JP4369306B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  TECHNICAL FIELD The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and mainly an internal combustion engine that can activate an exhaust gas purification catalytic converter disposed in an exhaust passage at an early stage, immediately after starting an internal combustion engine mounted on a motorcycle. The present invention relates to an exhaust emission control device for an engine.

2. Description of the Related Art Conventionally, for example, an exhaust gas purification apparatus for an internal combustion engine such as a gasoline engine mounted on a motorcycle has an exhaust gas purification catalytic converter attached in an exhaust passage. However, since this catalytic converter is generally mounted at a position away from the exhaust outlet of the engine body due to its structure, it takes time to reach catalyst activation (activation temperature about 300 ° C.). Therefore, for example, in a four-cylinder engine, an exhaust control valve is provided at the rear end of four exhaust pipes connected to a plurality of exhaust ports formed in the cylinder head of the engine, and by switching the exhaust control valve, the engine rotates at a low speed. In some cases, there is an exhaust gas purification apparatus in which the exhaust gas purification efficiency is improved by bringing the exhaust gas into contact with one catalytic converter via a single collecting passage (see, for example, Patent Document 1).
JP 2001-342828 A

  However, in the case of the exhaust purification device, since the exhaust control valve is provided at the downstream end of the four exhaust pipes, the exhaust gas flowing in one exhaust pipe is merged with the exhaust gas in the other exhaust pipe. As a result, the temperature of the exhaust gas in the exhaust pipe has dropped, and even when the exhaust control valve is switched during low-speed rotation of the engine, the heat capacity before the catalytic converter does not change much, and the effect of early activation of the catalytic converter is low.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an internal combustion engine exhaust gas purification apparatus capable of early activation of an exhaust gas purification catalytic converter immediately after engine startup and during low-speed rotation.

  In order to achieve the above object, an exhaust gas purification apparatus for an internal combustion engine according to the present invention has an exhaust pipe connected to an exhaust port of each cylinder of a multi-cylinder internal combustion engine, and an exhaust pipe is provided with a catalytic converter for exhaust gas purification. A pair of exhaust pipes communicated by a communication path upstream of the catalytic converter, and the exhaust gas in the one exhaust pipe is closed to one of the pair of exhaust pipes when the internal combustion engine is rotated at a low speed. There is provided an exhaust control valve that leads to the other exhaust pipe.

  According to this configuration, when the engine is rotating at a low speed (for example, during warm-up operation), the exhaust gas in one exhaust pipe is guided into the other exhaust pipe via the communication path, and one exhaust gas is located downstream of the exhaust pipe. Since the exhaust pipe is made to flow intensively, heat dissipation in the exhaust pipe is reduced, and as a result, the exhaust gas is brought into contact with the catalytic converter while maintaining a high temperature. Thereby, early activation of the catalytic converter can be achieved. In addition, since the exhaust control valve is added to the existing structure in which a pair of adjacent exhaust pipes communicate with each other through the communication path, the manufacturing cost is also low.

  In a preferred embodiment of the present invention, the internal combustion engine is a four-cylinder engine, and the exhaust control valve is provided in the exhaust pipes on both outer sides. According to this configuration, as compared with the case where the exhaust control valve is provided in the inner exhaust pipe, the driving force transmission member such as a wire or a cable for driving the exhaust control valve can be easily handled. Contact with the exhaust pipe can be prevented as much as possible.

In a preferred embodiment of the present invention, the internal combustion engine is mounted on a motorcycle, and the exhaust port is disposed on a front surface of the internal combustion engine facing the front of the motorcycle, and is provided in the exhaust pipe. Is arranged in front of the internal combustion engine. According to this configuration, since the exhaust control valve is located in front of the internal combustion engine, that is, relatively upstream in the exhaust pipe, the temperature reduction of the exhaust gas is suppressed and the high temperature is maintained through the communication passage. Since it is led to one exhaust pipe, the early activation effect of the catalytic converter can be further increased.

  According to the exhaust gas purification apparatus for an internal combustion engine of the present invention, the exhaust gas can be brought into contact with the catalytic converter while maintaining a high temperature when the engine is rotated at a low speed with a simple structure. Thereby, early activation of the catalytic converter can be achieved, and the exhaust gas is effectively purified.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side view showing a motorcycle equipped with an exhaust gas purification apparatus for an internal combustion engine according to the present invention. In the motorcycle shown in the figure, a front fork 2 is supported at the front end of a main frame 1 constituting the front half of a vehicle body frame FR via a head pipe 11, an upper bracket 12, and a lower bracket 13. A front wheel 3 is supported at the lower end, and an upper portion thereof is covered with a fender 4. A handle 5 is attached to the upper bracket 12. A swing arm bracket 6 is formed at the lower rear end of the main frame 1, and the front ends of a pair of left and right swing arms 7 are supported on the swing arm bracket 6 via a pivot shaft 8 so as to be swingable up and down. A rear wheel 9 is supported at the rear end of the swing arm 7. A seat rail 10 connected to the rear portion of the main frame 1 constitutes the rear half of the vehicle body frame FR. A four-cycle engine E, which is a reciprocating internal combustion engine, is supported at the center lower portion of the main frame 1, and a radiator 31 is disposed in front of the engine E. Further, exhaust pipes 14A, 14B, 14C, and 14D (FIG. 2) are connected to four exhaust ports 33 formed in the cylinder head 32 of the engine E, respectively.

  A rider's seat 18 and a passenger's seat 19 are supported on the seat rail 10. A fuel tank 20 is attached between the handle 5 and the rider's seat 18 at the upper part of the main frame 1, that is, at the upper part of the vehicle body. Further, a resin cowling 21 that covers a portion from the front of the handle 5 to the side of the front of the vehicle body is attached to the front of the vehicle body, and the rear portion of the cowling 21 includes a side portion and a lower portion of the engine E. Covering.

  The four exhaust pipes 14 </ b> A to 14 </ b> D of the engine E are gathered into one at a position where it hits the lower side of the engine E. That is, as shown in FIG. 2 which is a plan view, two adjacent ones in the first collecting pipe 15A on the front side are gathered together, one in total, and the two first collecting pipes 15A are in the rear part. The second collecting pipe 15B on the side gathers together. Each of the first collecting pipes 15A and 15A incorporates one catalytic converter 22 for purifying exhaust gas, and the exhaust gas from the corresponding pair of exhaust pipes 14A / B and 14C / D is used as a common catalytic converter. Purify by 22 A joint pipe 16 is connected to the rear end of the second collecting pipe 15B, and a silencer 17 shown in FIG.

  As the exhaust purification catalytic converter 22, for example, a honeycomb type or a punching plate type is used. In the honeycomb type, alumina is coated on a cylindrical catalyst carrier made of honeycomb-shaped ceramics or metal called a monolithic carrier, and platinum, palladium, etc. as a catalyst for an oxidation reaction, rhodium, etc. as a catalyst for a reduction reaction, Each is coated. In the punching plate type, a catalyst such as platinum and rhodium is supported on the outer peripheral surface of a cylindrical catalyst carrier made of a punching plate having a large number of small holes.

  FIG. 3 is an enlarged front view of the exhaust pipes 14 </ b> A to 14 </ b> D, which are main parts of FIG. 2, as viewed from the front. As shown in the figure, among the four exhaust pipes 14 to D connected to the exhaust port 33, each pair of adjacent exhaust pipes 14A (outside) / 14B (inside) and 14C (inside) / 14D (outside) ) Are communicated with each other through a communication passage 23 provided in the middle, and the exhaust gas in the outer exhaust pipes 14A, D is closed to the outer (one) exhaust pipes 14A, D when the engine E rotates at a low speed. An exhaust control valve 24 that leads to the inner (other) exhaust pipes 14B and C through the communication path 23 is provided. The communication passage 23 is provided at a portion extending vertically at a position substantially half the passage length in the outer exhaust pipes 14A and 14D, that is, the length from the exhaust port 33 to the first collecting pipe 15A. The valve 24 is provided near the downstream side of the communication passage 23 in the outer exhaust pipes 14A and 14D. An actuator 35 for opening and closing the exhaust control valve 24 is supported on the main frame 1 of FIG. 1, and an electronic control unit 36 for controlling the electric system including the control of the actuator 35 is disposed below the rider seat 18. .

  The exhaust control valve 24 is a butterfly valve, and has a valve body 24a that is located in the exhaust pipe 14A and rotates about the axis C1, as shown by the outer exhaust pipe 14A in FIG. One end portion of the valve shaft 24b of the valve body 24a protrudes from the front portion of the exhaust pipe 14A, and a pulley 25 is fixed to one end portion of the valve shaft 24b. The pulley 25 and the actuator 35 are connected by a wire (or cable) 26 which is an example of a driving force transmission member, and an electronic control unit 36 which receives a signal indicating the engine speed from the rotation sensor 37 as an input. In response to the control signal, the actuator 35 is driven to rotate the valve body 24a around the axis C1 via the wire 26 to open and close the exhaust control valve 24. That is, the exhaust control valve 24 is rotated to control the exhaust gas to flow to the exhaust pipe 14 </ b> A or to the communication pipe 23. In the case of FIG. 4, the exhaust control valve 24 shows the opened state A, and the valve body 24a is positioned in parallel with the pipe axis direction of the exhaust pipe 14A. On the other hand, in the state B in which the exhaust control valve 24 is closed, the valve body 24a is in a posture orthogonal to the pipe axis direction of the exhaust pipe 14A. In this valve-closed state, the valve body 24a is located on the downstream side of the exhaust pipe 14A with respect to the communication hole 23a to the exhaust pipe 14A of the communication path 23.

  By switching the exhaust control valve 24, the outer exhaust pipes 14A and 14D shown in FIG. 3 are closed so that the upstream portion of the exhaust control valve 24 and the inner exhaust pipes 14B and 14C communicate with each other through the communication passage 23. The exhaust gas G2 flowing in the pipes 14A and D can be merged with the flow of the exhaust gas G1 flowing in the other exhaust pipes 14B and 14C. When the outer exhaust pipes 14A and 14D are opened, the exhaust gases G1 and G2 flow through the exhaust pipes 14B and 14C and the exhaust pipes 14A and 14D over the entire length, respectively. A rotary valve may be used as the valve body 24a.

  In the above configuration, in the case of low speed rotation where the engine speed is not more than a certain value and the exhaust gas flow rate is small, such as during warm-up operation immediately after the engine is started, the electronic control unit 36 that receives a signal from the rotation sensor 37 in FIG. The actuator 35 is actuated by the control signal from, and the exhaust control valve 24 is closed. As a result, the exhaust gas G2 exhausted from the exhaust port 33 of FIG. 3 and flowing in the outer exhaust pipes 14A and 14D is communicated from the communication holes 23a and 23a in front of the exhaust control valves 24 and 24, as indicated by the one-dot chain line. 2 enters the communication passages 23, 23, flows through the communication passages 23, 23 into the inner exhaust pipes 14B, C, and merges with the exhaust gases G1, G1 flowing through the exhaust pipes 14B, C. Guided to the catalytic converters 22 and 22 in the pipes 15A and 15A. As described above, the exhaust gases G2 and G2 are joined to the exhaust gases G1 and G1 via the communication passages 23 and 23, so that the exhaust gases G2 and G2 are exhaust pipe 14A downstream of the communication passages 23 and 23. , D is eliminated, so that the temperature drop is suppressed and introduced into the catalytic converter 22 while maintaining a high temperature state. Therefore, the catalytic converters 22 and 22 reach the activation temperature at an early stage, and the early activation of the catalyst. Can be achieved.

  On the other hand, when the engine speed is higher than the predetermined value, the exhaust control valves 24 and 24 shown in FIG. 3 are controlled to open, and as a result, the exhaust ports 33 and 33 are exhausted and the outer exhaust pipes are exhausted. Exhaust gases G2 and G2 flowing through 14A and D are introduced as they are into the catalytic converters 22 and 22 shown in FIG. The exhaust gases G1 and G1 flowing in the inner exhaust pipes 14B and 14C flow in the exhaust pipes 14B and C as they are and are introduced into the catalytic converters 22 and 22 as in the case of low speed rotation. At the time of this high speed rotation, the amount of the exhaust gases G1 and G2 is large, so the influence of the temperature drop due to heat radiation from the exhaust pipes 14A to 14D is small. In this state, the exhaust gas G1 and G2 can be effectively purified by the catalytic converters 22 and 22. The communication passages 23 and 23 effectively use exhaust pulsation to improve output performance.

  Further, as shown in FIG. 1, the exhaust control valve 24 is positioned in front of the engine E (that is, on the upstream side of the exhaust pipes 14A, D), so that the exhaust gas G2 is exhausted from the exhaust pipes 14A, D. 2 is led from the one exhaust pipe 14A, D to the other exhaust pipe 14B, C through the communication passages 23, 23 in a state where the temperature is kept as low as possible and kept at a high temperature. The early activation effect of the converters 22 and 22 is further increased.

  Furthermore, since the exhaust control valve 24 is provided in the exhaust pipes 14A and 14D on both outer sides, it is easy to route the wire 26 that drives the exhaust control valve 24, and the wire 26 contacts the exhaust pipes 14A to 14D. Can be prevented as much as possible, and maintenance and inspection of the exhaust control valve 24 can be easily performed.

  Further, as is clear from the above-described embodiment, the exhaust emission control device has a simple structure in which the exhaust control valve 24 is provided in parallel with the existing communication passage 23 that communicates a pair of adjacent exhaust pipes 14A / B or 14C / D. As a result, the manufacturing cost is reduced.

  In the above-described embodiment, the application example for the four-cylinder engine is shown, but the present invention can be similarly applied to the case of the two-cylinder engine. Further, in the embodiment, the common catalytic converters 22 and 22 are provided downstream of the pair of exhaust pipes 14A / B and 14C / D, but each of the exhaust pipes 14A to 14D is provided in the collecting pipes 15A and 15A. A pair of individually connected catalytic converters may be provided.

1 is a side view showing a motorcycle equipped with an exhaust gas purification apparatus for an internal combustion engine according to the present invention. It is a top view which expands and shows the principal part of FIG. It is the enlarged front view which looked at the exhaust pipe which is the principal part of FIG. 2 from the front. FIG. 4 is a sectional view taken along line IV-IV in FIG.

Explanation of symbols

14A to D Exhaust pipe 22 Catalytic converter 23 Communication path 24 Exhaust control valve 33 Exhaust port E Engine (internal combustion engine)

Claims (3)

An exhaust pipe is connected to the exhaust port of each cylinder of the multi-cylinder internal combustion engine,
A catalytic converter for exhaust purification is provided in the exhaust pipe,
A pair of adjacent exhaust pipes are communicated by a communication path on the upstream side of the catalytic converter,
One of the pair of exhaust pipes is provided with an exhaust control valve that is closed during low-speed rotation of the internal combustion engine and guides exhaust gas in the one exhaust pipe to the other exhaust pipe through the communication path. Exhaust purification device.   2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the internal combustion engine has four cylinders, and the exhaust control valves are provided in exhaust pipes on both outer sides. 3. The exhaust control valve according to claim 1, wherein the internal combustion engine is mounted on a motorcycle, and the exhaust port is disposed on a front surface of the internal combustion engine facing the front of the motorcycle and is provided in the exhaust pipe. An exhaust gas purification apparatus for an internal combustion engine, in which is disposed in front of the internal combustion engine.

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