JP2010168931A - Ignition timing control device for spark ignition type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology achieving the suppression of the deviation of an ignition timing from the optimum ignition timing when air in an intake passage reversely flows through an EGR passage at the time of acceleration transition from a valve opening state of the EGR valve in a spark ignition type internal combustion engine equipped with an EGR device. <P>SOLUTION: The device is equipped with an EGR device which includes an EGR passage for connecting an exhaust passage and intake passage of an engine and an EGR valve capable of changing a flow passage cross-sectional area of the EGR passage and recirculates to an intake passage part of exhaust flowing through an exhaust passage as EGR gas, and with a throttle valve provided upstream of a connection part with the EGR passage in the intake passage. When air in the intake passage reversely flows through the EGR passage from the intake passage side to the exhaust passage side at the time of acceleration transition from a valve opening state of the EGR valve, correction of advancing the ignition timing of the engine is made. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ignition timing control device for a spark ignition type internal combustion engine.

  An EGR passage that connects the exhaust passage and the intake passage of the internal combustion engine is provided, and an EGR device that recirculates (recirculates) a part of the exhaust discharged from the internal combustion engine to the intake passage through the EGR passage as EGR gas is provided. Internal combustion engines are known.

  Patent Document 1 discloses a technique for estimating an EGR gas reverse flow timing from a temporal change in EGR flow rate in an internal combustion engine including an EGR device and a supercharger, and closing the EGR valve before the reverse flow occurs. It is disclosed.

  Patent Document 2 discloses a technique for preventing a backflow of EGR gas by providing a check valve in the middle of the EGR passage.

  Patent Document 3 discloses a technique for providing a passage that communicates an intake passage and an exhaust passage for supplying air to an exhaust purification catalyst, and preventing a reverse flow of exhaust to the intake passage based on the exhaust pressure and the intake pressure. Has been.

JP 2008-101498 A JP 2005-133605 A JP 2007-332925 A

  When the opening of the throttle valve is increased to the opening on the open side due to an acceleration request, both the intake pressure and the exhaust pressure (back pressure) increase, but the exhaust pressure begins to increase later than the intake pressure. Therefore, when the exhaust pressure has not risen much compared to before the throttle valve opening (before acceleration), the intake pressure rises to near the pressure that converges after the throttle valve opening increases (after acceleration). There is.

  In particular, when accelerating from a light load operation state to a high load operation state, the exhaust pressure before the throttle valve opening increases (exhaust pressure in the light load operation state) is relatively low, and after the throttle valve opening increases When the intake pressure that converges (the intake pressure in the high-load operation state) is relatively high, the intake pressure may temporarily become higher than the exhaust pressure during a period in which the increase in the exhaust pressure is delayed.

  In an internal combustion engine equipped with an EGR device, when the intake pressure becomes higher than the exhaust pressure in response to such an acceleration request from the state where the EGR valve is opened, a part of the air in the intake passage flows backward through the EGR passage. There is a possibility of flowing to the exhaust passage side. In that case, the amount of intake air actually sucked into the cylinder (cylinder) is smaller than the measured value of the air flow meter.

Incidentally, MBT (Minimum spark advance for Best Torque), which is the ignition timing at which the generated torque can be maximized in the relationship between the ignition timing in the spark ignition internal combustion engine (the timing at which the spark plug emits an electric spark) and the generated torque. Exists. Since this MBT can be said to be the ignition timing at which the fuel consumption is the smallest, controlling the ignition timing to MBT can be said to be the optimal ignition timing in terms of both fuel efficiency improvement and output improvement. However, if the octane number of the fuel is not sufficiently high with respect to the operating conditions, knocking is likely to occur, and in order to avoid this knocking, it is necessary to control the ignition timing to the retard side. For this reason, it is not easy to advance the ignition timing to MBT. Therefore, in the ignition timing control of the spark ignition type internal combustion engine, in order to control the ignition timing as close to MBT as possible while avoiding knocking, the engine speed, engine load (intake air amount), etc. are used as parameters (for example, engine The ignition timing is controlled (based on an ignition timing map using the rotational speed and the intake air amount as parameters).

  However, if part of the air in the intake passage flows back through the EGR passage during acceleration transient as described above, the actual intake air amount will be smaller than the measured value of the air flow meter, so the ignition timing is less than the optimal timing. There is a risk of shifting.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a spark ignition internal combustion engine equipped with an EGR device in an intake passage during acceleration transient from a state in which the EGR valve is opened. An object of the present invention is to provide a technology capable of suppressing the ignition timing from deviating from the optimal ignition timing when air flows backward through the EGR passage.

  In order to achieve the above object, a control device for a spark ignition type internal combustion engine equipped with an EGR device according to the present invention is such that air in an intake passage passes through an EGR passage during acceleration transient from a state in which the EGR valve is opened. In the case of backflow from the intake passage side to the exhaust passage side, the greatest feature is to advance the ignition timing of the internal combustion engine.

  In view of this, a control apparatus for a spark ignition internal combustion engine according to the present invention firstly includes an EGR passage that connects an exhaust passage and an intake passage of the internal combustion engine, and an EGR valve that can change the cross-sectional area of the EGR passage. And an EGR device that recirculates a part of the exhaust gas flowing through the exhaust passage to the intake passage as EGR gas, a throttle valve provided upstream of the connection portion of the intake passage to the EGR passage, and the EGR valve is opened. Ignition timing correction that corrects the ignition timing of the internal combustion engine when the throttle valve opening is increased to a more open position that is more than a certain amount of opening difference when in the valved state And means.

  Here, the “open state” of the EGR valve refers to a state in which the closed (fully closed) state is released. In addition, the “opening difference of a predetermined amount or more” is a standard for determining whether the intake pressure becomes higher than the exhaust pressure in the process of changes in the intake pressure and the exhaust pressure accompanying the opening of the throttle valve. Is the difference in opening. Here, when the opening degree difference when increasing the opening degree of the throttle valve is a predetermined amount or more, it is determined that the intake pressure is temporarily (transiently) higher than the exhaust pressure.

  When the intake pressure becomes transiently higher than the exhaust pressure, a part of the air in the intake passage flows into the EGR passage, and thereby flows backward from the intake passage side toward the exhaust passage side. Then, the amount of air actually sucked into the cylinder (hereinafter referred to as “actual intake air amount”) is smaller than the measured value of the intake air amount by the air flow meter (hereinafter referred to as “backflow air”). It is reduced by the amount “).

  Here, if the optimal ignition timing is referred to as “optimum ignition timing” in order to achieve both avoidance of knocking and improvement of generated torque, knocking is unlikely to occur due to a transient backflow of intake air. For this reason, the control value of the ignition timing obtained by substituting the measured value of the intake air amount by the air flow meter into the ignition timing map is shifted to the retard side as compared with the original optimum ignition timing.

  In this respect, according to this configuration, when the throttle valve is opened with an opening difference of a predetermined amount or more from the opened state of the EGR valve, the ignition timing of the internal combustion engine is corrected in advance. Even when the air in the intake passage flows backward through the EGR passage during acceleration transition, the ignition timing can be maintained at the optimum ignition timing. That is, even when air flows backward through the EGR passage, it is possible to suppress the ignition timing from deviating from the optimal ignition timing. Therefore, it is possible to bring the ignition timing closer to the MBT side (push it in) while avoiding knocking. Therefore, deterioration in fuel consumption, output reduction, deterioration in acceleration response (acceleration response), and the like due to the air in the intake passage flowing back through the EGR passage during acceleration transition are suppressed.

  As a situation in which the opening difference when the throttle valve opening is increased becomes a predetermined amount or more, from a light load operation state in which the opening of the throttle valve is a relatively closed opening, An example of the acceleration transient when shifting to a high-load operation state in which the valve opening is a relatively large opening such as an opening close to full open can be illustrated. Therefore, the ignition timing correction means is used when the engine load shifts from the light load operation state belonging to the light load region to the high load operation state belonging to the high load region when the EGR valve is in the opened state. It may be one that corrects the timing. Here, the “light load region” and the “high load region” mean a set of load regions having a relationship such that the difference in opening of the throttle valve in both regions is a predetermined amount or more. As a result of the throttle valve being suddenly opened to the opening side of the opening side at the acceleration transition when shifting from the light load operation state to the high load operation state, the intake pressure rises rapidly and significantly. The possibility of temporarily exceeding the low-pressure exhaust pressure in the light load operation state is increased. In such a situation, by correcting the advance of the ignition timing of the internal combustion engine, it is possible to accurately control the ignition timing at the acceleration transition time to the optimal timing.

  Further, the ignition timing correction means, when the accelerator opening is increased by a certain amount or more when the EGR valve is opened and the engine load is in a light load operation state belonging to the light load region, The ignition timing may be corrected to advance. In this case, the “increase amount of the accelerator opening more than a certain amount” means that the accelerator opening when the throttle valve is opened (increase in the throttle valve opening) with an opening difference of the predetermined amount or more. Can be taken as an increase in

  Second, the present invention includes an EGR passage that connects an exhaust passage and an intake passage of an internal combustion engine, and an EGR valve that can change a flow passage cross-sectional area of the EGR passage. When the EGR device recirculates to the intake passage as an EGR gas, a throttle valve provided upstream of the connection portion of the intake passage to the EGR passage, and the EGR valve is opened. When increasing the opening of the throttle valve to the opening on the more open side, it is determined whether or not the air in the intake passage flows backward through the EGR passage from the intake passage side to the exhaust passage side. An ignition timing control device for a spark ignition type internal combustion engine, comprising: an ignition timing correction means for correcting an advance of the ignition timing of the internal combustion engine when it is determined that the engine is flowing backward.

  According to this configuration, when it is detected that the air is flowing backward through the EGR passage when opening the throttle valve with an arbitrary opening difference in the operation state in which the EGR valve is opened, the ignition timing is advanced. Corner correction is performed. As a result, even when air flows back through the EGR passage as the throttle valve opening increases, it is possible to suppress the ignition timing from deviating from the optimal ignition timing due to this.

Here, for determining whether or not air is flowing backward through the EGR passage when the opening of the throttle valve is increased, for example, the amount of EGR gas flowing through the EGR passage when the throttle valve is opened, That is, the amount of EGR gas that flows forward through the EGR passage from the exhaust passage toward the intake passage is estimated, and if the estimated amount of EGR gas is a negative value, it is determined that air is flowing backward through the EGR passage. it can. Here, the “EGR gas amount” means the amount of gas that flows forward through the EGR passage, that is, the amount of gas that flows through the EGR passage from the exhaust passage side to the intake passage side.

  The amount of EGR gas flowing through the EGR passage is determined by the pressure on the upstream side (exhaust passage side) of the EGR passage from the EGR valve, the pressure on the downstream side (intake passage side) of the EGR passage, and the EGR valve opening degree. Can be estimated. Therefore, the EGR gas amount when the throttle valve is opened can be calculated based on the intake pressure, the exhaust pressure, and the EGR valve opening degree when the throttle valve is opened.

  In the first or second aspect of the invention, the ignition timing correction means estimates a backflow air amount that is an amount of air that flows back through the EGR passage, and the larger the estimated backflow air amount, the more the ignition timing advance correction amount. It is good to set a lot. According to this configuration, the ignition timing can be corrected to the advance side by an amount corresponding to the amount of backflow air that flows back through the EGR passage, so that the ignition timing can be matched with the optimal timing more accurately.

  According to the present invention, in a spark ignition internal combustion engine equipped with an EGR device, the ignition timing is optimal even when the air in the intake passage flows back through the EGR passage during acceleration transient when the EGR valve is opened. Deviation from the ignition timing can be suppressed.

It is a figure which shows schematic structure of the engine which concerns on an Example, and its intake / exhaust system. It is the map which defined the corresponding | compatible relationship between the engine operating area | region and the opening degree control of an EGR valve in an Example. It is the map which showed the relationship between the engine operating state and ignition timing in an Example. 6 is a time chart showing an example of temporal changes in an intake air amount KL, a throttle valve opening degree Dth, an EGR valve opening degree Deg, an intake pressure, and an exhaust pressure when performing an ignition timing correction process during acceleration transition in the embodiment. . (A) is the time chart which showed the time change of the amount of intake air. (B) is a time chart showing the time change of the throttle valve opening Dth. (C) is a time chart showing the time change of the EGR valve opening degree Deg. (D) is a time chart showing an example of a time change of the intake pressure Pin and the exhaust pressure Pex. It is the flowchart which showed the ignition timing correction processing routine at the time of acceleration transition in the execution example.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the component parts described in the present embodiment are not intended to limit the technical scope of the invention only to those unless otherwise specified.

  FIG. 1 is a diagram showing a schematic configuration of an engine and its intake / exhaust system according to the present embodiment. In FIG. 1, an engine 1 is a spark ignition type gasoline engine having four cylinders 2. A piston 3 is slidably provided in the cylinder 2. The piston 3 is connected to a crankshaft 5 via a connecting rod 4, and the crankshaft 5 rotates as the piston 3 reciprocates. An intake port 7 and an exhaust port 8 are connected to the combustion chamber 6 in the upper part of the cylinder 2. The openings of the intake port 7 and the exhaust port 8 to the combustion chamber 6 are opened and closed by an intake valve 9 and an exhaust valve 10, respectively.

  Each cylinder 2 is provided with a spark plug 15 that ignites the air-fuel mixture in the combustion chamber 6. The spark plug 15 has an electrode portion that generates sparks (sparks) facing the combustion chamber 6 and ignites the air-fuel mixture in the combustion chamber 6 by generating sparks. The applied voltage to the spark plug 15 is supplied by an ignition coil (not shown).

  The intake port 7 is provided with a fuel injection valve 18 that injects fuel into the intake port 7. The intake port 7 is connected to the intake passage 19, and the exhaust port 8 is connected to the exhaust passage 20. The intake passage 19 is provided with an air flow meter 21 that outputs an electrical signal corresponding to the mass of air flowing through the intake passage 19. A throttle valve 22 that adjusts the amount of air flowing through the intake passage 19 is provided in the intake passage 19 on the downstream side of the air flow meter 21. The exhaust passage 20 is provided with an exhaust purification device (for example, a three-way catalyst) 23.

  In the intake system of the engine 1 having the above configuration, the intake air amount is adjusted by the throttle valve 22, and an air-fuel mixture is formed in the intake port 7 together with the fuel injected from the fuel injection valve 18. This air-fuel mixture is distributed to each cylinder 2 and burned by being ignited by a spark plug 15. As a result, the piston 3 reciprocates, the crankshaft 5 rotates, and the driving torque of the engine 1 is generated.

  Further, according to the exhaust system of the engine 1, the exhaust valve 10 opens the exhaust port 8 so that the exhaust from each cylinder 2 is discharged to the exhaust passage 20. Then, after harmful substances contained in the exhaust gas are purified by the exhaust gas purification device 23, they are released into the atmosphere through a muffler (not shown).

  The engine 1 includes an EGR device 25 that recirculates a part of the exhaust discharged to the exhaust passage 20 to the intake passage 19 as EGR gas. The EGR device 25 includes an EGR passage 26 and an EGR valve 27. The EGR passage 26 connects the exhaust passage 20 upstream of the exhaust purification device 23 and the intake passage 19 downstream of the throttle valve 22. The EGR valve 27 is provided in the EGR passage 26, and adjusts the amount of EGR gas by changing the cross-sectional area of the EGR gas flowing through the EGR passage 26.

  Here, when the EGR valve 27 is opened, a part of the exhaust gas flowing through the exhaust passage 20 is recirculated (recirculated) to the intake passage 19 via the EGR passage 26. The EGR gas is introduced into each cylinder 2 while being mixed with air (fresh air) flowing through the intake passage 19. The EGR gas contains an inert gas component that does not burn itself and has a high heat capacity, such as water and carbon dioxide. Therefore, when the EGR gas is contained in the air-fuel mixture, the combustion temperature of the air-fuel mixture is lowered, thereby reducing the amount of nitrogen oxide (NOx) generated. Moreover, when EGR gas is contained in the air-fuel mixture, an effect of improving fuel efficiency can be expected.

  The engine 1 is provided with an ECU 30 that is an electronic control unit for controlling the engine 1. In addition to the CPU, the ECU 30 includes a ROM, a RAM, and the like that store various programs and maps, and controls the operating conditions of the engine 1 according to the operating conditions of the internal combustion engine 1 and the driver's request. Further, the engine 1 is provided with an accelerator opening sensor 32, a crank position sensor 33, and an EGR opening sensor 34. The accelerator opening sensor 32 is a sensor that outputs an electrical signal corresponding to the operation amount (accelerator opening) of the accelerator pedal. The crank position sensor 33 is a sensor that detects the rotation angle of the crankshaft 5. The EGR opening sensor 34 is a sensor that outputs an electrical signal corresponding to the valve opening of the EGR valve 27.

  Various devices and various sensors described above are connected to the ECU 30 via electric wiring, and various devices are controlled based on control signals from the ECU 30. That is, the ECU 30 acquires the operating state of the engine 1 and the driver's request based on the signals output from various sensors, and based on this, the opening degree of the throttle valve 22, the opening degree of the EGR valve 27, and the spark plug 15 are controlled. The

  FIG. 2 is a map that defines a correspondence relationship between the operation region of the engine 1 and the opening degree control of the EGR valve 27 in the embodiment. In the figure, the vertical axis represents the engine load TQ (intake air amount KL), and the horizontal axis represents the engine speed NE. The operation area A in the figure is an idle operation area, and here, the EGR valve 27 is closed, and EGR is not performed.

  The operation region B is a light load operation region, and here, EGR is performed by opening the EGR valve 27. Actually, the engine speed NE detected from the output signal from the crank position sensor 33 and the engine load TQ calculated based on the accelerator opening detected from the output signal from the accelerator opening sensor 32 are more detailed. A target value for the EGR valve opening is determined. The operation region C is a high load operation region in which the throttle valve 22 is fully opened or opened to a large opening degree close to full open, and can also be called a so-called full load operation region (WOT: Wide Open Throttle). Here, the EGR valve 27 is closed, and EGR is not performed.

  Next, the ignition timing Ig of the engine 1 (the timing at which the spark plug 15 generates spark) Ig will be described. FIG. 3 is a map showing the relationship between the operating state of the engine 1 and the ignition timing (hereinafter referred to as “ignition timing map”). This ignition timing map is a map stored in the ROM of the ECU 30, and determines the ignition timing Ig using the intake air amount KL of the engine 1 and the engine speed NE as parameters.

  Here, the MBT (Minimum Advance for Best Torque) at which the generated torque of the engine 1 becomes maximum varies depending on the combination of the intake air amount KL and the engine speed NE. In this embodiment, the MBT is experimentally obtained in advance for each combination of the intake air amount KL and the engine speed NE, and the ignition timing Ig is set so as to coincide with the MBT corresponding to the intake air amount KL and the engine speed NE. It is determined. Specifically, the ignition timing Ig is derived as a retarded phase as the engine speed NE is higher under the condition where the intake air amount KL is equal, and the intake air is generated under the condition where the engine speed NE is equal. The larger the amount KL, the more retarded the phase is derived.

  The engine 1 is provided with a knock sensor 35. Knock sensor 35 is a sensor that detects vibration generated when knocking occurs and outputs a knock signal corresponding to the magnitude of the vibration, and this knock signal is input to ECU 30. In this embodiment, when knocking occurs for several cycles, the ignition timing Ig is immediately delayed (corrected to the retarded angle side) and retracted until no knocking occurs. Then, the ECU 30 stores and learns the ignition timing Ig after the delay angle correction, and sequentially updates the ignition timing map. By controlling the control command value of the ignition timing Ig based on such an ignition timing map, the ignition timing Ig is controlled to the optimal ignition timing that is as close as possible to the MBT while avoiding knocking. .

  Next, a high load operation region where the EGR valve 27 is closed and the throttle valve 14 is opened to a large opening degree from the operation state belonging to the light load operation region B operated with the EGR valve 27 opened. The control related to the opening degree of the EGR valve 27 and the opening degree of the throttle valve 22 when there is a request for acceleration to the operating state belonging to C will be described.

The time chart of FIG. 4 shows an example of temporal changes in the intake air amount, the opening degree of the throttle valve 22, the opening degree of the EGR valve 27, the intake pressure, and the exhaust pressure when such an acceleration request is made. As shown in FIG. 4, a high load operation state in which the opening degree of the throttle valve 22 changes from the light load operation state in which the EGR valve 27 is opened by the depression of the accelerator at time t <b> 1 to the opening degree on the open side. Assume that acceleration is required.

  In response to the acceleration request, the throttle valve 22 starts to be opened at the acceleration request time t1 from the relatively small opening Dth1 in the light load operation state to the relatively large opening Dth2 as the target opening. That is, the opening degree is increased from the opening degree Dth1 toward the target opening degree Dth2 on the opening side.

  In response to the acceleration request, the EGR valve 27 starts to close at the acceleration request time t1 with the opening degree Deg2 as the target opening degree from the opening degree Deg1 in the light load operation state simultaneously with the throttle valve 22. The target opening degree Deg2 here is assumed to be fully closed.

  By the way, the intake pressure Pin and the exhaust pressure Pex increase with the opening of the throttle valve 22. However, as shown in (D), the increase in the exhaust pressure Pex tends to be delayed for a moment with respect to the increase in the intake pressure Pin. . In the example shown in (D), the exhaust pressure Pex starts to rise at time t3 delayed by a period Δt0 with respect to time t1 at which the intake pressure Pin starts to rise. Due to the delay in the pressure increase, the possibility that the intake pressure Pin is temporarily higher than the exhaust pressure Pex is increased. In particular, at the time of acceleration transient in which the throttle valve opening Dth is fully opened or opened to a large opening close to full opening from a light load operation state where the throttle valve opening Dth is small, the exhaust pressure Pex during light load operation is low, Further, since the intake pressure Pin rapidly rises to near atmospheric pressure during acceleration transition, a state in which the intake pressure Pin becomes higher than the exhaust pressure Pex tends to occur.

  In the example shown in FIG. 3, in a period Δt1 from time t2 when the intake pressure Pin has finished increasing from the pressure Pin1 before acceleration to the pressure Pin2 that converges after acceleration to time t3 when the exhaust pressure Pex starts to increase, The intake pressure Pin is higher than the exhaust pressure Pex. The intake pressure referred to here is the pressure in the intake passage 19 on the downstream side of the throttle valve 22 or a portion where the pressure is equivalent to that portion (for example, the downstream side of the EGR valve 27 in the EGR passage 26 (the intake passage 19 side). Further, the exhaust pressure refers to the pressure in the exhaust passage 20 upstream of the exhaust purification device 23 or a portion where the pressure is equivalent to the relevant portion (for example, upstream from the EGR valve 27 in the EGR passage 26). The pressure on the side (exhaust passage 20 side) is indicated.

  As described above, in the period Δt1 in which the intake pressure Pin is temporarily (transiently) higher than the exhaust pressure Pex immediately after the throttle valve 22 is opened, it is downstream of the upstream side of the EGR passage 26 (exhaust passage 20 side). Since the pressure on the (intake passage 19 side) increases, if the EGR valve 27 is open at this time, a part of the air in the intake passage 19 moves from the intake passage 19 side to the exhaust passage 20 side. Backward toward.

  Then, as shown in FIG. 4A, the intake air amount KL decreases by an amount corresponding to the amount of air that has flowed back through the EGR passage 26 (hereinafter referred to as “backflow air amount RA”). In this case, the actual intake air amount KLr actually sucked into the cylinder 2 is smaller than the measured intake air amount KLc, which is the intake air amount calculated from the measured value of the air flow meter 21 (KLr = KLc−RA). . Therefore, the ignition timing obtained by substituting the measured intake air amount KLc based on the measurement value of the air flow meter 21 into the ignition timing map shown in FIG. 3 is substituted with the original optimum ignition timing (actual intake air amount KLr). Compared to the ignition timing required).

Therefore, in the ignition timing control of the engine 1 in this embodiment, when the opening of the throttle valve 22 is increased to the opening on the open side when the EGR valve 27 is in the opened state,
It is determined whether or not the air in the intake passage 19 is flowing backward through the EGR passage 26. When it is determined that the air is flowing backward, the control command value of the ignition timing Ig is corrected to advance.

  Regarding the determination of whether or not the backflow of air occurs in the EGR passage 26, the amount of EGR gas flowing through the EGR passage 26 is estimated. When the estimated amount of EGR gas is a negative value, the air flows through the EGR passage 26. It is determined that the flow is backward. Here, the “EGR gas amount” is defined as the amount of gas flowing through the EGR passage 26 from the upstream side (exhaust passage 20 side) to the downstream side (intake passage 19 side).

  The amount of EGR gas flowing through the EGR passage 26 can be estimated based on the pressure at the upstream end of the EGR passage 26, the pressure at the downstream end, and the opening degree of the EGR valve 27. In the present embodiment, the pressure at the upstream end of the EGR passage 26 is acquired based on the measured value of the exhaust pressure Pex by the exhaust pressure sensor 37. Further, the pressure at the downstream end of the EGR passage 26 is acquired based on the measured value of the intake pressure Pin by the intake pressure sensor 38. Further, the opening degree of the EGR valve 27 is acquired based on the measured value by the EGR opening degree sensor 34. Based on these acquired values, the amount of EGR gas flowing through the EGR passage 26 is estimated.

  If the estimated EGR gas amount is a negative value, the air of the gas amount obtained as the absolute value of the EGR gas amount flows back through the EGR passage 26 from the intake passage 19 side to the exhaust passage 20 side. It is determined that When it is determined that air is flowing backward in the EGR passage 26, the ignition timing control command value is advanced to correct the ignition timing Ig of the engine 1 by an amount corresponding to the backflow air amount RA. The corrected ignition timing Igc, which is a target value after correction, is changed.

Next, an execution procedure of the advance angle correction process of the ignition timing Ig during the acceleration transition of the engine 1 described above will be described based on the flowchart of FIG. FIG. 5 is a flowchart showing an ignition timing correction processing routine during acceleration transition in this embodiment. This routine is repeatedly executed by the ECU 30 at regular intervals while the engine 1 is operating.

  In step S <b> 101, the ECU 30 determines whether or not there is a request to open the throttle valve 22 to an opening on the opening side with respect to the current opening of the throttle valve 22. Here, the operation of “opening” the throttle valve 22 means increasing its opening degree. If it is determined in step S101 that the opening of the throttle valve 22 is requested (Yes), the ECU 30 proceeds to step S102. If it is determined in step S101 that the opening of the throttle valve 22 is not requested (No), the ECU 30 once ends the execution of this routine.

  In step S102, the ECU 30 determines whether or not the current EGR valve 27 is open. The “open state” refers to a state where the closed (fully closed) state is released. If it is determined in step S102 that the EGR valve 27 is in the opened state (Yes), the ECU 30 proceeds to step S104. On the other hand, when it is determined in step S102 that the EGR valve 27 is not opened, that is, it is determined that the valve is closed (fully closed) (No), the ECU 30 once ends the execution of this routine.

  In step S103, the ECU 30 estimates the EGR gas amount. Here, the EGR gas amount is the amount of gas flowing from the exhaust system to the intake system through the EGR passage 26 as described above, and is estimated based on the intake pressure Pin, the exhaust pressure Pex, and the EGR valve opening degree Deg. .

In step S104, the ECU 30 determines whether air is flowing backward through the EGR passage 26. Specifically, when the amount of EGR gas estimated in step S103 is a negative value, it is determined that an amount of air equal to the absolute value is flowing backward through the EGR passage 26. If it is determined in step S104 that air is flowing backward through the EGR passage 26 (Yes), the ECU 30 proceeds to step S105. On the other hand, when it is determined in step S104 that the air does not flow backward through the EGR passage 26 (No), the ECU 30 once ends the execution of this routine. If it is determined in step S104 that air is flowing back through the EGR passage 26, the process proceeds to the next step with the estimated value of the backflow air amount RA temporarily stored.

  In step S105, the ECU 30 calculates a corrected ignition timing Igc based on the estimated backflow air amount RA. The corrected ignition timing Igc is obtained by substituting the actual intake air amount KLr into the ignition timing map of FIG. The actual intake air amount KLr is calculated as a value obtained by subtracting the backflow air amount RA from the measured intake air amount KLc measured by the air flow meter 21. Here, when the engine speed NE is equal, knocking is less likely to occur as the intake air amount KL is smaller, so the ignition timing is also set as a more advanced phase. Since the actual intake air amount KLr decreases as the backflow air amount RA increases, in this step, the ignition timing advance correction amount ΔIg is set to a larger value as the backflow air amount RA increases. Here, the advance correction amount ΔIg is the control command value of the ignition timing Ig before correction (ignition timing obtained by substituting the advance correction amount ΔIg into the ignition timing map of FIG. 3) and the corrected ignition timing. It is a phase difference from Igc, and is a correction amount when the ignition timing is advanced.

  In step S106, the ECU 30 corrects the ignition timing Ig from the current control command value to the corrected ignition timing Igc calculated in step S105. The current control command value (ignition timing before correction) here is an ignition timing obtained by substituting the measured intake air amount KLc (and engine speed NE) into the ignition timing map of FIG. When the process of this step is completed, the ECU 30 once ends the execution of this routine.

  As described above, by executing the ignition timing advance correction process at the time of acceleration transient when the EGR valve 27 is opened, even when the air flows back through the EGR passage 26 after the throttle valve 22 is opened, It is possible to suppress the ignition timing Ig from deviating from the original optimum ignition timing to the retard side. Accordingly, it is possible to bring the ignition timing Ig closer to the MBT (push it in) while avoiding knocking. Therefore, during acceleration transients, deterioration of fuel consumption, output reduction, and acceleration response (acceleration response) due to the backflow of air are reliably suppressed.

  In this embodiment, the ECU 30 that executes the processing routine of FIG. 5 corresponds to the ignition timing correction means in the present invention.

  The embodiment described above is an example for explaining the present invention, and various modifications can be added to the above-described embodiment without departing from the gist of the present invention. For example, in the above embodiment, the ignition timing advance correction processing at the time of acceleration transition from the operating state belonging to the light load operating region B to the operating state belonging to the high load operating region C has been described. However, the EGR valve 27 is opened. The present invention can be suitably applied in the acceleration transient in which the opening degree of the throttle valve 22 is increased to the opening degree on the open side from the state that has been achieved. For example, the operation region before and after acceleration may be the light load operation region B. Further, the map shown in FIG. 2 shows an example of the correspondence relationship between the operation region of the engine 1 and the opening degree control of the EGR valve 27, and is not limited to this. Therefore, the EGR valve 27 may not be closed simultaneously with the opening of the throttle valve 22, but may be controlled so that the opening degree of the EGR valve 27 is increased. In such a case, since the EGR valve is always opened in the process of pressure change accompanying the opening of the throttle valve, the problem of air flowing back through the EGR passage is more likely to occur, and the present invention is applied. The effect by doing becomes more remarkable.

  Further, in this embodiment, when it is detected that air is flowing backward through the EGR passage 27 after the throttle valve 22 is opened, an advance angle correction of the ignition timing Ig is performed according to the backflow air amount RA. As described above, acceleration transient conditions that are likely to cause backflow of air through the EGR passage 26 are obtained in advance, and when an acceleration transient condition corresponding to this acceleration transient condition is reached, The advance angle correction of the ignition timing Ig can be performed on the assumption that a reverse flow has occurred (judged). In such a case, the degree of backflow that has occurred is obtained in advance through experiments and calculations in accordance with the opening difference of the throttle valve 22 before and after acceleration, operating conditions, etc., and the ignition timing Ig due to the backflow is optimal. The advance correction amount ΔIg of the ignition timing can be set so that the deviation from the ignition timing can be corrected.

  Here, as an acceleration transient condition in which a backflow of air is highly likely to occur, the exhaust valve Pex is low in an operating state before acceleration in a light load region, and the throttle valve 22 is opened to an opening close to full open during acceleration transient. The acceleration conditions that can be opened can be exemplified. Therefore, when the EGR valve 27 is in the opened state, the acceleration condition for shifting the engine load TQ from the light load operation state belonging to the light load operation region to the high load operation state belonging to the high load operation region is satisfied. In addition, it is determined that a back flow of air occurs through the EGR passage 26, and the advance angle correction of the ignition timing Ig is preferably performed. As described above, the backflow air amount RA here can be estimated according to a difference in opening of the throttle valve 22 before and after acceleration, an operating condition, and the like.

  Alternatively, when the EGR valve 27 is in the opened state, when the opening degree of the throttle valve 22 is increased to an opening side that is more open than a certain degree of opening difference, the advance angle of the ignition timing Ig It is good to make corrections. Here, the “predetermined amount” refers to whether or not the intake pressure Pin becomes transiently higher than the exhaust pressure Pex in the process of changing the intake pressure Pin and the exhaust pressure Pex as the opening of the throttle valve 22 increases. This is the difference in opening of the throttle valve 22 that serves as a reference for determination, and can be determined in advance based on empirical rules based on experiments and the like. For example, when the opening degree of the throttle valve 22 is increased, the lower limit value of the opening degree difference that may cause a phenomenon in which the intake pressure Pin becomes transiently higher than the exhaust pressure Pex is set as a value that allows for a certain margin. Also good.

  According to this control, even if the backflow of air occurs during acceleration transient such that the opening degree difference when the throttle valve 22 is opened is equal to or greater than the predetermined amount, the ignition timing is corrected by performing advance correction of the ignition timing Ig. Ig can be maintained at an optimal ignition timing.

  Further, when the EGR valve 27 is opened and the engine load TQ is in the light load operation state belonging to the light load region, the ignition timing Ig is advanced at the acceleration transient when the accelerator opening increases by a predetermined amount or more. It can also be corrected. This also makes it possible to maintain the ignition timing Ig of the engine 1 at the time of acceleration transient at the optimal ignition timing, as in any of the above-described controls, resulting in deterioration of fuel consumption, output reduction, and acceleration caused by the backflow of air. Deterioration of responsiveness (acceleration response) can be suitably suppressed.

DESCRIPTION OF SYMBOLS 1 Engine 2 Cylinder 5 Crankshaft 15 Spark plug 18 Fuel injection valve 19 Intake passage 20 Exhaust passage 21 Air flow meter 22 Throttle valve 23 Exhaust purification device 25 EGR device 26 EGR passage 27 EGR valve 30 ECU
34 EGR opening sensor 37 Exhaust pressure sensor 38 Intake pressure sensor

Claims (3)

An EGR passage that connects the exhaust passage and the intake passage of the internal combustion engine and an EGR valve that can change the flow passage cross-sectional area of the EGR passage are recirculated to the intake passage as a part of the exhaust gas that flows through the exhaust passage. An EGR device;
A throttle valve provided upstream of the connection point with the EGR passage in the intake passage;
When the EGR valve is in the opened state, the ignition timing of the internal combustion engine is advanced when the opening of the throttle valve is increased to an opening on the open side with a difference of opening of a predetermined amount or more. Ignition timing correction means for correcting;
An ignition timing control device for a spark ignition type internal combustion engine. An EGR passage that connects the exhaust passage and the intake passage of the internal combustion engine and an EGR valve that can change the flow passage cross-sectional area of the EGR passage are recirculated to the intake passage as a part of the exhaust gas that flows through the exhaust passage. An EGR device;
A throttle valve provided upstream of the connection point with the EGR passage in the intake passage;
When the opening degree of the throttle valve is increased to an opening degree on the open side when the EGR valve is in the opened state, the air in the intake passage causes the air from the intake passage side to pass through the EGR passage. An ignition timing correction means for determining whether the exhaust gas is flowing backward to the exhaust passage side, and for correcting the advance of the ignition timing of the internal combustion engine when it is determined that the air is flowing backward;
An ignition timing control device for a spark ignition type internal combustion engine.   The ignition timing correction means estimates a backflow air amount, which is an amount of air flowing back through the EGR passage, and sets a larger advance amount of ignition timing as the estimated backflow air amount increases. Item 3. An ignition timing control device for a spark ignition type internal combustion engine according to Item 1 or 2.

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