JPS608456A - Fuel supply device for internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve atomization of fuel and provide a variable sonic nozzle carburetor with good responseability, by sucking fuel as preliminarily mixed with air at a second sonic nozzle into a first sonic nozzle as annularly formed. CONSTITUTION:When a valve 16a is opened and closed by operating accelerator pedal, a vacuum induction passage of an outlet 7 downstream of a variable sonic nozzle 21 is opened and closed to adjust a vacuum in a chamber 14 of a diaphragm 12 thereby raise and lower a nozzle member 8 forming the variable sonic nozzle 21. In response thereto, an opening degree of a fuel nozzle 31 is adjusted by a needle 33, and a metered fuel is mixed with air flowing from an opening 6 through a passage 34 to a fixed sonic nozzle 32. Such a preliminarily mixed fuel is sucked to the variable sonic nozzle 21, and is completely atomized to be uniformly distributed to each cylinder of an engine.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel supply system used in an internal combustion engine such as a gun-nine engine, and more particularly to one using a variable sonic velocity nozzle to control the intake air leaf.

For example, carburetors that are widely used as fuel supply devices for gasoline engines are broadly classified into fixed venturi type carburetors and variable venturi type carburetors, such as the SU carburetor. A butterfly-type throttle valve linked to the accelerator is arranged, and the amount of intake air is controlled by the opening degree of the throttle valve. Measure it as a balance position, and also change the vertical pressure difference or opening area of the fuel metering orifice in relation to this! The system measures fuel to obtain a predetermined air-fuel ratio.

In such conventional carburetors, for example, there are problems with the connection between the slow system and the main system with a fixed venturi carburetor, or between the primary side and the secondary side, or with the stability of the air-fuel ratio with a variable venturi carburetor. Various problems have been pointed out, such as problems with performance, and the responsiveness of the fuel during acceleration and the distribution characteristics of the air-fuel mixture in multi-cylinder engines are also far from satisfactory.

By the way, in recent years, instead of the butterfly type throttle valve as mentioned above, the amount of intake air is fli controlled by a variable sonic nozzle, and at the same time, the amount of intake air is detected from the area of the throat part (the narrowest part) of the sonic nozzle. This type of intake air amount control mechanism is disclosed in Japanese Patent Application Laid-open No. 51-29629 and
-35821 publication.

This method has been proposed in Japanese Patent Application Laid-Open No. 50-97731.

This is because when the pressure difference between the top and bottom of a Laval nozzle sonic nozzle is larger than a certain value, the gas flow velocity reaches the sonic velocity at the throat, and under this sonic velocity condition, the flow rate is proportional to the area of the throat regardless of pressure fluctuations. This relationship is utilized, and if the nozzle shape is appropriately set, it is actually possible to maintain the sonic speed state in most operating ranges of the engine except for the full-throttle operating range. If this sonic nozzle is used to control the amount of intake air to construct a fuel supply system, the following various advantages can be obtained. First of all, it is extremely easy to measure the amount of intake air.As mentioned above, the nozzle flow rate is proportional to the throat area within the range where the sound velocity at the throat can be maintained. Since the amount of air can be measured with high precision and can be measured as a mass flow rate, high altitude correction etc. are not required. Also the second
A major advantage of this is that by mixing the fuel with an air flow at or near the sonic speed, it is possible to significantly atomize the fuel. For example, in a normal carburetor, the fuel particle size is 100 to 200μ. However, at a flow velocity close to the speed of sound, particles can be atomized to about 20μ. This speeds up the fuel vaporization time and suppresses fuel adhesion to the intake pipe wall, contributing to improved distribution characteristics, greatly improving L6 response during acceleration, and preventing the intake pipe wall from getting cold. There is also the possibility that it may be possible to eliminate the need to increase the amount of fuel when starting the engine.

However, in order to put the sonic nozzle type fuel supply system, which has various advantages as described above, into practical use, there are several issues that must be resolved. One of the issues is how to configure the variable structure of the Laval nozzle and how to specifically supply fuel to the airflow that reaches the speed of sound at its throat. That is, as a type of variable sound velocity nozzle, for example, Japanese Patent Application Laid-Open No. 51-55823
An annular nozzle as shown in Figure 6 of the publication has been considered, but how should the fuel be distributed evenly around the entire circumference and how can the sonic flow be effectively used to atomize the fuel? has become a major issue.

This invention was made in view of the above background.1
, its purpose is to solve the above-mentioned problem of fuel supply to an annular variable sonic velocity nozzle and to provide a new fuel supply device that can be used in place of the conventional carburetor.

That is, the fuel supply device for an internal combustion engine according to the present invention has the following features:
A throttle body having an air intake and a mixture outlet, a throttle piston disposed to be movable linearly with respect to the throttle body, and a piston drive mechanism that controls the movement position of the throttle piston in response to accelerator operation. and a variable sound velocity nozzle which is formed in an annular shape by the mutually opposing nozzle wall surfaces of the throttle body and the throttle piston, and whose throat area can be changed according to the moving position of the throttle piston, and a fixed sonic velocity nozzle formed radially or annularly on the inner circumferential side of the variable sonic velocity nozzle, whose upstream end communicates with the upstream side of the variable sonic velocity nozzle, and whose downstream end communicates with the vicinity of the throat of the variable sonic velocity nozzle; , a fuel metering orifice located near the upstream end of the fixed sonic nozzle and at its center; and a fuel metering orifice integrally supported by the throttle piston and advancing and retreating into the fuel metering orifice;
a needle valve that changes the effective area of the orifice in proportion to the area of the throat portion of the variable sonic speed nozzle; and a fuel pressure that corrects the fuel pressure upstream of the fuel metering orifice in accordance with the flow velocity of the throat portion of the variable sonic speed nozzle. It is equipped with an adjustment mechanism.

Hereinafter, one embodiment of the present invention will be described in detail based on FIG. 1.

In the figure, i-1 is a throttle body that forms the outer shell of this fuel supply device, and this throttle body 1 includes a main body 2 whose upper half is formed into a hollow cylindrical shape, and an upper end surface of the main body 2. It is roughly composed of a negative royal cuckoo 3 that covers the main body 2, a diaphragm housing 4 attached to the lower end of the main body 2, and a dome-shaped air guide 5 screwed to the center of the main body 2. An air intake port 6 is provided in the upper part of the hollow cylindrical shape, and a plurality of air intake ports (usually the number corresponding to the number of cylinders) are provided in the relatively lower part of the air guide 5 so as to be smoothly connected to the outer peripheral surface of the air guide 5. Mixing index lowers are formed approximately radially around the air guide 5.

First, to explain the intake air amount control system, 8 is a throttle piston having a substantially cylindrical shape with an opening at the lower end: , y, 9fd
A hollow piston support shaft is press-fitted into the center of the upper end of the upper ffe throttle piston 8, and this piston support shaft 9 is slidably fitted into and held in the guide sleeve 10 of the negative pressure chamber cover 3. The lower limit position of the throttle piston 8 is regulated by a stopper 11 screwed onto the threaded portion 9a at the base end. Further, the throttle piston 8 is connected to a diaphragm 12 constituting a piston drive mechanism, and is always urged downward by a coil spring 13, and the diaphragm 12 creates a negative pressure inside the throttle body l. The vertical sliding position is controlled by the negative pressure in the chamber 14,
Specifically, the mixture high lower part on which the engine suction negative pressure acts is communicated with the negative pressure chamber 14 through the negative pressure passage 15, and
A needle valve 16a and a return spring 1 are installed in the passage 15.
A negative pressure control valve 16 consisting of 6b is interposed, and the needle valve 16
A is configured to open and close in conjunction with an accelerator (not shown). Incidentally, in order to release the negative pressure, an atmospheric passage 19 is connected to the negative pressure passage 15 via the orifices 17 and 18.
is connected.

On the other hand, the variable 2-bar nozzle 21, which is a variable sonic velocity nozzle, is continuous in an annular manner by a nozzle wall surface 22 on the inner periphery of the lower end of the throttle piston 8, and a nozzle wall surface 23 extending over the air guide 5 and the main body 2 opposite thereto. A throat portion (the narrowest portion) 24 is formed slightly above the lower edge of the air guide 5, and the position of this throat portion 24 is fixed relative to the vertical sliding of the throttle piston 8. The shapes of both nozzle wall surfaces 22 and 23 are set so that the area of the throat portion does not change as much as possible and the substantial area of the throat portion can change according to the amount of movement of the throttle piston 8. A plurality of openings are formed in the upper part of the throttle piston 8, and a seal member 26 slidably seals between the outer peripheral surface of the throttle piston 8 and the throttle body I.

In this fuel supply system, the intake air 1'' is controlled by the variable Laval nozzle 21 configured as described above. That is, when the negative pressure control valve 16 is opened in conjunction with the accelerator (not shown), the air-fuel mixture height increases. When the lower engine suction negative pressure is introduced into the negative pressure chamber 14 and the throttle piston 8 moves upward in the figure, conversely, when the negative pressure control valve 16 is closed, the negative pressure chamber 14
As the negative pressure inside weakens and the throttle piston 8 moves downward in the figure, as the throttle piston 8 moves up and down, the throat part 240 of the variable rubber nozzle 21
The area increases or decreases, and the air flowing from the upstream side of the throttle piston 8 to the air-fuel mixture high lower part is appropriately throttled to adjust the flow rate. If the difference between the pressure PA (approximately equal to atmospheric pressure) in the vicinity of the nozzle upstream pawl opening portion 25 and the pressure PB (engine suction negative pressure) at the downstream pawl mixture outlet 25 is large, , a constant flow rate determined by the area of the throat portion 24 is given at the speed of sound at the throat portion 24 .

Specifically, the engine suction negative pressure PB is -150 to -200 H
The speed of sound can be maintained sufficiently up to about 2. Further, when the idling brake negative pressure control valve 16 is fully closed, the stopper 11 maintains the small area of the throat portion 24. Conversely, when the accelerator is fully opened, that is, when the negative pressure control valve 16 is fully opened, the suction negative pressure is set to the minimum setting value (for example, -15 to -30 an, %) depending on the balance with the load of the coil spring 13.
) is regulated so that it does not go below, and a certain amount of flow velocity is ensured in the throat section.

Next, we will explain the fuel supply system that measures and supplies fuel to the air whose flow rate is controlled as described above.On the front throttle body l side, there is a fuel metering orifice 31 and a fixed Laval nozzle 32 as a fixed sonic nozzle. A needle valve 33 is provided on the other side of the throttle piston 8. The fixed Laval nozzle 32 is configured in a continuous annular shape between the lower surface of the umbrella-shaped insert portion 5a of the air guide 5 and the curved surface of the main body portion 2 opposing this, and its upstream end That is, the inner circumferential end portion is connected to the air guide 5 through the plurality of communication holes 5b of the upper six private guides 5.
The outer circumferential end of the downstream end tab that communicates with the central recess 34 is connected to the throat portion 2 of the oT variable Clavar nozzle 1.
It opens at a position slightly downstream from 4.

Similar to the variable Laval nozzle 21, this fixed Laval nozzle 32 allows a small amount of air to flow through it due to the difference between the upstream pressure PA (almost atmospheric pressure) and the downstream pressure PR (engine suction negative pressure). The above variable Laval nozzle 21
In other words, the Laval nozzle 21 has a characteristic similar to
The change is approximately equal to the throat portion 24 of . The air guide 5 is screwed onto the main body 2 via a coil spring 36 for removing backlash.
The opening area of the fixed Laval nozzle 32 can be adjusted by moving it forward and backward. On the other hand, the fuel metering orifice 31 opens at the tip of the fuel passage 37 provided in the vertical direction of the main body 2, and is located at the bottom surface of the recess 34 of the upper six-pier air guide 5, that is, the fixed rubber nozzle 32
It is located near the upstream end of and at its center.

Further, the needle valve 33 has a shaft portion 33a slidably inserted into the piston support shaft 9, and is substantially secured to the throttle piston 8 by a cap nut 38 and a coil spring 39 screwed onto the base end thereof. It moves forward and backward into the fuel metering orifice 31 as the throttle piston 8 moves up and down, thereby controlling the effective area of the fuel metering orifice 31. That is, when the throttle piston 8 moves upward, the fuel metering orifice 31
The effective area is expanded, and conversely, when the throttle piston 8 is moved downward, the effective area is reduced. Specifically, the effective area is changed in proportion to the area of the throat arm of the variable Laval nozzle 21. The shape of the needle valve 33 is set. By rotating the cap nut 38 and finely adjusting the position of the needle valve 33 with respect to the throttle piston 8, the air-fuel ratio at idle can be adjusted.

On the other hand, if the effective area of the fuel metering orifice 31 is made proportional to the area of the throat portion 24 of the variable Laval nozzle 21 as described above, even if the fuel pressure PF is assumed to be constant,
Under the condition that the throat section 24 is a sonic viper, the air flow rate (proportional to the area of the throat section 24) and the fuel flow rate (if the vertical pressure difference between the fuel gauge and the orifice 31 is constant, the effective area Proportional) is obtained,
It is possible to maintain a constant air-fuel ratio. However, when the flow velocity at each throat does not reach the speed of sound,
Since the air flow rate is not proportional to the area of the throat portion 24, significant fluctuations in the air-fuel ratio occur. Therefore, in order to maintain the desired air-fuel ratio in this case, the fuel gauge 1 orifice 31
Upstream fuel pressure P? is corrected by the fuel pressure adjustment mechanism 41. The fuel pressure adjustment mechanism 41 includes two diaphragms 42 attached to the diaphragm housing 4,
43, a shaft 44 that integrally connects both diaphragms 42 and 43, and a fuel valve 46 that is opened and closed by a swinging lever 45 that interlocks with this shaft 44. A chamber 47 and a first pressure chamber 48 are defined, and a second pressure chamber 49 and a sixth pressure chamber 50 are defined by the other diaphragm 43, and the first pressure chamber 48 and the third pressure chamber The pressure PA on the upstream side of the variable Laval nozzle 21 is introduced into the second pressure chamber 49 through a passage 51, and the throat portion 3 of the fixed Laval nozzle 32 is introduced into the second pressure chamber 49 through a passage 52.
5 contains the ocher pressure Pt of 2-. Further, the fuel pressure chamber 47 communicates with the fuel port 53 via the fuel valve 46, and is connected to the fuel passage 37 upstream of the fuel metering orifice 31. The fuel valve 46 has a fulcrum 45
The lever 45 is normally biased in the closing direction by the return spring 54 at the other end of the lever 45, and is normally biased by the vertical movement of the shaft 44. It is opened and closed, and functions as a single-volume pressure regulating valve that regulates the pressure of the fuel fed under pressure from the fuel tank 53. That is, in the configuration shown in the upper ml, the pressure receiving areas of the diaphragms 12 and 43 are AI and A, respectively.
s, the fuel pressure PF in the fuel pressure A compartment 47 due to the balance of forces is PF= (PA Pt)+
The shaft 44 is positioned so that PAA+, and at this time, the pressure difference between the upper and lower sides of the fuel metering orifice 31 is PPPA=AI (PA-Pt), and the fuel flow is f.
On the other hand, if it is assumed that the air flow velocity at the throat section 35 of the fixed Laval nozzle 32 is always equal to the air flow velocity at the throat section 24 of the variable Laval nozzle 21, the air flow rate is Similarly, in a relatively small range, the value is proportional to 49. Therefore, even in operating ranges where the flow velocity at the throat portion 24 is significantly reduced, such as when the throttle piston 8 is fully opened, the ratio between the air flow rate and the fuel flow rate is The air-fuel ratio is maintained approximately constant.Of course, strictly speaking, due to the influence of the compressibility of air, there is a slight difference between when the throat section is at the sonic speed and when the flow velocity is the lowest (such as at low speed and high load). Although the air-fuel ratio changes, the width of the change is relatively small, and can be suppressed to a range that does not pose a practical problem by regulating the minimum value of the intake negative pressure PB when the accelerator is fully opened, as described above.

In addition, by setting the pressure receiving areas A, A, of both diaphragms 4R, 43 so that AI > A- as shown in the figure, it is possible to set the fuel pressure P1 applied to the fuel metering orifice 31 as low as an arbitrary value. As a result, the opening area of the fuel metering orifice 31 required to ensure the same fuel flow rate is small, which has the advantage that the processing accuracy of the fuel metering orifice 31 and needle valve 33 is not required to be so strict. .

Now, as mentioned above, the fuel metering orifice 31 and the needle valve 3
3 according to the air flow rate is discharged from the fuel meter ψ orifice 3 and mixed with the air flowing through the fixed Laval nozzle 32.

Here, since the fuel metering orifice 31 is located at the center of the fixed rubber nozzle 32, the fuel is distributed uniformly in the circumferential direction. The flow velocity within the fixed Laval nozzle 32 reaches the sonic velocity at its throat portion 35 in the normal operating range, and the fuel is well atomized within this air flow. Then, the rich mixture air flow is further merged with the air flowing through the variable Laval nozzle 21 downstream of the throat portion 24 of the variable Laval nozzle 21, and is atomized into smaller fuel particles by the air flow that is also close to the sonic speed. , homogenization of the mixture is promoted. Here again, the fixed Laval nozzle 32 is replaced by the variable Laval nozzle 21.
The rich air-fuel mixture is uniformly supplied over the entire circumference of the air-fuel mixture, and therefore the air-fuel mixture supplied from the mixture finding lower to each cylinder is extremely homogeneous and atomized.

Note that the position of the confluence of the fixed Laval nozzle 32 with respect to the variable Laval nozzle 21 is disadvantageous in terms of atomization because if the position is too far away from the throat section 24, the air flow velocity will decrease. If it is too close, the flow of air within the variable Laval nozzle 21 will be disturbed and the operating range where the speed of sound will be achieved will be narrowed, so it is necessary to take both into consideration when making a decision. Incidentally, when the area of the throat portion 24 of the variable Laval nozzle 32 is Ai, and the nozzle area at the merging portion is Ao, A@/At is 1.05 to 1 within the 10-mode operating range of the automobile engine. .0
It is preferable to set it to a value of about 6 to 1.

Further, in this invention, the fixed rubber nozzle 32
As shown in FIG. 2, it is also possible to have a configuration in which they merge slightly upstream of the throat section of the variable Laval nozzle 21, and in this case, the ratio A e of the throat section U area and the merging section area described above is It is also preferable to set /At to a value of about 1.0 to 1.6 within the 10-mode operation region.

Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment. For example, in the above embodiment, the fixed Laval nozzles 32 are continuous in an annular shape, but the same effect can be achieved even if a plurality of fine H11 Laval nozzles are arranged radially. Furthermore, the fuel pressure adjustment mechanism 41 is not limited to the mechanical mechanism described above, but can also be controlled by the variable rubber nozzle 2 by means of a control of a solenoid valve.
It may be configured to supply fuel pressure according to the flow velocity of the throat section 24 of the first embodiment.

As is clear from the above explanation, in the fuel supply device for an internal combustion engine according to the present invention, the sonic flow in the annular variable sonic velocity nozzle is effectively utilized over the entire circumference to atomize and homogenize the fuel. This not only improves the distribution characteristics to each cylinder compared to previous carburetors, but also suppresses fuel adhesion to the intake pipe wall and improves response during acceleration. You can improve your sexuality. In addition, extremely stable air-fuel ratio characteristics can be obtained within a wide range of operating ranges in which the sonic velocity can be maintained at the variable sonic velocity nozzle throat, and even in operating ranges where the flow velocity is below the sonic velocity, it is possible to easily maintain a predetermined air-fuel ratio by correcting the fuel pressure. It has advantages such as being able to maintain

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG. 2 is a sectional view of only essential parts showing a different embodiment of the invention. l...Throttle body, 5...Air guide, 6.
... Air intake, 7... Mixture outlet, 8... Throttle piston, 11... Stop collar, 12... Diaphragm, 13... Coil spring, 14... Negative pressure chamber, ■6... ...Negative pressure control valve, 21...Variable Laval nozzle, 22, 23...Nozzle wall surface, 24...Throat portion, 26...Seal member, 31...Fuel metering orifice, 32...Fixed Laval nozzle, 33... needle valve, 35... throat section, 41... fuel pressure adjustment mechanism,
42, 43...Diaphragm, 46...Fuel valve, 47...Fuel pressure chamber, 53...Fuel inlet.

Claims (1)

[Claims] (1) A throttle body having an air intake and a mixture outlet, a throttle piston disposed to be movable directly with respect to the throttle body, and controlling the movement position of the throttle piston in response to accelerator operation. a piston drive mechanism; a variable sound velocity nozzle that is formed in an annular shape by mutually opposing nozzle wall surfaces of the throttle body and the throttle piston, and whose throat portion area can be changed according to the movement position of the throttle piston; and the throttle body. A fixed sound velocity is formed radially or annularly on the inner peripheral side of the variable sound velocity nozzle, the upstream end thereof communicates with the upstream side of the variable sound velocity nozzle, and the lower fi mVJ end communicates with the vicinity of the throat portion of the variable sound velocity nozzle. a nozzle, a fuel metering orifice located near the upstream end of the fixed sonic nozzle and at its center; and an effective area of the orifice that is integrally supported by the throttle piston and advances and retreats into the fuel metering orifice. a needle valve that changes the pressure in proportion to the throat area of the variable sonic nozzle; and a fuel pressure adjustment mechanism that corrects the fuel pressure upstream of the fuel electrically resistant orifice in accordance with the flow velocity of the throat of the variable sonic nozzle. A fuel supply system for an internal combustion engine.