JPS6060324A - Dynamic pressure bearing vertical type spindle device - Google Patents

Abstract

PURPOSE:To prevent a receiving surface of a thrust bearing from being contacted to a rotary shaft in time of low revolution, by constituting a device so as to make it shiftable selectively to a first position separating the rotary shaft from the receiving surface of the thrust bear and a second position supporting it with the thrust bearing. CONSTITUTION:Immediately after starting, a push rod 42 still remains pushed upward by a compression spring 44, while a rotary shaft 10 is also deviated upward via a ball body 45, and a pair of receiving surfaces making up a thrust bearing 12 are isolated in an axial direction. In consequence, the rotary shaft 10 rotates as sliding between a sliding piece 13 and the ball body 45. At this time, since a contact part between the sliding piece 13 and the ball body 45 is low in rotation speed, wear or abrasion is seldom or never produced there. When several seconds pass away after starting, dynamic pressure is produced in the thrust bearing as well, increasing load capacity, and when a solenoid 48 is energized with current, the push rod 42 is made to go down against the compression spring 44 so that thrust load is supported by the thrust bearing 12 which comes to have the load capacity ample enough.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a vertical spindle device using a hydrodynamic bearing, which is used in machine tools, audio equipment, information equipment, and the like.

In spindle devices using conventional hydrodynamic bearings, during high-speed rotation, the rotating and stationary members (2) do not come into contact with each other due to the effect of hydrodynamic pressure, so there is no wear and very high rotational accuracy can be achieved. I can do it. However, when the rotation speed is low, such as when starting or stopping, the bearing surfaces of the rotating and stationary components come into contact and cause relative slippage, which causes wear on the bearing surfaces, resulting in various problems such as a shortened bearing life. occurs. In particular, in the case of a vertical spindle, the relative sliding speed of the contact part increases due to the large contact area of the thrust bearing, and the thrust bearing part is particularly problematic because gravity is supported by the thrust bearing. . It has been confirmed that radial bearings can be used without problems by applying hard chrome plating or other appropriate surface treatment.

Purpose of the Invention The present invention provides a vertical dynamic pressure bearing that can prevent the bearing surfaces from coming into contact with each other when the rotation speed is low, such as when starting and stopping the thrust bearing, and can solve the above-mentioned problems. The present invention aims to provide a spindle device.

(3) Structure of the Invention In order to achieve the above object, the hydrodynamic bearing vertical spindle device of the present invention includes a hydrodynamic thrust bearing (12) and a hydrodynamic thrust bearing (12) each having bearing surfaces facing each other. a first position in which a rotating shaft (10) is supported by a radial bearing (11), and the rotating shaft (10) is pushed upward to separate the bearing surfaces of the hydrodynamic thrust bearing (12) from each other; The rotating shaft (10) is spaced apart from the rotating shaft (10).
a push rod (10) extending coaxially with the rotating shaft (10) that can selectively move in the axial direction between a second position where the gravity of the dynamic pressure type thrust bearing (12) is supported; 42
), first means (44) for biasing said push bar (42) to said first position, and second means (48) for biasing said push bar (42) to said second position. do.

Effect of the Invention In the above configuration, the first means (44) is configured such that the rotational speed of the rotating shaft (10) is low during starting and stopping, and the load capacity (4) of the hydrodynamic thrust bearing (12) is low. By holding the push rod (42) in the first position when it is still not sufficient, the dynamic pressure type thrust bearing (12),
The receiving surfaces constituting the are separated from each other. As soon as the rotational speed becomes high and the dynamic pressure type thrust bearing has sufficient load capacity, the second means (48) is activated and the push 1 (42) is activated.
) to the second position. As a result, the rotation axis (1
The gravity of 0) is now supported by the dynamic pressure type thrust bearing (12). Note that selective movement of the push rod (42) between the first position and the second position can be performed, for example, by a predetermined number of rotations, or by interlocking with a start button and a stop button. can.

Effects of the Invention According to the present invention, since undesirable contact does not occur in the dynamic pressure type thrust bearing even during low speed rotation, wear and damage to the bearing portion does not occur, and the life span is improved.

Examples The feature of this invention is (5) regarding the embodiment shown in the drawings. This will become clearer from what follows.

In Figure 1, the spindle device has a vertical axis of rotation (10
), a case (
20) and a rotor (31) fixed to the rotating shaft (10)
and a stator (32) fixed to the case (20).
).

Although the drawing is simplified, it is a dynamic pressure type radial bearing (
11) and the dynamic pressure type thrust bearing (12) are composed of a pair of mutually facing and cooperating bearing surfaces, one of which has a groove for generating dynamic pressure. A sliding piece (13) made of a self-lubricating material such as oil-impregnated bearing material or tetrafluoroethylene resin is fixed to the lower end of the rotating shaft (10).

The member (40) attached to the lower part of the case (20) has an opening (41) in the center, and the rotating shaft (
The upper part of the push rod (42) extending coaxially with 10) is visible. The push rod (42) has a recess (43) formed at its lower end.
) and the bottom of the case (20) and (6) is biased upward by a compression spring (44), which causes the rotating shaft (1
It collides with the sliding piece (13) of 0). The sphere (45) is made of a quench-hardened material, for example, a hard ball for rolling bearings, and is connected to the upper end of the push rod (42). The push rod (42) is threaded, and the positioning plate (46) is screwed onto it and fixed with a nut (47). The positioning plate (46) plays the role of determining the tip position of the sphere (45) by coming into contact with the member (40). The lower part of the push rod (42) is located within the center hole of the solenoid (48). Therefore, when the solenoid (48) is energized and energized, the push rod (42) is attracted downward against the elasticity of the compression spring (44). Note that the push rod (42) is allowed to descend due to the weight of the rotary shaft (]0).

The motor (30) and solenoid (48) are connected to an electrical circuit as shown in FIG. That is, the switch (
FBI), the motor (30) will start rotating. After starting the motor, the solenoid (48) is energized and energized as soon as a certain period of time set by the timer (TR) has elapsed (7). When the machine is stopped, pressing the switch (PB2) turns off the motor (30) and at the same time the solenoid (4th).

The operation of this embodiment having the above-described structure will be described as follows, as an example, at the time of startup.

Immediately after starting, the push rod (42) is still pressed by the compression spring (44).
) has been pushed upwards, so the sphere (
The rotation axis (10) is also shifted upward via 45),
A pair of bearing surfaces constituting the thrust bearing (12) are separated from each other in the axial direction. As a result, the rotation axis (10) is shaped like a sphere (4
5), the sliding piece (13) and the sphere (4)
5) It rotates while sliding between the two. At this time, the sliding piece (13
) and the sphere (45) correspond to the center of rotation,
Since the rotational speed is low, the relative sliding speed is also low, and almost no wear occurs.

A few seconds after startup, the rotation speed of the rotating shaft (10) will reach ID.
OOrpm or higher, dynamic pressure is generated in the thrust (8) and bearing (12) as well, and the thrust (8) and bearing (12) have sufficient load capacity. Therefore, at this time, the solenoid (4
8), the solenoid (48) is energized to lower the push rod (42) against the elasticity of the compression spring (44), and the thrust load including the weight of the rotating shaft (10) is now a sufficient load. Thrust bearings (12
).

When stopped, press the switch (PB2) to turn off the motor and the solenoid (48) at the same time, the rotation shaft (10) is pushed up by the compression spring (44), and the thrust bearing (12) does not come into contact. rotate until it stops.

In this way, the motor switch (F
The structure is such that the protection device is automatically controlled by simply turning ON and OFF BI) and (PB2), so operation is easy and the device is compact. In addition, it functions normally even during a power outage, just as it does during a normal stop, and is maintenance-free.

In this embodiment, the solenoid (48) is kept energized for a certain period of time after pressing the start button 9) until the stop button is pressed. However, especially when the operating time is long, it is preferable to perform sequence control according to the operating specifications, etc., without being limited to this.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a hydrodynamic bearing vertical spindle device according to an embodiment of the present invention, and FIG. 2 is an electric circuit diagram of the same device. (10) - Rotating shaft, (12) - Hydrodynamic thrust bearing, (42) - Push rod, (44) - First means (compression spring), (48) - Second means (solenoid) Patent applicant NCH Toyo Bearing Co., Ltd. Agent Sho Ehara ~ Hide Ehara (10)

Claims (5)

[Claims] (1) A rotating shaft is supported by a hydrodynamic thrust bearing and a hydrodynamic radial bearing each having mutually opposing bearing surfaces, and the rotating shaft is pushed upward to support the hydrodynamic thrust bearing. The first part that separates the surfaces from each other
and a second position that is spaced apart from the rotation shaft and allows the hydrodynamic thrust bearing to support an axial load. A hydrodynamic bearing vertical spindle apparatus comprising a push rod, first means for biasing the push bar to the first position, and second means for biasing the push bar to the second position. (2) The first means is a compression spring interposed between the lower end of the push rod and the support member, and the second means is configured to pivot the push rod against the elasticity of the compression spring when energized. The hydrodynamic bearing vertical spindle device according to claim 1, characterized in that it is a solenoid (1) for directional movement. (3) The hydrodynamic bearing vertical spindle device according to claim 1, further comprising positioning means for defining the axial position of the push rod at the first position. (4) The hydrodynamic bearing vertical spindle device according to claim 1, wherein the upper end of the push rod is spherical. (5) The dynamic pressure bearing vertical spindle device according to claim 1, characterized in that a sliding piece is fixed to the lower end of the rotating shaft.