JP7486291B2 - Bearing device and spindle device - Google Patents

Description

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

Patent document 1 (JP Patent Publication 2003-120666) describes a bearing device. The bearing device described in Patent document 1 has a first rolling bearing, a second rolling bearing, an inner ring spacer, an outer ring spacer, and a strain sensor.

A preload is applied to the first rolling bearing and the second rolling bearing. The inner ring spacer is disposed between the inner ring of the first rolling bearing and the inner ring of the second rolling bearing. The outer ring spacer is disposed 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.

JP 2003-120666 A

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. This makes it possible to manage the preload and apply an appropriate preload 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 may be superimposed on the output from the strain sensor, and the strain measurement results in the outer ring spacer may be affected by the noise. If the strain measurement results are affected by noise, it may not be possible to accurately grasp the preload applied to the first rolling bearing and the second rolling bearing.

The present invention has been made in consideration of the problems of the conventional technology as described above. More specifically, the present invention provides a bearing device and a spindle device that can reduce the effects of noise when measuring strain.

The bearing device according to the present invention comprises 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, to which a preload is applied, a non-rotating member arranged on the path of the preload, and at least one strain sensor attached to the non-rotating member. The first inner ring is rotatable relative 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 to which the signal is input. The processing unit includes an amplifier that amplifies the signal.

In the above-mentioned bearing device, the processing unit may further include an output unit that calculates the strain based on the signal amplified in the amplifier unit.

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

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

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

The bearing device may further include a memory unit and a calculation unit. The number of strain sensors may be more than one. The calculation unit may be configured to calculate a representative value based on the strain from each strain sensor. The memory unit may store information indicating the relationship between the representative value and the preload. The calculation unit may be configured to calculate the preload based on the representative value and the information.

The 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 bearing device may further include a second rolling bearing having a second inner ring, a second outer ring, and a second rolling element arranged between the second inner ring and the second outer ring, to which a preload is applied. The second inner ring may be rotatable relative 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-mentioned bearing device, the outer ring spacer may have an outer peripheral surface that includes a flat portion. The strain sensor may be attached to the flat portion.

In the above-mentioned bearing device, the outer ring spacer may have an inner peripheral surface and an outer peripheral surface. The inner peripheral surface may have a recess that is recessed toward the outer peripheral surface. The bottom surface of the recess may be a flat surface. The strain sensor may be attached to the flat surface.

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

The bearing device and spindle device of the present invention can reduce the effects of noise when measuring strain.

FIG. 2 is a cross-sectional view of the spindle device 100. FIG. 2 is an enlarged view of II in FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. 2 is a schematic structural diagram of a strain sensor 40 in a spindle device 100. FIG. FIG. 2 is a block diagram of a strain sensor 40 in the spindle device 100. 4 is a schematic graph showing the relationship between the preload applied to the bearing device 30 and the strain signals SG4a to SG4d. 2 is a cross-sectional view perpendicular to the central axis A of rotation of the spindle device 110. FIG. 2 is a schematic structural diagram of a strain sensor 40 in a spindle device 120. FIG.

Details of the embodiment will be described with reference to the drawings. In the following drawings, the same or corresponding parts are given the same reference symbols, and overlapping descriptions will not be repeated.

First Embodiment
A spindle device according to a first embodiment (hereinafter, referred to as "spindle device 100") will be described below.

<Overall Configuration of Spindle Device 100>
Fig. 1 is a cross-sectional view of a spindle device 100. Fig. 2 is an enlarged view of II in Fig. 1. 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 has a shaft 10, an outer cylinder 20, a bearing device 30, a motor 50, and a bearing device 60.

<Detailed configuration of shaft 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 in a direction along the central axis A of rotation of the shaft 10. Hereinafter, the direction along the central axis A of rotation is referred to as the "axial direction". The second end 10b is an end opposite to 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 step portion 10d on the outer peripheral surface 10c. The outer diameter of the shaft 10 at the step portion 10d is larger than the outer diameter of the shaft 10 at a 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 cylindrical 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 the end on the first end 10a side. The second end 20b is the end opposite the first end 20a. The outer cylinder 20 has an inner circumferential surface 20c.

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

The housing 31 has a cylindrical 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 first end 10a side, and the second end 31b is the end opposite the first end 31a. The housing 31 has an inner circumferential surface 31c and an outer circumferential surface 31d. The housing 31 is disposed so that the outer circumferential surface 31d is in contact with the inner circumferential surface 20c. A groove 31da is formed in the outer circumferential surface 31d. The groove 31da and the inner circumferential surface 20c define a flow path through which the refrigerant flows.

The rolling bearing 32 is, for example, an angular ball bearing. The rolling bearing 32 supports the shaft 10 so that it can rotate around the central axis of rotation A. The rolling bearing 32 has an inner ring 32a, an outer ring 32b, rolling elements 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 disposed adjacent to the second end 10b side of the stepped 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 disposed so that the inner peripheral surface 32ba faces the outer peripheral surface 31ab.

The rolling elements 32c are disposed between the inner ring 32a and the outer ring 32b. More specifically, the rolling elements 32c are disposed so as to be in contact with the outer peripheral surface 32ab and the inner peripheral surface 32ba. There are multiple rolling elements 32c.

The retainer 32d is disposed between the inner ring 32a and the outer ring 32b. The retainer 32d holds the rolling elements 32c so that the spacing between them in the circumferential direction is within a certain range. The circumferential direction is the direction along the circumference centered on the central axis of rotation A.

The rolling bearing 33 is, for example, an angular ball bearing. The rolling bearing 33 supports the shaft 10 so that it can rotate around the central axis of rotation A. The rolling bearing 33 has an inner ring 33a, an outer ring 33b, rolling elements 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 disposed so that the inner peripheral surface 33ba faces the outer peripheral surface 31ab.

The rolling elements 33c are disposed between the inner ring 33a and the outer ring 33b. More specifically, the rolling elements 33c are disposed so as to be in contact with the outer peripheral surface 33ab and the inner peripheral surface 33ba. There are multiple rolling elements 33c.

The retainer 33d is disposed between the inner ring 33a and the outer ring 33b. The retainer 33d holds the rolling elements 33c so that the spacing in the circumferential direction is within a certain range.

The rolling bearings 32 and 33 are installed in a back-to-back combination (DB combination). The rolling bearings 32 and 33 may also be installed in a face-to-face combination (DF combination).

The inner ring spacer 34 has a cylindrical 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 disposed between the inner ring 32a and the inner ring 33a in the axial direction.

The outer ring spacer 35 has a cylindrical 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 disposed 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 disposed between the outer ring 32b and the outer ring 33b in the axial direction.

Figure 3 is a cross-sectional view taken along III-III in Figure 2. Note that the outer cylinder 20 and the housing 31 are omitted from Figure 3. As shown in Figure 3, the outer peripheral surface 35b has flat portions 35ba. It is preferable that there are multiple flat portions 35ba. In the example of Figure 3, the number of flat portions 35ba is four. However, the number of flat portions 35ba is not limited to this. The number of flat portions 35ba may be, for example, two. It is preferable that the flat portions 35ba are formed at equal intervals along the circumferential direction.

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

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

The spacer 38 has a cylindrical 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 disposed 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 elements 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 elements 33c, the outer ring 33b, and the outer ring spacer 35. In other words, the outer ring spacer 35 is a non-rotating member arranged on the path of the preload.

<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 the strain sensors 40 is preferably more than one. The number of the strain sensors 40 is preferably equal to the number of the flat portions 35ba.

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

The substrate 41 is fixed to the flat portion 35ba by adhesive or the like. The substrate 41 is preferably formed from a material having a thermal expansion coefficient 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, for example, by lead wires (not shown).

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

The processing unit 43 receives the electrical signal SG1 output from the detection unit 42. The processing unit 43 has an amplifier 43a and an output unit 43b. The amplifier 43a amplifies the electrical signal SG1 and outputs an amplified signal SG2. The amplifier 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 amplified 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 digitizes the amplified signal SG2 in the ADC circuit to generate a digital signal SG3, and performs signal processing on the digital signal SG3 in the CPU to calculate the strain of the outer ring spacer 35. Note that by generating the digital signal SG3 from the amplified signal SG2, the influence of noise can be further reduced. The output section 43b outputs a strain signal SG4 that indicates the strain of the outer ring spacer 35.

The strain sensor 40 may further include a temperature sensor (not shown) to correct for the effects of changes in the surrounding temperature. The output unit 43b may correct the calculated strain value based on the surrounding temperature detected by the temperature sensor.

The bearing device 30 may further include a memory unit 44 and a calculation unit 45. The memory 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 that has been 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 strain signal SG4 and the information stored in the memory unit 44.

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

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

The memory unit 44 may store information indicating the relationship between the 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 representative value and the information stored in the memory unit 44. In order to suppress fluctuations in the value of the calculated preload, 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, or may perform low-pass filter processing on the calculated preload.

The bearing device 30 may further include a diagnostic unit 46. The diagnostic 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 the predetermined threshold value, the diagnostic unit 46 may output a signal indicating that an abnormality has occurred in the rolling bearing 32 or the rolling bearing 33.

The memory unit 44 is configured, for example, by a memory circuit mounted on a microcontroller, and the calculation unit 45 and the diagnosis unit 46 are configured, for example, by a CPU mounted on the microcontroller.

The strain signals SG4a and SG4c are strain signals SG4 from strain sensors 40 located symmetrically with respect to the rotation center axis A, and the strain signals SG4b and SG4d are strain signals SG4 from strain sensors 40 located symmetrically with respect to the rotation center axis A. The calculation unit 45 may be configured to calculate the vertical bending moment load applied to the outer ring spacer 35 based on the strain signals SG4a and SG4c, and to calculate the horizontal bending moment load applied to the outer ring spacer 35 based on the strain signals SG4b and SG4d. 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). This allows early detection of temperature rises in the rolling bearings 32 and 33, and by taking this into consideration together with the comparison results in the diagnosis unit 46, it becomes possible to make a more comprehensive judgment on abnormalities in the rolling bearings 32 and 33.

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

The cylindrical member 51 has a cylindrical shape. The cylindrical member 51 extends along the axial direction. The cylindrical member 51 has an inner peripheral surface 51a and an outer peripheral surface 51b. The cylindrical member 51 is attached to the shaft 10. More specifically, the cylindrical member 51 is attached to the shaft 10 so that the inner peripheral surface 51a contacts the outer peripheral surface 10c. The cylindrical 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 this rotational force rotates the shaft 10 around the central axis of rotation A.

<Detailed configuration of bearing device 60>
The bearing device 60 has an end member 61 , a rolling bearing 62 , an inner race pressing 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 passes through the end member 61 in the axial direction. The shaft 10 is inserted through the through hole 61a.

The rolling bearing 62 is, for example, a cylindrical roller bearing. The rolling bearing 62 supports the shaft 10 so that it can rotate around the central axis of rotation A. The rolling bearing 62 is arranged so that its inner ring is in contact with the end of the cylindrical 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 pressing 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 pressing member 63 contacts 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 contacts 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 between 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. As the shaft 10 expands and contracts, the inner ring of the rolling bearing 62 slides axially along the through hole 61a integrally with the shaft 10.

The nut 66 is screwed onto the outer circumferential surface 10c so as to sandwich the inner ring holding member 63 between the nut 66 and the inner ring of the rolling bearing 62. In other words, the nut 66 prevents the inner ring holding member 63 from falling off.

<Effects of the 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 path of the preload. That is, in the bearing device 30, since the detection unit 42 and the processing unit 43 are both attached to the same member, noise is unlikely to be carried on the lead wire connecting the detection unit 42 and the processing unit 43. Furthermore, the processing unit 43 has an amplifier 43a, and the electric signal SG1 output from the detection unit 42 is amplified in the amplifier 43a to become an amplified signal SG2. When the electric signal SG1 is amplified to become the amplified signal SG2, it becomes less susceptible to the influence of noise. From this viewpoint, the bearing device 30 is less susceptible to the influence of noise when measuring the strain of a non-rotating member on the path of the preload.

In the bearing device 30, the detection unit 42 and the processing unit 43 are attached to the substrate 41, so that the strain sensor 40 can be constructed within the substrate 41. Therefore, in the bearing device 30, the strain sensor 40 is easy to handle (operability is improved).

In the bearing device 30, a location for the strain sensor 40 can be secured simply by forming the flat portion 35ba on the outer peripheral surface 35b, so that a location for the strain sensor 40 can be secured without significantly changing the structure of the outer ring spacer 35 or significantly reducing the rigidity of the outer ring spacer 35.

Figure 6 is a schematic graph showing the relationship between the preload applied to the bearing device 30 and the strain signals SG4a to SG4d. As shown in Figure 6, it is assumed that the strain caused in the outer ring spacer 35 due to the preload is not uniform along the circumferential direction, in which case the values of the strain signals SG4a to SG4d will vary. In the bearing device 30, the calculation unit 45 calculates a representative value of the strain in the outer ring spacer 35 based on the strain signals SG4a to SG4d, and calculates the preload applied to the outer ring spacer 35 based on the representative value and the information stored in the memory unit 44, thereby making it possible to more accurately calculate the preload applied to the outer ring spacer 35.

For example, when the shaft 10 is rotated at high speed, the rolling bearings 32 and 33 may generate heat due to an excessive load or damage to the rolling bearings 32 and 33, and the preload may become excessive due to thermal expansion caused by the heat generated, causing the rolling bearings 32 and 33 to burn out. Since the bearing device 30 has a diagnostic unit 46, the diagnostic unit 46 can determine an abnormality in the rolling bearings 32 and 33 by comparing the preload calculated by the calculation unit 45 with a predetermined threshold value. As a result, appropriate avoidance measures can be taken to prevent the rolling bearings 32 and 33 from burning out.

For example, when a signal indicating that the preload calculated by the calculation unit 45 exceeds a predetermined threshold is output from the diagnosis unit 46, the spindle device 100 may control the motor 50 to reduce the rotation speed of the shaft 10, and may control the pump that circulates the refrigerant to increase the amount of refrigerant circulating through the flow path defined by the groove 31da and the inner surface 20c.

Second Embodiment
A spindle device according to the second embodiment (hereinafter, referred to as "spindle device 110") will be described below. Here, differences from spindle device 100 will be mainly described, and overlapping descriptions will not be repeated.

The spindle device 110 has 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 differs from the spindle device 100 in terms of the structure of the outer ring spacer 35 and the arrangement of the strain sensor 40.

Figure 7 is a cross-sectional view perpendicular to the central axis A of rotation of the spindle device 110. The outer cylinder 20 is not shown in Figure 7. As shown in Figure 7, the outer peripheral surface 35b does not have a flat portion 35ba. A recess 35aa is formed in 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 toward the outer peripheral surface 35b at 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, a location for the strain sensor 40 can be secured simply by forming the recess 35aa on the inner peripheral surface 35a, so that a location for the strain sensor 40 can be secured without significantly changing the structure of the outer ring spacer 35 or significantly reducing the rigidity of the outer ring spacer 35.

Third Embodiment
A spindle device according to the second embodiment (hereinafter, referred to as a "spindle device 120") will be described below. Here, differences from the spindle device 100 will be mainly described, and overlapping descriptions will not be repeated.

The spindle device 120 has 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 differs from the spindle device 100 in terms of the structure of the strain sensor 40.

Figure 8 is a schematic structural diagram of the strain sensor 40 in the spindle device 120. As shown in Figure 8, the strain sensor 40 has a semiconductor integrated circuit 47. The semiconductor integrated circuit 47 is attached to a substrate 41. The detection unit 42 and processing unit 43 are monolithically formed in the semiconductor integrated circuit 47. That is, in the strain sensor 40 of the spindle device 120, the detection unit 42 and processing unit 43 are integrated into a single chip IC (Integrated Circuit).

The strain sensor 40 of the spindle device 120 has a semiconductor integrated circuit 47 in which the detection section 42 and processing section 43 are monolithically formed, which allows the strain sensor 40 to be miniaturized and makes it easier to incorporate into the outer ring spacer 35.

Although the embodiment of the present invention has been described above, the above-mentioned embodiment can be modified in various ways. Furthermore, the scope of the present invention is not limited to the above-mentioned 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 applicable to bearing devices and spindle devices used in machine tools.

10 shaft, 10a first end, 10b second end, 10c outer peripheral surface, 10d step portion, 20 outer cylinder, 20a first end, 20b second end, 20c inner peripheral surface, 30 bearing device, 31 housing, 31a first end, 31b second 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 retainer, 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 spacer, 35a Inner peripheral surface, 35aa Recess, 35ab Bottom surface, 35b Outer peripheral surface, 35ba Flat portion, 36 Cover member, 36a First portion, 36b Second portion, 37 Nut, 38 Spacer, 38a Inner peripheral surface, 38b Outer peripheral surface, 40 Strain sensor, 41 Substrate, 42 Detection unit, 43 Processing unit, 43a Amplification unit, 43b Output unit, 44 Memory unit, 45 Calculation unit, 46 Diagnosis unit, 47 Semiconductor integrated circuit, 50 Motor, 51 Cylindrical 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 shaft, SG1 electrical signal, SG2 amplified signal, SG3 digital signal, SG4b, SG4c, SG4a, SG4d, SG4 strain signal.

Claims (8)

a first rolling bearing having a first inner ring, a first outer ring, and a first rolling element disposed between the first inner ring and the first outer ring, the first rolling bearing being preloaded;
a non-rotating member disposed on a path of the preload;
at least one strain sensor attached to the non-rotating member;
the first inner ring is rotatable relative to the first outer ring and the non-rotating member,
The strain sensor includes a detection unit that outputs a signal corresponding to the strain of the non-rotating member, and a processing unit to which the signal is input,
The processing unit includes an amplifier unit that amplifies the signal , and an output unit that calculates the distortion based on the signal amplified by the amplifier unit ,
A storage unit;
A calculation unit is further provided,
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,
the storage unit stores information indicating a relationship between the representative value and the preload,
The calculation unit is configured to calculate the preload based on the representative value and the information. The strain sensor further includes a substrate attached to the non-rotating member;
The bearing device according to claim 1 , wherein the detection unit and the processing unit are mounted on the substrate. 3. The bearing device according to claim 1 , wherein the strain sensor has a semiconductor integrated circuit in which the detection portion and the processing portion are monolithically formed. Further comprising a diagnostic unit,
The bearing device according to claim 1 , wherein the diagnosing unit is configured to compare the preload calculated by the computing unit with a predetermined threshold value. a second rolling bearing having a second inner ring, a second outer ring, and a second rolling element disposed between the second inner ring and the second outer ring, to which the preload is applied;
the second inner ring is rotatable relative to the second outer ring and the non-rotating member,
5. The bearing device according to claim 1 , wherein the non-rotating member is an outer ring spacer disposed between the first outer ring and the second outer ring. The outer ring spacer has an outer circumferential surface including a flat portion,
The bearing device according to claim 5 , wherein the strain sensor is attached to the flat portion. The outer ring spacer has an inner circumferential surface and an outer circumferential surface,
A recess is formed on the inner circumferential surface so as to recess toward the outer circumferential surface,
The bottom surface of the recess is a flat surface,
The bearing assembly according to claim 5 , wherein the strain sensor is attached to the flat surface. The bearing device according to any one of claims 1 to 7 ,
a shaft rotatably supported by the first rolling bearing;
and a motor for rotating the shaft.

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