Casting method of cast aluminum cylinder cover and casting mold thereof

Abstract

The casting method comprises the following steps that S1, sand cores of a lower water jacket core, an upper water jacket core, an air channel core and an oil pool core are assembled and combined with a mold insert body with a pre-casting pin to form a combined mold of the air cylinder cover, and the size of the pre-casting pin is matched with that of an oil sprayer hole; s2, after components of casting molten aluminum are adjusted, the molten aluminum is injected into a cavity of the sand core from a sprue cup of the cylinder cover combined mold according to the set pouring speed when the molten aluminum reaches the set pouring temperature; s3, after the set solidification time, the peripheral mold is separated from the casting, the casting is taken out, and finally the molding sand attached to the inner surface and the outer surface of the casting is cleaned up; and S4, the casting is machined, so that a corresponding oil sprayer hole is machined.

Description

Technical Field

[0001] The invention relates to the technical field of automobile molds, in particular to a casting method of a cast aluminum cylinder head and a casting mold thereof. Background Art

[0002] The diesel engine cylinder head is not only complex in structure, but also has harsh working conditions and complex stress conditions. The bottom of the cylinder head is in direct contact with high-temperature and high-pressure combustion gas, which generates great mechanical stress under the explosion pressure of the combustion gas; the bottom of the injector hole is subjected to a large preload of the injector pressure plate bolt; when the cylinder head is repeatedly heated and cooled, the temperature difference causes thermal expansion and thermal strain of various parts to generate thermal stress; these factors are concentrated at the fillet of the injector, making the fillet of the injector more susceptible to high-cycle fatigue damage.

[0003] In the related art, the fillet at the bottom of the injector hole is far away from the cooling surface of the mold, and the cooling and solidification conditions are poor, resulting in slightly poor metallographic properties at the fillet at the bottom of the injector hole, which in turn results in poor mechanical properties of the material at the fillet at the bottom of the injector hole, affecting the durability and reliability of the engine. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a casting method for a cast aluminum cylinder head, which can improve the cooling conditions of the cylinder head injector hole during casting, thereby improving the regional metallographic structure, increasing the local strength of the injector fillet, and increasing the durable fatigue life of the cylinder head.

[0005] The present invention further provides a casting mold for a cast aluminum cylinder head.

[0006] According to the casting method of the cast aluminum cylinder head of the first embodiment of the present invention, the following steps are included: S1, assembling the sand cores of the lower water jacket core, the upper water jacket core, the airway core and the oil pool core, and combining them with the mold insert with the precast pin to form a cylinder head assembly mold, wherein the precast pin matches the injector hole size; S2, after adjusting the composition of the casting molten aluminum, when the molten aluminum reaches the set pouring temperature, injecting the molten aluminum from the pouring cup of the cylinder head assembly mold into the sand core cavity according to the set pouring speed; S3, after the set solidification time, the surrounding molds are separated from the casting and the casting is taken out, and finally the molding sand attached to the inner and outer surfaces of the casting is cleaned; S4, machining the casting to machine the corresponding injector hole.

[0007] The casting method of the cast aluminum cylinder head according to the embodiment of the present invention can improve the cooling conditions during the casting of the cylinder head injector hole, thereby improving the regional metallographic structure, increasing the local strength of the injector fillet, and improving the durable fatigue life of the cylinder head.

[0008] According to some embodiments of the present invention, in S1, the precast pin is integrally formed on the mold insert.

[0009] According to some embodiments of the present invention, the mold insert and the precast pin are integrally formed by a casting process.

[0010] According to the casting mold for the cast aluminum cylinder head of the second embodiment of the present invention, the pre-casting pin extends vertically relative to the surface of the mold insert, and the mold insert is tapered from one end connected to the mold insert to the direction away from the other end of the mold insert.

[0011] According to some embodiments of the present invention, the angle between the side of the precasting pin and the horizontal plane where the mold insert surface is located is α, and α satisfies the relationship: 91°≤α≤95°.

[0012] According to some embodiments of the present invention, the distance from the side of the precast pin to the final machined surface of the injector hole is L, and L satisfies the relationship: L≥1.25 mm.

[0013] According to some embodiments of the present invention, one end of the precasting pin away from the mold insert is rounded.

[0014] According to some embodiments of the present invention, a periphery of one end of the precasting pin close to the mold insert is rounded.

[0015] According to some embodiments of the present invention, the dimension of the precast pin in the vertical direction is H1, the dimension of the injector hole in the vertical direction is H2, and H1 and H2 satisfy the relationship: H1>H2.

[0016] According to some embodiments of the present invention, the diameter of one end of the precast pin connected to the mold insert is D1, the diameter of the injector hole is D2, and D1 and D2 satisfy the relationship: D2>D1.

[0017] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0019] Figure 1 is a structural schematic diagram of a mold inlay according to an embodiment of the present invention from a first perspective;

[0020] Figure 2 is a structural schematic diagram of a mold inlay according to a second viewing angle of an embodiment of the present invention;

[0021] Figure 3 is a schematic structural diagram of a precast pin in a mold insert according to an embodiment of the present invention;

[0022] Figure 4 is a cross-sectional view of a cylinder head assembly mold and a mold insert according to an embodiment of the present invention (including a schematic diagram of the final processing of the injector nozzle hole);

[0023] Figure 5 Schematic diagram of a precasting process scheme of a cylinder head assembly mold and a mold insert according to an embodiment of the present invention;

[0024] Figure 6 This is a metallographic image of the area around the injector hole cast using a cylinder head assembly mold without a pre-cast pin;

[0025] Figure 7 This is a metallographic image of the area around the injector hole cast using a cylinder head assembly mold containing a precast pin.

[0026] Reference numerals:

[0027] 1. Mold insert; 11. Precast pin; 12. Mold surface (cooling surface);

[0028] 2. Injector hole; 21. Fillet at the bottom of the injector; 22. Injector nozzle hole. DETAILED DESCRIPTION

[0029] Embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. Embodiments of the present invention are described in detail below.

[0030] Reference below Figure 1-Figure 7 A cylinder head assembly mold according to an embodiment of the present invention is described.

[0031] like Figure 1-Figure 7 As shown, the cylinder head assembly mold includes: a lower water jacket core, an upper water jacket core, an airway core, an oil pool core and a mold inlay 1.

[0032] The mold insert 1 has a precast pin 11, which is used to cast the injector hole 2 in the cylinder head. The injector is installed in the cylinder head through the injector hole 2 to receive the injection pulse signal sent by the engine ECU, so as to accurately control the fuel injection amount. In the cylinder head, the injector hole 2 is a hollow stepped hole, which may include an upper first hole, an upper second hole, a middle hole and an injector nozzle hole 22.

[0033] Specifically, the precast pin 11 is used for casting the injector nozzle hole 22 in the cylinder head.

[0034] Since the bottom surface of the cylinder head is in direct contact with the high-temperature and high-pressure combustion gas, a large mechanical stress is generated under the action of the explosion pressure of the combustion gas; the bottom of the injector hole 2 is borne by a large pre-tightening force of the injector pressure plate bolt; when the cylinder head is repeatedly heated and cooled, the temperature difference causes thermal expansion and thermal strain of various parts to generate thermal stress.

[0035] The above factors will be concentrated at the fillet 21 at the bottom of the injector, that is, the fillet at the bottom of the middle hole, making the fillet 21 at the bottom of the injector more susceptible to high cycle fatigue damage.

[0036] To this end, the present invention provides a casting method for a cast aluminum cylinder head, comprising the following steps:

[0037] S1, assembling the sand cores of the lower water jacket core, the upper water jacket core, the airway core and the oil pool core, and combining them with the mold insert 1 with the precast pin 11 to form a cylinder head assembly mold, wherein the precast pin 11 matches the size of the injector hole 2;

[0038] S2. After adjusting the composition of the molten aluminum, when the molten aluminum reaches the set pouring temperature, the molten aluminum is poured from the pouring cup of the cylinder head assembly mold into the cavity of the sand core at the set pouring speed;

[0039] S3. After the set solidification time, the surrounding molds are separated from the casting and the casting is taken out, and finally the molding sand attached to the inner and outer surfaces of the casting is cleaned;

[0040] S4. Machining the casting to produce the corresponding injector hole 2.

[0041] Specifically, after the sand cores of the lower water jacket core, the upper water jacket core, the airway core and the oil pool core are assembled, the mold insert 1 with the precast pin 11 is assembled together, thus forming a cylinder head assembly mold. Next, the adjusted casting aluminum water is poured into the sand core cavity from the pouring cup of the cylinder head assembly mold at a set pouring speed, and demolding is performed after solidification and cooling, and finally the cast injector hole 2 is processed to complete the casting of the cylinder head.

[0042] In the present invention, the cylinder head assembly mold realizes precasting of the injector nozzle hole 22 by adding a precast pin 11 to the mold insert 1. In the mold insert 1 at the bottom of the cylinder head blank and matched with it for casting, adding the precast pin 11 on its mold surface 12 (i.e., cooling surface) can improve the cooling and solidification conditions of the molten metal in the injector nozzle hole 22 area, thereby improving the metallographic structure of the injector nozzle hole 22 and its fillet and surrounding area, improving the mechanical properties of the regional material, and improving the durability of the engine cylinder head.

[0043] Combination Figure 6 and Figure 7As shown, the cylinder head cast by using the cylinder head assembly mold containing the precast pin 11 can significantly improve the metallographic structure of the surrounding area of ​​the injector nozzle hole 22, effectively improving the local safety factor.

[0044] Compared with the prior art, most of the cylinder heads are cast by molten iron, while the cylinder head of the present invention is cast by molten aluminum. Moreover, the casting molds and casting methods corresponding to different casting materials are different. In other words, it can be understood that the mold and method of the cylinder head cast by molten iron are different from the mold and method of the cylinder head cast by molten aluminum. Since the materials of the two are very different in various aspects, the molds and casting methods used for the corresponding casting are different and cannot be used for mutual reference.

[0045] In addition, in the prior art, some molds are provided with a precast structure specifically for casting the injector hole in the cylinder head. However, the precast structure is directly fused with molten iron, so that the precast structure can only be used once, that is, one precast structure is used for casting one cylinder head, and the precast structure is not integrated with the mold, but is only fixedly connected to the mold. After the casting is completed, the precast structure is discarded and cannot be used a second time. At the same time, since it is not an integrated structure with the mold, the connection stability of the precast structure cannot be guaranteed during installation. The precast pin 11 on the mold inlay 1 in the present invention is an integrated structure with the mold inlay 1, and can be reused like the mold inlay 1, and there is no risk of detaching from the mold inlay 1.

[0046] Moreover, the present invention improves the metallographic structure of the injector hole 2 and its surrounding areas from a microscopic perspective, thereby improving the mechanical properties of the injector hole 2 of the engine cylinder head. In the existing technology, only a restrictive fixed structure is used to solve the shrinkage problem of the cylinder head from an apparent perspective. The present invention studies and improves the material properties. The starting point of the problem is different, and the actual problem solved is also different.

[0047] Therefore, by adding the precast pin 11 to the mold insert 1, the precasting of the injector nozzle hole 22 is achieved. The addition of the precast pin 11 can improve the cooling and solidification conditions of the molten metal in the injector nozzle hole 22 area, thereby improving the metallographic properties of the fillet and surrounding area of ​​the injector nozzle hole 22, improving the mechanical properties of the regional material, and improving the durability of the engine cylinder head.

[0048] Specifically, in step S1, the precasting pin 11 is integrally formed on the mold insert 1. In this way, the precasting pin 11 and the mold insert 1 are integrally formed, which is convenient for manufacturing and use. Compared with the prior art, the precasting pin 11 and the mold insert 1 can be reused, and there is no risk of the precasting pin 11 being separated from the mold insert 1.

[0049] Moreover, the mold insert 1 and the precast pin 11 are integrally formed by a casting process. Thus, the casting process is simple, which is conducive to forming, and the overall strength of the integral forming is high, thereby improving the service life of the mold insert 1 and the precast pin 11.

[0050] According to the second embodiment of the present invention, the casting mold for the cast aluminum cylinder head, the precast pin 11 extends vertically relative to the surface of the mold insert 1, and the precast pin 11 is tapered from one end connected to the mold insert 1 to the other end away from the mold insert 1. Figure 3 As shown, that is, the mold insert 1 is tapered in the vertical direction from the bottom to the top, so that it is convenient for rapid demoulding after the casting of the injector nozzle hole 22 is completed.

[0051] Furthermore, the angle between the side of the precast pin 11 and the horizontal plane where the surface of the mold insert 1 is located is α, and α satisfies the relationship: 91°≤α≤95°. In other words, the inclination angle of the side of the precast pin 11 is between 91° and 95°, which is conducive to rapid demoulding after the casting work is completed. If the inclination angle is too small, it is not conducive to the demoulding work and will also affect the molding of the product; if the inclination angle is too large, it is easy to make the top of the precast pin 11 become a pointed structure, which is not conducive to improving the fillet of the injector nozzle hole 22 and the metallographic structure of the surrounding area.

[0052] Preferably, the angle between the side of the precast pin 11 and the horizontal plane where the surface of the mold insert 1 is located is 92°±1°, which can meet the demolding requirements and effectively improve the cooling and solidification conditions of the molten metal in the injector nozzle hole 22 area, thereby improving the metallographic structure of the fillet of the injector nozzle hole 22 and the surrounding area, and improving the mechanical properties of the regional material.

[0053] Furthermore, the distance from the side of the precast pin 11 to the final machined surface of the injector nozzle hole 22 is L, and L satisfies the relationship: L≥1.25 mm.

[0054] Due to the casting process conditions, the distance between the precast pin 11 and the final processed surface of the injector nozzle hole 22 needs to be greater than or equal to 1.25 mm to facilitate the precasting effect of the injector nozzle hole 22.

[0055] Generally, considering that the machining error is about 0.7 mm, the distance from the side of the precast pin 11 to the final machining surface of the injector nozzle hole 22 can be designed to be 1.5 mm to meet the machining accuracy requirements.

[0056] In addition, the end of the precast pin 11 away from the mold insert 1 is rounded. That is to say, the top of the precast pin 11 is rounded near the fillet 21 at the bottom of the injector, which is further beneficial to the demoulding effect and can also prevent scratches and breakages during storage and transportation.

[0057] And, the periphery of one end of the precast pin 11 connected to the mold insert 1 is rounded. That is to say, the connection between the precast pin 11 and the mold insert 1 is rounded to reduce stress concentration, thereby improving the structural stability of the precast pin 11 on the mold insert 1.

[0058] Specifically, the size of the precast pin 11 in the vertical direction is H1, and the size of the injector nozzle hole 22 in the vertical direction is H2, and H1 and H2 satisfy the relationship: H1>H2. In other words, the size of the precast pin 11 in the vertical direction is larger than the size of the injector nozzle hole 22 in the vertical direction, so that while achieving the precasting of the injector nozzle hole 22, the cooling and solidification conditions of the metal liquid in the injector nozzle hole 22 area can be better improved, thereby improving the fillet of the injector nozzle hole 22 and the metallographic structure of the surrounding area, improving the mechanical properties of the regional material, and improving the durability of the engine cylinder head.

[0059] And, the diameter of one end of the precast pin 11 connected to the mold insert 1 is D1, and the diameter of the injector nozzle hole 22 is D2, and D1 and D2 satisfy the relationship: D2>D1. In other words, the diameter of the bottom of the precast pin 11 is smaller than the diameter of the injector nozzle hole 22, and the injector nozzle hole 22 can be precast by the precast pin 11, and then the injector nozzle hole 22 with relatively accurate dimensional accuracy can be obtained through subsequent machining, so that the precasting effect of the injector nozzle hole 22 can be effectively achieved, and the cooling and solidification conditions of the molten metal in the injector nozzle hole 22 area can be improved.

[0060] The mold inlay 1 is one of the auxiliary parts of the cylinder head assembly mold. The mold inlay 1 can be designed to be replaceable. In this way, for different types of product structures, mold inlays 1 of different specifications can be replaced, which can reduce mold costs and be economical, and can also achieve the versatility of the cylinder head assembly mold.

[0061] Therefore, in the present invention, the cylinder head assembly mold realizes precasting of the injector nozzle hole 22 by adding a precasting pin 11 to the mold insert 1. In the mold insert 1 at the bottom of the cylinder head blank and matched with it for casting, adding the precasting pin 11 on its mold surface (i.e., cooling surface) can improve the cooling and solidification conditions of the molten metal in the injector nozzle hole 22 area, thereby improving the fillet of the injector nozzle hole 22 and the metallographic structure of the surrounding area, improving the mechanical properties of the regional material, and improving the durability of the engine cylinder head.

[0062] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0063] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0064] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A casting method for a cast aluminum cylinder head, characterized in that: The following steps are involved: S1. Assemble the sand cores of the lower water jacket core, the upper water jacket core, the airway core and the oil pool core, and combine them with the mold insert with the precast pin to form a cylinder head assembly mold, wherein the precast pin matches the size of the injector hole; S2. After adjusting the composition of the molten aluminum, when the molten aluminum reaches the set pouring temperature, the molten aluminum is poured from the pouring cup of the cylinder head assembly mold into the cavity of the sand core at the set pouring speed; S3. After the set solidification time, the surrounding molds are separated from the casting and the casting is taken out, and finally the molding sand attached to the inner and outer surfaces of the casting is cleaned; S4. Machining the casting to produce corresponding injector holes.

2. The casting method of the cast aluminum cylinder head according to claim 1, characterized in that: In S1, the precast pin is integrally formed on the mold insert.

3. The casting method of the cast aluminum cylinder head according to claim 2, characterized in that: The mold insert and the precast pin are integrally formed through a casting process.

4. A casting mold for a cast aluminum cylinder head, applied to the casting method of the cast aluminum cylinder head according to claim 1, characterized in that: The precasting pin extends vertically relative to the surface of the mold insert, and the precasting pin is tapered from one end connected to the mold insert to the other end away from the mold insert.

5. The casting mold for the cast aluminum cylinder head according to claim 4, characterized in that: The angle between the side of the precasting pin and the horizontal plane where the surface of the mold insert is located is α, and α satisfies the relationship: 91°≤α≤95°.

6. The casting mold for the cast aluminum cylinder head according to claim 4, characterized in that: The distance from the side of the precast pin to the final machined surface of the injector hole is L, and L satisfies the relationship: L≥1.25mm.

7. The casting mold for the cast aluminum cylinder head according to claim 4, characterized in that: One end of the precasting pin away from the mold insert is rounded.

8. The casting mold for the cast aluminum cylinder head according to claim 4, characterized in that: The periphery of one end of the precasting pin close to the mold insert is rounded.

9. The casting mold for the cast aluminum cylinder head according to claim 4, characterized in that: The dimension of the precast pin in the vertical direction is H1, and the dimension of the injector hole in the vertical direction is H2, and H1 and H2 satisfy the relationship: H1>H2.

10. The casting mold for the cast aluminum cylinder head according to claim 8, characterized in that: The diameter of one end of the precast pin connected to the mold insert is D1, and the diameter of the injector hole is D2. D1 and D2 satisfy the relationship: D2>D1.

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