JPH02214438A - Supporting device for pneumatic and magnetic bearing type rotary body - Google Patents

Abstract

PURPOSE:To break contact between a fixed shaft and a rotary shaft during low speed rotation by making a conical magnet arranged at the tip of a hollow rotary shaft fittable to at least one of a magnet arranged at the tip of the fixed shaft such that it faces to the aforementioned magnet or a magnet arranged on the inner circumferential face of the upper wall of casing. CONSTITUTION:A conical magnet 11 projecting downward toward a magnet 12 arranged at the tip of a fixed shaft 9, and a reverse conical magnet 12 facing therewith are provided. When the magnets having such shape are employed and the component of magnetic force functions in radial direction, contact between a hollow rotary shaft 2 and the fixed shaft 9 is broken. Since the hollow rotary shaft does not contact with the fixed shaft during low speed rotation, a pneumatic and magnetic optical deflector (scanner) having long service life and high reliability can be obtained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is applicable to optical deflectors used in laser beam writing systems such as laser printers, digital copying machines, and facsimiles, or rotating parts of AV equipment such as VTRs. The present invention relates to a rotating body support device.

[Conventional technology]

In recent years, the speed and density of laser-applied devices and various AV devices have significantly increased, and rotating parts such as scanners used in these devices are also required to have higher rotation speeds and higher II degrees. For this reason, non-contact type dynamic pressure fluid bearings have been attracting attention and being used instead of ball bearings, which are conventional contact type bearings.

FIG. 6 is a longitudinal cross-sectional view of a scanner using a hydrodynamic bearing, where l is a dynamic pressure generating groove, 2 is a rotating shaft, 3 is a polygon mirror, 4 is an entrance/exit window, 5 is a case, and 6 is an electric device. Child coil, 7
8 is a rotor magnet, 8 is a pedestal, and 9 is a fixed shaft.

In the figure, by applying power to the armature coil 6,
As the rotational speed of the zero-rotation shaft 2 increases, the dynamic pressure generating groove 1 formed on the fixed shaft 9 generates dynamic pressure (air bearing), and the fixed shaft 9 and the rotary shaft 2 is in a non-contact state, allowing high-speed, high-precision rotation.

In this method, the rotating shaft 2 rotates while contacting the fixed shaft 9 until a dynamic pressure sufficient to levitate the rotating shaft 2 is generated. For this reason, there was a problem of performance deterioration due to wear.

To solve this problem, proposals have been made to use materials with high wear resistance (for example, ceramics such as silicon carbide and silicon nitride) or to enhance wear resistance through surface treatment (for example, titanium nitride coating).

However, since the former is a soft-processed material, processing costs are high. Also, the material cost is high. In the latter case, there are problems such as deterioration of shaft accuracy and peeling of the coating film, so neither can be said to be at a practical mass production level.

FIG. 7 is a vertical cross-sectional view showing the other side of a conventional scanner (air magnetic bearing type optical deflector) which employs a magnetic bearing based on magnetic repulsion.

This device has magnets 10, 11, and 12 attached to the inner surface of the earthen wall of the case 5, the tip of the hollow rotating shaft 2, and the tip of the fixed shaft 9, respectively.
, and the magnet 11 at the tip of the hollow rotating shaft 2 has a magnetic pole arrangement such that it receives a repulsive force from the opposing magnet 10.12. This constitutes a magnetic bearing.

In addition, as conventional examples of the rotating body support device in this case, Japanese Patent Application Laid-Open No. 63-173011, Japanese Patent Application Laid-Open No. 63-17301
Publication No. 4 can be mentioned.

[Problem to be solved by the invention]

In the conventional device described above, the magnetic bearing acts in the thrust direction from a stationary state, but in the radial direction air bearing, dynamic pressure is generated between it and the dynamic pressure generating groove 1 due to the high speed rotation of the hollow rotating shaft 2. It is only through Kodome that it is composed.

As shown in B of FIG. 5, a rotation speed of 11,000 rpm or more was required for the fixed shaft 9 and the rotating shaft 2 to come out of contact.

Therefore, at lower rotational speeds, the configuration shown in FIG. 7 also has the same problem as described above.

Note that A indicates the characteristics of the device shown in FIG. 6, which includes dynamic pressure air bearings in both the radial and thrust directions, and C indicates the characteristics according to the configuration of the present invention, which will be described later.

SUMMARY OF THE INVENTION An object of the present invention is to provide an air-magnetic bearing type rotating body support device that eliminates the drawbacks of the prior art described above and allows a fixed shaft and a rotating shaft to be out of contact during low-speed rotation.

[Means to solve the problem]

The above purpose is to install a magnet at the tip of the fixed shaft, which is sandwiched between a magnet provided at the tip of the fixed shaft and a magnet provided on the inner surface of the upper wall of the case so that they repel each other. In an air-magnetic bearing rotating body support device having a hollow rotating shaft that forms a magnetic bearing and forms an air bearing between it and a fixed shaft when rotated by a drive source, a magnet provided at the tip of the hollow rotating shaft and This is achieved by forming at least one of the magnet at the tip of the fixed shaft facing the magnet and the magnet provided on the inner surface of the upper wall of the case into a similar conical shape that fits into the magnet.

[Effect]

The magnetic force of the magnet used in the magnetic bearing in the thrust direction can be applied in the radial direction.1. The result was 500r.
An air bearing can be constructed at pm or less.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

1, 2, 3, and 4 are vertical cross-sectional views of the magnetic bearing portion of the air-magnetic bearing type optical deflector according to each embodiment of the rotating body support device of the present invention. The same reference numerals are given to parts that are or can be considered to be the same as those in the example.

In the present invention, the magnet 1 installed between the magnet IO and the magnet 12
1 and at least one of the magnet 10 and the magnet 12 facing it are formed into similar conical shapes that can fit into each other.

That is, in the embodiment shown in FIG. 1, the magnet 11 is provided at the tip of the fixed shaft 9 and has a conical shape protruding downward toward the magnet 2 side, and the magnet 12 facing the magnet 12 has a concave conical shape. It is said that

In the embodiment shown in FIG. 2, on the contrary, the magnet 11
has a concave conical shape, and the magnet 12 has a convex conical shape.

Further, in the embodiment shown in FIG. 3, the upper and lower sides of the magnet 11 have convex conical shapes, and the opposing magnets 10 and 12 each have concave conical shapes.

In the embodiment shown in FIG. 4, the top and bottom of the magnet 11 in the axial direction are formed into a concave conical shape, and the magnet 10.1 facing the magnet 11 has a concave conical shape.
2 each have a convex conical shape.

The magnets used in these embodiments are molded plastic magnets, and the apex angle of the conical shape is approximately 90''. Alternatively, other materials such as sintered magnets may be used.

When the magnet is shaped like this and its magnetic force is exerted in the radial direction, the hollow rotating shaft 2 and the fixed shaft 9 come out of contact at about 200 to 300 rpm, as is clear from the characteristic indicated by the symbol C in Fig. 5. .

As a result, the dynamic pressure generating grooves 1 need only be designed with a pattern shape that provides high rigidity at high rotation speeds, and an improvement in performance is expected.

〔Effect of the invention〕

As explained above, according to the present invention, (1) the hollow rotating shaft and the fixed shaft come out of contact at a lower rotation speed than conventional ones, so the air-magnetic bearing type optical deflector has a long life and high reliability ( (2) It becomes possible to design dynamic pressure generating grooves suitable for high-speed rotation, and the performance can be improved.

[Brief explanation of the drawing]

1, 2, 3, and 4 are longitudinal cross-sectional views of the magnetic bearing portion of the air-magnetic bearing type rotating body support device according to each embodiment of the present invention, and FIG. 5 is a diagram showing the prior art and the present invention. Comparative characteristics diagram, No. 6
7 and 7 are vertical cross-sectional views of a conventional hydrodynamic bearing type rotary body support device and an air magnetic bearing type rotary body support device. 2...Hollow rotating shaft, 9...Fixed shaft, 10, 11.1
2...Magnet. Figure 1] 0 Figure 3] O Figure 2 Figure 4 Figure Group offering (r, p, m) Figure not shown

Claims (1)

[Claims] It is equipped with a magnet provided at the tip of the fixed shaft and a magnet provided on the inner surface of the upper wall of the case, which are held in such a way that they repel each other.The repulsive force of these magnets forms a magnetic bearing, and it is rotated by a drive source. In an aeromagnetic bearing type rotating body support device that has a hollow rotating shaft that forms an air bearing with a fixed shaft, a magnet is installed at the tip of the hollow rotating shaft, and a magnet is installed at the tip of the fixed shaft facing the magnet. An air-magnetic bearing type rotating body support device, characterized in that at least one pair of opposing surfaces of the magnet and the magnet provided on the inner surface of the upper wall of the case have similar conical shapes.