Spindle device, load sensor calibration method and machining load calculation method

Abstract

To provide a spindle device, load sensor calibration method and machining load calculation method that can calculate a machining load correctly.SOLUTION: A spindle device 100 is provided with a bearing unit 1. The bearing unit has a load sensor 11 mounted. The spindle device 100 has: a computation unit 31; and a storage unit 32. The computation unit 31 is configured to calculate a machining load F to be applied to the bearing unit 1 from output information S to be output from the load sensor 11. The bearing unit 1 has a rotatable main shaft 4. In the storage unit 32, stored are a first relation R1 between a measurement load F1 and the first output information S1. The measurement load F1 is applied to the bearing unit 1 in a standing still state of the main shaft 4. First output information S1 is output from the load sensor 11 when the measurement load F1 is applied to the bearing unit 1. The computation unit 31 is configured to calculate a machining load F from the output information S based on the first relation R1.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a spindle device, a method for calibrating a load sensor, and a method for calculating a processing load. [Background technology]

[0002] In spindle devices such as machine tools, management of processing loads and bearing preloads is required to improve processing accuracy and efficiency. Spindle devices are also required to detect signs of bearing abnormalities before they occur and prevent bearing abnormalities before they occur.

[0003] Japanese Patent Application Laid-Open Publication No. 2023-47505 (Patent Document 1) discloses a spindle device in which a pair of angular contact ball bearings are placed back to back with a spacer in between, and a strain sensor is attached to the spacer to measure the amount of preload on the bearings from the amount of strain on the spacer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-47505 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in order to obtain the relationship between the output of a load sensor such as a strain sensor and the load, a calibration test is generally performed on the load sensor alone. The load detected by the load sensor during machining includes not only the machining load applied to the spindle but also the load generated as the spindle rotates. Therefore, it has been difficult to accurately calculate the machining load actually applied to the spindle from the relationship between the load and the output of the load sensor obtained through a calibration test of the load sensor alone.

[0006] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to provide a spindle device capable of accurately calculating a processing load, a method for calibrating a load sensor, and a method for calculating a processing load. [Means for solving the problem]

[0007] A spindle device according to the present disclosure includes a bearing unit. The bearing unit is equipped with a load sensor. The spindle device has a calculation unit and a memory unit. The calculation unit calculates a processing load applied to the bearing unit from output information output from the load sensor. The bearing unit has a rotatable main shaft. The memory unit stores a first relationship between the measured load and first output information. The measured load is applied to the bearing unit when the main shaft is stationary. The first output information is output from the load sensor when the measured load is applied to the bearing unit. The calculation unit calculates the processing load from the output information based on the first relationship.

[0008] A method for calibrating a load sensor according to the present disclosure includes a step of preparing a spindle device having a bearing unit and a load measuring jig, and a storing step. The bearing unit is equipped with a load sensor. The bearing unit has a rotatable main shaft. The storing step includes a step of storing a first relationship used to calculate a processing load applied to the bearing unit. In the step of storing the first relationship, the first relationship between the measured load and first output information is stored. The measured load is measured with the bearing unit pressing the load measuring jig while the main shaft is stationary. The first output information is output from the load sensor when the measured load is measured. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a spindle device capable of accurately calculating a processing load, a method for calibrating a load sensor, and a method for calculating a processing load. [Brief explanation of the drawings]

[0010] [Figure 1]1 is a cross-sectional view showing a schematic configuration of a bearing unit according to a first embodiment. [Figure 2] FIG. 2 is a partially enlarged cross-sectional view of the main part on the left side of FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] FIG. 2 is a schematic structural diagram of a load sensor. [Figure 5] FIG. 2 is a diagram illustrating a schematic configuration of a load sensor. [Figure 6] FIG. 3 is a functional block diagram of a data processing unit that processes output information from a load sensor. [Figure 7] 10 is a flowchart illustrating a method for calibrating a load sensor. [Figure 8] FIG. 2 is a side view of a spindle device in which an axial load is measured. [Figure 9] 4 is a graph showing the relationship between first output information output from a plurality of load sensor elements and a measured load in an axial direction. [Figure 10] FIG. 10 is a side view of a spindle device in which a radial load is measured. [Figure 11] FIG. 2 is a plan view of a spindle device in which a radial load is measured. [Figure 12] 10 is a graph showing the relationship between first output information output from a plurality of load sensor elements and a measured load in the radial direction. [Figure 13] 1 is a graph showing a first relationship and a second relationship. [Figure 14] FIG. 10 is a cross-sectional view of a bearing unit according to a second embodiment. [Figure 15] FIG. 10 is a cross-sectional view of a bearing unit according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the embodiments described below, when numbers, quantities, etc. are mentioned, the scope of the present disclosure is not necessarily limited to those numbers, quantities, etc., unless otherwise specified. The same reference numerals are used for the same or equivalent parts, and redundant descriptions may not be repeated. It is intended from the beginning that the configurations in the embodiments may be used in appropriate combinations.

[0012] (Embodiment 1) Fig. 1 is a cross-sectional view showing a schematic configuration of a bearing unit 1 according to a first embodiment. Fig. 2 is a partially enlarged view of a main portion on the left side of Fig. 1. Fig. 2 mainly shows a bearing device 50. Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2.

[0013] The bearing unit 1 shown in Fig. 1 is a part of a spindle device 100, and is used, for example, as a built-in motor type bearing unit for a machine tool. A motor 40 is built into one end of the spindle 4. A cutting tool such as an end mill is connected to the other end of the spindle 4.

[0014] The bearing unit 1 includes a bearing 5 including bearings 5a and 5b, a spacer 6 arranged adjacent to the bearings 5a and 5b, a spacer 9 located on the opposite side of the spacer 6 from the bearing 5b and arranged adjacent to one end of the bearing 5b, a motor 40, and a bearing 16 arranged rearward of the motor 40. The main shaft 4 extends along a central axis A. The main shaft 4 is supported by a plurality of bearings 5a and 5b so as to be rotatable about the central axis A. The plurality of bearings 5a and 5b are provided in a housing 3 embedded in the inner diameter portion of the outer cylinder 2.

[0015] As shown in Fig. 2, bearing 5a includes an inner ring 5ia, an outer ring 5ga, rolling elements Ta, and a cage Rta. Bearing 5b includes an inner ring 5ib, an outer ring 5gb, rolling elements Tb, and a cage Rtb. Bearing 5a and bearing 5b are arranged spaced apart from each other in a direction along central axis A (axial direction z). Spacer 6 includes an inner ring spacer 6i and a first outer ring spacer 6g.

[0016] An inner ring 5ia of bearing 5a and an inner ring 5ib of bearing 5b are fitted in an interference fit (press-fit) state onto the main shaft 4. An inner ring spacer 6i is disposed between the inner ring 5ia and the inner ring 5ib. A first outer ring spacer 6g is disposed between the outer ring 5ga and the outer ring 5gb.

[0017] 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. The plurality of rolling elements Ta are arranged along the circumferential direction of the central axis A. The plurality of rolling elements Ta are spaced apart by a cage 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. The plurality of rolling elements Tb are arranged along the circumferential direction of the central axis A. The plurality of rolling elements Tb are spaced apart by a cage Rtb.

[0018] The bearings 5a and 5b may be bearings capable of bearing a load in the axial direction z. The bearings 5a and 5b may be any of angular contact ball bearings, deep groove ball bearings, tapered roller bearings, etc. The bearing device 50 shown in Fig. 2 uses angular contact ball bearings. The two bearings 5a and 5b are installed in a back-to-back (DB) configuration.

[0019] The bearing unit 1 according to this embodiment 1 is a bearing unit 1 that uses a structure in which the main shaft 4 is supported by three bearings 5a, 5b, and 16, but it may also be a bearing unit 1 that uses a structure in which the main shaft 4 is supported by two or four or more bearings.

[0020] Bearing 16 is a single-row rolling bearing, such as a cylindrical roller bearing. Bearings 5a and 5b, which are angular contact ball bearings, receive a load in the radial direction θ and a load in the axial direction z acting on main shaft 4. Single-row bearing 16, which is a cylindrical roller bearing, receives a load in the radial direction θ acting on bearing unit 1.

[0021] The housing 3 fixes the outer ring 5ga of the bearing 5a and the outer ring 5gb of the bearing 5b. A coolant flow path G1 is provided in the housing 3. Specifically, the coolant flow path G1 is provided between the housing 3 and the outer cylinder 2. By flowing a coolant through the coolant flow path G1, the bearings 5a and 5b can be cooled.

[0022] The assembly of bearing unit 1 will now be described. First, bearing 5a, spacer 6, bearing 5b, and spacer 9 are inserted onto main shaft 4 in this order. Next, nut 10 is tightened to fix bearing 5a, spacer 6, bearing 5b, and spacer 9 in place. In this way, a preload is applied along a path that follows line of force P1, as shown in Figure 2.

[0023] Specifically, by tightening the nut 10, a pressing force acts on the end face of the inner ring 5ib of the bearing 5b via the spacer 9. This pressing force presses the inner ring 5ib toward the inner ring spacer 6i. This pressing force is transmitted to the inner ring 5ib, the rolling element Tb, and the outer ring 5gb. In other words, this pressing force applies a preload between the raceway surfaces of the inner ring 5ib and the outer ring 5gb and the rolling element Tb.

[0024] Tightening the nut 10 also applies a pressing force from the outer ring 5gb to the first outer ring spacer 6g. This pressing force is transmitted to the outer ring 5ga, rolling element Ta, and inner ring 5ia in the bearing 5a. In other words, this pressing force also applies a preload between the raceway surfaces of the inner ring 5ia and outer ring 5ga of the left-side bearing 5a and the rolling element Ta.

[0025] The preload applied to the bearings 5a and 5b is determined, for example, by the amount of movement of the nut 10. However, the amount of movement of the nut 10 is limited by the difference in width between the first outer ring spacer 6g and the inner ring spacer 6i.

[0026] Next, as shown in FIG. 2, the main shaft 4 with the bearings 5a and 5b attached is inserted into the housing 3. Specifically, one end of the second outer ring spacer 7, which is disposed to the right of the outer ring 5gb of bearing 5b, abuts against a stepped portion 3a provided on the housing 3. The other end of the second outer ring spacer 7 abuts against the right end face of the outer ring 5gb of bearing 5b. Finally, the front cover 12 is fixed to the housing 3 using bolts (not shown) or the like. In this way, the front cover 12 presses against the outer ring 5ga of bearing 5a, the first outer ring spacer 6g, the outer ring 5gb of bearing 5b, and the second outer ring spacer 7, thereby fixing the main shaft 4 in the housing 3 via the bearings 5a and 5b.

[0027] When front cover 12 is fixed to housing 3, a load is applied in the direction of force line P2 shown in Figure 2 according to the torque applied to tighten the bolts. The load applied when fixing front cover 12 displaces outer ring 5ga, first outer ring spacer 6g, outer ring 5gb, and second outer ring spacer 7 in the direction along central axis A of main shaft 4. The preload applied to the path along force line P1 changes depending on the amount of displacement.

[0028] As shown in Figure 1, the position of inner ring 16a of single-row bearing 16 in the axial direction z is determined by cylindrical member 15 and inner ring retainer 19. Cylindrical member 15 is fitted onto the outer periphery of main shaft 4. Inner ring retainer 19 is fixed by a nut 20 threaded onto main shaft 4. Outer ring 16b of bearing 16 is sandwiched between positioning member 21 fixed to end member 17 and positioning member 18. Inner ring 16a slides integrally with main shaft 4 relative to end member 17 as main shaft 4 expands and contracts.

[0029] As shown in FIG. 1 , a motor 40 that drives the main shaft 4 is disposed between bearings 5a, 5b and a single-row bearing 16 in a space 22 provided between the main shaft 4 and the outer cylinder 2. A rotor 14 of the motor 40 is fixed to a cylindrical member 15 that fits onto the outer periphery of the main shaft 4. A stator 13 of the motor 40 is fixed to a housing 8 that is fixed to the inner periphery of the outer cylinder 2. A coolant flow path G2 is provided in the housing 8. Specifically, the coolant flow path G2 is provided between the housing 8 and the outer cylinder 2. The rotor 14 and the stator 13 can be cooled by flowing a coolant through the coolant flow path G2.

[0030] When the bearing unit 1 is in operation (while the main shaft 4 is rotating), the preload changes as the rotational speed of the main shaft 4 increases. Specifically, the centrifugal force acting on the rolling elements Ta and Tb increases as the rotational speed of the main shaft 4 increases. As a result, the first outer ring spacer 6g is compressed in the axial direction z, and the second outer ring spacer 7 expands in accordance with the amount of deformation of the first outer ring spacer 6g, changing the preload applied to the bearings 5a and 5b.

[0031] Furthermore, as the rotational speed of the main shaft 4 increases, the temperature inside the bearing unit 1 increases. As a result, a pressing force is generated along the path of the force line P1 due to thermal expansion of the components that make up the bearing unit 1. The pressing force caused by thermal expansion resulting from this temperature change changes the preload applied to the bearings 5a and 5b.

[0032] During machining, when a load is applied to the cutting tool attached to the tip of the spindle 4, a load associated with machining (machining load F) is applied to the spindle 4 of the bearing unit 1. The machining load F and preload are detected by a load sensor 11 mounted on the bearing unit 1, as shown in Figures 1 and 2.

[0033] The load sensor 11 may include a plurality of load sensor elements 11a. Specifically, as shown in FIG. 3, each of the load sensor elements 11a is fixed to a flat portion 6ga of a first outer ring spacer 6g. The first outer ring spacer 6g has, for example, a cylindrical shape. The plurality of flat portions 6ga are provided on the outer diameter surface of the first outer ring spacer 6g.

[0034] The multiple load sensor elements 11a are arranged on the same circumference with respect to the central axis A along which the main shaft 4 extends. As shown in FIG. 3, in the bearing unit 1 of embodiment 1, flat portions 6ga are provided at four locations equally spaced at 90 degrees on the outer diameter surface of the first outer ring spacer 6g. The load sensor 11 may include four load sensor elements 11a. Each of the four load sensor elements 11a is fixed to a respective flat portion 6ga.

[0035] The load sensor 11 may be fixed to a non-rotating ring member, and may be fixed to the outer diameter surface of the first outer ring spacer 6g, the outer diameter surface of the outer rings 5ga, 5gb, the inner diameter surface of the front cover 12, or the inner diameter surface of the housing 3.

[0036] Next, a description will be given of the load sensor 11. Fig. 4 is a schematic structural diagram of the load sensor 11. Fig. 5 is a diagram showing a schematic configuration of the load sensor 11.

[0037] The load sensor 11 may be, for example, a strain sensor. The strain sensor detects, for example, the amount of strain in the first outer ring spacer 6g. When the load sensor 11 is a strain sensor, for example, the strain sensor detects the amount of strain and outputs output information S corresponding to the amount of strain.

[0038] 4 and 5, the load sensor 11 includes a detection unit 24 and a processing unit 25. When the load sensor 11 is a strain sensor, the detection unit 24 may be, for example, a strain gauge.

[0039] As shown in FIG. 5, processing unit 25 includes amplifier 25a and output unit 25b. Amplifier 25a electrically amplifies the signal from the strain gauge. Output unit 25b outputs the amplified signal from the strain gauge to an external device (e.g., calculation unit 31) as output information S. The amplified signal from the strain gauge may be, for example, a voltage value. Processing unit 25 may also include a bridge circuit as pre-processing for amplifier 25a. The bridge circuit converts the amount of change in resistance of the strain gauge into a voltage value and outputs the voltage value.

[0040] As shown in FIG. 4, the load sensor 11 includes a substrate 23. The detection unit 24 and the processing unit 25 are disposed on the substrate 23. The substrate 23 may be, for example, a metal plate having a linear expansion coefficient similar to that of the first outer ring spacer 6g. The detection unit 24 is fixed onto the substrate 23 by adhesive or mechanical bonding. The processing unit 25 is an electric circuit board that is miniaturized and fixed onto the substrate 23. The detection unit 24 and the processing unit 25 are electrically connected by wiring or the like.

[0041] The load sensor 11 may be configured only with a strain gauge that serves as the detection unit 24. The processing unit 25 may be provided outside the bearing unit 1. When the processing unit 25 is provided outside the bearing unit 1, the processing unit 25 may be disposed close to the detection unit 24. In this way, the wiring connecting the detection unit 24 and the processing unit 25 is shorter than when the detection unit 24 and the processing unit 25 are located far apart, and the influence of electrical noise is reduced.

[0042] The detection unit 24 is fixed to the outer diameter surface of the first outer ring spacer 6g via the substrate 23. This allows the load sensor 11 to be constructed within the substrate 23, improving the ease of assembly of the load sensor 11. The substrate 23 is fixed to a flat portion 6ga on the outer diameter surface of the first outer ring spacer 6g. This makes it easy to fix the substrate 23, improving the stability of the output of the load sensor 11. Furthermore, because the flat portion 6ga is provided on the outer diameter surface of the first outer ring spacer 6g, less additional processing of the first outer ring spacer 6g is required. In other words, a simple configuration can be achieved that does not require major changes to the structure of the first outer ring spacer 6g, and a decrease in the rigidity of the first outer ring spacer 6g can be suppressed.

[0043] The above describes the case where the load sensor 11 is a strain sensor, but the load sensor 11 may be any sensor that can detect information corresponding to the load, and may be a thin film sensor or a pressure sensor in addition to a strain sensor. The load sensor 11 may also be configured to output the output information S by combining these sensors.

[0044] The output information S output from the load sensor 11 does not have to be a voltage value, and may be, for example, a current value in addition to a voltage value. The output information S may be, for example, either a strain amount or a load converted from a voltage value.

[0045] 6 is a functional block diagram of a data processing unit 30 that processes the output information S of the load sensor 11. The output information S of the load sensor 11 is output to the data processing unit 30. The data processing unit 30 may be provided inside the bearing unit 1, and the output information S may be output to the data processing unit 30 via a wired connection. The data processing unit 30 may be provided outside the bearing unit 1, and the output information S may be output to the data processing unit 30 wirelessly. The data processing unit 30 may be, for example, a data processing device such as a personal computer installed outside the bearing unit 1.

[0046] The data processing unit 30 includes a calculation unit 31 and a storage unit 32. The calculation unit 31 calculates the processing load F from the output information S of the load sensor 11. The storage unit 32 stores a first relationship R1 and a second relationship R2 obtained in a calibration method for the load sensor 11, which will be described later. The calculation unit 31 calculates the processing load F from the output information S based on the first relationship R1 and the second relationship R2.

[0047] The data processing unit 30 may further include a preload calculation unit 33 and a life estimation unit 34. The preload calculation unit 33 may calculate the preload of the bearing 5 from the output information S of the load sensor 11. The preload of the bearing 5 is the load applied to the bearings 5a and 5b. The preload of the bearing 5 includes, for example, not only the pressing force after the bearing unit 1 is assembled, but also centrifugal force generated with the rotation of the main shaft 4 and pressing force due to thermal expansion generated with a temperature rise of the bearing unit 1.

[0048] As a countermeasure against electrical noise, the output information S may be subjected to low-pass filtering before calculating the processing load F and the preload of the bearing 5. The obtained processing load F and the preload of the bearing 5 may also be subjected to low-pass filtering to suppress fluctuations in the measurement values ​​of the processing load F and the preload of the bearing 5.

[0049] The life estimation unit 34 is configured to notify the remaining bearing life and the timing for bearing replacement based on at least one of the processing load F, the preload of the bearing 5, and bearing information (bearing internal specifications, rotation speed N, number of operations, temperature, etc.). In particular, if the processing load F and the preload of the bearing 5 can be accurately calculated, damage to the components constituting the bearing unit 1 (bearings 5a, 5b, spindle 4, cutting tool, etc.) can be suppressed by monitoring the processing load F and the preload of the bearing 5 during processing. Furthermore, if damage to the components occurs, the processing load F and the preload of the bearing 5 can be used to investigate the cause. Furthermore, the processing quality and productivity of the objects processed by the bearing unit 1 can be improved.

[0050] The storage unit 32 is configured by a memory circuit mounted on the microcontroller. The calculation unit 31, preload calculation unit 33, and life estimation unit 34 are configured by, for example, a CPU mounted on the microcontroller. Note that a temperature sensor (not shown) may be installed to add temperature correction as needed.

[0051] (Load sensor calibration method) The following describes a method for calibrating the load sensor 11. Fig. 7 is a flowchart showing the method for calibrating the load sensor 11.

[0052] First, a step (S1) of preparing a spindle device 100 is performed. The spindle device 100 has a bearing unit 1, a load measurement jig 61, and a tool 70. The load measurement jig 61 is fixed to a table 62. The tool 70 is attached to the tip of the spindle 4.

[0053] Next, the storing step (S2) is carried out. The storing step (S2) includes a step (S2a) of storing the first relationship R1 and a step (S2b) of storing the second relationship R2.

[0054] In the step (S2a) of storing the first relationship R1, the first relationship R1 between the measured load F1 and the first output information S1 is stored in the memory unit 32. The measured load F1 is measured in a state where the bearing unit 1 presses the load measuring jig 61 with the spindle 4 in a stationary state.

[0055] The measured load F1 is a load displayed as a true value, which is calculated from information output from a load sensor mounted on the load measuring jig 61, for example. For example, the measured load F1 is applied to the spindle 4 of the bearing unit 1 by pressing a tool 70 attached to the tip of the spindle 4 against the load measuring jig 61. When the measured load F1 is applied to the bearing unit 1, first output information S1 is output from the load sensor 11. In other words, the first output information S1 is output from the load sensor 11 as information corresponding to the measured load F1.

[0056] By measuring a plurality of measured loads F1 each having a different absolute value, first output information S1 corresponding to each of the measured loads F1 is output. In this way, a first relationship R1 between the plurality of measured loads F1 and the first output information S1 corresponding to each of the measured loads F1 is stored in the storage unit 32.

[0057] In the step (S2a) of storing the first relationship R1, a plurality of measurement loads F1 having different vectors may be measured. Specifically, a measurement load F1 in the axial direction z and a measurement load F1 in the radial direction θ may be measured. The axial direction z is the direction in which the main shaft 4 extends. The radial direction θ is a direction perpendicular to the direction in which the main shaft 4 extends. In other words, the radial direction θ is a direction perpendicular to the axial direction z.

[0058] FIG. 8 is a side view of the spindle device 100 in which the measured load F1 in the axial direction z is measured. As shown in FIG. 8, the tool 70 may be pressed against the load measuring jig 61 in a direction D1. The direction D1 is a direction along the axial direction z. In this way, the measured load F1 is measured while the bearing unit 1 is pressed in the axial direction z. First output information S1 corresponding to the measured load F1 in the axial direction z is output from the load sensor 11.

[0059] 9 is a graph showing the relationship between the first output information S1 output from the plurality of load sensor elements 11a and the measured load F1 in the axial direction z. In FIG. 9, the horizontal axis represents the measured load F1 (unit: N) in the axial direction z, and the vertical axis represents the first output information S1. The first output information S1 is, for example, a voltage value (unit: V). For the measured load F1 in the axial direction z, each of the four load sensor elements 11a outputs first output information Sz1, Sz2, Sz3, and Sz4. One of the first output information Sz1, Sz2, Sz3, and Sz4 output from each of the plurality of load sensor elements 11a may be used as the output information S corresponding to the measured load F1 in the axial direction z.

[0060] 9, the first output information Sz1, Sz2, Sz3, and Sz4 output from each of the plurality of load sensor elements 11a is not uniform in the circumferential direction of the first outer ring spacer 6g, but varies due to the influence of the dimensional accuracy of the first outer ring spacer 6g, the housing 3, the front cover 12, the bearing 5, etc., assembly variations, radial load, and misalignment of the center of the load application point. Therefore, as shown in FIG. 9, the value Sz1, Sz2, Sz3, and Sz4 obtained by averaging the plurality of first output information Sz1, Sz2, Sz3, and Sz4 is ave may be used as the output information S corresponding to the measured load F1 in the axial direction z. The output information S corresponding to the measured load F1 in the axial direction z may be any of the following: a total value of the plurality of first output information Sz1, Sz2, Sz3, Sz4, a maximum value of the plurality of first output information Sz1, Sz2, Sz3, Sz4, a minimum value of the plurality of first output information Sz1, Sz2, Sz3, Sz4, a difference between the maximum and minimum values ​​of the plurality of first output information Sz1, Sz2, Sz3, Sz4, or a value obtained by correcting the plurality of first output information Sz1, Sz2, Sz3, Sz4 depending on the arrangement relationship in the load sensor element 11a.

[0061] FIG. 10 is a side view of the spindle device 100 in which the measurement load F1 in the radial direction θ is measured. FIG. 11 is a plan view of the spindle device 100 in which the measurement load F1 in the radial direction θ is measured. As shown in FIG. 10, the tool 70 may be pressed against the load measurement jig 61 along direction D2. Direction D2 is a direction perpendicular to the direction in which the spindle 4 extends (axial direction z). From a different perspective, direction D2 is a direction along the radial direction θ. In this way, the measurement load F1 is measured while the bearing unit 1 is pressed in the radial direction θ.

[0062] A first relationship R1 between the measured load F1 in at least four directions in the radial direction θ and the first output information S1 corresponding to each of the measured loads F1 may be stored in the memory unit 32. Specifically, as shown in FIG. 11 , the radial direction θ includes a first radial direction θ1 and a second radial direction θ2. The second radial direction θ2 is a direction perpendicular to the first radial direction θ1. The tool 70 may be pressed against the load measuring jig 61 along each of directions D2a, D2b, D2c, and D2d. Note that the direction D2a is the negative direction of the first radial direction θ1 in FIG. 11. The direction D2b is the negative direction of the second radial direction θ2 in FIG. 11. The direction D2c is the positive direction of the first radial direction θ1 in FIG. 11. The direction D2d is the positive direction of the second radial direction θ2 in FIG. 11.

[0063] 12 is a graph showing the relationship between the first output information S1 output from the plurality of load sensor elements 11a and the measured load F1 in the radial direction θ. In FIG. 12, the horizontal axis represents the measured load F1 (unit: N) in the radial direction θ, and the vertical axis represents the first output information S1. For the measured load F1 in the radial direction θ, each of the plurality of load sensor elements 11a outputs first output information Sθ1, Sθ2, Sθ3, and Sθ4. For the measured load F1 in the radial direction θ, the values ​​of the first output information Sθ1, Sθ2, Sθ3, and Sθ4 output from each of the plurality of load sensor elements 11a differ depending on the direction in which the tool 70 is pressed against the load measuring jig 61. Therefore, the direction and absolute value of the measured load F1 may be uniquely determined from the relationship between the values ​​of the first output information Sθ1, Sθ2, Sθ3, and Sθ4 output from each of the plurality of load sensor elements 11a.

[0064] The load conversion jig 61 used when measuring the measurement load F1 in the axial direction z may be different from the load conversion jig 61 used when measuring the measurement load F1 in the radial direction θ. The shape of the load conversion jig 61 may be, for example, a regular hexahedron. When measuring the measurement load F1 in the radial direction θ, the shape of the load conversion jig 61 used may be, for example, a hemisphere. In this way, the measurement load F1 in the radial direction θ can be measured with higher accuracy.

[0065] In this way, the first relationship R1 between the measured load F1 measured when the bearing unit 1 is pressing the load measuring jig 61 while the spindle 4 is stationary and the first output information S1 output from the load sensor 11 when the measured load F1 is measured is stored in the memory unit 32.

[0066] In the step (S2a) of storing the first relationship R1, a tool 70 attached to the tip of the spindle 4 presses the load measuring jig 61. The tool 70 may be a cutting tool such as an end mill, a reamer, or a cutting tool that is actually used in machining.

[0067] In the step (S2a) of storing the first relationship R1, a dedicated tool for load conversion may be used to ensure stable contact with the load measurement jig 61 when pressing the tool 70 against the load measurement jig 61. The dedicated tool for load conversion may have the same weight as the cutting tool. In this way, in the storing step (S2), the first relationship R1 corresponding to the cutting tool used during processing can be obtained with high accuracy. In other words, the processing load F can be accurately calculated according to the cutting tool used during processing.

[0068] Next, a step (S2b) of storing the second relationship R2 is performed. In this step (S2b), the second relationship R2 between the rotation speed N of the main shaft 4 in the rotation state of the main shaft 4 and the second output information S2 is stored in the memory unit 32.

[0069] As described above, when the bearing unit 1 is in operation (while the main shaft 4 is rotating), centrifugal force is generated as the main shaft 4 rotates, and pressing force is generated due to thermal expansion as the temperature of the bearing unit 1 rises. That is, while the main shaft 4 is rotating, the preload changes due to the influence of the centrifugal force and pressing force due to thermal expansion. As a result, the value of the output information S output from the load sensor 11 changes as the preload changes. In accordance with the amount of change in the preload while the main shaft 4 is rotating, the second output information S2 is output from the load sensor 11 as the output information S. That is, the second output information S2 is output from the load sensor 11 as information corresponding to the rotation speed N of the main shaft 4.

[0070] In the rotation state of the spindle 4, the second output information S2 corresponding to each of the plurality of rotation speeds N is output at each of the plurality of rotation speeds N. In this manner, the second relationship R2 between the plurality of rotation speeds N and the second output information S2 corresponding to each of the rotation speeds N is stored in the memory unit 32.

[0071] In this way, in the above-mentioned method for calibrating the load sensor 11, a spindle device 100 is obtained in which the load sensor 11 mounted on the bearing unit 1 is calibrated based on the first relationship R1 and the second relationship R2 obtained from the storage step (S2).

[0072] (Calculation method for processing load) A method for calculating the processing load F will be described below. As shown in Fig. 7, a processing step (S3) is performed using the bearing unit 1. The memory unit 32 of the bearing unit 1 stores the first relationship R1 and the second relationship R2.

[0073] FIG. 13 is a graph showing the first relationship R1 and the second relationship R2. Based on the first relationship R1 and the second relationship R2 obtained in the storing step (S2), a map such as that shown in FIG. 13 is obtained. In FIG. 13, the horizontal axis represents load (unit: N), and the vertical axis represents, for example, voltage value (unit: V) as output information S. Load F10 is, for example, the preload when the spindle 4 is stationary after the bearing unit 1 is assembled (when the rotation speed N of the spindle 4 is 0 rpm). Voltage value V0 is the voltage value output from load sensor 11 when no load is applied to the spindle 4 of the bearing unit 1 when the spindle 4 is stationary. Voltage value V0 corresponds to load F10.

[0074] Each of the loads F11 to F1n is the measured load F1 measured when the spindle 4 is in a stationary state in the step (S2a) of storing the first relationship R1. 01 ~V 0n are the first output information S1 output from the load sensor 11 when the loads F11 to F1n are applied to the bearing unit 1 while the spindle 4 is stationary in the step (S2a) of storing the first relationship R1. That is, the voltage value V01 ~V 0n The first relationship R1 is a relationship between the loads F10 to F1n and the voltage values ​​V0 to V 0n The relation may be:

[0075] Voltage values ​​V1 to V N are the second output information S2 output from the load sensor 11 in the rotation state at each rotation speed N of the spindle 4 in the step (S2b) of storing the second relationship R2. N Each of these corresponds to the rotation state when the rotation speed N of the spindle 4 is 0 to N rpm. For example, the rotation state of the spindle 4 at 1000 rpm may correspond to the voltage value V1. The second relationship R2 is the relationship between the rotation speeds 0 to N of the spindle 4 and the voltage values ​​V0 to V N The relation may be:

[0076] As shown in Fig. 13, for example, when the bearing unit 1 performs machining at a rotation speed N of 1000 rpm of the spindle 4, a voltage value V is output as output information S from the load sensor 11. At this time, a machining load F is calculated from the voltage value V based on the first relationship R1 and the second relationship R2. Specifically, a value is calculated by subtracting the difference between the voltage value V1 and the voltage value V0 from the voltage value V based on the second relationship R2. The value to be subtracted from the voltage value V based on the second relationship R2 is the value obtained by subtracting the difference between the voltage values ​​V1 and V0 from the voltage value V based on the rotation speeds 0 to N and the voltage values ​​V0 to V N The value to be subtracted from the voltage value V may be calculated from a relational expression using any interpolation method based on the rotation speed 0 to N and the voltage value V0 to V N The interpolation method may be, for example, linear interpolation, polynomial interpolation, or spline interpolation.

[0077] Next, the processing load F corresponding to the value obtained by subtracting the difference between the voltage value V1 and the voltage value V0 from the voltage value V is calculated based on the first relationship R1. The processing load F calculated based on the first relationship R1 is calculated based on the loads F10 to F1n and the voltage values ​​V0 to V 0n The processing load F may be calculated from a relational expression using any interpolation method based on the loads F10 to F1n and the voltage values ​​V0 to V 0nAlternatively, the calculation may be performed by interpolating or extrapolating based on the above. As the interpolation method, for example, linear interpolation, polynomial interpolation, or spline interpolation may be used. In this way, the processing load F applied to the spindle 4 of the bearing unit 1 during processing can be accurately calculated.

[0078] By monitoring the accurately calculated processing load F and preload during processing, it is possible to reduce the occurrence of damage to the components (bearings 5a, 5b, spindle 4, cutting tool, etc.) that make up the bearing unit 1, and if damage does occur, the processing load F and preload can be used to identify the cause. Furthermore, it is possible to improve the processing quality and productivity of the object processed by the bearing unit 1.

[0079] (Action and effect) A spindle device 100 according to the present disclosure includes a bearing unit 1. The bearing unit 1 is equipped with a load sensor 11. The spindle device 100 has a calculation unit 31 and a memory unit 32. The calculation unit 31 calculates a processing load F applied to the bearing unit 1 from output information S output from the load sensor 11. The bearing unit 1 has a rotatable main spindle 4. The memory unit 32 stores a first relationship R1 between a measured load F1 and first output information S1. The measured load F1 is applied to the bearing unit 1 when the main spindle 4 is stationary. The first output information S1 is output from the load sensor 11 when the measured load F1 is applied to the bearing unit 1. The calculation unit 31 calculates the processing load F from the output information S based on the first relationship R1.

[0080] In this way, it is possible to accurately calculate the processing load F applied to the spindle 4 of the bearing unit 1 during processing. As a result, by monitoring the processing load F and preload during processing, it is possible to reduce the occurrence of damage to the components that make up the bearing unit 1 (bearings 5a, 5b, spindle 4, cutting tool, etc.), and if damage does occur, the processing load F and preload can be used to identify the cause. Furthermore, it is possible to improve the processing quality and productivity of objects processed with the bearing unit 1.

[0081] In the spindle device 100, the memory unit 32 stores a second relationship R2 between the rotation speed N of the spindle 4 and second output information S2 in the rotation state of the spindle 4. The second output information S2 is output from the load sensor 11 in the rotation state of the spindle 4. The calculation unit 31 calculates the processing load F from the output information S based on the first relationship R1 and the second relationship R2.

[0082] In this way, the processing load F applied to the spindle 4 of the bearing unit 1 during processing can be accurately calculated.

[0083] In the spindle device 100, the load sensor 11 includes a plurality of load sensor elements 11a. The plurality of load sensor elements 11a are arranged on the same circumference with respect to the central axis A along which the main shaft 4 extends.

[0084] In this way, the vector and absolute value of the processing load F can be calculated from the output information S output from the multiple load sensor elements 11a. As a result, the processing load F applied to the spindle 4 of the bearing unit 1 during processing can be accurately calculated.

[0085] The spindle device 100 further includes a load measuring jig 61. The measurement load F1 is measured in a state where the bearing unit 1 presses the load measuring jig 61.

[0086] In this way, the load measuring jig 61 can be used to obtain the first relationship R1 between the measured load F1 and the first output information S1.

[0087] In the spindle device 100, the direction in which the main shaft 4 extends is defined as the axial direction z. The measurement load F1 is measured in a state in which the bearing unit 1 presses the load measurement jig 61 in the axial direction z.

[0088] In this way, the load measuring jig 61 can be used to obtain the first relationship R1 between the measured load F1 in the axial direction z of the spindle 4 and the first output information S1.

[0089] In the spindle device 100, the direction perpendicular to the direction in which the main shaft 4 extends is defined as the radial direction θ. The measurement load F1 is measured in a state in which the bearing unit 1 presses the load measurement jig 61 in the radial direction θ.

[0090] In this way, the load measuring jig 61 can be used to obtain the first relationship R1 between the measured load F1 in the radial direction θ of the spindle 4 and the first output information S1.

[0091] A method for calibrating a load sensor 11 according to the present disclosure includes a step (S1) of preparing a spindle device 100 having a bearing unit 1 and a load measuring jig 61, and a storing step (S2). The bearing unit 1 is equipped with a load sensor 11. The bearing unit 1 has a rotatable main shaft 4. The storing step (S2) includes a step (S2a) of storing a first relationship R1 used to calculate a processing load F applied to the bearing unit 1. In the step (S2a) of storing the first relationship R1, the first relationship R1 between a measured load F1 and first output information S1 is stored. The measured load F1 is measured in a state in which the bearing unit 1 presses the load measuring jig 61 with the main shaft 4 stationary. The first output information S1 is output from the load sensor 11 when the measured load F1 is measured.

[0092] In this way, it is possible to obtain the first relationship R1 that can accurately calculate the processing load F applied to the spindle 4 of the bearing unit 1 during processing. As a result, by monitoring the processing load F and preload during processing, it is possible to reduce the occurrence of damage to the components that make up the bearing unit 1 (bearings 5a, 5b, spindle 4, cutting tool, etc.), and if damage does occur, the processing load F and bearing preload can be used to identify the cause. Furthermore, it is possible to improve the processing quality and productivity of objects processed with the bearing unit 1.

[0093] In the above-described method for calibrating the load sensor 11, the storing step (S2) includes a step (S2b) of storing a second relationship R2 used to calculate the processing load F. In the storing step (S2b) of the second relationship R2, the second relationship R2 between the rotation speed N of the spindle 4 and second output information S2 in the rotation state of the spindle 4 is stored. The second output information S2 is output from the load sensor 11 in the rotation state of the spindle 4.

[0094] In this way, the second relationship R2 can be obtained, which allows accurate calculation of the processing load F applied to the spindle 4 of the bearing unit 1 during processing.

[0095] A method for measuring a processing load F according to the present disclosure includes a step (S1) of preparing a spindle device 100 having a bearing unit 1, and a step (S3) of processing using the bearing unit 1. In the processing step (S3), the processing load F applied to the bearing unit 1 is calculated from output information S output from the load sensor based on a first relationship R1 obtained using a calibration method for the load sensor 11.

[0096] In this way, the processing load F applied to the spindle 4 of the bearing unit 1 during processing can be accurately calculated based on the first relationship R1 and the second relationship R2. As a result, by monitoring the processing load F and preload during processing, it is possible to reduce the occurrence of damage to the components that make up the bearing unit 1 (bearings 5a, 5b, spindle 4, cutting tool, etc.), and if damage does occur, the processing load F and preload can be used to identify the cause. Furthermore, it is possible to improve the processing quality and productivity of objects processed with the bearing unit 1.

[0097] (Embodiment 2) FIG. 14 is a cross-sectional view of a bearing unit 1 according to a second embodiment. FIG. 14 corresponds to FIG. 3. The bearing unit 1 shown in FIG. 14 basically has the same configuration as the bearing unit 1 shown in FIGS. 1 to 3 and can achieve the same effects, but differs in that the load sensor 11 includes three load sensor elements 11a. Specifically, flat portions 6ga are provided at three locations equally spaced 120 degrees apart on the outer diameter surface of the first outer ring spacer 6g. Each of the three load sensor elements 11a is fixed to a respective flat portion 6ga.

[0098] In this way, the processing load F can be calculated accurately if there are at least three or more load sensor elements 11a.

[0099] (Embodiment 3) Figure 15 is a cross-sectional view of a bearing unit 1 according to a third embodiment. Figure 15 corresponds to Figure 14. The bearing unit 1 shown in Figure 15 basically has the same configuration as the bearing unit 1 shown in Figure 14 and can achieve the same effects, but differs in that flat portions 6gb are provided at three locations equally spaced 120 degrees apart on the inner diameter surface of the first outer ring spacer 6g. Each of the three load sensor elements 11a is fixed to one of the flat portions 6gb.

[0100] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims.

[0101] (Addendum) Various aspects of the present disclosure are summarized below as appendices. (Appendix 1) A spindle device equipped with a bearing unit, The bearing unit is equipped with a load sensor, The spindle device a calculation unit that calculates a processing load applied to the bearing unit from output information output from the load sensor; a storage unit; The bearing unit has a rotatable main shaft, The storage unit includes: a measurement load applied to the bearing unit when the spindle is stationary; and a first relationship between the load sensor and the bearing unit when the load is applied to the bearing unit; and The calculation unit calculates the processing load from the output information based on the first relationship. (Appendix 2) The storage unit includes: the rotation speed of the spindle in a rotating state; and and second output information output from the load sensor in a rotation state of the spindle, and a second relationship between the second output information and the load sensor is stored; 2. The spindle device according to claim 1, wherein the calculation unit calculates the processing load from the output information based on the first relationship and the second relationship. (Appendix 3) the load sensor includes a plurality of load sensor elements; 3. The spindle device according to claim 1, wherein the plurality of load sensor elements are arranged on the same circumference with respect to a central axis along which the spindle extends. (Appendix 4) Further provided with a load measuring jig, 4. The spindle device according to claim 1, wherein the measured load is measured in a state in which the bearing unit presses the load measuring jig. (Appendix 5) If the direction in which the main axis extends is defined as the axial direction, 5. The spindle device according to claim 4, wherein the measured load is measured in a state in which the bearing unit presses the load measuring jig in the axial direction. (Appendix 6) If the direction perpendicular to the direction in which the main axis extends is defined as the radial direction, 5. The spindle device according to claim 4, wherein the measured load is measured in a state in which the bearing unit presses the load measuring jig in the radial direction. (Appendix 7) preparing a spindle device having a bearing unit and a load measurement jig; and storing the information; The bearing unit is equipped with a load sensor, The bearing unit has a rotatable main shaft, the storing step includes a step of storing a first relationship used to calculate a processing load applied to the bearing unit, In the step of storing the first relationship, a measured load measured in a state in which the bearing unit presses the load measuring jig while the spindle is stationary; and and storing the first relationship between the load and first output information output from the load sensor when the load is measured. (Appendix 8) the storing step includes a step of storing a second relationship used to calculate the processing load, In the step of storing the second relationship, the rotation speed of the spindle in a rotating state; and and second output information output from the load sensor in a rotation state of the spindle. (Appendix 9) Providing a spindle assembly having a bearing unit; and a step of processing the bearing unit using the bearing unit. In the processing step, A method for calculating a processing load, which calculates the processing load applied to the bearing unit from output information output from the load sensor based on the first relationship obtained using the load sensor calibration method described in Appendix 7 or Appendix 8. [Explanation of symbols]

[0102] 1 bearing unit, 2 outer cylinder, 3, 8 housing, 3a step portion, 4 main shaft, 5, 5a, 5b, 16 bearing, 5ga, 5gb, 16b outer ring, 5ia, 5ib, 16a inner ring, 6, 9 spacer, 6g first outer ring spacer, 6ga, 6gb flat portion, 6i inner ring spacer, 7 second outer ring spacer, 10 nut, 11 load sensor, 11a load sensor element, 12 front cover, 13 stator, 14 rotor, 15 cylindrical member, 17 end member, 18 member, 19 inner ring holder, 20 nut, 21 member, 22 space portion, 23 substrate, 24 detection unit, 25 processing unit, 25a amplification unit, 25b output unit, 30 data processing unit, 31 calculation unit, 32 memory unit, 33 preload load calculation unit, 34 Life estimation unit, 40 motor, 50 bearing device, 61 load measurement jig, 62 table, 70 tool, 100 spindle device, A central axis, D1, D2, D2a, D2b, D2c, D2d direction, F processing load, F1 measurement load, G1, G2 coolant flow path, N rotation speed, P1, P2 force line, R1 first relationship, R2 second relationship, Rta, Rtb cage, S output information, S1 first output information, S2 second output information, Ta, Tb rolling element, z axis direction, θ radial direction, θ1 first radial direction, θ2 second radial direction.

Claims

1. A spindle device equipped with a bearing unit, The bearing unit is equipped with a load sensor, The spindle device a calculation unit that calculates a processing load applied to the bearing unit from output information output from the load sensor; a storage unit; The bearing unit has a rotatable main shaft, The storage unit includes: a measurement load applied to the bearing unit when the spindle is stationary; and a first relationship between the load sensor and the bearing unit when the load is applied to the bearing unit; and The calculation unit calculates the processing load from the output information based on the first relationship.

2. The storage unit includes: the rotation speed of the spindle in a rotating state; and and second output information output from the load sensor in a rotation state of the spindle, and a second relationship between the second output information and the load sensor is stored. The spindle device according to claim 1 , wherein the calculation unit calculates the processing load from the output information based on the first relationship and the second relationship.

3. the load sensor includes a plurality of load sensor elements; 3. The spindle device according to claim 1, wherein the plurality of load sensor elements are arranged on the same circumference with respect to a central axis along which the main shaft extends.

4. Further provided with a load measuring jig, 3. The spindle device according to claim 1, wherein the load is measured in a state where the bearing unit presses against the load measuring jig.

5. If the direction in which the main axis extends is defined as the axial direction, 5. The spindle device according to claim 4, wherein the load is measured in a state where the bearing unit presses the load measuring jig in the axial direction.

6. If the direction perpendicular to the direction in which the main axis extends is defined as the radial direction, 5. The spindle device according to claim 4, wherein the load to be measured is measured in a state in which the bearing unit presses the load measuring jig in the radial direction.

7. preparing a spindle device having a bearing unit and a load measurement jig; and storing the information; The bearing unit is equipped with a load sensor, The bearing unit has a rotatable main shaft, the storing step includes a step of storing a first relationship used to calculate a processing load applied to the bearing unit, In the step of storing the first relationship, a measured load measured in a state in which the bearing unit presses the load measuring jig while the spindle is stationary; and and storing the first relationship between the load and first output information output from the load sensor when the load is measured.

8. the storing step includes a step of storing a second relationship used to calculate the processing load, In the step of storing the second relationship, the rotation speed of the spindle in a rotating state; and 8. The load sensor calibration method according to claim 7, further comprising the step of storing the second relationship between the load sensor and second output information output from the load sensor in a rotational state of the spindle.

9. Providing a spindle assembly having a bearing unit; and a step of processing the bearing unit using the bearing unit. In the processing step, 9. A method for calculating a processing load, comprising: calculating the processing load applied to the bearing unit from output information output from the load sensor based on the first relationship obtained using the method for calibrating a load sensor according to claim 7 or 8.

Images