Die casting apparatus

Abstract

To provide a die casting apparatus capable of reducing the entry of molten metal at a low temperature at the tip of the molten metal into a cavity even when the molten metal runs ahead.SOLUTION: A die casting apparatus 1 includes a molding die 3 having a product cavity 21, a runner 23 and a plurality of gates 25, an injection part 5 for injecting molten metal into the product cavity 21, a decompression part 7 for decompressing the inside of the product cavity 21, and a gate opening / closing part 9 for opening / closing the plurality of gates 25. The mold 3 has a molten metal pool part 27 connected to the 23b of the leading end part of the runner 23. The gate opening / closing part 9 opens at least one gate 25 positioned at the 23b side of the tip part when the pressure reduction by the pressure reducing part 7 is started, and opens all of the plurality of gates 25 when a prescribed time passes after the injection of the molten metal into the product cavity 21 in the reduced pressure state by the injection part 5 is started.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to a die casting apparatus. [Background technology]

[0002] Die-casting molds are known that are designed to prevent the occurrence of casting defects such as gas defects, molten metal wrinkles, and cold shuts in products cast by die casting. The die-casting mold includes a cavity, a runner, and multiple gates connecting the cavity and the runner. The die-casting mold is equipped with a filter in at least one of the gates to reduce the flow rate of the molten metal. The die-casting mold is installed in a die-casting machine. The cavity is also called the product cavity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-193241 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in die-casting machines equipped with die-casting dies, when the interior of the die-casting die is vacuum-suctioned, a phenomenon known as "running" occurs, in which the molten metal is sucked into the cavity along with the air inside the die. This running can cause the low-temperature molten metal at the tip of the molten metal to enter the cavity, potentially resulting in the formation of a cold shut in the die-cast product. Furthermore, the filter can slow the flow of the molten metal. An excessive slowdown in the flow of the molten metal can result in the formation of a cold shut in the die-cast product.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a die casting apparatus that can prevent the low-temperature molten metal at the leading edge from entering the product cavity due to leading edge molten metal. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, a die-casting machine according to an embodiment of the present invention comprises a molding die having a product cavity, a runner that guides molten metal into the product cavity, and multiple gates provided between the runner and the product cavity for molding a predetermined die-cast product; an injection section that injects the molten metal into the product cavity through the runner and the multiple gates; a pressure reduction section that reduces the pressure inside the product cavity; and a gate opening / closing section that opens and closes the multiple gates, wherein the runner has an introduction section located on the injection section side and a tip section that includes the tip of the runner, and the molding die has a well section connected to the tip of the runner, and when the pressure reduction section begins to reduce the pressure, the gate opening / closing section opens at least one of the multiple gates that is located on the tip side of the runner, and when a predetermined time has elapsed since the injection section began injecting the molten metal into the product cavity in a depressurized state. [Effects of the Invention]

[0007] The present invention provides a die casting apparatus that can prevent the low-temperature molten metal at the front end from entering the product cavity due to leading edge molten metal. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a side view showing an example of the configuration of a die-casting device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing an example of a molding die provided in the die-casting machine according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of a die-casting apparatus according to the present invention will be described with reference to FIGS.

[0010] FIG. 1 is a side view showing an example of the configuration of a die-casting device according to an embodiment of the present invention.

[0011] In FIG. 1, the front-rear direction D L indicates the front-rear direction of the die-casting apparatus 1, which coincides with the length direction of the die-casting apparatus 1. Also, the up-down direction D H indicates the up-down direction of the die-casting apparatus 1, and coincides with the height direction of the die-casting apparatus 1. The same applies to Fig. 2 described below.

[0012] The die-casting apparatus 1 shown in Fig. 1 injects molten metal, which is a melted metal alloy, into a precision mold to produce highly accurate castings with excellent casting surfaces in a short period of time at a high cycle rate. In this embodiment, the material of the molten metal may be, for example, an aluminum alloy, a zinc alloy, a magnesium alloy, or a copper alloy. Hereinafter, the molten metal of the metal alloy used in the die-casting apparatus 1 may be referred to as "molten metal."

[0013] As shown in Fig. 1, the die-casting apparatus 1 includes a molding die 3, an injection section 5 that injects molten metal into the internal space of the molding die 3, and a pressure reduction section 7 that reduces the pressure in the internal space of the molding die 3. The molding die 3 and the injection section 5 are directly connected to each other so that the molten metal can flow through them. The molding die 3 and the pressure reduction section 7 are indirectly connected to each other via a pipe 8 so that air can flow through them.

[0014] FIG. 2 is a cross-sectional view showing an example of a molding die provided in a die-casting apparatus according to an embodiment of the present invention.

[0015] In addition, Figure 2 is based on the line AA in Figure 1, and is in the vertical direction D H 2 is a cross-sectional view of the forming die 3 taken parallel to the left-right direction D. W indicates the left-right direction of the die-casting apparatus 1, which coincides with the width direction of the die-casting apparatus 1. Furthermore, the left-right direction D W coincides with the width direction of the forming die 3 when the forming die 3 is provided in the die-casting apparatus 1.

[0016] As shown in FIG. 2 in addition to FIG. 1, the molding die 3 has, as an internal space, a product cavity 21 having a shape corresponding to the die-cast product, a runner 23 for guiding molten metal to the product cavity 21, a plurality of gates 25 provided between the runner 23 and the product cavity 21, and an exhaust path 29 connected to the piping 8.

[0017] Furthermore, the molding die 3 has a fixed die and a movable die that is movable relative to the fixed die, both of which are not shown. The molding die 3 is in a closed state (mold clamping) when the fixed die and the movable die are brought close to each other, and in an open state when the fixed die and the movable die are moved away from each other. When the molding die 3 is in a closed state, the product cavity 21, the runner 23, the multiple gates 25, and the exhaust path 29 are provided inside the molding die 3. In other words, when the molding die 3 is in a closed state, the product cavity 21, the runner 23, the multiple gates 25, and the exhaust path 29 are formed and surrounded by the fixed die and the movable die.

[0018] The product cavity 21 is a hollow (space) that follows the shape of the die-cast product to be cast. In other words, the product cavity 21 has the shape of the die-cast product.

[0019] The runner 23 is a passage through which the molten metal injected from the injection section 5 flows. Multiple runners 23 may be provided depending on the shape of the die-cast product to be molded, i.e., the shape of the product cavity 21. In the example shown in FIG. 2, two runners 23 are provided on the molding die 3. The runner 23 has an introduction section 23a located on the injection section 5 side and guiding the molten metal injected from the injection section 5 into the molding die 3, and a tip section 23b including the tip of the runner 23 farthest from the introduction section 23a. The introduction section 23a includes an introduction port for guiding the molten metal injected from the injection section 5 into the molding die 3. The runner 23 also has a linear shape extending linearly from the introduction section 23a to the tip section 23b. This eliminates abrupt changes in the angle of the wall surface of the runner 23 or abrupt changes in the cross-sectional area of ​​the runner 23, thereby reducing turbulence in the flow of the molten metal and air entrainment in the molten metal that would occur due to these changes. That is, the injected molten metal reaches the tip 23b of the runner 23 without being hindered in its progression within the runner 23.

[0020] The multiple gates 25 are paths through which the molten metal flows from the runner 23 into the product cavity 21. The number and cross-sectional area of ​​the multiple gates 25 can be set appropriately depending on the shape of the product cavity 21.

[0021] Exhaust path 29 is connected to pressure reduction unit 7 via piping 8. Exhaust path 29 is a path through which the air inside product cavity 21 is discharged to the outside of casting mold 3 when vacuum suction is performed by pressure reduction unit 7.

[0022] The injection section 5 has a sleeve 31 connected to the runner 23 of the molding die 3 , and a plunger 33 slidably disposed inside the sleeve 31 .

[0023] The sleeve 31 has an inlet 31a for injecting molten metal into the sleeve 31. The sleeve 31 stores the molten metal injected from the inlet 31a inside.

[0024] The plunger 33 pressurizes the molten metal stored inside the sleeve 31 and injects it into the product cavity 21. Specifically, as the plunger 33 moves in the direction of arrow X, the molten metal inside the sleeve 31 passes through the runner 23 and multiple gates 25 in order, and is injected into the product cavity 21 to fill it.

[0025] Decompression section 7 uses vacuum suction to expel air from inside product cavity 21. Generally, when casting a large die-cast product, if air is present inside product cavity 21, this air will become entrained in the molten metal, causing gas defects (blowholes) in the die-cast product. Decompression section 7 expels air from inside product cavity 21, suppressing gas defects and also suppressing the generation of oxides that degrade the quality of the die-cast product.

[0026] Specifically, the pressure reducing section 7 is equipped with a vacuum pump (not shown). The pressure reducing section 7 uses the vacuum pump to suction the inside of the product cavity 21 and create a reduced pressure state just before filling with molten metal. Creating a reduced pressure state suppresses the occurrence of gas defects and oxides when filling with molten metal, and also improves the flowability of the molten metal.

[0027] The die-casting method in which the air inside the product cavity 21 is reduced in pressure by the pressure reducing section 7 is called a vacuum die-casting method (reduced pressure die-casting method). In other words, the die-casting apparatus 1 is a vacuum die-casting apparatus.

[0028] The die casting apparatus 1 also includes gate opening / closing units 9 for opening and closing the multiple gates 25. The gate opening / closing units 9 have, for example, a movable flat-plate-shaped member, and open and close the multiple gates 25 by moving this flat-plate-shaped member in parallel. The number of gate opening / closing units 9 may, for example, be the same as the number of runners 23. However, the number of gate opening / closing units 9 may also be the same as the number of multiple gates 25. In this case, the gate opening / closing units 9 may be configured as, for example, a piston-like mechanism that opens and closes each gate 25. The size of the gate opening / closing units 9 is set appropriately depending on the number of multiple gates 25 to be opened and closed.

[0029] As mentioned above, in a die-casting apparatus equipped with a conventional die-casting mold, there is a risk that molten metal with a low temperature at the front end of the molten metal will enter the cavity due to leading edge running during vacuum suction, resulting in the formation of a cold shut in the die-cast product. Furthermore, there is a risk that a filter will reduce the speed of the molten metal flow, resulting in the formation of a cold shut. Hereinafter, the molten metal with a low temperature at the front end caused by leading edge running of the molten metal will sometimes be referred to as "leading edge molten metal."

[0030] Therefore, the casting mold 3 has a well portion 27 connected to the tip portion 23b of the runner 23. When the pressure reducing unit 7 starts depressurizing, the gate opening / closing unit 9 opens at least one of the multiple gates 25 that is located on the side of the tip portion 23b of the runner 23, and opens all of the multiple gates 25 when a predetermined time has passed since the injection unit 5 started injecting the molten metal into the product cavity 21 in a depressurized state.

[0031] Specifically, in the example shown in FIG. 2 , when the injection unit 5 injects the molten metal into the casting mold 3, the gate opening / closing unit 9 opens only one gate 25 located on the tip end 23b side of the runner 23. Therefore, even if the molten metal runs ahead, most of the molten metal traveling straight along the linear runner 23 does not flow into the open gate 25, but instead flows into the well portion 27 by inertia, retaining its momentum. Moreover, the gate opening / closing unit 9 opens all of the gates 25 a predetermined time after the injection unit 5 starts injecting the molten metal into the product cavity 21. This allows the molten metal, whose temperature has not yet decreased and is extruded from the sleeve 31 of the injection unit 5 following the ahead-running molten metal, to be guided into the product cavity 21 without impeding its flow. This prevents the ahead-running molten metal from entering the product cavity 21. In other words, this prevents the formation of a cold shut due to the ahead-running molten metal in the resulting die-cast product. The predetermined time from when the injection section 5 starts injecting the molten metal into the product cavity 21 in a decompressed state is, for example, the time until the leading molten metal enters and is retained in the well section 27. However, this is not limited to this, and the predetermined time can be set to any time after the leading molten metal has passed through the gate 25 located closest to the tip end 23b of the runner 23.

[0032] The well portion 27 may also have a curved or inclined wall surface 27a against which the molten metal flowing through the runner 23 strikes. The molten metal striking such a wall surface 27a is efficiently guided into the well portion 27. This makes it possible to reliably retain the molten metal in the well portion 27 without directing it toward the open gate 25.

[0033] Furthermore, when the forming die 3 is mounted in the die-casting apparatus 1, in the width direction of the forming die 3 which coincides with the width direction of the die-casting apparatus 1, if the width of the well portion 27 is W1 and the width of the runner 23 is W2, it is preferable that the following relational expression (1) is satisfied. W1>W2 (1)

[0034] By satisfying the above relational expression (1), the well portion 27 has a space (depth) for guiding the molten metal that strikes the curved or inclined wall surface 27a. This makes it possible to more reliably retain the molten metal in the well portion 27 without directing it toward the open gate 25.

[0035] The volume of the well portion 27 is preferably within the range of 5% to 20% of the volume of the product cavity 21.

[0036] Specifically, if the volume of the well portion 27 is less than 5% of the volume of the product cavity 21, it may be difficult to sufficiently retain the molten metal that has run ahead in the well portion 27. In this case, there is a risk that some of the molten metal will flow toward the open gate 25. On the other hand, if the volume of the well portion 27 is more than 20% of the volume of the product cavity 21, an excessive amount of molten metal, including the molten metal that has run ahead, may be retained in the well portion 27. In this case, there is a risk that it will take an excessive amount of time to fill the product cavity 21, or that the amount of molten metal required to fill the product cavity 21 will be excessively large. Therefore, if the volume of the well portion 27 is within the range of 5% to 20% of the volume of the product cavity 21, the well portion 27 will have a space that is more suitable for guiding the molten metal that has struck the curved or inclined wall surface 27a. In other words, the well portion 27 makes it possible to more reliably retain the molten metal in the well portion 27 without directing the molten metal that has run ahead toward the open gate 25.

[0037] The predetermined die-cast product molded by the mold 3 is preferably a cylinder block, a transmission case, a crankcase, or a cylinder block integrated with a crankcase. Die-cast products that are relatively large and have complex shapes are prone to cold shuts, a casting defect caused by pre-running molten metal. In particular, when the cylinder block is, for example, a cylinder block for a multi-cylinder engine having multiple cylinder bores, cold shuts, a casting defect caused by pre-running molten metal, are more likely to occur. Therefore, by molding a cylinder block, a transmission case, a crankcase, or a cylinder block integrated with a crankcase as the die-cast product molded by the mold 3, it is possible to significantly reduce the occurrence of cold shuts caused by pre-running molten metal in these die-cast products.

[0038] As described above, the die-casting apparatus 1 according to this embodiment includes a molding die 3 having a well portion 27 connected to the tip end 23b of the runner 23, and a gate opening / closing unit 9 that opens at least one of the gates 25 located near the tip end 23b of the runner 23 when the pressure reducing unit 7 begins depressurizing, and opens all of the gates 25 a predetermined time after the injection unit 5 begins injecting molten metal into the product cavity 21 in a depressurized state. Therefore, even if forward running of molten metal occurs in the molding die 3, most of the molten metal traveling straight along the linear runner 23 does not flow into the open gate 25, but instead flows into the well portion 27 by inertia, maintaining its momentum. Therefore, the die-casting apparatus 1 can prevent forward running molten metal from entering the product cavity 21. In other words, the die-casting apparatus 1 can prevent cold shuts caused by forward running molten metal from forming inside the die-cast product.

[0039] Furthermore, the die-casting apparatus 1 according to this embodiment includes a molding die 3 having a runner 23 with a curved or inclined wall surface 27a against which the molten metal flowing through the runner 23 strikes. Therefore, the die-casting apparatus 1 efficiently guides the molten metal that strikes the wall surface 27a into the well portion 27. Therefore, the die-casting apparatus 1 can reliably retain the ahead-running molten metal in the well portion 27 without directing it toward the open gate 25. In other words, the die-casting apparatus 1 can further prevent the ahead-running molten metal from entering the product cavity 21, and further prevent the formation of a cold shut due to the ahead-running molten metal inside the die-cast product.

[0040] Furthermore, the die-casting apparatus 1 according to this embodiment is equipped with a forming die 3 that satisfies the above-mentioned relational expression (1) when the width of the well portion 27 is W1 and the width of the runner 23 is W2 in the width direction of the forming die 3. Therefore, the die-casting apparatus 1 can further prevent the leading molten metal from entering the interior of the product cavity 21, and can further prevent the formation of a cold shut inside the product due to the leading molten metal.

[0041] Furthermore, the die-casting apparatus 1 according to this embodiment is provided with a molding die 3 having a well portion 27 with a volume that is within a range of 5% to 20% of the volume of the product cavity 21. Therefore, the die-casting apparatus 1 can further prevent the infiltration of the leading molten metal into the product cavity 21, and can further prevent the formation of cold shuts inside the product due to the leading molten metal.

[0042] The die-casting apparatus 1 according to this embodiment is equipped with a molding die 3 for molding die-cast products such as cylinder blocks, transmission cases, crankcases, or cylinder blocks integrated with crankcases. Therefore, the die-casting apparatus 1 can significantly reduce the occurrence of cold shuts due to leading molten metal in these die-cast products, which are relatively large in size and have complex shapes.

[0043] Therefore, with the die-casting apparatus 1 according to this embodiment, it is possible to prevent the low-temperature molten metal at the front end from entering the interior of the product cavity 21 due to the molten metal running ahead.

[0044] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0045] 1...die casting device, 3...molding mold, 5...injection section, 7...pressure reduction section, 8...piping, 9...gate opening / closing section, 21...product cavity, 23...runner, 23a...introduction section, 23b...tip section, 25...gate, 27...well section, 27a...wall surface, 29...exhaust path, 31...sleeve, 31a...inlet, 33...plunger

Claims

1. a molding die for molding a predetermined die-cast product, the molding die having a product cavity, a runner for guiding molten metal to the product cavity, and a plurality of gates provided between the runner and the product cavity; an injection unit that injects the molten metal into the product cavity through the runner and the plurality of gates; a pressure reducing section that reduces the pressure inside the product cavity; a gate opening / closing unit that opens and closes the plurality of gates, the runner has an introduction portion located on the injection portion side and a tip portion including a tip of the runner, the molding die has a well portion connected to the tip end portion of the runner, The gate opening / closing unit is When the pressure reducing unit starts decompression, at least one gate located on the tip end side of the runner is opened among the plurality of gates; a die-casting device that opens all of the plurality of gates when a predetermined time has elapsed since the injection section started to inject the molten metal into the product cavity while the injection section is in a decompressed state;

2. 2. The die casting apparatus according to claim 1, wherein the well portion has a curved or inclined wall surface against which the molten metal flowing through the runner strikes.

3. 3. The die casting apparatus according to claim 2, wherein, when the width of the well portion is W1 and the width of the runner is W2 in the width direction of the mold, the following relational expression (1) is satisfied: W1>W2 (1)

4. 3. The die casting apparatus according to claim 2, wherein the volume of the well portion is within a range of 5% to 20% of the volume of the product cavity.

5. 2. The die casting apparatus according to claim 1, wherein the predetermined die casting product is a cylinder block, a transmission case, a crankcase, or a cylinder block integrated with a crankcase.

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