JP3518356B2 - Control method of hydraulic bulging of metal tube - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic bulge control method for applying a pressure to a liquid introduced into a metal tube to process the metal tube into an irregular shape.

[0002]

2. Description of the Related Art In hydraulic bulging of a metal pipe, a liquid (hereinafter referred to as a working liquid) is injected into a metal pipe (hereinafter referred to as a raw pipe) which is a material, and the pressure of the working liquid (hereinafter referred to as a molding internal pressure). ) And an axial compressive force (hereinafter referred to as an axial pushing force) to the tube end of the raw tube are added in combination to obtain deformed tube products having various cross-sectional shapes.

FIG. 1 is a side view showing an outline of the entire hydraulic bulge processing apparatus.

As shown in FIG. 1, the hydraulic bulge processing apparatus includes devices 21 and 22 (hereinafter, referred to as an axial pressing device) that combine an upper die 5, a lower die 6 and an axial compression of a blank pipe and supply of a working fluid. Device 2
1, 22), the shaft pressing cylinders 1 and 2, the shaft pressing tools 3 and 4 which are also tools for pressing the metal pipe ends against the metal pipe to enclose the working liquid and perform compression processing (high pressure (several hundreds to thousands). k
gf / cm ² ) and a press device 17 for lowering the upper mold 5 and pressing it against the lower mold 6.

FIG. 2 is a vertical cross-sectional view showing an outline of the hydraulic bulge working process. FIG. 2 (a) shows the state before the hydraulic bulge working.
(b) is the state at the end of hydraulic bulging. In the figure, the same parts as those in FIG. 1 are represented by the same reference numerals.

As shown in FIG. 1 (a), first, the base pipe 7 is set in the lower mold 6, and the upper mold 5 is lowered by a press device (not shown) and pressed against the lower mold 6 from the left and right directions. The axial pressing tools 3 and 4 attached to the axial pressing cylinders 1 and 2 are moved forward, the axial pressing tools 3 and 4 are pressed against both pipe ends of the raw pipe 7 to perform sealing, and a supply flow path in the axial pressing tool 4 is provided. While injecting the working fluid 8 from 9, the air in the raw pipe 7 is discharged together with the working fluid 8 through the discharge passage 19 in the axial pressing tool 3, and a valve (not shown) on the extension of the discharge passage 19 is closed. The raw liquid 7 is filled with the working liquid 8. In the following, it is assumed that the shell 7 is placed horizontally, and the axial direction of the shell is “left and right”.
Also called direction.

Next, as shown in FIG. 2 (b), the axial pressing tools 3 and 4 are advanced in the direction of compressing the raw pipe 7, and the molding internal pressure is gradually increased by a pressure generator (not shown), The tube 7 is expanded so as to follow the inner contours of the upper mold 5 and the lower mold 6 to obtain a product 10. Next, after lowering the molding internal pressure, the upper mold 5 is raised, the axial pressing tools 3, 4 are retracted, and the product 10 is taken out.

Although a method of performing bulge processing by axially pushing from both sides of the pipe has been described above, there is also a bulge working method of axially pushing from one side of the closed pipe. The control method of the present invention can be applied to bulging of a closed pipe, but in the following description, a method of axially pushing from both sides of an open pipe will be described as an example.

In hydraulic bulging of a metal tube, in the process of increasing the molding internal pressure and expanding it, the relationship between the compression amount of the raw pipe by the axial pressing tool (hereinafter referred to as the axial pressing amount) and the molding internal pressure. However, it has a great influence on the shape of the product after molding.

When the metal tube is expanded, the wall thickness of the metal tube decreases, but if an appropriate axial pushing amount is given in the process of increasing the molding internal pressure, the wall thickness reduced portion is caused by the principle of plastic flow. The wall thickness can be appropriately compensated to prevent thinning and rupture.

The following techniques have been proposed for controlling the molding internal pressure and the axial pressing amount. For example, JP-A-56-
No. 22285, the molding internal pressure is controlled by a servo pump so that the pressure of the shaft pressing cylinder is controlled so that the pressure difference from the molding internal pressure has a proportional relationship, and at the same time, the shaft pressing amount of a pair of shaft pressing cylinders is controlled. A method of controlling the pressure of the axial push cylinder to be synchronized is disclosed.

However, according to this method, the pressure control of the shaft pressing cylinder includes a shaft pressing amount control for synchronizing a pair of shaft pressing cylinders, and a pressure difference control for maintaining a pressure difference with the molding internal pressure in a proportional relationship. (These two variables are controlled by one operation amount.) When both controls interfere with each other and either the axial pushing amount or the axial pushing is disturbed by the external disturbance, the other is also disturbed. There is a problem of becoming stable.

Japanese Examined Patent Publication No. 56-25333 discloses a relation between molding internal pressure, axial pressure cylinder pressure, and axial pressure amount in a hydraulic bulge processing apparatus equipped with an electro-hydraulic control device using various types of molds. A technique of performing control by switching control programs is disclosed. As a detailed control example thereof, a technique is disclosed in which the molding internal pressure and the axial pressing cylinder pressure are controlled so that the pressure difference between the molding internal pressure and the axial pressing cylinder pressure has a proportional relationship.

However, this method controls the molding internal pressure and the shaft pressing cylinder pressure (or the shaft pressing amount) so as to always have a proportional relationship, and is applicable to a cylinder having a simple molding shape, a square cylinder, or the like. However, there is a problem that thinning or buckling occurs in a molded shape having complicated unevenness.

In recent years, there has been an increasing need for molding left and right asymmetrical products by bulge processing, but in the above-mentioned Japanese Patent Laid-Open No. 56-22285, the axial pressing in which the left and right axial pressing amounts are synchronized is described. In some cases, the product may have local thin-walled and thick-walled mixture, and countermeasures against it have been desired.

[0016]

SUMMARY OF THE INVENTION An object of the present invention is to provide a control method for obtaining a high quality bulging product by preventing buckling, thinning and bursting in hydraulic bulging. .

[0017]

Means for Solving the Problems The inventors have conducted a bulge processing test using molds of various shapes and examined the appropriate relationship between the axial pressing amount and the molding internal pressure, and as a result, obtained the following findings.

(A) If the molding shape is a simple shape (square tube, round tube overhanging at one location, shape of circular cross section, simple axisymmetric shape, etc.) Except for the portion immediately after and immediately before the end of processing, the relationship between the two is almost proportional and can be processed without any problems by the technique disclosed in Japanese Patent Publication No. 56-25333.

(B) If the molding shape becomes complicated (asymmetrical shaft center, shape with branches or protrusions, etc.), the proper relationship between the axial pressing amount and the molding internal pressure is not proportional.

FIG. 3 is a graph showing the relationship between the axial pressing amount and the molding internal pressure during hydraulic bulging. As shown in the figure, the proper relationship between the axial pressing amount and the molding internal pressure is a curve that rises to the right. The shape of the curve varies depending on the molding shape, but it can be roughly divided into the first rising part, the middle part where the slope of the graph becomes gentle in the middle, and the final part where the slope becomes steep again before the completion of processing. There may be multiple intermediate parts where the slope is gentle.

(C) When the curve of the above graph is processed along the curve indicated by the dotted line below (right side), molding is possible, but the wall tends to be thick. Beyond this curve,
Buckling will occur if the axial pushing amount is too large.

On the other hand, if it is possible to perform molding along the curve shown by the dotted line on the upper side (left side) of this curve, it tends to be thin. If the internal pressure of the molding is excessively advanced beyond this curve, the wall thickness will become extremely thin, and the tube will burst. Therefore, the relationship between the axial pressing amount and the molding internal pressure has upper and lower limits of the allowable range depending on the allowable ranges of buckling, thickening, and thinning.

(D) Two broken straight lines shown in FIG. 3 show the permissible range of the conventional method (method of proportionally increasing the axial pressing amount and the molding internal pressure). As shown in the figure, since the axial pressing amount and the molding internal pressure must be between the two curves indicated by the dotted lines, the allowable range of the two broken lines is very limited. I understand. Furthermore, when the two curved curved lines have large bends and the intervals are narrow, two broken straight lines cannot be drawn between the two curved lines. That is, bulging may not be possible with the conventional method.

(E) When the axial pressing amount and the molding internal pressure are applied to the hydraulic servo system at the same time, when the capacity of one of the hydraulic systems is insufficient, the proper relationship shown in FIG. / It may burst or buckle. This is because the set speed of the control device is too fast. For example, if the control of the molding pressure is checked and then the control of the molding internal pressure is followed (synchronized), such a problem does not occur.

(F) When bulging an open pipe, when the forming shape is roughly left-right symmetrical, the axial pushing amount changes by the same amount at the same time on the left and right sides, but when it is asymmetric, the left and right axial pushing amounts for proper working are formed. Are not necessarily equal to each other, or if the axial pressing amounts are equal, a thin portion and a thick portion are mixed. In such a case, for example, when a thin wall is likely to be formed on one side of the pipe, it can be improved by increasing the axial pushing amount on this side. For that reason, the synchronization of the left and right axial pushing amounts as in the past becomes rather harmful.

The present invention was made on the basis of the above findings, and the gist of the invention lies in the following (1) to (5) .

[0027]

(1) In hydraulic bulging of a metal pipe, which applies a molding internal pressure while compressing the metal pipe in the axial direction with a shaft pressing tool,
The proper relationship between the axial pressing amount and the molding internal pressure is obtained in advance , the molding internal pressure is controlled so as to satisfy the above relationship, and the axial pressing amount is set as the target with the axial pressing amount value obtained from the molding internal pressure detection value according to the above relationship. Axial unpaired, characterized by controlling quantity
Control method for hydraulic bulging of metal pipes with complicated shapes, such as bearings and branches . (2) The internal pressure of the molding is controlled while compressing the metal tube in the axial direction with a shaft pushing tool.
Axial pushing amount and forming in hydraulic bulging of added metal pipe
Obtain an appropriate relationship with the internal pressure in advance, and
Control the axial push amount so that
The target is the molding internal pressure value obtained from the amount detection value.
Axial asymmetry, branches or protrusions, characterized by controlling pressure
Control Method for Hydraulic Bulging of Complex-Shaped Metal Pipes with Parts
Law.

[0029]

[0030] (3) a metal tube open at both ends, a pair of axial押工
Liquid pressure of metal pipe that applies internal pressure while being axially compressed by a tool
Appropriateness of one axial pressing amount and molding internal pressure in bulging
And a proper relationship between the axial pressing amount and the molding internal pressure on the other side.
Request separately separately in advance and request separately
To control the molding internal pressure so that
According to the relationship we have obtained,
Arithmetic mean, maximum value or maximum of the calculated two axial push amount values
It is special to control the axial pushing amount with one of the small values as the target.
Control method for hydraulic bulging of metal pipes. (4) In hydraulic bulging of a metal pipe, in which a metal pipe whose both ends are open is compressed axially by a pair of shaft pressing tools while applying molding internal pressure, an appropriate relationship between one axial pressing amount and molding internal pressure And an appropriate relationship between the other shaft pushing amount and the molding internal pressure are separately obtained in advance, and one shaft pushing amount and the other shaft pushing amount are
The respective axial pressing amounts are controlled so as to satisfy the separately determined relationship, and the arithmetic mean of the two molding internal pressures obtained from the respective axial pressing amount detection values according to the separately determined relationship. A method for controlling hydraulic bulging of a metal pipe, wherein the molding internal pressure is controlled with a target of either the maximum value or the minimum value.

(5) In hydraulic bulging of a metal tube, which applies a molding internal pressure while compressing the metal tube in the axial direction with an axial pressing tool,
When a proper relationship between the axial pushing amount and the molding internal pressure is obtained and an allowable range of the proper relation between the axial pushing amount and the molding internal pressure is obtained, and a warning is issued when the relation between the axial pushing amount and the molding internal pressure exceeds the above allowable range. And / or at least the axial pressing amount and the molding internal pressure.
The above (1) to (1) characterized in that one control is changed
The method for controlling hydraulic bulging of a metal tube according to any one of (4) .

[0032]

FIG. 4 is a schematic diagram showing a configuration example of a control device for carrying out the control method of the present invention. In the figure, the same parts as those in FIGS. In the figure, reference numeral 12 is a molding internal pressure setting device, 13 and 14 are first and second axial pressing position setting devices for setting the positions of the axial pressing cylinders 1 and 2, respectively, and 15 and 16 are axial pressing cylinders 1 and 2, respectively. The first and second shaft pushing position detectors 18 for detecting the position of the molding machine, and 18 are the molding internal pressure detectors, and the controller 20
Connected as an input or output to. Also,
In the figure, symbols Pi and Ps are respectively detected values and set values of the molding internal pressure, Xi1 and Xs1 are respectively detected values and set values of the first shaft pressing position, and Xi2 and Xs2 are respectively detection values of the second shaft pressing position. It is a set value.

FIG. 5 is a schematic diagram for explaining the internal control method of the control device 20, where FIG. 5 (a) is a control method for independently setting the molding internal pressure and the axial pushing amount, and FIG. 5 (b) is the axial pushing amount. The control method to set the molding internal pressure according to the detected value of, the figure (c) is the control method to set the molding internal pressure and the axial pushing amount of the axial push cylinders 1 and 2 independently, and the figure (d) is the axial push cylinder. The control method for setting the molding internal pressure according to the detected values of the shaft pressing amounts of 1 and 2 will be described.

In the figure, reference numeral 23 is a clock generator,
Reference numeral 24 is a time forming internal pressure function generator, 25 is a time axis pressing amount function generator, 26 is an axial pressing amount forming internal pressure function generator, and 27 is a calculator. Input / output signal names for the control device 20 correspond to the signal names shown in FIG. Some of the input signals are not used in the control device 20, and, for example, in FIG.
In (d), it is not used in any case of the molding internal pressure Pi.

In FIGS. 4 and 5, the molding internal pressure is set and controlled by the molding internal pressure setting device 12 and the pressure generating device 11. As a concrete device, a known hydraulic servo mechanism or the like is used. Similarly, the axial pushing amount is set and controlled by the first and second axial pushing position setting devices 13 and 14 and the axial pushing cylinders 1 and 2, but as a specific device, a known hydraulic servo mechanism or the like is used. It

4 and 5, input / output signals to / from the control device 20 are as follows: the set value of the molding internal pressure is Ps, the detected value (actually measured value) is Pi, and the set value of the axial pressing amount is Xs1, Xs2.
The detected values are represented by Xi1 and Xi2.

Embodiments of the present invention will be described below. In any of the first method to the fourth method, the control of the present invention is started after the upper die 5 and the lower die 6 are combined and the working liquid 8 fills the raw pipe 7.

(1) First method (reference example) In the control method of independently setting the molding internal pressure and the axial pressing amount, as shown in FIG.
This is performed by the configuration of the control device 20 shown in (a).

When the clock signal t is sent from the clock generator 23 to the time shaping internal pressure function generator 24 and the time axis pushing amount function generator 25, the shaping internal pressure set value Ps which increases with the passage of time from each function generator, Axis push amount set value Xs
1, Xs2 is obtained. Here, assuming that the shaft pushing cylinders 1 and 2 are pushed in synchronously, Xs1 and Xs
The same value as 2 is used. As another example of an aspect, in order to strictly synchronize the left and right of the axial pushing amount, only the axial pushing amount set value Xs1 is given, and the other axial pushing amount set value Xs2 is set to the detected value Xi of the first axial pushing amount.
It may be given from 1. This control is performed by the control device 2
0 may be performed directly by the DDC method (Direct Digital Control) or may be performed by a method of giving a set value to the hydraulic servo system. The first method to the fifth method will be described in the latter method.

The clock generator 23 has a variable clock rate, and when the clock rate is increased, the shaft pushing speed or the molding internal pressure pressurizing speed is increased.

Although it is preferable to use a control computer for the control device 20, a method of rotating a cam having a predetermined function pattern engraved at a constant speed (an analog type program setting device) or the like may be used.

Prior to actual production, trial processing is performed in advance. A processing speed, that is, a clock rate is selected appropriately (at a lower level), and bulge processing is performed for several types to several tens of types of relationships (patterns) between the appropriate forming internal pressure Ps and the axial pressing amount Xs1. This may result in desirable qualities, excessive thinning and thickening, and in some cases, tube rupture. After making these prototypes, Ps and Xs1
When the relationship is plotted as a graph, the shape of the graph as shown in FIG. 3, that is, a curve having an appropriate relationship (solid line) and an allowable range (dotted line) is obtained. Further, the time t is applied as a parameter to each point on the proper relationship (solid line) in FIG. 3, the molding internal pressure Ps (t) and the axial pressing amount Xs1 (t) at that time are obtained, and the time molding of the controller 20 is performed. The functions of the internal pressure function generator 24 and the time axis push amount function generator 25 are set.

By properly selecting the relationship between Ps and Xs1, the functions of the time forming internal pressure function generator 24 and the time axis pushing amount function generator 25 are set appropriately, and buckling and thin wall thickness are controlled under this control. / Good quality product can be obtained without rupture.

Here, in FIG. 5A, the clock generator 23
, Ps and Xs1 are obtained through the time forming internal pressure function generator 24 and the time axis pushing amount function generator 25. However, it is not always necessary to use the clock generator 23 and the clock signal t
May be set manually. Similarly in the following second to fourth methods, the signal of the clock generator 23 may be manually set.

(2) Second Method The control method of the first method is only to give a setting signal from the controller 20 to the hydraulic servo system for the molding internal pressure and the axial pressing amount. When there is a problem in the hydraulic servo system, the proper relationship between the molding internal pressure and the axial pressing amount as shown in FIG. 3 may not be achieved. That is, when the set speed of the clock generator 23 is excessively high and either the molding internal pressure or the hydraulic pressure control of the axial pressing amount cannot catch up, either delays, the machining fluid 8 leaks, or the axial pressing cylinder 1 or 2 fails for some reason. For example, when it is burned in. In such a case, the proper relationship shown in FIG.
Buckling and thinness / burst may occur.

The second method takes such a case into consideration. That is, this is a control method for setting the molding internal pressure according to the detected value of the shaft pressing amount, and is performed by the configuration of the control device 20 shown in FIG. 5 (b).

In FIG. 7B, the function of the time axis pushing amount function generator 25 and the function of the shaft pushing amount forming internal pressure function generator 26 are obtained by the method described in the above item (1) (first method). .
The shape of the function of the axial pressure forming internal pressure function generator 26 is shown in FIG.
It is the same as the curve of the proper relationship shown in.

When the clock signal t is sent from the clock generator 23 to the time axis push amount function generator 25, the axis push amount set value Xs1,
Xs2 is obtained. Depending on this set value, the shaft push cylinder 1
And 2 move to detect the actual position of the shaft pressing cylinder (in the figure (b), the detected value Xi1 from the first shaft pressing position detector 15 is detected).
Express).

When the detected value Xi1 is input to the axial pressing amount forming internal pressure function generator 26, the forming internal pressure Ps is obtained. In this way, by making the molding internal pressure follow the detected value of the axial pressing amount, the problems of buckling and thin wall / rupture of the first method can be solved.

(3) Third method (reference example) This is a control method in which the molding internal pressure and the shaft pressing amounts of the shaft pressing cylinders 1 and 2 are independently set, and is performed by the configuration of the control device 20 shown in FIG. 5 (c). .

This control method is effective when the shape of the product 10 is left-right asymmetric. For example, it has been empirically known that when the product to be molded is a gourd type, it is preferable to increase the axial pushing amount on the larger side of the sphere.

FIG. 6 shows the molding internal pressure and the shaft pressing cylinders 1 and 2.
3 is a graph showing the relationship of the shaft pushing amount of. As shown in the figure, in order to reduce the variation in wall thickness between the left and right parts of the product, it is necessary to change the left and right axial pushing amounts.

The relationship shown in the figure is the same as in the above item (1) (first method).
In the same manner as the method for obtaining the molding internal pressure Ps and the axial pressing amount Xs1 described in the above, the molding internal pressure Ps and the two axial pressing amounts Xs1 and Xs.
2. Prototype processing is performed for 2 to obtain it in advance. The functions of the time shaping internal pressure function generator 24 and the pair of time axis pushing force function generators 25 are similar to the method of obtaining the time t as a parameter from FIG. 3 described in the item (1) (first method). From FIG. 6, a pair of functions of the time axis pushing amount function generator 25 are set in advance.

Under the above-mentioned preparations, when the clock signal t is sent from the clock generator 23 to the time shaping internal pressure function generator 24 and the pair of time axis pushing amount function generators 25, the shaping internal pressures are generated from the respective function generators. Set value Ps, shaft push amount set value Xs1,
Xs2 is obtained. In this case, the time axis pushing amount function generators 25 have different function shapes, and Xs1 and Xs
Values different from 2 are obtained. The setting and control operations for the molding internal pressure setting device 12 and the left and right shaft pressing position setting devices (13, 14) are the same as those described in the item (1).

As described above, by changing the axial pushing amount between the left and right axial pushing cylinders, even if the product shape is asymmetrical to the left and right,
It is possible to prevent local thickening and thinning.

(4) Fourth control method A control method for setting the molding internal pressure in accordance with the detected values of the axial pushing amounts of the axial pushing cylinders 1 and 2 is shown in FIG. 5 (d).
0 configuration.

This control method is intended for left-right asymmetric products, as in (3) above. Even in the control of (3) above, if there is a problem with the hydraulic servo system in (1) above, the same problem as in (1) above will occur. This is the setting method.

In FIG. 5D, a pair of time axis pushing amount function generators 25 and a pair of shaft pushing amount forming internal pressure function generators 26.
The function form of is set in advance according to the method described in the above (2) and (3).

Based on the above preparations, when the clock signal t is sent from the clock generator 23 to the pair of time axis push amount function generators 25, the axis push amount set values Xs1, Xs from the respective function generators are sent.
s2 is obtained.

The shaft pushing cylinders 1 and 2 are moved by this set value, and the actual shaft pushing amounts Xi1 and Xi2 are obtained from the first and second shaft pushing position detectors 15 and 16.

When these Xi1 and Xi2 are input to the pair of shaft pressing amount forming internal pressure function generators 26, respectively, Ps1 and Ps
2 is obtained as an output, and when these are further input to the computing unit 27, the molding internal pressure set value Ps is obtained. If this Ps is given to the molding internal pressure setting device 12, the following (1) to (3)
Perform the same control as.

The calculator 27 calculates and outputs either the average of Ps1 and Ps2, or the maximum or minimum value. Which calculation is used is set in the control device 20 in advance.

Corresponding to the relationship between the axial pressing amount and the molding internal pressure for the two axial pressing cylinders 1 and 2 in FIG. 6, 1 in FIG.
If the functions of the pair of time axis pushing amount function generators 25 and the pair of shaft pushing amount forming internal pressure function generators 26 are set correctly,
Outputs Ps1 and P of the pair of shaft pressing amount forming internal pressure function generators 26
Although s2 is not so different, Ps1 and Ps2 may be different due to some trouble of the hydraulic servo system. As a countermeasure, the calculator 27 calculates the average, maximum value or minimum value of both. In general, it is desirable to perform the maximum value calculation when there is no risk of buckling in a thick-walled pipe, the minimum value calculation in the case of a thin-walled pipe, and the average calculation when neither.

In contrast to the control method described in the second method in which the axial pressing amount is controlled first to follow the molding internal pressure, the molding internal pressure is controlled first to follow the axial pressing amount. Can also be considered. This method has the advantage that buckling is less likely to occur.

However, as shown in FIG. 3, in the curve of the axial pressing amount vs. the molding internal pressure, the inclination of the curve becomes small at the intermediate portion, and the method of controlling the molding internal pressure first changes the axial pressing amount largely, so that the control is performed. However, since it may be unstable or the amount of axial pushing cannot follow, it is not a desirable control method in the case of processing thin-walled raw pipes.

Also in the fourth method, it is possible to control the molding internal pressure first and follow the axial pressing amount (axial pressing cylinders 1 and 2), and the advantages and disadvantages are the same as above.

(5) The fifth method is a method of managing the relationship between the axial pressing amount and the molding internal pressure within an allowable range. When the allowable range is exceeded, a warning is given to the operator,
When automatic control is performed, this is an alarm function that automatically takes measures such as interruption of control (holding of shaft pressing amount, molding internal pressure or reduction).

As shown in FIG. 3, there is an upper and lower limit (dotted line curve) of an allowable range with respect to an appropriate relationship between the axial pressing amount and the molding internal pressure (solid line curve). This allowable range is obtained in advance by the method described in the item (1) (first method).

In the fifth method, the controller 2 shown in FIG.
The alarm device (not shown) at 0 displays the shaft pushing amounts Xi1 and Xi.
2. The detected value of the molding internal pressure Pi is input and the allowable range corresponding to FIG. 3 is constantly monitored. Second method and fourth method of the present invention
When the law is applied, it does not usually exceed the above allowable range, but in the case of some electrical or mechanical trouble,
For example, it is effective in the case of a leak of machining fluid, a hydraulic system failure of a shaft pressing cylinder, and the like. This alarm function is also effective when automatic setting is not performed.

The above-mentioned monitoring of the permissible range can be applied even when the axial pressing amount differs between the left and right. That is, by setting the respective allowable ranges in the same manner as in FIG. 3 with respect to the proper relationship of the left and right shaft pressing amounts in FIG. 6, an appropriate alarm function can be obtained even in the case of forming a left-right asymmetric product.

[0071]

EXAMPLES Been axis押量and the molding pressure with the conventional method for proportionally increasing the comparative experiment of Example and the present invention and by way.

The control parameters (proportional coefficient between the molding internal pressure and the axial pressing amount in the conventional method, and the shape of the function of the function generator in the method of the present invention) were previously obtained each time bulge molding of various shapes was performed. In the conventional method, the coefficient of the proportional relationship between the axial pressing amount and the molding internal pressure is determined by performing trial manufacturing of about 10 pieces, and further corrected when a defect occurs in the processing lot, and finally an appropriate proportional coefficient is determined. I asked.

In the case of the method of the present invention, the proper relationship between the axial pressing amount and the molding internal pressure corresponding to the solid line graph in FIG. 3 and the allowable range are determined in advance by performing trial manufacture of about 15 pieces, and shown in FIG. The function setting of the axial pressure forming internal pressure function generator 26 was performed. Further, the functions of the time forming internal pressure function generator 24 and the time axis pressing amount function generator 25 (see FIG. 4) were set while considering this relationship and the capability of the hydraulic servo.

FIGS. 7 (a) to 7 (c) are schematic views of the cross-sectional shape of the prototype product when comparing the conventional method and the method of the present invention. FIG. 7 (a) shows a cylindrical overhang, and FIG. 7 (b). Is a brim-shaped overhang, same figure
(c) is the case of a left-right asymmetrical umbrella-shaped overhang. Each of the base pipes is a stainless steel (SUS430) pipe with an outer diameter of 100 mm and a wall pressure of 2.0 mm, and the base pipe length is 300 m in the same figure (a).
m, 400 mm in the same figure b, and 350 mm in the same figure (c).

( Reference Example 1) Cylindrical overhang bulging with a sectional shape shown in FIG.
It was performed using the control of the control method of the conventional method and the first method. Table 1 shows the processing results.

[0076]

[Table 1]

As shown in Table 1, there was no difference between the conventional method and the first method . It is considered that this is because the formed shape is simple and the processing is not so severe (processing with large plastic flow).

[0078] Next, a cylindrical projecting bulging sectional shape shown in FIG. 7 (b), was performed using the control of the control method of the conventional method and the first method. Table 2 shows the processing results.

[0079]

[Table 2]

As shown in Table 2, in the shape of FIG. 7 (b) in which the overhang is larger than that of FIG. 7 (a), the conventional method causes thinning (burst) or buckling due to insufficient axial pushing amount. While the number was large, when the control method of the first method was used, the yield rate was significantly improved.

This is because in the conventional method, since the axial pressing amount and the molding internal pressure are increased proportionally, the allowable range of the relationship between the two is narrow as shown by the two broken straight lines in FIG. It is considered that some variations were beyond the allowable range shown by the dotted curve.

On the other hand, as in the method of the present invention, by working along the proper relationship shown by the solid curve, there is a margin for the allowable range shown by the dotted curve, and it is not affected by variations in the raw pipes. It is thought to be a tame.

Example 1 The first method and the second method of the present invention were compared. The molded shape of the product used in the test is the shape shown in Fig. 7 (b). In each control method, the clock rate of the clock generator 23 shown in FIG. 5 was successively increased to increase the processing speed. When the clock rate exceeds a certain limit, thinning or rupture frequently occurs in both the first method and the second method. Processing was performed at a clock rate (processing speed) of 95% of this limit clock rate. Table 3 shows the comparison results of the first method and the second method.

[0084]

[Table 3]

As shown in Table 3, in the first method, the axial pushing speed could not catch up and a thin wall was generated, whereas in the second method, the non-defective rate was improved. Even in the case of the first method, if the clock rate (processing speed) is decreased, the non-defective rate is improved, but
It was found that according to the method, the processing speed can be increased to the limit.

Reference Example 2 The first method and the third method were compared. The molded shape of the product used in the test is a left-right asymmetrical umbrella shape as shown in Fig. 7 (c). In the third method, as shown in FIG. 6, the time forming internal pressure function generator 24 and the two time axis pressing amount functions are set so that the shaft pressing amount of the shaft pressing cylinder 1 becomes smaller than the shaft pressing amount of the shaft pressing cylinder 2. Generator 2
The functional relationship of 5 was adjusted. In the first method, the same functional relationship as that of the time axis pushing amount function generator 25 of the shaft pushing cylinder 1 of the third method is set. Table 4 shows the processing results.

[0087]

[Table 4]

As shown in Table 4, thinning or buckling frequently occurred in the first method, whereas it was greatly improved in the third method.

This is because the left and right asymmetric products, as shown in FIG. 7 (c), have different plastic flow states on the left and right, and when the axial pushing amount of the axial pushing cylinders is synchronized as in the first method, the overhang is overhang. It is considered that the large side became thin (or burst), and the small side became thick or buckled.

It was found that the third method (or the fourth method) can give a shaft pressing amount in consideration of this point and is effective for asymmetrical machining.

[0091]

According to the control method of the present invention, buckling, thinning or rupture can be prevented, a high-quality hydraulic bulging product can be obtained, and productivity is improved.

[Brief description of drawings]

FIG. 1 is a side view showing an outline of the entire hydraulic bulge processing apparatus.

FIG. 2 is a vertical cross-sectional view showing an outline of a hydraulic bulging process,
The figure (a) shows the state before hydraulic bulging, and the figure (b) shows the state at the end of hydraulic bulging.

FIG. 3 is a graph showing the relationship between the axial pressing amount and the molding internal pressure during hydraulic bulging.

FIG. 4 is a schematic diagram showing a configuration example of a control device for carrying out the control method of the present invention.

5A and 5B are schematic diagrams illustrating a control method inside the control device 20, wherein FIG. 5A is a control method for independently setting the molding internal pressure and the axial pressing amount, and FIG. 5B is the detection of the axial pressing amount. The control method to set the molding internal pressure according to the value, the figure (c) is the control method to set the molding internal pressure and the axial pushing amount of the axial pushing cylinders 1 and 2 independently,
(d) shows a control method for setting the molding internal pressure in accordance with the detected values of the shaft pressing amounts of the shaft pressing cylinders 1 and 2.

FIG. 6 is a graph showing the relationship between the molding internal pressure and the shaft pressing amounts of the shaft pressing cylinders 1 and 2.

FIG. 7 is a schematic diagram of the cross-sectional shape of the prototype product, which is shown in FIG.
Shows the case of cylindrical overhang, Figure (b) shows the case of flange-like overhang, and Figure (c) shows the case of left-right asymmetrical umbrella-like overhang.

[Explanation of symbols]

1, 2 axis push cylinder 3, 4 axis push tool 5 Upper mold 6 Lower mold 7 Tube 8 working fluid 9 supply channels 10 products 11 Pressure generator 12 Molding internal pressure setting device 13 Axis 1 push position setting device 14 2nd axis push position setting device 15 1st axis push position detector 16 2nd axis push position detector 17 Press machine 18 Molding internal pressure detector 19 discharge channel 20 Control device 21,22 Axial pusher 23 clock generator 24-hour molding internal pressure function generator 25 time axis function generator 26 Axial displacement forming internal pressure function generator 27 arithmetic unit Pi Molding internal pressure detection value Ps molding internal pressure set value Xi1 Axis 1 push position detection value Xi2 Axis 2 push position detection value Xs1 Axis 1 push position setting value Xs2 Axis 2 push position setting value t clock signal

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B21D 26/02

Claims (5)

(57) [Claims] 1. A hydraulic bulging the metal tube to apply a molding pressure while compressing axially the metal tube in the axial押工instrument, obtained in advance the proper relationship between the shaft押量the molding pressure, the relationship controlling the forming pressure so as to satisfy the, and controlling the axial押量 the goal axis押量 value determined from the forming pressure sensing value in accordance with said relationship, the axis unpaired
Control method for hydraulic bulging of metal pipes with complicated shapes, such as bearings and branches . 2. A hydraulic bulging the metal tube to apply a molding pressure while compressing axially the metal tube in the axial押工instrument, obtained in advance the proper relationship between the shaft押量the molding pressure, the relationship The axial pressing amount is controlled so as to satisfy the above condition, and the molding internal pressure is controlled by targeting the molding internal pressure value obtained from the axial pressing amount detection value according to the above relationship .
Control method for hydraulic bulging of metal pipes with complicated shapes, such as bearings and branches . 3. In hydraulic bulging of a metal pipe in which a metal pipe whose both ends are open is axially compressed by a pair of shaft pressing tools and a molding internal pressure is applied, one of the shaft pressing amount and the molding internal pressure is appropriate. and Do relationship, the other axis押量and to previously obtain the proper relationship between the molding pressure in advance separately, so as to satisfy the pre-Symbol separately determined in advance relationship, controls the molding pressure, the separately axis arithmetic mean of the two axes押量 value determined from the forming pressure sensing value according to the relationship which has been determined, either a maximum or minimum value as the target
A control method for hydraulic bulging of a metal tube, which is characterized by controlling a pressing amount . 4. In hydraulic bulging of a metal pipe, in which a metal pipe whose both ends are open is axially compressed by a pair of shaft pressing tools and a molding internal pressure is applied, the proper amount of one shaft pressing amount and the molding internal pressure is applied. Relationship and the proper relationship between the other shaft pressing amount and the molding internal pressure are separately obtained in advance, and the one shaft pressing amount and the other shaft pressing amount are obtained separately as described above. Each axial pushing amount is controlled so as to satisfy, and either the arithmetic mean, the maximum value or the minimum value of the two molding internal pressures obtained from the respective axial pushing amount detected values according to the separately obtained relation. A method for controlling hydraulic bulging of a metal tube, characterized in that the internal pressure of the molding is controlled with the goal of. 5. In hydraulic bulging of a metal pipe in which a metal pipe is compressed axially by a shaft pressing tool and a molding internal pressure is applied to the metal pipe, an appropriate relationship between the shaft pressing amount and the molding internal pressure is obtained and the shaft pressing amount and the molding are performed. An allowable range of an appropriate relationship with the internal pressure is obtained, and when the relationship between the axial pressing amount and the molding internal pressure exceeds the allowable range, a warning is issued, and / or at least one of the axial pressing amount and the molding internal pressure is issued.
5. The control according to any one of the claims 1 to 4 is changed.
A method for controlling hydraulic bulging of a metal tube according to any one of 1 .