JP2009538396A - Cylinder head for internal combustion engine - Google Patents

Abstract

  The present invention comprises a lightweight structural internal combustion engine comprising at least one cast body (4) cast in the outer structure (2), wherein the outer structure (2) and the cast body (4) are made of different materials. Cylinder head (1). In order to achieve a high fatigue strength and a high thermal shock resistance, the at least one cast body (4) forms a support structure (3) and at least one screw nozzle (5) which accommodates the cylinder head screw. Is formed.

Description

  The present invention relates to a cylinder head for a lightweight internal combustion engine, comprising at least one cast body cast in an outer structure, and made of a material different from that of the outer structure and the cast body. Furthermore, the present invention has at least one gas exchange passage hole that can be sealed by a stroke valve and that opens into the combustion chamber, and the stroke valve is in contact with a valve seat formed by a cylinder head in a sealed state. The invention relates to a cylinder head made of gray cast iron for a piston reciprocating engine, particularly an internal combustion engine. The present invention further relates to a method for manufacturing the cylinder head.

  In particular, the increase in power density of passenger car diesel engines and cylinder heads is limited by the fatigue strength and thermal shock resistance of the cylinder head. The lack of fatigue strength can lead to fatigue failure with increasing peak pressure, especially in the water jacket and gas exchange path region. The heat transfer to the cylinder head is approximately a constant ratio with respect to the output. As a result, the surface temperature amplitude increases at least in proportion to the power density. Therefore, if the thermal shock resistance is insufficient, the cylinder head is damaged during each thermal cycle.

  High fatigue strength can be achieved with a cylinder head made of gray cast iron, in particular GJV (Vermicular Graphite Cast Iron). Switching from aluminum alloy to gray cast iron results in an approximately 50% increase in the fatigue strength of the danger zone. However, a disadvantage of the gray cast iron cylinder head is a deterioration in thermal conductivity that is reduced to about one-fifth that of an Al—Si—Mg alloy. This further increases the maximum temperature of the gray cast iron cylinder head (approximately 400 ° C.). This temperature level is achieved at moderate power densities. An increase in temperature load due to an increase in power density leads to a significant decrease in strength and a significant decrease in life due to the occurrence of thermomechanical cracks. In addition, the geometric conditions of the relatively densely arranged engines in the case of passenger cars also lead to a significant reduction in life under thermal alternating loads. Accordingly, a steel or gray cast iron cylinder head is advantageous when considering the requirements for fatigue strength and rigidity, and an aluminum cylinder head is rather advantageous when considering the requirements for thermal shock resistance.

  It is already known to produce cylinder heads from composite materials. European Patent Publication No. 0262240 (Patent Document 1) describes a cylinder head having a bottom plate and a separately manufactured upper member, which are detachably connected to each other. In this technique, the bottom plate is made of a material having higher heat resistance than the upper member and at the same time lower thermal conductivity than the upper member. Disadvantages are the formation of a composite zone in the high load area and a reduction in heat transfer due to the bottom plate, which exposes the material to high thermal alternating loads during the power cycle and causes damage to the material and high component temperatures on the gas side. Will occur.

  From European Patent Publication No. 0462850 (Patent Document 2), it is known that a fiber reinforced insert is cast between valve holes in order to increase wall strength in a cylinder head. This technique presents a problem with connection in the transition zone. Further, the disadvantage is that the decrease in thermal conductivity leads to an increase in temperature amplitude. In addition, composite materials have a strong tendency to embrittle, which results in a significant decrease in life under thermal alternating loads.

  German Patent Publication No. 3100755 (Patent Document 3) describes a cylinder head for an internal combustion engine in which the valve bridges are reinforced by one or more insertion methods made of dispersion strengthened sintered aluminum. However, the connection of the aluminum sintered member in the casting process is very difficult because the transition region is in the thermal and mechanical high load region. Long-term durability characteristics cannot be improved by these measures.

  In order to produce a valve seat for an internal combustion engine cylinder head, it is known to fuse additional material to the cylinder head by supplying energy to the location where the valve seat is to be formed. This type of valve seat and valve seat manufacturing method are as follows: International Publication No. 2004/048756 (Patent Document 4), German Patent Publication No. 19912889 (Patent Document 5), German Patent Publication No. 10329912 (Patent Publication) Document 6) or WO 99/02839 (Patent Document 7). Furthermore, from German Patent Publication No. 10218563 (Patent Document 8), a valve seat manufacturing method using a laser plating method is known.

  Furthermore, it is known to change the structure of the metal casting material by a local melting process in order to increase the wear resistance. Melt coating is relatively time consuming and costly because it must be layered with a wear resistant material that is different from the cast structure. Furthermore, it is known to heat and quench the valve seat. However, the structure of the induction-heat-quenched valve seat has a disadvantage that sufficient stability cannot be maintained at a high temperature that can be achieved by, for example, an exhaust valve of a supercharged internal combustion engine.

European Patent Publication No. 0262240 European Patent Publication No. 0462850 German Patent Publication No. 3100755 International Publication No. 2004/048756 German Patent Publication No. 19912889 German Patent Publication No. 10329912 International Publication No. 99/02839 German Patent Publication No. 10218563

  An object of the present invention is to provide a cylinder head having high fatigue strength and high thermal shock resistance while avoiding the above problems. A further object of the invention is to produce a stable wear-resistant valve seat in the cylinder head of the type mentioned at the outset in the simplest possible way.

  The object is achieved according to the invention by the casting forming a support structure and at least one screw nozzle for accommodating a cylinder head screw. Preferably, the cast body forms, for each cylinder, at least one, preferably centrally located, insertion member that is used to accommodate a component that opens into the combustion chamber.

  In order to improve the fatigue strength, it is preferred that the at least two screw nozzles are connected to each other via at least one first stiffener arranged preferably perpendicular to the nozzle axis. In this case, the screw nozzle and / or the insertion member may be formed as a cylindrical sleeve. In this case, the insertion member located at the center is separated from the gas side of the combustion chamber partition so as not to adversely affect the heat conduction in the same place. The outer structure region is disposed between the insertion member and the gas side, and the insertion member is embedded in the outer structure. The cylindrical insertion member accommodates a spark plug or an injector depending on the engine type. The shape of the insertion member is determined according to the intended use. When the insertion member is formed for the purpose of accommodating an injector, it is preferable that a screw nozzle for accommodating a screw for fixing the injector screw is integrally cast on the insertion member. Therefore, the screw nozzle has a tightening screw screw insertion hole for fixing the injector screw. As a result, the necessary clamping force for the aluminum material becomes very high, so that there is no problem zone for the cylinder head.

  The cast body is formed of a truss-like frame which is formed by a screw nozzle for a cylinder head screw and further incorporates an insertion member located at the center via an oblique second reinforcing material. The first reinforcing material between the screw nozzles prevents structural distortion on the upper surface of the cylinder head and prevents periodic bending on the cylinder head seating surface. The central cylinder formed by the insertion member functions like a stabilizing post. The first reinforcing material and the second reinforcing material support the gas exchange path.

  In a preferred embodiment of the invention, the screw nozzles of the respective cylinders are connected to one another in the region of the combustion chamber partition, preferably via a ring-shaped third reinforcement, particularly preferably the third reinforcement. The material is arranged in the area of the cylinder head gasket in plan view. The contour of the third reinforcing material is adapted to the cylinder head gasket in order to strengthen its sealing action.

  In yet another embodiment of the present invention, the cast body forms at least one valve guide receiver of a gas exchange valve, preferably the valve guide receiver is connected to the screw nozzle or the insertion member, and a valve spring receiver. May be integrated with the valve guide receiver. In this case, at least one valve guide receptacle of the gas exchange valve can be incorporated into the conical first or second reinforcement.

  It is particularly advantageous that the casting is formed in a multi-body fashion, preferably forming one cylinder section per cylinder, in which case the cylinder sections of adjacent cylinders are preferably connected to each other via plug-in connections. It may be connectable. In this case, preferably each individual cylinder section has two screw nozzles connected to each other via a first stiffener and a further first stiffener for each screw nozzle, said further Both other first stiffeners can be connected to the screw nozzles of adjacent cylinder sections, and can preferably be plugged into the screw nozzles. Further, the cast body has a ring-shaped third reinforcing material for each cylinder, and the ring-shaped third reinforcing material can be connected to the screw nozzles of the respective cylinders. It can be inserted. Furthermore, the third reinforcing member of at least one cylinder may be insertable into the screw nozzle of the cylinder. These measures facilitate the incorporation of the casting into the mold.

  The outer structure may be formed of a light metal, such as an aluminum alloy or a copper alloy. As a result, the cylinder head has as high a thermal conductivity as possible on the combustion chamber side, thereby realizing a configuration in which the stress caused by the thermal alternating load is minimized.

  In order to allow a high level of fatigue strength of the cylinder head, the cast body is made of steel or preferably spheroidal graphitized gray cast iron. Unlike the outer structure, the support structure formed by the cast body is made of a metal having a high modulus of elasticity so that a low strain level is guaranteed. The high degree of fatigue strength is essential to withstand periodic gas loads. These requirements are met by the use of steel or pre-cast high strength spheroidal graphite gray cast iron. The support structure is pre-cast for each cylinder, set in a mold together with the core, and cast. In this case, the support structure is formed in a truss shape, and the shape is matched to the specifications of the gas exchange path. In this case, it is possible to cast the valve seat ring in one piece and to incorporate a threaded pipe or camshaft bearing. Further, it is possible to assist the injector support. If the cast body is formed into a multi-body type, it can be easily and accurately placed in the mold, and in this case, individual members, for example, screw nozzles, insertion members, member receivers and / or reinforcements, can be used. Can be connected to each other by plug-in coupling.

  In order to produce a stable and wear-resistant valve seat, the cast structure in the valve seat area is remelted. In this case, no material is added and only the original cast structure is remelted.

  In order to reduce the risk of crack formation as well as the tendency to strain, the member is preferably preheated to a temperature above the martensitic transformation start temperature of the cast material (about 300 ° C.) prior to the remelting process. Said remelting process is preferably performed by a laser remelting process.

  In the remelt zone, a redeburite structure is generated from the melt by rapid cooling. This solidification is substantially defined by the high thermal conductivity from the melt to the matrix. Therefore, the solidified surface moves from the melt boundary toward the member surface, and thus redebrite is generated from the aligned structure. Further, the solidified surface sends defects to the member surface. These defects are removed by finishing.

  Clearance is taken into account so that distortions as well as surface ripples occurring during remelting can be corrected, which are processed after remelting, for example together with a valve guide.

  Unlike known melting methods, the method according to the invention does not add material and only the cast structure is remelted. Therefore, the valve seat is composed of a cast iron base material of the cylinder head.

  Therefore, the remelting process realizes a wear-resistant valve seat structure without the need to press-fit the valve seat ring. This avoids radial press fit, improves heat removal in the valve seat area and achieves savings in structural space and manufacturing costs.

  Compared to induction heat-hardened valve seats, the re-melted tissue is stable at temperatures as achieved, for example, in supercharged engine exhaust valves.

1 is a first perspective view of a cylinder head according to the present invention. FIG. It is the perspective view which looked at the combustion chamber side of the cylinder head from the upper part. It is a figure which shows the cylinder head seen from the combustion chamber side. It is a figure which shows the cylinder head seen from upper direction. It is a side view of a casting. It is a perspective view of a casting. It is a top view of a casting. It is a perspective view of the cylinder division of a casting. It is a side view of a cylinder division. It is another side view of a cylinder division. It is a perspective view of the edge part of a casting. It is a perspective view of a 3rd reinforcing material. It is sectional drawing of the cylinder head valve seat area | region after a process. It is a figure which shows the valve seat area | region after the remelting process before a finishing process.

Hereinafter, the present invention will be described in detail with reference to the drawings.
The multi-cylinder cylinder head 1 has an outer structure 2 made of a light metal, for example, an aluminum alloy or a copper alloy, and a cast body 4 forming a support structure 3 is embedded in the outer structure. The support structure 3 is formed in a truss shape and is made of steel or gray cast iron. The casting 4 forms a screw nozzle 5 for a cylinder head screw, an insertion member 6 for accommodating an injector or spark plug, and a valve guide receiver 7. The screw nozzles 5 are connected to each other via a first reinforcing member 8 formed perpendicular to the nozzle axis 5a. The second reinforcing member 9 connects the screw nozzle 5 to the insertion member 6. These second reinforcements 9 are inclined at an angle α <90 °, preferably <60 ° with respect to the nozzle axis 5a and the insertion member axis 6a, starting from the screw nozzle 5 in the direction of the combustion chamber partition wall 17 It extends toward the insertion member 6. In this embodiment, the second reinforcing material 9 inclined obliquely in the direction of the combustion chamber partition also forms a valve guide receiver 10. Each insertion member 6 is integrally cast with a screw nozzle 16 having a fastening screw screw insertion hole 16a for fixing an injector screw.

  Further, in the region of the combustion chamber partition wall 17, a ring-shaped third reinforcing material 11 is provided in accordance with the contour of each cylinder head gasket, and the screw nozzles 5 are connected to each other by this reinforcing material.

  In the present embodiment, the cast body 4 includes a cylinder section 19 and a ring-shaped third reinforcing material 11 provided in the region of the combustion chamber partition wall 17 for each cylinder 20. Both of these castings for each cylinder 20 are mutually fitted to form a casting 4 in a continuous and periodic manner. Further, a terminal member 21 shown in FIG. 11 is provided as an end portion of the cylinder head, which includes two screw nozzles 5 and one first reinforcing member 8.

  Each cylinder section 19 is composed of at least two screw nozzles 5 and at least three first reinforcing members 8. Further, the cylinder section 19 may include the insertion member 6 and the second reinforcing member 9 as illustrated in FIGS. 9 to 14. The first and third reinforcing members 8 and 11 have ring-shaped holes 12 and 13 into which the screw nozzle 5 is inserted. By fitting the holes 12 into the screw nozzle 5, the cylinder sections 19 of the plurality of cylinders 20 can also be connected to each other.

  As can be understood from FIGS. 8 and 10, the first reinforcing member 8 may be connected to the screw nozzle 16 of the insertion member 6 via the rib 8 a for each cylinder. The cylinder head 1 is formed of an outer structure 2 on the surface of the combustion chamber partition wall 17 made of a material having as high a thermal conductivity as possible, and is configured so that the stress caused by the thermal alternating load is as small as possible. . The material of the outer structure 2 is, for example, an aluminum alloy or a copper alloy. On the other hand, the casting 4 embedded in the outer structure 2 is made of a material having a high Young's modulus in order to make the strain level small. The cast body 4 must also have a high degree of fatigue strength to withstand periodic gas loads. Therefore, high strength spheroidal graphite gray cast iron (GJS) or steel is suitable as the material of the cast body 4. In this case, the support structure 3 is pre-cast for each cylinder, is set in a mold together with the gas exchange path core, and is cast. The insertion method of the support structure 4 illustrated in FIGS. 9 to 14 facilitates the incorporation into the mold.

  The gas side of the cylinder head 1 may be formed as a spherical depression in order to enable a valve tilting structure. The aluminum alloy of the outer structure 2 has a high thermal conductivity and has the required structural properties without the heat treatment to be avoided for the casting liquid. This is therefore ideally a low alloy aluminum with a structure that is as homogeneous as possible, without internal flaws and having the highest possible elongation.

  The steel or spheroidal graphitized cast body 4 is formed in a truss shape, and its shape is adapted to the need for a gas exchange path. It is possible to cast the valve seat ring integrally. Threaded pipes can also be incorporated. Furthermore, it is possible to incorporate an injector support aid into the casting 4.

  The combination of the outer structure 2 and the support structure 3 can substantially cope with the extreme requirements arising at various locations by appropriate selection of materials and appropriate shaping of the support structure 3 or combustion chamber partition. Therefore, this combination is far better than a uniform member made of cast iron that can withstand extreme loads or an aluminum alloy that does not have sufficient levels of rigidity and fatigue strength to withstand thermal loads. Is suitable.

  The piston reciprocating engine shown in FIGS. 13 and 14, for example, a gray cast iron cylinder head 101 for an internal combustion engine, opens into the combustion chamber 108 and can be sealed by a stroke valve 104 for at least one for the gas exchange path 103. Two gas exchange holes 102 are provided. In a sealed state, the stroke valve 104 is in contact with a valve seat 105 formed by the cylinder head 101 itself. The valve seat 105 is hardened by a local laser remelting process, in which case the cast structure 106 in the region of the valve seat 105 is brought to the melting temperature. Prior to the actual remelting process, the cylinder head 101 is heated to the preheat temperature (about 300 ° C.) of the respective material to reduce the tendency to strain as well as the risk of crack formation. Rapid cooling results in a redebrite structure from the melt in the melting zone. This creates a defect-free microstructured remelted layer in the valve seat region 105 with high hardness (500 to 600 Hv5) and excellent ductility that has a high resistance to wear and fatigue.

  In order to be able to correct the distortions and ripples that occur during remelting, a correction margin 107 is taken into account, which is processed after remelting, for example with a valve guide.

Claims (23)

A cylinder head for a lightweight internal combustion engine comprising at least one cast body (4) cast in the outer structure (2), wherein the outer structure (2) and the cast body (4) are made of different materials. 1)
Cylinder head (1), characterized in that at least one casting (4) forms a support structure (3) and at least one screw nozzle (5) for receiving a cylinder head screw.   2. The cast body (4) according to claim 1, characterized in that for each cylinder (20) at least one insert member (6), preferably in the center, which accommodates a component opening in the combustion chamber is formed. Cylinder head (1) as described.   At least two screw nozzles (5) are connected to one another via at least one first reinforcement (8) arranged preferably perpendicular to the nozzle axis (5a). Cylinder head (1) according to claim 1 or 2.   At least one screw nozzle (5) is connected to the insertion member (6) via at least one second reinforcement (9), in which case the reinforcement is connected to the nozzle axis (5a). Cylinder head (1) according to claim 2 or 3, characterized in that an included angle (α) <90 °, preferably <60 °, is formed between the insertion member axis (6a).   Cylinder head (1) according to any one of claims 1 to 4, characterized in that the screw nozzle (5) and / or the insertion member (6) are formed as a cylindrical sleeve.   Cylinder head (1) according to any one of claims 2 to 5, characterized in that the insertion member (6) is separated from the gas side of the combustion chamber partition (17) by the outer structure (2). 1).   The cylinder head (1) according to any one of claims 2 to 6, wherein a screw nozzle (16) for accommodating a screw for screwing an injector is integrally cast on the insertion member (6). ).   The screw nozzles (5) of the respective cylinders (20) are connected to each other in the region of the combustion chamber partition wall (17), preferably via a ring-shaped third reinforcement (11), which is particularly preferred here. The third reinforcing member (11) is arranged in a region of the cylinder head gasket in a plan view and basically conforms to the contour of the cylinder head gasket. The cylinder head (1) according to one item.   The cast body (4) forms at least one valve guide receptacle (10) of a gas exchange valve, preferably the valve guide receptacle (10) is connected to the screw nozzle (5) or the insertion member (6). Cylinder head (1) according to any one of the preceding claims, characterized in that it is provided.   The cylinder head (1) according to any one of claims 1 to 9, characterized in that a valve spring receiver of the gas exchange valve is integrated with the valve guide receiver (10).   Cylinder according to any one of the preceding claims, characterized in that at least one valve guide receptacle (10) is integrated with the first reinforcement or the second reinforcement (8, 9). Head (1).   12. The cast body (4) according to any one of the preceding claims, characterized in that the cast body (4) is formed in a multi-body fashion, preferably with one cylinder section (19) per cylinder (20). Cylinder head (1).   Cylinder head (1) according to claim 12, characterized in that the cylinder sections (19) of adjacent cylinders (20) are connectable to one another, preferably via a plug-in connection.   Two screw nozzles (5) in which individual cylinder sections (19) are connected to each other via a first reinforcement (8), and a further first first for each screw nozzle (5). It has a reinforcement (8), said further first reinforcement (8) being connectable with a screw nozzle (5) of an adjacent cylinder section (19), preferably said screw nozzle (5) The cylinder head (1) according to claim 12 or 13, characterized in that the cylinder head (1) can be inserted into the cylinder head.   15. The third reinforcement of at least one cylinder (20) can be inserted into the screw nozzle (5) of the cylinder (20). Cylinder head (1).   Cylinder head (1) according to any one of the preceding claims, characterized in that the outer structure (2) is made of a light metal alloy, preferably an aluminum alloy or a copper alloy.   Cylinder head (1) according to any one of the preceding claims, characterized in that the cast body (4) is made of steel or preferably spheroidal graphitized gray cast iron.   Cylinder head (1) according to any one of the preceding claims, characterized in that the cast body (4) has a truss shape. It has at least one hole (102) for the gas exchange path (103) that opens into the combustion chamber (108) and can be sealed by the stroke valve (104), the stroke valve (104) being sealed, A piston reciprocating engine configured to contact a valve seat (105) formed by a cylinder head (101), particularly a gray cast iron cylinder head (101) for an internal combustion engine,
Cylinder head (101) characterized in that the cast structure (106) in the region of the valve seat (105) has been hardened by a remelting process, preferably a laser remelting process. A manufacturing method for manufacturing a cylinder head according to claim 19,
The method for manufacturing a cylinder head (101), wherein the cast structure (106) in the region of the valve seat (105) is remelted.   The cast structure (106) is preheated to a preheat temperature before the remelting process, the preheat temperature being equal to or higher than a martensitic transformation start temperature of the cast material of the cylinder head (101). The method described.   The method according to claim 20 or 21, characterized in that recasting of the cast structure (106) is performed by a laser remelting process.   23. A method according to any one of claims 20 to 22, wherein the remelted cast structure (106) has a redebrite structure produced by quenching.

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