JP3005733B2 - Injection pressure selection mechanism of injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine, and more particularly to an injection pressure selecting mechanism.

[0002]

2. Description of the Related Art Conventionally, an injection pressure is used as a primary pressure used when filling a molten material into a mold and a holding pressure for preventing sink marks, shrinkage, etc. after the filling of the mold is completed. And secondary pressure. In this case, the injection primary pressure is generally set high and the injection secondary pressure is set low.

[0003] Recently, low-pressure, high-speed injection of resin into a low-viscosity state eliminates burrs and shots.
Further, molding with less deformation such as warping and twisting has been performed. In such molding, it is necessary to switch the injection pressure in multiple stages so as to mold from a general-purpose resin to a low-viscosity resin.

[0004]

However, the injection pressure selection mechanism for performing the above-described multi-stage switching tends to have a somewhat complicated structure.

An object of the present invention is to provide an injection pressure selection mechanism capable of performing multistage switching of injection pressure with a relatively simple structure.

[0006]

Means for Solving the Problems In order to achieve the above object, the constitution of the present invention is as follows. That is, a piston is formed in an intermediate portion, and large- and small-diameter rods facing the piston are inscribed in the outer peripheral surface of the piston,
A rod cover disposed around the rod, a bush penetrating through the center of the small-diameter rod, and attached to one side of the rod cover; and a bush attached from one end of the large-diameter rod to the piston. A ram having an inner hole inserted into a bore formed to face the air, and a ram disposed around the large-diameter rod into which the ram is inserted, and attached to the other side of the rod cover; An end cover having a hole, wherein a space formed by the piston, the small diameter side rod, the rod cover and the bush is a first chamber, and the piston, the large diameter side rod, the rod cover, and the the space formed from the end cover and the second chamber, wherein a space formed in the lumen of the large diameter side rod and the third chamber, the pressure receiving <br/> area of the piston in said first chamber, said Greater than the sum of the effective pressure receiving area of the lumen of the large-diameter rod in said third chamber and the pressure receiving area of the piston in two chambers, the piston in the second chamber
Yes receiving area of the lumen of the large-diameter side rod definitive in the third chamber
Equipped with an injection cylinder set to be larger than the effective pressure area,
The first chamber, the second chamber, and the third chamber are connected to a hydraulic operating circuit that changes the injection pressure of the screw in a stepwise manner via a connecting member connected to an end of the small-diameter rod. .

[0007]

With the above construction, the pressure receiving area formed in the injection cylinder is reduced by the operation of the hydraulic operation circuit.
Hydraulic oil can be selectively introduced or discharged into different first, second, or third chambers, and hydraulic pressure can be applied to the piston or rod in a stepwise manner to change the screw injection pressure in a stepwise manner.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the accompanying drawings. The injection pressure selection mechanism of the present embodiment includes a double rod type injection cylinder 10 shown in FIG. 3 and an operation circuit shown in FIG.
60 is a four-stage switching type injection pressure selection mechanism.

First, the double rod type injection cylinder 10 will be described with reference to FIG. The injection cylinder 10 has a piston 12 formed at an intermediate portion, and is formed into a rod 14 composed of a large-diameter rod 14a located on the left side in the drawing and a small-diameter rod 14b located on the right side, and a large-diameter rod 14a. lumen
It is schematically composed of a ram 16 inserted concentrically into 15.

An outer peripheral surface of the piston 12 is slidably inscribed on an inner peripheral surface of a rod cover 18 connected to an injection device main body (not shown). A bush 20 is fitted between the small-diameter side rod 14b and the rod cover 18 so as to face the piston 12, and a flange 22 formed integrally with the bush 20 is bolted by a bolt 24 to the side surface of the rod cover 18. It is fixed to.

On the other hand, an end cover 26 is disposed concentrically around the large diameter rod 14a, and a bolt is attached to the side surface of the rod cover 18 so that the end of the enlarged diameter portion 26a faces the piston 12. Fixed by 28. Also, end cover
An opening 30 is formed in the opposite side surface 26b of the enlarged diameter portion 26a of the 26, and the ram 16 is inserted into the lumen 15 of the large diameter rod 14a through the opening 30 as described above. The flange 32 formed integrally with the ram 16 is a side surface 26b of the end cover 26.
Are fixed by bolts 34. Note that an inner hole 36 is formed along the longitudinal direction of the ram 16.

With such a configuration, the piston 12, the small diameter side rod 14a, the rod cover 18, and the bush 20 form a first space, that is, a first chamber 38.
Large diameter rod 14a, rod cover 18 and end cover 26
Is the flange 26a second chamber 40 is formed, a further, ram
The rod 15 is inserted into the bore 15 of the large diameter rod 14a
A third chamber 42 is formed which expands and contracts as the 14 moves forward and backward.
Ri, third chamber 42 is communicated directly to the inner bore 36 of the ram 16.
A fourth chamber 44 is formed between the outer peripheral surface of the large-diameter rod 14a and the inner peripheral surface of the end cover 26, and is opened to the atmosphere through an atmosphere communication hole 46 provided in the end cover 26. I have.
The first chamber 38 is connected to a later-described operating circuit 60 via a passage 48, the second chamber 40 is connected via a passage 50, and the third chamber 42 is connected via an inner hole 36 and a port 52 of the ram 16. Have been.

It should be noted that, in the above configuration, the piston 12 which is actuated by hydraulic pressure to drive the rod 14 in the first chamber 38
Area (pressure receiving area) is driven by the rod 14 in the second chamber 40.
The area of the piston 12 (the pressure receiving surface)
Product) and hydraulic pressure to drive the rod 14 in the third chamber 42
Effectively acts on the cross-sectional area of the bore 15 of the large diameter rod 14a
That is, the effective pressure receiving area ( in the example shown in FIG.
Including the inner hole 36 of the inserted ram 16 (that is,
The cross-sectional area (assuming a solid without holes 36)
Greater than the sum of the that), also the pressure receiving area of the second chamber 40 and the third
It is set larger than the effective pressure receiving area of the chamber 42 . The difference between these pressure receiving areas is necessary for applying hydraulic pressure to the screw stepwise as described later.

The proximal end of the small-diameter rod 14b is shown in FIG.
Is connected to a screw 56 via a connecting member 54 as schematically shown in FIG. 5, whereby the screw 56 moves forward and backward with respect to a mold (not shown) by the action of the injection cylinder 10. It is.

Next, the operation circuit 60 will be described with reference to FIG. A hydraulic motor 62 is connected to the screw 56, and thereby the screw 56 is rotated to melt and knead the appropriately supplied resin. The first chamber 38 is connected to a three-position four-way switching valve 66 via a first two-position four-way switching valve 64, and further connected to a hydraulic oil tank T. The hydraulic motor 62 is the first
It is connected to a screw rotation back pressure relief valve 68 via a position 4-way switching valve 64. The second chamber 40 is connected to a three-position four-way switching valve 66 via a second two-position four-way switching valve 70,
Further, it is connected to a hydraulic oil tank T via a hydraulic pump 72. An original pressure safety relief valve 74 is interposed between the three-position four-way switching valve 66 and the hydraulic pump 72.

The port 52 of the ram 16 is connected to the hydraulic oil tank T via a third two-position four-way switching valve 76.
Also, a three-position four-way switching valve 66 and a first two-position four-way switching valve
Two branch pipes 80 and 82 are branched from a pipe 78 connecting the pipes 64, and one of the branch pipes 80 is a second and third two-position four-way switching valve 70,7.
6 and the other branch pipe 82 is connected to a fourth two-position four-way switching valve 84. Also, the fourth two positions 4
The hydraulic oil tank T and the injection pressure relief valve 86 are connected via the direction switching valve 84. This injection pressure relief valve 86
Thereby, an operating oil pressure higher than a predetermined pressure is released to the tank.

Next, the operation of the injection pressure selection mechanism configured as described above will be described with reference to the function tables shown in FIGS. First, when obtaining the injection pressure of the first stage, the three-position four-way switching valve 66, the second,
The solenoids I, I ₂ , I ₃ and I _{4 of} the third and fourth two-position four-way switching valves 70, 76 and 84 are excited. Thereby, the first chamber 38 of the injection cylinder 10 is connected to the second two-position four-way switching valve 64 via the first two-position four-way switching valve 64.
Via 70, the third chamber 42 is all in communication with the hydraulic pump 72 via a two-position four-way switching valve 76 and further via a three-position four-way switching valve 66.

Therefore, the hydraulic oil in the hydraulic oil tank T is
The hydraulic pump 72 passes through the three-position four-way switching valve 66 and further to the first chamber 38 through the first two-position four-way switching valve 64.
The gas is introduced into the second chamber 40 via the second two-position four-way switching valve 70 and into the third chamber 42 via the third two-position four-way switching valve 76, respectively. As a result, the working oil pressure introduced into the first chamber 38 and applied to the piston 12 to the left in the drawing becomes the second hydraulic pressure.
Introduced into the chamber 40, the hydraulic pressure applied to the piston 12 to the right in the drawing and, in addition to this, introduced into the third chamber 42,
The hydraulic pressure applied to the rod 14 on the right side of the drawing is overcome, and the piston 12 and the rod 14 are shown above the chain line in FIG.
Moved to the position where it was connected by the connecting member 54
Move the screw 56 to the left in the drawing .

At this time, the first chamber 38, the second chamber 40 and the third
The chamber 42 passes through a corresponding pipe, and is further connected to an injection pressure relief valve 86 via a branch pipe 82 and a fourth two-position four-way switching valve 84, so that a hydraulic pressure equal to or higher than a predetermined pressure acts on each chamber. Has been prevented.

In the case of the second stage of the injection pressure, the three-position four-way switching valve 66 and the second and fourth two-position four-way switching valves 7
The solenoids I, I ₂ and I _{4 of} 0,84 are excited. As a result, the first chamber 38 and the second chamber 40 are further moved to the third position 4 via the first or second two-position four-way switching valve 64, 70, respectively.
It is connected to a hydraulic pump 72 via a direction switching valve 66. At this time, the third chamber 42 is in communication with the hydraulic oil tank T via a third two-position four-way switching valve 76.

Therefore, the hydraulic oil in the hydraulic oil tank T is
The hydraulic pump 72 passes through the three-position four-way switching valve 66 and further to the first chamber 38 through the first two-position four-way switching valve 64.
Further, they are introduced into the second chamber 40 through the second two-position four-way switching valve 70, respectively. At this time, since the third chamber 42 communicates with the hydraulic oil tank T, no hydraulic pressure is generated in the third chamber 42, and no resistance is given to the movement of the rod 14.
As a result, the operating oil pressure of the first chamber 38 overcomes the operating oil pressure of the second chamber 40, and the piston 12 and the rod 14 are moved from the chain line in FIG.
Move to the position shown above, and
Move the connected screw 56 to the left in the drawing . Therefore, in this case, a larger injection pressure can be applied to the screw 56 as compared with the first stage of the injection pressure.

In the case of the third stage of the injection pressure, the three-position four-way switching valve 66, the third and fourth two-position four-way switching valves 7
The 6,84 solenoids I, I ₃ and I ₄ are excited. As a result, the first chamber 38 and the third chamber 42 become the first or third chamber, respectively.
Through a two-position four-way switching valve 64,76, and further through a three-position four-way switching valve 66 to a hydraulic pump 72. At this time, the second chamber 40 is communicated with the hydraulic oil tank T via the second two-position four-way switching valve 70 and the three-position four-way switching valve 66.

Therefore, the hydraulic oil in the hydraulic oil tank T is
The hydraulic pump 72 passes through the three-position four-way switching valve 66 and further to the first chamber 38 through the first two-position four-way switching valve 64.
Further, they are introduced into the third chamber 42 via the third two-position four-way switching valve 76, respectively. At this time, since the second chamber 42 communicates with the hydraulic oil tank T, no hydraulic pressure is generated in the second chamber 42 and no resistance is given to the movement of the piston 12. Thereby, the operating oil pressure of the first chamber 38 overcomes the hydraulic pressure of the third chamber 42, a chain line a piston 12 and rod 14 in FIG. 3
Moved to the position shown above, via the connecting member 54
The connected screw 56 is moved to the left in the drawing . Therefore, in this case, a larger injection pressure can be applied to the screw 56 as compared with the second stage of the injection pressure.

In the case of the fourth injection pressure, the third position 4
Solenoid I of the directional control valve 66 and a fourth two-position four-way switching valve 84, I ₄ is energized. As a result, only the first chamber 38 has the first two-position four-way switching valve 64 and the three-position four-way switching valve 66.
Through the hydraulic pump 72. The second chamber 40 is connected to the hydraulic oil tank T via a second two-position four-way switching valve 70 and a three-position four-way switching valve 66, and the third chamber 42 is provided with a third two-position four-way switching valve 76. The hydraulic fluid is communicated with the hydraulic oil tank T through the intermediary.

Therefore, the hydraulic oil in the hydraulic oil tank T is
It is introduced into the first chamber 38 via the three-position four-way switching valve 66 and further through the first two-position four-way switching valve 64 by the hydraulic pump 72. On the other hand, since the second chamber 40 and the third chamber 42 are in communication with the hydraulic oil tank T, no hydraulic pressure is generated in both chambers, and there is no resistance to the movement of the piston 12 or the rod 14, respectively. Not. Thereby, the piston 12 and the rod 14 are moved to the position shown above the chain line in FIG. 3 without receiving any resistance to the operating oil pressure of the first chamber 38 ,
Screw 56 connected via connecting member 54 to the left in the drawing
Move to Therefore, in this case, a larger injection pressure can be applied to the screw 56 as compared with the third stage of the injection pressure.

Next, a case where the screw 56 is retracted will be described. In this case, only the solenoid B of the three-position four-way switching valve 66 is excited, and the second chamber 40 is hydraulically driven through the second two-position four-way switching valve 70 and further through the three-position four-way switching valve 66. It is connected to the pump 72. On the other hand, the first chamber 38 and the third chamber 42 are connected to the hydraulic oil tank T via a three-position four-way switching valve 66 or a third two-position four-way switching valve 76, respectively.

Therefore, the hydraulic oil in the hydraulic oil tank T is
Introduced only to the second chamber 42 by the hydraulic pump 72, the piston
Since the hydraulic pressure acts on the valve 12 in the reverse direction, the first chamber 38 and the third chamber 42 are both in communication with the hydraulic oil tank T.
Moving the piston 12 and rod 14 from the chain line in FIG. 3 to <br/> position shown downwardly, i.e., is coupled through a coupling member 54
Screw 56 is retracted.

When rotating the screw 56,
3-position 4-way switching valve 66 and first 2-position 4-way switching valve 64
The solenoids I and P are excited, and the hydraulic motor 62
Is connected to the hydraulic pump 72 via the two-position four-way switching valve 64 and the three-position four-way switching valve 66. At this time, injection cylinder
The 10 first chamber 38 is connected to a screw rotation back pressure relief valve 68 via a first two-position four-way switching valve 64. Therefore, the hydraulic oil in the hydraulic oil tank T is introduced into the hydraulic motor 62 by the hydraulic pump 72, and the screw 56 rotates in a predetermined direction, so that the raw material is transferred forward while being melted and kneaded.

[0029]

As is apparent from the above description, the injection cylinder is composed of large-diameter and small-diameter rods facing each other with the piston as a boundary, and an inner cylinder formed from the end of the large-diameter rod toward the piston. A first chamber, a second chamber, and a third chamber are formed in the injection cylinder, and a pressure receiving area of the piston in the first chamber is roughly constituted by a ram having an inner hole inserted into the cavity. There greater than the sum of the effective pressure receiving area of the lumen of the large-diameter rod in said third chamber and the pressure receiving area of the piston in the second chamber, receiving the piston in the second chamber
Effective pressure area of the lumen of the large diameter side rod definitive in the third chamber
It is set larger than the pressure receiving area, further, the first chamber, by connecting the second chamber and the third chamber to the hydraulic circuit, the pressure-receiving surface
Hydraulic oil can be selectively introduced or discharged into the first, second, or third chambers having different products, and hydraulic pressure can be applied to the piston or rod in a stepwise manner. It is possible to obtain an injection pressure selection mechanism capable of performing multi-stage switching of the injection pressure of a screw which is relatively inexpensive.

[Brief description of the drawings]

FIG. 1 is an operation circuit diagram showing one embodiment of the present invention.

FIG. 2 is a function table of the operation circuit diagram of FIG. 1;

FIG. 3 is a sectional view showing a double rod type cylinder according to the present invention.

[Explanation of symbols]

 10 Injection cylinder 12 Piston 14 Rod 14a Large diameter rod 14b Small diameter rod 16 Ram 18 Rod cover 22 Bush 26 End cover 38 First chamber 40 Second chamber 42 Third chamber 54 Connecting member 56 Screw 60 Hydraulic operation circuit

Claims (1)

(57) [Claims] A piston having a large diameter and a small diameter facing each other with respect to the piston; a rod cover inscribed in an outer peripheral surface of the piston and disposed around the rod; A bush penetrating the center of the small-diameter rod and attached to one side of the rod cover; and an inner hole inserted into a bore formed from the end of the large-diameter rod toward the piston. Ram and
An end cover provided around the large-diameter rod in which the ram is inserted and attached to the other side surface of the rod cover and having an air communication hole; and the piston and the small-diameter rod A space defined by the rod cover and the bush is defined as a first chamber, and a space defined by the piston, the large diameter rod, the rod cover and the end cover is defined as a second chamber, and the large diameter rod is defined as a second chamber. The space formed in the lumen of the third chamber is a third chamber, and the pressure receiving area of the piston in the first chamber is the second chamber.
Put to the third chamber and the pressure receiving area of the piston in the chamber
That greater than the sum of the effective pressure receiving area of the lumen of the large-diameter rod, the pressure receiving area of the piston in the second chamber is set larger than the effective pressure receiving area of the lumen of the large diameter side rod definitive in the third chamber An injection cylinder, wherein the first chamber, the second chamber, and the third chamber form a hydraulic operation circuit that changes the injection pressure of the screw in a stepwise manner through a connecting member connected to an end of the small diameter rod. Injection pressure selection mechanism for an injection molding machine characterized by being connected to each other