JPH06108917A - Light alloy made cylinder block of multiple cylinder engine and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent failure of a crank shaft metal fitted in a crank bearing part, deterioration of engine starting performance, and seizure between the crank shaft metal and a crank shaft, even if the temperature is low (below freezing point). CONSTITUTION:After cylinder liners 16 are tightly fitted in respective cylinder bores 18 of a light alloy made cylinder block main body 14, the inner circumferential surfaces of respective crank bearing parts 20 are worked. This inner circumferential surface work is carried out in such condition that the cylinder block main body 14 is curved by a prescribed distance so as to project a cylinder linear direction center part upward (b). In the cylinder block 12 manufactured in a such way, the axial line of each crank bearing part 20 is curved in down-projection shape (c). When the temperature is reduced, the cylinder block main body 14 is going to bend in up-projection curved shape. Therefore, do projection curved condition of the axial line is released gradually, and the axial line is arranged on a straight line L at a prescribed temperature (d). It is thus possible to prevent abrasion between the crank shaft metal and the crank shaft at the time of the low temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light alloy cylinder block for a multi-cylinder engine and a method for manufacturing the same.

[0002]

2. Description of the Related Art In a multi-cylinder engine in which a large number of cylinder bores are formed in a row above a cylinder block,
Since the weight tends to be large, the cylinder block is often made of a light alloy such as an aluminum alloy. In such a cylinder block made of light alloy, the wear resistance of the piston sliding surface of the cylinder is insufficient, and therefore, as disclosed in Japanese Utility Model Laid-Open No. 63-110649, the cylinder block body is not Separately, a cylinder liner made of cast iron or the like is provided to ensure wear resistance.

[0003]

The above cylinder liner is formed in the cylinder block body by being cast together with the cylinder block body or tightly fitted into the cylinder bore of the cylinder block body by press fitting or shrink fitting. In the latter case, the force for expanding the cylinder bore always acts on the cylinder block body from the cylinder liner, so that the following problems occur.

That is, since the cast iron or the like forming the cylinder liner has a smaller coefficient of thermal expansion than the light alloy forming the cylinder block body, when the temperature of the cylinder block decreases, the cylinder liner is attached to the cylinder block. The amount of heat shrinkage is larger in the lower part than in the upper part, and at that time, the effect of internal stress due to the tight fitting appears, and the cylinder block bends in the direction in which the central part in the cylinder row direction is convex upward. Becomes

After the cylinder liner is mounted, the inner circumference is arranged so that the axes of the crank bearings are aligned with respect to the plurality of crank bearings arranged in a row below the cylinder bores of the cylinder block body. Surface machining is performed.However, no matter how accurately this inner peripheral surface machining is performed, if the temperature of the cylinder block drops below the temperature at the time of this inner peripheral surface machining, the central portion of the cylinder block in the cylinder row direction is Since it curves in a direction that is convex upward, the axis line of each crank bearing portion is also arranged on a curved line that is curved in a direction convex upward.

Therefore, at a low temperature such as below freezing, the crankshaft metal fitted into the crankshaft bearing and the crankshaft rub against each other, which may damage the crankshaft metal or make it difficult to start the engine. In the worst case, the phenomenon of the crankshaft metal sticking to the crankshaft will also occur. Moreover, at low temperature, the viscosity of the oil is high and the fluidity is poor, so that the oil cannot be sufficiently supplied to the crank bearing portion, and the inner diameter of the crank bearing portion is also small, so that the above problems are more likely to occur. There is.

The present invention has been made in view of the above circumstances, and damage to the crankshaft metal fitted in the crankshaft bearing portion, deterioration of engine startability, and crankshaft metallization even at low temperatures. An object of the present invention is to provide a light alloy cylinder block for a multi-cylinder engine capable of preventing seizure with a crankshaft, and a method for manufacturing the same.

[0008]

SUMMARY OF THE INVENTION A light alloy cylinder block for a multi-cylinder engine and a method for manufacturing the same according to the present invention include:
Machining the inner peripheral surface of each crank bearing while forcibly bending the cylinder block body in the same direction as the direction in which the cylinder block bends due to temperature decrease so that the axes of the crank bearings are aligned in a straight line at low temperatures. By doing so, it is possible to prevent the crankshaft metal and the crankshaft from rubbing against each other at a low temperature, thereby achieving the above object.

That is, according to the method of manufacturing a light alloy cylinder block for a multi-cylinder engine according to the present invention, as described in claim 1, a plurality of light alloy cylinder block bodies are formed in a row on the upper part of the cylinder block body. After a cylinder liner is tightly fitted to each of the cylinder bores, a plurality of crank bearing portions provided in a row below the cylinder bores of the cylinder block body are machined on the inner peripheral surface to form a light alloy cylinder of a multi-cylinder engine. A method of manufacturing a block, wherein the inner peripheral surface of each of the crank bearing portions is machined by bending a predetermined amount of the cylinder block body in a direction in which a central portion in the cylinder row direction of the cylinder block body is convex upward. It is characterized by doing in.

A light alloy cylinder block for a multi-cylinder engine according to the present invention has the following features.
A cylinder block body made of a light alloy, in which a plurality of cylinder bores are formed in a row in the upper part and a plurality of crank bearing portions are provided in a row below the cylinder bore, and a tight fit is provided in each of the cylinder bores of the cylinder block body. A cylinder block made of a light alloy of a multi-cylinder engine including: a cylinder liner, and an axis of each of the crank bearings arranged in a straight line at a predetermined temperature at a low temperature, and a temperature higher than the predetermined temperature. Then, the axis line of each of the crank bearings is arranged so as to be arranged on a curved line which is curved so as to be convex downward.

[0011]

As described above, the cylinder block main body is moved by a predetermined amount in the direction in which the central portion of the cylinder block main body in the cylinder row direction is convex upward, that is, in the same direction as the direction in which the cylinder block is curved due to the temperature decrease. Since the inner peripheral surface of each crank bearing is machined while it is forcibly curved, after machining the inner peripheral surface, at normal temperature, the axis of each crank bearing is curved in a downward convex direction. Although it will be arranged on a curve, when the temperature decreases, the cylinder block begins to bend in a direction that is convex upward, so the convex curved state below the axis of each crank bearing portion is gradually alleviated,
The axis line of each crank bearing portion is arranged in a straight line at a predetermined temperature when the temperature is low, so that it is possible to prevent friction between the crankshaft metal and the crankshaft of the crank bearing portion when the temperature is low.

Therefore, according to the present invention, it is possible to prevent damage to the crankshaft metal fitted in the crankshaft bearing, deterioration of engine startability, and seizure between the crankshaft metal and the crankshaft even at low temperatures. be able to.

When the above-mentioned structure is adopted, at normal temperature or warm time, the axis line of each crank bearing portion is arranged on a curved line in a direction in which it is convex downward.
At room temperature or warm temperature, the viscosity of oil is low and its fluidity is good, so the oil is sufficiently supplied to the crank bearing part, and the inner diameters of the crank bearing part and crankshaft metal are also large due to thermal expansion. Therefore, there is no risk of the crankshaft metal and the crankshaft rubbing against each other.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a process outline view showing an embodiment of a method for manufacturing a light alloy cylinder block for a multi-cylinder engine according to the present invention, and FIG. 2 is a partial sectional view showing the multi-cylinder engine. .

As shown in FIG. 2, the multi-cylinder engine 10 is shown.
Is a V-type 8-cylinder engine, and its cylinder block 12 includes a cylinder block body 14 made of a light alloy (aluminum alloy) and a cylinder liner 16 made of cast iron.

At the upper part of the cylinder block body 14, 8
Each of the four cylinder bores 18 is formed in two rows, and a plurality of crank bearing portions 20 are provided in a row below the cylinder bores 18. Also, the cylinder liner 1
6 is tightly fitted in each cylinder bore 18 of the cylinder block body 14.

The crankshaft 22 is supported by the cylinder block main body 14 at the plurality of crank bearing portions 20. Each of the crank bearing portions 20 is formed in the cylinder block main body 14 and has a semi-arcuate concave portion 14.
a and a recess 24 a of the bearing cap 24. The bearing cap 24 is adapted to abut against the recess 14a in the recess 24a, and is attached to the cylinder block body 14 by tightening bolts 34 on both sides of the recess 24a. Then, a ring-shaped crankshaft metal 26 is fitted into each of the crank bearing portions 20 so as to be inscribed in both the recesses 14a and 24a, and the crankshaft 22 is rotated at the inner peripheral surface of the crankshaft metal 26. It is slidably supported in the direction.

Between the crank bearings 20 of the crankshaft 22, one end is connected to a piston 28.
The other ends of the pair of connecting rods 30 are connected to each other via a big end metal 32.

The cylinder block 12 is manufactured as shown in FIG.
It is performed as shown in.

FIG. 1A shows the cylinder block body 14
The cylinder liner 16 is tightly fitted in each cylinder bore 18 of each of the
It is a figure which shows the cylinder block 12 after the bearing cap 24 was attached to 4a and each crank bearing part 20 was provided. The tight fitting is performed by shrink fit by inserting the cylinder liner 16 into each cylinder bore 18 while the cylinder block body 14 is heated.

The cylinder block 12 shown in FIG.
Indicates that the inner peripheral surface of each crank bearing portion 20 has not been processed yet. For this cylinder block 12,
As shown in FIG. 2B, by inserting spacers Sc and Se having a predetermined thickness on the lower side of the cylinder block body 14, the cylinder block body 14 is oriented so that the central portion in the cylinder row direction is convex upward. Is bent by a predetermined amount, and in this state, the inner peripheral surface of each crank bearing portion 20 is machined. The spacer Sc that is inserted below the central portion of the cylinder block main body 14 in the cylinder row direction is thicker by a predetermined amount (about 9 μm) than the spacers Se that are inserted below the both ends of the cylinder row direction. By this inner peripheral surface processing, the axes of the crank bearing portions 20 are arranged on a straight line L.

3 and 4 are views specifically showing a state of the inner peripheral surface machining.

As shown in these figures, the cylinder block body 14 to which the bearing cap 24 is attached is shown.
Is mounted on the pedestal 36 via the spacers Sc and Se, and then the cylinder block body 14 is clamped by the clamp member 38.
Clamp with. Of the above spacers, two spacers Sc are provided on the right and left sides and four spacers Se are inserted on the left and right sides, for a total of six spacers. The clamp member 38 is the cylinder block body 1
The plate 38a for pressing the flange of the skirt portion of No. 4 is fixed to the fixing portion 38c with the bolt 38b, so that the cylinder block body 14 is clamped. The clamp member 38 is provided near each of the spacers Sc and Se.

As shown in FIG. 4, by inserting the spacers Sc and Se, the cylinder block main body 14 curved in a direction in which the central portion in the cylinder row direction is convex upward, the inner circumference of each crank bearing portion 20 is increased. The surface processing tool 40 is inserted. Then, the tool 40 is rotated by the main shaft 42, and the inner peripheral surface of each crank bearing portion 20 is machined by the tips 44 provided on the outer peripheral surface of the tool 40 at predetermined intervals. In order to secure the processing accuracy of this inner peripheral surface processing, the tool 4
The leading end of 0 is rotatably supported by a support member 46 fixed to the pedestal 36.

Although the cylinder head 44 is shown by a chain double-dashed line in FIG. 3, it is not yet connected to the cylinder block 12 when the inner peripheral surface is machined. Further, as shown in FIG. 4, an oil passage 48 for supplying oil to the crank bearing portion 20 is formed in the cylinder block body 14.

After machining the inner peripheral surface, the bolts 34 are loosened to remove the bearing cap 24, the crankshaft metal 26 is fitted in each crank bearing portion 20, and then the bolts 34 are tightened again to mount the bearing cap 24 on the cylinder block body. Attach to 14.

After the inner peripheral surface is machined, the spacers Sc and Se are removed to release the curved state of the cylinder block body 14, and the axis line of each crank bearing portion 20 becomes as shown in FIG.
As shown in (c), the central portion in the cylinder row direction is arranged on the curved line C that is curved in a downward convex direction.

The cylinder block 12 is used by being incorporated in the engine 10 in a state where the axis line of each crank bearing portion 20 is curved as described above.

Next, the operation of this embodiment will be described.

The cylinder block 12 manufactured by the above process is in a curved state in which the axis of each crank bearing portion 20 is convex downward at room temperature, but when the temperature of the cylinder block 12 decreases, The curved state is relieved.

That is, since the cast iron forming the cylinder liner 16 has a smaller coefficient of thermal expansion than the light alloy forming the cylinder block body 14, when the temperature of the cylinder block 12 decreases, the cylinder block 12 is The amount of heat shrinkage in the lower part is larger than that in the upper part where 16 is mounted, and at that time, the influence of internal stress due to the tight fitting appears, and as shown in FIG.
The cylinder block 12 begins to curve in a direction in which the central portion in the cylinder row direction is convex upward. Due to this bending, when the temperature reaches a predetermined temperature (about −35 ° C.) at a low temperature, the axes of the crank bearing portions 20 are arranged on a straight line L. This allows
It is possible to prevent friction between the crank bearing portion 20 and the crankshaft 22 at low temperatures.

In the above description, for the sake of simplification of the description, only the bending of the cylinder block 12 due to thermal deformation has been described. However, in reality, the cylinder block 12 is assembled with the cylinder head 44, and thus the cylinder block 12 is actually bent. It is also necessary to consider the effect of bending.

That is, the cylinder block 12 and the cylinder head 44 are assembled by bolting via a gasket between them, as shown in FIG.
The axial force for tightening the bolt is substantially constant over the entire cylinder row direction of the cylinder block 12, whereas the elastic reaction force of the gasket is larger at the central portion in the cylinder row direction than at both ends of the cylinder block 12 in the cylinder row direction. Therefore, the cylinder head 44 is attached to the cylinder block 12.
When assembled, this allows cylinder block 1
2 tends to curve in a direction in which the central portion in the cylinder row direction is convex downward.

Therefore, in setting the degree of curvature when machining the inner peripheral surface, it is necessary to subtract the amount of curvature due to the assembly of the cylinder head 44. The thickness difference (about 9 μm) between the spacer Sc at the central portion in the cylinder row direction and the spacers Se at both ends set in the above-described embodiment is a set value after subtracting the bending amount due to such cylinder head assembly.

FIG. 6 is a diagram showing the result of an experiment conducted to examine the influence of thermal deformation of the cylinder block 12 and assembly of the cylinder head 44 on the bending of the cylinder block 12 in comparison with a conventional example.

In the figure, the solid line is the experimental result of the conventional example, and the coaxiality of the axis line of each crank bearing portion 20 when the inner peripheral surface is simply machined without inserting the spacer is the upper limit of the variation. It is a graph shown with a value and a lower limit. The term "coaxiality" as used herein refers to the amount of vertical displacement of the central portion of the cylinder block 12 in the cylinder row direction with respect to both ends of the cylinder block 12 in the cylinder row direction, and the axis of each crank bearing portion 20 is straight. The state of being arranged on a line is zero, a positive value when the axis is arranged on a curved line that is convex upward, and the axis is arranged on a curved line that is convex downward. Sometimes it is shown as a negative value.

In the above-mentioned conventional example, the coaxiality is substantially zero (15 μm at the upper limit and −1 at the lower limit) in the free state after the inner peripheral surface is machined.
5 μm), but when the cylinder head 44 is assembled, a negative value (upper limit value is −23 μm) due to the influence of this assembly.
m, and the lower limit value is −53 μm) (that is, a downwardly convex curve). When the engine durability test is performed at room temperature, the cylinder block 12 deteriorates and the cylinder head 4
The curvature due to the assembly of No. 4 becomes more remarkable (upper limit is -67 μm, lower limit is -97 μm). After that, when an engine durability test is performed at 35 ° C. below freezing point, a bending amount due to thermal deformation of the cylinder block 12 appears, and the coaxiality becomes substantially zero (upper limit value is 11 μm, lower limit value is −19 μm).

However, in the above-mentioned conventional example, when an engine durability test is performed at 35 ° C. below freezing after the cylinder head 44 is assembled, no bending due to deterioration of the cylinder block at room temperature does not appear, so the cylinder block 12 is thermally deformed. When the curved part due to appears, the coaxiality has a large positive value (upper limit value is 55 μm, lower limit value is 25 μm) (that is, an upward convex curve).

On the other hand, in this embodiment, since the inner peripheral surface is machined in a convex curved state, the experimental result is as follows.
As shown by the broken line in the figure, in the free state after the inner peripheral surface processing, the coaxiality is small but negative (upper limit is -3 μm,
Although the lower limit value is −33 μm), when the cylinder head 44 is assembled, it becomes a large negative value (upper limit value is −41 μm, lower limit value is −71 μm) due to the influence of this assembly. Then, when the engine durability test is performed at room temperature, a curved portion due to deterioration of the cylinder block appears, and becomes a larger negative value (upper limit value is −85 μm, lower limit value is −114 μm). However, when an engine durability test at 35 ° C. below freezing is further performed thereafter, a bending amount due to thermal deformation of the cylinder block 12 appears, and the coaxiality becomes a negative small value (lower limit value is −37 μm).

Further, in this embodiment, when the engine durability test is performed at 35 ° C. below freezing immediately after the cylinder head 44 is assembled, no bending due to deterioration of the cylinder block at room temperature does not appear, and the cylinder block 12 does not appear. Bending due to thermal deformation appears, and the coaxiality is a positive value (upper limit is 37 μm)
However, the value is considerably smaller (55-37 = 18 μm) than the coaxiality of the conventional example.

As described in detail above, according to this embodiment,
In consideration of the bending amount due to the assembly of the cylinder head 44, the cylinder block main body 14 is oriented such that the central portion of the cylinder block main body 14 in the cylinder row direction is convex upward.
That is, since the inner peripheral surface of each crank bearing portion 20 is processed in a state in which the crank bearing portion 20 is forcibly bent in the same direction as the bending direction due to the temperature decrease, the crank bearing portion 20 is processed even at low temperatures. It is possible to prevent damage to the engine, deterioration of engine startability, and seizure between the crank bearing portion 20 and the crankshaft 22.

When the axes of the crank bearings 20 are arranged on a straight line L at a predetermined temperature when the temperature is low, the crank bearings 2 are kept at room temperature or warm.
The axis of 0 is arranged on a curved line C curved so as to be convex downward, but at room temperature or warm temperature, the viscosity of oil is low and its fluidity is good, so Since the oil is sufficiently supplied and the inner diameter of the crank bearing portion is increased due to thermal expansion, there is no possibility that the crank bearing portion 20 and the crankshaft 22 will rub against each other.

[Brief description of drawings]

FIG. 1 is a process schematic diagram showing an embodiment of a method for manufacturing a light alloy cylinder block for a multi-cylinder engine according to the present invention.

FIG. 2 is a partial cross-sectional view showing the multi-cylinder engine of the above embodiment.

FIG. 3 is a diagram specifically showing how the inner peripheral surface is machined in the above embodiment.

FIG. 4 is a diagram specifically showing how the inner peripheral surface is machined in the above embodiment.

FIG. 5 is a diagram showing the influence of the cylinder head assembly on the bending of the cylinder block.

FIG. 6 is a diagram showing the results of an experiment conducted to investigate the effect of thermal deformation of the cylinder block and assembly of the cylinder head on the curvature of the cylinder block, in comparison with a conventional example.

[Explanation of symbols]

 10 Multi-cylinder Engine 12 Cylinder Block 14 Cylinder Block Main Body 16 Cylinder Liner 18 Cylinder Bore 20 Crank Bearing Part 22 Crank Shaft 24 Bearing Cap 26 Crank Shaft Metal

Claims (4)

[Claims] 1. A cylinder block liner is tightly fitted to each of a plurality of cylinder bores formed in a row on an upper portion of a cylinder block body made of a light alloy, and is then provided in a row below the cylinder bore of the cylinder block body. A method of manufacturing a light alloy cylinder block of a multi-cylinder engine by processing the inner peripheral surface of a plurality of crank bearing parts, wherein the inner peripheral surface processing of each of the crank bearing parts is performed by a cylinder of the cylinder block body. A method of manufacturing a light alloy cylinder block for a multi-cylinder engine, comprising: performing the cylinder block main body in a state in which a predetermined amount is curved in a direction in which a central portion in the row direction is convex upward. 2. The method for manufacturing a light alloy cylinder block of a multi-cylinder engine according to claim 1, wherein the tight fitting is a shrink fit performed by heating the cylinder block body. 3. A cylinder block body made of a light alloy, in which a plurality of cylinder bores are formed in a row in the upper part and a plurality of crank bearing portions are provided in a row below the cylinder bore, and each of the cylinder block bodies. A cylinder block made of a light alloy of a multi-cylinder engine having a cylinder liner tightly fitted in a cylinder bore, wherein the axis lines of the crank bearing parts are arranged in a straight line at a predetermined temperature at a low temperature, and A cylinder block made of a light alloy for a multi-cylinder engine, characterized in that at a temperature higher than a predetermined temperature, the axis lines of the crank bearings are arranged on a curved line curved in a downward convex direction. 4. The light alloy cylinder block for a multi-cylinder engine according to claim 3, wherein the cylinder liner is made of a material containing iron as a main component.