JP5319235B2 - Hydraulic circuit of injection cylinder in die casting machine - Google Patents

Description

  The present invention relates to a hydraulic circuit that controls a piston operation of an injection cylinder that advances and retracts a plunger of a die casting machine.

  The die casting machine has a hydraulic circuit for advancing the piston of an injection cylinder by pressure oil supplied from a pressure oil source such as an accumulator or a hydraulic pump, and for injecting and filling molten metal into a mold cavity with a plunger attached to the piston. (For example, patent document 1).

  As shown in FIG. 4, the conventional hydraulic circuit 1 includes a pressure oil supply passage 4 that supplies the pressure oil from the pressure oil source 2 to the injection cylinder 3, and a pressure that discharges the pressure oil from the injection cylinder 3 to the oil tank X. A flow rate control valve 6 for controlling the flow rate of the pressure oil flowing through the oil discharge path 5, the pressure oil supply path 4, and a flow rate control valve for supplying pressure oil for opening and closing the flow rate control valve 6 from the pressure oil source 2 A direction switching valve 6b which is attached to the pipe 6a and is controlled to be opened and closed, a logic valve 7 (detailed later) attached between the flow rate control valve 6 and the pressure oil source 2 in the pressure oil supply path 4, and a logic A pilot pressure oil supply path 8 that supplies pilot pressure oil from the pressure oil source 2 to the valve 7, a state in which pilot pressure oil is supplied to the logic valve 7 (hereinafter referred to as “pilot pressure oil supply state”), and logic. The valve 7 is connected to the oil tank X via the pilot pressure oil discharge passage 8a. State of discharging the lot pressurized oil (hereinafter, referred to as. "Pilot pressure oil discharged state") is composed of a switching valve 9 for switching the. FIG. 4 shows a “pilot pressure oil supply state”.

  The logic valve 7 is used to turn on / off the supply of pressure oil from the pressure oil source 2 to the injection cylinder 3, and includes a pilot pressure oil chamber 7a. The pilot pressure oil is contained in the pilot pressure oil chamber 7a. When filled, the pressure oil supply passage 4 is closed to turn off the supply of pressure oil, and when the pressure oil is discharged from the pilot pressure oil chamber 7a, the pressure oil supply passage 4 is opened to turn on the supply of pressure oil. It is supposed to be.

  An operation when the piston 3a of the injection cylinder 3 is advanced using the hydraulic circuit 1 will be described. When the piston 3a starts to advance, the piston 3a is pulled into the rear end (the right end in FIG. 4). Further, since the switching valve 9 is in the “pilot pressure oil supply state” and the pilot pressure oil chamber 7a is filled with the pilot pressure oil, the logic valve 7 is in a state in which the pressure oil supply path 4 is closed. ing.

In the above state, when the solenoid 9 a of the switching valve 9 is turned on and the switching valve 9 is switched to the “pilot pressure oil discharge state”, the pressure oil filled in the pilot pressure oil chamber 7 a of the logic valve 7 is changed to the switching valve 9. The logic valve 7 opens the pressure oil supply path 4 by passing through the interior, being discharged to the oil tank X via the pilot pressure oil discharge path 8a, and being discharged from the pilot pressure oil chamber 7a. Then, after the pressure oil stored in the pressure oil source 2 passes through the logic valve 7 and the flow rate is controlled by the flow rate control valve 6 opened by the pressure oil supplied via the flow rate control valve pipe 6a, The injection cylinder 3 is rapidly filled and pushed by the filled pressure oil to advance the piston 3a.
JP 2000-52021 A

  However, at the moment when the switching valve 9 is switched to the “pilot pressure oil discharge state”, the poppet 7b in the logic valve 7 moves back shockingly, and the pressure oil that has been filled in the pilot pressure oil chamber 7a at a high pressure until then. By flowing into the pilot pressure oil supply passage 8 all at once toward the oil tank X opened to the atmosphere, the time width is extremely short and a surge pressure much higher than the pressure of the pressure oil source 2 is generated. In this case, the switching valve 9 attached to the pilot pressure oil supply path 8 may be damaged by the surge pressure.

  By the way, since the amount of the pressure oil to be discharged increases and the pipe diameter of the pilot pressure oil supply path 8 is large, that is, the logic valve 7 is large, this surge pressure tends to increase. It is conceivable to reduce the surge pressure to be generated and to prevent the switching valve 9 from being damaged by reducing the pressure.

  However, making the logic valve 7 smaller is not only narrowing the pressure oil supply path 4 for supplying the pressure oil from the pressure oil source 2 to the injection cylinder 3, but if the pressure oil supply path 4 becomes narrower, the unit time The amount of pressure oil that can be supplied to the injection cylinder 3 decreases, and the forward speed of the piston 3a cannot be sufficiently increased, resulting in another problem that the quality of the molded product is deteriorated.

  In addition, it has been attempted to relieve the surge pressure by attaching a known surge absorbing cylinder S to the pilot pressure oil supply path 8 or the pilot pressure oil discharge path 8a, but the time width of the surge pressure is as described above. Since it is extremely short, the surge absorbing cylinder S cannot respond following the surge pressure.

  The present invention has been developed in view of such problems of the prior art. Therefore, the main problem of the present invention is to avoid breakage of the switching valve by reducing the surge pressure acting on the switching valve without reducing the amount of pressure oil that can be supplied to the injection cylinder per unit time. An object of the present invention is to provide a hydraulic circuit for an injection cylinder in a die casting machine.

The invention described in claim 1 is described as follows: “The pressure oil supply passage 30 for supplying the injection cylinder C with the pressure oil from the pressure oil source 49;
A pressure oil discharge passage 32 for returning the pressure oil discharged from the injection cylinder C to the oil tank 50;
It is attached to the pressure oil supply passage 30 and includes a pilot pressure oil chamber 36a. When the pilot pressure oil chamber 36a is filled with pressure oil, the pressure oil supply passage 30 is closed and the pilot pressure oil chamber 36a is closed. A main logic valve 36 that opens the pressure oil supply passage 30 when the pressure oil is discharged from
A pilot pressure oil discharge passage 38 for returning the pressure oil discharged from the pilot pressure oil chamber 36a of the main logic valve 36 to the oil tank 50;
A pilot pressure oil chamber 40a, which is attached to the pilot pressure oil discharge passage 38 and has a smaller volume than the pilot pressure oil chamber 36a of the main logic valve 36, is filled with the pressure oil. The pilot pressure oil discharge passage 38 is closed, and when the pressure oil is discharged from the pilot pressure oil chamber 40a, the sub logic valve 40 opens the pilot pressure oil discharge passage 38;
A pilot pressure oil supply passage 42 for supplying pressure oil from the pressure oil source 49 to the pilot pressure oil chamber 40a of the sub logic valve 40;
A “pilot pressure oil supply state” that is attached to the pilot pressure oil supply passage 42 and supplies pressure oil to the pilot pressure oil chamber 40a of the sub logic valve 40, and the pilot pressure oil chamber 40a of the sub logic valve 40. A switching valve 44 for alternately switching the “pilot pressure oil discharge state” for returning the pressure oil discharged from the oil tank 50 to the oil tank 50;
Communication between the pilot pressure oil supply path 42 between the sub logic valve 40 and the switching valve 44 and the pilot pressure oil discharge path 38 between the main logic valve 36 and the sub logic valve 40. Passage 46,
In the hydraulic circuit 10 "of the injection cylinder C in the die-casting machine 12, the communication passage 46 includes a check valve 47 attached in a direction to supply pressure oil to the pilot pressure oil discharge passage 38. is there.

  The operation when the piston P of the injection cylinder C is advanced using this hydraulic circuit 10 will be described. As shown in FIG. 2, the piston P is at the rear end (right end in the drawing) when the piston P starts to advance. Has been drawn into. Further, since the switching valve 44 is in the “pilot pressure oil supply state” and the pilot pressure oil chamber 40a of the sub logic valve 40 is filled with the pressure oil, the pilot pressure oil discharge passage 38 is closed. .

  Further, the pressure oil from the pressure oil source 49 passes through the communication path 46 and the check valve 47 branched from the pilot pressure oil supply path 42 in the forward direction and flows into the pilot pressure oil discharge path 38. As described above, Since the pilot pressure oil discharge passage 38 is closed by the secondary logic valve 40, the pressure oil flowing into the pilot pressure oil discharge passage 38 is filled in the pilot pressure oil chamber 36 a of the main logic valve 36. When the pilot pressure oil chamber 36a is filled with the pressure oil, the pressure oil supply passage 30 is closed so that the pressure oil from the pressure oil source 49 does not flow into the injection cylinder C.

  In the above state, when the switching valve 44 is switched to the “pilot pressure oil discharge state”, the sub logic valve 40 opens the pilot pressure oil discharge passage 38 as shown in FIG. When opened, the pressure oil is discharged from the pilot pressure oil chamber 36 a of the main logic valve 36 to the oil tank 50, and the main logic valve 36 opens the pressure oil supply path 30. Then, the pressure oil stored in the pressure oil source 49 is rapidly filled into the injection cylinder C through the pressure oil supply path 30, and the piston P moves forward by being pushed by the filled pressure oil.

  In the hydraulic circuit 10 according to the present invention, the pressure oil charged in the pilot pressure oil chamber 36a of the main logic valve 36 passes through the pilot pressure oil discharge passage 38 to the oil tank 50 without passing through the switching valve 44. Only a small amount of pressure oil that has been guided and filled in the pilot pressure oil chamber 40 a of the sub logic valve 40 passes through the switching valve 44 and is guided to the oil tank 50.

  For this reason, only a small surge pressure generated from the sub-logic valve 40 smaller than the main logic valve 36 acts on the switching valve 44, and a large surge pressure generated from the main logic valve 36 acts on the switching valve 44. Therefore, the surge pressure generated by using the small slave logic valve 40 is kept within the pressure resistance range of the switching valve 44 to prevent the switching valve 44 from being damaged, and the pressure using the large main logic valve 36 is avoided. By increasing the diameter of the oil supply passage 30, a sufficient amount of pressurized oil can be supplied to the injection cylinder C per unit time.

  According to the present invention, it is possible to avoid breakage of the switching valve by reducing the surge pressure acting on the switching valve without reducing the amount of pressure oil that can be supplied to the injection cylinder per unit time. A hydraulic circuit of the injection cylinder in the machine can be provided.

  Hereinafter, the present invention will be described in detail with reference to illustrated embodiments. FIG. 1 is a schematic view showing a main part of a die casting machine 12 to which a hydraulic circuit 10 of the present invention is applied. FIG. 2 is a circuit diagram showing the main part of the hydraulic circuit 10 of the present invention (when the piston moves backward), and FIG. 3 shows the main part of the hydraulic circuit 10 of the present invention (when the piston moves forward). FIG. In FIG. 1, 14 is a fixed die plate, 16 is a moving die plate, 18 is a fixed die, 20 is a moving die, and 22 is a die cavity.

  Among these, the fixed die plate 14 is provided with a cylindrical sleeve 24 whose inside communicates with the mold cavity 22, and a pouring port 24 a is provided on the sleeve 24. A plunger 26 is slidably inserted into the sleeve 24, and an injection cylinder C is connected to the plunger 26 to move it back and forth inside the sleeve 24.

  The injection cylinder C has a sealed cylindrical cylinder body 28, and a piston P is accommodated in the cylinder body 28 so as to be slidable in the axial direction. For this reason, the internal space of the cylinder main body 28 is divided into a piston projecting side pressure oil chamber R1 (right side in FIG. 1) and a piston immersion side pressure oil chamber R2 (left side in FIG. 1). In addition, one end of the piston P is connected to the piston P on the side of the pressure oil chamber R2 and the other end protrudes outside the cylinder body 28 and is connected to the plunger 26 via the plunger rod 26a. A long piston rod Pr is attached.

  A hydraulic circuit 10 as shown in FIGS. 2 and 3 is connected to the injection cylinder C. The hydraulic circuit 10 generally includes a pressure oil supply path 30, a pressure oil discharge path 32, a flow control valve 34, a direction switching valve 35, a main logic valve 36, a pilot pressure oil discharge path 38, a sub logic valve 40, a pilot pressure oil. The supply path 42, the switching valve 44, the communication path 46, the check valve 47, and the control means 48 are configured.

  One end of the pressure oil supply passage 30 is connected to the piston protruding side pressure oil chamber R1 of the injection cylinder C, and the other end is connected to an accumulator (of course, a hydraulic pump or the like) as a pressure oil source 49. It is a flow path for supplying pressure oil to the piston protruding side pressure oil chamber R1.

  One end of the pressure oil discharge passage 32 is connected to the piston immersion side pressure oil chamber R2 of the injection cylinder C, and the other end is connected to the oil tank 50, so that the piston P moves forward (left direction in FIG. 1). This is a flow path for returning the pressure oil filled in the piston immersion side pressure oil chamber R <b> 2 to the oil tank 50.

  The flow rate control valve 34 is attached to the pressure oil supply path 30 and controls the amount of pressure oil flowing through the pressure oil supply path 30. In the hydraulic circuit 10 of this embodiment, the flow rate control valve 34 As the control valve 34, a control valve having high-speed response that can immediately respond to a desired flow rate by controlling the valve opening degree from fully closed to fully open of the pressure oil supply passage 30 by driving a pulse motor or a servo motor is used. ing. The opening and closing of the valve at the controlled valve opening is performed by balancing the pressure oil supply / cutoff from the direction switching valve 35 and the resilience of the built-in spring.

  The direction switching valve 35 is connected to a hydraulic pressure source 49 and attached to a flow rate control valve pipe 35 a that reaches the flow rate control valve 34, and is controlled to be opened and closed by a control means 48.

  The main logic valve 36 is attached to the upstream side of the flow rate control valve 34 in the pressure oil supply passage 30 and includes a pilot pressure oil chamber 36a that receives the pressure oil. The pilot pressure oil chamber 36a is filled with the pressure oil. When the pressure oil supply passage 30 is closed, the pressure oil supply passage 30 is opened when the pressure oil is discharged from the pilot pressure oil chamber 36a.

  The main logic valve 36 has a conical tip portion 36b1 and a cylindrical main body portion 36b2. The main logic valve 36 slides in the left and right direction in the casing 36b in which the space X is provided, and the space X is piloted. A piston 36d for partitioning into a pressure oil chamber 36a (right space in the figure) and a pressure oil flow chamber 36c (left space in the figure), and projecting from the left side surface of the piston 36d, the tip surface being the top of the tip portion 36b1 A needle 36e formed to be flush with the inner surface (a poppet 36j is formed by the piston 36d and the needle 36e), and a pressing member 36f that presses the piston 36d in a direction away from the bottom surface of the casing 36b; It consists of In this embodiment, a spring is used as the pressing member 36f. However, as long as the piston 36d can be pressed away from the bottom surface of the casing 36b, the present invention is not limited to this, and other materials can be used. .

  In addition, the casing 36b has an opening / closing hole 36g provided at a position corresponding to the tip end surface of the needle 36e, and a pressure oil flow hole 36h provided on the side of the opening / closing hole 36g on the side surface of the main body 36b2. And a pilot pressure oil flow hole 36i provided on the bottom surface. As will be described later, when the tip of the needle 36e is separated from the opening / closing hole 36g, the pressure oil flow hole 36h Pressure oil can flow through the pressure oil flow chamber 36c to the opening / closing hole 36g (and vice versa). In the present embodiment, the pressure oil flow hole 36 h and the opening and closing hole 36 g of the casing 36 b are connected to the pressure oil supply path 30.

  One end of the pilot pressure oil discharge passage 38 is connected to the pilot pressure oil flow hole 36 i of the main logic valve 36 and the other end is connected to the oil tank 50, and the pilot pressure oil chamber of the main logic valve 36 is connected. This is a flow path for discharging the pressure oil filled in 36 a to the oil tank 50.

  The sub logic valve 40 is attached to the pilot pressure oil discharge passage 38 and includes a pilot pressure oil chamber 40a for receiving the pressure oil, like the main logic valve 36. The pilot pressure oil chamber 40a is filled with the pressure oil. In this case, the pilot pressure oil discharge passage 38 is closed, and when the pressure oil is discharged from the pilot pressure oil chamber 40a, the pilot pressure oil discharge passage 38 is opened.

  The size of the sub logic valve 40 is set smaller than that of the main logic valve 36, and the volume of the pilot pressure oil chamber 40a is smaller than that of the pilot pressure oil chamber 36a of the main logic valve 36. Since the functions and the like are the same as those of the main logic valve 36, the parts having the same functions are denoted by the same alphabet, and the description of the main logic valve 36 is used for the description of each part.

  One end of the pilot pressure oil supply path 42 is connected to the pilot pressure oil flow hole 40 i of the sub logic valve 40 and the other end is connected to the pressure oil source 49. Is a flow path for supplying the pilot pressure oil chamber 40a of the sub logic valve 40 to the pilot pressure oil chamber 40a.

  The switching valve 44 is a valve for switching the flow direction of the pressure oil supplied as a pilot signal to the main logic valve 36 and the sub logic valve 40, and switches between the two-position four-way valve 44a and the two-position four-way valve 44a. And a solenoid 44b.

  When the solenoid 44b of the switching valve 44 is off, as shown in FIG. 2, the A port and the P port of the two-position four-way valve 44a are in communication, and the B port and the T port are connected to any port. When the solenoid 44b is turned on without being connected to each other, the A port and the T port of the two-position four-way valve 44a communicate with each other as shown in FIG. And the P port communicate with each other.

  Further, a pilot pressure oil supply passage 42 toward the pilot pressure oil chamber 40a of the secondary logic valve 40 is connected to the A port of the two-position four-way valve 44a, and the pilot pressure from the pressure oil source 49 is connected to the P port. An oil supply path 42 is connected, and a pressure oil discharge path 54 toward the oil tank 50 is connected to the T port.

  One end of the communication path 46 communicates between the secondary logic valve 40 and the switching valve 44 in the pilot pressure oil supply path 42 and between the main logic valve 36 and the secondary logic valve 40 in the pilot pressure oil discharge path 38. Road.

  The check valve 47 is connected to the pilot pressure oil discharge passage 38 in the direction in which the pressure oil is supplied to the pilot pressure oil discharge passage 38 (that is, this direction is the forward direction and the pilot pressure oil supply passage from the pilot pressure oil discharge passage 38 which is the reverse direction). 42 is a check valve attached so that pressure oil does not flow toward 42).

  The control means 48 controls the operations of the flow control valve 34 and the switching valve 44 so that the injection cylinder C performs a predetermined operation, and includes a sequencer 48a, an operation unit 48b, and a display unit 48c.

  The sequencer 48a transmits a command signal (such as a pulse signal) based on a predetermined program to the flow control valve 34, the switching valve 44, the direction switching valve 35, and the like connected to the wirings 60a, 60b, and 60c. Thus, the operation of the injection cylinder C is controlled. The operation unit 48b is provided with a switch for starting and stopping the injection cylinder C, a keyboard and a touch panel for changing the program of the sequencer 48a, and the display unit 48c is provided with the injection cylinder C by the sequencer 48a. The control status etc. are displayed graphically.

  Further, in the hydraulic circuit 10 configured as described above, a known return circuit (not shown) of the piston P of the injection cylinder C is integrated with the pressure oil supply path 30, the pressure oil discharge path 32 and other piping systems. At the time of return, the pressure oil is supplied to the piston immersion side pressure oil chamber R2, and the pressure oil in the piston protrusion side pressure oil chamber R1 is returned to the oil tank 50.

  Next, a method for controlling the injection cylinder C using the hydraulic circuit 10 described above will be described. First, as shown in FIG. 2, the piston P of the injection cylinder C is in a retracted start position (closed to the right end in the figure), the solenoid 44 b of the switching valve 44 is turned off, and the direction switching valve 35 is turned off. The solenoid 35b is turned on.

  At this time, since the A port and the P port of the two-position four-way valve 44a of the switching valve 44 are in communication with each other, the pressure oil from the pressure oil source 49 passes through the pilot pressure oil supply passage 42. The pilot pressure oil chamber 40a of the secondary logic valve 40 is flowed and the pressure oil filled in the pilot pressure oil chamber 40a presses the piston 40d in the left direction in the figure, and the pressing force of the pressing member 40f is changed to the piston. By adding to 40d, the needle 40e closes the opening / closing hole 40g of the casing 40b. As a result, the pilot pressure oil discharge passage 38 is closed.

  The pressing force of the pressing member 40f is applied to the piston 40d because the pressure of the pressure oil supplied from the pilot pressure oil supply passage 42 acts on the piston 40d from the right in the figure, The pressure of the pressure oil flowing in the order from the communication passage 46 branched from the pilot pressure oil supply passage 42 to the pilot pressure oil discharge passage 38 acts from the left in the figure to the tip of the needle 40e from the opening / closing hole 40g. Since the pressure from the direction is theoretically the same, the piston 40d does not move unless there is a pressing force from the pressing member 40f, and there is a possibility that the pilot pressure oil chamber 40a cannot be filled with the pressure oil. .

  Further, the pressure oil from the pressure oil source 49 passes through the communication path 46 and the check valve 47 branched from the pilot pressure oil supply path 42 in the forward direction and flows into the pilot pressure oil discharge path 38. As described above, Since the pilot pressure oil discharge passage 38 is closed by the sub logic valve 40, the pressure oil flowing into the pilot pressure oil discharge passage 38 is filled in the pilot pressure oil chamber 36 a of the main logic valve 36. When the pilot pressure oil chamber 36a is filled with the pressure oil, the piston 36d is pressed in the left direction in the figure, and the pressing force of the pressing member 36f is applied to the piston 36d, so that the needle 36e is opened / closed hole 36g of the casing 36b. Is closed and the pressure oil supply passage 30 is closed, so that the pressure oil from the pressure oil source 49 does not flow into the piston protruding side pressure oil chamber R1 of the injection cylinder C. Note that the pressing force of the pressing member 36f is applied to the piston 36d for the same reason as described in the sub logic valve 40.

  In this state, the direction switching valve 35 is closed, and the flow control valve 34 is also closed.

  When an operator instructs the control means 48 to advance the piston, the sequencer 48a of the control means 48 transmits an ON signal to the solenoid 44b of the switching valve 44 via the wiring 60b, and the solenoid 44b receiving the ON signal. As shown in FIG. 3, the A port and the T port of the two-position four-way valve 44a communicate with each other, and the B port and the P port communicate with each other.

  Then, the pressure oil filled in the pilot pressure oil chamber 40a of the secondary logic valve 40 flows back through the pilot pressure oil supply passage 42 and passes from the A port to the T port of the two-position four-way valve 44a, and then the pressure oil is discharged. The oil tank 50 is guided through the path 54.

  Thus, when the pressure oil filled in the pilot pressure oil chamber 40a is discharged, the needle 40e of the sub logic valve 40 moves rightward in the figure to open the opening / closing hole 40g, and the main logic valve 36 The pressure oil filled in the pilot pressure oil chamber 36a (and the pressure oil in the pilot pressure oil discharge passage 38 between the main logic valve 36 and the sub logic valve 40) is the opening / closing hole 40g to the pressure of the sub logic valve 40. After passing through the oil flow chamber 40c to the pressure oil flow hole 40h in this order, the oil flow chamber 40c is led to the oil tank 50 through the pilot pressure oil discharge passage 38.

  When the pressure oil filled in the pilot pressure oil chamber 36a is discharged, the needle 36e of the main logic valve 36 moves to the right in the figure to open the opening / closing hole 36g, and the pressure oil from the pressure oil source 49 is the main. After passing through the pressure oil flow hole 36h to the pressure oil flow chamber 36c to the opening / closing hole 36g of the logic valve 36 in this order, it passes through the pressure oil supply path 30 and the flow control valve 34 (off signal from the sequencer 48a). In response, the direction switching valve 35 is opened, and pressure oil is supplied to the flow rate control valve 34 via the flow rate control valve pipe 35a, whereby the flow rate control valve 34 has a controlled valve opening. .) Is supplied to the piston protruding side pressure oil chamber R1 of the injection cylinder C, and the piston P moves forward, whereby the molten metal in the sleeve 24 is injected into the mold cavity 22.

  In the hydraulic circuit 10 according to the present embodiment, the pressure oil filled in the pilot pressure oil chamber 36a of the main logic valve 36 passes through the pilot pressure oil discharge passage 38 without passing through the switching valve 44, and the oil tank 50. Thus, only a small amount of pressure oil filled in the pilot pressure oil chamber 40a of the sub logic valve 40 passes through the switching valve 44 and is guided to the oil tank 50.

  Thus, only a small surge pressure generated from the sub logic valve 40 smaller than the main logic valve 36 acts on the switching valve 44, and a large surge pressure generated from the main logic valve 36 acts on the switching valve 44. Therefore, the surge pressure generated by using the small sub logic valve 40 is kept within the pressure resistance range of the switching valve 44 to prevent the switching valve 44 from being damaged, and the large main logic valve 36 is used. By increasing the diameter of the pressure oil supply passage 30, a sufficient amount of pressure oil per unit time can be supplied to the injection cylinder C.

  2 and 3, a known surge absorbing cylinder S may be attached to the pressure oil discharge passage 32 as indicated by a two-dot chain line. As described above, since the time width of the surge pressure generated from the logic valves 36 and 40 is very short, the surge absorption cylinder S cannot absorb the surge pressure, but the piston P of the injection cylinder C moves forward. In this case, since the time width of the surge pressure in the pressure oil discharge passage 32 caused by the flow of the pressure oil discharged from the piston immersion side pressure oil chamber R2 toward the oil tank 50 is slightly long, the effect of the surge absorbing cylinder S is effective. Because it can be expected. Further, when the surge absorbing cylinder S is attached to the pressure oil discharge passage 32, it is preferable to attach it as close to the injection cylinder C as possible.

  2 and 3, it is preferable that the pilot pressure oil discharge passage 38 and the pressure oil discharge passage 54 are connected to the oil tank 50 independently of each other without joining together. If the pressure oil discharge passage 54 is merged with the pilot pressure oil discharge passage 38, the surge pressure generated in the main oil pressure valve 36 and the piston immersing side pressure oil chamber R2 of the injection cylinder C becomes the pressure oil discharge passage 32 and the pilot pressure oil. This is because the pressure is transmitted from the discharge passage 38 to the pressure oil discharge passage 54 and in the worst case, the switching valve 44 may be damaged. Of course, a second oil tank (not shown) different from the oil tank 50 may be prepared, and only the pressure oil discharge path 54 may be connected to the second oil tank.

It is the schematic which showed the principal part of the die-casting machine to which the hydraulic circuit of this invention is applied. It is a circuit diagram which shows the principal part of the hydraulic circuit (at the time of piston backward movement) of this invention. It is a circuit diagram which shows the principal part of the hydraulic circuit (at the time of piston advance) of this invention. It is a figure which shows a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Hydraulic circuit 12 ... Die casting machine 14 ... Fixed die plate 16 ... Moving die plate 18 ... Fixed die 20 ... Moving die 22 ... Mold cavity 24 ... Sleeve 26 ... Plunger 28 ... Cylinder body 30 ... Pressure oil supply path 32 ... pressure oil discharge path 34 ... flow control valve 36 ... main logic valve 36a ... pilot pressure oil chamber 36b ... casing 36c ... pressure oil flow chamber 36d ... piston 36e ... needle 36f ... pressing member 36g ... open / close hole 36h ... pressure oil Flow hole 36i ... Pilot pressure oil flow hole 38 ... Pilot pressure oil discharge passage 40 ... Subordinate logic valve 40a ... Pilot pressure oil chamber 40b ... Casing 40c ... Pressure oil flow chamber 40d ... Piston 40e ... Needle 40f ... Pressing member 40g ... Open / close hole 40h ... Pressure oil flow hole 40i ... Pilot pressure oil flow hole 42 ... Pilot pressure Oil supply path 44 ... switching valve 44a ... two-position four-way valve 44b ... solenoid 46 ... communication passage 47 ... check valve 48 ... control means 48a ... sequencer 48b ... operation part 48c ... display part 49 ... pressure oil source 50 ... oil tank 54 ... Pressure oil discharge path 60 ... wiring

Claims (1)

A pressure oil supply passage for supplying pressure oil from a pressure oil source to the injection cylinder;
A pressure oil discharge passage for returning the pressure oil discharged from the injection cylinder to the oil tank;
It is attached to the pressure oil supply passage and has a pilot pressure oil chamber. When the pilot pressure oil chamber is filled with pressure oil, the pressure oil supply passage is closed and the pressure oil is discharged from the pilot pressure oil chamber. A main logic valve that opens the pressure oil supply passage when
A pilot pressure oil discharge passage for returning the pressure oil discharged from the pilot pressure oil chamber of the main logic valve to the oil tank;
A pilot pressure oil chamber attached to the pilot pressure oil discharge passage and having a volume smaller than that of the pilot pressure oil chamber of the main logic valve is provided. When the pilot pressure oil chamber is filled with the pressure oil, the pilot pressure oil chamber is provided. A secondary logic valve that closes the pressure oil discharge passage and opens the pilot pressure oil discharge passage when pressure oil is discharged from the pilot pressure oil chamber;
A pilot pressure oil supply passage for supplying pressure oil from the pressure oil source to the pilot pressure oil chamber of the sub logic valve;
A pilot pressure oil supply state that is attached to the pilot pressure oil supply passage and supplies pressure oil to the pilot pressure oil chamber of the slave logic valve, and pressure oil discharged from the pilot pressure oil chamber of the slave logic valve A switching valve for alternately switching a pilot pressure oil discharge state to be returned to the oil tank;
A communication path that communicates the pilot pressure oil supply path between the slave logic valve and the switching valve, and the pilot pressure oil discharge path between the main logic valve and the slave logic valve;
A hydraulic circuit for an injection cylinder in a die casting machine, wherein the communication path includes a check valve attached in a direction to supply pressure oil to the pilot pressure oil discharge passage.

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