JPS6113106B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an exhaust gas recirculation device that suppresses the generation of NOx by recirculating a portion of exhaust gas emitted from an engine from the exhaust system to the intake system. .

Generally, in an exhaust gas recirculation system, when part of the exhaust gas is recirculated from the exhaust system to the intake system through a recirculation passage, a recirculation control valve is provided in the recirculation passage to control the amount of exhaust gas recirculated according to the operating state of the engine. I'm trying to control it. Additionally, since exhaust gas recirculation has a negative impact on engine drivability and fuel economy, electronically controlled exhaust gas recirculation devices are used to strictly control the amount of recirculation to the minimum necessary at all times. It's becoming like that. This electronically controlled exhaust gas recirculation system detects the operating state of the engine by detecting the carburetor throttle valve opening, the engine speed, etc., and uses the control device to set the optimum recirculation amount stored in advance for this operating state. It is designed to operate a reflux control valve.

However, even if the amount of recirculation of exhaust gas is strictly controlled by the above-mentioned control device, after long-term operation, the exhaust gas flowing through the recirculation passage causes carbon to adhere to the inside of the recirculation passage, reducing the effective opening area of the passage.
Even if the recirculation control valve is operated to a predetermined opening degree, the amount of recirculation of exhaust gas actually supplied is smaller than the set value.
It has a problem that the NOx suppression effect is insufficient.

In other words, the exhaust gas purification performance deteriorates with the passage of operating time, and replacing parts of the reflux passage and reflux control valve just because of carbon buildup poses a cost problem. Countermeasures are required.

Therefore, the present invention provides a recirculation control valve that controls the recirculation amount of exhaust gas by moving a valve body in the recirculation passage,
The control device controls the reflux control valve so that the target amount of movement of the valve body matches the measured amount of movement, and also detects the pressure downstream of the reflux control valve in the reflux passage to match the actual pressure in the reflux passage. Provided is an engine exhaust gas recirculation device that controls the amount of movement of a valve body to be increased by comparing the target pressure with a target pressure and detecting a decrease in the amount of exhaust gas recirculation due to carbon deposition, thereby dealing with carbon deposition. The purpose is to maintain good exhaust gas purification performance by correcting the decrease in the exhaust gas recirculation amount and always obtaining the desired recirculation amount.

Embodiments of the present invention will be described below with reference to the drawings. In Figure 1, 1 is an engine (not shown)
This is an intake system for supplying intake air to the intake passage 2, and the flow rate of intake air flowing into the intake passage 2 from the direction of the arrow is controlled by a throttle valve 3. Reference numeral 4 refers to a recirculation passage that recirculates exhaust gas from an exhaust system (not shown) connected to the engine to the intake system 1 (intake passage 2 downstream of the throttle valve 3);
is a reflux control valve installed in the reflux passage 4.

The reflux control valve 5 includes a diaphragm 5c to which a valve element 5a for opening and closing the reflux passage 4 is attached via a rod 5b, a negative pressure chamber 5d and an atmospheric chamber 5e partitioned by the diaphragm 5c, and the valve element 5c. 5a
The negative pressure acting on the negative pressure chamber 5d is used as an opening source, and this negative pressure biases the diaphragm 5c against the spring force of the spring 5f to close the valve body. 5a is opened, and the amount of recirculation of exhaust gas is controlled according to the amount of movement of the valve body 5a.

A negative pressure passage 6 is provided in the negative pressure chamber 5d of the recirculation control valve 5.
One end 6a of the negative pressure passage 6 opens to the intake passage 2 downstream of the throttle valve 3, and the other end 6b opens to the atmosphere via the negative pressure solenoid valve 7 and the atmospheric solenoid valve 8, and the negative pressure A negative pressure passage 6 between the solenoid valve 7 and the atmospheric solenoid valve 8 is connected to the negative pressure chamber 5d. The negative pressure and atmospheric solenoid valves 7 and 8 are opened and closed for a predetermined period of time by a control signal from the control device 9, and the negative pressure chamber 5d of the recirculation control valve 5 is operated.
is adjusted to a predetermined pressure, and the amount of movement of the valve body 5a is controlled.

Next, 10 is a load sensor that detects the load condition of the engine based on the opening degree of the throttle valve 3, 11 is a rotation sensor that detects the engine speed, and 12 is disposed downstream of the reflux control valve 5 in the reflux passage 4 and is connected to the reflux control valve 5. Reflux passage 4
A pressure sensor 13 is attached to the reflux control valve 5 and is a valve body position detection center that detects the moving position of the valve body 5a, and detection signals from each of the sensors are input to the control device 9. Ru.

Further, 14 is a valve body of the recirculation control valve 5 that corresponds to the optimum exhaust gas recirculation amount determined through experiments in accordance with the engine operating state due to an arbitrary combination of engine load (throttle valve opening) and engine speed. 5
A first memory device 15 stores the target movement amount of a in advance, as shown in map _M1 of FIG.
Similarly, the value of the recirculation passage 4 downstream of the recirculation control valve 5 corresponding to the optimum exhaust gas recirculation amount determined experimentally corresponding to the engine operating state due to an arbitrary combination of engine load (throttle valve opening) and engine speed. A second memory device stores the target pressure in advance as shown in map _M2 in FIG. 3, and the first and second memory devices 14 and 15 are each connected to the control device 9.

The control device 9 controls the reflux control valve 5 by outputting a control signal to the negative pressure and atmospheric solenoid valves 7 and 8 so that the target movement amount and the measured movement amount of the valve body 5a match. While controlling the recirculation of exhaust gas according to the operating state, when the measured pressure in the recirculation passage 4 is lower than the target pressure, the valve body 5a of the recirculation control valve 5
The control signal to the negative pressure and atmospheric solenoid valves 7 and 8 is corrected so that the amount of movement of the exhaust gas becomes larger than the target amount of movement, and the reduction in the amount of exhaust gas recirculation due to carbon deposition is corrected and controlled.

To explain the operation of the above embodiment, the control device 9
is the target value of the valve body 5a corresponding to the optimum exhaust gas recirculation amount according to the current operating condition, based on the combination of the rotation speed signal from the rotation sensor 11 and the load signal corresponding to the throttle valve opening from the load sensor 10. The amount of movement is calculated from the map _M1 of the first memory device 14, and this target amount of movement and the valve body position detection sensor 13 are calculated.
A control signal corresponding to the difference is output to the negative pressure and atmospheric solenoid valves 7 and 8, and the solenoid valves 7 and 8 are opened and closed for a predetermined period of time. Depending on the opening/closing times of the negative pressure solenoid valve 7 and the atmospheric solenoid valve 8, a predetermined negative pressure is introduced into the negative pressure chamber 5d of the reflux control valve 5, and the valve body 5a is operated to a target movement amount to open the reflux passage 4. This system recirculates a predetermined amount of exhaust gas depending on the current operating conditions, thereby suppressing the generation of NOx.

Next, due to long-term operation, carbon in the exhaust gas adheres to the wall surface of the recirculation passage 4 and its effective passage area becomes narrow, even if the valve body 5a is opened at the target movement amount according to the current operating condition. , the actual exhaust gas recirculation amount is lower than the optimum recirculation amount, and as a result, the measured pressure in the recirculation passage 4 downstream of the recirculation control valve 5 is:
The pressure is lower than the target pressure when the set amount of exhaust gas is recirculated.

Therefore, the control device 9 includes the rotation sensor 11
The target pressure in the recirculation passage 4 corresponding to the optimum exhaust gas recirculation amount according to the current operating condition is determined from the map M in the second memory device 15 by the combination of the rotation speed signal from the M and the negative pressure signal from the negative pressure sensor 10. ₂ , and compares this target pressure with the measured pressure from the pressure sensor 12. If the measured pressure is lower than the target pressure, the negative pressure and atmospheric pressure are The control signals to the solenoid valves 7 and 8 are corrected to increase the negative pressure introduced into the negative pressure chamber 5a of the reflux control valve 5. Due to this increase in negative pressure, the amount of movement of the valve body 5a becomes greater than the target amount of movement of the first memory device 14, and the actual amount of exhaust gas recirculation is corrected and controlled to the optimum amount of recirculation.

The operation of the control device 9 will be explained using the flowchart shown in FIG. The control device 9 inputs the rotation signal N from the rotation sensor 11, the load signal L from the load sensor 10, and the pressure signal _P2 (actual pressure) from the pressure sensor 12 in step 20 at predetermined time intervals, In Steps 22 and 23, the target movement amount _S1 of the valve body _5a is calculated and imported from the map M1 stored in advance in the first memory device 14 according to the engine speed and engine load.
From _M1 , it is determined whether the engine speed and engine load are within the range for correction, and if YES, in step 24, the engine speed and engine load are stored in advance in the second memory device 15 according to the engine speed and engine load. The target pressure _P1 of the recirculation passage 4 is calculated and taken in from the map _M2 , and if NO, the process proceeds to step 28 and feedback control is performed to close the valve body 5a.

Subsequently, in step 25, the target pressure P ₁
and the actual measured pressure _P2 of the pressure sensor 12 P=
P ₁ −P ₂ is calculated, and in step 26 it is determined whether the pressure difference P is greater than or equal to the set value α,
In the case of YES, the target movement amount S ₁ is multiplied by the correction coefficient K (K>1) in step 27 to increase the target movement amount S ₁ , while in the case of NO, the process proceeds to step 28 where the valve body 5a is Performs feedback control.

Next, in step 28, the measured movement amount _S2 of the valve body 5a is input from the valve body position detection sensor 13,
In step 29, the difference between the target movement amount S ₁ (the value stored in the first memory device 14 in step 21 or the value corrected for increase in step 27) and the measured movement amount S ₂ is calculated as follows: S = S ₁ - S ₂
In step 30, a pulse control signal corresponding to the sign and magnitude of the difference S is outputted to drive the negative pressure and atmospheric solenoid valves 7 and 8.

Repeat the above operation to remove the valve body 5a of the reflux control valve 5.
is feedback-controlled to the target movement amount _S1 , and at the same time, in step 26, the state of decrease in the exhaust gas recirculation amount due to carbon deposition is determined, and this decrease in the recirculation amount is corrected by increasing the target movement amount _S1 of the valve body 5a. Control.

In the above embodiment, the correction control according to the difference between the target pressure P ₁ and the measured pressure P ₂ of the recirculation passage 4 is performed by continuously correcting the movement amount of the valve body 5a or by changing the set value in stages. Whether or not to provide and correct it is done arbitrarily as necessary.

Therefore, according to the exhaust gas recirculation device of the present invention as described above, by performing feedback control of the recirculation control valve according to the engine speed and engine load, accurate optimal exhaust gas recirculation control corresponding to the operating state of the engine can be performed. I can do it. In addition, the system detects a decrease in the amount of exhaust gas recirculation depending on the state of carbon accumulation based on the difference between the target pressure and the measured pressure in the recirculation passage, and performs correction control to increase the amount of movement of the valve body of the recirculation control valve. , corrects for the decrease in exhaust gas recirculation amount due to carbon deposition due to increased operating time and the deterioration of exhaust gas purification performance, and always ensures the minimum necessary recirculation amount to maintain the NOx suppression effect. Driving performance and fuel efficiency can be improved.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is an overall configuration diagram, FIGS. 2 and 3 are explanatory diagrams showing maps stored in a memory device, and FIG. 4 is an explanation of the operation of the control device. FIG. 1... Intake system, 2... Intake passage, 3... Throttle valve,
4...reflux passage, 5...reflux control valve, 5a...valve body, 5b...rod, 5c...diaphragm, 5
d...Negative pressure chamber, 5e...Atmospheric chamber, 5f...Spring, 6...Negative pressure passage, 7...Negative pressure solenoid valve, 8...Atmospheric solenoid valve, 9...Control device,
10...load sensor, 11...rotation sensor,
12...Pressure sensor, 13...Valve body position detection sensor, 14...First memory device, 15...Second
memory device.

Claims (1)

[Claims] 1. A recirculation control valve that is installed in a recirculation passage that takes out a portion of exhaust gas from the exhaust system and recirculates it to the intake system, and controls the amount of recirculation of the exhaust gas by moving a valve body;
A load sensor that detects the engine load condition,
a rotation sensor that detects the engine rotation speed; a valve body position detection sensor that detects the movement position of the valve body of the recirculation control valve; a pressure sensor that is provided in the recirculation passage and detects the pressure downstream of the recirculation control valve; a first memory device that stores in advance a target movement amount of the valve body of the recirculation control valve determined experimentally for an arbitrary combination of load and engine speed; A second memory device that stores the target pressure controls the reflux control valve so that the target movement amount and the measured movement amount of the valve body match, and reflux control when the measured pressure of the reflux passage is lower than the target pressure. An exhaust gas recirculation device for an engine, comprising: a control device that controls the amount of movement of a valve body of a valve to be larger than the target amount of movement.