JP5675904B2 - Casting die apparatus and cylinder head casting method using the same - Google Patents

Description

  The present invention relates to a casting mold apparatus for obtaining a cylinder head having a plurality of combustion chambers arranged in parallel along the longitudinal direction, and a casting method of a cylinder head using the same.

  A cylinder head constituting the internal combustion engine is formed with a plurality of combustion chambers into which lean fuel and air are introduced, and a port communicating with each combustion chamber. The boundary between the combustion chamber and the port is a valve seat portion in which a valve seat on which the cam valve is seated and separated is disposed.

  This type of cylinder head is generally obtained by low pressure casting. In this case, the casting mold apparatus has a lower mold, an upper mold approaching or separating from the lower mold, and a plurality of sliding molds interposed between the lower mold and the upper mold. A cavity is formed by these lower mold, upper mold and sliding mold.

  Here, the said combustion chamber is shape | molded by the combustion chamber shaping | molding part provided in the lower mold | type. The combustion chamber forming part is provided with a valve seat part forming part for forming the valve seat part.

  The port is formed by a sand core. That is, a baseboard portion is provided at one end of the sand core, and the baseboard portion is supported by a baseboard and a sliding type that are formed on the lower mold so as to protrude vertically upward (for example, Patent Documents). 1). On the other hand, the other end is seated on the valve seat part molding part.

  In this state, a molten aluminum alloy is poured into the cavity, and the molten metal cools and solidifies to obtain a cylinder head. Of course, in the cylinder head, a combustion chamber is formed by the lower combustion chamber forming portion, and a port is formed by the sand core. That is, a combustion chamber is formed on the surface of the cylinder head facing the lower mold.

JP 2006-272426 A

  During the casting operation, the lower mold undergoes thermal expansion. Further, in the process where the molten metal solidifies after casting to become a cast product (cylinder head), the cast product causes solidification shrinkage. For the reasons described above, the cylinder head tends to be warped (curved and deformed) such that the middle part in the longitudinal direction bulges vertically upward. If the degree of warpage increases, there is a concern that the shape of the port is affected and engine characteristics as designed cannot be obtained.

  Therefore, it is recalled that the die is shaped in consideration of the warpage of the cylinder head so that a flat cylinder head can be obtained after cooling so that the port is formed in a desired shape. However, in this case, not only the lower mold but also the sliding mold and the upper mold must be designed in an arc shape, which causes a problem that the capital investment increases.

  The present invention has been made in order to solve the above-described problems, and it is easy to obtain a flat cylinder head after cooling while having a simple configuration, and can avoid an increase in capital investment. An object of the present invention is to provide a metal mold apparatus and a cylinder head casting method using the same.

To achieve the above object, the present invention provides a casting mold apparatus for obtaining a cylinder head having a plurality of combustion chambers arranged in parallel along a longitudinal direction.
A port forming sand core comprising a port shaping portion for forming a port communicating with the combustion chamber;
A mold comprising a baseboard for supporting the baseboard part of the port forming sand core;
A sliding mold that supports the baseboard together with the mold;
Have
The mold further includes a plurality of combustion chamber molding portions that mold the plurality of combustion chambers, and a valve seat portion molding portion that is formed to protrude from a bottom wall of the combustion chamber molding portion and on which the port shaping portion is seated. And
The height in the protruding direction of the baseboard is set such that the end in the longitudinal direction is larger than the middle part in the longitudinal direction,
And the protrusion direction height of what is located in a longitudinal direction edge part among the said valve seat part shaping | molding parts is set largely compared with the thing located in a longitudinal direction middle part.

  In the casting mold apparatus configured as described above, the port forming portion of the port forming sand core has a longitudinal shape when the base plate portion of the port forming sand core is supported only by the baseboard base. What is located at the end in the direction is seated on the valve seat part molding part, while what is located at the middle part in the longitudinal direction is separated from the valve seat part molding part.

  When the skirting board portion is pressed from the sliding mold by clamping, the longitudinal halfway portion of the skirting board is bent so as to approach the valve seat part forming portion and comes into contact with the skirting board stand. As a result, all the port shaping parts are seated on the individual valve seat part forming parts. At this time, the port-forming sand core is shaped so as to rise from the longitudinal middle portion toward the longitudinal end.

  When casting is performed in this state, the obtained cylinder head is curved so that the mid-section in the longitudinal direction bulges toward the surface side where the combustion chamber is formed. When this cylinder head is cooled to room temperature, the middle part in the longitudinal direction of the cylinder head is curved so as to bulge to the side opposite to the surface on which the combustion chamber is formed. As a result, a flat cylinder head is obtained.

  As described above, a flat cylinder head can be easily obtained by adopting a simple configuration in which a height difference is provided in the height of the baseboard and the valve seat portion molding portion in the protruding direction. In a flat cylinder head, the valve guide height at each port is substantially the same. That is, it is possible to obtain a cylinder head excellent in dimensional accuracy and having a desired shape in which a port is designed in advance with a high yield.

  In addition, in this case, the existing type can be used as the other type, so that it is possible to avoid an increase in capital investment.

  It is preferable to form a protruding portion on the baseboard portion. When the projecting portion is pressed against the protrusion, the longitudinally middle portion of the baseboard portion is easily displaced toward the baseboard side. Therefore, it becomes easy to seat the port shaping part spaced apart from the valve seat part molding part on the valve seat part molding part.

  The height of the baseboard in the protruding direction is preferably gradually reduced from the longitudinal end portion to the longitudinal middle portion. This is because this structure makes it easier for the baseboard portion to be curved than when the height in the protruding direction is reduced stepwise.

Also, the present invention provides a cylinder head casting method for obtaining a cylinder head having a plurality of combustion chambers arranged in parallel along the longitudinal direction.
A port forming sand core comprising a port shaping portion for forming a port communicating with the combustion chamber;
A mold comprising a baseboard for supporting the baseboard part of the port forming sand core;
A sliding mold that supports the baseboard together with the mold;
Have
The mold further includes a plurality of combustion chamber molding portions that mold the plurality of combustion chambers, and a valve seat portion molding portion that is formed to protrude from the bottom wall of the combustion chamber molding portion and on which the port shaping portion is seated. And
The height in the protruding direction of the baseboard is set such that the longitudinal end is larger than the midway in the longitudinal direction,
And, among the valve seat part molding part, using a casting mold apparatus in which the height in the protruding direction of the one located at the longitudinal end is set larger than that located in the middle part in the longitudinal direction,
By supporting the baseboard part only with the baseboard of the mold, among the valve seat part molding part, the one located at the longitudinal end is seated on the port shaping part, and in the longitudinal direction The step of positioning the abdomen away from the port shaping part; and
By supporting the baseboard part with the baseboard and the sliding mold, all the valve seat part molding parts are in a state of being seated on the port shaping part,
A step of pouring hot water into the cavity in a state where all of the valve seat part molding part is seated on the port shaping part;
It is characterized by having.

  By going through such a process, a cylinder head that is curved so that the middle part in the longitudinal direction bulges toward the surface side on which the combustion chamber is formed is produced. By cooling the cylinder head to room temperature, it is possible to obtain a cylinder head that is flat and has a desired shape as described above.

  In addition, you may make it press the said protrusion part with the said sliding type | mold, when a protruding part is formed in a baseboard part and the said base board part is supported with a base board stand and a sliding type | mold. Thereby, a baseboard part can be curved still more easily and can be made to contact | abut to a baseboard stand.

  According to the present invention, since the height difference in the protruding direction of the base plate and the valve seat portion molding portion is provided, the base plate portion of the port forming sand core is slid from the base plate by clamping. When supported by the moving mold, the port-forming sand core is shaped so as to rise from the longitudinal middle portion toward the longitudinal end portion.

  When casting is performed in this state, a slightly curved cylinder head is produced. When this cylinder head is cooled to room temperature, the cylinder head bends (warps) in the direction opposite to the bending direction, and a flat cylinder head is easily obtained after all.

  That is, it is possible to obtain a cylinder head having a high dimensional accuracy and a port having a desired shape with a high yield while simplifying the configuration of the casting mold apparatus and avoiding a rise in capital investment.

It is a principal part schematic longitudinal cross-sectional view of the die apparatus for casting which concerns on embodiment of this invention. It is a top view which shows the state which supported the sand core for port formation in the lower mold | type which comprises the said casting mold apparatus. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. It is a schematic side surface longitudinal cross-sectional view of the baseboard provided in the said lower mold | type. FIG. 5 is a cross-sectional view taken along line VV in FIG. 2. FIG. 6 is a main part schematic front view showing a state in which the port forming portion of the port forming sand core pressed by the side die which is a sliding die is seated on the valve seat portion forming portion from FIG. 5. FIG. 4 is a schematic side view showing a state in which the port forming portion of the port forming sand core pressed by the side die that is a sliding die is seated on the valve seat portion forming portion from FIG. 3.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a cylinder head casting method according to the present invention will be described in detail with reference to the accompanying drawings by giving preferred embodiments in relation to a casting mold apparatus used therefor.

  FIG. 1 is a schematic longitudinal sectional view of a main part of a casting mold apparatus 10 according to the present embodiment. The casting mold apparatus 10 includes a lower mold 12, a first side mold 14 and a second side mold 16 as sliding molds, and an upper mold 18, and the lower mold 12 and the first side mold 14. In the cavity 20 formed by the second side mold 16 and the upper mold 18, a port forming sand core (hereinafter also simply referred to as “sand core”) 22 is disposed.

  The casting mold apparatus 10 is for obtaining a cylinder head (for example, see FIG. 1 of JP-A-2000-33459) by casting, and the shape of the cavity 20 corresponds to the shape of the cylinder head. Since this type of cylinder head is well known, its detailed description is omitted.

  As shown in FIG. 2, the lower mold 12 is formed with a plurality of (for example, four) combustion chamber forming portions 24 for forming the combustion chamber of the cylinder head. The combustion chamber forming portions 24 are arranged in parallel along the longitudinal direction of the lower mold 12 (the direction of the arrow X in FIG. 2).

  In one combustion chamber forming portion 24, for example, four valve seat portion forming portions 26 for providing a valve seat portion in the cylinder head are provided. Each valve seat portion molding portion 26 has a substantially cylindrical shape, and protrudes vertically upward (in the direction of arrow Z in FIG. 1) from the upper end surface of the combustion chamber molding portion 24.

  As shown in FIG. 3, in the valve seat part molding part 26a located at the end in the longitudinal direction and the valve seat part molding part 26b located in the middle abdomen, the protruding height (the height in the vertical direction along the arrow Z direction). There is a difference, in other words, a height difference. In other words, the protruding height H1 of the valve seat portion molding portion 26a is set to be larger than the protruding height H2 of the valve seat portion molding portion 26b.

  As described above, when the cylinder head cast by the casting mold apparatus according to the prior art is cooled to room temperature, the cylinder head is curved so that the mid-section in the longitudinal direction bulges upward. Therefore, the protruding height of the valve seat portion molding portion 26 may be sequentially changed from the longitudinal end portion toward the middle abdominal portion. For example, the height difference between the valve seat part molding part 26a located at the end in the longitudinal direction and the valve seat part molding part 26c located in the middle part in the longitudinal direction and close to the valve seat part molding part 26a is 0.1 to 0. The height difference between the valve seat molded part 26c and the valve seat molded part 26b located in the middle part in the longitudinal direction is within a range of 0.1 to 0.2 mm. You may make it make it smaller than the height difference with the valve seat part shaping | molding part 26a, 26c.

  As shown in FIG. 1, on the upper end surface of the lower mold 12, baseboards 30 a and 30 b that are directed vertically upward are formed to protrude. These skirting boards 30 a and 30 b extend along the longitudinal direction of the lower mold 12.

  The baseboards 30a and 30b are provided with a height difference. That is, as shown in FIG. 4, inclined bases 30 a and 32 b are formed in the baseboards 30 a and 30 b so as to approach vertically downward from each end side in the longitudinal direction toward the middle abdomen side. For this reason, in the skirting boards 30a and 30b, the protruding height (vertical height along the arrow Z direction) H3 of the longitudinal direction end is larger than the protruding height H4 of the longitudinal middle part. In short, H3> H4, and therefore the baseboards 30a and 30b have a shape in which the midsection in the longitudinal direction is depressed.

  Since the inclined portions 32a and 32b are interposed, the projecting height of the baseboards 30a and 30b is gradually reduced from the longitudinal end portion to the longitudinal middle portion.

  The difference between H1 and H2 and the difference between H3 and H4 are the same as the casting mold apparatus configured in accordance with the casting mold apparatus 10, except that the lower mold is not provided with these height differences. Is set according to the warpage of the cylinder head to be cast. Typically, it is 0.5 mm or less, for example, about 0.3 mm, more preferably about 0.2 mm.

  The sand cores 22 are supported on the baseboards 30a and 30b, respectively. These sand cores 22 are for forming a supply / exhaust port in the cylinder head. In addition, although the component which attached | subjected the referential mark 34 is also a sand core, this sand core 34 shape | molds cavities etc. other than the said port.

  As understood from FIG. 2, the sand core 22 extends along the longitudinal direction of the lower mold 12, and is sandwiched between the baseboards 30 a and 30 b, the first side mold 14, and the second side mold 16. The baseboard 36 is provided. The sand core 22 is further provided with a port shaping portion 38 having a shape protruding substantially horizontally from the baseboard portion 36 toward the cavity 20 and curved toward the valve seat portion molding portion 26. As will be described later, when the mold clamping is performed, each end portion of all the port shaping portions 38 is seated on each valve seat portion molding portion 26.

  Since the baseboards 30a and 30b and the valve seat portion molding portion 26 are provided with a height difference, the width of the baseboard portion 36 is not pressed by the first side die 14 or the second side die 16 under the condition that the width As shown in phantom lines in FIG. 4, the lower end surface of the wooden part 36 is in contact with the upper end surface of the baseboards 30a and 30b while the longitudinal middle part thereof is in the baseboards 30a and 30b. (See FIG. 5).

  The port shaping portions 38 of the sand core 22 are set to have substantially the same shape and dimensions. For this reason, when the baseboard part 36 is supported by the baseboards 30a and 30b, as shown in FIG. 3, the lower end surface of the baseboard part 36 comes into contact with the upper end surfaces of the baseboards 30a and 30b and the valve seat The port shaping portion 38 is seated on the valve seat portion forming portion 26 at the longitudinal end portion where the protruding height of the portion forming portion 26 is large. On the other hand, in the longitudinal middle part where the baseboard part 36 is separated from the upper end surfaces of the baseboards 30a and 30b and the protruding height of the valve seat part forming part 26 is small, the port shaping part 38 is connected to the valve seat part forming part 26. Separate from.

  As shown in FIGS. 2, 3, and 5, a hemispherical potch 40 (protrusion) is formed on the upper end surface of the baseboard portion 36. The position of the potch 40 corresponds to the position of the combustion chamber forming part 24.

  The radius of each potch 40 is set within a range of 1 to 2 mm, for example. As will be described later, a part of the potch 40 is crushed by the first side mold 14 or the second side mold 16 when the mold clamping is performed.

  The first side mold 14 and the second side mold 16 slide on the upper end surface of the lower mold 12 under the action of a drive mechanism (for example, a hydraulic cylinder) (not shown). The sliding direction is the arrow Y direction shown in FIGS.

  Each of the first side mold 14 and the second side mold 16 is formed with a holding recess 42 that can be fitted into the baseboard portion 36 of the sand core 22 (see FIGS. 1 and 5). In other words, the holding recess 42 is fitted to the baseboard portion 36 at the time of clamping.

  The upper die 18 is lowered or raised so as to be relatively close to or separated from the lower die 12 under the action of a drive mechanism (for example, a hydraulic cylinder) (not shown). Of course, the mold is clamped as it descends, and as a result, the cavity 20 is formed. On the other hand, the mold is opened by raising.

  The mold apparatus 10 for casting according to the present embodiment is basically configured as described above. Next, with respect to the function and effect, the casting method of the cylinder head according to the present embodiment is described. Explain in relation.

  First, the baseboard part 36 of the sand core 22 is supported on the baseboard boards 30a and 30b of the lower mold 12. The skirting board 36 and the skirting boards 30a and 30b are provided with engaging parts / engaged parts (not shown) that engage with each other (for example, a concave part and a convex part). It is avoided that the baseboards 30a and 30b fall off.

  As described above, the height difference is provided in the baseboards 30a and 30b, and the height difference is also provided in the valve seat portion molding portion 26. Therefore, as shown in FIG. The modeling part 38 is seated on the valve seat part forming part 26 at the end in the longitudinal direction. On the other hand, in the middle part in the longitudinal direction, as shown in FIGS. 3 and 5, the port shaping portion 38 is separated from the valve seat portion forming portion 26.

  In FIGS. 3 and 5, the separation distance is remarkably large for easy understanding, but the actual separation distance is 0.5 mm or less, typically within the range of 0.1 to 0.3 mm. is there.

  Next, in order to perform mold clamping, the first side mold 14 and the second side mold 16 slide on the upper end surface of the lower mold 12 along the arrow Y direction in FIGS. 1, 2, and 5. As a result, as shown in FIG. 6, the baseboard portion 36 is accommodated in each holding recess 42 of the first side mold 14 and the second side mold 16. As a result, the sand core 22 is sandwiched between the baseboards 30a and 30b and the first side mold 14 or the second side mold 16.

  At this time, the potch 40 provided on the upper end surface of the baseboard portion 36 contacts the ceiling surface of the holding recess 42. Further, the potch 40 is partially crushed by being pressed from the ceiling surface of the holding recess 42. As a result, as shown in FIG. 7, the lower end surface of the baseboard part 36 is seated on the baseboards 30 a and 30 b, and one end of all the port shaping parts 38 is seated on the valve seat part molding part 26.

  Since the baseboards 30a and 30b are formed with the inclined portions 32a and 32b (see FIG. 4), the baseboard portion 36 is vertically lowered from the longitudinal end portion toward the longitudinal middle portion with the seating. Curve to bulge. In addition, as understood from the broken line shown in FIG. 7, the upper part of the port shaping part 38 of the sand core 22 is positioned so that the longitudinal end part side is vertically above the longitudinal middle part. become. That is, the position of the upper part of the port shaping part 38 is lowered sequentially or stepwise as it goes from the longitudinal end part side to the longitudinal middle part part side.

  The upper die 18 is lowered so as to approach the lower die 12 substantially simultaneously with or after the sliding of the side wall, and the first side die 14 and the second side die 16 are brought into contact with each other to be clamped. Along with this, a cavity 20 is formed (see FIG. 1).

  Next, molten aluminum alloy is introduced into the cavity 20. As the molten metal cools and solidifies, a cylinder head is obtained. In this cylinder head, a combustion chamber corresponding to the shape of the combustion chamber forming portion 24 and a valve seat portion corresponding to the shape of the valve seat portion forming portion 26 are formed, and the sand core 22 is used for supply and exhaust. A port is formed.

  As the upper die 18 moves up, the first side die 14 and the second side die 16 slide in a direction away from each other, thereby opening the die and exposing the cylinder head. The cylinder head is slightly curved so that the middle part in the longitudinal direction swells vertically downward. This is because the port shaping part 38 of the sand core 22 descends sequentially or stepwise from the longitudinal direction end part side toward the longitudinal direction abdominal part side (see FIG. 7).

  The cylinder head thus obtained is allowed to cool to room temperature, for example. Shrinkage occurs with this cooling, and the middle part in the longitudinal direction warps in the vertical upward direction. Thereby, the lower end surface and upper end surface of a cylinder head become substantially flat. This is because the cylinder head is curved in advance as described above.

  That is, a cylinder head that becomes flat after cooling can be obtained by using the casting mold apparatus 10 including the lower mold 12 provided with a height difference in the baseboards 30a and 30b and the valve seat portion molding portion 26. .

  In this case, the first side mold 14, the second side mold 16, and the upper mold 18 do not need to have a shape that takes into account the warpage that occurs in the cylinder head. For this reason, it is avoided that capital investment soars. That is, according to the present embodiment, the cylinder head after cooling can be easily obtained while the lower mold 12, the first side mold 14, the second side mold 16, and the upper mold 18 are simply configured. It becomes. Therefore, a cylinder head having excellent dimensional accuracy can be obtained with a high yield.

  In this cylinder head, the port has a predetermined shape designed in advance. That is, the port can be formed in a desired shape by performing casting as described above. For this reason, it becomes easy to obtain desired engine characteristics.

  The present invention is not particularly limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

  For example, in this embodiment, the potch 40 is provided at a position corresponding to the position of the four combustion chamber forming portions 24, but the potch 40 has two combustion chamber forming portions 24 in the middle in the longitudinal direction. You may make it provide only in the position corresponding to this position. Or you may make it make the radius of the potch 40 located in a longitudinal direction edge part small compared with the potch 40 located in a longitudinal direction middle part, and may omit all the potches 40.

  Further, the height difference between the baseboards 30a and 30b or the valve seat part molding part 26 may be the same or different between the valve seat part molding part 26 for supplying air and the valve seat part molding part 26 for exhausting. You may make it make it.

DESCRIPTION OF SYMBOLS 10 ... Mold apparatus for casting 12 ... Lower mold 14 ... 1st side mold 16 ... 2nd side mold 18 ... Upper mold 20 ... Cavity 22 ... Sand core for port formation 24 ... Combustion chamber molding part 26, 26a-26c ... Valve seat portion forming portion 30a, 30b ... Baseboard 32a, 32b ... Inclined portion 36 ... Baseboard portion 38 ... Port shaping portion 40 ... Potch

Claims (5)

In a casting mold apparatus for obtaining a cylinder head having a plurality of combustion chambers arranged in parallel along the longitudinal direction,
A port forming sand core comprising a port shaping portion for forming a port communicating with the combustion chamber;
A mold comprising a baseboard for supporting the baseboard part of the port forming sand core;
A sliding mold that supports the baseboard together with the mold;
Have
The mold further includes a plurality of combustion chamber molding portions that mold the plurality of combustion chambers, and a valve seat portion molding portion that is formed to protrude from a bottom wall of the combustion chamber molding portion and on which the port shaping portion is seated. And
The height in the protruding direction of the baseboard is set such that the end in the longitudinal direction is larger than the middle part in the longitudinal direction,
A casting mold characterized in that, among the valve seat portion molding portions, the height in the protruding direction of the one located at the end portion in the longitudinal direction is set larger than that in the middle portion in the longitudinal direction. apparatus.   2. The mold apparatus for casting according to claim 1, wherein a projecting portion protrudes from the baseboard portion.   3. The mold apparatus according to claim 1, wherein a height of the baseboard in a protruding direction is gradually reduced from a longitudinal end portion to a longitudinal middle portion. 4. In a cylinder head casting method for obtaining a cylinder head having a plurality of combustion chambers arranged in parallel along the longitudinal direction,
A port forming sand core comprising a port shaping portion for forming a port communicating with the combustion chamber;
A mold comprising a baseboard for supporting the baseboard part of the port forming sand core;
A sliding mold that supports the baseboard together with the mold;
Have
The mold further includes a plurality of combustion chamber molding portions that mold the plurality of combustion chambers, and a valve seat portion molding portion that is formed to protrude from the bottom wall of the combustion chamber molding portion and on which the port shaping portion is seated. And
The height in the protruding direction of the baseboard is set such that the longitudinal end is larger than the midway in the longitudinal direction,
And, among the valve seat part molding part, using a casting mold apparatus in which the height in the protruding direction of the one located at the longitudinal end is set larger than that located in the middle part in the longitudinal direction,
By supporting the baseboard part only with the baseboard of the mold, among the valve seat part molding part, the one located at the longitudinal end is seated on the port shaping part, and in the longitudinal direction The step of positioning the abdomen away from the port shaping part; and
By supporting the baseboard part with the baseboard and the sliding mold, all the valve seat part molding parts are in a state of being seated on the port shaping part,
A step of pouring hot water into the cavity in a state where all of the valve seat part molding part is seated on the port shaping part;
A method of casting a cylinder head, comprising:   5. The casting method according to claim 4, wherein a projecting portion is formed to protrude from the baseboard portion, and when the baseboard portion is supported by the baseboard base and the sliding mold, the projecting portion is formed by the sliding mold. A method of casting a cylinder head, characterized by pressing.

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