Internal combustion engine and camshaft thereof

Abstract

Cams are formed on a camshaft that correspond to intake valves so that intake flow of an internal combustion engine may be improved. The cams each have a cam lobe and the lobes of different cams are formed in different shapes.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of Korean Application No. 10-2003-0074756, filed Oct. 24, 2003, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

[0002] The present invention relates to an internal combustion engine and a structure of a camshaft for the internal combustion engine. More specifically, the engine and camshaft structure are capable of improving the flow of intake entering into a cylinder.

BACKGROUND OF THE INVENTION

[0003] Internal combustion engines are widely used. The engines often employ a plurality of intake valves in each cylinder. Intake valves of an internal combustion engine are driven by a camshaft, and more specifically, the intake valves are driven by a cam formed on the camshaft.

[0004] Operation timing and pattern of the intake valve are determined by the cam of the camshaft. Therefore, as multiple intake valves are driven, cams are formed on a camshaft following the number of intake valves in the engine. Nevertheless, according to the available arts, the shape of the cam that drives the intake valves are identically formed. In other words, the intake valves that are arranged in a plurality in each cylinder operate in the same operation and timing.

[0005] If flow of air, intake flow, that enters the engine through the intake valves can be improved, complete combustion and output power of the internal combustion engine can be improved.

SUMMARY OF THE INVENTION

[0006] According to a preferred embodiment, a camshaft structure for an internal combustion engine includes a plurality of cams. The plurality of cams include a first and a second cam to individually drive a first and a second intake valve, respectively, arranged for a single cylinder. The first and the second cam lobes of the first and second cams are formed in different shapes.

[0007] It is preferred that the first and second cam lobes have a principal axes offset from each other in terms of their offset angle settings. It is also preferable that the offset angle is an angle of less than about 60 degrees.

[0008] Preferably, the internal combustion engine of the present invention is an internal combustion engine that includes at least one cylinder and includes a first and a second intake valve that are arranged for one cylinder and a camshaft that is provided with a plurality of cams, including at least a first and a second cam to individually drive the first and second intake valves, respectively. The first and second cam lobes of the first and second cams are formed in different shapes. It is preferable for the first and second cam lobes have a principal axes offset from each other in terms of their offset angle settings. It is also preferable that the offset angle is an angle of less than about 60 degrees.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] For better understanding of the nature and objects of the invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which:

[0010] FIG. 1 is a cross-sectional view of a camshaft according to an embodiment of the present invention taken along line I-I of FIG. 2;

[0011] FIG. 2 is a cross-sectional view of an internal combustion engine showing a camshaft according to an embodiment of the present invention employed therein; and

[0012] FIGS. 3-5 illustrate a beginning period of an intake stroke, a middle period of an intake stroke, and a final period of an intake stroke, respectively, of an engine following revolution of a camshaft according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] FIG. 2 shows a cross-section of an internal combustion engine 200 with a camshaft 100 disposed within the engine 200 and FIG. 1 shows an axial view of a cross-section of the camshaft 100 of FIG. 2 taken along line I-I. As shown in the FIGS. a cylinder block 250 and a cylinder head 260 are combined to form a cylinder 205 of the engine 200. A plurality of intake valves, for example, a first and a second intake valve 210, 220 are respectively arranged in a first and a second intake port 261, 262 of the cylinder 205.

[0014] According to an embodiment, the camshaft 100 is furnished with a first and a second cam 110, 120. The first and second cams, 110 and 120, drive the first and second intake values 210, 220, respectively. Furthermore, the first and second cams 110, 120 have their first and second lobes 115, 125 formed in different shapes. More specifically, as illustrated in FIG. 1, the first and second cam lobes 115, 125 are formed such that their principal axes 112, 122 are offset from each other in terms of their offset angle (.theta.) settings. Such an offset angle (.theta.) may be clearly set by a person of ordinary skill in the art depending upon the intended intake inflow. However, according to an embodiment, it is desirable that the offset angles (.theta.) of the first and second cam lobes 115, 125 is formed to be less than about 60 degrees.

[0015] According to FIG. 2, the internal combustion engine 200 is provided with at least one cylinder 205 while the first and second intake valves 210, 220 are arranged in the cylinder (205). The camshaft 100 is installed in the top of the first and second intake values 210, 220. The first and second cams 110, 120 formed on the camshaft 100 drive the first and second intake valves 210, 220, respectively.

[0016] An exemplary process of intake flow generated within a cylinder following revolution of the camshaft 100 in the internal combustion engine 200 according to an embodiment of the present invention is shown in FIGS. 3-5. More specifically, FIG. 3 shows an intake flow generated in the beginning period of an intake stroke in the internal combustion engine 200 utilizing an embodiment of the present invention. FIG. 4 shows an intake flow generated in the middle period of an intake stroke in the internal combustion engine 200 utilizing an embodiment of the present invention. And, FIG. 5 shows an intake flow generated in the final period of an intake stroke in the internal combustion engine 200 utilizing an embodiment of the present invention. FIGS. 3b, 4b, and 5b are top views schematically illustrating the cylinder 205, intake valves 210, 220, and exhaust valves 310, respectively. While FIGS. 3a, 4a, and 5a are cross-sectional views of FIGS. 3b, 4b, and 5b taken along lines III-III, IV-IV, and V-V, respectively.

[0017] In the beginning period of an intake stroke, as illustrated in FIG. 3a, the first cam 110 first drives the first intake valve 210 by revolution of the camshaft 100. Therefore, the first intake valve 210 opens first, as illustrated in FIG. 3b, such that intake flow in a clockwise direction takes place in the beginning period of the intake stroke. In the middle period of the intake stroke, as illustrated in FIG. 4a, the first and second cams 110, 120, respectively drive the first and second intake valves 210, 220 by revolution of the camshaft 100. As a result, the first and second intake valves 210, 220 become open at the similar extents so intake flow is either slight or not formed in the middle period of the intake stroke, as illustrated in FIG. 4b. In the final period of the intake period, as illustrated in FIG. 5a, drive of the first intake valve 210 by the first cam 110 is terminated by revolution of the camshaft 100, and drive of the second intake valve 220 by the second cam 120 becomes in a maintained state. Therefore, only the second intake valve 220 becomes open so intake flow in a counterclockwise direction takes places in the final period of the intake period, as illustrated in FIG. 5b.

[0018] Preferred embodiments concerning the present invention are described in the above. However, this invention is not intended to be limited to the described embodiments, but include all modifications and alterations as will be appreciated by one of ordinary skill in the art that fall within the scope of the appended claims.

[0019] According to embodiments of the present invention, operation timing of the first and second intake valves arranged such that intake flow of air sucked into a cylinder may be improved. Therefore, since degrees of mixing of air and fuel may be improved in a cylinder, contributions may be made to complete combustion, reduction of harmful exhaust gas, and improvement of output of an internal combustion engine.

Claims

What is claimed is:

1. A camshaft structure for an internal combustion engine, comprising: a plurality of cams including a first and a second cam to respectively drive a first and a second intake valve arranged for a cylinder, wherein first and second cam lobes of said first and said second cams are formed in different shapes.

2. The camshaft structure according to claim 1, wherein said first and second cam lobes are offset from each other on their principal axes by their offset angle settings.

3. The camshaft structure according to claim 2, wherein said offset angle is less than about 60 degrees.

4. An internal combustion engine, comprises: at least one cylinder; at least a first and a second intake valve arranged for said one cylinder; and a camshaft provided with a plurality of cams that include a first and a second cam to respectively drive the first and the second intake valves, wherein first and second cam lobes of said first and second cams are formed in different shapes.

5. The internal combustion engine according to claim 4, wherein said first and second cam lobes are offset from each other on their principal axes with their offset angle settings.

6. The internal combustion engine according to claim 5, wherein said offset angle is less than about 60 degrees.

7. A camshaft for an internal combustion engine, comprising: a generally linear shaft having a length and a width; and at least two intake cams coupled with said generally linear shaft, said at least two intake cams configured and dimensioned to operate independent intake valves of a particular cylinder, wherein said at least two intake cams include cam lobes and said cam lobes are of different shapes from each other.

8. The camshaft of claim 7, wherein said different shape is an offset of rotation about a longitudinal axis of said generally linear shaft.

9. The camshaft of claim 8, wherein said offset is about 60 degrees or less.

10. The camshaft of claim 7, further comprising a plurality of intake cams configured and dimensioned to operate a plurality of independent intake valves of the particular cylinder.