JP3225195B2 - Gas fuel supply system for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gas fuel supply device for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine using liquefied petroleum gas (LPG) as fuel, in order to prevent the air-fuel ratio from fluctuating with time due to the degree of clogging of an air cleaner, as shown in FIG. A secondary pressure reducing chamber 101 of the regulator 100 communicates with a venturi section 103 of the intake pipe 102 through a fuel pipe 104, a balance chamber 105 of the regulator 100 communicates with an upstream section of the venturi of the intake pipe 102 through an air pipe 106, and an air cleaner 107. When the negative pressure in the intake pipe 102 increases due to the clogging of the filter, 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 move to the secondary pressure reducing chamber 101. There is one that reduces the inflow of fuel gas and controls the air-fuel ratio to be constant.

As described above, the balance chamber 105 and the intake pipe 10
In the case where the upstream portion of the second venturi communicates 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, thereby causing an air-fuel ratio variation due to the intake pulsation.

Conventionally, as shown in FIG. 4, a throttle 109 is interposed in the air pipe 106 to suppress pulsation propagating to the balance chamber 105 through the air pipe 106 and to suppress fluctuations in the air-fuel ratio. Japanese Patent Application Laid-Open No. 4-284
No. 145 gazette.

[0005]

However, even in the case where the throttle 109 is interposed as described above, the balance chamber 10 is not provided.
5 can be reduced, but the intake passage 102
Of the intake air in the venturi 103 portion propagates through the fuel pipe 104 into the secondary decompression chamber 101 of the regulator 100, and the fluctuation waveform of the pressure transmitted to the secondary decompression chamber 101 and the fluctuation waveform of the pressure transmitted to the balance chamber 105 , A large amplitude difference occurs, and a large variation in the air-fuel ratio still occurs.

That is, the fuel pipe 104 and the air pipe 10
6, there is a difference in the pipe diameter, the pipe length, and the like, so that the fluctuation waveforms of the pressure P ₁ in the secondary decompression chamber 101 and the pressure P ₂ in the balance chamber 105 have a phase as shown in FIG. 5 and a difference in amplitude occurs, and in a portion A shown by oblique lines in FIG. 5, a large valve closing load acts on the valve 108 to make the air-fuel mixture too thin, so that the air-fuel mixture with a stable air-fuel ratio cannot be supplied to the internal combustion engine. In particular, there is a problem that the driving performance in a high-load low-speed range deteriorates.

Accordingly, the present invention stabilizes the pressure difference between the two chambers by matching the cycle of the intake pulsation acting on the decompression chamber via the fuel pipe with the cycle of the intake pulsation acting on the balance chamber via the air pipe. The object is to improve the operability of the engine by bringing the air-fuel ratio closer to the ideal air-fuel ratio.

[0008]

According to a first aspect of the present invention, there is provided a pressure reducing chamber (5) of an LPG regulator (1) and a venturi (16) of an intake pipe (12). A fuel pipe (17) communicating with the pressure reducing chamber (5) through a diaphragm (10), and an air pipe (11) communicating with a balance chamber (11) and an upstream portion of the venturi in the intake pipe (12). 18), the pipe diameter of the fuel pipe (17) and the pipe diameter of the air pipe (18) are determined by adjusting the cycle of intake pulsation acting on the decompression chamber (5) through the fuel pipe (17), The cycle of intake pulsation acting on the balance chamber (11) via the pipe (18) is set to coincide.

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

According to a second aspect of the present invention, the diameter of the air pipe (18) is set to be equal to or larger than the diameter of the fuel pipe (17), and the decompression chamber (5) and the balance chamber are set. (1
The cycle of the intake pulsation acting on 1) is matched.

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

According to the present invention, the above-mentioned effect can be exerted only by providing a throttle 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 denotes a regulator for decompressing and evaporating LPG and supplying the gaseous fuel to an intake passage, and LP in a fuel tank (not shown).
G is introduced into the primary pressure reducing chamber 4 from the tank side fuel passage 2 via the primary valve 3. Reference numeral 5 denotes a secondary decompression chamber, which 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, which is swingably provided around a support shaft 8, and is urged by a spring 9 in a valve closing direction. 10 is the secondary decompression chamber 5 and the balance chamber 1
1 and a rear end of the secondary valve 7 is engaged with the diaphragm. The diaphragm 1 has a pressure difference between the pressure in the secondary pressure reducing chamber 5 and the pressure in the balance chamber 11.
0 moves in the front and back direction to open and close the secondary valve 7 and regulate the pressure in the secondary decompression chamber 5 to a predetermined value.

Reference numeral 12 denotes an intake pipe for communicating 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 pressure reducing chamber 5 in the regulator 1 is connected to the intake pipe 12 in 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 mounting port of the fuel pipe 17 in the regulator 1 is 17a, and the venturi 16
The fuel take-out port at the section is 17b, the mounting port of the air pipe 18 to the balance chamber 11 is 18a, and the air pipe 1
The mounting port of the intake pipe 8 to the intake pipe 12 is 18b.

In the above structure, when the air introduced from the air cleaner 13 is drawn into the engine 14 through the intake pipe 12 by the operation of the engine 14, the gas in the secondary pressure reducing chamber 5 of the regulator 1 The gas is introduced into the intake pipe 12 from the venturi 16 through the pipe 17, mixed with the intake air, and supplied to the engine 14.

When the filter of the air cleaner 13 is clogged due to aging or the like, and the amount of intake air into the intake pipe 12 decreases, the negative pressure in the intake pipe 12 increases. 1, the diaphragm 10 is sucked to the balance chamber 11 side, the 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 prevented. 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 portion is reduced, and the air-fuel ratio is adjusted.

In such a configuration, the present invention relates to a method of reducing the diameter of the fuel pipe 17 (specifically, the inner diameter) and the diameter of the air pipe 18 (specifically, the inner diameter) through the fuel pipe 17 to the secondary pressure reducing chamber 5. The cycle of the intake pulsation propagating to the balance chamber 11 via the air passage 18 is set to coincide with the cycle of the intake pulsation propagating to the balance chamber 11. That is, Venturi 1
Pressure P ₃ at the 6 parts of a pulsation of P ₃ shown by a dotted line in FIG. 2, also, pressure pulsations P ₄ at the Venturi upstream part 2
In the case of a pulsation of P ₄ indicated by the solid line, the pressure P ₁ that propagates to the secondary vacuum chamber 5 via a fuel pipe 17 is the P
₃ and becomes substantially equal pulsations, in which the pressure P ₂ that propagates in the balance chamber 11 through the air pipe 18 is set to be substantially equal to the pulsation and the P _4.

In order to make such a setting, the inventors conducted experiments with variously changed fuel pipes, air pipes and other conditions. Table 1 shows several of the experiments. Note that the inner diameter of the venturi 16 is φ32, and the fuel pipe 17 and the air pipe 1
8 used a rubber hose. The engine was tested at 800 rpm with the engine warmed up.

[0019]

[Table 1]

When the venturi pressure P ₃ and the venturi upstream pressure P ₄ are pulsating as shown in FIG. 2, in the experiment, the pressure P ₁ in the secondary pressure reducing chamber 5 of the regulator ₁ and the pressure P ₂ in the balance chamber 11 were measured. The pulsation showed a value as shown in FIG. That is, almost as it propagates the period and amplitude of the pulsation of the pressure P ₃ and the pressure P _4, the period of the pulsation of the pressure P ₁ and the pressure P ₂ matches. As a result, the experimental air-fuel ratio (A /
F) shows a value of 15.6, which is a value close to the ideal air-fuel ratio 15.

Also in the above experiments, the pulsation similar to FIG. 3 is shown. In the experiment, the air-fuel ratio shows a value of 15.2, in the experiment, the air-fuel ratio shows a value of 15.0, and in the experiment, the air-fuel ratio shows a value of 15.0. A value of 13.4 was shown.

Further, 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 as in the experiment, the pulsation period as shown in FIG. Further, the pressure P ₂ in the balance chamber 11 is raised to the atmospheric pressure side from the pressure P ₁ in the secondary pressure reducing chamber 5 so that the secondary valve 7
Was prevented from closing more than necessary, and the mixture was prevented from becoming too thin.

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

Further, when the tube diameter D ₂ of the air pipe 18 was smaller than the pipe diameter D ₁ of the fuel pipe is an air-fuel ratio becomes lean. From the above experimental results, the pressure P ₁ and the to match the period of the pressure P ₂ obtained an ideal air-fuel ratio, the tube diameter (inner diameter) D ₁ and D ₂ of the fuel pipe 17 and the air pipe 18 D ₁ ≦ D If it is set to ₂ , it can be seen that the values of the pipe lengths L ₁ , L ₂ and the inner diameters D ₄ , D ₆ of the two pipes 17, 18 may be different.

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

In the above 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 are made to coincide with each other. Of the fuel pipe 17 and the air pipe 18
The pressure reduction chamber 5 is partially provided with a throttle in one or both pipes.
And the period of the intake pulsation acting on the balance chamber 11 may be matched. Note that this throttle may be formed by narrowing the tube itself or by providing a throttle member.

[0027]

As described above, according to the first aspect of the present invention, the influence on the control of the valve 4 due to the pulsation of the intake air can be prevented. Also in the range, 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, and the shortage of the fuel supply can be resolved to improve the driving performance.

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

[Brief description of the drawings]

FIG. 1 is a schematic cross-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 a pressure P _{1 in} a decompression chamber and a pressure P _{2 in} a balance chamber of the regulator according to the present invention.

FIG. 4 is a schematic side sectional view of the prior art.

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 the related art.

[Explanation of symbols]

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

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Isamu Ota 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References Real Opening Sho 59-68171 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) F02M 21/02 F02M 21/02 311 F02M 21/04 F02M 21/06 F02M 37/00

Claims (3)

(57) [Claims] 1. A fuel pipe which communicates a pressure reducing chamber of an LPG regulator with a venturi section of an intake pipe, and an air pipe which communicates a balance chamber partitioned from the pressure reducing chamber via a diaphragm with an upstream of a venturi in an intake pipe. In the equipment provided, the pipe diameter of the fuel pipe and the pipe diameter of the air pipe match 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, wherein the gaseous fuel supply device is set to perform the following. 2. The method according to claim 1, wherein the pipe diameter of the air pipe is set to be equal to or larger than the pipe diameter of the fuel pipe so that the period of the intake pulsation acting on the decompression chamber and the balance chamber is matched. Gas fuel supply device for an internal combustion engine. 3. The method according to claim 1, wherein a partial throttle is provided in one or both of the fuel pipe and the air pipe so that the periods of the intake pulsation acting on the decompression chamber and the balance chamber are matched. A gas fuel supply device for an internal combustion engine.