JPS6299626A - Exhaust device for motorcycle - Google Patents

Abstract

PURPOSE:To secure a well-balanced torque characteristic in the whole driving range, by interconnecting a pair of adjacent cylinders being unadjoined in firing order, at the inner side of an exhaust pipe, to an interconnecting pipe. CONSTITUTION:Exhaust pipes of an engine setting its firing order to #1, #2, #4 and #3 are extendedly installed as an independent cylinder each, and converged by two cylinders a set at the upstream of a muffler 7. In these #2 and #3 cylinders, each firing order is unadjoined, but they are formed into adjacent cylinders to each other in design, whereby these exhaust pipes are interconnected to each other by an interconnecting pipe 8.

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 cylinders of a four-stroke parallel four-cylinder engine mounted on a motorcycle. The present invention relates to a device for improving the output characteristics of.

[Conventional technology and its problems]

Conventionally, in nine-wheeled motorcycles equipped with four-stroke parallel four-cylinder engines, the exhaust pipes leading from each cylinder are connected to two exhaust silencers for each cylinder installed on both sides of the rear of the vehicle. This is done by reducing ventilation resistance, and by setting the length of each exhaust pipe connected to the engine to be the same, so as to synchronize it with the engine speed at maximum output (for example, Publication No. 54-10412,
(Japanese Unexamined Patent Publication No. 178820/1982).

In recent years, motorcycle engines have increased from 1.00 ORPM during idling operation to a maximum of 15. Extremely wide speed range up to OOORPM @ degree and 2 per 1000cc displacement
In order to obtain a high output of around 00 horsepower, the length of the exhaust pipe is set to match the total maximum output speed. This occurs in 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 a torque valley in the negative part, This may cause inconvenience when driving.

To solve this problem, in conventional motorcycles equipped with four-cylinder engines, among the different exhaust pipes connected to each cylinder, those with close ignition order are all connected to each other to improve engine performance. However, when this method is used, the torque valley becomes shallow, and even if performance at low and medium speeds is improved, there is a problem in that the maximum output is reduced.

[Objective of the invention, summary of means for solving problems] This invention reduces the depth of the aforementioned torque valley by improving the exhaust pipe, prevents torque reduction in the high speed range, and improves the engine speed over a wide speed range. The purpose of this system is to obtain the entire engine with high output torque, and the 4 cylinders are arranged in parallel with 4 exhaust pipes #1, s2, s3, and #4, which are connected to the cylinders. The ignition order of the exhaust pipes is #1, #2, #4, and #3, and the two inner exhaust pipes #2 and #3 are characteristically connected to the first communication pipe.

[LOL example]

The present invention will be fully explained below with reference to the illustrated example. In the figure, a motorcycle 9 has an engine 5 mounted on a body frame 4 and located between a front wheel 2 and a rear wheel 3. The engine 5 has four cylinders in parallel, and four exhaust pipes #1, #2, #2 are led from each cylinder as shown in Figure 3.
It is fully equipped with a three-way exhaust #4, a flute collecting section 6 that collects each of these two outer cylinders, and an exhaust silencer 7 provided at the rear end of the exhaust assembly section 6. 8 is the two inner exhaust pipes #2 and #3
A first communication pipe 9 communicates with each other, and a second communication pipe 9 communicates with each other within the first expansion chamber Ta of the two left and right exhaust silencers 77.
The communication pipe comes out. Note that the first expansion chamber γa refers to a vacant space in the exhaust silencer 7 in which the downstream end of the gathering portion 6 is open. 7b indicates a partition wall that partitions the first expansion chamber 7a. In addition, in this example, the ignition order is #1, #2, #4, #3.
They are each made with a phase difference of 180°. On the back, two exhaust pipes #2 and #3 are connected to the first communication pipe 8.
The length of the pipe is shortened, and there is a gap between the cylinders connected to the outer exhaust pipes #1 and #4, as shown by X and Y in Fig.
In other words, the output torque undergoes a horizontal displacement, and the torque valley of the above-mentioned integrated characteristic is made shallower.

On the other hand, as shown by curve Y in FIG. 5, this configuration lowers the maximum output of the integrated characteristic, so this is compensated for as follows.

That is, the two exhaust pipes #3 on the outside of exhaust pipes #2 and #3.
, joins #4 at an acute angle, narrows the entire end of exhaust pipe #4 to form a nozzle N, increases the flow velocity of the exhaust, and makes it rush into the upstream end of the collecting part 6. A small diameter opening 6a is provided near the nozzle N, and the other exhaust pipe #3'(!") is welded there. As mentioned above, the exhaust pipe #4 is connected to the other exhaust pipe #3 1 corner
Since the firing order is earlier by 80 degrees, exhaust pipe #4 is discharged before exhaust pipe #3, and thus the exhaust flow from exhaust pipe #4 exiting from nozzle N has a suction effect of =9. Exhaust pipe #3 under low ventilation resistance due to its suction effect
The maximum torque of exhaust pipe #3 is improved by taking advantage of the fact that exhaust pipe #3 is exhausted.

Furthermore, in this example, exhaust pipes #2 and #3 and the first communication W
8, the diameter of the first communication pipe 8 is a small diameter of the exhaust pipe F, and two pipes on the left and right are used because the effect of shortening the total length of the exhaust pipes #2 and #3 is insufficient. This is supplemented by making the exhaust muffler γ of 19 communicate with the second communication pipe 9 in its first expansion chamber.

A cover 10 is provided on the outer surface of the exhaust pipe #4 on the merging side, and is provided on the front outer surface in the opening direction of the exhaust pipe #3 on the merging side.

To fully explain the operation of the exhaust pipes #3 and #4 assembling the exhaust pipes, as shown in Fig. 5, in the figure, X is the output torque of the exhaust pipes #3 and #4 when they are not assembled, and X is the exhaust pipe #. 3,
#4 Shows the total torque of two fully connected cylinders. Now, when an N-type nozzle throttle 9 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 total output torque of the two cylinders increases. As for the torque, as shown by Y, the torque valley becomes shallow, but the large torque decreases. Therefore, if a suction action is applied to the exhaust pipe #3 of the cylinder that is fired next behind the exhaust flow of #4 that is fired first, the maximum torque of that cylinder increases as shown in 2, and as a result, As shown by Z in the figure, the torque valley of the total torque characteristic becomes shallower, and the decrease in maximum torque is also slight.

〔Effect of the invention〕

As described above, this invention connects four exhaust pipes #1, #2, #3, #4 to four 7t cylinders arranged in parallel, and sets the firing order of the connected cylinders to #1, #2, #3, and #4. #2, #4,
#3 and none, the two inner exhaust pipes #2, #
3 are communicated with each other through the first communication pipe, and the length of the exhaust pipes #2 and #3, which can cause fire hazards, is completely shortened, increasing the suitability for high-speed operation, improving the high-speed performance of the engine, and reducing the All performance in the medium speed range will be improved. 'E7t, 2 exhaust pipes #
2 and #3 have a large ignition timing difference, but since they are close to each other, they are easier to connect.

[Brief explanation of drawings]

The south side shows 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 ■-■. 5 is a sectional view, FIG. 5 is a characteristic diagram of the engine, and FIG. 6 is a valve diagram. 5...Engine, 7...Exhaust silencer, #1. $
2. #3. #4...Exhaust pipe, 6...1 gathering part, 6
a... snout opening, 8----first delivery tube, 9...second delivery tube.

Claims (2)

[Claims] (1) Four exhaust pipes #1 for four cylinders arranged in parallel
, #2, #3, and #4 are connected, and the firing order of those connected cylinders is #1, #2, #4, and #3, and the two inner exhaust pipes #2, An exhaust system for a motorcycle, in which #3 is made to communicate with each other through a first communication pipe. (2) The exhaust system for a motorcycle according to claim 1, wherein the four cylinders arranged in parallel are a four-stroke engine.