JP2687406B2 - 4 cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Use) The present invention relates to a four-cycle engine having a plurality of intake valves and a plurality of exhaust valves interposed in a combustion chamber.

(Prior Art) In a 4-cycle engine, two intake ports and two exhaust ports are installed in parallel, and an intake valve and an exhaust valve are provided in each unit in order to expand the port area and obtain high output. There is a so-called 4-valve type.

Further, there is a so-called top field intake in which the intake passage is introduced substantially parallel to the cylinder axis in order to reduce the intake resistance and increase the intake charging efficiency, so that the intake flow is linear.

A four-cycle engine of these four-valve models equipped with a top field intake is disclosed in, for example, Japanese Patent Laid-Open No. 61-261644.
No. in the official gazette. In this case, the intake cam shaft that controls the intake valve and the exhaust cam shaft that controls the exhaust valve are arranged in parallel in parallel with the crankshaft,
Each valve is directly controlled by each cam, and the intake passage is connected between the cam shafts and the intake port.

However, it is desirable to arrange the spark plug in the center of the combustion chamber. For this reason, a spark plug insertion hole is provided in the center of the cylinder head. The spark plug needs to be inclined toward the exhaust valve side in order to avoid interference with the intake passage. However, no obstacle is allowed in the direction in which the spark plug is inserted, so that it is necessary to expand the space between the cam shafts, and the angle between the valves is increased.

If the angle of the valves is large, they tend to interfere with each other, so the lift amount and the valve area are limited, resulting in a reduction in the port area as a whole, and a negative factor for combustion efficiency. It was On the contrary, if the angle of the valve is made small, there is a problem that the intake passage is bent to avoid interference with the spark plug and the intake efficiency is reduced.

(Problems to be Solved by the Invention) The present invention is a four-valve type conventional four-cycle engine adopting a top field intake system, even if the angle of the valve is increased or the intake passage is bent. This was done in consideration of the existence of any defect.

In consideration of the above-mentioned circumstances, the present invention provides a four-cycle engine in which the intake passage can be formed straight without interfering with the spark plug even if the valve holding angle is made small, and also has the advantage of top field intake. The purpose is to

[Configuration of the invention]

(Means for Solving the Problems) In order to achieve the above object, a four-cycle engine according to the present invention virtually divides a combustion chamber formed in a cylinder vertically with a vertical center plane orthogonal to a crankshaft. One intake port on one side and multiple exhaust ports on the other side. Each intake port and exhaust port has an intake valve and an exhaust valve, and two overhead camshafts parallel to the crankshaft. The intake cam and the exhaust cam are installed side by side to control the opening and closing of each intake valve and the exhaust valve, and within the projected area of the combustion chamber where the combustion chamber is projected in the cylinder axial direction, from above the cylinder head. One intake that extends between both overhead cam shafts and extends almost linearly toward the combustion chamber The passage is communicated with each intake port by an intake branch passage branched after passing the overhead cam shaft, while an exhaust branch passage extending from each exhaust port is connected to one exhaust passage outside the projected area of the combustion chamber. A spark directed toward the center of the combustion chamber in the space of the cylinder head surrounded by the intake branch passage and the exhaust branch passage so that the exhaust passage is led out to the outside of the cylinder head so as to be substantially parallel to the crankshaft and the overhead cam shaft. It has a plug inserted.

(Operation) In the four-cycle engine according to the present invention, a plurality of intake ports and exhaust ports are arranged in a direction orthogonal to the crankshaft and the overhead cam shaft so as to adopt a top field intake layout. Therefore, when inclining the spark plug while avoiding interference with the intake passage, the inclination direction is parallel to the cam shaft, so that the cam shaft does not interfere with the spark plug insertion direction.

Therefore, it is not necessary to bend the intake passage, and the interval between the cam shafts, that is, the valve holding angle can be made sufficiently small as necessary. All of the advantages of the top field intake and valve wrap angle are satisfied, and a high-performance 4-cycle engine can be obtained.

(Embodiment) A description will be given below with reference to the drawings showing an embodiment of the present invention.

FIG. 1 shows the basic structure of a 4-cycle engine according to the present invention. The piston 2 sliding in the cylinder 1 moves up and down by the rotation of the crankshaft 4 via the connecting rod 3. In the combustion chamber 5 formed at the upper end of the cylinder 1,
Two intake ports 6a, 6b are respectively provided on one side that is virtually divided into two parts in a vertical center plane orthogonal to the crankshaft 4, that is, a plane passing through the centerline XX orthogonal to the crankshaft 4. Two exhaust ports 7a, 7b are arranged on the other side, and intake valves 6a, 6b and exhaust ports 7a, 7b are respectively provided with intake valves 8a, 8b and exhaust valves 9a, 9b.

Two overhead cam shafts 10a and 10b parallel to the crankshaft 4 are mounted above the combustion chamber 5. An intake cam 11a and an exhaust cam 12a are installed in parallel on one of the overhead cam shafts 10a to control the intake valve 8a and the exhaust valve 9a. Similarly, the other overhead cam shaft 10b is provided with an intake valve 8b, an intake cam 11b for controlling the exhaust valve 9b, and an exhaust cam 12b in parallel.

The intake passage 13 connected to the intake ports 6a, 6b linearly passes between the overhead cam shafts 10a, 10b substantially parallel to the cylinder axis, and the overhead cam shafts 10a, 10b are connected to the intake branch passages 13a, 13b. After passing, it is branched and introduced.
On the other hand, exhaust branch paths 14a, 14b connecting to the exhaust ports 7a, 7b
Is bent upward toward the outside of the cylinder head 17 as shown in FIGS. 4 and 5, and is outside the cylinder head 17 substantially parallel to the crankshaft 4 and the overhead cam shafts 10a and 10b. Exhausted to one exhaust passage
Merge into 14.

The spark plug 15 is attached to the cylinder head toward the center of the combustion chamber 5 in the space surrounded by the intake branch passages 13a and 13b and the exhaust branch passages 14a and 14b. In this case, the spark plug 15 for avoiding interference with the intake passage 13 is inclined toward the exhaust passage 14. Since the overhead cam shafts 10a and 10b do not exist on the axial extension line of the spark plug 15, the space for insertion can be easily secured by this inclination.

In this way, this 4-cycle engine can skillfully avoid the interference between the intake passage 13 and the spark plug 15, and the interference between the space for inserting the spark plug 15 and the overhead cam shafts 10a and 10b. Can be formed into an ideal top field system, and the valve holding angle can be reduced without any obstacle, and the overall fuel filling efficiency can be increased, high combustion efficiency can be obtained, and engine output can be improved.

Next, FIG. 2, FIG. 3, FIG. 4 and FIG. 5 show a square 4 mounted on a motorcycle according to another embodiment of the present invention.
It shows an engine.

In the engine unit 16, the four-cycle engines shown in the above basic form are arranged in a four-cylinder front-rear, left-right rectangular shape, two front and rear crankshafts are arranged in parallel, and the front row cylinders 1a and 1b share the front crankshaft 4a and the rear row The cylinders 1c and 1d of the same share the rear crankshaft 4b. Left and right cylinders 1a and 1b and 1c
1d intake valves 8a, 8b, exhaust valves 9a, 9
b, intake cams 11a, 11b, exhaust cams 12a, 12
b, the intake passage 13, and the exhaust passage 14 are arranged symmetrically.

As shown in FIG. 4, one intake passage 13 and the intake branch passages 13a and 13b branched from the intake passage 13 are the combustion chambers in which the combustion chambers in the cylinders 1a to 1d are projected in the cylinder axial direction. Each intake branch passage 13a, 13b is arranged within a projected area (corresponding to the area surrounded by the peripheral walls of the cylinders 1a to 1d).
Are communicated with the intake ports 6a, 6b within the projected area of the combustion chamber.

Further, as shown in FIG. 4, the exhaust branch passages 14a, 14b extending from the exhaust ports 7a, 7b are connected to one exhaust passage 14 outside the projected area of the combustion chamber, and the exhaust passages 14 are
The exhaust pipe 18 is connected to the outside of the cylinder head 17.

The exhaust passage 14 is open to both outsides of the cylinder head 17 and is connected to an exhaust pipe 18. The exhaust pipe 18 extends laterally and then hangs downward to the front and is guided downward below the engine unit 16.

The intake passage 13 has a cylinder head 17 and a head cover 19
And is opened on the upper surface of the head cover 19. Intake passage
A carburetor 20 connected to 13 is mounted on the upper surface of the head cover 19. A box-type frame 21 is connected to the upper surface of the head cover 19 and houses the carburetor 20. The inside of the box type frame 21 functions as an air cleaner case together with the cap 22. 23 is an air cleaner element and 24 is an inlet. A steer grin head 25 is detachably fixed to the front end of the box-shaped frame 21, and a fuel tank 26 is continuous behind the cap 22.

The steering head 25 supports the front wheels 27 so that they can be steered,
The rear wheel 28 is pivotally supported at the rear end of a swing arm 29 pivotally supported at the rear edge of the engine unit 16, and is a rear cushion unit.
Buffered suspension by 30. Reference numeral 31 denotes a seat rail fixed to the engine unit 16, on which a seat 32 is mounted.

Each of the two overhead cam shafts of the four cylinders 1 is a left and right continuous cam shaft 33a, 33b, 33c, 33d that sandwiches the driven gears 32a, 32b, 32c, 32d as parallel cam shafts 33a, 33b, 33c, 33d. Be prepared.

The rear crankshaft 4b end projects to the side surface of the engine unit 16, and the cam drive sprocket gear 34 is pivotally supported.
A cam drive gear shaft 35 is rotatably mounted on the cylinder head 17, and a driven sprocket gear 36 is pivotally supported at an outer end protruding to the side thereof, and a cam chain 37 is provided between the cylinder head 17 and the cam drive sprocket gear 34. Is suspended, and rotation is transmitted from the crankshaft 4b.

The cam drive gear 38 is attached to the inner end of the cam drive gear shaft 35.
Is fixed and simultaneously meshes with the driven gears 32b, 32c of the cam shafts 33b, 33c in the intermediate portion. The driven gears 32b and 32c are driven by the idle gears 39a and 39b, respectively.
Works with a, 32d. In this way, the cam shafts 33a, 33b, 33c, 33d are simultaneously driven.

In the figure, 40 is a spark plug insertion hole formed in the cylinder head 17, 41 is an idle sprocket gear for guiding the cam chain 37, 42 is a tensioner, and 43
Is a cam chain housing and 44 is its cover.

In this way, this 4-cycle engine can independently obtain a high output, and at the same time, by constituting the square 4 engine, the carburetor 23 can be mounted on the head cover 19 to downsize the engine unit, and the exhaust pipe 18 Since it is derived from the side, it is easy to handle and the tube can be shortened.

〔The invention's effect〕

As described above, the 4-cycle engine according to the present invention is
The combustion chamber formed in the cylinder is virtually divided vertically by the vertical center plane orthogonal to the crankshaft, and one intake port is arranged on one side and multiple exhaust ports are arranged on the other side. An intake valve and an exhaust valve are respectively installed in the ports, and an intake cam and an exhaust cam are installed in parallel on two overhead cam shafts parallel to the crankshaft to control the opening and closing of each intake valve and the exhaust valve. In the projected area of the combustion chamber in which the combustion chamber is projected in the cylinder axis direction, one intake passage extending substantially linearly from above the cylinder head, passing between both overhead cam shafts, toward the combustion chamber, Each intake port by the intake branch path branched after passing the overhead cam shaft While communicating with each other, one exhaust branch passage extending from each exhaust port is coupled to the exhaust passage outside the projected area of the combustion chamber, and the exhaust passage is formed so as to be substantially parallel to the crankshaft and the overhead cam shaft. A spark plug, which is led out to the outside, is inserted into the space of the cylinder head surrounded by the intake branch passage and the exhaust branch passage toward the center of the combustion chamber. The two overhead cam shafts are substantially linear near each other. Since the intake passages that extend to one are grouped together and the valve scissor angle can be made small, it is easy to make it compact, and the intake passage is a top field intake system that can improve intake filling efficiency, and the exhaust passage has a crank. The exhaust branch from each exhaust port is formed parallel to the shaft and overhead cam shaft. Converging to one exhaust passage outside the projected area of the combustion chamber (cylinder axis direction), it is possible to avoid sudden changes in the exhaust passage shape, and perform smooth exhaust of the exhaust flow to improve engine performance. Can be achieved.

Moreover, even if the spark plug is inserted into the space of the cylinder head surrounded by the intake branch passage and the exhaust branch passage toward the center of the combustion chamber, the spark plug inserted is between the two overhead cam shafts. Since there is a large opening between the exhaust passage that is located substantially parallel to these overhead cam shafts and the intake passage of the top field intake system,
The spark plug is easily accessible and can be easily attached and detached to improve workability. On the other hand, the spark plug is located in the center of the combustion chamber, so that combustion efficiency can be improved and engine performance can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view of a 4-cycle engine showing an embodiment of the present invention, and FIG. 2 is a side view of a motorcycle equipped with a square 4 engine according to another embodiment of the present invention, FIG. 3, FIG. 4 and 5 show the main part of the square 4 engine of FIG. 2, FIG. 3 is a vertical sectional side view, FIG. 4 is a partially cutaway plan view, and FIG. 5 is a vertical sectional rear view. 1,1a, 1b, 1c, 1d …… Cylinder, 4,4a, 4 …… Crankshaft,
5 ... Combustion chamber, 6a, 6b ... Intake port, 7a, 7b ...
Exhaust port, 8a, 8b …… Intake valve, 9a,
9b ... Exhaust valve, 10a, 10b ... Overhead cam shaft, 11a, 11b ... Intake cam, 12a, 12b ... Exhaust cam, 13 ... Intake passage, 13a, 13b ... Intake branch passage, 14 ... Exhaust Passages, 14a, 14b ... Exhaust branch, 15 ...
…Spark plug.

Claims (1)

(57) [Claims] 1. A combustion chamber formed in a cylinder is virtually divided vertically by a vertical center plane orthogonal to a crankshaft, and one intake port is arranged on one side and a plurality of exhaust ports are arranged on the other side. An intake valve and an exhaust valve are provided in each intake port and an exhaust port, and two intake cams and exhaust cams are installed in parallel on the two overhead cam shafts parallel to the crankshaft to install each intake valve and the exhaust valve. Opening / closing control is performed, and within the projected area of the combustion chamber in which the combustion chamber is projected in the cylinder axis direction, one straight line extending from above the cylinder head, passing between both overhead cam shafts, and extending toward the combustion chamber. The intake passage is branched by the intake branch passage after passing through the overhead cam shaft. The exhaust branch passage extending from each exhaust port is connected to one exhaust passage outside the projected area of the combustion chamber while communicating with the exhaust port, and the exhaust passage is substantially parallel to the crankshaft and the overhead cam shaft. Out to the outside of the head,
A four-cycle engine characterized in that a spark flag directed toward the center of a combustion chamber is inserted in a space of a cylinder head surrounded by the intake branch passage and the exhaust branch passage.