JPS639645A - Fuel cut control method for electronic control engine - Google Patents

Abstract

PURPOSE:To prevent the engine stall reliably, when resetting to fuel supply after fuel cut, by obtaining a correcting quantity of fuel for every predetermined period according to the droppage of engine rotation. CONSTITUTION:During operation of an engine 10, ECU 56 calculates an injection quantity Q according to the outputs from an accelerator 20 and an engine rotation sensor 46. Then it is decided whether an accelerator is fully closed, the engine rotation is higher than a predetermined level (about 850rpm) and the engine rotation is lower than a setting level (about 1,300rpm). When the answer is YES for all decisions, it is decided that the conditions for performing the reset increment are satisfied, thereby the reset increment of injection quantity is calculated according to the droppage of engine rotation during predetermined time (about 0.1sec). Then said reset increment is added to the injection quantity Q so as to obtain a final injection quantity thus controlling a solenoid spill valve 50.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a fuel cut control method for an electronically controlled engine, and is particularly suitable for use in an electronically controlled diesel engine for automobiles, when a fuel cut condition is satisfied in an engine deceleration state. The present invention relates to an improvement in a fuel cut control method for an electronically controlled engine in which the fuel supply is cut and the fuel supply is restored when the engine speed drops to a predetermined fuel return speed.

[Conventional technology]

2. Description of the Related Art So-called electronically controlled diesel engines, in which injection cans are electronically controlled according to engine operating conditions, have been put into practical use. In this electronically controlled diesel engine, similarly to a gasoline engine, when the fuel cut condition is satisfied in the engine deceleration state with the accelerator opening 0%, fuel injection is stopped and the engine speed reaches the predetermined fuel return speed. A so-called fuel cut is performed in which fuel injection is restarted when the amount of fuel has dropped to a certain level. However, if the fuel return speed is low,
The engine speed drops too much before the torque generated by the engine becomes large enough, resulting in engine stall. On the other hand, if the fuel return rotation speed is increased to prevent engine stalling, the amount of white smoke and HC discharged during deceleration increases, and fuel efficiency deteriorates. In order to solve such problems, for example,
No. 188,737 proposes that when the fuel supply is restored, the fuel injection amount is corrected only once by anticipatory control in accordance with the amount of drop in engine speed.

Problem 1 to be Solved by the Invention However, in this case, anticipatory control of the fuel injection tA base in response to a drop in engine speed is performed only once. Therefore, in order to prevent engine stall from occurring under all operating conditions, such as whether the engine is new or after sufficient running-in, the friction state of the engine, variations in torque converter engagement time lag, high or low engine water temperature, etc. In order to do so, the fuel correction amount at the time of recovery (expected injection ■) must be set to a large value, taking into account the individual differences in rotational speed drop due to variations between engines and transmissions. Therefore, depending on the engine, there is a problem in which the engine speed increases abnormally when performing anticipatory injection to prevent engine stalling, or the problem that engine stalling still occurs under special conditions. It was inevitable. OBJECT OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and is capable of preventing engine stalls and engine rotational speeds upon recovery from fuel cut, regardless of individual differences in engines, speed change gears, etc. It is an object of the present invention to provide a fuel cut control method for an electronic combustion engine that can reliably prevent abnormal revving.

[Means to solve the problem]

The present invention provides a fuel cut for an electronically controlled engine that cuts the fuel supply when a fuel cut condition is met while the engine is decelerating, and restores the fuel supply when the engine speed drops to a predetermined fuel return speed. In the control method,
As summarized in Fig. 1, there are a procedure for detecting a state in which fuel supply should be restored, a procedure for calculating the maximum engine speed drop for each predetermined period when fuel supply is restored, and a procedure for calculating the maximum engine speed drop for each predetermined period when fuel supply is restored. Depending on the situation, fuel correction a is carried out at each predetermined period.
The above object has been achieved by including a procedure for determining the amount of fuel supplied at predetermined intervals, and a procedure for repeatedly correcting the fuel supply amount at predetermined intervals based on the fuel correction amount at the time of return.

[Operation 1] In the present invention, when the fuel cut condition is satisfied in the engine deceleration state, the fuel supply is cut, and when the fuel supply is restored when the engine speed has decreased to a predetermined fuel return speed, the fuel supply is restored. At times, the return fuel correction value is calculated every predetermined period in accordance with the drop in engine speed for each predetermined period, and the fuel supply is repeatedly corrected every predetermined period based on the return fuel correction value. Therefore, engine stall can be reliably prevented by absorbing friction differences between engines, shift time lag differences between torque converters, differences in deceleration conditions, and the like. Further, an abnormal increase in engine speed does not occur. Embodiments Hereinafter, embodiments of an electronically controlled diesel engine for automobiles in which the fuel cut control method according to the present invention is adopted will be described in detail with reference to the drawings. As shown in FIG. 2, the first embodiment of the present invention is equipped with an intake temperature sensor 1-2 for detecting the temperature of intake air, which is disposed downstream of an air cleaner (not shown). . Downstream of the intake air temperature sensor 12, there is a turbine 14A that is rotated by the thermal energy of exhaust gas;
A turbocharger 14 consisting of a compressor 14B rotated in conjunction with a compressor 4A is provided. The upstream side of the turbine 14A of the turbocharger 14 and the compressor 1
The downstream side of 4B is communicated via a wastegate valve 15 for preventing an excessive rise in intake pressure. The venturi 16 downstream of the compressor 14B includes:
A main intake throttle valve 18 is provided, which is configured to rotate non-linearly in conjunction with an accelerator pedal 17 disposed at the driver's seat, for restricting the flow of intake air during idling and the like. The opening degree of the accelerator pedal 17 (hereinafter referred to as accelerator opening degree) A ccp is detected by an accelerator position sensor 20 . A DI intake throttle valve 22 is provided in parallel with the main intake throttle valve 18 , and the opening degree of the auxiliary intake throttle valve 22 is controlled by a diaphragm device 24 . Negative pressure generated by a negative pressure pump 26 is supplied to the diaphragm device 24 via a negative pressure switching valve (hereinafter referred to as ■S■) 28 or 30. An intake pressure sensor 32 for detecting the pressure of intake air is provided downstream of the intake throttle valve 18.22. In the cylinder head 1°A of the diesel engine 10,
An injection nozzle 34 whose tip faces the engine combustion chamber 10B, a glow plug 36, and an ignition timing sensor 38 are provided. A glow current is supplied to the glow plug 36 via a glow relay 37. In addition, the cylinder block 10C of the diesel engine 10 includes:
A water temperature sensor 40 is provided for detecting engine cooling water temperature. Fuel is fed under pressure to the injection nozzle 34 from an injection pump 42 . The injection pump 42 includes a pump drive shaft 42A that rotates with the rotation of the crankshaft of the diesel engine 10.
, a feed pump 42B (FIG. 2 shows a 90° expanded state) fixed to the pump drive shaft 42A for pressurizing fuel, and a fuel pressure i for adjusting the fuel supply pressure.
A reference position sensor 44 made of, for example, an N magnetic pickup, for detecting a crank angle reference position, for example, top dead center (TOO>) from the rotational displacement of the u-valve 42C and the pump drive pulley 420 fixed to the pump drive shaft 42A. For example, a roller ring 42H is provided on a roller ring 42H for detecting the engine rotation angle and the position of missing teeth from the rotational displacement of a gear 42E, which is also fixed to the pump drive shaft 42A and has missing teeth corresponding to the number of cylinders. An engine rotation sensor 46 consisting of an electromagnetic pickup, an O-ring 42H for reciprocating the face cam 42F and the plunger 42G, and changing the timing thereof, and a timer for changing the rotational position of the roller ring 42H. By controlling the position of the piston 42J (FIG. 2 shows the state expanded by 90 degrees) and the timer piston 42J, the injection timing can be adjusted by 1 yen.
Timing for ilJ 119 1ill 611
Valve (hereinafter referred to as TCV) 48 and spill boat 42
An electromagnetic spill valve 50 for controlling the speed of fuel injection by changing the timing of releasing fuel from the plunger 42G via K, a fuel cut valve 52 for cutting fuel, and a fuel cut valve 52 for preventing fuel backflow and post molding. A delivery valve 42L for preventing this is provided. The intake temperature sensor 12, the accelerator position sensor 20, the intake pressure sensor 32, the ignition timing sensor 38, the water temperature sensor 40,
A reference position sensor 44, an engine rotation sensor 46, a glow current sensor 54 that detects the glow current flowing through the glow plug 36, a key switch, an air conditioner switch, a neutral save switch output, a vehicle speed signal, etc. are controlled by an electronic control unit (hereinafter referred to as ECLJ). ) 56 and is processed, and the output of the ECU 36 causes the VS
V28.30. 0-'JL/-37, TCV48, electromagnetic spill valve 50. The fuel cut valve 52 and the like are controlled. As shown in detail in FIG. 3, the ECU 36 includes a central processing unit (hereinafter referred to as CPU) 56A for performing various calculation processes, and a read-only memory (hereinafter referred to as CPU) for storing control programs, various data, etc. 56B (referred to as ROM), and a random access memory (referred to as ROM) for temporarily storing calculation data etc. in the CPLJ 56A.
(hereinafter referred to as RAM) 56C, a clock 56D for generating a clock signal, the output of the water wetness sensor 40 inputted via a buffer 56E, the output of the intake air temperature sensor 12 inputted via a buffer 56F, Buffer 56G
A multiplexer (hereinafter referred to as MPX) 56 for sequentially taking in the output of the intake pressure sensor 32 inputted via the buffer 561-1, the output of the accelerator position sensor 20 inputted via the buffer 561-1, etc. Analog - for converting the output analog signal into a digital signal
Digital converter (hereinafter referred to as A/D converter) 56L
, an input/output port 56M for taking the output of the A/D converter 56L into the CPU 56A, a starter signal inputted via the buffer 56N, an air conditioner signal inputted from the air conditioner via the buffer 56P, and a buffer. 56Q
an input/output boat 56S for inputting the torque converter signal inputted from the automatic transmission via the automatic transmission, the output of the ignition timing sensor 38 inputted via the waveform shaping circuit 56R, etc. to the CPU 56A; the waveform shaping circuit 56R for shaping the waveform and directly importing it into the input interrupt port ICAP2 of the CPU 56A; and the waveform shaping circuit 56R for shaping the output of the reference position sensor 44 and directly importing it into the same input interrupt port rCAP2 of the CPU 56A. A shaping circuit 56T and a waveform shaping circuit 56T waveform-shape the output of the engine rotation sensor 46 and input it to the input interrupt port [CA] of the CPU 56A.
A waveform shaping circuit 561J for direct input to Pl, and the electromagnetic spill valve 50 according to the calculation result of the CPU 56A.
a drive circuit 56V for driving the CPU 56A;
a drive circuit 56W for driving the TCV 48 according to the calculation result of the CPU 56A; and a drive circuit 56X for driving the fuel cut valve 52 according to the calculation result of the CPU 56A.
and a common bus 56Y for connecting each of the components and transferring data and instructions. Here, the ignition signal output from the waveform shaping circuit 56R is
In addition to the input interrupt port ICAP2 of PU56A,
Also input to the input/output port 56S is a waveform shaping circuit 56T that is input to the same input interrupt port ICAP2.
This is to distinguish it from the output reference position signal. The operation of the first embodiment will be explained below. The calculation of the fuel injection amount in this first embodiment is performed in the 41i
i! Fuel injection 1ff during the main routine as shown in l.
This is done according to the i calculation routine. That is, first, in step 110, the fuel injection IQ is calculated from the engine speed NE and the accelerator opening A cap using a known method. Next, the process proceeds to step 112, where it is determined whether the accelerator opening degree Accp is 0% and the accelerator is fully open. If the judgment result is positive, step 1
14, the engine speed NE is set to a predetermined value, for example 85.
It is determined whether or not the speed is higher than 0 rpm. If the determination result is positive, the process proceeds to step 116, where it is determined whether or not the engine rotational speed NE is below a set value, for example 1300 rpm. If the determination result in either step 112, 114 or 116 is negative, it is determined that the conditions for performing the return increase when transitioning from the no-fuel injection state during engine deceleration to idle rotation are not satisfied. In some cases, the routine proceeds to step 118, where the fuel injection [iQ calculated in step 110 is used as the final injection flQr, and this routine ends. On the other hand, if the determination results in steps 112, 114, and 116 are all positive, and it is determined that the conditions for performing the return increase ω are satisfied, the process proceeds to step 120, and the process is continued for a predetermined period, for example, 0.1 seconds. The return increase value Q rec of the fuel injection l)j concavity Q is calculated according to the engine rotation drop ff1ND. Next, the process proceeds to step 122, where the fuel injection tJJ calculated in step 110 is calculated by adding the return increase value Q rec to Q to obtain the final injection [tQf, as shown in the following equation, and this routine ends. Qf −Q+Qrec −(1) In this first example, the return increase value Q rec is calculated each time the main routine runs, so the optimum return increase value Q rec is calculated according to the engine conditions that change from moment to moment. is given feedback. In this first embodiment, the program is simple. Next, a second embodiment of the present invention will be described in detail. This second embodiment is an electronically controlled diesel engine for automobiles similar to the first embodiment.
The calculation of Q is performed according to the routine shown in the fifth section. The other points are the same as those of the first embodiment, so the explanation will be omitted. In the routine shown in FIG. 5, first step 210
For example, if the accelerator is fully closed and the engine speed is decelerating, 40 Or 91 or more 1300 rll-
or below, or the engine speed NE is 400 rpI11 or more 1300r while driving with a vehicle speed signal
It is determined whether the conditions for calculating the return increase value Q rec are satisfied, such as being less than or equal to p- and within 2 seconds after a shift from the drive range to the neutral range occurs in the automatic transmission. . If the determination result is positive, the process proceeds to step 212, where the engine rotational speed drop ff1ND for a predetermined period of time, for example, 0.1 seconds, is calculated. Next, the process proceeds to step 214, where it is determined whether the calculated engine rotation drop ff1ND is greater than a set value Kt (for example, zero). If the determination result is negative, or if the determination result of step 210 is negative, return increase 1 @ Q
When it is determined that there is no need to apply rec, the process proceeds to step 216 and the return increase value Q rec is set to zero. On the other hand, if the determination result in step 214 is positive, steps 216 and 218 change the upper limit value to the set value.
Guard with (for example 400). Here, the reason why the upper limit value of the engine rotation drop ff1ND is guarded at a set value of 2 is to prevent the return increase value QreC from becoming abnormally large. Next, the process proceeds to step 220, where a return increase value Q is calculated according to the engine speed drop amount ND using a map as shown in FIG. 6 or a calculation formula as shown in the following equation (2).
Calculate rec. Qrec-3XND-Ks = (2>Here, K
S and KS are constants. After step 216 or 2201, the process proceeds to step 222, in which fuel injection I is determined based on engine speed NE, accelerator opening, A, ccp, intake pressure PiI, etc., using a known method.
Calculate Q. Next, the process proceeds to step 224, where the above (1)
) As shown in the formula, the return increase value Q re is determined by the fuel injection IQ.
This routine ends with the addition of c as the final injection ff1Qf. In this second embodiment, as shown in FIG. 7, the current return increase value Qrf is determined according to the engine rotation drop it N D 2 when the previous return increase value QreC+ was injected.
30z will be calculated, and detailed control will be performed. In contrast, in the method proposed in Japanese Patent Laid-Open No. 57-188737, the return increase m value Qrec is calculated only once. Next, a third embodiment of the present invention will be described in detail. As shown in FIG. 8, in the third embodiment, in the same fuel injection date calculation routine as in the second embodiment, the I return date value Q rec is determined not by the fuel injection layer but by the accelerator opening A cc.
This embodiment differs from the second embodiment in that it is set for p. Along with this, in step 220, the engine speed decreases f
The map used to calculate the return increase value Qrec- corresponding to f1ND is as shown in FIG. Further, step 310 is provided after step 212, in which it is determined whether a predetermined time has elapsed after entering the return Masuda value Qrl-heading routine, and if the determination result is negative, step 220 is performed. It is made to jump later. Further, step 312 is provided after step 220, and the detected accelerator opening degree ACCI) is calculated in step 220 as the accelerator opening corresponding restoration life increase value Qr.
It is determined whether or not it is smaller than ec', and if the determination result is positive, in step 314, the return increase value Qrec = is set as the pseudo accelerator opening AccpA for calculating the fuel injection ■.
It is designed to be placed in Further, after step 314 is completed, in step 316, the injection fFlffi is calculated from the pseudo accelerator fm[AccpA and the engine speed NE. The other points are the same as those of the second embodiment, so the explanation will be omitted. According to this third embodiment, it is possible to increase the return amount based on the accelerator opening degree. In addition, in each of the above embodiments, the recovery increase with respect to the engine speed drop ff1ND! 1iIQrec or QreG- was assumed to be constant, but the return increase m value QreC (Qrec-) changes depending on the shift position of the transmission and its changes, vehicle speed, accelerator opening, engine water temperature, intake pressure, etc.
It is also possible to change the number of companies or, in some cases, to return to work or reduce the number of companies. Although the present invention is applied to a diesel engine in each of the above embodiments, the scope of application of the present invention is not limited thereto, and it is clear that the present invention can be similarly applied to a gasoline engine.

【Effect of the invention】

As explained above, according to the present invention, by performing fuel recovery control according to the rotation reduction rate during engine deceleration, which varies depending on each condition, each engine, and each vehicle, engine stall is prevented and fuel is prevented from blowing up during fuel recovery. , a smooth transition from engine deceleration to idle rotation can be performed. In addition, in order to prevent the engine speed from rapidly decreasing and resulting in an engine stall when shifting from the drive range to the neutral range in conventional automatic transmissions, the system prevents the engine from stalling when shifting from the drive range to the neutral range. However, according to the present invention, it is no longer necessary to perform special control for this purpose, and the control software etc. can be simplified, which is an excellent effect.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the gist of the fuel cut control method for an electronically controlled engine according to the present invention, and FIG.
FIG. 3 is a cross-sectional view including a partial block diagram showing the overall configuration of the embodiment; FIG. 3 is a block diagram showing the configuration of the electronic control unit used in the first embodiment; FIG. FIG. 5 is a flowchart showing a routine in the main routine for calculating fuel injection 611, and FIG. 6 is a flowchart showing a routine for calculating fuel injection maximum used in the second embodiment of the present invention. 5 is a diagram showing an example of a map used in the routine shown in FIG.
FIG. 8 shows an example of the engine speed in the engine deceleration state, the engine speed drop a, and the change state of the return increase value in the engine deceleration state in the example. FIG. 9 is a flowchart showing an example of the routine for calculating the engine rotation speed, and FIG. 9 is a diagram showing an example of a map for calculating the return increase R value corresponding to the accelerator distance from the engine rotation speed drop point used in the routine of FIG. It is. DESCRIPTION OF SYMBOLS 10... Diesel engine, 20... Accelerator position sensor, A ccp... Accelerator opening degree, 42... Injection pump, 46... Engine rotation sensor, NE... Engine rotation speed, 50...・Electromagnetic spill valve, 56...Electronic control unit (ECU), Q...Fuel injection tJJffl, Qf...R final injection l)J amount, NO...engine speed drop amount, Q rec, Q rec = -...Return increase value.

Claims (1)

[Claims] (1) Fuel cut control for an electronically controlled engine that cuts the fuel supply when the fuel cut condition is met while the engine is decelerating, and restores the fuel supply when the engine speed drops to a predetermined fuel return speed. The method includes a step of detecting a state in which fuel supply should be restored, a step of calculating an amount of drop in engine speed at each predetermined period when restoring fuel supply, and a step for restoring at each predetermined period according to the amount of drop in engine speed. A fuel cut control method for an electronically controlled engine, comprising: a step of determining a fuel correction amount at the time of recovery; and a step of repeatedly correcting the fuel supply amount at predetermined intervals using the fuel correction amount at the time of return.