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, a first magnetostrictive material 11, and a second magnetostrictive material 12, and is configured in a ring shape so that the magnetic flux generated by the magnetic flux generating unit 13 flows in the order of the magnetic flux generating unit 13, the first magnetostrictive material 11, the gap 14, the second magnetostrictive material 12, and the magnetic flux generating unit 13. The first transmission member 31 transmits a load applied from the outside of one side in the axial direction of the magnetic circuit 10 to the first magnetostrictive material 11 and the second magnetostrictive material 12. The second transmission member 32 transmits a load applied from the outside of the other side in the axial direction of the magnetic circuit 10 to the first magnetostrictive material 11 and the second magnetostrictive material 12. The magnetic detection element 20 is provided at a position opposite to the gap 14 or inside the gap 14 and outputs a signal corresponding to the magnetic flux flowing through the magnetic circuit 10.

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 in a loop 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 called 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, the load detection device described in Patent Document 1 has gaps or layers with lower relative 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 a problem in that the amount of change in magnetic flux density detected by the magnetic detection element in response to changes in the externally applied load (hereinafter referred to as "magnetic flux density gain ΔB") becomes small, and the detection accuracy deteriorates.

[0006] 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 magnetic path 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.

[0007] Specifically, the load detection device described in the first to fourth embodiments of Patent Document 1 has a magnetic circuit configured such that magnetic flux flows in the order of magnet → gap → magnetostrictive material → gap → yoke → gap where a magnetic detection element is provided → magnet. Furthermore, the load detection device described in the fifth embodiment of Patent Document 1 has a magnetic circuit configured such that magnetic flux flows in the order of magnet → gap → yoke → gap → load transmission member → magnetostrictive material → load transmission member → gap → yoke → gap → magnet. As a result, as described above, the magnetic flux density flowing through the magnetostrictive material is reduced due to the gaps in multiple locations within the magnetic circuit, and the length of the magnetic path of the magnetostrictive material is made relatively short by the yoke. Consequently, this load detection device has the problem of a small magnetic flux density gain ΔB and a deterioration in detection accuracy.

[0008] 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]

[0009] 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 a first magnetostrictive material (11) and a second magnetostrictive material (12) whose permeability changes according to an external force, and the magnetic flux generated by the magnetic flux generating unit flows in the order of the first magnetostrictive material, gap (14), second magnetostrictive material, and back to the magnetic flux generating unit. A first transmission member (31) 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 first magnetostrictive material and the second magnetostrictive material, A second transmission member (32) transmits a load applied from the outside on the other side in the direction in which the axis extends to the first magnetostrictive material and the second magnetostrictive material, The device includes a magnetic detection element (20) located opposite or within the gap, which outputs a signal corresponding to the magnetic flux flowing through the magnetic circuit.

[0010] As a result, when an externally applied load is transmitted to the first and second magnetostrictive materials via the first or second transmission member, the permeability of the first and second magnetostrictive materials changes, and the amount of magnetic flux generated in the magnetic flux generation section that passes through the magnetic circuit changes. Therefore, the magnetic flux density detected by the magnetic detection element changes, and the externally applied load can be measured.

[0011] With this configuration, except for the gap at the location where the magnetic detection element detects the change in magnetic flux, there is no need to provide a gap or a layer with a lower relative permeability than the magnetostrictive material between the magnetostrictive material and the yoke, as described in Patent Document 1. Therefore, it is possible to increase the magnetic flux density in the parts of the first and second magnetostrictive materials to which the load is transmitted from the first and second transmission members. Consequently, this load detection device can increase the magnetic flux density gain ΔB and improve detection accuracy. In the following description, the part of the first magnetostrictive material to which the load is transmitted from the first and second transmission members is referred to as the first pressed part, and the part of the second magnetostrictive material to which the load is transmitted from the first and second transmission members is referred to as the second pressed part.

[0012] Furthermore, since this load detection device has a configuration in which the first and second transmission members transmit the load to both the first and second magnetostrictive material, it is possible to secure longer magnetic paths for the first and second pressed parts compared to a 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 for the first and second pressed parts can be reduced, and the magnetic flux density of the pressed parts can be increased accordingly. Consequently, this load detection device can increase the magnetic flux density gain ΔB and improve detection accuracy.

[0013] Furthermore, since the magnetic circuit of this load detection device is configured in a ring shape so that the magnetic flux flows from the magnetic flux generation unit to the first magnetostrictive material, gap, second magnetostrictive material, and back to the magnetic flux generation unit, a gap can be provided at the position furthest from the magnetic flux generation unit, and the magnetic detection element can be placed on the side of that gap. As a result, the magnetic flux density of the first and second pressed parts can be increased, and the magnetic paths of these pressed parts can be made longer. Consequently, this load detection device can increase the magnetic flux density gain ΔB and improve detection accuracy.

[0014] 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, passing through each member.

[0015] 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]

[0016] [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] It is an exploded perspective view of a load detection device according to the first embodiment. [Figure 6] It is a perspective view showing a magnetic circuit, a first transmission member, and a second transmission member. [Figure 7] It is a cross-sectional view excluding the mold member at the VII-VII line in FIG. 3 (i.e., the boundary between the first transmission member and the magnetic circuit). [Figure 8] It is a side view showing a magnetic circuit, a first transmission member, and a second transmission member. [Figure 9] It is a view taken in the direction of the arrow in the IX direction of FIG. 8. [Figure 10] It is a cross-sectional view taken along the X-X line in FIG. 8. [Figure 11] It is a plan view showing only the magnetic circuit and the magnetic detection element included in the load detection device according to the second embodiment. [Figure 12] It is a plan view showing only the magnetic circuit and the magnetic detection element included in the load detection device according to the third embodiment. [Figure 13] It is a plan view showing only the magnetic circuit and the magnetic detection element included in the load detection device according to the fourth embodiment. [Figure 14] It is a plan view showing only the magnetic circuit and the magnetic detection element included in the load detection device according to the fifth embodiment. [Figure 15] It is a graph showing ΔB and ΔB / B0 in the magnetic circuit included in the load detection device according to the second to fifth embodiments. [Figure 16] It is a diagram showing the magnetic flux density distribution of the magnetostrictive material in the magnetic circuit included in the load detection device according to the sixth embodiment. [Figure 17] It is a diagram showing the magnetic flux density distribution of the magnetostrictive material in the magnetic circuit included in the load detection device according to the seventh embodiment. [Figure 18] It is a table showing ΔB, B0, and ΔB / B0 in the magnetic circuit included in the load detection device according to the second, sixth, and seventh embodiments. [Figure 19] It is a perspective view showing a magnetic circuit, a first transmission member, and a second transmission member in the load detection device according to the eighth embodiment. [Figure 20]This is a perspective view showing the magnetic circuit, the first transmission member, and the second transmission member in the load detection device according to the ninth embodiment. [Figure 21] This is a perspective view showing the magnetic circuit, the first transmission member, and the second transmission member in the load detection device according to the 10th embodiment. [Figure 22] This is a side view showing the magnetic circuit, the first transmission member, and the second transmission member in a load detection device according to the 11th embodiment. [Figure 23] This is a plan view showing the magnetic circuit, the first transmission member, and the second transmission member in a load detection device according to the 12th embodiment. [Figure 24] Figure 23 shows the view in the direction of the arrow XXIV. [Figure 25] Figure 24 is a cross-sectional view of the line XXV-XXV. [Figure 26] This is a perspective view showing the magnetic circuit, the first transmission member, and the second transmission member in the load detection device according to the 13th embodiment. [Figure 27] This is a view from the arrow pointing in direction XXVII in Figure 26. [Figure 28] Figure 27 shows a cross-sectional view along the line XXVIII-XXVIII. [Figure 29] This graph shows the relationship between the rate of change Δμm of the maximum relative permeability and the magnetic flux density gain ΔB in the load detection device according to the 14th embodiment. [Figure 30] This graph shows the relationship between the maximum relative permeability μm of a magnetostrictive material and the rate of change of the maximum relative permeability Δμm_F0-330. [Figure 31] This graph shows the relationship between a given surface pressure Fα and the rate of change of the maximum relative permeability Δμm_F0-α. [Figure 32] This is a cross-sectional view along the X-plane showing a magnetic circuit, a first transmission member, a second transmission member, and a magnetic detection element in a load detection device according to the 15th embodiment. [Figure 33] This is a cross-sectional view of the line XXXIII-XXXIII in Figure 32. [Figure 34] This is a cross-sectional view along the X-plane showing a magnetic circuit, a first transmission member, a second transmission member, and a magnetic detection element in a load detection device according to the 16th embodiment. [Figure 35] This is a cross-sectional view along the line XXXV-XXXV in Figure 34. [Figure 36] This is a cross-sectional view along the X-plane showing a magnetic circuit, a first transmission member, a second transmission member, and a magnetic detection element in a load detection device according to the 17th embodiment. [Figure 37] This is a cross-sectional view of the line XXXVII-XXXVII in Figure 36. [Figure 38] This is a cross-sectional view along the X-plane showing a magnetic circuit, a first transmission member, a second transmission member, and a magnetic detection element in a load detection device according to the 18th embodiment. [Figure 39] This is a cross-sectional view of the line XXXIX-XXXIX in Figure 38. [Figure 40] This is a cross-sectional view along the X-plane showing a magnetic circuit, a first transmission member, a second transmission member, and a magnetic detection element in a load detection device according to the 19th embodiment. [Figure 41] Figure 40 is a cross-sectional view of the XLI-XLI line. [Figure 42] This is a cross-sectional view along the X-plane showing a magnetic circuit, a first transmission member, a second transmission member, and a magnetic detection element in a load detection device according to the 20th embodiment. [Figure 43] Figure 42 is a cross-sectional view of the XLIII-XLIII line. [Figure 44] This is a plan view showing the magnetic circuit, magnetic detection element, and second transmission member in the load detection device of the first comparative example. [Figure 45] This is a plan view showing the magnetic circuit, magnetic detection element, and second transmission member in the load detection device of the second comparative example. [Modes for carrying out the invention]

[0017] 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.

[0018] (First Embodiment) The first embodiment will be described with reference to Figures 1 to 10. The load detection device 1 of the first embodiment is a load sensor that detects an externally applied load using the inverse magnetostrictive effect.

[0019] As shown in Figures 5 to 7, 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.

[0020] The magnetic circuit 10 includes a magnet 13 as a magnetic flux generating unit, a first magnetostrictive material 11, and a second magnetostrictive material 12. The magnet 13 is a permanent magnet that generates magnetic flux and is composed of, for example, a samarium-cobalt magnet, a neodymium magnet, or the like.

[0021] The first magnetostrictive material 11 and the second magnetostrictive material 12 are magnetic materials 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.

[0022] 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 opposite to the magnet 13) and the other end of the second magnetostrictive material 12 (i.e., the end 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.

[0023] 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.

[0024] 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".

[0025] As shown in Figures 5 and 8, 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. 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.

[0026] As shown in Figures 5 to 8, 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.

[0027] 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.

[0028] 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.

[0029] In the following explanation, the surface of the first transmission member 31 that contacts the sensor magnetostrictive materials 11 and 12 is referred to as the "contact surface 33 of the first transmission member 31," and the surface of the first transmission member 31 opposite to the sensor magnetostrictive materials 11 and 12 is referred to as the "interface surface 34 of the first transmission member 31." Similarly, the surface of the second transmission member 32 that contacts the sensor magnetostrictive materials 11 and 12 is referred to as the "contact surface 35 of the second transmission member 32," and the surface of the second transmission member 32 opposite to the sensor magnetostrictive materials 11 and 12 is referred to as the "interface surface 36 of the second transmission member 32."

[0030] As shown in Figures 9 and 10, in the first embodiment, the circumferential length D1 of the contact surface 33 of the first transmission member 31 (i.e., the circumferential length of the first pressed portion 15 and the second pressed portion 16) is longer than the circumferential length D2 of the interface surface 34 of the first transmission member 31. This suppresses the application of local loads to the first pressed portion 15 and the second pressed portion 16 from the first transmission member 31 and the second transmission member 32. Similarly, the circumferential length of the contact surface 35 of the second transmission member 32 (i.e., the circumferential length of the first pressed portion 15 and the second pressed portion 16) may be longer than the circumferential length of the interface surface 36 of the second transmission member 32.

[0031] 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 plane 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.

[0032] 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.

[0033] 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 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 a portion of the first magnetostrictive material 11 where the magnetic flux density is greater than that of the end on the gap 14 side, that is, a portion of the first magnetostrictive material 11 where the change in permeability in response to the application of a load (i.e., the magnetostrictive constant) is greater than that of the end on the gap 14 side. Similarly, the second pressed portion 16 is a portion of the second magnetostrictive material 12 where the magnetic flux density is greater than that of the end on the gap 14 side, that is, a portion of the second magnetostrictive material 12 where the change in permeability in response to the application of a load (i.e., the magnetostrictive constant) is greater than that of the end on the gap 14 side.

[0034] As shown in Figures 1 to 5 and Figure 7, the magnetic shield 40 is formed from a magnetic material and is a housing that encloses the first transmission member 31, a part of the second transmission member 32, the magnetic circuit 10, and the magnetic detection element 20. The magnetic shield 40 is formed from, for example, electromagnetic pure iron such as SUY-0 equivalent to JISC2504. In the following description, the first transmission member 31, the second transmission member 32, the magnetic circuit 10, and the magnetic detection element 20 are collectively referred to as the internal structure.

[0035] 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 on the radially outer side of 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 on the radially inner side of 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 cylinders, etc.

[0036] 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 a first shield member 41, and the top plate portion 45 is composed of a second shield member 42. 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 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. Note that the method of fixing the first shield member 41 and the second shield member 42 is not limited to crimping, but may also be welding, adhesive, etc.

[0037] The top plate portion 45 has a first insertion hole 48 through which the end of the first transmission member 31 on the interface surface 34 side is inserted. Therefore, the end of the first transmission member 31 on the interface surface 34 side protrudes to the outside from the magnetic shield 40 through the first insertion hole 48. The bottom plate portion 46 has a second insertion hole 49 through which the end of the second transmission member 32 on the interface surface 36 side is inserted. Therefore, the end of the second transmission member 32 on the interface surface 36 side also protrudes to the outside from the magnetic shield 40 through the second insertion hole 49. The first insertion hole 48 and the second insertion hole 49 are provided in the magnetic shield 40 in areas excluding the parts on one and the other sides in the axial direction relative to the magnet 13 and the magnetic detection element 20. Therefore, the magnetic shield 40 covers the region on one side and the other side in the axial direction relative to the magnet 13 and the magnetic detection element 20.

[0038] 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.

[0039] As shown in Figure 5, the molded member 50 resin-moldes 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 except for 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 compounded 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 parts of the molded member 50 where the material-reducing portions 51 are formed are not in contact with the outer cylinder portion 43 and the inner cylinder portion 44.

[0040] As an example of a manufacturing method for the load detection device 1, first, a magnet 13, a first magnetostrictive material 11, a second magnetostrictive material 12, a first transmission member 31, a second transmission member 32, and a terminal 22 are placed in a mold (not shown), and molten resin is injected into the mold. This forms a molded member 50 in which these components are integrally molded in resin. Next, a 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. Finally, a 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] Here, in order to compare with the load detection device 1 of the first embodiment described above, several comparative load detection devices will be described.

[0042] (Comparative Example 1) Figure 44 shows only the magnetic circuit 10, magnetic detection element 20, and second transmission member 32 of the load detection device of the first comparative example. The first transmission member 31 is assumed to have the same shape as the second transmission member 32 and is provided on the near side of the page. Note that the first transmission member 31 and the second transmission member 32 are not limited to a configuration that transmits the load to the entire range of the sensor magnetostrictive materials 11 and 12 as shown in Figure 44, but may also be configured to transmit the load to the portion of the sensor magnetostrictive materials 11 and 12 excluding the end on the magnetic detection element 20 side.

[0043] As shown in Figure 44, in the first comparative example, the sensor magnetostrictive materials 11 and 12 are asymmetric with respect to both the X and Y planes. Also, the first pressed portion 15 and the second pressed portion 16 are asymmetric with respect to both the X and Y planes. Therefore, in the first comparative example, when a uniform load is applied to the first transmission member 31 and the second transmission member 32 of the first comparative example with respect to the axis CL of the magnetic circuit 10, the load applied to one of the first transmission member 31 and the second transmission member 32 will be greater than the load applied to the other. Consequently, when the load applied to one of them reaches the magnetic degradation surface pressure, there is a problem in that the detection accuracy deteriorates. Note that the magnetic degradation surface pressure is the surface pressure applied to the magnetostrictive material that causes an irreversible change in the inverse magnetostrictive properties of the magnetostrictive material due to excessive pressure.

[0044] (Comparative Example 2) Figure 45 shows only the magnetic circuit 10, magnetic detection element 20, and second transmission member 32 of the load detection device of the second comparative example. The first transmission member 31 is assumed to have the same shape as the second transmission member 32 and is provided on the near side of the paper. Note that the first transmission member 31 and the second transmission member 32 are not limited to a configuration that transmits the load around the entire circumference of the sensor magnetostrictive materials 11 and 12 as shown in Figure 45, but may also be configured to transmit the load to the portion of the sensor magnetostrictive materials 11 and 12 excluding the end on the magnetic detection element 20 side.

[0045] As shown in Figure 45, in the second comparative example, the radially inner edges 300 (i.e., edges) of the first transmission member 31 and the second transmission member 32 are located in the middle of the radial width of the sensor magnetostrictive materials 11 and 12. Therefore, in the second comparative example, the first transmission member 31 and the second transmission member 32 press on a portion of the radially outer area of ​​the first pressed portion 15 and the second pressed portion 16. In this case, the second comparative example forms two magnetic circuits in the sensor magnetostrictive materials 11 and 12, one in the radially inner portion and one in the radially outer portion, resulting in variations in the detection accuracy of the magnetic detection element 20 and a deterioration in the straight-line propagation of the detection signal with respect to the applied load.

[0046] Furthermore, in the second comparative example, the local load applied to the first pressed portion 15 and the second pressed portion 16 from the radially inner edge 300 (i.e., edge) of the first transmission member 31 and the second transmission member 32 increases. As a result, the variation in surface pressure applied to the sensor magnetostrictive materials 11 and 12 from the first transmission member 31 and the second transmission member 32 increases, leading to problems such as a deterioration in detection accuracy.

[0047] (Effects of the first embodiment) The load detection device 1 of the first embodiment has the following advantages and disadvantages compared to the first comparative example, the second comparative example, and the load detection device described in Patent Document 1.

[0048] (1) In the first embodiment, the load detection device 1 comprises a magnetic circuit 10, a first transmission member 31, a second transmission member 32, and a magnetic detection element 20. 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 magnet 13, first magnetostrictive material 11, gap 14, second magnetostrictive material 12, and magnet 13. The first transmission member 31 and the second transmission member 32 transmit the load applied from the outside to the sensor magnetostrictive materials 11 and 12. The magnetic detection element 20 is provided at a position opposite the gap 14 in the axial direction and outputs an electrical signal corresponding to the magnetic flux flowing through the magnetic circuit 10.

[0049] With this configuration, except for the gap 14 where the magnetic detection element 20 is provided, there is no need to provide a gap between the magnetostrictive material and the yoke, or a layer with a relative permeability lower than that of the magnetostrictive material, in the middle of the magnetic circuit 10, 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 of the sensor magnetostrictive materials 11 and 12.

[0050] 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"). 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 by increasing the magnetic flux density of the first pressed portion 15 and the second pressed portion 16 of the sensor magnetostrictive materials 11 and 12, thereby improving the detection accuracy.

[0051] Furthermore, since the load detection device 1 is configured such that 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, it is possible to secure a longer magnetic path for the first pressed part 15 and the second pressed part 16 compared to a 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 path for the first pressed part 15 and the second pressed part 16 can be reduced, and the magnetic flux density of the first pressed part 15 and the second pressed part 16 can be increased accordingly. Consequently, the load detection device 1 can increase the magnetic flux density gain ΔB and improve detection accuracy.

[0052] Furthermore, since the magnetic circuit of this load detection device 1 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, a gap 14 can be provided at the position furthest from the magnet 13, and the magnetic detection element 20 can be placed on the side of the gap 14. As a result, the magnetic flux density of the first pressed part 15 and the second pressed part 16 can be increased, and the magnetic paths of these pressed parts can be made longer. Therefore, this load detection device 1 can increase the magnetic flux density gain ΔB and improve detection accuracy.

[0053] (2) In the first embodiment, the first pressed portion 15 of the first magnetostrictive material 11 and the second pressed portion 16 of the second magnetostrictive material 12 are symmetrical with respect to the X plane. Alternatively, the first magnetostrictive material 11 and the second magnetostrictive material 12 are symmetrical with respect to the X plane.

[0054] Incidentally, the load detection device described in Patent Document 1 has a gap between the magnet and the magnetostrictive material in the magnetic circuit, and also a gap between the magnetostrictive material and the yoke. As a result, in the magnetic circuit described in Patent Document 1, magnetic flux leakage increases at the gap-side end of the magnetostrictive material, and the magnetic flux density distribution becomes larger at the gap-side end of the magnetostrictive material and at the parts of the magnetostrictive material excluding the end. Therefore, when an uneven load is applied in the circumferential direction around the axis of a circular magnetostrictive material, the magnetic flux density gain ΔB may change significantly depending on the state of the uneven load. Consequently, the load detection device described in Patent Document 1 has problems such as reduced reliability of load detection and deterioration of detection accuracy.

[0055] Furthermore, in the first comparative example described above, the first pressed portion 15 and the second pressed portion 16 are asymmetric with respect to both the X-plane and the Y-plane. Also, the sensor magnetostrictive materials 11 and 12 are asymmetric with respect to both the X-plane and the Y-plane. In this case, when a uniform load is applied to the first transmission member 31 and the second transmission member 32 of the first comparative example with respect to the axis CL of the magnetic circuit 10, the load applied to one of the first transmission member 31 and the second transmission member 32 will be greater than the load applied to the other. Therefore, when the load applied to one of them reaches the magnetic degradation surface pressure, the reverse magnetostrictive properties of the magnetostrictive material change irreversibly, leading to problems such as a deterioration in detection accuracy.

[0056] In contrast, in the first embodiment, the first pressed portion 15 of the first magnetostrictive material 11 and the second pressed portion 16 of the second magnetostrictive material 12 are symmetrical with respect to the X plane. Alternatively, the first magnetostrictive material 11 and the second magnetostrictive material 12 are symmetrical with respect to the X plane. As a result, when a uniform load is applied to the first transmission member 31 and the second transmission member 32 in the circumferential direction around the axis CL of the magnetic circuit 10, the load applied to the first magnetostrictive material 11 and the load applied to the second magnetostrictive material 12 become almost uniform. Therefore, the load applied to the sensor magnetostrictive materials 11 and 12 is prevented from reaching the magnetic degradation surface pressure. Consequently, even if an uneven load is applied in the circumferential direction around the axis CL of the magnetic circuit 10, in the first embodiment, the load applied to the sensor magnetostrictive materials 11 and 12 is prevented from reaching the magnetic degradation surface pressure compared to the configurations in Patent Document 1 and the first comparative example. Therefore, the load detection device 1 of the first embodiment can improve the reliability and detection accuracy of load detection.

[0057] (3) In the first embodiment, both the first pressed portion 15 and the second pressed portion 16 have a shape in which the radial width of the magnetic circuit 10 gradually changes from the magnet 13 side toward the gap 14 side. According to this, the first pressed portion 15 and the second pressed portion 16 can be adjusted to achieve the "target magnetic flux density," thereby improving the signal-to-noise ratio (SNR). The target magnetic flux density refers to the range of magnetic flux density in which the change in the permeability of the sensor magnetostrictive materials 11 and 12 is greatest, between the maximum design load (hereinafter referred to as the "rated load") and no load applied to the first transmission member 31 and the second transmission member 32. In other words, the target magnetic flux density is the range in which the magnetostrictive constant is greatest for the magnetostrictive material used. Specifically, when the magnetomotive force of the magnet 13 is large, the magnetic path on the magnet 13 side of the sensor magnetostrictive materials 11 and 12 is initially increased to achieve the target magnetic flux density. Subsequently, the magnetic path is gradually reduced as it moves towards the magnetic detection element 20 to suppress the decrease in magnetic flux density due to magnetic flux leakage, thereby ensuring a longer range of the target magnetic flux density. Therefore, this load detection device 1 can increase the magnetic flux density gain ΔB, improve the signal-to-noise ratio, and improve detection accuracy.

[0058] (4) In the first embodiment, both the first pressed portion 15 and the second pressed portion 16 have a shape in which the radial width of the magnetic circuit 10 gradually decreases from the magnet 13 side toward the gap 14 side. According to this, in the first pressed portion 15 and the second pressed portion 16, the decrease in magnetic flux density due to magnetic flux leakage from the magnet 13 side toward the gap 14 side is suppressed, and the region of the target magnetic flux density can be secured for a longer period. This load detection device 1 can increase the magnetic flux density gain ΔB, improve the signal-to-noise ratio, and improve detection accuracy.

[0059] (5) In the first embodiment, both the first magnetostrictive material 11 and the second magnetostrictive material 12 have a shape in which the radial width of the magnetic circuit 10 gradually increases from the part of the pressed portion opposite to the magnet 13 toward the end toward the gap 14. According to this, it is possible to reduce the magnetic flux density passing through the magnetic detection element 20. Here, as explained with reference to Equation 1 above, the larger ΔB and the smaller B0 (i.e., the larger ΔB / B0), the higher the detection accuracy of the magnetic detection element 20. Therefore, the load detection device 1 can reduce the no-load magnetic flux density B0 by reducing the magnetic flux density passing through the magnetic detection element 20, thereby improving detection accuracy.

[0060] (6) In the first embodiment, the first pressed portion 15 is a portion of the first magnetostrictive material 11 in which the change in permeability in response to the application of a load is greater than that of the end on the gap 14 side, and the second pressed portion 16 is also a portion of the second magnetostrictive material 12 in which the change in permeability in response to the application of a load is greater than that of the end on the gap 14 side. The first transmission member 31 and the second transmission member 32 press the first pressed portion 15 and the second pressed portion 16, but do not press 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. According to this, by making the change in magnetic permeability in response to the application of load greater at the first pressed portion 15 and the second pressed portion 16 than at the end on the gap 14 side, the magnetic flux density gain ΔB can be increased, and the no-load magnetic flux density B0 can be decreased. Therefore, this load detection device 1 can improve the signal-to-noise ratio and improve detection accuracy.

[0061] (7) In the first embodiment, the first transmission member 31 and the second transmission member 32 press over the entire radial width range at the first pressed portion 15 and the second pressed portion 16.

[0062] By the way, in the second comparative example described above, the first transmission member 31 and the second transmission member 32 are configured to press a portion of the radial range in the first pressed portion 15 and the second pressed portion 16. In this case, in the second comparative example, two magnetic circuits are formed in the sensor magnetostrictive materials 11 and 12, one in the radially inner portion and the other in the radially outer portion, resulting in variations in the detection accuracy of the magnetic detection element 20 and a deterioration in the straight-line propagation of the detection signal with respect to the applied load.

[0063] Furthermore, in the second comparative example, the local load applied to the first pressed portion 15 and the second pressed portion 16 from the radially inner edge 300 (i.e., edge) of the first transmission member 31 and the second transmission member 32 increases. As a result, the variation in surface pressure applied to the sensor magnetostrictive materials 11 and 12 from the first transmission member 31 and the second transmission member 32 increases, leading to problems such as a deterioration in detection accuracy.

[0064] In contrast, in the first embodiment, 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. As a result, multiple magnetic circuits are not formed in the radially inner portion and radially outer portion of the sensor magnetostrictive material 11 and 12, and variations in the detection accuracy of the magnetic detection element 20 can be prevented. Furthermore, in the first embodiment, the local load applied to the first pressed portion 15 and the second pressed portion 16 from the first transmission member 31 and the second transmission member 32 is reduced. Therefore, variations in the surface pressure applied to the sensor magnetostrictive material 11 and 12 from the first transmission member 31 and the second transmission member 32 are reduced, and detection accuracy can be improved.

[0065] (8) In the first embodiment, the circumferential length D1 of the contact surface 33 of the first transmission member 31 (i.e., the circumferential length of the first pressed portion 15 and the second pressed portion 16) is longer than the circumferential length D2 of the interface surface 34 of the first transmission member 31. Alternatively, the circumferential length of the contact surface 35 of the second transmission member 32 (i.e., the circumferential length of the first pressed portion 15 and the second pressed portion 16) is longer than the circumferential length of the interface surface 36 of the second transmission member 32. According to this, the application of localized loads from the first transmission member 31 and the second transmission member 32 to the first pressed portion 15 and the second pressed portion 16 can be suppressed. As a result, the variation in surface pressure applied from the first transmission member 31 and the second transmission member 32 to the sensor magnetostrictive materials 11 and 12 is reduced. Furthermore, since localized loads are suppressed, the loads applied to the sensor magnetostrictive materials 11 and 12 from the first transmission member 31 and the second transmission member 32 are prevented from reaching the magnetic degradation surface pressure. Therefore, this load detection device 1 can improve the reliability and detection accuracy of load detection.

[0066] (9) In the first embodiment, the interface surface 34 of the first transmission member 31 is symmetric with respect to the X plane, and the interface surface 36 of the second transmission member 32 is also symmetric with respect to the X plane. According to this, in the first embodiment, compared to the first comparative example, when a uniform load is applied to the first transmission member 31 and the second transmission member 32 in the circumferential direction around the axis CL of the magnetic circuit 10, the load applied to the first magnetostrictive material 11 and the load applied to the second magnetostrictive material 12 become almost uniform. Therefore, the load applied to the sensor magnetostrictive materials 11 and 12 is suppressed from reaching the magnetic degradation surface pressure. Consequently, even if an uneven load is applied in the circumferential direction around the axis CL of the magnetic circuit 10, in the first embodiment, the load applied to the sensor magnetostrictive materials 11 and 12 is suppressed from reaching the magnetic degradation surface pressure compared to the first comparative example. Thus, the load detection device 1 of the first embodiment can improve the reliability and detection accuracy of load detection.

[0067] (10) In the first embodiment, the magnetic shield 40 provided by the load detection device 1 has an outer cylinder portion 43, an inner cylinder portion 44, a top plate portion 45, and a bottom plate portion 46. According to the inventors' studies, the load detection device 1 includes a magnetic shield 40 having an outer cylinder portion 43, an inner cylinder portion 44, a top plate portion 45, and a bottom plate portion 46. This causes the magnetic flux flowing through the magnetic circuit 10 to leak into the magnetic shield 40, reducing the no-load magnetic flux density B0. The magnetic flux density gain ΔB also decreases, 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, the load detection device 1 can improve detection accuracy. This will also be explained in the seventh embodiment described later.

[0068] (Second to fifth embodiments) The second to fifth embodiments will now be described. The second to fifth embodiments modify the configuration of the magnetic circuit 10 and the magnetic detection element 20 compared to the first embodiment, and investigate ΔB and ΔB / B0, which are indicators of detection accuracy. In the description of the second to fifth embodiments, the left side of the paper in the figure is referred to as one side in the X direction, and the right side of the paper is referred to as the other side in the X direction. Also, the upper side of the paper in the figure is referred to as one side in the Y direction, and the lower side of the paper is referred to as the other side in the Y direction.

[0069] Furthermore, in Figures 11 to 14, which are referenced in the second to fifth embodiments, the magnitude of the magnetic flux density flowing through the magnetic circuit 10 is shown using multiple types of hatching. First, the configuration of the magnetic circuit 10 and the magnetic detection element 20 will be described for the second to fifth embodiments.

[0070] (Second Embodiment) As shown in Figure 11, in the second 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. That is, the magnetic circuit 10 and magnetic detection element 20 in the second embodiment are arranged in the same way as in the first embodiment. The first magnetostrictive material 11 and the second magnetostrictive material 12 in the second embodiment are symmetrical with respect to the X plane. Also, the first magnetostrictive material 11 is symmetrical with respect to the Y plane, and the second magnetostrictive material 12 is also symmetrical with respect to the Y plane.

[0071] (Third embodiment) As shown in Figure 12, in the third embodiment, in the annular magnetic circuit 10, a first magnet 131 is provided on one side in the X direction, a second magnet 132 is provided on the other side in the X direction, a first magnetic detection element 24 is provided on one side in the Y direction, and a second magnetic detection element 25 is provided on the other side in the Y direction. In the third embodiment, the multiple magnetostrictive materials constituting the magnetic circuit 10 are referred to as the first magnetostrictive material 101, the second magnetostrictive material 102, the third magnetostrictive material 103, and the fourth magnetostrictive material 104, starting from the side of the first magnet 131 and moving clockwise in Figure 12. The third embodiment features an improved average magnetic flux density compared to the second embodiment.

[0072] (Fourth Embodiment) As shown in Figure 13, in the fourth embodiment, in the annular magnetic circuit 10, a first magnet 131 is provided on one side in the X direction, a second magnet 132 is provided on the other side in the X direction, and a magnetic detection element 20 is provided only on one side in the Y direction. In the fourth embodiment, the multiple magnetostrictive materials constituting the magnetic circuit 10 are referred to as the first magnetostrictive material 101, the second magnetostrictive material 102, and the third magnetostrictive material 103, starting from the side of the first magnet 131 and moving clockwise in Figure 12. In the fourth embodiment, compared to the second embodiment, the magnetic flux density is increased by a third magnetostrictive material 103 provided on the other side in the Y direction with respect to the X plane.

[0073] (Fifth embodiment) As shown in Figure 14, in the fifth embodiment, in the annular magnetic circuit 10, the first magnet 131, the magnetic detection element 20, and the second magnet 132 are arranged in this order circumferentially on the other side in the X direction. In the fifth embodiment, there is one magnetostrictive material 100 constituting the magnetic circuit 10. In the fifth embodiment, the average magnetic flux density is made more uniform compared to the second embodiment.

[0074] (Analysis results of the second to fifth embodiments) Next, we will explain the results of the analysis of the second to fifth embodiments. The graph in Figure 15 shows the magnetic flux density gain ΔB and the result of dividing the magnetic flux density gain ΔB by the no-load magnetic flux density B0 (i.e., ΔB / B0) for the second to fifth embodiments described above. The dashed bar graphs show the magnetic flux density gain ΔB, and the open bar graphs show ΔB / B0. As explained with reference to Equation 1 above, the larger ΔB / B0, the better the detection accuracy of the magnetic detection element 20. In the graph in Figure 15, "Fourth Embodiment_Lower Half of Load" refers to the analysis results when a load is applied only to the third magnetostrictive material 103 of the magnetic circuit 10 of the fourth embodiment. The other results are the analysis results when a load is applied uniformly to all magnetostrictive materials in each embodiment.

[0075] As shown in the graph in Figure 15, among the configurations described in the second to fifth embodiments, the configuration of the second embodiment has the largest ΔB / B0. Therefore, as in the first and second embodiments, if the magnetic circuit 10 is configured so that the magnetic flux flows in the order of the north pole of the magnet 13, the first magnetostrictive material 11, the gap 14, the second magnetostrictive material 12, and the south pole of the magnet 13, and the magnetic detection element 20 is placed on the gap 14 side, then ΔB / B0 will be large and the detection accuracy will be improved.

[0076] (Sixth and seventh embodiments) The sixth and seventh embodiments will now be described. In the sixth and seventh embodiments, the shapes of the sensor magnetostrictive materials 11 and 12 constituting the magnetic circuit 10 are changed compared to the second embodiment, and ΔB and ΔB / B0, which are indicators of detection accuracy, are investigated.

[0077] Furthermore, in Figures 16 and 17, which are referenced in the sixth and seventh embodiments, the magnitude of the magnetic flux density flowing through the magnetic circuit 10 is shown using multiple types of hatching. Note that Figure 17 only shows one side in the Y direction with respect to the X plane. First, the configuration of the magnetic circuit 10 and the magnetic detection element 20 will be described for the sixth and seventh embodiments.

[0078] (Sixth Embodiment) In the second embodiment described above, as shown in Figure 11, both the first pressed portion 15 and the second pressed portion 16 had the same radial width of the magnetic circuit 10 from the magnet 13 side toward the gap 14 side.

[0079] In contrast, as shown in Figure 16, in the sixth embodiment, both the first pressed portion 15 and the second pressed portion 16 have a shape in which the radial width of the magnetic circuit 10 gradually decreases from the magnet 13 side toward the gap 14 side. This allows the first pressed portion 15 and the second pressed portion 16 to be adjusted to achieve the target magnetic flux density. Specifically, when the magnetomotive force of the magnet 13 is large, the magnetic path on the magnet 13 side of the sensor magnetostrictive materials 11 and 12 is first made larger to achieve the target magnetic flux density. Then, as it moves toward the magnetic detection element 20 side, the magnetic path is gradually made smaller to suppress the decrease in magnetic flux density due to magnetic flux leakage and to ensure that the region of the target magnetic flux density is maintained for a longer period.

[0080] Furthermore, in the sixth embodiment, both the first magnetostrictive material 11 and the second magnetostrictive material 12 have a shape in which the radial width gradually increases from the part of the pressed area opposite to the magnet 13 toward the end toward the gap 14. This makes it possible to reduce the magnetic flux density passing through the magnetic detection element 20.

[0081] (Seventh Embodiment) As shown in Figure 17, the seventh embodiment is equipped with a magnetic shield 40 compared to the sixth embodiment. Therefore, the shape of the sensor magnetostrictive materials 11 and 12 differs from that of the sixth embodiment so that the magnetic circuit 10 and the magnetic detection element 20 can be inserted between the outer cylinder portion 43 and the inner cylinder portion 44 of the magnetic shield 40. However, in the seventh embodiment as in the sixth embodiment, both the first pressed portion 15 and the second pressed portion 16 have a shape in which the radial width of the magnetic circuit 10 gradually decreases from the magnet 13 side toward the gap 14 side. Also, both the first magnetostrictive material 11 and the second magnetostrictive material 12 have a shape in which the radial width gradually increases from the part of the pressed portion opposite to the magnet 13 toward the end toward the gap 14 side.

[0082] (Analysis results of the second, sixth, and seventh embodiments) Next, we will explain the results of our analysis of the second, sixth, and seventh embodiments. The table in Figure 18 shows the magnetic flux density gain ΔB, the no-load magnetic flux density B0, and the result of dividing the magnetic flux density gain ΔB by the no-load magnetic flux density B0 (i.e., ΔB / B0) for the second, sixth, and seventh embodiments described above. As explained with reference to Equation 1 above, the larger ΔB / B0, the better the detection accuracy of the magnetic detection element 20.

[0083] As shown in the table in Figure 18, it can be seen that the ΔB / B0 is larger in the 6th and 7th embodiments, in which the sensor magnetostrictive materials 11 and 12 have a gradually changing shape, than in the 2nd embodiment. Furthermore, it can be seen that the ΔB / B0 is larger in the 7th embodiment, in which the magnetic shield 40 is provided, than in the 6th embodiment. In other words, in the 7th embodiment, by providing a magnetic shield 40 having 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 of the magnetic flux density gain ΔB is smaller than the rate of decrease of the no-load magnetic flux density B0. Therefore, by providing a gradually changing shape for the magnetostrictive material as in the 7th embodiment, and further by providing the magnetic shield 40, ΔB / B0 becomes larger, and the detection accuracy is improved.

[0084] (Embodiments 8-13) Embodiments 8 to 13 will now be described. Embodiments 8 to 13 are modified versions of Embodiment 1, in which the shape of the first transmission member 31 and the like are changed.

[0085] (Eighth embodiment) As shown in Figure 19, in the eighth embodiment, both circumferential ends of the first transmission member 31 have an inclined shape 37 that gradually lengthens circumferentially from the interface surface 34 toward the contact surface 33. In addition, the contact surface 33 side of both circumferential ends of the first transmission member 31 is provided with a stepped shape 38 that extends toward the circumferential gap 14. In other words, in the eighth embodiment, both circumferential ends of the first transmission member 31 have a shape that combines the inclined shape 37 and the stepped shape 38.

[0086] Furthermore, both circumferential ends of the second transmission member 32 are provided at the same axial position as both circumferential ends of the first transmission member 31.

[0087] In the eighth embodiment described above, the application of local load from the first transmission member 31 to the first pressed portion 15 and the second pressed portion 16 can be suppressed. As a result, the variation in surface pressure applied from the first transmission member 31 and the second transmission member 32 to the sensor magnetostrictive materials 11 and 12 is reduced.

[0088] Furthermore, in the eighth embodiment, since local load is suppressed, the load applied to the sensor magnetostrictive materials 11 and 12 from the first transmission member 31 and the second transmission member 32 is prevented from reaching the magnetic degradation surface pressure. Therefore, this load detection device 1 can improve the reliability and detection accuracy of load detection.

[0089] (Ninth Embodiment) As shown in Figure 20, in the ninth embodiment, the first transmission member 31 is provided with stepped shapes 38 that extend toward the circumferential gap 14 on the contact surface 33 side at both circumferential ends. Furthermore, the corners of the stepped shapes 38 have curved shapes 39 that are convex toward the magnetostrictive material side. In other words, in the ninth embodiment, the circumferential ends of the first transmission member 31 have a shape that combines the stepped shape 38 and the curved shape 39.

[0090] Furthermore, both circumferential ends of the second transmission member 32 are provided at the same axial position as both circumferential ends of the first transmission member 31.

[0091] The ninth embodiment described above can also achieve the same effects and advantages as the eighth embodiment and the like.

[0092] (Tenth embodiment) As shown in Figure 21, in the tenth embodiment, both circumferential ends of the first transmission member 31 have an inclined shape 37 that gradually lengthens circumferentially from the interface surface 34 toward the contact surface 33. Furthermore, the contact surface 33 side of both circumferential ends of the first transmission member 31 is provided with a stepped shape 38 that extends toward the circumferential gap 14. Moreover, the corner between the stepped shape 38 and the inclined shape 37 has a curved surface shape 39 that is convex toward the magnetostrictive material side. In other words, in the tenth embodiment, both circumferential ends of the first transmission member 31 have a shape that combines the inclined shape 37, the stepped shape 38, and the curved surface shape 39.

[0093] Furthermore, both circumferential ends of the second transmission member 32 are provided at the same axial position as both circumferential ends of the first transmission member 31.

[0094] The tenth embodiment described above can also achieve the same effects as the eighth and ninth embodiments, etc.

[0095] (11th embodiment) As shown in Figure 22, in the 11th embodiment, a chamfered or curved shape 301 is provided on the outer edge of the contact surface 33 of the first transmission member 31 that faces the sensor magnetostrictive materials 11 and 12. In addition, a chamfered or curved shape 301 is also provided on the outer edge of the contact surface 35 of the second transmission member 32 that faces the sensor magnetostrictive materials 11 and 12.

[0096] According to this, it is possible to suppress the application of local loads to the first pressed portion 15 and the second pressed portion 16 from the outer edges of the contact surfaces 33 and 35 of the first transmission member 31 and the second transmission member 32. As a result, the variation in surface pressure applied from the first transmission member 31 and the second transmission member 32 to the sensor magnetostrictive materials 11 and 12 is reduced. Furthermore, since localized loads are suppressed, the loads applied to the sensor magnetostrictive materials 11 and 12 from the first transmission member 31 and the second transmission member 32 are prevented from reaching the magnetic degradation surface pressure. Therefore, this load detection device 1 can improve the reliability and detection accuracy of load detection.

[0097] (12th embodiment) As shown in Figures 23 and 24, in the twelfth embodiment, the interface surface 34 of the first transmission member 31 has both circumferential ends 34a and 34b at the same angle from the Y plane. That is, the angle θ1 from one circumferential end 34a to the Y plane and the angle θ2 from the other circumferential end 34b to the Y plane are the same. Furthermore, the interface surface 34 of the first transmission member 31 is symmetrical with respect to the X plane.

[0098] In this specification, "identical" includes not only complete identicalness but also substantial identicalness, such as within the range of manufacturing tolerances. Furthermore, in this specification, "symmetrical" includes not only perfect mirror symmetry but also substantial symmetry, such as within the range of manufacturing tolerances.

[0099] Furthermore, in the twelfth embodiment, the interface surface 36 of the second transmission member 32 also has both circumferential ends 36a and 36b positioned at the same angle from the Y plane. That is, the angle from one circumferential end 36a to the Y plane and the angle from the other circumferential end 36b to the Y plane are the same. Also, the interface surface 36 of the second transmission member 32 is symmetrical with respect to the X plane.

[0100] Furthermore, as shown in Figure 25, in the twelfth embodiment, the first pressed portion 15 of the first magnetostrictive material 11 and the second pressed portion 16 of the second magnetostrictive material 12 are also at the same angle from the Y plane at both circumferential ends. In Figure 25, the first pressed portion 15 and the second pressed portion 16 are shown with dashed hatching, although this is not a cross-section. For the first pressed portion 15, the angle θ5 from one circumferential end 15a to the Y plane is the same as the angle θ6 from the other circumferential end 15b to the Y plane. Similarly, for the second pressed portion 16, the angle θ7 from one circumferential end 16a to the Y plane is the same as the angle θ8 from the other circumferential end 16b to the Y plane. Also, the first pressed portion 15 and the second pressed portion 16 are symmetrical with respect to the X plane; that is, θ5 to θ8 are the same.

[0101] In the twelfth embodiment described above, when a uniform load is applied to the first transmission member 31 and the second transmission member 32 in the circumferential direction around the axis CL of the magnetic circuit 10, the load applied to the first magnetostrictive material 11 and the load applied to the second magnetostrictive material 12 become substantially uniform. Therefore, the load applied to the sensor magnetostrictive materials 11 and 12 is prevented from reaching the magnetic degradation surface pressure. Consequently, even if an uneven load is applied in the circumferential direction around the axis CL of the magnetic circuit 10, in the first embodiment, the load applied to the sensor magnetostrictive materials 11 and 12 is prevented from reaching the magnetic degradation surface pressure. Thus, the load detection device 1 of the first embodiment can improve the reliability and detection accuracy of load detection.

[0102] (13th embodiment) As shown in Figures 26 and 27, in the 13th embodiment, the interface surface 34 of the first transmission member 31 has the same area for parts facing the Y-plane. That is, the interface surface 34 of the first transmission member 31 has the same area S1 for one part on the circumferential side with respect to the Y-plane and the same area S2 for the other part on the circumferential side with respect to the Y-plane. Furthermore, the interface surface 34 of the first transmission member 31 is symmetrical with respect to the X-plane.

[0103] Furthermore, in the 13th embodiment, the interface surface 36 of the second transmission member 32 also has the same area for parts facing the Y-plane. That is, the interface surface 36 of the second transmission member 32 has the same area for one part on the circumferential side with respect to the Y-plane. Also, the interface surface 36 of the second transmission member 32 is symmetrical with respect to the X-plane.

[0104] Furthermore, as shown in Figure 28, in the 13th embodiment, the first pressed portion 15 of the first magnetostrictive material 11 and the second pressed portion 16 of the second magnetostrictive material 12 also have the same area when facing each other in the Y-plane. In Figure 28, the first pressed portion 15 and the second pressed portion 16 are shown with dashed hatching, although this is not a cross-section. For the first pressed portion 15, the area S5 of the portion on one side in the circumferential direction with respect to the Y-plane is the same as the area S6 of the portion on one side in the circumferential direction with respect to the Y-plane. Similarly, for the second pressed portion 16, the area S7 of the portion on one side in the circumferential direction with respect to the Y-plane is the same as the area S8 of the portion on one side in the circumferential direction with respect to the Y-plane. Also, the first pressed portion 15 and the second pressed portion 16 are symmetrical with respect to the X-plane. That is, S5 to S8 are the same.

[0105] The 13th embodiment described above can also achieve the same effects as the 12th embodiment and the like.

[0106] (14th Embodiment) A 14th embodiment will now be described. The 14th embodiment examines the material properties of the sensor magnetostrictive materials 11 and 12, and the surface pressure applied to the sensor magnetostrictive materials 11 and 12, which can improve detection accuracy compared to the first embodiment and the like.

[0107] Figure 29 is a graph showing the results of a magnetic field analysis using the magnetic circuit 10 shown in the first embodiment, based on the surface compression BH characteristics measured by surface compression of a ring-shaped magnetostrictive material test piece (hereinafter referred to as "magnetostrictive material ring piece"). The horizontal axis of Figure 29 shows the rate of change Δμm of the maximum relative permeability of the sensor magnetostrictive materials 11 and 12, and the vertical axis shows the magnetic flux density gain ΔB.

[0108] From the graph in Figure 29, the relationship between the rate of change Δμm of the maximum relative permeability of the sensor magnetostrictive materials 11 and 12 and the magnetic flux density gain ΔB can be expressed by the following equation 2, where x is the rate of change Δμm of the maximum relative permeability and y is the magnetic flux density gain ΔB. y = 0.00003x 3 -0.0022 x 2 +0.184x+0.1232...(Formula 2) Note that Equation 2 is an empirical formula.

[0109] As explained with reference to Equation 1 above, the detection accuracy of the magnetic detection element 20 improves as the magnetic flux density gain ΔB increases. Therefore, a larger magnetic flux density gain ΔB indicates a better characteristic, i.e., a desirable characteristic. Furthermore, according to Equation 2, the larger the rate of change Δμm of the maximum relative permeability of the sensor magnetostrictive materials 11 and 12, the larger the magnetic flux density gain ΔB. Therefore, the rate of change Δμm of the maximum relative permeability of the sensor magnetostrictive materials 11 and 12 is also a desirable characteristic.

[0110] Next, the inventors investigated what materials are preferable for the sensor magnetostrictive materials 11 and 12, and what surface pressure should be applied to the sensor magnetostrictive materials 11 and 12, in order to stably increase the rate of change Δμm of the maximum relative permeability of the sensor magnetostrictive materials 11 and 12.

[0111] First, the inventors will explain the results of their investigation into what materials are preferable for the sensor magnetostrictive materials 11 and 12 in order to stably increase the rate of change Δμm of the maximum relative permeability of the sensor magnetostrictive materials 11 and 12 (i.e., material properties of sensor magnetostrictive materials 11 and 12 that can improve detection accuracy).

[0112] Figure 30 is a graph showing the results of calculating the rate of change Δμm of the maximum relative permeability when the surface pressure applied to the magnetostrictive ring pieces was changed from 0 MPa to 330 MPa, using the surface compression BH characteristics results obtained by surface compression of multiple magnetostrictive ring pieces with different compositions. In the following explanation, the rate of change of the maximum relative permeability when the surface pressure applied to the magnetostrictive ring pieces is changed from 0 MPa to 330 MPa will be referred to as "rate of change of maximum relative permeability Δμm_F0-330".

[0113] In Figure 30, the horizontal axis represents the maximum relative permeability μm of the magnetostrictive ring piece, and the vertical axis represents the rate of change Δμm_F0-330 of the maximum relative permeability.

[0114] From the graph in Figure 30, it was found that the rate of change of the maximum relative permeability Δμm_F0-330 has a critical point when the maximum relative permeability μm of the magnetostrictive ring piece is 5000. In detail, when the maximum relative permeability μm of the magnetostrictive ring piece is less than 5000, the rate of change of the maximum relative permeability Δμm_F0-330 increases or decreases sharply with increasing or decreasing the maximum relative permeability μm of the magnetostrictive ring piece. On the other hand, when the maximum relative permeability μm of the magnetostrictive ring piece is 5000 or more, the increase or decrease of the rate of change of the maximum relative permeability Δμm_F0-330 becomes more gradual with increasing or decreasing the maximum relative permeability μm of the magnetostrictive ring piece. From this, it can be seen that by using sensor magnetostrictive materials 11 and 12 with a maximum relative permeability μm of 5000 or more, it is possible to stably increase the rate of change of the maximum relative permeability Δμm.

[0115] Furthermore, as shown in Figure 29, the inventors have found through experiments and analysis that the magnetic flux density gain ΔB increases as the rate of change Δμm of the maximum relative permeability of the sensor magnetostrictive materials 11 and 12 increases. Therefore, by using materials with a maximum relative permeability μm of 5000 or more, the rate of change Δμm of the maximum relative permeability can be stably increased, and thereby the magnetic flux density gain ΔB can be stably increased, improving the signal-to-noise ratio and detection accuracy.

[0116] Next, the inventors will explain the results of their investigation into what surface pressure should be applied to the sensor magnetostrictive materials 11 and 12 in order to stably increase the rate of change Δμm of the maximum relative permeability of the sensor magnetostrictive materials 11 and 12 (i.e., the surface pressure applied to the sensor magnetostrictive materials 11 and 12 that can improve detection accuracy).

[0117] Figure 31 is a graph showing the results of calculating the rate of change Δμm of the maximum relative permeability when the surface pressure applied to the magnetostrictive ring piece is changed from 0 to a predetermined surface pressure Fα, using the surface compression BH characteristics obtained by surface compression of the magnetostrictive ring piece. In the following explanation, the rate of change of the maximum relative permeability when the surface pressure applied to the magnetostrictive ring piece is changed from 0 to a predetermined surface pressure Fα is referred to as "rate of change of maximum relative permeability Δμm_F0-α".

[0118] In Figure 31, the horizontal axis represents a predetermined surface pressure Fα, and the vertical axis represents the rate of change of the maximum relative permeability Δμm_F0-α.

[0119] From the graph in Figure 31, it was found that the rate of change of the maximum relative permeability Δμm_F0-α has a critical point at a predetermined surface pressure Fα of 150 MPa. In detail, when the predetermined surface pressure Fα is less than 150 MPa, the rate of change of the maximum relative permeability Δμm_F0-α increases or decreases sharply with increases or decreases in the predetermined surface pressure Fα. On the other hand, when the predetermined surface pressure Fα is 150 MPa or higher, the increase or decrease in the rate of change of the maximum relative permeability Δμm_F0-α becomes more gradual with respect to increases or decreases in the predetermined surface pressure Fα. From this, it is possible to stably increase the rate of change of the maximum relative permeability Δμm by setting the average surface pressure applied to the sensor magnetostrictive materials 11 and 12 to 150 MPa or higher for the rated load. In general, magnetostrictive materials have a magnetic degradation surface pressure. Therefore, the sensor magnetostrictive materials 11 and 12 are selected from materials whose magnetic degradation surface pressure is greater than the average surface pressure set to a predetermined value of 150 MPa or higher.

[0120] Furthermore, as shown in Figure 29, the inventors have found through experiments and analysis that the magnetic flux density gain ΔB increases as the rate of change Δμm of the maximum relative permeability of the sensor magnetostrictive materials 11 and 12 increases. Therefore, by setting the average surface pressure applied to the sensor magnetostrictive materials 11 and 12 to 150 MPa or more relative to the rated load, the rate of change Δμm of the maximum relative permeability can be stably increased, and thereby the magnetic flux density gain ΔB can be stably increased, improving the signal-to-noise ratio and detection accuracy.

[0121] Based on the experimental and analytical results described above, the load detection device 1 of the 14th embodiment provides the following effects. (1) The sensor magnetostrictive materials 11 and 12 in the load detection device 1 are made of materials with a maximum relative permeability of 5000 μm or more. This allows for a stable increase in the rate of change Δμm of the maximum relative permeability. As a result, the magnetic flux density gain ΔB can be stably increased, thereby improving the signal-to-noise ratio and detection accuracy.

[0122] (2) The load detection device 1 is configured such that the average surface pressure applied to the sensor magnetostrictive materials 11 and 12 is set to 150 MPa or higher relative to the rated load. Furthermore, the sensor magnetostrictive materials 11 and 12 are made of materials whose magnetic degradation surface pressure is greater than the set average surface pressure. This allows for a stable increase in the rate of change Δμm of the maximum relative permeability. As a result, the magnetic flux density gain ΔB can be stably increased, thereby improving the signal-to-noise ratio and detection accuracy.

[0123] (Embodiments 15-20) Embodiments 15 to 20 will now be described. Embodiments 15 to 20 are modified versions of Embodiment 15, 16, and 20, respectively, by changing the configuration of the magnetic circuit 10 and the magnetic detection element 20. Otherwise, they have the same configuration as Embodiment 1 and 20. In the description of Embodiments 15 to 20, the left side of the paper in the figures 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.

[0124] (15th Embodiment) As shown in Figures 32 and 33, in the 15th 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. That is, the magnetic circuit 10 of the 15th embodiment has substantially the same arrangement as that of the first and second embodiments. 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.

[0125] (16th Embodiment) As shown in Figures 34 and 35, in the 16th 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 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 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.

[0126] (17th Embodiment) As shown in Figures 36 and 37, in the 17th 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 arrangement of the magnetic circuit 10 and the magnetic detection element 20 in the 17th embodiment is substantially the same as in the 15th 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.

[0127] (18th embodiment) As shown in Figures 38 and 39, in the 18th 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. The magnetostrictive material 100 is formed in a continuous annular shape except for the area where the magnetic detection element 20 is 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 provided between one end 100a of the magnetostrictive material 100 and the magnet 13.

[0128] (19th embodiment) As shown in Figures 40 and 41, the 19th 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 (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.

[0129] (20th embodiment) As shown in Figures 42 and 43, the 20th 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 than 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.

[0130] The 15th to 20th embodiments described above can also achieve the same effects as the first embodiment and others described above.

[0131] (Other embodiments) (1) In the above embodiments, the first, second, twelfth, and thirteenth embodiments, etc., described load detection devices 1 that satisfy requirements such as "symmetrical with respect to the X plane," "symmetrical with respect to the Y plane," "the areas of parts facing each other on the Y plane are the same," and "both ends in the circumferential direction are at the same angle from the Y plane," but are not limited to these.

[0132] For example, the first pressed portion 15 and the second pressed portion 16 may satisfy any of the following requirements (A) to (C). (A) Satisfying at least one of the following requirements: "symmetric in the X-plane" and "symmetric in the Y-plane" (B) Or, satisfying at least one of the following requirements: "symmetrical with respect to the X plane" and "the areas of the parts facing each other in the Y plane are the same." (C) Or, satisfying at least one of the following requirements: "symmetrical in the X-plane" and "both ends in the circumferential direction around the axis CL of the magnetic circuit 10 are at the same angle from the Y-plane".

[0133] Furthermore, for example, the first magnetostrictive material 11 and the second magnetostrictive material 12 may satisfy any of the requirements (A) to (C) above.

[0134] Furthermore, for example, the interface surface 34 of the first transmission member 31 and the interface surface 36 of the second transmission member 32 may satisfy any of the requirements (A) to (C) above.

[0135] Furthermore, for example, the contact surface 33 of the first transmission member 31 and the contact surface 35 of the second transmission member 32 may satisfy any of the requirements (A) to (C) above.

[0136] (2) In the first embodiment described above, the magnetic detection element 20 was provided at a position facing the gap 14 in the axial direction. In the second, fifteenth, and sixteenth embodiments, the magnetic detection element 20 was provided inside the gap 14. In the nineteenth and twentieth 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 also be provided at an intermediate position between the positions shown in each embodiment.

[0137] 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.

[0138] 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 a first magnetostrictive material (11) and a second magnetostrictive material (12) have permeability that changes according to an external force, and the magnetic flux generated by the magnetic flux generating unit flows in the order of the first magnetostrictive material, gap (14), second magnetostrictive material, and the magnetic flux generating unit. A first transmission member (31) 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 first magnetostrictive material and the second magnetostrictive material, A second transmission member (32) transmits a load applied from the outside on the other side in the direction in which the axis extends to the first magnetostrictive material and the second magnetostrictive material, A load detection device comprising a magnetic detection element (20) provided at a position opposite to or within the gap, which outputs a signal corresponding to the magnetic flux flowing through the magnetic circuit. [Claim 2] When the line connecting the center of the magnetic flux generating part and the axis, and the plane containing the axis are referred to as the X-plane, and the plane perpendicular to the X-plane and containing the axis is referred to as the Y-plane, The first pressed portion (15) of the first magnetostrictive material that is pressed by the first transmission member or the second transmission member, and the second pressed portion (16) of the second magnetostrictive material that is pressed by the first transmission member or the second transmission member, satisfy at least one of the following requirements: symmetrical with respect to the X plane, symmetrical with respect to the Y plane, the areas of the portions facing each other on the Y plane are the same, and both ends in the circumferential direction around the axis are at the same angle from the Y plane. Alternatively, the load detection device according to claim 1, wherein the first magnetostrictive material and the second magnetostrictive material satisfy at least one of the following requirements: symmetrical with respect to the X plane, symmetrical with respect to the Y plane, the areas of the portions facing each other on the Y plane are the same, and both ends in the circumferential direction around the axis are at the same angle from the Y plane. [Claim 3] The load detection device according to claim 2, wherein both the first pressed portion and the second pressed portion have a shape in which the width in the radial direction of a virtual circle centered on the axis gradually changes from the magnetic flux generating portion side toward the gap side. [Claim 4] The load detection device according to claim 2 or 3, wherein both the first pressed portion and the second pressed portion have a shape in which the width in the radial direction of a virtual circle centered on the axis gradually decreases from the magnetic flux generating portion side toward the gap side. [Claim 5] The load detection device according to any one of claims 2 to 4, wherein both the first magnetostrictive material and the second magnetostrictive material have a shape in which the width in the radial direction of a virtual circle centered on the axis gradually increases from the portion of the first pressed portion and the second pressed portion opposite to the magnetic flux generating portion toward the end toward the gap. [Claim 6] The first pressed portion is a part of the first magnetostrictive material in which the amount of change in magnetic permeability in response to the application of load is greater than that of the end on the gap side. The second pressed portion is also a part of the second magnetostrictive material in which the amount of change in magnetic permeability in response to the application of load is greater than that of the end on the gap side. The load detection device according to any one of claims 2 to 5, wherein the first transmission member and the second transmission member press the first pressed portion and the second pressed portion, but do not press the end of the first magnetostrictive material on the gap side and the end of the second magnetostrictive material on the gap side. [Claim 7] The load detection device according to any one of claims 1 to 6, wherein the first transmission member and the second transmission member are configured to press the entire width range in the radial direction of a virtual circle centered on the axis of the first magnetostrictive material and the second magnetostrictive material. [Claim 8] In the first transmission member, the circumferential length (D1) of the contact surface (33) in contact with the first magnetostrictive material and the second magnetostrictive material is longer than the circumferential length (D2) of the interface surface (34) of the first transmission member opposite to the first magnetostrictive material and the second magnetostrictive material, Alternatively, the load detection device according to any one of claims 1 to 7, wherein the circumferential length of the contact surface (35) of the second transmission member that is in contact with the first magnetostrictive material and the second magnetostrictive material side is longer than the circumferential length of the interface surface (36) of the second transmission member that is opposite to the first magnetostrictive material and the second magnetostrictive material, in the direction of the axis. [Claim 9] The load detection device according to any one of claims 1 to 8, wherein both ends of the first transmission member in the circumferential direction centered on the axis are inclined (37), stepped (38), curved (39), or a combination thereof, gradually becoming longer in the circumferential direction from the interface surface opposite to the first and second magnetostrictive material toward the contact surface in contact with the first and second magnetostrictive material. [Claim 10] The load detection device according to any one of claims 1 to 9, wherein the outer edge of the surface of the first transmission member that contacts the first magnetostrictive material and the second magnetostrictive material is chamfered or curved (301). [Claim 11] When the line connecting the center of the magnetic flux generating part and the axis, and the plane containing the axis are referred to as the X-plane, and the plane perpendicular to the X-plane and containing the axis is referred to as the Y-plane, The first pressed portion of the first magnetostrictive material that is pressed by the first transmission member or the second transmission member, and the second pressed portion of the second magnetostrictive material that is pressed by the first transmission member or the second transmission member, satisfy at least one of the following requirements: symmetrical with respect to the X plane, symmetrical with respect to the Y plane, the areas of the portions facing each other on the Y plane are the same, and both ends in the circumferential direction around the axis are at the same angle from the Y plane. The load detection device according to any one of claims 1 to 10, wherein the interface surface of the first transmission member facing away from the first magnetostrictive material and the second magnetostrictive material satisfies at least one of the following requirements: symmetrical with respect to the X plane, symmetrical with respect to the Y plane, the areas of the parts facing each other on the Y plane are the same, and both ends in the circumferential direction around the axis are at the same angle from the Y plane, or the load detection device according to any one of claims 1 to 10, wherein the interface surface of the second transmission member facing away from the first magnetostrictive material and the second magnetostrictive material satisfies at least one of the following requirements: symmetrical with respect to the X plane, symmetrical with respect to the Y plane, the areas of the parts facing each other on the Y plane are the same, and both ends in the circumferential direction around the axis are at the same angle from the Y plane. [Claim 12] It is further equipped with a magnetic shield (40) made of magnetic material, 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) provided radially outside 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 inside the magnetic circuit, the first transmission member, the second transmission member, and the magnetic detection element, The magnetic circuit, the first transmission member, the second transmission member, and the top plate portion (45) provided on one side in the axial direction of the magnetic detection element, A load detection device according to any one of claims 1 to 11, comprising the magnetic circuit, the first transmission member, the second transmission member, and a bottom plate portion (46) provided on one side in the axial direction of the magnetic detection element. [Claim 13] The load detection device according to any one of claims 1 to 12, wherein the first magnetostrictive material and the second magnetostrictive material have a maximum relative permeability (μm) of 5000 or more. [Claim 14] The average surface pressure applied to the first magnetostrictive material and the second magnetostrictive material is set to 150 MPa or more for the maximum design load applied to the first and second transmission members. The load detection device according to any one of claims 1 to 13, wherein the first magnetostrictive material and the second magnetostrictive material are materials whose magnetic degradation surface pressure is greater than the average surface pressure. [Explanation of Symbols]

[0139] 1. Load detection device 10 Magnetic Circuit 11. First Magnetostrictive Material 12. Second Magnetostrictive Material 13. Magnet (magnetic flux generating part) 14 Gap 20 Magnetic detection element 31 First transmission member 32 Second transmission member CL axis center

Claims

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 a first magnetostrictive material (11) and a second magnetostrictive material (12) whose permeability changes according to an external force, and the magnetic flux generated by the magnetic flux generating unit flows in the order of the first magnetostrictive material, gap (14), second magnetostrictive material, and the magnetic flux generating unit. A first transmission member (31) 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 first magnetostrictive material and the second magnetostrictive material, A second transmission member (32) transmits a load applied from the outside on the other side in the direction in which the axis extends to the first magnetostrictive material and the second magnetostrictive material, A load detection device comprising a magnetic detection element (20) provided at a position opposite to or within the gap, which outputs a signal corresponding to the magnetic flux flowing through the magnetic circuit.

2. When the line connecting the center of the magnetic flux generating section and the axis, and the plane containing the axis are referred to as the X-plane, and the plane perpendicular to the X-plane and containing the axis is referred to as the Y-plane, The first pressed portion (15) of the first magnetostrictive material that is pressed by the first transmission member or the second transmission member, and the second pressed portion (16) of the second magnetostrictive material that is pressed by the first transmission member or the second transmission member, satisfy at least one of the following requirements: symmetrical with respect to the X plane, symmetrical with respect to the Y plane, the areas of the portions facing each other on the Y plane are the same, and both ends in the circumferential direction around the axis are at the same angle from the Y plane. Alternatively, the load detection device according to claim 1, wherein the first magnetostrictive material and the second magnetostrictive material satisfy at least one of the following requirements: symmetrical with respect to the X plane, symmetrical with respect to the Y plane, the areas of the portions facing each other on the Y plane are the same, and both ends in the circumferential direction around the axis are at the same angle from the Y plane.

3. The load detection device according to claim 2, wherein both the first pressed portion and the second pressed portion have a shape in which the width in the radial direction of a virtual circle centered on the axis gradually changes from the magnetic flux generating portion side toward the gap side.

4. The load detection device according to claim 2 or 3, wherein both the first pressed portion and the second pressed portion have a shape in which the width in the radial direction of a virtual circle centered on the axis gradually decreases from the magnetic flux generating portion side toward the gap side.

5. The load detection device according to claim 2 or 3, wherein both the first magnetostrictive material and the second magnetostrictive material have a shape in which the width in the radial direction of a virtual circle centered on the axis gradually increases from the portion of the first pressed portion and the second pressed portion opposite to the magnetic flux generating portion toward the end toward the gap.

6. The first pressed portion is a part of the first magnetostrictive material in which the amount of change in magnetic permeability in response to the application of load is greater than that of the end on the gap side. The second pressed portion is also a part of the second magnetostrictive material in which the amount of change in magnetic permeability in response to the application of load is greater than that of the end on the gap side. The load detection device according to claim 2 or 3, wherein the first transmission member and the second transmission member press the first pressed portion and the second pressed portion, but do not press the end of the first magnetostrictive material on the gap side and the end of the second magnetostrictive material on the gap side.

7. The load detection device according to claim 1 or 2, wherein the first transmission member and the second transmission member are configured to press the entire width range in the radial direction of a virtual circle centered on the axis of the first magnetostrictive material and the second magnetostrictive material.

8. In the first transmission member, the circumferential length (D1) of the contact surface (33) in contact with the first magnetostrictive material and the second magnetostrictive material is longer than the circumferential length (D2) of the interface surface (34) of the first transmission member opposite to the first magnetostrictive material and the second magnetostrictive material, Alternatively, the load detection device according to claim 1 or 2, wherein the circumferential length of the contact surface (35) of the second transmission member that is in contact with the first magnetostrictive material and the second magnetostrictive material side is longer than the circumferential length of the interface surface (36) of the second transmission member that is opposite to the first magnetostrictive material and the second magnetostrictive material, in the direction of the axis.

9. The load detection device according to claim 1 or 2, wherein both ends of the first transmission member in the circumferential direction centered on the axis are inclined (37), stepped (38), curved (39), or a combination thereof, gradually lengthening in the circumferential direction from the interface surface opposite to the first and second magnetostrictive material toward the contact surface in contact with the first and second magnetostrictive material.

10. The load detection device according to claim 1 or 2, wherein the outer edge of the surface of the first transmission member that contacts the first magnetostrictive material and the second magnetostrictive material is chamfered or curved (301).

11. When the line connecting the center of the magnetic flux generating section and the axis, and the plane containing the axis are referred to as the X-plane, and the plane perpendicular to the X-plane and containing the axis is referred to as the Y-plane, The first pressed portion of the first magnetostrictive material that is pressed by the first transmission member or the second transmission member, and the second pressed portion of the second magnetostrictive material that is pressed by the first transmission member or the second transmission member, satisfy at least one of the following requirements: symmetrical with respect to the X plane, symmetrical with respect to the Y plane, the areas of the portions facing each other in the Y plane are the same, and both ends in the circumferential direction around the axis are at the same angle from the Y plane. The load detection device according to claim 1 or 2, wherein the interface surface of the first transmission member facing away from the first magnetostrictive material and the second magnetostrictive material satisfies at least one of the following requirements: symmetrical with respect to the X plane, symmetrical with respect to the Y plane, the areas of the parts facing each other on the Y plane are the same, and both ends in the circumferential direction around the axis are at the same angle from the Y plane, or the load detection device according to claim 1 or 2, wherein the interface surface of the second transmission member facing away from the first magnetostrictive material and the second magnetostrictive material satisfies at least one of the following requirements: symmetrical with respect to the X plane, symmetrical with respect to the Y plane, the areas of the parts facing each other on the Y plane are the same, and both ends in the circumferential direction around the axis are at the same angle from the Y plane.

12. It further includes a magnetic shield (40) made of a magnetic material, 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) provided radially outside the magnetic circuit, the first transmission member, the second transmission member, and the magnetic detection element, A cylindrical inner cylinder portion (44) provided radially inside the magnetic circuit, the first transmission member, the second transmission member, and the magnetic detection element, The magnetic circuit, the first transmission member, the second transmission member, and the top plate portion (45) provided on one side in the axial direction of the magnetic detection element, The load detection device according to claim 1 or 2, comprising the magnetic circuit, the first transmission member, the second transmission member, and a bottom plate portion (46) provided on one side in the axial direction of the magnetic detection element.

13. The load detection device according to claim 1 or 2, wherein the first magnetostrictive material and the second magnetostrictive material have a maximum relative permeability (μm) of 5000 or more.

14. The average surface pressure applied to the first magnetostrictive material and the second magnetostrictive material is set to 150 MPa or more for the maximum design load applied to the first and second transmission members. The load detection device according to claim 1 or 2, wherein the first magnetostrictive material and the second magnetostrictive material are materials whose magnetic degradation surface pressure is greater than the average surface pressure.

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