JP2015178778A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of combustion properties caused by excessive EGR in the case of decelerating from a state involving recirculation of EGR gas in an internal combustion engine with a supercharger including an EGR device.SOLUTION: A control device for an internal combustion engine includes: an EGR passage 30 for connecting an exhaust passage 12 downstream of a turbine 142 of a turbocharger 14 to a compressor downstream side intake passage 102; an EGR valve 32 disposed in an EGR passage 30; an EGR bypass passage 36 branched from the intake side of the EGR valve 32 in the EGR passage 30 and connected to a compressor upstream side intake passage 101; flow passage selector valves 38 and 40 that can select a communication destination on the intake side of the EGR valve 32 in the EGR passage 30 between the downstream side intake passage 102 and the upstream side intake passage 101. When the EGR valve 32 is closed during deceleration of the engine, the flow passage selector valves 38 and 40 are controlled to switch the communication destination on the intake side of the EGR valve 32 from the downstream side intake passage 102 to the upstream side intake passage 101.

Description

  The present invention relates to a control device for an internal combustion engine.

  Conventionally, for example, Japanese Patent Application Laid-Open No. 2008-38767 discloses an engine with a supercharger that includes an EGR device that recirculates EGR gas from the downstream side of the turbine to the intake manifold of the intake passage. Such an apparatus that recirculates EGR gas from the low-pressure turbine downstream side is called an LPL (Low-Pressure Loop) -EGR apparatus. According to the LPR-EGR device, it is possible to perform EGR in which a decrease in supercharging response after deceleration is suppressed.

JP 2008-38767 A

  Since the LPL-EGR device recirculates the exhaust gas downstream of the turbine, there is a potential problem that the piping volume of the EGR passage is large. For this reason, in the above-described conventional apparatus, even if the EGR valve is closed in response to an acceleration / deceleration request in the EGR gas recirculation region, EGR gas corresponding to the remaining pipe volume in the EGR passage is recirculated to the intake manifold. Therefore, there is a concern about deterioration of combustibility due to excessive EGR.

  The present invention has been made in view of the above-described problems. In an internal combustion engine equipped with a supercharger equipped with an EGR device, when decelerating from a state involving recirculation of EGR gas, combustibility deterioration due to excessive EGR is reduced. An object of the present invention is to provide a control device for an internal combustion engine that can be suppressed.

In order to achieve the above object, a first invention provides a control device for an internal combustion engine,
A turbocharger having a compressor disposed in the intake passage and a turbine disposed in the exhaust passage;
An EGR passage connecting the exhaust passage downstream of the turbine and the compressor downstream intake passage which is the intake passage downstream of the compressor;
An EGR valve disposed in the EGR passage;
An EGR bypass passage branched from the downstream side of the EGR valve of the EGR passage and connected to a compressor upstream intake passage which is the intake passage upstream of the compressor;
A flow path switching means capable of selecting a communication side on the intake side of the EGR valve in the EGR path between the compressor downstream side intake path and the compressor upstream side intake path;
Control means for controlling the flow path switching means so that the communication destination is switched from the compressor downstream intake passage to the compressor upstream intake passage when the EGR valve is closed during deceleration of the internal combustion engine;
It is characterized by having.

  According to the first aspect of the present invention, when the EGR valve is closed during deceleration, the flow on the intake side of the EGR valve in the EGR passage is switched from the compressor downstream intake passage to the compressor upstream intake passage. The path switching means is controlled. According to such an operation, it is avoided that the EGR gas remaining on the intake side of the EGR valve in the EGR passage is recirculated to the compressor downstream intake passage, and the remaining EGR gas is further reduced. The refrigerant is returned to the compressor upstream intake passage with a large transport delay. As a result, it is possible to suppress a situation in which EGR suddenly becomes excessive when the EGR valve is closed, so that it is possible to effectively avoid the occurrence of misfiring due to deterioration of combustibility.

It is a figure which shows the structure of the engine system to which the control apparatus of Embodiment 1 of this invention is applied. It is a flowchart which shows the routine for the transient engine control performed by the control apparatus of Embodiment 1 of this invention. It is a figure which shows the structure of the engine system with which the control apparatus of Embodiment 2 of this invention is applied. It is a flowchart which shows the routine for the transient engine control performed by the control apparatus of Embodiment 2 of this invention. It is a flowchart which shows the routine for the transient engine control performed by the control apparatus of Embodiment 3 of this invention.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of an engine system to which a control device of the present invention is applied in the first embodiment. The internal combustion engine provided in this engine system is a gasoline engine with a turbocharger (hereinafter simply referred to as an engine). The engine body 2 is provided with four cylinders in series, and an injector 8 is provided for each cylinder. An intake manifold 4 and an exhaust manifold 6 are attached to the engine body 2.

  An intake passage 10 through which fresh air taken in from the air cleaner 20 flows is connected to the intake manifold 4. A compressor 141 of a turbocharger 14 is attached to the intake passage 10. In the intake passage 10, an intercooler 22 is provided downstream of the compressor 141, and a throttle valve 24 is provided downstream thereof. In the following description, the intake passage 10 upstream of the compressor 141 is also referred to as “compressor upstream intake passage 101”, and the intake passage 10 downstream of the compressor 141 is also referred to as “compressor downstream intake passage 102”. To do.

  The exhaust manifold 6 is connected to an exhaust passage 12 for releasing the exhaust gas emitted from the engine body 2 into the atmosphere. A turbine 142 of the turbocharger 14 is attached to the exhaust passage 12. In the exhaust passage 12, S / C 42 and U / F 44 as a three-way catalyst are provided downstream of the turbine 142.

  The engine system includes an LPL-EGR device that recirculates exhaust gas from the exhaust system to the intake system. In the EGR device, a position downstream of the throttle valve 24 in the compressor downstream intake passage 102 and a position downstream of the turbine 142 in the exhaust passage 12 are connected by the EGR passage 30. An EGR valve 32 is provided in the EGR passage 30. An EGR cooler 34 is provided on the exhaust side of the EGR valve 32 in the EGR passage 30.

  Further, the EGR device connects the intake side position of the EGR valve 32 in the EGR passage 30 and the compressor upstream side intake passage 101 by an EGR bypass passage 36. A flow path switching valve 38 is provided at a connection portion of the EGR passage 30 to the compressor downstream side intake passage 102. Further, a flow path switching valve 40 is provided at a connection portion of the EGR bypass passage 36 with the EGR passage 30.

The engine system includes an ECU (Electronic Control Unit) 50. The ECU 50 is a control device that comprehensively controls the entire engine system. The ECU 50 captures and processes signals from various sensors included in the engine system. Sensors are installed in various parts of the engine system. For example, a boost pressure sensor 54 is attached downstream of the throttle valve 24 in the intake passage 10. Further, a rotation speed sensor 52 for detecting the rotation of the crankshaft, an accelerator pedal opening sensor 56 for outputting a signal corresponding to the opening degree of the accelerator pedal, an air flow meter 58 for outputting a signal corresponding to the intake air amount Ga, and an air cleaner 20 A pressure sensor 60 and a temperature sensor 62 for detecting the internal pressure _Pac and the temperature _Tac are also attached. The ECU 50 processes the signals of the acquired sensors and operates the actuators according to a predetermined control program. The actuator operated by the ECU 50 includes the injector 8, the throttle valve 24, the EGR valve 32, the flow path switching valves 38 and 40, and the like. There are many actuators and sensors connected to the ECU 50 other than those shown in the figure, but the description thereof is omitted in this specification.

  In the present embodiment, the engine control executed by the ECU 50 includes EGR control. In the EGR control, the operation amounts of the throttle valve 24, the EGR valve 32, and the flow path switching valves 38 and 40 that affect the EGR rate are cooperatively controlled. Specifically, the EGR control includes steady EGR control executed in a steady state and transient EGR control executed in a transient state. The engine control executed in the present embodiment is characterized by transient EGR control, more specifically, transient EGR control when decelerating from a steady state. Hereinafter, the details of the transient engine control executed in the present embodiment will be described using a flowchart.

  The flowchart of FIG. 2 shows a routine for transient engine control executed by the ECU 50 in the present embodiment. In step S2 of this routine, it is determined whether the ignition (IG) is turned on. Until the ignition is turned on, this step is in a standby state. When the ignition is turned on, the process proceeds to the next step S4.

  In step S4, the gradient of the accelerator pedal opening calculated from the signal of the accelerator pedal opening sensor 56, that is, the time differential value Ps is acquired. The accelerator pedal opening gradient Ps is used as information for determining whether the driver has started deceleration of the vehicle.

  In the next step S6, it is determined whether or not the execution condition of the transient EGR control is satisfied depending on whether or not the absolute value of the accelerator pedal opening gradient Ps acquired in step S4 exceeds a predetermined start reference value. While the absolute value of the accelerator pedal opening gradient Ps is equal to or less than the start reference value, the execution of the transient control is suspended by repeatedly performing the steps S2 to S6. When the absolute value of the accelerator pedal opening gradient Ps exceeds the start reference value, the transient engine control is started, and the processes of the following steps S8 to S24 are sequentially executed.

  In step S8, the flow path switching valve 38 is closed (fully closed). In step S10, the EGR valve 32 is closed. In step S12, the flow path switching valve 40 is opened (fully opened). By the processing from step S8 to S12, the EGR passage 30 is blocked by the EGR valve 32, and the communication side on the intake side of the EGR valve 32 in the EGR passage 30 is changed from the compressor downstream intake passage 102 to the compressor upstream intake passage 101. Can be switched. The EGR gas remaining on the intake side of the EGR valve 32 in the EGR passage 30 is returned to the compressor upstream intake passage 101 via the EGR bypass passage 36.

  In step S14, the EGR gas temperature is acquired. Then, in the next step S16, whether or not the steady condition of EGR control is satisfied depending on whether or not the difference between the EGR gas temperature acquired in step S14 and the gas temperature Tac in the air cleaner 20 is below a predetermined reference value, That is, it is determined whether or not all the EGR gas remaining on the intake side of the EGR valve 32 in the EGR passage 30 has been recirculated. As a result, while the difference value is equal to or larger than the reference value, the subsequent processes are suspended by repeatedly performing the processes from step S14 to S16.

  When the difference value falls below the reference value, the process proceeds to the next step S18. In step S18, the flow path switching valve 40 is closed (fully closed). In step S20, the flow path switching valve 38 is opened (fully opened).

  In step S22, the gradient of the accelerator pedal opening calculated from the signal of the accelerator pedal opening sensor 56, that is, the time differential value Ps is acquired. Then, whether or not the termination condition of the transient engine control is satisfied depending on whether or not the absolute value of the acquired accelerator pedal opening gradient Ps falls below a predetermined termination reference value, that is, whether the driver has finished decelerating the vehicle. Judgment is made. While the absolute value of the accelerator pedal opening gradient Ps is equal to or greater than the end reference value, the end of the transient engine control is suspended by repeatedly performing the process of step S22. The transient engine control is ended when the absolute value of the accelerator pedal opening gradient Ps falls below the end reference value, and the EGR valve 32 is opened in the next step S24.

  The ECU 50 closes the EGR valve 32 during acceleration / deceleration of the vehicle as described above, and the EGR gas remaining on the intake side of the EGR valve 32 in the EGR passage 30 passes through the EGR bypass passage 36 to the compressor upstream intake passage 101. To reflux. As a result, it is possible to prevent the EGR rate from rapidly rising and the combustion state from deteriorating in a transient state immediately after acceleration / deceleration of the vehicle.

  By the way, in the apparatus of the first embodiment described above, the communication side on the intake side of the EGR passage 30 is switched using the flow path switching valves 38 and 40. However, the configuration capable of switching the communication destination is not limited to this. That is, instead of the flow path switching valves 38 and 40, a three-way valve may be installed at the connection portion between the EGR passage 30 and the EGR bypass passage 36 to switch the communication side on the intake side of the EGR valve 32.

  In the embodiment described above, the flow path switching valves 38 and 40 correspond to the “flow path switching means” in the first invention. Further, the “control means” according to the first aspect of the present invention is realized by the ECU 50 executing the processes of steps S2 to S12.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to the drawings.

  FIG. 3 is a diagram showing a configuration of an engine system to which the control device of the present invention is applied in the second embodiment. The engine system shown in this figure has the same configuration as the engine system shown in FIG. 1 except that the EGR bypass passage 36 and the flow path switching valves 38 and 40 are not provided. The second embodiment of the present invention is characterized in that the reduced-cylinder operation is performed during deceleration of the vehicle in the transient EGR control executed by the ECU 50. Hereinafter, the details of the transient EGR control executed in the present embodiment will be described using a flowchart.

  The flowchart of FIG. 4 shows a routine for transient EGR control executed by the ECU 50 in the present embodiment. This routine includes the same processing as the transient EGR control routine shown in FIG. In the flowchart of FIG. 4, steps that perform the same processing as the transient EGR control shown in FIG. 2 are assigned the same step numbers as the step numbers assigned in the routine.

  In S6 of the routine shown in FIG. 4, it is determined whether or not the execution condition of the transient EGR control is satisfied depending on whether or not the absolute value of the accelerator pedal opening gradient Ps acquired in Step S4 exceeds the start reference value. . Then, the transient EGR control is started when the absolute value of the accelerator pedal opening gradient Ps exceeds the start reference value, and the processes of the following steps S30 to S48 are executed in order.

In step S30, the engine rotational speed NE calculated from the signal from the rotational speed sensor 52 is acquired, and the intake air amount Ga calculated from the signal from the air flow meter 58 and the EGR valve opening that is the opening of the EGR valve 32 are obtained. θ _EGR is obtained. In step S32, the EGR flow rate Ge is calculated using the three-dimensional map of the engine speed NE, the intake air amount Ga, and the EGR valve opening degree θ _EGR acquired in step S30.

Next, in step S34, using the following equation (1), the target load factor Ga _t in the case of performing the reduced-cylinder operation of the cylinder speed Ns is calculated by the engine of the total number of cylinders N.

At step S36, signal calculated intake pipe pressure Pm from the boost pressure sensor 54, an air cleaner in pressure is calculated from the signal of the pressure sensor 60 and temperature sensor 62 provided in the air cleaner 20 P _ac and the air cleaner in the temperature T _ac is acquired. Then, in step S38, the using the following equation (2), the target throttle opening degree TA _t for achieving the target load factor Ga _t calculated in step S34 is calculated. Incidentally, the A _t in equation (2) is the cross-sectional area of the throttle, the μ is the channel coefficient.

Next, in step S40, a reduced cylinder process is executed. Here, specifically, with the throttle opening is controlled to the target throttle opening degree TA _t calculated in the process at step S38, the fuel injection of the specific cylinder is stopped. Next, in step S42, the intake pipe pressure Pm is acquired again. In the next step S42, the time differential value of the intake pipe pressure Pm is calculated from the history of the intake pipe pressure Pm. Then, in the next step S44, it is determined whether or not it is in a steady state depending on whether or not the calculated time differential value has fallen below a preset threshold value. While the time differential value of the intake pipe pressure Pm is equal to or greater than the threshold value, the subsequent process is suspended by repeatedly performing the process of step S42. When the time differential value of the intake pipe pressure Pm falls below the threshold value, it is determined that the steady state has been reached in the reduced-cylinder operation, and the process proceeds to the next step.

  In the next step S46, vehicle deceleration processing is performed. More specifically, the throttle valve 24 is closed, the ignition timing is retarded, the fuel injection is cut off, or the EGR valve 32 is closed according to the accelerator pedal opening, the engine speed, and the like. The engine is decelerated. In the next step S48, the gradient of the accelerator pedal opening calculated from the signal of the accelerator pedal opening sensor 56, that is, the time differential value Ps is acquired. Then, whether or not the termination condition of the deceleration process is satisfied depending on whether or not the absolute value of the acquired accelerator pedal opening gradient Ps falls below a predetermined termination reference value, that is, whether or not the driver has finished deceleration of the vehicle. Is judged. While the absolute value of the accelerator pedal opening gradient Ps is equal to or greater than the end reference value, the end of the deceleration process is suspended by repeatedly performing the process of step S46. The deceleration process is terminated when the absolute value of the accelerator pedal opening gradient Ps falls below the end reference value.

  The ECU 50 performs the deceleration process of the vehicle after performing the cylinder reduction process in this way. As a result, it is possible to suppress the EGR rate from rapidly rising and the combustion state from deteriorating in a transient state immediately after deceleration of the vehicle.

Embodiment 3
Next, Embodiment 3 of the present invention will be described with reference to the drawings.

  The third embodiment of the present invention is control applicable to an engine capable of performing air amount control by adjusting a valve lift or valve overlap of the air amount. The third embodiment is characterized in that in the transient engine control executed by the ECU 50, the air amount adjustment immediately after deceleration is performed by a valve lift or a valve overlap. Hereinafter, the details of the transient engine control executed in the present embodiment will be described using a flowchart.

  The flowchart of FIG. 5 shows a routine for transient engine control executed by the ECU 50 in the present embodiment. This routine includes the same processing as the transient engine control routine shown in FIG. In the flowchart of FIG. 5, steps that perform the same processing as the transient engine control shown in FIG. 4 are given the same step numbers as the step numbers assigned in the routine.

When the process of step S36 of the routine shown in FIG. 5 is executed, in the next step S50, the target valve lift for achieving the target load factor Ga _t calculated in step S34 L _t or target valve overlap OL _t Is calculated. Next, in step S40, a reduced cylinder process is executed. Next, in step S42, the intake pipe pressure Pm is acquired again. Then, in the next step S44, it is determined whether or not it is in a steady state depending on whether or not the time differential value of the intake pipe pressure Pm is below a preset threshold value.

  In the next step S52, vehicle deceleration processing is performed. More specifically, the engine is decelerated by decreasing the valve lift or increasing the valve overlap in accordance with the accelerator pedal opening, the engine speed, and the like. In the next step S48, it is determined whether or not the condition for terminating the deceleration process is satisfied, that is, whether or not the driver has finished decelerating the vehicle. While the absolute value of the accelerator pedal opening gradient Ps is equal to or greater than the end reference value, the end of the deceleration process is suspended by repeatedly performing the process of step S52. The deceleration process is terminated when the absolute value of the accelerator pedal opening gradient Ps falls below the end reference value.

  The ECU 50 performs the deceleration process of the vehicle after performing the cylinder reduction process in this way. As a result, it is possible to suppress the EGR rate from rapidly rising and the combustion state from deteriorating in a transient state immediately after deceleration of the vehicle. At this time, the ECU 50 performs a deceleration process by controlling the valve lift or the valve overlap. As a result, the air amount can be quickly adjusted in a transient state immediately after the vehicle is decelerated.

2 Engine body 4 Intake manifold 6 Exhaust manifold 8 Injector 10 Intake passage 101 Compressor upstream side intake passage 102 Compressor downstream side intake passage 12 Exhaust passage 14 Turbo supercharger 141 Compressor 142 Turbine 20 Air cleaner 22 Intercooler 24 Throttle valve 30 EGR passage 32 EGR valve 34 EGR cooler 36 EGR bypass passage 38, 40 Flow path switching valve 42 Three-way catalyst (S / C)
44 Three-way catalyst (U / F)
50 ECU
52 Rotational Speed Sensor 54 Supercharging Pressure Sensor 56 Accelerator Pedal Opening Sensor 58 Air Flow Meter 60 Pressure Sensor 62 Temperature Sensor

Claims (1)

A turbocharger having a compressor disposed in the intake passage and a turbine disposed in the exhaust passage;
An EGR passage connecting the exhaust passage downstream of the turbine and the compressor downstream intake passage which is the intake passage downstream of the compressor;
An EGR valve disposed in the EGR passage;
An EGR bypass passage branched from the intake side of the EGR valve of the EGR passage and connected to a compressor upstream intake passage that is the intake passage upstream of the compressor;
A flow path switching means capable of selecting a communication side on the intake side of the EGR valve in the EGR path between the compressor downstream side intake path and the compressor upstream side intake path;
Control means for controlling the flow path switching means so that the communication destination is switched from the compressor downstream intake passage to the compressor upstream intake passage when the EGR valve is closed during deceleration of the internal combustion engine;
A control device for an internal combustion engine, comprising:

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