JP2003084087A - Device for compensating dead weight of vertical stage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve concurrently both elimination of disturbance applied when a stage is positioned and restraint of heat generated in a stage driving system, to the utmost, so as to provide highly precise positioning precision for the stage. SOLUTION: This device is provided with a Z-axis stage 1 movable along a gravitational direction, a counter-weight 41 balanced with the whole stage weight including the Z-axis stage 1 and a mounted body on the Z-axis stage 1, a connection member 43a for connecting the counter-weight 41 to the Z-axis stage 1, pullies 44a, 44c for supporting the connection member 43a windingly, and for compensating the dead weight of whole stage, and a counter-weight guide 42 for making the counter-weight 41 movable only along the gravitational direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-weight compensating mechanism capable of compensating for the weight of the entire stage including a mounted object in a vertical stage device that is movable in the direction of gravity and performs precise positioning. It can be used as a self-weight compensating device for a vertical stage device used in various precision measuring devices and various precision processing devices, and in particular, among those having multiple axes.

[0002]

2. Description of the Related Art In a vertical stage movable in the direction of gravity, thrust is required for a drive system of the stage. The purpose of compensating for the weight of the entire stage, including the load on the stage, is to reduce the thrust generated to support gravity, thereby suppressing the force generated. As a result, the size of the drive system can be reduced.

For example, when a motor is used as a drive system, the amount of heat generated by the motor can be suppressed, and accuracy deterioration due to thermal expansion of constituent members, which is a problem when precision positioning is required, can be minimized. it can.

Several methods have been proposed for such a stage gravity compensation mechanism. For example, JP-A-5-5
In the device of Japanese Patent No. 7606, the Z-arm for measurement and the balance weight are connected by a steel belt via a pulley to compensate for gravity.

In the apparatus disclosed in Japanese Patent Laid-Open No. 7-115056, a tension spring is used to cancel the tension of the spring and the gravity of the moving table. Although the tension of the constant tension spring changes when the movable table reciprocates in a predetermined direction, this tension change is compensated by the tension compensating means to keep the tension of the constant tension spring constant.

Further, in the apparatus disclosed in Japanese Unexamined Patent Publication No. 2000-163130 and the apparatus disclosed in Japanese Unexamined Patent Publication No. 5-57606, the weight of the stage is compensated by using the thrust of a linear motor or an air cylinder.

[0007]

However, the conventional gravity compensating mechanism and device have the following technical problems. That is, in the counterweight method disclosed in Japanese Patent Laid-Open No. 5-57606, since the balancing weight does not have a guide mechanism, the lower shaft moves when the stage moves in the direction of gravity or while the vertical axis stage of the multi-axis constituent device is mounted. At that time, the balancing weight sways in various directions. For this reason, when performing the positioning of the stage, the swing becomes a disturbance, which causes a problem that the accurate positioning cannot be performed.

Further, in the constant tension spring system disclosed in Japanese Patent Laid-Open No. 7-115056, the tension compensating means is complicated and large, and the uneven tension cannot be eliminated at all over the movable range of the stage. In addition, the provision of compensation means adversely affects the responsiveness of the stage. In addition, the constant tension spring has an external force generated by a deformation that bulges in the direction perpendicular to the extended spring surface and an external force caused by rolling friction generated by the bearing portion that rotatably supports the rotating shaft around which the upper end of the constant tension spring is wound. This acts as a disturbance and causes a problem that the stage cannot be accurately positioned. Furthermore, there is also a problem that the fine adjustment of the tension compensating means must be performed periodically with the change of the tension of the constant tension spring with time.

Further, in the method of compensating by using the thrust force of the linear motor or the air cylinder of Japanese Patent Laid-Open No. 2000-163130, in the case of the linear motor method, in order to compensate the gravity, the thrust force is continuously output correspondingly. Due to the generated heat, thermal expansion of the constituent members occurs, and the positioning accuracy of the stage cannot be improved. In addition, in the case of the air cylinder system, there is sliding friction between the piston and cylinder, sliding friction between rod bearings, and sliding friction with sealing materials and packing materials. Thrust fluctuation of about 2% occurs and acts as a disturbance, which causes a problem that the stage cannot be accurately positioned.

Therefore, an object of the present invention is, in a vertical stage movable in the direction of gravity, in compensating for the weight of the entire stage including the object mounted on the stage. A vertical stage self-weight compensator that eliminates as much as possible, secondly suppresses heat generation from the stage drive system, and simultaneously solves the above two technical issues to obtain highly accurate stage positioning accuracy. To provide.

[0011]

In order to achieve the above object, the invention of claim 1 includes a vertical stage movable in the direction of gravity, the vertical stage and a mounted object on the vertical stage. A counterweight that balances the weight of the entire stage, a connecting member that connects the counterweight and the vertical stage, a pulley that rotatably supports the connecting member and compensates the own weight of the entire stage, and the counter. A weight compensation device for a vertical stage, which is provided with a movement direction restricting means that allows the weight to move only in the direction of gravity.

According to a second aspect of the present invention, in the vertical stage self-weight compensating device according to the first aspect, the moving direction regulating means applies a counter weight to the stationary counter weight guide and the counter weight via the counter weight guide. It is characterized by comprising a hydrostatic bearing which slidably supports in the rotational direction and the axial direction.

According to a third aspect of the present invention, in the vertical stage self-weight compensating device according to the first aspect, the moving direction restricting means comprises one or a plurality of linear motion rolling guides.

According to a fourth aspect of the invention, in the vertical stage self-weight compensating apparatus according to the first aspect, the moving direction regulating means includes one or a plurality of rectangular static pressure bearings. I am trying.

According to a fifth aspect of the present invention, in the vertical stage self-weight compensating device according to the first aspect, the pulley is fixed to a rotary shaft, and is rotatable by rotary support members provided at both ends of the rotary shaft. It is characterized by having a different structure.

[0016] According to a sixth aspect of the present invention, in the vertical stage self-weight compensating device according to the fifth aspect, the static pressure for slidably supporting the rotary shaft in the rotation direction and the axial direction as the rotation support member. It is characterized by using bearings.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 is a plan view of a vertical stage self-weight compensator according to a first embodiment of the present invention, FIG. 2 is a side view of the same, and FIG. 3 is a rear view of the same.

As shown in FIGS. 1 to 3, the vertical stage includes a Z-axis stage 1 for mounting a mounted object, a Z-axis guide 2 for guiding the Z-axis stage 1, an electric motor, a hydraulic motor, and an oil-air cylinder. It comprises a Z-axis actuator 3 such as a pressure cylinder, and a counterweight mechanism 4 for compensating the movable weight of the Z-axis.

The vertical stage is mounted on the Z-axis stage 1 on which various precision measuring devices and measuring heads 5 or machining heads of various precision machining devices are mounted so as to be movable in the direction of gravity.

In this embodiment, in order to improve the accuracy of the vertical stage, a rectangular static pressure air bearing having extremely high rigidity is adopted for the Z-axis guide 2, and the Z-axis actuator 3 has extremely high responsiveness. Adopting a high linear motor, both have realized contact and drive without contact. As a result, the disturbance generated in the guide system and the drive system is suppressed.

The counterweight mechanism 4 includes a counterweight 41, a cylindrical counterweight guide 42 provided on the fixed side for guiding the counterweight 41 in the gravity direction, and a rotary type for guiding the counterweight guide 42. Hydrostatic bearing 42a, connecting members 43a and 43b that connect counterweight 41 and Z-axis stage 1, and pulleys 44a to 44d that wind and support these connecting members 43a and 43b.
And a rotary shaft 45 on which the pulleys 44a to 44d are fixedly arranged.
a and 45b, and rotation support members 46a to 46d that support both ends of the rotation shafts 45a and 45b. Rotating shafts 45a and 45b to which the pulleys 44a to 44d are fixed
Are arranged in two rows in parallel.

FIG. 6 (A) is a horizontal sectional view of the counterweight portion in a horizontal plane, FIG. 6 (B) is an enlarged sectional view of the rotary hydrostatic bearing, and FIG. 6 (C) is a vertical sectional view of the counterweight.

The rotary hydrostatic bearing 42a is made of, for example, a porous material, and as shown in FIGS. 6 (A) to 6 (B), its outer diameter is fixed to the counter weight 41 by fitting. ing.

As shown in FIG. 6 (C), the compressed air is supplied from the intake port 41a provided in the counter weight 41.
As indicated by the arrow (B), the pressure is supplied between the inner circumference of the rotary static pressure bearing 42a and the outer circumference of the counterweight guide 42. As a result, a static pressure air film can be formed between the inner circumference of the rotary static pressure bearing 42a and the outer circumference of the counterweight guide 42, and the rotary static pressure bearing 42a has high rigidity and is in non-contact with the counterweight 41. Can be supported.

By using two or more rotary hydrostatic bearings 42a, the counter weight 41 is guided by the counter weight guide 42 and slides only in the vertical direction. That is,
The moving direction restricting means is two or more rotary hydrostatic bearings 42a that are fixed to the counterweight 41 and that slide their inner diameters with the counterweight guide 42.

The pulleys 44a to 44d are attached to rotary shafts 45a,
Pulleys 44a to 4a by fixing to 45b with a key
4d, the rotating shafts 45a and 45b are rotated, and both ends of the rotating shafts 45a and 45b are attached to the rotation supporting members 46a to 46.
It is supported by d. Rotational hydrostatic bearings are used as the rotation support members 46a to 46d.

The counterweight mechanism 4 includes two connecting members 43a and 43b, and each connecting member 43a and 43b.
Four pulleys 44a to 44d for winding b are provided in two rows. The rotary shaft 4 is provided between the pulleys 44a and 44b.
A rotary static pressure bearing 46e is provided as a rotation support member that rotatably supports 5a. Similarly, the pulley 44c and the pulley 44
A rotary hydrostatic bearing 46f is provided as a rotary support member that rotatably supports the rotary shaft 45b between the rotary static pressure bearing 46f and the rotary shaft 45b.

In the counterweight mechanism 4, the connecting members 43a and 43b can be easily removed by turning the turnbuckle 83 to the left to loosen and remove it, and then removing the upper plate 47 from the Z-axis scale 6. It has become.

As shown in FIG. 2, when a plurality of, for example, two connecting members 43a and 43b are used, the connecting member 43 is used.
The tension adjusting mechanism 8 is provided so that the tension applied to a and 43b can be equalized.

Z-axis stage 1 of connecting members 43a and 43b
Turn the right-hand thread on the external thread to be connected to the
An intermediate plate 81 is provided on the shaft stage side, male screws are attached to the intermediate plate 81 on both sides with a right screw, and a connecting screw 82 cut with a left screw is provided on the opposite side.
The turnbuckle 83 in which a right-handed thread is cut on the female thread on the side connecting a and 43b, and the left-hand thread is cut on the female thread on the side connecting the connecting thread 82 is connected.

At this time, the turnbuckle 83 has a hexagonal columnar outer shape and can be easily turned by applying a spanner. When the turnbuckle 83 is turned to the right, the connecting members 43a, 43b and the Z-axis stage 1 approach, and when turned to the left, they are separated from each other. The tension adjusting mechanism 8 can be used to adjust the tension applied to the two connecting members 43a and 43b to be equal.
Once the adjustment is completed, the right-hand screw and the left-hand screw are attached with nuts so as to have a double nut structure so as not to be loosened.

As the connecting members 43a and 43b, a stranded wire made of stainless steel is used.
Moreover, in order to extend the life of the wire, for example, a nylon coating is applied to the surface. This prolongs the service life and prevents the characteristics of the wire from changing over time.

At this time, it is necessary to take care that the material of the coating used for the wire and the material of the pulley are not the same in the sliding portion between the wire and the pulley. Here, if the same material is used, the wire coating is easily peeled off at the sliding portion, and the life of the wire is shortened. Most preferably, the pulley is made of a material having excellent slidability with respect to the material of the wire coating. Duracon (polyacetal) is used here. Avoid using nylon material such as nylon 66.

The rotary static pressure bearing 42a, which is the counterweight guide, is provided between the upper plate 47 and the lower plate 48, as shown in FIGS.
The upper plate 47 and the lower plate 48 are connected so as to be parallel to each other by a pillar 49 (in the figure, it is composed of four pieces provided at four corners) and a support bracket. By attaching the upper plate 47 to the upper portion of the Z-axis scale 6, the counterweight mechanism 4 is attached to the Z-axis scale 6.

In the counterweight mechanism 4 as described above, the counterweight 41 is restricted in its moving direction by the rotary hydrostatic bearing 42a which is a counterweight guide so as to guide it only in the gravity direction. When the Z-axis stage 1 is moved in any direction, or when the lower axis, for example, the X-axis stage 7 is moved while the Z-axis stage 1 of the multi-axis component device is mounted, the counterweight 41 moves in various directions. I try not to shake.

As shown in FIG. 2, the counter weight 41
As a counterweight guide that regulates the moving direction of
Two rotary hydrostatic bearings 42a are used. Further, at least two rotary hydrostatic bearings 42a are required in order to regulate the rotational movement of the counterweight 41 about the Z axis.

As the material of the counter weight 41,
We chose a material with a high density and used a metal such as brass or tungsten alloy.

According to the vertical stage of the first embodiment described above, in the vertical stage movable in the force direction, the counterweight that balances the weight of the entire stage including the weight of the mounted object on the stage is used. By using the counter weight, which is provided with a moving direction regulating means having a guide mechanism that is movable only in the direction of gravity, firstly, the disturbance applied at the stage positioning is eliminated as much as possible, and secondly, it occurs from the stage drive system. It becomes possible to suppress heat generation as much as possible, and by solving the above two technical problems, it becomes possible to provide a vertical stage self-weight compensator capable of obtaining highly precise positioning accuracy of the stage.

Further, since the counterweight can be guided in a non-contact manner by using two or more rotary hydrostatic bearings as a moving direction restricting means for allowing movement only in the gravity direction, the stage can be guided in a non-contact manner. It is possible to provide a vertical stage self-weight compensator capable of obtaining a highly accurate positioning accuracy of the stage, since it is possible to avoid generating a disturbance applied at the time of positioning. Further, since this rotary hydrostatic bearing can be obtained at a much lower price than a general rectangular air slider, the counterweight mechanism can be inexpensively and highly accurately configured.

Further, in the counterweight mechanism, by fixing the pulley around which the connecting member is wound and supported to the rotary shaft and supporting the rotary shaft by the rotary support members provided at both ends, the moment rigidity of the rotary shaft can be increased. The connection member can be smoothly wound. As a result, it is possible to provide a self-weight compensation device for a vertical stage that can obtain highly accurate positioning accuracy of the stage.

Further, since the rotary shaft having the pulley for supporting the connecting member wound thereon is fixed by using the rotary type hydrostatic bearings provided at both ends, the rotary shaft is rotatably supported in a non-contact manner.
It is possible to provide a self-weight compensation device for a vertical stage that can obtain high-precision positioning accuracy of the stage without causing a disturbance applied at the time of positioning the stage in the winding portion of the connecting member. .

Further, by arranging the rotary shafts, to which the pulleys for supporting the connecting member are wound, in two rows in parallel with each other at intervals, without increasing the size of the pulleys for supporting the winding.
The distance between the connecting member on the stage side and the connecting member on the counter weight side can be widened, the depth of the counter weight can be increased, and the weight of the counter weight can be increased. As a result, gravity compensation of a large stage can be achieved. It is possible to provide a vertical stage self-weight compensating device that can be performed.

Further, a pulley used for changing the direction of the connecting member for connecting the stage and the counterweight is fixed to the rotating shaft, and is supported by the rotating support members provided at both ends of the rotating shaft, whereby gravity compensation of the heavy stage is performed. In order to achieve this, a plurality of connecting members and pulleys are required in terms of strength. In addition, if the rotary shaft whose both ends are rotatably supported is also supported only at both ends, the weight of the stage and the counterweight acts on the rotary shaft in the direction of gravity, causing bending and damaging the rotary support member. Therefore, by providing a rotary support member composed of this rotary hydrostatic bearing between the pulleys located at the intermediate position of the shaft, uneven rotation support due to bending of the rotary shaft does not occur, and the weight is large. It is possible to provide a vertical stage self-weight compensation device capable of compensating for stage gravity.

Further, as a connecting member for connecting the stage and the counter weight, the life is extended and the characteristic is less changed with time, and a material different from the material of the pulley is used, so that the wear amount is reduced and the sliding property with the pulley is reduced. It becomes possible to provide a vertical stage self-weight compensator capable of obtaining highly accurate positioning accuracy of the stage by minimizing the disturbance acting on the stage.

On the other hand, in the counterweight method disclosed in Japanese Patent Laid-Open No. 5-57606, a steel belt is used as the connecting member, but this is the same as the constant tension spring in the direction perpendicular to the unwound belt surface. The external force generated by the bulging deformation acts as a disturbance, which causes a problem that the stage cannot be accurately positioned.

When a plurality of connecting members are used in terms of strength as a connecting member for connecting the stage and the counterweight in order to perform gravity compensation of a heavy stage, the tension applied to each connecting member should be equal. By providing a tension adjustment mechanism that can make the lengths of the connecting members equal,
An unbalanced force does not act during movement of the stage, and as a result, it is possible to provide a vertical stage self-weight compensator that can obtain highly accurate positioning accuracy of the stage.

On the other hand, in the counterweight method disclosed in Japanese Patent Laid-Open No. 57606/1993, although two steel belts are used, a mechanism for equalizing the tension applied to each is not specially provided. An unbalanced force acts on the stage as a disturbance, and the stage cannot be accurately positioned.

Further, when the stage weight is large, it is necessary to increase the weight of the counter weight, and by using a material having a high density for the counter weight, it is possible to reduce the occupied space including the movement of the counter weight. As a result, it is possible to provide a vertical stage self-weight compensating device capable of downsizing the entire device.

Further, since the self-weight compensator can be unitized, it becomes possible to provide a self-weight compensator for a vertical stage which can be easily attached and detached when the connecting members and the like are replaced over the life.

FIG. 4 is a side view of a vertical stage self-weight compensating apparatus according to a second embodiment of the present invention. As shown in FIG. 4, in this vertical stage, one linear motion rolling guide 42b is used as a counterweight guide for restricting the moving direction of the counterweight 41. Of course, when one linear motion rolling guide 42b is insufficient in moment rigidity due to the size of the counterweight 41 or the like, a plurality of linear motion rolling guides 42b may be used. Reference numeral 50 is a support plate that connects the upper plate 47 and the lower plate 48 in parallel, and other configurations are similar to those of the vertical stage of the first embodiment.

According to the second embodiment, one or a plurality of linear motion rolling guides are used as the moving direction restricting means for allowing the counterweight to move only in the gravity direction. Since the counterweight does not sway in directions other than the direction of gravity, it is possible to eliminate the disturbance caused thereby, and to provide a vertical stage self-weight compensator capable of obtaining highly accurate positioning accuracy of the stage. It becomes possible.

FIG. 5 is a side view of a vertical stage self-weight compensator according to a third embodiment of the present invention. As shown in FIG. 5, in this vertical stage, one rectangular static pressure bearing guide 42c is used as a counterweight guide for restricting the moving direction of the counterweight 41. Of course, when the moment rigidity is insufficient by one due to the size of the counterweight 41, a plurality of rectangular hydrostatic bearing guides 42c may be used. The rest of the configuration is similar to that of the vertical stage of the second embodiment.

According to the third embodiment, one or a plurality of rectangular static pressure bearings are used as the moving direction restricting means for allowing the counterweight to move only in the direction of gravity, so that the counterweight can be guided in a non-contact manner. Therefore, it is possible to provide a vertical stage self-weight compensation device that can obtain high-precision positioning accuracy of the stage, since it is not necessary to generate a disturbance applied during stage positioning. .

The present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the gist of the present invention.

[0055]

As described above, according to the inventions of claims 1 to 6, it is possible to simultaneously eliminate the disturbance applied at the stage positioning and suppress the heat generated from the stage drive system at the same time. Therefore, it is possible to provide a vertical stage self-weight compensator capable of obtaining highly accurate positioning accuracy of the stage.

According to the second aspect of the present invention, the rotary hydrostatic bearing can be obtained at a much lower cost than a general rectangular air slider, so that the counterweight mechanism can be manufactured at a low cost. It is possible to configure with accuracy.

According to the invention of claim 5, the moment rigidity of the rotary shaft can be increased, and the connecting member can be smoothly wound.

[Brief description of drawings]

FIG. 1 is a plan view of a vertical stage self-weight compensation device according to a first embodiment of the present invention.

FIG. 2 is a side view of the same.

FIG. 3 is a rear view of the same.

FIG. 4A is a side view of a vertical stage self-weight compensating apparatus according to a second embodiment of the present invention, and FIG. 4B is a plan view showing a portion of a moving direction restricting means used in the second embodiment. .

FIG. 5A is a side view of a vertical stage self-weight compensating apparatus according to a third embodiment of the present invention, and FIG. 5B is a plan view showing a portion of a moving direction restricting means used in the third embodiment. .

FIG. 6 (A) is a horizontal cross-sectional view of a counterweight portion taken along a horizontal plane, (B) is an enlarged cross-sectional view of a rotary hydrostatic bearing,
(C) is a longitudinal sectional view of the counterweight.

[Explanation of symbols]

1 Z-axis stage (vertical stage) 2 Z-axis guide 3 Z-axis actuator 4 Counter weight mechanism 5 measuring head 6 Z axis scale 7 X-axis stage 8 Tension adjustment mechanism 41 counter weight 42 Counter weight guide 42a Rotary hydrostatic bearing 42b Linear motion rolling guide (counterweight guide) 42c Rectangular hydrostatic bearing guide (counterweight guide) 43a, 43b Connection member 44a-44d pulley 45a-45b rotating shaft 46a-46d Rotation support member 46e, 46f Rotary hydrostatic bearing

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2F078 CA03 CB10 CB12 CB16 CC02                       CC11 CC14 CC15 CC16                 3C048 AA01 BB01 BC01 CC07 DD02                       EE06                 5F031 CA01 CA04 KA06 KA07 LA02                       LA03 LA11 MA27 MA33 PA08                       PA11 PA30                 5F046 CC05

Claims (6)

[Claims] 1. A vertical stage movable in the direction of gravity, a counterweight that balances the weight of the entire stage including the vertical stage and a mounted object on the vertical stage, the counterweight and the vertical stage. A mold stage, a pulley for supporting the coil member by winding, and a pulley for compensating the weight of the entire stage, and a moving direction restricting means for allowing the counterweight to move only in the gravity direction. Vertical stage self-weight compensation device. 2. The moving direction restricting means is composed of a fixed counter weight guide and a hydrostatic bearing for slidably supporting the counter weight in the rotational direction and the axial direction via the counter weight guide. The self-weight compensation device for a vertical stage according to claim 1, wherein: 3. The moving direction restricting means comprises one or a plurality of linear motion rolling guides.
Vertical stage self-weight compensation device described. 4. The self-weight compensator for a vertical stage according to claim 1, wherein the moving direction restricting means includes one or a plurality of rectangular static pressure bearings. 5. The self-weight compensator for a vertical stage according to claim 1, wherein the pulley is fixed to a rotary shaft and is rotatable by rotary support members provided at both ends of the rotary shaft. . 6. The self-weight compensator for a vertical stage according to claim 5, wherein a static pressure bearing for slidably supporting the rotary shaft in the rotational direction and the axial direction is used as the rotary support member. .