JP6108789B2 - 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 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 vehicle is traveling at a low vehicle speed, the intake air amount and fuel injection amount charged in the cylinder are small. Under such circumstances, if the fuel cut condition is satisfied and the ignition timing is remarkably retarded, the combustion of the air-fuel mixture in the cylinder becomes unstable and may cause misfire. Accordingly, 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 low vehicle speeds.

Japanese Patent Laid-Open No. 10-030477

  At present, the ignition timing retardation correction amount is uniformly set regardless of the vehicle speed. For this reason, when the fuel cut condition is satisfied during traveling at a high vehicle speed, the delay time required for the engine torque to sufficiently decrease 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 when a predetermined fuel cut condition is satisfied, and the cylinder is actually operated after the fuel cut condition is satisfied. During the delay time until the fuel supply to the vehicle is stopped, the ignition timing is retarded, and if the vehicle speed is high immediately before, when, or just after the fuel cut condition is met, compared with the case is low, the control unit of the larger setting to an internal combustion engine the amount of delay of the maximum value of either the ignition timing to more the retard amount of the ignition timing per definitive unit time or unit cycle in the delay time Configured.

  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.

  An ECU (Electronic Control Unit) 0 that is a 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 is output to the igniter of the spark plug 12, a fuel injection signal j is output to the injector 11, an opening operation signal k is output to the throttle valve 32, and the like.

  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, 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 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. 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 vehicle speed at the time immediately before the fuel cut condition is satisfied, or at the time immediately after the fuel cut condition is satisfied, and calculates the retard correction amount of the ignition timing in the delay time. Determine (step S2). That is, as shown in FIG. 3, when the vehicle speed is high, the ignition timing retard amount per unit time or unit cycle is increased and / or when the vehicle speed is low and / or the ignition timing is delayed. Set the maximum angular amount to a larger value. In FIG. 3, the solid line represents the case where the vehicle speed is relatively high, and the broken line represents the case where the vehicle speed 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 vehicle speed is relatively high, and t ₂ is the fuel supply to the cylinder 1 when the vehicle speed is relatively low. It is time. 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.

  Then, while retarding the ignition timing (step S3), the operation of injecting and burning fuel into the cylinder 1 is maintained (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. Since the accelerator pedal is not depressed when the fuel cut condition is satisfied, 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 significantly reduced. Furthermore, since the ignition timing is retarded, the engine torque decreases rapidly even though the fuel supply to the cylinder 1 is continued.

  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 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, 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, 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. If the vehicle speed of the vehicle is high immediately before, when, or just after the fuel cut condition is satisfied, compared to when the vehicle speed is low at the same time The control device 0 for an internal combustion engine is characterized in that the amount by which the ignition timing is retarded during the delay time is increased.

  According to this embodiment, compared with the conventional fuel cut control, the delay time from the fuel cut condition establishment to the fuel injection stop at the high vehicle speed is shortened (in other words, the fuel cut period is effectively extended). ), And waste of fuel can be reduced. In addition, when the vehicle speed is low, it is possible to prevent the misfire in the cylinder 1 by slowing the correction of the ignition timing during the delay time and / or suppressing the maximum delay amount.

  The present invention is not limited to the embodiment described in detail above. Various modifications can be made to the specific configuration of each part, processing procedure, and the like 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

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,
During the delay time from when the fuel cut condition is satisfied until the fuel supply to the cylinder is actually stopped, the ignition timing is retarded.
Established immediately before the fuel cut-off condition, when the vehicle speed of the vehicle is high at timing immediately after the establishment or during establishment, as compared with the case where the vehicle speed at the same time is low, the ignition timing per definitive unit time or unit cycle in the delay time slow A control device for an internal combustion engine that sets a larger amount of angular amount or a larger maximum value of a retard amount of ignition timing .

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