JP6103901B2 - Control device - Google Patents

Description

  The present invention relates to a control device that executes fuel cut processing of 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 or the engine speed has decreased to the fuel cut return speed, the fuel cut ends and 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. Conventionally, in order to reduce this torque shock, even if the fuel cut condition is satisfied, the fuel injection is not stopped immediately, but the fuel injection is stopped after the delay time elapses (for example, the following patents) See literature). During the delay time, the ignition timing is corrected to be retarded, and the engine torque is actively reduced.

  When the fuel cut condition is satisfied and the ignition timing is remarkably retarded in a situation where the amount of intake air (and fuel injection amount) charged into the cylinder is originally low, such as when the vehicle is traveling at a low vehicle speed, Combustion of the air-fuel mixture in the cylinder becomes unstable and may cause misfire. Therefore, the retard correction amount of the ignition timing after the fuel cut condition is satisfied is suppressed to such an extent that misfire is not caused at a low vehicle speed or the like.

Japanese Patent Laid-Open No. 10-030477

  At present, the ignition timing retardation correction amount is uniformly set regardless of the intake air amount immediately before the fuel cut condition is established. Therefore, when the fuel cut condition is satisfied under a condition where the intake air amount is large, such as when the vehicle is traveling at a high vehicle speed, the delay time required to sufficiently reduce the engine torque becomes long. Needless to say, fuel injection and combustion are continued during the delay time, and the effective fuel consumption is deteriorated accordingly.

  An object of the present invention is to further improve fuel efficiency while suppressing torque shock at the time of fuel cut.

In order to solve the above-described problems, the present invention performs a fuel cut that temporarily stops the fuel supply to the cylinder in accordance with the establishment of a predetermined fuel cut condition. perform delay correction of increasing generated power of a generator driven by the internal combustion engine during a until the stop of fuel supply to, established immediately before the fuel cut-off condition, the intake passage at the time immediately after the establishment or during establishment If the pressure is high, as compared with the case the intake passage pressure in the same period is low, to constitute a control apparatus characterized by a larger amount of electric power generated in the delay time.

  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 flowchart which shows the example of the procedure of the process which the control apparatus of the internal combustion engine of the embodiment implements. The timing diagram 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.

  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.

  A generator (alternator or motor generator, not shown), which is a source of electric power to be supplied to an electrical system of a vehicle or a starter motor, is rotated by receiving a driving force transmitted from a crankshaft of an internal combustion engine to generate electric power. . The generator is connected to the crankshaft via, for example, a winding transmission mechanism including a belt and a pulley as elements.

  The magnitude of the voltage generated and output by the generator can be controlled via a regulator. The regulator is a known IC type attached to the generator, and performs a switching operation for switching on / off the energization of the field coil of the generator.

  The output voltage of the generator, that is, the voltage induced in the stator coil of the generator increases in proportion to fDUTY, which is the DUTY ratio of the field current flowing through the field coil. The regulator receives a signal 1 for instructing an output voltage of a generator 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 generator can be increased or decreased. The amount of power generated by the generator increases as fDUTY increases and decreases as fDUTY decreases.

  In the widely used regulators for vehicle generators, the output voltage of the generator can be switched in two stages. In this case, the ECU 0 inputs a signal l for instructing whether the output voltage is the HI potential or the LO potential to the regulator.

  As the regulator, a linear regulator capable of continuously changing the output voltage of the generator within a predetermined range may be employed. In this case, the ECU 0 inputs a signal l for instructing to the regulator which value in the range the output voltage is to be set.

  The generator is a mechanical load when viewed from the internal combustion engine. When the output voltage of the generator exceeds the voltage of the in-vehicle battery, the battery is charged and power is supplied from the generator to the electric load. That is, the generator spends the energy of rotation of the crankshaft to generate electrical energy.

  Conversely, when the output voltage of the generator is less than or close to the battery voltage, the battery is not charged, and no electric power is supplied from the generator to the electric load (the electric power is supplied from the battery to the electric load). There is a thing). That is, the generator does not do 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, the mechanical load of the generator with respect to engine rotation increases, and when a low output voltage is commanded, the mechanical load of the generator 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 Cam angle signal g output from the cam angle sensor at a plurality of cam angles of the camshaft or exhaust camshaft, battery current signal indicating the charge state of the vehicle-mounted battery, battery status signal h output from the sensor detecting the battery temperature, etc. Is entered.

  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, an output voltage command signal l for the generator, etc. Is output.

  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, and h necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and is filled in the cylinder 1. Estimate the intake volume. Based on the engine speed, intake air amount, etc., various required fuel injection amounts, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, ignition timing, power generation amount by generator, etc. Determine operating parameters. As the operation parameter determination method itself, a known method can be adopted. The ECU 0 applies various control signals i, j, k, and l 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 fuel cut condition is satisfied, the fuel injection to the cylinder 1 is not stopped immediately. FIG. 2 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 refers to the pressure in the intake passage 3 (surge tank 33) immediately before, when, or just after the fuel cut condition is satisfied, and performs ignition in the delay time. A timing delay correction amount is determined (step S2). The pressure in the intake passage 3, that is, the intake pressure indicates the amount of intake air that is filled in the cylinder 1. The higher the intake pressure, the greater the intake air amount and fuel injection amount charged into the cylinder 1.

  As shown in FIG. 3, in step S2, when the intake pressure when the fuel cut condition is satisfied is high, the retard amount of the ignition timing per unit time or unit cycle is increased as compared with the case where the intake pressure is low. And / or a larger maximum value of the retard amount of the ignition timing is set.

In FIG. 3, the solid line represents a case where the intake pressure is relatively high, and the broken line represents a case where the intake pressure is relatively low. t ₀ is the time when the fuel cut condition is satisfied, t ₁ is the time when fuel supply to the cylinder 1 is stopped when the intake pressure is relatively high, and t ₂ is the fuel supply to the cylinder 1 when the intake pressure is relatively low. It is time to stop. The period from time t ₀ to time t ₁ and the period from time t ₀ to time t ₂ are delay times before the start of fuel cut.

  The purpose of retarding the ignition timing in the delay time is, as already described, intended to suppress or avoid a torque shock when the engine torque is reduced and fuel injection is stopped. Since the accelerator pedal is not depressed when the fuel cut condition is satisfied, the throttle valve 32 is fully closed or its opening is very small. However, even if the throttle valve 32 is closed, the amount of intake air flowing into the cylinder 1 is not immediately reduced. If the ignition timing is retarded, the engine torque can be reduced while the fuel supply to the cylinder 1 is continued.

  In FIG. 3, the alternate long and short dash line for the engine torque and the retard correction amount represents conventional control when the intake pressure is high. Compared with the control (solid line) of the present embodiment, in the conventional control, it is delayed that the engine torque decreases to a level suitable for stopping fuel injection. On the other hand, according to the control of the present embodiment, the engine torque can be quickly reduced even when the fuel cut condition is satisfied at a stage where the intake pressure is high.

  The ECU 0 maintains the operation of injecting and burning the fuel into the cylinder 1 while retarding the ignition timing (step S3) after the fuel cut condition is satisfied (step S4). Accordingly, at the timing when it is considered that the situation where the fuel injection can be stopped is ready (step S5), the fuel injection (and ignition) is stopped (step S6).

  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. 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 fuel 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 transmission and a differential device), wheels, and the like, for example, 0.9. The gear ratio of the transmission 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 due to the fuel cut includes the engine speed and engine cooling temperature after the fuel cut condition is satisfied, the operating condition of the air conditioner compressor, and the power generation amount of the alternator. It is a value according to etc. 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 increases. The amount of power generated by the alternator also depends on the operating status of the electrical load at that time and the state of charge of the battery (for example, if the electrical load is almost not operating and the battery is almost fully charged, the high output voltage is regulated. The alternator will be close to no-load operation even if the command is issued. If the power generation amount (output current or output power) of the alternator can be directly measured, the mechanical loss may be calculated using the measured value. Otherwise, the power generation amount of the alternator is estimated based on the DUTY ratio (fDUTY) of energization to the field coil, 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, the ECU 0 compares the estimated current engine torque with the allowable torque in step S4, and the fuel injection may be stopped when the current engine torque is equal to or less than the allowable torque. 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 fuel cut condition is established is counted, and in step S4, the fuel injection can be stopped because the elapsed time has reached the delay time determined from the map data. (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, the fuel cut is performed to temporarily stop the fuel supply to the cylinder 1 when the predetermined fuel cut condition is satisfied, and the fuel supply to the cylinder is actually stopped after the fuel cut condition is satisfied. When the ignition timing delay correction is performed during the delay time until the fuel cut condition is satisfied and the intake passage 3 internal pressure is high immediately before, when, or just after the fuel cut condition is satisfied, the intake passage 3 internal pressure at the same time The control device 0 for the internal combustion engine is configured to increase the amount of retarding the ignition timing during the delay time as compared with the case where the engine is low.

  According to the present embodiment, compared with the conventional fuel cut control, the delay time from the fuel cut condition establishment to the fuel injection stop when the intake pressure is high, such as at high vehicle speed, is shortened (in other words, the fuel cut control The period is effectively extended) and fuel waste can be reduced. In addition, in situations where the intake pressure is low, such as at low vehicle speeds, the ignition timing retard correction during the delay time is slowed and / or the maximum retard amount is suppressed to prevent misfire in the cylinder 1. Can do.

  The present invention is not limited to the embodiment described in detail above. In the above embodiment, the ignition timing is retarded during the delay time after the fuel cut condition is satisfied. However, in addition to or instead of this, control for increasing the generated power of the generator driven by the internal combustion engine. May be implemented.

  At that time, the magnitude of the output voltage commanded to the generator during the delay time is determined according to the pressure in the intake passage 3 immediately before, when, or just after the fuel cut condition is satisfied (step S2). . That is, when the intake pressure when the fuel cut condition is satisfied is high, the amount of increase in the output voltage per unit time or unit cycle is increased and / or the maximum output voltage is compared to when the intake pressure is low. Set a larger value. Then, the output voltage of the generator during the delay time is manipulated (step S3).

  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 and / or a generator mounted on a vehicle.

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

Claims (1)

A fuel cut for temporarily stopping the fuel supply to the cylinder in accordance with the establishment of a predetermined fuel cut condition,
Performs increase correction of the generated power of the generator driven by the internal combustion engine during the delay time until fuel cut-off condition to stop the fuel supply to the actual cylinder from satisfied,
Established immediately before the fuel cut-off condition, when the intake passage pressure in the timing immediately after the establishment or when established higher, as compared with the case the intake passage pressure in the same period is low, the power generation to be more power during the delay time A control device characterized by.

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