JP2007113428A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of improving exhaust gas characteristics by ensuring the favorable combustion state of an air-fuel mixture immediately after starting the control of an air-fuel ratio to a rich side in the case of changing over a recirculation gas channel when controlling the air-fuel ratio of the air-fuel mixture to a side richer than a stoichiometric air-fuel ratio. <P>SOLUTION: This control device 1 for the internal combustion engine 3 is provided with an ECU 2. When a condition to change over the air-fuel ratio to the side richer than the stoichiometric air-fuel ratio is satisfied, the ECU 2 controls a channel selector valve 15 so that the recirculation gas channel is changed over from an EGR passage 11 to a bypass passage 14 (steps 1 and 5 to 7), and also controls that air-fuel ratio changing over timing is made to be later than recirculation gas channel changing over timing (steps 23 to 35). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that controls an air-fuel ratio of an air-fuel mixture and controls an exhaust gas recirculation operation.

  2. Description of the Related Art Conventionally, as a control device for an internal combustion engine that executes air-fuel ratio control and EGR control, for example, one described in Patent Document 1 is known. This internal combustion engine is of a compression ignition type, and includes an EGR device that recirculates the exhaust gas in the exhaust passage as a recirculation gas to the intake side, a NOx purification catalyst that purifies the exhaust gas flowing through the exhaust passage, and the like. Yes. In the example shown in FIG. 5 of this Patent Document 1, the EGR device is provided in the EGR passage and the bypass passage, the flow switching valve for switching the flow path of the reflux gas to the EGR passage side or the bypass passage side, and the EGR passage. The cooling unit is configured to cool the reflux gas flowing in the EGR passage.

  In this control device, when the amount of NOx trapped in the NOx purification catalyst reaches the upper limit value, rich spike control is executed in order to avoid deterioration of exhaust gas characteristics due to a reduction in purification capacity of the NOx purification catalyst. . Specifically, by enriching the air-fuel ratio of the air-fuel mixture, exhaust gas in a rich atmosphere is supplied to the NOx purification catalyst, and thereby NOx captured by the NOx purification catalyst is reduced.

  In EGR control, the flow path of the reflux gas is normally held on the EGR passage side by the flow path switching valve, so that the reflux gas is cooled by the cooling device when passing through the EGR passage. Return to the intake side. On the other hand, when the execution request for the rich spike control is made, the flow path of the reflux gas is switched to the bypass passage side by the flow path switching valve, whereby the reflux gas having a temperature higher than that in the normal state is returned to the intake side. This is to ensure combustion stability by increasing the combustion temperature of the air-fuel mixture during rich spike control.

JP 2004-27946 A

  According to the above-described conventional control device for an internal combustion engine, when a request for executing rich spike control is generated, the flow path of the reflux gas is switched by the flow path switching valve. Therefore, it takes time until the flow path of the reflux gas is actually switched to the bypass passage side. As a result, immediately after the start of the rich spike control, the recirculation gas cooled by the cooling device is supplied to the intake side until the recirculation gas flow path is actually switched to the bypass passage side. The combustion state of the gas may become unstable, and in such a case, the exhaust gas characteristics are deteriorated.

  The present invention has been made in order to solve the above-described problems. When the flow path of the recirculation gas is switched when the air-fuel ratio of the air-fuel mixture is controlled to be richer than the stoichiometric air-fuel ratio, the air-fuel ratio is made rich. An object of the present invention is to provide a control device for an internal combustion engine that can ensure a good combustion state of the air-fuel mixture immediately after the start of the control, thereby improving the exhaust gas characteristics.

  In order to achieve the above object, the invention according to claim 1 is directed to an exhaust gas recirculation passage (EGR) for recirculating a part of exhaust gas in the exhaust system (exhaust passage 7) as a recirculation gas to the intake system (intake air passage 5). A passage 11), a reflux gas cooling device (EGR cooler 12) for cooling the reflux gas flowing in the exhaust gas reflux passage, a bypass passage 14 for refluxing the reflux gas to the intake system while bypassing the reflux gas cooling device, A control device 1, 1A for an internal combustion engine 3 comprising a flow path switching device (flow path switching valve 15) for switching the flow path of the recirculation gas from one of the exhaust gas recirculation path and the bypass path to the other. Air-fuel ratio control means (ECU2, steps 8 to 14) for controlling the air-fuel ratio of the air-fuel mixture supplied between the lean side and the rich side with respect to the stoichiometric air-fuel ratio; From air / fuel ratio When the air-fuel ratio switching condition for switching from the lean side to the rich side is satisfied (when the determination result in steps 21 and 51 is YES), the flow path of the recirculation gas is switched from the exhaust recirculation path to the bypass path. A flow path switching control means (ECU2, steps 1, 5-7, 23-32, 52-57) for controlling the flow path switching device, and the air-fuel ratio control means is configured when the air-fuel ratio switching condition is satisfied. The air-fuel ratio switching timing is controlled to be later than the flow path switching timing of the recirculation gas by the flow path switching control means (steps 5, 8, 23 to 32, 35, 56, 59). .

  According to this control device for an internal combustion engine, when the air-fuel ratio switching condition for switching the air-fuel ratio of the air-fuel mixture from the lean side to the rich side with respect to the stoichiometric air-fuel ratio is established, the flow switching control means causes the flow of the recirculation gas. The flow path switching device is controlled so that the path is switched from the exhaust gas recirculation path to the bypass path, and the air-fuel ratio switching timing is controlled by the air-fuel ratio control means from the recirculation gas flow path switching timing by the flow path switching control means. Is also controlled to be slower. Accordingly, by appropriately setting the degree of delay of the air-fuel ratio switching timing with respect to the flow path switching timing, the air-fuel ratio of the air-fuel mixture is changed after the recirculation gas flow path is switched from the exhaust recirculation passage side to the bypass passage side. Can be controlled to be richer than the stoichiometric air-fuel ratio. As a result, unlike the conventional case, the recirculation gas that has passed through the bypass passage and is higher in temperature than the recirculation gas cooled by the cooling device is supplied to the intake side even immediately after the start of control when the air-fuel ratio is controlled to the rich side. And a good combustion state of the air-fuel mixture can be secured. Thereby, exhaust gas characteristics can be improved.

  The invention according to claim 2 includes an exhaust gas recirculation passage (EGR passage 11) for recirculating part of the exhaust gas in the exhaust system (exhaust passage 7) as a recirculation gas to the intake system (intake air passage 5), and an exhaust gas recirculation passage. A recirculation gas cooling device (EGR cooler 12) that cools the recirculation gas flowing inside, a bypass passage 14 for recirculating the recirculation gas to the intake system while bypassing the recirculation gas cooling device, and exhaust gas recirculation of the recirculation gas flow path A control device 1B for an internal combustion engine 3 provided with a flow path switching device (flow path switching valve 15) for switching from one of the passage and the bypass passage to the other, wherein the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine 3 is reduced. An air-fuel ratio control means (ECU 2, steps 78 to 84) for controlling between the lean side and the rich side with respect to the stoichiometric air-fuel ratio, and a reflux gas temperature detecting means for detecting the temperature of the reflux gas as the reflux gas temperature TEGR (EGR temperature sensor 24) and when the air-fuel ratio switching condition for switching the air-fuel ratio of the air-fuel mixture from the lean side to the rich side with respect to the stoichiometric air-fuel ratio is satisfied (when the determination result in steps 77 and 91 is YES) When the detected recirculation gas temperature is lower than the predetermined temperature (target value TEGCMD) (when the determination result in step 94 is NO), the recirculation gas flow path is switched from the exhaust recirculation passage to the bypass passage. When the flow path switching control means (ECU 2, steps 74 to 77) for controlling the path switching apparatus and the air-fuel ratio switching condition are satisfied, the flow path switching of the reflux gas by the flow path switching control means is started (in step 77). After the determination result is YES), prohibiting means (ECU2, step) prohibiting switching of the air-fuel ratio by the air-fuel ratio control means until the reflux gas temperature becomes equal to or higher than a predetermined temperature. Characterized in that it comprises a flop 78,94,96,98), the.

  According to the control device for an internal combustion engine, when the air-fuel ratio switching condition for switching the air-fuel ratio of the air-fuel mixture from the lean side to the rich side with respect to the stoichiometric air-fuel ratio is satisfied, the flow path of the recirculation gas is controlled by the flow path switching control means. The flow path switching device is controlled to switch the exhaust gas recirculation path to the bypass path, and after the flow path switching of the recirculation gas is started by the flow path switching control means, the recirculation gas temperature becomes equal to or higher than a predetermined temperature. During this time, switching of the air-fuel ratio by the air-fuel ratio control means is prohibited by the prohibiting means. Therefore, when the recirculation gas flow path is switched from the exhaust recirculation passage side to the bypass passage side, it is confirmed that the recirculation gas is considerably hotter than the recirculation gas cooled by the cooling device. It is possible to control the air / fuel ratio to a richer side than the stoichiometric air / fuel ratio. As a result, unlike the conventional case, a recirculation gas having a temperature higher than that of the recirculation gas cooled by the cooling device can be supplied to the intake side even immediately after the start of control when the air-fuel ratio is controlled to the rich side. A good combustion state can be secured. Thereby, exhaust gas characteristics can be improved.

  Hereinafter, a control apparatus for an internal combustion engine according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of an internal combustion engine (hereinafter referred to as “engine”) 3 to which the control device of the first embodiment is applied, and FIG. 2 shows a schematic configuration of the control device 1. As shown in FIG. 2, the control device 1 includes an ECU 2, which executes various control processes including EGR control according to the operating state of the engine 3 as will be described later.

  The engine 3 is a multi-cylinder diesel engine mounted on a vehicle (not shown), and includes a fuel injection valve 4 provided for each cylinder so as to face the combustion chamber (only one is shown in FIG. 2). The fuel injection valve 4 is electrically connected to the ECU 2, and the ECU 2 controls the valve opening time and the valve opening timing, thereby executing fuel injection control.

  The engine 3 is provided with a crank angle sensor 20. The crank angle sensor 20 includes a magnet rotor and an MRE pickup, and outputs a CRK signal and a TDC signal, which are pulse signals, to the ECU 2 as the crankshaft (not shown) rotates. The CRK signal is output at one pulse every predetermined crank angle (for example, 10 °), and the ECU 2 calculates the engine speed (hereinafter referred to as “engine speed”) NE of the engine 3 based on the CRK signal. The TDC signal is a signal indicating that the piston (not shown) of each cylinder is at a predetermined crank angle position slightly before the TDC position of the intake stroke, and one pulse is output for each predetermined crank angle. Is done.

  Furthermore, an air flow sensor 21 and a throttle valve mechanism 6 are provided in the intake passage 5 (intake system) of the engine 3 in order from the upstream side. The air flow sensor 21 is constituted by, for example, a hot-wire air flow meter, detects the flow rate of air flowing through the intake passage 5, and outputs a detection signal representing it to the ECU 2. The ECU 2 calculates the intake air amount Gcyl estimated to be actually taken into the cylinder of the engine 3 based on the detection signal of the air flow sensor 21.

  The throttle valve mechanism 6 includes a throttle valve 6a and a TH actuator 6b for driving the throttle valve 6a. The throttle valve 6a is rotatably provided in the middle of the intake passage 5, and changes the flow rate of the air passing through the throttle valve 6a by the change in the opening degree accompanying the rotation. The TH actuator 6b is a combination of a motor and a reduction gear mechanism (both not shown), and is electrically connected to the ECU 2. The ECU 2 changes the opening degree of the throttle valve 6a via the TH actuator 6b, thereby controlling the intake air amount.

  Further, the engine 3 is provided with an exhaust gas recirculation device 10. The exhaust gas recirculation device 10 recirculates a part of the exhaust gas flowing in the exhaust passage 7 (exhaust system) to the intake passage 5 via the EGR passage 11 and the like. In the following description, the exhaust gas recirculated by the exhaust gas recirculation device 10 is referred to as “reflux gas”.

  One end of the EGR passage 11 (exhaust gas recirculation passage) opens to a portion downstream of the throttle valve 6a of the intake passage 5, and the other end of the exhaust passage 7 is a portion upstream of a NOx purification catalyst 8 described later. Is open. The EGR passage 11 is provided with an EGR cooler 12 and an EGR control valve 13 in order from the upstream side. The EGR cooler 12 (reflux gas cooling device) is a water-cooled type that uses the coolant of the engine 3 as a refrigerant, and the reflux gas is cooled by heat exchange with the coolant when passing through the EGR cooler 12. The

  Further, the EGR control valve 13 is of a linear electromagnetic valve type whose lift changes linearly between a maximum value and a minimum value, and is electrically connected to the ECU 2. The ECU 2 controls the opening degree of the EGR passage 11, that is, the flow rate of the reflux gas, by driving the EGR control valve 13, as will be described later.

  The exhaust gas recirculation device 10 includes a bypass passage 14 in addition to the EGR passage 11. The bypass passage 14 is for returning the reflux gas to the intake passage side while bypassing the EGR cooler 12. One end of the bypass passage 14 is connected to a portion upstream of the EGR cooler 12 of the EGR passage 11. The portion is connected to a portion of the EGR passage 11 between the EGR cooler 12 and the EGR control valve 13.

  Further, a flow path switching valve 15 is provided at a connection portion of the EGR passage 11 with the bypass passage 14 upstream of the EGR cooler 12. The flow path switching valve 15 (flow path switching device) is an electric type that can switch the flow path of the reflux gas to the EGR cooler 12 side or the bypass path 14 side, and is electrically connected to the ECU 2. As will be described later, the ECU 2 drives the flow path switching valve 15 to switch the flow path of the reflux gas to the EGR cooler 12 side or the bypass path 14 side.

  In this case, when the flow path of the recirculation gas is set on the EGR cooler 12 side, the recirculation gas cooled by the EGR cooler 12 is supplied to the intake passage 5 side, and the recirculation gas flow path is set on the bypass passage 14 side. When this is done, reflux gas that is hotter than when it has passed through the EGR cooler 12 is supplied to the intake passage 5 side. In the following description, supplying the recirculation gas to the intake passage 5 side via the EGR cooler 12 is referred to as “cold EGR”, and supplying the recirculation gas to the intake passage 5 side via the bypass passage 14 is referred to as “cold EGR”. This is called “hot EGR”.

  On the other hand, a NOx purification catalyst 8 is provided in the exhaust passage 7 of the engine 3. The NOx purification catalyst 8 captures NOx in the exhaust gas when the exhaust gas in the lean atmosphere flows in, and reduces the captured NOx when the exhaust gas in the rich atmosphere flows in by rich spike control or the like described later.

  Further, an accelerator opening sensor 22 is connected to the ECU 2 (see FIG. 2). The accelerator opening sensor 22 detects a depression amount (hereinafter referred to as “accelerator opening”) AP of an accelerator pedal (not shown) of the vehicle, and outputs a detection signal indicating it to the ECU 2.

  The ECU 2 is composed of a microcomputer including a CPU, a RAM, a ROM, an I / O interface (all not shown), and the engine 3 according to the detection signals of the various sensors 20 to 22 described above. The operating state is determined, and various control processes such as flow path switching control are executed according to the operating state, as will be described later. In the present embodiment, the ECU 2 corresponds to air-fuel ratio control means and flow path switching control means.

  Next, various control processes executed by the ECU 2 will be described with reference to FIG. In this process, as described below, flow path switching control, EGR control, fuel injection control, and throttle valve control are executed in a predetermined control cycle (for example, a cycle synchronized with the generation of a TDC signal).

  First, in step 1 (abbreviated as “S1” in the figure, the same applies hereinafter), it is determined whether or not a cold EGR flag F_COLDEGR described later is “1”. If the determination result is YES and the engine 3 is in an operating state in which cold EGR is to be executed, the process proceeds to step 2 to determine whether or not the previous value F_COLDEGRZ of the cold EGR flag is “1”.

  When the determination result is NO and the current loop is the first time when the engine 3 has shifted from the operating state in which the hot EGR is to be executed to the operating state in which the cold EGR is to be executed, the process proceeds to step 3 and the flow path switching valve 15 Is controlled so that the flow path of the reflux gas is switched from the bypass passage 14 side to the EGR cooler 12 side.

  The flow path switching control to the EGR cooler 12 side is continuously executed until a predetermined time elapses after the determination result of the above step 2 becomes YES, and during that time, the EGR cooler 12 side In order to indicate that the flow path switching control to be continued, the cooler side drive flag F_COOLER is set to “1”. Then, when the predetermined time has elapsed, the flow path switching control is stopped, and the cooler side drive flag F_COOLER is set to “0” to indicate it. After executing step 3 as described above, the process proceeds to step 8 described later.

  On the other hand, when the determination result of step 2 is YES, that is, when the engine 3 is in the operating state in which the cold EGR should be executed in the previous loop, the process proceeds to step 4 and the cooler side drive flag F_COOLER is “1”. It is determined whether or not. When the determination result is YES, it is assumed that the flow path switching control to the EGR cooler 12 side should be continued, and after performing step 3 as described above, the process proceeds to step 8 described later. On the other hand, when the determination result of step 4 is NO, the process directly proceeds to step 8 described later.

  On the other hand, if the determination result in step 1 is NO and the engine 3 is in an operating state in which hot EGR is to be executed, the process proceeds to step 5 to determine whether or not the previous value F_COLDEGRZ of the cold EGR flag is “1”. . When the determination result is YES and the current loop is the first time when the engine 3 has shifted from the operating state in which the cold EGR should be performed to the operating state in which the hot EGR should be performed, the process proceeds to step 6 and the flow path switching valve 15 Is controlled so that the flow path of the reflux gas is switched from the EGR cooler 12 side to the bypass passage 14 side.

  The flow path switching control to the bypass passage 14 side is continuously executed until a predetermined time elapses after the determination result of step 5 becomes YES, and during that time, the bypass passage side In order to indicate that the flow path switching control to be continued, the bypass side drive flag F_BYPASS is set to “1”. Then, when the predetermined time has elapsed, the flow path switching control is stopped, and the bypass side drive flag F_BYPASS is set to “0” to indicate it. After executing step 6 as described above, the process proceeds to step 8 described later.

  On the other hand, when the determination result of step 5 is NO, that is, when the engine 3 is in the operation state in which the hot EGR should be executed in the previous loop, the process proceeds to step 7 and the bypass side drive flag F_BYPASS is “1”. It is determined whether or not. When the determination result is YES, it is assumed that the flow path switching control to the bypass passage 14 side should be continued, and after executing step 6 as described above, the process proceeds to step 8 described later. On the other hand, when the determination result of step 7 is NO, the process directly proceeds to step 8 described later.

  In Step 8 following any of Steps 3, 4, 6, and 7 described above, it is determined whether or not a rich permission flag F_RICHON described later is “1”. When the determination result is YES and the rich spike control is to be executed, the rich spike control is executed in steps 9 to 11 as described below.

  That is, first, in step 9, EGR control for rich spike is executed. Specifically, the required torque PMCMD is calculated by searching a map for a rich spike (not shown) according to the engine speed NE and the accelerator pedal opening AP, and according to the required torque PMCMD and the engine speed NE, By searching a map for rich spike (not shown), the target intake air amount Gcyl_cmd is calculated, and the EGR control valve 13 is feedback-controlled so that the intake air amount Gcyl converges to the target intake air amount Gcyl_cmd.

  Next, at step 10, a fuel injection control process for rich spike is executed. In this control process, a fuel injection amount is calculated by searching a map for a rich spike (not shown) according to the required torque PMCMD calculated in step 9 and the engine speed NE, and based on this fuel injection amount, The fuel injection timing is determined. Accordingly, fuel is injected into the cylinder via the fuel injection valve 4 in accordance with the fuel injection amount and the fuel injection timing.

  In step 11 following step 10, a throttle valve control process for rich spike is executed. In this control process, the TH actuator 6b is driven to control the throttle valve 6a so that the opening degree of the throttle valve 6a becomes a predetermined rich spike value smaller than that in the fully opened state. After executing step 11 in this way, the present process is terminated.

  By executing the rich spike control in steps 9 to 11 as described above, the air-fuel ratio of the air-fuel mixture is controlled so that the exhaust gas has a rich atmosphere. As a result, the exhaust gas in a rich atmosphere is supplied to the NOx purification catalyst 8, whereby the NOx adsorbed on the NOx purification catalyst 8 is reduced.

  On the other hand, when the determination result in step 8 is NO and the normal-time air-fuel ratio control is to be executed, normal-time EGR control is executed in step 12. Specifically, the required torque PMCMD is calculated by searching a map for normal time (not shown) according to the engine speed NE and the accelerator pedal opening AP, and according to the required torque PMCMD and the engine speed NE, By searching a map for normal time (not shown), the target intake air amount Gcyl_cmd is calculated, and the EGR control valve 13 is feedback-controlled so that the intake air amount Gcyl converges to the target intake air amount Gcyl_cmd.

  Next, in step 13, a normal fuel injection control process is executed. In this control process, a fuel injection amount is calculated by searching a map for normal time (not shown) according to the required torque PMCMD and the engine speed NE calculated in step 12, and based on this fuel injection amount, The fuel injection timing is determined. Accordingly, fuel is injected into the cylinder via the fuel injection valve 4 in accordance with the fuel injection amount and the fuel injection timing.

  In step 14 following step 13, the normal time throttle valve control process is executed, and then this process ends. In this control process, the opening degree of the throttle valve 6a is controlled to be fully opened by driving the TH actuator 6b. As described above, the air-fuel ratio of the air-fuel mixture is controlled so that the exhaust gas has a lean atmosphere by executing the normal-time air-fuel ratio control processing in steps 12 to 14.

  Hereinafter, various flag setting processes executed by the ECU 2 will be described with reference to FIG. As will be described below, this process sets values of various flags such as the rich permission flag F_RICHON, and is executed at a predetermined control cycle (for example, 10 msec).

In this process, first, in step 20, the rich condition flag F_RICH is set. Specifically, when both of the following two conditions (a) and (b) are satisfied, the rich condition flag F_RICH is set to “1”, assuming that the execution condition of the rich spike control is satisfied. The On the other hand, when at least one of the condition (a) and the condition (b) is not satisfied, or when a predetermined time has elapsed after the rich condition flag F_RICH is set to “1”, the rich condition flag F_RICH is “ 0 "is set.
(A) The NOx trapping amount S_QNOx is greater than or equal to a predetermined value SREF.
(B) The engine speed NE and the accelerator pedal opening AP are in a region where the rich spike control process can be executed.

  Here, the NOx trapping amount S_QNOx under the condition (a) corresponds to an estimated value of the NOx trapping amount by the NOx purification catalyst 8, and is specifically calculated as follows. First, a required torque PMCMD is calculated by searching a map (not shown) according to the engine speed NE and the accelerator pedal opening AP, and then a map (not shown) is searched according to the required torque PMCMD and the engine speed NE. Thus, the map search value is calculated, and further, the NOx trapping amount S_QNOx is calculated by integrating the map search value. The NOx trapping amount S_QNOx calculated as described above is reset to 0 when the rich condition flag F_RICH is set to “1”.

  In step 21 following step 20, it is determined whether or not the rich condition flag F_RICH is “1”. If the determination result is YES and the execution condition of the rich spike control is satisfied, the process proceeds to step 22 to determine whether or not the previous value F_RICHONZ of the rich permission flag is “0”.

  When the determination result is NO, that is, when the rich permission flag F_RICHON is set to “1” in the previous loop, the process proceeds to step 32 described later.

  On the other hand, if the determination result in step 22 is YES and the rich permission flag F_RICHON is set to “0” in the previous loop, the process proceeds to step 23 to determine whether or not the delay flag F_DELAY is “1”. . If the determination result is NO and F_DELAY = 0, the process proceeds to step 24 to determine whether or not the previous value F_COLDEGRZ of the cold EGR flag is “1”.

  When the determination result is NO, that is, when the engine 3 is in an operating state in which hot EGR is to be executed in the previous loop, the process proceeds to step 32 described later.

  On the other hand, if the decision result in the step 24 is YES and the engine 3 is in an operating state in which the cold EGR should be executed in the previous loop, the process proceeds to a step 25 to execute a cold EGR flag F_COLDEGR setting process. Specifically, the value of the cold EGR flag F_COLDEGR is set by searching a map (not shown) according to the required torque PMCMD and the engine speed NE calculated in step 20.

  Next, the routine proceeds to step 26, where it is determined whether or not the cold EGR flag F_COLDEGR set at step 25 is “1”. When the determination result is YES, the process directly proceeds to step 32 described later.

  On the other hand, when the determination result of step 26 is NO, that is, when the current loop is the first time when the engine 3 has shifted from the operating state in which cold EGR should be performed to the operating state in which hot EGR should be performed, the process proceeds to step 27. The delay timer set value TMSET is calculated by searching a map (not shown) according to the required torque PMCMD and the engine speed NE calculated in step 20. In this map, the set value TMSET is higher than that when it passes through the EGR cooler 12 side because the flow path of the reflux gas is completely switched from the EGR cooler 12 side to the bypass passage 14 side by the flow path switching valve 15. The value is set such that the reflux gas is supplied to the intake passage 5.

  Next, at step 28, the time value TM_DELAY of the delay timer is set to the set value TMSET, and the delay flag F_DELAY is set to “1” to indicate that the delay process is being executed. As a result, in the next and subsequent loops, the determination result of step 23 is YES, and in this case, the process proceeds to step 29 to decrement the time value TM_DELAY of the delay timer.

  In step 30 following step 28 or 29 described above, it is determined whether or not the measured value TM_DELAY of the delay timer is 0. When the determination result is NO, the process proceeds to step 35, and the rich permission flag F_RICHON is set to “0” to indicate that the air-fuel ratio control for normal time should be executed, and then the present process is terminated. .

  On the other hand, if the decision result in the step 30 is YES, the process advances to a step 31 to set a delay flag F_DELAY to “0” in order to indicate that the delay process has ended.

  Next, the process proceeds to step 32, and the rich permission flag F_RICHON is set to “1” to indicate that the rich spike control should be executed, and then the present process is terminated.

  On the other hand, if the determination result in step 21 is NO and the execution condition of the rich spike control is not satisfied, the process proceeds to step 33, and the cold EGR flag F_COLDEGR is set as in step 25 described above. That is, the cold EGR flag F_COLDEGR is set by searching a map (not shown) according to the required torque PMCMD and the engine speed NE calculated in step 20.

  Next, the routine proceeds to step 34, where the time value TM_DELAY of the delay timer is set to 0 and the delay flag F_DELAY is set to “0”. Thereafter, as described above, the rich permission flag F_RICHON is set to “0” in step 35, and then this process is terminated.

  As described above, according to the control device 1 of the first embodiment, when the execution condition of the rich spike control is satisfied and the switching condition for switching the flow path of the reflux gas to the bypass passage 14 side is satisfied (steps 21 and 26). When the determination result is YES), the flow path switching valve 15 is controlled so as to switch the flow path of the reflux gas from the EGR cooler 12 side to the bypass passage 14 side. Then, after this flow path switching control is started, rich spike control is executed when a time corresponding to the set value TMSET of the delay timer has elapsed. That is, EGR control for rich spike, fuel injection control, and throttle valve control are executed. The set value TMSET of this delay timer is higher than that when passing through the EGR cooler 12 side because the flow path of the reflux gas is completely switched from the EGR cooler 12 side to the bypass passage 14 side by the flow path switching valve 15. Since the value is set such that the recirculated gas is supplied to the intake passage 5, the rich spike control can be started in such a state that the high-temperature recirculated gas is supplied to the intake passage 5. As a result, unlike the conventional case, the recirculation gas that has passed through the bypass passage 14 and is higher in temperature than the recirculation gas cooled by the EGR cooler 12 can be supplied to the intake side immediately after the start of the rich spike control. A good combustion state can be secured. Thereby, exhaust gas characteristics can be improved.

  In addition, although 1st Embodiment is an example which used the flow-path switching valve 15 as a flow-path switching apparatus, the flow-path switching apparatus of this invention is not restricted to this, The flow path of recirculation | reflux gas is made into the bypass passage 14 side. What is necessary is just to be able to switch to the EGR cooler 12 side. For example, a three-way valve driven by an electric motor may be used as the flow path switching device.

  Moreover, although 1st Embodiment is an example using the water-cooled EGR cooler 12 as a reflux gas cooling device, the reflux gas cooling device of this invention is not restricted to this, What is necessary is just what can cool a reflux gas. . For example, an air-cooled EGR cooler may be used as the reflux gas cooling device.

  Next, a control device 1A for an internal combustion engine according to a second embodiment will be described with reference to FIG. As shown in the figure, the control device 1A of the second embodiment is configured in the same manner except for a part of the control device 1 of the first embodiment. The same reference numerals are assigned and explanations thereof are omitted, and differences from the control device 1 are mainly described.

  The control device 1A includes an ECU 2 and a flow path position sensor 23 connected thereto. The flow path position sensor 23 detects the switching state of the flow path of the reflux gas by the flow path switching valve 15 and outputs a detection signal representing it to the ECU 2.

  In the control device 1A, in the control process of FIG. 3 described above, the processes other than steps 3 and 6 are executed in the same manner as the control process of FIG. 3, and the processes of steps 3 and 6 are executed as described below. Is done. That is, in step 3 of FIG. 3, the flow path switching valve 15 is driven so that the flow path of the reflux gas is switched from the bypass passage 14 side to the EGR cooler 12 side. At that time, based on the detection signal of the flow path position sensor 23, the flow path switching valve 15 is continuously driven until the flow path of the recirculation gas is switched from the bypass passage 14 side to the EGR cooler 12 side. The side drive flag F_COOLER is set to “1”. When the flow path of the reflux gas is completely switched to the EGR cooler 12 side, the driving of the flow path switching valve 15 is stopped and the cooler side drive flag F_COOLER is set to “0”.

  On the other hand, when the flow path of the recirculation gas is switched from the EGR cooler 12 side to the bypass passage 14 side in step 6, the recirculation gas flow path is changed based on the detection signal of the flow path position sensor 23. Until switching from the 12th side to the bypass passage 14 side, the drive of the flow path switching valve 15 is continued and the bypass side drive flag F_BYPASS is set to "1". When the flow path of the reflux gas is completely switched to the bypass passage 14 side, the driving of the flow path switching valve 15 is stopped and the bypass side drive flag F_BYPASS is set to “0”.

  Further, in the control device 1A, various flag setting processes are executed as shown in FIG. As shown in the figure, in this process, steps other than steps 53 and 58 are configured in the same manner as steps 20 to 22, 24 to 26, 32, 33 and 35 in FIG. Now, the steps 53 and 58 will be mainly described.

  That is, in step 52, it is determined whether or not the previous value F_RICHONZ of the rich permission flag is “0”. If this determination result is YES, in step 53, the bypass passage by the flow path switching valve 15 in the previous loop. It is determined whether or not the flow path switching to the 14 side has been executed. When the determination result is NO, steps 54 to 56 are executed in the same manner as steps 24 to 26 described above.

  When the determination result in step 56 is YES, that is, when the engine 3 is in an operating state in which cold EGR is to be executed, the routine proceeds to step 57 to indicate that rich spike control is to be executed. After the flag F_RICHON is set to “1”, this process ends.

  On the other hand, when the determination result in step 56 is NO, that is, when the current loop is the first time when the engine 3 has shifted from the operating state in which cold EGR is to be executed to the operating state in which hot EGR is to be executed, the process proceeds to step 60. In order to indicate that the normal-time air-fuel ratio control should be executed, the rich permission flag F_RICHON is set to “0”, and then this process ends.

  On the other hand, when the determination result in step 53 is YES and the flow path switching to the bypass passage 14 side by the flow path switching valve 15 has been executed in the previous loop, the process proceeds to step 58 where the detection signal of the flow path position sensor 23 is detected. Based on the above, it is determined whether or not the flow path switching to the bypass passage 14 side by the flow path switching valve 15 has been completed. When the determination result is NO, as described above, after executing step 60, the present process is terminated.

  On the other hand, when the determination result in step 58 is YES and the flow path switching to the bypass passage 14 side is completed, as described above, the process proceeds to step 57 to indicate that the rich spike control should be executed. After the rich permission flag F_RICHON is set to “1”, this process ends.

  As described above, according to the control device 1A of the second embodiment, after the execution condition of the rich spike control is satisfied, when the flow path switching to the bypass passage 14 side is completed (the determination result of steps 51 and 58 is Rich spike control is started at the time when both are YES), that is, when the recirculated gas having a temperature higher than that when passing through the EGR cooler 12 is supplied to the intake passage 5. As a result, the same effect as the control device 1 of the first embodiment described above can be obtained. That is, immediately after the start of rich spike control, a good combustion state of the air-fuel mixture can be ensured, and thereby the exhaust gas characteristics can be improved.

  Next, an internal combustion engine control apparatus 1B according to a third embodiment will be described with reference to FIG. As shown in the figure, the control device 1B of the third embodiment is configured in the same manner except for a part of the control device 1 of the first embodiment. The same reference numerals are assigned and explanations thereof are omitted, and differences from the control device 1 are mainly described.

  The control device 1B includes an ECU 2 and an EGR temperature sensor 24 connected thereto. The EGR temperature sensor 24 (recirculation gas temperature detection means) is provided in the vicinity of the EGR control valve 13, and the temperature of the recirculation gas (hereinafter referred to as “EGR temperature”) flowing through the EGR cooler 12 side or the bypass passage 14 side TEGR. , And a detection signal representing it is output to the ECU 2.

  In this control device 1B, various control processes such as flow path switching control are executed by the control method shown in FIG. 8 instead of the control method shown in FIG. As is clear from FIG. 6, in this process, each step other than step 77 is configured in the same manner as steps 1 to 14 in FIG. 3, and therefore, step 77 will be mainly described here.

In this process, if the determination result in step 76 is NO and F_BYPASS = 0, it is determined in step 77 whether or not the following two conditions (c) and (d) are both satisfied.
(C) The previous value F_RICHZ of the rich condition flag is “0”.
(D) The rich condition flag F_RICH is “1”.

  When the determination result is YES and the current loop is the first time when the execution condition of the rich spike control is satisfied, the process proceeds to step 75, and the flow path to the bypass passage 14 side as in step 6 of FIG. Execute switching control. Next, similarly to steps 8 to 14 in FIG. 3 described above, steps 78 to 84 are executed, and then this process is terminated. On the other hand, when the determination result of step 77 is NO, as described above, after executing steps 78 to 84, the present process is terminated.

  In the control device 1B, various flag setting processes are executed by the control method shown in FIG. 9 instead of the control method of FIG. 4 described above. That is, first, in step 90, the processing for setting the rich condition flag F_RICH is executed as in step 20 of FIG. 4 described above. Next, the process proceeds to step 91, where it is determined whether or not the rich condition flag F_RICH set in step 90 is “1”.

  When the determination result is YES, the process proceeds to step 92, and a target value TEGRCMD (predetermined temperature) of the EGR temperature is calculated. Specifically, the required torque PMCMD is calculated by searching a map (not shown) according to the engine speed NE and the accelerator pedal opening AP, and then not shown according to the required torque PMCMD and the engine speed NE. By searching the map, the target value TEGCMD for the EGR temperature is calculated. In this map, the target value TEGCMD is set to the temperature of the recirculated gas that can ensure a good combustion state of the air-fuel mixture even when the rich spike control is executed.

  Next, the routine proceeds to step 93, where it is determined whether or not the previous value F_RICHONZ of the rich permission flag is “0”. When the determination result is NO, that is, when the rich permission flag F_RICHON is set to “1” in the previous loop, the process proceeds to Step 95 described later.

  On the other hand, if the determination result in step 93 is YES and the rich permission flag F_RICHON was set to “0” in the previous loop, the process proceeds to step 94 to determine whether or not the EGR temperature TEGR is equal to or higher than the target value TEGRCMD. To do.

  When the determination result is NO, it is determined that the engine 3 is in an operating state in which hot EGR is to be executed, the process proceeds to step 96, and the cold EGR flag F_COLDEGR is set to “0” to indicate that. Next, in step 98, in order to indicate that the air-fuel ratio control for normal time should be executed, the rich permission flag F_RICHON is set to “0”, and then this process is terminated.

  On the other hand, if the determination result in step 94 is YES and the EGR temperature TEGR has reached a temperature that can ensure a good combustion state of the air-fuel mixture even when the rich spike control is executed, the routine proceeds to step 95, where the rich spike control is performed. Is set to “1”, and then this process is terminated.

  On the other hand, if the decision result in the step 91 is NO, the process advances to a step 97, and a setting process for the cold EGR flag F_COLDEGR is executed in the same manner as the step 33 described above. Next, as described above, in step 98, the rich permission flag F_RICHON is set to “0”, and then this process is terminated.

  As described above, according to the control device 1B of the third embodiment, after the execution condition of the rich spike control is satisfied, when the EGR temperature TEGR becomes equal to or higher than the target value TEGRCMD (the determination results of steps 91 and 94 are Rich spike control is started at the time when the answer is YES). That is, even when rich spike control is executed, rich spike control is started when high-temperature recirculation gas that can ensure a good combustion state of the air-fuel mixture is supplied to the intake passage 5. As a result, the same operational effects as those of the control devices 1 and 1A of the first and second embodiments described above can be obtained. That is, immediately after the start of rich spike control, a good combustion state of the air-fuel mixture can be ensured, and thereby the exhaust gas characteristics can be improved.

  The third embodiment is an example in which the EGR temperature sensor 24 is used as the recirculation gas temperature detection means. However, the recirculation gas temperature detection means of the present invention is not limited to this, and other temperature parameters and the operating state of the engine 3 are also used. You may use what estimates the temperature of recirculation | reflux gas based on a parameter. For example, a sensor for detecting the temperature of the EGR control valve 13 itself may be provided, and the temperature of the reflux gas may be estimated based on the detection signal.

  Moreover, although 3rd Embodiment is an example using the target value TEGRCMD calculated by the map search as predetermined temperature, the predetermined temperature of this invention is not restricted to this, You may use a fixed value.

1 is a diagram schematically showing a schematic configuration of an internal combustion engine to which a control device according to a first embodiment of the present invention is applied. It is a block diagram which shows schematic structure of the control apparatus of 1st Embodiment. It is a flowchart which shows the various control processing by the control apparatus of 1st Embodiment. It is a flowchart which shows the various flag setting processes by the control apparatus of 1st Embodiment. It is a block diagram which shows schematic structure of the control apparatus of 2nd Embodiment. It is a flowchart which shows the various flag setting processes by the control apparatus of 2nd Embodiment. It is a block diagram which shows schematic structure of the control apparatus of 3rd Embodiment. It is a flowchart which shows the various control processing by the control apparatus of 3rd Embodiment. It is a flowchart which shows the various flag setting processes by the control apparatus of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control apparatus 1A Control apparatus 1B Control apparatus 2 ECU (air-fuel ratio control means, flow-path switching control means, prohibition means)
3 Internal combustion engine 5 Intake passage (intake system)
7 Exhaust passage (exhaust system)
11 EGR passage (exhaust gas recirculation passage)
12 EGR cooler (reflux gas cooling device)
14 Bypass passage 15 Flow path switching valve (flow path switching device)
24 EGR temperature sensor (reflux gas temperature detection means)
TEGR Reflux gas temperature TEGCMD Target value (predetermined temperature)

Claims (2)

An exhaust gas recirculation passage for recirculating a part of the exhaust gas in the exhaust system to the intake system as a recirculation gas, a recirculation gas cooling device for cooling the recirculation gas flowing in the exhaust gas recirculation passage, and a detour of the recirculation gas cooling device Control of an internal combustion engine comprising a bypass passage for returning the recirculated gas to the intake system and a flow path switching device for switching the flow path of the recirculated gas from one of the exhaust recirculation passage and the bypass passage to the other A device,
Air-fuel ratio control means for controlling the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine by switching between the lean side and the rich side with respect to the theoretical air-fuel ratio;
When the air-fuel ratio switching condition for switching the air-fuel ratio of the air-fuel mixture from the lean side to the rich side from the stoichiometric air-fuel ratio is satisfied, the flow path of the recirculation gas is switched from the exhaust recirculation passage to the bypass passage. Channel switching control means for controlling the channel switching device;
With
The air-fuel ratio control means controls the air-fuel ratio switching timing to be later than the flow-path switching timing of the recirculation gas by the flow path switching control means when the air-fuel ratio switching condition is satisfied. A control device for an internal combustion engine. An exhaust gas recirculation passage for recirculating a part of the exhaust gas in the exhaust system to the intake system as a recirculation gas, a recirculation gas cooling device for cooling the recirculation gas flowing in the exhaust gas recirculation passage, and a detour of the recirculation gas cooling device Control device for an internal combustion engine, comprising: a bypass passage for recirculating the recirculated gas to the intake system; and a flow path switching device for switching the flow path of the recirculated gas from one of the exhaust recirculation passage and the bypass passage to the other Because
Air-fuel ratio control means for controlling the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine between the lean side and the rich side from the stoichiometric air-fuel ratio;
Reflux gas temperature detection means for detecting the temperature of the reflux gas as the reflux gas temperature;
When the air-fuel ratio switching condition for switching the air-fuel ratio of the air-fuel mixture from the lean side to the rich side with respect to the stoichiometric air-fuel ratio is satisfied, when the detected recirculation gas temperature is lower than a predetermined temperature, the flow of the recirculation gas Flow path switching control means for controlling the flow path switching device so as to switch the path from the exhaust gas recirculation path to the bypass path;
When the air-fuel ratio switching condition is satisfied, after the flow path switching of the recirculation gas by the flow path switching control means is started, the air-fuel ratio control means by the air-fuel ratio control means until the recirculation gas temperature becomes equal to or higher than the predetermined temperature. Prohibiting means for prohibiting switching of the air-fuel ratio;
A control device for an internal combustion engine, comprising:

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