Patent ID: 12196257

DESCRIPTION OF EMBODIMENT

With reference to the drawings, an embodiment of the present invention will be described below. In the following drawings, the same or corresponding component is designated by the same reference numeral, and the overlapping description will be omitted.

FIG.1is a sectional diagram illustrating a schematic configuration of a spindle device according to an embodiment.FIG.2is an enlarged view of a left side main portion inFIG.1.FIG.2mainly illustrates a bearing device30.

For example, a spindle device1inFIG.1is used as a built-in motor type spindle device of a machine tool. In this case, a motor40is incorporated on one end side of a main shaft4supported by spindle device1for a machine tool spindle, and a cutting tool such as an end mill (not illustrated) is connected to the other end side.

With reference toFIGS.1and2, spindle device1includes bearings5a,5b, spacer6disposed adjacent to bearings5a,5b, motor40, and a bearing16disposed behind the motor. Main shaft4is rotatably supported by the plurality of bearings5a,5bprovided in a housing3embedded in an inner diameter portion of an outer cylinder2. Bearing5aincludes an inner ring5ia, an outer ring5ga, a rolling element Ta, and a retainer Rta. Bearing5bincludes an inner ring5ib, an outer ring5gb, a rolling element Tb, and a retainer Rtb. Spacer6includes an inner-ring spacer6iand an outer-ring spacer6g.

A load sensor element (pressure-sensitive sensor element)50is fixed to one end face6gaof outer-ring spacer6gby adhesion or the like. In the case of fixing by the adhesion, an adhesive having excellent oil resistance and heat resistance is desirably used,

Inner ring5iaof bearing5aand inner ring5ibof bearing5b, which are separated in an axial direction, are fitted to main shaft4in an interference fit state (press-fitted state). Inner-ring spacer6iis disposed between inner rings5ia,5ib, and outer-ring spacer6gis disposed between outer rings5ga,5gb.

Bearing5ais a rolling bearing in which a plurality of rolling elements Ta are disposed between inner ring5iaand outer ring5ga. These rolling elements Ta are spaced by retainer Rta. Bearing5bis a rolling bearing in which a plurality of rolling elements Tb are disposed between inner ring5iband outer ring5gb. These rolling elements Tb are spaced by retainer Rtb.

Bearings5a,5bare bearings capable of applying a preload by force in an axial direction, and an angular ball bearing, a deep groove ball bearing, a tapered roller bearing, or the like can be used. The angular ball hearing is used as bearing device30inFIG.2, and two bearings5a,5bare installed in a back-surface combination (DB combination).

In this case, a structure in which main shaft4is supported by three bearings5a,5b,16will be described as an example, and a structure in which main shaft4is supported by at least three bearings may be used.

Single-row rolling bearing16is a cylindrical roller bearing. A radial load and an axial load that act on spindle device1are supported by bearings5a,5bthat are angular ball bearings. A radial load acting on spindle device1for the machine tool spindle is supported by single-row beating16that is the cylindrical roller bearing,

A cooling medium passage G is formed in housing3. Bearings5a,5bcan be cooled by allowing a cooling medium to flow between housing3and outer cylinder2.

A lubricating oil supply passage is not required when a grease lubrication bearing is used as bearings5a,5b, and the lubricating oil supply passage is provided in outer-ring spacer6gwhen lubrication of air oil or the like is required. At this point, the lubricating oil supply passage is not illustrated.

At the time of assembly, first, bearing5a, spacer6, bearing5b, and spacer9are sequentially inserted into main shaft4, and an initial preload is applied by tightening a nut10. Then, main shaft4to which bearings5a,5bare attached is inserted into housing3until a right side of outer ring5gbof bearing5binFIG.2hits a step3aprovided in housing3. Finally, a front lid12pushes outer ring5gaof left bearing5ato fix main shaft4to housing3.

When nut10is tightened, the force acts on the end face of inner ring5ibof hearing5bthrough spacer9, and inner ring5ibis pushed toward inner-ring spacer6i. This force is transmitted to inner ring5ib, rolling element Tb, and outer ring5gbto apply the preload between raceway surfaces of inner ring5iband outer ring5gband rolling element Tb, and also transmitted from outer ring5gbto outer-ring spacer6g. Pressing force acts on outer-ring spacer6gfrom right outer ring5gb, and force is also transmitted to load sensor element50.

This force is transmitted to outer ring5ga, rolling element Ta, and inner ring5iain bearing5a, and also applies the preload between the raceway surfaces of inner ring5iaand outer ring5gaof left bearing5aand rolling element Ta. The preload applied to bearings5a,5bis determined by, for example, a movement amount restricted by a dimensional difference between widths of outer-ring spacer6gand inner-ring spacer6i.

In single-row hearing16ofFIG.1, an inner ring16ais positioned in the axial direction by a cylindrical member15fitted to an outer periphery of main shaft4and an inner-ring retainer19. Inner-ring retainer19is prevented from coming off by a nut20screwed to main shaft4. An outer ring16bof hearing16is sandwiched between a positioning member21fixed to cylindrical member15and a positioning member18fixed to inner-ring retainer19, and slides integrally with inner ring16awith respect to an end member17in accordance with expansion and contraction of main shaft4.

Motor40that drives main shaft4is disposed at an intermediate position in the axial direction sandwiched between bearings5a,5band single-row bearing16in a space portion22formed between main shaft4and outer cylinder2. A rotor14of motor40is fixed to cylindrical member15fitted to the outer periphery of main shaft4, and a stator13of motor40is fixed to an inner peripheral portion of outer cylinder2.

The cooling medium passage for cooling motor40is not illustrated here.

Load sensor element50measuring the preload (load) of hearing5(5a,5b) is mounted on a preload path of spindle device1. As illustrated inFIG.2, load sensor element50is fixed to end face6gaof outer-ring spacer6gby the adhesion or the like, abuts on the end face of outer ring5gaof bearing5a, and measures the preload applied to bearing5(5a,5b).

When the output of load sensor element50is observed at the time of assembling spindle device1, whether the preload is set in advance can be checked, and the number of assembling steps can be reduced. In addition, a preload amount increased by thermal expansion due to heat generation during operation can be known when the output of load sensor element50is observed during, the operation of the machine tool. When a preload change during the operation is observed, degradation of cutting performance and seizure of bearing5can be prevented in advance.

For example, load sensor element50is a pressure-sensitive sensor including a thin film pattern (thin film resistor) that measures a load (preload) from a change in electric resistance, and is disposed on the path through which pressing force generating the preload is transmitted.

FIG.3is a view illustrating a first arrangement example of the load sensor element taken along a line III-III inFIG.2.FIG.4is a view illustrating a second arrangement example of the load sensor element taken along the inFIG.2. InFIGS.3and4, components unnecessary for the description are omitted.

FIG.3illustrates the arrangement example of load sensor element50mounted on end face6gaof outer-ring spacer6g. In this case, load sensor elements50a,50b,50c,50dare arranged at equal intervals of 90 degrees in a circumferential direction of outer-ring spacer6g.

In the example ofFIG.4, load sensor elements50a,50b,50care arranged at equal intervals of 120 degrees in the circumferential direction of outer-ring spacer6g.

The number of load sensor elements50is preferably at least3as long as the end face of outer ring5gacan be uniformly pressed with good balance through load sensor elements50. In addition, load sensor elements50are preferably arranged at equal intervals on substantially the same circumference.

With reference toFIGS.5and6, the structure of the load sensor element will be described below.FIG.5is a sectional view illustrating load sensor element50taken along a line X-X inFIG.3.FIG.6is a front view illustrating load sensor element50inFIG.5.

Load sensor element50includes a substrate51having an insulating property, a thin film pattern (thin film resistor)52disposed on substrate51to change resistance with a change in surface pressure, an electrode53connected to thin film pattern52, and a protective layer54having the insulating property protecting thin film pattern52. Because protective layer54is not formed on electrode53, wiring can be directly connected to electrode53.

For example, a ceramic material containing mainly zirconia (ZrO2) or alumina (Al2O3) is used for substrate51. The ceramic material has high rigidity and high insulating property, and can process the surface flatness of substrate51with high accuracy, which is advantageous. For example, a thickness of substrate51is 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 load sensor element50and securing strength in a compression direction.

For example, thin film pattern52is made of nickel chromium (NiCr) or chromium (Cr)-based material, and 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. In addition, protective layer54is made of an insulating material, and for example, a thin film of alumina (Al2O3) or silicon dioxide (SiO2) is formed by sputtering or the like. For example, the film thickness of protective layer54is about 2 μm.

The surface of electrode53may be coated with a material such as copper, silver, or gold to facilitate soldering with the wiring.

An upper surface of substrate51on which thin film pattern52is formed may be polished so as to have flatness less than or equal to 1 μm. In addition, parallelism between the upper surface and the lower surface of substrate51is preferably less than or equal to 1 μm.

As described above, load sensor element50on which thin film pattern52is formed is fixed to outer-ring spacer6gby the adhesion or the like, so that it is easier to manufacture than directly forming the thin film pattern on outer-ring spacer6g.

The load applied to outer-ring spacer6gis divided by the contact area of load sensor element50abutting on the end face of outer ring5gaof bearing5a. In the above-described example, because the applied load is divided by the total area of each load sensor element50abutting on protective layer54, the sensitivity of load detection is increased when the contact area with protective layer54is reduced. However, the shape of load sensor element50is set in consideration of each material physical property value of load sensor element50. In this case, the shape of load sensor element50is rectangular. However, the shape is not limited thereto.

FIG.7is a view illustrating a modification of the shape of the thin film pattern. Thin film pattern52has a U-shape in the example ofFIG.6, but may be a continuous rectangular pattern as illustrated inFIG.7, and the shape of thin film pattern52is not limited thereto. When the continuous rectangular pattern is formed on substrate51, a pressure-sensitive area is widened, and the load can be stably detected.

FIG.8is a view illustrating a first improvement example of the structure of the load sensor element. InFIG.5, protective layer54is the thin film made of the insulating material and formed by vapor deposition or sputtering, but in a load sensor element50A ofFIG.8, for example, a plate material made of a ceramic material containing mainly zirconia (ZrO2) or alumina. (Al2O3) is used as a protective layer54A. Protective layer54A is bonded and fixed so as to cover thin film pattern52formed on the surface of substrate51through an adhesive layer55made of the adhesive. For example, the thickness of protective layer54A is about 0.3 mm to about 5 mm, which is the same as the thickness of substrate51.

When the plate material made of the insulating material is used as protective layer54A, manufacturing is facilitated as compared with the film formation of protective layer54by sputtering or the like. In addition, the insulation between thin film pattern52and outer ring5gacan be further enhanced, and the load can be stably detected. In addition, because thin film pattern52is pressed through adhesive layer55, adhesive layer55serves as a cushion layer and can uniformly press thin film pattern52, so that load detection accuracy is improved.

FIG.9is a view illustrating a second improvement example of the structure of the load sensor element. InFIGS.5and8, the insulating material is used as substrate51. In a load sensor element50B ofFIG.9, a metal material is used as a substrate51A, and an insulating layer58is formed on the surface of substrate51A. For example, insulating layer58is made of the insulating material, and the thin film of alumina (Al2O3) or silicon dioxide (SiO2) is formed by sputtering or the like. For example, the thickness of insulating layer58is about 2 μm.

The same material as that of outer-ring spacer6g, for example, bearing steel (SUJ2) is used as the metal material of substrate51A. Carbon steel (S45C or the like) is used other than the bearing steel. These metal materials are cut to a certain size and subjected to a heat treatment, and thereafter, and a surface requiring processing accuracy is polished and lapped to be finished to have target flatness and surface roughness. For example, the flatness is set to less than or equal to 1 μm, and the surface roughness is set to less than or equal to Ra 0.1.

Then, after insulating layer58is formed on one surface of substrate51A, thin film pattern (thin film resistor)52of which resistance changes due to the change in surface pressure and electrode53connected to thin film pattern52are formed similarly toFIG.5, and protective layer54having the insulating property protecting thin film pattern52is further formed. Because protective layer54is not formed on electrode53, the wiring can be directly connected to electrode53.

For example, the thin film of alumina (Al2O3) or silicon dioxide (SiO2) is formed as protective layer54by sputtering or the like. For example, the film thickness is about 2 μm.

When the material of substrate51A is the metal material, substrate51A is not cracked by a load, and reliability is improved. In addition, manufacture by forming thin film pattern52on substrate51A made of small metal pieces is easier than manufacture by forming the thin film pattern52directly on the end face of outer-ring spacer6g, and the manufacturing cost can be suppressed.

FIG.10is a view illustrating a third improvement example of the structure of the load sensor element that is the improvement example inFIG.9. InFIG.9, protective layer54is the thin film made of the insulating material and formed by vapor deposition or sputtering, but in a load sensor element50C ofFIG.10, for example, the plate material made of the ceramic material containing mainly zirconia (ZrO2) or alumina (Al2O3) is used as protective layer54A. Protective layer54A is bonded and fixed so as to cover thin film pattern52formed on the surface of substrate51through adhesive layer55made of the adhesive. For example, the thickness of protective layer54A is about 0.3 mm to about 5 mm, which is the same as the thickness of substrate51.

When the plate material made of the insulating material is used as protective layer54A, manufacturing is facilitated as compared with the film formation by sputtering or the like. In addition, the insulation from thin film pattern52can be further enhanced, and the load can be stably detected. In addition, because thin film pattern52is pressed through adhesive layer55, adhesive layer55serves as a cushion layer and can uniformly press thin film pattern52, so that load detection accuracy is improved.

As protective layer54A, the insulating film made of the insulating material may be formed on the plate material made of the metal material, and the side on which the insulating film is formed may face the side of thin film pattern52. In this case, cracking of protective layer54A can be prevented.

FIG.11is a view illustrating an example in which a processing unit that electrically processes the output of the load sensor element is disposed in the outer-ring spacer. Load sensor element50(50a,50b,50c,50d) fixed at equal intervals in the circumferential direction and a processing unit70of load sensor element50are fixed to one end face6gaof outer-ring spacer6g. For example, processing unit70has a shape that does not interfere with load sensor element50, and is manufactured so as to be thinner than load sensor element50to prevent the contact with outer ring5ga.

The output of load sensor element50is connected to processing unit70by wiring71. An amplifier72(72a,72b,72c,72d) that detects and amplifies a resistance change of load sensor element50(50a,50b,50c,50d) is mounted on processing unit70, and processing unit70obtains an output value corresponding to the resistance change. In addition, an arithmetic unit73may be disposed in processing unit70. Arithmetic unit73may process a resistance change amount of the plurality of load sensor elements50, convert the resistance change amount into a load applied to outer-ring spacer6g, and output the load to the outside.

FIG.12is a circuit configuration diagram illustrating a configuration of the amplifier that detects the resistance change of the load sensor element.

Amplifier72inFIG.12includes resistors R1to R3and load sensor element50that are connected to a DC power supply VSDC and a differential amplifier AMP. Resistors R1to R3and load sensor element50configure a bridge circuit. Resistor R1and resistor R2are connected in series between a positive electrode and a negative electrode of DC power supply VSDC. Load sensor element50and resistor R3are connected in series between the positive electrode and the negative electrode of DC power supply VSDC. One input node of differential amplifier AMP is connected to a connection node between resistor R1and resistor R2. The other input node of differential amplifier AMP is connected to the connection node between load sensor element50and resistor R3.

With the bridge circuit configuration as illustrated inFIG.12, the resistance change of load sensor element50can be detected by differential amplifier AMP when the load changes.

The electric processing is performed near load sensor element50by disposing amplifier72as illustrated inFIG.11, so that an electric noise can be reduced. In addition, the number of wires to be drawn to the outside can be reduced, and bearing device30and spindle device1can be easily assembled.

FIG.13is a view illustrating a configuration in which the preload (load) applied to the bearing is calculated from the output of the load sensor element. In this case, an example in which four load sensor elements are used will be described.

A calculation circuit inFIG.13includes arithmetic unit73that performs arithmetic processing on an output value (5a,5b,5c,5d) of load sensor element50(50a,50b,50c,50d) and a storage74that stores a relationship between the output value measured using outer-ring: spacer6gto which load sensor element50is fixed in advance and the load or an approximate expression. Arithmetic unit73calculates the load from a sensor output representative value and data of storage74. Arithmetic unit73and storage74may be provided outside bearing device30or inside processing unit70.

The preload applied to outer-ring spacer6gis not uniform in the circumferential direction, and it is also assumed that a difference in output value depending on a detection location is generated due to the dimensional accuracy of outer-ring spacer6g, housing3, front lid12, bearing5, and the like. When main shall4rotates, it is also assumed that a circumferential load distribution fluctuates due to influence of a moment load applied to main shaft4or movement of rolling elements Ta, Tb of bearing5.

For this reason, a maximum value, a minimum value, a difference between the maximum value and the minimum value, and the like are set as the sensor output representative value in addition to an addition value or an average value of the output values of load sensor elements50(50a,50b,50c,50d), and the preload (load) is calculated.

The output of the obtained preload (load) may be passed through a low-pass filter to reduce output fluctuation due to the passage of rolling elements Ta, Tb or the noise.

During the assembly of bearing device30, fastening of a preload adjusting component, for example, nut10, or mounting of a fixing screw of front lid12can be also adjusted while viewing the preload.

In addition, when bearing device30is mounted on spindle device1to rotate main shaft4at a high speed by motor40, it is assumed that bearing5generates heat due to damage of bearing5, the preload becomes excessive, and bearing5burns out. However, when the preload is calculated and monitored from load sensor element50, an avoidance measure can be taken so as not to burn out beating5.

For example, when the preload measured by load sensor element50exceeds a reference value set in advance, bearing5is determined to be abnormal, and measures such as lowering the rotational speed of main shaft4, increasing the circulation amount of the cooling medium, and reducing the machining load are taken to prevent burning of bearing5.

In addition, because load sensor element50is fixed to outer-ring spacer6glocated on the transmission path of the force generating the preload, the initial preload of bearing5(5a,5b) can be grasped from the output of load sensor element50when spindle device1is assembled, and the fastening amount of nut10can be adjusted while viewing the preload amount.

Arithmetic unit73may calculate a moment load applied to main shaft4from the difference between outputs of load sensor elements50facing each other at 180 degrees. For example, in the arrangement of load sensor element50(50a,50b,50c,50d) inFIG.11, the magnitude and direction of the moment load in the vertical direction of main shaft4can be calculated from the difference between load sensor elements50a,50b. The magnitude and direction of the moment load in the left-right direction of main shall4can also be calculated from the difference between load sensor elements50c,50d. Even when the number of load sensor elements is not four, the magnitude and direction of the moment load can be calculated.

For example, when a metal workpiece is cut with a cutting tool such as an end mill fixed to the other end side of spindle device1, the load and the load direction applied to the cutting tool can be grasped from the moment load. In addition, it is also possible to detect that the cutting tool collides with the metal workpiece from the moment load.

In order to increase the reliability of an abnormal diagnosis with an increase in the preload (load), it is also possible to comprehensively determine by further considering outputs of other sensors such as a temperature sensor, a heat flux sensor, and an acceleration sensor. For example, when the heat flux sensor is fixed to a non-rotating member (for example, outer-ring spacer6g) near bearing5and disposed to face the rotating member (for example, main shaft4), a sign of temperature rise due to the seizure of bearing5can be detected early.

FIG.14is a view illustrating a modification in which the mounting position of the load sensor element is fixed to the end face of the non-rotating wheel of the bearing.

For example, load sensor element50is fixed to the end face of outer ring5gaof bearing5aby the adhesion or the like. When the plurality of load sensor elements50are fixed, it is desirable to fix the load sensor elements using a bonding jig (not illustrated) or the like such that the heights of the load sensor elements become uniform. Even in this structure, processing unit70may be provided on the end face of outer ring5ga. In this case, processing unit70is preferably mounted integrally with a fixed ring (outer ring5ga).

Load sensor element50is fixed to the end face of bearing5, so that a load detection unit can be compactly mounted.

FIG.15is a view illustrating a modification in which the fixed position of the load sensor element is changed. InFIG.15, load sensor element50is fixed to an end face6g1aof one outer-ring spacer6g1obtained by dividing outer-ring spacer6ginto two in the axial direction, and an end face6g2aof the other outer-ring spacer6g2abuts on load sensor element50.

Because the side view in which load sensor element50is mounted is the same as that inFIG.3,4, or11, the description thereof is omitted.

End face6g1aof outer-ring spacer6g1to which load sensor element50is fixed and end face6g2aof outer-ring spacer6g2that presses load sensor element50need to be processed such that flatness and surface roughness and the parallelism of these end faces6g1a,6g2aare less than or equal to reference values, and each of outer-ring spacers6g1,6g2can be processed with high accuracy.

In end face6g2aof outer-ring spacer6g2, a convex surface (not illustrated) may be provided such that the convex surface and load sensor element50abut on each other. In addition, in end face6g1aof outer-ring spacer6g1, the convex surface (not illustrated) may be provided, and load sensor element50may be fixed to the convex surface.

Furthermore, outer-ring spacers6g1,6g2divided into two may be aligned by pins (not illustrated) so as not to be separated.

In this case, the area for which the machining accuracy is required can be reduced, so that the machining time can be shortened while the machining is facilitated.

Alternatively, an intermediate layer (cushion layer) (not illustrated) may be inserted between load sensor element50and end face6g2aof outer-ring spacer6g2to press load sensor element50.

For example, a coating thin film of a metal material (for example, aluminum, copper, or a metal alloy) having lower rigidity (longitudinal elastic modulus) than the material of outer-ring spacer6g, a resin material (for example, a fluorine-based resin), or the like can be used as the material of the intermediate layer.

The intermediate layer is deformed by the pressing through the intermediate layer having lower rigidity than outer-ring spacer6g, and load sensor element50can be uniformly and stably pressed.

In addition, with the configuration in which load sensor element50is pressed through the intermediate layer, the processing accuracy (surface roughness, flatness, and the like) of the end face of outer-ring spacer6gcan be reduced as compared with the case where the intermediate layer is not used, and the processing is facilitated.

Load sensor element50and processing unit70or a part of processing unit70may be integrally mounted.

FIG.16is a side view illustrating a modification in which a method for fixing the load sensor element is changed.FIG.17is an arrow view of a section taken along a line XVII-XVII inFIG.16.

Load sensor element50is disposed between the two divided outer-ring spacers6g1,6g2, and the preload is applied to load sensor element50by fastening outer-ring spacers6g1,6g2with a screw B. Although load sensor element50can be fixed without applying the adhesive to the contact surfaces of outer-ring spacers6g1,6g2and load sensor element50, the adhesive may be used in combination.

End faces6g1a,6g2aof outer-ring spacers6g1,6g2on which load sensor element50abuts have a structure in which protrusions are not provided on end faces6g1a,6g2ato easily obtain surface accuracy by flat grinding such that the processing can be performed with high accuracy in surface roughness and flatness.

When being provided on the outer diameter surface of outer-ring spacer6g, a planarizing portion6gbcan be used as a mark of the arrangement position of load sensor element50.

When the preload is applied to load sensor element50, a dead zone is eliminated in the output of load sensor element50, and the reduction of hysteresis and the improvement of linearity can be expected.

FIG.18is a sectional view illustrating the outer-ring spacer as an improvement example ofFIG.16.

When bearing5for air-oil lubrication is used, a nozzle for air oil is processed in outer-ring spacer6g, and the air oil is injected from the nozzle toward bearing5. An oil seal member6ghmay be disposed between outer-ring spacers6g1,6g2such that the air oil does not leak from a gap of divided inter-outer-ring spacer6gto the side of wiring71. Oil seal member6ghmay be made of a metal material. However, preferably oil seal member6ghis made of a resin material so as to be able to be pressed and deformed at outer-ring spacers6g1,6g2to prevent the formation of the gap.

When load sensor element50is sandwiched between two divided outer-ring spacers6g1,6g2and fastened with screw B, a jig (not illustrated) is preferably used when it is difficult to align outer-ring spacers6g1,6g2. For example, when outer-ring spacer6gis inserted into the cylindrical jig inner diameter portion to perform the assembly, the centering is easy.

FIG.19is a sectional view illustrating the outer-ring spacer as an improvement example ofFIG.18.

As illustrated inFIG.19, steps6g1m,6g2mare provided in the inner diameter portions of outer-ring spacers6g1,6g2, and an oil seal member6gkis disposed so as to be fitted to the steps.

Oil seal member6gkenables alignment of outer-ring spacer6g1,6g2, and the jig can be omitted.

FIG.20is a sectional view illustrating the outer-ring spacer as an improvement example ofFIG.19.

As illustrated inFIG.20, a flange6g1nis provided on the inner diameter side of outer-ring spacer6g1, a step6g2ninto which flange6g1nis fitted is provided on the inner diameter surface of the other outer-ring spacer6g2, and flange6g1nand step6g2nare fitted. Thus, the alignment of outer-ring spacer6g1,6g2can be performed. In addition, leakage of the air oil can be prevented to have a sealing function.

In this structure, the oil seal member is not required, the number of components can be reduced, and assemblability is improved.

As described in the above embodiment, in the bearing device of the embodiment, load sensor element50(pressure-sensitive sensor element) is disposed on outer-ring spacer6gon the load path in which the preload (load) is applied to the bearing or on the end face of bearing5. Load sensor element50(pressure-sensitive sensor element) on which the thin film resistor capable of measuring the load is formed is fixed by the adhesion or the like in the circumferential direction of outer-ring spacer6g, and load sensor element50has a structure in which the pressing is performed through the member abutting on load sensor element50. Thus, the manufacturing can be simplified as compared with the case where the thin film sensor that detects the load is directly formed on the metal component such as the outer-ring spacer.

(Summary)

Finally, the embodiment will be summarized again with reference to the drawings.

The present disclosure relates to bearing device30. Bearing device30includes at least one bearing5including the rolling element and the raceway surface to support main shaft4, the member (6or5ga) disposed on the path through which the pressing force generating the preload is transmitted between the rolling element and the raceway surface, and at least one load sensor element50fixed to the member (6or5ga) to be capable of measuring the pressing force. At least one load sensor element50is a chip component including thin film pattern52of which resistance changes according to the pressing force and protective layer54that insulates and protects thin film pattern52.

Load sensor element50is small in size, and the plurality of load sensor elements50can be stably manufactured at once. For this reason, the manufacturing can be simplified as compared with the case where the thin film sensor that detects the load is directly formed on the metal component such as the outer-ring spacer. Consequently, the improvement in reliability and the reduction in manufacturing cost can be expected.

Preferably, the pressing force is applied by the load in the direction along main shaft4. As illustrated inFIG.3or4, at least one load sensor element50is the plurality of load sensor elements50a,50b,50c,50darranged at equal intervals on the same circumference in the plane intersecting the direction along main shaft4.

As described above, the plurality of load sensor elements50a,50b,50c,50dare dispersedly arranged, so that the chip component is easily adopted as the load sensor element.

More preferably, the bearing device further includes arithmetic unit73that calculates the magnitude and direction of the moment load in the direction orthogonal to main shaft4using the outputs of the plurality of load sensor elements50ato50d.

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

Preferably, as illustrated inFIGS.1and2, at least one bearing5is the plurality of bearings5a,5b. The member to which load sensor element50is fixed is non-rotation-side outer-ring spacer6ginserted between two bearings5a,5bamong the plurality of bearings. At least one load sensor element50is fixed to end face6gaof the spacer, and abuts on the fixed ring (outer ring5ga) of one of two bearings5a,5bto transmit the pressing force.

The structure in which the spacer is arranged between the plurality of hearings is common for the spindle devices. Thus, the bearing device of the embodiment is easily applied to the spindle device.

Preferably, as illustrated inFIG.14, the member to which load sensor element50is fixed is the fixed ring (outer ring5ga) of at least one hearing. At least one load sensor element50is fixed to the end face of the fixed ring (outer ring5ga) and abuts on the end face of spacer6disposed adjacent to the fixed ring (outer ring5ga) to transmit the pressing force.

In this manner, the load sensor element may be fixed to the bearing side instead of the spacer. Load sensor element50is fixed to the end face of bearing5, so that the load detection unit can be compactly mounted.

Preferably, the member to which load sensor element50is fixed is first spacer6g1obtained by dividing spacer6disposed adjacent to at least one bearing into first spacer6g1and second spacer6g2. At least One load sensor element50is fixed to the end face of first spacer6g1and abuts on the end face of second spacer6g2to transmit the pressing force.

As described above, when the spacer is divided into two to sandwich load sensor element50therebetween, the spacer can be carried while load sensor element50is set in the spacer at a manufacturing stage.

Preferably, as illustrated inFIG.11, bearing device30further includes processing unit70that is disposed near at least one load sensor element50to process the output of at least one load sensor element50. Processing unit70includes amplifier72that detects and amplifies the resistance change of at least one load sensor element50.

Preferably, bearing device30further includes processing unit70that is disposed near at least one load sensor element to process the output of at least one load sensor element50. As illustrated inFIG.13, at least one load sensor element50is the plurality of load sensor elements50ato50d. Processing unit70includes the plurality of amplifiers72ato72dthat process outputs of the plurality of load sensor elements50ato50d, arithmetic unit73, and storage74. Arithmetic unit73calculates the load from the sensor output representative value including at least one of the addition value, the average value, 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 amplifiers72ato72d, the relationship between the load stored in advance in storage74and the sensor output representative value, or the approximate expression of the relationship.

Preferably, as illustrated inFIGS.16and17, the member to which load sensor element50is fixed is any one of first outer-ring spacer6g1and second outer-ring spacer6g2in which the spacer disposed adjacent to at least one bearing is divided into two. First outer-ring spacer6g1and second outer-ring spacer6g2sandwich at least one load sensor element50. First outer-ring spacer6g1and second outer-ring spacer6g2are fastened by screw B, and the pressing force by the fastening force of screw B is applied in advance to at least one load sensor element50.

When the preload is applied to load sensor element50, the dead zone is eliminated in the output of load sensor element50, and the reduction of hysteresis and the improvement of linearity can be expected.

Preferably, as illustrated inFIGS.16and17, the member to which load sensor element50is fixed is any one of first outer-ring spacer6g1and second outer-ring spacer6g2in which the spacer disposed adjacent to at least one bearing is divided into two. First outer-ring spacer6g1and second outer-ring spacer6g2sandwich at least one load sensor element50. End faces6g1a,6g2a, which are sandwiching surfaces sandwiching at least one load sensor element50of first outer-ring spacer6g1and second outer-ring spacer6g2, are flat surfaces without protrusions.

Because the end face is the flat surface without the protrusion as described above, the surface, accuracy can be easily obtained by flat grinding, and the processing with high accuracy of surface roughness and accuracy of flatness can be performed on the installation surface and the abutment surface of load sensor element50.

More preferably, as illustrated inFIGS.18and19, bearing device30further includes oil seal members6gh,6gkdisposed between first outer-ring spacer6g1and second outer-ring spacer6g2of the spacer.

Preferably, as illustrated inFIG.20, the member to which load sensor element50is fixed is any one of first spacer6g1and second spacer6g2in which the spacer disposed adjacent to at least one bearing is divided into two. First spacer6g1and second spacer6g2sandwich at least one load sensor element50. Flange6g1n, which is a convex portion in which the position of second spacer6g2is limited, is formed in first spacer6g1. Flange6g1nis fitted into step6g2n, which is a concave portion of second spacer6g2, to regulate the position of second spacer6g2.

Thus, the alignment of outer-ring spacer6g1,6g2cart be performed. In addition, the leakage of the air oil can be prevented to have the sealing function. In this structure, the oil seal member is not required, the number of components can be reduced, and the assemblability is improved.

In another aspect, the present disclosure relates to spindle device1including bearing device30described in any one of the above,

In still another aspect, the present disclosure relates to bearing5a. As illustrated inFIG.14, bearing5aincludes rolling element Ta, inner ring5ia, outer ring5ga, and at least one load sensor element50that is disposed on the end face of the fixed ring (outer ring5ga) in inner ring5iaand outer ring5gato be capable of measuring the pressing force generating the preload between rolling element Ta and the raceway surface of the fixed ring. As illustrated inFIG.6and the like, at least one load sensor element50is a chip component including thin film pattern52of which resistance changes according to the pressing force and protective layer54that insulates and protects thin film pattern52.

Preferably, bearing5afurther includes processing unit70that processes the output of the at least one load sensor element. Processing unit70is integrally mounted on the fixed ring (outer ring5ga).

In still another aspect, the present disclosure relates to spacer6disposed adjacent to bearing5including the rolling element and die raceway surface. Spacer6includes outer-ring spacer fig that is the member to which the pressing force generating the preload between the rolling element and the raceway surface is transmitted, and at least one load sensor element50that is fixed to outer-ring spacer6gto be capable of measuring the pressing force. As illustrated inFIGS.5to10, at least one load sensor element50is the chip component including thin film pattern52of which resistance changes according to the pressing force and protective layer54that insulates and protects thin film pattern52.

Preferably, as illustrated inFIG.11, spacer6further includes processing unit70that is integrally mounted on the member, to which the pressing force generating the preload is transmitted, to process the output of at least one load sensor element50.

Preferably, as illustrated inFIG.15, the member to which load sensor element50is fixed is first spacer6g1obtained by dividing outer-ring spacer6ginto first spacer6g1and second spacer6g2. At least one load sensor element50is fixed to end face of first spacer6g1, and abuts on end face6g2aof second spacer6g2to transmit the pressing force.

Preferably, as illustrated inFIGS.16and17, first spacer6g1and second spacer6g2sandwich at least one load sensor element50. First spacer6g1and second spacer6g2are fastened by screw B. The pressing force by fastening force of screw B is applied in advance to at least one load sensor element50.

More preferably, as illustrated inFIGS.18and19, outer-ring spacer fig further includes oil seal members6gh,6gkdisposed between first spacer6g1and second spacer6g2.

More preferably, as illustrated inFIG.19, the step that enables the alignment of first spacer6g1and second spacer6g2is formed on the inner diameter portion side of first spacer6g1and second spacer6g2by fitting with oil seal member6gk.

With such a configuration, outer-ring spacers6g1,6g2can be aligned by oil seal member6gk, and the jig for aligning outer-ring spacers6g1,6g2can be omitted.

It should be considered that the disclosed embodiment is an example in all respects and not restrictive. The scope of the present invention is defined by not the description of the embodiment, but the claims, and it is intended that all changes within the meaning and scope of the claims are included in the present invention.

REFERENCE SIGNS LIST

1: spindle device,2: outer cylinder,3: housing,3a,6g2n: step,4: main shaft,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: step,6g1n: flange,6gb: planarizing portion,6gh,6gk: oil seal member,6i: inner-ring spacer,10,20: nut,12: front lid,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: storage,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