JPS5888447A - Correction device for air-fuel ratio of engine - Google Patents

Abstract

PURPOSE:To prevent in advance the lowering of purification efficiency of exhaust gas for those with a deceleration richer to enrich the air-fuel ratio of mixture at the deceleration of an engine by correcting the air-fuel ratio of the mixture to a lean side when a choke is operated and the speed is decelerated. CONSTITUTION:When an engine 1 is started at the time of low temperature, a choke valve 6 is completely closed by an unillustrated bimetal. When the engine 1 is perfectly ignited, the suction negative pressure in a suction passage 2 in the downstream of a throttle valve 5 is led to a diaphragm device 22 via a passage 24, and thereby, this valve 6 is opened at a fixed degree via a diaphragm 22a and a rod 22h. Under this condition, when the speed is decelerated during driving, the air-fuel ratio is shifted to an excessively rich side by the function of a deceleration richer in an air-fuel ratio control circuit 33 via a solenoid valve 17. But, at the same time, the suction negative pressure is also introduced into the second negative pressure chamber 22e via a cross valve 25, and the choke valve 6 is further opened via a diaphragm 22d and a rod 22h for restraining the excessive enrichment of air-fuel mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio correction device for an engine that operates during choke operation and during deceleration.

Conventionally, as shown in Jikko Sho Guar 2-15, for example, there has been a choke valve that operates depending on the engine temperature, and a deceleration richer that enriches the air-fuel ratio of the mixture supplied to the engine when the engine is decelerating. Engine air-fuel ratio control devices (carburetors) are known, but in such air-fuel ratio control devices, the air-fuel ratio of the mixture supplied to the engine becomes too rich when the choke is activated and during deceleration. However, there is a problem in that it adversely affects exhaust purification performance and fuel efficiency.

In other words, the choke valve enriches the air-fuel ratio by closing the intake passage when the engine is cold, thereby improving startability and warm-up performance at low temperatures.On the other hand, the deceleration richer closes the air-fuel mixture when the engine is decelerating. The purpose is to increase the ignition rate by enriching the air-fuel ratio of the engine, suppress the emission of unburned components, and improve drivability. In addition to the air-fuel ratio becoming richer, the air-fuel ratio becomes richer due to the operation of the deceleration richer, resulting in a mixture that is too rich for the engine's required air-fuel ratio.
A large amount of unburned components are discharged into the exhaust system, deteriorating the exhaust purification performance, and in combination with the supply of secondary air, the catalyst device is damaged due to the reaction of a large amount of unburned components. The temperature of the fuel cell increases excessively, deteriorating its durability, and the fuel efficiency also deteriorates.

In view of this, the present invention provides an air-fuel ratio correction device for an engine, which includes an air-fuel ratio adjustment device that corrects the air-fuel ratio of the air-fuel mixture supplied to the engine to the lean side during choke operation and deceleration. The purpose is to prevent the supply of an overly rich air-fuel mixture to protect the exhaust purification device, and to improve exhaust purification performance and fuel efficiency.

Embodiments of the present invention will be described below with reference to the drawings.

This embodiment basically consists of an exhaust sensor (
02 The air-fuel ratio of the mixture is detected by Sensoro 2, and the air-fuel ratio of the mixture supplied to the engine is controlled by controlling the duty ratio of the solenoid valve of the carburetor, which adjusts the amount of fuel supply and bleed air accordingly. This is an electronically controlled air-fuel ratio control device that performs feedback control on the stoichiometric air-fuel ratio. - A deceleration richer function that controls the solenoid valve at a preset fixed duty ratio to enrich the air-fuel ratio of the air-fuel mixture by stopping the feedback control during deceleration (the above-mentioned feedback control) to make the air-fuel mixture a predetermined rich air-fuel ratio. Furthermore, the feedback control is stopped even when the engine temperature or outside temperature is lower than the set value, and the feedback control is fixed in advance according to the engine temperature, outside temperature, and operating condition (intake negative pressure and engine rotation speed). The solenoid valve of the carburetor is controlled by the duty ratio, and the air-fuel mixture is adjusted to a rich air-fuel ratio throughout.The choke valve operates and is almost fully closed during deceleration. This is an example of an air-fuel ratio correction device that corrects the air-fuel ratio to the lean side by using an air-fuel ratio adjustment device that opens to a predetermined opening degree, and the air-fuel ratio adjustment device also has a choke valve complete explosion correction function. During deceleration, the choke valve was opened even wider due to complete explosion compensation.

In FIG. 1, 1 is an engine, 2 is an intake passage of the engine 1, and a carburetor 3 is interposed in the intake passage 2. In FIG. The carburetor 3 has a throttle valve 5 on the downstream side of the venturi section 4, and has a choke valve 6 on the upstream side of the venturi section 4 that is operated depending on the temperature by a bimetal (not shown).

Further, in the carburetor 3, 7 is a main fuel passage that supplies the fuel in the float chamber 8 to the main nozzle 10 of the venturi section 4 via the main jet 9, and 11 is the main fuel passage 7.
A main air bleed 12 mixes air upstream of the venturi section 4 into the main fuel passage 7, and a slow port 13 and an idle port 12 branch from the main fuel passage 7 (not shown) and open the fuel into the intake passage 2 near the throttle valve 5. 14, a slow fuel passage 15 supplies the venturi portion 4 to the slow fuel passage 12;
This is a Neslo air bleed that mixes upstream air. still,
16 is an idle adjustment screw.

Furthermore, 17 is a solenoid valve that can adjust the air-fuel ratio of the air-fuel mixture supplied to the engine 1 independently of the opening and closing of the throttle valve 5 in the carburetor 3, and the solenoid valve 17 is connected to an air-fuel ratio control circuit 6 to be described later.
Auxiliary fuel passage 1 according to the duty ratio control signal from 6
8 and the auxiliary air bleed passage 19. That is, the auxiliary twisting material passage 18 supplies the main fuel passage 7 on the downstream side of the main jet 9 via the fuel main auxiliary jet 20 of the float chamber 8, while the auxiliary air bleed passage 19 supplies air upstream of the venturi section 4 to slow air. The solenoid valve 17 supplies the slow fuel passage 12 downstream of the bleed 15, and the solenoid 17a? The valve body 17 operates according to the applied duty ratio control signal.
The first valve portion 17C at one end (lower end) of the valve body 17b opens and closes the auxiliary fuel passage 18, and the second valve portion 17d at the other end (upper end) of the valve body 17b opens and closes the auxiliary air bleed passage 19. It is something to do. Note that when the duty ratio of the duty ratio control signal from the air-fuel ratio control circuit 36 is a small value, the valve body 17b of the solenoid valve 17 increases the opening degree of the auxiliary fuel passage 18 and decreases the opening degree of the auxiliary air bleed passage 19. When the duty ratio is large, the valve body 17b of the solenoid valve 17 operates in the opposite manner to reduce the air supply amount. This increases the air-fuel ratio of the air-fuel mixture supplied to the engine 1.

Further, 21 is an air-fuel ratio adjustment device attached to the choke valve 6 of the carburetor 3, and the air-fuel ratio adjustment device 21 slightly opens the choke valve 6, which is in a fully open state after the engine 1 has completely exploded, by a set opening degree. In addition to performing complete explosion correction, during deceleration, the choke valve 6, which is at the complete explosion correction opening, is further opened by a predetermined opening to perform air-fuel ratio correction.

The air-fuel ratio adjusting device 21 has a diaphragm device 22, and in the diaphragm device 22, 22a is the atmospheric chamber 2.
2b,! ? A first diaphragm 2.2d partitions the first negative pressure chamber 22c and the second negative pressure chamber 22.
22f is a first spring compressed into the first negative pressure chamber 22c, 22q is a second spring compressed into the second negative pressure chamber 22e, and 22h is a second diaphragm compressed into the first diaphragm. The rod 22i, whose proximal end is supported, is connected to the second diaphragm 22 opposite to the proximal end of the rod 22h.
A contact member 2'2m is fixed to the first diaphragm 22a and controls the most forward position of the rod 22h, and a contact member 22n is a first stopper fixed to the rod 22h. The rod 2 is connected by the contact member 22i.
The second stopper 22p stops the rod 2h at the complete explosion correction position, and the third stopper 22p is fixed to the second diaphragm 22d and restricts the most retracted position of the rod 22h. Further, the tip of the rod 22h is connected to the tip of a rotating lever 23 that is linked to the valve shaft 6a of the choke valve 6.

The first negative pressure chamber 22c of the diaphragm device 22 is connected to the other end of a negative pressure passage 24 whose one end opens to the intake passage 2 downstream of the throttle valve 5, and the second negative pressure chamber 22e is connected to the negative pressure passage 24. are connected via a three-way solenoid valve 25, and the three-way solenoid valve 25 normally connects the second negative pressure chamber 22e to the atmosphere opening 25a in response to a drive signal from an air-fuel ratio control circuit 63, which will be described later. During deceleration, the air opening 25a is closed and the second negative pressure chamber 22e is connected to the negative pressure passage 24.

The air-fuel ratio adjusting device 21 regulates the minimum opening degree of the choke valve 6, and is constructed so as not to restrict the choke valve 6 from being opened more than this minimum opening degree using a bimetal or the like.

On the other hand, 26 is an exhaust passage of the engine 1, and the exhaust passage 26 is connected from the upstream side to a reburning device 27, a three-way catalyst 28 (
A secondary air supply passage 30 that supplies secondary air from an air pump 29 is connected to the upstream side of the reburning device 27, and the secondary air supply passage 60 is connected to a control valve 31. It is opened and closed by - Also, the reburning device 27 of the exhaust passage 26 and the three-way catalyst 2
A 02 sensor 32 is provided between the 8 and 8. This 0
The 02 sensor 32 detects the oxygen concentration in the exhaust gas and outputs a signal correlated with the air-fuel ratio of the intake air-fuel mixture.
3, and the air-fuel ratio control circuit 33 receives the output signal of the 02 sensor 32, the intake negative pressure signal S1, the engine speed signal S2, the cooling water temperature signal S3, and the outside air temperature signal S4. , the control valve 31 of the secondary air supply passage 60, and the three-way solenoid valve 25 of the air-fuel ratio adjusting device 21, respectively.

In the air-fuel ratio control circuit 33, 64 is the 02 sensor 6
The duty ratio control circuit 34 receives the output signal of the 02 sensor 32 and outputs the duty ratio signal of the solenoid valve 17 so that the air-fuel ratio detected by the 02 sensor 32 becomes the stoichiometric air-fuel ratio. Ratio control circuit 34
The output signal is outputted to the solenoid valve 17 of the carburetor 3 via the switching circuit 35, the discrimination circuit 36, and the -drive circuit 37. The switching circuit 65 receives a signal from a deceleration detection surface path 68 that detects the deceleration state of the engine 1 from the intake negative pressure signal S1 and the engine rotational speed signal S2, and when decelerating, outputs an output signal to the discrimination circuit 36 to the duty ratio control circuit. 34 to a signal from a fixed duty ratio generating circuit 39, and the fixed duty ratio generating circuit 69 is fixed at a small value (for example, 20%) in order to make the air-fuel ratio during deceleration richer than the stoichiometric air-fuel ratio. This outputs a duty ratio signal.

The discrimination circuit 66 receives the cooling water temperature signal S3 and the outside air temperature signal S4, and determines whether the cooling water temperature is a set value (for example, 5θ°C).
), or when the outside air temperature is below a set value (for example, /j °C), in other words, at low temperatures, the duty ratio is The output signal of the determination circuit 40 is output to the drive circuit 37. The duty ratio determining circuit 40 is configured to set a duty ratio in advance according to the operating state from a control map as shown in FIG. The map selection circuit 41 is used to select a map within a predetermined temperature range from several maps preset for the values of the cooling water temperature signal S6 and the outside air temperature signal S4. be.

The map shown in Figure 2 shows the cooling water temperature force! It is set under the conditions that jθ℃ or less and the outside air temperature is 7.5℃ or less. In this map, the set duty ratio in deceleration area A is set to a small value to enrich the air-fuel ratio, It has a deceleration richer function.

The output signal of the deceleration detection circuit 68 is input to the control valve 31 of the secondary air supply passage 30 to control its opening/closing, and from this secondary air supply passage 60, as shown in FIG. A and low rotation range B have secondary air in exhaust passage 2.
6.

Further, the output signal of the deceleration detection circuit 68 is inputted to the choke drive circuit 42 together with the engine rotation speed signal S2,
The drive signal power from the choke drive circuit 42! The input signal is input to the three-way solenoid valve 25 of the air-fuel ratio adjusting device 21, and as shown in FIG. Intake negative pressure is introduced into the negative pressure n22e.

Next, to explain the operation of the above embodiment, when starting the engine 1 at a low temperature, the choke valve 6 is in a fully closed state, and when the engine 1 completely explodes and starts rotating, the throttle valve 5 downstream The intake negative pressure generated in the intake passage 2 is transferred to the negative pressure passage 2.
4 into the first negative pressure chamber 22C of the diaphragm device 22.

Therefore, the first diaphragm 22a is connected to the first spring 22.
The rod 22h is displaced against the force 22h until it contacts the contact member 221, and the choke valve 6 is opened by a predetermined opening degree from the fully closed state to perform a complete explosion correction, which increases the amount of intake air and the air-fuel ratio. Move to the dilute side.

After the above-mentioned complete explosion correction is performed, when the engine 1 enters the operating state and enters the deceleration state, the deceleration richer function of the air-fuel ratio control circuit 33 outputs a control signal with a small duty ratio to the solenoid valve 17, causing the engine to decelerate. Together with the operation of the choke valve 6, the fuel ratio becomes rich and shifts to a superrich state, but at the time of deceleration, the drive signal of the choke drive circuit 42 is applied to the three-way renoid valve 25.
is input into the second negative pressure chamber 22e of the diaphragm device 22.
Intake negative pressure of the negative pressure passage 24 is introduced into the negative pressure passage 24 . Therefore, the second diaphragm 22d is displaced in the backward direction against the second spring 22q, and the rod 22h is also moved backward accordingly, and the choke valve 6 is further opened by a predetermined opening degree from the complete explosion correction opening degree, and the suction The air amount further increases, the air-fuel ratio is corrected to the lean side, and supply of an overly rich mixture is suppressed.

In the above embodiment, an example of the air-fuel ratio adjusting device 21 that increases the opening degree of the choke valve 6 to dilute the air-fuel ratio is shown, but the present invention is not limited to this. An air-fuel ratio adjustment device may be adopted that detects the activation time and dilutes the air-fuel ratio by narrowing the fuel passage or changing the duty ratio during deceleration. However, in the above embodiment, the air-fuel ratio adjustment device Since it is not necessary to detect μ, the structure has the advantage of being simple.

Further, in the above embodiment, a correction device for an air-fuel ratio control device using a feedback control method is explained, but the present invention is also applicable to an air-fuel ratio control device that does not have such a feedback control function. be.

Therefore, according to the present invention as described above, an air-fuel ratio adjustment device is provided which corrects the air-fuel ratio of the air-fuel mixture supplied to the engine to the lean side when the choke valve and the deceleration richer are activated, that is, when the choke is activated and when the engine is decelerated. This prevents the supply of a mixture that is too rich for the engine's required air-fuel ratio, and prevents a decline in exhaust gas purification performance and fuel consumption performance due to large amounts of unburned components being discharged into the exhaust system. In particular, it is possible to prevent early deterioration of the catalyst device due to overheating.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is an overall configuration diagram;
Fig. 2 is a diagram showing an example of a control map in the air-fuel ratio control circuit, Fig. 3 is a diagram showing an example of the supply timing of secondary air, and Fig. 3 is a diagram showing an example of the operation timing of the air-fuel ratio adjustment device. It is a line diagram. 1...Engine, 2...Intake passage, 6
... Carburizer, 4 ... Venturi section, 5
... Throttle valve, 6... Choke valve, 7...
...Main fuel passage, 11... Main air boolean lead, 12... Slow fuel passage, 15...
... Slow air bleed, 17 ... Solenoid valve, 18 ... Auxiliary fuel passage, 19 ... Auxiliary air bleed passage, 21 ... Air-fuel ratio Adjustment device, 22...Diaphragm device, 24...
・Negative pressure passage, 25...Three-way solenoid valve, 26
...exhaust passage, 27...reburner,
28... Three-way catalyst, 30... Secondary air supply passage, 31... Control valve, 642...
・02 sensor, 339. -, -Air-fuel ratio control circuit

Claims (1)

[Claims] V) In an air-fuel ratio control device equipped with a choke valve that operates according to the engine temperature, a deceleration IJ that enriches the air-fuel ratio of the air-fuel mixture supplied to the engine when the engine is decreasing, 1. An air-fuel ratio correcting device for an engine, characterized in that an air-fuel ratio adjusting device is provided for correcting the air-fuel ratio of an air-fuel mixture supplied to the engine during deceleration to a leaner side.