JPS6044096B2 - Mobile platform device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a moving platform device having a moving platform that is guided by guide means and movable in one direction.

BACKGROUND ART A movable table device having a movable table driven by a drive means such as a feed screw and movable in one direction guided by a guide means provided on a base is often used in machine tools and measuring instruments. Sliding guides or rolling guides are generally used as the guide means for such moving platform devices, but conventional moving platform devices that use sliding guides are limited by the relative precision of the guide surface with respect to the movement of the moving platform. The lubrication condition is not uniform, and on the other hand, in moving platform devices using rolling guides, there are variations in the relative accuracy of the guide surface with respect to the movement of the moving platform and in the dimensional accuracy of the rolling elements used. It was difficult to obtain suitable operating characteristics.

As a guide means that takes into consideration the working characteristics of the moving platform,
A static pressure guide means is also used, which supplies a fluid with pressure between guide surfaces that move relative to each other and supports and guides the movable table using the static pressure of the fluid.

This static pressure guide means supports the movable base with static pressure against a guide surface having a certain area, so that an average effect is obtained regarding the accuracy of the guide surface, and the resistance to the movement of the movable base is reduced by the fluid. Since there is only frictional resistance of
It has excellent advantages as a guide means for a moving platform that requires precise operating characteristics.

Furthermore, the static pressure guide means has the advantage that the support rigidity of the movable platform can be controlled to a desired value by controlling the pressure or flow rate of the fluid supplied between the relatively moving guide surfaces. A liquid or a gas is used as the fluid used in the static pressure guide means, and generally oil is used as the liquid and air is used as the gas.

A static pressure guide means using oil as a fluid is normally supplied with pressurized oil from a hydraulic device installed near the moving platform device, and the oil pressurized by the hydraulic device is Generally, there is a drawback that the temperature of the oil increases, which changes the temperature of the moving table device, causing thermal displacement in the moving table device.

In order to prevent such thermal displacement of the moving table device, it is necessary that there is no difference between the temperature of the supplied oil and the temperature of the moving table device. This has the drawback of requiring an oil temperature adjustment device with an expensive cooling device. Furthermore, since the hydraulic device that pressurizes the oil itself is a heat source, it also affects the room temperature, making it difficult to make the temperature of the movable table uniform. On the other hand, unlike static pressure guide means using oil, static pressure guide means that uses air as the fluid generally adopts a centralized supply system in which the compressed air generation source is located at a remote location. Since it is easy to obtain pressurized air, there is almost no problem of thermal displacement of the moving table due to the air used as the fluid.
In addition, since air has an extremely low viscosity compared to oil, it has the advantage that the resistance to the movement of the moving table and the generation of heat from viscous friction due to the movement of the moving table are negligible. However, the load capacity is small, and since air is a compressible fluid, self-excited vibrations are likely to occur, which is said to be due to a delay in response.

It has been proposed to provide pockets on the guide surface of the guide means and to use control throttles to control the supply gas in order to improve the load capacity and rigidity of the static pressure guide means using air. Hydrostatic gas guide bearings that have pockets on the guide surface of the pressure guide means and static pressure gas guide bearings that use a controlled throttle have the disadvantage that self-excited vibrations are particularly likely to occur. This made it difficult to put gas bearings into practical use.

The above explanation uses oil as an example when the fluid used in the static pressure guide means is a liquid, and air as an example when the fluid is a gas, but the same applies when other liquids or gases are used. Let's say.

This invention was made to eliminate the drawbacks of the conventional moving platform device, and its purpose is to increase rigidity and load capacity by suppressing self-excited vibration of the moving platform. It is an object of the present invention to provide a movable table device having a movable table capable of accurate operation, which hardly causes thermal displacement that adversely affects positional relationship accuracy.

In order to achieve this object, the present invention supports the movable table on the base by static pressure guide means, and also provides the base with a recess filled with a liquid having a predetermined viscosity. A loosely fitting protrusion is provided on the movable base, a thin film of liquid is interposed between the movable base and the base, and the self-excited vibration of the movable base is suppressed by the squeeze damping effect of this thin liquid film, thereby reducing the load. This makes it possible to obtain a moving platform device with large capacity, high rigidity, and good operating characteristics.

Next, an embodiment of the moving table device of the present invention will be described with reference to the drawings.

The base 1 has an opening at the top, and has a U-shaped cross section in both the vertical and cross sections.

The inner surface of the side wall 2 in the longitudinal direction of this base 1 has a rectangular recess whose bottom surface is a guide surface 3 that is parallel to this inner surface, and whose side surfaces are guide surfaces 4 and 5 that are orthogonal to the guide surface 3 and parallel to each other. A groove 6 is formed in the longitudinal direction, and the inner surface of the side wall 7 facing the side wall 2 has a guide surface 8 parallel to the guide surface 3 of the groove 6 as a bottom surface, and a guide surface 8 parallel to the guide surfaces 4 and 5 of the groove 6 as a bottom surface. A rectangular groove 11 having the guide surfaces 9 and 10 as side surfaces is formed in the longitudinal direction. Guide surface 3
, 4, 5, 8, 9, and 10, a required number of pockets 12, 13, 14, 15, 16, and 17 formed as recesses are provided at predetermined positions, and these pockets 12,
Gas passages 18, 19, 20, 21, 22, and 23 are opened in the base 1, respectively.

Below the concave grooves 6, 11 of the base, inner surfaces of the side walls 2, 7 parallel to the guide surfaces 3, 8, and a bottom surface 24 extending in the axial direction parallel to the guide surfaces 4, 5, 9, 10, A recess 27 is formed by the walls 25 and 26 at the longitudinal ends of the base 1 .

The moving table 28 has a dimension in the longitudinal direction smaller than the interval between the walls 25 and 26 of the base, and has protrusions 29 and 30 extending over the entire length in the longitudinal direction corresponding to the grooves 6 and 11 of the base, and It has a protrusion 31 extending over the entire length in the longitudinal direction corresponding to the recess 27, and is loosely fitted into the base 1.

The protrusion 29 of the moving platform is a corner protrusion having receiving surfaces 32, 33, 34 parallel to the guide surfaces 3, 4, 5 of the base and slightly spaced apart from the guide surfaces, respectively. A narrow gap is formed between the guide surface 34 and the opposing guide surfaces 3, 4, and 5 of the base.

The same applies to the other protrusion 30 of the moving table 28, and the protrusion 30 has a rectangular shape that corners the receiving surfaces 35, 36, 37, which are parallel to the guide surfaces 8, 9, 10 of the base and slightly spaced from the guide surfaces. Narrow gaps are formed between the receiving surfaces 35, 36, 37 and the opposing guide surfaces 8, 9, 10 of the base. The protrusion 31 of the movable table is a protrusion having an opposing surface 38 parallel to and slightly spaced apart from the bottom surface 24 of the base, and opposing surfaces 39 and 40 parallel to and slightly spaced apart from the inner surfaces of the side walls 2 and 7 of the base, respectively. , a narrow gap is formed between the opposing surface 38 and the bottom surface 24 of the base that opposes it, and between the opposing surfaces 39 and 40 of the movable table and the side walls 2 and 7 of the base that oppose this. ing.

The base 1 also includes base guide surfaces 3, 4, 5, 8, 9,
The feed screw 41 whose axis is parallel to 10 is connected to the bearings 42 and 4.
3, which is rotatably supported by the feed screw 41.
is fixed to the moving table 28;
0 hours. . A bearing spacer 47 is an outer cover for fixing the outer rings of the bearings 42 and 43, and a bearing nut 48 is for fixing the inner rings of the bearings 42 and 43.

The control throttles 49, 50, 51 are arranged in two vacuum chambers 57, 58 or 59, 60 or 61, respectively, which are regulated by control membranes 52, 53 or 54, which are valve bodies, and are connected to a compressed air source 56 by a conduit 55. , 62, and these decompression chambers 57, 58, 59, 60, 61, 62 have a control thin film 5.
2, 53 or 54 through a narrow gap.

The outlet 63 of the control throttle 49 is connected to the gas passage 19 of the base by a conduit 69, and the outlet 64 of the control throttle 49 is connected to the gas passage 19 of the base by a conduit 69.
It is connected by a conduit 70 to the gas passage 20 of the base.
The same applies to the control throttles 50 and 51, and the discharge port 65 of the control throttle 50 is connected to the gas passage 18 of the base.
The exhaust port 66 of 0 is connected to the gas passage 21 of the base, and
The outlet 67 of the control throttle 51 is connected to the gas passage 23 of the base, and the outlet 68 of the control throttle 51 is connected to the gas passage 22 of the base. Compressed air supplied from compressed air source 56 is passed through conduit 5
5 through the control throttle vacuum chambers 57, 58, 59, 60,
61 and 62, respectively, and a control membrane 52, 53 or 54, which is a valve body of the decompression chamber, and an outlet 63, which is opposite thereto.
64, 65, 66, 67 or 68, enters the pocket 12, 13, 14, 15, 16, 17 through the conduit 69, 70, 71, 72, 73, 74, and enters the guide surface 3. , 4, 5, 6, 7, 8 and the receiving surfaces 32, 33, 34, 35, 36, 37 facing thereto.

Static pressure is created by supplying compressed air between the guide surfaces 3, 4, 5, 6, 7, 8 of the base and the receiving surfaces 32, 33, 34, 35, 36, 37 of the movable table opposing thereto. A gas guide bearing is configured, and the movable table 28 is supported statically on the base 1.

This hydrostatic gas guide bearing has a control orifice 49, 50 or 5
The air supply from 1 is connected to mutually opposing guide surfaces 4 and 5 of the base.
3, 8 or 9, 10, and when the moving table 28 is displaced due to an external force acting on the moving surface 28 and the bearing clearance of the static pressure bearing changes, the opposing static pressure is applied in response to the change. When a pressure difference occurs in the bearing, the control membrane 52, 53 or 54, which is the valve body of the control throttle, is displaced in response to the pressure difference in the hydrostatic bearing, and the mutually opposing guide surfaces 4, 5 or 3 of the base are displaced.
.

A recess 27 provided in the base 1 is filled with a predetermined amount of turbine oil as a liquid 75, and the side walls 2 and 7 of the base, the pair 1 of the movable base facing this; the J surfaces 39 and 40; A thin film of liquid 75 is formed between the bottom surface 24 of the base and the facing surface 38 facing thereto.

This thin film of liquid 75 responds to the self-excited vibration of the moving table 28.
It has a film thickness that provides a squeeze damping effect that provides a deterrent force proportional to the speed. A groove 7 is formed in the protrusion 31 of the movable base over the entire length of the movable base 28 in the longitudinal direction.
6 is provided.

This groove 76 facilitates the movement of the liquid 75 as the moving table 28 moves, and the groove 75 allows the liquid level of the liquid 75 to be kept constant even if the moving table 28 moves at high speed. This groove 76 is partitioned by a movable base 28.
It is also possible to provide the liquid 75 on the side of the base 1 as long as the liquids 75 at the front and rear in the direction of movement of the liquid 75 are movably communicated with each other.

Note that when the moving speed of the moving table 28 is slow, this groove 76
does not need to be specifically provided. In this embodiment, the base 1 is provided with rectangular grooves 6, 11 having guide surfaces 3, 4, 5 and 8, 9, 10, and the movable table 28 is provided with receiving surfaces 32, 33, 34, 35, 36, Although a structure in which projections 29 and 30 having a diameter of 37 are provided is shown, it is also possible to provide a configuration in which a square projection is provided on the side of the base 1 and a corresponding square groove is provided on the side of the moving table 28. Of course.

Further, in this embodiment, the compressed air is supplied from the base 1 side, but the compressed air may be supplied from the movable table 28 side.

In this case, a pocket may be provided on the receiving surface of the movable table 28, a gas passage for supplying compressed air to the pocket may be opened, and a conduit from the control throttle may be connected to this gas passage. The dimensions of the moving table device of this embodiment are as follows: the axial length is 410Wrfn1, the width of the receiving surfaces 32 and 35 is 5-, and the receiving surface 33 is
, 34, 36, and 37 are 35T wide! Rlnl facing surface 38
The width of is 14-, and the vertical length of opposing surfaces 39 and 40 is 6
070F7! It is becoming.

The gap between the hydrostatic air bearings is 0.015wrIn, and the gap where the liquid is interposed is 0.030m1.
It is becoming.

The oil filled in the recess 27 of the base was turbine oil (32 turbine oil) with a viscosity coefficient of p=7.2×10 −7 k9S′d.

(This is 3900 times the viscosity coefficient of air.) In the moving table device of the present invention configured as described above, the moving table is supported on the base by the static pressure gas guide means, so that the guiding accuracy of the moving table can be improved. An averaging effect is obtained and precise guidance is possible, and since the moving table is supported by the base via gas, the sliding resistance of the moving table is extremely small, and there is no heat generated by fluctuations in sliding resistance or movement of the moving table. The occurrence of this can be ignored, and since the gas supplied to the static pressure gas guide can be easily obtained at room temperature, it is possible to obtain a moving table device in which almost no thermal displacement occurs on the moving table. By filling a predetermined amount of liquid into a recess in the base having a surface parallel to the moving direction, the surface of the recess in the base parallel to the moving direction of the moving table and the opposing surface of the moving table facing this surface are formed. A thin film of liquid is formed between the surface and the squeeze damping effect of this thin film to suppress the self-excited vibration of the moving platform, allowing accurate operation and precision without changing the relative position due to thermal displacement. This has the effect of providing a moving table device.

In addition, by forming a thin film of liquid between the recessed surface of the base that is parallel to the moving direction of the moving table and the opposing surface of the moving table that faces this surface, self-excited vibration of the moving table is effective. Conventionally, it was not possible to provide a pocket on the guide surface of the static pressure gas guide or use a control throttle to control the supplied gas due to the generation of self-excited vibrations, but the movable platform device of the present invention It is possible to provide a pocket on the guide surface of the static pressure gas guide or use a control throttle to control the supplied gas, and it is possible to obtain a moving platform device with a large load capacity and rigidity. In the case where the gas to be supplied is controlled by a control throttle, it is possible to obtain a moving platform device with extremely large load capacity and rigidity.

Furthermore, this moving table device is simple because a thin film of liquid is formed between the base and the moving table by simply filling a predetermined amount of liquid into the recess provided in the base. It also has the advantage of being easy to handle and maintain.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing one embodiment of the moving table device of the present invention, and FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1 with a fluid piping system diagram added for explanation. be. 1... Base, 3, 4, 5, 8, 9, 10...
... Guide surface, 6, 11 ... Concave groove, 12, 13
,14,15,16,17...pocket,18,
19, 20, 21, 22, 23... gas passage, 27
...Recess, 28...Movement table, 29,30.
...Protrusion, 31...Protrusion, 32, 33, 34
, 35, 36, 37... receiving surface, 38, 39, 40...
...Opposing surface, 49, 50, 51... Control aperture, 5
6... Compressed air source, 75... Liquid.

Claims (1)

[Scope of Claims] 1. In a moving table device equipped with a moving table that is relatively movable along a specific axis, an axial direction forming a pair of guide surfaces that are parallel to the axis and parallel to each other. a base having grooves or protrusions formed on the inner surfaces of facing walls, and a recess below the grooves or protrusions forming a bottom surface extending in the axial direction parallel to the axis; A protrusion or recess provided with a receiving surface that faces each of the guide surfaces of the groove or protrusion at a slight distance and forms a hydrostatic gas bearing by supplying pressurized gas between the guide surfaces. A thin film of liquid is formed by forming a groove, which further faces the bottom surface of the recess of the base and the inner surface of the side wall with a slight distance from each other, and interposes the liquid between the bottom surface and the inner surface of the side wall. a moving table having a protrusion provided with an opposing surface, and the base or the moving table has a gas passage opening on either the guide surface of the base or the receiving surface of the moving table on one side. the other end of the gas passage is connected to a pressurized gas supply source, the recess in the base is filled with liquid, and the recess in the base and the movement A moving platform device characterized in that self-excited vibration of a hydrostatic gas bearing is suppressed by the squeeze damping effect of a thin film of liquid formed between a protrusion of the platform. 2. The moving table device according to claim 1, wherein the guide surface of the base or the receiving surface of the moving table has a pocket formed as a recess at the opening of the gas passage. 3. Pressurized gas is supplied between the guide surface of the base and the receiving surface of the movable table opposing thereto by back pressure due to the difference in spacing between the two bearings of a pair of static pressure bearings facing each other. 3. The movable platform device according to claim 1, wherein the pressurized gas is controlled by a control throttle that adjusts the amount of fluid supplied to each opposing hydrostatic bearing surface by a variable valve body.