Engine control device

Abstract

To provide a control device of an engine capable of improving exhausting performance immediately after cold start of the engine.SOLUTION: When a temperature of an engine is equal to or less than a first determination temperature, an exhaust valve phase variable device is controlled so that a closing timing of an exhaust valve becomes a timing of an exhaust top dead center or a timing at a delay side with respect to the exhaust top dead center, an intake valve phase variable device is controlled so that an opening timing of the intake valve becomes a timing at a delay side with respect to the closing timing of the exhaust valve, and a fuel supply device is controlled to start fuel supply to a combustion chamber during an intake stroke. In a case when the temperature of the engine is higher than the first determination temperature, and equal to or less than a second determination temperature, the intake valve phase variable device and the exhaust valve phase variable device are controlled to generate negative overlap to close both of the exhaust valve and the intake valve during a prescribed period sandwiching the exhaust top dead center and to generate positive overlap to open both of the exhaust valve and the intake valve during a prescribed period sandwiching the exhaust top dead center.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an engine control device.

Background Art

[0002] Conventionally, it has been required to improve the exhaust performance of engines provided in vehicles and the like. In response to this, if a catalytic device for purifying exhaust gas is provided in the exhaust passage of the engine, the exhaust performance will be improved. However, when the engine temperature is low, such as during cold start, the catalytic device is not sufficiently activated. Therefore, there is a risk that the exhaust gas will not be sufficiently purified. In particular, when the engine temperature is low, the fuel does not sufficiently evaporate in the combustion chamber. Therefore, due to insufficient mixing of fuel and air, the amount of unburned HC and soot discharged from the engine body increases, and there is a risk that these will be discharged without being sufficiently purified by the catalytic device.

[0003] In response to the above problems, for example, Patent Document 1 discloses an engine in which the phase of an exhaust valve is advanced during cold start of the engine so that the exhaust valve is opened at a time when the pressure in the combustion chamber is relatively high. In this engine, the temperature of the exhaust gas discharged from the engine body to the exhaust passage is increased, and the flow rate thereof is increased, thereby attempting to activate the catalytic device at an early stage.

Prior Art Documents

Patent Documents

[0004] [[ID=--]] [[ID=--]]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] According to the engine described in Patent Document 1, it is believed that the catalytic converter is activated relatively soon after the engine is cold-started, thereby improving the subsequent exhaust performance of the engine. However, even with this engine, the exhaust performance before the catalytic converter is activated is still insufficient, and there is room for improvement in improving the engine's exhaust performance immediately after the engine is cold-started.

[0006] This invention has been made in view of the above circumstances, and aims to provide an engine control device that can improve the exhaust performance of the engine immediately after cold starting. [Means for solving the problem]

[0007] The present invention aims to solve the aforementioned problems. Engine control device relating to one aspect The control device for an engine comprising an engine body having a combustion chamber, a fuel supply device that supplies fuel to the combustion chamber, an intake valve that opens and closes an intake port for introducing intake air into the combustion chamber, and an exhaust valve that opens and closes an exhaust port for guiding exhaust gas out of the combustion chamber, further comprising an intake valve phase variable device capable of changing the phase of the intake valve, an exhaust valve phase variable device capable of changing the phase of the exhaust valve, and a control device that controls the fuel supply device, the intake valve phase variable device and the exhaust valve phase variable device, wherein when a first condition is met that the engine temperature is below a predetermined first determination temperature, the control device controls the exhaust valve phase variable device so that the closing timing of the exhaust valve is the same as or retarded to the exhaust top dead center, and controls the intake valve phase variable device so that the opening timing of the intake valve is retarded to the exhaust valve closing timing. and In both cases, the fuel supply device is controlled so that fuel supply to the combustion chamber begins during an intake stroke that is retarded to the closing timing of the exhaust valve, and the second condition is met, which is that the engine temperature is higher than the first determination temperature and below a predetermined second determination temperature. ,before A positive overlap occurs in which the exhaust valve and the intake valve are both open for a predetermined period of time encompassing the exhaust top dead center. Furthermore, the closing timing of the exhaust valve is set to be at a later angle than the closing timing of the exhaust valve when the first condition is met.The invention is characterized by controlling the intake valve phase variable device and the exhaust valve phase variable device.

[0008] In this invention, when the second condition is met, which is that the engine temperature is higher than the first determination temperature and below the second determination temperature, the exhaust valve and intake valve are controlled so that a negative overlap occurs, where both the exhaust valve and intake valve are closed during a predetermined period spanning the exhaust top dead center, or a positive overlap occurs, where both valves are open during a predetermined period spanning the exhaust top dead center. Therefore, when the second condition is met, a large amount of high-temperature burned gas remains in the combustion chamber, raising the temperature inside the combustion chamber and thereby promoting fuel evaporation. Consequently, according to this invention, the amount of unburned HC and soot discharged from the combustion chamber when the second condition is met can be kept to a minimum.

[0009] However, since the burnt gas is an inert gas, if a large amount of burnt gas remains in the combustion chamber as described above, especially when the engine temperature is low, combustion may become unstable. In contrast, in this invention, when the first condition is met, which is that the engine temperature is below the first judgment temperature, the exhaust valve closing timing is set to be the same as or retarded to the exhaust top dead center, and the intake valve opening timing is set to be retarded to the exhaust valve closing timing. Therefore, the amount of burnt gas remaining in the combustion chamber can be kept low, thereby improving combustion stability. Furthermore, the combustion chamber can be kept in a high negative pressure state during the intake stroke. In this invention, fuel is supplied to the combustion chamber during the intake stroke, which is in this high negative pressure state. Therefore, while improving combustion stability, the amount of unburned HC and soot discharged from the combustion chamber can be kept low by promoting fuel evaporation. In addition, because the combustion chamber is in a high negative pressure state, intake air can be forcefully drawn into the combustion chamber when the intake valve is opened. In other words, a strong intake airflow can be generated in the combustion chamber, which in turn can raise the temperature inside the combustion chamber. This, in turn, can reliably promote fuel evaporation.

[0010] As described above, according to the present invention, the amount of unburned HC and soot discharged from the combustion chamber into the exhaust passage when the engine temperature is low is reduced, so the engine's exhaust performance can be improved even when the catalytic converter is cold-started and not yet fully activated.

[0011] Furthermore, an engine control device according to another aspect of the present invention comprises an engine body having a combustion chamber formed therein, a fuel supply device that supplies fuel to the combustion chamber, an intake valve that opens and closes an intake port for introducing intake air into the combustion chamber, and an exhaust valve that opens and closes an exhaust port for discharging exhaust gas from the combustion chamber, wherein the control device comprises an intake valve phase variable device capable of changing the phase of the intake valve, an exhaust valve phase variable device capable of changing the phase of the exhaust valve, and a control device that controls the fuel supply device, the intake valve phase variable device and the exhaust valve phase variable device, wherein when a first condition is met that the engine temperature is below a predetermined first determination temperature, the control device advances the closing timing of the exhaust valve to a time that is the same as or retarded to the exhaust top dead center. The variable exhaust valve phase device is controlled so that the intake valve opening timing is retarded compared to the exhaust valve closing timing, and the fuel supply device is controlled so that fuel supply to the combustion chamber begins during the intake stroke retarded compared to the exhaust valve closing timing. If the second condition is met, that the engine temperature is higher than the first determination temperature and below a predetermined second determination temperature, the variable intake valve phase device and the variable exhaust valve phase device are controlled so that a negative overlap occurs in which the exhaust valve and the intake valve are closed for a predetermined period spanning the exhaust top dead center, or a positive overlap occurs in which the exhaust valve and the intake valve are open for a predetermined period spanning the exhaust top dead center. When the first condition is met, the fuel supply device is controlled so that fuel supply to the combustion chamber begins at a timing retarded to the opening timing of the intake valve. , characterized by (Claim 2).

[0012] With this configuration, fuel is supplied to the combustion chamber while intake airflow is occurring within the combustion chamber and the temperature inside the combustion chamber is being raised by this intake airflow. Therefore, fuel evaporation can be more reliably promoted, and the amount of unburned HC and soot emitted from the combustion chamber can be more reliably reduced.

[0013] Furthermore, an engine control device according to another aspect of the present invention comprises an engine body having a combustion chamber formed therein, a fuel supply device that supplies fuel to the combustion chamber, an intake valve that opens and closes an intake port for introducing intake air into the combustion chamber, and an exhaust valve that opens and closes an exhaust port for discharging exhaust gas from the combustion chamber, the engine control device comprising: an intake valve phase variable device capable of changing the phase of the intake valve, an exhaust valve phase variable device capable of changing the phase of the exhaust valve, and a control device that controls the fuel supply device, the intake valve phase variable device, and the exhaust valve phase variable device. The engine is equipped with a spark plug that ignites the fuel-air mixture supplied to the combustion chamber, and the control device is, If the first condition is met, that the engine temperature is below a predetermined first determination temperature, the exhaust valve phase variable device is controlled so that the closing timing of the exhaust valve is the same as or retarded to the exhaust top dead center, and the intake valve phase variable device is controlled so that the opening timing of the intake valve is retarded to the exhaust valve closing timing, and the fuel supply device is controlled so that fuel supply to the combustion chamber is started during the intake stroke retarded to the exhaust valve closing timing. If the second condition is met, that the engine temperature is higher than the first determination temperature and below a predetermined second determination temperature, the intake valve phase variable device and the exhaust valve phase variable device are controlled so that a negative overlap occurs in which the exhaust valve and the intake valve are closed during a predetermined period spanning the exhaust top dead center, or so that a positive overlap occurs in which the exhaust valve and the intake valve are open during a predetermined period spanning the exhaust top dead center. The spark plug is controlled such that the ignition timing of the spark plug is delayed when the first condition is met compared to when the second condition is met (Claim 3).

[0014] If the ignition timing is set to a retarded position, a relatively large amount of air will be introduced into the combustion chamber to achieve the torque required by the engine. When a large amount of air is introduced into the combustion chamber, the intake airflow within the combustion chamber is also increased. Therefore, with this configuration, when the ignition timing is set to a relatively retarded position when the first condition is met, the intake airflow within the combustion chamber and, consequently, the temperature within the combustion chamber can be increased, further promoting fuel evaporation.

[0015] Furthermore, an engine control device according to another aspect of the present invention comprises an engine body having a combustion chamber formed therein, a fuel supply device that supplies fuel to the combustion chamber, an intake valve that opens and closes an intake port for introducing intake air into the combustion chamber, and an exhaust valve that opens and closes an exhaust port for guiding exhaust gas out of the combustion chamber, the engine control device comprising an intake valve phase variable device capable of changing the phase of the intake valve, an exhaust valve phase variable device capable of changing the phase of the exhaust valve, and a control device that controls the fuel supply device, the intake valve phase variable device and the exhaust valve phase variable device. The engine is connected to a generator that is driven by the engine to generate electricity, and the control device is If the first condition is met, that the engine temperature is below a predetermined first determination temperature, the exhaust valve phase variable device is controlled so that the closing timing of the exhaust valve is the same as or retarded to the exhaust top dead center, and the intake valve phase variable device is controlled so that the opening timing of the intake valve is retarded to the exhaust valve closing timing, and the fuel supply device is controlled so that fuel supply to the combustion chamber is started during the intake stroke retarded to the exhaust valve closing timing. If the second condition is met, that the engine temperature is higher than the first determination temperature and below a predetermined second determination temperature, the intake valve phase variable device and the exhaust valve phase variable device are controlled so that a negative overlap occurs in which the exhaust valve and the intake valve are closed during a predetermined period spanning the exhaust top dead center, or so that a positive overlap occurs in which the exhaust valve and the intake valve are open during a predetermined period spanning the exhaust top dead center. The generator is controlled such that the amount of power generated by the generator is greater when the first condition is met than when the second condition is met (Claim 4).

[0016] When the generator powered by the engine generates more electricity, the engine needs to output greater torque, and to achieve this torque, a relatively large amount of air is introduced into the combustion chamber. When a large amount of air is introduced into the combustion chamber, the intake airflow within the combustion chamber is also increased. Therefore, with this configuration, when the first condition is met, the ignition timing is set to a relatively retarded position, which increases the intake airflow within the combustion chamber and, consequently, the temperature within the combustion chamber, thereby further promoting fuel evaporation.

[0017] Furthermore, an engine control device according to another aspect of the present invention comprises an engine body having a combustion chamber formed therein, a fuel supply device that supplies fuel to the combustion chamber, an intake valve that opens and closes an intake port for introducing intake air into the combustion chamber, and an exhaust valve that opens and closes an exhaust port for guiding exhaust gas out of the combustion chamber, wherein the control device comprises an intake valve phase variable device capable of changing the phase of the intake valve, an exhaust valve phase variable device capable of changing the phase of the exhaust valve, and a control device that controls the fuel supply device, the intake valve phase variable device and the exhaust valve phase variable device, wherein the control device determines that the engine temperature is below a predetermined first determination temperature. If the first condition is met, the exhaust valve phase variable device is controlled so that the closing timing of the exhaust valve is the same as or retarded to the exhaust top dead center, and the intake valve phase variable device is controlled so that the opening timing of the intake valve is retarded to the exhaust valve closing timing, and the fuel supply device is controlled so that fuel supply to the combustion chamber is started during the intake stroke retarded to the exhaust valve closing timing, and if the second condition is met, that the engine temperature is higher than the first determination temperature and below a predetermined second determination temperature, the exhaust valve and the intake valve are closed for a predetermined period of time spanning the exhaust top dead center. Control the intake valve phase variable device and the exhaust valve phase variable device so that negative overlap occurs (Claim 5).

[0018] In this configuration, the intake valve opening timing is retarded from exhaust top dead center at both the time the first condition is met and the time the second condition is met. Therefore, the change in the intake valve opening timing when switching from the state where the first condition is met to the state where the second condition is met, that is, when the engine temperature exceeds the first judgment temperature, can be kept to a minimum. Consequently, the intake valve opening timing can be changed to the appropriate timing for when the second condition is met at an earlier stage.

[0019] In the above configuration, preferably, when the second condition is met and the engine temperature is higher than the first determination temperature (a third determination temperature or higher), the control device controls the exhaust valve phase variable device such that the closing timing of the exhaust valve is retarded when the engine temperature is high compared to when it is low (Claim 6).

[0020] With this configuration, when the engine temperature is low and the combustion chamber temperature is low, the exhaust valve closing timing is advanced, increasing the amount of combustion gas remaining in the combustion chamber, thereby appropriately raising the combustion chamber temperature. Conversely, when the engine temperature is high and the combustion chamber temperature is high, the exhaust valve closing timing is retarded, reducing the amount of combustion gas remaining in the combustion chamber, thereby preventing the combustion chamber temperature from becoming excessively high.

[0021] In the above configuration, preferably, the control device controls the intake valve phase variable device such that the opening timing of the intake valve when the first condition is satisfied is at a retarded timing side than the opening timing of the intake valve when the second condition is satisfied (Claim 7).

[0022] According to this configuration, by setting the opening timing of the intake valve at a sufficiently retarded timing when the first condition is satisfied, the above-mentioned negative pressure action can be enhanced, and the evaporation of fuel can be more reliably promoted.

Effect of the Invention

[0023] As described above, according to the engine control device of the present invention, the exhaust performance can be improved immediately after the cold start of the engine.

Brief Description of the Drawings

[0024] [Figure 1] It is a system diagram showing a schematic configuration of a vehicle to which an engine control device according to an embodiment of the present invention is applied. [Figure 2] It is a schematic cross-sectional view showing the structure of the engine. [Figure 3] It is a functional block diagram showing the control system of the vehicle. [Figure 4] It is a flowchart showing a part of the vehicle control. [Figure 5] It is a flowchart showing a part of the vehicle control. [Figure 6] It is a diagram showing an example of valve lift of an intake valve and an exhaust valve in the LIVO mode. [Figure 7] It is a diagram showing an example of valve lift of an intake valve and an exhaust valve in the NVO mode. [Figure 8] It is a graph showing the relationship between the engine water temperature and the closing timing of the exhaust valve in the NVO mode. [Figure 9] It is a time chart showing an example of changes in the engine water temperature and valve timing after the engine is cold-started. [Figure 10]These are schematic cross-sectional diagrams illustrating the operation of valve timing in LIVO mode, where (a) shows the state of the combustion chamber before exhaust TDC, (b) shows the state of the combustion chamber after exhaust TDC and before the intake valve opens, and (c) shows the state of the combustion chamber after the intake valve opens. [Figure 11] This diagram shows another example of the valve lift of the intake and exhaust valves when the engine water temperature is higher than the first judgment temperature but below the second judgment temperature. [Modes for carrying out the invention]

[0025] [Overall vehicle configuration] Figure 1 is a system diagram showing the schematic configuration of a vehicle V to which an engine control device according to one embodiment of the present invention is applied. As shown in this figure, the vehicle V comprises an engine 1, a clutch 30, a motor 31, an inverter 32, a battery 33, a transmission 35, a differential 36, drive wheels 37, and a PCM 50. Both the engine 1 and the motor 31 are capable of driving the drive wheels 37 as power sources for driving. In other words, the vehicle V in this embodiment is a hybrid vehicle that uses both the engine 1 and the motor 31 as power sources. The PCM 50 described above corresponds to the "control device" of the present invention.

[0026] Engine 1 is a four-stroke internal combustion engine that generates power through the combustion of fuel. While the fuel used by Engine 1 is not particularly limited, in this embodiment, a gasoline engine is used as Engine 1. Details of Engine 1 will be described later.

[0027] Motor 31 is a motor generator that combines the functions of both a motor and a generator. For example, a three-phase AC synchronous electric motor is used as motor 31. Motor 31 operates as a motor when the vehicle V is accelerating, generating driving force to rotate the drive wheels 37. Motor 31 also operates as a generator when the vehicle V is decelerating, generating electricity by receiving rotational force transmitted from the drive wheels 37. When motor 31 operates as a generator, a braking force (regenerative braking) corresponding to the amount of electricity generated by motor 31 is applied to the drive wheels 37.

[0028] The inverter 32 is a converter that converts AC power to DC power and vice versa. When the motor 31 operates as a generator, the inverter 32 converts the AC power generated by the motor 31 into DC power and supplies it to the battery 33. On the other hand, when the motor 31 operates as a motor, the inverter 32 converts the DC power stored in the battery 33 into AC power and supplies it to the motor 31. The inverter 32 also has a function to adjust the output or power generation amount of the motor 31 through power transfer control between the motor 31 and the battery 33.

[0029] Battery 33 is a rechargeable secondary battery. For example, a lithium-ion battery or a nickel-metal hydride battery can be used as battery 33. Battery 33 supplies driving power to the motor 31 via inverter 32, and also receives and stores the power generated by the motor 31 via inverter 32.

[0030] Battery 33 is equipped with a battery sensor SN3 that detects the input and output current to and from the battery 33. The current value detected by the battery sensor SN3 is used to determine the battery state of charge (SOC), that is, the ratio of the current charge to the charge level when the battery 33 is fully charged. In other words, the battery sensor SN3 is a sensor for detecting the battery SOC. Specifically, the PCM 50 calculates the charge and discharge rates of the battery 33 per unit time based on the values ​​detected by the battery sensor SN3, and calculates the battery SOC by integrating these values.

[0031] The clutch 30 is a clutch that connects the engine 1 and the motor 31 so that they can be connected and disconnected. Specifically, the clutch 30 connects the output shaft of the engine 1 (crankshaft 7, described later) and the rotating shaft (rotor shaft) of the motor 31 in series, or disconnects them. When the clutch 30 is engaged and the engine 1 and motor 31 are connected, the torque of both the engine 1 and the motor 31 is transmitted to the drive wheels 37 via the transmission 35 and the differential 36. On the other hand, when the clutch 30 is disengaged, the motor 31 and the engine 1 are disconnected, and only the torque of the motor 31 is transmitted to the drive wheels 37.

[0032] The transmission 35 changes the rotation input from the engine 1 and motor 31 and outputs it to the differential 36. In this embodiment, the transmission 35 is an automatic transmission, and the gear ratio is automatically changed according to the vehicle speed and engine speed. The differential 36 distributes the rotation input from the transmission 35 to the left and right drive wheels 37.

[0033] The transmission 35 is equipped with a vehicle speed sensor SN1 for determining the vehicle speed of the vehicle V. Specifically, the vehicle speed sensor SN1 detects the rotational speed of the output shaft 43 of the transmission 35, and the vehicle speed is determined based on this detected value.

[0034] Vehicle V is equipped with an accelerator pedal 39 that is operated by the driver. An accelerator sensor SN2 is attached to the accelerator pedal 39 to detect the accelerator opening degree, which represents the degree to which the pedal is pressed.

[0035] The PCM50 is a control device whose main component is a microcomputer, which includes a processor (CPU) for calculations, memory such as ROM and RAM, and various input / output buses. The PCM50 comprehensively controls the engine 1, motor 31, and transmission 35. Specifically, the PCM50 controls the output of the engine 1 so that appropriate driving force is transmitted to the drive wheels 37 according to the driving conditions of the vehicle V, controls the output of the motor 31 through the inverter 32, and further controls the gear shift of the transmission 35.

[0036] [Engine structure] Figure 2 is a schematic cross-sectional view showing the structure of engine 1. Engine 1 comprises an engine body 2, an intake passage 17, and an exhaust passage 19.

[0037] The engine body 2 is a multi-cylinder type having, for example, multiple cylinders 2a arranged in a direction perpendicular to the plane of the paper in Figure 2. That is, the engine body 2 comprises a cylinder block 3 and a cylinder head 4 that define the multiple cylinders 2a inside, and multiple pistons 5 that are reciprocally housed in each cylinder 2a.

[0038] A combustion chamber C is formed above the piston 5 of each cylinder 2a. Each combustion chamber C is a space defined by the lower surface of the cylinder head 4, the side surface of the cylinder 2a (cylinder liner), and the upper surface (crown surface) of the piston 5. Injected fuel from the injector 8, which will be described later, is supplied to the combustion chamber C. The piston 5 reciprocates vertically in response to the expansion energy (combustion energy) from the combustion of the fuel supplied to the combustion chamber C.

[0039] Below the piston 5 is the crankshaft 7. The crankshaft 7 is the output shaft of the engine 1 (or engine body 2) and is rotatably supported at the bottom of the cylinder block 3. The crankshaft 7 is connected to the piston 5 of each cylinder 2a via a crank mechanism including a connecting rod 6 and rotates around its central axis in accordance with the reciprocating motion (up and down motion) of the piston 5.

[0040] A crank angle sensor SN4 is mounted on the cylinder block 3. The crank angle sensor SN4 is a sensor for detecting the crank angle, which is the rotation angle of the crankshaft 7, and the engine speed, which is the rotational speed of the crankshaft 7. An engine water temperature sensor SN5 is mounted on the cylinder block 3 for detecting the engine water temperature, which is the temperature of the coolant that cools the engine body 2. Specifically, a water jacket 10 through which coolant flows is formed in the cylinder block 3 and the cylinder head 4, and the engine water temperature sensor SN5 detects the temperature of the coolant flowing through the water jacket 10.

[0041] An injector 8 and a spark plug 9 are mounted on the cylinder head 4. The injector 8 is an injection valve that injects fuel into the combustion chamber C of each cylinder 2a. The spark plug 9 is a plug that ignites the fuel-air mixture injected from the injector 8 into the combustion chamber C. One injector 8 and one spark plug 9 are provided for each cylinder 2a. The injector 8 described above corresponds to the "fuel supply device" in this invention.

[0042] The cylinder head 4 has intake ports 11 and exhaust ports 12. The intake ports 11 are ports that connect the combustion chamber C of each cylinder 2a to the intake passage 17. The exhaust ports 12 are ports that connect the combustion chamber C of each cylinder 2a to the exhaust passage 19. Each intake port 11 of each cylinder 2a is provided with an intake valve 13, and each exhaust port 12 of each cylinder 2a is provided with an exhaust valve 14.

[0043] The cylinder head 4 is equipped with an intake valve mechanism 15 and an exhaust valve mechanism 16. The intake valve mechanism 15 includes an intake camshaft 15a located above the intake valve 13, and the exhaust valve mechanism 16 includes an exhaust camshaft 16a located above the exhaust valve 14. The intake camshaft 15a, the exhaust camshaft 16a, and the crankshaft 7 are connected to each other via a power transmission mechanism, for example, a chain. That is, the intake valve mechanism 15 and the exhaust valve mechanism 16 open and close the intake valve 13 and exhaust valve 14 of each cylinder 2a in conjunction with the rotation of the crankshaft 7. The intake valve 13 periodically opens and closes the opening on the combustion chamber C side of the intake port 11 in response to the drive of the intake valve mechanism 15, and the exhaust valve 14 periodically opens and closes the opening on the combustion chamber C side of the exhaust port 12 in response to the drive of the exhaust valve mechanism 16.

[0044] The exhaust valve train mechanism 16 is equipped with an exhaust SVT 20, and the intake valve train mechanism 15 is equipped with an intake SVT 21. The exhaust SVT 20 is a device that changes the phase (opening / closing timing) of the exhaust valve 14 by changing the rotational phase of the exhaust camshaft 16a relative to the rotational phase of the crankshaft 7. The intake SVT 21 is a device that changes the phase (opening / closing timing) of the intake valve 13 by changing the rotational phase of the intake camshaft 15a relative to the rotational phase of the crankshaft 7.

[0045] In this embodiment, the exhaust SVT20 is a variable device that changes the phase of the exhaust valve 14 while maintaining a constant lift amount and opening period of the exhaust valve 14. In other words, it is a variable device that changes the opening time (start of opening) EVO and closing time (closed time) EVC of the exhaust valve 14 by the same amount. Similarly, the intake SVT21 is a variable device that changes the phase of the intake valve 13 while maintaining a constant lift amount and opening period of the intake valve 13. In other words, it is a variable device that changes the opening time (start of opening) IVO and closing time (closed time) IVC of the intake valve 13 by the same amount. The exhaust camshaft 16a (intake camshaft 15a), whose phase is changed by the exhaust SVT20 (intake SVT21), is a camshaft common to all cylinders 2a. In other words, the exhaust SVT20 (intake SVT21) changes the rotational phase of the exhaust valve 14 (intake valve 13) of each cylinder 2a collectively by changing the rotational phase of the exhaust camshaft 16a (intake camshaft 15a). Furthermore, the exhaust SVT20 (intake SVT21) in this embodiment is hydraulic, and the rotational phase of the exhaust camshaft 16a (intake camshaft 15a) is changed by changing the hydraulic pressure. The exhaust SVT20 corresponds to the "variable exhaust valve phase device" in this invention, and the intake SVT21 corresponds to the "variable intake valve phase device" in this invention.

[0046] The intake passage 17 is a tubular passage for introducing intake air into the combustion chamber C of each cylinder 2a. The intake passage 17 is connected to the engine body 2 so as to communicate with the combustion chamber C of each cylinder 2a via the intake port 11. The intake passage 17 is provided with a throttle valve 18 that can be opened and closed to adjust the flow rate of intake air circulating inside it.

[0047] The exhaust passage 19 is a tubular passage for discharging exhaust gas discharged from the combustion chamber C of each cylinder 2a to the outside. The exhaust passage 19 is connected to the engine body 2 so as to communicate with the combustion chamber C of each cylinder 2a via the exhaust port 12. The exhaust passage 19 is equipped with a catalytic converter 23 for purifying harmful components in the exhaust gas. The catalytic converter 23 includes, for example, a three-way catalytic converter. The catalytic converter 23 is fitted with a catalytic temperature sensor SN6 for detecting the catalytic converter temperature, which is the temperature inside the catalytic converter 23.

[0048] [Control System] Figure 3 is a functional block diagram showing the control system of vehicle V. As shown in this figure, the PCM50 is electrically connected to the vehicle speed sensor SN1, accelerator sensor SN2, battery sensor SN3, crank angle sensor SN4, engine water temperature sensor SN5, and catalyst temperature sensor SN6 mentioned above. The PCM50 receives sequential input of information detected by each of these sensors, namely vehicle speed, accelerator opening, battery SOC, crank angle, engine speed, engine water temperature, and catalyst temperature.

[0049] The PCM50 controls the vehicle V's movement based on input information from the sensors SN1 to SN6. Specifically, the PCM50 is electrically connected to the injectors 8, spark plugs 9, throttle valve 18, exhaust SVT20, and intake SVT21 of the engine 1, as well as the clutch 30, motor 31, and inverter 32. The PCM50 outputs control signals to these devices, generated through calculations based on the input information from the sensors SN1 to SN6. Regarding the control of the exhaust SVT20 (intake SVT21), the PCM50 indirectly controls the exhaust SVT20 by controlling the hydraulic circuit device that supplies hydraulic pressure to the exhaust SVT20 (intake SVT21).

[0050] For example, the PCM50 calculates the required torque of the vehicle V, which is the torque to be transmitted to the drive wheels 37, based on the vehicle speed detected by the vehicle speed sensor SN1 and the accelerator opening detected by the accelerator sensor SN2. Based on the calculated required torque and the battery SOC detected by the battery sensor SN3, the PCM50 controls the engine 1, clutch 30, and motor 31 (inverter 32) while determining the driving mode of the vehicle V.

[0051] Specifically, if the required torque for vehicle V is relatively small and the battery SOC is relatively high, the motor driving mode is selected. In this case, the PCM 50 stops the engine 1 and releases the clutch 30. The PCM 50 also generates torque in the motor 31 that corresponds to the required torque for vehicle V, thereby driving vehicle V using only the motor 31. On the other hand, if the required torque for vehicle V is relatively high or the battery SOC is relatively low, the engine driving mode is selected. In this case, the PCM 50 drives the engine 1 (combustion) and engages the clutch 30. Furthermore, if, for example, the output torque of the engine 1 is insufficient for the required torque for vehicle V, the PCM 50 drives the motor 31 and generates assist torque in the motor 31 that corresponds to the torque deficit. In this case, the PCM 50 controls the engine 1 and motor 31 so that the combined torque of the engine 1 and motor 31 corresponds to the required torque for vehicle V. On the other hand, if the motor 31 is not driven, the engine 1 generates a torque equivalent to the required torque of the vehicle V, thereby driving the vehicle V using only the engine 1.

[0052] Next, the details of the control of the vehicle V when the engine temperature is low, which is a characteristic control of the present invention, will be explained using the flowcharts in Figures 4 and 5. The control shown in these figures is performed while driving in engine-driven mode.

[0053] When the control shown in Figure 4 starts, the PCM50 acquires various information regarding the driving state of the vehicle V and calculates the engine request torque (step S0). At a minimum, the PCM50 acquires the detection values ​​of each of the sensors SN1 to SN6, namely, vehicle speed, accelerator opening, battery SOC, engine speed, engine water temperature, and catalyst temperature. The PCM50 also calculates the engine request torque, which is the torque required for engine 1, based on the vehicle V's request torque calculated based on the vehicle speed and accelerator opening as described above.

[0054] Next, the PCM50 sets the throttle opening (the degree to which the throttle valve 18 is opened), the ignition timing (the timing at which the spark plug 9 ignites), and the injection amount (the amount of fuel injected from the injector 8) to achieve the engine torque calculated in step S0 (step S1).

[0055] At this time, the PCM50 sets the throttle opening and injection amount so that the air excess ratio λ of the air-fuel mixture formed in the combustion chamber C becomes 1. The air excess ratio λ is the value obtained by dividing the air-fuel ratio of the air-fuel mixture by the stoichiometric air-fuel ratio.

[0056] For example, the PCM50 extracts values ​​corresponding to the current engine speed and engine torque from maps of throttle opening, ignition timing, and injection volume that are pre-set and stored for engine speed and engine torque requirements, and sets each of the extracted values ​​as throttle opening, ignition timing, and injection volume, respectively.

[0057] Next, the PCM50 determines whether the temperature of the engine 1 is below a predetermined first determination temperature (step S2). In this embodiment, in step S2, the PCM50 determines whether the engine water temperature detected by the engine water temperature sensor SN5 is below a predetermined first determination temperature Tw1. The first determination temperature Tw1 is preset and stored in the PCM50. Specifically, the first determination temperature Tw1 is set to a temperature approximately the same as the maximum engine water temperature when the engine 1 is cold and the catalytic converter 23 is in an inactive state, for example, around 20°C. Thus, in this embodiment, the engine water temperature (engine coolant temperature) corresponds to the "engine temperature" in the present invention, and the first determination temperature corresponds to the "first determination temperature" in the present invention. Furthermore, the condition that the engine water temperature is below the first determination temperature Tw1 corresponds to the "first condition" in the present invention, and the time when the engine water temperature is below the first determination temperature Tw1 corresponds to "when the first condition is met".

[0058] If the determination in step S2 is YES and the engine water temperature is less than or equal to the first determination water temperature Tw1 (if the temperature of engine 1 is less than or equal to the first determination temperature), the PCM 50 sets the target intake valve timing, which is the target value for the opening and closing timing of the intake valve 13 (open timing IVO and closing timing IVC), and the target exhaust valve timing, which is the target value for the opening and closing timing of the exhaust valve 14 (open timing EVO and closing timing EVC), to the valve timings of LIVO mode (step S3).

[0059] As shown in Figure 6, the valve timing in LIVO mode is such that the exhaust valve 14 closes after exhaust TDC (exhaust top dead center), and the intake valve 13 opens during the subsequent intake stroke. Therefore, in step S3, the PCM 50 sets the target exhaust valve timing to a valve timing where the closing time EVC of the exhaust valve 14 is at or near exhaust TDC, or retarded to a time later than exhaust TDC. Also in step S3, the PCM 50 sets the target intake valve timing to a valve timing where the opening time IVO of the intake valve 13 is during the intake stroke and retarded to a time later than the closing time EVC of the exhaust valve 14.

[0060] In step S3, the PCM50 sets the intake target valve timing and exhaust target valve timing to satisfy the above conditions based on the engine speed and the engine request torque calculated in step S1. For example, the PCM50 extracts values ​​corresponding to the current engine speed and engine request torque from a map of target intake valve timing and target exhaust valve timing for LIVO mode that is pre-set and stored to satisfy the above conditions for engine speed and engine request torque, and sets each of the extracted values ​​as the target intake valve timing and target exhaust valve timing, respectively.

[0061] In this embodiment, the target intake valve timing in LIVO mode is set to be more retarded than the target intake valve timing in NVO mode, which will be described later. In other words, the opening timing IVO of the intake valve 13 in LIVO mode is set to be more retarded than the opening timing IVO of the intake valve 13 in NVO mode, which is set in step S13, which will be described later. Specifically, the opening timing IVO of the intake valve 13 in LIVO mode is set to be more retarded than the opening timing IVO of the intake valve 13 in NVO mode, under the same conditions of engine speed and engine torque requirement.

[0062] Next, the PCM50 sets the injection timing, which is the time when fuel injection to the injector 8 is initiated, to the timing of LIVO mode (step S4). As shown in Figure 6, the injection timing for LIVO mode (SOI) is set to a timing during the intake stroke that is retarded compared to the closing timing EVC of the exhaust valve 14 and the opening timing IVO of the intake valve 13.

[0063] Furthermore, in this embodiment, the injection timing in LIVO mode is set to be approximately 30°CA (Crank Angle) retarded from the opening timing IVO of the intake valve 13, and approximately 20°CA retarded from the time when the pressure in the combustion chamber C is at its minimum.

[0064] For example, the PCM50 extracts values ​​corresponding to the current engine speed and engine torque from a LIVO mode injection timing map that is pre-set and stored to satisfy the above conditions for engine speed and engine torque, and sets the extracted values ​​as the injection timing.

[0065] Next, the PCM50 determines whether the engine request torque calculated in step S0 is greater than or equal to a predetermined judgment torque (step S5). The judgment torque is pre-set to a value greater than 0 and less than the maximum value of the engine request torque and stored in the PCM50. Specifically, the judgment torque is set to the minimum value of the engine request torque at which, even if the throttle opening is increased by a predetermined amount from the opening set in step S1 while the intake valve 13 closing timing IVC is set to the time set in step S3, the increase in engine torque relative to the engine request torque calculated in step S0 is kept below a predetermined value.

[0066] If the determination in step S5 is YES and the engine required torque is equal to or greater than the determination torque, the PCM 50 issues commands to the throttle valve 18 (device that drives the throttle valve 18 to open and close), the injector 8, and the spark plug 9 so that the throttle opening, ignition timing, injection amount set in step S1 and the injection timing set in step S4 are realized (step S6). The PCM 50 also issues commands to the intake SVT 21 and exhaust SVT 20 so that the target valve timings set in step S3 are realized (step S6), and then terminates the process (returns to step S1). In this embodiment, in step S6, which proceeds when the determinations in steps S2 and S5 are YES, the motor 31 is stopped from being driven as a generator.

[0067] On the other hand, if the determination in step S5 is NO and the engine required torque is less than the determination torque, the PCM50 determines whether the battery SOC obtained in step S0 is less than a predetermined determination SOC (step S7). The determination SOC is pre-set to a value greater than 0 and less than 100% and stored in the PCM50.

[0068] If the determination in step S7 is YES and the battery SOC is less than the determination SCO, the PCM 50 sets the target power generation amount, which is the target value for the power generation amount of the motor 31 (step S8). In this embodiment, the PCM 50 sets the target power generation amount based on the battery SOC and the engine required torque calculated in step S1. Specifically, it is set so that the target power generation amount is smaller when the battery SOC and engine required torque are large than when they are small.

[0069] Next, the PCM50 corrects the throttle opening set in step S1 to the open side (step S9). In other words, it readjusts the throttle opening to a larger opening than the one set in step S1 so that more air is introduced into the combustion chamber C than the amount of air introduced into the combustion chamber C at the throttle opening set in step S1. The PCM50 also corrects the injection amount set in step S1 by increasing it (step S9). In other words, it readjusts the injection amount to a larger amount than the one set in step S1.

[0070] In step S9, the throttle opening and injection amount are reset so that the engine torque generated when the reset throttle opening and injection amount are achieved matches the sum of the engine torque required to make the motor 31 generate the target amount of power set in step S8 and the engine request torque calculated in step S0, and so that when the reset throttle opening and injection amount are achieved, the excess air ratio λ of the air-fuel mixture in the combustion chamber C becomes 1. Therefore, the larger the target amount of power generated, the larger the correction amount for the throttle opening and injection amount (the increase relative to the throttle opening and injection amount set in step S1) becomes.

[0071] Next, the PCM50 issues a command to the spark plug 9 so that the ignition timing set in step S1 is achieved (step S6). The PCM50 also issues commands to the intake SVT21 and exhaust SVT20 so that the target valve timings set in step S3 are achieved (step S6). Furthermore, in step S6, which proceeds if the determination in step S7 is YES, the PCM50 issues commands to the throttle valve 18 and injector 8 so that the throttle opening and injection amount set in step S9 are achieved, and the injection timing set in step S4 is achieved (step S6). In addition, in step S6, which proceeds if the determination in step S7 is YES, the PCM50 issues a command to the motor 31 (inverter 32) so that the motor 31 is driven as a generator and the amount of power generated is the target amount of power generated in step S8 (step S6), and then the process ends (return to step S1). In this embodiment, the power generated by the motor 31 is sent to the battery 33 and stored in the battery 33.

[0072] Returning to step S7, if the result of step S7 is NO and the battery SOC is equal to or greater than the determined SOC, the PCM50 corrects the ignition timing set in step S1 to a retarded timing (step S10). In other words, the ignition timing is reset to a timing that is retarded compared to the ignition timing set in step S1. In step S10, the ignition timing is reset based on the engine demand torque calculated in step S0. Specifically, the ignition timing is reset so that the amount of retardation of the ignition timing (the amount of retardation relative to the ignition timing set in step S1) is smaller when the engine demand torque is higher.

[0073] Next, the PCM50 corrects the throttle opening set in step S1 to the open side (step S11). In other words, it resets the throttle opening to a larger opening than the one set in step S1 so that more air is introduced into the combustion chamber C than the amount of air introduced into the combustion chamber C at the throttle opening set in step S1. The PCM50 also corrects the injection amount set in step S1 by increasing it (step S11). In other words, it resets the injection amount to a larger amount than the one set in step S1.

[0074] In step S11, the throttle opening and injection amount are reset so that when the throttle opening and injection amount reset in step S11 are achieved, and the ignition timing reset in step S10 is achieved, the resulting engine torque matches the engine requirement torque calculated in step S1, and the excess air ratio λ of the air-fuel mixture in combustion chamber C becomes 1 when the reset throttle opening and injection amount are achieved. Thus, the larger the amount of retardation of the ignition timing (the amount of retardation relative to the ignition timing set in step S1), the larger the correction amount for the throttle opening and injection amount (the increase relative to the throttle opening and injection amount set in step S1).

[0075] Next, the PCM50 issues a command to the injector 8 so that the injection timing set in step S4 is realized (step S6). The PCM50 also issues commands to the intake SVT21 and exhaust SVT20 so that the target valve timings set in step S3 are realized (step S6). Furthermore, in step S6, which proceeds if the determination in step S7 is NO, the PCM50 issues commands to the throttle valve 18 and injector 8 so that the throttle opening and injection amount set in step S11 are realized (step S6). In addition, in step S6, which proceeds if the determination in step S7 is NO, the PCM50 issues a command to the spark plug 9 so that the ignition timing set in step S10 is realized (step S6), and then the process ends (return to step S1). In this embodiment, in step S6, which proceeds if the determination in step S2 is YES and the determinations in steps S5 and S7 are NO, the drive of the motor 31 as a generator is stopped.

[0076] Returning to step S2, if the determination in step S2 is NO and the engine water temperature is higher than the first determination water temperature Tw1 (i.e., the temperature of engine 1 is higher than the first determination temperature), the PCM 50 determines whether the temperature of engine 1 is below a predetermined second determination temperature that is higher than the first determination temperature (step S12). In this embodiment, in step S12, the PCM 50 determines whether the engine water temperature detected by the engine water temperature sensor SN5 is below a predetermined second determination temperature Tw2. Thus, in this embodiment, the second determination temperature Tw2 corresponds to the "second determination temperature" in the present invention. Furthermore, the condition that the engine water temperature is higher than the first determination water temperature Tw1 and below the second determination water temperature Tw2 corresponds to the "second condition" in the present invention, and the time when the engine water temperature is higher than the first determination water temperature Tw1 and below the second determination water temperature Tw2 corresponds to "when the second condition is met".

[0077] The second judgment water temperature Tw2 is pre-set to a higher value than the first judgment water temperature Tw1 and stored in the PCM50. The second judgment water temperature Tw2 is set to a temperature similar to the maximum engine water temperature when the engine 1 is in a so-called semi-warm-up state before it has finished warming up and the catalytic converter 23 is in an active state, for example, around 60°C.

[0078] If the determination in step S12 is YES and the engine water temperature is less than or equal to the second determination water temperature Tw2 (and higher than the first determination water temperature Tw1: when the temperature of engine 1 is higher than the first determination temperature and less than or equal to the second determination temperature), the PCM 50 sets the target intake valve timing and target exhaust valve timing to the NVO mode valve timing, respectively (step S13). The NVO mode valve timing is a valve timing in which negative overlap occurs, as shown in Figure 7, in which the intake valve 13 and the exhaust valve 14 are both closed during a predetermined period (negative overlap period) that straddles the exhaust TDC. Accordingly, in step S13, the PCM 50 sets the target intake valve timing so that the opening timing IVO of the intake valve 13 is retarded compared to the exhaust TDC, and sets the target exhaust valve timing so that the closing timing EVC of the exhaust valve 14 is advanced compared to the exhaust TDC.

[0079] Furthermore, the PCM50 sets the target intake valve timing and target exhaust valve timing based on the engine demand torque, engine speed, and engine temperature calculated in step S0, to valve timings that satisfy the condition of negative overlap. In this embodiment, engine water temperature is used as the engine temperature, and each valve timing is set based on the engine demand torque, engine speed, and engine water temperature.

[0080] For example, the PCM50 extracts a map corresponding to the current engine temperature from the target intake valve timing and target exhaust valve timing maps for NVO mode, which are pre-set and stored for different engine water temperatures, for engine speed and engine torque requirements. It then extracts values ​​corresponding to the current engine speed and engine torque requirements in each extracted map and sets these extracted values ​​as the target intake valve timing and target exhaust valve timing.

[0081] Here, the target exhaust valve timing for NVO mode is set with respect to engine coolant temperature as shown in Figure 8. More specifically, under the same conditions of engine speed and engine torque requirement, the target exhaust valve timing for NVO mode is changed according to engine coolant temperature as shown in Figure 8.

[0082] Specifically, when the engine water temperature is in the range from the first determination water temperature Tw1 to the fourth determination water temperature Tw11 or lower, the target exhaust valve timing for NVO mode is set such that the closing timing EVC of the exhaust valve 14 advances as the engine water temperature increases. Furthermore, when the engine water temperature is in the range from the fourth determination water temperature Tw11 to the third determination water temperature Tw12 or lower, the target exhaust valve timing for NVO mode is set such that the closing timing EVC of the exhaust valve 14 remains constant regardless of the engine water temperature. Furthermore, when the engine water temperature is in the range from the third determination water temperature Tw12 to the second determination water temperature Tw2 or lower, the target exhaust valve timing for NVO mode is set such that the closing timing EVC of the exhaust valve 14 is retarded as the engine water temperature increases. The fourth determination water temperature Tw11 is higher than the first determination water temperature Tw1 and lower than the second determination water temperature Tw2, and the third determination water temperature Tw12 is higher than the fourth determination water temperature Tw11 and lower than the second determination water temperature Tw2. Here, the above third determination water temperature Tw12 corresponds to the "third determination temperature" in the claim.

[0083] After setting the target intake valve timing and target exhaust valve timing to the NVO mode valve timing as described above, the PCM50 sets the injection timing to the NVO mode timing (step S14). In this embodiment, the injection timing for NVO mode is set to a timing during the intake stroke that is retarded compared to the opening timing IVO of the intake valve 13. For example, the PCM50 extracts values ​​corresponding to the current engine speed and engine torque from a map of NVO mode injection timings that has been pre-set and stored to satisfy the above conditions for engine speed and engine torque, and sets the extracted values ​​to the injection timing.

[0084] Next, the PCM50 issues commands to the throttle valve 18, injector 8, and spark plug 9 so that the throttle opening, ignition timing, and injection amount set in step S1, and the injection timing set in step S14, are realized (step S6). The PCM50 also issues commands to the intake SVT21 and exhaust SVT20 so that the target valve timings set in step S13 are realized (step S6), and then the process ends (returns to step S1). In this embodiment, in step S6, which proceeds when the determination in step S2 is NO and the determination in step S12 is YES, the motor 31 is stopped from being driven as a generator.

[0085] Returning to step S12, if the determination in step S12 is NO and the engine water temperature is higher than the second determination water temperature Tw2 (i.e., the temperature of engine 1 is higher than the second determination temperature), the PCM 50 sets the target intake valve timing and target exhaust valve timing to the valve timing for normal mode (step S15). In other words, if the engine water temperature is higher than the second determination water temperature Tw2 and engine 1 has finished warming up, the opening and closing timing of the intake valve 13 and exhaust valve 14 is set to the valve timing for normal driving after warming up is complete. For example, the PCM 50 extracts values ​​corresponding to the current engine speed and engine demand torque from a map of target intake valve timing and target exhaust valve timing for normal mode that is pre-set and stored for engine speed and engine demand torque, and sets each of the extracted values ​​to the target intake valve timing and target exhaust valve timing, respectively.

[0086] Next, the PCM50 sets the injection timing to the timing of the normal mode (step S16). For example, the PCM50 extracts values ​​corresponding to the current engine speed and engine torque from a map of injection timings for the normal mode that is pre-set and stored for engine speed and engine torque, and sets the extracted values ​​to the injection timing.

[0087] After setting the target intake valve timing, target exhaust valve timing, and injection timing to the values ​​for normal mode as described above, the PCM50 issues commands to the throttle valve 18, injector 8, and spark plug 9 so that the throttle opening, ignition timing, and injection amount set in step S1 and the injection timing set in step S16 are realized (step S6). The PCM50 also issues commands to the intake SVT21 and exhaust SVT20 so that the respective target valve timings set in step S15 are realized (step S6), and then terminates the process (returns to step S1).

[0088] Figure 9 is a time chart showing the time changes of engine water temperature, intake valve 13 opening timing IVO, and exhaust valve 14 closing timing EVC from the time engine 1 is started when the engine water temperature is below the first judgment water temperature Tw1, that is, from the time engine 1 is cold-started.

[0089] In Figure 9, engine 1 is started at time t0. As described above, in the example of Figure 9, engine 1 is started when the engine water temperature is below the first determination water temperature Tw1. Therefore, after time t0, the opening and closing timing of the intake valve 13 and exhaust valve 14 is set to the valve timing of LIVO mode. Therefore, the closing timing EVC of the exhaust valve 14 is set to a time retarded compared to exhaust TDC. Also, the opening timing IVO of the intake valve 13 is set to a time retarded compared to the closing timing EVC of the exhaust valve 14. In this embodiment, while engine 1 is stopped, the phase of the intake valve 13 is maintained at a phase where its opening timing IVO is near exhaust TDC, and the phase of the exhaust valve 14 is maintained at a phase where its closing timing EVC is near exhaust TDC. Therefore, immediately after time t0, the phase of the intake valve 13 is significantly retarded.

[0090] Furthermore, after time t0, combustion begins in the combustion chamber C of engine 1. From this point onward, the engine water temperature gradually increases and reaches the first determination water temperature Tw1 at time t1.

[0091] During the period up to time t1, since the engine water temperature is below the first determination water temperature Tw1, the valve timing of the intake valve 13 and exhaust valve 14 is maintained at the valve timing of LIVO mode. In the example in Figure 9, the opening timing IVO of the intake valve 13 and the closing timing EVC of the exhaust valve 14 are maintained at approximately constant values ​​until time t1.

[0092] The engine water temperature exceeds the second judgment water temperature Tw2 at time t4, after time t1. Therefore, during the period from time t1 to time t4, the valve timing of the intake valve 13 and exhaust valve 14 is set to the valve timing of NVO mode. Specifically, when the engine water temperature rises above the first judgment water temperature Tw1 at time t1, both the opening timing IVO of the intake valve 13 and the closing timing EVC of the exhaust valve 14 are advanced. The opening timing IVO of the intake valve 13 is set to a time that is retarded compared to the exhaust TDC, and advanced compared to the opening timing IVO of the intake valve 13 in LIVO mode. Also, the closing timing EVC of the exhaust valve 14 in NVO mode is set to a time that is advanced compared to the exhaust TDC.

[0093] As described above, in NVO mode, within the range where the engine water temperature is below the fourth determination water temperature Tw11, the higher the engine water temperature, the more advanced the closing timing EVC of the exhaust valve 14 becomes. In this embodiment, in NVO mode, within the range where the engine water temperature is below the fourth determination water temperature Tw11, the higher the engine water temperature, the more advanced the opening timing IVO of the intake valve 13 becomes. Thus, from time t1 until time t2 when the engine water temperature reaches the fourth determination water temperature Tw11, the closing timing EVC of the exhaust valve 14 and the opening timing IVO of the intake valve 13 are advanced in accordance with the rise in engine water temperature.

[0094] Furthermore, in NVO mode, when the engine water temperature is in the range from the fourth determination water temperature Tw11 to the third determination water temperature Tw12 or less, the closing timing EVC of the exhaust valve 14 is set to a constant time regardless of the engine water temperature. In this embodiment, in NVO mode, when the engine water temperature is in the range from the fourth determination water temperature Tw11 to the third determination water temperature Tw12 or less, the opening timing IVO of the intake valve 13 is also set to a constant time regardless of the engine water temperature. Thus, from time t2 until time t3 when the engine water temperature reaches the third determination water temperature Tw12, the closing timing EVC of the exhaust valve 14 and the opening timing IVO of the intake valve 13 are maintained at a constant time.

[0095] Furthermore, in NVO mode, when the engine water temperature is higher than the third determination water temperature Tw12, the closing timing EVC of the exhaust valve 14 is retarded as the engine water temperature increases. Thus, from time t3 onward (until time t4 when the engine water temperature reaches the second determination water temperature Tw2), the closing timing EVC of the exhaust valve 14 is retarded as the engine water temperature rises. In this embodiment, in NVO mode, when the engine water temperature is higher than the third determination water temperature Tw12, the opening timing IVO of the intake valve 13 is advanced as the engine water temperature increases. Thus, from time t3 onward (until time t4 when the engine water temperature reaches the second determination water temperature Tw2), the opening timing IVO of the intake valve 13 is advanced as time progresses.

[0096] After time t4, when the engine water temperature exceeds the second judgment water temperature Tw2, the engine water temperature is maintained at a temperature higher than the second judgment water temperature Tw2 until the engine 1 stops. Therefore, after time t4, until the engine 1 stops, the valve timing of the intake valve 13 and exhaust valve 14 is set to the valve timing of the normal mode. In the example in Figure 9, after time t4, the opening timing IVO of the intake valve 13 is advanced compared to the exhaust TDC, and the closing timing EVC of the exhaust valve 14 is retarded compared to the exhaust TDC.

[0097] [Effect, etc.] As described above, in the above embodiment, when the engine water temperature is higher than the first determination water temperature Tw1 but less than or equal to the second determination water temperature Tw2, and the engine temperature is relatively low, the exhaust target valve timing and intake target valve timing are set to the valve timing of NVO mode, and the exhaust valve 14 and intake valve 13 are controlled so that a negative overlap occurs in which the exhaust valve 14 and intake valve 13 are closed during a predetermined period spanning the exhaust TDC. In other words, the exhaust valve 14 is closed while the combustible gas in the combustion chamber C is being led out to the exhaust port 12, and then the intake valve 13 is opened at a timing when the piston 5 is descending and backflow of the combustible gas to the intake port 11 is suppressed.

[0098] Therefore, according to the above embodiment, when the engine water temperature is higher than the first determination water temperature Tw1 but less than or equal to the second determination water temperature Tw2, a relatively large amount of high-temperature burned gas can be trapped in the combustion chamber C, thereby increasing the temperature inside the combustion chamber C. When the temperature inside the combustion chamber C rises, the evaporation of fuel supplied to the combustion chamber C and, consequently, the combustion of that fuel is promoted. Also, when the temperature inside the combustion chamber C rises, cooling losses are reduced. Accordingly, according to the above embodiment, when the engine water temperature is higher than the first determination water temperature Tw1 but less than or equal to the second determination water temperature Tw2, it is possible to improve fuel efficiency while keeping the amount of unburned HC and soot emitted from the combustion chamber C low, thereby improving exhaust performance.

[0099] However, since the burned gas is an inert gas, if a large amount of burned gas remains in the combustion chamber as described above, especially when the engine temperature is low, combustion may become unstable. In contrast, in the above embodiment, when the engine water temperature is below the first determination water temperature Tw1, the valve timing of the intake valve 13 and exhaust valve 14 is set to the valve timing of LIVO mode, the closing timing EVC of the exhaust valve 14 is set to a time after exhaust TDC, and the opening timing IVO of the intake valve 13 is set to a time retarded to the closing timing EVC of the exhaust valve 14, while the injection timing of the injector 8 is set to a time during the intake stroke that is retarded to the closing timing EVC of the exhaust valve 14 and the opening timing IVO of the intake valve 13. Therefore, according to the above embodiment, even when the engine water temperature is below the first determination water temperature Tw1, combustion stability can be ensured, and the evaporation of fuel supplied to the combustion chamber C can be promoted by the action of the negative pressure generated in the combustion chamber C, thereby reducing the amount of unburned HC and soot discharged from the engine body 2.

[0100] This will be explained in detail using Figure 10. Figure 10 is a schematic cross-sectional view to explain the operation of valve timing in LIVO mode, where (a) shows the state inside the combustion chamber C before exhaust TDC, (b) shows the state inside the combustion chamber C after exhaust TDC and before intake valve opening timing IVO, and (c) shows the state inside the combustion chamber C after intake valve opening timing IVO.

[0101] In LIVO mode, the closing timing EVC of the exhaust valve 14 is set to after exhaust TDC (at or after exhaust TDC), and as shown in Figure 10(a), the exhaust valve 14 remains open even when the volume of the combustion chamber C is at its smallest. Therefore, in LIVO mode, most of the already burned gas is discharged from the combustion chamber C to the exhaust port 12 and exhaust passage 19, preventing combustion instability caused by the already burned gas and ensuring combustion stability.

[0102] Furthermore, in LIVO mode, the intake valve 13 opens after the exhaust valve 14 closes (EVC), and for a predetermined period after the exhaust valve 14 closes (EVC) during the intake stroke, both the intake valve 13 and the exhaust valve 14 are closed, as shown in Figure 10(b). Here, as described above, most of the burnt gas is discharged outside the combustion chamber C. Consequently, during the predetermined period after the exhaust valve 14 closes (EVC), the combustion chamber C becomes negatively pressurized as the piston 5 descends from the dashed line to the solid line.

[0103] Furthermore, when the engine water temperature is below the first determination water temperature Tw1, the injection timing of the injector 8 is set to a time during the intake stroke that is retarded compared to the closing timing EVC of the exhaust valve 14. As shown in Figure 10(c), fuel F is injected from the injector 8 into the combustion chamber C while the combustion chamber C is under negative pressure. In other words, the fuel is supplied under an atmosphere where the pressure is significantly low, thereby keeping the fuel vaporization temperature low. Thus, according to the above embodiment, even when the engine water temperature is below the first determination water temperature Tw1, fuel evaporation is promoted, and the amount of unburned HC and soot emitted from the combustion chamber C is kept low.

[0104] Furthermore, in LIVO mode, as described above, the intake valve 13 opens when the combustion chamber C is under negative pressure. This causes intake air to flow vigorously from the intake port 11 into the combustion chamber C, creating a strong intake airflow within the combustion chamber C. In other words, the kinetic energy of the intake air is increased within the combustion chamber C. As a result, the temperature inside the combustion chamber C is also increased in LIVO mode, which further promotes fuel evaporation. In particular, in the above embodiment, the injection timing of the injector 8 is set to be retarded compared to the opening timing IVO of the intake valve 13. This ensures that fuel is supplied to the combustion chamber C while intake airflow is occurring, i.e., while the temperature inside the combustion chamber C is being increased by the intake airflow, thus reliably promoting fuel evaporation. Furthermore, in the above embodiment, the opening timing IVO of the intake valve 13 in LIVO mode is set to be more retarded than the opening timing IVO of the intake valve 13 in NVO mode, so that the intake valve 13 is opened when the negative pressure in the combustion chamber C is higher. This makes it possible to generate a particularly strong intake airflow in the combustion chamber C, and reliably promote fuel evaporation.

[0105] As described above, according to the above embodiment, when the engine water temperature is below the second determination water temperature Tw2, the amount of unburned HC and soot discharged from the combustion chamber C can be kept low while ensuring combustion stability. Therefore, exhaust performance can be improved immediately after the engine 1 is cold-started.

[0106] Furthermore, in the above embodiment, when the engine water temperature is below the first determination water temperature Tw1, and the engine required torque is less than the determination torque and the battery SOC is less than the determination SOC, the motor 31 is driven as a generator. Therefore, the torque to be transmitted from the engine 1 to the drive wheels 37 can be maintained at an appropriate level while further promoting fuel evaporation.

[0107] Specifically, the motor 31 is driven as a generator, and the throttle opening and injection amount are increased and corrected so that the engine torque matches the sum of the torque required to drive the motor 31 as a generator and the torque to be transmitted from the engine 1 to the drive wheels 37. As a result, the torque transmitted from the engine 1 to the drive wheels 37 is set to the required torque, and a large amount of air is introduced into the combustion chamber C, increasing the intake airflow and consequently the temperature within the combustion chamber C, thereby further promoting fuel evaporation. In addition, the engine torque exceeding the torque to be transmitted to the drive wheels 37 can be used as electricity, thus maintaining good fuel efficiency for the entire vehicle V. In particular, in the above embodiment, since the electricity is stored in the battery 33, it is possible to prevent the electricity from being wasted.

[0108] Furthermore, in the above embodiment, when the engine water temperature is below the first determination water temperature Tw1, and the engine required torque is less than the determination torque, and the battery SOC is above the determination SOC, and there is a risk of overcharging if power is supplied to the battery 33, the ignition timing is set to a more retarded timing than when the engine water temperature is below the first determination water temperature Tw1 and the above conditions are not met, and when the engine water temperature is higher than the first determination water temperature Tw1 and below the second determination water temperature Tw2. As a result, the torque to be transmitted from the engine 1 to the drive wheels 37 can be maintained at an appropriate torque while further promoting fuel evaporation.

[0109] Specifically, retarding the ignition timing reduces engine torque. In response to this, when the above conditions are met, the throttle opening and injection amount are increased while retarding the ignition timing so that the engine torque matches the torque that should be transmitted from engine 1 to drive wheels 37. In other words, while retarding the ignition timing, the decrease in engine torque associated with retarding the ignition timing is compensated for by increasing the throttle opening and injection amount.

[0110] Therefore, while the torque transmitted from the engine 1 to the drive wheels 37 is set to the required torque, a large amount of air can be introduced into the combustion chamber C, increasing the intake airflow within the combustion chamber C and consequently the temperature within the combustion chamber C, thereby further promoting fuel evaporation. In addition, when the ignition timing is retarded, the temperature of the exhaust gas at the time the exhaust valve 14 opens rises. As a result, a higher temperature exhaust gas can be introduced to the catalytic converter 23, and the activation of the catalytic converter 23 can also be promoted.

[0111] Furthermore, in the above embodiment, the target intake valve timing and target exhaust valve timing are set to the valve timing of NVO mode, and when the engine water temperature is 12 or higher than the third determination water temperature Tw12, the closing timing EVC of the exhaust valve 14 is set to be more retarded when the engine water temperature is high than when it is low. Therefore, when the engine water temperature is relatively low and the temperature of the combustion chamber C is low, closing the exhaust valve 14 earlier increases the amount of burnt gas remaining in the combustion chamber C, thereby appropriately raising the temperature of the combustion chamber C. Also, when the engine water temperature is relatively high and the temperature of the combustion chamber C is high, closing the exhaust valve 14 at a relatively late time reduces the amount of burnt gas remaining in the combustion chamber, preventing the temperature inside the combustion chamber C from becoming excessively high.

[0112] [Differentiation] In the above embodiment, the case was described in which the target intake valve timing and target exhaust valve timing are set to valve timings in which the intake valve 13 and exhaust valve 14 negatively overlap when the engine water temperature is higher than the first determination water temperature Tw1 and less than or equal to the second determination water temperature Tw2. However, instead, the target intake valve timing and target exhaust valve timing may be set to valve timings in which the intake valve 13 and exhaust valve 14 positively overlap when the engine water temperature is higher than the first determination water temperature Tw1 and less than or equal to the second determination water temperature Tw2.

[0113] Specifically, when the engine water temperature is higher than the first determination water temperature Tw1 and less than or equal to the second determination water temperature Tw2, as shown in Figure 11, the opening timing IVO of the intake valve 13 may be set to an advanced timing beyond the exhaust TDC, and the closing timing EVC of the exhaust valve 14 may be set to a retarded timing beyond the exhaust TDC, so that the exhaust valve 14 and the intake valve 13 are both open for a predetermined period spanning the exhaust TDC, resulting in a positive overlap.

[0114] In this configuration as well, similar to the case of negative valve overlap, a large amount of used gas can be retained in the combustion chamber C. Therefore, similar to the above embodiment, when the engine water temperature is higher than the first determination water temperature Tw1 and less than or equal to the second determination water temperature Tw2, the temperature in the combustion chamber C can be increased to promote fuel evaporation. In detail, in the case of positive overlap, both the intake valve 13 and the exhaust valve 14 are open for a predetermined period before exhaust TDC, so that used gas in the combustion chamber C is led to the intake port 11 and the exhaust port 12. However, since both the intake valve 13 and the exhaust valve 14 remain open even after exhaust TDC, the used gas led to these ports 11 and 12 can be reintroduced into the combustion chamber C, and a large amount of used gas can be retained in the combustion chamber C after the intake valve 13 is closed.

[0115] However, as described above, when the engine water temperature is below the first determination water temperature Tw1, the closing timing of the intake valve 13 is set to a time retarded compared to the exhaust TDC. Therefore, as in the above embodiment, when the engine water temperature is higher than the first determination water temperature Tw1 and below the second determination water temperature Tw2, setting the target intake valve timing and target exhaust valve timing to valve timings where the intake valve 13 and exhaust valve 14 have negative valve overlap, and setting the opening timing IVO of the intake valve 13 to a time retarded compared to the exhaust TDC, makes it possible to keep the change in the opening timing IVO of the intake valve 13 small when the engine water temperature rises from a temperature below the first determination water temperature Tw1 to a temperature above the first determination water temperature. Therefore, when the engine water temperature exceeds the first determination water temperature Tw1, the opening timing IVO of the intake valve 13 can be controlled to an appropriate time earlier.

[0116] Furthermore, in the above embodiment, the determination of whether the temperature of the engine 1 in step S2 is below the first determination temperature and the determination of whether the temperature of the engine 1 in step S12 is below the second determination temperature were described using the engine water temperature. However, these determinations may be made using the temperature of the catalytic converter 23 instead. Specifically, in step S2, instead of determining whether the engine water temperature is below the first determination temperature, the determination of whether the catalyst temperature detected by the catalyst temperature sensor SN6 is below a predetermined first determination catalyst temperature may be made. Similarly, in step S12, instead of determining whether the engine water temperature is below the second determination temperature, the determination of whether the catalyst temperature detected by the catalyst temperature sensor SN6 is below a predetermined second determination catalyst temperature (a temperature higher than the first determination catalyst temperature) may be made. Also, in the above embodiment, the case in which the closing timing EVC of the exhaust valve 14 is changed according to the engine water temperature in the valve timing of NVO mode was described, but the closing timing EVC of the exhaust valve 14 may be changed according to the catalyst temperature instead of the engine water temperature. For example, in NVO mode, when the catalyst temperature is above a predetermined third determination catalyst temperature (a temperature higher than the second determination catalyst temperature mentioned above), the valve timing of the exhaust valve 14 may be set such that the closing timing EVC of the exhaust valve 14 is more advanced when the catalyst temperature is high than when it is low.

[0117] In the above embodiment, intake SVT21 and exhaust SVT20, which are phase variable devices that change the phase of the intake valve 13 and exhaust valve 14 while maintaining a constant lift amount and valve opening period, were used as phase variable devices to change the phase (opening / closing timing) of the intake valve 13 and exhaust valve 14. However, instead, a phase variable device that changes the lift amount or valve opening period in conjunction with the valve phase may be used.

[0118] In the above embodiment, an injector 8 attached to the cylinder head 4 that injects fuel into the combustion chamber C was used. However, instead, an injector attached to the intake port 11 that injects fuel into the intake port 11 and supplies fuel to the combustion chamber C via the intake port 11 may be used.

[0119] In the above embodiment, a hybrid vehicle V is exemplified, which uses both an engine 1 consisting of a four-stroke gasoline engine that uses gasoline as fuel and an electric motor 31. However, the vehicles to which the present invention can be applied are not limited to this. For example, it may be applied to a vehicle that has only an engine as a drive source. Furthermore, the type of fuel for the engine is not limited to the above.

[0120] In the above embodiment, the case was described in which the injection timing of the injector 8 is set to a time retarded to the opening time IVO of the intake valve 13 when the engine water temperature is less than or equal to the first determination water temperature Tw1. However, this injection timing may be set to a time retarded to the closing time EVC of the exhaust valve 14 during the intake stroke, or to a time advanced to the opening time IVO of the intake valve 13. However, as described above, if the injection timing of the injector 8 is set to a time retarded to the opening time IVO of the intake valve 13, the evaporation of fuel can be effectively promoted by the action of intake airflow in the combustion chamber C.

[0121] In the above embodiment, we have described a case in which, when the engine water temperature is below the first determination water temperature Tw1 and the engine required torque is less than a predetermined determination torque, control is performed to increase the throttle opening while driving the motor 31 as a generator, or control is performed to increase the throttle opening while retarding the ignition timing. However, each of the above control methods may be performed regardless of the engine required torque. However, depending on the configuration of the throttle valve 18 and the device for changing the phase of the intake valve 13, if the engine required torque is high, the throttle opening required to achieve it may be close to the maximum opening, or the phase of the intake valve 13 required to achieve it may be close to the phase in which the amount of intake air introduced into the combustion chamber C is maximum, and the engine torque may not increase sufficiently even if the throttle opening is further increased. For this reason, in such cases, it is preferable to perform the above control method only when the engine required torque is relatively low, as described above.

[0122] Furthermore, the control described above, which increases the throttle opening while driving the motor 31 as a generator, may be omitted. For example, in vehicles that do not have a motor 31 driven by the engine 1 to generate electricity, this control may be omitted, and when the conditions are met that the engine water temperature is below the first determination water temperature Tw1 and the engine required torque is less than a predetermined determination torque, control may be implemented that retards the ignition timing while increasing the throttle opening, regardless of the battery SOC.

[0123] Furthermore, in the above embodiment, the case was described in which the motor 31 is driven as a generator only when the conditions are met that the engine water temperature is below the second determination water temperature Tw2, the engine water temperature is below the first determination water temperature Tw1, the engine required torque is less than the determination torque, and the battery SOC is less than the determination SOC. However, the motor 31 may be driven as a generator regardless of the engine water temperature, engine required torque, and battery SOC. However, when the motor 31 is driven as a generator regardless of the engine water temperature, etc., when the engine water temperature is below the second determination water temperature Tw2, it is preferable to make the amount of power generated when the above conditions are met (when the conditions are met that the engine water temperature is below the first determination water temperature Tw1, the engine required torque is less than the determination torque, and the battery SOC is less than the determination SOC) greater than when the conditions are not met. In this way, as described above, it is possible to improve exhaust performance while improving fuel efficiency when the above conditions are met. [Explanation of Symbols]

[0124] 1 Engine 8. Injector (fuel supply device) 9 Spark plugs 10 Engine body 13 Intake valve 14 Exhaust valve 20. Exhaust SVT (Variable Exhaust Phase Device) 21. Intake SVT (Intake Phase Variable Transmission) 31. Motor (Generator) 50 PCM (Control Device) C Combustion chamber

Claims

1. An engine control device comprising: an engine body having a combustion chamber formed therein; a fuel supply device that supplies fuel to the combustion chamber; an intake valve that opens and closes an intake port for introducing intake air into the combustion chamber; and an exhaust valve that opens and closes an exhaust port for releasing exhaust gas from the combustion chamber, An intake valve phase variable device capable of changing the phase of the intake valve, An exhaust valve phase variable device capable of changing the phase of the exhaust valve, The system comprises the fuel supply device, the intake valve phase variable device, and the exhaust valve phase variable device, The control device is When the first condition is met, that the engine temperature is below a predetermined first determination temperature, the exhaust valve phase variable device is controlled so that the closing timing of the exhaust valve is the same as or retarded to the exhaust top dead center, and the intake valve phase variable device is controlled so that the opening timing of the intake valve is retarded to the exhaust valve closing timing, and the fuel supply device is controlled so that fuel supply to the combustion chamber is started during the intake stroke retarded to the exhaust valve closing timing. An engine control device characterized by controlling the intake valve phase variable device and the exhaust valve phase variable device so that, when a second condition is met, the engine temperature is higher than the first determination temperature and below a predetermined second determination temperature, a positive overlap occurs in which the exhaust valve and the intake valve are both open for a predetermined period spanning the exhaust top dead center, and the closing timing of the exhaust valve is retarded compared to the closing timing of the exhaust valve when the first condition is met.

2. An engine control device comprising: an engine body having a combustion chamber formed therein; a fuel supply device for supplying fuel to the combustion chamber; an intake valve for opening and closing an intake port for introducing intake air into the combustion chamber; and an exhaust valve for opening and closing an exhaust port for discharging exhaust gas from the combustion chamber, An intake valve phase variable device capable of changing the phase of the intake valve, An exhaust valve phase variable device capable of changing the phase of the exhaust valve, The system comprises the fuel supply device, the intake valve phase variable device, and the exhaust valve phase variable device, The control device is When the first condition is met, that the engine temperature is below a predetermined first determination temperature, the exhaust valve phase variable device is controlled so that the closing timing of the exhaust valve is the same as or retarded to the exhaust top dead center, and the intake valve phase variable device is controlled so that the opening timing of the intake valve is retarded to the exhaust valve closing timing, and the fuel supply device is controlled so that fuel supply to the combustion chamber is started during the intake stroke retarded to the exhaust valve closing timing. When the second condition is met, which is that the engine temperature is higher than the first determination temperature and below a predetermined second determination temperature, the intake valve phase variable device and the exhaust valve phase variable device are controlled such that a negative overlap occurs in which the exhaust valve and the intake valve are closed for a predetermined period of time encompassing the exhaust top dead center, or a positive overlap occurs in which the exhaust valve and the intake valve are open for a predetermined period of time encompassing the exhaust top dead center. An engine control device characterized by controlling the fuel supply device so that, when the first condition is met, fuel supply to the combustion chamber is started at a timing retarded to the opening timing of the intake valve.

3. An engine control device comprising: an engine body having a combustion chamber formed therein; a fuel supply device for supplying fuel to the combustion chamber; an intake valve for opening and closing an intake port for introducing intake air into the combustion chamber; and an exhaust valve for opening and closing an exhaust port for discharging exhaust gas from the combustion chamber, An intake valve phase variable device capable of changing the phase of the intake valve, An exhaust valve phase variable device capable of changing the phase of the exhaust valve, The system comprises the fuel supply device, the intake valve phase variable device, and the exhaust valve phase variable device, The engine is equipped with a spark plug that ignites the fuel-air mixture supplied to the combustion chamber. The control device is When the first condition is met, that the engine temperature is below a predetermined first determination temperature, the exhaust valve phase variable device is controlled so that the closing timing of the exhaust valve is the same as or retarded to the exhaust top dead center, and the intake valve phase variable device is controlled so that the opening timing of the intake valve is retarded to the exhaust valve closing timing, and the fuel supply device is controlled so that fuel supply to the combustion chamber is started during the intake stroke retarded to the exhaust valve closing timing. When the second condition is met, which is that the engine temperature is higher than the first determination temperature and below a predetermined second determination temperature, the intake valve phase variable device and the exhaust valve phase variable device are controlled such that a negative overlap occurs in which the exhaust valve and the intake valve are closed for a predetermined period of time encompassing the exhaust top dead center, or a positive overlap occurs in which the exhaust valve and the intake valve are open for a predetermined period of time encompassing the exhaust top dead center. An engine control device characterized by controlling the spark plug such that the ignition timing of the spark plug is delayed when the first condition is met compared to when the second condition is met.

4. An engine control device comprising: an engine body having a combustion chamber formed therein; a fuel supply device for supplying fuel to the combustion chamber; an intake valve for opening and closing an intake port for introducing intake air into the combustion chamber; and an exhaust valve for opening and closing an exhaust port for discharging exhaust gas from the combustion chamber, An intake valve phase variable device capable of changing the phase of the intake valve, An exhaust valve phase variable device capable of changing the phase of the exhaust valve, The system comprises the fuel supply device, the intake valve phase variable device, and the exhaust valve phase variable device, The aforementioned engine is connected to a generator that is driven by the engine to produce electricity. The control device is When the first condition is met, that the engine temperature is below a predetermined first determination temperature, the exhaust valve phase variable device is controlled so that the closing timing of the exhaust valve is the same as or retarded to the exhaust top dead center, and the intake valve phase variable device is controlled so that the opening timing of the intake valve is retarded to the exhaust valve closing timing, and the fuel supply device is controlled so that fuel supply to the combustion chamber is started during the intake stroke retarded to the exhaust valve closing timing. When the second condition is met, which is that the engine temperature is higher than the first determination temperature and below a predetermined second determination temperature, the intake valve phase variable device and the exhaust valve phase variable device are controlled such that a negative overlap occurs in which the exhaust valve and the intake valve are closed for a predetermined period of time encompassing the exhaust top dead center, or a positive overlap occurs in which the exhaust valve and the intake valve are open for a predetermined period of time encompassing the exhaust top dead center. An engine control device characterized by controlling the generator such that the amount of power generated by the generator is greater when the first condition is met than when the second condition is met.

5. A control device for an engine comprising: an engine body having a combustion chamber formed therein; a fuel supply device for supplying fuel to the combustion chamber; an intake valve for opening and closing an intake port for introducing intake air into the combustion chamber; and an exhaust valve for opening and closing an exhaust port for discharging exhaust gas from the combustion chamber, An intake valve phase variable device capable of changing the phase of the intake valve, An exhaust valve phase variable device capable of changing the phase of the exhaust valve, The system comprises the fuel supply device, the intake valve phase variable device, and the exhaust valve phase variable device, The control device is When the first condition is met, that the engine temperature is below a predetermined first determination temperature, the exhaust valve phase variable device is controlled so that the closing timing of the exhaust valve is the same as or retarded to the exhaust top dead center, and the intake valve phase variable device is controlled so that the opening timing of the intake valve is retarded to the exhaust valve closing timing, and the fuel supply device is controlled so that fuel supply to the combustion chamber is started during the intake stroke retarded to the exhaust valve closing timing. An engine control device characterized by controlling the intake valve phase variable device and the exhaust valve phase variable device so that, when a second condition is met, the engine temperature is higher than the first determination temperature and below a predetermined second determination temperature, a negative overlap occurs in which the exhaust valve and the intake valve are closed during a predetermined period spanning the exhaust top dead center.

6. In the engine control device according to claim 5, An engine control device characterized in that, when the second condition is met and the engine temperature is higher than the first determination temperature (a third determination temperature or higher), the control device controls the exhaust valve phase variable device such that the closing timing of the exhaust valve is retarded when the engine temperature is high compared to when it is low.

7. In the engine control device according to claim 5, The control device for an engine is characterized in that the control device controls the intake valve phase variable device so that the opening timing of the intake valve when the first condition is met is at a later timing than the opening timing of the intake valve when the second condition is met.

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