JP5769506B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to control of an internal combustion engine associated with an exhaust gas recirculation device.

While reducing the emissions of the combustion temperature to reduce the by NO _x cylinders, a EGR device known to reduce the pumping loss (e.g., see Patent Document). The EGR device connects an exhaust path and an intake path via an EGR passage, and part of combustion gas generated in the cylinder is recirculated to the intake path via the EGR path and mixed into the intake air. The high-temperature and high-pressure exhaust gas immediately after being discharged from the cylinder is recirculated to the intake passage. What is refluxed is the low pressure loop EGR.

  The low pressure loop EGR is advantageous in that a large amount of EGR gas can be mixed into the intake air. On the other hand, the responsiveness of the control of the EGR rate or the EGR amount is higher in the high-pressure loop EGR. In the low pressure loop EGR, the outlet of the EGR passage is connected to the upstream side of the compressor of the exhaust turbocharger for the purpose of recirculating the EGR gas close to the atmospheric pressure. This is to reach the cylinder through a long path passing through the compressor, throttle valve, surge tank and intake manifold.

  When a deceleration request is made to loosen the depression of the accelerator pedal that the driver has depressed, it is necessary to quickly reduce the amount of EGR gas mixed in the intake air together with the intake air amount. However, there is a delay in the control of EGR, and a situation may occur in which the amount of EGR gas is excessive with respect to the amount of fresh air. Moreover, the temperature of the combustion chamber of the cylinder tends to be lower during EGR than in non-EGR, and the combustion in the combustion chamber becomes unstable due to an excessive amount of EGR gas, and sometimes misfires. This problem is particularly noticeable in a low-pressure loop EGR that recirculates a large amount of EGR gas.

JP 2004-245107 A

  The main object of the present invention is to stabilize combustion in a transition period in which the rotation of the engine or the vehicle speed decreases.

In the present invention, an in-cylinder injection type internal combustion engine attached with an EGR device is controlled, and when decelerating, transient control is performed in which fuel injection into a cylinder is divided into a plurality of times. The ratio of the amount of fuel injected after the second injection and the amount of fuel injected before that time is set according to the EGR rate or EGR amount at the time of deceleration, and the EGR rate or EGR amount is The larger the ratio is, the more the ratio of the former injection amount is increased, and the ratio of the injection amount of fuel injected after the second time and the injection amount of fuel injected before that in the transient control, or the injection after the second time. A control device for an internal combustion engine is characterized in that the timing of fuel injection is corrected in accordance with the ratio between the internal EGR gas amount and the external EGR gas amount in EGR .

  In other words, in the transient control period when the engine speed or the vehicle speed is decelerated, the ratio of the fuel injection amount to be injected from the second time onward is increased as a whole (as the fuel supply amount per one expansion stroke). While performing stoichiometric combustion at the stoichiometric air fuel ratio or an air fuel ratio close thereto, create a layer of gas rich in fuel components in the region near the injector in the combustion chamber to achieve stratified combustion, while stabilizing the combustion temperature It was made to raise.

  ADVANTAGE OF THE INVENTION According to this invention, the combustion in the transition period when engine rotation or a vehicle speed decelerates can be stabilized.

The figure which shows the whole structure of the internal combustion engine in one Embodiment of this invention. The flowchart which shows the example of a procedure of the process which the control apparatus of the embodiment performs in transient control.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle in the present embodiment. The internal combustion engine of the present embodiment supplies a plurality of cylinders 1 (one of which is shown in FIG. 1), an injector 11 that injects fuel into each cylinder 1, and intake air to each cylinder 1. An intake passage 3 for exhausting exhaust from each cylinder 1, an exhaust turbocharger 5 for supercharging intake air flowing through the intake passage 3, and from the exhaust passage 4 toward the intake passage 3. And an external EGR device 2 for refluxing the EGR gas.

  The internal combustion engine in the present embodiment is a three-cylinder four-cycle engine.

  The intake passage 3 takes in air from the outside and guides it to the intake port of the cylinder 1. On the intake passage 3, an air cleaner 31, a compressor 51 of the supercharger 5, an intercooler 32, an electronic throttle valve 33, a surge tank 34, an intake throttle valve 35, and an intake manifold 36 are arranged in this order from the upstream side.

  The exhaust passage 4 guides exhaust generated as a result of burning fuel in the cylinder 1 from the exhaust port of the cylinder 1 to the outside. An exhaust manifold 42, a drive turbine 52 for the supercharger 5, and a three-way catalyst 41 are disposed on the exhaust passage 4. In addition, an exhaust bypass passage 43 that bypasses the turbine 52 and a waste gate valve 44 that is a bypass valve that opens and closes the inlet of the bypass passage 43 are provided. The waste gate valve 44 is an electric waste gate valve that can be opened and closed by inputting a control signal l to the actuator, and a DC servo motor is used as the actuator.

  The exhaust turbocharger 5 is configured such that the drive turbine 52 and the compressor 51 are connected and linked in a coaxial manner. Then, the driving turbine 52 is rotationally driven by using the energy of the exhaust gas, and the compressor 51 is pumped by using the rotational force, whereby the intake air is pressurized and compressed (supercharged) and sent to the cylinder 1.

  The external EGR passage 2 realizes a so-called low pressure loop EGR. The pressure loss in the low-pressure loop EGR passage 2 is as small as several hundred Pa. The inlet of the external EGR passage 2 is connected to a predetermined location downstream of the three-way catalyst 41 in the exhaust passage 4. The outlet of the external EGR passage 2 is connected to a predetermined location in the intake passage 3 downstream of the intake throttle valve 35 and upstream of the compressor 51. An EGR cooler 21 and an EGR valve 22 are provided on the external EGR passage 2.

  In the low-pressure loop EGR, low-pressure exhaust gas close to atmospheric pressure is recirculated to the intake passage 3 through the EGR passage 2. For this purpose, the pressure around the outlet of the EGR passage 2 is reduced to a negative pressure by restricting the intake throttle valve 35 upstream of the outlet of the EGR passage 2. It should be noted that the pressure upstream of the intake throttle valve 35 in the intake passage 3 becomes substantially atmospheric pressure or becomes somewhat negative due to the operation of the compressor 51.

  Further, the internal combustion engine may include a variable valve timing mechanism that changes the opening / closing timing of the exhaust valve. The variable valve timing mechanism is a known one using, for example, a swing cylinder mechanism, and switches between a rotor fixed to the intake camshaft, a housing fitted on the outside of the rotor, and a hydraulic pressure for rotating the housing relative to the rotor. An oil control valve, which is a four-way electromagnetic switching control valve, and a pair of meshing gears, one attached to the housing and the other attached to the exhaust camshaft, are used as elements.

  The oil control valve switches the direction and amount of hydraulic oil flowing into and out of the housing. As a result, the relative angle of the housing with respect to the rotor is displaced, and a desired phase difference is generated between the intake cam shaft and the exhaust cam shaft. If the closing timing of the exhaust valve is advanced, the combustion gas can be left in the cylinder 1, and an internal EGR that mixes this with the intake air inside the cylinder 1 is realized.

  An ECU (electronic control unit) 0 that controls operation of the internal combustion engine is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like. The input interface outputs a vehicle speed signal a output from a vehicle speed sensor that detects the vehicle speed, a rotation speed signal b output from a rotation speed sensor that detects the engine rotation speed, and an accelerator sensor that detects the amount of depression of the accelerator pedal. An accelerator opening signal c, a temperature / pressure signal d output from a temperature / pressure sensor that detects intake air temperature and intake pressure (supercharging pressure) in the intake passage 3 (particularly, the surge tank 34), and cooling of the internal combustion engine A coolant temperature signal e output from a water temperature sensor for detecting the water temperature, a crank angle signal and cylinder discrimination signal f output from a timing sensor at the end of the intake camshaft, and a timing sensor at the end of the exhaust camshaft An exhaust cam signal g or the like output every rotation of a predetermined crank angle is input. From the output interface, the fuel injection signal h for the injector 11, the ignition signal i for the ignition plug (ignition coil thereof), the opening operation signal j for the EGR valve 22, and the opening operation for the throttle valve 33. Signal k, opening operation signal l for waste gate valve 44, opening operation signal m for intake throttle valve 35, direction of hydraulic oil corresponding to exhaust valve timing for oil control valve of variable valve timing mechanism And an amount control signal n and the like are output. The amount of depression of the accelerator pedal can be considered as a required load (engine output) commanded by the driver.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, and g necessary for operation control of the internal combustion engine via the input interface, and based on them, the intake air amount, the required fuel injection amount, the ignition timing, A required EGR rate (or EGR amount) or the like is calculated. Then, various control signals h, i, j, k, l, m, and n corresponding to the calculation result are applied through the output interface. Since the calculation method of the control inputs h, i, j, k, l, m, and n can be the same as the operation control of a known internal combustion engine, a detailed description is omitted.

  The ECU 0 serving as a control device performs transient control in which fuel injection into the cylinder 1 is divided into a plurality of times when the rotational speed of the internal combustion engine or the traveling speed of the vehicle is decelerated. The determination as to whether or not to implement transient control may be made on the condition that the rotational speed obtained by referring to the rotational speed signal b is reduced, or on the condition that the vehicle speed obtained by referring to the vehicle speed signal a can be reduced It is good. Alternatively, the condition may be that the accelerator pedal depression amount (or the opening degree of the throttle valve 33) obtained by referring to the accelerator opening degree signal c is reduced.

  In this embodiment, in the transient control at the time of deceleration, fuel injection into the cylinder 1 is divided into two times, the first time is performed during the intake stroke, and the second time is performed during the compression stroke or at the end of the intake stroke (lower intake stroke). Near the dead point).

  The timing of the second fuel injection is determined according to at least the required EGR rate or the opening degree of the EGR valve 22 at that time. The required EGR rate referred to here is the ratio of the total amount of required external EGR gas and internal EGR gas to the intake air charged in the cylinder 1. However, the required EGR rate may be considered using only the external EGR gas amount, such as when the internal EGR is not performed. The second fuel injection timing is retarded (delayed) as the required EGR rate or the opening degree of the EGR valve 22 is increased, and advanced (advanced) as the required EGR rate or the opening degree of the EGR valve 22 is decreased. This is because as the required EGR rate or the opening degree of the EGR valve 22 increases, the cylinder 1 is filled with more EGR gas and the temperature in the combustion chamber of the cylinder 1 also decreases.

  In addition, the timing of the second fuel injection can be corrected with reference to the engine speed at that time. That is, the timing of the second fuel injection is retarded as the engine speed is low, and advanced as the engine speed is high.

  Then, the ratio between the amount of the second fuel injection and the amount of the first fuel injection is set at least according to the required EGR rate or the opening degree of the EGR valve 22 at that time. Specifically, as the required EGR rate or the opening degree of the EGR valve 22 is larger, the second fuel injection amount is increased and the first fuel injection amount is decreased.

  The ratio between the amount of fuel injection for the second time and the amount of fuel injection for the first time can also be corrected with reference to the engine speed at that time. That is, the ratio of the second fuel injection amount is increased as the engine speed is lower, and is decreased as the engine speed is higher. This is because when the engine speed is high, the mixing time of the intake air and the fuel is short, and if the ratio of the second fuel injection amount is increased, smoke (black smoke) may be discharged.

  After the transient control is finished, the process shifts to steady control. In the steady control, the fuel injection into the cylinder 1 may be performed once per one expansion stroke or may be performed a plurality of times (split injection).

  FIG. 2 shows a procedure of processing executed by the ECU 0. When the ECU 0 detects the rotation of the engine or the deceleration of the vehicle speed (step S1), it shifts to the transient control. In the transient control, the second fuel injection amount and the first fuel injection amount are set according to the required EGR amount at that time or the opening degree of the EGR valve 22 (step S2), and the required EGR amount at that time Alternatively, the timing of the second fuel injection is determined according to the opening degree of the EGR valve 22 or the like (step S3). Then, split fuel injection and ignition are performed (step S4). These steps S2 to S4 are repeated continuously until a transition is made to steady control (step S5).

  In this embodiment, the EGR device 2 controls an in-cylinder injection type internal combustion engine, and when decelerating, performs transient control in which fuel injection into the cylinder 1 is performed in a plurality of times, In the transient control, the ratio of the amount of fuel injected after the second injection and the amount of fuel injected before that time is set according to the EGR rate (or EGR amount) at the time of deceleration. The control device 0 for the internal combustion engine is configured to increase the ratio of the former injection amount as the EGR rate is larger.

  According to the present embodiment, the ratio of the fuel injection amount to be injected after the second time is increased in the transient control period during deceleration, and as a whole (as the fuel supply amount per one expansion stroke), the stoichiometric air-fuel ratio. Alternatively, while performing stoichiometric combustion at an air-fuel ratio close to this, a layer of gas rich in the fuel component is created in the region near the injector 11 and the spark plug in the combustion chamber to achieve stratified combustion, and while stabilizing the combustion, The temperature can be raised. Therefore, even if more external EGR gas is recirculated through the intake passage 3 and / or more internal EGR gas is left in the cylinder 1, the risk of misfire is reduced. EGR can be actively used, which contributes to improved fuel efficiency.

  The present invention is not limited to the embodiment described in detail above. In the above-described embodiment, the fuel injection is performed twice in the transient control. However, the fuel injection is not prevented from being performed three times or more. In that case, it may be injected several times during the intake stroke, or it may be injected multiple times during the compression stroke or at the end of the intake stroke. In any case, the ratio between the amount of fuel injected during the intake stroke and the amount of fuel injected during the compression stroke or at the end of the intake stroke is set according to the EGR rate or the like.

  In transient control, the ratio of the amount of fuel injected after the second injection to the amount of fuel injected before that is expressed as the degree of deceleration (unit time of engine speed, vehicle speed or accelerator pedal depression amount at that time) You may correct | amend according to a hit reduction amount. That is, the greater the degree of deceleration, the greater the fuel injection amount that is injected after the second time, and the lower the fuel injection amount that is injected before that. Then, misfire due to excessive EGR during sudden deceleration can be effectively prevented.

  Even if the ratio of the injection amount of fuel injected after the second time and the injection amount of fuel injected before that in the transient control is corrected according to the ratio of the internal EGR gas amount and the external EGR gas amount in EGR Good. Since the temperature of the external EGR gas is lower than the temperature of the internal EGR gas, the higher the ratio of the external EGR gas amount, the larger the fuel injection amount to be injected after the second time and the lower the fuel injection amount to be injected before that. .

  Further, the timing of fuel injection to be injected after the second time in the transient control may be corrected according to the ratio between the internal EGR gas amount and the external EGR gas amount in the EGR. That is, as the ratio of the external EGR gas amount is higher, the timing of fuel injection to be injected after the second time is retarded.

  The EGR device is not limited to the one that realizes the low-pressure loop EGR. Even if what is attached to the internal combustion engine is a high-pressure loop EGR device, the same effects as in the above embodiment can be obtained. Needless to say, the low pressure loop EGR device and the high pressure loop EGR device may be used in combination.

  In addition, the specific configuration of each unit, the processing procedure, and the like can be variously modified without departing from the spirit of the present invention.

  The present invention can be used for an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
1 ... Cylinder 2 ... Exhaust gas recirculation device

Claims (1)

An in-cylinder injection type internal combustion engine attached with an exhaust gas recirculation device is controlled,
When decelerating, perform transient control to inject fuel into the cylinder in multiple times,
In the transient control, the ratio between the injection amount of fuel injected after the second time and the injection amount of fuel injected before that time is set according to the EGR rate or the EGR amount at the time of deceleration, and the EGR rate Or, as the EGR amount is larger, the ratio of the former injection amount is increased ,
In the transient control, the ratio of the injection amount of fuel injected after the second time and the injection amount of fuel injected before that time, or the timing of the fuel injection injected after the second time is expressed as the internal EGR gas amount in EGR. A control apparatus for an internal combustion engine, wherein the correction is made in accordance with a ratio to an external EGR gas amount .

Images