Control device for internal combustion engine and control method thereof

Abstract

The present application relates to a control device of an internal combustion engine and a control method thereof, the control device of the internal combustion engine (50) includes: a temperature acquisition unit (55) configured to acquire a temperature of the internal combustion engine at a time when start of the internal combustion engine is requested; a drag execution unit (56) configured to execute drag of the internal combustion engine by an electric motor at the time when the start of the internal combustion engine is requested; and an in-cylinder pressure control unit (58) configured to control in-cylinder pressure of the internal combustion engine during the drag based on the temperature of the internal combustion engine. The in-cylinder pressure control unit (58) is configured to execute, from a start time point of the drag, in-cylinder pressure increase control for increasing the in-cylinder pressure, compared with a case where the temperature of the internal combustion engine is higher than a threshold temperature, in a case where the temperature of the internal combustion engine is equal to or lower than the threshold temperature.

Description

Technical Field

[0001] This invention relates to a control device and a control method for an internal combustion engine. Background Technology

[0002] In vehicles equipped with internal combustion engines, when the internal combustion engine is started, the engine speed is increased to the specified starting speed by being driven by an electric motor, and then the combustion of the air-fuel mixture begins.

[0003] In the vehicle described in Japanese Patent Application Publication No. 2006-299812, during cold starts of the internal combustion engine, the intake valve closing timing is advanced before the engine speed reaches the starting speed in order to increase the combustion energy during initial detonation. On the other hand, when the engine speed is low while being driven, the intake valve closing timing is delayed in order to reduce cylinder pressure and promote an increase in engine speed. Summary of the Invention

[0004] The problem that the invention aims to solve

[0005] However, according to the inventors of this application, considering the lubrication state of the sliding parts of an internal combustion engine at low temperatures, the frictional torque increases and the mechanical losses caused by friction increase when the cylinder pressure decreases during cold starts of the internal combustion engine. Therefore, there is room for improvement in the drag control during cold starts of internal combustion engines.

[0006] Therefore, the present invention proposes a control device and a control method for an internal combustion engine, which reduces the electric motor torque required to start the internal combustion engine during low-temperature starting without deteriorating the startability of the internal combustion engine.

[0007] Technical solutions for solving the problem

[0008] A first aspect of the present invention relates to a control device for an internal combustion engine, which controls an internal combustion engine mounted in a vehicle, the vehicle having an electric motor and a battery. The control device includes a temperature acquisition unit, a drive execution unit, and a cylinder pressure control unit. The temperature acquisition unit is configured to acquire the temperature of the internal combustion engine at the time when starting the engine is requested. The drive execution unit is configured to drive the internal combustion engine via the electric motor when starting the engine is requested. The cylinder pressure control unit is configured to control the cylinder pressure of the engine during driving based on the engine temperature. Furthermore, the cylinder pressure control unit is configured to, when the engine temperature is below a predetermined threshold temperature, perform cylinder pressure increase control from the start time of driving, increasing the cylinder pressure compared to a case where the engine temperature is above the threshold temperature.

[0009] In the control device for an internal combustion engine according to the first aspect of the present invention, the cylinder pressure control unit may also be configured such that, when the temperature of the internal combustion engine is below the threshold temperature, the lower the temperature of the internal combustion engine, the greater the increase in cylinder pressure during the cylinder pressure increase control.

[0010] In the control device for an internal combustion engine according to the first aspect of the present invention, the cylinder pressure control unit may also be configured to keep the increase in cylinder pressure constant regardless of the temperature of the internal combustion engine when the temperature of the internal combustion engine is below the threshold temperature.

[0011] In the control device for the internal combustion engine according to the first aspect of the present invention, a SOC calculation unit may also be included, which is configured to calculate the SOC of the battery. Furthermore, the cylinder pressure control unit may be configured such that, when the temperature of the internal combustion engine is below the threshold temperature, the lower the SOC, the greater the increase in cylinder pressure during cylinder pressure increase control.

[0012] In the control device for an internal combustion engine according to the first aspect of the present invention, the cylinder pressure control unit may also be configured to use a variable valve timing mechanism provided in the internal combustion engine to change the closing timing of the intake valve of the internal combustion engine, thereby controlling the cylinder pressure.

[0013] In the control device of the internal combustion engine configured as described above, the variable valve timing mechanism can also be an electrically driven type.

[0014] In the control device of the internal combustion engine configured as described above, the variable valve timing mechanism can also be a hydraulically driven type. Furthermore, the cylinder pressure control unit can be configured to advance the closing timing when the internal combustion engine stops, provided that the engine temperature is below the threshold temperature.

[0015] In the control device of the internal combustion engine configured as described above, the cylinder pressure control unit may also be configured such that, when the temperature of the internal combustion engine is below the threshold temperature, the lower the temperature of the internal combustion engine, the greater the advance of the shut-off timing when the internal combustion engine stops.

[0016] In the control device of the internal combustion engine configured as described above, the cylinder pressure control unit may also be configured to keep the advance of the shut-off timing constant regardless of the temperature of the internal combustion engine when the temperature of the internal combustion engine is below the threshold temperature.

[0017] In the control device for an internal combustion engine according to the first aspect of the present invention, the cylinder pressure control unit may also be configured to use a variable valve lift mechanism provided in the internal combustion engine to change the lift of the intake valve of the internal combustion engine, thereby controlling the cylinder pressure.

[0018] In the control device for an internal combustion engine according to the first aspect of the present invention, the cylinder pressure control unit may also be configured to use a variable compression ratio mechanism provided in the internal combustion engine to change the mechanical compression ratio of the internal combustion engine, thereby controlling the cylinder pressure.

[0019] A second aspect of the present invention relates to a control method for an internal combustion engine, which controls an internal combustion engine mounted in a vehicle, the vehicle having an electric motor and a battery. The control method includes the following steps: (i) obtaining the temperature of the internal combustion engine at the time of requesting its start; (ii) when requesting its start, performing aspiration of the internal combustion engine via the electric motor; (iii) controlling the cylinder pressure of the aspirated internal combustion engine based on the engine temperature; and (iv) if the engine temperature is below a predetermined threshold temperature, performing cylinder pressure amplification control from the start time of aspiration to increase the cylinder pressure compared to a scenario where the engine temperature is above the threshold temperature.

[0020] Invention Effects

[0021] According to the control device and control method of the internal combustion engine of the present invention, when the internal combustion engine is started at low temperature, the electric motor torque required to start the internal combustion engine can be reduced without deteriorating the startability of the internal combustion engine. Attached Figure Description

[0022] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, wherein like symbols denote like elements, and wherein:

[0023] Figure 1 This is a diagram that schematically illustrates a vehicle to which the control device of the internal combustion engine according to the first embodiment of the present invention is applied.

[0024] Figure 2 It is a general representation Figure 1 A diagram showing the structure of an internal combustion engine.

[0025] Figure 3 It is a block diagram representing a part of the structure of the vehicle.

[0026] Figure 4 yes Figure 3 The first embodiment shown is a functional block diagram of the processor of the electronic control unit (ECU).

[0027] Figure 5 It is a Stribeck diagram representing the three states of lubrication friction.

[0028] Figure 6 This is a graph showing the relationship between the engine speed and friction torque of an internal combustion engine under extremely low temperature conditions.

[0029] Figure 7 It is a graph showing the time variation of the internal combustion engine speed and the friction torque calculated based on the internal combustion engine speed during low-temperature starting.

[0030] Figure 8 This is a flowchart illustrating the control routine for the internal combustion engine starting process in the first embodiment.

[0031] Figure 9 This is an example of a diagram showing the relationship between the temperature of an internal combustion engine and the advance of the intake valve closing timing.

[0032] Figure 10 This is a functional block diagram of the processor of the ECU in the second embodiment of the present invention.

[0033] Figure 11 This is a flowchart illustrating the control routine for the internal combustion engine starting process in the second embodiment.

[0034] Figure 12 This is an example diagram showing the relationship between the state of charge (SOC) of the vehicle's battery and the advance of the intake valve closing timing of the internal combustion engine.

[0035] Figure 13 It is a two-dimensional mapping diagram used to determine the intake valve closing timing advance based on the internal combustion engine temperature and the battery's SOC.

[0036] Figure 14 This is a flowchart illustrating the control routine for the internal combustion engine stop processing in the third embodiment of the present invention. Detailed Implementation

[0037] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same reference numerals will be used for the same constituent elements.

[0038] First, refer to Figures 1-9 The first embodiment of the present invention will now be described.

[0039] The explanation will begin with an overview of the vehicle. Figure 1 This is a schematic diagram of a vehicle 100 that applies the control device for an internal combustion engine according to the first embodiment of the present invention. The vehicle 100 includes an internal combustion engine 1, a power distribution mechanism 31, a first electric generator (MG1) 32, a second electric generator (MG2) 33, a power control unit (PCU) 34, a battery 35, and a reduction gear 36.

[0040] The vehicle 100 is equipped with an internal combustion engine 1 and a second electric generator 33 as power sources for driving. That is, the vehicle 100 is a so-called hybrid electric vehicle (HEV). The structure of hybrid electric vehicles is well known, so the functions of each component will be briefly explained below.

[0041] The output shaft (crankshaft 40) of the internal combustion engine 1 is mechanically connected to the power distribution mechanism 31, and the output of the internal combustion engine 1 is input to the power distribution mechanism 31. When the first electric generator 32 functions as a generator, the output of the internal combustion engine 1 is distributed to the first electric generator 32 and the reduction gear 36 via the power distribution mechanism 31. Electricity is generated by the first electric generator 32 using the output of the internal combustion engine 1 distributed to it. On the other hand, the output of the internal combustion engine 1 distributed to the reduction gear 36 is transmitted to the wheels 38 via the axle 37 as driving power.

[0042] The first electric generator 32 is mechanically connected to the crankshaft 40 of the internal combustion engine 1 via a power distribution mechanism 31. When the first electric generator 32 functions as an electric motor, the electricity stored in the battery 35 is supplied to the first electric generator 32 via the PCU 34. The output of the first electric generator 32 is supplied to the crankshaft 40 of the internal combustion engine 1 via the power distribution mechanism 31. As a result, combustion of the air-fuel mixture is not performed in the internal combustion engine 1, but the crankshaft 40 is driven to rotate, thus achieving so-called traction.

[0043] When the second electric generator 33 functions as an electric motor, the electricity stored in the battery 35 or generated by the first electric generator 32 is supplied to the second electric generator 33 via the PCU 34, and the output of the second electric generator 33 is supplied to the reducer 36. The output of the second electric generator 33 supplied to the reducer 36 is transmitted to the wheels 38 via the axle 37 as driving power.

[0044] On the other hand, when the vehicle decelerates, the rotation of the wheels 38 drives the second electric generator 33, which functions as a generator. The regenerative power generated by the second electric generator 33 is supplied to the battery 35 via the PCU 34.

[0045] Next, the internal combustion engine will be explained. Figure 2 It is a general representation Figure 1 A diagram showing the structure of internal combustion engine 1. Internal combustion engine 1 is a spark-ignition internal combustion engine, specifically a gasoline engine that uses gasoline as fuel.

[0046] The internal combustion engine 1 includes an internal combustion engine body comprising a cylinder block 2 and a cylinder head 4. Inside the cylinder block 2, multiple (e.g., four) cylinders are formed. In each cylinder, a piston 3 is disposed that reciprocates along the cylinder's axial direction. A combustion chamber 5 is formed between the piston 3 and the cylinder head 4.

[0047] An intake port 7 and an exhaust port 9 are formed on the cylinder head 4. The intake port 7 and the exhaust port 9 are respectively connected to the combustion chamber 5.

[0048] In addition, the internal combustion engine 1 has an intake valve 6 and an exhaust valve 8 disposed in the cylinder head 4, and an electrically operated variable valve timing (VVT) 61 capable of changing the opening and closing timing of the intake valve 6. The intake valve 6 opens and closes the intake port 7, and the exhaust valve 8 opens and closes the exhaust port 9.

[0049] In addition, the internal combustion engine 1 includes a spark plug 10 and a fuel injection valve 11. The spark plug 10 is disposed in the center of the inner wall of the cylinder head 4 and generates a spark according to the ignition signal. The fuel injection valve 11 is disposed in the periphery of the inner wall of the cylinder head 4 and injects fuel into the combustion chamber 5 according to the injection signal.

[0050] In addition, the internal combustion engine 1 includes an intake manifold 13, a pressure regulator 14, an intake pipe 15, an air filter 16, and a throttle valve 18. The intake ports 7 of each cylinder are connected to the pressure regulator 14 via the corresponding intake manifold 13, and the pressure regulator 14 is connected to the air filter 16 via the intake pipe 15. The intake ports 7, intake manifold 13, pressure regulator 14, and intake pipe 15 form an intake passage that guides air into the combustion chamber 5.

[0051] Throttle valve 18 is disposed in intake pipe 15 between pressure tank 14 and air filter 16, and is driven by throttle valve drive actuator 17 (e.g., DC motor). Throttle valve 18 rotates via throttle valve drive actuator 17, thereby changing the opening area of ​​intake passage according to its opening degree.

[0052] In addition, the internal combustion engine 1 includes an exhaust manifold 19, a catalyst 20, a housing 21, and an exhaust pipe 22. The exhaust ports 9 of each cylinder are connected to the exhaust manifold 19. The exhaust manifold 19 has multiple branches connected to each exhaust port 9 and a collection section formed by these branches. The collection section of the exhaust manifold 19 is connected to the housing 21, which houses the catalyst 20. The housing 21 is connected to the exhaust pipe 22. The exhaust ports 9, exhaust manifold 19, housing 21, and exhaust pipe 22 form an exhaust passage for discharging exhaust gases generated from the combustion of the air-fuel mixture in the combustion chamber 5.

[0053] Furthermore, the aforementioned internal combustion engine 1 is a non-turbocharged internal combustion engine that uses gasoline as fuel, but the structure of the internal combustion engine 1 is not limited to the aforementioned structure. Therefore, the specific structure of the internal combustion engine 1, such as cylinder arrangement, fuel injection method, intake and exhaust system structure, valve mechanism structure, and the presence or absence of a turbocharger, can be related to... Figure 1 The structures shown are different. For example, the fuel injection valve 11 can also be configured to inject fuel into the intake port 7. Additionally, a structure can be provided to allow EGR gas to flow back from the exhaust passage to the intake passage. Furthermore, the internal combustion engine 1 can also be a diesel engine.

[0054] Next, the control device of the internal combustion engine will be explained. Figure 3 This is a block diagram representing a part of the structure of vehicle 100. For example... Figure 3 As shown, the vehicle 100 includes an Electronic Control Unit (ECU) 50. The ECU 50 has a communication interface (communication I / F) 51, a memory 52, and a processor 53. The communication interface 51 and the memory 52 are connected to the processor 53 via signal lines. Furthermore, in this embodiment, only one ECU 50 is provided, but multiple ECUs may be provided for each function.

[0055] The communication interface 51 has interface circuitry for connecting the ECU 50 to an in-vehicle network based on standards such as CAN (Controller Area Network). The ECU 50 communicates with on-board devices connected to the in-vehicle network via the communication interface 51 and the in-vehicle network.

[0056] The memory 52 may be a volatile semiconductor memory (e.g., RAM) or a non-volatile semiconductor memory (e.g., ROM). The memory 52 stores computer programs executed by the processor 53, various data used by the processor 53 during various processes, etc. Furthermore, the computer programs executed by the processor 53 may also be provided in the form of recording media that can be read by a computer. Recording media that can be read by a computer may be, for example, magnetic recording media, optical recording media, or semiconductor memory.

[0057] The processor 53 has one or more CPUs (Central Processing Units) and their peripheral circuitry to perform various processes. In addition, the processor 53 may also have other arithmetic circuitry such as logic units, numerical processing units, or graphics processing units.

[0058] The ECU 50 performs various controls on the internal combustion engine 1 based on the outputs of various sensors installed in the vehicle 100 or the internal combustion engine 1. The ECU 50 is an example of a control device for controlling the internal combustion engine 1. In this embodiment, the battery sensor 41, air flow meter 42, water temperature sensor 43, oil temperature sensor 44, accelerator opening sensor 45, and crankshaft angle sensor 46 are electrically connected to the ECU 50, and their outputs are sent to the ECU 50.

[0059] like Figure 1 As shown, a battery sensor 41 is disposed on the battery 35. The battery sensor 41 detects the state of the battery 35. The battery sensor 41 may include, for example, a voltage sensor for detecting the voltage (single cell voltage) of the battery 35, a temperature sensor for detecting the temperature of the battery 35, and a current sensor for detecting the input and output current of the battery 35.

[0060] like Figure 2 As shown, the air flow meter 42 is disposed in the intake passage of the internal combustion engine 1, specifically in the intake pipe 15 upstream of the throttle valve 18. The air flow meter 42 detects the flow rate of air flowing in the intake passage.

[0061] The water temperature sensor 43 is installed in the cooling water circuit of the internal combustion engine 1 to detect the temperature of the cooling water (coolant) of the internal combustion engine 1. The oil temperature sensor 44 is installed in the oil circuit of the internal combustion engine 1 to detect the temperature of the lubricating oil that lubricates the sliding parts of the internal combustion engine 1.

[0062] Accelerator pedal position sensor 45 detects the amount of pressure applied to the accelerator pedal (accelerator pedal position) in vehicle 100. ECU 50 calculates the internal combustion engine load based on the output of accelerator pedal position sensor 45.

[0063] The crankshaft angle sensor 46 generates an output pulse whenever the crankshaft of the internal combustion engine 1 rotates by a specified angle (e.g., 10 degrees). The ECU 50 calculates the internal combustion engine speed based on the output of the crankshaft angle sensor 46.

[0064] In this embodiment, the first electric generator 32, the second electric generator 33, the spark plug 10, the fuel injection valve 11, the throttle actuator 17, and the VVT ​​61 are electrically connected to the ECU 50, which controls them. For example, the ECU 50 controls the output torque of the first electric generator 32 and the second electric generator 33 via the PCU 34. Furthermore, the ECU 50 controls the ignition timing of the spark plug 10, the injection timing and quantity of fuel injected from the fuel injection valve 11, the opening degree of the throttle valve 18, and the opening and closing timing of the intake valve 6.

[0065] Figure 4This is a functional block diagram of the processor 53 of the ECU 50 in the first embodiment. In this embodiment, the processor 53 includes a temperature acquisition unit 55, a drive execution unit 56, a combustion control unit 57, and an in-cylinder pressure control unit 58. The temperature acquisition unit 55, the drive execution unit 56, the combustion control unit 57, and the in-cylinder pressure control unit 58 are functional modules implemented by the processor 53 of the ECU 50 executing a computer program stored in the memory 52 of the ECU 50. Furthermore, these functional modules can also be implemented using dedicated arithmetic circuits provided in the processor 53.

[0066] The temperature acquisition unit 55 acquires the temperature of the internal combustion engine 1. For example, the temperature acquisition unit 55 acquires the temperature of the internal combustion engine 1 based on the output of at least one of the water temperature sensor 43 and the oil temperature sensor 44. In particular, in this embodiment, the temperature acquisition unit 55 acquires the temperature of the internal combustion engine 1 when the internal combustion engine 1 is requested to be started (hereinafter also referred to as "the initial temperature of the internal combustion engine 1").

[0067] When the internal combustion engine 1 is requested to start, the drive actuator 56 drives the internal combustion engine 1 via the first electric generator 32. Specifically, before the combustion of the air-fuel mixture begins in the internal combustion engine 1, the drive actuator 56 drives the crankshaft 40 of the internal combustion engine 1 by rotating the output of the first electric generator 32, thereby increasing the speed of the internal combustion engine. The first electric generator 32 is an example of an electric motor used for drive.

[0068] The combustion control unit 57 controls the spark plug 10, fuel injection valve 11, etc., thereby controlling the combustion of the air-fuel mixture in the combustion chamber 5. When the internal combustion engine speed is increased to the specified starting speed by means of a drive, the combustion control unit 57 starts the combustion of the air-fuel mixture and starts the internal combustion engine 1.

[0069] The cylinder pressure control unit 58 controls the cylinder pressure of the internal combustion engine 1. In this embodiment, the cylinder pressure control unit 58 uses VVT 61 to change the closing timing of the intake valve 6, thereby controlling the cylinder pressure. The intake valve 6 opens near the exhaust top dead center and closes during the compression stroke from the intake bottom dead center to the compression top dead center. Therefore, when the closing timing of the intake valve 6 is advanced, the closing timing of the intake valve 6 is close to the intake bottom dead center, and the cylinder pressure increases as the intake air volume increases. On the other hand, when the closing timing of the intake valve 6 is delayed, the closing timing of the intake valve 6 is close to the compression top dead center, and the cylinder pressure decreases as the intake air volume decreases. Therefore, the cylinder pressure control unit 58 advances the closing timing of the intake valve 6 when increasing the cylinder pressure and delays the closing timing of the intake valve 6 when decreasing the cylinder pressure.

[0070] Previously, in order to promote an increase in the speed of a driven internal combustion engine, it was considered effective to reduce the cylinder pressure of the driven internal combustion engine 1 regardless of its temperature. In contrast, the inventors of this application have discovered that if the lubrication state of the sliding parts (piston 3, crankshaft 40, etc.) of the internal combustion engine 1 at low temperatures is taken into account, the frictional torque increases and the mechanical losses caused by friction increase when the cylinder pressure is reduced during cold starting of the internal combustion engine 1.

[0071] Figure 5 This is a Stribek diagram representing the three states of lubrication friction. When the sliding part of the internal combustion engine 1 is lubricated by fluid lubrication, the frictional torque generated in the internal combustion engine 1 increases as the engine speed decreases. On the other hand, when the sliding part of the internal combustion engine 1 is lubricated by boundary lubrication or mixed lubrication, there exists a region where the frictional torque increases as the engine speed decreases.

[0072] Figure 6 This is a graph showing the relationship between the engine speed and friction torque of internal combustion engine 1 under extremely low temperature conditions. Figure 6 In the figure, the result is shown when the temperature of internal combustion engine 1 is -30℃. The smaller the absolute value of the friction torque, the smaller the friction torque. For example... Figure 6 As shown, when the internal combustion engine 1 is in an extremely low temperature state, the lower the engine speed, the smaller the friction torque. That is, when the internal combustion engine 1 is in an extremely low temperature state, regardless of the engine speed, it is presumed that the lubrication state of the sliding parts of the internal combustion engine 1 is fluid lubrication.

[0073] Therefore, when the internal combustion engine 1 is in an extremely low temperature state, reducing the speed of the internal combustion engine while it is being driven can reduce mechanical losses caused by friction. However, in order to initiate combustion of the air-fuel mixture, the speed of the internal combustion engine needs to be increased to the starting speed by being driven. Therefore, if the speed of the internal combustion engine is reduced simply by reducing the output torque of the first electric generator 32, even if mechanical losses can be reduced, the time required to start the internal combustion engine 1 will be prolonged, and the starting performance of the internal combustion engine 1 will deteriorate.

[0074] Therefore, in this embodiment, in order to reduce the electric motor torque required for towing without deteriorating the starting performance of the internal combustion engine 1, the cylinder pressure control unit 58 controls the cylinder pressure of the internal combustion engine 1 during towing based on the initial temperature of the internal combustion engine 1. Specifically, when the initial temperature of the internal combustion engine 1 is below a predetermined threshold temperature, the cylinder pressure control unit 58 performs cylinder pressure increase control from the start time of towing, which increases the cylinder pressure compared to the case where the initial temperature of the internal combustion engine 1 is above the threshold temperature.

[0075] In this embodiment, the cylinder pressure control unit 58 increases the cylinder pressure by advancing the closing timing of the intake valve 6 during cylinder pressure increase control. That is, when the initial temperature of the internal combustion engine 1 is below the threshold temperature, the cylinder pressure control unit 58 advances the closing timing of the intake valve 6 compared to when the initial temperature of the internal combustion engine 1 is above the threshold temperature.

[0076] Figure 7 This is a graph showing the time variation of the internal combustion engine speed during cold starts and the friction torque calculated from the engine speed. Figure 7 In the figures, solid lines show the results of the embodiments according to this implementation, and dashed lines show the results of the comparative examples. In the embodiments, the closing timing of the dragged intake valve 6 is advanced by 37°, while in the comparative examples, the closing timing of the dragged intake valve 6 is not advanced.

[0077] When the cylinder pressure increases due to the advance closing timing of intake valve 6, the engine speed decreases during the compression stroke due to the increased compression reaction force, but the engine speed increases rapidly during the expansion stroke due to the increased expansion energy. Therefore, from Figure 7 As can be seen, in the embodiment, the internal combustion engine speed is temporarily lower than in the comparative example during the intake stroke, but the rate of increase of the internal combustion engine speed during the subsequent expansion stroke is greater than in the comparative example. As a result, the time it takes for the internal combustion engine speed to rise to the starting speed is the same between the embodiment and the comparative example.

[0078] On the other hand, in the region where the internal combustion engine speed of the embodiment is lower than that of the comparative example, the friction torque of the embodiment is less than that of the comparative example. That is, in the embodiment, the average value of the friction torque during dragging can be reduced compared to the comparative example. Therefore, according to this embodiment, during the cold start of the internal combustion engine 1, the electric motor torque required to drive the internal combustion engine 1 can be reduced without deteriorating the starting performance of the internal combustion engine 1.

[0079] Furthermore, the lower the temperature of the internal combustion engine 1, the lower the output of the battery 35, and the lower the output torque of the first electric generator 32. Therefore, in this embodiment, when the initial temperature of the internal combustion engine 1 is below the threshold temperature, the lower the initial temperature of the internal combustion engine 1, the more the cylinder pressure control unit 58 increases the amount of cylinder pressure increase control in the cylinder pressure increase control. That is, when the initial temperature of the internal combustion engine 1 is below the threshold temperature, the lower the initial temperature of the internal combustion engine 1, the more the cylinder pressure control unit 58 increases the advance of the intake valve 6 closing timing. As a result, the electric motor torque required to drive the internal combustion engine 1 can be set to an appropriate value according to the initial temperature of the internal combustion engine 1.

[0080] Next, the starting procedure for an internal combustion engine will be explained. The following is a reference to... Figure 8 The control process described above will be explained. Figure 8 This is a flowchart illustrating the control routine for the internal combustion engine starting process in the first embodiment. This control routine is repeatedly executed by the processor 53 of the ECU 50.

[0081] First, in step S101, the drive actuator 56 determines whether the starting of the internal combustion engine 1 has been requested. For example, the starting of the internal combustion engine 1 is requested when the state of charge (SOC) of the battery 35 is below a predetermined value, or when the requested driving force to the vehicle 100 is above a predetermined value. If it is determined that the starting of the internal combustion engine 1 has not been requested, this control routine ends. On the other hand, if it is determined that the starting of the internal combustion engine 1 has been requested, this control routine proceeds to step S102.

[0082] In step S102, the temperature acquisition unit 55 acquires the temperature Ts of the internal combustion engine 1. For example, the temperature acquisition unit 55 acquires the lower of the temperature of the cooling water detected by the water temperature sensor 43 and the temperature of the lubricating oil detected by the oil temperature sensor 44 as the temperature Ts of the internal combustion engine 1. Alternatively, the temperature acquisition unit 55 may acquire the average of the cooling water temperature and the lubricating oil temperature as the temperature Ts of the internal combustion engine 1. Alternatively, the oil temperature sensor 44 may be omitted, and the temperature acquisition unit 55 may acquire the temperature of the cooling water as the temperature Ts of the internal combustion engine 1. Alternatively, the water temperature sensor 43 may be omitted, and the temperature acquisition unit 55 may acquire the temperature of the lubricating oil as the temperature Ts of the internal combustion engine 1.

[0083] Next, in step S103, the cylinder pressure control unit 58 uses a mapping or calculation formula to determine the advance of the intake valve 6 closing timing based on the temperature Ts of the internal combustion engine 1 obtained by the temperature acquisition unit 55. Figure 9 This is a diagram illustrating an example of a mapping showing the relationship between the temperature of the internal combustion engine 1 and the advance of the intake valve 6 closing timing. (See diagram for example.) Figure 9 As shown, when the temperature of the internal combustion engine 1 is higher than the threshold temperature Tth, the advance amount is set to zero. On the other hand, when the temperature of the internal combustion engine 1 is lower than the threshold temperature Tth, the advance amount is set to be larger as the temperature of the internal combustion engine 1 decreases. The threshold temperature Tth is preset such that the lubrication state of the sliding part of the internal combustion engine 1 in the extremely low temperature region below this temperature is fluid lubrication, for example, it is set to -5°C to -30°C.

[0084] Next, in step S104, the cylinder pressure control unit 58 controls VVT61 to advance the closing timing of the intake valve 6, thereby achieving the advance amount determined in step S103. For example, the cylinder pressure control unit 58 uses VVT61 to advance the center phase of the actuation angle of the intake valve 6, thereby advancing the closing timing of the intake valve 6.

[0085] Next, in step S105, the drive actuator 56 drives the internal combustion engine 1. Specifically, the drive actuator 56 rotates the crankshaft 40 of the internal combustion engine 1 by means of the output of the first electric generator 32, thereby increasing the speed of the internal combustion engine.

[0086] Next, in step S106, the drag actuator 56 determines whether the internal combustion engine speed is above the predetermined starting speed. The internal combustion engine speed is calculated based on the output of the crankshaft angle sensor 46. The starting speed is predetermined based on the characteristics of the internal combustion engine 1, as the internal combustion engine speed required for initial detonation, for example, set to 150 rpm to 400 rpm.

[0087] If, in step S106, it is determined that the internal combustion engine speed is less than the starting speed, this control routine returns to step S105 and continues to operate. On the other hand, if, in step S106, it is determined that the internal combustion engine speed is greater than or equal to the starting speed, this control routine proceeds to step S107.

[0088] In step S107, the combustion control unit 57 begins combustion of the air-fuel mixture. At this time, if the closing timing of the intake valve 6 is advanced, i.e., if the temperature Ts of the internal combustion engine 1 is below the threshold temperature Tth, the cylinder pressure control unit 58 controls the VVT ​​61 to delay the closing timing of the intake valve 6 to a predetermined target value. After step S107, this control routine ends.

[0089] Next, the second embodiment of the present invention will be described. The control device for the internal combustion engine according to the second embodiment is substantially the same in structure and control as the control device for the internal combustion engine according to the first embodiment, except for the points described below. Therefore, the second embodiment of the present invention will be described below focusing on the parts that differ from the first embodiment.

[0090] Figure 10 This is a functional block diagram of the processor 53 of the ECU 50 in the second embodiment. In this embodiment, the processor 53, in addition to the temperature acquisition unit 55, the drive execution unit 56, the combustion control unit 57, and the cylinder pressure control unit 58, also has a SOC calculation unit 59. The temperature acquisition unit 55, the drive execution unit 56, the combustion control unit 57, the cylinder pressure control unit 58, and the SOC calculation unit 59 are functional modules implemented by the processor 53 of the ECU 50 executing a computer program stored in the memory 52 of the ECU 50. Furthermore, these functional modules can also be implemented using dedicated arithmetic circuits provided in the processor 53.

[0091] The SOC calculation unit 59 calculates the SOC of the battery 35. When the SOC of the battery 35 is low, the output of the battery 35 decreases due to the decrease in the voltage of the battery 35. The lower the SOC of the battery 35, the lower the output of the battery 35, and the lower the output torque of the first electric generator 32. Therefore, in the second embodiment, when the initial temperature of the internal combustion engine 1 is below the threshold temperature, the lower the SOC of the battery 35, the more the cylinder pressure control unit 58 increases the amount of cylinder pressure increase in the cylinder pressure increase control. That is, when the initial temperature of the internal combustion engine 1 is below the threshold temperature, the lower the SOC of the battery 35, the more the cylinder pressure control unit 58 increases the advance of the intake valve 6 closing timing in the cylinder pressure increase control. Thus, the electric motor torque required to drive the internal combustion engine 1 can be set to an appropriate value based on the SOC of the battery 35.

[0092] Figure 11 This is a flowchart illustrating the control routine for the internal combustion engine starting process in the second embodiment. This control routine is repeatedly executed by the processor 53 of the ECU 50.

[0093] First, in step S201, with Figure 8 Similarly, in step S101, the drag execution unit 56 determines whether the starting of the internal combustion engine 1 has been requested. If it is determined that the starting of the internal combustion engine 1 has not been requested, this control routine ends. On the other hand, if it is determined that the starting of the internal combustion engine 1 has been requested, this control routine proceeds to step S202.

[0094] In step S202, with Figure 8 Similarly, in step S102, the temperature acquisition unit 55 acquires the temperature Ts of the internal combustion engine 1.

[0095] Next, in step S203, the SOC calculation unit 59 calculates the SOC of the battery 35 based on the output of the battery sensor 41. For example, since the voltage of the battery 35 is related to the SOC and temperature of the battery 35, the SOC calculation unit 59 calculates the SOC of the battery 35 based on the voltage and temperature of the battery 35 detected by the battery sensor 41. Alternatively, the SOC calculation unit 59 can also calculate the SOC of the battery 35 by accumulating the input and output currents of the battery 35 detected by the battery sensor 41. Furthermore, the SOC calculation unit 59 can also use a state estimation method such as a Kalman filter to calculate the SOC of the battery 35.

[0096] Next, in step S204, the cylinder pressure control unit 58 uses a mapping or calculation formula to determine the advance of the intake valve 6 closing timing based on the temperature Ts of the internal combustion engine 1 obtained by the temperature acquisition unit 55 and the SOC of the battery 35 calculated by the SOC calculation unit 59. For example, if the temperature Ts of the internal combustion engine 1 is below the threshold temperature Tth, the cylinder pressure control unit 58 uses... Figure 12 The mapping shown determines the advance of the intake valve 6 closing timing based on the SOC of the battery 35. Figure 12 This is a diagram illustrating an example of a mapping representing the relationship between the SOC of the battery 35 and the advance of the intake valve 6 closing timing. (See diagram for example.) Figure 12 As shown, the lower the SOC of the battery 35, the greater the lead time is set.

[0097] In addition, the cylinder pressure control unit 58 can also be used. Figure 13 The two-dimensional mapping shown determines the timing advance AA of the intake valve 6 based on the temperature Ts of the internal combustion engine 1 and the state of charge (SOC) of the battery 35. This mapping is created such that the lower the temperature Ts of the internal combustion engine 1, the greater the timing advance AA, and the lower the SOC of the battery 35, the greater the timing advance AA.

[0098] Then, steps S205 to S208 and Figure 8 Steps S104 to S107 are performed in the same way.

[0099] Next, the third embodiment of the present invention will be described. The control device for the internal combustion engine according to the third embodiment is substantially the same in structure and control as the control device for the internal combustion engine according to the first embodiment, except for the points described below. Therefore, the third embodiment of the present invention will be described below focusing on the parts that differ from the first embodiment.

[0100] In the third embodiment, VVT61 is configured to be hydraulically driven. That is, VVT61 is a hydraulic variable valve timing mechanism. When VVT61 is a hydraulic variable valve timing mechanism, the advance control based on VVT61 takes more time compared to when VVT61 is an electrically driven variable valve timing mechanism. Therefore, the effect of reducing frictional torque may be reduced during the period from the start of actuation until the advance completion of the intake valve 6's closing timing. Furthermore, if the internal combustion engine 1 is cold at startup, the temperature of the internal combustion engine 1 is more likely to be cold at the next startup.

[0101] Therefore, in the third embodiment, when the initial temperature of the internal combustion engine 1 is below a predetermined threshold temperature, the cylinder pressure control unit 58 advances the closing timing of the intake valve 6 when the internal combustion engine 1 is stopped. Thus, even if the VVT ​​61 is a hydraulic variable valve timing mechanism, it is possible to achieve an advance amount suitable for the starting state of the internal combustion engine 1 at the start time of the next start-up of the internal combustion engine 1.

[0102] For example, when the initial temperature of the internal combustion engine 1 is below the threshold temperature, the lower the initial temperature of the internal combustion engine, the more the cylinder pressure control unit 58 increases the advance of the closing timing of the intake valve 6 when the internal combustion engine 1 stops. As a result, the advance can be set to a more appropriate value, which can improve the effect of reducing friction torque during the next start-up.

[0103] In the third embodiment, except Figure 8 In addition to the control routines for the internal combustion engine starting process, it also executes Figure 14 The control routine for stopping the internal combustion engine. Figure 14 This is a flowchart illustrating the control routine for the internal combustion engine shutdown process in the third embodiment. This control routine is repeatedly executed by the processor 53 of the ECU 50.

[0104] First, in step S301, the combustion control unit 57 determines whether a request to stop the internal combustion engine 1 has been made. If it is determined that no request to stop the internal combustion engine 1 has been made, the control routine ends. On the other hand, if it is determined that a request to stop the internal combustion engine 1 has been made, the control routine proceeds to step S302.

[0105] In step S302, the cylinder pressure control unit 58 determines that... Figure 8 In step S102, the temperature Ts of the internal combustion engine 1, i.e., the initial temperature of the internal combustion engine, is obtained. Is it below a predetermined threshold temperature Tth? The threshold temperature Tth is preset so that the lubrication state of the sliding part of the internal combustion engine 1 in the extremely low temperature region below this temperature is fluid lubrication, for example, it is set to -5°C to -30°C.

[0106] If, in step S302, the temperature Ts of the internal combustion engine 1 is determined to be below the threshold temperature Tth, this control routine proceeds to step S303. In step S303, the cylinder pressure control unit 58 uses a mapping or calculation formula to determine the advance of the intake valve 6's closing timing based on the temperature Ts of the internal combustion engine 1. For example, the cylinder pressure control unit 58 uses... Figure 9 The mapping shown determines the advance amount of the intake valve 6 closing timing. In this case, the cylinder pressure control unit 58 sets the advance amount when the internal combustion engine 1 stops to the same value as the advance amount set during dragging.

[0107] Next, in step S304, the cylinder pressure control unit 58 controls VVT61 to advance the closing timing of the intake valve 6, thereby achieving the advance amount determined in step S303. For example, the cylinder pressure control unit 58 uses VVT61 to advance the center phase of the actuation angle of the intake valve 6, thereby advancing the closing timing of the intake valve 6.

[0108] After step S304, this control routine proceeds to step S305. On the other hand, if it is determined in step S302 that the temperature Ts of the internal combustion engine 1 is higher than the threshold temperature Tth, this control routine skips steps S303 and S304 and proceeds to step S305. In step S305, the combustion control unit 57 stops the combustion of the air-fuel mixture, thereby stopping the internal combustion engine 1. After step S305, this control routine ends.

[0109] Next, other embodiments of the present invention will be described. The embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and variations can be made within the scope of the claims. For example, when the initial temperature of the internal combustion engine 1 is below a threshold temperature, the cylinder pressure control unit 58 can keep the increase in cylinder pressure in the cylinder pressure increase control constant, regardless of the temperature of the internal combustion engine 1. That is, when the initial temperature of the internal combustion engine 1 is below a threshold temperature, the cylinder pressure control unit 58 can keep the advance of the closing timing of the intake valve 6 in the cylinder pressure increase control constant, regardless of the temperature of the internal combustion engine 1.

[0110] Alternatively, the internal combustion engine 1 may also be equipped with a known variable valve lift mechanism. The cylinder pressure control unit 58 controls the cylinder pressure by changing the lift of the intake valve 6 using the variable valve lift mechanism. In this case, the cylinder pressure control unit 58 increases the lift when increasing the cylinder pressure and decreases the lift when decreasing the cylinder pressure.

[0111] Furthermore, the internal combustion engine 1 can be equipped with a known variable compression ratio mechanism. The cylinder pressure control unit 58 controls the cylinder pressure by changing the mechanical compression ratio of the internal combustion engine 1 using the variable compression ratio mechanism. In this case, the cylinder pressure control unit 58 increases the mechanical compression ratio when increasing the cylinder pressure and decreases the mechanical compression ratio when decreasing the cylinder pressure. Examples of known variable compression ratio mechanisms include multi-link variable compression ratio mechanisms and variable length connecting rods.

[0112] Furthermore, the cylinder pressure control unit 58 can control the cylinder pressure by changing the opening of the throttle valve 18 using the throttle valve drive actuator 17. In this case, the cylinder pressure control unit 58 increases the opening of the throttle valve 18 when increasing the cylinder pressure, and decreases the opening of the throttle valve 18 when decreasing the cylinder pressure.

[0113] Furthermore, vehicles using internal combustion engine control devices can also be series hybrid vehicles that use only an electric motor as the power source for driving, or plug-in hybrid electric vehicles (PHEVs) that can charge their batteries from an external power source. Additionally, vehicles using internal combustion engine control devices can also have only an internal combustion engine as the power source for driving, provided they have an electric motor for propulsion. In this case, the internal combustion engine is requested to start when the vehicle's ignition switch is turned on.

[0114] Furthermore, the above-described embodiments can be implemented in any combination. For example, in the case of combining the third embodiment with the second embodiment, the control routine used for the internal combustion engine starting process can be replaced... Figure 8 The control routine executes Figure 11 The control routine.

Claims

1. A control device for an internal combustion engine, configured to control an internal combustion engine mounted in a vehicle equipped with an electric motor and a battery, characterized in that it comprises: The temperature acquisition unit is configured to acquire the temperature of the internal combustion engine when the requested internal combustion engine is started; The drive actuator is configured to drive the internal combustion engine via the electric motor when the internal combustion engine is requested to start; and The cylinder pressure control unit is configured to control the cylinder pressure of the internal combustion engine during operation based on the temperature of the internal combustion engine, wherein... The cylinder pressure control unit is configured to, when the temperature of the internal combustion engine is below a predetermined threshold temperature, perform cylinder pressure increase control from the start time of the drive, increasing the cylinder pressure compared to the case where the temperature of the internal combustion engine is above the threshold temperature. The cylinder pressure control unit is configured such that, when the internal combustion engine temperature is below the threshold temperature, the lower the internal combustion engine temperature, the greater the increase in cylinder pressure during cylinder pressure increase control. The cylinder pressure control unit is configured to use a variable valve timing mechanism provided in the internal combustion engine to change the closing timing of the intake valve of the internal combustion engine, thereby controlling the cylinder pressure. The variable valve timing mechanism is a hydraulically driven type, and, The cylinder pressure control unit is configured to advance the shut-off timing when the internal combustion engine stops, provided that the temperature of the internal combustion engine is below the threshold temperature. The cylinder pressure control unit is configured such that, when the temperature of the internal combustion engine is below the threshold temperature, the lower the temperature of the internal combustion engine, the greater the advance of the shut-off timing when the internal combustion engine stops.

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