JPH0663803A - Pressurized fluid journal bearing - Google Patents

Abstract

PURPOSE:To ensure an adequate bearing characteristic by varying the bearing characteristic in accordance with conditions of the rotation of a shaft. CONSTITUTION:A number of nozzles 15 are disposed at predetermined intervals along the same circumference on the surface of a bearing metal 3 that is opposite to a shaft 2. A number of supply and exhaust openings 18 are disposed at predetermined intervals between the nozzles 15 along substantially the same circumference where the nozzles 15 are disposed on the surface of a bearing metal 3 that is opposite to the shaft 2. The nozzles 15 are connected to a delivery side of a supply source 24 of pressurized fluid, whereas the supply and exhaust openings 18 are, in a switchable manner, connected to both inlet and delivery sides of the supply source 24 of pressurized fluid via valves 31 and 33 When the shaft 2 rotates at low speed, the supply and exhaust openings 18 are connected to the inlet side of the supply source 24 by switching the valves 31 and 33, and pressurized fluid is supplied from the nozzles 15 to a clearance 5 between the shaft 2 and the bearing metal 3. When the shaft 2 rotates at a high speed, a supply/exhaust opening 18 is connected to the delivery side of the supply source 24, and pressurized fluid is supplied to the clearance 5 from the nozzles 15 and the supply/exhaust opening 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure fluid journal bearing used for a spindle device of a machine tool.

[0002]

2. Description of the Related Art Conventionally, in a spindle device of a machine tool or the like, a pressure fluid made of lubricating oil is supplied to a gap between opposing surfaces of a shaft and a bearing metal so as to support the shaft statically. Pressure fluid journal bearings are widely used. Among the journal bearings of this type, the one having a small pocket portion cannot secure a high rigidity when the shaft rotates at a low speed because the static pressure in the pocket portion is insufficient. On the other hand, in a journal bearing that is not a pocket type, since the width of the gap between the shaft and the bearing metal, that is, the land, is wide, a large dynamic pressure is generated in this gap during high-speed rotation of the shaft, and high rigidity is obtained. Also, due to the high damping function of the wide land, good stability at high speed rotation can also be obtained.

[0003]

However, in this conventional pressure fluid journal bearing, since the land of the gap is wide and the gap is narrow, the calorific value is larger than that of the pocket type journal bearing, and the shaft bearing There are problems that the rotational speed is limited and that the shaft and the bearing metal are thermally deformed. That is, when the land of the gap is wide and the gap is narrow, the dynamic pressure effect is effectively exerted and the rigidity is increased, but the friction between the pressure fluid and the shaft or the bearing metal causes an excessive amount of the shaft or the bearing metal. Then, the above-mentioned problem of thermal deformation and the like occur. Then, when the pressure fluid (lubricating oil) becomes extremely high in temperature due to the heat generation, the viscosity of the lubricating oil is lowered and even the bearing rigidity is lowered.

The present invention has been made by paying attention to the problems existing in the prior art, and the purpose thereof is to change the bearing characteristics according to the rotating condition of the shaft, An object of the present invention is to provide a pressure fluid journal bearing that can obtain appropriate bearing characteristics.

[0005]

In order to achieve the above object, in the pressure fluid journal bearing of the present invention,
To direct the gap between the facing surfaces of the shaft and the bearing metal,
A plurality of nozzles are arranged at predetermined intervals on the same circumference, and a plurality of supply / discharge ports are arranged between the nozzles at a predetermined interval from the nozzles, and the nozzles serve as a pressure fluid supply source. In addition to being connected to the discharge side, the supply / discharge port is switchably connected via a valve to the suction side and the discharge side of the pressure fluid supply source.

[0006]

In the pressure fluid journal bearing configured as described above, when the shaft rotates at a low speed, the supply / discharge port is connected to the suction side of the supply source by switching the valve, and the shaft and the bearing are connected from the supply source through the nozzle. Pressure fluid is supplied to the gap with the metal. Therefore, at the time of low speed rotation, high rigidity can be secured by the static pressure effect of the pressure fluid.

Further, when the shaft rotates at a high speed, the supply / discharge port is connected to the discharge side of the supply source by switching the valve, and a large amount is provided in the gap between the shaft and the bearing metal from the supply source through the nozzle and the supply / discharge port. Pressure fluid is supplied. Therefore, at the time of this high speed rotation, heat generation of the shaft and the bearing metal can be suppressed, and high rigidity can be secured by the dynamic pressure effect of the pressure fluid.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a pressure fluid journal bearing embodying the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, the housing 1 is formed in a substantially cylindrical shape and is mounted on a spindle head or the like of a machine tool. The shaft 2 is rotatably supported in the housing 1 through a pair of front and rear bearing metals 3, 4, and a predetermined gap is provided between the outer peripheral surface of the shaft 2 and the inner peripheral surface of the bearing metal 3, 4. 5 and 6 are formed. The mounting hole 7 is formed at the front end of the shaft 2, and a tool 8 such as a rotary grindstone is removably mounted in the mounting hole 7. The pulley 9 is fixed to the rear end of the shaft 2,
The rotational force of a motor (not shown) is transmitted to the shaft 2 via the belt 10, the pulley 9 and the like.

The flange 11 is formed integrally with the outer periphery of the front end of the shaft 2 and is arranged to face the front end of the front bearing metal 3 with a predetermined gap. The seal cover 12 is fixed to the front surface of the housing 1 and covers the peripheral side of the flange 11 in an airtight state. The collar 13 is fixed to the outer periphery of the center of the shaft 2 and is arranged to face the rear end of the front bearing metal 3 with a predetermined gap. The chamber 14 is provided in the housing 1 between the bearing metals 3 and 4, and the rear end of the gap 5 and the front end of the gap 6 communicate with the chamber 14.

As shown in FIGS. 1 to 3, a plurality (three in this embodiment) of nozzles 15 are provided on the same circumference of the center of the inner peripheral surface land portion of the front bearing metal 3 at predetermined equal intervals. And is directed toward the gap 5. Plural (6 in this embodiment)
Nozzles 16 are provided on the same circumference in the land portion of the inner peripheral surface of the rear bearing metal 4 at predetermined equal intervals, and the gap 6
Is oriented. A plurality of pairs (six pairs in this embodiment) of nozzles 17 are provided on both front and rear end surfaces of the front bearing metal 3 in correspondence with each nozzle 15, and are directed toward the flange 11 and the collar 13.

Plural (three in this embodiment) supply / discharge ports 18
Are formed on the same circumference of the center of the inner peripheral surface land portion of the front bearing metal 3 at predetermined equal intervals, and are directed to the gap 5. Further, the supply / discharge ports 18 are arranged on the same circumference as the nozzle 15 so as to be positioned alternately with the nozzle 15 at equal intervals. Therefore, in this embodiment, the arrangement intervals of the nozzles 15 and the supply / discharge ports 18 are 6 degrees of 60 degrees.
They are evenly distributed.

The supply port 19 is formed in the front portion of the housing 1, and is connected to the nozzle 15 of the front bearing metal 3 and is also connected to the nozzle 17 through the conduction path 20. The supply port 21 is formed in the rear part of the housing 1 and communicates with the nozzle 16 of the rear bearing metal 4.
The supply / discharge port 22 is provided in the front part of the housing 1 and communicates with the supply / discharge port 18 of the front bearing metal 3. The exhaust port 23 is provided in the center of the housing 1, and the chamber 14
Is in communication with.

A pump 24 as a supply source of pressure fluid (lubricating oil) is provided outside the housing 1, and a suction fluid tank 26 is connected to a pressure fluid tank 26 via a cooler 25. The discharge side of the pump 24 is connected to the supply ports 19 and 21 via a pipe 27 and to the supply / discharge port 22 via a pipe 28. Further, to the tank 26 on the suction side of the pump 24, the supply / discharge port 22 is connected via a conduit 29, and the discharge port 23 is connected via a conduit 30.

The first valve 31 is provided in the conduit 28 and is opened / closed by an actuator 32 such as a solenoid. The second valve 33 is provided in the conduit 29 and is opened / closed by an actuator 34 such as a solenoid. The controller 35 is electrically connected to the actuators 32 and 34 of both valves 31 and 33, and the input end thereof has the shaft 2
The setting device 36 for setting the target value of the rotation speed of the above and the detector 37 for detecting the rotation speed of the shaft 2 are electrically connected.

Next, the operation of the pressure fluid journal bearing constructed as described above will be described. In this journal bearing, when a motor (not shown) is started, the shaft 2 is rotated via the belt 10 and the pulley 9 and the work is processed by the tool 8 at the tip thereof.

The controller 35 detects the rotational speed of the shaft 2 by the detector 37, compares the detected value with the target value from the setter 36, and depending on the difference between them, that is, the deviation, both valves 31, The actuators 32 and 34 of 33 are driven.

That is, when the rotation speed is low or the rotation is stopped as before starting, the detected value of the rotation speed is lower than the target value, so that the first valve 31 is closed and the second valve 31 is closed. The valve 33 is opened. By operating the pump 24 in this state, the pressure fluid is supplied to the supply ports 19 and 21 through the pipe line 27, and is jetted from the nozzles 15 and 16 toward the gaps 5 and 6 between the shaft 2 and the bearing metals 3 and 4. To be done. As a result, the function of the hydrostatic bearing is exhibited, and the shaft 2 is supported in a non-contact state with the bearing metals 3 and 4.

Further, a part of the pressure fluid supplied to the supply port 19 passes through the conduction path 20 and the front bearing metal 3
And is ejected toward the flange 11 and the collar 13 from the nozzle 17. As a result, the function of the thrust bearing is exerted and the movement of the shaft 2 in the axial direction is restricted. The pressure fluid injected into the gaps 5, 6 and the like is recovered from the supply / discharge port 18 into the tank 26 via the supply / discharge port 22 and the pipe line 29, and also from the chamber 14 to the discharge port 23 and the pipe line 30. It is collected in the tank 26 via the.

As shown in FIG. 4, the pressure distribution in the gap 5 at the time of forming the hydrostatic bearing becomes high at the position corresponding to the nozzle 15 and becomes gradually lower as it goes away from the position in the circumferential direction. Therefore, when forming this hydrostatic bearing,
As a bearing characteristic of the pressure fluid journal bearing, a relatively high rigidity can be secured.

On the other hand, when the rotation speed shifts to a high speed and the detected value of the rotation speed is higher than the target value, the first valve 31 is opened according to the deviation between the two, and the second valve 33 is opened.
Is closed. By operating the pump 24 in this state, the pressure fluid is supplied to the supply ports 19 and 21 through the pipe line 27, and is jetted from the nozzles 15 and 16 toward the gaps 5 and 6 between the shaft 2 and the bearing metals 3 and 4. To be done. At the same time, the pressure fluid is also supplied to the supply / discharge port 22 through the pipe line 28,
It is jetted from the supply / discharge port 18 toward the gap 5. As a result, a large amount of pressure fluid is supplied into the gap 5.

A part of the pressure fluid supplied to the supply port 19 is guided to both ends of the front bearing metal 3 via the conductive passages 20 as described above, and is guided from the nozzle 17 to the flange 11 and the collar 13. Is sprayed toward and the movement of the shaft 2 in the axial direction is restricted. Then, the pressure fluid injected into the gaps 5, 6 and the like is discharged from the chamber 14 to the exhaust port 23.
And collected in the tank 26 via the conduit 30.

Therefore, when the shaft 2 rotates at a high speed, the pressure distribution in the gap 5 becomes high at the positions corresponding to the nozzles 15 and the supply / discharge ports 18, as shown in FIG. 5, and the distribution in the high pressure region becomes dense. Become. Since a large amount of pressure fluid is supplied into the gap 5 as described above, the heat generated by the shaft 2 and the bearing metal 3 is reliably absorbed by the pressure fluid, and the heat is dissipated by the cooler 25. Therefore, even at high speed, the shaft 2
Heat generation of the bearing metal 3 and the like is effectively suppressed, the high speed rotation limit can be increased, and thermal deformation of the shaft 2 and the like can be prevented.

Further, when the shaft 2 rotates at a high speed, the rigidity due to the static pressure shown in FIG. 4 decreases, but as is clear from FIG. 5, a high dynamic pressure is generated around the shaft 2 and the rigidity further increases. To do. Therefore, during this high-speed rotation, it is possible to secure high rigidity as the bearing characteristics of the pressure fluid journal bearing and obtain stable rotation.

The present invention is not limited to the configuration of the above-described embodiment, and may be modified and embodied as follows without departing from the spirit of the present invention. (1) The nozzles 15 and 16 and the supply / discharge port 18 are provided on the outer peripheral surface side of the shaft 2 on the surface where the shaft 2 and the bearing metal 3 face each other.

(2) The number of nozzles 15 and supply / discharge ports 18 should be changed appropriately. For example, the nozzle 15 and the supply / discharge port 18
4 or 4 nozzles, 4 nozzles, 1 outlet
Equally divide 8 into 2.

(3) Arrange the nozzle 15 and the supply / discharge port 18 on different circumferences. (4) The setter 36 sets the temperature or pressure target value of the pressure fluid, and the detector 37 detects the temperature or pressure of the pressure fluid at the supply side of the circulation path,
The controller 35 compares the detected value with the target value and controls the valves 31 and 33 to open and close based on the result.

(5) The two valves 31 and 33 should be composed of one 3-port switching valve. (6) The valves 31 and 33 are connected to the actuators 32 and 34.
It must be configured so that it can be opened and closed by manual operation regardless of the above.

[0029]

Since the present invention is configured as described above, even if the rotational speed of the shaft changes, the bearing characteristics can be changed according to the rotating condition of the shaft, and it is always appropriate. It has an excellent effect that the bearing characteristics can be secured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a pressure fluid journal bearing embodying the present invention and a block diagram of a control system.

FIG. 2 is a cross-sectional view showing the arrangement of nozzles and supply / discharge ports in the journal bearing.

FIG. 3 is a developed cross-sectional view showing a supply / discharge path configuration of the pressure fluid for the nozzle and the supply / discharge port.

FIG. 4 is an explanatory view showing a pressure distribution state during low speed operation of the shaft.

FIG. 5 is an explanatory diagram showing a pressure distribution state during high-speed operation of the shaft.

[Explanation of symbols]

2 ... Shaft, 3 ... Bearing metal, 4 ... Bearing metal, 5 ... Gap,
6 ... Gap, 15 ... Supply nozzle, 16 ... Nozzle, 18 ... Supply / discharge port, 24 ... Pump as a supply source of pressure fluid, 26 ...
Tank, 31 ... First valve, 33 ... Second valve.

Claims (1)

[Claims] 1. A plurality of nozzles are arranged at predetermined intervals on the same circumference so as to direct a gap between facing surfaces of a shaft and a bearing metal, and a plurality of supply / discharge ports are provided between the nozzles. And the nozzle is connected to the discharge side of the pressure fluid supply source, and the supply / discharge port is connected to the suction side and the discharge side of the pressure fluid supply source via valves. A pressure fluid journal bearing characterized by being switchably connected.