Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2003-10-08
2004-10-26
Moulis, Thomas (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S456000, C123S468000
Reexamination Certificate
active
06807944
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for attenuating pressure pulsation in V-type engines, horizontally opposed engines, and other opposed engines, thereby preventing the degradation of fuel supply characteristics arising from pressure pulsation and the occurrence of pressure pulsation noise in opposed engines.
2. Background Art
Conventionally, fuel delivery pipes have been known that have a plurality of injection nozzles for feeding fuels such as gasoline to a plurality of engine cylinders. With such fuel delivery pipes, fuel from a fuel tank is sprayed in order by a plurality of injection nozzles into a plurality of engine intake pipes or cylinders; the fuel mixes with air and this mixture burns, causing engine output.
As described above, the function of such a fuel delivery pipe is to spray from injection nozzles fuel fed from the fuel tank via a supply pipe into engine intake pipes or cylinders. With a return-type fuel delivery pipe, when an excess of fuel has been fed into the fuel delivery pipe, a loop returns the excess fuel to the fuel tank using a pressure regulator. By contrast, a returnless-type fuel delivery pipe does not have such a loop for returning fed fuel to the fuel tank.
A fuel delivery pipe that returns excess fuel to the fuel tank has the advantage that pressure pulsation arising from fuel injection does not easily occur, as the amount of fuel in the fuel delivery pipe can be kept constant. However, fuel delivery pipes are disposed close to engine cylinders, which are hot, and fuel fed to a fuel delivery pipe also becomes heated; when heated excess fuel is returned to the fuel tank, the temperature of the gasoline in the fuel tank rises. This rise in temperature causes gasoline to vaporize, and this has harmful effects on the environment and thus is not desirable. For this reason, returnless-type fuel delivery pipes have been proposed that do not return excess fuel to the fuel tank.
Because such a returnless fuel delivery pipe does not have piping for returning excess fuel to the fuel tank, when fuel has been injected from injection nozzles into intake pipes or cylinders, there is large oscillation in pressure and large pressure waves arise, so that the occurrence of pressure pulsation is greater than with a return-type fuel delivery pipe.
The present invention uses a returnless fuel delivery pipe, in which pressure pulsation can easily occur. In the conventional art, when pressure inside a fuel delivery pipe is reduced by the injection of fuel from injection nozzles into intake pipes or cylinders, this sudden drop in pressure and the pressure waves arising from the stopping of fuel injection cause pressure pulsations within the fuel delivery pipe. These pressure pulsations are propagated from the fuel delivery pipe and a connecting pipe connected to the fuel delivery pipe to the fuel tank via a supply pipe, and then are reversed and sent back by a pressure adjustment valve within the fuel tank, propagating to the fuel delivery pipe via the supply pipe and connecting pipe. A fuel delivery pipe has a plurality of injection nozzles; these injections nozzles sequentially inject fuel, causing pressure pulsation.
As a result, these pressure pulsations cause pressure within the fuel delivery pipe to drop suddenly, leading to the phenomenon of less fuel being injected into the intake pipes or cylinders. This causes the mix ratio of fuel gas and air to be different from specifications, leading to adverse effects on exhaust gas and the engine not outputting the specified power. Pressure pulsation also causes mechanical vibrations in a supply pipe connected to a fuel tank, and these vibrations are transmitted as noise to the passenger compartment of a vehicle by clips holding the supply pipe to below the floor, and such noise is annoying for a driver and passengers.
Conventionally, the following method has been used to prevent the various above-described drawbacks arising from pressure pulsation and limit the ill effects caused by pressure pulsation. A pulsation damper containing a rubber diaphragm is disposed in a returnless fuel delivery pipe lacking pressure pulsation absorption function in its outer walls; pressure pulsation energy is absorbed by this pulsation damper, and a supply pipe disposed below the floor from the fuel delivery pipe to the fuel tank is secured to below the floor by vibration-absorbing clips (not shown in the drawings), thereby absorbing vibration arising in the fuel delivery pipes or in the supply pipe extending to the fuel tank. Methods such as this are relatively effective, and have the advantageous effect of limiting ill effects caused by pressure pulsation.
However, pulsation dampers and vibration-absorbing clips are expensive, and use thereof leads to an increase in number of parts and in cost; they also give rise to a new problem of securing space in which they can be disposed. For this reason, inventions have been proposed that have a pulsation-absorption function, capable of absorbing pressure pulsation in a fuel delivery pipe without the use of such pulsation dampers or vibration-absorbing clips.
Inventions described in Japanese Laid-open patents JP, 2000-329030, A, JP, 2000-320422, A, JP, 2000-329031, A, JP, 11-37380, A, JP, 11-2164, A, and JP, 60-240867, A are known as fuel delivery pipes having such a pressure pulsation-absorption function. These fuel delivery pipes having pressure pulsation-absorption function have the effect of absorbing and attenuating pressure pulsation arising from fuel injection and preventing a variety of ill effects arising from the occurrence of pressure pulsation.
When these fuel delivery pipes are used in an inline engine, except for a few cases, these advantageous effects are easily realized; however, when used in a V-type engine, horizontally opposed engine or other opposed engine, in which banks of a plurality of cylinders are disposed in parallel, a fuel delivery pipe is provided for each of these banks of a plurality of cylinders, this pair of fuel delivery pipes is connected by a connecting pipe, and a supply pipe connects a fuel tank to a part of this connecting pipe, or directly to one of the fuel delivery pipes, then such a fuel delivery pipe is not necessarily effective in mitigating the various above-described ill effects.
Specifically, as shown in
FIGS. 8 and 9
, a pair of fuel delivery pipes (
1
), (
2
) are connected in series by a connecting pipe (
3
) to a pair of cylinder banks of a horizontally opposed engine. These fuel delivery pipes (
1
), (
2
) do not themselves have a pressure pulsation-absorption function; however, fuel delivery pipes are known that, as shown in
FIG. 8
, have an aforementioned pulsation damper (
4
) attached thereto, or that, as shown in
FIG. 9
, have a pressure pulsation-absorption function in the outer walls thereof. These pairs of fuel delivery pipes (
1
), (
2
) are connected in series with a connecting pipe (
3
).
With a pair of such returnless fuel delivery pipes (
1
), (
2
) connected from the connecting pipe (
3
) to the fuel tank via a supply pipe (
5
), when fuel is injected from injection nozzles (
6
) of one or the other of the fuel delivery pipes (
1
), (
2
), pressure drops within one or the other fuel delivery pipes (
1
), (
2
) and a pressure wave is generated. When the pair of fuel delivery pipes (
1
), (
2
) is connected in series with the connecting pipe (
3
), the pressure pulsation caused by this pressure wave is transmitted without attenuation, and in the pulsation resonance period, a large pressure pulsation wave is propagated from the fuel delivery pipes (
1
), (
2
) to the supply pipe (
5
), which includes piping in the floor. This pressure pulsation becomes a large pulsation in the supply pipe (
5
), connecting pipe (
3
), and the pair of fuel delivery pipes (
1
), (
2
). As a result, fuel injection is affected as described above and the proper mix ratio of fuel and air is not achieved, so that there are unwanted effects in terms of exhaust emissions as well
Mizuno Kazuteru
Ogata Tetsuo
Serizawa Yoshiyuki
Tsuchiya Hikari
Jordan and Hamburg LLP
Moulis Thomas
Usui Kokusai Sangyo Kaisha Ltd.
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