Bearing arrangement, spindle arrangement, bearing and spacer

Abstract

A bearing device (30) includes at least one bearing (5) having rolling elements and track surfaces to support a main shaft (4), a member (6 or 5ga) disposed on a path that transmits a pressing force that generates a pre-pressure between the rolling elements and the track surfaces, and at least one load sensor element (50) fixed to the member (6 or 5ga) to measure the pressing force. The at least one load sensor element (50) is a chip component including a thin film pattern (52) whose resistance varies according to the pressing force and a protective layer (54) that insulates and protects the thin film pattern (52).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a bearing device, a spindle device, a bearing, and a spacer, the bearing device including a pre-load sensor that detects a pre-load of a bearing for a spindle of a machine tool or the like. BACKGROUND

[0002] In a spindle device of a machine tool or the like, in order to improve machining accuracy and efficiency, pre-load management of a bearing is required, and thus there is a demand for detecting a pre-load (load) of a bearing. There is also a demand for detecting a sign of an abnormality in a bearing before the abnormality occurs, to prevent a bearing abnormality.

[0003] In Japanese Patent Publication No. 2008-286219 (Patent Literature 1), in a bearing device in which a spacer is interposed between a plurality of rolling bearings arranged in an axial direction, a portion of the spacer is made of a magnetostrictive material, at least a portion of a remaining portion of the spacer other than the portion made of the magnetostrictive material is made of a non-magnetic material, and a pre-load of the bearing is detected based on a change in a magnetic property of the magnetostrictive material portion.

[0004] REFERENCE LIST

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Publication No. 2008-286219 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] In the bearing device disclosed in Japanese Patent Publication No. 2008-286219 (Patent Literature 1), the magnetostrictive material is sandwiched between a pair of spacers obtained by halving an outer ring spacer. Therefore, the structure is complicated, the pair of spacers needs to be put into a housing while being held so as not to be separated, and it is difficult to assemble the bearing device.

[0009] Further, in the pre-load detection using the magnetostrictive material, in addition to the selection of the magnetostrictive material, reduction of temperature drift, hysteresis, and the like of an output signal is also a problem.

[0010] The present disclosure aims to solve the above problems, and an object of the present disclosure is to provide a bearing device, a spindle device, a bearing, and a spacer, the bearing device including a pre-load sensor that detects a pre-load of a bearing in a simple configuration.

[0011] MEANS OF SOLVING THE PROBLEMS

[0012] The present disclosure relates to a bearing device. The bearing device includes at least one bearing that houses rolling elements and a race surface to support a shaft, a member disposed on a path that transmits a pressing force that generates a pre-press between the rolling elements and the race surface, and at least one load sensor element fixed to the member to measure the pressing force. The at least one load sensor element includes a thin film pattern whose resistance varies according to the pressing force, and a protective layer that insulates and protects the thin film pattern.

[0013] Preferably, the pressing force is applied by a load in a direction of the shaft. The at least one load sensor element is a plurality of load sensor elements arranged at equal intervals on a circumference in a plane intersecting the direction of the shaft.

[0014] Preferably, the at least one bearing is a plurality of bearings. The member is a spacer inserted between two bearings of the plurality of bearings on a non-rotation side. The at least one load sensor element is fixed to an end surface of the spacer and abuts a flange of one of the two bearings to transmit the pressing force.

[0015] Preferably, the member is a flange of the at least one bearing. The at least one load sensor element is fixed to an end surface of the flange and abuts an end surface of a spacer disposed adjacent to the flange to transmit the pressing force.

[0016] Preferably, the member is a first spacer obtained by dividing a spacer disposed adjacent to the at least one bearing into a first spacer and a second spacer. The at least one load sensor element is fixed to an end surface of the first spacer and abuts an end surface of the second spacer to transmit the pressing force.

[0017] Preferably, the bearing device further includes a processing unit disposed adjacent to the at least one load sensor element to process an output of the at least one load sensor element. The processing unit includes an amplifier that detects and amplifies a change in resistance of the at least one load sensor element.

[0018] Preferably, the bearing device further includes a processing unit disposed in the vicinity of the at least one load sensor element to process the output of the at least one load sensor element. The at least one load sensor element is a plurality of load sensor elements. The processing unit includes a plurality of amplifiers to process the output of the plurality of load sensor elements, an arithmetic unit to calculate the load based on a sensor output representative value including at least one of a sum, an average, a maximum value, a minimum value, and a difference between the maximum value and the minimum value of the output values obtained by the plurality of amplifiers, and a relationship or an approximate expression of the relationship between the load and the sensor output representative value stored in advance in a memory.

[0019] Preferably, the member is one of a first outer ring spacer and a second outer ring spacer obtained by halving a spacer disposed adjacent to the at least one bearing. The first outer ring spacer and the second outer ring spacer sandwich the at least one load sensor element. The first outer ring spacer and the second outer ring spacer are fastened by a screw, and a pressing force is applied to the at least one load sensor element in advance by the fastening force of the screw.

[0020] Preferably, the member is one of a first outer ring spacer and a second outer ring spacer obtained by halving a spacer disposed adjacent to the at least one bearing. The first outer ring spacer and the second outer ring spacer sandwich the at least one load sensor element. The sandwiching surface of the first outer ring spacer and the second outer ring spacer sandwiching the at least one load sensor element is a flat surface without a protrusion.

[0021] More preferably, the bearing device further includes an oil seal member disposed between the first outer ring spacer and the second outer ring spacer of the spacer.

[0022] Preferably, the member is one of a first spacer and a second spacer obtained by halving a spacer disposed adjacent to the at least one bearing. The first spacer and the second spacer sandwich the at least one load sensor element. A protrusion limiting the position of the second spacer is formed in the first spacer, and a recess fitting the protrusion is formed in the second spacer.

[0023] In another aspect, the present disclosure relates to a spindle device including the bearing device according to any one of the above.

[0024] In still another aspect, the present disclosure relates to a bearing. The bearing includes rolling elements, an inner ring, an outer ring, and at least one load sensor element disposed on an end surface of a fixed ring of the inner ring and the outer ring to measure a pressing force that generates a pre-press between the rolling elements and a raceway surface. The at least one load sensor element includes a thin film pattern whose resistance varies according to the pressing force, and a protective layer that insulates and protects the thin film pattern.

[0025] Preferably, the bearing further includes a processing unit that processes an output of the at least one load sensor element. The processing unit is integrally mounted to the fixed ring.

[0026] In still another aspect, the present disclosure relates to a spacer disposed adjacent to a bearing including rolling elements and a raceway surface. The spacer includes a member that transmits a pressing force that generates a pre-press between the rolling elements and the raceway surface, and at least one load sensor element fixed to the member to measure the pressing force. The at least one load sensor element includes a thin film pattern whose resistance varies according to the pressing force, and a protective layer that insulates and protects the thin film pattern.

[0027] Preferably, the spacer further includes a processing unit that is integrally mounted to the member to process an output of the at least one load sensor element.

[0028] Preferably, the member is a first spacer obtained by dividing the spacer into a first spacer and a second spacer. The at least one load sensor element is fixed to an end surface of the first spacer, and abuts against an end surface of the second spacer to transmit the pressing force.

[0029] Preferably, the first spacer and the second spacer clamp the at least one load sensor element. The first spacer and the second spacer are fastened by a screw. The pressing force is applied in advance to the at least one load sensor element by a fastening force of the screw.

[0030] More preferably, the spacer further includes an oil seal member disposed between the first spacer and the second spacer.

[0031] More preferably, by fitting the oil seal member, a stepped portion that enables the first spacer and the second spacer to be aligned is formed on an inner diameter portion side of the first spacer and the second spacer.

[0032] Preferably, the member is one of a first spacer and a second spacer obtained by dividing the spacer disposed adjacent to the bearing in two. The first spacer and the second spacer clamp the at least one load sensor element, a protrusion that limits a position of the second spacer is formed in the first spacer, and a recess that fits the protrusion is formed in the second spacer.

[0033] Inventive Effects

[0034] According to the present disclosure, a bearing device including a pre-press sensor that detects pre-press of a bearing in a simple configuration, a spindle device, a bearing, and a spacer can be implemented, and maintenance and management of the bearing can be easily performed. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a cross-sectional view showing a schematic configuration of a spindle device according to an embodiment.

[0036] Figure 2 is an enlarged view of a main part on the left side in Figure 1

[0037] Figure 3 is a view showing a first arrangement example of a load sensor element cut along line III-III in Figure 2

[0038] Figure 4 is a view showing a second arrangement example of a load sensor element cut along line III-III in Figure 2

[0039] Figure 5 is a cross-sectional view of a load sensor element 50 cut along line X-X in Figure 3

[0040] Figure 6 is a front view showing the load sensor element 50 in Figure 5

[0041] Figure 7 is a view showing a deformation of a shape of a thin film pattern.

[0042] Figure 8 is a view showing a first improvement example of a structure of a load sensor element.

[0043] Figure 9 is a view showing a second improvement example of a structure of a load sensor element.

[0044] Figure 10 is a view showing a third improvement example of a structure of a load sensor element as an improvement example in Figure 9

[0045] Figure 11 is a view showing an example in which a processing unit that electrically processes an output of a load sensor element is arranged in an outer ring spacer.

[0046] Figure 12 is a circuit configuration view showing a configuration of an amplifier that detects a resistance change of a load sensor element.​​​​​​

[0047] Figure 13 is a view showing a configuration of calculating a pre-press (load) applied to a bearing according to an output of a load sensor element.

[0048] Figure 14 is a view showing a deformation in which a mounting position of a load sensor element is fixed to an end surface of a non-rotating ring of a bearing.

[0049] Figure 15 is a view showing a deformation after changing a fixing position of a load sensor element.

[0050] Figure 16 is a side view showing a deformation after changing a method for fixing a load sensor element.

[0051] Figure 17 is a front view of a cross section cut along a line XVII-XVII in Figure 16 .

[0052] Figure 18 is a cross-sectional view showing an outer ring spacer as an example of improvement in Figure 16 .

[0053] Figure 19 is a cross-sectional view showing an outer ring spacer as an example of improvement in Figure 18 .

[0054] Figure 20 is a cross-sectional view showing an outer ring spacer as an example of improvement in Figure 19 . DETAILED DESCRIPTION

[0055] Embodiments of the present application will be described below with reference to the accompanying drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and overlapping description will be omitted.

[0056] Figure 1 is a cross-sectional view showing a schematic configuration of a spindle device according to an embodiment. Figure 2 is an enlarged view of a main part on the left side in Figure 1 . Figure 2 The bearing device 30 is mainly shown.

[0057] For example, the spindle device 1 in Figure 1 is used as a built-in motor type spindle device of a machine tool. In this case, the motor 40 is assembled at one end side of the spindle 4 supported by the spindle device 1 for a spindle of the machine tool, and a cutting tool such as an end mill (not shown) is connected to the other end side.

[0058] Referring to Figure 1 and 2The spindle device 1 includes bearings 5a, 5b; a spacer 6 disposed adjacent to the bearings 5a, 5b; a motor 40; and a bearing 16 disposed behind the motor. The spindle 4 is rotatably supported by a plurality of bearings 5a, 5b provided in a housing 3 embedded in an inner diameter portion of an outer cylinder 2. The bearing 5a has an inner ring 5ia, an outer ring 5ga, rolling elements Ta, and a retainer Rta. The bearing 5b includes an inner ring 5ib, an outer ring 5gb, rolling elements Tb, and a retainer Rtb. The spacer 6 includes an inner ring spacer 6i and an outer ring spacer 6g.

[0059] A load sensor element (pressure sensitive sensor element) 50 is fixed to one end face 6ga of the outer ring spacer 6g by adhesion or the like. In the case of fixation by adhesion, it is desirable to use an adhesive having excellent oil resistance and heat resistance.

[0060] The inner ring 5ia of the bearing 5a and the inner ring 5ib of the bearing 5b, which are separated in the axial direction, are fitted to the spindle 4 in an interference fit state (press fit state). The inner ring spacer 6i is disposed between the inner rings 5ia, 5ib, and the outer ring spacer 6g is disposed between the outer rings 5ga, 5gb.

[0061] The bearing 5a is a rolling bearing in which a plurality of rolling elements Ta are disposed between the inner ring 5ia and the outer ring 5ga. These rolling elements Ta are separated by the retainer Rta. The bearing 5b is a rolling bearing in which a plurality of rolling elements Tb are disposed between the inner ring 5ib and the outer ring 5gb. These rolling elements Tb are separated by the retainer Rtb.

[0062] The bearings 5a, 5b are bearings in which a preload can be applied using a force in the axial direction, and an angular ball bearing, a deep groove ball bearing, or a tapered roller bearing, or the like, can be used. The angular ball bearing is used as the bearing device 30 in Figure 2 in the axial direction. The two bearings 5a, 5b are mounted in a back-to-back combination (DB combination).

[0063] In this case, a description will be made taking an example of a structure in which the spindle 4 is supported by three bearings 5a, 5b, 16, and a structure in which the spindle 4 is supported by at least three bearings can be used.

[0064] The single-row rolling bearing 16 is a cylindrical roller bearing. The radial load and the axial load acting on the spindle device 1 are supported by the bearings 5a, 5b, which are angular ball bearings. The radial load acting on the spindle device 1 for a machine tool spindle is supported by the single-row bearing 16, that is, the cylindrical roller bearing.

[0065] A cooling medium passage G is formed in the housing 3. The bearings 5a, 5b can be cooled by allowing a cooling medium to flow between the housing 3 and the outer cylinder 2.

[0066] When the grease lubricated bearing is used as the bearing 5a, 5b, the lubricating oil supply passage is not required, and when lubrication with air oil or the like is required, the lubricating oil supply passage is provided in the outer ring spacer 6g. At this time, the lubricating oil supply passage is not shown.

[0067] At the time of assembly, first, the bearing 5a, the spacer 6, the bearing 5b, and the spacer 9 are inserted into the spindle 4 in this order, and initial pre-pressing is applied by tightening the nut 10. Then, the spindle 4 to which the bearings 5a, 5b are attached is inserted into the housing 3 until Figure 2 the right side of the outer ring 5gb of the bearing 5b in the housing 3 abuts on the step portion 3a provided in the housing 3. Finally, the front cover 12 pushes the outer ring 5ga of the left side bearing 5a to fix the spindle 4 to the housing 3.

[0068] At the time of tightening the nut 10, the force acts on the end surface of the inner ring 5ib of the bearing 5b through the spacer 9, and the inner ring 5ib is pushed toward the inner ring spacer 6i. This force is transmitted to the inner ring 5ib, the rolling element Tb, and the outer ring 5gb to apply pre-pressing between the track surfaces of the inner ring 5ib and the outer ring 5gb and the rolling element Tb, and from the outer ring 5gb to the outer ring spacer 6g. The pressing force acts on the outer ring spacer 6g from the right side outer ring 5gb, and the force is also transmitted to the load sensor element 50.

[0069] This force is transmitted to the outer ring 5ga of the bearing 5a, the rolling element Ta, and the inner ring 5ia, and pre-pressing is applied between the track surfaces of the inner ring 5ia and the outer ring 5ga of the left side bearing 5a and the rolling element Ta. The pre-pressing applied to the bearings 5a, 5b is determined by the amount of movement restricted by the dimensional difference between the widths of the outer ring spacer 6g and the inner ring spacer 6i.

[0070] In the single-row bearing 16 of Figure 1 the inner ring 16a is positioned in the axial direction by the cylindrical member 15 fitted to the outer periphery of the spindle 4 and the inner ring holder 19. The inner ring holder 19 is prevented from falling off by the nut 20 screwed to the spindle 4. The outer ring 16b of the bearing 16 is clamped between the positioning member 21 fixed to the cylindrical member 15 and the positioning member 18 fixed to the inner ring holder 19, and slides integrally with the inner ring 16a with respect to the end member 17 in accordance with the expansion and contraction of the spindle 4.

[0071] The motor 40 that drives the spindle 4 is disposed at a position in the axial direction that is interposed between the bearings 5a, 5b and the single-row bearing 16 clamped in the space portion 22 formed between the spindle 4 and the outer cylinder 2. The rotor 14 of the motor 40 is fixed to the cylindrical member 15 fitted to the outer periphery of the spindle 4, and the stator 13 of the motor 40 is fixed to the inner peripheral portion of the outer cylinder 2.

[0072] A cooling medium passage for cooling the motor 40 is not described here.

[0073] A load sensor element 50 that measures the pre-press (load) of the bearings 5 (5a, 5b) is installed in the pre-press path of the spindle device 1. As shown in Figure 2 , the load sensor element 50 is fixed to the end face 6ga of the outer ring spacer 6g by adhesion or the like, abuts against the end face of the outer ring 5ga of the bearing 5a, and measures the pre-press applied to the bearings 5 (5a, 5b).

[0074] When the output of the load sensor element 50 is observed when the spindle device 1 is assembled, it can be checked whether the pre-press is set in advance, and the number of assembly steps can be reduced. Furthermore, when the output of the load sensor element 50 is observed during the operation of the machine tool, it can be known that the amount of pre-press increased by thermal expansion due to heat generated during the operation. When the pre-press change is observed during the operation, it is possible to prevent the decrease in cutting performance and the seizure of the bearings 5 in advance.

[0075] For example, the load sensor element 50 is a pressure-sensitive sensor including a thin film pattern (thin film resistor) that measures the load (pre-press) according to the change in resistance, and is disposed in the path through which the pressing force for generating the pre-press is transmitted.

[0076] Figure 3 is a view showing a first arrangement example of the load sensor element cut along the line III-III in Figure 2 . Figure 4 is a view showing a second arrangement example of the load sensor element cut along the line III-III in Figure 2 . In Figure 3 and Figure 4 , components not needed in the description are omitted.

[0077] Figure 3 Arrangement examples of the load sensor element 50 installed to the end face 6ga of the outer ring spacer 6g are shown. In this case, the load sensor elements 50a, 50b, 50c, 50d are arranged at equal intervals of 90 degrees in the circumferential direction of the outer ring spacer 6g.

[0078] In the example of Figure 4 , the load sensor elements 50a, 50b, 50c are arranged at equal intervals of 120 degrees in the circumferential direction of the outer ring spacer 6g.

[0079] Preferably, the number of load sensor elements 50 is at least 3, as long as the end face of the outer ring 5ga can be pressed uniformly by the load sensor elements 50 in good balance. Furthermore, preferably, the load sensor elements 50 are arranged at equal intervals on substantially the same circumference.

[0080] Reference is made to Figure 5 andFigure 6 The structure of the load sensor element will be described below. Figure 5 is a sectional view of the load sensor element 50 taken along the line X-X in Figure 3 Figure 6 is a front view of the load sensor element 50 in Figure 5

[0081] The load sensor element 50 includes a substrate 51 having insulating properties, a thin film pattern (thin film resistor) 52 provided on the substrate 51 to change resistance in accordance with a change in surface pressure, an electrode 53 connected to the thin film pattern 52, and a protective layer 54 having insulating properties to protect the thin film pattern 52. Since the protective layer 54 is not formed on the electrode 53, a wiring can be directly connected to the electrode 53.

[0082] For example, a ceramic material mainly containing zirconium oxide (Zr02) or aluminum oxide (AI2O3) is used for the substrate 51. The ceramic material has high rigidity and high insulating properties, and is advantageous in that the surface flatness of the substrate 51 can be processed with high precision. For example, the thickness of the substrate 51 is preferably greater than or equal to 0.3 mm and less than or equal to 5 mm from the viewpoint of reducing the thickness of the load sensor element 50 and securing strength in the compression direction.

[0083] For example, the thin film pattern 52 is made of a nickel-chromium (NiCr) or chromium (Cr)-based material, and is formed by vapor deposition, sputtering, or the like. For example, the thickness of the thin film pattern is less than or equal to 1 μm. Further, the protective layer 54 is made of an insulating material, and a thin film of aluminum oxide (AI2O3) or silicon dioxide (Si02) is formed by sputtering or the like, for example. For example, the film thickness of the protective layer 54 is about 2 μm.

[0084] The surface of the electrode 53 can be coated with a material such as copper, silver, or gold to facilitate soldering with a wiring.

[0085] The upper surface of the substrate 51 on which the thin film pattern 52 is formed can be polished to have a flatness of less than or equal to 1 μm. Further, preferably, the parallelism between the upper surface and the lower surface of the substrate 51 is less than or equal to 1 μm.

[0086] As described above, the load sensor element 50 on which the thin film pattern 52 is formed is fixed to the outer ring spacer 6g by bonding or the like, so that it is easier to manufacture than when the thin film pattern is formed directly on the outer ring spacer 6g.

[0087] ​​The load applied to the outer ring spacer 6g is divided by the contact area of the load sensor element 50 abutting against the end surface of the outer ring 5ga of the bearing 5a. In the example described above, since the applied load is divided by the total area of each load sensor element 50 abutting against the protective layer 54, the sensitivity of the load detection increases when the contact area with the protective layer 54 decreases. However, the shape of the load sensor element 50 is set in consideration of the physical property values of each material of the load sensor element 50. In this case, the shape of the load sensor element 50 is rectangular. However, the shape is not limited thereto.

[0088] Figure 7 is a diagram showing a deformation of the shape of the thin film pattern. In Figure 6 the example, the thin film pattern 52 is in a U shape, but can also be a continuous rectangular pattern as Figure 7 indicated, and the shape of the thin film pattern 52 is not limited thereto. When a continuous rectangular pattern is formed on the substrate 51, the pressure sensitive region becomes wide, and the load can be stably detected.

[0089] Figure 8 is a diagram showing a first modified example of the structure of the load sensor element. In Figure 5 the load sensor element 50A of Figure 8 , for example, a plate material made of a ceramic material mainly containing zirconium oxide (Zr02) or aluminum oxide (AI2O3) is used as the protective layer 54A. The protective layer 54A is adhered and fixed so as to cover the thin film pattern 52 formed on the surface of the substrate 51 by an adhesive layer 55 made of an adhesive. For example, the thickness of the protective layer 54A is about 0.3 mm to about 5 mm, which is the same as the thickness of the substrate 51.

[0090] When a plate material made of an insulating material is used as the protective layer 54A, the manufacturing becomes easy compared to the film forming the protective layer 54 by sputtering or the like. Furthermore, the insulating property between the thin film pattern 52 and the outer ring 5ga can be further enhanced, and the load can be stably detected. Furthermore, since the thin film pattern 52 is pressed by the adhesive layer 55, the adhesive layer 55 functions as a buffer layer, and the thin film pattern 52 can be uniformly pressed, thereby improving the load detection accuracy.

[0091] Figure 9 is a diagram showing a second modified example of the structure of the load sensor element. In Figure 5 and Figure 8 , an insulating material is used as the substrate 51. In Figure 9In the load sensor element 50B, a metal material is used as the substrate 51A, and an insulating layer 58 is formed on the surface of the substrate 51A. For example, the insulating layer 58 is made of an insulating material and is formed into a thin film of aluminum oxide (Al2O3) or silicon dioxide (SiO2) by sputtering or the like. For example, the thickness of the insulating layer 58 is approximately 2 μm.

[0092] The metal material for base plate 51A is the same material as that for outer ring spacer 6g, such as bearing steel (SUJ2). In addition to bearing steel, carbon steel (S45C, etc.) is also used. These metal materials are cut to size and heat treated. Surfaces requiring precision are then ground and polished to achieve the desired flatness and surface roughness. For example, flatness is set to less than or equal to 1 μm, and surface roughness is set to less than or equal to Ra 0.1.

[0093] Then, after forming an insulating layer 58 on one surface of the substrate 51A, Figure 5 Similarly, a thin film pattern (thin film resistor) 52 whose resistance changes due to changes in surface pressure and an electrode 53 connected to the thin film pattern 52 are formed, and further a protective layer 54 having insulating properties for protecting the thin film pattern 52 is formed. Since the protective layer 54 is not formed on the electrode 53, wiring can be directly connected to the electrode 53.

[0094] For example, a thin film of aluminum oxide (Al2O3) or silicon dioxide (SiO2) is formed by sputtering or the like as the protective layer 54. For example, the film thickness is about 2 μm.

[0095] When the material of substrate 51A is a metal material, substrate 51A does not crack due to load, and reliability is improved. In addition, manufacturing by forming thin film pattern 52 on substrate 51A made of a small metal part is easier than manufacturing by forming thin film pattern 52 directly on the end surface of outer race spacer 6g, and manufacturing costs can be suppressed.

[0096] Figure 10 is shown as Figure 9 FIG3 is a diagram of a third modified example of the structure of the load sensor element of the modified example. Figure 9 In the embodiment, the protective layer 54 is a thin film made of an insulating material and formed by vapor deposition or sputtering, but in Figure 10 In the load sensor element 50C, for example, a plate material made of a ceramic material mainly containing zirconium oxide (ZrO2) or aluminum oxide (Al2O3) is used as the protective layer 54A. The protective layer 54A is bonded and fixed so as to cover the thin film pattern 52 formed on the surface of the substrate 51 through the adhesive layer 55 made of an adhesive. For example, the thickness of the protective layer 54A is about 0.3 mm to about 5 mm, which is the same as the thickness of the substrate 51.

[0097] When the plate material made of an insulating material is used as the protective layer 54A, manufacturing becomes easy compared to forming a film by sputtering or the like. Furthermore, insulation from the thin film pattern 52 can be further enhanced, and the load can be stably detected. Furthermore, since the thin film pattern 52 is pressed by the adhesive layer 55, the adhesive layer 55 functions as a cushioning layer, and the thin film pattern 52 can be uniformly pressed, thereby improving load detection accuracy.

[0098] As the protective layer 54A, an insulating film made of an insulating material can be formed on a plate material made of a metal material, and the side on which the insulating film is formed can face the side of the thin film pattern 52. In this case, cracking of the protective layer 54A can be prevented.

[0099] Figure 11 is a view showing an example in which a processing unit that electrically processes the output of the load sensor element is arranged in the outer ring spacer. The load sensor elements 50 (50a, 50b, 50c, 50d) fixed at equal intervals in the circumferential direction and the processing unit 70 of the load sensor elements 50 are fixed to one end surface 6ga of the outer ring spacer 6g. The processing unit 70 has a shape that does not interfere with the load sensor elements 50, for example, and is manufactured to be thinner than the load sensor elements 50 to prevent contact with the outer ring 5ga.

[0100] The output of the load sensor element 50 is connected to the processing unit 70 through a wiring 71. An amplifier 72 (72a, 72b, 72c, 72d) that detects and amplifies the resistance change of the load sensor element 50 (50a, 50b, 50c, 50d) is mounted on the processing unit 70, and the processing unit 70 obtains an output value corresponding to the resistance change. Furthermore, an arithmetic unit 73 can be arranged in the processing unit 70. The arithmetic unit 73 can process the resistance change amounts of a plurality of load sensor elements 50, convert the resistance change amounts to a load applied to the outer ring spacer 6g, and output the load to the outside.

[0101] Figure 12 is a circuit configuration view showing the configuration of an amplifier that detects the resistance change of the load sensor element.

[0102] Figure 12The amplifier 72 in the load sensor 50 includes a differential amplifier AMP and resistors R1 to R3 and the load sensor element 50 connected to a DC power source VSDC. The resistors R1 to R3 and the load sensor element 50 constitute a bridge circuit. The resistor R1 and the resistor R2 are connected in series between the positive and negative electrodes of the DC power source VSDC. The load sensor element 50 and the resistor R3 are connected in series between the positive and negative electrodes of the DC power source VSDC. One input node of the differential amplifier is connected to a connection node between the resistor R1 and the resistor R2. The other input node of the differential amplifier is connected to a connection node between the load sensor element 50 and the resistor R3.

[0103] By configuring the bridge circuit as shown in FIG. 8, the resistance change of the load sensor element 50 can be detected by the differential amplifier AMP when the load changes. Figure 12

[0104] As shown in FIG. 9, by configuring the amplifier 72 to perform the electrical processing in the vicinity of the load sensor element 50, the electrical noise can be reduced. In addition, the number of wirings to be led to the outside can be reduced, and the bearing device 30 and the spindle device 1 can be easily assembled. Figure 11

[0105] Figure 13 is a diagram showing a configuration of calculating the pre-press (load) applied to the bearing according to the output of the load sensor element. In this case, an example using four load sensor elements will be described.

[0106] Figure 13 The calculation circuit in the load sensor 50 includes an arithmetic unit 73 that performs an arithmetic process on the output values (Sa, Sb, Sc, Sd) of the load sensor elements 50 (50a, 50b, 50c, 50d) and a memory 74 that stores a relationship or an approximate expression between the output values and the load measured using the outer ring spacer 6g to which the load sensor elements 50 are fixed in advance. The arithmetic unit 73 calculates the load according to the sensor output representative value and the data of the memory 74. The arithmetic unit 73 and the memory 74 can be provided outside the bearing device 30 or inside the processing unit 70.

[0107] The pre-press applied to the outer ring spacer 6g is not uniform in the circumferential direction, and it is also assumed that a difference in the output value depending on the detection position occurs due to the dimensional accuracy of the outer ring spacer 6g, the housing 3, the front cover 12, the bearing 5, and the like. When the spindle 4 rotates, it is also assumed that the circumferential load distribution fluctuates due to the influence of the moment load applied to the spindle 4 or the movement of the rolling elements Ta, Tb of the bearing 5.

[0108] ​​For this reason, in addition to the added value or average value of the output values ​​of the load sensor elements 50 (50a, 50b, 50c, 50d), the maximum value, the minimum value, the difference between the maximum value and the minimum value, etc. are set as sensor output representative values, and the preload (load) is calculated.

[0109] The obtained preload (load) output can be passed through a low-pass filter to reduce output fluctuations caused by the passage of rolling elements Ta, Tb or noise.

[0110] During assembly of the bearing device 30 , the tightening of the preload adjustment member, such as the nut 10 , or the installation of the fixing screw of the front cover 12 , can also be adjusted while checking the preload.

[0111] Furthermore, when the bearing unit 30 is mounted on the spindle unit 1 to rotate the spindle 4 at high speed by the motor 40, it is assumed that the bearing 5 generates heat due to damage to the bearing 5, the preload becomes excessive, and the bearing 5 burns. However, when the preload is calculated and monitored from the load sensor element 50, preventive measures can be taken to prevent the bearing 5 from burning.

[0112] For example, when the preload measured by the load sensor element 50 exceeds a preset reference value, the bearing 5 is determined to be abnormal, and measures such as reducing the rotation speed of the spindle 4, increasing the circulation amount of the cooling medium, and reducing the processing load are taken to prevent the bearing 5 from burning.

[0113] In addition, since the load sensor element 50 is fixed to the outer ring spacer 6g located on the transmission path of the force generating the preload, when assembling the spindle device 1, the initial preload of the bearing 5 (5a, 5b) can be grasped based on the output of the load sensor element 50, and the tightening amount of the nut 10 can be adjusted while checking the preload amount.

[0114] The arithmetic unit 73 can calculate the moment load applied to the main shaft 4 based on the difference between the outputs of the load sensor elements 50 facing each other at 180 degrees. Figure 11 In the arrangement of load sensor elements 50 (50a, 50b, 50c, 50d) in FIG. 4 , the magnitude and direction of the moment load in the vertical direction of main shaft 4 can be calculated based on the difference between load sensor elements 50a and 50b. The magnitude and direction of the moment load in the left-right direction of main shaft 4 can also be calculated based on the difference between load sensor elements 50c and 50d. The magnitude and direction of the moment load can be calculated even when the number of load sensor elements is not four.

[0115] For example, when a cutting tool such as an end mill fixed to the other end side of the spindle device 1 is used to cut a metal workpiece, the load applied to the cutting tool and the load direction can be grasped from the moment load. In addition, it is also possible to detect the collision of the cutting tool with the metal workpiece from the moment load.

[0116] In order to improve the reliability of abnormality diagnosis in the case of pre-press (load) increase, it is also possible to comprehensively judge by further considering the output of other sensors such as temperature sensors, heat flux sensors, and acceleration sensors. For example, when a heat flux sensor is fixed to a non-rotating member (for example, an outer ring spacer 6g) near the bearing 5 and is arranged opposite to the rotating member (for example, the spindle 4), signs of temperature rise due to bearing 5 seizure can be detected early.

[0117] Figure 14 is a diagram showing deformation of an end face of a non-rotating ring of a bearing to which a mounting position of a load sensor element is fixed.

[0118] For example, the load sensor element 50 is fixed to an end face of the outer ring 5ga of the bearing 5a by adhesion or the like. When a plurality of load sensor elements 50 are fixed, it is desirable to use a combination jig (not shown) or the like to fix the load sensor elements so that the heights of the load sensor elements become uniform. Even in this structure, the processing unit 70 can be provided on the end face of the outer ring 5ga. In this case, the processing unit 70 is preferably mounted integrally with the fixed ring (outer ring 5ga).

[0119] The load sensor element 50 is fixed to the end face of the bearing 5, so the load detection unit can be installed compactly.

[0120] Figure 15 is a diagram showing deformation after changing the fixing position of the load sensor element. In Figure 15 , the load sensor element 50 is fixed to an end face 6g1a of one outer ring spacer 6g1 obtained by dividing the outer ring spacer 6g in half in the axial direction, and the end face 6g2a of the other outer ring spacer 6g2 abuts against the load sensor element 50.

[0121] Since the side view of the load sensor element 50 is installed in the same way as Figure 3 , Figure 4 or Figure 11 , a description thereof is omitted.

[0122] The end face 6gl a of the outer ring spacer 6gl on which the load sensor element 50 is fixed and the end face 6g2a of the outer ring spacer 6g2 that presses the load sensor element 50 need to be machined so that the flatness, surface roughness, and parallelism of these end faces 6gl a, 6g2a are less than or equal to a reference value, and each of the outer ring spacers 6gl, 6g2 can be machined with high precision.

[0123] In the end face 6g2a of the outer ring spacer 6g2, a convex surface (not shown) can be provided so that the convex surface and the load sensor element 50 abut against each other. Further, in the end face 6gl a of the outer ring spacer 6gl, a convex surface (not shown) can be provided, and the load sensor element 50 can be fixed to the convex surface.

[0124] Further, the outer ring spacers 6gl, 6g2 that are split in two can be aligned by a pin (not shown) so as not to be separated.

[0125] In this case, the area that requires machining precision can be reduced so as to shorten the machining time while facilitating machining.

[0126] Alternatively, an intermediate layer (cushion layer) (not shown) can be interposed between the load sensor element 50 and the end face 6g2a of the outer ring spacer 6g2 to press the load sensor element 50.

[0127] For example, a coated film of a metal material (for example, aluminum, copper, or a metal alloy) whose rigidity (longitudinal elastic modulus) is lower than that of a material of the outer ring spacer 6g such as a resin material (for example, a fluorine-based resin) can be used as a material of the intermediate layer.

[0128] Since the pressing is performed through the intermediate layer whose rigidity is lower than that of the outer ring spacer 6g, the intermediate layer deforms, and thus the load sensor element 50 can be pressed uniformly and stably.

[0129] Further, with the configuration in which the load sensor element 50 is pressed through the intermediate layer, compared to the case where the intermediate layer is not used, the machining precision (surface roughness, flatness, and the like) of the end face of the outer ring spacer 6g can be reduced, and machining is facilitated.

[0130] The load sensor element 50 and the processing unit 70 or a part of the processing unit 70 can be integrally installed.

[0131] Figure 16 is a side view showing a deformation of the method for fixing the load sensor element after the method is changed. Figure 17 is a front view of a cross section cut along the line XVII-XVII in Figure 16

[0132] ​The load sensor element 50 is disposed between the bisected outer ring spacers 6g1 and 6g2, and preload is applied to the load sensor element 50 by fastening the outer ring spacers 6g1 and 6g2 with screws B. Although the load sensor element 50 can be fixed without applying adhesive to the contact surfaces between the outer ring spacers 6g1 and 6g2 and the load sensor element 50, an adhesive may be used in combination.

[0133] The end faces 6g1a, 6g2a of the outer ring spacers 6g1, 6g2 abutting against the load sensor element 50 have a structure in which no protrusions are provided on the end faces 6g1a, 6g2a so that surface accuracy can be easily obtained by plane grinding, thereby enabling processing to be performed with high-precision surface roughness and flatness.

[0134] When provided on the outer diameter surface of the outer race spacer 6 g , the flattened portion 6 gb can serve as a mark for the arrangement position of the load sensor element 50 .

[0135] When pre-compression is applied to the load sensor element 50 , a dead band in the output of the load sensor element 50 is eliminated, and a reduction in hysteresis and an improvement in linearity can be expected.

[0136] Figure 18 is shown as Figure 16 A cross-sectional view of an outer ring spacer of an improved example.

[0137] When using an air-oil lubricated bearing 5, an air-oil nozzle is formed in the outer ring spacer 6g, from which air-oil is sprayed toward the bearing 5. An oil seal member 6gh is positioned between the outer ring spacers 6g1 and 6g2 to prevent air-oil from leaking from the gap between the divided outer ring spacers 6g to the wiring 71. The oil seal member 6gh can be made of a metal material. However, it is preferably made of a resin material so that it can be pressed and deformed by the outer ring spacers 6g1 and 6g2, thereby preventing the formation of gaps.

[0138] When the load sensor element 50 is clamped between the bisected outer ring spacers 6g1 and 6g2 and fastened with screws B, it is preferable to use a jig (not shown) if alignment of the outer ring spacers 6g1 and 6g2 is difficult. For example, centering is facilitated when the outer ring spacer 6g is inserted into the inner diameter portion of a cylindrical jig for assembly.

[0139] Figure 19 is shown as Figure 18 A cross-sectional view of an outer ring spacer of an improved example.

[0140] like Figure 19As shown, a step portion 6glm, 6g2m is provided in the inner diameter portion of the outer ring spacer 6gl, 6g2, and an oil seal member 6gk is arranged so as to fit into the step portion.

[0141] The oil seal member 6gk enables alignment of the outer ring spacers 6gl, 6g2, so that a jig can be omitted.

[0142] Figure 20 is a cross-sectional view showing an outer ring spacer as an improved example in Figure 19

[0143] As shown, a step portion 6glm, 6g2m is provided in the inner diameter portion of the outer ring spacer 6gl, 6g2, and an oil seal member 6gk is arranged so as to fit into the step portion. Figure 20

[0144] In this structure, the oil seal member is not required, the number of components can be reduced, and the assembly property is improved.

[0145] As described in the above-described embodiments, in the bearing device of the present embodiment, the load sensor element 50 (pressure-sensitive sensor element) is arranged at an end surface of the outer ring spacer 6g or the bearing 5 that is located in a load path that applies a pre-load (load) to the bearing. The load sensor element 50 (pressure-sensitive sensor element) in which a thin film resistor capable of measuring a load is formed is fixed in the circumferential direction of the outer ring spacer 6g by adhesion or the like, and the load sensor element 50 has a structure that is pressed by a member that abuts against the load sensor element 50. Therefore, compared to a case in which a thin film sensor that detects a load is directly formed on a metal member such as an outer ring spacer, the manufacturing can be simplified.

[0146] (SUMMARY)

[0147] Finally, the above-described embodiments will be summarized again with reference to the drawings.

[0148] The present disclosure relates to a bearing device 30. The bearing device 30 includes at least one bearing 5 having a rolling element and a track surface to support a main shaft 4, a member (6 or 5ga) arranged on a path through which a pressing force that generates a pre-load between the rolling element and the track surface is transmitted, and at least one load sensor element 50 fixed to the member (6 or 5ga) so as to be capable of measuring the pressing force. The at least one load sensor element 50 is a chip component including a thin film pattern 52 in which a resistance varies according to the pressing force, and a protective layer 54 that insulates and protects the thin film pattern 52. ​​

[0149] The load sensor element 50 is small in size, and a plurality of load sensor elements 50 can be stably manufactured at a time. Therefore, compared with a case where a thin film sensor that detects a load is directly formed on a metal member such as an outer ring spacer, the manufacturing can be simplified. Therefore, an improvement in reliability and a reduction in manufacturing cost can be expected.

[0150] Preferably, the pressing force is applied by a load in the direction of the main shaft 4. As Figure 3 or Figure 4 indicated, the at least one load sensor element 50 is a plurality of load sensor elements 50a, 50b, 50c, 50d arranged at equal intervals on the same circumference in a plane intersecting the direction of the main shaft 4.

[0151] As described above, the plurality of load sensor elements 50a, 50b, 50c, 50d are arranged dispersedly so that a chip member is easily used as a load sensor element.

[0152] More preferably, the bearing device further includes an arithmetic unit 73 that uses the outputs of the plurality of load sensor elements 50a to 50d to calculate the magnitude and direction of the moment load in the direction orthogonal to the main shaft 4.

[0153] For example, during machining of a workpiece using a cutting tool such as an end mill, the magnitude and direction of the load applied to the cutting tool can be grasped by such a configuration.

[0154] Preferably, as Figure 1 and Figure 2 indicated, the at least one bearing 5 is a plurality of bearings 5a, 5b. The member to which the load sensor element 50 is fixed is an outer ring spacer 6g inserted between the non-rotating side of the two bearings 5a, 5b among the plurality of bearings. The at least one load sensor element 50 is fixed to an end surface 6ga of the spacer, and abuts against a fixed ring (outer ring 5ga) of one of the two bearings 5a, 5b to transmit the pressing force.

[0155] The structure in which the spacer is arranged between the plurality of bearings is common to a main shaft device. Therefore, the bearing device of the present embodiment is easily applied to a main shaft device.

[0156] Preferably, as Figure 14 indicated, the member to which the load sensor element 50 is fixed is a fixed ring (outer ring 5ga) of the at least one bearing. The at least one load sensor element 50 is fixed to an end surface of the fixed ring (outer ring 5ga), and abuts against an end surface of a spacer 6 arranged adjacent to the fixed ring (outer ring 5ga) to transmit the pressing force.

[0157] In this way, the load sensor element can be fixed to the bearing side, rather than to the spacer. The load sensor element 50 is fixed to the end face of the bearing 5, and thus the load detection unit can be installed compactly.

[0158] Preferably, the member to which the load sensor element 50 is fixed is a first spacer 6gl obtained by dividing the spacer 6 adjacent to the at least one bearing into the first spacer 6gl and a second spacer 6g2. The at least one load sensor element 50 is fixed to the end face of the first spacer 6gl, and abuts against the end face of the second spacer 6g2 to transmit the pressing force.

[0159] As described above, when the spacer is divided in two to sandwich the load sensor element 50 therebetween, the load sensor element 50 can be set in the spacer while the spacer is carried at the manufacturing stage.

[0160] Preferably, as shown in Figure 11 The bearing device 30 further includes a processing unit 70 disposed in the vicinity of the at least one load sensor element 50 to process the output of the at least one load sensor element 50. The processing unit 70 includes an amplifier 72 that detects and amplifies the change in resistance of the at least one load sensor element 50.

[0161] Preferably, the bearing device 30 further includes a processing unit 70 disposed in the vicinity of the at least one load sensor element to process the output of the at least one load sensor element 50. As shown in Figure 13 The at least one load sensor element 50 is a plurality of load sensor elements 50a to 50d. The processing unit 70 includes a plurality of amplifiers 72a to 72d that process the outputs of the plurality of load sensor elements 50a to 50d, an arithmetic unit 73, and a memory 74. The arithmetic unit 73 calculates the load from a sensor output representative value having at least one of the sum, the average, the maximum value, the minimum value, and the difference between the maximum value and the minimum value of the output values obtained by the plurality of amplifiers 72a to 72d, and a relationship or an approximate expression of the relationship between the load and the sensor output representative value that is stored in advance in the memory 74.

[0162] Preferably, as shown in Figure 16 and Figure 17As shown in FIG. 6, the member to which the load sensor element 50 is fixed is either one of a first outer ring spacer 6gl and a second outer ring spacer 6g2 obtained by halving a spacer arranged adjacent to at least one bearing. The first outer ring spacer 6gl and the second outer ring spacer 6g2 sandwich at least one load sensor element 50. The first outer ring spacer 6gl and the second outer ring spacer 6g2 are fastened by a screw B, and a pressing force is applied in advance to at least one load sensor element 50 by the fastening force of the screw B.

[0163] When the pre-pressing is applied to the load sensor element 50, the dead zone in the output of the load sensor element 50 is eliminated, and a reduction in hysteresis and an improvement in linearity can be expected.

[0164] Preferably, as shown in FIG. 6, the member to which the load sensor element 50 is fixed is either one of a first outer ring spacer 6gl and a second outer ring spacer 6g2 obtained by halving a spacer arranged adjacent to at least one bearing. The first outer ring spacer 6gl and the second outer ring spacer 6g2 sandwich at least one load sensor element 50. The first outer ring spacer 6gl and the second outer ring spacer 6g2 are fastened by a screw B, and a pressing force is applied in advance to at least one load sensor element 50 by the fastening force of the screw B. Figure 16 Figure 17 As shown in FIG. 6, the member to which the load sensor element 50 is fixed is either one of a first outer ring spacer 6gl and a second outer ring spacer 6g2 obtained by halving a spacer arranged adjacent to at least one bearing. The first outer ring spacer 6gl and the second outer ring spacer 6g2 sandwich at least one load sensor element 50. The first outer ring spacer 6gl and the second outer ring spacer 6g2 are fastened by a screw B, and a pressing force is applied in advance to at least one load sensor element 50 by the fastening force of the screw B.

[0165] Since the end face is a flat surface without a protrusion as described above, surface accuracy can be easily obtained by plane grinding, and the installation surface and the abutment surface of the load sensor element 50 can be machined with high accuracy in surface roughness and flatness.

[0166] More preferably, as shown in FIG. 6, the bearing device 30 further includes an oil seal member 6gh, 6gk arranged between the first outer ring spacer 6gl and the second outer ring spacer 6g2 of the spacer. Figure 18 Figure 19 As shown in FIG. 6, the member to which the load sensor element 50 is fixed is either one of a first outer ring spacer 6gl and a second outer ring spacer 6g2 obtained by halving a spacer arranged adjacent to at least one bearing. The first outer ring spacer 6gl and the second outer ring spacer 6g2 sandwich at least one load sensor element 50. The first outer ring spacer 6gl and the second outer ring spacer 6g2 are fastened by a screw B, and a pressing force is applied in advance to at least one load sensor element 50 by the fastening force of the screw B.

[0167] Preferably, as shown in FIG. 6, the member to which the load sensor element 50 is fixed is either one of a first outer ring spacer 6gl and a second outer ring spacer 6g2 obtained by halving a spacer arranged adjacent to at least one bearing. The first outer ring spacer 6gl and the second outer ring spacer 6g2 sandwich at least one load sensor element 50. The first outer ring spacer 6gl and the second outer ring spacer 6g2 are fastened by a screw B, and a pressing force is applied in advance to at least one load sensor element 50 by the fastening force of the screw B. Figure 20 As shown in FIG. 6, the member to which the load sensor element 50 is fixed is either one of a first outer ring spacer 6gl and a second outer ring spacer 6g2 obtained by halving a spacer arranged adjacent to at least one bearing. The first outer ring spacer 6gl and the second outer ring spacer 6g2 sandwich at least one load sensor element 50. The first outer ring spacer 6gl and the second outer ring spacer 6g2 are fastened by a screw B, and a pressing force is applied in advance to at least one load sensor element 50 by the fastening force of the screw B.

[0168] ​​Accordingly, alignment of the outer ring spacers 6g1, 6g2 can be performed. Furthermore, air-oil leakage can be prevented, thereby having a sealing function. In this structure, an oil seal member is not required, the number of components can be reduced, and assemblyability is improved.

[0169] In another aspect, the present disclosure relates to a spindle device 1 including the bearing device 30 of any one of the above.

[0170] In yet another aspect, the present disclosure relates to a bearing 5a. As shown in Figure 14 the bearing 5a includes rolling elements Ta, an inner ring 5ia, an outer ring 5ga, and at least one load sensor element 50 configured on an end surface of the fixed ring (the outer ring 5ga) of the inner ring 5ia and the outer ring 5ga so as to be able to measure a pressing force that generates a pre-press between the rolling elements Ta and the track surface of the fixed ring. As shown in Figure 6 the at least one load sensor element 50 is a chip component including a thin film pattern 52 whose resistance changes according to the pressing force and a protective layer 54 that insulates and protects the thin film pattern 52.

[0171] Preferably, the bearing 5a further includes a processing unit 70 that processes the output of the at least one load sensor element. The processing unit 70 is integrally mounted to the fixed ring (the outer ring 5ga).

[0172] In yet another aspect, the present disclosure relates to a spacer 6 that is adjacently configured to a bearing 5 including rolling elements and a track surface. The spacer 6 includes an outer ring spacer 6g that is a member that transmits a pressing force that generates a pre-press between the rolling elements and the track surface, and at least one load sensor element 50 that is fixed to the outer ring spacer 6g so as to be able to measure the pressing force. As shown in Figures 5 to 10 the at least one load sensor element 50 is a chip component including a thin film pattern 52 whose resistance changes according to the pressing force and a protective layer 54 that insulates and protects the thin film pattern 52.

[0173] Preferably, as shown in Figure 11 the spacer 6 further includes a processing unit 70 that is integrally mounted to the member that transmits the pressing force that generates the pre-press, to process the output of the at least one load sensor element 50.

[0174] Preferably, as shown in Figure 15As shown, the member to which the load sensor element 50 is fixed is the first spacer 6gl obtained by dividing the outer ring spacer 6g into the first spacer 6gl and the second spacer 6g2. The at least one load sensor element 50 is fixed to an end face 6gla of the first spacer 6gl, and abuts against an end face 6ga of the second spacer 6g2 to transmit the pressing force.

[0175] Preferably, as shown in Figure 16 and Figure 17 The first spacer 6gl and the second spacer 6g2 sandwich the at least one load sensor element 50. The first spacer 6gl and the second spacer 6g2 are fastened by the screw B. The pressing force is applied in advance to the at least one load sensor element 50 by the fastening force of the screw B.

[0176] More preferably, as shown in Figure 18 and Figure 19 The outer ring spacer 6g further includes an oil seal member 6gh, 6gk arranged between the first spacer 6gl and the second spacer 6g2.

[0177] More preferably, as shown in Figure 19 By fitting the oil seal member 6gk, a stepped portion that enables the first spacer 6gl and the second spacer 6g2 to be aligned is formed on the inner diameter portion side of the first spacer 6gl and the second spacer 6g2.

[0178] With this configuration, the outer ring spacers 6gl, 6g2 can be aligned by the oil seal member 6gk, and a jig for aligning the outer ring spacers 6gl, 6g2 can be omitted.

[0179] It should be understood that the disclosed implementations are exemplary and non-limiting in all respects. The scope of the invention is not limited by the description of the implementations but is defined by the claims, and it is intended to include all modifications within the meaning and range of equivalency of the claims.

[0180] List of Reference Signs

[0181] 1: spindle device; 2: outer cylinder; 3: housing; 3a, 6g2n: stepped portion; 4: spindle; 5, 5a, 5b, 16: bearing; 5ga, 5gb, 16b: outer ring; 5ia, 5ib, 16a: inner ring; 6, 9: spacer; 6g, 6g1, 6g2: outer ring spacer; 6g1a, 6g2a, 6ga: end face; 6g1m, 6g2m: stepped portion; 6g1n: flange; 6gb: planarization portion; 6gh, 6gk: oil seal member; 6i: inner ring spacer; 10, 20: nut; 12: front cover; 13: stator; 14: rotor; 15: cylindrical member; 17: end member; 18, 21: positioning member; 19: inner ring retainer; 22: space portion; 27, 73: arithmetic unit; 28, 74: memory; 30: bearing device; 40: motor; 50, 50A, 50B, 50a, 50b, 50c, 50d: load sensor element; 51, 51A: substrate; 52: thin film pattern; 53: electrode; 54, 54A: protective layer; 55: adhesive layer; 58: insulating layer; 70: processing unit; 71: wiring; 72, 72a, 72d: amplifier; AMP: differential amplifier; B: screw; G: cooling medium passage; R1, R2, R3: resistor; Rta, Rtb: retainer; Ta, Tb: rolling element; VSDC: power supply.

Claims

1. A bearing device comprising: at least one bearing having rolling elements and a raceway surface for supporting the shaft; a member disposed on a path for transmitting a pressing force for generating a preload between the rolling element and the raceway surface; as well as at least one load sensor element fixed to the component to measure the pressing force, wherein: The at least one load sensor element includes a thin film pattern whose resistance changes according to a pressing force and a protection layer for insulating and protecting the thin film pattern. The pressing force is applied by a load in the direction along the axis, The at least one load sensor element is a plurality of load sensor elements arranged at equal intervals on a circumference within a plane intersecting the direction along the axis, The bearing device further includes an arithmetic unit that calculates the magnitude and direction of a moment load in a direction orthogonal to the axis using outputs from the plurality of load sensor elements.

2. The bearing device according to claim 1, wherein: The at least one bearing is a plurality of bearings, The member is a non-rotating spacer inserted between two bearings among the plurality of bearings. The at least one load sensor element is fixed to an end surface of the spacer and abuts against a fixing ring of one of the two bearings to transmit the pressing force.

3. The bearing device according to claim 1, wherein: The component is a retaining ring of the at least one bearing, The at least one load sensor element is fixed to an end surface of the fixing ring and abuts against an end surface of a spacer disposed adjacent to the fixing ring to transmit the pressing force.

4. The bearing device according to claim 1, wherein: The member is the first spacer obtained by dividing a spacer disposed adjacent to the at least one bearing into a first spacer and a second spacer. The at least one load sensor element is fixed to the end surface of the first spacer and abuts against the end surface of the second spacer to transmit the pressing force.

5. The bearing device according to claim 1, wherein: The bearing device further includes a processing unit, which is arranged near the at least one load sensor element to process the output of the at least one load sensor element. The processing unit includes an amplifier that detects and amplifies a change in resistance of the at least one load sensor element.

6. The bearing device according to claim 1, wherein: The bearing device further comprises a processing unit, which is arranged near the at least one load sensor element to process the output of the at least one load sensor element, wherein: said at least one load sensor element being a plurality of load sensor elements, The processing unit includes: a plurality of amplifiers that process outputs of the plurality of load sensor elements; arithmetic unit; and Memory, The operation unit calculates the load based on the sensor output representative value, the relationship between the load and the sensor output representative value pre-stored in the memory, or an approximate expression of the relationship, wherein the sensor output representative value includes at least one of the addition value, average value, maximum value, minimum value and difference between the maximum value and the minimum value of the output values ​​obtained by the multiple amplifiers.

7. The bearing device according to claim 1, wherein: The member is one of a first outer ring spacer and a second outer ring spacer obtained by dividing a spacer adjacently arranged on the at least one bearing into two. The first outer race spacer and the second outer race spacer clamp the at least one load sensor element, The first outer ring spacer and the second outer ring spacer are fastened by screws, A pressing force is applied in advance to the at least one load sensor element by the tightening force of the screw.

8. The bearing device according to claim 1, wherein: The member is one of a first spacer and a second spacer obtained by dividing a spacer disposed adjacent to the at least one bearing into two. The first spacer and the second spacer clamp the at least one load sensor element, A convex portion that restricts the position of the second spacer is formed on the first spacer.

9. A spindle device comprising the bearing device according to any one of claims 1 to 8.

10. A bearing for supporting a shaft, comprising: rolling elements; inner circle; outer ring; as well as At least one load sensor element is arranged on the end surface of the fixed ring of the inner ring and the outer ring to measure the pressing force that generates preload between the rolling element and the track surface of the fixed ring, wherein The at least one load sensor element includes a thin film pattern whose resistance changes according to a pressing force and a protection layer for insulating and protecting the thin film pattern. The pressing force is applied by a load in the direction along the axis, The at least one load sensor element is a plurality of load sensor elements arranged at equal intervals on a circumference within a plane intersecting the direction along the axis, The bearing further includes an arithmetic unit that calculates the magnitude and direction of a moment load in a direction orthogonal to the axis using outputs from the plurality of load sensor elements.

11. The bearing according to claim 10, wherein: The bearing further comprises a processing unit that processes the output of the at least one load sensor element, wherein The processing unit is integrally mounted on the fixing ring.

12. A spacer, the spacer being disposed adjacent to a bearing comprising rolling elements and a raceway surface, the bearing supporting a shaft, the spacer comprising: a member for transmitting a pressing force for generating a preload between the rolling element and the raceway surface; as well as at least one load sensor element fixed to the component to measure the pressing force, wherein: The at least one load sensor element includes a thin film pattern whose resistance changes according to a pressing force and a protection layer for insulating and protecting the thin film pattern. The pressing force is applied by a load in the direction along the axis, The at least one load sensor element is a plurality of load sensor elements arranged at equal intervals on a circumference within a plane intersecting the direction along the axis, The spacer further includes an arithmetic unit that calculates the magnitude and direction of a moment load in a direction orthogonal to the axis using outputs from the plurality of load sensor elements.

13. The spacer according to claim 12, wherein The spacer further comprises a processing unit integrally mounted to the member for processing an output of the at least one load sensor element.

Images