CN113613815A

CN113613815A - Lubricating oil supply unit and bearing device

Info

Publication number: CN113613815A
Application number: CN202080022435.XA
Authority: CN
Inventors: 桥爪翔平
Original assignee: NTN Corp
Current assignee: NTN Corp
Priority date: 2019-03-19
Filing date: 2020-02-25
Publication date: 2021-11-05
Anticipated expiration: 2040-02-25
Also published as: JP7411347B2; JP2020159547A; KR20210136064A

Abstract

The lubricating oil supply unit (40) and the bearing device (30) include: a tank (42) for containing lubricating oil; a pump (43) that supplies the lubricating oil contained in the oil tank (42) to the bearing (5); heat flux sensors (11a, 11b) mounted in the bearing (5) or on a spacer (6) as a member adjacent to the bearing; and a control device that controls the operation of the pump (43) in accordance with the output of the heat flux sensors (11a, 11 b). The heat flux sensors (11a, 11b) can accurately detect instantaneous and sudden heat generation in the rolling bearing (5), and therefore can evaluate the sign of abnormality based on the detection result and lubricate the bearing (5) at an appropriate timing.

Description

Lubricating oil supply unit and bearing device

Technical Field

The present invention relates to a lubricating oil supply unit that supplies lubricating oil to a bearing device that rotatably supports a main shaft or the like of a machine tool, and a bearing device including the lubricating oil supply unit.

Background

Bearings for machine tool spindles are often used at high speeds and low loads, and angular contact ball bearings are widely used for such bearings. Bearings for machine tool spindles are lubricated by oil-gas (mist) lubrication or grease lubrication. Oil-air lubrication is characterized by being capable of maintaining a stable lubrication state for a long period of time because of the external supply of lubricating oil. Grease lubrication is characterized by being cost effective because of no need for ancillary facilities and piping, and environmentally friendly because of the very small amount of mist generated.

A bearing used in a high speed region, such as a region where a value of dn calculated by multiplying an inner diameter of an inner race by the number of rotations is equal to or greater than one million, such as a spindle of a machining center in a machine tool, should operate in a more stable manner. However, due to various factors described below, the bearing may experience surface roughening or peeling at the bearing raceway surface, or abnormality of the retainer, and thereafter, the temperature of the bearing may excessively rise.

In oil-air lubrication, improper feeding and discharge of lubricating oil (too little or too much oil or insufficient oil discharge)

Deterioration of the grease sealed in the bearing

Entry of coolant, water or foreign bodies into the rolling bearing parts

Oil film break due to excessive preload, i.e. increased contact pressure in the rolling section

In order to prevent the bearing temperature from excessively rising due to the above-described factors, japanese patent laid-open No. 2017-26078 (PTL 1) discloses a technique in which a lubricant feed pump that feeds lubricant to the inside of the bearing in accordance with the temperature value of the bearing lubrication portion measured by a temperature sensor and a noncontact temperature sensor are included in a spacer adjacent to the bearing.

Reference list

Patent document

Patent document 1: japanese patent laid-open publication No. 2017-26078

Disclosure of Invention

Technical problem

Generally, in oil-air lubrication, oil mist is generated by intermittently adding oil from an oil valve to a continuously supplied compressed air in an air feeding path.

When the amount of oil added is insufficient, the friction in the bearing increases, resulting in seizure. On the other hand, when the amount of oil added is too large, the stirring resistance of the oil of the bearing portion increases, resulting in a temperature rise and seizure. Since the range of the appropriate amount of oil is relatively narrow for bearings that support a shaft rotating at high speed, and it is difficult to add the appropriate amount of oil.

Although the manufacturer indicates the recommended conditions for adding the oil amount, the appropriate amount of oil also varies depending on the operating conditions of the machine tool and the like. For example, when a working condition such as a rotation speed, a continuous operation time, a load when a workpiece is worked, or a position of a shaft during working is changed, adding in a uniform amount cannot solve such a change.

The amount of addition in the oil valve (mixing valve) can be adjusted while monitoring the condition of the bearing. However, the oil valve is usually arranged in the air passage at a position relatively distant from the bearing because the oil is cut into fine particles after dripping to be supplied to the bearing, and there is a time difference from dripping of the oil from the oil valve to spreading of the oil on the bearing. Therefore, adding oil after the change of state of the bearing is too late for lubrication.

The present invention has been made to solve the above-described problems, and an object thereof is to provide a lubricating oil supply unit that supplies lubricating oil to bearings at appropriate timings, and a bearing device including the lubricating oil supply unit.

Technical scheme for solving technical problem

The present disclosure relates to a lubricating oil supply unit. The lubricating oil supply unit includes: the lubricating oil supplying device includes an accommodating portion accommodating lubricating oil, a supplying portion supplying the lubricating oil in the accommodating portion to a bearing, a heat flux sensor provided in the bearing or a member adjacent to the bearing, and a controller controlling an operation of the supplying portion in accordance with an output of the heat flux sensor.

Preferably, the controller drives the supply portion to supply the lubricating oil to the bearing when the rate of change in heat flux detected by the heat flux sensor exceeds a judgment standard value.

Preferably, the controller drives the supply portion to supply the lubricating oil to the bearing when the heat flux detected by the heat flux sensor exceeds a judgment standard value.

Although the member adjacent to the bearing may be a member other than the spacer (a shoulder of the housing, a cover, or a spring bracket), preferably, the member adjacent to the bearing is a spacer, and the accommodating portion, the supplying portion, and the controller are disposed in the spacer.

More preferably, the spacer is provided with a lubricating oil passage for oil-air lubrication separately from the lubricating oil lubrication in the accommodating portion. When the controller detects that the lubricating oil supplied to the bearing by the oil-air lubrication is insufficient based on the output from the heat flux sensor, the controller drives the supply portion to add the lubricating oil.

Preferably, the bearing is lubricated with grease, and when the controller detects that the base oil of the grease is insufficient based on the output from the heat flux sensor, the controller controls the supply portion to add the lubricating oil.

Preferably, the lubricating oil supply unit further includes a load sensor that detects a preload or an external load applied to the bearing. The controller controls the operation of the supply portion according to the output of the load sensor.

In a further aspect, the present disclosure relates to a bearing arrangement comprising a lubrication oil supply unit and a bearing as described in any of the sections above.

Effects of the invention

According to this structure, the heat flux sensor is used to measure the temperature change inside the bearing when the bearing is in operation. Therefore, the indication of abnormality of the bearing can be sensed without delay, and the lubricating oil can be supplied to the bearing at an appropriate timing.

Drawings

Fig. 1 is a cross-sectional view showing a schematic configuration of a spindle device in a first embodiment.

Fig. 2 is a cross-sectional view schematically showing the configuration of a bearing device 30 incorporated in a spindle device according to a first embodiment.

Fig. 3 is a diagram schematically showing a cross section III of the spacer in fig. 2.

Fig. 4 is a diagram schematically showing a cross section IV of the spacer in fig. 2.

Fig. 5 is an enlarged cross-sectional view of the lubricating oil supply unit 40.

Fig. 6 is a block diagram showing the configuration of the lubricating oil supply unit 40 in the first embodiment.

Fig. 7 is a diagram showing the structure of the tester.

Fig. 8 is a graph showing test conditions in the performance evaluation test.

Fig. 9 is a graph showing various sensor outputs of the bearing device in the performance evaluation test.

Fig. 10 is a graph showing the relationship among heat flux, temperature, and rotation speed in the acceleration and deceleration tests.

Fig. 11 is an enlarged view of the abscissa in the section from t1 to t2 in fig. 10.

Fig. 12 is a graph showing the amount of oil supplied to the bearing versus temperature and friction loss.

Fig. 13 is a diagram showing the relationship between the oil pump unit for oil-air lubrication and the lubricating oil supply unit in the spacer.

Fig. 14 is a diagram showing a case where an abnormality in the bearing due to exhaustion of the lubricating oil is simulated in the test.

Fig. 15 is a graph showing the relationship among heat flux, temperature, and rotational speed in a test in which an abnormal condition of a bearing due to exhaustion of lubricating oil is simulated.

Fig. 16 is a waveform diagram for illustrating the operation of the bearing device in the first embodiment.

Fig. 17 is a waveform diagram for illustrating a state in an evaluation test in which actual bearing seizure is simulated.

Fig. 18 is a flowchart for illustrating control of the supply of lubricating oil by the controller.

Fig. 19 is a waveform diagram of an output signal of the heat flux sensor when spike-like noise is not generated.

Fig. 20 is a waveform diagram of an output signal of the heat flux sensor when spike-like noise is generated.

Fig. 21 is an enlarged view showing a section around the spike noise in fig. 20.

Fig. 22 is a flowchart illustrating control to which an upper limit value is applied.

Fig. 23 is a schematic cross-sectional view showing the configuration of a bearing device in the second embodiment.

Fig. 24 is a diagram schematically showing a cross section XXIV of the spacer in fig. 23.

Fig. 25 is a diagram schematically showing a cross section XXV of the spacer in fig. 23.

Fig. 26 is a block diagram showing the configuration of the lubricating oil supply unit 40 in the second embodiment.

Fig. 27 is a diagram illustrating a first exemplary arrangement of heat flux sensors.

Fig. 28 is a diagram illustrating a second exemplary arrangement of heat flux sensors.

Fig. 29 is a diagram showing a third exemplary arrangement of heat flux sensors.

Fig. 30 is a diagram illustrating a fourth exemplary arrangement of heat flux sensors.

Fig. 31 is a diagram illustrating a fifth exemplary arrangement of heat flux sensors.

Fig. 32 is a diagram illustrating a sixth exemplary arrangement of heat flux sensors.

Fig. 33 is a cross-sectional view of cross-section XXXIII of fig. 32.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the same or corresponding elements have the same reference numerals, and the description thereof will not be repeated.

[ first embodiment ]

Fig. 1 is a cross-sectional view showing a schematic configuration of a spindle device in a first embodiment. Fig. 2 is a cross-sectional view schematically showing the configuration of a bearing device 30 incorporated in a spindle device according to a first embodiment.

The spindle device 1 shown in fig. 1 is used as a spindle device of a built-in motor type for a machine tool, for example. In this case, the motor 50 is assembled at one end of the spindle 4 supported by the spindle device 1 serving as a spindle of a machine tool, and a not-illustrated cutting tool such as an end mill is attached to the other end.

The spindle device 1 comprises

bearings

5a, 5b, a spacer 106 arranged adjacent to the

bearings

5a, 5b,

heat flux sensors

11a, 11b, a motor 50 and a bearing 16 arranged at the rear of the motor. The main shaft 4 is rotatably supported by a plurality of

bearings

5a, 5b provided in the housing 3 embedded inside the bearing housing 2. The bearing 5a has an inner race 5ia, an outer race 5ga, rolling elements Ta, and a retainer Rta. The bearing 5b includes an inner race 5ib, an outer race 5gb, rolling elements Tb, and a retainer Rtb. The spacer 6 includes an inner race spacer 6i and an outer race spacer 6 g.

Heat flux sensors

11a, 11b that measure heat flux are fixed to the inner surface 6gA of the outer-ring spacer 6g, and are opposed to the outer surface 6iA of the inner-ring spacer 6 i. Heat flux refers to the amount of heat per unit time passing through a unit area.

The inner ring 5ia of the bearing 5a and the inner ring 5ib of the bearing 5b, which are distant in the axial direction, are fitted to the main shaft 4 by interference fit (press-fit). The inner ring spacer 6i is arranged between the inner rings 5ia, 5ib, and the outer ring spacer 6g is arranged between the outer rings 5ga, 5 gb.

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 5 ga. The intervals between the rolling elements Ta are held by the holders Rta. The bearing 5b is a rolling bearing in which a plurality of rolling elements Tb are arranged between the inner ring 5ib and the outer ring 5 gb. The intervals between the rolling elements Tb are held by the holders Rtb.

Angular contact ball bearings, deep groove ball bearings, or tapered roller bearings may be employed as the

bearings

5a and 5 b. Angular contact ball bearings are included in the bearing arrangement 30 shown in fig. 2, wherein two

bearings

5a, 5b are provided in a back-to-back Double Bearing (DB) arrangement.

Although a structure in which two

bearings

5a, 5b support the main shaft 4 is illustrated and described, as shown by way of example in fig. 27 later, a structure in which two or more bearings support the main shaft 4, including four bearings, is also applicable.

The single-row rolling bearing 16 is a cylindrical roller bearing. The

bearings

5a, 5b, which are angular contact ball bearings, support radial and axial loads applied to the main shaft device 1. The single-row bearing 16, which is a cylindrical roller bearing, supports a radial load applied to the spindle device 1 serving as a spindle of a machine tool.

A cooling medium flow passage is provided in the housing 3. The

bearings

5a, 5b can be cooled by feeding a cooling medium between the housing 3 and the bearing housing 2.

The lubricating

oil supply paths

67a, 67b provided for cooling and lubricating the

bearings

5a, 5b will be described later. The lubricating oil is sprayed from the discharge orifice (nozzle) in the state of oil gas or oil mist together with air carrying the lubricating oil. For simplicity, fig. 1 does not show the lubrication oil supply path. When grease-lubricated bearings are employed as the

bearings

5a, 5b, as shown in fig. 23 later, a lubricating oil supply path need not be provided.

A motor 50 that drives the main shaft 4 is arranged at an intermediate position in the axial direction between the bearings 16 of the single row and the

bearings

5a, 5b of the multiple rows arranged in the space 22 between the main shaft 4 and the bearing housing 2. The rotor 14 of the motor 50 is fixed to a cylindrical member 15 fitted to the outer periphery of the main shaft 4, and the stator 13 of the motor 50 is fixed to the inner peripheral portion of the bearing housing 2.

Fig. 1 does not show a cooling medium flow passage for cooling the motor 50.

Heat flux sensors

11a and 11b that measure heat flux are mounted on the spindle device 1. In the example shown in fig. 1 and 2, the

heat flux sensors

11a, 11b have one surface fixed to the inner surface 6gA of the outer-ring spacer 6g and the other surface opposite to the outer surface 6iA of the inner-ring spacer 6 i. Heat flux sensor 11a is arranged in the vicinity of bearing 5a, and heat flux sensor 11b is arranged in the vicinity of bearing 5 b.

The heat flux sensor is a sensor that converts heat flux into an electric signal based on the Seebeck (Seebeck) effect, and generates an output voltage from a slight temperature difference between the front side and the rear side of the sensor. Such heat flux sensors are more sensitive than temperature sensors such as non-contact temperature sensors or thermocouples and can track the heat changes inside the bearing in time with the rotation speed changes. The rotation speed is synonymous with the number of rotations per unit time.

In an attempt to measure the temperatures of the inner rings 5ia, 5ib, the outer rings 5ga, 5gb, and the spacer 6 to detect the signs of seizure of the

bearings

5a, 5b, although there is sudden heat generation, the signs may not be detected at an early stage due to a delay in temperature rise. In this case, sudden heat generation can be quickly detected by using the

heat flux sensors

11a, 11b because the heat flux starts to change earlier than the temperature.

The bearing arrangement 30 of fig. 2 will be described in further detail. Fig. 3 is a schematic view schematically showing a cross section III of the spacer in fig. 2. Fig. 4 is a schematic view schematically showing a cross section IV of the spacer in fig. 2. Fig. 5 is an enlarged cross-sectional view of one of the lubricating oil supply units 40.

Referring to fig. 2 to 5, the spacer 6 is disposed between the bearing 5a and the bearing 5 b. The spacer 6 includes an inner race spacer 6i and an outer race spacer 6 g. The inner-race spacer 6i is similar in construction to a general spacer. The outer-ring spacer 6g is provided with lubricating

oil supply paths

67a and 67b for oil-air lubrication at an upper portion thereof, and is provided with an air discharge port 68 at a lower portion thereof. The lubricating oil supply unit 40 is accommodated in the outer-ring spacer 6 g.

The lubricating oil supply unit 40 includes: a case 47, the case 47 being disposed in a housing space provided in the outer-ring spacer 6g, the electric circuit 41, the oil tank 42, the pump 43, the

nozzles

44a, 44b, and a cover 46 covering the housing space.

The lubricating oil stored in the oil tank 42 is of the same type as that used for oil-air lubrication.

As shown in fig. 2, 3 and 5, the circuit 41 is disposed in the case 47. As shown in fig. 2, 4 and 5, the oil tank 42 is disposed in the case 47. In the case 47, the electric circuit 41 and the oil tank 42 are arranged in a housing space provided on the inner peripheral side of the outer ring spacer 6 g.

A suction pipe and a nozzle 44b connected to the oil tank 42 are connected to the pump 43 for supplying the lubricating oil from the pump 43 to the inside of the bearing 5 b. In the oil-air lubrication, the tip of the nozzle 44b is arranged beside the oil-air injection port. Due to the injection of the oil gas, the lubricating oil discharged from the tip end of the nozzle 44b is supplied to the inside of the bearing. The inner diameter size of the nozzle hole in the nozzle 44b is appropriately set according to the relationship between the surface tension derived from the viscosity of the lubricating oil and the discharge amount.

Although not shown, a pump similar to the pump 43 that supplies lubricating oil to the inside of the bearing 5a is also provided separately for the nozzle 44 a. Lubricating oil may be supplied from the pump 43 to both

nozzles

44a, 44 b.

With respect to the positions of the

nozzles

44a and 44b in fig. 2, the distance from the center of the rotation axis and the positional relationship in the direction of the rotation axis are schematically shown. As shown in fig. 3 and 4, the outlets of the

nozzles

44a, 44b are arranged beside the oil and gas injection port.

As shown in fig. 3, a heat flux sensor 11a is provided in the inner peripheral surface of the outer ring spacer 6 g. Although not shown, a line for sending the detection signal from the heat flux sensor 11a to the circuit 41 is provided. As shown in fig. 4, a heat flux sensor 11b is provided in the inner peripheral surface of the outer ring spacer 6 g. Although not shown, a line for sending a detection signal from the heat flux sensor 11b to the circuit 41 is provided. Regarding the positions of the

heat flux sensors

11a and 44b in fig. 2, the distance from the center of the rotation axis and the positional relationship in the direction along the rotation axis are schematically shown. The

heat flux sensors

11a, 11b are arranged around the air discharge opening 68. According to experiments conducted by the inventors, it was confirmed that the

heat flux sensors

11a, 11b arranged around the air discharge port 68 react more sensitively than sensors arranged in other ways. Therefore, this arrangement is preferable.

Fig. 6 is a block diagram showing the configuration of the lubricating oil supply unit 40 in the first embodiment. Referring to fig. 6, the lubricant supplying unit 40 includes an electric circuit 41, a tank 42, a pump 43, and

nozzles

44a, 44 b. The appliance circuit 41 includes a power supply 51, a controller 53 and a drive device 52 that drives the pump.

The lubricating oil supply unit 40 supplies lubricating oil to the bearings 5 according to the outputs from the

heat flux sensors

11a, 11 b. The lubricating oil supply unit 40 further receives outputs from the temperature sensor 56, the vibration sensor 57, the rotation sensor 58, and the load sensor 59. A load sensor 59 is provided, for example, in the gap between the bearing and the spacer, in order to sense the preload and the external load applied to the bearing 5. The controller 53 may be configured to supply lubricating oil to the bearings 5 in addition to or instead of the outputs from the

heat flux sensors

11a, 11b, at a time that takes into account at least one of the outputs from these sensors. For example, in a machine tool, the preload applied to the bearing 5 may vary due to a variation in external force applied by a workpiece, or due to a variation in heat generated by high-speed operation or centrifugal force. As the preload increases, the amount of heat generated increases due to the frictional force caused by the oil film break. Therefore, when the load sensor 59 detects an increase in the preload, it is also effective to supply the lubricating oil to the bearings. Supplying lubrication oil to the bearings is also effective when an external load is directly sensed.

The power supply 51 is connected to a controller 53 (microcomputer). The driving device 52 receives power supply from the power source 51 and drives the pump 43 under the control of the controller 53. The drive device 52 is a circuit for operating the pump 43, such as a micro pump.

The electric power can be supplied to the power source 51 from outside the casing through a not-shown line or a power generation device 154 as shown in fig. 24 to 26 later.

The pump 43 is controlled by a controller 53 with a drive 52 interposed therebetween. The pump 43 sucks out the lubricating oil in the oil tank 42 and supplies the sucked-out lubricating oil to the inside of the bearing 5 through the

nozzles

44a and 44 b.

< Performance evaluation test >

The bearing device according to the embodiment of the present invention was incorporated into a tester simulating a spindle of a machine tool, and the state detection performance of the bearing device was evaluated.

Fig. 7 is a schematic diagram showing the structure of the tester. As shown in fig. 7, the tester has a main shaft 501 rotatably supported by a housing 506 with the aforementioned bearing device interposed therebetween. The drive motor 512 is coupled with one axial end of the main shaft 501 to rotationally drive the main shaft 501 about its axial center. The inner ring 507 and the outer ring 508 are fixed to the main shaft 501 and the housing 506 by an inner ring press-fit jig 513 and an outer ring press-fit jig 514, respectively.

The housing 506 has a double-layered structure of an inner housing 506a and an outer housing 506b, and a cooling medium flow passage 515 is provided between the inner housing 506a and the outer housing 506 b. The inner housing 506a is provided with an oil and gas supply path 516. The oil and gas supply path 516 communicates with an oil and gas supply port 517 in the outer ring spacer 504. The oil air supplied to the oil air supply port 517 is discharged from the discharge hole of the protrusion 504b, which also functions as a nozzle, and is injected to the inclined surface 507b of the inner ring 507 to lubricate the rolling bearing 502. In the inner housing 506a, an oil gas exhaust groove 518 is provided near a portion where each rolling bearing 502 is provided, and an oil gas exhaust path 519 which opens from the oil gas exhaust groove 518 to the atmosphere is provided.

Fig. 8 is a graph showing test conditions in the performance evaluation test. Referring to fig. 8, a super high speed angular contact ball bearing (HSE type manufactured by NTN corporation) incorporating ceramic balls was used as a test bearing. The dimensions of the bearing were Φ 70 × Φ 110 × 20 (equivalent to 5S-2LA-HSE 014). A fixed position preload (installation preload of 750N) was employed as the preload method. The rotation speed varies in the range of 0 to 16000 revolutions per minute. Oil-gas lubrication is adopted as a lubricating method, the oil inlet amount is set to be 0.03mL/10min, ISO VG32 is adopted as lubricating oil, and the flow rate of lubricating gas is set to be 30 NL/min. The bearing sleeve is cooled in a manner synchronized with room temperature, while the shaft is oriented horizontally.

< test results >

Fig. 9 is a graph showing various sensor outputs of the bearing device in the performance evaluation test. Each sensor was confirmed to be operating normally from a low speed region to a super high speed region (dn value of 1.12 million).

When the lubrication timing of the rolling bearing is determined by the controller 53 in fig. 6, it is preferable to check whether each sensor is operating normally. The applicant has confirmed in experiments that when the rotational speed of the bearing device is gradually increased from the low speed region to the ultra high speed region while each sensor is normally operated, the temperature, the rotational speed and the heat flux are gradually transited in a prescribed relationship. The controller 53 automatically determines that each sensor is operating normally based on the performance evaluation test, for example, at the time of initial diagnosis before starting operation, so that the determination result regarding the lubrication timing of the rolling bearing can be used more objectively.

Fig. 10 is a graph showing the relationship among heat flux, temperature, and rotation speed in the acceleration and deceleration tests. Fig. 11 is an enlarged view of the abscissa of the segment from t1 to t2 in fig. 10.

As shown in fig. 10, the sensor output from the heat flux sensor is more responsive to the increase and decrease in the rotation speed than the sensor output from the temperature sensor, and the sensing accuracy of the abnormal sign of the rolling bearing can be improved. The timing at which the output of the heat flux sensor starts to increase and decrease is substantially synchronized with the timing at which the rotational speed starts to increase and decrease.

< investigation on the amount and timing of lubrication of bearing >

Fig. 12 is a graph showing the relationship of the amount of oil supplied to the bearing with temperature and friction loss. The ordinate in fig. 12 represents the temperature and the friction loss, and the abscissa represents the amount of lubricating oil. In the region a, the friction loss L between the rolling elements and the bearing ring decreases with increasing amount of lubricating oil, and therefore the temperature T also decreases. In contrast, in the region C, as the amount of lubricating oil increases, the stirring resistance of the lubricating oil increases, the friction loss L increases, and the temperature T increases. In the region E where the amount of lubricating oil is large, and the lubricating oil itself takes away heat generated in the working machine to cool the working machine. Thereafter, the lubricating oil is discharged to the outside. Therefore, the larger the amount of lubricating oil, the lower the temperature T. However, excessive lubricating oil causes an increase in stirring resistance and a large friction loss L.

In high-speed rotation exceeding 10000 revolutions per minute like in a machine tool, a large power source is required in the regions C to E where friction loss is large, and it is not practical to use the machine tool in the regions C to E. Therefore, for bearings that rotate at high speed and are used for a rotating shaft of a machine tool or the like, the amount of lubricating oil in region B, in which the temperature reaches a relatively lowest value, is optimal between region a and region C.

The amount of lubricating oil at which the temperature reaches a relatively minimum is generally constant. In certain cases of machine tools, such as high-speed rotation, high rigidity (high load exerted on the bearings), or environmental adaptation (small oil volume), constant supply may not be able to solve the situation. In this case, the amount of lubricating oil in the bearing is constantly changing, and therefore, lubrication based on monitoring of the bearing temperature causes the oil to be exhausted when the temperature rises, and the raceway surfaces of the bearing inner and outer rings are damaged. In the bearing device in the present embodiment, the heat flux sensor senses the heat generated by the increase in frictional resistance due to the decrease in the amount of lubricating oil at the raceway surface at an early stage, and the amount of lubricating oil is optimally adjusted by adding lubricating oil without delay before the occurrence of damage to the raceway surface.

The lubricant is added at the point when the heat flux starts to increase due to insufficient lubricant. By repeating this process, the service life of the bearing can be reliably extended without the occurrence of insufficient amount of lubricating oil in the bearing.

Fig. 13 is a diagram showing the relationship between the oil pump unit for oil-air lubrication and the lubricating oil supply unit in the spacer. Referring to fig. 13, in the oil-air lubrication system, high-pressure air supplied via a solenoid valve 101 and lubricating oil supplied from an oil pump unit 103 are mixed in a mixing valve 102, and the mixture is sent to a passage 67 in a spacer through a passage 107. The oil pump unit 103 feeds the lubricating oil to the mixing valve 102 at a constant interval at the timing set by the timer 104.

When the lubricating oil passes through the air passage 105, the lubricating oil is cut into fine particles and supplied to the bearings. However, the necessary amount of lubricating oil increases or decreases depending on the type of work and the location of the work.

In oil-air lubrication, the range of the appropriate amount of oil is relatively narrow for bearings that support a shaft rotating at high speed, and it is difficult to add the appropriate amount of oil. For example, the amount of addition in the mixing valve 102 may be adjusted while monitoring the condition of the bearing. However, the mixing valve 102 is typically disposed at a location of the air passage 105 relatively far from the bearing, and there is a time difference between dropping oil from the oil valve until the oil spreads on the bearing. Therefore, adding oil after the state of the bearing changes is too late for lubrication.

Then, in the first embodiment, when the heat flux detected by the heat flux sensor starts to increase due to shortage of the lubricating oil lubricated with the oil gas alone, the lubricating oil supply unit 40 additionally supplies the lubricating oil to the bearings. Since a proper amount of lubricating oil is constantly present in the bearing, the machine tool or the like can be operated with less frictional loss while maintaining the service life of the bearing.

In order to sense the sign in the case where the rolling bearing is abnormal, a bearing abnormality simulation test is performed.

Fig. 14 is a diagram showing a case where an abnormality in the bearing due to exhaustion of the lubricating oil is simulated in the test. Referring to fig. 14, a super high speed angular contact ball bearing (HSE type manufactured by NTN corporation) incorporating ceramic balls was used as a test bearing. The dimensions of the bearing were Φ 70 × Φ 110 × 20 (equivalent to 5S-2LA-HSE 014). A fixed position preload (installation preload of 750N) was employed as the preload method. The rotation speed was set to a constant speed of 18000 revolutions per minute. The bearing sleeve is cooled in a manner synchronized with room temperature, while the shaft is oriented horizontally.

In this simulation test, the tester of fig. 7 was also used, as used in the performance evaluation test and the acceleration and deceleration test. In the present simulation test, by introducing a very small amount of lubricating oil into the rolling bearing only at the time of assembling the main shaft, a situation was created in which an abnormality due to exhaustion of lubricating oil could occur in the bearing under test. This is set so that when the drive motor 512 (fig. 7) is overloaded due to an abnormality in the bearing under test, the limiter is activated and the tester automatically stops.

< results of simulation test >

Fig. 15 is a graph showing the relationship among heat flux, temperature, and rotational speed in a test in which an abnormal situation in a bearing due to exhaustion of lubricating oil is simulated. The abscissa represents the operation period (seconds). The upper side shows the heat flux Q, the inner ring temperature t (i), the outer ring temperature t (g), and the casing temperature t (h), while the lower side shows the rotation speed N (number of rotations per minute).

Based on the relationship between the heat capacity and the heat radiation, the relationship of the inner ring temperature t (i) > the outer ring temperature t (g) > the case temperature t (h) is maintained.

After time 525 (seconds), the rotational speed N starts to decrease due to the detection of the overload of the drive motor 512 (fig. 7). Before the time 525 (sec), there was almost no change in each temperature, and it was found that it was difficult to detect the sign of abnormality based on the temperature. Based on the test results, it is expected that an increase in the output value of the heat flux Q is observed earlier than an increase in the inner ring temperature t (i), etc., and the heat flux Q is effective in early detection of the sign of occurrence of abnormality of the rolling bearing.

Fig. 16 is a waveform diagram for explaining the operation of the bearing device in the first embodiment. Fig. 16 shows a waveform when the lubricating oil is supplied from the lubricating oil supply unit 40 in the present embodiment, which is superimposed on the waveform in the simulation experiment shown in fig. 15.

The abscissa represents the operation period (seconds). The upper region shows the heat flux Q and the rate of change D of the heat flux, and the heat flux Qx and the rate of change Dx when supplying lubricating oil are shown superimposed thereon. The lower region shows the rotational speed N (number of revolutions per minute).

Unless the supply of lubricating oil is resumed, after time 525 (seconds), the rotational speed N starts to decrease due to the induction of overload of the motor due to damage of the bearing.

To avoid damage to the bearings, the oil should be added before time 525 (seconds). Since the temperature increases after time 525 (sec) as shown in fig. 15, the addition of the lubricating oil based on the temperature increase is too late. In contrast, the heat flux Q detected by the heat flux sensor increases from about time 523 (seconds). Therefore, the lubricant is preferably added upon sensing an increase in the output of the heat flux sensor. The threshold Qth, on which the increase is determined, should be set with a certain margin in consideration of the noise in the steady state. However, since individual variations of the machine of the set bearing or the operation conditions set by the user are different, it is difficult to set the threshold Qth for a slight increase.

In contrast, in the experiments conducted by the inventors, it was found that by calculating the rate of change D (the amount of change per unit time) of the heat flux Q, the signs of damage to the bearing could be found early. It has also been found that a relatively uniform threshold value can be used in practice with respect to the rate of change D in output even if the individual machine in which the bearing is set varies or the operating conditions set by the user vary. Therefore, it is more preferable to add the lubricating oil when the rate of change D of the output from the heat flux sensor exceeds the threshold value Dth.

The rate of change D is a parameter calculated from the time derivative of the heat flux Q detected by the heat flux sensor. By using the parameters derived from the time derivative of the heat flux Q, instantaneous and sudden heating can be accurately detected.

By dropping the lubricating oil from the lubricating oil supply unit 40 at a point of time (about 525 seconds) when the heat flux Q exceeds the threshold Qth or at a point of time (about 524 seconds) when the heat flux change rate D exceeds the threshold Dth, the bearing is not damaged. Therefore, in the waveform of fig. 16, as shown in the figure, it is also possible to continue the steady operation at the rotation speed Nx after the time 525 (sec) without imposing a limitation on the motor.

Since the determination criterion value Dth of the change rate D is different for each spindle of the machine tool or the output from the heat flux sensor, Dth is set to various values, for example, Dth is 0.1 and Dth is 10. The judgment criterion value Dth may be determined in an evaluation test simulating actual bearing seizure.

Fig. 17 is a waveform diagram for illustrating a state in an evaluation test in which actual bearing seizure is simulated. In the results of the evaluation test shown in fig. 17, during the time 20 seconds to the time 30 seconds of the operation period, the heat flux increases, and the rotation speed starts to decrease to protect the motor. In an example of obtaining such a result, the judgment criterion value Dth may be determined in accordance with the following expression.

Dth＝(Q2’-Q1’)/(t2’-t1’)

Fig. 18 is a flowchart for illustrating control of the supply of lubricating oil by the controller. The processing in this flowchart is called from the main routine every certain period of time (for example, every 2 to 3 msec). Referring to fig. 6 and 18, the controller 53 obtains determination values from the

heat flux sensors

11a and 11b in step S1. Although the heat flux Q may be employed as the judgment value, the rate of change D of the heat flux is preferable. When the heat flux Q is employed, for example, the judgment value may be obtained by checking the detection values from the

heat flux sensors

11a, 11b with a predetermined map stored in a memory in the controller. When the rate of change D of the heat flux is employed, the determination value may be obtained by dividing the difference between the previous heat flux Q and the present heat flux Q by the time interval, for example.

Continuously in step S2, the controller 53 determines whether the determination value is larger than the determination criterion value. In an example of adopting the heat flux Q as the determination value, the threshold value Qth shown in fig. 16 is adopted as the determination criterion value. In an example of adopting the rate of change D of the heat flux as the determination value, the threshold value Dth shown in fig. 16 is adopted as the determination criterion value.

The judgment criterion value may be determined, for example, in the tests described with reference to FIGS. 7 to 11. For example, in fig. 9, the heat flux Q increases with an increase in the rotation speed N. Therefore, the determination criterion value Qth may be set to a value calculated by multiplying the heat flux Q corresponding to the maximum rotation speed N under the operating condition of the spindle device by the safety factor.

The rotation speed N and the heat flux Q are correlated with each other, for example, based on either or both of the experiment and the simulation shown in fig. 9. The determination criterion value Qth may be predetermined for each rotation speed N based on the relationship. Therefore, the determination criterion value Qth may be determined in advance for each rotation speed N, the rotation speed N may be read from the rotation sensor 58, and the determination criterion value Qth corresponding to the read rotation speed N may be applied.

For example, based on the change in the heat flux from Q1 to Q2 during the period between time t1 and time t2 in fig. 11, the determination criterion value Dth may be determined according to the following expression:

Dth＝M×(Q2-Q1)/(t2-t1)

wherein M represents a safety factor. Since the safety factor M in the expression is different for each spindle of the machine tool, M is set to different values, such as M1 and M100.

Since it is known that the value of the rate of change D of heat flux at the time of abnormality occurrence of the bearing is significantly larger than that at the time of increase of the rotation speed N, a uniform threshold value Dth can be used for the rate of change D regardless of the change of the rotation speed N.

When the condition that the judgment value > judgment criterion value is satisfied (YES in S2), the controller 53 drives the pump 43 to supply lubricating oil to the bearing 5 for a certain period of time in step S3, and controls to return to the main routine in step S4. When the condition that the judgment value > judgment criterion value is not satisfied (NO in S2), control is returned to the main routine in step S4, and the processing in step S3 is skipped.

The temperature or vibration may gradually increase due to the progress of the surface roughening of the raceway surface, although the rate of change does not vary much. In this case, the use can be continued by increasing the amount of the lubricating oil. Therefore, the process in step S2 may be modified to perform the process in step S3 not only when the rate of change D of the output from the heat flux sensor exceeds the threshold value, but also when the temperature or vibration exceeds the threshold value.

Depending on the measurement environment, spike-like noise may be generated in the output from the heat flux sensor under the influence of electrical noise of a motor driven in or around the facility or vibration noise in the facility. When spike-like noise is introduced, it may be difficult to accurately determine an abnormality (seizure or a large amount of heat generation) in the bearing from the rate of change D of the heat flux. In order to solve such noise, it is effective to set an upper limit value for the signal from the heat flux sensor in addition to the above determination.

Fig. 19 is a waveform diagram of an output signal of the heat flux sensor when spike-like noise is not generated. Fig. 20 is a waveform diagram of an output signal of the heat flux sensor when spike-like noise is generated. Fig. 21 is a diagram showing a section around the spike noise in fig. 20 being enlarged.

When spike noise is observed, actually generated spike noise may be measured, the upper limit value Dth' may be set based on the noise observed value, and may be determined within the range of the following expression, which is similar to the determination of abnormality (seizure or a large amount of heat generation) of the bearing.

Dth’＝(Q2”-Q1”)/(t2”-t1”)

Fig. 22 is a flowchart illustrating control to which an upper limit value is applied. The processing in this flowchart is called from the main routine every certain period of time (for example, every 2 to 3 msec). Referring to fig. 6 and 22, the controller 53 obtains determination values from the

heat flux sensors

11a and 11b in step S11. In this case, the rate of change D of the heat flux is adopted as the judgment value. The rate of change D of the heat flux can be obtained by, for example, dividing the difference between the previous heat flux Q and the present heat flux Q by the time interval.

Continuously, in step S12, the controller 53 determines whether the determination value is larger than the determination criterion value Dth shown in fig. 16 and smaller than the upper limit value Dth' determined as shown in fig. 21.

For example, based on the change in the heat flux from Q1 to Q2 during the period between time t1 and time t2 in fig. 11, the determination criterion value Dth may be determined according to the following equation:

Dth＝M×(Q2-Q1)/(t2-t1)

When the condition of the upper limit value > judgment criterion value is satisfied (YES in S12), the controller 53 drives the pump 43 to supply lubricating oil to the bearing 5 for a certain period of time in step S3, and the control returns to the main routine in step S14. When the condition of the upper limit value > judgment criterion value is not satisfied (NO in S12), the controller 53 skips the process in step S13, and the control returns to the main routine in step S14.

As described above, the lubricating oil supply unit 40 and the bearing device 30 in the first embodiment include: a tank 42, which is a "containing portion" that contains lubricating oil; a pump 43, which is a "supply portion" that supplies the lubricating oil contained in the oil tank 42 to the bearings 5;

heat flux sensors

11a, 11b provided in the bearing 5 or the spacer 6, which are members adjacent to the bearing; and a controller 53 that controls the operation of the pump 43 according to the output of the

heat flux sensors

11a, 11 b. The

heat flux sensors

11a and 11b accurately detect instantaneous and sudden heat generation of the rolling bearing 5, and can determine an abnormal sign of the rolling bearing based on the result of the detection and can lubricate the bearing at an appropriate timing.

Preferably, the controller 53 drives the pump 43 as the supply portion to supply the lubricating oil to the rolling bearing 5 when the rate of change D of the heat flux detected by the

heat flux sensors

11a, 11b exceeds the determination criterion value Dth and does not exceed the upper limit value Dth'. When the heat flux change rate D detected by the

heat flux sensors

11a and 11b does not exceed the determination criterion value Dth or exceeds the upper limit value Dth', the controller 53 does not drive the pump 43 as the supply portion.

Preferably, the determination may be made based on the heat flux Q instead of the rate of change D. In this case, only the upper limit value Qth' should be determined. When the heat flux Q detected by the

heat flux sensors

11a, 11b exceeds the determination criterion value Qth and does not exceed the upper limit value Qth', the controller 53 drives the pump 43 to supply the lubricating oil to the bearings 5. When the heat flux Q detected by the

heat flux sensors

11a, 11b does not exceed the judgment criterion value Qth or exceeds the upper limit value Qth', the controller 53 does not drive the pump 43.

By providing the upper limit value Dth 'or the upper limit value Qth' in this way, it is possible to reduce the malfunction of the pump 43.

[ second embodiment ]

In the first embodiment, an example is described in which lubricating oil from a lubricating oil supply unit other than oil gas is added to a bearing. In the second embodiment, an example is described in which, for a grease-lubricated bearing, lubricating oil from a lubricating oil supply unit is added to the bearing. Since the configuration of the spindle device into which the bearing device in fig. 1 is incorporated is also common in the second embodiment, the description will not be repeated.

Fig. 23 is a schematic cross-sectional view showing the configuration of a bearing device in the second embodiment. Fig. 24 is a schematic view schematically showing a cross section XXIV of the spacer in fig. 23. Fig. 25 is a diagram schematically showing a cross section XXV of the spacer in fig. 23.

Referring to fig. 23 to 25, in the second embodiment, the spacer 106 is arranged between the bearing 5a and the bearing 5 b. The structures of the bearing 5a and the bearing 5b are the same as those in the first embodiment.

Spacers 106 include an inner race spacer 106i and an outer race spacer 106 g. The inner-race spacer 106i is configured similarly to a general spacer. The lubricating oil supply unit 140 is incorporated in the outer-ring spacer 106 g.

The lubricating oil supply unit 140 includes: a case 47, the case 47 being disposed in a housing space provided in the outer-ring spacer 106g, the electric circuit 141, the generator 154, the oil tank 42, the pump 43, the

nozzles

44a, 44b, and the cover 46 covering the housing space.

The same type of lubricating oil as the base oil of the grease sealed in the bearing 5 is stored in the oil tank 42.

As shown in fig. 24, the circuit 141 is disposed in the case 47. As shown in fig. 25, the oil tank 42 is disposed in the case 47. In the case 47, the circuit 141 and the oil tank 42 are arranged in a housing space provided on the inner peripheral side of the outer ring spacer 106 g.

A suction pipe and a nozzle 44b connected to the oil tank 42 are connected to the pump 43 for supplying the lubricating oil from the pump 43 to the inside of the bearing 5 b. The tip of the nozzle 44b extends to the inside of the bearing 5b (a position adjacent to the rolling element Tb, such as a position between a bearing ring on the fixed side of the bearing 5b and a bearing ring on the rotating side thereof). The inner diameter of the nozzle hole in the nozzle 44b is appropriately sized according to the relationship between the surface tension derived from the viscosity of the base oil and the discharge amount.

nozzles

44a, 44 b.

Fig. 26 is a block diagram showing the configuration of the lubricating oil supply unit 140 in the second embodiment. Referring to fig. 26, the lubricant supplying unit 140 includes a circuit 141, a tank 42, a pump 43, and

nozzles

44a, 44 b. The electric circuit 141 includes a power source 151, a controller 53, a driving device 52 that drives the pump, and a power storage device 155.

The lubricating oil supply unit 140 supplies lubricating oil to the bearings 5 according to the outputs from the

heat flux sensors

11a, 11 b. The lubricating oil supply unit 140 may be configured to further receive outputs from the temperature sensor 56, the vibration sensor 57, and the rotation sensor 58, and supply lubricating oil to the bearing 5 at a timing that takes these outputs into account.

In the structure shown in fig. 26, compared with fig. 6, a generator 154 and an electric power storage device 155 are added. The generator 154 and the power storage device 155 are included in the circuit 141 arranged in the housing portion of the outer ring spacer. The generator 154 is coupled with a power source 151, and the power source 151 is connected with a controller 53 (microcomputer) and a power storage device 155. The driving device 52 receives power supply from the power storage device 155, and drives the pump 43 under the control of the controller 53. The drive device 52 is a circuit for operating the pump 43, such as a micro pump.

For example, a thermoelectric element (Peltier) element) that generates electric power due to the seebeck effect may be employed as the generator 154 of the lubricating oil supply unit 140. Specifically, as shown in fig. 24 and 25, the generator 154 includes a heat sink 154g connected to the outer-ring spacer 106g, a heat sink 154i disposed opposite to the inner-ring spacer 6i, and a thermoelectric element 154d disposed between the two heat sinks.

As shown in fig. 23 to 25, when a rolling bearing is employed as the bearing 5, the temperatures of the inner rings 5ia, 5ib and the outer rings 5ga, 5gb increase due to frictional heat against the rolling elements Ta, Tb. Since the outer rings 5ga and 5gb are usually incorporated in the housing of the instrument, heat is radiated by heat conduction. Therefore, a temperature difference occurs between the inner rings 5ia, 5ib and the outer rings 5ga, 5gb (the temperature of the inner rings 5ia, 5ib is higher than that of the outer rings 5ga, 5 gb). This temperature is conducted to the

heat sinks

154g, 154 i. A temperature difference is generated between the opposite end surfaces of the thermoelectric element 154d disposed between the

heat sinks

154g and 154 i. Accordingly, the thermoelectric element 154d may generate electricity due to the seebeck effect.

The intimate contact surface of the heat sink 154g on the outer race side enhances the heat conduction (heat radiation) effect by intimate contact by being the same as the inner diameter curvature of the accommodation portion provided in the outer race spacer 106 g. The heat sink 154i on the inner ring side does not contact the inner ring spacer 6 i. The surface area of the inner circumferential surface of the heat sink 154i on the inner ring side is preferably large, if possible. In order to improve the thermal conductivity (and intimate contact), it is preferable to coat thermal radiation grease or the like between the inner peripheral surface of the outer ring spacer 106g and the outer peripheral surface of the heat sink 154g, between the heat sink 154g and the thermoelectric element 154d, and between the thermoelectric element 154d and the heat sink 154i on the inner ring side. Heat radiating grease is generally composed mainly of silicon. The heat sinks 154g, 154i are made of a metal having high thermal conductivity. Although examples of the metal include gold, silver, and copper, copper is generally employed from the viewpoint of cost. A copper alloy mainly composed of copper may be used. Sintering, forging or casting are working methods which are advantageous in terms of costs.

By including such a generator 154, it is not necessary to supply electric power to the lubricating oil supply unit 140 from the outside. Therefore, it is not necessary to connect a power supply line for supplying electric power from the outside to the spindle of the work machine.

The electric charge generated (generated) by the generator 154 is stored in the electric power storage device 155. The power storage device 155 includes an energy storage battery or a capacitor. An electric double layer capacitor (condenser) is preferably used as the capacitor.

nozzles

44a and 44 b.

As described with reference to fig. 16 and 18, the controller 53 controls the pump 43 based on the output from the

heat flux sensors

11a, 11b, which is also the case in the second embodiment.

Like the lubricating oil supply unit 40 and the bearing device 30 in the first embodiment, the lubricating oil supply unit 140 and the bearing device 130 shown in the second embodiment can accurately detect instantaneous and sudden heat generation in the rolling bearing 5 with the

heat flux sensors

11a, 11b, determine an indication of abnormality of the rolling bearing based on the detection results, and lubricate the bearing at an appropriate timing.

Since the lubricating oil supply unit 140 and the bearing device 130 further include the power supply generator 154, external power supply feeding is not necessary, and wiring or the like can be reduced.

[ variation of arrangement of Heat flux sensor ]

In the first and second embodiments, it is described that the main shaft 4 is supported by two

bearings

5a, 5b as the bearing device 30. Without being limited to such a configuration, the lubricating oil supply unit shown in the first or second embodiment may also be applied to a bearing device in which at least two bearings support the main shaft 4.

Fig. 27 is a diagram illustrating a first exemplary arrangement of heat flux sensors. Fig. 27 shows the structure of a bearing device 30A in which four bearings support a main shaft. The bearing arrangement 30A additionally comprises

spacers

31c, 31d and

bearings

5c, 5d outside both

bearings

5a, 5b of the bearing arrangement 30 in fig. 1. A heat flux sensor 11c is arranged at the inner surface 31gAc of the outer ring spacer 31gc of the additional spacer 31c, and a heat flux sensor 11d is arranged at the inner surface 31gAd of the outer ring spacer 31gd of the additional spacer 31 d. Since other structures are the same as those in fig. 1, a description will not be provided. Although the heat flux sensors are provided for all the bearings in fig. 27, a bearing more likely to be abnormal may be selected from a plurality of bearings in view of design or experience, and the heat flux sensors may be arranged therein.

Fig. 28 is a diagram illustrating a second exemplary arrangement of heat flux sensors. As shown in fig. 28,

projections

7a, 7b projecting from respective axial side surfaces into a gap between the inner ring and the outer ring are added in the outer ring spacer 6g on the fixed side, and

heat flux sensors

11a, 11b may be provided in the

projections

7a, 7b, respectively. Heat originates from the part where the bearing ring of the stationary side of the rolling elements is in contact with the rolling elements. In the example in which the heat flux sensor is provided in the bearing ring on the fixing side, the high cost of machining the bearing ring on the fixing side is a concern. By providing heat flux sensors in the

protrusions

7a, 7b of the spacer on the fixed side, this problem is solved and the heat flux sensors can be easily arranged. Since the

heat flux sensors

11a, 11b are provided in the

protrusions

7a and 7b that protrude into the gap between the inner ring and the outer ring, it is possible to directly detect a temperature change inside the bearing during operation.

The

projections

7a and 7b may also function as nozzles for discharging lubricating oil for oil-air lubrication to the rolling

bearings

5a, 5 b. In this case, the heat flux sensor may be provided by using an existing nozzle that discharges the lubricant oil. Thus, for example, the cost may be lower than in the example where a dedicated component for providing the heat flux sensor is provided.

Fig. 29 is a diagram showing a third exemplary arrangement of heat flux sensors. Although fig. 1 to 4 show an example in which the

heat flux sensors

11a and 11b are provided near the bearing 5 in the outer-ring spacer 6g on the fixed side, the heat flux sensors 11 may be provided around the center in the axial direction of the inner peripheral surface of the outer-ring spacer 6g, as shown in fig. 29.

When the heat flux sensor is disposed near the bearing 5 of the outer-ring spacer 6g on the fixed side as shown in fig. 1 to 4, the heat fluxes flowing between the inner ring and the outer ring of the bearing 5 can be detected separately with high sensitivity. When a heat flux sensor is provided around the center in the axial direction of the outer-ring spacer 6g on the fixed side, for example, as shown in fig. 29, a single heat flux sensor can detect the heat flux flowing between the inner ring and the outer ring of the bearing 5.

Fig. 30 is a diagram illustrating a fourth exemplary arrangement of heat flux sensors. As shown in fig. 30, the heat flux sensor 11a may be provided on the inner peripheral surface of the outer ring 5 ga. In this case, the heat flux sensor 11b may be similarly provided on the inner circumferential surface of the outer ring 5gb, although not shown.

Fig. 31 is a diagram illustrating a fifth exemplary arrangement of heat flux sensors. As shown in fig. 31, a heat flux sensor 11a may be provided on the inner peripheral surface of the outer ring 5ga, and a processing circuit 162 that processes an output signal from the heat flux sensor 11a may be disposed beside it. The heat flux sensor 11a is connected to the processing circuit 162 by line 161 and the signal processed by the processing circuit 162 is transmitted to another control circuit or the like by line 163. The processing circuit 162 performs, for example, processing for amplifying a signal or processing for a/D conversion.

In this case, when the size of the bearing is small, a space for arranging the heat flux sensor 11a and the processing circuit 162 becomes a problem. As shown in fig. 31, the inner circumferential surface of the outer ring 5ga of the bearing, in which the heat flux sensor 11a and the processing circuit 162 are arranged, may extend in the axial direction, and the inner ring 5ia opposed thereto may also similarly extend in the axial direction, as necessary. In this case, the rolling elements Ta are preferably arranged toward the side where the heat flux sensor 10a is not arranged, with respect to the center position in the axial direction of the outer ring 5 ga.

The configuration in fig. 30 or 31 can be applied to the configuration in fig. 27. In the description with reference to fig. 27, the heat flux sensors are arranged in the inner surfaces 6gA, 31gAc, and 31gAd of the non-rotating outer ring spacers 6g, 31gc, and 31 gd. However, the following structure is possible: the heat flux sensor is arranged in a rolling bearing ring (outer ring) on the non-rotating side of the bearings 5a to 5d so as to be opposed to the rotating ring (inner ring).

Fig. 32 is a diagram illustrating a sixth exemplary arrangement of heat flux sensors. Fig. 33 is a cross-sectional view of cross-section XXXIII of fig. 32. When the signal line of the heat flux sensor cannot be drawn from the side surface of the bearing in the axial direction, the exemplary arrangement shown in fig. 32 and 33 may be employed.

In the example shown in fig. 32, two angular contact ball bearings are arranged as double bearings back-to-back. The heat flux sensor 11a is provided on the inner peripheral surface of the outer ring 5ga, and the heat flux sensor 11b is provided on the inner peripheral surface of the outer ring 5 gb. Preferably, the outer ring 5ga and the inner ring 5ia each have an inner peripheral surface in which the heat flux sensor 11a is provided to extend in the axial direction, and the outer ring 5gb and the inner ring 5ib each have an inner peripheral surface in which the heat flux sensor 11b is provided to extend in the axial direction.

Since the heat flux sensor is arranged on the inner circumferential surface of the side where the bearing is arranged in contact with the adjacent bearing, no line can be led out from the side to the outside. Therefore, as shown in fig. 33, a hole 165 passing from the inner circumferential surface to the outer circumferential surface is provided in the outer ring 5gb, and a line 164 for taking a signal from the heat flux sensor 11b is led to the outside of the bearing through the hole 165. Although not shown, a through hole for leading out a similar wiring is also provided in the outer ring 5 ga.

As described above, the bearing device shown in fig. 31 to 33 includes the outer ring 5ga, the inner ring 5ia, the rolling elements Ta, the holder Rta, and the heat flux sensor 10 a. The inner circumferential surface 170 of the outer ring 5ga includes a raceway surface 172 with which the rolling elements Ta are in contact, and a first surface 171 and a second surface 173 positioned so as to sandwich the raceway surface 172 from opposite sides. The heat flux sensor 10a is disposed on the second surface 173 of the inner circumferential surface 170 of the outer ring 5 ga.

The axial width W0 of the bearing is the sum of the width W1 of the first surface 171, the width W2 of the raceway surface 172, and the width W3 of the second surface 173. In order to ensure the space arrangement of the heat flux sensors 10a, the outer ring 5ga is formed such that the width W3 of the second surface 173 is larger than the width W1 of the first surface 171.

This configuration can also be expressed as follows. Specifically, the axial width W0 of the bearing is the axial width W5 of the rolling elements Ta, and the sum of the width W4 of the first portion and the width W6 of the second portion other than the former. In order to secure a space for arranging the heat flux sensor 10a, the outer ring 5ga is formed such that the width W6 of the second portion is larger than the width W4 of the first portion excluding the rolling elements Ta.

Preferably, the processing circuit 162 that processes the signal from the heat flux sensor 10a is disposed on the second surface 173 of the inner peripheral surface 170 of the outer ring 5ga together with the heat flux sensor 10 a.

Preferably, a hole 165 passing from the inner peripheral surface to the outer peripheral surface is provided in the outer ring 5gb for passage of a line for taking out a signal from the heat flux sensor 10 b. Preferably, a similar hole, not shown, is provided in the outer ring 5ga from the inner peripheral surface to the outer peripheral surface for passage of a line for taking out a signal from the heat flux sensor 10 a.

Although the configuration in which the outer ring of the bearing is fixed and the inner ring rotates is described above by way of example, the present invention may also be applied to an example in which the outer ring rotates and the inner ring is fixed by attaching a heat flux sensor to the side where the ring is fixed.

Although the horizontal spindle 4 is illustrated in the above description, the bearing device in the present embodiment is also applicable to a machine tool including the vertical spindle 4.

Although the heat flux sensor is used for controlling lubrication with lubricating oil in the above description, it may be used for detecting an abnormal condition in the bearing device. For example, despite the lubrication of the lube oil supply unit, damage to the bearings may already occur when the heat flux is further increased. In this case, the controller 53 in fig. 6 may be used as an "abnormality determination unit". When the heat flux Q or the rate of change D of the heat flux exceeds the threshold value larger than Qth or Dth shown in fig. 16, the abnormality determination unit determines that an abnormality has occurred in the bearing. The abnormality determination unit may determine abnormality of the rolling bearing based on a relationship between the rotation speed N and the heat flux Q following the rotation speed. The abnormality determination unit may monitor the relationship between the rotation speed and the heat flux continuously or for a certain period of time, and when the relationship between the two becomes inconsistent, it may be determined that an abnormality has occurred in the rolling bearing. For example, when the heat flux abruptly changes with the rotation speed unchanged, the abnormality determining unit determines that an abnormality has occurred in the rolling bearing. For example, when the heat flux does not follow the change in the rotation speed while the change in the rotation speed is detected, the abnormality determining unit determines that an abnormality has occurred in the rolling bearing. Instantaneous and sudden heat generation in the rolling bearing can thus be accurately detected, and it can be determined whether an abnormality has occurred in the rolling bearing based on the detection result. When the rolling bearing is determined to be abnormal, the bearing device may be controlled to stop its rotation. In this case, the controller 53 may give a notification about the abnormality through the warning indicator, or provide a stop signal to stop the rotation of the motor, instead of adding the lubricating oil in step S3 in the flowchart of fig. 18. In this case, the abnormality determining unit may be arranged at another position than in the spacer of the bearing.

It is to be understood that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims rather than the description of the embodiments described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

List of reference numerals

1, a main shaft device; 2, bearing sleeves; 3. 506a housing; 4. 501, a main shaft; 5. 5a, 5b, 5c, 5d, 16, 502 bearings; 5ga, 5gb, 508 outer lane; 5ia, 5ib, 507 inner ring; 6. 31c, 31d, 106 spacers; 6g, 31gc, 31gd, 106g, 504 outer ring spacers; 6gA, 31gAc, 31gAd inner surface; 6i, 106i inner race spacer; 6iA outer surface; 7a, 7b, 504b protrusions; 11. 11a, 11b, 11c, 11d heat flux sensors; 13 a stator; 14 a rotor; 15 a cylindrical member; 22 space; 30. 30A, 130 bearing arrangement; 40. 140 a lubricating oil supply unit; 41. 141, a circuit; 42 an oil tank; 43 pump; 44a, 44b nozzles; 46 a cover; 47 shell; 50 electric motors; 51. 151 power supply; 52 a drive device; 53 a controller; 56 a temperature sensor; 57 a vibration sensor; 58 a rotation sensor; 67. 107 channels; 67a, 67b oil channels; 68 an air exhaust port; 101, a solenoid valve; 102 a mixing valve; 103 an oil pump unit; 104 a timer; 105 an air channel; 154 a generator; 154d thermoelectric elements; 154g, 154i heat sink; 155 a power storage device; 161. 163, 164 lines; 162 a processing circuit; 165 holes; 170 inner peripheral surface; 171 a first surface; 172 raceway surfaces; 173 second surface; 506a inner housing; 506b an outer shell; 507b inclined plane; 512 driving motor; 513 inner ring press-fit clamp; 514 outer ring press-fit clamp; 515 a flow channel; 516 an oil and gas supply path; 517 oil and gas supply port; 518 oil gas exhaust tank; 519 oil gas exhaust gas path; rta, Rtb holder; ta, Tb rolling elements.

Claims

1. A lube oil supply unit comprising:

an accommodating portion in which lubricating oil is accommodated;

a supply portion that supplies the lubricating oil accommodated in the accommodation portion to a bearing;

a heat flux sensor disposed in the bearing or in an adjacent component of the bearing; and

a controller that controls operation of the supply portion according to an output of the heat flux sensor.

2. Lubricating oil supply unit according to claim 1, characterised in that

The controller drives the supply portion to supply the lubricating oil to the bearing when a rate of change in the heat flux detected by the heat flux sensor exceeds a criterion value.

3. Lubricating oil supply unit according to claim 1, characterised in that

The controller drives the supply portion to supply the lubricating oil to the bearing when the heat flux detected by the heat flux sensor exceeds a judgment standard value.

4. Lubricating oil supply unit according to any of claims 1 to 3, characterised in that

The adjacent said member of the bearing is a spacer; and

the accommodating portion, the supplying portion, and the controller are disposed in the spacer.

5. Lubricating oil supply unit according to claim 4, characterised in that

The spacer is provided with a lubricating oil passage for oil-air lubrication separately from the lubricating oil lubrication in the accommodating portion, and

when the controller detects that the lubricating oil supplied to the bearing by the oil-air lubrication is insufficient based on the output from the heat flux sensor, the controller drives the supply portion to add the lubricating oil.

6. Lubricating oil supply unit according to any of claims 1 to 4, characterised in that

The bearing is lubricated with grease, and

when the controller detects that the base oil of the grease is insufficient based on the output from the heat flux sensor, the controller controls the supply portion to add lubricating oil.

7. The lubrication oil supply unit according to claim 1, further comprising a load sensor that detects a preload or an external load applied to the bearing, wherein

The controller controls the operation of the supply portion according to the output of the load sensor.

8. A bearing device, comprising:

the lubrication oil supply unit according to any one of claims 1-7, and

the bearing is provided.