JP2009148076A - Servo motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost servomotor smoothly rotating a motor shaft for a long time by stably holding rolling elements even in strong magnetic fields and under high temperature. <P>SOLUTION: In this servomotor, the rotational state of the motor shaft 4 is detected. The rotational state of the motor shaft is controlled based on the detected result. A current supplied from a power supply unit is changed to repeat rotation and stop of the motor shaft and increase/reduction in rotational speed. According to the change in current at acceleration/deceleration, a magnetic field is generated inside the motor and a change occurs in magnetic flux in the magnetic fields. The motor shaft is supported by a rolling bearing 20 in a freely rotating manner. The rolling bearing is provided with: at least a pair of bearing rings 22, 24 rotatably arranged facing each other; a plurality of rolling elements 26 mounted rollably between the bearing rings; and a retainer 28 for holding the rolling elements in a freely rotating manner and rolling the adjacent rolling elements with a predetermined gap. The retainer is made of non-magnetic austenitic stainless steel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a servo motor capable of controlling the rotation state (rotation speed, rotation speed, rotation direction, rotation angle, etc.) of a motor rotation shaft with high accuracy, and in particular, a rolling bearing for rotatably supporting the motor rotation shaft. Relates to a servo motor used in a strong magnetic field and at a high temperature.

  Conventionally, a servo motor is known as a drive device that can control the rotation state of a motor rotation shaft (hereinafter referred to as a motor shaft) with high accuracy, such as the rotation speed, rotation speed, rotation direction, and rotation angle. (See Patent Document 1). Normally, a servo motor is a motor (direct current (DC) motor or alternating current (AC) motor) unit that rotates a predetermined motor shaft, and the rotation state of the motor unit (for example, the rotation speed or rotation angle of the motor shaft). And a braking unit (for example, an electromagnetic brake) for decelerating or stopping the rotation of the motor. The motor shaft is rotated by electric power (in short, drive current) supplied to the motor unit from an external or built-in power supply device.

  As shown in FIG. 1, the motor shaft 4 of the servo motor is rotatably supported by a rolling bearing (hereinafter referred to as a servo motor bearing) 20, and in this state, it is mounted on various machine devices (machine tools, robots, etc.). Installed. The servo motor bearing 20 is formed on a pair of race rings 22 and 24 (a rotating wheel (inner ring) 22 and a stationary ring (outer ring) 24)) that are opposed to each other so as to be relatively rotatable, and the inner and outer rings 22 and 24, respectively. A plurality of rolling elements (balls) 26 are provided between the raceway grooves 22a and 24a facing each other so as to be able to roll. In this case, the rolling elements 26 are rotatably held one by one in pockets formed in an annular cage (for example, a corrugated matching cage) 28, and adjacent rolling elements 26 are spaced apart from each other by a predetermined distance. It is incorporated between the raceway grooves 22a and 24a so as to be able to roll while being maintained. As a result, each rolling element 26 can roll between the inner and outer rings 22 and 24 (between the raceway grooves 22a and 24a) without contact of the rolling surfaces with each other. The increase in rotational resistance and the seizure caused by the friction caused by contact with each other are prevented.

  Here, as the retainer 28, various metal retainers, resin retainers, and the like are properly used according to the use condition and purpose of use of the servo motor. For example, a cage made of metal (for example, a cold rolled steel plate (SPCC)) has an advantage that it can be used at high temperature and can be manufactured at low cost. On the other hand, since such a metal cage (SPCC cage) has magnetism, when incorporated in a servo motor having a braking portion (electromagnetic brake) 2, the electromagnetic brake is used when the motor shaft 4 is accelerated or decelerated. If the magnetic field (magnetic field) generated from the second magnet coil 6 or a peripheral device outside the motor generates a strong magnetic field, it may be magnetized.

  When the cage 28 is magnetized in this manner, the cage 28 comes into contact with the inner ring 22 or the outer ring 24 in a biased state, and there is a problem that wear (uneven wear) due to friction tends to be caused between them. During acceleration / deceleration of the motor shaft 4 or the like, the current flowing through the magnet coil 6 of the electromagnetic brake 2 changes, and the magnetic field (magnetic field) generated from the magnet coil 6 suddenly changes along with the change in current. This greatly changes the magnetic flux in the magnetic field.

On the other hand, when a cage made of resin (for example, plastic) is used, even if the servo motor bearing 20 is incorporated in the servo motor equipped with the electromagnetic brake 2 as described above, such a strong magnetic field is generated. It will not be affected. Therefore, by making the cage 28 made of resin (made of plastic), it is possible to avoid the occurrence of uneven wear on the cage 28, the inner ring 22 and the outer ring 24.
JP 2002-305852 A

By the way, 66 nylon is mentioned as one of the typical resin (plastic) cage materials that are widely used. However, the 66 nylon cage has an upper limit of the usable temperature range (that is, a service temperature) of up to about 150 ° C., and considering the possibility of deformation or alteration, the maximum temperature during use is It can be used stably only with a servo motor up to 150 ° C., and its application is limited.
In recent years, the use conditions of machine devices (machine tools, robots, etc.) on which servo motors are mounted have varied, and the temperature when using the servo motors often exceeds 150 ° C. There is a problem in using a 66 nylon cage for robots and robots.

  In this case, instead of 66 nylon, for example, a plastic (plastic) cage made of 46 nylon, which is a plastic resin that can be used under high temperature conditions (150 ° C. or higher) (that is, a high durability temperature), is used. By using it, it becomes possible to avoid the problem of the service temperature. However, since 46 nylon is more expensive than 66 nylon, if the cage is made of 46 nylon, the manufacturing cost increases, and as a result, the servo motor cannot be provided at low cost. End up.

  The present invention has been made in order to solve such a problem, the purpose of which is to make the retainer of the bearing for the servo motor made of non-magnetic austenitic stainless steel, so that the magnetic field and high temperature (for example, An object of the present invention is to provide a low-cost servo motor that can stably hold a rolling element even under a use environment of 150 ° C. or higher and can smoothly rotate a motor shaft over a long period of time.

  In order to achieve such an object, the servo motor according to the present invention detects the rotation state of the motor shaft, and the rotation state of the motor shaft is controlled based on the detection result, and the current supplied from the power supply device. The rotation and stop of the motor shaft and the acceleration / deceleration of the rotation speed are repeated due to the change of, and a magnetic field is generated inside the motor with the change of the current during the acceleration / deceleration, and the magnetic flux in the magnetic field Change has occurred. In such a servomotor, the motor shaft is rotatably supported by a rolling bearing, and the rolling bearing is capable of rolling between at least a pair of bearing rings disposed so as to be relatively rotatable and the bearing rings. A plurality of rolling elements incorporated therein, and a holder for rotatably holding these rolling elements, and rolling adjacent rolling elements in a state of maintaining a predetermined distance from each other; Is made of nonmagnetic austenitic stainless steel.

In this case, the motor shaft is decelerated or stopped by an electromagnetic brake, and the servo motor is supplied from the power supply device at the time of starting and stopping the rotation of the motor shaft in addition to the change in current at the time of acceleration / deceleration. A magnetic field is generated inside the motor as the current changes, and the magnetic flux in the magnetic field is changed.
The upper limit of the usable temperature range of the rolling bearing is set to a temperature higher than 150 ° C.

  According to the servo motor according to the present invention, the bearing of the servo motor bearing is made of a nonmagnetic austenitic stainless steel material, so that it can be used in a strong magnetic field and at a high temperature (for example, in a use environment of 150 ° C. or more). Also, the rolling element can be stably held by such a cage. As a result, the motor shaft can be smoothly rotated over a long period of time, and the cost of the servo motor can be reduced.

  Hereinafter, a servo motor according to an embodiment of the present invention will be described with reference to the accompanying drawings. The servo motor of the present invention is mounted on various mechanical devices (for example, machine tools and robots), and the motor rotation shaft of the servo motor (hereinafter referred to as the motor shaft) is rotatably supported by a servo motor bearing. It is used in the state that was done. Here, the case where the motor shaft 4 of the servomotor is rotatably supported by the servomotor bearing 20 as shown in FIG. 1 is assumed as an example.

  In this case, the servo motor includes a motor (direct current (DC) motor or alternating current (AC) motor) unit 40 that rotates the motor shaft 4 and a rotation state of the motor unit 40 (for example, the rotational speed of the motor shaft 4 or A control unit for controlling a rotation angle (not shown), and a braking unit (for example, an electromagnetic brake) 2 for decelerating or stopping the rotation of the motor unit 40. Yes. The motor shaft 4 is rotated by electric power (in short, a drive current) supplied from a predetermined power supply device. However, the power supply device may be built in the servo motor or may be external to the servo motor. The structure arrange | positioned in may be sufficient.

  The control unit detects the rotation state of the motor unit 40 (motor shaft 4), and compares the detection result with a target value (for example, a set rotation speed or a set rotation angle of the motor shaft 4) set in advance. To do. Based on the comparison result, that is, the comparison result is fed back to the amount of drive current supplied from the power supply device to the motor unit 40, so that the rotation state of the motor unit 40 is controlled to the target value. As a result, the rotation state (rotation speed, rotation angle, etc.) of the motor shaft 4 can be controlled with high accuracy. For example, the rotation and stop of the motor shaft 4 can be repeated frequently in a short cycle, and the rotation Speed acceleration / deceleration can always be performed with good response.

  The rotation state of the motor unit 40 (for example, the number of rotations and the rotation angle of the motor shaft 4) is detected by irradiating the detection target body with predetermined irradiation light and detecting the reflected light state with the detection body. What is necessary is just to use a sensor etc. For example, an encoder (not shown) is attached to a rotor (not shown) of the motor unit 40 and rotated together with the rotor, and irradiation light (laser light or the like) is emitted from a light emitter (not shown) to the rotating encoder. Then, the reflected light from the encoder is received by a light receiving element (not shown), and the state change per unit time of the reflected light is processed to calculate the rotational state of the motor unit 40 (the rotational speed of the motor shaft 4 and the like). Rotational angle etc.) can be measured (detected).

  In another way, according to the servo motor, the motor shaft 4 can be accurately stopped at a preset target position. That is, the servo motor can control the rotation speed or the stop position with high accuracy by repeatedly decelerating and stopping the motor shaft 4 by the braking unit (electromagnetic brake) 2.

  In this case, when the motor shaft 4 rotates, the magnet coil 6 of the electromagnetic brake 2 is energized (current is flowing). In this state, the amateur (non-rotating movable plate) 8 is attracted to the stator 12 and the coil spring 10 is pushed in and compressed. When the armature 8 is attracted to the stator 12 of the electromagnetic brake 2 as described above, a gap is formed between the armature 8 and the electromagnetic brake 2 is opened, thereby opening the motor shaft 4 and freely rotating. It becomes a state.

  On the other hand, when the motor shaft 4 is braked, the magnet coil 6 of the electromagnetic brake 2 is in a non-energized state (a state in which no current flows). In this state, the compressed coil spring 10 extends, and the armature 8 is pressed against the friction plate 14 by the biasing force of the coil spring 10. By pressing the armature 8 against the friction plate 14 in this way, a strong friction force is generated between the armature 8 and the friction plate 14, and the rotation speed of the motor shaft 4 can be reduced by the friction force. Finally, the motor shaft 4 can be completely stopped.

  The servomotor having such a structure has its motor shaft 4 rotatably supported by a servomotor bearing 20, and is mounted on various machine devices (machine tools, robots, etc.) in this state. The servo motor bearing 20 includes at least a pair of bearing rings 22 and 24 (a rotating ring (inner ring as an example) 22 and a stationary ring (same as the outer ring) 24) arranged opposite to each other so as to be relatively rotatable, and the bearing ring. A plurality of rolling elements (balls) 26 formed so as to be able to roll between the raceway grooves 22a and 24a that are formed on the opposite sides of the raceway grooves 22a and 24a, and these rolling elements 26 are rotatably held and adjacent to each other. A cage 28 is provided for rolling the rolling elements 26 while maintaining a predetermined distance from each other.

  As the rolling element 26, a ball as shown in FIG. 1 may be applied, and various types of rollers (such as a tapered roller, a cylindrical roller, and a spherical roller) may be used depending on the use condition or purpose of use of the servo motor. You may apply. Moreover, what is necessary is just to apply arbitrary types according to the kind of rolling element 26 as the retainer 28. For example, when the rolling element is a ball, a corrugated type or a crown type as shown in FIG. 1 can be applied, and the rolling element can be of various types of rollers (such as a tapered roller, a cylindrical roller, and a spherical roller). ), It is possible to apply types such as a machined die, a comb die and a cage die.

  In any case, the rolling elements 26 are rotatably held one by one in the pockets formed in the cage 28, and the adjacent rolling elements 26 are kept at a predetermined interval (for example, each rolling element 26). In a state in which the moving bodies 26 are arranged at equal intervals), they are incorporated into the servo motor bearing 20 so as to be able to roll between the raceway grooves 22a and 24a. Thereby, each rolling element 26 can roll between the inner and outer rings 22 and 24 (between the raceway grooves 22a and 24a) without the rolling surfaces (surfaces) coming into contact with each other. It is possible to prevent an increase in rotational resistance, seizure, and the like caused by friction between the rolling elements 26 that are in contact with each other.

  In the configuration shown in FIG. 1, the servo motor bearing 20 includes a sealing device (non-contact type shield) 30 for shielding the inside of the bearing from the outside to keep it sealed (airtight and liquid tight). Is attached to the open portion between the inner and outer rings 22 and 24, and the attachment of the sealing device 30 prevents foreign matter (for example, muddy water or dust) from entering the interior from the outside of the servo motor bearing 20. In addition, the lubricant (for example, grease and lubricating oil) enclosed inside is prevented from leaking to the outside. 1 shows a sealing structure with a non-contact type metal shield (for example, an iron shield), but a contact type elastic seal (for example, a nitrile rubber seal) is installed as a sealing device. A sealed structure may be used.

  In addition, for the servo motor bearing 20, friction and wear are reduced at portions where the raceway grooves 22a, 24a of the inner and outer rings 22, 24 and the rolling surfaces (surfaces) of the rolling elements 26 are in contact with each other. Lubrication is carried out for the purpose of preventing sticking and extending the fatigue life, and a lubricant is enclosed inside. The lubricant may have a configuration in which various base oils and thickeners are arbitrarily blended according to the use conditions and purpose of use of the servo motor. In the present embodiment, as an example, it is assumed that a lubricant composed of a synthetic hydrocarbon oil as a base oil and a urea compound as a thickener is sealed in the servo motor bearing 20. . At that time, a lubricant (for example, grease) may be generated by blending the following thickener with the synthetic hydrocarbon oil as the base oil based on the total amount of the composition. Specifically, synthesis is performed so that the gelling agent composed of a urea compound is 2 to 30% by weight, and sorbitan monooleate, barium sulfonate, and barium lanolinate are all 0.2 to 3.0% by weight. What is necessary is just to mix | blend with respect to hydrocarbon oil, respectively.

  Incidentally, in the servo motor according to the present embodiment, the control unit controls the magnitude (supply amount) of the drive current supplied from the power supply device to the motor unit 40, and the electromagnetic brake 2 brakes the motor shaft 4. Thus, the motor shaft 4 is accelerated or decelerated. At the time of acceleration / deceleration of the motor shaft 4, the current flowing through the magnet coil 6 of the electromagnetic brake 2 changes greatly, and a strong magnetic field (strong magnetic field) is generated inside the motor along with the current change, and the generated magnetic field is abrupt. Change will occur. That is, the magnetic flux in the magnetic field changes greatly with the change in the magnetic field.

  Similarly, when the rotation of the motor shaft 4 is started, a current starts to flow to the magnet coil 6 of the electromagnetic brake 2, whereas when the rotation is stopped, the current flowing through the magnet coil 6 is stopped. . Therefore, when the rotation of the motor shaft 4 is started and when the rotation is stopped, the current flowing through the magnet coil 6 of the electromagnetic brake 2 changes greatly, and a strong magnetic field is generated inside the motor along with the current change, and the generated magnetic field The magnetic flux in the magnetic field changes drastically with the rapid change.

  Furthermore, when not only the magnetic field generated from such a member of the servo motor itself (specifically, the electromagnetic brake 2) but also a peripheral device disposed outside the servo motor generates a strong magnetic field, Also by the magnetic field generated from the peripheral device, the magnetic field inside the motor is affected, and the magnetic flux in the magnetic field changes.

  Therefore, in this embodiment, a nonmagnetic austenitic stainless steel material is used as the cage 28 of the servo motor bearing 20. At this time, the cage 28 may be configured by arbitrarily selecting a non-magnetic austenitic stainless steel material according to the use condition or purpose of use of the servo motor. Here, the cage 28 is made of SUS304 stainless steel material. A case is assumed as an example.

  By making the cage 28 made of such a non-magnetic austenitic stainless steel material (made of SUS304 stainless steel material), the motor shaft 4 is strengthened inside the motor shaft at the time of acceleration / deceleration, at the start of rotation, and at the stop of rotation. Even when the magnetic field is generated and the magnetic flux changes, the cage 28 is not magnetized. That is, it is possible to reliably prevent the cage 28 from being attracted to the inner ring 22 and the outer ring 24 and coming into contact with the inner and outer rings 22 and 24 in a biased state, and wear due to friction generated between them (uneven wear). Can be significantly reduced.

  In addition, for example, the rigidity of the cage 28 can be maintained even at a high temperature of 150 ° C. or higher, and deformation or alteration as compared with a plastic resin cage (for example, a 66 nylon cage). Can be significantly reduced. As a result, the cage 28 can stably hold the rolling element 26 even under such a strong magnetic field and high temperature.

  Furthermore, by using a non-magnetic austenitic stainless steel material (made of SUS304 stainless steel material), a cage 28 capable of stably holding the rolling element 26 even under such a strong magnetic field and high temperature is used as a plastic. This can be realized at a lower cost than a resin cage (for example, a 46 nylon cage).

  As described above, according to the servo motor bearing 20 in which the cage 28 according to the present embodiment is incorporated, even when the servo motor bearing 20 is used in a strong magnetic field and a high temperature environment, The servo motor (motor shaft 4) can be smoothly rotated over a long period of time, and the cost of the servo motor can be reduced.

  In this embodiment, the servo motor in which the normal use temperature (normal temperature) is 120 ° C. or higher, or the upper limit of the usable temperature range (maximum use temperature) is set higher than 150 ° C. It is assumed that the servo motor bearing 20 is used in a temperature environment.

  In the above description, the materials (materials) of the inner ring 22, the outer ring 24, and the rolling elements 26 constituting the servo motor bearing 20 are not particularly mentioned, but these are used for the use condition and purpose of use of the servo motor. Accordingly, any material (raw material) may be selected and configured. As an example, in the present embodiment, it is assumed that the inner ring 22, the outer ring 24, and the rolling element 26 are all made of high carbon chrome bearing steel (SUJ2).

The schematic diagram which shows the structure of the servomotor which concerns on one Embodiment of this invention.

Explanation of symbols

4 Motor shaft 20 Servo motor bearings 22 and 24 Race ring 26 Rolling element 28 Cage

Claims (3)

The rotation state of the motor shaft is detected, the rotation state of the motor shaft is controlled based on the detection result, and the rotation and stop of the motor shaft and the acceleration / deceleration of the rotation speed are controlled by a change in current supplied from the power supply device. A servo motor that is repeated and generates a magnetic field inside the motor as the current changes during acceleration and deceleration, and changes in the magnetic flux in the magnetic field,
The motor shaft is rotatably supported by a rolling bearing, and the rolling bearing has at least a pair of bearing rings arranged to face each other so as to be relatively rotatable, and a plurality of rolling rings incorporated between the bearing rings. The rolling elements and these rolling elements are rotatably held, and are equipped with a cage for rolling adjacent rolling elements at a predetermined interval.
The said retainer is comprised with a nonmagnetic austenitic stainless steel material, The servomotor characterized by the above-mentioned.   The motor shaft is decelerated or stopped by an electromagnetic brake, and in addition to the change in current at the time of acceleration / deceleration, the motor is accompanied by a change in current supplied from the power supply device at the start and stop of rotation of the motor shaft. 2. The servo motor according to claim 1, wherein a magnetic field is generated therein and a change occurs in the magnetic flux in the magnetic field.   The servo motor according to claim 1 or 2, wherein an upper limit of a usable temperature range of the rolling bearing is set to be higher than 150 ° C.

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