JP2007298527A - Main spindle support device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine a defective lubricating state of rolling bearings 3, 3 before the occurrence of damage in each rolling bearing 3, 3. <P>SOLUTION: A potential difference between an outer ring 4 and an inner ring 5 of each rolling bearing 3, 3 incorporated with a conductive ceramic rolling elements 6 and 6. This potential difference is changed depending on the quality of the lubricating state, a signal showing the potential difference is input to a controller 15, whereby the problem can be solved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The rolling bearing operating state monitoring device according to the present invention is used to determine the quality of the lubricating state of a rolling bearing operated under a minute amount of lubrication, such as a rolling bearing for supporting the spindle of a machine tool.

  The spindle of a machine tool rotates at a high speed while being supported by a rolling bearing such as a ball bearing or a roller bearing. Such rolling bearings are lubricated by a small amount of lubrication using oil-air, oil mist, or the like in order to reduce rotational resistance and minimize fluctuations. Even when grease lubrication is used, the amount of grease is kept small. In other words, only the minimum necessary amount of lubricating oil is supplied into the rolling bearing. Therefore, when a lubrication means such as an oil / air supply device breaks down or grease is depleted and a lubrication failure occurs, it is likely to cause serious damage such as seizure in a short time.

  For this reason, conventionally, vibration or sound generated in the part where the rolling bearing is installed is detected, the temperature of this part is detected, or the operating time of a machine tool or the like incorporating the rolling bearing is measured. Thus, information for maintaining the rolling bearing is obtained.

Since the value of vibration, sound, or temperature information changes after a certain degree of damage has occurred based on poor lubrication, it cannot always be said that sufficient prevention of damage to the rolling bearing is achieved. Also, measuring the operating time cannot cope with poor lubrication due to a failure of the fueling device.
In consideration of these matters, it is desired to realize a monitoring device that can detect the fact that a poorly lubricated state has actually occurred before damage based on the poor lubrication occurs.

  On the other hand, a rolling element made of a ceramic such as silicon nitride may be used as a rolling element that constitutes a rolling bearing that is incorporated in various machine tools such as a machining center and supports a spindle that rotates at high speed. The reason for using such a ceramic rolling element is that the ceramic rolling element is lightweight, has a small amount of thermal expansion (low linear expansion coefficient), and has excellent wear resistance and seizure resistance. Because of that. However, ceramic rolling elements have different characteristics from ordinary rolling elements made of bearing steel, and accordingly, an abnormality monitoring method needs to be considered accordingly.

JP-A-62-87463 JP-A-62-265177 JP-A 64-15523 JP-A-2-43699 JP-A-3-29744 JP-A-10-87370 Japanese Patent Laid-Open No. 2000-154064 JP 2000-192969 A Japanese Patent Publication No.8-16030

  In view of such circumstances, the present invention has been devised in order to realize a rolling bearing operating state monitoring device that can quickly and accurately determine whether or not a rolling bearing incorporating a ceramic rolling element is abnormal. is there.

The rolling bearing operating state monitoring device according to the present invention includes a pair of race rings made of metal and facing each other, and raceway surfaces formed on surfaces facing each other of the raceways. Provided with a plurality of rolling elements each made of ceramic, and is operated in a state in which lubricating oil is interposed between contact portions of the raceway surfaces and the rolling surfaces of the rolling elements. This is for monitoring the operating condition of the rolling bearing.
For this purpose, at least one of the ceramic rolling elements is made of conductive ceramic, and one of the race rings or a member electrically connected to the one of the race rings, and the other The resistance value between the bearing ring of this or the member that is electrically connected to the other race ring or a potential difference that changes based on this resistance value is monitored, and the resistance value changes based on this resistance value or this resistance value. It is assumed that the lubrication state is poor when the potential difference is out of the predetermined range.

  According to the rolling bearing operating state monitoring device of the present invention configured as described above, it is possible to detect that the rolling bearing is in a poorly lubricated state before damage based on the poor lubrication occurs.

  FIG. 1 shows the rolling bearing operating state monitoring device of the present invention incorporated in a machine tool. A main shaft 2 made of metal such as steel is also rotatably supported by a pair of rolling bearings 3 and 3 inside a housing 1 made of metal such as steel. Each of these rolling bearings 3 and 3 includes a metal outer ring 4 having an outer ring raceway on its inner peripheral surface, a metal inner ring 5 having an inner ring raceway on its outer peripheral surface, and between these outer ring raceway and inner ring raceway. A plurality of rolling elements 6, 6 each made of ceramic and provided in a freely rolling manner, and a synthetic resin cage 7 for holding the rolling elements 6, 6 in a freely rolling manner. .

  Of the rolling elements 6 and 6, at least one (preferably, a plurality, more preferably all) of the rolling elements 6 that are spaced apart in the circumferential direction are made of conductive ceramic. As a conductive ceramic for constituting this rolling element 6, for example, various materials described in Patent Documents 1 to 9 and the like can be used. Furthermore, as disclosed in Japanese Patent Application No. 2001-203783, a conductive material containing 10 to 60% by weight of one or more selected from nitrides, carbides, borides and oxides of transition metals. Rolling elements made of conductive ceramic can also be used.

  As described above, various types of conductive ceramics have been known in the past, and the type of conductive ceramic that can be used in the practice of the present invention is not particularly limited. Is omitted. In addition, the same kind of rolling elements 6 and 6 to be incorporated in each of the rolling bearings 3 and 3 are used. When mixing rolling elements made of conductive ceramics and rolling elements made of non-conductive ceramics, make sure that the main components of both types of rolling elements are the same, so that the specific gravity, thermal expansion coefficient, etc. are as close as possible. use.

  In the rolling bearing operating state monitoring device of the present invention, the outer ring 4 is fitted and fixed in order to know the lubrication state of the rolling bearings 3 and 3 incorporating the conductive ceramic rolling elements 6 and 6 as described above. The potential difference between the housing 1 and the main shaft 2 to which the inner ring 5 is fitted and fixed can be measured.

  Therefore, in the illustrated example, a closed circuit is formed in which the housing 1, the main shaft 2, the rolling bearings 3 and 3, a DC power supply 8, and a resistor 9 are connected in series. Note that one end of the conducting wire 10 constituting the closed circuit is directly connected to the housing 1. On the other hand, the other end of the conducting wire 10 is electrically connected to the main shaft 2 via the brush 11. That is, the brush 11 supported on the holder 12 made of an insulating material such as a synthetic resin, which is supported on the end of the housing 1, is pressed against the outer surface of the main shaft 2 or the conductor fixed to the main shaft 2 by the spring 13, By connecting the other end of the conducting wire 10 to the brush 11, the other end of the conducting wire 10 and the main shaft 2 are electrically connected.

  A voltmeter 14 is provided in the middle of the conducting wire 10 in parallel with the DC power supply 8 and the resistor 9. Therefore, the voltmeter 14 detects a potential difference between the housing 1 and the main shaft 2 (equal to a potential difference between the outer ring 4 and the inner ring 5 constituting the rolling bearings 3 and 3). The voltage value of the DC power source 8 is determined in consideration of design within a range of about 0.1 to 10V. The resistance value of the resistor 9 is also determined in consideration of design within a range of about 1 kΩ to 1 MΩ.

  The measured value of the voltmeter 14 as described above is input to the controller 15 having a comparator and a determiner. The controller 15 compares the measured value of the voltmeter 14 with a preset reference value, and issues a warning when the measured value deviates to the poor lubrication side with the reference value as a boundary. The spindle 2 is stopped. In the illustrated example, a detection signal of the vibrometer 16 for detecting the vibration of the housing 1 is also input to the controller 15. The controller 15 issues an alarm and stops the spindle 2 when the vibration value of the housing 1 represented by the detection signal exceeds a predetermined value.

According to the operating condition monitoring apparatus of the rolling bearing of the present invention configured as described above, the fact that the rolling bearings 3 and 3 are in a poor lubrication state is indicated as follows. It is possible to know before the occurrence of damage due to poor lubrication.
First, when the lubrication state of the rolling bearings 3 and 3 is good, the electrical resistance between the housing 1 and the main shaft 2 is high. On the contrary, when the lubrication state is poor, Resistance becomes low. That is, when the lubrication state is good, a sufficient oil film is interposed between the outer ring raceway and the inner ring raceway and the rolling surfaces of the rolling elements 6 and 6. Then, the electrical resistance between the housing 1 and the main shaft 2 is increased by the presence of an oil film as an insulating material, and the potential difference between the housing 1 and the main shaft 2 is high (the voltage of the DC power supply 8). Close to).

On the other hand, when the lubrication state is poor, there is no oil film between the outer ring raceway and the inner ring raceway and the rolling surfaces of the rolling elements 6, 6, or even if it exists, it is insufficient. It becomes. In such a state, the contact state between the outer ring raceway and the inner ring raceway and the rolling surfaces of the rolling elements 6 and 6 becomes a contact state close to direct contact, and the housing 1 and the main shaft 2 are not in contact with each other. , And the potential difference between the housing 1 and the main shaft 2 is reduced. Therefore, if the measured value V ₁₄ of the voltmeter 14, the DC power supply 8 lower predetermined or than the voltage V ₈ of (that, for example, "V ₁₄ <0.8 V _8") becomes, the outer ring raceway and inner ring raceway It is determined that a sufficient oil film is not formed between the rolling elements 6 and the rolling surfaces of the rolling elements 6, 6, that is, a poorly lubricated state. Therefore, if the controller 15 determines that the lubrication state of each of the rolling bearings 3 and 3 is poor, the spindle 2 is stopped and an alarm is provided by an alarm device (buzzer or warning light) (not shown). To emit.

When a machine tool or the like is operated, a state of poor lubrication appears locally and may recover after a very short time. For this reason, if the spindle 2 is stopped or an alarm is issued at the moment when the controller 15 determines that the lubrication is poor, the emergency stop of the machine tool may be performed more than necessary. Therefore, it is possible to cause the controller 15 to stop the spindle 2 or issue an alarm only when the state of poor lubrication continues for a predetermined time (several seconds) or longer. Further, when the machine tool is operated (at the time of cutting), the blade supported on the housing 1 and the workpiece supported on the main shaft 2 side come into contact with each other, and the housing 1 and the main shaft 2 are electrically connected. May be short-circuited. In such a case, the measured value of the voltmeter 14 becomes substantially zero V. In such a case, if the controller 15 determines that the lubrication is defective, an unnecessary emergency stop is performed. Therefore, it is possible to determine whether the lubrication state is good or bad under the condition that the measured value of the voltmeter 14 is a predetermined value (for example, 0.01 V ₈ ) or more.

  Further, in the illustrated example, the vibration of the housing 1 is detected by the vibrometer 16, and the operating state of the machine tool can be determined by the magnitude of the vibration, so that the machine tool is seriously damaged. Things can be prevented more reliably. That is, if for some reason the state of poor lubrication cannot be determined from the detection value of the voltmeter 14 or if the rolling bearings 3 and 3 are damaged due to surface peeling or the like due to their life, The main shaft 2 can be stopped before the parts other than the rolling bearings 3 and 3 are damaged.

  The rolling bearing operating state monitoring device of the present invention is configured and operates as described above, but because it can detect that a poorly lubricated state has actually occurred before damage based on this poor lubrication occurs, It is possible to effectively prevent various rotating devices such as machine tools from failing due to poor lubrication. In addition, this invention can be utilized not only for a radial rolling bearing but for monitoring the operating state of a thrust rolling bearing.

1 is a circuit diagram showing an example of an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 2 Main shaft 3 Rolling bearing 4 Outer ring 5 Inner ring 6 Rolling body 7 Cage 8 DC power supply 9 Resistance 10 Conductor 11 Brush 12 Holder 13 Spring 14 Voltmeter 15 Controller 16 Vibrometer

Claims (1)

  A plurality of each made of ceramic, each provided between a pair of raceways made of metal and facing each other, and raceways formed on surfaces facing each other of both raceways In order to monitor the operating state of the rolling bearing operated with the lubricating oil interposed between the contact surfaces of the raceways and the rolling surfaces of the rolling elements, At least one of the rolling elements made of ceramic is made of a conductive ceramic, and one of the race rings or a member electrically connected to the one of the race rings and the other race ring or the other of the race rings The resistance value between the bearing ring and a member that is in electrical conduction or a potential difference that changes based on the resistance value is monitored, and the resistance value or the potential difference that changes based on the resistance value deviates from a predetermined range. If Slipping state is assumed to be defective, the operating condition monitoring apparatus of the rolling bearing.

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