JPS627924A - Exhaust control device - Google Patents

Abstract

PURPOSE:To enable an exhaust pulsation to be functional across a wide range of engine's operating condition, by providing a member capable of changing aperture area of an exhaust pipe's open end thereto, and making the aperture area adjustable in accordance with the engine's operating condition. CONSTITUTION:A shielding member 13 which is operated by an actuator 14 is provided on an end portion 10 where the exhaust pipe 2 of an engine 1 opens into a muffler 11. The actuator 14 works to let open the shielding member 13 in case of high speed rotations, for example, 10,000 rotations, and to close a part of the open end portion 10, in case of, for example, a degree of 6,000 rotations. Thereby, the open end portion 10 diminishes in size by an area S1 so that the most suitable reflected wave can be obtained by variation of a substantial length of the exhaust pipe, and so on.

Description

[Detailed Description of the Invention] L1 Shangxia M Hoki 1 The present invention is connected to a 1" 1-ki boat of a reciprocating internal combustion engine,
This invention relates to an exhaust control device in an exhaust pipe that outputs exhaust gas D1 to the outside.

In a two-cycle or four-stroke internal combustion engine, it has been conventionally practiced to improve scavenging efficiency and volumetric efficiency by utilizing pressure vibrations, or pulsations, that occur in an exhaust pipe when exhaust gas is discharged. Effective use of such dynamic effects of the exhaust system is particularly emphasized in two-stroke engines, but even in four-stroke engines, when the negative wave of the pulsating wave in the pipe overlaps in the latter half of the exhaust period, exhaust system use is promoted. It is also known that if the valve openings are covered at the same timing, the scavenging effect will be improved and the volumetric efficiency will be increased.

However, in an internal combustion engine that uses the pulsating waves generated in the exhaust pipe to improve output, the period of the pulsating waves, in other words, the period of the pulsating waves generated in the exhaust pipe, Since the time it takes for the reflected It power wave to reach the valve port is constant regardless of the engine speed, when the above-mentioned pulsating wave is adjusted so that it acts effectively in the rotation speed range, it will not work in other rotation speed ranges. In this case, the arrival timing of the pulsating waves no longer coincides with the desired stroke timing of the engine, and an inappropriate rotational speed region occurs in which the pulsating waves have the opposite effect.

Therefore, the present invention aims to eliminate the trough between 1 and 1 lb which occurs in the inappropriate rotational speed range by eliminating the pulsation effect in the inappropriate rotational speed range.

Therefore, in the present invention, a movable shielding member capable of changing the cross-sectional area is provided at the open end of the new trachea, which is connected to the II air boat of the internal combustion engine and has a substantially constant cross-sectional area.

The open end of the exhaust pipe mentioned above means the part where the cross-sectional area of the exhaust passage changes to widen. The part where the trachea opens into the muffler is the open end of the exhaust pipe.

At such an open end, the pressure wave propagating within the v1 trachea is reflected with a different sign. That is, the positive pressure wave becomes a negative pressure wave, and the negative RF wave becomes a positive pressure wave and is reflected. In a rotational speed range where the timing of this reflected wave reaching the valve port coincides with the desired stroke timing of the engine, the positive or negative pressure caused by the reflected wave acts advantageously to improve scavenging efficiency, volumetric efficiency, etc. However, the timing does not match in the inappropriate rotational speed range, and the reflected waves act disadvantageously, leading to a decrease in efficiency.

In the present invention, since a movable shielding member is provided at the open end, in an inappropriate rotation speed range, this shielding member can be moved to partially shield the cross section of the trachea. can. In this way, the pressure wave that reaches the open end will be reflected as a pressure wave with a different sign in the unshielded cross section, and in the shielded part, the sign will change because the shielding member becomes the fixed end. It is reflected as an unchanged pressure wave. For example, when a positive pressure wave reaches the open end, a negative pressure wave is reflected from the unshielded portion, and a positive pressure wave is reflected from the shielded portion.

Therefore, these positive and negative reflected waves cancel each other out, and the pulsating effect of the exhaust gas does not reach the valve port portion, making it possible to eliminate the decrease in efficiency in an inappropriate rotation speed range.

11) Hereinafter, an embodiment in which the present invention is applied to an exhaust pipe of a four-stroke internal combustion engine will be described. FIG. 1 is a schematic diagram showing an internal combustion engine 1 and a v1 trachea 2 connected thereto. internal combustion i seki 1
The engine is a four-cycle engine, and has an exhaust port 3 and an intake boat 4 at the head, and each of these boats communicates with a cylinder chamber 7 via an exhaust valve 5 and an intake valve 6, respectively. The exhaust pipe 2 is connected to an exhaust port 3. 8 is the intake pipe,
9 is a vaporizer. The exhaust pipe 2 extends downstream from the υI air boat 3 with substantially the same cross-sectional area, and the open end 10 at the rear end opens into a large-diameter exhaust muffler 11.

When the υ1 air valve 5 opens during the exhaust stroke of the internal combustion engine 1, combustion gas in the cylinder chamber 7 is released into the exhaust muffler 11 via the fresh air port 3 and the exhaust pipe 2, and then through the exhaust outlet 1.
2 is released into the atmosphere. Then, near the top dead center at the end of the exhaust stroke, the intake valve 6 opens to start sucking in fresh air, and then the exhaust valve 5 closes.

A movable shielding member 13 is provided at the open end 10 of the exhaust pipe 2 . This shielding member 13 has a structure similar to a normal gate valve, and has two positions: an open position where the cross section of the exhaust pipe 2 is opened at the front as shown by a dotted line 13a in FIG.
It is possible to move up and down in the figure between a shielding position where the cross section of the exhaust pipe 2 is partially shielded as shown by 3b. In this embodiment, the shielding member 13 is a solenoid 14.
The shielding member 13 is moved by actuation of a solenoid 14. The solenoid 14 is electrically connected to an engine speed detection device (not shown), and detects a range of engine speeds, for example, 2500.
The plunger 1 is energized by the electrical output from the detection device in the rotational speed range of ~8000 r, p, ra.
5 to move the shielding member 13 to the shielding position 13b.

Alternatively, the shielding member 13 can be connected to a mechanical rotational speed detection device that uses centrifugal force, and the shielding member 13 can be mechanically moved in accordance with the rotational speed as described above.

Below, in describing the operation of this embodiment, the above internal combustion engine 1
And the exhaust pipe 2 has the shielding member 13 in the rotation speed range around 10000r, p, IIl (suitable rotation speed range).
It is assumed that the setting is such that the dynamic effect of the exhaust can be effectively utilized when the exhaust gas is opened. Figure 3 shows this adaptation I.
This is a diagram showing the time course of pressure fluctuations occurring in the exhaust port 3 during operation at a rotation speed within the n1 rotation speed range, where the horizontal axis 1 represents time and the vertical axis p represents pressure. The period E between the bottom dead center BDC and the top dead center TDC is the exhaust stroke period. 1)
In period [0, υ1 Kiben 5 heard, iJF Kibow 1-3
The pressure suddenly reverses, producing a positive pressure pulse.

This positive pressure pulse propagates through the loss tube 2 at the speed of sound, and the open end 1
At 0 the negative pressure pulse is reflected. Since this negative pressure pulse reaches the exhaust boat 1-3 in the latter half of the υ1 electric culm F, a negative pressure indicated by (-) in the figure is generated in the exhaust boat 3 near the top dead center TDC. Therefore, the exhaust action is promoted by this negative pressure, and since the intake valve 6 is first opened at SO during this negative pressure period and then the exhaust valve 5 is closed at ES, the scavenging action is also improved and the volumetric efficiency is increased.

However, when the shielding member 13 is in the open position, the engine speed is out of the compatible speed range, for example, 6000r, p.
, about m t,: (If it is lowered, the reach of the negative pressure pulse is the same as before, so as shown in Fig. 4, the negative pressure period (-) occurs in the middle of the exhaust stroke E. , top dead center TD
In the vicinity of C, the pressure in the exhaust boat 3 becomes positive as shown by (+) in the figure. Therefore, due to this positive pressure, the exhaust action and the scavenging action are reduced by m1, and the volumetric efficiency is rather reduced. As a result, when the change in the volumetric efficiency ηV with respect to the engine speed Ne is expressed in a diagram, it becomes a curve a in FIG. 6. In the figure, A is the compatible rotation speed range where the negative pressure timing and υ1 electric stroke timing are compatible as shown in Figure 3, and B is the compatible rotation speed range where the negative pressure timing and exhaust stroke timing are compatible as shown in Figure 4. This is an inappropriate rotation speed range. In the inappropriate rotation speed range B, the output torque of the engine decreases, resulting in a so-called torque valley.

Therefore, in this embodiment, when the engine speed is within the inappropriate speed range B, the solenoid 14 is actuated by the electrical output from the engine speed detection device to move the shielding member 13 to the shielding position 13b. In this way the open end 1
In the exhaust pipe 2 in which 0 is partially closed, as shown in FIG. It is reflected as a negative open-end wave p2, and is also reflected as a positive closed-end wave p1 with an amplitude P1 at the shielding portion 10b. The open-end wave p2 and the closed-end wave p+ are canceled by interference. As a result, as shown in Fig. 5, the negative pressure generated by υ1 electric boat 3 becomes smaller, and the same goes for the subsequent secondary waves, so the positive pressure as shown in Fig. 4 near top dead center DC becomes smaller. Does not occur. Therefore this 1
There is no low t in the volumetric efficiency ηV due to the engine speed, and as shown by the broken line in FIG. 6, a relatively high volumetric efficiency ηV is maintained even in the inappropriate rotational speed range B, and the torque valley is eliminated. Although the dotted line C shows a convex ηV curve when the shielding member 13 is placed in the shielding position even in the compatible rotation speed range A, since the shielding member 13 occupies the release position in this region, high efficiency can be obtained along the curve a. As a result, a ηV convex curve as shown by curve I in the same figure is formed.

FIG. 8 shows the closed end reflectance P+/Po of the closed end wave p1, the open end reflectance IP2/pH1 of the open end wave p2, and the open end shielding ratio, that is, the cross section of the exhaust pipe 2 shielded by the shielding member 13. The area S1 (Fig. 2) is a diagram showing the relationship between the ratio SI/So and the total cross-sectional area So of the exhaust pipe 2, and the excitation pressure Pa increases from 0.2 Ky/c#i to 1.29. /c#i. When the closed-end reflectance and the open-end reflectance are equal, both reflected waves completely cancel each other out, so that such a shielding factor M becomes the optimum point. However, since this optimum point M varies somewhat depending on the excitation pressure Po, the shielding part 11
It is preferable that the shielding rate of the open end portion 10 by 3 is set to 20 to 40%.

As mentioned above, in the present invention, the cross-sectional area is changed at the open end of the air loss pipe, which is connected to the internal combustion engine's air port and has a substantially constant cross-sectional area. Since a movable shielding member is provided, it is possible to effectively utilize the exhaust pulsation effect in a predetermined engine speed range to improve engine output, and also to improve engine output in an inappropriate engine speed range where the exhaust pulsation effect is disadvantageous. In this case, it is possible to cancel out the loss-of-air pulsation effect and prevent a decrease in engine output.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing an embodiment of the present invention, Fig. 2 is an end view showing a shielding member provided at the open end of the exhaust pipe, and Fig. 3 is an exhaust boat in the appropriate rotation speed range when the shielding member is open. A line diagram showing pressure fluctuations, Figure 4 is a diagram showing force fluctuations in the inappropriate rotation speed range, and Figure 5 is a line diagram showing IJ force fluctuations in the inappropriate rotation speed range when the shielding member is shielded. , Fig. 6 is a diagram showing the relationship between engine speed and volumetric efficiency, Fig. 7 is a diagram for explaining the present invention in detail, and Fig. 8 is a diagram showing the relationship between the open end shielding ratio and the pressure wave reflectance. It is a one-line diagram showing the relationship. 1... Internal combustion engine, 2... TJ + trachea, 3... Exhaust boat, 4... Intake boat, 5... 1 no 1 air valve, 6
...Intake valve, 7...Cylinder chamber, 8...Intake pipe,
9... Carburizer, 10... Open end, 11... Exhaust muffler, 12... Exhaust outlet, 13... Shielding member,
14...Solenoid, 15...Plunger.

Claims (1)

[Claims] An exhaust control device characterized in that a movable shielding member capable of changing the cross-sectional area is provided at the open end of an exhaust pipe connected to an exhaust port of an internal combustion engine and having a substantially constant cross-sectional area.