JP2022153711A - Bearing device, spindle device and spacer - Google Patents

Abstract

To provide a bearing device capable of measuring a preload of a bearing with less temperature drift and with a simple configuration.SOLUTION: A bearing device comprises at least one bearing having a rolling element and a raceway surface and supporting a shaft; a member arranged on a path through which pressing force for generating a preload between the rolling element and the raceway surface is transmitted; a load sensor 50 that is fixed to the member and whose resistance value changes according to the pressing force; and a resistance circuit 60 that forms a bridge circuit by connecting with the load sensor. The load sensor 50 includes a thin film pattern whose resistance changes according to pressing force, and a protective layer that insulates and protects the thin film pattern. The resistance circuit 60 includes a plurality of resistances forming the bridge circuit with the load sensor.SELECTED DRAWING: Figure 3

Description

TECHNICAL FIELD The present disclosure relates to a bearing device, a spindle device, and a spacer provided with a preload sensor that detects preload (load) of a bearing used in a main spindle of a machine tool or the like.

2. Description of the Related Art Spindle devices such as machine tools are required to manage bearing preload in order to improve machining accuracy and efficiency. In addition, there is also a demand to detect signs of trouble before it occurs in the bearing and to prevent trouble in the bearing.

In Japanese Patent Application Laid-Open No. 2020-003385 (Patent Document 1), a thin film pattern that is formed on an insulating film and whose resistance changes with changes in surface pressure, and a protective film that is formed on the thin film pattern and protects the thin film pattern. A preload applied to the bearing is detected by arranging the thin film sensor including the thin film sensor as a preload sensor on the end surface of the member that applies preload to the bearing.

JP 2020-003385 A

In the bearing device disclosed in Japanese Patent Application Laid-Open No. 2020-003385 (Patent Document 1), a preload sensor made of a thin film pattern and a resistor form a bridge circuit, and a differential amplifier provided in the subsequent stage outputs the bridge circuit. Preload is detected by amplification.

Although Patent Document 1 does not describe the installation location of the bridge circuit, if the bridge circuit is provided outside the bearing device, the temperature environment of the resistors used in the preload sensor and the bridge circuit will be different.

For example, if the resistance of the bridge circuit is in a room temperature environment and the temperature of the bearing device rises, the resistance value of the preload sensor will change according to the temperature coefficient of resistance. However, since the temperature of the bridge circuit does not change and the resistance value does not change, a temperature drift occurs in the output of the differential amplifier due to the temperature change. Therefore, in order to detect an accurate preload amount, it is necessary to perform temperature correction, which complicates preload detection.

When the bridge circuit is placed inside the bearing device, the resistance of the preload sensor and the bridge circuit will be in the same temperature environment, but if the resistance temperature coefficients of each are different, the balance of the bridge circuit will be lost and the differential amplifier will be affected by the temperature rise. Output temperature drift occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a bearing device, a spindle device, and a spacer that are capable of measuring the preload of a bearing with little temperature drift and a simple configuration. is to provide

The present disclosure relates to bearing devices. The bearing device has rolling elements and raceway surfaces, and includes at least one bearing that supports a shaft; a member arranged on a path through which a pressing force that generates a preload between the rolling elements and the raceway surface is transmitted; A load sensor fixed to a member and having a resistance value that changes according to a pressing force, and a resistance circuit including a plurality of resistors connected to the load sensor to form a bridge circuit are provided. The load sensor includes a thin film pattern whose resistance changes according to pressing force, and a protective layer that insulates and protects the thin film pattern.

According to the bearing device of the present embodiment, it is possible to reduce the temperature drift when measuring the preload of the bearing with a simple configuration.

1 is a cross-sectional view showing a schematic configuration of a spindle device according to an embodiment; FIG. FIG. 2 is an enlarged view of the left main portion of FIG. 1; FIG. 3 is a diagram showing a first arrangement example of the load sensor element and the bridge circuit section in the III-III section of FIG. 2; 3 is a diagram showing a second arrangement example of the load sensor element and the bridge circuit section in the III-III section of FIG. 2; FIG. FIG. 4 is a cross-sectional view of the load sensor element 50a along the XX cross section of FIG. 3; FIG. 6 is a front view of the load sensor element 50a of FIG. 5; It is a figure which shows the modification of the shape of the thin film pattern of a load sensor element. FIG. 10 is a diagram showing a first improvement of the structure of the load sensor element; FIG. 10 is a diagram showing a second improved example of the structure of the load sensor element; FIG. 10 is a diagram showing the structure of a load sensor element that is an improved example of FIG. 9; FIG. 4 is a cross-sectional view of the resistance module 60a in the YY cross section of FIG. 3; 12 is a front view of the resistance module 60a of FIG. 11; FIG. 6 is a circuit diagram of a circuit formed on a substrate 61 of a resistor module 60a; FIG. It is a figure which shows the example which has arrange|positioned the process part which electrically processes the output of a load sensor in an outer ring spacer. FIG. 4 is a diagram showing the configuration of a bridge circuit that detects resistance changes of load sensor elements; FIG. 4 is a diagram showing a configuration for calculating a preload (load) applied to a bearing from the output of a load sensor element; FIG. 10 is a diagram showing a modification in which a bridge circuit is configured with one resistor circuit for a plurality of load sensor elements; FIG. 18 is a diagram showing a first configuration example of a bridge circuit for detecting a resistance change of a load sensor element in the configuration of FIG. 17; FIG. 18 is a diagram showing a second configuration example of a bridge circuit for detecting a resistance change of a load sensor element in the configuration of FIG. 17; It is a figure which shows the modification which changed the fixed position of the load sensor element. It is a side view of the modification which changed the fixing method of the load sensor element. 21. It is an arrow view of the POP cross section of FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings below, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

FIG. 1 is a sectional view showing a schematic configuration of a spindle device according to this embodiment. 2 is an enlarged view of the left main part of FIG. 1; FIG. FIG. 2 mainly shows the bearing device 30 .

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

1 and 2, the spindle device 1 includes bearings 5a and 5b, a spacer 6 arranged adjacent to the bearings 5a and 5b, a motor 40, and a bearing 16 arranged behind the motor. Prepare. The main shaft 4 is rotatably supported by a plurality of bearings 5 a and 5 b provided in a housing 3 embedded in the inner diameter of the outer cylinder 2 . The bearing 5a includes 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.

FIG. 3 is a diagram showing a first arrangement example of the load sensor element and the bridge circuit section in the III-III section of FIG. FIG. 4 is a diagram showing a second arrangement example of the load sensor element and the bridge circuit section in the III-III section of FIG. 3 and 4, parts unnecessary for explanation are omitted.

A load sensor 50 and a resistance circuit 60 are fixed by adhesion or the like to one end face 6ga of the outer ring spacer 6g or one end face of the outer ring 5ga. The load sensor 50 and the resistance circuit 60 form a bridge circuit. When the load sensor 50 and the resistance circuit 60 are fixed by adhesion, it is desirable to use an adhesive having excellent oil resistance and heat resistance.

For example, the thickness (height from the end surface) of the load sensor 50 is designed to be thicker than that of the resistance circuit 60, so that only the load sensor 50 is pressed.

It is important that only the pressure-receiving surface of the load sensor 50 contacts the mating member (the end surface of the outer ring 5ga in this example). The height of the base of the end face portion of the fixed member may be varied, or the height of the end face portion of the mating member that abuts may be changed.

The inner ring 5ia of the bearing 5a and the inner ring 5ib of the bearing 5b, which are spaced apart in the axial direction, are fitted to the main shaft 4 in an interference fit state (press fit state). An inner ring spacer 6i is arranged between the inner rings 5ia and 5ib, and an outer ring spacer 6g is arranged between the outer rings 5ga and 5gb.

The bearing 5a is a rolling bearing in which a plurality of rolling elements Ta are arranged between an inner ring 5ia and an outer ring 5ga. These rolling elements Ta are kept at intervals by a retainer Rta. The bearing 5b is a rolling bearing in which a plurality of rolling elements Tb are arranged between an inner ring 5ib and an outer ring 5gb. These rolling elements Tb are kept at intervals by a retainer Rtb.

The bearings 5a and 5b are bearings that can be preloaded by axial force, and angular ball bearings, deep groove ball bearings, tapered roller bearings, or the like can be used. Angular ball bearings are used in the bearing device 30 shown in FIG. 2, and two bearings 5a and 5b are installed in a back-to-back combination (DB combination).

Here, a structure in which the main shaft 4 is supported by three bearings 5a, 5b, and 16 will be described as an example, but a structure in which the main shaft 4 is supported by three or more bearings may also be used.

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

A cooling medium flow path G is formed in the housing 3 . By flowing a cooling medium between the housing 3 and the outer cylinder 2, the bearings 5a and 5b can be cooled. When grease-lubricated bearings are used as the bearings 5a and 5b, lubricating oil supply passages are not required. Note that the lubricating oil supply path is not shown here.

At the time of assembly, the bearing 5a, the spacer 6, the bearing 5b, and the spacer 9 are first inserted into the main shaft 4 in this order, and an initial preload is applied by tightening the nut 10. As shown in FIG. Thereafter, the main shaft 4 to which the bearings 5a and 5b are attached is inserted into the housing 3 until the right side of the outer ring 5gb of the bearing 5b in FIG. Finally, the main shaft 4 is fixed to the housing 3 by pushing the front cover 12 against the outer ring 5ga of the left bearing 5a.

By tightening the nut 10, a 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 elements Tb, and the outer ring 5gb to apply preload between the raceway surfaces of the inner ring 5ib and the outer ring 5gb and the rolling elements Tb, and is also transmitted from the outer ring 5gb to the outer ring spacer 6g. A pushing force acts on the outer ring spacer 6g from the outer ring 5gb on the right side, and the force is transmitted to the load sensor 50 as well.

This pressing force is transmitted to the outer ring 5ga, the rolling elements Ta, and the inner ring 5ia in the bearing 5a, and also applies preload between the raceway surfaces of the inner ring 5ia and the outer ring 5ga of the left bearing 5a and the rolling elements Ta. The preload applied to bearings 5a and 5b is determined by the amount of movement of nut 10, which is limited by the dimensional difference between the combined width of outer ring spacer 6g and load sensor 50 and the width of inner ring spacer 6i.

In the single-row bearing 16 shown in FIG. 1, the inner ring 16a is axially positioned by the cylindrical member 15 fitted to the outer periphery of the main shaft 4 and the inner ring retainer 19. As shown in FIG. The inner ring retainer 19 is retained by a nut 20 screwed onto the main shaft 4 . An outer ring 16 b of the bearing 16 is sandwiched between a positioning member 21 fixed to the end member 17 and a positioning member 18 fixed to the end member 17 . The inner ring 16a slides integrally with respect to the end member 17 as the main shaft 4 expands and contracts.

A motor 40 for driving the main shaft 4 is arranged at an axially intermediate position between the bearing 5b and the single-row bearing 16 in the space 22 formed between the main shaft 4 and the outer cylinder 2. . A rotor 14 of the motor 40 is fixed to a cylindrical member 15 fitted on the outer circumference of the main shaft 4 , and a stator 13 of the motor 40 is fixed to the inner circumference of the outer cylinder 2 .

A cooling medium flow path for cooling the motor 40 is not shown here.
A load sensor 50 that measures the preload (load) of the bearings 5 (5a, 5b) is mounted on a path that transmits the pressing force that generates the preload of the spindle device 1. FIG. As shown in FIG. 2, the load sensor 50 is fixed to the end surface 6ga of the outer ring spacer 6g by adhesion or the like, contacts the end surface of the outer ring 5ga of the bearing 5a, and is applied to the bearing 5 (5a, 5b). to measure.

By observing the output of the load sensor 50 during assembly of the spindle device 1, it is possible to confirm whether or not the preset preload is achieved, thereby reducing the number of assembly man-hours. Further, by observing the output of the load sensor 50 during operation of the machine tool, it is possible to know the amount of preload that has increased due to thermal expansion due to heat generated during operation. By observing the change in preload during operation, deterioration of cutting performance and seizure of the bearing 5 can be prevented in advance.

The load sensor 50 includes a pressure sensor made up of a thin film pattern (thin film resistor). For example, a load sensor 50 that measures a load (preload) from a change in electrical resistance is arranged on the path through which the pressing force that generates the preload is transmitted.

A method of detecting the load from changes in the electrical resistance of the load sensor 50 will be described later, but the detected load value is transmitted to the outside using a cable CB, for example. The cable CB is drawn out of the spindle device 1 through grooves 3b and 12a provided in the housing 3 and the front cover 12. As shown in FIG. When the load output is wirelessly transmitted to an external device, the cable CB and the grooves 3b and 12a may not be provided.

Load sensor 50 includes a plurality of load sensor elements. Resistor circuit 60 includes a plurality of resistor modules. FIG. 3 shows a first arrangement example of the load sensor elements 50a-50d and the resistance modules 60a-60d mounted on the end surface 6ga of the outer ring spacer 6g. Here, load sensor elements 50a-50d are arranged at equal intervals of 90 degrees in the circumferential direction of the outer ring spacer 6g, and resistance modules 60a-60d are arranged in the vicinity thereof.

By connecting the load sensor elements 50a to 50d and the resistance modules 60a to 60d respectively to form four bridge circuits, resistance changes of the load sensor elements 50a to 50d are detected. Details of the resistor modules 60a to 60d will be described later.

In the example of FIG. 4, the load sensor elements 50a to 50c are arranged at equal intervals of 120 degrees in the circumferential direction of the outer ring spacer 6g. Also, the resistance modules 60a to 60c are arranged at equal intervals of 120 degrees in the circumferential direction of the outer ring spacer 6g.

The number of the plurality of load sensor elements included in the load sensor 50 is preferably three or more as long as the end surface of the outer ring 5ga is evenly and well-balancedly pushed through the plurality of load sensor elements. Moreover, it is preferable to arrange a plurality of load sensor elements at equal intervals on substantially the same circumference.

In the arrangement examples shown in FIGS. 3 and 4, the number of resistance circuits 60 is equal to the number of load sensor elements of the load sensor 50 .

Next, the structure of the load sensor element will be described with reference to FIGS. 5 and 6. FIG. FIG. 5 is a cross-sectional view of the load sensor element 50a taken along the line XX in FIG. 6 is a front view of the load sensor element 50a of FIG. 5. FIG. The load sensor elements 50b to 50d also have the same structure.

The load sensor element 50a includes, for example, an insulating substrate 51, a thin film pattern (thin film resistor) 52 arranged on the substrate 51 and whose resistance changes with changes in surface pressure, an electrode 53 connected to the thin film pattern 52, and an insulating protective layer 54 that protects the thin film pattern 52 . Since the protective layer 54 is not formed on the electrodes 53 , wiring can be directly connected to the electrodes 53 .

Substrate 51 is made of a ceramic material whose main component is zirconia (ZrO ₂ ) or alumina (Al ₂ O ₃ ), for example. The ceramic material is highly rigid and highly insulating, and is convenient because the surface flatness of the substrate 51 can be processed with high accuracy. From the viewpoint of thinning the load sensor 50 and ensuring strength in the compression direction, the thickness of the substrate 51 is preferably 0.3 mm or more and 5 mm or less, for example.

The thin film pattern 52 is made of, for example, nickel chromium (NiCr) or chromium (Cr) based material, and is deposited by vapor deposition, sputtering, or the like. The thickness of the thin film pattern is, for example, 1 μm or less. A thin film of an insulating material such as alumina (Al ₂ O ₃ ) or silicon dioxide (SiO ₂ ) is formed as the protective layer 54 by sputtering or the like. The film thickness of the protective layer 54 is, for example, approximately 2 μm.

In order to facilitate soldering with wiring, the surface of the electrode 53 may be coated with a material such as copper, silver, or gold.

The upper surface of the substrate 51 on which the thin film pattern 52 is formed is preferably polished so that the flatness thereof is 1 μm or less. Moreover, it is preferable to set the parallelism between the upper surface and the lower surface of the substrate 51 to 1 μm or less.

The resistance value of the thin film pattern 52 (the resistance value between the two electrodes 53) is set in the range of several tens of ohms to several hundreds of ohms, and the temperature coefficient of resistance, which indicates the rate at which the resistance changes with temperature changes coefficient indicating the rate at which the value changes) is set to, for example, 10 ppm/° C. or less. Preferably, the temperature coefficient of resistance is set to 1 ppm/°C or less.

The smaller the temperature coefficient of resistance, the smaller the amount of change in resistance due to temperature change, and the temperature drift at the time of load detection can be reduced.

Since the thin film pattern is formed on the substrate 51, which is a component separate from the outer ring spacer 6g, manufacturing becomes easier than forming the thin film pattern directly on the outer ring spacer 6g.

In the above example, each of the load sensor elements 50a to 50d is sandwiched and pressed between the end face 6ga of the outer ring spacer 6g and the end face of the outer ring 5ga of the bearing 5a. For example, the substrate 51 of each of the load sensor elements 50a to 50d contacts the end surface 6ga of the outer ring spacer 6g, each protective layer 54 contacts the end surface of the outer ring 5ga of the bearing 5a, and each thin film pattern 52 contacts the substrate 51. and the protective layer 54 are pressed.

The shape of each of the load sensor elements 50a-50d is set in consideration of each material property value of each of the load sensor elements 50a-50d. Also, here, each of the load sensor elements 50a to 50d has a rectangular shape, but the shape is not limited to this.

FIG. 7 is a diagram showing a modification of the shape of the thin film pattern of the load sensor element. Although the thin film pattern 52 has a U-shape in the example of FIG. 6, the thin film pattern 52 may have a continuous rectangular pattern like the load sensor 50a1 shown in FIG. By forming a continuous rectangular pattern on the substrate 51, the pressure-sensitive length of the thin film pattern 52 is increased, and the load can be stably detected. The shape of the thin film pattern 52 is not limited to the shapes shown in FIGS.

FIG. 8 is a diagram showing a first improvement of the structure of the load sensor element. In _FIG . 5, the protective layer 54 is a thin film made of an insulating material by vapor deposition or sputtering _, but in the load sensor element 150a shown in _FIG . A plate material made of a composite ceramic material is used as the protective layer 54A. The protective layer 54A is adhesively fixed so as to cover the thin film pattern 52 formed on the surface of the substrate 51 via an adhesive layer 55 made of an adhesive. The plate thickness of the protective layer 54A is, for example, about 0.3 mm to 5 mm, which is the same as the plate thickness of the substrate 51 .

If a plate material made of an insulating material is used as the protective layer 54A, it is sufficient to adhere and fix the plate material made of an insulating material to the upper surface of the thin film pattern 52 as the protective layer 54A. Easier to manufacture. Moreover, the insulation between the thin film pattern 52 and the outer ring 5ga can be further increased, and the load can be stably detected. In addition, since the thin film pattern 52 is pressed through the adhesive layer 55, the adhesive layer 55 acts as a cushion layer and can uniformly press the thin film pattern 52, thereby improving load detection accuracy.

FIG. 9 is a diagram showing a second improved example of the structure of the load sensor element. 5 and 8, an insulating material is used as the substrate 51, but in the load sensor element 250a shown in FIG. 9, a metal material is used as the substrate 51A, and an insulating layer 58 is formed on the surface thereof. The insulating layer 58 is made of an insulating material, and for example, a thin film of alumina (Al ₂ O ₃ ) or silicon dioxide (SiO ₂ ) is formed by sputtering or the like. The film thickness of the insulating layer 58 is, for example, approximately 2 μm.

As the metal material of the substrate 51A, for example, the same material as the outer ring spacer 6g, for example, bearing steel (SUJ2) is used. Carbon steel (such as S45C) is used other than bearing steel. After cutting these metal materials to a certain size, they are heat-treated. After that, the surfaces requiring high processing accuracy are polished and lapped to achieve the target flatness and surface roughness. For example, the flatness is 1 μm or less and the surface roughness is Ra 0.1 or less.

Thereafter, after forming an insulating layer 58 on one surface of the substrate 51A, a thin film pattern (thin film resistor) 52 whose resistance changes with a change in surface pressure and an electrode 53 connected thereto are formed in the same manner as in FIG. Furthermore, 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 electrodes 53 , wiring can be directly connected to the electrodes 53 .

As protective layer 54, a thin film of alumina (Al ₂ O ₃ ) or silicon dioxide (SiO ₂ ) is formed by, for example, sputtering. These film thicknesses are, for example, approximately 2 μm.

If the material of the substrate 51A is a metal material, the substrate 51A will not crack due to the load, and the reliability will be improved. Forming the thin film pattern 52 on the substrate 51A made of a metal piece is easier than forming the thin film pattern 52 directly on the end surface of the outer ring spacer 6g, and the manufacturing cost can be reduced.

FIG. 10 is a diagram showing the structure of a load sensor element that is an improved example of FIG. In _FIG . 9, the protective layer 54 is a thin film made of an insulating material by vapor deposition or sputtering _, but in the load sensor element 350a shown in _FIG . A plate material made of a composite ceramic material is used as the protective layer 54A. The protective layer 54A is adhesively fixed so as to cover the thin film pattern 52 formed on the surface of the substrate 51 via an adhesive layer 55 made of an adhesive. The plate thickness of the protective layer 54A is, for example, about 0.3 mm to 5 mm, which is the same as the plate thickness of the substrate 51 .

If a plate material made of an insulating material is used as the protective layer 54A, manufacturing becomes easier than film formation by sputtering or the like. Moreover, the insulation from the thin film pattern 52 can be further increased, and the load can be stably detected. In addition, since the thin film pattern 52 is pressed through the adhesive layer 55, the adhesive layer 55 acts as a cushion layer and can uniformly press the thin film pattern 52, thereby improving load detection accuracy.

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

Next, the structure of the resistor module will be described with reference to FIGS. 11, 12 and 13. FIG. FIG. 11 is a cross-sectional view of the resistance module 60a along the YY cross section of FIG. 12 is a front view of the resistor module 60a of FIG. 11. FIG. FIG. 13 is a circuit diagram of a circuit formed on the substrate 61 of the resistance module 60a. The resistance modules 60b to 60d also have the same configuration as the resistance module 60a.

The resistor module 60a includes, for example, a substrate 61 having an insulating property, resistors R (R1, R2, R3) made up of a thin film pattern (thin film resistor) 62 arranged on the substrate 61, and an electrode T (T1 , T2, T3, T4). A protective layer 64 may be provided on the surface layer of the thin film pattern 62 excluding the electrodes T. FIG.

By connecting the load sensor element 50a to the electrodes T1 and T2 of the resistor circuit 60, the resistor R and a bridge circuit can be formed.

Substrate 61 is made of a ceramic material whose main component is zirconia (ZrO ₂ ) or alumina (Al ₂ O ₃ ), for example. The thickness of the substrate 61 is selected, for example, within a range of 0.3 mm or more and 5 mm or less. Since the resistance module 60a is made thinner than the load sensor element 50a, the resistance module 60a is not pressed.

Since the thin film pattern 52 of the load sensor element 50a and the resistor R of the resistance module 60a are provided on separate substrates, even when the load sensor element 50a is pressed, the resistance module 60a is not pressed and the substrate 61 is deformed. Therefore, the change in the resistance value of the resistor R due to substrate deformation is suppressed.

The thin film pattern 62 is made of, for example, the same nickel chromium (NiCr) or chromium (Cr) material as the load sensor element 50a, and is deposited by vapor deposition, sputtering, or the like. The thickness of the thin film pattern is, for example, 1 μm or less. The protective layer 64 is made of an insulating material, and is formed with a thin film of alumina (Al ₂ O ₃ ) or silicon dioxide (SiO ₂ ), for example, by sputtering. The film thickness of the protective layer 64 is, for example, approximately 2 μm.

As the protective layer 64, a curable resin or a silicone adhesive may be used. Also, the surface of the electrode T may be coated with a material such as copper, silver, or gold to facilitate soldering with wiring.

If the thin film pattern 62 of the resistance module 60a is formed of the same material as the thin film pattern 52 of the load sensor element 50a, the resistance values and resistance temperature coefficients of the resistors R1 to R3 and the resistance value and resistance temperature coefficient of the load sensor element 50a can be matched. becomes easier. If the resistance values of the resistors R1 to R3 vary, the resistance values may be adjusted by laser trimming, for example.

With the above configuration, only the resistance value of the load sensor element 50a changes in the bridge circuit, and the load can be measured.

Instead of forming the resistors R1 to R3 with the thin film pattern 62, commercially available chip resistors may be mounted on the thin film pattern 62 formed on the surface of the substrate 61. FIG. In this case, it is desirable to use a chip resistor whose resistance value and temperature coefficient of resistance are close to those of the load sensor element 50a. In order to adjust the resistance value, a variable resistor (not shown) may be connected in series with any one of the resistors R1 to R3.

If a cable CB is connected to the electrode 53 of the load sensor element 50a and the electrode T of the resistance module 60a and pulled out to the outside and connected to an external processing unit (not shown), the influence of temperature change can be reduced to calculate the load value. can do.

As described above, in the present embodiment, an example in which the resistance circuit of the bridge circuit and the load sensor element are provided on separate substrates has been described. However, the load sensor element and the resistors of the bridge circuit may be made of the same thin film material and arranged on the same substrate. In this case, the load sensor element and the resistor can be manufactured at once in the same process. In the case of this configuration, the resistors of the bridge circuit are arranged in positions where they are not pressed. Using the same substrate enables cost reduction, miniaturization, and a reduction in assembly man-hours due to a reduction in the number of parts.

FIG. 14 is a diagram showing an example in which a processing unit for electrically processing the output of the load sensor is arranged in the outer ring spacer.

Load sensor elements 50a to 50d, resistance modules 60a to 60d, and a processing portion 70 are fixed to one end surface 6ga of the outer ring spacer 6g. The load sensor elements 50a to 50d are fixed to the end face 6ga at equal intervals in the circumferential direction. The resistor modules 60a to 60d are fixed to the end surface 6ga at equal intervals in the circumferential direction.

The processing unit 70 has a shape that does not interfere with, for example, the load sensor elements 50a-50d and the resistance modules 60a-60d. Moreover, the processing portion 70 is manufactured so that the surface height thereof is lower than that of each of the load sensor elements 50a to 50d, thereby preventing contact between the outer ring 5ga and the processing portion 70. FIG.

Since the thickness of each of the resistance modules 60a-60d is also set to be thinner than each of the load sensor elements 50a-50d, the outer ring 5ga and the resistance modules 60a-60d do not come into contact with each other. Therefore, even if the load sensor elements 50a to 50d are pressed, the resistance values of the resistors R of the resistance modules 60a to 60d do not change, so the load can be detected.

The outputs of the load sensor elements 50a-50d and the resistance modules 60a-60d are connected to the processing section 70 by wirings 71,76.

The processing unit 70 is equipped with circuit units 72a to 72d for detecting and amplifying resistance changes of the load sensor elements 50a to 50d, respectively, and obtains output values corresponding to the resistance changes. Further, the calculation unit 73 may be arranged in the processing unit 70 . The calculation unit 73 may process the resistance change amount of the plurality of load sensor elements 50a to 50d, convert it into the load applied to the outer ring spacer 6g, and output it to the outside.

Although the resistance modules 60a to 60d are arranged on the end face 6ga of the outer ring spacer 6g here, the functions of the resistance modules 60a to 60d may be mounted on the processing section . In this case, commercially available chip resistors can be used as the resistors R1, R2 and R3 included in each of the resistor modules 60a-60d. A chip resistor is mounted on the processing unit 70 .

This eliminates the need to dispose the resistor modules 60a to 60d on the end surface 6ga of the outer ring spacer 6g, simplifying the configuration and wiring process.

If it is desired to finely adjust the resistance values of the resistance modules 60a to 60d, the circuit shown in FIG. Among the resistors R1, R2, R3 and the load sensor elements 50a to 50d, a variable resistor (not shown) is mounted in series with the resistor that requires fine adjustment, and by adjusting the variable resistor, the resistance can be balanced. good.

FIG. 15 is a diagram showing the configuration of a bridge circuit for detecting resistance changes of load sensor elements. The circuit portion 72 shown in FIG. 15 includes circuit portions 72a to 72d. The circuit section 72a includes a resistor module 60a connected to a DC power supply VSDC, a load sensor element 50a, and a differential amplifier AMPa. The circuit portion 72b includes a resistance module 60b connected to the DC power supply VSDC, a load sensor element 50b, and a differential amplifier AMPb. The circuit portion 72c includes a resistor module 60c connected to the DC power supply VSDC, a load sensor element 50c, and a differential amplifier AMPc. The circuit section 72d includes a resistance module 60d connected to the DC power supply VSDC, a load sensor element 50d and a differential amplifier AMPd.

Each of resistor modules 60a-60d includes resistors R1-R3. Each of the resistors R1-R3 and the load sensor elements 50a-50d constitutes a bridge circuit.

In the circuit section 72a, a resistor R1 and a resistor R2 are connected in series between the positive and negative electrodes of the DC power supply VSDC. A load sensor element 50a and a resistor R3 are connected in series between the positive and negative terminals of the DC power supply VSDC. One input node of the differential amplifier AMPa is connected to the connection node between the resistors R1 and R2. The other input node of the differential amplifier AMPa is connected to the connection node between the load sensor element 50a and the resistor R3.

In each of circuit portions 72b-72d, load sensor elements 50b-50d and differential amplifiers AMPb-AMPd are connected instead of load sensor element 50a and differential amplifier AMPa in the configuration of circuit portion 72a.

By adopting the bridge circuit configuration shown in FIG. 15, the resistance change of the load sensor elements 50a to 50d when the load changes is detected by the differential amplifiers AMPa to AMPd, and the output value S (Sa, Sb, Sc, Sd) is detected. can be obtained.

As shown in FIG. 14, each of the load sensor elements 50a to 50d is placed in the same environment as one of the corresponding resistor modules 60a to 60d, since they are placed in close proximity to each other. If the temperature coefficients of resistance are the same, the resistance value of the resistor module will change in the same way even if the temperature changes. Therefore, the resistance balance of the resistance modules 60a to 60d is maintained even if the temperature changes, so that the output temperature drift of the differential amplifiers AMPa to AMPd due to the temperature change can be suppressed. Therefore, it is possible to eliminate the step of correcting the outputs of the load sensor elements 50a to 50d using the temperature sensor values.

In the configuration shown in FIG. 14, the differential amplifiers AMPa to AMPd of the circuit sections 72b to 72d perform electrical processing in the vicinity of the load sensor elements 50a to 50d, respectively, so electrical noise can be reduced. In addition, the number of wires drawn out to the outside can be reduced, and the assembly of the bearing device 30 and the spindle device 1 is facilitated.

FIG. 16 is a diagram showing a configuration for calculating the preload (load) applied to the bearing from the output of the load sensor element. Here, an example using four load sensor elements 50a to 50d will be described.

The calculation circuit shown in FIG. 16 includes an arithmetic unit 73 for arithmetic processing of the output values S (Sa to Sd) of the bridge circuit including the load sensor 50 (load sensor elements 50a to 50d), and an output value S measured in advance and the load. A storage unit 74 is provided for storing relationships or approximate expressions. The calculator 73 calculates the load from the output value S and the data in the memory 74 . The calculation unit 73 and the storage unit 74 may be provided outside the bearing device 30 or may be provided inside the processing unit 70 .

The preload load applied to the outer ring spacer 6g is not uniform in the circumferential direction, and the dimensional accuracy of the outer ring spacer 6g, housing 3, front cover 12, bearing 5, etc. may cause differences in output values depending on detection locations. is assumed. Further, when the main shaft 4 rotates, it is assumed that the load distribution in the circumferential direction changes due to the influence of the moment load applied to the main shaft 4 and the movement of the rolling elements Ta and Tb of the bearing 5 .

Therefore, an added value or an average value of the output values S of the load sensor elements 50a to 50d may be employed as the sensor output processed by the calculation section 73. FIG. Also, as the range of the output value S, a maximum value, a minimum value, a difference between the maximum value and the minimum value, or the like may be set.

The output of the preload (load) obtained by the calculation unit 73 may be passed through a low-pass filter to reduce output fluctuation due to passage of the rolling elements Ta and Tb and noise.

When the spindle device 1 is mounted with the bearing device 30 and the motor 40 rotates the main shaft 4 at high speed, the temperature of the bearing 5 rises or the bearing 5 heats up due to damage to the bearing 5, resulting in an excessive preload. It is assumed that the bearing 5 will be burnt out. To deal with this, if the preload is calculated from the load sensor 50 and monitored, a workaround can be taken to prevent the bearing 5 from burning out.

For example, when the preload load measured by the load sensor 50 exceeds a preset reference value, the diagnostic unit 75 determines that the bearing 5 is abnormal, reduces the rotation speed of the main shaft 4, or reduces the circulation amount of the cooling medium. or reduce the machining load to prevent the bearing 5 from burning out.

In addition, since the load sensor 50 is fixed to the outer ring spacer 6g on the transmission path of the force that generates the preload, when the spindle device 1 is assembled, the output of the load sensor 50 is applied to the bearings 5 (5a, 5b). It is possible to grasp the initial preload of , and it is possible to adjust the tightening of the nut 10 or the attachment of the fixing screw of the front cover 12 while observing the amount of preload.

Note that the calculation unit 73 may calculate the moment load applied to the spindle 4 from the difference between the outputs of two of the load sensor elements 50a to 50d that face each other 180 degrees. For example, in the arrangement of the load sensor elements 50a to 50d shown in FIG. 14, the magnitude and direction of the moment load in the vertical direction of the spindle 4 can be calculated from the difference between the load sensor elements 50a and 50b. It is also possible to calculate the magnitude and direction of the moment load in the left-right direction of the spindle 4 from the difference between the load sensor elements 50c and 50d. Note that the magnitude and direction of the moment load can be calculated even if the number of load sensor elements is not four.

For example, when cutting a metal work with a cutting tool such as an end mill fixed to the other end of the spindle device 1, the load applied to the cutting tool and the direction of the load can be grasped from the moment load. It is also possible to detect the collision of the cutting tool with the metal workpiece from the moment load.

In order to increase the reliability of abnormality diagnosis, in addition to the increase in preload (load), the output of other sensors such as temperature sensor, heat flux sensor, and acceleration sensor may be further considered to make a comprehensive judgment. For example, if a heat flux sensor (not shown) is fixed to a non-rotating member (for example, the outer ring spacer 6g) near the bearing 5 and arranged to face the rotating member (for example, the main shaft 4), seizure of the bearing 5 can occur. It is possible to detect early signs of temperature rise due to

FIG. 17 is a diagram showing a modification in which a bridge circuit is configured with one resistor circuit for a plurality of load sensor elements. The modification shown in FIG. 17 is an improved example of FIG. FIG. 18 is a diagram showing a first configuration example of a bridge circuit for detecting resistance changes of load sensor elements in the configuration of FIG. FIG. 19 is a diagram showing a second configuration example of a bridge circuit for detecting a resistance change of a load sensor element in the configuration of FIG. 17. In FIG. Either one of the configuration examples of FIGS. 18 and 19 is used for FIG.

As shown in FIG. 17, on one end surface 6ga of the outer ring spacer 6g, a plurality of load sensor elements 50a to 50d fixed at equal intervals in the circumferential direction, one resistance circuit 60, and a processing section 70 are mounted. is fixed. For example, the processing portion 70 is manufactured to have a shape that does not interfere with the load sensor elements 50a to 50d and the resistance circuit 60, and is thinner than the load sensor elements 50a to 50d. Prevent contact.

In addition, since the thickness of the resistance circuit 60 is set to be thinner than the load sensor elements 50a to 50d, the resistance circuit 60 does not come into contact with the outer ring 5ga. Since the resistance value of resistor R of circuit 60 does not change, the load can be detected.

Outputs of the load sensor elements 50a to 50d and the resistance circuit 60 are connected to the processing section 70 by wirings 71 and 76. FIG.

The processing unit 70 is mounted with one circuit unit 172 (or 272) that detects and amplifies resistance changes of the load sensor elements 50a to 50d. The processing unit 70 obtains output values corresponding to resistance changes of the load sensor elements 50a to 50d. Further, the calculation unit 73 may be arranged in the processing unit 70 . The calculation unit 73 processes the amount of change in resistance of the load sensor 50, converts it into the load applied to the outer ring spacer 6g, and then outputs it to the outside.

A circuit portion 172 shown in FIG. 18 includes resistors R1 to R3 and load sensor elements 50a to 50d connected to a DC power supply VSDC, and a differential amplifier AMP. The resistors R1-R3 and the load sensor elements 50a-50d form a bridge circuit. A resistor R1 and a resistor R2 are connected in series between the positive electrode and the negative electrode of the DC power supply VSDC. Between the positive and negative terminals of the DC power supply VSDC, a load detecting section SR having the load sensor elements 50a to 50d connected in series and a resistor R3 are connected in series. One input node of the differential amplifier AMP is connected to the connection node between the resistors R1 and R2. The other input node of the differential amplifier AMP is connected to the connection node between the load detection section SR and the resistor R3.

The resistance values of the resistors R1, R2 and R3 are set to be the same as the series resistance value (combined resistance value) obtained by connecting the load sensor elements 50a to 50d in series.

By configuring as shown in FIG. 18, the configuration of the circuit section 172 can be simplified, so that the processing section 70 can be made smaller and simpler.

Moreover, the load sensor elements 50a to 50d and the resistance circuit 60 are located close to each other and placed in the same environment. If these resistance temperature coefficients are made uniform, the resistance balance of the bridge circuit will not be lost even if there is a temperature change, so the output temperature drift of the differential amplifier AMP due to the temperature change can be suppressed.

The configuration shown in FIG. 19 is a modification of FIG. 18, and is the same except that the load sensor elements are connected in parallel.

A circuit portion 272 shown in FIG. 19 includes resistors R1 to R3 and load sensor elements 50a to 50d connected to a DC power supply VSDC, and a differential amplifier AMP. The resistors R1-R3 and the load sensor elements 50a-50d form a bridge circuit. A resistor R1 and a resistor R2 are connected in series between the positive electrode and the negative electrode of the DC power supply VSDC. Between the positive and negative terminals of the DC power supply VSDC, a load detecting section PR in which the load sensor elements 50a to 50d are connected in parallel and a resistor R3 are connected in series. One input node of the differential amplifier AMP is connected to the connection node between the resistors R1 and R2. The other input node of the differential amplifier AMP is connected to the connection node between the load detection section SR and the resistor R3.

The resistance values of resistors R1, R2, and R3 are set to be the same as the parallel resistance value (combined resistance value) obtained by connecting load sensor elements 50a to 50d in parallel.

By configuring as shown in FIG. 19, the configuration of the circuit section 272 can be simplified as in FIG. 18, so that the size of the processing section 70 can be reduced.

Moreover, the load sensor elements 50a to 50d and the resistance circuit 60 are located close to each other and placed in the same environment. If these resistance temperature coefficients are made uniform, the resistance balance of the bridge circuit will not be lost even if there is a temperature change, so the output temperature drift of the differential amplifier AMP due to the temperature change can be suppressed.

17 to 19, the resistance circuit 60 is arranged on the end face 6ga of the outer ring spacer 6g, but the function of the resistance circuit 60 may be mounted on the processing section 70. FIG. In this case, commercially available chip resistors may be used as the resistors R1, R2, and R3 of the resistor circuit 60 and mounted on the processing unit 70. FIG. In this case, the resistor circuit 60 does not need to be arranged on the end face 6ga of the outer ring spacer 6g, simplifying the configuration.

FIG. 20 is a diagram showing a modification in which the fixed position of the load sensor element is changed. In FIG. 20, the load sensor 50 and the resistance circuit 60 are fixed to the end surface 6g1a of one spacer 6g1 obtained by dividing the outer ring spacer 6g into two in the axial direction. In this case, the end face 6g2a of the other spacer 6g2 contacts the load sensor 50. As shown in FIG.

A side view of the load sensor elements 50a to 50d and the resistance circuit 60 or the resistance modules 60a to 60d mounted is the same as that of FIGS.

The end face 6g1a of the spacer 6g1 that fixes the load sensor 50 and the end face 6g2a of the spacer 6g2 that presses the load sensor 50 have flatness, surface roughness, and parallelism of these end faces 6g1a and 6g2a below the reference values. It must be processed accordingly. The spacers 6g1 and 6g2 can be individually machined with high precision.

A convex surface (not shown) may be provided on the end surface 6g2a of the spacer 6g2, and the convex surface may contact the load sensor 50 only. Further, a convex surface (not shown) may be provided on the end surface 6g1a of the spacer 6g1, and the load sensor 50 may be fixed to the convex surface.

In this case, the top surface of the load sensor 50 protrudes from the top surface of the resistance circuit 60 .
Further, the spacers 6g1 and 6g2, which are obtained by dividing the outer ring spacer 6g into two parts, may be aligned with a pin (not shown) so as not to cause relative displacement.

In this case, the area required for machining accuracy can be reduced, so machining becomes easier and the machining time can be shortened.

Also, a step may be provided between the surface of the load sensor 50 and the surface of the resistance circuit 60 .
Alternatively, an intermediate layer (cushion layer) (not shown) may be inserted between the load sensor 50 and the end surface 6g2a of the spacer 6g2 to press the load sensor 50. FIG.

The material of the intermediate layer is, for example, a metal material (such as aluminum, copper, or metal alloy) having lower rigidity (longitudinal modulus) than the material of the outer ring spacer 6g, or a coating thin film of a resin material (such as fluorine resin). can be used.

By pressing through the intermediate layer having lower rigidity than the outer ring spacer 6g, the intermediate layer is deformed along the shape of the surface and the load is evened out, so that the load sensor 50 can be stably and uniformly pressed. can. In this case, since the rigidity of the bearing devices 30, 30A is lowered, an appropriate material is selected for the intermediate layer.

Further, with the configuration in which the load sensor 50 is pressed through the intermediate layer, the processing accuracy (surface roughness, flatness, etc.) of the end surface of the outer ring spacer 6g can be lowered compared to the case where the intermediate layer is not used. It can be processed easily.

Note that the load sensor 50 and the processing unit 70 or part of the processing unit 70 may be integrally mounted.

FIG. 21 is a side view of a modified example in which the method of fixing the load sensor element is changed. 22 is a cross-sectional view taken along line POP of FIG. 21. FIG.

The load sensor elements 50a to 50d are arranged between spacers 6g1 and 6g2 obtained by dividing the outer ring spacer 6g into two parts, and the spacers 6g1 and 6g2 are fastened with screws B to apply preload to the load sensor elements 50a to 50d. . Although the load sensor elements 50a to 50d can be fixed without applying an adhesive to the contact surfaces of the spacers 6g1 and 6g2 and the load sensor elements 50a to 50d, an adhesive may be used in combination.

The resistor circuit 60 (resistor modules 60a to 60d) is arranged on the circumference of the end surface 6g1a of the spacer 6g1, but is not in contact with the end surface 6g2a of the spacer 6g2 and is not pressed.

The end faces 6g1a and 6g2a of the spacers 6g1 and 6g2 with which the load sensor elements 50a to 50d abut are flat-ground without any projections so that the surface roughness and flatness can be processed with high accuracy. The structure is such that it is easy to obtain accuracy.

By applying a preload to the load sensor 50, the output of the load sensor 50 can be expected to have no dead zone, reduce hysteresis, and improve linearity. Further, since the spacers 6g1 and 6g2 obtained by dividing the outer ring spacer 6g into two parts are fixed by screws B, the handling of the outer ring spacer 6g is facilitated, and the assembling efficiency of the spindle device 1 is improved.

Further, if the resistance modules 60a to 60d are arranged near the load sensor elements 50a to 50d, respectively, and their temperature coefficients of resistance are made uniform, the resistance balance of the bridge circuit will not be lost even if temperature changes. Temperature drift of the dynamic amplifier AMP output can be suppressed. Therefore, it is possible to eliminate the step of correcting the outputs of the load sensor elements 50a to 50d using the temperature sensor values.

In the above example, the cable CB is used to transmit the output of the load sensor 50 and the bridge circuit unit, or the output obtained by electrically processing them. is also possible.

(summary)
The present embodiment will be summarized again with reference to the drawings.

The present disclosure relates to bearing device 30 . The bearing device 30 has rolling elements and raceway surfaces, and at least one bearing 5 that supports the shaft, and a member arranged on a path through which a pressing force that generates a preload between the rolling elements and the raceway surfaces is transmitted. , a load sensor 50 that is fixed to a member and whose resistance value changes according to the pressing force, and a resistor circuit 60 that includes a plurality of resistors R1 to R3 that are connected to the load sensor and form a bridge circuit. The load sensor 50 includes a thin film pattern 52 whose resistance changes according to pressing force, and a protective layer 54 that insulates and protects the thin film pattern 52 .

Preferably, the bearing device 30 further includes a processing section that detects the pressing force based on resistance change of the load sensor 50 .

The pressing force is applied by a load in the direction in which the main shaft 4 extends, and the load sensor 50 includes a plurality of load sensor elements 50a to 50a that are arranged at equal intervals on the same circumference in a plane that intersects the direction in which the main shaft 4 extends. 50d included.

The resistance circuit 60 includes a plurality of resistance modules 60a-60d respectively connected to a plurality of load sensor elements 50a-50d to form a plurality of resistance bridge circuits, each of the plurality of resistance modules 60a-60d connecting to the resistance module 60a. . . . 60d forming a resistance bridge circuit on the same circumference.

A plurality of load sensor elements 50a-50d are connected in series or in parallel to form a load detection section SR or PR. The load detection section SR or PR constitutes a bridge circuit together with a plurality of resistors R1-R3.

The at least one bearing 5 is a plurality of bearings 5a, 5b. The member is a non-rotating outer ring spacer 6g inserted between two bearings 5a and 5b out of the plurality of bearings. The load sensor 50 is fixed to the end face 6ga of the outer ring spacer 6g and arranged so as to contact the outer ring 5ga, which is the fixed ring of the bearing 5a, one of the two bearings 5a and 5b. The height of the surface of the resistance circuit 60 from the end face 6ga is lower than the height of the surface of the load sensor 50 from the end face 6ga. The pressing force is transmitted via the load sensor 50 .

Preferably, the resistance value and resistance temperature coefficient of each of the plurality of resistors R1 to R3 are substantially equal to the resistance value and resistance temperature coefficient of load sensor 50 .

Preferably, each of the plurality of resistors R1 to R3 is made of the same material as the thin film pattern 52 .

As shown in FIGS. 5-7, a thin film pattern 52 is formed on a substrate 51, and as shown in FIGS. It is formed.

As shown in FIGS. 1 and 2, the member is the outer ring spacer 6g arranged adjacent to at least one bearing 5a, the load sensor 50 is fixed to the end face 6ga of the outer ring spacer 6g, and the end face of the bearing 5a. , and the pressing force is transmitted via the load sensor 50 .

Preferably, as shown in FIG. 20, the member is one spacer obtained by dividing an outer ring spacer 6g arranged adjacent to at least one bearing 5a into a first spacer 6g1 and a second spacer 6g2. The load sensor 50 is fixed to the end face 6g1a of the first spacer 6g1 and comes into contact with the end face 6g2a of the second spacer 6g2.

More preferably, as shown in FIGS. 21 and 22, the first spacer 6g1 and the second spacer 6g2 sandwich the load sensor 50, and the first spacer 6g1 and the second spacer 6g2 are screwed with screws B The screw B is fastened, and the load sensor 50 is given a pressing force by the fastening force of the screw B in advance.

In another aspect, the present embodiment relates to a spindle device 1 including any of the bearing devices described above.

In still another aspect, the present embodiment relates to a spacer 6 which is arranged adjacent to a bearing 5a having rolling elements and raceway surfaces and to which a pressing force that generates a preload between the rolling elements and raceway surfaces is transmitted. The spacer 6 includes a load sensor 50 capable of measuring a pressing force, a resistance circuit 60 including a plurality of resistors R1 to R3 forming a bridge circuit together with the load sensor 50, and an end surface 6ga adjacent to the bearing 5a. An outer ring spacer 6g to which a resistance circuit 60 is fixed is provided.

Preferably, the spacer 6 further includes a processing section 70 integrally mounted on the outer ring spacer 6g and processing the output of the load sensor 50. As shown in FIG.

According to the bearing device of the embodiment described above, the following effects can be obtained.
In this embodiment, a load sensor element formed of a thin film resistor capable of measuring the load is formed on the load path where preload (load) is applied to the bearing, and a resistance circuit is arranged in the vicinity thereof. A bridge circuit was formed. Since the load sensor element and the resistance circuit are placed in the same temperature environment, the balance of the bridge circuit can be maintained even if the temperature changes by matching the resistance temperature coefficients or setting the resistance temperature coefficients small. Therefore, it is possible to suppress the temperature drift of the output obtained by electrically processing the signal of the load sensor element.

For example, if the thin film pattern (resistor) of the resistance circuit is formed from the same material as the load sensor element, the resistance value and the temperature coefficient of resistance (the rate at which the resistance value changes with temperature changes) can be made uniform, enabling the amplifier to respond to temperature changes. output drift can be further reduced. In this case, simplification or omission of temperature correction can be expected.

The embodiments disclosed this time should be considered as examples and not restrictive in all respects. The scope of the present invention is indicated by the scope of the claims rather than the description of the above-described embodiments, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

1 spindle device 2 outer cylinder 3 housing 3a stepped portion 3b, 12a groove 4 spindle 5, 5a, 5b, 16 bearing 5ga, 5gb, 16b outer ring 5ia, 5ib, 16a inner ring 6, 6g1, 6g2,9 spacer, 6g outer ring spacer, 6g1a, 6g2a, 6ga end face, 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 holder 22 space 30 bearing device 40 motor 50, 50a1 load sensor 50a to 50d, 150a, 250a, 350a load sensor element 51, 51A, 61 substrate 52, 62 thin film pattern, 53, T, T1 electrode, 54, 54A, 64 protective layer, 55 adhesive layer, 58 insulating layer, 60 resistance circuit, 60a to 60d resistance module, 70 processing unit, 71 wiring, 72, 72a to 72d, 172, 272 circuit Unit, 73 Operation Unit, 74 Storage Unit, 75 Diagnosis Unit, AMP, AMPa to AMPd Differential Amplifier, B Screw, CB Cable, G Flow Path, PR, SR Load Detection Unit, R, R1, R2, R3 Resistance, Rta , Rtb cage, Ta, Tb rolling elements, VSDC power supply.

Claims (15)

A bearing device,
at least one bearing having rolling elements and raceway surfaces for supporting a shaft;
a member arranged on a path through which a pressing force that generates a preload between the rolling elements and the raceway surface is transmitted;
a load sensor fixed to the member and having a resistance value that changes according to the pressing force;
a resistor circuit including a plurality of resistors connected to the load sensor to form a bridge circuit,
The load sensor is
a thin film pattern whose resistance changes according to the pressing force;
and a protective layer that insulates and protects the thin film pattern. 2. The bearing device according to claim 1, further comprising a processing unit that detects said pressing force based on a change in resistance of said load sensor. The pressing force is applied by a load in the extending direction of the shaft,
2. The bearing device according to claim 1, wherein said load sensor includes a plurality of load sensor elements arranged at equal intervals on the same circumference in a plane intersecting the extending direction of said shaft. The resistance circuit is
comprising a plurality of resistance circuit units respectively connected to the plurality of load sensor elements and forming a plurality of resistance bridge circuits;
4. Each of said plurality of resistance circuit portions is arranged adjacent to one of said plurality of load sensor elements forming a resistance bridge circuit together with each of said plurality of resistance circuit portions on said same circumference. The bearing device according to . the plurality of load sensor elements are connected in series or in parallel to form a load detection unit;
4. The bearing device according to claim 3, wherein said load detection section configures said bridge circuit together with said plurality of resistors. the at least one bearing is a plurality of bearings;
the member is a non-rotating spacer inserted between two of the plurality of bearings;
The load sensor is fixed to an end surface of the spacer and arranged to contact a fixed ring of one of the two bearings,
the height of the surface of the resistance circuit from the end face is lower than the height of the surface of the load sensor from the end face;
2. The bearing device according to claim 1, wherein said pressing force is transmitted via said load sensor. 2. The bearing device according to claim 1, wherein the resistance value and temperature coefficient of resistance of each of said plurality of resistors are substantially equal to the resistance value and temperature coefficient of resistance of said load sensor. 2. The bearing device according to claim 1, wherein each of said plurality of resistors is made of the same material as said thin film pattern. The thin film pattern is formed on a first substrate,
2. The bearing device according to claim 1, wherein said plurality of resistors are formed on a second substrate separate from said first substrate. the member is a spacer disposed adjacent to the at least one bearing;
The load sensor is fixed to an end surface of the spacer and contacts an end surface of the bearing,
2. The bearing device according to claim 1, wherein said pressing force is transmitted via said load sensor. The member is one spacer obtained by dividing an outer ring spacer arranged adjacent to the at least one bearing into a first spacer and a second spacer,
The load sensor is fixed to the end face of the first spacer and contacts the end face of the second spacer,
2. The bearing device according to claim 1, wherein said pressing force is transmitted via said load sensor. The first spacer and the second spacer sandwich the load sensor,
The first spacer and the second spacer are fastened with screws,
12. The bearing device according to claim 11, wherein said load sensor is pre-applied with a pressing force due to a fastening force of said screw. A spindle device comprising the bearing device according to any one of claims 1 to 12. A spacer disposed adjacent to a bearing having rolling elements and raceway surfaces and transmitting a pressing force that generates a preload between the rolling elements and the raceway surfaces,
a load sensor capable of measuring the pressing force;
a resistor circuit including a plurality of resistors forming a bridge circuit together with the load sensor;
A spacer comprising an outer ring spacer having the load sensor and the resistance circuit fixed to an end face adjacent to the bearing. 15. The spacer according to claim 14, further comprising a processing unit mounted integrally with said outer ring spacer and processing an output of said load sensor.

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