JP2004316561A - Start controller for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a start controller for an internal combustion engine capable of efficiently reducing rotary reaction force of an engine output shaft at the start of the engine. <P>SOLUTION: An electronic control unit 20 retards the closing timing of an inlet valve through a variable valve timing mechanism 11 at restarting and reduces an actual compression ratio to reduce a load on a generator motor 17 unavoidable for rotating a crankshaft 12 at restarting. At the same time the electronic control unit 20 estimates the rotary reaction force during restarting, and when the estimated rotary reaction force is small, the closing timing of the inlet valve is prohibited from being retarded and a reducing amount of the actual compression ratio during restarting is set smaller comparing to the case of the large rotary reaction force. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a start control device for an internal combustion engine, and more particularly to an improvement in a control structure for reducing a rotational reaction force of an engine output shaft at the time of start.
[0002]
[Prior art]
Starting of an engine such as an in-vehicle internal combustion engine is performed by drivingly connecting (cranking) a starting motor to an engine output shaft and rotating the engine output shaft by the output of the motor. During the start of the engine, a rotational reaction force such as an air compression reaction force in the cylinder during the compression stroke and a driving reaction force due to the depression of the engine valve of the cam act on the engine output shaft. Therefore, the starting motor is required to have a high output performance that can overcome such a rotational reaction force, which has been a factor that hinders the miniaturization, weight reduction, and reduction in power consumption of the starting motor.
[0003]
2. Description of the Related Art Conventionally, as disclosed in, for example, Patent Documents 1 and 2, there are known start control devices for an internal combustion engine that delay the closing timing of an intake valve at the time of engine start (Patent Documents 1 and 2 and the like). If the closing timing of the intake valve is retarded and the intake valve is opened even during the compression stroke, the actual compression ratio of the internal combustion engine is reduced, and the compression reaction force is reduced accordingly, The rotation reaction force of the engine output shaft at the time of starting is reduced.
[0004]
On the other hand, if the actual compression ratio at the time of starting the engine is reduced in this way, the rotation of the engine output shaft becomes easy, but the pressure in the cylinder at the time of fuel ignition decreases by that much, and combustion is established in the cylinder. It will be difficult to do so. Therefore, in the start control device for an internal combustion engine described in Patent Document 1, at the time of a cold start in which it is difficult to establish combustion in a cylinder, the reduction of the actual compression ratio is prohibited to prevent further deterioration of combustibility. I am trying to do it.
[0005]
[Patent Document 1]
JP-A-2000-34913
[Patent Document 2]
JP-A-2002-81332
[0006]
[Problems to be solved by the invention]
By the way, at the time of a cold start, the viscosity of the lubricating oil circulated through the internal combustion engine increases, and the friction torque of the internal combustion engine increases, so that the rotational reaction force acting on the engine output shaft increases. Therefore, in the start control device of Patent Document 1, the actual compression ratio is not reduced under the condition that the rotational reaction force is high, so that the output performance requirement of the start motor cannot be effectively reduced. . However, the starting control device of Patent Document 1 aims at suppressing the vibration generated due to the compression reaction force through reduction of the actual compression ratio. It is possible.
[0007]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide an internal combustion engine start control device that can more efficiently reduce the rotational reaction force of an engine output shaft at the time of engine start. It is in.
[0008]
[Means for Solving the Problems]
Hereinafter, means for achieving the above-described object and the effects thereof will be described.
According to a first aspect of the present invention, there is provided a start control apparatus for an internal combustion engine including an actual compression ratio reducing unit for reducing an actual compression ratio during engine start, wherein a rotational reaction force for estimating a magnitude of the rotational reaction force during engine start is provided. Estimating means, when the rotational reaction force estimated by the rotational reaction force estimating means is small, the amount of reduction of the actual compression ratio by the actual compression ratio reducing means is smaller than when the rotational reaction force is large. The gist of the present invention is to provide a reduction amount setting means for setting.
[0009]
In the above configuration, the actual compression ratio during engine startup is reduced, and the compression pressure in the cylinder, which is the rotational reaction force of the engine output shaft, is reduced, so that the engine output shaft can be easily rotated at the time of engine startup. . Therefore, the size and weight of the starting motor can be reduced, and the power consumption can be reduced.
[0010]
On the other hand, in the above configuration, the rotational reaction force during engine start is estimated, and when the estimated rotational reaction force during engine start is small, the reduction amount of the actual compression ratio is smaller than when the rotational reaction force is large. It will be set smaller. For this reason, while reducing the load on the starting motor, it is possible to avoid excessive reduction of the actual compression ratio and to appropriately suppress deterioration of combustion and prolonged startup time due to the reduction. Therefore, the rotational reaction force of the engine output shaft at the time of starting the engine can be reduced more efficiently.
[0011]
According to a second aspect of the present invention, in the start control device for an internal combustion engine according to the first aspect, the reduction amount setting means reduces the actual compression ratio when the estimated rotational reaction force is equal to or less than a predetermined value. The gist of the invention is to prohibit the means from reducing the actual compression ratio.
[0012]
With the above configuration, when the estimated rotational reaction force during engine start is sufficiently small, the actual compression ratio is not reduced. For this reason, while reducing the load on the starting motor, it is possible to preferably suppress the deterioration of combustion and the prolonged startup time due to the reduction.
[0013]
According to a third aspect of the present invention, in the starting control device for an internal combustion engine according to the first or second aspect, the rotational reaction force estimating means estimates the magnitude of the rotational reaction force based on an engine temperature state. Is the gist.
[0014]
The compression pressure in the cylinder and the mechanical friction of the internal combustion engine, which are the rotational reaction force of the engine output shaft at the time of starting, have a high correlation with the engine temperature state. Therefore, the magnitude of the rotational reaction force at the time of starting the engine can be easily and appropriately estimated based on the engine temperature state.
[0015]
According to a fourth aspect of the present invention, there is provided a start control device for an internal combustion engine including an actual compression ratio reducing means for reducing an actual compression ratio during engine start, wherein an output of a start motor for rotating an engine output shaft during engine start is provided. The gist of the present invention is to provide a reduction amount setting unit that sets a reduction amount of the actual compression ratio by the actual compression ratio reduction unit when the performance is reduced, compared to when the performance is not reduced.
[0016]
In the above configuration, the actual compression ratio during engine startup is reduced, and the compression pressure in the cylinder, which is the rotational reaction force of the engine output shaft, is reduced, so that the engine output shaft can be easily rotated at the time of engine startup. . On the other hand, since it becomes difficult to secure the in-cylinder pressure necessary for combustion, the engine rotation speed at which starting can be completed increases. On the other hand, the output performance of the starting motor changes depending on the state of power supply from the power supply, the deterioration with time of the core and the like, the temperature state of the motor, and the like. When the output performance is reduced, it becomes difficult to increase the engine rotation speed with the output of the starting electric motor to the rotation speed at which combustion can be started, which has been increased with the reduction of the actual compression ratio.
[0017]
In this regard, in the above configuration, when the output performance of the starting motor is reduced, the reduction in the actual compression ratio is suppressed, and the increase in the rotation speed at which the combustion can be started is suppressed. Therefore, even with a starting motor whose output performance has been reduced, the starting can be completed relatively easily. Therefore, it is possible to efficiently reduce the rotational reaction force of the engine output shaft at the time of starting the engine.
[0018]
According to a fifth aspect of the present invention, in the start control device for an internal combustion engine according to any one of the first to fourth aspects, the actual compression ratio reducing means delays the closing timing of an intake valve by retarding the actual timing. The gist is to reduce the compression ratio.
[0019]
If the intake valve is opened during the compression stroke by delaying the closing timing, the amount of air compressed in the cylinder is reduced, so that the actual compression ratio can be easily and appropriately reduced. Note that the delay of the closing timing of the intake valve can be easily performed by using a variable valve operating mechanism that varies the valve timing and operating angle of the intake valve.
[0020]
According to a sixth aspect of the present invention, in the start control apparatus for an internal combustion engine according to any one of the first to fifth aspects, the engine start is performed based on the reduction amount of the actual compression ratio set by the reduction amount setting means. The gist of the present invention is to further include start control changing means for changing at least one of an ignition timing at the time, an engine speed at which fuel injection is started, an engine speed at which ignition is started, a fuel injection amount, and a target air-fuel ratio. .
[0021]
If the amount of reduction of the actual compression ratio is changed, the state of the cylinder pressure during engine start also changes, and the ignition timing at engine start, the engine speed at which fuel injection and ignition are started, the fuel injection amount, or the target idle The adaptation value of the engine control amount such as the fuel ratio changes. In the above configuration, since the values of the engine control amounts are changed according to the reduction amount of the actual compression ratio, a good combustion state is ensured regardless of the change in the cylinder pressure during engine start due to the reduction of the actual compression ratio. It becomes possible.
[0022]
According to a seventh aspect of the present invention, in the start control device for an internal combustion engine according to any one of the first to sixth aspects, the internal combustion engine is automatically stopped according to a traveling state of a vehicle equipped with the internal combustion engine. -The gist is to be restarted.
[0023]
In an internal combustion engine that is automatically stopped and restarted in accordance with the running state of the vehicle, the frequency of engine start is high. Therefore, if the above-described configurations are applied to such an internal combustion engine, the effect can be more remarkably exhibited.
[0024]
According to an eighth aspect of the present invention, in the start control device for an internal combustion engine according to the seventh aspect, the automatic stop is performed based on the reduction amount of the actual compression ratio at the time of the previous start set by the reduction amount setting means. -The gist is to determine whether or not to execute restart.
[0025]
If the reduction amount of the actual compression ratio is greatly changed, the state of the internal combustion engine at the time of starting the engine is greatly changed, and deterioration of the starting state such as an increase in vibration and noise generated during engine starting may occur. is there. Therefore, if the reduction amount of the actual compression ratio is used as an index value indicating the degree of deterioration of the starting state and whether or not to execute the automatic stop / restart is determined, the deterioration of the starting state can be suitably avoided. .
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
(First Embodiment)
Hereinafter, a first embodiment of a start control device for an internal combustion engine according to the present invention will be described in detail with reference to FIGS.
[0027]
As shown in FIG. 1, an on-vehicle internal combustion engine 10 to which the present embodiment is applied is provided with a variable valve timing mechanism (VVT) 11 that makes the valve timing of an intake valve variable. Details of the variable valve timing mechanism 11 will be described later.
[0028]
A crankshaft 12 which is an engine output shaft of the internal combustion engine 10 is connected to driving wheels of the vehicle through an automatic transmission 13. Further, the crankshaft 12 is driven and connected to a starter 14 which is an electric motor for starting the engine, if necessary.
[0029]
Further, the crankshaft 12 is drivingly connected to a belt transmission mechanism 16 via an electromagnetic clutch 15. The belt transmission mechanism 16 is provided with accessories such as a compressor for an air conditioner and a water pump, and a generator motor 17 functioning as either a generator or a motor depending on the situation. The electromagnetic clutch 15 is configured so that the drive connection between the belt transmission mechanism 16 and the crankshaft 12 can be connected and disconnected as necessary.
[0030]
The starter 14 and the generator motor 17 are electrically connected to a battery 18. The battery 18 supplies electric power to the starter 14 and the generator motor 17 to make them function as a motor. The battery 18 is charged with electric power generated when the generator motor 17 functions as a generator.
[0031]
Various controls related to the running of the vehicle are performed by the electronic control device 20. The electronic control unit 20 includes a CPU that executes the various controls, a memory that stores information necessary for the control, an input port for inputting a signal from the outside, an output port for outputting a command signal to the outside, and the like. It is provided with.
[0032]
Various sensors for detecting information necessary for controlling the vehicle are connected to the input port of the electronic control device 20. For example, an NE sensor 21 for detecting the engine rotation speed, a vehicle speed sensor 22 for detecting the vehicle speed, a water temperature sensor 23 for detecting the temperature of the engine cooling water, a battery sensor 24 for detecting the output power of the battery 18, and an acceleration acting on the vehicle. A detection signal from the acceleration sensor 26 or the like to be detected is input to the electronic control device 20 through the input port. An ignition switch 25 is also connected to this input port, and a signal (IG signal) for notifying a driver of the operation state of the ignition switch 25 is input to the electronic control unit 20.
[0033]
On the other hand, an output port of the electronic control unit 20 is connected to a variable valve timing mechanism 11 of the internal combustion engine 10, a drive circuit of a spark plug, an injector, a throttle valve, and the like, and a hydraulic control circuit of the automatic transmission 13. The electronic control unit 20 controls the operating state of the internal combustion engine 10 and controls the shift of the automatic transmission 13 through the drive control. The output port is also connected to a control circuit for the starter 14, the generator motor 17, a drive circuit for the electromagnetic clutch 15, and the like. The operations of the starter 14, the generator motor 17, and the electromagnetic clutch 15 are also controlled by the electronic control unit 20. Have been.
[0034]
Next, the variable valve timing mechanism 11 will be described with reference to FIG. FIG. 2 shows a perspective sectional structure of the variable valve timing mechanism 11.
[0035]
As shown in the figure, the variable valve timing mechanism 11 is provided at one end of an intake side camshaft 30 provided with a cam 30a for opening and closing an intake valve. It is provided with.
[0036]
A cam sprocket 33 is disposed at an end of the intake camshaft 30 provided with the variable valve timing mechanism 11 so as to be rotatable relative to the intake camshaft 30. The cam sprocket 33 is drivingly connected to the crankshaft 12 via a timing belt 33a. The housing 32 is fixed to the cam sprocket 33 so as to be integrally rotatable.
[0037]
The vane rotor 31 is disposed inside the housing 32 so as to be relatively rotatable with respect to the housing 32. The vane rotor 31 is fixed to the intake camshaft 30 so as to be integrally rotatable. A plurality of vanes 34 are formed on the outer periphery of the vane rotor 31, and each vane 34 is accommodated in a recess 35 formed on the inner periphery of the housing 32 so as to be movable in the circumferential direction. On both sides in the circumferential direction of each vane 34, pressure chambers 36 and 37 are formed, which are defined by the outer peripheral surface of the vane rotor 31, the inner peripheral surface of the housing 32, and the like.
[0038]
Oil is fed into each of the pressure chambers 36 and 37, and the oil pressure acts on the circumferential side surface of the vane 34. In addition, power for rotating the vane rotor 31 relative to the housing 32 is generated according to the oil pressure difference between the two pressure chambers 36 and 37.
[0039]
When the vane rotor 31 and the housing 32 rotate relative to each other, the relative rotation phase of the intake camshaft 30 with respect to the cam sprocket 33 is changed, and the relative rotation phase of the cam 30a that opens and closes the intake valve with respect to the crankshaft 12 is changed. Is done. Thus, the valve timing of the intake valve is changed based on the control of the oil pressure in the pressure chambers 36 and 37.
[0040]
The control of the variable valve timing mechanism 11 configured as described above is performed as follows.
The electronic control unit 20 sets a target valve timing vtt, which is a target value of the valve timing of the intake valve, based on the engine operating state such as the engine speed and the engine load. Here, the target valve timing vtt is defined as a reference “0” with respect to the most retarded position of the range in which the valve timing of the intake valve is changed by the variable valve timing mechanism 11 and an advance amount [° CA] from the most retarded position. expressed.
[0041]
On the other hand, the electronic control unit 20 detects the actual valve timing of the intake valve based on, for example, a detected value of the rotational phase of the intake camshaft 30. Then, the electronic control unit 20 performs feedback control of the oil pressure in both the pressure chambers 36 and 37 so that the detected actual valve timing matches the target valve timing vtt. Thereby, the valve timing of the intake valve is adjusted to an optimal timing according to the engine operating state.
[0042]
On the other hand, in this vehicle, the electronic control unit 20 executes idle stop control for automatically stopping and restarting the operation of the internal combustion engine 10 in accordance with the running condition. Next, an outline of the idle stop control in the vehicle will be described with reference to FIG.
[0043]
When the driver operates the ignition switch 25 from the "OFF" position to the "ON" position and starts the electronic control device 20, the electronic control device 20 changes its control mode to a "mode" indicating a normal engine stop state. Set to "0". When the driver operates the ignition switch 25 to the “STA” position in the “mode 0” setting, the starter 14 is drivingly connected to the crankshaft 12, and the output of the starter 14 starts the internal combustion engine 10. Done. When the start is successfully completed, the control mode of the electronic control unit 20 is shifted to "mode 1" indicating a normal engine operating state.
[0044]
When “mode 1” is set, the belt transmission mechanism 16 is drivingly connected to the crankshaft 12 by the electromagnetic clutch 15, and the accessories are driven by the output of the internal combustion engine 10. The output of the internal combustion engine 10 is also transmitted to the generator motor 17 through the belt transmission mechanism 16. The generator motor 17 at this time functions as a generator, and the generated power is charged in the battery 18.
[0045]
If the driver operates the ignition switch 25 to the “OFF” position during the setting of the “mode 1”, the electronic control unit 20 executes a normal engine stop process to stop the internal combustion engine 10, and The control mode is shifted to the “mode 0”.
[0046]
On the other hand, if the idle stop execution condition is satisfied during the setting of “mode 1”, the control mode of the electronic control unit 20 is shifted to “mode 2” in which an engine stop process for automatically stopping the internal combustion engine 10 is executed. . In the present embodiment, the satisfaction of the idle stop execution condition is determined based on the satisfaction of all of the following conditions (a1) to (a5), for example, as the idle stop execution condition.
(A1) The accelerator operation amount is “0”.
(A2) The vehicle speed is equal to or lower than a predetermined speed.
(A3) The brake pedal is depressed.
(A4) The cooling water temperature is equal to or higher than a predetermined temperature Ta.
(A5) The operating oil temperature of the automatic transmission 13 is equal to or higher than a predetermined temperature.
(A6) The charge amount of the battery 18 is equal to or more than a predetermined value.
[0047]
When the control mode is shifted to “mode 2” in this way, the electronic control unit 20 stops the fuel supply and stops the internal combustion engine 10. When it is confirmed that the internal combustion engine 10 has been completely stopped, the control mode of the electronic control unit 20 is shifted to "mode 3" indicating an engine stop state due to idle stop.
[0048]
When the “mode 3” is set, the drive connection between the crankshaft 12 and the belt transmission mechanism 16 by the electromagnetic clutch 15 is released. At the same time, the generator motor 17 is operated as a motor, and the output drives the auxiliary machine. Thus, the driving of the auxiliary machine is maintained even during the stop of the internal combustion engine 10 due to the idle stop.
[0049]
When the engine restart execution condition is satisfied during the setting of “Mode 3”, the control mode of the electronic control unit 20 is shifted to “Mode 4” in which a restart process for restarting the internal combustion engine 10 is executed. . In this embodiment, the satisfaction of the engine restart execution condition is determined based on the satisfaction of any of the following conditions (b1) to (b4), for example, as the restart execution condition.
(B1) The depression of the brake pedal is released.
(B2) The accelerator operation amount is not “0”.
(B3) A shift operation was performed from the P (parking) range or the N (neutral) range to another shift range.
(B4) The charge amount of the battery 18 has dropped below a predetermined value.
[0050]
When the control mode is shifted to “mode 4” in this manner, the crankshaft 12 is reconnected to the belt transmission mechanism 16 by the electromagnetic clutch 15. At the same time, the generator motor 17 is operated as a motor, and the output of the generator motor 17 restarts the internal combustion engine 10. When the restart of the internal combustion engine 10 is successfully completed, the control mode of the electronic control unit 20 is shifted to the above-mentioned “mode 1”.
[0051]
When a problem occurs in restarting the internal combustion engine 10 in the "mode 4" due to a system abnormality or the like during the setting of the "mode 3", the control mode of the electronic control unit 20 is changed to the "mode 0". Will be migrated to. In this case, the restart of the internal combustion engine 10 is performed only by the direct operation of the driver, that is, the restart is not automatically performed.
[0052]
By the way, in the present embodiment, the "actual compression ratio reduction process" for reducing the actual compression ratio of the internal combustion engine 10 at the time of restart from idle stop, that is, at the time of restart in the "mode 4" is performed. . Hereinafter, the details of the “actual compression ratio reduction process” in the present embodiment will be described with reference to FIGS. 4 to 6.
[0053]
As described above, the restart of the internal combustion engine 10 in “mode 4” is performed while rotating the crankshaft 12 by the output of the generator motor 17. At this time, a compression reaction force due to the compression of air in the cylinder during the compression stroke, a friction torque of each part of the internal combustion engine 10 and the like act on the crankshaft 12 as a reaction force against the rotation. Therefore, the generator motor 17 is required to have a sufficient output to overcome such a reaction force. In particular, when the compression stroke is first performed after the start of the restart, it is necessary to rotate the crankshaft 12 almost exclusively with the output of the generator motor 17 with little assistance from the inertial force accompanying the rotation of the crankshaft 12 or the like. Therefore, a particularly high output is required.
[0054]
Therefore, in the actual compression ratio reduction process, the load on the generator motor 17 at the time of such restart is reduced by reducing the actual compression ratio of the internal combustion engine 10. The reduction of the actual compression ratio is achieved by controlling the variable valve timing mechanism 11 while the engine is stopped by an idle stop prior to restart, that is, during execution of the engine stop process in the "mode 2". This is performed by controlling the timing to the retard side. In other words, by delaying the closing timing of the intake valve, by sufficiently opening the intake valve even during the compression stroke, the amount of air actually compressed in the cylinder is reduced to reduce the actual compression ratio. , The compression pressure in the cylinder is reduced, and the rotational reaction force is reduced accordingly.
[0055]
On the other hand, if the actual compression ratio during the restart is reduced in this manner, the load on the generator motor 17 required for the rotation of the crankshaft 12 is certainly reduced, but the in-cylinder pressure at the end of the compression stroke also decreases accordingly. I will. For this reason, the engine speed at which the in-cylinder pressure necessary for starting combustion is secured increases, and the restart time becomes longer.
[0056]
Therefore, in the present embodiment, the magnitude of the rotational reaction force of the crankshaft 12 at the time of restart is estimated. If the rotational reaction force is small based on the estimation result and the crankshaft 12 can be relatively easily rotated at the time of restart, the actual compression ratio is not reduced as described above, and the restart is performed. We try to shorten the time.
[0057]
FIG. 4 shows an example of setting the valve timing in the actual compression ratio reduction processing according to the present embodiment. As shown in the figure, when the actual compression ratio is reduced, the closing timing of the intake valve is delayed until about the middle of the compression stroke (retardation setting). On the other hand, when the actual compression ratio is not reduced, the closing timing of the intake valve is set to a relatively early timing (advance angle setting). The closing timing of the intake valve at this time is set to a time advantageous for shortening the restart time.
[0058]
In the present embodiment, the magnitude of the rotational reaction force of the crankshaft 12 at the time of restart is determined as follows.
FIG. 5 shows the relationship between the cooling water temperature of the internal combustion engine 10, the friction torque, and the compression pressure. As shown in the figure, the magnitude of the friction torque or the compression pressure of the internal combustion engine 10 has a high correlation with the temperature state of the internal combustion engine 10. Therefore, the magnitude of the rotational reaction force of the crankshaft 12 at the time of restart can be estimated based on a parameter representing the engine temperature state such as the temperature of cooling water or oil circulated inside the internal combustion engine 10. .
[0059]
At a very low temperature, such as during a so-called cold start, the friction torque acting on the crankshaft 12 increases as the viscosity of the lubricating oil supplied to the internal combustion engine 10 increases. Further, when the engine temperature becomes higher than a certain level, the viscosity of the lubricating oil is excessively reduced, so that the lubricity is deteriorated and the friction torque is also increased. Therefore, as shown in FIG. 5, the friction torque becomes extremely high in a very low temperature range, decreases as the coolant temperature increases, and starts increasing when the coolant temperature rises to a certain degree. . Also, when the engine temperature increases, the air in the cylinder thermally expands to increase the cylinder pressure. Therefore, as shown in FIG. 5, the compression pressure of the internal combustion engine 10 increases as the engine temperature increases.
[0060]
FIG. 6 is a flowchart of the “actual compression ratio reduction process” in the present embodiment. This process is periodically executed by the electronic control unit 20 as a periodic interruption process.
[0061]
When the present process is started, first, in step S100, it is determined whether or not the engine stop process by the idle stop is being performed, that is, whether or not the current control mode is the “mode 2”. Here, if the engine stop processing is not being executed (NO), this processing is temporarily ended as it is.
[0062]
On the other hand, if the engine stop processing is being performed (YES), in step S110, the rotational reaction force of the crankshaft 12 at the time of restart is estimated based on the engine temperature state. Then, in the subsequent step S120, it is determined whether or not the rotational reaction force is in a large state based on the estimation result.
[0063]
Here, when it is determined that the rotational reaction force is large (S110: YES), in step S130, the closing timing of the intake valve at the time of restart is retarded. Specifically, by setting the target valve timing of the variable valve timing mechanism 11 to a value on the retard side that can sufficiently reduce the actual compression ratio, the closing timing of the intake valve during engine stop can be set to restart. It is retarded in advance.
[0064]
On the other hand, when it is determined that the rotational reaction force is not large (S110: NO), in step S140, the closing timing of the intake valve at the time of restart is advanced. Specifically, the target valve timing of the variable valve timing mechanism 11 is set to a value on the advance side capable of sufficiently reducing the restart time, and the closing timing of the intake valve during engine stop is prepared for restart. It has been retarded in advance.
[0065]
In the present embodiment, the variable valve timing mechanism 11 for delaying the closing timing of the intake valve and reducing the actual compression ratio corresponds to the above-mentioned "actual compression ratio reducing means". In addition, the process of step S110 in the actual compression ratio reduction process corresponds to the process of the “rotational reaction force estimating unit”, and the processes of steps S120 to S150 correspond to the process of the “reduction amount setting unit”. . Further, in the present embodiment, the generator motor 17 corresponds to the “starting motor”. Further, the retard amount of the closing timing of the intake valve when setting the retard angle with respect to the setting of the advance angle in the actual compression ratio reduction process corresponds to the above-mentioned "reduction amount of the actual compression ratio".
[0066]
According to the embodiment described above, the following effects can be obtained.
(1) In the present embodiment, the actual compression ratio at the time of restart is reduced to reduce the compression pressure, so that the rotation of the crankshaft 12 during restart is facilitated and the load on the generator motor 17 is reduced. I have to. On the other hand, the rotational reaction force of the crankshaft 12 at the time of restart is estimated based on the engine temperature state, and when the estimated rotational reaction force is small, the actual compression ratio at the time of restart is not reduced. Therefore, while reducing the load on the generator motor 17 at the time of restarting, it is possible to avoid excessive reduction of the actual compression ratio, and to suitably suppress deterioration of combustion and prolonged startup time due to the reduction. Therefore, the rotational reaction force of the crankshaft 12 at the time of starting the engine can be more efficiently reduced.
[0067]
(2) In the present embodiment, at the time of restart, the engine temperature state having a high correlation with the compression pressure in the cylinder, which is the rotational reaction force of the crankshaft 12 at the time of restart, and the mechanical friction of the internal combustion engine 10. The magnitude of the rotational reaction force is estimated. Therefore, the rotation reaction force can be easily and appropriately estimated.
[0068]
The present embodiment can be modified and implemented as follows.
(Modification 1)
In the above embodiment, the reduction of the actual compression ratio at the time of restart of the internal combustion engine 10 is achieved through the control of the valve timing of the intake valve by the variable valve timing mechanism 11. On the other hand, as a variable valve operating mechanism applied to an internal combustion engine, a mechanism that varies a cam operating angle of an engine valve, that is, a cam operating angle variable mechanism has been proposed and put into practical use. The reduction of the actual compression ratio can be similarly performed by changing the cam working angle by such a cam working angle variable mechanism.
[0069]
FIG. 7 shows an example of such a cam working angle variable mechanism. The cam working angle variable mechanism 40 illustrated in FIG. 7 is mainly configured to include a piston 41 and a casing 42.
[0070]
The intake camshaft 30 of the internal combustion engine to which the cam working angle variable mechanism 40 is applied is supported so as to be slidable in the axial direction. The cam disposed on the intake camshaft 30 is a three-dimensional cam 30b whose cam profile changes along the axial direction.
[0071]
One end of the intake-side camshaft 30 is fixed to the piston 41, and the piston 41 is accommodated inside the casing 42 so as to be slidable in the axial direction of the intake-side camshaft 30. Inside the casing 42, two pressure chambers 43 and 44 are defined by the inner wall and the piston 41. Oil is fed into each of the pressure chambers 43 and 44, and the oil pressure acts on the piston 41.
[0072]
When the oil pressures of the two pressure chambers 43 and 44 acting on the piston 41 become uneven, the piston 41 moves inside the casing 42 so as to balance the oil pressures, and as shown by arrows in FIG. The side camshaft 30 is displaced in the axial direction. As a result, the cam profile of the three-dimensional cam 30b at the position where it comes into contact with the valve lifter of the intake valve is changed, and as shown in FIG. 8, the cam working angle and the valve lift of the intake valve are changed. The electronic control unit 20 variably controls the cam working angle of the intake valve based on the oil pressure control in the pressure chambers 43 and 44.
[0073]
Here, if the cam operating angle of the intake valve at the time of restart is increased by the cam operating angle variable mechanism 40, the closing timing of the intake valve is delayed correspondingly. The actual compression ratio of the internal combustion engine is reduced by increasing the cam operating angle so that the intake valve is sufficiently opened even during the compression stroke during the closing timing.
[0074]
It is to be noted that both the cam working angle variable mechanism 40 and the variable valve timing mechanism 11 are arranged in the internal combustion engine, and the change of the cam working angle and the change of the valve timing are combined to reduce the actual compression ratio during engine stop. It is also possible to plan.
[0075]
FIG. 9 shows an example of a valve characteristic setting relating to the reduction of the actual compression ratio in such an internal combustion engine. In the setting example shown in the drawing, the cam timing of the intake valve is enlarged, the valve timing is delayed, and the closing timing is delayed while the opening timing is maintained as it is. By delaying the closing timing of the intake valve by changing both the cam working angle and the valve timing in this way, it is possible to reduce the actual compression ratio in a more suitable manner.
[0076]
(Modification 2)
In the actual compression ratio reduction process of FIG. 6, the closing timing of the intake valve at the time of restart is set to a retard setting capable of sufficiently reducing the actual compression ratio or the restart time in accordance with the rotational reaction force of the crankshaft 12. Is set to an advance setting that can be sufficiently shortened. The setting of the intake valve closing timing at the time of restart in the actual compression ratio reduction processing may be variably set between the retard setting and the advance setting according to the rotational reaction force.
[0077]
For example, FIG. 10 shows an example of a variable setting mode of the closing timing according to the estimated rotational reaction force. In the example shown in the drawing, the closing timing of the intake valve at the time of restart is set to the advance angle setting when the rotational reaction force is less than the predetermined value F1, and is set to the retard angle setting when the rotation reaction force exceeds the predetermined value F2. When the rotational reaction force is equal to or more than the predetermined value F1 and equal to or less than the predetermined value F2, the closing timing of the intake valve is gradually delayed from the value at the time of setting the advance angle to the value at the time of setting the retard angle in accordance with the increase of the rotation reaction force. Have been horned.
[0078]
(Modification 3)
Immediately after the restart is started, the generator motor 17 must rotate the crankshaft 12 only with its own output, and the rotation requires a larger torque. On the other hand, when the rotational speed of the crankshaft 12 is increased to some extent, the assist of the inertial force accompanying the rotation is obtained, so that the torque required for the generator motor 17 is relatively small.
[0079]
Therefore, it is possible to satisfactorily start the engine even if the amount of reduction of the actual compression ratio is gradually reduced in accordance with the elapsed time after the start of the restart or the increase in the engine speed during the restart. is there. In this case, while reducing the load on the generator motor 17 required for the rotation of the crankshaft 12 at the start of restart, the amount of reduction in the actual compression ratio at the start of fuel ignition can be reduced. The startability of the internal combustion engine 10 can be further improved.
[0080]
FIG. 11 shows an example of variably setting the closing timing of the intake valve according to the engine speed during restart. In the example shown in the figure, when the engine rotation speed is less than the predetermined value N1, the closing timing of the intake valve is set to the above-mentioned retard setting. When the engine speed is higher than the predetermined value N1, the closing timing of the intake valve is gradually changed from the retard setting to the advance side in accordance with the increase in the engine speed. In the example of FIG. 3, at the engine rotation speed N2 lower than the engine rotation speed N3 at which combustion is started in the internal combustion engine 10, the closing timing of the intake valve is advanced to the above-described advancement setting at which the restart time can be reduced. Have been. Therefore, while reducing the load on the generator motor 17 at the time of restart, it is possible to avoid deterioration in combustibility due to the reduction in the actual compression ratio.
[0081]
(Second embodiment)
Next, a second embodiment embodying the present invention will be described focusing on differences from the first embodiment.
[0082]
By the actual compression ratio reducing process, the closing timing of the intake valve during restart is retarded, and when the actual compression ratio of the internal combustion engine 10 is reduced, the in-cylinder pressure naturally decreases. In such a state, in order to establish combustion until the engine speed increases, the actual opening time of the intake valve during the compression stroke decreases, and the amount of air returned from the cylinder to the intake passage decreases. The required in-cylinder pressure cannot be secured. Therefore, when the actual compression ratio is reduced, the internal combustion engine 10 must be rotated by the generator motor 17 to a higher rotation speed in order to complete the start.
[0083]
On the other hand, the output performance of the generator motor 17 at the time of restart may decrease due to a decrease in the amount of power supplied from the battery 18 due to insufficient charging, a deterioration with time or demagnetization due to overheating. In such a case, it becomes difficult to increase the engine rotation speed by the generator motor 17 to a high rotation speed required to start the internal combustion engine 10 having the reduced actual compression ratio as described above, and the restart time is reduced. There is a possibility that the time may be prolonged or restart may not be possible. In addition, the decrease in the rate of increase of the engine rotation speed causes the engine rotation speed to stay longer in the resonance rotation speed range of the internal combustion engine 10, which may cause an increase in vibration and noise during restart.
[0084]
Therefore, in the present embodiment, the output performance of the generator motor 17 is estimated, and when the output performance is high, the reduction amount of the actual compression ratio at the time of restart is set smaller than when the output performance is low, that is, the intake air The valve closing timing is set to be more advanced. Thus, when the output performance of the generator motor 17 is reduced, a decrease in the in-cylinder pressure due to a reduction in the actual compression ratio is suppressed, and the internal combustion engine 10 can be restarted at a relatively low engine speed.
[0085]
In the present embodiment, the current output performance of the generator motor 17 is evaluated based on the maximum output power of the battery 18 and the allowable load factor of the generator motor 17.
[0086]
The maximum output power is obtained from the detection result of the battery sensor 24. The allowable load factor indicates the degree of the current output performance with respect to the rated output performance of the generator motor 17 as a ratio, and is determined based on the relationship between the supplied power of the generator motor 17 in operation and its output, and the like. . The allowable load factor obtained in this manner is used for various controls of the generator motor 17 as an index value of the maximum output currently allowed for the generator motor 17.
[0087]
FIG. 12 is a flowchart of “closing timing retarding amount setting processing” for setting the closing timing of the intake valve at the time of restart according to the output performance of the generator motor 17. This process is periodically executed by the electronic control unit 20 as a periodic interrupt process.
[0088]
When this process is started, first, in step S200, the maximum output power of the battery 18 and the allowable load factor of the generator motor 17 are read. Then, in the subsequent step S210, using a calculation map as exemplified in FIG. 13, based on the read maximum output power and the allowable load factor, the retard amount of the intake valve closing timing at the time of restart is determined. After the calculation, the process is temporarily terminated. The value of the retard amount of the closing timing is set based on the maximum advance of the valve timing of the intake valve by the variable valve timing mechanism 11 (retard amount = “0”).
[0089]
As shown in FIG. 13, the value of the retard amount of the closing timing is set to be smaller as the maximum output power of the battery 18 is lower and as the allowable load factor of the generator motor 17 is smaller. That is, the lower the output performance of the generator motor 17 is, the smaller the value is set.
[0090]
In this embodiment, the retard amount of the closing timing at the time of restart is the index value of the amount of reduction of the actual compression ratio. The closing timing retard amount setting process corresponds to the process of the “reduction amount setting unit”, and the generator motor 17 corresponds to the “starting motor”.
[0091]
According to the embodiment described above, the following effects can be obtained.
(3) In the present embodiment, the load on the generator motor 17 required for the rotation of the crankshaft 12 at the time of restart is reduced by reducing the actual compression ratio at the time of restart. On the other hand, when the output performance of the generator motor 17 is reduced, the reduction amount of the actual compression ratio at the time of restart is set to be smaller than when it is not. Therefore, when the output performance of the generator motor 17 is reduced, an increase in the combustible engine rotational speed in accordance with the reduction of the actual compression ratio is suppressed, so that the generator motor 17 whose output performance has been reduced can be restarted satisfactorily. become. Therefore, the rotational reaction force of the crankshaft 12 at the time of starting the engine can be more efficiently reduced.
[0092]
The embodiment described above can be modified and implemented as follows.
(Modification 4)
If the closing timing of the intake valve at the time of restart is set to a more advanced angle side, the compression pressure in the cylinder during restart excessively increases, the rotation fluctuation of the crankshaft 12 increases, and the first explosion occurs. The generated torque at the time may be excessively increased, resulting in an increase in vibration and noise during a restart or a shock. Therefore, whether or not to execute the idle stop control may be determined based on the set value of the retard amount of the closing timing. If the automatic stop / restart of the internal combustion engine 10 by the idle stop control is prohibited when the retard amount of the closing timing is set to a value that is more advanced than a certain value, the increase in the vibration and noise and the shock Can be avoided.
[0093]
FIG. 14 shows an example of a mode of determining whether or not to perform the idle stop control in accordance with the retard amount. In the example shown in the figure, when the retard amount of the intake valve closing timing at the time of the previous restart becomes a value on the more advanced side than the predetermined value β, the execution of the idle stop control is prohibited. The predetermined value β is set to a limit value on the advance side of the closing timing of the intake valve where the vibration, noise increase and occurrence of shock accompanying the advancement are within an allowable range. ing.
[0094]
Further, in the example of FIG. 5, after the execution of the idle stop control is prohibited, the predetermined amount α, which is a value that is more retarded than the predetermined value β, is greater than the predetermined value α that is more retarded. When the value becomes the value, the prohibition is released.
[0095]
In response to the prohibition of the execution of the idle stop control, a warning display notifying that the output performance of the battery 18 has decreased may be performed. However, even if there is no problem in the function of the battery 18 itself, its output may decrease at low temperatures. Therefore, such a warning is displayed when the battery 18 is sufficiently warmed up or when the outside temperature is sufficiently high. It is desirable to perform only.
[0096]
(Modification 5)
When the output performance of the generator motor 17 decreases, the rate of increase in the engine speed during restarting decreases. Therefore, the output performance of the generator motor 17 may be evaluated in accordance with the rate of increase of the engine speed during restart, and the retard amount of the closing timing may be set. That is, when it is confirmed that the rate of increase in the engine speed during the restart is low, it is determined that the output performance of the generator motor 17 is in a reduced state, and the closing timing of the intake valve is changed to the advanced side. Thus, the reduction amount of the actual compression ratio is reduced.
[0097]
Further, it is also possible to learn the retard amount thus set, and to determine an abnormality such as the output performance of the system or the battery 18 relating to the idle stop control based on the learned value.
[0098]
(Third embodiment)
Next, a description will be given of a third embodiment that embodies a start control device for an internal combustion engine of the present invention, focusing on differences from the above embodiments.
[0099]
If the reduction amount of the actual compression ratio at the time of restart is changed according to the rotational reaction force of the internal combustion engine 10 and the output performance of the generator motor 17 as described above, the state of the cylinder pressure during restart changes. In addition, the ignition timing at the time of restart, the start rotation speed of fuel injection or fuel ignition, the fuel injection amount, or the appropriate value of the control amount such as the target air-fuel ratio changes. Therefore, it is desirable to change the values of these control amounts in accordance with the setting of the retard amount of the closing timing of the intake valve at the time of restart.
[0100]
First, a description will be given of how these control amounts are set when priority is given to improving the startability. 15 shows an example of setting the ignition timing at this time, FIG. 16 shows an example of setting the target air-fuel ratio at this time, and FIG. 17 shows an example of setting the rotation speed at which fuel injection is started at this time.
[0101]
As shown in FIG. 15, when the improvement of the startability is prioritized, the ignition timing at the time of the restart is more advanced as the closing timing of the intake valve during the restart is set to the advanced side. Set to. Thus, the torque generated by the combustion is increased.
[0102]
As shown in FIG. 16, when priority is given to improvement of the startability, the target air-fuel ratio at the time of restarting is set when the closing timing of the intake valve during restarting is set to a more advanced side than a certain degree. , A value richer than the stoichiometric air-fuel ratio (for example, A / F = “12.5”). That is, the fuel injection amount at the time of restart is increased according to the advance of the closing timing.
[0103]
Further, as shown in FIG. 17, the engine speed at which fuel injection or ignition is started is reduced as the closing timing of the intake valve during restarting is set to the advanced side.
[0104]
On the other hand, when priority is given to prevention of deterioration of exhaust emission during restart, the ignition timing at restart is set to the retard side in accordance with advancement of the above-mentioned closing timing, so that the early temperature rise of the exhaust catalyst is reduced. At the same time, it is preferable to set the fuel injection amount so that the target air-fuel ratio becomes the stoichiometric air-fuel ratio.
[0105]
Furthermore, when priority is given to prevention of deterioration of vibration and noise during restart, the ignition timing at restart is set in accordance with advance of the closing timing of the intake valve during restart in order to suppress deterioration of the combustion state. It is preferable to set the fuel injection amount such that the target air-fuel ratio is set to the stoichiometric air-fuel ratio while setting the fuel injection amount to the retard side.
[0106]
In this embodiment, the change of each control amount at the time of the restart corresponds to the process of the "start control changing means".
Each of the embodiments described above can be further modified and implemented as follows.
[0107]
In each of the above embodiments, the restart state (the rate of increase of the engine speed, the time required for the completion of the restart, and the like) is detected, and based on the detected quality of the restart state, The setting of the amount of delay of the closing timing of the intake valve, that is, the amount of reduction in the actual compression ratio, may be changed. As a result, it becomes possible to absorb the effects of the aging and individual differences of the internal combustion engine 10 and to more appropriately reduce the rotational reaction force at the time of restart.
[0108]
In the first embodiment, the rotational reaction force at the time of restart is estimated based on the coolant temperature. However, the same estimation is performed on the internal combustion engine 10 and the automatic transmission 13 in addition to the coolant temperature. It can also be performed based on the temperature of the supplied oil, the elapsed time after stopping, or a combination thereof. In short, if a parameter representing the engine temperature state is used, the rotation reaction force of the crankshaft 12 at the time of restart can be easily and appropriately performed.
[0109]
When restarting is performed in a state where the internal combustion engine 10 and the automatic transmission 13 are drivingly connected, the friction torque according to the rotation of the automatic transmission 13 greatly affects the rotational reaction force of the crankshaft 12. Therefore, in such a case, it is desirable to take the temperature of the oil supplied to the automatic transmission 13 into consideration in the estimation.
[0110]
In addition, if there is a parameter other than the above parameters indicating the engine temperature state that affects the rotational reaction force of the crankshaft 12 at the time of restart, similar estimation may be performed using the parameter.
[0111]
-The actual compression ratio reduction process of the first embodiment and the closing timing retard amount setting process of the second embodiment may be performed together. In this case, the effects of both embodiments can be enjoyed together.
[0112]
The evaluation of the output performance of the generator motor 17 in the closing timing retard amount setting process in FIG. 12 may be performed based on other parameters such as the charge amount of the battery 18, for example.
[0113]
The configurations of the variable valve timing mechanism 11 and the cam working angle variable mechanism 40 are not limited to those exemplified above, such as an electrically driven mechanism, and may be arbitrarily changed. In short, any mechanism that can change the valve timing and cam working angle of the intake valve can delay the closing timing of the intake valve to reduce the actual compression ratio.
[0114]
Even if the actual compression of the internal combustion engine 10 can be changed by means other than retarding the closing timing of the intake valve, the actual compression ratio may be reduced by using the means. good.
[0115]
The control at the time of restart in each of the above embodiments is not limited to the restart of the internal combustion engine 10 by idling stop, but may be applied to the control of normal engine start by operating the ignition switch 25.
[0116]
Even in a hybrid vehicle having two driving sources, an internal combustion engine and an electric motor, and switching the driving source according to the situation, the internal combustion engine is automatically stopped and automatically started according to the switching of the driving source. The starting control of each of the above embodiments can be applied to the start of the internal combustion engine employed in such a hybrid vehicle. In this case, the same effects as those of the above embodiment or effects similar thereto can be obtained.
[0117]
Further, for an internal combustion engine that does not automatically stop the internal combustion engine 10 as described above, the control at the time of starting in each of the above embodiments can be applied as the control for starting the engine.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the entire structure of a first embodiment of the present invention.
FIG. 2 is a perspective sectional view of a variable valve timing mechanism applied to the embodiment.
FIG. 3 is a control mode diagram of an idle stop control of the embodiment.
FIG. 4 is an exemplary view showing an example of a valve timing setting in an actual compression ratio reduction process of the embodiment.
FIG. 5 is a graph showing a relationship among a cooling water temperature, a friction torque, and a compression reaction force.
FIG. 6 is a flowchart of an actual compression ratio reduction process in the embodiment.
FIG. 7 is a perspective sectional view of a cam working angle variable mechanism applied to a modification of the embodiment;
FIG. 8 is a time chart showing a valve lift curve in the internal combustion engine to which the variable cam working angle mechanism is applied.
FIG. 9 is a view showing an example of a valve timing setting in an actual compression ratio reducing process using the variable cam working angle mechanism and the variable valve timing mechanism.
FIG. 10 is a graph showing an example of a variable setting mode of an intake valve closing timing according to a rotational reaction force.
FIG. 11 is a graph showing an example of setting an intake valve closing timing according to an engine rotation speed.
FIG. 12 is a flowchart of a closing timing delay amount setting process according to the second embodiment.
FIG. 13 is a graph showing an example of setting the intake valve closing timing according to the output performance of the generator motor.
FIG. 14 is a diagram showing an example of a mode of determining whether or not idle stop control is possible according to an intake valve closing timing delay amount;
FIG. 15 is a graph showing an example of setting an ignition timing according to a setting of a retard amount.
FIG. 16 is a graph showing a setting example of a target air-fuel ratio according to a setting of a retard amount.
FIG. 17 is a graph showing a setting example of an injection start rotation speed according to a setting of a retard amount.
[Explanation of symbols]
Reference Signs List 10 internal combustion engine, 11 variable valve timing mechanism (VVT: 31 vane rotor, 32 housing, 34 vane, 35 recess, 36, 37 pressure chamber), 12 crankshaft, 13 automatic transmission, 14 ... Starter, 15 ... Electromagnetic clutch, 16 ... Belt transmission mechanism, 17 ... Generator motor, 18 ... Battery, 20 ... Electronic control device, 21 ... Rotation speed sensor, 22 ... Vehicle speed sensor, 23 ... Water temperature sensor, 24 ... Battery sensor 24 ... ignition switch, 30 ... intake side camshaft, 30a ... cam, 30b ... three-dimensional cam, 33 ... cam sprocket, 33a ... timing belt, 40 ... cam working angle variable mechanism (41 ... piston, 42 ... casing, 43, 44) ... pressure chamber).

Claims (8)

In a start control device for an internal combustion engine including an actual compression ratio reducing unit that reduces an actual compression ratio during engine start,
Rotation reaction force estimation means for estimating the magnitude of the rotation reaction force during engine start,
When the rotation reaction force estimated by the rotation reaction force estimation means is small, the reduction amount for setting the reduction amount of the actual compression ratio by the actual compression ratio reduction means to be smaller than when the rotation reaction force is large. Setting means;
A start control device for an internal combustion engine, comprising: 2. The internal combustion engine start control device according to claim 1, wherein the reduction amount setting unit prohibits the reduction of the actual compression ratio by the actual compression ratio reduction unit when the estimated rotational reaction force is equal to or less than a predetermined value. 3. The start control device for an internal combustion engine according to claim 1, wherein the rotation reaction force estimation unit estimates the magnitude of the rotation reaction force based on an engine temperature state. 4. In a start control device for an internal combustion engine including an actual compression ratio reducing unit that reduces an actual compression ratio during engine start,
When the output performance of the starting motor that rotates the engine output shaft during engine start is in a state of deterioration, the amount of reduction of the actual compression ratio by the actual compression ratio reducing means is set smaller than when it is not. A start control device for an internal combustion engine, comprising a reduction amount setting unit. 5. The start control device for an internal combustion engine according to claim 1, wherein the actual compression ratio reducing unit reduces the actual compression ratio by delaying a closing timing of an intake valve. 6. The start control device for an internal combustion engine according to any one of claims 1 to 5,
Based on the reduction amount of the actual compression ratio set by the reduction amount setting means, the ignition timing at the time of engine start, the engine rotation speed at which fuel injection is started, the engine rotation speed at which ignition is started, the fuel injection amount, the target idle A start control device for an internal combustion engine, further comprising start control changing means for changing at least one of the fuel ratios. The start control device for an internal combustion engine according to any one of claims 1 to 6, wherein the internal combustion engine is automatically stopped and restarted in accordance with a traveling state of a vehicle equipped with the internal combustion engine. 8. The start control apparatus for an internal combustion engine according to claim 7, wherein whether to execute the automatic stop / restart is determined based on the reduction amount of the actual compression ratio at the time of the previous start set by the reduction amount setting means.

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