JP2018025120A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of fuel economy during warming-up.SOLUTION: A control device 200 for an internal combustion engine 100 performs flame propagation combustion of a premixed air-fuel mixture when a temperature of an engine body 1 is lower than a switching temperature that is lower than a warming-up completion temperature, and performs compression self-ignition combustion of the premixed air-fuel mixture when the temperature is equal to or higher than the switching temperature. The control device 200 controls an opening of a throttle valve 36 to a prescribed opening, and determines whether predicted self-ignition timing of the premixed air-fuel mixture when opening/closing timing of an exhaust valve 60 is controlled to prescribed opening/closing timing that enables prescribed amount of exhaust gas to be present in a combustion chamber 11 at intake valve closing timing is delayed compared to target self-ignition timing. In the case where the temperature of the engine body 1 is the switching temperature or the higher and is lower than the warming-up completion temperature, if determining that the predicted self-ignition timing is delayed compared to the target self-ignition timing, the control device controls the opening of the throttle valve 36 to an opening smaller than the prescribed opening, and controls the opening/closing timing of the exhaust valve to the prescribed opening/closing timing. When the temperature of the engine body 1 is the warming-up completion temperature or higher, the control device controls the opening of the throttle valve 36 to the prescribed opening.SELECTED DRAWING: Figure 1

Description

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

  In Patent Literature 1, as a control device for a conventional internal combustion engine, in an operation region where the premixed gas is subjected to compression auto-ignition combustion and the operation of the engine body can be performed, the premixed gas is propagated to flame before warm-up is completed. The engine body is operated by burning, and the engine body is operated by performing compression auto-ignition combustion of the premixed gas after the completion of warm-up.

JP 2014-185623 A

  When the engine body is operated by flame propagation combustion of the premixed gas, the fuel efficiency deteriorates because the thermal efficiency is lower than when the engine body is operated by compression autoignition combustion of the premixed gas. To do. Therefore, when the engine body is operated by compressing and igniting combustion of the premixed gas after the completion of warm-up as in the conventional control device for an internal combustion engine described above, the fuel consumption during warm-up deteriorates. There is a point.

  The present invention has been made paying attention to such problems, and during the warm-up of an internal combustion engine that selectively switches the combustion mode to flame propagation combustion or premixed compression self-ignition combustion and operates the engine body. The purpose is to suppress the deterioration of fuel consumption.

  In order to solve the above problems, according to an aspect of the present invention, an engine body, a fuel supply device configured to be able to supply fuel to the combustion chamber of the engine body, and the combustion chamber face the combustion chamber. An ignition plug arranged, a throttle valve for adjusting the amount of air taken into the combustion chamber, an exhaust valve device configured to be able to change the opening and closing timing of an exhaust valve provided in the engine body, and the engine body An internal combustion engine control device for controlling the internal combustion engine comprising a temperature detector for detecting the temperature of the engine, wherein the engine operating state determined by the engine speed and the engine load compresses the premixed air in the combustion chamber. A combustion control unit for controlling the fuel supply device and controlling the ignition plug as necessary to burn the premixed gas based on the temperature of the engine body when in the self-ignition operation region for ignition and combustion; Ignition operation Pre-mixed gas when the throttle valve opening is controlled to a predetermined opening and the opening / closing timing of the exhaust valve is controlled to a predetermined opening / closing timing when a predetermined amount of exhaust exists in the combustion chamber. A determination unit that determines whether the expected self-ignition timing is retarded from the target self-ignition timing, and an intake control unit that controls at least the throttle valve and the exhaust valve operating device based on the determination result of the determination unit . The combustion control unit causes the premixed gas to undergo flame propagation combustion when the temperature of the engine body is lower than a predetermined switching temperature lower than a predetermined warm-up completion temperature, and causes the premixed gas to undergo compression self-ignition combustion when the temperature is equal to or higher than the switching temperature. Configured. When it is determined that the expected auto-ignition timing is retarded from the target auto-ignition timing when the temperature of the engine body is equal to or higher than the switching temperature and lower than the warm-up completion temperature, the intake control unit adjusts the throttle valve opening. The exhaust valve is controlled to an opening smaller than the predetermined opening, and the opening / closing timing of the exhaust valve is controlled to a predetermined opening / closing timing. Configured to control.

  According to this aspect of the present invention, it is possible to suppress deterioration in fuel consumption during warm-up of an internal combustion engine that selectively operates the combustion mode to flame propagation combustion or premixed compression self-ignition combustion and operates the engine body. .

FIG. 1 is a schematic configuration diagram of an internal combustion engine and an electronic control unit that controls the internal combustion engine according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the engine body of the internal combustion engine according to the embodiment of the present invention. FIG. 3 is a schematic perspective view of an intake valve operating device according to an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of a variable intake phase mechanism according to an embodiment of the present invention. FIG. 5 is a schematic perspective view of an exhaust valve operating apparatus according to an embodiment of the present invention. FIG. 6 is a schematic cross-sectional view of a lift characteristic switching mechanism according to an embodiment of the present invention. FIG. 7 is a diagram showing an operation region of the engine body. FIG. 8A is a diagram illustrating an example of opening operation of the intake valve and the exhaust valve during the SI mode. FIG. 8B is a diagram illustrating an example of the opening operation of the intake valve and the exhaust valve during the normal CI mode and the cold CI mode. FIG. 9 is a diagram comparing the internal EGR gas amount and the compression end temperature when the timing at which the exhaust valve opens during the intake stroke is controlled in the initial, middle, and late stages of the intake stroke. . FIG. 10 shows a case where the exhaust phase is advanced or retarded from the reference phase by the variable exhaust phase mechanism, and the timing at which the exhaust valve opens during the intake stroke is controlled in the initial, middle, and late stages of the intake stroke. It is the figure which showed the example. FIG. 11 is a flowchart for explaining the operation mode switching control according to the embodiment of the present invention. FIG. 12 is a flowchart illustrating the intake control according to the embodiment of the present invention that is performed when the operation mode is set to the normal CI mode. FIG. 13 is a flowchart for describing intake control according to an embodiment of the present invention that is performed when the operation mode is set to the cold CI mode. FIG. 14 is a table for setting the target throttle opening based on the absolute value of the temperature difference ΔT2. FIG. 15 is a table for setting the target exhaust phase based on the absolute value of the temperature difference ΔT2. FIG. 16 is a time chart for explaining the operation of intake control according to an embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals are assigned to similar components.

  FIG. 1 is a schematic configuration diagram of an internal combustion engine 100 and an electronic control unit 200 that controls the internal combustion engine 100 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the engine body 1 of the internal combustion engine 100.

  The internal combustion engine 100 includes an engine body 1 having a plurality of cylinders 10, a fuel supply device 2, an intake device 3, an exhaust device 4, an intake valve device 5, and an exhaust valve device 6.

  The engine body 1 burns fuel in a combustion chamber 11 (see FIG. 2) formed in each cylinder 10 to generate power for driving a vehicle, for example. The engine body 1 is provided with one spark plug 16 for each cylinder so as to face the combustion chamber 11 of each cylinder 10. The engine body 1 is provided with a pair of intake valves 50 and a pair of exhaust valves 60 for each cylinder. As shown in FIG. 2, pistons 12 that reciprocate within the cylinders 10 are received inside the cylinders 10 by receiving combustion pressure. The piston 12 is connected to a crankshaft via a connecting rod, and the reciprocating motion of the piston 12 is converted into rotational motion by the crankshaft.

  The fuel supply device 2 includes an electronically controlled fuel injection valve 20, a delivery pipe 21, a supply pump 22, a fuel tank 23, and a pressure feed pipe 24.

  The fuel injection valve 20 is disposed at the center top of the combustion chamber 11, and one fuel injection valve 20 is provided in each cylinder 10 so as to face the combustion chamber 11 of each cylinder 10. As shown in FIG. 2, in this embodiment, the electrode portion 16 a of the spark plug 16 is adjacent to the spark plug 16 so as to be located in the fuel injection region R of the fuel injection valve 20 or in the vicinity of the fuel injection region R. A fuel injection valve 20 is arranged. The valve opening time (injection amount) and valve opening timing (injection timing) of the fuel injection valve 20 are changed by a control signal from the electronic control unit 200. When the fuel injection valve 20 is opened, the fuel injection valve 20 changes to the combustion chamber. The fuel is directly injected into 11.

  The delivery pipe 21 is connected to the fuel tank 23 via a pressure feed pipe 24. A supply pump 22 for pressurizing the fuel stored in the fuel tank 23 and supplying it to the delivery pipe 21 is provided in the middle of the pressure feeding pipe 24. The delivery pipe 21 temporarily stores the high-pressure fuel pumped from the supply pump 22. When the fuel injection valve 20 is opened, the high-pressure fuel stored in the delivery pipe 21 is directly injected into the combustion chamber 11 from the fuel injection valve 20. The delivery pipe 21 is provided with a fuel pressure sensor 211 for detecting the fuel pressure in the delivery pipe 21, that is, the pressure (injection pressure) of the fuel injected from the fuel injection valve 20 into the cylinder.

  The supply pump 22 is configured to be able to change the discharge amount, and the discharge amount of the supply pump 22 is changed by a control signal from the electronic control unit 200. By controlling the discharge amount of the supply pump 22, the fuel pressure in the delivery pipe 21, that is, the injection pressure of the fuel injection valve 20 is controlled.

  The intake device 3 is a device for introducing intake air into the combustion chamber 11 and changes the state of intake air (intake pressure, intake air temperature, external EGR (Exhaust Gas Recirculation) gas amount) sucked into the combustion chamber 11. It is configured to be able to. The intake device 3 includes an intake passage 30, an intake manifold 31, and an EGR passage 32.

  One end of the intake passage 30 is connected to the air cleaner 34, and the other end is connected to the intake collector 31 a of the intake manifold 31. In the intake passage 30, an air flow meter 212, a compressor 71 of the exhaust turbocharger 7, an intercooler 35, and a throttle valve 36 are provided in order from the upstream.

  The air flow meter 212 detects the flow rate of air that flows through the intake passage 30 and is finally sucked into each cylinder 10 (hereinafter referred to as “actual intake air amount”).

  The compressor 71 includes a compressor housing 71a and a compressor wheel 71b disposed in the compressor housing 71a. The compressor wheel 71b is rotationally driven by the turbine wheel 72b of the exhaust turbocharger 7 mounted on the same axis, and compresses and discharges the intake air flowing into the compressor housing 71a.

  The intercooler 35 is a heat exchanger for cooling the intake air that has been compressed by the compressor 71 to a high temperature with, for example, traveling wind or cooling water.

  The throttle valve 36 adjusts the flow rate of air introduced into the intake manifold 31 by changing the cross-sectional area of the intake passage 30. The throttle valve 36 is driven to open and close by a throttle actuator 36a, and its opening (throttle opening) is detected by a throttle sensor 213.

  The intake manifold 31 is connected to an intake port 14 (see FIG. 2) formed in the engine body 1, and distributes the intake air flowing in from the intake passage 30 to each cylinder 10 evenly through the intake port 14. . An intake collector 31a of the intake manifold 31 detects an intake pressure sensor 214 for detecting the pressure of intake air (intake pressure) sucked into the cylinder and a temperature of intake air (intake air temperature) sucked into the cylinder. An intake air temperature sensor 215 is provided.

  The EGR passage 32 communicates the exhaust manifold 41 and the intake collector 31a of the intake manifold 31, and is a passage for returning a part of the exhaust discharged from each cylinder 10 to the intake collector 31a by a pressure difference. Hereinafter, the exhaust gas flowing into the EGR passage 32 is referred to as “external EGR gas”. By recirculating the external EGR gas to the intake collector 31a and thus to each cylinder 10, it is possible to reduce the combustion temperature and suppress the emission of nitrogen oxides (NOx). The EGR passage 32 is provided with an EGR cooler 37 and an EGR valve 38 in order from the upstream.

  The EGR cooler 37 is a heat exchanger for cooling the external EGR gas with, for example, traveling wind or cooling water.

  The EGR valve 38 is an electromagnetic valve whose opening degree can be adjusted continuously or stepwise, and the opening degree is controlled by the electronic control unit 200 according to the engine operating state. By controlling the opening degree of the EGR valve 38, the flow rate of the external EGR gas to be recirculated to the intake collector 31a is adjusted.

  The exhaust device 4 is a device for exhausting exhaust from the cylinder, and includes an exhaust manifold 41, an exhaust passage 42, and an exhaust post-treatment device 43.

  The exhaust manifold 41 is connected to an exhaust port 15 formed in the engine body 1, and exhausts exhausted from the cylinders 10 are collectively introduced into the exhaust passage 42.

  The exhaust passage 42 is provided with a turbine 72 of the exhaust turbocharger 7 and an exhaust aftertreatment device 43 in order from the upstream.

  The turbine 72 includes a turbine housing 72a and a turbine wheel 72b disposed in the turbine housing 72a. The turbine wheel 72b is rotationally driven by the energy of the exhaust gas flowing into the turbine housing 72a, and drives the compressor wheel 71b mounted coaxially.

  The variable nozzle 72c described above is provided outside the turbine wheel 72b. The variable nozzle 72 c functions as a throttle valve, and the nozzle opening (valve opening) of the variable nozzle 72 c is controlled by the electronic control unit 200. By changing the nozzle opening degree of the variable nozzle 72c, the flow rate of the exhaust for driving the turbine wheel 72b can be changed in the turbine housing 72a. That is, by changing the nozzle opening degree of the variable nozzle 72c, the supercharging pressure can be changed by changing the rotational speed of the turbine wheel 72b. Specifically, when the nozzle opening of the variable nozzle 72c is reduced (the variable nozzle 72c is throttled), the exhaust flow rate increases, the rotational speed of the turbine wheel 72b increases, and the supercharging pressure increases.

  The exhaust aftertreatment device 43 is a device for purifying exhaust gas and discharging it to the outside air, and includes various exhaust purification catalysts for purifying harmful substances, filters for collecting harmful substances, and the like.

  The intake valve operating device 5 is a device for opening and closing the intake valve 50 of each cylinder 10 and is provided in the engine body 1. The intake valve operating device 5 according to the present embodiment is configured such that the intake valve 50 of each cylinder 10 can be opened during the intake stroke. A detailed configuration of the intake valve operating device 5 will be described later with reference to FIGS. 3 and 4.

  The exhaust valve device 6 is a device for opening and closing the exhaust valve 60 of each cylinder 10 and is provided in the engine body 1. The exhaust valve operating device 6 according to the present embodiment is configured so that the exhaust valve 60 of each cylinder 10 can be opened during the exhaust stroke, and can also be opened during the intake stroke as necessary. The detailed configuration of the exhaust valve device 6 will be described later with reference to FIGS. 5 and 6.

  The electronic control unit 200 is composed of a digital computer and is connected to each other by a bi-directional bus 201. 206.

  An output signal from the above-described fuel pressure sensor 211 or the like is input to the input port 205 via each corresponding AD converter 207. Also, the output voltage of the load sensor 217 that generates an output voltage proportional to the amount of depression of the accelerator pedal 220 (hereinafter referred to as “accelerator depression amount”) as a signal for detecting the engine load corresponds to the input port 205. Is input via the AD converter 207. The input port 205 is supplied with an output signal of a crank angle sensor 218 that generates an output pulse every time the crankshaft of the engine body 1 rotates, for example, 15 °, as a signal for calculating the engine rotational speed and the like. Further, an output signal of a water temperature sensor 219 for detecting a temperature of cooling water for cooling the engine body 1 (hereinafter referred to as “cooling water temperature”) is detected at the input port 205 as a signal for detecting the temperature of the engine body 1. Input via the corresponding AD converter 207. The signal for detecting the temperature of the engine body 1 is not limited to the output signal of the water temperature sensor 219. For example, an oil temperature sensor that detects the temperature of the lubricating oil that lubricates the friction sliding portion of the engine body 1 is provided. In that case, the output signal of the oil temperature sensor may be used. As described above, output signals of various sensors necessary for controlling the internal combustion engine 100 are input to the input port 205.

  The output port 206 is connected to each control component such as the fuel injection valve 20 via a corresponding drive circuit 208.

  The electronic control unit 200 controls the internal combustion engine 100 by outputting a control signal for controlling each control component from the output port 206 based on the output signals of various sensors input to the input port 205.

  FIG. 3 is a schematic perspective view of the intake valve operating device 5 according to the present embodiment.

  The intake valve operating device 5 includes an intake camshaft 51 extending in the cylinder row direction, an intake valve drive mechanism 52 for driving the intake valve 50, and a phase of the intake camshaft 51 with respect to the crankshaft (hereinafter referred to as "intake phase"). And a variable intake phase mechanism 53 for changing.

  The intake camshaft 51 is attached to the engine body 1 so that it can freely rotate with respect to the engine body 1. The intake camshaft 51 is linked to the crankshaft by a belt or chain via a sprocket 55 provided at one end thereof, and rotates around the axis in conjunction with the crankshaft. An intake cam 54 that rotates integrally with the intake camshaft 51 is fixed to the intake camshaft 51 for each cylinder.

  The intake valve drive mechanism 52 includes an intake support shaft 521 and a Y-shaped rocker arm 522.

  The intake support shaft 521 is disposed below the intake camshaft 51 and extends in the cylinder row direction in parallel with the intake camshaft 51 and is fixedly supported by the engine body 1.

  The Y-shaped rocker arm 522 has a bifurcated front end side, and intake air is provided at the base end side so that the Y-shaped rocker arm 522 can be swung (moved up and down) within a predetermined rotation range around the axis of the intake support shaft 521. A support shaft 521 is inserted. The stem portion 50a of the intake valve 50 is fixed to the tip of the Y-shaped rocker arm 522 divided into two branches. Further, the Y-shaped rocker arm 522 includes a needle roller 522a with which the intake cam 54 is slidably contacted at the center thereof. When the intake camshaft 51 rotates in conjunction with the crankshaft, the needle roller 522a is pushed down by the intake cam 54. . As a result, the Y-shaped rocker arm 522 swings within a predetermined rotation range about the axis of the intake support shaft 521, and the intake valve 50 is opened.

  The variable intake phase mechanism 53 is provided at one end of the intake camshaft 51. The variable intake phase mechanism 53 will be further described with reference to FIG.

  FIG. 4 is a schematic sectional view of the variable intake phase mechanism 53.

  As shown in FIG. 4, the variable intake phase mechanism 53 includes a cylindrical housing 531 that rotates together with the sprocket 55, and a rotation shaft that rotates together with the intake camshaft 51 and can rotate relative to the cylindrical housing 531. 532, a plurality of partition walls 533 extending from the inner peripheral surface of the cylindrical housing 531 to the outer peripheral surface of the rotating shaft 532, and the inner peripheral surface of the cylindrical housing 531 from the outer peripheral surface of the rotating shaft 532 between the partition walls 533 The hydraulic oil chamber 535 and the retard hydraulic chamber 536 formed on both sides of each vane 534, and the hydraulic oil is supplied to the advance hydraulic chamber 535 and the retard hydraulic chamber 536. And a hydraulic oil supply control valve 56 for performing supply / discharge control.

  The hydraulic oil supply control valve 56 is discharged from an advance hydraulic port 561 connected to the advance hydraulic chamber 535, a retard hydraulic port 562 connected to the retard hydraulic chamber 536, and the hydraulic pump 57. Supply port 563 to which hydraulic fluid is supplied, first drain port 564, second drain port 565, and each port (advance hydraulic port 561, retard hydraulic port 562, supply port 563, first drain) And a spool valve 566 that performs communication cutoff control between the port 564 and the second drain port 565).

  When the intake phase should be advanced, the spool valve 566 is moved to the right in FIG. 4, and the hydraulic oil supplied from the supply port 563 enters the advance angle hydraulic chamber 535 via the advance angle hydraulic port 561. The hydraulic oil in the retarding hydraulic chamber 536 is discharged from the second drain port 565 while being supplied. At this time, the rotation shaft 532 is rotated relative to the cylindrical housing 531 in the arrow direction.

  On the other hand, when the intake phase should be retarded, the spool valve 566 is moved to the left in FIG. 4, and the hydraulic oil supplied from the supply port 563 is used for retarding via the retarding hydraulic port 562. While being supplied to the hydraulic chamber 536, the hydraulic oil in the advance hydraulic chamber 535 is discharged from the first drain port 564. At this time, the rotation shaft 532 is rotated relative to the cylindrical housing 531 in the direction opposite to the arrow.

  If the spool valve 566 is returned to the neutral position shown in FIG. 4 while the rotation shaft 532 is rotated relative to the cylindrical housing 531, the relative rotation operation of the rotation shaft 532 is stopped, and the rotation shaft 532 is The relative rotation position at that time is held. In this way, the intake phase can be advanced or retarded by a desired amount by the variable intake phase mechanism 53.

  FIG. 5 is a schematic perspective view of the exhaust valve device 6 according to the present embodiment.

  The exhaust valve device 6 has an exhaust camshaft 61 extending in the cylinder row direction, an exhaust valve drive mechanism 62 for driving the exhaust valve 60, and a phase of the exhaust camshaft 61 with respect to the crankshaft (hereinafter referred to as "exhaust phase"). ), The lift characteristic of the exhaust valve 60, the first lift characteristic that opens the exhaust valve 60 in the exhaust stroke, and the exhaust valve 60 is opened in the exhaust stroke and the intake stroke. A lift characteristic switching mechanism 64 that can be switched to the second lift characteristic is provided.

  The exhaust camshaft 61 is attached to the engine body 1 so as to be freely rotatable with respect to the engine body 1. The exhaust camshaft 61 is linked to the crankshaft by a belt or chain via a sprocket 67 provided at one end thereof, and rotates around the axis in conjunction with the crankshaft.

  A set of a first exhaust cam 65 and a second exhaust cam 66 that rotate integrally with the exhaust camshaft 61 are fixed to the exhaust camshaft 61 for each cylinder. The first exhaust cam 65 is a cam for opening the exhaust valve 60 of each cylinder 10 in the exhaust stroke. The second exhaust cam 66 is a cam for opening the exhaust valve 60 of each cylinder 10 in the exhaust stroke and the intake stroke. The second exhaust cam 66 includes a cam crest 66a for opening the exhaust valve 60 in the exhaust stroke, and a cam crest 66b for opening the exhaust valve 60 in the intake stroke. The cam crest 66a and the cam crest 66b of the second exhaust cam 66 are formed so that the lift amount of the exhaust valve 60 in the intake stroke is smaller than the lift amount of the exhaust valve 60 in the exhaust stroke.

  The exhaust valve drive mechanism 62 includes an exhaust support shaft 621 and a Y-shaped rocker arm 622.

  The exhaust support shaft 621 is disposed below the exhaust camshaft 61 and extends in the cylinder row direction in parallel with the exhaust camshaft 61 and is fixedly supported by the engine body 1.

  The Y-shaped rocker arm 622 is bifurcated at the tip end, and the exhaust support shaft 621 is located at the base end side so that the Y-shaped rocker arm 622 can be swung within a predetermined rotation range about the axis of the exhaust support shaft 621. Has been inserted. The stem portion 60a of the exhaust valve 60 is fixed to the tip of the Y-shaped rocker arm 622 divided into two branches. The Y-shaped rocker arm 622 is provided with a needle roller 622a at the center of which one of the first exhaust cam 65 and the second exhaust cam 66 slides in accordance with the switching state of the lift characteristic switching mechanism 64. When the exhaust camshaft 61 rotates in conjunction with the crankshaft, the needle roller 522a is pushed down by either the first exhaust cam 65 or the second exhaust cam 66 in accordance with the switching state of the lift characteristic switching mechanism 64. As a result, the Y-shaped rocker arm 622 swings within a predetermined rotation range about the axis of the exhaust support shaft 621, and the exhaust valve 60 opens.

  The variable exhaust phase mechanism 63 is provided at one end of the exhaust camshaft 61. Since the configuration of the variable exhaust phase mechanism 63 is the same as that of the variable intake phase mechanism 53, the description thereof is omitted here. The variable exhaust phase mechanism 63 can advance or retard the exhaust phase by a desired amount.

  The lift characteristic switching mechanism 64 is provided at the other end of the exhaust camshaft 61. The lift characteristic switching mechanism 64 will be further described with reference to FIG.

  FIG. 6 is a schematic sectional view of the lift characteristic switching mechanism 64.

  The lift characteristic switching mechanism 64 includes a cylindrical housing 641, a slider 642, an electromagnet 643, and a coil spring 644.

  The cylindrical housing 641 is a housing that is provided on the other end side of the exhaust camshaft 61 and accommodates the slider 642, the electromagnet 643, the coil spring 644, and a part of the exhaust camshaft 61 therein.

  The slider 642 is provided at the other end of the exhaust camshaft 61 and rotates integrally with the exhaust camshaft 61. The slider 642 is made of a magnetic material. When an excitation current is passed through the electromagnet 643, the slider 642 resists the spring force of the coil spring 644 and is connected to the exhaust camshaft 61 along one axial end of the exhaust camshaft 61 (see FIG. It is housed inside the cylindrical housing 641 so that it can move toward the middle right).

  The electromagnet 643 is disposed around the slider 642. Control of the excitation current for the electromagnet 643 is performed by the electronic control unit 200.

  The coil spring 644 is disposed inside the cylindrical housing 641 in a state shorter than the natural length, and always presses the slider 642 toward the other axial end side (left side in the figure) of the exhaust camshaft 61.

  Hereinafter, control of the internal combustion engine 100 performed by the electronic control unit 200 will be described.

  When the engine operation state determined by the engine rotation speed and the engine load is within the self-ignition operation region RR surrounded by the solid line in FIG. 7, the electronic control unit 200 performs the temperature of the engine body 1 (in this embodiment, the cooling water temperature). In accordance with Tw), the operation mode of the engine body 1 is set to a spark ignition operation mode (hereinafter referred to as “SI mode”), a normal compression auto-ignition operation mode (hereinafter referred to as “normal CI mode”), or a cold compression auto-ignition. Switch to one of the operation modes (hereinafter referred to as “cold CI mode”). Electronic control unit 200 switches the operation mode of engine body 1 to the SI operation mode regardless of the temperature of engine body 1 when the engine operation state is outside the self-ignition operation region RR. The electronic control unit 200 performs combustion control corresponding to each operation mode, that is, control of the fuel supply device 2 and control of the spark plug 16 as necessary to burn the premixed gas.

  When the operation mode is the SI mode, the electronic control unit 200 basically ignites by injecting fuel in the intake stroke to form a homogeneous premixed gas in the combustion chamber 11 or near the stoichiometric air / fuel ratio. Ignition by the plug 16 is performed, and the premixed gas is burnt and burned to operate the engine body 1.

  In addition, when the operation mode is the normal CI mode or the cold CI mode, the electronic control unit 200 basically injects fuel in the compression stroke and has an air-fuel ratio (for example, 30) leaner than the stoichiometric air-fuel ratio in the combustion chamber 11. The engine main body 1 is operated by performing compression auto-ignition combustion of the pre-mixed gas.

  Premixed compression auto-ignition combustion can be performed even when the air-fuel ratio is lean as compared with flame propagation combustion, and can be performed even when the compression ratio is increased. Therefore, by performing premixed compression auto-ignition combustion, fuel efficiency can be improved and thermal efficiency can be improved. In addition, since premixed compression self-ignition combustion has a lower combustion temperature than flame propagation combustion, generation of NOx can be suppressed. Furthermore, since there is sufficient oxygen around the fuel, the generation of unburned HC can be suppressed.

  In order to perform the premixed compression self-ignition combustion, it is necessary to raise the in-cylinder temperature to a temperature at which the premixed gas can be self-ignited. It is necessary to make the in-cylinder temperature higher than in the case where all the flame propagation combustion is performed.

  Therefore, in the present embodiment, as shown in FIG. 8A, during the SI mode, the lift characteristic of the exhaust valve 60 is switched to the first lift characteristic by the lift characteristic switching mechanism 64 so that the exhaust valve 60 opens only for the exhaust stroke. I have to. Further, as shown in FIG. 8B, during the normal CI mode and during the cold CI mode, the lift characteristic switching mechanism 64 switches the lift characteristic of the exhaust valve 60 to the second lift characteristic, so that the exhaust valve 60 is switched to the other of the exhaust stroke. The valve is also opened during the intake stroke.

  As shown in FIG. 8B, the exhaust valve 60 is opened twice during the intake stroke, so that the high-temperature exhaust exhausted from the cylinder during the exhaust stroke can be removed immediately after the intake stroke. It can be sucked back into its own cylinder. During normal CI mode and during cold CI mode, the exhaust valve is opened twice to increase the in-cylinder temperature, and the in-cylinder temperature of each cylinder 10 can be subjected to premixed compression auto-ignition combustion. Maintained at an appropriate temperature. In the following description, in order to distinguish from the external EGR gas, the exhaust sucked back into the cylinder by the opening operation of the exhaust valve twice is referred to as “internal EGR gas”.

  FIG. 9 shows the amount of internal EGR gas and the compression when the exhaust valve 60 is opened during the intake stroke in the initial, middle, and late stages of the intake stroke by the variable exhaust phase mechanism 63 as shown in FIG. It is the figure which compared and showed end temperature, respectively.

  As shown in FIG. 9, the amount of internal EGR gas increases when the exhaust valve 60 is opened during the intake stroke in the middle of the intake stroke, compared to when it is controlled in the early and late stages of the intake stroke. As a result, the compression end temperature (in-cylinder temperature) can be increased.

  Since the piston 12 reciprocates inside each cylinder 10, the moving speed of the piston in each stroke is relatively faster in the middle period than in the early and late stages of each stroke. That is, the rate of change in the volume of the combustion chamber 11 in each stroke is relatively greater in the middle period than in the early and late stages of each stroke.

  If the volume change rate of the combustion chamber 11 is larger during the intake stroke, the flow rate of the gas sucked into the combustion chamber 11 per unit time increases. Therefore, by controlling the valve opening timing of the exhaust valve 60 during the intake stroke to the middle period of the intake stroke where the volume change rate of the combustion chamber 11 is relatively large, the volume change rate of the combustion chamber 11 is relatively The amount of exhaust gas sucked back into the combustion chamber 11 through the exhaust port 15 during the intake stroke can be increased as compared with the case where the control is performed in the early and late stages of the intake stroke that becomes smaller. As a result, the amount of internal EGR gas can be increased to increase the compression end temperature (in-cylinder temperature).

  On the other hand, when the timing at which the exhaust valve 60 opens during the intake stroke is controlled in the early and late stages of the intake stroke, the internal EGR gas amount and the compression end temperature (in-cylinder temperature) are reduced as compared with the case where the exhaust valve 60 is controlled in the middle. To do.

  At this time, the internal EGR gas amount can be reduced when the timing at which the exhaust valve 60 opens during the intake stroke is controlled in the later stage of the intake stroke, compared to when the control is performed initially. This is because, when the valve opening timing of the exhaust valve 60 during the intake stroke is controlled in the later stage of the intake stroke, exhaust is sucked back after a certain amount of air (fresh air) is sucked into the cylinder. It is.

  Contrary to this, with respect to the compression end temperature, it is possible to lower the valve opening timing of the exhaust valve 60 during the intake stroke at the initial stage of the intake stroke than when it is controlled at the later stage. This is because when the valve opening timing of the exhaust valve 60 during the intake stroke is controlled at the beginning of the intake stroke, the amount of internal EGR gas itself is larger than when it is controlled later, but the in-cylinder gas during the intake stroke is increased. This is because the period during which the air is cooled by heat exchange with the inner wall surface of the cylinder 10 becomes longer.

  In this way, the increase range of the in-cylinder temperature can be controlled according to the timing at which the exhaust valve opening operation is performed twice.

  FIG. 11 is a flowchart for explaining the operation mode switching control according to the present embodiment. The electronic control unit 200 repeatedly executes this routine at a predetermined calculation cycle.

  In step S1, the electronic control unit 200 reads the engine rotational speed calculated based on the output signal of the crank angle sensor 218 and the engine load detected by the load sensor 217, and detects the engine operating state.

  In step S2, the electronic control unit 200 determines whether or not the engine operation state is outside the self-ignition operation region RR. The electronic control unit 200 proceeds to the process of step S3 if the engine operating state is outside the self-ignition operation region RR. On the other hand, if the engine operation state is within the self-ignition operation region RR, the electronic control unit 200 proceeds to the process of step S4.

  In step S3, the electronic control unit 200 operates the engine body 1 with the operation mode set to the SI mode. When the operation mode is set to the SI mode, the electronic control unit 200 controls the lift characteristic switching mechanism 64 so that the lift characteristic of the exhaust valve 60 becomes the first lift characteristic, and also according to the engine operating state. The throttle valve, the variable intake phase mechanism, and the variable exhaust phase mechanism are controlled so that the target throttle opening, the target intake phase, and the target exhaust phase are obtained.

  In step S4, the electronic control unit 200 determines whether or not the coolant temperature Tw is lower than a predetermined switching temperature Tw1. The switching temperature Tw1 is a temperature lower than a warm-up completion temperature Tw2, which will be described later, and the engine body 1 is operated by spark ignition combustion in the self-ignition operation region RR, or the premixed gas is used. It is a threshold value for determining whether to perform the operation of the engine body 1 by performing compression self-ignition combustion. If the cooling water temperature Tw is lower than the switching temperature Tw1, the electronic control unit 200 proceeds to the process of step S3. On the other hand, if the cooling water temperature Tw is equal to or higher than the switching temperature Tw1, the electronic control unit 200 proceeds to the process of step S5.

  In step S5, the electronic control unit 200 determines whether or not the coolant temperature is equal to or higher than the warm-up completion temperature Tw2. The warm-up completion temperature Tw2 is a threshold value for determining that the warm-up of the engine body 1 has been completed. If the coolant temperature Tw is equal to or higher than the warm-up completion temperature Tw2, the electronic control unit 200 proceeds to the process of step S6. On the other hand, when the cooling water temperature is lower than the warm-up completion temperature Tw2, that is, when the cooling water temperature Tw is within the range from the switching temperature Tw1 to the warm-up completion temperature Tw2, the electronic control unit 200 proceeds to the process of step S7. .

  In step S6, the electronic control unit 200 operates the engine body 1 with the operation mode set to the normal CI mode.

  In step S7, the electronic control unit 200 operates the engine body 1 with the operation mode set to the cold CI mode.

  FIG. 12 is a flowchart for explaining the control (intake control) of the throttle valve 36 and the exhaust valve operating device 6 that is performed when the operation mode is set to the normal CI mode. The electronic control unit 200 repeatedly executes this routine at a predetermined calculation cycle when the operation mode is set to the normal CI mode.

  In step S11, the electronic control unit 200 controls the lift characteristic switching mechanism 64 so that the lift characteristic of the exhaust valve 60 becomes the second lift characteristic.

  In step S <b> 12, the electronic control unit 200 refers to a map created in advance through experiments or the like, and calculates the target throttle opening and the target exhaust phase for the normal CI mode based on the engine operating state. In the present embodiment, the target throttle opening degree in the normal CI mode according to the engine operating state is basically the maximum opening degree (fully opened in the present embodiment). Further, the target exhaust phase in the normal CI mode according to the engine operating state is basically an exhaust phase in which the opening / closing timing of the exhaust valve during the intake stroke is the latter stage of the intake stroke.

In step S13, the electronic control unit 200 requires the in-cylinder temperature required value (hereinafter referred to as the target self-ignition time) at which the premixed gas can be self-ignited at the target self-ignition time (optimum self-ignition time) according to the engine operating state. It is referred to as “required in-cylinder temperature”.) T _ign is calculated. The electronic control unit 200 in the present embodiment, by referring to a map that associates a request cylinder temperature T _ign the engine operating state, and calculates a required cylinder temperature T _ign based on the engine operating state. If the engine speed is the same, the required in-cylinder temperature _Tign basically tends to increase as the engine load increases. If the engine load is the same, the required in-cylinder temperature _Tign basically increases as the engine speed increases. It tends to be higher.

In step S14, the electronic control unit 200 determines the in-cylinder temperature at the intake valve closing timing when the throttle opening and the exhaust phase are respectively controlled to the target values for the normal CI mode corresponding to the engine operating state. Estimated value (hereinafter referred to as “initial in-cylinder temperature during normal CI mode”) T _ivc is calculated. In general, the in-cylinder temperature at the intake valve closing timing varies depending on the intake air temperature as well as the actual intake air amount (new air amount) and the internal EGR gas amount that change according to the throttle opening and the exhaust phase. Therefore, the electronic control unit 200 according to the present embodiment is based on the engine operating state and the intake air temperature by referring to a map in which the engine operating state and the intake air temperature are associated with the initial in-cylinder temperature T _ivc in the normal CI mode. Thus, the initial in-cylinder temperature T _ivc in the normal CI mode is calculated.

In step S15, the electronic control unit 200 determines the in-cylinder temperature at the target self-ignition timing when the throttle opening degree and the exhaust phase are respectively controlled to the target values for the normal CI mode according to the engine operating state. An estimated value (hereinafter referred to as “reference estimated in-cylinder temperature in the normal CI mode”) T _mbt is calculated from the following (1).
_{T mbt = T ivc × (V} ivc / V mbt) k-1 × α ... (1)

  Equation (1) is a correction according to the current cooling water temperature Tw detected by the water temperature sensor 219 to the estimated value of the in-cylinder temperature at the target self-ignition timing when it is assumed that adiabatic compression is performed from the intake valve closing timing. Multiplication by coefficient α (<1). The correction coefficient α is set to a smaller value as the cooling water temperature Tw becomes lower. This is because the cooling loss increases as the cooling water temperature Tw decreases.

In the equation (1), V _ivc is the combustion chamber volume at the intake valve closing timing, V _mbt is the combustion chamber volume at the target self-ignition timing, and k is a specific heat ratio (polytropic index). The combustion chamber volume V _ivc is a value that is mechanically determined when the target intake phase (target intake valve closing _timing ) is determined. Similarly, the combustion chamber volume V _W2 is mechanical when the target self-ignition timing is determined. It is a value determined by. Therefore, in this embodiment, when calculating the reference estimated in-cylinder temperature T _mbt in the normal CI mode, a table in which the target intake phase and the combustion chamber volume V _ivc are associated with each other is created in advance through experiments or the like. By referencing, the combustion chamber volume V _ivc is calculated based on the target intake phase. Similarly, previously created in advance by experiments or the like a table associating the target ignition timing combustion chamber volume V _mbt, by referring to the table, the combustion chamber volume V _mbt based on the target ignition timing Calculated.

In step S16, the electronic control unit 200 determines that the expected self-ignition timing of the premixed gas when the throttle opening and the exhaust phase are controlled to the target values for the normal CI mode corresponding to the engine operating state is the target self-ignition timing. Determine whether it is time to ignite. The electronic control unit 200 in the present embodiment, the determination of the absolute value of the temperature difference ΔT1 obtained by subtracting the reference estimated in-cylinder temperature T _mbt the normal CI mode from the required cylinder temperature T _ign whether less than the allowable temperature difference T _req If the absolute value of the temperature difference ΔT1 is less than the allowable temperature difference T _req , it is determined that the predicted self-ignition timing of the premixed gas becomes the target self-ignition timing. If the absolute value of the temperature difference ΔT1 is less than the allowable temperature difference T _req , the electronic control unit 200 proceeds to step 17. On the other hand, if the absolute value of the temperature difference ΔT1 is greater than or equal to the allowable temperature difference T _req , the electronic control unit 200 proceeds to the process of step S18.

  In step S17, the electronic control unit 200 determines that the throttle valve 36 and the exhaust phase become the target throttle opening and target exhaust phase for the normal CI mode calculated in step S13, respectively. And the variable exhaust phase mechanism 63 is controlled.

  In step S18, the electronic control unit 200 delays the expected self-ignition timing of the premixed gas when the throttle opening degree and the exhaust phase are controlled to the target values for the normal CI mode from the target self-ignition timing. It is determined whether or not.

In this embodiment, if the temperature difference ΔT1 is a positive value, the electronic control unit 200 controls the throttle opening and the exhaust phase to the target values for the normal CI mode. It is determined that the temperature cannot be raised to the required in-cylinder temperature _Tign and the predicted autoignition timing of the premixed gas is retarded from the target autoignition timing, and the process proceeds to step S19. On the other hand, if the temperature difference ΔT1 is a negative value, the electronic control unit 200 controls the throttle opening and the exhaust phase to the target values for the normal CI mode. It is determined that the internal temperature has been raised to the required in-cylinder temperature _Tign and the predicted autoignition timing of the premixed gas is advanced from the target autoignition timing, and the process proceeds to step S21.

In step S19, the electronic control unit 200 changes the target exhaust phase in the normal CI mode so that the absolute value of the temperature difference ΔT1 is less than the allowable temperature difference T _req . In the present embodiment, the electronic control unit 200 increases the target temperature in the cylinder so that the temperature difference ΔT1 becomes less than the allowable temperature difference Tc _req so that the temperature difference ΔT1 is less than the allowable temperature difference Tc _req. The exhaust valve opening / closing timing during the intake stroke is changed to the exhaust phase where the exhaust valve opening / closing timing during the intake stroke is the middle of the intake stroke.

  In step S20, the electronic control unit 200 controls the throttle valve 36 so that the throttle opening becomes the target throttle opening for the normal CI mode calculated in step S12. Further, the electronic control unit 200 controls the variable exhaust phase mechanism 63 so that the exhaust phase becomes the target exhaust phase changed in step S19.

In step S21, the electronic control unit 200 changes the target exhaust phase in the normal CI mode so that the absolute value of the temperature difference ΔT1 is less than the allowable temperature difference T _req . In the present embodiment, the electronic control unit 200 reduces the increase range of the in-cylinder temperature so that the absolute value of the temperature difference ΔT is less than the allowable temperature difference T _req and the target exhaust gas phase calculated in step S12. From the exhaust phase (exhaust phase in which the opening / closing timing of the exhaust valve during the intake stroke is the latter stage of the intake stroke), the opening / closing timing of the exhaust valve during the intake stroke is changed to the exhaust phase in which the opening / closing timing of the intake stroke is the initial stage.

  In step S22, the electronic control unit 200 controls the throttle valve so that the throttle opening becomes the target throttle opening for the normal CI mode calculated in step S12. Further, the electronic control unit 200 controls the variable exhaust phase mechanism so that the exhaust phase becomes the target exhaust phase changed in step S21.

As described above, in the normal CI mode, if the absolute value of the temperature difference ΔT1 is equal to or _larger than the allowable temperature difference T _req , the target throttle opening is not changed and remains at the normal target value (maximum opening), and the target exhaust By changing only the phase, the in-cylinder temperature is adjusted so that the absolute value of the temperature difference ΔT1 is less than the allowable temperature difference Tc _req . Thereby, the premixed gas can be self-ignited at the target self-ignition timing while suppressing deterioration of fuel consumption due to an increase in pumping loss.

  FIG. 13 is a flowchart for explaining the content of intake control that is performed when the operation mode is set to the cold CI mode. The electronic control unit 200 repeatedly executes this routine during engine operation when the operation mode is set to the cold CI mode.

  In step S31, the electronic control unit 200 controls the lift characteristic switching mechanism 64 so that the lift characteristic of the exhaust valve 60 becomes the second lift characteristic.

In step S32, the electronic control unit 200, by referring to a map which associates with similarly engine operating condition and the step S13 described above and the requested cylinder temperature T _ign, requests cylinder temperature T _ign based on the engine operating condition Is calculated.

In step S33, the electronic control unit 200 sets the throttle opening to the maximum opening (fully open in the present embodiment), and sets the exhaust phase to the exhaust phase (hereinafter referred to as “reference phase”) that maximizes the internal EGR gas amount (compression end temperature). In this embodiment, the estimated value of the in-cylinder temperature at the closing timing of the intake valve when the opening / closing timing of the exhaust valve during the intake stroke is the middle phase of the intake stroke (hereinafter referred to as “reference in cold CI mode”). It is referred to as “initial in-cylinder temperature.”) T _{ivc_cool} is calculated. Specifically, the electronic control unit 200 refers to a map that associates the engine operating state and intake air temperature with the reference initial in-cylinder temperature T _{ivc_cool} during the cold CI mode, thereby determining the engine operating state and intake air temperature. Based on this, the reference initial in-cylinder temperature T _{ivc_cool} in the cold CI mode is calculated.

In step S34, the electronic control unit 200 estimates the in-cylinder temperature at the target self-ignition timing according to the engine operating state when the throttle opening is the maximum opening and the exhaust phase is the reference exhaust phase (hereinafter, “ It is referred to as “reference estimated in-cylinder temperature in the cold CI mode.”) T _{mbt_cool} is calculated from (2) below.
_{T mbt_cool = Tc ivc_cool × (V} ivc / V mbt) k-1 × α ... (2)

In step S35, the electronic control unit 200 determines whether or not the predicted self-ignition timing of the premixed gas when the throttle opening is the maximum opening and the exhaust phase is the reference exhaust phase is the target self-ignition timing. To do. The electronic control unit 200 in the present embodiment, the absolute value of the temperature difference ΔT2 from requesting cylinder temperature _{T ign} by subtracting the reference estimated in-cylinder temperature _{T Mbt_cool} cold CI mode is whether less than the allowable temperature difference _{T req} If the absolute value of the temperature difference ΔT2 is less than the allowable temperature difference T _req , it is determined that the predicted autoignition timing of the premixed gas becomes the target autoignition timing. If the absolute value of the temperature difference ΔT2 is less than the allowable temperature difference T _req , the electronic control unit 200 proceeds to the process of step 36. On the other hand, if the absolute value of the temperature difference ΔT2 is greater than or equal to the allowable temperature difference T _req , the electronic control unit 200 proceeds to the process of step S37.

  In step S36, the electronic control unit 200 controls the throttle opening to the maximum opening (fully opened in the present embodiment) and sets the exhaust phase to the reference exhaust phase (in this embodiment, the opening / closing timing of the exhaust valve during the intake stroke). (Exhaust phase in the middle of the intake stroke).

  In step S37, the electronic control unit 200 determines whether or not the predicted self-ignition timing of the premixed gas when the throttle opening is the maximum opening and the exhaust phase is the reference exhaust phase is retarded from the target self-ignition timing. Determine whether.

In this embodiment, if the temperature difference ΔT2 is a positive value, the electronic control unit 200 sets the in-cylinder temperature at the target self-ignition timing when the throttle opening is set to the maximum opening and the exhaust phase is set to the reference exhaust phase. It is determined that the temperature cannot be raised to the required in-cylinder temperature _Tign and the predicted autoignition timing of the premixed gas is retarded from the target autoignition timing, and the process proceeds to step S38. On the other hand, if the temperature difference ΔT2 is a negative value, the electronic control unit 200 determines that the in-cylinder temperature is earlier than the target self-ignition timing when the throttle opening is the maximum opening and the exhaust phase is the reference exhaust phase. There are accidentally heated to requests cylinder temperature T _ign determines the expected ignition timing of the premixture is advanced from the target ignition timing, the process proceeds to step S40.

  In step S38, the electronic control unit 200 refers to the table of FIG. 14 and sets the target throttle opening based on the absolute value of the temperature difference ΔT2.

  As shown in the table of FIG. 14, the target throttle opening basically becomes smaller than the maximum opening as the absolute value of the temperature difference ΔT2 increases.

  As the throttle opening is reduced, the actual intake air amount (fresh air amount) can be reduced, and the proportion of the internal EGR gas amount in the in-cylinder gas can be increased accordingly. This is because the in-cylinder temperature can be increased. In particular, as in the present embodiment, when the internal EGR gas is sucked into the cylinder by opening the exhaust valve 60 during the intake stroke, the in-cylinder pressure during the intake stroke decreases as the throttle opening decreases ( Therefore, more internal EGR gas can be sucked into the cylinder than when the throttle opening is the maximum opening. Therefore, in this case, the in-cylinder temperature can be increased more effectively. As shown in the table of FIG. 14, in the present embodiment, the target throttle opening is set so as not to be less than a predetermined lower limit opening. This is because the combustion stability rapidly decreases when the internal EGR gas amount exceeds a certain amount.

  In step S39, the electronic control unit 200 controls the throttle valve 36 so as to achieve the target throttle opening set in step S38, and also controls the variable exhaust phase mechanism 63 so as to become the reference exhaust phase.

  In step S40, the electronic control unit 200 refers to the table of FIG. 15 and sets the target exhaust phase based on the absolute value of the temperature difference ΔT2.

  As shown in the table of FIG. 15, the target exhaust phase is basically a reference exhaust phase in which the internal EGR gas amount (compression end temperature) becomes maximum as the absolute value of the temperature difference ΔT2 increases, that is, exhaust during the intake stroke. The opening / closing timing of the valve 60 is an exhaust phase that is retarded from the exhaust phase that is the middle stage of the intake stroke. This is because, as shown in FIG. 9, the in-cylinder temperature can be lowered by reducing the internal EGR gas amount by retarding the opening / closing timing of the exhaust valve 60 during the intake stroke from the middle of the intake stroke. is there.

  The target exhaust phase may be an exhaust phase in which the opening / closing timing of the exhaust valve 60 during the intake stroke is advanced from the exhaust phase in the middle of the intake stroke, but in the present embodiment, the target exhaust for the normal CI mode is used. The phase is basically set to an exhaust phase in which the opening / closing timing of the exhaust valve 60 during the intake stroke is the latter stage of the intake stroke. Therefore, in the present embodiment, the target exhaust phase is set so that the opening / closing timing of the exhaust valve 60 during the intake stroke is the middle of the intake stroke so that the operation mode can be smoothly switched from the cold CI mode to the normal CI mode. The exhaust phase is retarded from the phase.

  In step S41, the electronic control unit 200 controls the throttle valve 36 so that the maximum opening degree is obtained, and controls the variable exhaust phase mechanism 63 so that the target exhaust phase set in step S40 is obtained.

  FIG. 16 is a time chart for explaining the operation of intake control according to the present embodiment. FIG. 16 shows an example of the operation when the engine load is constant.

  When the coolant temperature Tw becomes equal to or higher than the switching temperature Tw1 at time t1, the operation mode is switched from the SI mode to the cold CI mode. When the operation mode is switched to the cold CI mode, intake control for the cold CI mode is performed.

  That is, it is determined whether or not the expected self-ignition timing of the premixed gas is retarded from the target self-ignition timing when the throttle opening is the maximum opening and the exhaust phase is the reference exhaust phase. Based on this, control of the throttle valve 36 and the exhaust valve device 6 is performed.

  In the example shown in FIG. 16, in the period from time t1 to time t2, the predicted self-ignition timing of the premixed gas when the throttle opening is the maximum opening and the exhaust phase is the reference exhaust phase is higher than the target self-ignition timing. It is determined to be retarded.

  Therefore, the variable exhaust phase mechanism 63 is controlled so that the exhaust phase becomes the reference exhaust phase, and the throttle valve 36 is controlled so that the throttle opening is smaller than the maximum opening. As a result, the amount of increase in the in-cylinder temperature can be increased by increasing the internal EGR gas amount as compared with the case where the throttle opening is controlled to the maximum opening.

  Therefore, since the engine body 1 can be operated by performing the compression auto-ignition combustion of the premixed gas from the time when the cooling water temperature Tw is lower than the warm-up completion temperature Tw2, the thermal efficiency is improved and the fuel efficiency is improved. be able to. Although the throttle valve 36 is controlled so that the throttle opening is smaller than the maximum opening, the throttle opening can be made larger than when the premixed gas is subjected to flame propagation combustion. Therefore, the pumping loss can be reduced.

  After the time t1, the amount of internal EGR gas necessary for increasing the in-cylinder temperature gradually decreases as the cooling water temperature Tw increases, so that the throttle opening is not increased during the period from the time t1 to the time t2. Gradually increase toward maximum opening.

  When the cooling water temperature Tw becomes somewhat higher than the switching temperature Tw1 at time t2, the expected self-ignition timing of the premixed gas when the throttle opening is the maximum opening and the exhaust phase is the reference exhaust phase becomes the target self-ignition timing. . As a result, from time t2, the throttle valve 36 is controlled so that the throttle opening becomes the maximum opening. Further, the exhaust phase is continuously maintained at the reference exhaust phase.

  When the coolant temperature Tw is further increased, the predicted self-ignition timing of the premixed gas when the throttle opening is set to the maximum opening and the exhaust phase is set as the reference exhaust phase may be advanced from the target self-ignition timing. . In the example shown in FIG. 16, at time t3, it is determined that the predicted self-ignition timing of the premixed gas when the throttle opening is the maximum opening and the exhaust phase is the reference exhaust phase is advanced from the target self-ignition timing. Has been.

  In this case, since the internal EGR gas amount is excessive, the internal EGR gas amount is decreased by gradually retarding the exhaust phase from the reference exhaust phase while maintaining the throttle opening at the maximum opening. Thus, the rise in the in-cylinder temperature is suppressed.

  When the coolant temperature T2 rises to the warm-up completion temperature Tw2 at time t4, the intake control for the normal CI mode is performed.

  That is, whether or not the predicted self-ignition timing of the premixed gas is retarded from the target self-ignition timing when the throttle opening and the exhaust phase are controlled to the target values for the normal CI mode according to the engine operating state, respectively. And the throttle valve 36 and the exhaust valve gear 6 are controlled based on the determination result.

  In the example shown in FIG. 16, after time t4, it is determined that the predicted self-ignition timing of the premixed gas when controlled to the target value for the normal CI mode according to the engine operating state becomes the target self-ignition timing. Yes. Therefore, after time t4, the throttle opening and the exhaust phase are controlled to the target values for the normal CI mode according to the engine operating state.

  According to the embodiment described above, the engine body 1, the fuel supply device 2 configured to be able to supply fuel to the combustion chamber 11 of the engine body 1, and the fuel supply device 2 arranged so as to face the combustion chamber 11. The spark plug 16, the throttle valve 36 for adjusting the amount of air taken into the combustion chamber 11, and the exhaust valve that is configured to change the opening / closing timing of the exhaust valve 60 provided in the engine body 1. An electronic control unit 200 (control device) for controlling the internal combustion engine 100 that includes the device 6 and a water temperature sensor 219 (temperature detector) for detecting the temperature of the engine body 1 includes an engine rotational speed and an engine load. And the fuel supply device 2 is controlled based on the temperature of the engine main body 1 when the engine operating state determined by the above is in the self-ignition operation region RR in which the premixed gas is compressed and self-ignited and combusted in the combustion chamber 11. In Next, in the combustion control unit for controlling the spark plug 16 to burn the premixed gas and the self-ignition operation region RR, the opening degree of the throttle valve 36 is controlled to a predetermined opening degree, and the opening / closing timing of the exhaust valve 60 is set. A determination unit that determines whether the expected self-ignition timing of the premixed gas is retarded from the target self-ignition timing when a predetermined amount of exhaust gas is controlled to a predetermined opening / closing timing in the combustion chamber 11 at the intake valve closing timing; And an intake control unit that controls at least the throttle valve 36 and the exhaust valve gear 6 based on the determination result of the determination unit.

  The combustion control unit flame-combusts the premixed gas when the temperature of the engine body 1 is lower than the predetermined switching temperature Tw1 lower than the predetermined warm-up completion temperature Tw2, and compresses the premixed gas when the temperature is equal to or higher than the switching temperature Tw1. It is configured to self-ignite and burn. In addition, when the temperature of the engine body 1 is equal to or higher than the switching temperature Tw1 and lower than the warm-up completion temperature Tw2, the intake control unit determines that the predicted self-ignition timing is retarded from the target self-ignition timing. The opening of the valve 36 is controlled to an opening smaller than the predetermined opening, and the opening / closing timing of the exhaust valve 60 is controlled to the predetermined opening / closing timing, and when the temperature of the engine body 1 is equal to or higher than the warm-up completion temperature Tw2, the throttle The opening degree of the valve 36 is controlled to a predetermined opening degree.

Thus, the amount of air taken into the combustion chamber 11 by reducing the throttle opening before the warm-up completion when the temperature of the engine body 1 is equal to or higher than the switching temperature Tw1 and lower than the warm-up completion temperature Tw2. It is possible to increase the ratio of the internal EGR gas in the in-cylinder gas. As a result, the increase range of the in-cylinder temperature can be increased, so that the in-cylinder temperature is raised to the required in-cylinder temperature _Tign before the warming-up is completed, and the premixed gas is _subjected to compression self-ignition combustion to cause the engine body 1 Thus, it is possible to suppress the deterioration of fuel consumption during warm-up.

  The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

  For example, in the above-described embodiment, the internal EGR gas is introduced into the combustion chamber 11 by performing the opening operation of the exhaust valve twice by the lift characteristic switching mechanism 64, but the internal EGR gas is introduced by this method. It is not limited. For example, even if the lift characteristic switching mechanism 64 is not provided, by setting the exhaust valve closing timing during the exhaust stroke by the variable exhaust phase mechanism 63, a part of the exhaust in the combustion chamber 11 is left as it is in the combustion chamber. 11 may be allowed to remain. In this case, the amount of internal EGR gas can be increased as the exhaust valve closing timing is retarded from the exhaust top dead center.

  In the above-described embodiment, the intake air amount is basically adjusted by controlling the throttle valve 36. However, the intake air amount may be adjusted by controlling the opening / closing timing of the intake valve 50, for example.

DESCRIPTION OF SYMBOLS 1 Engine main body 2 Fuel supply apparatus 11 Combustion chamber 16 Spark plug 20 Fuel injection valve 36 Throttle valve 60 Exhaust valve 100 Internal combustion engine 200 Electronic control unit (control apparatus)

Claims (1)

The engine body,
A fuel supply device configured to supply fuel to the combustion chamber of the engine body;
A spark plug disposed to face the combustion chamber;
A throttle valve for adjusting the amount of air sucked into the combustion chamber;
An exhaust valve device configured to be able to change the opening and closing timing of the exhaust valve provided in the engine body;
A temperature detector for detecting the temperature of the engine body;
An internal combustion engine control apparatus for controlling an internal combustion engine comprising:
The fuel supply device is based on the temperature of the engine body when the engine operating state determined by the engine speed and the engine load is in a self-ignition operation region in which the premixed gas is compressed and self-ignited and combusted in the combustion chamber. And a combustion control unit for controlling the spark plug as necessary and burning the premixed gas,
In the self-ignition operation region, the opening degree of the throttle valve is controlled to a predetermined opening degree, the opening / closing timing of the exhaust valve is set to the closing timing of the intake valve, and the predetermined opening / closing timing at which a predetermined amount of exhaust exists in the combustion chamber. A determination unit that determines whether or not the expected self-ignition timing of the premixed gas when controlled is retarded from the target self-ignition timing;
An intake control unit that controls at least the throttle valve and the exhaust valve operating device based on a determination result of the determination unit;
With
The combustion control unit
When the temperature of the engine body is lower than a predetermined switching temperature lower than a predetermined warm-up completion temperature, the premixed gas is subjected to flame propagation combustion, and when the temperature is equal to or higher than the switching temperature, the premixed gas is subjected to compression self-ignition combustion,
The intake control unit
When it is determined that the predicted autoignition timing is retarded from the target autoignition timing when the temperature of the engine body is equal to or higher than the switching temperature and lower than the warm-up completion temperature, the throttle valve is opened. The degree of opening is controlled to be smaller than the predetermined opening, and the opening / closing timing of the exhaust valve is controlled to the predetermined opening / closing timing,
When the temperature of the engine body is equal to or higher than the warm-up completion temperature, the opening of the throttle valve is controlled to the predetermined opening.
Control device for internal combustion engine.

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