JPH04272461A - Egr device - Google Patents

Abstract

PURPOSE:To control an EGR amount optimum from the time when an engine is started despite tolerance of parts and the secular change, and secure the EGR amount of max limit within the extent in which no surge appears. CONSTITUTION:An EGR valve 24 driven by a stepping motor 25 is installed at an EGR tube 23. The fundamental degree of opening of EGR valve is stored in a ROM 34, while a correction value for the EGR valve 24 in accordance with the engine 1 operating condition is stored in a backup RAM 36. A CPU 33 multiplies the fundamental opening with this correction value to calculate the valve opening, and pulse signal is given to the stepping motor 25 so that the openings become identical. The CPU 33 senses the combusting condition from variation of the engine revolving speed in case operation lies in the surge judged region, and the correction value is modified in the case of unstable combustion in the direction of stabilizing the combustion.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an exhaust gas recirculation system (EGR) that recirculates part of the exhaust gas of a vehicle internal combustion engine to the intake system.
equipment).

0002

2. Description of the Related Art Conventionally, some internal combustion engines for vehicles are equipped with an EGR device for reducing NOx contained in exhaust gas. This EGR device recirculates a portion of exhaust gas from the exhaust system to the intake system.More specifically, the EGR device installs a flow control valve (EGR) in the exhaust recirculation path that connects the intake system and exhaust system of an internal combustion engine. The EGR valve is opened and closed according to the operating state of the internal combustion engine to control the amount of recirculation of exhaust gas (EGR flow rate).

Furthermore, as such an EGR device, for example, Japanese Utility Model Application Publication No. 61-66640 discloses engine vibration,
This technology is equipped with a roughness sensor that detects roughness such as torque fluctuations and rotational fluctuations, and when the sensor detects an unstable combustion condition in the engine, the EGR amount is corrected within a range that exceeds a preset lower limit EGR amount. is disclosed. According to the EGR device, the roughness can be efficiently reduced without reducing the engine output.

0004

However, in the conventional EGR device, deposits on the EGR valve, injection variations in the fuel injection valve, deviations in air flow meter characteristics,
If there are aging changes such as deposits on the throttle valve or component tolerances, the above control (
The EGR amount will not be accurate until the control for detecting roughness and correcting the EGR amount is completed. In particular, if there is an excessive amount of EGR during the above period, drivability may decrease due to misfires, etc., or a stall may occur (engine torque decreases for some reason, engine speed drops, and the engine stops). There was a risk that the

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide an EGR system that can control the EGR amount to the optimum level from the time of starting the engine even when there are changes over time or component tolerances.
The goal is to provide equipment.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention is arranged in an exhaust gas recirculation path M2 connecting an exhaust system and an intake system of an internal combustion engine M1, as shown in FIG.
A flow control valve M that recirculates a part of the exhaust gas to the intake system
3, basic opening storage means M4 that stores in advance the basic opening of the flow control valve M3 according to the operating state of the internal combustion engine M1, and correction value storage means M5 that stores in advance the correction value of the flow control valve M3. and an opening control means M6 for controlling the opening degree of the flow control valve M3 based on the basic opening degree stored in the basic opening degree storage means M4 and the correction value stored in the correction value storage means M5. , during the opening control of the flow rate control valve M3 by the combustion state detection means M7 for detecting the combustion state of the internal combustion engine M1, and the opening control means M6, the combustion state detection means M7 detects the internal combustion engine M at that time.
A correction value updating means M8 is provided for correcting the correction value in the correction value storage means M5 in a direction that stabilizes the combustion of the internal combustion engine M1 when the combustion state of the internal combustion engine M1 is unstable.

[0007]

[Operation] The opening degree control means M6 controls the basic opening degree of the flow rate control valve M3 stored in the basic opening degree storage means M4 and the flow rate control value stored in the correction value storage means M5 according to the operating state of the internal combustion engine M1. Based on the correction value of valve M3, the flow rate control valve M3
Controls the opening degree. As a result, when the flow control valve M3 is opened and the exhaust system and the intake system communicate with each other, an amount of exhaust gas corresponding to the opening degree of the flow control valve M3 is returned to the intake system via the exhaust gas recirculation path M2. be done.

[0008]Furthermore, the combustion state detection means M7 is connected to the internal combustion engine M.
The combustion state of No. 1 is detected. and the opening control means M
If combustion in the internal combustion engine M1 is unstable when the opening degree of the flow rate control valve M3 is controlled by 6, the correction value updating means M8 updates the correction value in the correction value storage means M5 with respect to the combustion state of the internal combustion engine M1. Correct it in the direction of stability. For this reason, EGR
Even if there are component tolerances or changes over time in the device, the correction value in the correction value storage means M5 is updated so that combustion in the internal combustion engine M1 does not become unstable, so-called learning control is performed. The values updated in this manner are stored in the correction value storage means M5 as correction values corresponding to component tolerances and changes over time. Therefore, when starting the internal combustion engine M1, the flow control valve M3 is adjusted based on the updated correction value and the basic opening degree.
Since the opening degree of the flow control valve M3 is controlled, it becomes possible to optimally control the opening degree of the flow rate control valve M3 from the time of starting.

[0009]

Embodiments (First Embodiment) A first embodiment embodying the present invention will be described below with reference to FIGS. 2 to 4. Figure 2 shows EGR
1 is a diagram showing a schematic configuration of an automotive multi-cylinder engine 1 as an internal combustion engine equipped with a device. Engine 1 has cylinder 2
A combustion chamber 4 is formed above the piston 3, and an intake passage 5 forming part of an intake system and an exhaust passage 6 forming part of an exhaust system communicate with each other. ing. The communication portion between the combustion chamber 4 and the intake passage 5 and the communication portion between the combustion chamber 4 and the exhaust passage 6 are opened and closed by an intake valve 7 and an exhaust valve 8.

The engine 1 introduces a mixture consisting of intake air from an intake passage 5 and fuel injected from a fuel injection valve 9 into a combustion chamber 4 via an intake valve 7. An ignition plug 11 is attached to the engine 1, and an ignition voltage distributed by a distributor 12 is applied to the ignition plug 11. The distributor 12 is
This is for distributing the high voltage output from the igniter 13 to each spark plug 11 in synchronization with the crank angle of the engine 1, and the ignition timing of each spark plug 11 is determined by the high voltage output timing from the igniter 13. be done. Then, the engine 1 causes the air-fuel mixture to explode in the combustion chamber 4 using the spark plug 11 to obtain driving force, and then discharges the exhaust gas to the exhaust passage 6 via the exhaust valve 8.

A surge tank 14 is provided in a part of the intake passage 5 to suppress pulsation of intake air. Upstream of the surge tank 14, there is a throttle valve 15 that opens and closes in conjunction with the operation of an accelerator pedal (not shown).
is provided, and the amount of intake air into the intake passage 5 is adjusted by opening and closing the throttle valve 15. A throttle sensor 16 is provided near the throttle valve 15 to detect its opening degree. Further, on the upstream side of the throttle valve 15, an air flow meter 17 for detecting the amount of intake air and an air cleaner 18 are arranged.

On the other hand, an oxygen sensor 19 for detecting the oxygen concentration in the exhaust gas and a three-way catalytic converter 21 for purifying the exhaust gas are attached to the exhaust passage 6. An EGR device 22 is provided between the exhaust passage 6 and the intake passage 5 to recirculate the exhaust gas in the exhaust passage 6 to the intake passage 5. That is,
From the exhaust passage 6 is an EGR pipe 23 as an exhaust recirculation path.
The other end is connected to the intake passage 5 between the surge tank 14 and the throttle valve 15. In the middle of this EGR pipe 23, there is an EGR valve as a flow control valve.
A valve 24 is provided.

The EGR valve 24 is of a so-called step motor type, in which a rotor 26 of a step motor 25 rotates in response to a pulse signal, thereby changing the lift amount of the valve body 27 and changing the opening area of the valve. By controlling the opening degree of the EGR valve 24, the amount of exhaust gas recirculated to the intake passage 5 is controlled. In addition to the above-mentioned throttle sensor 16, air flow meter 17, and oxygen sensor 19, the engine 1 includes a combustion state sensor that detects the rotation speed of the engine 1 from the rotation of the rotor 12a of the distributor 12 in order to detect its operating state. A rotation speed sensor 28 as a detection means and a water temperature sensor 29 for detecting the temperature of the cooling water of the engine 1 are attached. Further, a vehicle speed sensor 31 for detecting vehicle speed is attached to a transmission (not shown) that is drivingly connected to the engine 1.

The various sensors described above are electrically connected to the input side of an electronic control unit (hereinafter simply referred to as "ECU") 32. In addition, each fuel injection valve 9, igniter 13 and E
The GR valve 24 is electrically connected to the output side of the ECU 32. The ECU 32 includes a central processing unit (hereinafter referred to as CPU) 33 as an opening control means and a correction value updating means.
, a read-only memory (hereinafter referred to as ROM) 34 as a basic opening storage means, and a random access memory (
35, a backup RAM 36 as a correction value storage means, an input port 37, and an output port 38, which are connected to each other by a bus 39. The CPU 33 executes various calculation processes according to a preset control program, and the ROM 34
A control program and initial data necessary for executing arithmetic processing in U33 are stored in advance. Also, RAM35
temporarily stores the calculation results of the CPU 33. The backup RAM 36 is backed up by a battery so that it retains various data even after the power is turned off.

As shown in FIG. 3, the ROM 34 stores the basic EGR valve opening degree ETEG, which is determined based on the relationship between the engine speed NE and the intake air amount QN per engine speed.
RB is stored in advance as a two-dimensional map. A correction value EGX for the EGR valve 24 according to the operating state of the engine 1 is stored in the backup RAM 36. That is, the intake air amount QN per rotational speed is divided into a plurality of regions, guarded to a range of 0.5≦EGX≦1.0, and a correction value EGX is set for each region. In this embodiment, the correction value EGX is EG1 in the region of 0.0≦QN<0.2, and EG1 is 0.2≦Q.
In the region of N<0.4, EG2, 0.4≦QN<0.6
EG3 in the region, EG4 in the region 0.6≦QN<0.8, EG5 in the region 0.8≦QN<1.0,
In the region of 1.0≦QN, EG6 is set, and 1.0 is set as the initial value of the correction value EGX. The reason why the correction value EGX is set for each region of the intake air amount QN per rotational speed is as follows. That is, the EGR rate (ratio of EGR amount to intake air amount) is generally required to be as large as possible without affecting the operating state of the engine 1. On the other hand, this required EGR rate tends to increase as the amount of intake air QN per rotational speed increases. Therefore, by setting the correction value EGX for each region as described above, it becomes possible to perform more fine-grained control than when a single correction value is used.

The CPU 33 receives signals from the throttle sensor 16, air flow meter 17, oxygen sensor 19, rotational speed sensor 28, and water temperature sensor 29 through an input port 37. The CPU 33 controls the fuel injection valve 9 and the igniter 13 connected to the output port 38 based on these detection signals. That is, the CPU 33 determines the throttle opening TA, the intake air amount Q, the oxygen concentration in the exhaust gas, the cooling water temperature THW, and the engine speed NE based on the detected values of the sensors, etc., and based on these determined values. Calculate the target fuel injection amount. Then, based on the target fuel injection amount, a valve opening time signal is output to the fuel injection valve 9 to inject fuel.

Next, the operation of this embodiment configured as described above will be explained. The CPU 33 uses the rotation speed sensor 28
Based on the signal from the air flow meter 17, the engine rotational speed NE and the intake air amount QN per rotational speed are determined. Based on these determined values, the CPU 33
By determining the basic EGR valve opening degree ETEGRB and the correction value EGX at that time, and multiplying the two,
Calculate the GR valve opening degree ETEGR (ETEGR=E
TEGRB×EGX). Then, the CPU 33 outputs a pulse signal to the step motor 25 of the EGR valve 24 via the output port 38 so that the EGR valve opening degree ETEGR obtained in this manner is achieved. As a result, the rotor 26 of the step motor 25 rotates by a predetermined angle, the lift amount of the valve body 27 changes, the opening area of the valve changes, and the EGR pipe 23 is opened and closed. EGR valve 2 like this
4, the CPU 33 executes the scheduled interrupt process shown in FIG. 4 every 64 ms.

When the process moves to this routine, the CPU
33, it is determined in step 101 whether or not the area is a surge determination area. That is, the CPU 33 controls the throttle sensor 1
The minute change Δ in the throttle opening TA detected by 6
The absolute value of TA is less than or equal to a predetermined value (for example, |ΔTA|
≦2°/sec), and also determines whether the slight change ΔSPD in the vehicle speed SPD detected by the vehicle speed sensor is less than or equal to a predetermined value (for example, |ΔSPD|≦1km/h
/sec). If both of the above conditions are met, the CPU 33 determines that the running conditions are stable and there is no risk of misjudging the combustion state, and proceeds to step 102. In this way, the CPU 33 performs surge determination only under conditions where the throttle opening TA and vehicle speed SPD have little variation and are almost constant.

It should be noted that if the CPU 33 determines in step 101 that at least one of the absolute value of the minute change ΔTA in the throttle opening TA and the absolute value of the minute change ΔSPD in the vehicle speed SPD is larger than a predetermined value, then If the operating state is not in the surge judgment region, this routine ends. In the following step 102, the CPU 33 performs a surge determination. In other words, the absolute value of the minute change ΔNE in the engine speed NE detected by the rotation speed sensor 28 is greater than or equal to a predetermined value (for example, |ΔNE|≧20 rpm
/sec). If the value is greater than or equal to the predetermined value, the CPU 33 determines that the combustion state is unstable (surge is occurring), and proceeds to the next step 103, which is determined by the intake air amount QN per rotation speed. From the correction value EGX at that time to the update amount (sensitivity coefficient) α (for example, 0
．． 01) is performed. And CPU3
Step 3 moves to step 104, sets the value obtained in step 103 as a new correction value EGX, stores it in the backup RAM 36, and ends this routine.

Note that if the CPU 33 determines in step 102 that the absolute value of the minute change ΔNE in the engine speed NE is less than a predetermined value, it concludes that no surge has occurred and ends this routine. In this way, E
According to the GR device 22, first, it is determined whether the vehicle speed SPD and the throttle opening TA are stable or not, and whether or not the surge determination region is reached. The combustion state of the engine 1 is detected based on the fluctuation of the number NE. And the rotation speed sensor 28
If the combustion state of the engine 1 at that time is unstable, the correction value EGX used to set the opening degree of the EGR valve 24 is corrected according to the intake air amount QN per rotation speed at that time. It is updated to a value obtained by subtracting the update amount α from the value EGX.

Therefore, the EGR valve opening ETEGRB is determined by multiplying the updated correction value EGX by the basic EGR valve opening ETEGRB.
By controlling the opening degree of the EGR valve 24, the combustion of the engine 1 is corrected in the direction of stabilization, and the occurrence of a surge due to an excessive amount of EGR is prevented. Furthermore, in this embodiment, since the correction value EGX updated as described above is stored in the backup RAM 36, this correction value EGX is retained even when the key switch is turned off. For this reason, if there were changes over time or component tolerances, there was a risk of excessive EGR from the time the engine was started until the opening of the EGR valve was controlled to the required value in the conventional technology. In this example, the amount of EGR can be controlled to the optimum level from the time the engine is started, and it is possible to prevent deterioration in drivability due to misfires and the occurrence of stalls.

Furthermore, in this embodiment, once a surge is detected as described above, the EG is
When the R amount is reduced and the surge is no longer detected, the EG
The amount of R is maintained. Therefore, the maximum amount of EGR is ensured within the range where surges do not occur, and exhaust emissions (NOx
) is effectively reduced. Also, as mentioned above, EGR
If the amount is large, less fresh air is drawn into the combustion chamber 4 of the engine 1 at the same throttle opening, so the throttle opening TA is controlled to be large in order to obtain the same engine torque. This reduces pumping loss and improves fuel efficiency.

Furthermore, in this embodiment, the intake air amount QN per rotational speed is divided into a plurality of regions, and the correction value EGX is set for each region.
By setting , it is possible to deal with complex deviations such as those caused by a combination of changes over time and the effects of component tolerances. (Second Embodiment) Next, a second embodiment of the present invention will be described.

This embodiment differs from the first embodiment in that when no surge occurs, the correction value EGX is updated to increase the amount. As shown in FIG. 5, in step 102, the CPU 33 detects a slight change Δ in the engine speed NE.
The absolute value of NE is less than a predetermined value (in this case, |ΔNE|<2
0 rpm/sec), it is assumed that no surge has occurred and the process moves to the next step 105. In step 105, the CPU 33 performs arithmetic processing to add an update amount (sensitivity coefficient) β (for example, 0.005) to the current correction value EGX determined by the intake air amount QN per rotational speed. The CPU 33 then proceeds to step 104, sets the value obtained in step 105 as a new correction value EGX, stores it in the backup RAM 36, and ends this routine. Note that the correction value EGX in this case is guarded to a range of 0.5≦EGX≦1.5, and is set for each region of the intake air amount QN per rotational speed.

Therefore, according to this embodiment, in addition to producing the same functions and effects as those of the first embodiment, the EGR amount is actively increased when no surge is detected, and when a surge is detected, the EGR amount is decreased. It is possible to always maintain the maximum EGR amount within a range where surges do not occur, and the optimal EGR amount can always be ensured from the time the engine is started. It should be noted that the present invention is not limited to the configuration of the embodiments described above, and may be modified as desired without departing from the spirit of the invention, for example, as described below. (1) In the embodiment described above, the combustion state is detected using the existing rotation speed sensor 28, but the combustion state may be detected using a combustion pressure sensor, an acceleration sensor, or the like. Even when these sensors are used, surges can be avoided in the same way as in the embodiments described above. (2) In the above embodiment, the intake air amount QN per rotational speed is divided into a plurality of regions, and the correction value EGX is set for each region. You can set the correction value for each region, and adjust the engine speed NE.
Correction values may be set for each of a plurality of regions in relation to the intake air amount QN per rotational speed. In addition, in the case of an engine control system that measures the intake manifold pressure and performs fuel injection, so-called D-J, the intake pipe pressure PM is divided into multiple regions, and a correction value is set for each region (two-dimensional). may be set. (3) As the two-dimensional map of the basic EGR valve opening degree ETEGRB, a map value may be used that has map values set over the entire NE-QN range including the high-load, high-speed range.

[0026]

As described in detail above, according to the EGR device of the present invention, when the combustion state of the internal combustion engine becomes unstable while controlling the opening of the flow control valve, the opening of the flow control valve is determined. The correction value for internal combustion engine combustion is adjusted in the direction that stabilizes combustion in the internal combustion engine, so even if there are component tolerances or changes over time, the EGR amount can be controlled to the optimum level from the start of the engine, and surges due to excessive EGR amount can be prevented. At the same time, it has the excellent effect of ensuring the maximum amount of EGR within a range where surges do not occur.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of the present invention.

FIG. 2 is a diagram showing a schematic configuration of an engine equipped with an EGR device in the first embodiment.

FIG. 3 is a diagram showing a map of basic EGR valve opening degrees in the first embodiment.

FIG. 4 is a flowchart for updating the EGR valve correction value EGX according to the operating state of the engine in the first embodiment.

FIG. 5 is a flowchart for updating the correction value EGX of the EGR valve according to the operating state of the engine in the second embodiment.

[Explanation of symbols]

Claims (1)

[Claims] 1. A flow control valve disposed in an exhaust gas recirculation path connecting an exhaust system and an intake system of an internal combustion engine to recirculate a portion of exhaust gas to the intake system; and an internal combustion engine in which the flow control valve is connected. a basic opening storage means that stores in advance a basic opening according to the operating state of the flow control valve; a correction value storage means that stores a correction value of the flow control valve in advance; a basic opening stored in the basic opening storage means; and an opening control means for controlling the opening of the flow rate control valve based on the correction value by the value storage means.
In the R device, while the combustion state detection means detects the combustion state of the internal combustion engine and the opening control means is controlling the opening of the flow rate control valve, the combustion state detection means detects the combustion state of the internal combustion engine at that time. When in an unstable state,
An EGR device comprising: correction value updating means for correcting the correction value in the correction value storage means in a direction that stabilizes combustion in the internal combustion engine.