JPH1052748A - Valve for controlling injection of die casting machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute the opening/closing of a run-around circuit and the return- back of working oil at a rod side with one valve by shutting off the run-around circuit with a signal from a filling completion detecting means and opening the circuit for discharging the working oil in an injection cylinder to an oil tank. SOLUTION: A valve chamber in the advancing direction of a spool is used as an oil supplying chamber 220d and the working oil supplied from an accumulator 240 is introduced through a control valve 2. Then, the spool 220b is shifted in the right side direction by overcoming the force in the left direction as the sam of the energizing force of a compressed coil spring 220c and hydraulic force loaded to the end surface at the right side of the spool 200b. When the spool 220b exists at the advancing limit in the right side direction, a rod side port P and a head side port H are communicated to shut off an oil tank port T. When the spool 220b exists at the retracting position in the left side, the large diameter part at the right part shuts off the head side port H and run- around circuit is shut off and at the same time, the working oil at the rod side is returned back to the oil tank 280.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection control valve of a die casting machine used for an injection circuit of a die casting machine, having an injection cylinder having a run-around circuit.

[0002]

2. Description of the Related Art Conventionally, an injection cylinder device such as a die-casting machine includes a rod for reducing the amount of hydraulic oil supplied from a hydraulic source to a head side chamber of a cylinder and for advancing a piston with as little hydraulic oil as possible. A run-around circuit connecting the side chamber and the head side chamber is provided to return the hydraulic oil discharged from the rod side chamber to the head side chamber at the time of forward operation, and to advance the piston together with hydraulic oil sent from a hydraulic source such as an accumulator or a hydraulic pump. It is known that

[0003] Conventionally, a hydraulic circuit as shown in FIG.
The hydraulic fluid is supplied from the accumulator 240 to control the advance speed of the piston rod 200a of the injection cylinder 200 while maintaining the control valve 210 at the specified opening at the start of operation, and the molten metal is supplied to the mold. Inject and fill into the cavity. When shutting off the run-around circuit 260, the solenoid valve 150
Is excited, the pilot check valve 140 is opened, and the hydraulic oil flows from the rod side to the head side via the cartridge valve 110 and the flow control valve 130, so that the pressure difference acting on the poppet of the run-around valve 160 and the right and left The runaround valve 160 automatically closes due to the difference in cross-sectional area. In the figure, reference numeral 310 indicates an electromagnetic valve, 320 indicates a cartridge valve, and 352 and 380 indicate check valves.

[0004]

However, in such a run-around circuit, separate valves are used for opening and closing the run-around circuit and opening and closing the circuit for returning the hydraulic oil on the rod side of the injection cylinder to the oil tank. I was doing it. Therefore, there is a problem that it is difficult to open and close the two series of circuits, that is, to perform cooperative control of adjusting the opening degrees of the two valves. An object of the present invention is to solve such a problem and to provide an injection control valve that can simultaneously open and close a run-around circuit and return rod-side hydraulic oil to an oil tank with a single valve. I do.

[0005]

In order to solve such a problem, in the present invention, in the first invention,
An injection cylinder having a run-around circuit, which is used in an injection circuit of a die-casting machine that controls a flow rate of hydraulic oil supplied to the injection cylinder by a control valve connected to a head side of the injection cylinder, and is attached to the injection cylinder. And a configuration having a function of receiving a signal transmitted from the filled completion detection means and shutting off the run-around circuit, and communicating a circuit for releasing hydraulic oil in the rod side chamber of the injection cylinder to the oil tank. did. According to a second aspect of the present invention, in the injection control valve for a die-casting machine according to the first aspect, both ends of the valve chamber formed in the manifold in an axially cylindrical shape have the same diameter as the diameter of the valve chamber and an intermediate portion. Is provided with a small-diameter spool slidably forward and backward, a hydraulic fluid port (rod-side port) communicating with the rod-side chamber of the injection cylinder on the spool forward side of the valve chamber, and a hydraulic oil communicating with the port. The manifold has an oil tank port (oil tank port) and a hydraulic oil port (head port) communicating with the head chamber of the injection cylinder on the retreat side of the spool of the valve chamber. At the position, the large-diameter portion blocks the head-side port and communicates with the oil tank port, and at the retreat limit position of the spool, communicates the rod-side port with the head-side port. Further, the spool is disposed so as to shut off the oil tank port, and a compression coil spring for urging the spool to abut against the wall in the forward limit direction is elastically mounted in the valve chamber, and the spool is moved forward. A hydraulic oil supply chamber is provided in the valve chamber for pressing the side end face in the retreating direction by overcoming the pressing force acting on the retraction side end face of the compression coil spring and the spool. Further, in the third invention, in the injection control valve of the second invention, the hydraulic oil in the oil supply chamber is shut off from the outside, and
A cartridge valve for shutting off communication with the oil tank port was housed in the manifold. In the fourth aspect of the present invention, a closed circuit is provided in the manifold on the side of the forward end of the spool, the closed circuit having one end communicating with the oil supply chamber and the other end communicating with a path having a large passage area that communicates with the outside. An aperture formed by an orifice was provided in the closed circuit.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, there is provided a die casting machine having an injection cylinder having a run-around circuit, wherein a control valve connected to a head side of the injection cylinder controls a flow rate of hydraulic oil supplied to the injection cylinder. Receiving the signal transmitted from the filling completion detecting means attached to the injection cylinder, shuts off the run-around circuit, and transfers the operating oil in the rod side chamber of the injection cylinder to the oil tank. Due to the configuration having the function of communicating the circuit to be opened, that is, specifically, specifically,
As in the second invention, a spool having a large diameter at both ends and a small diameter at an intermediate portion is disposed slidably forward and backward in a valve chamber bored in an axially cylindrical shape in the manifold. A port of hydraulic oil (rod-side port) communicating with the rod-side chamber of the injection cylinder on the spool advance side of the valve chamber; a port (oil tank port) of hydraulic oil communicating with the port to the oil tank; A hydraulic oil port (head side port) communicating with the head side chamber of the injection cylinder is provided in each of the manifolds on the retreat side of the spool in the valve chamber, and the large diameter portion shuts off the head side port at the forward limit position of the spool. And the oil tank port is communicated, and at the retreat limit position of the spool, the spool is arranged to communicate the rod side port and the head side port and to shut off the oil tank port, A compression coil spring for urging the spool to abut against the wall in the forward limit direction is elastically mounted in the valve chamber, and a pressing force acting on the forward end surface of the spool on the compression coil spring and the retreat side end surface of the spool. A hydraulic oil supply chamber is provided in the valve chamber to overcome the pressure and press in the backward direction, so that the hydraulic oil of the hydraulic power source is supplied to the oil supply chamber, the spool is held at the retreat limit position, and the run-around circuit is connected. Conversely, by releasing the hydraulic oil in the oil supply chamber to the oil tank, the spool is moved to the forward limit position, the run-around circuit is shut off, and at the same time, the hydraulic oil on the rod side is returned to the oil tank from the discharge passage. did. In the third invention, the oil supply chamber and the hydraulic oil on the rod side are returned to the oil tank by the cartridge valve incorporated in the manifold. Further, in the fourth aspect, during the forward movement of the spool, the impact caused by the collision of the spool with the forward limit is reduced to protect the device.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 4 relate to an embodiment of the present invention. FIG. 1 is a longitudinal sectional view of an injection control valve according to a first embodiment. FIG. 2 is a longitudinal sectional view of an injection control valve according to a second embodiment. 3 is a hydraulic circuit diagram showing a first embodiment of the injection control device, FIG. 4 is a hydraulic circuit diagram showing a second embodiment of the injection control device, and FIG. 5 is a longitudinal sectional view showing an embodiment of the first control valve. . FIG. 6 is a hydraulic circuit diagram showing one conventional example.

[0008] The injection control valve 220 (functionally called a run-around valve) of the die-casting machine of the first embodiment shown in Fig. 1 is provided in a valve chamber having a cylindrical space provided in a manifold 220a. A spool 220b having a large diameter at both ends and a small diameter at an intermediate portion is disposed slidably forward and backward. The upper half shows the spool retracted, and the lower half shows the spool forward. The injection control valve 220 includes a rod-side port R and a head-side port H of the injection cylinder 200 above both sides of the manifold 220a, and a hydraulic oil discharge passage (oil tank) communicating with the oil tank 280 below the forward side of the spool 220b. Port) T, and accommodates a spool 220b which can move forward and backward in the axial direction in a valve chamber formed of a cylindrical hollow portion in the manifold 220a. Direction).

On the other hand, the valve chamber in the spool forward direction forms an oil supply chamber 220d, and the hydraulic oil supplied from the accumulator 240 is introduced via the control valve 240, thereby causing the compression coil spring 220c to rotate. The spool 220b is moved rightward by overcoming the leftward force which is the sum of the urging force and the hydraulic pressure applied to the right end face of the spool 220b. When the spool 220b is at the rightward forward limit position, the rod side port R and the head side port H communicate with each other and shut off the oil tank port T. When the spool 220b is at the leftward backward limit position,
A large diameter portion on the right side of the spool 220b closes the head side port H, and the runaround circuit is shut off. At the same time, the oil tank port T is opened and the hydraulic oil on the rod side is returned to the oil tank 280. Reference numeral 220f is a plug. A closed circuit is provided at the forward end of the manifold 220a. The closed circuit has one end communicating with the oil supply chamber 220d and the other end communicating with a path having a large passage area that communicates with the outside. The throttle 220f is provided to reduce the impact of the collision with the manifold 220a at the forward limit position of the leftward movement of the spool 220b.

FIG. 2 shows an injection control valve 2 according to a second embodiment.
1A is different from the first embodiment shown in FIG. 1 in that a cartridge valve 330 is disposed below the forward limit direction of the manifold 220a, and the hydraulic oil in the oil supply chamber 220d and the hydraulic oil on the rod side are discharged. The communication of the hydraulic oil flowing through the oil tank port T, which is a passage, to the outside is performed. That is, the operating oil is supplied from the accumulator 240 via the solenoid valve 340 to the poppet 330b housed in the body 330a so as to be slidable in the vertical direction, the cartridge valve 330 is closed, and the control valve 340 is excited. And the poppet 330b is lowered to a neutral (neutral) state, and the above-described hydraulic oil is supplied to the oil tank 280.
To return to

FIG. 3 shows such injection control valves 220 and 22.
FIG. 3 shows an injection circuit of an injection cylinder 200 provided with a run-around circuit incorporating 0A, which is driven by a servomotor 210a to a hydraulic oil supply circuit 290 connected to an accumulator 240 of hydraulic oil supplied and accumulated from a hydraulic source 300a. A first control valve 210 whose detailed structure is shown in FIG. 5 is provided, and an injection cylinder 200 and a first control valve 2 are provided.
A bleed-off circuit 270 that communicates with the oil tank 280 via the throttle 230 is provided between the bleed-off circuit 10 and the oil tank 280. On the other hand, on the rod side of the injection cylinder 200, a hydraulic oil supply circuit 290 is provided.
And a second control valve for returning the hydraulic oil of the run-around circuit 260 to the oil tank 280, that is, an injection control valve 220, is provided on the way. Although not shown, the servomotor 210a of the first control valve 210, the injection control valve 220, the pressure detectors installed in the head side chamber and the rod side chamber of the injection cylinder 200, and the piston rod 200a of the injection cylinder 200 are attached. There is provided a control device which is connected to a position detector (or a speed / acceleration detector) which inputs and outputs various detection signals.

A hydraulic circuit 300 shown in FIG. 3 includes a hydraulic source 300a, control valves 310 and 32, in addition to the components already described.
0, 330, 340, 350, 360, 370, a check valve 380, etc.
50 is a cartridge valve, reference numerals 310, 340, 360,
370 is a direction switching valve). The reason why the cartridge valve 330 is used in the hydraulic circuit 300 of FIG. 3 and the hydraulic circuit 300A of FIG.
0, it is necessary to switch the valve in a short time of several milliseconds to the damping start position near the forward limit position, so that the hydraulic oil flows into the A and B chambers of the injection control valve 220 at a high speed, and Pp It is necessary to drain the hydraulic oil from the chamber at a high speed. Therefore, the hydraulic oil flow path from the Pp chamber to the oil tank must be made as wide as possible. This is why the cartridge valve 330 is used. Although the solenoid valve has a narrow hydraulic oil flow path, in the case of a cartridge valve, it is possible to drain the hydraulic oil on the back surface and open a flow path for allowing a large amount of hydraulic oil to flow at once with a slight stroke of the poppet. In order to quickly switch the injection control valve 220 which is a run-around valve, FIG.
In the embodiment shown in FIG. 2 and FIG. 2, the diameter of the large-diameter portion on the head side is made larger than the diameter of the large-diameter portion on the rod side of the spool 220b, so that steps are provided on the left and right sides. While the area is increased to prevent pressure loss, Pp
The volume of hydraulic oil required for switching rooms is reduced, and a structure that can be switched by simply removing a small amount of hydraulic oil is considered.

FIG. 4 shows an injection cylinder 20 with a run-around circuit incorporating injection control valves 220 and 220A.
0 shows the second embodiment (hydraulic circuit 300A) of the injection circuit. The difference from the injection circuit (hydraulic circuit 300) of FIG. 3 is that there is no bleed-off circuit 270 and the injection control valve 220
Relief valve 3 between cartridge and cartridge valve 350
90 and a flow control valve 392 are provided. That is, the hydraulic circuit 300 shown in FIG. 3 is different from the hydraulic circuit 300 shown in FIG.
0A is a circuit for performing rod pressure control.

FIG. 5 shows one of the first control valves 210.
The embodiment is shown, and is roughly divided into a drive unit 10 and a flow control unit 30. In the drive unit 10, reference numeral 14 denotes a servomotor having a rotation amount detection device (angle detector), and the output shaft of the servomotor 14 attached to the frame 15 is
It is connected to one end of a ball screw shaft 17 via a coupling 16. This ball screw shaft 17 has a ball screw shaft 1
The ball nut 18 which moves forward and backward by the rotation of the screw 7 is screwed in. An edge flange of the ball nut 18 is connected to a spool 36 of a flow rate adjusting unit 30 to be described later via a connecting rod 20, and the ball nut 18 and the spool 36 is configured to move forward and backward integrally. The driving method is not limited to the reciprocating motion conversion by the above-described servo motor or pulse motor by the ball screw mechanism (the ball screw shaft 17 and the ball nut 18), but may be a reciprocating mechanism that directly moves the spool 36 back and forth by a hydraulic cylinder. .

As shown in FIG. 5, the flow control section 30 has a valve chamber 38 (specifically, a hollow section) formed in a cylindrical manifold 32 having a flange 34 fixed to the rear end side. , A front valve chamber 38a and a rear valve chamber 38b), and a spool 36 is disposed to be able to move forward and backward freely. At the retracted position of the spool 36, the hydraulic oil inlet 50 and the hydraulic oil outlet 60 communicate with each other (the state shown in FIG. 3). It is controlled by the gap amount formed in the front valve chamber 38a. That is, when the retreat amount of the spool 36 is reduced, the hydraulic oil flow rate is reduced,
When the retreat amount is increased, the flow rate of the hydraulic oil also increases, and since the retreat amount of the spool and the flow rate of the hydraulic oil have a certain relationship that is approximately linearly approximated, the flow rate of the hydraulic oil can be arbitrarily controlled.

The spool 36 is provided with a pilot passage 36a for communicating the front valve chamber 38a and the rear valve chamber 38b, and penetrates the spool 36 at the center thereof.
A stepped through hole 42 having a larger diameter on the front valve chamber side than the rear valve chamber side is formed in the axial direction, and has a large diameter portion and a small diameter portion respectively corresponding to the large diameter and the small diameter of the stepped through hole 42. A stepped rod 40 fastened to a screw hole 34c provided in a flange 34 connected to the manifold 32 behind the rear valve chamber is slidably disposed on a spool 36 for moving forward and backward. Stepped rod 4
Reference numeral 0 denotes a piston 40a having a large-diameter portion in which a packing 44 for an oil seal is housed in an intermediate portion, and a small-diameter portion 40b having a rod-like shape having the same diameter and having an air vent hole 34b connected to a screw hole 34c therein. Air vent 40c communicating with
Are drilled in the axial direction.

The first control valve 210 can perform both speed control and pressure control if a position detector is attached to the first control valve 210 if a position detector is attached, and can perform cycle feedback control. It is better to drive with a servo motor as in

The first control valve 210 constructed as described above
Hydraulic circuit 300 or 300A having the second control valve 220
The operation of the injection control method of the die casting machine in the injection circuit having the above will be described below. First, in FIGS. 3 and 4, the solenoid SOLa on the right side of the control valve 370 is used.
And the hydraulic oil is sent from the hydraulic pressure source 300a to the accumulator 240 to accumulate the pressure. Next, the solenoid SOLb on the left side of the control valve 340 is excited to send hydraulic oil to the oil supply chamber 220d, and the spool 220b shown in FIGS. The run-around circuit 260 shown in FIG. 4 is brought into a communicating state, and the first control valve (spool 3) shown in FIG.
6 is located at the leftmost forward limit position) 210, an opening command is given based on a preset program, and an opening command is issued according to the degree of the low-speed injection command or the high-speed injection command, and the required angle is given to the servomotor 14. And the spool 36 is moved backward to a predetermined position. At this time, the air behind the piston 40a is replenished via the air vent hole 40c and the air vent hole 34b (inversely, the spool 36
When the piston moves forward, the air behind the piston 40a is released to the atmosphere via the air vent hole 40c and the air vent hole 34b. With the movement of the spool 36, the inflow port 50 and the discharge port 60 of the flow rate adjusting section 30 communicate with each other, and the hydraulic oil flows through the first control valve 210 at a flow rate corresponding to a predetermined opening degree. Supply hydraulic oil to the side chamber. When giving a change to the injection speed, the spool 36 is moved to a predetermined position in accordance with the opening degree corresponding to the speed. Thus, the piston rod 200 of the injection cylinder 200
a is advanced.

In the first control valve 210 used in this embodiment, when the spool 36 is in an open state other than the fully closed position of the forward limit, the driving force due to a power failure or some failure of the drive unit 10 is increased. Becomes zero, the pilot passage 36
a, the pressure in the front valve chamber 38a and the pressure in the rear valve chamber 38b are equal, and the presence of the stepped through hole 42 formed in the spool 36 reduces the pressure receiving area of the front valve chamber 38a to the rear valve chamber 38b. , The forward force of the spool 36 exceeds the backward force, the spool 36 automatically moves to the forward limit position, and the first control valve 210 is fully closed. Therefore, there is a merit that the on-off valve conventionally disposed before and after the flow control valve can be omitted.

During the forward injection, the opening of the first control valve 210 is changed at any time at the set position given to the position detector by the setting program, and the speed is changed. While the injection is being advanced, as described above, the control valve 340 in FIGS. 3 and 4 is in the left position, and the Pp chamber of the injection control valve 220 is pressurized and the injection control valve 2
20 to overcome the sum of the biasing force of the spring provided in the A chamber at the right end and the hydraulic pressure acting on the right end in the left direction.
Moves to the retreat limit position, the discharge port (rod side port) R and the discharge port (head side port) H communicate, and the run-around circuit is in communication. Then, by the filling completion detecting means, for example, the control valve 340 returns to the neutral state at the filling completion position given to the position detector or returns to the left position, the pressurization of the Pp chamber is released, and the spool 20b is quickly moved. Then, it moves to the left (forward direction) (the valve may be switched before the completion of filling by a position signal or the like instead of switching the valve after the completion of filling). Then, the hydraulic oil on the rod side is supplied to the oil tank 2 via the cartridge valve 350.
Returned to 80. In this way, injection filling is completed,
After the speed control, the process proceeds to pressure control in the next pressure increasing step. As described above, since the ratio of the opening areas of the rod side R, the head side port, and the oil tank port T is an integrated valve, the injection control valve 220 can maintain a constant relationship with the stroke. In addition, complete cooperative control is possible, and pressure control on the rod side for switching the runaround circuit becomes easy. On the other hand, in the related art, these operations are performed by two valves, and the control accuracy deteriorates due to the occurrence of a time lag that occurs when the two valves are switched. In addition, the amount of deviation slightly changes for each casting due to the influence of the oil temperature, the scan time of the controller, and the like.

In the pressure control after the filling is completed, the opening degree of the first control valve 210 is adjusted by a preset program, the pressure of the injection cylinder 200 is set to a predetermined pressure, and the pressure is set by a timer in the control device. The injection is completed after the elapse of the pressurized time. After the injection is completed, open the mold,
Take out the molded product.

In the embodiment of the present invention using the hydraulic circuit shown in FIG. 3, the run-around circuit 260 is closed immediately before the molten metal is completely filled in the mold cavity, and the operating oil in the rod chamber of the injection cylinder 200 is supplied to the tank 280. Before performing pressure control, the rod pressure (rod-side indoor hydraulic oil pressure) and the head pressure (head-side indoor hydraulic oil pressure) are once reduced to normal pressure, and the head pressure is reduced to 0 after filling is completed. , The firing power can be controlled only by the pressure on the head side. On the other hand, in the conventional example or the embodiment of FIG. 4, since the firing force is determined by both the head pressure and the rod pressure, it is necessary to control both the pressures and switch the control target. Is complicated and difficult.

[0023]

As described above, according to the injection control valve of the present invention, complete cooperative control can be performed at the time of switching the communication cutoff of the run-around circuit. The hydraulic oil on the rod side can be quickly returned to the oil tank. In addition, the flow rate of the hydraulic source hydraulic oil and the return hydraulic oil of the run-around circuit can be controlled simply and easily at the same time and safely. In addition, for example, by forming a hydraulic circuit as shown in the embodiment of FIG. Speed control and pressure control can be performed only with the motor-driven first control valve. Therefore, driving operability and driving reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an injection control valve according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of an injection control valve according to another embodiment of the present invention.

FIG. 3 is a hydraulic circuit diagram showing a first embodiment of the present invention.

FIG. 4 is a hydraulic circuit diagram showing a second embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of a first control valve according to the embodiment of the present invention.

FIG. 6 is a hydraulic circuit diagram according to a conventional example.

[Explanation of symbols]

 Reference Signs List 10 Drive unit 11 Flow control valve 14, Servo motor (pulse motor) 14A Hydraulic cylinder 15, 115A Frame 16 Coupling 16A Connection plate 17 Ball screw shaft 17a Bearing 18 Ball nut 20 Connection rod 30 Flow adjustment unit 32 Manifold 34 Flange 34a Guide Bush 34b Air vent hole 34c Screw hole 36 Spool 36a Pilot passage 38 Valve chamber 38a Front valve chamber 38b Rear valve chamber 40 Stepped rod 40a Piston 40b Small diameter portion 40c Air vent hole 42 Stepped through hole 44 Packing 46 Packing 50 Inlet 60 Outlet REFERENCE SIGNS LIST 100 pressure increase level adjustment valve 110 cartridge valve 120 relief valve 130 pressure increase time adjustment valve 140 solenoid valve 150 pilot check valve 160 run around valve 170 Solenoid valve 180 Solenoid valve 200 Injection cylinder 200a Piston rod 202b Position detector (or speed / acceleration detector) 210 First control valve 210a Servo motor 220 Second control valve (injection control valve) 220A Second control valve (injection control valve) 220a manifold 220b spool 220c compression coil spring 220d oil supply chamber 220e throttle 220f plug 230 throttle 240 accumulator 250 controller 270 bleed-off circuit 280 oil tank 290 hydraulic oil supply circuit 300 hydraulic circuit 300A hydraulic circuit 300a hydraulic power source 310 solenoid valve (control valve) ) 320 cartridge valve 330 cartridge valve 340 solenoid valve (control valve) 350 cartridge valve 350a body 350b poppet 351 cartridge cover 352 check valve 60 electromagnetic valve (control valve) 370 solenoid valve (control valve) 380 check valve 390 the relief valve 392 flow regulating valve H head-side port R rod side port T oil tank port

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[Procedure amendment]

[Submission date] October 25, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

On the other hand, the valve chamber in the spool forward direction forms an oil supply chamber 220d, and the hydraulic oil supplied from the accumulator 240 is introduced via the control valve 240, thereby causing the compression coil spring 220c to rotate. The spool 220b is moved rightward by overcoming the leftward force which is the sum of the urging force and the hydraulic pressure applied to the right end face of the spool 220b. When the spool 220b is at the rightward forward limit position, the rod side port R and the head side port H communicate with each other and shut off the oil tank port T. When the spool 220b is at the leftward backward limit position,
A large diameter portion on the right side of the spool 220b closes the head side port H, and the runaround circuit is shut off. At the same time, the oil tank port T is opened and the hydraulic oil on the rod side is returned to the oil tank 280. Reference numeral 220f is a plug. A closed circuit is provided at the forward end of the manifold 220a. The closed circuit has one end communicating with the oil supply chamber 220d and the other end communicating with a path having a large passage area that communicates with the outside. A throttle 220e is provided to reduce the impact of the collision with the manifold 220a at the forward end position of the leftward movement of the spool 220b.

Claims (4)

[Claims] 1. An injection circuit for a die casting machine, comprising: an injection cylinder having a run-around circuit, wherein the control valve is connected to a head side of the injection cylinder to control a flow rate of hydraulic oil supplied to the injection cylinder. A function of receiving a signal transmitted from the filling completion detecting means attached to the injection cylinder, interrupting the run-around circuit, and communicating with a circuit for releasing hydraulic oil in a rod side chamber of the injection cylinder to an oil tank. An injection control valve for a die casting machine, comprising: 2. A spool having a large diameter at both ends and a small diameter at an intermediate portion thereof is slidably disposed in a valve chamber bored in a cylindrical shape in the axial direction in the manifold at both ends thereof. A hydraulic fluid port (rod-side port) communicating with the rod-side chamber of the injection cylinder, a port (hydraulic tank port) of hydraulic fluid communicating with the port, to the spool advance side of the valve chamber, Port (head side port) of hydraulic oil that communicates with the head side chamber of the injection cylinder on the retreat side of the spool
The large diameter portion blocks the head side port and communicates with the oil tank port at the forward limit position of the spool, and the rod side port and the head side at the retract limit position of the spool. The spool is disposed so as to communicate with the port and shuts off the oil tank port, and a compression coil spring for biasing the spool to abut against a wall in the forward limit direction is elastically mounted in the valve chamber. A hydraulic oil supply chamber is provided in the valve chamber for pressing the forward end surface of the spool in the backward direction by overcoming the pressing force acting on the compression coil spring and the backward end surface of the spool. An injection control valve for a die casting machine according to claim 1. 3. The injection control valve of a die casting machine according to claim 2, wherein a cartridge valve for shutting off the hydraulic oil in the oil supply chamber to the outside and shutting off the oil tank port is housed in the manifold. 4. A closed circuit is provided in the manifold on the forward end side of the spool, the closed circuit having one end communicating with the oil supply chamber and the other end communicating with a path having a large passage area communicating with the outside, and
4. The injection control valve for a die casting machine according to claim 2, wherein a throttle formed by an orifice is disposed in the closed circuit.