JP4858289B2 - Exhaust gas recirculation device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine that includes a plurality of EGR passages that connect an exhaust passage and an intake passage.

  An exhaust pipe connected to an outlet portion of a catalytic converter incorporating a filter carrying an exhaust purification catalyst and an air suction pipe upstream of the compressor of the exhaust turbocharger are connected by a first EGR passage, and the exhaust of the exhaust turbocharger is connected. An internal combustion engine is known in which an exhaust manifold located upstream of a turbine and a surge tank connected to an intake port of the internal combustion engine are connected by a second EGR passage (see Patent Document 1). In addition, there is Patent Document 2 as a prior art document related to the present invention.

Japanese Patent Laying-Open No. 2005-076456 JP-A-10-141147

  In an internal combustion engine having a plurality of EGR passages such as the internal combustion engine of Patent Document 1, the flow rate of exhaust gas (hereinafter sometimes referred to as EGR gas) recirculated to the intake passage through each EGR passage is appropriately set. Need to control. In an internal combustion engine having a plurality of EGR passages, an EGR valve provided in any one of the EGR passages may be open-loop controlled based on a correspondence relationship between a preset opening degree of the EGR valve and the flow rate of EGR gas. . The flow rate of EGR gas is affected by the pressure difference between the exhaust pressure at the exhaust intake position and the intake pressure at the exhaust introduction position, and this pressure difference changes according to the pressure loss in the exhaust passage and each EGR passage. For example, when the soot discharged from the internal combustion engine adheres to the inner wall of the exhaust passage, the EGR valve, or the like and the pressure loss in the exhaust passage or the EGR passage increases, the pressure of the exhaust at the exhaust intake position increases and the pressure difference increases. In this case, the flow rate of the exhaust gas recirculated to the intake passage increases. Thus, the flow rate of EGR gas changes according to the state of the exhaust passage and the like. For this reason, it is necessary to appropriately correct the correspondence between the opening degree of the EGR valve and the flow rate of the EGR gas so that an appropriate amount of EGR gas is introduced into the intake passage. In the internal combustion engine of Patent Document 2, the opening degree of the EGR valve is controlled according to the oxygen concentration of the intake air. This is an EGR passage applied to one internal combustion engine, and has a plurality of EGR passages. It is difficult to apply to an internal combustion engine.

  Accordingly, an object of the present invention is to provide an exhaust gas recirculation device for an internal combustion engine capable of appropriately controlling the flow rate of exhaust gas introduced into an intake passage in an internal combustion engine having a plurality of EGR passages.

An exhaust gas recirculation device for a first internal combustion engine according to the present invention includes a first EGR passage for taking a part of exhaust gas from an exhaust passage and introducing it into an intake passage, and an upstream side of the exhaust passage from an exhaust take-out position of the first EGR passage. An exhaust take-out position and a second EGR passage in which an exhaust introduction position is provided downstream of the intake passage from the exhaust introduction position of the first EGR passage, and an exhaust gas recirculated to the intake passage through the first EGR passage. An exhaust gas recirculation apparatus for an internal combustion engine, comprising: a first EGR valve that adjusts a flow rate; and a second EGR valve that adjusts the flow rate of exhaust gas recirculated to the intake passage through the second EGR passage. A detecting means that is disposed downstream of the intake passage from the exhaust introduction position and detects a physical quantity of intake air that changes in accordance with a flow rate of exhaust gas introduced into the intake passage; Serial engine operating condition is in a predetermined state, and the intake passage exhaust through the first 1EGR passage opening a target flow rate corresponding to the predetermined state in the state of being maintained in the fully closed of the first 2EGR valve The opening degree of the first EGR valve when the adjustment for adjusting the opening degree of the first EGR valve is performed so as to be introduced into the engine is stored as a target opening degree, and the detection means detects the opening degree when the adaptation is performed. Storage means in which the value of the physical quantity of intake air is stored as a reference value; the opening of the first EGR valve is adjusted to the target opening; the opening of the second EGR valve is fully closed; based operating state of the engine to a difference between the reference value stored in the value and the storage means of the physical quantity detected the intake by the detecting means when adjusted to the predetermined state opening of the first 1EGR valve And the correction means for correcting the correspondence between the flow rate of the first EGR gas that is the exhaust gas introduced into the intake passage through the first EGR passage, to solve the above-described problem. 1).

  When the pressure loss in the exhaust passage or the like changes, the flow rate of the first EGR gas is equal to the target flow rate even if the operating state of the internal combustion engine, the opening degree of the first EGR valve, and the opening degree of the second EGR valve are adjusted to the adapted state. Is different. At this time, the difference between the physical quantity value of the intake air detected by the detecting means and the reference value correlates with the difference between the flow rate of the first EGR gas and the target flow rate at that time. Therefore, the reference value stored in the storage means, the operating state of the internal combustion engine, the opening degree of the first EGR valve, and the opening degree of the second EGR valve are detected by the detecting means when adjusted to the state at the time of adaptation, respectively. By correcting the correspondence between the opening degree of the first EGR valve and the flow rate of the first EGR gas based on the difference from the physical quantity of intake air, this correspondence is appropriately corrected in consideration of changes in pressure loss such as in the exhaust passage. can do. Therefore, it is possible to appropriately control the flow rate of the exhaust gas recirculated to the intake passage through the first EGR passage.

An exhaust gas recirculation device for a second internal combustion engine according to the present invention includes a first EGR passage for extracting a part of exhaust gas from an exhaust passage and introducing it into the intake passage, and an upstream side of the exhaust passage from an exhaust extraction position of the first EGR passage. An exhaust take-out position and a second EGR passage in which an exhaust introduction position is provided downstream of the intake passage from the exhaust introduction position of the first EGR passage, and an exhaust gas recirculated to the intake passage through the first EGR passage. An exhaust gas recirculation device for an internal combustion engine, comprising: a first EGR valve that adjusts a flow rate; and a second EGR valve that adjusts the flow rate of exhaust gas recirculated to the intake passage via the second EGR passage. A detecting means that is disposed downstream of the intake passage from the exhaust introduction position and detects a physical quantity of intake air that changes in accordance with a flow rate of exhaust gas introduced into the intake passage; When the operating state of the internal combustion engine is a predetermined state and the opening degree of the first EGR valve is kept fully closed, the exhaust gas having a target flow rate corresponding to the predetermined state passes through the second EGR passage to the intake passage. The opening degree of the second EGR valve when the adjustment is performed to adjust the opening degree of the second EGR valve so as to be introduced into the engine is stored as a target opening degree, and the detection means detects the opening degree when the adaptation is performed. Storage means in which the value of the physical quantity of the intake air is stored as a reference value; the opening of the first EGR valve is adjusted to be fully closed; the opening of the second EGR valve is adjusted to the target opening; When the engine operating state is adjusted to the predetermined state, the opening of the second EGR valve is based on the difference between the physical quantity value of the intake air detected by the detecting means and the reference value stored in the storage means. By being and a correcting means for correcting the relationship between the first 2EGR gas flow rate is the exhaust gas introduced into the intake passage through the first 2EGR passage, to solve the problems described above (claim 2 ). According to the second exhaust gas recirculation device of the present invention, it is possible to appropriately control the flow rate of the exhaust gas recirculated to the intake passage via the second EGR passage.

In the first or second exhaust gas recirculation apparatus of the present invention, the physical quantity of the intake air is an intake air temperature, and the correction means is a reference in which the temperature of the intake air detected by the detection means is stored in the storage means. When the value is higher than the value, the opening degree of the EGR valve to be corrected and the EGR valve are provided so that the flow rate of the exhaust gas introduced into the intake passage through the EGR passage provided with the EGR valve to be corrected is reduced. It may be corrected correspondence relationship between the flow rate of exhaust gas introduced into the intake passage via the EGR passageway (claim 3). As the flow rate of EGR gas introduced into the intake passage increases, the temperature of the intake air increases. Therefore, when the temperature of the intake air detected by the detection means is higher than the reference value, it is considered that EGR gas having a flow rate higher than the target flow rate is introduced into the intake passage. Therefore, the correspondence relationship is corrected so that the flow rate of the EGR gas decreases.

In the first or second exhaust gas recirculation system of the present invention, the physical quantity of the intake air, may be a pressure or flow of the intake air in the intake (claim 4). Since these physical quantities also change according to the flow rate of the EGR gas, the correspondence can be corrected based on them.

  As described above, according to the exhaust gas recirculation device of the present invention, the reference value stored in the storage means, the operating state of the internal combustion engine, the opening degree of the first EGR valve, and the opening degree of the second EGR valve are adapted. Correspondence between the opening degree of the EGR valve to be corrected and the flow rate of the EGR gas in the EGR passage in which the EGR valve is provided based on the difference between the physical quantity of the intake air detected by the detecting means when each is adjusted to the time state Since the relationship is corrected, this correspondence can be appropriately corrected in consideration of a change in pressure loss such as in the exhaust passage. Therefore, the flow rate of the exhaust gas recirculated to the intake passage can be appropriately controlled.

(First form)
FIG. 1 shows an internal combustion engine in which an exhaust gas recirculation apparatus according to a first embodiment of the present invention is incorporated. An internal combustion engine (hereinafter sometimes referred to as an engine) 1 shown in FIG. 1 is a diesel engine mounted on a vehicle as a driving power source, and includes a plurality (four in FIG. 1) of cylinders 2, An intake passage 3 and an exhaust passage 4 connected to the cylinder 2 are provided. In the intake passage 3, an air filter 5 for filtering the intake air, an air flow meter 6 for outputting a signal corresponding to the intake air amount, a throttle valve 7 for adjusting the intake air amount, a compressor 8a of the turbocharger 8, and An intercooler 9 for cooling the intake air is provided. The exhaust passage 4 is provided with a turbine 8b of the turbocharger 8, an exhaust purification catalyst 10 for purifying exhaust, and an exhaust throttle valve 11 for adjusting the exhaust flow rate.

The exhaust passage 4 and the intake passage 3 are connected by a low pressure EGR passage 20 and a high pressure EGR passage 21. As shown in FIG. 1, the low pressure EGR passage 20 connects the exhaust passage 4 downstream of the exhaust purification catalyst 10 and the intake passage 3 upstream of the compressor 8a. On the other hand, the high pressure EGR passage 21 connects the exhaust passage 4 upstream of the turbine 8b and the intake passage 3 downstream of the compressor 8a. Therefore, the low pressure EGR passage 20 corresponds to the first EGR passage of the present invention, and the high pressure EGR passage 21 corresponds to the second EGR passage of the present invention. The low pressure EGR passage 20 has exhaust gas guided to the intake passage 4, that is, an EGR cooler 22 for cooling the EGR gas, and EGR gas recirculated to the intake passage 3 through the low pressure EGR passage 20 (hereinafter referred to as first EGR gas). The low pressure EGR valve 23 is provided as a first EGR valve for adjusting the flow rate. The high pressure EGR passage 21 has a high pressure EGR as a second EGR valve for adjusting the flow rate of EGR gas (hereinafter sometimes referred to as second EGR gas) recirculated to the intake passage 3 through the high pressure EGR passage 21. A valve 24 is provided.

  The operations of the throttle valve 7, the low pressure EGR valve 23, and the high pressure EGR valve 24 are controlled by an engine control unit (ECU) 30, respectively. The ECU 30 is configured as a computer including a microprocessor and peripheral devices such as a RAM and a ROM necessary for its operation, and controls the operating state of the engine 1 based on output signals from various sensors provided in the engine 1. Computer unit. For example, when introducing EGR gas into the intake passage 3, the ECU 30 determines whether to introduce exhaust gas into the intake passage 3 via the low pressure EGR passage 20 or the high pressure EGR passage 21 according to the rotational speed and load of the engine 1. The opening degree of each low pressure EGR valve 23 and the opening degree of the high pressure EGR valve 24 are controlled so that EGR gas having a target flow rate is introduced into the intake passage 3 according to the operating state of the engine 1. For example, a crank angle sensor 31 that outputs a signal corresponding to the crank angle and an air flow meter 6 are connected to the ECU 30 as sensors to be referred to when performing such control. In addition to this, the ECU 30 includes an intake air temperature sensor 32 as a detection unit that outputs a signal corresponding to the temperature of the intake air, an oxygen concentration sensor 33 that outputs a signal corresponding to the oxygen concentration of the intake air, and before and after the exhaust purification catalyst 10. A differential pressure sensor 34 that outputs a signal corresponding to the differential pressure, an accelerator opening sensor 35 that outputs a signal corresponding to the accelerator opening, and the like are connected. As shown in FIG. 1, the intake air temperature sensor 32 is provided in the intake passage 3 downstream of the exhaust introduction position of the low pressure EGR passage 20. Since these may be known sensors generally provided in the engine, a detailed description thereof will be omitted.

  The ECU 30 controls the operations of the low pressure EGR valve 23 and the high pressure EGR valve 24, respectively, but the control method is different. The high pressure EGR valve 24 is feedback controlled so that the oxygen concentration of the intake air sucked into each cylinder 2 becomes a target value set according to the operating state of the engine 1. On the other hand, the low pressure EGR valve 23 has a target flow rate set based on the operating state of the engine 1 such as the rotational speed and load of the engine 1, and the ECU 30 introduces the first EGR gas at the target flow rate into the intake passage 3. The opening degree of the low pressure EGR valve 23 is controlled. That is, the low pressure EGR valve 23 is controlled by open loop control. In this control, for example, the correspondence relationship between the opening degree of the low pressure EGR valve 23 and the flow rate of the first EGR gas shown as an example in FIG. 2 is stored in the RAM of the ECU 30 as a map, and the low pressure EGR valve is referenced with reference to this map. What is necessary is just to control the opening degree of 23. The flow rate of the first EGR gas varies depending on the pressure loss of the low pressure EGR passage 20 and the pressure loss of the exhaust purification catalyst 11. Therefore, the ECU 30 appropriately corrects the correspondence relationship between the opening degree of the low pressure EGR valve 23 and the flow rate of the first EGR gas.

First, a method for correcting the correspondence relationship between the opening degree of the low pressure EGR valve 23 and the flow rate of the first EGR gas will be described. As is well known, as the amount of EGR gas introduced into the intake passage 3 increases, the intake air temperature rises, and there is a correlation between them. Therefore, when the operating state of the engine 1 is a predetermined state and the opening degree of the high pressure EGR valve 24 is maintained at the predetermined opening degree, the first EGR gas having a target flow rate corresponding to the predetermined state passes through the low pressure EGR passage 20. The opening of the low-pressure EGR valve 23 is adjusted in advance so as to be introduced into the intake passage 3, and the opening of the low-pressure EGR valve 23 at that time is stored in the ROM of the ECU 30 as the target opening, and at that time The temperature detected by the intake air temperature sensor 32 is stored in the ROM of the ECU 30 as a reference value. Thereby, ECU30 functions as a memory | storage means of this invention. When soot or the like adheres to the exhaust passage 4 and the pressure loss in the exhaust passage 4 changes, the pressure difference between the exhaust take-out position and the exhaust introduction position of the low-pressure EGR passage 20 changes. In this case, the operating state of the engine 1 is adjusted to a predetermined state, the opening degree of the high pressure EGR valve 24 is adjusted to a predetermined opening degree, and the opening degree of the low pressure EGR valve 23 is adjusted to the target opening degree adjusted at the time of adaptation. Since the flow rate of the first EGR gas deviates from the target flow rate, the intake air temperature sensor 32 detects the intake air temperature different from the reference value. At this time, the difference between the temperature of the intake air detected by the intake air temperature sensor 32 and the reference value (hereinafter sometimes referred to as a temperature difference) is the flow rate of the first EGR gas and the target flow rate that were flowing at that time. The correlation is corrected according to the temperature difference. FIG. 3 shows an example of the relationship between the flow rate of the first EGR gas and the intake air temperature. Note that a point P in FIG. 3 shows the intake air temperature when the first EGR gas having the target flow rate is introduced into the intake passage 3, that is, the relationship at the time of adaptation. When the detected intake air temperature is the temperature T2 in FIG. 3 and is higher than the reference value T1, it is considered that more first EGR gas than the target flow rate is introduced into the intake passage 3. Therefore, a correction amount may be calculated according to the temperature difference (T2-T1), and the map of FIG. 2 may be corrected according to the correction amount. For example, if the detected intake air temperature is higher than the reference value , the correspondence is corrected in the direction of arrow B in FIG . On the other hand, if the detected intake air temperature is lower than the reference value , the correspondence is corrected in the direction of arrow A in FIG . For example, an idling state is set as the operating state of the engine 1 when performing this correction. Further, as the predetermined opening degree at which the high-pressure EGR valve 24 is adjusted, for example, fully closed is set.

  The ECU 30 repeats the correspondence learning routine shown in FIG. 4 at predetermined intervals during the operation of the engine 1 in order to correct the correspondence between the opening degree of the low pressure EGR valve 23 and the flow rate of the first EGR gas by the correction method described above. Execute. By executing the routine of FIG. 4, the ECU 30 functions as the correcting means of the present invention. In the routine of FIG. 4, the ECU 30 first acquires the operating state of the engine 1 in step S11. As the operating state of the engine 1, the rotational speed of the engine 1, the load of the engine 1, the accelerator opening, and the like are acquired. In subsequent step S12, ECU 30 determines whether or not a predetermined learning condition is satisfied. As described above, when correcting the correspondence, the engine 1 is adjusted to the idling state and the high-pressure EGR valve 24 is adjusted to be fully closed. Therefore, the operating state of the engine 1 and the opening degree of the high pressure EGR valve 24 can be adjusted in this way. For example, it is determined that a predetermined learning condition is satisfied when the vehicle on which the engine 1 is mounted is stopped. The If it is determined that the predetermined learning condition is not satisfied, the current routine is terminated.

  On the other hand, if it is determined that the predetermined learning condition is satisfied, the process proceeds to step S13, where the ECU 30 adjusts the opening degree of the low pressure EGR valve 23 to the target opening degree adjusted at the time of adaptation and the opening degree of the high pressure EGR valve 24. The engine 1 is adjusted to be fully closed and the operating state of the engine 1 is adjusted to the idling state. In subsequent step S14, the ECU 30 detects the temperature of the intake air based on the output signal of the intake air temperature sensor 32. In the next step S15, the ECU 30 calculates a correction amount based on the temperature difference between the detected intake air temperature and the reference value stored in the ROM of the ECU 30. Thereafter, in step S16, the correspondence relationship between the opening degree of the low pressure EGR valve 23 and the flow rate of the first EGR gas, that is, the map of FIG. 2 is corrected. Thereafter, the current routine is terminated.

  As described above, according to the first embodiment, the operating state of the engine 1, the opening degree of the high pressure EGR valve 24, and the opening degree of the low pressure EGR valve 23 are respectively adjusted to the adapted state, The correspondence between the opening of the low pressure EGR valve 23 and the flow rate of the first EGR gas is corrected based on the temperature difference between the temperature detected by the temperature sensor 32 and the reference value detected at the time of adaptation. And it can correct easily. Therefore, the flow rate of the first EGR gas can be controlled appropriately. In addition, this makes it possible to suppress fluctuations in the intake air temperature and stably control the intake air temperature, so that the exhaust emission of the engine 1 can be improved.

(Second form)
The second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a diagram corresponding to FIG. 1 of the first embodiment. As shown in FIG. 5, the second embodiment is different from the first embodiment except that the intake air temperature sensor 32 is provided in the intake passage 3 downstream of the exhaust introduction position of the high-pressure EGR passage 21. is there. Therefore, in FIG. 5, the same reference numerals are given to the same parts as in FIG. In this embodiment, the correspondence between the opening degree of the high-pressure EGR valve 24 and the flow rate of the second EGR gas is stored in the RAM of the ECU 30 as a map. The ECU 30 also refers to this map to open the opening degree of the high-pressure EGR valve 24. To control.

  In the first embodiment described above, the correspondence between the opening degree of the low pressure EGR valve 23 and the flow rate of the first EGR gas is corrected, but the change in the pressure loss in the exhaust passage 4 is caused by the opening degree of the high pressure EGR valve 24 and the second EGR gas. The correspondence with the flow rate is also changed. Therefore, in the second embodiment, the correspondence relationship between the opening degree of the high pressure EGR valve 24 and the flow rate of the second EGR gas is corrected. This correction method for the correspondence relationship may be performed in the same manner as in the first embodiment. In the second embodiment, since the correspondence between the opening degree of the high pressure EGR valve 24 and the flow rate of the second EGR gas is corrected, the operating state of the engine 1 is in a predetermined state and the opening degree of the low pressure EGR valve 23 is Adapting to adjust the opening degree of the high-pressure EGR valve 24 so that the second EGR gas having a target flow rate corresponding to the predetermined state is introduced into the intake passage 3 through the high-pressure EGR passage 21 in a state where the predetermined opening degree is maintained. The opening of the high pressure EGR valve 24 at that time is stored in the ROM of the ECU 30 as a target opening, and the temperature detected by the intake air temperature sensor 32 is stored in the ROM of the ECU 30 as a reference value. . Note that the idling state is set as the operating state of the engine 1 at the time of adaptation, and the opening degree of the low pressure EGR valve 23 is set to be fully closed. FIG. 6 shows a correspondence learning routine that the ECU 30 repeatedly executes at a predetermined cycle during operation of the engine 1 to correct the correspondence between the opening degree of the high-pressure EGR valve 24 and the flow rate of the second EGR gas. In FIG. 6, the same processes as those in FIG. 4 are denoted by the same reference numerals, and description thereof is omitted.

  In the routine of FIG. 6, the ECU 30 proceeds to the same process as in FIG. 4 until step S12. If the determination in step S12 is affirmative, the process proceeds to step S21, in which the ECU 30 adjusts the opening of the high pressure EGR valve 24 to the target opening adjusted during adaptation, adjusts the opening of the low pressure EGR valve 23 to fully closed, and The operating state of the engine 1 is adjusted to the idling state. In subsequent step S14, ECU 30 detects the temperature of the intake air, and then calculates a correction amount based on the temperature difference between the intake air temperature detected in step S15 and the reference value stored in the ROM of ECU 30. In the next step S22, the ECU 30 corrects the correspondence relationship between the opening degree of the high pressure EGR valve 24 and the flow rate of the second EGR gas, that is, the map stored in the RAM of the ECU 30. Thereafter, the current routine is terminated.

  Thus, the flow rate of the second EGR gas can be appropriately controlled by correcting the correspondence relationship between the opening degree of the high pressure EGR valve 24 and the flow rate of the second EGR gas.

  Next, reference examples related to the present invention will be described with reference to FIGS.

  As described above, the engine 1 determines whether exhaust is introduced into the intake passage 3 via the low pressure EGR passage 20 or the high pressure EGR passage 21 according to the rotational speed and load of the engine 1. A plurality of types of EGR modes for returning the exhaust gas to the intake passage 3 are set in association with the operating state of the engine 1. The EGR mode includes a low pressure loop (LPL) mode as a low pressure EGR mode in which exhaust gas is returned to the intake passage 3 only through the low pressure EGR passage 20, and exhaust gas is returned to the intake passage 3 only through the high pressure EGR passage 21. The high pressure loop (HPL) mode as the high pressure EGR mode and the MPL mode as the mixed EGR mode for introducing the exhaust gas to the intake passage 3 through both the low pressure EGR passage 20 and the high pressure EGR passage 21 are set. Yes. FIG. 7 is a diagram illustrating an example of a correspondence relationship between each EGR mode and the operating state of the engine 1. When the ECU 20 performs the recirculation of the exhaust gas to the intake passage 3, the ECU 20 refers to the correspondence relationship in FIG. 7 and selects any one of the LPL mode, the MPL mode, and the HPL mode according to the rotation speed and the load indicating the operating state of the engine 1. Select the EGR mode. The LPL mode is executed when the high pressure EGR valve 24 is kept fully closed and the low pressure EGR valve 23 is opened. The HPL mode is executed by keeping the low pressure EGR valve 23 fully closed and opening the high pressure EGR valve 24. The MPL mode is executed when both the low pressure EGR valve 23 and the high pressure EGR valve 24 are opened. It should be noted that the relationship shown in FIG. 7 is obtained in advance by experiment or numerical calculation and stored as a map in the ROM of the ECU 20.

  For example, when the engine 1 is operated in the LPL mode, the high pressure EGR valve 24 is kept fully closed, so that the correspondence between the opening of the low pressure EGR valve 23 and the flow rate of the first EGR gas is corrected based on the temperature difference. By doing so, the temperature difference can be appropriately reflected in the correction of the flow rate of the EGR gas.

  When operating in the MPL mode, since the EGR gas is introduced into the intake passage 3 through both the low pressure EGR passage 20 and the high pressure EGR passage 21, the correspondence between the EGR valves 23 and 24 is corrected. By doing so, the control accuracy of EGR gas can be improved. At this time, the correspondence relationship between the low-pressure EGR valve 23 and the correspondence relationship between the high-pressure EGR valve may be corrected by the same amount, or the degree of reflection in each correspondence relationship (hereinafter sometimes referred to as the reflection degree). And the correspondence relationship between the EGR valves 23 and 24 may be corrected according to the set reflection degree.

  A method for setting the reflection level will be described. FIG. 8 is a diagram showing the gas flow of each part in the engine 1 of FIG. The change in the pressure loss in the region A in FIG. 8, that is, the change in the pressure loss in the low pressure EGR passage 20 affects the flow rate of the first EGR gas. The change in the pressure loss in the regions B and C of FIG. 8, that is, the change in the pressure loss in the high pressure EGR passage 21, and the exhaust passage 4 between the exhaust extraction position of the high pressure EGR passage 21 and the exhaust extraction position of the low pressure EGR passage 20. The change in the pressure loss affects the flow rate of the second EGR gas. The change in the pressure loss in the region D in FIG. 8, that is, the change in the pressure loss in the exhaust passage 4 on the downstream side of the exhaust extraction position of the low pressure EGR passage 20 affects both the flow rate of the first EGR gas and the flow rate of the second EGR gas. give. The change in pressure loss in each of the regions A to D affects the flow rate of the first EGR gas and the flow rate of the second EGR gas, and thus affects the intake air temperature. Therefore, if the change in pressure loss in these regions A to D is replaced with the change in intake air temperature ΔTA to ΔTD, the intake air temperature and the reference value when the opening of the low pressure EGR valve 23 is adjusted to the target opening at the time of adaptation. As shown in the equation (1), the temperature difference ΔTH between the intake air temperature and the reference value when the opening of the high-pressure EGR valve 24 is adjusted to the target opening at the time of adaptation is expressed by the equation (2). ), Respectively.

ΔTL = ΔTA + ΔTD (1)
ΔTH = ΔTB + ΔTC + ΔTD (2)

  Here, assuming that the high-pressure EGR passage 21 is more easily clogged than the low-pressure EGR passage 20, it can be expressed as a function of the operation history of the engine 1, for example, the rotational speed NE, the torque Trq, or the operation time time of the engine 1. The relationship between the change in intake temperature ΔTBC (= ΔTB + ΔTC) corresponding to the change in pressure loss in region C and the change in intake temperature ΔTA corresponding to the change in pressure loss in region A is expressed by the following equation (3). Can do.

  ΔTBC / ΔTA = f (NE, Trq, time) (3)

  When the relationship of the expression (3) is replaced with a constant C, the expressions (3) ′ and (3) ″ can be derived.

ΔTBC / ΔTA = C (3) ′
ΔTBC = CΔTA (3) ''

  Substituting this equation (3) ″ into equation (2), the following equation (4) can be derived.

  ΔTH = CΔTA + ΔTD (4)

  Then, by subtracting the equation (4) from the equation (1), the change ΔTD in the intake air temperature corresponding to the change in the pressure loss in the region D can be expressed by the following equation (5).

  ΔTD = (ΔTL−CΔTH) / (1-C) (5)

  By substituting the relationship of the equation (5) into the equations (1) and (2), the change ΔTA in the intake air temperature corresponding to the change in the pressure loss in the region A is expressed by the equation (6). The change in the intake air temperature ΔTBC corresponding to the change in the pressure loss can be expressed by equation (7).

ΔTA = ΔTL− (ΔTL−CΔTH) / (1-C) (6)
ΔTBC = ΔTH− (ΔTL−CΔTH) / (1-C) (7)

When the opening of the low pressure EGR valve 23 is adjusted to the target opening at the time of adaptation, the temperature difference ΔTL between the intake air temperature and the reference value, and the opening of the high pressure EGR valve 24 are adjusted to the target opening at the time of adaptation. Since the temperature difference ΔTH between the intake air temperature and the reference value can be calculated by performing the correction method described above, since there are two unknowns and two equations, it corresponds to a change in pressure loss in the region A. It is possible to calculate the change ΔTAC in the intake air temperature corresponding to the change ΔTAC in the intake air temperature and the pressure loss in the regions B and C. The ratio between the change ΔTA in intake air temperature and the change ΔTBC in intake temperature corresponds to the degree to which the change in pressure loss in the exhaust passage 4 or the like changes the flow rate of the first EGR gas and the flow rate of the second EGR gas. Therefore, the degree of reflection on the correspondence relationship between the EGR valves 23 and 24 is set according to the ratio of the change ΔTAC of the intake air temperature and the change ΔTBC of the intake air temperature, and the EGR valves 23, 24 are set according to the set reflection degree. A correction amount used for correcting the corresponding relationship is set, and each corresponding relationship is corrected by the correction amount. In this case, the correspondence between the EGR valves 23 and 24 can be corrected with higher accuracy .

  Since soot and the like in the exhaust gas easily adhere to the exhaust purification catalyst 10, it can be considered that the change in pressure loss in the region C in FIG. 8 is almost determined by the degree of clogging of the exhaust purification catalyst 10. Therefore, the reflection degree may be set in consideration of the degree of clogging of the exhaust purification catalyst 10. In this case, the reflection degree can be set more easily.

  Even when the engine 1 is operating in the MPL mode, only the correspondence relationship of the low pressure EGR valve 23 may be corrected based on the temperature difference. The influence of the opening degree of the low pressure EGR valve 23 on the flow rate of the first EGR gas is larger than the influence of the opening degree of the high pressure EGR valve 24 on the flow rate of the second EGR gas. Therefore, only the correspondence relationship of the low pressure EGR valve 23 is corrected based on the temperature difference. In this case, since it is not necessary to consider the degree of reflection, the correspondence can be easily corrected.

This invention is not limited to each form mentioned above, It can implement with a various form. For example, the present invention is not limited to a diesel engine, and may be applied to various internal combustion engines that use gasoline or other fuels .

  In each embodiment described above, the correspondence is corrected according to the temperature of the intake air at the time of adaptation, but the pressure of the intake air and the flow rate of the intake air also change according to the amount of EGR gas introduced into the intake passage. Therefore, these values at the time of adaptation may be stored as a reference value, and the correspondence relationship may be corrected according to the stored reference value and the actually detected value.

In each embodiment described above, the adaptation is performed by setting the operation state of the engine 1 to the idling state, but the operation state at the time of adaptation is not limited to this state. For example, the adjustment may be performed in various operating states that can stabilize the temperature of the intake air during the correction period .

The figure which shows an example of the internal combustion engine in which the exhaust gas recirculation apparatus which concerns on the 1st form of this invention was integrated. The figure which shows an example of the correspondence of the opening degree of a low pressure EGR valve, and the flow volume of 1st EGR gas. The figure which shows an example of the relationship between the flow volume of 1st EGR gas, and intake air temperature. The flowchart which shows the correspondence learning routine which ECU of FIG. 1 performs. The figure which shows an example of the internal combustion engine in which the exhaust gas recirculation apparatus which concerns on the 2nd form of this invention was integrated. The flowchart which shows the correspondence learning routine which ECU of FIG. 5 performs. The figure which shows an example of the correspondence of each EGR mode and the driving | running state of an engine. The figure which shows the gas flow of each part in the engine of FIG.

Explanation of symbols

1 Internal combustion engine 3 Intake passage 4 Exhaust passage 7 Throttle valve 10 Exhaust purification catalyst 20 Low pressure EGR passage (first EGR passage)
21 High pressure EGR passage (second EGR passage)
23 low-pressure EGR valve 24 the high-pressure EGR valve 30 engine control unit (storage means, correcting hand stage)
32 Intake air temperature sensor (detection means)

Claims (4)

A first EGR passage for extracting a part of the exhaust from the exhaust passage and introducing it into the intake passage, and an exhaust extraction position is provided upstream of the exhaust passage from the exhaust extraction position of the first EGR passage, and the exhaust of the first EGR passage A second EGR passage in which an exhaust introduction position is provided downstream from the introduction position, a first EGR valve for adjusting a flow rate of exhaust gas recirculated to the intake passage through the first EGR passage, and the second EGR passage. An exhaust gas recirculation device for an internal combustion engine, comprising: a second EGR valve that adjusts a flow rate of exhaust gas recirculated to the intake passage through
A detecting means disposed downstream of the intake passage from the exhaust introduction position of the first EGR passage and detecting a physical quantity of intake air that changes in accordance with a flow rate of the exhaust gas introduced into the intake passage; and an operating state of the internal combustion engine. The exhaust gas having a target flow rate corresponding to the predetermined state is introduced into the intake passage through the first EGR passage in a predetermined state and in a state where the opening degree of the second EGR valve is kept fully closed. The opening degree of the first EGR valve when the adjustment for adjusting the opening degree of the first EGR valve is performed is stored as a target opening degree, and the physical quantity value of the intake air detected by the detecting means at the time of the adaptation is used as a reference. Storage means stored as a value; adjusting the opening of the first EGR valve to the target opening; adjusting the opening of the second EGR valve to fully closed; The opening degree of the first EGR valve and the first EGR passage based on the difference between the value of the physical quantity of the intake air detected by the detection means and the reference value stored in the storage means when adjusted to a constant state An exhaust gas recirculation device for an internal combustion engine, comprising: correction means for correcting a correspondence relationship with a flow rate of the first EGR gas that is exhaust gas introduced into the intake passage through the exhaust gas. A first EGR passage for extracting a part of the exhaust from the exhaust passage and introducing it into the intake passage, and an exhaust extraction position is provided upstream of the exhaust passage from the exhaust extraction position of the first EGR passage, and the exhaust of the first EGR passage A second EGR passage in which an exhaust introduction position is provided downstream from the introduction position, a first EGR valve for adjusting a flow rate of exhaust gas recirculated to the intake passage through the first EGR passage, and the second EGR passage. An exhaust gas recirculation device for an internal combustion engine, comprising: a second EGR valve that adjusts a flow rate of exhaust gas recirculated to the intake passage through
A detecting means disposed downstream of the intake passage from the exhaust introduction position of the second EGR passage and detecting a physical quantity of intake air that changes in accordance with a flow rate of the exhaust gas introduced into the intake passage; and an operating state of the internal combustion engine. The exhaust gas having a target flow rate corresponding to the predetermined state is introduced into the intake passage through the second EGR passage in a predetermined state and in a state in which the opening degree of the first EGR valve is kept fully closed. The opening degree of the second EGR valve when the adjustment for adjusting the opening degree of the second EGR valve is performed is stored as a target opening degree, and the value of the physical quantity of the intake air detected by the detection means at the time of the adaptation is used as a reference Storage means stored as a value, the opening degree of the first EGR valve is adjusted to be fully closed, the opening degree of the second EGR valve is adjusted to the target opening degree, and the operating state of the internal combustion engine is The opening degree of the second EGR valve and the second EGR passage based on the difference between the value of the physical quantity of the intake air detected by the detection means and the reference value stored in the storage means when adjusted to a constant state An exhaust gas recirculation device for an internal combustion engine, comprising: correction means for correcting a correspondence relationship with a flow rate of the second EGR gas that is exhaust gas introduced into the intake passage via the exhaust gas. The physical quantity of the intake air is the intake air temperature,
The correction means is introduced into the intake passage through an EGR passage provided with an EGR valve to be corrected when the temperature of the intake air detected by the detection means is higher than a reference value stored in the storage means. Correcting the correspondence between the opening degree of the EGR valve to be corrected and the flow rate of the exhaust gas introduced into the intake passage through the EGR passage provided with the EGR valve so that the flow rate of the exhaust gas is reduced. The exhaust gas recirculation device for an internal combustion engine according to claim 1 or 2, wherein the exhaust gas recirculation device is an internal combustion engine. The exhaust gas recirculation device for an internal combustion engine according to claim 1 , wherein the physical quantity of the intake air is an intake air pressure or an intake air flow rate.

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