JPH0771730B2 - Die casting machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit of a die casting machine, and more particularly to a differential pressure type check valve used for switching from an injection process to a pressure increasing process of the die casting machine.

[Conventional technology]

FIG. 2 is a diagram showing an example of an injection side hydraulic circuit in a conventional die casting machine.

In the figure, 1 is an injection cylinder of a die casting machine, which is in front of the injection rod 2 (on the left side in the drawing).
An injection plunger (not shown) mounted on the mold is advanced at a low speed or a high speed by an injection accumulator 3 of a pressure oil source to inject and fill a mold cavity (not shown) with a molten metal such as aluminum. . When the injection is almost completed,
The pressure oil source is switched to the pressure-increasing accumulator 4 to enter a pressure-increasing step, and a high pressure is applied to the molten metal filled in the cavity to cool while precisely transferring the fine shape of the cavity to the molten metal.

Generally, the pressure of the pressure increasing accumulator 4 is set to about twice the pressure of the injection accumulator 3.

In the figure, 5 is a differential pressure check valve, 6 is an injection pilot check valve, 9, 10, 14, 15, 17, 19, 22 are pipelines, 16
Is a low speed injection pilot check valve, 18 is a high speed injection pilot check valve, 20 is a tank, 21 is a pressure boosting pilot check valve, 23 is a pressure increase rising speed control valve, 31 is a cam, S is a low speed start limit switch, A is a limit switch for starting high-speed injection, and B is a limit switch for starting pressure increase.

The above is the main configuration of the injection side hydraulic circuit in the die casting machine, but the differential pressure type check valve 5 plays an important role in the above hydraulic circuit in order to perform this injection operation.

The differential pressure type check valve 5 is used for low speed or high speed injection.
The pressure oil from the injection accumulator 3 is flowed into the head chamber 1a of the injection cylinder 1 while appropriately adjusting the flow rate, and the forward speed of the injection rod 2 is controlled. When entering the boosting process,
The differential pressure type check valve 5 is closed so that the high pressure of the pressure increasing accumulator 4 does not flow back to the injection accumulator 3 through the injection pilot check valve 6.
You need to shut off quickly and reliably.

In order to satisfy this requirement, the differential pressure type check valve 5 is
The structure is as shown in FIG. That is, the valve body 8 including the large-diameter portion 8a, the small-diameter portion 8b, and the medium-diameter portion 8c is axially slidably mounted in the valve box 7 including the large-diameter portion 7a, the small-diameter portion 7b, and the inclined portion 7c. Has been done. The conduit 9 into which the pressure oil from the injection accumulator 3 flows is communicated with the small diameter portion 7b of the valve box 7, and the conduit 10 from the head chamber 1a of the injection cylinder 1 is communicated with the large diameter portion 7a of the valve box 7. Has been done.

Also, a small hole communicating from the peripheral surface of the medium diameter portion 8c to the side surface of the large diameter portion 7a.
11 is provided, and the hydraulic pressure applied to the head chamber 1a of the injection cylinder 1 passes through the conduit 10 to the large diameter portion of the differential pressure check valve 5.
It is also designed for 8a.

Reference numeral 12 is a rod body screwed to the large diameter portion 7a of the valve box 7, and is a stop position when the valve body 8 moves rightward toward the drawing by the rotation of the handle 12a connected thereto, that is, the valve body 8 It is designed to adjust the stroke. Reference numeral 13 denotes a spring, which constantly presses the valve element 8 to the left in the drawing.

In the differential pressure type check valve 5 configured as described above, when the valve body 8 moves to the left and the edge portion of the middle diameter portion 8c presses the inclined portion 7c of the valve box 7, the differential pressure type check valve 5 causes the check valve to move. And disconnects the communication between the conduit 9 and the conduit 10.
When the valve body 8 shifts to the right from its position, the medium diameter portion 8c
A gap is formed between the edge portion of the valve box 7 and the inclined portion 7c of the valve box 7, and as a result, the pipeline 9 and the pipeline 10 communicate with each other, and the pressure oil from the injection accumulator 3 is transferred to the head chamber 1a of the injection cylinder 1. Is flowed into.

The flow rate of the pressure oil is adjusted by setting the stroke for shifting the valve body 8 to the right from the closed position with the rod body 12 as described above. Therefore, the differential pressure type check valve 5
From the viewpoint of the injection cylinder 1, it functions as a flow rate adjusting valve during the injection filling process and as a check valve during the pressure increasing process.

The reason why the check valve 5 is of the differential pressure type will now be described with reference to FIG.

In this differential pressure check valve 5, the cross-sectional area of the large-diameter valve body 8a ………… A ₁ cm ² The cross-sectional area of the medium-diameter valve body 8b ………… A ₂ cm ² The cross-sectional area of the small-diameter valve body 8c ………… A ₃ cm ² Hydraulic pressure from the line 9 ……………… p ₁ kg / cm ² Hydraulic pressure from the line 10 ………… p ₂ kg / cm ² Valve body 8 to the right Force to push to ... F ₁ kg Force to push valve body 8 to the left ... If F ₂ kg, F ₁ = p ₁ (A ₂ −A ₃ ) + p ₂ (A ₁ −A ₂ ) F ₂ = p ₂ · A ₁ .

Here, considering the balance of the axial force applied to the valve body 8 when the differential pressure type check valve 5 is closed, the valve body 8 is balanced at the point where F ₁ = F ₂ . As a concrete numerical example, for example, p ₁ = 120 kg / cm ² A ₁ = 100 cm ² A ₂ = 20 cm ² Becomes That is, when the hydraulic pressure applied to the head chamber 1a of the injection cylinder 1 reaches 96 kg / cm ² , the differential pressure type check valve 5 is closed.

If there is no small diameter portion 8b in FIG. 4, that is, A ₃ = 0.
Considering the simple check valve of, the check valve 5 does not close unless the hydraulic pressure applied to the head chamber 1a of the injection cylinder 1 rises to p ₂ = 120 kg / cm ² .

As is apparent from this description, since the differential pressure type structure as shown in FIG. 4 is used, the differential pressure check valve 5 can be closed while the hydraulic pressure applied to the head chamber 1a of the injection cylinder 1 is relatively low, and the pressure increasing step is performed. It is possible to make the pressure rise of as fast as possible.

This is very important for ensuring the quality of cast products,
This is the reason why the differential pressure type check valve 5 is used.

[Problems to be solved by the invention]

The operation of the hydraulic circuit will be described again with reference to FIG. When the injection process is started, the hydraulic pressures in the pilot pipe line 14 of the injection pilot check valve 6 and the pilot pipe line 17 of the low speed pilot check valve 16 both become 0, and the pressure oil from the injection accumulator 3 becomes zero. It flows into the head chamber 1 a of the injection cylinder 1 via the valve 6, the pipe 9, the differential pressure check valve 5 and the pipe 10.

At the same time, the return oil pushed out from the rod chamber 1b of the injection cylinder 1 returns to the tank 20 via the pipe line 15 and the low speed injection pilot check valve 16. The low-speed injection pilot check valve 16 acts as a low-speed throttle valve during injection, and the valve element moves by the stroke set by the adjustment handle 16a,
The injection plunger moves forward at a low speed and pushes the molten metal into the plunger.

When the tip of the injection plunger passes the molten metal supply port of the plunger sleeve, the hydraulic pressure in the pilot conduit 19 of the high speed injection pilot check valve 18 becomes zero. Therefore pipeline 15
Return oil from the tank is divided into the high-speed injection pilot check valve 18 and the low-speed injection pilot check valve 16.
Returning to 20, the injection brazier 1 advances at high speed to inject the molten metal into the mold cavity.

Next, when the pressure increasing process is started, the pressure increasing pilot check valve 21
, The hydraulic pressure of the pilot pipe line 22 becomes 0, and the high pressure oil from the pressure increasing accumulator 4 is applied to the head chamber 1a of the injection cylinder 1 via the pressure increasing pilot check valve 21 and the pressure increasing rising speed adjusting valve 23, and the pressure increasing is performed. Is done. At this time, as described above, it is important to quickly close the differential pressure check valve 5 so that the high-pressure oil from the pressure increasing accumulator 4 does not flow backward toward the injection accumulator 3.

The problem here is that the pressure oil flowing from the pipe line 9 to the pipe line 10 in the injection process flows by forcibly opening the valve body 7 of the differential pressure type check valve 5 toward the drawing and to the right. , Hydraulic p ₂
Can be further reduced compared to the hydraulic pressure p ₁ compared to the pressure balance state of equation (1).

If the sliding resistance of the injection plunger increases even a little during injection forward when the differential pressure type check valve 5 is forced to flow through the differential pressure type check valve 5 in this way, especially at low speed injection, the low speed forward stops momentarily. try to. Immediately thereafter, the hydraulic pressure in the injection head chamber 1a increases, and the injection plunger is advanced. At the beginning of the forward movement, it will stop again due to sliding resistance, and will move forward again. This causes a so-called "chattering" phenomenon, which adversely affects the injection of the molten metal.

From the viewpoint of preventing the occurrence of this “chattering” phenomenon, the smaller the value of A ₃ / A _{2 in} the above formula (2) is, the smaller the pressure reduction rate may be. Check valve 5
The value of A ₃ / A _{2 in} Eq. (1) should be large in order to quickly perform the closing operation of. It is difficult to meet such conflicting requirements, and the hydraulic circuit of the conventional die casting machine is designed based on appropriate experience values, and there is a problem in quality stability, and it is necessary to obtain precise cast products. It was difficult.

The object of the present invention is to eliminate such drawbacks of the prior art,
It is an object of the present invention to provide a die casting machine in which the response of the differential pressure type check valve is good and a precision cast product can be obtained.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention provides an injection cylinder for extruding molten metal, an injection hydraulic source such as an accumulator communicating with the head chamber of the injection cylinder, and an accumulator communicating with the head chamber of the injection cylinder. The present invention is intended for a die casting machine including a pressure increasing hydraulic power source and a differential pressure type check valve interposed between the injection cylinder and the injection hydraulic pressure source.

The differential pressure check valve includes a large diameter portion having a hole communicating with the head chamber of the injection cylinder, a small diameter portion having a hole communicating with the injection hydraulic power source, and a large diameter portion and a small diameter portion thereof. And a large diameter part slidably disposed in the valve box and sliding in the large diameter part of the valve box, and an inclined part of the valve box. With a medium diameter part,
The rod chamber of the injection cylinder includes a piston portion that slides in a small-diameter portion of a valve box, and a valve body that has a small-diameter portion that connects the piston portion and the medium-diameter portion and has a smaller cross-sectional area than the piston portion. From the middle of the pipe from the low-speed injection pilot check valve to the tank, and a check valve is provided midway between the branch point and the pilot oil chamber of the small diameter part of the valve box of the differential pressure check valve. In addition to the connection by a pilot line, the pilot line between the check valve and the differential pressure type check valve is connected to the tank via a switching valve.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a hydraulic system diagram of a main part of an injection side of a die casting machine according to an embodiment, and FIG. 3 is a cross-sectional view of a differential pressure type check valve. In these drawings, a conventional die casting machine (FIGS. 2 and 4).
The same parts as those of the above are denoted by the same reference numerals and detailed description thereof is omitted.

First, the internal structure of the differential pressure type check valve 24 will be described with reference to FIG. In order to improve the drawbacks of the conventional differential pressure type check valve 5 shown in FIG. ₄ , a piston portion having a cross-sectional area A ₄ larger than the cross-sectional area A ₃ of the small diameter portion 8b at the tip of the small diameter portion 8b of the valve body 8. Provide 8d. Further, the small diameter portion 7b of the valve box 7 also forms a cylinder chamber 7d having a size in which the piston portion 8d can slide, and a small hole 7e for pilot piping is provided on the side surface of the small diameter portion. is there.

FIG. 1 is a hydraulic system diagram using the differential pressure type check valve 24. As shown in the figure, from the middle of the return oil line 15,
Small hole 7e for pilot piping of the differential pressure check valve 24
(That is, the pilot oil chamber, which is a control chamber in which the pilot pressure on the outer end side is guided to the small diameter portion 7b of the valve box 7 of the differential pressure type check valve 24), the pilot pipe line 26 provided with the check valve 25 midway. It communicates with. Further, a pilot pipe 30 is provided branching from the middle of the pilot pipe 26, and is connected to the tank 29 via a switching valve 28 operated by an electromagnetic solenoid 27 at the tip thereof.

A cam 31 interlocking with the injection rod 2 is provided.
The low-speed injection start limit switch S, the high-speed injection start limit switch A, the depressurization start limit switch C, and the pressure increase start limit switch B, which are operated at 1, are respectively installed at predetermined positions. The decompression starting limit switch C is a limit switch that is operated near the end of the high-speed injection process.

Next, the operations of the differential pressure type check valve 24 and the hydraulic system using the differential pressure type check valve 24 will be described separately for each item of low speed injection, high speed injection, pressure reduction start and pressure increase start.

1. During low-speed injection As the rod 2 of the injection cylinder 1 moves, the limit switch S for low-speed injection starts to operate, and the pilot line 14 in the injection pilot check valve 6 and the pilot pipe in the low-speed injection check valve 16 When both the hydraulic pressures in the passages 17 are set to 0, the pressure oil from the injection accumulator 3 set to, for example, 120 kg / cm ² passes through the injection pilot check valve 6 and the differential pressure check valve 24 to reach the head chamber of the injection cylinder 1. Flow into 1a.

At the same time, the return oil from the rod chamber 1b of the injection cylinder returns to the tank 20 through the line 15 and the low speed injection pilot check valve 16. The flow rate of this return oil is adjusted by the adjusting handle 16 which adjusts the valve stroke of the pilot check valve 16.
Meter-out throttling is performed by setting a. Therefore, the pipe 15 has a resistance pressure at this time, for example, several tens of kg / cm ² . Since this resistance pressure is applied to the cylinder chamber 7d of the small diameter portion of the differential pressure type check valve 24 via the check valve 25 and the pilot conduit 26, the valve body 8 of the differential pressure type check valve 24 is
, The force to passively shift to the right acts.
Therefore, the gap between the medium-diameter portion 8c of the valve body 8 and the inclined portion 7c of the valve box 7 is passively widened shortly after the start of resistance injection, so that the injection cylinder 1 of the injection cylinder 1 is injected during low-speed injection. The pressure p ₂ applied to the head chamber 1a has almost no pressure loss in the differential pressure check valve 24 as compared with the set pressure p ₁ of the injection accumulator 3. As a result, there is no so-called “chatter” phenomenon, and smooth low-speed injection is performed.

2. During high-speed injection If the limit switch A for high-speed injection is activated and the pressures of the pilot line 14 and the pilot line 17 remain 0, the pressure of the pilot line 19 of the injection high-speed injection check valve 18 is also set to 0. The return oil from the injection cylinder 1 is branched from the pipe 15 through the high-speed injection pilot check valve 18 and the low-speed injection pilot check valve 16 and returned to the tank 20.

Also at this time, since the resistance pressure generated in the pipe 15 is continuously applied to the cylinder chamber 7d of the differential pressure check valve 24 through the check valve 25 and the pipe 26 at the time of low-speed injection, the differential pressure check valve 24 A gap is secured between the valve body middle diameter portion 8c and the inclined portion 7c of the valve box 7, and the gap stroke is accurately adjusted by the rod body 12 to accurately determine the injection speed.

3. Decompression start When the limit switch C for decompression starts to operate, the switching valve 28
The solenoid 27 is turned on, and the resistance hydraulic pressure in the pilot pipe line 26 flows to the tank 29 via the pipe line 30 and the switching valve 27, so that the cylinder chamber of the differential pressure check valve 24 is closed.
The hydraulic pressure of 7d becomes zero. Accordingly, the pressure oil flowing from the pipe line 9 through the pipe line 10 into the head chamber 1a of the injection cylinder 1 must open the valve body 8 of the differential pressure check valve 24 by itself, so that the pressure oil is decompressed at the same time. Since the hydraulic pressure p ₂ is reduced, the speed of the injection cylinder 1 is also reduced, and the surge pressure generated at the time of completion of filling can be suppressed to a low level due to the effects of both deceleration and pressure reduction. This will be described later with reference to FIGS. 5 and 6.

4. At the start of boosting pressure When pressure is applied to the pilot pipe line 14 and the limit switch B for boosting pressure is stepped on, the pressure in the pilot pipe line 22 is set to 0, and the head chamber 1a of the injection cylinder 1 is discharged from the injection accumulator 3 The pressure oil from the pressure increasing accumulator 4 set to a higher pressure is applied in place of the pressure oil.

The closing characteristic of the differential pressure type check valve 24 of the present invention at this time is calculated as follows.

Cross-sectional area of large-diameter valve body 8a ………… A ₁ cm ² Cross-sectional area of medium-diameter valve body 8b ………… A ₂ cm ² Cross-sectional area of small-diameter valve body 8c ………… A ₃ cm ² Cross-sectional area of the piston 8d ………… A ₄ cm ² Hydraulic pressure from the pipeline 9 ……………… p ₁ kg / cm ² Hydraulic pressure from the pipeline 10 ………… p ₂ kg / cm ² Force to push the valve body 8 to the right ………… F ₁ kg Force to push the valve body 8 to the left ………… If F ₂ kg, F ₁ = p ₁ (A ₂ −A ₃ ) + P ₂ (A ₁ −A ₂ ) F ₂ = p ₁ (A ₄ −A ₃ ) + p ₂ · A ₁ where the axial force applied to the valve body 8 when the differential pressure check valve 24 is closed. Considering the equilibrium of, the valve body 8 is balanced at a point such that F ₁ = F ₂ , That is, since the area A ₃ of the small diameter portion 8b of the valve body 8 is erased and the value of A ₄ / A ₂ is made large, the hydraulic pressure p ₂ for closing the differential pressure type check valve 24 becomes small, in other words By doing so, the differential pressure type check valve 24 can be closed even if the pressure oil applied to the head chamber 1a of the injection cylinder 1 is considerably low.

As a specific numerical example, for example, p ₁ = 120 kg / cm ² , A ₂ = 100 cm ² , A ₄ = 50 cm ₂ [Effects of the Invention] FIG. 5 and FIG. 6 show the characteristics of the changes in the injection pressure and the injection speed in each step of the die casting machine according to the embodiment of the present invention and the conventional die casting machine in the positional relationship of the limit switch. It is a figure.

In these figures, (a) shows the positional relationship among the low-speed injection start limit switch S, the high-speed injection start limit switch A, the decompression start limit switch C, the pressure increase start limit switch B, and the like. (B) of the same figure
Indicates process regions such as a low-speed injection process, a high-speed injection process, a pressure reduction process and a pressure increase process. (C) of the figure is
In the injection pressure characteristic, the time point X in the figure indicates the completion of filling, and the time point Y indicates the surge pressure. (D) of the figure shows that Z (see FIG. 6) in the figure has a “chattering” phenomenon in the injection speed characteristic.

As is clear from the comparison between FIG. 5 and FIG. 6, the conventional one (FIG. 6) causes the “chatter” phenomenon (Z) during the low-speed injection process, but the present invention does not cause the “chatter”. Not only is there a stable injection with no phenomenon, but the injection speed during the high-speed injection process is higher than that of the conventional one. on the other hand,
Conventionally, the surge pressure (Y) generated when the filling is completed is more than 100
The been made in kg / cm ² is is suppressed low as a few tens kg / cm ² those of the present invention. Further, the time required to complete the pressure increase after the point (Y) is shortened, and the disturbance due to the surge is small.

Since the present invention is configured as described above, the following operational effects can be achieved.

． The "chattering" phenomenon that occurs during the low-speed injection process can be eliminated, and smooth injection is possible.

． Near the completion of the high-speed injection process, the hydraulic pressure applied to the head chamber of the injection cylinder can be reduced, so the thrust of the injection cylinder decreases and the speed also decreases.
The surge pressure at the time of completion of filling can be kept low, and the occurrence of burrs in cast products can be greatly reduced.

． At the beginning of boosting, pressure differential from the booster accumulator reaches the head chamber of the injection cylinder at the initial stage, and the differential pressure check valve can be surely closed to achieve quick boosting start, which is very useful for precision casting. Be advantageous.

[Brief description of drawings]

FIG. 1 is a main part hydraulic system diagram of an injection side hydraulic circuit of a die casting machine according to an embodiment of the present invention, FIG. 2 is a main part hydraulic system part of an injection side hydraulic circuit of a conventional die casting machine, and FIG. Sectional view of a differential pressure type check valve according to an embodiment of the invention,
FIG. 5 is a sectional view of a conventional differential pressure type check valve, FIG. 5 is an injection characteristic diagram of a die casting machine according to an embodiment of the present invention, and FIG. 6 is an injection characteristic diagram of a conventional die casting machine. 1 ... Injection cylinder, 1a ... Head chamber, 1b ... Rod chamber, 3 ... Injection accumulator, 4 ... Increase pressure accumulator, 7 ... Valve box, 7a ... Large diameter part, 7b ... Small diameter part ,
7c …… Inclined part, 7d …… Cylinder chamber, 7e …… Small hole, 8 ……
Valve body, 8a ... large diameter part, 8b ... small diameter part, 8c ... medium diameter part, 8d
...... Piston, 24 ...... Differential pressure check valve.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-59-35871 (JP, A) JP-A-59-42169 (JP, A) JP-A-59-61561 (JP, A) JP-B 54- 18218 (JP, B2) JP-B 55-36430 (JP, B2) JP-B 58-19383 (JP, B2) JP-B 55-20784 (JP, B2) JP-B 54-45368 (JP, Y2)

Claims (1)

[Claims] 1. An injection cylinder for extruding molten metal, an injection hydraulic source communicating with the head chamber of the injection cylinder, a pressure increasing hydraulic source communicating with the head chamber of the injection cylinder, the injection cylinder and the injection hydraulic source. In a die casting machine having a differential pressure type check valve interposed between and, the differential pressure type check valve, a large diameter portion provided with a hole communicating with the head chamber of the injection cylinder, and the injection hydraulic source. A valve box having a small diameter portion provided with a communicating hole and an inclined portion connecting between the large diameter portion and the small diameter portion, and a slidably arranged inside the valve box, inside the large diameter portion of the valve box. A large-diameter portion that slides along the middle-diameter portion that contacts the inclined portion of the valve box,
A rod portion of the injection cylinder, comprising a piston portion that slides in a small-diameter portion of the valve box, and a valve body that has a small-diameter portion having a smaller cross-sectional area than the piston portion that connects the piston portion and the medium-diameter portion, To the tank via the pilot injection valve for low speed injection to the tank, and a check valve is provided midway between the branch point and the pilot oil chamber in the small diameter part of the valve box of the differential pressure check valve. A die casting machine characterized in that the pilot pipe line between the check valve and the differential pressure type check valve is connected to the tank via a switching valve while being connected by a pilot pipe line.