JPH09324704A - Exuast reflux device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of a bad start and the deterioration of an operation property by the generation of dew formation and freezing to a fuel injection valve by an exhaust reflux. SOLUTION: When a water temperature is a prescribed temperature A or more (S1), a car speed is a prescribed speed B or more (S2) and they are within an exhaust reflux area set in advance in response to an engine rotation speed and an engine load (S3), the completion of the execution condition of an exhaust reflux is discriminated. Here, even if it is such state that the execution condition of the exhaust reflux is completed, when a fuel temperature relating the temperature of the injection hole of a fuel injection valve is a prescribed temperature C or less (S4), the generation of dew formation and freezing by the execution of the exhaust reflux is forecasted and the exhaust reflux is stopped (S6).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation device for an internal combustion engine, and more particularly to a technique for preventing dew condensation and icing from occurring on a fuel injection valve due to exhaust gas recirculation.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine, a part of exhaust gas is recirculated to an intake passage to lower a combustion temperature.
There is known an exhaust gas recirculation device that reduces NOx. Further, a sequential type electronically controlled fuel injection device is known in which a fuel injection valve is provided in an intake port and fuel is supplied to each cylinder.

[0003]

When exhaust gas recirculation is performed in an internal combustion engine equipped with the above-mentioned sequential type electronically controlled fuel injection device, generally, the exhaust gas is exhausted to the intake passage upstream of the fuel injection valve. However, if exhaust gas recirculation is performed under low temperature conditions, the water introduced into the intake passage due to exhaust gas recirculation will be injected into the injection hole of the fuel injection valve. Condensation and icing on the part could cause poor starting and poor drivability.

[0004] Although blow-by gas and intake air from the atmosphere also contain moisture, especially the recirculated exhaust gas contains a large amount of moisture, and the recirculation of exhaust gas is the main cause of condensation and icing of the fuel injection valve. Had become. The present invention has been made in view of the above problems, and it is an object of the present invention to reliably reduce dew condensation and icing of a fuel injection valve due to exhaust gas recirculation.

[0005]

Therefore, the invention according to claim 1 is constructed as shown in FIG. In FIG. 1, the fuel injection valve is provided in the intake port portion and supplies fuel to the engine. The exhaust gas recirculation device is a device that recirculates a part of the exhaust gas to the intake passage on the upstream side of the fuel injection valve, and includes an injection hole temperature detection means and an exhaust gas recirculation amount control means.

The injection hole temperature detecting means detects the temperature of the injection hole of the fuel injection valve. Then, the exhaust gas recirculation amount control means controls the exhaust gas recirculation amount according to the temperature of the injection hole portion detected by the injection hole portion temperature detecting means. That is, when the temperature of the injection hole portion is low, the water contained in the recirculated exhaust gas may be condensed and frozen in the injection hole portion. Therefore, the exhaust gas recirculation amount, in other words, the exhaust gas recirculation causes the intake passage to enter the intake passage. Control the amount of water brought in to reduce the condensation and freezing.

According to the second aspect of the present invention, the injection hole temperature detection means detects the fuel temperature as a temperature correlated with the temperature of the injection hole portion. The temperature of the injection hole may be detected directly by attaching a temperature sensor to the injection hole, but the temperature of the injection hole and the fuel temperature (the fuel temperature in the fuel pipe near the injection hole is Since it is substantially proportional to (preferably) (see FIG. 5), instead of directly detecting the temperature of the injection hole portion, the temperature of the injection hole portion may be indirectly detected from the fuel temperature.

According to the third aspect of the present invention, the exhaust gas recirculation amount control means stops the exhaust gas recirculation when the detected temperature of the injection hole portion is equal to or lower than a preset temperature. According to such a configuration, it is possible that moisture brought into the intake passage due to exhaust gas recirculation may cause dew condensation or icing in the injection hole portion of the fuel injection valve. Judge by whether or not. When the temperature of the nozzle hole is below a predetermined temperature and there is a risk of dew condensation or icing, the exhaust gas recirculation is stopped to prevent water from being brought into the intake passage due to the exhaust gas recirculation, thereby preventing dew condensation or icing. To reduce.

According to a fourth aspect of the present invention, the exhaust gas recirculation amount control means reduces the exhaust gas recirculation amount as the detected temperature of the injection hole portion is lower. That is, according to the third aspect of the invention, when the temperature of the injection hole portion is equal to or lower than a predetermined temperature, it is judged on / off that there is a risk of dew condensation or freezing, and the exhaust gas recirculation is controlled on / off. However, in the invention according to claim 4, the exhaust gas recirculation amount is reduced as the temperature of the injection hole portion is lower, and it does not lead to poor starting or drivability even under low temperature conditions. Exhaust gas recirculation was performed while allowing dew condensation and freezing within the range.

[0010]

According to the invention described in claim 1, the water contained in the recirculated exhaust gas is condensed and frozen in the injection hole portion,
There is an effect that it is possible to prevent the occurrence of poor starting and deterioration of drivability. According to the invention described in claim 2,
It is possible to easily detect a condition where the temperature of the injection hole portion is low and there is a risk of dew condensation or icing based on the fuel temperature.

According to the third aspect of the present invention, there is an effect that it is possible to surely avoid the occurrence of dew condensation and freezing due to exhaust gas recirculation. According to the invention described in claim 4, there is an effect that the exhaust gas recirculation can be performed as much as possible and the occurrence of dew condensation and icing due to the exhaust gas recirculation can be avoided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In FIG. 2 showing the system configuration,
An exhaust gas recirculation passage 4 that connects the intake manifold 2 and the exhaust manifold 3 of the engine 1 is provided, and the exhaust gas recirculation passage 4 is opened and closed by an EGR control valve 5 (exhaust gas recirculation control valve). .

The EGR control valve 5 is a diaphragm type valve which is opened by applying a suction negative pressure to the engine against the biasing force of the coil spring in the valve closing direction. A negative pressure introducing passage 7 that communicates with the intake manifold 2 on the downstream side is provided, and the intake negative pressure of the engine 1 is introduced into the pressure chamber through the negative pressure introducing passage 7 to open the valve.

An EGR control solenoid 9 which is on / off controlled by a control unit 8 is provided in the negative pressure introducing passage 7. The opening / closing control of the EGR control solenoid 9 controls the EGR control valve 5 to operate. The opening / closing, that is, the exhaust gas recirculation amount can be controlled. Reference numeral 10 is a diaphragm type BPT valve that determines the negative pressure for controlling the EGR control valve 5 by operating the diaphragm by the exhaust pressure and the manifold negative pressure.

The control unit 8 receives detection signals such as cooling water temperature, engine speed, intake air amount, vehicle speed, etc. from each sensor, and also inputs an ON / OFF signal of an ignition switch, and determines from these. The EGR control solenoid 9 is controlled based on the engine operating conditions. The exhaust gas recirculation passage 4, the EGR control valve 5, the negative pressure introduction passage 7, and the EGR control solenoid 9 constitute a basic hardware part of the exhaust gas recirculation device. However, the hardware configuration of the exhaust gas recirculation device is not limited to the above.

The control unit 8 includes:
A fuel temperature detection signal from a fuel temperature sensor 12 that detects the temperature of the fuel supplied to the fuel injection valve 11 provided in the intake port portion is input. The fuel temperature detected by the fuel temperature sensor 12 is a temperature substantially proportional to the temperature of the injection hole portion of the fuel injection valve 11 (see FIG. 5). Here, the fuel temperature is the injection hole of the fuel injection valve 11. Treat as equivalent to the temperature of the section. Therefore, the fuel temperature sensor 12 corresponds to the injection hole temperature detecting means. In order to accurately estimate the temperature of the injection hole portion of the fuel injection valve 11 from the fuel temperature, the fuel temperature sensor 12 is
It is preferable that the fuel temperature is detected in the fuel pipe near the fuel injection valve 11 (either on the feed side or the return side). Also, instead of the fuel temperature sensor 12,
A sensor that directly detects the temperature of the injection hole portion of the fuel injection valve 11 may be provided.

The state of exhaust gas recirculation control by the control unit 8 will now be described with reference to the flowchart of FIG. The control unit 8 has the function of the exhaust gas recirculation amount control means as software, as shown in the flowchart of FIG. In the flowchart of FIG. 3, first, in step 1 (denoted as S1 in the figure; the same applies hereinafter), it is determined whether or not the water temperature is equal to or higher than a predetermined temperature A. If the water temperature is equal to or higher than the predetermined temperature A, step 2 is performed.
Proceed to.

In step 2, it is determined whether or not the vehicle speed is equal to or higher than the predetermined speed B. If the vehicle speed is equal to or higher than the predetermined speed B, the process proceeds to step 3. In step 3, it is determined whether or not the preset exhaust gas recirculation region corresponds to the engine speed and the engine load.
When it is judged that the conditions for executing the exhaust gas recirculation are satisfied, the routine proceeds to step 4.

In step 4, it is judged whether or not the fuel temperature detected by the fuel temperature sensor 12 is a predetermined temperature C or higher. When the fuel temperature is equal to or higher than the predetermined temperature C, that is, when the temperature of the injection hole portion of the fuel injection valve 11 is sufficiently high, even if exhaust gas recirculation is performed and exhaust gas containing much water is recirculated to the intake passage, the injection hole When it is judged that the dew condensation and frost formation on the part are sufficiently small, the process proceeds to step 5 and exhaust gas recirculation is executed.

On the other hand, even if it is determined in step 1 to 3 that the execution condition of the exhaust gas recirculation is satisfied, if it is determined in step 4 that the fuel temperature is lower than the predetermined temperature C, that is, the fuel injection valve
If the temperature of the nozzle hole of 11 is low and the exhaust gas recirculates and the exhaust gas containing a large amount of water is returned to the intake passage, if there is a possibility that a large amount of dew condensation or icing will occur in the nozzle hole step, 1
In the same manner as when it is determined that the exhaust gas recirculation condition is not satisfied in to 3, the process proceeds to step 6 and the exhaust gas recirculation is stopped.

As described above, when the temperature of the injection hole portion of the fuel injection valve 11 estimated from the fuel temperature is low and the exhaust gas recirculation is performed, there is a possibility that dew condensation or icing may occur, so the exhaust gas recirculation may occur. If it is forcibly stopped, the condensation and freezing can be prevented from occurring. It should be noted that when the exhaust temperature is high, the amount of water contained in the exhaust increases, so that the higher the exhaust temperature is, the lower the predetermined temperature C is set, and the exhaust gas recirculation is stopped under the condition that the fuel temperature is higher. You may do it.

In the above description, the possibility of dew condensation or freezing is judged on / off and exhaust gas recirculation is controlled on / off. However, the EGR control solenoid 9 may be duty controlled. , Exhaust gas recirculation passage 4
When the exhaust gas recirculation rate is controlled by, for example, duty-controlling an EGR valve as an electromagnetic actuator interposed in the fuel injection valve 11, the fuel temperature is correlated with the temperature of the injection hole portion of the fuel injection valve 11 according to the fuel temperature. The exhaust gas recirculation rate may be corrected, and such an embodiment will be described with reference to the flowchart of FIG.

Steps in the flowchart of FIG.
In Steps 11 and 12, similarly to Steps 1 and 2, it is determined whether the water temperature is equal to or higher than the predetermined temperature A and the vehicle speed is equal to or higher than the predetermined speed B. And the water temperature is the predetermined temperature A
If the vehicle speed is equal to or higher than the predetermined speed B,
In step 13, the target exhaust gas recirculation rate corresponding to the current operating condition is searched by referring to the map in which the target exhaust gas recirculation rate (target EGR rate) is stored in advance corresponding to the engine speed and the engine load.

In step 14, a correction coefficient K corresponding to the current fuel temperature is obtained by referring to a map in which the correction coefficient K of the exhaust gas recirculation rate (EGR rate) is stored in advance corresponding to the fuel temperature. The correction coefficient K is set to 1.0 when the fuel temperature is equal to or higher than the predetermined temperature D, and is set to a smaller value when the fuel temperature is lower than the predetermined temperature D. The reflux rate is modified to be smaller.

As a result, as the fuel temperature, that is, the temperature of the injection hole of the fuel injection valve is lower, and the dew condensation or icing is more likely to occur due to the exhaust gas recirculation, the exhaust gas recirculation rate is corrected to be reduced and exhaust gas recirculation is performed as much as possible. At the same time, it is possible to prevent the above-mentioned dew condensation and freezing. In step 15, the target exhaust gas recirculation rate obtained in step 13 is corrected by the correction coefficient K obtained in step 14 to set the final exhaust gas recirculation rate, and the EGR control solenoid 9 is set accordingly. Control.

On the other hand, in step 11, it is determined that the water temperature is lower than the predetermined temperature A, or in step 12, the vehicle speed is the predetermined speed B.
If it is determined that the exhaust gas recirculation is less than the above, the execution condition of the exhaust gas recirculation is not satisfied, so the routine proceeds to step 16, and the exhaust gas recirculation is stopped. The characteristic of the correction coefficient K may be changed in accordance with the temperature of the recirculated exhaust gas. For example, when the correction coefficient K is 1.0 at a predetermined temperature D or higher, the correction coefficient K is commonly lower than the predetermined temperature D. A plurality of tables with different change characteristics of the correction coefficient K are prepared in advance, selected from the plurality of tables according to the exhaust gas temperature, and the selected table is used to correspond to the fuel temperature at that time. Correction coefficient K
It may be configured to determine. In this case as well, the amount of water contained increases when the exhaust temperature is high, so if the table selected when the exhaust temperature is high has a characteristic in which the drop of the correction coefficient K due to the decrease of the fuel temperature is made steeper. good.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the invention according to claim 1;

FIG. 2 is a system configuration diagram of an internal combustion engine in the embodiment.

FIG. 3 is a flowchart showing a first embodiment of exhaust gas recirculation control.

FIG. 4 is a flowchart showing a second embodiment of exhaust gas recirculation control.

FIG. 5 is a diagram showing a correlation between fuel temperature and injection hole temperature.

[Explanation of symbols]

 1 Internal Combustion Engine 2 Intake Manifold 3 Exhaust Manifold 4 Exhaust Gas Recirculation Passage 5 EGR Control Valve 6 Throttle Valve 7 Negative Pressure Introduction Passage 8 Control Unit 9 EGR Control Solenoid 10 BPT Valve 11 Fuel Injection Valve 12 Fuel Temperature Sensor

Claims (4)

[Claims] 1. An exhaust gas recirculation device for recirculating a part of exhaust gas to an intake passage upstream of a fuel injection valve in an internal combustion engine in which fuel is supplied by a fuel injection valve provided in an intake port portion, A nozzle hole temperature detecting means for detecting the temperature of the nozzle hole portion of the fuel injection valve, and an exhaust gas recirculation amount for controlling the exhaust gas recirculation amount according to the temperature of the nozzle hole portion detected by the nozzle hole temperature detecting means. An exhaust gas recirculation system for an internal combustion engine, comprising: a control unit. 2. The exhaust gas recirculation system for an internal combustion engine according to claim 1, wherein the injection hole temperature detecting means detects the fuel temperature as a temperature correlated with the temperature of the injection hole portion. 3. The exhaust gas recirculation amount control means stops the exhaust gas recirculation when the detected temperature of the injection hole portion is equal to or lower than a preset temperature. An exhaust gas recirculation device for an internal combustion engine as described above. 4. The exhaust gas of an internal combustion engine according to claim 1, wherein the exhaust gas recirculation amount control means decreases the exhaust gas recirculation amount as the detected temperature of the injection hole portion is lower. Reflux device.