JP2013036377A - Control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a temperature rising effect of an in-cylinder combustion chamber by an internal EGR.SOLUTION: When the internal EGR is performed by controlling the opening/closing timing of an intake valve and an exhaust valve in an internal combustion engine provided with a variable valve timing mechanism, the exhaust valve is closed in a low and middle load region on and after the exhaust top dead center, then the intake valve is opened after a required crank angle is passed. An overlapped period when both the intake valve and the exhaust valve are opened is not provided, consequently a part of the exhaust gas in the cylinder is prevented from flowing out to an intake air passage side, and being cooled and refilled in the cylinder, and the temperature drop in the in-cylinder combustion chamber is effectively avoided.

Description

  The present invention relates to a control device that controls a variable valve timing mechanism provided in an internal combustion engine.

  2. Description of the Related Art An internal combustion engine mounted on a vehicle or the like is known that includes a variable valve timing mechanism that can variably control the valve timing of an intake valve and / or an exhaust valve (see, for example, the following patent document).

  One of uses of the variable valve timing mechanism is internal EGR (Exhaust Gas Recirculation). In the internal EGR, by delaying the closing timing of the exhaust valve, the valve overlap period in which both the intake valve and the exhaust valve are open is lengthened, and the exhaust gas discharged from the cylinder is put into the cylinder at the beginning of the intake stroke. Back flow. By this internal EGR, the temperature of the in-cylinder combustion chamber can be raised to promote the vaporization of fuel, and the combustion can be stabilized particularly in the low and medium load regions.

  However, during the valve overlap period, part of the exhaust gas in the cylinder flows out from the intake port to the intake passage side. The exhaust gas that has flowed out is cooled in the intake passage and then filled into the cylinder again. Therefore, there is a problem that the temperature rise effect of the in-cylinder combustion chamber is reduced.

Japanese Patent Laid-Open No. 01-187356

  An object of the present invention is to further increase the temperature rise effect of the in-cylinder combustion chamber by the internal EGR.

  The present invention relates to a control device for controlling the opening and closing timings of an intake valve and an exhaust valve in an internal combustion engine having a variable valve timing mechanism capable of changing the opening and closing timings of an intake valve and an exhaust valve. The control device is configured to perform control to close the exhaust valve after exhaust top dead center and open the intake valve after closing the exhaust valve in an operation region where the load is equal to or less than a predetermined value.

  That is, when carrying out the internal EGR, the valve overlap period in which both the intake valve and the exhaust valve are open is not intentionally provided, but the exhaust gas in the cylinder is prevented from flowing out to the intake passage side. .

  According to the present invention, the temperature rise effect of the in-cylinder combustion chamber by the internal EGR can be further enhanced.

The figure which shows the whole structure of the internal combustion engine in one Embodiment of this invention. The timing diagram explaining the content of the valve timing control which the control apparatus of the embodiment performs.

  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. This internal combustion engine is of a direct injection type, and includes a plurality of cylinders 1 (one of which is shown in FIG. 1), an injector 11 for injecting fuel into each cylinder 1, An intake passage 3 for supplying intake air to the cylinder 1, an exhaust passage 4 for discharging exhaust from each cylinder 1, an exhaust turbocharger 5 for supercharging intake air flowing through the intake passage 3, and an exhaust passage And an external EGR device 2 that recirculates external EGR gas from 4 toward the intake passage 3.

  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, and an intake manifold 35 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 device 2 realizes a so-called high-pressure loop EGR. The inlet of the external EGR passage is connected to a predetermined location upstream of the turbine 52 in the exhaust passage 4. The outlet of the external EGR passage is connected to a predetermined location downstream of the throttle valve 33 in the intake passage 3, specifically to a surge tank 34. An EGR cooler 21 and an EGR valve 22 are also provided on the external EGR passage.

  The internal combustion engine in this embodiment is equipped with a variable valve timing mechanism that changes the opening / closing timings of the intake valve 12 and the exhaust valve 13. The specific mode of the variable valve timing mechanism is arbitrary and not uniquely limited. For example, the intake valve 12 and the exhaust valve 13 are electromagnetic valves, the intake camshaft and the exhaust camshaft are each advanced or retarded by the hydraulic pressure, and the intake valve 12 is opened. Various known mechanisms such as a valve-driven intake cam and a plurality of exhaust cams that open and drive the exhaust valve 13 are prepared and the cams are properly used, and the lever ratio of the rocker arm is changed by an electric motor. It is permissible to select from among them.

  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 includes a vehicle speed signal a output from a vehicle speed sensor that detects the vehicle speed, an engine rotation signal b output from the engine rotation sensor that detects the rotation angle of the crankshaft and thus the engine speed, and the amount of depression of the accelerator pedal (or , An accelerator opening signal c output from an accelerator opening sensor that detects the opening of the throttle valve 33, and an intake air temperature output from a temperature sensor that detects the intake air temperature in the intake passage 3 (particularly, the surge tank 34). A signal d, an intake pressure signal e output from a pressure sensor for detecting an intake pressure (supercharging pressure) in the intake passage 3, a cooling water temperature signal f output from a water temperature sensor for detecting a cooling water temperature of the internal combustion engine, an intake cam An exhaust cam signal g and the like output from the cam angle sensor are input at a plurality of cam angles of the shaft. The engine rotation sensor generates a pulse signal b every 10 ° CA (crank angle), for example. The cam angle sensor generates a pulse signal g every 240 ° CA for an angle obtained by dividing 720 ° CA by the number of cylinders, or for a three-cylinder engine. The amount of depression of the accelerator pedal (or the opening of the throttle valve 33) c can be regarded as a required load commanded by the driver, in other words, an engine output. However, the intake pressure e or the filling amount of the intake air into the cylinder 1 calculated based on the intake pressure e may be regarded as the required load.

  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. The operation signal l is output to the signal k, the waste gate valve 44, and the control signals m and n are output to the variable valve timing mechanism. The control signals m and n are signals for controlling the opening / closing timing of the intake valve 12 and the opening / closing timing of the exhaust valve 13, respectively. For example, if the intake valve 12 and the exhaust valve 13 are each a solenoid valve, the signal m input to the solenoid when the intake valve 12 is opened, and the signal input to the solenoid when the exhaust valve 13 is opened. n. If the mechanism is such that the rotational phase of each of the intake camshaft and the exhaust camshaft with respect to the crankshaft is operated by hydraulic pressure, an OCV that controls the flow direction and flow rate of hydraulic fluid applied to the hydraulic vane attached to the intake camshaft ( DUTY signal m to be input to Oil Control Valve), and DUTY signal n to be input to OCV for controlling the flow direction and flow rate of hydraulic fluid applied to the hydraulic vane attached to the exhaust camshaft. If the intake cam and the exhaust cam are used separately, the signal m to be input to the switching valve that controls the flow direction of the hydraulic fluid that switches the intake cam profile, and the switching valve that controls the flow direction of the hydraulic fluid that switches the exhaust cam profile The signal n is input. If the lever ratio of the rocker arm is changed by an electric motor, the signal m defines the amount and direction of rotation of the electric motor that drives the intake-side rocker arm, and the rotation of the electric motor that drives the exhaust-side rocker arm. The signal n defines the amount and the direction of rotation.

  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), a required valve timing of the intake valve 12, and the like are calculated. Then, various control signals h, i, j, k, l, and m corresponding to the calculation result are applied through the output interface.

  The ECU 0 serving as the control device performs the valve timing control described below when the required load (or engine output) for the internal combustion engine is in a low load to medium load operation region where the required load is less than a predetermined value.

  That is, as shown in FIG. 2, the exhaust valve 13 that is opened in the exhaust stroke (the valve lift amount is indicated by a broken line in the figure) is closed after a predetermined crank angle t has passed after the exhaust top dead center. I speak. At the same time, the intake valve 12 to be opened in the intake stroke (the valve lift amount is indicated by a solid line in the figure) is opened after the exhaust valve 13 is closed. This control is performed for the purpose of increasing the temperature of the combustion chamber in the cylinder 1 by the internal EGR. However, unlike the conventionally known internal EGR control, both the intake valve 12 and the exhaust valve 13 are opened. The valve overlap period is not provided.

  The crank angle t from the exhaust top dead center to the closing of the exhaust valve 13, that is, the retard amount t from the exhaust top dead center to the closing of the exhaust valve 13, ensures the necessary internal EGR gas amount. Set as possible. Therefore, the retard amount t from the exhaust top dead center to the closing of the exhaust valve 13 is smaller as the required load is lower and larger as the required load is higher. This is because the amount of required EGR is smaller in the low load operation. Further, the retard amount t from the exhaust top dead center to the closing of the exhaust valve 13 is set to 90 ° CA at the maximum, for example.

  In the present embodiment, the opening / closing timing of the intake valve 12 and the exhaust valve 13 in the internal combustion engine provided with a variable valve timing mechanism capable of changing the opening / closing timing of the intake valve 12 and the exhaust valve 13 is controlled. A control device 0 that performs control for closing the exhaust valve 13 after exhaust top dead center and opening the intake valve 12 after closing the exhaust valve 13 in an operating region where the required load on the internal combustion engine is a predetermined value or less. Configured.

  According to the present embodiment, since there is no valve overlap period in which both the intake valve 12 and the exhaust valve 13 are open, a part of the exhaust gas in the cylinder 1 flows out to the intake passage side and is cooled. Therefore, the temperature drop of the combustion chamber in the cylinder 1 can be effectively avoided. Therefore, the vaporization of the fuel in the combustion chamber in the cylinder 1 is promoted and the combustion is stabilized particularly in the low and medium load operation region. The stabilization of combustion increases the EGR resistance, and the risk of misfire is reduced even when a larger amount of EGR gas is recirculated. Since the limit of the amount of EGR including external EGR can be raised, it contributes to improvement of fuel consumption.

  The present invention is not limited to the embodiment described in detail above. The specific configuration of each part can be variously modified without departing from the spirit of the present invention.

  The present invention can be applied to control of an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
12 ... Intake valve 13 ... Exhaust valve

Claims (1)

A control device for controlling the opening and closing timings of an intake valve and an exhaust valve in an internal combustion engine having a variable valve timing mechanism capable of changing the opening and closing timings of an intake valve and an exhaust valve,
A control device that performs control to close an exhaust valve after exhaust top dead center and open an intake valve after closing the exhaust valve in an operation region where a required load on the internal combustion engine is a predetermined value or less.

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