JPH06207518A - Intake device for engine - Google Patents

Abstract

PURPOSE:To eliminate torque valley (output reduction) at the time of comparatively low speed rotation by branching and opening an air mixture gas in/out branch pipe whose one end is closed, in the vicinity of an intake valve between the throttle valve and the intake valve of the intake passage of an engine, and conserving fluid motion inertia. CONSTITUTION:An intake valve 21 and an exhaust valve 22 are provided on the upper part of a combustion chamber 4 in an engine main body 1, and an intake passage 7 and an exhaust passage 9 are communicated thereto. The intake passage 7 is communicated with the throttle valve 14 of a carburetor 15 through a spacer 13. An air fuel mixture in/out branch pipe 18 is constituted in such a way that a pipe 16 is installed on the spacer 13, and a pipe 17 whose one end is closed is connected to the top end of the pipe 16. In a position where the air-fuel mixture in/out branch pipe 18 is opened to the intake passage 7, its cross sectional area is set to the minimum level, and the cross sectional area of the pipe 17 is set to a level a little larger than that. Since it is possible to make an air column in the branch pipe 18 resonant with some comparatively low speed engine rotating speed, flow motion inertia is conserved by resonance after the intake valve 21 is closed, even if the throttle valve 14 is in a low opening range. It is thus possible to eliminate reduction of engine output at the time of comparatively low speed rotation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine intake system in which the engine intake passage is improved to improve the engine characteristics.

[0002]

2. Description of the Related Art Generally, an engine is designed so that the pulsation effect of exhaust gas is best matched at high speed rotation near the maximum output speed. Therefore, the low speed rotation of the engine tends to cause a reduction in output, that is, a so-called torque valley. This is because the positive pressure wave from the exhaust system applied to the cylinder or crankcase at the beginning of the intake stroke acts to block the inflow of the air-fuel mixture from the intake valve, but the throttle valve is high even at low speed rotation. When operating in the opening range, the intake amount is large and the resistance of the throttle valve is also small, so the intake inertia effect can compensate for the decrease in the intake amount and prevent the output from decreasing. In the above, since the intake amount is small, the throttle valve has a large resistance, and the inertia effect is extremely weak, the torque valley becomes remarkable.

[0003]

In the intermittent flow phenomenon, the engine is operated in a high opening range exceeding half the opening of the throttle valve for adjusting the intake flow rate, or is operated at a high speed even if it is less than that. There is no problem when the engine is operated, but the engine performance may be significantly reduced when the engine is operated in a low opening range below that range, particularly when the engine is operated at a relatively low speed. That is,
As described above, in the high opening range of the throttle valve, generally, the resistance of the throttle valve is small, the intake flow rate is large, and the flow inertia is large, so that the intake valve is only compressed in the vicinity of the intake valve, and is stable upstream. Is flowing. This means that closing the intake valve does not cause a decrease in charging efficiency, and does not cause a reduction in output, that is, a so-called torque valley.

However, since the intake flow is restricted by the throttle valve in the low opening range, the throttle valve has a large resistance and a small intake flow rate, and its flow inertia is not so large. Therefore, the intake valve is closed. Since the intake air flow is stopped, the filling efficiency is reduced, and as a result, the output is reduced.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to reduce intake air in a low opening range, particularly in an intake passage at a relatively low speed operation. It is an object of the present invention to provide an intake device for an engine, in which the flow inertia is preserved as much as possible to improve the intake charging efficiency and prevent the engine performance from being deteriorated.

[0006]

In order to achieve the above object, an engine intake system according to the present invention is an air-fuel mixture whose one end is closed between a throttle valve and an intake valve in an intake passage in the vicinity of the intake valve. The inflow / outflow branch pipe is branched and opened.

[0007]

When the engine is operated in the low opening range of the throttle valve, a large negative pressure is generated in the intake passage between the throttle valve and the intake valve. In addition, since a pressure difference occurs before and after the intake valve due to the resistance of the intake valve, the negative pressure is greatest on the cylinder or crankcase side. Therefore, between the throttle valve and the intake valve, a mixture gas inlet / outlet branch pipe with one end closed, which is set so that the air column in the branch pipe resonates at a certain low rotational speed at which a torque valley appears remarkably, is opened and the engine is When operating at the rotational speed, the branch pipe pushes the air-fuel mixture sucked into the branch pipe in the intake stroke of the engine into the intake passage, and the intake valve is closed until the end of the intake stroke and the start of the next intake stroke. During the period, a two-cycle supercharging action is performed in which the air-fuel mixture passing through the throttle valve is sucked into the branch pipe and is pushed out again in the next intake stroke. Therefore, the pressure rises naturally in the intake passage between the throttle valve and the intake valve, and the pressure difference between the inside of the cylinder or the crankcase increases. Due to this increase in pressure difference, the amount of air-fuel mixture passing through the intake valve increases. Then, these operations of the branch pipe do not stop the flow of the air-fuel mixture in the intake passage at all when the intake valve is closed, and preserve the flow inertia in the intake passage.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes an engine body, which has a combustion chamber 5 formed by a cylinder 2, a piston 3 and a cylinder head 4. In addition, a poppet-shaped intake valve 21 is provided above the combustion chamber 5.
Further, an exhaust valve 22 is provided, and the intake passage 7 and the exhaust passage 9 communicate with the combustion chamber 5 via these.

The intake passage 7 communicates with a carburetor 15 equipped with a throttle valve 14 via a spacer 13, and is open to the atmosphere through an air filter (not shown). In addition,
The vaporizer 15 is of a negative pressure-responsive variable venturi type.

Further, a pipe 16 is attached to the spacer 13, and a pipe 17 having a closed end is connected to the pipe 16, and the pipes 16 and 17 open the inside of the intake passage 7. The air inlet / outlet branch pipe 18 is configured.

The gas mixture inlet / outlet branch pipe 18 has a minimum cross-sectional area in the portion open to the intake passage 7, that is, the pipe 16, and the cross-sectional area of the pipe 17 is slightly larger than this. Further, it is preferable to set the internal volume of the air-fuel mixture branch pipe 18 to 1/6 or more of the volume of the intake passage downstream of the throttle valve 14, and at least the opening of the air-fuel mixture branch pipe 18 from the throttle valve 14. 1 / the volume of the intake passage to the
It is desirable to have 10 or more.

As a means for increasing the volume of the air-fuel mixture branch pipe 18, the air-fuel mixture branch pipe 1 is used as shown in FIG.
It is also very advantageous to enlarging a part of 8 and providing the enlarged closed chamber 19. In this case, the total length of the air-fuel mixture inlet / outlet pipe 18 can be shortened, and the assemblability in the vehicle can be improved. In this embodiment, the lead valve 12 of the two-stroke engine is used as the intake valve, and the rest of the structure is substantially the same as that of the embodiment of FIG. 1, so the description thereof will be omitted.

With the above construction, the air column in the branch pipe 18 can resonate at a relatively low engine speed. Therefore, even in the low opening range of the throttle valve 14, even after the intake valve 21 is closed and the intake stroke of the engine ends, the resonance causes the air-fuel mixture generated by the carburetor 15 to pass through the throttle valve 14. Flow and intake can be made to preserve flow inertia. The pressure in the intake passage 7 between the throttle valve 14 and the intake valve 21 naturally rises due to the supercharging action of the branch pipe 18, and the pressure difference between the inside of the cylinder 2 or the crankcase increases.

As a result, the positive pressure wave from the exhaust system acts to reduce the amount of intake air, and this pressure difference increases even in the low opening range of the throttle valve 14 where the flow inertia becomes extremely weak. As a result, the amount of the air-fuel mixture passing through the intake valve 21 increases to prevent the engine output from decreasing. Further, the supply of the air-fuel mixture from the air-fuel mixture inlet / outlet pipe 18 is performed from the opening in the vicinity of the intake valve 21, so that its responsiveness is good.

In the four-cycle engine, since the intake valve closing delay is provided so that the inertia effect can be obtained at high speed rotation, blowback is always generated at low speed rotation, and this blowback enters the branch pipe. The supercharging effect of the pipe is reduced,
Also, in a 4-cycle engine, compression / explosion /
Since there are three strokes of exhaust, and then intake comes again, it is difficult to match the supercharging action of the branch pipe for two cycles. For example, the intake manifold of a two-cylinder engine with a crank having a phase difference of 180 degrees. The configuration such as attaching one branch pipe to the field is specified. Since the supercharging action of the branch pipe is due to the vibration of the air column in the branch pipe, this intake manifold
It is easily affected by the resistance of the intake valve and the resistance of the intake valve.

[0016]

According to the present invention, since the air-fuel mixture branch pipe is formed at a position downstream of the throttle valve in the intake passage, the flow inertia of the intake air in the intake passage is preserved, that is, the air-fuel mixture branch pipe. Due to the supercharging action of, the pressure in the intake passage between the throttle valve and the intake valve rises, the pressure difference between the cylinder and the crankcase increases, and the increase in this pressure difference increases the amount of the air-fuel mixture passing through the intake valve. Can be increased, and the problem of the low opening degree of the throttle valve and the decrease in engine output at relatively low speed, that is, the torque valley, which have been problems in the past, can be eliminated.

Further, in this case, when the mixture gas inlet / outlet branch pipe has an enlarged closed chamber, its capacity can be set to any value and the branch pipe itself can be made short. Moreover, since the opening of the branch pipe serves as both the inlet and the outlet of the air-fuel mixture, it can be made compact as a whole.

Further, since the opening of the air-fuel mixture branch pipe is located near the intake valve, the supply of the air-fuel mixture from the air-fuel mixture branch pipe has a positive effect on the combustion chamber or the crank chamber immediately. It further improves the combustion efficiency in the engine.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of an intake device according to the present invention.

FIG. 2 is a sectional view showing the main part of another embodiment of the intake device according to the present invention.

[Explanation of symbols]

 1 Engine Main Body 7 Intake Passage 12, 21 Intake Valve 14 Throttle Valve 15 Vaporizer 18 Mixture Inlet / Outlet Pipe 19 Expanded Sealed Chamber

Claims (1)

[Claims] 1. An engine in which a carburetor and a throttle valve for adjusting an intake flow rate are provided in an intake passage, and an intake valve is provided on a downstream side of the throttle valve, the engine is provided between the throttle valve and the intake valve in the intake passage. An intake system for an engine, characterized in that a mixture gas inlet / outlet branch pipe having one end closed is branched and opened near the intake valve.