JP2674440B2 - EGR control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

This invention relates to exhaust gas recirculation (hereinafter referred to as EG
(Referred to as R) to an improvement of the control device.

[0002]

2. Description of the Related Art A so-called EGR device is known in which an inert exhaust gas is recirculated through an intake pipe in order to suppress the generation of NOx which is a harmful component in the exhaust gas. This EG
In the R device, an EGR valve is installed in the EGR passage (a passage for returning a part of the exhaust gas to the intake pipe), and the EGR valve is opened in a region where EGR is required so that a certain amount of the exhaust gas (EGR
Gas) is mixed with the intake air to lower the maximum temperature during combustion.

By the way, the EGR rate (EG for the fresh air amount
The NOx emission decreases as the R gas flow rate) increases, but on the other hand, when the EGR rate increases, a surge (low-frequency vibration in the front-rear direction of the vehicle) occurs during steady running or acceleration / deceleration due to combustion fluctuations. Drivability deteriorates.

In order to prevent the deterioration of the drivability, it is effective to close the swirl control valve provided near the intake port to generate swirl in the combustion chamber. This is because the amount of EGR gas can be recirculated as much as the combustion is improved by the swirl, so that the combined use of the swirl as shown in FIG.
The amount of emissions is reduced.

However, when the EGR rate is increased, if the region where the EGR valve is opened and the region where the swirl control valve is closed are set independently, FIG.
As described above, EGR gas may be introduced with the swirl control valve open, and combustion fluctuations are exposed in the shaded region, causing a surge.

Therefore, in order to eliminate this surge, in Japanese Patent Laid-Open Nos. 63-9669 and 59-49359, the EGR valve is always opened with the swirl control valve closed, and the swirl control valve is opened. EG when opened
I try not to open the R valve. That is, the open operating range of the EGR valve and the close operating range of the swirl control valve are matched.

[0007]

By the way, in the above device, since the response delay of the EGR valve and the supply delay of the EGR gas are not taken into consideration, the operating condition shifts from the open operating range of the EGR valve to the closed operating range. A surge may occur during operation.

For example, the transition of the operating condition from the open operating range to the closed operating range instructs the EGR valve to close and the swirl control valve to open. In this case, if the EGR passage is open to the collector section of the intake pipe, there is no response delay in the switching of the EGR valve itself, and even if the EGR valve is immediately closed, from the intake pipe collector section to the intake port. The remaining EGR gas flows into the combustion chamber with the swirl control valve open. Further, if there is a response delay in closing the EGR valve, the flow rate of the EGR gas that flows in later increases correspondingly. As described above, when the EGR valve is moved from the open operating region to the closed operating region, a large amount of EGR gas is introduced without swirl due to the response delay of the EGR valve and the supply delay of the EGR gas to the combustion chamber. In some cases, combustion fluctuations occur.

In view of this, the present invention makes the closing operation range of the swirl control valve wider than the opening operation range of the EGR valve so that E
An object of the present invention is to prevent the surge by preventing the EGR gas from being introduced in a swirl-free state at the time of transition from the open operating region of the GR valve to the closed operating region.

[0010]

The first invention, as shown in FIG. 1, is an EGR passage 33 for returning a part of exhaust gas to the intake pipe 32 as EGR gas, and an EGR passage for opening and closing the EGR passage 33. The valve 34 and the EGR at the time of transition from the open operating region to the closed operating region which is determined according to the engine speed and the load.
In an EGR control device provided with a means 35 for switching the valve 34 from an open state to a closed state, a swirl control valve 36 for causing a swirl in a combustion chamber, and the swirl control valve 3
Means 37 for setting the closing operation range of 6 wider than the opening operation range of the EGR valve 34, and means for switching the swirl control valve 36 from the open state to the closed state when the operating condition reaches the closing operation range of the swirl control valve. And 38.

A second invention is the first invention, wherein the EG
Both of the R valve and the swirl control valve were set such that the width of the closed operation region was wider at low water temperature than at high water temperature.

A third invention is the EG according to the first invention.
Both the R valve and the swirl control valve were set such that the width of the closed operation region was wider as the engine speed became lower or the engine load became lower.

In a fourth aspect of the present invention, in any one of the first to third aspects of the invention, the EGR valve is in a range from the open operating region to the EGR valve closing operating region and the swirl control valve opening operating region. When shifting to a certain region, the swirl control valve is forcibly closed until a predetermined time elapses from the closing operation timing of the EGR valve.

According to a fifth aspect of the invention, in the fourth aspect of the invention, the predetermined time is changed depending on the water temperature, and the low water temperature is set longer than the high water temperature.

[0015]

When, for example, the EGR valve is opened and EGR is being performed for a while, the accelerator pedal is further stepped on to accelerate the vehicle, so that the operating condition deviates from the open operating range of the EGR valve to the open operating range of the swirl control valve. And move on.

At this time, even if the EGR valve is immediately closed at the timing when the operating condition shifts to the closing operation range of the EGR valve, EGR gas remains between the intake pipe collector section 32 and the intake port at that moment. To do. Further, when the EGR valve is not immediately closed and is closed with a certain response delay, the EGR gas flows into the intake pipe collector section 32 even during the response delay. That is, the EGR continues for a while from the timing when the EGR valve is closed.

In this case, according to the first invention, the EGR
Even after the valve is closed, the swirl control valve is kept fully closed until the operating condition deviates from the closing operation range of the swirl control valve, and swirl is given to the intake air mixed with the EGR gas and flowing into the combustion chamber. By operating the swirl until the EGR gas remaining in the intake pipe has finished flowing into the combustion chamber at the timing when the EGR valve is closed, E
This prevents combustion fluctuations associated with GR.

Thus, when the EGR valve moves from the open operating region to the closed operating region, even if there is a response delay of the EGR valve or a supply delay of the EGR gas, a surge does not occur.

By the way, when the engine water temperature is low, the region where combustion is unstable spreads out compared to when the engine water temperature is high. Correspondingly, both the EGR valve and the swirl control valve are in the closed operation region according to the second invention. If the region width is made wider at low water temperature than at high water temperature, swirl control is performed after the EGR valve is closed at low water temperature when the EGR valve moves from the open operating region to the closed operating region. Because the valve is closed for a longer period of time, the engine speed stabilizes as it does when the water temperature is high.

Further, even with an equal EGR rate, the stability of the engine tends to be worse in the low rotation range or the low load range.

On the other hand, in the third aspect of the invention, when the widths of the EGR valve and the swirl control valve, which are the closing operation regions, are made wider as the rotation speed becomes lower or the load becomes lower,
When the transition from the open operating range of the R valve to the closed operating range is performed in the low rotation range or the low load range, the swirl control is performed after the EGR valve is closed rather than in the high rotation range or the high load range. Since the valve is closed for a longer period of time, the same engine stability can be obtained regardless of the level of engine rotation or the magnitude of engine load.

Further, the swirl control valve needs to be closed corresponding to the time when the EGR gas remaining in the intake pipe flows into the combustion chamber at the closing operation timing of the EGR valve.

Correspondingly, in the fourth invention, E
At the time of transition from the opening range of the GR valve to the closing range of the EGR valve and the opening range of the swirl control valve, E
If the swirl control valve is forcibly closed until a predetermined time elapses from the closing timing of the GR valve, the residual EGR
Fluctuation of combustion due to gas is prevented.

In the fourth invention, the predetermined time is EGR
This corresponds to the time until the EGR gas remaining in the intake pipe has finished flowing into the combustion chamber at the valve closing operation timing, and when this time is further set to a value according to the cooling water temperature according to the fifth invention, Control accuracy is improved.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 2, 1 is an engine body, 2 is an intake pipe, 3 is an exhaust pipe, 4 is an exhaust pipe and a collector portion 2a of the intake pipe.
Is an EGR passage communicating with the EGR passage 5 and a diaphragm type E attached to the EGR passage near the intake pipe collector portion 2a.
It is a GR valve.

Reference numeral 6 denotes a pressure switching valve for selectively introducing a constant negative pressure or atmospheric pressure into the working chamber 5a of the EGR valve 5, and introducing a negative pressure of the intake pipe downstream of the throttle valve 8 to a constant negative pressure. It consists of a constant pressure valve portion 6a for producing pressure and a solenoid valve portion 6b for receiving ON and OFF signals from the control unit 21, and when the solenoid valve portion 6b is opened by the ON signal, the EGR valve 5 is closed by the spring 5b. , O
When the solenoid valve portion 6b is closed by the FF signal and the negative pressure from the constant pressure valve portion 6a is introduced into the working chamber 5a instead of the atmospheric pressure, the EGR valve 5 is opened against the spring 5b.

In order to control the switching of the pressure switching valve 6 according to the operating conditions of the engine, a control unit 21 composed of a microcomputer is provided. The control unit 21 operates based on signals from the air flow meter 22 and the crank angle sensor 23. Is within the opening range of the EGR valve 5 (steps 1 and 2 in FIG. 3).

As shown in FIG. 4, whether or not the operating condition is in the EGR valve open operation range is a map determined from the engine speed Ne and the basic injection pulse width (engine load equivalent amount) Tp (EGR valve switching map). ), This EG
If the R-valve switching map is looked up and the EGR valve is in the open operating range, an OFF signal is output to the pressure switching valve 6 to output EGR.
Open the valve 5 (steps 2 and 4 in FIG. 3). In the open operation range of the EGR valve provided in the low load and low rotation range in FIG. 4, a large amount of EGR gas is introduced into the intake pipe 2, and the NOx emission amount is reduced. Note that Tp is a value determined from the engine speed Ne and the air flow meter output Q.

On the other hand, when the EGR valve 5 is opened, the swirl control valve 11 provided in the vicinity of the intake port 2b is closed in order to avoid a surge caused by combustion fluctuations associated with EGR. When the EGR valve 5 opens, the swirl control valve 11 is fully closed to throttle the intake air.
The flow velocity of intake air is increased to generate swirl in the combustion chamber (steps 2 and 3 in FIG. 3).

The swirl control valve 11 having a notch (not shown) in a part thereof is driven by the diaphragm actuator 12, and when the swirl control solenoid valve 13 is turned on by a signal from the control unit 21, the vacuum tank 14 outputs a signal. Negative pressure (operating pressure) is introduced to the actuator 12, the swirl control valve 11 is closed, and conversely, when the solenoid valve 13 is turned off, the swirl control valve 11 returns to the fully open position.

By the way, if the open operating range of the EGR valve 5 and the close operating range of the swirl control valve 11 are made to coincide with each other, EG
When the R valve 5 shifts from the open operating region to the closed operating region, the EGR
Due to the response delay of the valve 5 and the supply delay of the EGR gas to the combustion chamber, the EGR gas remaining from the intake pipe collector portion 2a to the intake port 2b flows into the combustion chamber with the swirl control valve 11 opened. A surge occurs immediately after the EGR valve enters the closed operation range.

To deal with this, in this example, as shown in FIG. 5, the closed operation range of the swirl control valve 11 is set wider than the open operation range of the EGR valve 5. Corresponding to the EGR valve switching map of FIG. 4, the engine speed Ne and the basic injection pulse width T
A map (swirl control valve switching map) determined by p is prepared as shown in FIG.

In this way, in the operating range defined by Ne and Tp, when the closed operating range of the swirl control valve 11 is made wider than the open operating range of the EGR valve 5, unlike the conventional device,
An area (area indicated by hatching in FIG. 5) in which both the EGR valve 5 and the swirl control valve 11 are closed occurs. Therefore, in the control unit 21, it is confirmed whether or not the EGR valve is in the closed operation range and the swirl control valve is in the close operation range. In this range, both the EGR valve 5 and the swirl control valve 11 are operated. It is closed (steps 2, 5, 6, 7 in FIG. 3).

When the swirl control valve 11 opens, the swirl control valve 11 is opened (step 2, FIG. 3).
5, 8, 10).

The operation of this example will be described below.

For example, when the EGR valve is opened and EGR is being performed for a while, the accelerator pedal is further depressed to accelerate the vehicle, and the operating condition is EGR as shown in FIG.
Move out of the open operating range of the valve in the direction of the arrow and move to the open operating range of the swirl control valve.

At this time, the EGR valve 5 is operated at the timing (point B) when the operating condition shifts from the open operating range of the EGR valve to the close operating range.
Even if is closed with good response, at that moment, EGR gas remains between the intake pipe collector portion 2a and the intake port 2b in FIG. In addition, the pressure switching valve 6
When the N signal (valve closing signal) is output, the EGR valve 5
Is not closed immediately and the EGR valve 5 is closed with a certain response delay, the EG is also closed during the response delay.
R gas flows into the intake pipe collector portion 2a. That is, E
Even after the GR valve is closed, the EGR gas flows into the combustion chamber for a while.

In this case, according to this example, even after the EGR valve is closed, the swirl control valve is kept fully closed until the operating condition deviates from the swirl control valve closing operation range (point C). The swirl is given to the intake air that is mixed with the EGR gas and flows into the combustion chamber. Even when the EGR gas remaining in the intake pipe has finished flowing into the combustion chamber at the timing when the EGR valve is closed, the swirl works and combustion fluctuations associated with EGR are prevented.

As a result, the response delay of the EGR valve and E
Even if there is a delay in the supply of GR gas, surge does not occur.

By the way, in FIG. 6, from the point A which is the opening operation range of the EGR valve to the opening operation range D of the swirl control valve.
Up to the point, the operating conditions may change instantaneously. At this time, the swirl control valve is opened immediately after the EGR valve is closed, and a surge occurs. When the operating conditions change at a speed higher than the behavior speed of EGR gas (fluid), EGR
This is because the swirl control valve is opened before all the EGR gas remaining in the intake pipe flows into the combustion chamber at the timing when the valve is closed.

On the other hand, in this example, as shown in FIG. 3, the swirl control valve is kept closed until a predetermined time elapses from the closing operation timing of the EGR valve (step 9 in FIG. 3). , 7). The time slightly longer than the time required from the closing operation timing of the EGR valve until all the EGR gas remaining in the intake pipe flows into the combustion chamber is selected as the predetermined time.

As a result, the swirl control valve is always opened with a delay from the closing operation timing of the EGR valve.
Even when the operating conditions instantaneously shift from the open operating range of the EGR valve to the open operating range of the swirl control valve, no surge occurs.

It is desirable that the above-mentioned predetermined time is further set according to the cooling water temperature. For example, at low water temperature,
Shorten at high water temperatures. As a result, the operating condition becomes smooth in all water temperature regions, and control accuracy improves.

7, FIG. 8, FIG. 9 (FIG. 7 is shown in FIG. 3, FIG.
FIG. 9 corresponds to FIG. 5) is a second embodiment.

This is because the region where combustion is not stable spreads when the engine water temperature is low compared to when the engine water temperature is high. Therefore, as shown in FIG. 8 and FIG. 9, both the EGR valve and the swirl control valve correspond to this. The width of the closed operating region is wider at low water temperature than at high water temperature. In addition,
In FIG. 8 and FIG. 9, the width of the above region at low water temperature is wider than at high water temperature only on the high rotation side and the high load side, and the low rotation side and the low load side do not change.

Regarding the opening range of the EGR valve itself, the low water temperature is narrower than the high water temperature as shown in FIGS. 8 and 9 (also in FIGS. 10 and 10 described later). This is because the combustion temperature becomes lower when the water temperature is low, so that the region where EGR is applied can be narrowed in terms of the equivalent NOx emission amount.

When different maps are used for low water temperature and high water temperature as shown in FIGS. 8 and 9, the control flow chart is as shown in FIG. In FIG. 7, by looking up the respective maps (EGR valve switching map and swirl valve switching map) for low water temperature during low water temperature and for high water temperature during high water temperature, the operating conditions are Whether or not it is in the open operation range and whether or not it is in the close operation range of the swirl control valve is determined (steps 23 and 24, steps 25 and 26 in FIG. 7). The swirl valve in FIG. 7 is an abbreviation for the swirl control valve.

According to this example, when the EGR valve shifts from the open operating region to the close operating region and the water temperature is low, the swirl control valve is closed for a long time after the EGR valve is closed. As a result, the engine speed stabilizes in the same way as when the water temperature is high.

10 and 11 show the third embodiment. Considering that the engine stability tends to be worse in the low rotation range and the low load range as shown in FIGS. 12 and 13, even when the EGR rate is equal, as shown in FIGS. 10 and 11, EGR
Both the valve and the swirl control valve are such that the width of the region which is the closing operation region is widened as the rotation speed becomes lower and the load becomes lower.

Also in FIGS. 10 and 11, the width of the above region widens as the rotation speed decreases and the load decreases, only on the high rotation side and the high load side, and on the low rotation side and the low load side. unrelated.

In this example, when the transition from the open operating range to the close operating range of the EGR valve is performed in the low rotation speed range or the low load range,
Since the swirl control valve is closed for a longer time after the EGR valve is closed than when the engine is operated in the high speed range or the high load range, the same engine is used regardless of the high or low speed of the engine rotation or the magnitude of the engine load. The stability of is obtained.

In the embodiment, the EGR valve 5 has been described as being in either the fully open position or the fully closed position, but it is also applicable to the EGR valve opening determined according to the duty given to the solenoid valve portion 6b. can do.

[0053]

According to the first aspect of the present invention, the EG is set when the engine is moved from the open operating range to the closed operating range, which is determined according to the engine speed and the load.
EGR in which the R valve is switched from the open state to the closed state
The control device is provided with a swirl control valve that throttles intake air to generate a swirl in the combustion chamber, and sets the closing operation range of this swirl control valve to be wider than the opening operation range of the EGR valve, and the operating condition is to close this swirl control valve. When the operating range is reached, the swirl control valve is switched from the open state to the closed state.
Even when there is a delay in the response of the EGR valve or a delay in the supply of the EGR gas when the GR valve shifts from the open operating region to the closed operating region, no surge occurs.

A second aspect of the invention is the same as the first aspect of the invention.
Since both the R valve and the swirl control valve have been set such that the width of the closed operating region is wider at low water temperature than at high water temperature, in addition to the effect of the first invention, the EGR valve is closed from the open operating region. When transitioning to the operating range, the engine speed will be stable at low water temperature as well as at high water temperature.

A third aspect of the invention is the same as the first aspect of the invention.
Since both the R valve and the swirl control valve set the width of the region of the closed operation region to be wider as the engine speed becomes lower or the engine load becomes lower, in addition to the effect of the first invention,
The same engine stability can be obtained regardless of whether the engine speed is high or low or the engine load is large or small.

A fourth aspect of the present invention is the invention of any one of the first to third aspects, wherein the EGR valve is in the closed operating range from the EGR valve open operating range to the swirl control valve open operating range. When a transition to a certain region is made, the swirl control valve is forcibly closed until a predetermined time elapses from the closing operation timing of the EGR valve, so that the EG remaining in the intake pipe is
It is possible to reliably prevent combustion fluctuations due to R gas.

In the fifth aspect of the invention, in the fourth aspect, the predetermined time is changed depending on the water temperature, and the low water temperature is set longer than the high water temperature, so that the control accuracy is improved.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to a claim of the first invention.

FIG. 2 is a configuration diagram of an EGR control device according to an embodiment.

FIG. 3 is a flowchart for explaining switching control between an EGR valve and a swirl control valve.

FIG. 4 is a characteristic diagram of an EGR valve switching map.

FIG. 5 is a characteristic diagram of a switching map of a swirl control valve.

FIG. 6 is a region diagram for explaining the operation of the embodiment.

FIG. 7 is a flow chart for explaining switching control between the EGR valve and the swirl control valve according to the second embodiment.

FIG. 8 is a characteristic diagram of a switching map of the swirl control valve when the water temperature is low according to the second embodiment.

FIG. 9 is a characteristic diagram of a switching map of the swirl control valve at the time of high water temperature according to the second embodiment.

FIG. 10 is a characteristic diagram of a switching map of the swirl control valve when the water temperature is low according to the third embodiment.

FIG. 11 is a characteristic diagram of a switching map of the swirl control valve at high water temperature according to the third embodiment.

FIG. 12 is a characteristic diagram of engine stability with respect to the engine speed Ne of the third embodiment.

FIG. 13 is a characteristic diagram of engine stability against engine load according to the third embodiment.

FIG. 14 is a characteristic diagram of EGR rate and NOx emission amount in a conventional example.

FIG. 15 is a characteristic diagram showing the open operating range of the EGR valve and the closed operating range of the swirl control valve in the conventional example in an overlapping manner.

[Explanation of symbols]

 2 intake pipe 3 exhaust pipe 4 EGR passage 5 EGR valve 6 pressure switching valve 6b solenoid valve section 8 throttle valve 11 swirl control valve 12 diaphragm actuator 13 swirl control solenoid valve 21 control unit 22 airflow meter 23 crank angle sensor 32 intake pipe 33 EGR Passage 34 EGR valve 35 EGR valve switching means 36 Swirl control valve 37 Swirl control valve open operating range setting means 38 Swirl control valve switching means

Claims (5)

(57) [Claims] 1. An EGR passage for returning a part of exhaust gas as EGR gas to an intake pipe, and an E for opening and closing the EGR passage.
An EGR control device comprising a GR valve and means for switching the EGR valve from an open state to a closed state at the time of shifting from an open operating region to a closed operating region which is determined according to an engine speed and a load, a swirl in a combustion chamber. A swirl control valve that causes the above-mentioned swirl control valve, a means for setting the close operation range of this swirl control valve wider than the open operation range of the EGR valve, and the swirl control valve opens when the operating condition reaches the close operation range of this swirl control valve. An EGR control device comprising means for switching from a closed state to a closed state. 2. The EGR control according to claim 1, wherein both the EGR valve and the swirl control valve are set such that the width of the region of the closing operation region is wider at low water temperature than at high water temperature. apparatus. 3. The EGR according to claim 1, wherein both the EGR valve and the swirl control valve are set such that the width of the region of the closed operation region is set wider as the engine speed is lower or the engine load is lower. Control device. 4. The EGR from the opening range of the EGR valve
When transitioning to the region where the valve is closed and the swirl control valve is open, the swirl control valve is forcibly closed until a predetermined time elapses from the EGR valve closing operation timing. The EGR control device according to any one of claims 1 to 3, characterized in that. 5. The predetermined time is changed by water temperature,
The EGR control device according to claim 4, wherein the low water temperature is set longer than the high water temperature.