JP2010064135A - Drive unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel drive unit which can simultaneously satisfy a fast-forwarding function and an axial load application, and can exert high positioning accuracy. <P>SOLUTION: The invented drive unit includes a straight rail 10, a first slider 20 and a second slider 30 which are slidably engaged with the rail 10, a toggle mechanism 40 which connects the first slider 20 and the second slider 30, a ball screw mechanism 50 which drives the first slider 20 along the rail 10, and thereby the drive unit can simultaneously satisfy the fast-forwarding function of the second slider 30 and the application of axial load force, and can exert the high positioning accuracy. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a drive unit that can be applied as an actuator for a high load device such as a welding gun, a press machine, or an injection molding machine.

2. Description of the Related Art Conventionally, devices that require a high load (high load) such as a spot welding gun, a press machine, and an injection molding machine are provided with a drive unit for generating a high load.
For example, in a spot welding gun as shown in Patent Document 1 below and a resistance welding machine as shown in Patent Document 2, a ball screw mechanism is used as a drive unit for moving and press-contacting a gun arm equipped with an electrode to a workpiece. A pressure driving mechanism and an electrode driving mechanism using the above are used.

Further, in an injection molding apparatus as shown in Patent Document 3 below, a screw nut mechanism is used as a drive unit for moving one mold (moving mold) close to or away from the other mold (fixed mold). A mold clamping device in which a toggle mechanism which is a booster mechanism is combined with a (ball screw mechanism) is used.
Japanese Patent Laid-Open No. 10-34346 JP 2000-17455 A Japanese Patent Application Laid-Open No. 60-112417

By the way, in the case of the drive unit using the ball screw mechanism as shown in Patent Document 1, since the lead of the ball screw is constant, the gun arm of the gun arm is divided into a section in which the gun arm is fast-forwarded and a section in which welding is performed (high load section). There is a disadvantage that the feed speed becomes the same.
That is, the welding gun and the resistance welding machine require the largest axial load when the electrode and the workpiece are in contact with each other. Therefore, the lead of the ball screw should be as small as possible. Further, by reducing the lead, a small motor can exert a sufficient axial load. On the other hand, since it is necessary to move the electrode quickly except during welding, it is desirable that the lead of the ball screw be as large as possible.

Therefore, in a drive unit using a ball screw with a constant lead, if a small motor is used as the drive source, it is difficult to satisfy these conflicting requirements, so an expensive high-performance (large) motor Has the disadvantage of increasing the cost. Such a problem also occurs in the mold clamping shaft of the injection molding machine, and a fast feed operation is required for opening and closing the mold, but a large axial load is required during mold clamping.
On the other hand, in the case of a drive unit in which a toggle mechanism is combined with a screw nut mechanism as shown in Patent Document 3, a rapid feed function such as a die supported by the toggle mechanism by the boosting action of the toggle mechanism and the axial direction It is possible to satisfy the load force at the same time.

However, such a drive unit has a problem that its toggle mechanism is twisted by the torsion torque of the ball screw, and positioning accuracy is low. That is, for example, when this toggle mechanism is used as a booster mechanism such as a welding gun, the electrode comes into contact with the work piece before the link is fully extended, that is, in a state where the ball screw torque is applied. The position and angle may shift.
Therefore, the present invention has been devised to solve the above-described problems, and the object thereof is a novel that can exhibit excellent positioning accuracy while simultaneously satisfying the rapid feed function and the axial load force. A drive unit is provided.

In order to solve the above problems, the first invention
A linear rail, first and second sliders slidably engaged with the rail, a toggle mechanism connecting the first slider and the second slider, and the first slider along the rail And a ball screw mechanism for driving the drive unit.
According to such a configuration, the fast-forward function and the axial load force of the second slider with respect to the first slider can be satisfied simultaneously by the boosting action of the toggle mechanism that connects the first slider and the second slider.

  Further, since the first slider and the second slider are slidably engaged with the same rail, the torque of the ball screw mechanism generated in the first slider is not transmitted to the toggle mechanism or the second slider as it is. As a result, since the toggle mechanism and the second slider are not greatly twisted, excellent positioning accuracy can be exhibited. In addition, the drive unit can be designed compactly and simply by using the same rail for the first slider and the second slider.

In addition, the second invention,
In the first invention, the rail is constituted by a pair of rail members extending in parallel to each other, and the first slider driven by the ball screw mechanism 50 is arranged so as to be bridged between the rail members. Drive unit.
According to such a configuration, since the ball screw torque generated in the first slider can be received by the pair of rail members, it is possible to more reliably prevent the toggle mechanism and the second slider from being twisted due to the torque of the ball screw mechanism.

In addition, the third invention,
In the first or second invention, the screw shaft of the ball screw mechanism is arranged parallel to the rail member and in the center between the rail members, and the toggle mechanism has a bilaterally symmetric structure with the screw shaft as a boundary. It is the drive unit characterized.
According to such a configuration, since the toggle mechanism expands and contracts in parallel with the screw shaft, there is no or almost no axial position error (geometric error) when the toggle mechanism expands and contracts.

In addition, the fourth invention is
In the first to third inventions, the drive unit is characterized in that a cross arm extending in a direction intersecting with the rail and having both ends coupled to the toggle mechanism is pin-coupled to the second slider.
According to such a configuration, even when an axial position error (geometric error) occurs when the toggle mechanism expands and contracts, the error can be absorbed by the pin coupling portion of the second slider. As a result, moment force is not generated at the connecting portion between the toggle mechanism and the second slider, so that more excellent positioning accuracy can be exhibited. In addition, since excessive force is not applied to the toggle mechanism and the second slider, it is possible to prevent a decrease in life due to wear and friction.

  According to the present invention, the first and second sliders are slidably engaged with the linear rail, and the sliders are connected by the toggle mechanism, and the first slider is driven by the ball screw mechanism. The second slider can be fast-forwarded in the initial to mid-term section, and a large axial load can be exhibited by the boosting action in the extension end section. In addition, since the toggle mechanism and the second slider are not twisted by the torsion torque generated by the ball screw mechanism, excellent positioning accuracy can be exhibited.

Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
1 to 3 show an embodiment of a drive unit 100 according to the present invention. FIG. 1 is a plan view of the drive unit 100, FIG. 2 is a sectional view taken along line AA, and FIG. FIG.
As shown in the figure, the drive unit 100 mainly includes a rail 10, a first slider 20 and a second slider 30, a toggle mechanism 40, and a ball screw mechanism 50.

First, the rail 10 has a configuration in which a pair of rail members 11 and 11 having a rectangular cross section are arranged in parallel and at equal intervals, and both ends thereof are connected and supported by end plates 15 and 15.
As shown in FIG. 2, a pair of upper and lower arc-shaped grooves 12, 12 are formed in parallel along the longitudinal direction on the inner surfaces (opposing surfaces) of the rail members 11, 11. A plurality of balls B roll along the arcuate grooves 12 and 12 respectively.

Next, the first slider 20 and the second slider 30 respectively form a pair of upper and lower circulation paths 22 and 22 on both side surfaces of the slider body 21 having a rectangular cross section located between the rail members 11 and 11 of the rail 10. It has a structure.
The plurality of balls B accommodated in the circulation path 22 circulate in the circulation path 22 and the arc-shaped grooves 12, 12, 12, 12 on the rail members 11, 11 side, so that the slider is moved along the rail 10. The main body 21 is slidably engaged along the longitudinal direction.

That is, the slider main body 21 is provided with four rows of arc-shaped grooves 23, 23, 23, 23 parallel to the longitudinal direction of the rail 10 on both side surfaces thereof, like a known linear guide bearing main body. The arc-shaped grooves 23, 23, 23, 23 and the arc-shaped grooves 12, 12, 12, 12 on the rail members 11, 11 side move while rolling along the longitudinal direction. . When the ball B reaches the end of the slider body 21, the ball B is scooped up at the tip of an end cap (not shown) provided at the end of the slider body 21, and each curved path 24 provided therein is squeezed. , 24, 24, 24 are led to circulation holes 25, 25, 25, 25 provided in the slider body 21. Eventually, these balls B pass through the respective circulation holes 25, 25, 25, 25 to reach the other end of the slider body 21, and this time on the curved path (not shown) of the opposite end cap (not shown). Guided and returned between the original arc-shaped grooves 23, 23, 23, 23 and the arc-shaped grooves 12, 12, 12, 12. In this manner, each ball B circulates infinitely through the circulation path 22 so that the slider body 21 can be smoothly slid in the longitudinal direction while being engaged with the rail 10.
Further, a nut member 51 of a ball screw mechanism 50 described later is integrally provided in the center of the first slider 20 among the first slider 20 and the second slider 30. The first slider 20 is reciprocated along the rail 10.

Next, the toggle mechanism 40 connects the first slider 20 and the second slider 30 as shown in FIG. 1, and includes a base link 41, a pair of first links 42 and 42, and a pair of second links. It is comprised from the link 43,43 and a pair of 3rd link 44,44.
The base link 41 is formed integrally with one end plate 15 of the rail 10 described above, and includes a pair of arms 41 a and 41 a extending along the longitudinal direction so as to sandwich the rail 10. Yes.

One end of each of the first links 42 and 42 is fixed to the upper surface of the first slider 20 and is pivotally connected to the end of the cross arm 26, and the other end of each of the second links 43 and 43. Similarly, it is configured to be pin-coupled to the center side so as to be freely rotatable.
One end of each of the second links 43 and 43 is pivotally connected to the ends of the arms 41 a and 41 a of the base link 41, and the other end of the second links 43 and 43 is also turned to the ends of the third links 44 and 44. It is configured to be freely pin-coupled.
One end of each of the third links 44 and 44 is pivotally connected to the end of the second link 43 and 43, and the other end is fixed to the upper surface of the second slider 30. Similarly, it is configured to be pin-coupled to the end so as to be freely rotatable.
The toggle mechanism 40 has a left-right symmetric structure with respect to the central axis of the rail 10 as shown in FIG.

Next, as described above, the ball screw mechanism 50 includes the nut member 51 provided at the center inside the first slider 20, the screw shaft 52 positioned at the center axis of the rail 10, and a servo motor 53 capable of forward / reverse rotation control. And is composed mainly of.
The nut member 51 has a structure in which a spiral screw groove 51b is formed on the inner surface of a through hole 51a through which the screw shaft 52 passes, and return tubes 51c are connected to both ends of the screw groove 51b. A plurality of balls B are rotatably accommodated in a spiral passage formed by the thread groove 51b and a spiral thread groove 52a formed on the surface of the screw shaft 52. A plurality of balls b reaching the end of the passage are circulated through the return tube 51c.

One end of the screw shaft 52 located on the second slider 30 side is pivotally supported on the end plate 15 side of the rail 10, and the end portion on the first slider 20 side is the end of the rail 10 that also serves as the base link 41. It is pivotally supported so as to penetrate the plate 15 side.
The servo motor 53 is fixed to the end plate 15 side of the rail 10 that also serves as the base link 41, and the rotation shaft 53 a is connected to the screw shaft 52 via the coupling 54.

  Then, by rotating the screw shaft 52 by the servo motor 53, the first slider 20 provided with the nut member 51 screwed to the servo shaft 53 can be forcibly reciprocated along the rail 10. . A through hole (not shown) for simply passing through the screw shaft 52 is formed at the center of the second slider 30, and the second slider 30 and the screw shaft 52 are not screwed together. It has become.

Next, the operation and effect of the drive unit 100 configured as described above will be described.
As shown in FIG. 1, when the first slider 20 is moved to the second slider 30 (rightward in the drawing) side by the ball screw mechanism 50, the cross arm 26 of the first slider 20 is moved via the first links 42 and 42. The second links 43, 43 connected in this manner rotate away from the rail 10 about the pin coupling portion of the arms 41a, 41a of the base link 41 as an axis.
Then, the second links 44, 44 pin-coupled to the other ends of the second links 43, 43 rotate so as to be separated from the rail 10 about the pin coupling portion of the cross arm 31 of the second slider 30.

As a result, the second slider 30 moves to the end of the rail 10 (right side in the figure), and the first slider 20 moves to the end of the rail 10 (right side in the figure) by the toggle mechanism 40. The moving amount of the second slider 30 becomes gradually shorter than the moving amount of.
As a result, as shown in FIG. 3, a boosting action is exerted, and a large axial load can be generated on the second slider 30.

FIG. 3 shows the relationship between the moving amount (screw feed amount) of the second slider 30 and the axial load.
As shown in the drawing, the axial load of the second slider 30 is not so large until the first slider 20 moves (screw feed amount) from the initial stage to the middle stage (fast forward section). When reaching the end of extension (boost section) where the screw feed amount becomes maximum, the axial load increases at a stretch.

  Therefore, if the moving unit 100 is applied to, for example, the spot welding gun described above and one gun arm (electrode) is attached to the second slider 30, the moving amount (screw feed amount) of the first slider 20 will be described. Even in the fast feed section, the gun arm can be moved quickly, and in the boost section receiving the load, the axial load can be increased while lowering the moving speed. Thereby, an efficient and good welding operation can be realized.

  FIG. 4 shows the principle of the fast-forward function and the boost function by the toggle mechanism 40. Here, the position of the common node of the link shown in FIGS. 4A and 4B is the position of the first slider 20, and the arrow extending downward from the common node indicates the moving direction of the first slider 20, the width of the link tip (horizontal). ) Direction moving distance is assumed to be the axial load of the second slider 30. Then, when the common node is at a position higher than the reference plane as shown in FIG. 4 (A), the angle between the links is small, so when the common node moves from the position in the reference plane direction, In addition, the movement distance in the width (lateral) direction of the link tip (the axial load of the second slider 30) is large. However, as shown in FIG. 5B, when the common node further approaches the reference plane direction, the movement distance in the width (lateral) direction of the link tip is the same even though the movement speed of the common node is the same. The axial load) of the second slider 30 is reduced at a stretch. Based on such a principle, the toggle mechanism 40 of the present invention can exert a fast-forwarding action and a boosting action on the second slider 30.

In the drive unit 100 of the present invention, since the first slider 20 and the second slider 30 are slidably engaged with the same rail 10, the torque of the ball screw mechanism 50 generated in the first slider 20 is toggled as it is. There is no transmission to the mechanism 40 or the second slider 30.
Therefore, the toggle mechanism 40 and the second slider 30 are not greatly twisted, so that excellent positioning accuracy can be exhibited. In addition, since the first slider 20 and the second slider 30 use the same rail 10, the whole can be designed more compactly and simply.

  In addition, the rail 10 is composed of a pair of rail members 11 and 11 extending in parallel with each other, and the first slider 20 driven by the ball screw mechanism 50 is arranged so as to be bridged between the rail members 11 and 11. The torque generated by the ball screw mechanism 50 in the first slider is supported by the pair of rail members 11 and 11. As a result, the torsion is not transmitted to the toggle mechanism 40 and the second slider 30 due to the torque of the ball screw mechanism 50, so that position errors due to these torsion can be prevented more reliably.

Further, in the drive unit 100 of the present invention, the screw shaft 52 of the ball screw mechanism 50 is disposed in parallel to the rail members 11 and 11 and in the center between the rail members 11 and 11, and the toggle mechanism 40 includes the screw shaft 52. It has a symmetrical structure at the border.
For this reason, since the toggle mechanism 40 expands and contracts in parallel with the screw shaft 52, an axial position error (geometric error) when the toggle mechanism 40 expands and contracts can be eliminated or almost eliminated.

By the way, in the case of the drive unit 100 having the above-described configuration, there is a backlash at each node (pin coupling portion) of the toggle mechanism 40 caused by wear of each member, processing accuracy of each member, assembly accuracy, etc. If an error occurs, for example, as shown in FIG.
In the example of FIG. 5, backlash or an error occurs in the pin joint portion (node) of the first link 42 of one (upper side in the drawing) of the pair of first links 42 and 42 constituting a part of the toggle mechanism 40. Thus, the second link 43 connected to this, the arm 41a of the base link 41, and the third link 44 are not linear, and as a result, the cross arm 31 fixed to the upper surface of the second slider 30 is tilted. This shows a state in which the shaft of the second slider 30 is greatly twisted.

Therefore, as shown in FIG. 7, the cross arm 31 fixed to the upper surface of the second slider 30 is separated from the second slider 30, and the central portion of the cross arm 31 is set to the central portion (screw) of the second slider 30. Such inconvenience can be eliminated by pin coupling to the shaft 52).
That is, as shown in FIG. 7, even when the cross arm 31 is inclined because only the second link 43 and the arm 41 a of the base link 41 and the third link 44 are not linear, the inclination ( Moment) is absorbed by the pin coupling portion, so that the shaft of the second slider 30 is not twisted. On the other hand, the axial load force transmitted from the toggle mechanism 40 to the cross arm 31 is reliably transmitted from the pin coupling portion to the second slider 30.

Therefore, according to such a configuration, even if an axial position error occurs when the toggle mechanism 40 expands and contracts, moment force is not generated in the second slider 30 as it is. Can demonstrate. In addition, since excessive force is not applied to the toggle mechanism 40 and the second slider 30, it is possible to prevent a decrease in life due to wear and friction.
The error of the toggle mechanism 40 also acts as an offset load on the first slider 20. However, since the rotation of the first slider 20 is restricted by the rail 10, the offset load acts on the screw shaft 52 and the like. Accordingly, the life of the ball screw mechanism 50 can be prevented from being reduced.
Further, as shown in FIGS. 8 and 9, the rail 10 described above is configured by a general-purpose (known) linear motion guide device (linear guide) 60, and the ball screw mechanism 50 is formed by a general-purpose (known) nut member. If constituted by a ball screw device, the drive unit 100 of the present invention can be obtained at a lower cost.

8 shows the drive unit 100 in which the cross arm 31 is integrally provided on the second slider 30 as described above, and FIG. 9 shows the cross arm 31 on the second slider 30 via the pin coupling portion. The drive unit 100 provided is shown.
When the drive unit 100 of the present invention is applied to a welding gun or the like, the drive unit 100 is attached to a common base, one of the gun arms is attached to the common base, and the other gun arm is attached to the second slider 30. The other gun arm is driven so as to be close to and away from the one gun arm.

It is a top view which shows embodiment of the drive unit 100 which concerns on this invention. It is an AA line expanded sectional view in FIG. It is a graph which shows the relationship between the screw feed amount of the 2nd slider 30, and an axial load. FIG. 5 is a conceptual diagram showing an operation principle of a toggle mechanism 40. FIG. 6 is a plan view showing a state in which the second slider 30 is displaced due to play of the toggle mechanism 40 or the like. It is a top view which shows other embodiment (at the time of reduction) of the drive unit 100 which concerns on this invention. It is a top view which shows other embodiment (at the time of expansion | extension) of the drive unit 100 which concerns on this invention. It is a top view which shows other embodiment (without a pin coupling | bond part) of the drive unit 100 which concerns on this invention. It is a top view which shows other embodiment (with a pin coupling | bond part) of the drive unit 100 which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Drive unit 10 ... Rail 20 ... 1st slider 26 ... Cross arm 30 ... 2nd slider 31 ... Cross arm 40 ... Toggle mechanism 41 ... Base link 41a ... Base link arm 42 ... 1st link member 43 ... 2nd link member 44 ... Third link member 50 ... Ball screw mechanism

Claims (4)

  A linear rail, first and second sliders slidably engaged with the rail, a toggle mechanism connecting the first slider and the second slider, and the first slider along the rail And a ball screw mechanism for driving the drive unit. The drive unit according to claim 1, wherein
A drive unit, wherein the rail is constituted by a pair of rail members extending in parallel with each other, and the first slider driven by the ball screw mechanism is arranged so as to be bridged between the rail members. The drive unit according to claim 1 or 2,
A drive unit characterized in that a screw shaft of the ball screw mechanism is arranged parallel to the rail member and in the center between the rail members, and the toggle mechanism has a left-right symmetrical structure with respect to the screw shaft. In the drive unit as described in any one of Claims 1-3,
A drive unit characterized in that a cross arm extending in a direction crossing the rail and having both ends coupled to the toggle mechanism is pin-coupled to the second slider.

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