JPS6343606B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a rotating device supported by a fluid bearing. ,
The present invention provides a bearing structure that minimizes changes in the thrust direction due to the posture of the device by having characteristics that are more sensitive to gaps than the other surface.

BACKGROUND OF THE INVENTION In order to support thrust loads, a collar-shaped spiral groove bearing provided on a shaft is used, for example as shown in FIG. In FIG. 1a, 1 is a rotating shaft, 2 is a flywheel provided on the rotating shaft 1, 3 is a rib of a thrust bearing, 4 is one rib surface, 5 is another rib surface, 6 is a housing, and 7
This is lubricating oil sealed between the collar 3 and the housing 6. FIG. 1b shows the shape of the collar surface 4, and FIG. 1c shows the shape of the collar surface 5.

Spiral grooves are formed in the flange surfaces 4 and 5, and the spiral grooves cause the lubricating oil 7 to move toward the shaft 1 as shown by the arrow by the relative rotation of the flange surfaces 4 and 5 and the housing 6. Since there is a force-feeding action toward the center, pressure is generated on both sides of the collar surfaces 4 and 5, and the rotating shaft 1 can be supported in the axial direction.

Furthermore, if a radial spiral groove is also formed on the rotating shaft 1, support in the radial direction can also be provided.

Problems to be Solved by the Invention However, when this hydrodynamic bearing structure was applied to portable VTR cylinders, etc., which have become increasingly precise in recent years, the following problems arose.

That is, in the case of a portable VTR, the VTR set is used in various positions, not only in a horizontal position as shown in FIG. 1, but also in a vertical position. In the horizontal state, for example, the axial position of the flywheel 2 (corresponding to a rotating cylinder) on which a head (not shown) is provided is as follows:
This is determined by the balance between the pumping pressures generated at two locations on the flange surfaces 4 and 5, and the load W on the flywheel 2 does not affect the balance position.

However, if the posture of the device changes, the axial component of the load W will be applied to the thrust bearings 4 and 5, so the force equilibrium condition will change from the horizontal state.
The axial position of the head provided on the flywheel 2 changes depending on the attitude.

Therefore, in the cylinder of a portable VTR,
When a hydrodynamic bearing structure as shown in FIG. 1 is applied, the above-mentioned difference in the axial posture of the head position becomes a serious defect.

VTR cylinders are becoming more and more precise due to the compactness of the equipment and the increase in recording density.
There was a request to keep it within 2μ.

The present invention solves the above-mentioned problems associated with conventional hydrodynamic bearing structures.

Means for Solving the Problems In order to solve the above problems, a rotating device of the present invention includes a shaft having a flange portion and a housing rotatably engaged with the shaft via a lubricating fluid. The flange has two flange surfaces perpendicular to the axis, and one of the two flange surfaces has a ring having an outer diameter smaller than the diameter of the flange and a small width. A spiral groove bearing having a larger outer diameter and width than the ring-shaped spiral groove bearing is formed on the other flange surface, and under normal conditions, either the shaft or the housing is It has a rotating configuration and a configuration that supports an axial load acting on the shaft or housing in a direction in which a gap between a surface on which the narrow spiral groove bearing is formed and a surface opposite thereto becomes smaller; The second invention comprises a shaft having a spherical portion having a center on a central axis, and a housing that is relatively rotatably engaged with the shaft via a lubricating fluid,
A spherical spiral groove bearing is formed on one of the surfaces of the spherical part divided into two in the axial direction,
A ring-shaped spiral groove bearing having a smaller outer diameter and width than the spherical spiral bearing is formed on the other surface, and the ring-shaped spiral groove bearing has a structure in which either the shaft or the housing rotates in a normal state. The housing is configured to support the axial load acting on the shaft or the housing in a direction that reduces the gap between the surface where the shaft is formed and the surface opposite thereto.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a basic configuration diagram of a rotating device in a horizontal state showing the principle of the present invention, in which 8 is a rotating shaft, 9 is a flywheel provided on the rotating shaft 8, and 10 is a thrust bearing provided on the rotating shaft 8. 11 is a housing that accommodates the rotating shaft 8 and the collar 10; 12 is a lubricating oil sealed between the rotating shaft 8 and the collar 10 and the housing 11; 13 is a shaft formed on the right collar surface of the collar 10; This is a double spiral groove in the direction regulating part.

Further, a ring-shaped protrusion 14 is formed on the left brim surface of the brim 10, and a ring spiral groove 13', which is also a double spiral groove, is formed on the surface of the protrusion 14.

Both the double spiral groove 13 and the ring spiral groove 13' have spiral grooves in different directions formed inside, and the relative rotation of the collar 10 and the housing 11 causes the lubricating oil 12 to form a pattern of spiral grooves. It has the effect of forcing the middle part of the pipe to be fed as shown by the arrow.

Therefore, from the equilibrium condition of three forces: the positive pressure generated on the surfaces of the double spiral groove 13 and the ring spiral groove 13', and the axial component force of the flywheel 9, the axial direction of the flywheel 9 is determined. The location will be determined.

FIG. 3 shows each parameter of the dimensions of the bearing portion of the rotating device.

The rotating device is characterized by a thrust bearing (double spiral groove 13) formed in the collar 10 with a large outer diameter (φd ₃ ), an outer diameter (φd ₁ ) smaller than φd ₃ , and a width ( Thrust bearing (ring spiral groove 1) consisting of a double spiral groove shaped into a small ring-shaped protrusion
3') by combining double spiral groove 13 and ring spiral groove 1.
The difference in the load capacity characteristics of the flywheel 9 is minimized by utilizing the difference in the load capacity characteristics of the flywheel 9 due to changes in the attitude of the device.

The principle of this rotating device will be explained.

In FIG. 4, curve A shows the load capacity characteristic of the double spiral groove with respect to the gap δ ₁ . The reason why curve A exhibits characteristics that are extremely sensitive to changes in the gap δ ₁ is as follows.

The load capacity of a spiral groove thrust bearing that pumps lubricating fluid only in one direction, either from the center toward the outer circumference or from the outer circumference toward the center, is generally expressed by the following equation.

F=fωR _p ⁴ −R _i ⁴ /δ ² ...(1) In the above equation (1), f is a value determined by the shape of the spiral groove, ω is the rotational angular velocity, R _p is the outer radius of the spiral groove thrust bearing, R _i represents the inner radius, and δ represents the thrust bearing clearance.

R _p in equation (1) corresponds to half (d ₁ /2) of the outer diameter φd ₁ in this embodiment, and R _i corresponds to (d ₁ /2−t). Therefore, as φd ₁ and t become smaller, (R _p
⁴ −R _i ⁴ ) suddenly becomes small, and δ<<R _p
Therefore, the value of F changes rapidly with a change in δ. This means that fω(R _p ⁴ − R _i ⁴ ) = constant (=
In a), it can be easily considered by drawing a graph of F=a/δ ² with a as a parameter and observing the range of δ<<R _p .

Curve B shows the relationship between the external force (axial force) that balances the force due to the pressure generated by the ring spiral groove 13' and the clearance δ ₁ when the rotation center axis of the device is in a horizontal state. C shows a similar relationship when the double spiral groove 13 is located above the ring spiral groove 13' and the rotation center axis is vertical. That is, curve C is the value obtained by adding the dead weight W of the flywheel 9 to the value of curve B at the same gap _δ1 .

In Fig. 4, the gap δ ₁ when the rotation center axis of the device is horizontal is the value of δ ₁ at the intersection of curves A and B, and the rotation center axis is vertical and the double spiral groove 13 is in the ring. The gap δ ₁ when located above the spiral 13' is determined as the value of δ ₁ at the intersection of curves A and C. Therefore, the value of ε shown in the graph of FIG. 4 indicates the amount by which the gap δ ₁ decreases when the center axis of rotation changes from horizontal to vertical.

In the graph of FIG. 4, the gap δ ₁ is set at the X coordinate, but if the gap δ ₁ is determined, the gap δ ₃ is also determined.

In FIG. 4, as the gap δ ₁ increases, the curves B and C tend to increase.As the gap δ ₃ decreases, the double spiral groove 13
This is because the force in the axial direction due to the pressure generated on the surface increases.

Further, in curves B and C, since the bearing outer diameter φd ₃ is large, the change in pressure is insensitive to the gap δ ₃ (the same applies to the gap δ ₁ ).

This means that in the above formula (1), R _p is d ₃ /2, R _i
Since it corresponds to the case of <<R _p , R _p ⁴ - R _i ⁴ is extremely large compared to the ring spiral groove 13', so the ring spiral groove 1
This is clear from the same consideration as in the case of 3'.

Therefore, as shown in FIG. 4, regardless of whether the device is in the horizontal or vertical position, the load equilibrium condition is established at the location where the ring spiral groove 13' has a sensitive characteristic, so that the difference in the equilibrium position is ε (posture difference) can be made small.

This rotating device has two types of force generated in different directions.
In a combination of two thrust bearings, one of the thrust bearings has a narrow ring shape to obtain sensitive pressure characteristics against the gap.

In this way, this rotating device has a thrust bearing using a ring spiral groove that is highly dependent on the gap, and a thrust bearing that applies force in the direction of reducing the gap between the thrust bearing and is less dependent on the gap.
In other words, it is characterized by the combination of thrust bearings that have a small restoring force against changes in clearance per unit.
The present rotating device can be applied to a bearing structure as shown in FIG. 2, in which the collar 10 of the thrust bearing is housed in the middle part of the housing 11.

Both ends of the shaft may have a structure open to the atmosphere as shown in FIG. 2, or one end may have a sealed structure.

Further, in the embodiment, the housing 11 is fixed and the rotating shaft 8 rotates, but on the contrary, the shaft is fixed,
A structure in which the housing rotates may also be used.

In this rotating device (Fig. 2), a double spiral bearing is used as a bearing that is less dependent on the gap, but for example, a unidirectional flow such as one where the flow only flows toward the center of the rotating shaft 8 is used. A spiral groove may also be used.

Alternatively, a step bearing may be used in which the groove shape does not change in the radial direction and the groove depth changes only in the circumferential direction.

FIG. 5 shows another example of a rotating device to which the idea of the present invention is applied, in which a ring spiral groove 16 is formed on a spherical surface 15.

17 is a rotating shaft, 18 is a radial spiral groove bearing formed on the rotating shaft 17, and 19 is a spherical surface 1.
This is a spherical spiral groove formed in 5.

Similar to the structure shown in FIG. 2, the ring spiral groove 16 is formed with a sufficiently small ring width t, and generates a large positive pressure on the ring surface only when the gap is small.

On the other hand, when the spherical spiral groove 19 is combined with the radial spiral groove bearing 18, it has the effect of pumping the lubricating fluid in the direction of the arrow, so a large positive pressure is generated at the joint between the spherical surface 15 and the rotating shaft 17. . the result,
Since the rotary shaft 18 can be supported in both the radial direction and the thrust direction, and the bearing structure is combined with the ring spiral groove 16, the difference in the posture of the device in the axial direction can be minimized.

In this way, the bearing to which the present invention can be applied may be either spherical or planar, or may be conical or hemispherical.

FIG. 6 shows an embodiment of the present invention applied to a hydrodynamic bearing in which one side of the shaft has a sealed structure.

20 is a spherical pivot bearing, 21 is a ring spiral groove, 22 is a double spiral groove,
23 is the collar of the thrust bearing, 24 is the shaft, and 25 is the housing.

One of the shaft 24 and the collar 23 is housed in a housing 25 having a sealed structure, and a V-groove 24a is formed at the tip of the shaft 24.

Furthermore, a spherical pivot bearing 20 is formed in the V-groove 24a to make point contact.

A double spiral groove 22 is formed on the side of the spherical pivot bearing 20 of the collar 23.
On the opposite side of 3, there is a ring spiral groove 21.
is formed.

With the above configuration, the present rotating device can start rotation with extremely low torque, and can have a bearing structure in which the change in the thrust direction due to the difference in the posture of the device is small. When there is no relative rotation between the shaft 24 and the housing 25, the relative position between the collar 23 and the housing 25 (the state of close contact between the collar 24 and the housing 25) changes depending on the attitude of the device.

For example, in a structure in which the shaft 24 is fixed to the substrate and the housing 25 is rotatably engaged with the shaft 24, when the housing 25 is placed in the upright position in FIG.
Due to its own weight, the spherical pivot bearing 20 is in close contact with the facing surface of the housing 25.

However, since it is a point contact, the torque at the time of starting rotation is small.

In the rotating state, the gap δ ₄ increases even with the oil film pressure generated in the double spiral groove 22, and is balanced with the pressure of the ring spiral groove 21 floating by a minute gap δ ₅ . At this time, the spherical pivot bearing 20 is in a non-contact state and no wear occurs. When the device is in an inverted state, the ring spiral groove 2 is also damaged due to the weight of the housing 25.
1 comes into close contact with the opposing housing surface, but in this case as well, since the contact area is small, the starting torque can be small.

In the structure shown in FIG. 6, the amount of protrusion of the spherical pivot bearing 20 from the collar 23 may be made smaller than the gap δ ₄ between the double spiral grooves 22 in the rotational equilibrium state.

In addition, if the posture of the device changes only from normal to horizontal, the spherical pivot bearing 20 can be omitted.
The ring spiral groove 21 and the double spiral groove 22 may be replaced upside down.

In this case, it goes without saying that when starting in the vertical position, since the contact area of the surface of the ring spiral groove 21 is small, low torque starting can be achieved.

FIG. 7 is a sectional view of a cylinder of a VTR showing an embodiment of the present invention.

101 is an upper cylinder, 102 is a head attached to the upper cylinder, 103 is a lower cylinder, and the lower cylinder 103 is a lower housing 1 which is a board.
It is fixed at 05.

106 and 107 are the rotating side and fixed side of the rotary transformer, and transmit the signal of the head 102 from the rotating side to the fixed side without contact.

108 is a magnetic case connected to a rotating shaft 109, and the upper cylinder 101 is removably attached to the magnetic case 108 with bolts 123.

A bush 110 is fixed to the lower end of the rotating shaft 109, and the rotating side 106 of the rotary transformer is attached to the bush 110 by adhesive.
fixed side 107 of the rotary transformer.
is also fixed to the lower surface of the lower housing 105 with adhesive.

111 is a motor magnet, 112 is an armature coil, 113 is a motor stator, 114 is a fixed stator, and 114 is a fixed sleeve. The magnet 111 is housed inside the magnet case 108, and the stator 113 is fixed to a fixed sleeve 114 with bolts 115.

Magnet 111, magnet case 108,
The armature coil 112 and the stator 113 constitute a driving section of this device.

The fixed sleeve 114 is fixed to the lower housing 105 by bolts 116, and a rotary shaft 119 is rotatably supported by the fixed sleeve 114.

117 is an upper radial spiral groove formed on the rotating shaft 109; 118 is a lower radial spiral groove; 119 is a collar of the thrust bearing; 120 is a visco seal formed at the lower end of the collar 119; 121 is a bush 110; Lower seal magnet for fixed magnetic seal. A ring spiral similar to the ring spiral 13' shown in FIG. 2 is formed on the upper surface of the collar 119, and a second ring spiral is formed on the lower surface of the collar 119.
2 similar to the double spiral groove 13 shown in the figure.
A heavy spiral is formed. A magnetic fluid 122 as lubricating oil is sealed between the rotating shaft 109 and the collar 119, the fixed sleeve 114 and the lower housing 105, and the upper seal magnet 124 and the lower seal magnet 121 also contain the lubricating oil. Leakage is prevented.

The visco seal 120 has a spiral groove that more effectively prevents leakage of the lubricating fluid, that is, the viscous fluid 122 during rotation, and has the function of pumping the magnetic fluid 122 from the atmospheric opening toward the collar 119 .

Effects of the Invention As described above, according to the present invention, it is possible to suppress the displacement of the rotating part in the axial direction due to the influence of gravity due to the difference in the posture of the device. It is possible to create a VTR cylinder using a hydrodynamic bearing that eliminates this problem.

Furthermore, the present invention can be applied to various rotating devices using fluid bearings, such as video disk players, gyroscopes, machine tools, etc.
Applicable to rotating equipment in various fields.

[Brief explanation of the drawing]

Fig. 1a is a side sectional view of a conventional hydrodynamic bearing structure, Fig. 1b is a left front view of the rib of a thrust bearing of the same hydrodynamic bearing structure, Fig. 1c is a right rear view of the same brim, Fig. 2a 2 is a side sectional view of a rotating device showing an embodiment of the present invention, FIG. 2b is a left front view of the rib of the thrust bearing of the same device, FIG. 4 is a gap/pressure characteristic diagram of the bearing portion of the rotating device; FIGS. 5 and 6 are side sectional views of the rotating device showing other embodiments of the present invention, respectively; FIG. 7 is a longitudinal sectional view of a VTR cylinder equipped with a rotating device showing another embodiment of the present invention. 8, 17... Rotating shaft (shaft), 11, 25... Housing, 12... Lubricating oil (lubricating fluid), 13,
22...Double spiral groove (axial direction regulation part), 13', 16, 21...Ring spiral (grooved fluid thrust bearing), 19...Spherical pivot bearing (axial direction regulation part), 24...Shaft, 105...
Lower housing (housing), 109... Rotating shaft (shaft), 119... Thrust bearing collar, 12
2...Magnetic fluid (lubricating fluid).

Claims (1)

[Scope of Claims] 1. Consisting of a shaft having a flange portion and a housing that is engaged with the shaft through a lubricating fluid so as to be relatively rotatable, the flange portion having two flange surfaces perpendicular to the axis. A ring-shaped spiral groove bearing having an outer diameter smaller than the diameter of the flange portion and a small width is formed on one of the two flange surfaces, and a ring-shaped spiral groove bearing having a small width is formed on the other flange surface. A spiral groove bearing having a larger outer diameter and width than the ring-shaped spiral groove bearing is formed, and either the shaft or the housing rotates in a normal state, and the spiral groove bearing having a smaller width is formed. A rotating device that supports an axial load acting on the shaft or housing in a direction that reduces a gap between a surface and a surface facing the same. 2. Consisting of a shaft including a spherical part centered on the central axis, and a housing engaged with the shaft through a lubricating fluid so as to be relatively rotatable, two parts of the surface of the spherical part in the axial direction A spherical spiral groove bearing is formed on one of the separated surfaces, and a ring-shaped spiral groove bearing having a smaller outer diameter and width than the spherical spiral bearing is formed on the other surface. A rotating device configured to rotate one of the bearings and to support an axial load acting on the shaft or housing in a direction in which a gap between a surface on which the narrow ring-shaped spiral groove bearing is formed and a surface facing the same becomes smaller.