JP2008291757A - Fuel control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel control device for controlling a fuel injection amount in response to a rotation variation after a cold engine starts, capable of preventing overlean, an increase of an HC exhaust amount, and rotation speed drop caused by fluctuation of friction torque of an engine. <P>SOLUTION: The fuel control device comprises fuel injection valves provided on suction ports of respective cylinders or in the respective cylinders, a rotation variation calculating means for calculating the rotation variation for each ignition cycle, and an injection amount control means for regulating an injection amount of the fuel injection valve in response to the rotation variation. The injection amount control means inhibits injection amount regulation by the rotation variation or changes a control parameter for injection amount regulation in response to a warming-up state in previous operation or an engine stop time. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  Vaporization characteristics of internal combustion engines vary, and when starting with heavy gasoline that does not easily evaporate during cold start, a large amount of fuel adheres to the intake port walls and intake valves. As a result, the combustion state deteriorates and the amount of unburned gas (HC) is increased, and rotation fluctuations are likely to occur. In addition, due to variations in the characteristics of parts such as injectors, air flow meters that measure the amount of air, or intake pipe pressure sensors, the fuel supply amount decreases, causing the air-fuel mixture in the cylinder to become lean and cause the same problems as described above. There is a case.

  On the other hand, when the amount of fuel is increased so that it does not become lean even when heavy gasoline is used, the amount of unburned gas (HC) emitted increases due to over-richness when using light gasoline that tends to evaporate.

  In contrast, the instability of the combustion state due to leaning due to variations in fuel properties, etc., is detected by rotational fluctuations between ignitions, and the fuel injection amount is controlled to prevent over-richness in light gasoline. Patent Document 1 discloses a technology that suppresses leaning of heavy gasoline while it is used.

  In Patent Document 1, the crank angular velocity in a predetermined angular range after ignition is measured for each ignition, the amount of rotational fluctuation is obtained from the amount of crank angular speed change between ignitions, and when the amount of rotational fluctuation increases, fuel is increased to prevent leaning. Like to do.

JP-A-8-86237

  Generally, the rotational fluctuation amount (angular speed change amount) between ignitions at the time of idling is expressed by Equation 1, and when the combustion state is stable, the engine generated torque TQe and the friction torque TQf are substantially balanced, so the rotational fluctuation amount DNE is small. However, when the engine generated torque TQe decreases due to leaning, the rotation decreases and DNE increases.

  Further, from Equation 1, the rotational fluctuation amount changes depending on the engine friction torque TQf (negative torque).

DNE∝ | (TQe−TQf) ^* Δt / I |
DNE: Amount of rotational fluctuation during ignition
TQe: Engine generated torque
TQf: Engine friction torque
I: Crankshaft moment of inertia
Δt: Time interval between ignitions If the generated torque of a cylinder in which combustion is unstable due to leaning temporarily decreases, if the generated torque of the cylinder is the same, the larger the friction torque, the more the rotational fluctuation amount As the friction torque decreases, the rotational fluctuation amount decreases.

  That is, when the friction torque is reduced, the detection sensitivity of the lean state due to rotational fluctuation is lowered.

  According to the present invention, in a fuel control device that controls a fuel injection amount after starting in accordance with a rotational fluctuation amount, the friction torque of the engine is reduced and the rotational fluctuation amount is reduced, so that the detection sensitivity of a lean state due to the rotational fluctuation amount is reduced. An object of the present invention is to maintain a stable combustion state and prevent an increase in HC emission amount and a drop in rotation by determining a decreasing operating state and appropriately performing fuel control according to the operating state.

According to a first configuration of the present invention, a fuel injection valve provided in each cylinder or an intake port of each cylinder, a rotation fluctuation amount calculating means for calculating a rotation fluctuation amount for each ignition cycle, and the rotation fluctuation amount An injection amount control means for adjusting the injection amount of the fuel injection valve, an operation state detection means for detecting the operation state of the internal combustion engine, and a warm-up state that stores a warm-up state of the internal combustion engine calculated from the operation state of the internal combustion engine Machine state storage means,
The injection amount control means prohibits the injection amount adjustment based on the rotation fluctuation amount or changes the control parameter for adjusting the injection amount in accordance with the warm-up state during the previous operation.

According to a second configuration of the present invention, a fuel injection valve provided in each cylinder or an intake port in each cylinder, a rotation fluctuation amount calculating means for calculating a rotation fluctuation amount for each ignition cycle, and the rotation fluctuation amount An injection amount control means for adjusting the injection amount of the fuel injection valve; and an operating state detection means for detecting any one of a cooling water temperature, a lubricating oil temperature, a load, an air amount, a rotation speed, and a vehicle speed of the internal combustion engine. ,
The injection amount control means increases the fuel when the rotational fluctuation amount exceeds a predetermined threshold value,
When either the coolant temperature or the lubricating oil temperature of the internal combustion engine during the previous operation is less than a predetermined value, the integrated value of the load, air amount, rotation speed, or vehicle speed of the internal combustion engine is less than the predetermined value. In either case, the injection amount adjustment based on the rotational fluctuation amount is prohibited, the threshold value of the rotational fluctuation amount is changed, or the fuel increase characteristic with respect to the rotational fluctuation amount is changed.

According to a third configuration of the present invention, a fuel injection valve provided in each cylinder or a fuel injection valve provided in each cylinder, a rotation fluctuation amount calculating means for calculating a rotation fluctuation amount for each ignition cycle, and the rotation fluctuation amount An injection amount control means for adjusting the injection amount of the fuel injection valve, and a stop time measuring means for measuring a stop time of the internal combustion engine,
The injection amount control means prohibits the injection amount adjustment based on the rotation fluctuation amount or changes the control parameter for adjusting the injection amount according to the stop time.

According to a fourth configuration of the present invention, a fuel injection valve provided in each cylinder or a fuel injection valve provided in each cylinder, a rotation fluctuation amount calculating means for calculating a rotation fluctuation amount for each ignition cycle, and the rotation fluctuation amount An injection amount control means for adjusting the injection amount of the fuel injection valve, an engine temperature detection means, and a storage means for storing the engine temperature at the previous engine stop,
The injection amount control means prohibits the injection amount adjustment based on the rotation fluctuation amount or changes the control parameter for adjusting the injection amount when the difference between the engine temperature at the previous engine stop and the engine temperature at the current start is small. I made it.

  According to the present invention, in the case where the fuel injection amount is controlled by the rotational fluctuation amount after the cold start, the operating condition in which the friction torque of the engine decreases and the detection sensitivity of the lean state due to the rotational fluctuation decreases is determined, and the operating state is set. Accordingly, the fuel control is appropriately performed, so that the combustion state can be kept stable, and an increase in the HC emission amount and a drop in rotation can be prevented.

  A configuration of an engine control apparatus to which the present invention is applied will be described below with reference to the drawings.

  The intake pipe 1 is provided with an intake pipe pressure sensor 9 for detecting the intake air amount and a throttle valve 2 for controlling the intake air amount of the engine.

  Air is introduced into the cylinder 14 via the intake manifold 3 and the intake port 6. The intake port 6 is provided with an injector 4. The injector 4 injects fuel toward the intake valve 5.

  A crank angle detection plate 7 is attached to the crankshaft of the engine, and a crank angle sensor 8 is provided.

  11 is an ignition plug, 10 is an ignition coil, and 17 is a coolant temperature sensor.

  19 is an oil pan, and 20 is a lubricating engine oil.

  An oxygen concentration sensor 16 is provided in the exhaust pipe 12 of the engine.

  Signals from the intake pipe pressure sensor 9, the coolant temperature sensor 17, the crank angle sensor 8, the oxygen concentration sensor 16, and the like are input to a control device (controller 30), and the controller 30 receives the fuel injection amount, ignition timing, throttle from these input signals. The opening degree is calculated, and control signals are output to the injector 4, the ignition coil 10, the throttle valve 2, etc., respectively.

  The controller 30 is provided with a CPU 31, a read only memory (ROM) 32 for storing a control program and control data, a writable memory (RAM) 33 for storing control variables, and an input / output circuit 34. It is done. A part of the memory 33 has a backup function in which stored data is retained even after the engine is stopped.

  As described above, immediately after the start of the cold engine, fluctuations in the fuel properties and fluctuations in the air-fuel ratio due to variations in the characteristics of the components occur. However, the oxygen concentration sensor 16 is not activated for several tens of seconds after the cold start, and the air-fuel ratio is reduced. It is impossible to detect and control the fuel injection amount.

  For this reason, a method of controlling the fuel injection amount by detecting the instability of the combustion state when the air-fuel ratio becomes lean after start-up by rotational fluctuation is disclosed in the above-mentioned Patent Document 1 and the like.

  In general, when the air-fuel ratio of the air-fuel mixture exceeds the appropriate air-fuel ratio and becomes lean, the combustion state becomes unstable, and the torque fluctuation increases to increase the rotation fluctuation amount.

  Here, the rotational fluctuation amount is obtained, for example, by measuring the crank angular velocity in a predetermined angle range from the explosion stroke to the exhaust stroke for each ignition and calculating the crank angular velocity change amount between ignitions.

  Therefore, the air-fuel ratio in the cylinder can be estimated by measuring the rotational fluctuation amount. Here, if the fuel injection amount increase correction is performed according to the rotational fluctuation amount after the cold start, the leanness of the air-fuel ratio can be suppressed.

  Here, according to the experiments by the inventors, if fuel control by the rotation fluctuation is performed at the cold start after the running pattern of stopping the engine before the engine temperature sufficiently rises after the cold start, Compared with the cold start after the machine is started, the air-fuel ratio becomes over lean, the combustion becomes unstable, and the HC emission amount increases or the rotation decreases.

  The cause of this is that if the engine is stopped before the engine temperature rises sufficiently after starting the cold engine, the moisture in the exhaust gas flowing into the crankcase does not evaporate and remains in the engine oil, and this driving pattern is repeated. This is considered to be due to a decrease in engine friction torque due to an increase in water concentration in engine oil and a decrease in oil viscosity.

  With reference to FIG. 2, the rotational fluctuation and the influence on the fuel control when the engine friction torque is reduced will be described.

  (A) is a crank angular velocity for each ignition, and (b) is a predetermined crank angle range (angular velocity detection window) for detecting the crank angular velocity for each ignition.

  The crank angular velocity is obtained by measuring the time (window passing time) required to shift the predetermined crank angle range after ignition.

  When the torque of a certain ignition decreases due to leaning, the angular velocity after ignition decreases (the window passing time increases) as shown in (c). At this time, a decrease in torque can be detected by comparing the difference between the window passage time of the previous ignition and the window passage time of the current ignition with a predetermined threshold as shown in FIG. The solid line indicates the operation in the case of starting after the complete warm-up (when the friction is normal), and the dotted line indicates the operation when the warm-up is insufficient and moisture remains in the engine oil (when the friction is reduced). In normal friction, when the torque decreases due to lean air-fuel ratio, if the difference in window passage time exceeds a predetermined threshold as indicated by the solid line in (d) due to the decrease in crank angular speed, the solid line in (e) appears. In addition, the amount of fuel is increased to suppress leaning. On the other hand, when the friction is reduced, even if the amount of torque decrease is the same for the above-described reason, the amount of decrease in the crank angular speed is reduced and the difference in window passing time is reduced. As a result, the difference in the window passage time does not exceed the threshold value as indicated by the dotted lines in (d) and (e), that is, the decrease in torque cannot be detected, and the fuel increase is not performed. In the case where it is set in accordance with the above, there is a case where the difference in the window passing time is reduced, so that the fuel increase is reduced and the leaning cannot be suppressed.

  On the other hand, the present invention determines the operating state in which the friction torque of the engine decreases and the detection sensitivity of the lean state due to rotational fluctuations decreases in advance, and performs fuel control according to the operating state, thereby deteriorating the combustion state. The trouble by was prevented.

  FIG. 3 shows an example of the control method of the present invention. The friction torque decreases due to residual moisture in the engine oil when the engine is stopped while the engine oil temperature (oil temperature) is low in the previous operation as described above. In the first embodiment of the present invention, The degree of increase in oil temperature in the previous operation was estimated, and when it was determined that the increase in oil temperature was insufficient, fuel control due to rotational fluctuation was prohibited.

  Here, after the cold start, the coolant temperature generally rises faster than the oil temperature as in (1). However, in general, the sensor for detecting the oil temperature is often not provided in the vehicle. Was simply estimated from the integrated value of the engine load.

  The engine load can generally be detected from a pressure sensor 9 or an air flow meter signal.

  Of course, when an oil temperature sensor is provided, this control may be performed using the detection value of the oil temperature sensor.

  Also, depending on the vehicle, the change in the cooling water temperature and the oil temperature almost coincide with each other. Therefore, in such a vehicle, an increase in the oil temperature is simply determined based on the cooling water temperature TWEND when the engine is stopped during the previous operation. Also good.

  (A) is a case where the engine is operated for a short time at a low load after starting, or when the operation time is very short, and neither the cooling water temperature nor the oil temperature rises. (B) is the cooling water temperature after warming up. Although the temperature rises, the oil temperature does not reach the temperature after warm-up (such as 85 ° C. or higher) because the rise is slow. (C) is a case where the oil temperature has reached the temperature after warming up when operating at a high load after starting or when the operation time is long. The oil temperature has a correlation with the integrated value of the load, and the integrated value of the load when reaching the oil temperature after warm-up is used as the oil temperature increase determination threshold value, and does not reach the oil temperature increase determination threshold value (a) (b (3) In order to prevent the engine oil from remaining in the engine oil at the cold start after the operation of), and to prevent the rotation fluctuation level from being reduced due to a decrease in friction and becoming overlean. Fuel control based on the rotational fluctuation level is prohibited. At this time, the fuel injection amount is set to an amount that does not lean even when heavy gasoline is used. In the operation of (c), since the oil temperature rise determination threshold is exceeded, it is considered that the oil temperature has risen sufficiently, the water has evaporated and the residual water is low, so the cold start after the operation of (c) To allow fuel control by rotational fluctuation.

  Here, when the engine stop time TEGOFF is very long, moisture in the air may be mixed into the engine oil, and there is a risk of leaning due to reduced friction as in the case of residual moisture due to insufficient warm-up. Therefore, the engine stop time may be measured, and if the predetermined time is exceeded, fuel control due to rotational fluctuation may be prohibited.

  Next, the operation of this control will be described in detail with reference to the flowchart of FIG. In step 100, it is determined whether the engine has been started or not started. If the engine has not been started, it is determined in step 110 whether the previous operating state is a condition suitable for fuel control due to rotational fluctuation. More specifically, the load integrated value SUMTP (stored in the backup memory of the memory 33) in the previous operation is referred to and compared with a predetermined load integrated value threshold value KTPL for determining oil temperature rise, KTPL If it is less than that, it is determined that the oil temperature has not risen, and in step 130, the control permission flag based on the previous operation state is set to 0 (control prohibited).

  Here, KTPL is set to a load integrated value at which the oil temperature rises and water mixed in the engine oil evaporates.

  If SUMTP is equal to or higher than KTPL, it is determined that the oil temperature has risen sufficiently. In step 115, the engine stop time TMOFF is compared with a predetermined stop time threshold value KTMH, and if TMOFF exceeds KTMH, the previous time in step 130. The control permission flag #FPREC depending on the operating state is set to 0 (control prohibited). Here, the engine stop time is set in KTMH so that moisture in the air is mixed in the engine oil and does not affect the controllability.

  If TMOFF is within KTMH, the control permission flag #FPREC is set to 1 (control permission) in step 120. After completion of the control permission determination in step 120 or 130, SUMTP is reset to 0 in step 140 for calculating the load integrated value at the current start.

  Here, when a sensor capable of detecting the oil temperature is provided, in step 110, not the load integrated value but the detected value of the oil temperature and a predetermined threshold value (oil temperature at which water in the engine oil evaporates). Of course, it is possible to carry out the control permission determination by comparing with the above.

  Further, an integrated value of the intake air amount may be used instead of the integrated load value. Further, instead of the load integrated value, a value corresponding to the travel distance (vehicle speed integrated value), a rotational speed integrated value, or the like may be used as a value by which an increase in oil temperature can be determined.

  Further, depending on the vehicle, the change in the cooling water temperature and the oil temperature almost coincide with each other. Therefore, in such a vehicle, the increase in the oil temperature may be simply determined based on the cooling water temperature TWEND when the engine is stopped during the previous operation. good. In this case, in step 110, control is permitted when TWEND exceeds a predetermined threshold value.

  If the control device does not have a function for measuring the engine stop time, step 115 may be omitted.

  If the engine has been started in step 100, it is determined in step 150 whether the engine temperature (cooling water temperature, etc.) is within a temperature range suitable for fuel control due to rotational fluctuations. Specifically, it is in a cold state where the air-fuel ratio fluctuates due to the difference in fuel properties, and when the fuel increase is extremely large at extremely low temperatures, it may become overrich and the rotational fluctuation may increase. Then, if fuel control based on rotational fluctuation is carried out, there is a risk of excessive increase. Therefore, fuel control based on rotational fluctuation is permitted within a range excluding such temperature conditions.

  If the temperature condition is within a controllable range, it is determined in step 160 whether idling is in progress. This is because the air-fuel ratio may change abruptly during traveling and is not suitable for fuel control due to rotational fluctuations.

  If it is during idling, it is determined in step 170 whether the oxygen concentration sensor 16 is before activation.

  If the oxygen concentration sensor 16 is activated, fuel control by the oxygen concentration sensor 16 is performed. When the oxygen concentration sensor 16 is not activated, it is checked in step 180 whether the control permission flag #FPREC according to the previous operation state is 1 (permitted). If #FPREC is 1, calculation of the fuel correction amount FRBS due to rotational fluctuation is performed at step 190.

  A method for calculating the fuel correction amount FRBS due to the rotational fluctuation will be described later.

  If any of steps 150, 160, 170, and 180 is not established, the fuel correction amount is not calculated based on the rotational fluctuation, and the fuel correction amount FRBS is set to a predetermined maximum value FRBSMAX in step 200. Here, FRBSMAX is a fuel correction amount that does not become overlean even with heavy gasoline.

  After calculating the FRBS, the injection pulse width TI is calculated in step 210. Here, TP is a detected value of the intake pipe pressure sensor 9 or, if an intake air amount sensor is provided, a basic injection pulse width obtained from the intake air amount / rotation speed, and FTW is a fuel correction coefficient depending on the engine temperature. A pulse width obtained by correcting the TP with a correction coefficient such as FTW or FRBS is set to TI.

  In step 220, the load integrated value SUMTP in the current operation is calculated in order to perform control permission determination at the next start. Here, since the basic injection pulse width TP corresponds to the load, TP is integrated in the ignition cycle. Here, an integrated value of the intake air amount may be used instead of the integrated load value. Further, instead of the load integrated value, a travel distance, a vehicle speed integrated value (corresponding to the travel distance), a rotational speed integrated value, or the like may be used as a value by which the oil temperature rise can be determined.

  Next, the calculation method of the fuel correction amount FRBS due to the rotational fluctuation in step 190 will be described in detail with reference to FIG. In step 300, the rotational fluctuation level is calculated. As an example of the calculation method of the rotational fluctuation level, as described above, the time for displacing the predetermined crank angle range after ignition from the signal of the crank angle sensor 8: the window passing time (corresponding to the reciprocal of the crank angular velocity) is measured, and the window The amount of change DTM between ignitions of the passage time is obtained by the following equation.

DTM = Tn−Tn−1 Formula 2
Tn: This ignition ignition window passing time
Tn-1: previous ignition window passage time Next, in step 310, the rotation fluctuation level DTM is compared with a predetermined threshold value KSL.
If DTM is equal to or greater than KSL, it is determined that the air-fuel ratio is lean, and in step 320, a predetermined fuel increase FSTEPA is added to the fuel correction amount FRBS. Here, FSTEPA may be changed according to the difference KSL between the rotational fluctuation level and the threshold value.

  If DTM is less than KSL, it is determined that the air-fuel ratio is rich with respect to stoichiometry, and at step 330, a predetermined fuel decrement FSTEP is subtracted from the fuel correction amount FRBS.

  The calculation of the fuel correction amount FRBS is performed every ignition cycle.

  With the above control, the engine friction torque is reduced, and the operating state where the detection sensitivity of the lean state due to the rotational fluctuation decreases is judged in advance, and the fuel control due to the rotational fluctuation is prohibited, thereby suppressing leaning and reducing the HC emission amount. Increase and rotation drop can be prevented.

  In the first embodiment, fuel control is permitted or prohibited by estimating the degree of increase in oil temperature in the previous operation. However, in the second embodiment of the present invention, the increase in oil temperature in the previous operation is performed. By changing the threshold value of the rotational fluctuation level according to the degree, over-leaning due to friction torque fluctuation is prevented.

  A control method in the second embodiment will be described with reference to the flowchart of FIG. Steps 100 to 140 and steps 150 to 180 are the same as in the first embodiment.

  If the control permission flag #FPREC by the previous operation state is 1 in step 180, it is determined that the engine is started after warming up, and the threshold value KSL is adjusted to the threshold value KSL in step 400 according to the rotational fluctuation level during normal friction after warming up. Set KSL1.

  If the control permission flag #FPREC is 0, it is determined that the warm-up is insufficient. In step 410, the threshold value KSL2 is adjusted to the rotational fluctuation level in the friction when water remains in the engine oil at the threshold value KSL. Set. KSL2 is set so that the detection sensitivity of the rotational fluctuation level is improved (in the direction of decreasing the rotational fluctuation level) with respect to KSL1.

  Steps 190 to 220 are the same as those in the first embodiment.

  With the above control, even when the engine is warmed up sufficiently, even if the friction torque decreases due to residual moisture in the engine oil and the rotational fluctuation level decreases, the amount of fuel is increased in the same way as when the engine is warmed up. Therefore, it is possible to prevent overleaning as in the first embodiment.

  Here, instead of changing the threshold value of the rotational fluctuation level in accordance with the degree of increase in oil temperature in the previous operation in steps 400 and 410, the fuel increase characteristic is changed in accordance with the degree of increase in oil temperature in the previous operation. You may make it do. In this case, if the control permission flag #FPREC by the previous operation state is 1 in step 180, it is determined that the engine is started after warming up, and in step 400, the fuel corresponding to the difference between the rotational fluctuation level and the threshold value (DTM-KSL) in FIG. The characteristic indicated by the solid line (fuel increase characteristic during normal friction) is selected as the characteristic of the increase FSTEPA. If the control permission flag #FPREC is 0, it is assumed that there is a possibility that the warm-up is insufficient and moisture remains in the engine oil. In step 410, the characteristic indicated by the dotted line in FIG. Select the fuel increase characteristic).

  Here, in order to secure detection sensitivity when the friction is reduced, the threshold value KSL is set in accordance with when the friction is reduced, and the fuel increase characteristic at the time of normal friction (solid line) is less than the fuel increase characteristic at the time of friction decrease (dotted line). Try to set it.

  As a result, even when the rotational fluctuation level is reduced when the friction is reduced, the fuel increase can be made substantially the same as during normal friction, and the threshold value of the rotational fluctuation level is changed according to the degree of increase in the oil temperature described above. Similarly, fuel increase is performed, and overleaning can be prevented.

  Engine friction varies not only with residual moisture in engine oil but also with oil temperature. In general, a vehicle is provided with a cooling water temperature sensor, but an oil temperature sensor is often not provided. Therefore, in a vehicle equipped with only a cooling water temperature sensor, fuel control based on rotational fluctuation is performed within a predetermined range of the cooling water temperature. When it is within. When the elapsed time after engine stop is long (steady state), the coolant temperature and oil temperature are almost the same as the outside air temperature, but when the elapsed time after engine stop is short, the coolant temperature and oil temperature are In general, the cooling water temperature often falls quickly with respect to the oil temperature. For this reason, when the elapsed time after engine stop is short, the oil temperature becomes higher than the cooling water temperature. As a result, if the engine is started when the elapsed time after the engine stops is short, the friction is reduced and the rotational fluctuation level is reduced compared to the starting from the steady state. In some cases, the combustion state deteriorated.

  In this embodiment, fuel control is appropriately performed based on the rotational fluctuation level to prevent overleaning against fluctuations in friction torque due to changes in oil temperature after the engine is stopped.

  The control method of the present embodiment will be described with reference to FIG. (A) is the case where the elapsed time TEGOFF from the engine stop to the start of the previous operation is short, and the oil temperature at the start becomes higher than the coolant temperature, so the friction at that time is left at that temperature for a long time Reduced against friction in (steady state). In such a case, there is a risk of overlean if the fuel control at the rotational fluctuation level is performed. Therefore, when the engine stop time can be measured, the fuel control at the rotational fluctuation level is prohibited when the engine stop time is less than a predetermined value. (B) is the case where the elapsed time TEGOFF from the engine stop to the start of the previous operation is long, and since the oil temperature at the start almost coincides with the cooling water temperature, the friction at that time almost coincides with the steady state, so the rotational fluctuation Allow fuel control by level.

  Here, when the engine stop time cannot be measured, the cooling water temperature TWEND at the time of the engine stop in the previous operation is stored in the backup memory of the memory 33, and the engine stop time is determined by the difference DTW between TWEND and the cooling water temperature TWS at the time of the current start. Can be simply estimated.

  That is, if the DTW is less than the predetermined value KDTWL, it is possible that the engine stop time may be short, and fuel control based on the rotational fluctuation level is prohibited at the current start. If the DTW is equal to or greater than the predetermined value KDTWL, it is considered that the engine stop time is long. Therefore, fuel control based on the rotational fluctuation level is permitted at the current start.

  The control method of the present embodiment will be described in detail with reference to the flowchart of FIG. When it is determined in step 100 that the engine is not started, in step 500, the difference between the coolant temperature TWEND at the time of engine stop in the previous operation (stored in the backup memory of the memory 33) and the water temperature TWS at the time of the current start is obtained as DTW. . In step 510, DTW is compared with a predetermined threshold value KDTWL. If DTW ≧ KDTWL, it is considered that the engine stop time is long, and in step 520, the previous operation state determination flag # FPREC = 1 is set. If DTW <KDTWL, the engine stop time may be short, and # FPREC = 0 is set in step 530.

  When it is determined in step 100 that the engine has been started, steps 150 to 180 perform the same processing as in the first embodiment.

  If # FPREC = 1 in step 180, it is considered that the engine stop time is long. Therefore, in step 190, the fuel correction amount FRBS based on the rotational fluctuation level is calculated. If # FPREC = 0 in step 180, the engine stop time may be short, so the fuel correction amount is not calculated based on the rotational fluctuation level, and FRBS is set to a predetermined maximum increase FRBSMAX in step 200. The processing in steps 190, 200 and 210 is the same as that in the first embodiment.

  Here, in step 510, the engine stop time is simply determined from the difference between the coolant temperature at the time of engine stop and the coolant temperature at the time of start this time in the previous operation, but if the engine stop time can be measured, the measured engine stop time is determined. Of course, the time may be compared with a predetermined threshold value.

  In step 510, the control method for performing fuel control based on the rotational fluctuation level when the difference between the cooling water temperature at the time of stopping the engine and the cooling water temperature at the time of starting this time is equal to or greater than a predetermined threshold in step 510 is, in other words, this time. Since the control is performed when the cooling water temperature at the previous stop is higher by the threshold than the cooling water temperature at the start, if the threshold is set so that the cooling water temperature at the previous stop is close to the temperature after warm-up The control is performed after the engine is warmed up in the previous operation, and the effect of preventing overleaning due to residual moisture in the engine oil as described in the first embodiment can be obtained.

  Further, when it is determined that the engine stop time is short, the threshold value of the rotational fluctuation level may be changed instead of prohibiting the fuel control based on the rotational fluctuation level. A flowchart of the control method in this case is shown in FIG.

  The processing in steps 100 to 180 and steps 500 to 530 is the same as that in FIG. If # FPREC = 1 in step 180, the threshold value KSL is set to the threshold value KSL1 that matches the rotational fluctuation level when the engine stop time is long (normal friction). If # FPREC = 0 in step 180, the threshold value KSL is set to the threshold value KSL2 that matches the rotational fluctuation level when the engine stop time is short (during low friction).

  The subsequent steps 190 to 220 are the same as those in FIG.

  Here, instead of changing the threshold value in accordance with #FPREC in steps 400 and 410, the fuel increase characteristic with respect to the rotational fluctuation level may be changed in accordance with #FPREC as shown in FIG. 7 of the second embodiment. .

  With the above control, even if the engine friction fluctuates due to a change in oil temperature due to the engine stop time from the previous operation, it is possible to prevent overlean.

  Here, the control of the first or second embodiment and the control of the third embodiment are combined to determine and control the friction reduction due to residual moisture in the oil and the friction reduction due to the oil temperature fluctuation after the engine is stopped. May be.

  The control method of the present invention is not limited to a port injection engine having an injector 4 in an intake port, but also in a cylinder injection type engine having an injector 4 in each cylinder. Since the amount of fuel adhering to the wall surface changes and the air-fuel ratio around the spark plug fluctuates, the present invention can be similarly applied.

  When the engine is stopped before the temperature of the engine oil 20 is sufficiently increased under conditions such as traveling for a short distance after the start of the cold machine, moisture in the exhaust gas flowing into the crankcase 19 does not evaporate, and the engine It remains mixed in the oil 20. According to the results of experiments by the inventors, when such a running pattern is repeated, the moisture concentration in the engine oil gradually increases and the viscosity of the oil decreases, thereby reducing the friction torque of the engine and making it leaner. It was found that the amount of rotational fluctuation was smaller even when the torque fluctuation due to was caused, compared to the case where the moisture in the oil was small. As a result, when such a running pattern is repeated, the rotational fluctuation amount does not increase even if the air-fuel ratio is lean. In the control method disclosed in Patent Document 1, the increase in fuel is reduced and the air-fuel ratio is exceeded. In some cases, the engine becomes lean, the combustion becomes unstable, the amount of HC emission increases, and the rotation decreases.

  In addition, fuel control is performed by rotational fluctuation when the engine temperature is low. Generally, the engine temperature is detected by a coolant temperature sensor. Here, when the elapsed time (engine stop time) from the previous engine stop to the current start is short according to experiments by the inventors, the engine oil temperature decreases slowly with respect to the cooling water temperature. The temperature becomes higher than the cooling water temperature, and the oil friction decreases, so the friction torque of the engine decreases and the rotational fluctuation amount decreases. In the control method disclosed in the above-mentioned patent document, the increase in fuel decreases and the air becomes empty. The fuel ratio becomes over lean, and the HC emission amount may increase or the rotation may decrease as in the above example.

  According to the embodiment of the present invention, the sensor for detecting the crank angular velocity of the internal combustion engine and the sensor for detecting the operating state such as the engine temperature are provided, and the optimal fuel injection amount corresponding to the operating state is controlled from the signal of the sensor. By doing so, it is possible to prevent an increase in HC emissions and a drop in rotation.

The structure of the engine control apparatus of this invention. Rotational fluctuation due to fluctuation of friction torque, influence on fuel control. Explanatory drawing of control operation | movement of 1st Example of this invention. The control flowchart of 1st Example of this invention. The flowchart of the fuel control with respect to the rotation fluctuation level of 1st Example of this invention. The control flowchart of 2nd Example of this invention. The fuel increase characteristic with respect to the rotation fluctuation level of 2nd Example of this invention. Explanatory drawing of control operation | movement of 3rd Example of this invention. The control flowchart 1 of 3rd Example of this invention. The control flowchart 2 of 3rd Example of this invention.

Explanation of symbols

1 Intake Pipe 4 Injector 7 Crank Angle Detection Plate 8 Crank Angle Sensor 9 Intake Pipe Pressure Sensor 16 Oxygen Concentration Sensor 17 Cooling Water Temperature Sensor 30 Controller

Claims (8)

Rotational fluctuation amount calculating means for calculating the rotational fluctuation amount for each ignition cycle, injection amount control means for adjusting the injection amount of the fuel injection valve in accordance with the rotational fluctuation amount, and operating state detection for detecting the operating state of the internal combustion engine Means, and warm-up state storage means for storing the warm-up state of the internal combustion engine calculated from the operating state of the internal combustion engine,
The fuel control for the internal combustion engine, wherein the injection amount control means prohibits the injection amount adjustment by the rotation fluctuation amount or changes a control parameter for adjusting the injection amount according to a warm-up state at the time of the previous operation. apparatus.   The warm-up state storage means is an internal combustion engine that is calculated from any one of a cooling water temperature, a lubricating oil temperature, a load, an air amount, a rotation speed, a vehicle speed, and a travel distance obtained from the vehicle speed detected by the operation state detection means. 2. The fuel control apparatus for an internal combustion engine according to claim 1, wherein a warm-up state of the engine is stored.   The warm-up state storage means stores a warm-up state of the internal combustion engine determined by an integrated value of any of the load, air amount, rotation speed, and vehicle speed of the internal combustion engine detected by the operating state detection means. The fuel control device for an internal combustion engine according to claim 1. A rotational fluctuation amount calculating means for calculating a rotational fluctuation amount for each ignition cycle; an injection amount control means for adjusting an injection amount of the fuel injection valve in accordance with the rotational fluctuation amount; a cooling water temperature of the internal combustion engine; a lubricating oil temperature; A driving state detecting means for detecting any one of a load, an air amount, a rotation speed, and a vehicle speed,
The injection amount control means increases the fuel when the rotational fluctuation amount exceeds a predetermined threshold value,
When either the coolant temperature or the lubricating oil temperature of the internal combustion engine during the previous operation is less than a predetermined value, the integrated value of the load, air amount, rotation speed, or vehicle speed of the internal combustion engine is less than the predetermined value. 2. In any of the cases, the injection amount adjustment by the rotation variation amount is prohibited, the threshold value of the rotation variation amount is changed, or the fuel increase characteristic with respect to the rotation variation amount is changed. A fuel control device for an internal combustion engine according to claim 1. A fuel injection valve provided in each cylinder intake port or in each cylinder, a rotation fluctuation amount calculating means for calculating a rotation fluctuation amount for each ignition cycle, and adjusting an injection amount of the fuel injection valve according to the rotation fluctuation amount Injection amount control means for performing, and stop time measuring means for measuring the stop time of the internal combustion engine,
The fuel control apparatus for an internal combustion engine, wherein the injection amount control means prohibits the injection amount adjustment based on the rotation fluctuation amount or changes a control parameter for adjusting the injection amount according to the stop time.   The injection amount control means prohibits the injection amount adjustment based on the rotation fluctuation amount or changes a control parameter for adjusting the injection amount when the stop time is longer than a predetermined threshold value. A fuel control device for an internal combustion engine according to claim 1.   6. The injection amount control means, when the stop time is shorter than a predetermined threshold, prohibits the injection amount adjustment by the rotation fluctuation amount or changes a control parameter for adjusting the injection amount. A fuel control device for an internal combustion engine according to claim 1. A fuel injection valve provided in each cylinder intake port or in each cylinder, a rotation fluctuation amount calculating means for calculating a rotation fluctuation amount for each ignition cycle, and adjusting an injection amount of the fuel injection valve according to the rotation fluctuation amount Injection amount control means, engine temperature detection means, and storage means for storing the engine temperature at the previous engine stop,
The injection amount control means prohibits the injection amount adjustment based on the rotation fluctuation amount or changes the control parameter for adjusting the injection amount when the difference between the engine temperature at the previous engine stop and the engine temperature at the current start is small. A fuel control device for an internal combustion engine.

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