JP2009269051A - Molding method of cylinder block - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding method of a cylinder block capable of securely preventing a shrinkage cavity from being generated at a part of a product of a cylinder block, specifically in the vicinity of a lower hole to be a bolt hole formed at an end of a crank journal wall for supporting a crank shaft of a skirt part, and accordingly improving mechanical properties such as strength so as to increase output of an internal-combustion engine configured by the cylinder block in a simple configuration. <P>SOLUTION: A cylinder liner 2 is cast by disposing the cylinder liner 2 in a mold 3 and injecting and filling a melt M. The cylinder liner 2 is preheated to increase temperature of a side 21 at which the melt M flows in the cylinder liner 2 in the mold 3 to be in a predetermined temperature distribution state, and disposed in the mold, and then the melt M is injected and filled into the cylinder liner 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for forming a cylinder block, and more particularly to a method for forming a cylinder block in which the cylinder liner is cast by placing a cylinder liner in a mold and injecting and filling molten metal.

  Generally, a cylinder block of an internal combustion engine is formed by die casting in which a metal mold such as an aluminum alloy that is a material of the cylinder block is injected and filled into a mold. As shown in FIG. 8 and the like, the cylinder block 1 includes a bore portion 11 in which a piston is slidably accommodated, and a skirt portion 12 constituting a crankcase. A cylinder head is assembled to the front end surface of the bore portion 11 (left end surface in FIG. 8), and an oil pan is assembled to the skirt portion 12 to form a crankcase that accommodates the crankshaft. The cylinder block 1 generally has a cylinder liner 2 cast in each bore 10 and a water jacket 14 formed around the cylinder liner 2. As shown in FIG. 5, a lower hole 15 serving as a bolt hole for attaching the cylinder head is formed at a position orthogonal to the arrangement of the bores 10 between the bores 13. Further, as shown in FIG. 8 and the like, the crank journal for supporting the journal portion of the crankshaft at a position corresponding to the bore 13 in the skirt portion 12 (that is, the partition of the crank chamber corresponding to each bore). A wall 16 is formed. A lower hole 17 serving as a bolt hole for attaching a bearing cap is formed at the end of the crank journal wall 16. Furthermore, a so-called breathing hole 18 is formed in the crank journal wall 16 in order to allow ventilation between the crank chambers adjacent to each other and reduce an internal pressure difference. When molding such a cylinder block 1, the cylinder liner 2 is set in the bore forming portion 31b (see FIG. 1) of the cavity 3a having a shape corresponding to the shape of the cylinder block 1 to be molded in the mold 3. The cylinder liner 2 is casted by clamping the mold and injecting the molten metal M into the mold 3.

  By the way, when the cylinder block is formed by die casting, the molten metal contracts when it solidifies in the cavity of the mold, but a shrinkage cavity due to a contraction hole or a gas pore is generated at the final solidification position. For this reason, in die casting, the solidification of the molten metal starts from the position farthest from the gate so that the non-solidified portion (unsolidified portion) remains in the feeder such as the runner 3b or the biscuit forming portion 3c. In order to prevent the occurrence of shrinkage in the cylinder block 1 to be molded, the directional solidification for finally solidifying the feeder portion has been conventionally performed (see, for example, Patent Document 1).

  In Patent Document 1, in a heating furnace that is divided into a plurality of parts in the height direction and can be individually adjusted in temperature, the molten metal is injected into a ceramic mold heated at a higher temperature than the lower part and solidified. A directional solidification method for precision casting is disclosed. In Patent Document 1, a model made of a wax model that becomes a casting part and a wax model that becomes a feeder part is manufactured, and a ceramic mold is manufactured outside the model (0009). Wax is eluted in the crepe and heated for 3 hours in an electric furnace divided into three in the height direction by adjusting the lower heater to 800 ° C, the middle heater to 1000 ° C, and the upper heater to 1300 ° C. After that, it is described that SCS6 (cast iron) is poured into this mold at 1580 ° C. in a state where the mold is set in these heaters after firing, and solidified as it is (0010).

  Here, in FIG. 8, when the cylinder block 1 in which the cylinder liner 2 is cast is formed by die casting, injection filling is performed in the mold 3 when directional solidification is achieved by a conventional general technique. A solidified portion (shaded portion) M1 and a non-solidified portion (stipled portion) M2 of the molten metal M are shown. In this case, the entire cylinder liner 2 has a uniform temperature distribution at about 100 ° C. The molten metal injected and filled into the mold 3 flows from the skirt portion 12 toward the bore portion 11 in the cavity 3a through the runner 3b.

  As is apparent from FIG. 8, the unsolidified portion M2 of the molten metal extends from the skirt portion 12 to the feeder portion (3b, 3c) of the cylinder block 1, and as a result of directional solidification, the end of the crank journal wall 16 is obtained. It reaches to the vicinity of the lower hole 17 which becomes a bolt hole for attaching the bearing cap of the part. When the unsolidified portion M2 is finally solidified, a shrinkage nest is generated as described above. In this way, when shrinkage cavities are generated not only in the feeder parts (3b, 3c) but also in the skirt part 12 of the cylinder block 1, particularly in the vicinity of the lower hole 17 serving as the bolt hole at the end of the crank journal wall 16, the strength (particularly Mechanical properties such as fatigue strength will be reduced. For this reason, the cylinder block 1 formed by the conventional technique has a skirt portion 12 that is liable to generate shrinkage due to unsolidification, particularly the crank journal wall, in order to ensure the strength even when shrinkage is generated. It was set so that even the end of 16 would be thick.

Japanese Patent Application Laid-Open No. 11-57984

  Among the above conventional techniques, in Patent Document 1, it is necessary to mold the size of the heating furnace to such a size that a mold can be installed therein. There was a problem that the sheath shape was limited. Moreover, in patent document 1, since a heating furnace was divided | segmented into plurality, there existed a problem that a structure became complicated, cost started, and temperature control of each heating furnace became complicated. Further, in Patent Document 1, since the temperature of the molten metal is as high as 1580 ° C, the lower stage is set to 800 ° C, the middle stage is set to 1000 ° C, and the upper stage is set to 1300 ° C. There is also a problem that it cannot be applied to a cylinder block of an internal combustion engine generally made of an aluminum alloy at a proper temperature setting.

  Further, among the above prior arts, even if shrinkage nests are generated in the crank journal wall 16 by directional solidification as shown in FIG. 8, the crank journal wall of the skirt portion 12 is secured in order to secure the strength. When the thickness of the end of 16 is set to be thick, the amount of molten metal required for molding the cylinder block 1 is increased and the cost is increased, and the output of the internal combustion engine is reduced because the cylinder block 1 is increased in weight. There was a problem such as.

  The present invention has been made in view of the above-described problems, and has a simple structure and a bolt hole formed at a portion of a cylinder block, particularly an end portion of a crank journal wall that supports a crankshaft of a skirt portion. It is possible to reliably prevent the occurrence of shrinkage in the vicinity of the prepared pilot hole, improve the mechanical properties such as strength, and increase the output of the internal combustion engine that constitutes the cylinder block. An object is to provide a forming method.

  In order to achieve the above object, the invention according to claim 1 is a method of forming a cylinder block in which the cylinder liner is cast by placing a cylinder liner in a mold and injecting and filling a molten metal. The liner is placed in a mold in a preheated state so as to have a predetermined temperature distribution, and molten metal is injected and filled.

  In the first aspect of the invention, the cylinder liner is placed in the mold in a preheated state so as to have a predetermined temperature distribution, and the molten metal is injected and filled. Coagulation is delayed. Therefore, the unsolidified portion of the molten metal moves from the end portion of the conventional crank journal wall to the vicinity of the portion where the temperature of the cylinder liner is high. And it becomes a feeder part that solidifies finally. Therefore, it is possible to reliably prevent the formation of shrinkage cavities on the crank journal wall of the skirt portion of the cylinder block, particularly the end thereof, and therefore the mechanical properties such as strength (particularly fatigue strength) are improved and the cylinder is improved. It becomes possible to increase the output of the internal combustion engine constituted by the block.

(Aspect of the Invention)
In the following, the invention that is claimed to be claimable in the present application (hereinafter referred to as “claimable invention”. The claimable invention is at least the “present invention” to the invention described in the claims. Some aspects of the present invention, including subordinate concept inventions of the present invention, superordinate concepts of the present invention, or inventions of different concepts) will be illustrated and described. As with the claims, each aspect is divided into sections, each section is numbered, and is described in a form that cites the numbers of other sections as necessary. This is for the purpose of facilitating the understanding of the claimable invention, and is not intended to limit the combinations of the constituent elements constituting the claimable invention to those described in the following sections. In other words, the claimable invention should be construed in consideration of the description accompanying each section, the description of the embodiments, etc., and as long as the interpretation is followed, another aspect is added to the form of each section. In addition, an aspect in which constituent elements are deleted from the aspect of each item can be an aspect of the claimable invention. In each of the following items, item (1) corresponds to claim 1.

(1) A cylinder block molding method for casting the cylinder liner by placing a cylinder liner in a mold and injecting and filling molten metal,
A cylinder block molding method, wherein the cylinder liner is placed in a mold in a preheated state so as to have a predetermined temperature distribution, and molten metal is injected and filled.

  In the invention of the item (1), when the cylinder liner to be cast is preheated to have a predetermined temperature distribution, the cylinder liner in such a preheated state is placed in the mold and the molten metal is injected and filled. Solidification of the portion near the high temperature of the cylinder liner is delayed. Therefore, the unsolidified portion of the molten metal moves from the end portion of the conventional crank journal wall to the vicinity of the portion where the temperature of the cylinder liner is high. And it becomes a feeder part that solidifies finally. Therefore, it is possible to reliably prevent the formation of shrinkage cavities on the crank journal wall of the skirt portion of the cylinder block, particularly the end thereof, and therefore the mechanical properties such as strength (particularly fatigue strength) are improved and the cylinder is improved. It becomes possible to increase the output of the internal combustion engine constituted by the block.

  (2) The method for forming a cylinder block according to (1), wherein preheating is performed so as to raise the temperature of the side of the cylinder liner where the molten metal flows into the mold.

  In the invention of (2), in the invention of (1), by preheating the cylinder liner so as to raise the temperature on the side where the molten metal flows into the mold, The solidification of the part away from the end is delayed. Therefore, the directional solidification of the cylinder block moves. It is possible to reliably prevent the formation of shrinkage cavities at the end of the cylinder journal wall, in particular the crank journal wall, and therefore the mechanical properties such as strength are improved and the output of the internal combustion engine constituted by the cylinder block is increased. It becomes possible.

  (3) When the material is FC230, the temperature distribution of the cylinder liner is 680 plus or minus 20 ° C. on the side where the molten metal flows into the mold, and 150 plus or minus 20 on the opposite side. When preheating is performed in the range of ° C and the material is A390 (AA standard), the temperature on the side where the molten metal flows into the mold is 530 to 30 ° C and the temperature on the opposite side is 50 plus. The cylinder block forming method according to any one of (1) and (2), wherein preheating is performed so that the temperature falls within a range of minus 20 ° C.

  In the invention of the item (3), in the invention described in the item (1) or (2), when the material is FC230, the temperature at which the molten metal flows into the mold is preheated and the temperature is adjusted. When the temperature distribution is 680 plus or minus 20 ° C and the opposite temperature is in the range of 150 plus or minus 20 ° C, and the material is A390 (AA standard), the molten metal flows into the mold. The cylinder block, in particular the crank journal, is preheated so that the temperature distribution is such that the temperature is 530 (upper limit) minus 30 ° C and the temperature on the opposite side is in the range of 50 plus or minus 20 ° C. It is possible to surely prevent the occurrence of shrinkage nests on the wall, and therefore it is possible to improve the mechanical properties such as strength and increase the output of the internal combustion engine constituted by the cylinder block.

An embodiment of a method for forming a cylinder block according to the present invention will be described with reference to the drawings in the case of forming a cylinder block of a multi-cylinder engine having a plurality of bores. The same reference numerals indicate similar or corresponding parts.
The method of forming the cylinder block 1 according to the present invention is generally to cast the cylinder liner 2 by placing the cylinder liner 2 in the mold 3 and injecting and filling the molten metal M. The cylinder liner 2 is predetermined. The molten metal M is injected and filled in a mold preheated so as to have a temperature distribution of
The cylinder block 1 molding method of the present invention is characterized in that, in addition to the above-described configuration, preheating is performed so as to raise the temperature of the side 21 where the molten metal M flows into the mold 3 of the cylinder liner 2. To do.
Furthermore, in addition to the above-described configuration, the molding method of the cylinder block 1 of the present invention is such that when the material is FC230, the temperature of the side 20 where the molten metal M flows into the mold 3 is 680 plus or minus 20 ° C. When the temperature of the opposite side 21 is preheated to a temperature gradient of 150 plus or minus 20 ° C., and the material is A390 (AA standard), the molten metal M flows into the mold 3. The temperature of the side 20 is preheated to a temperature gradient of 530 to 30 ° C., and the temperature of the opposite side 21 is set to a range of 50 plus or minus 20 ° C.

  A cylinder block 1 formed in this embodiment constitutes a multi-cylinder engine having a plurality of bores 10 as shown in FIGS. 3 to 5 and the like, and a bore 10 in which pistons are slidably accommodated. Is formed by a bore portion 11 formed with a skirt portion 12 constituting a crankcase. 3 is a cross-sectional view between the bores 13, and FIG. 4 is a cross-sectional view at the center of the bore 10. A cylinder head is assembled to the front end surface of the bore portion 11 (the left end surface in FIGS. 3 and 4), and an oil pan is assembled to the skirt portion 12 to form a crankcase that houses the crankshaft. Each bore 10 is casted with a cylinder liner 2 made of cast iron or aluminum alloy, and a water jacket 14 is formed around the cylinder liner 2. A pilot hole 15 serving as a bolt hole for attaching the cylinder head is formed at a position orthogonal to the arrangement direction of the bores 10 between the bores 13. A crank journal wall 16 is formed at a position corresponding to the bore 13 of the skirt portion 12 to form a crank chamber corresponding to each bore 10 and to support the journal portion of the crankshaft. A lower hole 17 serving as a bolt hole for attaching a bearing cap is formed at the end of the crank journal wall 16. Further, a so-called breathing hole 18 is formed in the crank journal wall 16 in order to allow ventilation between the crank chambers adjacent to each other and reduce the internal pressure difference.

  As shown in FIGS. 1, 3, and 4, the mold 3 for forming the cylinder block 1 is provided so as to be able to approach and move away from the fixed mold 30. The movable mold 31 and a slide mold 32 provided on the surface of the movable mold 31 facing the fixed mold 30 so as to be movable in a direction D2 intersecting with the opening / closing direction D1. The fixed mold 30 and the movable mold 31 are detachably attached to the fixed plate 33 and the movable plate 34, respectively. A plunger device 35 for injecting and filling the molten metal M is connected to the fixed mold 30. On the back surface of the movable platen 34 to which the movable mold 31 is attached, there is provided a mold clamping device for opening and closing the movable mold 31 by moving it toward and away from the fixed mold 30 and clamping the mold with a predetermined force. Each slide mold 32 is held on the surface of the movable mold 31 facing the fixed mold 30 so as to be movable in a direction D2 intersecting the opening / closing direction D1 of the movable mold 31. Is provided with a slide actuator for moving the slide mold 32 to open and close.

  The mold 3 in this embodiment is configured such that the molten metal M injected and filled in the internal cavity 3 a flows from the side corresponding to the skirt portion 12 of the cylinder block 1 toward the side corresponding to the bore portion 11. Has been. Accordingly, in this embodiment, the side where the molten metal M flows into the mold 3 of the cylinder liner 2 encased in the cylinder block 1, that is, the side preheated to raise the temperature, is the skirt portion 12 side (crankcase side). ) To be arranged at the end 21. However, the present invention is not limited to this embodiment, and the mold 3 is directed from the side (head surface side) corresponding to the bore portion 11 of the cylinder block 1 of the cavity 3a to the side corresponding to the skirt portion 12. When the molten metal M is configured to be injected and filled, the end portion 20 disposed on the end surface side (head surface side) of the bore portion 11 of the cylinder liner 2 is preheated.

  As shown in FIG. 1, in the vicinity of the mold 3, a heating unit 4 for heating a predetermined position of a cylinder liner 2 cast into the cylinder block 1, and the cylinder liner 2 from the heating unit 4 to the mold 3. A robot 5 to be moved is provided. The heating means 4 includes a support base 40 that supports a number of cylinder liners 2 according to the number of bores 10 of the cylinder block 1 to be molded, and a support base 40 corresponding to the arranged cylinder liners 2. And a high-frequency induction heating coil 41 disposed at a predetermined height from the surface. The robot 5 is provided with a clamper 51 for holding each cylinder liner 2 at the tip of the arm 50.

  When the cylinder block 1 is molded as described above using the apparatus configured as described above, as shown in FIG. 2, the mold is first opened (S1) and the mold release agent is sprayed onto the mold 3 ( S2). In parallel or before and after this, the cylinder liner 2 is placed in the high-frequency induction heating coil 41 of the support base 40 and energized, and the predetermined side 21 is preheated (S3). Immediately thereafter, each cylinder liner 2 is gripped by the clamper 51 of the robot 5, and in the embodiment shown in FIG. 1, it is inserted and set in the bore forming portion 31a of the movable mold 31 (S4), and the movable mold 31 is fixed. The slide mold 32 is moved close to the mold 30 and moved toward each other toward the center of the movable mold 31 to close the mold and clamp with a predetermined force (S5). The mold 3 is injected and filled at a pressure / predetermined speed (S6), and the molten metal M is pushed and held at a predetermined pressure (S7). When the molten metal M is solidified after a predetermined time has elapsed, the movable die 31 is moved back and forth from the fixed die 30 and the slide die 32 is moved back and forth radially outward to open the die (S8). The cylinder block 1 in which 2 is cast is taken out (S9), and one molding cycle is completed.

  Here, a specific example of the temperature distribution due to the material of the cylinder liner 2 and preheating (step S3 in FIG. 2) will be described together with a comparative example. As shown in FIG. 6, in the present invention, the crankcase side 21 located on the upstream side of the flow of the molten metal M of the cylinder liner 2 is heated to raise the temperature, and the head surface side 20 located on the opposite downstream side is changed. As a temperature distribution that lowers the temperature, the molten steel M constituting the cylinder block 1 is cast with a temperature gradient in advance.

  More specifically, when the material of the cylinder liner 2 is FC230, the crankcase side 21 of the cylinder liner 2 is heated in the range of 660 to 700 ° C. by the high frequency induction heating coil 41 (FIG. 1). At this time, the temperature on the head surface side 20 of the cylinder liner 2 is 130 to 170 ° C. When the material of the cylinder liner 2 is A390 (AA standard), the crankcase side 21 of the cylinder liner 2 is heated by the high frequency induction heating coil 41 in a range from 500 ° C. to 530 ° C. (upper limit). At this time, the temperature on the head surface side 20 of the cylinder liner 2 is 30 to 150 ° C.

  FIG. 3 shows a portion (indicated by hatching) M1 where the molten metal M solidifies in the process of solidifying the molten metal M when the crankcase side 21 of the cylinder liner 2 is preheated (in the present invention) as described above. And a portion M2 where the molten metal M has not yet solidified (portion indicated by stippling) M2. Further, as a comparative example of the present invention, FIG. 7 shows a case where the molten metal M solidifies in the process of solidifying the molten metal M when the entire cylinder liner 2 is preheated to 600 ° C. FIG. 8 shows a portion M2 where the molten metal M has not yet solidified (portion shown by stippling), and FIG. 8 shows a conventional technique in which the cylinder liner 2 is not preheated and is uniform at 100 ° C. as a whole. In the process where the molten metal M is solidified when the temperature is high, a portion M1 where the molten metal M has solidified (a portion indicated by hatching) and a portion where the molten metal M has not yet solidified (a portion indicated by stippling) M2 It is shown.

  As shown in FIG. 8, when the cylinder liner 2 is cast in a state where the whole is approximately 100 ° C. without preheating, the molten metal M is not solidified by directional solidification. A portion M2 exists at the end of the crank journal wall 16 of the skirt portion 12 of the cylinder block 1 and reaches the vicinity of the lower hole 17 serving as a bolt hole for attaching a bearing cap to the end surface. May occur and fatigue strength may decrease.

  As a comparative example of the present invention, when the entire cylinder liner 2 is cast in a state of being heated approximately uniformly at about 600 ° C., solidification of the bore 13 is delayed and an unsolidified portion M2 is generated. However, it takes time to solidify, and there is a possibility that a shrinkage nest is generated in such a portion and the fatigue strength is lowered.

  On the other hand, when the crankcase side 21 of the cylinder liner 2 is cast in a preheated state according to the present invention as shown in FIG. 6, the molten metal M is solidified by directional solidification as shown in FIG. The portion M2 which is not formed does not become the end portion of the crank journal wall 16 of the skirt portion 12 of the cylinder block 1 as in the prior art (FIG. 8), and therefore the pilot hole 17 which becomes a bolt hole for attaching the bearing cap. It exists between the bore part 11 and the skirt part 12 instead of near. For this reason, no shrinkage is generated in the crank journal wall 16 of the skirt portion 12, and therefore, the fatigue strength of the crank journal wall 16 is improved, and it is not necessary to increase the thickness thereof. As a result, the output of the internal combustion engine formed by the cylinder block 1 can be increased.

  The present invention is not limited to the above-described embodiment, and can be applied to a cylinder block of a single-cylinder internal combustion engine. In the case where a plurality of bores are provided, the present invention is in series or V-shaped. The present invention can also be applied to a cylinder block of an internal combustion engine. The heating means 4 is not limited to the high frequency induction heating coil 41 as long as the cylinder liner 2 can have a predetermined temperature distribution.

It is the front view shown in order to demonstrate the principal part of one Embodiment of the whole shaping | molding apparatus used by this invention. It is the flowchart shown in order to demonstrate one process cycle process of the molding method of the cylinder block by this invention. According to the present invention, when the crankcase side of the cylinder liner is preheated, in the process where the molten metal solidifies, the portion where the molten metal has solidified (the portion indicated by hatching) and the portion where the molten metal has not yet solidified (the portion indicated by the stippling) It is sectional drawing between the bores shown in order to explain. It is sectional drawing in the center of the bore part shown in order to demonstrate the cylinder block shape | molded by this invention. It is sectional drawing which looked at the bore part to the axial direction. It is a perspective view of a cylinder liner shown in order to explain the present invention. For comparison with the present invention, when the entire cylinder liner is preheated, in the process where the molten metal solidifies, the portion where the molten metal has solidified (the portion indicated by the oblique lines) and the portion where the molten metal has not yet solidified (shown in stippling) It is sectional drawing between the bores shown for demonstrating. For comparison with the present invention, in the case of the general prior art in which the entire cylinder liner is not preheated, in the process of the solidification of the molten metal, the portion where the molten metal has solidified (the portion indicated by hatching) and the molten metal are still solidified. It is sectional drawing between the bore | bore shown in order to demonstrate the part (part shown with stippling) which is not.

Explanation of symbols

1: cylinder block, 2: cylinder liner, 3: mold, 4: heating means, 10: bore, 11: bore, 12: skirt, 13: between bores, 16: crank journal wall, 17: bolt hole The lower hole, 18: breathing hole

Claims (1)

A cylinder block molding method for casting the cylinder liner by placing a cylinder liner in a mold and injecting and filling molten metal,
A cylinder block molding method, wherein the cylinder liner is placed in a mold in a preheated state so as to have a predetermined temperature distribution, and molten metal is injected and filled.

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