JP2013113358A - Variable throttle type hydrostatic bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable throttle type hydrostatic bearing in which a throttle ratio can be surely set to a predetermined throttle ratio corresponding to pressure of a pocket 2a by preventing a movable object 32 from tilting.SOLUTION: A variable throttle 3 which throttles a flow rate of a fluid and causes the fluid to flow into a hydrostatic bearing pocket 2a is partitioned into a fluid supply chamber 3a and a fluid discharge chamber 3b by the movable object 32. An outflow port 31b communicating with the pocket 2a is provided in the center of an end face of the fluid discharge chamber 3b, a fluid storage groove 31c, a first discharge groove 31d and a second discharge groove 31e are disposed along the outer periphery of the outflow port 31b. Recesses 32a1, 32a2, 32a3 are provided in a part opposed to a part between the first discharge groove 31d and the second discharge groove 31e on the end face 32e of the movable object 32. A flow passage 32d communicating between the fluid supply chamber 3a and the fluid storage groove 31c and a flow passage 32c communicating the fluid supply chamber 3a and the recesses 32a1, 32a2, 32a3 and having a fixed throttle 32b are provided.

Description

  The present invention relates to a variable throttle hydrostatic bearing provided with a variable throttle using a movable object.

  The inflow path to the pocket of the fluid supply chamber and the hydrostatic bearing is divided by a movable object with a fixed restrictor, and the fluid supply chamber has an opening arranged to face the movable object, corresponding to the pressure of the pocket inflow path. There is a variable-throttle type hydrostatic bearing using a variable throttle that sets a predetermined throttle ratio corresponding to the pressure in the pocket inflow path by changing the gap between the movable object and the opening. (Patent Document 1)

JP 2002-286037 A

  In the prior art described in Patent Document 2, a pocket is provided on the side surface of the movable object to change the weight applied to the movable object or prevent contact with the guide portion when the movable object moves. The tilt of the movable object cannot be prevented. The flow rate flowing out from the opening varies according to the inclination of the movable object with respect to the opening even if the pressure in the pocket inflow path is the same. For this reason, even if the pressure in the pocket inflow path is the same, the aperture ratio varies depending on the inclination of the movable object. That is, there is a possibility that the predetermined throttle ratio corresponding to the pressure in the pocket inflow path cannot be set.

  The present invention has been made in view of the above circumstances, and provides a variable throttle-type hydrostatic bearing that can prevent a movable object from tilting and can be reliably set to a predetermined throttle ratio corresponding to the pressure of a pocket inflow path. .

In order to solve the above-described problem, the feature of the invention according to claim 1 is that a bearing body disposed at a distance from a member;
A pocket disposed in the bearing body facing the member;
A fluid supply port for supplying fluid to the pocket;
A variable restrictor for restricting the flow rate of the fluid supplied from the fluid supply port and allowing the fluid to flow into the pocket;
The variable aperture is
Variable aperture body,
A movable object that is movably housed in an internal space of the variable throttle body and that partitions the interior of the variable throttle body into a first chamber that communicates with the fluid supply port and a second chamber that communicates with the pocket. Is
A first end surface that is an end surface facing the first chamber; a second end surface that is an end surface facing the second chamber and perpendicular to the moving direction of the movable object; and the first chamber and the second chamber. In a circumferential direction of a circle centered on a point where the centroid of the first end surface of the second end surface is projected onto the second end surface in the moving direction of the movable object, etc. And a fixed throttle that communicates the depression and the first chamber with at least three depressions,
On the wall surface perpendicular to the moving direction of the movable object in the second chamber,
A second flow path communicating with the pocket in a portion facing the point, and a fluid storage groove formed of an annular groove on the outer periphery by a predetermined radius from the second flow path; and an outer periphery of the fluid storage groove; Provided with a discharge groove in a portion not facing the depression, further provided with a discharge flow path communicating with the discharge groove,
The opening in the second end surface of the first flow path is disposed at a portion facing the fluid storage groove,
The projected area of the first end surface onto the plane perpendicular to the moving direction of the movable object is the projected area of the second flow path, the fluid storage groove, and the depression onto the plane perpendicular to the moving direction of the movable object. It is less than the sum.

  According to the first aspect of the present invention, the resultant force of the force acting on the first end surface by the fluid pressure in the first chamber and the force acting on the second end surface by the fluid pressure in the fluid storage groove and the second flow path, The action point on the second end face is at a position facing the second flow path. Since the depression is arranged at a part equally divided in the circumferential direction of the circle centering on the position facing the second flow path, the action point on the second end face of the force due to the fluid pressure in the depression is the action point of the resultant force. It is arranged so as to surround it. The pressure in the depression decreases as the gap between the second end surface and the wall surface of the second chamber increases, and increases as the gap decreases, thereby preventing the movable object from tilting with respect to the moving direction of the movable object. The power to do works. For this reason, the second end face of the movable object and the wall surface of the second chamber are always kept in parallel, and the gap increases or decreases depending on the fluid pressure acting on the second flow path. The flow rate of the fluid flowing out is a predetermined flow rate corresponding to the fluid pressure acting on the second flow path. In other words, the variable throttle-type static pressure is such that the weight acting on the movable object does not change or the movable object does not tilt even if the movable object moves, and the degree of change in the throttle ratio corresponding to the pressure in the pocket is constant. A bearing can be provided.

It is the schematic which shows the whole structure of the slide table apparatus of this embodiment. It is AA sectional drawing of FIG. FIG. 6 is a detailed view of the portion B in FIG. 1 (cross-sectional view taken along line EE in FIG. 5). It is CC sectional drawing of FIG. It is DD sectional drawing of FIG.

Hereinafter, the embodiment of the present invention will be described using a case where the present invention is used in a table feeder.
As shown in FIG. 1, the table feeder 1 has a table 2 (bearing body) slidably mounted on a slide portion of a base 10 (member), and a pair of back plates 5 (bearings) at lower portions of both ends of the table 2. This is a structure that can be moved only in the X-axis direction by attaching the main body.
As shown in FIG. 2, the surface of the table 2 facing the base 10 is provided with two pockets 2a facing downward and a pair of pockets 2c facing laterally. The variable throttle 3 communicates with the pockets 2a and 2c, and the oil supply conduit 4 communicates with the variable throttle 3 respectively. A discharge groove 2b is provided on the outer periphery of the pocket 2a.
The back plate 5 is also provided with a pocket 5a facing upward, and the variable throttle 3 communicates with the pocket 5a, and the oil supply conduit 4 communicates with each variable throttle 3. A discharge groove 5b is provided on the outer periphery of the pocket 5a.

  FIG. 3 shows details of the variable diaphragm 3. The variable diaphragm 3 includes a variable diaphragm base 31 having a hollow cylinder (constituting a variable diaphragm body) and a cap 33 having a hollow cylinder having a smaller diameter than the variable diaphragm base 31 (variable diaphragm). The main body is configured with bolts 34 so that the hollow cylinders face each other, and the movable object 32 is housed in the internal space so as to be movable in the axial direction of the cylinder. As shown in FIG. 4, the hollow cylindrical wall surface 31a of the variable throttle base 31 is provided with an outlet 31b (second channel) communicating with the pocket inlet 2c of the table 2 at the center thereof, and the outer periphery of the outlet 31b. In addition, an annular fluid storage groove 31c, a first discharge groove 31d, and a second discharge groove 31e are provided in order from the inside so as to be concentric. Further, the first discharge groove 31d and the second discharge groove 31e are connected to the discharge groove 2b through the discharge flow path 2d of the table 2 and the discharge flow path 31f. A discharge passage 31g having an opening is provided.

The movable object 32 has a shape in which two-stage cylinders having different diameters are concentrically stacked, an end surface 32e of the large diameter cylindrical portion, an end surface 32f which is an end surface of a step between the large diameter cylindrical portion and the small diameter cylindrical portion, and an end surface of the small diameter cylindrical portion. 32 g, an outer peripheral surface 32 h of the large diameter cylindrical portion, and an outer peripheral surface 32 i of the small diameter cylindrical portion, and the end surface 32 e is disposed so as to face the wall surface 31 a of the variable aperture base 31. As shown in FIG. 5, the recesses 32 a ₁ , 32 a ₂ , and 32 a ₃ are divided into three equal parts in the circumferential direction at the portion of the end surface 32 e that faces the wall surface 31 a between the first discharge groove 31 d and the second discharge groove 31 e. And a channel 32c having a fixed restrictor 32b that communicates with the recesses 32a ₁ , 32a ₂ , 32a ₃ and the end face 32f. Furthermore, a flow path 32d (first flow path) communicating with a portion of the end surface 32e facing the fluid storage groove 31c and a portion of the outer peripheral surface 32i near the end surface 32f is provided.
The cap 33 includes a combination surface 33a with the variable throttle base 31 and a hollow cylindrical inner peripheral surface 33b. The cap 33 communicates with the discharge passage 33c that connects the inner peripheral surface 33b and the flow passage 31g, and the conduit 4 and the combination surface 33a. A flow path 33d is provided.

The area of the end face 32f is set to be smaller than the total area of the outlet 31b, the fluid storage groove 31c, and the recesses 32a ₁ , 32a ₂ , 32a ₃ .
The depth of the hollow cylinder of the variable aperture base 31 and the hollow cylinder of the cap 33 and the thickness dimension of the cylindrical portion of the movable object 32 in the moving direction of the movable object 32 are determined by a predetermined distance in the axial direction of the movable object 32. It has a value that can be moved.
With the above configuration, as shown in FIG. 3, the internal space formed by the hollow cylindrical portion of the variable throttle base 31 and the hollow cylindrical portion of the cap 33 is a fluid supply chamber divided by the end surface 32 f of the movable object 32 and the outer peripheral surface 32 i. 3a (first chamber), a fluid discharge chamber 3b (second chamber) divided by an end surface 32e, and a fluid discharge chamber 3c divided by an end surface 32g.

The operation of the variable throttle bearing will be described with reference to FIG.
When the fluid is supplied to the pipe 4, the fluid supply chamber 3 a is filled with the fluid, and the fluid flows into the annular fluid storage groove 31 c via the flow channel 32 d of the movable object 32 and is fixed to the flow channel 32 c. The reduced pressure fluid flows into the depressions 32a ₁ , 32a ₂ , 32a ₃ via the restriction 32b. The fluid in the fluid storage groove 31c is squeezed by the gap between the wall surface 31a of the variable throttle base 31 and the end surface 32e of the movable object 32. A part of the fluid flows into the pocket 2a via the outlet 31b, and the remaining fluid is It flows into the first discharge groove 31d and is discharged to the discharge groove 2b via the discharge flow path 31f and the discharge flow path 2d of the table 2.
The fluid in the recess _{32a 1,} 32a 2, 32a _3, via the gap between the recess _{32a 1,} 32a 2, the end surface 32e of the outer periphery of the 32a ₃ and variable throttle wall 31a of the base 31, a first discharge groove 31d It flows into the second discharge groove 31e and is discharged to the discharge groove 2b via the discharge flow path 31f and the discharge flow path 2d of the table 2. The fluid leaking from the gap between the outer peripheral surface 32 h of the large-diameter cylindrical portion of the movable object 32 and the hollow cylindrical portion of the variable throttle base 31 is discharged into the second discharge groove 31 e, and the outer peripheral surface 32 i of the small-diameter cylindrical portion of the movable object 32. The fluid leaking from the opposing gap between the inner peripheral surface 33b of the cap 33 is discharged to the discharge groove 2b via the fluid discharge chamber 3c, the discharge channel 33c, the discharge channel 31g, and the discharge channel 2d.

Here, when the pressure of fluid supplied to the fluid supply chamber 3a and P _0, the pressure in the fluid storage groove 31c of the annular becomes P _0. The fixed throttle 32b, the depressions 32a ₁ , 32a ₂ , 32a ₃ and the wall surface 31a constitute a hydrostatic bearing, and the pressure P ₁ inside the depressions 32a ₁ , 32a ₂ , 32a ₃ is a gap t ₂ between the end face 32e and the wall surface 31a. It fluctuates within a range not exceeding P ₀ according to the interval of. The pressure of the outflow port 31b and the pocket 2a becomes _{P 2} reduces the pressure for throttled by the clearance of the end surface 32e and the wall surface 31a. The pressure _{P 2} of the outlet port 31b and the pocket 2a varies within a range that does not exceed the _{P 0} in accordance with the width of the gap _{t 3} pockets 2a and the base 10. The pressure in the fluid discharge chamber 3b and the fluid discharge chamber 3c is atmospheric pressure.
Accordingly, the pockets 2a and the base 10 is held at a distance t ₃ when generating the pressure P ₂ in the pocket 2a to balance the load acting between the two. The above also occurs in the pocket 2e installed in the horizontal direction of the table 2 and the pocket 5a portion of the back plate 5. As a result, the base 10 and the table 2 is maintained in a state having an interval t ₃ in the pocket 2a portion.

When downward load is applied to the table 2 in this state, the table 2 is closely spaced t ₃ pockets 2a to move downward, the outflow of fluid from the gap t ₃ is reduced, the pressure in the pocket 2a Since it rises, the pressure at the outlet 31b communicating with the pocket 2a also rises. Then, an upward force is increased to receive the surface facing the outlet 31b of the end surface 32e, the movable object 32 is moved parallel to the fluid supply chamber 3a direction, increases clearance t ₁ between the end face 32e and the wall surface 31a . As a result, the flow rate flowing into the pocket 2a through the outlet 31b and the clearance t ₁ is increased. Accordingly, it is necessary to increase the flow rate flowing out from the interval t ₃ of the pocket 2a and the base 10, acts as the function of preventing the reduction of the interval t ₃ of the pocket 2a and the base 10. That is, (to increase the rigidity) reduce the variation of the interval t ₃ to the load action works.

Here, the balance of the forces acting on the movable object 32 is as follows.
The force _{F 1} acting on the end surface 32f of the fluid supply chamber 3a side of the movable object 32 by pressure _{P 0,} and the force _{F 2} acting on a surface facing the fluid storage groove 31c of the movable object 32 by pressure _{P 0,} the pressure P _2, the force F ₃ acting on the surface facing the outlet 31 b, the forces F ₄₁ , F ₄₂ , F ₄₃ acting on the depressions 32 a ₁ , 32 a ₂ , 32 a ₃ due to the pressure P ₁ , and the weight of the movable object 32 ( The weight of the movable object 32 is small compared to the pressure and can be ignored. In the following description, the weight of the movable object 32 is ignored). That is, F ₁ = F ₂ + F ₃ + F ₄₁ + F ₄₂ + F ₄₃ .

When the resultant force of F ₁ , F ₂ , and F ₃ is a concentrated load, the action point on the end surface 32e is a point P (the projection point of the end surface 32f onto the end surface 32e of the centroid of the end surface 32f, and the fluid The force F ₀ acting in the direction of the wall surface 31a is F ₀ = F ₁ −F ₂ − and coincides with the centroid of the end surface 32e facing the storage groove 31c and the centroid of the end surface 32e facing the outlet 31b. F is _3. The depressions 32a ₁ , 32a ₂ , 32a ₃ are arranged at positions that surround the application point of the force F ₀ , and the pressure P ₁ in the depressions 32a ₁ , 32a ₂ , 32a ₃ is large if the gap between the end face 32e and the wall surface 31a is large. Decreases, rises if narrow. Therefore, the widths of the gaps between the recesses 32a ₁ , 32a ₂ , 32a ₃ and the wall surface 31a are t ₂₁ , t ₂₁ , and t ₂₁ , and the end surface 32e and the wall surface 31a are inclined so that t ₂₁ <t ₂₁ <t ₂₁ . In this case, the force acting on each of the depressions is F ₄₁ > F ₄₂ > F ₄₃ and the force for preventing the inclination acts, and when the end surface 32e and the wall surface 31a are parallel, F ₄₁ = F ₄₂ = F _{43 and is} stable. .
As described above, even if a force for tilting the movable object 32 acts on the axis of the moving direction of the movable object 32, the force is canceled and the end surface 32e of the movable object 32 is always held in parallel with the wall surface 31a. I have.

According to the present invention, the force that keeps the end surface 32e and the wall surface 31a of the movable object 32 in parallel is always received, so that the weight acting on the movable object 32 does not change, and the movable object 32 does not tilt even if it moves. . Therefore, the aperture ratio becomes a predetermined value corresponding to the size of the gap t ₁ of the end face 32e and the wall surface 31a. That is, it is possible to provide a variable throttle type hydrostatic bearing that is set to a predetermined throttle ratio corresponding to the pressure in the pocket 2a.

In the above description, the table feed of the linear motion has been described. However, the member in this case, which may be used for the rotating shaft, becomes the rotating shaft.
Further, a throttle may be provided in the discharge flow path from the flow path 32d and the first discharge groove 31d.
Although an example in which the wall surface 31a facing the depressions 32a ₁ , 32a ₂ , 32a ₃ is formed in an annular shape without restricting the rotation of the movable object 32 with respect to the moving axis is shown, the rotation of the movable object 32 with respect to the moving axis is restricted. The wall surfaces facing the depressions 32a ₁ , 32a ₂ , 32a ₃ may be discontinuous in the circumferential direction.
Although the example which made the movable object 32 the cylindrical shape was shown, another shape may be sufficient.

2: Table 2a: Pocket 3: Variable throttle 3a: Fluid supply chamber 3b, 3c: Fluid discharge chamber 4: Pipe line 31: Variable throttle base 31a: Wall surface 31b: Outlet 31c: Fluid storage groove 31d: First discharge groove 31e : second discharge groove 31f, 31 g: discharge passage 32: movable object _{32a 1, 32a 2, 32a 3} : recess 32 b: fixed stop 32d: passage 33: cap t _1: clearance

Claims (1)

A bearing body disposed at a distance from the member;
A pocket disposed in the bearing body facing the member;
A fluid supply port for supplying fluid to the pocket;
A variable restrictor for restricting the flow rate of the fluid supplied from the fluid supply port and allowing the fluid to flow into the pocket;
The variable aperture is
Variable aperture body,
A movable object that is movably housed in an internal space of the variable throttle body and that partitions the interior of the variable throttle body into a first chamber that communicates with the fluid supply port and a second chamber that communicates with the pocket. Is
A first end surface that is an end surface facing the first chamber; a second end surface that is an end surface facing the second chamber and perpendicular to the moving direction of the movable object; and the first chamber and the second chamber. In a circumferential direction of a circle centered on a point where the centroid of the first end surface of the second end surface is projected onto the second end surface in the moving direction of the movable object, etc. And a fixed throttle that communicates the depression and the first chamber with at least three depressions,
On the wall surface perpendicular to the moving direction of the movable object in the second chamber,
A second flow path communicating with the pocket in a portion facing the point, and a fluid storage groove formed of an annular groove on the outer periphery by a predetermined radius from the second flow path; and an outer periphery of the fluid storage groove; Provided with a discharge groove in a portion not facing the depression, further provided with a discharge flow path communicating with the discharge groove,
The opening in the second end surface of the first flow path is disposed at a portion facing the fluid storage groove,
The projected area of the first end surface onto the plane perpendicular to the moving direction of the movable object is the projected area of the second flow path, the fluid storage groove, and the depression onto the plane perpendicular to the moving direction of the movable object. Variable throttle hydrostatic bearing smaller than the total.

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