JP4949322B2 - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel supply controller by which the control for NO<SB>x</SB>-reduction is appropriately exerted in an internal combustion engine provided with a NO<SB>x</SB>-adsorption catalyst, and exhaust characteristics are inhibited from being degraded in the case where reduction control is exerted on the engine-output torque. <P>SOLUTION: When a reduction flag FRICH is established to "1", a pilot-injection quantity QP and a main-injection quantity QM are determined in response to engine-operation conditions; a total fuel-injection quantity QTOTAL is determined so that detected oxygen concentration O2C agrees with a target oxygen concentration O2COBJ; by subtracting the pilot injection quantity QP and the main injection quantity QM from the total fuel injection quantity QTOTAL, a post injection quantity QPST is computed (S13, S14). When the torque-reduction demand flag FTDWN is established to "1", the pilot injection quantity QP and the main injection quantity QM are reduced, and at the same time the post injection quantity QPST is reduced to a specified injection quantity QPSTL (S17). <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a control device for an internal combustion engine that includes a NOx adsorption catalyst in an exhaust system, and more particularly, to a device that performs control for reducing NOx adsorbed on a NOx adsorption catalyst.

  Patent Document 1 discloses a control device for an internal combustion engine that includes a NOx adsorption catalyst in an exhaust system. According to this device, when it is expected that the shift operation of the automatic transmission will be performed before a predetermined time elapses from now, the air-fuel ratio enrichment for reducing the NOx adsorbed on the NOx adsorption catalyst is performed. Is prohibited. As a result, it is possible to avoid the occurrence of a torque shock due to gear shifting and a torque shock due to enrichment of the air-fuel ratio.

  In Patent Document 2, when performing fuel supply control (hereinafter referred to as “regeneration control”) for removing sulfur oxide deposited on the NOx adsorption catalyst, regeneration is performed from the shift operation of the automatic transmission and normal fuel supply control. A technique is disclosed in which switching to control or vice versa is not performed simultaneously. As a result, torque shock caused by the interference between the switching of the fuel supply control and the shift of the automatic transmission is prevented.

Japanese Patent No. 3085065 JP 2007-99079 A

  The techniques disclosed in Patent Documents 1 and 2 described above start or end the regeneration control of the NOx adsorption catalyst (reduction of adsorbed NOx or fuel supply control for removal of sulfur oxide). Assuming that the engine output torque fluctuates, the torque fluctuation accompanying the shift of the automatic transmission and the torque fluctuation accompanying the fuel supply control switching occur continuously in a short time, or both occur simultaneously. This is to prevent this.

  However, it is possible to perform regeneration control of the NOx adsorption catalyst by performing fuel injection (post-injection) for the purpose of supplying a reducing component to the exhaust system after fuel injection according to the required torque of the engine. In the case of adopting such a regeneration control method, the torque fluctuation of the engine does not occur depending on whether or not regeneration control is performed.

  However, even when performing regeneration control by post-injection, there are the following problems when performing torque reduction control that temporarily reduces engine output torque in order to suppress torque shock during transmission shifting.

  An oxygen concentration sensor is provided on the upstream side of the NOx adsorption catalyst in order to make the concentration of the reducing component in the exhaust flowing into the NOx adsorption catalyst appropriate when performing regeneration control, and in post injection according to the oxygen concentration sensor output There is a case where feedback control for setting the total fuel injection amount including the fuel injection amount is performed. In that case, the main fuel injection amount (and the pilot fuel injection amount) is reduced during execution of torque reduction control, so the fuel injection amount in post injection increases. Therefore, part of the post-injected fuel is discharged as it is without being used for the reduction of the NOx adsorbed by the NOx adsorption catalyst, which may deteriorate the exhaust characteristics.

  The present invention has been made paying attention to this point, and appropriately performs control for NOx reduction in an internal combustion engine equipped with a NOx adsorption catalyst, and exhaust characteristics deteriorate when performing reduction control of engine output torque. An object of the present invention is to provide a control device for an internal combustion engine that can suppress the above-described problem.

In order to achieve the above object, an invention according to claim 1 is directed to an NOx adsorption catalyst that adsorbs NOx in the exhaust when the exhaust of the internal combustion engine is in an oxidizing atmosphere and reduces the adsorbed NOx when the exhaust is in a reducing atmosphere. 11) is a control apparatus for an internal combustion engine provided in an exhaust system, a fuel supply means for supplying fuel to the engine in accordance with a required torque (TRQ) of the engine, and after the fuel supply by the fuel supply means, Reducing component supply means for supplying a reducing component to the combustion chamber of the engine or an upstream side of the NOx adsorption catalyst in the exhaust system to reduce NOx adsorbed by the NOx adsorption catalyst, and operation of a vehicle driven by the engine comprising a driving mode determining means for determining that the mode is a predetermined operation mode to reduce the output of the engine, an oxygen concentration detection means for detecting the oxygen concentration in the exhaust gas, before The fuel supply means executes fuel supply according to the required torque by main injection of fuel and pilot injection preceding the main injection, and the operation mode of the vehicle is the predetermined operation mode by the operation mode determination means. When it is determined that the fuel injection amount in the pilot injection and the main injection is reduced, the reducing component supply means detects that the detected oxygen concentration (O2C) coincides with the target oxygen concentration (O2COBJ) when the reducing component is supplied. The total fuel injection amount (QTOTAL) is calculated so that the fuel injection amount (QP, QM) in the pilot injection and the main injection is subtracted from the total fuel injection amount (QTOTAL). The fuel injection amount (QPST) in the post-injection to be calculated is calculated, the reducing component is supplied by the post-injection, The operation mode determining means, when the operating mode of the vehicle is determined to the a predetermined operating mode, met the supply amount of the reducing component (Qpst) less than the value just before it is determined that the a predetermined operating mode It is characterized in that it is set to a value (QPSTL) larger than “0” .

  According to a second aspect of the present invention, in the fuel supply control device for an internal combustion engine according to the first aspect, the predetermined operation mode is an operation mode for changing a gear position of a transmission connected to the output shaft of the engine or This is an operation mode for reducing drive wheel slip of the vehicle.

According to the first aspect of the present invention, when it is determined that the operation mode of the vehicle driven by the engine is the predetermined operation mode for reducing the output of the engine, the reduction component supply amount by the reduction component supply means is the predetermined operation. It is set to a value equal to or less than the value immediately before being determined as the mode and greater than “0” . Further, when fuel supply corresponding to the required torque is executed by the main injection of fuel and the pilot injection preceding the main injection, and it is determined that the operation mode of the vehicle is the predetermined operation mode, the fuel in the pilot injection and the main injection The total fuel injection amount is calculated so that the injection amount is reduced and the detected oxygen concentration matches the target oxygen concentration when the reducing component is supplied, and the fuel injection amounts for pilot injection and main injection are subtracted from the total fuel injection amount By doing so, the fuel injection amount in the post injection executed after the main injection is calculated, and the supply of the reducing component is executed by the post injection. As a result, the concentration of the reducing component in the exhaust supplied to the NOx adsorption catalyst in the predetermined operation mode is suppressed, and deterioration of the exhaust characteristics can be suppressed.

  According to the second aspect of the present invention, when the operation mode is to change the gear position of the transmission or the operation mode is to reduce the drive wheel slip of the vehicle, the reduction component supply amount by the reduction component supply means. Therefore, the deterioration of the exhaust characteristics can be suppressed when the gear position is changed or when the drive wheel slip reduction control is executed.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing the configuration of a vehicle control system according to an embodiment of the present invention. An internal combustion engine (hereinafter referred to as “engine”) 1 is a diesel engine that directly injects fuel into a combustion chamber, and a fuel injection valve 16 is provided in each cylinder. The fuel injection valve 16 is electrically connected to an engine control electronic control unit (hereinafter referred to as “EC-ECU”) 20, and the valve opening time and timing of the fuel injection valve 16 are controlled by the EC-ECU 20. The

  The engine 1 includes an intake pipe 2, an exhaust pipe 4, and an exhaust gas recirculation passage 6. The exhaust gas recirculation passage 6 is provided between the intake pipe 2 and the exhaust pipe 4, and the exhaust gas recirculation passage 6 has an exhaust gas recirculation control valve (hereinafter referred to as “EGR valve”) 7 for controlling the exhaust gas recirculation amount. Is provided. The valve opening degree of the EGR valve 7 is controlled by the EC-ECU 20.

  The exhaust pipe 4 is provided with a NOx adsorption catalyst 11 for purifying NOx in the exhaust and a diesel particulate filter (hereinafter referred to as “DPF”) 12. The NOx adsorption catalyst 11 adsorbs NOx when it is in an oxidizing atmosphere where the oxygen concentration in the exhaust gas is relatively high, and desorbs and reduces the adsorbed NOx when it is in a reducing atmosphere where the concentration of reducing components in the exhaust gas is relatively high. discharge. Since there is a limit to the NOx adsorption capacity of the NOx adsorption catalyst 11, when the NOx adsorption amount reaches a predetermined amount, reduction control is performed to make the exhaust a reducing atmosphere. In the normal fuel injection control, the fuel injection amount is set according to the operating state of the engine 1 (engine speed NE and required torque TRQ), and the main injection by the fuel injection valve 16 and the pilot injection preceding the main injection are performed. . In the reduction control, fuel injection (hereinafter referred to as “post-injection”) is executed in the expansion stroke or the exhaust stroke after execution of the main injection (in other words, at a timing that does not contribute to the output torque of the engine 1). The fuel, that is, the reducing component is supplied to the combustion chamber by the post injection, and the exhaust is made a reducing atmosphere.

  When the exhaust gas passes through fine holes in the filter wall, the DPF 12 converts soot, which is particulate (particulate matter) mainly composed of carbon (C), into the filter wall surface and the filter wall. Collect by depositing in the pores inside.

  The intake pipe 2 is provided with an intake air flow rate sensor 21 that detects a flow rate of fresh air (hereinafter referred to as “intake air flow rate”) MAIR sucked into the engine 1. An oxygen concentration sensor 22 that detects the oxygen concentration O2C in the exhaust gas is provided on the exhaust pipe 4 upstream of the NOx adsorption catalyst 11. Further, a crank angle position sensor 24 for detecting the rotation angle of the crankshaft of the engine 1 and an accelerator sensor 25 for detecting an operation amount (hereinafter referred to as “accelerator pedal operation amount”) AP of a vehicle driven by the engine 1. Is provided. Detection signals from these sensors are supplied to the EC-ECU 20. The rotational speed NE of the engine 1 is calculated from the output of the crank angle position sensor 24. Further, the required torque TRQ of the engine is calculated according to the accelerator pedal operation amount AP, and is set to increase as the accelerator pedal operation amount AP increases.

  A shift control electronic control unit (hereinafter referred to as “AT-ECU”) 30 and a traction control electronic control unit (hereinafter referred to as “TC-ECT”) 40 are connected to the EC-ECU 20 via the data bus 10. These ECUs 20, 30 and 40 mutually transmit detection parameters and control parameters via the data bus 10.

  The EC-ECU 20 forms an input signal waveform from various sensors, corrects a voltage level to a predetermined level, and converts an analog signal value into a digital signal value. CPU ”), a storage circuit that stores various calculation programs executed by the CPU, calculation results, and the like, a fuel injection valve 16, and an output circuit that supplies a control signal to the EGR valve 7. The other ECUs 30 and 40 similarly have an input circuit, a CPU, a memory circuit, and an output circuit.

  The AT-ECU 30 performs shift control of the transmission 31 connected to the output shaft of the engine 1 in accordance with operation parameters such as the vehicle speed VP and the required torque TRQ. When the AT-ECU 30 changes the shift position (shift stage) of the transmission 31, the AT-ECU 30 sets the output torque of the engine 1 for a predetermined time TSFT (for example, 200 to 350 milliseconds) in order to suppress torque shock accompanying the shift operation. A torque reduction request signal for requesting reduction is output (specifically, the shift torque reduction flag FSHCNG is set to “1” for a predetermined time TSFT).

  Connected to the TC-ECU 40 are drive wheel speed sensors 41 and 42 for detecting left and right drive wheel speeds VDL and VDR of the vehicle, and driven wheel speed sensors 43 and 44 for detecting left and right driven wheel speeds VNL and VNR. The detection signals of these sensors are supplied to the TC-ECU 40. The vehicle speed VP is calculated as an average value of the driven wheel speeds VNL and VNR. The TC-ECU 40 determines the slip state of the drive wheel based on the drive wheel speeds VDL, VDR and the driven wheel speeds VNL, VNR, and reduces the output torque of the engine 1 when determining that excessive slip has occurred. A torque reduction request signal requesting this is output (specifically, the traction control flag FTC is set to “1” until the excessive slip state is resolved).

  FIG. 2 is a flowchart of processing for controlling fuel injection by the fuel injection valve 16. This process is executed in synchronization with the rotation of the engine 1 by the CPU of the EC-ECU 20.

  In step S11, it is determined whether or not the reduction control flag FRICH is “1”. When the reduction control flag FRICH = 0 and no reduction control is performed, the process proceeds to step S12, and normal fuel injection control is executed.

  When FRICH = 1 in step S11 and reduction control is executed, the fuel injection amount in the pilot injection (hereinafter referred to as “pilot injection amount”) QP and the fuel in the main injection according to the engine speed NE and the required torque TRQ An injection amount (hereinafter referred to as “main injection amount”) QM is calculated (step S13).

  In step S14, the total fuel injection amount QTOTAL is determined so that the oxygen concentration O2C detected by the oxygen concentration sensor 22 matches the target oxygen concentration O2COBJ in the reduction control, and the pilot injection amount QP and the main injection amount QP are determined from the total fuel injection amount QTOTAL. By subtracting the injection amount QM, a fuel injection amount (hereinafter referred to as “post injection amount”) QPST (= QTOTAL−QP−QM) in post injection is calculated.

  In step S15, it is determined whether or not a torque reduction request flag FTDWN is “1”. The torque reduction request flag FTDWN is set in the process of FIG.

  In step S31 of FIG. 3, it is determined whether or not the shift torque reduction flag FSHCNG is “1”. If the answer is negative (NO), it is determined whether or not the traction control flag FTC is “1”. It discriminate | determines (step S32). When the answer to steps S31 and S32 is negative (NO), the torque reduction request flag FTDWN is set to “0” (step S33). On the other hand, if the answer to step S31 or S32 is affirmative (YES), a torque reduction request flag FTDWN is set to “1” (step S34).

  Returning to FIG. 2, when the answer to step S15 is negative (NO), it is determined whether or not the value of the downcount timer TMTR is “0” (step S19). Since the predetermined transient control time TTR is set in step S18, the timer TMTR is TMTR = 0 except immediately after the torque reduction request flag FTDWN has changed from “1” to “0”, and this processing is immediately terminated. .

  When the torque reduction request flag FTDWN is set to “1”, the process proceeds from step S15 to step S16, and the pilot injection amount QP and the main injection amount QM are reduced by a predetermined ratio. Thereby, the output torque of the engine 1 is reduced. In step S17, the post injection amount QPST is set to a predetermined injection amount QPSTL. The predetermined injection amount QPSTL is set to a value smaller than the latest post injection amount QPST calculated when the torque reduction request flag FTDWN is “0” or to “0”. By fixing the post injection amount QPST to a small value in this way, it is possible to prevent the reduction component amount in the exhaust from becoming excessive and deteriorating the exhaust characteristics when a torque reduction request is issued during execution of the reduction control. Can do.

  In step S18, the downcount timer TMTR is set to a predetermined transient control time TTR (for example, set to about 0.5 to 1.5 seconds) and started.

  When the torque reduction request flag FTDWN returns from “1” to “0”, the process proceeds from step S15 to step S19. Then, transient control is executed while TMTR> 0 (step S20). In step S20, since the torque change increases when the post injection amount QP and the main injection amount QM corrected in the decreasing direction in step S16 are immediately returned to the values calculated in step S13, control for gradually returning is performed. When the value of the timer TMTR becomes “0”, this process is terminated immediately after the execution of step S19.

  As described above, in the present embodiment, the torque reduction request flag FTDWN is set to “1” when the shift operation of the automatic transmission is performed, or when the excessive slip state of the drive wheels is detected, and the reduction control is being executed. The post-injection amount QPST is decreased when the torque reduction request is not made, and is fixed to a smaller value. Therefore, the concentration of reducing components in the exhaust supplied to the NOx adsorption catalyst when a torque reduction request is made is suppressed, and deterioration of exhaust characteristics can be suppressed.

  Moreover, by setting the predetermined injection amount QPSTL to “0” and substantially stopping the post injection, it is possible to reliably prevent the discharge of unburned fuel.

In this embodiment, the fuel injection valve 16 and the EC-ECU 20 constitute a fuel supply means and a reducing component supply means, and the EC-ECU 20 constitutes an operation mode determination means. Specifically, steps S13 and S16 in FIG. 2 correspond to the fuel supply means, steps S14 and S17 correspond to the reducing component supply means, steps S15 and FIG. 3 correspond to the operation mode determination means, and oxygen The concentration sensor 22 corresponds to oxygen concentration detection means .

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the above-described embodiment, the fuel injection valve 16 and the EC-ECU 20 constitute the reducing component supply means. However, a hydrocarbon supply device that supplies hydrocarbons to the upstream side of the NOx adsorption catalyst 11 in the exhaust pipe 4 is provided. The reducing component supply means may be configured by controlling the hydrocarbon supply device by the EC-ECU 20.

  In the above-described embodiment, the post injection amount QPST is fixed to the predetermined injection amount QPSTL when the shift operation of the automatic transmission is performed during execution of the reduction control or when the excessive slip state of the drive wheel is detected. However, the post injection amount QPST may be fixed to the predetermined injection amount QPSTL when the driver returns the accelerator pedal when shifting up in a vehicle equipped with a manual transmission, for example.

  Further, fuel injection control may be performed by the process shown in FIG. 4 instead of the process shown in FIG. The process of FIG. 4 is obtained by changing step S17 of the process of FIG. 2 to step S17a and adding step S21. In step S21, the post injection amount QPST calculated in step S14 is stored as a stored value QPSTM. In step S17a, the post injection amount QPST is set to the stored value QPTM.

  According to the processing of FIG. 4, the post injection amount when the torque reduction request flag FTDWN is “0” is stored as the stored value QPSTM, and the torque reduction request flag FTDWN becomes “1” to execute the torque reduction control. Since the post injection amount QPST is set to the stored value QPST, the post injection amount during the torque reduction control becomes an appropriate value without excess or deficiency, and is adsorbed by the NOx adsorption catalyst 11 without deteriorating the exhaust characteristics. NOx reduction can be continued.

  Further, the present invention can also be applied to fuel supply control of a marine vessel propulsion engine such as an outboard motor having a vertical crankshaft.

It is a figure which shows the structure of the control system of the vehicle concerning one Embodiment of this invention. It is a flowchart of the fuel-injection control process of the internal combustion engine which drives a vehicle. It is a flowchart of the process which sets the flag referred by the process of FIG. It is a flowchart which shows the modification of the process of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 11 NOx adsorption catalyst 16 Fuel injection valve (fuel supply means, reducing component supply means)
20 Engine control electronic control unit (fuel supply means, reducing component supply means, operation mode discrimination means)
22 Oxygen concentration sensor (oxygen concentration detection means)
30 Transmission control electronic control unit 40 Traction control electronic control unit

Claims (2)

In a control apparatus for an internal combustion engine in which an exhaust system is provided with a NOx adsorption catalyst that adsorbs NOx in exhaust when the exhaust of the internal combustion engine is in an oxidizing atmosphere and reduces NOx adsorbed when the exhaust is in a reducing atmosphere.
Fuel supply means for supplying fuel to the engine according to the required torque of the engine;
After the fuel supply by the fuel supply means, a reducing component supply means for supplying a reducing component to the combustion chamber of the engine or the upstream side of the NOx adsorption catalyst in the exhaust system in order to reduce NOx adsorbed by the NOx adsorption catalyst. When,
An operation mode determination means for determining that the operation mode of the vehicle driven by the engine is a predetermined operation mode for reducing the output of the engine ;
Oxygen concentration detecting means for detecting the oxygen concentration in the exhaust ,
The fuel supply means performs fuel supply according to the required torque by fuel main injection and pilot injection preceding the main injection, and the operation mode determination means determines that the vehicle operation mode is the predetermined operation mode. When it is determined that there is a fuel injection amount in the pilot injection and the main injection,
The reducing component supply means calculates the total fuel injection amount so that the detected oxygen concentration matches the target oxygen concentration at the time of supplying the reducing component, and the fuel injection amount in the pilot injection and main injection from the total fuel injection amount Is subtracted to calculate the fuel injection amount in post-injection executed after the main injection, supply of the reducing component is executed by the post-injection , and the vehicle operation mode is determined by the operation mode determination means. When it is determined that the operation mode is the predetermined operation mode, the supply amount of the reducing component is set to a value that is equal to or less than a value immediately before the operation mode is determined to be the predetermined operation mode and greater than “0”. Control device for internal combustion engine.   The said predetermined operation mode is an operation mode which changes the gear stage of the transmission connected to the output shaft of the said engine, or the operation mode which reduces the driving wheel slip of the said vehicle. Control device for internal combustion engine.

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