JP5649343B2 - Intake throttle control method for internal combustion engine - Google Patents

Description

  The present invention includes an exhaust turbine supercharger, an exhaust gas recirculation device (hereinafter referred to as an EGR device) that mixes a part of the exhaust gas with intake air, and an intake throttle valve that controls the air flowing into the compressor. The present invention relates to an intake throttle valve control method in an internal combustion engine.

  Conventionally, as an EGR device, for example, as described in Patent Document 1, a part of exhaust gas (hereinafter referred to as EGR gas) is taken from an exhaust passage on the turbine downstream side of the turbocharger, and upstream of the compressor of the turbocharger. It is known that a low-pressure EGR passage is recirculated to the intake passage on the side, and a high-pressure EGR passage that takes in EGR gas from the exhaust passage on the upstream side of the turbine and recirculates it to the intake passage on the downstream side of the compressor. .

  In the recirculation of EGR gas through the low-pressure EGR passage, so-called low-pressure loop type, since the pressure of the EGR gas is low, the negative pressure in the intake passage is used to control the amount of EGR gas. In an internal combustion engine including a low-pressure loop EGR device having such a configuration, an intake throttle valve is provided upstream of the intake passage from a position where the low-pressure EGR passage is connected in order to generate a negative pressure in the intake passage. When increasing the amount of EGR gas, the intake throttle valve is controlled to be closed.

  By the way, depending on the operation state of the internal combustion engine when the internal combustion engine starts decelerating, the fuel cut is not necessarily executed even when the internal combustion engine starts decelerating. In other words, the fuel cut is executed when an operating condition such as the engine speed being equal to or higher than the predetermined speed is satisfied. Therefore, depending on the time when the internal combustion engine starts to decelerate, the fuel cut is performed immediately after the start of deceleration. It will not be.

  In the above-described low-pressure loop type EGR device, when such an internal combustion engine is in an operating state, the EGR gas may be excessive depending on the operating state at the time of starting deceleration. For example, when deceleration is started in a relatively high load operation state, the intake throttle valve is controlled to close in accordance with the state of the load after deceleration, and a large amount of EGR gas increases as the negative pressure in the intake passage increases. It is captured. This is because when the intake throttle valve is changed suddenly in accordance with the change in the load, the negative pressure in the intake passage increases along with the change, so that the EGR amount increases, This is because the opening degree of the intake throttle valve is set so that a large amount of EGR gas can be taken in in the middle load operation region.

  However, in this case, when the amount of EGR gas taken in increases, the ratio of the amount of EGR gas to fresh air, that is, the EGR rate increases, so that combustion is likely to be reduced, leading to misfire.

JP 2007-221767 A

  Accordingly, the present invention focuses on the above points and aims to limit the increase in the amount of EGR gas in accordance with the operating state at the time of deceleration, and to suppress problems associated with the increase in the amount of EGR gas.

  That is, according to the intake throttle valve control method for an internal combustion engine of the present invention, the internal combustion engine has a turbocharger having a turbine driven by exhaust energy and a compressor driven by the turbine to compress intake air, and upstream of the compressor. An intake throttle valve provided, and an exhaust gas recirculation device that recirculates a part of the exhaust gas upstream of the compressor and downstream of the intake throttle valve. A method for controlling an intake throttle valve of an internal combustion engine to be controlled, wherein when the detected operating state is determined to be deceleration, a lower limit value for limiting the opening of the intake throttle valve is set. To do.

  According to such a configuration, when the internal combustion engine is decelerated, the opening of the intake throttle valve is limited by the lower limit value. For this reason, the increase in the negative pressure upstream of the compressor, which increases when the intake throttle valve is closed, is limited. Therefore, it is possible to suppress an excessive amount of EGR gas generated by closing the intake throttle valve too much.

In order to make maximum use of the EGR gas amount even during deceleration, the present invention is characterized in that the EGR gas amount is changed according to the degree of deceleration in the operating state in which the lower limit value is detected.

  The present invention is configured as described above, and it is possible to suppress the occurrence of problems such as misfiring due to an excessive amount of EGR gas caused by closing the intake throttle valve too much.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic structure explanatory drawing of the engine of embodiment of this invention. The flowchart which shows the control procedure of the embodiment. Action | operation explanatory drawing of the same embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  The engine 100 has a two-cylinder 360 ° phase, and includes a cylinder 1, an intake passage 2 for supplying intake air to each cylinder 1, an exhaust passage 3 for discharging exhaust gas, and an exhaust passage 3. An exhaust turbine turbocharger 4 having a turbine 4a and a compressor 4b disposed in the intake passage 2 is basically provided.

  In addition to the compressor 4 b, an air cleaner 7, an air flow meter 6, an intake throttle valve 8, an intercooler 9, and an electronically controlled throttle valve 10 are arranged in the intake passage 2 in this order from upstream to downstream of the intake passage 2. Yes. That is, the air flow meter 6 for detecting the air flow rate is disposed downstream of the air cleaner 7 and thus upstream of the intake throttle valve 8. In addition, in the intake passage 2 between the air flow meter 6 and the intake throttle valve 8, a fresh air bypass passage 12 a that communicates downstream of the throttle valve 10 and an intake bypass passage that communicates upstream of the throttle valve 10 and downstream of the intercooler 9. A supercharging pressure bypass mechanism 24 including an intake bypass valve 24b that opens and closes the intake bypass passage 24a is provided. The fresh air bypass passage 12a is provided with a fresh air bypass valve 12b for controlling the amount of fresh air flowing.

  The intercooler 9 is provided with an intercooler bypass passage 11a through which intake air bypasses the intercooler 9, and an intercooler bypass valve 11b is attached to the intercooler bypass valve 11a. In the figure, 13 is a canister that adsorbs fuel evaporative gas generated in the fuel tank, and the fuel evaporative gas adsorbed by opening the purge valve 14 is introduced into the intake passage 2 at a position downstream of the throttle valve 10. .

  A spark plug 15 and a fuel injection valve 16 are attached to each cylinder 1. Fuel is supplied to the fuel injection valve 16 from a high-pressure fuel pump 18 via a delivery pipe 17. Similarly, a swirl control valve 19 for generating a swirling flow in the cylinder 1 is attached to each cylinder 1.

In addition to the turbine 5, an air-fuel ratio sensor 20, a three-way catalyst 21, and a rear O ₂ sensor 22 are disposed in the exhaust passage 3 in this order from upstream to downstream of the exhaust passage 3. That is, the air-fuel ratio sensor 20 is disposed downstream of the turbine 5, the three-way catalyst 21 is disposed downstream of the air-fuel ratio sensor 20, and the rear O ₂ sensor 22 is disposed downstream of the three-way catalyst 21. The air-fuel ratio sensor 20 and the rear O ₂ sensor 22 are electrically connected to an electronic control device 33 described later.

  As the turbocharger 4, a well-known one in this field can be applied. In order to control the supercharging pressure, the turbocharger 4 includes an exhaust bypass passage 23 a that allows communication between the upstream side and the downstream side of the turbine 5. A waste gate valve 23b for opening and closing the bypass passage 23a is provided.

  The engine 100 is provided with a so-called low-pressure loop type EGR device 25 between the intake passage 2 and the exhaust passage 3 for mixing exhaust gas with fresh air flowing into the intake passage 2 via the air cleaner 7. The EGR device 25 includes an exhaust gas recirculation pipe (hereinafter referred to as an EGR pipe) 26 that selectively communicates the intake passage 2 and the exhaust passage 3, and an EGR pipe 26 that is provided in the EGR pipe 26. An exhaust gas recirculation control valve (hereinafter referred to as an EGR valve) 27 that controls the amount of EGR gas that passes through, and an EGR cooler 28 that is provided upstream of the EGR valve 27 and cools the EGR gas are provided. One end of the EGR pipe 26 is connected to a portion of the intake passage 2 downstream of the intake throttle valve 8, and the other end is connected to a portion of the exhaust passage 3 downstream of the three-way catalyst 20.

  The engine 100 of this embodiment further includes a variable valve timing mechanism 29 that can control the opening / closing timing of the intake valve with respect to the exhaust valve, that is, the valve timing, according to the operating state. The variable valve timing mechanism 29 is controlled by the electronic control unit 33.

The electronic control device 33 is a computer system including a processor 33a, a memory 33b, an input interface 33c, an output interface 33d, and the like. The input interface 33c includes an air flow rate signal a output from the air flow meter 6, a vehicle speed signal b output from a vehicle speed sensor that detects the vehicle speed, a rotation speed signal c output from a rotation speed sensor that detects the engine speed, An accelerator opening signal d output from an accelerator sensor that detects the amount of operation (depression) of the accelerator pedal, and is output from an intake pressure sensor 38 that is mounted downstream of the throttle sensor in the intake passage 2 and detects the intake pipe pressure. Intake pressure signal e, water temperature signal f output from a water temperature sensor for detecting the cooling water temperature, first air-fuel ratio signal g output from the air-fuel ratio sensor 20, second air-fuel ratio signal h output from the rear O ₂ sensor, etc. Is entered. Further, from the output interface 33d, the throttle valve opening signal k for the intake throttle valve 8, the valve drive signal m for the throttle valve 10, the EGR valve opening signal for the EGR valve 27, and the fuel injection valve 15 The fuel injection signal o, the ignition signal p to the ignition plug 16, the valve timing signal q to the variable valve timing mechanism 29, and the like are output.

  In such a configuration, the electronic control unit 33 controls the opening degree of the intake throttle valve in accordance with the traveling state of the vehicle, detects the operating state of the internal combustion engine, and the detected operating state is deceleration. Is determined, an intake throttle valve control program programmed to set a lower limit value for limiting the opening of the intake throttle valve is executed. The intake throttle valve control program is configured to change the lower limit value in accordance with the detected degree of deceleration in the operating state. The control procedure of this intake throttle valve control program will be described with reference to FIG.

  In FIG. 2, in step S1, it is determined whether the engine 100 has been decelerated. Deceleration is determined based on a change in intake pipe pressure, that is, a change in load, and is determined based on a decrease in intake pipe pressure (load). The load of engine 100 is detected based on the intake pipe pressure.

  In step S2, it is determined whether or not a fuel cut condition is satisfied. For example, the fuel cut condition is that the vehicle speed is equal to or higher than a predetermined speed, the engine speed is equal to or higher than the predetermined speed, the accelerator opening is substantially zero, and the transmission is set to a travel range.

  When it is determined in step S2 that the fuel cut condition is satisfied, in step S3, the intake throttle valve 8 is fully opened. During the fuel cut, EGR gas is not required, so that the intake throttle valve 8 is fully opened.

  On the other hand, if it is determined in step S2 that the fuel cut condition is not satisfied, a deceleration start point is determined in step S4. The deceleration start point is determined based on the torque, that is, the load on the engine 100. That is, the deceleration start point when the deceleration is started in an operation state where the load of the engine 100 is a predetermined value or more is set as the first position, and the deceleration start point when the deceleration is started in an operation state where the load is less than the predetermined value. The second position.

  As shown in FIG. 3, the required EGR rate changes in response to a change in the load of engine 100. The required EGR rate is small at high and low loads and is maximum at medium loads. In order to achieve such a required EGR rate, the opening degree of the intake throttle valve 8 is controlled so as to increase at high and low loads and decrease toward the middle load as shown in FIG. That is, the required EGR rate is controlled by controlling the intake throttle valve 8. Therefore, the above-mentioned predetermined value is set in correspondence with the load with the maximum required EGR rate. In the figure, changes in the opening of the throttle valve 10 and the EGR valve as factors for changing the required EGR rate are shown.

  In step S5, an opening lower limit value of the intake throttle valve 8 is set. The lower limit of the opening is set based on an EGR rate that does not cause an excess of EGR gas when the opening of the intake throttle valve 8 is controlled based on the required EGR rate when the deceleration start point is the first position.

  In step S6, the opening degree of the intake throttle valve 8 is controlled to the target throttle valve opening degree. That is, the opening degree of the intake throttle valve 8 is closed or opened according to the deceleration from the operation state at the deceleration start point. When the deceleration is performed from the first position of the deceleration start point, when the opening of the intake throttle valve 8 reaches the opening lower limit, the opening lower limit is set so that the opening is not lower than the opening lower limit. Retained.

  In such a configuration, when the engine 100 is decelerated, the control of the intake throttle valve 8 is changed according to the start point of the deceleration to control the EGR gas amount so that the operating state of the engine 100 does not become unstable. To. When the engine 100 is decelerated at a relatively high load, for example, at the deceleration start point indicated by T1 in FIG. 3, and when the engine 100 is decelerated to an operation state that does not satisfy the fuel cut condition, the load on the engine 100 is a predetermined value or more. In some cases, the deceleration start point is the first position.

  In this case, the electronic control unit 33 executes Step S1, Step S2, and Step S4 to Step S6, sets the opening lower limit value according to the deceleration start point of the first position, and sets the target intake throttle according to the operating state. The intake throttle valve 8 is controlled to the valve opening degree. In this case, if the opening of the intake throttle valve 8 reaches the lower limit of the opening before reaching the target intake throttle valve opening even if the load of the engine 100 changes suddenly, the intake throttle valve 8 is opened. Keep the degree at the lower limit of opening.

  In this way, when the engine 100 is decelerated and the required EGR rate changes, the opening of the intake throttle valve 8 is set to the opening lower limit value according to the required EGR rate at the time of starting deceleration, and the target Since the opening degree of the intake throttle valve 8 is controlled so as to be the intake throttle valve opening degree, the intake throttle valve 8 is closed too much even if it is suddenly decelerated from the first position of the deceleration start point. It is possible to suppress an excessive increase in the negative pressure at the recirculation position of the EGR gas downstream. Therefore, excessive recirculation of the EGR gas in a decelerating operating state can be suppressed, and problems such as misfire due to excessive EGR gas can be prevented.

  On the other hand, as shown in FIG. 3, when the deceleration start point is the second position indicated by T2 less than the predetermined value, step S1, step S2, step S4, and step S6 are executed to set the opening lower limit value. Instead, the intake throttle valve 8 is controlled to the target intake throttle valve opening degree according to the operating state. In this case, even if the load of the engine 100 changes suddenly, that is, changes so as to decelerate rapidly, the opening of the intake throttle valve 8 is increased, that is, controlled in the fully open direction. The negative pressure downstream does not increase.

  Therefore, the opening degree of the intake throttle valve 8 according to the load of the engine 100 can be maintained, and the EGR gas does not become excessive.

  As described above, the opening degree of the intake throttle valve 8 is controlled based on the load of the engine being decelerated. While the above-described control is being executed, that is, steps S4 to S6 are being executed. If the fuel cut condition is satisfied in the meantime, the intake throttle valve 8 is immediately fully opened. By controlling the opening degree of the intake throttle valve 8 in this way, it is possible to suppress the actual EGR rate from being increased by the EGR gas remaining in the EGR pipe line 26.

  In addition, this invention is not limited to the above-mentioned embodiment.

  In the above-described embodiment, the first position and the second position are determined using a predetermined value corresponding to the load of the engine 100 as a determination criterion. However, the load of the engine 100 when decelerated is a predetermined value. It may be determined whether or not it is included in the range, and when it is determined that it is included in the predetermined range, the deceleration start point is determined to be the first position. The specific predetermined range in this case is, for example, a load region that is equal to or higher than the load at which the required EGR rate is the highest value. The load is set on the basis of the load range in the operating state until the required EGR rate gradually increases from the low value to the maximum value as the load decreases.

  In the case of such a deceleration start point determination, even if the first position is determined, the deceleration start point varies depending on the load of the engine 100, and the required EGR rate also varies. Therefore, the opening lower limit value may be set as one as in the above-described embodiment, but is preferably set higher as the load increases according to the load of the engine 100.

Further, the opening lower limit values are assumed to be set according to the degree of deceleration. That is, the degree of deceleration is determined based on the change in the load of engine 100 per unit time, and when the determined degree of deceleration is high, the deceleration is abrupt, and thus the opening lower limit value is set large. Thereby, the opening degree of the intake throttle valve 8 is limited not on the closed side but on the open side, and it is possible to suppress excessive recirculation of the EGR gas.

  In the case of slow deceleration, the opening lower limit value is set small. Therefore, the time until the opening of the intake throttle valve 8 reaches the opening lower limit value becomes long, and the EGR gas can be recirculated as long as possible. That is, since the driving time during which the EGR control during deceleration is increased, the fuel consumption can be improved.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  As an application example of the present invention, there is an internal combustion engine of a type that includes a so-called low-pressure loop type EGR device and controls an EGR gas amount by an intake throttle valve.

4a ... Turbine 4b ... Compressor 4 ... Turbocharger 8 ... Intake throttle valve 25 ... Exhaust gas recirculation device 33 ... Electronic control unit

Claims (1)

An internal combustion engine having a turbine driven by exhaust energy and a turbocharger driven by the turbine and compressing intake air, an intake throttle valve provided upstream of the compressor, an upstream of the compressor, and an intake throttle An intake throttle valve control method for an internal combustion engine, comprising an exhaust gas recirculation device that recirculates a part of the exhaust gas downstream of the valve, and controlling the opening of the intake throttle valve in accordance with the running state of the vehicle,
Detecting the operating state of the internal combustion engine,
When it is determined that the detected operating state is deceleration, a lower limit value for limiting the opening of the intake throttle valve is set .
An intake throttle valve control method for an internal combustion engine, which is changed according to the degree of deceleration of the operating state in which the lower limit value is detected .

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