JP2010005670A - Die for die casting - Google Patents

Description

  The present invention relates to a die casting mold in which a conductor bar and an end ring are cast with a high melting point metal material such as pure copper or copper alloy for a rotor of a cage induction motor or the like.

  First, the general rotor structure of the squirrel-cage induction motor described above is shown in FIGS. As is well known, a rotor 1 of a squirrel-cage induction motor includes a conductor bar 2 made of an aluminum alloy and a cage 4 composed of a pair of end rings (short-circuiting rings) 3 coupled to both ends of the conductor bar 2 made of a steel plate laminate. The structure is combined with the iron core 5. Generally, the iron core 5 is inserted and set in a die-casting mold, and a molten aluminum alloy is pressurized and injected into the mold to cast the cage 3. It has been. In addition, 5a is a slot for casting the conductor bar 2 formed along the circumference of the iron core 5, 6 is a heat radiating fin that is also integrally formed on the end face of the end ring 3, and 7 is a weight mounting pin for balancing. .

  Next, a basic mold structure of a die casting machine for casting the above-described aluminum alloy rotor 1 is shown in FIG. 4 as a schematic diagram. In FIG. 4, a die casting mold 8 includes a fixed mold 9, a movable mold 10, and an intermediate mold 11 into which the iron core 5 described above is inserted and set, and a sleeve for feeding molten aluminum alloy into the mold 8. 12 are combined to form a die casting machine. Here, the fixed mother die 9 and the movable mother die 10 are equipped with a cavity block 13 constituting an annular cavity corresponding to the end ring 3 of the rotor 1 shown in FIG.

  In order to cast the rotor 1 of the cage induction motor with the above die casting mold, the rotor core 5 (see FIG. 3B) is inserted and set in the intermediate mold 11 of the mold 8, and the mold 8 is mounted. In a state where the mold is clamped, a molten aluminum alloy (molten aluminum alloy) A is supplied to the sleeve 12, and the molten metal is pushed out toward the mold at a high speed by the pressing operation of the plunger 12a. Thereby, the molten metal A is filled in the cavity in the mold and the slot 5a of the iron core 5 through the gate 14, and the conductor bar 2 and the end ring 3 are cast on the iron core 5.

  In addition, as for the die material of the above-described aluminum alloy die-casting die, alloy tool steel for hot die such as SKD61 is generally used.

  In this case, in the die casting mold 8, the thermal and mechanical load acting on the surface of the mold as a result of friction with the molten metal A flowing at a high temperature and high pressure, solidification and demolding of the aluminum alloy are repeated. As a result, the cavity surface of the mold 8 is damaged by heat check (fine cracks), melting damage, etc., and the life of the mold is reduced, but the molten metal is an aluminum alloy of a low melting point metal. In some cases, the life of a practical mold is said to be about 100,000 shots or more.

  On the other hand, in order to improve the efficiency and characteristics of the squirrel-cage induction motor, the conductor bar 2 and end ring 3 shown in FIG. 3 are made of pure copper or copper alloy having high conductivity instead of aluminum alloy. Some are configured (see, for example, Patent Document 1 and Patent Document 2).

  In this case, if a pure copper conductor bar and end ring are cast using the aluminum alloy die casting mold 8 as described above, the melting point of pure copper is as high as 1083 ° C., so the thermal shock acting on the mold is large. For this reason, a heat check for fine cracks occurs on the cavity surface of the mold that comes into contact with the molten metal in a few shots, and the life of the mold is significantly reduced.

  Therefore, various contrivances have been made for die casting molds applied to casting of high melting point metal materials such as pure copper and copper alloys as countermeasures for their lifetimes. As an example, they have higher heat resistance than SKD61. A mold is formed using a heat-resistant alloy such as a Ni-based alloy or Co-based alloy, or a special material such as ceramic or cermet, and the cavity surface of the mold is modified by nitriding treatment Has been proposed (see, for example, Patent Document 3).

  Further, as shown in FIG. 5, the cavity block 13 ("nested") fitted into the fixed and movable base dies 9 and 10 is made of a material having high heat resistance as described above, and copper or copper alloy is used. Cavity block 13 with the aim of reducing the thermal shock caused by the difference between the temperature immediately after filling from the molten metal A and the mold temperature, shortening the heating start-up time, and improving the product yield by reducing the amount of molten metal discarded. Is provided with a preheating heater (cartridge heater) 15 so that the mold is pre-ripened to 200 to 650 ° C. Further, in order to keep this preheating temperature stable, the cavity block 1 and the mother dies 9 and 10 are provided with Die-casting mold products have also appeared that are additionally equipped with a heat insulating material 16 made of resin or ceramic that can sufficiently withstand high clamping pressure.

In addition, as a measure for extending the life of die casting molds, a mold repairing method in which local build-up welding is performed on the damaged portion of the cavity surface is also known.
JP 58-86847 A JP-A-6-86516 JP 2003-10958 A

  By the way, even if measures such as using an expensive heat-resistant material for the die-casting die as described above are taken to extend the life of the die, a heat check is performed with repeated shots of molten metal such as copper. The occurrence of damage to the mold due to melting damage is not completely eliminated, and the effect of extending the mold life is limited. In addition, since it is difficult to predict the time of occurrence of a large crack so that the mold breaks, the cavity block 13 (see FIG. 5) that is “nested” according to the degree of damage that has occurred in the mold. It is necessary to continue operation of the die-casting machine by changing from time to time.

  For this reason, in order to mass-produce die cast products (cage-type induction motor rotors) by operating the die casting machine for a long period of time, a management system that has many spare parts for expensive molds from normal times, and There is a problem that an expensive investment required for holding the reserve mold is required, resulting in increased production costs.

  In addition, since the heat insulating material 16 additionally provided in the mold of FIG. 5 is required to have a strength (rigidity) that can withstand a large clamping force, a heat insulating material having a high heat insulating performance cannot be used. The heat insulation effect cannot be expected.

  The present invention has been made in view of the above points, and is intended for mass production of die-cast products of refractory metal materials such as copper and copper alloys for the rotor of a cage induction motor described above. In this way, the die is made of expensive heat-resistant material, or the idea is changed from life-time measures to extend the life by repairing the die that has been damaged during operation, such as overlay welding. An object of the present invention is to provide a die casting mold having an improved mold structure so that mass production can be realized.

In order to achieve the above object, according to the present invention, there is provided a die for die casting of a high melting point metal such as copper or copper alloy, and the mother die has a replaceable “nesting” in a part constituting the cavity. In what we have,
The “nesting” is constituted by a drawn metal molded product of a general metal sheet (Claim 1), and specifically, realized in the following manner.
(1) In the above-mentioned die casting mold, the “nesting” is assembled to a holder with a preheating heater, and then the holder is fitted into a recess formed in the mother die (Claim 2).
(2) In the preceding item (1), a heat insulating gap is secured between the outer surface of the holder and the recess of the mother die via a protruding retainer member (claim 3).
(3) The die-casting die having the above configuration is applied to a squirrel-cage induction motor in which pure copper or a copper alloy conductor bar or end ring is cast into the rotor core, and has a shape corresponding to the end ring. The “nesting” is detachably installed on the mother die (claim 4).

  By adopting the die casting die having the above configuration, the following effects can be obtained.

  First, the “nesting” manufactured by drawing a general-purpose metal sheet is cheaper than the high heat-resistant metal material described above, and the drawing process is easy and inexpensive. It is possible to have a large number of spare “nests” without incurring the additional burden.

  Therefore, compared with a conventional mold manufactured using an expensive heat-resistant material for the cavity block 13 (see FIG. 5), the progress of the “nesting” damage due to the operation is accelerated, and therefore “nesting” is performed. Although the frequency of parts replacement is increased and the used “nesting” replaced is disposable (one-way), a large amount of die-cast products can be mass-produced at a low production cost.

  Moreover, even when the mold “nesting” is damaged during the operation and the parts are replaced with a new “nesting”, the “nesting”, which is a drawn metal thin plate product, has a small heat capacity and can respond to a quick rise in temperature. In addition, since the replacement work can be completed in a short time without taking much time to replace the “nested” parts, it is possible to mass-produce die cast products while maintaining high operational efficiency.

  Further, the “nesting” holder has a heat insulating gap between the mold base and the mold via a protruding retainer member, thereby suppressing the thermal shock caused by molten metal injection and generating heat in the “nesting”. Stress can be reduced to extend the life of parts. Moreover, according to the “nested” heat insulating structure by the heat insulating gap, it is not necessary to attach an expensive heat insulating material such as hard resin or ceramic to the cavity block as in the prior art (see FIG. 5), and it is high at low cost. Insulation effect can be demonstrated.

  Hereinafter, an embodiment of the present invention will be described based on examples shown in FIGS. 1 and 2 for a die casting die applied to casting of a rotor of a cage induction motor. 1 is a schematic diagram of a mold structure showing a cast state, FIGS. 2A and 2B are a front view and a cross-sectional view of “nesting” in the mold of FIG. 1, and FIG. 4 and FIG. The members corresponding to the mold are denoted by the same reference numerals and the description thereof is omitted.

  That is, in the mold structure of the illustrated embodiment, instead of the cavity block 13 in the conventional structure of FIG. 5, a “nesting” 17 formed by drawing a thin general-purpose metal thin plate and a preheating heater (cartridge heater) 15 are provided. A built-in component assembly with the holder 18 superimposed on the back side of the “nesting” 17 is mounted in fitting recesses formed in the fixed-side and movable-side dies 9, 10. A cavity corresponding to the end ring 3 (see FIG. 3) is formed. The holder 18 does not come into direct contact with the molten metal, and is made of, for example, alloy tool steel for a hot mold such as SKD 61 similar to the mother dies 9 and 10.

  Here, the shape of the “nesting” 17 is a shape corresponding to the outer shape (annular shape) of the end ring 3 of the rotor shown in FIG. 3, and the center of the bottom surface as shown in FIGS. A circular step portion 17a is swelled, an annular cavity portion 17b is formed between the step portion and the outer peripheral surface, and a hat-shaped drawing processed product having a flange portion 17c formed on the outer peripheral edge. The material of the “nesting” 17 is a general-purpose metal plate such as stainless steel, alloy steel, carbon steel, etc., and its practical thickness is about 0.5 to 3.0 mm.

  Further, the holder 18 superimposed on the back surface of the “nesting” 17 is formed with a protruding retainer 19 distributed on the back surface and outer peripheral surface thereof, and the tip of the retainer 19 is fixed to the fixed side and movable side mother. A heat insulating gap 20 is secured between the holder 18 and the mother dies 9 and 10 by abutting against the inner surfaces of the recesses of the dies 9 and 10. The retainer 19 may protrude from the inner surfaces of the mother dies 9 and 10.

  The die casting mold 8 having the above-described configuration preheats the “nesting” 17 to 200 ° C. or more by energizing the preheating heater 15 during operation. Then, in a state where the rotor core 5 of the cage induction motor shown in FIG. 3 is inserted into the intermediate mold 11 of the mold 8 and clamped, the pure copper / copper alloy melt A supplied to the sleeve 12 is replaced with the plunger 12a. When it is sent out toward the mold by the pressing operation, the molten metal (copper, molten metal of copper alloy) is formed on the inner surface side of the “nesting” 17 through the gate 14 of the runner, as described in the die casting mold of FIG. The copper conductor bar 2 and the end ring 3 are cast by filling the cavity 5 and the slot 5 a of the iron core 5.

  When the damage of the “nesting” 17 progresses due to repeated die-casting shots and reaches the end of its life, the damaged “nesting” 17 is removed and replaced with a spare “nesting” owned by the user. To continue.

  In addition, by casting the conductor bar 2 and end ring 3 of the rotor of the squirrel-cage induction motor with pure copper or copper alloy having higher conductivity and heat conductivity than the aluminum alloy, the Joule heat generation of the rotor accompanying the operation of the motor Therefore, the radiating fins 6 formed on the end ring 3 of the aluminum alloy rotor 1 in the rotor structure of FIG. 3 can be omitted. Further, since the balance of the rotor 1 can be dealt with by a method of trimming a part of the circumference of the end ring 3 without using a balance weight, the “nesting” used in the die casting die 8 of the illustrated embodiment is used. 17 eliminates the complicated concave and convex shape of the cavity corresponding to the heat dissipating fin 6 and the weight mounting pin 7 for balancing shown in FIG. 3, and simplifies the shape of the cavity surface so that the drawing can be easily performed. ing.

  As described above, the “nesting” 17 of the die manufactured by the drawing process of the general-purpose metal thin plate is lower in material cost than the high heat-resistant metal material and can be easily manufactured at a low cost. Users can have many spare “nests” without incurring significant costs. Therefore, compared to conventional molds manufactured using expensive heat-resistant materials for the cavity block, the mold life (number of die casting shots) is shortened, and the frequency of replacement of the “nesting” 17 is increased, and replacement is used. Although the existing “nesting” becomes disposable (one-way), it is possible to obtain an economical effect in terms of operation that enables mass production of a large amount of die-cast products at a low total production cost.

Schematic structural diagram of a die casting die according to an embodiment of the present invention FIG. 1 is a structural diagram of “nesting” in FIG. 1, (a) and (b) are a front view and a cross-sectional view, respectively. Rotor conductor bar and end ring ring-cast rotor induction structure made of aluminum alloy. (A), (b), (c) are rotor cage, iron core, and rotor assembly, respectively. External perspective view of Schematic structure diagram of die casting die applied to rotor casting shown in FIG. Schematic structural diagram of a conventional die casting mold that supports high melting point metal materials such as copper and copper alloys

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotor of cage induction motor 2 Conductor bar 3 End ring 5 Rotor core 5a Slot 8 Die-casting die 9 Fixed die 10 Movable die 11 Intermediate die 12 Sleeve 15 Preheating heater 17 Drawing processing of general-purpose metal sheet "Nesting" to become goods
18 “Nested” holder 19 Retainer 20 Thermal insulation gap A Molten metal

Claims (4)

In a die casting die for refractory metals such as copper and copper alloy, the mother die is provided with a replaceable “nesting” in the part constituting the cavity.
A die casting die characterized in that the "nesting" is constituted by a drawn metal molded product of a general-purpose metal sheet.   2. The die-casting die according to claim 1, wherein the "nesting" is assembled to a holder with a preheating heater, and the holder is fitted into a recess formed in the mother die. .   3. The die casting mold according to claim 2, wherein a heat insulating space is secured between the outer surface of the holder and the recess of the mother mold through a protruding retainer member.   The die-casting die according to any one of claims 1 to 3, wherein the die is applied to a squirrel-cage induction motor in which pure copper or a copper alloy conductor bar or end ring is cast into a rotor core. A die-casting die, wherein a “nesting” having a shape corresponding to the end ring is detachably installed on a mother die.

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