FOUR-CYCLE INTERNAL COMBUSTION ENGINE

Abstract: In a four-cycle combustion engine of the type having plurality of intake valves and of exhaust valves provided each cylinder, at least an additional intermediate intake vale (5′) is arranged in order to enlarge the number of intake valves. Said intermediate intake valve is arranged to face the combustion chamber of the cylinder at a smaller angle (α₁) of inclination with respect to the axis (ℓ₁) of the cylinder than that of the remaining intake valves (5) which are arranged at both sides of said intermediate intake valve. As a result, any interference between said valves can be avoided.

Description: FOUR-CYCLE INTERNAL COMBUSTION ENGINE The present invention relates to a four-cycle infernal combustion engine. in order to improve t output ner- formance of a four-cycle internal combustion engine at high speed running range, it is a current Dractice to increase the number of intake valves and the number of exhaust valves for each cylinder of the internal combustion engine. This is partly because the sum of the areas to be occupied in a combustion chamber by the intake and exhaust valves, i.e., the so-called "valve area" is increased to improve the charge and discharge efficiencies in accordance with increases in the intake and exhaust valves and partly because the respective valves themselves can have their sizes and weights reduced so that their followabilities at a high speed can be improved. However, there exist restrictions in that the area of the combustion chamber to be faced by the respective valves is limited and that the plural valves have to be arranged within that limited area without any inser- ference among the rural valves. In case the number of the valves is increased, there arises another problem in providing a suitable system for driving said valves. Specifically, in the structre having its valves driven by the cam shafts which are located just above then., a valve or valves may occasionally fail to b aligned with the corresponding cam shaft if the valve number is too large. In this case, connecting means for connecting the mis ' =ie valve or valves and its or their cam shaft is newly required or diving it or them, ths raising another problem that the construction of the valve driving system is complicated. From the reasons thus far discussed, according to the prior art, the respective nunbers of the intake and exhaust valves are t.io and are not increased further. The invention as claimed has been conceived in order to remedy these drawbacks and solves the problem to provide a four-cycle engine which is enabled to have at least three intake valves of the intake and exhaust valve without detrimental interferences in a combustion chamber -and to drive the three pairs of valves without rendering their driving system too comelicated. One way of carrying out the invention is described in detail below with reference to drawings which illustrate merely one specific embodiment, in which: Figure 1 is a longitudinal section sho@ing the engine according to the present invention; Figure 2 is @ section taken along line II - II of Figure l; Figure 3 is a section taken along line III - III of Figure 1; and nit-ure 4 is a section taken along line IV - IV of Figure 2. These drawings illustrate one cylinder of 2 four-cycle engine, in which reference letters a and b indicate a cylinder and a cylinder head, respectively, and reference numerals 1 and 2 indicate an intake passage and an exhaust passage, respectively. Numeral 3 indicates a combustion chamber which is formed belo the afore-mentioned cylinder head o and into which the intake -e nd exhaust passages 1 and 2 are opened. Numeral 4 indicates a threaded hole for mounting an ignition plug, which is opened at the center portion of the upper side of the afore-mentioned combustion chamber 3. umeral 5 indicates intake valves for opening and closing the afore-mentioned intake passage 1, and numeral 6 indicates exhaust valves for opening and closing the exhaust passage 2. 'Said intake and exhaust valves 5 and 6 have their respective lower ends facing the combustion chamber 3 to close the open ends of the intake passage 1 and the exhaust passage 2, respectively. Their respective intermediate portions are slidably supported in the wall of the cylinder head b )through guides 5a and 6a. Numerals 7 and 8 indicate lifters which are formed to extend from the upper ends of both the afore-mentioned valves 5 and 6 and through which both the valves 5 and 6 are connected to corresponding cam shafts 9 and 10 just thereabove so that they are driven by said- shafts 9 and 10. Numerals 11 and 12 indicate springs which are made oncrative to bias the intake and exhaust va valves 5 and 6 in their closing directions. Furthermore, the afore-mentioned cam shafts 9 and 10 arerotatably supported above the cylinder head b through a cam carrier 13 and cam caps 14 and 15. Numeral 16 indicates a cover which covers the aforementioned can shafts 9 and 10 and the cam caps 14 and 15 and which is formed to extend from the e upper end of the cam carrier 13. The four-cycle engine thus constructed is equipped,so as to inprove its output performance, with a plurality of intake yalves 5 and a plurality of exhaust valves 6 for eacb cylinder, of which at least; the intake valves 5 are three in number. incidentally, it is @uite natural that the numbers of the intake passage 1 and the exhaust passage 2 be increased in accordance with the respective numbers of the valves 5 arid 6. The afore-mentioned three intake valves 5 are arranged and constructed such that the intermediate one 5' faces the combustion chamber 3 at; a smaller angle of inclination with respect to the axis l1 of the cylinder a than that of the remaining to outer intake valves 5,5. Specifically, if the angle of inclination of the inter mediate intake valve 5' is designated at whereas the -angle of inclination of the two outer intake valves 5 is indicated at &alpha;2, then a relation of &alpha;1 < &alpha;2 exists. On the other hand, the afore-mentioned intake valves 5 are further arranged and constructed such that all their respective axes l2 extend through the center 01 of the cam shaft 9. Thus, the afore-nentioned intake valves 5 e-e arranged, as shown in inure 2, such that the intermediate one 5' is more offset to the outside with respect o the center line l3, which divides the combustion chamber 3 into intake and exhaust portions, than the two intake valves 5,5 at both sides, whereby the entirety o intake valves 5- does not interfere with one another. Moreover, since the respective intake valves 5 have their axes l2 extending through the center O of the cam shaft 91 nothing is newly required except the lifters 7 acting as means for connecting the intake valves 5 ':.Ith said shaft 9 On the contrary, the exhaust valves 6 provided are two in number and are arranged in the combustion chamber 3 on a plane l4 which is parallel to the afore-mentioned center line l3. moreover, the exhaust valves 6 are arranged to have their respective axes l5 extending through the center 02 of the cam shaft 10 and are set with an equa angle of inclination &alpha;3 with respect to the axis l1 of the cylinder a. Thus, since the afore-mentioned exhaust valves provided are two in number, they are prevented from interfering with each other, even if they are in the combustion chamber 3 on the straight line, and nothing is newly required except the lifters 8 acting as means for connecting the exhaust valves 6 with the cam shaft 10. Incidentally, although the intake valves 5 provided in the embodiment thus far described are three in number, three exhaust valves Ç may be provided if they adopt the arrange ment and construction similar to those of the intake valves 5. As has been described hereinbefore, according to the present invention, the intermediate intake valve 5' is arranged to face the combustion chamber at a smaller an.le &alpha;1 of inclination with respect to the axis ±1 of the cylinder than that of the remaining two intake valves 5 when the three intake valves are to be provided. As a result, the intermediate intake valve 5' is more offset to the outside than the intake valves at both sides so that said three intake valves can be arranged in the combustion chamber without any interference among them. Moreover, said three intake valves are so --ranged that their respective axes extend through the center ol of their cam shaft 9. The positional relationship between the respective valves and their cam shaft is not ctnanged fron that of the prior art, and no new one is required as the means or connecting the respective valves Tith their cam so so@that the valve driving system is not necessarily made complicated.

Claims: CLAIMS: 1. 4 four-cycle internal combustion engine of the three having for each of its cylinders a plurality of intake valves and a plurality of exhaust velvets, both types of valve being driven by respective cam shifts as are provided just above said intake and exhaust valves, respectively, characterized in that at least of said intake valves (5) are provided three in number such that the intermediate intake valve (5') is arranged to face a combustion chamber (3) at a smaller angle (&alpha;1) of inclinasion with respect to the axis (l1) of said cylinder (a) than the angle (&alpha; ;2) of inclination of the remaining intake valves (5) at both sides of said intermediate inta'e valve (5'); and in that said three intake valves (5,5'5) nave their respective axis (e2) extending o intersect the axis (01) of a cam shaft (9) driving said intake valves. 2. nine according to claim 1, characterized in that the intermediate intake valve (5') is more offset to the outside with respect to a centerline (Q3), which divides the combustion chamber (3) into intake and exhaust portions, than the two intake valves (5,5) at both sides of said intermediate valve (5').

Inventors: YOSHIKAWA, MASAAKI
Applicants: YAMAHA MOTOR CO., LTD.
Application year: 1982
Main classification: F01L1
IPC codes: F01L1, F02B1, F02B75, F02F1