JP2003049921A - Linear actuator generating less dust - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a linear actuator with generating a less dust in which dust generation amount to the outside is reduced as low as possible by reducing pressure inside the linear actuator itself. SOLUTION: A movable loop of a seal band 6 is formed via respective pulleys 5 disposed at both axial ends of the inside of a housing 1, one end of the loop is fixed to one end of a carriage 3, the other end of the loop is fixed to the other end of the carriage 3, and an opening of a slit S opening in the housing is sealed with the seal band 3. Air vent pipes 8A and 8B are disposed as a means for sucking air in the housing 1, suction ports 8Aa and 8Ba are disposed near both axial ends of the housing 1, and dust generation to the outside due to air pressure increase at ends of the housing in high speed moving of the carriage 3 is suppressed.

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an improvement of a low-dust generation linear motion actuator which can be suitably used in a clean room. 2. Description of the Related Art Conventionally, as a low-dust-generating linear motion actuator, there has been proposed, for example, one proposed by the present applicant and disclosed in Japanese Utility Model Laid-Open No. 7-7837. This device comprises a linear motion guide device provided in an elongated box-shaped housing, a carriage guided by the linear motion guide device, and a linear drive device for driving the carriage in the axial direction via a ball screw device. Has a slit opened long in the moving direction of the carriage. Then, the transported object is attached to the head of the carriage that protrudes from the housing to the outside through the slit, and is transported. However, since dust can freely enter and exit the housing with the slits opened, pulleys are provided at both ends of the housing and seal band loops are attached to the front and rear ends of the carriage. The band can be circulated along with the linear movement of the carriage via the pulley, and covers the opening of the slit. [0004] However, when such a dust-proof type linear actuator is used as a transfer means in a clean room, dust inside the linear actuator leaks out. In order to prevent contamination in the clean room, there is a demand for a clean room-specific low-dust-generation direct-acting actuator that is further dust-proof. Accordingly, an object of the present invention is to provide a low-dust direct-acting actuator in which the amount of dust generated to the outside is reduced as much as possible by reducing the pressure inside the dust-proof type direct-acting actuator itself. [0006] To achieve the above object, a low particle generation linear motion actuator of the present invention comprises an axially long housing, a linear motion guide device provided in the housing,
A carriage disposed in the housing movably in the axial direction via the linear motion guide device; and a linear drive device for moving the carriage in the axial direction. A long-acting slit is provided, and the carriage is provided at each of both axial ends inside the housing in a linear motion actuator having a work mounting seat surface protruding outside the housing through the slit. A movable loop of a seal band is formed via a pulley, and one end of the movable loop is fixed to one end of the carriage, and the other end of the movable loop is fixed to the other end of the carriage, and the opening of the slit is sealed with the seal band. And suction means for sucking air in the housing near both ends in the axial direction of the housing. Than it is. [0007] By sucking the air in the closed space inside the linear motion actuator surrounded by the seal band and the housing, the inside of the linear motion actuator is maintained at a negative pressure, thereby preventing external leakage of dust. In particular, when the carriage moves to the end of the housing, the air inside the housing is pushed into the end by the moving carriage and the pressure rises, which tends to cause external leakage of dust, but sucks air. Placing the openings near both ends of the housing effectively mitigates such pressure rises. Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding portions have the same reference characters allotted, and redundant description will be omitted. FIGS. 1 to 3 show a first embodiment of the present invention.
Is an overall perspective view, FIG. 2 is a sectional view perpendicular to the axis thereof, and FIG. 3 is a sectional view of a seal band guide groove. The housing 1 has an axially long box shape in which a bottom portion, a side surface portion, and an upper surface portion are integrally formed by extrusion. An end cover 1E is fixed to both ends, and an axial slit S is formed in the upper surface portion. Is open. Housing 1
Inside the linear guide device 2 as a linear motion guide device
And a carriage 3 that reciprocates linearly while being guided by the linear guide device 2, and a ball screw device 4 that is a driving device of the carriage 3. Carriage 3
Is projected to the outside of the housing 1 through the slit S, and the upper surface thereof is a work mounting seat surface 3a. A total of four pulleys 2 are provided, two at each end in the axial direction in the housing 1, and one end of the seal band 6 is fixed to one end of the carriage 3, and Is folded back through the pulley 5 on one end side, reaches the other end of the housing 1, is folded back through the other pulley 5 and is fixed to the other end of the carriage 3, thereby forming a movable loop of the seal band 6, The opening of the slit S is closed by a loop. The shape of the pulley 5 is
The central part is formed into a barrel mold having the largest diameter and being gradually reduced in diameter toward both ends. Seal band 6
Is a flat band made of polyurethane impregnated canvas, steel or plastic, for example. Further, both ends in the axial direction of the inside of the housing 1 which are isolated from the outside by the seal band 6 as described above,
Two air vent pipes 8A and 8B as means for sucking air in the housing are provided inside the housing 1 from the outside of the housing 1 through the end cover 1E. One air vent pipe 8A is short and protrudes inside, and a suction port 8Aa is opened at one end of the housing 1. The other air vent pipe 8B is long and extends inside, and a suction port 8Ba is opened at the other end of the housing 1. These air vent pipes 8A and 8B are connected to one common exhaust pump (not shown). In addition, instead of extending and arranging the other air vent pipe 8B inside the housing 1, the suction port 8Ba is passed through the outside of the housing 1 and penetrated through the end cover 1E at the opposite end, so that the suction port 8Ba is formed at the other end of the housing 1. It is also possible to make it open. Guide rail 11 of the linear guide device 2
Is disposed on the housing floor surface in the axial direction of the housing 1. The guide rail 11 has a concave shape with an open upper side, is fixed by a bolt (not shown) inserted into the mounting bolt hole 11a, and a pair of left and right ball rolling grooves 12 extending in the axial direction is formed on both opposed inner side surfaces. ing. The screw shaft 14 of the ball screw device 4 is disposed at the center of the housing along the axial direction of the housing 1, and is rotatably supported on the housing floor via bearings at both ends (not shown). A timing pulley (not shown) attached to an end and a timing pulley 16 attached to an external drive motor 15 are connected by a timing belt 17 so as to be able to be driven forward and reverse. The drive motor 15 and the pulley 16 are surrounded by a motor cover 50, and the joint between the housing 1 and the motor cover 50 is made airtight by a packing 51. A ball screw nut 18 screwed to the screw shaft 14 via a number of balls (not shown) also serves as a slider of the linear guide device 2 in this embodiment. It is fitted so that it can move in the direction. That is, on the left and right sides of the nut 18,
A ball rolling groove (not shown) is formed opposite to the ball rolling groove 12 of the guide rail 11, and a large number of balls (not shown) that roll in a ball rolling path formed by the opposed grooves. It is fitted on the guide rail 11. A ball circulation path (not shown) formed of a through hole parallel to the ball rolling groove on the outer surface is formed in a thick portion inside both right and left outer surfaces of the nut 18. The end cover 13 fixed with bolts 13B is provided with a curved ball groove for communicating the ball rolling groove on the outer surface and the ball circulation path, and the ball rolling groove, the ball circulation path, and the curved ball are provided. The groove and the groove form an infinite ball circulation path of the linear guide device, and through the rolling of a number of balls (not shown) rotatably mounted in the infinite ball circulation path, the nut 18 of the ball screw is connected to the guide rail 11. And smoothly move in a straight line. The carriage 3 is fixedly mounted on an upper surface of a nut 18 and has a slit S
The top plate 3c protrudes out of the housing 1 via a neck 3b having a width smaller than the opening width of the housing 1. Both sides of the seal band 6 for sealing the opening of the slit S are
Is engaged with the sealing groove 20 formed on the end face of the slit opening to enhance the sealing performance. The sealing groove 20
As shown in FIG. 3, the groove bottom surface 20a has a tapered shape with a downward slope going from the groove entrance to the back, and the entrance edge of the groove bottom surface 20a is a sliding contact portion 20b of the seal band 6. A wedge-shaped space 20c is formed between the tapered groove bottom surface 20a and the lower surface of the seal band 6. A magnet 21 is fixed to the lower side surface of the carriage 3, while a magnetic sensor 22 such as a Hall element facing the magnet 21 is attached to the inner side surface of the housing 1. The magnetic sensor 22 detects the origin position of the linear movement of the carriage 3, and controls the rotation of the drive motor 15 composed of an AC servomotor based on the origin detection signal, so that the linear movement can be positioned with high accuracy. It is configured as follows. Next, the operation of the above embodiment will be described. The work to be transferred is fixed to the work mounting seat surface 3a of the carriage 3 which is projected and exposed to the outside of the housing 1 with bolts. Then, first, one exhaust pump (not shown) to which the air vent pipes 8A and 8B are connected is driven to suck the air in the housing 1 to make the inside thereof a negative pressure. In this state, the drive motor 15 is rotated. The rotational force is transmitted to the ball screw device 4 via the timing belt 17 to rotate the screw shaft 14 and move the nut 18 in the axial direction, and at the same time, the carriage 3 fixed to the nut 18
Move in the axial direction to carry the work. During this movement, the nut 18 also serving as the slider of the linear guide device 2 is guided by the guide rail 11, and the smooth movement of the carriage 3 is ensured, so that accurate linear movement of the work is ensured. As the carriage 3 moves, the loop of the seal band 6 that seals the opening of the slit S also moves. For example, now, when the carriage 3 moves to the left in FIG. 1, the seal band 6
0, and is turned again through the two pulleys 50 at the opposite ends, and rotates while turning counterclockwise in FIG. In this rotation, both side edges of the seal band 6 engaged with the sealing groove 20 of the slit opening move while contacting the sliding contact portion 20b at the entrance of the groove bottom surface 20a to perform sealing. Since the barrel type pulley 50 has a centering property, the lateral displacement of the seal band 6 can be effectively prevented, and therefore both end portions of the seal band 6 do not contact the groove side surface 20 d of the sealing groove 20. . When the work is conveyed in this manner, in the ball screw device 4, when the hard steel ball spirally moves while rolling in the two ball screw grooves opposite to each other between the screw shaft 14 and the nut 18. Then, scattered particles of wear metal powder and lubricating grease are released. In addition, the linear guide device 2
In this case, a large number of balls made of steel also move while rolling in opposing rolling element rolling grooves of the rolling element rolling grooves 12 of the guide rail 11 and the rolling element rolling grooves of the nut 18 serving as the slider. At this time, scattered particles of wear metal powder and lubricating grease are released. Further, abrasion powder is also generated at the sliding contact portion 20b between the seal band 6 and the groove bottom surface 20a. However, in the low-dust-generation linear motion actuator of this embodiment, those dust particles are almost completely removed in the housing 1 and are hardly emitted to the outside (clean room). That is, the inside of the housing 1 is made to have a negative pressure by the exhaust pump, and the seal band 6 slides on the groove bottom surface 20a of the sealing groove 20b due to a pressure difference from the outside.
Is pressed against. At the same time, the tapered groove bottom 20
w and the lower surface of the seal band 6
Forms an extremely narrow air flow path, which generates a high air flow velocity toward the sliding contact portion 20b, so that almost all the dust particles are sucked into the housing 1 and do not dust outside. . Further, the groove bottom surface 20a of the sealing groove is tapered to seal the lower surface of the seal band 6 by line contact,
Since the seal gap is extremely small, the amount of suction air can be extremely small. As a result, it is possible to reduce the amount of exhaust of the exhaust pump, to reduce the cost of generating negative pressure, and to facilitate the operation of the suction pipe. Incidentally, in the experiments of the present inventors, the amount of dust generated outside the housing when the carriage 3 was moved at a speed of 3 m / min while sucking air in the housing at 25 Nl / min from the air vent pipes 8A and 8B. Is 8 per cubic foot
It was just an individual. At this time, the maximum gap of the wedge-shaped space 20c of the sealing groove is 0.3 mm, and the air flow rate is 55 cm / sec. Here, if the moving speed of the carriage 3 is increased, the air in the closed space of the housing 1 in the traveling direction is pushed by the carriage 3 and the nut 18 and is compressed, so that the air cannot be maintained at a negative pressure. Sex is considered. However, in the case of this embodiment, the air vent pipes 8A and 8B are connected to one common exhaust pump, and if the pressure in one space (air vent pipe 8A side) increases with the carriage 3 as a boundary, the air vent pipes 8A and 8B increase accordingly. Since the negative pressure in the other space (air bleeding tube 8B side) increases and the suction amount in one space (air bleeding tube 8A side) eventually increases, such a phenomenon that a pressure difference occurs on both sides of the carriage 3 is caused. Is unlikely to occur. According to this embodiment, the carriage 3
The work weight applied to the work mounting seat surface 3a is supported on the axis of the linear guide device 2, which is most advantageous in terms of rigidity, and the high rigidity required for the linear motion actuator is secured. Further, according to this embodiment, since the nut 18 of the ball screw device 4 also serves as the slider of the linear guide device 2, the whole device can be made very small and lightweight. 4 and 5 show another embodiment of the present invention.
The linear motion actuator of this embodiment is a linear motion actuator for transporting a large and heavy work, and two linear guide devices 2 are disposed in a housing 1 in parallel on both sides in the width direction. Have been. The large-sized carriage 3 is supported by a total of four sliders 10 each of which is attached to two guide rails 11 of each linear guide device. A ball screw device 4 for transporting the carriage 3 is disposed between the two linear guide devices 2. One end of a screw shaft 14 is supported by one end cover 1E via a bearing, and the other end is Is supported by the other end cover 1E via a bearing and protrudes outward to be connected to an output shaft of a drive motor (not shown). The screw shaft 14
The carriage 3 and the ball screw device 4 are connected by fitting a nut 18 screwed into the lower surface of the carriage 3 at the center of the lower surface. On both sides in the width direction of the upper surface of the carriage 3, convex portions 25 having a narrow width and the same length as the carriage are provided.
Is provided with a screw hole 25a into which the work mounting bolt is screwed, and projects outside through a slit S provided in the cover 1a of the housing 1.
Is the work mounting seat surface 3a. Slit S
In this case, are provided in a pair of left and right corresponding to the pair of left and right convex portions 25 of the carriage 3. In the thick floor of the housing 1, a closed space 26 is formed at the position directly below each guide rail 11, in which both end openings of through holes provided in the axial direction are closed by end covers 1 E.
Is formed. The closed space 26 of this embodiment has a rectangular cross section, and has ventilation holes 27a and 27 provided at both ends in the longitudinal direction.
It communicates with the internal space of the housing 1 only through b. The closed space 26 is divided into front and rear closed spaces 26a and 26b by a piston 28 slidably inserted. Suction ports 8Aa and 8Ba of an air vent pipe 8A and the like attached through the side surface of the housing 1 are opened in the vicinity of both ends of the closed space 26 in order to suck air inside each of these sections. In the case of this embodiment, the movable loop of the seal band 6, which is rotatable around the pulley 5,
Two lines are provided to seal the openings of the two slits S respectively. The seal band 6 is divided into two equal-length bands 6L and 6R, and one end of the left seal band 6L in FIG.
5 is fixed to the left end face 25L, and the other end is fixed to the left end face 28L of the piston 28 in the closed space 26 after changing direction through the upper and lower pulleys 5 attached to the left end cover 1E. Right seal band 6R
Has one end fixed to the right end face 25R of the convex portion 25 of the carriage 3 and the other end fixed to the right end face 28R of the piston 28 after changing direction through upper and lower pulleys 5 attached to the right end cover 1E. ing. The left seal band 6L, the right seal band 6R and the piston 28 constitute a movable loop of one seal band 6. The other structure is almost the same as that of the first embodiment. Now, when the carriage 3 is at the center in the longitudinal direction of the housing 1, the piston 28 is located at the center of the closed space 26 in the longitudinal direction. When the carriage 3 starts moving rightward in FIG. 4, the piston 28 starts moving in the opposite direction. In this state, the carriage 3 in the housing 1
The air in the space in the movement direction in the space partitioned by the air reaches the closed space 26b via the vent hole 27b, and the suction port 8b.
It is sucked from Ba to an air vent tube (not shown). On the other hand, the air in the front (left side) space in the moving direction of the piston 28 is supplied to the intake port 8A.
a to the air vent pipe 8A,
Through a, it also flows into the space behind the carriage, which is decompressed by the movement of the carriage 3. As a result, dust particles generated in the actuator are completely removed, and are not discharged outside the housing 1 (clean room). When the carriage 3 moves to the right in FIG. 4 at a high speed, the air in the space ahead in the moving direction is compressed.
However, in the case of this embodiment, at the same time, the piston 28 in the closed space 26 moves to the left at high speed.
6b is expanded rapidly in volume and decompressed. Therefore, the compressed air in front of the carriage flows from the ventilation hole 27b through the closed space 2b.
6b, the pressure increase of the air in front of the carriage is suppressed, and as a result, the emission of dust from the seal band 6 portion is effectively prevented. Further, when the carriage 3 moves rightward and approaches the stroke end, the piston 28 closes the left suction port 8Aa and increases the suction amount of the right suction port 8Ba. As a result, a pressure increase due to a sudden decrease in the volume of the carriage front space near the stroke end is canceled out, and dust generation is prevented. In each of the above embodiments, the ball screw device 4 is used as the linear driving means of the carriage 3. However, the present invention is not limited to this, and a linear motor may be used. The pulley 5 is used as a timing pulley, and the driving force of the drive motor 15 is transmitted to the seal band 6 to form the carriage 3 by meshing the teeth of the pulley with the teeth of the pulley (excluding the sliding contact with the sealing groove 20). You may make it move linearly. As described above, according to the low-dust-generating direct-acting actuator of the present invention, the slit provided with a part of the carriage provided in the actuator so as to move inside the actuator in the axial direction. And the opening of the slit is sealed with a movable loop of a seal band, and air in the housing is always sucked from the inside of the actuator near both ends in the axial direction of the housing by suction means. In addition, the inside of the actuator can be maintained at a negative pressure, and the effect of preventing external leakage of dust generated in the actuator can be obtained. In particular, when the carriage moves to the end of the actuator at high speed,
Although the air pressure rises at the end and the dust easily leaks to the outside, the opening of the suction means is located near both ends of the actuator, so that such pressure rise is effectively mitigated and the dust This has the effect of suppressing external leakage.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of one embodiment of the present invention. FIG. 2 is a sectional view in a direction perpendicular to the axial direction of FIG. FIG. 3 is an enlarged sectional view of a seal band guide groove of FIG. 2; FIG. 4 is a longitudinal sectional view of another embodiment of the present invention. FIG. 5 is a sectional view in a direction perpendicular to the axial direction of FIG. 4; [Description of Signs] 1 housing S slit 2 linear guide device (linear guide device) 3 carriage 3a work mounting seat surface 4 linear drive device (ball screw device) 5 pulley 6 seal band 8A suction means 8B suction means

Claims (1)

Claims: 1. An axially long housing, a linear motion guide device provided in the housing, and an axially movably disposed in the housing via the linear motion guide device. And a linear driving device for moving the carriage in the axial direction, a slit is provided on one surface of the housing that is long in the direction of movement of the carriage, and the carriage passes through the slit and moves out of the housing. In a linear motion actuator having a protruding work mounting seat surface, a movable loop of a seal band is formed via pulleys provided at both ends in the axial direction inside the housing, and one end of the movable loop is formed. At one end of the carriage, the other end of the movable loop is fixed to the other end of the carriage, and the opening of the slit is sealed with the seal band. Low dust linear actuator and air in the housing, characterized in that a suction means for sucking at near both ends in the axial direction of the housing.