JP2024010250A - motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor having a structure which enables a strain gauge to be arranged easily.

SOLUTION: A motor has: a rolling bearing which supports a rotor shaft in a rotatable state; a bearing housing which holds the rolling bearing; and a sensor unit. The sensor unit includes: an annular member fixed to an outer peripheral surface of the bearing housing; and a strain gauge fixed to the annular member and including a resistive element which detects a strain of the rolling bearing.

SELECTED DRAWING: Figure 4

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a motor.

In a motor equipped with a rolling bearing, when the motor rotates, the sphere inside the rolling bearing rotates, giving a slight strain to the rolling bearing. A motor having a sensor for detecting such strain has been proposed. A sensor that detects strain is provided, for example, between a side surface of a rolling bearing in the rotation axis direction and a housing of a motor (see, for example, Patent Document 1).

JP 2019-215057 Publication

However, for example, when using a strain gauge as a sensor for detecting strain, it is extremely difficult to arrange the strain gauge at a predetermined position inside the motor because it requires attachment to a narrow and curved surface.

The present invention has been made in view of the above points, and an object of the present invention is to provide a motor having a structure in which strain gauges can be easily arranged.

This motor includes a rolling bearing that rotatably supports a rotor shaft, a bearing housing that holds the rolling bearing, and a sensor unit, and the sensor unit is fixed to the outer peripheral surface of the bearing housing. and a strain gauge that is fixed to the annular member and includes a resistor that detects strain in the rolling bearing.

According to the disclosed technology, it is possible to provide a motor having a structure in which strain gauges can be easily arranged.

FIG. 1 is a cross-sectional view illustrating a motor according to a first embodiment. FIG. 3 is a partially enlarged sectional view of the vicinity of the rotor shaft of the motor according to the first embodiment. FIG. 3 is a partially enlarged plan view of section C in FIG. 2; FIG. 1 is a perspective view illustrating a sensor unit according to a first embodiment. FIG. 2 is a plan view illustrating a strain gauge according to the first embodiment. FIG. 1 is a cross-sectional view illustrating a strain gauge according to a first embodiment. FIG. 7 is a perspective view illustrating a sensor unit according to Modification 1 of the first embodiment. FIG. 7 is a perspective view illustrating a sensor unit according to a second modification of the first embodiment. FIG. 7 is a plan view illustrating a sensor unit according to a second modification of the first embodiment. FIG. 3 is a diagram (part 1) illustrating variations in the planar shape of the groove 110y. FIG. 7 is a diagram (part 2) illustrating variations in the planar shape of the groove 110y. FIG. 7 is a perspective view illustrating a sensor unit according to modification 3 of the first embodiment. FIG. 7 is a plan view illustrating a sensor unit according to a third modification of the first embodiment. FIG. 3 is a diagram (part 1) illustrating variations in the planar shape of the groove 110z. FIG. 7 is a diagram (part 2) illustrating variations in the planar shape of the groove 110z. FIG. 7 is a diagram (part 3) illustrating variations in the planar shape of the groove 110z.

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

<First embodiment>
(Overall structure of motor)
FIG. 1 is a cross-sectional view illustrating a motor according to a first embodiment. FIG. 2 is a partially enlarged sectional view of the vicinity of the rotor shaft of the motor according to the first embodiment. 3 is a partially enlarged plan view of section C in FIG. 2. FIG. FIG. 4 is a perspective view illustrating the sensor unit according to the first embodiment. In addition, in FIG. 3, the rolling bearing is illustrated in a simplified manner, and illustration of some members is omitted. Moreover, in FIG. 4, the bearing housing and the sensor unit are shown shifted in position from each other.

As shown in FIGS. 1 to 4, the motor 1 includes an impeller 10, a rotor shaft 20, a rolling bearing 30, a bearing housing 40, a stator 50, a rotor 60, a casing 70, and a sensor unit 100. It is an axial fan motor with.

The impeller 10 has a rotor housing 11 and blades 12 provided on the outer periphery of the rotor housing 11. A rotor shaft 20 having a rotation axis m is fixed to the center of the impeller 10. The rotor shaft 20 is rotatably supported by two rolling bearings 30 arranged near both ends in the longitudinal direction.

The rolling bearing 30 has an outer ring 31, an inner ring 32, and a plurality of rolling elements 33. The outer ring 31 is a cylindrical structure whose central axis is the rotation axis m. The inner ring 32 is a cylindrical structure disposed on the inner peripheral side of the outer ring 31 and coaxially with the outer ring 31 . Each of the plurality of rolling elements 33 is a spherical body disposed within a track formed between the outer ring 31 and the inner ring 32. A lubricant such as grease is sealed inside the raceway.

The rolling bearing 30 is fixed to the bearing housing 40 by press fitting, adhesive, etc., and is held by the bearing housing 40. The bearing housing 40 presses the outer peripheral surface of the outer ring 31 over the entire circumference. The bearing housing 40 can be made of metal such as brass, for example.

The stator 50 includes an insulator 51, a stator core 52, and a coil 53, and is arranged around the outer periphery of the bearing housing 40. The stator core 52 is, for example, fixed to the outer periphery of the bearing housing 40 by press fitting or the like.

The rotor 60 includes a rotor yoke 61 that is integrally provided inside the rotor housing 11 and a rotor magnet 62 that is attached to the inside of the rotor yoke 61. In the example shown in FIG. 1, the rotor yoke 61 is integrally provided inside the rotor housing 11, but the rotor yoke 61 is not limited to this, and the rotor yoke 61 may be installed inside the rotor housing 11. Further, although the rotor shaft 20 is attached to the rotor yoke 61 and fixed at the center of the rotor housing 11, the rotor shaft 20 may be fixed directly to the rotor housing 11.

The casing 70 includes a casing outer frame 71 that covers the outer periphery of the impeller 10, a base hub 72 that fixes the bearing housing 40, and stationary blades 73 that connect the casing outer frame 71 and the base hub 72. .

In addition, in the example of FIG. 1, the case where the casing outer frame 71 and the base part hub 72 are connected by the stationary blade 73 is shown, but the casing outer frame 71 and the base part hub 72 are connected to each other by the connecting shaft. They may also be connected in a rod-like structure.

Further, the bearing housing 40 may be fixed so as to be integrated with the base hub 72 when the casing 70 is injection molded with resin, but the casing 70 may be molded first and the base hub hub 72 may be fixed afterwards. It may be fixed to the part 72.

In the motor 1, the stator 50 and the rotor 60 constitute a motor section 80, and by supplying current to the coil 53 from a power supply section (not shown), the rotor is rotatably supported within the bearing housing 40. The impeller 10 rotates with the central axis of the shaft 20 serving as a rotation axis m. That is, the motor 1 is a so-called outer rotor type motor.

In the motor 1, the upper side in FIG. 1 is the suction port side, and the lower side is the outlet side. Therefore, in the motor 1, the impeller 10 is provided on the air inlet side of the casing outer frame 71, and the base hub 72 is provided on the air outlet side.

Sensor unit 100 includes a sensor ring 110 and a strain gauge 120. The sensor ring 110 is an annular member, for example, in the shape of a hollow cylinder. The sensor ring 110 may be, for example, a hollow cylindrical member that is partially processed. Machining refers to, for example, a case where a groove, hole, protrusion, step, etc. are provided in a part of the sensor ring 110. The sensor ring 110 has an outer peripheral surface 110a and an inner peripheral surface 110b.

The sensor ring 110 is fixed to the outer peripheral surface 40a of the bearing housing 40. The sensor ring 110 is, for example, press-fitted into the outer peripheral side of the bearing housing 40. In this case, the outer peripheral surface 40a of the bearing housing 40 and the inner peripheral surface 110b of the sensor ring 110 are in contact with each other. The sensor ring 110 may be fixed to the outer peripheral surface 40a of the bearing housing 40 using an adhesive, for example. In this case, the outer peripheral surface 40a of the bearing housing 40 and the inner peripheral surface 110b of the sensor ring 110 are opposed to each other with an adhesive interposed therebetween.

From the viewpoint of improving strain transmissibility, a method of fixing the sensor ring 110 by press-fitting is preferable to a method of fixing the sensor ring 110 to the outer circumferential surface 40a of the bearing housing 40 with an adhesive. When using an adhesive, it is preferable to use an adhesive that has relatively high hardness after curing and is as thin as possible.

The sensor ring 110 can be made of metal such as brass, stainless steel, aluminum, etc., for example. Considering thermal expansion, the sensor ring 110 is preferably made of the same material as the bearing housing 40. The thickness of the sensor ring 110 can be appropriately determined in consideration of strain transmissibility and required rigidity.

In order to position the sensor ring 110 in the direction of the rotation axis m, a step 40z is provided on the outer peripheral surface 40a of the bearing housing 40. However, this is not essential; for example, the upper end of the sensor ring 110 in the direction of the rotation axis m may be fixed flush with the upper end of the bearing housing 40 in the direction of the rotation axis m, without providing the step 40z. You can. Alternatively, it is also possible to position the sensor ring 110 in the direction of the rotation axis m depending on the shape of the jig into which the sensor ring 110 is press-fitted.

As shown in FIG. 4, in the motor 1, a sensor unit 100 having a strain gauge 120 fixed to the outer peripheral surface 110a of a sensor ring 110 is manufactured in advance, and the sensor unit 100 is fixed to the outer peripheral surface 40a of a bearing housing 40 by press fitting or the like. can.

The strain gauge 120 is fixed to the outer peripheral surface 110a of the sensor ring 110 with an adhesive or the like. The strain gauge 120 is a sensor that includes a resistor 123 that detects strain in the rolling bearing 30 (for example, strain in the outer ring 31).

The strain to be detected by the strain gauge 120 is largest on the side of the center of the rolling element 33 (around the point where the distance from the center is the minimum), so the strain gauge 120 detects the strain on the side of the center of the rolling element 33. It is preferable to place the Note that applying an appropriate preload to the outer ring 31 and the inner ring 32 can contribute to improving the runout accuracy of the rotating shaft and reducing vibration and noise. When such a preload is applied, it is preferable to arrange the strain gauge 120 on the preload side.

The strain gauge 120 has a pair of terminal portions 125 connected to both ends of the resistor 123 via wiring 124, and a wiring 90 is electrically connected to each terminal portion 125 by solder or the like. ing. The wiring 90 is, for example, a wire, a flexible substrate, or the like.

The wiring 90 passes through a notch 52x (a recess for passing the wiring) provided on the inner periphery of the stator core 52, and is drawn out to the lower side in the axial direction than the stator core 52, that is, to the outside of the motor 1. The notch 52x can be, for example, an elongated recess provided substantially parallel to the rotation axis m.

In FIG. 2, the wiring 90 electrically connected to the strain gauge 120 passes through a notch 52x provided on the inner periphery of the stator core 52, is pulled out axially lower than the stator core 52, and is connected to the outside of the motor 1. is drawn directly from the However, the wiring 90 electrically connected to the strain gauge 120 passes through a notch 52x provided on the inner periphery of the stator core 52, is pulled out axially lower than the stator core 52, and further It may be electrically connected to a circuit board 95 disposed inside the motor 1 through holes or grooves provided in the motor 1 .

Since the wiring 90 is subject to interference from electromagnetic noise generated from the coil 53 and the like, it is preferable that at least a portion passing through the notch 52x is shielded. The wiring 90 may be, for example, a coaxial cable, or may have a structure in which a solid GND is formed on at least one side of a flexible substrate. From the viewpoint of suppressing the influence of electromagnetic noise, it is preferable that the bearing housing 40 to which the strain gauge 120 is fixed is connected to GND, which has the same potential as the shield portion of the wiring 90.

By disposing the strain gauge 120 on the outer peripheral surface 110a of the sensor ring 110 fixed to the outer peripheral surface 40a of the bearing housing 40, strain in the rolling bearing 30 is transmitted to the strain gauge 120 via the bearing housing 40 and the sensor ring 110. , can be detected by the strain gauge 120. In this embodiment, the strain gauge 120 detects strain in the rolling bearing 30 as a change in the resistance value of the resistor 123.

Note that in the strain gauge 120, the resistor 123 is arranged with its longitudinal direction (gauge length direction) facing the circumferential direction of the sensor ring 110. Since the sensor ring 110 expands and contracts more easily in the circumferential direction than in the axial direction, a large strain waveform can be obtained by arranging the resistor 123 with its longitudinal direction facing the circumferential direction of the sensor ring 110.

In this way, in the motor 1, since the sensor unit 100 is fixed to the outer circumferential surface 40a of the bearing housing 40, which is a position where strain can be easily detected, the strain gauge 120 of the sensor unit 100 can detect even the slightest strain. That is, if the outer ring 31 of the rolling bearing 30 is even slightly distorted, the bearing housing 40 and the sensor ring 110 are also distorted, so this slight distortion can be detected by the strain gauge 120 fixed to the outer peripheral surface 110a of the sensor ring 110. .

The state of the rolling bearing 30 can be monitored by subjecting the strain waveform obtained between the terminal portions 125 of the strain gauge 120 to, for example, FFT analysis (fast Fourier transformation). Therefore, by monitoring changes in the strain waveform, it is possible to detect an abnormality in the rolling bearing 30, and to detect the abnormality before the motor 1 causes a rotational malfunction. For example, an axial fan motor used for cooling servers is constantly operating, and if it stops even temporarily, the cooling capacity decreases. In this case, it is particularly effective to monitor the state of the rolling bearing 30 because it is desired to detect an abnormality in the axial fan motor as soon as possible.

In the motor 1, the strain gauge 120 is arranged on the outer circumferential surface 110a of the sensor ring 110, but for example, it is also possible to arrange the strain gauge 120 on the rolling bearing 30 or the bearing housing 40. However, these methods are not preferable because it is difficult to assemble the motor and productivity is low.

That is, it is difficult to arrange the strain gauge 120 on the fixed rolling bearing 30 later. Furthermore, even if the strain gauge 120 is placed in advance on the rolling bearing 30, workability will be poor since the rolling bearing 30 must be fixed while assembling the motor while being careful not to break the wiring. Similarly, when the strain gauge 120 is disposed on the outer peripheral surface of the bearing housing 40, assembly is also difficult.

On the other hand, the motor 1 has a structure in which the strain gauge 120 can be easily arranged. That is, in the motor 1, the sensor unit 100 in which the strain gauge 120 is fixed to the outer peripheral surface 110a of the sensor ring 110 is manufactured in advance, and the sensor unit 100 can be fixed to the outer peripheral surface 40a of the bearing housing 40 by a simple process such as press-fitting. . Therefore, it is easy to manufacture the motor 1 having the strain gauge 120, and the productivity is excellent.

Furthermore, if the strain gauge 120 is to be disposed on the outer peripheral surface 40a of the bearing housing 40, in order to avoid interference with other members, a concave portion may be provided in the outer peripheral surface 40a, and the strain gauge 120 may be fixed within the recess. . However, if a recess is provided in the outer circumferential surface 40a of the bearing housing 40, the rigidity of the shaft may decrease, which may affect the life of the rolling bearing 30.

Since the motor 1 uses the sensor unit 100 in which the strain gauge 120 is fixed to the outer circumferential surface 110a of the sensor ring 110, there is no need to provide a recess in the outer circumferential surface 40a of the bearing housing 40. Therefore, in the motor 1, the rigidity of the shaft can be maintained and the life of the rolling bearing 30 can be extended. As a result, in the motor 1, the state of the rolling bearing 30 can be monitored stably.

Further, since the motor 1 uses the sensor unit 100 in which the strain gauge 120 is fixed to the outer peripheral surface 110a of the sensor ring 110, the position of the strain gauge 120 can be easily controlled and the strain gauge 120 can be placed at a desired position. Furthermore, in the motor 1, since the sensor unit 100 in which the strain gauge 120 is fixed to the outer peripheral surface 110a of the sensor ring 110 is prepared in advance, the fixing strength of the strain gauge 120 can be easily controlled.

Further, in the motor 1, the wiring 90 is passed through a notch 52x formed on the inner circumference of the stator core 52, and at least a portion of the wiring 90 passing through the notch 52x is shielded. As a result, the influence of electromagnetic noise can be significantly suppressed compared to, for example, the case where the wiring 90 is passed outside the stator core 52. As a result, the accuracy of abnormality detection of the rolling bearing 30 can be improved.

(strain gauge)
FIG. 5 is a plan view illustrating the strain gauge according to the first embodiment. FIG. 6 is a cross-sectional view illustrating the strain gauge according to the first embodiment, and shows a cross section taken along line AA in FIG. Referring to FIGS. 5 and 6, the strain gauge 120 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 necessary.

In this embodiment, for convenience, in the strain gauge 120, the side of the base material 121 where the resistor 123 is provided is referred to as the upper side or one side, and the side where the resistor 123 is not provided is referred to as the lower side or the other side. shall be. Moreover, the surface on the side where the resistor 123 of each part is provided is defined as one surface or the top surface, and the surface on the side where the resistor 123 is not provided is defined as the other surface or the bottom surface. However, the strain gauge 120 can be used upside down or placed at any angle. In addition, plan view refers to the object viewed from the normal direction of the upper surface 121a of the base material 121, and planar shape refers to the shape of the object viewed from the normal direction to the upper surface 121a of the base material 121. shall be.

The base material 121 is a member that becomes a base layer for forming the resistor 123 and the like, and has flexibility. The thickness of the base material 121 is not particularly limited and can be appropriately selected depending on the purpose, and may be, for example, about 5 μm to 500 μm. In particular, it is preferable that the thickness of the base material 121 is from 5 μm to 200 μm in terms of strain transmission from the sensor ring 110 bonded to the lower surface of the base material 121 via the adhesive layer and dimensional stability against the environment. A thickness of 10 μm or more is more preferable from the viewpoint of insulation properties.

The base material 121 is made of, for example, PI (polyimide) resin, epoxy resin, PEEK (polyetheretherketone) resin, PEN (polyethylene naphthalate) resin, PET (polyethylene terephthalate) resin, PPS (polyphenylene sulfide) resin, polyolefin resin, etc. It can be formed from an insulating resin film. Note that the film refers to a member having a thickness of about 500 μm or less and having flexibility.

Here, "formed from an insulating resin film" does not prevent the base material 121 from containing fillers, impurities, etc. in the insulating resin film. The base material 121 may be formed, for example, from an insulating resin film containing filler such as silica or alumina.

Examples of materials other than resin for the base material 121 include SiO ₂ , ZrO ₂ (including YSZ), Si, Si ₂ N ₃ , Al ₂ O ₃ (including sapphire), ZnO, perovskite ceramics (CaTiO ₃ , Examples include crystalline materials such as BaTiO ₃ ), and further examples include amorphous glass. Further, as the material of the base material 121, metals such as aluminum, aluminum alloy (duralumin), titanium, etc. may be used. In this case, for example, an insulating film is formed on the metal base material 121.

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 FIG.

In the present application, the functional layer refers to a layer having a function of promoting at least crystal growth of the resistor 123, which is the upper layer. It is preferable that the functional layer 122 further has a function of preventing oxidation of the resistor 123 due to oxygen and moisture contained in the base material 121 and a function of improving the adhesion between the base material 121 and the resistor 123. . Functional layer 122 may further include other functions.

Since the insulating resin film constituting the base material 121 contains oxygen and moisture, especially when the resistor 123 contains Cr (chromium), Cr forms a self-oxidation film, so the functional layer 122 prevents the oxidation of the resistor 123. It is effective to have a function to prevent this.

The material of the functional layer 122 is not particularly limited as long as it has the function of promoting crystal growth of the resistor 123, which is the upper layer, and can be selected as appropriate depending on 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), Fe (iron), Mo (molybdenum), W (tungsten), Ru (ruthenium), Rh (rhodium), Re (rhenium), Os (osmium), Ir One or more types selected from the group consisting of (iridium), Pt (platinum), Pd (palladium), Ag (silver), Au (gold), Co (cobalt), Mn (manganese), and Al (aluminum). metals of this group, alloys of any metals of this group, or compounds of any metals of this group.

Examples of the above-mentioned alloy include FeCr, TiAl, FeNi, NiCr, and CrCu. Moreover, examples of the above-mentioned compounds include TiN, TaN, Si ₃ N ₄ , TiO ₂ , Ta ₂ O ₅ , SiO ₂ and the like.

When the functional layer 122 is formed from a conductive material such as a metal or an alloy, the thickness of the functional layer 122 is preferably 1/20 or less of the thickness of the resistor. Within this range, α-Cr crystal growth can be promoted, and a portion of the current flowing through the resistor can be prevented from flowing into the functional layer 122, thereby preventing deterioration of strain detection sensitivity.

When the functional layer 122 is formed from a conductive material such as a metal or an alloy, the thickness of the functional layer 122 is more preferably 1/50 or less of the thickness of the resistor. Within this range, α-Cr crystal growth can be promoted, and a portion of the current flowing through the resistor can be prevented from flowing into the functional layer 122, thereby preventing deterioration in strain detection sensitivity.

When the functional layer 122 is formed of a conductive material such as a metal or an alloy, it is more preferable that the thickness of the functional layer 122 is 1/100 or less of the thickness of the resistor. Within this range, it is possible to further prevent a portion of the current flowing through the resistor from flowing into the functional layer 122 and reducing the strain detection sensitivity.

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

When the functional layer 122 is formed from an insulating material such as an oxide or a nitride, the thickness of the functional layer 122 is more preferably 1 nm to 0.8 μm. Within this range, α-Cr crystal growth can be promoted, and the functional layer 122 can be formed more easily without cracking.

When the functional layer 122 is formed from an insulating material such as an oxide or a nitride, the thickness of the functional layer 122 is more preferably 1 nm to 0.5 μm. Within this range, α-Cr crystal growth can be promoted and the functional layer 122 can be formed more easily without cracking.

Note that the planar shape of the functional layer 122 is patterned to be substantially the same as the planar shape of the resistor shown in FIG. 5, for example. However, the planar shape of the functional layer 122 is not limited to being substantially the same as the planar shape of the resistor. When the functional layer 122 is formed of an insulating material, it does not need to be patterned to have the same planar shape as the resistor. In this case, the functional layer 122 may be formed in a solid shape at least in the region where the resistor is formed. Alternatively, the functional layer 122 may be formed in a solid manner over the entire upper surface of the base material 121.

In addition, when the functional layer 122 is formed of an insulating material, the thickness of the functional layer 122 is formed relatively thick to be 50 nm or more and 1 μm or less, and is formed in a solid shape. Since the surface area increases, heat generated by the resistor can be radiated to the base material 121 side. As a result, in the strain gauge 120, deterioration in measurement accuracy due to self-heating of the resistor can be suppressed.

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

The resistor 123 can be formed of, for example, a material containing Cr (chromium), a material containing Ni (nickel), or a material containing both Cr and Ni. That is, the resistor 123 can be formed from a material containing at least one of Cr and Ni. Examples of materials containing Cr include a Cr mixed phase film. Examples of materials containing Ni include Cu--Ni (copper nickel). An example of a material containing both Cr and Ni is Ni--Cr (nickel chromium).

Hereinafter, the case where the resistor 123 is a Cr mixed phase film will be described as an example. Here, the Cr mixed phase film is a film in which Cr, CrN, Cr ₂ N, etc. are mixed in phase. The Cr mixed phase film may contain inevitable impurities such as chromium oxide. Further, a part of the material constituting the functional layer 122 may be diffused into the Cr mixed phase 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 mixed phase film may contain Ti or TiN (titanium nitride).

The thickness of the resistor 123 is not particularly limited and can be appropriately selected depending on the purpose, and may be, for example, about 0.05 μm to 2 μm. In particular, it is preferable that the thickness of the resistor 123 is 0.1 μm or more since the crystallinity of the crystal forming the resistor 123 (for example, the crystallinity of α-Cr) is improved, and that the thickness of the resistor 123 is 1 μm or less. This is more preferable in that cracks in the film caused by internal stress in the film constituting the film 123 and warping from the base material 121 can be reduced.

By forming the resistor 123 on the functional layer 122, the resistor 123 can be formed with a stable crystalline phase, improving the stability of gauge characteristics (gauge factor, temperature coefficient of gauge factor TCS, and temperature coefficient of resistance TCR). can.

For example, when the resistor 123 is a Cr mixed phase film, by providing the functional layer 122, the resistor 123 whose main component is α-Cr (alpha chromium) can be formed. Since α-Cr is a stable crystalline phase, the stability of gauge characteristics can be improved.

Here, the term "main component" means that the target substance occupies 50% by mass or more of all the substances constituting the resistor. When the resistor 123 is a Cr mixed phase film, the resistor 123 preferably contains α-Cr in an amount of 80% by weight or more, more preferably 90% by weight or more, from the viewpoint of improving gauge characteristics. Note that α-Cr is Cr having a bcc structure (body-centered cubic lattice structure).

Further, when the resistor 123 is a Cr multiphase film, it is preferable that the CrN and Cr ₂ N contained in the Cr multiphase film are 20% by weight or less. When the Cr mixed phase film contains 20% by weight or less of CrN and Cr ₂ N, a decrease in gauge factor can be suppressed.

Further, the proportion of Cr ₂ N in CrN and Cr ₂ N 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 Cr ₂ N in CrN and Cr ₂ N is 90% by weight or more and less than 95% by weight, the decrease in TCR (negative TCR) becomes more pronounced due to Cr ₂ N having semiconducting properties. . Furthermore, by reducing the amount of ceramic, brittle fracture can be reduced.

On the other hand, if a trace amount of N ₂ or atomic N is mixed or present in the film, it escapes from the film due to the external environment (for example, under a high temperature environment), causing a change in film stress. By creating chemically stable CrN, a stable strain gauge can be obtained without generating the above-mentioned unstable N.

Furthermore, the gauge characteristics can be improved by diffusing the metal (for example, Ti) constituting the functional layer 122 into the Cr mixed phase film. Specifically, the gauge factor of the strain gauge 120 can be set to 10 or more, 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.

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

Note that although the resistor 123, the wiring 124, and the terminal portion 125 are given different symbols for convenience, they can be integrally formed using the same material in the same process.

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 the wiring 124 and expose the terminal portion 125. By providing the cover layer 126, mechanical damage to the resistor 123 and the wiring 124 can be prevented. Further, by providing the cover layer 126, the resistor 123 and the wiring 124 can be protected from moisture and the like. Note that the cover layer 126 may be provided so as to cover the entire portion except the terminal portion 125.

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 (eg, silicone resin, polyolefin resin). The cover layer may contain filler or pigment. The thickness of the cover layer is not particularly limited and can be appropriately selected depending on the purpose, and may be, for example, about 2 μm to 30 μm.

In order to manufacture the strain gauge 120, 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 as necessary.

The functional layer 122 can be formed into a vacuum film by, for example, a conventional sputtering method using a raw material capable of forming the functional layer 122 as a target and introducing Ar (argon) gas into a chamber. By using the conventional sputtering method, the functional layer 122 is formed while etching the upper surface 121a of the base material 121 with Ar, so it is possible to minimize the amount of the functional layer 122 formed and obtain the effect of improving adhesion. can.

However, this is an example of a method for forming the functional layer 122, and the functional layer 122 may be formed by other methods. For example, before forming the functional layer 122, the upper surface 121a of the base material 121 is activated by plasma treatment using Ar or the like to obtain an adhesion improvement effect, and then the functional layer 122 is vacuum-coated by magnetron sputtering. A method of forming a film may also be used.

Next, after forming a metal layer that will become the resistor 123, the wiring 124, and the terminal part 125 on the entire upper surface of the functional layer 122, the functional layer 122, the resistor 123, the wiring 124, and the terminal part 125 are formed by photolithography as shown in FIG. Pattern it into the planar shape shown in . The materials and thicknesses of the resistor 123, the wiring 124, and the terminal portion 125 are as described above. The resistor 123, the wiring 124, and the terminal portion 125 can be integrally formed from the same material. The resistor 123, the wiring 124, and the terminal portion 125 can be formed, for example, by magnetron sputtering using a raw material capable of forming the resistor 123, the wiring 124, and the terminal portion 125 as a target. The resistor 123, the wiring 124, and the terminal portion 125 may be formed using a reactive sputtering method, a vapor deposition method, an arc ion plating method, a pulsed laser deposition method, or the like instead of the magnetron sputtering method.

The combination of the material of the functional layer 122 and the materials of the resistor 123, the wiring 124, and the terminal part 125 is not particularly limited and can be selected as appropriate depending on the purpose. 123, the wiring 124, and the terminal portion 125, a Cr mixed phase film containing α-Cr (alpha chromium) as a main component can be formed.

In this case, for example, the resistor 123, the wiring 124, and the terminal portion 125 can be formed by magnetron sputtering using a raw material capable of forming a Cr mixed phase film as a target and introducing Ar gas into a chamber. Alternatively, the resistor 123, the wiring 124, and the terminal portion 125 may be formed by reactive sputtering using pure Cr as a target and introducing an appropriate amount of nitrogen gas together with Ar gas into the chamber. At this time, by changing the introduction amount and pressure (nitrogen partial pressure) of nitrogen gas, and by providing a heating process and adjusting the heating temperature, the proportion of CrN and Cr ₂ N contained in the Cr multiphase film, as well as the ratio of CrN and Cr The proportion of Cr ₂ N in ₂ N can be adjusted.

In these methods, the growth surface of the Cr mixed phase film is defined by the functional layer 122 made of Ti, and a Cr mixed phase film mainly composed of α-Cr having a stable crystal structure can be formed. Furthermore, the gauge characteristics are improved by diffusing Ti constituting the functional layer 122 into the Cr mixed phase film. For example, the gauge factor of the strain gauge 120 can be set to 10 or more, and the gauge factor temperature coefficient TCS and resistance temperature coefficient TCR can be in the range of -1000 ppm/°C to +1000 ppm/°C.

Note that when the resistor 123 is a Cr mixed phase film, the functional layer 122 made of Ti has the function of promoting crystal growth of the resistor 123 and preventing oxidation of the resistor 123 due to oxygen and moisture contained in the base material 121. and the function of improving the adhesion between the base material 121 and the resistor 123. The same applies when Ta, Si, Al, or Fe is used as the functional layer 122 instead of Ti.

Thereafter, the strain gauge 120 is completed by providing a cover layer 126 covering the resistor 123 and the wiring 124 and exposing the terminal portion 125 on the upper surface 121a of the base material 121, if necessary. The cover layer 126 is formed by, for example, laminating a semi-cured thermosetting insulating resin film on the upper surface 121a of the base material 121 so as to cover the resistor 123 and the wiring 124 and exposing the terminal portion 125, and then heating the film. Can be made by curing. The cover layer 126 is formed by applying a liquid or paste thermosetting insulating resin to the upper surface 121a of the base material 121 so as to cover the resistor 123 and the wiring 124 and exposing the terminal portion 125, and then heating and hardening the resin. It may also be made by

By providing the functional layer 122 under the resistor 123 in this manner, crystal growth of the resistor 123 can be promoted, and the resistor 123 made of a stable crystal phase can be manufactured. As a result, the stability of the gauge characteristics of the strain gauge 120 can be improved. Further, by diffusing the material constituting the functional layer 122 into the resistor 123, the gauge characteristics of the strain gauge 120 can be improved.

Note that the strain gauge 120 using a Cr multiphase film as the material of the resistor 123 achieves high sensitivity (500% or more compared to the conventional one) and miniaturization (1/10 or less compared to the conventional one). For example, while the output of a conventional strain gauge is approximately 0.04 mV/2V, the strain gauge 120 can obtain an output of 0.3 mV/2V or more. Furthermore, while the size of a conventional strain gauge (gauge length x gauge width) is approximately 3 mm x 3 mm, the size of the strain gauge 120 (gauge length x gauge width) is 0.3 mm x 0.3 mm. It can be downsized to a certain degree.

In this way, the strain gauge 120 using the Cr mixed phase film as the material of the resistor 123 is small and can be easily attached to the outer peripheral surface 110a of the sensor ring 110. Therefore, it is particularly suitable for use in a motor 1 using a small rolling bearing 30 having a diameter (outer diameter of the outer ring 31) of 30 mm or less. Furthermore, the strain gauge 120 using a Cr multiphase film as the material for the resistor 123 is highly sensitive and can detect small displacements, so it is possible to detect minute strains that were conventionally difficult to detect. That is, by having the strain gauge 120 using a Cr multiphase film as the material of the resistor 123, it is possible to realize the motor 1 having a function of accurately detecting strain.

<Modification of the first embodiment>
In a modification of the first embodiment, an example of a motor is shown in which a sensor ring is provided with a strain transmission structure that promotes transmission of strain to the strain gauge 120. In addition, in the modified example of the first embodiment, description of the same components as those of the already described embodiment may be omitted.

FIG. 7 is a perspective view illustrating a sensor unit according to Modification 1 of the first embodiment. In addition, in FIG. 7, the bearing housing and the sensor unit are shown shifted in position from each other.

Referring to FIG. 7, in the sensor unit 100A, the sensor ring 110 is provided with a recess 110x that opens toward the outer peripheral surface 110a. A strain gauge 120 is fixed within the recess 110x with an adhesive or the like. The recessed portion 110x may be provided in a part of the outer circumferential surface 110a of the sensor ring 110 in the circumferential direction, or may be provided over the entire circumference of the outer circumferential surface 110a of the sensor ring 110.

The recess 110x is thinner than other parts of the sensor ring 110. Therefore, the portion of the recessed portion 110x transmits the strain generated in the rolling bearing 30 to the strain gauge 120 more easily than other portions of the sensor ring 110. That is, the recess 110x is an example of a strain transmission structure that promotes transmission of strain from the rolling bearing 30 to the resistor 123 of the strain gauge 120. By providing the strain transmission structure, for example, even if the thickness of the sensor ring 110 is increased in consideration of rigidity, strain can be detected.

Furthermore, when the recess 110x is made large enough to accommodate the strain gauge 120, the position where the strain gauge 120 is fixed becomes clear by providing the recess 110x, thereby reducing variations in the position where the strain gauge 120 is fixed. Can be reduced.

Furthermore, in the sensor unit 100A, the strain gauge 120 is fixed to a recess 110x provided in the outer circumferential surface 110a of the sensor ring 110, and the strain gauge 120 does not protrude outside the outer circumferential surface 110a. Therefore, the strain gauge 120 is less likely to interfere with other members.

FIG. 8 is a perspective view illustrating a sensor unit according to a second modification of the first embodiment. FIG. 9 is a plan view illustrating a sensor unit according to Modification 2 of the first embodiment. Referring to FIGS. 8 and 9, in the sensor unit 100B, the sensor ring 110 is provided with a plurality of grooves 110y that are open toward the inner circumferential surface 110b and whose longitudinal direction is in the direction of the rotation axis m. That is, each groove 110y is depressed from the inner peripheral surface 110b side of the sensor ring 110 toward the outer peripheral surface 110a side. Each groove 110y may be provided so as to reach from the upper end surface to the lower end surface of the sensor ring 110. Each groove 110y has a triangular planar shape.

The number of grooves 110y is preferably a multiple of the number of rolling elements 33. For example, if there are eight rolling elements 33, it is preferable that the number of grooves 110y is eight or sixteen. Further, it is preferable that the plurality of grooves 110y are arranged at equal intervals in the circumferential direction of the sensor ring 110.

The portion where the groove 110y is provided easily transmits the strain generated in the rolling bearing 30 to the strain gauge 120. That is, the groove 110y is an example of a strain transmission structure that promotes the transmission of strain from the rolling bearing 30 to the resistor 123 of the strain gauge 120. By providing the strain transmission structure, for example, even if the thickness of the sensor ring 110 is increased in consideration of rigidity, strain can be detected.

From the viewpoint of easily transmitting strain to the resistor 123, when a line _L1 passing through the center of the gauge length of the resistor 123 and parallel to the rotation axis m is assumed, as shown in FIG. Preferably, L ₁ overlaps one of the grooves 110y. Furthermore, it is particularly preferable that the line _L1 overlaps the center of the groove 110y in the circumferential direction of the sensor ring 110 in a side view. For example, if the groove 110y has a triangular planar shape as in the example shown in FIG. 8, it is particularly preferable that the line _L1 overlaps the vertex closest to the triangular outer peripheral surface of the groove 110y. Note that the side view in this case refers to viewing the object (line L ₁ ) from the normal direction of the side surface (outer peripheral surface) of the sensor ring.

From the viewpoint of promoting strain transmission, it is preferable that the groove 110y has a triangular planar shape, but in consideration of fatigue failure, it is preferable that the groove 110y has an R-shaped portion. If the planar shape of the groove 110y is, for example, a shape in which a circle is combined at one vertex of a triangle shown in FIG. 10, or a semicircular shape shown in FIG. 11, it is advantageous for fatigue failure.

FIG. 12 is a perspective view illustrating a sensor unit according to Modification 3 of the first embodiment. FIG. 13 is a plan view illustrating a sensor unit according to Modification 3 of the first embodiment. Referring to FIGS. 12 and 13, in the sensor unit 100C, the sensor ring 110 is provided with a plurality of grooves 110z that are open on the upper end surface side and/or the lower end surface side and whose longitudinal direction is in the direction of the rotation axis m. . Each groove 110z is not open to the outer peripheral surface 110a side and the inner peripheral surface 110b side of the sensor ring 110. Each groove 110z may be provided so as to reach from the upper end surface to the lower end surface of the sensor ring 110. The planar shape of each groove 110z is circular. In addition, in this application, the case where the groove reaches from the upper end surface to the lower end surface is also included in the groove.

The number of grooves 110z is preferably a multiple of the number of rolling elements 33. For example, if there are eight rolling elements 33, it is preferable that the number of grooves 110z is eight or sixteen. Moreover, it is preferable that the plurality of grooves 110z are arranged at equal intervals in the circumferential direction of the sensor ring 110.

The portion where the groove 110z is provided easily transmits the strain generated in the rolling bearing 30 to the strain gauge 120. That is, the groove 110z is an example of a strain transmission structure that promotes the transmission of strain from the rolling bearing 30 to the resistor 123 of the strain gauge 120. By providing the strain transmission structure, for example, even if the thickness of the sensor ring 110 is increased in consideration of rigidity, strain can be detected.

From the viewpoint of easily transmitting strain to the resistor 123, when a line _L2 passing through the center of the gauge length of the resistor 123 and parallel to the rotation axis m is assumed as shown in FIG. Preferably, _L2 overlaps one of the grooves 110z. Furthermore, it is particularly preferable that the line _L2 overlaps the center of the groove 110z in the circumferential direction of the sensor ring 110 in a side view. For example, if the groove 110z has a circular planar shape as in the example shown in FIG. 12, it is particularly preferable that the line _L2 overlaps the center of the circle of the groove 110z.

Note that the planar shape of the groove 110z does not have to be circular, and may be, for example, a semicircular shape shown in FIG. 14 or a shape in which circles are combined at both ends of a straight line shown in FIG. 15. Further, as shown in FIG. 16, in FIG. 15, the width of the straight line and the diameter of the circle may be the same.

Although the preferred embodiments have been described in detail above, they are not limited to the above-described embodiments, and various modifications and substitutions may be made to the above-described embodiments without departing from the scope of the claims. can be added.

For example, in the above embodiment, an axial fan motor is used as an example of the motor, but the present invention is not limited to this, and the present invention can be widely applied to motors other than axial fan motors.

Further, in the above embodiment, an example is shown in which only a strain gauge is provided to detect the strain of the rolling bearing disposed on the upper side in FIG. 1 and the like. However, only a strain gauge for detecting strain in the rolling bearing disposed on the lower side in FIG. 1 etc. may be provided, or strain gauges for detecting strain in both rolling bearings may be provided. Furthermore, a plurality of strain gauges may be provided on one or both of the rolling bearing arranged on the upper side and the rolling bearing arranged on the lower side in FIG. 1 and the like.

Further, Modifications 1 to 3 of the first embodiment can be implemented in combination as appropriate. Any two of Modifications 1 to 3 of the first embodiment may be combined, or all three may be combined. That is, one sensor ring may have multiple types of strain transmission structures.

1 motor, 10 impeller, 11 rotor housing, 12 blade, 20 rotor shaft, 30 rolling bearing, 31 outer ring, 40a, 110a outer circumferential surface, 32 inner ring, 33 rolling element, 40 bearing housing, 40b, 110b inner circumferential surface, 110x recess , 40z step, 50 stator, 51 insulator, 52 stator core, 52x notch, 53 coil, 60 rotor, 61 rotor yoke, 62 rotor magnet, 70 casing, 71 casing outer frame, 72 base hub, 73 stationary blade, 80 motor section, 90 wiring, 100, 100A, 100B, 100C sensor unit, 110 sensor ring, 110y, 110z groove, 120 strain gauge, 121 base material, 122 functional layer, 123 resistor, 124 wiring, 125 terminal section, 126 cover layer

Claims (11)

a rolling bearing that rotatably supports the rotor shaft;
a bearing housing that holds the rolling bearing;
It has a sensor unit;
The sensor unit is
an annular member fixed to the outer peripheral surface of the bearing housing;
A motor comprising: a strain gauge fixed to the annular member and including a resistor for detecting strain in the rolling bearing. The motor according to claim 1, wherein the annular member has a strain transmission structure that promotes transmission of strain from the rolling bearing to the resistor. The strain transmission structure is a recess opening on the outer peripheral surface side of the annular member,
The motor according to claim 2, wherein the strain gauge is fixed within the recess. The motor according to claim 2 or 3, wherein the strain transmission structure is a plurality of grooves that are open on the inner circumferential surface side of the annular member and whose longitudinal direction is the rotation axis direction of the rotor shaft. Any one of claims 2 to 4, wherein the strain transmission structure is a plurality of grooves that are open on the upper end surface side and/or the lower end surface side of the annular member and whose longitudinal direction is the rotational axis direction of the rotor shaft. Motors listed in section. The motor according to claim 4 or 5, wherein the groove reaches from an upper end surface to a lower end surface of the annular member. The motor according to any one of claims 4 to 6, wherein the grooves are arranged at equal intervals in a circumferential direction of the annular member. The resistor is arranged with the gauge length direction facing the circumferential direction of the annular member,
The motor according to any one of claims 4 to 7, wherein when a line passing through the center of the gauge length of the resistor and parallel to the rotation axis is assumed, the line overlaps the groove in a side view. . The motor according to claim 8, wherein the line overlaps the center of the groove in the circumferential direction of the annular member in a side view. The motor according to any one of claims 1 to 9, wherein the resistor is formed from a Cr mixed phase film. The motor according to any one of claims 1 to 10, wherein the rolling bearing has an outer diameter of 30 mm or less.

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