CN113056620B - Bearing device - Google Patents

Abstract

A bearing device (2) comprising: bearings (5 a, 5 b) comprising inner rings (5 ia, 5 ib), outer rings (5 ga, 5 gb) and rolling elements (Ta, tb); a spacer (6) arranged adjacent to the bearings (5 a, 5 b) on the main shaft (4) supported by the bearings (5 a, 5 b), the spacer including an inner ring spacer (6 i) and an outer ring spacer (6 g); and a sensor unit (9) disposed in the inner-race spacer (6 i) or the outer-race spacer (6 g). The sensor unit (9) includes a first sensor and a second sensor. The first sensor is a heat flux sensor (10), and the second sensor includes at least any one of a vibration sensor (11), a temperature sensor (12), and a load sensor (13). The bearing device (2) further includes an abnormality diagnosis processing device (15) that diagnoses an abnormality of the bearing based on outputs from the first and second sensors and the rotation speed (N) of the main shaft (4).

Description

Bearing device

technical field

The present invention relates to a bearing device, and particularly relates to a bearing device having a function of diagnosing symptoms such as burning of a bearing used in a main shaft of a machine tool.

Background technique

In the spindle device of the machine tool, it is required to detect the sign of the abnormality of the bearing before the occurrence of the abnormality in order to prevent the abnormality of the bearing.

In the diagnostic device for diagnosing the state of components described in Japanese Patent Laid-Open No. 2017-90318 (Patent Document 1), the part where the thermal buffer is positioned between two heat flux sensors (also called heat flow sensors) is Fixed to the measurement target. The diagnostic means diagnoses the proper preload state of the bearing based on the signals from the two heat flux sensors and determines the state of assembly.

In the bearing device with sensors described in Japanese Patent Laid-Open No. 2004-169756 (Patent Document 2), the sensor unit is provided in the outer ring spacer. The sensor unit includes at least one of a vibration sensor, a temperature sensor and a rotational speed sensor. An abnormal state of the bearing is detected based on a sensor signal from at least one of a vibration sensor, a temperature sensor, and a rotational speed sensor.

The apparatus for diagnosing an abnormality of a rotor described in Japanese Patent Laid-Open Publication No. 2004-93185 (Patent Document 3) detects fluctuations caused by the rotor, the temperature of the rotor, and the rotational speed of the rotor, and performs a diagnosis based on these information. Abnormal diagnosis.

reference list

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2017-90318

Patent Document 2: Japanese Patent Laid-Open No. 2004-169756

Patent Document 3: Japanese Patent Laid-Open No. 2004-93185

Patent Document 4: Japanese Patent Laid-Open No. 2014-071085

Contents of the invention

technical problem

With the heat flux sensor described in Japanese Patent Laid-Open No. 2017-90318 (Patent Document 1), it may be difficult to determine the proper assembly state of the bearing. For example, cooling medium flow passages are generally provided on the outer peripheral surface of the housing of the spindle device of the machine tool, so that the spindle device is cooled by the flow of the cooling medium. When the sensor unit is fixed to the outer cylindrical surface of the housing in the vicinity of the cooling medium flow passage, the heat flux sensor may not accurately measure heat generated due to a difference in rotational speed or preload of the running bearing.

Furthermore, the sensor unit described in Japanese Patent Laid-Open No. 2017-90318 (Patent Document 1) is a structure in which a thermal buffer is located between the first heat flux sensor and the second heat flux sensor, and a heat sink is placed between The second heat flux sensor is arranged on the side facing away from the housing. In this structure, there are a large number of components, a space for arranging the sensor unit is required, and two heat flux sensors are included in a single sensor unit, which leads to an increase in the cost of the device.

The cooling medium flow channel is usually arranged in the housing of the spindle arrangement of the machine tool. The bearings are cooled by the flow of cooling medium in the housing. In an application for diagnosis of a bearing of a spindle device of a machine tool, a sensor unit fixed to an outer cylindrical surface of a housing may have an influence on measurement sensitivity, and correct measurement may not be performed.

Metal parts such as housings, spacers, spindles have a large heat capacity. Therefore, in Japanese Patent Laid-Open No. 2004-169756 (Patent Document 2), since it takes time to measure the temperature change of the target member when abnormal heat generation occurs in the bearing, the temperature sensor attached to the outer ring spacer It is difficult to quickly detect an abnormal state.

The vibration sensor of Japanese Patent Application Laid-Open No. 2004-93185 (Patent Document 3) detects abnormal vibration caused by damage to a bearing. Since the vibration is caused by the damage of the bearing, it is difficult for the vibration sensor in Patent Document 3 to detect signs of abnormality at an early stage.

The present invention was made to solve the above problems, and an object of the present invention is to provide a bearing device having an abnormality diagnosis function capable of rapidly and accurately detecting symptoms such as burning of a bearing used in a main shaft of a machine tool.

Technical solutions adopted to solve technical problems

The present disclosure relates to a bearing device. The bearing device includes: a first bearing, the above-mentioned first bearing includes an inner ring, an outer ring and rolling elements; a spacer, the above-mentioned spacer is arranged adjacent to the first bearing on the main shaft supported by the first bearing, and the above-mentioned spacer includes an inner ring spacer and an outer ring spacer; a first sensor, said first sensor being arranged in the first bearing or the spacer; and a second sensor. The first sensor is a heat flux sensor. The second sensor includes at least any one of a heat flux sensor, a vibration sensor, a temperature sensor, and a load sensor. The bearing device further includes an abnormality diagnosis device that determines abnormality based on the output from the first sensor and the output from the second sensor.

Preferably, the second sensor includes at least any one of a vibration sensor, a temperature sensor and a load sensor. The abnormality diagnosis device diagnoses an abnormality of the bearing based on outputs from the first sensor and the second sensor and the rotation speed of the main shaft.

More preferably, the abnormality diagnosis device includes a threshold value storage unit and a diagnosis processing unit that performs diagnosis processing on signals from a sensor unit including the first sensor and the second sensor based on the threshold value stored in the threshold value storage unit.

Further preferably, the threshold storage unit stores thresholds corresponding to a plurality of rotational speeds for each of the first sensor and the second sensor.

Further preferably, when the output from the first sensor does not exceed the threshold corresponding to the first sensor stored in the threshold storage unit, the diagnostic processing unit does not perform abnormality diagnosis based on the output from the second sensor, and when the output from the first sensor When the output of the first sensor exceeds the threshold value corresponding to the first sensor, the diagnosis processing unit performs abnormality diagnosis based on the output from the second sensor.

Further preferably, the threshold storage unit stores coefficients for weighting outputs from the first sensor and the second sensor according to the rotation speed.

More preferably, when the sum of values calculated by multiplying the output from the first sensor and the output from the second sensor by respective corresponding coefficients exceeds a predetermined threshold, the abnormality diagnosis means provides abnormality diagnosis according to the magnitude of the sum the result of.

Preferably, the bearing device further includes a second bearing, and the above-mentioned second bearing supports the main shaft together with the first bearing. The first sensor is a first heat flux sensor provided corresponding to the first bearing. The second sensor is a second heat flux sensor provided corresponding to the second bearing. The abnormality diagnosing device includes an abnormality judging unit that judges the difference between the first bearing and the second heat flux sensor based on the difference between the outputs from the first heat flux sensor and the second heat flux sensor or the difference between the output change rates. Abnormal occurrence in the bearing part of the bearing is detected.

More preferably, the first bearing and the second bearing respectively support first and second parts of the main shaft remote from each other.

Further preferably, the spacer is arranged between the first bearing and the second bearing. The first heat flux sensor and the second heat flux sensor are arranged in the spacer. The first heat flux sensor is arranged in the spacer closer to the first bearing than the second heat flux sensor is arranged in the spacer. The second heat flux sensor is arranged in the spacer closer to the second bearing than the first heat flux sensor is arranged in the spacer.

More preferably, the abnormality judging unit judges in which of the first bearing and the second bearing the abnormality has occurred based on the sign of the difference.

More preferably, the bearing arrangement includes N heat flux sensors, where N is a natural number equal to or greater than three. The first heat flux sensor and the second heat flux sensor are two of the N heat flux sensors. Between the previous time point and the next time point after a prescribed period of time has elapsed, when the output from a sensor group other than the first heat flux sensor among the N heat flux sensors changes by more than the first threshold, and the amount of change in the output from the first heat flux sensor is smaller than a second threshold equal to or smaller than the first threshold, the abnormality judging unit judges that the first heat flux sensor has failed.

In another aspect, the present disclosure relates to a spindle arrangement comprising any bearing arrangement as described above.

Invention effect

According to the present disclosure, it is possible to quickly and accurately detect symptoms such as burnout of a bearing used in a main shaft of a machine tool.

Description of drawings

FIG. 1 is a cross-sectional view of a schematic structure of a spindle device including an abnormality diagnosis device.

FIG. 2 is a block diagram showing details of the sensor unit 9 and the abnormality diagnosis processing device 15 .

FIG. 3 is a flowchart for explaining abnormality diagnosis processing performed by the diagnosis processing unit 16 .

FIG. 4 shows a schematic diagram of a list of sensor output thresholds for each rotational speed stored in the threshold storage section 17 .

FIG. 5 is a diagram showing an example where a plurality of thresholds are set.

FIG. 6 is a waveform diagram showing exemplary changes over time of each sensor output and abnormality diagnosis level (E).

FIG. 7 is a diagram showing a list of weighting coefficients for each rotational speed stored in the threshold storage unit 17 .

8 is a block diagram of an abnormality diagnosis processing device according to a second embodiment.

FIG. 9 is a flowchart for explaining processing performed by the diagnosis processing unit 16A in the abnormality diagnosis processing device 15A.

Fig. 10 is a cross-sectional view showing a schematic structure of a spindle device in a third embodiment.

FIG. 11 is an enlarged view of a main part on the left side in FIG. 10 .

FIG. 12 is a waveform diagram showing exemplary outputs from two heat flux sensors when the bearing is normal.

FIG. 13 is a waveform diagram showing exemplary outputs from two heat flux sensors when the bearing is abnormal.

FIG. 14 is a block diagram of an abnormality judging unit 125 that judges abnormality of a bearing based on outputs from two heat flux sensors employed in the third embodiment.

FIG. 15 is a block diagram showing the configuration of an abnormality judging unit 125A which is an improvement of FIG. 14 .

FIG. 16 is a diagram showing a configuration of a bearing device 130A in which four bearings support a main shaft in a fourth embodiment.

FIG. 17 is a block diagram of an abnormality judging unit 125B that judges abnormality of a bearing based on outputs from two heat flux sensors employed in the fourth embodiment.

FIG. 18 is a diagram showing another configuration of an abnormality judging unit.

FIG. 19 is a flowchart for explaining processing executed by the processor 202 of FIG. 18 .

FIG. 20 is a flowchart for explaining the process of judging whether a sensor has failed.

Detailed ways

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same or corresponding elements in the following drawings have the same reference numerals, and descriptions thereof will not be repeated.

[first embodiment]

FIG. 1 is a cross-sectional view of a schematic structure of a spindle device including an abnormality diagnosis device. The spindle device 1 is applied to, for example, a built-in motor spindle device of a machine tool. In this case, a motor (not shown) is assembled on one end side of the spindle 4 supported by the spindle device 1, and a cutting tool (not shown) such as an end mill is attached to the other end. The main shaft 4 is rotatably supported by a plurality of bearings 5 a, 5 b provided in the housing 3 embedded in the bearing housing 7 .

The bearing device 2 according to the first embodiment has bearings 5 a , 5 b , a spacer 6 , a sensor unit 9 and an abnormality diagnosis processing device 15 . The bearing 5a has an inner ring 5ia, an outer ring 5ga, a rolling element Ta, and a holder Rta. The bearing 5b includes an inner ring 5ib, an outer ring 5gb, a rolling element Tb, and a retainer Rtb. The spacer 6 is arranged adjacent to the bearings 5a, 5b on the main shaft 4 supported by the bearings 5a, 5b. The bearing 5a supports the main shaft 4 at a position Pa, and the bearing 5b supports the main shaft 4 at a position Pb. The position Pa and the position Pb are separated from each other by the size of the spacer 6 . The spacer 6 includes an inner ring spacer 6i and an outer ring spacer 6g.

The inner ring 5ia of the bearing 5a and the inner ring 5ib of the bearing 5b separated 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, 5gb.

The bearing 5a is a rolling bearing in which a plurality of rolling elements Ta are arranged between an inner ring 5ia and an outer ring 5ga. The space between the rolling elements Ta is maintained by the retainer Rta. The bearing 5b is a rolling bearing in which a plurality of rolling elements Tb are arranged between an inner ring 5ib and an outer ring 5gb. The space between the rolling elements Tb is maintained by the retainer Rtb.

Although the structure in which the main shaft 4 is supported by two bearings 5 a and 5 b has been shown and described, a structure in which the main shaft 4 is supported by two or more bearings may also be applied.

FIG. 2 is a block diagram showing details of the sensor unit 9 and the abnormality diagnosis processing device 15 . Referring to FIGS. 1 and 2 , the sensor unit 9 is arranged in the inner ring spacer 6i or the outer ring spacer 6g (the outer ring spacer 6g in FIG. 1 ). The sensor unit 9 includes a first sensor and a second sensor. The first sensor is a heat flux sensor 10 , and the second sensor includes at least any one of a vibration sensor 11 , a temperature sensor 12 and a load sensor 13 . The second sensor may include at least two of a vibration sensor 11 , a temperature sensor 12 and a load sensor 13 . In other words, the sensor unit 9 includes at least one of a vibration sensor 11 , a temperature sensor 12 and a load sensor 13 in addition to the heat flux sensor 10 .

The rotation sensor 14 may be provided in the sensor unit 9 , or a motor-controlled rotation sensor attached to a motor on the spindle may also be used as the rotation sensor 14 .

When the load sensor 13 is a thin film sensor that measures preload, the load sensor 13 may be arranged between the outer ring spacer 6g and the outer ring 5ga, as shown at position 9c in FIG. 1 . For example, a thin film sensor described in Japanese Patent Laid-Open No. 2014-071085 can be used as such a thin film sensor. The abnormality diagnosis processing device 15 performs abnormality diagnosis of the bearing based on the outputs of the first sensor and the second sensor and the rotation speed N of the main shaft 4 .

The bearing arrangement 2 comprises two angular contact ball bearings as bearings 5a, 5b. An outer ring spacer 6g and an inner ring spacer 6i are inserted between the bearings 5a, 5b to apply preload. In the bearing device 2, the sensor unit 9 is fixed near the bearings 5a, 5b that generate heat and vibration, for example, in the outer ring spacer 6g.

The abnormality diagnosis processing device 15 is fixed to the outer ring spacer 6g, for example. The abnormality diagnosis processing means 15 processes the sensor signal SS from the sensor unit 9 and provides a judgment result JR.

By arranging the heat flux sensor 10 near the heat source of the bearing (the contact portion between the inner ring, the outer ring and the rolling elements), the heat generation state of the bearings 5a, 5b can be quickly detected. In order to accurately determine whether the heating is normal or abnormal, the abnormality diagnosis processing device 15 uses a signal from at least one of the vibration sensor 11 , the temperature sensor 12 , and the load sensor 13 to perform abnormality diagnosis. In the spindle device 1 used under various conditions, it is difficult to judge abnormality or estimate the cause of the abnormality based only on the signal from the heat flux sensor 10 . However, by knowing the state of the spindle device 1 using other sensors, it is possible to more accurately diagnose the abnormality or estimate the cause of the abnormality more accurately.

The abnormality diagnosis processing means 15 executes a function of performing abnormality diagnosis based on sensor signals and providing a judgment result JR. By arranging the abnormality diagnosis processing device 15 in the spacer 6 and close to the sensor unit 9, it is possible to reduce the influence of electromagnetic noise and improve the accuracy of measurement.

Preferably, as shown in FIG. 2 , the abnormality diagnosis processing device 15 includes a threshold value storage unit 17 and a diagnosis processing unit 16, and the above-mentioned diagnosis processing unit 16 executes on the sensor signal SS from the sensor unit 9 based on the threshold value stored in the threshold value storage unit 17. Diagnostic processing.

FIG. 3 is a flowchart for explaining abnormality diagnosis processing performed by the diagnosis processing unit 16 . First, in steps S1 , S2 , the diagnostic processing unit 16 acquires a sensor signal from the heat flux sensor 10 and acquires a sensor signal from the rotation sensor 14 . In steps S3 to S5 , the diagnosis processing unit 16 acquires a sensor signal from at least one of the vibration sensor 11 , the temperature sensor 12 , and the load sensor 13 .

The threshold value for each sensor output corresponding to the rotational speed is stored in the threshold value storage unit 17 in advance. In step S6 , the diagnosis processing unit 16 compares each sensor signal with a threshold value for each sensor output corresponding to the rotational speed stored in the threshold value storage section 17 , and performs abnormality diagnosis processing.

When each sensor signal does not exceed the corresponding threshold in step S7 (NO in S7), the diagnostic processing unit 16 judges that there is no abnormality, and provides a judgment result JR indicating "OK" in step S8. When the sensor signal from the heat flux sensor 10 exceeds the threshold and other sensors also provide sensor signals exceeding the threshold in step S7 (YES in S7), the diagnosis processing unit 16 judges that there is an abnormality, and provides an indication in step S9. Judgment result of "NG" JR. For example, when the sensor output from the heat flux sensor 10 and at least one other sensor output exceed a preset threshold, the diagnostic processing unit 16 provides "NG" as a judgment result JR.

Some exemplary abnormality diagnosis processing performed in step S6 of FIG. 3 will be described below.

(First Exemplary Abnormality Diagnosis Processing)

FIG. 4 is a diagram showing a list of sensor output thresholds for each rotational speed stored in the threshold storage unit 17 . In the first exemplary abnormality diagnosis processing, when the output from the heat flux sensor 10, the output item from at least one of the vibration sensor 11, the temperature sensor 12, and the load sensor 13 exceeds a threshold value, the abnormality diagnosis processing means 15 provides an indication Abnormal judgment result.

As shown in FIG. 4, the sensor output (H) from the heat flux sensor 10, the time-varying amount (ΔH/Δt) of the sensor output from the heat flux sensor 10, the sensor output from the load sensor 13, Sensor output (L), amount of change with time of sensor output from load sensor 13 (ΔL/Δt), sensor output from temperature sensor 12 (T), amount of change with time of sensor output from temperature sensor 12 ( ΔT/Δt), the sensor output (V) from the vibration sensor 11, and the maximum value of the frequency-analyzed power spectrum of the vibration sensor 11 or the integrated value (Vf) in a specific frequency region are set as sensor output items. As shown in FIG. 4 , the threshold values of these sensor output items are set in advance according to the rotation speed N.

As shown in FIG. 4 , the threshold value storage unit 17 stores a plurality of threshold values corresponding to a plurality of rotational speeds for each of the first sensor (heat flux sensor 10 ) and the second sensor (sensors other than the heat flux sensor).

The heat flux and temperature will be specifically described. For the heat flux sensor 10 as the first sensor, the threshold H1 corresponding to the rotational speed satisfying the condition of N<2000 (1/min) and the rotational speed satisfying the condition of 2000≤N<4000 (1/min) are preset. The corresponding threshold H2, the threshold H3 corresponding to the rotational speed satisfying the condition of 4000≤N<6000 (1/min), the threshold H4 corresponding to the rotational speed satisfying the condition of 6000≤N<8000 (1/min), and the threshold H4 corresponding to the rotational speed satisfying the condition of 8000 Threshold value H5 corresponding to the rotation speed satisfying the condition of ≤N<10000 (1/min) and threshold H6 corresponding to the rotation speed satisfying the condition of N≥10000 (1/min) are stored in the threshold storage unit 17 . For the temperature sensor 12 as one of the second sensors, the threshold value T1 corresponding to the rotating speed satisfying the condition of N<2000 (1/min) and the threshold value T1 corresponding to the rotating speed satisfying the condition of 2000≤N<4000 (1/min) are set in advance. The threshold T2 corresponding to the speed, the threshold T2 corresponding to the speed satisfying the condition of 2000≤N<4000 (1/min) <4585), the threshold T2 corresponding to the speed satisfying the condition of 4000≤N<6000 (1/min) Threshold T3, threshold T4 corresponding to the rotational speed satisfying the condition of 6000≤N<8000 (1/min), threshold T5 corresponding to the rotational speed satisfying the condition of 8000≤N<10000 (1/min), and threshold T5 corresponding to the rotational speed satisfying N≥10000 The threshold value T6 corresponds to the rotation speed under the condition of (1/min), and is stored in the threshold value storage unit 17 .

For example, exemplary three Boolean expressions (Boolean expressions) for abnormality judgment at a rotational speed of 3000 min-1 are shown below as (1) to (3).

(H≥H2 ORΔH/Δt≥Ht2) AND (L≥L2 ORΔL/Δt≥Lt2)...(1)

(H≥H2 ORΔH/Δt≥Ht2) AND (T≥T2 ORΔT/Δt≥Tt2)...(2)

(H≥H2 ORΔH/Δt≥Ht2) AND (V≥V2 OR Vf≥Vf2)...(3)

A plurality of threshold values prestored in the threshold value storage section 17 can be set within the rotation speed region, and results of abnormality judgment such as "normal", "caution" and "warning" can be provided according to the level of abnormality diagnosis. FIG. 5 is a diagram showing an example where a plurality of thresholds are set. FIG. 5 shows a list of thresholds in an example in which thresholds at a rotational speed of 3000 min −1 are classified into two levels. Although not shown, multiple thresholds are similarly set for other rotational speeds. In this case, exemplary Boolean expressions for abnormal judgment are shown in (4) to (10) below.

Exemplary boolean expressions that make "normal" decisions

H<H2L ORΔH/Δt<Ht2L...(4)

Exemplary boolean expression for making "attention" judgment

(H2L≤H<H2H OR Ht2L≤ΔH/Δt<Ht2H) AND (L2L≤L<L2H OR Lt2L≤ΔL/Δt<Lt2H)...(5)

(H2L≤H<H2H OR Ht2L≤ΔH/Δt<Ht2H) AND (T2L≤T<T2H OR Tt2L≤ΔT/Δt<Tt2H)...(6)

(H2L≤H<H2H OR Ht2L≤ΔH/Δt<Ht2H) AND (V2L≤V<V2HOR Vf2L≤Vf<Vf2H)...(7)

Exemplary boolean expression making a "warning" judgment

(H2H≤H OR Ht2H≤ΔH/Δt) AND (L2H≤L OR Lt2H≤ΔL/Δt)...(8)

(H2H≤H OR Ht2H≤ΔH/Δt) AND (T2H≤T OR Tt2H≤ΔT/Δt)...(9)

(H2H≤H OR Ht2H≤ΔH/Δt) AND (V2H≤V OR Vf2H≤Vf)...(10)

The damage state of the bearing or the cause of the damage can be inferred based on a combination of outputs from the heat flux sensor 10 and other sensors, and an inferred result can be provided. For example, when an excessive load is applied from a working tool attached to the front end of the main shaft, the contact pressure of the rolling elements with the inner and outer rings of the bearing increases, thereby generating heat. When an abnormality judgment is made based on the combination of the heat flux sensor 10 and the load sensor 13 , an estimated result indicating "abnormal heat generation due to overload" is provided.

When surface roughening of the raceway surface caused by insufficient lubrication of the bearing or introduction of foreign matter progresses, the raceway surface is damaged and heat is generated. When an abnormality judgment is made based on the combination of the heat flux sensor 10 and the vibration sensor 11, a presumed result indicating "abnormal heat generation due to damage to the rail surface" is provided.

(Second Exemplary Abnormality Diagnosis Processing)

In the first exemplary abnormality diagnosis process, a simple comparison of sensor output with a threshold corresponding to the sensor output is described. Not limited thereto, the sensor output from the heat flux sensor 10 and at least other sensor outputs may be weighted, and when the sum exceeds a preset threshold, a judgment result JR indicating abnormality may be provided. By providing thresholds corresponding to the rotational speed and weighting coefficients, more accurate abnormality diagnosis suitable for the purpose of abnormality diagnosis can be performed.

Specifically, the diagnosis processing unit 16 weights the output from the heat flux sensor 10 and the output from at least one of the vibration sensor 11, the temperature sensor 12, and the load sensor 13, and when the sum of the weighted sensor outputs (abnormality diagnosis When the level (E)) exceeds a preset threshold, the diagnostic processing unit 16 provides a judgment result indicating abnormality.

FIG. 6 is a waveform diagram showing exemplary changes over time of each sensor output and abnormality diagnosis level (E). FIG. 7 is a diagram showing a list of weighting coefficients for each rotational speed stored in the threshold storage unit 17 .

As shown in Figure 7, the output of the heat flux sensor (H), the amount of change with time of the output of the heat flux sensor (ΔH/Δt), the output of the load sensor (L), the change with time of the load sensor The amount (ΔL/Δt), the temperature sensor output (T), the temperature sensor’s change over time (ΔT/Δt), the vibration sensor output (V) and the frequency analysis of the vibration sensor in a specific frequency region of the power spectrum The maximum value or integral value (Vf) is set as a weighting coefficient item. The weighting coefficients of these sensor output items are set in advance according to the rotational speed.

As shown in FIG. 7 , the threshold storage section 17 stores coefficients for weighting outputs from the first sensor (heat flux sensor 10 ) and the second sensor (sensors other than the heat flux sensor) according to the rotational speed.

Specifically, in the heat flux sensor 10 as the first sensor, the threshold storage unit 17 stores the coefficient kh1 corresponding to the rotation speed satisfying the condition of N<2000(min-1), and the coefficient kh1 corresponding to the rotation speed satisfying the condition of 2000≤N<4000(min-1). 1) The coefficient kh2 corresponding to the rotational speed of the condition, the coefficient kh3 corresponding to the rotational speed satisfying the condition of 4000≤N<6000(min-1), and the coefficient corresponding to the rotational speed satisfying the condition of 6000≤N<8000(min-1) The coefficient kh4, the coefficient kh5 corresponding to the rotational speed satisfying the condition of 8000≤N<10000 (min-1), and the coefficient kh6 corresponding to the rotational speed satisfying the condition of N≥10000 (min-1).

The temperature sensor 12 as one of the second sensors will be representatively described. The threshold storage unit 17 stores the coefficient kt1 corresponding to the rotational speed satisfying N<2000 (min-1), the coefficient kt2 corresponding to the rotational speed satisfying 2000≤N<4000 (min-1), and the coefficient kt2 corresponding to the rotational speed satisfying 4000≤N<6000 (min-1). -1) The coefficient kt3 corresponding to the rotational speed, the coefficient kt4 corresponding to the rotational speed satisfying 6000≤N<8000(min-1), the coefficient kt5 corresponding to the rotational speed satisfying 8000≤N<10000(min-1), and the Satisfy the coefficient kt6 corresponding to the rotational speed of N≥10000 (min-1).

For example, a mathematical expression for calculating the sum (E) of weighted sensor outputs in the example where the rotational speed N is lower than 2000 min-1 is shown in Expression (11).

E=H*kh1+ΔH/Δt*kht1+L*kl1+ΔL/Δt*klt1+T*kt1+ΔT/Δt*ktt1+V*kv1+Vf*kvf1...(11)

Preferably, as shown in FIG. 6, when the sum (E) of values calculated by multiplying the output of the first sensor and the output of the second sensor by corresponding coefficients respectively exceeds preset thresholds EtL, EtH, The abnormality diagnosis processing means 15 provides the result of abnormality diagnosis according to the magnitude of the sum (E). For example, when the size of the sum (E) does not exceed the threshold EtL, the abnormal diagnosis processing device can provide normal (Normal) as the result of abnormal diagnosis, and when the sum satisfies the condition EtL≤E<EtH, it can provide attention (Caution) as abnormal The result of the diagnosis, and when the condition E≥EtH is satisfied, a warning (Warning) may be provided as the result of the abnormal diagnosis.

As described above, in the bearing device shown in the first embodiment, the sensor unit including the heat flux sensor provided near the bearing is provided in the spacer so that signs of abnormal heat generation in the bearing can be detected at an early stage. By performing diagnosis using the signal from the heat flux sensor and the signal from another sensor mounted on the sensor unit, the accuracy of the result of abnormality diagnosis can be improved, and the type of abnormal condition of the bearing can be estimated.

[Second Embodiment]

In the second embodiment, improvements to the abnormality diagnosis processing device described in the first embodiment will be described. The second embodiment is also common in the configurations of the spindle device 1 and the bearing device 2 shown in FIG. 1 .

8 is a block diagram of an abnormality diagnosis processing device according to a second embodiment. An abnormality diagnosis processing device 15 a shown in FIG. 8 includes a power switch 18 in addition to a diagnosis processing unit 16A and a threshold storage unit 17A.

During normal operation, the diagnosis processing unit 16A performs abnormality diagnosis based on the rotational speed N indicated by the sensor signal SS1 from the heat flux sensor 10 and the sensor signal from the rotation sensor 14 . When the diagnosis is “abnormal” at this time, diagnosis processing unit 16A activates power switch 18 by issuing a power ON command PON, and supplies power PWR to vibration sensor 11 , temperature sensor 12 and load sensor 13 . Then, the diagnosis processing unit 16A acquires the sensor signal SS2 from the vibration sensor 11, the temperature sensor 12, and the load sensor 13, and makes a higher-precision abnormality diagnosis.

By providing the power switch 18 in the abnormality diagnosis processing device 15A, power saving of the vibration sensor 11, the temperature sensor 12, and the load sensor 13 can be realized.

FIG. 9 is a flowchart for explaining processing performed by the diagnosis processing unit 16A in the abnormality diagnosis processing device 15A.

First, in steps S11 , S12 , the diagnostic processing unit 16A acquires a sensor signal from the heat flux sensor 10 , and acquires a sensor signal from the rotation sensor 14 . During this period, the diagnostic processing unit 16A controls the power switch 18 to be in an off state.

In step S13, the diagnosis processing unit 16A compares the threshold value corresponding to the heat flux sensor 10 stored in the threshold value storage unit 17 with the sensor signal from the heat flux sensor 10, and checks whether the sensor signal from the rotation sensor 14 is Indicates that the main shaft 4 is rotating for judgment.

In step S14, when the sensor signal from the heat flux sensor 10 does not exceed the threshold value ("No" in S14), the diagnosis processing unit 16A judges that there is no abnormality, and provides a judgment indicating "OK" in step S15 Results JR. The process returns to steps S11, S12.

In step S14, when the sensor signal from the heat flux sensor 10 exceeds the corresponding threshold (YES in S14), the diagnostic processing unit 16A temporarily judges that there is an abnormality, and controls the power switch 18 in step S16. become connected.

Then, the power supply voltage is supplied to the vibration sensor 11, the temperature sensor 12, and the load sensor 13, and sensor signals can be acquired from these sensors. In steps S17 to S19 , the diagnosis processing unit 16A acquires a sensor signal from at least one of the vibration sensor 11 , the temperature sensor 12 , and the load sensor 13 .

The threshold value storage unit 17A stores in advance a threshold value corresponding to the rotational speed for each sensor output. In step S20 , the diagnosis processing unit 16A compares each sensor signal with the threshold value stored in the threshold value storage section 17A, and performs abnormality diagnosis processing.

When each sensor signal does not exceed the corresponding threshold in step S21 ("No" in S21), the diagnosis processing unit 16A judges that there is no abnormality, and provides a judgment result JR indicating "OK" in step S23, And thereafter the power switch 18 is controlled to be turned off in step S24. The process returns to steps S11, S12. In step S21, when there is a sensor providing a sensor signal exceeding the threshold value among the sensors other than the heat flux sensor 10 (YES in S21), the diagnostic processing unit 16A determines that there is an abnormality. In step S22 , the diagnostic processing unit 16A provides a judgment result JR indicating “NG”, and also provides an estimation result of an abnormal state corresponding to a sensor whose sensor signal exceeds a threshold value. The process returns to steps S11, S12.

As shown in the block diagram of FIG. 8 and the flow chart of FIG. 9, when the output from the first sensor (heat flux sensor 10) does not exceed the threshold value corresponding to the first sensor stored in the threshold value storage unit 17 (in S14 "No"), the diagnosis processing unit 16 does not perform abnormality diagnosis based on the output from the second sensor (at least one of the vibration sensor 11, the temperature sensor 12 and the load sensor 13), and when the output from the first sensor exceeds the first When the sensor corresponds to the threshold ("YES" in S14), the diagnostic processing unit performs abnormality diagnosis based on the output from the second sensor (S20).

As for the abnormality diagnosis processing, the first exemplary abnormality diagnosis processing and the second exemplary abnormality diagnosis processing described in the first embodiment can also be applied to the second embodiment.

In the bearing device shown in the second embodiment, the same effects as those of the bearing device shown in the first embodiment are obtained. Furthermore, power saving of the vibration sensor 11, the temperature sensor 12, and the load sensor 13 can be realized by providing the power switch 18 in the abnormality diagnosis processing device 15a.

[Third Embodiment]

Although the heat flux sensor is combined with another sensor in the first and second embodiments, the accuracy of abnormality determination can also be improved by combining the heat flux sensors with each other.

Fig. 10 is a cross-sectional view showing a schematic structure of a spindle device in a third embodiment. FIG. 11 is an enlarged view of a main part on the left side in FIG. 10 . FIG. 11 mainly shows the bearing arrangement 130 .

The spindle device 101 shown in FIG. 10 is used, for example, as a built-in motor spindle device of a machine tool. In this case, a motor 140 is assembled on one end side of a main shaft 104 supported by a main shaft device 101 serving as a main shaft of a machine tool, and an unillustrated cutting tool such as an end mill is attached to the other end side.

The spindle arrangement 101 comprises bearings 105a, 105b, a spacer 106 arranged adjacent to the bearings 105a, 105b, heat flux sensors 111a, 111b, a motor 140 and a bearing 116 arranged at the rear of the motor. The main shaft 104 is rotatably supported by a plurality of bearings 105 a , 105 b provided in a housing 103 embedded in the bearing housing 102 . The bearing 105a includes an inner ring 105ia, an outer ring 105ga, a rolling element Ta, and a retainer Rta. The bearing 105b includes an inner ring 105ib, an outer ring 105gb, a rolling element Tb, and a retainer Rtb. The spacer 106 includes an inner ring spacer 106i and an outer ring spacer 106g.

Heat flux sensors 111a, 111b, which measure heat flux, are fixed to the inner surface 106gA of the outer ring spacer 106g, and are opposed to the outer surface 106iA of the inner ring spacer 106i.

The inner ring 105ia of the bearing 105a and the inner ring 105ib of the bearing 105b separated in the axial direction are fitted to the main shaft 104 by interference fit (press fit). The inner ring spacer 106i is arranged between the inner rings 105ia, 105ib, and the outer ring spacer 106g is arranged between the outer rings 105ga, 105gb.

The bearing 105a is a rolling bearing in which a plurality of rolling elements Ta are arranged between an inner ring 105ia and an outer ring 105ga. The space between the rolling elements Ta is maintained by the retainer Rta. The bearing 105b is a rolling bearing in which a plurality of rolling elements Tb are arranged between an inner ring 105ib and an outer ring 105gb. The space between the rolling elements Tb is maintained by the retainer Rtb.

Bearings 105a, 105b are bearings that can be preloaded by axial force, and angular contact ball bearings, deep groove ball bearings, or tapered roller bearings may be used as bearings 105a, 105b. Angular contact ball bearings are included in the bearing arrangement 130 shown in Figure 11, where the two bearings 105a, 105b are arranged in a back-to-back double bearing (DB) arrangement.

Although the configuration in which the main shaft 104 is supported by two bearings 105a and 105b has been shown and described, a configuration in which the main shaft 104 is supported by two or more bearings may also be applied.

The single row rolling bearing 116 is a cylindrical roller bearing. The bearings 105a, 105b, which are angular contact ball bearings, support radial loads and axial loads applied to the spindle device 101 . The single-row bearing 116, which is a cylindrical roller bearing, supports a radial load applied to the spindle device 101 serving as the spindle of the machine tool.

A cooling medium flow passage G is provided in the housing 103 . The bearings 105a, 105b can be cooled by the flow of cooling medium between the housing 103 and the bearing sleeve 102 .

A lubricating oil supply channel is provided for cooling and lubrication of the bearings 105a, 105b. The lubricating oil is injected through the discharge hole (nozzle) in the state of air oil or oil mist together with the air carrying the lubricating oil. The lubricating oil supply passage is not shown. When a grease lubricated bearing is used as the bearings 105a, 105b, no lubricating oil supply passage is required.

When assembling, first, the bearing 105 a , the spacer 106 , the bearing 105 b , and the spacer 109 are sequentially inserted around the main shaft 104 , and an initial preload is applied by tightening the nut 110 . Thereafter, the main shaft 104 with the bearings 105a, 105b attached is inserted into the housing 103 until the right side of the outer ring 105gb of the bearing 105b of FIG. Then, the front cover 112 presses the outer ring 105ga of the left bearing 105a to fix the main shaft 104 to the housing 103 .

By tightening the nut 110, force is applied to the end surface of the inner ring 105ib of the bearing 105b in a state where the spacer 109 is inserted, so that the inner ring 105ib is pressed against the inner ring spacer 106i. This force is transmitted to the inner ring 105ib, the rolling elements Tb, and the outer ring 105gb to apply a preload to the bearing 105b, and is also transmitted from the outer ring 105gb to the outer ring spacer 106g. Pressing force is applied to the outer ring spacer 106gb from the outer ring 105gb on the right, and the force is transmitted to the outer ring 105ga, the rolling element Ta, the inner ring 105ia of the bearing 105a, and the preload is also applied to the bearing 105a on the left. For example, the preload applied to the bearings 105a, 105b is determined by the amount of movement limited by the difference in width dimension between the outer ring spacer 106g and the inner ring spacer 106i.

For the single-row bearing 116 , the inner ring 116 a is positioned in the axial direction by the cylindrical member 115 fitted to the outer periphery of the main shaft 104 and the inner ring press-fit jig 119 . The inner ring press-fit jig 119 is prevented from coming off by screwing the nut 120 to the main shaft 104 . The outer ring 116b of the bearing 116 is clamped by the positioning member 121 fixed to the cylindrical member 115 and the positioning member 118 fixed to the inner ring press-fit jig 119, and is integrally opposed to the end with the inner ring 116a as the main shaft 104 expands and contracts. Member 117 slides.

A motor 140 driving the main shaft 104 is arranged at an intermediate position in the axial direction between the multi-row bearings 105 a , 105 b and the single-row bearing 116 provided in the space 122 between the main shaft 104 and the bearing housing 102 . The rotor 114 of the electric motor 140 is fixed to the cylindrical member 115 fitted to the outer periphery of the main shaft 104 , and the stator 113 of the electric motor 140 is fixed to the inner peripheral portion of the bearing housing 102 .

A cooling medium flow channel for cooling the electric motor 140 is not shown.

Heat flux sensors 111 a and 111 b for measuring heat flux are attached to the spindle device 101 as the sensor unit 111 . In the example shown in FIGS. 10 and 11, the heat flux sensors 111a, 111b have one surface fixed to the inner surface 106gA of the outer ring spacer 106g and the other surface opposite the outer surface 106iA of the inner ring spacer 106i. . The heat flux sensor 111a is arranged near the bearing 105a, and the heat flux sensor 111b is arranged near the bearing 105b.

As the contact pressure between the rolling elements Ta, Tb of the bearings 105a, 105b and the raceway surfaces of the inner rings 105ia, 105ib, 105ga, 105gb increases, the temperatures of the inner rings 105ia, 105ib, and the outer rings 105ga, 105gb rise. At this time, the heat generated between the rolling elements Ta, Tb and the raceway surfaces of the inner rings 105ia, 105ib and the outer rings 105ga, 105gb is first conducted to the inner ring spacer 106i, the outer ring spacer 106g, the main shaft 104 and the housing 103 . A delay occurs in the temperature rise of the housing 103 and the outer ring spacer 106g having a high heat capacity. Since the housing 103 has already been cooled, a further delay occurs in the temperature rise.

In an attempt to measure the temperature of the inner rings 105ia, 105ib, the outer rings 105ga, 105gb, and the spacer 106 to detect signs of burning of the bearings 105a, 105b, it may not be detected at an early stage due to a delay in temperature rise above symptoms. In this case, by using the heat flux sensors 111a and 111b, since the heat flux changes quickly, rapid heat generation can be quickly detected.

The control device 150 that controls the motor 140 includes an abnormality determination unit 125 and a motor controller 123 . The heat flux sensors 111a, 111b provide output signals HSa, HSb output to the abnormality judging unit 125, respectively.

Fig. 12 is a waveform diagram showing an exemplary output from a heat flux sensor when the bearing is normal. Fig. 13 is a waveform diagram showing an exemplary output from a heat flux sensor when a bearing is abnormal. 12 and 13 show the waveform of the output signal HSa from the heat flux sensor 111a with a solid line, and the waveform of the output signal HSb from the heat flux sensor 111b with a two-dot chain line.

During normal operation, as the rotational speed of the spindle 104 of the spindle arrangement 101 increases, the temperature of the two bearings 105a, 105b increases substantially similarly. Therefore, as shown in FIG. 12, the two output signals HSa, HSb from the heat flux sensors 111a, 111b also show a similar upward tendency when the rotation speed increases, and when the rotation speed of the main shaft 104 is constant, after a certain Time, the output signals HSa, HSb become stable.

In the method of judging as abnormal when the output signal HSa, HSb or the rate of change (time differential) of the output signal HSa, HSb exceeds a preset threshold, it is difficult to set the threshold, and wrong judgment may be made in some cases.

Therefore, in this embodiment, when the absolute value of the difference between the output signals HSa, HSb from the two heat flux sensors 111a, 111b or the absolute value of the difference between the change rates of the output signals HSa, HSb exceeds the predetermined When the threshold range is set, it is judged as abnormal, thus improving the judgment accuracy. The judgment is made based on the absolute value of the difference between the two signals because the difference can be positive or negative depending on which bearing an abnormality has occurred. The judgment may be made based on the square of the difference instead of the absolute value.

In FIG. 13, at time T1, a symptom of temperature rise is observed in one bearing 105a, and the output signal HSa from the heat flux sensor 111a rises sharply. In contrast, the output signal HSb from the heat flux sensor 111b monitoring the other bearing 105b was normal, and no rise in output was observed.

In the event of an abnormality, simultaneous melting of both bearings 105a, 105b is rare, and in most cases, one of the bearings is burned. Therefore, when an abnormality occurs, the output signals HSa, HSb show a tendency as shown in FIG. 13 . In this case, the output signal HSa rises first due to the melting of the bearing 105a, and heat flow is conducted from this bearing 105a. Therefore, the output signal HSb starts to rise slightly later, as indicated by time T2. Melting of one bearing 105a may subsequently lead to melting of the other bearing 105b.

10 and 11 again, the bearing device 130 includes at least a bearing portion 105 having at least a first bearing 105a and a second bearing 105b supporting the main shaft 104, and a first bearing 105a and a second bearing 105b corresponding to the first bearing 105a and the second bearing 105b respectively. A heat flux sensor 111 a and a second heat flux sensor 111 b , and an abnormality determination unit 125 that makes an abnormality diagnosis of the bearing portion 105 . The abnormality judging unit 125 determines based on the difference |HSa-HSb| between the outputs of the first heat flux sensor 111a and the second heat flux sensor 111b or the difference |ΔHSa/Δt−ΔHSb/Δt| Occurrence of an abnormality in the bearing unit 105 is detected.

Preferably, the first bearing 105a and the second bearing 105b respectively support a first portion (Pa in FIG. 11 ) and a second portion (Pb in FIG. 11 ) of the main shaft 104 that are distant from each other.

More preferably, the bearing device 130 further includes a spacer 106 arranged between the first bearing 105a and the second bearing 105b, and the first heat flux sensor 111a and the second heat flux sensor 111b are mounted on the spacer 106 . The first heat flux sensor 111A is arranged in the spacer 106 closer to the first bearing 105a than the second heat flux sensor 111b is arranged in the spacer 106, and the second heat flux sensor 111b is arranged in the spacer The location in 106 is closer to the second bearing 105b than the location where the first heat flux sensor 111A is arranged in the spacer 106 .

FIG. 14 is a block diagram of an abnormality judging unit 125 that judges abnormality of a bearing based on outputs from two heat flux sensors employed in the third embodiment. Referring to FIG. 14 , output signals HSa, HSb from the two heat flux sensors 111 a , 111 b installed in the spindle device 101 are supplied to the abnormality judging unit 125 .

The abnormality judging unit 125 includes a subtractor D and a comparator C. A subtractor D receives output signals (or rates of change of output signals) HSa, HSb from the two heat flux sensors 111a, 111b, and calculates a differential output. The comparator C compares the absolute value of the output from the subtractor D with a preset reference (threshold value) JS. When the absolute value of the differential output is greater than the reference (threshold) JS, the comparator C determines that the bearing is abnormal.

The abnormality determination means 125 may further include a bearing identification means PJ which determines whether an abnormality or a symptom of an abnormality is observed in which of the bearings 105a, 105b. The bearing identification unit PJ can provide the bearing identification result to the outside. From the sign of the output from the subtractor D, it is possible to identify which of the bearings 105a, 105b exhibits an abnormality or a sign of an abnormality. The bearing identification unit PJ may provide a bearing identification result only when the judgment result of the comparator C indicates that there is an abnormality or an abnormal symptom.

Therefore, the abnormality judging unit 125 judges which of the first bearing and the second bearing abnormality has occurred in the bearing identifying unit PJ of FIG. 14 based on the sign of the difference provided by the subtractor D. Specifically, when the condition of HSa-HSb>0 (sign is positive), the bearing recognition unit PJ judges that an abnormality has occurred in the bearing 105a, and when the condition of HSa-HSb<0 (sign is negative), the bearing The recognition unit PJ determines that an abnormality has occurred in the bearing 105b.

FIG. 15 is a block diagram showing the structure of an abnormality judging unit 125A which is an improvement of FIG. 14 . In addition to the output of the subtractor D and the threshold value JS, the comparator C of the abnormality judging unit 125A shown in FIG. Information). Comparator C can also take this information into account to make a judgment on whether an abnormality has occurred.

When the abnormality judging unit 125 or 125A predicts that any one of the bearings 105a, 105b is melted, the motor controller 123 in FIG. Avoid melting of bearings.

When the output signals HSa, HSb (or the rate of change of the output signals HSa, HSb) from the two heat flux sensors 111a, 111b differ by a certain degree or more, the abnormality judging unit 125 judges that the bearing is abnormal. Compared with the judgment of the output signals of the heat flux sensors 111a and 111b, the judgment accuracy can be improved. Therefore, erroneous judgment can be prevented, and more accurate abnormality (prediction) detection can be realized. By applying the abnormality determination method performed by the abnormality determination unit 125 to the bearing device 130 and the spindle device 101 including the bearing device 130 , melting of bearings in the bearing device 130 and the spindle device 101 can be prevented.

As described above, in the third embodiment, in the bearing device 130 including two angular contact ball bearings as the bearings 105a, 105b with the outer ring spacer 106g and the inner ring spacer 106i inserted between the above bearings to apply preload , the heat flux sensors 111a, 111b are arranged near the bearings 105a, 105b, respectively. The heat flux sensors 111a, 111b are arranged such that one surface thereof is fixed to the inner surface 106gA of the outer ring spacer 106g and the other surface thereof is opposite to the inner ring 105iA, 105ib or the outer surface 106iA of the inner ring spacer 106i.

When the spindle device 101 is operating normally, as the rotation speed of the spindle 104 of the spindle device 101 increases, the heat generated from the bearings 105a, 105b increases, and the temperature of the spacer 106 also rises. Therefore, the value of the output signal from heat flux sensor 111a, 111b also rises.

In a general judging method, when the output signals HSa, HSb or the rate of change (time differential) of the output signals HSa, HSb from the heat flux sensors 111a, 111b exceed a preset threshold, it is judged that the bearing is abnormal. With this method, it is difficult to set an appropriate threshold due to the influence of the operating state of the spindle device or changes in preload over time, and erroneous judgments may be made. Therefore, in the present embodiment, when the difference between the output signals from the heat flux sensors arranged near the bearing, or the difference between the change rates of the output signals from two heat flux sensors exceeds a preset When it is within the reference range, it is judged that the bearing is abnormal.

Simultaneous melting of both bearings is rare in the event of an anomaly. First, the heat generated from either bearing increases, and sooner or later the bearing will burn out. Thus, in the third embodiment, when the difference between the output signals from the heat flux sensors 111a and 111b is observed, it is determined that the bearing is abnormal. Therefore, erroneous judgments can be prevented, and more accurate predictive judgments can be made. By applying such a determination method, it is possible to prevent the bearings of the bearing device and the spindle device from being melted.

[Fourth embodiment]

In the third embodiment, the structure of the bearing device 130 in which the two bearings 105a, 105b support the main shaft 104 is described. Not limited to such a structure, the abnormality determination method according to the present invention can be similarly applied to a structure in which two or more bearings support the main shaft 104 .

FIG. 16 is a diagram showing a configuration of a bearing device 130A in which four bearings support a main shaft in a fourth embodiment. The spindle device according to the fourth embodiment includes a bearing device 130A shown in FIG. 16 instead of the bearing device 130 in the configuration of the spindle device 101 in FIG. 10 .

The bearing device 130A shown in FIG. 16 further includes spacers 131c, 131d and bearings 105c, 105d outside the two bearings 105a, 105b of the bearing device 130 in FIG. 11 . The heat flux sensor 111c is arranged on the inner surface 131gAc of the outer ring spacer 131gc of the additional spacer 131c, and the heat flux sensor 111d is arranged on the inner surface 131gAd of the outer ring spacer 131gd of the additional spacer 131d. Since other structures are the same as in FIG. 11 , no description will be provided. Although a heat flux sensor is provided for each bearing in FIG. 16 , a bearing more likely to be abnormal may be selected from a plurality of bearings in view of design or experience, and a heat flux sensor may be arranged therein.

FIG. 17 is a block diagram of an abnormality judging unit 125B that judges abnormality of a bearing based on outputs of two heat flux sensors employed in the fourth embodiment.

Abnormality judging section 125B shown in FIG. 17 has a subtractor D2, a comparator C2, and a logical sum circuit OR in addition to the configuration of abnormality judging section 125 shown in FIG. 14 . Subtractor D2 receives output signals (rates of change of output signals) HSc, HSd from additional heat flux sensors 111c, 111d, and calculates their differential output. Comparator C2 compares a preset standard (threshold value) JS with the absolute value of the differential output calculated by subtractor D2.

The logical sum circuit OR calculates the logical sum of the output signal from the comparator C and the output signal from the comparator C2. When an abnormality or an abnormality prediction is detected in the comparator C or the comparator C2, the logic AND circuit OR judges that there is an abnormality or a sign of abnormality, and provides the judgment result to the outside.

Bearing recognition unit PJ judges in which of bearings 105a, 105b, 105c, and 105d, an abnormality or a sign of abnormality is observed. The bearing identification unit PJ may be based on the sign of the output signal from the subtractor D for the two heat flux sensors 111a, 111b, the sign of the output signal from the subtractor D2 for the two heat flux sensors 111c, 111d, And the output signals from the two comparators C and C2 identify the abnormal bearing.

When four bearings are provided, based on the comparison of the output of the heat flux sensors 111a, 111b monitoring from the central two bearings 105a, 105b, and the heat flux from the monitoring of the outer two bearings 105c, 105d The output of the flux sensors 111c and 111d is compared to judge an abnormality or a symptom of an abnormality. However, the combination of the heat flux sensors 111a to 111d for comparison is not limited thereto. Preferably, the accuracy of the measurement is improved by comparison of the outputs from heat flux sensors monitoring distant bearings, since there is less mutual influence.

When the number of bearings to be monitored is an odd number, it is possible to select two heat flux sensors for monitoring the bearings, and to judge abnormality or a sign of abnormality based on the result of the comparison.

The above shows a method of directly comparing the outputs from the two heat flux sensors with each other. When a large number of heat flux sensors are used, an average value of the outputs from the heat flux sensors can be calculated, and the output from each heat flux sensor can be compared to the average value. Alternatively, output signal maximums and output signal minimums can also be detected from the outputs of a plurality of heat flux sensors and compared with one another. In this way, it is possible to prevent erroneous judgments when the outputs from the plurality of heat flux sensors start to capture signs of abnormality at the same time.

In the above description, the heat flux sensors are arranged on the inner surfaces 106gA, 131gAc, 131gAd of the non-rotating outer ring spacers 106g, 131gc, 131gd. However, there may be a structure in which the heat flux sensor is arranged in the rolling bearing ring (outer ring) on the non-rotating side of the bearings 105a to 105d so as to be opposed to the rotating ring (inner ring).

Although the structure in which the outer ring of the bearing is fixed and the inner ring rotates has been described above by way of example, the present invention can also be applied to examples in which the outer ring rotates and the inner ring is fixed by attaching a heat flux sensor on the side where the ring is fixed .

In the fourth embodiment, the heat flux sensors are arranged near three or more heat-generating bearings, the output signals or the change rates of the output signals from the plurality of heat flux sensors are compared with each other, and when the difference between them exceeds Bearing abnormalities are judged within the preset standard range (threshold value). Therefore, as in the third embodiment, predictive judgment can be more accurate than judgment of abnormality using a single heat flux sensor. The bearing identification unit PJ can identify which of the three or more bearings is abnormal or exhibits signs of abnormality.

Although the configuration in which the abnormality judging unit in Fig. 14, Fig. 15 and Fig. 17 is realized by hardware is shown, it may also be realized by a microcomputer and software.

FIG. 18 is a diagram showing another configuration of an abnormality judging unit. Referring to Fig. 18, abnormality judging unit 125 or 125A includes: A/D converter 201, above-mentioned A/D converter 201 receives the output from sensor part 111; A conversion result of the /D converter 201 is processed; and a memory 203 which stores programs read by the processor 202 and stores data in calculation processing by the processor 202 .

FIG. 19 is a flowchart for explaining processing executed by the processor 202 of FIG. 18 .

The abnormality judging method performed in the third and fourth embodiments is a method of judging an abnormality of the bearing device 130 including at least the first bearing 105a and the second bearing 105b that support the main shaft. The bearing part 105, and the first heat flux sensor 111a and the second heat flux sensor 111b provided correspondingly to the first bearing 105a and the second bearing 105b, respectively. The abnormality judging method performed by the processor 202 includes a step S51 of calculating the difference between the outputs from the first heat flux sensor 111a and the second heat flux sensor 111b or the difference between the output change rates, and calculating Steps S52 to S54 of detecting whether an abnormality has occurred in the bearing unit 105 based on the difference obtained.

More specifically, in step S51, the processor 202 calculates the difference |HSa-HSb| between the outputs from the first heat flux sensor 111a and the second heat flux sensor 111b or the difference |ΔHSa /Δt-ΔHSb/Δt| is calculated.

Next, in step S52, the processor 202 judges whether the calculated difference is greater than a threshold. When the difference is greater than the threshold (YES in S52), the processor 202 determines in step S53 that the bearing is abnormal. When the difference does not exceed the threshold (NO in S52), the processor 202 determines in step S54 that the bearing is normal. When the judgment in step S53 or step S54 is confirmed, in step S55, the process returns to the main routine.

When more than three sensors are used in this way, noting the fact that simultaneous failure of two sensors is rare, a judgment on sensor failure can also be made based on a similar concept.

FIG. 20 is a flowchart for explaining the process of judging whether a sensor has failed. In this flowchart, an example in which the A/D converter shown in FIG. 18 converts outputs from N (N is a natural number equal to or greater than three) sensors into digital values and sends the digital values to the CPU 202 is described. . For example, in this process, when the output from the normal sensor gradually increases as the rotation speed increases as in the early stages in FIGS. 12 and 13 , a malfunctioning sensor exhibiting a fixed value can be detected.

20, in step S61, CPU 202 acquires data D1(1) to D1(N) from sensors 1 to N, respectively. Next, in step S62, the CPU waits until a predetermined period of time Δt elapses. When the prescribed time period Δt has elapsed, in step S63, the CPU 202 acquires data D2(1) to D2(N) from the sensors 1 to N, respectively. In step S64 , the CPU 202 calculates, for each of the sensors 1 to N, the differences ΔD(1) to ΔD(N) of the previous and subsequent time points after the prescribed time period Δt has elapsed. In the following processing, it is investigated whether there is one sensor whose variation amount is significantly smaller than the other sensors among the differences ΔD(1) to ΔD(N).

Between before and after the lapse of the prescribed time period Δt, when the amount of change in the output of the sensor group of N heat flux sensors other than the Mth heat flux sensor is greater than the first threshold value, and the Mth heat flux sensor If the amount of change in the output of the flux sensor is smaller than the second threshold equal to or smaller than the first threshold, the CPU 202 determines that the Mth heat flux sensor has failed. This judgment processing will be described in detail below.

First in step S65, the variable M is initialized to 1. Next, in step S66, an average value AVE(M) of a set of differences ΔD(1) to ΔD(N) other than ΔD(M) is calculated. By comparing ΔD(M) and AVE(M) with each other, it can be judged whether the change of sensor M is significantly smaller than that of other sensors. Specifically, in step S67, the CPU 202 checks whether the magnitude of the average value |AVE(M)| The second threshold is small for judgment. When the condition in step S67 is met, it is considered that the change of sensor M is smaller than that of other sensors. In this case, it is presumed that a failure such as an open circuit or a short circuit has occurred in the sensor M. Therefore, the CPU 202 determines in step S68 that the sensor M has failed, and the process proceeds to step S69. At this time, the CPU 202 may turn on a warning indicator for giving notification about the occurrence of a failure, or may provide an alarm sound or a notification signal as necessary. When the condition in step S67 is not satisfied, the process proceeds to step S69, and the process in step S68 is skipped. In the above processing, the average value of the outputs from sensors other than sensor M is calculated to detect the sensor M whose change is small compared with other sensors, but other methods may be used to detect the output from sensors other than sensor M. Output performance is evaluated. For example, maximum value, minimum value or variance can be used for evaluation.

When the variable M has not reached N in step S69, the variable M is incremented in step S70, and the processing after step S66 is executed again. When the variable M has reached N in step S69, the process ends in step S71, and control is transferred to the main routine.

As described above, the judgment of the failure of the sensor can also be performed by providing a plurality of sensors and referring these sensors to each other. Therefore, abnormality of the bearing can be distinguished from failure of the sensor.

It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is limited by the claims rather than the description of the above embodiments, and any modifications within the scope of the claims and with meanings equivalent to the claims are intended to be included.

List of reference signs

1, 101 main shaft device; 2 bearing device; 3, 103 shell; 4, 104 main shaft; 5a, 5b, 105a, 105b, 105c, 105d, 116 bearing; 5ga, 5gb, 105g, 105ga, 105gb, 116b outer ring; 5ia, 5ib, 105i, 105ia, 105ib, 116a inner ring; 6, 106, 109, 131c, 131d spacer; 6g, 106g, 106gb, 131gc, 131gd outer ring spacer; 6i, 106i inner ring spacer; 7 bearings Set; 9 sensor units; 10, 111, 111a, 111b, 111c, 111d heat flux sensor; 11 vibration sensor; 12 temperature sensor; 13 load sensor; 14 rotation sensor; 15, 15a abnormal diagnosis processing device; 16, 16A diagnosis Processing unit; 17, 17A threshold storage unit; 18 power switch; 102 bearing sleeve; 103a step; 105 bearing; 106gA, 131gAc, 131gAd inner surface; 106iA outer surface; 110, 120 nut; 114 rotor; 115 cylindrical member; 117 end member; 118, 121 positioning member; 119 inner ring press fit fixture; 122 space; 123 motor controller; Motor; 150 control device; 201A/D converter; 202 processor; 203 memory; C, C2 comparator; D, D2 subtractor; OR logic and circuit; PJ bearing identification unit; Rta, Rtb holder; Ta, Tb rolling element

Claims (12)

1. A bearing device, comprising:

a first bearing comprising an inner race, an outer race, and rolling elements;

a spacer disposed adjacent the first bearing on a main shaft supported by the first bearing, the spacer including an inner race spacer and an outer race spacer;

a first sensor disposed in the first bearing or the spacer;

the second sensor is provided with a second sensor,

the first sensor is a heat flux sensor and,

the second sensor includes at least any one of a heat flux sensor, a vibration sensor, a temperature sensor, and a load sensor;

abnormality diagnostic means that determines an abnormality based on an output from the first sensor and an output from the second sensor; and

a second bearing that supports the main shaft together with the first bearing,

the first sensor is a first heat flux sensor provided in correspondence with the first bearing,

the second sensor is a second heat flux sensor provided in correspondence with the second bearing,

the abnormality diagnostic device includes an abnormality determination unit that detects occurrence of an abnormality in a bearing portion including the first bearing and the second bearing based on a difference between outputs from the first heat flux sensor and the second heat flux sensor or a difference between output change rates.

2. Bearing device according to claim 1,

the second sensor includes at least any one of the vibration sensor, the temperature sensor, and the load sensor, an

The abnormality diagnostic device diagnoses an abnormality of the bearing based on outputs from the first and second sensors and a rotation speed of the main shaft.

3. The bearing device of claim 2,

the abnormality diagnostic device includes:

a threshold value storage unit; and

a diagnostic processing unit that performs diagnostic processing on a signal from a sensor unit including the first sensor and the second sensor based on the threshold value stored in the threshold value storage section.

4. The bearing device of claim 3,

the threshold value storage unit stores threshold values corresponding to a plurality of rotational speeds for each of the first sensor and the second sensor.

5. The bearing device of claim 3,

the diagnosis processing unit does not perform abnormality diagnosis based on the output from the second sensor when the output from the first sensor does not exceed the threshold corresponding to the first sensor stored in the threshold storage section, an

The diagnosis processing unit performs abnormality diagnosis based on the output from the second sensor when the output from the first sensor exceeds the threshold corresponding to the first sensor.

6. The bearing device of claim 3,

the threshold value storage section stores a coefficient for weighting the outputs from the first sensor and the second sensor in accordance with the rotation speed.

7. The bearing device of claim 2,

the abnormality diagnostic device provides a result of abnormality diagnosis in accordance with a magnitude of a sum when the sum of values calculated by multiplying the output from the first sensor and the output from the second sensor by respective corresponding coefficients exceeds a predetermined threshold.

8. The bearing device of claim 1,

the first and second bearings support first and second portions of the main shaft, respectively, which are distant from each other.

9. The bearing device of claim 8,

the spacer is disposed between the first bearing and the second bearing and when the first heat flux sensor and the second heat flux sensor are disposed in the spacer,

the first heat flux sensor is disposed in the spacer at a position closer to the first bearing than the second heat flux sensor is disposed in the spacer, and

the second heat flux sensor is disposed in the spacer at a position closer to the second bearing than the first heat flux sensor is disposed in the spacer.

10. The bearing device of claim 1,

the abnormality determination unit determines which of the first bearing and the second bearing an abnormality has occurred based on the sign of the difference.

11. The bearing assembly of claim 1, comprising N heat flux sensors, wherein N is a natural number equal to or greater than three, wherein

The first and second heat flux sensors are two of N heat flux sensors, an

The abnormality determination unit determines that the first heat flux sensor has failed, when a variation in the output from a sensor group other than the first heat flux sensor among the N heat flux sensors is larger than a first threshold value and a variation in the output from the first heat flux sensor is smaller than a second threshold value equal to or smaller than the first threshold value between a preceding time point and a succeeding time point after a prescribed period of time has elapsed.

12. A spindle arrangement comprising a bearing arrangement according to any one of claims 1 to 11.

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