JPH0346744Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) This invention relates to a handpiece for medical use, especially dental treatment, and more specifically, it has a built-in brushless motor for driving a cutting tool at the tip of the handpiece, and and to an improvement in a handpiece equipped with cooling means for a cutting tool.

(Prior art) A handpiece for dental treatment is equipped with a cutting tool for teeth at the tip end of the grip, and is driven by a built-in micromotor. Furthermore, during cutting treatment, the tooth and cutting tool are cooled. Therefore, a coolant such as water or air is supplied.

(Problem that the invention aims to solve) By the way, if this cooling passage is exposed outside the handpiece body and is piped, the outer diameter of the handpiece will be different and larger, and the handpiece will become larger. Poor grip and therefore poor operability.
Not favorable for treatment. Therefore, it has been proposed to pass this coolant passage inside the handpiece body, but since the coolant passage in this case inevitably passes through the built-in part of the micromotor, it has a large effect on the magnetic path of the motor. Decrease in motor torque,
This causes problems such as the occurrence of torque ripple.

That is, the general structure of a brushless micromotor is as shown in Fig. 1, in which a coil B fixed to a rotor magnet A and a yoke C are coaxially fitted with each other with a required space D between them, and the magnetic path is is formed as shown by the arrow in the figure. Conventionally, in this motor, the coolant passages E are formed by cutting the outer circumferential surface of the yoke C, as shown in FIG. 2, to form, for example, two straight coolant passages parallel to the motor axis. Therefore, yoke C
The cross-sectional area of is significantly reduced in the C ₁ -C ₁ portion shown in the developed view in Figure 3, and becomes as shown in Figure 4. this
The yoke cross-sectional area S of the C ₁ - C ₁ portion is S = (a-c) x l. However, a: Thickness of the yoke c: Depth of the groove of the coolant passage l: Length of the yoke, For example, a=1.9m/m, c=0.8m/
When m and l are set to 49 m/m, the cross-sectional area decreases by about 42%. Therefore, a saturation phenomenon occurs in the yoke C at this reduced cross-sectional area, and a normal magnetic path as shown in FIG. 1 is not formed, resulting in a decrease in torque. This decrease in torque prompts the use of a larger micromotor to compensate for the decrease, which is a drawback that leads to an increase in the diameter of the handpiece.

In addition, in the micromotor in which the coolant passage is carved, the rotor magnet A is
When looking at the magnetic flux distribution when rotating over two directions, it is clear from the figure that at points A, B, C, and D, the magnetic flux distribution sandwiching the rotor magnet A fluctuates due to the coolant passage E. However, torque ripple occurs based on such fluctuations in magnetic flux distribution,
The motor characteristics deteriorate, which directly causes problems in dental treatment.

The applicant has already proposed a medical handpiece in which coolant passages carved on the outer peripheral surface of the yoke are arranged in a spiral direction around the yoke, without being parallel to the axis of the yoke. (Sho 60-104115).
In this prior art, as shown in FIG. 13a, the coolant passage is wound around the outer periphery of the yoke once, so the cross section of the yoke is provided with the coolant at the outer periphery, as shown in FIG. 13c. Only one groove with a small cross section is formed in which the coolant passage is cut out, and as shown in FIG. Therefore, the groove is uniformly formed on any yoke cross section. As a result, even by carving a spiral coolant passage, the yoke cross-sectional area decreases little, magnetic flux saturation does not occur, and the motor torque hardly decreases.
Torque ripple does not occur either. However, if two or more coolant passages are to be installed to increase the amount of coolant supplied, the same number of cutout grooves as the number of coolant passages are formed on the outer periphery of the yoke cross section. Therefore, the cross section of the yoke is reduced, and the torque of the motor is reduced.

This idea was devised in view of the above-mentioned conventional problems, and has multiple improved coolant passages arranged on the outer circumferential surface of the yoke of the brushless micromotor built into the handpiece body, thereby reducing the motor torque. The purpose of the present invention is to provide a medical handpiece that does not generate torque or torque clips.

(Means for Solving Problems) The structure of this invention will be explained based on FIG. 6 showing its principle structure. As shown in the figure, θ=360°/N×M, 1≦M≦N-1 (where θ: set angle, N: number of multiple passages,
M: positive integer) A plurality of the angles are arranged within the angle range. However, the set angle θ means the rotation angle of the coolant passage spirally rotated from one end of the yoke to the other end as seen from the yoke axis.

(Function) The function of this invention will be explained with reference to FIG. 6. In this invention, a coolant passage 1 connecting both ends of the yoke is provided on the outer peripheral surface of the yoke 2 of the brushless micro motor from one end of the yoke to the other. A plurality of yokes 2 are wound toward the end and arranged in a spiral shape in the following angular range.

Setting angle θ=360°/N×M, 1≦M≦N−1 (N: number of multiple passages, M: positive integer) The C ₂ - C ₂ portion in the developed view of Fig. 6 shown as a figure, that is, the 8th section showing its cross section
It is determined based on the figure and FIG. 9, which is an enlarged view of the main part A of FIG. 7. When the yoke length l is 49 m/m and the yoke outer circumference length l is 49 m/m, the inclination angle ψ of the passage with respect to the yoke axis when the yoke is deployed is ψ = tan ^-1 e/2l = tan ^-1 49/ 2×49=26.6°. Therefore, when the coolant passage groove width d is 0.8 m/m, the groove length b of the passage forming part is: b=d/sinψ=0.8/sin26.6°=1.8 As mentioned above, the thickness of the yoke Thickness a is 1.9m/m,
When the groove depth c of the coolant passage is 0.8 m/m, from the cross-sectional area S = al-bc, S = 1.9 x 49 - 1.8 x 0.8 = 91.7, and the following formula, that is, S': When there is no groove Yoke cross-sectional area R: Ratio of yoke cross-sectional area with groove to yoke cross-sectional area without groove, S'=al=1.9×49=93.1, R=91.7/93.1×100=98.5 From now on , the reduction in cross-sectional area S is suppressed to about 1.5%.

Therefore, in the case of the spiral arrangement of the two coolant passages 1, 1, the cross-sectional area of the yoke 2 is reduced by about 1.5% at any part, but the saturation phenomenon of the yoke does not occur and the magnetic path continues normally. Therefore, no reduction in motor torque occurs. Further, since the cross-sectional area of the yoke in the entire circumferential direction is uniformly and slightly reduced, the magnetic flux distribution during rotation of the rotor magnetic path is symmetrical at any rotational angular phase position of the rotor magnet.

Therefore, there is no motor cogging and no torque ripple occurs.

(Example) Hereinafter, an example of this invention will be described in detail with reference to FIG. 10 and subsequent drawings.

FIG. 10 shows a cross section of the grip portion of the handpiece, and 3 is a frame.
The built-in micro motor 4 includes a cylindrical stator coil 5, a rotor shaft 7 rotatably supported on the frame side by a pair of front and rear bearings 6, a rotor magnet 8 coaxially fixed to the shaft 7, It includes a cylindrical yoke 2 that holds the stator coil 5, and the yoke is fixed to a frame 3. As shown in FIG. 11, a coolant passage 1 is provided on the outer peripheral surface of the yoke 2 in a spiral direction winding around the yoke 2 from the rear end 2a of the yoke to the front end 2b of the yoke. 9 is similarly fitted from the rear end 2a of the yoke to the front end 2b of the yoke. Note that, as is clear in light of the above description, the carved passageway 1 is formed from the rear end 2a of the yoke in order to keep the cross-sectional area of the yoke constant at any location along the entire circumference of the yoke 2, regardless of the presence of the groove. Set angle θ = 360°/N x M, 1≦M≦N-1 (where N: number of multiple passages, M: positive integer) so that the yoke 2 is wound around the front end 2b of the yoke. In this state, the yoke 2 is wound in less than one rotation.
Note that, of course, one end 9a of the coolant pipe 9 is connected to a coolant supply source (not shown), and the other end 9b is led out to the distal end side of the handpiece body 10.

In addition, in the above-mentioned configuration, as shown in FIG. 6, for example, the coolant passage 1 disposed on the outer peripheral surface of the yoke 2 is set at a set angle θ=360°/N ( However, the coolant passages 1 should be twisted over a range of N (number of passages), and furthermore, the coolant passages 1 should be equally distributed in the same direction on the outer peripheral surface of the yoke, and should be formed by winding in the same direction. or,
If the starting ends or terminal ends of the passages 1 are connected and the passages 1 are wound in opposite directions as shown in FIGS. Despite the arrangement, the reduction in the yoke cross-sectional area can be suppressed to the necessary minimum, and the cross-sectional area at each part of the yoke is uniform, so problems such as a decrease in motor torque and the occurrence of torque ripple can be avoided. can be eliminated as much as possible.

Note that the arrangement of the coolant passage 1 according to the invention is not limited to the scope of the above embodiment, and may be formed by varying the arrangement angle and the arrangement direction of the passage 1 as appropriate. Accordingly, modifications can be made within the scope of the gist of the present invention.

(Effect of the invention) As is clear from the above description, when forming the coolant passage inside the medical handpiece, this invention aligns the coolant passage carved in the yoke of the brush micromotor with the yoke axis. Instead of making them parallel, a plurality of them are arranged in a helical direction around which the yoke is wound within the specific angle range, so that the cross-sectional area of the yoke is made approximately constant at any part in the circumferential direction of the yoke, regardless of the carved passage. This prevents the yoke cross-sectional area from becoming extremely reduced and saturated at a specific location, and therefore does not cause the torque drop or torque ripple that occurs in conventional micro motors. By using a motor, it is possible to prevent the handpiece from increasing in size. Therefore, it is possible to provide a handpiece that has a good grip and generates stable rotational torque, which is useful for treatment.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a brush micromotor, Figure 2
The figure is a perspective view of a yoke with a conventional coolant passage, Figure 3 is a developed view of Figure 2, and Figure 4 is Figure 3.
C ₁ -C ₁ line cutaway view, Figures 5A to 5D are diagrams showing changes in magnetic flux distribution as the rotor magnet rotates, Figure 6 is a perspective view of the yoke showing the principle configuration of this invention, Figure 7 The figure is a developed view of Figure 6, and Figure 8 is a diagram of Figure 7 C ₂ -C ₂
Fig. 9 is an enlarged view of the main part of Fig. 7, Fig. 10 is a sectional view of the main part of the handpiece main body showing an embodiment of this invention, and Fig. 11 also shows the existence of a coolant passage. A cross-sectional view of the built-in part of the micromotor, showing
FIGS. 12a and 12b are explanatory diagrams showing another configuration in which the coolant passage is provided on the outer circumferential surface of the yoke, FIG. 13a is a perspective view of the conventional yoke shape, and FIG.
Figure b is a developed view of figure a, Figure 13c is figure b.
It is a sectional view taken along the _C2 - _C2 arrow. Explanation of symbols: 1...Coolant passage, 2...Yoke, 3...Handpiece body frame, 4...Micro motor, 9...Coolant pipe, 10...Handpiece body.

Claims (1)

[Claims for Utility Model Registration] 1. A medical handpiece with a built-in brushless micromotor, comprising: a coolant passage connecting both ends of the yoke on the outer peripheral surface of the yoke of the brushless micromotor fixed to the handpiece body frame; A medical handpiece consisting of a plurality of pieces arranged in a helical direction around a yoke wound within an angle range defined by the following formula. θ=360°/N×M, 1≦M≦N-1 (However, θ: Setting angle, N: Number of multiple passages,
(M: positive integer) 2 A utility model registration claim in which a plurality of coolant passages connecting both ends of the yoke are arranged on the outer circumferential surface of the yoke in a spiral direction in which the yoke is wound within an angle range expressed by the following formula. A medical handpiece according to scope 1. θ=360°/N (where θ: set angle, N: number of passages) 3. Request for registration of a utility model in which the passages are equally distributed in the same direction and wound in the same direction on the outer peripheral surface of the yoke. The medical handpiece according to item 1. 4. The medical handpiece according to claim 1, wherein a plurality of the passages are arranged with their starting ends or terminal ends connected and wound in opposite directions. 5 Utility model registration claims 1 to 4, in which the passage is carved on the outer peripheral surface of the yoke
A medical handpiece as described in any of the paragraphs.