JPH09303208A - Fuel gas supply device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply mixture of a stable air-fuel ratio by setting the diameter of a fuel pipe and the diameter of an air pipe such that the period of an intake pulsation acting on a decompression chamber via a fuel pipe corresponds to the period of an intake pulsation acting on a balance chamber via the air pipe. SOLUTION: The diameter (inside diameter) of a fuel pipe 17 and the diameter (inside diameter) of an air pipe 18 are set such that the period of an intake pulsation propagating to a secondary decompression chamber 5 via a fuel pipe 17 corresponds to the period of an intake pulsation propagating to a balance chamber 11 via an air passage 18. Accordingly, the variation of the differential pressure between the chambers 5, 11 caused by the intake pulsation is suppressed and the differential pressure is stabilized to thereby prevent the influence of the intake pulsation on controlling a valve. The air-fuel ration approaches a desired air-fuel ratio to thereby improve the operability of an engine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas fuel supply system for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine using liquefied petroleum gas (LPG) as a fuel, as shown in FIG. 4, in order to prevent the air-fuel ratio from varying with time due to the degree of clogging of the air cleaner, The secondary decompression chamber 101 of the regulator 100 and the venturi portion 103 of the intake pipe 102 communicate with each other through a fuel pipe 104, the balance chamber 105 of the regulator 100 and the venturi upstream portion of the intake pipe 102 communicate with each other through an air pipe 106, and an air cleaner 107. When the negative pressure in the intake pipe 102 becomes large due to the clogging of the filter of No. 2, the negative pressure is applied to the balance chamber 105 of the regulator 100, and the opening operation of the valve 108 of the regulator 100 is suppressed to the secondary decompression chamber 101. There is a method in which the inflow amount of the fuel gas is reduced and the air-fuel ratio is controlled to be constant.

In this way, the balance chamber 105 and the intake pipe 10
In the case where the second venturi upstream portion is communicated with the air pipe 106, there is a problem that the intake pulsation generated in the intake passage 102 propagates to the balance chamber 105 through the air pipe 106 and causes the air-fuel ratio variation due to the intake pulsation.

Therefore, conventionally, as shown in FIG. 4, a throttle 109 is provided in the air pipe 106 to suppress the pulsation propagating to the balance chamber 105 through the air pipe 106 and suppress the fluctuation of the air-fuel ratio. What was done is JP-A-4-284.
It is disclosed in Japanese Patent Publication No. 145.

[0005]

However, even in the case where the diaphragm 109 is interposed as described above, the balance chamber 10
Although the propagation of pulsation to 5 can be reduced, the intake passage 102
The intake pulsation at the venturi 103 part propagates into the secondary decompression chamber 101 of the regulator 100 through the fuel pipe 104, and the fluctuation waveform of the pressure that propagates to the secondary decompression chamber 101 and the fluctuation waveform of the pressure that propagates to the balance chamber 105. A phase is generated in the cycle of, and a large amplitude difference is generated, and a large fluctuation of the air-fuel ratio still occurs.

That is, the fuel pipe 104 and the air pipe 10
6 has a difference in the pipe diameter, the pipe length, etc., the fluctuation waveform of the pressure P ₁ in the secondary decompression chamber 101 and the pressure P ₂ in the balance chamber 105 has a phase as shown in FIG. Occurs or an amplitude difference occurs, and the valve closing load is largely applied to the valve 108 in the portion A shown by the slanted line in FIG. 5, and the air-fuel mixture becomes too thin, so that the air-fuel mixture having a stable air-fuel ratio cannot be supplied. However, there is a problem that the driving performance is deteriorated particularly in a high load and low speed range.

Therefore, according to the present invention, the cycle of the intake pulsation acting on the decompression chamber via the fuel pipe and the cycle of the intake pulsation acting on the balance chamber via the air pipe are made coincident to stabilize the differential pressure between the two chambers. The purpose of this is to improve the drivability of the engine by bringing the air-fuel ratio close to the ideal air-fuel ratio.

[0008]

In order to solve the above-mentioned problems, the first invention according to claim 1 is the decompression chamber (5) of the LPG regulator (1) and the venturi (16) of the intake pipe (12). A fuel pipe (17) that communicates the parts, a balance chamber (11) that is separated from the decompression chamber (5) through a diaphragm (10), and an air pipe that communicates the venturi upstream part of the intake pipe (12) ( 18), the pipe diameter of the fuel pipe (17) and the pipe diameter of the air pipe (18) are the same as the cycle of the intake pulsation acting on the decompression chamber (5) via the fuel pipe (17), and the air. It is characterized in that the periods of intake pulsation acting on the balance chamber (11) via the pipe (18) are set to coincide with each other.

As in the present invention, by matching the cycle of the intake pulsation acting on the decompression chamber (5) of the LPG regulator (1) and the balance chamber (11), both chambers (5) ( 11) The fluctuation of the differential pressure is suppressed, the differential pressure is stabilized, and the influence of intake pulsation on the valve control is prevented.

In a second aspect of the present invention, the pipe diameter of the air pipe (18) is set to be equal to or larger than the pipe diameter of the fuel pipe (17) and the decompression chamber (5) and the balance chamber. (1
It is characterized in that the period of the intake pulsation acting on 1) is made to coincide.

According to the present invention, the above effect can be exhibited only by setting the pipe diameters of the fuel pipe (17) and the air pipe (18). Further, a third invention according to claim 3 is the above first invention.
A partial throttle is provided in the pipe of one or both of the fuel pipe (17) and the air pipe (18) of the invention of the present invention to match the cycle of the intake pulsation acting on the decompression chamber (5) and the balance chamber (11). It is characterized by that.

According to the present invention, the above effect can be exhibited only by providing the throttles in the fuel pipe (17) and the air pipe (18).

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described based on an embodiment shown in FIG. In FIG. 1, reference numeral 1 is a regulator for decompressing and vaporizing LPG to supply the gaseous fuel to the intake passage, which is an LP in a fuel tank (not shown).
G is introduced into the primary decompression chamber 4 from the tank-side fuel passage 2 via the primary valve 3. A secondary decompression chamber 5 communicates with the primary decompression chamber 4 through a communication passage 6. 7
Is a secondary valve that opens and closes the communication passage 6, is provided so as to be swingable around a support shaft 8, and is biased by a spring 9 in the valve closing direction. 10 is the secondary decompression chamber 5 and the balance chamber 1
1 is a diaphragm that divides 1 from which the rear end of the secondary valve 7 is engaged. Then, by the pressure difference between the pressure in the secondary decompression chamber 5 and the pressure in the balance chamber 11, the diaphragm 1
0 moves in the front-back direction to open and close the secondary valve 7, thereby adjusting the pressure in the secondary decompression chamber 5 to a predetermined value.

Reference numeral 12 is an intake pipe that connects the air cleaner 13 and the engine 14, and a venturi 16 is formed on the upstream side of the throttle valve 15. The secondary decompression chamber 5 in the regulator 1 is connected to the intake pipe 12 at the venturi 16 by the fuel pipe 17.
The balance chamber 11 communicates with the intake pipe 12 on the upstream side of the venturi 16 by an air pipe 18. Here, the attachment port of the fuel pipe 17 in the regulator 1 is set to 17a, and the venturi 16 of the fuel pipe 17 is
The fuel extraction port in the section is 17b, and the attachment port of the air pipe 18 to the balance chamber 11 is 18a.
The attachment port of 8 to the intake pipe 12 is 18b.

In the structure described above, when the air introduced from the air cleaner 13 is sucked toward the engine 14 through the intake pipe 12 by the operation of the engine 14, the gas in the secondary decompression chamber 5 of the regulator 1 becomes fuel. It is introduced into the intake pipe 12 from the venturi 16 through the pipe 17, mixed with intake air and supplied to the engine 14.

When the filter of the air cleaner 13 is clogged due to aging and the amount of intake air into the intake pipe 12 decreases, the negative pressure in the intake pipe 12 increases, and this high negative pressure is passed through the air pipe 18 to the regulator. It acts in the balance chamber 11 of No. 1, the diaphragm 10 is sucked toward the balance chamber 11 side, the valve closing force of the secondary valve 7 increases, and the flow of gas from the primary decompression chamber 4 into the secondary decompression chamber 5 is increased. Suppress. Therefore,
Venturi 16 from secondary decompression chamber 5 through fuel pipe 17
The amount of gas introduced into the intake pipe 12 from the section is reduced, and the air-fuel ratio is adjusted.

According to the present invention having such a structure, the secondary decompression chamber 5 is constructed so that the pipe diameter (specifically, inner diameter) of the fuel pipe 17 and the pipe diameter (specifically, inner diameter) of the air pipe 18 are set through the fuel pipe 17. The cycle of the intake pulsation propagating to the balance chamber 11 and the cycle of the intake pulsation propagating to the balance chamber 11 via the air passage 18 are set to coincide with each other. That is, Venturi 1
The pressure P ₃ at the 6th part is the pulsation of P ₃ shown by the dotted line in FIG. 2, and the pulsation of the pressure P ₄ at the upstream part of the venturi is shown in FIG.
In the case of the pulsation of P ₄ shown by the solid line, the pressure P ₁ propagating to the secondary decompression chamber 5 via the fuel pipe 17 is P
The pulsation is substantially equal to _3, and the pressure P ₂ propagating to the balance chamber 11 through the air pipe 18 is set to be substantially equal to P ₄ .

In order to make such a setting, the inventors conducted various experiments by changing the fuel pipe, the air pipe and other conditions. Table 1 shows several of the experiments. The venturi 16 has an inner diameter of 32, and the fuel pipe 17 and the air pipe 1
8 used a rubber hose. Further, the engine was tested at 800 rpm while warmed up.

[0019]

[Table 1]

In the pulsating state shown in FIG. 2, the venturi pressure P ₃ and the venturi upstream pressure P ₄ are the same as the pressure P ₁ in the secondary decompression chamber 5 of the regulator ₁ and the pressure P ₂ in the balance chamber 11 in the experiment. The pulsation showed a value as shown in FIG. That is, the pulsation cycle and amplitude of the pressure P ₃ and the pressure P ₄ propagated as they were, and the pulsation cycle of the pressure P ₁ and the pressure P ₂ matched. As a result, the air-fuel ratio (A /
F) shows a value of 15.6, which is close to the ideal air-fuel ratio 15.

Also in the above-mentioned experiments and, the same pulsation as in FIG. 3 is exhibited, the air-fuel ratio shows a value of 15.2 in the experiment, the air-fuel ratio shows a value of 15.0 in the experiment, and the air-fuel ratio shows in the experiment. A value of 13.4 was shown.

Further, as in the experiment, even if the pipe diameter D ₂ of the air pipe 18 is made larger than the pipe diameter D ₁ of the fuel pipe 17, the pulsation cycle as shown in FIG. 3 can be matched, Further, the pressure P ₂ in the balance chamber 11 is made higher than the pressure P ₁ in the secondary decompression chamber 5 to the atmospheric pressure side, and the secondary valve 7 of the regulator 1 is increased.
Was prevented from being closed more than necessary, and the mixture could be prevented from becoming too thin.

In the experiment, the pulsation as shown in FIG. 5 was obtained, and the pulsation cycles of the pressure P ₁ and the pressure P ₂ were in phase, and as a result, the air-fuel ratio showed a value of 21.8. Also in the experiment, the pulsation cycle of the pressure P ₁ and the pressure P ₂ were in phase as in FIG. 5, and as a result, the air-fuel ratio showed a value of 18.6. The air-fuel ratio in these experiments became larger than the ideal air-fuel ratio of 15, and a lean mixture was supplied.

Further, when the pipe diameter D ₂ of the air pipe 18 is made smaller than the pipe diameter D _{1 of the} fuel pipe, the air-fuel ratio becomes too thin. From the above experimental results, in order to obtain the ideal air-fuel ratio by matching the periods of the pressure P ₁ and the pressure P ₂ , the pipe diameters (inner diameters) D ₁ and D ₂ of the fuel pipe 17 and the air pipe 18 should be D ₁ ≦ D If set to ₂ , it is understood that the values of the pipe lengths L ₁ and L ₂ and the mounting port inner diameters D ₄ and D ₆ between the two pipes 17 and 18 may be different.

However, it was found that the air-fuel ratio deteriorates when the air pipe 18 is set to φ16 or less.
Is preferably 16 or more. Therefore, D ₁ ≦ D ₂ and D
₂ ≧ φ16 is the best specification.

In the above-described embodiment, the pipe diameters of the fuel pipe 17 and the air pipe 18 are set so that the periods of the intake pulsation acting on the decompression chamber 5 and the balance chamber 11 coincide with each other. Fuel pipe 17 and air pipe 18 instead of setting
One or both of the pipes are partially provided with a restrictor and the decompression chamber 5
And the cycle of the intake pulsation acting on the balance chamber 11 may be matched. The diaphragm may be formed by narrowing the tube itself or by providing a diaphragm member.

[0027]

As described above, according to the first aspect of the present invention, the influence of the intake pulsation on the valve 4 can be prevented, so that the operating range with a large intake pressure fluctuation (high load low speed (Region), the fluctuation of the supplied fuel due to the intake pulsation is suppressed, the air-fuel mixture having a stable air-fuel ratio is supplied to the internal combustion engine, the insufficient fuel supply is eliminated, and the operating performance can be improved.

Further, according to the second aspect of the invention, the above effects can be easily and inexpensively achieved only by setting the pipe diameter.
Further, according to the invention of claim 3, the above effect can be easily achieved only by providing a diaphragm.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a piping state according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a pulsating state of a venturi pressure P ₃ and a venturi upstream pressure P ₄ .

FIG. 3 is a characteristic diagram showing a pulsating state of pressure P _{1 in} the decompression chamber and pressure P _{2 in} the balance chamber of the regulator according to the present invention.

FIG. 4 is a schematic side sectional view of a conventional technique.

FIG. 5 is a characteristic diagram showing a pulsating state of a pressure P _{1 in} a decompression chamber and a pressure P _{2 in} a balance chamber of a regulator according to a conventional technique.

[Explanation of symbols]

 1 ... LPG regulator 5 ... Decompression chamber 10 ... Diaphragm 11 ... Balance chamber 12 ... Intake pipe 16 ... Venturi 17 ... Fuel pipe 18 ... Air pipe

Front Page Continuation (72) Inventor Yu Ota 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd.

Claims (3)

[Claims] 1. A fuel pipe connecting a decompression chamber of an LPG regulator and a venturi portion of an intake pipe, an air pipe connecting a balance chamber defined by the decompression chamber via a diaphragm and a venturi upstream portion of the intake pipe. In the equipment provided, the pipe diameter of the fuel pipe and the pipe diameter of the air pipe are the same as the cycle of the intake pulsation acting on the decompression chamber via the fuel pipe and the cycle of the intake pulsation acting on the balance chamber via the air pipe. A gaseous fuel supply device for an internal combustion engine, characterized in that 2. The pipe diameter of the air pipe is set to be equal to or larger than the pipe diameter of the fuel pipe to match the cycle of intake pulsation acting on the decompression chamber and the balance chamber. Gas supply device for internal combustion engine. 3. The intake pulsation cycle acting on the decompression chamber and the balance chamber is made coincident with each other by providing a partial restriction in the pipe of one or both of the fuel pipe and the air pipe. Gas fuel supply system for internal combustion engine.