JP2014188551A - Sand type molding method and sand type molding device - Google Patents

Abstract

When a foamed sand is filled into a mold cavity and heated and solidified to obtain a molded product, water vapor and gas generated during the heating and solidification of the foamed sand are smoothly discharged from the cavity.
A mold 2 is clamped to form a cavity C, and foamed sand S is filled into the cavity C. When the foamed sand S is heated and solidified, a slight gap L is formed between the molds 2 while reducing the mold clamping force and maintaining the cavity C. Since the gas and water vapor generated when heating and solidifying the foamed sand S are smoothly discharged from the cavity C through the gap L, the firing time of the foamed sand S can be shortened. Even when the solidified binder accumulates in the slit 16, the gas and water vapor can be reliably discharged from the cavity C to the outside by the gap L.
[Selection] Figure 2

Description

  The present invention relates to a sand mold making method and a sand mold making apparatus for filling a mold with foamed sand and solidifying it to form a sand mold such as a sand core.

  When casting a cylinder block or a cylinder head of an engine, a collapsible sand core (sand mold) is used to form a hollow portion such as a water jacket or an intake / exhaust port. The sand core is formed into a predetermined shape by, for example, blowing shell sand coated with a thermoplastic resin into a mold with compressed air from a nozzle of a sand blowing device, filling the cavity, and heating and solidifying. The

  On the other hand, there is a technique for forming a sand mold such as a core by using foamed sand obtained by stirring and foaming water and a water-soluble binder together with an aggregate. Thus, when molding is performed by filling the mold cavity with foam sand, the internal pressure of the cavity increases due to evaporation of moisture and thermal expansion of bubbles during the heating and curing (firing) process of the foam sand. In the product, a water-soluble binder and aggregate are accumulated on the surface layer portion to form a dense hardened layer having high strength, while a brittle portion having a low density is formed inside. For this reason, the core made of foam sand is excellent in disintegration after casting and can be easily removed from the cast product while ensuring sufficient strength as a core during casting.

  Foamed sand generates water vapor and gas when heated and cured in the mold, and therefore it is necessary to smoothly discharge these to the outside of the mold cavity. Accordingly, a mold for foaming sand is provided with a slit or a passage for discharging water vapor and gas. Further, Patent Document 1 is not for foaming sand, but a gas vent hole is provided in the mold, and when the shell sand is fired in the mold cavity, the generated gas is discharged from the mold cavity. The point to do is described.

JP 2002-192305 A

When forming a sand mold using foam sand, there are the following problems.
In order to shorten the heating and curing time (baking time) of the foam sand, it is important how quickly water vapor is discharged from the mold cavity. However, since the water-soluble binder flows out from the degassing slits and passages with the steam and gas during the process of heating and hardening the foam sand, the binder solidified in the degassing slits and passages by repeated molding May accumulate and hinder the discharge of water vapor and gases. If smooth discharge of water vapor and gas is hindered, it takes time to fire the foamed sand, which is a problem.

  The present invention has been made in view of the above points, and when heating and curing foam sand in a mold cavity, water vapor and gas are smoothly discharged from the cavity to shorten the curing time. With the goal.

In order to solve the above problems, the present invention provides a sand mold molding method and a sand mold molding method in which a foamed sand obtained by stirring a binder together with an aggregate and foaming is filled in a cavity of a mold and heated and solidified to obtain a molded product. In the device
The mold is clamped to form the cavity, and the cavity is filled with foamed sand, and then the mold is slightly opened to provide a gap between the molds while maintaining the cavity. And

(Aspect of the Invention)
In the following, some aspects of the invention that can be claimed in the present invention (hereinafter sometimes referred to as “claimable invention”) will be exemplified and described. As with the claims, each aspect is divided into sections, each section is numbered, and is described in a form that cites the numbers of other sections as necessary. This is for the purpose of facilitating the understanding of the claimable invention, and is not intended to limit the combinations of the constituent elements constituting the claimable invention to those described in the following sections. In other words, the claimable invention should be construed in consideration of the description accompanying each section, the description of the embodiments, etc., and as long as the interpretation is followed, another aspect is added to the form of each section. In addition, an aspect in which constituent elements are deleted from the aspect of each item can be an aspect of the claimable invention. The following contents (1) to (4) correspond to claims 1 to 4, respectively.

(1) In a sand molding method of filling a mold cavity with foamed sand that is stirred and foamed with an aggregate, heated and solidified to obtain a molded product,
The mold is clamped to form the cavity, and the cavity is filled with foamed sand, and then the mold is slightly opened to provide a gap between the molds while maintaining the cavity. Sand mold making method.
(2) In the method of (1), the mold clamping force of the mold is reduced, and a gap is provided between the molds by a reaction force from the mold.
(3) A mold that forms a cavity by mold clamping, a mold clamping apparatus that opens and closes the mold, a filling apparatus that fills the cavity with foamed sand that is stirred and foamed with a binder, and the cavity. A heating device for heating the foamed sand inside,
The mold clamping device is characterized in that after filling the cavity with foamed sand, the mold is slightly opened to form a gap between the molds while maintaining the cavity (4). ) In (3), the mold clamping device reduces a mold clamping force and forms a gap between the molds by a reaction force from the molds.
According to the sand mold making method and apparatus of (1) and (3), when foaming sand is heated and cured in the cavity of the mold, a small gap is provided between the molds, so that water vapor and gas are transferred to the mold. Since it is smoothly discharged to the outside through the gaps between them, the curing time can be shortened.
Even when the solidified binder accumulates in the passage for discharging water vapor and gas from the mold cavity, the water vapor and gas can be reliably discharged from the cavity to the outside by the gap between the molds.
At this time, since the gap between the molds is sufficiently small and the shape and dimensions of the cavity are maintained, the dimensional accuracy of the molded product is not affected.
Further, according to the sand mold making method and apparatus of (2) and (4), the gap between the molds can be adjusted according to the reaction force from the molds.
(5) In (4), the mold clamping device clamps the mold by an air cylinder and reduces the pressure of compressed air supplied to the air cylinder to reduce the mold clamping force. Sand mold making equipment.

  According to the present invention, when foaming sand is heated and cured in the mold cavity, water vapor and gas can be smoothly discharged from the cavity through the gap between the molds, and the curing time can be shortened. .

It is the schematic which shows the sand mold making apparatus which concerns on one Embodiment of this invention. It is a figure which shows the molding process of foaming sand by the sand mold molding apparatus of FIG. In the sand mold making device of FIG. 1, it is a chart which shows the relationship between a clamping setting pressure and the clearance gap between dies. In the sand mold making apparatus of FIG. 1, it is a graph which shows the relationship between a clamping setting pressure and the clearance gap between dies. In the sand mold making device of FIG. 1, it is a table | surface which shows the relationship between a clamping setting pressure and the quality of a molded product. It is an image figure which shows a composition of foaming sand. It is explanatory drawing which shows the process in which foaming sand heats and hardens | cures within the cavity of a metal mold | die.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, a sand mold making apparatus 1 according to the present embodiment forms a sand core (sand mold) by solidifying foam sand, and includes a mold 2 that forms a cavity C, and a mold 2. A filling device 3 for filling the cavity C with foam sand S and a mold clamping device 4 for opening and closing the mold 2.

  The foamed sand S used in the present embodiment is a mixture of sand as an aggregate, water glass (sodium silicate), water-soluble inorganic binder containing water and a surfactant, and kneaded into a foamed state. is there. An image of the state of the particles constituting the foamed sand S is shown in FIG. 6A shows a state in which the bubbles 8 are adsorbed on the surface of the sand particles 7, and FIG. 6B shows a part of the bubbles 8 in an enlarged manner. As shown in FIG. 6 (B), the foam sand S forms a foam 8 by covering the surface of a water glass aqueous solution (water is indicated by reference numeral 10 and water glass is indicated by reference numeral 11) with a surfactant 9. 8 is adsorbed on the surface of the sand particles 7 through the surfactant 9 to be in a foamed state, and has an appropriate viscosity. Here, the molar ratio of water glass to sand is 1.0 to 3.0, the weight ratio is 0.4 to 3.0%, the weight ratio of water is 1.5 to 5.0%, and the weight of the surfactant. By setting the ratio to about 0.003 to 2.0%, foamed sand S having an appropriate viscosity can be obtained.

  Referring to FIG. 1, the mold 2 includes a fixed mold 12 and a movable mold 13 that are divided by a parting line P, and the fixed mold 12 and the movable mold 13 are clamped to form a cavity C. The fixed mold 12 is fixed to the fixed base 14. The movable mold 13 is fixed to a movable movable base 15 and moves together with the movable base 15 to open and close the mold 2. The fixed mold 12 and the movable mold 13 are heated to about 150 ° C. to 300 ° C. by a heating device H such as a heater, and the moisture of the foamed sand S filled in the cavity C is evaporated to solidify the foamed sand S. The mold 2 may be provided with a discharge passage such as a slit 16 for discharging gas and water vapor to the outside when the foamed sand S is heated and hardened in the cavity C.

  A mold release device 17 is provided on each of the fixed mold 12 and the movable mold 13 of the mold 2. The mold release device 17 includes a plurality of extrusion pins 18 provided so as to be movable back and forth in the cavity C, an extrusion plate 19 connected to the bases of the plurality of extrusion pins 18, a fixed base 14 and a movable base 15. An extrusion spring 20 provided between the extrusion plate 19 and the extrusion plate 19 is provided. Then, the plurality of push pins 18 are pressed through the push plate 19 by the spring force of the push springs 20 so that the tips of the push pins 18 protrude into the cavity C. Retraction pins 21 whose front ends are opposed to each other are attached to the extrusion plates 19 on both sides. When the fixed mold 12 and the movable mold 13 are closed, the tip portions of the retreat pins 21 come into contact with each other, and the push plate 19 is moved against the spring force of the push spring 20 to thereby push the push pin. 18 is retracted from the cavity C. Thus, the extrusion pin 18 is interlocked with the opening and closing of the mold 2, retracted from the cavity C when the mold 2 is closed, and the core formed by projecting into the cavity C when the mold 2 is opened. Release the mold.

  The filling device 3 kneads and stores foam sand S, a pressurizing mechanism 23 that pressurizes foam sand S in the sand tank 22, and filling that connects the sand tank 22 to the cavity C of the mold 2. And a mouth 24. Then, the sand tank 22 is set on the mold 2 which is closed and clamped by closing the fixed mold 12 and the movable mold 13, and the foaming sand S in the sand tank 22 is pressurized by the pressurizing mechanism 23, thereby filling the filling port 24. The foamed sand S is filled into the cavity C of the mold 2 via.

  The mold clamping device 4 switches the double-acting air cylinder 26 that drives the movable base 15, the air source 27 that supplies compressed air to the air cylinder 26, and the supply of compressed air from the air source 27 to the air cylinder 26. The switching valve 28 for moving the movable base 15 forward and backward, the pressure adjusting valve 29 for adjusting the pressure of the compressed air supplied to the air cylinder, and the pressure gauge 30 for detecting the pressure of the compressed air supplied to the air cylinder 26 And a control device 31 that controls the operation of the switching valve 28 and the pressure regulating valve 29.

  The control device 31 controls the switching valve 28, switches the supply of compressed air, and expands / contracts the actuating rod 26A of the double-acting air cylinder 26, thereby moving the movable mold 13 together with the movable base 15 to move the mold. 2 is opened and closed. Further, the mold clamping force is adjusted by operating the pressure adjustment valve 29 based on the pressure detected by the pressure gauge 30 during mold clamping and adjusting the pressure of the compressed air supplied to the air cylinder 26. Thereby, when foaming sand S is heated and hardened in the cavity C of the mold 2, if the clamping force by the air cylinder 26 is reduced, the pressure in the cavity C and the spring force of the extrusion spring 20 of the mold release device 17 are reduced. Due to the reaction force caused by the warp of the mold 2, the movable mold 13 is slightly retracted, and a minute gap L (see FIG. 2C) is formed in the parting line P between the fixed mold 12 and the movable mold 13. It is formed and this gap L can be adjusted.

Next, a process for forming a sand core by the sand mold making apparatus 1 will be described.
As shown in FIG. 2A, the movable mold 13 is driven by the mold clamping device 4 to close the mold 2, the mold is clamped to form a cavity C, and the filling device 3 is set in the mold 2. At this time, the extrusion pin 18 of the mold release device 17 moves backward from the cavity C in conjunction with the mold clamping as described above. In a state where the mold 2 is preheated by the heating device H, the pressurizing mechanism 23 of the filling device 3 is operated, and the foamed sand S in the sand tank 22 enters the cavity C of the mold 2 heated through the filling port 24. Fill. FIG. 2B shows a state where the filling of the foam sand S into the cavity C is completed. The foamed sand S filled in the cavity C of the mold 2 evaporates and hardens when heated.

  Here, a process in which the foamed sand C filled in the cavity C is heated and hardened will be described with reference to FIG. As shown in FIG. 7A, in the cavity C of the mold 2, the bubbles 8 of the foamed sand S expand due to heating, and the internal pressure of the cavity C rises. Then, as shown in FIG. 7B, the bubbles 8 move along the inner wall of the cavity C of the mold 2 to the outside through a passage formed by the slit 16 or the like provided in the parting line P. Discharged. At this time, the water glass (binder) and the aggregate composing the foam sand S are pushed toward the inner wall side of the cavity C, and the density of the water glass and the aggregate near the inner wall of the cavity C is increased. As a result, the sand core W solidified in the cavity C is formed with a dense hardened layer 33 having a high density of water glass and aggregate on the surface layer portion in contact with the inner wall of the cavity C, and the internal density decreases. A fragile portion 34 that easily collapses is formed at the center.

  Further, the water glass (binder) pushed to the inner wall side of the cavity C enters the passage made of the slit 16 and the like together with water vapor and gas and is discharged to the outside. The binder that has entered the passage is cured and fixed to the passage. When the binder fixed in the passage is deposited in this way and the passage is blocked, smooth discharge of water vapor and gas is hindered, and the firing time becomes longer, resulting in molding failure.

  In the present embodiment, after the filling of the foam sand S into the cavity C of the mold 2 is completed, the controller 31 of the mold clamping device 4 operates the pressure adjustment valve 29 based on the pressure detected by the pressure gauge 30 to operate the air cylinder 26. The pressure for supplying compressed air to the chamber is reduced by a predetermined pressure to reduce the clamping force. As a result, as shown in FIG. 2C, the pressure in the cavity C increased by heating and hardening of the foamed sand S, the spring force of the extrusion spring 20 of the mold release device 17, and the warpage due to the warp of the mold 2. Due to the force, the movable mold 13 is slightly retracted, and a minute gap L is formed in the parting line P between the fixed mold 12 and the movable mold 13. The gas and water vapor generated during heating and hardening of the foamed sand S in the cavity C of the mold 2 are smoothly discharged to the outside through the minute gap L. As a result, solidification of the foamed sand S can be promoted, and the firing time can be shortened.

  At this time, the minute gap L is a slight gap that allows the gas and water vapor to be smoothly discharged, and the amount of movement of the movable mold 13 is also small, so that the shape and dimensions of the cavity C are maintained. Does not affect the core shape and dimensional accuracy. Further, the movable mold 13 is slightly moved by the pressure in the cavity C, the spring force of the extrusion spring 20 of the mold release device 17, and the warping reaction force of the mold 2, so that the movable mold 13 is slightly moved from the fixed mold 12. Since the gap L is formed, a constant minute gap L can be secured regardless of the amount of binder deposited on the parting line P and the slit 16 between the molds 2. As a result, the gas and water vapor generated during the heating and curing of the foamed sand S can be reliably discharged to the outside, and a good molded product can be obtained by shortening the firing time.

  After the foamed sand S in the cavity C of the mold 2 is solidified, the control valve 31 is operated by the control device 31 to switch the supply of compressed air to the double-acting air cylinder 26, and the movable base 15 is moved together with the movable base 15. 13 is retracted, the mold 2 is opened, and the molded sand core is taken out. At this time, the tip of the retreat pin 21 of the mold release device 17 is separated in conjunction with the mold opening, the push plate 19 is moved by the spring force of the push spring 20, and the push pin 18 protrudes into the cavity C to make a mold. Release the sand core.

  Next, in the above-described steps, the pressure of the compressed air supplied to the air cylinder 26 and the size of the gap L when the gap L is formed in the parting line P between the molds 2 (see FIG. 2C). The relationship between the quality of the molded sand core and quality will be described with reference to FIGS.

  As shown in FIGS. 3 and 4, the supply pressure is reduced to 0.15 MPa, 0.10 MPa, and 0.05 MPa against the supply pressure of 0.35 MPa of compressed air to the air cylinder 26 during mold clamping. As a result, the gaps L were 0.22 mm, 0.25 mm, and 0.36 mm on average, respectively. Accordingly, as shown in FIG. 5, when the supply pressure is set to 0.35 MPa while the mold is clamped and the gap L is not provided, the molded product is 60% non-defective product and 40% defective product. When the supply pressure is reduced to 0.10 MPa and the gap L is provided, the non-defective product is 80% and the defective product is 20%. When the supply pressure is further reduced to 0.05 MPa and the gap L is increased, 100% good product is obtained. Could get.

  In the above embodiment, the supply pressure (clamping force) of the compressed air to the air cylinder 26 of the mold clamping device 4 is reduced, and the reaction force between the molds 2 causes the space between the fixed mold 12 and the movable mold 13. However, the predetermined gap L may be formed by directly controlling the movement amount of the movable mold 13.

  DESCRIPTION OF SYMBOLS 1 ... Sand mold making apparatus, 2 ... Mold, C ... Cavity, H ... Heating apparatus, L ... Crevice, S ... Foam sand

Claims (4)

In the sand mold making method, the foamed sand which is foamed by stirring the binder together with the aggregate is filled into the mold cavity, heated and solidified to obtain a molded product.
The mold is clamped to form the cavity, and the cavity is filled with foamed sand, and then the mold is slightly opened to provide a gap between the molds while maintaining the cavity. Sand mold making method.   The sand mold making method according to claim 1, wherein a clamping force of the mold is reduced and a gap is provided between the molds by a reaction force from the mold. A mold for forming a cavity by mold clamping, a mold clamping apparatus for opening and closing the mold, a filling apparatus for filling the cavity with foamed sand obtained by stirring and foaming a binder together with an aggregate, and foaming in the cavity A heating device for heating the sand,
The mold clamping device is characterized in that after filling the cavity with foamed sand, the mold is slightly opened to form a gap between the molds while maintaining the cavity.   The sand mold molding apparatus according to claim 3, wherein the mold clamping device reduces a mold clamping force and forms a gap between the molds by a reaction force from the mold.

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