JPS6030444Y2 - Engine secondary air supply system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a secondary air supply device for an engine, and more particularly to a secondary air supply device for an engine having a three-way catalytic converter in the engine exhaust system.

As one of the secondary air supply devices for an engine having a three-way catalytic converter in the exhaust system, there is provided a first passage means for guiding secondary air to the engine exhaust system, and a second passage means for guiding secondary air to the engine intake system. an exhaust sensor that detects the concentration of exhaust components in the exhaust gas discharged from the engine and generates a corresponding signal; and a correction air amount necessary for correcting the air-fuel ratio of the engine based on the signal generated by the exhaust sensor. a flow control valve that is controlled by the calculation device to control the flow rate of secondary air; and a flow rate control valve that controls the flow rate of secondary air by the flow rate control valve to the first passage means and the second passage means. A secondary air supply system is currently proposed having a secondary air control valve selectively supplying the passage means.

In the secondary air supply device as described above, secondary air is selectively supplied to the engine exhaust system or the engine intake system in order to correct the air-fuel ratio of exhaust gas to a corrected target air-fuel ratio, that is, the stoichiometric air-fuel ratio. By supplying this secondary air, the air-fuel ratio of the exhaust gas is corrected to the stoichiometric air-fuel ratio, and the three-way catalytic converter is heated to
It works effectively for purifying the three components of CXCO and NOx.

By the way, it is known that when the engine is idling or operating at low load, the warm-up performance of the three-way catalytic converter is improved if the air-fuel ratio of the exhaust gas is set to be higher than the stoichiometric air-fuel ratio to some extent, that is, to be lean.

In view of the above-mentioned circumstances, the present invention has been developed to reduce the air-fuel ratio of exhaust gas to a certain degree from the stoichiometric air-fuel ratio during idling or low-load operation without making major changes to the conventionally known control system of the secondary air supply device as described above. It is an object of the present invention to provide an improved secondary air supply device that can be made larger and improve the warm-up performance of a three-way catalytic converter.

According to the present invention, this purpose is to provide a first passage means for guiding secondary air to the engine exhaust system, a second passage means for guiding secondary air to the engine intake system, and a second passage means for guiding the secondary air to the engine intake system. an exhaust sensor that detects the concentration of the component and generates a signal corresponding to the concentration; an arithmetic device that determines a correction air amount necessary for correcting the air-fuel ratio of the engine based on the signal generated by the exhaust sensor; a flow control valve that operates to increase the amount of secondary air in response to an increase in negative pressure;
a secondary air control valve that selectively supplies secondary air whose flow rate is controlled by the flow rate control valve to the first passage means and the second passage means; and an electromagnetic negative pressure switching valve that controls the negative pressure to be introduced, and the electromagnetic negative pressure switching valve is a first valve that is always located downstream of a throttle valve provided in the engine intake system in response to energization control. The pressure appearing at the intake pipe negative pressure take-out port and the second intake pipe negative pressure take-out port located downstream of the throttle valve in the fully closed position and located upstream of the throttle valve when the throttle valve is opened to a predetermined opening or more. This is closely related to the engine's secondary air supply device, which is configured to selectively supply the pressure appearing in the diaphragm chamber to the diaphragm chamber.

According to this configuration, the negative pressure switching valve always supplies intake pipe negative pressure to the flow rate control valve until the throttle valve is opened to a predetermined opening degree or more, so the flow rate control valve is fully open and the maximum flow rate is reached. Secondary air is now supplied.

As a result, the air-fuel ratio of the exhaust gas becomes larger than the stoichiometric air-fuel ratio to some extent.

In this way, when the air-fuel ratio of exhaust gas is set to a value larger than the stoichiometric air-fuel ratio, the three-way catalytic converter converts HCl
01 purification is not performed.

However, during idling or low-load operation, the concentration of NOx in exhaust gas is relatively low, so NOx in exhaust gas
There are no problems with this.

The secondary air is supplied to the engine exhaust system at least during idling to ensure good idling performance.

Further, this secondary air may be supplied to the engine intake system during low-load operation, and in this case, fuel efficiency can be further improved compared to when a mixture at a stoichiometric air-fuel ratio is supplied to the engine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings.

The figure is a schematic diagram showing one embodiment of the secondary air supply device according to the present invention.

In the figure, 1 is an engine, which inhales a mixture of air and fuel through an air cleaner 2, a carburetor 3, a throttle valve 4, an intake manifold 5, an exhaust manifold 6, an exhaust pipe 60, and its Exhaust gas is discharged through a three-way catalytic converter 61 provided midway.

The carburetor 3 is designed to supply an air-fuel mixture with an air-fuel ratio smaller than the stoichiometric air-fuel ratio, that is, a rich air-fuel mixture, to the engine intake system.

The exhaust manifold 6 has a port 7 for exhaust gas recirculation and secondary air supply, and a part of the exhaust gas flowing inside the exhaust manifold 6 is transferred from the port 7 to the passage 9a, the control valve 8, The air flows through a passage 9b to an injection port 10 from which it is recirculated into the intake manifold 5.

The control valve 8 has a valve element 12 for opening and closing the valve port 11 , and the valve element 12 is connected via a valve rod 13 to a diaphragm device 14 .
4.

The diaphragm device 14 includes a diaphragm 15, and when a negative pressure of a predetermined value or more is not supplied to the diaphragm chamber 16, the diaphragm 15 is pressed downward in the figure by the action of a compression coil spring 17. The valve element 12 is pushed down to close the valve port 11. On the other hand, when a negative pressure of a predetermined value or more is supplied to the diaphragm chamber 16, the valve element 12 is pushed down and the valve port 11 is closed, against the action of the compression coil spring 17, as shown in the figure. is driven upwards to lift the valve element 12 and open the valve port 11.

The diaphragm chamber 16 is located upstream of the throttle valve 4 when it is in the fully closed position as shown by the solid line in the figure, and is located upstream of the throttle valve 4 when it is opened beyond a relatively small predetermined opening. It is connected via a conduit 19 to an intake pipe negative pressure outlet port 18 which is located on the downstream side and opens into the intake passage of the carburetor 3.

A negative pressure regulating valve 20 for exhaust pressure control is provided in the middle of the conduit 19.
is provided.

This negative pressure regulating valve 20 includes a diaphragm 21,
This diaphragm 21 defines a first diaphragm chamber 22 on the lower side in the figure and a second diaphragm chamber 23 on the upper side in the figure, and also has a compression coil spring 24.
A spring force is applied downward in the figure.

This negative pressure regulating valve 20 has a valve port 25 that opens toward the second diaphragm chamber 23 in the middle of the conduit 19, and this valve port 25 is carried by the diaphragm 21 and is supported by a valve element 26. It is designed to be opened and closed.

The diaphragm 21 is connected to the first diaphragm chamber 22
When the pressure of the second diaphragm chamber 23 is higher than the pressure of the second diaphragm chamber 23 by a predetermined value or more, the valve element 26 is displaced upward in the figure against the spring force of the compression coil spring 24 to close the valve port 25 by the valve element 26; On the other hand, when the pressure in the first diaphragm chamber 22 is not higher than the pressure in the second diaphragm chamber 23 by more than a predetermined value, the spring force of the compression coil spring 24 positions the position as shown in the figure; The valve element 26 is pulled away from the valve port 25 to open it.

The first diaphragm chamber 22 has a conduit 2 connected to a pressure chamber 28 defined between the orifice element 27 provided upstream of the valve port 11 of the control valve 8 and the valve port 11.
9, and the exhaust gas pressure in the pressure chamber 28 is introduced.

Further, the second diaphragm chamber 23 is connected to the atmosphere opening port 3.
0 and is open to the atmosphere.

The device consisting of the negative pressure regulating valve 20 and the orifice element 27 is a device for controlling the negative pressure supplied to the diaphragm chamber 16 of the control valve 8 so as to keep the exhaust gas pressure in the pressure chamber 28 substantially constant. This serves to maintain the amount of fluid drawn into the intake manifold 5 from the injection port 10 in a proportional relationship to the total intake air amount of the engine 1.

31 is a reed valve for supplying secondary air;
This reed valve 31 is a flow control valve 32 in this embodiment.
It is built into an integrated casing.

The reed valve 31 has a check reed valve 35 that only allows fluid to flow from the port 33 to the port 34.
Due to the negative pressure appearing at 4, secondary air is sucked in from the secondary air intake port 36 via the port 33 and the check reed valve 35.

The port 34 is connected via a passage 50 to the passage 9a downstream of the orifice element 27 for supplying secondary air to the passage 9a.

The port 33 is opened and closed by a valve element 38 of the flow control valve 32, and its effective opening area is controlled.

The valve element 38 is connected to the diaphragm device 4 via a valve rod 39.
0 and is adapted to be driven by this diaphragm device.

The diaphragm device 40 includes a diaphragm 41, which moves downward in the figure against the action of a compression coil spring 43 in response to an increase in the negative pressure introduced into its diaphragm chamber 42, thereby closing the valve. Element 38 is pulled down to open port 33.

The effective opening area of port 33 increases as valve element 38 moves downward in the view.

The diaphragm chamber 42 is connected to an electromagnetic negative pressure switching valve 44 through which atmospheric pressure or negative pressure can be selectively introduced.

The switching valve 44 is connected at one port to a first intake pipe negative pressure outlet port 46 provided in the intake manifold 5 via a conduit 45, and at another port to the first intake pipe negative pressure outlet port 46 provided in the intake manifold 5.
7 to a second intake pipe negative pressure outlet port 52 provided in the carburetor 3.

The first intake negative pressure takeout port 46 is always located downstream of the throttle valve 4, but the second intake pipe negative pressure takeout port 52 is located downstream of the throttle valve 4 in the fully closed position. When the throttle valve 4 is opened to a relatively small predetermined opening degree or more, the throttle valve 4 is located upstream thereof.

The switching valve 44 is driven by a pulse signal generated by an arithmetic unit included in the control device 48.

The calculation device of the control device 48 calculates the correction air amount necessary to substantially correct the air-fuel ratio to the stoichiometric air-fuel ratio based on the signal generated by the 02 sensor 49 provided in the exhaust manifold 6, and adjusts the duty based on the correction air amount necessary to substantially correct the air-fuel ratio to the stoichiometric air-fuel ratio. It is designed to generate a ratio pulse signal.

The apparatus constructed as described above operates as follows.

When the throttle valve 4 is between the fully closed position as shown by the solid line in the figure and an opening position slightly opened from the fully closed position, that is, during idling or low load operation,
No intake pipe negative pressure acts on the intake pipe negative pressure outlet port 18,
Substantially atmospheric pressure is present and the control valve 8 is therefore in the closed state.

At this time, the exhaust gas is not recirculated, and air is injected into the exhaust manifold 6 from port 7 through the secondary air intake port 36, port 33, check reed valve 35, port 34, and passage 50.9a due to exhaust pulsation. be done.

At the same time, based on the signal generated by the 02 sensor 49, the correction air amount necessary to correct the air-fuel ratio of the exhaust gas containing secondary air to approximately the stoichiometric air-fuel ratio is calculated by the calculation device of the control device 48. The electromagnetic negative pressure switching valve 44 is driven by a pulse signal based on the calculation result.

However, at this time, the second intake pipe negative pressure outlet port 52 is located downstream of the throttle valve 4, and intake pipe negative pressure is applied to this port in the same way as the first intake pipe negative pressure outlet port 46. Therefore, even when the electromagnetic negative pressure switching valve 44 is driven, the intake pipe negative pressure is always supplied to the diaphragm chamber 42. Therefore, the diaphragm 41 largely pulls down the valve element 38, and the port 33 is fully opened.

Therefore, at this time, secondary air is supplied to the engine exhaust system at a predetermined maximum flow rate, and the air-fuel ratio of the exhaust gas becomes a predetermined air-fuel ratio greater than the stoichiometric air-fuel ratio.

By correcting the air-fuel ratio of the exhaust gas in this way, the warm-up performance of the three-way catalytic converter is improved.

At this time, the three-way catalytic converter acts as an oxidation catalytic converter that purifies HC and Co.

When the throttle valve 4 is opened to a relatively small predetermined opening degree or more, substantial intake pipe negative pressure appears at the intake pipe negative pressure outlet port 18, and the intake pipe negative pressure is reduced to a negative pressure by the negative pressure regulating valve 20 via the conduit 19. The control valve opens by being introduced into the diaphragm chamber 16 of the control valve 8 while its pressure is adjusted.

As a result, a part of the exhaust gas flowing through the exhaust manifold 6 flows back from the port 7 through the passage 9a, the control valve 8, and the passage 9b into the intake manifold 5 from the injection port 10, and also reduces the intake pipe negative pressure in the intake manifold 5. The secondary air is supplied into the intake manifold 5 from the injection port 10 along with the recirculated exhaust gas through the secondary total intake port 36, port 33, check reed valve 35, port 34, passage 50, control valve 8, and passage 9b. be done.

At this time, the electromagnetic negative pressure switching valve 44 is driven by a pulse signal based on the signal generated by the 02 sensor 48.

At the same time that substantial intake pipe negative pressure appears at the intake pipe negative pressure outlet port 18, the throttle valve 4 crosses the second intake pipe negative pressure outlet port 52, so that substantial intake pipe negative pressure is applied to the port. , if the second intake pipe negative pressure outlet port 52 is provided, the exhaust gas is recirculated as described above, and at the same time, the electromagnetic negative pressure switching valve 44 opens the second intake pipe based on the pulse signal. Atmospheric pressure from the tube negative pressure outlet port 52 and intake pipe negative pressure from the first intake tube negative pressure outlet port 46 are selectively supplied to the diaphragm chamber 42.

This introduces a modified intake pipe negative pressure into the diaphragm chamber 42 , which drives the diaphragm 41 so that the valve element 38 controls the effective opening area of the port 33 .

By controlling the opening degree of the port 33 in this manner, a predetermined amount of secondary air flows into the engine intake system, and the engine 1 is supplied with an air-fuel mixture at a substantially stoichiometric air-fuel ratio.

At this time, secondary air is not supplied to the engine exhaust system, so the air-fuel ratio of the exhaust gas is approximately the stoichiometric air-fuel ratio, and the three-way catalytic converter is capable of purifying the three components of HC, GO, and NOx. It operates effectively against.

Further, when the throttle valve 4 is opened to an opening degree at which substantial intake pipe negative pressure appears at the intake pipe negative pressure extraction port 18, and when the throttle valve 4 is further opened, the second intake pipe negative pressure extraction is performed. If the port 52 is provided so that atmospheric pressure appears at the port 52, a relatively large amount of secondary air will flow into the engine intake system until the throttle valve 4 is opened to that degree, and the engine 1 will have no theoretical air. A lean air-fuel mixture with a stoichiometric air-fuel ratio greater than the fuel ratio is supplied.

Note that this operating range is a low-load operating range, so engine 1
Even if a lean mixture is supplied to the engine, engine drivability is not significantly impaired, and fuel efficiency is improved.

In the above, the present invention has been described in detail with respect to specific embodiments, but it will be appreciated by those skilled in the art that the present invention is not limited thereto and that various embodiments are possible within the scope of the present invention. It should be obvious.

[Brief explanation of the drawing]

The figure is a schematic diagram showing one embodiment of the secondary air supply device according to the present invention. 1... Engine, 2... Air cleaner, 3... Carburetor, 4... Throttle valve, 5... Intake manifold, 6... ...Exhaust manifold, 7...Port, 8...
・Control valve, 9a, 9b...Passage, 10...
...Injection port, 11...Valve port, 12...
...Valve element, 13...Valve rod, 14...
... Shio diaphragm device, 15...Diaphragm, 16...Diaphragm chamber, 17...
...Compression coil spring, 18...Intake pipe negative pressure extraction port, 19...Conduit 1.20...Negative pressure regulating valve, 21...Diaphragm , 22...
...First diaphragm chamber, 23... Second diaphragm chamber, 24... Compression coil spring, 2
5... Valve port, 26... Valve element, 2
7... Orifice element, 28... Pressure chamber, 29... Conduit, 3o/bent/atmosphere release port, 31... Reed valve, 32... ...Flow rate control valve, 33...Port, 34, curve, port, 3
5. Curved check reed valve, 36... Secondary air intake port, 38... Valve element, 39. Curved valve rod, 4o. Curved diaphragm device, 41... Curved diaphragm, 42... Diaphragm chamber, 43... Curved compression coil spring, 44... Electromagnetic negative pressure switching valve, 4
5...Curved groove pipe, 46...First intake pipe negative pressure extraction port, 47...Conduit, 48...ml
J Miso L 49...02 sensor, 5o/curve/passage, 52...second intake pipe negative pressure extraction port, 6
0...Exhaust pipe, 61...Three-way catalytic converter.

Claims (1)

[Scope of utility model registration request] a first passage means for guiding secondary air to the engine exhaust system; a second passage means for guiding secondary air to the engine intake system; and a first passage means for guiding secondary air to the engine intake system; an exhaust sensor that generates a signal; an arithmetic unit that determines the corrected air amount necessary for correcting the air-fuel ratio of the engine based on the signal generated by the exhaust sensor; a flow control valve that operates to increase the amount of secondary air; and a secondary air whose flow rate is controlled by the flow control valve and which selectively supplies the secondary air to the first passage means and the second passage means. It has a control valve, and an electromagnetic negative pressure switching valve that is energized and controlled by the arithmetic unit to control the negative pressure introduced into the diaphragm, and the electromagnetic negative pressure switching valve controls the engine intake system according to the energization control. The pressure that appears at the first intake pipe negative pressure outlet port, which is always located on either side of the throttle valve provided, and the pressure that appears downstream of the throttle valve that is in the fully open position, and the pressure that appears upstream when the throttle valve is opened beyond a predetermined opening degree. A secondary air supply device for an engine, characterized in that it is configured to selectively supply pressure appearing at a second intake pipe negative pressure outlet port located on the side to the diaphragm chamber.