JPH11153060A - Air-cooled multicylinder four cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve cooling efficiency by a method wherein a gap between cylinders is sufficiently ensured without extending the length of an engine to form a cooling air passage. SOLUTION: In this multicylinder four cycle engine, a plurality of cylinders 7 are arranged in juxtaposition and cooling air is applied from a direction crossing orthogonally to a cylinder alignment direction. In this case, a shaft drive device 21 for driving a cam shaft 2 is separately arragned on one end side of an engine 1 body, a distance between the adjoining cylinders 7 is ensured, and a colling air passage 9 is formed in a manner to longitudinally extend through a gap between the cylinders 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-cooled multi-cylinder four-cycle engine in which a plurality of cylinders are arranged in parallel to receive cooling air from a direction orthogonal to the cylinder arrangement direction, and more particularly to an overhead cam type engine. It is about.

[0002]

2. Description of the Related Art This type of engine is mainly mounted on a motorcycle, but conventionally, a rotation transmission system such as a cam chain or a cam gear for transmitting the rotational force of a crankshaft to an overhead camshaft is used. And those arranged between the cylinders.

In the prior art, there is an engine described in Japanese Utility Model Publication No. Sho 63-29161. In this engine, the gap between the plurality of cylinders located near the center in the longitudinal direction of the engine is slightly wider than the others. A vertically extending cam chain chamber for accommodating the cam chain is provided in the widened gap.

[0004]

The above-described conventional four-stroke engine has room for improvement in the following points. That is, in order to arrange a rotation transmission system such as a cam chain between cylinders, it is necessary to provide a considerably wide gap. On the other hand, if an attempt is made to secure a sufficient cooling air passage between the cylinders, the overall length of the engine will increase, and if the engine is arranged to receive wind from the front when mounted on a motorcycle, the length of the engine will decrease. And may protrude to the side.

[0005] When the length of the engine is increased, the crankshaft must be correspondingly lengthened. Therefore, if the engine has the same diameter, the crankshaft becomes less rigid when the engine is longer. On the other hand, if the shaft diameter is increased and reinforced to prevent this, the weight of the engine increases and the performance of the engine decreases.

It is necessary to arrange a lubricating oil supply pipe for supplying lubricating oil from an oil reservoir at the bottom of the crankcase and a pipe for returning the lubricating oil supplied to each drive unit of the overhead cam. Are arranged in a cam chain chamber or as a passage vertically penetrating an engine body (particularly, a cylinder block), but in any case, lubricating oil passing through those pipes is not hit by cooling air. It is difficult to cool down. On the other hand, if the pipe is provided outside the engine body, it is advantageous in terms of cooling, but the pipe is exposed, which causes inconvenience in design and also complicates the layout.

When a cam chain, for example, is provided at one end of an engine body as a rotation transmission system for driving a camshaft, a chain cover is attached to one end surface of the engine body. Often becomes.

The present invention has been made in view of the above points, and in an air-cooled multi-cylinder four-cycle engine, a sufficient air gap is provided between cylinders without increasing the length of the engine to provide a cooling air passage, thereby providing cooling efficiency. The primary purpose is to improve

A second object is to make it possible to cool the lubricating oil passing through the lubricating oil supply pipe and the return pipe and to make the appearance (design) of the engine clear.

A third object is to provide a rotation transmission system for driving a camshaft at one end of the engine body and to improve the design of the engine by making use of its functional beauty.

[0011]

In order to achieve the first object, a four-stroke engine according to the present invention has a plurality of cylinders arranged in parallel so as to receive cooling air from a direction orthogonal to the cylinder arrangement direction. In the air-cooled multi-cylinder four-stroke engine, a rotation transmission system for driving an overhead camshaft is provided at one end of the engine body to secure an interval between the cylinders and to provide a cooling air passage penetrating between the cylinders in the front-rear direction. Has formed.

[0012] According to the four-stroke engine of the present invention having the above-described structure, the space of the rotation transmission system between the cylinders is smaller than that of the conventional four-cycle engine in which the rotation transmission system for driving the camshaft is arranged between the cylinders. Can be applied to the gap without extending the length of the engine body.
A sufficient cooling air passage can be ensured between the cylinders, which increases the cooling efficiency of the engine, thereby improving the performance of the engine. Further, since it is not necessary to extend the length of the crankshaft, the rigidity does not decrease and the weight of the engine does not increase.

According to a second aspect of the present invention, the engine is a two-cylinder four-stroke engine and a cooling air passage is formed between the cylinders. The lubricating oil supply pipe and the lubricating oil return pipe are arranged, or the lubricating oil supply pipe and the lubricating oil return pipe are positioned at the central position in the front-rear direction of the engine in the cooling air passage. The lubricating oil return pipe is disposed in front of the lubricating oil supply pipe, or the lubricating oil return pipe is disposed in front of the lubricating oil supply pipe.

[0014] According to the four-cycle engine having the above-described structure, the pipe for supplying and discharging the lubricating oil is accommodated in the cooling air passage and is not exposed to the outside, so that the appearance is excellent and the layout is simple. United. Further, since the cooling air blows against the lubricating oil supply / discharge pipe to cool it, the lubricating oil passing through the pipe is cooled. Further, by arranging the position of the pipe rearward from the intermediate position in the front-rear direction in the cooling air passage as described in claim 3, the cooling air smoothly flows into the cooling air passage without being hindered by the pipe. The flow rate of the cooling air passing through the cooling air passage is sufficiently ensured, and the cooling capacity is improved. Further, by arranging the lubricating oil return pipe in front of the lubricating oil supply pipe as described in claim 4, the lubricating oil pipe on the return side having a higher oil temperature than the lubricating oil on the supply side has a lower temperature. Since the cooling wind hits first,
Cooling of the lubricating oil is also effectively performed.

In order to achieve the third object, a rotation transmission system transmits a rotation of a crankshaft to a camshaft via a pair of bevel gears, a drive shaft, and a pair of bevel gears. The drive device has a boss portion of a bevel gear at both ends of the drive shaft extending in a base axial direction, and sliding the shaft bevel gear in the axial direction with respect to the drive shaft. It is movably mounted, and a cylindrical bearing housing is rotatably mounted around a boss of each bevel gear via a bearing. A screw portion is formed on the outer peripheral surface of the bearing housing, and the crankshaft is rotated. Nenets communicating with opposing surfaces of a crankcase that freely supports and a cylinder head that rotatably supports the camshaft. A hole is provided, a screw portion of the bearing housing is screwed into the screw hole, a cylindrical case is connected to each bearing housing at both ends of the drive shaft so as to be integrally rotatable, and a cylindrical portion is provided between the base ends of the cases. The drive shaft can be relatively rotatably connected by a shaped sleeve case to cover the drive shaft, and by selectively rotating the bearing housings on both sides, the clearances of the meshing portions of the bevel gears at both ends of the shaft can be adjusted. .

According to the four-stroke engine of the present invention, unlike the case where the rotational force is transmitted by the cam chain or the cam belt, it is not necessary to directly attach the cover to the engine body. Despite the arrangement, the layout can be determined relatively freely, the degree of design freedom is high, and the design is excellent. In addition, the clearance between the meshing portions of the camshaft-side bevel gear and the crankshaft-side bevel gear can be easily and continuously adjusted by an external operation even when the engine is running, and each drive unit including the drive shaft has a cylindrical shape. Because it is covered with a case and a sleeve cover,
Dust and the like do not enter the drive unit. Further, the clearance of the meshing portion of the bevel gear can be easily adjusted without disassembling the engine and the like, and can be adjusted even in the operating state of the engine, so that accurate adjustment can be performed.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an air-cooled multi-cylinder four-cycle engine according to the present invention will be described below with reference to the drawings.

FIG. 1 is a central sectional view in front view showing an embodiment of a four-cycle engine. FIG. 2 shows a cylinder block of the engine of FIG. 1, in which the left half is a front view and the right half is a central longitudinal sectional view. 3 is a plan view of the cylinder block of FIG. 2, and FIG. 4 is a bottom view of the cylinder block of FIG. 5 is a sectional view taken along line AA of FIG. 6, and FIG. 6 is a sectional view taken along line BB of FIG.
It is a line sectional view. FIG. 7 is a side view showing a state where the engine of this embodiment is mounted on a motorcycle.

As shown in FIG. 1, an engine 1 is an air-cooled single overhead cam (SOHC) for a motorcycle.
In a four-valve horizontal (parallel) two-cylinder engine, two cylinders 7 are arranged in parallel along the width direction of the motorcycle G (FIG. 7), and the cooling air is directed in a direction orthogonal to the arrangement direction of the cylinders 7. It is mounted on the motorcycle G (FIG. 7) so as to receive from the (front). A crankshaft 3 rotatably supported in a lower crankcase 5 of the engine 1 via a bearing 3A, and a camshaft chamber 6 on an upper cylinder head 6
A shaft driving device 21 is interposed between the camshaft 2 and the camshaft 2 rotatably supported via a bearing 2A in the shaft A. As shown in FIG.
Is arranged at one end side of the cylinder block 7B away from one end of the cylinder block 7B.

A cylinder 7 is formed at the center of each cylinder block 7B, and screw holes 7C (FIG. 3) for connecting the cylinder head 6 and the crankcase 5 are formed on both upper and lower surfaces of the cylinder block 7B. It is provided at intervals in the direction. The two cylinders 7 are arranged side by side at predetermined intervals (parallel), and as shown in FIG. 2, cooling fins 8 projecting outward around the outer peripheral wall of the cylinders 7 are arranged at regular intervals in the vertical direction. The cooling fins 8 are protruded in the horizontal direction and are connected by vertical ribs 8B arranged at intervals in the circumferential direction. The projecting length of each cooling fin 8 gradually increases from the lower end to the upper end of the cylinder 7, and each rib 8B also gradually increases from the lower end to the upper end.

As shown in FIG. 5, a cooling air passage 9 having the same width and extending in the front-rear direction is formed between the cylinders 7. In the cooling air passage 9, as shown in FIG. 2, a connecting plate 8 A (see FIG. 6) traverses in a horizontal direction together with cooling fins 8 straddling the left and right cylinders 7, and a horizontally long window 9 A as viewed from the front is vertically arranged. A plurality (four in this example) are formed side by side. In FIG. 5, the arrow W indicates the direction of the flow of the traveling wind (cooling wind), and in each of the drawings, the arrow F indicates the traveling direction of the vehicle body.

As shown in FIGS. 5 and 6, a large-diameter hole 10 vertically penetrating a connecting plate 8A extending across the two cylinders 7.7 crosses an intermediate position of the engine 1 in the front-rear direction. A small-diameter hole 11 is drilled toward the rear in contact with the center line C-C, and is spaced behind the large-diameter hole 10 so as to penetrate the connecting plate 8A in the vertical direction. The upper ends of the large-diameter hole 10 and the small-diameter hole 11 each reach the camshaft chamber 6A. A lubricating oil return pipe 12 is inserted through the large diameter 10, and a lubricating oil supply pipe 13 is inserted through the small diameter 11. The upper end openings of the return pipe 12 and the supply pipe 13 face the interior of the camshaft 6A.
Is connected to one end of a sub-pipe 14 for supplying to the sub-pipe. On the other hand, lubricating oil return pipe 12 and supply pipe 1
Although not shown, the lower end of 3 is inserted into the crankcase 5. O-rings 12A and 13A are attached and sealed around the upper and lower ends of the pipes 12 and 13, respectively. In this example, a steel pipe is used for the lubricating oil return pipe 12 and an aluminum alloy pipe is used for the supply pipe 13. Is also possible. By making both the pipes 12 and 13 made of aluminum and making the return side thicker, it is possible to improve heat dissipation.

An embodiment of the cooling structure of the engine 1 is described above. Such a cooling structure is conventionally realized by being provided vertically through the cooling air passage 9 between the cylinders 7 and 7. This is because a shaft driving device 21 for transmitting the rotational force of the crankshaft 3 to the camshaft 2 is provided at one end of the engine 1 in order to eliminate the cam chain chamber. Therefore, the shaft driving device 21 will be described below.

As shown in FIG. 1, the shaft drive 21
Has a drive shaft 22 having spherical splines 22a and 22b formed at both upper and lower ends, an upper bevel gear 24, and a lower bevel gear 34. Upper bevel gear 24
The boss 24a extends downward (proximal end side) along the axial direction, and a large number of linear splines 2 engageable with the spherical splines 22a are formed on the inner peripheral surface of the lower end of the cylindrical extension.
4c is protruded in parallel along the vertical direction (axial direction), and is engaged with the spherical spline 22a so as to be slidable in the axial direction and swingable in any direction.

A cylindrical metal bearing housing 25 is rotatably mounted around the bevel gear 24. A pair of upper and lower bearings 26 is fitted in the housing 25, and the inner ring side of the bearing 26 is fitted to the outer peripheral surface of the bevel gear 24 by tightening a nut 27. A metal cylindrical case 28 is connected to the lower end of the housing 25 so as to be integrally rotatable. On the outer peripheral surface of the housing 25, a male screw portion (not shown) is formed except for an upper end portion. The lower bevel gear 34 and the surrounding members engaged with the lower spherical spline 22b also have the same structure as the upper bevel gear 24 and the surrounding members 25 to 28. Therefore, the common members are denoted by reference numerals obtained by adding 10 to the reference numerals of the members around the upper bevel gear 24, and are shown in FIG. Then, the upper case 28
A metal cylindrical sleeve case 39 is interposed between the outer peripheral surface of the lower cylindrical portion and the outer peripheral surface of the upper cylindrical portion of the lower case 38, and covers the drive shaft 22. Via an O-ring 60, it is connected to the upper case 28 and the lower case 38 so as to be relatively rotatable.

The camshaft 2 is rotatably disposed via a bearing 2A at a central portion in a camshaft chamber 6A formed above the cylinder head 6 as shown in FIG.
A bevel gear 42 is provided at one end (right end in the figure) of the camshaft 2.
Are attached so as to be integrally rotatable by set screws (not shown). On the other hand, a bevel gear 52 is attached to one end (right end in the drawing) of the crankshaft 3 in the crankcase 5 so as to be integrally rotatable by a set screw. The above-described shaft drive device 21 for connecting between the bevel gears 42 and 52 is mounted as follows.

On one side (right side) of the engine 1,
A through hole 43 communicating with the inside is formed on the lower surface of the cylinder head 6, and a female screw portion is formed on the inner peripheral surface of the through hole 43, which is a so-called screw hole. The female screw portion is provided except for an upper end portion in a through hole (hereinafter, also referred to as a screw hole) 43, and an annular groove for mounting the O-ring 44 is formed in the upper end portion. Similarly, a through-hole 53 communicating with the inside is formed on the upper surface of the crankcase 5, and a female screw portion is formed on the inner peripheral surface of the through-hole 53 to form a screw hole. The female screw portion is provided except for a lower portion in a through hole (hereinafter, also referred to as a screw hole) 53, and an annular groove for mounting an O-ring 54 is formed in the lower portion.

The upper housing 25 is screwed into the screw hole 43 of the cylinder head 6 and the lower housing 35
Is screwed into a screw hole 53 of the crankcase 5. In this state, the upper bevel gear 24 of the drive shaft 22
Meshes with the bevel gear 42 on the camshaft 2 side, and the lower bevel gear 34 meshes with the bevel gear 52 on the crankshaft 3 side. Also, at the lower end of the male screw portion of the upper housing 25,
The locking nut 30 is screwed, and the upper surface thereof is in contact with the lower surface of the cylinder head 6 around the screw hole 43 in a state where the nut 30 is tightened. Also, the lower housing 3
The locking nut 40 is screwed to the upper end of the male screw portion 5 as well. When the nut 40 is tightened, its upper surface is brought into contact with the upper surface of the crankcase 5 around the screw hole 53. .

As shown in FIG. 1, a piston 61 is inserted into a cylinder liner 7D of the cylinder 7 so as to be slidable in the vertical direction, and the piston 61 is connected to the crankshaft 3 via a connecting rod 62. The cylinder head 6 is provided with two intake ports (not shown) and two exhaust ports 63 respectively. Reference numeral 64 denotes an ignition portion at the lower end of the ignition plug disposed substantially at the center of the combustion chamber 65 (FIG. 1).

The four-stroke engine 1 according to the embodiment of the present invention is constructed as described above. The four-stroke engine 1 according to the present embodiment is, as shown in FIG. 1) is directed forward, in other words, the shaft drive device 21 is mounted in a direction exposed to the right side of the vehicle body. The engine 1 is cooled by receiving traveling wind from the front when the motorcycle G is traveling. As shown in FIG. 1, the traveling wind further passes through the cooling air passage 9, cools the cylinder 7 also from the inner surface, and hits the lubricating oil return pipe 12 in the cooling air passage 9 to flow down the lubricating oil pipe 12. Cool the oil. The cooling air that has passed back and forth on both sides of the pipe 12 cools the lubricating oil being supplied to the lubricating oil supply pipe 13 and passes backward. The arrangement order of these pipes 12 and 13 before and after is not limited, but since the temperature of the lubricating oil on the return side is considerably higher than that on the supply side, the cooling air first hits the pipe 12 in this example. The arrangement is excellent in terms of cooling efficiency. In addition, the diameter of the return pipe 12 is made larger than that of the supply pipe 13 so that the contact area of the cooling air is also increased to increase the cooling efficiency.

By the way, although one embodiment of the four-cycle engine has been described above, the present invention can be implemented as follows.

Instead of the shaft driving device 21, a cam shaft driving system using a cam chain or a cam belt can be arranged on one end side of the main body of the engine 1.

Not limited to two-cylinder engines, three-cylinder, four-cylinder
It can be applied to multi-cylinder engines such as cylinders. In this case,
A plurality of cooling air passages 9 are formed between the cylinders 7. Further, a pipe for supplying and discharging the lubricating oil may be arranged in each cooling air passage 9.

It is not always necessary to arrange a pipe for lubricating oil in the cooling air passage 9.

[0035]

As is apparent from the above description,
The air-cooled multi-cylinder four-cycle engine of the present invention has the following excellent effects.

(1) According to the present invention, a sufficient cooling air passage can be secured between the cylinders without increasing the length of the engine body, so that the cooling efficiency of the engine is improved and the performance of the engine is improved. Further, since the length of the engine body is the same as the conventional one, the rigidity of the crankshaft can be maintained as it is, and the weight of the engine is not increased.

(2) In each of the second to fourth aspects of the present invention, since the lubricating oil supply / discharge pipe is accommodated in the cooling air passage and is not exposed from the engine body, the appearance is excellent and the layout is simple. It can also cool the lubricating oil that passes through the supply and discharge pipes.

(3) According to the third aspect of the present invention, the position of the lubricating oil supply / discharge pipe is located rearward of the intermediate position in the cooling air passage in the front-rear direction, so that the cooling air flows into the cooling air passage. Since it flows smoothly, the flow rate of the cooling air is sufficiently ensured, and the engine cooling effect is high.

(4) According to the fourth aspect of the present invention, the lubricating oil return pipe is arranged in front of the lubricating oil supply pipe, so that the lubricating oil on the return side having a higher oil temperature than the supply side flows down. Since the cooling air having a low temperature is applied first, the lubricating oil is sufficiently cooled, and the cooling effect of the lubricating oil is high.

(5) According to the fifth aspect of the present invention, unlike the case where torque is transmitted by a cam chain or a cam belt, it is not necessary to directly attach a cover to the engine body, and the shaft drive device is disposed at one end of the engine. In spite of this, since the shaft drive device is disposed apart from the engine body and exposed to the outside, the shaft drive device serves as a part of the engine to enhance the overall design, and is excellent in design. Further, the clearance of the meshing portion of the bevel gear can be easily adjusted without disassembling the engine or the like, and can be adjusted even in the operating state of the engine, so that accurate and accurate adjustment can be performed.

[Brief description of the drawings]

FIG. 1 is a front cross-sectional central view showing an embodiment of a four-cycle engine according to the present invention.

FIG. 2 shows a cylinder block of the engine of FIG. 1, in which a left half is a front view and a right half is a central vertical sectional view.

FIG. 3 is a plan view showing the cylinder block of FIG. 2;

FIG. 4 is a bottom view showing the cylinder block of FIG. 2;

FIG. 5 is a sectional view taken along line AA of FIG. 6;

FIG. 6 is a sectional view taken along line BB of FIG. 5;

FIG. 7 is a side view showing a state where the four-cycle engine according to the embodiment of the present invention is mounted on a motorcycle.

[Description of Signs] 1 Engine 2 Camshaft 3 Crankshaft 6 Cylinder head 7 Cylinder 7B Cylinder block 8 Cooling fin 8A Connecting plate 8B Rib 9 Cooling air passage 9A Window 12 Lubricating oil supply pipe 13 Lubricating oil return pipe 21 Shaft driving device 22 Drive shaft 24, 34, 42, 52 Bevel gear 25, 35 Bearing housing 26, 36 Bearing 28, 38 Cylindrical case 39 Sleeve case 43, 53 Through hole (screw hole)

Claims (5)

[Claims] 1. An air-cooled multi-cylinder four-cycle engine in which a plurality of cylinders are arranged in parallel to receive cooling air from a direction orthogonal to the cylinder arrangement direction, a rotation transmission system for driving an overhead camshaft is provided in the engine body. An air-cooled multi-cylinder four-stroke engine characterized by being provided on one end side to secure an interval between the cylinders and to form a cooling air passage penetrating between the cylinders in the front-rear direction. 2. The engine according to claim 1, wherein the engine is a two-cylinder four-stroke engine, a cooling air passage is formed between the cylinders, and a lubricating oil supply pipe and a lubricating oil return pipe are arranged in the cooling air passage. Air-cooled multi-cylinder 4-cycle engine. 3. An air-cooled air-cooling system according to claim 1, wherein a lubricating oil supply pipe and a lubricating oil return pipe are arranged in front of and behind the central position in the front-rear direction of the engine in the cooling air passage. Multi-cylinder 4-cycle engine. 4. The air-cooled multi-cylinder 4 according to claim 3, wherein the lubricating oil return pipe is disposed in front of the lubricating oil supply pipe.
Cycle engine. 5. A drive system for transmitting rotation of a crankshaft to a camshaft through a pair of bevel gears, a drive shaft, and a pair of bevel gears, wherein the rotation transmission system includes a drive shaft of the drive shaft. The boss portions of the bevel gears at both ends are respectively extended in the base end side axial direction, the shaft side bevel gears are slidably mounted in the drive shaft in the axial direction, respectively, around the bosses of the bevel gears, via bearings. A cylindrical bearing housing is rotatably mounted, a screw portion is formed on the outer peripheral surface of the bearing housing, and a crankcase rotatably supporting the crankshaft and the camshaft are rotatably supported. A screw hole communicating with the inside of the cylinder head is provided in each of the surfaces facing the cylinder head. And a cylindrical case is integrally rotatably connected to each bearing housing at both ends of the drive shaft, and the base end side of each case is relatively rotatably connected by a cylindrical sleeve case. The air-cooled multi-unit according to any one of claims 1 to 4, wherein the drive shaft is covered with the drive shaft, and the clearances of the meshing portions of the bevel gears at both ends of the shaft can be adjusted by selectively rotating the bearing housings on both sides. 4 cylinder engine.