JPH0692738B2 - Engine intake system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an intake system for an engine mounted on a motorcycle or the like.

(Prior Art) It is known that an improvement in engine output is achieved by improving intake efficiency of intake air that is drawn into a cylinder through an intake passage.

Here, the suction efficiency refers to the supply state of the mixed gas to the cylinder, and is the maximum value when the following inertial supply characteristic number Z has a certain appropriate experimental value.

The above-mentioned characteristic number Z is Is the angular velocity of the crankshaft, a is the speed of sound in the intake passage, V is the volume of the cylinder, l is the length of the intake passage, and A is the cross-sectional area of the intake passage.

Therefore, based on the above points, in order to improve the engine performance, a valve for opening and closing the intake passage according to each engine speed is provided, and the opening / closing operation of the valve adjusts the cross-sectional area A of the intake passage. Therefore, the desired number of habituation characteristics Z
Is obtained (for example, in Japanese Utility Model Sho 60-3252).
No. 5 bulletin).

(Problems to be Solved by the Invention) By the way, normally, the air-fuel mixture is introduced into the combustion chamber while being unevenly flown in the intake passage, and the air-fuel mixture is unevenly distributed in a part of the combustion chamber. To do. Therefore, it is conceivable to obtain stable ignition by utilizing this property, but in the above-mentioned conventional configuration, since no consideration is given to this point, there is still room for improvement in improving engine performance. It is left.

(Object of the Invention) The present invention has been made by paying attention to the above circumstances. When a valve for opening and closing the intake passage is provided to improve engine performance, the closing operation of the valve is utilized. And further to improve the engine performance.

(Structure of the Invention) In order to achieve the above object, the present invention is characterized in that the discharge portion of the spark plug is exposed to the top of the combustion chamber and the intake passage is curved upward in a convex arc shape. In the intake device for an engine provided with a valve for opening and closing the intake passage, the space on the lower wall side of the intake passage near the combustion chamber can be opened and closed by the valve, and as the engine speed increases, The above-mentioned valve is operated so as to open the space on the lower wall side of the intake passage, and conversely, the above-mentioned valve is operated so as to close the space between the lower walls of the intake passage as the engine speed decreases. It is in.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

1 and 2, E is a 4-cycle engine,
Reference numeral 1 is a cylinder of this engine E, 2 is a cylinder block, 3 is a cylinder head, and 4 is a piston.

An intake passage 6 and an exhaust passage 7 are formed in the cylinder head 3, and the intake passage 6 opens to a combustion chamber 8 in the cylinder 1.
Intake valve 9 for opening and closing the opening of the cylinder and the cylinder 1
An exhaust valve 10 is provided for opening and closing the opening of the exhaust passage 7 that opens inside. Each of these valves 9 and 10 has an intake passage 6
A spring 12 is biased to close each opening of the exhaust passage 7 to the inside of the cylinder 1.

On the other hand, a cam shaft 13 is provided above each of the intake valve 9 and the exhaust valve 10, and the cam shaft 13 is interlocked with the crank shaft of the engine E via a timing chain device (not shown).

Then, the cam shaft 13 rotates with the rotation of the crank shaft,
During the intake stroke and exhaust stroke of the engine E, the camshaft 13 pushes the intake valve 9 and the exhaust valve 10 against the elastic force of the spring 12 to open and close them.

A carburetor 14 is provided in the intake passage 6.

The intake inlet of the carburetor 14 communicates with the atmosphere via an air cleaner (not shown).

The vaporizer 14 has a piston valve 16, and the piston valve 16
Is biased by a spring 18 so as to close an intake passage 17 formed in the carburetor 14.

A metering needle 21 is projectingly provided at a projecting end of the piston valve 16 into the intake passage 17, and the metering needle 21 is fitted into a main nozzle 22 formed in the intake passage 17. The main nozzle 22 is connected to a float chamber (not shown).

The piston valve 16 is connected to an operation unit (not shown) via a wire 23, and the operation of this operation unit opens and closes the intake passage 17 via the wire 23. With the opening of the intake passage 17, metering is performed. The needle 21 will open the main nozzle 22 larger.

When the engine E is operated, the air-fuel mixture in the intake passage 6 is sucked to a negative pressure, and the negative pressure causes combustion in the funnel chamber to be sucked out into the intake passage 17 via the main nozzle 22. Then, this fuel is mixed with the air from the air cleaner and supplied into the cylinder 1.

When the cylinder 1 is viewed with its axis oriented vertically as shown in FIG. 1, the discharge portion 24a of the spark plug 24 faces the top of the combustion chamber 8. The intake passage 6 is curved upward in a convex arc shape.

A valve 25 is provided near the combustion chamber 8 to open and close the space on the lower wall side of the intake passage 6.
That is, the valve 25 is composed of a recess 26 having a semicircular cross section formed on the lower surface of the intake passage 6, and a valve body 27 having a semicircular cross section that is rotatably fitted in the recess 26. . And
When the valve body 27 rotates, the valve body 27 enters the recess 26, thereby opening the intake passage 6 (shown by the solid line in the figure).

On the other hand, a part of the valve body 27 projects into the intake passage 6 to close the space on the lower wall side of the intake passage 6 (indicated by a chain double-dashed line in the figure). In this case, the fuel sucked out from the main nozzle 22 of the carburetor 14 and flowing along the lower surface of the intake passage 17 is guided to the central portion of the intake passage 6 by the valve body 27 protruding into the intake passage 6 (in the figure). Arrow A). And
At the protruding end of the valve body 27, it is mixed with intake air (arrow B in the figure) and supplied into the cylinder 1.

The valve 25 is opened / closed as follows according to the engine speed.

In FIG. 3, the rotation speed detector 29 for the engine E is shown.
Is provided. The rotation speed detector 29 detects, for example, an ignition signal of an igniter unit for operating the engine E as an engine speed. On the other hand, the valve body 27 is linked to a servomotor 30. Then, the detection signal of the rotation speed detector 29 is a comparator.
It is input to the servo motor 30 via 31 and the amplifier 32, whereby the servo motor 30 operates and the valve body 27 is rotated. The rotation of the valve body 27 is stopped by the position detector 33.

In the above case, the valve body 27 is operated so as to open the intake passage 6 as the engine speed increases. Further, the valve main body 27 is operated so as to close the intake passage 6 as the engine speed becomes lower (shown by a chain double-dashed line in FIG. 1).

That is, for example, as shown in FIG. 4, when the desired characteristic output is obtained by setting the desired characteristic number Z to a desired value when the engine E is rotating at a high speed of 9000 rpm or higher, the desired characteristic number Z is Since the cross-sectional area of the intake passage 6 is used as the denominator and the angular velocity of the crankshaft corresponding to the engine speed is guided as the numerator, when the engine speed becomes lower than this, the cross-sectional area of the intake path 6 does not change in the conventional configuration. Therefore, the value of the above-mentioned intake characteristic number Z changes so as to become smaller than a desired value, and as a result, the output of the engine E decreases (shown by the chain double-dashed line in the figure).

However, in the configuration of the above-described embodiment, when the engine speed decreases, the cross-sectional area of the intake passage 6 also decreases due to the operation of the valve 25. Therefore, the inertia characteristic number Z is a desired value even if the engine speed varies. Therefore, the output is improved in this low rotation speed range (shown by the solid line in the figure).

(Effect of the Invention) According to the present invention, the valve is operated to open the intake passage as the engine speed increases, and the valve is operated to close the intake passage as the engine speed decreases. With this configuration, the intake characteristic number, which is guided with the cross-sectional area of the intake passage as the denominator and the angular velocity of the crankshaft corresponding to the engine speed as the numerator, can be maintained at a substantially desired value even if the engine speed changes.

Therefore, the intake efficiency can be improved and the output can be improved at each engine speed in all operating states ranging from the low engine speed to the high engine speed. Then, in the above case, the discharge portion of the spark plug is exposed to the top of the combustion chamber, the intake passage is curved upward in a convex arc shape, and the intake air of the engine is provided with a valve for opening and closing the intake passage. In the device, since the space on the lower wall side of the intake passage near the combustion chamber can be opened and closed by the valve, the valve that operates to close the space is a mixture that tries to pass through the lower wall side of the intake passage. Will guide the intake passage to the upper wall side.

At this time, as described above, since the combustion chamber side end of the intake passage has a circular arc shape that is convex upward, as described above, the air-fuel mixture guided to the upper wall side in the intake passage has its inertia By force, it is introduced into the combustion chamber along the upper wall side of the intake passage, and the air-fuel mixture is intensively supplied to the top side of this combustion chamber.

Since the discharge part of the spark plug is located at the top of the combustion chamber as described above, the above-mentioned air-fuel mixture is concentratedly supplied to this discharge part, and stable ignition is obtained. Therefore, the combustion is stabilized and the engine performance is improved.

[Brief description of drawings]

1 shows an embodiment of the present invention, FIG. 1 is a longitudinal sectional view of an engine, FIG. 2 is a view taken along the line II--II of FIG. 1, FIG. 3 is an electric circuit block diagram, and FIG. 4 is an engine. FIG. 4 is a graph showing the relationship between the rotation speed and the passage area and output of the intake passage. 1 ... Cylinder, 6 ... Intake passage, 8 ... Combustion chamber, 24 ...
… Spark plug, 24a… Discharge part, 25… Valve, E… Engine.

Claims (1)

[Claims] 1. When an axis of the cylinder is oriented vertically, the discharge portion of the spark plug is exposed to the top of the combustion chamber, and an intake passage communicating with the outside of the cylinder from the combustion chamber is provided. In an intake device for an engine, which is provided with a valve that opens and closes the intake passage by bending the intake passage upward in a convex arc shape, the intake passage on the lower wall side of the intake passage near the combustion chamber The space can be opened and closed by the valve, and the valve is operated so as to open the space on the lower wall side of the intake passage as the engine speed increases, and conversely, as the engine speed decreases, the lower side of the intake passage An intake system for an engine, characterized in that the valve is configured to operate so as to close a space on the wall side.