JP2017002725A - Control device of internal combustion engine and control method of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine which does not freeze a water droplet between a valve and a valve seat even if it is difficult to completely abolish a valve which is in a minutely-opened state, and a control method of the internal combustion engine.SOLUTION: A control device includes: ice freeze occurrence condition establishment determination means which determines whether or not there arises a condition that ice is generated between valves of a plurality of cylinders and valve seats which are arranged in response to the valves at a stop of an internal combustion engine; minute-open valve estimation means which estimates a valve whose valve opening is not larger than a prescribed opening out of the valves of a plurality of the cylinders; and valve timing control means which controls an electric variable valve timing mechanism so that the valve whose opening is estimated to be not larger than the prescribed opening by the minute-open valve estimation means reaches the prescribed opening or larger when it is determined that there arises the condition that the ice is generated by the ice freeze occurrence condition establishment determination means.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a control device and a control method for an internal combustion engine, and more particularly to a control device and a control method for an internal combustion engine including an electric variable valve timing mechanism.

  Patent document 1 discloses a hybrid vehicle. In this hybrid vehicle, the stop angle position of the crankshaft when the engine is stopped is adjusted by the motor generator. When stopping the engine, the motor generator adjusts the stop angle position of the crankshaft so that the valve opening degrees of the intake valve and the exhaust valve are larger than predetermined opening degrees.

  As a result, in this hybrid vehicle, water droplets do not enter and stay in the gap between the valve and the valve seat while the engine is stopped. Therefore, even if the outside air temperature becomes below freezing point, there will be a situation in which the valve cannot be fully closed at the next engine start without ice interposing between the valve and the valve seat. Absent. As a result, according to this hybrid vehicle, it is possible to prevent the compression failure of the air-fuel mixture in the compression process of the engine.

JP 2014-58217 A

  In an engine having multiple cylinders, in general, the phase in which the valves of some cylinders are opened differs from the phase in which the valves of other cylinders are opened. Therefore, it may be difficult to completely eliminate a valve having a valve opening equal to or less than a predetermined opening (a valve in a slightly opened state). In such a case, the stop angle position of the crankshaft cannot be adjusted so that the valve openings of all the valves are larger than the predetermined opening at a specific time. Therefore, it is difficult to avoid freezing of water droplets generated between the valve and the valve seat while the engine is stopped by the means disclosed in Patent Document 1.

  The present invention has been made to solve such a problem, and its purpose is to prevent water droplets between the valve and the valve seat even when it is difficult to completely eliminate the slightly opened valve. It is an object to provide a control device for an internal combustion engine and a control method for the internal combustion engine that are not frozen.

  In the control apparatus for an internal combustion engine according to an aspect of the present invention, the internal combustion engine includes a plurality of cylinders, an intake valve and an exhaust valve provided in each of the plurality of cylinders, and an electric variable valve timing mechanism. The electric variable valve timing mechanism changes the valve timing of at least one of the intake valve and the exhaust valve by changing the rotational phase of the camshaft with respect to the crankshaft. The control device includes icing occurrence condition establishment determination means, slightly opened valve estimation means, and valve timing control means. The icing generation condition establishment means determines whether or not the condition is that ice is generated between the valves of the plurality of cylinders and the valve seats provided corresponding to the valves when the internal combustion engine is stopped. The slight opening valve estimation means estimates a valve whose valve opening is equal to or less than a predetermined opening among the valves of the plurality of cylinders. When it is determined by the icing occurrence condition establishment determining means that the ice is generated, the valve timing control means causes the valve that is estimated to be less than or equal to the predetermined opening by the slightly opened valve estimation means to be greater than or equal to the predetermined opening. The electric variable valve timing mechanism is controlled.

  As a result, even when the internal combustion engine is stopped, the valve in the slightly open state is opened when the predetermined condition for determining whether or not ice is generated between the valve and the valve seat is satisfied. It is driven by the electric variable valve timing mechanism so that the degree is larger than a predetermined opening degree. If the valve opening of each valve is fixed while the internal combustion engine is stopped, there is a high possibility that ice will be generated between the valve in the slightly open state and the valve seat. Therefore, such a situation can be avoided by increasing the valve opening of the slightly opened valve while the internal combustion engine is stopped.

  Preferably, the control device for the internal combustion engine measures a stop time that is a time during which the stop state of the internal combustion engine continues after the drive of the internal combustion engine is finished, and a drive time that is a time from the start of the drive of the internal combustion engine to the end of the drive. A timer is provided. The internal combustion engine further includes a temperature sensor that detects the temperature of cooling water for cooling the internal combustion engine. The condition for generating ice is that the temperature of the cooling water detected by the temperature sensor is 0 ° C. or lower, and the stop time measured by the timer is shorter than the first predetermined time, and is measured by the timer. Including that the driving time is shorter than the second predetermined time. Here, the first predetermined time is, for example, the time required for water droplets generated between the phase variable valve and the valve seat to freeze. The second predetermined time is a time required for the temperature of the phase variable valve to rise to a predetermined temperature, for example, by driving the internal combustion engine.

  Since the predetermined condition that the temperature of the cooling water is 0 ° C. or less is included, the valve opening degree is adjusted when there is a high possibility that water droplets generated around the slightly opened valve are frozen. . As a result, the finely opened valve is not driven until water droplets generated around the finely opened valve cannot freeze, and deterioration of fuel consumption can be suppressed. In addition, since the predetermined condition includes that the stop time of the internal combustion engine is shorter than the first predetermined time, the valve opening degree is maintained for a long time even after water droplets generated around the slightly opened valve are frozen. No adjustment is made. As a result, deterioration of fuel consumption can be suppressed. Further, since the predetermined condition includes that the driving time of the internal combustion engine is shorter than the second predetermined time, the temperature around the slightly opened valve becomes higher than the predetermined temperature, The valve opening is not adjusted until there is a high possibility that water droplets will not be generated. As a result, deterioration of fuel consumption can be suppressed.

  More preferably, the first predetermined time is a time required until ice is generated between each valve of the plurality of cylinders and each valve seat provided corresponding to each valve. The second predetermined time is a time required for the temperature of each valve of the plurality of cylinders to rise to a predetermined temperature by driving the internal combustion engine.

  Thus, the valve opening is adjusted before water droplets generated around the slightly opened valve are frozen. As a result, the valve opening is not adjusted after water droplets generated around the slightly opened valve are frozen, and deterioration of fuel consumption can be suppressed. Further, when water droplets are generated around the slightly opened valve, the valve opening degree is adjusted. As a result, the valve opening is not adjusted when water droplets are not generated around the slightly opened valve, and deterioration of fuel consumption can be suppressed.

  Preferably, the condition for generating ice is considered to be satisfied by satisfying the condition continuously for a certain period of time.

  Thereby, adjustment of the valve opening is not always started when a predetermined condition is satisfied. As a result, the valve opening is not adjusted more frequently than necessary, and the deterioration of fuel consumption can be reduced.

  In the method for controlling an internal combustion engine according to another aspect of the present invention, the internal combustion engine includes a plurality of cylinders, an intake valve and an exhaust valve provided in each of the plurality of cylinders, and an electric variable valve timing mechanism. The electric valve timing mechanism changes the valve timing of at least one of the intake valve and the exhaust valve by changing the rotational phase of the camshaft with respect to the crankshaft. The control method includes a step of determining whether or not ice is generated between the valves of the plurality of cylinders and the valve seats when the internal combustion engine is stopped, and among the valves of the plurality of cylinders. The step of estimating a valve whose valve opening is less than or equal to a predetermined opening and the valve estimated to be less than or equal to the predetermined opening when determined to be a condition that causes ice And a step of controlling the electric variable valve timing mechanism.

  As a result, even when the internal combustion engine is stopped, the valve in the slightly open state is opened when the predetermined condition for determining whether or not ice is generated between the valve and the valve seat is satisfied. It is driven by the electric variable valve timing mechanism so that the degree is larger than a predetermined opening degree. If the valve opening of each valve is fixed while the internal combustion engine is stopped, there is a high possibility that ice will be generated between the valve in the slightly open state and the valve seat. Therefore, such a situation can be avoided by increasing the valve opening of the slightly opened valve while the internal combustion engine is stopped.

  According to the present invention, it is possible to provide a control device for an internal combustion engine and a control method for an internal combustion engine that does not cause water droplets to freeze between the valve and the valve seat even when it is difficult to completely eliminate the valve in the slightly open state. it can.

1 is an overall configuration diagram of a hybrid vehicle according to an embodiment. It is a figure which shows the structure of an engine and its peripheral device. It is a figure which shows the change of the relationship between the valve opening degree and crank angle which are implement | achieved by the electric VVT mechanism. It is a figure for demonstrating the case where a valve opening degree will be in a slightly open state. It is a flowchart which shows the process of the control apparatus in an engine stop. It is a figure for demonstrating the specific example which enlarges the valve opening degree of a slightly open cylinder with an electric VVT mechanism. It is a flowchart which shows the confirmation process of ice production | generation conditions.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

(Embodiment 1)
<1. Configuration of hybrid vehicle>
FIG. 1 is an overall configuration diagram of a hybrid vehicle 1 shown as an example of a vehicle equipped with a control device for an internal combustion engine according to this embodiment. Referring to FIG. 1, hybrid vehicle 1 includes an engine 100, motor generators MG1 and MG2, a power split device 4, a speed reducer 5, drive wheels 6, a power storage device 10, and a PCU (Power Control Unit). 20 and a control device 200.

  Hybrid vehicle 1 travels by the driving force output from at least one of engine 100 and motor generator MG2. The engine 100 is configured by an internal combustion engine such as a gasoline engine or a diesel engine, for example. Engine 100 supplies power to at least one of drive wheel 6 and motor generator MG1 that can operate as a generator via power split device 4.

  The engine 100 is a multi-cylinder engine. As an example, engine 100 includes four cylinders 106 therein. Engine 100 is cranked and started by motor generator MG1. The engine 100 includes an electric variable valve timing mechanism (hereinafter referred to as an electric VVT (Variable Valve Timing) mechanism) 400 that uses the electric actuators 402 and 403 to change the operation characteristics of the intake valve and the exhaust valve, respectively. Specifically, electric VVT mechanism 400 changes the opening / closing timing of the intake valve and the exhaust valve with respect to the rotational position (crank angle) of crankshaft 116. Electric VVT mechanism 400 is controlled by control device 200 in accordance with the traveling state of hybrid vehicle 1 and the startability of engine 100. The engine 100 and the electric VVT mechanism 400 will be described in detail later.

  Power split device 4 splits the driving force generated by engine 100 into power for driving motor generator MG1 and power for driving drive wheels 6 via reduction gear 5. The power split device 4 is constituted by, for example, a planetary gear mechanism.

  Motor generators MG1 and MG2 are AC rotating electric machines, and are constituted by, for example, three-phase AC synchronous motor generators. Motor generator MG <b> 1 generates power using the power of engine 100 received via power split device 4. The electric power generated by motor generator MG1 is voltage-converted by PCU 20, and is temporarily stored in power storage device 10, or directly supplied to motor generator MG2.

  Motor generator MG2 generates a driving force using at least one of the electric power stored in power storage device 10 and the electric power generated by motor generator MG1. The driving force of motor generator MG2 is transmitted to driving wheels 6 via reduction gear 5.

  PCU 20 is a drive device for driving motor generators MG1 and MG2. PCU 20 includes an inverter for driving motor generators MG <b> 1 and MG <b> 2, and may further include a converter for voltage conversion between the inverter and power storage device 10.

  The power storage device 10 is a rechargeable DC power source, and includes, for example, a secondary battery such as a nickel metal hydride battery or a lithium ion battery. Power storage device 10 stores electric power generated by motor generators MG1 and MG2.

  The control device 200 is configured to include an ECU (Electronic Control Unit) including a CPU (Central Processing Unit), a storage device, an input / output buffer, and the like (all not shown). The control device 200 inputs signals from various sensors (accelerator opening ACC, vehicle speed VSS, etc.) and outputs control signals to each device, and controls each device in the hybrid vehicle 1. Mainly, the control device 200 executes the travel control of the hybrid vehicle 1 and the control of the engine 100 according to the travel control (for example, control of the electric VVT mechanism 400 and the like).

<2. Engine configuration>
FIG. 2 is a diagram showing the configuration of the engine 100 and its peripheral devices. Referring to FIG. 2, the intake air amount to engine 100 is adjusted by throttle valve 104 driven by throttle motor 312. The injector 108 injects fuel into the intake port. Fuel and air are mixed in the intake port. The air-fuel mixture is introduced into the cylinder 106 by opening the intake valve 118.

  The air-fuel mixture in the cylinder 106 is ignited by the spark plug 110 and burns. The piston 114 is pushed down by the combustion of the air-fuel mixture, and the crankshaft 116 rotates. The air-fuel mixture after combustion, that is, exhaust gas, is discharged to the exhaust passage. The exhaust passage is provided with an exhaust purification device that purifies exhaust gas using a catalyst. The exhaust emission control device includes a catalyst 112S and a catalyst 112U disposed on the downstream side of the catalyst 112S. The exhaust gas is purified by the catalyst 112S and the catalyst 112U, and then discharged outside the vehicle.

  An intake valve 118 and an exhaust valve 120 are provided at the top of the cylinder 106. The amount and timing of air introduced into the cylinder 106 are controlled by the intake valve 118. The amount and timing of exhaust gas discharged from the cylinder 106 are controlled by the exhaust valve 120. The intake valve 118 is driven by a cam 122, and the exhaust valve 120 is driven by a cam 124.

  Valve seats are disposed at the intake and exhaust ports of the cylinder 106. In a state where the intake valve 118 and the exhaust valve 120 are closed, the intake valve 118 and the exhaust valve 120 come into contact with the valve seat. The valve seat is a valve seat of the intake valve 118 and the exhaust valve 120. By arranging the valve seats at the intake port and the exhaust port of the cylinder 106, the airtightness in the cylinder 106 is maintained when each valve is fully closed.

  The opening / closing timing of intake valve 118 and exhaust valve 120 is changed by electric VVT mechanism 400. Electric VVT mechanism 400 includes a camshaft, a cam sprocket (none of which are shown), and electric actuators 402 and 403 (FIG. 1). The camshaft is rotatably provided on a cylinder head (not shown) of engine 100 such that the direction of the rotation axis is parallel to the rotation axis of the crankshaft. The camshaft includes an exhaust side camshaft that opens and closes an exhaust valve provided in each cylinder by a cam, and an intake side camshaft that opens and closes an intake valve provided in each cylinder by a cam. A plurality of cams 124 are fixed to the exhaust side camshaft at a predetermined interval. A plurality of cams 122 are fixed to the intake side camshaft at a predetermined interval.

  A cam sprocket is provided at one end of each of the intake and exhaust camshafts. The same timing chain is wound around both cam sprockets. The timing chain is also wound around a timing rotor (not shown) provided on the crankshaft 116. Therefore, the crankshaft and the camshaft rotate in synchronization with the timing chain.

  An electric actuator 402 is provided between the intake camshaft and the cam sprocket. The electric actuator 402 changes the rotational phase between the intake side camshaft and the cam sprocket. An electric actuator 403 is provided between the exhaust camshaft and the cam sprocket. The electric actuator 403 changes the rotational phase between the camshaft on the exhaust side and the cam sprocket. Electric actuators 402 and 403 are controlled based on control signal VVT transmitted from control device 200. When the electric actuator 402 changes the rotational phase of the intake-side camshaft and cam sprocket, the intake valve 118 maintains the valve opening period and changes the valve opening timing and the valve closing timing. That is, the valve position of the intake valve 118 with respect to the rotational position of the crankshaft 116 changes. Similarly, in the exhaust valve 120, when the rotational phase of the exhaust camshaft and the cam sprocket is changed by the electric actuator 403, the valve opening period is maintained and the valve opening timing and the valve closing timing are changed. To do. Electric VVT mechanism 400 can change the opening timing and closing timing of intake valve 118 and exhaust valve 120 even when engine 100 is stopped. The manner in which the opening timing and closing timing of the intake valve 118 and the exhaust valve 120 by the electric VVT mechanism 400 are changed will be described later.

  In addition to signals indicating the accelerator opening ACC and the vehicle speed VSS, the control device 200 receives signals from the cam angle sensor 300, the crank angle sensor 302, the throttle opening sensor 306, and the temperature sensor 130. The cam angle sensor 300 outputs a signal indicating the cam position CMA. The crank angle sensor 302 outputs signals representing the rotational speed (hereinafter also referred to as engine rotational speed) NE of the crankshaft 116 and the rotational angle CRA of the crankshaft 116. The throttle opening sensor 306 outputs a signal representing the throttle opening θth. Temperature sensor 130 outputs a signal indicating the temperature of cooling water of engine 100.

  Control device 200 controls engine 100 based on signals from these sensors. Specifically, the control device 200 controls the throttle opening θth, the ignition timing, and the fuel injection timing so that the engine 100 is operated at a desired operating point in accordance with the vehicle traveling state and the exhaust purification device warm-up state. The fuel injection amount and the operating state (opening / closing timing) of the intake valve 118 and the exhaust valve 120 are controlled. The operating point is an operating point of engine 100 at which the output, torque, and rotation speed of engine 100 are determined.

  In addition, the control device 200 includes a timer 202 inside. Timer 202 measures a drive time that is a time from the start of driving of engine 100 to the end of driving. Timer 202 measures a stop time that is a time during which the stop state continues after driving of engine 100 ends. Based on the measurement result of timer 202 and the output of temperature sensor 130, control device 200 controls electric VVT mechanism 400 so as not to cause icing of water droplets between intake valve 118 and exhaust valve 120 of engine 100 and the valve seat. Control. This control is executed while the engine 100 is stopped. Details will be described later.

  FIG. 3 is a diagram showing a change in the relationship between the valve opening degree and the crank angle realized by the electric VVT mechanism 400. The vertical axis in FIG. 3 indicates the valve opening, and the horizontal axis indicates the crank angle. In FIG. 3, transitions of the valve opening degrees of the intake valve 118 and the exhaust valve 120 in one cylinder among a plurality (four) of cylinders of the engine 100 are shown.

  Referring to FIG. 3, the valve openings of the exhaust valves are shown in waveforms EX1 and EX2, and the valve openings of the intake valves are shown in waveforms IN1 and IN2. In the exhaust stroke, the exhaust valve 120 is first opened, and the exhaust valve 120 is closed after the valve opening reaches its peak. Thereafter, the intake valve 118 is opened in the intake stroke, and the intake valve 118 is closed after the valve opening reaches its peak.

  The valve opening refers to the interval between the intake valve 118 or the exhaust valve 120 and the valve seat. Further, the valve opening when the valve opening of the intake valve 118 and the exhaust valve 120 reaches the peak is called a lift amount, and the crank angle range from when the intake valve 118 and the exhaust valve 120 are opened to when it closes is the working angle. That's it.

  The electric VVT mechanism 400 changes the cam angle of the camshaft and rotates the cams 122 and 124 so that the opening timing and closing timing of the intake valve 118 and the exhaust valve 120 are maintained while maintaining the lift amount and the operating angle. change. For example, regarding the exhaust valve 120, the electric VVT mechanism 400 can change the position of the waveform between the waveform EX1 (solid line) and the waveform EX2 (broken line) while maintaining the waveform shape. Similarly, the electric VVT mechanism 400 can change the position of the waveform between the waveform IN1 (solid line) and the waveform IN2 (broken line) while maintaining the waveform shape with respect to the intake valve 118 as well.

  FIG. 3 shows the transition of the valve opening degree of each valve in one of the plurality of cylinders of engine 100, but in actuality, in each cylinder, intake valve 118 and exhaust valve 120 are shown. Is opening and closing. In addition, the phase of the opening / closing operation of some cylinders is shifted from the phase of the opening / closing operations of other cylinders. Note that a configuration in which the phases of the opening / closing operations of the cylinders are all shifted from each other may be employed. Further, control device 200 stores valve opening information, which is a relationship between the crank angle, the cam angle, and the valve opening, for each valve in each cylinder of engine 100 in an internal memory (not shown). Therefore, the control device 200 can calculate the valve opening of each valve by obtaining information on the crank angle and the cam angle from the crank angle sensor 302 and the cam angle sensor 300 and referring to the valve opening information.

  In the following description, changing the valve opening timing from the crank angle CA (0) to the crank angle CA (1) and from the crank angle CA (2) to the crank angle CA (3) It is said to be retarded. Further, the valve opening timing is advanced by changing the valve opening timing from the crank angle CA (1) to the crank angle CA (0) and from the crank angle CA (3) to the crank angle CA (2). That's it. In this embodiment, in the exhaust valve 120, the crank angle CA (0) is the most advanced valve opening timing, and the crank angle CA (1) is the most retarded valve opening timing. . In the intake valve 118, the crank angle CA (2) is the most advanced valve opening timing, and the crank angle CA (3) is the most retarded valve opening timing.

  Generally, when the engine is stopped with the distance between each valve and the valve seat being about 1 mm, water droplets that have entered between each valve and the valve seat move along the outer edge of each valve due to the surface tension. Will spread in the circumferential direction. When the water droplets freeze, the valve cannot be fully closed due to the presence of ice between the valve and the valve seed at the initial start of the next engine. As a result, there is a possibility that the operation of the engine may be adversely affected at the initial stage of engine startup, for example, because the valve is not fully closed in the compression process of the engine, leading to poor compression of the air-fuel mixture. Control device 200 according to the present embodiment aims to eliminate such disadvantages. Therefore, the control device 200 detects whether or not there is a valve whose valve opening is in a minute state (slightly open state).

  FIG. 4 is a diagram for explaining a case where the valve opening of intake valve 118 is slightly opened. The vertical axis in FIG. 4 indicates the valve opening, and the horizontal axis indicates the crank angle. In FIG. 4, only a change in the valve opening of the intake valve 118 is shown for simplicity of explanation, and the exhaust valve 120 is omitted.

  Referring to FIG. 4, intake valve 118 starts to open when crank angle becomes crank angle CA (4), and when the crank angle becomes crank angle CA (5), the valve opening becomes the opening degree V1. Become. Thereafter, the valve opening reaches a peak, and when the crank angle reaches the crank angle CA (6), the valve opening again becomes the opening V1. Thereafter, the valve opening is further reduced, and the intake valve 118 is fully closed when the crank angle becomes the crank angle CA (7). Here, a state in which the valve opening is greater than 0 (zero) and less than or equal to the opening V1 is assumed to be a slightly opened state. Here, the opening degree V <b> 1 is determined in advance through an experiment as an interval at which water droplets entering between the intake valve 118 and the valve seat do not spread in the circumferential direction along the outer edge of the intake valve 118.

  That is, in the example of the intake valve 118 shown in FIG. 4, when the crank angle is between the crank angle CA (4) and the crank angle CA (5), or the crank angle is the crank angle CA (6). It can be said that the intake valve 118 is in a slightly opened state when it is between the crank angle CA (7).

  Here, in order to prevent ice from being generated between the intake valve 118 and the valve seat, the stop angle of the crankshaft when the engine is stopped so that the distance between the intake valve 118 and the valve seat becomes equal to or larger than a certain value. A method of adjusting the position is conceivable. However, in this engine 100 having multiple cylinders, the phase in which the valves of some cylinders are opened differs from the phase in which the valves of other cylinders are open, and the valve in the slightly open state cannot be completely eliminated.

  Therefore, control device 200 according to the present embodiment is configured to control electric VVT mechanism 400 while engine 100 is stopped. Then, the control device 200 takes the intake valve 118 when a predetermined condition for determining whether ice is generated between the intake valve 118 or the exhaust valve 120 and the valve seat is satisfied while the engine 100 is stopped. Alternatively, when the valve opening degree of the exhaust valve 120 is equal to or less than the predetermined opening degree V1, the electric VVT mechanism 400 is controlled so that the valve opening degree of the intake valve 118 or the exhaust valve 120 is larger than the predetermined opening degree V1.

  Thus, even when the engine 100 is stopped, when the predetermined condition for determining whether ice is generated between the intake valve 118 or the exhaust valve 120 and the valve seat is satisfied, the slightly opened state The valve is driven by the electric variable VVT mechanism 400 so that the valve opening is larger than a predetermined opening. If the valve opening degree of each valve is fixed while the engine 100 is stopped, there is a high possibility that ice will be generated between the slightly opened valve and the valve seat. Therefore, such a situation can be avoided by making the valve opening of the slightly opened valve larger than the predetermined opening while the engine 100 is stopped. Next, a specific operation while the engine 100 is stopped will be described.

<3. Processing of control device while engine is stopped>
FIG. 5 is a flowchart showing processing of the control device 200 while the engine 100 is stopped. Referring to FIG. 5, control device 200 determines whether stop of engine 100 is continued (step S100). If it is determined that engine 100 is not stopped (NO in step S100), control device 200 proceeds to the process in step S200. On the other hand, when engine 100 is determined to be stopped (YES in step S100), control device 200 executes a process for confirming ice generation conditions (predetermined conditions) (step S110). The ice generation condition is a condition that if this condition is satisfied, there is a high possibility that water droplets generated between the intake valve 118 or the exhaust valve 120 and the valve seat are frozen. The confirmation process of the ice generation conditions will be described in detail later.

  When the ice generation condition confirmation process is executed, the control device 200 determines whether or not the ice generation condition is satisfied (step S120). If it is determined that the ice generation condition is not satisfied (NO in step S120), control device 200 proceeds to the process in step S200. On the other hand, when it is determined that the ice generation condition is satisfied (YES in step S120), control device 200 adds an ice generation counter (step S130). The ice generation counter is a counter that is added when an ice generation condition is satisfied. When the ice generation counter is added, the control device 200 determines whether or not the value of the ice generation counter is greater than a predetermined value (step S140). That is, in steps S130 and S140, it can be said that it is determined whether or not the ice generation condition is satisfied for a predetermined time. By performing these processes, the control of the electric VVT mechanism 400 is not immediately started when the ice generation condition is satisfied.

  If it is determined that the value of the ice generation counter is equal to or smaller than the predetermined value (NO in step S140), control device 200 proceeds to the process in step S200. On the other hand, when it is determined that the value of the ice generation counter is larger than the predetermined value (YES in step S140), control device 200 determines that the ice generation condition is satisfied, and intake valve 118 and exhaust in each cylinder of engine 100 are determined. The phase information of the valve 120 is acquired (step S150). Specifically, for each cylinder, control device 200 obtains crank angle information from crank angle sensor 302 and obtains cam angle information from cam angle sensor 300. When the phase information is acquired, the control device 200 determines each of the cylinders based on the valve opening information, the acquired crank angle information, and the acquired cam angle information stored in an internal memory (not shown). The valve opening of the valve is calculated (step S160).

  When the valve opening of each valve of each cylinder is calculated, control device 200 specifies a valve whose valve opening is equal to or less than opening V1 (step S170). When a valve whose valve opening is equal to or smaller than the opening V1 is identified, the control device 200 calculates a phase change amount of the camshaft such that the valve opening of the identified valve is larger than the opening V1 (step). S180). Specifically, the control device 200 calculates the minimum phase change amount in order to make the valve opening degree of the specified valve larger than the opening degree V1. The minimum phase change amount is the minimum rotation amount of the camshaft for increasing the valve opening degree of the specified valve to the opening degree V1, and the control device 200 stores it in an internal memory (not shown). The minimum phase change amount can be calculated based on the valve opening information, the crank angle information, and the cam angle information. When the phase change amount of the camshaft is calculated, the control device 200 controls the electric VVT mechanism 400 (electric actuator 402 or 403) so as to cause the calculated phase change, and the valve opening degree is less than the opening degree V1. A certain valve is operated (step S190).

  FIG. 6 is a diagram for explaining a specific example in which the valve opening degree of the intake valve 118 is increased by the electric VVT mechanism 400 in the example in which the intake valve 118 is slightly opened. The vertical axis in FIG. 6 indicates the valve opening, and the horizontal axis indicates the crank angle. The solid line shows the relationship between the crank angle and the valve opening of the intake valve 118 in the state of the cam angle before the electric VVT mechanism 400 is driven. On the other hand, the broken line indicates the relationship between the crank angle and the valve opening of the intake valve 118 in the cam angle state after the electric VVT mechanism 400 is driven.

  It is assumed that the crank angle is the crank angle CA (8) in the cam angle state before the electric VVT mechanism 400 is driven. In this case, the valve opening degree of the intake valve 118 is not more than the opening degree V1. Therefore, control device 200 controls electric VVT mechanism 400 so that the valve opening degree of the intake valve is larger than opening degree V1. Specifically, control device 200 controls electric VVT mechanism 400 so as to advance the valve timing of intake valve 118. Then, the waveform indicating the valve opening degree of the intake valve 118 moves from the solid line waveform to the broken line waveform, and the valve opening degree of the intake valve 118 becomes larger than the opening degree V1.

  Thus, control device 200 of engine 100 according to this embodiment is configured to control electric VVT mechanism 400 while engine 100 is stopped. When the predetermined condition (ice generation condition) for determining whether or not ice is generated between intake valve 118 or exhaust valve 120 and valve seat is satisfied while control apparatus 200 is stopped, control device 200 In addition, when the valve opening of the intake valve 118 or the exhaust valve 120 is equal to or less than the predetermined opening V1, the electric VVT mechanism is set so that the valve opening of the intake valve 118 or the exhaust valve 120 is larger than the predetermined opening V1. 400 is controlled.

  Thus, even when the engine 100 is stopped, when the predetermined condition for determining whether ice is generated between the intake valve 118 or the exhaust valve 120 and the valve seat is satisfied, the slightly opened state The valve is driven by the electric variable VVT mechanism 400 so that the valve opening is larger than a predetermined opening. If the valve opening degree of each valve is fixed while the engine 100 is stopped, there is a high possibility that ice will be generated between the slightly opened valve and the valve seat. Therefore, such a situation can be avoided by making the valve opening of the slightly opened valve larger than the predetermined opening while the engine 100 is stopped.

<4. Confirmation process of ice generation conditions>
FIG. 7 is a flowchart showing the ice generation condition confirmation process executed in step S110 of FIG. Referring to FIG. 7, control device 200 determines whether or not the stop time from the end of driving of engine 100 is shorter than the first predetermined time (step S111). Here, the first predetermined time is set to a time (for example, 30 minutes) required for water droplets generated between the intake valve 118 and the exhaust valve 120 and the valve seat to freeze. When it is determined that engine 100 is stopped for a first predetermined time or longer (NO in step S111), the processing shown in FIGS. 5 and 7 ends. That is, the processing shown in FIGS. 5 and 7 is performed at a stage before water droplets generated between the valves and the valve seat are frozen.

  On the other hand, when it is determined that the stop time of engine 100 is shorter than the first predetermined time (YES in step S111), control device 200 determines that the coolant temperature of engine 100 is 0 based on the output of temperature sensor 130. It is determined whether the temperature is equal to or lower than ° C. (step S112). If the temperature of the cooling water is 0 ° C. or lower, it is considered that there is a high possibility that the water droplets will freeze when water droplets are generated between each valve and the valve seat. Step S112 to perform is provided.

  When it is determined that the temperature of the cooling water is 0 ° C. or less (YES in step S112), control device 200 causes the time when engine 100 was previously driven to be longer than the second predetermined time. It is determined whether or not it is short (step S113). Here, as the second predetermined time, a time (for example, 5 minutes) required for sufficiently warming up the vicinity of the intake valve 118 and the exhaust valve 120 is set. Here, being sufficiently warmed up means that the valve is warmed up so that no condensation occurs between each valve and the valve seat. If the surroundings of each valve are not sufficiently warmed up, water vapor contained in the mixture or exhaust gas will condense between each valve and the valve seat as condensed water, and the water droplets will freeze. There is a risk that. Therefore, step S113 for making such a determination is provided.

  If it is determined that the time during which engine 100 was driven last time is shorter than the second predetermined time (YES in step S113), control device 200 satisfies the condition for generating ice. (Step S114). If the ice generation condition is satisfied, the process of step S120 of FIG. 5 is executed (step S115).

  On the other hand, if it is determined in step S112 that the temperature of the cooling water is higher than 0 ° C., or if it is determined in step S113 that the time that the engine 100 was last driven is equal to or longer than the second predetermined time, The control device 200 resets the ice generation counter (step S116). In such a case, there is a low possibility that ice is generated between each valve and the valve seat. Then, control device 200 determines that the ice generation condition is not satisfied (step S117), and the process of step S120 in FIG. 5 is executed (step S115).

  As described above, control device 200 of engine 100 according to the present embodiment is a stop time that is a time during which engine 100 is stopped after the end of driving of engine 100 and a time from the start of driving of engine 100 to the end of driving. A timer 202 for measuring a certain driving time is provided. Engine 100 further includes a temperature sensor 130 that detects the temperature of cooling water for cooling engine 100. The predetermined condition is that the temperature of the cooling water detected by the temperature sensor 130 is 0 ° C. or less, the stop time measured by the timer 202 is shorter than the first predetermined time, and the driving measured by the timer 202 is performed. It includes that the time is shorter than the second predetermined time. Here, the first predetermined time is, for example, the time required for water droplets generated between the intake valve 118 or the exhaust valve 120 and the valve seat to freeze. Further, the second predetermined time is a time required for the temperature of the intake valve 118 or the exhaust valve 120 to rise to a predetermined temperature by driving the engine 100, for example.

  Since the predetermined condition that the temperature of the cooling water is 0 ° C. or less is included, the valve opening degree is adjusted when there is a high possibility that water droplets generated around the slightly opened valve are frozen. . As a result, the finely opened valve is not driven until water droplets generated around the finely opened valve do not become ice, and deterioration of fuel consumption can be suppressed. In addition, since the predetermined condition includes that the stop time of the engine 100 is shorter than the first predetermined time, the valve opening degree is maintained for a long time even after water droplets generated around the slightly opened valve are frozen. No adjustment is made. As a result, deterioration of fuel consumption can be suppressed. In addition, since the predetermined condition that the driving time of engine 100 is shorter than the second predetermined time is included in the predetermined condition, the temperature around the slightly opened valve becomes higher than the predetermined temperature. The valve opening is not adjusted until there is a high possibility that water droplets will not be generated. As a result, deterioration of fuel consumption can be suppressed.

  In this embodiment, the predetermined condition (ice generation condition) is considered to be satisfied by satisfying the predetermined condition continuously.

  Thereby, adjustment of the valve opening is not always started when a predetermined condition is satisfied. As a result, the valve opening is not adjusted more frequently than necessary, and the deterioration of fuel consumption can be reduced.

(Other embodiments)
The first embodiment has been described above as the embodiment of the present invention. However, the present invention can be applied to various other embodiments. Next, a part of various other embodiments will be described.

  In the first embodiment, both intake valve 118 and exhaust valve 120 are electrically driven by electric VVT mechanism 400. However, it is not necessarily limited to such a configuration. For example, only one of intake valve 118 and exhaust valve 120 may be driven by electric VVT mechanism 400. In this case, for example, when the engine 100 is stopped, the stop angle position of the crankshaft is set so that the valve opening degree of the valve that cannot be driven by the electric VVT mechanism 400 is larger than the predetermined opening degree V1. It is good also as a structure which determines. Thus, even when only one valve can be driven by the electric VVT mechanism 400, the valve opening of each valve can be kept larger than a predetermined opening.

  Further, in the first embodiment, the phase of the opening / closing operation of each valve is shifted between some cylinders 102 of engine 100 and other cylinders 102. However, it is not necessarily limited to such a configuration. For example, all of the plurality of cylinders may perform the opening / closing operation of each valve with the phases shifted from each other.

  In the first embodiment, the ice generation condition is satisfied only when all of the plurality of conditions are satisfied as the ice generation condition. However, it is not necessarily limited to such a configuration. For example, it may be determined that the ice generation condition is satisfied only when the output of the temperature sensor 130 indicates 0 ° C. or less. When the temperature is 0 ° C. or lower, there is a possibility that water drops may freeze, and when the temperature is 0 ° C. or lower, the ice generation condition is satisfied. The possibility that the generated water droplets freeze can be further reduced.

  In the first embodiment, engine 100 has four cylinders 106 inside. However, it is not necessarily limited to such a configuration. For example, the engine 100 may have two cylinders 106 or six cylinders. In short, the engine 100 may be a multi-cylinder engine having a plurality of cylinders.

  In the first embodiment, the example in which the control device 200 of the engine 100 is mounted on the hybrid vehicle 1 has been described. However, it is not necessarily limited to such a configuration. For example, control device 200 can be installed in a gasoline vehicle not equipped with motor generators MG1 and MG2. In short, the technology disclosed herein can be applied to any vehicle as long as it is a vehicle having an electric VVT mechanism.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Hybrid vehicle, 4 Power split device, 5 Reducer, 6 Drive wheel, 10 Power storage device, 20 PCU, 100 Engine, 102 cylinder, 104 Throttle valve, 106 cylinder, 108 Injector, 110 Spark plug, 112S, 112U Catalyst, 114 Piston, 116 Crankshaft, 118 Intake valve, 120 Exhaust valve, 122,124 Cam, 130 Temperature sensor, 200 Control device, 202 Timer, 300 Cam angle sensor, 302 Crank angle sensor, 306 Throttle opening sensor, 312 Throttle motor, 400 Electric VVT mechanism, 402,403 Electric actuator.

Claims (5)

A control device for an internal combustion engine,
The internal combustion engine
Multiple cylinders,
An intake valve and an exhaust valve provided in each of the plurality of cylinders;
An electric variable valve timing mechanism that changes the valve timing of at least one of the intake valve and the exhaust valve by changing the rotational phase of the camshaft relative to the crankshaft;
The controller is
An icing generation condition establishment determining means for determining whether or not ice is generated between each valve of the plurality of cylinders and each valve seat provided corresponding to each valve when the internal combustion engine is stopped. When,
Of the valves of the plurality of cylinders, a fine opening valve estimation means for estimating a valve whose valve opening is a predetermined opening or less,
When it is determined by the icing generation condition establishment determination means that the ice is generated, the valve estimated by the slightly opened valve estimation means to be less than or equal to the predetermined opening is greater than or equal to the predetermined opening. A control device for an internal combustion engine, comprising: valve timing control means for controlling the electric variable valve timing mechanism. A timer for measuring a stop time that is a time during which the stop state of the internal combustion engine continues after the drive of the internal combustion engine is completed, and a drive time that is a time from the start of driving of the internal combustion engine to the end of driving;
The internal combustion engine further includes a temperature sensor that detects a temperature of cooling water for cooling the internal combustion engine,
The conditions for the ice are as follows:
The temperature of the cooling water detected by the temperature sensor is 0 ° C. or less, and the stop time measured by the timer is shorter than a first predetermined time, and the driving time measured by the timer The control device for an internal combustion engine according to claim 1, comprising a time shorter than a second predetermined time. The first predetermined time is a time required until ice is generated between the valves of the plurality of cylinders and the valve seats.
The control apparatus for an internal combustion engine according to claim 2, wherein the second predetermined time is a time required for the temperature of each valve of the plurality of cylinders to rise to a predetermined temperature by driving the internal combustion engine.   The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the condition for generating ice is considered to be satisfied by satisfying a condition for a certain period of time. A control method for an internal combustion engine comprising:
The internal combustion engine
Multiple cylinders,
An intake valve and an exhaust valve provided in each of the plurality of cylinders;
An electric variable valve timing mechanism that changes the valve timing of at least one of the intake valve and the exhaust valve by changing the rotational phase of the camshaft relative to the crankshaft;
The control method is:
Determining whether or not it is a condition in which ice is generated between each valve of the plurality of cylinders and each valve seat provided corresponding to each valve when the internal combustion engine is stopped; and
Estimating a valve whose valve opening is equal to or less than a predetermined opening among the valves of the plurality of cylinders;
Controlling the electric variable valve timing mechanism so that a valve that is estimated to be less than or equal to the predetermined opening is greater than or equal to the predetermined opening when it is determined that the condition for generating ice is present. How to control the engine.

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