JPH0385358A - Gas injector - Google Patents

Abstract

PURPOSE:To improve accuracy for an air fuel ratio control by connecting a first diaphragm to which an intake negative pressure is applied and a second disphragm to which the negative pressure corresponding to the pressure loss generated by means of measure contraction is applied, together through a connecting member provided with a valve, and by opening/closing a gas discharge port through the valve. CONSTITUTION:In a gas injecting means 4 provided on a venturi 2 which is provided on an intake tube 1, a first diaphragm 8 is provided so as to partition an air pressure chamber 6 communicating to the upper stream side of the venturi 2, and a negative pressure chamber 7 to which venturi negative pressure is applied through an opening port 7a, to one another. The negative pressure chamber 7 is communicated to the upper and lower stream sides of a throttle valve 3 by a communicating path 9 provided with an idle adjusting screw 10. A second diaphragm 23 is provided so as to partition an upper chamber 21 connected to a gas passage 13 on which a regulator 14 is placed, and a lower chamber 22 communicating to the venturi 2 through a discharge port 22a, to one another, and both of the diaphragms 8, 23 are connected together by a rod 25 provided with a valve 26 by which the discharge port 22a is opening/closed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pressure-balanced gas injection device for an internal combustion engine that accurately measures the flow rate of gas to be supplied according to the flow rate of intake air. related.

[Problems to be solved by conventional technology and invention] CNG
Conventionally, gas injection devices for internal combustion engines that use compressed natural gas (compressed natural gas) or LNG (liquefied natural gas) as fuel have a means of detecting the intake air flow rate as pressure and an amount of gas corresponding to this air flow rate. Separate means for metering and injecting as pressure were provided to control the mixing ratio of the air flow rate and the gas flow rate.

However, the gum and carbon contained in the blow-by gas that leaks into the intake pipe adheres to the fuel gas discharge port, and as time passes, the discharge port area becomes smaller and the amount of gas injected decreases. However, there was a problem in that the mixture ratio of the supplied air-fuel mixture fluctuated.

In view of these problems, the present invention adopts the principle of a pressure-balanced fuel injection device proposed by the applicant and described in Japanese Utility Model Application Publication No. 1-74362, to accurately control the air-fuel ratio of the air-fuel mixture. It is an object of the present invention to provide a gas injection device that is easy to use and has little deterioration.

[Means to solve the problem]

The gas injection device according to the present invention includes a first diaphragm to which a negative pressure corresponding to the flow rate of intake air is applied, an upper chamber to which gas is supplied from a gas supply source through a gas passage, and a venturi provided with a discharge port. a second diaphragm that partitions the lower chamber, a metering orifice that communicates the royal chamber with the lower chamber, and a connecting member that connects the first and second diaphragms and is provided with a valve that can open and close the discharge port. There is.

Further, a regulator may be provided in the gas passage to adjust the pressure on the lower side.

[For production]

When a negative pressure corresponding to the intake air flow rate flowing through the venturi is applied, the first diaphragm is displaced by the load, moving the connecting member and the second diaphragm, and the metered gas flow rate passing through the metering orifice is Gas is injected from the discharge port when the valve has retreated, and at the same time, due to the pressure loss of the metering orifice, a load is generated on the second diaphragm in the opposite direction to the first diaphragm, the loads on both diaphragms are balanced, and the gas flow rate is injected according to the intake air flow rate. As a result, the air-fuel ratio of the air-fuel mixture is controlled to be constant.

Furthermore, since the pressure in the gas passage on the downstream side of the regulator is kept constant, variations in the amount of gas in the metering orifice are prevented.

〔Example〕

Hereinafter, a preferred embodiment of the present invention will be described based on the accompanying drawings.

In the figure, 1 is an intake pipe, 2 is a venturi provided in the intake pipe 1, 3 is a throttle valve provided on the downstream side of the venturi 2, and 4 is a gas injection means provided in the venturi 2. In the gas injection means 4, 6 is an atmospheric pressure chamber that communicates with the upstream side of the venturi 2 to which, for example, the atmospheric pressure P0 of an air horn is applied, and 7 is an atmospheric pressure chamber that communicates with the upstream side of the venturi 2.
8 is a first diaphragm that partitions both chambers 6 and 7; 9 is a first diaphragm that communicates with the negative pressure chamber 7 at one end and has the other end; is branched through the adjustment port 9a and communicates with the intake pipe 1 on the upstream and downstream sides of the throttle valve 3, and the communication path 10 moves back and forth with respect to the adjustment port 9a to control the negative pressure P in the negative pressure chamber 7. This is an idle adjustment screw whose size can be adjusted.

Further, I2 is a gas cylinder, that is, a gas supply source, 13 is a gas passage that sends gas supplied from the gas cylinder 12 to an upper chamber described later, and 14 is provided in the middle of the gas passage 13 to maintain the gas pressure on the downstream side. The regulator controls the size P2, and a diaphragm 17 partitions a chamber 15 into which gas flows into and out of the gas passage 13 from a chamber 16 to which atmospheric pressure P0 is applied. A valve 18 that can control the opening amount of the gas inlet 15a is connected to the valve 18, and is pressed in the opening direction by the elasticity of a spring 19. 21 is an upper chamber connected to the other end of the gas passage 13 and controlled by pressure P2, 22 is a lower chamber that communicates with the venturi 2 via the discharge port 22a, and 23 is a chamber that partitions the upper chamber 21 and the lower chamber 22. The second diaphragm 24 is a fixed or metering orifice for gas measurement that communicates the upper chamber 21 and the lower chamber 22.
A negative pressure P is created in the lower chamber 22 due to the pressure loss or drop caused by the gas flow rate passing through the chamber.

(P2) is applied. 25 is a rod or connecting member that passes through the opening lower a and the discharge port 22a and connects the first and second diaphragms 8 and 23 at both ends; 26 is formed on the rod 25;
This is a valve that can open and close the discharge port 22a in conjunction with the discharge port 22a.

28 is a spring that presses the second diaphragm 23 in the direction of closing the valve 26 in the upper chamber 21, and 29 is an initial load set screw that adjusts the elasticity of the spring 28. The load applied to the first and second diaphragms 8 and 23 is adjusted by the idle adjustment screw 10 and the initial load Serato screw L-29, respectively, to control the position of the valve 26, that is, the opening area, and to mix the gas flow rate with respect to the intake air flow rate. The initial error in the ratio can be adjusted.

The present embodiment is constructed as described above, and its operation will be explained next.

When the intake air passes through the venturi 2, a negative pressure P1 is generated in the venturi 2 according to the air flow rate, and this is applied to the negative pressure chamber 7. Then, the pressure P in the atmospheric pressure chamber 6. Since the differential pressure (P, -P,) between , the second diaphragm 23 is also displaced downward, and the volume of the lower chamber 22 increases. When the valve 26 opens, gas is injected from the discharge port 22a to the venturi 2,
This gas passes through the throttle 24 and is metered, and a negative pressure P is generated due to the pressure loss that occurs depending on the flow rate and is applied to the lower chamber 22. Then, a differential pressure CP, -Pa) between the pressures P2 and P8 in the upper chamber 21 is applied to the second diaphragm 23,
Moreover, this differential pressure (Pz P,) is the first diaphragm 8
The load is in the opposite direction (upward) to the load due to the differential pressure (P, -P,) applied to the diaphragms 8 and 23, and the opening area of the discharge port 22a and the valve 26 is determined at a position where the pressures of both diaphragms 8 and 23 are balanced. It is measured by the throttle 24 and discharged from the discharge port 22a.
The flow rate of gas injected from is determined. Since this gas flow rate corresponds to the intake air flow rate, the air-fuel ratio of the air-fuel mixture can be controlled to be constant.

To further explain the relationship between the gas flow rate of the throttle 24 and the gas flow rate of the discharge port 22a, if the former is larger than the latter, the negative pressure P becomes smaller, so the differential pressure (P, -P, '
) becomes smaller than the differential pressure (P, -PI'), so the valve 26 is further opened, and the gas flow rate at the discharge port 22a increases, and conversely, when the latter is larger, the negative pressure P, increases. Since the differential pressure (Pg P-) becomes larger than the differential pressure (p, -p,), the valve 26 moves in the closing direction and the gas flow rate at the discharge port 22a decreases. Therefore, it can be understood that in a balanced state, the gas flow rate of the throttle 24 and the gas flow rate of the discharge port 22a are equal, and the gas flow rate measured by the throttle 24 is injected from the discharge port 22a.

Next, to explain the above relationship using a formula, Q:: intake air flow rate, Q: gas flow rate, Nl: first diaphragm 8
load, N2: load on second diaphragm 23, K1: flow coefficient of venturi 2 x area of venturi 2, K, flow coefficient of second throttle 24 x area of throttle 24, Ao:
When the effective area of each of the first and second diaphragms 8 and 23, A/F is the air-fuel ratio, A/F=Q-/Q+, so Q,=, 1 completedQ,=, 2. Also, Nl = Ao M (PG PI ), N 2 = A
o H(P 2 P s ).

Now, since the first and second diaphragms 8, 23 are balanced at the position where N, = N, Pa P+ = Pi Ps , °, Q, =, rr7:1 lower, after all, A/F =
Q, /Qt = (77': lower /KL o
+ = to -/Kt = constant.

As the intake air flow rate increases, the negative pressure P1 also increases, resulting in a differential pressure (PIl-Pl) applied to the first diaphragm 8.
increases, and the amount of downward displacement of the first and second diaphragms 8, 23 and the opening area of the valve 26 also increase. Then, the gas flow rate at the discharge port 22a and the throttle 24 increases, and the negative pressure P also increases due to the pressure loss, and the upward differential pressure (pt - Ps) applied to the second diaphragm 23 increases, eventually resulting in a balanced state. The air-fuel ratio of the air-fuel mixture is also maintained constant.

Note that if the opening area of the discharge port 22a becomes smaller due to adhesion of gum, carbon, etc. to the discharge port 22a, the gas flow rate decreases and the differential pressure (p2-Ps) becomes smaller than (P, -P,). As a result, the second diaphragm 23 is further displaced downward, the valve 26 is further retreated from the discharge port 22a, the opening area is increased, and the gas flow rate is corrected to increase. A balanced state is maintained, and the air-fuel ratio is also controlled at a constant level.

Further, since the rod 25 is always pressed in opposite directions by the diaphragms 8 and 23, the connection position with the diaphragms 8 and 23 does not have to be precise.

As described above, according to this embodiment, the air-fuel ratio of the air-fuel mixture can be controlled with high precision and feedback control, and furthermore, the opening area is reduced due to the adhesion of gum, carbon, etc. to the gas discharge port 22a. Even if there is a change in the mixing ratio, it can be automatically corrected and fluctuations in the mixing ratio can be suppressed.

In addition, a regulator 14 is connected to the gas passage 13,
Since the pressure on the downstream side is controlled to a constant level P2, even if the density of the gas supplied from the gas cylinder 12 is not constant, variations in the gas flow rate measured by the throttle 24 are prevented. be able to. In particular, in the case of this example, a throttle is used as the gas metering means, and the pressure loss is greater than when using a venturi, so by keeping the pressure on the upstream side constant, the metering accuracy is significantly improved. do.

Note that the pressure in the atmospheric pressure chamber 6 may not be the atmospheric pressure P0 as long as it is a constant pressure greater than the negative pressure P1.

〔Effect of the invention〕

As described above, the gas injection device according to the present invention includes a first diaphragm to which a negative pressure is applied depending on the intake air flow rate, a metering orifice that measures the flow rate of gas to be injected, and a metering orifice that measures the flow rate of gas to be injected, and A second diaphragm to which negative pressure is applied, and a connecting member connecting both diaphragms on the low pressure side and provided with a valve, so that the opening area of the gas discharge port can be controlled by the valve. Therefore, the air-fuel ratio of the air-fuel mixture can be controlled with high accuracy, and there is little deterioration.Even if the opening area becomes smaller due to gum or carbon deposits on the gas discharge port, the opening area can be automatically corrected. ,
Fluctuations in the mixing ratio can be suppressed.

Furthermore, since the regulator is connected to the gas passage, it is possible to prevent variations in gas flow rate measurement, and further improve measurement accuracy.

[Brief explanation of drawings]

The accompanying drawing is a schematic sectional view showing an embodiment of a gas injection device according to the present invention. ■...Intake pipe, 2...Venturi, 4...
Gas injection means, 6... atmospheric pressure chamber, 7... negative pressure chamber, 8... first diaphragm, 12... gas cylinder, 13... gas passage, 14...・Regulator, 21...Upper chamber, 22...Lower chamber, 22a...
・Discharge port, 23...Second diaphragm, 25...
・Rod, 26... Valve.

Claims (2)

[Claims] (1) In a gas injection device for an internal combustion engine that discharges gas in an amount that corresponds to the intake air flow rate, there is a negative pressure chamber that opens in the venturi and applies negative pressure that corresponds to the intake air flow rate, and atmospheric pressure. a first diaphragm that partitions the chamber, a gas passage to which gas is supplied from the gas supply source, and a second diaphragm that partitions the upper chamber connected to the gas passage and the lower chamber that communicates with the venturi via the discharge port. It is characterized by comprising a diaphragm, a metering orifice that communicates the upper chamber and the lower chamber, and a connecting member that connects the first and second diaphragms and is provided with a valve that can open and close the discharge port. Gas injection device. (2) The gas injection device according to claim (1), wherein a regulator is connected to the gas passage to adjust the pressure on the downstream side thereof.