JPS6319702B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an air-fuel ratio correction device for an engine.

(Prior art) Conventionally, as shown in Japanese Utility Model Publication No. 47-29154, for example, there has been a system that uses a choke valve that operates depending on the engine temperature and enriches the air-fuel ratio of the air-fuel mixture supplied to the engine when the engine is decelerating. Engine air-fuel ratio control device (carburetor) equipped with a reduction richer
is generally known.

(Problems to be Solved by the Invention) In such an air-fuel ratio control device, the air-fuel ratio of the air-fuel mixture supplied to the engine becomes too rich when the choke valve is closed and during deceleration, resulting in poor exhaust purification performance. It has problems that adversely affect fuel efficiency.

That is, the above-mentioned chioke valve closes the intake passage when the engine is cold, thereby increasing the air-fuel ratio and improving startability and warm-up performance at low temperatures. On the other hand, a reduction richer enriches the air-fuel ratio of the air-fuel mixture during engine deceleration to increase the ignition rate, suppress emissions of unburned components, and improve driveability. Therefore, when the engine is cold and the engine is decelerating, the air-fuel ratio of the mixture becomes richer due to the operation of the choke valve, and the air-fuel ratio becomes richer due to the operation of the deceleration richer.
A mixture that is too rich for the engine's required air-fuel ratio will be supplied, and a large amount of unburned components will be discharged into the exhaust system, deteriorating the exhaust purification performance. Combined with the supply of secondary air, the temperature of the catalyst device rises excessively due to the reaction of a large amount of unburned components, which deteriorates its durability and has the problem of deteriorating fuel efficiency. be.

(Means for solving the problems) The present invention, as a means for solving the above problems,
Air-fuel ratio equipped with a choke valve that closes depending on the engine temperature and enriches the air-fuel ratio of the air-fuel mixture at low temperatures, and a reduction enricher that enriches the air-fuel ratio of the air-fuel mixture supplied to the engine when the engine decelerates. In the control device, an air-fuel ratio adjusting device is provided which corrects a position corresponding to the engine temperature of the chiyork valve during the closing operation in a direction in which the opening degree of the chiyork valve increases only during the deceleration. The present invention provides a fuel ratio correction device.

(Function) In the above air-fuel ratio correction device, when the engine is in a low-temperature state and the choke valve is closed, when the engine enters deceleration operation, the deceleration richer operates, but at the same time the opening of the choke valve increases. As a result, the amount of intake air increases, and the air-fuel ratio of the air-fuel mixture is corrected to the lean side.

(Effects of the Invention) Therefore, according to the present invention, an air-fuel ratio adjustment device is provided that corrects the position corresponding to the engine temperature during the closing operation of the Chiyork valve in a direction in which the opening degree of the Chiyork valve increases when the engine decelerates. Therefore, it prevents the supply of a mixture that is too rich for the engine's required air-fuel ratio, and reduces the deterioration of exhaust gas purification performance and fuel efficiency due to large amounts of unburned components being discharged into the exhaust system.
It is possible to prevent premature deterioration of the catalyst device due to overheating, and since the air-fuel ratio is corrected to the lean side by increasing the opening of the chiyork valve, there is no need to separately detect the operation of the chiyork valve. The structure of the air-fuel ratio correction device can be simplified.

(Example) Examples of the present invention will be described below with reference to the drawings. This embodiment basically uses an exhaust sensor ( _O2 sensor) installed in the exhaust system to detect the air-fuel ratio of the air-fuel mixture, and adjusts the fuel supply amount and bleed air amount according to this detection signal. This is an electronically controlled air-fuel ratio control device that controls the duty ratio of a solenoid valve to feed back the air-fuel ratio of the air-fuel mixture supplied to the engine to the stoichiometric air-fuel ratio. It has a choke valve that closes at low temperatures due to the action of Equipped with a deceleration richer function to maintain a predetermined rich air-fuel ratio,
The feedback control is also stopped when the engine temperature or outside temperature is lower than the set value, and is controlled by a fixed duty ratio set in advance according to the engine temperature, outside temperature, and operating conditions (intake negative pressure and engine speed). It is configured to control the solenoid valve of the carburetor to adjust the air-fuel mixture to an overall rich air-fuel ratio. In this embodiment, the air-fuel ratio is leanened by the air-fuel ratio adjustment device which opens the chi-yok valve to a larger extent than the opening degree of the complete explosion correction, which will be described later, when the chi-yok valve operates and decelerates. This figure shows an example of an air-fuel ratio correction device that corrects the air-fuel ratio to the side.

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 bench lily portion 4.
On the upstream side of the engine, a bimetallic valve 6 (not shown) is provided which operates according to the engine temperature.

Further, in the carburetor 3, 7 is a main fuel passage that supplies fuel from the float chamber 8 to the main nozzle 10 of the bench lily portion 4 via the main jet 9;
11 is a main air bleed that mixes air upstream of the bench lily portion 4 into the main fuel passage 7; 12 is a main air bleed that branches off from the main fuel passage 7 (not shown) and opens the fuel into the intake passage 2 near the throttle valve 5; slow port 13
A slow fuel passage 15 that supplies the idle port 14 is a slow air bleed that mixes air upstream of the bench lily portion 4 into the slow fuel passage 12. Note that 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. The auxiliary fuel passage 18 and the auxiliary air bleed passage 19 are configured to open and close in accordance with the ratio control signal. That is, the auxiliary fuel passage 18 supplies the fuel in the float chamber 8 to the main fuel passage 7 on the downstream side of the main jet 9 via the auxiliary jet 20, while the auxiliary air bleed passage 19 supplies the air upstream of the bench lily portion 4 to the slow air bleed 15. The solenoid valve 17 is a first valve at one end (lower end) of a valve body 17b that is operated in response to a duty ratio control signal applied to a solenoid 17a.
The auxiliary fuel passage 18 is opened and closed by the valve part 17c, and the auxiliary air bleed passage 19 is opened and closed by the second valve part 17d at the other end (upper end) of the valve body 17b. Note that when the duty ratio of the duty ratio control signal from the air-fuel ratio control circuit 33 is a small value, the valve body 17b of the solenoid valve 17 increases the opening degree of the auxiliary fuel passage 18, and the auxiliary air bleed passage 1
9 is decreased to increase the amount of fuel supplied and enrich the air-fuel ratio of the air-fuel mixture supplied to the engine 1. On the other hand, when the duty ratio is a large value, the valve body 17b of the solenoid valve 17 is operated in the opposite manner to the above. It operates to increase the air supply amount and thin the air-fuel ratio of the air-fuel mixture supplied to the engine 1.

Further, 21 is an air-fuel ratio adjusting device attached to the choke valve 6 of the carburetor 3, and the air-fuel ratio adjusting device 21 serves as an actuator for operating the choke valve 6, and the air-fuel ratio adjusting device 21 is set to a fully closed state after the complete explosion of the engine 1. A complete explosion correction means is used that slightly opens a certain throttle valve 6 by a set opening degree, and during deceleration, the stopper that regulates the throttle valve 6 to the complete explosion compensation opening position increases the opening of the throttle valve 6. The air-fuel ratio is corrected by moving the air-fuel ratio in this direction.

The air-fuel ratio adjusting device 21 is a diaphragm device 2
2, and in the diaphragm device 22, 2
2a is a first diaphragm that partitions an atmospheric chamber 22b and a first negative pressure chamber 22c; 22d is a first diaphragm 22;
22f is a first spring compressed into the first negative pressure chamber 22c; 22g is a second spring compressed into the second negative pressure chamber 22e; 22h is a rod whose base end is supported by the first diaphragm, and 22i is a second diaphragm 2 opposite to the base end of the rod 22h.
A contact member 2d is fixed to the rod 2d, a first stopper 22m is fixed to the first diaphragm 22a and restricts the most advanced position of the rod 22h, and a contact member 22n is a contact member 22i that restricts the forward displacement position of the second diaphragm 22d. The second stopper 22p that stops the rod 22h at the complete explosion correction position is a third stopper that 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 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, one end of which opens to the intake passage 2 downstream of the throttle valve 5, and a second negative pressure chamber 22e.
The negative pressure passage 24 is connected via a three-way solenoid valve 25, and the three-way solenoid valve 25 normally opens the second negative pressure chamber 22e to the atmosphere opening 25a in response to a drive signal from an air-fuel ratio control circuit 33, which will be described later. On the other hand, when decelerating, the atmosphere opening 25a is closed and the second
It operates to connect the negative pressure chamber 22e to the negative pressure passage 24.

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

On the other hand, 26 is the exhaust passage of the engine 1,
The exhaust passage 26 is provided with a reburning device 27 from the upstream side.
A three-way catalyst 28 (catalyst device) is interposed, and 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. 30 is opened and closed by a control valve 31.

Further, an O ₂ sensor 32 is provided between the reburning device 27 and the three-way catalyst 28 in the exhaust passage 26 . This O ₂ sensor 32 detects the oxygen concentration in the exhaust gas _and outputs a signal that is correlated with the air-fuel ratio of the intake air-fuel mixture. and the air-fuel ratio control circuit 33 controls the O ₂ sensor 32.
, the intake negative pressure signal S ₁ , the engine speed signal S ₂ , the cooling water temperature signal S ₃ , and the outside air temperature signal S ₄ , the solenoid valve 17 of the carburetor 3 and the secondary air supply passage 30 are activated. Control valve 31 and air-fuel ratio adjustment device 2
The three-way solenoid valves 25 of 1 are controlled respectively.

In the air-fuel ratio control circuit 33, 34 is O ₂
A duty ratio control circuit receives the output signal of the sensor 32, and the duty ratio control circuit 34 outputs a duty ratio signal of the solenoid valve 17 so that the air-fuel ratio detected by the O ₂ sensor 32 becomes the stoichiometric air-fuel ratio. The output signal of the duty ratio control circuit 34 is outputted to the electromagnetic valve 17 of the carburetor 3 via a switching circuit 35, a discrimination circuit 36, and a drive circuit 37. The switching circuit 35 receives a signal from a deceleration detection circuit 38 that detects the deceleration state of the engine 1 from the intake negative pressure signal S ₁ and the engine rotation speed signal S ₂ , and controls the duty ratio of the output signal to the discrimination circuit 36 during deceleration. circuit 3
4 to the signal of the fixed duty ratio generating circuit 39.
Reference numeral 9 outputs a duty ratio signal 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.

The discrimination circuit 36 receives the cooling water temperature signal S ₃ and the outside air temperature signal S ₄ , and when the cooling water temperature is below a set value (for example, 50°C) or the outside air temperature is below a set value (for example, 15°C). At certain times, that is, at low temperatures, the output signal of the duty ratio determining circuit 40 is output to the drive circuit 37 in place of the output signal of the switching circuit 35 in order to make the air-fuel ratio richer than the stoichiometric air-fuel ratio. This duty ratio determining circuit 40
is the intake negative pressure signal S ₁ and the engine speed signal S ₂
Corresponding to this, a duty ratio preset according to the operating condition is determined from a control map as shown in FIG. 2, which is selected by a map selection circuit 41. A map in a predetermined temperature range is selected from several types of maps preset for the values of the signal _S3 and the outside temperature signal _S4 . The map shown in Fig. 2 was set under the conditions that the cooling water temperature was 50°C or lower and the outside air temperature was 15°C or lower. It is set to a small value to make it darker, and has a deceleration richer function.

The output signal of the deceleration detection circuit 38 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 30, as shown in FIG. A and low rotation range B are configured so that secondary air is supplied to the exhaust passage 26.

Further, the output signal of the deceleration detection circuit 38 is sent to the engine speed signal S 2 as well as the engine rotation speed signal S ₂ .
A drive signal from the yoke drive circuit 42 is input to the three-way solenoid valve 25 of the air-fuel ratio adjusting device 21, and the three-way solenoid valve 25
As shown in Fig. 4, the deceleration area above the specified rotation speed
It operates upon receiving a drive signal at A', and the second negative pressure chamber 22
This is to introduce negative intake pressure to e.

Next, to explain the operation of the above embodiment, when starting the engine 1 at a low temperature, the throttle valve 6 is in a fully closed state, and when the engine 1 completes explosion and starts rotating, the throttle valve 5 downstream Intake negative pressure generated in the intake passage 2 is introduced into the first negative pressure chamber 22c of the diaphragm device 22 via the negative pressure passage 24.
Therefore, the first diaphragm 22a resists the first spring 22f, and the rod 22h presses against the abutting member 22i.
The combustion valve 6 is displaced from a fully closed state to a predetermined opening degree to perform a complete explosion correction, and the amount of intake air increases and the air-fuel ratio shifts to the lean 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, and the air-fuel ratio changes. Coupled with the operation of the yoke valve 6, the state shifts to an overconcentrated state, but during the above deceleration, the yoke drive circuit 42
A drive signal is input to the three-way solenoid valve 25,
The intake negative pressure of the negative pressure passage 24 is introduced into the second negative pressure chamber 22e of the diaphragm device 22. Therefore, the second diaphragm 22d is displaced in the backward direction against the second spring 22g, the rod 22h is also moved backward accordingly, and the choke valve 6 is further opened by a predetermined opening degree from the full explosion correction opening degree. The intake air amount further increases, the air-fuel ratio is corrected to the lean side, and supply of an overly rich mixture is suppressed.

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

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; 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, and FIG. 3 is an example of the supply timing of secondary air. FIG. 4 is a diagram showing an example of the operating timing of the air-fuel ratio adjusting device. DESCRIPTION OF SYMBOLS 1... Engine, 2... Intake passage, 3... Carburetor, 4... Bench lily part, 5... Throttle valve, 6... Chyoke valve, 7... Main fuel passage, 11... Main air bleed, 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... Reburning device,
28...Three-way catalyst, 30...Secondary air supply passage,
31... Control valve, 32... O ₂ sensor, 33...
Air fuel ratio control circuit.

Claims (1)

[Claims] 1 An air valve equipped with a check valve that closes depending on the engine temperature and enriches the air-fuel ratio of the air-fuel mixture at low temperatures, and a deceleration richer that enriches the air-fuel ratio of the air-fuel mixture supplied to the engine when the engine decelerates. In the fuel ratio control device, an air-fuel ratio adjustment device is provided which corrects a position corresponding to the engine temperature of the chiyork valve during the closing operation in a direction in which the opening degree of the chiyork valve increases only during the deceleration. Air-fuel ratio correction device.