JPS6332327Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of an exhaust pipe in a motorcycle engine, for example, in which cylinders are arranged in a V-shape at the front and rear, and a supercharger is arranged at the front or rear.

In a turbocharged engine, it is desirable to locate the supercharger immediately downstream of the engine's exhaust port in order to reduce exhaust energy loss, but if there are other reasons, e.g. A supercharger is often placed at the front or rear for reasons such as effective use of vehicle space, structural relationship with the vehicle body, or overall balance of the engine.

When such a supercharger arrangement is adopted, for example, in a front-rear V-type engine as described above, the exhaust pipe leading from the cylinder farthest from the supercharger to the supercharger is connected to the rear end of the engine. Since the piping is routed from the front end to the front end, or from the front end to the rear end, bypassing the sides of the engine, the length is quite long, and the following problems arise.

When the engine's exhaust valve is opened, the combustion gas in the cylinder is discharged into the exhaust pipe and sent to the turbocharger turbine. At this time, the exhaust pressure in the exhaust pipe is reflected by the turbine and becomes a reflected pressure wave. Go up the exhaust pipe towards the exhaust valve. This pressure wave is 1
Instead, first to third order pressure waves are usually observed. The friction of this pressure wave varies greatly depending on the length of the exhaust pipe.

FIG. 1 is a diagram showing the progression of the lift height h of the exhaust valve and intake valve and the pressure p at the exhaust valve position, with time t plotted on the horizontal axis. The top curve E is the exhaust valve,
S indicates the lift of the intake valve, the middle curve Pf is the pressure curve at the exhaust valve position of the cylinder closer to the supercharger, and the lower curve Pr is the pressure curve at the exhaust valve position of the cylinder farther from the supercharger. shows.

As can be seen from Figure 1, the appearance of the pressure reflected wave in the exhaust pipe differs between the case where the cylinder is close to the supercharger and therefore a short exhaust pipe, and the case where the cylinder is far from the supercharger and therefore a long exhaust pipe. Very different. In other words, the pressure wave Pf in a short exhaust pipe where the cylinder is close to the supercharger is
1st, 2nd, and 3rd order pressure waves (as shown in Figure 1)
, , occur almost simultaneously at the exhaust valve position, whereas the pressure waves Pr in the long exhaust pipe where the cylinder is far from the supercharger are the second and third order pressure waves,
(shown in FIG. 1) are separated from each other and occur at the exhaust valve position with a certain time difference. This also means that, for example, the secondary pressure waves or reflected waves arrive at the exhaust valves farther from the supercharger much later than at the exhaust valves closer to the supercharger.

By the way, as is well known, there is an overlap period L between the opening and closing timings of the exhaust valve and the intake valve, in which both the intake and exhaust valves are open at the same time. When the peak of the reflected wave reaches the exhaust valve position during this overlap period, the pressure in the exhaust pipe is transmitted to the intake pipe through the cylinder, temporarily blocking intake air from entering the cylinder. Therefore, a reduction in intake efficiency within the cylinder and residual exhaust gas result in a reduction in engine output.

As the engine speed increases, the overlap timing L moves to the left in FIG. 1, and the second reflected wave finally overlaps with the overlap timing L. At this time, the engine output decreases as described above. In other words, a trough in the engine output occurs in the range of engine speeds where such a state occurs. Note that the tertiary wave usually has a small amplitude, so its influence on the engine output is small.

In view of the above points, the present invention uses a resonant box to absorb reflected waves in the exhaust pipe in the rotational speed region.
It is intended to attenuate it.

The present invention will be described below with reference to the embodiments shown in FIGS. 2 and 4.

FIG. 2 shows a motorcycle equipped with an engine to which the present invention is applied. Engine 1 has head pipe 2
In the space formed by the main tube 3 whose front end is fixed to the main tube 3, the center tube 4 extending downward from the rear end of the main tube 3, and the down tube 5 whose both ends are connected to the head pipe 2 and the center tube 4. A rear fork 7 is attached to these tubes 3, 4, and 5 via a pivot shaft 8 to a joining member 6 of the center tube 4 and down tube 5 so as to be able to swing up and down.
9 is a sheet.

The illustrated engine 1 includes cylinders 10 arranged in a V-shape in the front and rear, as shown in FIGS. 2 to 4.
In a two-cylinder, four-stroke gasoline engine with a cylinder head of 10 mm (FIG. 4 is shown without the cylinder head cover), the pistons 11 of each cylinder 10 are connected to a common crankshaft via a connecting rod 12. ing.

A supercharger S is arranged at the front lower part of the engine 1. This supercharger S consists of a turbine 13 disposed on the right side with respect to the direction of travel of the vehicle, and a compressor 14 disposed on the left side. , exhaust pipe 17f,
17r. 18f and 1
8r is an exhaust valve for each cylinder. turbine 1
Turbine outlet 19 provided in the center of the right side of 3
is connected to the muffler 20, and the exhaust pipe 1
The engine exhaust gas sent to the turbine 13 via 7f and 17r rotates the blades of the turbine 13, and then passes through the muffler 20 and is discharged to the rear of the vehicle body.

An air cleaner 21 is provided at the front upper part of the vehicle body, and the air taken in here passes through a connecting pipe 22, enters the compressor 14 from the inlet in the center of the left side of the compressor 14, and is transferred to the output shaft of the turbine 13. After being compressed by the rotor that rotates, it passes through the charge pipe 23 and enters the surge tank or pre-chamber 24, and then the carburetor 2 of each cylinder 10f, 10r.
5f, 25r, each with an intake port 26
f, 26r. 27f and 27r are intake valves.

28 is an oil pan of the engine 1, and 29 is an oil circulation pipe provided between the bottom of the supercharger S and the oil pan 28. An oil pan dedicated to the supercharger may be provided below the supercharger, and the oil accumulated in this oil pan may be pumped up to the oil pan 28 by a pump.

As mentioned above, each cylinder 10f, 10r
The exhaust ports 16f and 16r are respectively exhaust pipes 17
f, 17r, but since the turbine 13 is provided at the front lower part of the engine 1, the exhaust gas is led from the cylinder farthest from the turbine 13, that is, the rear cylinder 10r. The pipe 17r is significantly longer than the exhaust pipe 17f from the cylinder 10f. The exhaust pipe 17r runs from the exhaust port 16r located at a relatively high position at the rear of the engine to the crankcase 3.
After bypassing the side of the engine above 0,
It descends and reaches the turbine inlet 15. An expansion joint 31 is provided in the middle of the exhaust pipe 17r, which absorbs the influence of thermal expansion of the exhaust pipe 17r and serves as a buffer.

Since the exhaust pipe 17r becomes longer as described above, the phenomenon described above with respect to FIG. 1 occurs. That is, the turbine 13 generated in the exhaust pipe 17r during exhaust
As shown by the curve Pr at the bottom of FIG. 1, the pressure reflected waves from the secondary wave reach the exhaust port 16r much later than the primary wave. Therefore, when the engine speed increases, the overlap timing L coincides with the arrival timing of the secondary wave. In such an engine speed range, the engine output decreases. On the other hand, as for the reflected wave in the exhaust pipe 17f from the front cylinder 10f, as shown by the curve Pf in the middle part of Figure 1, the primary wave and the secondary wave reach the exhaust port 16f at an early stage almost at the same time. ,
The above problems do not occur in the normal rotation range.

Therefore, in the present invention, a resonance chamber 32 is provided in the middle of the exhaust pipe 17r. This resonance chamber 32
is inserted into the piping with the front and back connected to the piping,
This is a pass-through type resonance chamber in which the fluid in the piping passes from upstream to downstream within the resonance chamber. As shown in the drawing, the resonance chamber 32 is provided in a portion of the exhaust pipe 17r on the side of the engine, closer to the engine than the expansion joint.

The resonant frequency of the resonant box constituted by the resonant chamber 32 is matched to the engine rotational speed when the above-mentioned overlap timing and the second arrival timing coincide. At this time, the frequency of the secondary wave and the engine rotational speed are approximately the same, so the resonance chamber 32 absorbs the energy of the secondary wave by resonating with the secondary wave. Therefore, the secondary wave itself is attenuated, the pressure rise at the exhaust port 16r is also small, and the secondary wave does not block intake air and reduce the engine output.

FIG. 5 shows a resonance chamber 3 in another embodiment of the present invention.
2' is shown. In the resonance chamber 32 shown in FIGS. 2 to 4, the exhaust pipe 17r opens in the resonance chamber, the front wall, and the rear wall, respectively, but in the resonance chamber 32' in FIG. 5, the exhaust pipe 17r resonates. The inside of the resonance chamber and the inside of the exhaust pipe are communicated by providing communication holes 33, 33 through the chamber and in the exhaust pipe inside the resonance chamber.

In the above description, the second-order reflected wave within the exhaust pipe 17r is targeted and the second-order reflected wave is attenuated, but of course other reflected waves may be attenuated. For example, the tertiary wave is normally weak and has little effect on engine output, but depending on the required output characteristics of the engine, the tertiary wave may target the rotational speed region during the overlap period and cause the resonance chamber to resonate. You may also set the frequency.

Furthermore, in this embodiment, since the supercharger S is provided at the front of the engine, the exhaust pipe 17r from the rear cylinder 10r is longer, and therefore the exhaust pipe 17r is longer.
Although the resonance chamber 32 is provided in the engine r, it goes without saying that if the supercharger is provided at the rear of the engine, a resonance chamber is provided in the exhaust pipe from the front cylinder.

As described above, in the present invention, a resonance chamber is provided in the middle of the exhaust pipe leading from the cylinder farthest from the turbocharger to the turbocharger, and this resonance chamber is used to absorb pressure reflected waves from the turbine generated in the exhaust pipe. The reflected waves are attenuated by resonance. Therefore, the output does not decrease in a certain engine speed range due to the intake air into the cylinder being obstructed by the reflected wave that reaches the exhaust port at the time of overlap of the intake and exhaust valves.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the time course of the lift of the intake and exhaust valves and reflected waves in the exhaust pipe, Fig. 2 is a side view of a motorcycle equipped with the engine according to the present invention, and Fig. 3 is a diagram showing the main parts of the engine. FIG. 4 is a side view, FIG. 4 is a plan view of the same, and FIG. 5 is a drawing showing a resonance chamber in another embodiment. 1...Engine, 2...Headpipe, 3...
Main tube, 4... Center tube, 5...
Down tube, 6... Joining member, 7... Rear fork, 8... Pivot shaft, 9... Seat, 10
...Cylinder, 11...Piston, 12...Connecting rod, 13...Turbine, 14...
...Compressor, 15...Turbine inlet, 16
...Exhaust port, 17...Exhaust pipe, 18...Exhaust valve,
19...Turbine outlet, 20...Muffler, 21
... Air cleaner, 22 ... Connection pipe, 23 ... Charge pipe, 24 ... Prechamber, 25 ... Carburetor, 26 ... Intake port, 27 ... Intake valve,
28... Oil pan, 29... Piping, 30... Crank case, 31... Expansion joint, 32... Resonance chamber, 33... Communication hole.

Claims (1)

[Scope of utility model registration request] In an engine in which a plurality of cylinders are arranged in front and rear and a supercharger is installed on either the front or rear side, a resonance chamber is installed in the middle of the exhaust pipe leading from the cylinder farthest from the supercharger to the supercharger. An exhaust pipe structure for a supercharged engine, characterized by having the following features: