JP4171666B2 - Actuator capable of linear and rotary motion - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an actuator for a positioning device, and more particularly to an actuator for a positioning device that enables a movable part to perform linear motion and rotational motion, and enables precise positioning thereof.
[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 a chip mounter, for example. This will be described with reference to FIG.
[0003]
In FIG. 5, the chip mounter is formed by combining a Z-axis feeding device 100 and a holder support device 200 that is driven up and down by the Z-axis feeding device 100. In the Z-axis feeding device 100, a servo motor 102 is installed on an apparatus frame 101, and a ball screw mechanism 103 extending in the vertical direction is driven by the servo motor 102. 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 support device 200 is attached to the opposite side of the ball screw mechanism 103 from 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 hydrostatic air bearing 204 so as to be movable up and down. That is, the static pressure air bearing 204 uniformly supports the lower portion of the tool holder 203 in a non-contact state by uniformly dispersing the compressed air supplied from the hole 205 provided in the air cylinder 202 with the porous body.
[0005]
Further, the vertical movement of the tool holder 203 is controlled by the differential pressure between the compressed air supplied from the pressurization port 206 and the balance pressure port 207 opened in the air cylinder 202. A tool 209 for holding the chip 300 is attached to the lower end portion of the tool holder 203.
[0006]
A 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 height position feedback control (see, for example, Patent Document 1).
[0007]
In order to enable precise positioning, the above device requires two drive mechanisms, that is, the Z-axis feeding device 100 using the ball screw mechanism 103 and the holder support device 200 using the air cylinder 203.
[0008]
As a positioning device in the Z-axis direction, a combination of a pneumatic cylinder or a linear motor in addition to a combination of a servomotor and a feed mechanism (ball screw or the like) as a linear motion mechanism as described above is known.
[0009]
[Patent Document 1]
Japanese Unexamined Patent Publication No. 2000-353725 (page 3, FIG. 1)
[0010]
[Problems to be solved by the invention]
Incidentally, in addition to the linear motion mechanism as described above, it may be required that the movable portion has a rotational motion function. In order to satisfy these requirements, there is a problem that if the rotational motion mechanism is added to the linear motion mechanism, the apparatus becomes complicated and large.
[0011]
Therefore, an object of the present invention is to realize an actuator capable of giving a linear motion and a rotational motion to a movable portion with a fluid pressure cylinder having a simple structure.
[0012]
Another object of the present invention is to provide an actuator that can perform linear motion and rotational motion positioning with high accuracy.
[0013]
Still another object of the present invention is to provide an actuator capable of load control (force control) in addition to the control for positioning the linear motion.
[0014]
[Means for Solving the Problems]
According to the present invention, a piston having a fluid pressure cylinder, a piston head slidably accommodated in the fluid pressure cylinder via a hydrostatic bearing and a rod extending in the axial direction from the piston head. A constant pressure fluid is supplied to one pressure chamber between the body and the piston head in the fluid pressure cylinder, and the other pressure chamber is supplied by controlling the fluid pressure or flow rate via a servo valve. comprising a fluid circuit for the said rod with supports axially slidable state, and a rotation drive mechanism for rotating said rod around its central axis together with the piston head, the fluid pressure A hole extending in the central axis direction away from the other pressure chamber is formed in the center of the portion facing the other pressure chamber side of the cylinder. The piston head facing the chamber is provided with a position detection rod extending in the center axis direction and inserted into the hole at the center thereof, and the position detection rod is also provided in the hole. Provided is an actuator characterized in that a position sensor for detecting the position of the piston body is configured by fixing a sensor unit for detecting the amount of movement by combining the rods for insertion therethrough. Is done.
[0015]
In this actuator, the rotational drive mechanism includes a cylindrical guide flange rotatably supported on the fluid pressure cylinder side via a bearing, and the guide flange has a through hole having a polygonal cross section. 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.
[0016]
In this actuator, the hydrostatic bearing is formed with a plurality of circumferentially spaced grooves on the outer periphery of the axial end of the piston head, and the one pressure chamber and the other are formed in these grooves. The fluid is introduced from the pressure chamber and is applied to the inner wall of the fluid pressure cylinder.
[0018]
The actuator further includes first and second pressure sensors for detecting the pressures of the one pressure chamber and the other pressure chamber, and the first and second pressure sensors and the position sensor are provided. using the detection signals, the position control of the drive unit to be combined to the rod of the piston body through the servo valve, obtain Bei a controller for performing switching load control.
[0019]
The actuator further includes a rotation angle sensor for detecting a rotation angle of the rotation portion including the guide flange, and the controller further performs rotation angle control using a detection signal from the rotation angle sensor. Is done.
[0020]
In the present actuator, any one of a ball bearing, a static pressure bearing, and a sliding bearing is used as the bearing of the guide flange.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of an actuator according to the present invention will be described with reference to FIGS. FIG. 1 shows a cross-sectional structure of an actuator according to the invention using compressed air as a fluid.
[0022]
In FIG. 1, the 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 pressure chambers on both sides of the piston head 51, and an air passage for introducing compressed air into the pressure chambers. A passage portion (fluid circuit) 12 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. Here, the passage portion 12 forms a part of the cylinder 10.
[0023]
The passage portion 12 includes an air introduction portion 12-1 having a passage for introducing compressed air, an air passage of the air introduction portion 12-1, an air inlet and an air outlet to the servo valve 60, and two cylinder bodies 11. It comprises a passage body 12-2 having passages communicating with the two pressure chambers. A servo valve 60 is installed and fixed in the passage portion 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 portion 12-1 into the pressure chamber on the right side of the cylinder main body 11 in the drawing, and the servo valve. A passage 12-2a for introducing the air into the air inlet 60 and a passage 12 for receiving the adjusted pressure or flow of air from the air outlet of the servo valve 60 and introducing it into the pressure chamber on the left side of the cylinder body 11 in the figure. -2b. Hereinafter, the pressure chamber on the right side in the figure is referred to as a constant pressure chamber (one pressure chamber), and the pressure chamber on the left side is referred to as an adjustment pressure chamber (the other pressure chamber).
[0024]
The cylinder body 11 has a space with a circular cross section, and a piston head 51 with 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 (here, a square shape), and a rod 52 having the same square cross sectional shape is inserted into the hole so as to be slidable in the axial direction.
[0025]
In particular, the guide flange 13 is prevented from moving in the direction of the central axis, but is held in the air introduction portion 12-1 by the ball bearing 30 so as to be rotatable about the central axis. That is, the air introduction part 12-1 not only has an air introduction path, but also has an annular part that can accommodate the guide flange 13. As a result, the rod 52 is slidable in the axial direction with respect to the guide flange 13 and is configured to rotate together when the guide flange 13 rotates. 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).
[0026]
FIG. 1 shows a state in which the piston body 50 has moved to the rightmost side in the drawing, that is, to the bottom dead center.
[0027]
A hole 11a is formed in the central axis direction in a portion of the cylinder body 11 opposite to the guide flange 13, and the position sensor rod 41 is fixed to the center of the piston head 51 and extends in the central axis direction in the hole 11a. -1 is inserted, and a sensor part 41-2 for detecting the position of the piston body 50 together with the position sensor rod 41-1 is fixed. Since the position sensor 41 including the position sensor rod 41-1 and the sensor unit 41-2 is well known, in brief, in this embodiment, the position sensor rod 41-1 is made of a magnetic material at a constant pitch. Non-magnetic materials are alternately arranged. When the position sensor rod 41-1 moves in the direction of the central axis together with the piston body 50, the number of moved magnetic bodies and the position between the magnetic bodies are detected by the sensor unit 41-2 via a magnetic field. The movement amount or position of the piston body 50 is detected using this detection signal. The position sensor rod 41-1 is slidable in the direction of the central axis with respect to the sensor unit 41-2 and can be rotated together with the piston body 50.
[0028]
A connector 43 is installed in the cylinder body 11 in order to lead out a detection signal from the sensor unit 41-2 to the outside of the cylinder body 11 with a conducting wire (not shown). Since the inside of the hole 11a has the same pressure as that of the adjustment pressure chamber, a sealing structure that prevents air leakage from the installation portion of the connector 43 is applied.
[0029]
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 hole 11a. The cylinder body 11 is further provided with an auxiliary wall member 18 on the lower side in the figure. The auxiliary wall member 18 is formed with a passage 18a (only part of which is shown) communicating with the constant pressure chamber, and on the outlet side. Is provided with a pressure sensor (first pressure sensor) 16 for detecting the pressure in the constant pressure chamber. Reference numeral 19 denotes a sealing O-ring.
[0030]
In the actuator according to this embodiment, as shown in FIG. 3, shallow grooves 51 a and 51 b for introducing compressed air from the adjustment pressure chamber and the constant pressure chamber side are provided on the outer periphery of both ends of the piston head 51. A static pressure air bearing portion is formed which is formed at intervals in the direction and lifts the piston head 51 from the inner wall surface of the cylinder body 11. That is, 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 is in a non-contact state. The slide can be moved with. Exhaust grooves 51c and 51d for exhausting air that has acted on the inner wall of the cylinder body 11 to the outside are formed on the outer periphery of the piston head 51 in the vicinity of the static pressure air bearing portion. The compressed air collected by 51c and 51d is discharged out of the actuator from the end of the rod 52 through an exhaust passage 51e formed in the piston body 50. In other words, a driven portion (not shown) is provided at the end of the rod 52, and an air piping connector capable of discharging compressed air even when the rod 52 is rotating is connected.
[0031]
The actuator according to the present embodiment described above has the following features.
[0032]
1) By introducing a constant pressure air from a compressed air supply source (not shown) directly into the constant pressure chamber of the cylinder body 11 and introducing a regulated pressure or flow rate of air through the servo valve 60 into the adjustment pressure chamber. Only one servo valve is required for position control or load control described later.
[0033]
2) The piston head 51 is levitated from the inner wall of the cylinder body 11 by the static pressure air bearing portion.
[0034]
3) The piston body 50 is rotatable by the rotation of the guide flange 13 using a servo motor or the like as a rotational drive source.
[0035]
That is, a plurality of static pressure air bearing portions are provided around the piston head 51 having a circular cross section in the piston body 50 so as to be capable of linear motion 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 the position command value and the load command value, receives the detection signals from the respective sensors, and controls the fluid to the adjustment pressure chamber by the servo valve 60, thereby positioning the piston body 50 with high accuracy. Perform load control. As is well known, the servo valve 60 incorporates a spool position sensor for detecting the position of the spool, and the controller 1 uses the signal from the spool position sensor for positioning control. 60 is controlled.
[0036]
Further, the rod 52 of the piston body 50 has a square cross section so as not to rotate with respect to the guide flange 13, while the guide flange 13 is made rotatable via the ball bearing 30 so that the rod 52 is integrated. It can be rotated. When the guide flange 13 is rotated by a servo motor, a highly accurate rotation angle control is performed by configuring a feedback system in which the rotation angle is detected by a rotary encoder attached to the servo motor and output to the controller 1. Is called. Of course, another known rotation angle sensor may be used as the sensor for detecting the rotation angle.
[0037]
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 the piston head 51 is P1, and the pressure receiving area of the piston head 51 facing the constant pressure chamber is S2 (however, S1 > S2), assuming that the pressure acting thereon is P2 (where P1 ≦ P2), the load is applied to the driven portion provided at the end of the rod 52 based on the load F = P1, S1-P2, and S2. This is control for applying a load (force) based on the command value.
[0038]
The controller 1 is configured to perform switching between the position control and the load control of the piston body 50 as described above. Of course, this switching is performed only when position control is performed and when only load control is performed. During the control, for example, after positioning the piston body 50, that is, the driven part by a position control at a predetermined position, the load is changed. It includes switching to switch to control so that a predetermined load (force) is applied to the driven part.
[0039]
As shown in FIG. 1, the present actuator may be used horizontally or vertically. When used vertically, this actuator is used as a Z-axis (vertical direction) and a rotation drive mechanism. By assembling a chuck mechanism to the driven part, it is possible to move a moving object such as an IC component up and down at high speed and to position the moving object with high accuracy. Further, a load (force) can be applied to the moving object with high accuracy, and the rotation angle of the moving object can be positioned around the Z axis with high accuracy.
[0040]
In addition, as a bearing of the guide flange 13, it may replace with the ball bearing 30 and may use the same static pressure air bearing as the rod 51 side, or a sliding bearing.
[0041]
As an application field of the actuator according to the present invention, the actuator according to the present invention can be used in bio-related equipment and conveying equipment using a drive mechanism that uses a ball screw or a fluid pressure cylinder. used. Furthermore, it goes without saying that the actuator according to the present invention is not limited to that using compressed air, but can also be applied to those using other gases. The structure of the cylinder 10 shown in FIG. 1 is merely an example, and the cylinder body 11 may be formed by a single member instead of a plurality of members.
[0042]
【The invention's effect】
According to the present invention, an actuator capable of giving a linear motion and a rotational motion to a movable part can be realized with a fluid pressure cylinder having a simple structure. Moreover, the actuator according to the present invention can perform positioning of linear motion and rotational motion with high accuracy. The actuator according to the present invention can further perform load control (force control) in addition to the control for positioning.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a pneumatic actuator as an example of an actuator according to the present invention.
2 is a view of the actuator shown in FIG. 1 as viewed from the right in FIG.
FIG. 3 is a view for explaining the structure of a piston body in the present invention.
FIG. 4 is a block diagram for explaining the configuration of an actuator control system according to the present invention.
FIG. 5 is a diagram showing 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 1st, 2nd pressure sensor 17 Gear 18 Auxiliary wall member 19 O-ring 30 Ball bearing 41 Position sensor 43 Connector 50 Piston body 51 Piston head 52 Rod 60 Servo valve

Claims (5)

A fluid pressure cylinder;
A piston body having a piston head slidably received in a non-contact state via a hydrostatic bearing in the fluid pressure cylinder, and a rod extending in the axial direction from the piston head;
A constant pressure fluid is supplied to one pressure chamber between the piston heads in the fluid pressure cylinder, and a pressure or flow rate of the fluid is controlled and supplied to the other pressure chamber via a servo valve. A fluid circuit;
The rod is supported so as to be slidable in the axial direction, and includes a rotation drive mechanism for rotating the rod together with the piston head about its central axis,
A hole extending in the central axis direction away from the other pressure chamber is formed at the center of the portion facing the other pressure chamber side of the fluid pressure cylinder, and on the other side of the other pressure chamber The piston head that faces the center is provided with a position detecting rod extending in the center axis direction and inserted into the hole at the center thereof, and the hole is also provided with the position detecting rod. A sensor unit for detecting the amount of movement by combining the rods to be inserted is fixed to constitute a position sensor for detecting the position of the piston body ,
First and second pressure sensors for detecting the pressure of the one pressure chamber and the other pressure chamber are provided, and detection signals from the first and second pressure sensors and the position sensor are used, An actuator comprising: a controller for switching position control and load control of a driven part combined with the rod of the piston body via the servo valve . 2. The actuator according to claim 1 , wherein the rotation drive mechanism includes a cylindrical guide flange rotatably supported on the fluid pressure cylinder side via a bearing, and the guide flange has a through-hole having a polygonal cross section. And the rod having the same cross-sectional shape is inserted into the through hole, and the guide flange is configured to receive a rotational driving force from a rotational driving source. 3. The actuator according to claim 1, wherein the hydrostatic bearing includes a plurality of circumferentially spaced grooves on an outer periphery of an axial end portion of the piston head, and the one of the grooves is the one of the grooves. An actuator characterized in that a fluid is introduced from the other pressure chamber and the other pressure chamber to act on the inner wall of the fluid pressure cylinder. 3. The actuator according to claim 2 , further comprising a rotation angle sensor for detecting a rotation angle of a rotating portion including the guide flange, and the controller further controls the rotation angle using a detection signal from the rotation angle sensor. Actuator characterized by performing. The actuator according to claim 2 , wherein any one of a ball bearing, a static pressure bearing, and a sliding bearing is used as the bearing of the guide flange.

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