JPS61167151A - Exhaust-recirculation amount controller for internal-combustion engine - Google Patents

Abstract

PURPOSE:To maintain the superior exhaust-gas characteristic of an engine by increasing the max. valve opening-degree position of an exhaust recirculation valve larger than the valve opening-degree for the recirculation of the required max. exhaust recirculation amount. CONSTITUTION:In Steps 4-8, the perfect-closure standard-position value LO of an exhaust recirculation valve 15 is obtained. The correction valve lift value LMAP' is obtained by multiplying the standard valve lift value LMAP by the correction coefficient f(LO-LOO) set according to the deviation between the perfect-closure standard-position value LO and the correction value LOO from a variable voltage source 20. In Step 10, the valve opening-degree instruction value LCMD is calculated, and in Step 11, the control amount S of an exhaust recirculation valve 15 is determined. Thus, a prescribed max. exhaust recirculation amount can be secured, and the superior exhaust-gas characteristic of an engine can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an exhaust gas recirculation amount control device for an internal combustion engine, and more particularly to an exhaust gas recirculation amount control device that is capable of controlling an appropriate amount of exhaust gas recirculation even after a long period of engine operation.

(Technical background of the invention and its problems) A part of the exhaust gas of an internal combustion engine is recirculated to the intake passage,
BACKGROUND ART Methods for reducing nitrogen oxides (NOx), which is one of the harmful gases generated from engines, are widely used. Also,
In order to adjust the amount of exhaust gas recirculated to the intake passage to an appropriate amount depending on the engine operating condition, the valve opening degree of the exhaust recirculation valve disposed in the middle of the exhaust recirculation passage is detected, and the actual amount of exhaust gas recirculation is detected. A method is known in which the exhaust gas recirculation valve is controlled so that the valve opening value becomes a valve opening target value at which the exhaust gas recirculation amount is an appropriate amount.

In such a method, the actual valve opening value is determined by a valve opening sensor,
For example, it is detected by a riff 1 sensor.

However, due to thermal expansion, wear, etc., the fully closed reference position of the exhaust recirculation valve, that is, the detected value of the lift sensor when fully closed, may change, and as a result, the actual valve opening and the lift 1 to
An error may occur between the detected value of the sensor and, for example, even if the actual valve opening is zero, the detected value of the detector will indicate a non-zero value, and the exhaust will be performed based on the target value of the valve opening. This will interfere with the reflux control operation.

In order to eliminate such a problem, a state in which the basic valve lift value read out from a lift map preset according to the engine speed Ne and the intake road negative pressure PB continued to be zero for a predetermined period of time. In this case, the valve opening detection value after the predetermined period of time has elapsed shall be used as the new fully closed reference position, and this new fully closed reference position shall be subtracted from or added to either the actual valve opening detection value or the basic valve lift value, respectively. The applicant has proposed a device that automatically corrects the valve opening target value of the exhaust gas recirculation valve. (Unexamined Japanese Patent Publication No. 57-188753
issue).

In such conventional devices, in order to prevent deterioration of exhaust gas characteristics and engine operability due to an excessive amount of exhaust gas recirculation due to a malfunction of the device, for example, the maximum exhaust gas recirculation valve is Stroke length LMAXI is the maximum value LMAP of the preset basic valve lift value LMAP
Designed to a length that corresponds to MAX, the actual line work shown in Figure 1. As shown in the figure, the maximum amount QMAX of the exhaust gas recirculation amount Q is mechanically regulated.

By the way, when an engine operates for a long period of time, carbon, lead components, etc. in the exhaust gas accumulate around the valve seat of the exhaust gas recirculation valve. Now, as shown by the solid line ■ in Fig. 1, if the fully closed reference position is displaced by a value ΔL in the opening direction of the exhaust recirculation valve, the maximum stroke length of the exhaust recirculation valve is the value Since it is limited to LMAXI, the LMAP value is LMA
When the actual valve opening LACT of the exhaust recirculation valve exceeds the value LT1 obtained by subtracting the ΔL value equivalent from the PMAX value, the actual valve opening LACT of the exhaust recirculation valve cannot achieve the valve opening target value (broken line II'L in Figure 1) corrected by the ΔL value. It disappears. As a result, the exhaust gas recirculation amount Q also becomes unable to reach the target amount (broken line Il'o in FIG. 1), as shown by the solid line ■Q in FIG. Then, the LM AP value is the maximum value LM
In the case of AFMAX, the conventional device has the problem that the value ΔL is insufficient in the actual valve opening LACT, and accordingly, the amount ΔQ is insufficient in the exhaust gas recirculation amount Q, and as a result, the exhaust gas characteristics of the engine are deteriorated. there were.

(Object of the Invention) The present invention was made to solve the above-mentioned problems, and it is an object of the present invention to provide a device that can ensure the required maximum exhaust gas recirculation amount even after a long period of engine operation.

(Structure of the Invention) In order to achieve such an object, the present invention provides an exhaust gas recirculation passage that connects an exhaust pipe of an internal combustion engine to an intake pipe, and an exhaust gas recirculation passage that is provided in the middle of the exhaust gas recirculation passage. an exhaust recirculation valve having a maximum valve opening position that defines the maximum permissible amount of exhaust gas recirculation from the pipe to the intake pipe; an operating state detection means for detecting an operating state of the engine in which exhaust gas recirculation is to be performed;
A memory device that stores in advance the required valve opening degree of the exhaust recirculation valve according to the operating state of the engine, a valve opening degree detector that detects the actual valve opening degree of the exhaust recirculation valve, and a request valve read out from the memory device. a fully closed instruction determining means for determining whether the opening degree indicates fully closed; and a timer means for generating a signal when the generation time of the fully closed determining signal from the fully closed instruction determining means exceeds a predetermined time; a reference position storage means for storing a detected value of the excuse degree detector when the signal from the timer means is input; and an actual valve opening detected by the excuse degree detector based on the stored value of the reference position storage means. calculation means for correcting either one of the valve opening degree detection value and the required valve opening degree; In the exhaust gas recirculation amount control device comprising a degree difference determining means and a valve opening degree control means for controlling the exhaust gas recirculation valve so as to make the opening degree difference zero, the maximum valve opening degree position is determined for a predetermined period of the engine. An exhaust gas recirculation amount control device for an internal combustion engine, wherein the maximum required exhaust gas recirculation amount to be recirculated is larger than the valve opening position for recirculation based on the required valve opening read out from the storage device after operation for a period of is provided.

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

FIG. 2 is an overall configuration diagram showing an internal combustion engine equipped with an exhaust gas recirculation control device according to the present invention. Reference numeral 1 indicates, for example, a four-cylinder internal combustion engine, and an intake pipe 2 is connected to the engine 1. A throttle valve 3 is provided in the middle of the valve 2. Throttle valve 3 has throttle valve opening (OT
H) A sensor 4 is connected to convert the opening degree of the throttle valve 3 into an electrical signal and an electronic control unit (rE
CU").

A fuel injection valve 6 is provided in the intake pipe 2 between the engine 1 and the throttle valve 3. This fuel injection valve 6 is provided for each cylinder slightly upstream of an intake valve (not shown) in the intake pipe 2, and each injection valve 6 is connected to a fuel pump (not shown) and electrically connected to the ECU 3. Well, ECU3
The valve opening time of the fuel injection is controlled by the signal from the.

On the other hand, a negative pressure (PB) sensor 8 is located downstream of the throttle valve 3.
is provided via a pipe 7, and a negative pressure signal converted into an electrical signal by this negative pressure sensor 8 is sent to the ECU 3.

The engine body 1 is provided with an engine water temperature (Tw) sensor 9, which is made of a thermister or the like, and is inserted into the circumferential wall of the engine cylinder filled with cooling water, and supplies its detected water temperature signal to the ECU 3.

Engine speed sensor (hereinafter referred to as rNe sensor) 1
0 is attached around the camshaft or crankshaft (not shown) of the engine. The Ne sensor 10 is set at a predetermined crank angle position every 180' rotation of the engine crankshaft.
In other words, the top dead center (TDC) at the start of the intake stroke of each cylinder
Regarding this, a crank angle position signal (hereinafter referred to as "rTDC signal") is output at a crank angle position before a predetermined crank angle, and this TDC signal is sent to the ECU 3.

A three-way catalyst 12 is disposed in the exhaust pipe 11 of the engine 1, and performs a purifying action on HC, Go, and NOx components in the exhaust gas.

The exhaust recirculation passage 1 connects the exhaust pipe 11 to the intake pipe 2.
4, and an exhaust gas recirculation valve 15 is provided in the middle of this passage 14.
is provided. The exhaust gas recirculation valve 15 is a negative pressure responsive valve, and is mainly arranged to open and close the passage 14, and supports a valve body 15a connected to one end of the valve shaft 15c and the valve shaft 15c in an airtight and slidable manner. The seal portion 15d and the valve stem 1
5c, and is connected to a stopper 15e that defines the maximum valve opening position of the valve body 15a, that is, the maximum allowable exhaust gas recirculation amount when it comes into contact with the lower surface of the seal portion 15d, and the other end of the valve shaft 15C, which will be described later. A diaphragm 15f operated by a combined pressure of atmospheric pressure introduced via the electromagnetic control valve 17 or negative pressure introduced via a communication passage 16 described later, and a spring 15g urging the diaphragm 15f toward the valve seat 15b.
It consists of

The above-mentioned maximum valve opening position is determined by long-term test operation of the engine over a predetermined period of time (for example, 100,000 km in terms of mileage), as will be described later. The valve opening position is determined to allow reflux. A communication passage 16 is connected to the negative pressure chamber 15h defined by the diaphragm 15f, and the absolute pressure within the intake pipe 2 is introduced through the communication passage 16. Further, an atmospheric communication path 18 is connected to the communication path 16,
A normally open electromagnetic control valve 17 provided in the middle of the communication path 18
Atmospheric pressure is supplied to the communication passage 16 via the negative pressure chamber 15
It is intended to be introduced in e. The electromagnetic control valve 17
is connected to the ECU 3, is operated by a signal from the ECU 3, and controls the lift operation and speed of the valve body 15a of the exhaust gas recirculation valve 15.

The exhaust gas recirculation valve 15 is provided with a lift (Lv) sensor 19 that detects the operating position of the valve body 15a of the valve 15 and sends a detected value signal to the ECU 3.

Further, an atmospheric pressure (PA) sensor 13 is connected to the ECU 3, and a detected value signal thereof is sent to the ECU 3.

Furthermore, a valve opening target value adjustment function is used to artificially adjust a correction value related to the actual opening area of the exhaust gas recirculation valve 15 to compensate for a decrease in the actual opening area due to carbon deposition, etc. of the exhaust gas recirculation valve 15. A variable voltage power supply 20 is connected to the ECU 3.

The ECU 3 shapes input signal waveforms from various sensors and the variable voltage power supply 20, corrects the voltage level to a predetermined level,
The input circuit 5a has functions such as converting analog signal values into digital signal values, and the central processing circuit (rCPU)
5b, a storage means 5c for storing various calculation programs and calculation results executed by the CPU 5b, and an output circuit 5d for supplying drive signals to the fuel injection valve 6 and the electromagnetic control valve 17.

The CPU 5b determines the engine operating state based on the engine parameter signals etc. from the various sensors mentioned above via the input circuit 5a, and determines the engine operating state based on the engine parameter signals etc. from the various sensors mentioned above via the input circuit 5a, and determines the third
According to the program shown in the figure, the valve opening command value IJCMD of the exhaust recirculation valve]5 is set according to the intake pipe negative pressure PB, the engine speed Ne, the atmospheric pressure PA, and the correction value set by the variable voltage power supply 20, Valve opening command value L thus set
(The valve opening detection value LAOT of the exhaust recirculation valve 15 detected by the lift sensor 19 is output to the electromagnetic control valve 17 so as to reduce the deviation from the value corrected by the fully closed reference position value to zero. A driving signal is supplied via the circuit 5d, and a fuel injection time T o u T of the fuel injection valve 6 given by the formula shown below is calculated.

Tout = Ti Set. K1 and 2
are a correction coefficient and a correction coefficient calculated according to engine parameter signals from the various sensors described above, namely, the throat valve opening sensor 4, the negative pressure sensor 8, the engine water temperature sensor 9, the Ne sensor 10, and the atmospheric pressure sensor 13, respectively. It is a correction variable that changes starting characteristics, exhaust gas characteristics,
It is calculated based on a predetermined calculation formula so that various characteristics such as fuel efficiency characteristics and engine acceleration characteristics are optimized.

The CPU 5b calculates the fuel injection time T obtained as described above.
A drive signal for opening the fuel injection valve 6 based on outT is supplied to the fuel injection valve 6 via the output circuit 5d.

FIG. 3 is a flowchart showing the procedure for setting the control amount of the exhaust gas recirculation valve 15, and one program includes the aforementioned Ne sensor 10.
This is executed every time the TDC signal is generated.

First, the engine rotation value Ne, the intake pipe negative pressure value PB and the atmospheric pressure value PA, which are the values detected by the Ne sensor 10, the negative pressure sensor 8, and the atmospheric pressure sensor 13, and the variable voltage power source 20
Correction value from. 0 is read into the ECU 3 and stored in the storage means 5C (step 1). The correction value mentioned above. 0 is set to a predetermined value (for example, 0) by the variable voltage power supply 20, for example, at the time of shipping or maintenance of the internal combustion engine.

Next, proceed to step 2, and read out the basic valve list value LMAP stored in the storage means 5C.
yO is set in advance as a function of, for example, the intake pipe internal negative pressure PB and the engine rotational speed Ne. FIG. 4 is a map of the basic valve lift value LMAP, and the negative pressure Pn in the intake pipe is, for example, in the range of 560 to 0 mm (Ig) to PI3. ~PB1.
10 stages are provided, and the rotation speed Ne is, for example, 0.
N in the range of ~400 Orpm, ~N□. ] O stages are provided, and the engine speed N other than the map grid points
The basic valve lift value LMAP corresponding to e and negative pressure PB is obtained by interpolation calculation.

Next, proceed to step 3 and calculate the lift correction coefficient K. Calculate. This correction coefficient KE is a coefficient that is set depending on, for example, a change in atmospheric pressure PA, a degree of dilution (leaning) of fuel in the air-fuel mixture supplied to the engine in a lean operating region, and the like. To explain in more detail using the above-mentioned method of setting the correction coefficient KE due to changes in atmospheric pressure PA as an example, as atmospheric pressure PA decreases, the exhaust gas recirculation rate (ratio of exhaust gas recirculation amount to total intake air amount) is maintained constant. To do this, operate the exhaust recirculation valve in the opening direction. That is, the correction coefficient KE is set to a larger value as the atmospheric pressure PA decreases with respect to the correction coefficient KEo at standard atmospheric pressure. In this way, atmospheric pressure P
The reason why the correction coefficient KE is increased to keep the exhaust gas recirculation rate constant as A decreases is as follows.

That is, for example, when the atmospheric pressure changes, such as when driving at high altitudes, the amount of fuel supplied to the engine is corrected according to the change in atmospheric pressure, and the air-fuel ratio is maintained at the set air-fuel ratio under standard atmospheric pressure. Otherwise, it will not be possible to obtain the optimum air-fuel ratio. Therefore, the fuel injection amount obtained based on the above equation (1) includes correction by the air-fuel ratio atmospheric correction coefficient KPA. However, in engines that perform exhaust recirculation, when the atmospheric pressure decreases, the absolute pressure upstream of the exhaust recirculation valve (exhaust pipe back pressure) decreases, so the exhaust recirculation rate decreases in a variable manner. It changes to the lean side compared to the case where the atmospheric pressure decreases and becomes lean when it is not turned on. Therefore, if only the fuel amount is corrected using the above-mentioned air-fuel ratio atmospheric pressure correction coefficient KPA, the air-fuel ratio cannot be controlled accurately if exhaust gas recirculation is performed without any atmospheric pressure correction. .

=15- On the other hand, if the exhaust gas recirculation rate is kept constant even if there is a change in atmospheric pressure, the air-fuel ratio correction coefficient (KPA) that is used when the exhaust gas recirculation amount control is not performed can be used as is. The details of such an exhaust gas recirculation control method are disclosed in Japanese Patent Application Laid-Open No. 58-88430 by the present applicant.

Next, in steps 4 to 8, the fully closed reference position value of the exhaust gas recirculation valve 15 is determined. seek. First, step 4
Now, the basic valve list value LMA read in step 2 above.
It is determined whether P is zero, that is, whether the basic valve lift value LMAP is a value that commands the exhaust recirculation valve 15 to be fully closed. If the determination result is negative (NO), that is, the engine is in exhaust recirculation operation. If it is in the range, it is the fully closed reference position value of the exhaust recirculation valve 15. Since this cannot be corrected, the EGR timer in the CPU 5b is reset to a predetermined value (Step 8), and the process proceeds to Step 9.

On the other hand, if the determination result in step 4 is affirmative (Yes), the process proceeds to step 5, and the valve opening detection value LACTn of the current loop detected by the lift sensor 19 is set to the valve opening detection value LAQTn-+ of the previous loop. Determine whether it is equal to or not.

If the determination result in step 5 is negative (No), the process proceeds to step 8, and if the determination result is affirmative (Yes), that is, LAQT
n value and LAQTn-.

If the values are equal, proceed to step 6 and compare the LAQTn value and L
A state in which the AQTn-1 value is equal is maintained for a predetermined time t EGR (
For example, for 3 seconds), it is determined whether or not it has continued. If the determination result in step 6 is affirmative (Yes), that is, LAC, Tn
The state in which the value and the L A Q T n-1 value are equal continues for a predetermined time t EG! ! If it continues, the current loop's valve opening detection value LAQTn is changed to the new fully closed reference position value L0 (step 7
), this is stored in the storage means 5c in the ECU 3, and the process proceeds to step 9. If the answer is negative (No), EGR is continued.
The timer continues measuring time and proceeds to step 9.

In step 9, the basic valve lift value L'MAP read out in step 2 is converted into a fully closed reference position value stored in the storage means 5c in the ECU S. and the correction value from the variable voltage power supply 20. 0 which deviation (L o−L n
o ) is set according to the correction coefficient f(rn −L
n n ) by multiplying the correction valve lift I
- Find the value L'MAP. Correction coefficient f (LLl-Lo
, ) is the deviation (Lo-L[lG), as shown in FIG.
It is set to increase as the value increases.

Next, the process proceeds to step 10, where the correction valve lift value L'MAP set in step 9 is multiplied by the correction coefficient KE set in step 3 to calculate the valve opening command value LCMD.
Proceed to step 11.

In step 11, the fully closed reference position value set in step 7 and step 10 is determined. and valve opening command value L
The control amount S of the exhaust gas recirculation valve 15 is based on the CMD and the valve opening detection value LAcTn detected by the lift sensor 19.
That is, the deviation (2) is determined by the following equation (2), and the CPU 5b determines the drive time to be supplied to the electromagnetic control valve 17 via the output circuit 5d so as to make the deviation V thus obtained zero. That is, the duty ratio of the drive signal for the electromagnetic control valve 17 is determined so as to control the atmosphere or negative pressure introduced into the negative pressure chamber 15e so as to make the deviation V zero.

V=(LAcTn-Lo)-LCMI,-(2) In the above equation (2), the valve opening detection value LAQTn is set to the fully closed reference position value. The deviation V between the corrected value and the valve opening command value LCM+) was calculated by correctly correcting LAQ T n -Ln), but instead of this, the valve opening command values LC and MD were calculated.

The deviation V between this correction value and the detected valve opening value LAcTn may be calculated using the following equation (3).

V = (LcMf, +L.) - LAcTn ・= (
3) Here, the valve body 15a of the exhaust gas recirculation valve 15 according to the present invention
As shown in Fig. 1, the maximum stroke length LMAXII is the fully closed reference position of the engine after long-term operation.

(=ΔL) (dotted line 11 in Fig. 1)
'L), the maximum exhaust gas recirculation amount QMAX can be secured even after long-term operation.

The maximum stroke length LMAXπ of the valve body 15a is determined by the long-term test operation of the engine (for example, 100,000 km in terms of mileage
) after fully closed reference position. Determined based on.

In addition, the fully closed reference position value. The initial value when the ignition switch (not shown) is turned on is memorized and means 5C.
A predetermined value (for example, O) stored in is applied.

(Effects of the Invention) As detailed above, according to the exhaust gas recirculation amount control device for an internal combustion engine of the present invention, the maximum valve opening position of the exhaust gas recirculation valve is stored in the memory after the engine has been operated for a predetermined period. Since the maximum required exhaust gas recirculation amount to be recirculated based on the required valve opening read out from is greater than the valve opening position for recirculation,
Even after long-term operation of the engine, the required maximum exhaust gas recirculation amount can be ensured, and good exhaust gas characteristics of the engine can be maintained.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram of the exhaust recirculation amount control device, Fig. 2 is an overall configuration diagram of an internal combustion engine equipped with the exhaust recirculation amount control device according to the present invention, and Fig. 3 is a procedure for setting the control amount of the exhaust recirculation valve. The flow chart shown in FIG. 4 shows the basic valve lift value LMA determined by the engine speed Ne and the intake pipe negative pressure PB.
The map of F, Figure 5, shows the correction coefficient f(L, -L, ,) and the deviation, -L,. ) is a graph showing the relationship between DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 2... Intake passage, 5... Electronic control unit (ECU), 8... Negative pressure sensor, 10... Engine speed sensor (Ne sensor)
, 11... Exhaust passage, 13... Atmospheric pressure sensor, 14
...Exhaust recirculation passage, 15...Exhaust recirculation valve, 16...
・Communication path, 17...Solenoid control valve, 19...Deltitude detector (lift sensor), 20...Variable voltage power supply.

Claims (3)

[Claims] 1. An exhaust gas recirculation passage that connects the exhaust pipe of an internal combustion engine to the intake pipe, and a maximum valve opening that is provided in the middle of the exhaust gas recirculation passage and defines the maximum permissible amount of exhaust gas recirculation from the exhaust pipe to the intake pipe. an exhaust gas recirculation valve having a position, an operating state detection means for detecting an operating state of the engine in which exhaust gas recirculation is to be performed, a storage device that stores in advance a required valve opening degree of the exhaust recirculation valve according to the operating state of the engine; a valve opening degree detector that detects the actual valve opening degree of the reflux valve; a fully closed instruction determination means that determines whether the requested valve opening degree read from the storage device indicates a fully closed position; timer means for generating a signal when the generation time of the fully closed determination signal from the close instruction determination means exceeds a predetermined time; and a detection value of the valve opening degree detector when the signal from the timer means is inputted. a reference position storage means for correcting either the actual valve opening detection value detected by the excuse degree detector or the required valve opening with the stored value of the reference position storage means; an opening difference determining means for determining an opening difference between the one valve opening value and the other valve opening value corrected by the means; and controlling the exhaust gas recirculation valve so as to reduce the opening difference to zero. In the exhaust gas recirculation amount control device, the maximum valve opening position is determined based on the required valve opening read from the storage device after the engine has been operated for a predetermined period. An exhaust gas recirculation amount control device for an internal combustion engine, characterized in that the maximum required exhaust gas recirculation amount is larger than the valve opening position for recirculating the gas. 2. A detector for detecting a predetermined engine operating parameter is provided, and the calculation means is configured to further correct the corrected one valve opening value according to the parameter detection value detected by the parameter detector. An exhaust gas recirculation amount control device for an internal combustion engine according to claim 1, characterized in that: 3. 3. The exhaust gas recirculation amount control device for an internal combustion engine according to claim 2, wherein the engine operating parameter detected by the parameter detector is atmospheric pressure.