JP5482010B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly, to a control device suitable for controlling an internal combustion engine having an electric variable valve mechanism.

  Conventionally, for example, Patent Literature 1 discloses a start control device for an internal combustion engine. In this conventional start control device, in order to suppress the occurrence of self-ignition when the internal combustion engine is started, when it is determined that the possibility of self-ignition is higher than a predetermined level, the pressure in the combustion chamber is set to a predetermined level. The internal combustion engine is started after the valve operating characteristics of the intake and exhaust valves are changed by the valve operating mechanism so that the pressure does not rise above the pressure.

JP-A-2005-48718 JP 2007-292061 A JP 2007-198308 A

  As a variable valve mechanism that can change the opening / closing timing of an intake valve or an exhaust valve, a hydraulic or electric variable valve mechanism that uses a hydraulic or electric motor as a drive source is known. If an attempt is made to adjust the opening / closing timing of the intake valve or the like at the start of the hydraulic variable valve mechanism, since the operation is after the start of cranking, the start of the internal combustion engine may be delayed. Moreover, if it is an electric variable valve mechanism, an operation | movement can be started before cranking start, when a starting request | requirement is detected. However, when the temperature is extremely low, the viscosity of the lubricating oil increases, so that friction increases. Therefore, in order to operate the electric variable valve mechanism at the start from the cryogenic state, a large electric motor is required.

  The present invention has been made in order to solve the above-described problems, and does not cause an increase in the size of the electric motor, so that the closing timing of the intake valve at the start can be appropriately set regardless of the temperature conditions at the start. An object of the present invention is to provide a control device for an internal combustion engine that can be controlled to a value.

A first invention is a control device for an internal combustion engine,
An electric variable valve mechanism capable of changing the closing timing of the intake valve using an electric motor as a drive source;
Temperature acquisition means for acquiring engine temperature;
A closing timing setting means for setting a closing timing of the intake valve at the time of starting the internal combustion engine based on the engine temperature of the internal combustion engine being stopped;
When the engine temperature of the internal combustion engine that is stopped is lower than a predetermined determination value, the electric variable operation is performed so that the closing timing of the intake valve set by the closing timing setting means is reached. Control means for controlling the valve mechanism;
Equipped with a,
Battery state detecting means for detecting a state of a battery for supplying electric power to the electric motor;
Determination value changing means for changing the determination value of the engine temperature in accordance with the state of the battery;
Further comprising wherein the Rukoto a.

According to the first aspect of the present invention, when the engine temperature of the internal combustion engine that is stopped is lower than a predetermined determination value, the intake valve is closed at the start for improving the startability of the internal combustion engine. The valve timing is adjusted in advance while the internal combustion engine is stopped. This makes it possible to appropriately adjust the closing timing of the intake valve for the next start before the engine temperature drops too much while the internal combustion engine is stopped. For this reason, the closing timing of the intake valve at the start can be controlled to an appropriate value regardless of the temperature condition at the start without causing an increase in the size of the electric motor provided in the variable valve mechanism. . According to the present invention, the determination value of the engine temperature for determining whether or not to adjust the closing timing of the intake valve while the internal combustion engine is stopped is changed according to the state of the battery. Thus, it is possible to reliably control the closing timing of the intake valve for starting, regardless of the state of the battery (battery capacity or degree of deterioration).

It is a figure for demonstrating the structure of the internal combustion engine of Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. 3 is a flowchart showing a control routine for closing timing of an intake valve that is suitable for execution when the internal combustion engine is started. It is a figure showing the relationship of the map referred in FIG. 3 is a flowchart showing a control routine for closing timing of an intake valve that is suitable for execution when the internal combustion engine is started. 4 is a flowchart showing a control routine for closing timing of an intake valve suitable for execution when starting an internal combustion engine in a system including a hydraulic variable valve mechanism.

Embodiment 1 FIG.
FIG. 1 is a diagram for explaining a configuration of an internal combustion engine 10 according to a first embodiment of the present invention. The system of this embodiment includes an internal combustion engine 10. The system of this embodiment uses a mixed fuel in which a hydrocarbon fuel (here, gasoline as an example) and an alcohol fuel (here, ethanol as an example) are mixed at a predetermined ratio.

  A piston 12 is provided in the cylinder of the internal combustion engine 10. A combustion chamber 14 is formed in the cylinder of the internal combustion engine 10 on the top side of the piston 12. An intake passage 16 and an exhaust passage 18 communicate with the combustion chamber 14.

  An air flow meter 20 that outputs a signal corresponding to the flow rate of air sucked into the intake passage 16 is provided in the vicinity of the inlet of the intake passage 16. A throttle valve 22 is provided downstream of the air flow meter 20. The throttle valve 22 is an electronically controlled throttle valve that can control the throttle opening independently of the accelerator opening. In the vicinity of the throttle valve 22, a throttle sensor 24 for detecting the throttle opening is disposed. The intake passage 16 (surge tank) downstream of the throttle valve 22 is provided with an intake air temperature sensor 26 for detecting the temperature of intake air at that portion.

  A fuel injection valve 28 for injecting fuel into the intake port of the internal combustion engine 10 is disposed downstream of the throttle valve 22. A spark plug 30 is attached to the cylinder head provided in the internal combustion engine 10 so as to protrude from the top of the combustion chamber 14 into the combustion chamber 14. The intake port and the exhaust port are respectively provided with an intake valve 32 and an exhaust valve 34 for bringing the combustion chamber 14 and the intake passage 16 or the combustion chamber 14 and the exhaust passage 18 into a conduction state or a cutoff state.

  The system shown in FIG. 1 includes a variable valve mechanism 36 for opening and closing the intake valve 32. The variable valve mechanism 36 of the present embodiment is an electric variable valve mechanism (electric VVT mechanism) that continuously varies the phase of an intake cam (not shown) that drives the intake valve 32 using an electric motor as a drive source. ). A cam angle sensor 38 for detecting the rotational position (advance amount) of the intake camshaft is attached in the vicinity of the intake camshaft (not shown).

  The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 40. In addition to the various sensors described above, the ECU 40 inputs the crank angle sensor 42 for detecting the engine speed, the water temperature sensor 44 for detecting the cooling water temperature of the internal combustion engine 10, and the lubricating oil temperature of the internal combustion engine 10. An oil temperature sensor 46 for detection, an ethanol concentration sensor 48 for detecting the concentration of ethanol contained in the fuel supplied to the internal combustion engine 10, and an ignition switch (IG switch) 50 for the vehicle are connected. The various actuators described above are connected to the output of the ECU 40. The ECU 40 can control the operating state of the internal combustion engine 10 based on the sensor outputs. Further, the ECU 40 is configured to detect the battery capacity (deterioration degree) Bv of the battery 52 that supplies electric power to the electric motor provided in the variable valve mechanism 36 based on the voltage of the battery 52 and the like.

Ethanol fuel has the characteristics of poor evaporation characteristics at low temperatures and the high octane number that makes it difficult to knock. Therefore, in order to ensure good startability in the system of the present embodiment using fuel containing ethanol fuel, the intake valve 32 is closed at the start according to the ethanol concentration E% and the cooling water temperature. It is possible to adjust the timing tinc. More specifically, the ethanol concentration E% is high and the cooling water temperature is low Ihodo, closing timing of the intake valve 32 at the start tinc that is adjusted to more a timing close to the intake bottom dead center Conceivable. When the closing timing tinc of the intake valve 32 is closer to the intake bottom dead center, the actual compression ratio of the internal combustion engine 10 is increased (the compression end temperature is increased), and fuel vaporization is promoted. Can be improved.

  However, when the temperature is extremely low, the viscosity of the lubricating oil increases, so that friction increases. Therefore, a large electric motor is required to operate the electric variable valve mechanism 36 so that the target closing timing tinc of the intake valve 32 can be obtained at the time of starting from a cryogenic state. . Increasing the size of the electric motor causes an increase in cost and leads to deterioration of the mountability of the variable valve mechanism 36 to the internal combustion engine 10.

  Therefore, in the present embodiment, the cooling water temperature s-thw (which may be the stopped lubricating oil temperature s-oil) after the internal combustion engine 10 is stopped is monitored, and the internal combustion engine 10 is stopped (vehicle soak). When the cooling water temperature s-thw falls below the predetermined judgment value, the target value according to the current ethanol concentration E% and the cooling water temperature s-thw (to improve startability) The valve closing timing tinc of the intake valve 32 is adjusted by using the variable valve mechanism 36 so that the target valve value becomes equal to the target value).

  Furthermore, in this embodiment, when the charge capacity of the battery 52 is reduced based on the detection result of the battery capacity Bv, the determination value of the coolant temperature s-thw is changed. More specifically, when the charge capacity of the battery 52 is reduced, the determination value is changed to a higher temperature value.

  FIG. 2 is a flowchart of a routine executed by the ECU 40 in the first embodiment in order to realize the above function. The ECU 40 has a built-in soak timer for counting the elapsed time from when the IG switch 50 of the vehicle is turned off. This routine is started every time a predetermined time (for example, 2 hours) is counted by the soak timer during soaking of the vehicle.

  In the routine shown in FIG. 2, it is first determined whether or not the flag XS-VVT is 0 (step 100). This flag XS-VVT is a flag for determining whether or not the control of the closing timing tinc of the intake valve 32 for improving the startability has been executed while the internal combustion engine 10 is stopped.

  If it is determined in step 100 that the flag XS-VVT is not 0, that is, XS-VVT = 1, the control of the closing timing tinc of the intake valve 32 has already been performed during the current stop of the internal combustion engine 10. Is determined to have been executed, and the current processing cycle is immediately terminated. On the other hand, if it is determined in step 100 that the flag XS-VVT = 0, that is, it is determined that the control of the closing timing tinc of the intake valve 32 is not yet executed while the internal combustion engine 10 is stopped this time. If possible, the coolant temperature s-thw when the internal combustion engine 10 is stopped (during vehicle soak) is then acquired (step 102).

  Next, it is determined whether or not the coolant temperature s-thw acquired in step 102 is lower than a predetermined determination value (for example, 20 ° C.) (step 104). As a result, if the cooling water temperature s-thw <20 ° C. is established, then the current ethanol concentration E% is acquired (step 106).

  Next, the battery capacity (deterioration degree) Bv at the time before the internal combustion engine 10 is stopped is taken in (step 108). Then, it is determined whether or not the captured battery capacity Bv> predetermined determination value β is satisfied (step 110). This determination value β is a value for determining whether or not the charge capacity of the battery 52 has decreased to the extent that it is necessary to change the determination value of the cooling water temperature s-thw to a higher value. It is.

  If it is determined in step 110 that the battery capacity Bv> the determination value β is satisfied, it can be determined that the battery capacity Bv has not decreased to the level determined as described above. In this case, it is then determined whether or not the cooling water temperature s-thw acquired in step 102 is lower than a predetermined determination value (for example, 0 ° C.) (step 112).

As a result, when the cooling water temperature s-thw <0 ° C. is established, the valve closing timing tinc of the intake valve 32 is controlled so that the target value according to the ethanol concentration E% and the cooling water temperature s-thw is obtained. (Step 114). This target value is, as described above, a value for the favorable startability of the internal combustion engine 10, the ethanol concentration E% is high and the cooling water temperature is low Ihodo, intake valve at start The valve closing timing tinc of 32 is set so as to be closer to the intake bottom dead center (so that the actual compression ratio becomes higher). Further, when the processing of step 114 is executed, the XS-VVT flag is set to 1 (step 116).

  On the other hand, if it is determined in step 110 that the battery capacity Bv> the determination value β is not established, it can be determined that the battery capacity Bv has decreased to the level determined as described above. . In this case, at the present time (that is, when it is determined that the coolant temperature s-thw has become lower than the determination value (20 ° C.) on the high temperature side) Control is executed immediately.

  According to the routine shown in FIG. 2 described above, when the cooling water temperature s-thw is lower than the determination value (20 ° C. or 0 ° C.) while the internal combustion engine 10 is stopped (during vehicle soak), the internal combustion engine The adjustment of the closing timing tinc of the intake valve 32 at the time of starting to improve the starting property of the engine 10 is performed in advance while the internal combustion engine 10 is stopped. As a result, the closing timing tinc of the intake valve 32 can be appropriately adjusted for the next start before the cooling water temperature s-thw decreases too much while the internal combustion engine 10 is stopped. . For this reason, the valve closing timing tinc of the intake valve 32 at the start can be controlled to an appropriate value regardless of the temperature condition at the start, without increasing the size of the electric motor provided in the variable valve mechanism 36. It becomes like this.

  Further, according to the above routine, the coolant temperature s for determining whether or not to adjust the closing timing tinc of the intake valve 32 while the internal combustion engine 10 is stopped according to the battery capacity Bv (state of the battery 52). The above-described determination value (20 ° C. or 0 ° C.) of -thw is changed. Thereby, it is possible to reliably control the closing timing tinc of the intake valve 32 for starting regardless of the degree of deterioration of the battery 52.

[Other controls]
Next, in order to improve the startability of the internal combustion engine 10, control of the closing timing tinc of the intake valve 32 that is suitable for execution when the internal combustion engine 10 is started (when a start request is detected) is performed. Will be described.
FIG. 3 is a flowchart showing a control routine for the closing timing tinc of the intake valve 32, which is suitable for execution when the internal combustion engine 10 is started.

  In the routine shown in FIG. 3, first, based on a signal from the IG switch 50, it is determined whether or not there is a request for starting the internal combustion engine 10 (engine start) (step 200). As a result, when the determination in step 200 is not established, that is, after the internal combustion engine 10 is started, the VVT control after the engine is started, more specifically, the operating state of the internal combustion engine 10 after the start is performed. The control of the closing timing of the intake valve 32 according to the control is executed (step 202).

  On the other hand, if it is determined in step 200 that there is a request for starting the internal combustion engine 10, the starting water temperature thws, the starting intake air temperature thas, and the ethanol concentration E% are acquired (steps 204 to 208).

  Next, the closing timing tinc of the intake valve 32 corresponding to the starting water temperature thws, the starting intake temperature thas, and the ethanol concentration E% is calculated (step 210). The ECU 40 stores a map that defines the closing timing tinc of the intake valve 32 in relation to the starting water temperature thws, the starting intake temperature thas, and the ethanol concentration E%, and refers to such a map. Then, the closing timing tinc of the intake valve 32 is calculated. FIG. 4 is a diagram showing the relationship of such a map.

  According to the relationship shown in FIG. 4, the lower the starting water temperature thws and the higher the ethanol concentration E%, the closer the closing timing tinc of the intake valve 32 becomes closer to the intake bottom dead center (that is, It is set so that the actual compression ratio becomes high. In addition, as the starting water temperature thws is higher and the starting intake air temperature thas is higher, the closing timing tinc of the intake valve 32 is more distant from the intake bottom dead center (ie, closer to the intake top dead center). (That is, the actual compression ratio becomes low).

  Next, the valve closing timing tinc of the intake valve 32 is controlled using the electric variable valve mechanism 36 so as to be the valve closing timing tinc calculated according to the above relationship (step 212). Next, the internal combustion engine 10 is started (cranking and a predetermined starting operation thereafter) (step 214).

  In systems using ethanol-mixed fuel, fuel vaporization is accelerated as described above by controlling the actual compression ratio to be higher as the starting water temperature thws is lower and the ethanol concentration E% is higher. Therefore, startability can be improved. However, if such control is performed, the knock at the start becomes severe at the time of high temperature restart. The condition that the knocking at the high temperature restart becomes severe is the condition that the intake air temperature in the combustion chamber at the start of compression is high. Under such conditions, even when the octane number of the fuel is high due to the high ethanol concentration, the knocking becomes severe. Therefore, in order to perform optimal control, the correction of the closing timing tinc of the intake valve 32 is performed. Is required. The intake air temperature when compression is started at the time of starting is substantially determined by the intake air temperature remaining in the combustion chamber and the intake air temperature remaining in the surge tank when the internal combustion engine 10 is stopped. Moreover, since the temperature in the combustion chamber is affected by the water temperature, correction with the water temperature is also necessary.

  According to the routine shown in FIG. 3 described above, the closing timing tinc of the intake valve 32 at the start is adjusted so that the actual compression ratio becomes higher as the starting water temperature thws is lower and the ethanol concentration E% is higher. When the starting water temperature thws is high and the starting intake air temperature thas is high, the closing timing tinc of the intake valve 32 at the start is corrected so that the actual compression ratio is low. For this reason, it is possible to suitably achieve both startability improvement and knock avoidance under any starting conditions.

Further, when controlling the closing timing tinc of the intake valve 32 in the routine shown in FIG. 3, the difference between the actual IN closing timing Tinc and the target IN closing timing tinc is avoided in order to avoid knocking at a high temperature start. The fuel cut may be performed until Δtinc becomes sufficiently small.
FIG. 5 is a flowchart showing a control routine for the closing timing tinc of the intake valve 32 in which such a fuel cut is performed in addition to the processing shown in FIG. In FIG. 5, the same steps as those shown in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 5, after the control of the closing timing tinc of the intake valve 32 is started so as to reach the target IN closing timing tinc in step 212, then the actual IN closing timing Tinc and the target IN closing timing are set. A difference Δtinc from the timing tinc is calculated (step 300). Next, it is determined whether or not the difference Δtinc is equal to or smaller than a predetermined value α (step 302).

  In step 302, while the difference Δtinc ≦ predetermined value α is not established, fuel cut is performed (step 304). On the other hand, when it is determined that the above difference Δtinc ≦ predetermined value α is established, fuel cut is prohibited and a predetermined starting operation of the internal combustion engine 10 is performed (step 306).

  According to the routine shown in FIG. 5 described above, it is possible to avoid the occurrence of knocking at the start due to the operation delay of the electric variable valve mechanism 36. Further, at the time of high temperature restart, the friction is small and the responsiveness of the variable valve mechanism 36 is increased. For this reason, even if the fuel injection is started after the valve closing timing tinc of the intake valve 32 moves to a position away from the intake bottom dead center, the deterioration of the startability hardly becomes a problem.

  In the above description, the control of the system including the electric variable valve mechanism 36 has been described. Incidentally, even in a system including a hydraulic variable valve mechanism (not shown), in order to ensure a good startability, the closing timing of the intake valve 32 at the start-up depends on the ethanol concentration E% and the coolant temperature. It is desirable to adjust tinc.

  However, in the case of a hydraulic variable valve mechanism, the oil viscosity becomes high under extremely low temperature conditions, and the response in a low temperature range is greatly deteriorated. For this reason, it is difficult to control the closing timing tinc of the intake valve 32 to the target value when cranking is performed at a low temperature start. Therefore, in order to ensure startability at low temperature start, the closing timing tinc of the intake valve 32 is controlled to the intake bottom dead center side during the stop operation of the internal combustion engine 10 in response to the stop request, and the high temperature restart is performed. When the engine is started, it is preferable to control the closing timing tinc of the intake valve 32 to the intake top dead center side during cranking. Further, when performing the control as described above, it is desirable to also perform the control of the routine shown in FIG.

FIG. 6 is a flowchart showing a control routine for the closing timing tinc of the intake valve 32 that is suitable for execution when the internal combustion engine 10 is started in a system including a hydraulic variable valve mechanism.
In the routine shown in FIG. 6, first, based on the signal from the IG switch 50, it is determined whether or not there is a request for stopping the internal combustion engine 10 (step 400). As a result, when it is determined that there is no stop request, that is, when the internal combustion engine 10 is in operation, the VVT control after engine startup, more specifically, the operation state of the internal combustion engine 10 after startup is performed. The control of the closing timing of the intake valve 32 according to the control is executed (step 402).

  On the other hand, if it is determined in step 400 that there is a request to stop the internal combustion engine 10, the current (stopped) cooling water temperature (water temperature) thw (or oil temperature toil) is acquired (step 404). Next, it is determined whether or not the acquired water temperature thw is higher than a predetermined determination value (for example, 110 ° C.) (step 406).

  As a result, when the water temperature thw when the internal combustion engine 10 is stopped is equal to or lower than the above-described determination value, the control for adjusting the closing timing tinc of the intake valve 32 to the intake bottom dead center side is performed as prescribed (step). 408). On the other hand, when the water temperature thw when the internal combustion engine 10 is stopped is higher than the determination value, the control for adjusting the closing timing tinc of the intake valve 32 to the intake bottom dead center side is prohibited (step 410). In step 410, instead of prohibiting the control, the closing timing tinc of the intake valve 32 is controlled at a low temperature start request (control to the intake bottom dead center side) and a high temperature start request (control to the intake top dead center side). ), The control amount may be suppressed.

  After the processing of step 408 or 410 is executed, it is determined whether or not the control of the closing timing tinc of the intake valve 32 has been completed (position control when VVT is stopped) (step 412). As a result, when the completion of the control is recognized, a stop process (fuel cut) of the internal combustion engine 10 is performed (step 414).

  According to the routine shown in FIG. 6 described above, the closing timing tinc of the intake valve 32 is controlled to the intake bottom dead center side during the stop operation of the internal combustion engine 10 in response to the stop request, and the high temperature restart is performed. In the system that controls the closing timing tinc of the intake valve 32 to the intake top dead center side during cranking, the water temperature thw (or the oil temperature toil) when the internal combustion engine 10 is stopped (during the stop operation). Is higher than a certain level, the control of the closing timing tinc of the intake valve 32 toward the intake bottom dead center at the time of the stop is prohibited.

  When the temperature of the lubricating oil is high, the viscosity of the oil becomes very small, and the lubricating oil leaks from each clearance portion of the hydraulic system. As a result, even when the valve closing timing tinc of the intake valve 32 is controlled using the hydraulic variable valve mechanism at the start (cranking) of the internal combustion engine 10, the hydraulic variable valve mechanism is excellent due to insufficient hydraulic pressure. Therefore, it is difficult to operate, and there is a concern that knocking may occur at the start. Moreover, when the control routine shown in FIG. 5 is used to start (fuel injection) after the hydraulic variable valve mechanism is actuated to some extent during high temperature restart, the high temperature restart time becomes very long. There is a fear. On the other hand, according to the control of the above routine, in a system having a hydraulic variable valve mechanism, the adjustment of the closing timing tinc of the intake valve 32 is ensured when the internal combustion engine 10 is stopped for the case where the cold start is performed. The occurrence of knocking can be suppressed when a high-temperature restart is performed.

In the first embodiment described above, the ECU 40 executes the process of step 102, whereby the “temperature acquisition means” in the first invention executes the process of step 114. The “valve closing timing setting means” and the “control means” in the present invention are each realized.
Further, in the first embodiment described above, the ECU 40 executes the process of step 108, so that the “battery state detecting means” in the first aspect of the present invention is changed thereafter according to the determination result of step 110. By changing the processing, the “determination value changing means” in the first aspect of the invention is realized.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 16 Intake passage 18 Exhaust passage 26 Intake temperature sensor 32 Intake valve 34 Exhaust valve 36 Electric variable valve mechanism 38 Cam angle sensor 40 ECU (Electronic Control Unit)
44 Water temperature sensor 46 Oil temperature sensor 48 Ethanol concentration sensor 50 Ignition switch (IG switch)
52 battery

Claims (1)

An electric variable valve mechanism capable of changing the closing timing of the intake valve using an electric motor as a drive source;
Temperature acquisition means for acquiring engine temperature;
A closing timing setting means for setting a closing timing of the intake valve at the time of starting the internal combustion engine based on the engine temperature of the internal combustion engine being stopped;
When the engine temperature of the internal combustion engine that is stopped is lower than a predetermined determination value, the electric variable operation is performed so that the closing timing of the intake valve set by the closing timing setting means is reached. Control means for controlling the valve mechanism;
Equipped with a,
Battery state detecting means for detecting a state of a battery for supplying electric power to the electric motor;
Determination value changing means for changing the determination value of the engine temperature in accordance with the state of the battery;
Further comprising a control system for an internal combustion engine characterized by Rukoto a.

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