JP3713462B2 - Cylinder head and casting method thereof - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a cylinder head and a casting method thereof, and more particularly to a method for setting a sand core for a water jacket to a mold.
[0002]
[Prior art]
A cylinder head 101 formed with the conventional cylinder head casting mold shown in FIG. 8 is shown in FIGS. One end surface side of the conventional cylinder head is a gasket surface 102, and the other end surface forms a cam chamber 110. A combustion chamber 106 is formed on one end surface side, and a water jacket (corresponding to a sand core 140 for water jacket in FIG. 8) is formed in a position surrounding the combustion chamber between the one end surface side and the other end surface side. ing. A plurality of cooling water holes (corresponding to the baseboard 141 in FIG. 8) of the water jacket are arranged along substantially the same circumference and open to the gasket surface. Inside the same circumference of the cooling water hole, a top region of the combustion chamber is disposed, and an intake port 104 and an exhaust port 105 are opened.
[0003]
A chain chamber 108 is disposed outside the same circumference of the cooling water hole. A chain (not shown) for transmitting the rotational force of a crankshaft (not shown) to the valve mechanism in the cam chamber 110 is disposed in the space in the chain chamber 108.
[0004]
On the cam chamber 110 side, a pair of stem through-holes 104A and 105A through which a valve stem of an intake valve and an exhaust valve (not shown) reciprocally slide is formed. The stem through-holes 104A and 105A extend in directions intersecting each other toward the combustion chamber 106 so as to form a desired sandwich angle. In addition, a hole 110a is formed between the pair of stem through holes and at a position directly above the top of the combustion chamber.
[0005]
In order to drive the valve stem, the non-valve side end surface of the valve stem is urged against a rocker arm (not shown), and the rocker arm is swung by the rotation of a valve cam (not shown). The chain (not shown) passes through the chain chamber to reach the cam chamber, and drives the camshaft to rotate.
[0006]
When casting the cylinder head, as shown in FIG. 8, the fixed mold 121 and the movable mold 130 provided with a movable core (not shown) are slidably fitted to form a cylinder head. A cavity is defined. Here, when the cylinder head is manufactured from a light alloy typified by an aluminum alloy by a horizontal die casting machine, the water jacket sand core 140 is set in a fixed mold having a dividing surface 121a on a vertical surface. Specifically, on the combustion chamber side of the water jacket sand core 140, a plurality of combustion chamber side skirting boards 141 arranged on substantially the same circumference are provided so as to protrude, and the same circumference of the fixed mold 121 is provided. It engages with a plurality of skirting board engaging holes 124 arranged in a shape. This skirting board 141 becomes a cooling water hole that opens on the gasket surface of the product, and also becomes a sanding hole after the core sand for the water jacket 140 is collapsed by heating.
[0007]
In addition, in order to prevent the water jacket sand core 140 from falling and being displaced due to gravity and to prevent the core displacement due to molten metal pressure, the water jacket sand core 140 is also disposed on the anti-combustion chamber side. Further, an anti-combustion chamber side skirting board 142 protruding in a direction opposite to the plurality of skirting boards is provided, and a cast pin 132 that can be engaged with the anti-combustion chamber side skirting board 142 is provided on the movable mold 130 side. Is provided. Therefore, the water jacket sand core 140 is held by the molds 121 and 130 on both the combustion chamber side and the anti-combustion chamber side.
[0008]
In the product, the position corresponding to the anti-combustion chamber side skirting board 142 becomes a hole portion 110a that opens to the anti-combustion chamber side, and is used as a sanding hole when the water core sand core 140 is heated and collapsed. This is because the capacity of the core sand on the anti-combustion chamber side is large, so that heating is insufficient, and sand removal only from the cooling water hole opening in the gasket surface is insufficient.
[0009]
In addition, when injection molding the sand core for water jacket itself, the sand core 140 for water jacket having a substantially cylindrical shape is also used in order to improve the spread of the core sand in the sand core mold. Since it is effective to fill the core sand from the center portion of the anti-combustion chamber, the core sand filling port is provided at that position. The filling port has a protruding shape, and an anti-combustion chamber side skirting board 142 is formed at the center of the water jacket sand core 140 on the anti-combustion chamber side.
[0010]
In the case of casting a cylinder head by the gravity casting method, the plurality of baseboards on the combustion chamber side described above are set downward in the lower mold. Here, since the specific gravity of the sand core material for the water jacket is smaller than that of aluminum, which is a light alloy molten metal material, there is a risk that the sand core for the water jacket will be lifted by the molten metal filled in the cavity from below the lower mold. In order to prevent this, the above-described anti-combustion chamber side skirting board is provided on the anti-combustion chamber side, a pin is installed from the upper mold, and the anti-combustion chamber skirting board is pressed.
[0011]
[Problems to be solved by the invention]
In the conventional cylinder head, as described above, the hole 110a is formed between the pair of stem through-holes 104A and 105A and immediately above the top of the combustion chamber 106. This position is on the upper wall of the water jacket of the cam chamber 110 and is in the vicinity of the narrow angle between the intake valve stem and the exhaust valve stem. The narrow angle of the valve is a factor that greatly affects engine performance in terms of engine design, such as engine output performance, fuel consumption performance, and exhaust gas purification performance. Here, the hole 110a does not restrict the degree of freedom of design for the design that widens the valve narrow angle, but the design that narrows the valve narrow angle avoids the valve stem from interfering with the hole 110a. As a result, the degree of freedom in engine design is greatly limited.
[0012]
In the finished cylinder head 101, the hole 110a is closed with a stopper. This is because the cam chamber 110 is filled with the lubricating oil, so that mixing of the cooling water in the water jacket and the lubricating oil is avoided. For this purpose, a post-operation of tapping the hole 110a and screwing the stop plug is required.
[0013]
Therefore, the present invention can increase the degree of freedom in designing the included angle of the valve stem, and thus can exhibit the desired engine performance, eliminates the need for a stop plug, and simplifies the entire manufacturing process, and its cylinder head. An object is to provide a manufacturing method.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention , a combustion chamber 6 is formed on one end surface side, a gasket surface 2 is formed to open the combustion chamber, and the other end surface side forms a cam chamber 10. A water jacket 7 is formed at a position surrounding the combustion chamber between the first and second end surfaces, and a plurality of cooling water holes 7a of the water jacket are opened on the one end surface side. In order to cast a cylinder head in which the intake valve stem hole 4A and the exhaust valve stem hole 5A are opened to slide and guide the reciprocation of the intake valve stem and the exhaust valve stem toward the combustion chamber 6, a fixed mold is used. 21 and a movable mold 30 provided with a movable core so as to be slidable are combined to define a cylinder head forming cavity 50 and a plurality of baseboards on the gasket surface 2 side. 1 is held in place by engaging the plurality of baseboards 41 with the plurality of engaging holes arranged in the fixed mold 21. In the casting method of the cylinder head in which the cavity 50 is filled with the molten metal in this state, a holding area expanding portion 41A is integrally provided on at least one of the plurality of baseboards 41X and 41Y, and the fixed mold 21 A concave portion 25 capable of accommodating the holding area expanding portion 41A is provided on the split surface, and the holding area expanding portion 41A is fixed to the fixed mold 21 and the movable mold 30, or the fixed mold 21 and the moving core. Or a cylinder head casting method in which the water core sand core 40 is held at the predetermined position only on the gasket surface 2 side by being sandwiched between the fixed mold 21 and the movable mold 30 and the moving core. Provide That.
[0015]
Here, the holding area expanding portion 41 </ b> A is preferably provided in the vicinity of the pouring gate 22 that fills the cavity 50 with the molten metal.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
A cylinder head and a casting method thereof according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a plan view showing the gasket surface side of the cylinder head 1, and the gasket surface 2 is finished to be a flat end surface so as to abut a cylinder block (not shown). Near the outer contour of the gasket surface 2, head bolt insertion holes 3A, 3B, 3C, 3D for fixing to a cylinder block (not shown) are formed. The gasket surface 2 has a combustion chamber 6 which is part of a spherical surface and has an intake port 4 and an exhaust port 5 open. In the cylinder head 1, a water jacket 7 is formed at a position surrounding the combustion chamber 6, and a plurality of water jacket cooling water holes 7 a are arranged on the same circumference so as to open to the gasket surface 2.
[0017]
FIG. 2 shows the cam chamber 10 side of the cylinder head 1. In the cam chamber 10, an intake valve (not shown) for opening and closing the intake port 4 and the exhaust port 5, an intake valve stem of an exhaust valve, and an exhaust valve are shown. An intake valve guide insertion portion (intake valve stem hole) 4A and an exhaust valve guide insertion portion (exhaust valve stem hole) 5A into which a valve guide (not shown) for sliding and reciprocating the stem is inserted are opened. . These stem holes 4A and 5A extend in a direction intersecting with each other toward the combustion chamber 6 so as to form a desired sandwich angle θ as shown in FIG. A position corresponding to the upper wall of the water jacket 7 that forms the bottom wall of the cam chamber 10 and between the positions where the intake valve stem hole 4A and the exhaust valve stem hole 5A open is located above the combustion chamber 6. In this portion, the hole portion 110a shown in FIG. 6 is not formed, and it forms a continuous surface that is entirely occupied by a metal material. In FIG. 3, the intake valve stem hole 4 </ b> A and the exhaust valve stem hole 5 </ b> A are not shaped to penetrate into the combustion chamber 6. This is a shape at the time of casting, and is penetrated to the combustion chamber 6 by post-processing, and an intake valve guide and an exhaust valve guide (not shown) are fitted into the through holes.
[0018]
A chain chamber 8 is disposed outside a substantially circular region within the same circumference of the cooling water hole 7a. The chain chamber 8 is also opened on the cam chamber 10 (FIG. 2) side. A camshaft (not shown) for moving an intake valve and an exhaust valve (not shown) is disposed in the space in the cam chamber 10, and a rocker arm (not shown) that slides on the cam crest of the camshaft is swingable. Supported. The tip of the valve stem on the side opposite to the valve (not shown) is biased by the rocker arm. The above-described chain chamber 8 is for the passage of a chain (not shown) for transmitting the rotation of a crankshaft (not shown) to the camshaft via a sprocket (not shown). The rotation of the crankshaft rotates the camshaft through the chain, and the rotation of the camshaft swings the rocker arm. As a result, the intake valve and the exhaust valve reciprocate to open and close the intake port and the exhaust port, respectively. The chain chamber 8 is a space for running the chain, but may be an endless belt or a cam gear train instead of the chain.
[0019]
Next, the casting apparatus 20 and the water jacket sand core 40 for casting the cylinder head will be described with reference to FIGS. The casting apparatus of the present embodiment is a horizontal die casting apparatus having a fixed mold 21 and a movable mold 30, and a cylinder head-shaped cavity is formed when the fixed mold 21 and the movable mold 30 come into contact with each other. Defined. The fixed mold 21 forms a surface that forms the gasket surface 2 of the cylinder head 1 with a surface (dividing surface 21 a) facing the movable mold 30 extending in the vertical direction. On this surface, a gate 22 that is openly connected to the lower end portion of the mold cavity 50 is opened, and the gate 22 is connected to the runner portion 26. The runner part 26 is connected to an injection cylinder (not shown).
[0020]
Further, the fixed mold 21 is provided with a combustion chamber molding portion 23 protruding in the direction of the movable mold 30, and the combustion chamber molding portion 23 is surrounded by the same circumference from one end surface of the water jacket sand core 40. A plurality of skirting board engagement holes 24 through which a plurality of skirting boards 41 (described later) provided so as to protrude upward are formed on substantially the same circumference. In addition, the fixed mold 21 is provided with a port core skirting board engaging portion (not shown) that engages with the suction port sand core and the exhaust port sand core.
[0021]
As shown in FIG. 5, the water jacket sand core 40 includes a substantially cylindrical core body portion 40 </ b> A and a plurality of combustion chamber side skirting boards 41. The core body 40A has a shape surrounding the combustion chamber 6, and is formed with an intake port core insertion hole 41a (not shown) and an exhaust port core insertion hole 41b (not shown). The plurality of combustion chamber side skirting boards 41 are provided so as to protrude from the combustion chamber side end surface of the core main body 40A in the substantially axial direction of the core main body 40A. Further, when the water jacket sand core 40 is set in the fixed mold 21, the combustion chamber side skirting boards 41X and 41Y located closest to the gate 22 are integrally provided with holding area expanding portions 41A and 41A, and the combustion chamber. It is provided to extend outward in the radial direction of the core main body 40A in the direction perpendicular to the tips of the side skirting boards 41X and 41Y. A pair of recesses 25 that can accommodate the holding area expanding portions 41 </ b> A and 41 </ b> A are formed on the dividing surface 21 a of the fixed mold 21. The depth of the recess 25 is formed approximately equal to the thickness t of the holding area expanding portion 41A.
[0022]
The sand core 40 for water jacket is a collapsible core that is collapsed by applying vibration and is coated on the outer surface. In the core removal step, the molded cylinder head material is vibrated. It is preferable to use a commercially available easily disintegratable core sand for light alloys. For example, it is preferable to manufacture a core material and a coating mold using the materials described in Japanese Patent Application Laid-Open No. 1-133639 and Japanese Patent Application Laid-Open No. 64-48638.
[0023]
The movable mold 30 is provided so as to be movable in the horizontal direction so as to be able to contact and separate from the fixed mold 21, and mainly forms the cam chamber 10 side opposite to the gasket surface 2 of the cylinder head 1. The movable mold 30 is provided with a chain chamber forming protrusion 31 toward the fixed mold 21. The length of the chain chamber forming protrusion 31 is such that the tip surface 31A of the chain chamber forming protrusion 31 is located on substantially the same plane as the gasket forming surface 21a when the mold is closed, and the fixed mold 21 This is a length capable of being pressed and held so as not to collapse the holding area expanding portion 41A. Therefore, the chain chamber forming projection 31 allows the gasket surface 2 side and the cam chamber 10 side to communicate with each other, and the water jacket sand core 40 can be held at a predetermined position. The portion above the chain chamber forming protrusion 31 of the movable mold 30 is located at a position facing the upper surface 40a of the water jacket sand core 40, and forms a flat surface 31B where no core pin is inserted. The movable mold 30 is provided with a moving core (not shown) for forming an undercut portion of the product so as to be able to reciprocate in a predetermined direction.
[0024]
Next, a cylinder head casting process using the above-described cylinder head casting mold will be described. A plurality of skirting boards 41 of the water jacket sand core 40 are inserted into the skirting board engaging holes 24. When the engagement is completed, the holding area expanding portion 41A is located in the recess 25. Next, the movable core of the movable mold 30 is slid to a predetermined position, and after the movement is completed, the movable mold 30 is horizontally moved in the direction of the fixed mold 21 to perform mold matching. In this state, the tip end surface 31A of the chain chamber forming projection 31 is positioned substantially on the same plane as the gasket forming surface 21a and does not collapse the holding area expanding portion 41A in cooperation with the fixed mold 21. Pressing and holding to the extent. Therefore, the water jacket sand core 40 is held in the mold only on the combustion chamber side.
[0025]
Next, a molten metal such as an aluminum alloy is injected and filled into the mold cavity 50 through the runner portion 26 and the gate 22 to cast a cylinder head material. At this time, the holding area expanding portion 41A is provided integrally with the baseboards 41X and 41Y closest to the gate 22, so that the molten metal behaves most actively immediately after the molten metal flows into the cavity. Since the core 40 is held, it is possible to effectively prevent the sand core 40 for water jacket from shifting due to the molten metal flow.
[0026]
Further, the flat surface 31B of the movable mold 30 is opposed to the upper surface 40a of the water jacket sand core 40 with a predetermined gap, and this gap is the upper wall portion of the water jacket 7, and is the intake valve stem. It corresponds to a position between the position where the hole 4A and the exhaust valve stem hole 5A are open and above the combustion chamber 6. The molten metal is filled in the gaps in a flat shape without forming holes.
[0027]
After the molten metal is solidified, a moving core (not shown) is slid backward to separate the cylinder head material from the movable mold 30. After separation, a release agent is applied to the fixed mold 21 and the movable mold 30 and cleaned by air blowing. Next, when the cylinder head material is vibrated, the water jacket sand core 40 and the port core (not shown) collapse and are removed from the cylinder head material. In this case, the hole 110a opening on the cam chamber side as shown in FIG. 6 is not formed, but the water jacket sand core 40 is made of a light alloy easy-disintegrating core sand that collapses by vibration. Since it is molded, it can be collapsed only by vibration treatment without sanding such as heating, and the core sand can be discharged outside the water jacket only through the cooling water hole 7a.
[0028]
The cylinder head and the casting method thereof according to the present invention are not limited to the above-described embodiments, and various modifications and improvements can be made within the scope described in the claims. For example, in the above-described embodiment, the holding area expanding portion 41A is provided on the specific baseboards 41X and 41Y so that the holding area expanding portion 41A is arranged on the side of the gate 22, but the dimensional accuracy of the cast product can be maintained. If it is, the holding area expansion part may be provided in another baseboard other than a specific baseboard, and may be provided in both a specific baseboard and another baseboard.
[0029]
In the above-described embodiment, the holding area expanding portion 41A is held between the concave portion 25 of the fixed mold 21 and the tip surface 31A of the movable mold chain chamber forming projection 31. However, as long as the holding position of the water jacket sand core is only on the gasket surface side, it is not limited to such a place, and the shape of the holding area expansion portion and which baseboard the expansion portion is provided integrally with, etc. Depending on the situation, the holding may be performed between the fixed mold and the moving core or between the fixed mold, the movable mold and the moving core.
[0030]
Moreover, in embodiment mentioned above, although the collapsible core which can be collapsed only by an excitation process is used, it is not limited to such a material. In addition, when a collapsible core is used, in order to further facilitate the removal of the core by the vibration treatment, the cylinder head is heated to a temperature range where the core sand binder is thermally decomposed prior to the vibration treatment. The material may be heated.
[0031]
The above-described embodiment relates to a single-cylinder engine, but the present invention is also applicable to a multi-cylinder engine, and the total number of intake valves and exhaust valves per cylinder is 3 or more. It can also be applied to engines.
[0032]
【The invention's effect】
According to the casting method for a cylinder head according to claim 1 , the holding area expanding portion is provided on at least one of the plurality of baseboards on the gasket surface side of the sand core for water jacket, and the holding area expanding portion is a fixed mold. And the movable mold, or the fixed mold and the movable core, or the fixed mold, the movable mold, and the movable core only, and the sand core for the water jacket is held in a predetermined position only on the gasket surface side. Therefore, there is no need to install a baseboard on the anti-combustion chamber side of the sand core for the water jacket, and processing of the mold surface and installation of the casting pin to hold the anti-combustion chamber side of the sand core Is no longer necessary.
[0033]
According to the cylinder head casting method of the second aspect , since the holding area enlarged portion is in the vicinity of the pouring gate, the molten metal flowing out from the pouring gate flows into the vicinity of the holding area enlarged portion and then is filled in the cavity. Therefore, the shift | offset | difference of the sand core for water jackets by a molten metal flow can be prevented effectively.
[Brief description of the drawings]
FIG. 1 is a plan view of a cylinder head according to an embodiment of the present invention viewed from a gasket surface side.
FIG. 2 is a plan view of the cylinder head according to the embodiment of the present invention as viewed from the cam chamber side.
3 is a cross-sectional view taken along line III-III in FIG.
FIG. 4 is a schematic cross-sectional view of a horizontal casting apparatus for performing a cylinder head casting method according to an embodiment of the present invention.
FIG. 5 is a perspective view showing a sand core for a water jacket used in a cylinder head casting method according to an embodiment of the present invention.
FIG. 6 is a plan view of a conventional cylinder head as viewed from the cam chamber side.
7 is a cross-sectional view taken along the line VII-VII in FIG. 6 before the water jacket sand core is removed.
FIG. 8 is a schematic cross-sectional view of a horizontal casting apparatus for performing a conventional cylinder head casting method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Gasket surface 4A, 5A Valve stem hole 6 Combustion chamber 7 Water jacket 7a Cooling water hole 8 Chain chamber 10 Cam chamber 21 Fixed metal mold 24 Base board engagement hole 25 Recess 30 Movable metal mold 31 Protrusion for chain chamber formation Part 40 sand core 40A for water jacket core body part 41, 41X, 41Y combustion chamber side skirting board 41A holding area expansion part

Claims (2)

A combustion chamber is formed on one end surface side, a gasket surface is formed to open the combustion chamber, the other end surface side forms a cam chamber, and the combustion chamber is enclosed between the one end surface side and the other end surface side. A water jacket is formed at a position, a plurality of cooling water holes of the water jacket are opened on the one end surface side, and the reciprocating operation of the intake valve stem and the exhaust valve stem toward the combustion chamber on the other end surface side In order to cast a cylinder head with an intake valve stem hole and an exhaust valve stem hole for sliding guide, a fixed mold and a movable mold with a movable core slidable are matched. As a result, a cylinder head molding cavity is defined, and a plurality of engagements in which a sand core for a water jacket having a plurality of baseboards projecting on the gasket surface side are arranged in the fixed mold Parts held in place by engaging the baseboard of the plurality of, in the state of die matching the casting method of the cylinder head to fill the molten metal in said cavity,
  At least one of the plurality of skirting boards is integrally provided with a holding area extending portion, and a split surface of the fixed mold is provided with a recess capable of accommodating the holding area expanding portion, and the holding area expanding portion is The fixed core and the movable mold, or the fixed mold and the moving core, or the fixed mold, the movable mold, and the moving core are sandwiched between the sand core for the water jacket. A cylinder head casting method, wherein the cylinder head is held at the predetermined position only on the side. 2. The method of casting a cylinder head according to claim 1, wherein the holding area expanding portion is provided in the vicinity of a pouring gate for filling the molten metal into the cavity.

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