Air-cooled internal combustion engine

Abstract: To control noises emitted from various parts of engine and to minimize overall engine size, a cam shaft (14) and a balancing shaft (13) are arranged on one side of a crank-shaft (12) (the side where an air cleaner (9) is also mounted), and a starting motor (29) is arranged on the other side of the crank-shaft (12), and shaft portions of the balancing shaft (13) and the starting motor (29) are positioned lower than the crank shaft (12). An exhaust muffler (10) is arranged above the starting motor (29) so that the center of gravity of the entire engine is lowered and engine noises can be controlled. Noises emitted from various parts of engine can additionally be controlled by particular positions and for shapes of exhaust pipe (41), cylinder head cover (8) and fuel tank etc.

Description: This invention relates to an air-cooled internal combustion engine. Conventional air-cooled internal combustion engines have the problem that, as regards shaft arrangements, a cam shaft and a balancing shaft are arranged separately on left and right sides of a crank-shaft, and a heavy starting motor is arranged on an upper part of the crank-shaft at the balancing shaft side. Consequently, the center of gravity of the engine is located at a relatively high position, the overall height of the engine is large, and vibration sound is troublesome. In an air-cooled internal combustion engine, an object of invention is to control vibrations of the entire engine and to make the overall engine size small by ingeniously devising arrangements of respective shafts. In an air-cooled internal combustion engine according to the present invention an exhaust muffler and an air cleaner are arranged separately at left and right sides of an engine body, viewed from a power take-off side in a longitudinal direction of a crank-shaft, a cooling fan and a fan case are installed at a side opposite to the power take-off, and a fuel tank is mounted on an upper part of the fan case. In addition, a cam shaft and a balancing shaft are arranged in the engine body on the air cleaner side relative to the crank-shaft, a starting motor is arranged on a side face of the engine body at the exhaust muffler side relative to the crank-shaft, the balancing shaft and a shaft portion of the starting motor are positioned lower than the crank-shaft, and the exhaust muffler is arranged above the starting motor. In this way, the center of gravity of the entire engine can be lowered, engine vibration can be controlled, and the overall size of the engine can be minimised. The invention will be explained and described further with reference to the drawings, in which: Fig. 1 is a front view of a first engine embodiment; Fig. 2 is a plan view of same: Fig. 3 is a rear view of same; Fig. 4 is a right side view of same; Fig. 5 is a horizontal sectional view of a cylinder head of the same engine; Fig. 6 is a vertical sectional view of a cylinder head cover of the same engine; Fig. 7 is a sectional view taken on line VII - VII of Fig. 6; Fig. 8 is an enlarged vertical sectional view of an upper fitting portion of a fuel tank of the same engine; Fig. 9 is a vertical sectional view of an upper fitting portion of a fan case of the same engine; Fig. 10 is a vertical sectional view of a cooling fan of the same engine; Figs. 11 and 12 are sectional views taken on lines XI - XI and XII XII respectively of an air cleaner of Fig. 1; and Fig. 13 is a horizontal sectional schematic view of a second embodiment of internal combustion engine equipped with an exhaust duct and a partition plate. Figs. 1 to 10 show a horizontal type air-cooled internal combustion engine which embodies the invention. Fig. 1 is a front view, viewed from the power take-off side in a longitudinal direction of crank-shaft. The engine body is composed of a cylinder block 1 and a cylinder head 7 etc., and the cylinder block 1 integrally includes a cylinder 2 and a crank-case 3. An air cleaner 9 is arranged at the right side of the cylinder 2 and the exhaust muffler 10 is arranged at its left side. A cylinder head cover 8 is secured to a top surface of the cylinder head 7. A horizontal crank-shaft 12 is supported in the crank-case 3 within a vertical plane common with a cylinder center line C, a balancing shaft 13 and a cam shaft 14 are arranged on the air cleaner side (right side) of crank-shaft 12 in the crank-case 3, and a starting motor 29 is arranged at a side of crank-case on the exhaust muffler side (left side). The cam shaft 14 is located at a position above the level of the crank-shaft 12 and shaft portions of both the balancing shaft 13 and the starting motor 29 are located at positions lower than the crank-shaft 12, so that the height of the centre of gravity of the entire engine can be made small. The starting motor 29 is fastened together with an upper solenoid 35 to brackets 30 formed on the crank-case 3 by using bolts 31. The above-mentioned exhaust muffler 10 is installed directly above the starting motor 29. At the power take-off side of the crank-case 3, the balancing shaft 13 is equipped with a balancing shaft driven gear 24 and a cam shaft driving gear 25. The balancing shaft driven gear 24 meshes with a gear 23 of the crank-shaft 12. The cam shaft driving gear 25 meshes with a cam gear 26 so that the cam shaft 14 can be rotated in the same rotating direction as the crank-shaft 12. A cylinder-side cooling air passage 32 which allows cooling air to flow only to the power take-off side from an opposite side (the cooling fan side) is formed around the cylinder 2. A head-side cooling air passage 33 which allows cooling air to flow only from the cooling fan side to the power take-off side is formed in the cylinder head 7 too, and an exhaust port 34 of the cylinder head 7 opens at the power take-off side. A primary expansion chamber in combination with an exhaust pipe 41, which is formed lengthwise in a vertical direction so as to cover the power take-off sides of the cylinder head 7 and the cylinder 2, is formed on the exhaust muffler 10 to be connected to the foregoing exhaust port 34. An exhaust air flange 38 surrounding both the cooling air passages 32,33 is formed around the power take-off sides of the cylinder head 7 and the cylinder 2, and an exhaust air guide 42 is fastened by bolts to the exhaust air flange 38 in the single-engine state of Fig. 1. In Fig. 2, a fuel tank 19 is shown installed on the side opposite to power take-off. This fuel tank 19 extends fully from one end of the exhaust muffler 10 to the other end of the air cleaner 9 in a lateral direction. Thus, the four sides of the cylinder 2 are surrounded by the fuel tank 19, the air cleaner 9, the exhaust muffler 10 and the primary expansion chamber in combination with the exhaust pipe 41. In Fig. 3, a cooling fan 17 and a fan cover 18 covering the cooling fan are shown installed on the side opposite to the power take-off, and the fuel tank 19 is shown installed on an upper part of the fan cover 18. Fig. 4 shows that fan cover fitting surfaces 53 for the cylinder block 1 and the cylinder head 7 are made flush in the same vertical plane. The fan cover 18 is fitted to the fitting surface 53 through a seal 65. An upper part of the fan cover 18 is formed into an inclining face 18a, and an attaching plate 54 of the fuel tank 19 is mounted on the inclining face 18a with a vibration absorbing member 64 held between them. Upper and lower brackets 55 & 56 are provided on upper and lower ends of the attaching plate 54 respectively. The lower bracket 56 is secured to a side face of the fan cover 18 together with the lower end of the attaching plate 54 without using a vibration-proof mechanism, and the upper bracket 55 is flexibly mounted on the upper end of the cylinder head 7 through a vibration-proof rubber pad 63 together with the upper part of the attaching plate 54 and is secured by a bolt 61 as illustrated by Fig. 8. The fan cover 18 itself is flexibly mounted on the cylinder block 1 etc. through a vibration-proof damper 66 and is secured thereto by a bolt 68 as illustrated in Fig. 9. In Fig. 5, which is a horizontal sectional view of the cylinder head 7, the head-side cooling air passage 33 is shown divided into three branch passages 33-A, 33-B and 33-C, all of which are so formed as to allow cooling air to flow only in a direction from the cooling fan to the power take-off. 36 is a suction port. Fig. 6 is a vertical sectional view of the cylinder head cover 8. A fuel injection valve chamber 46, which is partitioned from a rocker arm chamber 47 housing a rocker arm 44 and has an integral covering wall 46a, is formed in the cylinder head cover 8. In Fig. 7, which is a section taken on line VII - VII of Fig. 6, shows that a cooling air intake port 49a, which connects the fan-side end of the fuel injection valve chamber 46 to the fan-side end of the head-side cooling air passage 33, is formed on a cylinder head upper wall. Also a cooling air outlet port 49b which connects the power take-off end of the fuel injection valve chamber 46 to the power take-off side end of the head-side cooling air passage 33, is formed thereon. Thus a portion of cylinder head cooling air is induced to flow through the fuel injection valve chamber 46 so as to positively cool the fuel injection valve 43. The pattern of flow of cooling air is as follows: Cooling air sucked by the cooling fan 17 from outside flows from the fan cover 18 into the cylinder 2 and the passages 32,33 of the cylinder head 7. Part of the cooling air in the cylinder head 7 further flows into the fuel injection valve chamber 46 of the cylinder head cover 8 to cool the cylinder 2, the cylinder head 7 and the fuel injection valve 43 respectively. All of these cooling air streams are exhausted from the power take-off side. In cases where the exhaust guide 42 is attached to the exhaust air flange 38, as illustrated in Fig. 1, exhausted cooling air is guided by the foregoing guide 42. With reference to Fig. 10, the cooling fan body 17 is made of resin independently from a flywheel 50. When assembled, the cooling fan 17 closely contacts an outer periphery of a starting pulley 70 secured to the flywheel 50. Cooling air is sucked by the cooling fan 17 from outside in the axial direction of the fan. The outer periphery of the cooling fan 17 is formed into a curved shape adapting to the flow of cooling air as shown by 17b. As a result of the independent resin-made fan 17 being in close contact with the outer periphery of the starting pulley 70 vibration of the starting pulley 70 can be controlled. Moreover, the shape of the fan 17 for adapting to the flow of cooling air can be formed easily, and volume of flow of cooling air is thereby increased. Furthermore the flow pattern of cooling air is smooth so that fan noise produced by fan blades 17a can be reduced. Also by forming the cooling fan 17 separately from the flywheel 50 weight-reduction such as drilling etc. of the flywheel 50 can be accomplished without minimising the volume of flow quantity of cooling air. The structure of the air cleaner 9, a fuel injection pump 112 and an intake passage 111 will now be described. In Fig. 1 the intake passage 111 opens to the right side and the fuel injection pump 112 is mounted on the crank-case 3 adjacent an intake passage inlet 111a. The fuel injection pump 112 is mounted at a small angle (20° for example) in relation to the cylinder center line, and the fuel injection pump 112 is connected to the fuel injection valve 43 (Fig. 6) via a fuel pipe. The air cleaner 9 installed on the fuel injection pump side (right side) of the cylinder head 7 is of such a large shape and a large capacity as to cover approximately the entire surfaces of the intake passage inlet sides of the cylinder head 7 and the cylinder 2. The air cleaner 9 comprises an air cleaner body 116 and an air cleaner cap 117. The air cleaner body 116 is spaced apart from an air cleaner fitting surface 114 of the cylinder head 3 by a specified distance. The above-mentioned fuel injection pump 112 is located at a position below the intake passage inlet 111a between the air cleaner body 116 and the air cleaner fitting surface 114. An intake passage pipe 123 extending to the cylinder head is integrally formed by resin on the air cleaner body 116. This pipe 123 is secured by bolts (not shown) to the air cleaner fitting surface 114 for connection to the inlet 111a of the intake passage 111 of the foregoing cylinder head 7. Another air suction pipe 120 is formed by resin integrally with the air cleaner body 116 at the cylinder head side surface of the air cleaner body 116. The air cleaner cap 117 is fitted to the air cleaner body 116 in a detachable manner by a fitting bolt 124 and a butterfly nut 125, and an element 121 is installed inside the air cleaner cap 117. Referring to Fig. 12 which shows the section on line XII - XII of Fig. 1, the air suction pipe 120 of the air cleaner 9 is formed into an L-shape and extends over the top of the intake passage pipe 123 in an approximately horizontal direction from an air inlet 120a to the front side where it bends downward, to terminate at its lower end in an outlet 120b which connects to an external space 128 of the element 121, as illustrated in Fig. 11. In Fig. 11, the element 121 is shown to comprise a rectangular frame-work, and its interior space 129 is connected to the intake passage pipe 123. Holes 130 are provided for air cleaner body fitting bolts. During operation of engine, fresh air sucked from the air intake port 120a of Fig. 12 flows into the element exterior space 128 of Fig. 11 from the suction pipe 120, passes the element 121, being cleaned thereby, and flows into the interior space 129. Then, the air flows via the air cleaner-side intake passage of pipe 123 to the intake passage 111 of the cylinder head 7. Fig. 13 shows another internal combustion engine, surrounded by a sound insulating cover 57, which embodies the invention. In this engine, a partition plate 58 is arranged between the fan case fitting surface 53 of the engine body and the fan case 18, so that a space in the sound insulating cover 57 is divided into a first chamber 73 located at the power take-off side of the partition plate 58 and a second chamber 74 located at the fan case side of the plate 58. The engine body, the exhaust muffler 10 and the air cleaner 9 are installed in the first chamber 73, and the fan case 18 and the fuel tank 19 located above it are installed in the second chamber 74. An exhaust air duct 59 is connected to the exhaust air flange 38 in order to induce exhaust air, which flows from the cylinder 2 and the cylinder head 7, collectively into a muffler cover 59a and then exhaust it to the exterior of the sound insulating cover 57. The primary expansion chamber in combination with the exhaust pipe 41 is housed in the exhaust air duct 59. The first chamber 73 becomes hot due to heat radiation of the engine body, air exhausted from the exhaust pipe 41 and exhausted cooling air. On the other hand, the second chamber 74 divided by the partition plate 58 is kept at a low temperature. An air intake port 9a of the air cleaner 9 pierces the partition plate 58 to open to the second chamber 74 of low temperature, so that it can always intake cool new air, which is particularly useful in enabling an increase in engine output. As described above, according to the invention, the cam shaft 14 and the balancing shaft 13 are installed on the air cleaner side of the crank shaft 12 and the starting motor 29 is installed on the exhaust muffler side thereof, the shaft portions of the balancing shaft 13 and the starting motor 29 being located at positions lower than the crank shaft 12, and the exhaust muffler 10 being horizontally arranged at a location somewhat higher than the starting motor 29. In this way, the center of gravity of the entire engine is lowered. As a result, the engine stability is enforced and vibration of the entire engine due to vibration of the starting motor itself can be controlled. Furthermore since the starting motor 29 is located at a low position so that the exhaust muffler 10 can be installed horizontally thereabove, the overall size of the entire engine can be minimized.

Claims: An air-cooled internal combustion engine in which an exhaust muffler (10) and an air cleaner (9) are arranged separately at left and right sides of an engine body, viewed from a power take-off side in a longitudinal direction of a crank-shaft (12), a cooling fan (17) and a fan case (18) are installed at a side opposite to the power take-off, and a fuel tank (19) is mounted on an upper part of the fan case (18), and in which a cam shaft (14) and a balancing shaft (13) are arranged in the engine body on the air cleaner side relative to the crank-shaft (12), a starting motor (29) is arranged on a side face of the engine body at the exhaust muffler side relative to the crank-shaft (12), the balancing shaft (13) and a shaft portion of the starting motor (29) are positioned lower than the crank-shaft, and the exhaust muffler (10) is arranged above the starting motor (29).

Inventors: IWATA MITSUNORI C O YANMAR DIE, SAMO JUNICHI C O YANMAR DIESEL, USUI KAZUTO C O YANMAR DIESEL, IWATA, MITSUNORI, C/O YANMAR DIESEL ENGINE, SAMO, JUNICHI, C/O YANMAR DIESEL ENGINE, USUI, KAZUTO, C/O YANMAR DIESEL ENGINE
Applicants: YANMAR DIESEL ENGINE CO, YANMAR DIESEL ENGINE CO. LTD.
Application year: 1991
Main classification: F02B75
IPC codes: F01P5, F02B67, F02B75, F02B63, F02B77, F02B3, F01P1, F02F7