JPH0227969Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial field of application] The invention is designed to prevent the molten metal poured into the casting sleeve from
This invention relates to an injection device for a die-casting machine that injects into a mold cavity by moving a plunger connected to a piston rod of an injection cylinder forward.

[Conventional technology]

Die casting machines are classified into vertical clamping dies and horizontal clamping dies according to the mold clamping direction, and are also classified into vertical casting dies and horizontal casting dies according to the casting direction. Fig. 2 is a partially cutaway schematic side view showing the injection device of the horizontal clamping horizontal casting type die casting machine. Other fixed plate (not shown)
are connected and fixed at their four corners by tie rods 3, and the tie rod 3 supports a movable platen 4 that moves forward and backward relative to the fixed platen 2 through a toggle mechanism or the like by a mold clamping cylinder on the other fixed platen side. has been done. Reference numerals 5 and 6 denote a fixed mold and a movable mold that are mounted on the fixed plate 2 and the movable plate 4 facing each other, respectively, and are provided with a cavity 8 divided by a dividing surface 7, so that the movable plate 4 can move forward and backward. The mold is configured to be clamped and opened by the . Further, an injection sleeve 10 having a pouring port 9 is inserted and fixed into the sleeve hole of the stationary platen 2, and the injection sleeve 10 and the cavity 8 are communicated with each other through a runner 11 and a gate 12. 13 indicates the molten metal injected from the pouring port 9 and stored in the injection sleeve 10. On the other hand, on the fixed platen 2 side, an injection cylinder 14 is provided, and a plunger tip, which is the head of a plunger 17, is connected via a coupling 16 to a piston rod 15 that moves forward and backward by the hydraulic pressure supplied to the injection cylinder 14. 18 is fitted into the injection sleeve 10 so as to be freely retractable. A striker 19 is fixed to the coupling ring 16 and extends along the injection cylinder 14, and the magnetic head 2 is attached to the fixed part.
0, and is configured such that the forward and backward movement of the plunger 17 is controlled by a signal generated by the magnetic head 20 detecting the position of the magnetic scale 21.

With the above configuration, after the mold clamping cylinder moves the movable platen 4 to clamp the molds 5 and 6, the injection sleeve 1 is inserted from the pouring port 9.
When the molten metal 13 is injected into the cavity 8 and the plunger 17 is advanced from the position shown in the figure by feeding pressure oil from the injection cylinder 14, the molten metal 13 is injected into the cavity 8 through the runner 11 and the gate 12, and the product is is obtained. After casting, the molds 5 and 6 are moved by moving the movable platen 4.
One casting cycle is completed by opening the mold and extruding the product from the cavity 8 using a product extrusion device (not shown).

Conventionally, the injection speed of the injection cylinder 14 in such a die-casting machine starts at a low speed, increases to high speed as soon as the molten metal 13 reaches the cavity 8, and stops the plunger after filling the molten metal at this high speed. This speed control is taken from the magnetic head 20.
This is done by changing the opening degree of a flow control valve or the like provided in the hydraulic circuit based on a plunger position detection signal from the hydraulic circuit.

However, in such an injection cylinder 14 and its hydraulic circuit, the plunger tip 18
If the load fluctuates due to galling between the plunger 17 and the inner wall of the sleeve 10 as it advances inside the injection sleeve 10, the forward speed of the plunger 17 will fluctuate, and the injection pressure will also fluctuate, resulting in uneven product quality. There was a problem with becoming.

Conventionally, this drawback has been solved by providing a hollow spool within the piston of the injection cylinder and providing a run-around circuit in the injection cylinder. FIG. 3 is a cross-sectional view of this type of injection cylinder and its hydraulic circuit diagram, and this will be explained based on the same figure. A piston rod 32 in the shape of a piston is integrally formed and projects from the cylinder 30, and this projecting portion is connected to a second
It is connected to a plunger 17 shown in the figure via a coupling ring 16. 33 is a hollow spool with a bottom fixed to one end of the cylinder 31,
It is inserted into the inner hole of the piston rod 32 via a sealing material 34, and is connected to the inner hole of the spool 33, the inner hole of the piston rod 32, and the piston rod 32.
The inner hole of the cylinder 30 and the inner hole of the cylinder 30 are communicated with each other through a plurality of ports 35 and 36, respectively.
On the other hand, the accumulator 37 has a pilot check valve 38 electrically connected to the magnetic head 20.
A high-speed pipe 40 equipped with a variable throttle valve 39 and a low-speed pipe 43 equipped with a pilot check valve 41 and a variable throttle valve 41, which are also electrically connected to the magnetic head 20, are connected in parallel. Further, the confluence of both pipes 40 and 43 is connected to the head end side port 45 of the cylinder 30 by a pipe 44, and a pipe 47 equipped with a check valve 46
The rod end side port 4 of the cylinder 30 is
8 and is also connected to a port 51 provided in the spool 33 by a pipe 50 provided with a check valve 49.

With this configuration, in the illustrated state, the pilot check valve 41 on the low-speed pipe 43 opens in response to a signal from the magnetic head 20, and the pressure oil from the accumulator 37 flows at the flow rate set in the variable throttle valve 42. It is sent to the port 45, the piston 31 moves forward, and injection starts at low speed. At this time, pressure oil on the rod end side flows from port 48 to pipe 4.
7 and joins the pipe 44 through the port 35, the inner hole of the spool 33, the port 51, and the pipe 50, thereby forming a run-a-land circuit.

When the molten metal 13 in FIG. 2 reaches the cavity 8, the magnetic head 20 detects the position of the plunger 17 and issues a signal, the pilot check valve 38 on the high-speed piping 40 side opens, and the pressure oil from the accumulator 37 is released. The flow rate set in the variable throttle valve 39 is sent to the port 45, and the injection speed is switched to high speed. The formation of a run-a-land circuit is the same as in the low-speed case.

With this configuration, pressure is applied to the rod end side of the cylinder 30 from the start of injection, so even if load fluctuations occur due to galling of the plunger tip 18, the injection speed is not affected.

[Problem that the invention attempts to solve]

However, in the conventional injection cylinder shown in FIG. 3, when switching from low speed injection to high speed injection, the pilot check valve 41 on the low speed side is closed and the pilot check valve 38 on the high speed side is closed.
If the injection speed is opened, the injection speed will suddenly drop at the moment of switching, causing the plunger tip 18 to hunt and create cavities in the product.To avoid this, the pilot check valve 38 on the low speed side is kept open when the injection speed is increased. As a result, the following problems occurred.

That is, for example, after performing injection work by setting the low injection speed by the variable throttle valve 42 to 0.1 m/sec and setting the high injection speed by the variable throttle valve 39 to 3 m/sec, the casting process may be performed due to a change in product specifications. When changing the setting value of the low-speed side variable throttle valve 42 from 0.1 m/sec to 0.5 m/sec in an attempt to change the injection conditions, the high-speed injection speed changes from 3.1 m/sec to 3.5 m/sec when switching to high-speed injection. There was a problem that this caused a negative impact on the product.

[Means for solving problems]

In order to solve these problems, the present invention connects the rod end side port and the head end side port of an injection cylinder equipped with a hollow spool that is inserted into the hollow piston rod and supports it slidably. A flow rate adjustment device for low-speed injection was provided in the run-a-land circuit, and a flow rate adjustment device for high-speed injection was provided in the run-a-land circuit that connected the port provided on the spool of the injection cylinder and the head end port of the cylinder.

[Effect]

When oil is sent to the head end side of the injection cylinder, the piston moves forward and the pilot check valve in the low speed run-around circuit opens, and the flow rate of pressure oil set in the low speed variable throttle valve joins and is sent to the head end port. and low-speed injection is performed. At this time, the high-speed side pilot check valve in the high-speed side run-a-land circuit is closed. When the tip of the molten metal reaches the cavity and the low speed side pilot check valve closes and the high pressure side pilot check valve opens, the pressure oil at the flow rate set in the high speed variable throttle valve joins and is sent to the head end side port for high speed injection. can be switched to In this case, even if both the high-speed and low-speed pilot check valves close at the same time when switching to high-speed injection, the main circuit continues to supply oil to the head end of the cylinder, so the speed of the piston rod increases. does not drop suddenly. Furthermore, even if the injection speed on the low speed side is changed, the high speed injection speed will not change because the run-around circuit on the high speed side is independent.

〔Example〕

FIG. 1 is a vertical sectional view of an injection cylinder and its hydraulic circuit diagram showing an embodiment of the injection device for a die-casting machine according to the present invention, and the structure of the injection cylinder is the same as that of the conventional injection cylinder shown in FIG. 3. Therefore, each member will be given the same reference numeral and detailed explanation thereof will be omitted. Furthermore, since the construction of the entire injection device other than the injection cylinder is the same as that of the conventional device shown in FIG. 2, the explanation thereof will be omitted and will be explained later with reference to the same drawing when necessary. In the figure, a piston accumulator 61 connected to a tank 60 for storing N ₂ gas has a piston 62 that moves forward due to the pressure of the N ₂ gas and sends out internal pressure oil 63 at a predetermined pressure. Head end side port 4 of piston accumulator 61 and cylinder 30
5 through a pipe 64, and this pipe 64
A pilot check valve 66 is provided inside, which opens when the pilot pressure from the solenoid valve 65 is cut off. Further, in the pipe 67 connecting the rod end side port 48 of the cylinder 30 and the pipe 64, there is a pilot check valve 69 which is closed by the action of the pilot pressure from the solenoid valve 68, and a pilot check valve 69 which is opened and closed by the signal from the magnetic head 20. an on-off valve 70 that
A low-speed variable throttle valve 71 that can set the flow rate for low-speed injection is provided, thereby forming a run-around circuit on the low-speed side that joins the pipe 64. Furthermore, port 5 of spool 33
A pilot check valve 74 that opens when the pilot pressure from the solenoid valve 73 is cut off, and a variable throttle valve 75 for high-speed injection that can set the flow rate for high-speed injection are provided in the pipe 72 that connects the injection valve 1 and the pipe 64. A run-around circuit on the high-speed side that joins the pipe 64 is formed.

The operation of the injection device configured as above will be explained. In the illustrated state, when the solenoid of the solenoid valve 65 is actuated by a command to start injection, the pilot pressure is cut off, the pilot check valve 66 opens, and the pressure oil 63 in the piston accumulator 61 is activated.
is fed to the head end side port 45 via the installation pipe 64. At this time, the pilot check valve on the high speed side is closed, and the pilot check valve 69 and switching valve 70 on the low speed side are open, so the pressure oil on the rod end side of the cylinder 30 is transferred to the variable throttle valve 7.
The pressure oil flows through the pipe 67 at a flow rate set to 1 and joins the pressure oil flowing within the pipe 64. Therefore, the piston rod 32 moves forward at a low speed of, for example, 0.1 m/sec, and the plunger tip 18 moves forward to inject the molten metal 13 into the cavity 8 at a low speed.

When the tip of the molten metal 13 reaches the cavity 8,
The piston rod 32 at this time when the magnetic head 20
This signal activates the solenoid of the solenoid valve 73 for high-speed injection, and the pilot pressure opens the pilot check valve 74, and the low-speed side on-off valve 70 closes, opening the pilot check valve. 69 is also closed by pilot pressure. Therefore, the pressure oil on the rod end side of the cylinder 30 flows into the pipe 72 through the ports 36, 35, and 51, and joins the pressure oil in the pipe 64 according to the flow rate set in the variable throttle valve 75. As a result, the piston rod 32 moves forward at a high speed of, for example, 3 m/sec, and the plunger tip 18
moves forward and the cavity 8 is filled with the molten metal 13.

When switching from low-speed injection to high-speed injection, even if both the low-speed and high-speed pilot check valves 69 and 74 are closed at the same time, pressure oil from the pipe 64 is fed to the port 45 during this time. Therefore, the forward speed of the piston rod 32 does not suddenly decrease.

In addition, after completing the injection work, in order to change the casting conditions due to a change in product specifications, the setting value of the low speed side variable throttle valve 71 may be changed from 0.1 m/sec to 0.5 m/sec, for example.
Even if the speed is changed to sec, the high-speed injection speed does not change when switching to high-speed injection because the run-a-land circuit on the high-speed side and the run-a-land circuit on the low-speed side are independent.

Note that if a variable throttle valve is also provided in the pipe 64,
It is easier to adjust the flow rate, but this does not necessarily have to be provided.

[Effect of idea]

As is clear from the above description, according to the present invention, in an injection device for a die-casting machine, a rod end side port of an injection cylinder equipped with a hollow spool that is inserted into a hollow piston rod and slidably supports it. A flow rate adjustment device for low-speed injection is installed in the run-a-land circuit that connects the head-end side port of the injection cylinder, and a flow rate adjustment device for high-speed injection is installed in the run-a-land circuit that connects the port provided on the spool of the injection cylinder and the head-end side port of the cylinder. By installing a flow rate adjustment device,
Even if both the low-speed and high-speed pilot check valves close at the same time when switching from low-speed injection to high-speed injection, pressure oil from the main piping continues to be supplied to the cylinder, so the forward speed of the piston rod will not suddenly drop. Therefore, the quality of the product can be maintained in good condition. In addition, even if the low injection speed is adjusted using a variable throttle valve due to changes in product specifications,
Since the low-speed circuit and the high-speed circuit are independent, the high-speed injection speed does not change, and the quality of the product is improved compared to the conventional method.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view of an injection cylinder and its hydraulic circuit diagram showing an embodiment of the injection device for a die-casting machine according to the present invention, Fig. 2 is a schematic side view of a conventional injection device for a die-casting machine, and Fig. 3 is a Similarly, it is a vertical sectional view of the injection cylinder and its hydraulic circuit diagram. 30...Cylinder, 32...Piston rod,
33... Spool, 45... Head end side port, 48... Rod end side port, 51... Port, 67, 73... Piping, 69, 74... Pilot check valve, 71... Variable throttle valve for low speed,
75...Variable throttle valve for high speed.

Claims (1)

[Scope of utility model registration request] An injection cylinder consisting of a hollow piston rod that moves forward and backward within the cylinder, a spool fixed to the head end of the cylinder and slidably inserted into the inner hole of the piston rod, a rod end side port and a head end side port of the cylinder. and a second run-around circuit that connects the port provided on the fixed side of the spool and the head end side port of the cylinder, and An injection device for a die-casting machine, characterized in that a flow rate adjustment device for low-speed injection is provided, and a flow rate adjustment device for high-speed injection is provided in a second run-a-land circuit.