JPH0726546B2 - Motorcycle exhaust system - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention improves a connection structure of exhaust pipes connected to four cylinders of a parallel four-cylinder engine mounted on a motorcycle to improve engine output. A device for improving characteristics.

[Conventional technology and its problems]

Conventionally, in a motorcycle equipped with a parallel 4-cylinder engine,
The exhaust pipe led from each cylinder is connected to two exhaust silencers for each cylinder installed on both sides of the rear part of the vehicle body to reduce the ventilation resistance of each exhaust pipe, and each exhaust pipe connected to the engine. It has been practiced to set the lengths of the tubes to be the same and to synchronize them with the engine rotation speed at the time of maximum engine output.

In recent years, motorcycle engines have been
The exhaust pipe length is set to match the maximum output speed because it has an extremely wide range from 000 RPM to a maximum of 150,000 RPM and a high output of around 200 horsepower per 1000 CC of displacement. In this case, as shown by A in FIG.
In the medium speed range, the output torque locally decreases, which is a so-called torque valley.

On the other hand, as described above, in a multi-cylinder engine, if the exhaust pipes of all cylinders are set to the same length, the overall characteristics of the engine will also have a torque valley in part, as in the case of a single cylinder. It may cause inconvenience in driving.

In order to solve this, in a conventional motorcycle equipped with a four-cylinder engine, among the exhaust pipes connected to each cylinder, those having a close ignition order are communicated with each other to improve engine performance. Although the technology is known (for example, Japanese Utility Model Publication No. 54-10412, Japanese Patent Publication No. 58-178820, etc.), when this method is used, the torque valley becomes shallow and the low / medium speed performance is improved. There is a problem that the maximum output is reduced.

[Outline of Object of Invention and Means for Solving Problem]

An object of the present invention is to obtain an engine with high output torque over a wide speed range by making the depth of the above-mentioned torque valley shallow by preventing the torque decrease in the high speed range by improving the exhaust pipe. Therefore, four exhaust pipes # 1, # 2, # 3, and # 4 are connected to four cylinders arranged in parallel, and the ignition order of the connected cylinders is # 1, # 2, # 4,
# 3, two inner pipes of these exhaust pipes are made to communicate with each other, and two outer outer pipes # 1, # 2 and # 3, # 4 are assembled on the downstream side thereof, and further, It is characterized in that exhaust mufflers are separately connected downstream of the collecting portion, and the first expansion chambers of the left and right exhaust mufflers are communicated with each other through a communication passage.

〔Example〕

The present invention will be described below with reference to the illustrated embodiment. In the figure, reference numeral 1 is a motorcycle, and an engine 5 is mounted on a vehicle body frame 4 located between a front wheel 2 and a rear wheel 3.
The engine 5 is a parallel four-cylinder type engine, and as shown in FIG. 3, four exhaust pipes # 1, # 2, # 3 and # 4 led from each cylinder and two cylinders outside of these are assembled. The collecting section 6 and the exhaust silencer 7 provided at the rear end of the collecting section 6 are provided. Reference numeral 8 is a first communication pipe that connects the two inner exhaust pipes # 2 and # 3 to each other, and 9 is a left and right exhaust silencer 7
Is a second communication pipe for communicating the two with each other in the first expansion chamber. The first expansion chamber refers to the empty chamber 7a in the exhaust silencer 7 whose rear end is open.

The ignition sequence of this engine is # 1, # 2, # 4, and # 3, each having a phase difference of 180 °. Yotsutte
Two exhaust pipes # 2, # connected by the first communication pipe 8
3 has a substantially shortened pipe length, and the outer exhaust pipes # 1 and # 4
As shown by x and y in FIG. 5, the output torque undergoes a horizontal displacement between the cylinders connected with the cylinders, and the torque valley of the above-mentioned comprehensive characteristic is made shallow. On the other hand, this configuration lowers the maximum output of the integrated characteristics as shown by the curve Y in FIG. 5, and this is compensated as follows. That is, the exhaust pipes # 2 and # 3 are connected to the two outer exhaust pipes # 3,
# 4 is merged with an acute angle, and the end of exhaust pipe # 4 is narrowed down slightly to form nozzle N, which increases the flow velocity of exhaust gas and causes it to rush into the upstream end of collecting part 6 while Is provided with an opening 6a having a slightly smaller diameter in the vicinity of the nozzle N, and another exhaust pipe # 3 is welded thereto. As described above, since the exhaust pipe # 4 has an ignition sequence earlier than the other exhaust pipes # 3 by 180 ° in crank angle, exhaust gas is discharged to the exhaust pipe # 4 prior to the exhaust pipe # 3. The exhaust flow from the exhaust pipe # 4 discharged from the nozzle N causes a suction action, and the exhaust effect causes the exhaust pipe # 3 to be exhausted under a low ventilation resistance. The maximum torque is improved.

Further, in this embodiment, the diameter of the first communication pipe 8 is smaller than that of the exhaust pipes because of the processing of the exhaust pipes # 2, # 3 and the first communication pipe 8, and the diameter of the exhaust pipes # 2, # 3 is smaller. Since the action of substantially shortening the pipe length is insufficient, the two exhaust silencers 7 on the left and right are made to communicate with each other by the second communication pipes 9 in the first expansion chamber to supplement this. Further, by adopting such a configuration, when the exhaust gas is discharged to the first expansion chamber (vacant chamber 7a) of one of the left and right exhaust silencers 7,7, the exhaust pressure of this exhaust gas becomes the second communication pipe. It is also propagated to the first expansion chamber of the other exhaust silencer 7 via 9. That is, since the exhaust gas expands by simultaneously using the first expansion chambers of the left and right exhaust silencers 7, 7, the substantial volume of the first expansion chamber is increased without increasing the size of the exhaust silencer 7, and the silencer is used. The effect can be enhanced.

10 is the exhaust pipe # 4 on the side to be merged with # 4
3 is a cover provided on the front outer surface in the opening direction of 3, and shields the outer surface of the collecting portion so that it may be discolored by exhaust heat.

Explaining the operation of the exhaust pipe assembly by the exhaust pipes # 3, # 4, as shown in FIG. 5, x is the output torque of the exhaust pipes # 3, # 4 when not assembled, and X is the exhaust pipe #.
The total torque of the two cylinders in which # 3 and # 4 are connected is shown. Here, if a nozzle N-type throttle is installed in the exhaust pipe 4, the output torque of that cylinder moves in parallel to the left in the figure as indicated by y, and as a result, the total torque of the two cylinders is increased. As indicated by Y, the torque valley becomes shallower but the maximum torque decreases. Therefore, when a suction action is exerted on the exhaust pipe # 3 of the cylinder that is subsequently ignited by the # 4 exhaust flow that is ignited first, the maximum torque of that cylinder increases as indicated by z, and as a result, As indicated by Z in the figure, the torque valley of the total torque characteristic becomes shallow, and the maximum torque can be reduced only slightly.

〔The invention's effect〕

As described above, according to the present invention, the four exhaust pipes # 1, # 2, # 3, and # 4 are connected to the four cylinders arranged in parallel, and the ignition order of the connected cylinders is # 1. , # 2, # 4, #
3 and none of those exhaust pipes, the two inner exhaust pipes #
Since 2 and # 3 are communicated with each other, the substantial pipe length of these two exhaust pipes # 2 and # 3 is shortened, and the high speed performance of the engine is improved. Further, on the downstream side, two outer exhaust pipes # 1, # 2 and # 3, # 4 are assembled together, and further exhaust mufflers are connected to the downstream of the assembly part, respectively. Since the first expansion chambers of No. 2 are communicated with each other through the communication passage, the depth of the torque valley on the performance curve is made shallow to improve the medium / low speed performance, and the torque decrease in the high speed range is prevented to prevent a wide speed range Thus, it is possible to obtain an engine with high output torque. Moreover, when the exhaust gas is discharged to the first expansion chamber of one of the left and right exhaust silencers, the exhaust pressure of this exhaust gas is also propagated to the first expansion chamber of the other exhaust silencer via the communication passage. The exhaust gas expands by simultaneously using the first expansion chambers of the left and right exhaust silencers. For this reason, the exhaust muffler can be
The substantial volume of the expansion chamber can be increased to enhance the silencing effect. In addition, when the first expansion chambers are communicated with each other, there is an advantage that the silencing effect is enhanced by the amount of the exhaust pressure being higher than when the second expansion chambers or the third expansion chambers are communicated with each other. Further, the entire structure of the exhaust pipe is symmetrical so that the engine output can be improved in a well-balanced manner.

[Brief description of drawings]

The drawings show an embodiment of the present invention. Fig. 1 is a side view of a motorcycle, Fig. 2 is an enlarged side view of essential parts, Fig. 3 is a plan view thereof, and Fig. 4 is IV-IV thereof. A sectional view, FIG. 5 is a characteristic diagram of the engine, and FIG. 6 is a valve diagram. # 1, # 2, # 3, # 4 ... Exhaust pipe, 6 ... Collecting part, 6a ... Opening, 7 ... Exhaust silencer, 8 ... First communicating pipe, 9 ... Second
Communication pipe.

Claims (1)

[Claims] 1. Exhaust pipes # 1, # 2, # 3, # 4 are connected to four cylinders arranged in parallel, and the ignition order of the connected cylinders is # 1, # 2. , # 4, # 3, the two inner exhaust pipes # 2, # 3 of these exhaust pipes are communicated with each other, and the two outer exhaust pipes # 1, # 2 are provided downstream of them. And # 3 and # 4 are gathered together,
Furthermore, an exhaust silencer is connected to each of the downstream of the gathering part,
An exhaust device for a motorcycle in which the first expansion chambers of the left and right exhaust silencers are connected to each other through a communication passage.