JP2514986Y2 - Dental spindle motor - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dental small spindle motor.

[0002]

2. Description of the Related Art In general, a handpiece having a drill at its tip is known as a dental instrument used for polishing teeth. In a conventional spindle motor for rotating a drill of this hand piece, a rotor arranged in a casing is rotatably supported by a casing via bearings for radial and thrust. The rotation of the rotor is transmitted to the drill. Conventionally, a bearing mainly consisting of a bearing has been used for such a motor, but in recent years,
As an alternative to such a bearing, a magnetic bearing utilizing the repulsive force of a magnetic member for thrust has been proposed. That is, according to such a magnetic bearing, two sets of magnetic members are arranged to face each other with a gap on the rotor side and the casing side, so that the wear and deterioration of the bearing can be avoided as much as possible. .

[0003]

However, when such a bearing is used, a load sometimes exceeds the repulsive force of the magnet. For example, it is stored in a storage holder with the drill side facing up. At that time, the hand piece may be randomly thrown into the holder.
At this time, in particular, the thrust bearing on the side opposite to the drill is likely to receive a shock exceeding the repulsive force of the magnet, and the magnets that are weak against shock and that face each other with a small gap contact each other and damage. There was a risk of This is one of the causes of shortening the life of the motor for the handpiece, so that it must be handled carefully.

The present invention has been made in view of the above problems, and an object thereof is to provide a dental spindle motor excellent in durability and handleability by improving a thrust magnetic bearing portion. It is in.

[0005]

In order to achieve the above object, the present invention provides a casing, a rotor rotatably arranged in the casing, and a rotor arranged near both ends of the rotor. And a magnetic bearing for restricting the movement of the rotor in the thrust direction, the magnetic bearing consisting of two sets of magnetic members facing each other with a gap on the rotor side and the casing side, A cushion material is arranged at least in the gap between the two magnetic members on the side that receives an impact on the rotor.

[0006]

Therefore, even if a shock exceeding the repulsive force of the magnets is applied in the thrust direction due to the presence of the cushioning material interposed in the gaps between the magnets facing each other, the magnets abut each other and are damaged. Is prevented in advance. As a result, the durability and handleability of the motor are improved.

It is desirable to use heat resistant rubber or heat resistant resin as the cushion material. The reason is,
This is because the handpiece is sterilized each time it is used in terms of hygiene, but the heat sterilization can be performed by using the heat resistant rubber or the heat resistant resin as described above. Further, as such a cushion material, it is preferable to use a fluororesin such as polytetrafluoroethylene. Since such a material has appropriate heat resistance and hardness, the impact can be sufficiently mitigated even when formed thin.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a brushless type spindle motor will be described in detail below with reference to the drawings. As shown in FIG. 1, a plate 2 having a through hole 2a formed in the center thereof is fixed to one end (right end) of the inside of a substantially cylindrical casing 1, and this plate 2 Circumference and case
An O-ring 3 is interposed between the inner peripheral surface of the casing 1 and the right end portion of the casing 1 is closed by these members 1, 2, 3. On the other hand, a mounting ring 4 extending over the entire inner peripheral surface of the casing 1 is formed at the other inner end (left end) of the casing 1. Also, on the outside on the left side of the attachment 5, an insertion hole 5a is provided at the center thereof.
Are fixed via an annular packing 6. The left end of the casing 1 is closed by these members 5 and 6. A motor chamber 7 is formed in a region of the casing 1 which is closed by the plate 2 and the attachment 5.

Further, as shown in FIG. 1, a cylindrical hand piece H having a thin tip portion is fitted on the outer peripheral surface of the attachment 5 to connect the attachment 5 and the hand piece H. The hand piece H is detachably locked to the casing 1 by a locking member P provided at the joining portion. A cutting drill (not shown) is provided at the tip portion of the hand piece H, and the drill is provided by a hand piece side shaft (not shown) rotatably supported in the insertion hole 5a of the attachment 5. Is rotated.
In the vicinity of the drill, an air ejection port, a water ejection port, and a light irradiation port, which are not shown, are provided.

Inside the attachment 5 and the handpiece H, a water pipe and an air pipe which communicate with each other are provided, and water is supplied to the air jet port through the pipe to the water jet port at the tip. Is supplied with air. Similarly, an optical fiber-9b for illumination is provided inside the both 5, H, and the optical fiber-9b is provided.
Light is transmitted to the irradiation port by b. On the other hand, the handpiece H is formed with a passage 5b communicating with the insertion hole 5a, and the air discharged from the motor chamber 7 side is supplied to the air ejection port at the tip portion through the passage 5b. It is like this.

As shown in FIG. 2, a plurality of motor wiring connector pins 28 and an air inflow hole 8 are concentrically provided through the plate 2, and an external blower (shown in the drawing) connected to these is provided. Air is sent into the motor chamber 7 of the casing 1 shown in FIG. Further, the plate 2 and the attachment ring 4 are formed with through holes 9 which face each other. The pipe 9a for sending water for dental treatment and the optical fiber 9b for illumination are inserted into the space 10 of the motor chamber 7 through the plate side through hole 9 and then the ring side transparent. It is inserted into the hole 9 and is connected to the attachment 5 side as shown in FIG.

As shown in FIG. 1, the motor chamber 7 accommodates a power transmission shaft 11 extending in the longitudinal direction thereof.
One end thereof is loosely inserted into the insertion hole 2a of the plate 2, and the other end is loosely inserted into the insertion hole 5a of the attachment 5. The shaft 11 is rotatably arranged such that its outer peripheral surface is separated from the inner peripheral surfaces of the insertion holes 2a and 5a by a space S3.

A rotor R is mounted on the power transmission shaft 11 in the motor chamber 7. Explaining this rotor R, annular bushes 12 are fixed to both ends of the power transmission shaft 11, and a field magnet 13 is held between them. As shown in FIG. 4, the field magnet 13 has the shaft 1
Around the circumference 1, four permanent magnet pieces 14 are alternately arranged so that the magnetic poles adjacent to each other are different poles, and are configured in a cylindrical shape. Further, as shown in FIG. 1, fitting step portions 15 are formed in an annular notch on the outer circumferences of the facing portions of the bushes 12, respectively, and a space between the bushes 12 is made of a silicon carbide sintered material. The cylindrical cover 16 is fitted in, and thereby the outer peripheral surface of the field magnet 13 is surrounded.

Annular magnets 17a and 17b as magnetic members are fixed to the outer surfaces of both bushes 12, respectively. An annular magnet 19a as a magnetic member is also fitted to the inner peripheral surface of the fitting stepped portion 18 of the plate 2 so as to face the annular magnet 17a. Similarly, an annular magnet 19b, which is also a magnetic member, is fitted to the inner peripheral surface of the mounting ring member 20 projecting from the attachment 5 so as to face the annular magnet 17b. These two sets of opposing annular magnets 1
7a, 19a and 17b, 19b are arranged so that the same magnetic poles face each other, and are separated by a repulsive force of both magnets with a space S1 therebetween. This allows
The movement of the power transmission shaft 11 in the thrust direction is restricted.

As described above, with respect to the power transmission shaft 11, the bush 12, the field magnet 13, and the tubular cover 1 are provided.
The rotor R is constructed by integrally fixing the 6 and the annular magnets 17a and 17b, and the thrust magnetic bearing is constructed by the annular magnets 19a and 19b. On the other hand, as shown in FIG.
An enclosing member 21 as a fixed peripheral surface ceramics member formed in a cylindrical shape by a silicon carbide sintered material is arranged outside the. The inner peripheral surface of the surrounding member 21 arranged to face the outer peripheral surface of the cylindrical cover 16 is processed into a peripheral surface having excellent contact slidability. One end of the surrounding member 21 is supported by the fitting step 22 of the plate 2, and the other end is supported by the fitting step 23 formed on the mounting ring 4 of the casing 1. There is.

As shown in FIG. 5, this enclosing member 21
Between one end of the plate 2 and the fitting step 22 of the plate 2,
An annular cushion member 24 located on the step portion 22 side and an annular packing 25 located on the surrounding member 21 side are closely arranged, and the cushion member 24 is
It is arranged in the gap between 7a and 19a. The cushion material 24 has a thickness of 0.2 mm and is made of heat-resistant polytetrafluoroethylene. The cushion material 24 alleviates the impact received by the opposed annular magnets 17a and 19a.

Further, the surrounding member 21 is provided with hole elements h arranged in the circumferential direction at the central portion in the lengthwise direction of the outer peripheral surface thereof, and a plurality of ventilation holes 26 are also provided through. Each vent hole 26 is a yoke Y provided on the inner peripheral surface of the casing 1.
The space S3 communicates with the space 10 between the outer peripheral surface of the surrounding member 21 and the space S3. Then, the air inflow hole 8 of the plate 2 → the space 10 between the outer peripheral surface of the surrounding member 21 → the pressure of the air pumped to the space S2 of the attachment 5 through the ventilation hole 26 causes the rotor R to move. Are held at positions separated from the inner peripheral surface of the surrounding member 21 by a space S2. Therefore, the outer peripheral surface of each end of the power transmission shaft 11 also has the insertion holes 2a, 5
The space S3 is held at a position separated from the inner peripheral surface of a. Further, the air pressure-fed to the space S3 of the attachment 5 flows into the passage 5b formed by the insertion hole 5a and the shaft 11 and is discharged from the air ejection port of the hand piece H.

In the drawing, the small space S2 is shown in actual size [several μm to several tens μm in order to emphasize the air introduction path.
(S2 = about 20 .mu.m in this embodiment)], but in reality, the cylindrical cover 16 and the surrounding member 2
Reference numeral 1 is for sliding contact through an air film, and is a small space S2.
Are extremely narrow enough to leak air. The tubular cover 16 and the surrounding member 21 constitute a radial air bearing.

Further, as shown in FIGS. 1 and 4, three electromagnetic coils 27 are arranged on the outer peripheral surface of the surrounding member 21 along the circumferential direction thereof. Then, each of the plurality of Hall elements h provided on the surrounding member 21 detects the magnetic pole of the permanent magnet piece 14, and based on the detected magnetic pole,
Is controlled, and the rotor R is rotated in either forward or reverse directions based on the interaction with the field magnet 13.

In the spindle motor configured as described above, when the energization control to each electromagnetic coil 27 is started based on the detection of the magnetic pole of the permanent magnet piece 14 by each hall element h, the rotor R is set to a predetermined value. Is rotated in the direction. This time,
Annular magnets 1 arranged on the left and right of the motor chamber 7, respectively
A small space S1 is secured by the repulsive force of 7a, 19a and 17b, 19b, and the load in the thrust direction is received. Further, air is introduced between the cylindrical cover 16 and the surrounding member 21 through the air inflow hole 8 and the ventilation hole 26, and the pressure of the air secures the minute space S2 and the load in the radial direction. Will be accepted. In this way,
The motor R is stably rotated while maintaining a non-contact state with each member in the motor.

When the hand piece of this embodiment is not used, the motor and the hand piece are usually integrated and are housed in the storage holder with the drill facing upward. In this case, it is sometimes thrown randomly into the holder. At this time, the repulsive force of the magnet (in this embodiment, about 0.
A shock (about 1 kgf in this embodiment) exceeding 8 kgf) is applied, and the shock is mitigated by the cushion material interposed in the gap of the magnets facing each other. As a result, the magnets are prevented from coming into contact with each other and being damaged,
The durability and handleability of the motor are improved. Further, polytetrafluoroethylene is used as a heat resistant resin in the cushion material. Therefore, even if the rotor comes into sliding contact with the cushion material, its wear resistance is high, and therefore the life of the spindle motor is not shortened. Furthermore, by using the above-mentioned material for the cushion material, it can be formed thin.

The present invention is not limited to the above-mentioned embodiment, but the structure can be modified as follows within the scope of the invention. For example, instead of providing silicone packing, silicone resin may be coated on the surface of the cushion material. Further, a cushion material may be arranged also on the drill side magnetic bearing portion of the rotor according to the direction in which the magnetic bearing is impacted.

[0023]

According to the dental spindle motor of the present invention, by improving the strength of the thrust magnetic bearing portion, the durability and handleability are improved.

[Brief description of drawings]

FIG. 1 is a front sectional view showing an embodiment of a dental spindle motor embodying the present invention.

FIG. 2 is a side view of the dental spindle motor of FIG.

FIG. 3 is a side view of an attachment mounted on the dental spindle motor of FIG.

FIG. 4 is a sectional view taken along line AA of the dental spindle motor of FIG.

5 is an enlarged sectional view of a thrust bearing portion of the dental spindle motor of FIG.

[Explanation of symbols]

1 casing, 17 magnetic members (17a, 17b annular magnet), 19 magnetic members (19a, 19b annular magnet), 24 cushion material, R rotor

Claims (3)

(57) [Scope of utility model registration request] 1. A casing (1), a rotor (R) rotatably arranged in the casing (1), and a rotor.
A magnetic bearing which is arranged near both ends of the rotor (R) and restricts the movement of the rotor (R) in the thrust direction. The magnetic bearing is on the rotor (R) side and the casing (1). Of the two magnetic members (17a, 17a), which are arranged to face each other with a gap therebetween.
b, 19a, 19b), two sets of magnetic members (17
a, 17b, 19a, 19b), a dental spindle motor, characterized in that a cushion material (24) is arranged at least in a space on the side that receives an impact on the rotor (R). 2. The dental spindle motor according to claim 1, wherein the cushion material (24) is made of heat resistant rubber or heat resistant resin. 3. The dental spindle motor according to claim 1, wherein the cushion material (24) is made of fluororesin.