JP2000167891A - Method for shortening injection starting-up time in controlling injecting speed - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for shortening a starting-up time when an injection is started. SOLUTION: A first directional switching valve SOL1 for supplying hydraulic oil of a retracting side oil chamber 3 and discharging hydraulic oil of an advancing side oil chamber 4 and a second direction switching valve SOL2 for supplying the oil to the chamber 4 are disposed at hydraulic pressure passages between first and second hydraulic pumps P1, P2 and an injection cylinder 1. An unloading valve V2 is switched to a loading state in the state that a valve V1 is blocked by both the valves SOL1, SOL2 to supply the oil from a second hydraulic pump P2, cut off by the valve V1, and then when the valve SOL2 is switched, the pump P1 is simultaneously driven to start injecting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for shortening the injection start time of a hydraulically operated injection cylinder.

[0002]

2. Description of the Related Art In a conventional injection hydraulic circuit shown in FIG. 2, supply of pressure oil from a retreating oil chamber 3 partitioned by a piston 2 to a hydraulic path between a hydraulic pump P1 having a variable discharge amount and an injection cylinder 1. And a direction switching valve SOL1 for discharging the pressure oil from the forward oil chamber 4 and a direction switching valve SOL2 for supplying the pressure oil to the forward oil chamber 4 and the hydraulic motor M.

In the conventional injection hydraulic circuit, at the start of injection, the hydraulic pump P1 is driven from the state shown in the figure, and at the same time, the direction switching valve SOL2 is switched to the side a. The pressure oil acts on the forward oil chamber 4, and the piston 2 moves forward while excluding the hydraulic oil in the backward oil chamber 3 to start injection.

[0004]

In the above conventional injection hydraulic circuit, the flow rate and the pressure of the hydraulic pump P1 rise simultaneously with the switching operation of the direction switching valve SOL2, and the piston 2 moves forward. Is greatly influenced by the rise of the hydraulic pump P1,
It is difficult for the injection to proceed quickly.

The present invention has been made to solve the above-mentioned conventional problems, and has as its object to provide a method capable of shortening the rise time at the start of injection.

[0006]

According to the present invention, there is provided a method for shortening an injection rising time in injection speed control according to the first and second aspects.
A first directional control valve for supplying pressure oil to the retreat-side oil chamber and discharging pressure oil from the forward-side oil chamber to the hydraulic path between the hydraulic pump and the injection cylinder, and supplying pressure oil to the forward-side oil chamber A second directional control valve is provided, the retreat oil chamber is connected to the tank side by the first directional control valve, the forward hydraulic path is blocked, and the second directional control valve is blocked. Then, the unload valve is switched to supply the pressure oil of the second hydraulic pump to cut off the valve, and then the second directional control valve is switched, and at the same time, the flow rate and pressure of the first hydraulic pump are raised. To start injection.

In this method, when the first hydraulic pump is started to start injection, the cut-off state of the valve is released, and hydraulic oil is supplied from the first and second hydraulic pumps to the forward hydraulic circuit. The piston rises to a predetermined value and moves forward quickly.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on embodiments with reference to the drawings. FIG. 1 is a hydraulic circuit diagram of one embodiment used for performing the method according to the present invention. Parts that are the same as or equivalent to the conventional example will be described using the same reference numerals.

In FIG. 1, reference numeral 1 denotes an injection cylinder, in which a piston 2 is slidably provided. The injection cylinder 1 is partitioned by a piston 2 into a backward oil chamber 3 and a forward oil chamber 4. A screw (not shown) is connected to the tip of the piston 2, and a hydraulic motor M is connected to the other end.

An A port and a B port of a first directional control valve SOL1 are connected to the retreating oil chamber 3 and the forward oil chamber 4 of the injection cylinder 1, respectively. The A port of the directional control valve SOL2 is connected, and the B port of the second directional control valve SOL2 is connected to the hydraulic motor M. The P ports of the two-way switching valves SOL1 and SOL2 are connected to a first hydraulic pump P1 as a variable discharge pump and a second hydraulic pump P2 as a fixed discharge pump via check valves C1 and C1, respectively. I have. An unload valve V2 is connected to a pipeline between the second hydraulic pump P2 and one check valve C1, and a valve is provided between the two check valves C1 and C1 and the two-way switching valves SOL1 and SOL2. P of V1
Port is connected.

Next, the operation will be described.

FIG. 1 shows a state in which the piston 2 has stopped retreating, the retreat oil chamber 3 is connected to the tank side by a first directional control valve SOL1, and the forward hydraulic path is blocked.
Further, the second direction switching valve SOL2 is blocked.

From this state, the pilot of the unload valve V2 is switched to the load state by the proportional valve or the directional switching valve, and the hydraulic oil is supplied from the second hydraulic pump P2 to the forward hydraulic path. As a result, the pilot pressure is supplied to the port side of the valve V1, but the pilot pressure is not supplied to the port side because the first hydraulic pump P1 is not driven.
Since the pressing force due to the pressure on the port side is larger than the pressing force of the spring S1 provided on the port side, the valve V1
Changes from the block state to the PT connection state, the pressure oil is released to the tank, and the cutoff state is established. The pressure in the cutoff state can be set to an arbitrary value by the spring S1 or a substitute proportional valve. It should be noted that driving the first hydraulic pump P1 means changing from the unload state to the on-load state.

Thereafter, to start injection, the second directional control valve SOL2 is switched to the a side to connect the ports P and A, and at the same time, the first hydraulic pump P1 is driven to supply pressure oil to the forward hydraulic path. When the supply is performed, the pilot oil is supplied to the port side of the valve V1, and the pressing force of the port side spring S1 and the pressure oil becomes larger than the pressing force of the port side pressure oil. The block is released and the forward side hydraulic circuit is supplied with the pressure oil of the two hydraulic pumps P1 and P2, rises to a predetermined value, and the piston 2 moves forward quickly. The timing for driving the first hydraulic pump P1 can be set arbitrarily.

As described above, only the first hydraulic pump P1 whose discharge amount is variable has a swash plate operation loss time because the swash plate acts to discharge the flow rate, but the second hydraulic pump P2 Is driven to be in the cut-off state by the valve V1, the loss time is eliminated, and at the same time, the second directional control valve SOL2 is switched to the a side in consideration of the timing, and at the same time, the first hydraulic pump P1 supplies the hydraulic oil. As a result, all the pressure oil in the forward hydraulic path is immediately
And the piston 2 is quickly moved forward.

In the case of the injection molding machine, after the injection is completed, the unload valve V2 is switched to put the second hydraulic pump P2 in the unload state, the second directional switching valve SOL2 is switched to the b side, and the ports P and B are disconnected. To supply hydraulic oil to the hydraulic motor M. With the rotation of the hydraulic motor M, the piston 2 and the screw rotate and the molten resin is sent to the screw tip side,
The screw and the piston 2 move backward due to the back pressure.
When the screw 2 moves backward to the home position, the second directional control valve SOL2 is set to the blocked state, and the first hydraulic pump P1
Is set to the unload state, and the valve V1 is set to the block state accordingly. This returns to the initial state.

FIG. 3 shows an injection start-up state by the injection hydraulic circuit of the above embodiment, and FIG. 4 shows an injection start-up state by the conventional injection hydraulic circuit. The rise (see the right side of the figure) is remarkable as compared with the conventional case.

[0018]

As described above, according to the present invention, during injection, pressure oil is supplied from the second pressure oil pump to the forward hydraulic path, cut off by the valve, and then the pressure oil of the first hydraulic pump is released. Since the injection is started by the supply of the liquid and the switching of the second direction switching valve, the following effects are obtained.

Even if there is an operation loss time in the swash plate of the first hydraulic pump having a variable discharge amount, pressure oil in a cutoff state acts on the forward oil chamber of the injection cylinder by the second hydraulic pump. Therefore, the injection speed of the piston can rise to the set speed in a shorter time than in the conventional circuit.

In molding with a short injection stroke, the injection stroke tends to end before reaching the set speed, depending on the rising response of the swash plate. Good products can be obtained.

The cut-off circuit improves the response of the flow rate due to the inertia and viscosity of the pressure oil in the hydraulic line, and reduces the flow resistance, so that the rise time is shortened from this point as well.

Even in the case of a variable discharge hydraulic pump using a proportional valve, there is no influence on the switching response of the proportional valve and without being affected by the inertial force of oil between the proportional valve and the injection cylinder. The injection speed can be increased in a short time.

[Brief description of the drawings]

FIG. 1 is an injection hydraulic circuit diagram of an embodiment of the method according to the present invention.

FIG. 2 is a conventional injection hydraulic circuit diagram.

FIG. 3 is a diagram showing an injection rising state by the injection hydraulic circuit of the present invention.

FIG. 4 is a diagram showing an injection startup state by a conventional injection hydraulic circuit.

[Explanation of symbols]

 Reference Signs List 1 injection cylinder 2 piston 3 retreat oil chamber 4 forward oil chamber SOL1 directional switching valve SOL2 directional switching valve C1 check valve M hydraulic motor V1 valve V2 unload valve P1 hydraulic pump (variable discharge pump) P2 hydraulic pump (fixed amount) Discharge pump) S1 Spring

Claims (2)

[Claims] 1. First and second hydraulic pumps (P1, P2)
In the hydraulic path between the cylinder and the injection cylinder (1), the retraction oil chamber (3)
A first directional control valve (SOL1) for supplying the pressurized oil and discharging the pressurized oil from the forward oil chamber (4), and a second directional switch valve for supplying the pressurized oil to the forward oil chamber (4) (SOL2), the unload valve (V2) is switched to the load state in a state where the two-way switching valves (SOL1, SOL2) are blocked, and hydraulic oil is supplied from the second hydraulic pump (P2). Injection in the injection speed control, wherein the cut-off state is set by the valve (V1), and thereafter, the second directional control valve (SOL2) is switched, and simultaneously, the first hydraulic pump (P1) is driven to start injection. How to shorten the rise time. 2. The injection speed control according to claim 1, wherein the first hydraulic pump (P1) is a variable discharge pump, and the second hydraulic pump (P2) is a fixed discharge pump. Injection rise time reduction method.