JP2621900B2 - Engine exhaust system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust device for an engine.

(Prior Art) A muffler is connected to an exhaust passage in order to reduce the exhaust noise of an engine. The type of this exhaust noise is roughly classified into airflow noise and muffled noise. The airflow noise is
Appears remarkably at high engine output when exhaust pressure increases,
It decreases as the exhaust pressure decreases. On the other hand, the muffled sound appears remarkably at low engine output when the exhaust pressure decreases, and decreases as the exhaust pressure increases.

As described above, the airflow sound and the muffled sound are large in the operation state in which one of them becomes small, so that it is difficult to effectively reduce both exhaust sounds by one muffler. For this reason, as shown in JP-A-59-74325, a plurality of mufflers having different characteristics are connected to the exhaust passage, and the flow to the exhaust to at least a part of the mufflers is reduced. There has been proposed a device in which switching is performed by a switching valve. More specifically, first, the exhaust passage is branched into a first branch exhaust passage and a second branch exhaust passage, and a first muffler set only for low speed is connected to the first branch exhaust passage, while A second silencer set exclusively for high speed is connected to the two-branch exhaust passage. Then, the switching valve provided in the exhaust passage is switched according to the engine load, that is, at low load, exhaust gas flows only through the first branch exhaust passage, while at high load, exhaust gas flows only through the second branch exhaust passage. I'm flowing.

(Problems to be Solved by the Invention) However, as described above, in the case where the exhaust flow is changed by the switching valve to effectively reduce the exhaust noise, the exhaust flow is changed before and after the switching of the exhaust flow. As a result, the pressure is greatly changed, so that a shock due to torque fluctuation is likely to occur.

In particular, the vehicle may be in an unstable state depending on its traveling state, and when the vehicle state is unstable, when the torque fluctuation accompanying the switching of the switching valve occurs, the vehicle state becomes more unstable. It is not preferable because it becomes more unstable.
Such unstable vehicle conditions include, for example, cornering, traction control (control for adjusting the applied torque to the drive wheels to prevent the slip ratio of the drive wheels from the road surface from becoming excessive), and the like. .

Therefore, an object of the present invention is to provide an engine which can prevent the vehicle state from becoming extremely unstable on the assumption that the exhaust sound is effectively reduced by switching the exhaust flow. An exhaust device is provided.

(Means and Actions for Solving the Problems) In order to achieve the above object, the present invention has the following configuration. That is, as shown in FIG. 7, a plurality of exhaust passages having different characteristics from each other, and at least a part of the plurality of exhaust passages are switched between inflow and outflow of exhaust gas, so that at least the exhaust pressure is reduced. A control valve for switching between two states, i.e., a first state and a second state in which exhaust pressure increases, switching control means for switching the control valve in accordance with predetermined switching conditions, and a state of the vehicle. Vehicle state detecting means for detecting that the vehicle is unstable, and switching inhibition means for inhibiting the switching operation of the control valve when the vehicle state detecting means detects that the state of the vehicle is unstable. , Is provided.

As described above, in the present invention, when the vehicle state is unstable, the switching of the exhaust flow is prohibited. Therefore, the switching of the exhaust flow makes the vehicle state more unstable. The situation can be prevented.

The most common situations where vehicle conditions become unstable are:
There is cornering. Therefore, when the vehicle state is unstable during the cornering, in other words, by setting the vehicle state detection means to detect that the vehicle is cornering, the vehicle state becomes extremely extreme during the cornering. Can be prevented from becoming unstable.

In addition, the time when the vehicle state becomes unstable includes the above-described traction control. That is, the traction control prevents the slip ratio of the drive wheels from becoming excessive with respect to the road surface by performing control such as reducing the engine output or applying a control force to the drive wheels. In such a case, if the torque transmitted to the drive wheels fluctuates due to the switching of the exhaust flow, the traction control becomes unstable. Therefore, by setting this traction control as when the vehicle state is unstable, in other words, by setting the vehicle state detection means to detect that the traction control is being performed, this traction control is performed. Extremely unstable vehicle conditions are prevented.

In addition, when the vehicle state is unstable, not only during the above-described cornering and traction control, but also during braking, during starting (acceleration), during deceleration, when traveling at extremely high speed, and when the load When it is large, an appropriate state may be included, such as during traveling on a steep slope (climbing or descending) and turning the rear wheels to the opposite phase side in a four-wheel steering vehicle.

(Example) Hereinafter, an example of the present invention will be described with reference to the attached drawings.

In FIG. 1, E is an engine.
Is a Wankel type rotary piston engine in the embodiment. That is, since the rotor 3 having a substantially triangular shape is accommodated in the casing 2,
The three working chambers 4, 5, 6 are defined therein, and the respective working chambers 4, 5, 6 are volume-changed to the rotor 3 with the planetary rotation. The casing 2 is provided with a suction port 7 and an exhaust port 8 at predetermined positions, and a spark plug 9 disposed therein. The working chambers 4, 4, and 6 perform suction, compression, Explosion and exhaust processes are performed sequentially.

The power taken from the output shaft 1 of the engine E is transmitted to drive wheels (not shown) via an automatic transmission AT. In the embodiment, the automatic transmission AT includes a torque converter TC with a lock-up clutch,
And a planetary gear type multi-stage transmission TS.

An air cleaner 12, an air flow meter 13, a compressor (wheel) 14 a of a supercharger 14, an intercooler 1
5, a throttle valve 16 and a fuel injection valve 17 are provided.

On the other hand, a turbine (wheel) 14b of the supercharger 14, an oxidation catalyst 22, and a three-way catalyst 23 are disposed in the exhaust passage 21 connected to the exhaust port 8 in this order from the upstream side.
In the exhaust passage 21, the downstream side of the three-way catalyst 23 has a first and a second
The first branch exhaust passage 21A is connected to a first muffler 24A, and the second branch exhaust passage 21B is connected to a second muffler 24B. I have. A first silencer 24A is provided in the first branch exhaust passage 21A.
A switching valve 25 as a control valve for switching the flow state of the exhaust gas is provided upstream of the valve. Thereby, the switching valve 25
Is closed, the exhaust is exhausted through the second branch exhaust passage 21B (second exhaust passage).
When the switching valve 25 is open only when the air flows only through the silencer 24B), the exhaust air flows through the two branch exhaust passages 21A and 21B (two silencers).
24A and 24B). In other words, the switching valve
When the valve 25 is open, the exhaust pressure is reduced to a first state, and when the switching valve 25 is closed, the exhaust pressure is increased to a second state. The silencers 24A and 24B will be described later.

The switching valve 25 is driven to open and close by a pressure-actuated actuator 26. For this reason, the pressure chamber 26a of the actuator 26 is connected to a negative pressure tank 28 through a three-way solenoid valve 27, and the negative pressure tank 28 is connected to a throttle pressure passage 30 through a negative pressure introduction passage 30 to which a check valve 29 is connected. It is connected to the intake passage 11 downstream of the valve 16. Accordingly, when the three-way solenoid valve 27 is excited, for example, the switching chamber 25 is closed by connecting the pressure chamber 26a to the negative pressure tank 28. Conversely, when the three-way solenoid valve 27 is demagnetized,
When the atmosphere is introduced into 26a, the negative pressure in the pressure chamber 26a is released, and the switching valve 25 is opened by the return spring 26b.

The exhaust passage 21 has a bypass passage 31 that bypasses the turbine 14b of the supercharger 14, and a waste gate valve 32 is disposed in the bypass passage 31. The waste gate valve 32 uses a pressure-actuated actuator 33 to determine a supercharging pressure when the valve is opened, that is, a maximum supercharging pressure. Therefore, the pressure chamber of the actuator 33 is
The compressor is connected to the intake passage 21 downstream of the compressor 14a of the supercharger 14 via 34. Further, in the middle of the introduction path 34, the intake path 21 upstream of the compressor 14a is connected via an atmospheric pressure introduction path 36 to which a duty solenoid valve 35 is connected. Above solenoid valve 35
Are the intake passages 2 upstream and downstream of the compressor 14a.
The communication ratio for 1 is changed, and the maximum supercharging pressure is changed by changing the communication ratio (duty ratio change).

The first silencer 24A is mainly set for high speed use, that is, mainly for reducing airflow noise, and a specific configuration example is shown in FIG. The first silencer 24A includes a casing 41, the inside of which is formed by partition walls 42A and 42B.
It is defined by three chambers 43A, 43B, 43C which are in series with each other. 44 is an inflow pipe, 45 is an outflow pipe, an inflow pipe 44 for inflow of exhaust gas passes through the chamber 43A and is opened to the chamber 43B, and an outflow pipe 45 for outflow of exhaust gas is in the chamber 43C.
And is open to the chamber 43B. In addition, a communication pipe in which the chambers 43B and 43C are arranged coaxially with the inflow pipe 44.
It is communicated via 46. The chamber 43A is filled with glass wool 49, and a number of small holes 44a are formed in the side wall of the inflow pipe 44 so as to open into the chamber 43A.

The second silencer 24B is mainly set for low speed use, that is, for mainly reducing the muffled sound, and a specific configuration example is shown in FIG. This second silencer 24B is
A casing 51 is provided, the inside of which is defined by partition walls 52A to 52C into four chambers 53A to 53D in series. 54 is an inflow pipe, 55 is an outflow pipe, the inflow pipe 54 for inflow of exhaust gas passes through the chamber 53A and is opened to the chamber 53B, and the outflow pipe 55 for outflow of exhaust gas is in the chambers 53B to 53B. The chamber 53A penetrates 53D and is open to the chamber 53A. And the communication pipe 56
The chambers 53A and 53C are communicated by the
53B and 53D are communicated, and chambers 53B and 53C are communicated by a communication pipe 58.
And are communicated. The communication pipe 57 is arranged coaxially with the inflow pipe 54. Of course, the first silencer
24A has a smaller exhaust resistance than the second silencer 24B.

In FIG. 1, reference numeral 61 denotes a control unit constituted by using a microcomputer. The control unit 61 includes not only an intake air amount signal from the air flow meter 13 but also various sensors.
Each signal from 62 to 66 is input. The sensor 62 detects the engine speed. The sensor 63 detects the accelerator opening. The sensor 64 detects the steering angle of the steering wheel. The sensor 65 detects the rotation speed of the drive wheel. The sensor 66 detects the rotation speed of the driven wheel.

Further, the control unit 61 outputs the ignition plug 9, the fuel injection valve 17, the three-way solenoid 27, the duty solenoid
In addition to 35, the actuator 71 and each solenoid described later
Output to 72 and 73. The actuator 71 is for driving the throttle valve 16, and is constituted by, for example, a step motor.

The control unit 61 controls each of the ignition timing, the fuel injection amount (air-fuel ratio), the switching of the switching valve 25, the maximum supercharging pressure, the opening degree of the throttle valve 16, and the shift (including lockup). The control of the ignition timing, the fuel injection amount, the shift, and the maximum supercharging pressure are not directly related to the present invention, and therefore, the description of these portions will be omitted. However, a solenoid for shifting or lock-up is indicated by reference numeral 72 or 73.

First, the control unit 61 controls the switching of the switching valve 25 between open and closed according to switching conditions set in advance. In the embodiment, the engine speed is set as a parameter as the switching condition. That is, as shown in FIG. 5, the switching speed NP is set, and the engine speed is changed to NP.
If so, the switching valve 25 is opened, and if the engine speed is lower than NP, the switching valve 25 is closed.

The control unit 61 also controls based on the throttle characteristics shown in FIG. 6 such that the throttle opening is associated with a fixed relationship with the accelerator opening.

The control unit 61 further performs traction control. In this traction control, as is known, a slip ratio of a drive wheel with respect to a road surface is calculated from a drive wheel rotation speed and a driven wheel rotation speed (assumed as a vehicle speed). When the calculated slip ratio is equal to or more than a predetermined value, it is determined that the slip ratio of the drive wheel with respect to the road surface has become excessive, for example, by lowering the engine output or applying a control force to the drive wheel, whereby Control is performed so that the slip ratio is equal to or less than a predetermined value. When traction control is performed by adjusting the engine output (adjusting the generated torque), the throttle opening is adjusted so that the actual slip rate of the driven wheel becomes the target slip rate without using the throttle characteristic shown in FIG. Is automatically controlled.

Such traction control itself is disclosed in, for example, Japanese Patent Application Laid-Open No. 58-16948 or Japanese Patent Application Laid-Open No. 60-56662, and a detailed description thereof will be omitted.

The control unit 61 performs the switching control of the switching valve 25 using the engine speed as a parameter during cornering (in the embodiment, when the steering wheel angle is equal to or larger than a predetermined value is during cornering) and during traction control. It is banned. Note that the control unit 61 actually has at least separate control units for switching control and traction control of the switching valve 25, and the switching control unit is a control signal from the traction control unit. Is used as an input signal (detection signal) indicating that traction control is being performed.

The control contents of the control unit 61 will be described with reference to a flowchart shown in FIG. In the following description, P indicates a step.

First, after the initialization of the entire system is performed in P1, the engine speed Ne, the steering wheel angle W, and the presence or absence of a signal indicating that traction control is being performed are read in P2.

Thereafter, when the steering angle is smaller than the predetermined value α, that is, the vehicle is not currently cornering (NO in P3),
And when the traction control is not currently underway.
If NO), the process proceeds to P5.

In P5, it is determined whether or not the engine speed NE is equal to or higher than the switching speed NP. When the determination in P5 is YES, it corresponds to the open area of the switching valve 25. In this case, the process proceeds to P6, and it is determined whether or not the flag F is 0. When the flag F is "1", it indicates that the switching valve 25 is open. If the determination in P6 is YES, that is, if the switching valve 25 is currently closed, the switching valve 25 is opened in P7, and then the flag F is set to 1 in P8. If the determination in P6 is NO, the switching valve 25 has already been opened, and the routine returns.

On the other hand, if the determination in P9 is NO, it is in the closed region of the switching valve 25, and in this case, it is determined whether or not the flag F is 0 in P9. If the determination in P9 is NO, the switching valve 25 is closed in P10, and then the flag F is set in P11.
Is reset to 0. Also, if the determination in P9 is YES,
Since the switching valve 25 has already been closed, the operation is returned as it is.

If the determination in P3 is YES (during cornering) or the determination in P4 is YES (during traction control), the routine returns without performing the processing of P5 to P11. That is, the switching of the switching valve 25 is not performed at all.

Although the embodiment has been described above, the present invention may be configured as follows without using furniture.

As a parameter of the switching condition of the switching valve 25, an engine load (for example, an intake air amount) may be used instead of the engine speed, or both the engine speed and the engine load (mapping) may be used. It can be set appropriately.

The number of silencers may be three or more. In this case, in order to create a plurality of exhaust flow states, for example, a third branch exhaust passage is further provided in parallel with the first and second branch exhaust passages 21A and 21B. Thus, while the third silencer is provided in the third branch exhaust passage,
The switching valve 25 may be provided only in the first branch exhaust passage 22A (only two types of exhaust flow states are provided), or a switching valve is further provided in the third branch exhaust passage to provide two switching valves. (E.g., engine speed) to change the exhaust conditions only through the first branch exhaust passage,
Exhaust through the two branch exhaust passages of Nos. 1 to 3
Three states may be created, such as exhaust through all three branch exhaust passages.

In order to prevent a torque shock caused by the switching of the switching valve 25 itself, a torque suppression control for compensating for a decrease in torque (from open to closed) or an increase (from closed to open) due to the switching is performed. You may. As this torque suppression control, an appropriate method such as adjusting the ignition timing, the fuel injection amount or the maximum supercharging pressure, forcibly disengaging the lock-up clutch, and gradually switching the switching valve 25 can be used.

(Effects of the Invention) As is apparent from the above description, when the vehicle state is originally unstable, switching of the flow of exhaust gas is prohibited to prevent torque fluctuation caused by the switching itself. Therefore, it is possible to prevent a situation where the vehicle state becomes extremely unstable.

Needless to say, the use of a plurality of exhaust passages having different characteristics is effective in reducing exhaust noise.

[Brief description of the drawings]

FIG. 1 is an overall system diagram showing one embodiment of the present invention. FIG. 2 and FIG. 3 are cross-sectional views showing examples of silencers having different characteristics. FIG. 4 is a diagram showing basic throttle characteristics. FIG. 5 is a diagram showing a setting example of a switching speed. FIG. 6 is a flowchart showing a control example of the present invention. FIG. 7 is a block diagram showing the configuration of the present invention. E: engine 21: exhaust passage 21A: first branch exhaust passage 21B: second branch exhaust passage 24A: first silencer 24B: second silencer 25: switching valve 26: actuator 27: three-way solenoid valve 64: control unit 62 : Sensor (steering wheel steering angle) 65, 66: Sensor (wheel rotation speed)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masanori Shibata 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Corporation (72) Inventor Takayoshi Hashimoto 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda (56) References JP-A-59-74325 (JP, A) JP-A-59-119017 (JP, A) JP-A-62-126217 (JP, A)

Claims (3)

(57) [Claims] 1. A first state in which at least exhaust pressure is reduced by switching between a plurality of exhaust passages having different characteristics from each other, and a flow of exhaust gas into and out of at least some of the plurality of exhaust passages. 2 with the second state where
Control valve for switching between the two states, switching control means for switching the control valve in accordance with predetermined switching conditions, and vehicle state detecting means for detecting that the state of the vehicle is unstable An exhaust system for an engine, comprising: switching prohibition means for prohibiting a switching operation of the control valve when the vehicle state detecting means detects that the state of the vehicle is unstable. . 2. A vehicle according to claim 1, wherein said vehicle state detecting means is set to detect that cornering is being performed. 3. A vehicle according to claim 2, wherein said vehicle state detecting means is set to detect that traction control is being performed.