JPS6098213A - Dynamic pressure fluid bearing - Google Patents

Abstract

PURPOSE:To enable checking of a bearing for clearance, by a method wherein a ceramic, by which a part of a dynamic pressure bearing is formed, is caused to have electrical conductivity. CONSTITUTION:Ceramic, which is applied on a thrust pad 6 and a shaft end 3, is prepared such that 25% or more in a weight ratio of metallic powder such as tungsten is contained in ceramic such as alumina, and as a result, volume specific resistance is 10<7> or less, and the ceramic has electrical conductivity. Generally, other part is formed by a SUS or S material, and taking sliding properties into consideration, Cr plating = tack treatment is applied thereon. This enables a bearing to be checked by energization for both a radial and a thrust direction by means of and oscillograph, and enables earlier and more reliable checking for the presence of noxious metallic fine powder in relative to the size of a clearance and contact of burr caused by a flaw, compared with aural observation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydrodynamic bearing, and in particular, examples include:
The present invention relates to hydrodynamic bearings used in high-speed rotating high-precision motors such as polygon drive motors used in laser beam printers, VTR motors, and magnetic disk motors.

Conventionally, in this type of device, a hydrodynamic bearing using a gas such as air as a medium has been used for excellent bearing performance during high-speed rotation, low torque, and prevention of low rotational unevenness. First, FIG. 1 shows a polygon drive motor as an example of a motor using such a hydrodynamic bearing.

FIG. 1 is a sectional view thereof. The drive motor shown in Fig. 1 is a sleeve rotation type motor mechanism using a dynamic pressure bearing using air as a medium, and a shaft 2 fixed to an outer cylinder 1 has a herribone-shaped groove 5 and a spiral groove. This shaft 2 is covered with a rotating sleeve 5 so that the radius gap is about 3 to 10 μm.

A thrust receiver 6 that comes into contact with the shaft end when the sleeve is stopped is press-fitted into the upper end of the sleeve, and the center of the thrust receiver generates pressure in the systhrust direction by a choke effect to raise the rotating part to a predetermined height. There is a hole 7.

Further, a balance ring 10 is attached to the sleeve 5 to balance the polygon 8 and the magnet 9 as a rotor. A reflection type upper ring 13 is installed to read the black and white pattern of the ring and obtain a tack signal for PLL control, and the whole constitutes a PLL controlled DO Hall motor.

Here, when current flows through the stator coil 11, the sleeve 5 rotates, and air flows into the grooves as shown in arrow 1:014.
Pressure is generated by the air film in the lateral and thrust direction, and the shaft and sleeve rotate without contacting each other, causing the PLL
It is controlled to a constant rotation speed and continues to rotate.

Here, in such a vertical configuration, the important element for a dynamic pressure bearing is the thrust bearing. While the groove on the outer periphery of the shaft and the inner surface of the sleeve form a radial bearing portion that has rigidity in the radial direction, this thrust receiver 6 is a thrust bearing portion that has sys-thrust rigidity due to the gas pumping action of the throttle hole 7 and the spiral groove 4. Work as. At low speeds, the pressure is low, so the bearing rotates in contact with the shaft end, so it is an important component that determines the life of the bearing.

Therefore, in order to reduce the contact resistance, the end surface of the pantyhose holder is made into a spherical shape with a large curvature, and the material is also alumina, since metal-to-metal contact can cause galling and increase torque. It is coated or coated with ceramic such as silicon nitride, and the mating shaft or glazed end is also coated with ceramic or ceramic coating in order to improve its resistance and durability. As a result, if the thrust load is about 5ooy, the torque change and amount of torque will remain at a level that does not cause any practical problems even after about 50,000 starts and stops.

Figure 2 is a cross-sectional view of a motor using a shaft-rotating power fluid bearing, which has the same DC ball motor configuration as Figure 1.
The same functional parts are given the same numbers and their explanations are omitted. In the case of this motor, the shaft 15 has a magnet 9, a balance ring 10. A polygon 8 is fixed, and herringbone grooves 1<S, 18 are carved on its outer periphery at two places, upper and lower, and a small gap (2 to 5μ) is formed between the surface and the circular surface of bearings 17 and 19 fixed to the outer cylinder. The radial direction is supported without contact by the pressure of the air film generated when the multiple shafts rotate facing each other through the shaft.The thrust direction is fixed to the shaft with spiral grooves carved on the top and bottom surfaces of the upper bearing 19. A gas film is formed between the thrust plate 20 and the groove, and is supported by the pressure generated in the groove.

In this case as well, when the motor is used vertically as in Figure 1, the durability of the thrust plate 2o greatly affects the performance life of the bearing, so the thrust plate 20 and the upper bearing 19 are Coated. The through-hole and dynamic pressure bearings shown in the above explanation are as follows.

During normal operation, there is a slight gap (2 to 10 mm) between the fixed side and the rotating side.
It is characterized by its non-contact rotation while maintaining a rotational speed of about μ), and its shelf support performance (rotation accuracy, unevenness, torque, etc.) also derives from this.

Ensuring this clearance is extremely important to prevent bearing seizure, which is a fatal problem for bearings. Therefore, during assembly, great care must be taken to ensure that fine powder does not enter the gap, and that there are no scratches on the bearing surface. The structure and assembly are such that once the Quen Air is sealed, no problems will occur once it is assembled.However, there is no effective way to check the condition immediately after assembly, so conventionally the rotating part was raised slightly in the thrust direction (1
If it warps, in the motor shown in Figure 1, you can raise the sleeve 5 a little, close the throttle hole 7 of the thrust receiver 6, and turn it by hand to hear the contact sound, or you can check the contact sound by ear. The method used was to increase the rotation speed and observe the occurrence of abnormal noises and vibrations, but both methods were dependent on the operator's intuition, and the workability was poor, making them extremely unsuitable for breeding. Ta.

Therefore, an object of the present invention is to provide a new hydrodynamic bearing that is improved in view of the above-mentioned drawbacks.

Another object of the present invention is to provide a hydrodynamic bearing in which the ceramic of the hydrodynamic bearing part is made electrically conductive so that continuity between the stationary side and the rotating side of the bearing part can be checked. That's true.

That is, the main structure of the present invention that can achieve the above object is that ceramic is used for part or all of the bearing that supports the rotating member by generating pressure due to rotation in the fluid interposed between the surfaces that move relative to each other. This is a dynamic pressure fluid bearing characterized by making the ceramic conductive.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. In Figures 1 and 2 described in nσ, the ceramic used for the thrust receiver 6, thrust plate 20, shaft end 6, bearing 19, etc. is a ceramic such as alumina containing metal powder such as tungsten at a weight ratio of 25 or more. Please include)
As a result, the volume resistivity is 107 or less, and it has electrical conductivity.In general, other parts of 5UI3fi are made of S material, and in consideration of sliding properties, they are treated with Ormetsukidax treatment, etc. Because of this, it is possible to check continuity using an oscilloscope in both the radial direction and the thrust direction. You will be able to do it faster and more confidently. Also, it becomes possible to check the presence or absence of vibrations (whirl, air) and vibrations (whirl, air) ＼marker 4) where the fixed 1) IQ and rotating side come into contact during steady rotation. In addition, it is necessary to check the floating shield, especially in the case of a rotating sleeve type as shown in Figure 1 of the 1st edition, if the relationship between the glaze and the inner surface of the IJ-spring is not good, it is natural that the floating shield will be checked at a certain rotation speed. Since there is no bearing, it is not possible to check the overall performance of the entire bearing, and floating at a predetermined rotation speed leads to limiting the number of starts and stops.

However, in general, when metal powder or the like is mixed into ceramic, its anti-magnetic resistance decreases a little, but it is sufficient for practical V-bells (starting and stopping tens of thousands of times). Furthermore, from the point of non-invention, it is necessary to make the ceramic part conductive, and it is also possible to make the ceramic part conductive by firing it using a ceramic material that itself has conductivity, such as titania-based or 7-orstethetan-based material. When it is bonded, a titanium layer is formed on the surface, which makes it possible to give it dielectric properties.

In addition, the motor configuration is not limited to those shown in Figures 1 and 2, but instead of a hydrodynamic bearing with grooves, a tail-tay/gupade or foil-type hydrodynamic bearing may be used, or a 7% (grooved) hydrodynamic bearing with a magnetic bearing may be used. Even with a ° type configuration, the ceramic part used in the dynamic pressure bearing part is made quadrielectric, allowing for non-contact confirmation.

As explained above, according to the configuration of the present invention, the gap in the bearing can be removed by checking the conductivity.

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views showing a first embodiment of the present invention. In the figure, 3 is a shaft end, 6 is a thrust bearing, 19 is a bearing, and 20 is a thrust plate.

Claims (1)

[Claims] (1) A dynamic pressure fluid bearing that uses ceramic for part or all of the bearing that supports a rotating member by generating pressure due to rotation in a fluid interposed between surfaces that move relative to each other. In A, there is provided a hydrodynamic bearing characterized in that the ceramic has electrical conductivity. (2) The dynamic pressure fluid bearing according to claim 1, wherein the chemical compound is alumina (AJ203) containing metal powder with a weight ratio of 25 inches or more. (6) The dynamic pressure fluid bearing according to claim 1, wherein the ceramic is a titanium-a-based or 7-orstetitanium-based ceramic whose material itself is electrically conductive.