JPH11193746A - Cylinder block of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine cylinder block in which cracking and peeling of the plate coating does not occur during hot operation, even when the sleeves have a positioning part of differing thickness. SOLUTION: According to the engine cylinder block, aluminum alloy sleeves 27 are cast in cylinder bore walls 22d of an aluminum alloy cylinder body 22c and have a positioning part 27f1, which is made thicker than the other parts, and a thin part 27f2 aside from the positioning part 27f1. A plate coating is formed on the inner surface of the sleeves 27. The aluminum alloy of the cylinder body 22c contains 5 to 20 wt.% of Si. The aluminum alloy of the sleeves 27 contains Si that satisfies the equation 50<α<150 (in the equation, a represents 100 times the Si weight percentage content of the sleeves 27 divided by the Si weight percentage content of the cylinder body 22c).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder block of an aluminum sleeve casting type suitable for, for example, a motorcycle or an automobile engine.

[0002]

2. Description of the Related Art Conventionally, as a cylinder block suitable for motorcycles and automobile engines, for example, wear resistance against lubrication against piston sliding and lubrication are provided on the inner wall surface of a cylinder bore of a cylinder body made of aluminum alloy which is lightweight and has good heat conductivity. In some cases, a plating film is formed to improve the properties. However, if the plating film is formed directly on the inner wall surface of the cylinder bore of the cast product, boring is performed on the cylinder bore wall surface of the casting surface prior to plating. Would. In such a case, the adhesion of the plating film is not sufficient, and cracking or peeling occurs in the plating film due to operation of the engine, which may adversely affect engine performance. In order to prevent such peeling of the plating film, a method of manufacturing a cylinder block in which an aluminum alloy sleeve is cast in a cylinder bore of the cylinder body and a plating film is formed on the inner surface of the sleeve is disclosed. (For example, JP-A-3-90594).

[0003] In the manufacturing method described in the above publication, a sleeve is formed from an extruded or drawn material of an aluminum alloy, a molten aluminum alloy such as AC4C is poured in a state where the sleeve is placed in a mold in advance, and the casting is performed. In this method, a boring process is performed on the inner peripheral surface of the coated sleeve, a plating film is formed on the inner peripheral surface of the processed sleeve, and a honing process is performed on the plating film.

[0004]

As the specific material of the cylinder body, for example, a material containing Si is selected from the viewpoints of castability and the like in addition to its thermal conductivity and light weight. Further, the material of the sleeve must be selected from the viewpoint of the hardness required for the piston sliding surface, the adhesion of the plating film, and the like.

However, in a cylinder block of the type in which an aluminum alloy sleeve is cast into the aluminum alloy cylinder main body, particularly when the sleeve has a positioning portion which is thicker than other portions, the cylinder main body and Depending on the selection of the material of the sleeve, the coefficient of linear expansion will differ, and the cracks will occur in the plating film during engine operation.
It has been found that peeling may occur.

That is, in any of low-pressure mold casting and high-pressure mold casting, that is, die casting, Si is contained in a gap between the outer periphery of the aluminum alloy sleeve held by the support member and the matrix. The aluminum alloy bath is filled, and as the whole mold cools, the bath solidifies and shrinks in volume,
An initial tension is created between the cylinder block and the sleeve. During operation of the engine, the temperature of the combustion chamber becomes high, so that both the sleeve and the cylinder body are heated.
If the linear expansion coefficient αb of the cylinder body is larger than the linear expansion coefficient αs of the sleeve, the cylinder body thermally expands more than the sleeve, so that the tightening force between the two becomes smaller than the initial one. In this case, if the coefficient of linear expansion αb of the cylinder body is excessively large as compared with the coefficient of linear expansion αs of the sleeve, the cylinder body side thermally expands to a larger diameter than the sleeve side beyond the permissible range. In such a case, a gap is generated between the inner wall surface of the cylinder bore and the outer surface of the sleeve.

On the other hand, in the case where the expansion coefficient αb of the cylinder body is larger than the linear expansion coefficient αs of the sleeve but not excessively, if the wall thickness of the cylinder body is small, the initial temperature caused by the solidification of the molten metal during casting is increased. Even if the tightening force itself is small and the decrease in the tightening force due to thermal expansion during operation is small, a gap may be generated between the cylinder bore wall surface and the sleeve outer surface. When the tension force is reduced or a gap is formed, the heat resistance when the combustion heat in the sleeve is conducted from the sleeve through the cylinder body increases, the sleeve is overheated, and the plating film is supported. The layer is thermally degraded, and cracks and peeling are likely to occur in the plating film.

If the coefficient of linear expansion αs of the sleeve is larger than the coefficient of linear expansion αb of the cylinder body, the sleeve tends to thermally expand more than the cylinder body, but the thermal expansion of the sleeve is suppressed by the cylinder body. As a result, the tension force between the two increases, and a compressive stress is generated on the sleeve side, and a tensile stress is generated on the cylinder body side. In such a case, if the sleeve has a thick portion and a thin portion, the expansion amount of the thin portion is more suppressed by the cylinder body portion than the thick portion, so that the expansion amount of the thin portion is large. It becomes smaller than the expansion amount of the portion, and when viewed as a whole, the inner surface of the sleeve is distorted, and the strength of the plating film against the piston is generated, which causes cracking and peeling of the plating film.

If the thickness of the aluminum alloy sleeve is made too thin to reduce the weight, the sleeve may be deformed by the pressure of the hot water during casting, and the thickness of the cylinder body may be reduced to reduce the weight. If the thickness is too thin, the supply of hot water to the cylinder body during casting may not be sufficient, and there is a possibility that the thickness of the cylinder will be reduced. In this case, there is a problem that a gap is generated between the underfilled portion and the sleeve, the sleeve in that portion is heated, and the support layer of the plating film is ignited, and the plating film is easily cracked or peeled. .

Further, in the case of a water-cooled engine in which a cooling water jacket is provided on the outer periphery of the sleeve and the engine cooling water flows through the cooling water jacket, if the outer periphery has irregularities, the cooling water stagnates and the sleeve and the cylinder body portion Is not sufficiently cooled, so that it is easily affected by thermal expansion, and even if the engine is a water-cooled engine, cracking and peeling of the plating film easily occur.

The present invention has been made in view of the above circumstances, and even when the sleeve has positioning portions having different thicknesses, the plating film does not crack or peel during hot operation. It is intended to provide a cylinder block for an engine.

Further, the present invention provides a cylinder block of an engine capable of preventing the sleeve from being heated due to the underfill during the casting and preventing the plating film from cracking or peeling by preventing the underfill during casting. The purpose is to provide.

Still another object of the present invention is to provide a cylinder block of an engine in which the engine is a water-cooled engine, the influence of thermal expansion is more reliably reduced, and the plating film is not cracked or peeled off.

[0014]

According to the first aspect of the present invention, there is provided a positioning portion formed of an aluminum alloy and having a greater thickness than other portions in a cylinder bore wall of an aluminum alloy cylinder main body, and a portion other than the positioning portion. In a cylinder block of an engine in which a sleeve having a thin portion is cast and a plating film is formed on the inner surface of the sleeve, the aluminum alloy of the cylinder main body contains 5 to 20% by weight of Si. Aluminum alloy: (Si weight content of the sleeve / Si weight content of the cylinder body) × 10
When 0 is α, Si that satisfies 50 <α <150 is included.

According to a second aspect of the present invention, in the first aspect, the thicknesses of the positioning portion and the thin portion of the sleeve are ts1, ts.
2, when the thickness of the outer peripheral portion of the positioning portion and the thin portion of the cylinder body is tb1 and tb2, 1.8 m
Each thickness is set so as to satisfy m <ts1 <tb1, 1.8 mm <ts2 <tb2.

According to a third aspect of the present invention, in the second aspect, a cooling water jacket is provided on an outer periphery of the sleeve, and engine cooling water flows through the cooling water jacket, and (ts1 + tb1) and (ts2 + tb2) are defined. It is characterized by having substantially the same thickness.

[0017]

When the coefficient of linear expansion αb of the cylinder body is too large compared to the coefficient of linear expansion αs of the sleeve, the tension between the cylinder body and the sleeve becomes small, and in extreme cases, Creates a gap between the two. However, according to the first aspect of the present invention, if the aluminum alloy of the sleeve is obtained by multiplying (the Si weight content of the sleeve / Si weight content of the cylinder body) by 100, α is 50 <α.
By including Si that is <150, FIG.
As can be seen from FIG. 4, the linear expansion coefficient αb of the cylinder main body was not made excessively larger than the linear expansion coefficient αs of the sleeve, so that a gap was formed between the inner surface of the cylinder bore of the cylinder main body and the outer surface of the sleeve. It does not occur, so that an increase in thermal resistance due to the gap can be prevented, thermal deterioration of the support layer of the film due to overheating of the sleeve can be prevented, and cracking and peeling of the plating film can be prevented.

Conversely, if the linear expansion coefficient αs of the sleeve is excessively large compared to the linear expansion coefficient αb of the cylinder body, a large compressive stress is generated in the sleeve because the thermal expansion of the sleeve is suppressed by the cylinder body. However, in such a case, if the sleeve has a thick portion and a thin portion, the amount of expansion of the sleeve is reduced, and the inner surface of the sleeve is distorted. However, according to the first aspect of the present invention, the aluminum alloy of the sleeve contains Si that satisfies 50> α with respect to the above α, so that the linear expansion coefficient αs of the sleeve can be understood from FIG.
Is not excessively large compared to the linear expansion coefficient αb of the cylinder body, so that the amount of suppression of the expansion of the sleeve by the cylinder body can be reduced, so that the sleeve has a thick portion and a thin portion. Even when there is, the occurrence of distortion on the inner surface of the sleeve can be prevented, and as a result, the strength of the plating film coming into contact with the piston can be prevented, and the cracking and peeling of the plating film can be prevented.

According to the second aspect of the present invention, when the thickness of the positioning portion and the thin portion of the sleeve are ts1 and ts2, respectively, the respective thicknesses satisfy 1.8 mm <ts1 and 1.8 mm <ts2. Is set, it is possible to eliminate the possibility that the sleeve is deformed by the pressure of the molten metal at the time of casting when the thickness of the aluminum alloy sleeve is made too thin to reduce the weight.

Further, the positioning portion,
When the thickness of the outer peripheral portion of the thin portion is tb1 and tb2, respectively, the thicknesses are set so as to satisfy ts1 <tb1 and ts2 <tb2. Therefore, the thickness of the cylinder body is reduced to reduce the weight. In the case where the time has passed, it is possible to eliminate the possibility that the molten metal is not sufficiently supplied to the cylinder main body during casting and the metal is thinned. If there is a gap, a gap is created between the gap and the sleeve, the sleeve overheats, the support layer of the plating film is thermally degraded, and the plating film cracks and peels off. However, the present invention does not cause any problem.

According to the third aspect of the present invention, a cooling water jacket is provided on the outer periphery of the sleeve, and the engine cooling water flows through the cooling water jacket.
+ Tb1) and (ts2 + tb2)) are substantially the same, so if there are irregularities on the outer periphery, the cooling water will stagnate and the sleeve and the cylinder body will not be sufficiently cooled and will be easily affected by thermal expansion, and the engine will be cooled. In this case, cracking and peeling of the plating film easily occur, but no problem occurs in the present invention.

[0022]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIGS. 1 to 24 are views for explaining a cylinder block and a seal structure of a motorcycle engine according to an embodiment of the present invention.
Fig. 2 is a left side view of the motorcycle equipped with the engine,
Is a right side view of the engine, FIG. 3 is a right side view of a cylinder block, a cylinder head, and a head cover of the engine, FIG. 4 is a sectional rear view of the engine, and FIG. 5 is a cross section showing a communication hole of the cylinder block. FIG. 6, FIG. 6 is a bottom view of the cylinder block viewed from the crankshaft side, FIG. 7 is a cross-sectional side view of a rightmost cylinder portion of the cylinder block, and FIG. 8 is a cross-sectional side view of a second cylinder portion from the right of the cylinder block. 9 is a plan view of the cylinder block seen from the cylinder head side, FIG. 10 is a plan view of the head gasket, FIG. 11 is an enlarged view showing the sealing state of the head block mating surface of the cylinder block, and FIG. 13 and 14 are enlarged plan views and enlarged cross-sectional views of the cylinder body and the sleeve, and FIGS. 15 to 18 are diagrams showing the results of a drilling test of the communication hole, and FIGS. Shows a state in which honing those of FIG. 17, FIGS. 20 and 21 is a schematic view showing a plating apparatus, Figure 22, Figure 23 showing the manufacturing process, Figure 24
FIG. 3 is a characteristic diagram showing a relationship between a Si weight content of an aluminum alloy and a linear expansion coefficient. Note that the terms front, rear, left and right in this embodiment mean front, rear, left, and right when viewed in a seated state.

In FIG. 1, reference numeral 1 denotes a motorcycle, and a vehicle body frame 2 has a seat rail 4 extending rearward of the vehicle body at a rear end of a pair of left and right main frames 3 having a substantially inverted L shape in side view. The fuel tank 5 is mounted on the upper part of the main frame 3, and the main seat 6 and the tandem seat 7 are mounted on the upper part of the seat rail 4, respectively.

At the front end of the main frame 3, a front fork 9 is pivotally supported by a head pipe 8, and at the lower end of the front fork 9, a front wheel 10 is pivotally supported. A rear arm 11 is pivotally supported by a pivot shaft 12 on a rear arm bracket 3a below the rear end of the main frame 3 so as to be able to swing up and down.
A rear wheel 13 is pivotally supported at the rear end.

A rear cushion 14 is interposed between the rear arm 11 and the vehicle body frame 2. The lower end of the rear cushion 14 is connected to the lower end of a first link 14a which is arranged upright on the rear side and is supported by the rear arm 11, and the upper end is supported by the body frame. The upper end of the first link 14a is connected to the vehicle body frame via a second link 14b provided upright on the rear side of the rear cushion 14, and the second link 14b and the first link 14a are connected to the rear cushion 14. Is forming a triangle. As described above, the lower end of the rear cushion 14 is supported by the first and second links 14a and 14b which are arranged upright, so that a large space is secured below the rear cushion 14 while ensuring so-called progressive characteristics. ing.

An engine unit 15 is suspended below the main frame 3.
A radiator 16 is provided on the front side of 5. The exhaust device of the engine unit 15 is disposed between an exhaust pipe 141 connected to each exhaust port opened to the front wall of the cylinder head 23, the engine unit 15 and the rear wheel 13, and below the rear cushion 14. The first muffler 14
2 and a second muffler 1 arranged on the upper right side of the rear wheel 13
43.

The engine unit 15 is a water-cooled 4-cycle parallel 4-cylinder 5-valve engine.
Is mounted forward with the crankshaft 21 oriented in the vehicle width direction. As shown in FIG. 2, the engine unit 15 has an aluminum alloy cylinder head 23 on the upper mating surface of the aluminum alloy cylinder block 22.
And the cylinder head 2 is fastened with a head bolt.
3 Attach the aluminum alloy head cover 24 to the upper mating surface,
Further, it has a schematic structure in which an aluminum alloy oil pan 28 is connected to a lower portion of the cylinder block 22.

The cylinder block 22 comprises a cylinder body 22c and a unit case 27 integrally formed by die casting using an aluminum alloy. The unit case 27 is provided with the crankshaft 21.
And a transmission case 26 for accommodating the transmission, and the crankcase 25 and the transmission case 26
Is divided into upper and lower parts by upper and lower crankcase parts 25a and 25b and upper and lower transmission case parts 26a and 26b.

The crankshaft 21 is supported via sliding bearings 30 by a plurality of bearing bosses 29 formed on the surface of the upper and lower crankcase portions 25a and 25b. The boss portion 29 divides the crank chambers 19, 19,... For each cylinder into independent chambers, and communicates with each other through communication holes 52 described later.

In the cylinder main body 22c of the cylinder block 22, sleeves 27 formed by processing four aluminum alloy drawn pipe members are cast in parallel and at equal intervals. On the inner surface at the lower end of the sleeve 27, a relief portion 27a for relieving the cutting tool at the time of honing is formed with a diameter larger than that of the other portion.
7 is formed with a chamfered portion 27b which serves as a stopper for the crankshaft 7. A chamfered portion 27c is formed on the inner surface of the upper end of the sleeve 27 to serve as a relief when the piston is inserted and assembled. On the outer surface, a locking step 27d for preventing the sleeve 27 from coming off to the cylinder head side is provided. It is formed smaller in diameter than the part.

The sleeve 27 has a piston sliding surface 22a having a plating film a formed on the inner surface. The piston sliding surface 22a is
7 is cast into the cylinder main body 22c, a boring process is performed to remove deformation of the cylinder bore due to thermal strain during the casting, and a plating film a is formed on the processed surface by a method described later.
And a honing process is applied to the plating film a.

Here, the plating film a is formed from the upper end of the sleeve 27 to the middle of the escape portion 27a. A piston pin 3 is slidably inserted into the piston sliding surface 22a.
The small end of the connecting rod 32 is connected via 1b. The large end of the connecting rod 32 is of an upper and lower split type with a main body portion and a cap member. The main body portion is placed above the crank pin 21a of the crankshaft 21, and the cap member is put on the lower side. It is connected to the crankshaft 21 by bolting and fixing. When assembling the piston 31, the piston 31
The main body and the piston 31 are inserted into the sleeve 27 from the cylinder head side, and the main body is connected to the crankpin 21a by the cap member.

The piston 31 has a piston skirt 3
1a piston pin 31b notch recess 31 at the shaft end
This is a so-called slipper type formed by forming c. When the piston 31 descends to its bottom dead center position, the lower end 31e of the piston skirt 31a
A clearance c is opened in the escape portion 27a of the vehicle. That is, the provision of the gap c prevents the piston 31 from contacting the lower edge a 'of the plating film a, thereby preventing the plating film a from peeling off from the lower edge a'.

In FIG. 6 showing the cylinder block 22 viewed from the crankshaft side, the crankshaft-side openings of the sleeves 27, 27, 27 of the three cylinders from the right end are located on the front side wall of the upper crankcase portion 25a. 25c, a partition wall 25d defining a crank chamber and a transmission chamber, and a crankshaft bearing boss 29 surround the periphery, so that an etchant or the like overflows in the plating film forming step as described later. , Mission room 26d
It can be prevented from flowing into the side.

On the other hand, the sleeve 27 of the left end cylinder in FIG. 6 corresponds to the above-mentioned partition wall 25d because it is necessary to secure a space for disposing the reduction gear 82 and the reduction gear 82 connecting the crankshaft 21 and the main shaft 72. Not equipped. Therefore, in the left end cylinder, the effect of preventing the etching liquid and the like from flowing into the mission chamber by the partition wall 25d in the plating film forming step cannot be obtained.

Therefore, in this embodiment, in the cylinder at the left end, the sleeve 27
Retaining chamfered portion 27b formed on the outer surface of the lower end of the
The portion is covered with an aluminum alloy, and a rib-shaped dam portion 25d 'is formed integrally with the other portion and protrudes slightly toward the crankshaft from the other portions. The dam portion 25d 'prevents the etchant or the like from overflowing to the transmission case 26 side in the plating process.

Each combustion recess 23 of the cylinder head 23
The three intake ports and two exhaust ports opening to a can be opened and closed by an intake valve 35 and an exhaust valve 36. The valves 35, 36 are opened and closed by an intake camshaft 40 and an exhaust camshaft 41 via bottomed tubular valve lifters 37, 37 mounted on the upper ends. Each camshaft 40, 41
Sprocket 40 attached to the axial right end of the
a, 41a and a crank sprocket 21b formed integrally with the right end of the crankshaft 21
They are connected by two.

The cam sprockets 40a, 41a and the timing chain 4 of the camshaft driving mechanism thus configured
2 and the crank sprocket 21b are accommodated in a chain arrangement chamber 43 integrally formed on the right outer end surfaces of the cylinder block 22 and the cylinder head 23. A rotor 44 having outer peripheral teeth is mounted inside the crank sprocket 21b of the crankshaft 21, and a pickup 45 for detecting a crank rotation angle is opposed to the rotor 44. An auto-tensioner 46 automatically adjusts the tension of the timing chain 42.
7 is a chain guide.

An opening 50 for assembling the camshaft drive mechanism is formed in a portion of the outer wall 22b of the cylinder block 22 that constitutes the chain arrangement chamber 43, facing the shaft end of the crankshaft 21. The opening 50 has a lid member 5.
1 is detachably bolted. By communicating the adjacent crank chambers 19 with each other, the communication hole 52 for reducing the pumping loss due to the reciprocating movement of the piston is positioned in the assembling opening 50 when viewed in the crankshaft direction. And is formed so as to form the same axis parallel to the crankshaft 21.

Here, the communication hole 52 has a circular cross section formed by inserting a long drill from the assembling opening 50 in a step between the plating process and the honing process. It is. And the communication hole 5
The machining center point 2 is set at a position deviated toward the cylinder head from the crankshaft end 27e of the sleeve 27. The sleeve 27 has a higher hardness than the upper crankcase portion 25a.

As described above, in this embodiment, when a circular hole is formed by drilling so as to extend over both the upper crankcase portion 25a and the sleeve 27 having different hardnesses,
Since the center of the drill is set to be deviated toward the high-hardness sleeve 27 side, escape of the drill can be avoided, and machining accuracy and workability can be improved. This escape avoiding effect is achieved by the overhang portion (FIG. 7, FIG. 7) that prevents the drill from moving toward the high-hardness member because the center of the drill is located on the high-hardness member side.
It can be considered that this is obtained by the presence of the region 52b in FIG. 8). By the way, when the processing center point b is deviated toward the upper crankcase portion 25a side with low hardness, there is a possibility that the drill processing center may be shifted away from the high hardness sleeve.

Further, the communication hole 52 is disposed so as to face the notch 31c and the piston pin 31b when the piston 31 descends to the bottom dead center.
The distance from the upper edge 52a to the lower edge of the oil ring 31d at the lower end of the piston 31 located at the bottom dead center is 3
The center position b is set to be not less than mm, preferably not less than 7 mm.

The center position of the communication hole 52 is set as described above for the following reason. That is, the communication hole 52
Is formed, burrs and deformations of an unacceptable degree occur on the periphery as a piston sliding surface. The burrs and the like are removed by the subsequent honing process. However, in a range of about 3 mm from the edge of the communication hole 52, it may not be possible to sufficiently remove the burrs as a piston sliding surface. Was found.

FIGS. 15 to 19 show the results of experiments conducted to investigate the state of occurrence of burrs and the like when the through holes 52 are formed and the surface finish by honing. In addition,
In each of the figures, the actual dimensions are shown in the vertical direction (cylinder axial direction), while 10 mm in the horizontal direction.
It is shown enlarged to 00 times.

FIGS. 15 to 18 show burrs and the like in the first to fourth cylinders when a through hole is formed by forming a plating film on each sleeve of the experimental cylinder block and then inserting a drill in the direction of the arrow shown in the drawing. Indicates the occurrence status. In each figure, the right part shows the situation when the drill penetrates the plating film and enters the sleeve, and the left part shows the situation when the drill penetrates the plating film from inside the sleeve and enters the cylinder body. Burrs are 5 to 3 in any cylinder.
It can be seen that it is about 0 μm.

FIG. 19 shows the state of the piston sliding surface after honing. As is apparent from the figure, the burrs and the like are removed by honing, and in a portion above a point 3 mm from the upper edge 52a of the through hole 52, α μm (for example, set as an allowable dimension as a piston sliding surface) (for example, 5 μm). Therefore, when the piston 31 is located at the bottom dead center, the lower edge of the oil ring 31d disposed at the bottom and the upper edge 5 of the through hole 52
By setting the dimension 2a to be larger than 3 mm, the gap between the oil ring 31d and the piston sliding surface can be set within an allowable range, and the occurrence of output loss due to an increase in sliding resistance can be prevented.

As shown in FIG. 5, each of the bearing bosses 29 of the upper crankcase portion 25a has
A lubricating oil passage 53 is formed to communicate the bearing 30 with the inner peripheral surface of the communication hole 52. A cooling nozzle 54 is inserted into the lubricating oil passage 53, and an injection port 54a of the nozzle 54 is directed so as to jet lubricating oil from the notch 31c of the piston 31 located at the bottom dead center to the back surface of the piston. doing. The thickness of the bearing boss portion 29 in the direction of the crankshaft at the communication hole 52 is W2 on the crankshaft side and W1 on the piston side. Therefore, the lubricating oil injected from the injection port 54a
Is reliably supplied to the back surface of the piston without being hindered by the periphery of the piston or the piston skirt, and the piston 31 can be cooled reliably.

The cylinder block 22 has a sleeve 2
A water cooling jacket 90 is formed so as to surround 7.
The depth of the portion of the water cooling jacket 90 excluding the chain arrangement chamber 43 side is 110 to 12 in crank angle from top dead center.
It is set so as to coincide with the upper end surface of the piston 31 at the position lowered by 0 °. On the other hand, the water cooling jacket 90
Is set so as to coincide with the vicinity of the upper end surface of the piston 31 located at the bottom dead center, and the height of the bottom wall 90b of the water cooling jacket portion 90a in the cylinder axial direction. The height is set to be slightly lower than the height of the upper edge 50a of the assembling opening 50. The water-cooled jacket 90 is open over the entire circumference at the head-side mating surface.
Blocked by 1.

Since the portion 90a of the water cooling jacket 90 on the side of the chain arrangement chamber 43 is formed deeper than the other parts, the provision of the chain arrangement chamber 43 improves the cooling performance of the arrangement chamber 43 of the cylinder block. It can compensate for the decrease. That is, the portion surrounding the sleeve 27 of the cylinder block 22 is also cooled by direct contact with the traveling wind, but the right end portion of the cylinder block 22 in FIG. , And there is a concern that the cooling performance is reduced. In the present embodiment, the chain arrangement chamber side portion 90 of the cooling jacket 90 is used.
Since a is formed deeper, it is possible to compensate for a decrease in cooling performance due to the absence of the traveling wind.

The height of the bottom wall 90b of the water cooling jacket portion 90a of the cylinder block 22 in the cylinder axial direction is set to be slightly lower than the height of the upper edge 50a of the mounting opening 50 (see FIG. 4). Therefore, the casting mold of the portion can be simplified. That is, the bottom wall 90
When b is higher than the upper edge 50a, a slide type is required, but is not required in the present embodiment.

A gasket 91 is interposed between the mating surfaces of the cylinder block 22 and the cylinder head 23.
The gasket 91 has three thin plates 92, 93, 94 cut in accordance with the mating surface shape of the cylinder block 22.
While overlapping with the same gap as the thin plate,
A concentric cylinder bore bead portion 91a having a diameter larger than that of the sleeve 27 is formed so as to surround the sourb 27, and a peripheral bead portion 91b having a shape along the periphery of the mating surface is formed.
Further, the chain chamber bead portion 91c and the like along the opening edge of the chain arrangement chamber 43 are formed by press molding or the like. Each of the bead portions 91a to 91c has a configuration in which the central thin plate 93 is kept flat, the upper and lower thin plates 92 and 94 are bent so as to abut on the central thin plate 93, and the peripheral edge is fixed by caulking. Has become. FIG. 11 is schematically shown to emphasize the bead portion and the gap.

The gasket 91 is connected to the cylinder block 2
2 and the cylinder head 23 are interposed between the mating surfaces, and the two are tightened with a head bolt.
The bending point p of 1b is pressed on the mating surface, and at the same time, the upper and lower thin plates 92 and 94 are pressed against the central thin plate 93, whereby the cylinder block 22 and the cylinder head 2 are pressed.
The space between the three is sealed.

In FIGS. 2 and 4, reference numeral 70 denotes a transmission mainly disposed in the upper transmission case 26a.
And a drive shaft (output shaft) 74 provided with an output gear group 73 which meshes with the input gear group 71 below the main shaft 72. They are arranged in parallel.

The drive shaft 74 is connected to the crankshaft 2.
1 is disposed between bearing surfaces of the upper and lower transmission case portions 26a and 26b in the same manner as that of the upper and lower crankcase portions 25a and 25b. Supported. The main shaft 72
Are arranged in the upper transmission case 26a,
The left end of the main shaft 72 is the upper transmission case 26a.
Are supported via bearings 76. The right side portion is supported by a right side wall 26g of the upper transmission case portion 26a via a bearing 77 and a flange 78, and the flange 78 is bolted and fixed to the right side wall 26g.

The left end of the drive shaft 74 protrudes outward from the transmission case 26, and the drive sprocket 79 mounted on the protrusion is connected to the rear wheel sprocket 13a of the rear wheel 13 via a chain 80. Have been. A clutch mechanism 8 is provided at the right end of the main shaft 72.
1 is attached. The clutch mechanism 81 meshes with a reduction gear 82 of the crankshaft 21, and is connected to an outer drum 84 via a damper to a reduction gear 83 supported on the main shaft 72, and is spline-connected to the main shaft 72. It has a structure in which a number of clutch plates 86 are interposed between the inner drum 85 and the clutch plate 86. The clutch mechanism 81 turns off and on the engine power by rotating a push lever 87 connected to the inner drum 85.

A shift drum 90, an input-side fork shaft 91, and an output-side fork shaft 92 are disposed in parallel with the main shaft 72 and the drive shaft 74 on the rear and obliquely rear side thereof. The right and left ends of the fork shafts 91 and 92 are supported by right and left bosses integrally formed with the upper transmission case 26a.

One input-side shift fork 93 is provided on the input-side fork shaft 91, and the output-side fork shaft 9 is provided on the input-side fork shaft 9.
2, two output-side shift forks 94, 94 are mounted movably in the axial direction. The shift fork 93,
The forked claw portion 94 has an input gear group 71 and an output gear group 73.
An engagement pin slidably engaged with the sliding grooves 71b, 73b formed on the gears of the first and second shift forks 93, 94 is formed on the outer peripheral surface of the shift drum 90. It is slidably engaged with the guide groove. By rotating the shift drum 90 by a change mechanism (not shown), the shift forks 93 and 94 slide in the axial direction to move the gears of the input gear group 71 and the output gear group 73, and as a result, Switching is performed between the lowest speed stage and the highest speed stage.

Next, the crankshaft 21, the main shaft 72,
The positional relationship between the drive shaft 74 and the drive shaft 74 will be described mainly with reference to FIG. In the main shaft 72, the first shaft angle θ1 formed between the crankshaft / main shaft straight line A connecting the shaft center of the main shaft and the shaft center of the crankshaft 21 and the cylinder axis 20 on the cylinder head side and the main shaft side is an acute angle. In other words, it is disposed at a position closer to the cylinder head 23 side than a straight line C passing through the axis of the crankshaft 21 and perpendicular to the cylinder axis 20.

The drive shaft 74 has a main shaft / drive shaft straight line B and a crank shaft / main shaft straight line A connecting the shaft center of the drive shaft 74 and the shaft center of the main shaft 72 on the drive shaft side and the crank shaft side. Are arranged so that the second axis angle θ2 formed by the first angle becomes an acute angle. In this manner, the main shaft 72 and the drive shaft 74 are arranged so as to be carried on the back surface of the cylinder block 22.

The maximum outer peripheral surface (the outer peripheral surface of the large reduction gear) 81a of the clutch mechanism 81 is formed by a straight line D passing through the top surface of the piston 31 'located at the bottom dead center and making a right angle with the cylinder axis 20. Located on the side. The main shaft 72, the shift drum 90, the fork shafts 91 and 92, and the drive shaft 74 are located in the axial projection plane of the reduction gear 83 of the clutch mechanism 81.

As shown mainly in FIG. 2, the cooling water pump 100 and the lubricating oil pump of the present embodiment are both housed and arranged in the lower transmission case portion 26b. It is arranged below and parallel to the shaft 21 and the drive shaft 74.
The driven sprocket 108 attached to the right end of the pump shaft 102 is connected to the main shaft 7 via a chain 109.
It is connected to a drive sprocket 110 mounted on a portion outside the second flange 78. The cooling water discharged from the cooling water pump 100 is supplied to the cooling water passages 119, 123a,
It is supplied to the cooling jacket 90 via 123b.

The lubricating pump sucks the lubricating oil in the oil pan 28 through the oil strainer 120 and removes the lubricating oil from the oil filter 121 attached to the front wall of the lower crankcase portion 25b to the main gallery 122. Via the crankshaft 21, the main shaft 72, the drive shaft 7
4 and the camshafts 40, 41 and the like to each engine lubrication section.

Here, as shown in FIG. 3, the lubricating oil for the valve operating mechanism is supplied from an oil passage 126 opened between the first cylinder intake side of the cylinder head 23 and the chain arrangement chamber 43 to the intake side camshaft. The oil is supplied to an oil passage 127 extending along 40 and is supplied to an oil passage 129 extending along the exhaust camshaft 41 by an oil passage 128.
The lubricating oil that has lubricated the camshaft bearings is recovered into the oil pan 28 through an oil return passage formed between the exhaust sides of the third and fourth cylinders of the cylinder head 23.

In FIG. 2, reference numeral 135 denotes a starting motor, which is arranged in parallel with the crankshaft 21 on the back of the cylinder body 22c of the upper transmission case 26a. The output of the starting motor 135 is transmitted to the crankshaft 21 via the intermediate gear 138, the starting gear 139, the one-way clutch 14, and the large reduction gear 83.

Here, the structure of the cylinder body 22c and the sleeve 27 of the cylinder block 22 will be described in more detail with reference to FIGS. The sleeve 27 of the present embodiment
Positioning part 27f of thickness ts1 and circumference L1 at every 0 degree interval
1 and a portion other than the positioning portion has a thickness ts.
2, a thin portion 27f2 having a circumference L2 (> L1). The thicknesses of the positioning portion 27f1 and the thin portion 27f2 of the cylinder bore wall 22d surrounding the sleeve 27 of the cylinder body 22c are tb1 and tb2, respectively. In this case, (ts1 + tb1) = (ts2 + t)
b2). That is, the cylinder bore wall 22d
The outer peripheral surface has a smooth shape with no irregularities to prevent stagnation of cooling water.

Here, the thickness ts of the positioning portion 27f1
1 is about 2.5 to 4.5 mm, the thickness ts2 of the thin portion 27f2 is about 1.25 to 3.25 mm, the thickness tb1 of the cylinder bore wall 22 is about 3.2 to 5.2 mm,
tb2 is set to about 4.25 to 6.25 mm, and within this range, the above (ts1 + tb1) =
A dimension that maintains (ts2 + tb2) is selected.

The position of the positioning portion 27f1 is set so that the cylinder bores are not located in the region A where the cylinder bores are adjacent to each other. The thickness of the sleeve 27 on the straight line C connecting the centers of the cylinder bores in the region A is set as follows. t
s2, and the thickness tb3 of the cylinder bore wall 22d is 2.
It is set to about 2 to 5.2 mm. The thicknesses are selected so as to satisfy the following relationship. (Tb3 + 2 × ts2)> (ts1 + tb1) = (ts
2 + tb2)> (tb3 + ts2) That is, when the total thickness of the cylinder bore wall and the sleeve is viewed, the thickness of the region A is greater than the thickness of the other region B, but the difference is the sleeve 27. Is set within the thickness ts2 of the thin portion 27f2. Since the thickness of the region A is shared by adjacent cylinder bores, the thickness of one cylinder bore is の of the above (tb3 + 2 × ts2), and the thickness of the region B
It can also be seen as thinner.

A groove M is formed on the outer periphery of the sleeve 27 by machining to surround the sleeve. The concave groove M locks the cylinder bore wall 22d by casting, and functions as a stopper.

Further, the cylinder body 22c of this embodiment,
Each of the sleeves 27 is made of an aluminum alloy. In the case of an aluminum alloy, as shown in FIG. 24, the coefficient of linear expansion changes according to the wt% (weight content) of Si. Specifically, S
When i changes from 23 to 0 wt%, the linear expansion coefficient becomes 16 to 2
It changes within a range of 3 × 10 ⁻⁶ / K. Therefore, a desired coefficient of linear expansion can be obtained by changing the weight content of Si. In the present embodiment, in view of appropriately setting the linear expansion coefficient in addition to ordinary castability, mechanical strength, and the like,
Is selected.

Here, the sleeve 27 of this embodiment has four positioning portions 27f1 on the outer surface at intervals of 90 degrees. This positioning portion 27f1 has a thicker thickness t than other portions.
s1 to prevent the sleeve 27 from moving in the circumferential direction within the cylinder bore wall 22d of the cylinder body 22c. The portion of the sleeve 27 other than the positioning portion 27f1 is
The thin portion 27f2 has a thickness ts2 smaller than f1.

In this embodiment, the aluminum alloy of the cylinder body 22c contains 5 to 20% by weight of Si, thereby improving the castability and improving the S alloy.
The deterioration of the machinability due to excessive i is prevented. The aluminum alloy of the sleeve 27 is (the sleeve 27
If the value obtained by multiplying the Si weight content of the cylinder body portion / Si weight content of the cylinder body portion 22c) by 100 is α, 50 <α
Si that satisfies <150, specifically, Si shown in Tables 1 to 3 described below.

Here, in this embodiment, the weight content of Si in the aluminum alloy of the sleeve 27 is expressed by the following formula: (Si weight content of the sleeve 27 / the cylinder body 2
If the value obtained by multiplying the Si weight content of 2c) by 100 is defined as α, 50 <α <150 is satisfied for the following reason.

That is, when α <50 for α, as can be seen from FIG. 24, the Si of the cylinder body 22c
The content is too small as compared with the Si content of the sleeve 27, so that the linear expansion coefficient αb of the cylinder body 22c is too large as compared with the linear expansion coefficient αs of the sleeve 27,
The cylinder body 22c side is thermally expanded to a larger diameter than the sleeve 27 side beyond the allowable range, and in extreme cases, a gap is generated between the inner surface of the cylinder bore wall 22d and the outer surface of the sleeve.
In order to prevent this, α> 50 in the present embodiment.

On the other hand, when α> 150, the Si content of the sleeve 27 becomes too small compared to the cylinder body 22c, so that the linear expansion coefficient α
s becomes excessively large as compared with the linear expansion coefficient αb of the cylinder body 22c, and the sleeve 27 tends to thermally expand beyond the allowable range more than the cylinder body 22c, and the thermal expansion is suppressed by the cylinder body 22c.
Excessive compressive stress is generated on the sleeve 27 side, and excessive tensile stress is generated on the cylinder body 22c side.

The sleeve 27 of the present embodiment has a thick part (positioning part 27f1) and a thin part (thin part 27f2), and the thin part is expanded more by the cylinder body 22c than the thick part. As a result, the inner surface of the sleeve 27 is distorted.
In this embodiment, α <150 is set to prevent this.

The positioning portion 27 of the sleeve 27
ts1 = 3.5 mm, f1 and the thickness of the thin portions 27f2 other than the positioning portion 27f1 of the sleeve, respectively.
Assuming that ts2 = 2.25 mm, 1.8 mm <ts1,
Since each thickness is set so as to satisfy 1.8 mm <ts2, a machining allowance is given to the cylinder bore side, and the thickness after machining after casting becomes 1.9 mm or 2.0 mm or more. .

Further, the positioning portion 2 of the sleeve 27
The cylinder body 22d which is the outer periphery of 7f1 and the cylinder body 22d which is the outer periphery of the thin portion 27f2 of the sleeve
Tb1 = tb1
4.0 mm and tb2 = 5.25 mm. That is,
The surface of the cylinder bore wall 22d surrounding the sleeve 27 of the cooling water jacket 90 has a smooth cylindrical shape without irregularities.

Next, the manufacturing process of the cylinder block 22 of this embodiment will be described. Cylinder block 22 of the present embodiment
As the aluminum alloy for die-casting of the cylinder body portion 22c, the upper crankcase portion 25a, and the upper transmission case portion 26a (hereinafter sometimes referred to as a cylinder block base material), the aluminum alloys in Table 1 below are used. use. In the case where the cylinder block 22 is formed by a low-pressure mold casting as another embodiment, a JIS standard aluminum alloy shown in Table 2 can be used. As the aluminum alloy for the sleeve 27 cast in both embodiments, the alloys shown in Table 3 can be used.

[0079]

[Table 1]

[0080]

[Table 2]

[0081]

[Table 3] As shown in Tables 1 to 3, the base aluminum alloy contains 5 to 20% (% by weight) of Si,
As the aluminum alloy, an aluminum alloy having a Si content such that 50 <α <150, where α is (weight content of Si in sleeve 27 / weight content of base material) × 100, is used.
By forming each of the base material and the sleeve using the aluminum alloy having such a configuration, the difference in the coefficient of thermal expansion between the base material and the sleeve is reduced, and a heat spot is generated between the base material and the sleeve, and the inner circumference of the sleeve is reduced. Thermal deformation of the surface is reduced, and peeling of the plating film a applied to the inner peripheral surface of the sleeve is suppressed.

For example, when the cylinder block base material is formed by AC4C shown in Table 2, since the Si content by weight of the base material is 6.5 to 7.5%, alloy 1 or alloy 2 shown in Table 3 is used. , The Si content is, for example, 3.75 to
An alloy changed to 9.75% by weight is used to satisfy the condition of Si content by weight of the sleeve / Si content by weight of the base material. Similarly, when the cylinder block base material 60 is formed by the ADC 10,
Since the weight content is 7.5 to 9.5%, in the alloy 1 or the alloy 2 in Table 3, the Si content is set to, for example, 4.7.
An alloy changed to 5 to 15% by weight is used so as to satisfy the condition of Si weight content of the sleeve / Si weight content of the base material.

Further, as shown in Table 3, the aluminum alloy of the sleeve has a C content of at least 0.2 to 10 each.
Contains both u and Mg. Thereby, the hardness can be easily increased to HB70 or more by performing the T6 treatment as described below. Even when only one of Cu and Mg is contained, the hardness can be easily increased to HB 70 or more by performing T6 treatment. Further, as shown in Tables 1 and 2, the base aluminum alloy contains one or both of Cu and Mg. This makes it possible to easily increase the hardness by performing T6 treatment on the base material together with the sleeve as described below, and to increase the rigidity of the entire cylinder block while improving the plating holding capacity of the plating layer support portion of the sleeve. And the durability of the engine can be improved.

FIG. 22 is a flowchart for explaining a manufacturing process of the cylinder block 22 by casting the sleeve 27. In this flow, step S
No. 0 is composed of an extrusion process using a standard aluminum alloy pipe material and a cutting process for providing the entire length as a material. Thick portion 27f1 which becomes a positioning portion on the periphery of the series by extrusion and thin portion 27f outside the positioning portion
The shape of No. 2 and the inner peripheral shape with the machining allowance are formed. In step S1, T6 processing is performed. This T6 treatment is based on JIS standard H5202, and after aging at a predetermined temperature, a single body of the sleeve or the entire cylinder block into which the sleeve is cast is heat-treated in order to increase the surface hardness of the inner peripheral surface serving as the plating film support portion of the sleeve. It will cure.

Thereafter, sleeve machining (step S)
In 3), the inner circumference of the sleeve, the inner ends of the outer circumference of the sleeve, and the middle part in the longitudinal direction of the outer circumference of the sleeve 27 as shown in FIG.
Then, in step S5, cylinder die casting for casting the sleeve 27 is performed. In the casting in this case, while the sleeve is housed in the mold and a part of the inner periphery of the sleeve is supported by a support member, a molten metal of a predetermined aluminum alloy is applied at a high pressure to a gap between the mold and the outer periphery of the sleeve. Perform by guiding. Then, in step S7, the cylinder block 2
2 and machining of the cylinder bores is performed.

Although the T6 process is performed in step S1 in the present embodiment, steps S1, S4, S6
May be performed only once. It is desirable that the surface hardness of the sleeve be HB 70 or more (70 to 150) by such T6 treatment. When the surface hardness of the inner peripheral surface is set to HB70 or more by extrusion or drawing of the sleeve, the surface hardening treatment can be omitted by the subsequent T6 treatment.

It should be noted that T in either of steps S1 and S4
According to the sixth treatment, the hardness of only the sleeve can be increased. At the time of casting, the hardness of the sleeve slightly decreases due to the heat of the base material in the molten state, but the casting time itself is shorter than that of the T6 treatment, and the hardness of the inner peripheral side of the sleeve can be maintained at HB70 or more. Further, according to the T6 process in step S6, the hardness of the base material of the cylinder block can be increased in addition to the increase of the hardness of the sleeve, the rigidity of the entire cylinder block can be increased, and the sliding of each part due to the engine vibration. It is possible to prevent a decrease in engine durability due to, for example, an increase in sliding wear due to a decrease in clearance of the portion. Then, at the time of casting, the molten metal shrinks in the process of solidifying in the gap, so that the sleeve is tightened from the outside. Therefore, T6 in steps S1 and S6 for the sleeve is effective.

In this embodiment, the outer peripheral shot blast (step S3) may be performed as needed. The outer peripheral shot blast (Step S3) is for forming fine irregularities on the outer peripheral surface of the sleeve to improve the bonding property with the base material. By forming the irregularities on the outer peripheral surface of the sleeve before casting the sleeve, the sleeve can be reliably prevented from coming off even if the tension force is reduced due to the difference in the coefficient of thermal expansion between the base material and the sleeve during operation. Such irregularities on the outer peripheral surface of the sleeve may be caused by other machining than shot blasting or by pickling (etching) the entire sleeve.
And the like. Further, instead of a method of forming irregularities on the outer periphery of the sleeve by shot blasting or the like to enhance the bonding property with the base material, the sleeve and the base material may be bonded by using low melting point solder to prevent the sleeve from coming off. .

Here, the shot blast means that the particle size is 50.
１５０150 μm steel balls, carbide beads, stainless steel balls, zinc beads, glass beads, river sand containing a lot of quartz having a slightly larger particle size, etc., with a projector, for example, 40 to 80 m /
This means that a workpiece is projected at a projection speed of s. In addition, after the plating process in step S8, a honing process (step S9) of the cylinder bore to be plated is performed.
Cleaning of the cylinder block 22 (Step S9) is performed.

FIG. 23 shows the plating process (step S).
8) is a detailed flowchart, and FIGS. 20 and 21 are block diagrams of a plating apparatus for performing this plating process.
In the flowchart of FIG. 22, the plating on the inner surface of the sleeve is basically performed by a degreasing process (step S11).
It consists of five steps: a pretreatment consisting of an alkali etching treatment (step S13) and a mixed acid etching treatment (step S15); an alumite treatment (step S17) of a base treatment; and a composite plating treatment (step S19). Washing process (steps S12, 14, 16, 1
8, 20) are performed.

In the above-mentioned water washing process, two separate water tanks (a total of 10 tanks) are used for each step, and the entire cylinder block is sequentially immersed in the two water tanks and moved up and down to remove the processing liquid of the previous step. Things. The water in the aquarium is regularly replaced with fresh clean water. It is desirable to move to the next step as soon as possible after completion of each water washing treatment, and to carry out the next treatment with a water film on the surface. Accordingly, it is possible to prevent dust or the like from adhering to the processing unit and to prevent oxygen in the air from directly touching, thereby preventing formation of an oxide film and the like, and improving reliability of processing in a later step. This is particularly effective in the case of plating.

As shown in FIGS. 20 and 21, the sleeve 2
The cylinder block 22 in which the base material 7 is cast is used to perform various treatments on the inner peripheral surface of the sleeve 27.
The gasket 101 for sealing is placed on a dedicated apparatus main body 100a, 100b in each process with the mating surface of 2c facing downward.
a, 101b. In each process, the processing solution 105a in the dedicated processing solution tank 102a, 102b,
105b is supplied into the apparatus main bodies 100a and 100b by dedicated pumps 106a and 106b,
7 and returns to the processing liquid tanks 102a and 102b through the inner cylinders 107a and 107b.

FIG. 20 shows the state of the alkali etching and the mixed acid etching. Since the range of the etching process needs to have a margin with respect to the range of formation of the plating film, the range of the etching process is set to the vicinity of the end of the escape portion 27a of the sleeve 27 on the crankshaft side. The management of the processing range in this case is performed by the upper end surface 107 of the inner cylinder 107a.
It is performed by controlling the liquid level of the processing liquid 105 according to the height position of a ', but there is a limit in performing this method with high accuracy. If the etching liquid 105 overflows to the transmission case 26 side or the like, the processed surface on the transmission case 26 side of the cylinder at the left end in FIG. 6 may be roughened.

Therefore, in the present embodiment, the left end cylinder is provided with the rib-shaped dam portion 25d 'on the transmission case 26 side portion as described above, whereby the etching solution is transferred to the transmission case side. Overflow can be prevented.

The gaskets 101a and 101b are sealing materials for preventing leakage of the processing liquid in each processing step, and are used in the alumite processing step (step S1).
7) and in the composite plating step (step S19), it functions as an insulating material for electrolytic action. In the alumite treatment step and the composite plating step, for example, as shown in FIG.
A DC voltage is applied between the cylinder main body 22c and the inner cylinder 107 via the control circuit 110 to flow a DC current into the electrolyte. In the other steps, no DC current is passed through the processing solution.

The composite plating process is a high-speed plating process. Under a predetermined plating condition, a plating solution 105b in a dedicated processing solution tank 102b is pumped by a pump 106b into the apparatus main body 10.
0b, and is supplied through the inner cylinder 107b.
A plating film is formed on the inner surface of the sleeve 27 while circulating a path such as returning to b at a high speed. In this high-speed plating step, the inner cylinder 107b is placed on the (+) side of the power supply circuit.
The cylinder body 22c is connected to the (-) side, and a direct current flows through the plating solution. As a result, Ni ⁺ and P ^{+ in} a plating solution having a composition described later adhere to the inner peripheral surface of the sleeve, and accordingly, SiC particles serving as a dispersant are caught in the plating layer. Thus, the plating film a containing SiC and having excellent wear resistance and circulating properties is formed on the inner peripheral surface of the sleeve.
It is formed to a thickness of 150 μm.

In the high-speed plating process in step S19, the cover 111 is attached to the upper end of the sleeve 27. This cover 111 is used for the plating solution 10 circulating at high speed.
5b is prevented from being scattered and spouted, and the plating range on the inner surface of the sleeve 27 is restricted. Plating range is sleeve 2
7 is restricted to the range from the gasket 101b which is the boundary with the cylinder head to the O-ring 112 of the cover 111. Therefore, by setting the position of the O-ring 112 in the middle of the escape portion 27a, the lower end of the outer peripheral surface of the piston 31 can be prevented from contacting the lower end a 'of the plating film a as described above.

After the composite plating process in step S19, the washing process is again performed in step S20 to remove the plating solution, and the water adhering to the cylinder block 22 is removed by air blowing in step S21. After the above plating step S8, a honing finish is applied to the plating layer on the inner peripheral surface of the sleeve 27 in a honing step S9, and the thickness of the plating film is preferably about 50 μm.
m, and in some cases, 20 μm to 100 μm, and the surface roughness of the plating layer is 1.0 μmRz or less. As a result, the surface of the plating layer can be surely smoothed, the coefficient of friction at the time of sliding of the piston 31 and the piston ring 31d can be reduced, and the retention of engine oil is improved and lubricity is improved. be able to. Note that Rz is defined in JIS B0601.

Next, the operation and effect of this embodiment will be described. In the present embodiment, the cylinder body 22c, the upper crankcase 25a, and the upper transmission case 26a are integrally formed by die casting of an aluminum alloy, so that the number of parts can be reduced and the weight can be reduced.

Further, a sleeve 27 made of an aluminum alloy drawn pipe material is cast into the cylinder main body 22c, and a plating film a is formed on the inner surface of the sleeve 27. Since there is no pit as in the case where a plating film is directly formed on a casting surface, the adhesion of plating is good and the defective production rate can be reduced.

In forming the plating film a,
Since the high-speed plating method in which the plating solution is circulated at a high speed between the inner surface of the sleeve 27 and the processing solution layer is adopted, the productivity is reduced as compared with the method of immersing the entire work in the stationary bath and plating. Can be improved.

The upper edge 26c of the upper transmission case 26a for accommodating the transmission is connected to the cylinder body 22c.
20 and 21, it is mounted on the plating apparatus main bodies 100a and 100b with the cylinder head side facing downward in the plating process as shown in FIGS. In this case, the upper edge portion 26c of the upper mission case portion 26a is
a, 100b, so that the work can be easily supported in the plating process, and the workability of the plating process can be improved.

Further, as shown in FIG. 2, the crankshaft 21, the main shaft 72, and the drive shaft 74 are connected to a first shaft angle θ1 between the crankshaft / main shaft straight line A and the cylinder shaft 20, and the shaft straight line. A and main axis / drive axis straight line B
Are arranged so as to form an acute angle with each other, the distance between the crankshaft 21 and the drive shaft 74 can be reduced, and the longitudinal length of the engine can be shortened. The amount of overhang from the portion 22c can be reduced, and from this point, the work can be easily supported, and the workability of the plating process can be improved.

Further, since the main shaft 72 is arranged closer to the cylinder head 23 side than the right-angled straight line C passing through the crankshaft 21, the main shaft 72 is arranged to be carried on the back of the cylinder block 22. 15 can be further reduced. Further, since the clutch mechanism 81 is disposed such that its maximum outer peripheral surface 81a is located on the cylinder head 23 side with respect to the right-angled straight line D passing through the piston top surface at the bottom dead center, the engine unit 15 can be downsized from this point as well.

Since the main shaft 72, the shift drum 90, the fork shafts 91 and 92, and the drive shaft 74 are arranged in the axial projection plane of the largest diameter portion of the clutch mechanism 81,
The arrangement of each shaft is compact, the protrusion of the unit case 25 can be reduced, and the engine can be downsized from this point as well.

The lower end of the sleeve 27 (cylinder inner wall) constituting the piston sliding surface 22a of the cylinder main body 22c and a portion on the side of the transmission case 26 project toward the crankshaft 21 as compared to the anti-transmission case. Since the rib-shaped weir portion 25d 'is provided, it is necessary to extend the sleeve 27 to the crankshaft 21 side more than necessary in the above-described plating process, especially when the processing liquid such as the etchant liquid overflows to the transmission case 26 side. It is possible to prevent the already processed surface from being roughened by an etching solution or the like.

In providing the weir 25d ',
The weir portion 25d 'is provided only on the transmission case side portion of the cylinder having the output take-out portion between the crankshaft bearing boss portions 29, and the other cylinders are partitioned between the crank chamber and the transmission chamber for the other cylinders. The partition wall 25d, which is higher than the lower end of the piston sliding surface 22a (sleeve 27) in the direction of the cylinder axis 21, is provided.
d 'can also be used.

Further, the sleeve 27 (cylinder inner wall)
A relief 27a having a diameter larger than that of the piston sliding surface 22a is formed at the end of the cran shaft side, and the plating film a is removed from the relief 27a.
And a gap c is formed between the lower end of the piston 31 and the lower edge a 'of the plating film when the piston 31 is lowered to the bottom dead center position. Therefore, the edge a 'of the plating film a is
Without coming into contact with the outer peripheral surface of the plating film a, the problem of peeling and falling off from the edge of the plating film a can be avoided.

When the piston 31 descends to the bottom dead center, the lower end of the piston 31 is made to overlap the relief 27a, so that the engine height can be reduced while having the same piston stroke. That is, when the relief portion is not provided, it is necessary to increase the length of the sleeve in order to prevent the lower end of the piston from abutting against the edge of the plating film, and the height of the engine increases accordingly.
In this embodiment, this problem can be avoided.

When a communication hole 52 having a circular cross section for communicating the cylinder crank chambers 19 with each other is formed at the boundary between the sleeve 27 inserted into the cylinder body 22c and the crankcase 25 by a drill. Machining center point b
Is displaced toward the sleeve 27 from the boundary between the sleeve 27 and the crankcase portion 25, so that the communication hole 52 can be easily and reliably formed at a predetermined position. Incidentally, when the processing center point b is deviated toward the upper rank case portion 25a side of low hardness, the drill processing center may be shifted away from the sleeve.

When the communication hole 52 is formed so as to penetrate the piston sliding surface 22a of the sleeve 27, when the piston 31 is located at the bottom dead center position from the communication hole upper edge 52a of the piston sliding surface 22a. Oil ring 31a at the lower end
Is set to 3 mm or more, the piston ring can be slid only in the portion where the surface roughness or the like is within an allowable range by honing the piston sliding surface 22a. The problem that the gap with 22a becomes narrower than the allowable dimension can be solved.

Further, since the communication hole 52 is formed so as to be located in the assembling opening 50 of the camshaft drive mechanism provided on the outer wall 22b of the cylinder block 22 when viewed in the crankshaft direction. The communication hole 52 can be formed by machining using the assembling opening 50, and there is no need to perform extra processing such as separately forming an opening for machining. It is possible to eliminate the need for closing with the dedicated cover member, and reduce the manufacturing cost.

Further, in the case where the lubricating oil passage 53 is formed in each boss portion 29 of the upper case 26 so as to open to the inner peripheral surface of the communication hole 52, and the lubricating oil is injected to the back surface of the piston through the passage 53. The width W of the upper part of the communication hole 52
1 is smaller than the lower width W2, the injected lubricating oil is reliably supplied to the back surface of the piston without being interrupted by the upper edge of the communication hole 52. The notch need not be formed,
The piston 31 can be efficiently cooled without increasing the cost.

Further, in the present embodiment, a slipper type piston 31 having a notch concave portion 31c formed in the piston skirt 31a is employed, and the injection port 54a of the lubricating oil passage 53 is provided at the bottom dead center of the piston 31. Since the piston skirt 31a is directed toward the back surface of the piston through the cutout recess 31c, the injection flow of the lubricating oil is not interrupted, and the cooling efficiency can be improved in this respect as well. Further, since the notch recess 31c is provided, the piston skirt 3
The problem that the effective area of the communication hole 52 is reduced by 1a can also be avoided. Alternatively, it is not necessary to lengthen the connecting rod in order to avoid area reduction due to the skirt.

Aluminum alloy cylinder block body 22
When a gasket 91 is interposed between the cylinder block 22 formed by casting the sleeve 27 constituting the piston sliding surface in the cylinder c and the aluminum alloy cylinder head 23,
The cylinder block body 22c and the cylinder head 2
3 and a material having substantially the same coefficient of thermal expansion.
Since the seal points p, p on the cylinder block side of the bead portion 91a of the gasket 91 are brought into contact only with the cylinder main body 22a side without crossing over the sleeve 27, the sealing performance can be ensured and the life of the gasket is ensured. it can.

That is, the sleeve 27 is mounted on the piston sliding surface 22.
a, it is often the case that the thermal expansion coefficient is different from that of the cylinder main body 22c. Therefore, in the hot operating state, the cylinder axial direction is formed between the mating surfaces of the cylinder main body 22c and the sleeve 27. Step may occur. If the seal points p, p of the bead portion 91 on the cylinder block side are assumed to be
When the contact is made over both of the above cases, a force in the shearing direction acts on the bead portion 91a of the gasket 91 due to the step, and there is a concern that the life of the bead portion 91a may be shortened or the sealing property may be reduced.

As described above, when the coefficient of linear expansion αb of the cylinder body 22c is excessively large compared to the coefficient of linear expansion αs of the sleeve 27, the tension between the cylinder body 22c and the sleeve 27 is small. In extreme cases, there is a gap between the two. However, in the present embodiment, since α> 50, that is, the linear expansion coefficient αb of the cylinder body 22c is prevented from becoming excessively large as compared with the linear expansion coefficient αs of the sleeve 27. No gap is formed between the inner surface of the cylinder bore and the outer surface of the sleeve, which prevents an increase in thermal resistance due to the gap, prevents thermal deterioration of the support layer of the film due to overheating of the sleeve, and prevents cracking and peeling of the plating film. Can be prevented.

If the coefficient of linear expansion αs of the sleeve 27 is excessively larger than the coefficient of linear expansion αb of the cylinder body 22c, the thermal expansion of the sleeve 27 is suppressed by the cylinder body 22c, so that a large compression is applied to the sleeve 27. When a stress is generated and the sleeve 27 has a thick portion and a thin portion in such a case, a difference occurs in the amount by which the expansion of the sleeve 27 is suppressed and the inner surface of the sleeve is distorted. However, in this embodiment, since α <150, that is, the linear expansion coefficient αs of the sleeve 27 is prevented from becoming excessively large as compared with the linear expansion coefficient αb of the cylinder main body 22c. Can be reduced by the cylinder body portion 22c, so that even when the sleeve 27 has a thick portion and a thin portion, it is possible to prevent the inner surface of the sleeve 27 from being distorted. And the occurrence of cracks and peeling of the plating film can be prevented.

The cylinder body 22c, the positioning portion 27f1 of the sleeve 27, and the thin portion 27f2
Each thickness is ts1 = 3.5 mm and ts2 = 2.2, respectively.
1.8 mm <ts1, 1.8 mm <ts
Since each thickness is set so as to satisfy 2, the machining allowance is given to the cylinder bore side, so the thickness at the time of casting becomes 1.9 mm or 2.0 mm or more, and the sleeve can be deformed by the pressure of the molten metal. Sex can be eliminated. In particular, in the present embodiment, the T6 treatment is performed before the casting, so that the possibility that the sleeve is deformed by the pressure of the molten metal can be more reliably eliminated.

Further, the sleeve positioning portion 27f
The cylinder body 22d, which is the outer periphery of the cylinder 1, the thin portion 27
When the thicknesses of the cylinder main body 22d, which is the outer periphery of f2, are tb1 and tb2, respectively, ts1 = 4.0 mm, t
s2 = 5.25 mm. That is, ts1 <tb
1. Since the thicknesses are set so as to satisfy ts2 <tb2, the supply of molten metal to the cylinder body during casting is sufficient when the thickness of the cylinder body 22d is excessively reduced for weight reduction. The possibility of losing meat can be eliminated.
If there is a further underfill, the underfill and the sleeve 27
And a gap is created between them, causing the sleeve in that part to overheat,
The support layer of the plating film is thermally deteriorated, and the plating film is easily cracked or peeled, but this problem does not occur.

Further, according to the embodiment, the sleeve 2
7, a cooling water jacket 90 is provided around the cooling water jacket 90, engine cooling water is allowed to flow through the cooling water jacket 90, (ts1 + tb1) is set to 7.5 mm, (ts2 + tb1).
2) is 7.5 mm, (ts1 + tb1) and (ts1)
2 + tb2) are substantially the same as each other, so if there are irregularities on the outer periphery, the cooling water will stagnate, the sleeve 27f and the cylinder body 22d will not be sufficiently cooled, and will be easily affected by thermal expansion. In this case, cracks and peeling of the plating film easily occur, but this problem does not occur.

[Brief description of the drawings]

FIG. 1 is a left side view of a motorcycle equipped with an engine according to an embodiment of the present invention.

FIG. 2 is a right side view of the engine.

FIG. 3 is a right side view showing a structure around a chain arrangement chamber of the engine.

FIG. 4 is a sectional rear view of the engine.

FIG. 5 is a sectional view showing a communication hole portion of the engine.

FIG. 6 is a bottom view of the cylinder block of the engine as viewed from a crankshaft side.

FIG. 7 is a sectional side view of a right end cylinder portion of the cylinder block.

FIG. 8 is a sectional side view of a second cylinder portion from the right end of the cylinder block.

FIG. 9 is a plan view of the cylinder block.

FIG. 10 is a plan view of a gasket between the cylinder block and the cylinder head.

FIG. 11 is an enlarged sectional view showing a seal structure between the cylinder block and a cylinder head.

FIG. 12 is an enlarged sectional view showing a lower end of a sleeve of the cylinder block.

FIG. 13 is an enlarged plan view of the cylinder block.

14 is an enlarged sectional view of the cylinder block (FIG. 13)
XIV-XIV section view of FIG.

FIG. 15 is a view showing a result of an experiment for forming a communication hole in the cylinder block.

FIG. 16 is a view showing a result of an experiment for forming a communication hole in the cylinder block.

FIG. 17 is a view showing a result of an experiment for forming a communication hole in the cylinder block.

FIG. 18 is a view showing a result of an experiment for forming a communication hole in the cylinder block.

FIG. 19 is a diagram showing a state after honing in an experiment for forming a communication hole in the cylinder block.

FIG. 20 is a schematic view showing an etching apparatus in the plating step.

FIG. 21 is a schematic view showing a high-speed plating apparatus in the plating step.

FIG. 22 is a flowchart showing a manufacturing process of the cylinder block.

FIG. 23 is a flowchart showing details of a plating process in the manufacturing process.

FIG. 24 is a characteristic diagram showing a relationship between a Si content by weight and a coefficient of linear expansion.

[Explanation of symbols]

 15 Engine 22 Cylinder block 22c Cylinder main body 22d Cylinder bore wall 27 Sleeve 27f1 Positioning part 27f2 Thin part 90 Cooling water jacket a Plating film

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02F 1/10 F02F 1/10 A

Claims (3)

[Claims] 1. A sleeve having a positioning part made of aluminum alloy and having a greater thickness than other parts and a sleeve having a thin part other than the positioning part are cast into a cylinder bore wall of a cylinder body made of aluminum alloy. In the cylinder block of the engine in which the plating film is formed on the inner surface of the sleeve, the aluminum alloy of the cylinder body is 5 to 20% by weight.
Wherein the aluminum alloy of the sleeve contains Si satisfying 50 <α <150, where α is (Si weight content of the sleeve / Si weight content of the cylinder body) × 100. Characteristic engine cylinder block. 2. The thickness of the positioning portion and the thin portion of the sleeve are ts1 and ts2, and the thickness of the outer peripheral portion of the positioning portion and the thin portion of the cylinder body are tb1 and tb2. 1.8 mm <ts1 <tb1, 1.8 mm <ts2 <t
A cylinder block for an engine, wherein each wall thickness is set so as to satisfy b2. 3. The cooling water jacket according to claim 2, wherein a cooling water jacket is provided on an outer periphery of the sleeve, and engine cooling water flows through the cooling water jacket, and (ts1 + tb1) and (ts2 + tb2) have substantially the same thickness. A cylinder block for an engine, characterized in that: