JP2021004823A - Load calculation system - Google Patents

Abstract

To provide a load calculation system capable of detecting a load of a roller bearing with higher accuracy by a simpler configuration.SOLUTION: A load calculation system 1 comprises: a coil 20 provided on an outer ring of a roller bearing 10; an excitation circuit 30 for exciting the coil 20; a coil 25 provided on the other side of a housing H; a current measuring circuit 40 for detecting a current generated in the coil 25 according to excitation of the coil 20; a voltage measuring circuit 50 for detecting a voltage generated in the coil 25 according to excitation of the coil 20; and an arithmetic unit 60 for calculating a radial load R applied to the roller bearing 10 on the basis of the detected current and voltage.SELECTED DRAWING: Figure 1

Description

The present invention relates to a load calculation system.

In order to detect a radial load on a rolling bearing, a method of attaching a sensor to the outer peripheral side of the outer ring of the rolling bearing is known (for example, Patent Document 1).

JP-A-2017-026570

It is the inductance of the coil that functions as a sensor that changes with load. In Patent Document 1, the load is obtained by referring to the change in voltage caused by the change in inductance. In order to obtain the load with higher accuracy, it is desirable to obtain the inductance itself, but the method described in Patent Document 1 cannot obtain the inductance because only the voltage is measured.

Further, in the method described in Patent Document 1, a space for mounting the sensor on the outer peripheral side of the bearing in the radial direction with respect to the outer ring is required. Further, in the method described in Patent Document 1, a reference sensor that is not affected by the load is required. As described above, the method described in Patent Document 1 has many design restrictions.

An object of the present invention is to provide a load calculation system capable of detecting the load of a rolling bearing with higher accuracy with a simpler configuration.

The load calculation system of the present invention for achieving the above object includes a first coil provided on one of the outer ring of the rolling bearing or a housing that comes into contact with the outer peripheral portion of the outer ring, and an excitation circuit that excites the first coil. A second coil provided on the outer ring or the other side of the housing, a current detection circuit that detects a current generated in the second coil in response to excitation of the first coil, and a first coil in response to excitation of the first coil. It includes a voltage detection circuit that detects the voltage generated in the two coils, and a computing device that calculates the radial load applied to the rolling bearing based on the current and the voltage.

Therefore, the inductance of the coil corresponding to the load applied to the rolling bearing can be calculated based on the current and the voltage, and the load corresponding to the inductance can be derived. That is, since the inductance can be obtained from the current and the voltage, the inductance and the load corresponding to the inductance can be obtained with higher accuracy. Further, a space for providing a pressure detection sensor and a reference sensor on the outer peripheral side in the radial direction of the rolling bearing is not required.

In the load calculation system of the present invention, one of the first coil and the second coil is fixed to one side surface of the outer ring orthogonal to the rotation axis direction of the rolling bearing, and the first coil or the second coil The other is fixed to the side surface of the housing which is coplanar to the one side surface or is parallel to the one side surface and is provided so as to form a step with the one side surface.

Therefore, the first coil and the second coil can be arranged side by side on the same plane orthogonal to the rotation axis.

In the load calculation system of the present invention, the first coil and the second coil are arranged on a linear line in the radial direction passing through the rotation axis.

Therefore, the change in the radial load and the change in the relationship between the first coil and the second coil can be made to correspond more linearly.

In the load calculation system of the present invention, the first coil and the second coil are parallel.

Therefore, the extension directions of the first coil and the second coil can be aligned.

According to the present invention, the load of the rolling bearing can be detected with higher accuracy with a simpler configuration.

FIG. 1 is a block diagram showing a main configuration of the load calculation system of the embodiment. FIG. 2 is a cross-sectional view showing the configurations of rolling bearings and housings and coils provided therein. FIG. 3 is a perspective view showing a specific configuration example of the coil. FIG. 4 is a graph showing an example of the relationship between the coil inductance value calculated by the arithmetic unit and the additional load (radial load) in the configuration shown in FIG.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings, but the present invention is not limited thereto. The requirements of each embodiment described below can be combined as appropriate. In addition, some components may not be used.

FIG. 1 is a block diagram showing a main configuration of the load calculation system 1 of the embodiment. The load calculation system 1 includes a rolling bearing 10, a coil 20 that functions as a first coil, a coil 25 that functions as a second coil, an excitation circuit 30, a current measurement circuit 40, a voltage measurement circuit 50, and a calculation device. 60 and. The load calculation system 1 detects, for example, a radial load R applied to an electric motor having an output shaft whose shaft S rotatably supported by the rolling bearing 10 is an output shaft or which has an output shaft connected to the shaft S.

The rolling bearing 10 rotatably supports the shaft S. The coil 20 is attached to the rolling bearing 10. The coil 20 is provided on the rolling bearing 10. The rolling bearing 10 and the coil 20 constitute a rolling bearing 5 with a sensor. The coil 25 is provided in the housing H to which the rolling bearing 10 is attached. The impedance and inductance of the coil 25 change according to the change in the radial load R applied to the rolling bearing 10.

FIG. 2 is a cross-sectional view showing the configurations of the rolling bearing 10, the housing H, and the coils 20 and 25 provided therein. FIG. 2 is a cross-sectional view of the rolling bearing 10, the housing H, and the coils 20 and 25 cut along a straight line passing through the rotation axis center line Ax of the rolling bearing 10. That is, the coil 20 and the coil 25 shown in FIG. 2 are arranged on a linear line in the radial direction passing through the rotation axis center line Ax. The rolling bearing 10 has an outer ring 11, an inner ring 12, a rolling element 13, and a cage 14. The outer ring 11 and the inner ring 12 are provided so as to be relatively rotatable with the rolling element 13 interposed therebetween. A plurality of rolling elements 13 are provided, and are arranged between the outer ring 11 and the inner ring 12 along the circumferential direction centered on the rotation axis center line Ax. The outer ring 11 is arranged on the outer peripheral side and the inner ring 12 is arranged on the inner peripheral side with the rolling element 13 interposed therebetween. The cage 14 maintains the distance between the plurality of rolling elements 13 arranged in the circumferential direction. In the embodiment, a ball bearing in which the shape of the rolling element 13 is a sphere is adopted, but this is an example of the form of the rolling bearing 10 and is not limited to this. The rolling bearing 10 may be a roller bearing or a needle-shaped bearing in which the rolling element 13 has a columnar shape. Further, the rolling bearing 10 may be a tapered roller bearing or a spherical roller bearing.

In the embodiment, the outer ring 11 is fixed to the housing H, and the inner ring 12 and the shaft S are rotatably supported by the housing H. That is, the outer ring 11 is a fixed ring of the rolling bearing 10. The housing H is, for example, a housing of a machine or other equipment to which the rolling bearing 10 is provided, but may have a configuration in which the rolling bearing 10 can be attached.

FIG. 3 is a perspective view showing a specific configuration example of the coils 20 and 25. The coils 20 and 25 include a core material 21, a conducting wire 22, and a coil case 23. The core material 21 is a magnetic material exhibiting soft magnetism. For example, soft ferrite, dust core, etc. can be used for the core material 21. The lead wire 22 is an insulating coated lead wire. Specifically, the lead wire 22 is a so-called magnet wire coated with a resin such as polyurethane-based, polyester-based, or polyamide-based. The conductive wire coated with the insulating film in the conducting wire 22 is, for example, a copper wire, but may be a conducting wire made of another material having conductivity. The coil case 23 is a tubular insulator that covers the outer circumference of the core material 21 and around which the lead wire 22 is wound. The coil case 23 is made of resin, for example, but other insulating materials may be adopted. The coil case 23 shown in FIG. 3 includes a collar 23a through which one end side of the core material 21 is exposed and exposed, and a collar 23b covering the other end side of the core material 21. The lead wire 22 is wound around the coil case 23 between the collar 23a and the collar 23b.

The coil 20 is fixed to one side surface 11a of the outer ring 11 (see FIG. 2). Specifically, the adhesive 24 or the fixing member into which the core material 21 of the coil 20 is fitted is used to face the side surfaces of the core material 21 and the outer ring 11 so that one side surface 11a of the outer ring 11 and the core material 21 are in contact with each other. The collar 23a is fixed to the outer ring 11. One side surface 11a is a side surface of the outer ring 11 orthogonal to the rotation axis center line Ax.

The coil 25 is fixed to one side surface Ha of the housing H so that the end portion of the core member 21 is in close contact with the housing H. Specifically, using a fixing member into which the adhesive 26 or the core material 21 of the coil 25 is fitted, a collar facing the core material 21 and one side surface Ha so that one side surface Ha of the housing H and the core material 21 come into contact with each other. The 23a is fixed to the outer ring 11. One side surface Ha is flush with one side surface 11a. The relationship between the one side surface Ha and the one side surface 11a is not limited to the same plane, and it is acceptable if the step between the one side surface Ha and the one side surface 11a is about 5 mm. Preferably, the step is a step of about several microns. That is, the one side surface Ha may be provided so as to be parallel to the one side surface 11a and form a step between the one side surface 11a and the one side surface 11a.

It is desirable that the coil 20 is attached so that the core material 21 is perpendicular to one side surface 11a. It is desirable that the coil 25 is attached so that the core material 21 is perpendicular to one side surface Ha. The core material 21 and the surface to be fixed may not be in close contact with each other, and may be spaced or intervened by other structures. The coil 20 is fixed to the rolling bearing 10 and the coil 25 is fixed to the housing H so that the change in the relationship between the rolling bearing 10 and the housing H due to the radial load R is reflected in the change in the positional relationship between the coil 20 and the coil 25. It suffices if it is done. As another method for fixing the coils 20 and 25, for example, an urging member such as a spring that presses the coils 20 and 25 from the collar 23b side may be provided externally on the surface to be fixed. Further, in the examples shown in FIGS. 2 and 3, one end of the core material 21 extends from the coil case 23 and the other end is housed in the coil case 23, but the present invention is not limited to this. The core material 21 may extend to the range in which the lead wire 22 is wound, both ends may extend from the coil case 23, or may extend to the same position or inside as the end of the coil case 23. It may be located.

The excitation circuit 30 shown in FIG. 1 applies an AC voltage to the coil 20. The exciting circuit 30 is connected to a power supply device (not shown), receives power from the power supply device, and applies an alternating current to the lead wire 22 of the coil 20. The lead wire 22 of the coil 20 and the exciting circuit 30 are electrically connected via the lead wire M1 to form an electric circuit.

The current measuring circuit 40 detects the current generated in the coil 25 in response to the excitation of the coil 20. The current measurement circuit 40 of the embodiment is a circuit that functions as an AC ammeter. The voltage measuring circuit 50 detects the voltage generated in the coil 25 in response to the excitation of the coil 20. The voltage measuring circuit 50 of the embodiment is a circuit that functions as an AC voltmeter. The lead wire 22 of the coil 25, the current measurement circuit 40, and the voltage measurement circuit 50 are electrically connected via the lead wire M2 to form an electric circuit.

The arithmetic unit 60 calculates the radial load R based on the current detected by the current measuring circuit 40 and the voltage detected by the voltage measuring circuit 50. The arithmetic unit 60 calculates the impedance Z of the coil 20 using the equation (1). The voltage value V is the voltage between both ends of the lead wire 22 wound around the core material 21. The voltage measuring circuit 50 of the embodiment detects the voltage value V between both ends of the conducting wire 22 wound around the core material 21.

The arithmetic unit 60 calculates the inductance L using the equation (2) based on the phase difference θ of the current value I and the voltage value V and the impedance Z. F in the formula (2) represents the frequency of the alternating current (predetermined frequency). For example, f = 128 [khz], but the present invention is not limited to this, and can be changed as appropriate. The unit of the phase difference θ is [degree (°)]. The phase difference θ is obtained based on the change in the current value I and the change in the voltage value V that occur within the same time according to the frequency (f). For example, the phase of the current value I is delayed by 90 degrees with respect to the phase of the voltage value V at the same time. The current value I and the voltage value V used in the equations (1) and (2) are values detected at the same time.

FIG. 4 is a graph showing an example of the relationship between the value of the inductance L of the coil 25 calculated by the arithmetic unit 60 and the additional load (radial load) in the configuration shown in FIG. The rotation speed of the shaft S is 200 rpm. FIG. 4 illustrates the inductance L (unit: microhenry [μH]) of the coil 25 that changes according to the gradual increase of the radial load (unit: kilonewton [kN]). As the rolling bearing 10 rotates, the impedance Z and the inductance L fluctuate due to the difference between when the rolling element 13 passes and when it does not pass. Further, the amount of fluctuation (fluctuation width) changes according to the radial load R. Specifically, as illustrated in FIG. 4, the larger the radial load R, the larger the swing width of the inductance L. The arithmetic unit 60 has a resolution set based on the frequency (f) of the alternating current, that is, the maximum value L1 and the inductance of the inductance L obtained within the calculation number of the inductance L per predetermined time (for example, 1 second). The minimum value L2 of L is acquired. The arithmetic unit 60 obtains the difference Q between the maximum value L1 and the minimum value L2. The arithmetic unit 60 derives the radial load R from the difference Q based on the data showing the correspondence between the difference Q and the radial load R derived by the prior measurement. The data may be stored in advance in the arithmetic unit 60, or may be stored in a storage device, a storage circuit, or a storage medium (not shown) that can be referred to by the arithmetic unit 60.

Although the derivation of the radial load R by the arithmetic unit 60 has been described above, the arithmetic unit 60 may be a dedicated circuit for performing the above-mentioned processing, or executes a software program including the above-mentioned processing contents. It may be a computer.

The coil 20 and the coil 25 may be arranged in reverse. That is, the coil provided in the housing H may be excited, and the radial load R may be obtained based on the inductance obtained from the electromotive force generated in the coil provided in the outer ring 11 in response to this excitation. As described above, the sensor-equipped bearing 5 includes a rolling bearing 10 and a coil 20 provided on the outer ring 11 of the rolling bearing 10, and one of the coil 20 or the coil 25 provided on the housing H to which the outer ring 11 is attached is excited. Then, the other generates a current and a voltage in response to the excitation of one, acquires the inductance L from the current and the voltage, and derives the radial load R based on the inductance L.

The mechanism for the arithmetic unit 60 to obtain the current value I and the voltage value V from the current detected by the current measuring circuit 40 and the voltage detected by the voltage measuring circuit 50 is arbitrary. For example, the current measured by the current measuring circuit 40 and the voltage measured by the voltage measuring circuit 50 are converted into digital information by using an A / D converter (not shown) or a circuit having a similar function to the arithmetic unit 60. The arithmetic unit 60 includes an A / D conversion function to be input or related. Further, the current measurement circuit 40 and the voltage measurement circuit 50 may each have an A / D conversion function, and may be configured to output the digitized current value I and voltage value V to the arithmetic unit 60.

For the housing H, for example, an alloy such as carbon steel, stainless steel, or aluminum, or a metal or resin is used. The material constituting the housing H can be appropriately selected according to the application of the equipment in which the rolling bearing 10 is provided. Similar to the housing H, the material constituting the shaft S provided so as to pass through the inside of the inner ring 12 of the rolling bearing 10 can be appropriately selected according to the application.

Further, an alloy (or metal) such as stainless steel or chrome steel or ceramics is used for the rolling element 13, and these materials can be appropriately selected depending on the use of the equipment in which the rolling bearing 10 is provided. Further, alloy, metal, resin or the like is used for the cage 14, and these materials can be appropriately selected according to the application of the equipment in which the rolling bearing 10 is provided. Further, even if the rolling bearing 10 is provided with a seal member (not shown) for the purpose of suppressing leakage of lubricating oil of the rolling element 13 and suppressing intrusion of foreign matter into the sliding portions of the outer ring 11, the inner ring 12 and the rolling element 13. Good. The material used for the sealing member can be appropriately selected depending on the application of the equipment provided with the rolling bearing 10, such as alloy, metal or resin (rubber).

According to the embodiment, the inductance L of the coil 25 corresponding to the radial load R applied to the rolling bearing 10 can be calculated based on the current value I and the voltage value V to derive the radial load R corresponding to the inductance L. it can. That is, since the inductance L can be obtained from the current value I and the voltage value V, the radial load R corresponding to the inductance L and the inductance L can be obtained with higher accuracy. Further, it is not necessary to provide a space for providing a pressure detection sensor and a reference sensor on the outer peripheral side of the outer ring 11 in the radial direction, and one of the coil 20 or the coil 25 is provided on one side surface 11a of the outer ring 11. If it is possible to provide the coil 20 or the other of the coils 25 on one side surface Ha of the housing H, the radial load R can be obtained. Further, the radial load R can be obtained with a simpler configuration without the need for an expensive system using a reference sensor, a load cell, a strain gauge amplifier, or the like. Further, since the inductance L of the coil 25 that functions as the sensor output corresponds to the change in the relationship with the coil 20 due to the change in the radial load R, it is possible to suppress the influence of the electrical characteristics of the rolling bearing 10 on the sensor output. it can.

Further, one of the coil 20 and the coil 25 is fixed to one side surface 11a orthogonal to the rotation axis center line Ax, and the other is fixed to one side surface Ha which is the same plane as the one side surface 11a. Therefore, the coil 20 and the coil 25 can be arranged side by side on the same plane orthogonal to the rotation axis center line Ax.

Further, the coil 20 and the coil 25 are arranged on a linear line in the radial direction passing through the rotation axis center line Ax. Therefore, the change in the radial load R and the change in the relationship between the coil 20 and the coil 25 can be made to correspond more linearly.

Further, the coil 20 and the coil 25 are parallel to each other. Therefore, the extension directions of the coil 20 and the coil 25 can be aligned.

Although the case where each of the coils 20 and the coil 25 is one is illustrated above, a plurality of coils 20 and the coils 25 may be provided in one rolling bearing 10 and the housing H. In this case, a plurality of pairs of the coil 20 and the coil 25 located on a linear line in the radial direction passing through the center line of the rotation axis are provided. The coils 20 and 25 are located on straight lines at different angles for each set, that is, on straight lines corresponding to radial loads R in different directions. Then, by configuring the load calculation system 1 with each set, the radial load R in a plurality of directions can be individually obtained with respect to the rotation axis center line Ax.

In the configuration including the plurality of coils 20 and 25, a load other than the radial load R applied to the rolling bearing 10 can be measured depending on the combination. Specifically, the radial load applied to the rolling bearing 10 at the timing when the inductance L of the plurality of coils 25 arranged at different positions with respect to the outer ring 11 and the inductance L of the plurality of coils 25 are obtained. The correlation with R, axial load, presence / absence of moment load, and magnitude is measured in advance. By storing and holding the data indicating the measurement result in a referenceable manner from the arithmetic unit 60, the radial load applied to the rolling bearing 10 by collating the inductance L of the plurality of coils 25 calculated by the arithmetic unit 60 with the data. R, axial load and moment load can be derived.

1 Load calculation system 10 Rolling bearing 11 Outer ring 12 Inner ring 13 Rolling element 14 Cage 20, 25 Coil 21 Core material 22 Lead wire 23 Coil case 30 Excitation circuit 40 Current measurement circuit 50 Voltage measurement circuit 60 Computing device

Claims (4)

A first coil provided on one of the outer ring of the rolling bearing or the housing in contact with the outer peripheral portion of the outer ring, and
An excitation circuit that excites the first coil and
A second coil provided on the outer ring or the other of the housing,
A current detection circuit that detects the current generated in the second coil in response to the excitation of the first coil, and
A voltage detection circuit that detects the voltage generated in the second coil in response to the excitation of the first coil, and
A load calculation system including an arithmetic unit that calculates a radial load applied to the rolling bearing based on the current and the voltage. One of the first coil and the second coil is fixed to one side surface of the outer ring orthogonal to the rotation axis direction of the rolling bearing.
The side surface of the housing provided so that the first coil or the other side of the second coil is coplanar with the one side surface or parallel to the one side surface and forms a step between the first coil and the other side surface. The load calculation system according to claim 1, which is fixed to. The load calculation system according to claim 2, wherein the first coil and the second coil are arranged on a linear line in the radial direction passing through the rotation axis. The load calculation system according to any one of claims 1 to 3, wherein the first coil and the second coil are parallel to each other.

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