Four-stroke cycle engine

Abstract: A four-stroke cycle engine having intake and exhaust passages openable to a combustion chamber by means of intake and exhaust valves, respectively: Said intake and exhaust valves being driven by cams on cam shafts, blow-by gas leaking from said combustion chamber into a crank chamber being introduced into a space within a cylinder head cover and returned to said intake passages from a circulation passage through a baffle plate within said cylinder head cover, whereby said baffle plate within said cylinder head cover is provided with an oil passage for supplying lubricating oil to said cam shafts.

Description: This invention relates to a four-stroke cycle engine according to the preamble part of the independent claim 1. A four-stroke cycle engine has been used, for example, having intake and exhaust passages open to a combustion chamber, and intake and exhaust valves for opening and closing the intake and exhaust passages, respectively, the intake and exhaust valves being driven by cams on cam shafts, blow-by gas leaking from the combustion chamber into a crank chamber being introduced into a space within a cylinder head cover and returned to the intake passages from a circulation passage through a baffle plate within the cylinder head cover. For such a four-stroke cycle engine, an idea is suggested that an oil passage is formed in a rigid body connecting cam caps, and oil is injected from injection holes for lubrication of a cam shaft, but such a system has a smaller degree of freedom in designing the configuration of the oil passage. Also, it is suggested that the oil passage is formed of a pipe, and in the pipe there are opened small injection holes, from which oil is injected to lubricate cam shafts. However, because of the pipe being fastened to the cylinder head by means of stays welded to the pipe, together with cam caps, workability is poor for attachment and detachment. In addition, since the pipe is attached directly to the cylinder head, components in the oil passage is apt to be subjected to vibration due to the valve drive system. From EP 0 471 886 A1 an internal combustion engine as indicated above is shown, wherein the baffle plate comprises a small drain opening for returning the oil into the cam cover cavity. DE 35 20 876 C1 discloses a device for supplying lubricating oil to wear points of a cam shaft, wherein the device consists of two preassembled deep-drawn plates between which conduits are formed. Here the lubricating oil has been pumped into the conduits, so that the lubricating oil can be supplied to the wear points. it is an objective of the present invention to improve a four-stroke cycle engine as indicated above so as to facilitate improvements of the degree of freedom in designing an oil passage and to improve the characteristics of such an oil passage. According to the present invention, this objective is solved for a four-stroke cycle engine as indicated above in that said baffle plate is fixed to said cylinder head cover and provided with an oil passage for supplying lubricating oil to said cam shafts, wherein said oil passage includes straight sections with injection holes disposed above said cam shafts. Since said oil passage is provided on said baffle plate fixed to the cylinder head cover, the degree of freedom in designing the oil passage is improved and pressure loss in the oil passage can be reduced. Further, it can be attached and detached together with the baffle plate, resulting in improved workability, and since it is not attached directly to the valve drive system, vibration on the oil passage can be reduced, improving reliability. According to another embodiment of the invention, said oil passage is constituted by a pipe attached to said baffle plate. According to this embodiment, the oil passage is constituted by a pipe attached to the baffle plate, therefore the degree of freedom in designing the oil passage is improved and pressure loss in the oil passage can be reduced. According to a further embodiment of the invention, said oil passage is constituted by said baffle plate, and a press-formed sheet metal fixed to said baffle plate. Accordingly, the oil passage is constituted by the baffle plate, and a press-formed sheet metal fixed to the baffle plate, therefore the oil passage can be made from a small number of components. Other preferred embodiments of the present invention are laid down in further dependent claims. In the following, the present invention is explained in greater detail with respect to several embodiments thereof in conjunction with the accompanying drawings, wherein: Fig. 1 is a side view of the front portion of a vehicle carrying a four-stroke cycle engine; Fig. 2 is a schematic diagram showing an oil circulation route of the four-stroke cycle engine; Fig. 3 is a plan view of a cylinder head with a head cover removed; Fig. 4 is a side view of the cylinder head with the head cover; Fig. 5 is a longitudinal sectional view of the cylinder head with the head cover; Fig. 6 is a bottom view of a baffle plate; Fig. 7 is a side view of the baffle plate of Fig. 6 as seen in the direction of an arrow A; Fig. 8 is a side view of the baffle plate of Fig. 6 as seen in the direction of an arrow B; Fig. 9 is a view showing an embodiment of a baffle plate unit; Fig. 10 is a view showing another embodiment of the baffle plate unit; Fig. 11 is a view showing still another embodiment of the baffle plate unit; Fig. 12 is a view showing yet another embodiment of the baffle plate unit; and Fig. 13 is a view showing further embodiment of the baffle plate unit. Now, an embodiment of a four-stroke cycle engine of this invention will be described below with reference to the accompanying drawings. Fig. 1 is a side view of the front portion of a vehicle carrying a four-stroke cycle engine; Fig. 2 a schematic diagram showing an oil circulation route of the four-stroke cycle engine; Fig. 3 a plan view of a cylinder head with a head cover removed; Fig. 4 a side view of the cylinder head with the head cover; Fig. 5 a longitudinal sectional view of the cylinder head with the head cover; Fig. 6 a bottom view of a baffle plate; Fig. 7 a side view of the baffle plate of Fig. 6 as seen in the direction of an arrow A; and Fig. 8 a side view of the baffle plate of Fig. 6 as seen in the direction of an arrow B. In the front portion of a vehicle 1 is provided an engine room 3 at the front side of front wheels 2, and in the engine room 3 is mounted a four-stroke cycle engine 4, in front of which is disposed a radiator 5. The engine 4 is of a two cylinder four-stroke cycle type, and at the bottom of an engine body 6 is provided an oil pan 700. The engine body 6 is provided, laterally of the vehicle, with a crank shaft 7, at the front and rear sides of which are provided balancer shafts 8, 9 laterally of the vehicle. On a cylinder block 90 constituting the engine body 6 is mounted a cylinder head 10, and in the cylinder head 10 are formed branched exhaust passages 11, 12 and branched intake passages 13, 14 for each cylinder. The branched exhaust passages 11, 12 and the branched intake passages 13, 14 are opened and closed by corresponding exhaust valves 15 and corresponding intake valves 16, respectively, and the exhaust and intake valves 15, 16 are driven by cams 19, 20 provided on cam shafts 17, 18. The branched exhaust passages 11, 12 are joined together to form an exhaust passage 21, to which are connected exhaust pipes 22. Exhaust pipes 22 connected to the respective cylinders are assembled into an exhaust pipe 23, which extends from the front side of the engine body 6 rearwardly thereunder. In addition, in the exhaust pipe 23 is provided a catalyst 24. The branched intake passages 13, 14 are joined together to form an intake passage 25, upstream of which is provided a throttle body 26 on the cylinder head 10. The throttle body 26 has intake passages 28 in communication with the intake passage 25 in the respective cylinders, and is also adapted to connect an intake manifold 30. In the cylinder head 10 are disposed injectors 35. In the throttle body 26 is provided a throttle valve 40 for controlling the flow rate for each intake passages 28. The throttle valve 40 is controlled according to information of engine speed and throttle opening. On one side of the engine body 6 is provided an oil pump 50, and operation of the oil pump causes oil collected in the oil pan 700 to be pumped up through an oil passage 51 and supplied to oil passages 57, 58 formed in the cam shafts 17, 18 from an oil passage 52 in the cylinder block 90, an oil passage 53 in the cylinder head 10, and an oil passage 54 extending perpendicular to the cam shafts 17, 18, through branched passages 55, 56. The cam shafts 17, 18 are journaled for rotation on bearings 62, 63 with cam caps 60, 61 and formed with injection holes 17a, 18a, in communication with oil passages 57, 58, corresponding to bearings 62, 63. Oil is supplied to bearings 62, 63 through the injection holes 17a, 18a. In the oil passage 54 is provided a filter 59, through which oil is fed to an oil control valve 65. A housing 66 of the oil control valve 65 is attached to the side wall of the cylinder head 10, and the oil control valve 65 is adapted to control oil supply from an oil passage 67 to a variable valve 68 so as to control a variable cam mechanism (not shown) in response to engine speed. In addition, an oil passage 69 is formed extending upwardly from the filter 59, and the oil passage 69 is in communication with an induction pipe 71 of a baffle plate unit 70. A ring pipe 72 is connected to the induction pipe 71, and the induction pipe 71 and the ring pipe 72 are fitted to a baffle plate 73 with fixtures 73a. One end 71 a of the induction pipe 71 is connected to the cylinder head 10 through a sealing member 74 or an O-ring, and the other end is fitted in a cylinder head cover 75. The baffle plate 73 is fastened with screws 76 to the cylinder head cover 75, a portion 73b of which is fixed to the same by caulking. The baffle plate 73 is provided with a baffle board 73c, which is disposed opposite to a baffle section 75a protruding inwardly of the cylinder head cover 75, so that a maze is formed in a cam chamber 77 to separate oil particles. The cylinder head cover 75 has a discharge section 75b. Blow-by gas leaking from a combustion chamber 78 into a crank chamber (not shown) is introduced into the cam chamber 77 within the cylinder head cover 75, and oil particles in the blow-by gas is separated by the baffle plate 73. The blow-by gas without oil particles is returned to the intake passage 28 from the discharge section 75b through a circulation passage 79. An oil passage for supplying lubricating oil to cam shafts 17, 18 is formed of the induction pipe 71 and the ring pipe 72, and the oil flow rate is regulated by an orifice 71c in the induction pipe 71. In addition, the ring pipe 72 is bent such that straight sections 72a, 72b are disposed above the cam shafts, and a bent section 72c is adapted to decrease the magnitude of the bend of the oil passage so as to reduce pressure loss. The straight sections 72a, 72b are formed with injection holes 72d, 72e, corresponding to cams 19, 20, through which oil is injected toward the cams 19, 20. In addition, the straight section 72b on the intake side and the straight section 72a on the exhaust side are connected to form a continuous oil passage 80, so that oil pressure at the pipe end is increased and the rising characteristics of the oil pressure is improved, providing uniformity in oil pressure between intake and exhaust sides. Thus, the baffle plate 73 within the cylinder head cover 75 is provided with the oil passage 80 formed by the induction pipe 71 and the ring pipe 72, therefore the degree of freedom in designing the oil passage 80 is increased and pressure loss in the oil passage 80 can be reduced. Further, the oil passage 80 formed by the induction pipe 71 and the ring pipe 72 can be attached and detached together with the baffle plate 73, resulting in improved workability, and since it is not attached directly to the valve drive system, vibration on the oil passage 80 can be reduced, improving reliability. Fig. 9 through Fig. 12 show embodiments of the baffle plate unit, in which the oil passage 80 is constituted by a pipe 81 attached to the baffle plate 73 and injection holes 81a are formed on the pipe 81. In the embodiment of Fig. 9, fixtures 82 are welded to the baffle plate 73 for attachment of the pipe 81. In the embodiment of Fig. 10, fixtures 82 are riveted to the baffle plate 73 with rivets 83 for attachment of the pipe 81. In the embodiment of Fig. 11, fixtures 82 are fastened to the baffle plate 73 with bolts 84 and nuts 85 for attachment of the pipe 81. In the embodiment of Fig. 12, the pipe 81 is attached to the baffle plate 73 directly by welding. Thus, the oil passage 80 is constituted by the pipe 81 attached to the baffle plate 73, therefore the degree to freedom in designing the oil passage 80 is increased and pressure loss in the oil passage can be reduced. Fig. 13 shows an embodiment of the baffle plate unit 70, in which the oil passage is constituted by the baffle plate 73, and a press-formed sheet metal 86 fixed to the baffle plate 73, and the oil passage can be made from a small number of components. Although this embodiment is exemplified by the press-formed sheet metal 86 brazed to the baffle plate 73, adhesives for metal parts may be used for bonding. The metal plate 86 has injection holes. As described above, an oil passage is provided on a baffle plate within a cylinder head cover, therefore the degree of freedom in designing the oil passage is increased and power loss in the oil passage can be reduced. Further, it can be attached and detached together with the baffle plate, resulting in improved workability, and since it is not attached directly to the valve drive system, vibration on the oil passage can be reduced, improving reliability. Further, an oil passage may be constituted by a pipe attached to a baffle plate, therefore the degree of freedom in designing the oil passage is increased and power loss in the oil passage can be reduced. Moreover, an oil passage may be constituted by a baffle plate, and a press-formed sheet metal fixed to the baffle plate, therefore the oil passage can be made from a smaller number of components.

Claims: A four-stroke cycle engine (4) having intake and exhaust passages (13,14;11,12) openable to a combustion chamber (78) by means of intake and exhaust valves (16;15), respectively, wherein said intake and exhaust valves (16;15) are driven by cams (19,20) on cam shafts (17,18), blow-by gas leaking from said combustion chamber (78) into a crank chamber are introduced into a space within a cylinder head cover (75) and returned to said intake passages (11,12) from a circulation passage (79) through a baffle plate (73) within said cylinder head cover (75), characterized in that said baffle plate (73) is fixed to said cylinder head cover (75) and provided with an oil passage (80) for supplying lubricating oil to said cam shafts (17,18), wherein said oil passage (80) includes straight sections (72a,72b) with injection holes (72d,72e,81a) disposed above said cam shafts (17,18). A four-stroke cycle engine (4) according to claim 1, characterized in that said oil passage (80) is constituted by a pipe (81) attached to said baffle plate (73). A four-stroke cycle engine (4) according to claim 1, characterized in that said oil passage (80) is constituted by said baffle plate (73), and a sheet metal (86) fixed to said baffle plate (73). A four-stroke cycle engine (4) according to claim 2, characterized in that said pipe (81) is attached to the baffle plate (73) by welding or by fixtures (82), which fixtures (82) are welded, riveted or fastened with bolts (84) and nuts (85). A four-stroke cycle engine (4) according to at least one of the preceding claims 1 to 4, characterized in that the baffle plate (73) is provided with a baffle board (73c), which is disposed opposite to a baffle section (75a) protruding inwardly to said cylinder head cover (75) such that a maze is formed in a cam chamber (77) to separate oil particles. A four-stroke cycle engine (4) according to claim 5, characterized in that said blow-by gas is introducable into the cam chamber (77) within the cylinder head cover (75), whereas the baffle plate (73) separates the oil particles contained in said blow-by gas. A four-stroke cycle engine (4) according to claim 6, characterized in that said blow-by gas being separated from oil particles is returnable to an intake passage (28) from a discharge section (75b) through said circulation passage (79). A four-stroke cycle engine (4) according to at least one of the preceding claims 3 to 7, characterized in that said sheet metal is a press-formed sheet metal (86). A four-stroke cycle engine (4) according to claim 8, characterized in that said press-formed sheet metal (86) is brazed or bonded with adhesive to the baffle plate (73). A four-stroke cycle engine (4) according to claim 8 or 9, characterized in that said press-formed sheet metal (86) is provided with injection holes (81a).

Inventors: KATO MASAKI, KATO, MASAKI, Kato, Masaki c/oYamaha Hatsudoki Kabushiki Kaisha
Applicants: YAMAHA MOTOR CO LTD, YAMAHA HATSUDOKI KABUSHIKI KAISHA
Application year: 2000
Main classification: F02B75
IPC codes: F02B75, F02B29, F01M9, F01M1, F02F7