JPH09267236A - Positioning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothly move a table, and secure reproducibility of stable positioning by defining a piston to move a table into two pressurizing chambers by loosely fitting it in a cylinder, and controlling pressure in both pressurizing chambers by pressure adjusting parts by introducing blowout gas here. SOLUTION: In the case of positioning a table on which a workpiece or the like is placed, first of all, gas is blown out in a clearance between a piston 1 and a cylinder 2, and the piston 1 is supported in the cylinder 2 under static pressure. At this time, blowout gas is respectively flowed into two pressurizing chambers 3 and 4, and is adjusted by respective pressure adjusting parts 5 and 6 so as to become constant pressure, and the piston 1 is rested in a prescribed position. In this condition, when a pressure difference is applied to the pressurizing chambers 3 and 4 by controlling current-carrying to piezoelectric actuators 53 and 63, the piston 1 moves according to this, and the table fixed to rods 11 and 12 is moved up to a prescribed position. Positioning of the piston 1 is controlled on the basis of output of a detecting head 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning device used for measuring devices and processing devices.

[0002]

2. Description of the Related Art Conventionally, as a relatively large stroke positioning device used in various machine tools and measuring devices, there are a cylinder servo type positioning device shown in FIG. 6 and a screw feed servo type positioning device shown in FIG.

The positioning device shown in FIG. 6 comprises a table 77 movably supported on a support base 76 in a linear direction, and an air cylinder 75 for driving the table 77. The table 77 is arranged in the cylinder 72. The piston 71 is driven by the pressure difference between the two pressurizing chambers 73 divided by the piston 71, and the table 77 connected to the piston 71 by the connecting rod 74 is driven.

In the positioning device shown in FIG. 7, a ball screw nut 8 is mounted on a table 77 supported on a support base 76.
2 is attached, and the screw shaft 81 engaging with the nut 82 is rotated by the motor 83 to drive the table 77 in the linear direction.

And, the table 7 of both positioning devices
7 is equipped with a linear scale 78, and the detection head 79 detects the position of the table 77 and feeds it back to the air cylinder 75 and the motor 83 to enable predetermined positioning.

[0006]

However, in the positioning device shown in FIG. 6, since the piston 71 forming the air cylinder 75 slides inside the cylinder 72 via the seal member 80, the operating resistance and the operating reaction force. Therefore, the positioning accuracy could not be increased due to the variations in the operating resistance and the operating reaction force. For example, a resin seal member 8
In the case where the linear motion cylinder 71 having a diameter of 40 and having a diameter of 0 is used, the average sliding resistance is 1.52 N and 2σ = 0.35.
In the servo mechanism using the hydraulic pressure of 2 MPa, the repeatable positioning accuracy (2σ) is 1.2.
The positioning reproducibility was poor because it could only be about μm.

Further, the variations in the operating resistance and the operating reaction force also affect the operating speed of the piston 1 and, for example, when a smooth machining such as a laser beam machine is required, a hydraulic servo is used. In the case of processing at a speed of 3 m / min, the dimensional variation (2σ) was as large as 4.5 μm.

Further, variations in operating resistance and operating reaction force cause variations in rigidity in the thrust direction, and when used for machining feed of lathes, milling machines, etc., a wavy pattern is produced on the machined surface, resulting in high machining accuracy. There was a problem that it could not be increased.

On the other hand, the positioning device shown in FIG. 7 has improved positioning accuracy as compared with the positioning device shown in FIG. 6, but since the contact point of the nut 82 and the screw shaft 81 is point contact or line contact, vibration and rigidity are increased. When the ball screw is used, it is difficult to suppress the fluctuation of the rigidity in the thrust direction due to the variation of the ball diameter, and there is a problem that the machining accuracy and the measurement accuracy are adversely affected.

As described above, in the conventional positioning device, it has not yet been possible to obtain smooth positioning reproducibility while having high rigidity like the cylinder servo type.

Therefore, the applicant of the present invention has previously proposed that FIG.
A positioning device as shown in (b) is proposed.

In this positioning device, a piston 81 integrally formed with a table 87 is arranged in a cylinder 82 so that the table 87 is exposed to the outside through an opening 82a of the cylinder 82, and is divided by the piston 81. The pressure adjusting valves 85 and 86 that communicate with the two pressurizing chambers 83 and 84 in the cylinder 82 are provided. Further, a gas ejection hole 91 is provided in a portion of the cylinder 82 that faces the side surface of the piston 81.
A linear scale 88 is provided on the other side surface of the cylinder, and a detection head 89 is provided on the wall surface of the cylinder 82 that faces the linear scale 88 to form a position encoder 90 so that the position of the piston 81 can be detected.

Then, gas is ejected from the gas ejection hole 91 into the gap between the piston 81 and the cylinder 82 to support the piston 81 in the silidan 82 under static pressure, and the ejected gas flows into the pressurizing chambers 83 and 84. The increase in pressure is adjusted to a constant pressure by the pressure adjusting valves 85 and 86. Then, the pressure adjusting valves 85, 86
If a pressure difference is created between the pressurizing chambers 83 and 84 by the, the piston 81 moves according to this pressure difference, so that the piston 81
The table 87 formed integrally with the table 87 can be moved to a predetermined position.

As described above, since the positioning device as shown in FIGS. 8A and 8B has the cylinder servo type mechanism, the rigidity in the thrust direction can be increased, and
Since the piston 81 is supported by static pressure, the operation resistance and the reaction reaction force are small, and since there is no sliding or bending portion, there is no change over time, so a positioning device with a long service life and stable positioning reproducibility is provided. be able to.

However, in the positioning device shown in FIGS. 8 (a) and 8 (b), when the effective stroke of the table 87 becomes long, the length of the piston 81 is reduced in order to reduce gas leakage from the opening 82a of the cylinder 82. Therefore, there is a problem that the entire device becomes large. For example, when the length of the table 87 is 100 mm and the effective stroke is 100 mm, the length of the piston 81 needs to be 200 mm or more, and the piston 81 is movable in the cylinder 82 by the effective stroke. The cylinder 82
Had to have a total length of 300 mm or more.

The opening 82a of the cylinder 82 must be opened by the length of the table 87 and its effective stroke, and a large amount of gas is discharged from this opening 82a, so that the positioning device is driven. It was difficult to reduce the amount of gas consumption required for the.

[0017]

SUMMARY OF THE INVENTION In view of the above problems, therefore, the present invention connects a table on which an object to be processed or a measuring device is placed to a rod protruding from a piston, and allows the piston to be loosely fitted in a cylinder. Each of the two pressurizing chambers in the cylinder divided by the piston is provided with a pressure adjusting portion, and gas is jetted into the gap between the piston and the cylinder to support the piston under static pressure. The positioning device is configured to drive the piston and the table by introducing the jetted gas into the two pressurizing chambers and controlling the pressure in both pressurizing chambers by the pressure adjusting section.

Further, according to the present invention, a table on which an object to be processed or a measuring instrument is placed is connected to a rod projecting from a piston, and the piston is loosely fitted in a cylinder so as to be movable and divided by the piston. Each of the two pressurizing chambers in the cylinder is equipped with a pressure adjusting portion, and gas is jetted into the gap between the rod of the piston and the rod bearing portion formed in the cylinder to support the rod under static pressure. Is introduced into the two pressurizing chambers, and the pressures in both pressurizing chambers are controlled by the pressure adjusting section to drive the piston and the table, thereby forming a positioning device.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

FIG. 1 is a perspective view showing an embodiment of a positioning device according to the present invention, and FIG. 2 is a transverse sectional view of FIG. 1, in which a piston 1 is loosely fitted in a cylinder 2 to be movable, The two pressurizing chambers 3 and 4 in the cylinder 2 divided by the piston 1 are provided with pressure adjusting portions 5 and 6, respectively. Further, the piston 1 penetrates the wall surface of the cylinder 2
A pair of rods 11 and 12 is provided, and a table 7 arranged on the upper portion of the cylinder 2 is integrally fixed to the rods 11 and 12. The piston 1 is hollow to reduce the weight.

Further, on one wall surface of the cylinder 2 facing the side surface of the piston 1, a gas ejection hole 13 for ejecting gas is provided in a gap between the piston 1 and the cylinder 2, and the other wall surface of the cylinder 2 is provided. Is equipped with a detection head 9, and a linear scale 8 is installed on the side of the piston 1 facing the detection head 9.
Is provided to form the position encoder 10, and the position of the piston 1 is detected.

The pressure adjusting portions 5 and 6 are nozzles 51 and 61 communicating with the pressurizing chambers 3 and 4, and pressure adjusting plates 52 and 6 as pressure adjusting bodies arranged on the ejection side of the nozzles 51 and 61.
2 and the nozzles 5 by driving the pressure adjusting plates 52 and 62.
₁ and 61 are provided with piezoelectric actuators 53 and 63 for varying the distances d ₁ and d _2, and pressure supply holes 5 for supplying gas around the nozzles 51 and 61.
4 and 64, and discharge holes 55 and 65 for releasing these supplied gases. However, each of the piezoelectric actuators 53 and 63 has a structure in which a large number of piezoelectric elements are laminated, and is configured to be slightly expanded and contracted in the laminating direction (arrow) when a voltage is applied.

Therefore, in the pressure adjusting parts 5 and 6, the gas in the pressurizing chambers 3 and 4 is ejected from the nozzles 51 and 61, and is combined with the gas from the pressure supply holes 54 and 64 to form the pressure adjusting plate 5.
It is discharged from the discharge holes 55 and 65 while receiving resistance due to 2 and 62. And the piezoelectric actuator 5
Nozzles 51, 61 and pressure adjusting plate 5 by extending 3, 63
If the distances d ₁ and d ₂ from ₂ , 62 are reduced, the nozzle 5
Since the opening degree of 1 and 61 becomes small, the resistance to gas ejection becomes large, and the pressure in the pressurizing chambers 3 and 4 can be made high. On the contrary, when the piezoelectric actuators 53 and 63 are contracted to increase the distance. , The opening degree of the nozzles 51 and 61 is increased, and thus the resistance to gas ejection is reduced,
It is possible to control the pressure in the pressurizing chambers 3 and 4 by controlling the energization of the piezoelectric actuators 53 and 63 to drive the expansion and contraction so that the pressures in the pressurizing chambers 3 and 4 can be lowered. it can. Although not shown, in order to improve the linearity of the piezoelectric actuators 53 and 63,
A preload may be applied in the contraction direction of the piezoelectric actuators 53 and 63 using a spring or the like.

Next, the operation of the positioning device of the present invention will be described. First, gas is jetted from the gas supply hole 13 into the gap between the piston 1 and the cylinder 2 to move the piston 1 into the cylinder 2
Support static pressure inside. This ejected gas has two pressure chambers 3,
Each of the pressure adjusting parts 5 and 6 is adjusted so as to have a constant pressure. Then, if energization of the piezoelectric actuators 53 and 63 of the pressure adjusting units 5 and 6 is controlled to create a pressure difference between the pressurizing chambers 3 and 4, the piston 1 moves according to the pressure difference, and thus the piston 1 The table 7 fixed to the rods 11 and 12 can be moved to a predetermined position.

At this time, as for positioning of the piston 1, a signal generated from the detection head 9 forming the position encoder 10 is used as absolute position information by the position counter 21 as shown in FIG. In comparison, the servo amplifier 23 controls the power supply from the DC power supply 24 to the piezoelectric actuators 53 and 63. Then, if the positioning information of the position counter 21 and the input pulse counter 22 are in the same range or there is a difference between the two, the piston 1 can be stopped and positioned in the same way as the energization of the piezoelectric actuators 53 and 63.

In this state, when the piston 1 starts to move to the one pressurizing chamber 3 side for some reason, a signal is sent from the detection head 9 and the differential pressure of the position counter 21 becomes negative, and the pressurizing chamber 3 becomes negative. Since the piezoelectric actuator 53 of the pressure adjusting section 5 is driven so as to increase the pressure on the 3 side, the piston 1 can be positioned at the set position, and conversely, the piston 1
When is moved to the pressurizing chamber 4 side, the piezoelectric actuator 63 of the pressure adjusting section 6 is driven so as to increase the pressure on the pressurizing chamber 4 side, and the piston 1 is automatically followed (servo) so that it is always at the set position. become. The servo amplifier 23 is an amplifier including follow-up response elements (proportional P, integral I, differential D), and is used to increase the voltage of the position counter 21 for driving the voltage-operated piezoelectric actuators 53 and 63. is there.

As described above, since the positioning device according to the present invention has the cylinder servo type mechanism, the axial rigidity can be increased to 10 kg / μm or more. Also,
Since the piston 1 has a structure to support the static pressure inside the cylinder 2, the operation resistance and the reaction reaction force are extremely small, and since there is no sliding or bending portion, there is no change with time, so that the table 7 moves smoothly. Can be done,
Excellent positioning repeatability (repeatability) over a long period of time
Is obtained.

Further, since the table 7 is provided on the rods 11 and 12 projecting from the piston 1, the length of the entire positioning device is equal to the length of the table 7 and the length of the effective stroke. Can be compactly assembled. Moreover, FIGS. 8 (a) and 8 (b)
Since the area of the table 7 can be made larger than that of the positioning device shown in (1), it can be suitably used as a positioning device that constitutes a table such as a milling machine.

Further, since there is no large opening 82a unlike the positioning device shown in FIGS. 8A and 8B, the consumption of gas used to drive the positioning device can be greatly suppressed. Very economical.

Further, in the positioning device according to the present invention, the pressure adjusting portions 5 and 6 are used as the nozzles 51 and 61 and the pressure adjusting plates 52 and 62 as the pressure adjusting bodies and the piezoelectric actuators 53 and 63.
Because of the above structure, the structure can be simplified and downsized as compared with the pressure adjusting valve using a diaphragm that has been conventionally used. Moreover, the nozzles 51 and 6
1 to increase the diameter to increase the amount of discharge,
Since the operating speed of the piston 1 can be further increased by increasing the pressure of the jetted gas supplied to the nozzles 4 and 64, the table 7 can be positioned at high speed.

Therefore, when the positioning device according to the present invention is used as a measuring device, the object to be measured or the measuring device can be moved smoothly, so that erroneous measurement due to rattling of the table 7 is prevented and accurate measurement is performed. Can be possible,
When used as a processing device, it absorbs vibration due to shocks and prevents wavy patterns from forming on the finished surface of the work piece, allowing for a smooth surface to be finished. Furthermore, processing can be performed while measuring the load capacity. it can.

The piston 1, the cylinder 2, the table 7, the pressure adjusting plate 52, which constitutes the positioning device of the present invention,
Materials such as 62 may be stainless steel that is lightweight and can be processed with relatively high accuracy, or aluminum that has been anodized, and is more preferably light and can be processed with high accuracy, and that has high rigidity and low thermal expansion coefficient. Having, alumina,
It is preferable to use ceramics such as zirconia, silicon carbide, and silicon nitride.

In the positioning device shown in FIGS. 1 and 2, the piston 1 has a quadrangular cross-sectional shape, but any cross-section having a shape such that the table 7 does not rotate when the piston 1 moves. It may have a shape.

Next, another embodiment of the positioning device according to the present invention will be described with reference to FIGS.

The positioning apparatus shown in FIG. 4 not only supports the piston 1 by static pressure as in the positioning apparatus shown in FIGS. 1 and 2, but also a rod bearing portion 211 formed on the wall surface of the cylinder 2.
In addition to engraving static pressure grooves 211a and 212a in 212, gas supply holes 14 and 15 for ejecting gas to the side surfaces of rods 11 and 12 are provided.
1 and 12 are supported by static pressure.

Thus, not only the piston 1 but also the rod 1
By supporting static pressures 1 and 12 as well, the rigidity in the thrust direction and the radial direction can be further improved. Therefore, even if a heavy object is placed at a position deviated from the center position of the table 7, it is No problems such as pitching occur.

In the positioning device shown in FIG. 3, instead of ejecting gas from the gas supply hole 13 provided in the wall surface of the cylinder 2 into the gap between the piston 1 and the cylinder 2 as in the positioning device shown in FIGS. , A gas ejection port 1a is provided on the side surface of the piston 1, and a gas supply hole 13 for supplying ejection gas to the gas ejection port 1a is provided in the piston 1
It is bored in one of the rods 11, and the compressed gas is supplied from the gas supply hole 13 so that the cavity 1b in the piston 1 is formed.
Gas is ejected from the gas ejection port 1a into the gap between the piston 1 and the cylinder 2 via the, to support the piston 1 in the cylinder 2 under static pressure.

In the positioning device shown in FIGS. 5A and 5B, instead of ejecting gas into the gap between the piston 1 and the cylinder 2 to support the piston 1 under static pressure, a rod formed on the wall surface of the cylinder 2 is used. Hydrostatic grooves 211 on the bearings 211, 212
a and 212a are engraved, and gas supply holes 14 and 15 for ejecting gas to the side surfaces of the rods 11 and 12 are provided so that only the rods 11 and 12 are statically supported. At this time, the piston 1 divides the inside of the cylinder 2 into two pressurizing chambers 3 and 4, and performs only the function as a seal member. Further, the position encoder 10 is configured such that the linear scale 8 is provided on the back surface of the table 7 and the detection head 9 is provided on the surface of the cylinder 2 facing the linear scale 8.
The position of is directly detected.

In this positioning device, the gas supply hole 14,
The rods 11 and 12 are statically supported by jetting gas from the side surfaces of the rods 11 and 12 from 15 and the jetted gases are taken into the pressurizing chambers 3 and 4 in the cylinder 2 divided by the piston 1, respectively. The pressure adjusting units 5 and 6 adjust the pressure to a constant pressure. Therefore, by controlling the energization to the piezoelectric actuators 53 and 63 provided in the pressure adjusting units 5 and 6,
The table 7 formed integrally with the piston 1 can be positioned with high accuracy.

In particular, this positioning device is suitable as a positioning device that requires a large stroke with a small table 7.

[0041]

As described above, according to the present invention, the table on which the object to be machined, the measuring instrument, etc. is mounted is connected to the rod protruding from the piston, and the piston is loosely fitted in the cylinder to move. Each of the two pressurizing chambers in the cylinder divided by the piston is provided with a pressure adjusting portion, and gas is jetted into the gap between the piston and the cylinder to support the piston at a static pressure. Is introduced into the two pressurizing chambers, and the positioning device is configured to drive the piston and the table by controlling the pressures in the two pressurizing chambers with the pressure adjusting section. Has high rigidity and extremely low motion resistance and motion reaction force, and since there are no sliding or bending parts, there is no deterioration over time, and excellent positioning reproduction over a long period of time. It can be obtained (repeatability).

Since the table is provided on the rod protruding from the piston, the positioning device itself can be compactly assembled. Moreover, since the table area can be increased, it is suitable as a positioning device that constitutes a table such as a milling machine.

Moreover, it is very economical because it consumes less gas to drive the positioning device.

Therefore, when the positioning device according to the present invention is used as a measuring device, the object to be measured or the measuring device can be moved smoothly, so that erroneous measurement due to rattling of the table can be prevented and accurate measurement can be performed. If it is used as a processing device, it is possible to prevent the vibration due to impact from being absorbed and prevent a wavy pattern from being formed on the finished surface of the workpiece.
Can be finished on a smooth surface.

Further, according to the present invention, a table on which an object to be machined, a measuring instrument or the like is placed is connected to a rod protruding from the piston, and the piston is loosely fitted in the cylinder to be movable. Each of the two pressurizing chambers in the divided cylinder is provided with a pressure adjusting portion, and gas is jetted into the gap between the rod of the piston and the rod bearing portion formed in the cylinder to support the rod under static pressure, and the jetting is performed. By introducing the gas into the two pressurizing chambers and controlling the pressures in both pressurizing chambers by the pressure adjusting section to drive the piston and the table, the positioning device is configured so that a large table can be obtained. It can be suitably used as a positioning device that requires a stroke.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a positioning device according to the present invention.

FIG. 2 is a cross-sectional view of FIG.

FIG. 3 is a diagram for explaining a control method of the positioning device according to the present invention.

FIG. 4 is a cross-sectional view showing another embodiment of the positioning device according to the present invention.

5A and 5B are views showing another embodiment of the positioning device according to the present invention, in which FIG. 5A is a cross-sectional view and FIG. 5B is a side view.

FIG. 6 is a partially cutaway plan view of a conventional positioning device.

FIG. 7 is a partially cutaway plan view of a conventional positioning device.

FIG. 8 is a diagram showing the previously proposed positioning device,
(A) is a perspective view, (b) is a cross-sectional view.

[Explanation of symbols]

1 ... Piston, 2 ... Cylinder, 3, 4 ...
・ Pressurizing chambers 5, 6 ... Pressure adjusting unit, 7 ... Table, 8 ... Linear scale, 9 ... Detection head,
10 ・ ・ ・ Position encoder, 11, 12 ・ ・ ・ Rod, 13
... Gas supply holes

Claims (2)

[Claims] 1. A table on which an object to be processed, a measuring instrument, etc. is placed is connected to a rod protruding from a piston, and
The piston is loosely fitted in the cylinder to be movable,
Each of the two pressurizing chambers in the cylinder divided by the piston is provided with a pressure adjusting portion, and gas is jetted into the gap between the piston and the cylinder to support the piston at a static pressure. A positioning device characterized in that the piston and the table are driven by being introduced into the pressurizing chambers and controlling the pressure in both pressurizing chambers by the pressure adjusting section. 2. A table on which an object to be processed, a measuring instrument, etc. is mounted is connected to a rod protruding from a piston, and
The piston is loosely fitted in the cylinder to be movable,
Each of the two pressurizing chambers in the cylinder divided by the piston is provided with a pressure adjusting portion, and gas is ejected into the gap between the rod of the piston and the rod bearing portion formed in the cylinder to support the rod under static pressure. At the same time, the ejecting gas is introduced into the two pressurizing chambers, and the piston and the table are driven by controlling the pressures in the two pressurizing chambers with the pressure adjusting section.