JP2009013872A - Intake control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an intake control device for an internal combustion engine which is equipped with two passages provided to branch the intake passage and selectively switches the passages at introduction and stop of EGR gas without deteriorating exhaust emission and combustion state of the internal combustion engine. <P>SOLUTION: An intake control device is applied to an internal combustion engine 1 equipped with a first branch passage 9 and second branch passage 10 which are provided to the lower reaches from a connection position in a low pressure EGR passage 20 so as to branch an intake passage 3, and introduces intake to a cylinder 2 through the first branch passage 9 when introducing EGR gas and trough the second branch passage 10 when stopping the EGR gas, wherein a first main regulating valve 11 and second main regulating valve 13 are gradually closed from fully opened positions to totally closed positions, respectively, and a first fresh air regulating valve 14 and second fresh air regulating valve 16 are gradually opened from totally closed positions to fully opened positions, respectively, when switching intake flow from the first branch passage 9 to the second branch passage 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an EGR passage that guides part of the exhaust gas from the exhaust passage to the intake passage as EGR gas, and a first passage and a second passage provided to branch the intake passage downstream from the connection position of the EGR passage, And an intake control device for an internal combustion engine.

  In the intake passage, an intercooler and a bypass passage that bypasses the intercooler and is shorter than the intake pipe provided with the intercooler are provided, and when the internal combustion engine is requested to accelerate and the EGR valve is closed, the intercooler An exhaust gas recirculation device that suppresses the introduction delay of fresh air by suppressing the inflow of intake air to the cylinder and guiding the intake air to the cylinder through a bypass passage is known (see Patent Document 1). In addition, Patent Documents 2 and 3 exist as prior art documents related to the present invention.

JP-A-2005-146919 JP 07-279778 A JP 2004-251201 A

  In an internal combustion engine in which two branch passages parallel to each other are provided in the intake passage as in the internal combustion engine of Patent Document 1 and these passages are selectively switched between when EGR gas is introduced and when the EGR gas is stopped, the entrance / exit of passages that are not used Some of them are fully closed. When the entrance / exit of the passage is fully closed in this way, the intake air flowing in the passage when the passage is in use is confined in the passage when the entrance / exit is fully closed. If the inlet / outlet is suddenly fully opened for use, the intake air confined in the passage flows into the cylinder at a time, which may deteriorate the combustion state and exhaust emission of the internal combustion engine. For example, the intake air confined in the passage is an intake air containing a large amount of EGR gas, and the intake air previously guided to the cylinder is an intake air that does not contain EGR gas (hereinafter sometimes referred to as fresh air). In such a case, the intake air containing a large amount of EGR gas is suddenly introduced into the cylinder, which causes the combustion state of the internal combustion engine to deteriorate or the amount of fuel supplied to the cylinder to be adjusted in time, resulting in smoke, etc. Exhaust emissions may deteriorate.

  Therefore, the present invention includes two passages provided so as to branch the intake passage, and in an internal combustion engine that selectively switches between when EGR gas is introduced and when it is stopped, the combustion state and exhaust emission of the internal combustion engine An object of the present invention is to provide an intake control device for an internal combustion engine capable of switching passages without deteriorating the engine.

  An intake control apparatus for an internal combustion engine according to the present invention includes an EGR passage that guides a part of exhaust gas from the exhaust passage to the intake passage as EGR gas, and an EGR valve that adjusts the flow rate of EGR gas that is guided from the EGR passage to the intake passage. Applied to an internal combustion engine including a first passage and a second passage provided so as to branch off the intake passage downstream from a connection position of the EGR passage, and an inlet and an outlet of the first passage are respectively opened. And can be switched between a first state in which the inlet and outlet of the second passage are closed and a second state in which the inlet and outlet of the first passage are closed and the inlet and outlet of the second passage are respectively opened. And when the EGR valve is open, the valve means is switched to the first state, and when the EGR valve is closed, the valve means And a control means for controlling the operation of the valve means to be switched to the second state, wherein the control means changes the state of the valve means to the first state and the first state. When switching from one of the two states to the other, the flow rate of the intake air led to the cylinders of the internal combustion engine gradually increases through the passages in which the inlet and the outlet are closed in the one state, respectively. By controlling the operation of the valve means so that the flow rate of the intake air guided to the cylinder of the internal combustion engine through the passages in which the inlet and the outlet are opened in the one state is gradually reduced, the above-described problem can be solved. This is solved (claim 1).

  According to the intake control device of the present invention, when the state of the valve means is switched, the flow rate of the intake air led to the cylinder through the passage where the inlet / outlet has been closed is gradually increased, so that it is confined in the passage. It is possible to prevent intake air from flowing into the cylinder at a time. Further, since the flow rate of the intake air led to the cylinder through the passage that has previously been opened and closed is gradually reduced, it is possible to prevent the intake air from being suddenly reduced. Therefore, the passage can be switched while preventing the combustion state of the internal combustion engine and the exhaust emission from deteriorating.

  In one form of the intake control device of the present invention, the turbocharger is provided in the intake passage downstream from the connection position of the EGR passage and upstream from the branch point where the intake passage branches into the first passage and the second passage. A pressure detection means provided so as to detect the pressure in the intake passage downstream from the compressor when the valve means is in the second state, and the state of the valve means is the second state. Storage means for storing the pressure detected by the pressure detection means when switching from the first state to the first state, and the control means is a predetermined switch for switching the valve means from the first state to the second state. When the state switching condition is satisfied, the higher the pressure stored in the storage means when the valve means was last switched from the second state to the first state, the higher the pressure means stored in the storage means. An increase in the flow rate of intake air led to the internal combustion engine via the second passage when switching from the state to the second state and the flow rate of intake air led to the internal combustion engine via the first passage The operation of the valve means may be controlled such that the amount of decrease per unit time becomes smaller. In general, the EGR valve is closed when a high output is required for the internal combustion engine. In such a case, the rotational speed of the turbocharger increases and the pressure in the intake passage increases. When the EGR valve is opened in such an operating state, the valve means is switched from the second state to the first state, so that intake air with high pressure is confined in the second passage. The higher the pressure of the intake air confined in the second passage, the easier the intake air is suddenly ejected from the second passage when the valve state is next switched from the first state to the second state. In this embodiment, the pressure when the valve means was switched from the second state to the first state last time is stored in the storage means, and the higher the pressure is, the more the internal combustion engine passes through the second passage when the valve means is switched. Since the amount of increase in the flow rate of the introduced intake air per unit time is reduced, it is possible to appropriately suppress the intake air trapped in the second passage from flowing into the cylinder at a time. Therefore, the control accuracy of the amount of fresh air flowing into the cylinder can be improved, and the amount of fresh air can be increased smoothly.

  In this form, the pressure control device further comprises pressure difference acquisition means for detecting a pressure in the first passage and a pressure in the second passage, and acquiring a pressure difference which is a difference between the detected pressures. When the predetermined state switching condition is satisfied, the larger the pressure difference acquired by the pressure difference acquisition means, the larger the pressure difference, the more the valve means is switched from the first state to the second state. The valve means so that the increase amount per unit time of the flow rate of intake air led to the internal combustion engine and the decrease amount per unit time of the flow rate of intake air led to the internal combustion engine via the first passage are further reduced. May be controlled (claim 3). In this way, the increase amount per unit time of the flow rate of the intake air guided to the internal combustion engine through the second passage at the time of switching the valve means in consideration of the pressure in the first passage in addition to the pressure in the second passage. By adjusting, the control accuracy of the amount of fresh air flowing into the cylinder can be further improved.

  Further, when the pressure in the second passage detected by the pressure difference acquisition means when the predetermined state switching condition is satisfied is lower than the pressure in the first passage, the second of the valve means by the control means. The apparatus may further include a prohibiting unit that prohibits switching to the state (claim 4). When the valve means is switched from the first state to the second state when the pressure in the second passage is lower than the pressure in the first passage, the intake air first increases until the pressure in the second passage becomes the pressure in the first passage. It flows into two passages and then begins to flow into the cylinder. Therefore, the time required for the intake air to flow into the cylinder becomes longer. In this case, since the reaction of the internal combustion engine is delayed with respect to the operation of the driver, drivability may be deteriorated. In this embodiment, when the predetermined state switching condition is satisfied, if the pressure in the second passage is lower than the pressure in the first passage, switching to the second state of the valve means is prohibited, so that deterioration of drivability can be prevented. .

  In one form of the intake control device of the present invention, the intake control device further comprises an intake amount acquisition means for acquiring an intake amount flowing into the cylinder of the internal combustion engine, wherein the control means sets the state of the valve means to the first state and the When switching from one state of the second states to the other state, the inlet and the outlet are closed in the one state based on the intake air amount acquired by the intake air amount acquiring means, respectively. The flow rate of the intake air guided to the cylinder of the internal combustion engine and the flow rate of the intake air guided to the cylinder of the internal combustion engine through the passages in which the inlet and the outlet are opened in the one state are adjusted to the respective target flow rates. Further, a feedback correction means for correcting the operation of the valve means may be provided (claim 5). As is well known, the correspondence between the opening degree of the valve means and the flow rate passing through the valve means at the opening degree changes due to deterioration over time. In this embodiment, the amount of intake air flowing into the cylinder is acquired, and the operation of the valve means is corrected based on the amount of intake air. Therefore, even if the correspondence between the opening degree of the valve means and the flow rate changes, the state of the valve means It is possible to appropriately control the flow rate of the intake air that should pass through each passage at the time of switching. Therefore, it is possible to switch the passage while more reliably preventing deterioration of the combustion state and exhaust emission of the internal combustion engine.

  As described above, according to the intake control device of the present invention, when the state of the valve means is switched, the flow rate of the intake air guided to the cylinder through the passage where the inlet / outlet has been closed is gradually increased. The passage can be switched while preventing the combustion state of the internal combustion engine and the exhaust emission from deteriorating.

  FIG. 1 shows an example of an internal combustion engine in which an intake air control device according to an 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. The intake passage 3 is provided with 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, and a compressor 8a of the turbocharger 8. ing.

  As shown in FIG. 1, the intake passage 3 branches at a branch point 3a set downstream of the compressor 8a and joins at a junction point 3b set downstream of the branch point 3a. A first branch passage 9 and a second branch passage 10 as a second passage are provided. The first branch passage 9 includes a first main regulating valve 11 provided at the inlet of the first branch passage 9, a first intercooler 12 for cooling the intake air, and a first main valve provided at the outlet of the first branch passage 9. 2 main adjusting valve 13 is provided. The second branch passage 10 is provided at the first fresh air regulating valve 14 provided at the inlet of the second branch passage 10, the second intercooler 15 for cooling the intake air, and the outlet of the second branch passage 10. A second fresh air adjustment valve 16 is provided. As the first main adjustment valve 11, the second main adjustment valve 13, the first fresh air adjustment valve 14, and the second fresh air adjustment valve 16, all the intake passages at positions where these valves are provided are fully closed. A valve capable of adjusting the opening degree between the closed position and the fully opened position for fully opening the intake passage is provided.

  The exhaust passage 4 is provided with a turbine 8b of the turbocharger 8, an exhaust purification catalyst 17 for purifying exhaust, and an exhaust throttle valve 18 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 11 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 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 an EGR valve that adjusts the flow rate. The high-pressure EGR passage 21 is provided with a high-pressure EGR valve 24 that adjusts 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. .

  The operations of the first main adjustment valve 11, the second main adjustment valve 13, the first fresh air adjustment valve 14, the second fresh air adjustment valve 16, and the EGR valves 23 and 24 are performed by an engine control unit (ECU) 30. Each is controlled. 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 EGR valve 23, 24 is controlled so that EGR gas having a predetermined flow rate set according to the operating state of the engine 1 is introduced into the intake passage 3. For example, a crank angle sensor 31 that outputs a signal corresponding to the crank angle, and a first pressure sensor that outputs a signal corresponding to the pressure in the first branch passage 9 are used as sensors to be referred to when performing such control. 32, a second pressure sensor 33 serving as a pressure detecting means for outputting a signal corresponding to the pressure in the second branch passage 10, the air flow meter 6, and the like are connected. In addition, the ECU 30 is connected to a differential pressure sensor 34 that outputs a signal corresponding to the differential pressure before and after the exhaust purification catalyst 10, an accelerator opening sensor 35 that outputs a signal corresponding to the accelerator opening, and the like.

  The ECU 30 includes the first main adjustment valve 11, the second main adjustment valve 13, the first main adjustment valve 11 so that only intake air including EGR gas flows through the first branch passage 9 and only fresh air flows through the second branch passage 10. The respective operations of the fresh air adjustment valve 14 and the second fresh air adjustment valve 16 are controlled. For example, when the low pressure EGR valve 23 is opened and the first EGR gas is guided to the intake passage 3, the first main adjustment valve 11 and the second main adjustment valve 13 are switched to the fully opened positions and the first fresh air adjustment is performed. The valve 14 and the second fresh air adjustment valve 16 are each switched to the fully closed position. By controlling the valves 11, 13, 14, and 16 in this way, the entire amount of intake air is guided to the cylinder 2 through the first branch passage 9. Hereinafter, the intake air introduction state in which the state of each valve 11, 13, 14, 16 is switched and the intake air is introduced into the cylinder 2 in this way may be referred to as a first state. On the other hand, when the low pressure EGR valve 23 is controlled to be fully closed and the introduction of the first EGR gas into the intake passage 3 is stopped, the first main adjustment valve 11 and the second main adjustment valve 13 are respectively switched to the fully closed position. At the same time, the first fresh air adjustment valve 14 and the second fresh air adjustment valve 16 are respectively switched to the fully open position. In this case, the entire amount of intake air is guided to the cylinder 2 via the second branch passage 10. Hereinafter, this intake state may be referred to as a second state. By switching the intake air introduction state in this way, the first main regulating valve 11, the second main regulating valve 13, the first fresh air regulating valve 14, and the second fresh air regulating valve 16 correspond to the valve means of the present invention. .

  FIG. 2 shows an intake air introduction state control routine that is repeatedly executed at a predetermined cycle during operation of the engine 1 so that the ECU 30 switches the intake air introduction state to the first state or the second state according to the operation state of the engine 1. . By executing this control routine, the ECU 30 functions as the control means of the present invention.

  In the control routine of FIG. 2, the ECU 30 first acquires the operating state of the engine 1 in step S11. In the next step S12, the ECU 30 determines whether or not a fresh air introduction condition for switching the intake air introduction state from the first state to the second state is satisfied. The new air introduction condition is that, for example, the accelerator opening is opened and the engine 1 is required to be accelerated, and the EGR valves 23 and 24 are fully opened from the open state to stop the introduction of the EGR gas into the intake passage 3. It is judged that it was established when switching to. When it is determined that the fresh air introduction condition is satisfied, the process proceeds to step S13, where the ECU 30 switches the intake air introduction state from the first state to the second state, that is, the first main adjustment valve 11 and the second main adjustment valve 13 are fully opened. A fresh air introduction control is performed in which the first fresh air adjustment valve 14 and the second fresh air adjustment valve 16 are switched from the fully closed position to the fully open position while switching from the position to the fully closed position. When the intake air introduction state has already been switched to the second state, the intake air introduction state is maintained. Thereafter, the current control routine is terminated.

  The fresh air introduction control will be described with reference to FIGS. FIG. 3 is a schematic diagram of the engine 1 showing only the parts related to the fresh air introduction control among the respective parts of the engine 1. 3 that are the same as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted. In FIG. 3, the compressor 8a and the turbine 8b are shown separately for convenience of illustration. As shown in FIG. 3, each cylinder 2 is provided with an injector 41 in which a piston 40 is inserted and fuel is injected into the cylinder 2. An intake valve 42 that opens and closes the intake passage 3 for the cylinder 2 and an exhaust valve 43 that opens and closes the exhaust passage 4 for the cylinder 2 are provided. FIG. 4 shows the accelerator opening when the intake intake state is switched from the first state to the second state in the fresh air introduction control from the top, the flow rate of the intake air flowing into the cylinder 2, and the opening of the low pressure EGR valve 23. An example of each time change of the opening degree of the first fresh air regulating valve 14, the opening degree of the second fresh air regulating valve 16, the opening degree of the first main regulating valve 11, and the opening degree of the second main regulating valve 13 Is shown. When the accelerator opening is opened at time T1 in FIG. 4, the low pressure EGR valve 23 is switched from the open state to the fully closed state, and it is determined that the fresh air introduction condition is satisfied. As a result, fresh air introduction control is started, and the first main adjustment valve 11 and the second main adjustment valve 13 are gradually closed from the fully open position to the fully closed position from time T1 to time T2, as shown in FIG. At the same time, the first fresh air adjustment valve 14 and the second fresh air adjustment valve 16 are gradually opened from the fully closed position to the fully opened position, respectively. Thus, by adjusting the opening degree of each of the valves 11, 13, 14, and 16, the flow rate of the intake air guided to the cylinder 2 through the first branch passage 9 is gradually reduced and the second branch passage 10 is used. The flow rate of the intake air guided to the cylinder 2 can be gradually increased.

  When the opening degree of each of the valves 11, 13, 14, and 16 is changed from time T1 in FIG. 4, the intake passage (hereinafter referred to as the downstream portion) between the junction 3b and the inlet of the cylinder 2 is first introduced into the cylinder 2. ) C intake air flows in. Since the intake air in the downstream portion C is intake air containing EGR gas, air and EGR gas flow into the cylinder 2 as shown in the second diagram from the top in FIG. Next, the intake air from the intake passage (hereinafter sometimes referred to as an intermediate portion) B between the branch point 3a and the junction 3b flows into the cylinder 2. The intermediate portion B includes a first branch passage 9 and a second branch passage 10, and as described above, the first main adjustment valve 11 and the second main adjustment valve 13 are gradually moved from the fully open position to the fully closed position, respectively. And the first fresh air regulating valve 14 and the second fresh air regulating valve 16 are gradually opened from the fully closed position to the fully opened position, so that the intake air containing EGR gas from the first branch passage 9. Is introduced to the cylinder 2 while gradually reducing the amount thereof, and fresh air is introduced from the second branch passage 10 to the cylinder 2 while gradually increasing the amount thereof. Therefore, as shown at times T3 to T2 in FIG. 4, the amount of EGR gas in the intake air flowing into the cylinder 2 can be gradually decreased and the amount of air in the intake air can be gradually increased. Thereafter, the intake air of the intake passage (hereinafter sometimes referred to as the upstream portion) A between the connection position of the low pressure EGR passage 20 and the branch point 3a is introduced into the cylinder 2. At this time, since the low pressure EGR valve 23 has already been switched to the fully closed state, only the fresh air that has been increased by the control on the opening side of the throttle valve 7 accompanying the increase in the accelerator opening, that is, only air is introduced into the cylinder 2. .

  Returning to FIG. 2, the description of the intake air introduction state control routine will be continued. When it is determined in step S12 that the fresh air introduction condition is not satisfied, the process proceeds to step S14, and the ECU 30 determines whether an EGR gas introduction condition for switching the intake air introduction state from the second state to the first state is satisfied. It is determined that the EGR gas introduction condition is satisfied when, for example, the engine 1 is requested to decelerate and the EGR valves 23 and 24 are switched from the fully closed state to the open state to introduce the EGR gas into the intake passage 3. The If it is determined that the EGR gas introduction condition is not satisfied, the current control routine is terminated. On the other hand, when it is determined that the EGR gas introduction condition is satisfied, the process proceeds to step S15, where the ECU 30 switches the intake air introduction state from the second state to the first state, that is, the first main adjustment valve 11 and the second main adjustment valve 13 are switched. EGR gas introduction control for switching from the fully closed position to the fully open position and switching the first fresh air adjustment valve 14 and the second fresh air adjustment valve 16 from the fully open position to the fully closed position is executed. When the intake air introduction state has already been switched to the first state, the intake air introduction state is maintained. Thereafter, the current control routine is terminated.

  In the EGR gas introduction control, the first main regulating valve 11 and the second main regulating valve 13 are gradually opened from the fully closed position to the fully opened position, and the first fresh air regulating valve 14 and the second fresh air regulating valve 16 are respectively opened. Are gradually closed from the fully open position to the fully closed position. In the second state, the intake air in both the upstream part A and the downstream part C is fresh air, and the EGR gas is only the amount confined in the first branch passage 9 of the intermediate part B. Even if the first main adjustment valve 11 and the second main adjustment valve 13 are suddenly opened from the fully closed position to the fully opened position, the amount of EGR gas flowing into the cylinder 2 is small, and the operation state of the engine 1 is hardly affected. It is thought not to give. Therefore, in the EGR gas introduction control, the first main adjustment valve 11 and the second main adjustment valve 13 are each suddenly opened from the fully closed position to the fully open position, and the first fresh air adjustment valve 14 and the second fresh air adjustment are performed. The valves 16 may each be suddenly closed from the fully open position to the fully closed position.

  FIG. 5 shows that the first main adjustment valve 11 and the second main adjustment valve 13 are suddenly closed from the fully open position to the fully closed position when the intake air introduction state is switched from the first state to the second state as a comparative example. When the first fresh air regulating valve 14 and the second fresh air regulating valve 16 are suddenly opened from the fully closed position to the fully opened position, the accelerator opening, the flow rate of the intake air flowing into the cylinder 2, and the low pressure EGR valve 23 Time variations of the opening, the opening of the first fresh air adjustment valve 14, the opening of the second fresh air adjustment valve 16, the opening of the first main adjustment valve 11, and the opening of the second main adjustment valve 13 An example is shown. 5 that are the same as those in FIG. 4 are denoted by the same reference numerals and description thereof is omitted. When the opening of each valve 11, 13, 14, 16 is suddenly changed in this way, the time when the intake of the downstream portion C ends and the intake of the intermediate portion B starts flowing as shown in FIG. Since fresh air confined in the second branch passage 10 is introduced from T11, the ratio of EGR gas in the intake air becomes zero. Thereafter, since the intake air of the upstream portion A including the EGR gas is introduced from the time T12 when the introduction of the intake air in the intermediate portion B ends, the ratio of the EGR gas in the intake air flowing into the cylinder 2 increases rapidly. Then, the introduction of only fresh air is started from time T13 when the introduction of the intake air in the upstream portion A ends. Thus, if the ratio of EGR gas in the intake air flowing into the cylinder 2 changes suddenly in a short time, the control of the amount of fuel supplied into the cylinder 2 cannot catch up, and the combustion state of the engine 1 may become unstable. Therefore, exhaust emission may be deteriorated. Further, in this case, fresh air is introduced into the cylinder 2 during the period of time T11 to T12, and the output of the engine 1 temporarily rises. Thereafter, EGR gas is reintroduced at time T12 to T13, and the output of the engine 1 decreases. Therefore, drivability may be deteriorated.

  As described above, when the control routine of FIG. 2 is executed and the intake air introduction state is switched from the first state to the second state, the first main adjustment valve 11 and the second main adjustment valve 13 are all opened from the fully open position. By gradually closing the first fresh air regulating valve 14 and the second fresh air regulating valve 16 from the fully closed position to the fully opened position, the second diagram from the top of FIG. As shown in Fig. 5, the ratio of the amount of air in the intake air can be increased smoothly. Therefore, it is possible to switch the passage through which the intake air is passed while preventing the combustion state of the engine 1 and the exhaust emission from deteriorating.

  The control method of each valve 11, 13, 14, 16 at the time of intake air introduction control is not limited to the method described above. For example, the pressure in the second branch passage 10 when the intake air introduction state is switched from the second state to the first state is detected by the second pressure sensor 32 and stored in the RAM of the ECU 30, and then the intake air introduction is performed. When the stored pressure is higher when the state is switched from the first state to the second state, the first main adjustment valve 11 and the second main adjustment valve 13 are gradually closed from the fully open position to the fully closed position, respectively. The amount of change in opening per unit time is reduced, and the opening per unit time when the first fresh air adjustment valve 14 and the second fresh air adjustment valve 16 are gradually opened from the fully closed position to the fully open position, respectively. The amount of change may be reduced. By adjusting the opening change amount in this way, the higher the stored pressure, the smaller the increase amount per unit time of the flow rate of the intake air guided to the engine 1 through the second branch passage 10, and the first branch A reduction amount per unit time of the flow rate of the intake air guided to the engine 1 through the passage 9 can be reduced.

  As the pressure of the intake air trapped in the second branch passage 10 is higher, the intake air is ejected from the second branch passage 10 when the first fresh air adjustment valve 14 and the second fresh air adjustment valve 16 are opened. It becomes easy. Therefore, by adjusting the opening change amount of each valve 11, 13, 14, 16 in this way, it is possible to appropriately suppress the intake air trapped in the second branch passage 10 from flowing into the cylinder 2 at a time. . Therefore, the control accuracy of the amount of air flowing into the cylinder 2 can be improved. Note that by storing the pressure in this way, the ECU 30 functions as the storage means of the present invention.

  Further, the ECU 30 calculates a pressure difference, which is a difference between the pressure in the first branch passage 9 and the pressure in the second branch passage 10, and the larger the calculated pressure difference is, the first main adjustment valve 11 and the second main control valve 11 are. The opening change amount per unit time when the regulating valve 13 is gradually closed from the fully open position to the fully closed position is corrected to be smaller, and the first fresh air regulating valve 14 and the second fresh air regulating valve 16 are adjusted. The opening change amount per unit time when the valve is gradually opened from the fully closed position to the fully open position may be corrected to be smaller. By this correction, the increase amount per unit time of the flow rate of the intake air guided to the engine 1 via the second branch passage 10 when the intake air introduction state is switched from the first state to the second state can be further reduced, and the first branch A reduction amount per unit time of the flow rate of the intake air guided to the engine 1 through the passage 9 can be further reduced.

  The amount of intake air ejected from the second branch passage 10 when the first fresh air adjustment valve 14 and the second fresh air adjustment valve 16 are opened is also affected by the first branch passage 9, and the larger the pressure difference is, The amount of inhaled air increases. Therefore, the control accuracy of the amount of air flowing into the cylinder 2 can be further improved by considering the pressure in the first branch passage 9 in this way. By calculating the pressure difference in this way, the ECU 30 functions as a pressure difference acquisition unit of the present invention.

  When switching the intake air introduction state from the first state to the second state, if the pressure in the second branch passage 10 is lower than the pressure in the first branch passage 9, switching the intake air introduction state to the second state is prohibited. Also good. When the pressure in the second branch passage 10 is lower than the pressure in the first branch passage 9, when the first fresh air adjustment valve 14 and the second fresh air adjustment valve 16 are opened, the intake air is first second. The intake air begins to flow into the cylinder 2 after being sucked into the branch passage 10 and then the pressure in the second branch passage 10 changes to the pressure in the first branch passage 9. Therefore, the time required for the intake air to flow into the cylinder 2 becomes longer, and drivability may be deteriorated. Therefore, in such a case, switching from the intake air introduction state to the second state is prohibited. Thereby, deterioration of drivability can be prevented. By prohibiting switching as described above, the ECU 30 functions as the prohibiting means of the present invention.

  As is well known, the correlation between the opening degree of each valve 11, 13, 14, 16 and the flow rate passing through the valve at that opening degree changes due to deterioration over time. Therefore, the intake air amount that flows into the cylinder 2 when the intake air introduction state is switched from the first state to the second state is acquired, and the opening degree of each valve 11, 13, 14, 16 based on the acquired intake air amount. May be feedback corrected. The amount of intake air flowing into the cylinder 2 may be acquired by providing a sensor in an intake manifold (hereinafter sometimes referred to as intake manifold) 50 that forms a part of the intake passage 3, for example. It may be estimated by a known estimation method that estimates based on the internal pressure, the temperature of the intake air in the intake manifold 50, the intake air amount detected by the air flow meter 6, and the like. By estimating the intake air amount in this way, the ECU 30 functions as the intake air amount acquisition means of the present invention. In this feedback correction, for example, the time change in the ratio of EGR gas in the intake air and the time change in the air ratio in the intake air shown in the second diagram from the top in FIG. 4 are respectively stored in the ROM of the ECU 30 as a map. Then, the operation of each valve 11, 13, 14, 16 is corrected so that the ratio of EGR gas during intake and the ratio of air during intake change with the time change of this map. As a result, the flow rate of the intake air introduced into the engine 1 via the second branch passage 10 and the flow rate of the intake air introduced into the engine 1 via the first branch passage 9 during the fresh air introduction control are controlled by the EGR gas in the intake air. The ratio and the ratio of air in the intake air can be adjusted to the target flow rate that changes with the time change shown in the map.

  By performing feedback correction in this way, the ratio of EGR gas in the intake air during the fresh air introduction control and the intake air even when the correspondence between the opening degree and the flow rate of each valve 11, 13, 14, 16 is changed. Therefore, the combustion state of the engine 1 and the deterioration of exhaust emission can be more reliably prevented. In addition, by performing feedback correction in this way, the ECU 30 functions as feedback correction means of the present invention.

  The present invention is not limited to the above-described form and can be implemented in various forms. 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. The valve means for switching the flow of intake air to the first branch passage or the second branch passage is not limited to the valve means of the above-described form. For example, various valves such as a three-way valve that can selectively switch the flow of intake air to the first branch passage or the second branch passage may be used.

The figure which shows an example of the internal combustion engine in which the intake control device which concerns on one form of this invention was integrated. The flowchart which shows the intake air introduction state control routine which ECU of FIG. 1 performs. The schematic of the engine which showed only the part relevant to fresh air introduction control among each part of the engine of FIG. The accelerator opening when the intake air introduction state is switched from the first state to the second state by the fresh air introduction control, the flow rate of the intake air flowing into the cylinder, the opening degree of the low pressure EGR valve, the opening of the first fresh air adjustment valve The figure which shows an example of each time change of a degree, the opening degree of a 2nd fresh air adjustment valve, the opening degree of a 1st main adjustment valve, and the opening degree of a 2nd main adjustment valve. When the intake intake state is switched from the first state to the second state, the first main adjustment valve and the second main adjustment valve are each suddenly closed from the fully open position to the fully closed position, and the first fresh air adjustment valve and the second Accelerator opening when the fresh air regulating valve is suddenly opened from the fully closed position to the fully opened position, the flow rate of the intake air flowing into the cylinder, the opening of the low pressure EGR valve, the opening of the first fresh air regulating valve, The figure which shows an example of each time change of the opening degree of a 2nd fresh air adjustment valve, the opening degree of a 1st main adjustment valve, and the opening degree of a 2nd main adjustment valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Intake passage 3a Branch point 4 Exhaust passage 8 Turbo supercharger 8a Compressor 9 1st branch passage 10 2nd branch passage 11 1st main adjustment valve (valve means)
13 Second main regulating valve (valve means)
14 First fresh air regulating valve (valve means)
16 Second fresh air regulating valve (valve means)
20 Low pressure EGR passage (EGR passage)
23 Low pressure EGR valve (EGR valve)
30 Engine control unit (control means, storage means, pressure difference acquisition means, prohibition means, intake air amount acquisition means, feedback correction means)
32 1st pressure sensor 33 2nd pressure sensor (pressure detection means)

Claims (5)

An EGR passage for leading part of the exhaust gas from the exhaust passage to the intake passage as EGR gas, an EGR valve for adjusting the flow rate of the EGR gas guided from the EGR passage to the intake passage, and the downstream of the connection position of the EGR passage. Applied to an internal combustion engine including a first passage and a second passage provided to branch the intake passage;
The first state where the inlet and outlet of the first passage are opened and the inlet and outlet of the second passage are closed respectively, and the inlet and outlet of the second passage are closed and the inlet and outlet of the second passage are closed respectively. Valve means that can be switched to a second state in which the valve is opened, and when the EGR valve is open, the valve means is switched to the first state, and when the EGR valve is closed, the valve means is An intake control device for an internal combustion engine comprising: control means for controlling the operation of the valve means so as to be switched to the second state;
When the control means switches the state of the valve means from one state of the first state and the second state to the other state, the control means passes through the passages in which the inlet and the outlet are closed in the one state, respectively. The flow rate of the intake air guided to the cylinder of the internal combustion engine gradually increases through the passage, and the flow rate of the intake air guided to the cylinder of the internal combustion engine through the passage in which the inlet and the outlet are opened in the one state is gradually decreased. An intake control device for an internal combustion engine, wherein the operation of the valve means is controlled as described above. A turbocharger compressor is provided in the intake passage downstream from the connection position of the EGR passage and upstream from the branch point where the intake passage branches into the first passage and the second passage,
Pressure detecting means provided so as to be able to detect the pressure in the intake passage downstream from the compressor when the valve means is in the second state, and the state of the valve means is switched from the second state to the first state Storage means for storing the pressure detected by the pressure detection means when
The control means, when a predetermined state switching condition for switching the valve means from the first state to the second state is satisfied, when the valve means was previously switched from the second state to the first state, As the pressure stored in the storage means is higher, the increase amount per unit time of the flow rate of the intake air guided to the internal combustion engine via the second passage when the valve means is switched from the first state to the second state. 2. The internal combustion engine according to claim 1, wherein the operation of the valve means is controlled such that a reduction amount per unit time of the flow rate of the intake air guided to the internal combustion engine via the first passage is reduced. Engine intake control device. A pressure difference acquisition means for detecting a pressure in the first passage and a pressure in the second passage and acquiring a pressure difference that is a difference between the detected pressures;
When the predetermined state switching condition is satisfied, the control unit is configured to switch the valve unit from the first state to the second state as the pressure difference acquired by the pressure difference acquisition unit increases. An increase amount per unit time of the flow rate of intake air guided to the internal combustion engine via the passage and a decrease amount per unit time of the flow rate of intake air guided to the internal combustion engine via the first passage are further reduced. 3. The intake control apparatus for an internal combustion engine according to claim 2, wherein the operation of the valve means is controlled.   When the pressure in the second passage detected by the pressure difference acquisition means when the predetermined state switching condition is satisfied is lower than the pressure in the first passage, the control means shifts the valve means to the second state. The intake control device for an internal combustion engine according to claim 3, further comprising prohibiting means for prohibiting switching of the internal combustion engine. An intake air amount obtaining means for obtaining an intake air amount flowing into the cylinder of the internal combustion engine;
When the control means switches the state of the valve means from one state of the first state and the second state to the other state, the one of the control means is based on the intake amount acquired by the intake amount acquisition means. In this state, the flow rate of the intake air introduced to the cylinder of the internal combustion engine through the passages in which the inlet and the outlet are closed and the passages in which the inlet and the outlet are opened in the one state, respectively. The feedback correction means for correcting the operation of the valve means so as to adjust the flow rate of the intake air guided to the cylinder to each target flow rate is provided. An intake control device for an internal combustion engine according to claim 1.

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