JP2007321651A - Start control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely prevent a battery voltage from falling to less than a voltage lower limit while an engine is started even if the temperature of a battery for supplying a power to a starter motor for starting the engine is low. <P>SOLUTION: When the battery temperature is less than a predetermined determination value α while the engine is started, the starter motor is actually driven with a trial cranking torque Tg to determined whether the crankshaft of the engine is rotated or not. When the crankshaft is not rotated, in consideration of a battery voltage reduction ratio [ΔVB/Δt], the trial cranking torque is gradually increased (steps ST1 to ST8). Consequently, the starter motor can be driven with a proper cranking torque matching the state of the engine. Also, even if the temperature of the battary is low, the battery voltage can be surely prevented from falling to less than the voltage lower limit. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a start control device for an internal combustion engine.

  When starting an internal combustion engine (hereinafter also referred to as an engine) mounted on an automobile or the like, the engine is cranked by supplying electric power from the battery to the starter motor by operating the ignition switch (IG-ON). Yes. Along with the cranking, fuel is supplied into the combustion chamber of the engine and the ignition plug is ignited to start the engine.

  In recent years, from the viewpoint of environmental protection, in an automobile equipped with an engine, for the purpose of improving fuel efficiency and reducing emissions, when a predetermined condition is satisfied when the automobile stops at an intersection signal, etc., Idling stop control that stops fuel supply (fuel cut) and stops the engine is adopted.

  In addition, when a predetermined engine start condition is satisfied from a state where the engine is stopped by the idling stop, cranking is performed by an electric motor such as a starter motor to restart the engine. As an automobile to which such idling stop control is applied, there is a so-called eco-run vehicle or a hybrid vehicle in which an engine and an electric motor such as a motor generator are mounted as a drive source.

  By the way, the capacity of a battery mounted on an automobile or the like varies depending on the outside air temperature. That is, the capacity of the battery at a low temperature (for example, −20 ° C.) is lower than the capacity of the battery at a normal temperature (for example, 20 ° C.). For this reason, if electric power corresponding to the engine starting torque (reference cranking torque) is supplied to an electric motor such as a starter motor at low temperatures, the battery voltage may fall below the lower voltage limit, and the battery may be damaged. There is.

As technologies that take into consideration the battery capacity and cranking torque at the time of starting, for example, there are technologies described in Patent Documents 1 and 2 below. In the technique disclosed in Patent Document 1, a torque limit value of the starter motor is calculated according to the battery temperature, and the starter motor is started so that the rotational speed of the starter motor matches the target rotational speed within the range of the torque limit value. By controlling the driving torque of the motor, the output voltage of the battery is prevented from being lowered or prematurely deteriorated. In the technique described in Patent Document 2, the driving torque of the motor (starter motor) at the start of the internal combustion engine is calculated in consideration of the maximum power that can be supplied by the battery and the energy loss at the time of cranking, The motor is driven using the drive torque obtained by this calculation.
JP 2004-044522 A JP-A-2005-180230 JP 2003-328910 A

  By the way, in the techniques described in the above-mentioned Patent Documents 1 and 2, etc., the cranking torque at the start is calculated by estimating the battery temperature / voltage, energy loss, etc. based on the detection values of various sensors. The estimation / calculation process inevitably includes errors. For this reason, it is difficult to perform the start control that accurately reflects the actually required cranking torque, and there is a possibility that the battery voltage falls below the voltage lower limit value at the start when the battery temperature is low.

  The present invention has been made in consideration of such circumstances, and even when the temperature of the battery supplying electric power to the engine starting motor is low, the battery voltage is reliably prevented from falling below the lower voltage limit at the time of starting. It is an object of the present invention to provide a start control device for an internal combustion engine that can be used.

  The start control device of the present invention includes an electric motor that starts an internal combustion engine, a battery that supplies electric power to the electric motor, battery temperature detection means that detects the temperature of the battery, and control means. When the battery temperature detected by the battery temperature detection means is less than a predetermined value when the internal combustion engine is started, the control means uses the trial cranking torque set lower than the reference cranking torque. When cranking is attempted by driving an electric motor, and the crankshaft of the internal combustion engine does not rotate, considering the rate of decrease in battery voltage per unit time, the cranking torque for trial is gradually increased to perform cranking. It is characterized by trying.

  In the present invention, when the battery temperature is lower than a predetermined value when the internal combustion engine is started, first, a trial cranking torque set to be smaller than a preset reference cranking torque (for example, a torque of 10% of the reference cranking torque). ) To drive the electric motor (starter motor) and try cranking. If the crankshaft of the internal combustion engine does not rotate in this cranking trie, increase the trial cranking torque and perform the cranking trie again. repeat. In this way, the cranking motor is actually driven to determine whether or not the crankshaft of the internal combustion engine rotates, and the cranking torque is gradually increased to perform the process of gradually increasing the internal combustion engine at the start. It becomes possible to find an appropriate cranking torque corresponding to the engine state (for example, energy loss). This makes it possible to perform start control that accurately reflects the cranking torque that is actually required at the start, compared to the case where the cranking torque is obtained by calculation, and at the start when the battery temperature is low. However, the possibility that the battery voltage falls below the voltage lower limit value is reduced. In addition, considering the battery voltage decrease rate per unit time, if the battery voltage decrease rate is greater than or equal to a predetermined value and the battery voltage may fall below the lower voltage limit, a cranking trie, that is, power from the battery to the motor By prohibiting the supply, it is possible to reliably prevent the battery voltage from falling below the voltage lower limit value.

  In the present invention, battery voltage detection means for detecting the voltage of the battery is provided, the battery temperature detected by the battery temperature detection means is less than a predetermined value, and the battery voltage detected by the battery voltage detection means is less than a predetermined value. Only in this case, the motor may be driven by the trial cranking torque so as to try the cranking.

  If such a configuration is adopted, it is determined that there is no possibility that the battery will deteriorate due to the cranking when the battery voltage is sufficiently high above the predetermined value, and the motor is driven with the cranking torque for trial use. Without this, it becomes possible to drive the motor with the reference cranking torque. Thereby, even when the battery temperature is low, the cranking trie can be omitted when the battery voltage is sufficiently high, and the time lag due to the cranking trie at the start can be eliminated.

  In the present invention, battery voltage detection means for detecting the voltage of the battery is provided, and when the battery voltage detected by the battery voltage detection means is equal to or higher than a predetermined lower limit value, the rate of decrease of the battery voltage per unit time is predetermined. Even if the value is greater than or equal to the value, the cranking may be attempted by driving the electric motor with the trial cranking torque.

  If such a configuration is adopted, even if the battery voltage drop rate becomes equal to or higher than a predetermined value during a cranking try, if the battery voltage is equal to or higher than the voltage lower limit value (battery voltage instantaneous lower limit value), Since it is possible to allow the motor to be driven with the trial cranking torque by determining that there is a capacity capable of executing the cranking trie, the start control is performed considering only the battery voltage drop rate. As compared with the case of performing the above, it becomes possible to increase the number of cranking tries of the internal combustion engine, so that the starting control of the internal combustion engine can be performed more finely.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an example of a hybrid vehicle to which an internal combustion engine start control device of the present invention is applied.

  1 includes an engine 1, a motor generator 2, a motor generator 3, a power split mechanism 4, an inverter 5, an HV battery 6, a converter 7, an auxiliary battery 8, a transmission 9, and an ECU (electronic control unit). 100 and the like.

  The engine 1 is a four-cylinder gasoline engine and includes a piston 1b that forms a combustion chamber 1a and a crankshaft 15 that is an output shaft, as shown in FIG. The piston 1b is connected to the crankshaft 15 via the connecting rod 16, and the reciprocating motion of the piston 1b is converted into rotation of the crankshaft 15 by the connecting rod 16.

  A signal rotor 17 having a plurality of protrusions (teeth) 17 a... 17 a on the outer peripheral surface is attached to the crankshaft 15. A crank position sensor 35 is disposed near the side of the signal rotor 17. The crank position sensor 35 is, for example, an electromagnetic pickup, and generates a pulse-like signal (output pulse) corresponding to the protrusion 17a of the signal rotor 17 when the crankshaft 15 rotates.

  A water temperature sensor 31 that detects the engine water temperature (cooling water temperature) is disposed in the cylinder block 1 c of the engine 1. A spark plug 22 is disposed in the combustion chamber 1 a of the engine 1. The ignition timing of the spark plug 22 is adjusted by the igniter 23. The igniter 23 is controlled by the ECU 100.

  An intake passage 11 and an exhaust passage 12 are connected to the combustion chamber 1 a of the engine 1. An intake valve 13 is provided between the intake passage 11 and the combustion chamber 1a. By opening and closing the intake valve 13, the intake passage 11 and the combustion chamber 1a are communicated or blocked. Further, an exhaust valve 14 is provided between the exhaust passage 12 and the combustion chamber 1a. By opening and closing the exhaust valve 14, the exhaust passage 12 and the combustion chamber 1a are communicated or blocked. The opening / closing drive of the intake valve 13 and the exhaust valve 14 is performed by each rotation of the intake camshaft and the exhaust camshaft to which the rotation of the crankshaft 15 is transmitted.

An air cleaner 26, a hot-wire air flow meter 32, an intake air temperature sensor 33 (built in the air flow meter 32), and an electronically controlled throttle valve 24 for adjusting the intake air amount of the engine 1 are disposed in the intake passage 11. Has been. The throttle valve 24 is driven by a throttle motor 25. The opening degree of the throttle valve 24 is detected by a throttle sensor 36. In the exhaust passage 12 of the engine 1, an O ₂ sensor 34 for detecting the oxygen concentration in the exhaust gas, a three-way catalyst 27, and the like are disposed.

  A fuel injection injector (fuel injection valve) 21 is disposed in the intake passage 11. Fuel of a predetermined pressure is supplied from the fuel tank to the injector 21 by a fuel pump, and the fuel is injected into the intake passage 11. This injected fuel is mixed with intake air to form an air-fuel mixture and introduced into the combustion chamber 1a of the engine 1. The air-fuel mixture (fuel + air) introduced into the combustion chamber 1a is ignited by the spark plug 22 and combusted and exploded. The piston 1b reciprocates due to combustion / explosion of the air-fuel mixture in the combustion chamber 1a, and the crankshaft 15 rotates. The operating state of the engine 1 is controlled by the ECU 100.

  On the other hand, the motor generator 2 is an AC synchronous motor that generates power by rotating a rotor by three-phase AC. The motor generator 2 is supplied with AC power obtained by converting DC power of the HV battery 6 by the inverter 5 and rotates. The motor generator 2 generates regenerative power during deceleration or braking.

  The motor generator 3 is an AC synchronous motor, similar to the motor generator 2 described above, and generates AC power by being driven by power distributed through the power split mechanism 4 out of power generated by the engine 1. The AC power generated by the motor generator 3 is converted into DC power by the inverter 5 and then charged to the HV battery 6. The motor generator 3 also functions as a starter motor that performs cranking when the engine 1 is started.

  Motor generator 2 and motor generator 3 are driven and controlled by ECU 100. The ECU 100 inputs signals necessary for driving and controlling the motor generator 2 and the motor generator 3 (for example, rotation speed, applied current, etc.) from the motor generator 2 and the motor generator 3 and outputs a switching control signal to the inverter 5.

  Note that the motor generator 2 connected to the transmission 9 mainly operates as an electric motor, and therefore may be simply referred to as a “motor”. Further, since the motor generator 3 coupled to the power split mechanism 4 often operates as a generator in general, it may be simply referred to as a “generator”.

  The power split mechanism 4 is a planetary gear including, for example, a ring gear coupled to the rotation shaft of the motor generator 2, a sun gear coupled to the rotation shaft of the motor generator 3, and a carrier coupled to the output shaft of the engine 1. The power of the engine 1 is divided into the rotation shaft of the motor generator 2 (connected to the drive wheels 10) and the rotation shaft of the motor generator 3.

  The HV battery 6 is a high voltage battery in which, for example, a predetermined number of nickel metal hydride battery cells are connected in series, and is charged by the generated power of the motor generator 3 as described above. The HV battery 6 is provided with a battery temperature detection sensor 37 for detecting the battery temperature and a battery voltage detection sensor 38 for detecting the terminal voltage. Output signals of the battery temperature detection sensor 37 and the battery voltage detection sensor 38 are input to the ECU 100.

  The inverter 5 is a power exchange device that converts a direct current of the HV battery 6 and a three-phase alternating current of the motor generator 2 and the motor generator 3. The inverter 5 is controlled by the ECU 100.

  The auxiliary battery 8 supplies power to lighting, audio equipment, an air conditioner compressor, the ECU 100, and the like.

  The converter 7 is a DC-DC converter that is connected to the DC side of the inverter 5 and charges the auxiliary battery 8 by stepping down the high-voltage DC to a low voltage (for example, 12 V).

  The transmission 9 is a mechanism for transmitting the power to the drive wheel 10 side of the power split mechanism 4 to the drive wheel 10 via the differential portion 9a, so that an automatic transmission fluid (ATF) for lubrication is circulated therein. It is configured.

  The ECU 100 includes a CPU, a ROM, a RAM, a backup RAM, and the like. The ROM stores various control programs, maps that are referred to when the various control programs are executed, and the like. The CPU executes various arithmetic processes based on various control programs and maps stored in the ROM. The RAM is a memory that temporarily stores the calculation results of the CPU, data input from each sensor, and the like. The backup RAM is a nonvolatile memory that stores data to be saved when the engine 1 is stopped, for example. Memory.

Connected to the ECU 100 are a water temperature sensor 31, an air flow meter 32, an intake air temperature sensor 33, an O ₂ sensor 34, a crank position sensor 35, a throttle sensor 36, a battery temperature detection sensor 37, and a battery voltage detection sensor 38. Furthermore, a starter switch 41, a shift sensor 42 for detecting the operation position of the shift lever, an accelerator sensor 43 for detecting the accelerator opening, a brake sensor 44, a vehicle speed sensor 45, and the like are connected.

  The ECU 100 calculates a driver's required torque, required engine output, motor torque, and the like based on the output signals of the various sensors described above, and powers one or both of the engine 1 and the motor generator 2. Hybrid control of driving the drive wheels 10 as a source is performed. For example, in a region where the engine efficiency is low, such as when starting or running at a low speed, the engine 1 is stopped and the drive wheels 10 are driven by the power of the motor generator 2 alone. Further, during normal traveling, control is performed such that the engine 1 is operated and the drive wheels 10 are driven by the power of the engine 1. Further, at the time of a high load such as full-open acceleration, in addition to the power of the engine 1, control is performed such that power is supplied from the HV battery 6 to the motor generator 2 and the power from the motor generator 2 is added as auxiliary power.

  Further, the ECU 100 executes idle stop control for automatically stopping the engine 1 when the engine stop condition is satisfied. Further, the ECU 100 executes the following start control process.

-Start control process-
An example of a start control processing routine executed by the ECU 100 will be described with reference to a flowchart shown in FIG.

  First, in step ST1, it is determined whether or not there is a start request for the engine 1, and if there is no start request, this routine is once ended. When the engine 1 is requested to start, the process proceeds to step ST2. The start request of the engine 1 is, for example, when a starter switch 41 (ignition switch) is turned on, or when a condition for starting the engine 1 is established during vehicle travel (travel by the driving force of only the motor generator 2). This is a request that occurs.

  In step ST2, the current (starting) temperature of the HV battery 6 is read from the output of the battery temperature detection sensor 37, and it is determined whether or not the battery temperature is less than a predetermined determination value α. When the determination result of step ST2 is negative (when the battery temperature is equal to or higher than the determination value α), it is determined that there is no problem even if cranking is performed with the preset reference cranking torque Tb, and step ST6. Proceed to On the other hand, if the determination result of step ST2 is affirmative, the process proceeds to step ST3.

  In step ST6, electric power is supplied from the HV battery 6 to the motor generator 3 based on a preset reference cranking torque Tb, thereby driving the motor generator 3 with the reference cranking torque Tb to try cranking. If the determination result of ST7 is affirmative determination “cranking OK”, that is, if the crankshaft 15 of the engine 1 rotates and the crank position sensor 35 outputs a signal indicating the rotation of the engine 1, this routine is executed. Exit once. Here, when the motor generator 3 is driven with the reference cranking torque Tb, the crankshaft 15 of the engine 1 always rotates unless the HV battery 6 is deteriorated. When the determination result in step ST7 is affirmative determination “cranking OK”, the ECU 100 supplies the fuel into each combustion chamber 1a of the engine 1 and the spark plug 22 in accordance with cranking (rotation of the crankshaft 15). The engine 1 is started by controlling ignition.

  In the determination process of step ST2, the determination value α set for the battery temperature is determined empirically in consideration of the preset reference cranking torque Tb, the temperature of the HV battery 6, the voltage drop of the HV battery 6, and the like. Set the obtained value. In addition, with respect to the reference cranking torque Tb, in consideration of energy loss during cranking, the starting torque capable of cranking the engine 1 (rotation of the crankshaft 15) is empirically obtained in advance through experiments and calculations. Are set and stored in the ROM of the ECU 100 or the like.

  In step ST3, the current (starting) voltage of the HV battery 6 is read from the output of the battery voltage detection sensor 38, and it is determined whether or not the battery voltage VB is less than a predetermined determination value β. Step ST3 is a step of determining whether or not there is a possibility that the battery voltage VB is lowered due to cranking and the HV battery 6 is deteriorated, and when the battery voltage VB is equal to or higher than a determination value β (step ST3). If the determination result is negative), it is determined that there is no problem even if cranking is performed with the reference cranking torque Tb, and the process proceeds to step ST6.

  In step ST6, electric power is supplied from the HV battery 6 to the motor generator 3 based on a preset reference cranking torque Tb, thereby driving the motor generator 3 with the reference cranking torque Tb to try cranking. If the determination result in ST7 is affirmative determination “cranking OK”, this routine is temporarily terminated. When the motor generator 3 is driven with the reference cranking torque Tb, the crankshaft 15 of the engine 1 always rotates.

  Here, in the determination process of step ST3, the determination value β set for the battery voltage VB is determined in advance in consideration of the reference cranking torque Tb, the temperature of the HV battery 6, the voltage drop of the HV battery 6, and the like. A value obtained empirically by calculation or the like is set.

  On the other hand, if the determination result of step ST3 is affirmative, it is determined that the HV battery 6 may be deteriorated due to cranking, and the process proceeds to step ST4. In step ST4, a cranking torque increase rate γ (γ = γ + a) is obtained. The initial value of the cranking torque increase rate γ is “0”, and the constant a is, for example, 10%. Therefore, when there is a request for starting the engine 1 and the determination results of both step ST2 and step ST3 are affirmative determinations, the first γ value is, for example, 10%, and for the second and subsequent times, for example, 20%, 30%, ... Changes in the order of 90% and 100%.

  In step ST5, the trial cranking torque Tg is obtained by multiplying the reference cranking torque Tb by the current cranking torque increase rate γ (for example, 10%). Next, in step ST6, electric power is supplied from the HV battery 6 to the motor generator 3 based on the trial cranking torque Tg obtained in step ST5, thereby driving the motor generator 3 with the trial cranking torque Tg. Try to crank. When the crankshaft 15 of the engine 1 rotates by the cranking trie (first time) and the crank position sensor 35 outputs a signal indicating the rotation of the engine 1 (when the determination result of step ST7 is affirmative determination). This routine is once terminated. On the other hand, when the crankshaft 15 of the engine 1 does not rotate (when the crank position sensor 35 does not output a signal indicating the rotation of the engine 1), the process proceeds to step ST8.

  In step ST8, the battery voltage decrease rate [ΔVB / Δt] per unit time shown in FIG. 4 is calculated based on the output signal of the battery voltage detection sensor 38, and the battery voltage decrease rate [ΔVB / Δt] is predetermined. It is determined whether or not it is less than the determination value η. Step ST8 is a step of determining whether or not the battery voltage VB is reduced by the cranking trie and may fall below the battery voltage instantaneous lower limit value ε (see FIG. 4). The determination result of step ST8 is If the determination is affirmative, that is, if the battery voltage drop rate [ΔVB / Δt] is less than the determination value η (ΔVB / Δt <η), there is no problem even if the cranking is performed with the trial cranking torque Tg. And return to step ST4.

  In the determination process of step ST8, the determination value η set for the battery voltage decrease rate [ΔVB / Δt] is determined in advance through experiments and calculations in consideration of the voltage decrease of the HV battery 6, the battery voltage instantaneous lower limit value ε, and the like. Set the value empirically obtained by the above. Note that Δt used for calculating the battery voltage drop rate [ΔVB / Δt] is, for example, the minimum unit of the sampling (reading) cycle of the battery voltage VB or the calculation cycle of the ECU 100.

  If the determination result in step ST8 is affirmative, after obtaining the cranking torque increase rate γ (γ = γ + a) in step ST4, in step ST5, the current cranking torque increase rate γ ( For example, the trial cranking torque Tg is obtained by multiplying by 20%).

  Next, in step ST6, by supplying electric power from the HV battery 6 to the motor generator 3 based on the trial cranking torque Tg obtained in step ST5, the motor generator 3 is driven with the trial cranking torque Tg. Try cranking. When performing this cranking trie (second time), since the current flows through the HV battery 6 at the time of the previous cranking trie, the battery temperature of the HV battery 6 rises due to self-heating due to the current flow, Further, since the trial cranking torque Tg is larger than the first time, there is a high possibility that the crankshaft 15 of the engine 1 will rotate due to the cranking trie, and “cranking OK” is obtained in step ST7. When the crankshaft 15 of the engine 1 rotates and the crank position sensor 35 outputs a signal indicating the rotation of the engine 1, this routine is temporarily terminated.

  On the other hand, when the crankshaft 15 of the engine 1 does not rotate due to the cranking trie (second time) (when the determination result in step ST7 is negative), in step ST8, the battery voltage decrease rate [ΔVB / Δt] Is less than the determination value η. If the determination result is affirmative, the process returns to step ST4 again to determine the cranking torque increase rate γ (γ = γ + a), and the current cranking torque increase rate γ (for example, 30%) is obtained as the reference cranking torque Tb. ) To obtain a trial cranking torque Tg (step ST5). Next, in step ST6, electric power is supplied from the HV battery 6 to the motor generator 3 based on the trial cranking torque Tg obtained in step ST5, thereby driving the motor generator 3 with the trial cranking torque Tg. Try to crank.

  When performing this cranking trie (third time), since the current flows through the HV battery 6 during the previous cranking trie, the battery temperature of the HV battery 6 has increased due to self-heating due to the current flow, Furthermore, since the trial cranking torque Tg is larger than the second time, the crankshaft 15 of the engine 1 is more likely to rotate due to the cranking trie, and “cranking OK” is obtained in step ST7. In the case (when the crankshaft 15 of the engine 1 rotates and the crank position sensor 35 outputs a signal indicating the rotation of the engine 1), this routine is temporarily terminated.

  On the other hand, when the crankshaft 15 of the engine 1 does not rotate (when the crank position sensor 35 does not output a signal indicating the rotation of the engine 1), the battery voltage decrease rate [ΔVB / Δt] is determined in step ST8. It is determined whether it is less than η. If the determination result is affirmative, the process returns to step ST4 again.

  Then, the above-described processing of Step ST4 to Step ST8, that is, the cranking trie in which the trial cranking torque Tg is gradually increased, is repeatedly performed until the crankshaft 15 of the engine 1 rotates, and the crankshaft of the engine 1 is thus repeated. Look for opportunities for 15 to rotate. However, when the battery voltage decrease rate [ΔVB / Δt] is equal to or greater than the determination value η (the determination result of step ST8 is negative), the battery voltage VB is less than the battery voltage instantaneous lower limit value ε (the determination result of step ST9 is In the affirmative determination), since the HV battery 6 may be deteriorated, this routine is ended without performing a cranking trie, that is, without supplying power from the HV battery 6 to the motor generator 3.

  As described above, according to the start control process of this example, when the temperature of the HV battery 6 is lower than a predetermined value at the time of low temperature start, the motor generator (starter motor) 3 is actually driven with the trial cranking torque. Thus, it is determined whether or not the crankshaft 15 of the engine 1 rotates, and when the crankshaft 15 is not rotating, the trial cranking torque is increased and the cranking try is performed again. Therefore, it is possible to find an appropriate cranking torque that matches the state of the engine 1 (for example, energy loss). This makes it possible to perform start control that accurately reflects the cranking torque that is actually required at the start, compared to the case where the cranking torque is obtained by calculation, and at the start when the battery temperature is low. Even if it exists, possibility that a battery voltage will fall below a voltage lower limit will decrease. Moreover, since the trial cranking torque Tg is gradually increased in consideration of the battery voltage drop rate [ΔVB / Δt] and the battery voltage instantaneous lower limit value ε, the battery voltage falls below the voltage lower limit value (battery voltage Can be reliably prevented.

  Further, in the start control process of this example, even when the battery voltage decrease rate [ΔVB / Δt] is equal to or greater than a predetermined determination value η, the battery voltage VB is equal to or greater than the battery voltage instantaneous lower limit value ε (in step ST9). If the determination result is negative), it is determined that the HV battery 6 has a capacity capable of executing a cranking trie, and the motor generator 3 is allowed to be driven by the electric power from the HV battery 6. Therefore, the number of cranking tries of the engine 1 can be increased as compared with the case where the start control is performed considering only the battery voltage decrease rate [ΔVB / Δt]. Furthermore, it can be performed with high precision.

  Further, in the start control process of this example, when the battery voltage VB of the HV battery 6 is sufficiently large at a predetermined determination value β or more, it is determined that there is no possibility that the HV battery 6 is deteriorated by cranking, Since the motor generator 3 is driven with the reference cranking torque, even if the battery temperature of the HV battery 6 is low, if the battery voltage VB is sufficiently high, the cranking trie with the trial cranking torque Tg is performed. It can be omitted, and the time lag due to the cranking try at the start can be eliminated.

-Other embodiments-
In the above example, the example in which the present invention is applied to the start control of the engine of the hybrid vehicle that performs cranking by the motor generator has been shown, but the present invention is not limited to this, and the starter motor for performing cranking It can be applied to the start control of the engine of a hybrid vehicle provided separately.

  In the above example, an example in which the present invention is applied to start control of an engine mounted on a hybrid vehicle has been shown. However, the present invention is not limited thereto, and an engine mounted on an eco-run vehicle that performs idle stop control, or The present invention can also be applied to start control of an engine mounted on a normal automobile that does not perform idle stop control.

  In the above embodiment, the example in which the present invention is applied to the start control of the four-cylinder gasoline engine has been described. However, the present invention is not limited to this, and the number of other arbitrary cylinders such as a cylinder six-cylinder gasoline engine can be increased. It can also be applied to start control of a cylinder gasoline engine.

  Furthermore, the present invention is not limited to a gasoline engine, but can be applied to ignition control using other fuels such as LPG (liquefied petroleum gas) and LNG (liquefied natural gas), or start control of a diesel engine or the like. Also, it can be applied to start control of an in-cylinder direct injection engine.

1 is a schematic configuration diagram illustrating an example of a hybrid vehicle to which an internal combustion engine start control device of the present invention is applied. It is a schematic block diagram of the engine (internal combustion engine) mounted in the hybrid vehicle of FIG. It is a flowchart which shows an example of the starting control process which ECU performs. It is a graph which shows typically a time change of battery voltage at the time of cranking.

Explanation of symbols

1 Engine 2 Motor generator 3 Motor generator (motor for starting the engine)
4 Power split mechanism 5 Inverter 6 HV battery 7 Converter 15 Crankshaft 17 Signal rotor 35 Crank position sensor 37 Battery temperature detection sensor 38 Battery voltage detection sensor 41 Starter switch 100 ECU

Claims (3)

An electric motor for starting an internal combustion engine, a battery for supplying electric power to the electric motor, battery temperature detection means for detecting the temperature of the battery, and control means,
When the battery temperature detected by the battery temperature detection means is less than a predetermined value when the internal combustion engine is started, the control means controls the electric motor with a trial cranking torque set lower than a reference cranking torque. When the crankshaft of the internal combustion engine does not rotate by driving, the cranking torque is tried by gradually increasing the trial cranking torque in consideration of the decrease rate of the battery voltage per unit time. A start control device for an internal combustion engine. The start control device for an internal combustion engine according to claim 1,
Battery voltage detection means for detecting the voltage of the battery, wherein the control means has a battery temperature detected by the battery temperature detection means that is less than a predetermined value and is detected by the battery voltage detection means. When the engine is less than a predetermined value, the engine is driven with a trial cranking torque to attempt cranking. The start control device for an internal combustion engine according to claim 1 or 2,
Battery voltage detection means for detecting the voltage of the battery, wherein the control means is a rate of decrease in battery voltage per unit time when the battery voltage detected by the battery voltage detection means is equal to or greater than a predetermined lower limit value. A starting control device for an internal combustion engine, wherein even if is equal to or greater than a predetermined value, cranking is attempted by driving the electric motor with a trial cranking torque.

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