JP2004301138A - Hydraulic actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic actuator capable of controlling a position of a driven part by one servo valve. <P>SOLUTION: This hydraulic actuator comprises a piston body 50 having a piston head 51 stored slidably in a hydraulic cylinder 10 in a non-contact condition through a hydrostatic bearing, a passage part 12 for supplying fluid having fixed pressure P into a pressure chamber on one side having the piston head arranged between both pressure chambers in the hydraulic cylinder and controlling and supplying pressure P1 of fluid through a servo valve into the pressure chamber on the other side, a first pressure sensor 15 and a second pressure sensor 16 for detecting pressure of the pressure chamber on one side and the pressure chamber on the other side, and a position sensor 41 for detecting a position of the piston body. There is difference between pressure receive area S of the piston head in the pressure chamber on one side and pressure receive area S1 of the piston head in the pressure chamber on the other side. A controller 1 receives each detection signal from the second pressure sensor and the position sensor as feedback value to control a position of the piston body. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hydraulic actuator suitable for a positioning device.
[0002]
[Prior art]
As an application example of a positioning device having a positioning function in one axis direction, for example, the Z-axis direction, there is, for example, a chip mounter. This will be described with reference to FIG.
[0003]
In FIG. 6, the chip mounter is composed of a Z-axis feeder 100 and a holder supporting device 200 driven up and down by the Z-axis feeder 100. In the Z-axis feeder 100, a servomotor 102 is installed on an apparatus frame 101, and the servomotor 102 drives a ball screw mechanism 103 extending in a vertical direction. The ball screw mechanism 103 has a slider 104, and the slider 104 is guided by a guide rail 105 provided on the apparatus frame 101.
[0004]
The holder supporting device 200 is attached to the ball screw mechanism 103 on the side opposite to the slider 104 via a holder bracket 201. The holder support device 200 has an air cylinder 202, and a tool holder 203 is arranged in the air cylinder 202 via a static pressure air bearing 204 so as to be vertically movable. In other words, the static pressure air bearing 204 uniformly disperses the compressed air supplied from the hole 205 provided in the air cylinder 202 with the porous body, and supports the lower portion of the tool holder 203 in a non-contact state.
[0005]
Further, the vertical movement of the tool holder 203 is controlled by the differential pressure between the compressed air supplied from the pressurizing port 206 and the balance pressure port 207 opened to the air cylinder 202. A tool 209 for holding the chip 300 is attached to the lower end of the tool holder 203.
[0006]
The substrate 401 on which the chip 300 is to be mounted is mounted on the substrate holding stage 400. The air cylinder 202 is provided with a position detector 210 for detecting the moving height, and is used for feedback control of the height position (for example, see Patent Document 1).
[0007]
The above device requires two driving mechanisms, a Z-axis feeder 100 using a ball screw mechanism 103 and a holder supporting device 200 using an air cylinder 203, in order to enable precise positioning.
[0008]
As the positioning device in the Z-axis direction, a device combining a feed mechanism (such as a ball screw) with a servomotor as a linear motion mechanism as described above, or a device combining a pneumatic cylinder or a linear motor is known.
[0009]
[Patent Document 1]
JP-A-2000-353725 (page 3, FIG. 1)
[0010]
[Problems to be solved by the invention]
By the way, in conventional actuators for a positioning device using a pneumatic cylinder, it is common to supply compressed air at a controlled pressure to each of two pressure chambers via a servo valve. Was needed.
[0011]
In addition, in addition to the above-described linear motion mechanism, there is a case where it is required that the movable portion has a rotary motion function. If the rotary motion mechanism is added to the linear motion mechanism to satisfy such demands, there is a problem that the device becomes complicated and large.
[0012]
Therefore, an object of the present invention is to provide a fluid pressure actuator capable of controlling the position of a piston body, that is, a driven portion with one servo valve.
[0013]
Another object of the present invention is to realize a fluid pressure actuator capable of giving a linear motion and a rotary motion to a driven portion with a simple structure.
[0014]
Still another object of the present invention is to provide a fluid pressure actuator capable of performing load control (force control) in addition to the linear motion position control.
[0015]
[Means for Solving the Problems]
According to the present invention, a hydraulic cylinder, a piston body having a piston head slidably housed in a non-contact state in the hydraulic cylinder, and the piston head in the hydraulic cylinder between the piston body A fluid circuit for supplying a fluid at a constant pressure P to the other pressure chamber and controlling and supplying a fluid pressure P1 to the other pressure chamber via a servo valve; the one pressure chamber and the other pressure; First and second pressure sensors for detecting the pressure of the chamber, and a position sensor for detecting the position of the piston body, wherein the pressure receiving area S of the piston head in the one pressure chamber and the other A difference between the pressure chamber and the pressure receiving area S1 of the piston head in the pressure chamber, receiving the detection signals from the first and second pressure sensors and the position sensor as feedback values, Hydraulic actuator, characterized in that it comprises a control means for controlling the position of the piston is provided.
[0016]
In the present fluid pressure actuator, the piston body has a rod extending in the axial direction from the piston head, supports the rod in a slidable state in the axial direction, and rotates the rod together with the piston head. In the case where the position sensor is further provided, the position sensor is configured on an axial extension line passing through the center of gravity of the piston body.
[0017]
In this fluid pressure actuator, the rotary drive mechanism further includes a cylindrical guide flange rotatably supported via a bearing on the fluid pressure cylinder side, and the guide flange has a through hole having a polygonal cross section. The rod having the same cross-sectional shape is inserted through the through hole, and the guide flange is also configured to receive a rotational driving force from a rotational driving source.
[0018]
In the fluid pressure actuator, the piston body is further housed in the fluid pressure cylinder via a static pressure bearing, and the static pressure bearing is provided on an outer periphery of an axial end of the piston head in a circumferential direction. A plurality of grooves are formed at intervals, and fluid is introduced into the grooves from the one pressure chamber and the other pressure chamber to act on the inner wall of the fluid pressure cylinder.
[0019]
In the present fluid pressure actuator, a hole extending in the axial extension direction away from the other pressure chamber is provided on the axial extension line of a portion of the fluid pressure cylinder facing the other pressure chamber side. On the other hand, on the axial extension line of the piston head facing the other pressure chamber side, a rod for position detection extends in the axial extension line direction and is inserted into the hole. And a sensor for detecting the amount of movement of the rod is fixed to the hole so that the rod for position detection is inserted through the hole for detecting the position of the piston body. The position sensor is configured.
[0020]
In the present fluid pressure actuator, further, the control means receives each detection signal from the first and second pressure sensors and the position sensor as a feedback value, and supplies the feedback signal to the rod of the piston body via the servo valve. Position control and load control of the driven parts to be combined can be performed.
[0021]
The fluid pressure actuator further includes a rotation angle sensor for detecting a rotation angle of a rotation portion including the guide flange, and the control unit further performs a rotation angle control using a detection signal from the rotation angle sensor. It can be carried out.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of a fluid pressure actuator according to the present invention will be described with reference to FIGS. FIG. 1 shows a cross-sectional structure of a fluid pressure actuator according to the present invention using compressed air as a fluid, and shows a form having not only a linear motion but also a rotary motion function of a movable portion.
[0023]
In FIG. 1, the present actuator includes a cylinder 10, a piston body 50, and a servo valve 60 that supplies and exhausts compressed air to and from the cylinder 10. The cylinder 10 forms a space for accommodating the piston head 51 of the piston body 50, that is, a cylinder body 11 for forming a pressure chamber on both sides of the piston head 51, and an air passage for introducing compressed air into the pressure chamber. And a cylindrical guide flange 13 for forming the pressure chamber between the piston body 50 and the cylinder body 11 on the rod 52 side of the piston body 50. Here, the passage portion 12 forms a part of the cylinder 10.
[0024]
The passage section 12 includes an air introduction section 12-1 having a passage for introducing compressed air, an air passage of the air introduction section 12-1, an air inlet and an air outlet to the servo valve 60, and a cylinder body 11. And a passage main body 12-2 having a passage communicating with each of the two pressure chambers. A servo valve 60 is installed and fixed in the passage section 12. More specifically, the passage main body 12-2 directly introduces air of a constant pressure introduced in communication with the passage of the air introduction part 12-1 into a pressure chamber on the right side in the figure of the cylinder main body 11 and a servo valve. A passage 12-2a for introducing the air into the air inlet of the servo valve 60 and a passage 12-2 for receiving the air having the adjusted pressure or flow rate from the air outlet of the servo valve 60 and introducing the air into the pressure chamber on the left side in the figure of the cylinder body 11. -2b. Hereinafter, the right pressure chamber in the figure is referred to as a constant pressure chamber (one pressure chamber), and the left pressure chamber is referred to as a regulated pressure chamber (the other pressure chamber).
[0025]
The cylinder body 11 has a space having a circular cross section, and a piston head 51 having a circular cross section is inserted into this space. On the other hand, the guide flange 13 has a hole having a polygonal cross section (a square shape in this case), and a rod 52 having the same square cross section is slidably inserted in the axial direction.
[0026]
In particular, the guide flange 13 is restrained from moving in the direction of the central axis, but is held by the ball bearing 30 in the air introducing portion 12-1 so as to be rotatable about the central axis. That is, the air introduction part 12-1 has not only a passage for air introduction but also an annular part capable of accommodating the guide flange 13. Thus, the rod 52 is configured to be slidable in the axial direction with respect to the guide flange 13 and to rotate together with the rotation of the guide flange 13. The guide flange 13 has a boss protruding from the annular portion of the air introduction portion 12-1, and a gear 17 is fixed to the boss. The gear 17 is rotationally driven by a rotational drive source such as a servo motor (not shown).
[0027]
FIG. 1 shows a state in which the piston body 50 has moved to the rightmost side in the figure, that is, to the bottom dead center.
[0028]
A hole 11a is formed in a portion of the cylinder body 11 opposite to the guide flange 13 in the center axis direction. The hole 11a is fixed to the center of the piston head 51 and extends in the center axis direction. In addition, a sensor unit 41-2 for detecting the position of the piston body 50 is fixed together with the position sensor rod 41-1. Since the position sensor 41 including the position sensor rod 41-1 and the sensor unit 41-2 is well known, the position sensor rod 41-1 has a magnetic material and a non-magnetic material at a constant pitch. And are alternately arranged. When the position sensor rod 41-1 moves in the central axis direction together with the piston body 50, the number of moved magnetic bodies is detected by the sensor unit 41-2. Using this detection signal, the movement amount or position of the piston body 50 is detected. The position sensor rod 41-1 is slidable in the central axis direction with respect to the sensor unit 41-2, and is rotatable together with the piston body 50.
[0029]
A connector 43 is provided on the cylinder body 11 in order to lead a detection signal from the sensor section 41-2 to the outside of the cylinder body 11 via a conductive wire (not shown). In this embodiment, in particular, the sensor fixing piece 42 is provided inside the hole 11a and outside the sensor section 41-2. The sensor fixing piece 42 is for sealing the pressure in the adjustment pressure chamber. That is, since the inside of the hole 11a has the same pressure as that of the adjustment pressure chamber, in order to lead the conducting wire to the outside of the cylinder body 11 through the passage communicating with the hole 11a, air leakage does not occur at the installation portion of the connector 43. A special sealing structure is required. On the other hand, in the present embodiment, by installing the sensor fixing piece 42, the sealing of a space outside the sensor fixing piece 42 can be simplified.
[0030]
Referring to FIG. 5, sensor fixing piece 42 is an annular body having a hole at the center for inserting position sensor rod 41-1 and has constricted portion 42-1 around the hole. The sensor fixing piece 42 is made of a resin material, and has a centering function by having a constricted portion 42-1. That is, even if the position sensor rod 41-1 rotates with a slight rattling, the rod is deformed in accordance with the rattling to absorb the rattling. Further, by providing a surface squeeze on the high pressure side of the inner diameter surface of the hole of the sensor fixing piece 42, it is prevented from contacting the position sensor rod 41-1. As shown in FIG. 5B, the surface squeezing is formed so as to extend in the axial direction at a high pressure side, here the right half side, of the inner diameter surface of the hole of the sensor fixing piece 42 with a circumferential interval therebetween. This is an inner diameter surface having a shallow groove 42a. When a plurality of such shallow grooves 42a are provided, the compressed air from the adjustment pressure chamber acts to allow the inner diameter portion of the sensor fixing piece 42 to function as a static pressure air bearing portion, thereby obtaining a certain degree of rigidity and holding force. Thus, even if the position sensor rod 41-1 slightly shakes, the sensor fixing piece 42 does not contact the position sensor rod 41-1. In addition, due to the rigidity of the static pressure bearing portion, the constricted portion 42-1 is slightly deformed, so that the contact with the position sensor rod 41-1 is further reduced.
[0031]
The cylinder body 11 is also provided with a pressure sensor (second pressure sensor) 15 for detecting the pressure in the adjustment pressure chamber through a hole 11b communicating with the adjustment pressure chamber. The cylinder main body 11 is further provided with an auxiliary wall member 18 at the lower side in the figure, and the auxiliary wall member 18 is formed with a passage 18a (only a part is shown) communicating with the constant pressure chamber and at the outlet side. Is provided with a pressure sensor (first pressure sensor) 16 for detecting the pressure of the constant pressure chamber. 19 is an O-ring for sealing.
[0032]
Further, in the actuator according to the present embodiment, as shown in FIG. 3, shallow grooves 51a and 51b for introducing compressed air from the adjustment pressure chamber and the constant pressure chamber, respectively, are formed on the outer periphery of both ends of the piston head 51. A static pressure air bearing portion is formed at intervals in the direction and floats the piston head 51 from the inner wall surface of the cylinder body 11. In other words, the static pressure air bearing portion causes the piston head 51 to float from the inner wall of the cylinder body 11 by causing the compressed air introduced from the adjustment pressure chamber and the constant pressure chamber to act on the inner wall of the cylinder body 11, and the non-contact state. To enable sliding movement and rotation. Although not shown in FIG. 1, exhaust grooves 51 c and 51 d for exhausting air acting on the inner wall of the cylinder body 11 to the outside are provided on the outer periphery of the piston head 51 near the static pressure air bearing portion, respectively. The compressed air formed over the entire circumference and collected by the exhaust grooves 51c and 51d is discharged from the end of the rod 52 to the outside of the actuator through an exhaust passage 51e formed inside the piston body 50. That is, a driven portion (not shown) is provided at the end of the rod 52, and a connector for an air pipe that can discharge compressed air even when the rod 52 is rotating is connected.
[0033]
Note that the position sensor 41 needs to be configured on an axial extension line passing through the center of gravity of the piston body 50. On the other hand, in the present embodiment, it is assumed that the center of gravity of the piston body 50 is located on the center axis thereof. Therefore, the position sensor rod 41-1 is also on the axial extension line passing through the center of gravity of the piston body 50, that is, the piston body 50 It is installed so as to be on the center axis of 50 and at its rotation center. Thus, the position sensor 41 can be configured by the rotating position sensor rod 41-1 and the fixed sensor unit 41-2 combined therewith.
[0034]
The actuator according to the present embodiment described above has the following features.
[0035]
1) By introducing air at a constant pressure from a compressed air supply source (not shown) directly into the constant pressure chamber of the cylinder body 11, and introducing air at a regulated pressure or flow rate through the servo valve 60 into the regulated pressure chamber. Only one servo valve for position control or load control described later is required.
[0036]
2) The piston head 51 is floated from the inner wall of the cylinder body 11 by the static pressure air bearing portion.
[0037]
3) The piston body 50 is made rotatable by the rotation of the guide flange 13 using a servo motor or the like as a rotation drive source.
[0038]
That is, a plurality of hydrostatic air bearings are provided around the piston head 51 having a circular cross section in the piston body 50, so that the piston body 50 can linearly move without frictional resistance. As a control system of the piston body 50, as shown in FIG. 4, a position feedback system by the position sensor 41 including the position sensor rod 41-1 and the sensor unit 41-2, and a pressure feedback system by the pressure sensors 15 and 16 are formed. . The controller 1 receives a position command value and a load command value, and receives a detection signal from each of the sensors to perform fluid control to the adjustment pressure chamber by the servo valve 60, thereby achieving high-precision positioning of the piston body 50, Perform load control. As is well known, the servo valve 60 has a built-in spool position sensor for detecting the position of the spool, and at the time of positioning control, the controller 1 also uses the signal from the spool position sensor to control the servo valve. 60 is controlled.
[0039]
The rod 52 of the piston body 50 has a rectangular cross section so as not to rotate with respect to the guide flange 13, while the guide flange 13 is rotatable via the ball bearing 30 so that the rod 52 is integrated. You can rotate to. When the guide flange 13 is rotated by a servomotor, a high-precision rotation angle control is performed by configuring a feedback system that detects the rotation angle by a rotary encoder attached to the servomotor and outputs the detected rotation angle to the controller 1. Is Of course, another known rotation angle sensor may be used as the sensor for detecting the rotation angle.
[0040]
The load control means that the pressure receiving area of the piston head 51 facing the adjustment pressure chamber is S1, the pressure acting on it is P1, and the pressure receiving area of the piston head 51 facing the constant pressure chamber is S (where S1 > S), and assuming that the pressure acting thereon is P (however, P> P1), a load is applied to the driven portion provided at the end of the rod 52 based on the load F = P1 · S1−PS · S. This is control for applying a load (force) based on a command value.
[0041]
The controller 1 can switch between position control and load control of the piston body 50 as described above. Needless to say, this switching is performed when only the position control is performed and when only the load control is performed. In addition, during the control, for example, after the piston body 50, that is, the driven portion is positioned at a predetermined position by the position control, the load is changed. The control includes switching to control to apply a predetermined load (force) to the driven portion.
[0042]
The present actuator may be used horizontally as shown in FIG. 1 or vertically. When used vertically, this actuator is used as a Z-axis (vertical direction) and a rotary drive mechanism. By assembling a chuck mechanism or the like to the driven portion, a moving object such as an IC component can be moved up and down at a high speed, and the moving object can be positioned with high accuracy. In addition, a load (force) can be applied to the moving object with high accuracy, and the rotation angle of the moving object around the Z axis can be positioned with high accuracy.
[0043]
In addition, as the bearing of the guide flange 13, instead of the ball bearing 30, the same static pressure air bearing as the rod 51 side or a slide bearing may be used.
[0044]
In addition, as an application field of the actuator according to the present invention, the actuator according to the present invention can be used in general bio-related devices and transfer devices using a drive mechanism using a ball screw or a fluid pressure cylinder. used. Further, it goes without saying that the actuator according to the present invention is not limited to the actuator using compressed air, but can be applied to an actuator using another gas. The structure of the cylinder shown in FIG. 1 is merely an example, and the cylinder body 11 may be formed of a single member instead of a plurality of members.
[0045]
【The invention's effect】
According to the present invention, it is possible to provide a fluid pressure actuator capable of controlling the position of a driven portion with one servo valve. Further, a fluid pressure actuator capable of giving a linear motion and a rotational motion to a driven portion by combining a rotary drive mechanism with a piston body can be realized with a simple structure. Moreover, the fluid pressure actuator according to the present invention can perform the positioning of the linear motion and the rotational motion with high accuracy. Further, it is possible to provide a fluid pressure actuator capable of performing load control (force control) in addition to the linear motion position control.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an embodiment of a pneumatic actuator as an example of a fluid pressure actuator according to the present invention.
FIG. 2 is a view of the fluid pressure actuator shown in FIG. 1 as viewed from the right in FIG.
FIG. 3 is a view for explaining a structure of a piston body in the present invention.
FIG. 4 is a block diagram for explaining a configuration of a control system of the fluid pressure actuator according to the present invention.
FIG. 5 is a view for explaining the structure and operation of the sensor fixing piece shown in FIG. 1;
FIG. 6 is a diagram illustrating an example of a conventional positioning device in the Z-axis direction.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Cylinder 11 Cylinder main body 12 Passage part 13 Guide flange 15, 16 First and second pressure sensor 17 Gear 18 Auxiliary wall member 19 O-ring 30 Ball bearing 41 Position sensor 42 Sensor fixed piece 43 Connector 50 Piston body 51 Piston head 52 Rod 60 Servo valve

Claims (7)

A fluid pressure cylinder,
A piston body having a piston head slidably housed in the fluid pressure cylinder;
A fluid for supplying a constant pressure P fluid to one pressure chamber between the piston heads in the fluid pressure cylinder and controlling and supplying a fluid pressure P1 to the other pressure chamber via a servo valve. A fluid circuit;
The first and second pressure sensors for detecting the pressure in the one pressure chamber and the other pressure chamber;
A position sensor for detecting the position of the piston body,
Giving a difference between the pressure receiving area S of the piston head in the one pressure chamber and the pressure receiving area S1 of the piston head in the other pressure chamber;
A fluid pressure actuator comprising control means for receiving the detection signals from the first and second pressure sensors and the position sensor as feedback values and controlling the position of the piston body. The fluid pressure actuator according to claim 1,
The piston body has a rod extending axially from the piston head,
While supporting the rod slidably in the axial direction, further comprising a rotation drive mechanism for rotating the rod together with the piston head,
The said position sensor was comprised on the axial direction extension line which passes through the center of gravity of the said piston body, The fluid pressure actuator characterized by the above-mentioned. 3. The fluid pressure actuator according to claim 2, wherein the rotary drive mechanism includes a cylindrical guide flange rotatably supported via a bearing on the fluid pressure cylinder side, and the guide flange has a polygonal cross section. The rod has a hole, and the rod having the same cross-sectional shape is inserted into the through hole, and the guide flange is also configured to receive a rotational driving force from a rotational driving source. Fluid pressure actuator. The hydraulic actuator according to any one of claims 1 to 3, wherein the piston body is housed in the hydraulic cylinder via a static pressure bearing, and the static pressure bearing is provided at an axial end of the piston head. A plurality of grooves are formed on the outer circumference at intervals in the circumferential direction, and a fluid is introduced into the grooves from the one pressure chamber and the other pressure chamber to act on the inner wall of the fluid pressure cylinder. A fluid pressure actuator characterized in that: 5. The fluid pressure actuator according to claim 2, wherein a portion of the portion of the fluid pressure cylinder facing the other pressure chamber side extends away from the other pressure chamber on the axial extension line. 6. A hole is formed extending in the direction extending in the axial direction, while a rod for position detection is provided in the axial direction on the axial extension of the piston head facing the other pressure chamber. The piston is provided so as to extend and be inserted into the hole, and a sensor portion for detecting the amount of movement of the rod is fixed to the hole so that the rod for position detection is inserted therethrough. A fluid pressure actuator comprising the position sensor for detecting a position of a body. The fluid pressure actuator according to any one of claims 1 to 5, wherein the control unit receives the detection signals from the first and second pressure sensors and the position sensor as feedback values, and controls the servo valve. A fluid pressure actuator for performing position control and load control of a driven part combined with the rod of the piston body via a piston. 7. The fluid pressure actuator according to claim 3, further comprising a rotation angle sensor for detecting a rotation angle of a rotation portion including the guide flange, wherein the control unit further detects the rotation angle from the rotation angle sensor. A fluid pressure actuator for performing rotation angle control using a signal.

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