JPS62298654A - Exhaust feedback control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To have precision control of the amount of exhaust feedback in response to the actual operating condition of an internal combustion engine by setting the amount of exhaust feedback in accordance with the load of engine and the pressure difference between suction and exhaust gases, and making correction of the amount of exhaust feedback with the pressure difference and the number of revolutions. CONSTITUTION:Signals from a pressure difference sensor 52, throttle sensor 48, lift position sensor 36, and coolant temp. sensor 50 are fed in an electronic control device 46 through an A-D converter circuit 68. Signal from a revolving speed sensor 49 is fed in the same electric control device 46 via a pulse generator circuit 69. In the ROM 62 of said electronic control device 46, the converted EGR ratio as the lift amount of an EGR control valve is stored upon preparing in the form of a two-dimensional map of the load of engine and the pressure difference between suction and exhaust gases. A map for correction of pressure difference is prepared and stored in this ROM 62. Thus the EGR ratio is set with the suction/exhaust pressure difference as parameter, and the EGR ratio is corrected with pressure difference and the number of revolutions.

Description

[Detailed description of the invention] 3. Detailed description of the invention [Industrial application field] The present invention relates to an exhaust gas recirculation control device for an internal combustion engine.

[Conventional technology]

2. Description of the Related Art Conventionally, so-called EC,R devices have been provided for recirculating a portion of exhaust gas into intake air for the purpose of purifying exhaust gas from internal combustion engines, particularly purifying NOx components. Typical conventional EGR
The device used pressure-operated valves driven directly by exhaust or intake pressure. However, since the amount of exhaust gas recirculation (EGR rate) affects not only the exhaust purification performance but also the output performance of the internal combustion engine, it has become important to obtain the optimal EGR rate according to the operating condition of the internal combustion engine. Electronic control of the EGR valve has come into practice.

Such electronic control is described, for example, in Utility Model Application Publication No. 54-6922.
As described in Japanese Patent No. 3, this is implemented by arranging a solenoid valve driven by a duty circuit based on the load and rotational speed of the internal combustion engine. This bulletin also includes E
By detecting the actual exhaust gas recirculation amount passing through the GR control valve and performing feedback control based on this detected value, the E
It is now possible to compensate for the effects of changes over time such as wear of the GR control valve. Also, JP-A-56-15125
Publication No. 2 is equipped with a load sensor and an engine rotation speed sensor that detect the position of the spill ring of the fuel injection pump, sets an EGR rate map based on the load and rotation speed, and calculates a target from the detected load and rotation speed. An exhaust gas recirculation control device that calculates an EGR rate is disclosed. Further, Japanese Patent Application Laid-open No. 162048/1983 provides means for detecting engine acceleration, and is designed to stop exhaust gas recirculation at the time of sudden acceleration.

[Problem that the invention seeks to solve]

Controlling an internal combustion engine based on load and rotation speed is a conventional technique, and for example, the amount of fuel injection is determined based on load and rotation speed. However, even if control is similarly performed based on load and rotational speed, controlling the EGR amount has different difficulties than controlling the fuel injection amount. That is, in the case of controlling the fuel injection amount, fuel is injected at a predetermined pressure, so it is only necessary to determine the opening time of the injection valve, whereas in the case of controlling the EGR amount, the recirculated exhaust gas changes. It is difficult to set the opening degree of the EGR valve so as to obtain the desired EGR rate depending on the operating condition of the internal combustion engine, as it is pushed into the intake passage by the differential pressure between the exhaust pressure and the intake pressure.
There was dissatisfaction with the accuracy of EGRt control.

[Means for solving problems]

An exhaust gas recirculation control device for an internal combustion engine according to the present invention includes a load detection means for detecting a load on the internal combustion engine, a rotation speed detection means for detecting the rotation speed of the internal combustion engine, and a pressure in an exhaust passage and an intake passage. differential pressure detection means for detecting the differential pressure between the internal pressure and the internal pressure, exhaust recirculation amount calculation means for calculating the exhaust recirculation amount based on the load and the differential pressure, and the detected differential pressure and rotation speed. The present invention is characterized by comprising a correction means for correcting the amount of exhaust gas recirculation.

〔Example〕

Figure 1 shows an example in which the present invention is applied to a diesel engine.
A piston 12 is inserted into the engine body 10 so as to be able to reciprocate, and a combustion chamber 14 is formed above the piston 12.

The combustion chamber 14 has an exhaust passage 16 and an intake passage 18, respectively.
are connected to each other so as to be able to communicate with each other, and an exhaust valve 20 and an intake valve 22 are provided at the ports connecting these passages and the combustion chamber 14, respectively.
is placed.

The exhaust passage 16 and the intake passage 18 are connected to provide exhaust gas recirculation (E
A G R) passage 24 is provided, and an EGR control valve 26 is disposed in the middle of the EGR passage 24.

EGR1IJ? The valve member 28 of the il valve 26 is attached to a diaphragm 30 within the valve case, and a negative pressure chamber 32 is formed on one side of the diaphragm 30, and the operating negative pressure introduced into the negative pressure chamber 32 causes the valve to operate. The lift position of member 28 is controlled. Further, a return spring 34 is arranged within the negative pressure chamber 32. moreover,
a lift position sensor 3 capable of detecting the lift position of the valve member 28 of the BGR control n-valve 26 in relation to the valve stem;
6 is provided.

The operating negative pressure in the negative pressure chamber 32 of the EGR control valve 26 is supplied from a vacuum pump 38 via a switching valve 40 . The switching valve 40 is a vacuum pump 38
It is equipped with a negative pressure regulating solenoid valve 42 that communicates and interrupts a negative pressure passage leading from to the negative pressure chamber 32 and an atmosphere regulating solenoid valve 44 that communicates and isolates an atmospheric passage that connects the negative pressure chamber 32 to the atmosphere. The desired operating vacuum is achieved by appropriately controlling the valves 42, 44, thereby controlling the EGR control valve 26.
can be controlled appropriately. In addition, the EGR control valve 26
The operating negative pressure to be supplied to the pump does not need to use the two electromagnetic valves 42 and 44 as in this embodiment (for example, a duty-controlled negative pressure regulating valve may be used).

Both of these solenoid valves 42 and 44 are electronic control units (ECU)
46. The electronic control device 46 receives detection signals from a throttle sensor 48 that detects the accelerator opening representing the engine load, a rotation speed sensor 49 that detects the engine speed, a cooling water temperature sensor 50, and a detection signal from the differential pressure sensor 52. receive. Furthermore, it receives a detection signal from the lift position sensor 36 mentioned above.

Preferably, the differential pressure sensor 52 is located near the connection to the EGR passage 24, or at a position upstream of the connection between the vibe 54 connected to the exhaust passage 16 and the EGR passage 24, or downstream of it. It is preferable to attach it at a position (more preferably near the intake manifold) so as to straddle the vibe 56 connected to the intake passage 18. FIG. 4 shows an example of a strain gauge type differential pressure sensor 52, in which exhaust pressure and intake pressure of vibrators 54 and 56 act on both sides of a silicon diaphragm 52a as a pressure receiving element, respectively. The silicon diaphragm 52a has a characteristic that it deforms according to the differential pressure and its resistance changes according to the amount of deformation. Therefore, the differential pressure can be taken out as an electrical signal from the terminal 52b. FIG. 5 shows an example of a potentiometer-type differential pressure sensor 52, with vibes 5 on both sides.
Diaphragm 52 receiving exhaust pressure and intake pressure of 4.56
A contactor 52d is attached to C, and this contactor 52d engages with the resistance element 52e at a position corresponding to the differential pressure.

Alternatively, a pressure sensor may be provided in each of the exhaust pipe and the intake pipe, and the differential pressure may be determined from the respective pressure values obtained. In addition, a damper 55.57 is provided in the middle of the vibrator 54.56,
By absorbing the influence of pulsation between intake and exhaust air, differential pressure detection becomes easier. It is particularly effective to provide it on the exhaust side because it can absorb large pulsations in the exhaust pipe.

FIG. 6 shows the structure of the electronic control unit 46 formed as a microcomputer, which includes a central processing unit (CPU) 60 having control and calculation functions, a ROM 62 for storing programs, and a ROM 62 for storing data and the like. and a random access memory (RAM) 64 for storage, which are interconnected by a bus 66. The detection signals of the differential pressure sensor 52, throttle sensor 48, lift position sensor 36, and cooling water temperature sensor 50 mentioned above are inputted via the A-D conversion circuit 68, and the detection signal of the rotation speed sensor 49 is inputted via the pulse generation circuit 69. is input. The output control signal is passed through the drive circuit 70 to iit [valve 4
It will be output on 2.44. Also provided is a clock 72 that provides a reference timing signal.

In the present invention, as shown in FIG.
The EGR rate converted as the lift amount of the control valve 26 is prepared as a two-dimensional map of the engine load and the differential pressure P between exhaust and intake air and is stored in the ROM 62. A map for pressure correction is prepared and RO
Stored in M62. In Fig. 2, curves a, b, and c indicate the boundaries of EGR regions A, B5C5D, respectively, and region A, which has a high load, has the lowest EGR rate, and regions B, C, and D
The EGR rate gradually increases in this order.

Each of the curves a, b, and c has an upward convex shape with respect to the differential pressure so that it reaches a maximum near a medium value P0. The differential pressure essentially corresponds to the engine speed, so E
The GR rate is small in the high rotational speed region, large in the mid-to-end rotational speed region, and small in the low rotational speed region including idle. In this way, in the present invention, the EGR rate is determined using the differential pressure as a parameter instead of the conventional engine speed, so the EGR rate can be controlled with high precision according to the operating state of the internal combustion engine. That is,
If the exhaust pressure is P Z , the intake pressure is P+, and the opening area of the EGR control well 26 is A, c, and k are constants, the EGR amount G E
GR=CAE2τ under τ−PI). In this way, the EGR amount is determined by the differential pressure between the exhaust pressure and the intake pressure (Pg-P
+) can be determined as a direct parameter, so the target E
Once the GR rate is determined, the opening area of the EGR control valve 26 can be reliably determined. In addition, the differential pressure between the exhaust pressure and the intake pressure is considered to be a better representative of the intake air amount than the engine speed, and therefore, the F and GR ratios are can be made smaller.

If the valve lift amount is constant, the differential pressure corresponds to the rotation speed. Curve A in FIG. 3 shows the relationship between engine speed and differential pressure at valve riffs 1-3t corresponding to the region in FIG. 2, and curves vAB, C, and D are similar. For example, the differential pressure corresponding to the rotation speed N1 on the curve A is P. If the EGR control valve 26 experiences changes over time such as clogging, the
The amount of exhaust gas passing through the GR control well 26 may vary.

In this case, the detected differential pressure also becomes the value P4 on the broken line.

If the EGR rate is calculated using this value P4, an error will occur in the control of the EGR amount. In order to correct this error, the initial setting differential pressure P and the detected differential pressure P are set based on the same rotation speed.
4 and corrected the amount of exhaust gas recirculation.

FIG. 7 is a diagram showing a flowchart of interrupt processing activated every 50+as for EGR control, and temperature control is omitted for the sake of simplification. In step 80, the throttle opening is applied as a load, and the differential pressure P
, actual valve lift amount S.

and read the rotation speed N. In step 81, the deviation amount ΔP of the differential pressure based on the rotational speed is determined from the differential pressure map shown in FIG. In step 82, it is determined whether the deviation amount ΔP of the differential pressure is larger than the allowable value K(N) for the rotation speed N, and if yes, the process proceeds to step 83, where the corrected differential pressure P=P- Let it be ΔP. If no, in step 84, P=P is set.

Subsequently, in step 85, the EGR shown in FIG.
From the rate map, the EGR rate valve lift ls+ corresponding to the load and the differential pressure P is calculated. In step 86
”' Calculate S z S +.

In step 87, it is determined that -α≦S≦α.

Here, α indicates the dead zone 2, and if yes, the EGR
When the control valve 26 is at the target control position, the negative pressure regulating solenoid valve 42 and the atmospheric regulating solenoid valve 44 are closed (step 88);
thereby maintaining the current negative pressure in the negative pressure chamber 32,
EGR? The current lift position of the tiii control valve 26 is maintained.

If NO in step 87, EGR control valve 1
Valve 26 will be controlled to either side closed.

For this purpose, in step 89, it is determined that 3<-α, and if YES, the valve opening time required to achieve valve lift S is calculated.In step 90), the atmosphere control solenoid valve 44 is kept closed. The negative pressure regulating solenoid valve 42 is controlled to open (step 91). As a result, when the negative pressure in the negative pressure chamber 32 increases, the valve lift amount increases, and the EGR rate increases.

If NO in step 89, the valve opening time is determined in step 92, and in step 93, the atmosphere regulating solenoid valve 44 is controlled to open while the negative pressure regulating solenoid valve 42 remains closed. The valve opening time can be mapped and stored as a function of the valve lift amount S and the deviation S between the actual lift amount St.

Note that the differential pressure correction process from step 81 to step 84 in the flowchart of FIG. 7 does not have to be performed every time, but calculations can be performed during idle time of the CPU 60, and the correction process can be performed after a positional difference is detected in the deviation amount ΔP. It can be implemented.

FIG. 8 is a diagram showing a flowchart of a second embodiment of the interrupt processing activated every 50 m5 for EGR control, and FIG. 9 is a diagram showing an interrupt routine for calculating the correction coefficient k used in FIG. 8. It is.

In FIG. 8, the throttle opening degree and the differential pressure P1 are read in step 96, and the differential pressure P1 is read in step 97.
is multiplied by the correction coefficient k to find the corrected differential pressure P. Next, the process proceeds to step 98, where the valve lift i of the EGR rate corresponding to the load and corrected differential pressure P detected from the map in FIG.
Calculate t. In step 99, the actual valve lift f
fi s z and in step 100 S =
Calculate S z −S l. Steps 101 to 107 are the same as steps 87 to 93 in FIG.
This is a process for controlling the control valve 26.

FIG. 9 shows the interrupt processing for calculating the corrected differential pressure P.
Although the illustrated process is activated every 50 m, it can be performed at larger time intervals or by using idle time of the CPtJ60. For example, it may be executed every time the cumulative number of revolutions, cumulative usage time, or travel distance of the internal combustion engine reaches a predetermined value. However, priority is given to processing of the EGR control routine every 50 m5. First, in step 108, the rotational speed N, actual valve lift tst, and detected differential pressure P are input. Next, in step 109, the initial differential pressure P0 at the rotation speed N is determined for the lift amount S2 detected. Here, the detected lift amount S2 is used as follows.
This is to identify the corresponding relationship at that time from among a plurality of relationships between the rotation speed and the initial set differential pressure depending on the valve lift amount, as shown in FIG. Next step 110
1 is obtained from the ratio of the initial pressure difference P0 obtained in step 1 and the detected pressure difference P. k in step 111.

is set to k and the process ends. This k is used in step 97 of FIG. This value of k will be updated as time passes.

Incidentally, instead of replacing 1 with k in step 111, it is also possible to calculate 1 for several cycles and replace the average value with k, so that the correction coefficient k
Variations can be reduced depending on the detected lift amount S2 and the detection state of the rotation speed N. In addition, in this embodiment, a correction coefficient k is obtained for one detected lift amount S2, and the correction coefficient k is used for all valve lift amounts, but the correction coefficient k for each valve lift amount is may be determined and stored as a map for the valve lift amount, so that the optimum correction coefficient for each valve lift amount can be obtained. In the above embodiment, the detected differential pressure P is corrected, but the amount of exhaust gas recirculation may be corrected by other means. For example, the EGR rate map itself in FIG. 2 may be rewritten using the correction coefficient k.

That is, the scale of the horizontal axis (negative pressure) in FIG. 2 is corrected using the correction coefficient k, and a new EGR rate map is created.
From the GR rate map, the valve lift amount can be determined from the detected load and differential pressure. Alternatively, the scale of the horizontal axis (negative pressure) may be left as is, and the shape of the map itself (EGR rate) may be changed.

〔Effect of the invention〕

As explained above, according to the present invention, the amount of exhaust gas recirculation is determined based on the load of the internal combustion engine and the differential pressure between intake and exhaust, and the differential pressure between intake and exhaust can represent the operating state of the internal combustion engine, and the amount of exhaust gas recirculation can be Since it is a directly related parameter, it is possible to achieve highly accurate exhaust recirculation control, and by correcting the amount of exhaust recirculation from the differential pressure and rotation speed, the effects of changes over time can be compensated for, resulting in high controllability. can be maintained.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of the exhaust gas recirculation control device for an internal combustion engine according to the present invention, Figure 2 is a diagram showing a map of the EGR rate based on load and differential pressure, and Figure 3 is a diagram showing the differential pressure based on the rotation speed. FIG. 4 is a diagram showing an example of a differential pressure sensor. FIG. 5 is a diagram showing another example of a differential pressure sensor. FIG. 6 is a diagram showing the structure of an electronic control device. FIG. 7 is a diagram showing a flowchart of control, FIG. 8 is a diagram showing a flowchart of another example of control, and FIG. 9 is a diagram showing a flowchart for determining the correction coefficient of FIG. 14... Combustion chamber, 16... Exhaust passage, 18...
...Intake passage, 24...EGR passage, 26...
EGR control valve, 49... rotation speed sensor, 50... throttle sensor, 52... differential pressure sensor. Figure 2 Figure 4 Figure 5 Figure 8

Claims (1)

[Claims] A load detection means for detecting the load of the internal combustion engine, a rotation speed detection means for detecting the rotation speed of the internal combustion engine, and a rotation speed detection means for detecting the pressure difference between the pressure in the exhaust passage and the pressure in the intake passage. The system includes a differential pressure detection means, an exhaust gas recirculation amount calculation means for calculating the exhaust gas recirculation amount based on the load and the differential pressure, and a correction means for correcting the exhaust gas recirculation amount based on the detected differential pressure and rotation speed. An exhaust gas recirculation control device for an internal combustion engine, characterized in that: