Four-cycle internal combustion engine

Abstract

 In a four-cycle combustion engine of the type having a plurality of intake valves and of exhaust valves provided in each cylinder, at least an additional intermediate intake valve (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 (a,) 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

[0001] The present invention relates to a four-cycle internal combustion engine. In order to improve the output performance of a four-cycle internal combustion engine atits high speed running range, it is a current practice to increase the number of intake valves and the number of exhaust valves for each cylinder of the internal combustion engine.

[0002] 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.

[0003] 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 interference among the plural valves.

[0004] In case the number of the valves is increased, there arises another problem in providing a suitable system -for driving said valves.

[0005] Specifically, in the structure having its valves driven by the cam shafts which are located just above then, a valve or valves may occasionally fail to be aligned with the corresponding cam shaft if the valve number is too large.

[0006] In this case, connecting means for connecting the nis- aligned valve or valves and its or their cam shaft is newly required for driving it or them, thus raising another problem that the construction of the valve driving system is complicated.

[0007] From the reasons thus far discussed, according to the prior art, the respective numbers of the intake and exhaust valves are two and are not increased further.

[0008] 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 complicated.

[0009] One way of carrying out the invention is described in detail below with reference to drawings which illustrate merely one specific embodiment, in which:-

[0010] Figure 1 is a longitudinal section showing the engine according to the present invention; Figure 2 is a section taken along line II - II of Figure 1; Figure 3 is a section taken along line III - III of Figure 1: and Firure 4 is a section taken along line IV - IV of Figure 2.

[0011] These drawings illustrate one cylinder of a 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.

[0012] Numeral 3 indicates a combustion chamber which is formed below the afore-mentioned cylinder head b and into which the intake and exhaust passages 1 and 2 are opened.

[0013] 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.

[0014] Nuneral 5 indicates intake valves for opening and closing the afore-mentioned intake passage 1, and numeral 6 Lndicates exhaust valves for opening and closing the exhaust passage 2.

[0015] 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.

[0016] 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.

[0017] Numerals 11 and 12 indicate springe which. are made operative to bias the intake and exhaust valves 5 and 6 in their closing directions.

[0018] Furthermore, the afore-mentioned cam shafts 9 and 10 are rotatably supported above the cylinder head b through a cam carrier 13 and cam caps 14 and 15.

[0019] Numeral 16 indicates a cover which covers the afore-mentioned cam shafts 9 and 10 and the cam caps 14 and 15 and which is formed to extend from the upper end of the cam carrier 13.

[0020] The four-cycle engine thus constructed is equipped, so as to improve its output performance, with a plurality of intake values 5 and a plurality of exhaust valves 6 for each cylinder, of which at least the intake valves 5 are three in number.

[0021] Incidentally, it is suite 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 and 6.

[0022] 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 two outer intake valves 5,5.

[0023] Specifically, if the angle of inclination of the intermediate intake valve 5' is designated at α1 whereas the angle of inclination of the two outer intake valves 5 is indicated at α2, then a relation of α1<α2 exists.

[0024] 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 O1 of the cam shaft 9.

[0025] Thus, the afore-mentioned intake valves 5 are arranged, as shown in Figure 2, such that the intermediate one 5' is more offset to the outside with respect to the center line ℓ3, which divides the conbustion chamber 3 into intake and exhaust portions, than the two intake valves 5,5 at both sides, whereby the entirety of intake valves 5 does not interfere with one another.

[0026] Moreover, since the respective intake valves 5 have their axes ℓ2 extending through the center O₁ of the cam shaft 9, nothing is newly required except the lifters 7 acting as means for connecting the intake valves 5 with said shaft 9.

[0027] 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.

[0028] 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 equal angle of inclination ℓ3 with respect to the axis ℓ1 of the cylinder a.

[0029] 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.

[0030] Incidentally, although the intake valves 5 provided in the embodiment thus far described are three in number, three exhaust valves 6 may be provided if they adopt the arrangement and construction similar to those of the intake valves 5.

[0031] 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 angle α1 of inclination with respect to the axis ℓ1 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.

[0032] Moreover, said three intake valves are so arranged that their respective axes extend through the center O₁ of their can shaft 9. The positional relationship between the respective valves and their cam shaft is not changed from that of the prior art, and no new one is required as the means for connecting the respective valves with their cam shaft so that the valve driving system is not necessarily made complicated.

Claims

1. A four-cycle internal combustion engine of the type having for each of its cylinders a plurality of intake valves and a plurality of exhaust velves, both types of valve being driven by respective cam shafts 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 (α₁) of inclination with respect to the axis (81) of said cylinder (a) than the angle (α2) of inclination of the remaining intake valves (5) at both sides of said intermediate intake valve (5'); and in that said three intake valves (5,5'5) have their respective axis (ℓ2) extending to intersect the axis (0₁) of a cam shaft (9) driving said intake valves.

2. Engine according to claim 1, characterized in that the intermediate intake valve (5') is more offset to the outside with respect to a centerline (ℓ3), 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').

Drawing