JPS6034766Y2 - Internal combustion engine exhaust gas recirculation control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-called back pressure control type exhaust gas recirculation control device.

In a back pressure controlled exhaust gas recirculation (EGR) system, a signal negative pressure level is formed in the EGR passage to the negative pressure operated exhaust gas flow control valve in the EGR passage connecting the exhaust manifold and intake manifold. The structure is controlled by a variable pressure valve that responds to the exhaust gas pressure in the constant pressure chamber.

By maintaining the exhaust gas pressure in the constant pressure chamber at a constant value close to atmospheric pressure, the effect of keeping the proportion of the amount of exhaust gas circulated (EGR rate) constant is achieved, as is well known.

However, if the EGR rate is always constant over each operating range of the engine, it will cause deterioration in driveability such as surging on the low load side.

This is because the limit of the EGR rate at which surging occurs is smaller on the lower load side.

Therefore, in order to obtain the maximum EGR effect while preventing surging, it is necessary to control the EGR rate according to the load.

In order to achieve this objective, the applicant of the present application, as one of the joint applicants, previously proposed EG
We proposed an exhaust gas recirculation control device with a new structure that makes it possible to control the R rate according to the load.

According to this prior invention, it is possible to change the EGR rate according to the load, but the operating range in which EGR is performed is limited to acceleration or steady driving, and for example, when shifting from second gear to third gear during acceleration. It was not possible to perform EGR during gear shifting or deceleration.

In order to improve this point, the present invention has a structure that allows EGR control to be achieved even during gear shifting or deceleration.
The purpose is to further reduce x.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

The accompanying drawing shows an embodiment of the exhaust gas recirculation control device according to the present invention, in which 10 is an engine body of an internal combustion engine, 12 is an intake manifold, 14 is a carburetor, and 16 is an exhaust manifold.

18 is an exhaust gas recirculation passage (EGR passage) connecting the exhaust manifold 16 and the intake manifold 12.

A flow control valve 20 is provided on the EGR passage 18 to control the flow rate of circulating exhaust gas introduced into the intake manifold 12.

The flow rate control valve 20 is a negative pressure operated type and includes a diaphragm 22 and a valve body 26 connected to the diaphragm 22 via a valve stem 24.

The diaphragm 22 holds the valve body 26 against the valve seat 3 by the spring 28.
0 in the direction of seating.

A negative pressure chamber 32 is formed above the diaphragm 22, and depending on the negative pressure level within this chamber 32, the internal pressure of the EGR valve 2 is reduced.
The circulating exhaust gas flow rate is controlled.

A back pressure control throttle 34 is provided on the exhaust manifold side (i.e., upstream side) of the zero seat 30 in the EGR valve 2, and thus the valve seat 30
A constant pressure chamber S having a relatively small volume is formed in the circulating gas path between the aperture 34 and the aperture 34 .

Reference numeral 36 denotes a first negative pressure signal extraction port (
The flow control valve 20 is operated by a negative pressure signal from this port 36 (so-called EGR port).

38 is the zero pressure chamber 32 in the EGR valve 2 from the EGR port 36
This is a variable pressure valve that controls the level of a negative pressure signal introduced through the negative pressure signal passages 40a and 40b in accordance with the exhaust gas pressure in the constant pressure chamber S.

The variable pressure valve 38 includes a diaphragm 44 biased by a spring 42, and a back pressure chamber 46 below the diaphragm 44 communicates with the constant pressure chamber S via a back pressure outlet passage 48 having a third restriction or orifice 74. The atmospheric chamber 50 on the upper side of the cage is opened to the atmosphere through an air purifying filter 52.

The diaphragm 44 is provided with a valve element 54, which operates to open and close a branch pipe 56a of a back pressure control pipe 56 connecting the negative pressure signal passages 40a and 40b.

The first restriction or orifice 60 in the pipe 56 is EG.
The negative pressure flow rate from the R port 36 toward the negative pressure chamber 32 of the flow control valve 20 is controlled.

Reference numeral 80 denotes a temperature-sensitive switching valve for EGR cut provided in the negative pressure signal passage 40a. For example, it detects the engine cooling water temperature and operates on and off, and when it is off, the negative pressure of the EGR port 36 is applied to the EGR valve. EGR is no longer performed because it no longer acts on the two-valve zero-pressure chamber 32.

In the so-called back pressure controlled EGR system using the flow rate control valve 20 and the pressure variable valve 38 described above, when the circulating exhaust gas pressure P in the constant pressure chamber S on the EGR passage 18 becomes small, the diaphragm 44 of the pressure variable valve 38 As a result, the pipe 56a is opened by being pushed down by the spring 42, and the air entering the atmospheric chamber 50 through the filter 52 is introduced into the negative pressure line 40b at a flow rate determined according to the dimensions of the second restriction or orifice 62. Then, the negative pressure level acting on the zero-pressure chamber 32 in the EGR valve 2 is weakened, and the diaphragm 22 moves the valve body 26 toward the valve seat 30 by the spring 28 .

As a result, the pressure of the circulating exhaust gas in the constant pressure chamber S increases, and as a result, the diaphragm 44 of the variable pressure valve 38 is pushed up against the spring 42, and the pipe 56a is closed.

Therefore, the introduction of atmospheric air into the pipe 56a is stopped, and the EGR
The level of the negative pressure signal that enters the zero pressure chamber 32 in the EGR valve 2 from the port 36 via the negative pressure line 40b in accordance with the dimensions of the second orifice 60 increases, and the diaphragm 22 is pulled up against the spring 28 and the valve body 26 is moved away from the valve seat 30, and thus the exhaust gas pressure in the constant pressure chamber S decreases again.

As is clear from the basic principle of the exhaust pressure controlled EGR system described above, the circulating exhaust gas pressure in the constant pressure chamber S is maintained constant at a predetermined value close to atmospheric pressure. The EGR rate, which is the proportion of exhaust gas introduced into the intake manifold through the throttle valve 14a, can be kept substantially constant regardless of the load of the throttle valve 14a, that is, the engine.

However, as mentioned above, if the EGR rate is kept constant in this way, in order to obtain the maximum EGR effect, that is, the NOx reduction effect, if the EGR rate is set high, poor driveability such as surging may occur on the low load side. It has the disadvantage of being easy.

In order to solve this problem, as mentioned above, the patent application No. 53-7857
In No. 5, it was proposed to provide a second negative pressure port 70 slightly upstream of the EGR port 36 from which a negative pressure signal corresponding to the engine load is taken out.

This second negative pressure port 70 is connected to the atmospheric chamber 50 of the pressure changing valve 38 via a negative pressure line 72, and also has a fourth restrictor that regulates the speed of air entering the atmospheric chamber 50 through the air filter 52. Alternatively, an orifice 75 is provided.

With this configuration, the second negative pressure port 70 is in a low load range from the idle opening θ shown by the solid line to the opening θ2 shown by the dashed-dotted line in the figure that just overlaps the EGR port 36. Since the pressure is approximately atmospheric, the pressure in the atmospheric chamber 50 of the variable pressure valve 38 is maintained at atmospheric pressure by introducing air through the filter 52 and the second orifice 62.

As a result, the exhaust gas pressure P in the constant pressure chamber S is maintained at a constant pressure substantially close to atmospheric pressure based on the principle described above.

When the throttle valve 14a is opened to a medium load region covering the negative pressure port 70 as shown by the two-dot chain line θ3 in the figure, negative pressure appears at the port 70, and this negative pressure is transferred to the atmospheric chamber 5 of the pressure variable valve 38.
As a result, the pressure in the atmospheric chamber 50 is corrected to the negative pressure side.

Since the negative pressure level of the port 70 increases between the throttle opening degrees θ2 and 03 depending on the extent to which the throttle valve 14a overlaps the port 70, the negative pressure in the atmospheric chamber 50 of the pressure variable valve 38 gradually increases.

As a result, the time for the valve element 54 of the pressure variable valve to close the pipe 56a becomes longer as the throttle valve 14a opens, and the E
A characteristic is obtained in which the negative pressure level in the zero-pressure chamber 32 within the GR valve 2 increases as the throttle valve opens.

Thus, the EGR rate, which is a proportion of the amount of circulating exhaust gas, has a characteristic that increases depending on the load between the throttle openings θ2 and 03.

When the opening degree of the throttle valve 14a becomes 03, the pressure transformer valve 38
Since the negative pressure in the atmospheric chamber increases to the point where it is always closed, the pressure change valve 38 does not control the negative pressure introduced into the EGR valve 2 at the opening after this point, and the The amount, that is, the EGR rate, is determined only by the negative pressure of the EGR port 36, and changes to the well-known negative pressure control type EGR characteristics.

The EGR rate decreases as the throttle valve opens.

According to the above configuration, the load control of the EGR rate can be performed by introducing the intake negative pressure that increases in accordance with the engine load into the pressure variable valve 38.

As a result, it is possible to achieve a high EGR rate in the medium to high load range while maintaining a necessary and sufficient margin for the surging limit in the light load range.

The present invention aims to further improve exhaust gas purification efficiency while maintaining such effects.

That is, in the above configuration, when the throttle valve 14a is at the opening position of 03, when the accelerator pedal is released from this state in order to shift to a higher speed gear, for example, the throttle valve 14a returns to the idle opening position θ1. As a result, the second negative pressure port 70, on which negative pressure had been applied until then, returns to substantially atmospheric pressure again, and the valve body 54 of the variable pressure valve 38 is opened.

As a result, the negative pressure chamber 32 of the EGR valve 20 is bled by the atmosphere, and the EGR valve 2 becomes zero-chain.

That is, as soon as the throttle valve 14a changes from the opening degree of 03 to the opening degree of 01, EGR is cut off.

This also applies when the throttle valve 14a is decelerating from the opening degree of 03 to the opening degree of 02.

In order to prevent this, according to the present invention, the negative pressure signal path 72
A negative pressure delay valve 82 is provided within.

The negative pressure delay valve 82 is composed of a fifth throttle 84 and an umbrella-shaped one-way valve 86, as is known per se.

The one-way valve 86 opens only when the pressure level on the second negative pressure port 70 side is low relative to the atmospheric chamber 50 of the pressure variable valve 38.
A large negative pressure of the negative pressure port 70 can be transmitted to the atmospheric chamber 50.

Therefore, when the second negative pressure port 70 temporarily reaches atmospheric pressure, for example, during gear shifting as described above, the one-way valve 86 is in the closed position, and this atmospheric pressure is applied only to the atmospheric chamber 5 through the throttle 84.
0 can be communicated.

That is, atmospheric pressure is transmitted to the atmospheric chamber 50 with a delay, and EGR cut is delayed by the delay time.

Therefore, especially when changing gears, the throttle valve 14a is
In the case where the temperature is immediately returned to θ3 after shifting from θ to θ, EGR cut is not substantially performed and intermittent EGR can be performed.

The delay time can be arbitrarily set depending on the size of the aperture 84.

As described above, the present invention satisfies the requirement of controlling the EGR rate in accordance with the engine load, and further reduces NOx in exhaust gas by maintaining EGR for a certain period of time even during deceleration or gear shifting. It is a distant relative of reduction.

[Brief explanation of the drawing]

The accompanying drawings are diagrams showing the basic configuration of an exhaust gas recirculation control device according to the present invention. 12...Intake manifold, 14...Carburizer, 16...Exhaust manifold, 18...
...EGR passage, 20...Flow control valve, 36.
...EGR port, 38...Transformer valve, 5
0... Atmospheric chamber, 70... Negative pressure port, 84... Negative pressure delay valve, S... Constant pressure chamber.

Claims (1)

[Scope of utility model registration request] A negative pressure-operated exhaust gas flow control valve is provided in the exhaust gas recirculation passage connecting the engine exhaust system and the intake system, and a first negative pressure valve is provided in which the negative pressure chamber of the exhaust gas flow control valve faces upstream of the throttle valve. The negative pressure chamber of the exhaust gas flow rate control valve is connected to the pressure port via a negative pressure signal passage, and the negative pressure signal passage is provided with a pressure variable valve with an atmospheric chamber that operates according to the back pressure of the recirculated exhaust gas. In the exhaust gas recirculation control device for an internal combustion engine, the atmospheric chamber of the pressure variable valve is arranged to face further upstream of the first negative pressure port. A negative pressure is communicated with the second negative pressure port via a negative pressure signal passage, and a negative pressure is released within the negative pressure signal passage only when the pressure level on the second negative pressure port side is lower than the atmospheric pressure of the pressure variable valve. An exhaust gas recirculation control device characterized by being provided with a delay valve.