JP6637844B2 - Method for determining warm-up operation time before bearing diagnosis in machine tool, machine tool - Google Patents

Description

  The present invention provides a method of determining a warm-up operation time associated with a bearing diagnosis and a bearing diagnosis in a machine tool including a bearing diagnosis unit for detecting an abnormality of a rolling bearing used for a bearing of a rotating shaft. Machine tools.

BACKGROUND ART In a rotating shaft device provided with a rotating shaft such as a main shaft provided in a machine tool, a rolling bearing (hereinafter simply referred to as a “bearing”) used to support the rotating shaft is provided between an inner ring, an outer ring, and both wheels. A plurality of rolling elements (balls, rollers, etc.) and a retainer for keeping the spacing between the rolling elements, the inner ring rotates integrally with the rotating shaft, and the outer ring is incorporated and fixed in the main shaft housing or the like. You.
Abnormalities that occur in the bearing include poor lubrication, inclusion of foreign matter, wear, and excessive load. When these abnormalities occur, rotation failure or seizure occurs, which hinders the normal operation of the machine tool. Therefore, it is desirable to diagnose bearing abnormalities.
Therefore, as a method for diagnosing an abnormality of a bearing, Patent Document 1 discloses monitoring a temperature and a stop time of a rotating device having a bearing and comparing the temperature with a reference stop time set in advance according to the temperature. An invention for determining the presence or absence of an abnormality is disclosed. Patent Document 2 discloses an invention in which a friction torque is calculated from a change in the number of revolutions during coasting rotation of a shaft, and the friction torque is compared with a reference value to determine an abnormality in the bearing.

Japanese Patent No. 4091885 Japanese Patent Publication No. 6-65189 JP 2005-34929 A JP 2009-113138 A

Since the index caused by the friction characteristics of the bearing as described in Patent Literatures 1 and 2 is delicate information affected by various factors, it is desirable to stabilize the bearing state at the time of measurement.
Here, it is known that the friction characteristics of a bearing depend on the bearing preload, the lubricating oil viscosity, and the rotation speed. Of these, the bearing preload and the lubricating oil viscosity are dependent on the temperature, so that a stable bearing is obtained. When performing a diagnosis, it is necessary to perform a warm-up operation to make the temperature conditions at the time of measurement uniform. In particular, regarding the bearing preload, it is necessary to consider the influence of thermal displacement due to temperature change.
As a technique for stabilization by such a warm-up operation, Patent Document 3 discloses that a warm-up operation is performed after the machine tool is started, and the warm-up operation is terminated when the temperature of the ball screw exceeds a threshold value at which the displacement amount saturates. The invention is described in which the machining is started. Further, in Patent Document 4, in order to prevent unnecessary warm-up operation, the tip position of a tool is calculated by analyzing imaging data of a camera or the like, and the amount of change in the tip position is within a set allowable accuracy. Discloses that the warm-up operation is terminated when the position of the tool tip is considered to be stable if the setting continues for the set range time.

  However, when the invention related to such a warm-up operation is adopted for the bearing diagnosis, in the invention of Patent Document 3, the amount of heat generated varies when a bearing is abnormal because the temperature threshold is simply used as a guideline for terminating the warm-up operation. If the temperature in the steady state changes, the timing of terminating the warm-up operation becomes inappropriate, and accurate bearing diagnosis cannot be performed. In the invention of Patent Document 4, although the reliability is improved using the tip position of the tool as a new index, an additional device such as a camera is required, which leads to an increase in cost.

  Accordingly, the present invention provides a warm-up operation before a bearing diagnosis in a machine tool, in which an appropriate warm-up operation time can be determined at low cost, unnecessary warm-up operation time can be eliminated, and an efficient bearing abnormality diagnosis can be performed. An object of the present invention is to provide a method for determining an operation time and a machine tool.

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 is a rotating shaft device in which a rotating shaft that is rotationally driven is supported by a bearing, control means for controlling rotation of the rotating shaft, After performing a warm-up operation of rotating the rotating shaft at a predetermined rotation speed by the control unit and the temperature detected by the temperature detecting unit to a steady state, In a machine tool comprising: a bearing diagnosis unit that performs a bearing diagnosis that detects an abnormality of the bearing, a method of determining the time of the warm-up operation,
During normal operation before the execution of the bearing diagnosis, a temperature detection step of detecting the temperature of the bearing by the temperature detection means,
A temperature time constant calculating step of calculating the temperature time constant during the normal operation based on the detected temperature change of the bearing and the rotation speed of the rotating shaft;
A storing step of storing the calculated temperature time constant;
When performing the warm-up operation, a time determining step of determining the time of the warm-up operation at the predetermined rotation speed based on the stored temperature time constant is performed.
According to a second aspect of the present invention, in the configuration of the first aspect, the temperature detecting step is executed only during a normal operation at the predetermined rotational speed, and in the temperature time constant calculating step, the temperature detecting step is performed at the predetermined rotational speed. The temperature time constant at the predetermined rotation speed is calculated from the change in temperature rise.
According to a third aspect of the present invention, in the configuration according to the first or second aspect, in the time determining step, a thermal displacement saturation time is estimated from the temperature time constant, and the thermal displacement saturation time is estimated as an arbitrary ratio of the estimated thermal displacement saturation time. The time of the warm-up operation is determined.
According to a fourth aspect of the present invention, in the configuration of the third aspect, the arbitrary ratio is 89% or more.
In order to achieve the above object, an invention according to claim 5 is directed to a rotating shaft device in which a rotating shaft that is rotationally driven is supported by a bearing, control means for controlling rotation of the rotating shaft, After performing a warm-up operation of rotating the rotating shaft at a predetermined rotation speed by the control unit and the temperature detected by the temperature detecting unit to a steady state, A machine tool comprising: a bearing diagnosis unit that executes a bearing diagnosis for detecting an abnormality of the bearing,
During normal operation before the execution of the bearing diagnosis, the temperature of the bearing is detected by the temperature detecting unit, and the temperature during the normal operation is determined based on the detected temperature change of the bearing and the rotation speed of the rotating shaft. Temperature time constant calculating means for calculating a time constant,
Storage means for storing the calculated temperature time constant,
When the warm-up operation is performed, a time determination unit that determines the time of the warm-up operation at the predetermined rotation speed based on the stored temperature time constant is provided.
According to a sixth aspect of the present invention, in the configuration of the fifth aspect, the temperature time constant calculating means detects the temperature of the bearing only during normal operation at the predetermined rotation speed, and detects the temperature at the predetermined rotation speed. A temperature time constant at the predetermined rotation speed is calculated from a change in temperature rise.
According to a seventh aspect of the present invention, in the configuration of the fifth or sixth aspect, the time determination means estimates a thermal displacement saturation time from the temperature time constant, and sets the thermal displacement saturation time at an arbitrary ratio of the estimated thermal displacement saturation time. The time of the warm-up operation is determined.
An eighth aspect of the present invention is characterized in that, in the configuration of the seventh aspect, the arbitrary ratio is 89% or more.

  According to the present invention, the warm-up operation time is determined based on the temperature time constant acquired during the normal operation, and the warm-up operation is performed according to the warm-up operation time. The determined warm-up operation time can be eliminated by the determination. Therefore, it is possible to efficiently diagnose the abnormality of the bearing.

It is a schematic diagram of a machine tool. It is a flowchart of normal operation. It is a flowchart of a bearing diagnosis.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing an example of a machine tool. This machine tool diagnoses a bearing used in a spindle device as a rotating shaft device for rotating a tool.
In the machine tool 1, reference numeral 2 denotes a spindle device. In a spindle housing 3, a spindle 4 having a tool 5 mounted at its tip and serving as a rotating shaft rotated by a spindle motor (not shown) is provided with a bearing (here, a rolling element is a ball). Ball bearings) 6,6. Reference numeral 7 denotes a rotation speed detector for detecting the rotation speed of the main shaft 4. The main shaft housing 3 is provided with a temperature sensor 8 having a probe inserted near the bearings 6, 6. The spindle motor of the spindle 4 is controlled by a control device 9 as a control unit that also controls a feed shaft motor of the machine tool 1 and the like.

  Reference numeral 10 denotes a bearing diagnostic device as bearing diagnostic means, which is a measuring device 11 to which a rotation detection signal from the rotation speed detector 7 and a temperature detection signal from the temperature sensor 8 are input, and that the rotation speed and the temperature of the main shaft 4 are measured. An arithmetic unit 12 as a temperature time constant calculating unit and a time determining unit which are input and calculate a bearing characteristic, a temperature time constant described later, and the like, and a storage in which the bearing characteristic, the temperature time constant, and the like calculated by the arithmetic unit 12 are stored. A storage device 13 as means is provided. The storage device 13 also stores a diagnostic program and the like at the time of bearing diagnosis. Reference numeral 14 denotes a display device on which the result of the bearing diagnosis by the arithmetic unit 12 is displayed. Here, the temperature sensor 8 and the measuring device 11 serve as temperature detecting means.

The normal operation of the machine tool 1 configured as described above will be described based on the flowchart of FIG.
First, when a spindle rotation command is input to the control device 9 in S1, the control device 9 controls the spindle motor to rotate the spindle 4 at the commanded rotation speed in S2. Processing is performed under control.
During machining, it is checked in step S4 whether the rotational speed of the spindle 4 is the rotational speed specified in advance for bearing diagnosis. If not, the machining is continued until the end of the machining program is confirmed in step S5. continue.

On the other hand, when the designated rotation speed is confirmed in the determination in S4, the temperature of the bearing 6 is detected by the temperature sensor 8 in S6, and the change in the detected temperature is recorded in the storage device 13 via the measuring device 11 (temperature detection). Steps).
Then, in S7, the arithmetic unit 12 calculates a temperature time constant at the current rotational speed from the recorded increase in the detected temperature (temperature time constant calculation step). The temperature time constant τ is calculated, for example, as a time at 63.2% or 50% of the temperature difference from the initial temperature to the temperature in the steady state.
Next, in S8, the calculated temperature time constant is stored in the storage device 13 together with the number of rotations (storage step), and the process returns to S5. Here, if the machining is not completed, the designated rotation speed is confirmed in S4, and if it is the designated rotation speed, the processing in S6 and thereafter is executed. Therefore, the recording of the bearing temperature and the calculation and storage of the temperature time constant at the specified number of rotations are repeated until the processing is completed, and the data is updated.

The bearing diagnosis for detecting the abnormality of the bearing 6 is executed according to the flowchart of FIG.
First, in S11, when a diagnosis start command is input to the bearing diagnosis device 10 by an input device (not shown), in S12, it is determined whether or not the main shaft 4 is at a designated rotational speed for bearing diagnosis. Here, if it is not the designated rotation speed, the control device 9 changes the rotation speed to the designated rotation speed in S13. When it is confirmed again at S12 that the rotation speed is the specified rotation speed, at S14, the arithmetic unit 12 calculates the warm-up operation time with reference to the specified rotation speed and the temperature time constant stored in the storage device 13. (Time determination step). This warm-up operation time is determined as an arbitrary ratio of the estimated thermal displacement saturation time by estimating the thermal displacement saturation time from the temperature time constant. For example, the temperature time constant τ is acquired as the time until a 63.2% change in the initial temperature difference, and if an arbitrary ratio is 89%, the warm-up operation time is (τ / 0.632). × 0.89.
Therefore, in S15, the control device 9 starts the warm-up operation according to the warm-up operation time thus calculated.
When the elapse of the calculated warm-up operation time is confirmed in S16, the warm-up operation is terminated in S17 and the bearing diagnosis is started in S18.

In this bearing diagnosis, for example, inertia rotation is performed by stopping power supply to the spindle motor, and the rotation speed and temperature are measured until the stop of the spindle 4 is confirmed. Based on the measured rotation speed, friction torque and rolling are determined. This is performed by calculating a speed, a bearing preload, and the like to obtain a bearing characteristic, and comparing the bearing characteristic with a reference bearing characteristic stored in advance in the storage device 13 to determine whether there is an abnormality.
As a result of the diagnosis, if it is determined in S19 that the bearing 6 is abnormal, the fact is displayed on the display device 14 to notify the occurrence of the abnormality in S20, and if there is no abnormality, the abnormality diagnosis is ended.

  As described above, according to the machine tool 1 and the method for determining the warm-up operation time of the embodiment, the warm-up operation time is determined based on the temperature time constant acquired during the normal operation, and the warm-up operation is performed according to the warm-up operation time. Therefore, an appropriate warm-up operation time can be determined at low cost, and unnecessary warm-up operation time can be eliminated. Therefore, it is possible to efficiently diagnose the abnormality of the bearing.

In the above embodiment, the temperature time constant is calculated only at the designated rotation speed during normal operation, but the temperature time constant may be calculated at all rotation speeds.
The rate at which the warm-up operation time is determined from the thermal displacement saturation time estimated from the temperature time constant is not limited to 89%, but may be a higher rate. It can also be.
Further, the rotary shaft is not limited to the main shaft for rotating the tool, and a rotary shaft device for gripping and rotating a work can determine the warm-up operation time and diagnose a bearing according to the present invention.

  1. Machine tool, 2. Spindle device, 3. Spindle housing, 4. Spindle, 5. Tool, 6. Bearing, 7. Rotation speed detector, 8. Temperature sensor, 9. Control device, 10 ... Bearing diagnostic device, 11 ... Measurement device, 12 ... Computing device, 13 ... Storage device, 14 ... Display device.

Claims (8)

A rotating shaft device that supports a rotating shaft that is rotationally driven by a bearing, a control unit that controls the rotation of the rotating shaft, a temperature detecting unit that detects the temperature of the bearing, and the control unit that controls the rotating shaft. Bearing diagnosis means for executing a bearing diagnosis for detecting an abnormality of the bearing after performing a warm-up operation of rotating at a predetermined rotation speed and for a time until the temperature detected by the temperature detection means reaches a steady state. A method for determining a time of the warm-up operation in a machine tool provided with:
During normal operation before the execution of the bearing diagnosis, a temperature detection step of detecting the temperature of the bearing by the temperature detection means,
A temperature time constant calculating step of calculating the temperature time constant during the normal operation based on the detected temperature change of the bearing and the rotation speed of the rotating shaft;
A storing step of storing the calculated temperature time constant;
When performing the warm-up operation, a time determination step of determining the time of the warm-up operation at the predetermined rotation speed based on the stored temperature time constant,
And determining the warm-up operation time before the bearing diagnosis in the machine tool. The temperature detection step is executed only during normal operation at the predetermined rotation speed,
The said temperature time constant calculation step calculates the temperature time constant at the said predetermined rotation speed from the temperature rise change at the said predetermined rotation speed, The bearing before the bearing diagnosis in the machine tool of Claim 1 characterized by the above-mentioned. How to determine the warm-up operation time.   The time determination step estimates a thermal displacement saturation time from the temperature time constant, and determines the warm-up operation time as an arbitrary ratio of the estimated thermal displacement saturation time. 3. The method for determining a warm-up operation time before bearing diagnosis in a machine tool according to item 1.   The method according to claim 3, wherein the arbitrary ratio is 89% or more. A rotating shaft device that supports a rotating shaft that is rotationally driven by a bearing, a control unit that controls the rotation of the rotating shaft, a temperature detecting unit that detects the temperature of the bearing, and the control unit that controls the rotating shaft. Bearing diagnosis means for executing a bearing diagnosis for detecting an abnormality of the bearing after performing a warm-up operation of rotating at a predetermined rotation speed and for a time until the temperature detected by the temperature detection means reaches a steady state. Machine tool with
During normal operation before the execution of the bearing diagnosis, the temperature of the bearing is detected by the temperature detecting unit, and the temperature during the normal operation is determined based on the detected temperature change of the bearing and the rotation speed of the rotating shaft. Temperature time constant calculating means for calculating a time constant,
Storage means for storing the calculated temperature time constant,
When performing the warm-up operation, time determining means for determining the time of the warm-up operation at the predetermined rotation speed based on the stored temperature time constant,
A machine tool comprising:   The temperature time constant calculating means detects the temperature of the bearing only during normal operation at the predetermined rotation speed, and calculates a temperature time constant at the predetermined rotation speed from a change in temperature rise at the predetermined rotation speed. The machine tool according to claim 5, wherein   The said time determination means estimates the thermal displacement saturation time from the said temperature time constant, and determines the time of the warm-up operation at an arbitrary ratio of the estimated thermal displacement saturation time. A machine tool according to claim 1.   The machine tool according to claim 7, wherein the arbitrary ratio is 89% or more.

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