Die-Cast Manufacturing Method and Die-Cast Manufacturing Apparatus, and Pressurization Means

The present invention relates to a die-cast manufacturing method and a die-cast manufacturing apparatus, and pressurization means, and, in particular, relates to a die-cast manufacturing method and a die-cast manufacturing apparatus, and pressurization means that enable simultaneously eliminating shrinkage and blowholes.

A method for casting a die-cast product includes pushing a molten metal, such as aluminum, into a cavity made by a metallic mold by a plunger and taking out a product in a shape following the cavity. Generation of shrinkage or a blowhole during shaping for a product turns out to be a product defect, and therefore, the generation thereof must be inhibited.

There has been proposed a runner pressurization method as a countermeasure for shrinkage in a die-cast product, and there also has been proposed a PF method (Pore Free: pore free die casting method) as a countermeasure for blowholes.

As the former countermeasure, there has been proposed a method that further pressurizes a runner in line with operating to pressurize a plunger. As the latter countermeasure, the inside of the cavity of the metallic mold is preliminarily substituted with oxygen and a chemical reaction with a molten metal filling the cavity is caused, and thus, a finer product is made.

The runner pressurization method is a method that further pressurizes the molten metal supplied in a pressurized manner to the cavity through a sleeve by further pressurizing a runner portion directly connected to the cavity by a pressure pin (Patent Document 1). However, this method has failed to obtain an expected cavity pushing effect as the molten metal pushed by the runner pressurization flows backward and is pushed back to a plunger side. From such an aspect, there has appeared a technique that ensures obtaining the pushing effect by reducing a gap between the pressure pin and a pressurization passage (Patent Document 2), but it has failed to provide a countermeasure for blowholes.

There also has been proposed a PF method as a countermeasure for not generating blowholes as a product failure. This is to manufacture a pressure casting product by substituting the inside of the cavity of the metallic mold with oxygen and locally pressurizing the molten metal filling the cavity by a squeeze pin or the like as described in Patent Document 3. However, this has failed to provide a countermeasure for shrinkage.

Furthermore, there is known a method described in Patent Document 4 as a method that has combined the PF method as a usual method supplying oxygen from a sleeve port and a local squeeze method in a product. This ejects oxygen from a pouring gate of a sleeve and supplies the oxygen to the sleeve, the runner, and the cavity, thereby having a problem of a reduced oxygen concentration. The local squeeze method performed as a countermeasure for shrinkage has a possibility of making a hit mark on a product, which may interfere with an ejector pin for the product or a cooling passage.

The present invention focuses on the above-described problems, and it is an object of the present invention to enable achieving a PF method that supplies oxygen to a cavity without reducing oxygen concentration and to inhibit generation of shrinkage of an entire product in a runner pressurization.

The present invention has been configured as follows in order to solve the above-described problems. It is to provide a die-casting method and a die-casting apparatus that enable producing a fine die-cast product in which blowholes and shrinkage are simultaneously inhibited by performing a preparation reaching a PF method by substituting the inside of a cavity with oxygen before molten metal injection by a plunger when molds are clamped, and subsequently solidifying the molten metal by secondarily pressurizing a runner at a high pressure and continuously pressurizing the molten metal after the molten metal injection by the plunger.

Specifically, a die-cast manufacturing method according to the present invention includes: injecting a molten metal from a sleeve by first pressurization means;

subsequently pressurizing a runner by second pressurization means; using a pressure pin of the second pressurization means to allow an oxygen supply passage provided in the pressure pin to supply oxygen through a distal end valve; and after the pressure pin of the second pressurization means is preliminarily moved to project into the runner, filling the cavity with the oxygen via the distal end valve to draw the pressure pin, subsequently filling the runner and the sleeve with oxygen, and afterwards, injecting the molten metal with the first pressurization means through the sleeve, and then performing the runner pressurization by the second pressurization means. It is sufficient that an orifice in a middle of a runner pressurization passage of the pressure pin of the second pressurization means is provided to allow preventing a gas and the molten metal from flowing backward.

Further, the present invention includes: injecting a molten metal from a sleeve by first pressurization means after molds are clamped; pressurizing a runner portion directly connected to a cavity by second pressurization means; providing an orifice in a runner pressurization passage of a pressure pin of the second pressurization means to prevent a gas and the molten metal from flowing backward; before the injection by the first pressurization means from the mold clamping starts, operating the pressure pin of the second pressurization means to move to a runner side and preventing the gas from flowing backward with the orifice while supplying oxygen to the cavity with an oxygen supply valve disposed in the pressure pin to return the pressure pin; after the molten metal injection by the first pressurization means, causing the orifice with the second pressurization means to prevent the molten metal from flowing backward while performing runner pressurization.

The die-cast manufacturing method according to the present invention includes: injecting a molten metal from a sleeve by first pressurization means after molds are clamped; and pressurizing a runner portion directly connected to a cavity by second pressurization means. The method performs steps of: a mold clamping operation; an oxygen supplying operation to the cavity from an oxygen supply valve disposed in the pressure pin of the second pressurization means while an orifice prevents a gas from flowing backward; a drawn-in operation of the pressure pin; a molten metal injection operation by the first pressurization means via the sleeve; and a runner pressurization operation by the second pressurization means by the pressure pin while the orifice prevents the molten metal from flowing backward.

In these cases, the pressure pin of the second pressurization means is formed with a poppet-type valve at a distal end portion, and a valve opening/closing operation thereof opens and closes an oxygen supply passage formed in a center portion to stop the supply of oxygen. The orifice is formed on a surface corresponding to the runner portion directly connected to the cavity in the runner to prevent the gas or the molten metal from flowing backward.

The molten metal is injected into the cavity via a plurality of branching runners, and the orifice is formed on a rising runner portion of a selected branching runner or on a surface corresponding to a neighboring portion of the rising runner portion to prevent the gas or the molten metal from flowing backward.

The pressure pin of the second pressurization means has a moving direction that is a direction intersecting with a plunger operation direction of the first pressurization means, or has a moving direction that is a direction parallel to a plunger operation direction of the first pressurization means.

The second pressurization to the cavity may be performed through a new branching runner coupled to a portion where a density improvement is desired.

A die-cast manufacturing method according to the present invention includes: when second pressurization means performs second pressurization through a runner directly connected to a cavity after first pressurization means injects a molten metal to clamped metallic molds, using an auxiliary runner disposed at a position where the molten metal filling the cavity by the first pressurization means overflows; after mold clamping, operating a pressure pin of the second pressurization means before the injection by the first pressurization means and preventing a gas from flowing backward with the orifice while supplying oxygen to the cavity by an oxygen supply valve disposed in the pressure pin to return the pressure pin; and after the pressurization by the first pressurization means is terminated, operating the second pressurization means to pressurize the cavity from the auxiliary runner.

A die-cast manufacturing apparatus according to the present invention includes: first pressurization means that injects a molten metal to a die-casting metallic mold; second pressurization means that pressurizes a runner communicated with a cavity; an oxygen supply passage formed with a pressure pin of the second pressurization means as a hollow pipe structure; and the valve disposed at a distal end of the pressure pin that opens and closes the oxygen supply passage. An orifice may be formed on a surface corresponding to the runner directly connected to the cavity. The pressure pin is inserted through the orifice.

A die-cast manufacturing apparatus according to the present invention includes: first pressurization means that injects a molten metal to a die-casting metallic mold; second pressurization means that pressurizes a runner communicated with a cavity; an orifice formed on a surface corresponding to the runner directly connected to the cavity, a pressure pin of the second pressurization means being inserted through the orifice; an oxygen supply passage internally formed as a hollow pipe structure of the pressure pin and a valve disposed in a distal end portion of the pressure pin, the valve opening and closing the oxygen supply passage.

In this case, the orifice is formed at proximity of a boundary between a sprue core runner portion leading the molten metal injection from the second pressurization means to the cavity and a rising runner portion.

The runner is formed of a plurality of branching runners, the orifice is formed on a surface corresponding to a selected branching runner, and a valved pressure pin of the second pressurization means is insertable into the orifice.

The valved pressure pin of the second pressurization means has a moving direction that is a direction intersecting with a plunger direction of the first pressurization means or has a moving direction that is a direction parallel to a plunger direction of the first pressurization means.

A new branching runner may be provided in the first pressurization means. The new branching runner being coupled to a portion where a density improvement is desired and second pressurization means having a valved pressure pin that moves in a direction identical to a direction of a flow of the molten metal within the new branching runner may be provided.

A die-cast manufacturing apparatus according to the present invention includes: first pressurization means that injects a molten metal to a die-casting metallic mold; second pressurization means that pressurizes a runner communicated with a cavity; the runner serving as an auxiliary runner disposed at a position where the molten metal filling the cavity by the first pressurization means overflows; an orifice through which a pressure pin of the second pressurization means is inserted, the orifice being formed on a surface corresponding to the runner directly connected to the cavity in the auxiliary runner; an oxygen supply passage internally formed as a hollow pipe structure of the pressure pin and a valve disposed in a distal end portion of the pressure pin, the valve opening and closing the oxygen supply passage; and control means that controls a sequence of operations of: after mold clamping, operating a pressure pin of the second pressurization means before the injection by the first pressurization means and preventing a gas from flowing backward by the orifice while supplying oxygen to the cavity by an oxygen supply valve disposed in the pressure pin to return the pressure pin; and after the pressurization by the first pressurization means is terminated, operating the second pressurization means to pressurize the cavity from the auxiliary runner.

The present invention is pressurization means for performing runner pressurization of a die-casting metallic mold. The pressurization means includes: a main actuator; a pressure pin operated in and out by the main actuator; a ring passage disposed inside the pressure pin; a poppet valve mounted on a top end surface of the pressure pin opening and closing the ring passage, the poppet valve having a diameter smaller than a diameter of the top end surface; a stem shaft that operates the poppet valve and forms the ring passage; and a secondary actuator that drives the stem shaft.

The above-described configuration ensures that the operation of the pressure pin substitutes the inside of the cavity with oxygen, and next, the molten metal is able to be secondarily pressurized while preventing the molten metal from flowing backward by the pressure pin after the molten metal injection by the plunger, and thus, the action by the former performs a PF method and the secondary pressurization by the latter enables manufacturing a fine die-cast product under a high pressure. In this case, disposing an orifice through which the pressure pin is inserted on a surface corresponding to a runner directly connected to the cavity enables preventing the oxygen gas and the molten metal from flowing backward. Thus, the PF method and the runner secondary pressurization are simultaneously achievable with one component, and a die-cast product in which generation of blowholes and shrinkage is prevented is completed.

The following will describe a die-cast manufacturing method and a die-cast manufacturing apparatus according to embodiments of the present invention in detail with reference to the drawings. Note that the following description is merely an example, and the present invention can include various kinds of modifications as long as the gist of the present invention is not changed.

illustrates a cross-sectional view of a relevant portion of a die-cast manufacturing apparatus according to a first embodiment. A die-cast manufacturing apparatusincludes a movable metallic moldmounted on a movable plate and a fixed metallic moldmounted on a fixed plate. The die-cast manufacturing apparatusinjects a molten metal into a cavityformed by bringing the two metallic moldsandin contact, and thus, a product in a shape following the cavityis made. The product can be taken out of the cavityby separating the metallic moldsandand operating a squeeze pin disposed in a back surface portion of the movable metallic mold.

As an injecting portion for supplying the molten metal to the cavityof the die-cast manufacturing apparatus, molten supply means is disposed below the cavity. This is configured of first pressurization meansmade of an injection sleevemounted passing horizontally through the fixed metallic moldto reach the cavity, a plungerarranged within the injection sleeve, and a pressure device (not illustrated) located at the rear of the plungerand able to push and pull the plunger.

A runnerthat serves as a passage of the molten metal reaching the cavityis formed in a direction of a front end of the injection sleeve. This runneris made of a sprue core runner portionapproximately horizontally extended from the injection sleeveand a rising runner portionoriented upward so as to be directly connected to a lower portion of the cavity. The runneris configured such that the molten metal extruded by the plungerof the first pressurization meansis injected out to the cavityafter the molten metal passes through the sprue core runner portionand is orientated upward by the rising runner portion.

The rising runner portionin such a runneris provided with second pressurization meansthat secondarily pressurizes the molten metal in the cavity. This second pressurization meansis configured of a main actuator (hydraulic cylinder)equipped in the lower portion of the metallic molds,and a pressure pin (operational piston)mounted so as to be moved in and out from a lower portion of the rising runner portionto an upper portion by the main actuator. The pressure pinhas a diameter d made to be smaller than an inner diameter D of the rising runner portionso as to allow the pressure pinto slide up and down in the rising runner portion. Accordingly, a press-fitting amount of the pressure pininto the rising runner portionimproves a product density by the cavity.

In the embodiment, in particular, an orificethat reduces the inner diameter is formed in a side of the rising runner portion(the part B in) that is above an intersecting portion (the section A to B in) between the rising runner portionand the sprue core runner portion. This is a ring projectionhaving a rectangular cross-section formed in an inner diameter portion of the rising runner portionand serves to make a metallic seal in a gap between the projectionand the pressure pin, which is achieved by adjusting a height of the projection(that is, an inner diameter dimension of the rising runner portion) to the outer diameter d of the pressure pinas close as possible. Specifically, the height of the ring projectionis determined such that, while it depends on the size of the cavity, a gap dimension Δ, which is ½ of the difference between the inner diameter D of the rising runner portionand the outer diameter d of the pressure pin, to be ½ to ⅓ or less. That is, ½ of the difference between the inner diameter of the ring projectionand the outer diameter d of the pressure pinis a gap dimension δ of a metallic seal portion, where δ=Δ×½, preferably δ=Δ×⅓, and the lower limit value is a value at which the metallic seal breaks. The ring projectionhas an axial length L of approximately 10 mm, which ensures reliable metallic sealing.

In the embodiment, as seen in, the pressure pinhas a stem shaftaxially inserted through an inside of the pin body to internally form a ring passage. The ring passagehas a hollow pipe structure opened on a top end surface of the pressure pin. On the top end surface of the pressure pin, a poppet valvehaving a diameter smaller than the diameter of the pressure pinis connected to an upper end of the stem shaftso as to allow opening and closing the ring passage. The poppet valveserves to open and close the ring passagein association with the up and down movement of the stem shaft. The poppet valveis flush with the top end surface of the pressure pinwhen the valve is closed, and projects from the top end surface of the pressure pinseparating away from a V-shaped valve seatby being pushed out by the stem shaftto release the ring passageon the top end surface of the pressure pinwhen the valve is opened. A lower portion of the stem shaftis connected to a secondary actuator (hydraulic cylinder)disposed inside the pressure pin. Accordingly, the secondary actuatormoved up and down within the pressure pinopens and closes the poppet valvethrough the stem shaft.

In order to cause the pressure pinto perform these sequence of operations, the oxygen/hydraulic system illustrated inis used. First, the ring passagedisposed in the pressure pinis connected to an oxygen supply port, and is able to supply oxygen to the cavitythrough the pressure pinwhile the valve is open from a tankas an oxygen supply source. In the course of the passage from the tankto the oxygen supply port, there are provided in parallel a flow passagein which a large flow rate control valveand an opening/closing valveare disposed and a flow passagein which a small flow rate control valveand an opening/closing valveare disposed, which allows adjustment of a supply amount of the oxygen.

Next, the configuration for causing the pressure pinto perform the secondary pressurization and the configuration for opening and closing the poppet valvemounted on the pressure pinare as follows. The hydraulic pressure is generated from a hydraulic tankusing a pump, and the pumpis connected to the main actuatorvia a direction switching valveso as to drive the pressure pinto move up and down. The hydraulic pressure of the pumpis also used for opening and closing the valve, and the hydraulic pressure is introduced to the secondary actuatorin a manner switchable up and down by a direction switching valve. This causes the main actuatorto move the pressure pinup, and subsequently the secondary actuatorto open the poppet valve, thereby enabling the oxygen to be introduced into the cavity. Raising only the pressure pinin a state where the oxygen supply is stopped by driving the secondary actuatordown to close the poppet valveenables the second pressurization meansto cause the pressure pinto operate to push the molten metal.

Note that, in a hydraulic pressure discharge pathwhen the pressure pinis raised, a piston driving amount of the main actuator, eventually a stroke of the pressure pinis measured from a discharged amount of oil. This stroke detecting deviceis configured of a cylinder piston structure, and this is configured of a cylinder bodyand a pistonslidable within the cylinder body. One chamber partitioned by the pistonin the cylinder bodyis connected to a hydraulic oil outlet of the pressure pin, and the other chamber is connected to the direction switching valve. This causes the hydraulic oil exiting from the main actuatorto enter the stroke detecting deviceby the exiting amount, and thus, the pistonis moved. The pistonis integrally provided with a rod, and this projects from one end portion of the cylinder bodyand is coupled to a linear-type potentiometer. An operation starting point of the rodis in one end portion side (the left end in) of the cylinder body, and at this time, it corresponds to a pressurization starting point (the lower end in) of the piston of the pressure pin. The linear-type potentiometeris arranged parallel to the rod, moves with the rod, and obtains its movement distance. In such a stroke detecting device, its pistonis provided with a through-hole communicating through the chambers partitioned by the piston, and a check valveand an orifice (throttle valve)are mounted in this through-hole. This check valveis a one-way valve that blocks the flow of the hydraulic oil discharged to the chamber in a side of the direction switching valvefrom the chamber into which the hydraulic oil of the pressure pinenters and allows the flow in the opposite direction. Thus, the whole amount of the hydraulic oil when the pressure pinperforms the pressurization operation is detected by the stroke detecting device. The orifice (throttle valve)restricts a flow rate of the check valve. Since a weak cracking pressure (spring force) of the check valvecauses the hydraulic oil to flow through the check valve with the piston stopped, it is solvable by reducing the flow rate.

Note that control means that controls the operation system as described above is additionally disposed to control it to properly operate.

A manufacturing process by thus configured die-cast manufacturing apparatusis illustrated in. The orificeis disposed in the runner pressurization passage of the pressure pinof the second pressurization means, and thus, the backward flow of the gas and the molten metal is preventable. First, the molds are clamped. When the molds are being clamped, the plungeris advanced to make an occlusion so as to stop the oxygen from exiting from the sprue (()). At this time, the pressure pinis at a standby position, that is, is in a drawn-in state from the rising runner portion.

After the molds are clamped, before the injection by the first pressurization means, the pressure pinof the second pressurization meansis moved to the runner side (()), and after it passes the orifice, the poppet valveis opened to supply oxygen to the cavityfrom the released ring passagedisposed in the pressure pinwhile the backward flow of the gas is prevented with the orifice(()). The gas remaining in the cavityis discharged by the oxygen and discharged from an air vent.

After an oxygen filling state is obtained, the poppet valveis opened and the pressure pinis returned to the standby position while the oxygen is discharged (()), and the poppet valveis closed at the standby position (()). At this time, while the plungerreturns to the injection position, the internal gas is discharged from the pouring gate by the oxygen.

After the pressure pinis returned to the standby position, the first pressurization meanscauses the plungerto inject the molten metal, thus performing casting (()). After the plungerreaches the advance limit, the runner pressurization is performed while the second pressurization meanscauses the orificeto prevent the molten metal from flowing backward (()). For the casting pressure by the cavityat this time, a pressure four times higher than the conventional pressure can be applied.

Thus, in the embodiment, while first, the molds are clamped and the plungeris in an advanced state, the pressure pinis passed through the orifice, and the poppet valvedisposed on the top end surface of the pressure pinis opened to blow the oxygen out, and thus, the internally remaining gas is discharged to the air vent to allow the cavity to be filled with the oxygen at a high concentration. Subsequently, the reaction with the molten metal injected into the cavitycan be sufficiently caused.

The runner portion pressurization is also possible by using the backward flow prevention effect by the orifice, and this reaches an applied pressure four times more than the conventional applied pressure, thus being considerably beneficial. That is, the second pressurization meansthus configured provides a shielding function with a portion of the metallic seal formed of the molten metal in the upper side entering into the portion of the orificewhen the pressure pinapproaches the ring projectionafter the plungerof the first pressurization meanshas completed the injection. In view of this, this metallic seal at the portion of the orificeincreases the molten metal filling amount into the cavity, and the pushing operation by the pressure pinlengthens the stroke, then, the operation is completed. As the result, when a product made in an ordinary casting method without the runner pressurization is set to “0,” a conventional local squeeze method that pressurizes a center portion of the cavityobserved an increase of +4 g (0.5%), and the runner pressurization method of this embodiment method observed an increase of +14 g (1.7%). Thus, the embodiment presented a remarkable effect.

Next, another method for achieving an oxygen supply method for performing the PF method will be described with reference to.() illustrates a mold opened state where the pressure pinis drawn from the rising runner portionand is in a standby state. The movable metallic moldand the fixed metallic moldin the right and left are in a separated state, and the two-dot chain line in the center portion indicates a die-cast product, a runner, and a biscuit. When the mold clamping operation starts from such a state, as illustrated in(), after the product is taken out, the hydraulic pressure is supplied to the secondary actuatorof the second pressurization meanswhile a spray of a mold release agent is operating, and the pressure pinis advanced to the advance limit. As illustrated in(), the mold clamping proceeds simultaneously with this, and the poppet valveis opened in the middle of this mold clamping to discharge oxygen. This oxygen enters the cavityand the remaining gas flows into the outside air through the air vent in the upper. The machining operation takes place while the oxygen is discharged, and as illustrated in(), the discharge amount of the oxygen is switched to a small flow rate at the lower limit, the sleeve side is also filled up with the oxygen to prevent the air from entering the sleevefrom the pouring gate in the sleeveside, and the valveis closed. The oxygen supply for performing such a PF method is included.

Note that while the ring projectionforming the orificemay have a square cross-sectional surface as in the embodiment, it is also allowed to have a cross-sectional shape in a V shape or an arc shape. In this case, if the tip of the V shape or the arc shape is sharp, the metallic seal is not taken, therefore, the shape of sharpened tip end is preferred.

The ring projectionforming the orificecan be provided with cooling means. This can be a horizontal system, a water-cooling system, or an oil-cooling system, and cooling is preferably performed when the injection by the first pressurization meansis completed, and the pressure by the second pressurization meansis applied to the ring projection. Thus, the metallic seal is easily formed.

In the above-described embodiment, the ring projectionforming the orificemay be formed as another component, and may be mounted in a fitting-in structure when the runneris formed. This is because installation to the rising runner portionhaving a semicircle structure can be easily performed since the runnerhas a structure dividable on a splitting line of the metallic molds.

The above-described embodiment can be applied to pushing a runner of a hot chamber or to the case of forming a plastic.