JPS6035165A - Air-fuel ratio control device for carburetor type engine - Google Patents

Abstract

PURPOSE:To extend a diluted region of an air-fuel ratio by providing a throttle valve and a control valve in order from the upstream side in a bypass passage provided so as to go around a carburetor, and controlling the control valve such that pressure difference between both of said valves changes to a large negative valve with the increase of the amount of intake air. CONSTITUTION:When an engine operation region falls into any of a low revolution region, a high revolution region, or a high load region, a changeover signal S0 of an H level is outputted from a control unit 15, and a three-way changeover valve 14 allows an operating passage 8 side of negative pressure release passage 9 to be opened to the atmosphere. Accordingly, working negaive pressure P1 is not introduced into a negative pressure chamber 7a of a control valve 7, and a valve body 7 of the control valve 7 allows a through hole 5a to be closed due to the force of a spring 7c. By contrast, in the low load middle revolution region, although the three-way changeover valve 14 is made to be a changeover state to open the control valve 7, the working negative pressure P1 is controlled by a negative pressure adjusting valve 10 adjusted in its opening in responce to the controlled negative pressure P0 corresponding to the pressure difference between the upstream and downstream of a throttle 6 in a bypass passage 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an air-fuel ratio control device for a carburetor engine that supplies fuel with a carburetor provided in an intake passage.

(Prior art) = 1 - Generally, in a carburetor engine, the air-fuel ratio of the mixture supplied to the combustion chamber is set to a constant value by the carburetor, but the setting The value is at high rotation or 1'! i-mouth 11! It is set based on the value required to bring the required output to 1, etc., or to maintain a stable combustion state at low rotation speeds. the/,
- Relatively! In the low load and medium speed range where good driving performance is achieved by a lean air-fuel mixture, the air-fuel mixture becomes unavoidably rich, and fuel is wasted.

To solve this problem, for example, by installing a bypass passage in the intake passage that bypasses the carburetor, and by sucking air from the bypass passage 1) using negative intake pressure, it is possible to create a mixture that is thinner than the air-fuel ratio set by the carburetor. There are ways to get your attention. However, due to this, Dothrowa 1 to Rubal I
When the throttle valve is closed, a large amount of air is sucked in from the bypass passage, but when the throttle valve starts to listen, the amount of air sucked from the bypass passage decreases, so that the air is diluted appropriately over a relatively wide operating range. It is not possible to supply a mixture -2- with a constant air-fuel ratio.

Furthermore, Japanese Utility Model Publication No. 1947/1987 discloses a carburetor that can variably control the air-fuel ratio, but this is mainly used to increase the amount of fuel at high loads, and also to control the amount of fuel. Because it is performed according to the intake negative pressure,
As in the above case, it is not possible to control the air-fuel mixture to a constant lean air-fuel ratio over a wide operating range, for example at low load and medium speed.

By the way, in electronic fuel injection engines, it is relatively easy to control the operating range by dividing the operating range into multiple ranges and setting the air-fuel ratio appropriately in each range, but this is not the case with carburetor-type engines. The structure is significantly more complex and the cost is higher than that of the previous model (disadvantages).

(Object of the Invention) The present invention deals with the above-mentioned actual situation regarding air-fuel ratio control of an engine. It is possible to control the air-fuel ratio to a constant air-fuel ratio which is leaner than the fuel ratio. This results in
The purpose is to improve fuel efficiency by expanding the lean range of the air-fuel ratio without using a complicated structure like an electronic fuel injection engine.

(Structure of the Invention) In order to achieve the above object, the air-fuel ratio control device for a carburetor engine according to the present invention is structured as follows.

That is, a bypass passage is provided in the intake passage that bypasses the carburetor and communicates the atmosphere side with the downstream side of the throttle valve, a throttle is provided in the bypass passage, and a flow passage of the bypass passage is provided on the downstream side. A control valve is provided to increase or decrease the cross-sectional area. Further, adjusting means adjusts the control valve so that the pressure between the d3G in the bypass passage and the control valve becomes a large negative pressure value as the amount of intake air passing through the carburetor increases. Equipped with This adjustment means allows the pressure between the throttle and the control valve to be increased within the bypass passage.
When the negative pressure (negative pressure) is adjusted to correspond to the amount of intake air passing through the carburetor, the amount of bypass air taken in through the bypass passage also corresponds to the amount of intake air passing through the carburetor. Therefore, in the operating range in which the control device operates, the air-fuel ratio is controlled to a constant air-fuel ratio that is leaner than the air-fuel ratio set by the carburetor.

(Example) Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

As shown in FIG. 1, an intake passage 3 leading from the air cleaner 1 to the engine (not shown) via the carburetor 2 communicates between the atmosphere side (air cleaner side) and the downstream side of the throttle valve 4 in the carburetor 2. A bypass passage 5 is provided to allow the air to flow, and this bypass passage 5 is also provided with a throttle 6 and a control valve 7 from the atmospheric side.

In the control valve 7, the diaphragm 7b is displaced in the direction a against the spring 7c by the operating negative pressure P1 introduced into the negative pressure chamber 7a, so that the valve body 7d connected to the diaphragm 7b is connected to the bypass passage 5. It is configured to move so as to increase the opening degree of the through hole 5a that communicates with the upper and downstream sides. -5- Then, the operating angle for introducing the operating negative pressure P1 into the negative pressure chamber 7a!
An earthen passageway 8 is led from the direct position of the throttle valve 4 in the carburetor 2.

However, a negative pressure relief passage 9 is branched from the working negative pressure passage 8, and the opening at the tip thereof is connected to the negative pressure chamber 10 of the negative pressure regulating valve 10.
In a, the diaphragms 10b are opposed to each other with a gap provided in the center thereof. lf' of this negative pressure regulating valve 10! !
A venturi angle pressure passage 11 led from the constriction part 2a of the vaporizer 2 is connected to the passage 10a.
The diaphragm 10b is displaced by the venturi negative pressure P2 introduced into the negative pressure chamber 10a from the opening 1 into the negative pressure chamber 10a in a direction (direction b) that narrows the gap A against the spring 10c.

As a result, the release amount of the working negative pressure P1 supplied to the control valve 7 by the working negative pressure passage 8 is controlled in accordance with the venturi negative pressure P2, and the working negative pressure P1 is adjusted to a value corresponding to the venturi negative pressure P2. , Venturi negative pressure P2
When the negative pressure value of the venturi negative pressure P1 is large, the negative pressure value of the operating negative pressure P1 becomes large because there is little relief, and when the negative pressure value of the venturi negative pressure P1 becomes small, the amount of relief increases and the operating negative pressure P1 becomes large. The negative pressure value of pressure P1 also becomes smaller. Venturi negative pressure P2 is placed on the platform and the carburetor 2
Since it corresponds to the intake air mQ passing through the
1 also corresponds to the intake air IQ.

In the control valve 7, as the negative pressure value of the operating negative pressure P1 increases, the cross-sectional area of the through hole 5a in the bypass passage 5 increases, so that the flow path between the through hole 5a and the throttle 6 increases. The amount of intake negative pressure introduced into the space 12 from the intake passage 3 side increases, and the negative pressure value of the control negative pressure Po in the space 12 increases. In other words, the IIi control negative pressure Po in the space 12 also corresponds to the intake air amount Q passing through the carburetor 2 via the operating negative pressure P1. Here, this control negative pressure Po is introduced into the feedback chamber 10d of the negative pressure regulating valve 10 through the feedback passage 13, and is subjected to feedback control. That is, if the control value of the controlled negative pressure Po is too large, the diaphragm 10b is displaced in a direction that widens the gap = 7 - to reduce the operating negative pressure P1, thereby reducing the controlled negative pressure PO. and the control 11
If the control value of the negative pressure Po is too small, the operating negative pressure P1 decreases, thereby increasing the control negative pressure PO. This J
: In this way, the controlled negative pressure Po corresponds accurately to the intake air IQ.

On the other hand, a three-way switching valve 14 is installed on a negative pressure relief passage 9 that branches off from the working negative pressure passage 8 and reaches a negative pressure regulating valve 10 . Normally, this switching valve 14 communicates the working negative pressure passage 8 side of the relief passage 'tR9 with the negative pressure regulating valve 10 side as shown in the figure.
[When the level switching signal SO is sent, it moves 90 degrees in the 0 direction.]
It is rotated and operates to open the operating negative pressure passage 8 side of the relief passage 9 to the atmosphere. Then, the control unit 15 receives a rotation speed signal @S1 from the engine rotation speed sensor 16, an intake negative pressure signal RS2 from the intake negative pressure sensor 17, and a throttle signal from the throttle opening sensor 18. Water thirst signal I'iS 3, water thirst signal 1'iS a from the engine coolant water temperature sensor 19, and gas water 8
- A low speed gear signal @S5 indicating that the transmission is being shifted to a low speed gear from the transmission 20 is input, and the operating state of the engine is determined based on these signals @81 to $5, and the above switching is performed. Controls the output of signal So.

This control unit 15 is configured as shown in FIG. 2, for example. That is, the first comparison circuit 21 outputs a low rotation signal 81' when the signal S1 from the engine rotation speed sensor 16 is input and the engine rotation speed indicated by the signal @ S1 is less than the first set rotation speed N1 (for example, 101000 RP). and a second comparison circuit 22 which outputs a high rotation signal 81'' when the signal S1 is input and the engine rotation speed is equal to or higher than the second set rotation speed N2 (for example, 3000 PPM), and a signal S2 from the intake negative pressure sensor 17. is input and the intake negative pressure is on the atmospheric side than the set negative pressure P (for example, -400vnH!J), the third comparison circuit 23 outputs the high load signal S2', and the signal S3 from the throttle opening sensor 18 a differentiation circuit 24 that receives input and calculates the rate of change in throttle opening;
A fourth comparison circuit 25 outputs an acceleration signal 83'' when the -9- output mark 83' of the differentiating circuit 24 is equal to or higher than a set value, that is, when the throttle opening is heard at a constant speed or higher, and Faith from Lensa 19 jj
A fifth comparison circuit 26 outputs a low-drying signal S4' when S4 is input and the engine cooling water temperature is below the set temperature.
and have. , and at least one of the low rotation signal 81', the high rotation signal 81'', the high load signal 82', the acceleration signal 83'', the low temperature signal 84', and the low speed gear signal 85 from the gas switch 20 is set to one torque. 1 level, the switching signal SO of level 111j is sent to the three-way switching valve 14 via the OR circuit 27.

Next, the operation of the embodiment will be explained.

First, the operating range of engine speed and intake negative pressure is the non-shaded area in Fig. 3, that is, the low speed range (below the first set speed N1).
, high rotation td (second set rotation speed N2 or more), or high load range (atmospheric side than the set negative pressure P), the control unit 15 outputs a low rotation signal 81', a high rotation signal 81'', or a high rotation signal 81''. -10- Since at least one of the load signals 82' is at the rl-IJ level, a switching signal @So at the rHJ level is sent from the control unit 15 to the three-way switching valve 14, and the switching valve 14 releases negative pressure. The working negative pressure passage 8 side of the passage 9 is open to the atmosphere.Therefore, the working negative pressure P1 in the working negative pressure passage 8 is released, and the working negative pressure P1 is in the negative pressure chamber 7a of the control valve 7. Therefore, in the control valve 7, the diaphragm 7b is pushed by the spring 7C and the valve body 7
d is in a state where the through hole 5a is closed.

In this case, since the bypass passage 5 is blocked, all the air taken into the engine passes from the air cleaner 1 through the carburetor 2 on the intake passage 3, corresponding to the intake air amount Q. The vaporizer 2 injects and supplies dark fuel. As a result, the air-fuel mixture adjusted to a predetermined set air-fuel ratio (for example, air (A)/fuel (F) = 14.7) is supplied to the engine.

Also, when the engine operating range is in the shaded area in Fig. 3, that is, in the low load and medium rotation range, when the throttle opening is increasing at a rate of change or higher, When the cold fJI water temperature is below a certain level or when the transmission is shifted to a low gear, the control unit 15 outputs one or more of the acceleration signal 83'', the low temperature signal 84', or the low gear signal 85. Tsui”-ga r l-
Since it is at the IJ level, the control unit l-15 switches the three-way switching valve 14 to WA (i'i @S
o is sent. Therefore, in this case as well, the air-fuel ratio of the air-fuel mixture supplied to the engine is set to the air-fuel ratio set by the carburetor 2 (A/I==14.7) as in the above case.

Here, in the low load medium rotation range, the air-fuel ratio of the mixture may be set to a value leaner (for example, A/F = 18.0) than the J-set air-fuel ratio (A/F = 14.7). The operating performance is 1q, but the set air fuel ratio in each of the above cases is:
This is because if the air-fuel mixture is lean, combustibility will deteriorate when the cooling water temperature is low, and acceleration response will deteriorate during acceleration.

Also, when the transmission is shifted to a low gear, it is often during acceleration, and generally the amount of air-fuel mixture is -
This is because when the air-fuel mixture becomes thinner in the low angle load/high rotation range where combustibility tends to deteriorate due to the small amount of 12-, combustibility deteriorates further.

However, if the engine operating range is in the low load/medium rotation range shown in Figure 3, the engine is not accelerating, the cooling water temperature is not low, and the transmission is shifted to a gear other than low speed, the control In unit 15, OR
Signals S++', Sl", 82' input to the circuit 27
, 83", 84'.

Since all of S5 are at the rLJ level, the three-way switching valve 14
The switching signal @SO sent to is also at the rLJ level. Therefore, the three-way switching valve 14 communicates the working negative pressure passage 8 side of the negative pressure relief passage 9 with the negative pressure regulating valve 10 side.

In this case, an operating angle rfP1 is introduced from the carburetor 2 into the negative pressure chamber 7a of the control valve 7 by the operating negative pressure passage 8, but this operating negative pressure P1 is applied to the venturi negative pressure P2 in the negative pressure regulating valve 10. The released acid is controlled accordingly, and the negative pressure value is adjusted to a value corresponding to the intake air amount Q passing through the carburetor 2. Along with this, the opening degree of the through hole 5a in the bypass passage 5, that is, the amount of negative pressure introduced into the space 12 is adjusted by the action of the control valve 7, and as a result, the control valve 611 M in the space 12 is adjusted.
In I-cho P o, the negative pressure 1st shift also corresponds to the above air amount Q. This control negative pressure 1)0 is caused by the pressure 1) of the throttle 6 in the bypass passage 5. This is a pressure difference between the flow side (atmosphere side) and the downstream side (space 12 side), and air is drawn from the atmosphere side to the space 12 side through the throttle 6 in proportion to this pressure difference. Then, this flows into the intake passage 3 as bypass air to dilute the air-fuel mixture, but as described above, the control negative pressure Po
Since this corresponds to the amount Q of intake air passing through the carburetor 2, IQ' of this bypass air also corresponds to the intake air IQ. This correspondence relationship is maintained even if the intake air IQ changes according to the opening degree of the throttle valve 4, so that the air-fuel mixture adjusted to the set air-fuel ratio (Δ/F = 14.7) by the carburetor 2 is When diluted by the confluence of bypass air, a constant air-fuel ratio (
For example, it will be adjusted to A/F=18.0>.

-14- In this way, a lean air-fuel ratio region is provided in the low-load, medium-speed rotation region where the required operating performance can be obtained even with a lean air-fuel mixture.

In this embodiment, the working negative pressure passage 8 is connected to the carburetor 2.
Since the operating negative pressure P1 is introduced from the position immediately upstream of the throttle valve 4 at , the operating negative pressure P1 is supplied to the control valve only when the throttle valve 4 is open. Therefore, when the throttle valve 4 is fully opened, the air-fuel ratio is set to the air-fuel ratio set by the carburetor 2, regardless of the control by the control unit 15.

(Effects of the Invention) As described above, according to the present invention, in a carburetor engine, it is possible to reach an operating range in which the required operating performance can be obtained even with a mixture leaner than the mixture at the set air-fuel ratio adjusted by the carburetor. ,
A region is provided over a relatively wide range in which the air-fuel mixture is adjusted to a constant air-fuel ratio thinner than the set air-fuel ratio. This makes it possible to effectively improve fuel efficiency even in the case of an engine using a carburetor, which has a simple structure and is low in cost. In particular, according to the present invention, it is possible to cope with the expansion of the range in which the air-fuel mixture can be diluted due to the recent trend of increasing the compression ratio.

In addition, as an adjustment means for adjusting the operating negative pressure of the control valve according to the present invention to correspond to the intake air passing through the carburetor (6),
-Negative ITL shown in the above embodiment: In addition to the valve regulation a, other means such as electrical means may be used.

[Brief explanation of the drawing]

The drawings (showing an embodiment of the present invention; FIG. 1 is a control system diagram, FIG. 2 is a block diagram showing an example of the configuration of the control unit 1-1, and FIG. 3 is a graph showing the control area). 2... Carburetor, 3... Intake passage, 4... Throttle valve, 5... Bypass passage, 6... Throttle, 7...
... illumination valve, 9.10, 11.13 ... adjustment means (9 ... negative pressure relief passage, 10 ... negative pressure regulating valve, 11
... Pengu 1 negative pressure passage, 13... Feedback passage) -16- N, N. Engineering line→

Claims (1)

[Claims] (1) A bypass passage that bypasses the carburetor in the intake passage and communicates the atmosphere side with the downstream side of the throttle valve, a restriction provided in the bypass passage, and a passage provided downstream of the restriction in the bypass passage. The control valve is adjusted so that the pressure between the control valve that controls increasing and decreasing the cross-sectional area, the throttle and the control valve in the bypass passage becomes a large negative pressure value as the amount of intake air passing through the carburetor increases. An air-fuel ratio control device for a carburetor engine, comprising an adjusting means.