Fluid pressure cylinder

A fluid pressure cylinder includes a displacement member, which is displaceable on an end side of a body, and a connecting body, which is connected to a piston rod of a cylinder unit, is inserted via a spring in a block body of the displacement member. A suction rod is connected substantially in parallel with the connecting body and a buffer rod connected to the connecting body. In addition, in a state where downward displacement of the block body is restricted, when additional loads are applied, the buffer rod is displaced relatively with respect to the block body in opposition to an elastic force of the spring, whereby an interval in a radial direction between a bushing and the buffer rod is enlarged.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2013-111481 filed on May 28, 2013, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fluid pressure cylinder in which a piston is displaced along an axial direction under the supply of a pressure fluid.

2. Description of the Related Art

Heretofore, as a means for transporting workpieces, for example, a fluid pressure cylinder has been used having a piston that is displaced under the supply of a pressure fluid. With such a fluid pressure cylinder, for example, a plate is disposed on an end of a piston rod, which is connected to the piston, and a suction pad, which is capable of attracting a workpiece, is installed on the plate. In addition, the piston is displaced by the pressure fluid that is supplied to the fluid pressure cylinder, whereby the plate moves toward the side of the workpiece, and by coming into abutment against the workpiece, the workpiece is attracted by suction to the suction pad. At this time, because a buffering mechanism is disposed on the plate, which is capable of buffering shocks (loads) applied in an axial direction, when the plate comes into abutment against the workpiece, application of loads with respect to the workpiece is suppressed by the buffering mechanism.

SUMMARY OF THE INVENTION

For example, with the fluid pressure cylinder disclosed in Korean Patent Registration No. 10-0840271, a piston rod and a suction pipe, which are disposed in parallel, are connected respectively to the same plate. Therefore, for example, in the fluid pressure cylinder, in the case that the piston rod and the suction pipe are not in parallel due to assembly conditions or manufacturing variances, or in the case that the piston rod, etc., is eccentric with respect to a hole in the plate, the piston rod, etc., tends to bite into a bushing that is disposed in the hole, and a locked condition is brought about in which the buffering mechanism cannot operate properly. As a result, when the plate is moved toward the workpiece and brought into abutment with the workpiece, loads are applied with respect to the workpiece without the buffering mechanism functioning properly. In the case of a fragile workpiece, such as a semiconductor chip or the like, for example, damage tends to occur to the workpiece.

For solving the aforementioned problems, although it might be considered to increase the degree of parallelism between the piston rod and the suction pipe, or in addition to securing such parallelism, to increase the size of a clearance between the bushing and the suction pipe and the piston rod for thereby absorbing any deviation therebetween, if the clearance is increased in size, the plate rotates as a result of the piston rod and the suction pipe deviating from their predetermined positions, accompanied by rotation of the workpiece that is retained by the suction pad. As a result, in the case that rotation of the workpiece is to be regulated during transport thereof, the workpiece cannot be placed at a desired position.

A general object of the present invention is to provide a fluid pressure cylinder in which rotational motion of a displacement block can be suppressed while enabling movement of the displacement block smoothly in an axial direction.

A fluid pressure cylinder according to the present invention includes:a body having therein a cylinder chamber to which a driving fluid is supplied;a cylinder unit disposed in the body and which has a piston disposed displaceably in the cylinder chamber, and a piston rod connected to the piston;a supply rod disposed displaceably and substantially in parallel with the piston rod in the body and having a fluid passage into which a workpiece retaining fluid is supplied, with a retaining member for retaining a workpiece being installed on an end of the supply rod, the retaining member communicating with the fluid passage;a displacement block connected to ends of the supply rod and the piston rod, and which is displaced under a displacement action of the piston; anda buffer mechanism, which buffers loads applied to the displacement block, and is disposed between the displacement block and the piston rod,wherein the buffer mechanism includes a buffer rod, which is disposed coaxially with the piston rod and is inserted through a hole of the displacement block, an outer circumferential surface of the buffer rod being formed in a tapered shape, which is reduced gradually in diameter toward the body.

According to the present invention, the piston rod of the cylinder unit, which is disposed displaceably in the interior of the body, and the supply rod, which is disposed displaceably in the body and has, on an end thereof, the retaining member capable of retaining a workpiece, are disposed substantially in parallel, with the displacement block being connected to ends of the supply rod and the piston rod. Together therewith, the buffer mechanism, which is disposed between the displacement block and the piston rod, is disposed coaxially with the piston rod, and includes the buffer rod, which is inserted through a hole of the displacement block. Further, as a result of the outer circumferential surface of the buffer rod being formed in a tapered shape, which is reduced gradually in diameter toward the body, it is possible for loads applied to the displacement block to be buffered.

Consequently, when the retaining member comes into abutment against and retains the workpiece under a driving action of the cylinder unit, since the interval in the radial direction between the displacement block and the buffer rod is kept small until abutment against the workpiece takes place, the buffer rod is maintained along the axial direction with high accuracy, and rotational movement of the displacement block about the supply rod can be suppressed.

On the other hand, after the retaining member has come into abutment against the workpiece, in the case that additional loads are applied toward the side of the workpiece, the buffer rod is displaced relatively in the axial direction with respect to the displacement block, whereby the interval in the radial direction between the buffer rod and the hole of the displacement block can be enlarged. Therefore, for example, even in the case that the hole of the displacement block becomes eccentric or offset with respect to the buffer rod, since such eccentricity can be absorbed by enlargement of the interval upon displacement of the displacement block, in any case, the buffer rod can be displaced smoothly in the axial direction with respect to the displacement block.

More specifically, rotational movement of the displacement block about the supply rod is suppressed by the buffer mechanism, while in addition, the buffer rod can smoothly be displaced relatively in the axial direction with respect to the displacement block, and loads that occur upon abutment against the workpiece can suitably be absorbed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown inFIG. 1, a fluid pressure cylinder10according to the present invention includes a body12, a cylinder unit16having a piston14disposed displaceably along an axial direction (the direction of arrows A and B) of the body12, a suction rod (supply rod)18disposed substantially in parallel with the piston14, and a displacement member20connected to the cylinder unit16and the suction rod18, and which is disposed so as to be capable of moving closer toward and separating away from the body12. A case will be described in which the displacement member20is used in a downwardly located orientation on the fluid pressure cylinder10.

As shown inFIGS. 1 and 2, the body12is formed with a substantially rectangular shape in cross section, for example, from a metal material. A first cylinder hole (cylinder chamber)22and a first rod hole24are formed in the interior of the body12and penetrate through the body12in the axial direction (the direction of arrows A and B). The first cylinder hole22and the first rod hole24are separated by a predetermined distance and are formed substantially in parallel. In addition, the first rod hole24penetrates from one end to another end of the body12, whereas the first cylinder hole22opens on the other end of the body12.

In addition, the piston14and a piston rod26that make up the cylinder unit16are disposed displaceably in the first cylinder hole22. On the other hand, the suction rod18is inserted through the first rod hole24, such that the suction rod18is supported displaceably in the axial direction (the direction of arrows A and B) by a pair of bearings28a,28b,which are disposed in the one end and the other end of the first rod hole24. The bearings28a,28bare cylindrically shaped, with the suction rod18being inserted through interior portions thereof.

First and second ports32,34, which supply a pressure fluid (driving fluid) to the first cylinder hole22, are formed in the one end of the body12. The first port32communicates through a first communication passage36with one end of the first cylinder hole22. The second port34is connected to and communicates with a portion in the vicinity of the other end of the first cylinder hole22, through a connecting passage38and a second communication passage40, the connecting passage38being formed between the first cylinder hole22and the first rod hole24, the second communication passage40being formed on an end of the connecting passage38.

Stated otherwise, via the first and second communication passages36,40, the first port32and the second port34are connected respectively to one end side (in the direction of the arrow A) and the other end side (in the direction of the arrow B) of the piston14in the first cylinder hole22.

Additionally, a non-illustrated pressure fluid supply source is connected via tubes to the first and second ports32,34, and pressure fluid is supplied selectively to one of the first and second ports32,34under a switching action of a switching means. Owing thereto, the pressure fluid, which is supplied to the first port32or the second port34, is introduced into the first cylinder hole22through the first and second communication passages36,40.

Further, in the other end of the body12, a region where the first rod hole24is formed projects a predetermined length in the axial direction (the direction of the arrow B) with respect to a region where the first cylinder hole22is formed, whereby the other end of the body12includes a first projection42. More specifically, the other end of the body12is formed in a stepped shape.

A machining hole44, which is used when the second communication passage40is fabricated, opens on one side surface of the body12adjacent to the first cylinder hole22. The machining hole44is formed perpendicularly to the first cylinder hole22. In addition, for example, a non-illustrated drill is inserted through the machining hole44from the exterior of the body12, whereby the second communication passage40is cut perpendicularly to the first cylinder hole22, and is formed to establish communication between the first cylinder hole22and the connecting passage38.

A plug46, which is formed from a metal material, for example, is press-inserted into the machining hole44after the second communication passage40has been formed. An expanded-diameter lid portion50, which is expanded in diameter with respect to a shaft portion48of the plug46, is mounted on an outer side of the body12. At this time, the plug46is mounted so as not to project outwardly from the side surface of the body12, and by mounting an o-ring52between the machining hole44and the lid portion50, leakage of pressure fluid or lubricating oil or the like, which passes between the machining hole44and the plug46, can reliably be prevented.

Instead of the plug46, for example, the machining hole44may be closed by inserting a steel ball (not shown) into the machining hole44. However, by closing the machining hole44using the plug46and the o-ring52, leakage of lubricating oil or the like can be prevented more reliably.

On the other hand, in the other side surface of the body12adjacent to the first rod hole24, for example, plural attachment holes54and locating holes56are formed, which are used when fixing the fluid pressure cylinder10to a transport arm or the like.

The cylinder unit16is disposed in the interior of the body12, and includes a piston14, which is disposed in the first cylinder hole22, the piston rod26connected to the piston14, and a rod cover58that supports the piston rod26displaceably.

The piston14is formed in a cylindrical shape, for example, with a pair of piston packings60a,60band a wear ring62being mounted respectively via annular grooves on the outer circumferential surface of the piston14. In addition, the piston packings60a,60band the wear ring62are arranged in sliding contact with the inner circumferential surface of the first cylinder hole22.

Further, in the interior of the piston14, a piston hole is formed that penetrates in the axial direction (the direction of arrows A and B), and one end of the piston rod26is inserted through the interior thereof.

The piston rod26is made up from a shaft having a predetermined length in the axial direction (the direction of arrows A and B). A first connector64, which is formed on one end of the piston rod26and is smaller in diameter than a central portion thereof, is connected by screw-engagement in the piston hole of the piston14. A damper66is mounted on a region that projects from the one end of the piston14. The damper66, for example, is made from an elastic material such as rubber or the like, which prevents direct contact when the piston14is displaced toward the one end side of the first cylinder hole22(in the direction of the arrow A) under a displacement action of the piston14, and further prevents the occurrence of shocks and shock noises at the displacement end position.

Further, a second connector68formed on the other end of the piston rod26is connected by screw-insertion into a connecting body70, to be described below, and is displaced integrally therewith in the axial direction (the direction of arrows A and B) upon displacement of the piston rod26.

The connecting body70is formed in a cylindrical shape from a metal material, for example, and as shown inFIGS. 1, 3 and 4, includes a large diameter portion72in which the piston rod26is screw-engaged in the interior thereof, and a small diameter portion74adjacent to the large diameter portion72and which is connected to a later-described buffer rod112. Additionally, the connecting body70is arranged coaxially with the piston14and the piston rod26, and between the body12and the displacement member20, such that the large diameter portion72is positioned on the side of the body12(in the direction of the arrow A), and the small diameter portion74is positioned on the side of the displacement member20(in the direction of the arrow B).

As shown inFIGS. 1 and 2, the rod cover58is formed in a cylindrical shape from a metal material, for example, and is screw-engaged with the other end side (in the direction of the arrow B) of the first cylinder hole22through a threaded part that is formed on the outer circumferential surface of the rod cover58. A seal ring76, which is mounted through an annular groove on the outer circumferential surface, abuts against the inner circumferential wall of the first cylinder hole22. Consequently, leakage of pressure fluid from between the first cylinder hole22and the rod cover58is prevented.

Further, in the interior of the rod cover58, a through hole78is formed that penetrates therethrough in the axial direction (the direction of the arrows A and B). The piston rod26is inserted displaceably in the through hole78, and by abutment of a rod packing80, which is mounted on the inner circumferential surface of the rod cover58, against the outer circumferential surface of the piston rod26, leakage of pressure fluid from between the rod cover58and the piston rod26is prevented. Moreover, an end of the rod cover58is disposed so as to project a predetermined length from the other end portion of the body12.

The suction rod18is made up from a shaft having a predetermined length in the axial direction (the direction of arrows A and B). A negative pressure supply port82, to which a non-illustrated negative pressure supply source is connected, opens on one end of the suction rod18, and a connection port86(seeFIG. 1), which is connected to a suction pad (retaining member)84, for example, opens on the other end of the suction rod18. In addition, the negative pressure supply port82and the connection port86are placed in communication through a supply passage (fluid passage)88that is formed to extend in the axial direction (the direction of arrows A and B) in the interior of the suction rod18, for example, for thereby supplying the negative pressure fluid (workpiece retaining fluid) with respect to the suction pad84.

As shown inFIGS. 1 and 3, on the other end of the suction rod18, a connector90is formed that is expanded in diameter in a radial outward direction. The connection port86is formed in the center of the connector90, and screw threads are formed along the axial direction on the outer circumferential surface of the connector90.

In addition, a central vicinity along the axial direction (the direction of arrows A and B) of the suction rod18is inserted through the first rod hole24of the body12, and the suction rod18is disposed for displacement along the axial direction (the direction of arrows A and B) by the pair of bearings28a,28b.Further, one end of the suction rod18projects beyond the one end of the body12, and the other end thereof projects beyond the other end of the body12. In addition, a later-described block body (displacement block)92of the displacement member20is connected to the other end of the suction rod18.

The displacement member20includes the block body92, and a buffer mechanism94, which is disposed in the interior of the block body92, for buffering loads applied in the axial direction (the direction of arrows A and B).

The block body92has a thickness dimension substantially the same as that of the body12, and one end thereof is formed in a stepped shape having a second projection96that projects toward the body12(in the direction of the arrow A). As shown inFIG. 1, the second projection96is disposed in facing relation to the first projection42of the body12, and the suction rod18is inserted through the interior of an annular damper98, which is disposed on the end surface of the second projection96. The damper98, for example, is made from an elastic material such as rubber or the like, which prevents direct contact when the second projection96is displaced toward the first projection42(in the direction of the arrow A) under a displacement action of the displacement member20, and further prevents the occurrence of shocks and shock noises at the time of contact.

On the other hand, the other end of the block body92is formed in a flat planar shape, which is perpendicular with respect to the axial direction (the direction of arrows A and B).

The block body92includes a second cylinder hole100formed coaxially with the first cylinder hole22and through which the connecting body70is inserted, and a second rod hole102, which is formed substantially in parallel with the second cylinder hole (hole)100and through which the suction rod18is inserted.

As shown inFIGS. 3 and 4, the second cylinder hole100includes a first hole portion104formed on the side of the body12(in the direction of the arrow A) and through which the second connector68is inserted, and a second hole portion106, which is smaller in diameter than the first hole portion104, and is formed on the other end side (in the direction of the arrow B). A spring108is interposed between a stepped part of the connecting body70and a boundary surface between the first hole portion104and the second hole portion106. The spring108has an elastic force that serves to bias the block body92in a direction (the direction of the arrow B) away from the connecting body70. A part of the connecting body70normally is inserted into the first hole portion104.

Further, on the other end of the second hole portion106, an annular groove is included, which is recessed in a radial outward direction on the inner circumferential wall of the second hole portion106, and a cylindrical bushing110is disposed in the annular groove. The bushing110is formed from a metal material such as an aluminum alloy or the like, and an inner circumferential surface110athereof is formed in a tapered shape, which is gradually reduced in diameter toward the body12(in the direction of the arrow A). In addition, a buffer rod112, which constitutes part of the buffer mechanism94, is inserted through the second hole portion106.

As shown inFIGS. 3 through 5, the buffer rod112includes a head portion114, which is formed with an oblong shape in cross section, for example, and a rod portion116, which extends in the axial direction (the direction of the arrow A) from the center of the head portion114. In addition, the end of the rod portion116is inserted through the second hole portion106, and is inserted into and connected by way of screw-engagement with the interior of the connecting body70, in a condition in which the head portion114is arranged on the outside of the other end of the block body92.

Further, an outer circumferential surface116aof the rod portion116is formed in a tapered shape, which is reduced in diameter gradually toward the connecting body70(in the direction of the arrow A), and as shown inFIG. 4, a first clearance C1having a substantially constant interval is provided along the axial direction between the outer circumferential surface116aof the rod portion116and the inner circumferential surface110aof the bushing110, which is disposed on the outer circumferential side of the rod portion116. More specifically, the angle of inclination of the outer circumferential surface116aon the rod portion116is formed with substantially the same angle as the angle of inclination on the inner circumferential surface110aof the bushing110, such that the outer circumferential surface116aand the inner circumferential surface110alie substantially in parallel.

In addition, the block body92is pressed toward the side of the head portion114(in the direction of the arrow B) under an elastic action of the spring108, and the end surface of the block body92is stopped by abutment against the head portion114.

On the other hand, in a state in which downward displacement (in the direction of the arrow B) of the block body92is restricted, upon displacement of the piston14, the buffer rod112is displaced in the axial direction (the direction of the arrow B) in opposition to the elastic force of the spring108, whereby as shown inFIGS. 6 and 7, the head portion114of the buffer rod112separates away from the other end of the block body92. At this time, the clearance between the rod portion116of the buffer rod112and the inner circumferential surface110aof the bushing110becomes enlarged, to thereby result in a second clearance C2, which is larger than the first clearance C1(C1<C2).

Stated otherwise, as shown inFIGS. 1 through 4, in a normal condition, in which a workpiece W is not attracted and the block body92remains in abutment against the head portion114of the buffer rod112, the buffer rod112and the block body92are arranged with the small first clearance C1, in which the interval in the radial direction therebetween is small. Therefore, the block body92is positioned with high accuracy through the second cylinder hole100(second hole portion106) with respect to the rod portion116of the buffer rod112, and rotational movement of the block body92is suppressed.

On the other hand, as shown inFIGS. 6 and 7, after the suction pad84has been placed in abutment against the workpiece W, in the event that a load is further applied toward the side of the workpiece W (in the direction of the arrow B), since a state is brought about in which the buffer rod112and the block body92are arranged via the large second clearance C2, in which the interval therebetween in the radial direction is enlarged, even in the case that the rod portion116and the second cylinder hole100(second hole portion106) become eccentric or offset from each other, such eccentricity can be absorbed by the interval of the second clearance C2, and displacement can proceed smoothly.

As shown inFIGS. 1 and 3, the second rod hole102includes an insertion hole118, which is formed on one end side of the block body92(in the direction of the arrow A), and a threaded hole120, which is formed on the other end side of the block body92on a straight line with the insertion hole118. Additionally, the suction rod18is inserted through the insertion hole118, and the connector90of the suction rod18is screw-engaged in the threaded hole120. At this time, the suction rod18is screw-engaged such that the end of the connector90projects a predetermined length from the other end of the block body92.

Further, since by being rotated with respect to the block body92, the suction rod18can be advanced and retracted along the axial direction (the direction of arrows A and B) by way of threaded action with respect to the threaded hole120, the projecting length L (seeFIG. 3) at which the connector90projects from the other end of the block body92can be freely adjusted.

In addition, the suction pad84, which is made from an elastic material such as rubber or the like, for example, is connected by screw-engagement to the connection port86, which is formed in the center of the connector90. Accordingly, the negative pressure fluid, which is supplied to the supply passage88of the suction rod18, is supplied through the connection port86to the interior of the suction pad84.

Further, a locking bolt (screw member)122is screw-engaged for advancement and retraction in a threaded hole provided in the side surface of the block body92and which extends to the insertion hole118. The locking bolt122is disposed through the threaded hole in facing relation to the outer circumferential surface of the suction rod18, such that by abutment of a distal end portion thereof against the outer circumferential surface of the suction rod18, the locking bolt122functions as a locking means for restricting displacement of the suction rod18in the axial direction (the direction of arrows A and B). More specifically, in a state in which the locking bolt122is rotated to separate away from the outer circumferential surface of the suction rod18, the suction rod18is rotated and the projecting length L at which the suction rod18projects from the other end of the block body92is adjusted. Further, by retightening the locking bolt122and bringing the locking bolt122into abutment against the outer circumferential surface, the suction rod18can be fixed with respect to the block body92with the projecting length L thereof in an adjusted state.

The fluid pressure cylinder10according to the embodiment of the present invention is constructed basically as described above. Next, operations and advantages of the present invention will be described with reference toFIGS. 8A through 8D. The condition shown inFIGS. 1, 2 and 8A, in which the piston14is displaced to the one end side of the body12(in the direction of the arrow A), will be referred to as an initial position. In this case, the first and second ports32,34are connected through a switching means to a non-illustrated pressure fluid supply source, and a negative pressure supply source is connected beforehand through a tube to the negative pressure supply port82of the suction rod18. A case will be described in which a workpiece W, which has been placed beneath the suction pad84(in the direction of the arrow B), is attracted and transported using the fluid pressure cylinder10.

First, in the initial position, by supply of a pressure fluid to the first port32from a non-illustrated pressure fluid supply source, the piston14is displaced toward the other end side of the body12(in the direction of the arrow B) by the pressure fluid that is introduced into the first cylinder hole22, accompanied by the piston rod26and the connecting body70being displaced together integrally (refer toFIG. 8B). At this time, since the elastic force of the spring108that is interposed between the block body92and the connecting body70is greater than the load applied from the connecting body70, the spring108is not compressed, and therefore, the block body92is displaced integrally therewith upon displacement of the connecting body70. In this case, the second port34is placed in a state of being open to atmosphere.

Further, by displacement of the block body92, the suction rod18, which is connected to the block body92, is displaced integrally therewith in the axial direction (the direction of the arrow B) in a state of being supported by the bearings28a,28b,and the suction pad84, which is connected to the other end of the suction rod18, is made to approach the workpiece W.

Additionally, as shown inFIG. 8B, the piston14is displaced further in a downward direction (in the direction of the arrow B), accompanied by the suction pad84coming into abutment against the workpiece W. By further lowering the piston14under a condition in which the workpiece W is abutted by the suction pad84, since the block body92is restricted from descending further after the suction pad84has abutted against the workpiece W, the additional load applied from the piston rod26overcomes the elastic force and compresses the spring108, whereby only the connecting body70and the buffer rod112are lowered relatively inside the second cylinder hole100, and the load is not transmitted to the block body92.

More specifically, as shown inFIGS. 6, 7, and 8C, the buffer rod112and the connecting body70are moved relatively downward (in the direction of the arrow B) with respect to the block body92, and the block body92, which is connected to the suction pad84, does not move.

As a result, after the suction pad84has abutted against the workpiece W, even in the event that a driving force from the cylinder unit16is transmitted to the displacement member20, owing to the buffer mechanism94of the displacement member20, an excessive load is prevented from being applied with respect to the workpiece W. For example, when a workpiece W such as a semiconductor chip or the like, which is susceptible to excessively applied loads, is transported, by using the fluid pressure cylinder10having the buffer mechanism94, application of excessive loads with respect to the workpiece W is prevented, the workpiece W can be abutted against and attracted at an optimal load, and the workpiece W can be transported safely.

Since a negative pressure is supplied through the supply passage88of the suction rod18and the connection port86to the interior of the suction pad84, the workpiece W is attracted to the suction surface of the suction pad84.

Next, after attraction of the workpiece W has been confirmed, by switching supply of the pressure fluid, which was supplied to the first port32, to the second port34under operation of the non-illustrated switching means, the piston14is pressed upwardly (in the direction of the arrow A) by the pressure fluid supplied to the first cylinder hole22, accompanied by the block body92being raised by way of the piston rod26so as to approach the body12(seeFIG. 8D). As a result, in a state of being attracted to the suction pad84, the workpiece W separates in an upward direction away from the base on which the workpiece W is placed. At this time, when the block body92is elevated, the suction rod18is displaced in an upward direction integrally with the block body92.

In addition, after the fluid pressure cylinder10has been moved to a predetermined transport position by a transporting device or the like fixed to the fluid pressure cylinder10in a condition in which the piston14is raised to the one end of the first cylinder hole22, by switching supply of the pressure fluid from the second port34to the first port32, the workpiece W is lowered together with the block body92, and in a state in which the workpiece W is placed at a predetermined position, supply of the negative pressure to the suction rod18from the negative pressure supply source is stopped. Consequently, the attracted state of the workpiece W on the suction pad84is released, and the transport operation is brought to an end with the workpiece W being placed at the predetermined position.

Further, when the load applied further from the cylinder unit16is buffered by the buffer mechanism94after the suction pad84has abutted against the workpiece W, by relative displacement of the buffer rod112in the axial direction (the direction of the arrow B) with respect to the block body92, accompanying displacement of the block body92, the interval in the radial direction between the rod portion116of the buffer rod112and the inner circumferential surface110aof the bushing110, which is formed in a tapered shape, is enlarged from the size of the first clearance C1to the size of the second clearance C2.

As a result, for example, even in the case that the bushing110becomes eccentric or offset with respect to the rod portion116of the buffer rod112, upon relative displacement of the buffer rod112with respect to the block body92, accompanying displacement thereof in the axial direction (the direction of the arrow B), since the range of possible movement in the diametrical direction is enlarged owing to the enlarged interval of the second clearance C2, interference with displacement in the axial direction caused by contact between the rod portion116and the bushing110does not occur.

More specifically, biting in of the buffer rod112and the bushing110is avoided, and by constantly changing, i.e., increasing, the interval (second clearance C2) between the buffer rod112and the bushing110, the buffer rod112can be displaced smoothly with respect to the block body92.

Further, in the aforementioned embodiment, a case has been described in which both the outer circumferential surface116aof the rod portion116and the inner circumferential surface110aof the bushing110in the buffer rod112are formed in tapered shapes, which are gradually reduced in diameter toward the body12(in the direction of the arrow A). However, the invention is not limited to this feature, and for example, only the outer circumferential surface116aof the rod portion116may be formed in a tapered shape. More specifically, the shapes are not particularly limited, insofar as a structure is provided in which, upon relative displacement in the axial direction between the buffer rod112and the block body92having the bushing110, the mutual interval therebetween in the radial direction can be changed so as to become larger than the interval prior to displacement.

In the foregoing manner, with the present embodiment, in the fluid pressure cylinder10, the buffer mechanism94is included, which is disposed on the other end of the body12, and for example, which is capable of buffering loads applied in the axial direction (in the direction of the arrow A) when the suction pad84abuts against the workpiece W to transport the workpiece W. The buffer mechanism94includes the connecting body70to which a driving force from the cylinder unit16in the axial direction is transmitted, the block body92having the second cylinder hole100therein through which the connecting body70is inserted, and the buffer rod112, which is connected to the connecting body70and is inserted through the second cylinder hole100. Further, the suction rod18is connected to the block body92in parallel with the buffer rod112, and the suction pad84is disposed on the connector90of the suction rod18.

In addition, on the buffer rod112, the outer circumferential surface116aof the rod portion116is formed in a tapered shape, which is reduced in diameter gradually toward the connecting body70(in the direction of the arrow A), and the inner circumferential surface110aof the bushing110, which is disposed on the outer circumferential side of the rod portion116, is formed in a tapered shape, which is reduced in diameter gradually toward the body12(in the direction of the arrow A).

Consequently, when the displacement member20is made to approach the workpiece W under a driving action of the cylinder unit16, and the workpiece W is attracted to the suction pad84, for example, since the interval (first clearance C1) in the radial direction between the buffer rod112and the bushing110is kept small until abutment against the workpiece W takes place, the buffer rod112is maintained along the axial direction with high accuracy. As a result, rotational displacement of the block body92about the suction rod18can be suppressed. Therefore, for example, when the block body92is raised after the workpiece W has been attracted, rotation of the block body92is suppressed, and accordingly rotation of the workpiece W also is prevented. Thus, in the case that a rectangular shaped workpiece such as a semiconductor chip is to be transported and placed, placement thereof on a rectangular pallet can be performed reliably.

Stated otherwise, in the case that the clearance between the piston rod and the suction pipe and the bushing is large, as in the case of the conventional fluid pressure cylinder, the workpiece W may undergo rotation together with the plate, whereby accurate placement of the rectangular workpiece on the rectangular pallet becomes difficult.

On the other hand, after the suction pad84has come into abutment against the workpiece W, in the case that additional loads are applied toward the side of the workpiece W, the buffer rod112is displaced relatively in the axial direction with respect to the block body92, whereby the interval (second clearance C2) in the radial direction between the rod portion116and the bushing110can be enlarged.

As a result, even in the case that the second cylinder hole100of the block body92is eccentric or is offset with respect to the buffer rod112, since such eccentricity can be absorbed by the second clearance C2, in any case, the buffer rod112can be displaced smoothly in the axial direction with respect to the block body92. More specifically, even in the case that additional loads are applied to the side of the workpiece W, the buffer rod112is displaced relatively in the axial direction with respect to the block body92, whereby further application of such loads can reliably be prevented, and the workpiece W can be protected from excessive loads.

More specifically, rotational movement of the block body92about the suction rod18is suppressed by the buffer mechanism94that is provided on the displacement member20, while in addition, the buffer rod112can smoothly be displaced relatively in the axial direction with respect to the block body92, and loads that occur upon abutment against the workpiece W can suitably be absorbed.

Stated otherwise, a structure is provided in which non-rotational precision is maintained, for keeping the block body92so as not to rotate about the suction rod18, while at the same time, the buffer rod112can be displaced smoothly with respect to the block body92toward the workpiece W.

Further, by rotation of the suction rod18, which is screw-engaged with the block body92, the projecting length L at which the suction rod18projects in the axial direction (the direction of arrows A and B) from the end surface of the block body92can be freely adjusted. Therefore, by adjusting the relative positioning of the suction rod18corresponding to the position of the workpiece W, fine adjustments can be carried out without adjusting the displacement amount of the piston14in the cylinder unit16.

Furthermore, by closing the machining hole44formed in the body12, by the plug46, and by contact of the o-ring52, which is mounted inside the machining hole44, with the plug46, a pressure fluid or a lubricating oil or the like inside the body12is prevented from leaking to the exterior through the machining hole44. As a result, dripping of lubricating oil, for example, which has leaked out to the exterior of the body12, onto the workpiece W and adhering to the workpiece W is prevented from occurring.

Further still, since the body12, the block body92, and the suction rod18that constitute the fluid pressure cylinder10are formed from a conductive metal material, for example, in the event that the workpiece W, which is attracted by the suction pad84, is statically charged, such electrostatic charge can be released or discharged to the exterior as a result of being passed conductively to the body12from the suction rod18and the block body92. More specifically, when conveyance of the attracted workpiece W is carried out, static electricity or the like that charges the workpiece W can be grounded to the exterior.

The fluid pressure cylinder according to the present invention is not limited to the embodiment described above. It is a matter of course that various alternative or additional structures may be adopted therein without departing from the scope of the invention as set forth in the appended claims.