JPS5999042A - Method and apparatus for supplying fuel to electronically controlled engine - Google Patents

Abstract

PURPOSE:To control acceleration of an engine appropriately at the time when the engine temperature is low, by effecting first increase of fuel for acceleration at the time when a throttle valve is opened in case that the engine temperature is lower than a prescribed value, and effecting second increase of fuel for acceleration calculated from the flow rate of intake air and the engine speed after passing of a prescribed time. CONSTITUTION:In operation of an engine, whether an idle switch 29 is ON or OFF is judged at first by an electronic control unit 31. When the switch 29 is turned from ON to OFF, that is, it is judged that an engine is in acceleration, judgement is then made on whether the temperature TW of cooling water detected by a water temperature sensor 22 is lower than 30 deg.C or not. In case of YES, an initial value A is substituted into a first fuel increasing rate F1 for acceleration and a fuel injection valve 7 is controlled on the basis of the value obtained by the above substitution. After passing of a prescribed time, the injection valve 7 is controlled on the basis of a second fuel increasing rate F2 for acceleration calculated from the outputs of an air-flow meter 2 and a crank angle sensor 26 in consideration of the engine load. After the engine is accelerated, the second fuel increasing rate F2 is decreased gradually until it is reduced to zero.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel supply method and apparatus for an electronically controlled engine, and more particularly to a fuel supply method and apparatus for controlling the amount of fuel supplied during acceleration when the engine is at low temperature.

The required acceleration increase in fuel when the engine is at low temperature is large immediately after the start of acceleration, and small after a predetermined period of time has passed since the start of acceleration. In conventional fuel supply methods and devices, the acceleration increase is set to a predetermined value at the start of acceleration, and the acceleration increase decreases approximately linearly over time. Therefore, the control result and 1
If the acceleration increase at ~ is matched with the requested acceleration increase immediately after acceleration starts, the mixture becomes overrich in the latter half of the acceleration period, causing problems such as black smoke and smoldering spark plugs. If the increase in acceleration as a result of the control is matched with the required increase in acceleration in the latter half of the acceleration period, the air-fuel mixture immediately after the start of acceleration becomes overlean, causing problems such as backfire.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel supply method and apparatus that can appropriately control the acceleration increase in fuel during the entire acceleration period when the engine is at low temperature.

According to the fuel supply method of the present invention, when the engine temperature is less than a predetermined value and the throttle valve is opened from the idling position, a first acceleration increase in fuel is calculated, and the intake air flow rate and engine rotation speed are calculated. A second acceleration increase is calculated based on the time change in the ratio, and the amount of fuel calculated based on the first acceleration increase is inhaled in a trench where a predetermined period of time has elapsed since the throttle valve was opened from idling. After a predetermined time has elapsed, an amount of fuel calculated based on the second acceleration increase is supplied to the intake system.

The fuel supply device of the present invention includes a throttle opening detection means for detecting when the throttle valve is opened from an idling opening, and a fuel supply system based on the output of the throttle opening detection means during a period when the engine temperature is less than a predetermined value. a first calculation means for calculating a first acceleration increase; a second calculation means for calculating a second acceleration increase of fuel based on a time change in the ratio of intake air flow rate and engine rotational speed; In the first period, the fuel calculated based on the first acceleration increase is supplied to the intake system, and in the latter half of the acceleration period, the fuel calculated based on the second acceleration increase is supplied to the intake system. There is.

Changes in the intake air flow rate and engine rotational speed that occur with the start of acceleration appear a while after the start of acceleration, so
If the amount of fuel supplied to the intake system immediately after the start of acceleration is calculated based on the second increase in acceleration, the responsiveness will deteriorate, but in the present invention, the amount of fuel supplied immediately after the start of acceleration is calculated based on the first increase in acceleration. Since the amount is calculated, it is possible to promptly increase the amount of acceleration in the first half of the acceleration period and to match the required amount of acceleration.

Preferably, an idle switch is utilized that changes from on to off when the throttle valve is opened from an idling opening, and when the idle switch changes from on to off when the engine temperature is below a predetermined value, the first acceleration increase is performed. An initial value is set for , and a first acceleration increase execution flag is set. Preferably, when a predetermined period of time has elapsed since the idle switch was turned from on to off, the second acceleration increase is set to an initial value and the first acceleration increase execution flag is reset.

Preferably, the value of the first acceleration increase or the second acceleration increase is decreased by a predetermined amount at a predetermined period to zero in relation to the value of the first acceleration increase execution flag.

The present invention will be explained with reference to the drawings.

FIG. 1 is a schematic diagram of an electronically controlled engine. In the intake passage 1, an air flow meter 2, an intake temperature sensor 3,
A throttle valve 4, a surge tank 5, and an intake pipe "6" are provided.A fuel injection valve 7 is attached to the intake pipe 6 and injects fuel into the intake system.The combustion chamber 11 is equipped with a spark plug 12, and a cylinder It is defined by a head 13, a cylinder block 14, and a piston 15, and is supplied with an air-fuel mixture through an intake valve 1G.The air-fuel mixture combusted in the combustion chamber 11 is discharged through an exhaust valve 19 to an exhaust pipe 20. Oxygen sensor 21
detects the oxygen concentration in the exhaust gas, and the water temperature sensor 22 is attached to the cylinder block 14 to detect the cooling water temperature.

The cylinder discrimination sensor 25 and the rotation angle sensor 26 are connected to the power distributor 2
The crank angle is detected from the rotation of the shaft 28 of No. 7. The cylinder discrimination sensor 25 and the rotation angle sensor 26 generate pulses every time the crank angle changes by 720° and 30°, respectively. The idle switch 29 changes from on to off when the throttle valve 4 becomes larger in V than the idle opening, or more precisely, when the opening reaches a predetermined opening which is slightly larger than the idle opening. The electronic control device 31 receives input signals from various sensors and sends output signals to the fuel injection valve 7 and the ignition device 32. The secondary ignition current of the ignition device 32 is sent to the spark plug 12 via the power distributor 27.

FIG. 2 is a block diagram of the inside of the electronic control device 31. As shown in FIG.

The RAM 35, ROM 36, CPU 37, input/output ports 38 and 39, and output ports 1-/10 and /II are connected to each other via a node 42. CLOCK42
sends a clock pulse to CPU37△. Analog outputs of the air flow meter 2, intake air temperature sensor 3, and water temperature sensor 22 are sent to a multiplexer 47 through buffers 45, 46, and 49. The multiplexer selects an input signal, and the selected input signal is A/D converted in an A/D (analog/digital) converter 48 and then sent to the input/output port 38. The output of the oxygen sensor 21 is ノ(
The output of the cylinder discrimination sensor 25 and the rotation angle sensor 26 is sent to the input/output port 39 via the sofa 50 and the comparator 51, the output of the idle switch 29 is sent to the input/output port 39 via the shaping circuit 53, and the output of the idle switch 29 is sent directly to the input/output port. Sent to 39. Fuel injection valve 7 is an output capo) 40 7
5- receives an input signal via the drive circuit 55, and the ignition device 3
2 receives an input signal from the output caponide 41 via the drive circuit 56.

FIG. 3 shows details of step 80 in the flowchart of FIG. 5, in which when the idle switch 29 changes from on to off, the initial value A of the first acceleration increase F1 is set and the first acceleration increase execution flag is set. It is a flowchart of the program which sets Fe. In step 60, it is determined whether the idle switch 29 is on or off, and if it is on, that is, if the throttle valve 4 is at the idling opening, the process proceeds to step 68, where the idle flag F/ is set, and if it is off, that is, If the throttle valve 4 is opened more than the idling opening, the process advances to step 61.

In step 61, it is determined whether Fl = 1 or not, and # =
If it is 1, that is, the idle switch 29 was on during the previous program execution, the process proceeds to step 62, and if FA=O, that is, when the idle switch 29 was off during the previous program execution, the process proceeds to step 62. 65 is omitted. In step 62, when j, that is, the idle switch 29 changes from on to off, the idle flag F7 is reset. In step 63, it is determined whether the engine cooling water temperature Tw<30°C TW<30
℃, that is, when the engine temperature is low, the process proceeds to step 64, and when TW>30'C, that is, when the engine temperature is not low, steps 64 and 65 are omitted. In step 64, the initial value A is substituted for the first acceleration increase amount F1. Step 6
5, the first acceleration increase execution flag Fe is set.

FIG. 4 is a flowchart of a program for attenuating the value of the acceleration increase coefficient F, showing details of step 80 in the flowchart of FIG. In step 71, it is determined whether or not the first acceleration increase execution flag pe=1. If Fe-1, the process proceeds to step 72; if Fe-0, step 7
Proceed to step 3.

In step 72, the value of the first acceleration increase amount F1 is decreased by a predetermined amount a. In step 72, the value of the second acceleration increase amount F2 is decreased by a predetermined amount. The lower limits of Fl and F2 are set to zero. In step 74, the acceleration increase F1 or F2, whichever was decreased in step 72 or 73, is substituted for the acceleration increase coefficient F, and the two F are stored. - Figure 5 is a flowchart of the main routine. In step 78, it is determined whether the crankshaft has rotated once,
If the determination result is positive, the process advances to step 79; if the determination result is negative, the process passes through step 79.

In step 7, the acceleration increase coefficient F is attenuated.

The details of step 79 are as explained in the flowchart of FIG. In step 80, idle switch 2
9 changes from on to off. The details of step 80 are as explained in FIG. In step 81, the engine load Q'/N (-intake air flow rate Q/engine rotational speed N) is detected. In step 82, it is determined whether it is time to switch from the first acceleration increase to the second acceleration increase, and if the determination result is positive, the process proceeds to step 83, and if not, the process passes through step 83. The switching timing is set at the time when the amount of change ΔQ/N in Q/N per predetermined time sufficiently reflects the acceleration state of the engine, for example, when two idle switches are switched from on to off. This is the time after a predetermined time 11'la has elapsed from the time. In step 83, the initial value B is assigned to the second acceleration increase F2, and the first acceleration increase execution flag Fe is reset. In step 84, the final fuel injection amount Tf is calculated according to the following equation.

Tf = TpXGX (1+F) However, Tp is the basic injection amount determined as a function of Q/N,
G is a correction coefficient determined from the feedback signal from the oxygen sensor 21, the cooling water temperature, etc. Since F=Fl from the time when the idle switch 29 changes from on to off until the predetermined time Ta has elapsed, the final injection amount Tf is calculated based on Fl, and after the predetermined time has elapsed, F=F2, and the final injection amount Tf is calculated based on F2.

FIG. 6 shows the change in the acceleration increase coefficient F during the acceleration period, comparing the present invention (a) and the prior art (b).

In the conventional technique (b) in which the acceleration increase coefficient F is calculated based on ΔQ/N, the calculation of ΔQ/N is performed at a predetermined period. It takes time to arrive at the calculation cycle of N, and it takes time to set the acceleration increase amount F, resulting in poor responsiveness.After the acceleration increase amount F is gradually set, the value of the acceleration increase coefficient is changed by a predetermined amount. is only reduced to zero, so the air-fuel mixture becomes oat-climate in the latter half of the acceleration period. On the other hand, in the present invention (a), the idle switch 29
When the idle switch 29 changes from on to off, it is immediately set to F=F1, and after a predetermined time Ta has passed since the idle switch 29 was turned off, it is reset to F=F2. Therefore, the acceleration increase coefficient is set during the acceleration period. can be adjusted appropriately to the required fuel injection amount.

FIG. 7 is a block diagram of the apparatus of the present invention. In FIG. 7, the first calculation means 90 sets the initial value A to the first acceleration increase F1 when the idle switch 29 is turned from on to off when the engine cooling water temperature is less than 30°C; Thereafter, Fl is decreased by a predetermined amount a at a predetermined period. Fl
The lower bound of is zero. The second calculation means 91 calculates B as a function of the amount of change in Q/N per predetermined time ΔQ/N when a predetermined time Ta has elapsed from 1 to 1 when the idle switch 29 changed from on to off. F2 is set at the acceleration increase F2 of
decrease by a predetermined amount. The lower limit of F2 is also zero. The fuel injection amount calculation means 92 calculates the final fuel injection amount Tf based on the first acceleration increase F1 until the predetermined time Ta has elapsed, and after the predetermined time Ta has elapsed, the final fuel injection amount Tf is calculated based on the second acceleration increase F2.
The final injection amount Tf is calculated based on Tf, and the fuel injection valve 7 is operated in relation to Tf.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the entire electronic control engine to which the present invention is applied, FIG. 2 is a block diagram of the electronic control device, and FIG.
FIG. 4 is a flowchart of a program to attenuate the value of the acceleration increase coefficient, FIG. 5 is a flowchart of the main routine, FIG. 6 is a graph showing changes over time in the acceleration increase coefficient, 7
The figure is a configuration diagram of the device of the present invention. 2... Air flow meter, 4... Throttle valve, 2
2...Water temperature sensor, 26...Crank angle sensor, 2
9... Idle switch, 31... Electronic control device,
90 first calculation means, 91... second calculation means, 9
2...Fuel injection amount calculation means. Figure 3 Step 81 Step 79 Step 81 Figure 6 (a) (b)

Claims (1)

[Claims] ■ When the engine temperature is less than a predetermined value, when the throttle valve is opened from the idling opening, a first acceleration increase in fuel is calculated, and the time of the ratio of the intake air flow rate to the engine rotation speed is calculated. A second acceleration increase is calculated based on the change, and the amount of fuel calculated based on the first acceleration increase is applied to the intake system from the time when the throttle valve is opened from idling until a predetermined period of time has elapsed. 1. A method for supplying fuel to an electronically controlled engine, the method comprising: supplying fuel to an intake system in an amount calculated based on a second acceleration increase after a predetermined time has elapsed. 2. The fuel supply method according to claim 1, characterized in that the values of the first and second acceleration increases are decreased by a predetermined amount at a predetermined period until they become zero. 3 When the throttle valve is opened from the idle link opening during warm-up, the execution flag of the first acceleration increase is set, and if this execution flag is set, the value of the first acceleration increase is kept at a predetermined value until it becomes zero. Claim 2, characterized in that the value of the second acceleration increase is decreased by a predetermined amount at a predetermined cycle until it becomes zero if this execution flag is reset. Fuel supply method described in section. 4. When the throttle valve is opened from an idling opening degree during warm-up, the first acceleration increase amount is set to an initial value, and when the predetermined time has elapsed, the second acceleration increase amount is set to an initial value. A fuel supply method according to claim 1. 5. A throttle opening detection means detects when the throttle valve is opened from an idling opening, and during a period when the engine temperature is less than a predetermined value, a first acceleration increase of the fuel is performed based on the output of the throttle opening detection means. a first calculation means for calculating a second acceleration increase in fuel based on a time change in the ratio between the intake air flow rate' and the engine rotational speed; The electronic device is characterized by having a supply means for supplying fuel calculated based on the acceleration increase to the intake system, and supplying fuel calculated based on the second acceleration increase to the intake system in the latter half of the acceleration period. Control engine fuel supply system.