JPS62349B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an exhaust gas recirculation device for an engine.

Conventionally, as shown in JP-A-51-151420, for example, as an exhaust gas recirculation device for an engine,
An exhaust gas recirculation passage that recirculates a portion of the engine's exhaust gas to the intake system; a recirculation control valve that is installed in the exhaust gas recirculation passage and controls the recirculation of the exhaust gas; It is known that the engine is equipped with an activated acceleration detection device, and the recirculation control valve is opened by the operation of the acceleration detection device, so that exhaust gas is recirculated during acceleration.

However, the acceleration detection device described above detects the start of an acceleration state in response to a change in the opening degree of the throttle valve, and operates for a predetermined period of time from then on as an acceleration time. Sometimes, exhaust gas is recirculated (or increased recirculation) even in a steady state, and there is a problem in that more exhaust gas than necessary is recirculated, which adversely affects drivability.

In other words, in a steady state of the engine, less NOx is generated than in an accelerated state, so it is necessary to stop or reduce the recirculation of exhaust gas to an appropriate amount, but when the engine operating state changes from an accelerated state to a steady state. However, when the acceleration detection device continues to operate, a large amount of exhaust gas is recirculated as in the acceleration state. In particular, since the activation time of the acceleration detection device is set to a relatively long time so as to cover the entire acceleration state, overflow occurs frequently in the steady state, and if the activation time is shortened, acceleration will occur. A sufficient NOx suppression effect cannot be expected under these conditions.

In view of these points, the present invention includes a steady operation detection device that detects steady operation of the engine, and receives the output of the steady operation detection device to cancel the opening operation of the recirculation control valve caused by the operation of the acceleration detection device during steady operation of the engine. An object of the present invention is to provide an exhaust gas recirculation device for an engine equipped with a control device, and to improve driveability by optimizing the amount of exhaust gas recirculation in a steady state.

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

This embodiment has an exhaust pressure control type recirculation control valve and an air-fuel ratio correction device that enriches the air-fuel ratio when exhaust gas is recirculated. During acceleration, the recirculation is controlled by operating an on-off valve linked to an acceleration detection device. The valve is opened and the air-fuel ratio is enriched, while during normal operation, the control device cuts off the interlock between the acceleration detection device and the opening/closing valve, and stops the opening operation of the recirculation control valve caused by the acceleration detection device. This is an example of an exhaust gas recirculation device that makes the air-fuel ratio lean.

In the figure, 1 is an exhaust gas recirculation passage that recirculates a part of exhaust gas from an engine (not shown) to an intake passage 2 (intake system), and 3 is an exhaust gas recirculation passage that is interposed in the exhaust gas recirculation passage 1 to recirculate the exhaust gas. The reflux control valve 3 opens and closes the valve body 3b according to the magnitude of the negative pressure introduced into the negative pressure chamber 3a. A first negative pressure passage 4 is connected to the chamber 3a, and the first negative pressure passage 4 communicates with a first negative pressure outlet 4a that opens into the intake passage 2 immediately upstream of the throttle valve 5 in the fully closed state. ing.

Reference numeral 6 denotes a negative pressure regulating valve that regulates the negative pressure introduced into the recirculation control valve 3, and a leak hole 4b of the first negative pressure passage 4 opens in the pressure regulating chamber 6a.
Adjustment of the opening degree of valve b is performed by a valve body 6c fixed to a diaphragm 6b. A pressure passage 7 is connected to the pressure chamber 6d at the back of the diaphragm 6b, and the pressure passage 7 communicates with the constant pressure chamber 1a of the exhaust gas recirculation passage 1. This constant pressure chamber 1a is an exhaust gas recirculation passage 1 between an orifice 8 provided upstream of the recirculation control valve 3 and a valve body 3b, and the negative pressure adjustment valve 6
The pressure regulating chamber 6a is opened to the atmosphere through an atmospheric hole 6e and is connected to a second negative pressure passage 9, which is connected to the first negative pressure outlet 4a via an on-off valve 10. It communicates with a second negative pressure outlet 9a that opens into the upstream intake passage 2.

Reference numeral 11 denotes an air-fuel ratio correction device that corrects the air-fuel ratio of the air-fuel mixture supplied to the engine, and is a fuel passage that supplies the fuel in the float chamber 12 to the nozzle 15 of the bench lily portion 14 together with the air from the main air bleed 13. 16, an auxiliary air bleed passage 17 that supplies air in parallel with the main air bleed 13 is opened and closed by the on-off valve 10.

The on-off valve 10 includes an acceleration detection device 18 that detects the acceleration state of the engine and operates for a predetermined period of time, and a control device 19 that stops the opening operation of the recirculation control valve 3 due to the operation of the acceleration detection device 18 during steady operation of the engine. It is integrated.

The acceleration detection device 18 includes a first negative pressure chamber 18b and a second negative pressure chamber 1 separated by a diaphragm 18a.
Intake negative pressure is introduced into the fourth negative pressure passages 20 and 8c, respectively, and the fourth negative pressure passages 20
is the fourth opening directly downstream of the throttle valve 5 which is in the fully closed state.
A check valve 18d (first
(which closes when the pressure in the negative pressure chamber 18b is low) is interposed, and the first negative pressure chamber 18b is closed by the throttle 18.
It is opened to the atmosphere via e and the first spring 18f is compressed. Also, the second negative pressure chamber 18 of the diaphragm 18a of this acceleration detection device 18
A first rod 18g is supported on the c side, and this first rod
The distal end of the rod 18g is linked to the proximal end of a second rod 19b supported by a diaphragm 19a of the control device 19 so as to be removable.

In the control device 19, a third negative pressure passage 21 is connected to a negative pressure chamber 19d separated from an atmospheric chamber 19c by a diaphragm 19a, and the third negative pressure passage 21 is located upstream of the second negative pressure outlet 9a. A steady operation detection device 22 is configured to communicate with a third negative pressure outlet 21a that opens into the intake passage 2 upstream of the opening of the throttle valve 5 during steady operation, and a third negative pressure outlet 21a is provided in the negative pressure chamber 19d. 2 spring 19e is compressed. The tip of the second rod 19b of this control device 19 is connected to the on-off valve 1.
It is linked to the diaphragm 10a of 0 so that it can come into contact with and separate from it.

The on-off valve 10 has a valve body 10b that acts on both sides of a diaphragm 10a, and a first chamber 10 that is closed by downward deflection of the diaphragm 10a.
c is a second negative pressure passage 9 for the negative pressure regulating valve 6;
On the other hand, the auxiliary air bleed passage 17 of the air-fuel ratio correction device 11 is connected to the second chamber 10d, which is closed by upward deflection of the diaphragm 10a, and the second chamber 10d is connected to the second chamber 10d, which is connected to the second chamber 10d. The third chamber 10e is opened to the atmosphere through a filter 10f and a throttle 10g, and a third spring 10h is compressed in the first chamber 10c.

To explain the operation of the above embodiment, first, in the state before acceleration, that is, when the opening degree of the throttle valve 5 is relatively small and the intake negative pressure downstream of the throttle valve 5 is acting on the fourth negative pressure outlet 20a. , the acceleration detection device 18 is in an inactive state. That is, the check valve 18d is open and intake negative pressure is introduced into both the first negative pressure chamber 18b and the second negative pressure chamber 18c, and the diaphragm 18a is deflected downward by the action of the first spring 18f. , the first rod 18g is in the protruding (lowering) position, the second rod 19b is also in the descending position, the diaphragm 10a of the on-off valve 10 is deflected downward, and the valve body 10b is in the second negative pressure passage. 9 is closed, while the auxiliary air bleed passage 17 is opened. Therefore, air is supplied from the auxiliary air bleed passage 17 through the throttle 10g of the third chamber 10e and the filter 10f to make the air-fuel ratio lean, and the recirculation control valve 3 closes the exhaust gas recirculation passage 1. Alternatively, a small amount of exhaust gas is recirculated. The third negative pressure outlet 21a is located upstream of the throttle valve 5 with a small opening, and is connected to the negative pressure chamber 19 of the control device 19.
No intake negative pressure is introduced into d.

At that time, since the second negative pressure passage 9 is closed, the pressure regulating chamber 6a of the negative pressure regulating valve 6 is only opened to the atmosphere through the atmospheric hole 6e, and the first
When negative pressure acts on the negative pressure outlet 4a and the recirculation control valve 3 opens, the degree of opening of the valve body 3b is controlled by the negative pressure regulating valve 6 in accordance with the pressure in the constant pressure chamber 1a. That is, the constant pressure chamber 1a averaged by the orifice 8
The pressure changes in accordance with the amount of exhaust gas, and when the pressure in the constant pressure chamber 1a increases, the amount of negative pressure leaking from the first negative pressure passage 4 at the negative pressure regulating valve 6 decreases, and the reflux control is performed. As the opening degree of the valve body 3b of the valve 3 increases and the amount of exhaust gas recirculation increases, the constant pressure chamber 1
The pressure in the constant pressure chamber 1a decreases, and the constant pressure chamber 1a
operates to maintain a substantially constant pressure, and controls the amount of exhaust gas recirculation in accordance with the amount of exhaust gas, that is, the amount of intake air.

When the operating state shifts to the acceleration state, that is, the throttle valve 5 is suddenly opened widely, and the intake negative pressure downstream of the throttle valve 5 acts on the first to third negative pressure outlets 4a, 9a, 21a. Fourth negative pressure outlet 20
When the atmospheric pressure upstream of the throttle valve 5 acts on a, the acceleration detection device 18 is activated. In other words, the second
The negative pressure chamber 18c becomes atmospheric pressure at the same time as the throttle valve 5 is opened, but negative pressure remains in the first negative pressure chamber 18b due to the closing of the check valve 18d, so the diaphragm 18
a is deflected upward against the first spring 18f, raising the first rod 18g. The operation of the acceleration detection device 18 is continued until the pressure in the first negative pressure chamber 18b is increased by the atmosphere introduced through the throttle 18e and the diaphragm 18a is deflected downward. It is set by the diameter of Further, by introducing negative intake pressure into the negative pressure chamber 19d of the control device 19, the second rod 19 follows the upward movement of the first rod 18g.
b also moves upward. Therefore, the diaphragm 10a of the on-off valve 10 is deflected upward by the third spring 10h, and the valve body 10b opens the second negative pressure passage 9 while closing the auxiliary air bleed passage 17. When the supply of air is stopped and the air-fuel ratio becomes rich, the recirculation control valve 3 increases the opening degree of the valve body 3b to start recirculating the exhaust gas or to increase the amount of recirculation.

That is, by opening the second negative pressure passage 9, negative pressure is introduced into the pressure regulating chamber 6a of the negative pressure regulating valve 6,
Even if the opening degree of the leak hole 4b of the first negative pressure passage 4 is the same, the negative pressure in the negative pressure chamber 3a of the recirculation control valve 3 increases, and as a result, the opening degree of the valve body 3b increases, and the exhaust gas recirculation amount increases. increases. Note that the control of the recirculation amount corresponding to the amount of exhaust gas by changing the pressure in the constant pressure chamber 1a is performed in the same manner as described above.

Further, when the acceleration state shifts to the steady state, if the acceleration detection device 18 is in operation, the second negative pressure passage 9 is open, so that the recirculation (increase in amount) of the exhaust gas continues. However, during steady operation, the opening degree of the throttle valve 5 is smaller than during acceleration, and the third negative pressure outlet 21a is located on the upstream side of the throttle valve 5, so that no intake negative pressure is applied. Therefore, as the diaphragm 19a of the control device 19 is deflected downward by the second spring 19e, the second
The rod 19b moves downward away from the first rod 18g, deflects the diaphragm 10a of the on-off valve 10 downward, closes the second negative pressure passage 9, and opens the auxiliary air bleed passage 17.
The recirculation control valve 3 and the air-fuel ratio correction device 11 return to the same operating state as when the acceleration detection device 18 is inactive.

That is, during steady state transition, exhaust gas recirculation is stopped or reduced to an appropriate value to obtain good drivability, and the air-fuel ratio of the air-fuel mixture is made lean to improve fuel efficiency.

In the above embodiment, during steady operation, the control device 19 cuts off the connection between the acceleration detection device 18 and the reflux control valve 3. However, for example, the detection operation of the acceleration detection device 18 itself can be stopped or Also, for detection during steady state, in addition to the method using the third negative pressure outlet 21a of the above embodiment, a throttle valve opening sensor may be used to detect changes in the opening of the throttle valve. , the detection may be made from fluctuations in intake negative pressure and engine speed, and furthermore, the control device 19 itself may be operated by a solenoid valve in addition to a diaphragm device.

Therefore, according to the present invention as described above, in a device in which the recirculation control valve is opened by the operation of the acceleration detection device that detects the acceleration state of the engine and operates for a predetermined period of time, the steady state operation that detects the steady operation of the engine is performed. By providing an operation detection device and a control device that receives the output of the steady operation detection device and cancels the opening operation of the recirculation control valve caused by the activation of the acceleration detection device during steady engine operation, the system transitions from an acceleration state to a steady state. This makes it possible to prevent unnecessary recirculation of exhaust gas when the engine is running, improve driveability by optimizing the amount of recirculation during steady state, and eliminate the negative effects of prolonging the activation time of the acceleration detection device. In addition, by setting the operating time to be long, exhaust gas is recirculated throughout the entire acceleration period, which has the effect of effectively suppressing the generation of NOx.

[Brief explanation of the drawing]

The drawing is an overall configuration diagram showing an embodiment of the present invention. 1...Exhaust gas recirculation passage, 2...Intake passage, 3
. . . Reflux control valve, 6 . . . Negative pressure adjustment valve, 10 .

Claims (1)

[Claims] 1. An exhaust gas recirculation passage that recirculates a portion of the exhaust gas of the engine to the intake system; a recirculation control valve that is interposed in the exhaust gas recirculation passage and controls the recirculation of the exhaust gas;
In an engine exhaust gas recirculation system that includes an acceleration detection device that detects the acceleration state of the engine and operates for a predetermined period of time, and that opens a recirculation control valve by the operation of the acceleration detection device, the steady operation detects steady operation of the engine. 1. An exhaust gas recirculation system for an engine, comprising: a detection device; and a control device for receiving an output from the steady operation detection device and canceling an opening operation of a recirculation control valve caused by the operation of the acceleration detection device during steady operation of the engine.