JPH0517964B2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention is applicable to motors that require high-speed, high-precision rotation, such as audio player motors,
The hydrodynamic bearing device is used as a bearing means for the motor of a VTR and the motor for driving the polygon mirror of a laser beam printer (LBP).For more information, see the radial hydrodynamic bearing section and the thrust hydrodynamic bearing section. The present invention relates to a hydrodynamic bearing device.

(b) Conventional technology In general, hydrodynamic bearing devices that use air, oil, etc. as a lubricating fluid are supported by a highly rigid lubricating fluid film during steady rotation, which causes uneven rotation and shaft runout. In recent years, it has been widely used as a bearing means with extremely high rotation accuracy, with extremely little rotation, noise and vibration during rotation. The hydrodynamic bearing device has characteristics such as a long life as it is non-contact during steady rotation, and is therefore used in audio player motors, VTR motors, and polygon mirrors in laser beam printers (LBP). It is used as a bearing means for a drive motor.

For example, as shown in FIG. 9, the above-mentioned LBP motor consists of a sleeve 9 that is a fixed member and a rotating shaft 6' fitted into the sleeve 9.
The rotary shaft 6' has a large number of shallow grooves formed of spiral grooves and herringbones (not shown) formed on its surface, and between these shallow grooves and the inner circumferential surface of the sleeve 9, a radial lubricating fluid with air is formed. A dynamic pressure fluid bearing section is configured for this purpose. Furthermore, the rotating shaft end 8'
A dynamic pressure fluid bearing for thrust, which uses air as the lubricating fluid, is formed between the and thrust bearing 5''.However, during normal operation, the dynamic pressure fluid bearing is connected to the rotating shaft 6'. The sleeve 9 rotates without contact, but at low rotational speeds, contact occurs.In the thrust direction, unlike the gas film that is immediately formed in the radial direction, the gas film rigidity The rotational speed must increase considerably to support the load. Therefore, until that rotational speed is reached, the rotating shaft end portion 8' and the thrust bearing portion 5'' continue to rotate while being in contact with each other.
For this reason, the thrust bearing portion 5'' has problems such as being susceptible to seizure.
In order to reduce the contact surface, in addition to reducing the weight of the rotating shaft 6', the rotating shaft end 8' may be processed into a spherical surface with a predetermined radius (for example, a radius of 750 mm), or the thrust bearing portion 5'' may be polished. Machining is performed to improve the plane accuracy and inclination accuracy. However, machining the rotating shaft end 8' into a spherical surface is extremely difficult.
This was also a factor in increasing product costs.

(c) Problems to be solved by the invention In order to reduce the contact surface between the above-mentioned rotating shaft end 8' and the thrust bearing section 5'', the rotating shaft end 8' is processed into a spherical surface with a radius of 750 mm. In addition, the thrust bearing part 5'' is polished to improve its flatness and inclination accuracy, but because the radius of the spherical surface is large, even if the thrust bearing part 5'' wears only 3μm, the sliding diameter will decrease to φ4mm. , the wear progresses at an accelerated pace. Furthermore, the conventional thrust bearing
In order to prevent the resin member 1'' from coming into contact with the heated metal member or sleeve 9 and being deformed by the stress corresponding to the shrink fit allowance during shrink fitting,
It was necessary to process it with a step as shown in Figure 10. However, even in this case, the resin member 1'' was deformed due to heating, as shown in FIG. 11, and the sliding contact diameter was increased from the initial stage. It would be better to make the radius of the spherical surface at the upper end smaller, but then the space volume between the rotating shaft end 8' and the thrust bearing part 5'' will increase, and the air in this space will cause self-excited vibration, causing the sleeve to It is not possible to reduce the radius of the spherical surface of the rotating shaft end 8' because this would cause vibration in the direction of the rotating shaft 6', a so-called air hammer phenomenon.

For this reason, conventional thrust bearings have had many problems both in terms of machining and operation.

(d) Means for Solving the Problems The present invention aims to solve the above-mentioned problems. A thrust receiving member at one end of the sleeve is composed of a first material member made of
Due to the difference in longitudinal elastic modulus between the material members, the first material member with a smaller longitudinal elastic modulus and a larger elastic modulus protrudes slightly compared to the surrounding second material member. .

(E) Effect With the above configuration, during low-speed rotation, the first rotating member that protrudes slightly slides on the rotating shaft to support the thrust force, and even if wear due to sliding progresses, the diameter of the protruding first material member remains constant. This prevents accelerated wear from increasing, and since the distance from the sleeve to the first material member is long, deformation of the first material member due to heating during shrink fitting is small.

(f) Examples Examples of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the thrust receiving member A is
It is constructed by inserting and forming a resin member 1 constituting the first material member into a metal member 2 constituting the second material member. The resin member 1 is made of polyacetal resin, 6.6 nylon, high density polyethylene, polyimide, polyamideimide,
It is made of commonly used self-lubricating resins such as PTFE, polyetheretherketone, polyethersulfone, and polyphenyline sulfide resins. Then, as shown in FIG. 1, the resin member end 3 and the metal member end 4 on the surface facing the rotating shaft 6 of the thrust receiving member A are held together and their planes are removed at the same time. The ends 3, 4 of the member are machined flush. However, since the longitudinal elastic modulus E is different between resin and metal, the resin member end 3 and metal member end 4, which are flat due to elastic deformation under pressure during processing, will elastically deform when the load is unloaded after processing. There will be a difference in level. That is, the elastic modulus E ₁ of the resin member 1 is the elastic modulus of the metal member 2.
Since the resin member 1 is smaller than E ₂ , the deformation during processing is larger than that of the metal member 2, and the amount of return after processing is also large. As shown in FIG. 2, the resin member end 3 The shape protrudes slightly compared to the metal member end 4. For example, if the thickness of the thrust receiving member A is 10 mm and the resin member 1 is polished using high-density polyethylene and the metal member 2 is polished using iron, 0.1
Assuming that a pressure of Kg/mm ² is applied, the return amount after processing is 0.05μm for iron and 10μm for high-density polyethylene.
There will be a step difference of approximately 10μm, and resin parts 1 due to use.
Since the amount of wear is less than 4μm, this level difference is sufficient. Further, even with other materials, appropriate steps can be created by appropriately changing the pressure applied during grinding.

Furthermore, when there is a 10μm step, the space volume increases,
The above-mentioned air hammer phenomenon may occur, but if the shaft diameter of the rotating shaft 6' is φ14 mm, the space volume created by a 10 μm step is 1.5 mm ³ , whereas the rotating shaft end 8' has a radius of 750 mm. The spatial volume created by the spherical surface is 2.5 mm ³ , totaling 4.0 mm ³ ,
Since the air hammer phenomenon occurs at about 6 mm ³ , there is no problem. Conversely, if the step is hμm and the radius of the rotating shaft end 8' is rmm, at least r ² h×10 ^-3 < to prevent the air hammer phenomenon.
6. Therefore, h<6000/r ² , and considering the amount of wear, 1<h, so it is possible to define the step range of 1<h<6000/r ² .

Further, as shown in FIG. 9, the rotary shaft end 8' is generally configured with a spherical surface, but it may also be configured with a flat surface. In this case, although the initial sliding contact diameter becomes larger, there is no problem because the sliding contact diameter is guaranteed to be below a certain value, and on the contrary, the space between the rotating shaft end 8 and the thrust bearing part 5' Since the volume can be reduced, it is very effective against the air hammer phenomenon as described above, and the processing of the thrust bearing part 5 and the rotary shaft end part 8 is also very easy, so that costs can be reduced.

Alternatively, as shown in FIG. 3, the resin member 3a may be provided only in the vicinity of the contact portion facing the shaft.

Furthermore, as shown in FIG. 4, a step may be provided on the inner circumferential surface 2b' of the space at the center of the metal member 2b, and the resin member 3b may be formed as an insert. It is also possible to extend the center part of the end face further as shown in FIG.

Further, as shown in FIG. 6, the inner circumferential surface of the metal member 2c may be made narrower toward the top, and the resin member 3c may be configured to expand toward the shaft contact surface. As shown in FIG. 7, the center portion of the resin member end portion 3c can be made to protrude further.

In the embodiment shown in FIG. 8, the metal member 2d of the thrust receiving member A is integrated into the sleeve 9', and the resin member 1' is inserted into the upper center of the sleeve 9'. be.

Furthermore, although not shown, by using conductive members as the first material member and the second material member, an electric potential is applied between the rotating shaft 6 and the sleeve 9,
By detecting the potential difference, it is also possible to check the contact between the rotating shaft 6 and the sleeve 9 and measure the floating of the bearing in the thrust direction.

In the above-mentioned embodiment, a self-lubricating resin was used for the first material member and a metal such as iron was used for the second material member, but the present invention is not limited to this. and a resin with a large longitudinal elastic modulus may be used for the second material member, a metal with a small longitudinal elastic modulus may be used for the first material member, and a metal with a large longitudinal elastic modulus may be used for the second material member. In short, the first material member and the second material member are made of materials with different longitudinal elastic modulus, and the longitudinal elastic modulus E ₁ of the first material member is smaller than the longitudinal elastic modulus E ₂ of the second material member. Good to have.

(G) Effects of the Invention As explained above, according to the present invention, the first material member is formed so as to be surrounded by the second material member, and the end face thereof extends a predetermined amount from the end face of the second material member. Therefore, even if wear progresses due to sliding contact with the shaft, the diameter will not exceed the diameter of the first material member, and it is possible to prevent accelerated wear of the thrust receiving member. Since the distance to the second material member in contact is long, deformation of the second material member due to heating during shrink fitting can be reduced. This eliminates the need for difficult work such as machining the shaft end surface into a spherical surface, thereby significantly reducing costs and significantly improving the accuracy and durability of the thrust receiving member.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the state of an embodiment of the present invention during processing, FIG. 2 is a sectional view showing the state after processing, and FIG. 3 is a sectional view showing a partially modified embodiment.
Fig. 4 is a sectional view showing the state of another embodiment during processing, Fig. 5 is a sectional view showing the state after processing, and Fig. 6 is a sectional view showing the state of a further modified embodiment during processing. , FIG. 7 is a sectional view showing the state after processing, and FIG. 8 is a sectional view showing still another embodiment. FIG. 9 is a sectional view showing an example of a conventional motor device, and FIGS. 10 and 11 are sectional views showing the thrust receiving member in different states. 1...First material member (resin member), 2...Second
Material member (metal member), 3...first material member end,
4... Second material member end, 5... Thrust bearing part, 6... Rotating shaft, 8... Rotating shaft end, 9... Sleeve, A... Thrust receiving member.

Claims (1)

[Claims] 1. A shaft that rotates relatively and a sleeve fitted onto the shaft, the outer circumferential surface of the shaft and the inner circumferential surface of the sleeve forming a radial hydrodynamic bearing section. , a dynamic pressure fluid bearing device in which one end surface of the shaft and a thrust receiving member provided on the sleeve constitute a thrust dynamic pressure fluid bearing section, wherein the thrust receiving member is connected to the one end surface of the shaft. A first material member having a longitudinal elastic modulus E ₁ forming the vicinity of the contact portion and a second material member having a longitudinal elastic modulus E ₂ forming the periphery of the first material member, and the first material The longitudinal elastic modulus E ₁ of the member is set smaller than the longitudinal elastic modulus E ₂ of the second material member,
A hydrodynamic bearing device, wherein the first material member projects a predetermined amount toward a shaft end surface with respect to the second material member in a state where pressure during processing is removed. 2 The protrusion amount h (μm) of the first material member relative to the second material member is the radius r (mm) of the shaft.
The hydrodynamic bearing device according to claim 1, wherein 1<h<6000/ ^R2 . 3. The hydrodynamic bearing device according to claim 1, wherein the first material member is made of a self-lubricating resin. 4. The hydrodynamic bearing device according to claim 1, wherein the first material member and the second material member are both made of conductive material.