Bearing arrangement

Abstract

A bearing device (30) includes a bearing (5a) rotatably supporting a main shaft (4) about a rotation axis (P0), a spacer (6) having 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 flux sensor (11a) provided in an inner surface (6gA) of the outer ring spacer (6g). A distance (L) from a center of the bearing (5a) to a center of the heat flux sensor (11a) in a direction along the rotation axis (P0) is longer than 0.5 times and shorter than 1 times a size (B) of the bearing (5b) in the direction along the rotation axis.

Description

Technical Field

[0001] The present invention relates to a bearing device that rotatably supports the spindle of a machine tool, etc. Background Technology

[0002] Bearings used in machine tool spindles are often used at high speeds and low loads, and angular contact ball bearings are widely used in this category. Machine tool spindle bearings are lubricated by either oil-air (oil mist) lubrication or grease lubrication. Oil-air lubrication is characterized by its ability to maintain a stable lubrication state over a long period due to the external supply of lubricating oil. Grease lubrication is characterized by its cost-effectiveness because it does not require auxiliary facilities and piping, and its environmental friendliness due to the minimal amount of mist produced.

[0003] Bearings used in high-speed regions should operate in a more stable manner. These high-speed regions are, for example, areas where the dn value, calculated by multiplying the inner diameter of the inner ring by the number of revolutions, is equal to or greater than one million, such as the spindle of a machining center in a machine tool. However, due to various factors described below, bearings may experience surface roughening or spalling at the bearing raceway surface, or abnormalities in the retaining elements, which may lead to an excessive rise in bearing temperature.

[0004] • In oil-air lubrication, improper feeding and drainage of lubricating oil (too little or too much oil, or insufficient drainage) can cause problems.

[0005] • Deterioration of the grease sealed in the bearing

[0006] • Coolant, water, or foreign matter enters the rolling parts of the bearing.

[0007] Excessive preload, i.e., increased contact pressure in the rolling parts, leads to oil film rupture.

[0008] To prevent excessive bearing temperature rise caused by the above factors, Japanese Patent Application Publication No. 2017-26078 (Patent Document 1) discloses a technology in which a lubricating oil feed pump and a non-contact temperature sensor are included in a spacer adjacent to the bearing. The lubricating oil feed pump feeds lubricating oil into the bearing based on the temperature value of the bearing lubrication part measured by the temperature sensor.

[0009] For example, Japanese Patent Publication No. 2016-166832 (Patent Document 2) discloses a heat flux sensor that senses heat flux generated by the temperature difference between the front and rear sides of the sensor, rather than by temperature changes. The heat flux sensor is characterized by higher sensitivity and response speed at its sensor output compared to temperature sensors (non-contact temperature sensors or thermocouples) used to measure the temperature of the inner and outer rings of a bearing.

[0010] Reference List

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent Application Publication No. 2017-26078

[0013] Patent Document 2: Japanese Patent Application Publication No. 2016-166832 Summary of the Invention

[0014] Technical issues

[0015] Within a bearing, the airflow can become substantial due to the air curtain generated by the bearing's rotation or the compressed air ejected from nozzles used for oil-air lubrication. Therefore, when using a heat flux sensor to sense temperature changes inside the bearing in the early stages, the sensor's sensitivity can decrease depending on its location.

[0016] The present invention was made to solve the above-mentioned problems, and its purpose is to achieve high sensitivity of the heat flux sensor included in the bearing device even in environments where the air flow in the bearing changes due to the rotation of the bearing or the injection of oil and gas.

[0017] Technical means used to solve technical problems

[0018] (1) The bearing device according to this disclosure includes: a bearing, said bearing including an inner ring, an outer ring, rolling elements and a retainer, said bearing rotatably supporting a rotating body about a rotation axis; a spacer, said spacer including an inner ring spacer adjacent to the inner ring and an outer ring spacer adjacent to the outer ring; and a heat flux sensor disposed in one of the components surrounding the spacer and the bearing. The distance from the center of the bearing to the center of the heat flux sensor in the direction along the rotation axis is longer than 0.5 times and shorter than 1 times the dimension of the bearing in the direction along the rotation axis.

[0019] (2) In one aspect, the distance from the outer surface of the inner ring spacer to the heat flux sensor in the radial direction of the rotation axis is equal to or less than 25% of the distance between the inner surface of the inner ring spacer and the outer surface of the outer ring spacer.

[0020] (3) In one aspect, the heat flux sensor is disposed in the inner surface of the outer ring spacer. The outer ring spacer is provided with a discharge port for discharging lubricating oil and gas. The angle from the center of the discharge port to the center of the heat flux sensor in the circumferential direction of the axis of rotation is less than 90°.

[0021] (4) In one aspect, the outer ring spacer is provided with a nozzle for injecting oil and gas. The nozzle is located in the area of ​​the outer ring spacer opposite to the discharge port.

[0022] (5) Another bearing device according to this disclosure includes: a bearing comprising an inner ring, an outer ring, rolling elements, and a retainer, the bearing rotatably supporting a rotating body about a rotation axis; a spacer comprising an inner ring spacer adjacent to the inner ring and an outer ring spacer adjacent to the outer ring; and a heat flux sensor disposed in one of the components surrounding the spacer and the bearing. The distance from the outer surface of the inner ring spacer to the heat flux sensor in the radial direction of the rotation axis is equal to or less than 25% of the distance between the inner surface of the inner ring spacer and the outer surface of the outer ring spacer.

[0023] (6) Another bearing device according to this disclosure includes: a bearing comprising an inner ring, an outer ring, rolling elements, and a retainer, the bearing rotatably supporting a rotating body about a rotation axis; a spacer comprising an inner ring spacer adjacent to the inner ring and an outer ring spacer adjacent to the outer ring; and a heat flux sensor disposed in one of the components surrounding the spacer and the bearing. The heat flux sensor is disposed in the inner surface of the outer ring spacer. The outer ring spacer is provided with a vent for discharging lubricating oil vapor. The angle from the center of the vent to the center of the heat flux sensor in the circumferential direction of the rotation axis is less than 90°.

[0024] (7) In one aspect, the outer ring spacer is provided with a cooling medium flow channel.

[0025] (8) In one aspect, the rotating body is the spindle of the machine tool.

[0026] Invention Effects

[0027] According to this design, even in environments where the airflow in the bearing varies due to the bearing's rotation or the injection of oil and gas, the sensitivity of the heat flux sensor contained in the bearing assembly can be very high. Attached Figure Description

[0028] Figure 1 This is a cross-sectional view showing a schematic structure of a spindle assembly equipped with bearings.

[0029] Figure 2 This is a schematic cross-sectional view showing the structure of the bearing assembly.

[0030] Figure 3 It is a graph showing the relationship between heat flux, temperature and rotational speed obtained in acceleration and deceleration tests.

[0031] Figure 4 This is a diagram illustrating an exemplary arrangement when the axial direction of the heat flux sensor is changed.

[0032] Figure 5 This is a diagram showing the state during a bearing abnormality simulation test.

[0033] Figure 6 This is a graph showing the relationship between the axial arrangement of each heat flux sensor and the output sensitivity of each heat flux detector.

[0034] Figure 7 This is a diagram illustrating an exemplary arrangement of the heat flux sensor in the radial direction.

[0035] Figure 8 This is a diagram (number 1) showing an exemplary arrangement of a heat flux sensor.

[0036] Figure 9 This is a diagram (number 2) showing an exemplary arrangement of a heat flux sensor.

[0037] Figure 10 The relationship between the radial arrangement of each heat flux sensor and the output sensitivity of each heat flux detector is shown.

[0038] Figure 11 This is a diagram illustrating an exemplary arrangement of a heat flux sensor in the circumferential direction.

[0039] Figure 12 This is a diagram illustrating an exemplary arrangement when the arrangement of the heat flux sensor in the circumferential direction is changed.

[0040] Figure 13 The relationship between the circumferential arrangement of each heat flux sensor and the output sensitivity of each heat flow sensor is shown.

[0041] Figure 14 This is a diagram showing an exemplary cooling structure disposed in the outer ring spacer.

[0042] Figure 15 It is along Figure 14 The cross-sectional view of XV-XV in the diagram.

[0043] Figure 16 This is a diagram showing a modified example of the arrangement of the heat flux sensor.

[0044] Figure 17 This is a diagram showing another variation of the arrangement of the heat flux sensor. Detailed Implementation

[0045] Embodiments of the present invention will now be described with reference to the accompanying drawings. The same or corresponding elements in the drawings below have the same reference numerals, and their descriptions will not be repeated.

[0046] Figure 1 This is a cross-sectional view showing a schematic structure of the spindle assembly 1 equipped with the bearing assembly 30 according to this embodiment. Figure 2This is a schematic cross-sectional view showing the structure of the bearing device 30 according to this embodiment.

[0047] Figure 1 The spindle assembly 1 shown is used, for example, as a machine tool's built-in motor type spindle assembly. In this case, the motor (not shown) is mounted on one end of the spindle 4, which serves as a rotating body supported by the spindle assembly 1 for the machine tool's spindle. Figure 1 (On the left side), a cutting tool, not shown, such as an end mill, is connected to the other end (in...). Figure 1 (The right side of the middle).

[0048] The spindle assembly 1 includes bearings 5 ​​with two bearings 5a and 5b, spacers 6 arranged adjacent to bearings 5a and 5b, and heat flux sensors 11a and 11b. The spindle 4 is rotatably supported about a rotation axis P0 by the two bearings 5a and 5b housed in a housing 3 embedded inside the bearing sleeve 2. Bearing 5a has an inner ring 5ia, an outer ring 5ga, a rolling element Ta, and a retainer Rta. Bearing 5b includes an inner ring 5ib, an outer ring 5gb, a rolling element Tb, and a retainer Rtb. Spacers 6 include an inner ring spacer 6i and an outer ring spacer 6g.

[0049] The inner rings 5ia and 5ib of bearing 5a and bearing 5b, which are axially separated (along the direction of the rotation axis P0), are assembled to the spindle 4 by an interference fit (press fit). The inner ring spacer 6i is arranged between the inner rings 5ia and 5ib, while the outer ring spacer 6g is arranged between the outer rings 5ga and 5gb.

[0050] Bearing 5a is a rolling bearing in which multiple rolling elements Ta are arranged between the inner ring 5ia and the outer ring 5ga. The spacing between the rolling elements Ta is maintained by a retainer Rta. Bearing 5b is a rolling bearing in which multiple rolling elements Tb are arranged between the inner ring 5ib and the outer ring 5gb. The spacing between the rolling elements Tb is maintained by a retainer Rtb.

[0051] Angular contact ball bearings, deep groove ball bearings, or tapered roller bearings can be used as bearings 5a and 5b. Angular contact ball bearings include... Figure 1 and Figure 2 In the bearing assembly 30 shown, two bearings 5a and 5b are arranged in a back-to-back double bearing (DB) arrangement. The bearing arrangement is not limited to a back-to-back double bearing arrangement, but a face-to-face double bearing arrangement, for example, can also be used.

[0052] Although a structure in which two bearings 5a and 5b support the spindle 4 has been shown and described, a structure in which more than two bearings support the spindle 4 can also be used.

[0053] A cooling medium flow channel (not shown) is located inside the housing 3. Cooling medium is fed through the cooling medium flow channel in the housing 3, so that bearings 5a and 5b can be cooled.

[0054] In the spindle assembly 1 according to this embodiment, such as Figure 2 As shown, lubricating oil supply paths 67a and 67b for injecting lubricating oil into bearings 5a and 5b to cool and lubricate them are provided in the outer ring spacer 6g. The lubricating oil is sprayed in the form of oil vapor or oil mist along with the air carrying the lubricating oil from nozzles (hereinafter also referred to as "lubricating nozzles") provided at each end of the lubricating oil supply paths 67a and 67b.

[0055] although Figure 2 The lubricating oil supply paths 67a and 67b (lubricating nozzles) shown are located close to the corresponding heat flux sensors 11a and 11b, but the lubricating oil supply channels 67a and 67b are actually arranged circumferentially away from the heat flux sensors 11a and 11b (see [reference]). Figure 11 The location (which will be described later) is shown. For the sake of brevity, Figure 1 The lubricant supply paths 67a and 67b are not shown.

[0056] Heat flux sensors 11a and 11b, which measure heat flux, are fixed to the inner surface 6gA of the outer ring spacer 6g, and are opposite to the outer surface 6iA of the inner ring spacer 6i. Heat flux refers to the amount of heat passing through a unit area per unit time.

[0057] Each heat flux sensor 11a and 11b is a sensor that converts heat flux into an electrical signal based on the Seebeck effect, and the output voltage is generated by the small temperature difference between the front and rear sides of the sensor. Compared with temperature sensors such as non-contact temperature sensors or thermocouples, heat flux sensors 11a and 11b are more sensitive to heat changes inside the bearing, and they can track heat changes inside the bearing in a timely manner.

[0058] A heat flux sensor 11a is arranged in the inner surface 6gA of the outer ring spacer 6g, at one end of the bearing 5a in the axial direction. A heat flux sensor 11b is arranged in the inner surface 6gA of the outer ring spacer 6g, at one end of the bearing 5b in the axial direction. Since the heat flux sensors 11a and 11b are thus positioned near the corresponding bearings 5a and 5b in the outer ring spacer 6g, they can directly detect the heat flux flowing between the inner and outer rings of the bearings 5a and 5b. The arrangement of the heat flux sensors 11a and 11b will be described in detail later.

[0059] In an attempt to detect signs of seizing in bearings 5a and 5b by measuring the temperatures of the inner rings 5ia and 5ib, the outer rings 5ga and 5gb, and the spacer 6, although there was a sudden heat generation, the signs may not be detected in the early stages due to the delay in the temperature rise.

[0060] Conversely, in this embodiment, signs of jamming in bearings 5a and 5b can be detected based on the outputs from heat flux sensors 11a and 11b. By using the outputs from heat flux sensors 11a and 11b, sudden heating can be detected quickly because heat flux begins to change earlier than temperature.

[0061] A wire (not shown) for sending a detection signal to a control device (not shown) is connected to the corresponding heat flux sensors 11a and 11b.

[0062] <Acceleration and Deceleration Test>

[0063] The applicant conducted acceleration and deceleration tests in which the bearing device according to an embodiment of the present invention was installed in a tester simulating a machine tool spindle, and the relationship between heat flux, temperature and rotational speed was evaluated when the rotational speed of the spindle 4 was increased and decreased.

[0064] Figure 3 This is a graph showing the relationship between heat flux, temperature, and rotational speed obtained during acceleration and deceleration tests. For example... Figure 3 As shown, the output (heat flux) from the heat flux sensor is more responsive to increases and decreases in rotational speed than the output (bearing temperature) from the temperature sensor, and can improve the accuracy of detecting abnormal signs in the bearing. The timing of the heat flux sensor output starting to increase and decrease is essentially synchronized with the timing of the rotational speed starting to increase and decrease.

[0065] Within bearings 5a and 5b, the airflow can become significant due to the air curtain generated by the rotation of bearings 5a and 5b with the spindle 4, as well as the influence of compressed air ejected from the lubrication nozzle. Therefore, depending on the position of the heat flux sensors 11a and 11b, there is a problem where the sensitivity of the heat flux sensors 11a and 11b decreases due to the influence of the airflow within bearings 5a and 5b.

[0066] When the temperature difference between the front and rear sides of the heat flux sensors 11a and 11b is also small, the sensitivity of the heat flux sensors 11a and 11b may decrease. For example, in the spindle assembly 1 according to this embodiment, the bearings 5a and 5b can be cooled by being fed cooling medium through a cooling medium flow channel inside the housing 3. However, when cooling is insufficient, a temperature difference between the inner and outer rings of the bearings 5a and 5b is unlikely to occur. Therefore, the temperature difference between the front and rear sides of the heat flux sensors 11a and 11b also becomes small, and there is a problem of reduced sensitivity of the heat flux sensors 11a and 11b.

[0067] In view of the above, in this embodiment, the arrangement of heat flux sensors 11a and 11b in the outer ring spacer 6g is optimized so as to improve the sensitivity of heat flux sensors 11a and 11b even in an environment where the air flow in bearings 5a and 5b varies due to the rotation of bearings 5a and 5b or the injection of compressed air (oil gas) from the lubrication nozzle.

[0068] Furthermore, in this embodiment, by providing a cooling structure not only inside the housing 3 but also in the outer ring spacer 6g where the heat flux sensors 11a and 11b are arranged, the surfaces of the heat flux sensors 11a and 11b opposite to the surface on one side of the spindle 4 (the surfaces in contact with the outer ring spacer 6g) are actively cooled. Therefore, when sudden heating occurs in the bearings 5a and 5b, such as during combustion, the temperature difference between the front and rear sides of the heat flux sensors 11a and 11b increases, and the heat flux sensors 11a and 11b can detect the sudden heating earlier.

[0069] The arrangement of heat flux sensors 11a and 11b and the cooling structure in the outer ring spacer 6g will be described in detail below.

[0070] <Arrangement of heat flux sensors in the axial direction>

[0071] As described above Figure 2 An exemplary arrangement of heat flux sensors 11a and 11b in the axial direction (along the direction of the rotation axis P0) according to this embodiment is shown. Heat flux sensor 11a according to this embodiment is arranged at a position satisfying the following relational expression (1):

[0072] B / 2 < L < M...(1)

[0073] Wherein, "B" represents the width (length in the axial direction) of bearing 5a, "L" represents the distance from the center of bearing 5a to the center of heat flux sensor 11a, and "M" represents the width (length in the axial direction) of outer ring spacer 6g.

[0074] Furthermore, according to this embodiment, the heat flux sensor 11a is arranged at a position that satisfies the following relational expression (2).

[0075] B / 2 < L < B...(2)

[0076] Relational expression (2) is the same as relational expression (1), except that “M” is replaced with “B”.

[0077] Figure 4 This is a diagram illustrating an exemplary arrangement when the axial direction of the heat flux sensor 11a is changed. Specifically, Figure 4 A heat flux sensor 11a1 is shown at a distance L from the center of the bearing 5a set to a "predetermined value L1", a heat flux detector 11a2 is shown at a distance L from the center of the bearing 5a set to a "predetermined value L2", and a heat flux detector 11a3 is shown at a distance L from the center of the bearing 5a set to a "predetermined value L3".

[0078] The value L1 is defined to satisfy the condition L1≤B / 2, but not to satisfy relational expressions (1) and (2). The value L2 is defined to satisfy the condition B / 2<L2<B, and to satisfy relational expressions (1) and (2). The value L3 is defined to satisfy the condition L3≥B, and to satisfy relational expression (1), but not to satisfy relational expression (2).

[0079] The applicant conducted a bearing malfunction simulation test in an attempt to check... Figure 4 The output sensitivity of the heat flux sensors 11a1 to 11a3 shown. Figure 5 The diagram illustrates a simulated bearing anomaly test. In this simulation, a condition that could lead to an anomaly in the tested bearing was created by introducing only a very small amount of lubricating oil into the rolling bearing during spindle assembly.

[0080] Figure 6 It is shown in Figure 5 The graph shows the relationship between the axial arrangement of each heat flux sensor (distances L1 to L3 from the center of bearing 5a) and the output sensitivity of each heat flux obtained from simulation tests conducted under the test conditions shown.

[0081] like Figure 6 As shown, the heat flux sensor 11a1, which satisfies the condition L1≤B / 2 regarding the distance L1 from the center of bearing 5a, does not satisfy the relational expressions (1) and (2), and its output sensitivity is the worst. This may be because the heat flux sensor 11a1 is most affected by the air injected from the lubrication nozzle and the air curtain generated by the high-speed rotation of bearings 5a and 5b, thus the sensitivity of the heat flux sensor 11a1 decreases the most.

[0082] Regarding the heat flux sensor 11a3, which is at a distance L3 from the center of bearing 5a, satisfying the condition L3≥B, it satisfies relational expression (1) but not relational expression (2), and the output sensitivity of the heat flux sensor is slightly worse. This may be because the heat flux sensor is least likely to be affected by the air ejected from the lubrication nozzle and the air curtain generated by the high-speed rotation of bearings 5a and 5b. However, since the heat flux sensor is farthest from bearing 5a, heat from bearing 5a is least likely to be conducted to the heat flux sensor.

[0083] Conversely, the heat flux sensor 11a2, which satisfies the condition B / 2 < L2 < B at a distance L2 from the center of bearing 5a, satisfies the relations (1) and (2), and has the highest output sensitivity. This is likely because the heat flux sensor is less likely to be affected by the air ejected from the lubrication nozzle and the air curtain generated by the high-speed rotation of bearings 5a and 5b, and because the heat flux sensor is also close to bearing 5a, it is able to detect heat generation in bearing 5a earliest (with the highest sensitivity).

[0084] According to this embodiment, the heat flux sensor 11a is arranged at a position that satisfies the relationship expressions (1) and (2) as described above. Therefore, even in an environment where the airflow in the bearing 5a varies due to the rotation of the bearing 5a or the injection from the lubrication nozzle, the sensitivity of the heat flux sensor 11a can be very high.

[0085] According to this embodiment, the heat flux sensor 11b is also arranged at a position that satisfies the relationships (1) and (2) described above. Therefore, the sensitivity of the heat flux sensor 11b can also be very high. When the relationships (1) and (2) described above are applied to the heat flux sensor 11b, "B" represents the width (length in the axial direction) 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.

[0086] <Arrangement of heat flux sensors in the radial direction>

[0087] Figure 7 This is a diagram showing an exemplary arrangement of the heat flux sensor 11b in the radial direction (radial direction of the rotation axis P0). Figure 7 It is shown Figure 2 A magnified view of the details in section C.

[0088] According to this embodiment, the heat flux sensor 11b is arranged at a position that satisfies the following relational expression (3):

[0089] do / 2 < P < Di / 2...(3)

[0090] Wherein, "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 flux sensor 11b.

[0091] Furthermore, according to this embodiment, the heat flux sensor 11b is arranged at a position that satisfies the following relational expression (4):

[0092] 0<ΔP≤(Do / 2-di / 2)×0.25...(4)

[0093] Wherein, “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 from the outer surface 6iA of the inner ring spacer 6i to the heat flux sensor 11b (=P-do / 2). The relational expression (4) indicates that the distance from the outer surface 6iA of the inner ring spacer 6i to the heat flux sensor 11b is greater than 0 and equal to or less than 25% of the distance between the inner surface of the inner ring spacer 6g and the outer surface of the outer ring spacer 6g (=Do / 2-di / 2, i.e., the radial dimension of the spacer 6).

[0094] Figure 8 This is a diagram showing an exemplary arrangement of a heat flux sensor 11b1 with a distance ΔP1 from the outer surface 6iA of the inner ring spacer 6i equal to or less than (Do / 2-di / 2)×0.25. Figure 9 This is a diagram showing an exemplary arrangement of a heat flux sensor 11b2 where the distance ΔP2 from the outer surface 6iA of the inner ring spacer 6i is greater than (Do / 2 - di / 2) × 0.25. For inspection... Figure 8 and Figure 9 The applicant conducted a bearing abnormality simulation test on the output sensitivity of each of the heat flux sensors 11b1 and 11b2 shown.

[0095] Figure 10 The relationship between the radial arrangement of each heat flux sensor 11b1, 11b2 and the output sensitivity of each heat flux detector 11b1, 11b2 obtained in the simulation experiment is shown.

[0096] like Figure 10 As shown, the distance ΔP2 from the outer surface 6iA of the inner ring spacer 6i is greater than (Do / 2-di / 2)×0.25 for the heat flux sensor 11b2 (see...). Figure 9 The relationship expression (4) is not satisfied, and the output sensitivity of the heat flux sensor is slightly worse. This may be because the heat flux sensor 11b2 is far from the inner ring 5ib that generates heat, and the heat from the inner ring 5ib is unlikely to be conducted to the heat flux sensor 11b2.

[0097] Conversely, the distance ΔP1 from the outer surface 6iA of the inner ring spacer 6i is equal to or less than (Do / 2-di / 2)×0.25 of the heat flux sensor 11b1 (see... Figure 8 The heat flux sensor 11b1 satisfies the relational expression (4) and has a high output sensitivity. This may be because the heat flux sensor 11b1 is close to the inner ring 5ib that generates heat and is able to detect the heating in the inner ring 5ib earlier (with higher sensitivity) when the bearing malfunction occurs.

[0098] According to this embodiment, the heat flux sensor 11b is arranged at a position that satisfies the relationships (3) and (4) described above. Therefore, the sensitivity of the heat flux sensor 11b can be very high.

[0099] According to this embodiment, the heat flux sensor 11a is also arranged at a position that satisfies the relationships (3) and (4) described above. Therefore, the sensitivity of the heat flux sensor 11a can also be very high. When the relationships (3) and (4) described above are applied to the heat flux sensor 11a, "P" represents the distance from the rotation axis P0 to the heat flux sensor 12a, and "ΔP" represents the distance from the outer surface 6iA of the inner ring spacer 6i to the heat flux sensor 11a.

[0100] <Circumferential arrangement of heat flux sensors>

[0101] Figure 11 This is a diagram showing an exemplary arrangement of the heat flux sensor 11b in the circumferential direction (circumferential direction of the rotation axis P0). Figure 11 It is along Figure 2 A cross-sectional view of XI-XI in the figure. The heat flux sensor 11b according to this embodiment is arranged at a position satisfying the following relational expression (5):

[0102] θ < -15°, +15° < θ...(5)

[0103] Here, "θ" represents the angle (from the lubrication nozzle to the center of the heat flux sensor) in the circumferential direction, with reference to the lubrication nozzle in the lubrication supply path 67b. θ in the clockwise direction is represented as positive (+).

[0104] The heat flux sensor 11b is preferably arranged on the rear side of the lubrication nozzle along the rotation direction of the inner ring spacer 6i. Therefore, when the inner ring spacer 6i rotates, for example, counterclockwise (-), the heat flux sensor 11b is preferably arranged on the rear side in the counterclockwise direction, i.e., in the range of 0° < θ < 180°. Figure 11 An example is shown with the arrangement angle θ set to approximately 110°.

[0105] Furthermore, according to this embodiment, the heat flux sensor 11b is arranged at a position that satisfies the following relational expression (6):

[0106] -90°<β<+90°...(6)

[0107] Wherein, "β" represents the angle in the circumferential direction from the center of the discharge port 6ge to the center of the heat flux sensor 11b. Relationship expression (6) indicates that the magnitude (absolute value) of the angle in the circumferential direction from the center of the discharge port 6ge to the center of the heat flux sensor 11a is less than 90°. Figure 11 In the example shown, the discharge port 6ge is arranged such that its center satisfies the condition θ = 180°. In other words, the lubrication nozzle is located in the region of the outer ring spacer 6g opposite to the discharge port 6ge.

[0108] Figure 12 This is a diagram illustrating an exemplary arrangement when the circumferential arrangement of the heat flux sensor is changed. Specifically, Figure 12 The diagram shows heat flux sensors with the lubrication nozzle defined as the reference and the arrangement angle θ set to specified angles θ1, θ2, θ3, and θ4, respectively, and heat flux sensors with the center of the discharge port 6ge defined as the reference and the angle β set to specified angle β1.

[0109] Angle θ1 is set to satisfy the condition -15° < θ1 < 0°, and does not satisfy relational expressions (5) and (6). Angle θ2 is set to satisfy the condition 0° < θ2 < 15°, and does not satisfy relational expressions (5) and (6). Angle θ3 is set to satisfy the condition -90° < θ3 < -15°, and satisfies relational expression (5), but does not satisfy relational expression (6). Angle θ4 is set to satisfy the condition 15° < θ4 < 90°, and satisfies relational expressions (5) and (6). Angle β1 is set to satisfy the condition -90° < β1 < 90°, and satisfies relational expressions (5) and (6).

[0110] In order to check Figure 12 The applicant conducted a bearing anomaly simulation test to demonstrate the output sensitivity of each heat flux sensor shown.

[0111] Figure 13 The relationship between the circumferential arrangement of each heat flux sensor and the output sensitivity of each heat flux obtained in the simulation experiment is shown.

[0112] Regarding the heat flux sensor whose arrangement angle θ1 satisfies the condition -15°<θ1<0°, the relational expressions (5) and (6) are not satisfied, and the output sensitivity of the heat flux sensor is poor. This may be because the heat flux sensor is affected by the air injected from the lubrication nozzle and by the air curtain generated by the rotation of the inner ring spacer 6i. Since the sensor is arranged in front of the lubrication nozzle in the rotation direction of the inner ring spacer 6i, its output sensitivity is reduced.

[0113] The heat flux sensor, which requires an angle θ2 of 0° < θ2 < 15°, does not satisfy the relationships (5) and (6), and its output sensitivity is poor. This may be because the output sensitivity is reduced by the air ejected from the lubrication nozzle.

[0114] Regarding the heat flux sensor whose arrangement angle θ3 satisfies the condition -90°<θ3<-15°, it satisfies relational expression (5), but not relational expression (6), and the output sensitivity of the heat flux sensor is slightly worse. This may be because the heat flux sensor is more than 15° away from the lubrication nozzle and is arranged on the front side of the inner ring spacer 6i in the rotation direction, so the heat flux sensor is slightly affected by the air ejected from the lubrication nozzle, and its output sensitivity becomes slightly sluggish.

[0115] Regarding the heat flux sensor with an arrangement angle θ4 satisfying the condition 15°<θ4<90°, it satisfies the relational expressions (5) and (6) and has a high output sensitivity. This is likely because the heat flux sensor is less likely to be affected by the air jet from the lubrication nozzle and the air curtain generated by the rotation of the inner ring spacer 6i, and is able to detect heat generation in the bearing earlier (with higher sensitivity) when an anomaly occurs.

[0116] Regarding the heat flux sensor whose center is defined as the reference angle β1, which satisfies -90°<β1<90°, it satisfies the relational expressions (5) and (6), and its output sensitivity is the highest. This is likely because the heat flux sensor is less susceptible to air influence and is positioned around the exhaust port 6ge where heat tends to be trapped, thus enabling earlier (with higher sensitivity) detection of heat generation in bearing 5b when an anomaly occurs.

[0117] With grease lubrication, no air flows into the vicinity of the heat flux sensor, so the sensor sensitivity will not become sluggish even when the heat flux sensor is placed anywhere in the circumferential direction.

[0118] <Cooling Structure in Outer Ring Spacer>

[0119] As described above, in this embodiment, a cooling structure is provided in the outer ring spacer 6g where the heat flux sensors 11a and 11b are arranged.

[0120] Figure 14 This is a diagram showing an exemplary cooling structure disposed in the outer ring spacer 6g. Figure 15 It is along Figure 14 The cross-sectional view of XV-XV in the diagram.

[0121] like Figure 14 As shown, two cooling medium paths 71 and 72 are provided in the housing 3, and a spiral groove 73 is provided on the outer surface of the outer ring spacer 6g. The spiral groove 73 has one end connected to the cooling medium paths 71 and 72 respectively, and the other end connected to the other of the cooling medium paths 71 and 72. Cooling medium (oil, water, compressed air, etc.) flows into the spiral groove 73 through one of the cooling medium paths 71 and 72, and the cooling medium flowing through the spiral groove 73 is discharged to the other of the cooling medium paths 71 and 72. Therefore, the spiral groove 73 serves as a cooling medium flow channel in the outer ring spacer 6g. Figure 15 As shown, the heat flux sensor 11a is connected to the outside of the outer ring spacer 6g via a wire W.

[0122] The outer ring spacer 6g can be equipped not only with heat flux sensors 11a, 11b and spiral groove 73, but also with a wireless transmitter, a self-generating device and a control device. The wireless transmitter transmits the data obtained by the sensor to the outside, the self-generating device drives the sensor or the wireless transmitter, the control device temporarily stores the data obtained by the sensor, and the control device includes a signal processor for converting the data.

[0123] [Modified arrangement of heat flux sensor]

[0124] Figure 16 This is a diagram illustrating a modified example of the arrangement of the heat flux sensor. In this modified example, as... Figure 16 As shown, protrusions 7a and 7b are added to the outer ring spacer 6g on the fixed side, protruding from their respective axial side surfaces into the gap between the inner and outer rings, and a heat flux sensor 11a can be disposed in one of the protrusions 7a. In this case, although not shown, the heat flux sensor 11b can also be disposed in the other protrusion 7b.

[0125] The heat originates from the portion of the bearing ring on the fixed side of the rolling element that contacts the rolling element. In this example, a heat flux sensor is disposed in the bearing ring on the fixed side, and the high cost of machining the bearing ring on the fixed side is a concern. This problem is solved by disposing the heat flux sensor in the protrusions 7a and 7b of the spacer on the fixed side, and the heat flux sensor can be easily disposed. Since the heat flux sensors 11a and 11b are disposed in the protrusions 7a and 7b, which protrude into the gap between the inner and outer rings, temperature changes inside the bearing during operation can be directly detected.

[0126] The protrusions 7a and 7b can also function as nozzles, discharging lubricating oil for oil-air lubrication into the bearings 5a and 5b. In this case, the heat flux sensor can be installed using existing lubricating oil discharge nozzles. Therefore, for example, the cost can be lower than in the example where a dedicated component for providing the heat flux sensor is used.

[0127] Figure 17 This is a diagram showing another variation of the arrangement of the heat flux sensor. Figure 1 and Figure 2 An example is shown where heat flux sensors 11a and 11b are positioned in the axial direction at the end of the inner surface of the outer ring spacer 6g (near the bearing 5). However, as... Figure 17 As shown, the heat flux sensor 11 can be disposed in the central portion of the inner surface of the outer ring spacer 6g in the axial direction.

[0128] The heat flux sensor can be arranged in housing 3 or front cover (not shown), and the cooling structure, wireless transmitter, self-generating device and control device can be arranged in housing 3 or front cover.

[0129] It should be understood that the embodiments disclosed herein are illustrative and non-limiting in all respects. The scope of the invention is limited by the claims rather than by the description of the embodiments described above, and is intended to be included within the scope of the claims and to have any variations thereof.

[0130] List of reference numerals

[0131] 1. Spindle assembly; 2. Bearing sleeve; 3. Housing; 4. Spindle; 5. Bearings 5a and 5b; 5ga and 5gb outer rings; 5ia and 5ib inner rings; 6. Spacer; 6g outer ring spacer; 6gA inner surface; 6ge discharge port; 6i inner ring spacer; 6iA outer surface; 7a and 7b protrusions; 11a and 11b heat flux sensors; 30. Bearing assembly; 67a and 67b lubricating oil supply paths; 71. Cooling medium path; 73. Spiral groove; P0 rotating axis; Rta and Rtb retainers; Ta and Tb rolling elements; W wire.

Claims

1. A bearing assembly, comprising: A bearing having an inner ring, an outer ring, rolling elements, and a retainer, the bearing rotatably supporting a rotating body about a rotation axis; The spacer includes an inner ring spacer adjacent to the inner ring and an outer ring spacer adjacent to the outer ring; as well as A heat flux sensor is disposed on the inner surface of the outer ring spacer, wherein... The distance from the center of the bearing to the center of the heat flux sensor along the axis of rotation is longer than 0.5 times and shorter than 1 times the dimension of the bearing along the axis of rotation. The outer ring spacer is provided with a discharge port for discharging lubricating oil and gas. The outer ring spacer is provided with a nozzle for spraying the oil and gas. The nozzle is located in the region of the outer ring spacer opposite to the discharge port. The heat flux sensor is positioned within a range that deviates from the direction of relative rotation of the inner ring spacer relative to the outer ring spacer by more than 0 degrees and less than 90 degrees from the direction of relative rotation of the inner ring spacer relative to the outer ring spacer.

2. The bearing device as described in claim 1, characterized in that, In the radial direction of the rotation axis, the distance from the outer surface of the inner ring spacer to the heat flux sensor is equal to or less than 25% of the distance between the inner surface of the inner ring spacer and the outer surface of the outer ring spacer.

3. The bearing device as described in claim 1 or 2, characterized in that, The angle from the center of the discharge port to the center of the heat flux sensor in the circumferential direction of the rotation axis is less than 90°.

4. The bearing device as described in claim 1 or 2, characterized in that, The outer ring spacer is provided with a cooling medium flow channel.

5. The bearing device as described in claim 1 or 2, characterized in that, The rotating body is the spindle of the machine tool.

Images