JP2007009741A - Engine cylinder block - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine cylinder block reducing weight in a more suitable manner using magnesium alloy. <P>SOLUTION: The cylinder block 12 is divided into a cylinder part 21 with a cylinder formed and a skirt part 41 with a crankcase formed. The cylinder part 21 is formed of aluminum alloy and the skirt part 41 is formed of the magnesium alloy. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an engine cylinder block.

The cylinder block of an in-vehicle engine is generally made of cast iron or aluminum alloy, but recently, in order to reduce the weight of the engine, the use of a structural material having a lower specific gravity has been studied.
For example, Patent Document 1 proposes a cylinder block in which fiber reinforced plastic (FRP: Fiber Reinforced Plastics) is partially employed. As shown in FIG. 7, this cylinder block 100 uses FRP, which is less formable than cast iron or aluminum alloy that can be cast, so that the upper structure 101 where the cylinder is formed and the crankcase are formed. It is divided into the lower structure 102. In addition, since the crankshaft bearing 104 is required to have wear resistance because it is slidably contacted with the crankshaft, and the cylinder liner 103 that is required to have wear resistance and heat resistance, separate metal members are interposed respectively. Yes. On the other hand, a magnesium alloy is known as a structural material having a low specific gravity. Magnesium alloy has a low specific gravity, high vibration isolation and weight specific strength, and satisfies the mechanical characteristics required for the cylinder block 100 in many respects, but has high reactivity and cooling water. Ingenuity is required for adopting the water-cooled engine in which the engine is circulated in the cylinder block 100. For example, a magnesium alloy / aluminum alloy cylinder block that has been put to practical use in the past has the following structure. That is, as shown in FIG. 8, the cylinder block 110 is formed by casting an inner shell portion 111 made of aluminum alloy into an outer shell portion 112 made of magnesium alloy that constitutes the periphery thereof. Further, the water jacket 113 through which the cooling water is circulated is formed in the inner shell portion 111 so that the magnesium alloy is not directly exposed to the cooling water.
Japanese Utility Model Publication No. 61-76149

  Thus, if the use location of the aluminum alloy / magnesium alloy is appropriately devised, a highly reactive magnesium alloy can be employed in the cylinder block 110 of the water-cooled engine. However, if the cylinder block 110 has a double structure of the inner shell portion 111 / outer shell portion 112 made of different materials as described above, the boundary between the cylinder block 110 and the outer shell portion 112 due to a difference in thermal expansion due to the high temperature during engine driving. A great amount of stress is generated in the portion. As a result, peeling between the magnesium alloy and the aluminum alloy occurs, and the bonding strength between the inner shell portion 111 and the outer shell portion 112 is lowered. Furthermore, such a decrease in joining strength may reduce the torsional rigidity of the entire cylinder block 110, and may increase vibration and noise. Further, due to such a difference in thermal expansion, a step is formed on the top surface 110a of the cylinder block 110, and the sealing performance may be deteriorated due to a decrease in the surface pressure of the cylinder head gasket. As described above, the adoption of the magnesium alloy for the cylinder block 110 of the water-cooled engine has the above-described problems, and still leaves room for improvement.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an engine cylinder block capable of reducing the weight by adopting a magnesium alloy in a more preferable manner.

  In order to achieve the above object, according to the first aspect of the present invention, a cylinder block is divided and formed in a cylinder part where a cylinder is formed and a skirt part where a crankcase is formed, and the cylinder part is made of an aluminum alloy. The gist is that the skirt is made of a magnesium alloy.

  In the above configuration, combustion is performed, and the aluminum alloy member and the magnesium alloy member are separately formed at a boundary portion between the cylinder portion and the skirt portion, which are spaced apart from the upper portion of the cylinder where the temperature is high. Therefore, it is possible to reduce the weight by adopting the magnesium alloy in a suitable manner while suppressing the influence due to the difference in thermal expansion between the two members during driving of the engine.

The invention according to claim 2 is characterized in that, in the invention according to claim 1, a water jacket is formed around the cylinder.
In the above configuration, the water jacket is formed in the cylinder portion formed of the aluminum alloy having lower reactivity and higher corrosion resistance so that the magnesium alloy is not directly exposed to the cooling water. Therefore, even if it is a cylinder block of a water cooling type engine, weight reduction by adoption of a magnesium alloy can be aimed at suitably.

  According to a third aspect of the present invention, in the second aspect of the present invention, the cylinder portion constitutes a cylinder liner portion constituting the cylinder side with a portion serving as the water jacket as a boundary, and an outer wall of the water jacket. The gist is that it is further divided into a cylinder outer wall portion.

  When the cylinder part is integrally cast and molded, in order to form a water jacket around the cylinder, it is necessary to provide a narrow convex part on the mold for molding or use a core. Since the shape becomes complicated, a casting defect such as a cast hole is likely to occur. In that respect, in the above configuration, the cylinder part is further divided and formed with the water jacket as a boundary, and each divided member can be cast with a relatively simple molding die. Yes. Therefore, it is possible to suppress the occurrence of casting defects such as a cast hole and to extend the life of the mold.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the cylinder portion and the skirt portion are cranked on a bearing portion integrally formed on a lower surface of the skirt portion. The gist is that the cap is integrally fixed by a bolt for tightening and fixing the cap.

  In this configuration, the cylinder portion and the skirt portion are fixed using bolts for fixing the crank cap, so that the cylinder portion and the skirt portion are fixed without adding separate fixing members. be able to. Accordingly, the cylinder portion and the skirt portion are fixed simultaneously with the fixing of the crank cap, and an increase in the number of assembling steps can be suppressed.

Hereinafter, an embodiment in which the present invention is embodied in a cylinder block of an in-line four-cylinder water-cooled engine will be described in detail with reference to FIGS.
As shown in FIG. 1, the engine 11 includes a cylinder block 12 and a cylinder head 17 assembled to the upper portion of the engine 11 via a head gasket 16. A head cover (not shown) is attached above the cylinder head 17, and an oil pan (not shown) is attached below the cylinder block 12.

Next, the configuration of the cylinder block 12 will be described with reference to FIGS.
As shown in FIG. 2, in the cylinder block 12, a cylinder part 21 including four cylinders 20 is provided at the upper part, and a skirt part 41 is provided at the lower part. A flat upper deck 22 on which the cylinder head 17 shown in FIG. 1 is placed is provided on the top of the cylinder block 12. The skirt portion 41 forms a crankcase together with an oil pan attached below the skirt portion 41. As shown in FIG. 3, the cylinder block 12 includes a water jacket 23 around each cylinder 20. The water jacket 23 is formed in a substantially annular shape so as to surround the outer periphery of each cylinder 20 while avoiding a connection portion between adjacent cylinders 20.

  As shown in FIG. 4, the cylinder block 12 is divided into a cylinder portion 21 and a skirt portion 41, and the cylinder portion 21 constitutes the cylinder 20 side with a portion that becomes a water jacket 23 as a boundary. It is divided into a cylinder liner portion 24 and a cylinder outer wall portion 34 constituting the outer wall of the water jacket 23. In the present embodiment, the cylinder block 12 is divided into three structures formed separately. Hereinafter, the configuration of the cylinder liner portion 24, the cylinder outer wall portion 34, and the skirt portion 41 will be described in detail.

  The cylinder liner portion 24 includes a cylinder coupling body 26 in which four cylinder liners 25 are integrally coupled, and the upper deck 22 provided on the upper portion thereof. The cylinder liner portion 24 is made of an aluminum alloy having a low specific gravity and an excellent weight specific strength, and is formed by integrally casting the upper deck 22 and the cylinder coupling body 26 described above.

  The cylinder coupling body 26 is integrally formed so that cylindrical cylinder liners 25 serving as the respective cylinders are linearly arranged and their outer peripheral surfaces are connected to each other. An upper deck 22 constituting the top of the cylinder block 12 is integrally formed at the upper end of the cylinder coupling body 26.

  The upper deck 22 has a flat plate shape, and the cylinder head 17 is placed on the upper surface 22a via the head gasket 16 (see FIG. 1). In the upper deck 22, a fastening hole 27 used for fastening the cylinder liner portion 24 and the cylinder outer wall portion 34, a cooling water passage 28 communicating with the water jacket 23, and the like are formed at predetermined positions. A support projection 29 is provided around the lower end portion of the cylinder coupling body 26 along the outer peripheral surface of each cylinder liner 25.

  As shown in FIGS. 4 and 5, the entire cylinder outer wall portion 34 has a rectangular frame shape, and the inner peripheral surface 34 a is formed in a curved shape so as to surround the outer periphery of the cylinder coupling body 26. . The cylinder outer wall portion 34 is made of an aluminum alloy and cast by molding in the same manner as the cylinder liner portion 24.

  A flange portion 36 is provided at the upper end portion of the cylinder outer wall portion 34, and the upper surface of the flange portion 36 is an upper receiving surface 36 a that abuts and supports the lower surface of the upper deck 22 of the cylinder liner portion 24. A fastening hole 37a used for fastening the cylinder liner portion 24 and the cylinder outer wall portion 34 is opened at a position corresponding to the fastening hole 27 of the upper deck 22 in the upper receiving surface 36a.

  A fastening hole 37 b used for fastening the skirt portion 41 and the cylinder outer wall portion 34 is opened on the lower surface 34 b of the cylinder outer wall portion 34. The fastening hole 37 b is formed coaxially with the fastening hole 37 a opened in the flange portion 36 of the cylinder outer wall portion 34. A cooling water hole 39 for introducing cooling water from the outside of the engine 11 to the water jacket 23 is formed in the cylinder outer wall portion 34, and a plurality of reinforcing ribs 35 are vertically and horizontally disposed on the outer periphery of the cylinder outer wall portion 34. It is formed to be stretched.

  The skirt portion 41 is a cylindrical body having a substantially semicircular cross section that extends along the axial direction of the crankshaft 52. The skirt portion 41 includes a substantially semicircular first outer wall 42 disposed at each end in the longitudinal direction, and a pair of second outer walls 43 and an upper wall 44 that connect the first outer walls 42. Inside, a storage space 41a for rotatably storing the crankshaft 52 is provided (see FIG. 6). The skirt portion 41 is made of a magnesium alloy that has a lower specific gravity than an aluminum alloy and is superior in weight specific strength, and is formed by casting.

  The upper wall 44 of the skirt portion 41 has a planar shape, and the upper surface of the upper wall 44 is an upper receiving surface 44 a that abuts and supports the lower surface of the cylinder outer wall portion 34. Four holes 46 are opened in the upper receiving surface 44 a so as to correspond to the cylinders 20 of the cylinder liner portion 24. In addition, a fastening hole 47 used for fastening the skirt portion 41 and the cylinder outer wall portion 34 is opened at a position corresponding to the fastening hole 37b of the cylinder outer wall portion 34 in the upper receiving surface 44a. The fastening hole 47 extends vertically downward from the upper receiving surface 44 a of the skirt portion 41 and is opened on the lower surface 41 b of the skirt portion 41.

  In the skirt portion 41, an inner wall portion 49 that divides the accommodation space 41a for each cylinder 20 is provided so as to connect between the second outer walls 43 that are arranged to face each other (see FIG. 6). The first outer wall 42 and the inner wall portion 49 are respectively formed with semicircular cutout portions 50a and 50b that constitute a bearing 53 for rotatably supporting the crankshaft 52. These notches 50 a and 50 b constitute the bearing 53 together with the crank cap 51 fixed to the lower surface of the skirt portion 41. Further, like the cylinder outer wall portion 34, a plurality of reinforcing ribs 45 are formed on the outer periphery of the second outer wall 43 so as to extend vertically. The cylinder liner portion 24, the cylinder outer wall portion 34, and the skirt portion 41 thus configured are assembled by a fastening structure shown in FIG.

  As shown in the figure, fastening holes 67 and 77 are formed in the head gasket 16 and the cylinder head 17 at positions corresponding to the fastening holes 27 of the upper deck 22, respectively. The fastening holes 67 and 77, the fastening hole 27 of the upper deck 22, and the fastening hole 37a opened on the upper surface of the cylinder outer wall portion 34 are arranged coaxially. Then, a cylinder head fixing bolt 87 inserted from above the fastening hole 77 of the cylinder head 17 passes through the fastening hole 67 of the head gasket 16 and the fastening hole 27 of the upper deck 22, and enters the fastening hole 37 a of the cylinder outer wall portion 34. It is tightened. Through the fastening by the cylinder head fixing bolt 87, the cylinder liner portion 24 and the cylinder outer wall portion 34 are integrally fixed in a state where the upper deck 22 is sandwiched between the cylinder head 17 and the flange portion 36.

  A fastening hole 57 is formed in the crank cap 51 at a position corresponding to the fastening hole 47 of the skirt portion 41. Further, a fastening hole 57 of the crank cap 51, a fastening hole 47 of the skirt portion 41, and a fastening hole 37b opened in the lower surface of the cylinder outer wall portion 34 are arranged coaxially. A crank cap fixing bolt 88 inserted from below the fastening hole 57 of the crank cap 51 is inserted into the fastening hole 47 of the skirt portion 41 and fastened to the fastening hole 37 b of the cylinder outer wall portion 34. Through such fastening with the crank cap fixing bolt 88, the crank cap 51 is fixed to the lower surface of the skirt portion 41, and the skirt portion 41 and the cylinder outer wall portion 34 are integrally fixed.

  Thus, in a state where the cylinder liner portion 24, the cylinder outer wall portion 34, and the skirt portion 41 are assembled together, the cylinder coupling body 26 is inserted inside the cylinder outer wall portion 34. Further, the lower surface of the upper deck 22 is in contact with and supported by the upper receiving surface 36a of the cylinder outer wall portion 34 at the upper end portion of the cylinder liner portion 24, and the tip surface of the support projection 29 is the inner peripheral surface of the cylinder outer wall portion 34 at the lower end portion. 34a is contacted and supported. The inner peripheral surface 34a of the cylinder outer wall 34 and the outer peripheral surface 26a of the cylinder coupling body 26 are arranged to face each other, and a water jacket 23 is formed between the inner peripheral surface 34a and the outer peripheral surface 26a. ing.

  Further, between the lower surface of the upper deck 22 and the upper receiving surface 36a of the cylinder outer wall 34, and between the tip surface of the support projection 29 of the cylinder coupling body 26 and the inner peripheral surface 34a of the cylinder outer wall 34, respectively. Seal members 59a and 59b are interposed. By these seal members 59a and 59b, the sealing performance is secured at the end on the cylinder head 17 side of the water jacket 23 and the end on the skirt 41 side located on the opposite side.

  Now, in the cylinder block 12 configured as described above, as shown in FIG. 6, a boundary portion between the cylinder portion 21 and the skirt portion 41, that is, a cylinder outer wall portion constituting a dividing surface of both the members 21 and 41. The lower surface 34b of 34 and the upper receiving surface 44a of the skirt portion 41 are set to positions spaced apart to some extent from the combustion chamber 56 formed in the upper portion of the cylinder 20. As a result, the boundary between the cylinder portion 21 and the skirt portion 41 is prevented from being affected by heat from the combustion chamber 56 as much as possible when the engine 11 is driven. For this reason, since the increase in dimensional change due to the thermal expansion of the cylinder portion 21 and the skirt portion 41 is suppressed at the boundary portion, due to the difference in thermal expansion occurring between different materials (aluminum alloy and magnesium alloy), It is possible to prevent a great amount of stress from being generated at a contact portion between the cylinder outer wall portion 34 and the skirt portion 41.

  In the cylinder block 12, a boundary portion between the cylinder portion 21 and the skirt portion 41 is set below the lower surface 23 a of the water jacket 23. In this case, the water jacket 23 is formed between the cylinder liner portion 24 made of aluminum alloy and the cylinder outer wall portion 34, so that the skirt portion 41 made of magnesium alloy does not appear on the wall surface of the water jacket 23. It has become. That is, while the water jacket 23 is formed on the cylinder part 21 made of aluminum alloy having low reactivity with water and high corrosion resistance, the water jacket is formed on the skirt part 41 made of magnesium alloy having high reactivity with water and low corrosion resistance. The cooling water of the jacket 23 is not directly exposed. Therefore, in the cylinder block 12, the weight reduction by adopting the magnesium alloy is suitably achieved while ensuring the reliability around the water jacket 23.

According to the above embodiment, the following effects can be obtained.
(1) The cylinder block 12 is divided into a cylinder part 21 and a skirt part 41. The cylinder part 21 is made of an aluminum alloy, and the skirt part 41 is made of a magnesium alloy. In this case, the cylinder block 12 has a cylinder part 21 made of aluminum alloy and a skirt made of magnesium alloy at the boundary part between the cylinder part 21 and the skirt part 41 that are spaced apart from the upper part of the cylinder 20 that becomes a high temperature during combustion of the engine 11 to some extent. A part 41 is formed separately. Therefore, in the cylinder block 12, while the engine 11 is driven, the weight reduction by adopting a magnesium alloy is achieved in a suitable manner while suppressing the influence due to the difference in thermal expansion between the cylinder portion 21 and the skirt portion 41. Can do.

  (2) In the cylinder block 12, the boundary portion between the cylinder portion 21 and the skirt portion 41 is set below the lower surface 23 a of the water jacket 23. In this case, in the cylinder block 12, the water jacket 23 is formed on the cylinder portion 21 formed of an aluminum alloy having lower reactivity and higher corrosion resistance, so that the magnesium alloy is not directly exposed to the cooling water. ing. Therefore, even if it is the cylinder block 12 of a water-cooled engine, weight reduction by adoption of a magnesium alloy can be achieved suitably.

  (3) When the cylinder portion 21 is integrally cast and molded, in order to form the water jacket 23 around the cylinder 20, a narrow convex portion is provided on the molding die or a core is used. It is necessary and the shape of the mold becomes complicated, so there is a concern that casting defects such as a casting hole are likely to occur. In that respect, in the cylinder block 12 of the present embodiment, the cylinder portion 21 further forms a cylinder liner portion 24 that forms the cylinder 20 and an outer wall of the water jacket 23 with a portion that becomes the water jacket 23 as a boundary. It is divided into a cylinder outer wall portion 34. As a result, the cylinder liner portion 24 and the cylinder outer wall portion 34 that are divided can be cast with a molding die having a relatively simple shape. Therefore, it is possible to suppress the occurrence of casting defects such as a cast hole and to extend the life of the mold.

  (4) In the cylinder block 12, the skirt portion 41 and the cylinder outer wall portion 34 are integrally fixed by fastening with the crank cap fixing bolt 88. In this way, the cylinder outer wall 34 and the skirt 41 are integrally fixed using the crank cap fixing bolt 88, so that the cylinder 21 and the skirt can be added without adding different fixing members. 41 can be fixed. Accordingly, the cylinder portion 21 and the skirt portion 41 are fixed simultaneously with the fixing of the crank cap 51, and an increase in assembly man-hour can be suppressed.

In addition, you may change the said embodiment as follows.
In the present embodiment, the engine 11 is a water-cooled engine having the water jacket 23 and cooling each part with cooling water, but the engine 11 may be changed to an air-cooled engine that directly cools the air.

  In the present embodiment, the cylinder portion 21 is divided and formed into the cylinder liner portion 24 and the cylinder outer wall portion 34 with the portion that becomes the water jacket 23 as a boundary. However, by integrally casting both the members 24 and 34, The cylinder part 21 may be formed.

  In the present embodiment, the cylinder portion 21 and the skirt portion 41 are fixed by the crank cap fixing bolt 88, but any fixing method can be adopted, for example, the crank cap fixing bolt 88 is You may make it fix using another bolt for fixation.

  In the present embodiment, the cylinder liner portion 24 and the cylinder outer wall portion 34 are fixed by the cylinder head fixing bolt 87. However, any fixing method can be adopted, for example, the cylinder head fixing bolt 87. You may make it fix using the bolt for fixation different from.

The perspective view which shows the main-body part of the water-cooled engine in this embodiment. The perspective view of the cylinder block in this embodiment. The top view of a cylinder block similarly. The disassembled perspective view which similarly shows the division | segmentation structure of a cylinder block. AA sectional drawing of FIG. BB sectional drawing of FIG. The disassembled perspective view which shows the example about the conventional cylinder block. Sectional drawing which shows the example about the conventional cylinder block.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine, 12 ... Cylinder block, 20 ... Cylinder, 21 ... Cylinder part, 23 ... Water jacket, 23a ... Lower surface, 24 ... Cylinder liner part, 34 ... Cylinder outer wall part, 41 ... Skirt part, 50a, 50b ... Bearing part 51 ... Crank cap, 88 ... Crank cap fixing bolt.

Claims (4)

A cylinder block is divided and formed in a cylinder part where a cylinder is formed and a skirt part where a crankcase is formed, the cylinder part is made of an aluminum alloy, and the skirt part is made of a magnesium alloy. Engine cylinder block. The cylinder block of the engine according to claim 1,
An engine cylinder block, wherein a water jacket is formed around the cylinder. The cylinder block of the engine according to claim 2,
The cylinder part is further divided and formed into a cylinder liner part constituting the cylinder side and a cylinder outer wall part constituting the outer wall of the water jacket, with the water jacket as a boundary. Engine cylinder block. In the cylinder block of the engine according to any one of claims 1 to 3,
The cylinder block of an engine, wherein the cylinder part and the skirt part are integrally fixed by a bolt for fastening and fixing a crank cap to a bearing part integrally formed on a lower surface of the skirt part.

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