JPS6181552A - Exhaust gas cleaning device for car-mounted internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent the deterioration of driving property, improve fuel consumption, and clean exhaust gas by providing a control circuit which detects engine load in three areas and sets air fuel ratio and the circulation rate of exhaust gas according to each loaded area. CONSTITUTION:When a car speed is above a defined speed and the negative pressure in an intake manifold is below a defined pressure, the output levels of an AND circuit 61 and an OR circuit 63 becomes high levels. And, the feed of fuel increases carrying out large reflux of exhaust. When the car speed is above the defined speed and the negative pressure in the intake manifold is above the defined pressure, the output level in the OR circuit 63 becomes a low level. Small exhaust recirculation is carried out by stopping the operation of a solenoid valve 38. Thereby, the deterioration of driving property can be prevented, and fuel consumption can be improved while cleaning exhaust gas.

Description

[Detailed description of the invention] Technical field The present invention relates to an exhaust gas purification device for a vehicle internal combustion engine.

2. Description of the Related Art In general, a carburetor of an on-vehicle internal combustion engine is provided with a power valve that adjusts the amount of fuel supplied to the engine according to the engine load in order to control the air-fuel ratio of the supplied air-fuel mixture.

On the other hand, in order to suppress the generation of NOx (nitrogen oxides), which is one of the harmful components in the exhaust gas of an internal combustion engine, it is necessary to lower the combustion temperature within the cylinder. Therefore, an exhaust gas recirculation system (21I device) is sometimes provided, which lowers the combustion temperature by returning a portion of the exhaust gas to the intake passage and recirculating it to an extent that does not impair driving performance.

Conventionally, in an internal combustion engine equipped with such a power valve and an exhaust gas recirculation system (II neck system) as an exhaust purification device, the vehicle speed is lower than a predetermined speed V+ (for example, 15 km/h) or the @suction in the intake manifold is lower than a predetermined negative pressure P+. (for example, 150+++ mHo) or less during high load during acceleration, the power valve is opened to provide high output (q), and the air-fuel ratio is enriched, to a value around 14.7, for example. At this time, since the concentration of NOx generated increases, the exhaust gas recirculation control device performs a large amount of exhaust gas recirculation in proportion to the engine load.

Furthermore, when the vehicle speed is above a predetermined speed of 71 and the negative pressure in the intake manifold is above a predetermined negative pressure, the power valve closes to make the air-fuel ratio leaner in order to improve fuel efficiency. value. At this point, the exhaust gas recirculation control device recirculates a small amount of exhaust gas in proportion to the engine load to ensure operational performance.

In this way, by closing the power valve to lean the air-fuel ratio when the engine is under low load, it is possible to improve fuel efficiency to some extent. In order to sufficiently improve fuel efficiency at this time, it is necessary to make the air-fuel ratio even leaner. However, during exhaust recirculation, the amount of air intake into the engine is proportional to the intake air amount, so by making the air-fuel ratio leaner, the amount of exhaust recirculation increases to 1
This makes it difficult to improve fuel efficiency and purify exhaust gas at the same time, as this results in deterioration of driving performance.

The purpose of the present invention is to reduce the deterioration of operating performance at low engine loads.
It is an object of the present invention to provide an exhaust purification device that improves fuel efficiency and purifies exhaust gas without causing excessive exhaust gas.

The exhaust gas purification device of the present invention is characterized in that the load state of the engine is detected in three load regions, and the air-fuel ratio and exhaust gas recirculation rate are set corresponding to each load region.

1iJ starvation Embodiments of the present invention will be described below with reference to the drawings.

In the exhaust gas purification device according to the present invention shown in FIG. 1, intake air is supplied from an atmospheric air intake port 1 to an engine 4 via an air cleaner 2 and a carburetor 3.

The carburetor 3 is provided with a throttle valve 5, a venturi 6 is formed upstream of the throttle valve 5, and a choke valve 7 is provided further upstream of the venturi 6.

A negative pressure detection hole 8 is formed near the throttle valve 5;
is located upstream of the throttle valve 5 when the throttle valve 5 is closed, and is located downstream of the throttle valve 5 when the throttle valve 5 is open. Further, a negative pressure detection hole 9 is formed in the venturi 6 as well.

A main nozzle 11 of the main fuel supply system opens in the venturi 6, and a main air bleed 15 communicates downstream of the main jet 14 in a main fuel passage 13 extending from the main nozzle 11 to the float chamber 12, and its auxiliary air bleed 16 also communicates with the main nozzle 11 of the main fuel supply system. It's communicating.

On the other hand, the slow port 17 and idle port 18 of the low-speed fuel supply system are opened on the inner wall surface near the throttle valve 5, and the slow port 17 and idle port 18 are connected to the slow fuel passage 1.
It communicates with the main fuel passage 13 through one. Further, a slow air bleed 20 and its auxiliary air bleed 21 communicate with the slow fuel passage 19. The auxiliary air bleed 16°21 is provided with a solenoid valve 22.23, and the electric area 1
When the valve 22.23 is activated, the auxiliary air bleed 16.21 is opened, and when the valve 22.23 is not activated, the auxiliary air bleed 16.21 is closed.

Further, a power valve 24 is provided in the float chamber 12,
Float ¥12 of fuel is supplied to the main fuel passage 13 downstream from the main jet 14 via the power valve 24.

The power valve 24 has a pressure receiving chamber 24a.
The opening degree changes depending on the pressure acting on the valve.

When the pressure in the pressure receiving chamber 24a drops to atmospheric pressure, the opening degree of the power valve 24 becomes fully open, and as the pressure in the pressure receiving chamber 248 becomes negative pressure and its magnitude increases, the opening degree decreases. The pressure receiving chamber 24a is connected to the throttle valve 5 via the negative pressure supply passage 25.
It communicates with the intake manifold 26 downstream. A three-way electric Ff1 valve 27 is provided in the negative pressure supply passage 25. The solenoid valve 27 communicates with the negative pressure supply passage 25 when not driven, and when driven closes the Ω pressure supply passage 25 on the side of the intake manifold 26 and opens the negative pressure supply passage 25 on the side of the pressure receiving chamber 24a to the atmosphere.

The inside of the intake manifold 26 and the inside of the exhaust manifold 31 are communicated through an exhaust gas recirculation path 32. The +i to air flow path 32 is provided with an exhaust gas recirculation control valve 33 . The exhaust gas recirculation control valve 33 includes a negative pressure constriction 33a, a valve chamber 331) forming a part of the exhaust gas recirculation path 32, a diaphragm 33c forming a part of the negative pressure 133a, and a mouth pressure 33a. The valve spring 33 (I) and the exhaust gas recirculation path 3 provided in the valve chamber 33b
A tapered valve body 33e is biased by a valve bone 33d through a diaphragm 33c so as to close the exhaust gas recirculation passage 32 according to the magnitude of the negative pressure acting on the negative pressure air 33a. The cross-sectional area of the passage is changed, and as the magnitude of the negative pressure increases, the cross-sectional area of the passage becomes larger.

On the other hand, a control intake passage 35 communicates with the intake manifold 26 from an atmospheric air intake port 34 . The control intake passage 35 is provided with a negative pressure responsive regulating valve 36 and an air valve 37. The adjustment valve 36 and the air valve 37 are negative pressure air 36
a, 37a, valve chambers 36b, 37b, diaphragms 36C, 370, valve springs 36d, 37d, and valve body 36
e and 37e, respectively. The negative pressure air 36a is provided in the control intake passage 35, and a valve chamber 37b is located downstream of the negative pressure air 36a. The valve body 37c in the valve chamber 37b is biased via the diaphragm 37c by a valve spring 37d so as to close the control intake passage 35.

Further, a solenoid valve 38 is provided upstream of the negative pressure chamber 36a of the 1ill III intake path 35. An auxiliary passage 35a is formed so as to bypass this solenoid valve 38.

A throttle 49 is provided in the auxiliary passage 35a, and a solenoid valve 38
closes the control intake passage 35 when not driven, and opens the control intake passage 35 when driven. The negative pressure chamber 37a of the air valve 37 communicates with the 9-pressure detection IL 8 via the negative pressure supply path 39. A three-way solenoid valve 40B is provided in the negative pressure supply passage 39, and the solenoid valve 40 connects the negative pressure supply passage 39 when not driven, and when driven, closes the negative pressure supply passage 39 on the negative pressure detection hole 8 side and The negative pressure supply passage 39 of the pressure chamber 37a is opened to the atmosphere via the atmosphere suction port 41. Further, the negative pressure supply passage 39 on the side of the regulating valve 36 from the electromagnetic valve 40 communicates with the negative pressure air 33a of the exhaust gas recirculation control valve 33 via the negative pressure supply passage 42. Valve chamber 36b
communicates with the CΩ pressure detection hole 9 via the negative pressure supply passage 43.

A three-way solenoid valve 44 is also provided in the negative pressure supply passage 43, and the solenoid valve 44 connects the negative pressure supply passage 43 when not driven, and closes the negative pressure supply passage 43 on the negative pressure detection hole 9 side when driven. The negative pressure supply passage 43 on the side of the valve chamber 36b is opened to the atmosphere via the atmosphere suction port 34. Further, the valve chamber 36b is connected to the negative pressure supply passage 3.
9, and the valve body 36 in the valve chamber 36b
The valve spring 36 (l biases the valve element 36e through the diaphragm 36c so as to close the passage from the valve 'l 36b to the three negative pressure supply passages. The negative pressure m 36 a of the passage 35 is provided with a passage 45 whose cross-sectional area is larger than that of the throttle 49 on the upstream side, and a throttle 46 on the downstream side of the negative pressure supply passage 39; A throttle 47 is provided on the side of the negative pressure detection hole 8 C), and a throttle 48 is also provided in the negative pressure supply passage 43 .

A control circuit 51 is connected to each solenoid of the electromagnetic valves 22, 23.27, 38.40.44.

The control p circuit 51 includes a negative pressure switch 52, 53, an intake temperature switch 54, a cooling water temperature switch 55, and a heavy speed switch 5.
6 is concubined by 1.

The negative pressure switch 52 controls the negative pressure Pe in the intake manifold 26.
is the first predetermined pressure P+ (for example, i5omm)
The negative pressure switch 53 is turned on when the negative pressure P8 in the intake manifold 26 is at a second predetermined pressure PZ that is higher than the first predetermined pressure P1 (for example, 3001111118 (1
) or more, it turns on. The intake air temperature switch 54 is turned on when the intake air temperature TA is equal to or lower than a first predetermined temperature -1 (for example, 15° C.). The cooling water temperature switch 55 controls the cooling water temperature TW.
is turned on when the temperature is lower than the second predetermined temperature T2 (for example, 40° C.).

Further, the vehicle speed switch 56 is turned on when the vehicle speed V is equal to or higher than a predetermined speed V+ (for example, 15 km/h).

These switches 52 to 56 output a high level signal of voltage VH when turned on.

As shown in FIG. 2, the control circuit 51 is an AN circuit that takes the AND of the output levels of the negative pressure switch 52 and the vehicle speed switch 56.
D circuit 61 , inverter 62 connected to the output of vehicle speed switch 56 , intake temperature switch 54 , AND circuit 61
and 01, which takes the logical sum of each output level of the inverter 62.
Further, the circuit 63, the inverter 4 connected to the output of the intake temperature switch 54, the inverter 965 connected to the output of the OR circuit 63, and the output of the negative pressure switch 53,
A predetermined period of time (for example, 2s) after the high level signal is supplied.
A delay circuit 66 that inverts the output level from a low level to a low level when ec> elapses, and an AND circuit 6 that takes the logical product of each output level of the inverters 64, 65 and the extension circuit 66.
7.

A drive circuit 68 for driving the electromagnetic valves 27, 38 is connected to the output of the OR circuit 63, and a drive J circuit 69 for driving the electromagnetic valves 22, 23, 44 is connected to the output of the AND circuit 67. Further, a drive circuit 70 for driving the solenoid valve 40 is connected to the output of the cooling water temperature switch 55.

In this configuration, first, the operation of the exhaust gas recirculation section will be explained. Now, the solenoid valve 38 is driven, and the solenoid valve 40
．． 44 is not driven. When the engine 4 is operated, negative pressure Pc acts on the negative pressure chamber 37a from the negative pressure detection hole 8 through the negative pressure supply passage 39 and the solenoid valve 40. When the air valve is larger, the valve body 37e moves in the valve opening direction.When the air valve 37 opens, the atmosphere flows from the atmosphere intake port 34 into the intake manifold 26 via the control intake path 35.The atmosphere passes through the negative pressure chamber 36a. The negative pressure pa in the valve chamber 37b and the negative pressure pb in the valve chamber 37b are determined by the throttle ratio of the throttle 45.46.

Next, the negative pressure pv acting on the valve chamber 36b from the negative pressure detection hole 9
When the pressure difference between the pressure and the negative pressure pa is greater than the biasing force exerted by the valve spring 36d, the valve body 36e moves in the valve opening direction. When the regulating valve 36 is opened, the negative pressure Pc that has passed through the throttle 47 is diluted by the negative pressure pv and becomes negative pressure pe.

Next, due to a decrease in the negative pressure Pc in the negative pressure supply passage 39, that is, a decrease in the negative pressure pe, the opening degree of the air valve 37 decreases, and the air flowing through the control intake passage 35 decreases. Due to this decrease in the amount of air, the negative pressure pa of the negative pressure W36a decreases, and the regulating valve 36 enters a closed state. Then, the negative pressure pc rises again and the above operation is repeated, and because this repetitive operation is performed at high speed, the pressure ratio between the negative pressure pv and Pe becomes negative pressure 1)
It becomes equal to the pressure ratio of d and pb.

Therefore, when the main intake air amount of the engine 4 is small, the negative pressure p
Since a is larger than the negative pressure Pv, the opening degree of the regulating valve 36 increases and the negative pressure pe decreases.As the main intake air amount increases, the negative pressure pv increases, so the opening degree of the regulating valve 36 decreases and the negative pressure pe decreases. Pressure pe becomes high. The negative pressure Pe acts on the negative pressure chamber 33a together with the negative pressure chamber 37a when the solenoid valve 40 is not activated, and opens the air valve 37 and the exhaust recirculation control valve 33. The exhaust gas recirculation flow through the exhaust gas recirculation path 32 when the
[l Since the amount of air flowing through the intake passage 35 is proportional to the amount of main intake air to the engine 4, the main intake air ω and the exhaust gas recirculation m are proportional.

Therefore, the negative pressure pe becomes a negative pressure proportional to the main intake air amount, and a predetermined exhaust gas recirculation rate can always be achieved in exhaust gas recirculation, and the exhaust gas recirculation rate is the pressure ratio of β pressure Pv and pc,
It is determined by the aperture ratio of 15.46/15.46.

Next, in the control circuit 51, when the vehicle speed is lower than the predetermined speed v1, the vehicle speed switch 56 is turned off, and the inverter 6 is turned off.
Since the input level of inverter 2 is low, the input level of inverter 6 is low.
Since a high level signal is supplied from 2 to the OR circuit 63, O
The output level of the R circuit 63 becomes high level. When the intake temperature is below the predetermined temperature T1, the intake temperature switch 54 is turned on, and a high level signal is sent from the intake temperature switch 54 to the OR circuit 63.
Since the signal is supplied to the OR circuit 63, the output level of the OR circuit 63 becomes high. Further, when the vehicle speed is higher than the predetermined speed 71 and the negative pressure P8 in the intake manifold 26 is lower than the first predetermined pressure P1, each input level of the AND circuit 61 becomes a high level,
Since the high level signal is supplied from the AND circuit 61 to the OR circuit 63, the output level of the OR circuit 63 becomes high level.

When the OR circuit 63 outputs a high level signal in this way,
The high level signal is supplied as a drive signal to the drive circuit 68, so that the drive circuit 68 drives the solenoid valves 27 and 38. When the solenoid valve 27 is driven, the solenoid valve 27 closes the intake manifold side of the negative pressure supply passage 25 and opens the negative pressure supply passage 25 on the power valve 24 side to the atmosphere. Therefore, since atmospheric pressure acts on the negative pressure chamber 24a of the power valve 24, the power valve 24 is closed and the float chamber 12a is closed.
The fuel from the main jet 14 and the power valve 2
4, the amount of fuel supplied increases. On the other hand, 1i is driven by the solenoid valve 38.
ll The intake passage 35 is in communication.

When the air valve 37 is closed, the atmosphere from the atmosphere intake port 34 flows through the control intake passage 35 without passing through the throttle 49 of the auxiliary passage 35a.
flows. Atmospheric air enters the negative pressure chamber 36a of the regulating valve 36 through a throttle 45.
Inflow only through. In this case, the pressure ratio between the negative pressure pv and Pe is determined by the throttle ratio of the throttles 45 and 46. When the negative pressure pa in the negative pressure chamber 36a is increased when the control intake passage 35 is closed, air passes through the throttle 49. Since the negative pressure p decreases compared to
The dilution type of negative pressure Pc due to v decreases. Therefore, negative pressure P
Since e increases and is proportional to the main intake air amount to the engine 4, the opening degree of the exhaust gas recirculation control valve 33 increases, the exhaust gas recirculation rate increases, and exhaust gas recirculation is performed with a large load proportionality.

That is, when the vehicle speed is below the predetermined speed v1, when the intake temperature is below the first predetermined temperature TI, or when the vehicle speed is below the predetermined speed V+
Even with the above, when the negative pressure Ps in the intake manifold 26 is lower than the first predetermined pressure P1, the air-fuel ratio is enriched by increasing the amount of fuel supplied to the engine 4 by the power valve 24, and is controlled to, for example, 14.7, and the load A proportionally large exhaust gas recirculation takes place.

When the vehicle speed is above the predetermined speed 71, the negative pressure Pa in the intake manifold 26 is above the first predetermined pressure P1, and the intake temperature is above the first predetermined temperature T+, each input level of the OR circuit 63 becomes a low level. Therefore, the output level of the OR circuit 63 becomes low level.

At this time, the drive circuit 68 stops driving the solenoid valves 27-, 38. When the solenoid valve 27 stops driving, the negative pressure supply passage 2
5 communicate with each other, and the negative pressure P8 in the intake manifold 26 flows through the negative pressure supply passage 25 to the negative pressure chamber 25a of the power valve 24.
The power valve 24 is closed. Therefore,
- The fuel from the float chamber 12 is sucked out from the main nozzle 11 via the main jet 14 only, and normal fuel supply is performed, so the air-fuel ratio is made lean and the base air-fuel ratio of the carburetor J3 (for example, 16.5> Also, when the solenoid valve 38 stops driving, the solenoid valve 38 controls the intake passage 3.
5 is closed, the atmosphere passes through the auxiliary passage 35a, and the four throttles cause a small amount of exhaust gas recirculation in proportion to the load.

Next, when the vehicle speed is equal to or higher than the predetermined speed V+, the intake manifold 2
When the negative pressure P8 in 6 becomes higher than the second predetermined pressure P2,
The negative pressure switch 53 is turned on, and a high bell signal is supplied from the negative pressure switch 53 to the delay circuit 2866. Delay circuit 6
6b is designed to provide hysteresis to the output signal of the negative pressure switch 53, and supplies a high level signal to the AND circuit 67 when the high level signal continues to be supplied for a predetermined period of time or more. At this time, when the intake temperature becomes equal to or higher than the predetermined temperature T1, the intake temperature switch 54 is turned off, and the input level of the inverter clock 4 becomes a low level.
The level signal is supplied to an AND circuit 67. Further, the output level of the AND circuit 67 becomes high since the inverter 65 supplies the high level signal to the AND circuit 67. Therefore, the drive circuit 69 drives the solenoid valves 22, 23, 44.

Auxiliary air bleed 16.
21 respectively communicate with the atmosphere together with the main air bleed 15 and the slow air bleed 20? +li assistant air bleed 1
It flows into 6.21. Therefore, the proportion of air in the supplied air-fuel mixture increases in both the main fuel supply system and the low-speed fuel supply system, and the air-fuel ratio is controlled to be leaner, for example, 18. Further, by driving the electromagnetic valve 44, the negative pressure supply passage 43 on the side of the negative pressure detection hole 9 is closed, and the negative pressure supply passage 43 on the side of the valve chamber 36b is opened to the atmosphere via the atmosphere suction port 34. Then, the negative pressure pv from the negative pressure detection hole 9 stops acting on the valve v3611, and the atmospheric pressure is supplied to the valve chamber 36b via the negative pressure supply passage 43.
Therefore, the regulating valve 36 becomes the Un valve, and the negative pressure Pc is diluted by the atmospheric pressure, so the magnitude of the negative pressure PO further decreases and becomes almost constant. Therefore, the opening degree of the exhaust gas recirculation control valve 33 becomes very small, resulting in a small amount of exhaust gas recirculation.

Therefore, if the above operation is represented in a diagram, if the atmospheric temperature is normal temperature, as shown in Figure 3, when the vehicle speed is below the predetermined speed V1,
Or, even if the vehicle speed is higher than the predetermined speed 11, when the negative pressure P8 in the intake manifold is lower than the first predetermined pressure P1, the engine load is high, the air-fuel ratio is richer than the base air-fuel ratio of the carburetor, and the exhaust gas recirculation is proportional to the load. This results in a large EGR (exhaust gas recirculation). When the vehicle speed is above the predetermined speed V1 and the negative pressure Ps in the intake manifold is above the first predetermined pressure P1 and below the second predetermined pressure P2, the load is medium, and the air-fuel ratio is slightly leaner than the base air-fuel ratio, that is, the stoichiometric air-fuel ratio. Therefore, the exhaust gas recirculation becomes a small EGR proportional to the load. Also, when the vehicle speed is equal to or higher than the predetermined speed 11 and the intake manifold internal negative pressure Pa is at the second level.
When the pressure is equal to or higher than the predetermined pressure P2, the engine load is low.

On the other hand, when the cooling water temperature is lower than the second predetermined temperature T2, the cooling water temperature switch 55 is turned on, and the cold section water temperature switch 55 is turned on.
Since a high level signal is supplied to the drive circuit 70, the drive circuit 70 drives the solenoid valve 4o. By driving the solenoid valve 40, the negative pressure supply passage 39 on the side of the negative pressure detection hole 8 is closed, and the negative pressure supply passage 3 on the side of the negative pressure chamber 37a and the negative pressure supply passage 42 is closed.
9 is opened to the atmosphere. Then, the supply of negative pressure Pc from the negative pressure detection hole 8 is stopped, and the atmospheric pressure changes to the negative pressure supply passage 39.
．． 42 to the negative pressure chamber 33a of the exhaust gas recirculation control valve 33, the exhaust gas recirculation control valve 33 closes and the exhaust gas recirculation path 32
occlusion. Therefore, exhaust gas recirculation is stopped.

Effects of the Invention As described above, in the exhaust gas purification device of the present invention, the engine load is controlled in the first load region and in the second load region, which is higher in load than the first load region.
Load area, 3 of the 3rd load area with lower load than the 1st load area
Since the system is configured to detect each region and set the air-fuel ratio and exhaust recirculation rate according to each load region, it improves fuel efficiency and purifies air without causing deterioration of drivability when the engine is under low load. It is possible.

[Brief explanation of the drawing]

Fig. 1 is a schematic layer diagram showing an embodiment of the present invention, Fig. 2 is a block diagram showing the specific configuration of the control circuit in the device shown in Fig. 1, and Fig. 3 shows the control state in each load range. It is a diagram. Explanation of symbols of main parts 3... Carburizer 5... Throttle valve 6
...Venturi 7 ...Choke valve 11 ...Main nozzle 12 ...Float chamber 13 ...Main fuel passage 15 ...・Main air bleed 16.21...Auxiliary air bleed 19...
... Slow fuel passage 20 ... Slow air bleed 22.23, 27.38.40.44 ... Solenoid valve 24 ... Power valve 26 ... Intake manifold 31... Exhaust manifold 32... Exhaust recirculation path 33... Exhaust recirculation control valve 35... Control intake path 36... Adjustment Valve 37...Air valve

Claims (1)

[Claims] Detects a plurality of operating parameters of the vehicle, determines the engine load based on the detection results, and when the engine load belongs to a first load region, controls the air-fuel ratio using the reference value as the target value, and performs exhaust recirculation at a predetermined recirculation rate. When the engine load belongs to a second load region that is higher than the first load region, the air-fuel ratio is controlled to a value smaller than the reference value as the target value, and the exhaust gas recirculation is controlled at a recirculation rate higher than the predetermined recirculation rate.The engine load belongs to the third page load region with a lower load than the first load region, the air-fuel ratio is controlled with a target value larger than the reference value, and the exhaust gas recirculation is performed at a recirculation rate smaller than the predetermined recirculation rate. Characteristic exhaust purification device.