Bearing device

Abstract

To make the sensitivity of a heat flow sensor included in a bearing device excellent even under an environment where an airflow in a bearing changes due to rotation of the bearing or injection of air oil.SOLUTION: A bearing device (30) comprises: a bearing (5a) that rotatably supports a spindle (4) around a rotational shaft (P0); a spacer (6) including an inner ring spacer (6i) adjacent to an inner ring (5ia) of the bearing (5a) and an outer ring spacer (6g) adjacent to an outer ring (5ga); and a heat flow sensor (11a) provided on an inner diameter surface (6gA) of the outer ring spacer (6g). A distance (L) in a direction along the rotational shaft (P0) from the center of the bearing (5a) to the center of the heat flow sensor (11a) is larger than 0.5 times and less than 1 time a dimension (B) in the direction along the rotational shaft of the bearing (5a).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a bearing device that rotatably supports a main spindle or the like of a machine tool. [Background technology]

[0002] Machine tool spindle bearings are often used at high speeds and with low loads, and angular contact ball bearings are widely used for these bearings. Machine tool spindle bearings are lubricated by air-oil (oil mist) lubrication or grease lubrication. Air-oil lubrication is characterized by the ability to maintain a stable lubricated state over the long term, as the lubricating oil is supplied from an external source. Grease lubrication, on the other hand, is economical as it does not require any additional equipment or piping, and is environmentally friendly as it generates very little mist.

[0003] Bearings used in machine tools, such as the spindles of machining centers, which operate at higher speeds, for example, where the dn value (inner ring bore diameter multiplied by the rotational speed) is over 1 million, require more stable operation. However, due to the various causes described below, bearing raceway surface roughness or peeling, cage abnormalities, and other causes can cause the bearing to heat up excessively. Improper oil supply and drainage in air-oil lubrication (too little or too much oil, poor drainage) Deterioration of the lubricating grease sealed inside the bearing - Coolant, water, or foreign matter has entered the rolling part of the bearing Excessive preload, i.e., increased contact pressure on the rolling parts, causing oil film breakdown To prevent the above-mentioned excessive temperature rise of the bearing, Japanese Patent Application Laid-Open No. 2017-26078 (Patent Document 1) discloses a technology in which a lubrication oil supply pump and a non-contact temperature sensor are built into a spacer adjacent to the bearing, and lubricating oil is supplied to the inside of the bearing by the lubrication oil supply pump according to the temperature measurement value of the part of the bearing that is to be lubricated by the temperature sensor.

[0004] Furthermore, a heat flow sensor that detects heat flux generated by the temperature difference between the front and back of the sensor, rather than temperature changes, is disclosed, for example, in JP 2016-166832 A (Patent Document 2). Heat flow sensors are characterized by better sensitivity and a faster response speed of the sensor output than temperature sensors (such as non-contact types and thermocouples) used to measure the temperature of the inner and outer rings of bearings. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-26078 [Patent Document 2] Japanese Patent Application Publication No. 2016-166832 Summary of the Invention [Problem to be solved by the invention]

[0006] The air flow inside the bearing can become large due to the effects of air curtains generated by the bearing's rotation and the compressed air sprayed from the air-oil lubrication nozzle. Therefore, when using a heat flow sensor to detect temperature changes inside the bearing at an early stage, there is a concern that the sensitivity of the heat flow sensor may decrease depending on the position of the heat flow sensor.

[0007] The present invention has been made to solve the above problems, and its purpose is to improve the sensitivity of a heat flow sensor built into a bearing device even in an environment where the air flow inside the bearing changes due to bearing rotation or air-oil injection. [Means for solving the problem]

[0008] (1) A bearing device according to the present disclosure includes a bearing including an inner ring, an outer ring, rolling elements, and a cage, and supporting a rotating body rotatably about a rotation axis, a spacer including an inner ring spacer adjacent to the inner ring and an outer ring spacer adjacent to the outer ring, and a heat flow sensor provided on either the spacer or a peripheral component of the bearing. The distance along the rotation axis from the center of the bearing to the center of the heat flow sensor is greater than 0.5 times and less than 1 time the dimension of the bearing along the rotation axis.

[0009] (2) In one embodiment, the radial distance of the rotating shaft from the outer diameter surface of the inner ring spacer to the heat flow sensor is 25% or less of the distance between the inner diameter surface of the inner ring spacer and the outer diameter surface of the outer ring spacer.

[0010] (3) In one embodiment, the heat flow sensor is provided on the inner diameter surface of the outer ring spacer. The outer ring spacer is provided with an exhaust port for discharging lubricating air oil. The angle between the center of the exhaust port and the center of the heat flow sensor in the circumferential direction of the rotation axis is less than 90°.

[0011] (4) In one embodiment, the outer ring spacer is provided with a nozzle for injecting air-oil. The nozzle is provided in an area of ​​the outer ring spacer opposite to the exhaust port.

[0012] (5) Another bearing device according to the present disclosure includes a bearing including an inner ring, an outer ring, rolling elements, and a cage, and supporting a rotating body rotatably about a rotation axis, a spacer including an inner ring spacer adjacent to the inner ring and an outer ring spacer adjacent to the outer ring, and a heat flow sensor provided on either the spacer or a peripheral component of the bearing. The radial distance of the rotation axis from the outer diameter surface of the inner ring spacer to the heat flow sensor is 25% or less of the distance between the inner diameter surface of the inner ring spacer and the outer diameter surface of the outer ring spacer.

[0013] (6) Another bearing device according to the present disclosure includes a bearing including an inner ring, an outer ring, rolling elements, and a cage, and supporting a rotating body rotatably about a rotation axis; a spacer including an inner ring spacer adjacent to the inner ring and an outer ring spacer adjacent to the outer ring; and a heat flow sensor provided on either the spacer or a peripheral component of the bearing. The heat flow sensor is provided on the inner diameter surface of the outer ring spacer. The outer ring spacer is provided with an exhaust port for discharging air-oil used for lubrication. The angle between the center of the exhaust port and the center of the heat flow sensor in the circumferential direction of the rotation axis is less than 90°.

[0014] (7) In one aspect, a refrigerant flow path is provided in the outer ring spacer. (8) In one aspect, the rotating body is a main spindle of a machine tool. [Effects of the Invention]

[0015] With this configuration, the sensitivity of the heat flow sensor built into the bearing device can be improved even in an environment where the air flow inside the bearing changes due to the rotation of the bearing or the injection of air oil. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of a spindle device incorporating a bearing device. [Figure 2] FIG. 2 is a schematic cross-sectional view showing the configuration of a bearing device. [Figure 3] FIG. 10 is a diagram showing the relationship between heat flux, temperature, and rotation speed obtained by an acceleration / deceleration test. [Figure 4] 10A and 10B are diagrams illustrating examples of arrangements when the axial arrangement of the heat flow sensor is changed. [Figure 5] FIG. 10 is a diagram showing the conditions for a test to reproduce a bearing abnormality. [Figure 6] FIG. 4 is a diagram showing the relationship between the axial arrangement of each heat flow sensor and the output sensitivity of each heat flow sensor. [Figure 7] FIG. 10 is a diagram illustrating an example of the radial arrangement of heat flow sensors. [Figure 8] FIG. 1 is a diagram (part 1) showing an example of the arrangement of heat flow sensors. [Figure 9] FIG. 2 is a diagram (part 2) showing an example of the arrangement of heat flow sensors. [Figure 10] 1 shows the relationship between the radial arrangement of each heat flow sensor and the output sensitivity of each heat flow sensor. [Figure 11] FIG. 10 is a diagram showing an example of the circumferential arrangement of heat flow sensors. [Figure 12] 10A and 10B are diagrams illustrating examples of arrangements when the circumferential arrangement of heat flow sensors is changed. [Figure 13] 1 shows the relationship between the circumferential arrangement of each heat flow sensor and the output sensitivity of each heat flow sensor. [Figure 14] FIG. 10 is a diagram showing an example of a cooling structure provided in the outer ring spacer. [Figure 15] 15 is a cross-sectional view taken along the line XV-XV in FIG. 14. [Figure 16] 10A and 10B are diagrams showing modified examples of the arrangement of the heat flow sensor; [Figure 17] 10A and 10B are diagrams showing other modified examples of the arrangement of the heat flow sensor. DETAILED DESCRIPTION OF THE INVENTION

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0018] Fig. 1 is a cross-sectional view showing a schematic configuration of a spindle device 1 incorporating a bearing device 30 according to this embodiment. Fig. 2 is a schematic cross-sectional view showing the configuration of the bearing device 30 according to this embodiment.

[0019] The spindle device 1 shown in Fig. 1 is used, for example, as a built-in motor type spindle device for a machine tool. In this case, a motor (not shown) is built into one end (left side in Fig. 1) of the spindle 4, which is a rotating body supported by the spindle device 1 for the machine tool main shaft, and a cutting tool (not shown), such as an end mill, is connected to the other end (right side in Fig. 1).

[0020] The spindle device 1 includes a bearing 5 including two bearings 5a and 5b, a spacer 6 disposed adjacent to the bearings 5a and 5b, and heat flow sensors 11a and 11b. The main shaft 4 is rotatably supported around a rotation axis P0 by the two bearings 5a and 5b provided in a housing 3 embedded in the inner diameter portion of the outer cylinder 2. The bearing 5a includes an inner ring 5ia, an outer ring 5ga, rolling elements Ta, and a cage Rta. The bearing 5b includes an inner ring 5ib, an outer ring 5gb, rolling elements Tb, and a cage Rtb. The spacer 6 includes an inner ring spacer 6i and an outer ring spacer 6g.

[0021] An inner ring 5ia of bearing 5a and an inner ring 5ib of bearing 5b, which are spaced apart in the axial direction (direction along rotation axis P0), are tightly fitted (press-fitted) onto main shaft 4. An inner ring spacer 6i is disposed between inner rings 5ia and 5ib, and an outer ring spacer 6g is disposed between outer rings 5ga and 5gb.

[0022] 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 spacing between the plurality of rolling elements Ta is maintained 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 spacing between the plurality of rolling elements Tb is maintained by a cage Rtb.

[0023] The bearings 5a and 5b may be angular contact ball bearings, deep groove ball bearings, tapered roller bearings, or the like. The bearing device 30 shown in Figures 1 and 2 uses angular contact ball bearings, and the two bearings 5a and 5b are installed in a back-to-back (DB) configuration. The bearing arrangement is not limited to a back-to-back configuration, and may also be, for example, a face-to-face configuration.

[0024] Here, a structure in which the main shaft 4 is supported by two bearings 5a and 5b is described as an example, but the main shaft 4 may be supported by three or more bearings.

[0025] A refrigerant flow path (not shown) is formed inside the housing 3. By flowing a refrigerant through the refrigerant flow path of the housing 3, the bearings 5a and 5b can be cooled.

[0026] 2, in the spindle device 1 according to this embodiment, lubricating oil supply passages 67a, 67b for injecting lubricating oil onto the bearings 5a, 5b for cooling and lubricating the bearings 5a, 5b are provided in the outer ring spacer 6g. The lubricating oil is sprayed in the form of air oil or oil mist together with air that carries the lubricating oil from nozzles (hereinafter simply referred to as "lubrication nozzles") provided at the ends of the lubricating oil supply passages 67a, 67b.

[0027] 2, the lubricating oil supply passages 67a and 67b (lubricating nozzles) are shown in positions close to the heat flow sensors 11a and 11b, respectively, but in reality, the lubricating oil supply passages 67a and 67b are arranged at positions shifted in the circumferential direction relative to the heat flow sensors 11a and 11b (see FIG. 11 described later). Also, to avoid complexity, the lubricating oil supply passages 67a and 67b are not shown in FIG.

[0028] Heat flow sensors 11a and 11b for measuring heat flux are fixed to an inner diameter surface 6gA of the outer ring spacer 6g and face an outer diameter surface 6iA of the inner ring spacer 6i. Note that heat flux is the amount of heat passing through a unit area per unit time.

[0029] Each of the heat flow sensors 11a and 11b uses the Seebeck effect to convert heat flow into an electrical signal, generating an output voltage from the slight temperature difference between the front and back of the sensor. Compared to temperature sensors such as non-contact temperature sensors or thermocouples, the heat flow sensors 11a and 11b are more sensitive to changes in heat inside the bearing and can follow changes in heat inside the bearing in a timely manner.

[0030] Heat flow sensor 11a is disposed at the end of the inner diameter surface 6gA of the outer ring spacer 6g that faces the bearing 5a in the axial direction. Heat flow sensor 11b is disposed at the end of the inner diameter surface 6gA of the outer ring spacer 6g that faces the bearing 5b in the axial direction. Because heat flow sensors 11a and 11b are installed near the bearings 5a and 5b on the outer ring spacer 6g in this manner, heat flow sensors 11a and 11b can directly detect the heat flux of heat flowing between the inner and outer rings of the bearings 5a and 5b. The placement of heat flow sensors 11a and 11b will be described in detail later.

[0031] If one were to try to detect signs of seizure in the bearings 5a and 5b by measuring the temperatures of the inner rings 5ia and 5ib, the outer rings 5ga and 5gb, the spacer 6, etc., it would be difficult to detect the signs early, since there would be a delay before the temperature rises even if sudden heat generation occurs.

[0032] In contrast, in this embodiment, the outputs of the heat flow sensors 11a and 11b can be used to detect signs of seizure in the bearings 5a and 5b. By using the outputs of the heat flow sensors 11a and 11b, it is possible to quickly detect a sudden heat generation because the heat flow begins to change earlier than the temperature.

[0033] The heat flow sensors 11a and 11b are each connected to a wire (not shown) for transmitting a detection signal to a control device (not shown).

[0034] <About acceleration / deceleration testing> The applicant installed the bearing device according to the embodiment in a testing machine simulating a machine tool main shaft spindle, and performed an acceleration / deceleration test to evaluate the relationship between heat flux, temperature, and rotation speed when the rotation speed of the main shaft 4 was accelerated and decelerated.

[0035] Figure 3 shows the relationship between heat flux, temperature, and rotational speed obtained through acceleration / deceleration testing. As shown in Figure 3, the output of the heat flow sensor (heat flow) is more responsive to acceleration / deceleration of the rotational speed than the output of the temperature sensor (bearing temperature), which can improve the accuracy of detecting signs of bearing abnormalities. The timing at which the output of the heat flow sensor starts to increase or decrease is approximately synchronized with the timing at which the rotational speed starts to increase or decrease.

[0036] The air flow inside bearings 5a and 5b may become large due to the influence of an air curtain generated by the rotation of bearings 5a and 5b in conjunction with the rotation of main shaft 4, or the influence of compressed air sprayed from the lubrication nozzle. Therefore, depending on the position of heat flow sensors 11a and 11b, they may be significantly affected by the air flow inside bearings 5a and 5b, which may reduce the sensitivity of heat flow sensors 11a and 11b.

[0037] Furthermore, the sensitivity of heat flow sensors 11a, 11b can also decrease if the temperature difference between the front and back surfaces of heat flow sensors 11a, 11b is small. For example, in spindle device 1 according to this embodiment, bearings 5a, 5b can be cooled by flowing refrigerant through a refrigerant flow path inside housing 3. However, if the cooling is insufficient, it is difficult to generate a temperature difference between the inner and outer rings of bearings 5a, 5b. As a result, the temperature difference between the front and back surfaces of heat flow sensors 11a, 11b also becomes small, which raises concerns about a decrease in the sensitivity of heat flow sensors 11a, 11b.

[0038] In view of the above, in this embodiment, the positioning of the heat flow sensors 11a, 11b is optimized within the outer ring spacer 6g, thereby improving the sensitivity of the heat flow sensors 11a, 11b even in an environment where the air flow within the bearings 5a, 5b changes due to the rotation of the bearings 5a, 5b or the injection of compressed air (air oil) from the lubrication nozzle.

[0039] Furthermore, in this embodiment, a cooling structure is provided not only inside the housing 3 but also in the outer ring spacer 6g on which the heat flow sensors 11a, 11b are arranged, thereby actively cooling the surfaces of the heat flow sensors 11a, 11b opposite to the surface facing the spindle 4 (the surface in contact with the outer ring spacer 6g). As a result, when a sudden heat generation occurs in the bearings 5a, 5b, for example, when the bearings 5a, 5b burn out, the temperature difference between the front and back of the heat flow sensors 11a, 11b becomes larger, and the sudden heat generation can be detected early by the heat flow sensors 11a, 11b.

[0040] The arrangement of the heat flow sensors 11a and 11b and the cooling structure of the outer ring spacer 6g will be described in detail below.

[0041] <Axial placement of heat flow sensor> 2 shows an example of the axial arrangement (direction along the rotation axis P0) of the heat flow sensors 11a and 11b according to this embodiment. The heat flow sensor 11a according to this embodiment is arranged at a position that satisfies the following relational expression (1).

[0042] B / 2 < L < M …(1) In relational expression (1), "B" represents the width dimension (axial length) of the bearing 5a, "L" represents the distance from the center of the bearing 5a to the center of the heat flux sensor 11a, and "M" represents the width dimension (axial length) of the outer ring spacer 6g.

[0043] Furthermore, the heat flux sensor 11a according to the present embodiment is arranged at a position that satisfies the following relational expression (2).

[0044] B / 2 < L < B …(2) Relational expression (2) is obtained by replacing "M" in relational expression (1) with "B".

[0045] FIG. 4 is a diagram showing an arrangement example when the axial arrangement of the heat flux sensor 11a is changed. Specifically, in FIG. 4, a heat flux sensor 11a1 arranged at a position where the distance L from the center of the bearing 5a is "predetermined value L1", a heat flux sensor 11a2 arranged at a position where the distance L from the center of the bearing 5a is "predetermined value L2", and a heat flux sensor 11a3 arranged at a position where the distance L from the center of the bearing 5a is "predetermined value L3" are shown.

[0046] Note that the predetermined value L1 satisfies L1 ≤ B / 2 and does not satisfy the above relational expressions (1) and (2). The predetermined value L2 satisfies B / 2 < L2 < B and satisfies the above relational expressions (1) and (2). The predetermined value L3 satisfies L3 ≤ B and satisfies the above relational expression (1) but does not satisfy relational expression (2).

[0047] To confirm the output sensitivity of each of the heat flux sensors 11a1 to 11a3 shown in FIG. 4, the applicant of the present application conducted a reproduction test for bearing abnormalities. FIG. 5 shows the reproduction test conditions for bearing abnormalities. In this reproduction test, a very small amount of lubricating oil was injected into the rolling bearing only when the main shaft was incorporated, creating a situation where abnormalities were likely to occur in the test bearing.

[0048] FIG. 6 shows the relationship between the axial arrangement (distances L1 to L3 from the center of the bearing 5a) of each heat flux sensor and the output sensitivity of each heat flux sensor obtained by the reproduction test conducted under the test conditions shown in FIG. 5.

[0049] As shown in FIG. 6, in the heat flux sensor 11a1 where the distance L1 from the center of the bearing 5a satisfies L1 ≦ B / 2, the above relational expressions (1) and (2) are not satisfied, resulting in the worst output sensitivity. This is presumably because the heat flux sensor 11a1 is most affected by the air ejected from the lubrication nozzle and the air curtain generated by the high-speed rotation of the bearings 5a and 5b, thus causing the most significant decrease in the sensitivity of the heat flux sensor 11a1.

[0050] In the heat flux sensor 11a3 where the distance L3 from the center of the bearing 5a satisfies L3 ≦ B, the above relational expression (1) is satisfied but relational expression (2) is not satisfied, resulting in a slightly inferior output sensitivity. This is presumably because the heat flux sensor 11a3 is least affected by the air ejected from the lubrication nozzle and the air curtain generated by the high-speed rotation of the bearings 5a and 5b, but it is the farthest from the bearing 5a and thus the heat from the bearing 5a is least likely to be transmitted.

[0051] On the other hand, in the heat flux sensor 11a2 where the distance L2 from the center of the bearing 5a satisfies B / 2 < L2 < B, the above relational expressions (1) and (2) are satisfied, resulting in the best output sensitivity. This is presumably because the heat flux sensor 11a2 is less affected by the air ejected from the lubrication nozzle and the air curtain generated by the high-speed rotation of the bearings 5a and 5b, and it is also close to the bearing 5a, so it can detect the heat generation of the bearing 5a the earliest (with high sensitivity).

[0052] The heat flux sensor 11a according to the present embodiment is arranged at a position that satisfies the above relational expressions (1) and (2). Therefore, even in an environment where the air flow in the bearing 5a changes due to the rotation of the bearing 5a or the injection of the lubrication nozzle, the sensitivity of the heat flux sensor 11a can be improved.

[0053] Also, the heat flux sensor 11b according to the present embodiment is also arranged at a position that satisfies the above relational expressions (1) and (2). Therefore, the sensitivity of the heat flux sensor 11b can also be improved. When applying the above relational expressions (1) and (2) to the heat flux sensor 11b, "B" represents the width dimension (axial length) of the bearing 5b, and "L" represents the distance from the center of the bearing 5b to the center of the heat flux sensor 11b.

[0054] <Radial arrangement of heat flow sensors> 7 is a diagram showing an example of the arrangement of the heat flow sensor 11b in the radial direction (radial direction of the rotation axis P0). Note that FIG. 7 is a partially enlarged view showing the details of part C in FIG.

[0055] The heat flow sensor 11b according to this embodiment is disposed at a position that satisfies the following relational expression (3).

[0056] do / 2 <P<Di / 2 …(3) In the relational expression (3), "do" represents the outer diameter of the inner ring spacer 6i, "Di" represents the inner diameter of the outer ring spacer 6g, and "P" represents the distance from the rotation axis P0 to the heat flow sensor 11b.

[0057] Furthermore, the heat flow sensor 11b according to this embodiment is disposed at a position that satisfies the following relational expression (4).

[0058] 0<ΔP≦<(Do / 2-di / 2)×0.25 …(4) In relational expression (4), "Do" represents the outer diameter of the outer ring spacer 6g, "di" represents the inner diameter of the inner ring spacer 6i, and "ΔP" represents the distance (=P-do / 2) from the outer diameter surface 6iA of the inner ring spacer 6i to the heat flow sensor 11b. Relational expression (4) means that the distance from the outer diameter surface 6iA of the inner ring spacer 6i to the heat flow sensor 11b is greater than 0 and is 25% or less of the distance between the inner diameter surface of the inner ring spacer 6i and the outer diameter surface of the outer ring spacer 6g (=Do / 2-di / 2, i.e., the radial dimension of the spacer 6).

[0059] Fig. 8 is a diagram showing an example of the arrangement of heat flow sensor 11b1 where distance ΔP1 to outer diameter surface 6iA of inner ring spacer 6i is equal to or less than (Do / 2-di / 2)×0.25. Fig. 9 is a diagram showing an example of the arrangement of heat flow sensor 11b2 where distance ΔP2 to outer diameter surface 6iA of inner ring spacer 6i is greater than (Do / 2-di / 2)×0.25. To confirm the output sensitivity of each heat flow sensor 11b1 and 11b2 shown in Figs. 8 and 9, the applicant conducted a reproduction test of a bearing abnormality.

[0060] FIG. 10 shows the relationship between the radial arrangement of the heat flow sensors 11b1 and 11b2 and the output sensitivity of the heat flow sensors 11b1 and 11b2, which was obtained through the reproduction test.

[0061] As shown in Figure 10, the heat flow sensor 11b2 (see Figure 9) in which the distance ΔP2 to the outer diameter surface 6iA of the inner ring spacer 6i is greater than (Do / 2 - di / 2) × 0.25 does not satisfy the above relational expression (4), resulting in slightly inferior output sensitivity. This is thought to be because the heat flow sensor 11b2 is far from the inner ring 5ib, which generates heat, and therefore the heat from the inner ring 5ib is not easily transmitted to the heat flow sensor 11b2.

[0062] In contrast, the heat flow sensor 11b1 (see Figure 8) in which the distance ΔP1 to the outer diameter surface 6iA of the inner ring spacer 6i is (Do / 2 - di / 2) × 0.25 or less satisfies the above relational expression (4) and has good output sensitivity. This is thought to be because the heat flow sensor 11b2 is close to the inner ring 5ib, which generates heat, and can detect heat generation in the inner ring 5ib in the event of a bearing abnormality more quickly (with good sensitivity).

[0063] Heat flow sensor 11b according to this embodiment is disposed at a position that satisfies the above-mentioned relations (3) and (4), thereby improving the sensitivity of heat flow sensor 11b.

[0064] Furthermore, the heat flow sensor 11a according to this embodiment is also disposed at a position that satisfies the above-described relational expressions (3) and (4). Therefore, the sensitivity of the heat flow sensor 11a can be improved. When the above-described relational expressions (3) and (4) are applied to the heat flow sensor 11a, "P" represents the distance from the rotation axis P0 to the heat flow sensor 11a, and "ΔP" represents the distance from the outer diameter surface 6iA of the inner ring spacer 6i to the heat flow sensor 11a.

[0065] <Circumferential arrangement of heat flow sensors> Fig. 11 is a diagram showing an example of the arrangement of heat flow sensor 11b in the circumferential direction (the circumferential direction of rotation axis P0). Fig. 11 is a cross-sectional view taken along line XI-XI in Fig. 2. Heat flow sensor 11b according to this embodiment is arranged at a position that satisfies the following relational expression (5).

[0066] θ<-15°, +15°<θ …(5) In the relational expression (5), "θ" represents the circumferential arrangement angle (the angle from the lubrication nozzle to the center of the heat flow sensor) when the lubrication nozzle of the lubricating oil supply passage 67b is used as the reference. Note that θ is expressed as a positive (+) sign in the clockwise direction.

[0067] The heat flow sensor 11b is preferably disposed on the rear side of the lubrication nozzle in the rotational direction of the inner ring spacer 6i. Therefore, for example, if the rotational direction of the inner ring spacer 6i is counterclockwise (-), it is desirable to dispose the heat flow sensor 11b on the rear side in the counterclockwise direction, that is, in the range of 0°<θ<180°. Note that Figure 11 shows an example in which the disposition angle θ is approximately 110°.

[0068] Furthermore, the heat flow sensor 11b according to this embodiment is disposed at a position that satisfies the following relational expression (6).

[0069] -90°<β<+90° …(6) In relational expression (6), "β" represents the circumferential angle from the center of the exhaust port 6ge to the center of the heat flow sensor 11b. Relational expression (6) means that the magnitude (absolute value) of the circumferential angle from the center of the exhaust port 6ge to the center of the heat flow sensor 11b is less than 90°. In the example shown in FIG. 11, the exhaust port 6ge is positioned so that the center of the exhaust port 6ge is at θ=180°. In other words, the lubrication nozzle is provided in an area of ​​the outer ring spacer 6g opposite the exhaust port 6ge.

[0070] Fig. 12 is a diagram showing an example of the arrangement of heat flow sensors when the circumferential arrangement is changed. Specifically, Fig. 12 shows heat flow sensors whose arrangement angles θ relative to the lubrication nozzle are predetermined angles θ1, θ2, θ3, and θ4, respectively, and heat flow sensors whose angle β relative to the center of the exhaust port 6ge is predetermined angle β1.

[0071] The predetermined angle θ1 is -15°<θ1<0°, and does not satisfy the above relational expressions (5) and (6). The predetermined angle θ2 is 0°<θ2<15°, and does not satisfy the above relational expressions (5) and (6). The predetermined angle θ3 is -90°<θ3<-15°, and satisfies the above relational expression (5), but does not satisfy the relational expression (6). The predetermined angle θ4 is 15°<θ4<90°, and satisfies the above relational expressions (5) and (6). The predetermined angle β1 is -90°<β1<90°, and satisfies the above relational expressions (5) and (6).

[0072] In order to confirm the output sensitivity of each heat flow sensor shown in FIG. 12, the applicant carried out a test to reproduce an abnormality in a bearing.

[0073] FIG. 13 shows the relationship between the circumferential arrangement of the heat flow sensors and the output sensitivity of each heat flow sensor, obtained through the reproduction test.

[0074] For heat flow sensors with an arrangement angle θ1 of -15°<θ1<0°, the above relational expressions (5) and (6) were not satisfied, resulting in poor output sensitivity. This is thought to be because the sensor is affected by the air sprayed from the lubrication nozzle, and because the sensor is located forward of the lubrication nozzle in the rotational direction of the inner ring spacer 6i, it is affected by the air curtain generated by the rotation of the inner ring spacer 6i, which reduces output sensitivity.

[0075] Even in the case of heat flow sensors with an arrangement angle θ2 of 0°<θ2<15°, the above relations (5) and (6) were not satisfied, and the output sensitivity was poor. This is thought to be due to the influence of the air sprayed from the lubrication nozzle, which reduces the output sensitivity.

[0076] For heat flow sensors with an arrangement angle θ3 of -90°<θ3<-15°, the above relational expression (5) is satisfied, but the relational expression (6) is not, resulting in slightly inferior output sensitivity. This is thought to be because the heat flow sensor is located more than 15° away from the lubrication nozzle, but on the forward side of the inner ring spacer 6i in the direction of rotation, and is therefore slightly affected by the air sprayed from the lubrication nozzle, which dulls the output sensitivity.

[0077] Heat flow sensors with an arrangement angle θ4 of 15°<θ4<90° satisfy the above relational expressions (5) and (6), and have good output sensitivity. This is thought to be because they are less susceptible to the effects of air sprayed from the lubrication nozzle and the air curtain generated by the rotation of the inner ring spacer 6i, and can detect bearing heat generation in the event of an abnormality more quickly (with good sensitivity).

[0078] The heat flow sensor with an angle β1 based on the center of the exhaust port 6ge of -90°<β1<90° satisfied the above relations (5) and (6), and had the best output sensitivity. This is thought to be because the heat flow sensor is installed near the exhaust port 6ge, where it is less susceptible to air and where heat tends to build up, allowing it to detect heat generation in the bearing 5b more quickly (with better sensitivity) in the event of an abnormality.

[0079] In the case of grease lubrication, no air flows into the vicinity of the heat flow sensor, so the sensitivity of the heat flow sensor will not be reduced no matter where on the circumference the sensor is placed.

[0080] <Cooling structure of outer ring spacer> As described above, in this embodiment, the cooling structure is provided in the outer ring spacer 6g on which the heat flow sensors 11a and 11b are arranged.

[0081] Fig. 14 is a diagram showing an example of a cooling structure provided in the outer ring spacer 6g, and Fig. 15 is a cross-sectional view taken along line XV-XV in Fig. 14.

[0082] As shown in FIG. 14, two refrigerant paths 71 and 72 are provided in the housing 3, and a spiral groove 73 is provided on the outer diameter surface of the outer ring spacer 6g. One end and the other end of the spiral groove 73 are connected to the refrigerant paths 71 and 72, respectively. A refrigerant (oil, water, compressed air, etc.) flows from one of the refrigerant paths 71 and 72 into the spiral groove 73, and the refrigerant that has flowed inside the spiral groove 73 is discharged to the other of the refrigerant paths 71 and 72. Therefore, this spiral groove 73 functions as a refrigerant flow path of the outer ring spacer 6g. As shown in FIG. 15, the heat flow sensor 11a is connected to the outside of the outer ring spacer 6g by wiring W.

[0083] In addition to the heat flow sensors 11a, 11b and the spiral groove 73, the outer ring spacer 6g may be provided with a wireless transmitter that transmits data acquired by the sensors to the outside, a self-power generating device that drives the sensors and wireless transmitters, and a control device that includes a signal processing unit that temporarily stores data acquired by the sensors and converts the data.

[0084] [Modification of heat flow sensor placement] Figure 16 is a diagram showing a modified example of the placement of the heat flow sensor. In this modified example, as shown in Figure 16, protrusions 7a, 7b are added to the outer ring spacer 6g, which is the fixed side, protruding from the axial side surface between the inner and outer rings, and a heat flow sensor 11a is installed on one of the protrusions 7a. In this case, although not shown, it is also advisable to similarly place a heat flow sensor 11b on the other protrusion 7b.

[0085] The heat source is the area of ​​the fixed raceway of the rolling bearing that comes into contact with the rolling elements, but installing a heat flow sensor on the fixed raceway would raise concerns about increased costs for processing the fixed raceway. Installing the heat flow sensor on the protrusions 7a and 7b of the fixed spacer eliminates this problem and makes it easy to install the heat flow sensor. Furthermore, because heat flow sensors 11a and 11b are installed on the protrusions 7a and 7b that protrude between the inner and outer races, it is possible to directly detect temperature changes inside the bearing during operation.

[0086] The protrusions 7a and 7b may also serve as nozzles for discharging lubricating oil for air-oil lubrication to the bearings 5a and 5b. In this case, the heat flow sensor can be installed using an existing nozzle for discharging lubricating oil, which reduces costs compared to, for example, providing a dedicated part for installing the heat flow sensor.

[0087] Fig. 17 shows another modified example of the arrangement of the heat flow sensors. Fig. 1 and Fig. 2 show an example in which the heat flow sensors 11a and 11b are installed at the axial end portions (near the bearing 5) on the inner diameter surface of the outer ring spacer 6g. However, as shown in Fig. 17, the heat flow sensor 11 may also be installed in the axial center portion on the inner diameter surface of the outer ring spacer 6g.

[0088] Alternatively, the heat flow sensor may be disposed on the housing 3 or a front cover (not shown), and the housing 3 or the front cover may be provided with a cooling structure, a wireless transmitter, a self-power generating device, and a control device.

[0089] 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 description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0090] 1 spindle device, 2 outer cylinder, 3 housing, 4 main shaft, 5, 5a, 5b bearings, 5ga, 5gb outer ring, 5ia, 5ib inner ring, 6 spacer, 6g outer ring spacer, 6gA inner diameter surface, 6ge exhaust port, 6i inner ring spacer, 6iA outer diameter surface, 7a, 7b protrusion, 11a, 11b heat flow sensor, 30 bearing device, 67a, 67b lubricating oil supply path, 71 refrigerant path, 73 groove, P0 rotating shaft, Rta, Rtb cage, Ta, Tb rolling element, W wiring.

Claims

1. a bearing including an inner ring, an outer ring, rolling elements, and a cage, and supporting a rotating body so that the rotating body can rotate about a rotation axis; a spacer including an inner ring spacer adjacent to the inner ring and an outer ring spacer adjacent to the outer ring; a heat flow sensor; a distance from a center of the bearing to a center of the heat flow sensor in a direction along the rotation axis is greater than 0.5 times and less than 1 time a dimension of the bearing in a direction along the rotation axis, the heat flow sensor is provided on an inner diameter surface of the outer ring spacer, The outer ring spacer is provided with an exhaust port for discharging air oil for lubrication, the angle from the center of the exhaust port to the center of the heat flow sensor in the circumferential direction of the rotation axis is less than 90°; a nozzle for injecting the air-oil is provided on the outer ring spacer, the nozzle is provided at a position shifted by 180 degrees from the exhaust port on the outer ring spacer, the heat flow sensor is disposed in a range from a position shifted 0 degrees to a position shifted 90 degrees from the exhaust port toward the rotation direction of the inner ring spacer relative to the outer ring spacer, a radial distance of the rotating shaft from an outer diameter surface of the inner ring spacer to the heat flow sensor is 25% or less of a distance between an inner diameter surface of the inner ring spacer and an outer diameter surface of the outer ring spacer.

2. The bearing device according to claim 1 , wherein a coolant flow path is provided in the outer ring spacer.

3. 3. The bearing device according to claim 1, wherein the rotating body is a main shaft of a machine tool.

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