JP2000158144A - Electric cylinder, welding gun unit using it, and welding robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a small and light cylinder while supporting a working rod against a moment load rigidly by constituting this invention with a power transmitting means for transmitting rotation of a motor fixed to a locus rail to a feeding screw, and a working rod which is fixed to a slide member, protruded from one end of the locus rail, and reciprocated corresponding to movement of the slide member. SOLUTION: A reaction force of a pressurizing force acts on a movable arm side electrode 84 during welding. However, since a locus rail 1 of an electric cylinder C is channel-shaped, which is strong against a bending moment, and rigidly fixed to a unit frame 80 with a fixing bolt, a working rod 7, to which a movable arm 83 is directly fixed, also has strong rigidity against the bending moment. Therefore, the movable arm 83 is prevented from being displaced by the bending moment as much as possible, so as to perform accurate welding. The electric cylinder C is constituted to be extremely light and compact, and the welding gun unit G is also lightened, whereby a driving load of a welding robot is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric cylinder for moving an operating rod forward and backward in accordance with the rotation of an electric motor, and for pushing and pulling an object to be controlled by the operating rod. The present invention relates to an electric cylinder suitable for a welding gun unit that automatically positions and welds a material to be joined. The present invention also relates to a welding gun unit and a welding robot using the electric cylinder.

[0002]

2. Description of the Related Art Conventionally, various welding operations such as arc welding and spot welding have been automated using robots in order to streamline welding operations, reduce costs, and stabilize welding quality. Such a welding robot includes a welding gun unit for performing a welding operation on a material to be joined, and an articulated robot for appropriately positioning the welding gun unit at a predetermined welding position.

The above-mentioned welding gun unit has a movable arm which advances and retreats toward a material to be welded such as a steel plate or a pipe to be welded, and has an electrode tip at the tip of the movable arm through which a welding current is applied. Further, by moving the movable arm forward and backward, the electrode tip can be pressed against the material to be joined or positioned at a predetermined distance from the material to be joined. The movement of the movable arm is performed by an electric cylinder, which converts the rotation of the servomotor into the movement of the operating rod by a ball screw or the like.

FIG. 9 shows a welding gun unit disclosed in JP-A-7-290251. This welding gun unit is for spot welding, and has a substantially C-shaped fixed arm 101 provided with an electrode tip 100 at the tip, a movable arm 103 provided with an electrode 102 facing the electrode tip 100 on the fixed arm 101 side, This movable arm 1
And a motor cylinder 104 for moving the actuator 03 toward and away from the fixed arm 101. By driving the motor cylinder 104, a steel plate is sandwiched between the electrode chips 100 and 102 on the movable arm 103 side and the fixed arm 101 side. At the same time, by passing a current between the electrode tips 100 and 102,
02 can be subjected to spot welding. The electric cylinder disclosed in the publication also has a ball nut 107 fixed to a rotor 106 of a servo motor 105 formed in a hollow shape, and a feed screw 10 serving as an operating rod penetrating the rotor 106.
8 is screwed into the ball nut 107. When the rotor 106 is rotated by the drive of the servo motor 105, the feed screw 108 advances and retreats according to the amount of rotation, and is provided at the tip of the feed screw 108. The movable arm 103 moves forward and backward.

[0005]

By the way, in spot welding, the energization path between the two electrodes is restricted by utilizing the stress concentration at the tip of the electrode sandwiching the steel plate, and as a result of the current concentration accompanying this, welding is performed. Since the portion is heated and melted, the electric cylinder must press the electrode tip of the movable arm against the material to be joined with a certain pressing force.

However, in the above-described conventional electric cylinder, since the feed screw penetrating through the rotor of the servomotor is used as the operating rod, the supporting rigidity of the operating rod is not sufficient, and the reaction force of the pressing force causes When a moment load acts on the operating rod, there is a concern that the electrode tip is displaced together with the movable arm, and there is a problem that the material to be joined cannot be appropriately pressed with both electrode tips.

In order to reduce the load on the robot handling the welding gun unit, it is necessary to reduce the weight of the welding gun unit. However, in the electric cylinder described above, the rotor of the servomotor is formed in a hollow shape. Therefore, there is also a problem that the servo gun itself becomes large in size, and it is difficult to reduce the size and weight.

Further, since the servo motor has a special structure in which the feed screw penetrates through the rotor, the cost of the electric cylinder increases, resulting in an increase in the cost of the welding gun unit and daily maintenance work. There is also a problem that it takes time and effort.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to be able to firmly support an operating rod against a moment load acting on the operating rod. An object of the present invention is to provide an electric cylinder which can be reduced in size and weight and is suitable for a welding gun unit.

It is another object of the present invention to provide a welding gun unit using such an electric cylinder and a welding robot using the same.

[0011]

In order to achieve the above object, an electric cylinder according to the present invention comprises a track rail having a concave groove and formed in a channel shape, and a groove inside the track rail. A slide member guided and moved on the inner surface of the track rail, a support plate fixed to one end of the track rail, and a feed screw rotatably supported only by the support plate and screwed to the slide member When,
A motor fixed to the track rail via the support plate, power transmission means for transmitting the rotation of the motor to the feed screw, and a motor fixed to the slide member and protruding from one end of the groove of the track rail. And an operating rod which moves forward and backward in response to the movement of the slide member.

Further, the welding gun unit of the present invention has an electrode tip at a tip end of a movable arm which advances and retreats toward a material to be joined, positions the electrode tip with respect to the material to be joined, and moves the electrode tip to the electrode tip. The present invention is characterized in that the movable arm is advanced and retracted by the above-described operating rod of the electric cylinder according to the present invention on the premise of a welding gun unit that welds a material to be joined by energization of the above.

Further, according to the welding robot of the present invention, it is provided that the welding robot has the above-mentioned welding gun unit of the present invention, and further has positioning means for positioning the electrode of the welding gun unit at a predetermined welding position of the workpiece. It is a feature.

According to such technical means, when the motor is driven, the rotation is transmitted to the feed screw via the power transmission means, and the slide member is formed in a channel shape according to the rotation amount of the feed screw. The operating rod fixed to the slide member moves in the concave groove of the track rail thus moved forward and backward. At this time, the slide member moves while being guided by the inner surface of the concave groove of the track rail, but since the track rail is formed in a channel shape, the rigidity against a moment load is high, and the moment load is applied to the operating rod. Does not easily deform. Therefore, according to the electric cylinder of the present invention, the operation rod can be prevented from being displaced by the reaction force acting on the advance / retreat of the operation rod as much as possible. In this method, the electrode tip can be appropriately positioned with respect to the material to be joined, or the material to be joined can be pressed by the electrode tip.

Further, since the slide member and the feed screw for moving the operating rod forward and backward are accommodated in the concave groove of the track rail, the electric cylinder of the present invention has an extremely compact structure with little unevenness in appearance. Further, since the motor for driving the feed screw can be a general-purpose motor instead of a special hollow motor, it is easy to reduce the size of the motor. Therefore, the electric cylinder according to the present invention can be configured to be extremely small and lightweight, and the load on the robot that handles the welding gun unit can be reduced as compared with the related art.

Further, the motor for driving the feed screw is fixed to the rigid track rail via the support plate and is configured to transmit the rotation of the motor to the feed screw via the power transmission means. Further, it is possible to replace only the motor without touching the feed screw or the slide member for moving the operating rod forward and backward, and it is also possible to reduce the labor required for maintenance work of the welding gun unit.

Here, as long as the operating rod advances and retreats in response to movement with the slide member, the manner of fixing the slide member to the slide member may be changed as appropriate. From the viewpoint of preventing the moment load from acting on the member and the track rail, it is preferable that the axis of the feed screw coincides with the axis of the operating rod.

Further, when the electric cylinder of the present invention is used for a welding gun unit, dust such as spatter and cooling water are scattered in the atmosphere around the operating rod, so that such an operating rod operates smoothly and with high precision. To achieve this, it is necessary to prevent dust and the like from adhering to the slide member and the feed screw. Accordingly, from this viewpoint, a tip plate having a through hole for the operating rod is fixed to one end of the track rail, and a concave strip of the track rail is provided between the tip plate and the support plate. Preferably, a cover plate covering the groove is attached. In the present invention, since the track rail is formed in a channel shape, if the tip plate, the support plate, and the cover plate are attached to the track rail in this way, the feed screw disposed in the concave groove of the track rail is used. Further, the slide member can be easily sealed from the outside of the track rail.

Further, since the operating rod advances and retreats so as to protrude from one end of the groove of the track rail, it is possible to completely prevent foreign matters such as dust adhering to the operating rod from entering the groove. From the viewpoint of doing so, it is preferable to attach a scraper to the end plate in which the through hole of the operating rod is formed, and remove foreign substances attached to the operating rod by the scraper as the operating rod advances and retreats.

Further, when it is necessary to adjust the advancing / retreating position of the operating rod due to a step-out of the servomotor or a power failure, one end of the feed screw is provided at one end of the feed screw so that the adjusting operation can be easily performed. Preferably, a handle for manually rotating the lead screw is mounted.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electric cylinder according to the present invention, a welding gun unit using the same, and a welding robot provided with the welding gun unit will be described in detail with reference to the accompanying drawings. 1 to 4 show an embodiment of an electric cylinder according to the present invention. FIG. 1 is a plan view and FIG.
3 is a front view, FIG. 3 is a right side view, and FIG. 4 is a left side view. In these figures, reference numeral 1 denotes a track rail formed in a channel shape, reference numeral 2 denotes a slide member which is guided and moved by the track rail 1, and reference numeral 3 denotes a support fixed to one end of the track rail 1 in the longitudinal direction. Plate, code 4
Is a servomotor fixed so as to be adjacent to the track rail 1 via the support plate 3, reference numeral 5 is a feed screw rotatably supported on the support plate 3, and reference numeral 6 is a feed screw 5 from the servomotor 4. Reference numeral 7 denotes a gear train as a power transmission means for transmitting rotation to the operating rod which moves forward and backward in accordance with the movement of the slide member 2.

First, as shown in FIGS. 5 and 6, the track rail 1 has a pair of side walls 11, 11 on both sides of a base 10.
Are formed in a channel shape, and are configured to accommodate the slide member 2 in a concave groove 12 provided along the longitudinal direction. The inner surface of each side wall 11 has two ball rolling grooves 1 along the longitudinal direction of the track rail 1.
The slide member 2 is adapted to move in the groove 12 along the ball rolling groove 13. The base 10 is provided with a plurality of fixing bolt insertion holes 14 so that the track rail 1 can be directly fixed to a frame of a welding gun unit described later.

On the other hand, the slide member 2 is a track rail 1
Is formed in a substantially rectangular shape to be loosely fitted in the concave groove 12 of
Load ball grooves 20 facing the ball rolling grooves 13 formed on the track rail 1 are formed on both outer surfaces thereof, and the ball rolling grooves 13 of the track rail 1 and the load ball grooves 20 of the slide member 2 are formed. The ball 8 is configured to roll while applying a load therebetween. The slide member 2 has an infinite circulation path 21 of the ball 8 corresponding to each load ball groove 20, and the slide member 2 is infinitely circulated through the load ball groove 20 so that the slide member 2 Can be moved along the stroke without restriction.

The slide member 2 has a through hole 22 through which the feed screw 5 is inserted. The feed screw 5 is screwed into the slide member 2 via the ball 9 in the through hole 22. . That is, a spiral ball rolling groove 50 is formed on the outer peripheral surface of the feed screw 5 by a predetermined lead, while the ball rolling groove of the feed screw 5 is formed on the inner peripheral surface of the through hole 22 of the slide member 2. Load ball groove 2 facing groove 50
3 are formed in a spiral shape.
The feed screw 5 and the slide member 2 are screwed together via the ball 9 rolling between the load ball grooves 23.
The slide member 2 is provided with a return tube 24 for returning the ball 9 spirally rolling between the ball rolling groove 50 and the load ball groove 23 to its original position. Is configured to circulate infinitely between the feed screw and the slide member. Therefore, when the feed screw 5 is rotated, the ball 9 rolls while applying a load between the ball rolling groove 50 of the feed screw 5 and the loaded ball groove 23 of the slide member 2, and the ball 9 The slide member 2 moves in the concave groove 12 of the track rail 1 with a stroke corresponding to the rotation speed.

Further, as shown in FIGS. 1 and 2, the operating rod 7 is fixed to the slide member 2 via a guide member 70 having a substantially L-shaped cross section. Are configured to advance and retreat from inside the groove 12 of the track rail 1 to outside the groove 12 according to the stroke of the slide member 2. The guide member 70 is fixed to the slide member 2 by a fixing bolt 71, while one end of the operating rod 7 is fitted to the guide member 70. Since the guide member 70 is formed in a substantially L-shape, the axis of the feed screw 5 and the axis of the operating rod 7 are aligned. Thereby, the external force acting on the operating rod 7 is prevented as much as possible from acting on the track rail 1 and the feed screw 5 as a moment load. 5 and 6, reference numeral 25 denotes a tap hole into which the fixing bolt 71 is screwed.

A support plate 3 is fixed to one end of the track rail 1 in the longitudinal direction so as to close the concave groove 12. The feed screw 5 penetrates the support plate 3 and the support plate 3 3 is rotatably supported by a pair of angular contact bearings 30 fitted into the bearing 3. The support plate 3 also serves as a bracket for fixing the servomotor 4 adjacent to the track rail 1, and the gear train 6 is provided on a surface opposite to the surface on which the track rail 1 and the servomotor 4 are fixed. The gear box accommodating the plates 31 and 32 and the cover 3
3 form a box.

The gear train 6 has an input gear 61 fixed to the output shaft 40 of the servomotor 4, an output gear 62 fixed to the feed screw 5, and transmits rotational power from the input gear 61 to the output gear 62. Two reduction gears 63 and 64
The transmission speed is reduced to, for example, 1/4 and transmitted to the feed screw. The two reduction gears 63 and 64 are studs 3 erected on the support plate 3.
4 is rotatably supported via a ball bearing, and is prohibited from rotating relative to each other by a set screw. The reduction gear 63 meshes with the input gear 61 while the reduction gear 64 is engaged with the output gear 62. And are engaged. Thus, the rotation of the output shaft 40 of the servo motor 4 is transmitted to the feed screw. In this embodiment, a gear train is used as a means for transmitting the rotational power from the servo motor 4 to the feed screw 5, but it is easy to transmit the rotational power by a pulley and a timing belt.

An end of the feed screw 5 to which the output gear 62 is fixed projects from a cover 33 constituting a gear box. A handle 51 as shown by a two-dot chain line in FIG. By mounting, the feed screw 5 can be rotated manually. Accordingly, even if the servo rod 4 loses synchronism or power failure, the position of the operating rod 7 can be adjusted by rotating the feed screw 5 manually even when the position of the rod 7 is deviated. Note that the cap 5 normally fixed to the cover 33 is
2, the projecting end of the feed screw 5 is covered.

On the other hand, one end of the track rail 1 on the side opposite to the support plate 3 in the longitudinal direction is also provided with a concave groove 12.
The end plate 72 is fixed so as to close the
The operating rod 7 is inserted through a through hole 73 formed in the end plate 72. A felt sealing member 74 is provided on the inner diameter of the through-hole 73 so as to be in sliding contact with the operating rod 7, and the outer surface of the through-hole 73 faces the outer peripheral surface of the operating rod 7 with a slight gap. When the scraper 75 is attached and the operating rod 7 moves forward and backward, relatively large foreign substances such as spatters attached to the scraper 75 are removed by the scraper 75, and fine dust and the like are further removed on the operating rod 7 by the seal member 74. It is to be removed from.

A cover plate 15 is provided between the support plate 3 and the end plate 72 so as to cover the concave groove 12 of the track rail 1. The rail 1 is fixed to the side wall 11. A rubber seal is sandwiched between the cover plate 15 and the side wall 11, the end plate 72, and the support plate 3 of the track rail 1, respectively, and is inserted into the concave groove 12 of the track rail 1 sealed by the cover plate 15. Intrusion of dust and cooling water from the outside is completely prevented. As a result, even when the electric cylinder is used in a bad environment where dust, cooling water, etc., scatter, the slide member 2 and the feed screw 5 disposed in the concave groove 12 are contaminated by dust and the like. However, the smooth movement of the slide member 2 due to the rotation of the feed screw 5 can be stably maintained for a long period of time.

Further, rubber stopper members 17 are fixed to the inner surfaces of the support plate 3 and the end plate 72 facing the concave groove 12 of the track rail 1, respectively. When the member 2 overruns from a predetermined stroke amount, the member 2 abuts on the slide member and locks it.

According to the thus-configured electric cylinder of this embodiment, when the servo motor is rotated, the rotation is transmitted to the feed screw via a gear train, and the rotation is transmitted in accordance with the rotation of the feed screw. As a result, the slide member strokes in the concave groove of the track rail, and the operating rod fixed to the slide member moves forward and backward in accordance with the stroke of the slide member.

FIG. 7 shows an example in which the electric cylinder C of this embodiment is applied to a C-type welding gun unit for spot welding. The welding gun unit G has a fixed arm 81 formed in a claw shape extending from the unit frame 80.
A fixed arm-side electrode 82 provided at the tip of the fixed arm 81; the electric cylinder C fixed to the unit frame 80;
And a movable arm electrode 84 mounted on the movable arm 83. The movable arm 83 is fixed to the movable arm electrode 84 in accordance with the advance and retreat of the operating rod 7 of the electric cylinder C. A steel plate, a pipe material, or the like as a material to be joined is sandwiched between the arm-side electrode 82 and a current is applied between the electrodes 82 and 84 to weld the material to be joined.

At this time, the movable arm-side electrode 84 needs to press the material to be joined toward the fixed arm-side electrode 82, and a reaction force of the pressing force acts on the movable arm-side electrode 84. However, as described above, the track rail 1 of the electric cylinder C for moving the movable arm 83 forward and backward is formed in a channel shape strong against bending moment, and the track rail 1 is fixed to the unit frame 80 by a fixing bolt.
The operating rod 7 to which the movable arm 83 is directly fixed also has a strong rigidity against bending moment. Accordingly, even if a bending moment acts on the movable arm 83, the welding arm unit G of the present embodiment using the electric cylinder C has the movable arm 8
3 can be prevented as much as possible from being displaced by the bending moment, and the movable arm-side electrode 84 can be appropriately brought into contact with the material to be joined to perform spot welding appropriately. is there.

Next, FIG. 8 shows a welding robot in which the welding gun unit G shown in FIG. 7 is mounted on an articulated robot R as positioning means. The articulated robot R includes a robot main body 90, a lower arm 91, an upper arm 92, and a wrist 93, and has the welding gun unit G mounted on the wrist 93. The θ axis, the W axis, the U axis, and the γ
It has six turning axes, an axis, a β axis, and an α axis, and positions the electrodes 82 and 84 of the welding gun unit G freely within a predetermined working range to perform spot welding on a predetermined portion of the workpiece. It can be applied.

In such an articulated robot R, in order to reduce the driving load on the wrist 93, the upper arm 92 and the lower arm 91, it is desirable that the welding gun unit G mounted on the wrist 93 be as light as possible. In the electric cylinder C, the feed screw 5 and the slide member 2 that guide the advance and retreat of the operating rod 7 are accommodated in the concave groove 12 of the channel-shaped track rail 1, and the electric cylinder C itself is extremely lightweight. Since it can be configured compact, the welding gun unit G in which the movable arm 83 is driven by the electric cylinder C can also be reduced in weight,
The drive load of the welding robot R can be reduced.

The positioning means for positioning the welding gun unit G is not limited to the above-mentioned articulated robot R, but may be of various constructions depending on the type of work.

[0038]

As described above, according to the electric cylinder of the present invention, it is possible to prevent the operation rod from being displaced by the reaction force acting on the advance / retreat of the operation rod as much as possible. Therefore, when this electric cylinder is used for driving the movable arm of the welding gun unit, the electrode tip mounted on the movable arm is appropriately positioned with respect to the workpiece, or the workpiece is applied by the electrode tip. The welding can be performed appropriately.

Further, since the electric cylinder of the present invention can have an extremely lightweight and compact structure, when it is used for driving the movable arm of the welding gun unit, the electric cylinder of the welding robot equipped with such a welding gun unit can be used. The drive load on the arm and wrist can be reduced, and a welding robot with good workability can be configured.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of an electric cylinder according to the present invention.

FIG. 2 is a front view showing an embodiment of the electric cylinder of the present invention.

FIG. 3 is a right side view showing the embodiment of the electric cylinder of the present invention.

FIG. 4 is a left side view showing an embodiment of the electric cylinder of the present invention.

FIG. 5 is a perspective view showing a track rail, a slide member, and a feed screw according to the embodiment.

FIG. 6 is a cross-sectional view illustrating an engaged state of a track rail, a slide member, and a feed screw according to the embodiment.

FIG. 7 is a schematic view showing a welding gun unit equipped with the electric cylinder according to the embodiment.

8 is a perspective view showing a welding robot equipped with the welding gun unit shown in FIG.

FIG. 9 is a schematic view showing a conventional welding gun unit.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 track rail 2 slide member 3 support plate 4 servo motor 5 feed screw 6 gear train (power transmission means) 7 operating rod 12 groove groove C electric cylinder , G: welding gun unit, R: articulated robot

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Wataru Yamakura 3-11-6 Nishigotanda, Shinagawa-ku, Tokyo, within TEK Corporation (72) Inventor Kazushige Suita 1 Toyota Town, Toyota City, Toyota City, Aichi Prefecture, Toyota (72) Inventor Morihiko Okura 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor Yutaka Konishi 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation ( 72) Inventor Hiroshi Chikawa 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation F-term (reference) 4E065 AA06 BA06

Claims (7)

[Claims] 1. A track rail having a concave groove and formed in a channel shape, a slide member guided in the concave groove of the track rail by an inner side surface of the track rail, and the track rail. , A feed screw rotatably supported only by the support plate and screwed to the slide member, a motor fixed to the track rail via the support plate, And a working rod fixed to the slide member, protruding from one end of the groove of the track rail, and moving forward and backward in accordance with the movement of the slide member. An electric cylinder, characterized in that: 2. The electric cylinder according to claim 1, wherein
An electric cylinder, wherein the axis of the feed screw and the axis of the operating rod coincide with each other. 3. The electric cylinder according to claim 1, wherein a tip plate having a through-hole for the operating rod is fixed to one end of the track rail, and between the tip plate and the support plate. A cover plate that covers the concave groove of the track rail is attached, and by these tip plate, support plate and cover plate,
The electric cylinder, wherein the feed screw and the slide member disposed in the concave groove are sealed from the outside of the track rail. 4. The electric cylinder according to claim 3, wherein
An electric cylinder, wherein a scraper for removing foreign matter attached to an operating rod is attached to the end plate. 5. The electric cylinder according to claim 1, wherein a handle for manually rotating the feed screw is attached to one end of the feed screw. 6. An electrode tip is provided at a tip of a movable arm which advances and retreats toward a material to be joined. The electrode tip is positioned with respect to the material to be joined, and welding of the material to be joined is performed by supplying electricity to the electrode tip. A welding gun unit, wherein the movable arm is moved forward and backward by the operating rod of the electric cylinder according to any one of claims 1 to 5. 7. A welding robot comprising: the welding gun unit according to claim 6; and positioning means for positioning an electrode of the welding gun unit at a predetermined welding position on a workpiece.