JPS6299627A - Exhaust device for motorcycle - Google Patents

Abstract

PURPOSE:To secure a well-balanced torque characteristic in the whole driving range of an engine, by interconnecting each pair of exhaust pipes for cylinders uncontinued in firing order, with each of first and second interconnecting pipes. CONSTITUTION:Four exhaust pipes #1, #2, #3 and #4 connected to four cylinders set up in parallel are connected with one another, while each firing order of these connected cylinders is set down to #1, #2, #4 and #3 each, and among these exhaust pipes, two exhaust pipes #2 and #3 at the inner side are interconnected with each other by an interconnecting pipe 8. With this connection, the substantial pipe length of these two exhaust pipes #2 and #3 comes to be shortened in consequence, whereby high speed performance of an engine is improved. Ant, at the downstream side, two exhaust pipes #1 and #2 at the outside and exhaust pipes #3 and #4 are converged with one another, and furthermore connected to each muffler 7 separately at the downstream of the converged part, thus each inside of these symmetrical exhaust pipes is interconnected with each other via a second interconnecting passage 9. With this constitution, the depth in a torque root area on a performance curve is made yet shallower, and thereby the performance at medium and low speeds is improved, while a torque decreased at a high speed range is checked, thus such an engine that is high in output torque over an extensive speed range is securable. In addition, the overall constitution of these exhaust pipes consists of a symmetrical form, so that engine output is improvable in a well-balanced manner.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention completely improves the connection structure of each exhaust pipe connected to four Q cylinders of a parallel four-cylinder engine mounted on a motorcycle, thereby increasing the engine output. The present invention relates to a device for improving properties.

[Conventional technology and its problems]

Conventionally, motorcycles fully equipped with parallel 4-cylinder engines,
All exhaust pipes leading from each cylinder were connected to two exhaust silencers for each cylinder installed on both sides of the rear of the vehicle to reduce the ventilation resistance of each exhaust pipe. The length of each exhaust pipe is set to be the same so that it is synchronized with the engine/engine rotational speed at maximum output of the engine.

In recent years, motorcycle engines have become
．． 00 ORPM to maximum l 0001 PM The widest delivery area in the case and 20 per 11000cc exhaust
In order to obtain a high output of around 0 horsepower, the length of the exhaust pipe is set to match the maximum output speed, but in this case, the output is reduced in the medium speed range as shown by the center figure in Figure 6. This causes a so-called torque valley, where the torque locally decreases.

On the other hand, as mentioned above, if the exhaust pipes of all cylinders in a multi-cylinder engine are set to the same length, the overall characteristics of the engine will be the same as those of a single cylinder, with some torque valleys, and it will be difficult to drive around town. Conventionally, in motorcycles equipped with 4-cylinder engines, exhaust pipes connected to each cylinder and those with close ignition order are connected to each other. There is a known technique for improving engine performance by making the engine fully open (for example, Meiko No. 54-10412, Japanese Unexamined Patent Publication No. 58-178820, etc.), but when this method is used, the torque valley becomes shallow, Although low and medium speed performance is improved, there is a problem that the maximum output is reduced.

[Objective of the invention, summary of means for solving all problems] This invention reduces the depth of the above-mentioned torque valley by improving the exhaust pipe, and completely prevents the torque from decreasing in the high speed range. The purpose is to write a complete engine with high output torque, and four exhaust pipes #1, #l, #3, and #4 connected to four cylinders arranged in parallel are connected. Set the firing order of the connected cylinders to #1, #2, #4,
Among these exhaust pipes, the inner two are communicated with each other, and the outer and outer two exhaust pipes are connected to each other on the downstream side.
1. Collect #2 and #3 and #4 together, and further connect each to the exhaust silencer separately downstream of the gathering part, and communicate the insides of the left and right exhaust pipes with each other via the second communication passage. There are nine characteristics.

〔Example〕

The present invention will be explained below with reference to the illustrated embodiment. In the figure, 1 is a motorcycle 9, and an engine 5 is mounted on a body frame 4 located between a front wheel 2 and a rear wheel 3. There is.

The engine 5 is a parallel four-cylinder type.As shown in Figure 3, there are four exhaust pipes #1, #2, #3 and #4 leading from the valley pipes, and two cylinders on the outside of these pipes. It is provided with a collecting part 6 in which each part is collected separately, and an fc exhaust muffler T provided at the rear end of the collecting part 6. 8 to 01 [) 2 exhaust pipes #2, #3
A first communication pipe 9 connects the left and right exhaust mufflers 7 with each other and a second communication pipe 9 communicates them with each other in the first expansion chamber. Note that the first expansion chamber refers to the empty space γa in the exhaust silencer 7 in which the rear end of the collecting portion 6 is open.

The ignition order of this engine is #1, #2, #4, and #3, each with a phase difference of 180°. Therefore, the two exhaust pipes #2 connected behind the first communication pipe 8,
The actual pipe length of #3 is shortened, and the outer exhaust pipes #1 and #3 are
Between cylinders 4 and 4, the output torque is horizontally displaced as shown by X and y in FIG. On the other hand, this configuration lowers the maximum output of the integrated characteristic as shown by curve MY in FIG. 5, so this is compensated for by the following measures.

That is, exhaust pipe '2, #3, two exhaust pipes s3 on the outside
, acute angle to s4? The end of the exhaust pipe #4 is narrowed and narrowed to form a nozzle N, increasing the flow rate of the exhaust gas and flowing into the upstream end of the collecting part 6. A small diameter opening 6a k is provided, and the other exhaust pipe #3 is placed there. As mentioned above, exhaust pipe #4 has a firing order earlier than other exhaust pipes by 180' in terms of crank angle, so exhaust pipe #4 is discharged with exhaust before exhaust pipe #3, and thus An L9 suction effect is produced in the exhaust flow from the exhaust pipe #41j and others discharged from the nozzle N, and the exhaust pipe The maximum torque of #3 has been improved.

Furthermore, in this embodiment, due to the processing of the exhaust pipes #2 and #3 and the first communication pipe 8, the diameter of the first communication pipe 8 is smaller than the diameter of the exhaust pipe back 9. Since the effect of shortening the actual pipe length is insufficient, this is compensated for by making the two left and right exhaust mufflers 77 communicate with each other in the second communication pipe 9 within their first expansion tubes. .

10 is a cuckoo lubrication applied to the front outer surface in the opening direction of the exhaust pipe #3 on the side merging with the exhaust pipe #4 on the merging side, which shields the outer surface of the convergence part from discoloration due to exhaust heat. Out.

To explain the effect of exhaust pipes #3 and #4 assembling the exhaust pipes, as shown in Fig. 5, in the figure, X is the output torque of exhaust pipes #3 and #4 when they are not assembled, and X is the output torque of exhaust pipes #3 and #4 when they are not assembled. 3,
The combined torque of the two cylinders connected #4 is shown. Now, when an N-type nozzle orifice is inserted in the exhaust pipe 4, the output torque of that cylinder shifts in parallel to the left in the figure, as shown by y, and as a result, the combined torque of the two cylinders decreases. As shown by Y, the torque valley becomes shallower, but the maximum torque decreases.

Therefore, when the exhaust flow of #4, which is ignited first, exerts a suction effect on the exhaust pipe #3 of the cylinder that is ignited subsequently,
In the process indicated by 2, the maximum torque of that cylinder increases, and as a result, as shown in the process 2 in the figure, the torque valley in the combined torque characteristic becomes shallow9, and the decrease in maximum torque is also small.

〔Effect of the invention〕

As described above, this invention connects four exhaust pipes #1, #2, #3, #4 connected to four cylinders arranged in parallel, and determines the firing order of the connected cylinders. #1, #2
, #4, and #3. Among these exhaust pipes, the two inner exhaust pipes #2 and #4 were made to communicate with each other, so those two
By shortening the length of exhaust pipes #2 and #4, the engine's high-speed performance improves. In addition, on the downstream side, the two outer exhaust pipes #1, #2 and #3,
#4 are gathered together, and further downstream of the gathering part, each is connected to the exhaust silencer 7 separately, and the left and right exhaust pipes are communicated with each other via the second communication passage, so the depth of the torque valley on the performance curve is reduced. This makes it possible to improve mid- and low-speed performance, and to prevent a decrease in torque in the high-speed range, resulting in an engine with high output torque over a wide speed range. The overall structure of the exhaust pipe is symmetrical, which has the effect of improving the overall balance of engine output.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; Fig. 1 is a side view of the motorcycle, Fig. 2 is an enlarged side view of its main parts, Fig. 3 is a plan view thereof, and Fig. 4 is its IV-■. A cross-sectional view is shown in Figure 5, which shows the characteristics of the engine, and Figure 6 is a valve diagram. #l, #2+'3+''...exhaust pipe, 6th race...gathering part, 6a...opening, 7...
・Exhaust silencer, 8...first communication pipe, 9...second
Communication pipe. s'i:, 5 f'7+φf\
6 Dopa 1

Claims (1)

[Claims] Four exhaust pipes #1, #2, #3, #4 connected to four cylinders arranged in parallel are connected, and the firing order of those connected cylinders is set to #1, #2, #4. 4, #3, and among these exhaust pipes, the two inner exhaust pipes #2 and #3 are made to communicate with each other, and the two outer exhaust pipes #1, #2 and #3 are connected to each other on the downstream side. 3. An exhaust system for a motorcycle, in which the exhaust pipes #4 are assembled together, each is further connected to an exhaust silencer separately downstream of the gathering part, and the left and right exhaust pipes are communicated with each other via a second communication path.