Rolling bearing holder unit

Abstract

To provide a rolling bearing holder unit which can suppress the lowering of the stiffness of a shaft resulting from a structure of a portion in which a strain gauge is arranged.SOLUTION: A rolling bearing holder unit comprises an outer ring, an inner ring arranged at an internal peripheral side of the outer ring coaxially with the outer ring, and a plurality of rolling bodies arranged between the outer ring and the inner ring. The rolling bearing holder unit also has a rolling bearing having a prescribed rotating shaft, a bearing holder arranged so as to contact with an external peripheral face of the outer ring of the rolling bearing or an internal peripheral face of the inner ring, and a strain gauge having a resistance body for detecting the strain of the outer ring or the inner ring. The bearing holder comprises a heavy thickness part and a thin thickness part which is thinner than the heavy thickness part in a thickness. The strain gauge is arranged at the thin thickness part. A preload being a prescribed contact angle is applied to the rolling bearing, and the heavy thickness part is arranged so as to contact with a region from at least a cross point between a linear line indicating the contact angle and the external peripheral face of the outer ring or the internal peripheral face of the inner ring up to a preload-side end face being an end face of the outer ring or the inner ring which is approximate to the cross point.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a rolling bearing holder unit.

Background Art

[0002] There is known a unit including a rolling bearing having an outer ring with a raceway surface on the inner peripheral side, an inner ring with a raceway surface on the outer peripheral side, and rolling elements interposed between the raceway surface of the outer ring and the raceway surface of the inner ring, and a strain gauge for detecting the strain of the outer ring or the inner ring. For example, there is a structure in which a double-cylindrical shaft member is provided on the rolling bearing, and the strain gauge is arranged on this shaft member (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the case of a rolling bearing holder unit in which a bearing holder is provided on the rolling bearing and a strain gauge is arranged on the bearing holder, depending on the structure of the bearing holder at the portion where the strain gauge is arranged, it is difficult to ensure the rigidity of the shaft inserted into the rolling bearing holder unit.

[0005] The present invention has been made in view of the above points, and an object thereof is to provide a rolling bearing holder unit capable of suppressing a decrease in the rigidity of the shaft caused by the structure of the portion where the strain gauge is arranged.

Means for Solving the Problems

[0006] The rolling bearing holder unit includes an outer ring, an inner ring coaxially arranged with the outer ring on the inner peripheral side of the outer ring, and a plurality of rolling elements arranged between the outer ring and the inner ring, and has a rolling bearing having a predetermined rotation axis, a bearing holder arranged to contact the outer peripheral surface of the outer ring or the inner peripheral surface of the inner ring of the rolling bearing, and a strain gauge including a resistor for detecting the strain of the outer ring or the inner ring. The bearing holder includes a thick portion and a thin portion having a thickness thinner than that of the thick portion. The thin part and the thick part are arranged at positions that do not overlap in plan view. The strain gauge is arranged in the thin portion, and a preload having a predetermined contact angle is applied to the rolling bearing. The thick portion is arranged to contact at least a region from the intersection of the straight line indicating the contact angle and the outer peripheral surface of the outer ring or the inner peripheral surface of the inner ring to the preload side end surface, which is the end surface of the outer ring or the inner ring closer to the intersection. The thin portion is arranged to press the outer peripheral surface of the outer ring or the inner peripheral surface of the inner ring over the entire circumference.

Advantages of the Invention

[0007] According to the disclosed technology, it is possible to provide a rolling bearing holder unit that can suppress a decrease in the rigidity of the shaft due to the structure of the portion where the strain gauge is arranged.

Brief Description of the Drawings

[0008]

Figure 1

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Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In each drawing, the same reference numerals are assigned to the same components, and redundant descriptions may be omitted.

[0010] 〈First Embodiment〉 FIG. 1 is a perspective view illustrating a rolling bearing holder unit according to the first embodiment. FIG. 2 is a view illustrating the rolling bearing holder unit according to the first embodiment, where FIG. 2(a) is a front view, FIG. 2(b) is a cross-sectional view, and FIG. 2(c) is a rear view.

[0011] Referring to FIGS. 1 and 2, the rolling bearing holder unit 1 has a rolling bearing 2, a bearing holder 60, and a strain gauge 100. The rolling bearing 2 has an outer ring 10, an inner ring 20, a plurality of rolling elements 30, a cage 40, and seals 51 and 52. In FIGS. 2(a) and 2(c), the illustration of the seals 51 and 52 is omitted for convenience.

[0012] The outer ring 10 is a cylindrical structure with the rotation axis m as the central axis. The inner ring 20 is a cylindrical structure coaxially arranged on the inner circumferential side of the outer ring 10. Each of the plurality of rolling elements 30 is a sphere disposed in a raceway 50 formed between the outer ring 10 and the inner ring 20. A lubricant (not shown) such as grease is enclosed in the raceway 50. The seals 51 and 52 project from the inner circumferential surface of the outer ring 10 toward the inner ring 20 side to block the raceway 50 from the outside.

[0013] On the inner circumferential surface of the outer ring 10, a concave portion 11 with an arcuate cross-section is formed in the circumferential direction of the outer ring 10. Also, on the outer circumferential surface of the inner ring 20, a concave portion 21 with an arcuate cross-section is formed in the circumferential direction of the inner ring 20. The plurality of rolling elements 30 are guided in the circumferential direction by the concave portions 11 and 21.

[0014] The cage 40 is disposed in the raceway 50 to hold the plurality of rolling elements 30. Specifically, the cage 40 is an annular body coaxial with the rotation axis m, and has a concave portion 41 for accommodating the rolling elements 30 on one side in the direction of the rotation axis m, and the other side is a back surface portion 42 continuous in the circumferential direction of the annular body.

[0015] The bearing holder 60 is arranged to be in contact with the outer peripheral surface of the outer ring 10, and presses the outer peripheral surface of the outer ring 10 over the entire circumference. Here, being in contact with the outer peripheral surface of the outer ring 10 includes not only the case where the bearing holder 60 is in direct contact with the outer peripheral surface of the outer ring 10 without passing through other members, but also the case of being indirectly in contact through other members such as an adhesive. The bearing holder 60 is, for example, press-fitted into the outer ring 10. Alternatively, the bearing holder 60 may be adhered to the outer ring 10. The bearing holder 60 can be formed of, for example, a metal such as brass, aluminum, stainless steel, or a resin.

[0016] The bearing holder 60 includes a cylindrical (hollow cylindrical) thick portion 61 and a cylindrical thin portion 62 having a smaller thickness in the radial direction than the thick portion 61. The bearing holder 60 has a length in the direction of the rotation axis m that is substantially equal to the length in the direction of the rotation axis m of the outer ring 10 and the inner ring 20. The length in the direction of the rotation axis m of each of the thick portion 61 and the thin portion 62 is shorter than the length in the direction of the rotation axis m of the outer ring 10 and the inner ring 20. The thick portion 61 and the thin portion 62 have an inner diameter that is substantially equal to the outer diameter of the outer ring 10 and are adjacent in the direction of the rotation axis m. The thick portion 61 and the thin portion 62 are, for example, integrally formed.

[0017] In the present embodiment, the thickness of each of the thick portion 61 and the thin portion 62 is substantially constant. The thin portion 62 is a strain transmission portion that transmits the strain generated in the outer ring 10 during the rotation of the rolling elements 30 to the strain gauge 100. The strain gauge 100 is disposed on the thin portion 62 via an adhesive layer.

[0018] The strain gauge 100 is a sensor that detects the strain of the outer ring 10 or the inner ring 20, and has a resistor 103 serving as a sensing portion, a wiring 104, a terminal portion 105, etc. The strain gauge 100 detects the strain of the outer ring 10 or the inner ring 20 as a change in the resistance value of the resistor 103.

[0019] In the strain gauge 100, the resistor 103 is arranged, for example, with its longitudinal direction (gauge length direction) oriented in the circumferential direction of the outer ring 10. Since the circumferential direction of the outer ring 10 is more likely to expand and contract than the axial direction, by arranging the longitudinal direction of the resistor 103 in the circumferential direction of the outer ring 10, a large strain waveform can be obtained. By monitoring the output of the strain gauge 100 with an external device, the strain occurring in the outer ring 10 can be monitored.

[0020] FIG. 3 is a diagram for explaining the contact angle, and is a cross-sectional view passing through the rotation axis m and the center of the rolling element 30. As shown in FIG. 3, a preload that gives a predetermined contact angle θ1 is applied to the outer ring 10 and the inner ring 20. By applying an appropriate preload to the outer ring 10 and the inner ring 20, it is possible to contribute to improving the runout accuracy of the rotation axis and reducing vibration and noise.

[0021] Here, the contact angle θ1 is, in a cross-sectional view, the angle formed by a straight line A connecting the contact point between the outer ring 10 and the rolling element 30 and the contact point between the inner ring 20 and the rolling element 30, and a straight line B extending in the radial direction. C O is, in a cross-sectional view, the intersection point between the extension line of the straight line A and the outer peripheral surface of the outer ring 10. D O is, in a cross-sectional view, the intersection point C O from, the intersection point C O to the preload-side end face, which is the end face of the outer ring 10 closer to the intersection point C O is the region where the displacement during the rotation of the rolling element 30 is relatively large. Incidentally, the extension line of the straight line A may be referred to as a straight line indicating the contact angle.

[0022] FIG. 4 is a diagram for explaining the arrangement of the thick portion of the bearing holder, and is a cross-sectional view corresponding to FIG. 2(b). As shown in FIG. 4, the thick portion 61 of the bearing holder 60 is arranged so as to be in contact with at least the region D O of the outer peripheral surface of the outer ring 10. Thus, the thick portion 61 of the bearing holder 60 is arranged so as to be in contact with the region D O where the displacement during the rotation of the rolling element 30 is relatively large. Thereby, it becomes possible to suppress a decrease in the rigidity of the shaft inserted into the rolling bearing holder unit 1 due to the structure of the portion where the strain gauge 100 is arranged, and the rigidity of the shaft can be ensured.

[0023] On the other hand, in the region D of the outer peripheral surface of the outer ring 10 O excluding the region, since the displacement during the rotation of the rolling element 30 is relatively small, the thin portion 62 of the bearing holder 60 can be disposed in that region. And, due to the thin thickness of the thin portion 62, the strain generated in the outer ring 10 during the rotation of the rolling element 30 can be suitably transmitted to the strain gauge 100.

[0024] From the viewpoint of strain transmissibility, it is desirable that the output voltage of the strain gauge 100 obtains an output about 10 times that of the noise component included in the output. When the strain gauge 100 constitutes one of the resistances of the Wheatstone bridge, for example, if the thin portion 62 has a cylindrical shape, the thickness of the thin portion 62 needs to be below the thickness that satisfies the following formula (1).

[0025]

Equation

[0026] Formula (1) can be derived as follows. That is, since the strain ε can be obtained from a simulation using the finite element method or the like by specifying the shape of the thin portion 62, the output voltage e can be approximated by introducing it into the following formula together with the parameters of the strain gauge. o The output voltage e o The thickness t of the thin portion 62 may be calculated backward so that it becomes about 10 times the average of the noise output e.

[0027] Specifically, the strain ε can be expressed by formula (2) using the bending moment M and the section modulus Z. Also, the bending moment M and the section modulus Z can be expressed by formula (3) and formula (4), respectively. Also, the output voltage eo When it is set to 10 times the noise voltage e, the output voltage e o and the noise voltage e can be expressed by Equation (5). Substituting Equations (2) to (4) into Equation (5) gives Equation (6), and by moving t in Equation (6) to the right side and arranging, Equation (1) is obtained.

[0028]

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[0029]

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[0030]

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[0031]

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[0032]

Number

[0033] For example, when the outer ring 10 has a small diameter (for example, about 30 mm in diameter), the thickness of the thick-walled portion 61 is desirably at least 10 times the bending rigidity of the thin-walled portion 62 from the viewpoint of ensuring the rigidity of the shaft inserted into the rolling bearing holder unit 1. For example, when the thin-walled portion 62 is cylindrical, the preferred thickness of the thick-walled portion 61 is about 3 times that of the thin-walled portion 62, and in this case, it becomes about 10 times the bending rigidity of the thin-walled portion 62.

[0034] Note that the position where the strain gauge 100 is arranged is preferably closer to the thick-walled portion 61 in the thin-walled portion 62. The intersection point C of the preload OThis is because when it is closer, the deformation due to the load transmission is larger. As a result, the thickness of the thin portion 62 can be more ensured. Further, by arranging the end portion of the strain gauge 100 on the thick portion 61 side to abut against the end surface of the thick portion 61 on the thin portion 62 side, the positioning of the strain gauge 100 can be easily performed.

[0035] For example, when the outer ring 10 has a small diameter (for example, about 30 mm in diameter) and it is difficult to arrange the strain gauge 100 on the outer ring 10. In such a case, a bearing holder 60 having a thick portion 61 and a thin portion 62 may be arranged on the outer peripheral side of the outer ring 10 of the rolling bearing 2, and the strain gauge 100 may be arranged on the thin portion 62. Thereby, the strain gauge 100 can be easily arranged. The strain of the outer ring 10 is transmitted to the strain gauge 100 through the thin portion 62 which is a strain transmission portion and can be detected by the strain gauge 100. Also, the thick portion 61 of the bearing holder 60 is at least in the region D of the outer peripheral surface of the outer ring 10 O By being arranged so as to be in contact with, the rigidity of the shaft inserted into the rolling bearing holder unit 1 can be ensured. Also, by arranging the bearing holder 60 on the outer peripheral side of the outer ring 10 of the rolling bearing 2, even when the rolling bearing 2 fails, the rolling bearing 2 can be easily replaced, and the maintainability is excellent.

[0036] FIG. 5 is a diagram (part 1) for explaining the usage method of the rolling bearing holder unit 1. As shown in FIG. 5, two rolling bearing holder units 1 may be arranged at a predetermined interval such that their respective rotation axes m coincide and the preload side end faces face each other, and the shaft 200 may be inserted. This is a back-to-back combination (DB) as the preload direction, and since the intersection of the straight line A and the rotation axis m faces outward, the rigidity is increased.

[0037] FIG. 6 is a diagram (part 2) for explaining the usage method of the rolling bearing holder unit 1. As shown in FIG. 6, two rolling bearing holder units 1 may be arranged at a predetermined interval such that their respective rotation axes m coincide, and the preload-side end faces face outward, and the shaft 200 may be inserted. This is a face combination (DF) in the preload direction, and since the intersection of the straight line A and the rotation axis m faces inward, it is disadvantageous for rigidity, but the allowable tolerance for mounting errors becomes larger. The usage method in FIG. 5 and the usage method in FIG. 6 can be appropriately selected according to the application.

[0038] FIG. 7 is a diagram for explaining the gauge length of the strain gauge. In FIG. 7, θ2 is the angle formed by two straight lines connecting the rotation axis m and the center of the adjacent rolling element 30. Also, R is the inner diameter of the thin-walled portion 62 of the bearing holder 60. The gauge length L of the strain gauge is preferably smaller than the distance between adjacent rolling elements 30 of the rolling bearing 2, that is, preferably θ2 / 360×2π×R>L. Thereby, the strain of the outer ring 10 due to a single rolling element 30 can be detected.

[0039] (Strain gauge) FIG. 8 is a plan view illustrating the strain gauge according to the first embodiment. FIG. 9 is a cross-sectional view illustrating the strain gauge according to the first embodiment, showing a cross-section along line A-A of FIG. 8. Referring to FIGS. 8 and 9, the strain gauge 100 has a base material 101, a functional layer 102, a resistor 103, a wiring 104, and a terminal portion 105. However, the functional layer 102 may be provided as necessary.

[0040] In this embodiment, for convenience, in the strain gauge 100, the side where the resistor 103 of the base material 101 is provided is defined as the upper side or one side, and the side where the resistor 103 is not provided is defined as the lower side or the other side. Also, the surface on the side where the resistor 103 of each part is provided is defined as one surface or the upper surface, and the surface on the side where the resistor 103 is not provided is defined as the other surface or the lower surface. However, the strain gauge 100 can be used in an upside-down state or arranged at an arbitrary angle. Also, the plan view means viewing the object from the normal direction of the upper surface 101a of the base material 101, and the planar shape means the shape of the object viewed from the normal direction of the upper surface 101a of the base material 101.

[0041] The base material 101 is a member that serves as a base layer for forming the resistor 103 and the like, and has flexibility. The thickness of the base material 101 is not particularly limited and can be appropriately selected according to the purpose. For example, it can be about 5 μm to 500 μm. In particular, when the thickness of the base material 101 is 5 μm to 200 μm, it is preferable in terms of the transmissibility of strain from the surface of the strained body (for example, the thin part of the bearing holder) joined to the lower surface of the base material 101 through the adhesive layer and the dimensional stability against the environment. When it is 10 μm or more, it is more preferable in terms of insulation.

[0042] The base material 101 can be formed from an insulating resin film such as a PI (polyimide) resin, an epoxy resin, a PEEK (polyetheretherketone) resin, a PEN (polyethylene naphthalate) resin, a PET (polyethylene terephthalate) resin, a PPS (polyphenylene sulfide) resin, or a polyolefin resin. Here, the film refers to a member having a thickness of about 500 μm or less and having flexibility.

[0043] Here, "formed from an insulating resin film" does not prevent the base material 101 from containing fillers, impurities, etc. in the insulating resin film. The base material 101 may be formed from an insulating resin film containing fillers such as silica or alumina, for example.

[0044] Examples of materials other than the resin of the base material 101 include crystalline materials such as SiO2, ZrO2 (including YSZ), Si, Si2N3, Al2O3 (including sapphire), ZnO, perovskite-based ceramics (CaTiO3, BaTiO3), etc. Further, amorphous glass, etc. are also included. Also, as the material of the base material 101, metals such as aluminum, aluminum alloy (duralumin), and titanium may be used. In this case, an insulating film is formed, for example, on the metal base material 101.

[0045] The functional layer 102 is formed as the lower layer of the resistor 103 on the upper surface 101a of the base material 101. That is, the planar shape of the functional layer 102 is substantially the same as the planar shape of the resistor 103 shown in FIG. 8.

[0046] In the present application, the functional layer refers to a layer having a function of promoting the crystal growth of at least the upper layer resistor 103. The functional layer 102 preferably further has a function of preventing the oxidation of the resistor 103 by oxygen or moisture contained in the base material 101 and a function of improving the adhesion between the base material 101 and the resistor 103. The functional layer 102 may further have other functions.

[0047] Since the insulating resin film constituting the base material 101 contains oxygen and moisture, especially when the resistor 103 contains Cr (chromium), Cr forms a self-oxidation film, so it is effective for the functional layer 102 to have a function of preventing the oxidation of the resistor 103.

[0048] The material of the functional layer 102 is not particularly limited as long as it has the function of promoting the crystal growth of at least the upper resistor 103, and can be appropriately selected according to the purpose. For example, it can be one or more metals selected from the group consisting of Cr (chromium), Ti (titanium), V (vanadium), Nb (niobium), Ta (tantalum), Ni (nickel), Y (yttrium), Zr (zirconium), Hf (hafnium), Si (silicon), C (carbon), Zn (zinc), Cu (copper), Bi (bismuth), Fe (iron), Mo (molybdenum), W (tungsten), Ru (ruthenium), Rh (rhodium), Re (rhenium), Os (osmium), Ir (iridium), Pt (platinum), Pd (palladium), Ag (silver), Au (gold), Co (cobalt), Mn (manganese), Al (aluminum), an alloy of any metal in this group, or a compound of any metal in this group.

[0049] Examples of the above alloys include FeCr, TiAl, FeNi, NiCr, CrCu, etc. Examples of the above compounds include TiN, TaN, Si3N4, TiO2, Ta2O5, SiO2, etc.

[0050] When the functional layer 102 is formed of a conductive material such as a metal or an alloy, the film thickness of the functional layer 102 is preferably 1 / 20 or less of the film thickness of the resistor. In such a range, the crystal growth of α-Cr can be promoted, and at the same time, a part of the current flowing through the resistor can be prevented from flowing into the functional layer 102, thereby preventing the detection sensitivity of strain from decreasing.

[0051] When the functional layer 102 is formed of a conductive material such as a metal or an alloy, the film thickness of the functional layer 102 is more preferably 1 / 50 or less of the film thickness of the resistor. In such a range, the crystal growth of α-Cr can be promoted, and at the same time, a part of the current flowing through the resistor can be further prevented from flowing into the functional layer 102, thereby further preventing the detection sensitivity of strain from decreasing.

[0052] When the functional layer 102 is formed of a conductive material such as a metal or an alloy, it is more preferable that the film thickness of the functional layer 102 is 1 / 100 or less of the film thickness of the resistor. When it is within such a range, a part of the current flowing through the resistor can flow into the functional layer 102, and it is possible to further prevent the detection sensitivity of strain from decreasing.

[0053] When the functional layer 102 is formed of an insulating material such as an oxide or a nitride, the film thickness of the functional layer 102 is preferably 1 nm to 1 μm. When it is within such a range, the crystal growth of α-Cr can be promoted, and the film can be easily formed without cracks in the functional layer 102.

[0054] When the functional layer 102 is formed of an insulating material such as an oxide or a nitride, the film thickness of the functional layer 102 is more preferably 1 nm to 0.8 μm. When it is within such a range, the crystal growth of α-Cr can be promoted, and the film can be more easily formed without cracks in the functional layer 102.

[0055] When the functional layer 102 is formed of an insulating material such as an oxide or a nitride, the film thickness of the functional layer 102 is even more preferably 1 nm to 0.5 μm. When it is within such a range, the crystal growth of α-Cr can be promoted, and the film can be even more easily formed without cracks in the functional layer 102.

[0056] Note that the planar shape of the functional layer 102 is patterned to be substantially the same as the planar shape of the resistor shown in FIG. 8, for example. However, the planar shape of the functional layer 102 is not limited to the case where it is substantially the same as the planar shape of the resistor. When the functional layer 102 is formed of an insulating material, it does not have to be patterned into the same shape as the planar shape of the resistor. In this case, the functional layer 102 may be formed in a solid shape at least in the region where the resistor is formed. Alternatively, the functional layer 102 may be formed in a solid shape over the entire upper surface of the base material 101.

[0057] Further, when the functional layer 102 is formed of an insulating material, by forming the functional layer 102 relatively thick so that its thickness is 50 nm or more and 1 μm or less, and forming it in a solid state, the thickness and surface area of the functional layer 102 increase, so that heat generated when the resistor heats up can be dissipated to the substrate 101 side. As a result, in the strain gauge 100, it is possible to suppress a decrease in measurement accuracy due to self-heating of the resistor.

[0058] The resistor 103 is a thin film formed in a predetermined pattern on the upper surface of the functional layer 102, and is a sensing portion that undergoes a change in resistance when receiving strain.

[0059] The resistor 103 can be formed of, for example, a material containing Cr (chromium), a material containing Ni (nickel), or a material containing both Cr and Ni. That is, the resistor 103 can be formed of a material containing at least one of Cr and Ni. Examples of the material containing Cr include a Cr mixed-phase film. Examples of the material containing Ni include Cu-Ni (copper nickel). Examples of the material containing both Cr and Ni include Ni-Cr (nickel chromium).

[0060] Hereinafter, the case where the resistor 103 is a Cr mixed-phase film will be described as an example. Here, the Cr mixed-phase film is a film in which Cr, CrN, Cr2N, etc. are mixed. The Cr mixed-phase film may contain unavoidable impurities such as chromium oxide. Further, a part of the material constituting the functional layer 102 may be diffused into the Cr mixed-phase film. In this case, the material constituting the functional layer 102 and nitrogen may form a compound. For example, when the functional layer 102 is formed of Ti, the Cr mixed-phase film may contain Ti or TiN (titanium nitride).

[0061] The thickness of the resistor 103 is not particularly limited and can be appropriately selected according to the purpose. For example, it can be about 0.05 μm to 2 μm. In particular, when the thickness of the resistor 103 is 0.1 μm or more, it is preferable in terms of improving the crystallinity of the crystal constituting the resistor 103 (for example, the crystallinity of α-Cr), and when it is 1 μm or less, it is more preferable in terms of reducing film cracks and warping from the substrate 101 due to internal stress of the film constituting the resistor 103.

[0062] By forming the resistor 103 on the functional layer 102, the resistor 103 can be formed with a stable crystal phase, so that the stability of the gauge characteristics (gauge factor, gauge factor temperature coefficient TCS, and resistance temperature coefficient TCR) can be improved.

[0063] For example, when the resistor 103 is a Cr mixed-phase film, by providing the functional layer 102, the resistor 103 mainly composed of α-Cr (alpha chromium) can be formed. Since α-Cr is a stable crystal phase, the stability of the gauge characteristics can be improved.

[0064] Here, the main component means that the target substance occupies 50 mass% or more of all the substances constituting the resistor. When the resistor 103 is a Cr mixed-phase film, from the viewpoint of improving the gauge characteristics, the resistor 103 preferably contains 80 wt% or more of α-Cr, and more preferably 90 wt% or more. Note that α-Cr is Cr with a bcc structure (body-centered cubic lattice structure).

[0065] Also, when the resistor 103 is a Cr mixed-phase film, it is preferable that CrN and Cr2N contained in the Cr mixed-phase film are 20 wt% or less. By having CrN and Cr2N contained in the Cr mixed-phase film be 20 wt% or less, a decrease in the gauge factor can be suppressed.

[0066] Also, the ratio of Cr2N in CrN and Cr2N is preferably 80 wt% or more and less than 90 wt%, and more preferably 90 wt% or more and less than 95 wt%. When the ratio of Cr2N in CrN and Cr2N is 90 wt% or more and less than 95 wt%, due to Cr2N having semiconductor properties, the decrease in TCR (negative TCR) becomes more significant. Furthermore, by reducing the ceramization, brittle fracture is reduced.

[0067] On the other hand, when a small amount of N2 or atomic N is mixed and present in the film, the external environment (for example, under a high-temperature environment) causes them to escape outside the film, resulting in a change in film stress. By creating chemically stable CrN, the generation of the above-mentioned unstable N can be avoided, and a stable strain gauge can be obtained.

[0068] In addition, the gauge characteristics can be improved by the diffusion of the metal (for example, Ti) constituting the functional layer 102 into the Cr mixed-phase film. Specifically, the gauge factor of the strain gauge 100 can be 10 or more, and the gauge factor temperature coefficient TCS and the resistance temperature coefficient TCR can be in the range of -1000 ppm / °C to +1000 ppm / °C.

[0069] The terminal portion 105 extends from both ends of the resistor 103 via the wiring 104, and in a plan view, it is formed in a substantially rectangular shape with a wider width than the resistor 103 and the wiring 104. The terminal portion 105 is a pair of electrodes for outputting to the outside the change in the resistance value of the resistor 103 caused by strain. The resistor 103 extends, for example, while being folded back in a zigzag manner from one of the terminal portion 105 and the wiring 104 and is connected to the other wiring 104 and the terminal portion 105. The upper surface of the terminal portion 105 may be coated with a metal having better solderability than the terminal portion 105.

[0070] Note that although the resistor 103, the wiring 104, and the terminal portion 105 are given different reference numerals for convenience, they can be integrally formed of the same material in the same process.

[0071] A cover layer 106 (insulating resin layer) may be provided on the upper surface 101a of the base material 101 so as to cover the resistor 103 and the wiring 104 and expose the terminal portion 105. By providing the cover layer 106, it is possible to prevent mechanical damage and the like from occurring to the resistor 103 and the wiring 104. In addition, by providing the cover layer 106, the resistor 103 and the wiring 104 can be protected from moisture and the like. Note that the cover layer 106 may be provided so as to cover the entire portion excluding the terminal portion 105.

[0072] The cover layer 106 can be formed from an insulating resin such as, for example, a PI resin, an epoxy resin, a PEEK resin, a PEN resin, a PET resin, a PPS resin, a composite resin (e.g., a silicone resin, a polyolefin resin), etc. The cover layer may contain a filler or a pigment. The thickness of the cover layer is not particularly limited and can be appropriately selected according to the purpose, but can be, for example, about 2 μm to 30 μm.

[0073] To manufacture the strain gauge 100, first, the base material 101 is prepared, and the functional layer 102 is formed on the upper surface 101a of the base material 101. The materials and thicknesses of the base material 101 and the functional layer 102 are as described above. However, the functional layer 102 may be provided as necessary.

[0074] For example, the functional layer 102 can be formed by vacuum deposition using a conventional sputtering method in which a raw material capable of forming the functional layer 102 is used as a target and Ar (argon) gas is introduced into the chamber. By using the conventional sputtering method, the functional layer 102 is formed while etching the upper surface 101a of the base material 101 with Ar, so that the deposition amount of the functional layer 102 can be minimized and the adhesion improvement effect can be obtained.

[0075] However, this is an example of a method for forming the functional layer 102, and the functional layer 102 may be formed by other methods. For example, a method may be used in which the upper surface 101a of the base material 101 is activated by plasma treatment or the like using Ar or the like before forming the functional layer 102 to obtain an adhesion improvement effect, and then the functional layer 102 is formed by vacuum deposition using a magnetron sputtering method.

[0076] Next, after forming a metal layer that will become the resistor 103, wiring 104, and terminal portion 105 over the entire upper surface of the functional layer 102, the functional layer 102, the resistor 103, the wiring 104, and the terminal portion 105 are patterned into the planar shape shown in FIG. 8 by photolithography. The materials and thicknesses of the resistor 103, the wiring 104, and the terminal portion 105 are as described above. The resistor 103, the wiring 104, and the terminal portion 105 can be integrally formed of the same material. The resistor 103, the wiring 104, and the terminal portion 105 can be formed, for example, by a magnetron sputtering method using a raw material capable of forming the resistor 103, the wiring 104, and the terminal portion 105 as a target. Instead of the magnetron sputtering method, the resistor 103, the wiring 104, and the terminal portion 105 may be formed by a reactive sputtering method, an evaporation method, an arc ion plating method, a pulsed laser deposition method, or the like.

[0077] There is no particular limitation on the combination of the material of the functional layer 102 and the materials of the resistor 103, the wiring 104, and the terminal portion 105, and it can be appropriately selected according to the purpose. For example, Ti can be used as the functional layer 102, and a Cr mixed-phase film mainly composed of α-Cr (alpha chromium) can be formed as the resistor 103, the wiring 104, and the terminal portion 105.

[0078] In this case, for example, the resistor 103, the wiring 104, and the terminal portion 105 can be formed by a magnetron sputtering method using a raw material capable of forming a Cr mixed-phase film as a target and introducing Ar gas into the chamber. Alternatively, pure Cr can be used as a target, and an appropriate amount of nitrogen gas can be introduced into the chamber together with Ar gas, and the resistor 103, the wiring 104, and the terminal portion 105 may be formed by a reactive sputtering method. At this time, by changing the introduction amount and pressure (nitrogen partial pressure) of the nitrogen gas or providing a heating step to adjust the heating temperature, the ratios of CrN and Cr2N contained in the Cr mixed-phase film and the ratio of Cr2N in CrN and Cr2N can be adjusted.

[0079] In these methods, the growth surface of the Cr mixed-phase film is defined by the functional layer 102 made of Ti, and a Cr mixed-phase film mainly composed of α-Cr with a stable crystal structure can be formed. Also, by the diffusion of Ti constituting the functional layer 102 into the Cr mixed-phase film, the gauge characteristics are improved. For example, the gauge factor of the strain gauge 100 can be 10 or more, and the gauge factor temperature coefficient TCS and the resistance temperature coefficient TCR can be in the range of -1000 ppm / °C to +1000 ppm / °C.

[0080] In addition, when the resistor 103 is a Cr mixed-phase film, the functional layer 102 made of Ti has all of the functions of promoting the crystal growth of the resistor 103, preventing the oxidation of the resistor 103 by oxygen and moisture contained in the base material 101, and improving the adhesion between the base material 101 and the resistor 103. The same applies when Ta, Si, Al, or Fe is used instead of Ti as the functional layer 102.

[0081] Thereafter, if necessary, a cover layer 106 that covers the resistor 103 and the wiring 104 and exposes the terminal portion 105 is provided on the upper surface 101a of the base material 101, and the strain gauge 100 is completed. The cover layer 106 can be produced, for example, by laminating a semi-cured thermosetting insulating resin film on the upper surface 101a of the base material 101 so as to cover the resistor 103 and the wiring 104 and expose the terminal portion 105, and then heating and curing it. The cover layer 106 may also be produced by applying a liquid or paste-like thermosetting insulating resin on the upper surface 101a of the base material 101 so as to cover the resistor 103 and the wiring 104 and expose the terminal portion 105, and then heating and curing it.

[0082] In this way, by providing the functional layer 102 under the resistor 103, it becomes possible to promote the crystal growth of the resistor 103, and a resistor 103 composed of a stable crystal phase can be produced. As a result, the stability of the gauge characteristics can be improved in the strain gauge 100. Also, by the diffusion of the material constituting the functional layer 102 into the resistor 103, the gauge characteristics can be improved in the strain gauge 100.

[0083] Note that the strain gauge 100 using a Cr mixed-phase film as the material of the resistor 103 has achieved high sensitivity (more than 500% compared to the conventional one) and miniaturization (1 / 10 or less compared to the conventional one). For example, while the output of a conventional strain gauge was about 0.04 mV / 2V, the strain gauge 100 can obtain an output of 0.3 mV / 2V or more. Also, while the size (gauge length × gauge width) of a conventional strain gauge was about 3 mm × 3 mm, the size (gauge length × gauge width) of the strain gauge 100 can be miniaturized to about 0.3 mm × 0.3 mm.

[0084] As described above, the strain gauge 100 using a Cr mixed-phase film as the material of the resistor 103 is small and can be easily attached to the thin portion 62 of the bearing holder 60. Therefore, it is particularly suitable for use in a rolling bearing holder unit using a small rolling bearing 2 having a diameter (outer diameter of the outer ring 10) of 30 mm or less. Also, the strain gauge 100 using a Cr mixed-phase film as the material of the resistor 103 is highly sensitive and can detect small displacements, so it can detect minute strains that were difficult to detect conventionally. That is, by having the strain gauge 100 using a Cr mixed-phase film as the material of the resistor 103, a rolling bearing holder unit 1 having a function of accurately detecting strain can be realized.

[0085] <Modification Example of the First Embodiment> In Modification Example 1 of the first embodiment, another example of a bearing holder attached to the outer peripheral surface of the outer ring is shown. In Modification Example 1 of the first embodiment, the description of the same components as those in the already described embodiment may be omitted.

[0086] FIG. 10 is a cross-sectional view illustrating a rolling bearing holder unit according to Modification Example 1 of the first embodiment, and shows a cross-section corresponding to FIG. 2(b). As shown in FIG. 10, the rolling bearing holder unit 1A is different from the rolling bearing holder unit 1 (see FIG. 2 etc.) in that the bearing holder 60 is replaced with a bearing holder 60A.

[0087] The bearing holder 60A has a cylindrical large-diameter portion 61A and a cylindrical small-diameter portion 62A. The small-diameter portion 62A is disposed on the entire outer peripheral side of the outer ring 10, and the large-diameter portion 61A is disposed on a part of the outer peripheral side of the small-diameter portion 62A. The inner diameter of the small-diameter portion 62A is substantially equal to the outer diameter of the outer ring 10, and the length in the direction of the rotation axis m is substantially equal to the length of the outer ring 10 in the direction of the rotation axis m. The inner diameter of the large-diameter portion 61A is substantially equal to the outer diameter of the small-diameter portion 62A, and the length in the direction of the rotation axis m is shorter than the length of the small-diameter portion 62A in the direction of the rotation axis m.

[0088] The large-diameter portion 61A and the small-diameter portion 62A are integrated by, for example, press-fitting or adhesion to form a bearing holder 60A having substantially the same shape as the bearing holder 60. In the bearing holder 60A, the portion where the large-diameter portion 61A is laminated on the outer peripheral surface of the small-diameter portion 62A is the thick portion, and the portion consisting only of the small-diameter portion 62A is the thin portion. A strain gauge 100 is disposed on the outer peripheral surface of the thin portion 62A via an adhesive layer.

[0089] Thus, the bearing holder is not limited to being integrally formed, and may be formed by joining separate bodies. For example, separate members having different diameters may be joined to each other. Also in this case, by disposing the strain gauge 100 in the thin portion, the strain of the outer ring 10 can be detected via the thin portion which is the strain transmission portion. Further, by arranging the thick portion so as to be in contact with at least the region D O (see FIG. 3) of the outer peripheral surface of the outer ring 10, the rigidity of the shaft inserted into the rolling bearing holder unit 1A can be ensured. Note that the point that it is not limited to being integrally formed and may be formed by joining separate bodies is the same for the examples of the bearing holder described hereinafter.

[0090] FIG. 11 is a cross-sectional view illustrating a rolling bearing holder unit according to a second modification of the first embodiment, and shows a cross-section corresponding to FIG. 2(b). As shown in FIG. 11, the rolling bearing holder unit 1B is different from the rolling bearing holder unit 1 (see FIG. 2 etc.) in that the bearing holder 60 is replaced with a bearing holder 60B.

[0091] The bearing holder 60B has a cylindrical thick portion 61B and a cylindrical thin portion 62B that is thinner in the radial direction than the thick portion 61B. The thick portion 61B has an inner diameter that is substantially equal to the outer diameter of the outer ring 10, and a length in the direction of the rotation axis m that is substantially equal to the length of the outer ring 10 in the direction of the rotation axis m. That is, the thick portion 61B is arranged so as to contact the entire outer peripheral surface of the outer ring 10.

[0092] The thin portion 62B has an inner diameter that is substantially equal to the outer diameter of the outer ring 10, and protrudes in a direction substantially parallel to the direction of the rotation axis m from the side closer to the rotation axis m of the end face of the thick portion 61B located on the preload side. The thick portion 61B and the thin portion 62B are integrally formed, for example. A strain gauge 100 is arranged on the outer peripheral surface of the thin portion 62B via an adhesive layer. Note that Fig. 11 shows an example in which the thin portion 62B protrudes from the end face of the thick portion 61B located on the preload side, but it may protrude from the end face on the side opposite to the preload side. Since strain is more easily transmitted when protruding from the end face on the preload side, it is preferable that the thin portion 62B protrudes from the end face on the preload side.

[0093] In this way, the length of the thick portion 61B in the direction of the rotation axis m may be substantially equal to the length of the outer ring 10 in the direction of the rotation axis m, and the thin portion 62B may protrude in a direction substantially parallel to the direction of the rotation axis m from the side closer to the rotation axis m of the end face of the thick portion 61B. Also in this case, by arranging the strain gauge 100 on the thin portion, it is possible to detect the strain of the outer ring 10 via the thin portion, which is a strain transmission portion. Further, since the thick portion can be arranged so as to contact the entire outer peripheral surface of the outer ring 10, sufficient rigidity of the shaft inserted into the rolling bearing holder unit 1B can be ensured.

[0094] Fig. 12 is a cross-sectional view illustrating a rolling bearing holder unit according to Modification 3 of the first embodiment, and shows a cross-section corresponding to Fig. 2(b). It is also possible to adopt a form in which the thin portion 62C protrudes in a direction substantially parallel to the direction of the rotation axis m from the side farther from the rotation axis m of the end face of the thick portion 61C located on the preload side, as in the bearing holder 60C of the rolling bearing holder unit 1C shown in Fig. 12. Also in this case, the same effects as in the case of Fig. 11 are obtained.

[0095] FIG. 13 is a cross-sectional view illustrating a rolling bearing holder unit according to Modification 4 of the first embodiment, showing a cross-section corresponding to FIG. 2(b). As shown in FIG. 13, the rolling bearing holder unit 1D is different from the rolling bearing holder unit 1 (see FIG. 2 etc.) in that the bearing holder 60 is replaced with a bearing holder 60D.

[0096] The bearing holder 60D has a cylindrical thick portion 61D and a cylindrical thin portion 62D that is thinner than the thick portion 61D. The inner diameter of the thick portion 61D is substantially equal to the outer diameter of the outer ring 10, and the length in the direction of the rotation axis m of the thick portion 61D is substantially equal to the length in the direction of the rotation axis m of the outer ring 10. That is, the thick portion 61D is arranged so as to be in contact with the entire outer peripheral surface of the outer ring 10.

[0097] The thin portion 62D extends in a direction substantially perpendicular to the rotation axis m from the end face of the thick portion 61D located on the preload side and is arranged in an annular contact with a part of the end face of the outer ring 10. The thickness of the thin portion 62D in the direction of the rotation axis m is thinner than the thickness of the thick portion 61D in the radial direction. The thick portion 61D and the thin portion 62D are integrally formed, for example. A strain gauge 100 is arranged on the surface of the thin portion 62D opposite to the side in contact with the end face of the outer ring 10 via an adhesive layer.

[0098] In this way, the thin portion of the bearing holder may be arranged in contact with the end face of the outer ring 10. Also in this case, by arranging the strain gauge 100 on the thin portion, it is possible to detect the strain of the outer ring 10 via the thin portion which is a strain transmission portion. Further, since the thick portion can be arranged so as to be in contact with the entire outer peripheral surface of the outer ring 10, the rigidity of the shaft inserted into the rolling bearing holder unit 1D can be sufficiently ensured.

[0099] <Second Embodiment> In the second embodiment, an example of a bearing holder attached to the inner peripheral surface of the inner ring is shown. In the second embodiment, the description of the same components as those in the embodiments already described may be omitted.

[0100] FIG. 14 is a cross-sectional view illustrating a rolling bearing holder unit according to the second embodiment, showing a cross-section corresponding to FIG. 2(b). As shown in FIG. 14, the rolling bearing holder unit 5 is different from the rolling bearing holder unit 1 (see FIG. 2 etc.) in that the bearing holder 60 is replaced with a bearing holder 70.

[0101] The bearing holder 70 is disposed on the inner circumferential side of the inner ring 20 and presses the inner circumferential surface of the inner ring 20 over the entire circumference. The bearing holder 70 is, for example, press-fitted into the inner ring 20. Alternatively, the bearing holder 70 may be adhered to the inner ring 20.

[0102] The bearing holder 70 has a cylindrical thick portion 71 and a cylindrical thin portion 72 having a smaller radial thickness than the thick portion 71. The bearing holder 70 has a length in the direction of the rotation axis m that is substantially equal to the length of the inner ring 20 in the direction of the rotation axis m. The thick portion 71 and the thin portion 72 have an outer diameter that is substantially equal to the inner diameter of the inner ring 20 and are adjacent to each other in the direction of the rotation axis m. The thick portion 71 and the thin portion 72 are, for example, integrally formed.

[0103] In the present embodiment, the thickness of each of the thick portion 71 and the thin portion 72 is substantially constant. The thin portion 72 is a strain transmission portion that transmits the strain generated in the inner ring 20 during the rotation of the rolling elements 30 to the strain gauge 100. The strain gauge 100 is disposed on the thin portion 72 via an adhesive layer.

[0104] In FIG. 14, C I is the intersection of the extension line of the straight line A and the inner circumferential surface of the inner ring 20 in a cross-sectional view. D I is, in a cross-sectional view, the region of the inner circumferential surface of the inner ring 20 from the intersection C I to the preload-side end face, which is the end face of the inner ring 20 closer to the intersection C I . The region D I is a region where the displacement during the rotation of the rolling elements 30 is relatively large.

[0105] In this way, the thin-walled portion of the bearing holder may be arranged in contact with the inner peripheral surface of the inner ring 20. Also in this case, by arranging the strain gauge 100 on the thin-walled portion, the strain of the inner ring 20 can be detected via the thin-walled portion which is the strain transmission portion. Further, the thick-walled portion is in contact with at least the region D of the inner peripheral surface of the inner ring 20 I By being arranged so as to contact, the rigidity of the shaft inserted into the rolling bearing holder unit 5 can be ensured.

[0106] <Modification Example of the Second Embodiment> In Modification Example 1 of the second embodiment, another example of the bearing holder attached to the inner peripheral surface of the inner ring is shown. In Modification Example 1 of the second embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0107] FIG. 15 is a cross-sectional view illustrating a rolling bearing holder unit according to Modification Example 1 of the second embodiment, and shows a cross-section corresponding to FIG. 2(b). As shown in FIG. 15, the rolling bearing holder unit 5A is different from the rolling bearing holder unit 5 (see FIG. 14 etc.) in that the bearing holder 70 is replaced with a bearing holder 70A.

[0108] The bearing holder 70A has a cylindrical small-diameter portion 71A and a cylindrical large-diameter portion 72A. The large-diameter portion 72A is arranged over the entire inner peripheral side of the inner ring 20, and the small-diameter portion 71A is arranged on a part of the inner peripheral side of the large-diameter portion 72A. The large-diameter portion 72A has an outer diameter substantially equal to the inner diameter of the inner ring 20 and a length in the direction of the rotation axis m substantially equal to the length of the inner ring 20 in the direction of the rotation axis m. The small-diameter portion 71A has an outer diameter substantially equal to the inner diameter of the large-diameter portion 72A and a length in the direction of the rotation axis m shorter than the length of the large-diameter portion 72A in the direction of the rotation axis m.

[0109] The small-diameter portion 71A and the large-diameter portion 72A are integrated, for example, by press-fitting or adhesion to form a bearing holder 70A having substantially the same shape as the bearing holder 70. In the bearing holder 70A, the portion where the small-diameter portion 71A is laminated on the inner peripheral surface of the large-diameter portion 72A is the thick-walled portion, and the portion consisting only of the large-diameter portion 72A is the thin-walled portion. The strain gauge 100 is arranged on the inner peripheral surface of the thin-walled large-diameter portion 72A via an adhesive layer.

[0110] Thus, the bearing holder is not limited to being integrally formed, and it may be formed by joining separate parts. Also in this case, by arranging the strain gauge 100 at the thin-walled portion, it is possible to detect the strain of the inner ring 20 through the thin-walled portion which is the strain transmission portion. Further, the thick-walled portion is arranged to be in contact with at least the region D I (see FIG. 14), it is possible to ensure the rigidity of the shaft inserted into the rolling bearing holder unit 5A. Note that the point that it is not limited to being integrally formed and it may be formed by joining separate parts is the same for the examples of the bearing holder described hereinafter.

[0111] FIG. 16 is a cross-sectional view illustrating a rolling bearing holder unit according to Modification 2 of the second embodiment, and shows a cross-section corresponding to FIG. 2(b). As shown in FIG. 16, the rolling bearing holder unit 5B is different from the rolling bearing holder unit 5 (see FIG. 14 etc.) in that the bearing holder 70 is replaced with a bearing holder 70B.

[0112] The bearing holder 70B has a cylindrical thick-walled portion 71B and a cylindrical thin-walled portion 72B having a smaller radial thickness than the thick-walled portion 71B. The outer diameter of the thick-walled portion 71B is substantially equal to the inner diameter of the inner ring 20, and the length in the direction of the rotation axis m is substantially equal to the length in the direction of the rotation axis m of the inner ring 20. That is, the thick-walled portion 71B is arranged to be in contact with the entire inner peripheral surface of the inner ring 20.

[0113] The thin-walled portion 72B has an outer diameter that is substantially equal to the inner diameter of the inner ring 20, and protrudes in a direction substantially parallel to the direction of the rotation axis m from the side far from the rotation axis m of the end face of the thick-walled portion 71B located on the preload side. The thick-walled portion 71B and the thin-walled portion 72B are integrally formed, for example. The strain gauge 100 is arranged on the inner peripheral surface of the thin-walled portion 72B via an adhesive layer.

[0114] In this way, the thin-walled portion of the bearing holder may protrude from the end face of the inner ring 20. Also in this case, by arranging the strain gauge 100 on the thin-walled portion, it is possible to detect the strain of the inner ring 20 through the thin-walled portion which is a strain transmission portion. Further, since the thick-walled portion can be arranged so as to contact the entire inner peripheral surface of the inner ring 20, the rigidity of the shaft inserted into the rolling bearing holder unit 5B can be sufficiently ensured.

[0115] FIG. 17 is a cross-sectional view illustrating a rolling bearing holder unit according to Modification 3 of the second embodiment, showing a cross-section corresponding to FIG. 2(b). Similar to the bearing holder 70C of the rolling bearing holder unit 5C shown in FIG. 17, the thin-walled portion 72C may protrude in a direction substantially parallel to the direction of the rotation axis m from the side closer to the rotation axis m of the end face of the thick-walled portion 71C located on the preload side. Also in this case, the same effects as in the case of FIG. 16 are obtained.

[0116] FIG. 18 is a cross-sectional view illustrating a rolling bearing holder unit according to Modification 4 of the second embodiment, showing a cross-section corresponding to FIG. 2(b). As shown in FIG. 18, the rolling bearing holder unit 5D is different from the rolling bearing holder unit 5 (see FIG. 14 etc.) in that the bearing holder 70 is replaced with a bearing holder 70D.

[0117] The bearing holder 70D has a cylindrical thick-walled portion 71D and a cylindrical thin-walled portion 72D that is thinner than the thick-walled portion 71D. The outer diameter of the thick-walled portion 71D is substantially equal to the inner diameter of the inner ring 20, and the length in the direction of the rotation axis m of the thick-walled portion 71D is substantially equal to the length in the direction of the rotation axis m of the inner ring 20. That is, the thick-walled portion 71D is arranged so as to contact the entire inner peripheral surface of the inner ring 20.

[0118] The thin-walled portion 72D extends in a direction substantially perpendicular to the rotation axis m from the end face of the thick-walled portion 71D located on the preload side, and is arranged in an annular contact with a part of the end face of the inner ring 20. The thickness of the thin-walled portion 72D in the direction of the rotation axis m is thinner than the thickness of the thick-walled portion 71D in the radial direction. The thick-walled portion 71D and the thin-walled portion 72D are integrally formed, for example. A strain gauge 100 is arranged on the surface of the thin-walled portion 72D opposite to the side in contact with the end face of the inner ring 20 via an adhesive layer.

[0119] Thus, the thin-walled portion of the bearing holder may be arranged in contact with the end face of the inner ring 20. Also in this case, by arranging the strain gauge 100 on the thin-walled portion, it is possible to detect the strain of the inner ring 20 through the thin-walled portion which is the strain transmission portion. Further, since the thick-walled portion can be arranged so as to be in contact with the entire inner peripheral surface of the inner ring 20, the rigidity of the shaft inserted into the rolling bearing holder unit 5D can be sufficiently ensured.

[0120] <Third Embodiment> In the third embodiment, an example of a bearing holder in which the thin-walled portion is provided partially instead of circumferentially is shown. In the third embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0121] FIG. 19 is a perspective view illustrating a rolling bearing holder unit according to the third embodiment. As shown in FIG. 19, the rolling bearing holder unit 6 is different from the rolling bearing holder unit 1 (see FIGS. 2 and the like) in that the bearing holder 60 is replaced with the bearing holder 80.

[0122] The bearing holder 80 is arranged on the outer peripheral side of the outer ring 10 and presses the outer peripheral surface of the outer ring 10 over the entire circumference. The bearing holder 80 is, for example, press-fitted into the outer ring 10. Alternatively, the bearing holder 80 may be adhered to the outer ring 10.

[0123] The bearing holder 80 is a cylindrical member, the length in the direction of the rotation axis m is substantially equal to the length in the direction of the rotation axis m of the outer ring 10, and the inner diameter is substantially equal to the outer diameter of the outer ring 10. A concave portion is provided on the outer peripheral surface of the bearing holder 80. In the bearing holder 80, the portion other than the concave portion is the thick-walled portion 81, and the inside of the concave portion is the thin-walled portion 82. That is, in the bearing holder 80, the thick-walled portion 81 is cylindrical, and the thin-walled portion 82 is a concave portion provided in the thick-walled portion 81.

[0124] The thin-walled portion 82 is a strain transmission portion that transmits the strain generated in the outer ring 10 during the rotation of the rolling elements 30 to the strain gauge 100. The strain gauge 100 is arranged on the thin-walled portion 82 via an adhesive layer.

[0125] In this way, a recess that forms a thin portion may be provided on the outer peripheral portion of the bearing holder, and the strain gauge may be disposed within the recess. Also in this case, the strain of the outer ring 10 can be detected via the thin portion that serves as the strain transmission portion. Further, the thick portion is disposed so as to be in contact with at least the region D O (see FIG. 3), thereby ensuring the rigidity of the shaft inserted into the rolling bearing holder unit 6. Note that in the modification of the first embodiment, the second embodiment, and the modification of the second embodiment, the thin portion may be provided as a partial recess instead of a circumferential shape.

[0126] <Fourth Embodiment> The fourth embodiment shows an example of a rolling bearing holder unit including two rolling bearings. In the fourth embodiment, the description of the same components as those in the embodiments already described may be omitted.

[0127] FIG. 20 is a cross-sectional view (part 1) illustrating a rolling bearing holder unit according to the fourth embodiment. The rolling bearing holder unit 7 shown in FIG. 20 includes two rolling bearings 2, one bearing holder 90, and one strain gauge 100. However, one strain gauge 100 may be provided for each rolling bearing 2.

[0128] In the rolling bearing holder unit 7, the two rolling bearings 2 are arranged at a predetermined interval such that the rotation axes m thereof coincide with each other, and the preload side end faces face each other. This arrangement is a back-to-back combination (DB) as the preload direction, similar to FIG. 5.

[0129] The bearing holder 90 includes a thick portion 91 and thin portions 92 disposed on both sides of the thick portion 91 in the direction of the rotation axis m. The thick portion 91 is disposed so as to be in contact with at least the region D O of each rolling bearing 2. The portion of the thick portion 91 that contacts one rolling bearing 2 extends to the other rolling bearing 2 side and is integrated with the portion that contacts the other rolling bearing 2.

[0130] FIG. 21 is a cross-sectional view (part 2) illustrating a rolling bearing holder unit according to the fourth embodiment. The rolling bearing holder unit 7A shown in FIG. 21 includes two rolling bearings 2, one bearing holder 90A, and one strain gauge 100. However, one strain gauge 100 may be provided for each rolling bearing 2.

[0131] In the rolling bearing holder unit 7A, the two rolling bearings 2 are arranged at a predetermined interval such that the respective rotation axes m coincide, and the preload side end faces face outward. This arrangement is a face combination (DF) as the preload direction, similar to FIG. 6.

[0132] The bearing holder 90A includes a thin-walled portion 92A and thick-walled portions 91A arranged on both sides of the thin-walled portion 92A in the direction of the rotation axis m. The thick-walled portions 91A are arranged so as to be in contact with at least the region D O of each rolling bearing 2. The portion of the thin-walled portion 92A in contact with one rolling bearing 2 extends to the side of the other rolling bearing 2 and is integrated with the portion in contact with the other rolling bearing 2.

[0133] Thus, one bearing holder may be provided for two rolling bearings. Also in this case, the strain of the outer ring 10 can be detected via the thin-walled portion which is a strain transmission portion. Further, by arranging the thick-walled portions so as to be in contact with at least the region D O of the outer peripheral surface of the outer ring 10 of each rolling bearing, the rigidity of the shaft inserted into the rolling bearing holder unit can be ensured. Note that the content described in this embodiment is also applicable to other embodiments and modifications.

[0134] Although the preferred embodiments etc. have been described in detail above, the present invention is not limited to the above-described embodiments etc., and various modifications and substitutions can be made to the above-described embodiments etc. without departing from the scope described in the claims.

[0135] For example, the thick portion and the thin portion are not limited to a cylindrical shape and may have any shape. For example, the thick portion and the thin portion may have a shape such that the cross-section is polygonal. Regarding the thick portion, any shape can be adopted as long as it does not affect the rigidity of the axis. Regarding the thin portion, any shape may be used as long as the thickness that ensures the necessary output described above is secured.

Explanation of Signs

[0136] 1, 1A to 1D, 5, 5A to 5D, 6, 7, 7A rolling bearing holder units, 2 rolling bearings, 10 outer rings, 20 inner rings, 30 rolling elements, 40 cages, 50 tracks, 51, 52 seals, 60, 60A to 60D, 70, 70A to 70D, 80 bearing holders, 61, 61B to 61D, 71, 71B to 71D, 81 thick portions, 61A, 72A large-diameter portions, 62A, 71A small-diameter portions, 62, 62B to 62D, 72, 72B to 72D, 82 thin portions, 100 strain gauges, 101 base materials, 101a upper surfaces, 102 functional layers, 103 resistors, 104 wirings, 105 terminal portions, 106 cover layers

Claims

1. An antifriction bearing having an outer ring, an inner ring coaxially disposed with the outer ring on the inner peripheral side of the outer ring, and a plurality of rolling elements disposed between the outer ring and the inner ring, and having a predetermined rotation axis; A bearing holder disposed so as to be in contact with the outer peripheral surface of the outer ring or the inner peripheral surface of the inner ring of the antifriction bearing; A strain gauge having a resistor for detecting strain of the outer ring or the inner ring; and having The bearing holder includes a thick portion and a thin portion having a thickness thinner than that of the thick portion; The thin portion and the thick portion are disposed at positions that do not overlap in plan view; The strain gauge is disposed in the thin portion; A preload that provides a predetermined contact angle is applied to the antifriction bearing; The thick portion is disposed so as to be in contact with at least a region from the intersection of the straight line indicating the contact angle and the outer peripheral surface of the outer ring or the inner peripheral surface of the inner ring to the preload side end surface, which is the end surface of the outer ring or the inner ring closer to the intersection; The thin portion is an antifriction bearing holder unit disposed so as to press the outer peripheral surface of the outer ring or the inner peripheral surface of the inner ring over the entire circumference.

2. The antifriction bearing holder unit according to claim 1, wherein the thin portion is press-fitted into the outer ring or the inner ring.

3. An antifriction bearing having an outer ring, an inner ring coaxially disposed with the outer ring on the inner peripheral side of the outer ring, and a plurality of rolling elements disposed between the outer ring and the inner ring, and having a predetermined rotation axis; A bearing holder disposed so as to be in contact with the outer peripheral surface of the outer ring or the inner peripheral surface of the inner ring of the antifriction bearing; A strain gauge having a resistor for detecting strain of the outer ring or the inner ring; and having The bearing holder includes a thick portion and a thin portion having a thickness thinner than that of the thick portion; The bearing holder is integrally formed with the thick portion and the thin portion; The strain gauge is disposed in the thin portion; A preload that provides a predetermined contact angle is applied to the antifriction bearing; The thick portion is disposed so as to be in contact with at least a region from the intersection of the straight line indicating the contact angle and the outer peripheral surface of the outer ring or the inner peripheral surface of the inner ring to the preload side end surface, which is the end surface of the outer ring or the inner ring closer to the intersection; The thin portion is an antifriction bearing holder unit disposed so as to press the outer peripheral surface of the outer ring or the inner peripheral surface of the inner ring over the entire circumference. **Claim 4**: A rolling bearing having an outer ring, an inner ring disposed coaxially with the outer ring on the inner peripheral side of the outer ring, and a plurality of rolling elements disposed between the outer ring and the inner ring, the rolling bearing having a predetermined rotation axis, a bearing holder disposed so as to be in contact with the outer peripheral surface of the outer ring or the inner peripheral surface of the inner ring of the rolling bearing, and a strain gauge including a resistor for detecting the strain of the outer ring or the inner ring, wherein the bearing holder includes a thick portion and a thin portion having a thickness thinner than that of the thick portion, the bearing holder is formed by joining the thick portion and the thin portion to each other, the strain gauge is disposed in the thin portion, a preload having a predetermined contact angle is applied to the rolling bearing, the thick portion is disposed so as to be in contact with at least a region from the intersection of the straight line indicating the contact angle and the outer peripheral surface of the outer ring or the inner peripheral surface of the inner ring to the preload-side end surface, which is the end surface of the outer ring or the inner ring closer to the intersection, the thin portion is disposed so as to press the outer peripheral surface of the outer ring or the inner peripheral surface of the inner ring over the entire circumference, a rolling bearing holder unit. **Claim 5** The rolling bearing holder unit according to claim 4, wherein the bearing holder is formed by joining the thick portion and the thin portion having different diameters to each other. **Claim 6** The bearing holder is disposed so as to be in contact with the outer peripheral surface of the outer ring of the rolling bearing, The rolling bearing holder unit according to claim 5, wherein the thick portion is disposed at a part on the outer peripheral side of the thin portion. **Claim 7** The bearing holder is disposed so as to be in contact with the inner peripheral surface of the inner ring of the rolling bearing, The rolling bearing holder unit according to claim 5, wherein the thick portion is disposed at a part on the inner peripheral side of the thin portion. **Claim 8** The rolling bearing holder unit according to any one of claims 1 to 7, wherein the bearing holder is formed of metal.

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