JPH04132834A - Air suction device of engine - Google Patents

Abstract

PURPOSE:To perform efficient scavenging suitable for strato-combustion at the time of low supercharge by providing scavenging ports which can introduce intake air in two direction, upwards and downward directions, and increasing the ratio of intake air introduced downward in accordance with rise of super charge pressure. CONSTITUTION:Scavenging ports 4a, 4b which can introduce intake air in two directions, comparatively upward direction and downward direction in comparison with the above in the combustion chamber 3 are provided in a two-cycle engine provided with an injector 10 and a spark plug 9 in the upper section of a combustion chamber 3. A scavenging adjusting valve 14 which adjusts the ratio of introduced intake air in two directions is provided in the scavenging port 4b on the lower side. Here, the ratio of introduced intake air in downward direction is increased in accordance with rise of supercharge pressure. Since the ratio of intake air introduced through the scavenging port 4b on the lower side is small at the time of low supercharge and much intake air is introduced through an air intake port 4a on the upper side, scavenging in the upper section of the combustion chamber 3 which is useful for strato-combustion is carried out efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an intake system for a two-stroke engine that is provided with intake supercharging means.

[Conventional technology]

2. Description of the Related Art Conventionally, it has been generally known that a two-stroke engine is provided with an intake air supercharging means in an intake passage leading to a scavenging port. For example, JP-A-59-49316
The device disclosed in the publication uses an upward flow uniflow system that has a scavenging port located below the combustion chamber of the cylinder and opened and closed by the vertical movement of the piston, and an exhaust port located above the combustion chamber and opened and closed by an exhaust valve. In a two-stroke engine, intake air pressurized by a supercharger is sent into a combustion chamber through a scavenging port, and waste gas is forced out through an upper exhaust port.

Although the engine shown in the above publication is a 2-stroke diesel engine, a 2-stroke gasoline engine may also be used.
The above-mentioned upward flow uniflow type and other types equipped with a supercharger are known, and in the case of a 2-stroke gasoline engine, in addition to the scavenging port, exhaust port, supercharger, etc. mentioned above, a spark plug, It is equipped with an injector, a throttle valve, etc. In particular, in a two-stroke engine that uses stratified combustion at low loads to save fuel consumption, an injector and a spark plug are provided in the upper part of the combustion chamber.

[Problem to be solved by the invention]

In a two-stroke engine in which the injector and spark plug are provided in the upper part of the combustion chamber as described above, fuel diffusion is suppressed by lowering the supercharging pressure by the intake supercharging means to some extent in the operating range where stratified charge combustion is desired. On the other hand, the supercharging pressure is adjusted according to the operating state so as to increase the supercharging pressure in an operating region where output is required. However, in the past, the direction in which scavenging air was introduced into the combustion chamber from the scavenging port was constant, so there remained points to be improved in terms of scavenging performance during low supercharging and improving output during high supercharging.

In view of the above-mentioned circumstances, the present invention provides a two-stroke engine equipped with an intake air supercharging means, which is capable of performing efficient scavenging suitable for stratified combustion during low supercharging, while filling the intake air in the combustion chamber during high supercharging. An object of the present invention is to provide an engine intake device that can increase engine output by increasing efficiency.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention provides a two-stroke engine equipped with an injector and a spark plug in the upper part of the combustion chamber. A scavenging port that allows intake air to be introduced in this direction, an air intake adjustment means that adjusts the ratio of intake air introduced in these two directions, and an air intake adjusting means that adjusts the supercharging pressure of the intake air sent from the intake supercharging means to the scavenging port. The engine is equipped with a supercharging pressure adjusting means and a scavenging control means for controlling the air intake regulating means so as to increase the intake air introduction ratio in the downward direction in accordance with the increase in the supercharging pressure.

The two-stroke engine to which the device with this configuration is applied is preferably an upward flow uniflow two-stroke engine having a scavenging port below the combustion chamber and an exhaust port above the combustion chamber. Further, in the above device, it is preferable to provide a supercharging control means for controlling the supercharging pressure adjusting means so as to increase the supercharging pressure in accordance with an increase in the load.

[Effect]

According to the above configuration, during low supercharging, the proportion of intake air introduced in the downward direction is small and a large amount of intake air is introduced in the upward direction, thereby efficiently scavenging the upper part of the combustion chamber, which is useful for stratified combustion. - On the other hand, during high supercharging, the ratio of intake air introduced in the downward direction is increased, so that the air fed at high supercharging pressure flows from the bottom to the top of the combustion chamber, and the entire combustion chamber due to supercharging is Filling with fresh air is performed efficiently.

In addition, when this configuration is applied to an upward flow uniflow type two-stroke engine, the exhaust port is located above the combustion chamber, and by suppressing the blow-through of intake air introduced in the downward direction, during high supercharging Filling efficiency can be effectively reduced.

Furthermore, when the supercharging pressure is increased in response to an increase in load, stratified combustion is performed favorably at low loads, and an effect of increasing supercharging efficiency in response to an increase in load can be obtained.

〔Example〕

Embodiments of the present invention will be described based on the drawings.

FIG. 1 schematically shows the overall structure of an apparatus according to an embodiment of the present invention, and FIG. 2 shows the specific structure of this apparatus. In these figures, a piston 2 is fitted inside a cylinder 1 of a two-stroke engine, and this piston 2
A combustion chamber 3 is formed above. A scavenging port 4 is provided below the combustion chamber 3 and is opened and closed by the vertical movement of the piston 2. On the other hand, the cylinder head 5 located above the combustion chamber 3 is provided with an exhaust port 7 that is opened and closed by an exhaust valve 6, and the exhaust valve 6 is opened and closed by a valve mechanism such as a camshaft 8. . Further, a spark plug 9 and an injector 10 for injecting fuel into the combustion chamber 3 are also attached to the cylinder head 5 and arranged above the combustion chamber 3.

The intake passage 11 communicating with the scavenging port 4 is provided with a supercharger and a feeder 1112 as an intake supercharging means, and the supercharger 12
The pressurized intake air is sent to the scavenging port 4 via the check valve 13. Then, when the piston 2 is in the downward position after the explosion and expansion, the exhaust valve 6 is opened and the intake air from the supercharger 12 is sent into the combustion chamber 3 through the scavenging port 4, causing the air to rise upward. Uniflow type scavenging is performed, and after the exhaust valve 6 is closed, the scavenging port 4 is closed by the rise of the piston 2.

The scavenging port 4 includes two types of ports 4a, an upper side and a lower side.
4b, it is possible to introduce intake air in two directions: a direction relatively upward into the combustion chamber and a direction downward. That is, the lower scavenging port 4b is provided at a position close to the lowest part of the combustion chamber 3 when the piston 2 is descending, and this lower scavenging port 4
An upper scavenging port 4a is provided above b.
These ports 4a and 4b are each arranged at a plurality of locations in the circumferential direction of the cylinder wall. The intake passage 11 branches near its downstream end into a passage 11a communicating with the upper scavenging port 4a and a passage 11b communicating with the lower scavenging port 4b. The lower scavenging air port 4b serves as a scavenging air adjusting means for adjusting the intake air introduction ratio in the two types of directions.
A scavenging adjustment valve 1 is operated by an actuator 14a to open and close this passage 11b.
4 is provided.

Further, the supercharger 12 is provided with supercharging pressure adjusting means. This supercharging pressure adjustment means is for adjusting the supercharging pressure of intake air sent from the supercharger 12 to the scavenging port 4, and in the embodiment shown in the figure, a relief passage 16 that communicates with the air to relieve a portion of the supercharged air, a relief valve 17 provided in the relief passage 16 to control the amount of relief, and an actuator 1 that operates the relief valve 17.
7a constitutes supercharging pressure adjusting means.

The intake passage 10 is also provided with a throttle valve 18 that operates in response to accelerator operation, an air flow meter (not shown) that detects the amount of intake air, and the like.

As shown in FIG. 1, the scavenging air adjustment valve 14 and the relief valve 17 of the supercharging pressure adjustment means are controlled by a control unit (ECU) 20 consisting of a microcomputer or the like.
are controlled via actuators 148.17a, respectively. The control unit 20 receives detection signals from a throttle opening sensor 26 that detects the opening of the throttle valve, a rotational speed sensor 27 that detects the engine rotational speed, and the like.

The control unit 20 includes a scavenging control means 21 and a supercharging control means 22. The scavenging control means 21
The scavenging adjustment valve 14 is controlled in response to the change in the boost pressure by the boost pressure adjustment means, and the scavenging adjustment valve 14 is opened in response to the increase in the boost pressure. This increases the proportion of intake air introduced into the lower scavenging port 4b. Further, the supercharging control means 22 controls the supercharging pressure adjusting means to relieve the supercharging pressure so as to increase the supercharging pressure in accordance with an increase in the load, based on a signal corresponding to the engine load from the throttle opening sensor 26 or the like. It controls valve 17.

A specific example of control by this control unit 20 as the scavenging control means 21 and supercharging control means 22 is as follows.
This will be explained with reference to the flowchart shown in FIG.

In this flowchart, first, in step S1, the throttle opening θ is read, and in step S2, it is determined whether the throttle opening θ is in a low load range smaller than the set WIa degree θ0.

At low load when the determination in step S2 is YES,
In step S3, the relief valve 17 is opened to a predetermined opening degree to set the supercharging pressure to a relatively low predetermined pressure, and in step S4, the scavenging adjustment valve 14 is closed, so that only the upper scavenging port 4a is set. Intake air is introduced relatively upward from.

In addition, when the load is high and the determination in step S2 is No, the relief valve 17 is closed in step S5 to increase the supercharging pressure compared to the low load, and in step S6, the scavenging air adjustment By opening the valve 14, intake air is introduced from both the upper and lower ports 4a, 4b.

In addition, in the example of this flowchart, the above boost pressure and intake air introduction direction are changed in two stages depending on low load and high load, but the above boost pressure etc. can be changed continuously depending on the operating condition. Alternatively, it can be controlled to change in multiple stages. For example, depending on the engine load (throttle opening degree) and engine speed, as the operating state changes to the load side and the rotation side, the supercharging pressure gradually increases and the intake air intake ratio of the lower scavenging port 4b gradually increases. The opening degree of the relief valve 17 and the opening degree of the scavenging adjustment valve 14 may be respectively controlled so as to increase the opening degree.

According to the device of this embodiment, at low load times when stratified combustion is required, the relief valve 17 is opened and the supercharging pressure is adjusted to a relatively low predetermined pressure (step 83).
>. Furthermore, at this time, the scavenging adjustment valve 14 is closed and intake air is introduced upward from the upper scavenging port 4a (step 84), thereby suppressing the scavenging action on the lower part of the combustion chamber that is not necessary for stratified combustion. Intake air is sent intensively to the upper part of the combustion chamber, which is the part necessary for stratified combustion. In this way, the scavenging air in the upper part of the combustion chamber is efficiently carried out in a low supercharging state, thereby achieving good stratified combustion.

On the other hand, when the load is high, the relief valve 17 is closed to increase the boost pressure (step 85).
Furthermore, at this time, the scavenging adjustment valve 14 is opened and intake air is also introduced from the lower scavenging port 4b (step Ss), so that the intake air flows from the lower part to the upper part of the combustion chamber 3. In this way, the scavenging action is applied to the entire combustion chamber while the boost pressure is increased, increasing the filling efficiency of the intake air, and as the boost pressure increases, the mixing effect of fuel and air is enhanced and uniform. Engine output is reduced by combustion. In particular, in an upward flow uniflow engine like the one in this example, the exhaust port 6 is provided at the top of the combustion chamber 3 and does not face the scavenging port 4, so the supercharging pressure is particularly high and the intake air is introduced downward. When the ratio is high and the load is high, blow-by of intake air to the exhaust port 6 is prevented, and the filling efficiency is effectively increased.

In addition, in the present invention, the structure that allows intake air to be introduced into the scavenging port 4 in two directions, relatively upward and downward, is as follows.
The present invention is not limited to the structure in which the upward scavenging port 4a and the downward scavenging port 4b are provided as in the above embodiment, but may be any structure shown in FIGS. 4 to 6, for example.

That is, in the example shown in FIG. 4, a flap-shaped intake guide member 31 is pivoted at a position near one end and rotated by an actuator (not shown) in the scavenging port 4 that opens at the bottom of the combustion chamber 3. It is provided. When the intake guide member 31 is in an inclined state, the intake air is introduced relatively upward into the combustion chamber 3 (the state shown by the solid line), and when the intake guide member 31 is in a horizontal state, the intake air is introduced relatively downward. The structure is such that the ratio of intake air introduced in the (approximately horizontal) direction is increased (as indicated by the two-dot chain line). In the example shown in FIG. 5, a pipe-shaped intake guide member 3 having a dogleg-shaped cross section is provided between the opening of the scavenging port 4 to the combustion chamber and the intake passage.
2 is provided, and this intake guide member 32 is rotatable around the zero point 33, and is actuated by an actuator (not shown), so that the direction of the combustion chamber side opening portion of the intake guide member 32 is directed upward and downward. It is configured to change over time. Also, the 611i! In the embodiment shown in I, an intake guide member 34 consisting of a pair of upper and lower plates parallel to each other is provided in the scavenging port 4 so that the angle can be changed. By changing the angle as shown by the two-dot chain line, the intake air introduction direction can be changed upward or downward. In these examples as well, the scavenging adjustment means may be constituted by an actuator or the like that operates the intake guide members 31, 32, 34, and may be controlled by the scavenging control means of the control unit.

In addition, although the above embodiment shows an application to an upward flow uniflow engine, other types of two-stroke engines can also be used by providing a supercharger in the intake passage leading to the scavenging port. The machine is provided with a supercharging pressure adjustment means, and a scavenging adjustment means is also provided to adjust the intake air introduction ratio in two directions, up and down, of the scavenging port, and the intake air introduction ratio in the downward direction is adjusted in response to an increase in the supercharging pressure. By providing a scavenging control means that controls the scavenging adjustment means so as to increase the amount, it is possible to improve the scavenging efficiency during low supercharging and to improve the intake air filling efficiency during high supercharging.

〔Effect of the invention〕

As described above, the present invention provides a two-stroke engine that has an injector and a spark plug in the upper part of a combustion chamber, and is also equipped with an intake supercharging means, in which the supercharging pressure adjusting means and the scavenging port are arranged relatively upwardly and downwardly. A scavenging adjustment means configured to allow intake air to be introduced in two directions, and a scavenging control means for increasing the intake air introduction ratio in the downward direction in response to an increase in boost pressure. Therefore, when the boost pressure is low, more intake air is introduced into the upper part of the combustion chamber, which allows efficient scavenging for stratified combustion, while when the boost pressure is high, more air is introduced into the lower part of the combustion chamber. Also, the engine output can be increased by sufficiently feeding intake air and performing uniform combustion in a state where the intake air filling efficiency for the entire combustion chamber is increased.

In addition, especially when this device is applied to an upward flow uniflow type two-stroke engine, when the above-mentioned downward intake air introduction ratio is increased in accordance with an increase in boost pressure, blow-by of intake air to the exhaust port is prevented. As a result, the effect of increasing filling efficiency can be more effectively exerted.

Furthermore, if the supercharging pressure is increased as the load increases, stratified charge combustion can be performed effectively at low loads, and uniform combustion can be achieved while increasing charging efficiency as the load increases. It is something that can be done.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the overall configuration of the device according to an embodiment of the present invention, Fig. 2 is a sectional view showing the specific structure, Fig. 3 is a control flowchart, and Figs. 4 to 6 are respectively FIG. 7 is a structural explanatory diagram of main parts showing another example of a structure that allows intake air to be introduced in two directions, upward and downward, through the scavenging port. 1... Cylinder, 3... Combustion chamber, 4... Scavenging port, 4a... Upper scavenging port, 4b-... Lower scavenging port, 6... Exhaust valve, 7... Exhaust port ,9...
Spark plug, 10... Injector, 12... Supercharger, 14... Scavenging air adjustment valve, 17... Relief valve, 20... Control unit, 21...
Scavenging control means, 22... supercharging control means. 1 Figure 1 Figure Figure 1

Claims (1)

[Claims] 1. In a two-stroke engine equipped with an injector and a spark plug in the upper part of the combustion chamber, intake air is introduced in two directions: relatively upwardly of the combustion chamber and downwardly. A scavenging port that has become possible, a scavenging adjusting means for adjusting the ratio of intake air introduced in these two directions, and a supercharging pressure adjusting means for adjusting the supercharging pressure of the intake air sent from the intake supercharging means to the scavenging port. and scavenging control means for controlling the scavenging air adjustment means so as to increase the intake air introduction ratio in the downward direction in accordance with the increase in the boost pressure. 2. The engine intake system according to claim 1, wherein the two-stroke engine is an upward flow uniflow two-stroke engine having a scavenging port below the combustion chamber and an exhaust port above the combustion chamber. 3. The intake system for an engine according to claim 1, further comprising supercharging control means for controlling the supercharging pressure adjusting means so as to increase the supercharging pressure in accordance with an increase in load.