JP2002283425A - Mold opening/closing device of injection foam molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately and stably control the movement and stop of a movable mold for the purpose of foam molding. SOLUTION: A mold opening/closing device is provided with a mold clamping cylinder 8, a booster cylinder 12 connected to the movable mold 2, a first hydraulic circuit for operating the mold clamping cylinder 8 in connection with the booster cylinder 12, and a second hydraulic circuit having a constant capacity type hydraulic pump 28 and a servo motor 30 for driving the same and operating the movable mold to move the same to a reference position of foam molding and further provided with a position feedback control means 38, which feeds back the position detection signal of the movable mold from position detection means 35, 36 and 37 and controls the servo motor in comparison with the reference position to set the movable mold to the reference position and a hydraulic circuit changeover means for changing over the flow channels of the first and second hydraulic circuits so that hydraulic force in a mold closing direction acts on the movable mold against foaming force when the movable mold arrives at a target position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold opening / closing apparatus for an injection foam molding machine, and more particularly to a mold opening / closing apparatus for an injection foam molding machine capable of accurately controlling a mold opening required for foam molding. About.

[0002]

2. Description of the Related Art In recent years, foam molding has attracted attention in order to reduce the weight of plastic molded articles and to add a soft feeling to the contact feeling of molded articles. This type of foam molding
A resin containing a foaming agent is injected into a cavity in a mold and molded by an injection molding machine. BACKGROUND ART Foam molded products are widely used, for example, as interior materials for automobiles.

In foam molding, a resin generates a foaming gas immediately after injection, expands the resin, and forms countless foam cells. In order to form a high-quality foam molded article, it is necessary to prevent the formation of foam cells from becoming uneven and to increase the expansion ratio.

Accordingly, the applicant of the present invention has disclosed in Japanese Patent Laid-Open No.
No. 26 proposes a method of molding an injection-foamed molded product that makes it possible to improve the expansion ratio by making the foam cells small and uniform. This injection foaming molding method is to inject a resin containing a foaming agent into a cavity in a mold closed state of an injection molding machine, and after the injection is completed, maintain the contact between the mold wall surface and the resin by expansion of the resin by a foaming gas. The movable die is stopped at a preset reference thickness position while cooling is completed, and the movable die is retracted to take out the product. According to this molding method, after the injection of the foaming agent-containing resin is completed, the movable mold is moved while maintaining the contact between the mold wall surface and the resin due to the expansion of the resin by the foaming gas. In addition, the expansion ratio is improved, and a molded product having a large elastic force can be formed even with a small thickness.

[0005] In order to carry out such an injection foaming molding method, it is necessary to accurately move the movable mold in accordance with the expansion of the resin by the foaming gas after the completion of the injection. In a conventional injection foam molding machine, a hydraulic servo mechanism is provided in a hydraulic circuit that supplies pressure oil to a mold closing cylinder that opens and closes a mold, together with a detector that detects the position of the movable mold, and the position and speed of the movable mold are provided. Is controlling.

[0006]

SUMMARY OF THE INVENTION In the case of injection foam molding,
After closing the mold and injecting the resin containing the foaming agent, it is necessary to move the resin in the mold opening direction by a very small distance in accordance with the expansion of the resin due to the generation of the foaming gas. As described above, it is important to accurately stop the movable mold at the preset position in order to keep the quality of the foam molded article constant.

However, in the conventional injection foam molding machine, since the position and the moving speed of the movable mold are controlled by controlling the hydraulic oil supplied to and discharged from the mold closing cylinder, an error occurs, and accurate control is difficult. It was difficult to stabilize the mold position. In addition, the positioning block is sandwiched between a mold or a die plate, and after the resin is injected, the movable die is moved and the movable block is stopped at a predetermined position by the positioning block, thereby stabilizing the opening amount of the movable die. However, there is a disadvantage that the mechanical mechanism for positioning becomes large-scale.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to accurately and stably move and stop the movable mold in accordance with the expansion of the resin by the foaming gas for foam molding. An object of the present invention is to provide a mold opening / closing device of an injection foam molding machine which can be controlled.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an injection foam molding for molding a foamed product by injecting a resin containing a foaming agent into a mold comprising a fixed mold and a movable mold. A hydraulic mold opening and closing device used in a machine includes a mold clamping cylinder for applying a mold clamping force to the closed mold, a boost cylinder connected to the movable mold to move the movable mold, and a hydraulic pressure source. A first oil supply / discharge system for supplying / discharging hydraulic oil to / from the mold clamping cylinder and the boost cylinder so that the mold clamping cylinder and the boost cylinder operate in conjunction with each other to perform a series of operations for mold opening / closing and mold clamping. It has a hydraulic circuit, a fixed displacement hydraulic pump and a servomotor for driving the same, and operates to move the movable mold to a foam molding reference position set in a mold opening direction by a predetermined distance from the mold closing position. Oil A second hydraulic circuit to be supplied to the strike cylinder, position detecting means for detecting the position of the movable type, and a position detecting signal of the movable type fed back from the position detecting means, and the detected position is compared with the reference position. Position feedback control means for controlling the rotation of the servomotor so that the movable mold reaches the reference position and positions the movable mold at the reference position, and when the movable mold reaches the target position, it resists the foaming force. Hydraulic circuit switching means for switching the flow paths of the first hydraulic circuit and the second hydraulic circuit so that the hydraulic pressure in the mold closing direction acts on the movable mold to maintain the position of the movable mold. It is a feature.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a mold opening and closing device for an injection foam molding machine according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a hydraulic circuit diagram of a mold opening / closing device of an injection foam molding machine according to the present embodiment. This figure 1
In the figure, 1 is a fixed mold and 2 is a movable mold. The fixed mold 1 is attached to the fixed die plate 3 and the movable mold 2
Is attached to the movable die plate 4. An injection device is arranged on the fixed die plate 3 side.
Here, the heating barrel 5 of the injection device is shown. A screw (not shown) is mounted inside the heating barrel 5. The resin mixed with the foaming agent is melted by the rotation of the screw, and the molten resin is injected from the nozzle 6 as the screw advances.

One end of a tie bar 7 is connected to the fixed die plate 3, and the tie bar 7 extends through the movable die plate 4 to the mold clamping cylinder 8.
Is connected to the mold clamping cylinder 8. A ram 10 is inserted into a cylinder chamber 9 inside the mold clamping cylinder 8, and a tip of the ram 10 extending from the mold clamping cylinder 8 is connected to the movable die plate 4.

In this embodiment, the mold clamping cylinder 8 is
This is for applying a mold clamping force after the fixed mold 1 and the movable mold 2 are closed. On the other hand, a pair of boost cylinders 12, 12 disposed on both left and right sides of the fixed die plate 3 move the movable mold 2 toward the fixed mold 1 in a direction approaching, and close the mold. Alternatively, the moving die 2 is moved in a direction in which the moving die 2 is moved to open the die, and the distal ends of the piston rods 13 extending outward from the boost cylinders 12 are respectively connected to the moving die plate 4.
It is connected to.

Next, a first hydraulic circuit for operating the mold closing cylinder 8 and the boost cylinder 12 when the mold is opened and closed and when the mold is closed will be described.

In FIG. 1, reference numerals 14a, 14b
Is a multiple hydraulic pump, 15 is a hydraulic pump 14a,
14b. Reference numeral 16 denotes a tank containing hydraulic oil. The hydraulic oil discharged from the hydraulic pumps 14a, 14b is supplied to the flow control valve 17, the mold opening / closing switching valve 1
After passing through the cylinder 8, it is supplied to the boost cylinders 12, 12 and the mold clamping cylinder 8. Here, the mold opening / closing switching valve 1
8, a 4-port 3-position electromagnetic switching valve is used, and a port extending to the cylinder chamber 12a on the mold opening side of the boost cylinder 12 is connected to the B port. A
The pipe line connected to the port is divided into two branches, one of which is a cylinder chamber 12b on the mold closing side of the boost cylinder 12.
Extending to

On the other hand, the other branched pipe is connected to the P port of the switching valve 20 for the mold closing cylinder. The pipeline connected to the port A of the mold-clamping cylinder switching valve 20 extends to the inlet port of the cylinder chamber 9 of the mold-clamping cylinder 8. The mold clamping cylinder 8 is provided with a prefill valve 22 and an opening / closing cylinder 23 for opening and closing the prefill valve 22. When the mold is opened, the operating oil in the cylinder chamber 9 is discharged to the drain side to speed up the mold opening operation. You can do it. 24 is a switching valve for the prefill valve. 26 is a pressure regulating valve for setting the pressure of the hydraulic oil.

The port A of the prefill valve switching valve 24 is connected to the open / close cylinder 2 for closing the prefill valve 22.
3 is connected to the lower cylinder chamber, and the B port is connected to the upper cylinder chamber to be opened. While the movable mold 2 is opened and closed, the solenoid 24b of the prefill valve switching valve 24 is excited to switch to a position where the P port and the B port communicate with each other, and the prefill valve 22 is opened. The cylinder chamber 9 of 8 communicates with the drain side.

In this state, when the solenoid 18b of the mold opening / closing switching valve 18 is excited, the P port communicates with the A port to supply the operating oil to the cylinder chamber 12b on the mold closing side of the boost cylinder 12 so that the movable mold is moved. When the solenoid 2a is energized and the solenoid 18a is excited, the P port communicates with the B port to supply hydraulic oil to the cylinder chamber 12a on the mold opening side, so that the movable mold 2 moves to the left and opens. It has become.

At the time of closing the mold, the solenoid 24a of the switching valve 24 for the prefill valve is closed with the movable mold 2 closed.
Is excited to switch to a position where the P port and the A port communicate, and the prefill valve 22 is closed. When the solenoid of the switching valve 20 for the mold closing cylinder is excited,
Since the hydraulic oil is supplied to the cylinder chamber 9 of the mold clamping cylinder 8, the mold can be clamped.

Next, after the mold is clamped to perform foam molding and the resin is injected, a hydraulic oil is supplied to the boost cylinder 12 to move the movable mold 2 in the mold opening direction by a predetermined distance from the mold closed position. The second hydraulic circuit to be supplied to is described.

In FIG. 1, the second hydraulic circuit includes a bi-directional constant displacement hydraulic pump 28. The constant displacement hydraulic pump 28 is driven by a servomotor 30. A check valve 3 with a pilot is provided in a pipe extending from each discharge port of the constant displacement hydraulic pump 28.
1, 32 are provided. The pipes downstream of the piloted check valve 31 are respectively connected to the cylinder chambers 12a on the mold opening side of the boost cylinder 12, and the pipes downstream of the piloted check valve 32 are connected to the boost cylinder 12
Is connected to the cylinder chamber 12b on the mold closing side. In such a second hydraulic circuit, a pipeline is formed so as to be a differential circuit for circulating hydraulic oil in the left and right cylinder chambers 12a and 12b of the boost cylinder. In addition, 33, 34
This is a check valve for supplying hydraulic oil from the tank to the operating circuit.

Next, in FIG. 1, reference numeral 35 is a linear scale. The linear scale 35 and the position detecting head 36 attached to the movable die plate 4
The means for detecting the position of the movable mold 2 is constituted by combining the and the counter 37. The output of the counter 37 is introduced to the control unit 38. The control unit 38 is configured by a programmable controller (PLC) and the like, and has the function of switching the above-described switching valve in a predetermined order in order to advance the injection foam molding process in accordance with a pre-set program, and moves as follows. A position control circuit for controlling the rotation of the servomotor 30 while feeding back the position of the mold 2 and a servomotor drive circuit are provided.

Therefore, during the foam molding, after the injection of the resin containing the foaming agent is completed, the position control for opening the movable mold 2 to a reference position for foam molding by a predetermined amount in accordance with the expansion of the resin by the foaming gas. Will be described. The control of the position of the movable mold 2 is started from the completion of the injection of the resin. First, the control unit 38 sets the switching valve 18 for opening and closing the mold to the neutral position shown in FIG. 1 to the cylinder chamber 9 of the mold clamping cylinder 8.
Open to the drain side.

Next, the control unit 38 controls the servo motor 30
Is rotated in the forward direction at a predetermined rotation speed in accordance with a preset program, thereby driving the bidirectional constant displacement hydraulic pump 28 at a predetermined rotation speed, and the cylinder on the mold opening side of the boost cylinder 12. A predetermined flow rate of hydraulic oil is introduced into the chamber 12a. As a result, the movable die plate 4 starts moving leftward along the tie bar 7. At this time, it is preferable that the flow rate of the working oil is such that the movable mold 2 moves in accordance with the expansion of the resin due to the foaming gas generated in the cavity.

While the moving mold 2 moves to the reference position set in advance by the program, the position detection signal of the moving mold 2 is fed back from the counter 37 to the control section 38. The position of the mold 2 is compared with the reference position, and the rotation of the servomotor 30 is continued until the position reaches the reference position. When the position of the movable mold 2 coincides with the reference position, the control unit 38 sends a stop command to a drive circuit (not shown) of the servomotor 22 to stop the rotation of the servomotor 30. In addition, when the moving mold 2 exceeds the reference position,
Since the constant displacement hydraulic pump 28 is a bidirectional pump, the servomotor 30 may be reversed.

As described above, since the constant displacement hydraulic pump 28 is stopped and the supply of the hydraulic oil to the boost cylinder 12 is stopped, the movable mold 2 can be stopped at the reference position. Moreover, since the constant displacement hydraulic pump 28 is driven by the servo motor 30 and the rotation of the servo motor 30 is controlled while feeding back the position of the movable mold 2, the movable mold 2 can be accurately positioned at the reference position. it can. Further, the hydraulic circuit necessary for controlling the position of the movable mold 2 is a differential circuit in which hydraulic oil circulates from the cylinder chamber 12a on the mold opening side of the boost cylinder 12 to the closed cylinder chamber 12b. The constant displacement type hydraulic pump 28 and the servomotor 30 can sufficiently cope with a small displacement.

After the movable mold 2 stops at the reference position, the control unit 38 excites the solenoid of the mold closing cylinder switching valve 20 to switch the P port to a position where the P port communicates with the A port. As a result, hydraulic oil from the two hydraulic pumps 14a and 14b is introduced into the cylinder chamber 9 of the mold clamping cylinder 8, and the ram 10 is pressed against the foaming pressure to move the moving mold 2 to the reference pressure based on the foaming pressure. Prevents further opening from position. At this time, the switching valve 18 for opening and closing the mold is switched to the neutral position shown in FIG.
The second cylinder chamber 12a is closed and the discharge of hydraulic oil is prevented by the check valve 31 with the pilot and the check valve 33, so that the boost cylinder 12 is pressurized by the mold clamping cylinder 8 to move the boost cylinder 12 in the mold closing direction. Since the pressure can be held so that the mold does not move, it is necessary to stabilize the position of the moving mold at the reference position until the foaming is completed without using a positioning block mechanically as in the related art. Becomes possible.

Next, FIG. 2 shows a modification of the boost cylinder, in which the direction of the boost cylinder 40 is reversed from that in FIG. 1 and the mold is closed when the piston rod 41 is extended, and when the piston rod 41 is retracted. This is an example in which the mold is opened. The same hydraulic circuit as that in FIG. 1 can be applied.

FIG. 3 shows a modification in which the boost cylinder is incorporated in the mold clamping cylinder 8. In this case, a cylinder chamber 42 on the mold opening side is formed on the outer peripheral portion of the ram 10, and a cylinder chamber 43 on the mold closing side is formed inside the ram 10.

[0029]

As is apparent from the above description, according to the present invention, the movement and stop of the moving mold are controlled accurately and stably in accordance with the expansion of the resin by the foaming gas for foam molding. Since it can be made, it greatly contributes to the molding of high quality and uniform quality foam molded products.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of a mold opening / closing device of an injection foam molding machine according to the present invention.

FIG. 2 is a sectional view showing a modified example of a boost cylinder of the mold opening / closing device of the injection foam molding machine.

FIG. 3 is a sectional view showing another modified example of the boost cylinder of the mold opening / closing device of the injection foam molding machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed mold 2 Moving mold 3 Fixed die plate 4 Moving die plate 5 Heating barrel 6 Nozzle 7 Tie bar 8 Mold closing cylinder 10 Ram 12 Boost cylinder 18 Mold opening / closing switching valve 20 Mold closing cylinder switching valve 22 Prefill valve 24 Switching valve for prefill valve 28 Constant displacement hydraulic pump 30 Servo motor 35 Linear scale

Continued on front page F term (reference) 4F202 AB02 AG20 AP06 AR09 CA11 CC01 CL09 CL13 CL18 CL22 CL42 CL44 4F206 AB02 AG20 AP067 AR097 JA04 JL02 JM02 JM04 JM05 JM16 JN33 JP11 JQ88 JT05 JT21 JT33

Claims (5)

[Claims] 1. A hydraulic mold opening / closing device used in an injection foam molding machine for molding a foamed product by injecting a resin containing a foaming agent into a mold comprising a fixed mold and a movable mold, wherein the mold is closed. A mold clamping cylinder for applying a mold clamping force to the mold, a boost cylinder connected to the movable mold to move the movable mold, and a hydraulic pressure source, wherein the mold clamping cylinder and the boost cylinder are used for opening and closing the mold and for clamping the mold. A first hydraulic circuit for supplying and discharging hydraulic oil to and from the mold clamping cylinder and the boost cylinder so as to operate in conjunction with each other to perform a series of operations, a constant displacement hydraulic pump and a servomotor for driving the same. A second hydraulic circuit that supplies hydraulic oil to the boost cylinder to move the movable mold to a foam molding reference position set in a mold opening direction by a predetermined distance from a mold closing position; Position detecting means for detecting the position of the movable type position feedback signal from the position detecting means, and the movable type reaches the reference position while comparing the detected position with the reference position, and moves to the reference position. Position feedback control means for controlling the rotation of the servomotor so as to perform positioning, when the movable mold reaches a target position, hydraulic pressure in a mold closing direction acts on the movable mold against foaming force. A hydraulic circuit switching means for switching the flow paths of the first hydraulic circuit and the second hydraulic circuit to maintain the position of the movable mold. 2. The first hydraulic circuit includes a mold closing switching valve for switching a flow path of hydraulic oil to the mold clamping cylinder, and three positions for opening and closing the mold for switching a flow path of hydraulic oil to the boost cylinder. A switching valve, and the second hydraulic circuit includes a differential circuit that circulates hydraulic oil between a cylinder chamber on the mold opening side and a cylinder chamber on the mold closing side of the boost cylinder. A mold opening and closing device for the injection foam molding machine according to claim 1. 3. The mold opening / closing device for an injection foam molding machine according to claim 1, wherein said constant displacement hydraulic pump comprises a two-way type fixed quantity hydraulic pump. 4. The mold opening / closing device for an injection foam molding machine according to claim 2, wherein the second hydraulic circuit is provided with a check valve for maintaining the pressure of the circuit when the fixed hydraulic pump is stopped. 5. The mold opening and closing device for an injection foam molding machine according to claim 1, wherein said boost cylinder is incorporated inside said mold clamping cylinder.