 is provided on one side in the X direction and a magnetic detection element 20 is provided on the other side in the X direction. The magnetic detection element 20 is provided at a position facing the gap 14. In detail, the magnetic detection element 20 is provided at a position facing the gap 14 on the side farther from the axis CL relative to the gap 14. The magnetic detection element 20 is capable of outputting a signal corresponding to the magnetic flux flowing through the magnetic circuit 10.

[0067] In the third to eighth embodiments described above, the magnetic shield 40 has an outer cylinder portion 43, an inner cylinder portion 44, a top plate portion 45, and a bottom plate portion 46, covering the internal structure. Therefore, the magnetic flux flowing through the magnetic circuit 10 is prevented from being affected by the disturbing magnetic field. Consequently, the load detection device 1 of the third to eighth embodiments can also prevent the influence of the disturbing magnetic field and improve detection accuracy.

[0068] (Other embodiments) (1) In the first embodiment described above, the first shield member 41 and the second shield member 42 were fixed by crimping, but the fixing method is not limited to this. For example, the outer cylinder portion 43 and the inner cylinder portion 44 of the first shield member 41 and the outer edge of the second shield member 42 may be fixed by welding. Alternatively, the outer cylinder portion 43 and the inner cylinder portion 44 of the first shield member 41 and the outer edge of the second shield member 42 may be fixed with adhesive.

[0069] (2) In the first, second, and fifth embodiments described above, the magnetic detection element 20 was provided at a position facing the gap 14 in the axial direction. In the third and fourth embodiments, the magnetic detection element 20 was provided inside the gap 14. In the seventh and eighth embodiments, the magnetic detection element 20 was provided at a position facing the gap 14 on the side closer to the axis CL or on the side farther from the axis CL. However, the magnetic detection element 20 may be provided at an intermediate position between the positions shown in each embodiment.

[0070] The present invention is not limited to the embodiments described above, and can be modified as appropriate within the scope of the claims. Furthermore, the embodiments and parts thereof are not unrelated to each other, and can be combined as appropriate, except in cases where the combination is clearly impossible. In addition, it goes without saying that the elements constituting the embodiments are not necessarily essential, except in cases where they are explicitly stated to be particularly essential or where they are clearly considered essential in principle. Furthermore, in the embodiments, when numerical values ​​such as the number, numerical values, quantities, or ranges of the components of the embodiments are mentioned, the invention is not limited to those specific numbers, except in cases where they are explicitly stated to be particularly essential or where they are clearly limited to a specific number in principle. Furthermore, when the shapes, positional relationships, etc., of the components, etc., are mentioned in the embodiments, the invention is not limited to those shapes, positional relationships, etc., except in cases where they are explicitly stated to be particularly essential or where they are clearly limited to a specific shape, positional relationship, etc., in principle.

[0071] The features of this invention are as follows: [Claim 1] In a load detection device that detects loads applied from an external source, A magnetic circuit (10) is configured in a ring shape such that the magnetic flux generated by the magnetic flux generating unit (13) generates magnetic flux, and magnetostrictive materials (11, 12, 100) whose permeability changes according to an external force, and the magnetic flux generated by the magnetic flux generating unit flows through the magnetic flux generating unit and the magnetostrictive materials. A first transmission member (31) made of a non-magnetic material transmits a load applied from the outside on one side in the direction in which the axis (CL) of the annular magnetic circuit extends to the magnetostrictive material, A second transmission member (32) made of a non-magnetic material transmits a load applied from the outside on the other side in the direction in which the axis extends to the magnetostrictive material, A magnetic detection element (20) is provided at a position opposite to or within a gap (14) provided between a plurality of magnetostrictive materials, or at a position opposite to or within a gap (141) provided between the magnetic flux generating unit and the magnetostrictive material, and outputs a signal corresponding to the magnetic flux flowing through the magnetic circuit. A load detection device comprising a magnetic material and a magnetic shield (40) covering at least a portion of the first transmission member and the second transmission member, the magnetic circuit, and the magnetic detection element. [Claim 2] The magnetic shield has a first through hole (48) through which a part of the first transmission member passes, and a second through hole (49) through which a part of the second transmission member passes. The portion of the first transmission member opposite to the magnetostrictive material protrudes from the magnetic shield through the first insertion hole, The load detection device according to claim 1, wherein the portion of the second transmission member opposite to the magnetostrictive material protrudes from the magnetic shield through the second insertion hole. [Claim 3] When the direction in which the aforementioned axis extends is called the axial direction, The first insertion hole and the second insertion hole are provided in locations excluding the portion on one side and the portion on the other side in the axial direction relative to the magnetic flux generating portion and the magnetic detection element. The load detection device according to claim 2, wherein the portion covered by the magnetic shield includes a portion on one side and a portion on the other side in the axial direction with respect to the magnetic flux generating portion and the magnetic detection element. [Claim 4] When, in the radial direction of a virtual circle perpendicular to the axis and centered on the axis, the side farther from the axis is called the radially outer side, the side closer to the axis is called the radially inner side, and the direction in which the axis extends is called the axial direction, The aforementioned magnetic shield is A cylindrical outer cylinder portion (43) is provided radially outward from the magnetic circuit, the first transmission member, the second transmission member, and the magnetic detection element, A cylindrical inner cylinder portion (44) is provided radially inward from the magnetic circuit, the first transmission member, the second transmission member, and the magnetic detection element, A top plate portion (45) is provided on one side in the axial direction relative to the magnetic circuit, the first transmission member, the second transmission member, and the magnetic detection element, A load detection device according to any one of claims 1 to 3, comprising the magnetic circuit, the first transmission member, the second transmission member, and a bottom plate portion (46) provided on the other side in the axial direction relative to the magnetic detection element. [Claim 5] The magnetic shield comprises a first shielding member (41) and a second shielding member (42). The first shield member comprises the outer cylinder portion, the inner cylinder portion, and the bottom plate portion. The load detection device according to claim 4, wherein the second shield member constitutes the top plate portion. [Claim 6] The first shield member has a claw portion (47) that protrudes from one of the outer edges of the outer cylinder portion in the axial direction, The load detection device according to claim 5, wherein the outer edge of the second shield member is fixed by bending and crimping the claw portion of the first shield member. [Claim 7] The load detection device according to claim 5, wherein the outer cylindrical portion and the inner cylindrical portion of the first shield member are fixed to the outer edge of the second shield member by welding. [Claim 8] The load detection device according to claim 5, wherein the outer cylindrical portion and the inner cylindrical portion of the first shield member and the outer edge of the second shield member are fixed together with an adhesive. [Claim 9] The load detection device according to any one of claims 1 to 8, wherein the magnetic shield has a maximum magnetic permeability of 10,000 or more. [Claim 10] The magnetostrictive material comprises a first magnetostrictive material (11) and a second magnetostrictive material (12). The magnetic circuit is configured in a ring shape such that the magnetic flux generated by the magnetic flux generating unit flows in the following order: from the magnetic flux generating unit, through the first magnetostrictive material, through the gap, through the second magnetostrictive material, and back to the magnetic flux generating unit. The load detection device according to any one of claims 1 to 9, wherein the magnetic detection element is provided at a position opposite to the gap (14) provided between the end of the first magnetostrictive material opposite to the magnetic flux generating portion and the end of the second magnetostrictive material opposite to the magnetic flux generating portion, or within the gap, and outputs a signal corresponding to the magnetic flux flowing through the magnetic circuit. [Explanation of Symbols]

[0072] 1. Load detection device 11. First Magnetostrictive Material 12. Second Magnetostrictive Material 10 Magnetic Circuit 13. Magnetic flux generating section (magnet) 14, 141 gap 20 Magnetic detection element 31 First transmission member 32 Second transmission member 40 Magnetic Shield

Claims

1. In a load detection device that detects loads applied from an external source, A magnetic circuit (10) is configured in an annular shape such that the magnetic flux generated by the magnetic flux generating unit flows through the magnetic flux generating unit and the magnetostrictive material, and the magnetic flux generated by the magnetic flux generating unit flows through the magnetic flux generating unit and the magnetostrictive material. A first transmission member (31) made of a non-magnetic material transmits a load applied from the outside of one side in the direction in which the axis (CL) of the annular magnetic circuit extends to the magnetostrictive material, A second transmission member (32) made of a nonmagnetic material transmits a load applied from the outside on the other side in the direction in which the axis extends to the magnetostrictive material, A magnetic detection element (20) is provided at a position opposite to or within a gap (14) provided between a plurality of magnetostrictive materials, or at a position opposite to or within a gap (141) provided between the magnetic flux generating unit and the magnetostrictive material, and outputs a signal corresponding to the magnetic flux flowing through the magnetic circuit. A load detection device comprising a magnetic material and a magnetic shield (40) covering at least a portion of the first transmission member and the second transmission member, the magnetic circuit, and the magnetic detection element.

2. The magnetic shield has a first through hole (48) through which a part of the first transmission member passes, and a second through hole (49) through which a part of the second transmission member passes. The portion of the first transmission member opposite to the magnetostrictive material protrudes from the magnetic shield through the first insertion hole. The load detection device according to claim 1, wherein the portion of the second transmission member opposite to the magnetostrictive material protrudes from the magnetic shield through the second insertion hole.

3. When the direction in which the aforementioned axis extends is called the axial direction, The first insertion hole and the second insertion hole are provided in locations excluding the portion on one side and the portion on the other side in the axial direction relative to the magnetic flux generating portion and the magnetic detection element. The load detection device according to claim 2, wherein the portion covered by the magnetic shield includes a portion on one side and a portion on the other side in the axial direction with respect to the magnetic flux generating portion and the magnetic detection element.

4. When, in the radial direction of a virtual circle perpendicular to the axis and centered on the axis, the side farther from the axis is called the radially outer side, the side closer to the axis is called the radially inner side, and the direction in which the axis extends is called the axial direction, The aforementioned magnetic shield is A cylindrical outer cylinder portion (43) is provided radially outward from the magnetic circuit, the first transmission member, the second transmission member, and the magnetic detection element, A cylindrical inner cylinder portion (44) is provided radially inward from the magnetic circuit, the first transmission member, the second transmission member, and the magnetic detection element, The top plate portion (45) is provided on one side in the axial direction relative to the magnetic circuit, the first transmission member, the second transmission member, and the magnetic detection element, A load detection device according to any one of claims 1 to 3, comprising the magnetic circuit, the first transmission member, the second transmission member, and a bottom plate portion (46) provided on the other side in the axial direction relative to the magnetic detection element.

5. The magnetic shield comprises a first shielding member (41) and a second shielding member (42). The first shield member comprises the outer cylinder portion, the inner cylinder portion, and the bottom plate portion. The load detection device according to claim 4, wherein the second shield member constitutes the top plate portion.

6. The first shield member has a claw portion (47) that protrudes from one of the outer edges of the outer cylinder portion in the axial direction, The load detection device according to claim 5, wherein the outer edge of the second shield member is fixed by bending and crimping the claw portion of the first shield member.

7. The load detection device according to claim 5, wherein the outer cylindrical portion and the inner cylindrical portion of the first shield member are fixed to the outer edge of the second shield member by welding.

8. The load detection device according to claim 5, wherein the outer cylindrical portion and the inner cylindrical portion of the first shield member and the outer edge of the second shield member are fixed together with an adhesive.

9. The load detection device according to claim 1 or 2, wherein the magnetic shield has a maximum magnetic permeability of 10,000 or more.

10. The magnetostrictive material comprises a first magnetostrictive material (11) and a second magnetostrictive material (12). The magnetic circuit is configured in a ring shape such that the magnetic flux generated by the magnetic flux generating unit flows in the following order: from the magnetic flux generating unit, through the first magnetostrictive material, through the gap, through the second magnetostrictive material, and back to the magnetic flux generating unit. The load detection device according to claim 1 or 2, wherein the magnetic detection element is provided at a position opposite to the gap (14) provided between the end of the first magnetostrictive material opposite to the magnetic flux generating portion and the end of the second magnetostrictive material opposite to the magnetic flux generating portion, or within the gap, and outputs a signal corresponding to the magnetic flux flowing through the magnetic circuit.

Images