JP2004180457A - Driving servomotor for medical equipment and servomotor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure high positioning accuracy even if sterilizing process by high-temperature pressurized steam is performed. <P>SOLUTION: Ball bearings 2 are fitted to both ends in the axial direction of a casing 1 functioning as a stator core. The ball bearings 2 have rollers made of ceramics. A stainless shaft 3 having a permanent magnet 4 and a magnetic disk 5 on the outside circumferential part is supported between the ball bearings 2 in such a way as to be rotatable. On the inside circumferential surface of the casing 1, 6 pieces of air-core coils 7 fixed to the outside circumferential surface of a thin wall ring 8 is arranged. Also, a Hall element 9 for detecting the magnetic poles of the permanent magnet 4 and an MR element 10 for detecting the magnetic poles of the magnetic disk 5 are arranged on the inside circumferential surface of the casing. The air-core coil 7, the Hall element 9, and the MR element 10 are integrally formed with a resin 12. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a servomotor and a servomotor for driving medical equipment that can withstand high-temperature pressurized steam.
[0002]
[Prior art]
Medical equipment, especially medical equipment used in the field of surgery or dental care, is used, for example, under high pressure before and after use in order to prevent bacteria and viruses from infecting patients through the equipment. Sterilization by steam is performed. Therefore, it is necessary to reduce the size of the driving motor incorporated in the medical device and to have a structure capable of withstanding high-temperature pressurized steam, and as a countermeasure to this, a thin rust-resistant metal layer is formed on the yoke surface of the brushless motor. Has been proposed (see, for example, Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 6-351221
[Problems to be solved by the invention]
However, the brushless motor is for rotating a polishing drill of a dental polishing apparatus at a high speed, and is not suitable for a motor requiring high positioning accuracy such as a motor for driving a medical manipulator. The drive motor of the medical manipulator needs to be composed of an encoder for detecting the rotational position of the rotor with high accuracy, a servomotor including a bearing for securely holding the rotary shaft at a predetermined position, and the like. Therefore, the configuration of the entire motor is complicated, and it is not sufficient to simply perform rust prevention treatment on the yoke surface.
[0005]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a servomotor and a servomotor for driving a medical device that can ensure high positioning accuracy even when performing sterilization by high-temperature pressurized steam. To provide.
[0006]
[Means for Solving the Problems]
A servo motor for driving a medical device according to claim 1 of the present invention and a servo motor according to claim 5 include a cylindrical stator yoke, bearings provided at both axial ends of the stator yoke, and a stator yoke. A rotor disposed on an inner peripheral portion and rotatably supported by the bearing and a rotor including a permanent magnet mounted on an outer peripheral surface of the shaft; and a rotor provided on an inner peripheral surface of the stator yoke and facing the permanent magnet. A plurality of air-core coils arranged in the circumferential direction as described above, comprising an encoder provided on the inner peripheral surface of the stator yoke and having a detection unit for detecting the rotational position of the rotor, the outer peripheral surface of the permanent magnet A thin sheet made of a non-magnetic material that holds the air-core coil and the detection unit is provided between the stator and the stator yoke and is disposed opposite to each other with a predetermined gap therebetween. Ku and also the rolling element is characterized by being configured of ball bearings made of ceramic.
[0007]
According to the configuration, the air-core coil and the detection unit of the encoder can be protected from high-temperature pressurized steam by the thin sheet, and a predetermined gap is secured between the air-core coil and the outer peripheral surface of the permanent magnet. Can be. For this reason, it is possible to prevent the occurrence of malfunctions and a decrease in rotational accuracy due to repeated sterilization. Further, since the shaft is supported by the ball bearing, the shaft can be reliably held at a predetermined stop position. Further, since at least the rolling elements of the ball bearings are made of ceramic which is hardly damaged and has excellent wear resistance, a lubricant can be eliminated.
[0008]
According to a second aspect of the present invention, there is provided a drive servomotor for a medical device, wherein the air core coil and the detection unit are molded with resin.
According to the above configuration, it is possible to prevent the high-temperature pressurized steam from reaching the air core coil and the detection unit. Further, even if the mold resin swells due to the high-temperature pressurized steam, the thin sheet prevents the resin from expanding radially inward. Therefore, it is possible to prevent the dimensions between the permanent magnet and the rotor from being disturbed by the sterilization process.
[0009]
According to a third aspect of the present invention, there is provided a drive servomotor for medical equipment, comprising: an encoder, a magnetic disk provided on a shaft and rotating integrally with the shaft, and a magnetic sensor for detecting a magnetic signal of the magnetic disk. It is characterized by having done.
According to the above configuration, the rotation angle of the rotor can be accurately detected.
[0010]
In this case, it is preferable that the magnetic sensor is constituted by an MR element (the invention of claim 4). By making the magnetic sensor from an MR element, it is possible to further reduce the size.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The servomotor according to the present embodiment is used for driving an arm of a medical device, for example, a medical manipulator, and includes a cylindrical case 1 as a stator core as shown in FIG. The case 1 is made of, for example, a magnetic material SUS, and its surface is subjected to rust prevention processing, for example, Ni plating.
[0012]
Ball bearings 2 are fitted to both ends of the case 1 in the axial direction. In the ball bearing 2, the outer ring 2a, the inner ring 2b, and the rolling elements 2c are all made of ceramic. A shaft 3 made of stainless steel is rotatably supported between the ball bearings 2. A cylindrical permanent magnet 4 and a magnetic disk 5 are fixed to an outer peripheral portion of a portion of the shaft 3 located in the case 1 at an interval in the axial direction. The permanent magnet 4 is magnetized to, for example, eight poles along the circumferential direction. The magnetic disk 5 has a large number of magnetic poles on its peripheral edge. The shaft 3 and the permanent magnet 4 constitute a rotor 13.
[0013]
On the other hand, a flexible PC board 6 is fixed to one inner peripheral surface of the case over the entire circumference. A plurality of, for example, six air-core coils 7 are arranged at predetermined intervals in the circumferential direction at a portion of the inner peripheral surface of the PC plate 6 facing the permanent magnet 4. As shown in FIG. 2, the air-core coil 7 is arranged on the inner peripheral surface of the PC plate 6 in a state of being fixed to the outer peripheral surface of a cylindrical thin ring 8 (corresponding to a thin sheet) made of a non-magnetic material. ing. Although not shown, a circuit pattern such as a drive circuit for rotating the rotor 13 and a control circuit for controlling the drive circuit is printed on the PC board 6, and the coil 7 is connected to a predetermined land position. ing.
[0014]
On the right side of the air core coil 7 in the PC board 6 in FIG. 1, a Hall element 9 and an MR element 10 as magnetic sensors are mounted side by side. The Hall element 9 detects a magnetic change of the permanent magnet 4 according to the rotation position of the shaft 3 (the rotor 13). The MR element 10 detects a magnetic change of a magnetic pole of the magnetic disk 5 according to a minute rotation position of the shaft 3. The magnetic disk 5 and the MR element 10 or the encoder 11 are configured.
[0015]
In this embodiment, the air core coil 7, the Hall element 9, and the MR element 10 are integrally formed with the PC board 6 with the resin 12. Therefore, the space between the case 1 and the thin ring 8 is filled with the resin 12 including the air core coil 7, the Hall element 9, and the MR element 10.
[0016]
In the above configuration, the energization of the air-core coil 7 is controlled based on the rotational position signals output from the Hall element 9 and the MR element 10, whereby the positioning of the shaft 3 is controlled with high accuracy. At this time, since the shaft 3 is supported by the ball bearing 2, it can be reliably held at the predetermined stop position.
[0017]
By the way, each time the medical manipulator is used, the medical manipulator is subjected to a cleaning process and a sterilization process (3 atm, 133 ° C. steam treatment) with high-temperature pressurized steam. Even if such a process is repeatedly performed, the servo motor according to the present embodiment is configured so that an operation failure does not occur.
[0018]
That is, the ball bearing 2 is made of ceramic. Accordingly, the shaft 3 is not rusted by the high-temperature pressurized steam, and rotation failure of the shaft 3 due to rust can be prevented. Further, since the ceramic has excellent wear resistance, a stable rotation operation can be maintained without using a lubricant. Therefore, the lubricant does not deteriorate due to the sterilization process, and the rotation performance does not decrease.
[0019]
Further, the PC plate 6, the air-core coil 7, the Hall element 9, and the MR element 10 were covered with the resin 12 to shut out the air. For this reason, the high-temperature pressurized steam does not reach the PC board 6, the air-core coil 7, and the like, and the occurrence of operation failure can be prevented as much as possible.
[0020]
The resin 12 may swell due to the high-temperature pressurized steam. However, since the thin ring 8 is provided on the radially inner peripheral surface of the resin 12, the resin 12 is prevented from swelling radially inward. it can. Therefore, even if the sterilization process is repeatedly performed, the permanent magnet 4 does not come into contact with the resin 12. If the thin ring 8 is not provided, the distance between the resin 12 and the permanent magnet 4 needs to be set to a size that allows for the swelling of the resin 12. However, since the thin ring 8 is provided, the dimension between the resin 12 and the permanent magnet 4 can be set as small as possible, so that the size can be further reduced.
[0021]
Since the stator core is also used as the case 1, the size of the servomotor can be further reduced.
[0022]
The present invention is not limited to the embodiments described above, and for example, the following modifications are possible.
In the above embodiment, all the components constituting the ball bearing are made of ceramic. However, only the rolling elements may be made of ceramic, and the other parts may be made of stainless steel. That is, when the rolling elements are made of a hard ceramic having excellent wear resistance, a lubricant can be eliminated.
[0023]
The MR element has a smaller number of terminals than the Hall element and can be downsized. Therefore, a change in the magnetic strength of the permanent magnet 4 may be detected by an MR element instead of the Hall element 9.
[0024]
The whole of the PC board 6, the air-core coil 7, the Hall element 9, and the MR element 10 may be covered with a thin sheet so as to be shielded from the outside air. In this case, molding the air core coil 7 and the like with resin can be omitted.
[0025]
INDUSTRIAL APPLICABILITY The present invention is applicable not only to a servomotor for driving a medical device, but also to a servomotor for driving a device used in a hot and humid environment.
[0026]
【The invention's effect】
As is clear from the above description, the present invention provides an air core coil and a detector of an encoder on the inner peripheral surface of a stator yoke, and holds the air core coil and a detector between the stator yoke and a permanent rotor of the rotor. Since the thin film sheet is provided so as to be opposed to the outer peripheral surface of the magnet with a predetermined gap therebetween, it is possible to prevent malfunctions due to sterilization processing and deterioration of motor performance. In addition, since the shaft is supported by the ball bearings and at least the rolling elements of the ball bearings are made of ceramic, stable rotation can be maintained without using a lubricant, and the shaft is stopped at a predetermined stop. The position can be securely held.
[Brief description of the drawings]
FIG. 1, showing an embodiment of the present invention, is a longitudinal side view showing the entire configuration of a servomotor. FIG. 2 is a perspective view for explaining a state in which an air core coil is fixed to the outer peripheral surface of a thin ring. Figure [Explanation of symbols]
In the figure, 1 is a case (stator core), 2 is a ball bearing, 3 is a shaft, 4 is a permanent magnet, 5 is a magnetic disk, 7 is an air-core coil, 8 is a thin ring (thin sheet), and 10 is an MR element (magnetic Sensor, detection unit), 11 denotes an encoder, and 12 denotes a resin.

Claims (5)

A cylindrical stator yoke,
Bearings provided at both axial ends of the stator yoke,
A rotor disposed on an inner peripheral portion of the stator yoke, a shaft rotatably supported by the bearing, and a permanent magnet mounted on an outer peripheral surface of the shaft;
A plurality of air-core coils provided on the inner peripheral surface of the stator yoke and arranged in the circumferential direction so as to face the permanent magnets;
An encoder provided on the inner peripheral surface of the stator yoke and having a detection unit for detecting the rotational position of the rotor;
A thin sheet made of a non-magnetic material that holds the air-core coil and the detection unit is provided between the stator yoke and the outer peripheral surface of the permanent magnet so as to face the outer peripheral surface of the permanent magnet with a predetermined gap therebetween. A servomotor for driving medical equipment, wherein the moving body is formed of a ball bearing made of ceramic. The servomotor for driving a medical device according to claim 1, wherein the air core coil and the detection unit are molded with resin. 2. The encoder according to claim 1, wherein the encoder includes a magnetic disk provided on the shaft and rotating integrally with the shaft, and the detection unit includes a magnetic sensor that detects a magnetic signal of the magnetic disk. Servo motor for driving medical equipment. 4. The servomotor for driving medical equipment according to claim 3, wherein the magnetic sensor comprises an MR element. A cylindrical stator yoke,
Bearings provided at both axial ends of the stator yoke,
A rotor that is disposed on an inner peripheral portion of the stator yoke and that is constituted by a shaft rotatably supported by the bearing and a permanent magnet mounted on an outer peripheral surface of the shaft;
A plurality of air-core coils provided on the inner peripheral surface of the stator yoke and arranged in the circumferential direction so as to face the permanent magnets;
A servo motor including an encoder provided on an inner peripheral surface of the stator yoke and having a detection unit for detecting a rotational position of the rotor.
A thin sheet made of a non-magnetic material that holds the air-core coil and the detection unit is provided between the stator yoke and the outer peripheral surface of the permanent magnet so as to face the outer peripheral surface of the permanent magnet with a predetermined gap therebetween. A servomotor, wherein the moving body is constituted by a ball bearing made of ceramic.

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