JP2014141884A - Control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a delay time until start of fuel cut after establishment of a fuel cut condition; and to improve fuel economy.SOLUTION: When a stepping amount of an accelerator pedal is 0 or a threshold close to 0 or less, idling rotation stabilizing control is executed for correcting ignition timing in accordance with variation of rotation speed of a crankshaft of an internal combustion engine, and fuel cut is executed for temporarily stopping fuel supply to a cylinder accompanied by the establishment of a fuel cut condition, and during a delay time until the fuel supply to the cylinder is actually stopped after the fuel cut condition is established, idling rotation stabilizing control is forbidden. Torque-down in the delay time can be executed without worrying about excessive retardation of the ignition timing caused by idling rotation stabilizing control by forbidding idling rotation stabilizing control during the delay time.

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. For the purpose of reducing this torque shock, it is customary not to stop fuel injection immediately even if the fuel cut condition is satisfied, but to stop fuel injection after the delay time has elapsed (for example, the following) (See Patent Document 1). During the delay time, the ignition timing is corrected to be retarded, and the engine torque is actively reduced.

  In addition, when the amount of depression of the accelerator pedal is 0 or less than a threshold value and the internal combustion engine shifts to an idling state, the engine rotational speed fluctuates in order to suppress idle engine stall or waste of fuel. The idle rotation stabilization control is performed to correct the ignition timing in response to the above (for example, see Patent Document 2 below).

Japanese Patent Laid-Open No. 10-030477 JP-A-11-324877

  In the conventional control logic, during the delay time after the fuel cut condition is satisfied, the ignition timing is corrected by the idle rotation stabilization control, and this may overlap with the correction of the ignition timing for the purpose of torque reduction.

  In a vehicle equipped with an automatic transmission, after the fuel cut condition is satisfied, an operation of changing the transmission gear ratio of the automatic transmission to the lowest gear (the reduction ratio is large) is performed. This is intended to increase fuel efficiency by extending the inertial traveling period in which the axle rotates the engine crankshaft during the fuel cut as much as possible, that is, delaying the establishment of the fuel cut end condition as much as possible.

  However, if the gear ratio of the automatic transmission is operated to the low gear side, the engine speed increases. In order to suppress this acceleration, idle rotation stabilization control retards the ignition timing. If the retardation correction for the purpose of torque reduction is added to the retardation correction, the ignition timing is excessively retarded, which may cause misfire in the cylinder.

  Therefore, conventionally, the delay correction amount for the purpose of torque reduction during the delay time is set to a small value with a safety margin so that misfire does not occur even if the ignition timing retardation correction by idle rotation stabilization control occurs simultaneously. Was.

  However, as a result of reducing the retardation correction amount for the purpose of torque reduction, the delay time from establishment of the fuel cut condition to the start of fuel cut becomes longer. Needless to say, the fuel injection and combustion are continued during the delay time, and the effective fuel consumption deteriorates accordingly.

  In other words, the length of the delay time varies depending on whether or not the ignition timing retardation correction by the idle rotation stabilization control occurs.

  The present invention has been made by paying attention to the above-mentioned problem for the first time, and aims to shorten the delay time from establishment of the fuel cut condition to the start of fuel cut and to further improve the fuel consumption. .

  In the present invention, when the amount of depression of the accelerator pedal becomes 0 or less than a threshold value close to 0, idle rotation stabilization control is performed to correct the ignition timing in response to fluctuations in the rotational speed of the crankshaft of the internal combustion engine. The fuel cut for temporarily stopping the fuel supply to the cylinder in accordance with the establishment of the fuel cut condition is performed between the time when the fuel cut condition is established and the time when the fuel supply to the cylinder is actually stopped. The control device is configured to prohibit the idle rotation stabilization control during the delay time.

  If the idle rotation stabilization control during the delay time is prohibited, there is no possibility of excessive retarding of the ignition timing due to the idle rotation stabilization control. Therefore, the delay time can be uniformly shortened regardless of whether or not the ignition timing is corrected by the idle rotation stabilization control.

  According to the present invention, the delay time from establishment of the fuel cut condition to the start of fuel cut can be shortened, and fuel consumption can be further improved.

The figure which shows the structure of the internal combustion engine in one Embodiment of this invention. The figure which shows the structure of the drive system in the embodiment. The flowchart which shows the example of the procedure of the process which the control apparatus of the embodiment implements. The timing diagram which compares the conventional control and the control by the control apparatus of the embodiment.

  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.

  FIG. 2 shows an example of a drive system provided in the vehicle. This drive system includes a torque converter 7 and automatic transmissions 8 and 9. In particular, in the present embodiment, a forward / reverse switching device 8 using a planetary gear mechanism and a belt-type CVT (Continuously Variable Transmission) 9 which is a type of continuously variable transmission are adopted as components of the automatic transmissions 8 and 9. doing.

  The rotational torque output from the internal combustion engine is input from the crankshaft of the internal combustion engine to the pump impeller 71 on the input side of the torque converter 7 and transmitted to the turbine runner 72 on the output side. The rotation of the turbine runner 72 is transmitted to the drive shaft 94 of the CVT 9 via the forward / reverse switching device 8 and rotates the driven shaft 95 through a shift in the CVT 9. The rotation of the driven shaft 95 is transmitted to the output gear 101. The output gear 101 meshes with the ring gear 102 of the differential device, and rotates the axle 103 and the drive wheels (not shown) via the differential device.

  The torque converter 7 includes a lockup mechanism. The lock-up mechanism is known in this field, and a lock-up clutch 73 that fastens the input side and the output side of the torque converter 7 so as not to rotate relative to each other, and an operation for switching the connection of the lock-up clutch 73. A lock-up solenoid valve (not shown) for controlling the hydraulic pressure (hydraulic pressure) is used as an element. The lockup solenoid valve is a flow rate control valve that receives a control signal l and changes its opening.

  In a vehicle equipped with CVT 9, when the vehicle speed is a predetermined value (for example, 10 km / h) or more, the torque converter 7 is almost always locked up. When the vehicle speed is equal to or lower than the predetermined value, the lockup of the torque converter 7 is released. During lockup, the lockup clutch 73 is pressed against the torque converter cover 74 and rotates together with the torque converter cover 74. The engine torque input to the input side (drive plate) of the torque converter 7 at the time of lock-up is output from the torque converter cover 74 via the lock-up clutch 73 and thus to the forward / reverse switching device 8. Communicated directly to. At the time of lockup, the speed ratio, which is the ratio of the output side rotational speed of the torque converter 7 to the input side rotational speed, is 1.

  In turn, the lock-up clutch 73 is separated from the torque converter cover 74 at the time of non-lock-up. At the time of non-lock-up, the engine torque input to the input side of the torque converter 7 is transmitted from the torque converter cover 74 to the pump impeller 71 and the turbine 72 and is transmitted to the forward / reverse switching device 8. At the time of non-lock-up, the speed ratio of the torque converter 7 becomes smaller or larger than 1 depending on the driving state.

  The CVT 9 includes a driving pulley 91 and a driven pulley 92, and a belt 93 wound around the pulleys 91 and 92 as elements. The drive pulley 91 is disposed behind the movable sheave 912, a fixed sheave 911 fixed to the drive shaft 94, a movable sheave 912 supported on the drive shaft 91 via a roller spline so as to be displaceable in the axial direction. A hydraulic servo 913 is provided, and the gear ratio can be changed steplessly by operating the hydraulic servo 913 and displacing the movable sheave 912. The driven pulley 92 is disposed on the back of the movable sheave 922, a fixed sheave 921 fixed to the driven shaft 95, a movable sheave 922 supported on the driven shaft 95 via a roller spline so as to be axially displaceable. A hydraulic servo 923 is provided, and a belt thrust necessary for torque transmission is applied by operating the hydraulic servo 923 and displacing the movable sheave 922.

  A hydraulic pump (hydraulic fluid) supplied to the forward brake 84 or the reverse clutch 85 to operate the travel range, and a hydraulic pump (discharge fluid) supplied to the hydraulic servos 913 and 923 to operate the gear ratio. (Not shown) is a known mechanical type (non-electric type) that operates by receiving torque transmitted from the crankshaft of the internal combustion engine. This hydraulic fluid is common to the fluid used for the torque converter 7.

  An ECU 0 (Electronic Control Unit), which 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. The accelerator opening signal c output from a sensor that detects the amount or the opening of the throttle valve 32 as an accelerator opening (so-called required load), the intake air temperature and the intake pressure in the intake passage 3 (particularly, the surge tank 33). An intake air temperature / intake pressure signal d output from a temperature / pressure sensor to be detected, a cooling water temperature signal e output from a water temperature sensor to detect the cooling water temperature of the engine, and a sensor (or shift) to know the range of the shift lever Shift range signal f output from the position switch), multiple intake camshafts or exhaust camshafts The cam angle signal g output from the cam angle sensor at the cam angle, the battery current (or voltage) indicating the charge state of the on-vehicle battery, the battery status signal h output from the sensor detecting the battery temperature, and the like are input. The

  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 lock for connection / disconnection switching of the lockup clutch 73. Opening control signal l for up solenoid valve, opening control signal m for solenoid valve for switching connection / disconnection of forward brake 84 or reverse clutch 85, transmission ratio control signal n for CVT9, rotation from crankshaft An output voltage command signal o or the like is output to an IC regulator attached to a generator that generates power upon receiving the driving force.

  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 and intake air amount, etc., the required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, ignition timing, and torque converter 7 lock-up are adjusted. Various operation parameters such as whether or not to perform the transmission, the gear ratio of the automatic transmissions 8 and 9, and the amount of power generated by the generator (output voltage) are determined. As the operation parameter determination method itself, a known method can be adopted. Thus, the ECU 0 applies various control signals i, j, k, l, m, n, and o corresponding to the operation parameters via the output interface.

  The ECU 0 of the present embodiment executes idle rotation stabilization control when the amount of depression of the accelerator pedal becomes 0 or less than a threshold value close to 0 and the internal combustion engine shifts to an idling state. That is, the ignition timing is corrected in response to fluctuations in the rotational speed of the crankshaft of the internal combustion engine in order to suppress idle engine stall or fuel waste.

  In the idle rotation stabilization control, the time required for the crankshaft to rotate by a predetermined angle (for example, 30 ° CA (crank angle)) is repeatedly measured as an index value representing the rotation speed of the engine. Then, the difference between the required time measured at the previous measurement opportunity and the required time measured this time is obtained, and when the difference exceeds a predetermined value, the correction amount of the ignition timing is determined according to the magnitude of the difference.

  For example, if the current required time is smaller than the previous required time and the difference between the two exceeds a predetermined value, it means that the rotation of the crankshaft tends to accelerate, so the absolute value of the difference is large. As the ignition timing is retarded more greatly, the engine torque is reduced to suppress the acceleration of crankshaft rotation. Conversely, if the current required time is longer than the previous required time, it means that the rotation of the crankshaft tends to decelerate, so the larger the difference, the larger the ignition timing. And increasing the engine torque to suppress the deceleration of the crankshaft rotation.

  Alternatively, in idle rotation stabilization control, an average of a plurality of required times measured over a plurality of past measurement opportunities is obtained, and a difference between this average and the required time measured this time is obtained, and according to the magnitude of the difference The correction amount of the ignition timing may be determined.

  In addition, 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) in accordance with 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. 3 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, during the delay time. An ignition timing retardation correction amount for the purpose of torque reduction 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. In step S2, when the intake pressure when the fuel cut condition is established is high, the retard amount of the ignition timing per unit time or unit cycle is increased and / or the ignition timing compared to when the intake pressure is low. Set the maximum value of the retard amount of to a larger value.

  The ignition timing is corrected during the delay time from the establishment of the fuel cut condition to the start of the fuel cut, as described above, to suppress or avoid the torque shock when the fuel injection is stopped by reducing the engine torque. Is intention. 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 addition, after the fuel cut condition is satisfied, the idle rotation stabilization control (correction of ignition timing) is temporarily prohibited until the delay time is removed (step S3).

  After the fuel cut condition is established, the ECU 0 operates the gear ratio of the CVT 9 to the low gear side (step S4) and retards the ignition timing (step S5) and performs an operation of injecting and burning fuel into the cylinder 1. Maintain (step S6). Accordingly, at the timing when it is considered that the situation where the fuel injection can be stopped is ready (step S7), the fuel injection (and ignition) is stopped (step S8).

  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 S7 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 status 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 loss of the alternator is estimated based on the DUTY ratio (fDUTY) of energization to the field coil of the generator, 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 S7, and the fuel injection may be stopped when the current engine torque is equal to or lower 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.

  Accordingly, the elapsed time from the establishment of the fuel cut condition is counted, and in step S7, 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 S8), any fuel cut end condition 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. When the soot has been reached (step S9), the fuel cut ends and fuel injection (and ignition) is resumed (step S10).

  Incidentally, 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 is a value close to the original target theoretical air-fuel ratio. Execute air-fuel ratio control to converge to

FIG. 4 shows a comparison between the conventional control and the control of the present embodiment. In the conventional control, during the delay time after the fuel cut condition satisfaction time t ₀ , the ignition timing retardation correction by the idle rotation stabilization control (in the column of “ignition timing correction amount by idle rotation stabilization control”) Can be generated). If this delay angle correction is added to the desired ignition timing in the delay time (shown by the solid line in the “ignition timing” column), the ignition timing is excessively retarded (indicated by the broken line in the “ignition timing” column). There is a concern that the combustion of the air-fuel mixture may become unstable. Therefore, in the conventional control, a safety margin is given to the retard of the ignition timing during the delay time (represented by a chain line in the “ignition timing” column). When the delay angle correction by the idle rotation stabilization control does not occur, the ignition timing is operated along the chain line in FIG. 4, and therefore, the time t ₂ when the engine torque decrease is delayed and actually enters the fuel cut. Will be late.

On the other hand, in the control of this embodiment, the idle rotation stabilization control during the delay time is uniformly prohibited. Therefore, after the fuel cut condition establishment time t ₀ , the ignition timing can always be operated along the solid line in FIG. 4, and the time t ₁ when actually entering the fuel cut can be advanced, that is, the delay time Can be shortened.

  In the present embodiment, when the accelerator pedal depression amount is 0 or less than a threshold value close to 0, idle rotation stabilization control is performed to correct the ignition timing in response to fluctuations in the rotational speed of the crankshaft of the internal combustion engine. Along with the establishment of the fuel cut condition, the fuel cut is performed to temporarily stop the fuel supply to the cylinder 1 until the fuel supply to the cylinder 1 is actually stopped after the fuel cut condition is established. The control device 0 is configured to prohibit the idling rotation stabilization control during the delay time.

  According to the present embodiment, there is no possibility of excessive retarding of the ignition timing by the idle rotation stabilization control during the delay time. Therefore, it is possible to take a sufficiently large retard correction amount for the purpose of torque reduction during the delay time without considering the correction of the ignition timing by the idle rotation stabilization control. Therefore, the delay time is shortened, that is, the fuel cut period is effectively extended, and the fuel consumption can be reduced and the fuel consumption performance can be improved.

  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 S5).

  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 8, 9 ... Automatic transmission (forward / reverse switching device, CVT)

Claims (1)

When the accelerator pedal depression amount is 0 or below a threshold value close to 0, idle rotation stabilization control is performed to correct the ignition timing in response to fluctuations in the rotational speed of the crankshaft of the internal combustion engine,
A fuel cut for temporarily stopping the fuel supply to the cylinder in accordance with the establishment of the fuel cut condition,
A control device that prohibits the idling rotation stabilization control during a delay time from when the fuel cut condition is satisfied to when the fuel supply to the cylinder is actually stopped.

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