JPH02248231A - Hydraulic circuit of injection molding machine - 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 [Field of Industrial Application] The present invention relates to an improvement of a hydraulic circuit in a hydraulic injection molding machine.

[Prior art and problems to be solved by the present invention] The hydraulic circuit of conventional medium-sized and small-sized injection molding machines usually uses a single hydraulic pump, and an operating cylinder is connected to one hydraulic line. Therefore, if a compound operation is performed, such as ejecting after opening the mold, they will interfere with each other and the operation will become extremely unstable.The next operation must be performed until mold clamping, injection, holding pressure, and other processes are completed. This prevented the process from becoming more cyclical.

[Purpose of the invention]

The present invention was made in view of the problems of the conventional example, and its purpose is to improve the hydraulic circuit and to achieve a high cycle of operation that has not been seen in the past in medium and small hydraulic injection molding machines. The purpose is to provide a hydraulic circuit that achieves this goal.

[Means for solving problems]

In an injection molding machine, the present invention achieves a high cycle through a combined operation that simultaneously performs mold opening and ejection. In an injection molding machine operated in
■ Hydraulic pump (1) via on-off valve (6)
A hydraulic line connected to the eject cylinder (1'J) and having an accumulator (7) is connected to the eject cylinder (1'J).

In claim (2), the resin injected into the mold is cooled while the raw resin is being charged, and the subsequent mold opening, ejection, etc. are performed sequentially to achieve a high cycle speed. In order to achieve this, ■ In an injection molding machine where most of the injection molding process is performed by hydraulic operation, ■ Mold opening/closing cylinder c! 0) and eject cylinder (1
(1) Connect the screw 0υ to the hydraulic pump (separate drive source 07 that rotates independently from 11).

; is adopted as a technical means.

Furthermore, in claim (3), in order to perform the highest speed operation of simultaneously performing cooling of the resin injected in the mold during charging of raw materials, subsequent mold opening, and ejecting, the following steps are taken: ■ The injection molding process. In an injection molding machine that is mostly operated by hydraulic operation, ■ The head side (10a) of the injection cylinder 0ω is connected to the hydraulic pump (1) via the on-off valve (6), and has an accumulator (7). Connect to the hydraulic line, and connect the screw aυ to a hydraulic pump (a separate drive source that rotates independently from 11).

■ Connect the mold opening/closing cylinder (2) to the hydraulic pump (1), and ■ Connect the hydraulic line with the accumulator (7) connected to the hydraulic pump (11) via the opening/closing valve (6) and the eject cylinder α. Connecting.

; is adopted as a technical means.

[For production]

As shown in Figure 3, there are three ways to achieve a high cycle.The first is to eject the molded product inside the cavity while opening the mold, and the second is to eject the molded product while charging the resin. The third case is to open the mold and then eject the molded product in the mold cavity, and the third case is to open and eject the mold at the same time while charging the resin.

In the first case, as stated in claim (1),
The mold opening/closing cylinder 0ω is connected to the hydraulic pump (1), and the hydraulic line connected to the hydraulic pump (1) via the opening/closing valve (6) and having an accumulator (7) is connected to the eject cylinder 0 wound. For, on-off valve (6)
By closing the hydraulic pump (11) line and the line containing the accumulator (7) become independent.
As a result, it is possible to stably operate the mold opening/closing cylinder Q and the eject cylinder O at the same time, and the cycle time can be shortened accordingly.

In addition, the second high cycle is to connect the mold opening/closing cylinder QO1 and the eject cylinder 01 to the hydraulic line, and to connect the screw 0Φ to a separate drive source 0η that rotates independently from the hydraulic pump (11). The mold opening and ejecting operations can be performed using the hydraulic line, and the rotation operation of the screw Oe can be performed using a separate drive source Q71. As a result, the mold opening and ejecting operations can be performed sequentially while the raw material is being charged by the screw rotation operation. Compared to the conventional method, which requires sequential mold opening and ejection after charging, it has become possible to achieve a much higher cycle speed.

Furthermore, in claim (3), the screw 0υ is connected to a separate drive source 07 that rotates independently from the hydraulic pump (1), and the mold opening/closing cylinder (2ψ is connected to the hydraulic pump (11) and the opening/closing valve The eject cylinder 091 is connected to the hydraulic line which is connected to the hydraulic pump (1) through the hydraulic pump (1) and has the accumulator (7) through the hydraulic pump (6). The operation of the mold opening/closing cylinder (2Q is performed by the hydraulic pump (1, 1 line), and the eject cylinder a1 is operated by the hydraulic bomb line by closing the opening/closing valve (6). It was separated and operated by an accumulator (hydraulic line with power), and as a result, the above three operations could be performed simultaneously, achieving even higher cycles.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings. In Figure 1 (1)
is a variable discharge amount pump driven by an electric motor (2), and a swash plate angle adjustment cylinder (4) is controlled by a pump control device (3).
), the required pump pressure and discharge amount are set and pressure oil is delivered for each injection molding process. The set values of the pressure and discharge amount are set by the set values of the microcomputer type control device (24). In addition, the pipe line (a
), the pump control device (3) adjusts so that the pressure oil of the load element α is automatically discharged even if a load occurs.

From the branch point (5) through the electromagnetic shut-off valve (6), the pipe line (b
1, an accumulator (7) and a pressure sensor (8) are attached to the pipe (b), and are connected to the P bow 1- of a directional flow rate control valve (9) of a proportional solenoid valve type. The pipe (C) from the A boat of the directional flow rate control valve (9) is connected to the nozzle touch directional control valve 02 via the head side (10a) of the injection cylinder a0 and the boat (lla) of the shuttle valve QO.
1 P baud 1-. Directional flow control valve (9
) is connected to the P boat of the suckback directional control valve Q31 and the eject directional control valve Q.
4) is connected to the P boat. The pipe line (g) of the suckback directional control valve (13) from the A boat is connected to the rond side (10b) of the injection cylinder 0ω, and is connected to the pipe line (C) from the B boat.

Another pipe line (fe) from the branch point (5) is connected to a boat (llb) with a shuttle valve 0υ, and a third pipe line (fl from the branch point (5) is a directional control valve for mold opening/closing ( lsi's P
Attached to the boat.

The piston body (10c) of the injection cylinder 0 (6) is installed to penetrate the injection cylinder Ql and to be slidable forward and backward.

The screw Oe is attached to the piston body (10c) so as to be able to move forward and backward integrally and rotate freely, and is rotationally driven by an electric motor (AC servo motor) fixed to the rear part of the piston body (10c). The plastic resin supplied from a hopper (not shown) is melted and kneaded while being transferred to the front of the screw O[9, and as a reaction, the screw Oe retreats together with the piston body (10c) to perform a charging action. At the end of the charging process, suckback is performed in which the piston body (10c) is slightly retracted using pressure oil from the A boat of the suckback directional control valve α. In the injection process of the next cycle, pressure oil is supplied from the pipe ic> to the head side (10a) of the injection cylinder 0[+1], the piston body (loc) presses the screw Q6), and the melt charged at the tip of the screw is Inject the resin into the mold cavity.

The nozzle touch cylinder α moves the entire injection device forward and backward, and is operated by the nozzle touch directional control valve. The eject cylinder 0 is used to prevent the molded product from being ejected after molding is completed, and is operated by the eject directional control valve αa. Mold opening/closing cylinder C! ω is operated by the mold opening/closing directional control valve Q51, but the mold is closed by a safety door (not shown).
The safety door valve (21) operates only when it is in the restored state.

The proportional electromagnetic valve type directional flow control valve (9) will be described in detail. This directional flow control valve (9) is operated by the proportional solenoid valve method, but has a function similar to a servo valve, and its spool is driven by a torque motor (9a), (9b).
) is operated in positive and negative directions with high response according to the electric signal applied to the control valve (9), and controls the flow and pressure of the pressure oil passing through the control valve (9).

When the spool operates to its final end, the A and B boats are switched in the same way as a conventional directional switching valve.

■ A differential transformer (9c) is installed inside the control valve (9), which feeds back electrical output proportional to the opening of the spool to the electrical signal input terminal (25), and the valve itself generates meteor feedback. have the ability to do so. Therefore, unlike in the case of conventional servo valves, there is no need to input electrical signals from a position sensor attached to the injection member, and feedback control of the injection speed and back pressure during charging can be performed.

■ Furthermore, it is less susceptible to the effects of hydraulic fluid dirt and foreign matter, which are the disadvantages of servo valves, and is easier to maintain.

It has this feature.

Injection pressure/flow rate setting signals are input from the input device of the microcomputer controller (24) via the signal line (k) to the input terminal (23) of the comparator (22) for the above-mentioned directional flow rate control valve (9). and the output terminal (25) of the input amplifier (22)
The control valve (9) is connected to a torque motor (9a) (9b) which operates the spool of the directional flow rate control valve (9) via an amplifier (9d) inside the control valve (9). Further, for the pressure feedback function, an electric signal line (0) from a pressure sensor (26) mounted on the head side of the injection cylinder 0ω is connected to an input terminal (27) of the comparator (22).

A three-phase wattmeter (28
) is installed to measure the momentary power flowing into the molding machine from the input power supplies R, S, and T, and the measured values are input to the microcomputer type control panel (24) via the signal line (n). . In addition, the signal from the pressure sensor (8), which is constantly sensing the state of source pressure drop during the injection process of the accumulator (7), is sent to the microcomputer control device (2) through the signal line (1'l).
4) is entered. On the other hand, the microcomputer type control device (24
), a signal line (m) for controlling the AC servo motor 0η, and a signal line (7) for controlling the pump control device (3) are respectively output.

Comparing the hydraulic circuit configuration of the present invention shown in FIG. 1 with the conventional hydraulic circuit configuration shown in FIG. 2, the present invention has the following structure. (In Figure 2, parts with the same functions as in Figure 1 are numbered the same.) ■ A proportional electromagnetic type directional flow control valve (9) that allows minor closed control of the valve opening using a differential transformer (9c). , the pressure sensor (26) attached to the head side (10a) of the injection cylinder u0 performs feedback control of the injection pressure and back pressure during charging in the same way as a servo valve, and the injection speed is controlled by the pressure sensor (26) mounted on the head side (10a) of the injection cylinder Although it does not use a position sensor, it performs control similar to Habo feedback control.

■ In the conventional circuit, the pipe line (
The pipe (X) was connected to the P boat of the directional control valve for all cylinders, but in the present invention, it is divided into three pipes from the branch point 5, and the pipe (b ), a pipe line fO) is connected to the nozzle touch cylinder, and a pipe line ([) is connected to the mold opening/closing cylinder, and the rotation of the screw αe is driven by an AC servo motor (an) instead of the conventional hydraulic motor (53). This is done independently of the hydraulic circuit.

As a result, a compound operation, which will be described later, is performed and the cycle is shortened.

(2) A power measuring device (28) is installed on the power input side of the pump electric motor (2) and the screw drive electric motor (On) so that the load power can be measured moment by moment.

■ The microcomputer type control device (24) that controls the entire operating system of the hydraulic circuit and electric motor (2) also has a counting ability, and the output circuit is connected to the signal line (G) leading to the directional flow control valve (6).
), a signal line (1) leading to the control device (3) of the variable discharge pump <1), and a signal line (@) leading to the AC servo motor aη for charging.In addition, the input circuit includes the injection cylinder a [Signal line from pressure sensor (26) of Il (
(b) The operation of the present invention having two or more configurations including a signal line (P) from the accumulator pressure sensor (8) will be described with reference to FIG.

■Mold clamping process The variable discharge oil pump (1) applies the hydraulic pressure and oil amount required for the load to the mold opening/closing cylinder Qφ as measured. At this time, the electromagnetic on-off valve (6) and the directional flow control valve (9) are fully closed.
Mold clamping is performed only with the variable discharge amount pump (1).

■In the injection speed process in which the cavity is filled with the molten resin charged in the cycle before the injection process, the directional flow control valve (9) is
→A, 13→T, the pressure oil from the accumulator (7) is controlled by the injection speed setting value from the input terminal (23), and the flow rate of the control valve (9) itself by the differential lance (9C). Controlled semi-closed by feedback action. At this time, open the electromagnetic on-off valve (6) and
The pressure sensor (8) measures the drop in the pressure of the rotor (7) due to discharge, and controls the variable discharge amount pump (1) via the microcomputer control device (24) and pump control device (3).
) to replenish the accumulator (7) with pressure oil.

In the pressure holding process in which filling pressure is applied to the molten resin filled in the cavity and the pressure is moved to holding pressure, the directional flow control valve (9)
The pressure is controlled while remaining at P-+, and the input terminal (2
Closed control is performed so that the filling/holding pressure set value from 3) and the actual value from the pressure sensor (26) are equal.

In this way, accurate and stable injection is performed without variations in surface quality and weight of the molded product. Also in this pressure holding step, the accumulator (7) is replenished with pressure oil.

■Charging process The AC servo motor 0η rotates the screw 0[9 according to the command from the control device (24) and charges the front of the screw 0[9 while melting and kneading the plastic resin. Body (1
0c) and retreat. The proportional solenoid type directional flow control valve (9) can be switched from P-+B, A to T, but A-
The resistance value when passing +T, that is, the back pressure, is controlled in a closed manner so that the set value and the actual value measured by the pressure sensor (26) are equal. Conventional back pressure control uses a relief valve (5
2), the opening was only controlled by 2).

Also, at the end of the charging process, the suckback directional control valve α becomes P-+8, and the piston body (10c) is slightly retracted by the pressure oil from the A boat, but the speed at this time is the differential transformer (9C). ) is controlled in a semi-closed manner by the flow rate fee 1' back action of the control valve (9) itself, ensuring an accurate amount of suck back. Even during this pressure holding and sack pack process, the electromagnetic on-off valve (6) is open, and the accumulator (7) is replenished with pressure oil.

■About compound operations such as ejecting and charging while opening the mold.

In the conventional circuit shown in Figure 2, if ejection is not performed after the mold opening is completed, the mold opening/closing and eject cylinders are operated by a single hydraulic power source, making both operations uncertain. In the circuit of the present invention shown in the figure, the mold is opened and closed by a pump, and the directional flow control valve (9) is switched from P- to B to eject from the accumulator (7) to the pipe (bl).
, (Since this can be performed via di, it is possible to perform a combined operation by superimposing the mold opening by hydraulic pressure and the ejecting operation by the accumulator.)

In addition, by shortening the cooling time of the molded product by using a chiller, etc., the mold can be opened quickly after cooling, but in the conventional circuit shown in Figure 2, the screw drive for charging was performed by a hydraulic rotor. So I had to wait until charging was completed. In the circuit of the present invention shown in FIG. 1, the screw is driven by an AC servo motor aη that is not related to the hydraulic circuit, so that the compound operation of charging can be performed freely while opening the mold.

If we summarize the above-mentioned complex operations according to Figure 3, we get
If the mold opening and ejecting operations that are performed after charging are performed simultaneously as shown in figure (b) to shorten the process,
There are cases where the mold opening and ejection are performed sequentially during charging to shorten the process as shown in C1, and there are also cases where the mold opening and ejection are performed simultaneously during charging as shown in the same figure (di). is the fastest cycle.

Furthermore, since the screw is connected to a separate drive source that rotates independently from the hydraulic pump, it is possible to charge it while injecting it. For example, for large molded products, the charge determined by the screw diameter x screw stroke can be charged. If the amount of injection is insufficient, it is possible to perform so-called rotary injection, in which injection is performed using hydraulic pressure and charging is performed using an electric motor 0η. This is performance improvement due to composite operation.

As described above, the actuation system according to the present invention has three independent systems: the hydraulic line from the pump (1), the hydraulic line from the accumulator (7), and the screw rotation drive by the electric motor, so the above-mentioned combined operation cannot be performed. It is.

■About calculation control using load power measurement.

In the present invention, the input LJ of the electric motor (2), which is the input of the hydraulic load, and the charging AC servo motor αη.

A power needle (28) is installed on the power supplies R, S, and T that combine V and W wires to measure the total load power throughout the entire injection molding process, and the microcomputer type control device (
24). An example of the measurement results is shown in Fig. 3. The average power W for one cycle is calculated from this power fluctuation curve, and the power is adjusted to replenish the accumulator (7) so that the peaks and troughs for W are averaged. Adjust W8.

〔effect〕

The present invention provides an injection molding machine in which all or most of the injection molding process is performed by hydraulic operation, in which a mold opening/closing cylinder is connected to a hydraulic pump and is also connected to the hydraulic pump via an opening/closing valve. Since the hydraulic line with the accumulator and the eject cylinder are connected, the hydraulic pump line and the line with the accumulator become independent by closing the opening/closing valve, and as a result, the mold opening/closing cylinder and the eject cylinder are connected to each other. It has the advantage that it can operate stably at the same time, and the cycle time can be shortened accordingly.

Further, in claim (2), in an injection molding machine in which most of the injection molding process is performed by hydraulic operation, the mold opening/closing cylinder and the eject cylinder are connected to a hydraulic line, and the screw is rotated independently from the hydraulic pump. Since it is connected to a separate drive source, the mold opening and ejecting operations can be performed using the hydraulic line, and the screw rotation operation can be performed using a separate drive source.As a result, while the material is being charged by the screw rotation operation, The mold opening and ejecting operations can be performed sequentially, making it possible to achieve a much higher cycle speed than the conventional method, which required mold opening and ejecting to be performed sequentially after charging.

Furthermore, in claim (3), Suf'), -x, 'Jω
A separate drive source 0η that rotates independently from the hydraulic pump (1)
and connect the mold opening/closing cylinder CHI to a hydraulic pump (1
) is connected to the hydraulic pump (1) via the on-off valve (6), and the hydraulic line having the accumulator (7) is connected to the eject cylinder α, so the on-off valve (6) is By closing, the screw rotation operation is performed by a drive source αη separate from the hydraulic pump, and the operation of the mold opening/closing cylinder (21) is performed in the hydraulic pump (1) line, and the eject cylinder 0 and opening/closing valve (6 ), it is separated from the hydraulic pump line and operates on the hydraulic line with the accumulator (7).As a result, the above three operations can be performed at the same time, achieving even higher cycles. It was completed.

[Brief explanation of drawings]

Fig. 1: Hydraulic circuit diagram of the present invention Fig. 2: Hydraulic circuit diagram of a conventional example Fig. 3: 1 cycle process during conventional injection molding and 1st to 3rd implementations of the present invention Comparison diagram of an example 1-cycle process. TI)...Hydraulic pump, (6)...Opening/closing valve, (7)...Accumulator, 0ω...Injection cylinder, (10a)...Head side of injection cylinder, O
6)...Screw oD...separate drive source,
0 scratches...Eject cylinder, Q...Mold opening/closing cylinder.

Claims (3)

[Claims] (1) In an injection molding machine in which all or most of the injection molding process is performed by hydraulic operation, a mold opening/closing cylinder is connected to a hydraulic pump, the mold opening/closing cylinder is connected to the hydraulic pump via an opening/closing valve, and the hydraulic accumulator has an accumulator. A hydraulic circuit for an injection molding machine characterized by connecting a line and an eject cylinder. (2) In an injection molding machine where most of the injection molding process is carried out hydraulically, the mold opening/closing cylinder and eject cylinder are connected to a hydraulic line, and the screw is connected to a separate drive source that rotates independently of the hydraulic pump. A hydraulic circuit for an injection molding machine characterized by comprising: (3) In an injection molding machine in which most of the injection molding process is carried out by hydraulic operation, the screw is connected to a separate drive source that rotates independently from the hydraulic pump, and the mold opening/closing cylinder is connected to the hydraulic pump and opens and closes at the same time. A hydraulic circuit for an injection molding machine, comprising an eject cylinder and a hydraulic line connected to a hydraulic pump via a valve and having an accumulator.