WO2021010247A1

WO2021010247A1 - Bearing device and spindle device

Info

Publication number: WO2021010247A1
Application number: PCT/JP2020/026670
Authority: WO
Inventors: 小池　孝誌; 靖之福島; 勇介澁谷; 大地近藤
Original assignee: Ntn株式会社
Priority date: 2019-07-12
Filing date: 2020-07-08
Publication date: 2021-01-21
Also published as: JP2021014886A; CN114207305A; JP7486291B2; DE112020003361T5

Abstract

A bearing device (30) comprises: a first rolling bearing (32) which has a first inner ring (32a), a first outer ring (32b), and a first rolling element (32c) arranged between the first inner ring (32a) and the first outer ring (32b), and to which a preload is applied; a non-rotating member (35) arranged on the preload path; and at least one strain sensor (40) attached to a non-rotating member (34). The first inner ring (32a) is rotatable with respect to the first outer ring (32b) and the non-rotating member (35). The strain sensor (40) has a detection unit (42) that outputs a signal (SG1) corresponding to the strain of the non-rotating member (35), and a processing unit (43) that receives input of the signal (SG1). The processing unit (43) includes an amplification unit (43a) that amplifies the signal (SG1).

Description

Bearing equipment and spindle equipment

The present invention relates to a bearing device and a spindle device.

Patent Document 1 (Japanese Unexamined Patent Publication No. 2003-120666) describes a bearing device. The bearing device described in Patent Document 1 includes a first rolling bearing, a second rolling bearing, an inner ring spacer, an outer ring spacer, and a strain sensor.

Preload is applied to the first rolling bearing and the second rolling bearing. The inner ring spacer is arranged between the inner ring of the first rolling bearing and the inner ring of the second rolling bearing. The outer ring spacer is arranged between the outer ring of the first rolling bearing and the outer ring of the second rolling bearing. The strain sensor is attached to the outer ring spacer.

Japanese Unexamined Patent Publication No. 2003-120666

In the bearing device described in Patent Document 1, the preload applied to the first rolling bearing and the second rolling bearing is adjusted while measuring the strain of the outer ring spacer with a strain sensor. As a result, the preload can be managed, and an appropriate preload can be applied to the first rolling bearing and the second rolling bearing.

However, in the bearing device described in Patent Document 1, the details of the configuration of the strain sensor are not clear. As a result, noise is superimposed on the output from the strain sensor, and the measurement result of strain in the outer ring spacer may be affected by the noise. If the strain measurement result is affected by noise, the preload applied to the first rolling bearing and the second rolling bearing may not be accurately grasped.

The present invention has been made in view of the above-mentioned problems of the prior art. More specifically, the present invention provides a bearing device and a spindle device capable of reducing the influence of noise when measuring strain.

The bearing device according to the present invention has a first rolling bearing having a first inner ring, a first outer ring, and a first rolling element arranged between the first inner ring and the first outer ring, and a preload is applied to the first rolling bearing. A non-rotating member arranged on the preload path, and at least one strain sensor attached to the non-rotating member. The first inner ring is rotatable with respect to the first outer ring and the non-rotating member. The strain sensor has a detection unit that outputs a signal corresponding to the strain of the non-rotating member, and a processing unit that inputs the signal. The processing unit includes an amplification unit that amplifies the signal.

In the above bearing device, the processing unit may further include an output unit that calculates strain based on the signal amplified by the amplification unit.

In the above bearing device, the strain sensor may further have a substrate attached to a non-rotating member. The detection unit and the processing unit may be mounted on the substrate.

In the above bearing device, the strain sensor may have a semiconductor integrated circuit in which a detection unit and a processing unit are monolithically formed.

The above bearing device may further include a storage unit and a calculation unit. Information indicating the relationship between strain and preload may be stored in the storage unit. The calculation unit may be configured to calculate the preload based on the strain and information.

The above bearing device may further include a storage unit and a calculation unit. The number of strain sensors may be plural. The calculation unit may be configured to calculate a representative value based on the strain from each strain sensor. Information indicating the relationship between the representative value and the preload may be stored in the storage unit. The calculation unit may be configured to calculate the preload based on the representative value and the information.

The above bearing device may further include a diagnostic unit. The diagnostic unit may be configured to compare the preload calculated by the calculation unit with a predetermined threshold value.

The above bearing device has a second inner ring, a second outer ring, and a second rolling element arranged between the second inner ring and the second outer ring, and further adds a second rolling bearing to which a preload is applied. You may have. The second inner ring may be rotatable with respect to the second outer ring and the non-rotating member. The non-rotating member may be an outer ring spacer arranged between the first outer ring and the second outer ring.

In the above bearing device, the outer ring spacer may have an outer peripheral surface including a flat portion. The strain sensor may be mounted on a flat surface.

In the above bearing device, the outer ring spacer may have an inner peripheral surface and an outer peripheral surface. The inner peripheral surface may be formed with a recess that is recessed toward the outer peripheral surface side. The bottom surface of the recess may be a flat surface. The strain sensor may be mounted on a flat surface.

The spindle device according to the present invention includes the above-mentioned bearing device, a shaft rotatably supported by the first rolling bearing, and a motor for rotating the shaft.

According to the bearing device and spindle device according to the present invention, the influence of noise can be reduced when measuring strain.

It is sectional drawing of the spindle device 100. It is an enlarged view in II of FIG. It is sectional drawing in III-III of FIG. It is a schematic structural drawing of the strain sensor 40 in the spindle device 100. It is a block diagram of the strain sensor 40 in the spindle device 100. 6 is a schematic graph showing the relationship between the preload applied to the bearing device 30 and the strain signals SG4a to the strain signals SG4d. It is sectional drawing which is orthogonal to the rotation center axis A of the spindle device 110. It is a schematic structural drawing of the strain sensor 40 in the spindle device 120.

The details of the embodiment will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and duplicate explanations will not be repeated.

(First Embodiment)
Hereinafter, the spindle device according to the first embodiment (hereinafter referred to as “spindle device 100”) will be described.

<Overall configuration of spindle device 100>
FIG. 1 is a cross-sectional view of the spindle device 100. FIG. 2 is an enlarged view of FIG. 1 II. The spindle device 100 is a built-in motor type spindle device used in, for example, a machine tool. As shown in FIGS. 1 and 2, the spindle device 100 includes a shaft 10, an outer cylinder 20, a bearing device 30, a motor 50, and a bearing device 60.

<Detailed configuration of axis 10>
The shaft 10 has a first end 10a and a second end 10b. The first end 10a and the second end 10b are ends of the shaft 10 in the direction along the rotation center axis A. In the following, the direction along the rotation center axis A is referred to as "axial direction". The second end 10b is the opposite end of the first end 10a. A cutting tool such as an end mill is attached to the first end 10a. The shaft 10 has an outer peripheral surface 10c. The shaft 10 has a stepped portion 10d on the outer peripheral surface 10c. The outer diameter of the shaft 10 in the step portion 10d is larger than the outer diameter of the shaft 10 in the portion adjacent to the second end 10b side of the step portion 10d. The step portion 10d is located on the first end 10a side.

<Detailed configuration of outer cylinder 20>
The outer cylinder 20 has a tubular shape. The outer cylinder 20 extends along the axial direction. The shaft 10 is housed inside the outer cylinder 20. The outer cylinder 20 has a first end 20a and a second end 20b in the axial direction. The first end 20a is an end on the first end 10a side. The second end 20b is the opposite end of the first end 20a. The outer cylinder 20 has an inner peripheral surface 20c.

<Detailed configuration of bearing device 30>
The bearing device 30 includes a housing 31, a rolling bearing 32, a rolling bearing 33, an inner ring spacer 34, an outer ring spacer 35, a lid member 36, a nut 37, a spacer 38, and a strain sensor 40. Have.

The housing 31 has a tubular shape. The housing 31 has a first end 31a and a second end 31b in the axial direction. The first end 31a is the end on the side of the first end 10a, and the second end 31b is the end on the opposite side of the first end 31a. The housing 31 has an inner peripheral surface 31c and an outer peripheral surface 31d. The housing 31 is arranged so that the outer peripheral surface 31d is in contact with the inner peripheral surface 20c. A groove 31da is formed on the outer peripheral surface 31d. A flow path through which the refrigerant flows is defined by the groove 31da and the inner peripheral surface 20c.

The rolling bearing 32 is, for example, an angular contact ball bearing. The rolling bearing 32 rotatably supports the shaft 10 around the rotation center axis A. The rolling bearing 32 has an inner ring 32a, an outer ring 32b, a rolling element 32c, and a cage 32d.

The inner ring 32a has an inner peripheral surface 32aa and an outer peripheral surface 32ab. The inner ring 32a is attached to the shaft 10. More specifically, the inner ring 32a is attached to the shaft 10 so that the inner peripheral surface 32aa is in contact with the outer peripheral surface 10c. The inner ring 32a is arranged adjacent to the second end 10b side of the step portion 10d. The inner ring 32a rotates relative to the outer ring 32b and the outer ring spacer 35 as the shaft 10 rotates.

The outer ring 32b has an inner peripheral surface 32ba and an outer peripheral surface 32bb. The outer ring 32b is attached to the housing 31. More specifically, the outer ring 32b is attached to the housing 31 so that the outer peripheral surface 32bb is in contact with the inner peripheral surface 31c. The outer ring 32b is arranged so that the inner peripheral surface 32ba faces the outer peripheral surface 31ab.

The rolling element 32c is arranged between the inner ring 32a and the outer ring 32b. More specifically, the rolling element 32c is arranged so as to be in contact with the outer peripheral surface 32ab and the inner peripheral surface 32ba. The number of rolling elements 32c is plural.

The cage 32d is arranged between the inner ring 32a and the outer ring 32b. The cage 32d is held so that the distance between the rolling elements 32c in the circumferential direction is within a certain range. The circumferential direction is a direction along the circumference centered on the rotation center axis A.

The rolling bearing 33 is, for example, an angular contact ball bearing. The rolling bearing 33 rotatably supports the shaft 10 around the rotation center axis A. The rolling bearing 33 has an inner ring 33a, an outer ring 33b, a rolling element 33c, and a cage 33d.

The inner ring 33a has an inner peripheral surface 33aa and an outer peripheral surface 33ab. The inner ring 33a is attached to the shaft 10. More specifically, the inner ring 33a is attached to the shaft 10 so that the inner peripheral surface 33aa is in contact with the outer peripheral surface 10c. The inner ring 33a rotates relative to the outer ring 33b and the outer ring spacer 35 as the shaft 10 rotates.

The outer ring 33b has an inner peripheral surface 33ba and an outer peripheral surface 33bb. The outer ring 33b is attached to the housing 31. More specifically, the outer ring 33b is attached to the housing 31 so that the outer peripheral surface 33bb is in contact with the inner peripheral surface 31c. The outer ring 33b is arranged so that the inner peripheral surface 33ba faces the outer peripheral surface 31ab.

The rolling element 33c is arranged between the inner ring 33a and the outer ring 33b. More specifically, the rolling element 33c is arranged so as to be in contact with the outer peripheral surface 33ab and the inner peripheral surface 33ba. The number of rolling elements 33c is plural.

The cage 33d is arranged between the inner ring 33a and the outer ring 33b. The cage 33d is held so that the distance between the rolling elements 33c in the circumferential direction is within a certain range.

The rolling bearing 32 and the rolling bearing 33 are installed in a back combination (DB combination). The rolling bearing 32 and the rolling bearing 33 may be installed in a front combination (DF combination).

The inner ring spacer 34 has a tubular shape. The inner ring spacer 34 extends along the axial direction. The inner ring spacer 34 has an inner peripheral surface 34a and an outer peripheral surface 34b. The inner ring spacer 34 is attached to the shaft 10. More specifically, the inner ring spacer 34 is attached to the shaft 10 so that the inner peripheral surface 34a is in contact with the outer peripheral surface 10c. The inner ring spacer 34 is arranged between the inner ring 32a and the inner ring 33a in the axial direction.

The outer ring spacer 35 has a tubular shape. The outer ring spacer 35 extends along the axial direction. The outer ring spacer 35 has an inner peripheral surface 35a and an outer peripheral surface 35b. The outer ring spacer 35 is arranged so that the inner peripheral surface 35a faces the outer peripheral surface 34b and the outer peripheral surface 35b faces the inner peripheral surface 31c. The outer ring spacer 35 is arranged between the outer ring 32b and the outer ring 33b in the axial direction.

FIG. 3 is a cross-sectional view taken along the line III-III of FIG. In FIG. 3, the outer cylinder 20 and the housing 31 are not shown. As shown in FIG. 3, the outer peripheral surface 35b has a flat portion 35ba. The number of flat portions 35ba is preferably a plurality. In the example of FIG. 3, the number of flat portions 35ba is 4. However, the number of flat portions 35ba is not limited to this. The number of flat portions 35ba may be 2, for example. The flat portions 35ba are preferably formed at equal intervals along the circumferential direction.

As shown in FIGS. 1 and 2, the lid member 36 has a first portion 36a and a second portion 36b. The lid member 36 is attached to the housing 31 in the first portion 36a. The second portion 36b extends from the first portion 36a along the axial direction so as to be in contact with the outer ring 32b.

The nut 37 is screwed onto the outer peripheral surface 10c. The nut 37 is located closer to the second end 10b than the rolling bearing 33.

The spacer 38 has a tubular shape. The spacer 38 has an inner peripheral surface 38a and an outer peripheral surface 38b. The spacer 38 is attached to the shaft 10. More specifically, the spacer 38 is attached to the shaft 10 so that the inner peripheral surface 38a is in contact with the outer peripheral surface 10c. The outer peripheral surface 38b faces the inner peripheral surface 31c. The spacer 38 is arranged between the inner ring 33a and the nut 37 in the axial direction.

By moving the nut 37 toward the first end 10a, a preload is applied to the inner ring 33a. By moving the nut 37 toward the first end 10a, a preload is applied to the outer ring 33b via the inner ring 33a and the rolling element 33c. By moving the nut 37 toward the first end 10a, a preload is applied to the inner ring 32a via the inner ring 33a and the inner ring spacer 34. By moving the nut 37 toward the first end 10a, a preload is applied to the outer ring 32b via the inner ring 33a, the rolling element 33c, the outer ring 33b, and the outer ring spacer 35. That is, the outer ring spacer 35 is a non-rotating member arranged on the preload path.

<Detailed configuration of strain sensor 40>
The strain sensor 40 is attached to the outer ring spacer 35. More specifically, the strain sensor 40 is attached to the flat portion 35ba. The number of strain sensors 40 is preferably a plurality. The number of strain sensors 40 is preferably equal to the number of flat portions 35ba.

FIG. 4 is a schematic structural diagram of the strain sensor 40 in the spindle device 100. As shown in FIG. 4, the strain sensor 40 includes a substrate 41, a detection unit 42, and a processing unit 43.

The substrate 41 is fixed to the flat portion 35ba by adhesion or the like. The substrate 41 is preferably made of a material having a coefficient of thermal expansion similar to that of the outer ring spacer 35. The detection unit 42 and the processing unit 43 are attached to the substrate 41. The detection unit 42 and the processing unit 43 are electrically connected by, for example, a lead wire (not shown).

The detection unit 42 is, for example, a strain gauge. The detection unit 42 is preferably formed of a material having a small resistance temperature coefficient (the rate at which the electric resistance value fluctuates with respect to a temperature change) in order to prevent the output from the detection unit from drifting due to a change in ambient temperature. There is. FIG. 5 is a block diagram of the strain sensor 40 in the spindle device 100. As shown in FIG. 5, the detection unit 42 outputs an electric signal SG1 corresponding to the strain of the outer ring spacer 35. More specifically, the detection unit 42 outputs an electric signal SG1 according to the strain of the outer ring spacer 35 in the axial direction.

The electric signal SG1 output from the detection unit 42 is input to the processing unit 43. The processing unit 43 has an amplification unit 43a and an output unit 43b. The amplification unit 43a amplifies the electric signal SG1 and outputs the amplification signal SG2. The amplifier unit 43a is, for example, an amplifier circuit. The output unit 43b is configured to calculate the strain of the outer ring spacer 35 based on the amplification signal SG2. More specifically, the output unit 43b has a CPU (Central Processing Unit) and an ADC (Analog to Digital Converter) circuit. The output unit 43b calculates the distortion of the outer ring spacer 35 by digitizing the amplification signal SG2 in the ADC circuit to generate the digital signal SG3 and performing signal processing on the digital signal SG3 in the CPU. By generating the digital signal SG3 from the amplified signal SG2, the influence of noise can be further reduced. The output unit 43b outputs a strain signal SG4 indicating the strain of the outer ring spacer 35.

The strain sensor 40 may further have a temperature sensor (not shown) in order to compensate for the influence of ambient temperature changes. The output unit 43b may correct the calculated strain value based on the ambient temperature detected by the temperature sensor.

The bearing device 30 may further include a storage unit 44 and a calculation unit 45. The storage unit 44 stores information indicating the relationship between the strain in the outer ring spacer 35 and the preload applied to the bearing device 30. This information is a relational expression or table between the strain in the outer ring spacer 35 measured or analyzed in advance and the preload applied to the bearing device 30. The calculation unit 45 calculates the preload applied to the bearing device 30 based on the information stored in the strain signal SG4 and the storage unit 44.

The four strain signals SG4 output from the four strain sensors 40 included in the bearing device 30 are the strain signal SG4a, the strain signal SG4b, the strain signal SG4c, and the strain signal SG4d, respectively. The calculation unit 45 may be configured to calculate a representative value of strain in the outer ring spacer 35 based on the strain signals SG4a to SG4d.

The representative values of the strain in the outer ring spacer 35 are, for example, the average value of the strain values indicated by the strain signal SG4a to the strain signal SG4d, the maximum value of the strain value indicated by the strain signal SG4a to the strain signal SG4d, and the strain signal SG4a to the strain. It is the minimum value of the strain value indicated by the signal SG4d, the difference between the maximum and minimum values of the strain value indicated by the strain signal SG4a to the strain signal SG4d, or the total value of the strain values indicated by the strain signal SG4a to the strain signal SG4d.

The storage unit 44 may store information indicating the relationship between the above representative value and the preload applied to the bearing device 30. The calculation unit 45 may calculate the preload applied to the bearing device 30 based on the above representative value and the information stored in the storage unit 44. In order to suppress fluctuations in the calculated preload value, the calculation unit 45 may calculate the preload applied to the bearing device 30 after performing low-pass filter processing on the strain signals SG4a to SG4d. Often, a low-pass filter process may be performed on the calculated preload.

The bearing device 30 may further include a diagnostic unit 46. The diagnosis unit 46 is configured to compare the preload calculated by the calculation unit 45 with a predetermined threshold value. When the preload calculated by the calculation unit 45 exceeds a predetermined threshold value, the diagnosis unit 46 may output a signal indicating that an abnormality has occurred in the rolling bearing 32 or the rolling bearing 33.

The storage unit 44 is composed of, for example, a memory circuit mounted on the microcontroller, and the arithmetic unit 45 and the diagnostic unit 46 are composed of, for example, a CPU mounted on the microcontroller.

The strain signal SG4a and the strain signal SG4c are the strain signals SG4 from the strain sensor 40 located at positions symmetrical with respect to the rotation center axis A, and the strain signal SG4b and the strain signal SG4d are located at positions symmetrical with respect to the rotation center axis A. Let the strain signal SG4 from the strain sensor 40. The calculation unit 45 calculates the bending moment load in the vertical direction applied to the outer ring spacer 35 based on the strain signal SG4a and the strain signal SG4c, and the lateral direction applied to the outer ring spacer 35 based on the strain signal SG4b and the strain signal SG4d. It may be configured to calculate the bending moment load of. This makes it possible to grasp the load applied to the cutting tool attached to the first end 10a.

A sensor other than the strain sensor 40 may be attached to the outer ring spacer 35. For example, a heat flux sensor (not shown) may be attached to the outer ring spacer 35 so as to face the inner ring 32a (inner ring 33a). As a result, the temperature rise of the rolling bearing 32 and the rolling bearing 33 can be detected at an early stage. Therefore, by considering this together with the comparison result in the diagnostic unit 46, the abnormalities of the rolling bearing 32 and the rolling bearing 33 can be more comprehensively detected. It becomes possible to judge.

<Detailed configuration of motor 50>
As shown in FIG. 1, the motor 50 includes a tubular member 51, a rotor 52, and a stator 53.

The tubular member 51 has a tubular shape. The tubular member 51 extends along the axial direction. The tubular member 51 has an inner peripheral surface 51a and an outer peripheral surface 51b. The tubular member 51 is attached to the shaft 10. More specifically, the tubular member 51 is attached to the shaft 10 so that the inner peripheral surface 51a is in contact with the outer peripheral surface 10c. The tubular member 51 is located closer to the second end 10b than the nut 37.

The rotor 52 is attached to the outer peripheral surface 51b. The stator 53 is attached to the inner peripheral surface 20c so as to face the rotor 52. By sequentially switching the direction of the current flowing through the stator 53, a rotational force is generated on the rotor 52, and the rotational force causes the shaft 10 to rotate around the rotation center axis A.

<Detailed configuration of bearing device 60>
The bearing device 60 includes an end member 61, a rolling bearing 62, an inner ring holding member 63, a positioning member 64, a positioning member 65, and a nut 66.

The end member 61 is attached to the second end 20b. A through hole 61a is formed in the end member 61. The through hole 61a penetrates the end member 61 along the axial direction. A shaft 10 is inserted through the through hole 61a.

The rolling bearing 62 is, for example, a cylindrical roller bearing. The rolling bearing 62 rotatably supports the shaft 10 around the rotation center axis A. The rolling bearing 62 is arranged so that the inner ring is in contact with the end of the tubular member 51 on the second end 10b side. The inner ring of the rolling bearing 62 is attached to the shaft 10, and the outer ring of the rolling bearing 62 is attached to the inner wall surface of the through hole 61a.

The inner ring holding member 63 is attached to the shaft 10 at a position closer to the second end 10b than the rolling bearing 62. The inner ring holding member 63 is in contact with the inner ring of the rolling bearing 62 from the second end 10b side. The positioning member 64 is attached to the end member 61. The positioning member 64 is in contact with the outer ring of the rolling bearing 62 from the second end 10b side. The positioning member 65 is attached to the end member 61 so as to sandwich the outer ring of the rolling bearing 62 with the positioning member 64 in the axial direction. The outer ring of the rolling bearing 62 is sandwiched between the positioning member 64 and the positioning member 65. The inner ring of the rolling bearing 62 slides in the axial direction along the through hole 61a integrally with the shaft 10 according to the expansion and contraction of the shaft 10.

The nut 66 is screwed onto the outer peripheral surface 10c so as to sandwich the inner ring holding member 63 with the inner ring of the rolling bearing 62. That is, the nut 66 prevents the inner ring holding member 63 from falling off.

<Effect of bearing device 30>
In the bearing device 30, a strain sensor 40 having a detection unit 42 and a processing unit 43 is attached to a non-rotating member (outer ring spacer 35) on the preload path. That is, in the bearing device 30, since the detection unit 42 and the processing unit 43 are both attached to the same member, it is difficult for noise to get on the lead wire connecting the detection unit 42 and the processing unit 43. Further, the processing unit 43 has an amplification unit 43a, and the electrical signal SG1 output from the detection unit 42 is amplified by the amplification unit 43a to become the amplification signal SG2. When the electric signal SG1 is amplified to become the amplified signal SG2, it becomes less susceptible to noise. From this point of view, the bearing device 30 is less susceptible to noise when measuring the strain of the non-rotating member on the preload path.

In the bearing device 30, since the detection unit 42 and the processing unit 43 are attached to the substrate 41, the strain sensor 40 can be constructed in the substrate 41. Therefore, in the bearing device 30, the strain sensor 40 can be easily handled (operability is improved).

In the bearing device 30, since the installation location of the strain sensor 40 can be secured only by forming the flat portion 35ba on the outer peripheral surface 35b, the structure of the outer ring spacer 35 is not significantly changed, and the outer ring spacer 35 is used. The installation location of the strain sensor 40 can be secured without significantly reducing the rigidity of the strain sensor 40.

FIG. 6 is a schematic graph showing the relationship between the preload applied to the bearing device 30 and the strain signals SG4a to the strain signals SG4d. As shown in FIG. 6, it is assumed that the strain generated in the outer ring spacer 35 due to the preload is not uniform along the circumferential direction. In this case, the values of the strain signal SG4a to the strain signal SG4d vary. Occurs. In the bearing device 30, the calculation unit 45 calculates the representative value of the strain in the outer ring spacer 35 based on the strain signals SG4a to SG4d, and based on the representative value and the information stored in the storage unit 44. By calculating the preload applied to the outer ring spacer 35, the preload applied to the outer ring spacer 35 can be calculated more accurately.

For example, when the shaft 10 is rotated at high speed, the rolling bearing 32 and the rolling bearing 33 generate heat due to an excessive load or damage to the rolling bearing 32 and the rolling bearing 33, and the preload becomes excessive due to the thermal expansion due to the heat generation. The rolling bearing 32 and the rolling bearing 33 may be burnt out. Since the bearing device 30 has a diagnostic unit 46, the diagnostic unit 46 determines the abnormality of the rolling bearing 32 and the rolling bearing 33 by comparing the preload calculated by the calculation unit 45 with a predetermined threshold value. be able to. As a result, appropriate workarounds can be taken so that the rolling bearing 32 and the rolling bearing 33 do not burn out.

For example, the spindle device 100 reduces the rotation speed of the shaft 10 when a signal indicating that the preload calculated by the calculation unit 45 exceeds a predetermined threshold value is output from the diagnosis unit 46. The pump may be controlled to circulate the refrigerant so as to increase the circulation amount of the refrigerant flowing through the flow path defined by the groove 31da and the inner peripheral surface 20c.

(Second Embodiment)
Hereinafter, the spindle device according to the second embodiment (hereinafter referred to as “spindle device 110”) will be described. Here, the differences from the spindle device 100 will be mainly described, and the overlapping description will not be repeated.

The spindle device 110 includes a shaft 10, an outer cylinder 20, a bearing device 30, a motor 50, and a bearing device 60. The bearing device 30 has a strain sensor 40. In these respects, the spindle device 110 is common to the spindle device 100.

However, the spindle device 110 is different from the spindle device 100 in terms of the structure of the outer ring spacer 35 and the arrangement of the strain sensor 40.

FIG. 7 is a cross-sectional view orthogonal to the rotation center axis A of the spindle device 110. In FIG. 7, the outer cylinder 20 is not shown. As shown in FIG. 7, the outer peripheral surface 35b does not have a flat portion 35ba. A recess 35aa is formed on the inner peripheral surface 35a. A plurality of recesses 35aa may be formed at equal intervals along the circumferential direction. The inner peripheral surface 35a is recessed on the outer peripheral surface 35b side in the recess 35aa.

The recess 35aa has a bottom surface 35ab. The bottom surface 35ab is a flat surface. The sensor 40 is attached to the bottom surface 35ab.

In the bearing device 30 of the spindle device 110, the installation location of the strain sensor 40 can be secured only by forming the recess 35aa on the inner peripheral surface 35a, so that the structure of the outer ring spacer 35 is not significantly changed. The installation location of the strain sensor 40 can be secured without significantly reducing the rigidity of the outer ring spacer 35.

(Third Embodiment)
Hereinafter, the spindle device according to the third embodiment (hereinafter referred to as “spindle device 120”) will be described. Here, the differences from the spindle device 100 will be mainly described, and the overlapping description will not be repeated.

The spindle device 120 includes a shaft 10, an outer cylinder 20, a bearing device 30, a motor 50, and a bearing device 60. The bearing device 30 has a strain sensor 40. In these respects, the spindle device 120 is common to the spindle device 100.

However, the spindle device 120 is different from the spindle device 100 in terms of the structure of the strain sensor 40.

FIG. 8 is a schematic structural diagram of the strain sensor 40 in the spindle device 120. As shown in FIG. 8, the strain sensor 40 has a semiconductor integrated circuit 47. The semiconductor integrated circuit 47 is attached to the substrate 41. In the semiconductor integrated circuit 47, a detection unit 42 and a processing unit 43 are monolithically formed. That is, in the strain sensor 40 of the spindle device 120, the detection unit 42 and the processing unit 43 are one-chip ICs (Integrated Circuits).

Since the strain sensor 40 of the spindle device 120 has a semiconductor integrated circuit 47 in which the detection unit 42 and the processing unit 43 are monolithically formed, the strain sensor 40 can be miniaturized, and the outer ring spacer 35 can be used. Will be easier to incorporate.

Although the embodiment of the present invention has been described as described above, it is also possible to modify the above-described embodiment in various ways. Moreover, the scope of the present invention is not limited to the above-described embodiment. The scope of the present invention is indicated by the claims and is intended to include all modifications within the meaning and scope equivalent to the claims.

The above embodiment is particularly advantageously applied to bearing devices and spindle devices used in machine tools.

10 shafts, 10a 1st end, 10b 2nd end, 10c outer peripheral surface, 10d stepped portion, 20 outer cylinder, 20a 1st end, 20b 2nd end, 20c inner peripheral surface, 30 bearing device, 31 housing, 31a 1st End, 31b 2nd end, 31c inner peripheral surface, 31d outer peripheral surface, 31da groove, 32 rolling bearing, 32a inner ring, 32aa inner peripheral surface, 32ab outer peripheral surface, 32b outer ring, 32ba inner peripheral surface, 32bb outer peripheral surface, 32c rolling element , 32d cage, 33 rolling bearing, 33a inner ring, 33aa inner peripheral surface, 33ab outer peripheral surface, 33b outer ring, 33ba inner peripheral surface, 33bb outer peripheral surface, 33c rolling element, 33d cage, 34 inner ring spacer, 34a inner peripheral surface , 34b outer peripheral surface, 35 outer ring bearing, 35a inner peripheral surface, 35aa recess, 35ab bottom surface, 35b outer peripheral surface, 35ba flat part, 36 lid member, 36a first part, 36b second part, 37 nut, 38 spacer 38a inner peripheral surface, 38b outer peripheral surface, 40 strain sensor, 41 board, 42 detection unit, 43 processing unit, 43a amplification unit, 43b output unit, 44 storage unit, 45 arithmetic unit, 46 diagnostic unit, 47 semiconductor integrated circuit, 50 Motor, 51 tubular member, 51a inner peripheral surface, 51b outer peripheral surface, 52 rotor, 53 stator, 61 end member, 61a through hole, 62 rolling bearing, 63 inner ring holding member, 64 positioning member, 65 positioning member, 66 nut, 100, 110, 120 Spindle device, A rotation center axis, SG1 electric signal, SG2 amplification signal, SG3 digital signal, SG4b, SG4c, SG4a, SG4d, SG4 distortion signal.

Claims

A first rolling bearing having a first inner ring, a first outer ring, and a first rolling element arranged between the first inner ring and the first outer ring, and to which a preload is applied.
The non-rotating member arranged on the preload path and
It comprises at least one strain sensor attached to the non-rotating member.
The first inner ring is rotatable with respect to the first outer ring and the non-rotating member.
The strain sensor has a detection unit that outputs a signal corresponding to the strain of the non-rotating member, and a processing unit that inputs the signal.
The processing unit is a bearing device including an amplification unit that amplifies the signal.
The bearing device according to claim 1, wherein the processing unit further includes an output unit that calculates the strain based on the signal amplified by the amplification unit.
The strain sensor further comprises a substrate attached to the non-rotating member.
The bearing device according to claim 1 or 2, wherein the detection unit and the processing unit are mounted on the substrate.
The bearing device according to any one of claims 1 to 3, wherein the strain sensor has a semiconductor integrated circuit in which the detection unit and the processing unit are monolithically formed.
Memory and
With a calculation unit
Information indicating the relationship between the strain and the preload is stored in the storage unit.
The bearing device according to any one of claims 1 to 4, wherein the calculation unit is configured to calculate the preload based on the strain and the information.
Memory and
With a calculation unit
The number of the strain sensors is plural,
The calculation unit is configured to calculate a representative value based on the strain from each of the strain sensors.
Information indicating the relationship between the representative value and the preload is stored in the storage unit.
The bearing device according to any one of claims 1 to 4, wherein the calculation unit is configured to calculate the preload based on the representative value and the information.
With more diagnostics
The bearing device according to claim 6, wherein the diagnostic unit is configured to compare the preload calculated by the calculation unit with a predetermined threshold value.
A second rolling bearing having a second inner ring, a second outer ring, a second rolling element arranged between the second inner ring and the second outer ring, and the preload applied to the second rolling bearing is further provided.
The second inner ring is rotatable with respect to the second outer ring and the non-rotating member.
The bearing device according to any one of claims 1 to 7, wherein the non-rotating member is an outer ring spacer arranged between the first outer ring and the second outer ring.
The outer ring spacer has an outer peripheral surface including a flat portion, and has an outer peripheral surface.
The bearing device according to claim 8, wherein the strain sensor is attached to the flat portion.
The outer ring spacer has an inner peripheral surface and an outer peripheral surface.
The inner peripheral surface is formed with a recess that is recessed toward the outer peripheral surface side.
The bottom surface of the recess is a flat surface.
The bearing device according to claim 8, wherein the strain sensor is mounted on the flat surface.
The bearing device according to any one of claims 1 to 10.
A shaft rotatably supported by the first rolling bearing and
A spindle device including a motor for rotating the shaft.