JP2004276071A - Controlling method for injection cylinder, and hydraulic circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controlling method for an injection cylinder capable of controlling riser pressure widely by controlling a pressure loaded on a rod side widely. <P>SOLUTION: A hydraulic circuit for controlling the injection cylinder is composed of: an inner run-around circuit communicating from the rod side of an injection cylinder piston to the head side thereof; an external run-around circuit communicating from the rod side to the head side via an output open/close valve; an injection circuit connected from an injection accumulator to the head side of the injection cylinder via an injection open/close valve; an output circuit connected from an output accumulator to the external run-around circuit via the output open/close valve; and a hollow deceleration rod, which is slidably fitted in the injection piston and has a through hole in an axial direction. The injection piston blocks the through hole of the deceleration rod at a designated injection stroke position to shut off the inner run-around circuit, the injection speed is rapidly decelerated by a deceleration-speed control valve, and the hydraulic pressure of the output accumulator is introduced into the rod side to widely control a pressure that acts on molten metal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and a hydraulic circuit for controlling the speed and pressure of a cylinder such as an injection operation of an injection cylinder in an injection molding apparatus such as a die casting machine.
[0002]
[Prior art]
[Patent Document 1]
JP-A-8-114203 [Patent Document 2]
JP-A-51-89822 [0003]
2. Description of the Related Art Recently, in molded products mainly composed of automobile parts such as pillars and subframes (also referred to as cross members), thin materials having a thickness of 2 to 3 mm are subjected to high vacuum at an injection speed of 3 to 4.5 m / sec. Casting is increasing, and a machine that can cope with this is required. Many of these thin objects have a large projected area, and the prior art cannot be cast unless a large machine is used. There has been a strong demand for a technique for molding these large and thin molded articles with a small-to-medium-sized machine, that is, a machine (wide platen machine) having a larger platen for mounting a mold than an injection mechanism.
In order to realize this, it is necessary to keep the metal pressure (pressurizing pressure into the mold cavity) after high-speed injection (short-time filling) and filling of the molten metal as low as about 10 to 30 MPa. For this purpose, it is necessary to lower the accumulator pressure, and as a result, problems such as a lack of injection speed, a slow start-up of injection, and large variations in molded products due to instability of molding conditions occur. become.
[0004]
On the other hand, Japanese Patent Application Laid-Open No. Hei 8-114203 discloses a prior art in which the injection speed and pressure of an injection cylinder are controlled simply and easily with a single control valve. JP-A-51-89822 discloses a prior art in which an ideal speed pattern and pressure pattern are realized by using a special injection cylinder.
JP-A-8-114203 discloses the following technology. That is, two load-side ports A and B can be switched to communicate with the pressure source port P and the tank port T, and the opening degree of each valve passage corresponding to the pressure source port P and the tank port T is input. By providing a high-response control valve composed of a servo valve and the like that continuously changes in the hydraulic circuit of the cylinder, and operating this control valve, the flow rate of inflow from the pressure source port P to the cylinder head side can be reduced. The flow rate is controlled by meter-in control, and the speed is controlled by restricting the oil flowing out from the cylinder rod side by meter-out control so as to cause a predetermined pressure loss, while the oil flows from the pressure source port P to the cylinder head side. At least one of the flow rate and the outflow flow rate from the cylinder head side to the tank port T is flow-controlled, and the cylinder rod side is connected to the tank port T to control the pressure on the cylinder head side. It is described that performs control.
[0005]
Japanese Patent Application Laid-Open No. S51-89822 discloses the following technology. That is, a check valve is provided in a passage leading from the rod side to the head side of the injection cylinder of the die casting machine to form a run-around circuit, and a passage (through hole) is provided in the run-around circuit to be closed by the advancement of the piston rod. Die casting with a valve (check valve) that opens when the pressure on the rod side of the cylinder becomes higher than the pressure on the head side, and a throttle valve for adjusting the speed of the piston and a relief valve for controlling the output of the piston An injection device for the machine is described.
[0006]
However, in the technique described in Japanese Patent Application Laid-Open No. 8-114203, since the control of the metal pressure after the completion of the filling of the molten metal is performed by the accumulator 17, it is difficult to lower the feeder pressure. That is, the accumulator 7 is provided in a line connected to the rod side of the injection cylinder, and this accumulator is for discharging a large volume of oil spilled from the rod side at a low pressure during high-speed injection. Therefore, the accumulator 7 does not have a function as a counter pressure against the high-pressure radiation output from the accumulator 17 and is a technology which is in the category of the conventional technology.
[0007]
Japanese Patent Application Laid-Open No. S51-89822 discloses an external runaround in which a runaround circuit at the time of high-speed injection has a complicated structure and operation inside the injection cylinder. However, as in the technique described in Japanese Patent Application Laid-Open No. H08-114203, it is difficult to reduce the riser pressure. That is, the control of the metal pressure after the completion of the filling of the molten metal is performed by controlling the hydraulic pressure of the injection accumulator and the back pressure of the relieving valve 44, and is in the category of the prior art. The reason why it is difficult to lower the feeder pressure described above is as follows. That is, the rod pressure of the injection piston is at most the same as the pressure of the head (pressure of the accumulator for injection), and the ratio of the area where the oil pressure on the rod side and the hydraulic pressure on the head act is about 1: 2. The pressure acting on the piston as counter pressure is at most half the pressure on the head. Therefore, it has been difficult to reduce the riser pressure.
[0008]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to solve the problems of the prior art and to cope with further high-speed injection (high-speed injection while maintaining a high injection pressure enabling high-speed injection), Provided is a hydraulic circuit having a simple control method and structure of an injection cylinder capable of controlling a pressure (also referred to as a counter pressure) applied to a rod side in a wide range and controlling a riser pressure (also referred to as a metal pressure) in a wide range. It is in.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, in the first invention, an internal run-around circuit provided with a check valve in a flow path from the rod side of the injection piston of the injection cylinder to the head side, and an output opening / closing valve from the rod side An external run-around circuit communicating with the head side via a deceleration speed control valve, an injection circuit connected from the injection accumulator to the head side of the injection cylinder via an injection opening / closing valve and a speed control valve, and an output circuit. An output circuit connected to the external run-around circuit from the accumulator via the output opening / closing valve, and a plurality of axial through holes slidably fitted in the injection piston to form the flow path. At the start of injection, pressurized oil of the injection accumulator is introduced into the injection piston head side by using an injection cylinder control hydraulic circuit consisting of a hollow deceleration rod. The output piston is moved forward to raise the oil pressure on the rod side, open the check valve to make the internal run-around circuit open, and operate the output on-off valve to make the external run-around circuit open. High-speed injection, and at a predetermined injection stroke position, the injection piston sequentially closes the through-hole of the deceleration rod to shut off the internal run-around circuit and to rapidly decelerate by the deceleration speed control valve to increase the surge pressure. After the filling of the molten metal is completed, the output opening / closing valve is operated to introduce the hydraulic pressure of the output accumulator to the rod side to control the pressure acting on the molten metal in a wide range.
[0010]
Further, in the second invention, a pressure regulating valve is provided in the output circuit of the first invention, and the pressure acting on the molten metal after the filling of the molten metal is controlled in two stages.
Further, in the third invention, an internal run-around circuit provided with a check valve in a flow path from the rod side of the injection piston of the injection cylinder to the head side, and an output opening / closing valve and a deceleration speed control valve from the rod side. An external run-around circuit that communicates with the head side via an injection accumulator, an injection circuit that is connected to the head side of the injection cylinder via an injection open / close valve and a speed control valve, and an output accumulator from the output accumulator. And an output circuit connected to the external run-around circuit through the injection cylinder, and the injection cylinder having a hollow reduction rod having a plurality of axial passages slidably fitted in the injection piston. And
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
First, a configuration of a hydraulic circuit for controlling an injection cylinder according to the present invention will be described with reference to FIGS. An injection piston 11 is slidably housed in the injection cylinder 10 having a special structure shown in FIG. 3, and the piston 11 partitions the head side A and the rod side B. The injection piston 11 has a hollow structure, and the injection cylinder 10 has a deceleration rod 12 fixed to the injection cylinder main body 18 rotatably integrally with the deceleration position adjustment handle 13 by screws. By rotating the deceleration position adjusting handle 13, the axial relative position of the deceleration rod 12 with respect to the injection cylinder body 18 can be changed.
The injection piston 11 includes a large diameter portion P, a medium diameter portion Q, and a small diameter portion R, and the middle diameter portion Q is provided with a through hole X connecting the outside and the inside. Further, the inside of the speed reduction rod is also hollow, forming a passage for hydraulic oil (part of the internal run-around circuit), and a plurality of through holes Y (outside and outside) in the distal end side of the speed reduction rod. To communicate with the inside).
[0012]
A check valve 14 of a spring type is disposed on the base side (deceleration position adjustment handle side) of the deceleration rod 12. The outer side and the inner side of the deceleration rod are also provided on the base side of the seal portion of the check valve 14. Is provided. From the through hole X of the injection piston portion to the inside of the piston rod (outside of the reduction rod), the through hole Y on the tip side of the reduction rod, the inside of the reduction rod, the above-described check valve, and the through hole Z on the base side of the reduction rod. An internal run-around circuit is constituted by a circuit leading to the head side of the injection piston.
Further, the rod side B of the injection cylinder and the head side A of the injection cylinder are connected by an external pipe via an output on-off valve 31 and a deceleration speed adjusting valve 32, thereby forming an external run-around circuit. The aforementioned output on-off valve 31 is also connected to the output accumulator 30.
On the other hand, the injection accumulator 20 is connected to the injection piston head side via an injection opening / closing valve 21 and an injection speed control valve (throttle valve) 22.
[0013]
Next, an injection control method using the above-described hydraulic circuit 1 for controlling an injection cylinder will be described. First, the operation at the start of injection will be described. With the injection on-off valve 21 in a communicating state, pressure oil of the injection accumulator 20 is introduced into the head side A of the injection piston. This causes the injection piston 11 to start moving forward (moving to the left in FIG. 1). The hydraulic oil on the rod side B pushes the check valve 14 from the through hole X of the injection piston and the through hole Y of the reduction rod through the inside of the reduction rod 12 and flows into the head side through the through hole Z. (Internal runaround circuit). Further, by switching the output on-off valve 31 to the right position, the hydraulic oil on the rod side B flows into the head side A via the output on-off valve 31 and the deceleration speed control valve 32 (external run-around circuit). In this manner, by using the internal run-around circuit and the external run-around circuit together, the high-pressure and high-flow characteristics of the injection accumulator 20 can be sufficiently exhibited, so that a higher-speed and higher-output injection operation can be performed. Become. At this time, the injection speed is controlled by the injection speed control valve 22.
Can be controlled freely.
[0014]
Next, the operation during deceleration will be described. As the high-speed injection proceeds, the injection piston 11 sequentially blocks the through-hole Y of the deceleration rod 12, and the deceleration is gradually performed. When the injection piston 11 completely shuts off the through hole Y at the tip of the deceleration rod, the internal run-around circuit is shut off and the injection piston 11 moves forward only by the external run-around circuit. The injection speed at this time is adjusted by the opening of the deceleration speed control valve (throttle valve) 32. Although the injection speed is rapidly reduced by the deceleration speed control valve 32, a surge phenomenon of the molten metal (metal) pressure generated by the impact can be prevented. The deceleration start position can be adjusted by moving the deceleration rod 12 in the axial direction with respect to the injection cylinder 10 by the deceleration position adjustment handle 13.
[0015]
Finally, it is necessary to apply the riser effect to the molten metal after the filling of the molten metal into the mold cavity is completed. For this purpose, the output on-off valve 31 is switched to the left position to bring the output accumulator 30 into communication with the rod side B, and the hot water pressure is adjusted by the counter pressure with respect to the pressure of the injection accumulator 20. it can. That is, by increasing the pressure of the output accumulator 30, the riser pressure can be reduced. In this way, it is possible to adjust the feeder pressure over a wide range while maintaining the high pressure and high flow rate function of the injection accumulator 20.
[0016]
Next, two-stage control of metal pressure (water pressure) will be described with reference to FIG. The purpose of controlling the metal pressure in two stages is as follows. In other words, the mating surface of the mold has irregularities, and if the pressure in the cavity (hot water pressure) is too high, the viscosity of the molten metal is low immediately after filling, and the molten metal may be ejected from the irregularities. In order to prevent the molten metal from being ejected immediately after the filling, the mold is clamped at a very low pressure for a certain time and then the pressure is increased to a normal mold clamping force. At this time, burrs (material which has intruded into the mating surface of the mold and solidified) generated on the mating surface of the mold are taken out integrally with the molded product.
The two-stage control method of the metal pressure will be described in detail. That is, the injection start operation, the high-speed injection operation, the deceleration operation, and the like are as described above. Next, when the filling effect is applied to the molten metal in the cavity after the filling is completed, the charge pressure of the output accumulator 30 is increased. By doing so, the feeder pressure becomes low immediately after filling. After that, the switching valve 34 is switched, and the setting of the pressure adjusting valve 33 is lowered, so that the pressure can be increased to the target metal pressure (water pressure). In this way, even if the molten metal slightly enters the mold mating surface, it is immediately cooled by the mold, so that the molten metal does not erupt from the mating surface. By increasing the metal pressure (feeder pressure) after a predetermined time has elapsed, it is possible to prevent the occurrence of cavities and the like. All of these operations are automatically performed by a control device (not shown).
[0017]
Using the above-described technology of the present invention, a medium-sized thin product was actually formed using a die-casting machine having a mold clamping force of 500 tons. The molding conditions at this time are as follows.
Molding conditions Molded product: OA floor, projected area: 1100 CM ² , thickness: 3 to 8 mm (in the prior art, a molded product requiring a large machine with a mold clamping force of 1000 tons or more)
Molding material: ADC10, mold clamping force: 500 tons, charge pressure of injection accumulator: 15 MPa, charge pressure of output accumulator: 14 MPa
Deceleration position: 20 mm before stroke end
Injection speed setting: rising (stroke up to 380 mm) / low speed injection (0.2 m / sec), high speed injection area (stroke 380 to 510 mm) / high speed injection (3.5 m / sec), deceleration injection area (stroke 510 to 530 mm) / Deceleration injection (1.5m / sec)
Specifications of the injection device Injection piston head diameter: 190 mm, rod diameter: 135 mm, reduction rod diameter: 70 mm, plunger tip diameter: 80 mm, injection stroke: 530 mm
Accumulator pressure fluctuation:
(1) When holding pressure (metal pressure control) is set to one stage:
The injection accumulator went down from 15 MPa when charging was completed to 12 MPa when injection and filling were completed. On the other hand, the output accumulator went down from 14 MPa when charging was completed to 13.5 MPa when injection and filling were completed. The metal pressure at this time was 31.1 MPa.
(2) When holding pressure (metal pressure control) is set to two stages:
The set value of the first stage metal pressure was 20 MPa, and the set value of the second stage metal pressure was 31 MPa. At this time, the injection accumulator went down from 15 MPa when charging was completed to 12 MPa when injection and filling were completed. On the other hand, the output accumulator went down from 19.7 MPa when charging was completed to 19.0 MPa when injection and filling were completed. The metal pressure at this time is 20 MPa, and the switching valve 34 is switched 30 msec after the completion of the injection filling.
The set value of the pressure regulating valve 33 is 13.5 MPa, whereby the counter pressure (back pressure) drops from 19.0 MPa to 13.5 MPa. In this way, the metal pressure (feed pressure) rises from 20 MPa to 31.1 MPa.
[0018]
In the actual molding of the present invention, it is common to adjust the injection speed to 4 to 4.5 m / sec and the riser pressure (metal pressure) to 10 to 30 MPa. It became possible to.
[0019]
【The invention's effect】
As described above, according to the technology of the present invention, as in the embodiment, the molding of a large and thin object, which conventionally required a large machine with a mold clamping force of 1000 tons or more, is performed by a medium machine with a mold clamping force of 500 tons. Now you can. That is, it became possible to perform casting with a molding machine in which the mold clamping force in the prior art was reduced by half.
Further, it has become possible to make the configuration simpler than the conventional hydraulic circuit.
[Brief description of the drawings]
FIG. 1 is a hydraulic circuit diagram for controlling an injection cylinder according to an embodiment of the present invention.
FIG. 2 is a hydraulic circuit diagram for controlling an injection cylinder according to another embodiment of the present invention.
FIG. 3 is a structural explanatory view of an injection cylinder according to one embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Hydraulic circuit 10 for injection cylinder control 10 Injection cylinder 11 Injection piston 12 Deceleration rod 13 Deceleration position adjustment handle 14 Check valve (check valve)
15 Pressure control valve 16 Tank 17 Hydraulic pump 18 Injection cylinder body 19 Piston rod 20 Injection accumulator 21 Injection opening / closing valve 22 Injection speed control valve 30 Output accumulator 31 Output opening / closing valve 32 Deceleration speed control valve 33 Pressure adjusting valve 34 Switching Valve A Head side B Rod side P Large diameter part of injection piston Q Medium diameter part of injection piston R Small diameter part X of injection piston Through hole (injection piston)
Y Through hole (Deceleration rod tip side)
Z Through hole (at the base of deceleration rod)

Claims (3)

An internal run-around circuit provided with a check valve in a flow path leading from the rod side to the head side of the injection piston of the injection cylinder, and an external passage leading from the rod side to the head side via an output opening / closing valve and a deceleration speed control valve. A run-around circuit, an injection circuit connected from the injection accumulator to the head side of the injection cylinder via the injection open / close valve and the speed control valve, and an external accumulator from the output accumulator to the external run-around circuit via the output open / close valve. An injection cylinder control hydraulic pressure comprising a connected output circuit and a hollow reduction rod having a plurality of through holes in the axial direction and slidably fitted in the injection piston to form the flow path. Using the circuit, at the start of injection, pressurized oil of the injection accumulator is introduced into the head side of the injection piston, and the injection piston is advanced to move the rod on the rod side. When the pressure is increased, the check valve is opened to make the internal run-around circuit open, and the output on-off valve is operated to make the external run-around circuit open, and high-speed injection is performed. At the position, the injection piston sequentially closes the through-hole of the deceleration rod to shut off the internal run-around circuit, and the deceleration speed control valve suddenly decelerates to prevent generation of surge pressure, thereby completing the filling of the molten metal. A method for controlling an injection cylinder, wherein the output opening / closing valve is later operated to introduce the oil pressure of the output accumulator to the rod side to control the pressure acting on the molten metal in a wide range. 2. The control method for an injection cylinder according to claim 1, wherein a pressure regulating valve is provided in the output circuit, and the pressure acting on the molten metal after the filling of the molten metal is controlled in two stages. An internal run-around circuit provided with a check valve in a flow path leading from the rod side to the head side of the injection piston of the injection cylinder, and an external passage leading from the rod side to the head side via an output opening / closing valve and a deceleration speed control valve. A run-around circuit, an injection circuit connected from the injection accumulator to the head side of the injection cylinder via the injection open / close valve and the speed control valve, and an external accumulator from the output accumulator to the external run-around circuit via the output open / close valve. For controlling an injection cylinder, comprising: a connected output circuit; and the injection cylinder having a hollow reduction rod having a plurality of axial passages slidably fitted in the injection piston. Hydraulic circuit.

Images