JP6012400B2 - Control device for internal combustion engine - Google Patents

Description

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

  In an internal combustion engine mounted on a vehicle or the like, it is known to perform a fuel cut that temporarily stops fuel injection in accordance with the operation state. Normally, when the accelerator pedal depression amount is 0 or less than a threshold value close to 0 and the engine speed is equal to or higher than the fuel cut permission speed, the fuel cut is started assuming that the fuel cut condition is satisfied. Then, when any fuel cut end condition is satisfied, such as when the accelerator pedal depression amount exceeds the threshold value, or the engine speed decreases to the fuel cut return speed, the fuel cut ends and the fuel injection resumes. .

  If the fuel supply is cut off suddenly when the engine torque is relatively large, a torque shock that causes the engine speed and the vehicle speed to drop stepwise occurs, causing the passengers including the driver to feel the shock. In order to reduce this torque shock, conventionally, even if the fuel cut condition is satisfied, the fuel injection is not stopped immediately, and the fuel injection is stopped after waiting for a certain delay time (for example, (See Patent Document 1 below).

  It is also known to perform regenerative braking in which the amount of power generated by the alternator is increased simultaneously with the stop of fuel injection, and kinetic energy is converted into electric energy and recovered (see, for example, Patent Document 2 or 3 below). .

Japanese Patent Laid-Open No. 10-030477 JP-A-11-107805 Japanese Patent Application Laid-Open No. 2004-064811

  Fuel injection and combustion are also continued during the delay time from when the fuel cut condition is satisfied to when fuel cut is actually started. Therefore, the effective fuel consumption is deteriorated accordingly.

  Further, increasing the amount of power generated by the alternator with the start of fuel cut tends to increase torque shock due to a combination of a decrease in engine torque due to the interruption of fuel supply and an increase in mechanical load due to the alternator.

  The present invention has been made paying attention to the above-described problem, and an object of the present invention is to further improve fuel consumption while suppressing torque shock at the time of fuel cut.

In the present invention, when a predetermined fuel cut condition is satisfied, a fuel cut is performed to temporarily stop the fuel supply to the cylinder. When the fuel cut condition is satisfied, the driving force is supplied from the crankshaft of the internal combustion engine. subject to reduce the forward rotational direction of the torque supplied toward the axle from the internal combustion engine while continuing the fuel supply to temporarily cylinder in Rukoto increase power generation by the power generator to generate power, then, actually cylinders Before stopping the fuel supply to the engine, the control device for the internal combustion engine is configured to reduce the increased power generation amount.

  That is, by increasing the amount of power generation during the period from when the fuel cut condition is established until the fuel supply is actually cut off, the engine torque is quickly reduced while converting the kinetic energy into electric energy and collecting it. If the engine torque is sufficiently reduced before the fuel supply is cut off, a large torque shock will not occur even if the fuel supply is cut off. When the fuel supply is actually cut off, the amount of power generated by the generator has already been reduced, so that a decrease in engine torque due to the cut off of the fuel supply does not overlap with an increase in mechanical load caused by the generator.

  According to the present invention, it is possible to further improve fuel efficiency while suppressing torque shock at the time of fuel cut.

The figure which shows schematic structure of the internal combustion engine in one Embodiment of this invention. The figure which shows the electric circuit for the control apparatus of the embodiment to operate the compressor of an air conditioner, and various electric loads. The timing chart which shows the content of the control which the control apparatus of the embodiment implements in the period from fuel cut condition establishment to the fuel cut start. The flowchart which shows the example of a procedure of the process which the control apparatus of the embodiment implements.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle in the present embodiment. The internal combustion engine in the present embodiment is a spark ignition gasoline engine and includes a plurality of cylinders 1 (one of which is shown in FIG. 1). In the vicinity of the intake port of each cylinder 1, an injector 11 for injecting fuel is provided. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives spark voltage generated by the ignition coil and causes spark discharge between the center electrode and the ground electrode.

  The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream.

  The exhaust passage 4 for discharging the exhaust guides the exhaust generated as a result of burning the fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42 and an exhaust purification three-way catalyst 41 are disposed on the exhaust passage 4.

  The vehicle is accompanied by a plurality of external loads. Specific examples of external loads include air conditioner refrigerant compression compressors, various electrical loads such as air conditioner blowers, defoggers for removing fog on rear glass, audio equipment, car navigation systems, and lighting (heads) Lamps, tail lamps, fog lamps, turn signals (turn signal lamps, etc.), radiator fans for cooling cooling water, electric power steering devices, and the like.

  The compressor of the air conditioner is rotationally driven in response to transmission of rotational torque from the crankshaft of the internal combustion engine, and compresses the refrigerant. As shown in FIG. 2, a magnet clutch 61 that can be connected and disconnected is interposed between the compressor and the crankshaft. When operating the air conditioner, the magnet clutch 61 is energized with current from the in-vehicle battery 62 and / or the alternator 63 and the magnet clutch 61 is engaged. On the contrary, when the air conditioner is not operated, the magnet clutch 61 is not energized and the clutch 61 is disconnected. Energization and disconnection of the magnet clutch 61 is performed by turning ON / OFF the relay switch 64.

  A motor 66 that rotationally drives the blower for blower and a heating wire heater 68 laid on the rear glass as a defogger operate by receiving power supply from the battery 62 and / or the alternator 63. Energization and interruption of the motor 66 and the heater 68 are performed by turning on / off the relay switch 67 or starting / extinguishing a semiconductor switching element (power device represented by a power transistor, power MOSFET, etc.) 69.

  Audio devices, car navigation systems, illumination lights, motors for rotating the radiator fan, and other electrical loads are the same as described above.

  An alternator 63, which is a source of power supply to an electric load, is a type of generator that generates power by being rotationally driven by receiving a driving force transmitted from a crankshaft of an internal combustion engine. The alternator 63 is connected to the crankshaft via a winding transmission mechanism having a belt and a pulley as elements. The magnitude of the voltage generated and output by the alternator 63 can be controlled via the regulator 65. The regulator 65 is a known IC type attached to the alternator 63 and performs a switching operation for switching ON / OFF the energization of the field coil of the alternator 63.

  The output voltage of the alternator 63, that is, the voltage induced in the stator coil of the alternator 63 increases in proportion to fDUTY which is the DUTY ratio of the field current flowing through the field coil. The regulator 65 receives a signal r for instructing an output voltage of an alternator from an ECU (Electronic Control Unit) 0, and performs PWM control for adjusting fDUTY so as to realize the instructed output voltage. With this PWM control, the power generated by the alternator 63 can be increased or decreased. The amount of power generated by the alternator 63, in other words, the amount of charge to the battery 62 and / or the amount of power supplied to the electrical load increases as fDUTY increases and decreases as fDUTY decreases.

  In the regulator 65 of the vehicular alternator 63 that is widely used, the output voltage of the alternator 63 can be switched to two stages, for example, 14.5V or 12.8V. In this case, the ECU 0 inputs to the regulator 65 a signal r that instructs whether the output voltage of the alternator 63 is HI potential = 14.5V or LO potential = 12.8V.

  As the regulator 65, a linear regulator capable of continuously changing the output voltage of the alternator 63 within a predetermined range, for example, between 12V and 15.5V may be employed. In this case, the ECU 0 inputs a signal r that instructs the regulator 65 to set the output voltage of the alternator 63 to any value within the range.

  The LO potential or minimum output voltage of the alternator 63 is preferably set to a voltage lower than the voltage of the battery 62 or a low voltage close to the voltage of the battery 62. The battery voltage varies depending on the state of charge of the battery 62 and the like, but is usually a predetermined voltage, for example, 12 V or more.

  The alternator 63 becomes a mechanical load when viewed from the internal combustion engine. When the output voltage of the alternator 63 exceeds the voltage of the battery 62, the battery 62 is charged and power is supplied from the alternator 63 to the electric load. That is, the alternator 63 performs the work of generating electric energy by consuming energy of rotation of the crankshaft. The amount of charge to the battery 62 and the amount of power supplied to the electrical load depend on the potential difference between the output voltage of the alternator 63 and the battery voltage.

  Conversely, when the output voltage of the alternator 63 is less than or close to the battery voltage, the battery 62 is not charged, and no power is supplied from the alternator 63 to the electric load (power supply from the battery 62 to the electric load). Sometimes). That is, the alternator 63 does not perform work that consumes the energy of rotation of the crankshaft, or the work is reduced.

  In short, when a high output voltage is commanded from the ECU 0 to the regulator 65, the mechanical load of the alternator 63 with respect to engine rotation increases, and when a low output voltage is commanded, the mechanical load of the alternator 63 with respect to engine rotation decreases.

  The ECU 0 as the control device of the present embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from an engine rotation sensor that detects the rotation angle and engine speed of the crankshaft, and depression of an accelerator pedal. A sensor for knowing an accelerator opening signal c output from a sensor that detects the amount or the opening of the throttle valve 32 as an accelerator opening (engine output required by the driver, that is, a required load), and a shift lever range ( Shift range signal d output from the shift position switch), intake air temperature / intake pressure signal e output from the temperature / pressure sensor for detecting the intake air temperature and intake pressure in the intake passage 3 (especially the surge tank 33), internal combustion Cooling water temperature signal f output from a water temperature sensor that detects the cooling water temperature indicating the temperature of the engine, intake camshaft Detect cam angle signal g output from cam angle sensor at multiple cam angles of the camshaft or exhaust camshaft, and indicators (battery current, battery voltage, and / or battery temperature) that indicate the state of charge of in-vehicle battery 62 The battery status signal h output from the sensor to be output, the power generation amount signal s output from the sensor for detecting the index (output current or output power) indicating the power generation amount by the alternator, and the like are input.

  From the output interface, an ignition signal i for the igniter of the spark plug 12, a fuel injection signal j for the injector 11, an opening operation signal k for the throttle valve 32, and a switch on the electric circuit for energizing the magnet clutch 61 A voltage regulator that controls the clutch engagement signal o for 64, the switch ON signals p and q for the switches 67 and 69 on the electric circuit for energizing the motor 66, the heater 68 and other electric loads, and the voltage generated by the alternator 63. A voltage instruction signal r or the like is output to 65.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance, calculates operation parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, h, and s necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and fills the cylinder 1 Estimate the amount of intake air. Based on the engine speed, the intake air amount, and the like, various operating parameters such as required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, and ignition timing are determined. As the operation parameter determination method itself, a known method can be adopted. The ECU 0 applies various control signals i, j, k, o, p, q, r corresponding to the operation parameters via the output interface.

  The ECU 0 of the present embodiment executes a fuel cut that temporarily stops fuel injection from the injector 11 (and ignition by the spark plug 12) according to the driving situation. Normally, it is assumed that the fuel cut condition is satisfied when the accelerator pedal depression amount is 0 or less than a threshold value close to 0 and the engine speed is equal to or higher than the fuel cut permission speed.

  However, even if the combustion cut condition is satisfied, the fuel injection to the cylinder 1 is not immediately stopped. FIG. 4 shows a procedure of processing executed by the ECU 0 of the present embodiment at the time of fuel cut.

  When the fuel cut condition is satisfied (step S1), the ECU 0 maintains the operation of injecting and burning fuel into the cylinder 1 (step S2), and increases the output voltage (fDUTY) of the alternator 63 by increasing the alternator 63. The amount of power generated by is increased (step S3). Then, at the timing when it seems that the situation where fuel injection can be stopped is ready (step S4), the power generation amount temporarily increased is decreased (step S5), and the fuel injection (and ignition) is stopped ( Step S6).

  FIG. 3 is a timing chart for explaining the content of the fuel cut control by the ECU 0 of the present embodiment. In FIG. 3, the solid lines indicate engine torque (torque in the positive rotation direction supplied from the internal combustion engine toward the axle, which is negative during fuel cut) caused by control by the ECU 0 of the present embodiment, power generation amount, and fuel cut flag. The chain line represents the transition according to the conventional control.

In FIG. 3, the time t ₀ when the accelerator pedal depression amount (accelerator opening) becomes close to ₀ is the time when the fuel cut condition is satisfied. When the fuel cut condition is satisfied, since the accelerator pedal is not depressed, the opening degree of the throttle valve 32 is reduced, and the intake air amount and the fuel injection amount charged into the cylinder 1 are remarkably reduced. In addition, since the mechanical load of the alternator 63 on the internal combustion engine is increased (step S3), the engine torque decreases rapidly even though the fuel supply to the cylinder 1 is continued (step S2).

  The situation where the fuel injection may be stopped is a situation where the engine torque is sufficiently low and does not cause a large torque shock even if the fuel injection is stopped. When the engine torque drops below the allowable torque, the ECU 0 reduces the mechanical load of the alternator 63 on the internal combustion engine (step S5) and shuts off the fuel supply to the cylinder 1 (step S6).

As a result, as compared with the conventional control, the delay time from when the fuel cut condition is satisfied until the fuel cut flag is turned ON and fuel injection is actually stopped is shortened. As shown in FIG. 3, at time t ₁ is the control of this embodiment the fuel cut flag is ON, it first fuel cut flag becomes later point in time t ₂ than is the ON in the conventional control Become. That is, the delay time from time t ₀ is shortened only in the section from time t ₁ to time t ₂ . As a result, useless fuel consumption is reduced.

In addition, in the control of the present embodiment, power generation by the alternator 63 is continued even during the fuel cut (after time t ₁ ), but the power generation at that time is after the start of the fuel cut in the conventional control (after time t ₂ ). Is less than the amount of electricity generated. Thus, drop T ₁ of the engine torque in the fuel cut start time t ₁ by the control of the present embodiment is smaller than the drop T ₂ of the engine torque in the fuel cut start time t ₂ according to the conventional control.

  There are several possible modes for the condition at which the branch determination in step S4 is true, that is, the condition for actually stopping the combustion injection. A typical method is to repeatedly estimate the engine torque after the fuel cut condition is established and stop the fuel injection when the engine torque reaches the allowable torque.

The allowable torque is the amount of torque reduction corresponding to the deceleration of the vehicle speed that does not cause the driver or passenger to feel an impact;
Torque reduction amount = allowable deceleration × (vehicle weight + passenger weight) ÷ transmission efficiency × wheel (tire) diameter ÷ transmission gear ratio ÷ differential ratio. The allowable deceleration is 0.08G, for example. The crew weight is, for example, 60 kg multiplied by the assumed number of people. If mainly two passengers are assumed, the crew weight is 120 kg. The transmission efficiency is the overall transmission efficiency of a transmission (including a torque converter, a forward / reverse switching device, a CVT and a differential device) and wheels, and is set to, for example, 0.9. The gear ratio of the transmissions 8 and 9 is a value corresponding to the gear ratio and shift position when the fuel cut condition is satisfied.

The allowable torque is the maximum value allowed for a reduction in engine torque due to fuel cut or fuel injection stop;
Allowable torque = torque reduction amount−defined by the mechanical loss of the engine and the engine after the fuel cut condition is satisfied. The term of mechanical loss in the decrease in engine torque caused by fuel cut includes the engine speed and engine cooling temperature after the fuel cut condition is satisfied, the operating condition of the compressor of the air conditioner, and the power generation of the alternator 63. The value depends on the amount. The term of mechanical loss increases as the engine speed increases, and increases as the cooling water temperature decreases. In particular, the cooling water temperature suggests friction in various parts of the engine. The lower the coolant temperature, the lower the engine temperature, the higher the viscosity of the lubricating oil, and the greater the friction.

  When the compressor is operating, the mechanical loss is greater than when it is not.

  Furthermore, it goes without saying that the mechanical loss increases as the power generation amount of the alternator 63 increases. The amount of power generated by the alternator 63 also depends on the operating state of the electric load at that time and the state of charge of the battery 62 (for example, when the electric load is almost not operating and the battery 62 is nearly fully charged, a high output is obtained. Even if the voltage is commanded to the regulator 65, the alternator 63 is in a state close to no-load operation). If the power generation amount (output current or output power) of the alternator 63 can be directly measured, the mechanical loss may be calculated using the measured value. Otherwise, the power generation amount of the alternator 63 is estimated based on fDUTY, the state of charge of the battery, the engine speed, etc., and the mechanical loss is calculated.

  On the other hand, the engine torque in the delay time after the fuel cut condition is established and before the fuel cut is started is estimated based on the engine speed, the fuel injection amount, the coolant temperature, and the like at that time. A known engine torque calculation method can be used.

  Generally speaking, in step S4, the ECU 0 compares the estimated current engine torque with the allowable torque, and if the current engine torque is less than the allowable torque, the ECU 0 may stop the combustion injection. Judgment is made (the fuel cut flag is turned ON).

  Another method is to determine the delay time until the fuel injection is actually stopped based on the situation when the fuel cut condition is satisfied.

  For example, the map data that prescribes the relationship between the engine speed, the coolant temperature, the operating condition of the air conditioner and the electric load, the state of charge of the battery, and the state of charge of the battery and the delay time to be set in the memory of the ECU 0 Is stored. When the fuel cut condition is satisfied, the ECU 0 searches the map using the engine speed, the coolant temperature, etc. at that time as keys, and reads the delay time.

  Thus, the elapsed time since the combustion cut condition is established is counted, and in step S4, the elapsed time has reached the delay time determined from the map data, and the combustion injection may be stopped. (The fuel cut flag is set to ON).

  After the fuel cut is started, that is, the fuel injection is stopped (step S6), one of the fuel cut end conditions is satisfied, such as the accelerator pedal depression amount exceeds the threshold value, or the engine speed is reduced to the fuel cut return speed. In step S7, the fuel cut is terminated and fuel injection (and ignition) is resumed (step S8). When recovering from a fuel cut, the fuel injection amount is increased for a certain period to enrich the air-fuel ratio in order to recover the reduced engine speed, and then the air-fuel ratio converges to a value close to the theoretical target air-fuel ratio. The air-fuel ratio control is performed.

  In the present embodiment, when a predetermined fuel cut condition is satisfied, a fuel cut that temporarily stops the fuel supply to the cylinder 1 is performed. When the fuel cut condition is satisfied, the driving force is reduced from the crankshaft of the internal combustion engine. An internal combustion engine characterized by temporarily increasing the amount of power generated by a generator 63 that generates power upon receipt of power, and then decreasing the amount of power that has been increased before actually stopping the fuel supply to the cylinder 1 A control device 0 was configured.

  According to this embodiment, it is possible to shorten the delay time (time from the time when the fuel cut condition is established until the actual fuel cut is started) necessary to reduce the torque shock, and waste of fuel in the delay time. Can be reduced. In addition, converting kinetic energy into electrical energy and recovering it during the delay time also contributes to improved fuel efficiency. In addition, it is possible to maintain the drivability by suppressing the torque shock accompanying the stop of the fuel supply to the cylinder 1.

  The present invention is not limited to the embodiment described in detail above. For example, in the above-described embodiment, the timing for reducing the power generation amount that has been once increased (step S5) and the timing for stopping the fuel supply to the cylinder 1 (step S6) are the same or substantially the same. There may be a time lag between.

  Further, the generator 63 may be a motor generator that has a function of performing cranking at the start of the internal combustion engine and / or assisting rotation of the crankshaft after the internal combustion engine is started.

  In addition, the specific configuration of each unit, the processing procedure, and the like can be variously modified without departing from the spirit of the present invention.

  The present invention can be applied to control of an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 11 ... Injector 12 ... Spark plug 63 ... Generator (alternator)

Claims (1)

A fuel cut for temporarily stopping fuel supply to the cylinder when a predetermined fuel cut condition is satisfied,
With the establishment fuel cut-off condition, toward the axle from even the internal combustion engine while continuing the fuel supply to the cylinders at Rukoto temporarily increase the power generation amount by the power generator that generates electric power by being supplied with driving force from the crankshaft of the internal combustion engine Reduce the torque in the forward rotation direction
After that, before the fuel supply to the cylinder is actually stopped, the power generation amount that has been increased is reduced.

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