JP6690621B2 - Hydrostatic bearing - Google Patents

Description

  The present invention relates to a hydrostatic bearing, and more particularly to a hydrostatic bearing that rotatably supports a shaft by hydrostatic pressure in a non-contact state.

  Conventionally, there has been provided a hydrostatic bearing which is disposed between a housing (not shown) and a shaft and which rotatably supports the shaft in a non-contact state by hydrostatic pressure. For example, in Patent Document 1, a shaft and a bearing body having a bearing surface facing the shaft via a bearing gap are provided, and gas pressurized in the bearing gap is applied to the bearing surface. A static pressure gas bearing that rotatably supports the shaft is described by introducing a plurality of slot openings that are respectively provided in the circumferential direction around the rotation axis of the shaft and extend along the circumferential direction. There is.

  A conventional slot throttle type hydrostatic bearing has a structure in which a slot throttle having a gap of several tens of μm is arranged on the central circumference of the bearing surface. There are cases where the slot throttles for supplying fluid are annular, and there are cases where a plurality of slot throttles are arranged at equal intervals as in Patent Document 1. The fluid supplied from the slot throttle flows into the bearing gap and then is released to the atmosphere. The fluid pressure supplied from the slot throttle gives rigidity to the bearing, and the characteristics change depending on the shape of the slot throttle and its arrangement. The pressure of the fluid flowing out from the throttle supports the load such as the shaft mass and the centrifugal force during rotation. When supporting a large load with this bearing, it was necessary to increase the bearing diameter and the fluid supply pressure.

  Further, in the conventional hydrostatic bearing, the slot throttle is arranged at the center of the bearing surface in the axial direction, so that when the load during rotation is biased with respect to the axial direction of the bearing (hereinafter, referred to as unbalanced load), the bearing surface There was a high probability of contact at the edges and a high risk of damage. Further, since the conventional fluid bearing mainly uses a metal material, if the shaft and the bearing come into contact with each other at the time of high speed rotation, there is a problem that damage such as seizure is caused. In order to reduce this, a coating is applied to the bearing surface to reduce damage, but the unit price of the bearing is high because it is expensive.

  Patent Document 2 discloses a hydrostatic bearing in which radial slot throttles extending in the circumferential direction are provided at two locations apart from each other in the axial direction, but it is configured by combining a large number of complicated parts. Therefore, the cost is high.

  Therefore, the applicant of the present application, as described in Patent Document 3, is composed of a first member and a second member made of a synthetic resin which are combined to form a cylindrical bearing body, and the first member and the second member. Each have an axially and radially extending fluid surface, and a groove-shaped slot throttle extending in the axial direction of the shaft is formed between the fluid surfaces facing each other when the first member and the second member are combined. A hydrostatic bearing was proposed. As a result, a hydrostatic bearing that exhibits high rigidity against an eccentric load on the bearing can be configured with a minimum of two members, and the slot throttle extends in the direction of the tightening force by the bolt that joins the two members. Therefore, there is a secondary effect that the deformation of the member has almost no effect on the groove width of the slot diaphragm.

JP, 2009-092196, A JP, 2003-074555, A JP, 2005-175484, A

  However, in the hydrostatic bearing made of synthetic resin described in Patent Document 3, the dowel and the engaging hole are provided for positioning at the time of joining the two members. However, due to the influence of the accuracy of producing the dowel and the engaging hole. It was difficult to make the assembly accuracy of the two members in units of μm, that is, it was difficult to define the groove width of the slot in units of μm. In particular, in the case of having a plurality of slots, it was difficult to make all the groove widths uniform. However, conventionally, a method of securing a gap with a member such as a spacer has been used, but there has not been a method of making the groove-shaped slots radially arranged uniform.

  Therefore, in view of the above-mentioned situation, the present invention aims to solve the problems by providing a hydrostatic bearing which has a small number of parts, high assembly accuracy, and in particular can accurately define a supply hole for producing a fluid pressure. There is a point to do.

  In order to solve the above problems, the present invention constitutes a hydrostatic bearing shown below.

(1)
A bearing surface disposed between the shaft and the housing, facing each other with a bearing gap between the shaft and the shaft; and a plurality of air supply holes opened in the bearing surface and provided around the rotation axis of the shaft, In a hydrostatic bearing that rotatably supports the shaft in a non-contact state by introducing a pressurized fluid into the bearing gap through the air supply hole,
At least two members, that is, a first member and a second member, are fixed to each other in a fitted state, and each member has a convex portion and a concave portion which are fitted in a nest shape to form a substantially cylindrical shape in the circumferential direction. A plurality of them are provided, and the inner peripheral surface of the convex portion of at least one of the first member and the second member constitutes a part of the bearing surface and is formed between the convex portions of the first member and the second member. The airtight fitting portion is provided with a play portion capable of relative displacement in the circumferential direction for adjusting the size of the air supply hole. A hydrostatic bearing characterized in that the air supply hole is formed therebetween.

(2)
The play part has a first barrier part formed of a cylindrical surface provided on the inner peripheral side of the convex part of the first member and a second barrier part formed of a cylindrical surface provided on the outer peripheral side of the convex part of the second member. The hydrostatic bearing according to (1), wherein and are formed in airtight contact with each other while allowing the circumferential displacement.

(3)
The hydrostatic bearing according to (1) or (2), wherein the play portion is formed in a stepped shape.

(4)
The hydrostatic bearing according to any one of (1) to (3), wherein the air supply hole is a groove-shaped slot extending in the axial direction and the radial direction.

(5)
The hydrostatic bearing according to (4), wherein the groove width of the groove-shaped slot is 5 to 40 μm.

(6)
The hydrostatic bearing according to any one of (1) to (5), wherein at least the constituent material of the air supply hole portion is a synthetic resin.

(7)
The hydrodynamic bearing according to any one of (1) to (6), wherein an adjustment member can be inserted into the play portion.

  The hydrostatic bearing of the present invention as described above has the following effects.

  According to the configuration of (1), the number of parts is small, the assembling accuracy is high, the size of the air supply hole can be adjusted to a desired width particularly in the interval of the play portion, and the telescopic fitting portion can prevent air from entering. Since it does not flow, the air pressure released from the air supply hole becomes uniform.

  According to the configuration of (2), since the air does not flow between the first barrier portion and the second barrier portion, it is possible to prevent fluid from entering the bearing gap through a portion other than the air supply hole and preventing the fluid from leaking outside through the bearing gap. The pressure distribution of the fluid can be made uniform.

  According to the configuration of (3), the play portion can be manufactured easily and can be constructed at low cost.

  With the configuration (4), the groove width of the grooved slot can be accurately defined, and the bearing rigidity can be increased.

  According to the configuration of (5), the flow rate of fluid such as air supplied to the air supply hole can be reduced, and high fluid pressure can be generated.

  According to the configuration of (6), it is possible to form the air supply hole with high accuracy even with a synthetic resin that is difficult to produce with high processing accuracy.

  According to the configuration of (7), the width of the play portion can be accurately defined, and thus the groove width of the groove-shaped slot can be accurately defined.

It is the whole hydrostatic bearing perspective view of the present invention. It is an exploded perspective view of a hydrostatic bearing similarly. It is the perspective view which looked at the 2nd member from the convex part side. It is the top view which looked at the 1st member from the convex part side. It is the top view which looked at the 2nd member from the convex part side. It is a radial center sectional view in the state where the 1st member and the 2nd member were fitted. It is a center sectional view of the axial direction in the state where the 1st member and the 2nd member were fitted. FIG. 6 is a perspective view of the first member and the second member taken along the axial center of the fitted state. It is sectional drawing which shows the use condition of the hydrostatic bearing of this invention. It is a perspective view showing the state in the middle of assembling the hydrostatic bearing of the present invention. It is a partial expanded sectional view of the state where the groove width of the grooved slot (air supply hole) was maximized by utilizing the play part. FIG. 6 is a partially enlarged cross-sectional view showing a state in which a groove width is defined by sandwiching an adjusting member in a groove-shaped slot (air supply hole).

  Next, the present invention will be described in more detail based on the embodiments shown in the accompanying drawings. FIG. 1 is an overall perspective view of a hydrostatic bearing according to the present invention, FIGS. 2 to 8 show the details thereof, and FIG. 9 shows a usage state. In FIG. Indicates the housing.

  As shown in FIGS. 1 and 9, a hydrostatic bearing 1 according to the present invention is arranged between a shaft 2 and a housing 3, and a bearing surface 5 facing the shaft 2 with a bearing gap 4 therebetween. And a plurality of air supply holes 6 respectively provided on the bearing surface 5 and provided around the rotation axis of the shaft 2, and by introducing a pressurized fluid into the bearing gap 4 through the air supply holes 6, the shaft 2 is rotatably supported in a non-contact state. In the present embodiment, the hydrostatic bearing 1 has a cylindrical shape as a whole, and the air supply hole 6 is composed of a groove-shaped slot extending in the axial direction and the radial direction of the shaft 2. The positions of the plurality of air supply holes 6 are preferably rotationally symmetrical positions so that an isotropic static pressure acts on the shaft 2, and are preferably equidistant in the circumferential direction.

  As shown in FIG. 1, the hydrostatic bearing 1 is entirely cylindrical and preferably has a ratio (L / D) of the bearing length L and the diameter D of the bearing surface 5 of 1 to 4 and an axial direction. It has a structure in which eight air supply holes 6 extending in the circumferential direction are arranged in the circumferential direction (similar to the needle bearing in the mechanical type). The air supply hole 6 extends in the radial direction from the bearing surface 5 to the inside of the cylindrical portion and communicates with a supply passage 7 provided on the outer peripheral portion of the cylindrical portion. Here, the air supply hole 6 has a groove shape, a circular shape, or the like. The groove width is 5 to 40 μm, more preferably 20 to 30 μm, and the axial groove length is 1/2 or more of the bearing length L in order to exhibit high rigidity against uneven load on the bearing. Is the best.

  The fluid supplied through the supply passage 7 flows through the eight air supply holes 6 into the bearing surface 5, passes through the bearing gap 4, and is then opened to the atmosphere. Here, the working fluid may be any one such as pressurized air, pressurized nitrogen gas, carbon dioxide gas, etc., as long as the fluid can generate a high pressure. Pressurized air is excellent because it is particularly cost-effective and can use a compressor attached to the factory. The supply passage 7 is composed of an annular groove 8 formed on the outer peripheral surface of the cylindrical portion in the circumferential direction, and a vertical groove 9 intersecting the annular groove 8 and communicating with the outer peripheral opening of each of the air supply holes 6. It is preferable. Further, as shown in FIGS. 1 and 9, O-ring grooves 10 and 11 are formed on the outer circumference of both axial ends of the hydrostatic bearing 1 so as to include the supply passage 7 inside. By pressing the O-ring 12 fitted in the O-ring grooves 10 and 11 against the inner peripheral surface of the housing 3, the supply passage 7 is formed in an airtight state. The pressurized fluid is supplied to the supply passage 7 through a supply hole (not shown) penetrating the housing 3.

  Since it is difficult to manufacture the hydrostatic bearing 1 having the above-mentioned structure by machining, at least two members are combined and configured. The hydrostatic bearing 1 may be made of any material such as metal or synthetic resin, but the effect of the present invention is more remarkable when the hydrostatic bearing 1 is made of a resin that is difficult to achieve machining accuracy.

  The resin constituting the hydrostatic bearing 1 is polyphenylene sulfide (PPS), polyetherimide (PEI), polyetheretherketone (PEEK), polyimide (PI), polyacetal (POM), polyamide (PA) and phenol resin. Any of polypropylene, polypropylene and polyethylene may be used, but PPS is the best because of its excellent processing accuracy in cutting.

  The member constituting the hydrostatic bearing 1 can be formed by cutting or injection molding, but cutting is the best in terms of processing accuracy. Here, the cutting process includes a case of cutting from a block-shaped material and a case of cutting an intermediate molded product injection-molded into a rough shape in advance.

  In the hydrostatic bearing 1 according to the present invention, at least two members are axially fitted and positioned, and then both members are fixed. The fixing method may be screwing, bolting, bonding, welding, or any other method. Even after fixing, bolting is especially good because it can be readjusted and disassembled easily.

  Next, the hydrostatic bearing 1 according to the present invention will be specifically described with reference to the drawings. The hydrostatic bearing 1 of the present embodiment is composed of a first member 21 and a second member 22 which are combined to form a cylindrical bearing body. The first member 21 and the second member 22 have a concavo-convex shape that can be combined in a nested manner in the axial direction.

  First, as shown in FIGS. 2 and 4, the first member 21 has eight protrusions 24 of the same shape formed on the inner surface of the annular portion 23 in the circumferential direction at equal intervals so as to be adjacent to each other. A concave portion 25 having the same shape is formed between the convex portions 24. The end surface of each convex portion 24 of the first member 21 constitutes the same plane, and each convex portion 24 is formed with a screw hole 26 that is open to the end surface and extends in the axial direction. The screw hole 26 does not penetrate to the outer side surface of the annular portion 23. Further, the O-ring groove 10 is formed on the outer circumference of the annular portion 23. The inner peripheral surface of each convex portion 24 of the first member 21 is a cylindrical surface and constitutes a part of the bearing surface 5.

  Next, as shown in FIGS. 2, 3 and 5, the second member 22 has eight projections 28 of the same shape formed on the inner surface of the annular portion 27 so as to project in the axial direction at equal intervals in the circumferential direction. However, a concave portion 29 having the same shape is formed between the adjacent convex portions 28. The end surfaces of the convex portions 28 of the second member 22 form the same plane, the through holes 30 extending in the axial direction are formed in the concave portions 29, respectively, and the through holes 30 are formed on the outer surface of the annular portion 27. A spot facing hole 31 is formed around the. Further, the O-ring groove 11 is formed on the outer circumference of the annular portion 27. The inner peripheral surface of each convex portion 28 of the second member 22 is a cylindrical surface and constitutes a part of the bearing surface 5. Note that only the inner peripheral surface of either one of the convex portions 28 of the first member 21 and the second member 22 may form a part of the bearing surface 5.

  As shown in FIGS. 1 and 2, the first member 21 and the second member 22 are nested with each other to form a substantially cylindrical shape. That is, the convex portion 24 of the first member 21 is fitted in the concave portion 29 of the second member 22, and the convex portion 28 of the second member 22 is fitted in the concave portion 25 of the first member 21 in a nested manner, respectively, to complement each other. Have a positive relationship. Here, at least 3 pairs of the convex portion 24 and the concave portion 25 of the first member 21 and the pair of the convex portion 28 and the concave portion 29 of the second member 22 are necessary, but in the present embodiment, 8 pairs are provided. ing.

  Further, as shown in FIGS. 2, 3 and 6, the convex portion 24 of the first member 21 and the convex portion 28 of the second member 22 are structured to be fitted in an airtight state, and this airtight fitting As shown in FIGS. 10 and 12, the portion 32 is provided with a play portion 34 which is relatively displaceable in the circumferential direction so that the adjusting member 33 can be inserted into the air supply hole 6, and the play portion of the convex portion 24 is provided. The air supply hole 6 is formed between the opposite side of the convex portion 28 and the other convex portion 28 adjacent thereto, and between the opposite side of the convex portion 28 to the play portion 34 and the other convex portion 24 adjacent thereto. The air supply hole 6 is formed in the. That is, the side surface of the convex portion 24 opposite to the play portion 34 is defined as the fluid surface 35 extending in the axial and radial directions, and the side surface of the convex portion 28 opposite to the play portion 34 is defined in the axial and radial direction. As the fluid surface 36 extending in the vertical direction, the air supply hole 6 composed of a groove-shaped slot is formed between the fluid surface 35 of the convex portion 24 and the fluid surface 36 of the convex portion 28.

  The play portion 34 includes a first barrier portion 37 formed of a cylindrical surface provided on the inner peripheral side of the convex portion 24 of the first member 21, and a cylindrical surface provided on the outer peripheral side of the convex portion 28 of the second member 22. The second barrier portion 38 made of is formed in airtight contact with the circumferential displacement. The first barrier portion 37 and the second barrier portion 38 form the airtight fitting portion 32. The first member 21 and the second member 22 can be relatively displaced in the circumferential direction due to the existence of the play portion 34 in a state of being fitted in a nest shape, whereby the groove width of the air supply hole 6 is formed. Can be adjusted.

  The play part 34 and the barrier parts 37, 38 may be any structure such as a concavo-convex structure, a step structure, and a laminated structure, but the step structure of the present embodiment is most suitable because it is easy to manufacture and inexpensive. Further, the play width of the play portion 34 may be designed to be longer than the designed groove width of the groove-shaped slot because the groove-shaped slot (air supply hole 6) can be adjusted to a desired groove width.

  In order to accurately set the groove width of the air supply hole 6 to the designed value, first, as shown in FIG. 11, the play portion 34 is inserted in a state where the first member 21 and the second member 22 are fitted in a nested manner. 12 is used to relatively rotate to widen the groove width of the air supply hole 6, and then the plate-like or sheet-like adjusting member 33 having a specified thickness is inserted into the air supply hole 6, and then, FIG. As shown in FIG. 1, the first member 21 and the second member 22 are relatively rotated to sandwich the adjusting member 33 in the air supply hole 6, and in that state, the first member 21 and the second member 22 are And as shown in FIG. 10, it is fixed by pulling in the axial direction with bolts 40.

  In the present embodiment, all the air supply holes 6 are radially formed from the inner peripheral side to the outer peripheral side, so that the adjusting member 33 can be inserted into all the air supply holes 6. Thereby, the groove widths of all the air supply holes 6 can be accurately matched. The adjusting member 33 may be inserted into at least one air supply hole 6.

  The bolt 39 is inserted from the through hole 30 of the second member 22 and screwed into the screw hole 26 of the first member 21, so that the head of the bolt 39 is buried in the counterbore hole 31. There is. Before inserting the adjusting member 33 into the air supply hole 6, the bolt 39 may be loosely screwed, the diameter of the through hole 30 is sufficiently larger than the shaft portion of the bolt 39, and the play portion 34 is formed. Since it is larger than the play width, the adjustment member 33 does not hinder the setting of the groove width of the air supply hole 6. That is, since the screw hole 26 is formed only in the first member 21 and the screw hole 26 is not formed in the second member 21, the air supply hole 6 by the adjusting member 33 is increased by the play width of the through hole of the second member. The groove width can be set. Further, by tightening the bolt 39, the screw hole 26 into which the head of the bolt 39 and the bolt 39 are screwed is attracted in the axial direction, and the first member 21 is sandwiched, whereby the first member 21 and the second member 22. Is firmly fixed.

  Since the hydrostatic bearing according to the present invention is used without grease, it is suitable for use in manufacturing equipment for foods and pharmaceuticals. Furthermore, the hydrostatic bearing according to the present invention also has a sealing effect that prevents foreign matter from entering the bearing due to air pressure or the like.

DESCRIPTION OF SYMBOLS 1 Hydrostatic bearing 2 Shaft 3 Housing 4 Bearing gap 5 Bearing surface 6 Air supply hole 7 Supply path 8 Annular groove 9 Vertical groove 10 O-ring groove 11 O-ring groove 12 O-ring 21 First member 22 Second member 23 Annular portion 24 Convex portion 25 Concave portion 26 Screw hole 27 Annular portion 28 Convex portion 29 Concave portion 30 Recessed hole 31 Counterbore hole 32 Airtight fitting portion 33 Adjusting member 34 Play portion 35 Fluid surface 36 Fluid surface 37 First barrier portion 38 Second barrier portion 39 bolt

Claims (7)

A bearing surface disposed between the shaft and the housing, facing each other with a bearing gap between the shaft and the shaft; and a plurality of air supply holes opened in the bearing surface and provided around the rotation axis of the shaft, In a hydrostatic bearing that rotatably supports the shaft in a non-contact state by introducing a pressurized fluid into the bearing gap through the air supply hole,
At least two members, that is, a first member and a second member, are fixed to each other in a fitted state, and each member has a convex portion and a concave portion which are fitted in a nest shape to form a substantially cylindrical shape in the circumferential direction. A plurality of them are provided, and the inner peripheral surface of the convex portion of at least one of the first member and the second member constitutes a part of the bearing surface and is formed between the convex portions of the first member and the second member. The airtight fitting portion is provided with a play portion capable of relative displacement in the circumferential direction for adjusting the size of the air supply hole, and the opposite side of the play portion of the convex portion and another convex portion adjacent thereto A hydrostatic bearing characterized in that the air supply hole is formed therebetween.   The play part has a first barrier part formed of a cylindrical surface provided on the inner peripheral side of the convex part of the first member and a second barrier part formed of a cylindrical surface provided on the outer peripheral side of the convex part of the second member. The hydrostatic bearing according to claim 1, wherein and are formed in airtight contact with each other while permitting displacement in the circumferential direction.   The hydrostatic bearing according to claim 1, wherein the play portion is formed in a stepped shape.   The hydrostatic bearing according to any one of claims 1 to 3, wherein the air supply hole is a groove-shaped slot extending in the axial direction and the radial direction.   The hydrostatic bearing according to claim 4, wherein the groove width of the groove-shaped slot is 5 to 40 μm.   The hydrostatic bearing according to claim 1, wherein at least the constituent material of the air supply hole portion is a synthetic resin.   The hydrostatic bearing according to any one of claims 1 to 6, wherein an adjustment member can be inserted into the play portion.

Images