JPH02259217A - Exhaust device of engine - Google Patents

Abstract

PURPOSE:To hold silencing characteristics always at a constant level so as to suppress air current noise and filled noise, by correcting an exhaust passage area in response to the change of an exhaust gas capacity caused by an exhaust temperature, when the exhaust passage area is changed in response to an of intake air quantity. CONSTITUTION:The exhaust passage area of an engine is changed by a means A. On the other hand, an intake air quantity of the engine is detected by a means B. And, the exhaust passage area corresponding to the detected intake air quantity is set, while a control signal corresponding to the set exhaust passage area is generated by a means C. Moreover, the exhaust temperature is detected by a means D. And then, the exhaust passage area corresponding to the intake air quantity is corrected by a means E, according to the detected exhaust temperature. Namely, when the exhaust passage area corresponding to the intake air quantity is changed, silencing characteristics is held always at a constant level by correcting the exhaust passage area in response to the change of an exhaust gas capacity caused by the exhaust temperature.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention reduces the exhaust passage area when the exhaust flow rate is low and increases it when the exhaust flow rate is high, thereby reducing exhaust noise at low rotation speeds. The present invention relates to an engine exhaust system that increases engine output during high loads.

(Prior Art) One of the most important technical challenges today is to make the engine noise lower and more pleasant in engines for vehicles and the like. One type of engine noise that must be reduced is exhaust noise, and muffled noise, which tends to occur in low engine speed ranges, is particularly problematic. This muffled sound is caused by the exhaust pulsation caused by pressure fluctuations during the exhaust stroke, which creates a large pressure difference when released from the muffler to the atmosphere, causing the exhaust sound to resonate with the passenger compartment and become muffled. This produces an unpleasant sound. In particular, in a low engine speed range, the period of exhaust pulsation becomes long, and the frequency becomes, for example, about 100 Hz, which is close to the resonance point of the passenger compartment, so that muffled noise is more likely to occur. Note that in a region where the engine rotation is high, the frequency of pulsation becomes high, the amplitude of the pressure wave becomes small, and the pressure wave moves away from the resonance point, so muffled noise is less likely to occur. Furthermore, the amplitude of the exhaust pulsation increases as the exhaust flow rate increases, and therefore, the higher the load, the more muffled noise is likely to occur. Particularly in the region of low rotation and high load, the above-mentioned generation conditions overlap, so muffled noise becomes an even bigger problem.

By the way, as a means to reduce exhaust noise, for example, as described in Japanese Utility Model Application Publication No. 183012/1983, a silencer is provided with two outlet pipes, one of which is provided with a switching valve, It is known that the switching valve is closed when the amount of fuel injected is small and opened when the amount of fuel injected is large.

Here, the amount of fuel injection is correlated with the amount of intake air and ultimately the flow rate of the exhaust gas.In this way, when the amount of fuel injection is small, the muffler outlet is narrowed and the amplitude of the pressure wave is reduced, reducing muffled noise. On the other hand, when the fuel injection amount is large, the diameter of the exhaust passage becomes substantially large, so the exhaust pressure decreases and the engine output can be improved.

However, when the switching region is set by the fuel injection amount or intake air amount in this way, the exhaust gas volume increases as the exhaust temperature rises, and the gas flow rate increases accordingly, so when the exhaust gas temperature is high, Air flow noise may increase in the area where the switching valve is closed and the actual exhaust passage diameter is reduced. Also, in order to prevent this air flow noise from increasing, the switching line may have been set to the low intake air amount side.
The muffled sound cannot be suppressed.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems, and provides an engine exhaust system in which the area of the exhaust passage is changed according to the amount of intake air. The purpose is to keep the silencing characteristics constant regardless of the

(Structure of the Invention) The present invention achieves the above object by correcting the exhaust passage area corresponding to the intake air amount according to the exhaust temperature, and the structure is as shown in FIG. be. That is, the engine exhaust system according to the present invention includes: an exhaust passage area changing means for changing the exhaust passage area of the engine; an intake air amount detecting means for detecting the intake air amount of the engine;
Control signal generating means receives the output of the intake air amount detection means, sets an exhaust passage area corresponding to the intake air amount, and outputs a control signal corresponding to the set exhaust passage area to the exhaust passage area changing means. and an exhaust gas temperature detection means for detecting the exhaust gas temperature, and an exhaust passage area correction means for receiving the output of the exhaust gas temperature detection means and correcting the exhaust passage area corresponding to the intake air amount according to the exhaust temperature. It is characterized by

(Function) The exhaust passage area of the engine is changed according to the amount of intake air, thereby achieving a balance between reducing exhaust noise and increasing engine output. At this time, the area of the exhaust passage corresponding to the amount of intake air is corrected according to the exhaust temperature, thereby controlling the area of the exhaust passage in response to changes in the exhaust gas volume due to temperature, and keeping the silencing characteristics constant. dripping

(Example) Examples will be described below based on the drawings.

FIG. 2 is an overall system diagram showing a first embodiment of the present invention. In this embodiment, the present invention is applied to a Wankel-type rotary piston engine. A substantially triangular rotor 3 is housed in a casing 2 of an engine 1, and three working chambers 4 are formed by the planetary rotation of the rotor 3. , 5.6 changes sequentially. In the casing 2, an intake boat 7 and an exhaust boat 8 are formed at predetermined positions, and a spark plug 9 is also arranged, and each stroke of suction, compression, explosion, and exhaust is caused by a change in the volume of each working chamber. are performed sequentially.

In the intake passage IO connected to the intake boat 7, air cleaners 11. Air flow meter 12. Blower (wheel) 13a of exhaust turbo supercharger 13, intercooler 14. A throttle valve 15 and a fuel injection valve 16 are provided.

On the other hand, in the exhaust passage 17 connected to the exhaust boat 8, the turbine (wheel) 13 of the supercharger 13 is arranged in order from the upstream side.
b. An exhaust catalyst 1B and a three-way catalyst 19 are provided. Further, this exhaust passage 17 is branched into two branch exhaust passages 20a and 20b, a first and a second branch exhaust passage, on the downstream side of the three-way catalyst 19, and the first branch exhaust passage 20a has a first
A muffler 21& is connected to the muffler 21&, and a second muffler 21b is connected to the second branch exhaust passage 20b. A switching valve 22 is disposed in the first branch exhaust passage 20a upstream of the first muffler 21a. As a result, when the switching valve 22 is closed, the exhaust gas flows only toward the second branch exhaust passage 20b and the second muffler 21b, while when the switching valve 22 is open, the exhaust gas flows through both the branch exhaust passages 20a. ,
20b and both silencers 21a, 21b.

The switching valve 22 is driven to open and close by a pressure-operated actuator 23. For this purpose, the actuator 23
The pressure chamber 23a is connected to a negative pressure tank 25 via a three-way solenoid valve 24, and this negative pressure tank 25 is connected to the intake passage downstream of the throttle valve 15 via a negative pressure introduction path 27 in which a check valve 26 is provided. Connected to IO. Thereby, when the three-way solenoid valve 24 is energized, the pressure chamber 232L is communicated with the negative pressure tank 25, and the switching valve 22 is closed. Further, when the three-way solenoid valve 24 is demagnetized, the atmosphere is introduced into the pressure chamber 23a, and the switching valve is opened by the spring force of the return spring 23b.

The exhaust passage 17 has a bypass passage 28 that bypasses the turbine 13b of the supercharger 13.
A waste gate valve 29 is disposed at. This waste gate valve 29 is driven to open and close by a pressure-operated actuator 30, thereby adjusting the maximum boost pressure. Therefore, the pressure chamber of the actuator 30 is connected to the intake passage 10 downstream of the blower 13a of the supercharger 13 via the introduction passage 31.
An atmospheric pressure introduction passage 32 that opens into the intake passage IO upstream of the blower 13a is connected to the air pressure introduction passage 32, and a duty solenoid valve 33 is interposed in the atmospheric pressure introduction passage 32. This duty solenoid valve 33 changes the communication ratio of the pressure chamber of the actuator 30 to the upstream side and the downstream side of the blower 13a,
As a result, the opening degree of the waste gate valve 29 is changed, and the maximum boost pressure is changed.

Note that the first muffler 21a is set for use at high speeds, and the second muffler 21b is set for use at low speeds.

34 in the figure is a control unit configured using a microcomputer, and this control unit 34
In addition to the intake air amount signal from the air flow meter 12, signals from each sensor or switch are input. Then, from the control unit 34, the spark plug 9. Fuel injection valve 16. Control signals are output to the duty solenoid valve 33 and the actuator 35 for driving the throttle valve 15, thereby controlling the ignition timing,
The fuel injection amount, boost pressure, and throttle opening are controlled respectively. Further, a switching signal is output to the three-way solenoid valve 24 to open and close the switching valve 22.

FIG. 3 shows the setting range of opening and closing of the switching valve 22, in which the vertical axis is the throttle opening (TVO), that is, the engine load, and the horizontal axis is the engine rotation speed.

The switching valve 22 is based on the line indicated by Q, (equal intake air amount) and R1 (equal engine speed) in the figure, and is closed on the lower intake air amount (low exhaust flow rate) side than this line, and when this line is reached. Then it opens. Here, the switching line is based on the equal intake air amount line of Ql, and the throttle opening is 13
In the above high load range, the engine speed line is set to be equal to R3. As a result, in areas where the exhaust flow rate is low, by closing the switching valve 22 and substantially reducing the exhaust passage diameter, it is possible to reduce the muffled noise that is likely to occur especially at low rotation speeds. In a region with a large amount of exhaust gas, the diameter of the exhaust passage can be increased to lower the exhaust pressure and improve the engine output.

Further, in this embodiment, the exhaust gas temperature is indirectly determined based on the pulse width of the injection signal output to the fuel injection valve 16, and the switching line is corrected in accordance with the determined exhaust gas temperature.

In other words, in operating ranges such as during acceleration, where the injection pulse width is large, the air-fuel ratio is richer than normal, and the exhaust temperature is high, the switching line is set to low intake as shown by the broken lines R', Q in Figure 3. I try to shift it towards the air volume side. This suppresses an increase in gas flow velocity when the switching valve 22 is closed, and prevents an increase in air flow noise. In addition, in Figure 3, R
The lines indicated by z, Qt, Rt, and Q'- are related to a modification described later.

The configuration of the circuit for controlling the switching valve 22 is as shown in FIG. That is, the control unit 34 reads the engine rotation speed (rpm), reads out the engine rotation speed reference value R, from the memory 35, and determines whether the engine rotation speed is equal to or higher than the reference value R. a number determination circuit 36; and an intake air amount determination circuit 38 that reads the intake air amount (Q), reads the intake air amount reference value Q1 from the memory 37, and determines whether the intake air amount is equal to or greater than the reference value 91. Then, read the throttle opening (TvO) and set the reference value T of the throttle opening.

A throttle opening determination circuit 40 reads out from the memory 39 and determines whether the throttle opening is equal to or greater than the reference value T3, and receives the output of each of these determination circuits 36°38.40, and determines the control area in FIG. a control signal generation circuit 41 that determines and outputs a control signal to the three-way solenoid valve 24;
It is equipped with Further, an exhaust temperature determination circuit 42 is provided, and the engine rotation speed reference value RI and the intake air amount reference value Q are corrected based on the output of the exhaust temperature determination circuit 42. The air-fuel ratio (A/F) determined by inputting the injection pulse width and the intake air amount is input to the exhaust temperature determination circuit 42, as shown by ■ in FIG. 4.

Further, the present invention can also be implemented in such a manner that the exhaust gas temperature is determined based on the output of an air-fuel ratio sensor (for example, an Ot sensor), as shown by ■ in FIG. 4 (second embodiment).

Furthermore, since the exhaust gas temperature also changes depending on the octane number of the fuel, a method for detecting the octane number based on the number of knocking occurrences as described in Japanese Patent Application Laid-Open No. 63-263246 is used to detect the octane number as shown in (■) in Figure 4. , it can also be implemented by changing the switching line depending on the octane number, that is, depending on whether it is high octane or regular (third
example). In this case, if it is high octane, the combustion will be quick and the gas salt in the exhaust passage will be low, so the switching line should be set to the low flow rate side, and if it is regular, the ignition timing will be retarded and the exhaust temperature will rise, so the switching line should be set to the low flow side. Set the line to the high flow side.

The present invention can also be applied to an exhaust system having a switching structure as shown in FIG. 5 as a modification of each of the above embodiments.

In this embodiment, as shown in FIG.
is on the way! and second branch exhaust passages 102a, 10
2b, and a catalytic converter 103a, a sub-silencer 104a, and a main silencer 105a are connected to the first branch exhaust passage 102a in this order from the upstream side to the downstream side. Similarly, a catalytic converter 103b, a sub muffler 104b, and a main muffler 105b are connected to the second branch exhaust passage 102b.

Each main silencer 105a, 105b includes an exhaust inlet pipe portion 106a connected to each branch exhaust passage 102a, 102b,
Large-diameter first exhaust outlet pipes 107a, 107b located substantially in a straight line with respect to 106b, and first exhaust outlet pipes 107a, 1
The second exhaust outlet pipe 108a has a diameter smaller than that of the second exhaust outlet pipe 108a and forms a long passage by meandering inside the silencers 105a and 105b.

108b, respectively. A switching valve 109a is connected to each of the first exhaust outlet pipes 107a and 107b.
109b is interposed.

Each of the switching valves 109a and 109b is connected to link 1.
10a, 110b to rods 112a, 112b of the first and second actuators 1lla, 1llb. And each actuator 1lla,
The 1llb pressure chamber is connected to the first and second branch negative pressure passages 1
13a, 113b and a common negative pressure passage 114 to a negative pressure tank 115, and the negative pressure tank 115 is connected to an intake passage downstream of a throttle valve (not shown) via a check valve 116. And each branch negative pressure passage 113
A, 113b are provided with first and second three-way solenoid valves 118a, 118b that receive the output from the control unit 117 and introduce negative pressure or atmospheric air into the pressure chamber of each actuator 1lla111b. These three-way solenoid valves 118a and 118b switch the introduction pressure to each of the first and second actuators l1la and 1llb, thereby opening and closing the first and second switching valves 109a and 109b. Among these, the first switching valve 109a provided in the first exhaust outlet pipe 107a of the main muffler 105a on the side of the first branch exhaust passage 102a is opened and closed based on the R, Q lines in FIG. . That is, the first switching valve 109a is closed on the lower intake air amount side than the RI and Q+ lines, and is opened when this line is reached. Further, the second switching valve 109b is closed on the lower intake air amount side than the R1, Q+ line with reference to the Rt, Q* line, which is on the higher intake air amount side than the R1, Q+ line, and is opened when it reaches this line. Note that the R, line and Q, line are similar to the RI, Q+ line when the throttle opening is T.
It is set at 1.

In the area where the amount of intake air is lower than the RI and Q+ lines, the first
Both the second switching valves 109a and 109b are closed, and the exhaust gas is discharged from both main silencers 105a.

This is done only with the second exhaust outlet pipes 108a and 108b of 105b. These second exhaust outlet pipes 108a.

Since 108b forms a long passage with a small diameter as described above, exhaust pulsation is suppressed and generation of muffled noise is suppressed.

In addition, in the region where the intake air amount is higher than the Rt and Qt lines, both switching valves IQ9a and 109b are opened, and exhaust is performed through all exhaust outlet pipes 107a, 107b, 108λ, and 108b, thereby reducing the exhaust pressure. engine power increases.

Further, in this device, two switching valves 109 are provided as described above.
Since a and 109b are configured to switch at predetermined intervals, noise reduction and output control are performed in a well-balanced manner, and the occurrence of shocks is suppressed.

In this device as well, the exhaust temperature is determined based on the air-fuel ratio determined by the injection pulse width and the output of the Ot sensor, or the height of the exhaust temperature is determined based on the octane number, and the above-mentioned implementation is performed based on the determination result. Correct the above switching line in the same way as in the example. In other words, when the exhaust temperature is low, each switching line is set to the high intake air amount side (RI Q, R
t Qt), and when the exhaust temperature is high, set each switching line to the low intake air amount side (R' + Q' +,
R' t Q' t ).

FIG. 6 shows a circuit for executing the above switching control in this embodiment. That is, the control unit 117 reads the engine speed (r p m ), reads the first reference value R1 of the engine speed from the memory 121, and determines whether the engine speed is equal to or higher than this reference value R. The first engine speed determination circuit 122 to determine the engine speed similarly reads the engine speed (rpm), and also reads the second reference value R1 of the engine speed from the memory 123, and determines that the engine speed is equal to or higher than this reference value R2. The second to determine whether
The rotation speed determination circuit 124 reads the intake air amount (Q), reads out the first reference value Q of the intake air amount from the memory 125, and determines whether the intake air amount is equal to or greater than this reference value Q. The first intake air amount determination circuit 126 similarly reads the intake air amount (Q), reads out the second reference value Q of the intake air amount from the memory 127, and determines whether the intake air amount is equal to or greater than this reference value 91. The second intake air amount determination circuit 128 reads the throttle opening (TVO), reads out the reference value T of the throttle opening from the memory 129, and determines whether the throttle opening is equal to or greater than the reference value 14. a throttle opening degree determination circuit 130, a first rotation speed determination circuit 122, and a first intake air amount determination circuit 12.
6 and the output of the throttle opening determination circuit 130;
a first control signal generation circuit 131 that determines a control region and outputs a control signal to the first three-way solenoid valve 118a;
Rotation speed determination circuit 124. Second intake air amount determination circuit 128
and a second control signal generation circuit 132 that receives the output of the throttle opening determination circuit 130, determines the control region, and outputs a control signal to the second three-way solenoid valve 118b, and determines the exhaust temperature based on the air-fuel ratio and octane number, An exhaust temperature determination circuit 133 is provided for correcting reference values of engine speed and intake air amount.

(Effects of the Invention) The present invention is configured as described above, and in an engine exhaust system in which the area of the exhaust passage is changed depending on the amount of intake air, the area of the exhaust passage is corrected according to the change in the exhaust gas volume due to the exhaust temperature. As a result, the silencing characteristics are always kept constant.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of the present invention, FIG. 2 is an overall system diagram showing a first embodiment of the present invention, FIG. 3 is a control characteristic diagram of the same embodiment and other embodiments, and FIG. 4 is a diagram of control characteristics of the same embodiment and other embodiments. FIG. 5 is a control circuit diagram of the first embodiment, second and third embodiments, FIG. 5 is an exhaust route diagram of a modification of each of the embodiments, and FIG. 6 is a control circuit diagram of the modification. 1: Engine, 12; Air flow meter, 17°101
: Exhaust passage, 20a, l02a: First branch exhaust passage, 2
0b, 102b: Second branch exhaust passage, 22: Switching valve, 3
4,117+control unit, 42.133: exhaust temperature determination circuit, l09a: first switching valve, 109b: second switching valve, 107a, 107b: first exhaust outlet pipe, 108a, 1
08b: Second exhaust outlet pipe.

Claims (1)

[Claims] (1) Exhaust passage area changing means for changing the exhaust passage area of the engine, intake air amount detecting means for detecting the intake air amount of the engine, and receiving the output of the intake air amount detecting means and corresponding to the intake air amount. control signal generating means for setting an exhaust passage area and outputting a control signal corresponding to the set exhaust passage area to the exhaust passage area changing means; exhaust temperature detecting means for detecting exhaust temperature; An exhaust system for an engine, comprising an exhaust passage area correction means for correcting an exhaust passage area corresponding to the intake air amount in accordance with an exhaust temperature in response to an output of the means.