JP2003322139A - Crankshaft bearing structure and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crankshaft bearing structure and manufacturing method therefor capable of decreasing a difference in thermal expansion coefficient with a crankshaft and having excellent cutting performance. <P>SOLUTION: When the crankshaft bearing 6 is cast, a fixing element having good cutting performance is arranged and molded between a casting mold and a ceramic molding element having a thermal expansion coefficient smaller than an aluminum material, so that the molding element is molded in a bearing body 6e to form a layer (b) of a metal matrix composite. In both the sidewall of a specified height H and the bottom 6d of the bearing body 6e, a fixing element layer (a) is formed, and on a recessed 6e surface and both the side wall of a specified range W of the bearing body 6e, an aluminum layer (c) is formed. At the specified height H of an insertion hole 6b into which a fixing bolt is inserted, the fixing element layer (a) is formed, and in the specified range W, the aluminum layer (c) is formed. Therefore, the crankshaft bearing 6 is decreased in a difference between the thermal expansion coefficient and the crankshaft, and improved in cutting performance. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crankshaft bearing structure for supporting a crankshaft between a cylinder block of an engine and a lower crankcase, and a manufacturing method thereof.

[0002]

2. Description of the Related Art FIG. 1 shows a conventional crankshaft bearing structure.
It will be explained based on. As shown in FIG. 1, generally, an engine of a vehicle is provided with a cylinder block 2 and a lower crankcase 3 arranged below the cylinder block 2, and a crankshaft 4 is provided in the cylinder block 2. It is pivotally supported by the crankshaft bearing portion 5 and the crankshaft bearing portion 6 of the lower crankcase 3.

The crankshaft bearing portion 6 of the lower crankcase 3 is block-shaped and has a crankshaft 4
A plurality of them are continuously arranged at a predetermined interval in the axial direction of
A semi-circular recess 6a is formed in a substantially central portion of the crankshaft bearing portion 6 to form a bearing body 6e. The journal portion 4a of the crankshaft 4 is pivotally supported in the recess 6a of the bearing body 6e. Further, at both ends of the recess 6a, insertion holes 6b are formed through which fixing bolts 10 for connecting the cylinder block 2 and the lower crankcase 3 are inserted. Then, the crankshaft 4 is rotatably supported by the crankshaft bearing portions 5 and 6 of the cylinder block 2 and the lower crankcase 3, and the lower crankcase 3
The fixing bolt 10 is inserted into the insertion hole 6b of the above and is fixed to the cylinder block 2.

Therefore, in recent years, the lower crankcase 3 for pivotally supporting the crankshaft 4 shown in FIG. 1 has been made of a light alloy due to the demand for weight reduction of the engine, but the crankshaft 4 is required to maintain rigidity. Since it is generally made of an iron-based material, the difference in the coefficient of thermal expansion between the two causes a problem. That is, the coefficient of thermal expansion of the steel crankshaft is 11 × 1
The lower crankcase made of aluminum has a temperature of about 22 × 10 ^-6 / ° C., While the temperature of the lower crankcase is about 0 ^-6 / ° C. The clearance between the portion 6 and the bearing main body 6e increases, which causes problems such as an increase in vibration noise and a decrease in hydraulic pressure.

Therefore, in order to solve the above-mentioned problems,
Bearing body 6e of crankshaft bearing 6 and insertion hole 6
In b, a metal matrix composite material in which an aluminum material is impregnated into a ceramic molded body is formed to reduce the difference in coefficient of thermal expansion from the crankshaft 4.

Japanese Patent Publication No. 7-113367 discloses a crankshaft bearing structure in which a crankshaft is supported between a main bearing portion of a light alloy cylinder block and a light alloy main bearing portion. Both the main bearing cap and the main bearing cap were made to contain a reinforcing fiber having a thermal expansion coefficient lower than that of the crankshaft, and the content of the reinforcing fiber in the main bearing portion was made larger than that in the main bearing cap. An engine crankshaft bearing structure is disclosed.

Further, in Japanese Unexamined Patent Publication No. 2001-317534, a crank which axially supports an iron-based crankshaft via bearing metal by a lower case bearing portion of a crank lower case made of a light alloy and a block bearing portion of a cylinder block. In the bearing structure of a shaft, the lower case bearing portion is composed of a bearing peripheral portion in which an iron-based member is cast around the bearing metal and a lower bearing portion made of a light alloy integrally provided under the bearing peripheral portion. However, there is disclosed a crankshaft bearing structure in which an engaging portion that engages with a positioning pin of a mold is provided in a region around the bearing when the crank lower case is cast by the mold.

Furthermore, in Japanese Patent Laid-Open No. 11-336740, through bolts are respectively inserted through at least a pair of bolt holes sandwiching the shaft hole so as to form a shaft hole for receiving a journal of a crankshaft together with a cylinder block. In a crankshaft bearing member that is joined to a cylinder block by fastening and at least a reinforcing member that can firmly receive a journal is cast in a light metal, the reinforcing member is located between a pair of bolt holes and A crankshaft bearing member that is open on the outside is disclosed.

[0009]

As described above, due to the difference in the coefficient of thermal expansion between the iron-based crankshaft and the light alloy crankshaft bearing portion, the crankshaft and the crankshaft bearing portion are separated from each other at high temperature by high temperature. As a result, the clearance increases, which causes problems such as an increase in vibration noise and a decrease in hydraulic pressure. Furthermore, in order to reduce the difference in the coefficient of thermal expansion between the crankshaft and the crankshaft bearing, the aluminum body is made to penetrate into the ceramic body in the bearing body of the crankshaft bearing to partially form the metal matrix composite material. However, in order to partially form the metal matrix composite material as described above, it is necessary to fix the ceramic molded body to the casting mold in advance during casting. In this case, since the ceramic molded body inevitably comes into contact with the casting mold, there is a problem that after casting, the metal-based composite material, which is difficult to cut, is exposed at the machining allowance portion of the surface, which significantly deteriorates the machinability. is there.

According to the crankshaft bearing structure of an engine disclosed in Japanese Patent Publication No. 7-113367, a reinforcing fiber having a coefficient of thermal expansion lower than that of the crankshaft, such as carbon, is provided in a main bearing portion supporting the crankshaft and a main bearing cap. Although fibers or ceramic fibers are contained, the reinforcing fibers are exposed on the machined surface, and there is a problem that the machinability is significantly deteriorated.

Further, a bearing structure of a crankshaft disclosed in Japanese Patent Laid-Open No. 2001-317534 and Japanese Patent Laid-Open No. 11-33.
The crankshaft bearing member of Japanese Patent No. 6740 is made by casting an iron-based member into the crankshaft bearing portion of the crank lower case made of light alloy to reduce the difference in thermal expansion coefficient between the crankshaft and the crankshaft bearing portion. However, since iron-based materials are used, there is still room for improvement in response to the demand for weight reduction of the crank lower case.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a crankshaft bearing structure and a manufacturing method that reduce the difference in coefficient of thermal expansion from the crankshaft and that are excellent in machinability. To aim.

[0013]

As a means for solving the above-mentioned problems, the present invention relates to a method for manufacturing a crankshaft bearing according to claim 1, which is a metal having a coefficient of thermal expansion smaller than that of an aluminum material. In a method of manufacturing an aluminum crankshaft bearing in which a ceramic molded body capable of forming a base composite material is cast, a fixed body having better machinability than the molded body is provided between the molded body and a casting mold. Then, the molded body is fixed in the casting mold by the fixed body. By arranging in this way and casting the aluminum material, the metal matrix composite material is partially formed on the crankshaft bearing, and the difference in the coefficient of thermal expansion between the crankshaft and the crankshaft bearing can be reduced. . Further, since the fixed body having good machinability is cast between the molded body and the casting mold, the metal matrix composite material, which is difficult to cut, is not exposed to the outside. Further, it is not necessary to form a fixing portion having a complicated shape and high precision for fixing the molded body to the casting die.

The invention relating to the method for manufacturing a crankshaft bearing according to claim 2 is the invention according to claim 1, wherein the molded body and the fixed body form an insertion hole for a bolt for fixing the crankshaft bearing. It is characterized in that it is fixed to a cast pin that does. With this configuration, the casting die does not need to have a special shape for disposing the fixed body, and thus the shape is simple. Further, since the crankshaft bearing is not formed with a special shape for disposing the fixed body in the casting mold, it is possible to prevent the strength from being lowered.

The invention relating to the method for manufacturing a crankshaft bearing according to claim 3 is the invention according to claim 1, wherein the fixed body has a higher strength than an aluminum material and forms a solid solution with the aluminum material. It is characterized by consisting of.
With this configuration, a solid solution is formed at the boundary between the aluminum material and the fixed body, so that the bond strength at the boundary is secured without providing a peeling prevention shape. Further, the machinability of the crankshaft bearing is improved and the strength of the crankshaft bearing itself can be improved.

According to a fourth aspect of the present invention, there is provided a crankshaft bearing manufacturing method according to the first aspect, wherein the fixed body has a preheating temperature of 150 ° C. to 250 ° C. The temperature of the molten aluminum is 67
It is characterized by being set to a predetermined value within 0 ° C to 700 ° C. With this configuration, it is possible to secure rigidity that the fixed body is not deformed by the casting pressure during casting, and it is possible to form a solid solution with the aluminum material.

The invention relating to the crankshaft bearing structure described in claim 5 is an aluminum crankshaft bearing in which a ceramic molded body capable of forming a metal matrix composite material having a thermal expansion coefficient smaller than that of an aluminum material is cast. A fixed body, which has better machinability than the metal-based composite material and forms a solid solution with an aluminum material, is cast between the body and the insertion hole of the fixing bolt of the crankshaft bearing. With this structure, the difference in the coefficient of thermal expansion between the crankshaft and the crankshaft bearing can be reduced, and a fixed body with good machinability is cast into the insertion hole through which the fixing bolt of the crankshaft bearing is inserted. Therefore, the insertion hole of the fixing bolt can be easily cut.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION A crankshaft bearing structure and a manufacturing method according to an embodiment of the present invention will be described in detail below with reference to FIGS. In the description of the embodiments of the present invention, the same members and corresponding parts as those in the conventional example are designated by the same reference numerals, and the description thereof will be appropriately omitted. Generally, an engine of a vehicle has a cylinder block 2 as shown in FIG.
And the lower crankcase 3 at the bottom of the cylinder block 2.
Are provided, and the crankshaft 4 is axially supported by the crankshaft bearing portion 5 of the cylinder block 2 and the crankshaft bearing portion 6 of the lower crankcase 3.

The crankshaft 4 is composed of a plurality of journal portions 4a pivotally supported by the crankshaft bearing portions 5 and 6 of the cylinder block 2 and the lower crankcase 3, and a plurality of crank portions 4b. The cylinder block 2 is a bore portion 2a that contains a cylinder (not shown).
Are formed in the axial direction of the crankshaft 4, and a plurality of crankshaft bearings 5 having semicircular recesses 5a for axially supporting the crankshaft 4 are formed on the bottom of the cylinder block 2. ing. Further, the bottom of the cylinder block 2 is formed with a plurality of insertion holes at predetermined positions through which the fixing bolts 10 that are connected to the lower crankcase 3 are inserted.

The lower crankcase 3 has a structure shown in FIGS.
As shown in FIG. 3, a plurality of crankshaft bearing portions 6 are continuously provided along the axial direction of the crankshaft 4 between the side walls 3a, 3a parallel to the axial direction of the crankshaft 4 with a predetermined gap. ing. The crankshaft bearing portion 6 has a block shape, and forms a bearing body 6e having a semicircular recess 6a that pivotally supports each journal portion 4a of the crankshaft 4. Further, the bearing body 6e of the crankshaft bearing portion 6 is formed with insertion holes 6b through which the fixing bolts 10 that are connected to the cylinder block 2 are inserted, on both sides of the recess 6a.

FIG. 3 is a diagram showing a material distribution in a cross section taken along the line AA in FIG. 2, in which the bold shaded area is the layer B of the fixed body, and the spotted area is the metal matrix composite of the ceramic molded body and the aluminum material. The material layer B and the shaded area indicate the aluminum material layer C. As shown in FIGS. 2 and 3, a ceramic molded body capable of forming a metal-based composite material having a smaller coefficient of thermal expansion than an aluminum material is cast into the bearing body 6e of the crankshaft bearing portion 6, and the aluminum material is It penetrates into this ceramic molded body to form a layer B of the metal-based composite material. Further, a layer C of aluminum material is formed on the surface of the recess 6a of the bearing body 6e and the predetermined height W of the side walls 6c of the bearing body 6e. Further, a layer B of a fixed body is formed on both side walls 6c of the predetermined height H of the bearing body 6e and the bottom portion 6d. Further, a layer A of the fixed body is formed up to a predetermined height H in the insertion hole 6b through which the fixing bolt 10 connected to the cylinder block 2 is inserted, and a layer C of the aluminum material is formed at the predetermined height W. Has been formed. This fixed body is formed of a zinc material or a zinc alloy material having higher mechanical strength than an aluminum material.

FIG. 4 is a diagram showing a metal layer at the boundary between the aluminum material and the fixed body in the portion A of FIG. 3, reference numeral a is a fixed body layer (bold-shaded portion), and reference numeral d is a solid solution layer ( Vertical line),
Reference numeral C indicates a layer of aluminum material (hatched portion with fine letters). Therefore, the range H of the insertion hole 6b through which the fixing bolt 10 is inserted
As shown in FIG. 4, the boundary between the layer (a) of the fixed body and the layer (c) of the aluminum material in FIG.
(Zn alloy) to form an alloy, and this solid solution can secure the bonding strength at the boundary between the fixed body and the aluminum material.

The crankshaft bearing portion 6 described above
The manufacturing method will be described below with reference to FIG. Figure 5
The shaded parts and the horizontal parts shown in are the pair of upper and lower casting molds 15.
A casting die 15 composed of A and 15B, a speckled portion shows a ceramic molded body 16, and a bold diagonal line portion shows a fixed body 17. As shown in FIG. 5, the fixed body 17 is made of a zinc material or a zinc alloy material, holds the ceramic molded body 16, and has a predetermined height so that the lower casting mold 15B and the ceramic molded body 16 do not come into contact with each other. It is formed in a bottomed substantially rectangular tube shape having H, and has insertion holes 17a through which vertically inserted casting pins 15b of a lower casting die 15B are inserted at both ends in the longitudinal direction. Further, the ceramic molded body 16 is formed in a block shape having a semicircular recess 16a.

Then, as shown in FIG. 5, the fixed body 1 whose preheating temperature is set to a predetermined temperature within 150 ° C. to 250 ° C.
7 is arranged at a predetermined position in the lower casting mold 15B. The preheating temperature is a temperature at which the rigidity not to be deformed by the casting pressure at the time of casting is secured and a solid solution with the aluminum material can be formed.

Next, the ceramic compact 16 preheated to a predetermined temperature is inserted into the fixed body 17 so as not to contact the lower casting mold 15B, and then the upper casting mold 15A is lowered to move the upper and lower casting molds 15A. , 15B are closed. Therefore,
The ceramic molded body 16 and the fixed body 17 have insertion holes 6 through which the fixing bolts 10 connected to the cylinder block 2 are inserted.
The upper and lower casting pins 15a and 15b forming b are inserted into the insertion holes 17a of the fixed body 17 to form the upper and lower casting molds 15A and 1A.
Fixed between 5B. In addition, between the ceramic molded body 16 and the casting mold 15, a portion where the fixed body 17 is not provided has a gap T because the ceramic molded body 16 and the casting mold 15 are not in contact with each other.

Then, a molten aluminum material whose preheating temperature is set to a predetermined temperature of 670 ° C. to 700 ° C. is injected and filled into the casting mold 15.

Then, referring also to FIG. 2 and FIG. 3, the aluminum material is melted into the ceramic molded body 16, and the bearing body 6e of the crankshaft bearing portion 6 has the ceramic molded body 1
A layer B of a metal-based composite material of 6 and an aluminum material is formed.
Further, a layer c of aluminum material is formed on the surface of the recess 6a of the bearing body 6e and the predetermined height W of both side walls 6c, and a predetermined insertion hole 6b through which the fixing bolt 10 connected to the cylinder block 2 is inserted. Also in the range W, a layer C of aluminum material is formed.

At the same time, the fixed body 17 is cast into the predetermined height H and the bottom portion 6d of both side walls 6c of the bearing body 6e, and further, the fixing bolt 10 for connecting with the cylinder block 2 is formed.
The fixed body 17 is also cast into the predetermined height H of the insertion hole 6b through which the fixed body 17 is inserted.

In addition, as shown in FIG. 4, in the range H in which the fixed body 17 of the insertion hole 6b is cast, the aluminum material melts into the surface layer a of this fixed body, and the aluminum material and the fixed body are separated. A solid solution layer is formed at the boundary of the alloy and alloyed.

Here, the results of a cutting test carried out on the specimen of the crankshaft bearing structure of the present invention manufactured by the above manufacturing method will be shown. First, a Zn alloy fixed body preheated to 200 ° C. is fixed to a casting mold, and a ceramic molded body preheated to 700 ° C. is inserted into the fixed body and fixed,
A sample of the metal-based composite material was manufactured by casting with a molten aluminum material at 700 ° C. When this sample and a conventional metal-based composite bearing were compared in a cutting test, this sample exhibited a tool life of 20 times or more that of the conventional metal-based composite bearing. Furthermore, the strength of the bearing was found to increase by 20%.

As described above, according to the crankshaft bearing structure and the manufacturing method according to the embodiment of the present invention, the crankshaft bearing portion is formed with a ceramic molding capable of forming a metal matrix composite material having a thermal expansion coefficient smaller than that of an aluminum material. Since the body is cast, the difference in the coefficient of thermal expansion from the crankshaft is small. Further, since the fixed body is arranged in the casting mold so that the ceramic molded body and the casting mold do not come into contact with each other, the difficult-to-cut metal-based composite material is exposed in the machining allowance portion of the crankshaft bearing portion. The cutting workability is improved. Further, since the solid solution is alloyed at the boundary between the fixed body and the aluminum material, the bond strength between the fixed body and the aluminum material is improved.

In the above, when casting the crankshaft bearing portion that supports the crankshaft, the form in which the fixed body is fixed in advance in the casting die and the molded body is cast is described.
The crankshaft bearing structure and the manufacturing method can be applied to other bearing parts such as a crank bearing cap, a vertically split crankcase bearing part for two wheels, a camshaft housing and a bearing part of a transmission case.

[0033]

As described above, according to the invention described in claim 1, the aluminum material permeates the molded body to form the metal matrix composite material in the crankshaft bearing portion, and Since the difference in the coefficient of thermal expansion can be reduced, it is possible to prevent an increase in vibration noise and a decrease in hydraulic pressure.
In addition, since the fixed body is cast between the molded body and the casting mold and the difficult-to-cut metal matrix composite material is not exposed to the outside, the machinability is improved and the work efficiency is improved. Further, since it is not necessary to form a fixing portion having a complicated shape and high precision in order to fix the molded body to the casting mold, the manufacturing cost can be reduced.

According to the second aspect of the invention, it is not necessary to form a special shape for fixing to the casting mold, the shape is simple, and the manufacturing cost can be reduced.

According to the third aspect of the invention, since the solid solution is formed at the boundary between the aluminum material and the fixed body, the bonding strength at the boundary is secured without providing a peeling prevention shape. Further, the machinability of the crankshaft bearing is improved and the strength of the crankshaft bearing itself can be improved.

According to the invention described in claim 4, it is possible to secure the rigidity that the fixed body is not deformed by the casting pressure during casting, and it is possible to form the solid solution with the aluminum material.

According to the invention described in claim 5, in the crankshaft bearing portion, the aluminum material penetrates into the molded body to partially form the metal matrix composite material, and the difference in the coefficient of thermal expansion from the crankshaft is obtained. Since it can be reduced, it is possible to prevent an increase in vibration noise and a decrease in hydraulic pressure. Further, since the fixed body is cast in the crankshaft bearing portion and the metal-based composite material, which is difficult to cut, is not exposed, the machinability of the fixing bolt insertion hole and the like is improved and the work efficiency is improved.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a cylinder block, a crankshaft, and a lower crankcase which form an engine.

FIG. 2 is a perspective view showing a lower crankcase which is a component of the crankshaft bearing structure according to the embodiment of the present invention.

3 is a diagram showing a material distribution in a cross section taken along the line AA of FIG.

4 is a diagram showing a metal layer at a boundary between an aluminum material and a fixed body in a portion A of FIG.

FIG. 5 is a cross-sectional view showing a method for casting a crankshaft bearing according to an embodiment of the present invention.

[Explanation of symbols]

2 cylinder block 3 lower crankcase 4 crankshaft 5, 6 Crankshaft bearing 6a recess 6b insertion hole 6c side wall 6d bottom 6e Bearing body 10 Fixing bolt 15 casting mold 15a, 15b Cast pin 16 Ceramic molded body 17 Fixed body Layer of fixed body B Metal matrix composite layer Ha aluminum material layer D Solid solution layer

Claims (5)

[Claims] 1. A method of manufacturing a crankshaft bearing made of aluminum in which a ceramic molded body capable of forming a metal matrix composite material having a thermal expansion coefficient smaller than that of an aluminum material is cast, comprising: A method for manufacturing a crankshaft bearing, comprising disposing a fixed body having better machinability than the molded body, and fixing the molded body in the casting mold with the fixed body. 2. The method of manufacturing a crankshaft bearing according to claim 1, wherein the molded body and the fixed body are fixed to a cast pin that forms an insertion hole for a fixing bolt of the crankshaft bearing. . 3. The fixed body has a higher strength than an aluminum material,
The method for manufacturing a crankshaft bearing according to claim 1, wherein the crankshaft bearing is made of an aluminum material and a material that forms a solid solution. 4. The preheating temperature of the fixed body is 150.degree.
The method for manufacturing a crankshaft bearing according to claim 1, wherein a predetermined value within ℃ and the corresponding molten metal temperature of the aluminum material are set to a predetermined value within 670 ° C to 700 ° C. 5. A crankshaft bearing made of aluminum in which a ceramic molded body capable of forming a metal matrix composite material having a thermal expansion coefficient smaller than that of an aluminum material is cast, in which a bolt for fixing the molded body and the crankshaft bearing is inserted. A crankshaft bearing structure characterized in that a fixed body that forms a solid solution with an aluminum material is cast between the metal base composite material and the metal matrix composite material.