JP3962170B2 - Injection rise time reduction method in injection speed control - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for reducing the injection rise time of a hydraulically operated injection cylinder.
[0002]
[Prior art]
In the conventional injection hydraulic circuit shown in FIG. 2, the supply of pressure oil and the forward side oil chamber of the reverse side oil chamber 3 partitioned by the piston 2 are provided in the hydraulic path between the hydraulic pump P1 and the injection cylinder 1 whose discharge amount is variable. A direction switching valve SOL1 that discharges pressure oil 4 and a direction switching valve SOL2 that supplies pressure oil to the forward oil chamber 4 and the hydraulic motor M are disposed.
[0003]
In the conventional injection hydraulic circuit, at the start of injection, the hydraulic pump P1 is driven from the state shown in the drawing, and at the same time, the direction switching valve SOL2 is switched to the a side, and the pump side hydraulic path and the forward side hydraulic path are connected to each other. Pressure oil acts on the chamber 4, and the piston 2 moves forward while excluding the pressure oil in the retreat-side oil chamber 3 to start injection.
[0004]
[Problems to be solved by the invention]
In the conventional injection hydraulic circuit, the flow rate and pressure of the hydraulic pump P1 rise simultaneously with the switching operation of the direction switching valve SOL2, and the piston 2 moves forward. The injection advance is difficult to be performed quickly because it is greatly influenced by the rise.
[0005]
The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide a method capable of shortening the rise time at the start of injection.
[0006]
[Means for Solving the Problems]
Injection rise time shortening method in injection speed control according to the present invention, the hydraulic passage between the first and second hydraulic pump and the injection cylinder, the pressure oil of the advancing side oil chamber and the supply of pressure oil retreating side oil chamber A first direction switching valve that discharges the pressure and a second direction switching valve that supplies pressure oil to the forward oil chamber, and the first and second hydraulic pumps and the first and second direction switching. connect the valve to the hydraulic path between the valve, the unloading valve disposed in a hydraulic passage between the second pump and the first and second directional control valve, a two-way switching valve to the block state, Ann The load valve is switched to the load state, pressure oil is supplied from the second hydraulic pump and cut off by the valve, and then the second direction switching valve is switched and simultaneously the first hydraulic pump is driven to start injection. There is to do.
[0007]
In this method, when the first hydraulic pump is started to start injection, the cut-off state of the valve is released, and pressure oil is supplied to the forward hydraulic circuit from the first and second hydraulic pumps up to a predetermined value. The rising piston moves forward quickly.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described based on examples with reference to the drawings. FIG. 1 is a hydraulic circuit diagram of one embodiment used to carry out the method according to the present invention. Note that portions that are the same as or equivalent to those of the conventional example will be described using the same reference numerals.
[0009]
In the drawing, reference numeral 1 denotes an injection cylinder, and a piston 2 is slidably provided therein. The injection cylinder 1 is divided into a backward oil chamber 3 and a forward oil chamber 4 by a piston 2. A screw (not shown) is connected to the tip of the piston 2, and a hydraulic motor M is connected to the other end.
[0010]
The reverse side oil chamber 3 and the forward side oil chamber 4 of the injection cylinder 1 are respectively connected to the A port and the B port of the first direction switching valve SOL1, and the forward side oil chamber 4 is connected to the second direction switching valve. The A port of SOL2 is connected, and the B port of the second direction switching valve SOL2 is connected to the hydraulic motor M. The P ports of the bidirectional switching valves SOL1 and SOL2 are connected to a first hydraulic pump P1 that is a variable discharge pump and a second hydraulic pump P2 that is a fixed discharge pump via check valves C1 and C1, respectively. Yes. An unload valve V2 is connected to a pipe line between the second hydraulic pump P2 and one check valve C1, and a valve is connected to the hydraulic path between the check valves C1 and C1 and the two-way switching valves SOL1 and SOL2. V1 P port is connected.
[0011]
Next, the operation will be described.
[0012]
FIG. 1 shows a state in which the piston 2 is reversely stopped, and the reverse side oil chamber 3 is connected to the tank side by the first direction switching valve SOL1, and the forward side hydraulic path is blocked. Further, the second direction switching valve SOL2 is blocked.
[0013]
From this state, the pilot of the unload valve V2 is switched to the loaded state by a proportional valve or a direction switching valve, and pressure 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 {circle around (1)} of the valve V1, but the pilot pressure is not supplied to the port {circle around (2)} because the first hydraulic pump P1 is not driven. Since the pressing force by the pressure on the side becomes larger than the pressing force of the spring S1 provided on the port (2) side, the valve V1 is changed from the block state to the PT connection state, and the pressure oil is released to the tank and cut off. It becomes a state. The pressure in the cut-off state can be set to an arbitrary value by the spring S1 or the substitute proportional valve. The driving of the first hydraulic pump P1 means that the unload state is changed to the on-load state.
[0014]
Thereafter, the second directional control valve SOL2 is switched to the a side to start injection, the ports P and A are connected, and simultaneously the first hydraulic pump P1 is driven to supply pressure oil to the forward hydraulic path. Pilot oil is supplied to the port {circle around (2)} of the valve V1, and the pressing force of the spring S1 and pressure oil on the port {circle around (2)} side is greater than that of the pressure oil on the port {circle around (1)} side. The cut-off state is released and a block state is established, and the hydraulic oil from both hydraulic pumps P1 and P2 is supplied to the forward hydraulic circuit, and the piston 2 rises to a predetermined value and moves forward rapidly. In addition, the timing which drives the 1st hydraulic pump P1 can be set arbitrarily.
[0015]
In this way, only the first hydraulic pump P1 with variable discharge amount has a loss of operation time of the swash plate because the swash plate acts to discharge the flow rate, but the second hydraulic pump P2 is driven. By making the cut-off state with the valve V1, the lost time is eliminated, and at the same time as switching the second direction switching valve SOL2 to the a side in anticipation of timing, the pressure oil is also supplied from the first hydraulic pump P1, All the pressure oil in the advance side hydraulic path immediately acts on the advance side oil chamber 4 to quickly move the piston 2 forward.
[0016]
In the case of an injection molding machine, after the injection is completed, the unload valve V2 is switched to place the second hydraulic pump P2 in the unload state, the second direction switching valve SOL2 is switched to the b side, and the ports P and B are connected. Then, pressure oil is supplied to the hydraulic motor M. With the rotation of the hydraulic motor M, the piston 2 and the screw rotate to send the molten resin to the screw tip side, and 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 in the blocked state, the first hydraulic pump P1 is set in the unloaded state, and accordingly the valve V1 is set in the blocked state. This returns to the initial state.
[0017]
FIG. 3 shows the injection rising state by the injection hydraulic circuit of the above embodiment, and FIG. 4 shows the injection rising state by the conventional injection hydraulic circuit. As is clear from both, the injection rising (FIG. (See the right side of Fig. 5)) is remarkable compared to the conventional case.
[0018]
【The invention's effect】
In the present invention, as described above, the pressure oil is supplied from the second pressure oil pump to the forward hydraulic path at the time of injection and cut off by the valve, and then the supply of the pressure oil from the first hydraulic pump and the second Since the injection is started by switching the direction switching valve, the following effects are obtained.
[0019]
Even if there is an operation loss time in the swash plate in the first hydraulic pump with variable discharge amount, the hydraulic oil in the cutoff state is acting on the forward oil chamber of the injection cylinder by the second hydraulic pump. The injection speed of the piston can be raised to the set speed in a shorter time than this circuit.
[0020]
In molding with a short injection stroke, the injection stroke tends to end before the set speed is reached, depending on the rise response of the swash plate. It is done.
[0021]
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 the flow resistance is reduced, so that the rise time is also shortened from this point.
[0022]
Even in the case of a variable discharge hydraulic pump using a proportional valve, the injection speed is not affected by the switching response of the proportional valve, and is not affected by the inertial force of oil between the proportional valve and the injection cylinder. You can get up in a short time.
[Brief description of the drawings]
FIG. 1 is an injection hydraulic circuit diagram of one embodiment of a 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 an injection hydraulic circuit of the present invention.
FIG. 4 is a view showing an injection rising state by a conventional injection hydraulic circuit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Injection cylinder 2 Piston 3 Back side oil chamber 4 Forward side oil chamber SOL1 Direction switching valve SOL2 Direction switching valve C1 Check valve M Hydraulic motor V1 Valve V2 Unload valve P1 Hydraulic pump (variable discharge amount pump)
P2 Hydraulic pump (fixed discharge pump)
S1 spring

Claims (2)

The hydraulic path between the first and second hydraulic pumps (P1, P2) and injection cylinder (1), the pressure oil of the pressure oil supplied forward side oil chamber of the retraction-side oil chamber (3) (4) A first directional switching valve (SOL1) that discharges the pressure and a second directional switching valve (SOL2) that supplies pressure oil to the forward oil chamber (4), and the first and second hydraulic pumps A valve (V1) is connected to the hydraulic path between (P1, P2) and the first and second directional control valves (SOL1, SOL2), and the second pump (P2) is connected to the first and second directions. An unloading valve (V2) is disposed in the hydraulic path between the switching valves (SOL1, SOL2) , the bidirectional switching valves (SOL1, SOL2) are set in a blocking state, and the unloading valve (V2) is switched in a loading state, Pressure oil is supplied from the second hydraulic pump (P2) and cut off by the valve (V1). Injection rise time shortening method in an injection speed control when switching the second directional control valve (SOL2) drives the first hydraulic pump (P1) at the same time, characterized in that initiating the injection to.   2. The method for shortening an injection rise time in 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. .

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