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.

Claims

1. A method of manufacturing a grooved block that includes a plane surface and at least one groove on the 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 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 at least one groove, the grooved block and the opposite block are plate-shaped and opposite to each other and joined to each other, and the at least one throttle fluid path is formed by the at least one groove and the plane surface of the opposite block, the method comprising: a cutting of cutting a plane surface of a workpiece block to form the groove, at least one surface of the 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 of calculating a groove depth of the groove that has been formed in the cutting, observing the groove with a microscope from a direction perpendicular to the plane surface of the workpiece block; and a correcting of making a correction of a machining device that performs the cutting, based on the calculated groove depth.

2. The method according to claim 1, wherein the calculating comprises calculating the groove depth based on a shape of a machine tool used by the machining device in the cutting, or a width of the inclined surface.

3. The method according to claim 1, wherein the cutting comprises cutting the plane surface of the workpiece block to form the groove having the at least one surface being constituted by the inclined surface, and the calculating comprises calculating the groove depth based on a width of the inclined surface.

4. The method according to claim 1, wherein the cutting comprises cutting the plane surface of the workpiece block to form a single supply hole and a plurality of grooves linearly extending from the single supply hole to the at least one discharge hole.

5. The method according to claim 1, wherein the cutting comprises cutting the plane surface of the workpiece block to form a single supply hole and a plurality of grooves arranged on a same line through the single supply hole.

6. The method according to claim 1, wherein the cutting comprises cutting the plane surface of the workpiece block to form a single supply hole, a plurality of throttle fluid paths connected to the single supply hole, and a plurality of discharge holes, which are independent from each other, and communicate with the plurality of throttle fluid paths.

7. The method according to claim 1, wherein the cutting comprises cutting the plane surface of the workpiece block in a single machining path to form a plurality of grooves.

8. The method according to claim 1, wherein the cutting comprises cutting the plane surface of the workpiece block to form a plurality of grooves, at least one of the plurality of grooves has continuously-changed width and depth at least partially in its overall length.

9. The method according to claim 1, wherein the cutting comprises cutting the plane surface of the workpiece block to form the at least one groove having a groove depth of 1000 μm or less from the at least one supply hole to the at least one discharge hole.

10. The method according to claim 1, wherein the cutting comprises cutting the plane surface of the workpiece block to form the at least one groove having a trapezoidal shape, which is the same as a shape of a machine tool used by the machining device to perform the cutting.

11. The method according to claim 1, wherein the cutting comprises cutting the plane surface of the workpiece block to form the at least one groove having an arcuate or circular shape, which is the same as a shape of a machine tool used by the machining device to perform the cutting.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic cross sectional view of a static pressure bearing device according to an embodiment of the present invention;

(2) FIG. 2 is an exploded perspective view of a throttle unit of the static pressure bearing device shown in FIG. 1;

(3) FIG. 3A is a plan view of a grooved block on which a minute groove is formed according to a first example;

(4) FIG. 3B is a cross sectional view taken along a line IIIB-IIIB in FIG. 3A;

(5) 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;

(6) FIG. 4B is a cross sectional view taken along a line IVB-IVB in FIG. 4A;

(7) FIG. 5A is a plan view of a grooved block on which a minute groove is formed according to a second example;

(8) FIG. 5B is a cross sectional view taken along a line VB-VB in FIG. 5A;

(9) 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;

(10) FIG. 6B is a cross sectional view taken along a line VIB-VIB in FIG. 6A;

(11) FIG. 7A is a plan view of a grooved block on which a minute groove is formed according to a third example;

(12) FIG. 7B is a cross sectional view taken along a line VIIB-VIIB in FIG. 7A;

(13) 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;

(14) FIG. 8B is a cross sectional view taken along a line VIIIB-VIIIB in FIG. 8A;

(15) FIG. 9A is a plan view of a grooved block on which a minute groove is formed according to a fourth example;

(16) FIG. 9B is a cross sectional view taken along a line IXB-IXB in FIG. 9A;

(17) FIG. 9C is a cross sectional view taken along a line IXC-IXC in FIG. 9A;

(18) FIG. 10A is a schematic cross sectional view of a static pressure bearing device according to another embodiment of the present invention;

(19) FIG. 10B is an exploded perspective view of a throttle unit of the static pressure bearing device shown in FIG. 10A;

(20) FIG. 11 is an exploded perspective view of a static pressure bearing device according to still another embodiment of the present invention; and

(21) 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

(22) 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.

(23) 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.

(24) 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.

(25) 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.

(26) 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.

(27) 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 μm or less, in the fluid path from the supply hole 16 to the discharge holes 20.

(28) 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.

(29) 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.

(30) 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.

(31) 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.

(32) 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.

(33) 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.

(34) 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.

(35) 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.

(36) 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.

(37) 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.

(38) 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.

(39) 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.

(40) 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.

(41) 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.

(42) 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.

(43) 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.

(44) 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.

(45) 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.

(46) 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.

(47) 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.

(48) 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 24b 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.

(49) 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.

(50) 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.

(51) 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.

(52) 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.

(53) 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.

(54) 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.

(55) 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.