JP2008006469A - Die-casting method and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable smooth discharge of a gas from a cavity by controlling the melt flow in the cavity, and to obtain good quality castings with less entrainment of gas regardless of shape or size. <P>SOLUTION: The die-casting method comprises pressure-filling a cavity 2 with a molten metal while eliminating the back pressure of the cavity 2 in a die 1 from an exhaust passage 22 and a gas venting runner 21 by opening a pressure reducer 26. Further, the valve devices 27A and 27B are installed in a main runner 21A open to a first area A including a portion apt to accumulate a gas in the cavity 2 and in another main runner 21B open to a second area B adjacent to the first area A, respectively. In the initial stage of injection into the cavity 2, the opening of one valve device 27A is made larger than that of the other device 27B so that the melt flows into the first area A preferentially. After the melt is filled in the area A, the openings of the valve devices 27A and 27B are switched reversely to change the melt flow to the area B, thus running out the gas to the main runner 21B side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to die casting, and more particularly, to a die casting method and apparatus for pressurizing and filling molten metal into a cavity while removing back pressure of a cavity of a mold.

  In this type of die casting method, by removing the back pressure of the mold cavity, the gas generated in response to the injection of the molten metal into the cavity is discharged out of the mold, and good quality with little gas entrainment The cast product can be obtained. By the way, if the product to be cast has a complicated shape and a large size, degassing will be insufficient if only degassing is performed from one place of the cavity. For this reason, when casting a large product having a complicated shape, a plurality of degassing runners are provided in the mold, and degassing is performed from a plurality of locations in the cavity.

  However, when casting a product in which a thick part and a thin part are mixed, i.e., when a region with a large volume and a region with a small volume are mixed in the cavity, generally, there is a delay in filling the molten region with a large volume. As a result, the volume is large and gas tends to accumulate in a portion away from the gate. However, the number and location of venting runners are limited by the relationship between the mold structure and product shape, or the yield, and depending on the product, the gas can be vented from the portion where gas tends to accumulate. However, there was a problem that quality was inevitably deteriorated.

  For example, Patent Document 1 proposes that the back pressure of the cavity is detected, and if the back pressure is high, it is determined that the amount of remaining gas is large and the injection speed of the molten metal is reduced. However, as described above, when the setting of the venting runner is restricted, the venting is still insufficient, and the fundamental countermeasure is not achieved.

JP 2005-313231 A

  The present invention has been made in view of the above-described conventional problems, and the problem is that the gas flow from the cavity can be smoothly discharged by controlling the flow of hot water in the cavity, and the shape, It is an object of the present invention to provide a die casting method and apparatus capable of obtaining a cast product of good quality with little gas entrainment regardless of size.

  In order to solve the above problems, a die casting method according to the present invention includes a die casting method in which a back pressure of a cavity of a mold is removed through a plurality of venting runners, and the cavity is filled with molten metal under pressure. The hot water flow in the cavity is controlled by changing the sectional area of the degassing runner in a predetermined order. In this case, the cross-sectional area of each degassing runner is changed so that the molten metal flows preferentially into a region in the cavity that includes a portion where gas tends to accumulate. In this case, it is desirable to change the cross-sectional area by adjusting the opening degree of the valve means set in the gas vent runner.

  In the die casting method performed in this way, in the initial stage of injection into the cavity, the cross-sectional area of the degassing runner opening in the area including the portion where gas tends to accumulate is compared with the cross-sectional area of the degassing runner opening in the other area. The back pressure on the region side including the portion where gas tends to accumulate is removed preferentially over other regions, so that the molten metal flows preferentially into the region. That is, the molten metal is preferentially filled in the region including the portion where the gas tends to accumulate, whereby the gas in the region moves to the other region, and then the cross-sectional area of the degassing runner opening in the other region is increased. Then, the back pressure on the other region side is lowered, and the molten metal flows into this region, and the gas is smoothly discharged by being pushed by the flow of the molten metal.

  In this die casting method, the back pressure of the cavity of the mold may be forcibly removed by the decompression means. In this case, since the removal of the back pressure is promoted, the sectional area of the gas vent runner is increased. It is possible to control the hot water flow in the cavity more reliably by changing the above.

  In order to solve the above problems, a die casting apparatus according to the present invention includes a die casting apparatus for removing a back pressure of a cavity of a mold through a plurality of venting runners and pressurizing and filling a molten metal into the cavity. Further, the valve means capable of changing the cross-sectional areas of the plurality of venting runners is provided. In this case, the valve means can be constituted by a valve body capable of appearing and retracting in the degassing runner and a driving means for driving the valve body. Further, the mold may be provided with a decompression passage communicating with the decompression means, and the plurality of degassing runners may be communicated with the decompression passage.

  According to the die casting method and apparatus of the present invention, since the hot water flow in the cavity is controlled by changing the cross-sectional area of the plurality of venting runners, the gas can be smoothly discharged from the cavity. Therefore, it is possible to obtain a cast product of good quality with less gas entrainment regardless of the shape and size.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

  1 and 2 show a die casting apparatus as an embodiment of the present invention. As shown in FIG. 2, the present die casting apparatus includes a mold 1, an injection device 10 for pressurizing and filling molten metal into a cavity 2 of the mold 1, and a back pressure for removing the cavity 2. The back pressure removing mechanism 20 and a controller (control means) 30 for controlling the operation of the back pressure removing mechanism 20 are schematically configured.

  The mold 1 includes a fixed mold 3 and a movable mold 4, and the cavity 2 is formed between the fixed mold 3 and the movable mold 4 in a closed state. Further, in this mold closed state, between the fixed mold 3 and the movable mold 4, a gate 5 that opens to the cavity 2 and a runner 7 that communicates the gate 5 with a gate 6 to which the injection device 10 is connected. And are formed. The injection device 10 includes an injection sleeve 11 coupled to the gate 5 and an injection plunger 12 slidably disposed in the injection sleeve 11, and the injection plunger 12 is a driving means (not shown). As a result, the injection sleeve 11 is moved back and forth. The injection sleeve 11 has a hot water supply port 13 for receiving the molten metal at the upper part on the rear end side. After supplying a predetermined amount of molten metal into the injection sleeve 11 from the hot water supply port 13, the injection plunger 12 is advanced. The molten metal is injected from the gate 6 into the cavity 2 through the runner 7 and the gate 5.

  The back pressure removing mechanism 20 is connected to a degassing runner 21 and an exhaust passage 22 formed at a joint portion of the fixed mold 3 and the movable mold 4 constituting the mold 1, and connected to the exhaust passage 22 via an exhaust pipe 23. And a vacuum pump 25 that generates a negative pressure stored in the vacuum tank 24, and a pressure reducing valve 26 that is interposed in the exhaust pipe 23 and opens and closes a pipe line in the exhaust pipe 23. Yes.

  As shown in FIG. 1, the degassing runner 21 is branched from a plurality (here, two) of main runners 21A and 21B, one end of which is connected to the exhaust passage 22, and the main runners 21A and 21B. The cavity 2 includes a plurality of (here, three) auxiliary runners 21Aa and 21Bb each having one end opened. In this embodiment, the cavity 2 is composed of a first area A having a relatively large volume and a second area B having a relatively small volume, and the sub-runner 21Aa branched from one main runner 21A is the first area. Corresponding to A, the sub-runner 21Bb branched from the other main runner 21B is arranged corresponding to the second region B, respectively.

  In the back pressure removing mechanism 20 configured as described above, the inside of the vacuum tank 24 is maintained at a predetermined degree of vacuum by the intermittent operation of the vacuum pump 25, and the molten metal is injected into the cavity 2 now. When the pressure reducing valve 26 is opened at the timing, the back pressure in the cavity 2 is removed to the vacuum tank 24 through the gas vent runner 21, the exhaust passage 22 and the exhaust pipe 23. Therefore, the vacuum tank 24, the vacuum pump 25, etc. constitute decompression means for decompressing the inside of the cavity 2.

  In the present embodiment, the fixed mold 3 constituting the mold 10 is provided with a valve device 27 (27A, 27B) capable of independently changing the cross-sectional areas of the main runners 21A, 21B constituting the degassing runner 21. It is installed. As shown in FIG. 2, the valve device (valve means) 27 is composed of a valve body 28 that can be moved in and out of the main runners 21A and 21B, and a hydraulic servo cylinder (drive means) 29 that drives the valve body. Yes. The valve body 28 can be positioned at an arbitrary position between a position where the main runners 21A and 21B are completely opened (opening degree 100%) and a position where the main runners 21A and 21B are completely closed (opening degree 0%). The cross-sectional areas of the main runners 21A and 21B are changed according to the position of the valve body 28.

  The controller 30 has a function of controlling the opening and closing of the pressure reducing valve 26 and a function of controlling the operation of the hydraulic servo cylinder 29 constituting the valve device 27. In the present embodiment, the pressure reducing valve 26 is opened at the timing when the molten metal is injected into the cavity 2, and the opening degree of the valve device 27 is 2 at the timing when the molten metal is filled in the first region A in the cavity 2. The change is made between the two main runners 21A and 21B. Each timing described above can be grasped by, for example, the position (stroke) of the injection plunger 12 of the injection device 10 or the elapsed time after the injection plunger 12 starts moving forward, and the controller 30 can detect the position signal of the injection plunger 12. The pressure reducing valve 26 and the hydraulic servo cylinder 29 are controlled based on the timer signal.

  Hereinafter, a die casting method performed by the die casting apparatus configured as described above will be described with reference to FIGS.

  At the start of casting, the pressure reducing valve 26 is closed. Further, the valve device 27 provided in the gas vent runner 21 is a valve device 27A (hereinafter referred to as A-side valve device 27A) disposed in one main runner 21A that opens to the first region A in the cavity 2. The opening degree is set to be larger than the opening degree of the valve device 27B (hereinafter referred to as the B-side valve device 27B) disposed in the other main runner 21B that opens to the second region B in the cavity 2. As an example, the opening degree of the A-side valve device 27A is set to 100%, and the opening degree of the B-side valve device 27B is set to 50%. Under the state described above, a predetermined amount of the molten metal M is supplied into the injection sleeve 11 through the hot water supply port 13, and when the supply of the molten metal M is completed, the driving means of the injection device 10 is operated, and the injection plunger 12 is moved at a predetermined speed. Advance. As the injection plunger 12 advances, the molten metal M in the injection sleeve 11 is injected into the cavity 2 through the runner 7 and the gate 5 of the mold 1.

  Then, the pressure reducing valve 26 is opened by a command from the controller 30 in time with the start of injection. Then, the negative pressure in the vacuum tank 24 is introduced into the cavity 2 from the exhaust passage 22 through the gas vent runner 21, whereby most of the gas in the cavity 2 is exhausted to the vacuum tank 24 side that is an exhaust means. At this time, since the opening degree of the A-side valve device 27A in the cavity 2 is larger than the opening degree of the B-side valve device 27B, the cavity 2 generated in the main runner 21A opening in the first region A The back pressure is removed in preference to the back pressure of the cavity 2 generated in the main runner 21B opening in the second region B. Thereby, as indicated by an arrow in FIG. 3, the molten metal M injected into the cavity 2 flows preferentially into the first region A, and as a result, the molten metal M is preferentially filled into the first region A. The By the way, since the volume of the first region A is relatively large as described above, gas tends to accumulate in a portion C (portion surrounded by a dotted line in FIG. 3) that is away from the gate 4. However, in the present embodiment, since the molten metal M flows preferentially into the first region A including the portion C, the gas in the portion C is pushed by the molten metal M toward the second region B side. Moving.

  In the present embodiment, a change command is output from the controller 30 to the hydraulic servo cylinder 29 at the timing when the molten metal M is filled in the first region A in the cavity 2, and the A side valve device 27A and the B side valve device 27B are output. And the opening degree is changed. The change of the opening degree in this case includes the content of making the B side valve device 27B larger than the opening degree of the A side valve device 27A. As an example, the opening degree of the A-side valve device 27A is set to 80%, and the opening degree of the B-side valve device 27B is set to 100%. Thereby, the back pressure of the cavity 2 generated in the main runner 21B opening in the second region B is removed in preference to the back pressure of the cavity 2 generated in the main runner 21A opening in the first region A. As a result, as indicated by an arrow in FIG. 4, the flow of the molten metal M in the cavity 2 moves from the first region A to the second region B, and the gas that is pushed by the molten metal M and stays in the second region B The secondary runner 21 </ b> Bb is discharged to the main runner 21 </ b> B, and is further discharged to the vacuum tank 24 through the exhaust passage 22.

  As described above, according to the present embodiment, since the molten metal M flows preferentially into the first region A including the portion C in the cavity 2 where gas tends to accumulate, the gas remains in the portion C. As a result, the gas in the cavity 2 is smoothly discharged to the outside. Therefore, by controlling the hot water flow in the cavity 2 according to the shape and size of the product to be cast, it is possible to obtain a cast product of good quality without gas entrainment.

  In the above embodiment, the hydraulic servo cylinder 29 is used as the drive means of the valve body 28 in the valve device 27 (27A, 27B). However, the type of the drive means is arbitrary, and a motor (servo motor) is used. Can be used. However, in this case, a motion conversion mechanism that converts the rotation of the motor into a linear motion is required.

  Moreover, in the said embodiment, although the thing of the horizontal type which arranged the fixed mold | type 3 and the movable mold | type 4 in the horizontal direction was used as the metal mold | die 1, this metal mold | die has a fixed mold | type and a movable mold | type up and down. Of course, it may be a vertical format arranged in the above.

  Further, in the above embodiment, the back pressure of the cavity 2 generated in the gas vent runner 21 is forcibly removed by the exhaust means (vacuum tank 24, vacuum pump 25, etc.). In this case, one end of the venting runner 21 is simply opened to the atmosphere.

  1 and 2, the degassing runner 21 (21A, 21B) is set to have a cross-sectional size of 15 mm in width and 8 mm in height, and an injection sleeve 13 having an inner diameter of 140 mm is used to form aluminum made of ADC12. The molten alloy was injected under the condition of a forward speed (injection speed) of the injection plunger 12 of 2.0 m / s. At the same time as the start of injection, the pressure reducing valve 26 is opened. On the other hand, for the valve device 27, the opening degree of the A-side valve device 27A is set to 100% until 100 ms elapses from the start of injection (when the region A is completely filled). In addition, the opening degree of the B-side valve device 27B is set to 0%, and thereafter, the opening degree of the A-side valve device 27A is set to 30%, and the opening degree of the B-side valve device 27B is set to 100%. Casting was performed while controlling the flow of hot water in the cavity 2 (method of the present invention). For comparison, the valve device 27 was cast with the opening degree fixed at 100% for both the A-side valve device 27A and the B-side valve device 27B under the same apparatus and injection conditions (comparative method). And the fracture surface inspection by a fracture | rupture was performed about the obtained casting. As a result, in the casting obtained by the method of the present invention, no gas nest caused by air entrainment was observed, whereas in the casting obtained by the comparative method, the portion C (FIG. ), A gas nest caused by air entrainment was observed, and it was confirmed that the method of the present invention for controlling the hot water flow greatly contributes to the improvement of casting quality.

It is a top view which shows typically the principal part structure of the die-casting apparatus which concerns on this invention. It is sectional drawing which shows the whole structure of this die-casting apparatus. It is sectional drawing which shows the initial stage of the implementation of die-casting by this die-casting apparatus, and a middle stage. It is sectional drawing which shows the last stage of implementation of die-casting by this die-casting apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mold, 2 Cavity 3 Fixed type, 4 Movable type 5 Gate, 6 Runner 10 Injection device, 11 Injection sleeve, 12 Injection plunger 20 Back pressure removal mechanism 21 Degassing runner 21A, 21B Main runner 22 Exhaust passage 24 Vacuum tank ( Exhaust means)
25 Vacuum pump (exhaust means)
26 Pressure reducing valve 27 (27A, 27B) Valve device (valve means)
28 Valve body 29 Hydraulic servo cylinder (drive means)
30 controller (control means)
M molten metal

Claims (7)

  In a die casting method in which the back pressure of a mold cavity is removed through a plurality of venting runners, and the molten metal is pressurized and filled into the cavities, the sectional areas of the plurality of venting runners are changed in a predetermined order, A die casting method characterized by controlling the hot water flow in the inside.   2. The die casting method according to claim 1, wherein the cross sectional area of each degassing runner is changed so that the molten metal flows preferentially into a region including a portion in which the gas tends to accumulate.   3. The die casting method according to claim 1, wherein the sectional area is changed by adjusting the opening of the valve means provided in the gas vent runner.   4. The die casting method according to claim 1, wherein the back pressure of the mold cavity is forcibly removed by a decompression means.   In a die-casting apparatus that pressurizes and fills molten metal into the cavity while removing the back pressure of the mold cavity through a plurality of gas vent runners, a valve that can change the sectional area of each of the gas vent runners in the mold. A die casting apparatus characterized by comprising means.   6. The die casting apparatus according to claim 5, wherein the valve means comprises a valve body capable of appearing and retracting in the venting runner and a driving means for driving the valve body. The die casting apparatus according to claim 5 or 6, wherein a pressure reducing passage communicating with the pressure reducing means is provided in the mold, and a plurality of venting runners are communicated with the pressure reducing passage.

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