JPS6212850Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The disclosed technology belongs to a technology in which bleed air control of air bleed of a variable bench lily carburetor is performed using a bypass passage.

Therefore, in this invention, the fuel in the well drawn from the float chamber of the variable bench lily carburetor is mixed with bleed air from the air bleed, and a bypass passage is formed in the air bleed passage. In particular, this invention relates to an air bleed structure for a variable bench lily carburetor in which a bypass passage is branched from the front stage of the air bleed hole, upstream of the throttle valve of the mixing chamber, and downstream of the main nozzle. It is an idea.

<Prior Art> As is well known, variable ventilator carburetors are used for internal combustion engines because of their advantages such as good transient response characteristics and no need for yoke valves.
Recently, not only sports cars but also general cars are being equipped with such systems, but there are still various problems to be solved.

One of them is the problem of air bleed control.

That is, in a normal variable bench lily carburetor, the first
As shown in figures a, 1b, and 1c, the suction piston 2 moves forward and backward with respect to the bench lily portion 1 according to the amount of intake air, and the metering needle 4 provided on the head 3 of the suction piston 2 is moved by the negative pressure of the bench lily. In the process of moving forward and backward, and the suction fuel from the suction pipe 5 flows through the well 6, it is mixed with the bleed air from the air bleed 8 by the metering jet 7 and metered.
The liquid is spouted from the bench lily part 1.

Therefore, the air bleed hole 10 is formed in the constricted part of the metering jet 7 shown in FIG. 1a, and the air bleed hole 10 is formed between the twin type metering jets 7 and 7 as shown in FIG. 10,
10 facing the metering jet 7, or having a plurality of air bleed holes 10 facing the upstream side of the metering jet 7 as shown in Fig. 1c. The amount of bleed air can be adjusted by changing the diameter of the air bleed jet installed in a predetermined air bleed control device A, and the operating status of the engine can be adjusted by controlling the diameter of the air bleed jet. This has the potential advantage of being able to freely obtain the required air-fuel ratio A/F from low to high temperatures.

<Problems to be solved by the invention> Therefore, experiments were conducted by changing the air bleed jet diameter D, which determines the amount of bleed air, and examining the characteristics of the air-fuel ratio A/F using the intake air amount g/sec as a parameter. By the way, if we take the air bleed jet diameter D (m/m) on the horizontal axis and the required air-fuel ratio A/F on the vertical axis, we get the intake air amount Q ₁ (10g/m) as shown in Figure 2.
sec), Q ₂ (4 g/sec), and Q ₃ (2 g/sec), the rate of change in A/F is small even if the air bleed jet diameter D is made larger than 1 mm with a small amount of intake air, making it difficult to use. Medium, minimal intake air amount Q ₃ (2g/sec)
It can be seen that when the air bleed jet diameter D is 1 mm or more, the rate of change is close to saturation and does not change.

Therefore, the air bleed jet diameter D is 1 mm.
With the above, it is difficult to change the A/F significantly.

To deal with this, the A/
It is conceivable to control F, but in reality, even if tested in this way, the metering jet that affects the metering mechanism is According to actual measurements, the annular cross-sectional area of 7 is equivalent to the air bleed jet diameter D of 1 mm or less, so no matter how large the air bleed jet 7 itself is, the amount of bleed air will change. is substantially suppressed and is not increased, the bleed sensitivity remains unchanged, and as a result, the air-fuel ratio is fixed at saturation with a small amount of intake air.

On the other hand, when actually forming an annular cross section of the metering jet 7 when controlling the amount of intake air corresponding to an air bleed jet diameter D of 1 mm or less, the air bleed jet diameter D is For example, since the A/F change rate is extremely sensitive to air bleed control device A, it is necessary to significantly improve the processing accuracy of air bleed control device A, and the molding and processing thereof requires skill. In order to prevent this from occurring and to avoid changes in the required air-fuel ratio, the seal must also be highly accurate, which has the disadvantage of complicating molding and assembly, and resulting in higher costs. Ta.

The purpose of this invention is to solve the above-mentioned technical problem of air bleed in the variable bench lily carburetor that has existed latently in the past, and to reduce the range of change in the air-fuel ratio with respect to changes in the air bleed jet diameter. By opening and branching a bypass passage into the air bleed downstream of the metering jet and upstream of the throttle valve of the mixing chamber, it is possible to change the air-fuel ratio even in a straight line. It is an object of the present invention to provide an excellent air bleed structure for a variable bench lily carburetor that is useful for industrial engine applications.

<Means/effects for solving the problems> In accordance with the above-mentioned purpose, the structure of this invention, which is summarized in the above-mentioned utility model registration claims, is to solve the above-mentioned problems by providing a variable bench lily carburetor with a The suction piston moves forward and backward into the suction chamber according to the amount of intake air, and the metering needle integrally provided from the head of the suction piston moves into the metering chamber according to the degree of opening of the suction piston with respect to the bench lily. The fuel from the well and the mixed fuel with the bleed air from the air bleed are measured and sucked into the bench lily in cooperation with the et, and
The amount of bleed air can be changed by controlling the bleed air jet attached to the air bleed control device, and the bleed air of the air bleed is located at the upstream side of the air bleed hole in the air bleed passage. The air-fuel ratio in the mixing chamber with the highest atomization efficiency is linearly changed by bypassing the metering jet to the negative pressure section before the throttle valve in the downstream mixing chamber via a bypass passage that branches from the downstream side. In that case, the smaller the air bleed jet diameter, the larger the bypass amount, and vice versa, the smaller the air bleed jet diameter, the smaller the air-fuel ratio change rate. Therefore, the air bleed jet diameter can be substantially expanded, the air-fuel ratio characteristic can be made linear, and when the bleed air amount is reduced to zero, the fuel can be bypassed. This technology takes technical measures to achieve a rich air-fuel ratio and improve low-temperature startability.

<Embodiment - Configuration> Next, one embodiment of this invention will be described as follows based on the drawings from FIG. 3 onwards.

Note that the same parts as in FIGS. 1a, 1b, 1c, and 2 will be described with the same reference numerals.

In the variable bench lily carburetor of the illustrated embodiment,
An air horn 11 and a mixing chamber 12 are formed between the upstream and downstream sides of the barrel with the bench lily section 1 in between, and a suction chamber 13 is connected to the suction piston via a suction spring 14 on one side. The main nozzle 15 and the metering jet are inserted into the well 6 provided on the other side, and the metering needle 4 provided integrally with the head 3 is inserted into the well 6 provided on the other side. 7 is loosely inserted.

5 is a suction pipe, and a float chamber 17
of fuel 18 is supplied to the well 6.

In addition, 19 is a throttle valve, 20 is a bridge that is integrally installed from the barrel to the bench lily part 1, and 21 is an air hole that connects the atmospheric chamber 22 of the suction chamber 13 and the air horn 11. .

An air bleed hole 10 is attached to the metering jet 7 with a bleed amount changing mechanism (not shown) similar to the conventional system, and is connected to a well-known appropriate air bleed control device A via a passage 23. It is connected to the air bleed passage 8.

The air bleed control device A is connected to the air horn 11 via passages 24 and 25.

Reference numeral 26 denotes a bypass passage, and in this embodiment, it branches from the front part of the air bleed hole 10 of the air bleed passage 8 and the setting upstream position of the throttle valve 19 of the mixing chamber 12, and is connected to the bypass passage immediately before the opening. Equipped with bypass jet 27.

In fact, it is also possible to improve the metering jet 7 according to the design and obtain the desired effect without performing any processing on the barrel.

In the above configuration, when the engine enters the operating state, the suction piston 2 moves forward and backward based on the pressure balance according to the amount of intake air from the air horn 11, opens and closes the bench lily portion 1, and connects the metering needle 4 and metering dial. The mixed fuel of the fuel 18 sucked from the well 6 and the bleed air, which will be explained in detail below, is measured and sent to the main nozzle 1 by the cooperation of the et 7.
5, is atomized in a mixing chamber 12, and is supplied to the engine via a throttle valve 19.

The bleed air from the air horn 11 enters the bleed air control device A through passages 24 and 25, the supply amount is controlled, and enters the air bleed passage 8;
When the control amount is small, the bypass passage 26 is increased by the amount set in the bypass jet 27 at a large rate.
Air bleed hole 10 is bypassed and a small amount
On the other hand, when the amount of air controlled by the air bleed control device A increases, the bypass amount becomes smaller and becomes close to zero depending on the control.

The part of the bleed air that passes through the bypass passage 26 is sent to the mixing chamber 12 downstream of the metering jet and upstream of the throttle valve 19, so that it is most efficiently mixed with the atomized fuel and the air-fuel ratio is adjusted. Express changes linearly and faithfully.

According to the experiment according to the above embodiment, as shown in FIG. 4, the horizontal axis represents the air bleed jet diameter D (m/m) corresponding to the metering jet 7 of the air bleed control device A, and the vertical axis represents Taking the air-fuel ratio A/F as a parameter and taking the diameter d (m/m) of the bus pass jet 27 as a parameter and taking data for the minimum intake air amount of 2 g/sec, as the diameter d of the bypass jet 27 is increased, It was found that the rate of change in the air-fuel ratio A/F with respect to the air bleed jet diameter D is small and linear. Although it could only be used in an area equivalent to the diameter of the air bleed jet, it was found in this experiment that it can be used up to an effective maximum area of 1.8 to 2 mm equivalent to the air bleed jet diameter.

Furthermore, once the diameter d of the bus pass jet 27 is determined, the rate of change in the air-fuel ratio A/F with respect to the amount of change in the air bleed jet diameter D is determined.
As shown in the figure, the diameter d of the bypass jet 27 is 1.0.
Air bleed jet 7 diameter D when set to mm
If we consider the air-fuel ratio A/F for (m/m) using the intake air amount Q as a parameter in the same way as in Figure 2, we get
Q' ₁ (20g/sec), Q' ₂ (10g/sec), Q' ₃ (2
g/sec), it does not saturate even when D>1 mm and can be controlled linearly, making it extremely effective for A/F control using air bleed control.

<Effects of the invention> As described above, according to this invention, in a structure in which a bypass passage is provided in the air bleed provided close to the metering needle of the variable bench lily carburetor and the metering part of the metering jet, the metering jet A bypass passage branched from the air bleed on the upstream side of the air bleed hole and downstream of the air bleed control device is connected in an open manner to the front stage of the throttle valve in the suction chamber downstream of the metering jet. As a result, bypass air is supplied to the connection area, and the amount of bleed air for the air bleed jet is reduced accordingly, and the smaller the amount of bleed air, the larger the amount of bypass air is. If the amount of bleed air is large, the amount of bypass air can be made relatively small.
As shown in Figure 5, the rate of change in the air-fuel ratio characteristics with respect to changes in the bleed air jet diameter becomes gradual and the changes become linear. maximum
It can be expanded to about 1.8 to 2 mm, and an excellent effect of extremely good control characteristics can be achieved.

Furthermore, even when the air bleed amount is set to zero, fuel is supplied to the bench lily section and the negative pressure section of the mixing chamber through the bypass passage, which has the effect of improving cold startability.

Furthermore, since the air bleed structure can be as simple as just adding a bypass passage, it has the advantage of being easy to manufacture and requiring almost no maintenance.

By connecting the bypass passage downstream of the metering jet and upstream of the throttle valve, the atomized fuel is mixed in the mixing chamber with high atomization efficiency, so the air-fuel ratio can be improved. Excellent effects can be achieved by faithfully reflecting changes and slowing down the rate of change in the air-fuel ratio characteristics.

[Brief explanation of the drawing]

1a, 1b and 1c are partial sectional views of an air bleed of a variable bench lily carburetor based on the prior art;
Fig. 2 is a graph showing the characteristic relationship between the air bleed jet diameter and the air-fuel ratio of the variable bench lily carburetor of the prior art, Fig. 3 is an overall schematic illustration of an embodiment of this invention, and Fig. 4 is a bypass A graph of the characteristic relationship between the air bleed jet and the air-fuel ratio according to the jet diameter of the passage, and FIG. 5 is a graph corresponding to FIG. 2 according to this invention. 9... Variable bench lily carburetor, 1... Bench lily portion, 2... Suction piston, 3... Head, 4... Metering needle, 7... Metering jet, 10... Air bleed hole, 6...
... Well, 27 ... Bypass jet, 8 ... Air bleed, 15 ... Main nozzle, 26 ... Bypass passage, 19 ... Throttle valve.

Claims (1)

[Scope of utility model registration request] An air bleed hole is formed in the vicinity of the metering jet of the well into which the metering needle, which is integrated into the head of the suction piston that can move forward and backward, is inserted into the head of the suction piston provided in the bench lily of the variable bench lily carburetor. In an air bleed structure connected to an air bleed passage in which a control device is installed, a bypass passage having a bypass jet is branched from a portion of the air bleed passage upstream of the air bleed hole and downstream of the air bleed control device. An air bleed structure for a variable bench lily carburetor is characterized in that the metering jet is downstream of the metering jet and the mixing chamber is open-connected to the upstream part of the throttle valve.