JPH01255709A - Crankshaft bearing of engine - Google Patents

Abstract

PURPOSE:To eliminate the generation of thermal stress on an abutting surface and to prevent vibration, noise and lowering of hydraulic pressure, by forming a crankshaft bearing part from light metal containing reinforcing fibers, and by giving a specific relationship to the volumetric rate of the reinforcing fibers. CONSTITUTION:A crankshaft bearing structure 1 in an engine supports a crankshaft 5 made of steel, and is made of light metal containing reinforcing fibers. The volumetric rate Vf (abscissa) of an inner peripheral part 9 does not vary with the distance (I) (ordinate) from its innermost layer 6c, but the volumetric rate Vf of an outer peripheral part 10 linearly decreases with the distance (I). Thus, since no thermal stress occurs on an abutting surface and a necessary rigidity is ensured by reinforcing fibers, it is possible to prevent vibration, noise and lowering of hydraulic pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in the structure of an engine crankshaft bearing that supports a cast iron crankshaft of an engine.

(Prior Art) For example, a bearing that supports the journal of a crankshaft of an engine is shaped like a bearing and is integrally formed in the lower part of a cylinder block. Conventionally, cylinder blocks and crankshafts have been made of cast iron, but due to demands for lighter engines, cylinder blocks made of light alloys have become popular.

Accordingly, the main bearing portion of the cylinder block is also made of a light alloy such as AQJ alloy. However, the crankshaft is made of cast iron in order to maintain its rigidity, and the difference in thermal expansion coefficient between the two poses a problem. That is, 1. The coefficient of thermal expansion of a cast iron crankshaft is 14XIO'/"C, while the coefficient of thermal expansion of an aluminum alloy is 22X 10-6
/''C, which increases the metal clearance between the shaft and bearing, causing problems such as increased vibration noise and decreased oil pressure.

Furthermore, problems such as poor roundness of the crankshaft receiving portion arise due to insufficient rigidity due to the small Young's modulus of aluminum.

In order to solve these problems, we have developed a crankshaft made of a light alloy such as A9J alloy that contains reinforcing fibers that have a coefficient of thermal expansion lower than that of the crankshaft to increase its rigidity. A bearing structure has been developed.

As shown in Japanese Patent Application No. 61-265474, for example, the bearing structure of such a rank shaft is shown in FIG. 6A and FIG. There is a crankshaft bearing member 30 shown in the figure, which contains the reinforcing fibers at a constant fiber volume percentage. In other words, the fiber volume fraction Vfl is close to the thermal expansion coefficient of the cast iron crankshaft 5.
The reinforcing fibers are uniformly contained in the member 30 whose base material is Ai alloy, and the innermost circumference 30a of the bearing part
The distance from the contact surface of the crankshaft 5 to the outer side of the member! The fiber volume fraction vr (horizontal axis) remains constant (V't) regardless of the response (vertical axis).

However, in the receiving part made of such a member 30, thermal stress is generated at the joint interface 30b with the cylinder block due to the difference in coefficient of thermal expansion with the A9J alloy forming the cylinder block, which is not preferable.

In order to solve this inconvenience, patent application Sho 6l-2G88
As shown in Publication No. 91, FIGS. 7A and 7
The volume fraction Vf of the reinforcing fibers in the innermost periphery 31a of the crankshaft bearing member 31 shown in FIG.
(horizontal axis) is the set value Vrl, and the crankshaft 5
As the distance 2 (vertical axis) from the contact surface to the outer side of the member increases, the volume ratio V' is linearly decreased to a predetermined value VI'2, and the thermal expansion coefficient vr on the crankshaft side is There is one that has a low coefficient of thermal expansion on the cylinder block side and a high coefficient of thermal expansion on the cylinder block side to match the respective coefficients of thermal expansion of the crankshaft and cylinder block.

(Problem to be Solved by the Invention) However, in this method of gradually decreasing the volume fraction Vr of the reinforcing fibers of the member 31, the rigidity of the member 31 is reduced, and the crankshaft supporting portion is not sufficiently rounded during processing. j)
However, there are disadvantages such as not being able to perform accurate calculations, and it is not preferable in terms of accuracy.

In view of the above circumstances, the present invention aims to provide a crankshaft bearing for an engine that ensures rigidity and does not generate thermal stress at the joint interface with other members.

(Means for Solving the Problems) The crankshaft bearing structure of the present invention is an engine crankshaft bearing structure that supports a crankshaft made of iron-based material, in which the crankshaft bearing portion is made of a light metal containing reinforcing fibers. , the volume fraction of the reinforcing fibers is formed such that it is approximately constant in the inner circumferential portion inside the set range from the innermost circumference of the bearing portion, and gradually decreases toward the outside in the outer circumferential portion outside the set range. Features.

Note that the innermost periphery of the bearing portion is a portion that comes into contact with and pivotally supports the crankshaft.

In addition, the reinforcing fibers are dispersed within the light alloy member, and when the volume fraction of the reinforcing fibers is large, the thermal expansion coefficient is low, and when the volume fraction is small, the thermal expansion coefficient is lower than that of the light alloy that is the base material. It approaches the value and becomes higher.

(Function) Since the present invention adopts the above-mentioned configuration, the bearing part and the crankshaft support side of the inner peripheral part can suppress the coefficient of thermal expansion to a low level by containing a predetermined amount of reinforcing fibers, and are within the set range. Since the reinforcing mII contains a certain amount of H within a certain range, rigidity is maintained, and the coefficient of thermal expansion of the outer peripheral portion is gradually increased to match the coefficient of thermal expansion of the joining member, such as a cylinder block made of Al alloy. I can do it.

(Example) An example of the present invention will be described below with reference to the drawings. 1st
As shown in the figure, in the engine crankshaft bearing 1 of the present invention, an upper deck 2a and a lower deck 2b are connected to each other by bolts 4.
It consists of a crankshaft bearing part (bearing part) 6 that supports a crankshaft 5 which is passed through a cylinder block 2 made of aluminum alloy and fastened by.

The crankshaft 5 is made of cast iron, and the cylinder block 2 is made of an aluminum alloy (equivalent to JIS ADC10) with an Ai-gold alloy composition of Cu 3.0 and Si 8.
5, MgO,2.

Mn O,1, Fe O,5, Zn O,3 (unit: v
t%) is appropriate. The cylinder block 2 is formed by forging by such an Ai gold alloy molten metal forging method. In this case, an elution pressure of 400 kg/c♂ and a molten metal temperature of 740°C are appropriate.

Also, to give an example of the material of the crankshaft 5,
The crankshaft 5 is made of ductile cast iron in which graphite is spheroidized, and after this material is austempered, the crankshaft 5 is made through machining, rolling of the journal and crank pin, and a finishing process of grinding. be. In the austempering treatment, for example, the material is heated at a temperature of 890°C for about 2 hours to austenite, then rapidly cooled to a temperature of 395°C, quenched, and held at this temperature for about 2 hours to change the structure. After most of it is turned into bainite, it is cooled to room temperature and washed with hot water. This austempering process provides a crankshaft 5 that is strong and has high bending strength.

Further, the roll processing of the journal of the crankshaft 5 and the fillet portion of the crank pin applies residual compressive stress to the fillet portion to transform the structure into martensite, thereby improving fatigue strength.

The crankshaft 5 thus obtained contains 3.62% carbon.
, silicon 2.44%, manganese 0.4%, phosphorus 0.03
It contains 1% sulfur, 0.001% sulfur, 0.31% molybdenum, 09% nickel, and 0.039% magnesium, and its coefficient of thermal expansion is 17. IX 10
°6/'C.

On the other hand, the coefficient of thermal expansion of the cylinder block 1 made of aluminum alloy is 21.8 x 10-6/°C, which is higher than that of the crankshaft.

The bearing part 6, which has a central circular hole that holds the crankshaft 5, is composed of a block bearing part 6a and a bearing cap 6b, and each member has an inner diameter D=corresponding to the diameter of the crankshaft 5, as shown in FIG. 50m
The cylinder block has a central perfect circle forming part 7 of m, and has a thickness of a-40 mm in the vertical direction and b=25 mm in the left-right direction. This bearing part 6 is made of alumina A9Jz 03
, alumina, silica (Amenz 03, Sl 0□)
A fiber molded body (preform) containing reinforcing fibers made of short ceramic fibers such as The content volume ratio of this reinforcing fiber is shown in Fig. 3A and C in Fig. 3A.
The third graph is a graph showing the results measured on the -C cross section.
As shown in Figure B, the inner circumferential portion from the innermost circumference 6c of the bearing part to the inside of the boundary line of the setting range 8 is approximately constant, and within the setting range 8
The outer peripheral portion 10 is formed so as to gradually decrease toward the outside. In other words, as shown in FIG. 3B, the volume fraction Vf (horizontal axis) of the inner circumferential portion 9 does not change as the distance from the innermost circumference 6c increases (vertical axis), but the volume ratio Vr of the outer circumferential portion 10 changes as the distance increases (vertical axis). Decrease linearly.

However, since the side surface 10a of the bearing portion 6 is a contact portion of the cylinder block 2, it forms the outer peripheral portion 10.

In this example f', the boundary line of the setting range 8 is formed in a shape surrounding the crankshaft 5 and within 15 mm outward from the innermost circumference 6C of the bearing part 6,
The fiber volume fraction Vr of the inner peripheral portion is Vr3-20% (vol.
), and the volume fraction vf of the outer circumferential portion 10 gradually decreases as it goes outward from the boundary line of the setting range 8, and is Vf'A-7% (vol) near the outermost circumference.

Therefore, the coefficient of thermal expansion is low in the inner circumferential portion, and the coefficient of thermal expansion in the outer circumferential portion 10 increases as it goes outward.

Alumina mentioned above (A9Jz 03), alumina.

A fiber molded body (preform) using ceramic such as silica (Alz 03 φ5I02) or short fibers is produced in substantially the same manner as a known pressure casting method. The process is briefly shown below.

As shown in FIG. 4A, ceramic short fibers 13, 1 to 10% (vt) of cationized starch as an organic binder, and 1 to 1096 (vt) of silica sol as an inorganic binder are used.
t) The binder, antifoaming agent, and fiber aggregation inhibitor are mixed to form a slurry solution 13a, which is filled into the resin preform mold 11.

The resin preform mold II has a filter II on the bottom.
A is provided, and is connected to a suction hose 11b that performs suction in the direction of arrow A through this filter lla. The mold 11 is filled with molten metal by the suction of the suction hose Ilb, unnecessary solution is dehydrated by the filter Ila, and the short fibers 13 are laminated in a predetermined shape.

The mold 11 has an inclined portion lie in which the amount of stacked short fibers 13 in the outer circumferential portion IO of the set range decreases toward the outside so that the amount of stacked short fibers 13 in the outer circumferential portion IO of the setting range gradually decreases toward the outer periphery. is formed. Therefore, when this laminated product is dried and placed in a press mold 12 as shown in FIG. 3B and pressed from above in the direction of arrow B, the rolling reduction rate differs depending on the part of the press, so the outer peripheral part 10, which is an inclined part, is not laminated. Fiber density can be tapered.

Note that this suction is performed via the filter 12a provided at the bottom of the mold 12, so the filter 12a
Short fibers 13 tend to aggregate on the opposing bottom surface.

After this pressing, the binder is burned off and a preform with intertwined fibers is created.

The roundness of the bearing portion 6 made of the preform thus formed was measured. Note that this measurement method involves assembling the upper deck 2a and lower deck 2b by fastening them with bolts 4, co-processing the bearing part 6, removing the upper deck 2a and lower deck 2b, and then reinstalling the upper deck 2.
A and the lower deck 2b are assembled by measuring the roundness of the inner diameter of the bearing part 6. As a result of comparing the above-mentioned embodiment of the present invention with a comparative example of a bearing part made only of A9J alloy and without composite or iron-based materials, the roundness error in the embodiment was 8 μm, but in the comparative example was as large as 20 μm and was practically unusable.

Next, the relationship between the fiber volume fraction (Vf), the coefficient of thermal expansion α, and the Young's modulus E is shown in FIG. Note that A9J alloy (ADC
Measurements were made using a bearing part containing 95A9Jz 03 .5S10° alumina short fibers using IO) as a base material. It can be seen from the graph that as the fiber volume fraction (Vf) increases, the thermal expansion coefficient α (left vertical axis) decreases and the Young's modulus E (right vertical axis) increases. Therefore, the coefficient of thermal expansion α can be increased. The inner peripheral portion 9 with a large fiber volume ratio Vr has a low coefficient of thermal expansion α similar to that of a cast iron crankshaft, and a Young's modulus E
The outer circumferential portion IO has a high rigidity and has a low fiber volume fraction, and can have a high coefficient of thermal expansion α in accordance with the coefficient of thermal expansion of the cylinder block.

In addition, when installing such a bearing part in the cylinder block, if the cylinder block is made by high-pressure casting, it is sufficient to set the above-mentioned molded product in the mold and combine it when the block is cast. When making bearing parts using gravity casting or low-pressure casting, it is appropriate to manufacture the bearing parts in advance as a composite member, set it in a mold, and cast it in.Effects are the same with either method. .

(Effects of the Invention) In the crankshaft bearing of the present invention, the body ratio of reinforcing fibers is approximately constant in the inner circumferential portion inside the set range from the innermost circumference of the bearing portion, and as it increases toward the outer circumference in the outer circumferential portion outside the set range. The inner circumferential portion on the crankshaft side has a coefficient of thermal expansion close to that of the crankshaft, so no thermal stress is generated on the contact surface, and the reinforcing fibers ensure the necessary rigidity. This makes it possible to prevent vibration noise and oil pressure drop.

In addition, the outer peripheral part can be formed so that the coefficient of thermal expansion gradually increases as it goes outward, so it can be made close to the coefficient of thermal expansion of the cylinder block, and the difference in coefficient of thermal expansion at the interface with the cylinder block can be alleviated. , the occurrence of thermal stress can be significantly reduced.

Further, since the inner side of the setting range of the bearing part has the above-mentioned rigidity, the roundness of the inner diameter can be increased, which is also preferable in terms of accuracy.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a crankshaft bearing in a cylinder block, FIG. 2 is a partial cross-sectional schematic diagram of an embodiment of the crankshaft bearing of the present invention, and FIG. 3A is a graph-corresponding cross-sectional diagram of the aforementioned embodiment. Figure 3B is a graph showing the fiber volume fraction and distance from the innermost periphery of the example shown in Figure 3A, Figure 4A is an explanatory diagram showing an example of the manufacturing method of the example, Figure 4B is the graph shown in Figure 4A. FIG. 5 is a graph showing the relationship between fiber volume fraction, thermal expansion coefficient, and Young's modulus; FIG. 6A is a sectional view showing an example of a conventional crankshaft bearing; FIG. 6B Figure 6A is a graph showing the fiber volume fraction and distance from the innermost circumference of the conventional example; Figure 7A is a sectional view showing another example of the conventional crankshaft bearing; Figure 7B is Figure 7A. 2 is a graph showing the fiber volume fraction and the distance from the innermost periphery of the conventional example shown in FIG. Crankshaft bearing structure...1 Crankshaft...5 Crankshaft receiving part (bearing part)...6 Innermost circumference...6c Setting range...8 Inner circumference...9 Outer circumference...・10 Reinforcing fiber (short fiber)...13 Figure 1 Figure 2 Figure 34 @l Figure 48 Figure 511
8d 1 Figure 6B 5

Claims (1)

[Claims] In a crankshaft bearing structure for an engine that supports a crankshaft made of iron-based material, the crankshaft bearing portion is made of a light metal containing reinforcing fibers, and the volume percentage of the reinforcing fibers is within a set range from the innermost periphery of the bearing portion. 1. A crankshaft bearing for an engine, characterized in that an inner circumferential portion on the inside is substantially constant, and an outer circumferential portion on the outside of a setting range is formed so as to gradually decrease toward the outside.