Strain detection device

Abstract

To provide a bearing device which outputs signals which may reduce influence of electromagnetic noise from strain gauges.SOLUTION: A bearing device includes: a rotary shaft; a first rolling bearing supporting the rotary shaft; a bearing housing holding the first rolling bearing; and first and second strain gauges disposed in the bearing housing. The bearing housing has: a first strain transmission part to which strain occurring in the first rolling bearing is transmitted by rotation of the rotary shaft; and a first strain non-transmission part to which the strain is not transmitted. The first strain gauge is disposed at the first strain transmission part and the second strain gauge is disposed at the first strain non-transmission part.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention , hi relates to a strain detection device.

Background Art

[0002] A bearing device provided with a rolling bearing housed inside a cylindrical bearing housing is known (for example, see Patent Document 1). Such a bearing device is mounted on, for example, a motor. In a motor provided with a bearing device, when the motor rotates, the spheres inside the rolling bearing rotate, and the rolling bearing is slightly deformed. The deformation of the rolling bearing varies depending on the wear state inside the rolling bearing. Therefore, in order to detect a change in the state inside the rolling bearing, a sensor such as a strain gauge may be arranged on the bearing housing.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, since electromagnetic noise is generated from the coil during the rotation of the motor, the strain gauge may be affected by the electromagnetic noise, and it may be difficult to obtain a normal signal from the strain gauge.

[0005] The present invention has been made in view of the above points, and an object thereof is to provide a bearing device that outputs a signal capable of reducing the influence of electromagnetic noise from a strain gauge. Strain detection device having

Means for Solving the Problems

[0006] This Strain detection device is The system comprises a bearing device or a motor having the bearing device, and a bridge circuit, wherein the bearing device isThe device comprises a rotating shaft, a first rolling bearing supporting the rotating shaft, a bearing housing holding the first rolling bearing, and first and second strain gauges disposed in the bearing housing, wherein the bearing housing has a first strain transmission section through which strain generated in the first rolling bearing by the rotation of the rotating shaft is transmitted, and a first non-strain transmission section through which the strain is not transmitted, the first strain gauge is disposed in the first strain transmission section, and the second strain gauge is disposed in the first non-strain transmission section. The first strain gauge constitutes one side of the four sides of the bridge circuit on the side of the output voltage extraction point, and the second strain gauge constitutes one side of the four sides of the bridge circuit on the other side of the output voltage extraction point. . [Effects of the Invention]

[0007] According to the disclosed technology, a bearing device outputs a signal from a strain gauge that can reduce the effects of electromagnetic noise. Strain detection device having We can provide this. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view illustrating a bearing device according to the first embodiment. [Figure 2] This is a cross-sectional view illustrating a bearing device according to the first embodiment. [Figure 3] Figure 2 is a magnified view of the area near recess 40h. [Figure 4] Figure 1 is a magnified view of the area near recess 40h. [Figure 5] This is a schematic diagram illustrating a strain detection device according to the first embodiment. [Figure 6] This is a plan view illustrating a strain gauge according to the first embodiment. [Figure 7] This is a cross-sectional view illustrating a strain gauge according to the first embodiment. [Figure 8] This is a cross-sectional view illustrating a motor equipped with a bearing device according to the first embodiment. [Figure 9] This is an example of a waveform when motor 5 is stopped. [Figure 10] This is an example of a waveform when motor 5 is rotating. [Figure 11]Partial enlarged view (part 1) of the strain transmission part and strain non - transmission part according to a modification of the first embodiment. [Figure 12] Partial enlarged view (part 2) of the strain transmission part and strain non - transmission part according to a modification of the first embodiment. [Figure 13] Partial enlarged view (part 3) of the strain transmission part and strain non - transmission part according to a modification of the first embodiment. [Figure 14] Partial enlarged view (part 4) of the strain transmission part and strain non - transmission part according to a modification of the first embodiment. [Figure 15] Partial enlarged view (part 5) of the strain transmission part and strain non - transmission part according to a modification of the first embodiment. [Figure 16] Partial enlarged view (part 6) of the strain transmission part and strain non - transmission part according to a modification of the first embodiment. [Figure 17] Partial enlarged view (part 7) of the strain transmission part and strain non - transmission part according to a modification of the first embodiment. [Figure 18] Partial enlarged view (part 8) of the strain transmission part and strain non - transmission part according to a modification of the first embodiment. [Figure 19] Partial enlarged view (part 9) of the strain transmission part and strain non - transmission part according to a modification of the first embodiment. [Figure 20] Partial enlarged view (part 10) of the strain transmission part and strain non - transmission part according to a modification of the first embodiment. [Figure 21] Partial enlarged view (part 11) of the strain transmission part and strain non - transmission part according to a modification of the first embodiment. [Figure 22] Partial enlarged view (part 12) of the strain transmission part and strain non - transmission part according to a modification of the first embodiment.

Modes for Carrying Out the Invention

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

[0010] <First Embodiment> (Bearing device) Figure 1 is a perspective view illustrating a bearing device according to the first embodiment. Figure 2 is a cross-sectional view illustrating a bearing device according to the first embodiment, showing a cross-section passing through the axis m of the rotating shaft 20.

[0011] As shown in Figures 1 and 2, the bearing device 1 includes a rotating shaft 20, a first rolling bearing 30A, a second rolling bearing 30B, a bearing housing 40, a first strain gauge 100A, and a second strain gauge 100B.

[0012] The rotating shaft 20 is supported in a rotatable manner by first rolling bearings 30A and second rolling bearings 30B, which are located near both ends in the longitudinal direction.

[0013] The first rolling bearing 30A and the second rolling bearing 30B are installed spaced apart from each other in the direction of the axis m. In the example shown in Figure 2, the second rolling bearing 30B is installed on one side in the direction of the axis m, and the first rolling bearing 30A is installed on the other side in the direction of the axis m. For the sake of explanation, the side on which the second rolling bearing 30B is installed will be referred to as the upper side, and the side on which the first rolling bearing 30A is installed will be referred to as the lower side.

[0014] The first rolling bearing 30A and the second rolling bearing 30B each have an outer ring 31, an inner ring 32, and a plurality of rolling elements 33. The outer ring 31 is a cylindrical structure with axis m as its central axis. The inner ring 32 is a cylindrical structure arranged coaxially with the outer ring 31 on its inner circumference. Each of the plurality of rolling elements 33 is a sphere placed in a raceway formed between the outer ring 31 and the inner ring 32. A lubricant such as grease is sealed inside the raceway.

[0015] The first rolling bearing 30A and the second rolling bearing 30B are fixed to the bearing housing 40 by press-fitting, adhesive, or the like, and are held by the bearing housing 40. The bearing housing 40 presses against the outer circumferential surface of the outer ring 31 around its entire circumference. The bearing housing 40 can be made of a metal such as brass. On the side of the bearing housing 40 facing the first rolling bearing 30A, a recess 40h is provided in the outer circumferential surface 40a that is recessed toward the side facing the rotating shaft 20.

[0016] The first strain gauge 100A and the second strain gauge 100B are sensors equipped with a resistor 103 (described later) capable of detecting the strain of the first rolling bearing 30A (for example, the strain of the outer ring 31). The first strain gauge 100A and the second strain gauge 100B are arranged in the bearing housing 40 spaced apart from each other in the axial direction m. The first strain gauge 100A and the second strain gauge 100B are fixed to the recess 40h of the bearing housing 40 with adhesive or the like. In the example shown in Figures 1 and 2, the first strain gauge 100A is provided on the upper side in the axial direction m within the recess 40h of the bearing housing 40, and the second strain gauge 100B is provided on the lower side in the axial direction m.

[0017] The first strain gauge 100A and the second strain gauge 100B are arranged, for example, such that the line connecting their respective centers is parallel to the axis m. In the direction of the axis m, the second strain gauge 100B is positioned, for example, below the outer ring 31 of the first rolling bearing 30A.

[0018] Figure 3 is a magnified view of the vicinity of the recess 40h shown in Figure 2. As shown in Figure 3, the bearing housing 40 has a first strain transmission section 401 to which strain generated in the first rolling bearing 30A due to the rotation of the rotating shaft 20 is transmitted, and a first strain non-transmission section 402 to which strain generated in the first rolling bearing 30A due to the rotation of the rotating shaft 20 is not transmitted.

[0019] The first strain transmission section 401 and the first non-strain transmission section 402 are parts where the average value of strain when the rotating shaft 20 rotates at its rated rotational speed is relatively different. Specifically, the first non-strain transmission section 402 is defined as the part where, when the average value of strain when the rotating shaft 20 rotates at its rated rotational speed is measured using a strain gauge of the same specifications, the average value of strain measured in the first strain transmission section 401 is 1 / 2 or less. In other words, the "first non-strain transmission section 402, where strain generated in the first rolling bearing 30A is not transmitted" does not indicate a part where no strain is transmitted at all. Furthermore, when the average value of the strain when the rotating shaft 20 rotates at the rated rotational speed is measured using a strain gauge of the same specifications, it is preferable that the average value of the strain measured in the first strain non-transmission section 402 is 1 / 5 or less of the average value of the strain measured in the first strain transmission section 401.

[0020] In the example shown in Figure 3, the portion within the recess 40h that overlaps with the outer circumferential surface of the first rolling bearing 30A in a radial view is the first strain transmission portion 401. This portion is a location where strain generated in the first rolling bearing 30A due to the rotation of the rotating shaft 20 is easily transmitted. On the other hand, the portion within the recess 40h that does not overlap with the outer circumferential surface of the first rolling bearing 30A in a radial view is the first non-strain transmission portion 402. This portion is a location where strain generated in the first rolling bearing 30A due to the rotation of the rotating shaft 20 is less likely to be transmitted.

[0021] The first strain gauge 100A is positioned on the first strain transmission section 401. In the example shown in Figure 3, the first strain transmission section 401 has an inner surface that contacts the outer surface of the first rolling bearing 30A, and an outer surface that is recessed toward the rotating shaft 20 than the outer surface 40a of the bearing housing 40, and the first strain gauge 100A is positioned on the outer surface of the first strain transmission section 401.

[0022] The second strain gauge 100B is positioned in the first non-strain transmission section 402. In the example shown in Figure 3, the first non-strain transmission section 402 has an inner surface facing the outer surface of the rotating shaft 20 and an outer surface that is recessed toward the rotating shaft 20 than the outer surface 40a of the bearing housing 40, and the second strain gauge 100B is positioned on the outer surface of the first non-strain transmission section 402. In the example shown in Figure 3, the radius of the outer surface of the first non-strain transmission section 402 is the same as the radius of the outer surface of the first strain transmission section 401.

[0023] One side of the recess 40h (the lower side in Figure 3) is an open end. Almost no strain from the first rolling bearing 30A is transmitted to the open end of the recess 40h. Therefore, it is preferable to place the second strain gauge 100B near the open end of the recess 40h, where strain is particularly difficult to transmit, within the first strain non-transmission section 402. Here, the vicinity of the open end is defined as the range L / 2 from the open end, where L is the axial distance m between the open end and the end of the first rolling bearing 30A on the open end side, as shown in Figure 3. It is more preferable to place the second strain gauge 100B within the range L / 3 from the open end of the recess 40h, and even more preferable to place it within the range L / 4 from the open end of the recess 40h.

[0024] In order to facilitate the transmission of strain generated in the first rolling bearing 30A by the rotation of the rotating shaft 20, the thickness of the first strain transmission portion 401 is preferably 3 / 4 or less of the radial distance between the outer circumferential surface of the outer ring 31 and the outer circumferential surface 40a of the bearing housing 40. In the example of Figure 3, the first non-strain transmission portion 402 has the same thickness as the first strain transmission portion 401. Here, the statement that the first non-strain transmission portion 402 has the same thickness as the first strain transmission portion 401 means that the thickness of the first non-strain transmission portion 402 is within ±3% of the thickness of the first strain transmission portion 401.

[0025] In the examples shown in Figures 1 and 2, the recess 40h is provided around the entire circumference of the outer circumferential surface 40a of the bearing housing 40. However, it is not limited to this, and the recess 40h only needs to be provided in the area where the first strain gauge 100A and the second strain gauge 100B are positioned.

[0026] In this manner, by arranging the first strain gauge 100A in the first strain transmission section 401 of the bearing housing 40, the strain of the first rolling bearing 30A is transmitted to the first strain gauge 100A via the bearing housing 40 and can be detected by the first strain gauge 100A. In this embodiment, the first strain gauge 100A detects the strain of the first rolling bearing 30A as a change in the resistance value of the resistor 103.

[0027] Figure 4 is a magnified view of the vicinity of the recess 40h shown in Figure 1. As shown in Figure 4, in the first strain gauge 100A, it is preferable that the resistor 103 is positioned with its longitudinal direction (gauge length direction) facing the circumferential direction of the bearing housing 40. Since the circumferential direction of the bearing housing 40 is more prone to expansion and contraction than the axial direction m, a large strain waveform can be obtained by positioning the longitudinal direction of the resistor 103 facing the circumferential direction of the bearing housing 40.

[0028] The first strain gauge 100A has a pair of terminals 105 connected to both ends of the resistor 103 via wiring 104, and wiring 200A is electrically connected to each terminal 105 by solder or the like. Wiring 200A may be, for example, a coaxial cable, or a structure in which a solid GND is formed on at least one side of a flexible substrate.

[0029] By connecting the electrical signal obtained from the 200A wiring to a bridge circuit or the like, the output of the first strain gauge 100A is obtained. The first strain gauge 100A is subject to interference from electromagnetic noise. Therefore, the output of the first strain gauge 100A includes electromagnetic noise in addition to the strain of the first rolling bearing 30A. The electromagnetic noise referred to here is, for example, noise generated from the motor's coils, etc., when the bearing device 1 is mounted on a motor.

[0030] The second strain gauge 100B is a sensor equipped with a resistor 103, wiring 104, and terminals 105, similar to the first strain gauge 100A. The second strain gauge 100B can have the same structure and size as the first strain gauge 100A, for example. In the second strain gauge 100B, the longitudinal direction of the resistor 103 can be the same as the longitudinal direction of the resistor 103 in the first strain gauge 100A, for example.

[0031] Each terminal portion 105 of the second strain gauge 100B is electrically connected to a wiring 200B by solder or the like. The wiring 200B may be, for example, a coaxial cable, or it may be a structure in which a solid ground plane is formed on at least one side of a flexible circuit board.

[0032] The output of the second strain gauge 100B can be obtained by connecting the electrical signal obtained from wiring 200B to a bridge circuit or the like. The second strain gauge 100B is susceptible to electromagnetic noise interference, just like the first strain gauge 100A. The second strain gauge 100B can detect strain by changing the resistance value of resistor 103, just like the first strain gauge 100A.

[0033] However, in the bearing device 1, the second strain gauge 100B is located in the first non-strain transmission section 402. Therefore, the second strain gauge 100B hardly detects any strain in the first rolling bearing 30A, and the output of the second strain gauge 100B consists almost entirely of electromagnetic noise. As mentioned above, a large strain waveform can be obtained by aligning the longitudinal direction of the resistor 103 with the circumferential direction of the bearing housing 40. Therefore, in order to further reduce the strain detected by the second strain gauge 100B, the second strain gauge 100B may be positioned with the longitudinal direction of the resistor 103 facing the direction of the axis m.

[0034] Furthermore, wiring 200A and wiring 200B may be routed to the underside of recess 40h at different radial positions. For example, as shown in Figure 1, wiring 200A may be routed along the outer surface of recess 40h for about one-quarter of its circumference in a direction perpendicular to axis m, and then bent and routed to the underside of recess 40h. This routing can suppress interference between wiring 200A and wiring 200B.

[0035] Since both the first strain gauge 100A and the second strain gauge 100B are fixed to the bearing housing 40, the influence of electromagnetic noise is almost the same. Therefore, by placing the first strain gauge 100A in the first strain transmission section 401 of the bearing housing 40 and the second strain gauge 100B in the first non-strain transmission section 402 of the bearing housing 40, the influence of electromagnetic noise can be eliminated using the outputs of both, and strain with a good signal-to-noise ratio can be detected. A specific circuit connection example is shown below.

[0036] Figure 5 is a schematic diagram illustrating a strain detection device according to the first embodiment. As shown in Figure 5, the strain detection device 3 includes a bearing device 1 and a bridge circuit 2.

[0037] In Figure 5, the first side of the bridge circuit 2 is composed of a resistor 103 between a pair of terminals 105 of the first strain gauge 100A, the second side of the bridge circuit 2 adjacent to the first side is composed of a resistor 103 between a pair of terminals 105 of the second strain gauge 100B, and the third and fourth sides are composed of fixed resistors R. In other words, the first strain gauge 100A constitutes one side of the four sides of the bridge circuit 2 on one side of the output voltage extraction point, and the second strain gauge 100B constitutes one side of the four sides of the bridge circuit 2 on the other side of the output voltage extraction point.

[0038] A DC voltage E is supplied between the connection point between one terminal 105 of the first strain gauge 100A and the fixed resistor R, and between the connection point between one terminal 105 of the second strain gauge 100B and the fixed resistor R. This allows the output voltage e0 to be obtained as the output of the bridge circuit 2. For example, if strain ε and electromagnetic noise N are detected in the first strain gauge 100A, and only electromagnetic noise N is detected in the second strain gauge 100B, the electromagnetic noise N is canceled out, and the output voltage e0 = E / 4 × Ks × ε, where Ks is the gauge factor.

[0039] In this way, by arranging the first strain gauge 100A in the first strain transmission unit 401 and the second strain gauge 100B in the first non-strain transmission unit 402, a bearing device 1 can be realized that outputs signals from the first strain gauge 100A and the second strain gauge 100B that can reduce the influence of electromagnetic noise N. Then, by configuring a strain detection device 3 using the bearing device 1, a strain ε with a good signal-to-noise ratio, from which the influence of electromagnetic noise N has been removed, can be detected as the output voltage ε0.

[0040] The strain detection device 3 may further include a power supply capable of supplying a DC voltage E, an amplifier that amplifies the output voltage e0, an A / D converter that converts the output of the amplifier into a digital signal, and a signal processing unit that performs calculations on the output of the A / D converter. The state of the first rolling bearing 30A can be monitored by, for example, performing an FFT analysis (Fast Fourier Transform) on the output voltage e0 of the bridge circuit 2 in the signal processing unit.

[0041] (Strain gauge) Figure 6 is a plan view illustrating a strain gauge according to the first embodiment. Figure 7 is a cross-sectional view illustrating a strain gauge according to the first embodiment, showing a cross-section along line AA in Figure 6. Referring to Figures 6 and 7, the first strain gauge 100A has a base material 101, a functional layer 102, a resistor 103, wiring 104, and a terminal portion 105. However, the functional layer 102 may be provided as needed. Although the first strain gauge 100A is described here, the second strain gauge 100B can have the same structure as the first strain gauge 100A.

[0042] In the explanation of Figures 6 and 7, for convenience, in the first strain gauge 100A, the side of the base material 101 on which the resistor 103 is provided will be referred to as the upper side or one side, and the side on which the resistor 103 is not provided will be referred to as the lower side or the other side. Also, the surface on which the resistor 103 is provided in each part will be referred to as one surface or the upper surface, and the surface on which the resistor 103 is not provided will be referred to as the other surface or the lower surface. However, the first strain gauge 100A can be used upside down or positioned at any angle. Furthermore, "planar view" refers to viewing the object from the direction normal to the upper surface 101a of the base material 101, and "planar shape" refers to the shape of the object viewed from the direction normal to the upper surface 101a of the base material 101.

[0043] The base material 101 is a member that serves as a base layer for forming the resistor 103, etc., and is flexible. The thickness of the base material 101 is not particularly limited and can be appropriately selected depending on the purpose, but for example it can be about 5 μm to 500 μm. In particular, a thickness of 5 μm to 200 μm for the base material 101 is preferable in terms of the transmission of strain from the surface of the strain-generating body (for example, the outer peripheral surface 40a of the bearing housing 40) that is joined to the lower surface of the base material 101 via the adhesive layer 150, and dimensional stability against the environment, and a thickness of 10 μm or more is even preferable in terms of insulation.

[0044] The base material 101 can be formed from an insulating resin film such as PI (polyimide) resin, epoxy resin, PEEK (polyether ether ketone) resin, PEN (polyethylene naphthalate) resin, PET (polyethylene terephthalate) resin, PPS (polyphenylene sulfide) resin, or polyolefin resin. Note that "film" refers to a flexible material with a thickness of approximately 500 μm or less.

[0045] Here, "formed from an insulating resin film" does not prevent the base material 101 from containing fillers or impurities in the insulating resin film. For example, the base material 101 may be formed from an insulating resin film containing fillers such as silica or alumina.

[0046] Other materials for the substrate 101 besides resin include crystalline materials such as SiO2, ZrO2 (including YSZ), Si, Si2N3, Al2O3 (including sapphire), ZnO, and perovskite ceramics (CaTiO3, BaTiO3), as well as amorphous glass. Furthermore, metals such as aluminum, aluminum alloys (duralumin), and titanium may be used as the material for the substrate 101. In this case, an insulating film is formed on the metallic substrate 101.

[0047] The functional layer 102 is formed on the upper surface 101a of the base material 101 as a lower layer of the resistor 103. That is, the planar shape of the functional layer 102 is substantially the same as the planar shape of the resistor 103 shown in Figure 6.

[0048] In this application, the functional layer refers to a layer that has the function of promoting the crystal growth of the resistor 103, which is at least the upper layer. Preferably, the functional layer 102 further has the function of preventing oxidation of the resistor 103 by oxygen and moisture contained in the substrate 101, and the function of improving the adhesion between the substrate 101 and the resistor 103. The functional layer 102 may further have other functions.

[0049] Since the insulating resin film that makes up the base material 101 contains oxygen and moisture, and especially when the resistor 103 contains Cr (chromium), the Cr forms an oxidation film, it is effective for the functional layer 102 to have a function to prevent oxidation of the resistor 103.

[0050] The material of the functional layer 102 is not particularly limited as long as it is a material that has the function of promoting crystal growth of the upper layer resistor 103, and can be appropriately selected according to the purpose. For example, 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) Examples include one or more metals selected from the group consisting of 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), and Al (aluminum), an alloy of any of these metals, or a compound of any of these metals.

[0051] Examples of the alloys mentioned above include FeCr, TiAl, FeNi, NiCr, and CrCu. Examples of the compounds mentioned above include TiN, TaN, Si3N4, TiO2, Ta2O5, and SiO2.

[0052] When the functional layer 102 is formed from a conductive material such as a metal or alloy, it is preferable that the thickness of the functional layer 102 be 1 / 20 or less of the thickness of the resistor. Within this range, the crystal growth of α-Cr can be promoted, and a portion of the current flowing through the resistor flows into the functional layer 102, preventing a decrease in strain detection sensitivity.

[0053] When the functional layer 102 is formed from a conductive material such as a metal or alloy, it is more preferable that the thickness of the functional layer 102 be 1 / 50 or less of the thickness of the resistor. Within this range, the crystal growth of α-Cr can be promoted, and a portion of the current flowing through the resistor flows into the functional layer 102, further preventing a decrease in strain detection sensitivity.

[0054] If the functional layer 102 is formed from a conductive material such as a metal or alloy, it is even more preferable that the thickness of the functional layer 102 be 1 / 100 or less of the thickness of the resistor. Within this range, it is possible to further prevent a decrease in strain detection sensitivity due to a portion of the current flowing through the resistor flowing into the functional layer 102.

[0055] When the functional layer 102 is formed from an insulating material such as an oxide or nitride, the thickness of the functional layer 102 is preferably 1 nm to 1 μm. Within this range, the crystal growth of α-Cr can be promoted, and the functional layer 102 can be easily formed without cracking.

[0056] When the functional layer 102 is formed from an insulating material such as an oxide or nitride, the film thickness of the functional layer 102 is more preferably 1 nm to 0.8 μm. Within this range, the crystal growth of α-Cr can be promoted, and the film can be formed more easily without cracking in the functional layer 102.

[0057] When the functional layer 102 is formed from an insulating material such as an oxide or nitride, it is even more preferable that the film thickness of the functional layer 102 be 1 nm to 0.5 μm. Within this range, the crystal growth of α-Cr can be promoted, and the film can be formed more easily without cracking in the functional layer 102.

[0058] The planar shape of the functional layer 102 is patterned to be substantially the same as the planar shape of the resistor shown in Figure 6. However, the planar shape of the functional layer 102 is not limited to being substantially the same as the planar shape of the resistor. If the functional layer 102 is formed from an insulating material, it does not need to be patterned to be the same as the planar shape of the resistor. In this case, the functional layer 102 may be formed as a solid block at least in the region where the resistor is formed. Alternatively, the functional layer 102 may be formed as a solid block over the entire upper surface of the substrate 101.

[0059] Furthermore, when the functional layer 102 is formed from an insulating material, forming the functional layer 102 relatively thick, such as 50 nm to 1 μm, and forming it in a solid form increases the thickness and surface area of ​​the functional layer 102, allowing the heat generated when the resistor heats up to be dissipated to the base material 101. As a result, the decrease in measurement accuracy due to self-heating of the resistor can be suppressed in the first strain gauge 100A.

[0060] The resistor 103 is a thin film formed in a predetermined pattern on the upper surface of the functional layer 102, and is a sensitive part that undergoes a change in resistance when subjected to strain.

[0061] The resistor 103 can be formed from, 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 from a material containing at least one of Cr and Ni. An example of a material containing Cr is a Cr multiphase film. An example of a material containing Ni is Cu-Ni (copper nickel). An example of a material containing both Cr and Ni is Ni-Cr (nickel chromium).

[0062] The following explanation will use the case where the resistor 103 is a Cr multiphase film as an example. Here, a Cr multiphase film is a film in which Cr, CrN, Cr2N, etc., are mixed. The Cr multiphase film may contain unavoidable impurities such as chromium oxide. In addition, some of the material constituting the functional layer 102 may be diffused into the Cr multiphase film. In this case, the material constituting the functional layer 102 and nitrogen may form a compound. For example, if the functional layer 102 is made of Ti, the Cr multiphase film may contain Ti or TiN (titanium nitride).

[0063] The thickness of the resistor 103 is not particularly limited and can be appropriately selected depending on the purpose, but for example, it can be about 0.05 μm to 2 μm. In particular, a thickness of 0.1 μm or more is preferable because it improves the crystallinity of the crystals constituting the resistor 103 (for example, the crystallinity of α-Cr), and a thickness of 1 μm or less is even preferable because it can reduce cracks in the film and warping from the substrate 101 caused by internal stress in the film constituting the resistor 103.

[0064] By forming the resistor 103 on the functional layer 102, the resistor 103 can be formed using a stable crystalline phase, thereby improving the stability of the gauge characteristics (gauge factor, gauge factor temperature coefficient TCS, and resistance temperature coefficient TCR).

[0065] For example, if the resistor 103 is a Cr multiphase film, a resistor 103 mainly composed of α-Cr (alpha-chromium) can be formed by providing a functional layer 102. Since α-Cr is a stable crystalline phase, the stability of the gauge characteristics can be improved.

[0066] Here, "main component" means that the substance in question accounts for 50% or more by mass of the total substances constituting the resistor. When the resistor 103 is a Cr multiphase film, from the viewpoint of improving gauge characteristics, it is preferable that the resistor 103 contains 80% or more by weight of α-Cr, and more preferably 90% or more by weight. Note that α-Cr is Cr with a bcc structure (body-centered cubic lattice structure).

[0067] Furthermore, if the resistor 103 is a Cr multiphase film, it is preferable that the amount of CrN and Cr2N contained in the Cr multiphase film be 20% by weight or less. By having CrN and Cr2N contained in the Cr multiphase film at 20% by weight or less, the decrease in gauge factor can be suppressed.

[0068] Furthermore, the proportion of Cr2N in CrN and Cr2N is preferably 80% by weight or more and less than 90% by weight, and more preferably 90% by weight or more and less than 95% by weight. When the proportion of Cr2N in CrN and Cr2N is 90% by weight or more and less than 95% by weight, the decrease in TCR (negative TCR) becomes even more pronounced due to the semiconducting properties of Cr2N. In addition, brittle fracture is reduced by reducing the ceramicization.

[0069] On the other hand, if trace amounts of N2 or atomic N are mixed into the film, external environmental factors (such as high temperatures) can cause them to escape from the film, resulting in changes in film stress. By creating chemically stable CrN, the generation of the aforementioned unstable N is avoided, and a stable strain gauge can be obtained.

[0070] Furthermore, the gauge characteristics can be improved by the diffusion of the metal (e.g., Ti) constituting the functional layer 102 into the Cr multiphase film. Specifically, the gauge factor of the first strain gauge 100A can be set to 10 or higher, and the gauge factor temperature coefficient TCS and resistance temperature coefficient TCR can be set within the range of -1000 ppm / °C to +1000 ppm / °C.

[0071] The terminal portion 105 extends from both ends of the resistor 103 via the wiring 104, and in a plan view, it is wider than the resistor 103 and the wiring 104 and is formed in a substantially rectangular shape. 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 from one of the terminal portion 105 and the wiring 104, for example, by folding back in a zigzag pattern, and is connected to the other wiring 104 and terminal portion 105. The upper surface of the terminal portion 105 may be covered with a metal that has better solderability than the terminal portion 105.

[0072] Although the resistor 103, wiring 104, and terminal portion 105 are given different reference numerals for convenience, they can all be formed integrally from the same material in the same process.

[0073] 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 wiring 104 and expose the terminal portion 105. Providing the cover layer 106 prevents mechanical damage to the resistor 103 and wiring 104. In addition, providing the cover layer 106 protects the resistor 103 and wiring 104 from moisture, etc. Note that the cover layer 106 may be provided so as to cover the entire portion excluding the terminal portion 105.

[0074] The cover layer 106 can be formed from an insulating resin such as PI resin, epoxy resin, PEEK resin, PEN resin, PET resin, PPS resin, or composite resin (e.g., silicone resin, polyolefin resin). The cover layer may contain fillers or pigments. There are no particular restrictions on the thickness of the cover layer, and it can be appropriately selected depending on the purpose, but for example, it can be about 2 μm to 30 μm.

[0075] To manufacture the first strain gauge 100A, first, a base material 101 is prepared, and a 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 only if necessary.

[0076] The functional layer 102 can be deposited using a conventional sputtering method, for example, by targeting a raw material capable of forming the functional layer 102 and introducing Ar (argon) gas into a chamber. By using the conventional sputtering method, the functional layer 102 is deposited while etching the upper surface 101a of the substrate 101 with Ar, thus minimizing the amount of functional layer 102 deposited and achieving improved adhesion.

[0077] However, this is just one example of a method for forming the functional layer 102, and the functional layer 102 may be formed by other methods. For example, the upper surface 101a of the substrate 101 may be activated by plasma treatment using Ar or the like before forming the functional layer 102 to improve adhesion, and then the functional layer 102 may be formed in a vacuum by magnetron sputtering.

[0078] Next, a metal layer forming the resistor 103, wiring 104, and terminal portion 105 is formed on the entire upper surface of the functional layer 102. Then, the functional layer 102, resistor 103, wiring 104, and terminal portion 105 are patterned into the planar shape shown in Figure 6 by photolithography. The material and thickness of the resistor 103, wiring 104, and terminal portion 105 are as described above. The resistor 103, wiring 104, and terminal portion 105 can be formed integrally from the same material. The resistor 103, wiring 104, and terminal portion 105 can be deposited, for example, by a magnetron sputtering method targeting a raw material capable of forming the resistor 103, wiring 104, and terminal portion 105. The resistor 103, wiring 104, and terminal portion 105 may also be deposited using reactive sputtering, evaporation, arc ion plating, pulsed laser deposition, etc., instead of magnetron sputtering.

[0079] There are no particular restrictions on the combination of materials for the functional layer 102, the resistor 103, the wiring 104, and the terminal portion 105, and they can be appropriately selected according to the purpose. For example, Ti can be used as the functional layer 102, and a Cr multiphase film mainly composed of α-Cr (alpha-chromium) can be formed for the resistor 103, the wiring 104, and the terminal portion 105.

[0080] In this case, for example, the resistor 103, wiring 104, and terminal portion 105 can be formed by magnetron sputtering with Ar gas introduced into the chamber, using a raw material capable of forming a Cr multiphase film as the target. Alternatively, the resistor 103, wiring 104, and terminal portion 105 can be formed by reactive sputtering with pure Cr as the target, using a reactive sputtering method with an appropriate amount of nitrogen gas introduced into the chamber along with Ar gas. In this case, the ratio of CrN and Cr2N in the Cr multiphase film, as well as the ratio of Cr2N within CrN and Cr2N, can be adjusted by changing the amount and pressure (partial pressure of nitrogen) of nitrogen gas introduced or by adjusting the heating temperature by providing a heating step.

[0081] In these methods, the functional layer 102 made of Ti initiates the growth surface of the Cr multiphase film, enabling the formation of a Cr multiphase film mainly composed of α-Cr, which has a stable crystalline structure. Furthermore, the diffusion of Ti constituting the functional layer 102 into the Cr multiphase film improves the gauge characteristics. For example, the gauge factor of the first strain gauge 100A can be set to 10 or higher, and the gauge factor temperature coefficient TCS and resistance temperature coefficient TCR can be set within the range of -1000 ppm / °C to +1000 ppm / °C.

[0082] Furthermore, when the resistor 103 is a Cr multiphase film, the functional layer 102 made of Ti has all of the following functions: promoting crystal growth of the resistor 103, preventing oxidation of the resistor 103 by oxygen and moisture contained in the substrate 101, and improving the adhesion between the substrate 101 and the resistor 103. The same applies when Ta, Si, Al, or Fe is used instead of Ti as the functional layer 102.

[0083] Subsequently, if necessary, a cover layer 106 is provided on the upper surface 101a of the base material 101 to cover the resistor 103 and wiring 104 and expose the terminal portion 105, thereby completing the first strain gauge 100A. The cover layer 106 can be made, for example, by laminating a semi-cured thermosetting insulating resin film onto the upper surface 101a of the base material 101 to cover the resistor 103 and wiring 104 and expose the terminal portion 105, and then heating and curing it. Alternatively, the cover layer 106 may be made by applying a liquid or paste-like thermosetting insulating resin to the upper surface 101a of the base material 101 to cover the resistor 103 and wiring 104 and expose the terminal portion 105, and then heating and curing it.

[0084] In this way, by providing a functional layer 102 in the lower layer of the resistor 103, crystal growth of the resistor 103 can be promoted, and a resistor 103 consisting of a stable crystalline phase can be fabricated. As a result, the stability of the gauge characteristics can be improved in the first strain gauge 100A. Furthermore, the diffusion of the material constituting the functional layer 102 into the resistor 103 can improve the gauge characteristics of the first strain gauge 100A.

[0085] Furthermore, the first strain gauge 100A, which uses a Cr multiphase film as the material for the resistor 103, achieves high sensitivity (more than 500% compared to conventional models) and miniaturization (less than 1 / 10 of conventional models). For example, while the output of a conventional strain gauge was about 0.04mV / 2V, the first strain gauge 100A can obtain an output of 0.3mV / 2V or higher. In addition, while the size (gauge length × gauge width) of a conventional strain gauge was about 3mm × 3mm, the size (gauge length × gauge width) of the first strain gauge 100A can be miniaturized to about 0.3mm × 0.3mm.

[0086] Thus, the first strain gauge 100A, which uses a Cr multiphase film as the material for the resistor 103, is small and can be easily attached to the recess 40h provided on the outer circumferential surface 40a of the bearing housing 40. For this reason, it is particularly suitable for use in a bearing device 1 that uses a small first rolling bearing 30A and a second rolling bearing 30B with a diameter (outer diameter of the outer ring 31) of 30 mm or less. Furthermore, the first strain gauge 100A, which uses a Cr multiphase film as the material for the resistor 103, is highly sensitive and can detect small displacements, making it possible to detect minute strains that were previously difficult to detect. In other words, by having a first strain gauge 100A that uses a Cr multiphase film as the material for the resistor 103, a bearing device 1 equipped with the function of accurately detecting strain can be realized.

[0087] (motor) The bearing device 1 can be mounted on a motor. Figure 8 is a cross-sectional view illustrating a motor equipped with the bearing device according to the first embodiment. As shown in Figure 8, the motor 5 is an axial flow fan motor having the bearing device 1, an impeller 10, a stator 50, a rotor 60, and a casing 70. Note that the bearing device 1 can also be mounted on motors other than axial flow fan motors.

[0088] The impeller 10 has a rotor housing 11 and blades 12 provided on the outer circumference of the rotor housing 11. A bearing device 1 is fixed to the center of the impeller 10. The stator 50 has an insulator 51, a stator core 52, and a coil 53, and is arranged on the outer circumference of the bearing housing 40 of the bearing device 1. The stator core 52 is fixed to the outer circumference of the bearing housing 40 by, for example, press-fitting.

[0089] The rotor 60 has a rotor yoke 61 integrally provided inside the rotor housing 11 and a rotor magnet 62 mounted inside the rotor yoke 61. In the example shown in Figure 8, the rotor yoke 61 is integrally provided inside the rotor housing 11, but this is not limited to this, and the rotor yoke 61 may be mounted inside the rotor housing 11. Also, the rotating shaft 20 is mounted on the rotor yoke 61 and fixed to the center of the rotor housing 11, but the rotating shaft 20 may be directly fixed to the rotor housing 11.

[0090] The casing 70 includes a casing outer frame 71 that covers the outer circumference of the impeller 10, a base hub 72 that fixes the bearing housing 40, and stationary vanes 73 that connect the casing outer frame 71 and the base hub 72.

[0091] In the example shown in Figure 8, the casing outer frame 71 and the base hub 72 are connected by a stationary vane 73. However, the casing outer frame 71 and the base hub 72 may also be connected by a rod-shaped structure such as a connecting shaft.

[0092] Furthermore, the bearing housing 40 of the bearing device 1 may be fixed to the base hub 72 when the casing 70 is injection molded from resin, or the casing 70 may be molded first and then fixed to the base hub 72 later.

[0093] In motor 5, the motor section 80 is composed of a stator 50 and a rotor 60. By supplying current to a coil 53 from a power supply unit (not shown), the impeller 10 rotates around the central axis m of the rotating shaft 20, which is rotatably supported within the bearing housing 40. In other words, motor 5 is a so-called outer rotor type motor.

[0094] In motor 5, the upper side of Figure 8 is the intake side, and the lower side is the outlet side. Therefore, in motor 5, the impeller 10 is provided on the air intake side of the casing outer frame 71, and the base hub 72 is provided on the outlet side.

[0095] When wiring 200A and 200B have shielded portions, it is preferable that the bearing housing 40 to which the strain gauge 100 is fixed is at the same potential as the shielded portions of wiring 200A and 200B and is connected to GND, from the viewpoint of suppressing the effects of electromagnetic noise. For example, by bonding the bearing housing 40 and the shielded portions of wiring 200A and 200B with a conductive adhesive, both can be connected to GND at the same potential. Examples of conductive adhesives include pastes in which particles such as silver, nickel, gold, copper, and carbon black are dispersed in the adhesive.

[0096] The wiring 200A and 200B may, for example, be directly routed from the recess 40h to the outside of the motor 5, or they may be electrically connected to a circuit board located inside the motor 5.

[0097] It is also possible to configure a strain detection device similar to that shown in Figure 5 by combining the motor 5 with the bridge circuit 2. In this case, it is also possible to mount the bridge circuit 2 shown in Figure 5 onto the motor 5. By monitoring the changes in the strain waveform of the first rolling bearing 30A using the strain detection device, it is possible to detect abnormalities in the first rolling bearing 30A and detect the abnormality before the motor 5 experiences rotational malfunction. For example, an axial flow fan motor used for cooling servers is constantly operating, and even a temporary stop reduces its cooling capacity. In this case, monitoring the condition of the first rolling bearing 30A is particularly effective in order to detect abnormalities in the axial flow fan motor as quickly as possible.

[0098] Figure 9 shows an example of a waveform when motor 5 is stopped. In Figure 9, 100A and 100B, indicated by the upper arrows, represent the output of the wiring 200A and 200B, which is brought out from motor 5 to the outside, connected to separate bridge circuits while motor 5 is stopped, and their respective outputs are amplified. In other words, 100A, indicated by the upper arrow in Figure 9, is the output of the first strain gauge 100A alone while motor 5 is stopped, and 100B, indicated by the upper arrow in Figure 9, is the output of the second strain gauge 100B alone while motor 5 is stopped.

[0099] The first strain gauge 100A and the second strain gauge 100B are positioned as shown in Figures 1 to 4. Since the motor 5 is stopped, only electromagnetic noise is detected in the first strain gauge 100A and the second strain gauge 100B. However, the output of the second strain gauge 100B has its phase inverted by 180 degrees by the amplifier. Considering this, it can be said that the output of the first strain gauge 100A and the output of the second strain gauge 100B are almost identical when the motor 5 is stopped.

[0100] The lower side of the arrow in Figure 9 represents the output voltage e0 obtained when the motor 5 is stopped and the wiring 200A and 200B, which are drawn out from the motor 5 to the outside, are connected as shown in Figure 5. The horizontal and vertical axes on the upper side of the arrow in Figure 9 and the horizontal and vertical axes on the lower side of the arrow in Figure 9 are in the same range. Comparing the upper and lower sides of the arrow in Figure 9, it can be seen that the electromagnetic noise component included in the output voltage e0 of the bridge circuit 2 can be reduced to about 1 / 4 of the electromagnetic noise component included in the output of the first strain gauge 100A and the second strain gauge 100B individually.

[0101] Figure 10 shows an example of a waveform when motor 5 is rotating. The top of Figure 10 shows the output of a bridge circuit connected to a 200A wire brought out from motor 5 while motor 5 is rotating, with the output amplified. In other words, the 100A at the top of Figure 10 is the output of the first strain gauge 100A alone while motor 5 is rotating.

[0102] Furthermore, when the motor 5 is rotating, the waveform obtained based on the output of the first strain gauge 100A is a periodic waveform in which the amount of strain (output intensity) peaks when the rolling element 33 passes directly below the resistor 103 of the first strain gauge 100A, and bottoms out at the midpoint between adjacent rolling elements 33, repeating peaks and bottoms.

[0103] The second image from the top in Figure 10 shows the output voltage e0 obtained when the motor 5 is rotating and the wiring 200A and 200B, which are brought out from the motor 5 to the outside, are connected as shown in Figure 5. Even when the motor 5 is rotating, the electromagnetic noise component included in the output voltage e0 of the bridge circuit is reduced compared to the electromagnetic noise component included in the output of the first strain gauge 100A alone, just as when the motor 5 is stopped.

[0104] The bottom of Figure 10 shows the second state from the top of Figure 10, where the GND of the bridge circuit and the bearing housing 40 are at the same potential. For example, at the output voltage e0 in the bottom of Figure 10, the electromagnetic noise is further reduced in the area circled by the dashed line compared to the second state from the top of Figure 10.

[0105] Figure 10 shows that by connecting the outputs of the first strain gauge 100A and the second strain gauge 100B to the bridge circuit, electromagnetic noise included in the output voltage e0 can be reduced even when the motor 5 is rotating. Furthermore, by setting the GND of the bridge circuit and the bearing housing 40 to the same potential, electromagnetic noise included in the output voltage e0 can be further reduced.

[0106] <Variations of the first embodiment> A modified example of the first embodiment shows variations in the strain transmission section and the non-strain transmission section. In the modified example of the first embodiment, descriptions of components that are the same as those described in the previously described embodiment may be omitted.

[0107] Figure 11 is a partially enlarged view (part 1) of the strain transmission section and the strain non-transmission section according to a modified example of the first embodiment. Figure 12 is a partially enlarged view (part 2) of the strain transmission section and the strain non-transmission section according to a modified example of the first embodiment.

[0108] As shown in Figure 11, the bearing housing 40 may have a groove 40i recessed from the outer circumferential surface toward the rotating shaft 20 in a region located between the first strain gauge 100A and the second strain gauge 100B in the axial direction m of the rotating shaft 20. Multiple grooves 40i may be provided spaced apart in the axial direction M. In this case, the area below the lowest groove 40i becomes the first strain non-transmission portion 402. Furthermore, one or more grooves 40i may be provided around the entire circumference, or only in the portion where the first strain gauge 100A and the second strain gauge 100B face each other.

[0109] This structure makes the portion of the bearing housing 40 with one or more grooves 40i more susceptible to strain, thereby further reducing strain transmission to the first strain non-transmission portion 402. The cross-sectional shape and length of the grooves can be determined arbitrarily. For example, as shown in Figure 12, a groove 40j may be provided that is longer than the first strain non-transmission portion 402 in the axial direction m.

[0110] Figure 13 is a partially enlarged view (part 3) of the strain transmission section and the strain non-transmission section according to a modified example of the first embodiment. As shown in Figure 13, a thin-walled section 40k may be provided in a recess 40h located at a position overlapping with the outer circumferential surface of the first rolling bearing 30A in radial view, and the first strain gauge 100A may be placed in the thin-walled section 40k. In this case, the thin-walled section 40k of the bearing housing 40 becomes the first strain transmission section 401. Thus, in order to more easily transmit the strain generated in the first rolling bearing 30A by the rotation of the rotating shaft 20, the first strain transmission section 401 may be thinner than the first strain non-transmission section 402.

[0111] Figure 14 is a partially enlarged view (part 4) of the strain transmission section and the strain non-transmission section according to a modified example of the first embodiment. The bearing housing 40 shown in Figure 14 has the same shape as in Figure 3. However, Figure 14 differs from Figure 3 in that the second strain gauge 100B is positioned on the inner circumferential surface of the first strain non-transmission section 402. Since the strain on the inner circumferential surface of the first strain non-transmission section 402 is smaller than that on the outer circumferential surface of the first strain non-transmission section 402, the structure in Figure 14 can further reduce the strain transmitted to the first strain non-transmission section 402 compared to the structure in Figure 3.

[0112] Figure 15 is a partially enlarged view (5) of the strain transmission section and the strain non-transmission section according to a modified example of the first embodiment. As shown in Figure 15, the bearing housing 40 may be provided with a recess 40l that is recessed from the side of the rotating shaft 20 toward the outer circumferential surface 40a, which may be designated as the first strain non-transmission section 402. In this case, the first strain non-transmission section 402 has an inner circumferential surface that faces the outer circumferential surface of the first rolling bearing 30A in a radial view, and the second strain gauge 100B is positioned on the inner circumferential surface of the strain non-transmission section 402. In this structure, as with Figure 14, the first strain non-transmission section 402 is a cantilevered structure, and the inner circumferential surface of the first strain non-transmission section 402 does not come into contact with the outer circumferential surface of the first rolling bearing 30A, so strain is not easily transmitted.

[0113] As shown in Figure 16, the recess 40h may be provided only in the vicinity of the portion where the first strain gauge 100A is placed. Also, as shown in Figure 17, the first non-strain transmission portion 402 has an inner surface facing the outer surface of the first rolling bearing 30A in a radial view, and the second strain gauge 100B may be placed on the outer surface of the non-strain transmission portion 402. Furthermore, as shown in Figure 18, strain is not easily transmitted to the end face of the bearing housing 40, so the end face of the bearing housing 40 becomes the first non-strain transmission portion 402. Therefore, the second strain gauge 100B may be placed on the end face of the bearing housing 40, which is the non-strain transmission portion.

[0114] Furthermore, as shown in Figure 19, the first non-strain transmission section 402 may be positioned on the second rolling bearing 30B side of the first rolling bearing 30A and have an inner circumferential surface facing the rotating shaft 20 and an outer circumferential surface recessed on the side of the rotating shaft 20 compared to the outer circumferential surface of the bearing housing 40. In this case, the second strain gauge 100B is positioned, for example, on the outer circumferential surface of the first non-strain transmission section 402. In the example of Figure 19, the first non-strain transmission section 402 is continuous with the first strain transmission section 401. However, as shown by the recesses 40h and 40m in Figure 20, the first non-strain transmission section 402 does not have to be continuous with the first strain transmission section 401.

[0115] Figure 21 shows an example of detecting strain in the first rolling bearing 30A and the second rolling bearing 30B. In Figure 21, the bearing housing 40 further includes a recess 40n which is a second strain transmission part 403 to which strain generated in the second rolling bearing 30B due to the rotation of the rotating shaft 20 is transmitted, and a recess 40o which is a second non-strain transmission part 404 to which strain generated in the second rolling bearing 30B due to the rotation of the rotating shaft 20 is not transmitted. The inner circumferential surface of the second strain transmission part 403 is in contact with the outer circumferential surface of the second rolling bearing 30B, and the outer circumferential surface is recessed on the side of the rotating shaft 20 that is further recessed than the outer circumferential surface 40a of the bearing housing 40.

[0116] The second strain transmission section 403 and the second non-strain transmission section 404 are parts where the average value of strain when the rotating shaft 20 rotates at its rated rotational speed is relatively different. Specifically, the second non-strain transmission section 404 is defined as the part where, when the average value of strain when the rotating shaft 20 rotates at its rated rotational speed is measured using a strain gauge of the same specifications, the average value of strain measured in the second strain transmission section 403 is 1 / 2 or less. In other words, the "second non-strain transmission section 404, where strain generated in the second rolling bearing 30B is not transmitted" does not indicate a part where no strain is transmitted at all. Furthermore, when the average value of the strain when the rotating shaft 20 rotates at the rated rotational speed is measured using a strain gauge of the same specifications, it is preferable that the average value of the strain measured in the second strain non-transmission section 404 is 1 / 5 or less of the average value of the strain measured in the second strain transmission section 403.

[0117] A third strain gauge 100C and a fourth strain gauge 100D are positioned in the bearing housing 40. The third strain gauge 100C is positioned in the second strain transmission section 403, and the fourth strain gauge 100D is positioned in the second non-strain transmission section 404. The third strain gauge 100C and the fourth strain gauge 100D can, for example, have the same structure and size as the first strain gauge 100A. The first non-strain transmission section 402 and the second non-strain transmission section 404 may be continuous in the circumferential direction of the bearing housing 40. In other words, the recess 40m and the recess 40o may be a single continuous recess in the circumferential direction of the bearing housing 40.

[0118] In this way, by placing the third strain gauge 100C in the second strain transmission section 403 of the bearing housing 40 and the fourth strain gauge 100D in the second non-strain transmission section 404 of the bearing housing 40, and connecting them to the bridge circuit 2 as in Figure 5 to configure a strain detection device, the influence of electromagnetic noise N can be eliminated for the second rolling bearing 30B as well, and a strain ε with a good S / N ratio can be detected. As shown in Figure 22, the recesses 40m and 40o may be filled with a filler 45. This further suppresses the transmission of strain to the recesses 40m and 40o. As the filler 45, for example, acrylic, epoxy, or heat-curing resins can be used. The filler 45 may be hardened into a shape that can be fixed in the recesses 40m and 40o, and then fitted into the recesses 40m and 40o.

[0119] Furthermore, the structure of the second strain transmission unit 403 and the second strain non-transmission unit 404 when detecting strain in the first rolling bearing 30A and the second rolling bearing 30B is not limited to the example in Figure 21, and any of the structures exemplified as the first strain transmission unit 401 and the first strain non-transmission unit 402 may be adopted.

[0120] Although preferred embodiments have been described in detail above, the invention is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims.

[0121] For example, the present invention can also be applied to bearing devices, motors, and strain detection devices having only one of the first rolling bearing and the second rolling bearing. [Explanation of Symbols]

[0122] 1 Bearing device, 3 Strain detection device, 5 Motor, 10 Impeller, 11 Rotor housing, 12 Blades, 20 Rotating shaft, 30A First rolling bearing, 30B Second rolling bearing, 31 Outer ring, 32 Inner ring, 33 Rolling element, 40 Bearing housing, 40a Outer surface, 40h, 40l, 40m, 40n Recess, 40i, 40j Groove, 40k Thin-walled section, 45 Filler, 51 Insulator, 52 Stator core, 53 Coil, 60 Rotor, 61 Rotor yoke, 62 Rotor magnet, 70 Casing, 71 Casing outer frame, 72 Base hub, 73 Stator vanes, 80 Motor section, 100A First strain gauge, 100B Second strain gauge, 100C Third strain gauge, 100D Fourth strain gauge, 101 base material, 102 functional layer, 103 resistor, 104 wiring, 105 terminal section, 106 cover layer, 200A, 200B wiring, 401 first strain transmission section, 402 first non-strain transmission section, 403 second strain transmission section, 404 second non-strain transmission section

Claims

1. A motor having a bearing device or the bearing device, and a bridge circuit, The bearing device is Rotation axis and A first rolling bearing supporting the aforementioned rotating shaft, A bearing housing that holds the first rolling bearing, The bearing housing includes first and second strain gauges, The bearing housing has a first strain transmission section through which strain generated in the first rolling bearing by the rotation of the rotating shaft is transmitted, and a first strain non-transmission section through which the strain is not transmitted. The first strain gauge is positioned in the first strain transmission section. The second strain gauge is positioned in the first non-strain transmission section. The first strain gauge constitutes one of the four sides of the bridge circuit, on the side of the output voltage extraction point. The second strain gauge is a strain detection device that forms one of the four sides of the bridge circuit, on the side other than the output voltage extraction point.

2. The first strain transmission section has an inner circumferential surface that contacts the outer circumferential surface of the first rolling bearing, and an outer circumferential surface that is recessed on the side of the rotating shaft compared to the outer circumferential surface of the bearing housing. The strain detection device according to claim 1, wherein the first strain gauge is arranged on the outer circumferential surface of the first strain transmission section.

3. The first strain non-transmission portion is located in a position that does not overlap with the outer circumferential surface of the first rolling bearing in a radial view. The strain detection device according to claim 1 or 2, wherein the second strain gauge is arranged on the inner or outer surface of the first non-strain transmission portion.

4. The strain detection device according to any one of claims 1 to 3, wherein the first strain transmission portion has the same thickness as the first non-strain transmission portion.

5. The strain detection device according to any one of claims 1 to 3, wherein the first strain transmission section is thinner than the first non-strain transmission section.

6. The strain detection device according to any one of claims 1 to 5, wherein the bearing housing has one or more grooves recessed from the outer circumferential surface toward the rotating shaft in a region located between the first strain gauge and the second strain gauge in the axial direction of the rotating shaft.

7. The first strain non-transmission portion has an inner surface that faces the outer surface of the first rolling bearing in a radial view, The strain detection device according to claim 1 or 2, wherein the second strain gauge is arranged on the inner or outer surface of the first non-strain transmission portion.

8. The first strain non-transmission portion has an inner circumferential surface facing the rotating shaft and an outer circumferential surface that is recessed on the side of the rotating shaft compared to the outer circumferential surface of the bearing housing, The strain detection device according to any one of claims 1 to 5, wherein the second strain gauge is arranged on the outer circumferential surface of the first non-strain transmission portion.

9. The strain detection device according to claim 1 or 2, wherein the first strain non-transmission portion is the end face of the bearing housing.

10. A second rolling bearing is held in the bearing housing and supports the rotating shaft, The bearing housing further comprises third and fourth strain gauges, The bearing housing has a second strain transmission section through which strain generated in the second rolling bearing due to the rotation of the rotating shaft is transmitted, and a second strain non-transmission section through which strain generated in the second rolling bearing due to the rotation of the rotating shaft is not transmitted. The second strain transmission portion has an inner circumferential surface that contacts the outer circumferential surface of the second rolling bearing, and its outer circumferential surface is recessed on the side of the rotating shaft compared to the outer circumferential surface of the bearing housing. The third strain gauge is positioned in the second strain transmission section. The strain detection device according to any one of claims 1 to 9, wherein the fourth strain gauge is located in the second non-strain transmission section.

11. The strain detection device according to any one of claims 1 to 10, wherein the first strain gauge and the second strain gauge each have a resistor formed from a Cr multiphase film.

Images