JPS60261700A - Control device for press load - Google Patents

Abstract

PURPOSE:To prevent the generation of shape defects such as surface distortion and cracks in press formed articles in a mechanical double-acting press by making variable the air pressure in a hydro-blank holder so that press load can be controlled. CONSTITUTION:A control device 1 for press load having an air source 57, a pressure control valve 3 and an accumulator 59 is connected to a hydro-blank holder 50 for detecting over load during press forming with the mechanical double-acting press machine. A pressure switch 11a of the device 1 is set at the air pressure at which surface distortion, crack, etc. are not generated to the formed articles. A relief valve 10 operates to suppress the increase of the air pressure in the holder 50 to maintain the specified press load when the air pressure in the holder 50 increases on progression of the press forming and rises up to the air pressure set to the switch 11a. The generation of the surface distortion and cracks owing to the over load in the press formed articles is thus automatically prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a device for controlling press load in a mechanical double-action press machine, and particularly to a device for controlling press load in hydrozone molding.

(Prior Art) Mechanical double-acting press machines are usually equipped with a hydro blank holder for detecting overload during press forming. This hydro blank holder corresponds to the number 5 in Fig. 4.
As shown by 0, a piston 53 that defines a hydraulic chamber 51 and a pneumatic chamber 52 is contained therein. The hydraulic pressure chamber 51 is supplied with hydraulic pressure from a hydraulic source 56 that includes an oil tank 54 and a hydraulic pump motor 55, while the pneumatic chamber 52 is supplied with an air source 57, a regulator 58, and an accumulator 59. Air pressure is supplied from an air pressure source 60 provided. Further, the hydraulic chamber 51 of the hydro blank halter 50 is connected to a hydraulic chamber 64 in the protector cylinder 3, which is a connecting portion between the connecting rod 61 and the slurry 2. This hydraulic chamber 64 is connected to the connecting rod 6.
If an overload occurs during press molding, the oil pressure inside the protector cylinder 3 increases, causing the piston 53 to rise and actuating a limit switch (not shown). By doing so, the operation of the press machine is stopped.

Therefore, the mechanical double-acting press machine equipped with the hydraulic pressure system exhibits two different press forming behaviors depending on the balance state of the piston 53 within the hydro blank holder 50.

That is, one is called mechanical molding, and when the regulator pressure supplied to the air pressure chamber 52 is set to a high level,
Because there is no hydraulic operation, '1v-x*@cy>ka.

The work force 43 is transmitted from the cylinder 63 to the slide 62 and the press die. The other method is called hydrozone molding, in which if the piston 53 is properly balanced with respect to the hydraulic pressure and the regulator pressure, the increase in load is absorbed by the operation of the piston 53, and therefore the press mold has no hydraulic pressure. The load will be transmitted through the

It is known that the mechanical zone molding and the hydrozone molding have completely different effects on the relationship between the amount of slide thrust and the press load. Figure 5 shows this relationship. In the case of mechanical zone molding, the load increases rapidly as the amount of penetration increases, as shown by line M, while in the case of hydrozone molding, the load increases rapidly as shown by line H. As shown in FIG.
(represented by P3), the load level changes.

Based on this technical background, conventionally, in order to set the press load of a mechanical double-acting press machine, the slide depth was adjusted using mechanical zone molding, or the slide depth and regulator pressure were adjusted using hydrozone molding. I was trying to adjust it.

(Problem to be Solved by the Invention) However, especially in hydrozone molding, as mentioned above, setting the press load requires two adjustments: slide push-in amount and regulator pressure, which makes it difficult to set the conditions. This makes me think about the accuracy of setting the press load.”
-There was a problem that it was impossible to do so. In addition, the tendency for the press load to increase with respect to the amount of slide thrust differs depending on the press machine, and together with the above problem, there is a problem that molding defects such as surface distortion and cracks are likely to occur. Furthermore, due to the accuracy problem mentioned above, it is necessary to improve the accuracy of the press mold itself, and in some cases, it is necessary to adjust the fit of the mold, which inevitably increases mold production costs. there were.

(Means for Solving the Problems) The present invention attempts to solve the problems described in item 1, and includes an air supply means for supplying air to the hydro blank holder, including an air source and an accumulator; An air pressure setting means is installed in the means for setting the air pressure to be supplied to the hydro blank holder, and an air pressure setting means is also installed in the air supply means to detect an increase in the air pressure of the hydro blank holder during press forming and keep it constant. It consists of a depressurizing means for suppressing the pressure.

(Function) In the press load control device having the configuration described above, by setting a predetermined air pressure in the air pressure setting means and the pressure reducing means in advance, the piston of the hydro blank holder moves during press forming to reduce the air pressure. When the pressure rises, the pressure reducing means operates to perform exhaustion, suppressing the rise of the air pressure above a predetermined pressure, and as a result, fluctuations in the press load with respect to the sliding amount can be suppressed to a small level.

(Example) Hereinafter, an example of the present invention will be described based on the accompanying drawings.

Fig. 1 shows the system of the press load control device according to the present invention. In the figure, the same components as those shown in Fig. 4 are designated by the same reference numerals. The explanation is omitted.In the figure, 1 is a press load control device provided in place of the conventional air pressure source (see FIG. 4), and a pipe 2 connects the air pressure chamber 51 of the hydro blank holder 50 and the air source 57. As in the conventional case, the piping 2 is equipped with an accumulator 59.The piping 2 is also equipped with a pressure control valve 3.The air source 57 side of the piping 2 is equipped with an accumulator 59. A first bypass pipe 4 that connects one end to the pressure control valve 3
are arranged in parallel, and a regulator 5 and a first directional control valve 6 are interposed in the first heave bus piping 4. The regulator 5 is for setting the air pressure, and the pressure control valve 3 is operated by the excitation of the first directional control valve 6, so that the accumulator 59 is supplied with air at a predetermined pressure set by the regulator 5. Become.

Further, in the pipe 2, a second bypass pipe 7 connected to the downstream side of the pressure control valve 3 is installed in parallel, and in this second pipe, a second directional control valve 8 and a third directional control valve A valve 9 is interposed. A relief valve 1o is connected to the third directional control valve 9, and the second directional control valve 8 is now connected to the relief valve 1o.
When the third directional control valve 9 is activated by the excitation, the relief valve 10 is activated and the pressure inside the accumulator 59 is reduced.

On the other hand, pressure switches lla and llb for detecting the back pressure of the hydro blank holder 50 are attached to the piping 2 on the upstream side of the accumulator 59. These pressure switches lla and llb are provided to control the excitation timing of the second directional control valve 8, and one pressure switch lla receives air pressure to excite the second directional control valve 8, while the other pressure switch lla receives air pressure to excite the second directional control valve 8. The air pressure for canceling the excitation of the directional control valve 8 is set in the pressure switch llb.

The present control device 1 is therefore provided with a control circuit as shown in FIG. 2, for example. In the figure, 12 is a changeover switch that excites the first directional control valve 6, 13 is a relay coil connected to pressure switches lla and llb, and 14a, 14b.
If is determined by the operation of the relay coils 14a and 14b.
l closing contacts, these are the hydro blank holder 5
It works to control the air pressure within 0.

Hereinafter, the operation of the press load control device 1 having the above structure will be explained with reference to FIG. 3 as well.

First, the regulator 5 and pressure switch llb are set to a predetermined air pressure (2), and the pressure switch lla is set to an air pressure (2) at which no defects such as surface distortion or cracks occur in the press-molded product. At the same time, the slide push-in amount is set to a value {circle over (2)} that allows an appropriate press load to be obtained.

Now, when the changeover switch 12 is pressed, the first directional control valve 6 is energized and the predetermined air pressure set by the regulator 5 is supplied to the hydro blank holder 50, and under the above state, After that, press forming is performed.

As the press forming progresses, the air pressure inside the hydro blank holder 50 increases, and when this air pressure rises to the set air pressure (2) of the pressure switch 11a, the relay coil 13 is activated and the second directional control valve 8 is energized. Then, the third directional control valve 9 is switched and the relief valve 10 is activated, thereby suppressing the increase in air pressure within the hydro blank holder 50 and keeping the press load constant.

That is, even if the slide thrust amount is changed as shown in (1) and (2), fluctuations in the press load can be suppressed, and thereby the press load can be set only by the regulator pressure.

By changing the set pressure of the pressure switch lla, it is also possible to set, for example, pneumatic pressure, and in this case, the push-in amount can be expanded as shown in (1) to (2).

(Effects of the Invention) As explained above in detail, the present invention makes it possible to control the press load by making the air pressure inside the hydro blank holder variable, thereby controlling the press load regulator pressure. It is now possible to set highly accurate settings using a chisel, and also eliminates press machine differences, which has the effect of reducing molding defects such as surface distortion and cracks.

Furthermore, since it has become easier to set the press load, the accuracy requirements for the press die have been eased, which has the effect of reducing die manufacturing costs.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing the configuration of a press load control device according to the present invention, Fig. 2 is a diagram showing a control circuit included in this control device, and Fig. 3 shows a control method by this control device. An explanatory diagram, FIG. 4 is an explanatory diagram showing the functions of a conventional hydro blank holder, and FIG. 5 is a correlation diagram showing the relationship between the amount of slide thrust and the press load. 2...Piping, 3...Pressure control valve 5...Reculator, 6.8.9...Direction control valve 1
0... Relief valve, lla, Ilb... Pressure switch 50... Hydro blank holder 57... Air source, 59 Akiyumureta Patent Applicant
Toyota Motor Corporation Fig. 2 Fig. 3 Pick-up 2H amount No. 4 C Fig. 5 2° IH 1 Naoshige ON

Claims (2)

[Claims] (1) An air supply means that includes an air source and seven cumulators and supplies air to the hydro blank holder; an air pressure setting means that is interposed in the air supply means and sets the air pressure to be supplied to the hydro blank holder; 1. A press load control device comprising: a pressure reducing means which is interposed in the means and detects an upper air pressure A in the hydro blank holder during press forming, and suppresses it to a constant pressure. (2) The pressure reducing means includes a relief valve, a directional control valve that operates the relief valve, a pressure switch that detects back pressure in the air pressure chamber in the hydro blank holder, and a directional control valve that operates based on a signal from the pressure switch. 2. The press load control device according to claim 1, further comprising a control circuit for controlling the operation of the press load control device.