JPH0830419B2 - Exhaust device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust system for an internal combustion engine that switches between two exhaust pipes according to the rotational speed of the internal combustion engine.

[Prior Art] Since the output characteristics of an internal combustion engine largely depend on the volume of the exhaust pipe, the volume of the exhaust pipe is changed in accordance with the rotation speed, and the internal combustion engine that focuses on medium and low speeds and the high speed priority. It is known that the internal combustion engine of

Therefore, in order to obtain output characteristics from low speed to high speed with one internal combustion engine, for example, as disclosed in JP-B-58-49381, a separate branch exhaust pipe is provided on the side of the exhaust pipe. Alternatively, as disclosed in Japanese Utility Model Laid-Open No. 60-139034, the exhaust pipes of two systems are provided, and the switching valve provided in the connecting pipe is operated to allow the exhaust gas to flow to the branch exhaust pipe in the medium and low speed rotation range.
In the high-speed rotation range, there is a system in which the branch exhaust pipe is closed to allow the exhaust pipe to flow.

[Problems to be Solved by the Invention] By the way, in a structure in which two systems of exhaust pipes are connected to a plurality of cylinders and switching is performed by a switching valve, a switching valve mechanism is required to be simple and capable of operating accurately.

Further, when two exhaust pipes are provided, they are separately arranged, so that it is not easy to secure a space for disposing them, and the exhaust pipes of two systems are required to have a structure for suppressing an adverse effect due to reflected waves of exhaust gas.

Further, the exhaust system may be provided with a catalyst for purifying the exhaust, and the catalyst is arranged in the exhaust passage on the low speed side. However, a structure that can maintain the activation temperature of the catalyst especially in the arrangement passage on the low speed side is provided. preferable.

The present invention has been made in view of the above circumstances, and in a parallel multi-cylinder engine, the structure of the switching valve for the exhaust pipe is simple, the operability is excellent, and the space for disposing the exhaust pipe is easily secured, and the reflection of the exhaust gas is reflected. It is an object of the present invention to provide an exhaust system for an internal combustion engine that suppresses the adverse effects of waves and that can accommodate the placement of a catalyst.

[Means for Solving the Problem] In order to solve the above problem, an exhaust system for an internal combustion engine according to the present invention is an automatic multi-cylinder engine in which exhaust pipes are connected in front of a plurality of cylinders. In a two-wheeled vehicle, the exhaust pipe is connected to each cylinder via a connection pipe separate from the cylinder, the connection pipe straddles integrally between a plurality of cylinders, while the exhaust pipe is a large-diameter exhaust pipe. A small-diameter exhaust pipe is arranged in the large-diameter exhaust pipe, and the small-diameter exhaust pipe is configured to be displaced toward the vehicle rear side in the large-diameter exhaust pipe, and the small-diameter exhaust pipe and the large-diameter exhaust pipe are connected to the exhaust pipe connecting portion of the connecting pipe. A switching valve that opens and closes an exhaust pipe line formed between the exhaust pipe and a front end portion of the exhaust pipe is disposed in proximity to the exhaust pipe, and a muffler-side connecting portion to which a muffler at a rear end portion of the exhaust pipe is connected exhausts before and after the exhaust pipe. The cross-sectional area of the passage is the same, and further switching The valve is attached to each cylinder on a drive shaft arranged so as to pass through each exhaust passage, and by operating this drive shaft, the switching valve is closed below a predetermined rotation speed of the internal combustion engine and exhausted by the small diameter exhaust pipe, It is characterized in that it is configured to open at a predetermined rotation speed or higher and to exhaust the gas through the small diameter exhaust pipe and the large diameter exhaust pipe.

[Operation] In the present invention, the switching valve is exhausted by the closed small-diameter exhaust pipe below the predetermined rotation speed of the internal combustion engine, and is opened by the open small-diameter exhaust pipe and the large-diameter exhaust pipe above the predetermined rotation speed, and the two-system exhaust pipe structure is provided. With this, one internal combustion engine can obtain output characteristics from low speed to high speed.

Further, the small-diameter exhaust pipe arranged inside the large-diameter exhaust pipe is cooled without being directly hit by traveling wind, and when the catalyst is provided on the small-diameter exhaust pipe side, the activation temperature of the catalyst can be maintained.

Further, in the muffler side connection portion at the rear end portion of the exhaust pipe, when the switching valve is open, the cross-sectional area of the exhaust passage is the same before and after the switching valve, and between the large diameter exhaust pipe and the small diameter exhaust pipe. The small-diameter exhaust pipe can be used as an exhaust passage in both high and low speeds, because there is no adverse effect that two types of reflected waves are generated due to the long and short exhaust pipes.

In addition, the connection pipe that is separate from the cylinder can suppress the heat of the internal combustion engine that reaches the switching valve by heat conduction, and the exhaust pipe is connected to the front side of the cylinder. It is easy and the surroundings of the switching valve are easily cooled.

Further, the switching valve is attached to each cylinder on a drive shaft arranged so as to pass through each exhaust passage, and the dimensional accuracy such as the interval between the switching valves of each cylinder is good, and the switching characteristics are linked together with good cooling performance. It is done without any problems.

[Embodiment] An embodiment in which the present invention is applied to a motorcycle will be described in detail below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 is a body frame, and a front wheel 2 is attached to the body frame 1 via a front suspension.
However, the rear wheels 3 are respectively provided via the rear suspension. A parallel multi-cylinder internal combustion engine 4 is mounted on the vehicle body frame 1.

As shown in FIG. 2, in this internal combustion engine 4, a piston 7 is provided in a cylinder 6 of a cylinder block 5, and a combustion chamber 9 is provided between the piston 7 and a cylinder head 8 mounted on the cylinder block 5. Has been formed. Each combustion chamber 9 has an intake passage formed in the cylinder head 8.
10 and the exhaust passage 11 are communicated with each other, and the intake passage 10 and the exhaust passage 11 are moved up and down by the operation of the camshafts 12 and 13.
It is opened and closed by the exhaust valve 15.

A connection pipe 16 separate from the cylinder is provided in the exhaust passage 1 of the cylinder block 5, and a large-diameter exhaust pipe 17 is connected to the connection pipe 16. The large-diameter exhaust pipe 17 is provided from the front side of the internal combustion engine 4. Passes downward, bends downward and extends rearward, and
Equipped with a system exhaust pipe.

In the large-diameter exhaust pipe 17, a small-diameter exhaust pipe 18 is inserted between the connection pipe 16 and the muffler-side connecting portion 19a of the muffler 19, and the exhaust pipe has the small-diameter exhaust pipe 18 arranged in the large-diameter exhaust pipe 17. The small-diameter exhaust pipe 18 is not concentric in the large-diameter exhaust pipe 17 but is displaced toward the vehicle rear side. The small-diameter exhaust pipe 18 is fixed to the inner wall of the large-diameter exhaust pipe 17 on the internal combustion engine 4 side by welding 20 at a predetermined position. Further, in the muffler-side connecting portion 19a to which the muffler 19 at the rear end portion of the exhaust pipe is connected, the cross-sectional area of the exhaust passage is the same before and after that.

The connecting pipe 16 extends integrally between a plurality of cylinders, and a switching valve 21 is arranged in the exhaust pipe connecting portion of the connecting pipe 16 in the vicinity of the front end portion of the exhaust pipe. Accordingly, the exhaust pipe line formed between the small-diameter exhaust pipe 18 and the large-diameter exhaust pipe 17 is opened / closed to switch between the two systems of exhaust pipes. Switching valve 21
Are fixed to drive shafts 22, respectively, as shown in FIG. This switching valve 21 is formed in a crescent shape, and its inner peripheral portion
21a is in close contact with the outer peripheral surface of the small-diameter exhaust pipe 18, and the outer peripheral portion 21b is in close contact with the inner peripheral surface of the large-diameter exhaust pipe 17 and operates in conjunction with the drive shaft 22. The exhaust pipe line 23, which is kept calm by the inner circumference of the exhaust pipe 17, is opened and closed.

The drive shaft 22 is rotatably supported by the connection pipe 16 so as to penetrate through each exhaust passage, and the switching valve 21 is attached to each drive cylinder 22 for each cylinder. Is pulley 24
Is screwed on. The pulley 24 is covered with a housing 25, and the pulley 24 is a servo motor unit 26.
The pulley 27 and the wire 28 are connected to each other. The servo motor unit 26 is mounted on the vehicle body frame 1 above the internal combustion engine 4 as shown in FIG. A power supply voltage is applied to the control unit 30 from a battery 31 provided near the control unit 30, and the servo motor unit 26 is driven based on an engine rotation speed signal from a capacitor discharge ignition (CDI) unit 32. There is.

The servo motor unit 26 and the control unit 30 are constructed as shown in FIG.

The servo motor unit 26 includes a motor 33, a speed reducer 34, a pulley 27 and a potentiometer 35.
33 is a motor drive signal of the control unit 30, which rotates in the forward rotation direction and the reverse rotation direction, and the rotational force thereof is reduced by the reduction gear 34 and transmitted to the pulley 27.

The potentiometer 35 detects the rotational position of the pulley 27 that rotates via the speed reducer 34, and the switching valve that is opened and closed from the rotational position of the pulley 27 via the wire 28 and the pulley 24.
The valve opening of 21 is detected, and this valve opening signal is output to the control unit 30.

The control unit 30 has an input interface 36,3
7, an output interface 38, a microcomputer 39 and a power supply stabilization circuit 40, and a main switch 41.
When is turned on, the battery 31 is connected to the power stabilizing circuit 40. A power supply voltage is supplied from the power supply stabilizing circuit 40 to the input interfaces 36, 37, the output interface 38, and the microcomputer 39.

An engine speed signal from the CDI unit 32 is input to the microcomputer 39 via the input interface 37, and a valve opening signal from the potentiometer 35 is input via the input interface 36. The microcomputer 39 outputs a motor drive signal for driving the motor 33 from the engine rotation speed signal and the valve opening signal via the output interface 38.

As a result, as shown in FIG. 6, the motor 33 closes the switching valve 21 to discharge the exhaust gas from the small-diameter exhaust pipe 18 in the medium and low speed rotation range, and when the engine rotation speed becomes the switching point a or more,
Open the switching valve 21 and maintain it in the direction parallel to the flow rate of exhaust gas,
The small-diameter exhaust pipe 18 and the exhaust pipe line 23 formed between the small-diameter exhaust pipe 18 and the large-diameter exhaust pipe 17 are also discharged to obtain a wide range of engine torque T from low speed to high speed. Has become.

 Next, the operation of this embodiment will be described.

Due to the operation of the internal combustion engine 4, the air-fuel mixture is burned in the combustion chamber 9, and the exhaust gas thereof is discharged through the exhaust pipe including the large-diameter exhaust pipe 17 and the small-diameter exhaust pipe 18. The rotation speed of the internal combustion engine 4 at this time is detected by the CDI unit 32, and the engine rotation speed signal is input to the microcomputer 39 of the control unit 30.

On the other hand, the valve opening signal from the potentiometer 35 of the servo motor unit 26 is input to the microcomputer 39, and the switching valve is based on this valve opening signal.
21 open / close positions are monitored.

Now, when the switching valve 21 is open and the operating state of the internal combustion engine 4 is in the medium to low speed rotation range, the microcomputer 39 outputs a motor drive signal in the closing direction to drive the motor 33 in the closing direction to reduce the speed. 34, pulley 27, wire 28 and pulley
The switching valve 21 is operated in the closing direction via 24. As a result, the switching valve 21 closes the exhaust pipe line 23 between the large-diameter exhaust pipe 17 and the small-diameter exhaust pipe 18, and exhausts the exhaust gas only from the small-diameter exhaust pipe 18.

When the rotation speed of the internal combustion engine 4 rises to a predetermined rotation speed, the microcomputer 39 outputs a motor drive signal in the opening direction, and the motor 33, the speed reducer 34, and the pulley.
The switching valve 21 is opened through the wire 27, the wire 28, and the pulley 24, and the exhaust gas is discharged from the small-diameter exhaust pipe 18 and the exhaust pipe line 23 between the small-diameter exhaust pipe 18 and the large-diameter exhaust pipe 17, thereby reducing the speed. It has a wide range of engine torque T from high speed to high speed.

As described above, the switching valve 21 is exhausted by the closed small-diameter exhaust pipe 18 below the predetermined rotation speed of the internal combustion engine 4, and is opened by the open small-diameter exhaust pipe 18 and the large-diameter exhaust pipe 17 at a predetermined rotation speed or more, and the exhaust of two systems. With a tubular structure, one internal combustion engine can obtain output characteristics from low speed to high speed.

Also, the small-diameter exhaust pipe 18 is inserted into the large-diameter exhaust pipe 17,
Since it is bent so as to have the same shape, the direction of the exhaust gas flow does not change significantly when the switching valve 21 is opened or closed.

Further, since the small-diameter exhaust pipe 18 arranged in the large-diameter exhaust pipe 17 is not directly hit by the traveling wind and is difficult to be cooled, when the catalyst is provided on the small-diameter exhaust pipe 18 side, the activation temperature of the catalyst can be maintained.

Further, in the muffler-side connecting portion 19a to which the muffler 19 at the rear end of the exhaust pipe is connected, when the switching valve 21 is open,
The cross-sectional area of the exhaust passage is the same before and after, and the large-diameter exhaust pipe
Since there is no adverse effect that two types of reflected waves are generated between the small diameter exhaust pipe 18 and the small diameter exhaust pipe 18, there is no adverse effect that two types of reflected waves are generated. In addition, it can be used as an exhaust passage, has good space efficiency, and can easily secure a space for disposing the exhaust pipe. Since the small-diameter exhaust pipe 18 is inserted into the large-diameter exhaust pipe 17, it cannot be recognized from the outside that the exhaust pipe is doubled, and the external appearance becomes a preferable shape. There is.

In addition, the connection valve 16 that is separate from the cylinder uses heat conduction to switch the valve.
The heat of the internal combustion engine 4 reaching 21 can be suppressed to a low level,
Further, an exhaust pipe is connected to the front side of the cylinder, and the connecting pipe 16
The traveling wind is apt to hit, and the surroundings of the switching valve 21 are easily cooled.

Furthermore, a switching valve 21 is attached to each cylinder on a drive shaft 22 arranged so as to pass through each exhaust passage, and the dimensional accuracy such as the interval between the switching valves 21 for each cylinder is good and good. Coupled with the cooling property, the interlocking can be performed without any problems.

Further, a switching valve 21 is arranged in the exhaust pipe connecting portion of the connecting pipe 16 in the vicinity of the front end portion of the exhaust pipe, and the switching valve 21 has a large diameter exhaust pipe 17
It is not necessary to make the inside of the connecting pipe 16 a special passage structure because the end portion of is directly opened and closed.

[Advantages of the Invention] As described above, according to the present invention, the switching valve is closed at a speed lower than a predetermined rotation speed to be exhausted by the small diameter exhaust pipe, and opened at a speed equal to or higher than the predetermined rotation speed by the small diameter exhaust pipe and the large diameter exhaust pipe. Since the exhaust pipe structure has two systems, one internal combustion engine can obtain output characteristics from low speed to high speed.

Also, since the small-diameter exhaust pipe is displaced toward the vehicle rear side in the large-diameter exhaust pipe, it is difficult for the small-diameter exhaust pipe to be cooled because the running wind does not directly hit it. The catalyst activation temperature can be maintained.

Further, in the muffler side connection portion at the rear end portion of the exhaust pipe, when the switching valve is open, the cross-sectional area of the exhaust passage is the same before and after the switching valve, and between the large diameter exhaust pipe and the small diameter exhaust pipe. Since there is no adverse effect that two kinds of reflected waves are generated due to the long and short exhaust pipes of the small diameter exhaust pipe, the small diameter exhaust pipe can be used as the exhaust passage in both high speed and low speed, and space efficiency can be improved. It is easy to secure the space for the exhaust pipe.

Also, since the exhaust pipe is connected to each cylinder through a connection pipe separate from the cylinder, the heat of the internal combustion engine reaching the switching valve by heat conduction can be suppressed to a small amount, and the exhaust pipe is provided in front of the cylinder. Is connected, traveling wind is likely to hit the connecting pipe, and the surroundings of the switching valve are easily cooled.

Further, since the switching valve is attached to each cylinder on the drive shaft arranged so as to pass through each exhaust passage, the dimensional accuracy such as the interval between the switching valves of each cylinder is good, and the interlocking with good cooling performance is achieved. Is performed without any trouble, and it is not necessary to provide a driving means such as a motor for each cylinder, and the apparatus is simplified.

Further, since the switching valve is arranged in the exhaust pipe connecting portion of the connecting pipe in the vicinity of the front end portion of the exhaust pipe, it is not necessary to have a special passage structure inside the connecting pipe.

[Brief description of drawings]

FIG. 1 is a side view of a motorcycle to which the invention is applied, and FIG.
The figure is an enlarged cross-sectional view of the main part, FIG. 3 is the III-III cross-sectional view of FIG. 2, FIG. 4 is the IV-IV cross-sectional view of FIG. 2, and FIG. 5 is the circuit diagram of the servo motor unit and the control unit. , FIG. 6 is a diagram showing output characteristics. 4 ... Internal combustion engine 16 ... Connection pipe 17 ... Large diameter exhaust pipe 18 ... Small diameter exhaust pipe 21 ... Switching valve 23 ... Exhaust pipe line 26 ... Servo motor unit 30 ... Control unit 32 ... CDI unit 33 ... Motor 39 ... Microcomputer

Claims (1)

[Claims] 1. A motorcycle equipped with a parallel multi-cylinder engine in which exhaust pipes are connected in front of a plurality of cylinders, wherein the exhaust pipes are connected to the respective cylinders via connection pipes separate from the cylinders. And the connection pipe straddles a plurality of cylinders integrally, while the exhaust pipe has a small-diameter exhaust pipe disposed inside a large-diameter exhaust pipe, and the small-diameter exhaust pipe is a rear part of the vehicle in the large-diameter exhaust pipe. A switching valve that is configured to be displaced to the side and that opens and closes an exhaust pipe line formed between the small-diameter exhaust pipe and the large-diameter exhaust pipe at the exhaust pipe connecting portion of the connecting pipe is close to the front end portion of the exhaust pipe. In the muffler-side connecting portion to which the muffler at the rear end portion of this exhaust pipe is connected, the cross-sectional area of the exhaust passage is the same before and after that, and further, the switching valve passes through each exhaust passage. Each cylinder is attached to the drive shaft that is arranged. By operating the drive shaft, the switching valve is configured to be closed at a speed lower than a predetermined rotation speed of the internal combustion engine to be exhausted by the small diameter exhaust pipe, and opened at a speed equal to or higher than the predetermined rotation speed to be exhausted by the small diameter exhaust pipe and the large diameter exhaust pipe. A characteristic exhaust system for an internal combustion engine.