JP2003130169A - Magnetic screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic screw which can reduce the increase in temperature in case of high engine speed, raising a small dust by micro abrasion or decrease in torque transmitting efficiency. SOLUTION: This magnetic screw is equipped with a magnetic nut 3, whose inner peripheral surface is smoothly formed and the magnetic pole is magnetized in spiral manner in the inner peripheral surface, and a screw shaft 6, which consists of magnetic material and has threads 4, 5 corresponding to the magnetic poles in an outer peripheral surface and a guiding means 7, which are provided at the both ends of the axial direction of the magnetic nut 3 and holds the screw shaft 6 nearly concentrically at a minute interval in the magnetic nut 3 to guide it freely in relative rotation to the spiral direction. Each guiding means 7 is arranged at a almost same interval in a peripheral direction and has at least three balls 15a, in a peripheral direction which contacts freely in rolling with the outer peripheral surface of the threads 4, 5.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a magnetic screw,
By rolling contact of the spherical body, the screw shaft in the magnetic nut is held substantially concentrically and is guided so as to be relatively rotatable in the spiral direction.

[0002]

2. Description of the Related Art In machine tools and other various precision instruments, magnetic screws are used as a feeder and the like. In this magnetic screw, as described in Japanese Patent Application Laid-Open No. 10-220548, a magnetic nut having an inner peripheral surface formed in a smooth shape and a magnetic pole spirally magnetized in the inner peripheral surface, and a magnetic material have been conventionally used. And a screw shaft having a screw thread corresponding to a magnetic pole on the outer periphery, and the screw shaft is held substantially concentrically in both ends of the magnetic nut with a minute gap in the both ends of the magnetic nut so as to face each other in the spiral direction. Some have a guide ring that rotatably guides.

The guide ring is made of a synthetic resin material or the like having excellent wear resistance and slidability, and the inner peripheral surface of the guide ring slidably contacts the outer peripheral surface of the screw thread so that the screw shaft slides by sliding contact. It is designed to guide you freely.

[0004]

Since the magnetic screw does not require mechanical contact between the magnetic nut and the screw shaft, heat generation due to friction of the metal contact portion and mechanical precision deterioration due to wear are lower than those of the ball screw. , No dust generated by abrasion powder,
It has the advantage that it can be used without lubrication.

However, in the conventional magnetic screw, the inner peripheral surface of the guide ring is slidably contacted with the outer peripheral surface of the thread of the screw shaft, and the guide shaft is guided by the sliding contact of the guide ring without lubrication. The internal structure of the guide ring increases the temperature during high-speed rotation due to friction on the inner peripheral surface of the guide ring, minute dust generation due to minute wear on the inner peripheral surface of the guide ring, and torque due to sliding contact between the guide ring and the screw shaft. There is a risk that the transmission efficiency will be reduced and the advantages peculiar to magnetic screws will be impaired.

In view of the above-mentioned conventional problems, the present invention adopts a structure in which a screw shaft is held and guided by rolling contact of a spherical body, and temperature rise during high speed rotation, minute dust generation due to slight wear, and torque. An object of the present invention is to provide a magnetic screw that can reduce a decrease in transmission efficiency and the like.

[0007]

According to the present invention, there is provided a magnetic nut having a spiral magnetic pole on an inner peripheral surface thereof, a screw shaft made of a magnetic material and having a screw thread corresponding to the magnetic pole on the outer periphery, and the magnetic nut. A guide screw that is provided on both axial ends of the magnetic nut and that guides the screw shaft in the magnetic nut substantially concentrically and relatively rotatably in the spiral direction. , At least three spheres are provided in the circumferential direction that are rotatably abutted on the outer peripheral surface of the screw shaft.

Still another aspect of the present invention corresponds to a magnetic nut having an inner peripheral surface formed to be smooth and having a magnetic pole spirally magnetized on the inner peripheral surface, and a magnetic nut made of a magnetic material and having an outer periphery corresponding to the magnetic pole. A screw shaft having a thread and a magnetic shaft are provided at both ends in the axial direction of the magnetic nut, and the screw shaft is held substantially concentrically within the magnetic nut with a minute gap and is guided to be relatively rotatable in a spiral direction. In the magnetic screw, the guide means are arranged at substantially equal intervals in the circumferential direction, and at least three spherical bodies in the circumferential direction are in rolling contact with the outer peripheral surface of the screw thread. It is equipped with.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. 1 to 4 illustrate a first embodiment of a magnetic screw according to the present invention. As shown in FIGS. 1 to 3, the magnetic screw has a smooth inner peripheral surface, and the magnetic poles 1 and 2 of N pole 1 and S pole 2 are spirally magnetized on the inner peripheral surface. A magnetic nut 3, a screw shaft 6 made of a magnetic material and having threads 4 and 5 corresponding to the magnetic poles 1 and 2 on the outer periphery, and a screw provided in both ends of the magnetic nut 3 in the axial direction and screwed in the magnetic nut 3. A guide means 7 is provided for holding the shaft 6 substantially concentrically with a minute gap and guiding the shaft 6 so as to be relatively rotatable in the spiral direction.

The screw shaft 6 is made of a ferrous metal material such as SUS4.
It is made of a ferromagnetic material such as 40C. The screw shaft 6 has two threads 4 and 5 spirally formed at the same lead on the outer periphery at the same pitch and at the same pitch.
A non-magnetic material, for example, an embedding material 8 such as nylon having abrasion resistance, or another synthetic resin material is embedded over the entire length of the thread groove 6a between the five grooves 5, and the entire outer peripheral surface is formed over substantially the entire length of the thread region. It is formed in a smooth shape.

The screw shaft 6 is a double-threaded screw having a square cross section of the screw threads 4 and 5 and a cylindrical outer peripheral surface, but other screw thread shapes may be used. Good, 1
A thread or a multiple thread having two or more threads may be used. Embedded material 8
Is a non-magnetic material, and a non-magnetic metal material or a non-magnetic non-metal material may be used in addition to the synthetic resin material. Further, the filling material 8 may be omitted.

The magnetic nut 3 is provided with a housing 9 constituting a nut body and a plurality of (for example, four) cylindrical permanent magnets 10 fitted in the housing 9 in the axial direction. The housing 9 is formed of a magnetic material such as S25C into a cylindrical shape or a ring shape, and a mounting flange 11 is integrally provided on one end side in the axial direction on the outer peripheral side.
Further, on the inner peripheral side of the housing 9, fitting portions 12 of the guide means 7 are formed in a cylindrical surface shape at both end portions in the axial direction, and a protruding portion in the circumferential direction is formed on one end side between the both fitting portions 12. Each of the portions 13 is formed with a cylindrical magnet mounting portion 14 over substantially the entire length from the protruding portion 13 to the fitting portion 12 at the other end, and the guiding means 7 and the magnet mounting portion 14 are formed in the fitting portion 12. Permanent magnet 10 inside
Are fitted together. The housing 9 may be made of a non-magnetic material such as SUS.

The outer peripheral side of each permanent magnet 10 is fixed to the magnet mounting portion 14 of the housing 9 with an adhesive or the like, and the inner peripheral surface thereof is formed in a smooth shape so as to have the same diameter. Then, on the inner peripheral surface of each permanent magnet 10, as shown in FIG.
N pole 1 and S corresponding to each thread 4, 5 of the screw shaft 6.
The magnetic poles 1 and 2 of the pole 2 are magnetized so as to be spirally continuous over the permanent magnets 10 with the same leads as the screw threads 4 and 5.

The permanent magnet 10 is made of a rare earth magnet material such as a neodymium magnet material containing neodymium, iron and boron, or other suitable magnet material such as a sintered body. The permanent magnet 10 may be long in the axial direction, and one permanent magnet 10 may be provided in the housing 9. Further, the gap between the inner peripheral surface of the permanent magnet 10 and the outer peripheral surfaces of the threads 4 and 5 of the screw shaft 6 is
The gap is small enough to ensure sufficient magnetic coupling between the two and prevent mechanical contact between the two.

As shown in FIGS. 2 and 3, the guide means 7 are arranged at substantially equal intervals in the circumferential direction and rotatably abut on the outer peripheral surfaces of the threads 4, 5 of the screw shaft 6. At least three, for example, four spheres 15a to 15d in the circumferential direction, and a ring-shaped retainer 16 rotatably holding each of the spheres 15a to 15d are provided, and are detachably attached to the fitting portion 12 of the housing 9. It is fitted. In addition, each sphere 15a-15d
A ceramic ball, a steel ball, or the like having wear resistance is used for this.

The cage 16 is made of a synthetic resin material such as polyimide resin, nylon or the like having abrasion resistance, slipperiness and the like, and a retaining portion 17 for retaining each of the spheres 15a to 15d.
4 are formed at equal intervals in the circumferential direction. Each holding portion 17 is formed by a through hole having a drop-out preventing portion 18 of a conical surface shape or other appropriate shape on the inner end side in the radial direction, and spheres 15a to 15d are rotatably fitted to each holding portion 17. ing.

The cage 16 is, as shown in FIGS. 2 and 3,
It is positioned in the fitting portion 12 of the housing 9 through the positioning means 19 provided at an appropriate position such as the outer peripheral side (or the inner end side in the axial direction) and is prevented from coming off by the retaining means 22 such as a retaining ring. ing. The positioning means 19 includes a recess 20 formed on the housing 9 (or the retainer 16) side,
Convex portion 2 formed on the retainer 16 (or housing 9) side
1 and the convex portion 21 and the concave portion 20 are engaged with each other to determine the position of the cage 16 in the circumferential direction.

A roll pin or the like may be driven into the housing 9 and the retainer 16 so that the retainer 16 can be positioned and removed. Further, a nut or the like is screwed on the outer end side of the housing 9, and the cage 16 is sandwiched and fixed between the nut 16 and the step portion on the inner end side of the fitting portion 12 by the nut. Is also good. Also in this case, it is desirable to provide the positioning means 19.

As shown in the development view of FIG. 4, each guide means 7 has two spherical bodies 15a, 15 corresponding to one screw thread 4.
b and two spheres 15c, 1 corresponding to the other thread 5
5d and 5d in the circumferential direction, each corresponding to each thread 4, 5
Of the individual spheres 15a to 15d, the single sphere 15a,
15c are arranged at axially symmetrical positions with respect to the screw shaft 6 at substantially the same position in the axial direction and at intervals of approximately 180 degrees in the circumferential direction, and the other one spherical body 15b, 15d is arranged in the axial direction from the spherical bodies 15a, 15c. It is arranged in a position symmetrical with respect to the screw shaft 6 at a position separated by 3/4 lead. Therefore, the four spheres 15a to 15d in the circumferential direction are arranged in one lead L of the threads 4 and 5. Each of the spheres 15a to 15d is in rolling contact with the outer peripheral surfaces of the threads 4 and 5 inside the retainer 16 and the inner peripheral surface of the fitting portion 12 outside the retainer 16.

In the magnetic screw having the above structure, a magnetic circuit is formed between the magnetic poles 1 and 2 of the N pole 1 and the S pole 2 on the inner peripheral surface of the magnetic nut 3 and the threads 4 and 5 of the screw shaft 6, The magnetic nut 3 and the screw shaft 6 are magnetically coupled by the magnetic circuit. Therefore, when the screw shaft 6 is rotated around its axis in the magnetic nut 3, the magnetic coupling causes the magnetic nut 3 to move relatively in the axial direction.

In this case, the screw shaft 6 is guided by the guide means 7 on both ends of the magnetic nut 3, and the guide means 7 are four spherical bodies 15a to 15 arranged at substantially equal intervals in the circumferential direction.
Since each of the spherical bodies 15a to 15d is provided in contact with and guides the outer peripheral surfaces of the screw threads 4 and 5, the spherical body 15a to 15d is provided.
The screw shaft 6 can be guided by rolling contact with the outer peripheral surface of the thread ridges 4 and 5 of ~ 15d, temperature rise during high speed rotation as in the case of conventional sliding contact, minute dust generation due to minute wear, and decrease in torque transmission efficiency. Etc. can be reduced.

Each guide means 7 is a ring-shaped cage 16 fitted to the axial end of the housing 9 on the magnetic nut 3 side.
And the sphere 1 rotatably held by the holder 16.
Since 5a to 15d are provided, the structure of the guide means 7 can be simplified, and the spherical bodies 15a to 15d can be reliably held at positions at substantially equal intervals in the circumferential direction. Further, the retainer 16 has spherical bodies 15a to 15d inserted into the respective retaining portions 17 from the outer peripheral side, and the spherical bodies 15a to 15d are prevented from coming off by the radially inner detachment preventing portion.
Can be easily incorporated into the housing 9 or the like on the magnetic nut 3 side.

Moreover, the screw shaft 6 is a two-thread screw having two threads 4, 5 and each guiding means 7 has two spheres 15a, 15b corresponding to one thread 4 and the other thread. 5
With two spheres 15c and 15d corresponding to the two spheres 15a and 1d corresponding to the screw threads 4 and 5, respectively.
One of spheres 15a, 1 among 5b, 15c, 15d
5c is arranged at an axially symmetrical position with respect to the screw shaft 6, and the other one spherical body 15b, 15d is axially symmetrical with respect to the screw shaft 6 with an interval of 3/4 lead from the spherical bodies 15a, 15c in the axial direction. Since the balls 15a to 15d are arranged at positions, the spherical bodies 15a to 15d can be guided substantially evenly on the outer peripheral surfaces of the two threads 4 and 5, and
The axial length of the guide means 7 can be shortened. Also sphere 15
Although a to 15d correspond to the two threads 4,5, since the retainer 16 is fitted into the housing 9 via the positioning means 19, each sphere 15a to 15d has threads 4,5.
It does not shift in the circumferential direction.

In this embodiment, four spheres 15a to 15d of the guide means 7 are arranged in the circumferential direction with respect to the screw shaft 6 of the double thread, and each of the two spheres 15a, 15b and 15 is arranged.
Although c and 15d correspond to the respective screw threads 4 and 5, three or more spheres corresponding to the double thread may be arranged at equal pitches in the spiral direction. Also each sphere 15a
˜15d may be arranged over the range of one lead or more in the axial direction. However, in the case of the two threads 4 and 5, each of the spheres 15a to 15a to be axially symmetrical with each other.
It is desirable to arrange 15d at equal intervals in the circumferential direction. It is also possible to use the screw shaft 6 having three or more threads.

5 and 6 illustrate a second embodiment of the present invention. In this magnetic screw, spheres 15a to 15d corresponding to the respective screw threads 4 and 5 are axially spaced apart by 1/4 lead. Is provided. Each of the two spherical bodies 15a, 15b, 15c, 15d corresponding to each of the threads 4, 5 is axisymmetric, and the other configurations are the same as those of the first embodiment.

In this way, the screw shaft 6 of the double thread is used,
Two spheres 15a, 15b, 15c, for each thread 4, 5
Even when the four spheres 15a to 15d are arranged at substantially equal intervals in the circumferential direction so that 15d corresponds to each other, the other one sphere 15b, 15d is replaced by the other one sphere 15b, 15d as in the first embodiment. In addition to arranging the spherical bodies 15a and 15c axially symmetrically with respect to the screw shaft 6 at a position 3/4 lead away from the spherical bodies 15a and 15c, the other spherical body 1 as illustrated in this embodiment.
It is also possible to dispose 5b, 15d at an axially symmetric position with respect to the screw shaft 6 at a position ¼ lead away from one of the spherical bodies 15a, 15c in the axial direction. With this structure, the axial length of the cage 16 can be further shortened.

As in the first and second embodiments,
The screw shaft 6 is a double thread having two threads 4, 5 and each guiding means 7 corresponds to a plurality of spheres 15a, 15b corresponding to one thread 4 and the other thread 5. A plurality of spheres 15c, 15d, each of which has a screw thread 4, 5
A plurality of spheres 15a, 15b, 15c, 1 corresponding to
When one of the spheres 15a, 15c of 5d is arranged at an axially symmetric position, each one of the spheres 15a, 15c corresponding to each screw shaft 4, 5 includes the one sphere 15a, 15c. The other spheres 15b and 15d may be arranged at axially symmetrical positions where the circumferential intervals between the spheres 15a to 15d are substantially equal. In this case, the number of other spheres is 1 or 2
More than one is acceptable.

FIG. 7 illustrates a third embodiment of the present invention,
In this case, the retaining portion 17 of the retainer 16 is provided with fall-off preventing portions 18a and 18b on both inner and outer sides thereof. And
The opening diameter of the holding portion 17 on the outer side (or inner side) of the drop prevention portion 18b is slightly smaller than the diameter of the spherical body 15a, and the spherical body 15a is fitted into the holding portion 17 from the side of the drop prevention portion 18b. There is. In addition, the inner peripheral surface of the holding portion 17 has a conical surface shape (or a spherical surface shape) corresponding to the spherical body 15a. Note that other configurations are similar to those of the first or second embodiment.

When a cage made of synthetic resin is used as the cage 16, the opening diameter of the retaining section 17 on the side of the one drop prevention section 18b is set to be slightly smaller than the diameter of the spherical body 15a. It is also possible to forcibly spread the fall-off preventing portion 18b with the sphere 15a and fit it into the holding portion 17. In this case, the sphere 15a can be reliably held by the retainer 16 even before the guide means 7 is incorporated into the housing 9. In addition, the retainer 16 may include one ring-shaped member inside and outside, and may be provided with the holding portion 17 having the fall prevention portions 18 on both inner and outer sides in the radial direction, straddling both the link-shaped members.

8 and 9 illustrate a fourth embodiment of the present invention. In this case, the guide means 7 includes three spherical bodies 15a to 15c arranged at equal intervals in the circumferential direction, and the three spherical bodies 15a to 15c. And a retainer 16 that rotatably holds each of the spheres 15a to 15c, and the two spheres 15a and 15b are one screw thread 4
In addition, another one sphere 15c is provided so as to correspond to the other screw thread 5, respectively. Other configurations are similar to those of the first embodiment.

As described above, the guide means 7 may be provided with three spheres 15a to 15c in the circumferential direction so as to correspond to the outer circumferences of any of the threads 4 and 5, respectively. In this case, the axial distance between the spheres 15a to 15c is 1 /
It becomes 6 leads, and it is possible to fit all the spheres 15a to 15c into the 2/3 leads of the threads 4 and 5. The same applies when the number of spheres is an odd number of 5 or more in the circumferential direction.

10 and 11 exemplify a fifth embodiment of the present invention, in which the guide means 7 is at least three axially substantially equidistantly arranged at equal intervals in the circumferential direction.
The number of spheres 15 (for example, three) and a retainer 16 that rotatably holds each sphere 15 are provided. Cage 16
A holding portion 17 whose outer peripheral side is closed is formed in this, and the spherical body 15 is rotatably fitted in the holding portion 17. Other configurations are similar to those of the first embodiment.

When the screw shaft 6 is a double-threaded screw and three spheres 15 are arranged at substantially equal intervals in the circumferential direction, the guide means 7 is arranged so that one sphere 15 corresponds to the threads 4, 5. When the screw shaft 6 is rotated, the other spheres 15 roll on portions other than the outer peripheral surfaces of the screw threads 4 and 5 even if they are assembled to the housing 9. However, since the embedding material 8 is embedded in the screw groove 6a of the screw shaft 6 to make the outer peripheral surface of the screw shaft 6 smooth,
Can be guided in the spiral rotation direction while maintaining approximately concentricity.

Therefore, when the outer peripheral surface of the screw shaft 6 is smooth, at least three spherical bodies 15 are arranged in the circumferential direction at substantially the same position in the axial direction regardless of the threads 4, 5, etc. of the screw shaft 6. It is possible to reduce the axial length of the guide means 7 including the retainer 16.

FIG. 12 illustrates a sixth embodiment of the present invention. In this case, a guide groove 25 having a shallow cross section corresponding to each sphere 15 is formed on the outer peripheral surface of the threads 4, 5 of the screw shaft 6. Are formed along the spiral direction, and the sphere 1 is formed in the guide groove 25.
5 rolls in the spiral direction, and the spherical body 15 is guided by the guide groove 25 so as to be rollable. The filling material 8 for the thread groove 6a of the screw shaft 6 may be provided or may be omitted.

Even in such a case, torque is transmitted between the magnetic nut 3 and the screw shaft 6 by magnetic coupling, and the sphere 15 rolls in the guide groove 25 when the two rotate relative to each other in the spiral direction. According to this structure, the magnetic screw can be similarly implemented without impairing its original function, and the guide groove 25 can surely guide the spherical body 15. Also, the sphere 15 and the guide groove 25
It is also possible to prevent out-of-step between the magnetic poles 1 and 2 of the magnetic nut 3 and the threads 4 and 5 of the screw shaft 6 when a load is secured to a certain extent. is there.

Although the respective embodiments of the present invention have been exemplified above, the present invention is not limited to the respective embodiments.
Various changes can be made without departing from the spirit of the invention. For example, in each of the embodiments, the case of a two-thread screw having two threads (even-number multi-thread screw) is illustrated, but one thread having one thread and an odd thread having three or more threads are illustrated. The same can be applied to the odd-numbered multiple-thread screw and the even-numbered multiple-thread screw having four or more threads.

The magnetic nut 3 is integrally made of a ferromagnetic material such that the housing 9 and the permanent magnet 10 of the first embodiment are integrally formed, and its inner peripheral surface is made smooth. The magnetic poles 1 and 2 may be magnetized. A plurality of magnetic nuts 3 are formed on the inner peripheral side of the housing 9 on the inner peripheral surface thereof so as to correspond to the threads 4 and 5 of the screw shaft 6 and are arranged at predetermined intervals in the axial direction. And a ring-shaped permanent magnet 10 disposed between the yokes and magnetized with magnetic poles 1 and 2 of N pole 1 and S pole 2 at both ends in the axial direction. Anything is fine. Therefore, the structure on the magnetic nut 3 side is not limited to each embodiment.

At least three spheres 15, 15a to 15d of the guiding means 7 may be arranged in the circumferential direction.
5a to 15d are preferably arranged at substantially equal intervals in the circumferential direction, but if the screw shafts 6 can be held substantially concentrically, they need not be arranged at equal intervals in the circumferential direction. Each sphere 1
5, 15a to 15d are all screw threads 4,5
It is preferable that the outer peripheral surface of the sphere be rolled, and the spheres 15 and 15a to 1a corresponding to the respective screw threads 4 and 5 are formed.
It is desirable to set the numbers of 5d to be the same or different by about one. At least 3 spheres 1
It is desirable that 5,15a to 15d be arranged within the range of one lead of the screw shaft 6 as much as possible, but it is also possible to provide them beyond the range of one lead.

When the number of spheres 15, 15a to 15d is three or more in the circumferential direction and all of the spheres 15, 15a to 15d are arranged corresponding to the outer peripheral surfaces of the single or multiple threads 4,5, Spheres 15, 15a to 15d corresponding to one screw thread
May be arranged at a predetermined interval in the spiral direction so that all of the spheres 15, 15a to 15d are arranged at equal intervals in the circumferential direction.

Ceramic balls, steel balls or the like are suitable for the balls 15, 15a to 15d of the guiding means 7, but synthetic resin balls may be used. In addition, spheres 15 and 15a-1
5d may be made of a magnetic material or a non-magnetic material. Cage 1
6 is sufficient as long as it can rotatably hold the spheres 15 and 15a to 15d. For example, the outer peripheral side ball receiving plate part and the inner peripheral side ball holding plate part are integrally provided in a U-shaped cross section. Using the ring body of, in the holding hole formed in the ball holding plate portion,
Spheres 15 and 15 from outside so that part of them protrudes toward the inner circumference
a to 15d are fitted and the spherical bodies 15 and 15a to 15d
May be received from the outer peripheral side by the ball receiving portion on the outer peripheral side. Each guide means 7 may be detachably attached to both axial ends of the housing 9 of the magnetic nut 3 with screws or the like. When the magnetic nut 3 is long in the axial direction, the guide means 7 may be provided at both ends in the axial direction, or may be provided at an intermediate portion thereof.

[0042]

According to the present invention, a magnetic nut having spiral magnetic poles on its inner peripheral surface, a screw shaft made of a magnetic material and having threads corresponding to the magnetic poles on its outer periphery, and both ends of the magnetic nut in the axial direction are provided. And a guide means for holding the screw shaft substantially concentrically in the magnetic nut and guiding the screw shaft so as to be rotatable relative to each other in a spiral direction. Since at least three spheres that movably abut each other are provided in the circumferential direction, the screw shaft can be held and guided by rolling contact by the spheres, and the temperature rise during high-speed rotation as in the case of conventional sliding contact. Therefore, it is possible to reduce minute dust generation due to minute wear and decrease in torque transmission efficiency.

According to another aspect of the present invention, a magnetic nut having an inner peripheral surface formed to be smooth and having magnetic poles spirally magnetized on the inner peripheral surface, and a screw made of a magnetic material and corresponding to the magnetic pole on the outer periphery. A threaded shaft having a ridge and a guide means provided at both axial ends of the magnetic nut and holding the screw shaft substantially concentrically in the magnetic nut with a minute gap therebetween so as to relatively rotate in a spiral direction. In the magnetic screw with and, each guide means,
Since at least three spheres are provided at substantially equal intervals in the circumferential direction and rotatably contact the outer peripheral surface of the screw thread in the circumferential direction, the screw shaft is held and guided by rolling contact of the spheres. It is possible to increase the temperature during high-speed rotation as in the case of conventional sliding contact, minute dust generation due to minute wear,
It is possible to reduce a decrease in torque transmission efficiency.

Further, each guide means comprises a ring-shaped retainer fitted to the end of the housing on the magnetic nut side, and a sphere rotatably retained by the retainer. It is possible to easily hold each sphere.

Further, the screw shaft is an even multiple thread having an even number of threads, and each guide means is provided with a sphere corresponding to one thread and a sphere corresponding to another thread. Is arranged within one lead in the axial direction, each sphere can be guided by the outer peripheral surface of each screw thread, and the axial length of the guide means can be shortened.

Moreover, since the guide groove for guiding the spherical body in the spiral direction is formed on the outer peripheral surface of the screw thread, the spherical body can be reliably guided by the guide groove.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view of a magnetic screw according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of the magnetic screw according to the first embodiment of the present invention.

FIG. 3 is a transverse cross-sectional view of the magnetic screw according to the first embodiment of the present invention.

FIG. 4 is a development view of a main part of the magnetic screw according to the first embodiment of the present invention.

FIG. 5 is a partially cutaway front view of a magnetic screw according to a second embodiment of the present invention.

FIG. 6 is a development view of the essential parts of the magnetic screw according to the second embodiment of the present invention.

FIG. 7 is an enlarged sectional view of a main part of a magnetic screw according to a third embodiment of the present invention.

FIG. 8 is a transverse sectional view of a magnetic screw according to a fourth embodiment of the present invention.

FIG. 9 is a development view of a main part of a magnetic screw according to a fourth embodiment of the present invention.

FIG. 10 is an enlarged sectional view of a main part of a magnetic screw according to a fifth embodiment of the present invention.

11 is a cross-sectional view taken along the line AA of FIG.

FIG. 12 is an enlarged cross-sectional view of a main part of a magnetic screw according to a sixth embodiment of the present invention.

[Explanation of symbols]

1 N pole 2 S pole 3 magnetic nuts 4,5 thread 6 screw groove 7 guidance means 9 housing 10 permanent magnet 15,15a-15d sphere 16 cage 25 guide groove

Claims (5)

[Claims] 1. A magnetic nut having a spiral magnetic pole on the inner peripheral surface thereof, a screw shaft made of a magnetic material and having a screw thread corresponding to the magnetic pole on the outer periphery, and provided on both end sides in the axial direction of the magnetic nut. And a guide means for holding the screw shaft substantially concentrically in the magnetic nut and guiding the screw shaft so as to be rotatable relative to each other in a spiral direction. A magnetic screw comprising at least three spheres in a circumferential direction in which they rollably abut. 2. A magnetic nut having an inner peripheral surface formed to be smooth and having a magnetic pole spirally magnetized on the inner peripheral surface, and a screw made of a magnetic material and having a screw thread corresponding to the magnetic pole on the outer periphery. A shaft and guide means provided at both axial ends of the magnetic nut and holding the screw shaft in the magnetic nut substantially concentrically with a minute gap and guiding the screw shaft in a relatively rotatable manner in a spiral direction. In the magnetic screw provided, each of the guide means includes at least three spherical bodies arranged in the circumferential direction at substantially equal intervals and rollingly contacting the outer peripheral surface of the screw thread in the circumferential direction. Characteristic magnetic screw. 3. The guide means comprises a ring-shaped retainer fitted to an end of the magnetic nut side housing, and the sphere rotatably retained by the retainer. The magnetic screw according to claim 1 or 2. 4. The screw shaft is an even multi-thread screw having an even number of threads, and each of the guiding means has one sphere corresponding to one of the threads and the sphere corresponding to another of the threads. The magnetic screw according to any one of claims 1 to 3, wherein each of the spherical bodies is arranged in one lead in the axial direction. 5. The magnetic screw according to claim 1, wherein a guide groove is formed on an outer peripheral surface of the screw thread so as to guide the sphere to roll in a spiral direction.