JPS6033863A - Piston speed control device in injection molding equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for controlling the piston speed of an injection cylinder that advances a plunger tip of a shot plunger in an injection molding apparatus such as a die casting machine or an injection molding machine.

For injection molding such as general die casting machines,
The shape and volume of the cavity in the mold, the temperature of the mold, etc.
Accordingly, if the injection speed, injection pressure, etc. of the molten metal are inappropriate, the molten metal may flow into the cavity.

Various problems occur, such as when breakage occurs, when cavities occur in the injection molded product, and when dimensional accuracy and product strength decrease.

In order to prevent the harmful effects of stiffness, conventional meter-in circuits include a meter-in circuit in which a flow control valve is provided in the hydraulic oil inflow circuit to the piston rear chamber of the injection cylinder, or a flow control valve is provided in the hydraulic oil outflow circuit from the piston front chamber. Meter error: The piston speed of the injection cylinder, that is, the injection speed of the molten metal is controlled by the circuit, etc.

For example, basic circuit 11 in the meter-in circuit, Fig. 1f
As shown, a hydraulic source 1 such as a hydraulic pump or an accumulator
An inflow circuit 16 from 1 to the piston rear chamber 221 connected to the injection cylinder through the switching valve 12 via the flow control valve 14, and an outflow circuit from the piston front chamber n connected to the injection cylinder to the oil tank 15 through the switching valve 1λ 17, the flow control valve 1
4) controlling the amount of hydraulic oil flowing into the piston rear chamber n; controlling the forward speed of the piston 21, that is, the forward speed of the plunger tip 4 in the injection sleeve row;
This determines the injection speed of the molten metal.

Further, as shown in FIG. 2, there is also a meter-in circuit constituting a run-around circuit 18 that communicates between the piston front chamber of the injection cylinder and the okara piston rear chamber 221.

By the way, the inventors of the present invention have developed a conventional flow control valve 141 that controls the injection speed of molten metal, that is, the amount of hydraulic oil flowing into the injection cylinder or the amount of hydraulic oil flowing out from the injection cylinder.
As an alternative, we have recently developed a flow control valve 30 that is driven by a pulse motor and has faster response.

This flow rate control valve is of course axially oriented as shown in Figure 3. An axially moving valve spool 34 is provided.

Furthermore, an integral nut shaft 35 is connected to the rear part of the valve spool 34, and the internal shaft center part of the nut shaft is screwed into the threaded shaft part by a ball screw a'7+.

This screw shaft 36 is connected to a pulse motor 41 whose rotation amount can be controlled.
The rotation axis f is connected to the coupling 38 so that it rotates.

In addition, 45 is a key to prevent rotation of the nut shaft, and a permanent magnet 46 is fixed to a part of the surface of the nut shaft, and a part of this permanent magnet and a part of the opposing casing 47 is equipped with a sensor called, for example, a zero cross sensor. A position detector 48 based on magnetic action is attached. The position detector 48 is composed of a proximity switch that is sensitive to the movement of a permanent magnet, and is designed to accurately detect the distance traveled in the axial direction of the nut shaft or valve spool, and provide feedback to the control device. . In addition, the zero position of the valve spool is detected using a permanent magnet and a position detector 48.
As a result of the action 1, the electrical E can be detected and the pulse motor 41 can be accurately stopped at that position via the control device, and this position detector 48 has an accuracy of 0.
01% is used.

This flow rate control valve (equipment) is connected to the valve spool 34 via a ball screw and nut shaft 35 according to the rotation of the pulse motor 41.
moves back and forth in the axial direction to instantaneously adjust the opening/closing and opening degree of the valve to control the flow rate of hydraulic oil.

As described above, this flow rate control valve 3Q has the hydraulic oil inlet 31 on the end face in the axial direction, and the hydraulic oil outlet &t on the side surface.
f Inside the cylindrical valve body.

The valve spool 34 is driven in the axial direction by the operation of the pulse motor 41 to control the flow rate, and in one operation, the axial thrust of the valve spool 34 caused by the oil 1 is controlled according to the opening amount of the valve spool and the increase in the movement speed. To rapidly reduce depression
This reduces the driving force necessary for high-speed switching of the flow rate, further improves the performance of high-speed switching of the flow rate of the hydraulic oil that tends to cloud the flow rate control valve (9), and also reduces the driving force.

Therefore, in this flow rate control valve (9), the amount of opening of the valve spool 34 is determined by the amount of rotation, that is, the angle of rotation, of the pulse motor 41 based on the command signal from the control device.

The flow rate of hydraulic oil to the injection cylinder 20 is controlled, and the rate of change in the opening of the flow control valve (supplement) is determined by the speed of rotation of the pulse motor 41. The rising state of the injection speed in the injection cylinder 201 is determined. The flow rate control valve 3o having such a structure and operation has a time delay nJ knee 1-. ) The flow rate can be controlled within seconds, and the response is extremely good compared to normal flow control valves.

In addition, the operability and operational accuracy of valve opening and closing have become extremely high.

In this way, controlling the hydraulic fluid at a very high speed and accurately makes it possible to control the injection speed of the molten metal even more accurately, and as shown in the solid line in the figure, changes in the injection speed of the molten metal can be finely (controlled). It became a thing.

The injection speed of the molten metal controlled by the flow rate control valve 30 having such high-speed response has a first half in the low injection speed section T1.
and the molten metal filled in the injection sleeve is at a low injection speed V
This is the section for extruding into the cavity at T, and the low-speed injection section T
The initial value of 1 is to gradually increase the injection speed to a low injection speed v1 of 1, thereby preventing the molten metal filled in the injection sleeve from backflowing out from the molten metal inlet of the injection sleeve to the outside of the injection sleeve. Then, the final stage T61 of the low-speed injection section T1
The injection speed Vl f is once decelerated at the entrance of the molten metal, and when the molten metal reaches the cavity, it is ejected from the runner, which is a narrow gap, into the cavity, which is a relatively wide space.

Prevents the gas (air) in the cavity from mixing with the molten metal, eliminating the risk of creating cavities in the product.
"r.

Inlet Then, after the molten metal reaches the cavity △1 and the molten metal slightly flows into the cavity, the high injection speed v2 is increased at once or stepwise to fill the molten metal into the cavity as a cavity filling section T2. to prevent missing products and a decrease in dimensional accuracy. Note that at the completion of injection in the filling section T2 (iQ), the cavity is filled with molten metal and the injection speed suddenly drops to zero.

Due to the cylinder pressure at this time, the molten metal completely fills every corner of the cavity. Then, depending on the size or shape of the cavity, change the final injection speed v3 to high injection speed ■2
This reduces the impact pressure at the end of injection, which can cause problems such as when the injection molded product is thin, due to the molten metal flowing into the mating surface of the mold from the cylinder pressure. May prevent puffiness.

By the way, the total injection time of the above-mentioned molten metal is generally as short as several seconds.
In particular, the rise time and fall time that change the injection speed are extremely short, ranging from several hundredths of a second to several tens of hundredths of a second.

Therefore, increasing or decreasing the injection speed has an extremely quick response.
Moreover, accurate speed control is required.

However, when the above-mentioned meter-in circuit is used to control the injection speed of the molten metal, there may be a characteristic in which a time sequence occurs at the falling edges 81 and 821, as shown by the broken line in FIG.

This is the piston 21. The inertia caused by the kinetic energy f of the mechanically moving parts such as the cylinder rod and the hydraulic oil is large, and as mentioned above, the fall time 81.82 is extremely short, so deceleration cannot be performed as specified.A'? 0, and there are many things that reduce the quality of injection molded products.

The present invention eliminates these drawbacks and the piston 21. It is possible to suddenly decelerate the cylinder rod and therefore the plunger tip 4 during high-speed movement, and in conjunction with the highly responsive flow control valve (capital), instantaneous acceleration and deceleration can be made to produce high-quality injection molded products. This is a piston speed control device for

In this embodiment of the present invention, as shown in FIGS. 5 and 6, a first flow control valve 30 is provided in the inflow circuit 16 to the piston rear chamber 22, and a first flow control valve 30 is provided in the inflow circuit 17E from the piston front chamber. An injection molding apparatus that includes two flow control valves 50'E and controls the injection speed of molten metal by changing the opening degree of the second flow control valve button in accordance with the opening degree of the first flow control valve (9). piston speed control device.

Providing the outflow circuit 171 and the second flow rate control valve 50 in this manner is as follows: The inventor conducted a detailed measurement and investigation into the relationship between the injection speed and the quality of the finished product, and found that the time delay during deceleration makes it difficult to maintain high quality. This time delay is caused by the large inertia of the mechanically moving parts and the hydraulic oil, external forces such as the load on the cylinder rod 16, frictional force of the sliding part, and discharge resistance of the hydraulic oil. This is because the fluid pressure applied to the front surface of the cylinder of the piston 21 is possible within the range of E.

In other words, only the main part of the meter-in circuit shown in Fig. 1 is
As shown in the figure, the flow rate control valve 141 limits the inflow amount of hydraulic oil per unit time E, and the amount of hydraulic oil flowing into the piston rear chamber 4 is controlled by the piston 21 and the cylinder rod 26. As a result, the plunger tip 4 moves forward.

At this point, from the plunger 29 + the cavity I, the resistance of the injected molten metal, etc.) from the cylinder rod, the load F
l is added, and the frictional force F2 of the sliding parts such as the piston 21
As the piston 21 moves forward, the piston front chamber 2
In order to discharge the hydraulic oil of No. 3, a reaction force F3 is generated on the piston 21 from the hydraulic oil here, and these forces (Fl, F2.F3)
prevents the piston 21 from moving forward.

However, the load Fl due to the resistance of the molten metal, etc. becomes a large load when the injection speed is increased, but when the injection speed is decelerated, the load Fl can become a large load.The frictional force F2 of the sliding part is also extremely small. Further, the reaction force F3 that the piston 21 receives from the hydraulic oil is also usually a small value. For this reason, it takes time for the inertia of the moving parts and the hydraulic oil to be canceled out, and as shown in the broken line in Figure 4, the fall 81.82 In other words, when the injection speed is decelerated, I
This caused a time delay.

This causes a deterioration in the quality of injection molded products.

Also, in FIG. 8, which shows only the essential parts of FIG. 2, which is a meter-in circuit with a run-around circuit 18, the load Pi applied to the cylinder rod, the frictional force F2 of the sliding part, and the hydraulic fluid are transferred from the front of the piston to the rear of the piston. The reaction force IP3 that the piston 21 receives from the hydraulic oil when moving to the chamber 22 is small, as in the case of the basic meter-in circuit shown in FIG. 7, and a time delay occurs when the injection speed is decelerated. .

In addition, in the case of a cylinder with run completion land circuit 18'i-T, the area of the rear surface U of the piston is equal to the area of the front surface of the piston plus the cross-sectional area of the piston rod. No.

A force equal to the area multiplied by the pressure P2 of the hydraulic oil is applied to move the piston rod 26 forward, and an amount of actuating oil equal to the moving distance l times the cross-sectional area of the piston rod, f, moves behind the piston through the flow rate control valve force. It is supplied to chamber n.

In this way, in the conventional meter-in circuit, there is a time delay in response to sudden deceleration. Therefore, in the present invention, a second flow rate control valve is provided in the outflow circuit of the okara in the piston front chamber, and the forward movement of the piston 21 is controlled. Accordingly, it provides resistance to the flow of hydraulic oil discharged from the piston front chamber, increases the reaction force Fr5 that the piston 21 receives from the hydraulic oil, and uses it as a brake during deceleration. did.

As described above, the present invention provides an inflow circuit 16 to the piston rear chamber 22.
In this injection speed control device, a first flow rate control valve 3o is provided, and a second flow rate control valve 50 that is linked to the opening and closing of the first flow rate control valve 30 is provided in an outflow circuit 171 from the piston front chamber 23. Since the inflow circuit 16f is provided with a flow control valve 30, when the flow control valve 301 controls the flow of hydraulic oil into the piston rear chamber 22, injection is performed at a high injection speed v2. The oil pressure P2 in the piston rear chamber in the filling section T2 also becomes lower than the oil pressure PI at the oil pressure source 111, as shown in FIG.

On the other hand, in the speed control of cylinder acceleration, the meter-out circuit, which is often used in conjunction with the aforementioned meter-in circuit as well as the conventional force), uses the piston rear chamber 22 as shown in FIGS. 9 and 10.
The pressure P1 of the hydraulic power source 11 is directly applied to this.

Since the forward speed of the piston 21 is controlled by controlling the amount of oil discharged from the piston front chamber 23, the gL.
・ Low injection speed section Tl as shown in β diagram T Filling section T21 where injection is performed at high injection speed
The hydraulic pressure that opens 21 degrees is equal to the hydraulic pressure Pi t of the hydraulic source 11. For this reason, when the impact pressure F3 at χOI is applied at the completion of injection, a large abnormally high pressure 'I-5' will be generated even if it is for a short time.

In a device having such a circuit, as described above, the oil pressure P2 of the piston rear chamber 22 in the filling section T21 is 5 lower than the oil pressure source Pl, so that the impact pressure is Even if P3 is applied, the peak value of the abnormally high pressure is low and has the advantage that there is no risk of adversely affecting the hydraulic circuit system.

In addition, if the $1 flow control valve used in the present invention E and the second flow control valve group are made equal in opening degree change, the second flow control valve 5 is used.
If a flow rate control valve having the same size and structure as the first flow rate control valve and having high-speed response is used, the injection speed can be controlled extremely accurately.

In short, the present invention provides a piston speed control device for an injection cylinder or the like of an injection molding device, and a first flow control valve is provided in the inflow oil path to the piston rear chamber.

A second flow rate control valve is provided in the outflow oil path from the piston front chamber, and a second flow rate control valve is provided in a manner corresponding to the opening degree of the first flow rate control valve.
This is a piston speed control device for an injection molding machine equipped with a device that changes the opening degree of a flow control valve.

In this manner, the present invention provides a flow control valve 3 having high-speed response.
0, and the passage resistance of the hydraulic oil in the outflow circuit 17 was increased appropriately using the second flow control valve 501 to increase the reaction force IF58 that the piston 21 of the injection cylinder receives from the hydraulic oil. It is possible to accelerate and decelerate, accurately control changes in injection speed within a short injection time, obtain high quality injection molded products, and reduce the peak pressure of impact pressure at the completion of injection. This piston speed control device has various advantages such as being able to prevent adverse effects on the hydraulic circuit by pressing the piston.

[Brief explanation of the drawing]

41 is a T diagram showing a meter-in circuit, FIG. 2 is a T diagram showing a meter-in circuit with a Ryaland circuit, FIG. 3 is a T diagram showing an example of a flow rate control valve using the present invention 1, Figure 1 shows the change in injection speed. 5 and 6 are diagrams showing the main parts of the hydraulic circuit of the control device according to the present invention, FIGS. γ and 8 are diagrams showing the main parts of the meter-in circuit, and FIGS. 9 and 10 are FIG. 1M11 showing the main part of the meter-out circuit is a diagram showing the cylinder oil pressure in the present invention f, and FIG. 12 is a diagram showing the cylinder oil pressure in the meter-out circuit. 11=hydraulic source, 12=switching valve, 14=control valve. 16 = inflow circuit, 17 = outflow circuit, 18 = run-a-land circuit, & 4-conflict, 20 injection cylinder, 21 = piston, 22 - piston rear chamber, 23 = screw) 76 chamber, 2
6 = cylinder rod s 'zs = shot tB sleeve, 29
= plunger tip, 30-first flow control valve, 5Q = second flow control valve.

Claims (1)

[Scope of Claims] In a piston speed control device for an injection cylinder or the like of an injection molding device, a first flow control valve is provided for an inflow circuit to the piston rear chamber, and an outflow circuit from the piston front chamber is provided. A second flow control valve is provided, and. A piston speed control device for an injection molding apparatus, comprising a control device that changes the opening degree of a second flow rate control valve in correspondence with the degree of opening f of the first flow rate control valve.