JPH04132824A - Control device for engine - Google Patents

Abstract

PURPOSE:To enhance supercharging effect by advancing closing timing of an exhaust port in accordance with rise of supercharging pressure while maintaining scavenging operation when the supercharging pressure is low and suppressing outflow of fresh air from the exhaust port when the supercharging pressure is high. CONSTITUTION:In a two-cycle engine wherein a supercharger 11 is installed in an intake passage 10 leading to a scavenging port 4, a relief valve 17 for adjusting supercharging pressure and an exhaust timing changing device 15 for changing closing timing of an exhaust port 7 are provided. In this case, closure timing of an exhaust port 7 is advanced in accordance with rise of the supercharging pressure. Accordingly, when the supercharging pressure is low, the closing timing of the exhaust port 7 is delayed so as to secure the scavenging function. Then, when the scavenging pressure is high, the closing timing of the exhaust port 7 is advanced to suppress outflow of fresh air from the exhaust port 7 and supercharging effect can be thereby enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for a two-stroke engine 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.

[Problem to be solved by the invention]

In conventional two-stroke engines of this type, scavenging ports are opened and closed at predetermined constant timings. By the way, in order to properly perform the supercharging by the intake supercharging means, it is desirable to be able to change the supercharging pressure according to the operating condition by using the supercharging pressure adjusting means.
If the scavenging port is only opened and closed at a certain timing,
It was difficult to perform appropriate scavenging according to the boost pressure.

In other words, when the supercharging pressure of the intake air sent into the combustion chamber from the scavenging port is relatively low, the amount of scavenging air per unit time is relatively small. It is necessary to set the exhaust port closing timing to take a relatively long time, but if you set it like this, when the above boost pressure becomes ﾾ,
Because the exhaust gas is discharged quickly, a blow-by occurs in which fresh air flows out of the exhaust port following the exhaust gas, which causes a problem in that the effect of supercharging is reduced.

In view of the above circumstances, the present invention provides a two-stroke engine equipped with an intake supercharging means that allows the supercharging pressure to be adjusted, while ensuring scavenging action when the supercharging pressure is low. An object of the present invention is to provide an engine control device capable of suppressing the outflow of fresh air from an exhaust port when the charging pressure is high, thereby increasing the supercharging effect.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a supercharging pressure adjustment method for adjusting the supercharging pressure by the intake supercharging means in a two-stroke engine in which an intake supercharging means is provided in an intake passage leading to a scavenging port. means, an exhaust timing variable means for varying the closing timing of the exhaust port, and an exhaust timing control means for integrating the timing variable means so as to advance the closing timing of the exhaust port in accordance with an increase in the supercharging pressure. It is equipped with the following.

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 this 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 load.

[Effect]

According to the above configuration, when the boost pressure is low, the closing timing of the exhaust port is relatively late, so sufficient scavenging is performed before the exhaust port is closed, while when the boost pressure is high, the closing timing of the exhaust port is relatively late. By making this happen earlier, the supercharging time from when the exhaust port is closed until when the scavenging port is closed is lengthened.

Further, when this configuration is applied to an upward flow uniflow type two-stroke engine, the generation of longitudinal vortices in the combustion chamber is promoted during high supercharging.

Furthermore, if the supercharging pressure is increased in accordance with the increase in load, stratified combustion will be performed well under low supercharging conditions at low loads, and the filling rate will be increased under high supercharging conditions at high loads. Uniform combustion takes place.

〔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
11 above! A baking chamber 3 is formed. This combustion chamber 3
A scavenging port 4 that is opened and closed by the vertical movement of the piston 2 is provided below the cylinder head 5 , and an exhaust port 7 that is opened and closed by an exhaust valve 6 is provided in the cylinder head 5 located above the combustion chamber 3 . ing. Furthermore, spark plug 8
An injector 9 for injecting fuel into the combustion chamber 3 is also attached to the cylinder head 5 and arranged above the combustion chamber 3.

A supercharger 11 is provided in the intake passage 1o leading to the scavenging port 4.
is provided, and intake air pressurized by the supercharger 11 is sent to the scavenging port 4 via the check valve 12. Then, when the piston 2 is in the downward position after undergoing explosive expansion, the exhaust valve 6 is opened, and
The intake air from the supercharger 11 is sent into the combustion chamber 3 through the scavenging port 4, thereby performing upward uniflow scavenging, and after the exhaust valve 6 is closed, the scavenging port 4 is closed by the rise of the piston 2. It is now possible to

The opening/closing operation of the exhaust valve 6 is performed by a valve mechanism such as a camshaft 14, and this valve mechanism is equipped with variable exhaust timing means (VVT) 15. This exhaust timing variable means 15 is for making at least the closing timing of the exhaust valve 6 variable, and for example, as shown in FIG. It is variable. This exhaust timing variable means 15 is used for the intake of a four-stroke engine.

Since it is sufficient to apply a variable valve timing mechanism such as that known in the valve operating mechanism of an exhaust valve, detailed illustrations and explanations of its structure will be omitted, but for example, a rotation input such as a cam pulley that rotates in synchronization with the engine may be used. The exhaust timing variable means 15 is constituted by a movable member provided between the camshaft 14 and the camshaft 14 to change the relative phase thereof, and an operating mechanism for operating the movable member.

Further, the supercharger 11 is provided with a supercharging pressure adjusting means. This supercharging pressure adjustment means is for adjusting the supercharging pressure of intake air sent from the supercharger 11 to the scavenging port 4, and in the embodiment shown in the figure, a relief passage 16 that communicates with the side and relieves a portion of the supercharged air; a relief valve 17 that is provided in the relief passage 16 and controls the amount of relief;
Actuator 18 that operates this relief valve 17
The supercharging pressure adjusting means is constituted by the above. The intake passage 10 is also provided with a throttle valve 19 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 exhaust timing variable means 9 and the relief valve 17 of the supercharging pressure adjusting means are operated by a control unit (ECU) consisting of a microcomputer, etc.
20. This control unit 20
Detection signals are input from a throttle opening sensor 26 that detects the opening of the throttle valve, a rotation speed sensor 27 that detects the engine rotation speed, and the like.

The control unit 20 includes an exhaust timing control means 21 and a supercharging control means 22. The exhaust timing control means 21 controls the exhaust timing variable means 1 in response to the supercharging pressure being changed by the supercharging pressure adjusting means.
5, and the closing timing of the exhaust valve 6 is made earlier in accordance with the increase in the supercharging pressure. 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.

t! by this control unit 20 as the exhaust timing control means 21 and supercharging control means 22! 1
A specific example of step III will be explained with reference to the flowchart of 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 opening 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 exhaust valve closing timing is set at the basic timing shown by the solid line in FIG. The exhaust timing variable means 15 is controlled so as to achieve the following. This basic timing is predetermined to be a timing suitable for ensuring scavenging when the boost pressure is at the predetermined pressure.

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 timing for closing the exhaust valve is increased. The exhaust timing variable means 15 is controlled so that the early opening timing is set to the early opening timing shown by the broken line in FIG.

In addition, in the example of this flowchart, the above-mentioned boost pressure and exhaust valve closing timing are changed depending on low load and high load.
Although the boost pressure and the like are changed in stages, it is also possible to control the boost pressure and the like to be changed continuously or in multiple stages depending on the operating state. For example, as shown in Fig. 5, depending on the engine load (throttle opening θ) and the engine speed Ne, the boost pressure gradually increases as the operating state becomes high load side and high speed side, and the exhaust valve The opening degree of the relief valve 18 and the timing change amount of the exhaust timing variable means 15 may be controlled so that the closing timing becomes gradually earlier.

According to the device of this embodiment, the boost pressure is adjusted according to the operating condition, and when the boost pressure is set to a relatively low predetermined pressure (step 83), the exhaust valve closing timing is adjusted. By controlling the basic timing as described above (step S4), the exhaust port is opened until a relatively late period within the period in which the scavenging port 4 is open, and scavenging is achieved in a low boost pressure state. On the other hand, when the boost pressure is controlled to a high pressure (step 85), the amount of scavenging air per unit time increases and the time required to achieve scavenging becomes shorter, so the exhaust valve closing timing is accelerated to compensate for this. (step Ss), the exhaust port 7
This prevents fresh air from flowing out after the exhaust gas flows out from the exhaust valve 6.
The supercharging time from when the scavenging port 4 is closed to when the scavenging port 4 is closed is lengthened. Therefore, the supercharging effect during high supercharging is effectively exerted, and the intake air filling rate is increased.

Furthermore, in the upward flow uniflow two-stroke engine as in this embodiment, during the supercharging time after the exhaust valve 6 is closed, supercharged air flows into the combustion chamber 3 from the lower scavenging port 4. Since tumbles (vertical vortices) are generated within the engine, when the supercharging pressure is increased and the exhaust valve closing timing is advanced accordingly, the tumble generation is promoted and the mixing effect with air is enhanced.

In addition, if this engine is controlled to increase the boost pressure at high loads depending on the engine load, at low loads the boost pressure will be set low, suppressing fuel diffusion and stratified combustion. When the engine is loaded, the fuel is diffused due to the promotion of tumble generation, and uniform combustion is performed.

Therefore, at high loads, the air utilization rate increases due to uniform combustion.
In addition, the filling rate is also increased by controlling the exhaust timing in accordance with the supercharging pressure control as described above.

Although the above embodiment shows an application to an upward flow uniflow engine, other types of two-stroke engines can also be used by installing a supercharger in the intake passage leading to the scavenging port and using this supercharging. The exhaust system is equipped with a supercharging pressure adjustment means for the machine, and an exhaust timing variable mechanism for varying the closing timing of the scavenging port, and the exhaust port closing timing is accelerated as the supercharging pressure increases. By providing the timing control means, it is possible to secure scavenging air during low supercharging and improve the intake air filling rate during high supercharging.

Further, in this type of engine, the injector 9 for injecting the fuel in the combustion chamber 3 is shown in FIGS. 6 and 7.
If the structure shown in the figure is used, it will be advantageous to change between stratified combustion and uniform combustion.

That is, the injector 9 shown in FIG. 6 includes a two-dollar valve 91, an injection control electromagnetic coil 92 that operates the valve 91 in the opening direction, a movable stopper 93 for the valve 91, and a lift that moves the movable stopper 93. and a control electromagnetic coil 94, and when the lift control electromagnetic coil 94 operates the movable stopper 93,
The opening lift amount of the needle valve 91 is switched between high lift and low lift. The spray angle is configured to be small in the high lift state shown in FIG. 7(a), and large in the low lift state shown in FIG. 7(b). When using an injector with this structure, a high lift state with a small spray angle at low loads is advantageous for stratified combustion, and a low lift state at high loads injects fuel over a wide angle, which is advantageous for uniform combustion. Become.

〔Effect of the invention〕

As described above, the present invention provides a two-stroke engine equipped with an intake supercharging means, which includes a supercharging pressure adjusting means, an exhaust timing variable means, and an exhaust port closing timing earlier in accordance with an increase in supercharging pressure. Since the exhaust timing control means is provided to control the exhaust timing variable means so as to control the exhaust timing variable means so that scavenging is performed well even when the boost pressure is relatively low, the exhaust port is By suppressing the outflow of fresh air from the engine, it is possible to effectively increase the charging amount and increase the engine output.

In addition, especially when this device is applied to an upward flow uniflow type two-stroke engine, when the boost pressure is high, the generation of tumbles due to the flow of intake air flowing into the combustion chamber from the scavenging port is promoted, resulting in increased output. It becomes even more advantageous.

Furthermore, if it is applied to an upward flow uniflow two-stroke engine and the boost pressure is increased as the load increases, stratified combustion will be effective at low loads, and uniform combustion will be achieved at high loads. In combination with the increased filling amount, the engine output is increased.

[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 an explanatory diagram showing exhaust timing, and Fig. 4 is a control flowchart. , Fig. 5 is an explanatory diagram showing an example of the control characteristics of boost pressure and exhaust timing, Fig. 6 is a sectional view showing an example of the structure of the injector, and Figs. 7 (a) and (b) are explanations of the operation of the same injector. It is a diagram. 1... Cylinder, 3... Combustion chamber, 4... Scavenging port, 6... Exhaust valve, 7... Exhaust port, 11...
Supercharger, 15... Exhaust timing variable means, 17...
・Relief valve, 20...control unit,
21... Exhaust timing control means, 22... Supercharging control means. Figure 1 Figure 2 Figure 3 Figure Figure Figure e Figure

Claims (1)

[Claims] 1. In a two-stroke engine in which an intake supercharging means is provided in an intake passage leading to a scavenging port, a supercharging pressure adjusting means for adjusting the supercharging pressure by the intake supercharging means, and an exhaust port. and an exhaust timing control means that controls the timing variable means to advance the closing timing of the exhaust port in accordance with the rise in the supercharging pressure. control device for the engine. 2. The engine control device 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 engine control device according to claim 2, 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.