JPH07111161B2 - Gas injection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is designed to accurately measure a gas flow rate to be supplied according to an intake air flow rate by using slow-type and main-type gas measuring means. The present invention relates to a pressure balance type gas injection device in an internal combustion engine.

[Problems to be Solved by Prior Art and Invention]

In a gas injection device for an internal combustion engine that uses CNG (compressed natural gas) or LNG (liquefied natural gas) as fuel, conventionally, a means for detecting the intake air flow rate as pressure and a gas injection amount according to the intake air flow rate Are provided separately from each other, and the air-fuel ratio of the air-fuel mixture is controlled by adjusting the gas flow rate according to the intake air flow rate.

However, gum and carbon contained in blow-by gas that leaks into the intake pipe adhere to the gas outlet, so the area of the outlet becomes smaller over time and the amount of gas injected decreases, so that the gas is not supplied. There was a problem that the mixing ratio of the air-fuel mixture changed.

In order to improve such a problem, it is conceivable to adopt the principle of the pressure balance type fuel injection device described in Japanese Utility Model Application Laid-Open No. 1-74362 proposed by the applicant of the present invention. However, the practical controllable range of the air flow rate and the fuel amount is only about 8 to 10 times. On the other hand, in an internal combustion engine that requires a wide control range, such as an automobile engine,
The air flow rate and the fuel amount to be controlled in the usage range require that the ratio of the minimum value and the maximum value is about 60 times.

Therefore, even if the above-mentioned pressure balance type injection device is used as the gas injection device, it cannot be used as a gas injection device for automobiles or the like.

In view of such a problem, the present invention adopts the principle of the pressure-balance type fuel injection device described in Japanese Patent Application No. 63-12254 proposed by the present applicant, and is small in size and has a wide control range. An object is to provide a balanced gas injection device.

[Means for Solving the Problems]

The gas injection device according to the present invention includes a negative pressure diaphragm for a main to which a negative pressure is applied according to the intake air flow rate of a venturi, a main throttle for measuring a gas injection amount according to the intake air flow rate, and a main throttle that passes through the main throttle. A main system having a main fuel diaphragm to which a differential pressure due to a pressure loss of the gas to be measured is applied, and a main interlocking member provided with a valve capable of interlocking both diaphragms and opening / closing a gas discharge port. It is connected to the gas metering means, the negative pressure diaphragm for slowing to which a negative pressure is applied according to the intake air flow rate flowing through the opening of the air valve or the piston valve at the initial opening position on the downstream side of the venturi, and the downstream side of the main throttle. Difference between the slow throttle that measures the gas injection amount according to the intake air flow rate and the pressure loss of the gas that is measured after passing through this slow throttle. A slow system gas metering means having a slow fuel diaphragm to which pressure is applied and a slow interlocking member provided with a valve capable of interlocking both diaphragms and opening and closing a gas outlet, and a main throttle from a gas supply source. A regulator provided in a gas passage for supplying gas to the chamber.

[Operation] In the slow zone, intake air flows through the opening of the air valve or piston valve at the initial opening position, and a negative pressure corresponding to this small amount of air is applied to the negative pressure diaphragm for the slow displacement to displace it. When the interlocking member and the fuel diaphragm for the slow move in conjunction with each other, a small amount of gas corresponding to the measured intake air flow rate flowing through the slow throttle is injected from the discharge port to balance both diaphragms, and then to the main zone. , A relatively large amount of intake air flows through the venturi by the air valve or piston valve whose opening changes, and the negative pressure corresponding to this is applied to the main negative pressure diaphragm to interlock the main interlocking member and the main fuel diaphragm. However, a relatively large amount of gas corresponding to the intake air flow rate measured by the main throttle is injected from the discharge port and both diaphragms are There is balance.

〔Example〕

A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

In the figure, 1 is an intake pipe, 2 is a venturi provided in the intake pipe 1, 3 is an opening in the venturi 2, and a main pressure sensing port for detecting a negative pressure P ₁ according to the air flow rate of the venturi 2; Is an air valve which is provided on the downstream side of the venturi 2 and whose initial opening (see the drawing) is set by an idle adjustment screw (not shown). 5 is an opening on the downstream side of the opening 4a of the air valve 4 at the initial opening position. Is a pressure sensing port for throw that detects a negative pressure P ₂ corresponding to the air flow rate of the opening 4a, and 6 is an actuator that detects a negative pressure on the downstream side of the air valve 4 and controls the opening of the air valve 4. In the zone, the air valve 4 is maintained at the initial opening because the downstream negative pressure is small. 7 is a throttle valve provided on the downstream side of the air valve 4,
8 is the negative pressure P ₂ detected by the pressure sensing port 5 for slow
The slow system gas metering means for injecting a small amount of gas according to the small air flow rate based on the above, 9 is a relatively large amount according to the relatively large air flow rate based on the negative pressure P ₁ detected by the main pressure sensing port 3. It is a main system gas metering means for injecting the above gas.

In the slow system gas metering means 8, 10 is a negative pressure chamber to which the negative pressure P ₂ detected by the slow pressure sensing port 5 is applied, and 11 is negative pressure P ₁ detected by the main pressure sensing port 3. Is the atmospheric pressure chamber to which the negative pressure is applied because the air flow rate of the venturi 2 is small in the slow zone.
P ₁ is maintained at about atmospheric pressure P ₀ . 12 is negative pressure chamber 10 and atmospheric pressure chamber
Negative pressure diaphragm for throw that separates 11 and 13, gas passage
An upstream chamber into which gas is introduced from the downstream chamber of the main gas metering means 9 via 14, a downstream chamber 15 capable of injecting gas from the discharge port 15a to the bleed air passage 16, and 17 upstream chambers 13 and downstream chambers.
A fuel diaphragm for slowing that divides 15, a slow throttle 18 that communicates the upstream chamber 13 and the downstream chamber 15 and measures the amount of gas injected from the discharge port 15a, and 19 and 20 rotate about axes 19a and 20a, respectively. A lever whose one end is pressed against the negative pressure diaphragm 12 for throw, the fuel diaphragm 17 for throw, and 21 is pressed between the other ends of both levers 19 and 20, and both diaphragms 12,
It is a rod or throw interlocking member formed with a valve 21a capable of opening and closing the discharge port 15a in conjunction with the displacement of 17, and the bleed air passage 16 opens to the intake pipe 1 on the downstream side of the throttle valve 7, From here, the gas injected from the discharge port 15a is discharged to the manifold.

The main gas measuring means 9 also has the same structure and function as the slow gas measuring means 8 (the same parts are indicated by the same reference numerals with "'"), and 23 is a main pressure sensing port. The negative pressure chamber to which the negative pressure P ₁ detected in 3 is applied, 24 is a constant pressure on the upstream side of the venturi 2, for example, atmospheric pressure
P ₀ is an atmospheric pressure chamber, 25 is a gas cylinder or gas supply source for supplying gas to the upstream chamber 13 ′ through the gas passage 26, and 27 is provided in the middle of the gas passage 26 and is downstream thereof. Is a regulator for controlling the gas pressure of P to a constant magnitude P ₃ , and a chamber 30 into which gas flows in and out and a chamber 29 to which atmospheric pressure P ₀ is applied are partitioned by a diaphragm 30.
A valve 31 for adjusting the opening area of the gas inlet 28a is connected to the diaphragm 30, and a spring 31
The valve 32 is elastically pressed in the opening direction of the valve 31.

Then, in the main gas measuring means 9, the discharge port 15 '
The amount of gas corresponding to the amount of gas injected from a is the main throttle 1
Pressure loss is generated by passing through 8'and
The pressure P ₄ at 5'decreases. The gas having the pressure P ₄ is applied to the upstream chamber 13 of the slow system gas metering means 8, and a gas amount corresponding to the gas injection amount from the discharge port 15a passes through the slow throttle 18 to cause a pressure loss, which results in the downstream. The pressure P _{5 in the} chamber 15 is designed to decrease.

The present embodiment is configured as described above, and the operation will be described next.

In the slow zone, since the intake air flow rate is small, the air valve 4 is held at the initial opening position, the intake air flow rate flowing through the opening 4a is detected as the negative pressure P ₂ by the slow pressure sensing port 5, and the negative pressure chamber 10 Applied to. Since the pressure P _{1 of the} Venturi 2 is applied to the atmospheric pressure chamber 11,
Due to the differential pressure (P ₁ -P ₂ ), the slow negative pressure diaphragm 12 is displaced downward, the rod 21 is moved upward via the lever 19 which is pushed and turned clockwise, and the valve 21a opens the discharge port 15a. When the rod 20 is pushed by the rod 21 and the lever 20 is rotated rightward, the throw fuel diaphragm 17 is displaced downward, and the volume of the downstream chamber 15 increases. Discharge port 1 by opening valve 21a
Gas is injected from the bleed air passage 16 into the bleed air passage 16 and the gas passes through the slow throttle 18. As a result, a pressure loss corresponding to the flow rate of the gas occurs, and the pressure P ₅ of the downstream chamber 15 decreases. Thus the pressure difference between the pressure P ₄ of the upstream chamber 13 (P ₄ -P ₅₎ is applied to the slow fuel diaphragm 17, yet the pressure difference (P ₄ -
P ₅ ) is the differential pressure (P ₁ −
P ₂ ) and the load in the opposite direction (upward), and the pressure at both diaphragms 12 and 17 is balanced.
And the valve 21a determine the opening area, and the slow throttle 1
The gas flow rate measured at 8 and injected from the discharge port 15a 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.

The relationship between the gas flow rate of the slow throttle 18 and the gas flow rate of the discharge port 15a will be further described. If the former is larger than the latter, the pressure P ₅ will be large, so the differential pressure (P ₄ -P ₅ ) Is smaller than the differential pressure (P ₁ -P ₂ ), the valve 21a is further opened, and the gas flow rate at the discharge port 15a increases. On the contrary, when the latter is larger, the pressure P ₅ becomes smaller, so the differential pressure (P ₄ −
P ₅₎ is a valve 21a to become larger than the pressure difference (P ₁ -P ₂₎
Moves in the closing direction, and the gas flow rate at the discharge port 15a decreases.
Therefore, in a balanced state, the flow rate of the slow throttle 18 and the discharge port 15
It can be understood that the gas flow rate equal to the flow rate of a and measured by the slow throttle 18 is injected from the discharge port 21a.

Next, the above-mentioned relationship in the slow zone will be described by formulas: Q _a : intake air flow rate, Q _f : gas flow rate, N ₁ : load of negative pressure diaphragm 12 for slow, N ₂ : load of fuel diaphragm 17 for slow, K _a : Venturi 2 flow coefficient * Venturi 2 area, K _f : Slow throttle 18 flow coefficient * Slow throttle 18 area, A ₀ : Throw negative pressure and effective area of fuel diaphragms 12 and 17, A / F: air-fuel ratio, A / F: Q _a / Q _f , _{N 1 = A 0 * (P} 1 -P 2), a _{N 2 = A 0 * (P} 4 -P 5).

Now, at the position where N ₁ = N ₂ , the negative pressure for slow and the fuel diaphragms 12 and 17 are balanced, so P ₁ −P ₂ = P ₄ −P ₅ , And eventually, Becomes

Then, as the intake air flow rate increases, the negative pressure P ₂ also increases, and the differential pressure (P ₁ −P ₂ ) applied to the negative pressure diaphragm 12 increases, and the downward displacement of both diaphragms 12 and 17 and the valve The opening area of 21a also increases. Then, the gas flow rates of the discharge port 21a and the slow throttle 18 increase, and the pressure P ₅
Becomes smaller and the upward differential pressure (P ₄ -P ₅ ) applied to the slow fuel diaphragm 17 increases, so that the balance state is maintained and the air-fuel ratio of the air-fuel mixture is also maintained constant.

In the slow zone, since the pressure P ₁ is almost equal to the atmospheric pressure P ₀ , no gas is discharged from the main-system gas measuring means 9 and the pressures P ₃ and P ₄ are maintained at substantially the same level.

The gas flow rate measured by the slow throttle 18 is the main throttle.
The gas is supplied to the upstream chamber 13 through the gas passage 14 after passing through 18 ', and in the slow zone, a small amount of intake air is supplied within the range of the minimum gas flow rate that can be measured by the main throttle 18'. A small amount of gas will be metered by the slow throttle 18 and injected.

Then, when the intake air flow rate increases and the air valve 4 begins to open, and the operation moves to the main zone, the intake air flow rate flowing through the venturi 2 is reduced to a negative pressure at the main pressure sensing port 3.
Since it is detected as P ₁ and the differential pressure (P ₀ −P ₁ ) is applied to the main negative pressure diaphragm 12 ′ of the main system gas metering means 9 and is displaced downward, as in the above description of the slow zone. , The rod 21 ', that is, the main interlocking member and the main fuel diaphragm 17' are moved, the gas flow rate measured by the main throttle 18 'is injected from the discharge port 15'a, and the pressure P in the downstream chamber 15' is generated by the pressure loss. _{for 4} drops, main fuel diaphragm 17 'in an upward differential pressure (P ₃ -P ₄₎ both diaphragms 12 are applied', 17 'are balanced, the air-fuel ratio of the mixture is maintained at a constant It

When the negative pressure P ₁ in the venturi 2 increases, the slow negative pressure diaphragm 12 in the slow system gas measuring means 8
The differential pressure (P ₁ -P ₂ ) applied to the gas is reduced, and the gas injection amount from the slow system gas metering means 8 is reduced.

As described above, according to this embodiment, in the slow zone, a small amount of gas is injected in response to a small amount of intake air by the slow system gas measuring means 8, and in the main zone, the main system gas measuring means 9 is used for comparison. Since a relatively large amount of gas is injected in response to a large amount of intake air, even if the controllable width of the air flow rate and gas flow rate by each gas metering means 8 and 9 is about 8 times, A control width of about 64 times can be secured, and it can be sufficiently used as a gas injection device for automobiles and the like. Further, according to the structure of this embodiment, the device can be downsized and the air-fuel ratio of the air-fuel mixture can be controlled with high accuracy.

Also, connect the regulator 27 to the upstream side of the gas passage 26 of the main diaphragm 18 ', it is so arranged to control a certain size P ₃ the pressure on the downstream side with respect to the atmospheric pressure P _0, the gas cylinder 25
Even if the density of the gas supplied from the device varies depending on the conditions, it is possible to prevent the measurement flow rate of the gas measured by the main throttle 18 'and the slow throttle 18 from being varied. Since the gas injected by the slow system gas metering means 8 is sent through the main throttle 18 ', it is a part of the gas measured by the main throttle 18' in the main zone.
Does not affect the accuracy of weighing.

Although the air valve 4 is used in this embodiment, it goes without saying that a piston valve or the like may be used instead of the air valve 4.

〔The invention's effect〕

As described above, according to the gas injection device of the present invention, the narrow-slow gas metering means of control width and the main gas metering means are combined, and the pressure of the gas to be supplied to the upstream side thereof is controlled to be constant. Since the regulator is provided, the control range of the intake air flow rate and the gas flow rate can be widened, and the size is small, the air-fuel ratio of the air-fuel mixture can be accurately controlled, and the variation in the measurement of the gas flow rate is prevented. be able to.

[Brief description of drawings]

The accompanying drawings are schematic sectional views showing an embodiment of a gas injection device according to the present invention. 2 ... Venturi, 4 ... Air valve, 8 ... Slow gas measuring means, 9 ... Main gas measuring means, 12 ... Slow negative pressure diaphragm, 12 '... Main negative pressure diaphragm, 15a, 15 'A ... Discharge port, 17 ... Slow fuel diaphragm, 17' ... Main fuel diaphragm, 18 ...
... Slow throttle, 18 '... Main throttle, 21,21' ... Rod, 21a, 21'a ... Valve, 25 ... Gas cylinder, 27 ...
regulator.

Claims (1)

[Claims] 1. A negative pressure diaphragm for a main body in which a negative pressure is applied in accordance with the intake air flow rate of a venturi in a gas injection device for an internal combustion engine adapted to discharge an amount of gas according to the intake air amount, and a suction A main throttle capable of measuring a gas injection amount according to an air flow rate, a main fuel diaphragm to which a differential pressure due to a pressure loss of gas measured by the main throttle is applied, and both diaphragms are interlocked with each other, and a gas discharge is performed. A main gas measuring means having a main interlocking member provided with a valve capable of opening and closing the outlet, and a negative pressure depending on the intake air flow rate of the opening of the air valve or the piston valve at the initial opening position on the downstream side of the venturi. Slow negative pressure diaphragm to which is applied, and a slow throttle connected downstream of the main throttle and capable of measuring the gas injection amount according to the intake air flow rate. A slow fuel diaphragm to which a differential pressure due to a pressure loss of gas measured by the slow throttle is applied, and a slow interlocking member provided with a valve for interlocking both diaphragms and opening and closing a gas discharge port. A gas injection device comprising: a slow system gas metering means provided; and a regulator provided in a gas passage for supplying gas from a gas supply source to the main throttle.