JP3098421B2 - Static pressure air bearing type guide device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a guide device in which a bearing side and a shaft side are relatively movable (linear movement or rotary movement) by a static pressure air bearing. The present invention relates to a hydrostatic air bearing type guide device in which a reference air pad is provided on at least one surface, and an auxiliary air pad having a biasing force in a direction opposed to the reference air pad via the shaft side is provided on the bearing surface.

[0002]

2. Description of the Related Art Hydrostatic air bearings are widely used in guide devices of precision measuring equipment because of their extremely low coefficient of friction and low occurrence of stick-slip. For example, in a roundness measuring machine of a rotary detector type, a linear motion type (hereinafter, simply referred to as a "linear motion type") is used to guide a Z-axis supporting a detector and an XY table on which a work is placed. A rotary motion system (hereinafter, simply referred to as a “rotation system”) is used for the support unit. Further, in a table rotation type roundness measuring machine, a rotation method is used for a table rotation support portion. In addition, in a three-dimensional coordinate measuring machine of a rectangular coordinate system, a linear motion method is used for guiding three axes of XYZ.

[0003] Among them, an example of a roundness detector of the detector rotation type will be described. As shown in FIG. 1, an XY table 12 supported on a base 11 so as to be movable in the XY directions is provided. A column 13 is provided upright on the column 11, and a Z table 14 is supported on the column 13 so as to be movable in the Z direction. On the front side of the Z table 14, the rotation support portion 1 is provided.
5 is provided, and a vertical spindle 16
Is built-in. A support arm 17 is fixed to the lower end of the vertical spindle 16, and a detector holder 18 is supported by the support arm 17 so as to be movable in a horizontal uniaxial direction. Further, the detector holder 18 includes an extension rod 18.
A detector 19 is provided via a.

A detector rotation type roundness measuring machine is configured as described above, and a detector 19 is rotated by a vertical spindle 16 while the work is placed on the XY table 12 and fixed, and the roundness is measured. Measure. The detector 19 is a Z table 14
Since it can be moved up and down, the roundness can be measured at an arbitrary height of the work, and the straightness can be measured by moving the detector 19 up and down without rotating it.

In this case, since the rotation accuracy of the spindle 16 is directly related to the roundness measurement accuracy, a rotation type static pressure air bearing is used for the rotation support portion 15 of the spindle 16. On the other hand, the XY table 12 and the Z table 14
In the past, sliding guides, linear bearings, and the like have been used, but static pressure air bearings are increasingly used from the viewpoint of improving measurement accuracy. The example shown in FIG. 1 also employs a static pressure air bearing for guiding the XY table 12 and the Z table 14.

In the case of a direct-acting static air bearing or a rotating static air bearing in the thrust direction, a disk-shaped or rectangular plate member is provided between the fixed side and the movable side for convenience in processing and adjustment. In many cases, compressed air is blown out of the device. This plate member is called an air pad. The air pad is provided on the fixed side or on the movable side depending on the structure of the guide device. In this specification, the side supporting the air pad is referred to as a bearing side, and the side having a guide surface is referred to as a shaft side.

FIG. 2 shows a main part of the Z table 14 of the example shown in FIG. 1 as viewed from above. Reference axes 21 are provided at three places of the Z table 14, and the reference air pads 22 are respectively provided. An auxiliary air pad 24 is supported by an auxiliary shaft 23 having a biasing force on the side opposed to each reference pad 22 via the column 13. These are configured in two upper and lower stages, whereby the Z table 14 can be moved up and down along the columns 13. The Z table 14 is moved by a feed screw 25 provided on the column 13. In this case, the Z table 14 on the bearing side moves.

FIG. 3 shows a vertical cross section of the XY table 12 in the X direction. A plurality of air pads 32 for supporting the own weight of the XY table 12 are provided in the vertical direction via a support shaft 31. The table 12 moves along the upper surface 11a of the base 11. In this case, since the XY table 12 has a large mass, there is no need to provide an auxiliary air pad opposing the air pad 32 below the base 11.

In this example, the mechanism for guiding the moving direction is performed via the moving block 33. That is, a guide surface 33a is formed in the upper direction of the moving block 33 in the Y direction, and a reference shaft 34 and an auxiliary shaft 36 having a biasing force are provided in the lower portions 12a and 12b of the XY table 12, and each is provided with a reference air pad. 35 and the auxiliary air pad 37 are supported, and guide the XY table 12 in the Y direction. Further, a reference air pad and an auxiliary air pad (details are not shown) are provided on the lower side 33b of the moving block 33, and the moving block 33 moves along the guide surface 11b formed in the X direction of the base 11. Thus, the XY table 12 is guided in the X direction.

In this manner, the Z table 14 and the XY table 12 are guided and stick-slip hardly occurs, so that smooth movement is possible and high-precision measurement and positioning are possible.

[Problems to be solved by the invention]

However, when the movable members such as the XY table 12 and the Z table 14 are stopped and restrained, there arises a problem that the rigidity for stopping in the driving direction is insufficient. That is, since the static pressure air bearing has a very small coefficient of friction and generates little frictional force in the driving direction, it depends only on the stopping rigidity in the driving direction (for example, in the case of a screw drive system, the rigidity of the rotating bearing in the thrust direction). I do. The rigidity of the rotary bearing in the thrust direction, including its support block, is generally not large. If the stopping rigidity in the driving direction is small, the position in the driving direction becomes unstable due to the influence of external vibration or the like, and tends to fluctuate. Since the work is fixed to the XY table 12 and measured, if the position of the XY table 12 fluctuates during the measurement,
Unable to measure accurately. In addition, since the Z table 14 supports the detector 19, if the position fluctuates during the measurement, accurate measurement cannot be performed.

[0012] For this reason, it is possible to provide a separate brake device and use it at the time of stopping to increase the stopping rigidity in the driving direction. However, if the brake device is provided, the mechanism becomes complicated and the cost increases. There's a problem.

As a method of restraining movable bodies such as the XY table 12 and the Z table 14 in a stopped state,
There is a method of shutting off the compressed air supplied to the air pad. When the compressed air is shut off, the air pad comes into contact with the guide surface due to the urging force of the auxiliary shaft, so that the restraining force in the driving direction increases. In this state, the fluctuation in the driving direction becomes extremely small even if there is external vibration or the like. However, this method has the following problems.

FIG. 5 shows a part of a general linear motion type static pressure air bearing type guide device. In FIG.
A moving body 71 is formed so as to sandwich the guide block 51,
A reference shaft 53 is provided on one side 71a of the moving body 71,
An auxiliary shaft 73 having a biasing force is provided on the other side 71b. The reference shaft 53 and the auxiliary shaft 73 restrain and support the reference air pad 54 and the auxiliary air pad 56 on the guide block 51 side, respectively. The guide block 51 is different from the example shown in FIGS.
The moving body 71 corresponds to the XY table 12 and the Z table 14.

Tubes 61 and 62 are connected to the reference air pad 54 and the auxiliary air pad 56, respectively.
Reference numerals 1 and 62 are connected via an electromagnetic valve 63 to an air source 65 for supplying compressed air. As a result, compressed air is supplied to the reference air pad 54 and the auxiliary air pad 56, and the compressed air is supplied to the reference air pad 54 and the auxiliary air pad 5.
Nozzle hole 5 formed on each guide block 51 side of 6
4a, 56a, the reference air pad 54,
An air film is formed between the auxiliary air pad 56 and the guide block 51. As a result, the moving body 71 is guided by the guide block 51 via the reference air pad 54 and the auxiliary air pad 56.
, And is movable in a direction perpendicular to the paper surface. Although not shown, the left and right directions of the moving body 71 are also restrained in a non-contact manner.

In this case, the reference shaft 53 is screwed and fixed to the moving body 71, while the auxiliary shaft 73 is fixed to the moving body 71.
The guide block 51 is formed by an elastic body 74 (a disc spring in this example) via a bearing 72 screwed and fixed to
It is urged to the side and is supported. Thus, even if the width B of the guide block 51 changes or the width C of the moving body 71 changes, the auxiliary shaft 73 absorbs the change. 53), and moves along the E surface of the guide block 51 (the auxiliary shaft 73 side).
Move without being affected by the change in the straightness of the moving object or the change in the width C of the moving body 71.

However, if the supply of compressed air is interrupted to increase the stopping rigidity of the moving body 71, the state shown in FIG. 6 is obtained. That is, since the electromagnetic valve 63 is switched to the shut-off side and the supply of the compressed air is shut off, both the reference air pad 54 and the auxiliary air pad 56 have no force for forming the gap δ with the guide block 51. As a result, the auxiliary air pad 56 is pushed into the guide block 51 by the gap δ by the urging force of the auxiliary shaft 73, and the reference air pad 54 is drawn toward the guide block 51 by the gap δ. Therefore, the guide block 51
The distance Xc between the plane D and the moving body 71 becomes A, which is smaller by δ than the distance Xb when the compressed air is supplied.

If the position of the moving body 71 fluctuates between when the compressed air is supplied and when the compressed air is shut off, for example, the position of the work fluctuates on the XY table 12 and the position of the detector 19 fluctuates on the Z table 14. A problem arises in that the position to be measured cannot be set accurately or is unstable.

The present invention has been made in view of such circumstances, and in a static pressure air bearing type guide device, a fluctuation in a direction perpendicular to the driving direction of a movable body is extremely different between when compressed air is supplied and when compressed air is shut off. An object is to provide a small guide device at a low cost.

[0020]

In order to achieve the above object, according to the present invention, a reference air pad is provided on at least one of the bearing sides, and an auxiliary force having a biasing force in a direction opposed to the reference air pad via the shaft side. A hydrostatic air bearing type guide device in which an air pad is provided on an opposing surface on the bearing side and the bearing side and the shaft side are relatively movable is described below. That is, the supply and cutoff of the compressed air to the auxiliary air pad are independently controlled, and when the bearing side and the shaft side are relatively stopped, the auxiliary air pad is continuously supplied with the compressed air to the reference air pad. The supply of compressed air to the air pad can be shut off.

In this case, it is necessary that the auxiliary shaft supporting the auxiliary air pad has no play in a direction perpendicular to the urging direction. As one of the methods, the auxiliary shaft can be supported by a leaf spring. At this time, the biasing force can be generated by a leaf spring, or may be a method using another elastic body (such as a disc spring).

In addition, there are a linear movement type and a rotation type as a movable form. In the case of the linear movement type, a reference air pad and an auxiliary air pad are provided in a direction orthogonal to the moving direction. Provide air pad and auxiliary air pad.

[0023]

FIG. 4 shows an embodiment of a hydrostatic air bearing type guide device according to the present invention. FIG. 4 shows a part of a direct-acting, static-pressure air-bearing type guide device similar to FIGS. 5 and 6 described in the related art. Since there are many portions common to FIGS. 5 and 6, the same functional components are denoted by the same reference numerals.

In FIG. 4, a moving body 52 is formed so as to sandwich the guide block 51, and one side 52 of the moving body 52 is formed.
A reference shaft 53 is provided at a, and a reference air pad 54 is supported by the reference shaft 53. This part is the same as the conventional one. On the other hand, on the other side 52b of the moving body 52, an auxiliary shaft 55 is provided supported by a leaf spring 55a, and an auxiliary air pad 56 is supported on the auxiliary shaft 55. Auxiliary shaft 5
5 is further urged toward the guide block 51 by an elastic body 59 (in this example, a disc spring) via a bearing 57 screwed and fixed to the moving body 52.

The tube 61 connected to the reference air pad 54 is connected to the electromagnetic valve 63 in the same manner as in the prior art. In the present invention, the tube 62 connected to the auxiliary air pad 56 is connected to the electromagnetic valve 64 via the electromagnetic valve 64. Valve 63
It is connected to the. The electromagnetic valve 63 is connected to an air source 65 for supplying compressed air as in the conventional case. As a result, as shown in FIG. 4, the compressed air is supplied to the reference air pad 54 when the electromagnetic valve 63 is on the supply side, but the compressed air is supplied to the auxiliary air pad 56 even when the electromagnetic valve 64 is on the shut off side. No air is supplied.

Therefore, when the electromagnetic valves 63 and 64 are set as shown in FIG.
6 has no force for forming the gap δ with the guide block 51, so that the auxiliary air pad 5
6 is pushed into the guide block 51 side and abuts. When the auxiliary air pad 56 comes into contact with the guide block 51, the frictional force in the moving direction increases, and the stopping rigidity increases.
However, unlike the related art, since compressed air is supplied to the reference air pad 54, a gap δ is maintained between the guide block 51 and the guide block 51. The same state as the movable state can be maintained.

Although not shown, the electromagnetic valve 64 is also on the supply side, and the reference air pad 54 and the auxiliary air pad 56
When both are supplied with compressed air, the compressed air is blown out from the nozzle holes 54a and 56a of the reference air pad 54 and the auxiliary air pad 56 as in the conventional case, and the compressed air is blown between the reference air pad 54, the auxiliary air pad 56 and the guide block 51. A film of air is formed on the surface. As a result, the moving body 52 is guided in a non-contact manner (gap δ) by the guide block 51 via the reference air pad 54 and the auxiliary air pad 56, and becomes movable in a direction perpendicular to the paper surface.

In the embodiment described above, a linear motion type guide device is mainly described. However, it can be said that the present invention can be applied to a case where a rotary type guide device is used for guiding in a thrust direction. Not even. When the case of the rotation method is applied to the example shown in FIG. 4, the D surface and the E surface become the thrust surfaces, and the guide block 51 generally rotates.

Further, in the embodiment, an example in which the present invention is applied mainly to a roundness measuring machine has been described. it can.

Further, in the embodiment, the auxiliary shaft 55 is supported by the leaf spring 55a. However, another method, for example, a shaft guide like the auxiliary shaft 73 described in the example of the prior art is used as the shaft guide. A guide method using a support having no gap in the radial direction such as a ball bush may be used.

[0031]

As described above, in the present invention, the reference air pad is provided on at least one surface of the bearing side, and the auxiliary air pad having a biasing force in the direction opposed to the reference air pad via the shaft side is provided on the bearing side. The static pressure air bearing type guide device, which is provided on the opposing surface and is configured so that the bearing side and the shaft side are relatively movable, controls the supply and cutoff of the compressed air to the auxiliary air pad independently, and the bearing side When the shaft and the shaft are relatively stopped, the supply of compressed air to the auxiliary air pad can be shut off while the supply of compressed air to the reference air pad is continued.

Accordingly, in the guide device of the static pressure air bearing type, a guide device in which fluctuation in a direction perpendicular to the driving direction of the movable body is extremely small between the time of supplying compressed air and the time of shutting off compressed air can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is an external view of an example of a detector rotation type roundness measuring device.

FIG. 2 is a diagram illustrating a main part of the Z table of the example illustrated in FIG. 1 when viewed from above.

FIG. 3 is a diagram showing a vertical cross section in the X direction of the XY table of the example shown in FIG. 1;

FIG. 4 is a view showing an embodiment of a static pressure air bearing type guide device according to the present invention.

FIG. 5 is a diagram showing a configuration (compressed air supply state) of a conventional static pressure air bearing type guide device.

FIG. 6 is a diagram showing a configuration (a compressed air cutoff state) of a conventional static pressure air bearing type guide device.

[Explanation of symbols]

 51 guide block 52 moving body 53 reference axis 54 reference air pad 55 auxiliary shaft 55a leaf spring 56 auxiliary air pad 59 elastic bodies 61 and 62 air tubes 63 and 64 electromagnetic Valve 65: Air source

Claims (5)

(57) [Claims] A reference air pad is provided on at least one surface of the bearing side, and an auxiliary air pad having a biasing force in a direction opposed to the reference air pad via the shaft side is provided on an opposite surface on the bearing side. And the shaft side are relatively movable relative to each other, wherein the supply and cutoff of compressed air to the auxiliary air pad are controlled independently, and the bearing side and the shaft are controlled independently. Wherein the supply of the compressed air to the auxiliary air pad can be shut off while the supply of the compressed air to the reference air pad is continued when the side is relatively stopped. apparatus. 2. The static pressure air bearing type guide device according to claim 1, wherein an auxiliary shaft for supporting said auxiliary air pad is supported by a leaf spring and a biasing force is applied to said auxiliary shaft. . 3. A hydrostatic air bearing type guide device according to claim 1, wherein said bearing side and said shaft side are configured to relatively linearly move. 4. The guide device according to claim 3, wherein the guide surface on the shaft side is rectangular. 5. The system according to claim 1, wherein the bearing side and the shaft side are configured to rotate relatively, and the reference air pad and the auxiliary air pad are provided in a thrust direction. The static pressure pneumatic bearing type guide device according to 1.