JPH0819938B2 - Hydrodynamic bearing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydrodynamic bearing device that supports a rotating shaft, particularly a hydrostatic bearing device that has a dynamic pressure generating region to improve dynamic rigidity, a so-called hybrid fluid. Bearing device

(Prior Art) As a hydrodynamic bearing device of this type, if it collapses
Some are disclosed in Japanese Patent No.434. In this technique, a concave portion forming a static pressure generating region and a land portion forming a dynamic pressure generating region are provided on the bearing surface, and the working fluid drawn from the static pressure generating region between the land portion and the rotating shaft by the rotation of the shaft. To generate dynamic pressure. A large load such as a vibration load acts on the spindle of a machine tool during machining,
According to the fluid dynamic bearing device as described above, since the bearing rigidity increases when the main shaft rotates, it is possible to cope with a large load.

(Problems to be Solved by the Invention) However, the working fluid drawn between the land portion and the rotary shaft due to the generation of dynamic pressure generates heat due to fluid friction loss due to viscosity, and the generated heat amount increases the rotation speed. Increase accordingly. On the other hand, since the shaft radiates heat poorly to the bearing, the bearing gap decreases due to the thermal expansion due to the above-mentioned heat generation, and the set value of the bearing gap cannot be sufficiently reduced in order to prevent failures due to this, so dynamic pressure The increase in bearing rigidity is also limited, and there is a problem that the displacement of the rotary shaft cannot be sufficiently reduced when a load is applied. The present invention intends to solve such a problem by improving cooling when the rotational speed of the rotary shaft becomes large.

(Means for Solving the Problems) Therefore, in the hydrodynamic bearing device according to the present invention, as illustrated in the accompanying drawings, the bearing surface of the bearing member 20 supporting the rotating shaft 15 is circumferentially spaced. A plurality of recesses 23 and 223, which are provided in the static pressure generating area A by supplying the working fluid pressurized by the supply pump 40 through the throttle 30, and are provided adjacent to the static pressure generating area in the circumferential direction. A plurality of land portions 24, 124, 224 that form a dynamic pressure generation region B by the working fluid flowing from the static pressure generation region by the rotation of the rotary shaft 15.
And a flow groove surrounding the recesses 23,223 and lands 24,124,224
In the hydrodynamic bearing device having 25, the flow groove 25
With a pair of discharge grooves 25a spaced apart in the direction of the rotation axis, and a plurality of supply and discharge on the circumference for communicating the pair of discharge grooves 25a with each other to divide the static pressure and dynamic pressure generation regions A and B in the circumferential direction. The discharge groove 25a is formed by a groove 25b, and the discharge groove 25a always communicates with the reservoir 43. The supply / discharge groove 25b is formed by the reservoir 43 and the supply pump 4.
A switching valve 42 that selectively communicates with 0 is provided, and this switching valve 42 is provided with the supply / discharge groove 25b when the rotation speed of the rotating shaft 15 is low.
Is connected to the reservoir 43, and when the rotation speed of the rotating shaft 15 is high, the supply / discharge groove 25b is connected to the supply pump 40.

(Operation) While the rotary shaft 15 is stopped or its rotational speed is low, the switching valve 42 communicates the supply / discharge groove 25b with the reservoir 43, and the working fluid from the supply pump 40 is supplied only to the recesses 23, 223 of the bearing member 20. As a result, the rotary shaft 15 is supported mainly by the static pressure generated in the static pressure generating region A, and the working fluid passing through the recesses 23 and 223 is discharged to the reservoir 43 through the discharge groove 25a and the supply / discharge groove 25b. As the rotation speed of the rotating shaft 15 increases, the dynamic pressure generated in the dynamic pressure generation region B increases, and together with this, the dynamic pressure generation region B increases.
Also, the amount of heat generated in the heat source increases. When the dynamic pressure has a value sufficient to support the rotary shaft 15, the switching valve 42 operates to supply and discharge the groove 25b.
To the supply pump 40, the working fluid from the supply pump 40 is supplied in parallel not only to the recesses 23 and 223 but also to the supply / discharge groove 25b, and the working fluid passing through these is supplied from the discharge groove 25a to the reservoir 43. It will be discharged. In this state, the rotary shaft 15 is cooled by the working fluid passing through the supply / discharge groove 25b,
The heat generated in the dynamic pressure generation region B prevents the temperature of the rotary shaft 15 from rising.

(Effects of the Invention) As described above, according to the present invention, when the rotation speed of the rotary shaft increases and the amount of heat generated in the dynamic pressure generation region increases, the rotation is performed by the working fluid supplied to the supply / discharge groove. Since the temperature of the shaft is prevented from rising, it is possible to prevent the bearing gap from decreasing due to thermal expansion. As a result, the set value of the bearing gap can be sufficiently reduced without fear of seizure due to the insufficient bearing gap, so that the bearing rigidity can be sufficiently increased and the displacement of the rotating shaft when a load is applied is reduced. be able to.

In addition, by providing a switching valve that selectively connects the supply / discharge groove to the reservoir and the supply pump, during low speed rotation, the pressure oil is supplied from the supply pump to the static pressure generation region and discharged to the reservoir from the supply / discharge groove. It performs a static pressure support action, and at the time of high speed rotation, part of the pressure oil supplied from the supply pump to the static pressure generation area is supplied to the supply and discharge groove to cool the bearing.
It is not necessary to form a dedicated cooling passage for cooling the bearing or to prepare a cooling fluid separately from the bearing fluid, so that the bearing can be cooled with a simple configuration.

(Embodiment) First, a first embodiment shown in FIGS. 1 to 3 will be described.

As shown in FIGS. 1 to 3, the bearing surface 21 of the inner periphery of the bearing member 20 such as the bearing metal that is fitted and fixed to the bearing body 10 to support the rotating shaft 15 is along the circumferential direction of both ends. And a pair of the discharge grooves 25a, 25a provided at
A flow groove 25, which is composed of four supply / discharge grooves 25b to 25b that connect 5a and 25a in the axial direction, is formed, and divides the bearing surface 21 into four portions that are circumferentially spaced. Each of these parts has a rotating shaft 15
Is formed by the static pressure support portion 22 and the land portion 24 provided along the rotation direction of, and the gap between the land portion 24 and the rotary shaft 15 is smaller than the gap between the static pressure support portion 22 and the rotary shaft 15. is there. Mainly as shown in FIG. 3, each static pressure support portion 22 is formed with a concave portion 23 formed of a U-shaped supply groove having an open land portion 24 side directly adjacent to the static pressure support portion 22, and is surrounded by the supply groove 23 and the land portion 24. The closed portion forms a static pressure generation area A, and the upper portion of the land portion 24 forms a dynamic pressure generation area B. A throttle in each supply groove 23
The pressurized working fluid from the supply pump 40 is introduced through the supply passage 29 provided with 30, the annular groove 27 formed on the outer periphery of the bearing member 20, and the pressure reducing valve 41 whose setting pressure is electromagnetically switched between two stages. Thus, the static pressure is generated in the static pressure generation area A. Further, a part of the working fluid in the static pressure generation area A is drawn onto the land portion 24 by the rotation of the rotary shaft 15 to generate dynamic pressure in the dynamic pressure generation area B.

As shown in FIG. 2 and FIG. 3, weir portions 26, 26 are provided at the connecting portions with the discharge grooves 25a, 25a at both ends of each supply / discharge groove 25b, and are formed on the outer periphery of the bearing member 20 at the intermediate portion thereof. A supply / discharge passage 31 is provided which communicates with the annular groove 28. Also, bearing members
Discharge passages 32, 33 are provided on both sides of 20 so that the lower portions of both discharge grooves 25a, 25a communicate with the discharge passages 11, 12 provided in the bearing body 10.
The working fluid discharged from the static pressure generation area A and the dynamic pressure generation area B to the discharge grooves 25a, 25a passes through the discharge passages 32, 33, 11, 12 and the lower portion in the bearing body 10 or the reservoir 43 communicated with this. Is discharged to. As shown in FIG. 1, the electromagnetic switching valve 42 is a three-port two-position switching valve having one common port 42a and two switching ports 42b and 42c. The common port 42a includes the annular groove 28 and the supply / discharge passage 31. Through the supply and discharge groove 25b, one of the switching port 42b is connected between the pressure reducing valve 41 and the annular groove 27 described above,
The other switching port 42c communicates with the reservoir 43.

 Next, the operation of the above embodiment will be described.

As shown in FIG. 1, the common boat 42a of the electromagnetic switching valve 42 is communicated with the switching boat 42c side while the rotary shaft 15 is stopped or the rotation speed is low, and the pressure reducing valve 41 has a high outlet side pressure. (Eg 10 kgf / cm ² ) is set. In this state, the high-pressure working fluid from the supply pump 40 is
As shown by the solid line arrows in FIGS. 1 and 2, only the supply groove 23 is supplied from the annular groove 27 through the supply passage 23 provided with the throttle 30 to thereby generate a static pressure in the static pressure generation region A. Tightly support the rotating shaft 15. The working fluid discharged from the static pressure generation region A flows into the circulation groove 25 which is composed of the discharge groove 25a and the supply / discharge groove 25b and surrounds the supply groove 23 and the land portion 24, and the working fluid in the supply / discharge groove 25b is mainly The working fluid in the discharge groove 25a is discharged to the reservoir 43 via the supply / discharge passage 31, the annular groove 28 and the electromagnetic switching valve 42, and is discharged to the reservoir 43 via the discharge passages 32, 33, 11, 12. Further, the dynamic pressure generated in the dynamic pressure generating portion B in this case is small.

If the rotation speed of the rotary shaft 15 reaches a high-speed steady state and the dynamic pressure generated in the dynamic pressure generation region B is sufficiently increased, this is detected by a rotation sensor (not shown) or the like, and the electromagnetic switching valve 42 operates to be common. Port 42a comes to communicate with the switching port 42b side,
The pressure on the outlet side of the pressure reducing valve 41 is set to a low value ( ^{2 to 3} kgf / cm ² ). In this state, the working fluid from the supply pump 40 has a low pressure, and most of the fluid flows from the electromagnetic switching valve 42 to the annular groove 28 and the supply / discharge passage 31 as shown by the broken line arrows in FIGS. 1 and 2. Through which it flows into the supply / discharge groove 25b and fills the inside thereof, and is discharged into the discharge groove 25a, 25a through the gap between the dam portions 26, 26 at both ends and the rotating shaft 15, and from the supply pump 40. Part of the working fluid flows into the supply groove 23 from the annular groove 27 and is then discharged into the discharge grooves 25a, 25a. The static pressure generated in the static pressure generation area A is small, but the working fluid in the static pressure generation area A is drawn between the lands 24 by the high speed rotation of the rotating shaft 15 and is sufficiently large in the dynamic pressure generation area B. It produces a pressure, which supports the rotary shaft 15. Further, in this state, the amount of heat generated by the fluid friction loss of the working fluid in the dynamic pressure generation region B increases and the temperature of the rotary shaft 15 rises, but as described above, a large amount is supplied to the supply / discharge groove 25b. The rotating shaft 15 is cooled by the working fluid to prevent the temperature of the rotating shaft 15 and the bearing member 20 from rising.

The land portion for generating the dynamic pressure has a shape such as the land portion 124 of the second embodiment shown in FIG. 4 instead of the stepwise rising shape from the static pressure support portion 22 as in the first embodiment. The shape may be such that it stands up from the static pressure support portion 122 located inside 23 with a gentle inclination. Also, instead of the supply groove having a U-shape as in the first embodiment,
A frame shape like the supply groove 223 of the third embodiment shown in FIG.
The static pressure support portion 222 and the land portion 2 having a step inside each other
24 may be formed. The static pressure support portions 22, 222 located in the supply grooves 23, 223 have a low height, or the supply grooves 23, 2
A large rectangular recess may be formed so as to coincide with the bottom surface of 23.

Further, as shown by the two-dot chain lines 35 and 36 in FIG.
The weir portion 26 on one side may be removed, and the discharge passage 36 may be provided on the upper side except the discharge passages 33 and 12 on the lower side of the discharge groove 25a on that side. In this way, the working fluid supplied when the rotary shaft 15 rotates at high speed is stored in the discharge groove 25a on that side, so that the supply / discharge groove 25b can be sufficiently filled with the working fluid without providing the dam 26. Can be made.

[Brief description of drawings]

1 to 3 show a first embodiment of a hydrodynamic bearing device according to the present invention. FIG. 1 is a cross-sectional view of a main portion and a working fluid supply / discharge system passage, and FIG. 2 is a main portion. FIG. 3 is a developed view of a part of the bearing surface, FIG. 4 is a cross-sectional view of a main part of the second embodiment, and FIG. 5 is a developed view of a part of the bearing surface of the third embodiment. It is a figure. Explanation of code 15 …… Rotary shaft, 20 …… Bearing member, 21 …… Bearing surface, 23,223
...... Concave (supply groove), 24,124,224 …… Land, 25 ……
Distribution groove, 25a ... discharge groove, 25b ... supply / discharge groove, 30 ... throttle,
40 ... Supply pump, 42 ... Switching valve (solenoid switching valve), 43 ...
... reservoir, A ... static pressure generation area, B ... dynamic pressure generation area.

Claims (1)

[Claims] 1. A static pressure generating region is formed on a bearing surface of a bearing member that supports a rotary shaft, the working fluid being provided at intervals in a circumferential direction and pressurized by a supply pump is supplied through a throttle. And a plurality of land portions that are provided adjacent to the static pressure generation region in the circumferential direction and that form a dynamic pressure generation region by the working fluid flowing from the static pressure generation region by the rotation of the rotary shaft. A hydrodynamic bearing device having a flow groove surrounding the recess and the land, the pair of discharge grooves having the flow groove separated from each other in the rotation axis direction, and the pair of discharge grooves communicating with each other to form the static pressure. And the dynamic pressure generation region is formed by a plurality of supply / drain grooves on the circumference that divide the region in the circumferential direction, the discharge groove always communicates with the reservoir, and the supply / discharge groove selectively communicates with the reservoir and the supply pump. A switching valve for When the rotation speed of the shaft is low, the supply / drain groove is communicated with the reservoir, and when the rotation speed of the rotation shaft is high, the supply / drain groove is communicated with the supply pump. Hydrodynamic bearing device.