JP2008264987A - Robot arm - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a robot arm piping to a work holding means with high pressure air as its driving source of which is not exposed outside, capable of saving a space and capable of keeping its maintaining property favorable. <P>SOLUTION: This robot arm is constituted of an arm shaft 3 on which a large number of magnetic poles are arranged with prescribed pitches along the axial direction, a forcer having a through hole in which this arm shaft 3 is fitted with a play, constituting a linear motor with this arm shaft 3 and to advance and retreat the arm shaft 3 in the axial direction in correspondence with an applied electric signal and the work holding means 4 provided on one end of the arm shaft 3 and to move in correspondence with air pressure. A fluid supplying hole 30 to make the air pressure work on the work holding means 4 is formed to pass through along the axial direction on the arm shaft 3, and this fluid supplying hole 30 is connected to a supplying port of the work holding means 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a robot arm for holding and transferring a workpiece that is a transfer object in various industrial equipment, and more particularly to an improvement of a robot arm in which a workpiece holding means that operates by air pressure is provided at the tip of an arm shaft.

  Conventionally, as this type of robot arm, there is a robot arm that converts the rotational movement of the motor into a translational movement of the arm shaft by a ball screw, and thereby moves the workpiece holding means provided at the tip of the arm shaft forward and backward. Are known. However, in such a robot arm using a ball screw, there is a limit to speeding up the translation of the arm axis because of the relationship between the critical speed in the rotation of the ball screw and the noise generated by the high-speed rolling of the ball. is there.

  On the other hand, a robot arm that uses a rod-type linear motor actuator is known as a robot arm suitable for a purpose of conveying a lightweight workpiece at high speed. This rod type linear motor actuator has a rod shape and a magnet rod in which N poles and S poles are repeatedly arranged at a predetermined pitch along the axial direction, and a slight gap around the magnet rod. The magnetic rod is configured to advance and retract with respect to the forcer by energizing a coil member provided in the forcer.

In this rod type linear motor actuator, a coil member surrounds the magnet rod so that a strong thrust can be exerted, and a large thrust can be applied to the magnet rod while reducing the size. . In addition, since the translational motion of the magnet rod can be obtained directly by the linear motor, a robot arm that can handle the workpiece at high speed is constructed by providing a workpiece holding means at the tip of the magnet rod as the arm axis. Is possible.
WO2006 / 035946

  Various devices can be selected as the work holding means provided at the tip of the magnet rod. However, from the viewpoint of increasing the response speed of the work clamp and release, and reducing the weight and size, the air that operates according to the air pressure. Means such as a chuck are frequently used.

  However, when an air chuck as a work holding means is attached to the tip of the magnet rod, it is necessary to connect a pipe for supplying high-pressure air to the air chuck, and a piping space around the work holding means. There was a concern that the maintenance of the robot arm itself would deteriorate.

  The present invention has been made in view of such problems, and the object of the present invention is that the piping to the work holding means for reducing the drive of high-pressure air is not exposed to the outside, and space saving is possible. Another object is to provide a robot arm that can maintain good maintainability.

  The robot arm of the present invention that achieves the above object has an arm shaft in which a large number of magnetic poles are arranged at a predetermined pitch along the axial direction, a through hole into which the arm shaft is loosely fitted, and linearly coupled with the arm shaft. The motor comprises a forcer that advances and retracts the arm shaft in the axial direction in accordance with an applied electrical signal, and a work holding means that is provided at one end of the arm shaft and operates in accordance with air pressure. A fluid supply hole for allowing air pressure to act on the work holding means is formed through the arm shaft along the axial direction, and the fluid supply hole is connected to a supply port of the work holding means.

  According to the present invention, since the high-pressure air is supplied to the work holding means through the fluid supply hole penetrating the arm shaft functioning as a magnet rod, the work holding means is fixed to the arm shaft. If the fluid supply hole of the arm shaft is connected to the high pressure air supply port provided in the work holding means, it is not necessary to separately provide a high pressure air supply pipe outside the arm shaft. Thereby, a useless space is not required around the arm shaft and the work holding means, and the space of the robot arm can be saved. In addition, since the piping is not exposed around the arm shaft and the work holding means, the maintainability of the robot arm is also improved.

  Further, since the arm shaft is cooled by the high-pressure air passing through the fluid supply hole, even if the forcer constituting the linear motor coupled with the arm shaft generates heat due to energization, the forcer is indirectly connected via the arm shaft. It is possible to cool.

  Hereinafter, a robot arm of the present invention will be described in detail with reference to the accompanying drawings.

  1 and 2 are schematic views showing an example of an embodiment of a robot arm of the present invention. The robot arm 1 includes a linear motor actuator 2 having an arm shaft 3 as a magnet rod, and an air chuck 4 as a work holding means fixed to the tip of the arm shaft 3. 3 is moved forward and backward to allow the air chuck 4 to approach the work 5 as a conveyance object, and the work 5 can be held by the gripping claws 40 of the air chuck 4.

  In order to supply the air chuck 4 with high-pressure air serving as a driving source for the gripping claws 40, the arm shaft 3 is formed with a fluid supply hole 30 extending along the axial direction. 3, the fluid supply hole 30 is configured to be connected to a high-pressure air supply port provided in the air chuck 4.

  A compressor 7 is connected to the fluid supply hole 30 of the arm shaft 3 via a valve 6 that controls the operation of the air chuck 4. The compressor 7 is supplied by controlling the opening and closing of the valve 6. High-pressure air acts on the air chuck 4 through the fluid supply hole 30.

  FIG. 2 shows a first embodiment of the linear motor actuator 2. The linear motor actuator 2 includes the arm shaft 3 and a forcer 31 that has a through hole in which the arm shaft 3 is loosely fitted and moves the arm shaft 3 back and forth in response to application of a signal.

  The arm shaft 3 is formed by arranging a plurality of magnets magnetized in a hollow portion of a stainless steel pipe, and both ends of the stainless steel pipe are closed by plugs. As shown in FIG. 3, the magnets 3a adjacent to each other in the stainless steel pipe are arranged with their directions reversed alternately so that the N poles or the S poles face each other. As a result, N pole poles and S pole poles are alternately arranged on the arm shaft 3 along the longitudinal direction thereof, and this constitutes a magnet rod as a field magnet of the linear motor. Further, the fluid supply hole 30 is formed through the center of the arm shaft 3 along the axial direction. The fluid supply hole 30 is formed so as to penetrate each magnet, and also penetrates the plug, and is formed continuously along the axial direction of the arm shaft 3.

  On the other hand, the forcer 31 is formed in a quadrangular prism shape whose section perpendicular to the axial direction of the arm shaft 3 is rectangular, and a through hole through which the arm shaft 3 passes is formed at the center. The forcer 31 includes a forcer housing 33 in which a coil member 32 is housed, a pair of forcer ends 34 as bearing support members fixed to both longitudinal front and rear ends of the forcer housing 33, and the forcer end. 34 and a pair of bearing bushes 35 that support the advance and retreat of the arm shaft 3. The coil member 32 is arranged on the inner peripheral surface of a through hole formed in the forcer housing 33. The arm shaft 3 is in sliding contact with the bearing bush 35, but is not in contact with the forcer end 34 and the coil member 32 through a gap of about 0.2 mm. In addition, a plurality of heat radiating fins are provided on the surface of the forcer housing 33 to transmit heat generated in the coil member 32 to the forcer housing 33 when the coil member 32 is energized, The coil member 32 itself can be effectively cooled by dissipating heat into the atmosphere.

  3 and 4 show the operation principle of the linear motor actuator 2. FIG. The coil member 32 has a coil group including three coils of U, V, and W phases as one set. The coil member 32 of any phase is ring-shaped and faces the outer peripheral surface of the arm shaft 3 with a slight gap. Further, the arrangement pitch of the coil members 32 of each phase is set to be shorter than the arrangement pitch of the magnets 3 a of the arm shaft 3. A magnetic flux 3b is formed on the macnet rod 3 from the magnetic pole of the S pole toward the magnetic pole of the N pole, and the forcer 31 incorporates a magnetic pole sensor (not shown) for detecting the magnetic flux density. Therefore, the positional relationship of each magnetic pole (N pole and S pole) of the arm shaft 3 with respect to the coil member 32 is grasped from the detection signal output from the magnetic pole sensor. The controller that controls the energization of the coil member 32 receives the detection signal of the magnetic pole sensor, calculates the optimum current corresponding to the positional relationship between the coil member 32 and each magnet 3a of the arm shaft 3, and calculates it. Each coil member 32 is energized. As a result, due to the interaction between the current flowing through each coil member 32 and the magnetic flux 3b formed by the magnet 3a, an attraction force and a repulsive force are generated between the coil member 32 and each magnet 3a, and the forcer 31 becomes a magnet rod. 3 will be propelled in the axial direction.

  In the robot arm 1 configured as described above, the forcer 31 is fixed to a moving table or the like of various transfer devices, and the robot arm 1 is sent to an arbitrary work point using the transfer device, and the linear motor actuator 2 is operated to move the arm shaft 3 forward and backward so that the air chuck 4 as the work holding means approaches the work 5, and the work 5 is held by the air chuck 4 or the work 5 that has been conveyed is released. Is something that can be done.

  At this time, since the fluid supply hole 30 is formed through the arm shaft 3, high-pressure air necessary for the operation of the air chuck 4 can be performed through the fluid supply hole 30. As long as it is fixed to the tip of the arm shaft 3, it can be used immediately. For this reason, it is not necessary to separately provide piping for connecting the air chuck 4 to the valve 6 and the compressor 7, and no unnecessary space is required around the arm shaft 3 and the air chuck 4, thereby saving the space of the robot arm 1. Can be achieved. In addition, since the piping is not exposed around the arm shaft 3 and the air chuck 4, the maintainability of the robot arm 1 is also improved.

  Since the linear motor actuator 2 shown in FIG. 2 only moves the arm shaft 3 forward and backward, even if the work 5 is gripped by the air chuck 4, the posture of the work 5 cannot be changed. It can only be used for the purpose of transporting in a posture. However, the rotation control mechanism shown in FIG. 5 is attached to the linear motor actuator 2 and a spline groove is provided on the outer peripheral surface of the arm shaft 3 to give the arm shaft 3 any rotation around the axis. The posture of the work 5 gripped by the air chuck 4 can be arbitrarily changed.

  The rotation control mechanism 8 includes a housing 80 fixed to the forcer 31, a hollow connecting shaft 82 rotatably supported through a bearing 81 in the housing 80, and an arbitrary connection with respect to the hollow connecting shaft 82. The rotary motor unit 83 gives a rotation angle and the spline nut 84 accommodated in the hollow connecting shaft 82.

  On the other hand, the arm shaft 3 has a rotating shaft portion 3c in which a spline groove is formed at the end opposite to the fixed end of the air chuck 4, and the rotating shaft portion 3c has magnets 3a arranged thereon. It is formed continuously with the part of the magnet rod. The fluid supply hole 30 is also provided in the rotary shaft portion 3 c and is formed so as to penetrate the axis of the arm shaft 3. The spline nut 84 is fitted to the rotating shaft portion 3 c, and the spline nut 84 transmits the rotation to the rotating shaft portion 3 c of the arm shaft 3. On the other hand, the spline nut 84 is configured to freely guide the rotating shaft portion 3c in the axial direction, and is configured not to prevent the arm shaft 3 from moving forward and backward.

  A rotary encoder 85 that detects the rotation angle of the arm shaft 3 is fixed to the end of the housing 80, and the rotation motor 83 is controlled based on the detected value of the rotary encoder 85. .

  When the rotation control mechanism 8 configured as described above is attached to the linear motor actuator 2, not only the translational motion in the axial direction but also the rotational motion around the shaft can be given to the arm shaft 3. Thus, the workpiece 5 held by the air chuck 4 can be rotated at an arbitrary angle to change its posture.

  FIG. 6 shows a second embodiment of the linear motor actuator 2.

  The linear motor actuator includes a spline shaft 51 having a hollow portion 50 and formed in a substantially cylindrical shape, and a pair of spline nuts 52 fitted to the outside of the spline shaft 51 via a large number of balls. The spline shaft 51 can be reciprocated in the axial direction of the spline nut 52 using a thrust generated by a linear motor housed in the hollow portion 50 of the spline shaft 51.

  The spline shaft 51 has an opening along the longitudinal direction and is formed in a substantially U-shaped cross section, and two ball rolling grooves are formed on the outer peripheral surface thereof with a phase shift of 180 °. . On the other hand, the spline nut 52 is formed in a substantially cylindrical shape whose inner diameter is slightly larger than that of the spline shaft 51, and the spline shaft is inserted through a number of balls rolling in the ball rolling groove of the spline shaft 51. 51 is fitted to the outside. The spline nut 52 has an infinite circulation path for the ball. When the spline nut 52 is moved along the spline shaft 51, the ball applies a load between the spline nut 52 and the spline shaft 51. The spline nut 52 can be continuously moved along the spline shaft 51 by circulating inside the infinite circulation path. Each spline nut 52 is provided with a screw hole 53, and a fixing screw is screwed into the screw hole 54, whereby the spline nut 52 can be fixed to another mechanical device or the like. Yes.

  On the other hand, a magnet rod 53 as a stator of the linear motor is accommodated in the hollow portion 50 of the spline shaft 51. Such a magnet rod 53 is formed by alternately arranging N poles and S poles of permanent magnets along the axial direction, and may be manufactured by packing a large number of permanent magnets inside a steel pipe, or a molded round shape. The pole may be magnetized later to form a magnetic pole.

  A pair of end caps 55 are fitted in openings at both axial ends of the spline shaft 51 to close the hollow portion 50 of the spline shaft 51, and the magnet rod 53 is connected to both ends within the hollow portion of the spline shaft 51. I support it.

  A forcer 56 constituting a linear motor is loosely fitted around the magnet rod 53 with a slight gap. The forcer 56 is made of aluminum having excellent thermal conductivity, and has a hollow portion through which the magnet rod 53 penetrates. An excitation coil (not shown) as a stator is formed on the inner peripheral surface of the hollow portion. Is stored. The exciting coil has a coil group including three coils of U, V, and W phases. The excitation coils of any phase are ring-shaped and face the outer peripheral surface of the magnet rod 53 with a slight gap. The arrangement pitch of the excitation coils of each phase is set shorter than the arrangement pitch of the permanent magnets in the magnet rod 53. A magnetic flux is formed in the magnet rod 53 from the magnetic pole of the S pole toward the magnetic pole of the N pole, and a magnetic pole sensor for detecting the magnetic flux density is built in the coil member. Therefore, the positional relationship of each magnetic pole (N pole and S pole) of the magnet rod with respect to the exciting coil is grasped from the detection signal output from the magnetic pole sensor. The controller that controls the energization of the exciting coil receives the detection signal of the magnetic pole sensor, calculates the optimum current according to the positional relationship between the exciting coil and each magnetic pole of the magnet rod, and applies it to each exciting coil. Energize. As a result, due to the interaction between the current flowing through each exciting coil and the magnetic flux formed by the permanent magnet, an attractive force and a repulsive force are generated between the exciting coil and each magnetic pole of the permanent magnet. Will be propelled in the axial direction.

  The forcer 56 has an end portion in the longitudinal direction fixed to the spline nut 52, and the pair of spline nuts 52 are coupled by the forcer 56. For this reason, the forcer is positioned in the hollow portion 50 of the spline shaft 51 via a pair of spline nuts 52 that are spaced apart in the axial direction, and the forcer 56 is propelled along the magnet rod 53. Then, the spline nut 52 is propelled along the spline shaft 51. However, in this embodiment, since the spline nut 52 is fixed to another mechanical device, the spline shaft 51 is propelled in the axial direction with respect to the spline nut 52.

  The fluid supply hole is formed through the center of the magnet rod 53 along the axial direction. The fluid supply hole is formed so as to penetrate each magnet arranged in the magnet rod 53. A tap hole 57 for attaching the air chuck 4 is formed at the center of an end cap 55 that supports both ends of the magnet rod 53 at both ends of the spline shaft 51, and the tap hole 57 is formed in the magnet rod 53. The fluid supply hole is connected in communication. That is, in the linear motor actuator of the second embodiment, the spline shaft 51 that houses the magnet rod 53 corresponds to the arm shaft 3 shown in FIG.

  Also in the linear motor actuator of the second embodiment, since the fluid supply hole 30 is formed through the arm shaft 3, piping for connecting the air chuck 4 to the valve 6 and the compressor 7 is provided. There is no need to provide them separately, and no unnecessary space is required around the arm shaft 3 and the air chuck 4, so that the space of the robot arm 1 can be saved.

It is the schematic which shows embodiment of the robot arm of this invention. It is a perspective view which shows 1st embodiment of the linear motor actuator which can be used for a robot arm. It is a side view which shows the operation principle of the linear motor actuator which concerns on embodiment. It is a front view which shows the operation principle of the linear motor actuator which concerns on embodiment. It is sectional drawing which shows an example of the rotation control mechanism attached to a linear motor actuator. It is a perspective view which shows 2nd embodiment of the linear motor actuator which can be used for a robot arm.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Robot arm, 2 ... Linear motor actuator, 3 ... Arm axis, 4 ... Air chuck, 5 ... Workpiece, 30 ... Fluid supply hole, 31 ... Forcer

Claims (2)

An arm shaft in which a large number of magnetic poles are arranged at a predetermined pitch along the axial direction, and a through-hole into which the arm shaft is loosely fitted, constitutes a linear motor together with the arm shaft, and responds to an applied electrical signal A forcer that moves the arm shaft forward and backward in the axial direction, and a work holding means that is provided at one end of the arm shaft and operates according to air pressure,
The robot arm according to claim 1, wherein a fluid supply hole for allowing air pressure to act on the workpiece holding means is formed through the arm shaft along the axial direction. The arm shaft includes a magnet shaft portion in which the magnetic poles are arranged and a rotating shaft portion in which a spline groove is formed along the axial direction.
A spline nut that is assembled to the rotating shaft portion of the arm shaft and guides the arm shaft in the axial direction is rotatably held on the forcer, and the spline nut is driven to rotate according to an applied electric signal. The robot arm according to claim 1, wherein the rotating motor unit is fixed on the same axis as the arm shaft.

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