Control method of internal combustion engine and control device

Abstract

To stably switch a combustion mode from a spark ignition combustion mode to a premixed compression ignition mode while preventing a misfire and knocking in the switching.SOLUTION: A power generation internal combustion engine of a series hybrid vehicle comprises a variable compression ratio mechanism for changing a mechanical compression ratio. The internal combustion engine is started at a spark ignition combustion mode. When a temperature of cooling water reaches an HCCI-approval water temperature (time t1), fuel injection is stopped, a target rotational speed is set to zero, and a target compression ratio is set to an HCCI-switching compression ratio. When an actual compression ratio reaches the HCCI-switching compression ratio (time t2), the rotational speed is monitored to an HCCI-switching rotational speed. When an actual rotational speed reaches the HCCI-switching rotational speed (time t3), the fuel injection is restarted, and the internal combustion engine is operated at a premixed compression ignition combustion mode.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.

[0003] Patent Document 2 discloses an internal combustion engine equipped with a variable compression ratio mechanism that is capable of mechanically changing the compression ratio. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-140728 A [Patent Document 2] JP 2014-159770 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the technology of Patent Document 1, the effective compression ratio of the internal combustion engine is increased by changing the valve timing when switching from the spark ignition combustion mode to the homogeneous charge compression ignition combustion mode, but when the valve timing is changed, the effective compression ratio changes and at the same time the intake amount (in other words, the torque of the internal combustion engine) changes relatively significantly, making it difficult to obtain the desired stable homogeneous charge compression ignition combustion. Also, it is difficult to know the value of the effective compression ratio in real time, making it impossible to accurately control the timing of resuming fuel supply. [Means for solving the problem]

[0006] The present invention provides a method for controlling an internal combustion engine, comprising the steps of: When a switch from spark ignition combustion mode to homogeneous charge compression ignition combustion mode is required, The fuel supply is stopped and the target compression ratio of the variable compression ratio mechanism is changed to the HCCI switching compression ratio. After the actual compression ratio reaches the HCCI switching compression ratio, the fuel supply is resumed to switch to the homogeneous charge compression ignition combustion mode. Effect of the Invention

[0007] According to this invention, homogeneous charge compression ignition combustion is started in a state where the actual compression ratio is set to an HCCI switching compression ratio suitable for homogeneous charge compression ignition combustion via a variable compression ratio mechanism, so misfires and knocking can be prevented during switching. In particular, unlike the case where the valve timing is changed, there is no change in the intake amount, i.e., no change in the operating conditions. Also, it is possible to reliably detect when the HCCI switching compression ratio has actually been reached. [Brief description of the drawings]

[0008] [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 of control for 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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] 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.

[0010] 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.

[0011] 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).

[0012] 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.

[0013] 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.

[0014] 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).

[0015] 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.

[0016] 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.

[0017] The variable compression ratio mechanism 12 utilizes a known multi-link piston crank mechanism described in Patent Document 2, JP 2005-127200 A, etc., 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 a 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, i.e., swingable. 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. In such a variable compression ratio mechanism 12, it is possible to detect the actual compression ratio even when the crankshaft is stationary, i.e., not rotating.

[0018] 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 from 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 amount of fuel injected 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.

[0019] 4 is a flowchart showing the flow of the process of HCCI switching control executed by the engine controller 8 when the internal combustion engine 2 transitions from the spark ignition combustion mode to the homogeneous charge compression ignition combustion mode after the start of the internal combustion engine 2. The process shown in this flowchart is executed while the internal combustion engine 2 is in the spark ignition combustion mode after the start of the internal combustion engine 2.

[0020] In step 1, the detection values ​​of various necessary sensors are read out, and in step 2, a target output is calculated based mainly 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.

[0021] In step 3, an HCCI permission judgment is made, that is, a judgment is made as to whether the conditions are such that operation in the homogeneous charge compression ignition combustion mode is possible. Specifically, it is judged whether the target output is within a predetermined range and the coolant temperature is within a predetermined range. If these conditions are met, the process proceeds to step 4, where the HCCI permission flag is set to 1. If the HCCI permission conditions are not met, the process proceeds to step 5, where the HCCI permission flag and the switching flag are both set to 0.

[0022] In step 6, it is determined whether the HCCI permission flag has been inverted from 0 to 1. That is, it is determined whether the previous HCCI permission flag was 0 and the current HCCI permission flag is 1. If the result is YES, the process proceeds to step 7, where the switching flag is set to 1 and fuel injection is stopped. In addition, the target rotation speed is set to 0 and the internal combustion engine 2 and the motor generator 1 are stopped. Furthermore, the target compression ratio of the variable compression ratio mechanism 12 is set to an HCCI switching compression ratio suitable for homogenous charge compression ignition combustion. The HCCI switching compression ratio is generally a higher compression ratio than the compression ratio in the spark ignition combustion mode, and is calculated based on the coolant temperature, the intake air temperature, and the fuel ignition quality. The fuel ignition quality is obtained by searching for the knock limit using the knock sensor 39 while the spark ignition combustion is being performed.

[0023] Proceed from step 7 to step 8, and determine whether the switching flag is 1. If the switching flag is 1, this means that the switching process is not complete. If the answer is NO in step 6, proceed from step 6 to step 8.

[0024] If the answer is YES in step 8, the process proceeds to step 9, where it is determined whether the actual compression ratio has substantially reached the target compression ratio, specifically, whether the difference between the target compression ratio and the actual compression ratio is equal to or smaller than a relatively small predetermined value. If the answer is NO in step 8, the current routine is terminated. As described above, the variable compression ratio mechanism 12 of the embodiment is capable of detecting the actual compression ratio even when the rotation is stopped.

[0025] If the actual compression ratio substantially reaches the target compression ratio in step 9, the process proceeds to step 10, where the target rotation speed of the internal combustion engine 2 is set to an HCCI switching rotation speed suitable for homogeneous charge compression ignition combustion. As a result, the internal combustion engine 2 is motored at the HCCI switching rotation speed by the powering of the motor generator 1 mechanically connected to the internal combustion engine 2. If NO in step 9, the routine is repeated until the actual compression ratio substantially reaches the target compression ratio, and motoring is started at the stage where the actual compression ratio substantially reaches the target compression ratio. The HCCI switching rotation speed is calculated based on the coolant temperature, the intake air temperature, and the fuel ignition property so that stable homogeneous charge compression ignition combustion is realized. As an example of a numerical value, it is, for example, about 1000 to 2000 rpm.

[0026] In the next step 11, it is determined whether the actual rotation speed of the internal combustion engine 2 has substantially reached the HCCI switching rotation speed, specifically, whether the difference between the HCCI switching rotation speed, which is the target rotation speed, and the actual rotation speed is equal to or smaller than a relatively small predetermined value. If the actual rotation speed has substantially reached the HCCI switching rotation speed, the process proceeds to step 12, where fuel injection is resumed.

[0027] If NO in step 11, the routine is repeated until the actual rotation speed substantially reaches the HCCI switchover rotation speed, and fuel injection is resumed at the stage when the actual rotation speed substantially reaches the HCCI switchover rotation speed.

[0028] In step 13 following step 12, it is determined whether a predetermined period of time has elapsed since the restart of fuel injection. This "predetermined period of time" is the period of time until homogeneous charge compression ignition combustion is stabilized, and is determined by the elapsed time or the number of cycles (integrated value of the number of revolutions). The necessary elapsed time may be obtained by setting a target number of cycles and dividing this target number of cycles by the HCCI switching rotation speed.

[0029] When a predetermined period of time has elapsed since the fuel injection was restarted, the process proceeds from step 13 to step 14, where the switching flag is reset to 0. This ends the process of switching from the spark ignition combustion mode to the homogeneous charge compression ignition combustion mode. Until the predetermined period of time has elapsed, steady operation is performed using the HCCI switching compression ratio and HCCI switching rotation speed regardless of the target output. After the predetermined period of time has elapsed, homogeneous charge compression ignition combustion is performed in accordance with the target output.

[0030] FIG. 3 is a functional block diagram showing the control of the internal combustion engine 2 including the switching control from the spark ignition combustion mode to the homogeneous charge compression ignition combustion mode described above. 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 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 during switching of the combustion mode, 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 calculated by the target rotation speed calculation unit 62, the fuel injection amount calculated by the fuel injection amount calculation unit 63, the target compression ratio calculated by the target compression ratio calculation unit 64, the target boost pressure calculated by the target boost pressure calculation unit 65, and the like are calculated according to the target output.

[0031] 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 and the target output, and executes the switching control of the example described with reference to FIG. 4 when switching.

[0032] Figure 5 is a time chart showing the behavior of each part when switching from the spark ignition combustion mode to the homogeneous charge compression ignition combustion mode. From the top of the figure, (a) the rotation speed (the dashed line indicates the target rotation speed, and the solid line indicates the actual rotation speed), (b) the compression ratio (the dashed line indicates the target compression ratio, and the solid line indicates the actual compression ratio), (c) the coolant temperature, (d) fuel injection, (e) the HCCI permission flag, and (f) the switching in progress flag are shown.

[0033] At the beginning of this time chart, operation begins in the spark ignition combustion mode.

[0034] In the illustrated example, at time t1, the cooling water temperature reaches a predetermined HCCI permissible water temperature, causing the HCCI permission flag to become 1, and furthermore, the switching in progress flag, which indicates that the switching process is in progress, becomes 1. Then, substantially simultaneously, fuel injection is stopped (OFF), and furthermore, the target rotation speed is set to 0. The actual rotation speed becomes 0 after a slight delay. Further, substantially simultaneously, the target compression ratio of the variable compression ratio mechanism 12 becomes the HCCI switching compression ratio. The actual compression ratio (i.e., the rotational position of the control shaft 44) changes relatively slowly toward this target compression ratio.

[0035] After that, at time t2, the actual compression ratio reaches the HCCI switching compression ratio, which is the target compression ratio. Accordingly, the target rotation speed is set to the HCCI switching rotation speed. The actual rotation speed becomes the HCCI switching rotation speed with a slight delay.

[0036] At the point in time (time t3) when the actual rotation speed reaches the HCCI switching rotation speed, the homogeneous charge compression ignition combustion mode is established and fuel injection is resumed (ON). From time t3 until time t4, when a predetermined period of time has elapsed, homogeneous charge compression ignition combustion is continued while maintaining the HCCI switching compression ratio and the HCCI switching rotation speed regardless of the target output. As the torque of the internal combustion engine 2 rises, the motor generator 1 shifts from power running to regeneration.

[0037] At time t4 when a predetermined period has elapsed, the switching flag becomes 0 and the switching process ends. After that, the rotation speed and compression ratio are controlled to correspond to the target output.

[0038] As described above, according to the above embodiment, homogeneous charge compression ignition combustion is started with the actual compression ratio set to an HCCI switchover compression ratio suitable for homogeneous charge compression ignition combustion via the variable compression ratio mechanism 12 and the rotational speed set to the HCCI switchover rotational speed by motoring. Therefore, stable homogeneous charge compression ignition combustion can be started from the beginning and misfires and knocking during switchover can be prevented.

[0039] Also, unlike changing the effective compression ratio by changing the valve timing, changing the mechanical compression ratio of the internal combustion engine 2 does not change the intake amount, i.e., the operating conditions, and does not cause the control of homogeneous charge compression ignition combustion to become complicated due to the change in the intake amount. Furthermore, when changing the mechanical compression ratio due to the switch, the actual compression ratio can be detected in real time, and it is possible to reliably detect that the compression ratio for switching to HCCI has actually been reached. Therefore, the control of the switch from the spark ignition combustion mode to the homogeneous charge compression ignition combustion mode is stable.

[0040] 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, during the period from when fuel supply is stopped until the actual compression ratio reaches the HCCI switching compression ratio (the period from t1 to t2 in FIG. 5), the target rotation speed is set to 0 and motoring is temporarily stopped in order to suppress power consumption associated with motoring, but the rotation speed may be controlled to the HCCI switching rotation speed without stopping motoring. In this case, it is possible to immediately resume fuel supply (start homogenous charge compression ignition combustion) at the stage when the actual compression ratio reaches the HCCI switching compression ratio.

[0041] 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.

[0042] 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]

[0043] 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 a switch from spark ignition combustion mode to homogeneous charge compression ignition combustion mode is required, The fuel supply is stopped, and the target compression ratio of the variable compression ratio mechanism is changed to an HCCI switching compression ratio; After the actual compression ratio reaches the HCCI switching compression ratio, fuel supply is resumed as a homogeneous charge compression ignition combustion mode. A method for controlling an internal combustion engine.

2. The HCCI switching compression ratio is set based on at least one parameter among a cooling water temperature, an intake air temperature, and a fuel ignition property.

2. A method for controlling an internal combustion engine according to claim 1.

3. When the actual compression ratio reaches the HCCI switching compression ratio, a target rotation speed of the internal combustion engine controlled via the electric motor is set as an HCCI switching rotation speed; When the actual rotation speed of the internal combustion engine reaches the HCCI switching rotation speed, the combustion mode is changed to a homogeneous charge compression ignition combustion mode and fuel supply is resumed.

2. A method for controlling an internal combustion engine according to claim 1.

4. The HCCI switching rotation speed is set based on at least one parameter among a cooling water temperature, an intake air temperature, and a fuel ignition quality.

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

5. The internal combustion engine is not rotated via the electric motor until the actual compression ratio reaches the HCCI switching compression ratio.

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

6. After the fuel supply is resumed, homogeneous charge compression ignition combustion is performed with the target compression ratio and the target rotation speed fixed for a predetermined period of time.

2. A method for controlling an internal combustion engine according to claim 1.

7. The internal combustion engine is an internal combustion engine for a series hybrid vehicle that drives a generator.

2. A method for controlling an internal combustion engine according to claim 1.

8. The variable compression ratio mechanism is a multi-link piston crank mechanism including: a lower link rotatably supported on a crank pin of a crankshaft; an upper link connecting an upper pin at one end of the lower link and a piston pin of a piston; a control link having one end connected to a control pin at the other end of the lower link; and a control shaft having an eccentric shaft portion swingably supporting the other end of the control link; an actuator for controlling a rotational position of the control shaft; Equipped with an actual compression ratio is detected based on a rotational position of the control shaft; 2. A method for controlling an internal combustion engine according to claim 1.

9. 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 a switch from the spark ignition combustion mode to the homogeneous charge compression ignition combustion mode is requested, the fuel supply is stopped and the target compression ratio of the variable compression ratio mechanism is changed to a compression ratio for HCCI switchover, and after the actual compression ratio reaches the compression ratio for HCCI switchover, the fuel supply is resumed as the homogeneous charge compression ignition combustion mode. A control device for an internal combustion engine.

Images