JPH11343838A - Exhaust system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust system for an internal combustion engine capable of improving a purifying performance even immediately after switching. SOLUTION: In an exhaust system where an internal combustion engine, a low revolution area exhaust pipe 4 and a high revolution area exhaust pipe 5 are interconnected via a cut-off poppet valve 4, and exhaust gas from the internal combustion engine is changed to the low or high revolution area exhaust pipe 4 or 5 by the cut-off poppet valve 3, a low revolution area catalyst device 21 is disposed in the low revolution area exhaust pipe 4, a high revolution catalyst device 22 is disposed in the high revolution area exhaust pipe 5, the downstream portion of the low revolution catalyst device 21 of the low revolution area exhaust pipe 4 and the upstream portion of the high revolution catalyst device 22 of the high revolution area exhaust pipe 5 are connected to each other via a communication pipe 23. Thus, exhaust gas purified in the low revolution catalyst device 21 of the low revolution area exhaust pipe 4 is purified in the high revolution catalyst device 22 of the high revolution area exhaust pipe 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine connected to a low-speed exhaust pipe and a high-speed exhaust pipe via a switching valve. The present invention relates to an exhaust device for an internal combustion engine that can be switched to an exhaust pipe for a high-range or high-speed range.

[0002]

2. Description of the Related Art Conventionally, as an exhaust system capable of obtaining a high output by utilizing a pressure wave of an exhaust gas over a wide range of the rotation range of an internal combustion engine, for example, an exhaust system described in Japanese Utility Model Laid-Open No. 60-143125 is known. is there. This is because a switching valve for switching the flow direction of exhaust gas to one of two directions is provided in an exhaust passage of a single-cylinder internal combustion engine, and one of two outlets of the switching valve is adapted to a low rotation speed range which is suitable for a low rotation speed range. And a high-speed exhaust pipe suitable for the high-speed range.

In this switching valve, an exhaust passage is formed in a valve body by forming two branch passages having a common inlet in a forked shape, and a rotating body having a curved communication passage at a branch portion of the exhaust passage. Are fitted rotatably about a central axis. An exhaust pipe for a low rotation range is connected to one exhaust passage, and an exhaust pipe for a high rotation range is connected to the other exhaust passage.

[0004] By rotating the rotating body about a central axis, a curved communication passage is moved to select one of the exhaust passages.

[0005]

However, in such a conventional apparatus, when the catalyst devices are provided in both the low-speed range exhaust pipe and the high-speed range exhaust pipe, the two exhaust pipes are not provided. Immediately after is switched, the catalyst device is often cold, is not activated, and has a problem that the purification function is not good.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an exhaust system for an internal combustion engine capable of improving the purification function even immediately after switching.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, an internal combustion engine is connected to an exhaust pipe for a low speed range and an exhaust pipe for a high speed range via a switching valve. In the exhaust device, the exhaust from the internal combustion engine can be switched to a low-speed or high-speed exhaust pipe by the switching valve. A high-rotation region exhaust pipe is provided with a high-rotation region catalyst device, and the low-rotation region exhaust pipe downstream of the low-rotation region catalyst device, and the high-rotation region exhaust pipe. The high-speed range catalytic device is connected to the upstream portion of the high-speed range catalyst device through a communication pipe, so that the exhaust gas purified by the low-speed range catalytic device of the low-speed range exhaust pipe is converted to the high-speed range. Exhaust system of an internal combustion engine that is set to be purified by a high-range catalytic device for a high-range exhaust pipe Characterized in that it was.

[0008]

Embodiments of the present invention will be described below.

[First Embodiment of the Invention] FIGS. 1 to 6 show a first embodiment of the present invention.

First, the structure will be described. Reference numeral 1 in FIG. 1 denotes a two-cylinder engine as an "internal combustion engine" of a motorcycle, and the two-cylinder engine 1 has an exhaust pipe 2
The exhaust pipe 2 is connected via a switching valve 3 to an exhaust pipe 4 for a low rotation range suitable for a low rotation range and an exhaust pipe 5 for a high rotation range suitable for a high rotation range. I have.

Specifically, the exhaust pipe 2
Has two branch portions 2a and a collecting portion 2b in which these branch portions 2a are assembled, and the two branch portions 2a are connected to each cylinder of the two-cylinder engine 1. The switching valve 3 is connected to the collecting part 2a. The branch part 2 on the front side of the collection part 2b of the exhaust pipe 2
As shown in FIG. 4 and the like, a extends right and left so that the collecting portion 2b is exposed when viewed from the front.

As shown in FIGS. 3 and 4, the switching valve 3 includes a valve body 7 fixed to the collecting portion 2b and a rotating body 8 rotatably disposed on the valve body 7. have.

The valve body 7 has a bifurcated exhaust passage 7 formed by communicating one outlet 7a with two outlets 7b and 7c.
d is formed, the inlet 7a of which is connected to the collecting portion 2b.
5 is bolted through a heat insulating material 6, and this valve body 7
The exhaust pipe 4 for the low rotation range is connected to one of the outlets 7b, and the exhaust pipe 5 for the high rotation range is connected to the other outlet 7c (see FIGS. 3, 4 and the like).

As shown in FIG. 3, the rotating body 8 has a cylindrical shape having a curved communication path 8a.
The valve body 7 is fitted to a branch portion of the exhaust passage 7 d so as to be rotatable about the central axis O. This communication path 8a
The outlet 8b of the communication passage 8a is connected to the outlet 7b or 7c of the valve body 7 by the rotation of the rotating body 8.

The rotating body 8 is set to be rotationally driven by a driving device 9. Specifically, the driving device 9 is disposed between the low-speed exhaust pipe 4 and the high-speed exhaust pipe 5 on the rear side of the rotating body 8, and as shown in FIG. A rotating shaft 10 is protruded, and a small-diameter first shaft is provided on the rotating shaft 8 as shown in FIGS.
The gear 11 is fixed, and the second gear 12 having a large diameter is meshed with the first gear 11. When the second gear 12 is rotated by a motor (not shown), the rotating body 8 is rotated.
Are rotated about a central axis O. The driving device 9 is connected to a control device (not shown).

The control device is connected to a sensor provided on the crankshaft arrangement portion of the two-cylinder engine 1, which detects the rotational speed of the two-cylinder engine 1 and receives a signal from this sensor. The motor 13 of the switching valve 3 is driven according to the rotation speed.

The exhaust pipe 4 for the low revolution range and the exhaust pipe 5 for the high revolution range are branched right and left from the switching valve 3 and extend rearward of the vehicle, and as shown in FIG. The low-range exhaust pipe 4 is bent halfway toward the high-rotation range exhaust pipe 5, and the rear end 4 a side of the low-revolution range exhaust pipe 4 is arranged along the vicinity of the high-rotation range exhaust pipe 5. Has been established.

Further, a low-rotation-range catalyst device 21 is provided in the low-rotation-range exhaust pipe 4, and a high-rotation-range catalyst device 22 is provided in the high-rotation-range exhaust pipe 5. The low-rotation-range catalyst device 21 is disposed near the downstream side of the switching valve 3, and the high-rotation-range catalyst device 22 is disposed in the muffler 5b.

As shown in FIG. 6, a portion of the exhaust pipe 4 for the low revolution range on the downstream side of the catalyst device 21 for the low revolution range,
The low-rotation-range catalyst device 21 of the low-rotation-range exhaust pipe 4 is connected to the high-rotation-range exhaust pipe 5 at an upstream side of the high-rotation-range catalyst device 22 through a communication pipe 23.
The exhaust gas that has been purified is set to be purified by the high-rotation-range catalyst device 22 of the high-rotation-range exhaust pipe 5 through the communication pipe 23.

The low-rotation-range catalyst device 21 is close to the two-cylinder engine 1 and has a high purification amount and a high temperature. Therefore, the supported catalyst (noble metal) is durable and expensive, for example, rhodium. And the high-speed range catalytic device 22
Since the catalyst is far from the two-cylinder engine 1 and the purification amount is small and the temperature is relatively low, an inexpensive catalyst (noble metal) having low durability, for example, palladium is used.

As shown in FIGS. 1 and 5, the switching valve 3 is provided with a support piece 14 projecting upward, and this support piece 14 is bolted to a bracket 15 provided on the vehicle body side. ing. Also, a support piece 16 is protrudingly provided at an intermediate portion in the longitudinal direction of the exhaust pipe 4 for the low rotation range and the exhaust pipe 5 for the high rotation range, and the support piece 16 is bolted to a bracket provided on the vehicle body side. I have. Furthermore, the exhaust pipe 4 for the low rotation range
The support pieces 18 are provided on the mufflers 4b and 5b of the exhaust pipe 5 for the high rotation range.
Is fixed, and this support piece 16 is bolted to a bracket 19 provided on the vehicle body side. In this way,
Exhaust pipe 2, switching valve 3, exhaust pipe for low rotation range 4
The exhaust pipe 5 for the high rotation range is supported by the vehicle body.

Next, the operation of the exhaust device having the above configuration will be described.

The number of revolutions of the two-cylinder engine 1 is detected by a sensor, and a signal from the sensor is input to a control device.
When the rotation speed at this time is smaller than a predetermined value, the switching valve 3
3 is set at the position shown by the solid line in FIG. 3, and the exhaust gas passes from the combustion chamber of each cylinder of the two-cylinder engine 1 through the branch portion 2a and the collecting portion 2b of the exhaust pipe 2 to be connected to the rotary body 8. After passing through the passage 8a, the gas flows from the outlet 7b of the valve body 7 into the exhaust pipe 4 for the low rotation range and is exhausted.

The exhaust gas that has flowed into the low-speed exhaust pipe 4 is purified by the low-speed catalytic device 21 and then exhausted to the outside through the silencer 4b. Part of the gas flows into the muffler 5b of the high-speed exhaust pipe 5, and is purified and exhausted by the high-speed catalyst device 22. Due to this purification, part of the exhaust gas is purified twice, so that more purified exhaust gas is discharged and the temperature of the high-rotation-range catalyst device 22 rises due to a chemical reaction at the time of purification. Will be achieved.

On the other hand, when the rotation speed becomes larger than the predetermined value, the control device drives the motor to rotate the rotating body 8 about the central axis O via the first and second gears 11 and 12 and the like. Then, the exhaust gas is switched to the high-speed exhaust pipe 5 and exhausted.

The exhaust gas that has flowed into the high speed range exhaust pipe 5 is purified by the high speed range catalytic device 22 and
The gas is exhausted to the outside through b. At this time, since the high-rotational-range catalyst device 22 has been activated in advance as described above,
Immediately after switching, the purifying property is good.

Also, the exhaust gas heated to a high temperature in the low-rotation-range catalyst device 21 of the low-rotation-range exhaust pipe 4 is guided to the high-rotation-range catalyst device 22 through the communication pipe 23 for activation. By doing so, it is possible to set the catalytic converter 22 for the high revolution range at a position distant from the two-cylinder engine 1, so that a decrease in output can be suppressed.

Further, by providing the low-rotation region exhaust pipe 4 and the high-rotation region exhaust pipe 5 with a low-rotation region catalyst device 21 and a high-rotation region catalyst device 22, respectively, Since the catalyst can be set to correspond to the need, and it is not necessary to set the catalyst to correspond to the entire rotation range, the weight and cost can be reduced.

In consideration of the early activation of the low-speed range catalytic device 21, it is optimal to dispose the catalytic device 21 immediately after the two-cylinder engine 1, but it is not so close (100
mm) and the heat generated by the catalyst device 21, the temperature of the two-cylinder engine 1 itself rises, and the purified high-temperature gas returns into the two-cylinder engine 1 to adversely affect combustion and the like. There is. However, by arranging the low-rotational-range catalyst device 21 in the vicinity of the downstream side of the switching valve 3, it is possible to secure the purification function and to prevent the two-cylinder engine 1 from being adversely affected. That is, the distance from the two-cylinder engine 1 to the collecting part 2b of the exhaust pipe 2 needs to be 100 mm or more in consideration of the flow of exhaust gas depending on the collecting angle. , It is possible to suppress an increase in the temperature of the two-cylinder engine 1 itself due to the heat generated in the catalyst device 21 and an adverse effect due to the return of the high-temperature gas into the two-cylinder engine 1.

Further, by arranging the low-rotational-range catalytic device 21 near the downstream side of the switching valve 3, the catalytic device 2
The heat generated in step 1 is transmitted to the switching valve 3, and there is a risk that the temperature of the switching valve 3 rises. However, by arranging the heat insulating material 6 between the catalyst device 21 and the switching valve 3, heat conduction is performed. It can shut off and prevent malfunction.

Moreover, in such an exhaust system,
Exhaust pipe 2, switching valve 3, exhaust pipe for low rotation range 4
And the exhaust pipe 5 for the high-speed region is connected, and has a substantially X-shaped integral rigid body structure that intersects at the switching valve 3 portion. Compared to the one with two exhaust pipes,
It contributes to the improvement of the rigidity of the vehicle body, as well as less rolling.

Further, when such an integral rigid structure is attached to a vehicle body, the number of attachment points can be reduced as compared with a conventional arrangement in which two separate exhaust pipes are provided. Moreover, in this embodiment, since the relatively heavy switching valve 3 is directly supported on the vehicle body via the support piece 14 and the like, vibration can be effectively suppressed. In addition, by disposing the switching valve 3 at the center portion in the vehicle width direction, the weight of the switching valve 3 is not excessively biased to either of the left and right sides, can be supported in a well-balanced manner, and at the same time, twisting or the like hardly occurs. The car width itself can be reduced.

Further, since the exhaust pipe 2, the switching valve 3, the exhaust pipe 4 for the low rotation range and the exhaust pipe 5 for the high rotation range are connected in an X-shape, they can be simply extended backward as in the conventional case. As compared with the exhaust system, the overall length of the exhaust system can be increased. Further, the exhaust pipe 4 for the low revolution range and the exhaust pipe 5 for the high revolution range are branched right and left from the switching valve 3 and extended to the rear of the vehicle, and as shown in FIG. Is bent in the middle toward the high-speed exhaust pipe 5, and the rear end 4 a of the low-speed exhaust pipe 4 is disposed along the vicinity of the high-speed exhaust pipe 5. In particular, the entire length of the exhaust system on the side of the exhaust pipe 4 for the low rotation range can be effectively increased. In addition, the exhaust pipe 4 for the low rotation range and the exhaust pipe 5 for the high rotation range
And the rear end can be aligned, and the appearance quality can be improved.

Further, as shown in FIG. 4 and the like, the branch portion 2a on the front side of the collecting portion 2b of the exhaust pipe 2 is
Since the gathering portion 2b extends right and left so as to be exposed when viewed from the front, the traveling wind directly hits the gathering portion 2b and the switching valve 3, so that the gathering portion 2b can be provided without disposing the forced cooling device. And the cooling performance of the switching valve 3 can be ensured.

In addition, since the switching valve 3 is located above the lowest point of the exhaust pipe 2, the exhaust pipe 4 for the low revolution range and the exhaust pipe 5 for the high revolution range, when the curb or the like is crossed, each of the exhaust pipes is switched. Since 2, 4, and 5 hit first, damage to the switching valve 3 can be prevented. Further, by disposing the driving device 9 of the switching valve 3 between the exhaust pipe 4 for the low rotation range and the exhaust pipe 5 for the high rotation range, the driving device 9 is also protected from stones flying from the side. can do.

Further, by arranging the driving device 9 of the switching valve 3 behind the rotating body 8, the rotating shaft 10 can be shortened and at the same time as compared with the case where the driving device 9 is arranged before the collecting portion 2 b. The passage area can be ensured without the rotation shaft 10 passing through the inside of the portion 2b, and furthermore, the driving device 9 can be prevented from hitting against a stone during traveling.

[Second Embodiment of the Invention] FIG. 7 shows a second embodiment of the present invention.

In the first embodiment, the two-cylinder engine 1
In the second embodiment, one exhaust pipe 25 is connected to a single-cylinder engine (not shown), and the exhaust pipe 25 is connected to an exhaust pipe for a low rotation range. 4 and an exhaust pipe 5 for a high rotation range. The switching between the exhaust pipes 4 and 5 is performed by rotating the plate-like switching valve 26 as shown by a two-dot chain line or a solid line in the drawing.

The other configuration and operation are the same as those of the first embodiment, and the description is omitted.

In the above embodiment, the present invention is described as follows.
Although applied to the cycle engine, the invention is not limited to this, and can be applied to a four-cycle engine.

[0041]

As described above, according to the first aspect of the present invention, the low-rotation-range exhaust pipe has the low-rotation-range catalyst device, and the high-rotation-range exhaust pipe has the high-rotation-range exhaust device. And a downstream portion of the low-rotation-range catalyst device of the low-rotation-range exhaust pipe and an upstream portion of the high-rotation-range catalyst device of the high-rotation-range exhaust pipe. The exhaust gas purified by the low-rotation-range exhaust pipe catalyst device is purified by the high-rotation-range exhaust pipe high-rotation region catalyst device by being connected via the low-rotation-range exhaust pipe. Therefore, in the case of the low rotation range, a part of the exhaust gas flows into the high rotation range exhaust pipe through the communication pipe and is purified by the high rotation range catalytic device. As a result, the temperature of the catalyst device for the high rotation range rises and activation is achieved. Therefore, immediately after switching to the high-speed range exhaust pipe, the purification performance of the high-speed range catalyst device can be ensured.

Further, the exhaust gas heated to a high temperature in the low-rotation-range catalyst device of the low-rotation-range exhaust pipe is guided to the high-rotation-range catalyst device through the communication pipe to be activated. Since the high-speed range catalyst device can be set at a position distant from the internal combustion engine, a decrease in output can be suppressed.

Further, by providing a low-rotation-range catalyst device and a high-rotation-range catalyst device in each of the low-rotation-range exhaust pipe and the high-rotation-range exhaust pipe, catalysts corresponding to each rotation range are provided. Since there is no need to use a catalyst that supports the entire rotation range, there is a practically beneficial effect that weight and cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a side view showing an arrangement state of an exhaust device according to Embodiment 1 of the present invention.

FIG. 2 is a plan view of the exhaust device according to the first embodiment.

FIG. 3 is a cross-sectional view of the switching valve according to the first embodiment.

FIG. 4 is a plan view of a front portion of the exhaust device according to the first embodiment.

FIG. 5 is a side view of the exhaust device according to the first embodiment.

FIG. 6 is a schematic diagram of an exhaust device according to the first embodiment.

FIG. 7 is a schematic diagram of an exhaust device corresponding to FIG. 6 according to Embodiment 2 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Two-cylinder engine (internal combustion engine) 2,25 Exhaust pipe 2a Branch part 2b Assembly part 3,26 Switching valve 4 Exhaust pipe for low rotation range 5 Exhaust pipe for high rotation range 21 Catalyst device for low rotation range 22 For high rotation range Catalyst device 23 Communication pipe

Claims (1)

[Claims] An internal combustion engine is connected to an exhaust pipe for a low-speed range and an exhaust pipe for a high-speed range through a switching valve. In the exhaust device which can be switched to a low-range exhaust pipe, a low-rotation-range catalyst device is provided in the low-rotation-range exhaust pipe, and a high-rotation region catalyst device is provided in the high-rotation-range exhaust pipe. The low-rotation region exhaust pipe downstream portion of the low-rotation region catalyst device is connected to the high-rotation region exhaust pipe upstream portion of the high-rotation region catalyst device via a communication pipe. Thereby, the exhaust gas purified by the low-rotation-range exhaust pipe catalytic converter for the low-rotation-range exhaust pipe is set to be purified by the high-rotation-range catalytic device of the high-rotation-range exhaust pipe. An exhaust device for an internal combustion engine, comprising: