JPH0520179B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method of bending a straight pipe (tapered pipe, square pipe, round pipe, etc.) into an arbitrary curved shape such as a circular arc, parabola, or ellipse. , especially regarding bending methods that allow for highly accurate processing.

<Prior Art> Various methods of pipe bending have been known in the past. Typical examples are listed below.

Compression bending: As shown in FIG. 1, a method in which the pipe P is pressed against a fixed bending die A using a press die B and is bent along the curvature of the bending die.

Draw bending: This is similar to changing the tilting of the press mold in compression bending to the rotation of the bending mold, as shown in Figure 2 (A is the state before processing, B is the state in progress)
As shown in the figure, the bending die A is made rotatable, and a specific point of the pipe P is fixed to it with a fixed die 34, and in this state, the bending die A is rotated to create a space between the bending die and the corresponding press die B. A method of bending the tubes by pulling them out one after another. Mandrel 3 if necessary
5 is used.

Press bending: As shown in FIG. 3, a method in which a pipe P is placed across a pair of left and right receiving seats 36, 36, and the center portion is pressed by a press die B to bend the pipe P.

Roll bending: A method of sequentially bending the pipe P by passing it between three driven forming rolls 37, 37, 37 arranged in a staggered manner as shown in FIG.

Tensile bending: A method of pressing the pipe P against a fixed bending die A and bending it while pulling both ends of the pipe, as shown in Fig. 5.

Hamburg bending: As shown in FIG. 6, a method in which a pipe P of a fixed size is inserted from the proximal end into a pipe-like mandrel 38 with a thickened tip, and the tip is passed through and bent.

However, each of the above methods has its own drawbacks.

In particular, compression bending and press bending pose a problem in that the tube becomes flattened and wrinkles occur during processing. In all methods other than roll bending, the size of the mold (or mandrel in Hamburg bending) is changed each time the bending radius or other processing conditions change, and it is necessary to prepare many molds (mandrels). Changing setups takes time and effort. Moreover, the original aim of this type of method is circular bending,
Other methods, such as elliptical bending, are hardly considered. Regarding roll bending, although it is possible to adjust the bending radius by changing the mutual positional relationship of the forming rolls, the selection of the bending radius is limited to a relatively large range of values. In addition, Hamburg bending, in particular, can only be applied to short pipes that have been cut to a certain size in advance; for example, processing that only bends one end of a long pole cannot be performed at all, and this method cannot be used at all. In fact, it is used exclusively for the manufacture of elbows.

<Purpose of the invention> The present invention is capable of bending pipes along all kinds of curves, including circular arcs, parabolas, and ellipses, using the same equipment without changing setups such as changing molds.
Moreover, it is an object of the present invention to provide a bending method that has particularly good processing accuracy in bending shapes and is effective against flattening and wrinkles of the tube due to bending.

<Structure of the Invention> That is, the present invention grips a pipe to be bent at a position other than the part to be bent by a gripping device movable to any position on a specific plane, and holds the pipe to be bent at a position other than the part to be bent. It is set so as to be sandwiched between a circular receiving mold rotating in a plane parallel to the plane of movement of the gripping device and a straight pressing mold forming a pair therewith, and the straight pressing mold is pressed against the circular receiving mold. The target bending shape is then gradually tilted along its outer circumference, and the speed control system of the drive device that controls this tilting motion, the rotational motion of the circular receiving mold, and the planar motion of the gripping device is controlled from the target bending shape to each drive. The speed value determined as the required command speed by taking into account the response delay of the device in advance is input as a command signal, and the driving performance of each drive device is continuously detected and the error of the actual value with respect to the target value is sequentially determined. Bending the pipe is performed by correcting the indicated speed using proportional-integral control and managing the movements of the straight press die, circular receiving die, and gripping device so that they each match the target bending shape and are synchronized with each other. The gist of this paper is a pipe bending method characterized by the following. The forming method of the present invention is basically a combination of so-called compression bending and roll bending, and requires the necessary movement of three parts: a circular receiving mold, a straight pressing mold, and a gripping device that holds the tube itself. This involves bending the tube while applying the force. In such a method, the position control of the above-mentioned three persons during the molding process has an important meaning in terms of processing accuracy. Therefore, the present invention also specifies a method for synchronously controlling the positions of these three persons. be.

<Example> Hereinafter, the method of the present invention will be explained specifically and in detail.

FIG. 7 is a plan view schematically showing an apparatus for carrying out the molding method of the present invention.

In the figure, 1 is the straight pipe P to be bent.
This is a gripping device that grips the (round tube), and this is the fixed piece 2
A pipe P is provided between the movable piece 3 that moves forward and backward with respect to the fixed piece.
The structure is such that the pipe is held under pressure between the two pieces by pressing the movable piece 3 with the hydraulic cylinder 4. This gripping device needs to be movable to any position on a specific plane. In the illustrated structure, two tables 8 and 10 are combined, each having screw shafts 5 and 6 to which independent drive sources 7 and 9 are attached. That is, the gripping device 1 is first threadedly engaged with the screw shaft 5 of the table 8 and is driven along the guides 8a, 8a on the same table, and this table 8 itself is then driven along the other table 10 arranged at right angles thereto. It has a structure that engages with the screw shaft 6 and is driven along guides 10a, 10a on the table 10. As the drive sources 7 and 9, DC motors with high controllability are preferable. The same applies to all drive sources hereinafter.

Reference numeral 12 denotes a circular receiving die located at an appropriate distance from the gripping device, and has a semicircular groove 13 on its outer periphery having a shape corresponding to the outer diameter of the portion of the pipe P to be bent. The illustration shows an example in which a tapered pipe is to be bent. This circular receiving mold has a larger diameter and is placed concentrically on a fixed bed 14 having a gear 15 on its outer periphery, and is rotatable about a shaft 16 fixed at the center of the bed. This pivoting motion of the receiving mold is made to be performed in a plane parallel to the plane of movement of the gripping device 1. This circular receiving mold has a circular gear 17 concentric with the outer circle, and a small gear 20 connected to a drive source 18 installed on the bed 14 via a reducer 19 is meshed with the circular gear 17 to be driven. It is provided.

Reference numeral 21 denotes a rotating mount that rotates coaxially with the circular mold 12, and is rotatably supported at its base end by the rotation center axis 16 of the circular mold 12. In this frame 21, a small-diameter drive gear 24 connected to a drive source 22 installed on the frame via a reducer 23 is meshed with a large gear 15 on the outer periphery of the fixed bed, and the drive gear 24 is driven along the large gear 15. It is provided to rotate by moving around the bed.

Reference numeral 25 denotes a straight press die installed on the above-mentioned rotating frame 21, which has a semicircular groove 26 of a shape corresponding to the outer diameter of the portion of the pipe P to be bent, similar to the circular die, and is attached to the above-mentioned circular receiver. The mold 12 and the mutual semicircular groove 13,
26 facing each other. This straight press die 25 is installed on the turning frame 21 via a support device 27, and this support device 27 is connected to guides 21a, 21a provided in the normal direction of the turning locus of the frame 21. In other words, it can slide along the circular receiving mold 12 in the radial direction, and for the straight pressing mold 25, the pressing mold can be slid on its own by a total of four support rollers 28a, 28a corresponding to the upper and lower sides of the pressing mold. It is designed to be able to slide along the longitudinal direction. That is, the straight mold 25 is the same as the circular receiving mold 1.
It can move forward and backward in the radial direction of 2 and can slide in its own longitudinal direction.

Rack teeth 30 are provided along the longitudinal direction on the back surface of the straight mold 25, and a small gear 32 connected to a drive source 31 on the rotating frame 21 is meshed with the rack teeth 30. Shape mold 25
It is possible to position it in any position by sliding it.

Reference numeral 29 denotes a pressing mechanism for pressing the straight mold 25 onto the outer periphery of the circular receiving mold.
It is designed to press against the back of the Needless to say, the roller 28b is provided to enable pressing operation while keeping the mold movable in the longitudinal direction. This pressing mechanism 29 is a hydraulic cylinder,
It is used not only for pressing, but also for separating the pressing mold 25 from the circular receiving mold 12.

In the tube bending method of the present invention, bending is performed in the following manner using the apparatus configured as described above.

First, the pipe P to be bent is held by the gripping device 1 set at a predetermined position at a point other than the part to be bent, and at the same time, the pipe P is sandwiched between the circular receiving mold 12 and the straight pressing mold 25, and set. do. At this time, the outer periphery of the forming start position M of the pipe P is inscribed in the semicircular groove 13 of the circular receiving mold 12, and the straight pressing mold 25
The semicircular groove 26 corresponds to such a pipe P with a width in the axial direction, and its front surface is in contact with the outer periphery of the circular receiving mold 12. When the object to be bent is a tapered pipe as shown in the figure, it is especially important to make the forming start position M correspond accurately to the semicircular grooves 13 and 26 whose inner diameter matches the outer diameter at the same position. That's the important thing. The receiving mold and the pressing mold can be set using the driving sources 18 and 31, respectively.

After setting the positional relationship between the tube and each part of the device as described above, the pressing mechanism 29 is operated to press the straight mold 25.
is pressed against the outer periphery of the circular receiving mold 12 with a predetermined force.

After completing the above setting, move the rotating mount 21 to the drive source 2.
2, and rotate the straight mold 25 into the circular receiving mold 12.
While maintaining the state of pressure contact with the object, the object is gradually tilted along the outer periphery of the object. At this time, the circular receiving mold 12 and the gripping device 1 are simultaneously driven by the driving sources 18, 7, and 9, and these movements, namely, the tilting of the straight pressing mold 25, the turning of the circular receiving mold 12, The planar motion of the gripping device 1 is managed in accordance with the target bending shape.

FIGS. 8 and 9 show two specific examples of this management, with FIG. 8 showing arc bending and FIG. 9 showing elliptical bending. That is, in the figure,
P ₁ →P ₂ ... shows the tilting movement of the straight mold 25 due to the transition of the contact point of the straight mold 25 on the outer periphery of the circular receiving mold 12, and Q ₁ →Q ₂ ... shows the tilting movement of the straight mold 25 on the outer periphery of the circular receiving mold 12. M ₁ →M ₂ ... represents the transition of one point, that is, the rotational movement of the receiving mold, and the transition of the bending start point of the pipe P represents the planar movement of the gripping device 1, and P,
The same subscript number between Q and M means the positions at the same time.

By managing the movements of the straight mold 25, the circular receiving mold 12, and the gripping device 1 in synchronization with each other in this way, it is possible to produce a bent shape that follows an arbitrary curve that meets the target. In this case, it goes without saying that it is necessary to consider in advance the amount of spring back of the tube after molding and to carry out the molding taking into account this amount.

In addition, in the above-mentioned molding process, the straight mold 25 is slid in the longitudinal direction in accordance with the rotational movement of the circular receiving mold 12 that is in pressure contact with it; however, this movement is caused by the movement of the circular receiving mold 12. Either driven driving or active driving by the driving source 31 may be used. However, from the point of view of machining accuracy, it is preferable to use active drive to ensure synchronization with the movement of the circular receiving mold 12. Reliable synchronization between the pivoting of the circular receiving mold 12 and the sliding movement of the straight mold 25 can also be achieved by providing both molds with interlocking lock teeth.

By the way, in the above molding method, the device drive system in the molding process, that is, the straight mold 1
2. The accuracy of controlling the movements of the circular receiving mold 25 and the gripping device 1 governs the machining accuracy, but it is actually very difficult to accurately synchronize the movements of these three with each other. In other words, there is a delay in the speed control response of the drive source (DC motor) that controls each movement, the moment of inertia differs for each drive system, so the delay time between the actual speed and the commanded speed varies, and the drive system This can be attributed to the fact that the change pattern of the indicated speed is completely different depending on the unit.

The control method based on the present invention makes it possible to synchronously control the movement of such a device drive system with high precision. The control will be explained in detail below.

Regarding the movement of the device drive system mentioned above, the straight pressing die 2
The tilting movement of 5 is due to the rotation angle β of the rotating frame 21, the rotational movement of the circular receiving mold 12 is due to its own rotation angle γ, and the planar movement of the gripping device 1 is due to the direction along the two orthogonal screw axes 5 and 6. Each can be defined by displacement (X) and (Y). In other words, 4 axes (β, γ, X,
It is possible to specify the pipe bending shape even by changing the position with respect to Y).

By the way, in general, in order to eliminate operational delays in mechanical devices, it is necessary to take into account the response delay characteristics of the drive system in advance and issue instructions to the control system early.

Therefore, when we actually measured and investigated the response characteristics of the drive system for the four axes β, γ, It was found that sufficient control accuracy can be obtained by approximating it as a second-order lag system model.

Here, if the relationship between the speed instruction input and the response output is expressed mathematically, the following formula o(t)=∫ ^t _p g(t-τ)・i(t)dτ o(t): Output i at time t (t): Input at time t g(t): Function showing the relationship between input and output τ: Variable representing time. When this is Laplace transformed, it is expressed as O(s)=I(S)×G(S) G(s): Transfer function (specific to the equipment). To obtain the target output O(S) from this formula, It can be seen that the input I(S) should be O(S)/G(S). Therefore, the time t for obtaining the target output by inverse Laplace transform of O(S)/G(S)
If the input i'(t) of is calculated in advance and this speed value is given as input to the control system, basically the motor speed history will match the target and
The trajectory of β, γ) should match the target.

However, in general, the rotation speed of a motor depends on changes in voltage,
Some degree of variation is unavoidable due to unavoidable disturbances such as temperature changes, and therefore, in reality, sufficient results cannot be expected from the above predictive control alone.

However, based on the above predictive control and according to the so-called proportional-integral control method, the following formula i″(t)=i′(t)+a・Δx(t)+b∫ ^t _p Δx(s)ds a, b : Constant (adjustment parameter) Δx: By using control that corrects the motor instruction speed i'(t) based on the difference between the target position and the actual position, it is possible to obtain practically sufficient control accuracy.Proportional integral Under control applications, typically
In response to changes in the target value, the actual value will approach the target value with a delay, and in this sense an error will remain, but since the response delay of the system itself has been taken into account in advance to the indicated speed, the actual value When almost coincides with the target value, there is originally only a minute error due to disturbance, and therefore high precision control can be achieved by proportional-integral control.

That is, the control method according to the present invention is based on the above facts, and the specific method is as follows.

The equipment used for control is schematically shown in Figure 7 above, in which 33 ₁ , 33 ₂ ... are connected to the drive motors corresponding to the X, Y, β, and γ axes of the bending machine. A pulse generator generates a number of pulses according to the actual rotation amount of the drive motor. 34 is a speed control system for each of the drive motors mentioned above. 35 is a computer that gives instructions to this speed control system 34. The processing contents of this computer are shown in a block diagram in FIG.

In machining, first, the computer 35 calculates the instruction speed i'(t) to each drive system from information on the bending shape given in advance, taking into account the response delay of each drive system of the processing machine. That is, the calculation in part A of the block diagram of FIG. 11 is performed.

Next, the indicated speed i′(t) obtained by this calculation
is input to the control system 34 of each drive motor, and each drive motor is operated while controlling its speed. At this time, on the other hand, the computer 3 calculates the output pulses from the pulse generators 33 ₁ , 33 ₂ . . . connected to each drive motor.
5, the actual position of (X, Y, β, γ) is continuously detected, and the error (ΔX, ΔY, Δβ, Δγ) of the actual position with respect to the target position is calculated.
is calculated and correction is applied to the commanded speed i'(t) using proportional-integral control. This calculation is shown in part B of FIG.

The pipe is bent while continuously performing such speed control until (X, Y, β, γ) reaches the final position of the target trajectory.

The high accuracy of the control method based on the present invention is as follows.
Specific numerical values are listed below.
That is, Fig. 12 shows the results of a simulation study of the accuracy when using only normal proportional-integral control, while Fig. 13 shows the result of applying the control based on the present invention to an actual machine and examining its control accuracy. The results are shown below. In the example using only proportional-integral control, the accuracy of β and γ was within ±2.3°, and the accuracy of X and Y was within 15 mm, which was extremely poor and impractical, but in the example of the present invention, β and γ were 0.3°. Within 3 mm, X and Y were also within 3 mm, which showed a significant improvement in accuracy, and sufficient accuracy was obtained for practical use.

As is clear from the above explanation, according to the method of the present invention, it is possible to bend a pipe into any curved shape such as a circular arc, an ellipse, a parabola, etc., and the bending process can be performed with good accuracy. In addition, during the bending process, the part of the pipe that is being bent is always completely surrounded by the circular receiving mold and the straight stamping mold, which effectively prevents flattening and wrinkles of the pipe during processing. It can be expected to have excellent effects, such as prevention.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of compression bending, and Fig. 2 is an explanatory diagram of tension bending, where A shows the tube set state and B shows the state during processing. Fig. 3 is an explanatory diagram of press bending, Fig. 4 is an explanatory diagram of roll bending, Fig. 5 is an explanatory diagram of tension bending, Fig. 6 is an explanatory diagram of Hamburg bending, and Fig. 7 is an explanatory diagram of implementing the method of the present invention. A schematic plan view of a bending device for the purpose and a block diagram showing its control system, No. 8
Figure 9 is an explanatory diagram showing how to manage each drive system of the same device when bending a pipe by the method of the present invention.
FIG. 8 shows an example of arc bending, and FIG. 9 shows an example of elliptical bending. FIG. 10 is a diagram showing the state of response delay in speed control of the processing device shown in FIG. 7, FIG. 11 is a block diagram showing computer processing based on the control method of the present invention, and FIGS. 12 and 13 are FIG. 7 is a diagram showing the position control accuracy regarding each drive system (β, γ, X, Y) of the device shown in FIG. + Shows the case of applying proportional-integral control,
In both figures, A represents the γ-axis error, B represents the β-axis error, C represents the X-axis error, and D represents the Y-axis error. In the figure, 1...Gripping device, 5, 6...Screw shaft, 7, 9...Drive source, 8, 10...Table,
12...Circular receiving mold, 13...Semicircular groove, 14...Bed, 18...Drive source, 21...Swivel frame, 22
... Drive source, 25 ... Straight pressing die, 26 ... Semicircular groove, 27 ... Support mechanism, 29 ... Pressing mechanism, 31
... Drive source, 33 ... Pulse generator, 34 ... Speed controller, 35 ... Computer.

Claims (1)

[Claims] 1. A gripping device movable to any position on a specific plane grips the pipe to be bent at a position other than the portion to be bent, and the bent portion is held in a plane parallel to the plane of movement of the gripping device. The circular receiving mold is placed between the rotating circular receiving mold and the straight pressing mold that forms a pair with it, and the straight pressing mold is gradually pressed along the outer circumference of the circular receiving mold while keeping it in pressure contact with the circular receiving mold. The speed control system of the driving device that governs the tilting movement, the turning movement of the circular receiving mold, and the planar movement of the gripping device is adjusted in advance by taking into account the response delay of each driving device based on the target bending shape. In addition to inputting the speed value determined as the designated speed as a command signal, the driving performance of each drive device is continuously detected, the error of the actual value with respect to the target value is sequentially determined, and the said command speed is corrected by proportional-integral control. A method for bending a tube, characterized in that the tube is bent while controlling the movements of a straight die, a circular receiving die, and a gripping device so as to correspond to a target bending shape and to be synchronized with each other.