Control method of internal combustion engine and control device

Abstract

To suppress knocking and a misfire caused by the instability of a combustion chamber wall temperature and a residual gas temperature immediately after a start of an operation at a premixed compression ignition combustion mode.SOLUTION: A power generation internal combustion engine of a series hybrid vehicle comprises a variable compression ratio mechanism for changing a mechanical compression ratio. Within a prescribed period (ΔT1) after a time (t1) at which an operation at a premixed compression ignition combustion mode is started after a start at a spark ignition combustion mode, an operation at which a rotational speed or the like is fixed to a constant value is performed without following a required target output. At a time (t2) at which a second prescribed period (ΔT2) has elapsed, the feedback control of a compression ratio for converging θPmax to a target, and a fuel injection amount at each cylinder is started, and at a time (t3) at which a third prescribed period (ΔT3) has elapsed from the second prescribed period, an operation following the target output is started.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a method and device for controlling an internal combustion engine that has a variable compression ratio mechanism that can mechanically change the compression ratio and can switch between a spark ignition combustion mode and a homogeneous charge compression ignition combustion mode. [Background technology]

[0002] For example, homogeneous charge compression ignition internal combustion engines that use gasoline or the like as fuel and burn a premixed air-fuel mixture formed in a combustion chamber by compression ignition have been proposed. Patent Document 1 discloses a control method for an internal combustion engine that executes a spark ignition combustion mode when starting the internal combustion engine and then switches to homogeneous charge compression ignition combustion mode. In Patent Document 1, when switching from the spark ignition combustion mode to the homogeneous charge compression ignition combustion mode, the fuel supply is stopped, and during this fuel cut, the effective compression ratio of the internal combustion engine is increased by changing the valve timing and the rotation speed of the internal combustion engine is reduced, and then the fuel supply is resumed to switch to homogeneous charge compression ignition combustion mode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-140728 A Summary of the Invention [Problem to be solved by the invention]

[0004] Immediately after starting operation in the homogeneous charge compression ignition combustion mode, the combustion chamber wall temperature and residual gas temperature are unstable, which makes the homogeneous charge compression ignition combustion prone to destabilization and makes it prone to knocking and misfire. [Means for solving the problem]

[0005] The present invention provides a method for controlling an internal combustion engine, comprising the steps of: When the combustion mode is switched from the spark ignition combustion mode to the homogeneous charge compression ignition combustion mode, the homogeneous charge compression ignition combustion is executed with the target rotation speed, the target torque, the target intake pressure, and the target compression ratio set to fixed values ​​during a first predetermined period, regardless of the output demand. When the first predetermined period has elapsed, operation according to the output request is started. Effect of the Invention

[0006] According to this invention, combustion with fixed rotational speed, torque, etc. is carried out for a certain period of time immediately after switching to the homogeneous charge compression ignition combustion mode, so that knocking or misfire due to transient instability of combustion can be avoided. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating the configuration of a series hybrid vehicle. [Diagram 2] 1 is a diagram illustrating the configuration of an internal combustion engine according to an embodiment; [Diagram 3] FIG. 2 is a functional block diagram showing a main part of a control device. [Figure 4] 5 is a flowchart showing a process flow after switching from the spark ignition combustion mode to the homogeneous charge compression ignition combustion mode. [Diagram 5] 4 is a time chart showing the behavior of each part when switching from a spark ignition combustion mode to a homogeneous charge compression ignition combustion mode. [Figure 6] 4 is a time chart for explaining feedback control targeting θPmax. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment in which the present invention is applied to an internal combustion engine for generating electricity in a series hybrid vehicle will be described. FIG. 1 shows a schematic configuration of a series hybrid vehicle. The series hybrid vehicle is configured to include a power generating motor generator 1 that mainly operates as a generator, an internal combustion engine 2 used as a power generating internal combustion engine that drives the power generating motor generator 1 in response to an electric power request, a traveling motor generator 4 that mainly operates as a motor to drive driving wheels 3, and a battery 5 that temporarily stores the generated electric power. The electric power obtained by the internal combustion engine 2 driving the power generating motor generator 1 is stored in the battery 5 via an inverter device (not shown). The traveling motor generator 4 is driven and controlled using the electric power of the battery 5. The electric power generated by the traveling motor generator 4 during regeneration is stored in the battery 5 via an inverter device (not shown). In the illustrated example, the motor generator 1 and the internal combustion engine 2 are linked via a gear train, but they may be directly connected to each other.

[0009] The operation of the motor generators 1 and 4, the charging and discharging of the battery 5, and the operation of the internal combustion engine 2 are controlled by a controller 6. The controller 6 is composed of a plurality of controllers connected to each other so as to be able to communicate with each other, such as a motor controller 7 for controlling the motor generators 1 and 4, an engine controller 8 for controlling the internal combustion engine 2, and a battery controller 9 for managing the battery 5. Information such as the accelerator pedal opening degree and the vehicle speed (not shown) is input to the controller 6. The battery controller 9 also calculates the SOC of the battery 5 based on the voltage and current of the battery 5. When the SOC drops to a predetermined lower limit level, the internal combustion engine 2 is started via the engine controller 8 to generate electricity. The driving modes of such a series hybrid vehicle include an EV mode in which the vehicle runs on the power of the battery 5 without the combustion operation of the internal combustion engine 2, and an HEV mode in which the vehicle runs while generating electricity through the combustion operation of the internal combustion engine 2. Even if the SOC is equal to or higher than the lower limit level, when the required driving force of the vehicle is relatively large, the internal combustion engine 2 is driven and the vehicle runs in the HEV mode.

[0010] 2 shows the system configuration of the internal combustion engine 2. The internal combustion engine 2 is, for example, a four-stroke cycle turbocharged internal combustion engine equipped with a variable compression ratio mechanism 12 that utilizes a multi-link piston crank mechanism, and performs combustion by compression self-ignition of a premixed mixture in a homogeneous charge compression ignition combustion mode (HCCI mode) in a predetermined operating range. Also, in a predetermined operating range including the start-up, combustion by spark ignition is performed in a spark ignition combustion mode (SI mode).

[0011] A pair of intake valves 14 and a pair of exhaust valves 15 are arranged on the ceiling wall surface of the combustion chamber 13, and an ignition plug 16 for spark ignition in a specific operating region is arranged in the center surrounded by these intake valves 14 and exhaust valves 15. The combustion chamber 13 is provided with an in-cylinder pressure sensor 25 for detecting the in-cylinder pressure.

[0012] A fuel injection valve 18 that injects fuel toward the intake valve 14 is disposed for each cylinder in an intake port 17 that is opened and closed by the intake valve 14. The fuel injection valve 18 is an electromagnetic or piezoelectric injection valve that opens when a drive pulse signal is applied thereto, and injects an amount of fuel that is substantially proportional to the pulse width of the drive pulse signal.

[0013] An electronically controlled throttle valve 21, the opening of which is controlled by a control signal from the engine controller 8, is provided upstream of the collector section 19a of the intake passage 19 connected to the intake port 17, and a compressor 22A of a turbocharger 22 is provided further upstream of the electronically controlled throttle valve 21. An air flow meter 23 for detecting the amount of intake air and an air cleaner 24 are provided upstream of the compressor 22A. A heat exchanger for cooling the supercharged intake air by exchanging heat with cooling water, that is, a water-cooled intercooler 26, is built into the collector section 19a. An intercooler water temperature sensor 36 is provided in the intercooler 26 to detect the temperature of the cooling water flowing through the intercooler 26. An intake air temperature sensor 37 is provided on the intake air outlet side of the intercooler 26 to detect the temperature of the intake air that has passed through the intercooler 26. In addition to the intercooler water temperature sensor 36, a cooling water temperature sensor 38 for detecting the temperature of the cooling water flowing through the water jacket of the internal combustion engine 2 is provided at an appropriate position on the water jacket, etc. The cooling water circuit flowing through the intercooler 26 may be part of the cooling water circuit flowing through the water jacket, or may be configured independent of each other. The degree of heat exchange in the intercooler 26 can be variably adjusted via a cooling water valve, an intercooler cooling water pump, a cooling water bypass valve, or the like (not shown).

[0014] Furthermore, a knock sensor 39 for detecting knocking vibrations is provided at an appropriate position on the cylinder block of the internal combustion engine 2.

[0015] The turbine 22B of the turbocharger 22 disposed in the exhaust passage 31 is equipped with a wastegate valve 32 whose opening is controlled by a control signal from the engine controller 8. Catalyst devices 33, 34 are disposed downstream of the turbine 22B in the exhaust passage 31, and a silencer 35 is disposed further downstream.

[0016] The variable compression ratio mechanism 12 utilizes a known multi-link piston crank mechanism described in JP 2005-127200 A and includes a lower link 42 rotatably attached to a crank pin 41 of a crankshaft, an upper link 43 connecting an upper pin 48 at one end of the lower link 42 to a piston pin 49 of the piston 40, a control shaft 44 rotatably supported on the engine body, a control link 45 connecting a control pin 50 at the other end of the lower link 42 to the control shaft 44, and an electric actuator 46 for controlling the rotational position of the control shaft 44. The control shaft 44 has an eccentric shaft portion, and a base end of the control link 45 is supported on the eccentric shaft portion so as to be relatively rotatable. In the variable compression ratio mechanism 12, the attitude of each link changes according to the rotational position of the control shaft 44, and the top dead center position of the piston 40 changes up and down, thereby changing the mechanical compression ratio. The mechanical compression ratio is determined by the rotational position of the control shaft 44 moved by the electric actuator 46, and this rotational position is simultaneously detected as indicating the actual value of the mechanical compression ratio, i.e., the actual compression ratio. In other words, the electric actuator 46 itself is configured to also function as an actual compression ratio sensor.

[0017] In addition to the above-mentioned in-cylinder pressure sensor 25, air flow meter 23, intercooler water temperature sensor 36, cooling water temperature sensor 38, knock sensor 39, intake air temperature sensor 37, and actual compression ratio sensor (electric actuator 46), detection signals of various sensors such as a crank angle sensor 52 for detecting engine speed, an accelerator pedal opening sensor 53 for detecting the amount of depression of an accelerator pedal operated by a driver as a sensor for detecting a torque request by the driver, a boost pressure sensor 54 for detecting boost pressure, and an air-fuel ratio sensor 55 provided in the exhaust passage 31 are input to the engine controller 8. Based on these detection signals, the engine controller 8 optimally controls the fuel injection amount (corresponding to the target torque) by the fuel injection valve 18, the mechanical compression ratio by the variable compression ratio mechanism 12, the opening degree of the throttle valve 21, the opening degree of the wastegate valve 32, and the like, and realizes homogeneous charge compression ignition combustion (HCCI) by compression self-ignition of the premixed mixture in a predetermined operating range. In addition, in a certain operating range including start-up when homogenous charge compression ignition is likely to become unstable, spark ignition (SI) combustion using the spark plug 16 is performed.

[0018] In one embodiment, after starting in the spark ignition combustion mode, when HCCI permission conditions, including several conditions such as the cooling water temperature reaching a predetermined HCCI permission water temperature, are satisfied, the combustion mode is switched to the homogeneous charge compression ignition combustion mode. Specifically, fuel is temporarily cut off to switch the combustion mode, and under this fuel cut state, the mechanical compression ratio by the variable compression ratio mechanism 12 is set to a relatively high HCCI switching compression ratio suitable for switching to homogeneous charge compression ignition combustion, and motoring is performed by the motor generator 1 so that the rotation speed of the internal combustion engine 2 becomes an HCCI switching rotation speed suitable for switching to homogeneous charge compression ignition combustion. Then, when the actual compression ratio and actual rotation speed reach the HCCI switching compression ratio and the HCCI switching rotation speed, respectively, fuel injection is resumed, and homogeneous charge compression ignition combustion is started.

[0019] Here, immediately after the start of homogeneous charge compression ignition combustion, the combustion chamber wall temperature and the residual gas temperature are unstable, so homogeneous charge compression ignition combustion is likely to become unstable. Therefore, in this embodiment, homogeneous charge compression ignition combustion is executed with the target rotation speed, target torque, target boost pressure, and target compression ratio set to fixed values, regardless of the output demand, during a predetermined period ΔT1 (first predetermined period) from the start of combustion in the homogeneous charge compression ignition combustion mode. Then, after the predetermined period ΔT1 has elapsed, operation according to the output demand is started. In other words, the target rotation speed, etc. are variably set based on the output demand.

[0020] In this embodiment, in order to stabilize the homogeneous charge compression ignition combustion during operation according to the output demand, feedback control of the control parameters related to the combustion state is performed based on the detection parameters indicating the combustion state of the homogeneous charge compression ignition combustion. For example, in one embodiment, as an index indicating the combustion state due to the compression self-ignition, a maximum cylinder pressure crank angle (hereinafter abbreviated as θPmax), which is the crank angle at which the cylinder pressure becomes maximum due to combustion, is used. As an index indicating the combustion state, the so-called MB50, which is the crank angle at which 50% of the fuel is burned, can also be used, but θPmax can be most easily obtained by the cylinder pressure sensor 25.

[0021] Then, the mechanical compression ratio by the variable compression ratio mechanism 12 and the fuel injection amount for each cylinder are feedback-controlled so that this θPmax approaches the target θPmax. The details of this feedback control regarding θPmax will be described later.

[0022] Such feedback control for θPmax is started before transition to operation according to the output demand, and is started with a delay from the start of homogeneous charge compression ignition combustion. Specifically, feedback control for θPmax is started when a predetermined period ΔT2 (second predetermined period) has elapsed from the start of homogeneous charge compression ignition combustion, and operation according to the output demand is started when a further predetermined period ΔT3 (third predetermined period) has elapsed from this time. In other words, the sum of the second predetermined period ΔT2 and the third predetermined period ΔT3 is the first predetermined period ΔT1.

[0023] After the feedback control starts, the engine shifts to operation according to the output demand after a delay of a predetermined period ΔT3, so that operation according to the output demand (i.e., change in the target rotation speed, etc.) is started in a state where the feedback control has sufficiently converged to absorb various variations, etc. (i.e., a state where θPmax is maintained near the target). Therefore, transient instability of combustion is suppressed.

[0024] In addition, immediately after the start of homogeneous charge compression ignition combustion, θPmax, which is a detection parameter indicating the combustion state, is unstable, and feedback control may not be performed normally. By delaying the start of feedback control by a predetermined period ΔT2, feedback control can be performed appropriately.

[0025] 3 is a functional block diagram showing the control of the internal combustion engine 2 including the above-mentioned switching control from the spark ignition combustion mode to the homogeneous charge compression ignition combustion mode. As shown in the figure, the engine controller 8 functionally includes a target output calculation unit 61, a target rotation speed calculation unit 62, a fuel injection amount calculation unit 63, a target compression ratio calculation unit 64, a target boost pressure calculation unit 65, and an HCCI switching calculation unit 66. The target output calculation unit 61 calculates a target output (i.e., an output request) based on a power generation request based on the battery SOC output by the battery controller 9 and a vehicle driving force request output by the accelerator pedal opening sensor 53. Except when switching between combustion modes, the engine is operated in the spark ignition combustion mode or the homogeneous charge compression ignition combustion mode according to this target output. That is, the target rotation speed by the target rotation speed calculation unit 62, the fuel injection amount by the fuel injection amount calculation unit 63, the target compression ratio by the target compression ratio calculation unit 64, the target boost pressure by the target boost pressure calculation unit 65, etc. are calculated according to the target output.

[0026] The HCCI switching calculation unit 66 determines whether or not to switch from the spark ignition combustion mode after startup to the homogeneous charge compression ignition combustion mode based on the cooling water temperature, etc., and executes a predetermined switching control at the time of switching. As part of this switching control, operation for a predetermined period ΔT1 in which the above-mentioned target rotation speed, etc. are fixed, the start of feedback control, transition to operation according to the target output, etc. are performed.

[0027] 4 is a flowchart showing the flow of the HCCI switching control process executed by the engine controller 8 after the engine has transitioned from the spark ignition combustion mode to the homogeneous charge compression ignition combustion mode. The process shown in this flowchart is repeatedly executed after the homogeneous charge compression ignition combustion starts.

[0028] In step 1, the detection values ​​of various necessary sensors are read out, and in step 2, the target output (output requirement) is calculated mainly based on the SOC of the battery 5 and the accelerator pedal opening degree (vehicle required output). The target output corresponds to the amount of power generation required for the motor generator 1.

[0029] In step 3, it is determined whether a predetermined period ΔT2 has elapsed since the start of homogeneous charge compression ignition combustion. Until the predetermined period ΔT2 has elapsed, the process proceeds from step 3 to step 5, and feedback control targeting θPmax is turned off. When the predetermined period ΔT2 has elapsed, the process proceeds from step 3 to step 4, and feedback control is started.

[0030] In the next step 6, it is determined whether a predetermined period ΔT3 has elapsed since the start of feedback control. Until the predetermined period ΔT3 has elapsed, the process proceeds from step 6 to step 8, and the target output tracking control (control of the target rotation speed, etc. according to the output demand) is turned OFF. While the target output tracking control is OFF, homogeneous charge compression ignition combustion is performed with the target rotation speed, target torque, target boost pressure, and target compression ratio set to fixed values, regardless of the output demand. As the target rotation speed and the target compression ratio, for example, the HCCI switching rotation speed and the HCCI switching compression ratio may be maintained.

[0031] When a predetermined period ΔT3 has elapsed since the start of feedback control, the process proceeds from step 6 to step 7, where target output tracking control is turned ON. This starts operation by homogeneous charge compression ignition combustion according to the output request.

[0032] The above-mentioned "predetermined period" is defined by an elapsed time or a number of cycles (an integrated value of the number of rotations). A target number of cycles may be determined and divided by the rotation speed to obtain the required elapsed time.

[0033] Fig. 5 is a time chart showing the behavior of each part after switching from the spark ignition combustion mode to the homogeneous charge compression ignition combustion mode. From the top of the figure, (a) the output of the internal combustion engine 2 (the dashed line is the target output), (b) the rotation speed, (c) the boost pressure, (d) θPmax (the dashed line is the target value, and the solid line is the actual value), (e) ON / OFF of the fuel injection amount feedback control, and (f) ON / OFF of the compression ratio feedback control are shown.

[0034] At the beginning of this time chart, fuel is being cut off to switch from the spark ignition combustion mode to the homogeneous charge compression ignition combustion mode, and the engine speed is set to the HCCI switching speed by motoring. Although not shown, the compression ratio of the variable compression ratio mechanism 12 is at a relatively high HCCI switching compression ratio. The boost pressure shown in column (c) is substantially atmospheric pressure.

[0035] In the illustrated example, at time t1, fuel injection is resumed and operation with homogenous charge compression ignition combustion begins. At this time, from time t1 to time t3 when a predetermined period ΔT1 (first predetermined period) has elapsed, operation is performed with the rotation speed, torque, etc. fixed to constant values ​​regardless of the requested target output. In the illustrated example, they are fixed to a constant output that is relatively low compared to the requested target output (dashed line in column (a)).

[0036] In addition, at the stage when homogeneous charge compression ignition combustion starts at time t1, the compression ratio feedback control and the fuel injection amount feedback control targeting θPmax are stopped. Therefore, as shown in (d), θPmax, which is an index showing the combustion state, is relatively unstable.

[0037] At time t2, a predetermined period ΔT2 after time t1, the compression ratio feedback control and the fuel injection amount feedback control targeting θPmax are started. Through these feedback controls, θPmax converges to the target θPmax. For the sake of explanation, the characteristics of θPmax in (d) show the average characteristics of all cylinders.

[0038] At time t3, a predetermined period ΔT3 after feedback control was started, operation by homogenous charge compression ignition combustion is started according to the output demand. Therefore, after time t3, the actual output approaches the target output demanded at that time. Also, the rotation speed shown in (b) and the boost pressure shown in (c) change according to the target output.

[0039] In this way, in the above embodiment, the engine is operated with the rotational speed and other parameters fixed without following the output demand during the predetermined period ΔT1 from the start of homogeneous charge compression ignition combustion, so that the occurrence of knocking or misfire immediately after the start of homogeneous charge compression ignition combustion can be suppressed.

[0040] Furthermore, since operation in accordance with the output requirement is started after θPmax, an index showing the combustion state, is converged near the target value through compression ratio feedback control and fuel injection amount feedback control, stable combustion can be ensured from the initial stage of operation in accordance with the output requirement, and transient knocking and misfire can be avoided.

[0041] FIG. 6 is a time chart for explaining feedback control for converging θPmax to a target θPmax, and shows the change in θPmax during homogeneous charge compression ignition combustion, the change in mechanical compression ratio, and the change in fuel injection amount. In one embodiment, the target θPmax is calculated mainly based on the engine speed and load. The target θPmax is a target θPmax that will result in stable ignition and combustion and a good exhaust composition. Time t2 shown in FIG. 6 is the start point of feedback control.

[0042] The mechanical compression ratio by the variable compression ratio mechanism 12 is feedback-controlled with an appropriate gain based on the deviation between the target θPmax and the actual θPmax (for example, θPmax detected in the immediately preceding cycle) so as to reduce the deviation. The actual θPmax may be represented by the value of any one of the cylinders, but preferably, the cylinder average θPmax, which is the average of all the cylinders, is used. Here, if the actual θPmax is earlier than the target θPmax, the compression ratio is corrected in the direction of decreasing the mechanical compression ratio, and conversely, if the actual θPmax is later than the target θPmax, the compression ratio is corrected in the direction of increasing the mechanical compression ratio.

[0043] By such feedback control of the mechanical compression ratio, the cylinder average θPmax converges to near the target θPmax, thereby maintaining stable homogeneous charge compression ignition combustion overall.

[0044] On the other hand, in a multi-cylinder internal combustion engine, it is desirable to further reduce the variation in the combustion state of each cylinder (i.e., the difference between cylinders in θPmax). In the variable compression ratio mechanism 12 of the above-mentioned embodiment, the mechanical compression ratio of all cylinders is changed uniformly, so that the combustion state (θPmax) of each cylinder cannot be finely adjusted by the compression ratio. Therefore, in this embodiment, in addition to the compression ratio control for all cylinders, the combustion state of each cylinder is optimized by correcting the fuel injection amount for each cylinder. That is, in this embodiment, the mechanical compression ratio of all cylinders is controlled based on the cylinder average θPmax, while the fuel injection amount is corrected based on the actual θPmax of each cylinder so that the difference between cylinders in θPmax is reduced.

[0045] In the time chart of FIG. 6, for the sake of explanation, the cylinder average θPmax is shown assuming that there are two cylinders (cylinder #1 and cylinder #2), and the fuel injection amount of each cylinder is feedback controlled so that the deviation between the θPmax of each cylinder and the cylinder average θPmax becomes small. In the illustrated example, since the θPmax of cylinder #1 tends to be relatively more advanced than the θPmax of cylinder #2, the fuel injection amount of cylinder #1 is corrected to decrease, and the fuel injection amount of cylinder #2 is corrected to increase. As a result, the θPmax of cylinder #1 and the θPmax of cylinder #2 approach each other with some overshoot, and simultaneously converge to the target θPmax. Therefore, each cylinder maintains an appropriate combustion state (θPmax).

[0046] Such compression ratio feedback control and fuel injection amount feedback control are disclosed in JP 2023-122715 A, which was previously filed by the present applicant.

[0047] In addition, although the compression ratio and fuel injection amount are shown to vary greatly in Fig. 6, in reality, the changes are minute, and the basic target compression ratio and target torque do not vary even during the period from time t2 to t3 in Fig. 5. Therefore, the feedback control during the period from time t2 to t3 is not in any way contradictory to the concept of fixed operation that does not follow the output request during the period from time t1 to t3.

[0048] Although one embodiment of the present invention has been described above in detail, the present invention is not limited to the above embodiment and various modifications are possible. For example, in the above example, the compression ratio feedback control and the fuel injection amount feedback control are performed as feedback controls for stabilizing the combustion state of homogenous charge compression ignition combustion, but feedback control of either one of them may be performed, or feedback control of other control parameters may be performed. In addition, the center of gravity of combustion (MB50) or other detection parameters may be used instead of θPmax.

[0049] In addition, in the above embodiment, an example of application to a series hybrid vehicle has been described, but the present invention is not limited to the power generating internal combustion engine of a series hybrid vehicle, and can also be applied to other types of internal combustion engines in which the output of the internal combustion engine can be used as at least a part of the vehicle's propulsion power source.

[0050] Furthermore, the variable compression ratio mechanism may be any other known variable compression ratio mechanism, such as a type that changes the mechanical compression ratio by changing the positional relationship between the cylinder and the crankshaft. [Explanation of symbols]

[0051] 1...Motor generator 2. Internal combustion engine 8. Engine controller 12...Variable compression ratio mechanism 16…Spark plug 18...Fuel injector 21...Throttle valve 22...Turbocharger 23...Air flow meter 25...Cylinder pressure sensor 38...Coolant temperature sensor 39...Knock sensor 46...Electric actuator 52...Crank angle sensor 53...Accelerator pedal opening sensor 61...Target output calculation unit 62...Target rotation speed calculation unit 63…Fuel injection amount calculation section 64...Target compression ratio calculation unit 65...Target boost pressure calculation section 66...HCCI switching calculation section

Claims

1. An internal combustion engine having a variable compression ratio mechanism capable of mechanically changing the compression ratio and capable of switching between a spark ignition combustion mode and a homogeneous charge compression ignition combustion mode, When the combustion mode is switched from the spark ignition combustion mode to the homogeneous charge compression ignition combustion mode, the homogeneous charge compression ignition combustion is executed with the target rotation speed, the target torque, the target intake pressure, and the target compression ratio set to fixed values ​​during a first predetermined period, regardless of the output requirement. When the first predetermined period has elapsed, an operation according to the output request is started. A method for controlling an internal combustion engine.

2. When operating according to power demand, performing feedback control of a control parameter related to the combustion state based on a detection parameter indicating the combustion state of homogeneous charge compression ignition combustion; 2. A method for controlling an internal combustion engine according to claim 1.

3. When the combustion mode is switched from the spark ignition combustion mode to the homogeneous charge compression ignition combustion mode, the feedback control is stopped for a second predetermined period shorter than the first predetermined period, and after the second predetermined period has elapsed and the feedback control has been started, starting an operation in response to the output request.

3. A method for controlling an internal combustion engine according to claim 2.

4. when a third predetermined period has elapsed after the second predetermined period has elapsed, an operation in response to the output request is started.

4. A method for controlling an internal combustion engine according to claim 3.

5. As one of the above-mentioned feedback controls, a maximum cylinder pressure crank angle is detected, and the compression ratio is feedback-controlled so as to approach a target crank angle.

3. A method for controlling an internal combustion engine according to claim 2.

6. As one of the above-mentioned feedback controls, the maximum cylinder pressure crank angle is detected for each cylinder, and the fuel supply amount to each cylinder is feedback controlled so that the difference between the cylinders is reduced.

3. A method for controlling an internal combustion engine according to claim 2.

7. The internal combustion engine is an internal combustion engine for a series hybrid vehicle that drives a generator, controlling a rotation speed to a target rotation speed via the generator during the first predetermined period; 2. A method for controlling an internal combustion engine according to claim 1.

8. An internal combustion engine capable of switching between a spark ignition combustion mode and a homogeneous charge compression ignition combustion mode; A variable compression ratio mechanism capable of mechanically changing the compression ratio; A controller; Equipped with The above controller is When the combustion mode is switched from the spark ignition combustion mode to the homogeneous charge compression ignition combustion mode, the homogeneous charge compression ignition combustion is executed with the target rotation speed, the target torque, the target intake pressure, and the target compression ratio set to fixed values ​​regardless of the output demand for a first predetermined period, and when the first predetermined period has elapsed, the operation according to the output demand is started. A control device for an internal combustion engine.

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