U.S. patent application number 15/478445 was filed with the patent office on 2017-10-05 for throttle unit and a static pressure bearing device equipped with the throttle unit, and a method of manufacturing a grooved block.
The applicant listed for this patent is FANUC CORPORATION. Invention is credited to Masahiro MUROTA, Toyoaki SUZUKI.
Application Number | 20170284464 15/478445 |
Document ID | / |
Family ID | 59885320 |
Filed Date | 2017-10-05 |
United States Patent
Application |
20170284464 |
Kind Code |
A1 |
SUZUKI; Toyoaki ; et
al. |
October 5, 2017 |
THROTTLE UNIT AND A STATIC PRESSURE BEARING DEVICE EQUIPPED WITH
THE THROTTLE UNIT, AND A METHOD OF MANUFACTURING A GROOVED
BLOCK
Abstract
A throttle unit is equipped with a grooved block including at
least one minute groove formed on a plane surface, and an opposite
block having a plane surface which is opposite to the minute
groove. The grooved block and the opposite block are detachably
joined so as to be opposite to each other. A throttle fluid path is
formed by the minute groove and the plane surface of the opposite
block. At least one surface of each of the minute groove is
constituted by a curved surface or an inclined surface that is
inclined with respect to the plane surface of the grooved
block.
Inventors: |
SUZUKI; Toyoaki; (Yamanashi,
JP) ; MUROTA; Masahiro; (Yamanashi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FANUC CORPORATION |
Yamanashi |
|
JP |
|
|
Family ID: |
59885320 |
Appl. No.: |
15/478445 |
Filed: |
April 4, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16C 2322/39 20130101;
F16C 29/025 20130101; F16C 2220/60 20130101; F16C 32/0659 20130101;
F16C 32/0622 20130101; F16C 32/0625 20130101; F16C 32/0655
20130101; F16C 2240/42 20130101 |
International
Class: |
F16C 32/06 20060101
F16C032/06; F16C 29/02 20060101 F16C029/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 5, 2016 |
JP |
2016-076039 |
Claims
1. A throttle unit in which a working fluid is introduced from at
least one supply hole, the introduced working fluid flows in a
minute throttle fluid path, and the working fluid which has passed
through the throttle fluid path is discharged from at least one
discharge hole, the unit comprising: a grooved block including at
least one minute groove on a plane surface; an opposite block
including a plane surface that is opposite to the minute groove,
wherein the grooved block and the opposite block are opposite to
each other and detachably joined to each other, the throttle fluid
path is formed by the minute groove and the plane surface of the
opposite block, at least one surface of the minute groove is
constituted by a curved surface or an inclined surface that is
inclined with respect to the plane surface of the grooved
block.
2. The throttle unit according to claim 1, wherein the minute
groove extends linearly from the supply hole to the discharge
hole.
3. The throttle unit according to claim 1, wherein a plurality of
the minute grooves are arranged on a same line through the supply
hole.
4. The throttle unit according to claim 1, wherein a plurality of
the throttle fluid paths are connected to the single supply hole,
the discharge holes, which are independent from each other,
communicate with the plurality of throttle fluid paths, and the
working fluid that is supplied to the single supply hole branches
into the plurality of throttle fluid paths, and is discharged from
the plurality of discharge holes.
5. The throttle unit according to claim 1, wherein either the
grooved block or the opposite block functions as a slide component,
a guide component, or another throttle unit component.
6. The throttle unit according to claim 1, wherein a width and a
depth of the minute groove are continuously changed, at least along
part of a fluid path that extends from the supply hole to the
discharge hole.
7. The throttle unit according to claim 1, wherein a minimum depth
of a fluid path in the minute groove from the supply hole to the
discharge hole is 1000 .mu.m or less.
8. A static pressure bearing device in a structure with a linear
motion axis or a structure with a rotation axis, in which a static
pressure bearing is constituted between a movable portion and a
fixed portion of the structure with the linear motion axis or the
structure with the rotation axis, the device comprising: a fluid
supply line configured to supply a working fluid to a static
pressure pocket formed in the movable portion or the fixed portion;
and a throttle unit provided in the fluid supply line, wherein the
throttle unit is a throttle unit in which the working fluid is
introduced from at least one supply hole, the introduced working
fluid flows in a minute throttle fluid path, and the working fluid
which has passed through the throttle fluid path is discharged from
at least one discharge hole, the unit comprising: a grooved block
including at least one minute groove on a plane surface; an
opposite block including a plane surface that is opposite to the
minute groove, wherein the grooved block and the opposite block are
opposite to each other and detachably joined to each other, the
throttle fluid path is formed by the minute groove and the plane
surface of the opposite block, at least one surface of the minute
groove is constituted by a curved surface or an inclined surface
that is inclined with respect to the plane surface of the grooved
block.
9. A method of manufacturing a grooved block that includes at least
one minute groove on a plane surface, wherein the grooved block is
a component of a throttle unit, in which a working fluid is
introduced from at least one supply hole, the introduced working
fluid flows in a minute throttle fluid path, and the working fluid
which has passed through the throttle fluid path is discharged from
at least one discharge hole, wherein the throttle unit comprises
the grooved block and an opposite block including a plane surface
that is opposite to the minute groove, the grooved block and the
opposite block are opposite to each other and detachably joined to
each other, and the throttle fluid path is formed by the minute
groove and the plane surface of the opposite block, the method
comprising: a cutting step of cutting a plane surface of a
workpiece block to form the minute groove, at least one surface of
the minute groove being constituted by a curved surface or a
inclined surface that is inclined with respect to the plane surface
of the workpiece block; a depth calculating step of calculating a
groove depth of the minute groove that has been formed in the
machining step, observing the minute groove with a microscope from
a direction perpendicular to the plane surface of the workpiece
block; and a correcting step of making a correction of a machining
device that performs the cutting, based on the calculated groove
depth.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2016-076039 filed on
Apr. 5, 2016, the contents of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] Field of the Invention:
[0003] The present invention relates to a throttle unit and a
static pressure bearing device equipped with the throttle unit, and
a method of manufacturing a grooved block.
[0004] Description of the Related Art:
[0005] In machine tools, as a guide device for a table having a
linear motion axis or a rotational axis, static pressure bearings
are used. In a static pressure bearing, in a case of a structure
with a linear motion axis, for example, a static pressure pocket is
formed on a bearing surface of a slide or a guide, and a working
fluid such as oil or air is supplied to the static pressure pocket.
The slide floats above the guide as a fixed portion by the static
pressure of the working fluid, whereby the slide can be moved along
the guide in a non-contact manner.
[0006] Generally, to obtain rigidity of the static pressure
bearing, a throttle unit (pipe resistance device) needs to be
disposed in the middle of piping for supplying the working fluid
from a pump to the static pressure pocket, for restricting the flow
rate of the working fluid supplied from the pump. The pipe
resistance, i.e., restriction strength (degree of restriction)
increases as the cross sectional area of minute fluid path
(restriction path) becomes smaller or as the length thereof becomes
longer. The optimal restriction strength is obtained when the
pressure of the working fluid in the static pressure pocket is 0.5
times as large as the pressure from the pump, and at the same time
the largest rigidity of the bearing can be achieved.
[0007] General throttle units include a unit using a thin tube like
an injection needle (hereinafter referred to as a "needle throttle
unit"), and a unit using a minute fluid path for restriction
between a male thread and a female thread (hereinafter referred to
as a "screw throttle unit"). The screw throttle unit is disclosed,
for example, in Japanese Laid-Open Patent Publication No.
11-210905.
[0008] Problems of the needle throttle unit include the following
points: the man hours for assembling the unit are large since the
structure for incorporating the needle is complicated; the
individual differences in the restriction strength are large since
the variety of inner diameter errors of the respective needles is
likely to affect the restriction strength; the unit has low
reliability since the needle tends to fall off, and thus the
restriction strength may change over time; due to a limit to the
needle thinness, a thin needle is required to be long and have a
special shape, for securing a certain degree or more of the
restriction strength, so that the cost is high for preparing such a
needle; and it is difficult to clean the unit when the needle is
clogged with foreign material or the like.
[0009] Problems of the screw throttle unit include the following
points: The number of parts or components is large and the
structure of the unit is complicated, so that man hours for
assembling are large; Precise adjustment is indispensable and the
individual differences in the restriction strength become large
depending on the adjustment state; The restriction strength may
change in time due to looseness of the screw; The cost is high
because of the large number of components; And it is difficult to
clean the unit when the unit is clogged with foreign material or
the like.
[0010] For overcoming part of the above problems, there is a
throttle unit (hereinafter referred to as a "groove throttle unit")
in which a block with a plane surface having a groove thereon and
another block with a plane surface are overlapped with each other
to form a minute fluid path for realizing restriction. In a groove
throttle unit disclosed in Japanese Laid-Open Patent Publication
No. 2006-266358, a minute fluid path has a simple cross sectional
shape of a substantial square, and the minute fluid path is
constituted by a simple component. Thus, there is an advantageous
effect that the restriction strength is not changed over time after
assembly, the change of the restriction strength being caused by
the falling-off or displacement of the components in the case of a
needle throttle unit or a screw throttle unit.
[0011] Further, the throttle unit described in Japanese Laid-Open
Patent Publication No. 2006-266358 is capable of changing the
restriction strength stepwise by lengthening the fluid path (path
for restriction) which is achieved by stacking the blocks having
grooves machined on plane surfaces to form the minute fluid paths.
Thus, the individual differences in the restriction strength can be
suppressed within a certain range.
SUMMARY OF THE INVENTION
[0012] As described above, the restriction strength is increased,
as the sectional area of a minute fluid path (a path for
restriction) becomes smaller or the minute fluid path becomes
longer. Generally, the resistance of a fluid path is proportional
to a fluid path length, and inversely proportional to the fourth
power of a fluid path diameter (the second power of a sectional
area) of the fluid path. That is, a groove width and a groove depth
which define a sectional area, particularly the formation of the
groove depth which corresponds to the aforementioned fluid path
diameter, require further accuracy.
[0013] As described, the groove depth is an important factor that
influences the restriction strength. The groove disclosed in
Japanese Laid-Open Patent Publication No. 2006-266358 has a cross
section of a substantial square. Thus, by a general method as a
means for inspecting the groove depth, in which the groove is
observed from above with a microscope, even though the groove width
may be measured, the groove depth, which is defined in the depth
direction in the view field of the microscope, cannot be
measured.
[0014] When a shape of the groove is formed by machining, the
groove depth depends on a machine accuracy of the machine tool. In
a case of using a machine tool, the groove depth generally includes
an error of about 50 .mu.m with respect to a target value.
Therefore, even when a substantially square cross section having a
100 .mu.m groove depth is to be obtained, the groove depth after
machining has an error of .+-.25%, from 75 .mu.m to 125 .mu.m.
Thus, a single groove itself has a significantly large individual
difference of .+-.56% in the restriction strength.
[0015] In order to decrease the aforementioned individual
difference, it is necessary to reduce the influence of the error of
about 50 .mu.m included in the groove depth. Thus, it is necessary
to lengthen the groove width and the groove depth to enlarge a
cross sectional area, and further it is necessary to lengthen the
groove length. For example, if the target value of the groove depth
for a substantially square cross section is 1000 .mu.m (1 mm),
which is ten times as large as the aforementioned value, the error
included in the machined groove depth is reduced to one tenth
thereof, i.e., .+-.2.5%. Then, the single groove's individual
difference in the restriction strength can be suppressed to .+-.5%.
However, in order to secure restriction strength similar to the
conventional one, the fluid path length needs to be 100 times as
long as that of the conventional one.
[0016] According to Japanese Laid-Open Patent Publication No.
2006-266358, as a means for lengthening the groove, a plurality of
lines (grooves) are formed on one plane surface of the block, or an
additional block with a groove is provided. However, since the
groove shape to be machined is complicated, the cost becomes high
due to increased man hours, and the restriction strength may be
changed over time due to the clogging with foreign material.
Further, it is expected that cleaning such a groove is difficult.
Also, the number of components becomes large, undesirably resulting
in high cost and a large size of the unit.
[0017] Factors which affect the machine accuracy of a machine tool
include thermal displacement by the influence of atmospheric
temperature around the machine tool. If a groove depth is measured
after machining, it is possible to machine the groove more
accurately by adding some correction (thermal displacement
correction) to the machine tool. Thus, it is extremely important to
measure the groove depth after machining.
[0018] It is preferable for a throttle unit used in a static
pressure bearing to have a simple structure, minimize the
individual differences in the restriction strength, have constant
restriction strength without change over time, realize a low cost
and a small size, and achieve easy cleaning. However, no such a
throttle unit that satisfies all the aforementioned demands has
been proposed so far. Further, like the minute groove disclosed in
Japanese Laid-Open Patent Publication No. 2006-266358, if the cross
section of the groove has a substantially square shape, the shape
observed from above is the same even when the groove depth of the
cross sectional shape varies due to the machine accuracy of the
machine tool. Therefore, the groove depth, which is defined in the
depth direction in the view field of the microscope, cannot be
measured, and also it is difficult to machine the groove
accurately.
[0019] The present invention has been devised taking into
consideration the aforementioned problems, and has the object of
providing a throttle unit and a static pressure bearing device
equipped with the throttle unit, and a method of manufacturing a
grooved block, which make it possible to ensure accurate groove
machining and obtain an accurate groove shape, by enabling the
groove depth as well as the groove width to be measured according
to a general method in which the groove is observed from above with
a microscope.
[0020] In order to achieve the above object, the present invention
is characterized by a throttle unit in which a working fluid is
introduced from at least one supply hole, the introduced working
fluid flows in a minute throttle fluid path, and the working fluid
which has passed through the throttle fluid path is discharged from
at least one discharge hole, the unit comprising a grooved block
including at least one minute groove on a plane surface, an
opposite block including a plane surface that is opposite to the
minute groove, wherein the grooved block and the opposite block are
opposite to each other and detachably joined to each other, the
throttle fluid path is formed by the minute groove and the plane
surface of the opposite block, at least one surface of the minute
groove is constituted by a curved surface or an inclined surface
that is inclined with respect to the plane surface of the grooved
block.
[0021] With the throttle unit according to the present invention,
in which above configuration is adopted, the cross section of the
minute groove has a shape such as a triangle, a trapezoid, a
polygon (except for a substantial rectangle), an arc, or a
combination thereof. Thus, the groove depth as well as the groove
width of the minute groove can be measured by a general method in
which the groove is observed with a microscope from the direction
perpendicular to the plane. Since the groove depth of the minute
groove can be measured, more accurate machining can be achieved by
correcting the machining device (machine tool) based on the
machining result, and am accurate groove shape can be obtained.
[0022] In the throttle unit, the minute groove may extend linearly
from the supply hole to the discharge hole.
[0023] With this structure, the minute groove can be manufactured
(by cutting) easily, in contrast to a conventional polygonal-chain
minute groove constituted by a plurality of linear portions. Thus,
it is possible to prevent the corners (bent portions) of the minute
groove from being clogged with the foreign material.
[0024] In the throttle unit, a plurality of the minute grooves may
be arranged on a same line through the supply hole.
[0025] With this structure, at the time of machining the minute
grooves, a groove is machined only once across the supply hole.
Then, the groove divided by the supply hole can be used as
independent minute grooves. Since the plurality of minute grooves
are formed in a single machining path, it is possible to reduce man
hours for the machining.
[0026] In the throttle unit, a plurality of the throttle fluid
paths may be connected to the single supply hole. Also, the
discharge holes, which are independent from each other, may
communicate with the plurality of throttle fluid paths, and the
working fluid that is supplied to the single supply hole may
branches into the plurality of throttle fluid paths, and be
discharged from the plurality of discharge holes.
[0027] With this structure, the number of throttle units provided
in the static pressure bearing device can be reduced. Thus, it is
possible to lower the cost, simplify the structure, and omit some
piping. Accordingly, since additional parts for changing
restriction strength are unnecessary, it is possible to minimize
the number of parts, the portions to be sealed, and piping.
Further, the structure is simple, and the man hours for machining
and assembling are small. Also, individual differences in the
restriction strength are small, the cost is lowered, and it is easy
to clean the unit.
[0028] In the throttle unit, either the grooved block or the
opposite block may function as a slide component, a guide
component, or another throttle unit component.
[0029] In accordance with this feature, it is expected that the
structure can be simplified, the number of parts can be reduced,
the installation space can be saved, and some piping can be
omitted, and the like, since the throttle unit can be constituted
substantially by one component.
[0030] In the throttle unit, a width and a depth of the minute
groove may be continuously changed, at least along part of a fluid
path extending from the supply hole to the discharge hole.
[0031] With this structure, even if foreign material somewhat clogs
the minute groove, it is possible to easily gather the foreign
material at a small cross sectional portion of the minute groove.
Thus, the portion clogged with foreign material is easily confirmed
at the time of cleaning operation for the disassembled device, and
the foreign material can be removed efficiently.
[0032] In the throttle unit, a minimum depth of a fluid path in the
minute groove from the supply hole to the discharge hole may be
1000 .mu.m or less.
[0033] Further, the present invention is characterized by a static
pressure bearing device in a structure with a linear motion axis or
a structure with a rotation axis, in which a static pressure
bearing is constituted between a movable portion and a fixed
portion of the structure with the linear motion axis or the
structure with the rotation axis, the device comprising, a fluid
supply line configured to supply a working fluid to a static
pressure pocket formed in the movable portion or the fixed portion;
and a throttle unit provided in the fluid supply line, wherein the
throttle unit comprises any one of the above-described throttle
units.
[0034] Still further, the present invention is characterized by a
method of manufacturing a grooved block that includes at least one
minute groove on a plane surface, wherein the grooved block is a
component of a throttle unit, a working fluid is introduced from at
least one supply hole, the introduced working fluid flows in a
minute throttle fluid path, and the working fluid which has passed
through the throttle fluid path is discharged from at least one
discharge hole, wherein the throttle unit comprises the grooved
block, and an opposite block including a plane surface that is
opposite to the minute groove, the grooved block and the opposite
block are opposite to each other and detachably joined to each
other, and the throttle fluid path is formed by the minute groove
and the plane surface of the opposite block, the method comprising
a cutting step of cutting a plane surface of a workpiece block to
form the minute groove, at least one surface of the minute groove
being constituted by a curved surface or a inclined surface that is
inclined with respect to the plane surface of the workpiece block,
a depth calculating step of calculating a groove depth of the
minute groove that has been formed in the machining step, observing
the minute groove (25, 25A through 25D) with a microscope from a
direction perpendicular to the surface of the workpiece block, and
a correcting step of making a correction of a machining device that
performs the cutting, based on the calculated groove depth.
[0035] With the throttle unit according to the present invention,
it is possible to ensure accurate groove machining and obtain an
accurate groove shape, by enabling the groove depth as well as the
groove width to be measured in a general method in which the minute
groove is observed from above with a microscope. Therefore, by
installing the throttle unit, it is possible to reduce the weight
of parts, realize compact structure, reduce the cost by decreasing
the number of parts and manufacturing steps, achieve high
reliability, and improve maintainability due to easy disassembly
and cleaning.
[0036] The above and other objects, features, and advantages of the
present invention will become more apparent from the following
description when taken in conjunction with the accompanying
drawings, in which a preferred embodiment of the present invention
is shown by way of illustrative example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1 is a schematic cross sectional view of a static
pressure bearing device according to an embodiment of the present
invention;
[0038] FIG. 2 is an exploded perspective view of a throttle unit of
the static pressure bearing device shown in FIG. 1;
[0039] FIG. 3A is a plan view of a grooved block on which a minute
groove is formed according to a first example;
[0040] FIG. 3B is a cross sectional view taken along a line
IIIB-IIIB in FIG. 3A;
[0041] FIG. 4A is a plan view of a grooved block on which a minute
groove is formed according to the first example, while the groove
depth is deeper than that in FIG. 3A;
[0042] FIG. 4B is a cross sectional view taken along a line IVB-IVB
in FIG. 4A;
[0043] FIG. 5A is a plan view of a grooved block on which a minute
groove is formed according to a second example;
[0044] FIG. 5B is a cross sectional view taken along a line VB-VB
in FIG. 5A;
[0045] FIG. 6A is a plan view of a grooved block on which a minute
groove is formed according to the second example, while the groove
depth is deeper than that in FIG. 5A; FIG. 6B is a cross sectional
view taken along a line VIB-VIB in FIG. 6A;
[0046] FIG. 7A is a plan view of a grooved block on which a minute
groove is formed according to a third example;
[0047] FIG. 7B is a cross sectional view taken along a line
VIIB-VIIB in FIG. 7A;
[0048] FIG. 8A is a plan view of a grooved block on which a minute
groove is formed according to the third example, while the groove
depth is deeper than that in FIG. 7A;
[0049] FIG. 8B is a cross sectional view taken along a line
VIIIB-VIIIB in FIG. 8A;
[0050] FIG. 9A is a plan view of a grooved block on which a minute
groove is formed according to a fourth example;
[0051] FIG. 9B is a cross sectional view taken along a line IXB-IXB
in FIG. 9A;
[0052] FIG. 9C is a cross sectional view taken along a line IXC-IXC
in FIG. 9A;
[0053] FIG. 10A is a schematic cross sectional view of a static
pressure bearing device according to another embodiment of the
present invention;
[0054] FIG. 10B is an exploded perspective view of a throttle unit
of the static pressure bearing device shown in FIG. 10A;
[0055] FIG. 11 is an exploded perspective view of a static pressure
bearing device according to still another embodiment of the present
invention; and
[0056] FIG. 12 is a front view of a grooved block of the static
pressure bearing device shown in FIG. 11.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0057] A preferred embodiment of a throttle unit and a static
pressure bearing device having the throttle unit, and a method of
manufacturing a grooved block according to the present invention
will be described below with reference to the accompanying
drawings.
[0058] A static pressure bearing device 10A shown in FIG. 1 is
equipped with a bearing unit 12, and a throttle unit 14A attached
to the bearing unit 12. Though the detailed structure is not shown,
the bearing unit 12 is equipped with a structure with a linear
motion axis, in which a guide as a fixed portion and a slide as a
movable portion are provided. A plurality of static pressure
pockets are formed on a bearing surface of the slide or the guide.
When a working fluid such as air is supplied to the static pressure
pockets, the slide floats above the guide by the static pressure of
the working fluid and can move along the guide in a non-contact
manner. The bearing unit 12 may have a structure with a rotary
axis.
[0059] The throttle unit 14A is attached to the slide or guide of
the bearing unit 12. As shown in FIGS.1 and 2, the throttle unit
14A is equipped with a supply hole 16 through which the working
fluid is introduced, throttle fluid paths 18 for restricting the
flow rate of the introduced working fluid, and discharge holes 20
for discharging the working fluid which has passed through the
throttle fluid paths 18. To the supply hole 16, a pump 22 as a
supply source of the working fluid is connected through a fluid
path supply line. The discharge holes 20 communicate with the
static pressure pockets of the bearing unit 12.
[0060] More specifically, the throttle unit 14A is equipped with a
grooved block 24 including a plane surface 15 and minute grooves 25
formed on the plane surface 15, and an opposite block 26 detachably
attached to the grooved block 24 and having a plane surface 27
which is opposite to or face toward the minute grooves 25. The
grooved block 24 and the opposite block 26 are joined so as to be
opposite to each other in an assembled state. The throttle fluid
paths 18 are formed by the minute grooves 25 and the plane surface
27 of the opposite block 26.
[0061] The supply hole 16 is formed in the opposite block 26. The
supply hole 16 penetrates through the opposite block 26 in the
thickness direction. More specifically, the supply hole 16 has an
introduction portion 30, and a diffusion portion 32 that is formed
on the downstream side (grooved block 24 side) of the introduction
portion 30. The diffusion portion 32 diffuses the working fluid in
the directions that are perpendicular to the thickness direction of
the opposite block 26, i.e., the directions in which the plurality
of minute grooves 25 are separated from each other. The diffusion
portion 32 supplies the working fluid to the plurality of throttle
fluid paths 18 which will be described later.
[0062] The throttle fluid paths 18 are minute fluid paths for
reducing pressure of the working fluid by restricting the flow rate
of the working fluid. The throttle fluid paths 18 (minute grooves
25) linearly extend between the supply hole 16 and the discharge
holes 20. It is preferable that the minute grooves 25 have a
minimum depth of 1000 .mu.m or less, in the fluid path from the
supply hole 16 to the discharge holes 20.
[0063] The plurality of (three, in the illustrated embodiment)
minute grooves 25 are formed on the grooved block 24. Thus, the
throttle unit 14A has the plurality of (three, in the illustrated
embodiment) throttle fluid paths 18 which are independent of each
other. The plurality of throttle fluid paths 18 communicate with
the single supply hole 16. That is, the throttle unit 14A has the
single supply hole 16 which is commonly used for the plurality of
throttle fluid paths 18.
[0064] The discharge holes 20 are formed in the grooved block 24.
The discharge holes 20 penetrate through the opposite block 26 in
the thickness direction. The throttle unit 14A has the same number
of the discharge holes 20 as the throttle fluid paths 18. That is,
the discharge holes 20, which are independent from each other,
communicate with the respective throttle fluid paths 18. In the
throttle unit 14A, accordingly, the working fluid supplied to the
single supply hole 16 branches into the plurality of throttle fluid
paths 18, and is discharged from the plurality of discharge holes
20. Then, the working fluid is supplied to the plurality of static
pressure pockets formed in the bearing unit 12.
[0065] Next, the structure of the minute grooves 25, which are
formed on the grooved block 24, is more specifically described. At
least one surface of each of the minute grooves 25 is constituted
by a curved surface or an inclined surface that is inclined with
respect to the plane surface 15 of the grooved block 24. The cross
section of the minute groove 25 has a shape such as a triangle, a
trapezoid, a polygon (except for a substantial rectangle), an arc,
or a combination thereof. Due to this feature, the groove depth as
well as the groove width of the minute groove 25 can be measured by
a general method in which the groove is observed from above with a
microscope. The minute grooves 25 can be formed by machining or
cutting a plane surface of a workpiece block made of metal.
[0066] Hereinafter, some patterns of a cross sectional shape of the
minute groove 25 will be illustrated. In FIGS. 3A through 8B,
respectively, figures indicated by references with a suffix "A"
(e.g., 3A) show observational cases in which the minute groove 25
is observed from above (plan view), and figures indicated by
references with a suffix "B" (e.g., 3B) are cross sectional views
in which a cross sectional shape of the minute groove 25 is shown.
In each of these figures, e.g., an area surrounded by a broken line
V indicates a field of view when observed with a microscope.
[0067] In FIGS. 3A and 3B, a minute groove 25A, shown as one
example (first example) of the minute groove 25, has a trapezoidal
cross section. In the minute groove 25A, the width of a bottom
surface, which corresponds to a lower base of the trapezoid, is
smaller than the width of an opening (groove width), which
corresponds to an upper base of the trapezoid. In the illustrated
minute groove 25A, both side surfaces 34, which correspond to the
two legs of the trapezoid, are inclined with respect to the
thickness direction of the grooved block 24. In this case, either
one of the side surfaces 34 of the minute groove 25A may be formed
in parallel with the thickness direction of the grooved block 24.
FIGS. 4A and 4B show a case in which the minute groove 25A having a
trapezoidal cross sectional shape has been machined with a machine
tool having the same shape, but the groove depth of the cross
sectional shape becomes deeper than that of the minute groove 25A
shown in FIGS. 3A and 3B, depending on the machine accuracy of the
machine tool.
[0068] In FIGS. 5A and 5B, a minute groove 25B, shown as another
example (second example) of the minute groove 25, has an arcuate or
circular cross section. FIGS. 6A and 6B show a case in which the
minute groove 25B having an arcuate cross section has been machined
with a machine tool having the same shape, but the groove depth of
the cross sectional shape becomes deeper than that of the minute
groove 25B shown in FIGS. 5A and 5B, depending on the machine
accuracy of the machine tool.
[0069] In FIGS. 7A and 7B, a minute groove 25C, shown as still
another example (third example) of the minute groove 25, has a
polygonal cross section except for a substantial rectangular cross
section. FIGS. 8A and 8B show a case in which the minute groove 25C
having a polygonal cross section (except for a substantial
rectangular cross section) has been machined with a machine tool
having the same shape, but the groove depth of the cross sectional
shape becomes deeper than that of the minute groove 25C shown in
FIGS. 7A and 7B, depending on the machine accuracy of the machine
tool.
[0070] In comparison between FIGS. 3A and 4A, between FIGS. 5A and
6A, and between FIGS. 7A and 8A, in which the minute groove 25 is
observed from above, it is understood that the observed groove
width is changed depending on the change in the groove depth, even
if the groove is machined with the cutting tool having the same
shape. That is, when the machine tool having the same shape is
used, the deeper the groove depth is, the wider the groove width
is.
[0071] With regard to the minute grooves 25A through 25C having
these cross sectional shapes, since the shapes of the machine tools
are known, the groove depth can be calculated from the groove
width. For example, as to the minute groove 25A having a
trapezoidal cross section (see FIG. 3B), the groove depth D can be
calculated based on the groove width W1. Otherwise, as to the
minute groove 25A, the groove depth D can be calculated based on
the width W2 of the inclined surface (the width of inclined side
surface 34 as observed from above). Regarding other minute grooves
25 having respective cross sectional shapes as well, the groove
depth can be calculated based on the groove width or the width of a
portion that is part of the surface of the minute groove 25 and
varies based on the groove depth.
[0072] As described above, in the throttle unit 14A, at least one
surface of the minute groove 25 is constituted by a curved surface
or an inclined surface that is inclined with respect to the plane
surface 15 of the grooved block 24. The cross section of the minute
groove 25 has a shape such as a triangle, a trapezoid, a polygon
(except for a substantial rectangle), an arc, or a combination
thereof. Thus, due to this feature, the groove depth as well as the
groove width of the minute groove 25 can be measured by a general
method in which the minute groove 25 is observed from above (in the
direction that is perpendicular to the plane surface 15) with a
microscope. Since the groove depth of the minute groove 25 can be
measured, more precise machining can be achieved by correcting the
machining device (thermal displacement correction or the like)
based on the machining result, and a precise groove shape can be
obtained.
[0073] In this manner, the manufacturing method of the grooved
block 24 includes a cutting step, a calculating step, and a
correcting step. In the cutting step, the plane surface of a
workpiece block is cut to form the minute groove 25, and at least
one surface of the minute groove 25 is constituted by a curved
surface or an inclined surface that is inclined with respect to the
plane surface of the workpiece block. In the calculating step, the
minute groove 25 that has been formed in the cutting step is
observed with a microscope in the direction perpendicular to the
surface of the workpiece block (grooved block 24), and the groove
depth of the observed minute groove 25 is calculated. In the
correcting step, a machining device that performs the cutting is
corrected, based on the groove depth calculated in the calculating
step.
[0074] In the aforementioned Japanese Laid-Open Patent Publication
No. 2006-266358, since a total length of a fluid path is increased
by connecting a plurality of linear minute grooves that extend in
different directions from each other, corners (bent portions) of
the minute grooves tend to be clogged with foreign material. In
contrast, the throttle unit 14A according to the present
embodiment, preferable restriction strength can be obtained even if
the cross sectional shape of the throttle fluid path 18 is small
and a fluid path length of the throttle fluid path 18 is short.
Thus, the throttle fluid path 18 can be made linear, i.e., simply
extend from the supply hole 16 to the discharge hole 20 linearly.
Accordingly, the minute groove 25 can be manufactured (by cutting)
easily, and it is possible to suppress clogging with the foreign
material in the minute groove 25.
[0075] Further, in the throttle unit 14A, the plurality of throttle
fluid paths 18 communicate with the single supply hole 16, and the
discharge holes 20, which are independent from each other,
communicate with the respective throttle fluid paths 18. The
working fluid that is supplied to the single supply hole 16
branches into the plurality of throttle fluid paths 18, and is
discharged from the plurality of discharge holes 20. With this
feature, the number of throttle units 14A that are provided in the
static pressure bearing device 10A can be reduced. Thus, it is
possible to lower the cost, simplify the structure, and omit some
piping. Accordingly, since additional parts for changing
restriction strength are unnecessary, it is possible to minimize
the number of parts, the portions to be sealed, and piping.
Further, the structure is simple, and the man hours for machining
and assembling are small. Also, individual differences in the
restriction strength are small, the cost is lowered, and it is easy
to clean the unit.
[0076] Therefore, by installing the throttle unit 14A, it is
possible to reduce the weight of parts, realize compact structure,
reduce the cost by decreasing the number of parts and manufacturing
steps, achieve high reliability, and improve maintainability by
easy disassembly and cleaning.
[0077] In the meantime, the minute groove 25 can adopt a simple
linear shape, and thus it is possible to suppress clogging with the
foreign material. However, on the other hand it is impossible to
completely avoid the clogging with foreign material depending on
the cleanliness of supplied working fluid, also in view of the
smallness of the cross sectional shape of the throttle fluid path
18 (minute groove 25). Thus, it is necessary to confirm the
location of foreign material and remove it at the time of
disassembling and cleaning operations for the device.
[0078] In FIGS. 9A through 9C, a minute groove 25D, shown as still
another example (fourth example) of the minute groove 25, has
continuously-changed groove width and groove depth at least
partially in its overall length (from the supply hole 16 to the
discharge hole 20). The groove width and the groove depth of the
minute groove 25D may be continuously changed over its overall
length. In FIGS. 9A through 9C, the minute groove 25D having a
trapezoidal cross section is illustrated. More specifically, as
shown in FIG. 9A, the groove width of the minute groove 25D is
continuously changed in the longitudinal direction of the minute
groove 25D. In FIGS. 9B and 9C, sizes of a cross sectional shape
(groove width and groove depth) are different at different
positions.
[0079] The cross sectional shape of the minute groove 25D, the
groove width and the groove depth of which are continuously
changed, may have an arcuate cross section in a similar manner to
the minute groove 25B shown in FIGS. 5A through 6B. Alternatively,
it may have a polygonal cross section except for a substantial
rectangular cross section in a similar manner to the minute groove
25C shown in FIGS. 7A through 8B.
[0080] When the above-described minute groove 25D having
continuously-changed groove width and groove depth is adopted, even
if the foreign material somewhat clogs the minute groove 25D, it is
possible to easily gather foreign material at a portion having a
small cross sectional shape of the minute groove 25D. Thus, the
portion clogged with foreign material is easily confirmed at the
time of cleaning operation for the disassembled device, and the
foreign material can be removed efficiently.
[0081] A throttle unit 14B shown in FIGS. 10A and 10B is equipped
with a grooved block 24a and an opposite block 26a. The grooved
block 24a includes a plane surface, a supply hole 16, minute
grooves 25, and discharge holes 20. The opposite block 26a includes
a plane surface 27 that is opposite to the minute grooves 25. That
is, the throttle unit 14B corresponds to the aforementioned
throttle unit 14A, though the supply hole 16 is formed in the
grooved block 24 instead of the opposite block 26. The respective
minute grooves 25 can be any of the aforementioned minute grooves
25A through 25D. The static pressure bearing device 10B shown in
FIG. 10B is equipped with a bearing unit 12, and the throttle unit
14B that is detachably attached to the bearing unit 12. With the
throttle unit 14B constituted as above, the same advantageous
effects as those according to the aforementioned throttle unit 14A
can be obtained.
[0082] A static pressure bearing device 10C shown in FIG. 11 is
equipped with a bearing unit 12, and a grooved block 24b detachably
attached to the bearing unit 12. FIG. 11 shows a state in which the
grooved block 24b is detached from the bearing unit 12. The bearing
unit 12 has a guide 38 as a fixed portion and a slide (not shown)
as a movable portion. The guide 38 is provided with a plurality of
static pressure pockets 40.
[0083] The guide 38 has the plane surface 27 that is opposite to
the plurality of minute grooves 25 formed in the grooved block 24b,
in a state in which the grooved block 24b is attached (fixed) to
the bearing unit 12. In the state in which the grooved block 2b is
attached (fixed) to the bearing unit 12, a plurality of throttle
fluid paths 18 are formed by the plurality of minute grooves 25 and
the plane surface 27. Thus, a component of the guide 38 of the
bearing unit 12 also functions as an opposite block 26b that has
the plane surface 27 opposite to the plurality of minute grooves
25. The plurality of static pressure pockets 40 may be formed on
the slide which is a movable portion.
[0084] A single supply hole 16, the plurality of (six, in the
illustrated embodiment) minute grooves 25 which communicate with
the single supply hole 16, and the plurality of discharge holes 20
which communicate with the respective minute grooves 25, are formed
in the grooved block 24b. The minute grooves 25 can be any of the
aforementioned minute grooves 25A through 25D.
[0085] As shown in FIG. 12, each of the minute grooves 25 linearly
extend from the supply hole 16 to the discharge holes 20. The two
minute grooves 25 are arranged on the same line through the supply
hole 16. A plurality of (three, in the illustrated embodiment)
pairs of the two minute grooves 25 arranged on the same line are
provided. The plurality of minute grooves 25 (throttle fluid paths
18) communicate with the single supply hole 16. The working fluid
supplied to the single supply hole 16 branches into the plurality
of throttle fluid paths 18, and is discharged from the plurality of
discharge holes 20.
[0086] As shown in FIG. 11, a throttle unit 14C is constituted by
the grooved block 24b as configured above, and the opposite block
26b which also functions as a component of the guide 38. Thus, the
throttle unit 14C can be constituted only by attaching the grooved
block 24b to the guide 38 that has the plane surface 27 and is a
static pressure bearing component.
[0087] In this case, the grooved block 24b may function as a
component of the guide. Otherwise, the grooved block 24b or the
opposite block 26b may function as a component of the slide of the
bearing unit 12 or a component of another throttle unit.
[0088] With the throttle unit 14C, the same advantageous effects as
those according to the aforementioned throttle unit 14A can be
obtained. Further, according to the throttle unit 14C, at the time
of machining the minute grooves 25, one groove-forming operation
from one side of the supply hole 16 to the other side gives grooves
divided by the supply hole 16 such that the grooves can be used as
the independent minute grooves 25. Since the plurality of minute
grooves 25 are formed in a single machining path, it is possible to
reduce man hours for the machining.
[0089] Further, since the grooved block 24b or the opposite block
26b functions as a component of the slide (slide component), or a
component of the guide (guide component), or a component of another
throttle unit (another throttle unit component), the throttle unit
14C can substantially be configured by a single component. In
accordance with this feature, it is expected that the structure is
simplified, the number of parts is reduced, the installation space
is saved, and some piping is omitted.
[0090] The present invention is not limited to the embodiment
described above, and various modifications can be made to the
invention without deviating from the essential scope of the present
invention as set forth in the appended claims.
* * * * *