JPS5923920B2 - Pressure molding press control device for powder raw materials, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure molding press control device for powder raw materials such as ceramics, powder metallurgy, or sludge compression, and particularly for high precision molding with multi-stage pressure, shock prevention during molding, and low power consumption. The present invention relates to a control device for purposes such as the above.

Traditionally, molding control devices for powder raw materials have used a combination of multiple control valves to control each speed of multi-step molding speed changes or to control each pressure of multi-step pressure changes. A device that does this is known.

In this case, a very large number of control valves are required especially for multi-stage pressurization, depressurization, etc., and the configuration of the control device is extremely complicated.

On the other hand, the pump pressure is IJ for the work of the molding press.
It is determined by the set pressure of the IJ-F valve, and if the efficiency decreases, it will be converted into thermal energy and the oil temperature may rise. Therefore, the oil temperature is controlled with an oil cooler to keep it below a certain level. There is usually one.

However, as described above, using multiple control valves to change the speed and pressure of the upper ram and lower ram in stages (multi-stage) not only complicates the configuration of the control device, but also Frequent shocks occur when the valve is switched, and speed and pressure control becomes difficult due to the accumulation of leakage inside the valve, which can lead to adverse effects such as cracks on the powder compact.

Also, press efficiency (ratio of press work to input)
may be significantly reduced depending on the molding conditions, shortening the life of hydraulic equipment due to increases in oil temperature, etc., and causing oil leaks, etc., which may lead to a decrease in press efficiency.

The present invention has been made to solve the above-mentioned problems, and the first invention is to enable smooth control of pressure and flow rate at each stage of the press stroke and to obtain a highly accurate molded product. In addition to these, the second invention aims to further reduce power loss and prevent oil temperature from rising.

That is, in the first invention of the present application, the upper punch is attached to the lower end of the upper ram that is driven in the vertical direction by the upper ram cylinder, and the powder raw material in the mold surrounded by the fixedly installed lower bench and die is A control for a pressure forming press for powder raw materials, etc., which is shaped by the lowering of the upper punch, and further includes a die holder that holds the die, and is supported by a lower ram that is driven in the vertical direction by a lower ram cylinder. In the device,
Proportional electromagnetic flow connected in the hydraulic circuit between the hydraulic source pump and each upper and lower ram cylinder to control the stroke speed of the upper and lower rams in accordance with the operation and load pressure of each ram in each stroke. a control valve; a plurality of position detectors for detecting the positions of the respective rams; a first pressure detector for detecting the internal pressure of the pressurizing chamber of the upper ram cylinder; and a pressurizing chamber of the lower ram cylinder. A second pressure detector detects the internal pressure of the upper and lower rams, and position signals of the upper and lower rams from the position detector are used to switch the opening/closing timing of the flow rate control valve and the setting of the control flow rate, and also to switch the opening/closing timing of the flow rate control valve and the setting of the control flow rate during the pressurization process. an electrical control system for the flow rate control valve configured to switch a control pattern of a controlled flow rate of the flow rate control valve to be supplied to the pressurizing chamber of the upper ram cylinder based on an output signal of the first pressure detector; and a preset pressure for the internal pressure of the pressurizing chamber of the upper ram cylinder based on the output signal of the first pressure detector and the position signal of the upper ram from the position detector. A first proportional electromagnetic pressure control valve that controls the pressure according to a change pattern, and a pressurizing chamber of the lower ram cylinder based on the output signal of the second pressure detector and the lower ram position signal from the position detector. a second proportional electromagnetic pressure control valve that controls the IJ pressure to follow another preset pressure change pattern, in addition to any cylinder speed control. The pressure is also arbitrarily controlled according to the control pattern, and the movement of the die during pressure molding is freed from the friction generated therein, thereby preventing deviation in the vertical density distribution of the molded product.

In addition to the first invention, the second invention of the present application further includes a third pressure detector for detecting the load pressure of the oil passage on the outlet side of the flow rate control valve, and an output signal of the third pressure detector. A third controlling the IJ pressure of the inlet side oil passage of the flow control valve so that the pump discharge pressure of the inlet side oil passage of the flow control valve is always higher than the load pressure by a preset constant pressure value. By providing a proportional electromagnetic pressure control valve, when the constant pressure value is set to the minimum necessary small value that takes into account piping pressure loss, etc., it is possible to reduce power loss as much as possible and prevent oil temperature rise. That's how it is.

The present invention will be described below based on the drawings.

Fig. 1 is a circuit diagram showing an embodiment of the pressure molding press control device for powder raw materials, etc. of the present invention, Fig. 2 is an explanatory diagram showing the schematic configuration of the press method to which the present invention is applied, and Fig. 3 is In the timing chart diagram showing the power consumption and operation pattern, a shows the change over time between the inlet pressure Pi and the outlet pressure Po of the proportional electromagnetic flow control valve, b shows the change over time in the controlled flow rate F of the flow control valve, and C is the change over time in the position H□ of the upper ram, d
is the change over time between the IJ IJ-f constant pressure P2g of the first proportional electromagnetic pressure control valve and the actual internal pressure P2□ of the upper ram cylinder pressurizing chamber, e is the change over time in the position H2 of the lower ram, and f is the change over time in the position H2 of the lower ram. 2 proportional solenoid pressure control valve IJ-F set pressure p
The graph shows the change over time between ao and the actual internal pressure P22 of the lower ram cylinder pressurizing chamber.

The area within the solid curve corresponds to the actual power.

Fig. 4 is a diagram showing an example of the characteristic curve of solenoid excitation current versus control flow rate of the proportional electromagnetic flow control valve used in the present invention, and Fig. 5 is a diagram showing an example of the characteristic curve of solenoid excitation current versus control pressure of the proportional electromagnetic pressure control valve. A line drawing showing an example of a curve, Fig. 6 is a line drawing showing an example of an input vs. output characteristic curve of an amplifier used in a proportional solenoid control valve (pressure and flow rate), and Fig. 7 is a line drawing showing an example of a characteristic curve of input versus output of an amplifier used in a proportional solenoid control valve (pressure and flow rate). Schematic diagram of flow control circuit,
FIG. 8 is a schematic block diagram of a control circuit for reducing power loss.

In FIG. 1, an upper ram 1 and a lower ram 2 of the pressure forming press are connected to ram cylinders 3 and 4, respectively, and each ram cylinder 3 and 4 is supplied with pressure oil from a tank 5 or a lahonf 6. A proportional electromagnetic flow control valve 7 connected to the pump 6 and an electromagnetic switching valve 8 branched to the control valve 7.
, 9.

That is, the discharge port of the pump 6 driven by the motor 10 is connected to the inlet side port of the control valve 7 through the oil passage 11, and the outlet side port of the valve 7 is connected to the solenoid switching valve 8, which is connected to the ABR in the neutral state. The electromagnetic switching valve 9 is connected to the P port by an oil passage 12 and is connected to the same electromagnetic switching valve 9 by an oil passage 13.
The A port of one of the electromagnetic switching valves 8 is connected to the pressurizing chamber 3a of the upper ram cylinder 3 via the pilot check valve 14 by an oil passage 15.
Similarly, the B port is connected to the other chamber 3b of the upper ram cylinder 3 via the oil passage 16 and the check pressure control valve 17.
It is connected to the.

The A port of the other electromagnetic switching valve 9 is connected to the pressurizing chamber 4a of the lower ram cylinder 4 via the pilot check valve 18 and an oil passage 19, and the B port is connected to the other chamber 4b of the ram cylinder 4. They are connected by an oil passage 20.

Oil passage 1 communicating with the pressurizing chamber 3a of the upper ram cylinder 3
5 and an oil passage 19 communicating with the pressurizing chamber 4a of the lower ram cylinder 4, a first pressure detector 21 and a second pressure detector 22 are provided, respectively, for detecting the oil pressure in the oil passage. A plurality of position detectors 23.24, 25, 26, 27.28, for example limit switches, are provided and actuated by the movement of the rams, respectively, at positions corresponding to each travel stroke position of the upper ram 1 and lower ram 2. is provided.

Further, first and second proportional electromagnetic pressure control valves 29 and 30 are connected to the oil passages 15 and 19, respectively, and as shown in FIG. A pressure holding timer 34 that starts operating in response to a position signal, an output signal from the pressure detector 21 or 22 when the pressure in the oil passage 15 or 19 reaches a set value, or an output signal from the detector 21. The output of the setting circuit 35 generates the first and second solenoid excitation outputs, respectively, through a setting circuit 35 that generates a solenoid excitation output with a timing and change pattern set in advance as described below based on a time-up signal from the Proportional solenoid pressure control valve 29°30
is controlled so that the +)IJ-f pressure relative to the internal pressure of the pressurizing chamber of each ram cylinder follows a desired setting pattern.

Furthermore, a third pressure detector 31 for detecting the load pressure PO is installed in the outlet oil passage 12 of the proportional electromagnetic flow control valve T.
A third proportional electromagnetic pressure control valve 32 for controlling the pump discharge pressure Pi is provided in the inlet oil passage 11 of the control valve 7, and the pressure control valve 3
A two-position electromagnetic switching valve 33 is connected to the pilot flow path No. 2, and the pressure control valve 32 is connected to the output signal of the pressure detector 31 and a constant value setting signal by a control circuit 36, as shown in FIG. e.

Based on this, the pump discharge pressure is adjusted so that the pressure difference Pi-Po-△Pro between the load pressure Po and the pump discharge pressure Pi is always maintained at a predetermined constant value in consideration of piping pressure loss, etc. IJ IJ-F control.

In the figure, ga and Qb indicate the solenoid devices of the electromagnetic switching valve 8, 9a and 9b indicate the solenoid devices of the electromagnetic switching valve 9, and 33a indicates the solenoid device of the switching valve 33. Actuation switches or limit switches 23-28 as well as pressure detectors 21,22
The operation is controlled by signals from etc.

The flow rate control of the proportional electromagnetic flow control valve 7 is similar to the excitation control of the solenoid device of the pressure control valve 29. .28 and signals from the pressure detector 21 and timer 34, the opening/closing timing and flow rate change pattern are controlled in accordance with a predetermined operation sequence as described later.

The operation of the pressure molding press control device of the present invention as described above will be described with reference to FIG. T, and reaches each electromagnetic switching valve 8, 9 at a predetermined flow rate.

First, the solenoid device 33a is energized and the electromagnetic switching valve 33
The third proportional electromagnetic pressure control valve 32 is brought into a proportional operation state by switching from the state shown in the figure, and at time t1, the solenoid device 9a is energized to switch the electromagnetic switching valve 9 from the state shown in the figure to P-A, B. - When switched to the R connection position, oil passage 13
Pressure oil is supplied to the pressurizing chamber 4a of the lower ram cylinder 4 through the oil passage 19, and the lower ram 2 is raised.

In this case, the rising speed of the lower ram 2 is shown in FIG. Once activated, the flow rate control valve 7 is gradually throttled according to the set pattern according to the signal from the limit switch 27, and the speed at which the stroke reaches the final end is extremely slowed to weaken the impact when the lower ram 2 hits the stopper. is desirable.

At this time, the force by which the upper limit of the internal pressure of the pressurizing chamber 4a of the lower ram cylinder 4 is controlled by the proportional electromagnetic pressure control valve 30＼ In this case, the setting of the IJ-F pressure is such that the lower ram is connected to the die and the die holder. The pressure control valve 3 is controlled by the setting circuit 35 to perform excitation control to achieve such a relief pressure.
0 solenoid device.

By the above operation, the lower ram 2 brings the die holder 3B holding the die 37 to the proper position with respect to the lower bench 39 as shown in FIG. A powder raw material 40 is filled from a raw material hopper truck into a die set mold surrounded by a lower bench 39 .

In FIG. 2, reference numeral 41 indicates an upper punch driven by the upper ram 1.

When the lower ram 2 rises and reaches its rising end position at time t3, the limit switch 26 is activated, and then, at time t4 when the raw material hopper cart completes retraction, the solenoid device 9a is deenergized and the solenoid device 8a is energized instead. .

As a result, the switching valve 9 returns to the neutral position, but the pressure oil in the pressurizing chamber 4a of the lower ram cylinder 4 is prevented from flowing out by the pilot check valve 18, so that it does not directly flow into the tank.

As described above, the solenoid device 8a is energized to move the electromagnetic switching valve 8 to the P-A, B-R connection position, and as in the case of the lower ram 2 described above, the pressurizing chamber 3 of the upper ram cylinder 3
Pressure oil is supplied to a, and the ram 1 begins to descend.

That is, from the time when the supply of pressure oil to the upper ram cylinder 3 is started, the flow rate control valve 7 is gradually opened to a high set flow rate according to a set pattern by the control circuit 35 described above, as shown in FIG. By descending, time t5
When the limit switch 24 is activated, the flow control valve 7
The passing flow rate is throttled to a predetermined first flow rate f1, and the upper ram 1 pressurizes the powder raw material 40 with the upper punch 41 at a first pressurization speed determined thereby.

According to this first pressurization, the oil pressure P2□ in the pressurizing chamber 3a rises, and when it reaches a preset pressure value P1, the flow control valve 7 performs the above-described control based on the signal from the pressure detector 21. The circuit 35 adjusts the flow rate so that it becomes the second flow rate f2 according to the set pattern, thereby causing the upper ram 1 to pressurize at the second pressurization speed.

It goes without saying that these first and second pressurizing speed patterns can be arbitrarily set depending on the raw material or shape of the target molding, and if you want to select the third and subsequent pressurizing speeds, Another level output signal of the pressure sensor 21 also controls the flow rate control valve 7 via the control circuit 35.
All you have to do is control.

The illustrated limit switch 25 is an emergency recovery switch for regulating the maximum stroke limit of the upper ram 1.

A proportional electromagnetic pressure control valve 29 connected to the pressurizing chamber 3a of the upper ram cylinder 3 controls IJ with respect to the internal pressure of the pressurizing chamber 3a.
The IJ-fu pressure P29 is controlled as shown in FIG. This is performed by the setting circuit 35 in accordance with the setting control pattern in accordance with the sequence and timing.

At the above-mentioned time t, in the subsequent pressurizing stroke, the second proportional electromagnetic pressure control valve 30 connected to the pressurizing chamber 4a of the lower ram cylinder 4 controls the lower ram from the position detector 26 while the lower ram is rising. IJ in a predetermined pattern based on the ram position signal, etc.
Although IJ-F control is being carried out, after t5 at the start of pressure forming, the lower ram 2 The pressure detector 22 detects the opposing pressure generated in the pressure sensor 22 and performs an operation to release the pressure.

That is, at time t6 when the pressure detected by the pressure detector 22 becomes equal to or higher than the predetermined value 23, the second pressure control valve 30 performs a proportional IJ IJ-F operation toward a lower set pressure, and is therefore connected to the die 37. The movement of the lower ram 2, that is, the movement of the die 37 itself, is completely free from the forces generated by friction.

This makes it possible to always maintain the neutral position of compaction in the powder raw material at the middle part of the upper and lower punches 41.39, making it possible to make the vertical density distribution of the compact after compaction more uniform, and to create a longitudinal cross-sectional coarse/dense pattern. By making it vertically symmetrical, it is possible to reduce the cutting allowance in the firing pretreatment work.

To complete the molding, the pressure holding timer 34 shown in FIG. 7 is activated by the output of the pressure P2 detected by the pressure detector 21 at time t8 as shown in FIG. 3d, and the pressure is held for a predetermined time. After that, the time-up signal of the timer 34, which occurs at time t, causes the pressure control valve 29 to
- This is done by lowering the set pressure and releasing the pressure.

In this case, the pressure drop characteristic of the pressure control valve 29 during depressurization is also arbitrarily determined by the function pattern generated from the setting circuit 35.

After the above pressure relief is completed at time tto, the solenoid device 8
a is deenergized and 9b is energized instead, which controls the flow rate control valve 7 to gradually open so that the lower ram 2 starts lowering without a shock, and then the position detector 27 is activated at time t1□. Then, the flow control valve 7 is opened wide and lowered at high speed, and when the position detector 28 is activated at time t1□, it is gradually throttled and stopped slowly, and the solenoid device 9b is turned off at time tia based on the stoppage of the lower ram 2. Force,
Instead, 8b is excited to cause the upper ram 1 to start rising slowly in the same way, and from the time t14 when the position detector 24 is activated, the flow rate control valve 7 is opened to increase the speed of the upper ram rise, and then the position detector 23 is activated. At the time t15 of operation, the flow rate control valve 7
Gradually squeeze the upper ram 1 and stop it slowly without impact (
time t16).

In this case, the lower ram 2 is returned first, but the order in which the upper and lower rams are returned may be set first.

The proportional electromagnetic pressure control valve 32 connected to the discharge oil passage 11 of the pump 6 controls the load pressure detected by the pressure detector 31, that is, the pressure Po on the outlet side of the flow rate control valve 7, and the pump discharge pressure, that is, the flow rate control. The relationship with the inlet side pressure Pi of the valve 7 is set so that Pi=Po+ΔP (ΔP: pressure difference, constant).

As a result, as shown in Figure 3a, the power loss is the ratio of the pressure generated by the loads on the upper ram 1 and lower ram 2 to the pump discharge pressure, so △P in the above equation should be set to a value as small as possible. For example, it can be reduced by taking into account piping pressure loss, etc.

In addition, in FIG. 3a, the dashed line is the IJ of the pressure control valve 32.
A conventional example is shown in which the IJ-F set pressure is set to Pi=constant.

As described above, according to the first and second inventions of the present application,
With a simple circuit configuration, high-precision multi-stage pressure control is possible without using multiple control valves, and since there is no shock in the ram movement, there is no damage to the molded product, and the neutral position of molding pressure in the molded product is achieved. can be held in the middle between the upper and lower punches, making it possible to perform pressure molding with high molding accuracy.

In particular, in the second invention, in addition to this, power loss is reduced, and as a result, it is possible to prevent an increase in oil temperature due to a decrease in the amount of IJ flow from the circuit, thereby maintaining the life of the equipment and improving press efficiency. It is achievable.

[Brief explanation of the drawing]

Fig. 1 is an embodiment circuit diagram of the pressure molding press control device for powder raw materials, etc. of the present invention, Fig. 2 is an explanatory diagram showing an outline of the press operation powder compacting method, and Fig. 3 is the power consumption and operation pattern. FIG. 4 is a characteristic curve of the solenoid excitation current versus control flow rate of the proportional electromagnetic flow control valve. FIG. 5 is a characteristic curve of excitation current versus pressure of the proportional electromagnetic pressure control valve. The figure is an input/output characteristic curve diagram of a proportional electromagnetic flow control valve and an amplifier used in the electric control system of the same pressure control valve. Figure 7 is a schematic block diagram of a multi-stage pressure and flow rate control circuit. Figure 8 1 is a schematic block diagram of a pressure control circuit for reducing power loss; FIG. 1: Upper ram, 2: Lower ram, 6: Pump, 7: Proportional electromagnetic flow control valve, 21, 22, and 31: First, second
, and a third pressure detector, 23°24.25,26,
27, 28: Position detector (limit switch), 29.
30 and 32: first, second, and third proportional electromagnetic pressure control valves.

Claims (1)

[Scope of Claims] 1. An upper punch is attached to the lower end of an upper ram that is driven in the vertical direction by an upper ram cylinder, and the powder raw material in a mold surrounded by a fixedly installed lower bench and a die is A control device for a pressure molding press for powder raw materials, etc., which is configured to be molded by lowering an upper punch, and further includes a die holder that holds the die supported by a lower ram that is driven in the vertical direction by a lower ram cylinder. In the hydraulic circuit between the hydraulic source pump 6 and the upper and lower ram cylinders 3 and 4, in order to control the stroke speed of the upper ram 1 and the lower ram 2 in accordance with the operation and load pressure of each ram in each stroke. a proportional electromagnetic flow control valve 7 connected to the ram, and a plurality of position detectors 23 that respectively detect the position of each ram.
, 24, 26, 27, 28, a first pressure detector 21 that detects the internal pressure of the pressurizing chamber 3a of the upper ram cylinder 3, and a first pressure detector 21 that detects the internal pressure of the pressurizing chamber 4a of the lower ram cylinder 4. The opening/closing timing of the flow rate control valve 7 and the setting of the control flow rate are switched based on the position signals of the upper and lower rams from the pressure detector 22 of the upper ram cylinder 3 during the pressurizing process. electrical control of the flow rate control valve 7 configured to switch the control pattern of the controlled flow rate of the flow rate control valve 7 to be supplied to the pressurizing chamber 3a according to the output signal of the first pressure detector 21; The IJ-F pressure relative to the internal pressure of the pressurizing chamber 3a of the upper ram cylinder 3 is determined in advance by the output signal of the first pressure detector 21 and the position signal of the upper ram from the position detector. a first proportional electromagnetic pressure control valve 29 that controls the pressure according to a set pressure change pattern; A second proportional electromagnetic pressure control valve 30 that controls the IJ-F pressure relative to the internal pressure of the pressurizing chamber 4a of the ram cylinder 4 so as to follow another preset pressure change pattern. Pressure molding press control device 2 for powder raw materials, etc., characterized by: An upper punch is attached to the lower end of an upper ram that is driven vertically by an upper ram cylinder, and is surrounded by a lower punch and a die that are fixed to the upper punch. The powder raw material in the mold is molded by the lowering of the upper punch, and the die holder holding the die is supported by a lower ram that is driven once in the vertical direction by a lower ram cylinder. In the control device for the pressure molding press upper for raw materials, etc., a hydraulic source pump 6 and the upper and lower rams are used to control the stroke speed of the upper ram 1 and lower ram 2 in accordance with the operation and load pressure of each ram in each stroke. A proportional electromagnetic flow control valve 7 connected in a hydraulic circuit between the cylinders 3 and 4, and a plurality of position detectors 23 that respectively detect the position of each ram.
, 24, 26, 27, and 28, a first pressure detector 21 that detects the internal pressure of the pressurizing chamber 3a of the upper ram cylinder 3, and a first pressure detector 21 that detects the internal pressure of the pressurizing chamber 4a of the lower ram cylinder 4. 2 pressure detector 22; a third pressure detector 31 that detects the load pressure of the outlet side oil passage of the flow control valve 7; and a third pressure detector 31 that detects the load pressure of the outlet side oil passage of the flow control valve 7; In addition to switching the opening/closing timing of 7 and the setting of the controlled flow rate, the control pattern of the controlled flow rate of the flow control valve 7 to be supplied to the pressurizing chamber 3a of the upper ram cylinder 3 during the pressurizing process is changed as described above. an electrical control system for the flow rate control valve T configured to be controlled by the output signal of the first pressure detector 21; and a position of the upper ram based on the output signal of the first pressure detector 21 and the position detector. a first proportional electromagnetic pressure control valve 29 that controls the IJ pressure relative to the internal pressure of the pressurizing chamber 3a of the upper ram cylinder 3 according to a preset pressure change pattern by a signal; The IJ-F pressure relative to the internal pressure of the pressurizing chamber 4a of the lower ram cylinder 4 is determined by the output signal of the pressure detector 22 of No. 2 and the position signal of the lower ram from the position detector. A second proportional electromagnetic pressure control valve 30 that is controlled to follow a pressure change pattern and an output signal from the third pressure detector 31 cause the pump discharge pressure in the inlet oil passage of the flow rate control valve 7 to match the load pressure. a third proportional electromagnetic pressure control valve 32 that controls the relief pressure of the inlet side oil passage so that it is always higher by a preset constant pressure value than the powder. Pressure molding press control device for raw materials, etc.