JPH0569050A - Press - Google Patents

Abstract

PURPOSE:To provide the press capable of performing pressing in a pressure equalized state with respect to cushion load in a wide range without changing the number of cushion pins, etc. CONSTITUTION:This press is the press 1 to pressure and work a tabular workpiece 6 by upper dies 3 and lower dies 9, a specified stroke is provided movably on the lower dies 9 via hydraulic cylinders 54-55, the generation of wrinkles, etc., during pressing on the workpiece 6 is prevented by the plural cushion pins 52-52 to press a nonworking part of the workpiece 6 against the upper dies 3 during pressing and the smooth worked surface is obtained. In addition, the initial oil pressure supplied to the hydraulic cylinders 54-54 is adjusted by initial oil pressure adjusting means 59-70 and a pressure equalized area which is a function of the initial oil pressure is changed. The pressing in a pressure equalized state with respect to cushion load in the wide range is performed without changing the number of cushion pins and press type structure by changing the pressure equalized area in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a press machine equipped with a pressure equalizing device for equalizing the wrinkle holding force by a plurality of cushion pins, and more particularly to equalizing the wrinkle holding force over a wide press load range. Press machine that can do.

[0002]

2. Description of the Related Art In a drawing press machine, there is a drawing press machine in which a portion which is not a processed portion of a workpiece is pressed while being pressed by a cushion pin so as to prevent wrinkles and the like and obtain a smooth processed surface. In this case, the contact state between each cushion pin and the work piece may differ due to poor accuracy or wear of the cushion pin and each component,
The pressing force applied to the cushion pins during processing, that is, the wrinkle holding force for preventing the generation of wrinkles during processing may be uneven for each cushion pin. Therefore, a cushion pin pressure equalizing device for eliminating this non-uniformity has been developed and disclosed, for example, in Japanese Utility Model Laid-Open No. 1-60721. In this device, a hydraulic cylinder is arranged under each cushion pin, and the hydraulic cylinder absorbs and eliminates the above-mentioned error factors related to the contact state of the cushion pin.

At this time, a condition for obtaining a state in which the cushion pressure (wrinkle pressing force) applied to the cushion pins becomes equal for all the cushion pins, that is, a so-called pressure equalizing state will be considered. Generally, the initial hydraulic pressure supplied to the hydraulic cylinder provided on the cushion pin is P ₀ , the oil amount is V ₀ , the average thrust amount of the cushion pin in the hydraulic cylinder is X _av , the cushion load is F, and the hydraulic cylinder cross-sectional area is S, number of cylinders used (that is, number of cushion pins)
Where n is N and the bulk modulus of oil is K, the following equation (1) is established. X _av = (F−nSP ₀ ) V ₀ / (n ² S ² K) (1) In this formula (1), the horizontal axis represents the cushion load F and the vertical axis represents the number of cushion pins n. When a characteristic diagram is drawn with the average amount of drive X _av as a parameter, for example, a graph as shown in FIG. 5 is obtained.

Here, the average thrust amount X of the hydraulic cylinder
_{If av} is too small, the cushion pressure will not be applied to the short cushion pin, while if the average drive-in amount X _av is too large, it will collide with the cushion pad at the time when the press slide descending speed is fast during press working, so The pin is pushed all the way to the end of the stroke, resulting in a so-called body thrust state. In this way, even if X _av is too small or too large, a uniform pressure is not applied to all cushion pins. For this reason, the pressure equalizing state is obtained only in the region between the upper limit and the lower limit of the average drive amount X _av of the hydraulic cylinder. For example, in the example shown in FIG. 5, the average thrust amount X _av of the hydraulic cylinder is X _b mm ≦ X _av ≦ X _d.
A pressure equalized state is obtained in a region R of mm. Such a region R is called a pressure equalizing region. As can be seen from the above equation (1), this pressure equalizing region R is the initial hydraulic pressure P ₀ of the hydraulic circuit provided on the cushion pin, the oil amount V ₀ , the hydraulic cylinder cross-sectional area S, and the volume elastic coefficient K of the oil. It depends on.

[0005]

However, in the above-mentioned conventional technique, the initial oil pressure P ₀ cannot be changed, and the oil amount V ₀ , the hydraulic cylinder cross-sectional area S, and the bulk modulus K of oil are all constant. Therefore, the pressure equalizing region R is uniquely determined with respect to the cushion load F and the number of cushion pins n. Therefore, if the cushion load F is changed in order to change the material, thickness, etc. of the work piece, or to search for the optimum processing conditions in the trial-pressing press machine, the cushion load F may deviate from the pressure equalizing region R. In such a case, in order to perform the press working in the pressure equalizing region with the desired cushion load F, the number of cushion pins n
Alternatively, the structure of the press die has to be changed, which requires a great deal of labor and time. Therefore, it is an object of the present invention to provide a press machine capable of performing press working in a pressure-equalizing state for a wide range of cushion loads without changing the number of cushion pins or the press die structure.

[0006]

In order to solve the above problems, the press machine according to the invention of claim 1 of the present application is configured as follows. That is, this press machine is a press machine that presses a plate-shaped workpiece by an upper die and a lower die, and is provided on one of the upper die and the lower die so as to be movable by a predetermined stroke via a hydraulic cylinder. The
A plurality of cushion pins that press the non-processed portion of the workpiece against the other of the upper die or the lower die during press working,
Initial hydraulic pressure adjusting means for adjusting the initial hydraulic pressure supplied to the hydraulic cylinder.

In the press machine according to the first aspect of the present invention, it occurs when all the cushion pins are balanced with the press load by the hydraulic pressure that acts on each hydraulic cylinder in common without being pushed all the way to the stroke end of the hydraulic cylinder. A pressure equalization value calculating means for calculating a pressure equalization value which is a value of the hydraulic pressure,
Hydraulic pressure detection means for detecting the hydraulic pressure in the hydraulic cylinder,
Pressure equalization determining means for comparing the detected hydraulic pressure and the calculated pressure equalizing value to determine whether or not the pressure is equalized, and an initial hydraulic pressure adjusted by the initial hydraulic pressure adjusting means according to the determination result. The initial hydraulic pressure instructing means for instructing may be added.

[0008]

According to the press machine of the first aspect of the present invention having the above-mentioned structure, in the press machine in which the plate-like workpiece is strongly pressed by the upper die and the lower die, the upper die or A plurality of cushion pins are provided on one of the lower molds via a hydraulic cylinder so as to be movable by a predetermined stroke. The plurality of cushion pins press the non-processed part of the work piece against the other mold during press working, so that wrinkles and the like are prevented from occurring and a smooth processed surface is obtained. There is. Here, since the initial hydraulic pressure adjusting means for adjusting the initial hydraulic pressure supplied to the hydraulic cylinder is provided, the initial hydraulic pressure supplied to the hydraulic cylinder is adjusted by this initial hydraulic pressure adjusting means, thereby The correlating pressure equalizing region is changed. By changing the pressure equalizing region in this way, press working in a pressure equalizing state is performed for a wide range of cushion loads without changing the number of cushion pins or the press die structure.

Further, in the case of using the press machine according to the second aspect, the pressure equalizing value is calculated by the pressure equalizing value calculating means. Here, the pressure equalization value means the value of the hydraulic pressure that should be generated when all the cushion pins are not pushed all the way to the stroke end of the hydraulic cylinder and the hydraulic pressure commonly acting on each hydraulic cylinder balances the press load. Further, the hydraulic pressure in the hydraulic cylinder is detected by the hydraulic pressure detection means. Then, the calculated pressure equalization value and the detected hydraulic pressure are compared by the pressure equalization determining means to determine whether or not the pressure is equalized. If the pressure is not equalized, the initial oil pressure is changed. In this way, the press working in the pressure equalized state is performed more reliably.

[0010]

First Embodiment Next, a first embodiment embodying the present invention will be described with reference to FIGS.
And it demonstrates with reference to FIG. 1 is a partial vertical sectional view showing a first embodiment of a press machine according to claim 1 of the present invention. In FIG. 1, reference numeral 1 is a press machine, and the press machine 1 is configured as follows. Reference numeral 3 is an upper die composed of a press slide 2 and an upper die 4 fixed to the press slide 2. The upper mold 3 is movable in the vertical direction, and the lower mold 9 is fixed below the upper mold 3. Next, the lower mold 9 will be described. Reference numeral 8 is a lower mold fixed to the bolster 10, and 12 is a press carrier that supports the bolster 10. The press carrier 12 is fixed on a base 14. In the central portions of the upper mold 4 and the lower mold 8, cylindrical molding portions 4a and 8a are provided. Then, the workpiece 6 is placed between the upper mold 4 and the lower mold 8, and the upper mold forming portion 4 is pressed by the pressing pressure.
The processing site of the workpiece 6 is strongly pressed between a and the lower die forming portion 8a, and is pressed into a cylindrical shape.

Inside the lower mold 8, the upper mold forming portion 4a is formed.
A ring-shaped crease presser 50 is arranged so as to surround the lower mold forming portion 8a in the shape of a ring. The ring-shaped wrinkle retainer 50 includes a plurality of cushion pins 52 to
The cushion pins 52 are supported on the upper ends of the die cushions 52 via hydraulic cylinders 54.
Is connected to the cushion pad 16. In this way, the cushion pins 52 to 52 are fitted to the hydraulic cylinders 54 to 54 so as to be movable by a predetermined stroke. The die cushion 20 includes the cushion pad 16 and the cushion cylinder 1 that supports the cushion pad 16.
8. Die cushion plate 2 that fits in the cushion cylinder 18 and slides the cushion cylinder 18
2, an air pipe 24, an air tank 26, an air regulator 28, and a pressure air source 30.
Cushion cylinder 18 and die cushion plate 22
Between the pressure air source 30, a predetermined air pressure determined by the air regulator 28 is applied to the air tank 26 and the air pipe 24.
Is being supplied through.

In the press working by the press machine 1, the work 6 is first placed on the ring-shaped wrinkle retainer 50, and the press slide 2 is lowered. The descending force of the press slide 2 becomes a pressing force between the upper die 4 and the lower die 8 to press the workpiece 6. At the same time, the descending force of the press slide 2 is transmitted to the die cushion 20 via the cushion pins 52 to 52,
The die cushion 20 generates a constant cushion pressure, that is, a wrinkle holding force. In this manner, the non-processed parts of the workpiece 6 (the parts that do not contact the upper mold forming part 4a and the lower mold forming part 8a) are pressed against the lower surface of the upper mold 4 by the cushion pins 52 to 52 while being pressed. By performing the processing, it is possible to prevent wrinkles and the like from being generated on the workpiece 6 during the processing, and to obtain a smooth finished surface.

Therefore, the cushion pins 52 to 52 are provided on the lower die 9 via the hydraulic cylinders 54 to 54 so as to be movable by a predetermined stroke, and press the non-machined portion of the workpiece 6 against the upper die 3 during press working. Functions as multiple cushion pins.

On the other hand, the hydraulic cylinders 54 to 54 are connected to an oil supply pipe 59 via a common hydraulic pipe 56 and a flexible tube 58. This oil supply pipe 5
9 is connected to a hydraulic pump 64 via a check valve 62, and a hydraulic pressure adjusting valve 60 is provided in the middle of the oil supply pipe 59. The hydraulic pressure adjusting valve 60 is an opening / closing valve using an electromagnetic solenoid system, and when the hydraulic pressure adjusting valve 60 is opened, the oil in the oil supply pipe 59 is replaced by an oil tank 66.
Is discharged to. As a result, the hydraulic pressure supplied from the hydraulic pump 64 via the check valve 62 is adjusted, and the flexible tube 58 and the hydraulic pipe 5 are fed from the oil supply pipe 59.
It is supplied to the hydraulic cylinders 54 to 54 via 6. Further, the control box 7 controls the operation / stop of the hydraulic pump 64 and the hydraulic pressure adjustment in the hydraulic pressure adjustment valve 60.
Controlled by 0. The oil discharged to the oil tank 66 is automatically returned to the hydraulic pump 64 through the return pipe 68.
Returned to.

In this way, the oil supply pipe 59, the hydraulic pressure adjusting valve 60, the check valve 62, the hydraulic pump 64, the oil tank 66, the return pipe 68 and the control box 70.
The oil supply device consisting of has the functions of guaranteeing the amount of oil supplied to each of the hydraulic cylinders 54 to 54 and adjusting the initial hydraulic pressure supplied. Therefore, the refueling devices 59 to 7
Reference numeral 0 constitutes an initial hydraulic pressure adjusting means for adjusting the initial hydraulic pressure supplied to the hydraulic cylinders 54 to 54.

When the cushion pins 52 to 52 are in a so-called pressure equalizing state when the press machine 1 performs press working, a common hydraulic pressure is generated in the hydraulic cylinders 54 to 54, whereby each cushion pin is formed. Non-uniformity of the cushion pressure between 52 and 52 is absorbed, and uniform wrinkle holding force is generated over the entire surface, so that a better finished surface can be obtained. Therefore, a method of performing press working in a pressure equalized state by the press machine 1 of the present embodiment having the above configuration will be described next.

As described above, the region R where the pressure equalization is obtained with respect to the cushion load F and the number n of cushion pins is shown in a graph as shown in FIG. 5 with the average thrust amount X _av of the hydraulic cylinder 54 as a parameter. .. In a conventional press machine having normal characteristics, X _b mm ≦ X in FIG.
_A so-called pressure equalizing state is obtained in the region R exemplified in the range of _av ≤ X _d mm. That is, X _b mm ≦ X in FIG.
A region R where _av ≤ X _d mm is a pressure equalizing region.

The reason why the pressure equalizing region R has a limited range such as X _b mm ≤X _av ≤X _d mm is explained as follows. In a conventional press machine with normal characteristics,
Factors such as variations in the length of the cushion pin, inclination of the cushion pad, inclination of the press slide, and variations in the mounting height of the hydraulic cylinder cause uneven cushion loads. Assuming that the sum of squares of each of these factors is close to X _b mm, the hydraulic cylinder is X _b mm
If all the above is not pushed in, all the cushion pins will not be in the equalizing state stochastically. On the other hand, as described above, in the press working, the press pad collides with the cushion pad when the descending speed of the press slide is fast. Therefore, _assuming that the stroke of the hydraulic cylinder is X _s mm, the hydraulic cylinder when it is lowered at a very low speed. Drive-in amount is several meters from X _s mm
Unless the distance is smaller than X _d mm, the cushion pin is pushed all the way to the end of the stroke at high speeds, resulting in a so-called body thrust. For this reason, the equalized state is obtained only in the region R within a certain range where the average amount of drive X _av of the hydraulic cylinder is X _b mm ≤X _av ≤X _d mm. It should be noted that these ranges X _a mm to X _f mm are, for example, in the range of about 1 mm to 4 mm in an actual press machine, and the width of the pressure equalizing region R is, for example, about 2 mm.

As described above, the pressure equalizing state is shown with the cushion load F and the number of cushion pins n as variables and the average thrust amount X _av of the hydraulic cylinder as a parameter.
And this relationship is as shown in the above-mentioned formula (1),
It depends on the initial hydraulic pressure P ₀ supplied from the oil supply devices 59 to 70 to the hydraulic cylinders 54 to 54, the oil amount V _{0 in} the hydraulic cylinders, the hydraulic cylinder cross-sectional area S, and the bulk elastic coefficient K of the oil. In the conventional press machine, since the initial oil pressure P ₀ could not be changed, the pressure equalizing region R was uniquely determined in the machine manufacturing stage as shown in FIG. 5, and the required cushion load F was large. Depending on the size, the pressure may be out of the pressure equalizing region R.

On the other hand, in the press machine 1 of this embodiment, since the initial hydraulic pressure adjusting means 59 to 70 for adjusting the initial hydraulic pressure P ₀ supplied to the hydraulic cylinder are provided, the initial hydraulic pressure P ₀ is set. By changing it, the pressure equalizing region R can be changed as shown in FIG. 4, and the pressure equalizing state can be obtained for a wide range of combinations of the cushion load F and the number of cushion pins n.

Since the mechanical structure of the press machine 1 of this embodiment is similar to that of the conventional press machine shown in FIG. 5, the average driving amount X _av of the hydraulic cylinders 54 to 54 is X _b. A pressure equalized state is obtained in the range of mm ≦ X _av ≦ X _d mm. Therefore, different initial hydraulic pressure X _av = X _b
If each initial hydraulic pressure is selected so that the boundary of mm and the boundary of X _av = X _d mm match, the change of the initial hydraulic pressure can be minimized and the pressure equalizing region can be continuously expanded. In the press machine 1 of this embodiment, as shown in FIG. 4, P ₀ =
With three types of initial hydraulic pressure P01, P02, P03,
Corresponding pressure equalizing regions R ₀₁ , R ₀₂ , R ₀₃ are obtained,
The pressure equalizing region can be continuously expanded. By changing the pressure equalizing region R in this way, it is possible to perform press working in a pressure equalizing state for a wide range of cushion loads F without changing the number n of cushion pins or the press die structure.

Second Embodiment Next, a second embodiment of the press machine of the present invention will be described with reference to FIG. The same members as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. FIG. 2 is a partial vertical sectional view showing a second embodiment of the press machine according to claim 1 of the present invention. In the press machine 201 according to this embodiment, the initial hydraulic pressure P ₀ supplied to the hydraulic cylinders 54 to 54.
The initial oil pressure adjusting means for adjusting the oil supply pipe 2 has one end connected to the flexible tube 58 and the other end branched into three.
59, three sets of check valves 262a to 262c, hydraulic pumps 264a to 264c, and hydraulic control valves 260, an oil tank 266, and a control box 270, which are respectively connected to the three tips.

The three sets of hydraulic pumps 264a-264c are adjusted so as to send out oil at different hydraulic pressures. In this embodiment, the adjustment of the initial oil pressure P ₀ is
This is performed by selecting three sets of hydraulic pumps 264a to 264c having different hydraulic pressures in the control box 270. Further, in this embodiment, the oil is simply discharged to the oil tank 266 by the electromagnetic solenoid type hydraulic pressure adjusting valve 260, and the oil is automatically pumped by the hydraulic pump 264.
No return pipe for returning to ac is provided. The other points are the same as in the first embodiment. Therefore, if the hydraulic pressures of the three sets of hydraulic pumps 264a to 264c are preset to the hydraulic pressures corresponding to the three necessary initial hydraulic pressures P ₀ = P01, P02, P03 shown in FIG. Depending on the combination of the load F and the number n of cushion pins,
Pressing can be performed in a pressure equalized state simply by switching the hydraulic pump to be operated. Therefore, there is an advantage that the control in the control box 270 becomes simple.
The hydraulic pressure adjusting valve 260 may be finely adjusted only when an error occurs due to a change in various conditions.

Third Embodiment Next, a third embodiment of the press machine according to claim 2 will be described with reference to FIG. The same members as those of the first or second embodiment are designated by the same reference numerals and the description thereof will be omitted. 3 is a partial vertical sectional view showing a third embodiment of the press machine according to the second aspect of the present invention. In the press machine 301 according to the present embodiment, the oil supply device that adjusts the initial hydraulic pressure P ₀ supplied to the hydraulic cylinders 54 to 54 is configured as follows.

The flexible tube 58 is connected to the oil supply pipe 7
9 is connected, and a hydraulic pump 86 is connected to the tip of the oil supply pipe 79 via a check valve 84.
An oil tank 82 is connected to the middle of the oil supply pipe 79 via a pressure reducing valve 80. Further, a return pipe 83 for automatically returning oil from the oil tank 82 to the hydraulic pump 86 is provided. Therefore, in the present embodiment, the oil supply pipe 79, the pressure reducing valve 80, the oil tank 82, the return pipe 83, the check valve 84, and the hydraulic pump 86 constitute the initial hydraulic pressure adjusting means. An oil pressure sensor 88 is attached to the oil supply pipe 79, and the oil pressure in the hydraulic cylinders 54 to 54 can be measured through the oil supply pipe 79, the flexible tube 58, and the hydraulic pipe 56. An amplifier 90 for amplifying an output signal corresponding to the measured oil pressure is connected to the oil pressure sensor 88, and the amplified signal is A / D converted by an A / D converter 92 for calculation. The calculation is performed in the unit 94. These calculation results and the like are displayed on the display unit 96 using a CRT display.

Further, the control unit 98 has a computer system composed of a CPU (central processing unit), a memory device and the like. In the control unit 98, press working conditions such as press load are inputted, and the inputted press working is carried out. The pressure equalization value is calculated from the conditions. The results of these inputs and calculations are also displayed on the display unit 96 as appropriate. Here, the pressure equalization value means the value of the hydraulic pressure that should be generated when all the cushion pins 52 to 52 are not pushed all the way to the stroke end and the hydraulic pressure commonly acts on each hydraulic cylinder to balance the press load. A specific method of calculating the pressure equalization value will be described later. Then, the calculated pressure equalization value and the detected hydraulic pressure are compared to determine whether or not the pressure is equalized.
According to the determination result, the pressure reducing valve 80 and the hydraulic pump 86 are controlled by the output signal from the control unit 98, and the initial hydraulic pressure supplied to the hydraulic cylinders 54 to 54 is changed.

Therefore, the hydraulic sensor 88 is the hydraulic cylinder 5
The control unit 98 functions as a hydraulic pressure detection unit that detects the hydraulic pressure within 4 to 54, and the control unit 98 functions as a pressure equalization value calculation unit that calculates a pressure equalization value. Also, the amplifier 90 and the A / D converter 9
2. The calculation unit 94 and the control unit 98 function as a pressure equalization determination unit that compares the calculated pressure equalization value with the detected hydraulic pressure to determine whether or not the pressure is equalized. Then, the control unit 98 causes the initial hydraulic pressure adjusting means 79,
It functions as a hydraulic pressure instruction means for instructing the hydraulic pressure adjusted by 80, 82, 83, 84, 86.

The specific determination of the pressure equalizing state and the adjustment of the initial hydraulic pressure are performed as follows. When the initially set initial oil pressure P ₀ is too high, the die cushion 20 is pushed down due to the variation in the length of the cushion pins 52 to 52 without the wrinkle retainer 50 being in contact with the short cushion pins. Here, when there are m out of n cushion pins that have not been driven in, the detected hydraulic pressure P _S
Is expressed by the following equation (2). P _S = F / (n−m) S (2) Further, the pressure equalization value P ₁ is expressed by the following equation (3). P ₁ = F / nS (3) Therefore, from the equations (2) and (3), when the hydraulic pressure detected by the hydraulic pressure sensor 88 is P _S and the hydraulic pressure in the equalized state (equalized value) is P ₁ , The relationship of P _S > P ₁ is established, resulting in a non-uniform pressure state. Therefore, the hydraulic pressure instructing means instructs the initial hydraulic pressure adjusting means to lower the initial hydraulic pressure P ₀ , and an appropriate initial hydraulic pressure P ₀ is set so that a uniform pressure state is achieved.

On the contrary, if the initially set initial oil pressure P ₀ is too low, the die cushion 20 is pushed down in a state where the cushion pins 52 to 52 are partially or completely pushed to the stroke end of the hydraulic cylinder 54. ..
Here, when m of the n cushion pins are in the cylinder thrust state, a force P _B larger than the hydraulic pressure acts on those hydraulic cylinders, so the cushion load F is expressed by the following equation (4). To be done. F = (n−m) SP ₁ + mSP _B (4) At this time, the detected hydraulic pressure P _S is expressed by the following equation (5). _{P S = (F-mSP B} ) / {(n-m) S} = (nSP 1 -mSP B) / {(n-m) S} ... (5) where, because it is SP _B> SP ₁ From the equation (5), the following equation (6) is obtained. P _S = (nSP ₁ −mSP _B ) / {(n−m) S} <(nSP ₁ −mSP ₁ ) / {(n−m) S} = P ₁ (6) Therefore, P _S <P ₁ , It becomes a non-uniform pressure state. Therefore, the initial oil pressure P _{0 is applied} to the initial oil pressure adjusting means by the oil pressure instruction means.
You are instructed to raise.

To summarize the above, when P _S > P ₁ , there is a non-uniform pressure state, and there are cushion pins that have not been driven in. Also, when P _S <P ₁ , there is a non-uniform pressure state, but in this case, there is a cushion pin that is in the cylinder thrust state. On the other hand, when P _S = P ₁ , a common hydraulic pressure is applied to all the cushion pins.

For example, in a press die having a cushion load of F and a number of cushion pins of n, the initial hydraulic pressure P ₀ = P04
It is assumed that, when pressure is applied in this state, m of the n cushion pins have not been driven in because the initial hydraulic pressure is too high for the cushion load. In this case, since the effective number of pins is (n-m), the load P _S detected in the hydraulic pressure sensor 88 is represented by the formula (2), FuHitoshi圧state becomes P _S> P ₁ Becomes Then, the control unit 98 sends a signal to the initial hydraulic pressure adjusting means 79 to 86, and the initial hydraulic pressure is lowered to P ₀ = P05 (<P04). Then, test pressurization is performed again. Since the value of P ₀ is lowered, the number m of cushion pins that have not been driven in is reduced, and the detected hydraulic pressure P _S is also reduced. If this is still insufficient, the initial oil pressure P ₀ is further lowered, the number of effective pins becomes n, and the process is repeated until the pressure equalizing state of P _S = P ₁ is reached. In this way, for example, the initial hydraulic pressure is P ₀ =
When P06 (<P05), the pressure equalization state is achieved.

On the contrary, the initial hydraulic pressure is initially P ₀ = P07 (<P
If it is set to 06), the initial hydraulic pressure is too low for the cushion load, and some of the cushion pins are stuck in the trunk. In this case, some press load (pressure)
Is transmitted directly to the cushion pin without being transmitted to the oil, so that the detected hydraulic pressure P _S becomes small. Therefore, the initial hydraulic pressure P ₀
Is gradually increased to determine a value P ₀ = P 06 of the initial hydraulic pressure P _{0 in which} the pressure is equalized to P _S = P ₁ .

When the appropriate initial hydraulic pressure P ₀ is determined in this manner, the value of P ₀ is stored in the memory device of the control unit 98 and the press working is performed thereafter. During this processing, the value of the hydraulic pressure in the hydraulic cylinder 54 is detected by the hydraulic pressure sensor 88 while the cushion pin 52 is at the top dead center. The control unit 98 determines whether the value of the detected oil pressure P _S is kept at the set value of the initial oil pressure P ₀ , and if the detected oil pressure P _S does not match the value of the set initial oil pressure P _0. If the initial hydraulic pressure P
The operation for changing the value of ₀ is displayed on the screen of the display unit 96. The hydraulic pressure sensor 88 detects the detected hydraulic pressure P _S in the pressurized state and sends a signal to the calculation unit 94 while the initial hydraulic pressure P ₀ is determined in the first test pressurization as described above, and the initial hydraulic pressure P ₀ is temporarily sent. _When the appropriate value of ₀ is determined, the actual initial hydraulic pressure P ₀
The role of detecting (monitoring hydraulic pressure P _S at the top dead center) during the press working is monitored.

In this way, the press machine 3 of this embodiment is used.
In 01, it is determined whether or not the pressure is equalized based on the detected actual hydraulic pressure, and the initial hydraulic pressure is changed until the pressure equalized, so that the press working in the pressure equalized region is performed more reliably. Be seen.

In each of the above embodiments, the lower die is provided with the cushion pin to press the work piece against the upper die. However, by reversing this, the upper die is provided with the cushion pin and the work piece is attached. The structure may be such that the lower mold is pressed. Further, in the third embodiment, control is performed such that only the magnitude relationship between the detected hydraulic pressure P _S and the equalized pressure value P ₁ is determined and the initial hydraulic pressure is raised or lowered accordingly.
_{If the} adjustment range for raising and lowering the initial hydraulic pressure is controlled according to the difference between _S and the pressure equalizing value P _1, the pressure equalizing state can be obtained more quickly. Further, although one set is used in the first embodiment and three sets are used in the second embodiment, the check valves and hydraulic pumps are used, but other numbers may be used as necessary. The structure, shape, size, material, arrangement, etc. of the other parts of the press machine including the mechanism of the die cushion are not limited to those in the above embodiments.

Further, as an effect peculiar to the third embodiment, since the oil pressure of the hydraulic cylinder and the oil supply device can be constantly monitored by the oil pressure sensor, an accident such as an oil leak or an excessive oil pressure caused by an accidental trouble can be detected, and it can be detected beforehand. Can be prevented. Furthermore, stable press working can be performed by detecting and outputting the change in the press working conditions by hydraulic pressure.

[0037]

According to the present invention, since the cushion pin pressure equalizing device provided with the hydraulic pressure varying means for changing the initial hydraulic pressure supplied to the hydraulic cylinder, the pressure equalizing is performed for cushion loads of various sizes. The area can be set freely. As a result, it is possible to perform the production in the pressure equalizing region for any press machine, press die, or work shape, and it becomes a cushion pin pressure equalizing device for a very practical press machine. Further, as a spillover effect of the present invention, (1) since the pressure equalizing region is expanded, the optimum number of cushion pins and cushion load can be selected to prevent wrinkling and cracking of the pressed product, and the yield can be improved. Also,
Greater flexibility at the design stage. (2) Since the pressure equalizing areas can be easily matched even between press machines having different sizes and press capacities, quality reproduction between different press machines can be easily performed. Such an advantage is also obtained.

[Brief description of drawings]

FIG. 1 is a partial vertical cross-sectional view showing a first embodiment of a press machine according to the present invention.

FIG. 2 is a partial vertical cross-sectional view showing a second embodiment of the press machine according to the present invention.

FIG. 3 is a partial vertical cross-sectional view showing a third embodiment of the press machine according to the present invention.

FIG. 4 is a diagram showing the relationship between the cushion load and the number of cushion pins in the press machine according to the present invention, using the average thrust amount of the hydraulic cylinder and the initial hydraulic pressure as parameters.

FIG. 5 is a diagram showing a relationship between a cushion load and the number of cushion pins in a conventional press machine, using an average drive amount of a hydraulic cylinder as a parameter.

[Explanation of symbols]

 1 Press Machine 3 Upper Die 6 Workpiece 9 Lower Die 52-52 Cushion Pin 54-54 Hydraulic Cylinder 59-70, 79-86 Initial Hydraulic Pressure Adjusting Means 98 Equal Pressure Value Calculating Means 88 Hydraulic Pressure Detecting Means 90, 92, 94, 98 Equalization determination means 98 Initial hydraulic pressure instruction means

Claims (2)

[Claims] 1. A press machine for strongly pressing a plate-shaped workpiece by means of an upper die and a lower die, which is provided in one of the upper die and the lower die so as to be movable by a predetermined stroke via a hydraulic cylinder. A plurality of cushion pins that press a non-processed portion of the workpiece against the other of the upper die and the lower die during press working, and an initial hydraulic pressure adjusting means that adjusts an initial hydraulic pressure supplied to the hydraulic cylinder. Press machine having. 2. The press machine according to claim 1,
A pressure equalizing value calculating means for calculating a pressure equalizing value that is a value of the hydraulic pressure that should be generated when the cushion pins are not pushed all the way to the stroke end and the hydraulic pressure is commonly applied to each hydraulic cylinder to balance the press load. A hydraulic pressure detecting means for detecting a hydraulic pressure in the hydraulic cylinder; a pressure equalizing determining means for comparing the detected hydraulic pressure with the calculated pressure equalizing value to determine whether or not a pressure equalizing state; The press machine according to claim 1, further comprising an initial hydraulic pressure instructing means for instructing an initial hydraulic pressure adjusted by the initial hydraulic pressure adjusting means according to a result.