JP6742205B2 - Rotating shaft device and bearing abnormality diagnosis method in rotating shaft device - Google Patents

Description

The present invention relates to a rotary shaft device such as a spindle device of a machine tool in which a rotary shaft is supported by bearings, and a bearing abnormality diagnosis method in the rotary shaft device.

Bearings are used in many rotary shaft devices such as main shaft devices of machine tools. Among them, the rolling bearing is generally composed of an inner ring, an outer ring, a plurality of rolling elements, and a cage for keeping the rolling elements at equal intervals, the inner ring rotates together with the rotating shaft, and the outer ring is incorporated in the housing. It is fixed.
Abnormalities in such bearings include poor lubrication, contamination of foreign matter, wear, and excessive load. If defective rotation or seizure occurs due to these, the rotating shaft device cannot operate normally until the device is repaired. During that time, the stopped state continues. Therefore, in order to prevent such a situation, it is necessary to perform preventive maintenance for early diagnosis of bearing abnormality. For example, Patent Documents 1 to 3 disclose a method of monitoring the measurement information by a sensor such as a vibration sensor, a sound sensor, or a temperature sensor, and diagnosing an abnormality or life of the bearing in advance in real time.
However, in order to carry out these methods, additional cost of hardware (vibration, sound) and low detection sensitivity (temperature) pose a problem. Therefore, as disclosed in Patent Document 4, the resistance torque generated in the bearing is calculated from the change in the rotation speed when the rotation axis is inertially rotated by using the rotation speed detector that is standardly installed in the machine tool, If the bearing abnormality is diagnosed by comparing the resistance torque with a reference value, the bearing abnormality can be accurately diagnosed and no additional cost is required.

JP, 2009-20090, A JP, 2013-47690, A JP 2002-346884 A Japanese Patent Publication No. 6-65189

However, in the method using inertial rotation as in Patent Document 4, since the speed at which inertial rotation starts is arbitrary, the rotating shaft in which the bearing has an abnormality is inertially rotated from high speed rotation for abnormality diagnosis. If so, the bearing may be seized.

Therefore, the present invention makes it possible to diagnose the presence or absence of abnormality of the bearing by inertial rotation at low cost and with high accuracy, and also to reduce the risk of seizure of the bearing, and a rotating shaft. An object of the present invention is to provide a method for diagnosing a bearing abnormality in a device.

In order to achieve the above object, the invention according to claim 1 is a rotary shaft device in which a rotary shaft is supported by bearings.
Based on the inertial rotation means for inertially rotating the rotation shaft from a predetermined rotation speed, the rotation speed detection means for detecting the rotation speed during the inertial rotation, and at least the rotation speed during the inertial rotation and the time for the inertial rotation. The inertial rotation is provided with a bearing characteristic calculation means for calculating a resistance torque of the bearing during the inertia rotation, and a determination means for comparing the calculated resistance torque with a preset threshold value to determine whether or not there is an abnormality. In the means, the predetermined rotation speed is set as a low rotation speed set lower than a maximum rotation speed of the rotation shaft based on a predetermined index obtained from specifications of the bearing, and the inertia rotation is executed. To do.
According to a second aspect of the present invention, in the configuration of the first aspect, the specifications of the bearing are the heat generation amount of the bearing with respect to the rotation speed, and the predetermined index is a coefficient based on the heat generation amount. The low rotation speed is determined by multiplying the maximum rotation speed by the coefficient.
According to a third aspect of the present invention, in the configuration according to the first or second aspect, the inertial rotation means can execute the inertial rotation with the predetermined rotation speed as the maximum rotation speed, and at the low rotation speed. When performing the inertial rotation and the determination means determines that there is no abnormality in the bearing, the inertial rotation means executes the inertial rotation from the maximum rotation speed, the bearing characteristic calculation means, from the maximum rotation speed. The predetermined bearing characteristic is calculated based on the rotation speed during the inertia rotation and the time, and the determination means compares the calculated bearing characteristic with the reference bearing characteristic to determine whether there is an abnormality. It is characterized by
In order to achieve the above object, the invention according to claim 4 is a method for diagnosing the presence or absence of abnormality of the bearing in a rotating shaft device in which a rotating shaft is supported by a bearing.
An inertial rotation step of inertially rotating the rotation shaft from a predetermined rotation speed, a rotation speed detection step of detecting a rotation speed during the inertial rotation, and at least the rotation speed during the inertial rotation and the time of the inertial rotation. A bearing characteristic calculation step of calculating a resistance torque of the bearing during the inertia rotation, and a determination step of comparing the calculated resistance torque with a preset threshold value to determine whether or not there is an abnormality, In the rotating step, the inertial rotation is executed by setting the predetermined rotation speed as a low rotation speed set lower than a maximum rotation speed of the rotation shaft based on a predetermined index obtained from specifications of the bearing. And

According to the present invention, it is possible to diagnose the bearing by performing inertial rotation from a low rotation speed at which the main shaft cannot rotate even if the bearing has an abnormality. Therefore, the presence/absence of a bearing can be diagnosed at low cost and with high accuracy by utilizing inertial rotation, and the risk of seizure on the bearing can be reduced.

It is a schematic diagram of a spindle device. It is a flowchart of abnormality diagnosis control. It is explanatory drawing which shows the selection screen of a diagnostic mode. It is a graph which shows the relationship between rotation speed and the amount of heat generation of a bearing. Are rolling elements.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic view showing a spindle device of a machine tool which is an example of a rotary shaft device.
In this main spindle device 1, a main spindle 4 as a rotary shaft that is rotationally driven by a motor 3 is supported in a housing 2 by bearings 5 and 5 which are rolling bearings, and a tool is attached to and detached from the tip of the main spindle 4. It is possible. A rotation speed detector 6 is attached to the housing 2 as a rotation speed detecting means for detecting the rotation speed of the main shaft 4.

Reference numeral 7 is a control device, and the control device 7 is provided with a computing device 8, a storage device 9, a display device 10, and an input device 11. The control device 7 rotates the motor 3 in accordance with the machining program stored in the storage device 9 to perform machining, and also functions as inertial rotation means, bearing characteristic calculation means, and determination means of the present invention, and the input device 11 ( In response to a command from the keyboard, touch panel, etc., the mode is shifted to the diagnostic mode and the abnormality diagnosis of the bearing 5 is executed. Hereinafter, this abnormality diagnosis control will be described based on the flowchart of FIG.

First, in S1, the diagnosis mode is determined. This diagnostic mode has two modes of "safety mode" and "standard mode". As shown in FIG. 3, the selection screen is displayed on the display device 10 and the input device 11 selects one of the modes. It encourages choice.
When the safety mode is selected here, in S2, the spindle 4 is rotated at the first rotation speed. This first rotation speed is set to be lower than the maximum rotation speed of the main shaft 4, and is a low rotation speed at which the main shaft 4 does not become unrotatable even if the bearing 5 has an abnormality. It is preset based on the index. Here, the relationship between the rotation speed and the heat generation amount shown in FIG. 4 is selected as specifications, and based on this relationship, a coefficient that is one third of the heat generation amount at the maximum rotation is set as an index. Then, the first rotation speed (here, 7,000 min ⁻¹ ) is determined and stored in the storage device 9 by integrating the coefficient with the highest rotation speed (here, 15,000 min ⁻¹ ).

Next, in S3, the energization to the motor 3 is stopped and inertia rotation is performed (inertia rotation step), and in S4, the rotation speed of the spindle 4 is measured by the rotation speed detector 6 and the built-in timer is used. The time from the stop of energization is measured (rotational speed detection step).
When the rotation stop of the spindle 4 is confirmed in S5, the computing device 8 calculates the inertia rotation stop time and the resistance torque during inertia rotation as the bearing characteristics in S6 (bearing characteristic calculation step). The resistance torque T is calculated, for example, based on the following equation using the rotation speed V, the inertia inertia M, and the acceleration.
T=-(2πM/60)×(dV/dt)

Next, in S7, the arithmetic unit 8 determines whether the stop time of the spindle 4 is shorter than a preset threshold time or whether the resistance torque is larger than a preset threshold value (determination step), and either of them is determined. When it corresponds, it is determined in S8 that the bearing 5 has an abnormality, and the fact is displayed on the display device 10. On the other hand, if neither of them applies, it is determined in S9 that the bearing 5 is normal, and that fact is displayed on the display device 10.

When it is determined that the bearing 5 is normal in S9, a selection screen for determining whether or not the diagnosis is completed is also displayed in S10. If the diagnosis end is selected here, the abnormality diagnosis control ends, but if the diagnosis continuation is selected, the process returns to S1 and the selection screen of FIG. 3 is displayed. Therefore, if the standard mode is selected here, the spindle 4 is rotated at the second rotation speed in S11. The second rotation speed is higher than the first rotation speed, and is the set maximum rotation speed here.
The process after S3 is the same as the safety mode, the inertial rotation is performed, the rotation speed of the spindle 4 and the time from the stop of energization are measured in S4, and the stop of the spindle 4 is confirmed in S5. The stop time and the resistance torque are calculated, and in S7, it is determined whether the stop time is shorter than the threshold time or the resistance torque is larger than the threshold. If either of the conditions applies, it is determined in S8 that the bearing 5 has an abnormality, and the fact is displayed on the display device 10. On the other hand, if neither of them applies, it is determined in S9 that the bearing 5 is normal, and the fact is displayed on the display device 10.

Thus, according to the spindle device 1 of the above-described embodiment, the predetermined rotation speed at which the inertial rotation is started is determined based on the predetermined index (coefficient) obtained from the specifications of the bearing 5 (heat generation amount with respect to the rotation speed). By performing inertial rotation as the first rotational speed (low rotational speed) set lower than the maximum rotational speed of 4, even if there is an abnormality in the bearing 5, the main shaft 4 does not become unrotatable Then, the bearing 5 can be diagnosed. Therefore, the presence or absence of abnormality of the bearing 5 can be diagnosed at low cost and with high accuracy by utilizing inertial rotation, and the risk of seizure of the bearing 5 can be reduced.

In the above embodiment, the stop time during inertial rotation and the resistance torque are calculated as the bearing characteristics and compared with the threshold time or threshold value that is the reference bearing characteristic, but only one of them may be used. Further, other bearing characteristics such as rolling speed may be adopted. Further, the stop time may be a time for decelerating to a predetermined rotation speed or the like as long as the characteristic can be derived in relation to the rotation speed, and is not limited to the time until the stop.
On the other hand, the first rotation speed, which is a low rotation speed, is not limited to a coefficient by which the maximum rotation speed is multiplied by one-third the heat generation amount of the maximum rotation speed as a guide, and other ratios may be used.
In addition, the determination of the low rotation speed is not limited to the coefficient based on the heat generation amount. For example, as a specification, a coefficient based on the basic rated life of the bearing (for example, the rotational speed at which the basic rated life becomes 10 times is set. Coefficient) or a coefficient based on the contact surface pressure of the bearing (for example, a coefficient that makes the contact surface pressure the rotational speed at which the contact surface pressure is below the fatigue limit).

Further, by providing a temperature sensor near the bearing, the coefficient based on the temperature near the bearing (for example, the coefficient that makes the bearing rise temperature 10° C. or less after the rotation is stopped is a rotation speed), the rotation speed and the time A coefficient based on the total traveling distance of the bearing calculated from (for example, 1 when the total traveling distance is 10,000 m or less, 0.5 when the total traveling distance is 15,000 m or less) may be used.
In addition, the first rotation speed can be calculated by combining a plurality of these coefficients.

In the above embodiment, only one low rotation speed is set, but a plurality of low rotation speeds may be set to set a plurality of safety modes so that diagnosis can be performed from a mode having a low rotation speed.
Further, in the above embodiment, when the normal judgment is made in the safety mode, the selection screen is displayed again to prompt the user to select the mode, but when the normal judgment is made in the safety mode, the standard mode is automatically followed. The abnormality diagnosis control may be performed by.

In addition, the rotating shaft device and the bearing abnormality diagnosing method of the present invention can be applied not only to the spindle device of a machine tool but also to other mechanical equipment such as an automobile, a railroad vehicle, and a ship.

1...Main spindle device, 2...Housing, 3...Motor, 4...Main spindle, 5...Bearing, 6...Rotation speed detector, 7...Control device, 8...Calculation device, 9...Memory Device, 10... Display device, 11... Input device

Claims (4)

A rotary shaft device in which a rotary shaft is supported by bearings,
An inertial rotation means for inertially rotating the rotation shaft from a predetermined rotation speed,
Rotation speed detection means for detecting the rotation speed during the inertia rotation,
Bearing characteristic calculation means for calculating a resistance torque of the bearing during the inertial rotation based on at least the rotational speed during the inertial rotation and the time for the inertial rotation ,
And a determination unit that determines whether or not there is an abnormality by comparing the calculated resistance torque with a preset threshold value ,
In the inertial rotation means, the inertial rotation is performed by setting the predetermined rotation speed as a low rotation speed set lower than a maximum rotation speed of the rotation shaft based on a predetermined index obtained from specifications of the bearing. A rotary shaft device characterized by. The specifications of the bearing are the heat generation amount of the bearing with respect to the rotation speed, the predetermined index is a coefficient based on the heat generation amount, the low rotation speed is the coefficient to the maximum rotation speed The rotary shaft device according to claim 1, wherein the rotary shaft device is determined by multiplying by. The inertial rotation means can execute the inertial rotation with the predetermined rotation speed as the maximum rotation speed, and execute the inertial rotation at the low rotation speed and the determination means determines that there is no abnormality in the bearing. In this case, the inertial rotation means executes the inertial rotation from the maximum rotation speed, and the bearing characteristic calculation means determines the predetermined value based on the rotation speed and the time during the inertial rotation from the maximum rotation speed. The rotating shaft device according to claim 1 or 2, wherein a bearing characteristic is calculated, and the determining unit compares the calculated bearing characteristic with the reference bearing characteristic to determine whether there is an abnormality. In a rotating shaft device in which a rotating shaft is rotatably supported by a bearing, a method for diagnosing the presence or absence of abnormality of the bearing,
An inertial rotation step of inertially rotating the rotation shaft from a predetermined rotation speed,
A rotation speed detection step of detecting the rotation speed during the inertia rotation,
A bearing characteristic calculation step of calculating a resistance torque of the bearing during the inertial rotation based on at least the rotational speed during the inertial rotation and the time of the inertial rotation ,
A determination step of determining whether or not there is an abnormality by comparing the calculated resistance torque with a preset threshold value ,
In the inertial rotation step, the inertial rotation is executed by setting the predetermined rotation speed as a low rotation speed that is set lower than the maximum rotation speed of the rotation shaft based on a predetermined index obtained from the specifications of the bearing. A method for diagnosing a bearing abnormality in a rotating shaft device.

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