Patent ID: 12195286

MODE FOR CARRYING OUT THE INVENTION

In an actuator to which a negative pressure-generating structure according to the present invention is applied, a shaft is movable in an axial direction and/or rotatable about an axis. Furthermore, on a tip side of the shaft, a hollow part is formed so that an interior of the shaft is hollow. Consequently, if air is sucked from the hollow part of the shaft, a negative pressure is generated at the tip of the shaft.

Furthermore, the negative pressure-generating structure includes an insertion hole, an inner space, and an air passage. The shaft of the actuator is inserted into the insertion hole. At this time, a space is formed between a wall surface of the insertion hole and the shaft in a state where the shaft is inserted into the insertion hole. For that reason, the shaft is movable in the axial direction and/or rotatable about the axis even in the state where the shaft is inserted into the insertion hole.

Additionally, a communication hole is formed in the shaft. Then, in the state where the shaft is inserted into the insertion hole, the inner space formed inside the negative pressure-generating structure communicates with the hollow part of the shaft through the communication hole. Consequently, if air is sucked from the inner space of the negative pressure-generating structure, air is also sucked from the hollow part of the shaft through the communication hole. Then, in the negative pressure-generating structure, the inner space is connected to the air passage. When the negative pressure is generated at the tip of the shaft, air is sucked from the inner space through this air passage.

Thus, employment of the negative pressure-generating structure according to the present invention makes it possible to suck air from the hollow part of the shaft, without directly attaching an air pipe or rotation equipment to the shaft of the actuator, so that the negative pressure can be generated at the tip of the shaft. Therefore, it is possible to adjust a pressure at the tip of the shaft, without causing decrease in accuracy of movement control and/or rotation control of the shaft due to damage on the air pipe or rotation equipment or the attaching of the air pipe or rotation equipment to the shaft.

Note that according to the negative pressure-generating structure of the present invention, the space is formed between the wall surface of the insertion hole and the shaft in the state where the shaft is inserted into the insertion hole. Additionally, this space is configured to be comparatively small, so that a flow rate of air flowing through the space between the inner space of the negative pressure-generating structure and a space outside the negative pressure-generating structure can be suppressed. Therefore, even if the space is formed between the wall surface of the insertion hole and the shaft, the negative pressure can be generated at the tip of the shaft by sucking air from the inner space.

Furthermore, if a seal member made of an elastic material is provided between the wall surface of the insertion hole and the shaft, airtightness of the inner space increases. However, when the shaft moves and/or rotates in the case where the seal member is provided, sliding resistance is generated between the seal member and the shaft. This sliding resistance may be a cause of decrease in accuracy of the movement control and/or the rotation control of the shaft. On the other hand, in the present invention, the space remains to be formed between the wall surface of the insertion hole and the shaft without providing any seal members therebetween, so that the sliding resistance between the seal member and the shaft can be suppressed. This can increase the accuracy of the movement control and/or the rotation control of the shaft.

Additionally, the space formed between the wall surface of the insertion hole and the shaft is configured to be comparatively small, so that runout of the tip of the shaft when the shaft moves in the axial direction or rotates about the axis can be suppressed by the wall surface of the insertion hole.

Hereinafter, a specific example of the present invention will be described with reference to the drawings. A dimension, material, shape, relative arrangement and the like of a component described in the present example do not intend to restrict a technical scope of the invention unless otherwise described.

Embodiment

FIG.1is an appearance view of an actuator1according to the present embodiment. The actuator1includes a housing2having a substantially rectangular parallelepiped outer shape, and a lid200is attached to the housing2.FIG.2is a schematic configuration view illustrating an inner structure of the actuator1according to the present embodiment. A part of a shaft10is housed within the housing2. The shaft10is formed to be hollow on a tip10A side. In a material of the shaft10and the housing2, for example, a metal (e.g., aluminum) may be used, or a resin or the like may be used. Note that in the following description, an XYZ orthogonal coordinate system will be set, and positions of respective members will be described with reference to this XYZ orthogonal coordinate system. A long side direction of the largest surface of the housing2, i.e., a direction of a central axis100of the shaft10is a Z-axis direction, a short side direction of the largest surface of the housing2is an X-axis direction, and a direction that is orthogonal to the largest surface of the housing2is a Y-axis direction. The Z-axis direction is also a perpendicular direction. Note that hereinafter, an upper side in the Z-axis direction inFIG.2is an upper side of the actuator1, and a lower side in the Z-axis direction inFIG.2is a lower side of the actuator1. Furthermore, a right side in the X-axis direction inFIG.2is a right side of the actuator1, and a left side in the X-axis direction inFIG.2is a left side of the actuator1. Additionally, a front side in the Y-axis direction inFIG.2is a front side of the actuator1, and a back side in the Y-axis direction inFIG.2is a back side of the actuator1. The housing2is formed such that a dimension in the Z-axis direction is larger than a dimension in the X-axis direction, and a dimension in the X-axis direction is larger than a dimension in the Y-axis direction. In the housing2, a region corresponding to one surface (a front surface inFIG.2) orthogonal to the Y-axis direction is open, and this opening is closed with the lid200. The lid200is fixed to the housing2with, for example, screws.

The housing2houses therein a rotating motor20that rotates the shaft10about the central axis100, a linear motion motor30that moves the shaft10relatively straight in a direction along the central axis100(i.e., the Z-axis direction) relative to the housing2, and an air control mechanism60. Furthermore, a shaft housing50into which the shaft10is inserted is attached to a lower end face202of the housing2in the Z-axis direction. In the housing2, a recess202B is formed to be recessed from the lower end face202toward an interior of the housing2, and a part of the shaft housing50is inserted into the recess202B. A through hole2A in the Z-axis direction is formed in an upper end of the recess202B in the Z-axis direction, and the shaft10is inserted into the through hole2A and the shaft housing50. The tip10A of the shaft10on the lower side in the Z-axis direction protrudes outward from the shaft housing50. The shaft10is provided at a center of the housing2in the X-axis direction and a center of the housing in the Y-axis direction. That is, the shaft10is provided such that a central axis extending in the Z-axis direction through the center of the housing2in the X-axis direction and the center of the housing in the Y-axis direction is superimposed on the central axis100of the shaft10. The shaft10is moved straight in the Z-axis direction by the linear motion motor30, and is rotated about the central axis100by the rotating motor20.

A base end10B side of the shaft10that is an end on a side opposite to the tip10A (an upper end in the Z-axis direction) is housed in the housing2, and connected to an output shaft21of the rotating motor20. The rotating motor20rotatably supports the shaft10. A central axis of the output shaft21of the rotating motor20coincides with the central axis100of the shaft10. The rotating motor20includes, in addition to the output shaft21, a stator22, a rotor23that rotates in the stator22, and a rotary encoder24that detects a rotation angle of the output shaft21. The rotor23rotates relative to the stator22, and the output shaft21and the shaft10also rotate in conjunction with the stator22.

The linear motion motor30includes a stator31fixed to the housing2, and a mover32that relatively moves in the Z-axis direction relative to the stator31. The linear motion motor30is, for example, a linear motor. The stator31is provided with a plurality of coils31A, and the mover32is provided with a plurality of permanent magnets32A. The coils31A are arranged at a predetermined pitch in the Z-axis direction, and a plurality of sets of three coils31A of U, V, and W-phases are provided. In the present embodiment, a three-phase armature current is applied to the coils31A of the U, V, and W-phases to generate a straight moving magnetic field, and the mover32is straight moved relative to the stator31. The linear motion motor30is provided with a linear encoder38that detects a relative position of the mover32to the stator22. Note that in place of the above configuration, the stator31may be provided with a permanent magnet, and the mover32may be provided with a plurality of coils.

The mover32of the linear motion motor30is coupled to the stator22of the rotating motor20via a linear motion table33. The linear motion table33is movable with movement of the mover32of the linear motion motor30. The movement of the linear motion table33is guided in the Z-axis direction by a linear motion guide device34. The linear motion guide device34includes a rail34A fixed to the housing2, and a slider block34B attached to the rail34A. The rail34A is configured to extend in the Z-axis direction, and the slider block34B is configured to be movable along the rail34A in the Z-axis direction.

The linear motion table33is fixed to the slider block34B, and is movable together with the slider block34B in the Z-axis direction. The linear motion table33is coupled to the mover32of the linear motion motor30via two coupling arms35. The two coupling arms35couple opposite ends of the mover32in the Z-axis direction to opposite ends of the linear motion table33in the Z-axis direction. Furthermore, the linear motion table33is coupled, on a central side of the opposite ends, to the stator31of the rotating motor20via two coupling arms36. Note that the coupling arm36on the upper side in the Z-axis direction will be referred to as a first arm36A, and the coupling arm36on the lower side in the Z-axis direction will be referred to as a second arm36B. Furthermore, the first arm36A and the second arm36B will be referred to simply as the coupling arms36when the arms are not distinguished. For the stator22of the rotating motor20, since the linear motion table33is coupled to the stator22of the rotating motor20via the coupling arms36, the stator22of the rotating motor20also moves with the movement of the linear motion table33. The coupling arm36has a quadrangular cross section. A strain gauge37is fixed to a surface of each coupling arm36which faces upward in the Z-axis direction. Note that the strain gauge37fixed to the first arm36A will be referred to as a first strain gauge37A, and the strain gauge37fixed to the second arm36B will be referred to as a second strain gauge37B. The first strain gauge37A and the second strain gauge37B will be referred to simply as the strain gauges37when the gauges are not distinguished. Note that two strain gauges37of the present embodiment are provided on surfaces of the coupling arms36which face upward in the Z-axis direction, respectively. In place of the surfaces, the gauges may be provided on surfaces of the coupling arm36that face downward in the Z-axis direction.

The air control mechanism60is a mechanism to generate a positive pressure or a negative pressure at the tip10A of the shaft10. That is, the air control mechanism60sucks air in the shaft10during pickup of a workpiece W, to generate the negative pressure at the tip10A of the shaft10. Consequently, the workpiece W is suctioned onto the tip10A of the shaft10. Furthermore, air is supplied into the shaft10, to generate the positive pressure at the tip10A of the shaft10. Thus, the workpiece W is easily removed from the tip10A of the shaft10.

The air control mechanism60includes a positive pressure passage61A (see a dashed chain line) through which positive pressure air flows, a negative pressure passage61B (see a double-dashed chain line) through which negative pressure air flows, and a shared passage61C (see a broken line) shared by the positive pressure air and the negative pressure air. The positive pressure passage61A has one end connected to a positive pressure connector62A provided on an upper end face201of the housing2in the Z-axis direction, and the positive pressure passage61A has the other end connected to a solenoid valve for positive pressure (hereinafter, referred to as a positive pressure solenoid valve63A). The positive pressure solenoid valve63A is opened and closed by an after-mentioned controller7. Note that the positive pressure passage61A has one end portion constituted of a tube610, and the other end portion constituted of a hole made in a block600. The positive pressure connector62A extends through the upper end face201of the housing2in the Z-axis direction, and the positive pressure connector62A is connected to an external tube linked to an air discharging pump or the like.

The negative pressure passage61B has one end connected to a negative pressure connector62B provided on the upper end face201of the housing2in the Z-axis direction, and the negative pressure passage61B has the other end connected to a solenoid valve for negative pressure (hereinafter, referred to as a negative pressure solenoid valve63B). The negative pressure solenoid valve63B is opened and closed by the after-mentioned controller7. Note that the negative pressure passage61B has one end portion constituted of a tube620, and the other end portion constituted of a hole made in the block600. The negative pressure connector62B extends through the upper end face201of the housing2in the Z-axis direction, and the negative pressure connector62B is connected to an external tube linked to an air sucking pump or the like.

The shared passage61C is constituted of a hole made in the block600. The shared passage61C has one end branching into two to be connected to the positive pressure solenoid valve63A and the negative pressure solenoid valve63B, and the shared passage61C has the other end connected to an air flow passage202A that is a through hole formed in the housing2. The air flow passage202A communicates with the shaft housing50. The negative pressure solenoid valve63B is opened and the positive pressure solenoid valve63A is closed, to communicate between the negative pressure passage61B and the shared passage61C, thereby generating the negative pressure in the shared passage61C. Then, air is sucked from the shaft housing50through the air flow passage202A. On the other hand, the positive pressure solenoid valve63A is opened and the negative pressure solenoid valve63B is closed, to communicate between the positive pressure passage61A and the shared passage61C, thereby generating the positive pressure in the shared passage61C. Then, air is supplied into the shaft housing50through the air flow passage202A. The shared passage61C is provided with a pressure sensor64that detects a pressure of air in the shared passage61C and a flow sensor65that detects a flow rate of air in the shared passage61C.

Note that in the actuator1illustrated inFIG.2, the positive pressure passage61A and the negative pressure passage61B have a part constituted of a tube, and the other part constituted of a hole made in the block600. The present invention is not limited to this embodiment, and all the passages may be constituted of tubes, or all the passages may be constituted of holes made in the block600. This also applies to the shared passage61C, and the passage may be entirely constituted of a tube, or may be constituted by combined use of the tube. Note that a material of the tube610and the tube620may be a material such as a resin having flexibility, or may be a material such as a metal that does not have any flexibility. Furthermore, an atmospheric pressure may be supplied, instead of supplying the positive pressure to the shaft housing50by use of the positive pressure passage61A.

Additionally, on the upper end face201of the housing2in the Z-axis direction, provided are a connector (hereinafter, referred to as an inlet connector91A) that is an inlet of air for cooling the rotating motor20and a connector (hereinafter, referred to as an outlet connector91B) that is an outlet of air from the housing2. The inlet connector91A and the outlet connector91B extend through the upper end face201of the housing2so that air can flow through. A tube linked to an air discharge pump or the like is connected to the inlet connector91A from outside the housing2, and a tube that discharges air flowing out of the housing2is connected to the outlet connector91B from outside the housing2. The interior of the housing2is provided with a metal pipe (hereinafter, referred to as a cooling pipe92) through which air for cooling the rotating motor20flows, and the cooling pipe92has one end connected to the inlet connector91A. The cooling pipe92is formed to extend from the inlet connector91A in the Z-axis direction to a vicinity of the lower end face202of the housing2, and to curve in the vicinity of the lower end face202such that the pipe, at the other end, faces the rotating motor20. Thus, air is supplied from the lower side in the Z-axis direction into the housing2, thereby allowing efficient cooling. Furthermore, the cooling pipe92extends through the stator31, to take heat from the coils31A of the linear motion motor30. The coils31A are arranged around the cooling pipe92, to take more heat from the coils31A provided in the stator31.

The upper end face201of the housing2in the Z-axis direction is connected to a connector41including a power supplying wire and a signal line. Furthermore, the housing2is provided with the controller7. The wire or signal line pulled from the connector41into the housing2is connected to the controller7. The controller7is provided with a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), and an erasable programmable ROM (EPROM), which are connected to one another via a bus. In the EPROM, various programs, various tables and others are stored. The program stored in the EPROM is loaded and executed in a work area of the RAM by the CPU, and through the execution of this program, the rotating motor20, the linear motion motor30, the positive pressure solenoid valve63A, the negative pressure solenoid valve63B and others are controlled. Thus, the CPU achieves a function that meets a predetermined purpose. Furthermore, output signals of the pressure sensor64, the flow sensor65, the strain gauge37, the rotary encoder24and the linear encoder38are input into the controller7.

FIG.3is a cross-sectional view illustrating a schematic configuration including the shaft housing50and the tip10A of the shaft10. The shaft housing50includes a housing body51, two rings52, a filter53, and a filter stop54. In the housing body51, a through hole51A is formed into which the shaft10is inserted. The through hole51A extends through the housing body51in the Z-axis direction, and an upper end of the through hole51A in the Z-axis direction communicates with the through hole2A formed in the housing2. A diameter of the through hole51A is larger than an outer diameter of the shaft10. Consequently, a space is provided between an inner surface of the through hole51A and an outer surface of the shaft10. In opposite ends of the through hole51A, enlarged parts51B each having a hole diameter enlarged are provided. The rings52are fitted in two enlarged parts51B, respectively. Each ring52is formed in a cylindrical shape, and an inner diameter of the ring52is slightly larger than the outer diameter of the shaft10. Consequently, a space is also formed between an inner surface of the ring52and the outer surface of the shaft10. Therefore, the shaft10is movable in the Z-axis direction in the ring52, and the shaft10is rotatable about the central axis100in the ring52. However, the space formed between the inner surface of the ring52and the outer surface of the shaft10is smaller than the space formed between the inner surface of the through hole51A excluding the enlarged parts51B and the outer surface of the shaft10. Here, a size of the space formed between the inner surface of the ring52and the outer surface of the shaft10is, for example, 20 μm or less. Note that the ring52on the upper side in the Z-axis direction will be referred to as a first ring52A, and the ring52on the lower side in the Z-axis direction will be a second ring52B. The first ring52A and the second ring52B will be referred to simply as the rings52when the rings are not distinguished. In a material of the ring52, for example, a metal or a resin may be used.

A protrusion511protruding in opposite right and left directions in the X-axis direction is formed in a central part of the housing body51in the Z-axis direction. In the protrusion511, a mounting surface511A is formed which is a surface parallel to the lower end face202of the housing2, the surface coming in contact with the lower end face202, when the shaft housing50is mounted to the lower end face202of the housing2. The mounting surface511A is a surface orthogonal to the central axis100. Furthermore, a part512that is a part of the shaft housing50on the upper side of the mounting surface511A in the Z-axis direction is formed to fit in the recess202B formed in the housing2, when the shaft housing50is mounted to the housing2.

The space is provided between the inner surface of the through hole51A and the outer surface of the shaft10as described above. As a result, in the housing body51, an inner space500is formed which is a space surrounded with the inner surface of the through hole51A, the outer surface of the shaft10, a lower end face of the first ring52A, and an upper end face of the second ring52B. Furthermore, in the shaft housing50, a control passage501is formed which communicates between an opening of the air flow passage202A formed in the lower end face202of the housing2and the inner space500to form an air passage. The control passage501includes a first passage501A extending in the X-axis direction, a second passage501B extending in the Z-axis direction, and a filter part501C that is a space where the first passage501A and the second passage501B are connected and the filter53is disposed. The first passage501A has one end connected to the inner space500, and the other end connected to the filter part501C. The second passage501B has one end opened in the mounting surface511A and aligned to be connected to the opening of the air flow passage202A.

Furthermore, the second passage501B has the other end connected to the filter part501C. In the filter part501C, the filter53formed in a cylindrical shape is provided. The filter part501C is formed in a columnar space extending in the X-axis direction such that a central axis coincides with that of the first passage501A. An inner diameter of the filter part501C is substantially equal to an outer diameter of the filter53. The filter53is inserted into the filter part501C in the X-axis direction. After the filter53is inserted into the filter part501C, an end of the filter part501C which is an insertion port of the filter53is closed with the filter stop54. The other end of the second passage501B is connected to the filter part501C from a side of an outer circumferential surface of the filter53. Furthermore, the other end of the first passage501A communicates with a central side of the filter53. Therefore, air flowing through a space between the first passage501A and the second passage501B flows through the filter53. Therefore, foreign matter is captured by the filter53, even if the foreign matter is sucked together with air into the inner space500, for example, when the negative pressure is generated at the tip10A. In the one end of the second passage501B, a groove501D is formed to hold sealant.

In vicinities of opposite ends of the protrusion511in the X-axis direction, two bolt holes51G are formed into which bolts are inserted, when the shaft housing50is fixed to the housing2by use of the bolts. The bolt holes51G extend through the protrusion511in the Z-axis direction and opens in the mounting surface511A.

A hollow part11is formed on the tip10A side of the shaft10such that the shaft10is hollow. The hollow part11has one end opened at the tip10A. Furthermore, at the other end of the hollow part11, a communication hole12that communicates between the inner space500and the hollow part11in the X-axis direction is formed. The communication hole12is formed to communicate between the inner space500and the hollow part11, in an entire range of a stroke when the shaft10is moved in the Z-axis direction by the linear motion motor30. Therefore, the tip10A of the shaft10communicates with the air control mechanism60through the hollow part11, the communication hole12, the inner space500, the control passage501, and the air flow passage202A. Note that the communication hole12may be formed in the Y-axis direction in addition to the X-axis direction.

According to this configuration, the communication hole12always communicates between the inner space500and the hollow part11, even if the shaft10is at any position in the Z-axis direction when the linear motion motor30is driven to move the shaft10in the Z-axis direction. Furthermore, the communication hole12always communicates between the inner space500and the hollow part11, even if a rotation angle of the shaft10is any angle about the central axis100when the rotating motor20is driven to rotate the shaft10about the central axis100. Therefore, a communication state between the hollow part11and the inner space500is maintained even if the shaft10is in any state, and hence the hollow part11always communicates with the air control mechanism60. For that reason, air in the hollow part11is sucked through the air flow passage202A, the control passage501, the inner space500, and the communication hole12, if the positive pressure solenoid valve63A is closed and the negative pressure solenoid valve63B is opened in the air control mechanism60, regardless of the position of the shaft10. As a result, the negative pressure can be generated in the hollow part11. That is, the negative pressure can be generated at the tip10A of the shaft10, and hence the workpiece W can be sucked to the tip10A of the shaft10. Note that the space is also formed between the inner surface of the ring52and the outer surface of the shaft10as described above. However, this space is smaller than a space that forms the inner space500(i.e., the space formed between the inner surface of the through hole51A and the outer surface of the shaft10). Thus, in the air control mechanism60, the positive pressure solenoid valve63A is closed and the negative pressure solenoid valve63B is opened, so that a flow rate of air flowing through the space between the inner surface of the ring52and the outer surface of the shaft10can be suppressed, even if air is sucked from the inner space500. Consequently, the negative pressure at which the workpiece W can be picked up can be generated at the tip10A of the shaft10. On the other hand, the positive pressure can be generated in the hollow part11, if the positive pressure solenoid valve63A is opened and the negative pressure solenoid valve63B is closed in the air control mechanism60, regardless of the position of the shaft10. That is, since the positive pressure can be generated at the tip10A of the shaft10, the workpiece W can be quickly removed from the tip10A of the shaft10.

(Pick and Place Operation)

Description will be made as to pick and place of the workpiece W by use of actuator1. The controller7executes a predetermined program to perform the pick and place. During the pickup of the workpiece W, the positive pressure solenoid valve63A and the negative pressure solenoid valve63B are both in a closed state, until the shaft10comes in contact with the workpiece W. In this case, the pressure of the tip10A of the shaft10is the atmospheric pressure. Then, the linear motion motor30moves the shaft10downward in the Z-axis direction. Upon contact of the shaft10with the workpiece W, the linear motion motor30is stopped. After the linear motion motor30is stopped, the negative pressure solenoid valve63B is opened to generate the negative pressure at the tip10A of the shaft10, thereby sucking the workpiece W to the tip10A of the shaft10. Afterward, the linear motion motor30moves the shaft10upward in the Z-axis direction. At this time, the shaft10is rotated by the rotating motor20as required. Thus, the workpiece W can be picked up.

Next, during the placing of the workpiece W, the shaft10in a state where the workpiece W is suctioned onto the tip10A is moved downward in the Z-axis direction by the linear motion motor30. If the workpiece W is grounded, the linear motion motor30is stopped, to stop the movement of the shaft10. Furthermore, the negative pressure solenoid valve63B is closed and the positive pressure solenoid valve63A is opened, to generate the positive pressure in the tip10A of the shaft10. Afterward, the linear motion motor30moves the shaft10upward in the Z-axis direction, and the tip10A of the shaft10accordingly leaves the workpiece W.

Here, during the pickup of the workpiece W, it is detected, using the strain gauge37, that the tip10A of the shaft10comes in contact with the workpiece W. Hereinafter, this method will be described. Note that it is similarly detected that the workpiece W is grounded during the placing of the workpiece W. If the tip10A of the shaft10comes in contact with the workpiece W and the tip10A pushes the workpiece W, a load is generated between the shaft10and the workpiece W. That is, the shaft10receives a force from the workpiece W due to reaction when the shaft10applies the force to the workpiece W. The force received from the workpiece W by the shaft10acts in a direction to generate strain relative to the coupling arm36. That is, the strain is generated in the coupling arm36at this time. This strain is detected by the strain gauge37. Then, the strain detected by the strain gauge37has correlation with the force received from the workpiece W by the shaft10. Consequently, the force received from the workpiece W by the shaft10, that is, the load generated between the shaft10and the workpiece W can be detected based on a detected value of the strain gauge37. A relation between the detected value of the strain gauge and the load can be obtained beforehand by experiment, simulation or the like.

Thus, since the load generated between the shaft10and the workpiece W can be detected based on the detected value of the strain gauge37, for example, it may be determined, upon the generation of the load, that the tip10A of the shaft10comes in contact with the workpiece W, or it may be determined, in consideration of influence of error or the like, that the tip10A of the shaft10comes in contact with the workpiece W in a case where a detected load is equal to or larger than a predetermined load. Note that the predetermined load is a threshold by which it is determined that the shaft10comes in contact with the workpiece W. Furthermore, the predetermined load may be set as the load with which it is possible to more securely pick up the workpiece W while inhibiting damage on the workpiece W. Additionally, the predetermined load can be changed in accordance with a type of workpiece W.

(Effects of Configuration According to the Present Embodiment)

As described above, the actuator1according to the present embodiment includes the shaft housing50. A tip side of the shaft10is inserted into the shaft housing50. Then, in the housing body51of the shaft housing50, the space is formed between the inner surface of the ring52into which the shaft10is inserted and the outer surface of the shaft10. Therefore, the shaft10is movable in an axial direction and/or rotatable about an axis even in a state where the shaft10is inserted into the ring52.

Furthermore, in the shaft housing50, the inner space500formed in an interior of the housing body51communicates with the hollow part11of the shaft10through the communication hole12formed in the shaft10. Furthermore, the control passage501in communication with the air flow passage202A in the actuator1is connected to the inner space500. Therefore, air is sucked through the control passage501from the inner space500, so that air can be sucked from the hollow part11of the shaft10through the inner space500and the communication hole12.

Therefore, the configuration according to the present embodiment makes it possible to suck air from the hollow part11of the shaft10, without directly attaching rotation equipment such as a rotary joint or an air pipe to the shaft10of the actuator1, so that the negative pressure can be generated at the tip10A of the shaft10.

Furthermore, in the configuration according to the present embodiment, a seal member of an elastic material is not provided between the shaft10and the ring52. Therefore, as compared with a case where the seal member is provided between these components, sliding resistance generated with movement or rotation of the shaft10can be suppressed. This can increase accuracy of control of the movement of the shaft10by the linear motion motor30and control of the rotation of the shaft10by the rotating motor20.

Furthermore, in the configuration according to the present embodiment, the space formed between the outer surface of the shaft10and the inner surface of the ring52is configured to be comparatively small. Consequently, runout (position shift on an X-Y plane) of the tip10A of the shaft10when the shaft10moves and/or rotates can be suppressed by the inner surface of the ring52.

Note that in the present embodiment, a structure of the shaft housing50corresponds to “a negative pressure-generating structure” according to the present invention. Furthermore, in the present embodiment, an inner hole of the ring52corresponds to “an insertion hole” according to the present invention, the inner space500corresponds to “an inner space” according to the present invention, and the control passage501corresponds to “an air passage” according to the present invention.

(Modification)

In the above embodiment, the hollow part11is formed on the tip10A side of the shaft10. Therefore, in the actuator1, the shaft housing50is attached to the lower end face202of the housing2in the Z-axis direction, and the shaft10on the tip10A side is inserted into the shaft housing50. However, a position where the shaft housing50is installed is not limited to such a position.

For example, in the actuator, not only a shaft on a side of a tip protrudes below a housing, but also the shaft on a side of a base end (an end on a side opposite to the tip) protrudes above the housing, and a hollow part is formed from the tip to the base end in the shaft. In this case, a shaft housing may be attached to the housing of the actuator so that the shaft on the base end side is inserted into the shaft housing. Furthermore, in this case, the hollow part of the shaft may communicate with an inner space of the shaft housing through an opening in the shaft on the base end side.

Also in this configuration, air is sucked from the inner space of the shaft housing, so that air can be sucked from the hollow part of the shaft through the opening in the shaft on the base end side. Then, air is sucked from the hollow part of the shaft, so that a negative pressure can be generated at the tip of the shaft.

DESCRIPTION OF THE REFERENCE NUMERALS AND SYMBOLS

1actuator2housing10shaft10A tip11hollow part20rotating motor22stator23rotor30linear motion motor31stator32mover36coupling arm37strain gauge50shaft housing60air control mechanism500inner space501control passage