JPH064020Y2 - Exhaust device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an exhaust system for an internal combustion engine that improves the noise reduction effect.

[Prior Art] FIG. 5 shows an example of a conventional exhaust device disclosed in Japanese Utility Model Laid-Open No. 58-183922, in which a switching valve 1 utilizing an intake negative pressure that is switched according to an engine speed is exhausted. It is provided in the system. At the time of low speed rotation, the flow rate of exhaust gas is small and the switching valve 1 is switched to the a side, and the exhaust gas is exhausted via the resonance element as shown by the solid line flow. Switching valve 1 as exhaust flow rate is high at high speed
Is switched to the b side, and the exhaust is directly exhausted as shown by the dotted line flow. This improves the silencing performance.

However, according to this, since the switching valve is controlled only by the engine speed and the intake negative pressure, the sensitivity is low with respect to the engine load and the practicality is poor. That is, the exhaust gas flow rate is not uniquely determined by the engine speed, but is determined by the engine speed and the fuel flow rate (engine load) or the exhaust gas temperature, which is ignored.

FIG. 6 shows another example of the conventional exhaust device disclosed in Japanese Utility Model Laid-Open No. 59-19917, in which a branch portion of the bypass passage 3 communicating with the upstream side of the silencer 2 is opened / closed according to the exhaust pressure. The control valve 4 is provided. When the exhaust gas pressure is low, the control valve is opened so that the bypass passage and the silencer are merged to cause interference exhaust. When the exhaust gas pressure is high, the control valve is closed and the bypass passage 3 acts as a side branch inserted on the downstream side of the silencer 2 to enhance the noise reduction effect.

However, according to this, even when the exhaust gas pressure is high, when the exhaust temperature is high, and therefore the sound propagation speed is high and the exhaust pulsation sound becomes louder, it is not the sound that enters the silencer but the sound after exiting the silencer. Since the energy of the sound is consumed by the side branch, the sound is noisy and the silencing effect as the side branch cannot be expected so much.

Also, as can be said in common with the above-mentioned two conventional examples, since only one switching valve or control valve is provided, effective silencing with a degree of freedom according to engine operating conditions is expected. Can not.

[Problems to be Solved by the Invention] As described above, in the case where the switching valve is switched by the engine speed, it is not practical because the exhaust flow rate, especially the magnitude of the exhaust pulsation noise cannot be accurately grasped, and it is upstream of the silencer. In the case where the bypass valve is opened and closed by the control valve provided on the side, since the side branch is formed on the downstream side, there is a drawback that the silencing effect is small when the exhaust flow rate is large.

The object of the present invention is to accurately grasp the exhaust gas state quantity and to selectively form side branches on both the upstream side and the downstream side of the silencer, thereby eliminating the above-mentioned conventional drawbacks and improving the operation. An object of the present invention is to provide an exhaust system for an internal combustion engine that can obtain an optimum noise reduction effect according to the state.

[Means for Solving Problems] An exhaust system for an internal combustion engine according to the present invention is a silencer interposed in an exhaust system, which exhausts exhaust gas when the exhaust temperature or the engine load is at a medium level under a medium speed rotation of the engine. A silencer set to have a moderate pressure and silencing effect, a passage provided in the exhaust system connecting the upstream and downstream of the silencer, and a passage opened and closed upstream and downstream of the passage. When the exhaust temperature or engine load is high under high engine rotation speed and the control valve provided for this purpose, the upstream control valve is opened to absorb a part of the exhaust sound energy before the silencer, and the downstream valve is opened. When the engine speed is high and the exhaust temperature or the engine load is medium, the upstream control valve is closed and the downstream control valve is opened to absorb the exhaust pulsating noise from the silencer after the silencer. With control means configured Of.

[Operation] When the engine speed is high and the exhaust temperature or engine load is high, the upstream side control valve is opened by the control means and the downstream side control valve is closed, so that a side branch is formed on the upstream side of the silencer. It will be. Therefore, a part of the energy of the exhaust sound propagating through the exhaust system is directly absorbed by the side branch, and a great silencing effect is obtained.

On the other hand, even if the engine speed is high, if the exhaust temperature or the engine load is medium, the control means closes the upstream control valve and opens the downstream control valve, so that a side branch is formed downstream of the silencer. Will be done. Therefore, the remaining part of the energy of the exhaust sound after being absorbed by the silencer is absorbed by the side branch, so that a rather large silencing effect is obtained.

[Embodiment] The embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows an example of an exhaust system for an internal combustion engine of the present invention. Reference numeral 5 is an engine, and 6 is an exhaust system, and a silencer 7 provided in the middle of the exhaust system is connected to the upstream side and the downstream side by a passage, that is, a bypass passage 8. In the illustrated example, the bypass passage is a through type that penetrates the inside of the silencer 7, but it may be a non-penetrating type that passes outside the silencer 7 as shown in FIG. Control valves A and B for opening and closing the upstream side and the downstream side of the bypass passage 8 are provided on the upstream side and the downstream side of the bypass passage 8, respectively. These control valves A and B are driven by actuators. Although the motors 10 and 11 are shown as actuators in the illustrated example, pneumatic or hydraulic drive means may be used.

The control means 12 for controlling the opening and closing of the control valves A and B comprises a microcomputer 13, a motor control amplifier 14, and motors 10 and 11. The engine speed and the exhaust gas temperature are introduced to the microcomputer 13 as operating conditions. The exhaust temperature may be the engine load, that is, the fuel flow rate known from the rack position. This is because, as described above, the exhaust gas flow rate, especially the exhaust pulsation noise is determined by the engine speed and the exhaust temperature or the fuel flow rate.

As shown in the left part of Table 1, a valve opening / closing combination map corresponding to the engine speed and the exhaust temperature is stored in advance in the memory in the microcomputer 13. The microcomputer 13 has various functions shown in the flowchart of FIG. 2, selects a valve opening / closing combination based on the engine speed and exhaust temperature guided by the microcomputer 13, and outputs a control signal corresponding to the selection result to the motor. It outputs to each motor 10 and 11 via the control amplifier 14, and opens and closes each control valve A and B.

Now, in the above configuration, when the engine speed is medium speed and the exhaust temperature is in the medium sound range, both control valves A and B are closed, and the bypass passage 8 is completely closed as shown in FIG. It is closed and only the silencer 7 is provided. Therefore, if the performance of the silencer 7 is set in advance so that the muffling effect and the exhaust pressure are both in the middle under the operating conditions at this time, the effect shown in the right part of Table 1 can be obtained.

When the engine speed is low and the exhaust temperature is also in the low temperature range, both control valves A and B are opened contrary to the above, and the bypass passage 8 is completely opened as shown in FIG. 3D. Will be in parallel with. Therefore, although the noise reduction effect is small, there is no problem under this operating condition because the exhaust flow rate is small and the exhaust pulsation noise is small. On the other hand, the exhaust pressure is reduced, which is effective for improving fuel efficiency.

When the engine speed is in the high speed range, the combination of the valve opening degree differs depending on whether the exhaust temperature is high or medium. When the exhaust gas temperature is in the medium temperature range, the valve opening combination (C) is selected, the upstream side control valve A is closed, and the downstream side control valve B is opened.
As shown in FIG. 3C, the bypass 8 is closed on the upstream side and forms a side branch on the downstream side. Therefore, the exhaust pulsation sound coming out from the silencer 7 is absorbed by the side branch later, so that the sound deadening effect is slightly increased, and the sound deadening effect that matches the generated noise is obtained. However, when the exhaust temperature rises from the medium temperature range to the high temperature range, the exhaust pulsation noise becomes even louder, and thus the above-described muffling effect of the valve opening combination (c) cannot be applied.

However, in the present embodiment, when the exhaust gas temperature is in the high temperature range, the valve opening combination (B) in Table 1 is selected and the upstream side control valve A
Is opened and the downstream side control valve B is closed, so that FIG.
As shown in FIG. 3, the bypass 8 is closed on the downstream side and forms a side branch on the upstream side. Therefore, the engine 5
A part of the large sound wave energy exhausted from the side silencer is quickly absorbed by the side branch before entering the silencer 7, and the sound wave energy absorbed by the side branch and lowered is later absorbed by the silencer 7, so that the sound deadening effect is obtained. Will be very large. As a result, a large silencing effect corresponding to the large exhaust pulsation noise required under this operating condition can be obtained.

According to the present embodiment in which the control valve is provided on both the upstream side and the downstream side of the bypass passage as described above, the combination of the silencing effect and the exhaust pressure can be selected according to the operating conditions of the engine. The degree of freedom in selection is expanded, and it is effective for silencing and improving fuel efficiency. In particular, by adding the exhaust gas temperature to the engine operating conditions, the exhaust gas noise is generated even under high speed rotation, unlike the conventional engine that controls only the engine speed and exhaust pressure to control the valve opening. It becomes possible to form the side branch on the upstream side of the silencer instead of the downstream side of the silencer when the exhaust temperature becomes high, which makes it possible to absorb the exhaust pulsation noise more quickly by resonance, thus further improving operating conditions. A suitable sound deadening effect is obtained. Further, in addition to such control, the same control as the conventional one under low speed and medium speed rotation can be performed together, and it is significant that one device can perform such a valve opening control combination as a whole.

[Effects of the Invention] In summary, according to the present invention, when exhaust gas temperature or engine load is high under high engine rotation speed, a part of the sonic energy of exhaust gas can be absorbed before the silencer. When the exhaust temperature or the engine load is medium, the exhaust pulsation noise emitted from the silencer can be absorbed after the silencer, so that the silencing effect can be improved as much as possible.

[Brief description of drawings]

FIG. 1 is a block diagram of an exhaust system for an internal combustion engine according to an embodiment of the present invention, FIG. 2 is a flow chart illustrating the operation of the exhaust system shown in FIG. 1, and FIG. 3 is a flow chart shown in FIG. FIG. 4 is a schematic diagram showing the state of the bypass passage that can be adopted, FIG. 4 is a schematic configuration diagram showing another embodiment of the exhaust system of the present invention,
FIG. 6 and FIG. 6 are schematic configuration diagrams showing an example of a conventional exhaust device. In the figure, 5 is an engine, 6 is an exhaust system, 7 is a silencer, 8
Is a bypass path, 12 is a control means, and A and B are control valves.

Claims (1)

[Scope of utility model registration request] 1. A silencer provided in an exhaust system, the silencer comprising:
Provided in the exhaust system by connecting the silencer set so that the exhaust pressure and the silencing effect become medium when the exhaust temperature or engine load is medium under the medium speed rotation of the engine and the upstream and downstream of the silencer. And a control valve provided to open and close the passage upstream and downstream of the passage, and when exhaust gas temperature or engine load is high under high engine rotation speed, a part of the sonic energy of exhaust gas is discharged. The upstream control valve is opened to absorb before the silencer, the downstream valve is closed, and when the exhaust temperature or engine load is medium at high engine rotation speed, the exhaust pulsating noise from the silencer is absorbed after the silencer. An exhaust device for an internal combustion engine, comprising: a control means configured to close an upstream control valve and open a downstream control valve.