JP2009299590A - Egr control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately control a bypass valve provided in a bypass passage of a venturi device without having a special sensor in an EGR control device for an internal combustion engine. <P>SOLUTION: An intake air amount flowing through an intake passage 12 is detected by an intake air amount sensor Sc, a required EGR amount is calculated by a required EGR amount calculating means M2, and the bypass valve 25 disposed in the bypass passage 24 for bypassing the venturi device 19 is opened and a negative pressure of the venturi device 19 is increased when the intake air amount is equal to or less than the prescribed value and the required EGR amount is equal to or more than the prescribed value and it is difficult to secure an EGR amount by the venturi device 19, and thereby, the EGR amount circulated into the venturi device 19 from an exhaust passage 14 through an EGR passage 21 can be surely controlled regardless of an operation state of the internal combustion engine E. Parameters used for controlling the bypass valve 25 are only the intake air amount and the required EGR amount, and therefore, a sensor for detecting an exhaust pressure or a venturi pressure can be dispensed with, which contributes to reduction of the number of components and the cost reduction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention connects a venturi device provided in an intake passage of an internal combustion engine, an EGR passage that recirculates EGR gas from the exhaust passage of the internal combustion engine to the venturi, and an upstream side and a downstream side of the venturi device of the intake passage. The present invention relates to an EGR control device for an internal combustion engine, which includes a bypass passage that opens and a bypass valve that opens and closes the bypass passage.

In an internal combustion engine equipped with a turbocharger, an exhaust gas recirculation circuit 15 that recirculates EGR gas from an exhaust circuit 16 upstream of the turbine 11b to an intake circuit 12 downstream of the compressor 11a is connected to a venturi 12b provided in the intake circuit 12. The intake bypass circuit 12c connecting the upstream and downstream of the venturi 12b is provided with an intake bypass valve 12d so that the differential pressure (Pex−Pvr) between the exhaust pressure Pex and the venturi pressure Pvr becomes (Pex−Pvr)> 0. In other words, it is known from Patent Document 1 below that the opening degree of the intake bypass valve 12d is controlled so as to generate a pressure difference in which EGR gas recirculates from the exhaust side to the intake side.
JP 2001-165000 A

  By the way, the above-mentioned conventional one needs to detect the exhaust pressure Pex and the venturi pressure Pvr in order to control the opening degree of the intake bypass valve 12d of the intake bypass circuit 12c, and a special sensor for detecting them is provided. There was a problem that the cost increased by the amount provided.

  The present invention has been made in view of the above circumstances, and in an EGR control device for an internal combustion engine, it is possible to accurately control a bypass valve provided in a bypass passage of a venturi device without providing a special sensor. With the goal.

  To achieve the above object, according to the first aspect of the present invention, a venturi device provided in an intake passage of an internal combustion engine, and an EGR that recirculates EGR gas from the exhaust passage of the internal combustion engine to the venturi device. A passage, a bypass passage connecting the upstream and downstream sides of the venturi device of the intake passage, a bypass valve for opening and closing the bypass passage, an intake air amount sensor for detecting an intake air amount flowing through the intake passage, A required EGR amount calculating means for calculating a required EGR amount supplied from the EGR passage, and a bypass valve control for closing the bypass valve when the intake air amount is equal to or smaller than a predetermined value and the required EGR amount is equal to or larger than a predetermined value. An EGR control apparatus for an internal combustion engine is provided.

  According to the second aspect of the present invention, the venturi device provided in the intake passage of the internal combustion engine, the EGR passage for returning EGR gas from the exhaust passage of the internal combustion engine to the venturi device, and the intake passage A bypass passage connecting the upstream side and the downstream side of the venturi device, a bypass valve for opening and closing the bypass passage, an accelerator opening sensor for detecting an accelerator opening, a shift stage sensor for detecting a shift stage of the transmission, Requested torque calculating means for calculating a required torque from the accelerator opening, estimated internal combustion engine speed calculating means for calculating an estimated internal combustion engine speed from the required torque and the shift stage, the required torque and the estimated internal combustion engine speed An estimated intake air amount calculating means for calculating an estimated intake air amount from the number, an estimate from the required torque and the estimated internal combustion engine speed. An estimated EGR amount calculating means for calculating an EGR amount; and a bypass valve control means for closing the bypass valve when the estimated intake air amount is not more than a predetermined value and the estimated EGR amount is not less than a predetermined value. A characteristic EGR control device for an internal combustion engine is proposed.

  According to the configuration of the first aspect, the intake air amount sensor detects the intake air amount flowing through the intake passage, the required EGR amount calculating means calculates the required EGR amount, and the required EGR amount is less than or equal to a predetermined value. When it is difficult to secure the EGR amount by the venturi device provided in the intake passage above the predetermined value, the bypass valve provided in the bypass passage bypassing the venturi device is closed to increase the negative pressure of the venturi device. The amount of EGR recirculated from the exhaust passage to the venturi device via the EGR passage can be accurately controlled regardless of the operating state of the internal combustion engine. Since the parameters used for the control of the bypass valve are only the intake air amount and the required EGR amount, a sensor for detecting the exhaust pressure or the venturi pressure becomes unnecessary, which can contribute to the reduction of the number of parts and the cost reduction.

  According to the second aspect of the present invention, the estimated internal combustion engine speed calculation means calculates the estimated internal combustion engine speed based on the accelerator opening and the gear position, and the estimated intake air quantity calculation means calculates the estimated intake air quantity. When the estimated EGR amount is calculated by the estimated EGR amount calculating means, the estimated intake air amount is not more than a predetermined value, the estimated EGR amount is not less than the predetermined value, and it is difficult to secure the EGR amount by the venturi device provided in the intake passage. In addition, the bypass valve provided in the bypass passage for bypassing the venturi device is closed to increase the negative pressure of the venturi device, so that the amount of EGR returned from the exhaust passage to the venturi device via the EGR passage is increased. It can be accurately controlled regardless of the state. Since the parameters used for the control of the bypass valve are only the estimated intake air amount and the estimated EGR amount, a sensor for detecting the exhaust pressure and the venturi pressure becomes unnecessary, which can contribute to the reduction of the number of parts and the cost reduction.

  In addition, since the estimated internal combustion engine speed and the estimated intake air amount are calculated based on the accelerator opening and the gear position, the response delay of the internal combustion engine speed and the intake air amount with respect to the accelerator opening is compensated, and the negative pressure of the venturi device is compensated. This makes it possible to control the EGR amount with higher accuracy by avoiding the shortage.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  1 to 5 show a first embodiment of the present invention. FIG. 1 is an overall configuration diagram of an EGR control device for an internal combustion engine, FIG. 2 is a block diagram showing a circuit configuration of an electronic control unit, and FIG. FIG. 4 is a map for searching for the required EGR amount from the required torque and the internal combustion engine speed, and FIG. 5 is a diagram showing the valve opening region and the valve closing region of the bypass valve.

  As shown in FIG. 1, the internal combustion engine E using hydrogen as a fuel includes an intake passage 12 connected to the intake ports 11, and an exhaust passage 14 connected to the exhaust ports 13. The turbocharger 15 is formed by coaxially connecting a turbine 16 facing the exhaust passage 14 and a compressor 17 facing the intake passage 12, and transmits the rotation of the turbine 16 driven by the exhaust gas flowing through the exhaust passage 14 to the compressor 17. The intake air is compressed by the rotating compressor 17 to perform supercharging.

  An intercooler 18 is provided in the intake passage 12 that connects the compressor 17 of the turbocharger 15 and the intake ports 11 of the internal combustion engine E to cool intake air that has been compressed by the compressor 17 and has risen in temperature. A venturi device 19 is provided in the intake passage 12 upstream of the compressor 17, and the exhaust passage 14 between the turbine 16 and the exhaust gas purification catalyst 20 downstream thereof is connected to the venturi device 19 via the EGR passage 21. Is done. In the EGR passage 21, an EGR cooler 22 that cools the EGR gas is disposed on the upstream side, and an EGR control valve 23 that controls the flow rate of the EGR gas is disposed on the downstream side. An upstream side and a downstream side of the venturi device 19 are connected by a bypass passage 24, and a bypass valve 25 is provided in the bypass passage 24.

  The venturi device 19 includes a nozzle 26 that is tapered to throttle the intake air supplied from the upstream intake passage 12, and a diffuser 27 that extends from the downstream end of the nozzle 26. The downstream end of the EGR passage 21 opens in the gap of the diffuser 27.

  An electronic control unit to which the internal combustion engine speed NE detected by the internal combustion engine speed sensor Sa, the accelerator opening AP detected by the accelerator opening sensor Sb, and the intake air amount GAIR detected by the intake air amount sensor Sc are input. U controls the opening degree of the EGR control valve 23 and the bypass valve 25.

  As shown in FIG. 2, the electronic control unit U that controls the EGR amount includes a required torque calculation unit M1, a required EGR amount calculation unit M2, and an EGR amount control unit (bypass valve control unit) M3.

  The required torque calculation means M1 calculates the required torque BMEP of the internal combustion engine E based on the accelerator opening AP detected by the accelerator opening sensor Sb. The required EGR amount calculation means M2 calculates a required EGR amount GEGR based on the required torque BMEP and the internal combustion engine speed NE detected by the internal combustion engine speed sensor Sa. The EGR amount control means (bypass valve control means) M3 controls the opening degrees of the EGR control valve 23 and the bypass valve 25 based on the required EGR amount GEGR and the intake air amount GAIR detected by the intake air amount sensor Sc. .

  Next, the operation of the first embodiment of the present invention having the above configuration will be described.

  The internal combustion engine E is a type that does not include a throttle valve, and the output is controlled by controlling the fuel injection amount to the intake system.

  Exhaust gas discharged from the exhaust ports 13 of the internal combustion engine E to the exhaust passage 14 is driven in the exhaust gas purification catalyst 20 after being driven by the turbine 16 of the turbocharger 15 and discharged in a purified state. The intake air compressed by the compressor 17 driven by the turbine 16 of the turbocharger 15 is cooled by the intercooler 18 and then sucked into the internal combustion engine E from the intake ports 11 to be used for fuel combustion.

  The EGR gas introduced into the EGR passage 21 branched from the exhaust passage 14 downstream of the turbine 16 of the turbocharger 15 is cooled by the EGR cooler 22, then the flow rate is controlled by the EGR control valve 23, and is generated in the venturi device 19. By returning to the intake passage 12 with a negative pressure, it contributes to the reduction of NOx in the exhaust. At this time, if the EGR amount is insufficient even when the EGR control valve 23 is fully opened, the negative pressure generated in the venturi device 19 is increased by controlling the bypass valve 25 to close the EGR gas. Is recirculated to the intake passage 12.

  The above operation will be described in more detail based on the flowchart of FIG.

  First, in step S1, the internal combustion engine rotational speed sensor Sa detects the internal combustion engine rotational speed NE, the accelerator opening sensor Sb detects the accelerator opening AP, and the intake air amount sensor Sc detects the intake air amount GAIR. In the following step S2, the required torque BMEP is calculated from the accelerator opening AP, and in step S3, the required EGR amount GEGR is calculated from the required torque BMEP and the internal combustion engine speed NE.

  Since the internal combustion engine E of the embodiment does not include a throttle valve, the fuel injection amount of the internal combustion engine E can be calculated from the required torque BMEP.

  If the intake air amount GAIR is less than or equal to the predetermined value A in step S4 and the required EGR amount GEGR is greater than or equal to the predetermined value B in step S5, the bypass valve 25 is closed in step S6, and the intake air amount in step S5. If GAIR is not less than the predetermined value A or the required EGR amount GEGR is not greater than the predetermined value B in step S5, the bypass valve 25 is opened in step S7 and the EGR control valve is obtained so that the required EGR amount GEGR is obtained. The opening degree of 23 is controlled.

  FIG. 4 shows a map for retrieving the required EGR amount GEGR from the required torque BMEP and the internal combustion engine speed NE in step S3. In a region where the required torque BMEP is low, the fuel injection amount is small, and lean operation with a low air-fuel ratio is performed, so that NOx is hardly generated, and therefore the EGR rate can be made 0%. When lean operation becomes impossible due to an increase in the fuel injection amount accompanying an increase in the required torque BMEP, an EGR rate = 50% (intake air amount GAIR = required EGR amount GEGR) to suppress NOx emission, From this point, the EGR rate gradually decreases from 50% to 0% while the full load operation state (stoichiometric) is reached as the required torque BMEP increases.

  FIG. 5 shows a map for searching the valve opening region and the valve closing region of the bypass valve 25 using the intake air amount GAIR and the required EGR amount GEGR as parameters. As described with reference to FIG. 4, in the region where the required EGR amount GEGR> the intake air amount GAIR (the region where the EGR rate> 50%), the lean operation is possible, so the EGR gas is not introduced, and the EGR control valve 23 Is kept closed. On the other hand, EGR gas is introduced in the region where the required EGR amount GEGR ≦ the intake air amount GAIR (the region where the EGR rate ≦ 50%), but when the required EGR amount GEGR cannot be recirculated to the intake passage 12, the bypass passage 24 By closing the bypass valve 25 provided in the above, the flow rate of the intake air in the venturi device 19 is increased, and the negative pressure generated in the venturi device 19 is increased to return the required EGR amount GEGR to the intake passage 12.

  In the first case in which the required EGR amount cannot be secured, the internal combustion engine E is in the low load region and the intake air amount GAIR is not more than the predetermined value A (see step S4 in the flowchart of FIG. 3), which is sufficient for the venturi device 19. This is the case where no negative pressure is generated. The second case where the required EGR amount cannot be secured is when the required EGR amount GEGR is equal to or greater than the predetermined value B (see step S5 in the flowchart of FIG. 3), and the negative pressure generated by the venturi device 19 is insufficient.

  When the above two conditions overlap, the bypass valve 25 provided in the bypass passage 24 is closed so that the entire amount of intake air passes through the venturi device 19, and a sufficient negative pressure is generated there to generate the required EGR. The amount GEGR can be returned to the intake passage 12 to ensure an appropriate EGR rate. In other cases, the bypass valve 25 provided in the bypass passage 24 is opened to minimize the amount of intake air passing through the venturi device 19, and the intake resistance is reduced to improve the output of the internal combustion engine E. Can be planned.

  As described above, the opening / closing control of the bypass valve 25 can be performed using the internal combustion engine speed sensor Sa, the accelerator opening sensor Sb, and the intake air amount sensor Sc that are generally provided in the internal combustion engine E. The exhaust pressure sensor and the venturi pressure sensor required in the invention described in Document 1 are no longer necessary, which can contribute to a reduction in the number of parts and cost.

  6 and 7 show a second embodiment of the present invention. FIG. 6 is a block diagram showing the circuit configuration of the electronic control unit, and FIG. 7 is a flowchart for explaining the operation.

In the first embodiment described above, the intake air amount GAIR is directly detected by the intake air amount sensor Sc, and the required EGR amount GEGR is calculated by the required torque calculation means M1 and the internal combustion engine speed sensor Sa. In the second embodiment, the internal combustion engine speed NE is estimated (estimated internal combustion engine speed NE ^* ), and this estimated internal combustion engine speed NE is calculated. ^The intake air amount GAIR is estimated based on ^* (estimated intake air amount GAIR ^* ), and the estimated EGR amount GEGR ^* is calculated based on the estimated intake air amount GAIR ^* .

  As shown in FIG. 6, the electronic control unit U that controls the EGR amount includes a required torque calculating means M1, an estimated internal combustion engine speed calculating means M4, an estimated intake air amount calculating means M5, and an estimated EGR amount calculating means M6. And an EGR amount control means (bypass valve control means) M3.

The required torque calculation means M1 calculates the required torque BMEP of the internal combustion engine E based on the accelerator opening AP detected by the accelerator opening sensor Sb. The estimated internal combustion engine speed calculation means M4 calculates the estimated internal combustion engine speed NE ^* based on the required torque BMEP and the transmission speed SP detected by the speed sensor Sd. The estimated intake air amount calculation means M5 calculates an estimated intake air amount GAIR ^* based on the required torque BMEP and the estimated internal combustion engine speed NE ^* . The estimated EGR amount calculating means M6 calculates an estimated EGR amount GEGR ^* based on the required torque BMEP and the estimated internal combustion engine speed NE ^* . The EGR amount control means (bypass valve control means) M3 controls the opening degrees of the EGR control valve 23 and the bypass valve 25 based on the estimated EGR amount GEGR ^* and the estimated intake air amount GAIR ^* .

  The above operation will be described in more detail based on the flowchart of FIG.

First, in step S11, the accelerator opening degree AP is detected by the accelerator opening degree sensor Sb, and the shift stage SP of the transmission is detected by the shift stage sensor Sd. In the subsequent step S12, the required torque BMEP is calculated from the accelerator opening AP. In the next step S13, the estimated internal combustion engine speed NE ^* is calculated from the required torque BMEP and the shift speed SP, and in step S14, the estimated intake air amount GAIR ^* is calculated from the required torque BMEP and the estimated internal combustion engine speed NE ^*. . In step S15, an estimated EGR amount GEGR ^* is calculated from the required torque BMEP and the estimated internal combustion engine speed NE ^* .

In step S15, the map of FIG. 4 is used as in step S3 of the first embodiment, and the required EGR amount required when the internal combustion engine speed reaches the estimated internal combustion engine speed NE ^* is calculated. Estimated EGR amount is estimated as GEGR ^* .

Since the internal combustion engine E of the present embodiment is not provided with a throttle valve and performs output control with the fuel injection amount, if the estimated internal combustion engine speed NE ^* is known in step S14, the estimated intake at that time is estimated. The air amount GAIR ^* can be calculated.

If the estimated intake air amount GAIR ^* is less than or equal to the predetermined value A in step S16 and the estimated EGR amount GEGR ^* is greater than or equal to the predetermined value B in step S17, the bypass valve 25 is closed in step S18, and in step S16 If the estimated intake air amount GAIR ^* is not equal to or less than the predetermined value A or the estimated EGR amount GEGR ^* is not equal to or greater than the predetermined value B in step S17, the bypass valve 25 is opened in step S19 and the estimated EGR amount GEGR ^* Is controlled so that the opening degree of the EGR control valve 23 is obtained.

As described above, according to the second embodiment, the estimated internal combustion engine speed NE ^* that is reached from the required torque BMEP calculated from the accelerator opening AP is calculated, and is calculated from the estimated internal combustion engine speed NE ^*. When it is predicted that the negative pressure of the venturi device 19 is insufficient from the estimated intake air amount GAIR ^* and the estimated EGR amount GEGR ^* , the bypass valve 25 is closed in advance to prevent the accelerator pedal operation. The response delay of the internal combustion engine rotational speed NE and the intake air amount GAIR can be compensated, and the negative pressure of the venturi device 19 can be avoided and the EGR amount can be controlled with higher accuracy.

  The operational effects of the second embodiment other than those described above are the same as the operational effects of the first embodiment described above.

  As mentioned above, although embodiment of this invention was explained in full detail, this invention can perform a various design change in the range which does not deviate from the summary.

  For example, in the embodiment, the internal combustion engine E that uses hydrogen as fuel is illustrated, but the present invention applies to an internal combustion engine E that uses gasoline or light oil as fuel, and also to an internal combustion engine E that does not have the turbocharger 15. In addition, the internal combustion engine E having no throttle valve can be applied regardless of whether the fuel injection is port injection or direct injection.

Further, when the estimated internal combustion engine speed NE ^* is calculated from the required torque BMEP and the gear stage SP in step S13 of the flowchart of FIG. 7, if the vehicle load that changes according to the road surface inclination and the vehicle load is taken into consideration, The estimated internal combustion engine speed NE ^* can be calculated with higher accuracy.

1 is an overall configuration diagram of an EGR control device for an internal combustion engine according to a first embodiment. Block diagram showing circuit configuration of electronic control unit Flow chart explaining operation Map for retrieving requested EGR amount from requested torque and internal combustion engine speed It is a figure which shows the valve opening area | region and valve closing area | region of a bypass valve. The block diagram which shows the circuit structure of the electronic control unit which concerns on 2nd Embodiment. Flow chart explaining operation

Explanation of symbols

12 intake passage 14 exhaust passage 19 venturi device 21 EGR passage 24 bypass passage 25 bypass valve AP accelerator opening BMEP required torque E internal combustion engine GAIR intake air amount GAIR ^* estimated intake air amount GEGR required EGR amount GEGR ^* estimated EGR amount M1 required torque Calculation means M2 Required EGR amount calculation means M3 Bypass valve control means M4 Estimated internal combustion engine speed calculation means M5 Estimated intake air quantity calculation means M6 Estimated EGR amount calculation means NE ^* Estimated internal combustion engine speed SP Shift stage Sb Accelerator opening sensor Sc Intake air amount sensor Sd Shift speed sensor

Claims (2)

A venturi device (19) provided in the intake passage (12) of the internal combustion engine (E);
An EGR passage (21) for recirculating EGR gas from the exhaust passage (14) of the internal combustion engine (E) to the venturi device (19);
A bypass passage (24) connecting the upstream side and the downstream side of the venturi device (19) of the intake passage (12);
A bypass valve (25) for opening and closing the bypass passage (24);
An intake air amount sensor (Sc) for detecting an intake air amount (GAIR) flowing through the intake passage (12);
Requested EGR amount calculating means (M2) for calculating a requested EGR amount (GEGR) supplied from the EGR passage (21);
Bypass valve control means (M3) for closing the bypass valve (25) when the intake air amount (GAIR) is less than a predetermined value and the required EGR amount (GEGR) is more than a predetermined value;
An EGR control device for an internal combustion engine, comprising: A venturi device (19) provided in the intake passage (12) of the internal combustion engine (E);
An EGR passage (21) for recirculating EGR gas from the exhaust passage (14) of the internal combustion engine (E) to the venturi device (19);
A bypass passage (24) connecting the upstream side and the downstream side of the venturi device (19) of the intake passage (12);
A bypass valve (25) for opening and closing the bypass passage (24);
An accelerator opening sensor (Sb) for detecting an accelerator opening (AP);
A shift speed sensor (Sd) for detecting a shift speed (SP) of the transmission;
Requested torque calculating means (M1) for calculating required torque (BMEP) from the accelerator opening (AP);
Estimated internal combustion engine speed calculating means (M4) for calculating an estimated internal combustion engine speed (NE ^* ) from the required torque (BMEP) and the shift speed (SP);
Estimated intake air amount calculating means (M5) for calculating an estimated intake air amount (GAIR ^* ) from the required torque (BMEP) and the estimated internal combustion engine speed (NE ^* );
Estimated EGR amount calculating means (M6) for calculating an estimated EGR amount (GEGR ^* ) from the required torque (BMEP) and the estimated internal combustion engine speed (NE ^* );
A bypass valve control means (M3) for closing the bypass valve (25) when the estimated intake air amount (GAIR ^* ) is not more than a predetermined value and the estimated EGR amount (GEGR ^* ) is not less than a predetermined value;
An EGR control device for an internal combustion engine, comprising:

Images