JPS597567Y2 - Exhaust gas recirculation control device for internal combustion engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas recirculation control device for reducing harmful components, particularly nitrogen oxides NOx, in exhaust gas discharged from an internal combustion engine.

As a means of reducing the amount of NOx generated in internal combustion engines for vehicles, a portion of the exhaust gas is recirculated to the intake system and involved in combustion in the combustion chamber along with fresh air, thereby keeping the maximum combustion temperature low. Exhaust gas recirculation devices are generally known.

It is also known that the amount of NOx generated varies depending on the operating state of the engine, and is most likely to be generated during acceleration.

In order to sufficiently suppress the generation of NOx during acceleration, during normal exercise, suction negative pressure is applied to the negative pressure chamber of the exhaust gas recirculation control valve provided in the exhaust gas recirculation passage to operate the control valve. During acceleration, the large negative pressure stored in the negative pressure tank in advance acts on the negative pressure chamber of the exhaust recirculation control valve to operate the control valve, thereby increasing the amount of exhaust gas recirculation. It is also known that the generation of NOx can be sufficiently suppressed by
(See Publication No. 32221).

However, such an exhaust gas control device operates the switching valve with the suction pipe negative pressure, and operates the exhaust recirculation control valve by the normal suction negative pressure and the control valve by the large negative pressure in the negative pressure tank. Since the switching valve was activated even when the negative pressure was as low as when starting a normal vehicle, the exhaust gas recirculation control valve would be activated due to the large negative pressure in the negative pressure tank, resulting in a large amount of exhaust gas recirculation. If this happens too much, the problem arises that drivability deteriorates.

In order to solve this problem, for example,
Although it is conceivable to control the switching valve by detecting the vehicle speed as described in Japanese Patent No. 259, such a switching valve control means has a complicated structure and is expensive.

Therefore, the present invention aims to further improve what was previously proposed by the applicant and to solve the above-mentioned problems by a simple and inexpensive means.

That is, in order to achieve the above-mentioned purpose, the exhaust gas recirculation control device for an internal combustion engine of the present invention connects the exhaust passage and the intake passage via an exhaust recirculation control valve that operates with negative suction pressure to control the exhaust gas. One part of the negative pressure chamber of the control valve is opened immediately upstream of the idling opening of the throttle valve of the suction system through an electromagnetic three-way switching valve, and the other is opened directly upstream of the idling opening of the throttle valve of the suction system. In one connected to the downstream side of the throttle valve of the suction system via a pressure tank and a one-way valve, the excitation coil of the electromagnetic three-way switching valve is connected to a power source via a negative pressure switch, and the negative pressure chamber of the negative pressure switch is connected to the , open to the suction system at a position that is upstream of the idling opening of the slot valve and becomes downstream when the opening is over a predetermined opening,
The negative pressure switch is turned on when the suction negative pressure exceeds a predetermined value, and the negative pressure for operating the exhaust gas recirculation control valve is supplied from the negative pressure tank.

In addition, in the structure of the present invention, the negative pressure chamber of the exhaust recirculation control valve is communicated directly with the suction system via an electromagnetic three-way switching valve, and the other via a negative pressure tank and a one-way valve. A structure similar to that of JP-A-51-1833 can be seen, but the electromagnetic three-way switching valve in this prior art is
The structure of the electromagnetic three-way switching valve of the present invention differs greatly in that switching is controlled by a heat-sensitive switch, whereas switching is controlled by a negative pressure switch that turns on when the suction negative pressure exceeds a predetermined value. It is.

An embodiment of the present invention will be specifically described below with reference to the drawings.

In FIG. 1, numeral 1 is the engine, 2 is the exhaust passage, and 3 is the engine.
4 is an air cleaner, 4 is a throttle valve, and 5 is an intake pipe. This intake pipe 5 and exhaust passage 2 are connected by an exhaust gas recirculation passage 6, and an exhaust gas recirculation control valve 7 is provided in the middle of this passage 6.

This control valve 7 has a negative pressure chamber 9 partitioned by a diaphragm 8.
The negative pressure in the negative pressure chamber 9 causes the diaphragm 8 to
When the valve body 7a of the control valve 7 is displaced against the spring 10, the valve body 7a of the control valve 7 opens and the exhaust gas is recirculated from the exhaust passage 2 to the intake pipe 5 via the exhaust gas recirculation passage 6.

The negative pressure chamber 9 is connected to a valve chamber 12a of the electromagnetic three-way switching valve 12 through a negative pressure passage 11, and is connected to one port of the switching valve 12.
12b is connected via a negative pressure passage 13 to a negative pressure outlet 14 located immediately upstream of the idling opening of the throttle valve 4 and open to the suction system.

The other port 12C of the switching valve 12 is connected to the suction pipe 5 on the downstream side of the throttle valve 4 through a negative pressure passage 15 via a negative pressure tank 16 and a one-way valve 17.

Note that the one-way valve 17 is configured to open when the negative pressure in the negative pressure tank 16 is lower than the negative pressure in the suction pipe 5, and to close in the opposite case.

The excitation coil 18 of the switching valve 12 is connected to a power source 20 via a negative pressure switch 19.

The negative pressure switch 19 has a negative pressure chamber 22 partitioned by a diaphragm 21, and this negative pressure chamber 22 is connected to the idling opening upstream of the throttle valve 4 via a negative pressure passage 23.
The diaphragm 21 is connected to the negative pressure outlet 24 that opens to the suction system at a downstream position at a predetermined opening degree or more, and when the negative pressure in the negative pressure chamber 22 reaches a predetermined value or more, the diaphragm 21
5, the movable contact 19 a becomes the fixed contact 19
By closing b, the switch is turned on.

In the above structure, except during acceleration, which will be described later, the excitation coil 18 of the switching valve 12 is demagnetized, the port 12b is open and the port 12C is closed, and therefore the negative of the exhaust recirculation control valve 7 is The pressure chamber 9 is communicated with a negative pressure outlet 14 via a negative pressure passage 11, a switching valve 12, and a negative pressure passage 13, and the negative pressure in the suction pipe 5 is communicated with the negative pressure tank 16 through a one-way valve 17. It has been accumulated.

Therefore, during idling and operation under small load, the negative pressure outlet 14 is located upstream of the throttle valve 4, and no negative pressure is applied to the negative pressure chamber 9, so the exhaust recirculation control valve 7 is closed. Exhaust gas is not recirculated.

When the throttle valve 4 is open during normal driving and the negative pressure outlet 14 is located on the downstream side, suction negative pressure acts on the negative pressure chamber 9, causing the diaphragm 8 to displace and exhaust air. The valve body 7a of the recirculation control valve 7 opens, and exhaust gas is recirculated to the intake pipe 5 in accordance with the opening degree of the throttle valve 4.

In this case, in operating conditions near full load, the negative pressure acting on the negative pressure chamber 9 from the negative pressure outlet 14 is close to 0, so there is almost no recirculation of exhaust gas, which prevents a drop in engine output. I'm here.

Negative pressure chamber 22 of negative pressure switch 19 like when idling
When the negative pressure outlet 24 communicating with the throttle valve 4 is located on the upstream side of the throttle valve 4, the negative pressure switch 19 is off because no negative pressure is applied to the negative pressure chamber 22 of the negative pressure switch 19. The excitation coil 18 of the switching valve 12 is demagnetized, and the negative pressure chamber 9 of the exhaust recirculation control valve 7 is connected to the negative pressure tank 16.
There is no communication with.

However, during normal driving, the negative pressure chamber 2 of the negative pressure switch 19
2 is located downstream of the throttle valve 4, the negative pressure of the negative pressure outlet 24 acts on the negative pressure chamber 22, and the suction negative pressure exceeds a predetermined level during acceleration. When the pressure increases, the negative pressure switch 19 turns on and the switching valve 12
The excitation coil 18 of is excited, the port H2b opens, and the port H2b closes.

As a result, the negative pressure tank 16 communicates with the negative pressure chamber 9 of the exhaust gas recirculation control valve 7, and the large negative pressure accumulated in the negative pressure tank 16 acts on this negative pressure chamber 9. The body 7a opens wide and a large amount of exhaust gas is returned to the suction pipe 5.

Therefore, the combustion temperature is lowered, and the generation of NOx can be sufficiently suppressed.

Furthermore, when the acceleration operation is canceled, the suction negative pressure acting on the negative pressure chamber 22 of one negative pressure switch becomes small, so the negative pressure switch 19 is turned off, the excitation coil 18 is demagnetized, and the switching valve 12 exhausts the air. The negative pressure chamber 9 of the recirculation control valve 7 is cut off from communicating with the negative pressure tank 16, and the exhaust gas is recirculated in a state other than during acceleration as described above.

The operating negative pressure PE from the negative pressure outlet 14 of the exhaust gas recirculation valve 7 that performs the above-described operation and the operating negative pressure P of the negative pressure switch 19
An example of the relationship between 5 and the throttle valve opening is shown in FIG.

Note that in FIG. 2, a indicates a non-operating region of the exhaust gas recirculation control valve 7 due to the negative pressure tank 16, b indicates the same operating region, and PM indicates the suction pipe negative pressure.

In the present invention, the one-way valve 17 is the negative pressure tank 1
A damper valve may be used in which orifices are provided in parallel to communicate the 6 side and the suction pipe 5 side.

As explained above, in the exhaust gas recirculation control device of the present invention, during acceleration other than when starting, the negative pressure switch is turned on and the electromagnetic three-way selector valve is activated to recirculate the large negative pressure in the negative pressure tank. Since the exhaust gas recirculation control valve is applied to the negative pressure chamber of the control valve to widen the exhaust gas recirculation control valve and increase the amount of exhaust gas recirculation, the generation of NOx can be sufficiently suppressed.

In addition, since the throttle valve is not opened very widely during normal start-up, the negative pressure switch is not turned on, and a large amount of exhaust gas is not recirculated using the negative pressure in the negative pressure tank, so the engine will not breathe easily. It is possible to prevent deterioration of drivability such as stopping, and furthermore, other than when accelerating as mentioned above, suction negative pressure is applied to the negative pressure chamber of the exhaust recirculation control valve according to the opening degree of the throttle valve. The control valve can be opened to a certain opening degree to recirculate the exhaust gas, and therefore the amount of exhaust gas recirculation can be controlled to an appropriate amount according to the driving condition, and the switching valve can be controlled using a vehicle speed detector. A negative pressure switch, which has a simpler structure and is cheaper in comparison, has the effect of preventing deterioration of drivability when starting the vehicle.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between operating negative pressure and throttle valve opening. 1...Engine, 2...Exhaust passage, 3
... Air cleaner, 4 ... Throttle valve, 5 ... Intake pipe, 6 ... Exhaust gas recirculation passage, 7 ... Exhaust gas recirculation control Valve, 7a...
...Valve body, 8...Diaphragm, 9...
... Negative pressure chamber, 10... Spring, 11...
... Negative pressure passage, 12 ... Solenoid three-way switching valve,
12 a... Valve chamber, 12 b, 12 C...
... Port, 13 ... Negative pressure passage, 14 ...
... Negative pressure outlet, 15 ... Negative pressure passage, 16
... Negative pressure tank, 17 ... One-way valve, 18 ... Excitation coil, 19 ...
・Negative pressure switch, 19 a...Movable contact, 19
b...Fixed contact, 20...Power supply, 2
1...Diaphragm, 22...Negative pressure chamber, 23...Negative pressure passage, 24...Negative pressure outlet, 25... spring.

Claims (1)

[Scope of utility model registration request] The exhaust passage and the suction passage are configured to communicate with each other via an exhaust recirculation control valve operated by suction negative pressure to recirculate part of the exhaust gas to the suction system, and the negative pressure chamber of the control valve is connected to an electromagnetic three-way One side is opened immediately upstream of the idling opening of the throttle valve of the suction system through a switching valve, and the other side is connected to the downstream side of the throttle valve of the suction system through a negative pressure tank and a one-way valve. The excitation coil of the switching valve is connected to a power source via a negative pressure switch, and the negative pressure chamber of the negative pressure switch is opened to the suction system at a position upstream of the idling opening of the throttle valve and downstream at a predetermined opening or more. , an exhaust gas recirculation control device for an internal combustion engine, characterized in that the negative pressure switch is turned on in a region of suction negative pressure equal to or higher than a predetermined value, and the operating negative pressure of the exhaust recirculation control valve is supplied from a negative pressure tank. .