Rolling bearing with sensor

Abstract

To provide a rolling bearing with a sensor capable of directly and accurately detecting information related to loads of individual rolling elements inside the bearing.SOLUTION: This device has a plurality of rolling elements 4, a contact surface 6 of a member with which the rolling elements 4 are brought into contact, and a strain sensor 7 arranged on the contact surface 6, and is constituted for detecting a load acting on the contact surface 6 from the rolling elements 4 by the strain sensor 7.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a sensor-equipped rolling bearing. [Background technology]

[0002] In recent years, in the automotive and industrial machinery fields, there has been a growing need to detect the loads imposed on bearings, monitor their usage status, predict their lifespan, etc., from the perspective of more precise control, improved productivity and safety, improved functionality, and longer lifespans of machinery and equipment. Bearings are machine parts that are directly subjected to axial loads, and can detect axial loads with greater sensitivity than if load sensors were attached to the housings or other parts of machinery and equipment.

[0003] For example, in the automotive field, there is an increasing need to measure the load on axles using various sensors in order to precisely control the vehicle's driving conditions. In addition, in the fields of robotics and machine tools, bearing preload management is required to improve processing accuracy and efficiency, and there is also a demand to detect the preload and load on bearings in various machinery. In particular, in machine tools, detecting the load applied to bearings during operation can lead to optimization of the design and management of these machinery. Furthermore, in all fields, there is a growing demand for the ability to detect signs of bearing abnormalities before they occur and to prevent accidents and problems caused by bearing failure.

[0004] In particular, from the perspective of extending the life of rolling bearings, it is preferable to apply an appropriate preload during assembly and operation. However, due to variations in the dimensions of each component, such as the inner and outer rings, and individual differences in the way bearings are assembled into equipment, it is difficult to accurately set the preload. For example, a well-known method of controlling preload is to adjust the tightening torque or tightening amount of the mounting nut. However, even in this case, the preload itself is not directly measured but is merely an estimated value, so there is a limit to the accuracy of setting the preload. Furthermore, the load that a bearing bears after being assembled into equipment or during operation is only an estimated value, making it difficult to know the true load that the bearing is bearing.

[0005] Therefore, in Patent Document 1 listed below, a notch is provided on the outer peripheral surface of the outer ring of the bearing, and the load of the rolling elements inside the bearing can be measured by measuring the amount of strain of a strain gauge installed at a predetermined position. In particular, by arranging strain gauges in two locations, the accuracy of strain detection is improved compared to conventional methods when measuring the load on the rolling elements, whose contact angle changes when an axial load is applied.

[0006] In addition, in Patent Document 2 listed below, a magnetostrictive sensor is embedded in a part of the fixed raceway to detect changes in the contact position of the rolling element due to changes in load. The purpose is to determine the amount of change in the contact position of the rolling element, rather than the absolute value of the contact position of the rolling element, and by embedding the sensor inside the raceway member, it is possible to reduce errors caused by the influence of external magnetic fields, which is a problem with magnetostrictive sensors.

[0007] Furthermore, in Patent Document 3 listed below, multiple recesses are provided on the raceway surface of at least one of the inner and outer rings, and a temperature sensor and IC tag are placed inside these recesses, making it possible to accurately detect the temperature inside the bearing. Generally, temperature increases in bearings are caused by friction at the rolling contact points, so by detecting the temperature at the point closest to the rolling contact points, faster and more accurate detection is achieved compared to conventional structures in which a temperature sensor is placed on the end face of the bearing, for example.

[0008] Furthermore, in Patent Document 4 listed below, the radial load is estimated from the output of a strain sensor attached to the outer peripheral surface of the outer ring, and the centrifugal force acting on the rolling elements is calculated from the output of an orbital speed detection sensor attached to the inner peripheral surface of the outer ring, and the estimated radial load value is corrected based on the centrifugal force, thereby estimating the radial load value of the bearing with higher accuracy. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-249594 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-226477 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-138974 [Patent Document 4] Japanese Patent Publication No. 2022-030011 Summary of the Invention [Problem to be solved by the invention]

[0010] To accurately grasp the operating conditions of a rolling bearing, such as the applied load and rolling element contact angle, it is necessary to measure with high precision the load and contact angle of each rolling element inside the bearing, as well as the surface pressure distribution at the rolling element contact points.

[0011] However, although Patent Document 1 describes it as a "method for measuring rolling element load," if the notched groove in which the strain gauge is placed is, for example, on the outer peripheral surface of the outer ring, it is presumed that what the strain gauge detects is the resultant force of the loads of multiple rolling elements, and that it is not possible to accurately detect load information for a specific rolling element (such as the rolling element bearing the maximum load). As such, there is a large measurement error in the force that multiple rolling elements exert on the raceway member, and it is difficult to say that the load of the rolling element can be measured with high accuracy from the measurement value of the strain gauge.

[0012] In addition, Patent Document 2 uses a magnetostrictive sensor, which is considered to be more sensitive than a strain gauge, to measure slight distortions in the raceway member and calculate the force acting on the raceway member from the amount of distortion. However, as with Patent Document 1, this method is fundamentally affected by the loads of adjacent rolling elements, making it impossible to measure the loads of individual rolling elements. Furthermore, with regard to contact angle measurement, it is only possible to detect the amount of displacement from the initial position, and it is difficult to determine the absolute value of the contact angle. Furthermore, because magnetostrictive sensors are extremely sensitive, there is a concern that in environments made of magnetic materials such as bearings, the sensor may react to even minute changes in the magnetic field that occur when magnetic rolling elements or cages move toward or away from the sensor, reducing accuracy.

[0013] Furthermore, in Patent Document 3, multiple recesses are formed in the raceway surface in order to position a temperature sensor closest to the heat source (contact area between the rolling element and raceway surface) in order to accurately detect the temperature of the bearing. However, when recesses are provided in the raceway surface of a bearing, wear and noise increase in an actual usage environment, which is thought to lead to the risk of early failure and a shortened lifespan.

[0014] In addition, in Patent Document 4, a strain sensor is placed on the outer peripheral surface of the outer ring of a bearing to estimate the radial load acting on the bearing, and the radial load value is corrected based on the centrifugal force calculated from the orbital speed of the rolling elements, making it possible to estimate the radial load with high accuracy. However, because centrifugal force is a force that acts radially from the center of rotation, the magnitude and direction of the load acting on the entire bearing are all offsetting forces. Therefore, although the surface pressure on the raceway surface itself increases due to the centrifugal force generated by the rolling elements, it is thought that this does not affect the magnitude or direction of the radial load on the entire bearing.

[0015] Furthermore, although it can be applied to structures such as hub unit bearings where there is no fixed component such as a housing on the outer peripheral surface of the outer ring, in the case of general bearing fixing methods, the outer peripheral surface of the outer ring is held in place by fitting (press fitting, shrink fitting, etc.) into the housing, so there are concerns that additional processing will be required on the inner diameter surface of the housing to avoid sensors placed on the outer peripheral surface of the bearing, and that this will result in uneven fitting force between the bearing outer ring and housing in the circumferential direction.

[0016] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a rolling bearing with a sensor that can directly and accurately detect information relating to the load on each rolling element inside the bearing. [Means for solving the problem]

[0017] To solve the above problems, the present invention provides a sensor-equipped rolling bearing (first configuration) that has a plurality of rolling elements, a contact surface of a member with which the rolling elements come into contact, and a strain sensor provided on the contact surface, and is configured so that the strain sensor detects the load acting from the rolling elements on the contact surface. With the first configuration, it is possible to directly and accurately detect information related to the load on each rolling element inside the bearing after assembly and during operation.

[0018] The first configuration can be further configured as a second configuration, in which the bearing further includes an inner ring and an outer ring provided coaxially radially outward of the inner ring, and the contact surface is a raceway surface of at least one of the inner ring or the outer ring on which the rolling elements roll. With the second configuration, the preload applied to the bearing during assembly and operation can be directly and accurately controlled.

[0019] The first configuration can be configured as a third configuration, further comprising a cage that holds the rolling elements, and the contact surface is the inner surface of the cage. According to the third configuration, data on the load acting on the cage from the rolling elements can be used to calculate the strength of the cage.

[0020] In the first configuration, the rolling elements can be provided so as to be interposed between a housing and a rotating shaft rotatably held by the rolling elements, and the contact surface can be the surface of the rotating shaft or the inner surface of the housing (fourth configuration). According to the fourth configuration, even in a configuration in which the rolling elements come into direct contact with the rotating shaft or the housing, such as a needle bearing, information related to the load of each rolling element can be directly and accurately detected.

[0021] In the first to fourth configurations, the strain sensors may be provided at multiple locations along the rolling direction of the rolling elements (fifth configuration). With the fifth configuration, new information about the bearing can be obtained, for example, by converting the load difference at the multiple locations into the tilt of the rotation axis.

[0022] In the first to fifth configurations, the strain sensor may be provided in a concave groove formed in the contact surface, and the contact surface and the surface of the strain sensor may be flush (sixth configuration). The sixth configuration prevents a step from occurring between the contact surface and the surface of the strain sensor, preventing problems such as abnormal noise and vibration when the rolling element passes over the strain sensor.

[0023] In the first to sixth configurations, the strain sensor may have multiple measurement channels, and the detection lines of each measurement channel may be arranged in a line along the rolling direction of the rolling elements (seventh configuration). According to the seventh configuration, various information can be obtained from the detection results of each detection line, such as the surface pressure distribution and contact angle of the load between each rolling element and the contact surface, whether the rolling elements are riding on the shoulders of the inner and outer rings, and the load direction and moment acting on the raceways.

[0024] In the first to seventh configurations, the output value of the strain sensor may have a predetermined offset value corresponding to the temperature (eighth configuration). According to the eighth configuration, temperature information of the contact surface of the member with which the rolling element comes into contact can be obtained.

[0025] In the first to eighth configurations, by using a configuration in which the rolling elements are balls or rollers (ninth configuration), or by using a configuration in which the raceway surfaces have a single-row structure or a double-row structure (tenth configuration), the sensor-equipped rolling bearings according to the above configurations can be applied to various types of rolling bearings. [Effects of the Invention]

[0026] The sensor-equipped rolling bearing of the present invention is configured so that a strain sensor is provided on the contact surface of the member with which the rolling elements come into contact, and the strain sensor detects the load acting from the rolling elements on the contact surface.As a result, it is possible to directly and accurately detect information related to the load on each rolling element inside the bearing after assembly and during operation of the bearing. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a cross-sectional view showing an embodiment of a sensor-equipped rolling bearing (deep groove ball bearing) according to the present invention; [Figure 2] A perspective view of a cross section of the sensor-equipped rolling bearing shown in Figure 1 [Figure 3] 3 is a perspective view of the main part of FIG. 2; [Figure 4] FIG. 2 is a cross-sectional view showing a modified example of the sensor-equipped rolling bearing shown in FIG. 1. [Figure 5] Front view of the strain sensor (first example) used in the sensor-equipped rolling bearing shown in Figure 1 [Figure 6] Front view of the strain sensor (second example) used in the sensor-equipped rolling bearing shown in Figure 1 [Figure 7] Cross-sectional view taken along line VII-VII in Figure 6 [Figure 8] This shows a detection example (first example) when the strain sensor shown in Figure 6 is applied to the deep groove ball bearing shown in Figure 1, where (a) shows the contact state between each detection wire and the rolling element, and (b) shows the in-plane distribution of the voltage signal. [Figure 9] This shows a detection example (second example) when the strain sensor shown in Figure 6 is applied to the deep groove ball bearing shown in Figure 1, where (a) shows the contact state between each detection wire and the rolling element, and (b) shows the in-plane distribution of the voltage signal. [Figure 10] This shows a detection example (third example) when the strain sensor shown in Figure 6 is applied to the deep groove ball bearing shown in Figure 1, where (a) shows the contact state between each detection wire and the rolling element, and (b) shows the in-plane distribution of the voltage signal. [Figure 11] Conceptual diagram showing how to process the voltage signal output from the strain sensor [Figure 12] Conceptual diagram showing changes in the signal waveform of a strain sensor [Figure 13] Conceptual diagram showing an example of applying a strain sensor to temperature detection [Figure 14] FIG. 1 is a perspective cross-sectional view showing an example of application of a sensor-equipped rolling bearing according to the present invention to a cylindrical roller bearing. [Figure 15] FIG. 1 is a perspective view of a cross section showing an example of application of a sensor-equipped rolling bearing according to the present invention to a tapered roller bearing. [Figure 16]FIG. 1 is a perspective cross-sectional view showing an example of application of a sensor-equipped rolling bearing according to the present invention to a self-aligning roller bearing. [Figure 17] 14 shows an example of detection when the strain sensor shown in FIG. 6 is applied to the cylindrical roller bearing shown in FIG. 14, where (a) shows the contact state between each detection line and the rolling element, and (b) shows the in-plane distribution of the voltage signal. [Figure 18] A perspective view showing an example of applying a strain sensor to a stamped cage. [Figure 19] A perspective view showing an example in which a strain sensor is applied to a resin cage. [Figure 20] A perspective view showing an example of applying a strain sensor to a roller cage. [Figure 21] A perspective view showing an example in which a strain sensor is applied to a housing. [Figure 22] A perspective view showing an example in which a strain sensor is applied to a rotating shaft. [Figure 23] A perspective view showing an example of applying a strain sensor to a drawn cup needle roller bearing [Figure 24] A perspective view showing an example of applying a strain sensor to a linear flat roller. DETAILED DESCRIPTION OF THE INVENTION

[0028] An embodiment of a sensor-equipped rolling bearing 1 (hereinafter simply referred to as rolling bearing 1) according to the present invention will be described with reference to the drawings. As shown in Figs. 1 and 2, this rolling bearing 1 is a deep groove ball bearing that includes an inner ring 2, an outer ring 3 disposed coaxially radially outward of the inner ring 2, a plurality of rolling elements 4 arranged between the inner ring 2 and the outer ring 3, a cage 5 (not shown in Fig. 2) that holds the rolling elements 4 at equal intervals in the circumferential direction, a contact surface 6 of a member with which the rolling elements 4 come into contact, and a strain sensor 7 disposed on the contact surface 6, and uses balls (hereinafter designated by the same reference numerals as the rolling elements 4) as the rolling elements 4. Hereinafter, the direction along the rotation axis of rolling bearing 1 will be referred to as the axial direction, the direction perpendicular to the rotation axis as the radial direction, and the direction along the circumference going around the rotation axis as the circumferential direction.

[0029] An inner ring raceway surface 8 is formed on the outer peripheral surface of the inner ring 2, and an outer ring raceway surface 9 is formed on the inner peripheral surface of the outer ring 3. This outer ring raceway surface 9 becomes the contact surface 6 of the member with which the rolling elements 4 come into contact when the rolling bearing 1 is in use. A rotating shaft (not shown), such as a motor shaft, is fitted to the axis of the inner ring 2, and a housing (not shown) is fitted to the outer peripheral surface of the outer ring 3, with the inner ring 2 serving as the rotating ring and the outer ring 3 as the fixed ring. Various bearing steels, such as high-carbon chromium bearing steel (for example, SUJ2), can be used as the material for the inner and outer rings 2, 3 and the rolling elements 4.

[0030] As shown in FIG. 3, the strain sensor 7 is provided in a recessed groove 10 formed in the outer ring raceway surface 9 of the outer ring 3, which is the fixed ring, and is fixed in this groove 10 by a fixing means such as an adhesive. The strain sensor 7 is a sheet-like member with a uniform thickness of several μm to several tens of μm. The depth and shape of the groove 10 are approximately the same as the thickness and shape of the strain sensor 7, and when the strain sensor 7 is fixed in the groove 10, the outer ring raceway surface 9 and the surface of the strain sensor 7 are flush with each other, with almost no steps or gaps between them. The flushness referred to here does not only mean that there are no steps at all, but also includes small steps (for example, steps of more than 0% but not more than 1% of the diameter of the rolling element, or more than 0% but not more than 0.5% of the diameter of the rolling element) that keep abnormal noise and vibrations generated when the rolling element 4 rolls below a predetermined level.

[0031] The rolling bearing 1 shown in Figure 1 is configured with a strain sensor 7 provided at one location circumferentially on the outer ring raceway surface 9, but it can also be configured with strain sensors 7 provided at three equally spaced locations circumferentially on the outer ring raceway surface 9, as shown in Figure 4, for example. Also, as shown in Figure 1, it is preferable to provide the strain sensor 7 on the outer ring 3, which is the fixed ring, but it is also possible to provide the strain sensor 7 on the inner ring 2, which is the rotating ring, and then extract the output signal from the strain sensor 7 using a means such as a slip ring. It is also possible to provide strain sensors 7 on both the inner ring 2, which is the rotating ring, and the outer ring 3, which is the fixed ring.

[0032] The detailed structure of the strain sensor 7 is shown in Figures 5 to 7. This strain sensor 7 has multiple detection wires 11 and electrode portions 12 formed at both ends of each detection wire 11. The strain sensor 7 shown in Figure 5 (first example) has four measurement channels, and the strain sensor 7 shown in Figure 6 (second example) has eight measurement channels (CH1 to CH8 in Figures 8(a) and (b), etc.), with a detection wire 11 provided corresponding to each measurement channel. The electrode portions 12 are provided on a shoulder portion 13 axially adjacent to the outer ring raceway surface 9.

[0033] The length of each detection wire 11 along the circumferential direction is not particularly limited. However, if the length is shorter than the minor axis length (length along the circumferential direction) of the elliptical contact area (e.g., the area indicated by symbol A in FIG. 8(a)) formed between the balls 4 and the outer ring raceway surface 9, the surface pressure can be measured from the contact area determined by the length and width of the detection wire 11. Furthermore, the signal width relative to the time axis of the voltage waveform (see FIG. 12) described later can be converted into the circumferential passing speed of the contact area A. On the other hand, by making the length of each detection wire 11 along the circumferential direction longer than the minor axis length of the elliptical contact area A, the load associated with the contact can be reliably detected. Furthermore, by making the length of each detection wire 11 along the circumferential direction shorter than the spacing between adjacent balls 4 in the circumferential direction, it is possible to prevent the problem of multiple balls 4 coming into contact with a single detection wire 11 and making it impossible to individually detect the loads of each ball 4. For example, by making the length of the detection wire 11 along the circumferential direction 50 μm or more and 90% or less of the diameter of the ball 4, the load associated with the contact of the ball 4 can be accurately detected.

[0034] In order to more accurately detect the surface pressure distribution and contact angle at the contact area between the rolling elements 4 (balls 4) and the contact surface 6 (outer ring raceway surface 9), it is preferable to have more measurement channels in the strain sensor 7, as this increases precision and resolution. However, there may be limited space for arranging the electrode units 12, for example, on the shoulders 13 of a small ball bearing. In such cases, the electrode units 12 may be arranged using the shoulders 13 on both sides of the outer ring raceway surface 9, as shown in Figure 6. It is also possible to vary the density of the arrangement of the detection lines 11, for example by making the pitch between adjacent detection lines 11 finer as the position where more detailed measurement is desired.

[0035] This strain sensor 7 calculates a load by utilizing the change in electrical resistance of the detection wire 11 when the load is applied to the detection wire 11 from the rolling elements 4. To prevent short circuits between the outer ring raceway surface 9, the detection wire 11, and the rolling elements 4, a laminated structure is used in which insulating films 15 are provided on both the outer ring raceway surface 9 side and the rolling elements 4 side of the sensor film 14 in which the detection wire 11 is embedded, as shown in Figure 7. For this insulating film 15, it is preferable to use a material (such as alumina) that has high yield stress and hardness so that it will not break under load.

[0036] A cable (not shown) for extracting an output signal from the detection line 11 must be connected to the electrode portion 12 provided on the shoulder portion 13 by soldering or the like, and therefore, an insulating film 15 is formed only on the surface of the electrode portion 12 facing the shoulder portion 13. In Fig. 7, the thickness of the strain sensor 7 is drawn larger than it actually is to make the layered structure of the strain sensor 7 easier to see.

[0037] 8(a) and 8(b) show a conceptual diagram (first example) of the contact state between the balls 4 and the outer ring raceway surface 9 (contact surface 6) using the strain sensor 7 shown in Fig. 6, and the voltage signal output from the strain sensor 7 in this contact state. The arrow R in Fig. 8(a) indicates the direction of rotation of the balls 4. When the rolling elements 4 are balls 4 as in this embodiment, it is known that the contact area A between the balls 4 and the outer ring raceway surface 9 has an elliptical shape (see Fig. 8(a)).

[0038] In the case of deep groove ball bearings, a contact angle occurs depending on the relationship between the internal clearance and the load direction. The contact angle is the angle between the contact point between the ball 4 and the outer ring raceway surface 9 and the bearing center line, and is one of the parameters that greatly affects the performance and lifespan of a bearing. For example, if the input load to the bearing is only a radial load, contact point A will be located in the axial center of the outer ring raceway surface 9, and the voltage signal output from strain sensor 7 will also reach its maximum value at the center of the raceway width W (see symbol c in Figure 8(b)).

[0039] 9(a) and 9(b) show a conceptual diagram (second example) of the contact state between the balls 4 and the outer ring raceway surface 9 (contact surface 6) when an axial load (including preload) or moment load is applied to the rolling bearing 1, and the voltage signal output from the strain sensor 7 in this contact state. When an axial load or the like is applied, the contact point A between the balls 4 and the outer ring raceway surface 9 moves from the axial center of the outer ring raceway surface 9 (see FIG. 9(a)), and the maximum value of the voltage signal output from the strain sensor 7 also shifts to a position offset by an angle α from the center of the raceway surface width W (see symbol c' in FIG. 9(b)). The value of the angle α can be easily determined geometrically from the design value of the placement position of the strain sensor 7 relative to the shape of the outer ring raceway surface 9.

[0040] Furthermore, Figures 10(a) and 10(b) show the contact state between the balls 4 and the outer ring raceway surface 9 (contact surface 6) in a shoulder-riding state, where a portion of the major axis end of contact area A extends beyond the raceway surface width W due to factors such as an increase in axial load. This diagram also shows a conceptual diagram (third example) of the voltage signal output from the strain sensor 7 in this contact state. In this shoulder-riding state, contact area A between the balls 4 and the outer ring raceway surface 9 moves further away from the center of the raceway surface (see Figure 10(a)). The maximum value of the voltage signal output from the strain sensor 7 also shifts to a position offset by an angle β (β > α) from the center of the raceway surface width W (see symbol c'' in Figure 10(b)). When shoulder-riding occurs, the contact area between the balls 4 and the outer ring raceway surface 9 decreases, increasing the surface pressure and potentially shortening the bearing life. For this reason, the allowable contact angle and axial load limits are set to prevent shoulder-riding from occurring.

[0041] A conceptual diagram of the method for processing the voltage signal output from the strain sensor 7 is shown in Figure 11, and the changes in the waveform of the voltage signal of each channel (detection line 11) at each stage in Figure 11 are shown in Figure 12. In this processing method, each measurement channel of the strain sensor 7 is configured to form part of a bridge circuit 16. The voltage signal from the bridge circuit 16 passes through a filter circuit 17 for noise removal and is connected to an amplifier circuit 18 for amplifying the weak voltage signal. The voltage value and its fluctuation of the voltage signal from the amplifier circuit 18, as well as the correlation between each measurement channel, are processed by a calculation unit 19 to determine the contact state and contact angle of each rolling element 4 shown in Figures 8(a) and (b), etc.

[0042] The relationship (MPa / mV) between the signal voltage value (mV) and the surface pressure value (MPa) is determined by the sensor characteristics and circuit specification design of the strain sensor 7, so the signal voltage value of each measurement channel can be easily converted to a surface pressure value. Note that in environments where the effects of noise do not pose a problem to measurements, the filter circuit 17 may be omitted. The amplifier circuit 18 may be configured using a general-purpose operational amplifier or a dedicated IC such as an instrumentation amplifier.

[0043] A voltage signal is generated in real time each time a rolling element 4 passes by the strain sensor 7. For example, if the rolling bearing 1 comprises six rolling elements 4, a voltage signal is generated six times each time each rolling element 4 revolves once as the inner ring 2 rotates. The orbital speed of the rolling elements 4 and the rotational speed of the inner ring 2 are calculated from the period of this voltage generation. The number of rolling elements 4 is not limited to six, but the greater the number of rolling elements 4, the more accurate the calculation of changes in the orbital speed of the rolling elements 4 and the rotational speed of the inner ring 2.

[0044] Figure 13 shows a conceptual diagram of an example of applying the strain sensor 7 to temperature detection. Generally, the resistance of the strain sensor 7 changes slightly with temperature, and the reference voltage is offset (see V1 and V2 in Figure 13) in response to fluctuations in temperature. For example, the reference voltage can be set to 0 V, which is the voltage when no load from the rolling element 4 is acting on the strain sensor 7 at room temperature. Meanwhile, the amplitude of the voltage signal generated by the load acting on the strain sensor 7 from the rolling element 4 (see D1, D2, and D3 in Figure 13) is determined solely by the magnitude of the load, without being affected by fluctuations in temperature. Therefore, the temperature can be detected simultaneously from the reference voltage offsets V1 and V2, and the load can be detected from the voltage amplitudes D1, D2, and D3. The temperature used to determine the reference voltage is not limited to room temperature and can be changed as appropriate.

[0045] The above-mentioned rolling bearing 1 is configured so that the strain sensor 7 detects the load acting from the rolling element 4 on the contact surface 6 (outer ring raceway surface 9 in the above embodiment).Based on the voltage signal output from the strain sensor 7, information relating to the preload and load of each rolling element 4 inside the bearing after assembly and during operation can be directly and accurately detected in real time, and individual differences between each rolling element 4 can be easily grasped.

[0046] Furthermore, because the strain sensor 7 is equipped with multiple measurement channels in which the detection lines 11 are arranged in a line along the rolling direction of the rolling elements 4, various information such as the surface pressure distribution and contact angle of the load between each rolling element 4 and the contact surface 6, whether or not the rolling elements 4 have climbed onto the shoulders 13 of the inner and outer rings 2 and 3, and the load direction and moment acting on the raceway surfaces 8 and 9 can be obtained directly from the detection results of each detection line 11 without having to be estimated from the rolling marks of the rolling elements 4 formed on the raceway surfaces 8 and 9, and the deterioration state of the components can be grasped at an early stage based on changes in the surface pressure distribution, etc., to avoid failures.

[0047] In particular, by increasing the number of strain sensors 7 arranged as shown in Figure 4, it is possible to detect the direction of the load on the entire rolling bearing 1 and the moment load acting on the raceway surfaces 8 and 9, in addition to the individual load information for each rolling element 4, and to convert the load difference at multiple locations into the tilt of the rotation axis. In this case, it is preferable to provide multiple strain sensors 7 at equal angular intervals, but it is also possible to provide them at unequal angular intervals.

[0048] Furthermore, the rolling bearing 1 is configured such that the strain sensor 7 is provided in a concave groove 10 formed in the contact surface 6, and the surfaces of the contact surface 6 and the strain sensor 7 are flush with each other. This prevents a step from occurring between the contact surface 6 and the surface of the strain sensor 7, which would otherwise cause problems such as abnormal noise or vibration when the rolling element 4 passes over the strain sensor 7.

[0049] Furthermore, the above-mentioned rolling bearing 1 employs a strain sensor 7 having predetermined offset amounts V1, V2 whose output value corresponds to the temperature, so that temperature information on the contact surface 6 of the member with which the rolling element 4 comes into contact (the position closest to the heat source) can be obtained directly and accurately, compared to measuring the temperature of the rolling bearing 1 by, for example, providing a thermocouple on the width surface of the inner ring 2 or outer ring 3.

[0050] Although the above embodiment shows a single-row deep groove ball bearing as an example, the configuration according to the present invention can be widely applied to various types of ball bearings, such as angular contact ball bearings, self-aligning ball bearings, and thrust ball bearings, and can be applied not only to ball bearings with a single-row structure but also to ball bearings with a double-row structure.

[0051] Furthermore, rolling bearing 1 according to the present invention can be applied to a cylindrical roller bearing as shown in FIG. 14, a tapered roller bearing as shown in FIG. 15, and a self-aligning roller bearing as shown in FIG. 16, which have an inner ring 2 (rotating ring) with an inner ring raceway surface 8 formed on its outer peripheral surface, an outer ring 3 (fixed ring) with an outer ring raceway surface 9 formed on its inner peripheral surface, and rollers (hereinafter given the same reference numerals as the rolling elements 4) as a plurality of rolling elements 4 arranged between inner ring raceway surface 8 and outer ring raceway surface 9. In all of these roller bearings, a strain sensor 7 is provided on the outer ring raceway surface 9 of outer ring 3, which is the fixed ring. As the rest of the configuration is the same as that of rolling bearing 1 shown in FIG. 1 etc., repeated explanations will be omitted.

[0052] 17(a) and 17(b) show conceptual diagrams of the contact state between the roller 4 and the outer ring raceway surface 9 (contact surface 6) in the rolling bearing 1 (cylindrical roller bearing) shown in FIG. 14, and the voltage signal output from the strain sensor 7 in this contact state. The arrow R in FIG. 17(a) indicates the direction of rotation of the roller 4. When the rolling elements 4 are rollers 4, as in this embodiment, the contact area A between the roller 4 and the outer ring raceway surface 9 is linear, spreading slightly in the circumferential direction at both axial ends (see FIG. 17(a)). The pressure distribution in the longitudinal direction of the roller 4 is not uniform, and the surface pressure (edge ​​surface pressure) increases at both ends of the contact area A due to the influence of edge stress (see measurement channels CH1 and CH8 in FIG. 17(b)).

[0053] In the case of cylindrical roller bearings, the area where the edge surface pressure increases is often the starting point of fracture, so a more accurate understanding of the edge surface pressure is important when calculating the load and life of the roller bearing. Even in such cases, by applying the configuration of the present invention, information related to the edge surface pressure can be obtained directly, making it easy to determine whether the bearing load is appropriate. Note that the basic configuration of the strain sensor 7 and the method of processing the voltage signal are the same as those of the above-mentioned rolling bearing 1, so duplicated explanations will be omitted.

[0054] Although the above embodiments show examples of single-row cylindrical roller bearings, tapered roller bearings, and self-aligning roller bearings, the configuration according to the present invention can be widely applied to various types of roller bearings, such as needle roller bearings and thrust roller bearings, and can be applied not only to roller bearings with a single-row structure, but also to roller bearings with a double-row structure.

[0055] In each of the above embodiments, an example was shown in which the contact surface 6 of the member with which the rolling elements 4 come into contact is the outer ring raceway surface 9, but this contact surface 6 can also be configured to be the inner surface of a cage 5 that holds multiple rolling elements 4. Fig. 18 shows an example of a stamped cage, Fig. 19 shows an example of a crown-shaped resin cage, and Fig. 20 shows an example of a roller cage, and a strain sensor 7 is provided on the inner surface of each cage 5. By providing the strain sensor 7 on the cage 5 in this way, data on the load acting on the cage 5 from the rolling elements 4 can be used in calculating the strength of the cage 5. Note that the shapes of the cage 5 shown in Figs. 18 to 20 are merely examples, and strain sensors 7 can be provided on cages 5 of any shape.

[0056] Furthermore, in a configuration in which rolling elements 4 are provided between a housing 20 and a rotating shaft 21 rotatably held by the rolling elements 4, a strain sensor 7 can be provided on the inner surface of the housing 20 as the contact surface 6, as shown in Fig. 21, or on the surface of the rotating shaft 21 as the contact surface 6, as shown in Fig. 22. Note that the cage 5 is not shown in these figures. In this way, by providing a strain sensor 7 on the inner surface of the housing 20 or on the surface of the rotating shaft 21, it is possible to directly and accurately detect information related to the load of each rolling element 4, even in a configuration in which the rolling elements 4 are in direct contact with the housing 20 or the rotating shaft 21, as in a needle bearing.

[0057] Furthermore, in a rolling bearing 1 (dragonal cup needle roller bearing) having an outer ring 3 formed by deep drawing a steel plate, needle rollers (hereinafter given the same reference numerals as the rolling elements 4) as the rolling elements 4, and a cage (not shown in the figure) that guides the needle rollers 4, it is also possible to provide a configuration in which a strain sensor 7 is provided on the outer ring raceway surface 9 as the contact surface 6, as shown in FIG. 23. By providing the strain sensor 7 on the outer ring raceway surface 9 in this way, it is possible to directly and accurately detect information related to the load on each needle roller 4. The configuration according to the present application can also be applied to a full complement roller bearing that does not have a cage 5.

[0058] Furthermore, in a rolling bearing 1 (linear flat roller) having needle rollers 4 and a flat cage 5 that guides the needle rollers 4, as shown in FIG. 24, a strain sensor 7 can be provided on the flat contact surface 6 on which the linear flat roller makes a linear reciprocating motion. Dovetail groove-shaped connecting portions 22, 23 are formed on both ends of the cage 5 to connect the cages 5 together. By providing the strain sensor 7 on the contact surface 6 in this way, it is possible to directly and accurately detect information related to the load on each needle roller 4. Note that in this figure, the linear flat roller and contact surface 6 are shown separated to make the placement of the strain sensor 7 easier to see, but in reality the needle rollers 4 roll in contact with the contact surface 6.

[0059] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0060] 2. Inner circle 3 outer ring 4 Rolling elements (balls, rollers, needle rollers) 5 Cage 6 Contact surface 7 Strain Sensor 8 Inner ring raceway surface (raceway surface) 9 Outer ring raceway (raceway) 10 Groove 11 Detection line 20. Housing 21 Rotation axis

Claims

1. A plurality of rolling elements (4); a contact surface (6) of a member with which the rolling element (4) comes into contact; a strain sensor (7) provided on the contact surface (6); and a strain sensor (7) configured to detect a load acting on the contact surface (6) from the rolling element (4).

2. The bearing further includes an inner ring (2) and an outer ring (3) provided coaxially on the radially outer side of the inner ring (2), 2. The sensor-equipped rolling bearing according to claim 1, wherein the contact surface (6) is a raceway surface (8, 9) of at least one of the inner ring (2) or the outer ring (3) on which the rolling element (4) rolls.

3. The rolling element (4) further includes a cage (5) for holding the rolling element (4), 2. The sensor-equipped rolling bearing according to claim 1, wherein the contact surface (6) is an inner surface of the cage (5).

4. The rolling elements (4) are provided so as to be interposed between a housing (20) and a rotating shaft (21) rotatably held by the rolling elements (4), 2. The sensor-equipped rolling bearing according to claim 1, wherein the contact surface (6) is a surface of the rotating shaft (21) or an inner surface of the housing (20).

5. 2. The sensor-equipped rolling bearing according to claim 1, wherein the strain sensors (7) are provided at a plurality of locations along the rolling direction of the rolling elements (4).

6. 2. The sensor-equipped rolling bearing according to claim 1, wherein the strain sensor is provided in a concave groove formed in the contact surface, and the contact surface and the surface of the strain sensor are flush with each other.

7. 2. The sensor-equipped rolling bearing according to claim 1, wherein the strain sensor (7) has a plurality of measurement channels, and the detection lines (11) of each measurement channel are arranged side by side along the rolling direction of the rolling element (4).

8. 2. The sensor-equipped rolling bearing according to claim 1, wherein the output value of the strain sensor (7) has a predetermined offset value corresponding to temperature.

9. 2. The sensor-equipped rolling bearing according to claim 1, wherein the rolling elements (4) are balls (4) or rollers (4).

10. 3. The sensor-equipped rolling bearing according to claim 2, wherein the raceway surfaces (8, 9) have a single-row structure or a double-row structure.

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