Bearing devices, strain detection devices, motors

Abstract

To provide a sensor unit capable of improving rigidity of a housing which holds a rolling bearing.SOLUTION: A sensor unit is disposed at least partially in a gap between: a first housing which holds a rolling bearing on an inner peripheral side and is equipped with a first strain gauge as a stress sensor on an outer peripheral side; and a second housing which holds the first housing on an inner peripheral side. The sensor unit includes: a cylindrical gauge fixing component at least partially disposed in the gap and having its outer peripheral surface fixed to the inner surface of the second housing; and a second strain gauge provided on the gauge fixing component. The second strain gauge is a noise sensor.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention is, axis relates to a receiving device, a strain detection device, and a motor.

Background Art

[0002] In a motor provided with a rolling bearing, when the motor rotates, the balls in the rolling bearing rotate, and a slight strain is applied to the rolling bearing. And a motor having a sensor for detecting such a strain has been proposed. The sensor for detecting the strain is provided, for example, between the side surface in the rotation axis direction of the rolling bearing and the housing of the motor (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, for example, when a strain gauge is used as a sensor for detecting strain, in order to secure an area for arranging the strain gauge, it is necessary to partially thin the housing that holds the rolling bearing, so there is a problem that the rigidity of the housing that holds the rolling bearing decreases.

[0005] The present invention has been made in view of the above points, and aims to provide a Bearing device that can increase the rigidity of the housing that holds the rolling bearing.

Means for Solving the Problems

[0006] This Bearing device is A bearing device in which a first housing and a cylindrical member are held on the inner circumference side of a second housing, comprising: a rotating shaft; a first rolling bearing supporting the rotating shaft; a first housing holding the first rolling bearing on its inner circumference side and having a first strain gauge, which is a stress sensor, on its outer circumference side; a cylindrical member, at least a portion of which is disposed in the gap between the first housing and the second housing, with its outer circumference fixed to the inner circumference surface of the second housing; and a second strain gauge, which is a noise sensor, provided on the inner circumference surface of the cylindrical member, wherein the first strain gauge is located in a position that overlaps with the outer circumference surface of the first rolling bearing in a radial view, and there is a gap between the outer circumference surface of the first housing and the inner circumference surface of the cylindrical member on which the second strain gauge is provided. .

Effects of the Invention

[0007] According to the disclosed technology, it is possible to increase the rigidity of the housing that holds the rolling bearing. Bearing device We can provide this. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view illustrating a sensor unit according to the first embodiment. [Figure 2] This is a cross-sectional view illustrating a sensor unit according to the first embodiment. [Figure 3] This is a perspective view illustrating a bearing device according to the first embodiment. [Figure 4] This is a cross-sectional view (part 1) illustrating a bearing device according to the first embodiment. [Figure 5] This is a cross-sectional view (part 2) illustrating a bearing device according to the first embodiment. [Figure 6] This is a cross-sectional view (part 1) of the bearing device shown in Figure 5, perpendicular to the axis m. [Figure 7] Figure 5 shows a magnified view of the area near the first strain gauge. [Figure 8] This is a schematic diagram illustrating a strain detection device according to the first embodiment. [Figure 9] This is a cross-sectional view (part 2) of the bearing device shown in Figure 5, perpendicular to the axis m. [Figure 10] This is a plan view illustrating a strain gauge according to the first embodiment. [Figure 11] This is a cross-sectional view illustrating a strain gauge according to the first embodiment. [Figure 12] This is a cross-sectional view illustrating a motor equipped with a bearing device according to the first embodiment. [Figure 13] This is a cross-sectional view illustrating a bearing device according to a modified example 1 of the first embodiment. [Figure 14] This is a cross-sectional view (part 1) illustrating a bearing device according to a modified example 2 of the first embodiment. [Figure 15] This is a cross-sectional view (part 2) illustrating a bearing device according to a modified example 2 of the first embodiment. [Figure 16] Cross-sectional view (Part 3) illustrating a bearing device according to Modification Example 2 of the First Embodiment. [Figure 17] Partial enlarged view (Part 1) of a gauge fixing member according to Modification Example 3 of the First Embodiment. [Figure 18] Partial enlarged view (Part 2) of a gauge fixing member according to Modification Example 3 of the First Embodiment. [Figure 19] Partial enlarged view (Part 3) of a gauge fixing member according to Modification Example 3 of the First Embodiment. [Figure 20] Partial enlarged view (Part 4) of a gauge fixing member according to Modification Example 3 of the First Embodiment. [Figure 21] Partial enlarged view (Part 5) of a gauge fixing member according to Modification Example 3 of the First Embodiment. [Figure 22] Partial enlarged view (Part 6) of a gauge fixing member according to Modification Example 3 of the First Embodiment. [Figure 23] Partial enlarged view (Part 7) of a gauge fixing member according to Modification Example 3 of the First Embodiment. [Figure 24] Partial enlarged view (Part 8) of a gauge fixing member according to Modification Example 3 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 descriptions may be omitted in some cases.

[0010] 〈First Embodiment〉 (Sensor Unit) FIG. 1 is a perspective view illustrating a sensor unit according to the first embodiment. FIG. 2 is a cross-sectional view illustrating the sensor unit according to the first embodiment, showing a cross-section passing through the central axis of the gauge fixing member 110.

[0011] The sensor unit 100 shown in Figures 1 and 2 is used in combination with a first housing 40 (described later) which is equipped with a first strain gauge 120A and a third strain gauge 120C. The sensor unit 100 includes a gauge fixing member 110, a second strain gauge 120B, a fourth strain gauge 120D, and wiring 130B and 130D. The second strain gauge 120B and the fourth strain gauge 120D are provided on the gauge fixing member 110, which will be described later.

[0012] The gauge fixing member 110 is a cylindrical member attached between the outer circumferential surface of the first housing 40 (described later) and the inner circumferential surface of the second housing 140 (described later). In the examples shown in Figures 1 and 2, the gauge fixing member 110 is, for example, a hollow cylindrical shape with one end and the other end open in the central axis direction. The gauge fixing member 110 has an outer circumferential surface 110a and an inner circumferential surface 110b. It is preferable that the gauge fixing member 110 has higher rigidity than the first housing 40 (described later). Examples of materials for the gauge fixing member 110 include metal materials such as iron-based, aluminum-based, copper-based, and titanium-based materials, as well as ceramic materials and reinforced plastic materials. The thickness of the gauge fixing member 110 can be appropriately determined considering strain transmission and required rigidity, but for example, it may be about 1 mm.

[0013] Furthermore, cylindrical members include, for example, hollow cylindrical members that have been processed in part. Processing refers to cases where a slit, groove, hole, projection, step, etc., is provided in part of the hollow cylindrical member. Also, cylindrical members are not limited to structures where both ends are open, but also include structures where one end is open and the other end is closed.

[0014] The second strain gauge 120B and the fourth strain gauge 120D are provided on the inner circumferential surface 110b of the gauge fixing member 110. The second strain gauge 120B and the fourth strain gauge 120D are fixed to the inner circumferential surface 110b of the gauge fixing member 110, for example, by adhesive.

[0015] The second strain gauge 120B and the fourth strain gauge 120D are positioned at different circumferential positions on the gauge fixing member 110. The second strain gauge 120B and the fourth strain gauge 120D may be positioned at the same position in the central axis direction of the gauge fixing member 110, or they may be positioned at different positions.

[0016] The first strain gauge 120A and the third strain gauge 120C, provided in the first housing 40, are stress sensors, while the second strain gauge 120B and the fourth strain gauge 120D, provided in the gauge fixing member 110, are noise sensors. The stress sensors and noise sensors will be described later.

[0017] Although not shown in Figures 1 and 2, the second strain gauge 120B and the fourth strain gauge 120D each have two electrodes (see Figure 10, etc.). Therefore, each of the wirings 130B and 130D contains two conductive wires that are insulated from each other and connected to the two electrodes of each strain gauge.

[0018] (Bearing device) Figure 3 is a perspective view illustrating a bearing device according to the first embodiment. Figure 4 is a cross-sectional view (part 1) illustrating a bearing device according to the first embodiment, showing a cross-section passing through the axis m of the rotating shaft 20. Figure 5 is a cross-sectional view (part 2) illustrating a bearing device according to the first embodiment, showing a cross-section passing through the axis m of the rotating shaft 20. Figures 3 and 4 show the state before the sensor unit 100 is fixed to the second housing 140, and Figure 5 shows the state after the sensor unit 100 is fixed to the inner circumferential surface of the second housing 140.

[0019] As shown in Figures 3 to 5, the bearing device 1 includes a rotating shaft 20, a first rolling bearing 30A, a second rolling bearing 30B, a first housing 40, and a sensor unit 100. In the bearing device 1, the first housing 40 and the sensor unit 100 are held on the inner circumference side of the second housing 140.

[0020] The rotating shaft 20 is rotatably supported by a first rolling bearing 30A and a second rolling bearing 30B, which are arranged spaced apart from each other in the axial direction m. The first rolling bearing 30A and the second rolling bearing 30B are fixed to a first housing 40, which is a bearing housing, by press-fitting, adhesive, or the like, and are held by the first housing 40. The first housing 40 is a hollow cylindrical member made of a metal such as brass. Preferably, the first housing 40 presses against the outer circumferential surface of the outer ring 31 around its entire circumference.

[0021] The first rolling bearing 30A and the second rolling bearing 30B are held on the inner circumference side of the first housing 40, spaced apart from each other in the axial direction m. The first rolling bearing 30A and the second rolling bearing 30B are positioned, for example, on a stepped portion provided on the inner surface of the first housing 40. In the example shown in Figures 3 to 5, the second rolling bearing 30B is provided on one side in the axial direction m of the first housing 40, and the first rolling bearing 30A is provided on the other side in the axial direction m. Hereafter, for the sake of explanation, the side on which the second rolling bearing 30B is provided will be referred to as the upper side, and the side on which the first rolling bearing 30A is provided as the lower side.

[0022] 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.

[0023] The first housing 40 has a first outer circumferential surface 40a and a second outer circumferential surface 40b. The first outer circumferential surface 40a and the second outer circumferential surface 40b are arranged sequentially from the second rolling bearing 30B side toward the first rolling bearing 30A. The second outer circumferential surface 40b forms the bottom surface of a recess that is recessed from the first outer circumferential surface 40a toward the rotating shaft 20 side.

[0024] A first strain gauge 120A and a third strain gauge 120C, which are stress sensors, are provided on the outer circumference of the first housing 40. Specifically, the first strain gauge 120A and the third strain gauge 120C are positioned at different circumferential locations on the second outer surface 40b of the first housing 40. The first strain gauge 120A and the third strain gauge 120C are positioned, for example, at the same location in the axial direction m. The first strain gauge 120A and the third strain gauge 120C are located in a position that overlaps with the outer surface of the first rolling bearing 30A in a radial view. This position facilitates the transmission of strain generated in the first rolling bearing 30A due to the rotation of the rotating shaft 20.

[0025] Wiring 130A is connected to the electrode of the first strain gauge 120A. Wiring 130C is connected to the electrode of the third strain gauge 120C. Although not shown in Figures 3 to 5, the first strain gauge 120A and the third strain gauge 120C each have two electrodes (see Figure 10, etc.). Therefore, each of the wires 130A and 130C contains two conductive wires that are insulated from each other and connected to the two electrodes of each strain gauge.

[0026] The first housing 40 is press-fitted into the second housing 140, and then the sensor unit 100 is fixed to the second housing 140. At this time, the sensor unit 100 is fitted into one side of the first housing 40 in the axial direction m and fixed to the inner circumferential surface 140a of the second housing 140. There is a gap between the second outer circumferential surface 40b of the first housing 40 and the inner circumferential surface 140a of the second housing, and at least a portion of the sensor unit 100 is positioned in this gap.

[0027] In other words, at least a portion of the gauge fixing member 110 is positioned in the gap between the second outer surface 40b of the first housing 40 and the inner surface 140a of the second housing, and the outer surface 110a of the gauge fixing member 110 is fixed to the inner surface 140a of the second housing 140.

[0028] There is a gap between the second outer surface 40b of the first housing 40 and the inner surface 110b of the gauge fixing member 110, and each strain gauge is placed in this gap. The first strain gauge 120A and the second strain gauge 120B may be placed at different positions in the axial direction m, or at the same position. Similarly, the third strain gauge 120C and the fourth strain gauge 120D may be placed at different positions in the axial direction m, or at the same position.

[0029] The gauge fixing member 110 of the sensor unit 100 is fixed to the inner circumferential surface 140a of the second housing 140 by, for example, press-fitting or adhesive bonding. From the viewpoint of increasing the rigidity of the first housing 40, it is preferable that the gauge fixing member 110 of the sensor unit 100 is fixed to the inner circumferential surface 140a of the second housing 140 by press-fitting.

[0030] As described above, the first strain gauge 120A and the third strain gauge 120C are stress sensors that detect strain occurring in the first rolling bearing 30A, and the second strain gauge 120B and the fourth strain gauge 120D are noise sensors that detect noise.

[0031] Here, a stress sensor is a sensor that primarily detects strain occurring in an object, but it can also detect noise occurring in the vicinity of the object. Similarly, a noise sensor is a sensor that primarily detects noise occurring in the vicinity of an object, but it may also detect strain occurring in the object. The strain detected by a stress sensor is greater than the strain detected by a noise sensor. In contrast, the noise detected by a stress sensor is approximately equal to the noise detected by a noise sensor.

[0032] The strain detected by the first strain gauge 120A and the third strain gauge 120C is greatest on the side of the center of the rolling element 33 (around the point where the distance from the center is minimum). Therefore, as shown in Figure 5, it is preferable to position the first strain gauge 120A and the third strain gauge 120C on the side of the center of the rolling element 33.

[0033] On the other hand, the second strain gauge 120B and the fourth strain gauge 120D are noise sensors, and it is preferable that they do not detect strain as much as possible. For this reason, the second strain gauge 120B and the fourth strain gauge 120D are mounted on a gauge fixing member 110, which is a separate component from the first housing 40, so that the strain of the first housing 40 is not easily transmitted to them.

[0034] Furthermore, it is preferable that the first strain gauge 120A and the third strain gauge 120C are positioned so that the rolling element 33 passes directly beneath each of their respective resistors at the same time. The resistor 123 will be explained separately with reference to Figure 10, etc.

[0035] Figure 6 is a cross-sectional view (part 1) of the bearing device shown in Figure 5, perpendicular to the axis m, and shows a cross-section passing through the center of each rolling element 33 of the first rolling bearing 30A. In the example of Figure 6, the first rolling bearing 30A has 6 rolling elements 33, and the resistors 123 of the first strain gauge 120A and the resistors 123 of the third strain gauge 120C are positioned opposite each other, and the rolling elements 33 pass directly beneath each resistor 123 at the same time.

[0036] In Figure 6, θ is the angle between the center of the resistor 123 of the first strain gauge 120A and the center of the resistor 123 of the third strain gauge 120C, as viewed from the direction of the axis m of the rotation axis 20. In the example in Figure 6, the angle θ between the center of the resistor 123 of the first strain gauge 120A and the center of the resistor 123 of the third strain gauge 120C is 180 degrees.

[0037] However, the preferred arrangement of the first strain gauge 120A and the third strain gauge 120C is not limited to θ = 180 degrees. If N is the number of rolling elements 33 and n is an integer between 1 and (N-1), the first strain gauge 120A and the third strain gauge 120C can be positioned at θ = (360 × n) / N. Note that an error of ±3 degrees is allowed for the angle θ. For example, if θ = 183 degrees or θ = 177 degrees, they are considered to be positioned at θ = (360 × n) / N.

[0038] In the example shown in Figure 6, since N=6, the first strain gauge 120A and the third strain gauge 120C can be placed at positions where θ = 60 degrees, 120 degrees, 180 degrees, 240 degrees, or 300 degrees. In Figure 6, when the position of the first strain gauge 120A is fixed, the preferred positions for placing the third strain gauge 120C are indicated by dashed rectangles.

[0039] Since the second strain gauge 120B and the fourth strain gauge 120D are noise sensors, they can be placed at any position unrelated to the above-mentioned θ, as long as they are provided on the gauge fixing member 110.

[0040] Figure 7 is a magnified view of the vicinity of the first strain gauge shown in Figure 5, etc. As shown in Figure 7, in the first strain gauge 120A, it is preferable that the resistor 123 is positioned with its longitudinal direction (gauge length direction) facing the circumferential direction of the gauge fixing member 110. Since the circumferential direction of the gauge fixing member 110 is more flexible than the axial direction m, a large strain waveform can be obtained by positioning the longitudinal direction of the resistor 123 facing the circumferential direction of the gauge fixing member 110.

[0041] The first strain gauge 120A has a pair of terminals 125 connected to both ends of a resistor 123 via wiring 124, and wiring 130A is electrically connected to each terminal 125 by solder or the like. Wiring 130A may be, for example, a coaxial cable, or it may be a structure in which a solid GND is formed on at least one side of a flexible substrate. The second strain gauge 120B, third strain gauge 120C, and fourth strain gauge 120D shown in Figure 5 etc. have the same structure as the first strain gauge 120A.

[0042] The first strain gauge 120A, the second strain gauge 120B, the third strain gauge 120C, and the fourth strain gauge 120D are affected by electromagnetic noise interference. Therefore, the output of the first strain gauge 120A, the second strain gauge 120B, the third strain gauge 120C, and the fourth strain gauge 120D includes electromagnetic noise in addition to the strain of the first rolling bearing 30A. Electromagnetic noise, in this context, refers to noise generated from the motor's coils, etc., when the bearing device 1 is mounted on a motor.

[0043] However, in the bearing device 1, the second strain gauge 120B and the fourth strain gauge 120D are positioned on a gauge fixing member 110 that does not easily transmit strain. Therefore, the second strain gauge 120B and the fourth strain gauge 120D hardly detect any strain in the first rolling bearing 30A, and the output of the second strain gauge 120B and the fourth strain gauge 120D consists almost entirely of electromagnetic noise.

[0044] As mentioned above, a large strain waveform can be obtained by aligning the longitudinal direction of the resistor 123 with the circumferential direction of the first housing 40. Therefore, in order to further reduce the strain detected by the second strain gauge 120B and the fourth strain gauge 120D, the second strain gauge 120B and the fourth strain gauge 120D may be oriented with the longitudinal direction of the resistor 123 in the direction of axis m.

[0045] Since the first strain gauge 120A, the second strain gauge 120B, the third strain gauge 120C, and the fourth strain gauge 120D are located close to each other, the influence of electromagnetic noise is almost the same. Therefore, by placing the first strain gauge 120A and the third strain gauge 120C in the first housing 40, where strain is easily transmitted, and the second strain gauge 120B and the fourth strain gauge 120D in the gauge fixing member 110, where strain is not easily transmitted, the influence of electromagnetic noise can be eliminated by 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.

[0046] Figure 8 is a schematic diagram illustrating a strain detection device according to the first embodiment. As shown in Figure 8, the strain detection device 3 includes a bearing device 1 and a bridge circuit 2. R1, R2, R3, and R4 correspond to the resistors 123 of the first strain gauge 120A, second strain gauge 120B, third strain gauge 120C, and fourth strain gauge 120D, respectively.

[0047] In other words, in Figure 8, the first strain gauge 120A, the second strain gauge 120B, the third strain gauge 120C, and the fourth strain gauge 120D of the bearing device 1 constitute one of the four sides of the bridge circuit 2. A DC voltage E is supplied between the connection point of resistor R1 and resistor R2, and between the connection point of resistor R3 and resistor R4. As a result, an output voltage e0 can be obtained as the output of the bridge circuit from between the connection point of resistor R1 and resistor R4, and between the connection point of resistor R2 and resistor R3.

[0048] The first strain gauge 120A forms one side of the four sides of the bridge circuit 2 on one side of the first output voltage extraction point, and the fourth strain gauge 120D forms one side of the four sides of the bridge circuit 2 on the other side of the first output voltage extraction point. Furthermore, the second strain gauge 120B forms one side of the four sides of the bridge circuit 2 on the side of the second output voltage extraction point that is connected to the first strain gauge 120A, and the third strain gauge 120C forms one side of the four sides of the bridge circuit on the side of the second output voltage extraction point that is connected to the fourth strain gauge 120D.

[0049] Specifically, for example, in Figure 8, if the connection point between resistors R1 and R4 is the first output voltage extraction point, and the connection point between resistors R2 and R3 is the second output voltage extraction point, then in Figure 8, R1 can be the first strain gauge 120A, R2 the second strain gauge 120B, R3 the third strain gauge 120C, and R4 the fourth strain gauge 120D. However, the same output voltage e0 can be obtained even if the positions of the first strain gauge 120A and the third strain gauge 120C, and the second strain gauge 120B and the fourth strain gauge 120D are swapped.

[0050] Furthermore, in Figure 8, if the connection point between resistors R1 and R4 is the second output voltage extraction point, and the connection point between resistors R2 and R3 is the first output voltage extraction point, then in Figure 8, R1 can be the second strain gauge 120B, R2 the first strain gauge 120A, R3 the fourth strain gauge 120D, and R4 the third strain gauge 120C. However, the same output voltage e0 can be obtained even if the positions of the first strain gauge 120A and the third strain gauge 120C, and the second strain gauge 120B and the fourth strain gauge 120D are swapped.

[0051] For example, if strain ε and electromagnetic noise N are detected in the first strain gauge 120A and the third strain gauge 120C, and only electromagnetic noise N is detected in the second strain gauge 120B and the fourth strain gauge 120D, then the electromagnetic noise N is canceled out, and the output voltage e0 = E / 2 × Ks × ε, where Ks is the gauge factor.

[0052] In this way, by arranging the first strain gauge 120A and the third strain gauge 120C in the first housing 40, which facilitates strain transmission, and arranging the second strain gauge 120B and the fourth strain gauge 120D in the gauge fixing member 110, which does not easily transmit strain, a bearing device 1 can be realized that outputs a signal capable of reducing 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.

[0053] 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.

[0054] Figure 9 is a cross-sectional view (part 2) of the bearing device shown in Figure 5, perpendicular to the axis m, and shows a cross-section passing through the center of each rolling element 33 of the first rolling bearing 30A. The first strain gauge 120A and the third strain gauge 120C may be arranged as shown in Figure 9, unlike in Figure 6. That is, the first strain gauge 120A and the third strain gauge 120C may be arranged such that when a rolling element 33 passes directly below the resistor 123 of the first strain gauge 120A, the resistor 123 of the third strain gauge 120C is located between two adjacent rolling elements 33.

[0055] In the example shown in Figure 9, the first rolling bearing 30A has seven rolling elements 33, and the resistors 123 of the first strain gauge 120A and the resistors 123 of the third strain gauge 120C are positioned opposite each other. In other words, in the example shown in Figure 9, the angle θ between the center of the resistor 123 of the first strain gauge 120A and the center of the resistor 123 of the third strain gauge 120C is 180 degrees.

[0056] However, the preferred arrangement of the first strain gauge 120A and the third strain gauge 120C is not limited to θ = 180 degrees. If N is the number of rolling elements 33 and n is an integer between 0 and (N-1), then the first strain gauge 120A and the third strain gauge 120C can be positioned at θ = (360 × n) / N + 360 / 2N. Note that an error of ±3 degrees is allowed for the angle θ. For example, if θ = 183 degrees or θ = 177 degrees, they are considered to be positioned at θ = (360 × n) / N + 360 / 2N.

[0057] In the example shown in Figure 9, since N=7, the first strain gauge 120A and the third strain gauge 120C can be positioned at a location where θ = approximately 26 degrees, approximately 77 degrees, approximately 129 degrees, 180 degrees, approximately 231 degrees, approximately 283 degrees, or approximately 334 degrees. In Figure 9, when the position of the first strain gauge 120A is fixed, the preferred position for positioning the third strain gauge 120C is indicated by a dashed rectangle.

[0058] Since the second strain gauge 120B and the fourth strain gauge 120D are noise sensors, they can be placed at any position unrelated to the above-mentioned θ, as long as they are provided on the gauge fixing member 110.

[0059] Even when the first strain gauge 120A and the third strain gauge 120C are arranged as shown in Figure 9, the output voltage e0 can still be obtained with the circuit in Figure 8. However, in the circuit in Figure 8, the first strain gauge 120A constitutes one side of the four sides of the bridge circuit 2 on one side of the first output voltage extraction point, and the fourth strain gauge 120D constitutes one side of the four sides of the bridge circuit 2 on the other side of the first output voltage extraction point. Furthermore, the second strain gauge 120B constitutes one side of the four sides of the bridge circuit 2 on the fourth strain gauge 120D side of the second output voltage extraction point, and the third strain gauge 120C constitutes one side of the four sides of the bridge circuit 2 on the first strain gauge 120A side of the second output voltage extraction point.

[0060] Specifically, for example, in Figure 8, if the connection point between resistors R1 and R4 is the first output voltage point, and the connection point between resistors R2 and R3 is the second output voltage point, then in Figure 8, R1 can be the first strain gauge 120A, R2 the third strain gauge 120C, R3 the second strain gauge 120B, and R4 the fourth strain gauge 120D. However, the same output voltage e0 can be obtained even if the positions of the first strain gauge 120A and the third strain gauge 120C, and the second strain gauge 120B and the fourth strain gauge 120D are swapped.

[0061] Furthermore, in Figure 8, if the connection point between resistors R1 and R4 is the second output voltage extraction point, and the connection point between resistors R2 and R3 is the first output voltage extraction point, then in Figure 8, R1 can be the second strain gauge 120B, R2 the fourth strain gauge 120D, R3 the first strain gauge 120A, and R4 the third strain gauge 120C. However, the same output voltage e0 can be obtained even if the positions of the first strain gauge 120A and the third strain gauge 120C, and the second strain gauge 120B and the fourth strain gauge 120D are swapped.

[0062] For example, if strain ε and electromagnetic noise N are detected in the first strain gauge 120A and the third strain gauge 120C, and only electromagnetic noise N is detected in the second strain gauge 120B and the fourth strain gauge 120D, then the electromagnetic noise N is canceled out, and the output voltage e0 = E / 2 × Ks × ε, where Ks is the gauge factor.

[0063] (Strain gauge) Figure 10 is a plan view illustrating a strain gauge according to the first embodiment. Figure 11 is a cross-sectional view illustrating a strain gauge according to the first embodiment, showing a cross-section along line AA in Figure 10. While the first strain gauge 120A will be described below, the second strain gauge 120B, the third strain gauge 120C, and the fourth strain gauge 120D can have the same structure as the first strain gauge 120A. However, each strain gauge may have a partially different structure as needed. For example, the size of the base material, the presence or absence of a cover layer, and other specifications may be changed as necessary.

[0064] Referring to Figures 10 and 11, the first strain gauge 120A includes a base material 121, a functional layer 122, a resistor 123, wiring 124, and a terminal portion 125. However, the functional layer 122 may be provided as needed.

[0065] In the explanation of Figures 10 and 11, for convenience, in the first strain gauge 120A, the side of the base material 121 on which the resistor 123 is provided will be referred to as the upper side or one side, and the side on which the resistor 123 is not provided will be referred to as the lower side or the other side. Also, the surface on which the resistor 123 is provided in each part will be referred to as one surface or the upper surface, and the surface on which the resistor 123 is not provided will be referred to as the other surface or the lower surface. However, the first strain gauge 120A can be used upside down or positioned at any angle. Furthermore, "plan view" refers to viewing the object from the direction normal to the upper surface 121a of the base material 121, and "planar shape" refers to the shape of the object viewed from the direction normal to the upper surface 121a of the base material 121.

[0066] The base material 121 is a member that serves as a base layer for forming the resistor 123, etc., and is flexible. The thickness of the base material 121 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 121 is preferable in terms of the transmission of strain from the surface of the strain-generating body (for example, the outer peripheral surface 110a of the gauge fixing member 110) that is joined to the lower surface of the base material 121 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.

[0067] The base material 121 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.

[0068] Here, "formed from an insulating resin film" does not prevent the base material 121 from containing fillers or impurities in the insulating resin film. For example, the base material 121 may be formed from an insulating resin film containing fillers such as silica or alumina.

[0069] Other materials for the substrate 121 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 121. In this case, an insulating film is formed on the metallic substrate 121.

[0070] The functional layer 122 is formed on the upper surface 121a of the base material 121 as a lower layer of the resistor 123. That is, the planar shape of the functional layer 122 is substantially the same as the planar shape of the resistor 123 shown in Figure 10.

[0071] In this application, the functional layer refers to a layer that has the function of promoting the crystal growth of the resistor 123, which is at least the upper layer. Preferably, the functional layer 122 further has the function of preventing oxidation of the resistor 123 by oxygen and moisture contained in the substrate 121, and the function of improving the adhesion between the substrate 121 and the resistor 123. The functional layer 122 may further have other functions.

[0072] Since the insulating resin film that makes up the base material 121 contains oxygen and moisture, and especially when the resistor 123 contains Cr (chromium), the Cr forms an oxidized film, it is effective for the functional layer 122 to have a function to prevent oxidation of the resistor 123.

[0073] The material of the functional layer 122 is not particularly limited as long as it is a material that has the function of promoting crystal growth of the upper layer resistor 123, and can be appropriately selected according to the purpose. Examples include 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), and 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.

[0074] 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.

[0075] When the functional layer 122 is formed from a conductive material such as a metal or alloy, it is preferable that the thickness of the functional layer 122 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 122, preventing a decrease in strain detection sensitivity.

[0076] When the functional layer 122 is formed from a conductive material such as a metal or alloy, it is more preferable that the thickness of the functional layer 122 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 through the functional layer 122, further preventing a decrease in strain detection sensitivity.

[0077] If the functional layer 122 is formed from a conductive material such as a metal or alloy, it is even more preferable that the thickness of the functional layer 122 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 122.

[0078] When the functional layer 122 is formed from an insulating material such as an oxide or nitride, the thickness of the functional layer 122 is preferably 1 nm to 1 μm. Within this range, the crystal growth of α-Cr can be promoted, and the functional layer 122 can be easily formed without cracking.

[0079] When the functional layer 122 is formed from an insulating material such as an oxide or nitride, the film thickness of the functional layer 122 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 122.

[0080] When the functional layer 122 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 122 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 122.

[0081] The planar shape of the functional layer 122 is patterned to be substantially the same as the planar shape of the resistor shown in Figure 10. However, the planar shape of the functional layer 122 is not limited to being substantially the same as the planar shape of the resistor. If the functional layer 122 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 122 may be formed as a solid block at least in the region where the resistor is formed. Alternatively, the functional layer 122 may be formed as a solid block over the entire upper surface of the substrate 121.

[0082] Furthermore, when the functional layer 122 is formed from an insulating material, forming the functional layer 122 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 122, allowing the heat generated when the resistor heats up to be dissipated towards the base material 121. As a result, the decrease in measurement accuracy due to self-heating of the resistor can be suppressed in the first strain gauge 120A.

[0083] The resistor 123 is a thin film formed in a predetermined pattern on the upper surface of the functional layer 122, and is a sensitive part that undergoes a change in resistance when subjected to strain.

[0084] The resistor 123 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 123 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).

[0085] The following explanation will use the case where the resistor 123 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 122 may be diffused into the Cr multiphase film. In this case, the material constituting the functional layer 122 and nitrogen may form a compound. For example, if the functional layer 122 is made of Ti, the Cr multiphase film may contain Ti or TiN (titanium nitride).

[0086] The thickness of the resistor 123 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 of the resistor 123 is preferable because it improves the crystallinity of the crystals constituting the resistor 123 (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 121 caused by internal stress in the film constituting the resistor 123.

[0087] By forming the resistor 123 on the functional layer 122, the resistor 123 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).

[0088] For example, if the resistor 123 is a Cr multiphase film, a resistor 123 mainly composed of α-Cr (alpha-chromium) can be formed by providing a functional layer 122. Since α-Cr is a stable crystalline phase, the stability of the gauge characteristics can be improved.

[0089] 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 123 is a Cr multiphase film, from the viewpoint of improving gauge characteristics, it is preferable that the resistor 123 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).

[0090] Furthermore, if the resistor 123 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.

[0091] 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.

[0092] 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.

[0093] Furthermore, the gauge characteristics can be improved by the diffusion of the metal (e.g., Ti) constituting the functional layer 122 into the Cr multiphase film. Specifically, the gauge factor of the first strain gauge 120A 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.

[0094] The terminal portion 125 extends from both ends of the resistor 123 via the wiring 124, and in a plan view, it is wider than the resistor 123 and the wiring 124 and is formed in a substantially rectangular shape. The terminal portion 125 is a pair of electrodes for outputting to the outside the change in the resistance value of the resistor 123 caused by strain. The resistor 123 extends from one of the terminal portion 125 and the wiring 124, for example, by folding back in a zigzag pattern, and is connected to the other wiring 124 and terminal portion 125. The upper surface of the terminal portion 125 may be covered with a metal that has better solderability than the terminal portion 125.

[0095] Although the resistor 123, wiring 124, and terminal portion 125 are given different reference numerals for convenience, they can be formed integrally from the same material in the same process.

[0096] A cover layer 126 (insulating resin layer) may be provided on the upper surface 121a of the base material 121 so as to cover the resistor 123 and wiring 124 and expose the terminal portion 125. Providing the cover layer 126 prevents mechanical damage to the resistor 123 and wiring 124. In addition, providing the cover layer 126 protects the resistor 123 and wiring 124 from moisture, etc. The cover layer 126 may be provided so as to cover the entire portion excluding the terminal portion 125.

[0097] The cover layer 126 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.

[0098] To manufacture the first strain gauge 120A, first, a base material 121 is prepared, and a functional layer 122 is formed on the upper surface 121a of the base material 121. The materials and thicknesses of the base material 121 and the functional layer 122 are as described above. However, the functional layer 122 may be provided only if necessary.

[0099] The functional layer 122 can be deposited using a conventional sputtering method, for example, by targeting a raw material capable of forming the functional layer 122 and introducing Ar (argon) gas into a chamber. By using the conventional sputtering method, the functional layer 122 is deposited while etching the upper surface 121a of the substrate 121 with Ar, thus minimizing the amount of functional layer 122 deposited and achieving improved adhesion.

[0100] However, this is just one example of a method for forming the functional layer 122, and the functional layer 122 may be formed by other methods. For example, the upper surface 121a of the substrate 121 may be activated by plasma treatment using Ar or the like before forming the functional layer 122 to improve adhesion, and then the functional layer 122 may be formed in a vacuum by magnetron sputtering.

[0101] Next, a metal layer forming the resistor 123, wiring 124, and terminal portion 125 is formed on the entire upper surface of the functional layer 122. Then, the functional layer 122, resistor 123, wiring 124, and terminal portion 125 are patterned into the planar shape shown in Figure 10 by photolithography. The material and thickness of the resistor 123, wiring 124, and terminal portion 125 are as described above. The resistor 123, wiring 124, and terminal portion 125 can be formed integrally from the same material. The resistor 123, wiring 124, and terminal portion 125 can be deposited, for example, by a magnetron sputtering method targeting a raw material capable of forming the resistor 123, wiring 124, and terminal portion 125. The resistor 123, wiring 124, and terminal portion 125 may also be deposited using reactive sputtering, evaporation, arc ion plating, pulsed laser deposition, etc., instead of magnetron sputtering.

[0102] There are no particular restrictions on the combination of materials for the functional layer 122 and the resistor 123, wiring 124, and terminal portion 125, and they can be appropriately selected according to the purpose. For example, Ti can be used as the functional layer 122, and a Cr multiphase film mainly composed of α-Cr (alpha-chromium) can be formed for the resistor 123, wiring 124, and terminal portion 125.

[0103] In this case, for example, the resistor 123, wiring 124, and terminal portion 125 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 123, wiring 124, and terminal portion 125 can be formed by reactive sputtering with pure Cr as the target, using 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.

[0104] In these methods, the functional layer 122 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 122 into the Cr multiphase film improves the gauge characteristics. For example, the gauge factor of the first strain gauge 120A 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.

[0105] Furthermore, when the resistor 123 is a Cr multiphase film, the functional layer 122 made of Ti has all of the following functions: promoting crystal growth of the resistor 123, preventing oxidation of the resistor 123 by oxygen and moisture contained in the substrate 121, and improving the adhesion between the substrate 121 and the resistor 123. The same applies when Ta, Si, Al, or Fe is used instead of Ti as the functional layer 122.

[0106] Subsequently, if necessary, a cover layer 126 is provided on the upper surface 121a of the base material 121, covering the resistor 123 and wiring 124 and exposing the terminal portion 125, thereby completing the first strain gauge 120A. The cover layer 126 can be manufactured, for example, by laminating a semi-cured thermosetting insulating resin film onto the upper surface 121a of the base material 121 so as to cover the resistor 123 and wiring 124 and exposing the terminal portion 125, and then heating and curing it. Alternatively, the cover layer 126 may be manufactured by applying a liquid or paste-like thermosetting insulating resin to the upper surface 121a of the base material 121 so as to cover the resistor 123 and wiring 124 and exposing the terminal portion 125, and then heating and curing it.

[0107] In this way, by providing a functional layer 122 in the lower layer of the resistor 123, crystal growth of the resistor 123 can be promoted, and a resistor 123 consisting of a stable crystalline phase can be fabricated. As a result, the stability of the gauge characteristics of the first strain gauge 120A can be improved. Furthermore, the diffusion of the material constituting the functional layer 122 into the resistor 123 can improve the gauge characteristics of the first strain gauge 120A.

[0108] Furthermore, the first strain gauge 120A, which uses a Cr multiphase film as the material for the resistor 123, 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 120A 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 120A can be miniaturized to about 0.3mm × 0.3mm.

[0109] As described above, the first strain gauge 120A, which uses a Cr multiphase film as the material for the resistor 123, is small and therefore particularly suitable for use in a bearing device 1 that uses small first rolling bearings 30A and second rolling bearings 30B with a diameter (outer diameter of the outer ring 31) of 30 mm or less. Furthermore, the first strain gauge 120A, which uses a Cr multiphase film as the material for the resistor 123, 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 the first strain gauge 120A, which uses a Cr multiphase film as the material for the resistor 123, a bearing device 1 equipped with the function of accurately detecting strain can be realized.

[0110] (motor) The bearing device 1 can be mounted on a motor. Figure 12 is a cross-sectional view illustrating a motor equipped with the bearing device according to the first embodiment. As shown in Figure 12, 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.

[0111] 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 first housing 40 of the bearing device 1. The stator core 52 is fixed to the outer circumference of the first housing 40 by, for example, press-fitting.

[0112] 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 12, 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.

[0113] 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 first housing 40, and stationary vanes 73 that connect the casing outer frame 71 and the base hub 72.

[0114] In the example shown in Figure 12, 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.

[0115] Furthermore, the first 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. In other words, in the motor 5, the base hub 72 corresponds to the second housing 140 shown in Figure 5, etc.

[0116] In motor 5, the motor section 80 is composed of a stator 50 and a rotor 60. By supplying current to the 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 first housing 40. In other words, motor 5 is a so-called outer rotor type motor.

[0117] In motor 5, the upper side of Figure 12 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.

[0118] When the wiring 130A to 130D shown in Figure 5, etc., has a shielded portion, it is preferable that the first housing 40, to which the first strain gauge 120A, etc., is fixed, be grounded at the same potential as the shielded portion of the wiring 130A, etc., from the viewpoint of suppressing the influence of electromagnetic noise. Also, it is preferable that the gauge fixing member 110, to which the second strain gauge 120B, etc., is fixed, be grounded at the same potential as the shielded portion of the wiring 130B, etc. For example, by bonding the first housing 40 and the shielded portion of the wiring 130A with a conductive adhesive, both can be grounded at the same potential. Alternatively, by bonding the gauge fixing member 110 and the shielded portion of the wiring 130B with a conductive adhesive, both can be grounded 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.

[0119] The wiring 130A to 130D may, for example, be directly routed from the sensor unit 100 to the outside of the motor 5, or it may be electrically connected to a circuit board located inside the motor 5.

[0120] In the bearing device 1, the first housing 40 and the sensor unit 100 are separate parts. Therefore, when assembling the motor 5, each strain gauge mounted on the sensor unit 100 can be easily placed on the motor 5. That is, after press-fitting the first housing 40 into the base hub 72 which will become the second housing, the sensor unit 100 with the strain gauges mounted on it can be attached to the inner circumference side of the base hub 72 which will become the second housing.

[0121] In the bearing device 1 of the motor 5, the first housing 40 has a thin end (the portion of the second outer surface 40b) to secure the area for arranging the first strain gauge 120A and the third strain gauge 120C. As a result, the portion of the first housing 40 that can be press-fitted into the second housing 140 is reduced, and without any countermeasures, the rigidity of the first housing 40 may decrease. However, in the motor 5, the sensor unit 100 is press-fitted into the second housing 140, so the rigidity of the first housing 40 can be increased.

[0122] Furthermore, if the rigidity of the first housing 40, which holds the first rolling bearing 30A and the second rolling bearing 30B, decreases, runout occurs in the rotating shaft 20. As a result, fluctuations occur in the waveforms detected by the first strain gauge 120A and the third strain gauge 120C, which may reduce the accuracy of detecting abnormalities in the first rolling bearing 30A. However, in the motor 5, the sensor unit 100 is press-fitted into the second housing 140 to increase the rigidity of the first housing 40, thereby suppressing the runout of the rotating shaft 20. In addition, by suppressing the runout of the rotating shaft 20, the lifespan of the first rolling bearing 30A and the second rolling bearing 30B can be extended.

[0123] Furthermore, the motor 5 may have a strain detection device 3. That is, in addition to the bearing device 1, the motor 5 can also be equipped with the bridge circuit 2 shown in Figure 8. By monitoring the changes in the strain waveform of the first rolling bearing 30A using the strain detection device 3, it is possible to detect abnormalities in the first rolling bearing 30A and detect abnormalities before the motor 5 experiences rotational malfunctions. 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 state of the first rolling bearing 30A is particularly effective in order to detect abnormalities in the axial flow fan motor as early as possible.

[0124] <Variation 1 of the First Embodiment> Modification 1 of the first embodiment shows an example of a sensor unit having two strain gauges. In Modification 1 of the first embodiment, descriptions of components that are the same as those described in the previously described embodiment may be omitted.

[0125] Figure 13 is a cross-sectional view illustrating a bearing device according to modification 1 of the first embodiment, showing a cross-section passing through the axis m of the rotating shaft 20. Figure 13 shows the state after the sensor unit 100A has been attached to the outer circumferential surface of the first housing 40.

[0126] The bearing device 1A shown in Figure 13 differs from the bearing device 1 (see Figure 5, etc.) in that the sensor unit 100 has been replaced by the sensor unit 100A. The sensor unit 100A has a second strain gauge 120B but does not have a fourth strain gauge 120D. The sensor unit 100A is otherwise the same as the sensor unit 100. Also, the first housing 40 has a first strain gauge 120A but does not have a third strain gauge 120C.

[0127] Even when using only the first strain gauge 120A and the second strain gauge 120B of the bearing device 1A, a strain ε with a good signal-to-noise ratio, where the influence of electromagnetic noise N is removed, can be detected as the output voltage ε0, similar to the first embodiment.

[0128] Specifically, in the bridge circuit shown in Figure 8, R1 is the first strain gauge 120A, R4 is the second strain gauge 120B, and R2 and R3 are fixed resistors R. This allows us to obtain an output voltage e0 as the output of the bridge circuit. For example, if strain ε and electromagnetic noise N are detected by the first strain gauge 120A, and only electromagnetic noise N is detected by the second strain gauge 120B, the electromagnetic noise N is canceled out, and the output voltage e0 = E / 4 × Ks × ε.

[0129] Thus, the sensor unit may have one or two strain gauges. By placing at least one strain gauge each in the first housing 40, which transmits strain easily, and the gauge fixing member 110, which transmits strain poorly, the influence of electromagnetic noise N can be reduced. A sensor unit with two strain gauges is advantageous in that it can obtain a large output voltage e0. On the other hand, a sensor unit with one strain gauge is advantageous in that it can reduce the number of parts. Therefore, it is preferable to select either sensor unit according to the required specifications.

[0130] <Modification 2 of the First Embodiment> Modification 2 of the first embodiment shows an example of a bearing device equipped with two sensor units. In Modification 2 of the first embodiment, descriptions of components that are the same as those described in the previously described embodiment may be omitted.

[0131] Figure 14 is a cross-sectional view (part 1) illustrating a bearing device according to modification 2 of the first embodiment, showing a cross-section passing through the axis m of the rotating shaft 20. Figure 15 is a cross-sectional view (part 2) illustrating a bearing device according to modification 2 of the first embodiment, showing an example of a cross-section along line BB in Figure 14. Figure 16 is a cross-sectional view (part 3) illustrating a bearing device according to modification 2 of the first embodiment, showing another example of a cross-section along line BB in Figure 14. Note that Figure 14 shows the state after the two sensor units 100 have been attached to the inner circumferential surface 140a of the second housing 140.

[0132] As shown in Figures 14 to 16, the bearing device 1B includes a rotating shaft 20, a first rolling bearing 30A, a second rolling bearing 30B, a first housing 40, and two sensor units 100.

[0133] One end of the sensor unit 100 can be fitted into one side of the second housing 140 in the axial direction m (the first rolling bearing 30A side). The structure near one end of the sensor unit 100 is the same as that of the bearing device 1 shown in Figure 5, etc. The other end of the sensor unit 100 can be fitted into the other side of the first housing 40 in the axial direction m (the second rolling bearing 30B side). In other words, one end of the sensor unit 100 is located on the first rolling bearing 30A side, and the other end of the sensor unit 100 is located on the second rolling bearing 30B side.

[0134] In the first housing 40, a first strain gauge 120A and a third strain gauge 120C, which are stress sensors, are provided on the outer circumference of the first rolling bearing 30A and the outer circumference of the second rolling bearing 30B, respectively. One of the first strain gauge 120A and one of the third strain gauge 120C are located in a position that overlaps with the outer circumference of the first rolling bearing 30A in a radial view. The other of the first strain gauge 120A and the other of the third strain gauge 120C are located in a position that overlaps with the outer circumference of the second rolling bearing 30B in a radial view.

[0135] As shown in Figure 15, in the other sensor unit 100 (the sensor unit on the second rolling bearing 30B side), the wires (wiring 130A, etc.) connected to the electrodes of each strain gauge can be routed to the first rolling bearing 30A side, for example, through grooves 40x provided in the first housing 40. Alternatively, as shown in Figure 16, they may be routed to the first rolling bearing 30A side through holes 40y provided in the first housing 40.

[0136] Thus, a sensor unit 100 may be provided to detect the strain of the first rolling bearing 30A and the second rolling bearing 30B, respectively. Alternatively, instead of two sensor units 100, two sensor units 100A as shown in Figure 16 may be used. That is, each sensor unit may have two strain gauges (second strain gauge 120B and fourth strain gauge 120D), or it may have one strain gauge (second strain gauge 120B).

[0137] <Modification 3 of the First Embodiment> Modification 3 of the first embodiment shows an example of a variation in the gauge fixing member. Note that in Modification 3 of the first embodiment, the description of components that are the same as those described in the previously described embodiment may be omitted.

[0138] Figure 17 is a partially enlarged view (part 1) of the gauge fixing member according to Modification 3 of the First Embodiment. Figure 18 is a partially enlarged view (part 2) of the gauge fixing member according to Modification 3 of the First Embodiment. Figure 19 is a partially enlarged view (part 3) of the gauge fixing member according to Modification 3 of the First Embodiment. Figure 20 is a partially enlarged view (part 4) of the gauge fixing member according to Modification 3 of the First Embodiment. Figure 21 is a partially enlarged view (part 5) of the gauge fixing member according to Modification 3 of the First Embodiment.

[0139] As shown in Figure 17, the gauge fixing member 110 may be a flange type with a projection 110c that protrudes circumferentially outward from the other end in the direction of the central axis. By providing the projection 110c, the rigidity of the gauge fixing member 110 can be increased. As a result, the rigidity of the first housing 40 can be increased. Alternatively, as shown in Figure 18, the projection 110c may be structured to fit into a recess provided in the second housing 140. In this case, the lower surface of the projection 110c and the lower surface of the second housing 140 may be located on the same plane.

[0140] In Figures 17 and 18, the gauge fixing member 110 has an open structure on one end and the other end in the central axis direction. However, as shown in Figure 19, the gauge fixing member 110 may have an open structure on one end in the central axis direction and a closed structure on the other end. This structure allows for even greater rigidity of the gauge fixing member 110 than the structures in Figures 17 and 18. As a result, the rigidity of the first housing 40 can be further increased. In the example of Figure 19, one or more holes 110x are provided to secure passages for the wiring of each strain gauge.

[0141] To ensure a passage for the wiring of each strain gauge, a slit 110y extending in the direction of the central axis may be provided in the gauge fixing member 110, as shown in Figure 20. Alternatively, a groove 110z opening on the inner circumferential surface and extending in the direction of the central axis may be provided in the gauge fixing member 110, as shown in Figure 21. Of course, multiple slits or grooves may be provided in the gauge fixing member 110, or a combination of both may be present. Furthermore, slits or grooves may be provided in only a portion of the gauge fixing member 110 in the direction of the central axis.

[0142] Figure 22 is a partially enlarged view (part 6) of a gauge fixing member according to a modification 3 of the first embodiment. As shown in Figure 22, the gauge fixing member 110 has a thin-walled portion and a thick-walled portion in the area that is placed in the gap between the first housing 40 and the second housing 140, and a second strain gauge 120B may be provided on the inner circumferential surface of the thin-walled portion. In the example of Figure 22, the gauge fixing member 110 has a thin-walled portion in the area that overlaps with the first rolling bearing 30A in a radial view, and a thick-walled portion in the area that does not overlap with the first rolling bearing 30A in a radial view.

[0143] In the structure shown in Figure 22, the rigidity of the first housing 40 can be increased by bringing the inner circumferential surface of the thickened portion of the gauge fixing member 110 into contact with the second outer circumferential surface 40b of the first housing 40. In the structure shown in Figure 22, grooves or holes may be provided in the outer circumferential region M1 of the first housing 40 to allow wiring for connection to the strain gauge to pass through. Alternatively, grooves or holes may be provided in the region M2 of the gauge fixing member 110.

[0144] Figure 23 is a partially enlarged view (part 7) of a gauge fixing member according to a modification 3 of the first embodiment. In the example of Figure 23, in the gauge fixing member 110, a portion of the area that overlaps with the first rolling bearing 30A in a radial view is made into a thickened portion, and the area that does not overlap with the first rolling bearing 30A in a radial view is made into a thinned portion. In the structure of Figure 23, by providing a thickened portion in the gauge fixing member 110, the rigidity of the gauge fixing member 110 can be increased. As a result, the rigidity of the first housing 40 can be increased.

[0145] Figure 24 is a partially enlarged view (part 8) of the gauge fixing member according to modification 3 of the first embodiment. As shown in Figure 24, strain is not easily transmitted to the end face of the gauge fixing member 110, so the second strain gauge 120B may be placed on the end face of the gauge fixing member 110. When the second strain gauge 120B is placed on the end face of the gauge fixing member 110, it is preferable to use a flange type with a projection 110c that protrudes circumferentially outward from the lower end of the outer peripheral surface 110a of the gauge fixing member 110 in order to secure the mounting surface for the second strain gauge 120B.

[0146] Furthermore, the structures shown in Figures 17 to 24 can be combined as appropriate to the extent technically feasible.

[0147] 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.

[0148] For example, the present invention can also be applied to bearing devices having only one of the first rolling bearing and the second rolling bearing, strain detection devices, and motors. [Explanation of Symbols]

[0149] 1,1A,1B Bearing device, 2 Bridge circuit, 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 First housing, 40a First outer surface, 40b Second outer surface, 40x Groove, 40y Hole, 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 vane, 80 Motor section, 100,100A Sensor unit, 110 Gauge fixing member, 110a Outer surface, 110b Inner surface, 110c Protrusion, 110x Hole, 110y Slit, 110z Groove, 120A First Strain Gauge, 120B Second Strain Gauge, 120C Third Strain Gauge, 120D Fourth Strain Gauge, 121 Base Material, 122 Functional Layer, 123 Resistor, 124 Wiring, 125 Terminal Section, 126 Cover Layer, 130A, 130B, 130C, 130D Wiring

Claims

1. A bearing device in which a first housing and a cylindrical member are held on the inner circumference side of a second housing, The axis of rotation and A first rolling bearing supporting the aforementioned rotating shaft, A first housing is provided which holds the first rolling bearing on its inner circumference and which has a first strain gauge, which is a stress sensor, on its outer circumference. A cylindrical member is positioned in the gap between the first housing and the second housing, with at least a portion of it being placed there, and its outer surface is fixed to the inner surface of the second housing. The device comprises a second strain gauge, which is a noise sensor, provided on the inner circumferential surface of the cylindrical member, The first strain gauge is positioned so as to overlap with the outer surface of the first rolling bearing in a radial view. A bearing device in which there is a gap between the outer circumferential surface of the first housing and the inner circumferential surface of the cylindrical member on which the second strain gauge is provided.

2. The invention further comprises a second rolling bearing in addition to the first rolling bearing, The first housing holds the first rolling bearing and the second rolling bearing on its inner circumference, and the first strain gauge, which is a stress sensor, is provided on the outer circumference of the first rolling bearing and the outer circumference of the second rolling bearing, respectively. The device has two of the aforementioned cylindrical members, The first rolling bearing and the second rolling bearing each have rolling elements, One of the cylindrical members is positioned on the first rolling bearing side, The other end of the cylindrical member is positioned on the second rolling bearing side. One of the first strain gauges is positioned so as to overlap with the outer surface of the first rolling bearing in a radial view. The bearing device according to claim 1, wherein the other end of the first strain gauge is located in a position that overlaps with the outer circumferential surface of the second rolling bearing in a radial view.

3. A third strain gauge, which is a stress sensor, is further provided on the outer circumference of the first housing. The cylindrical member is further provided with a fourth strain gauge, which is a noise sensor. The first rolling bearing has rolling elements, The bearing device according to claim 1, wherein the third strain gauge is located in a position that overlaps with the outer circumferential surface of the first rolling bearing in a radial view.

4. The invention further comprises a second rolling bearing in addition to the first rolling bearing, The first housing holds the first rolling bearing and the second rolling bearing on its inner circumference, and the first strain gauge and the third strain gauge are provided on the outer circumference of the first rolling bearing and the outer circumference of the second rolling bearing, respectively. The device has two of the aforementioned cylindrical members, The first rolling bearing and the second rolling bearing each have rolling elements, One of the cylindrical members is positioned on the first rolling bearing side, The other end of the cylindrical member is positioned on the second rolling bearing side. One of the first strain gauges and one of the third strain gauges are positioned so as to overlap with the outer surface of the first rolling bearing in a radial view. The bearing device according to claim 3, wherein the other of the first strain gauge and the other of the third strain gauge are located in a position that overlaps with the outer circumferential surface of the second rolling bearing in a radial view.

5. The first strain gauge has a first resistor which serves as a sensing element, The third strain gauge has a third resistor which acts as a sensing element, The first strain gauge and the third strain gauge are positioned so that the rolling element passes directly beneath the first and third resistors at the same time. The bearing device according to claim 3 or 4, wherein, when viewed from the axial direction of the rotation shaft, the angle θ between the center of the first resistor and the center of the third resistor is θ = (360 × n) / N, where N is the number of rolling elements and n is an integer between 1 and (N-1).

6. The first strain gauge has a first resistor which serves as a sensing element, The third strain gauge has a third resistor which acts as a sensing element, The first strain gauge and the third strain gauge are arranged such that when the rolling element passes directly beneath the first resistor, the third resistor is positioned between two adjacent rolling elements. The bearing device according to claim 3 or 4, wherein, when viewed from the axial direction of the rotation shaft, the angle θ between the center of the first resistor and the center of the third resistor is θ = (360 × n) / N + 360 / 2N, where N is the number of rolling elements and n is an integer between 0 and (N-1) inclusive.

7. The bearing device according to claim 1 or 2, and a bridge circuit, The first strain gauge constitutes one of the four sides of the bridge circuit, on one side of the first 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 other side of the first output voltage extraction point.

8. The bearing device according to claim 5 and the bridge circuit are provided, The first strain gauge constitutes one of the four sides of the bridge circuit, on one side of the first output voltage extraction point. The fourth strain gauge constitutes one of the four sides of the bridge circuit, on the other side of the first output voltage extraction point. The second strain gauge constitutes one of the four sides of the bridge circuit on the side of the second output voltage extraction point that is on the side of the first strain gauge. The third strain gauge is a strain detection device that forms one of the four sides of the bridge circuit on the side of the second output voltage extraction point that is the fourth strain gauge.

9. The bearing device according to claim 6 and the bridge circuit are provided, The first strain gauge constitutes one of the four sides of the bridge circuit, on one side of the first output voltage extraction point. The fourth strain gauge constitutes one of the four sides of the bridge circuit, on the other side of the first output voltage extraction point. The second strain gauge constitutes one of the four sides of the bridge circuit on the side of the second output voltage extraction point that is connected to the fourth strain gauge. The third strain gauge is a strain detection device that forms one of the four sides of the bridge circuit on the side of the second output voltage extraction point that is on the first strain gauge side.

10. A motor having a bearing device according to any one of claims 1 to 6.

11. A motor having a strain detection device according to any one of claims 7 to 9.

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