JPS63113137A - Fuel supply controlling method for internal combustion engine - Google Patents

Abstract

PURPOSE:To perform a fuel cut early enough, by equalizing this time value of the engine speed detected by the specified sampling timing with the detected value of up to the last time, and increasing a fuel-cut speed at the time of deceleration at a time when a difference between this time value and the equalized value is more than the specified one. CONSTITUTION:Each detected value out of a throttle opening sensor 23, a suction absolute pressure sensor 24, a water temperature sensor 26 and a crank angle sensor 25 is inputted into a control circuit 30, and a fuel cut at time of deceleration is carried out on the basis of throttle opening and engine speed via a fuel-cut solenoid valve 15. The control circuit 30 detects the engine speed on the basis of the count value made by a TDC signal of the specified cylinder, and when it is decreased from the last time value, it judges to be deceleration, and this time value and the weighted average value are weightedly equalized, thereby calculating the equalized value. When a difference between this time value and the equalized valve is more than the specified one, the basis engine speed that performs the fuel cut as suddent deceleration time is set to the higher value.

Description

[Detailed description of the invention] Kugotachi 1 The present invention relates to a method for controlling the fuel supply of an internal combustion engine.

11. When deceleration operation is started in the high speed range of a dish internal combustion engine, the negative pressure in the intake pipe downstream of the throttle valve suddenly rises due to the closure of the throttle valve, so that the fuel that was on the inner wall of the intake pipe (=J @ ,
Fuel is also supplied to the engine from the low speed system of the carburetor. For this reason, during deceleration, the air-fuel ratio of the air-fuel mixture supplied to the engine becomes overrich, increasing the amount of unburned harmful components in the exhaust gas.To prevent this,
It is also known to cut off the fuel supply or reduce the amount of fuel supplied when deceleration operation is started in a high rotation range in order to save fuel. For example,
No. 51, Japanese Unexamined Patent Publication No. 51-35825, etc. disclose devices that increase the opening of the throttle valve during deceleration from a high speed range and cut fuel in the low speed system. JP-A-54-45423 discloses that when deceleration from a high rotation range is detected, the fuel supply to the engine is immediately stopped, and when deceleration from a rotation range smaller than the high rotation range is detected, the fuel supply to the engine is stopped after a time delay. Disclosed is an apparatus for stopping the fuel supply of a fuel cell. Further, Japanese Patent Application Laid-open No. 53-74625 discloses a device in which fuel cut start conditions are varied depending on the opening degree of a throttle valve when a rotation speed lower than a high rotation range is exceeded.

It is known that in a device that performs such a fuel cut, the lower the reference value for determining whether the engine rotational speed is such that fuel supply should be stopped during deceleration, the better the fuel efficiency will be. However, if this standard value is set too low, the engine may stall during sudden deceleration, and conversely, if the standard value is set too high, fuel cut may stop early during deceleration, resulting in poor fuel efficiency. Therefore, it has been difficult to set a reference value that will not cause engine stall and improve fuel efficiency. In addition, when determining sudden deceleration from the amount of change in engine speed per unit time, if the unit time is shortened, it will be more susceptible to noise, etc.; if the intermediate time is lengthened, the sudden deceleration of engine speed will increase. Therefore, it was difficult to detect the operating state in which fuel should be cut due to high viscosity.

1 ■ Standing and I Therefore, an object of the present invention is to provide a fuel supply for an internal combustion engine that accurately detects the operating state in which the fuel supply should be stopped or the supply port should be reduced, thereby preventing engine stall and improving fuel efficiency. 11I11 method.

The fuel supply control method of the present invention detects the engine rotation speed Ne at a predetermined sampling timing, and sets the currently detected value Nen of the detected engine rotation speed to a predetermined functional relationship based on the detected value of the engine rotation speed detected up to the previous time. Average by averaging (FINA VEN is calculated by °, and the difference ΔNE between the current detected value Nen and the averaged value NAVEn is calculated,
When the difference .DELTA.NE exceeds a predetermined value .DELTA.NETI-1, the fuel supply is stopped or the fuel supply m is set high.

Friend-Ei-1 Hereinafter, embodiments of Honzoku Otoko will be described with reference to the drawings.

FIG. 1 shows an on-vehicle internal combustion engine equipped with a device to which a fuel supply control method according to an embodiment of the present invention is applied. In this figure, a slow boat 11 and an idle boat 12 for a low speed system are formed on the inner wall surface of the carburetor 2 near the throttle valve 3. The slow boat 11 and the idle boat 12 communicate with a slow fuel supply passage 13, and the slow fuel supply passage 13 is provided with a fuel cut solenoid valve 15. The fuel cut solenoid valve 15 connects the slow fuel supply passage 13 when the solenoid (not shown) is energized, and closes the slow fuel supply passage 13 when the solenoid is not energized.

On the other hand, 23 is a throttle opening sensor that generates an output level that corresponds to the opening degree of the throttle valve 3, and 24 is an absolute pressure sensor that is provided in the intake pipe 4 and generates an output level that corresponds to the absolute pressure inside the intake pipe 4. Sensor 25 is the crankshaft of engine 1 (
A crank angle sensor 26 generates pulses in accordance with the rotation of the engine 1 (not shown), and a cooling water temperature sensor 26 generates an output at a level corresponding to the cooling water temperature of the engine 1. The solenoid valve 15 , throttle opening sensor 23 , absolute pressure sensor 24 , crank angle sensor 25 , and water temperature sensor 26 are connected to a control circuit 30 .

As shown in FIG. 2, the control circuit 30 includes a level conversion circuit 31 that converts the output levels of the throttle opening sensor 23, absolute pressure sensor 24, and water temperature sensor 26, and one of the sensor outputs that have passed through the level conversion circuit 31. a multiplexer 32 that selectively outputs the signal, and an A/D converter 33 that converts the signal output from the multiplexer 32 into a digital signal.
, a waveform shaping circuit 34 that shapes the output signal of the crank angle sensor 25, and a clock pulse generation circuit (not shown) that determines the generation interval of the TDC (top dead center) signal output as a pulse from the waveform shaping circuit 34. A counter 35 that measures the number of output clock pulses, a drive circuit 38 that drives the fuel cut solenoid valve 15, and a CPU (central processing circuit) 3 that performs digital calculations according to a program.
9, a ROM 40 in which various processing programs and data are written in advance, and a RAM 41. The multiplexer 32, A/D converter 33, counter 35, drive circuit 38, CPU 39, ROM 40, and RAM 41 are connected to each other by an input/output bus 42.

The CPLI 39 also has a timer TA (not shown).

In such a configuration, from the A/D converter 33 to the throttle valve 3
The information on the opening θth, the absolute pressure in the intake pipe 4, Pe A %, and the cooling water temperature Tw is alternatively sent to the CPU 39, and information on the count value Me between the TDC signals is sent from the counter 35 as information on the engine rotation speed. are respectively supplied via an input/output bus 42.

The CPU 39 performs a fuel cut control routine to be described later at TDC.
It is executed in synchronization with the signal, reads various information, detects the operating state in which fuel should be cut based on the information, generates a fuel cut command to the drive circuit 38, and after generating the fuel cut command, performs the fuel cut. Stop (detects the desired operating state and issues a fuel cut stop command to the drive circuit 38).

The drive circuit 38 drives the fuel cut solenoid valve 15 in response to the fuel cut stop command, and stops driving the fuel cut solenoid valve 15 in response to the fuel cut command.

Next, the procedure of the fuel supply control method of the present invention will be explained in detail according to the fuel cut control routine shown in FIG.

In the fuel cut 1lJtil routine, CPLJ3
9, each time the TDC signal is generated, as shown in FIG.
The count value Men is read (step 51), and the current detected value Nen of the engine rotation speed N+3 is calculated according to the count value Men (step 52). and,
A change mΔNe (=Nen −Nen−+) between the current detected value fsJen of the engine rotational speed and the previous detected value N e n−+ when this routine was executed 17 DC signals ago is calculated (step 53). For example, in the case of a four-cylinder internal combustion engine, normally the first cylinder, third cylinder,
The fourth cylinder is ignited, and then the second cylinder is ignited in that order, and a TDC signal is generated at that timing. Now, count fIiM e n by TDC signal light generation at the time of ignition of the third cylinder.
When read, the current count value Men, the count value M G n-1 obtained before 1TDC signal, the count value M e n-z obtained before 2TDC signal, and 3TDC
The count value obtained before the signal MO
1/ (Men + Men-+ + Mer
, 2+ M e 11-x ) ).

Therefore, the previous detected value Nen-+ is 1/(Men-++M
en-z + Men-s + Mer)4)
It is. In addition, in order to calculate the detection ff1Nen and the change amount ΔNe, a small amount (both count value M en s M e
n-+, Men-2, Men, 3 and current detection value Nen
are written and stored in each predetermined storage location of the RAM 41.

After calculating the change temperature Ne, the change amount ΔNe becomes the predetermined value ΔNeo
(For example, 0) or not is determined (step 54). If ΔNe≦ΔNeo, the engine is decelerating, so the constant Nrcf is set to the predetermined value Nrefo (step 55); if ΔNe>ΔNeo, the engine is accelerating, so the constant Nref is set to the predetermined value Nrefo.
Set to a larger predetermined value Nrer + (Step 5
6). After setting the constant N rer in this manner, an averaged value NAVEn of the engine speed Ne is calculated using the following equation (step 56).

NA V E n =N ref x N en+ (1-
Nref )
It is AVEn.

Next, calculate the averaged UIiNsvEn, the current detected value Nen, and the deviation ΔNε (step 58), read the operating parameters such as the throttle valve opening θth (step 59), and set the read throttle valve opening θth to the idle opening. It is determined whether the predetermined opening degree θIC)L+α is smaller than the predetermined opening degree θIC)L+α (step 60). θ [h≧θ
Since the throttle valve 3 is open at TDL+α, it is assumed that the operating state is not one in which fuel should be cut, and the timer TA is set to a predetermined time tFcDLY to start down measurement (step 61). A cut stop command is generated (step 62).

On the other hand, when θth<θIDL+α, it is assumed that the throttle valve 3 is almost fully closed, and the deviation ΔNE is set to the predetermined value ΔNET)4
It is determined whether or not the value is larger (step 63). ΔN
If E>ΔNET)I, it is assumed that there is a sudden deceleration, and the predetermined value NeTl-114 is used as the reference value in order to set the engine speed fuel cut discrimination reference value high, and the current detected value Nen is set higher than the predetermined value NeT HH. In step 64), if ΔNE≦ΔNETI−1, a predetermined value Ne is determined as a reference value in order to determine that it is a slow deceleration and to set a low fuel cut determination reference value of engine rotation speed.
Using a predetermined value NeTl-IL smaller than THH, it is determined whether the current detected value Nen is larger than the predetermined value NeTH (step 65). Nen>Ne1H1-1,
Or, if Nen>N1rHL, this is the engine rotational speed at which fuel should be cut, so it is determined whether the timer TA's 1st measurement value TA has reached O or not (Step 66), TA
If =O, the state in which the fuel cut condition is satisfied continues for a predetermined period of time tFc DL Yell, and the fuel cut operation state is definitely established, so a fuel cut command is issued to the drive circuit 38 (step 67). If T^>O, the fuel cut condition is not satisfied for the predetermined time tFC[)LY and there is a possibility of false detection due to noise, etc., so a fuel cut stop command is issued by executing step 62. .

If Nen≦NeTHH% or Nen≦NeTl-IL, it is not the engine rotational speed at which fuel cut should be made, so steps 61 and 62 are executed to generate a fuel cut stop command.

The drive circuit 38 drives the fuel cut l111 valve 15 in response to the fuel cut stop command, so the slow fuel supply passage 1
3 is connected to slow boat 11 and idle boat 1
Fuel is released from 2. Further, the drive circuit 38 stops driving the fuel cut MFIi valve 15 and closes the slow fuel supply passage 13 in response to the fuel cut command. As a result, fuel is not supplied to the slow boat 11 and the idle boat 12 (and a fuel cut state occurs).

In the fuel supply control method of the present invention, the averaged value NAvi:n of the engine speed Ne and the currently detected value Nen
When the deviation ΔNE from the engine speed is larger than the predetermined value ΔNETH, it means that rapid deceleration is occurring, so the fuel cut determination reference value of the engine speed is set high. That is, during sudden deceleration, the engine rotational speed at which the fuel supply is restarted is set higher than during slow deceleration. Also, the current detected value Nen of the engine rotation speed and the previous detected value N e n-+ which change mΔNe at the time of execution of this routine before the ITDC signal is the predetermined value ΔNe
When it is greater than O, the average value NA of the engine speed Ne
By setting the constant N ref to a large value, preferably 0.9 or more when calculating VEn, the influence of Nen on the averaged value NAVEn increases, and the averaged value NAvEo
almost approximates the current detection 11Nen. When deceleration occurs under this condition, the constant Nref becomes smaller, so the averaged value NAvsn changes slowly, whereas the actual detected value Nen rapidly decreases, so the deviation ΔNE and the predetermined value ΔN
Deceleration can be detected early from the comparison results with ETI-1. For example, as shown in FIG. 5, when the engine speed Ne changes as shown by the solid line, the change mΔ
If the constant N ref is kept constant regardless of Ne, the formula (1
) is the average value NAvε of the engine speed calculated by
changes as shown by the broken line a, but when the constant Nver is changed according to the change value ΔNe, the average value NAVε
As shown by one point gImb, when the engine speed increases, it changes by a value greater than the value of the broken line a, so the time point when the engine speed reaches the point where the difference of the predetermined value ΔNETH from the averaged value NAVε occurs during deceleration is the time. It becomes faster by T+.

In addition, in the embodiment of the present invention described above, the deviation ΔNE
The engine speed fuel cut determination reference value is set according to
THL and N e T +41-1, but continuous or two or more fuel cuts are performed so that the fuel cut determination reference value becomes higher as the deviation ΔNε becomes larger than the predetermined value ΔNεTH. A determination reference value may also be set.

Further, in the above-described practical examples of the present invention, the present invention is applied to a device that supplies fuel to an engine using a carburetor, but the present invention is not limited to this, but can also be applied to a device that injects and supplies fuel using an injector. be able to. Also, instead of completely cutting off the fuel supply during deceleration, the solenoid valve 15
The amount of fuel supplied may be reduced by providing a throttle passage that bypasses the fuel. .

As described above, in the fuel supply control method of the present invention, the average value NAven of the engine rotation speed Ne and the currently detected value N
Deceleration can be immediately detected according to the deviation ΔNE from en, and when the deviation ΔNE is larger than a predetermined value ΔNETH, it is determined based on the engine speed whether the fuel supply should be cut off or the amount of fuel supplied should be reduced. Since the reference value for this is set high, fuel supply can be controlled with high precision. Furthermore, when calculating the averaged value NAVEn, the degree of averaging of the averaged value is reduced during acceleration, so deceleration can be detected early, and fuel efficiency can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an outline of an on-vehicle internal combustion engine equipped with a device to which the fuel supply control method of the present invention is applied, and FIG. 2 is a block diagram showing a specific configuration of a control circuit in the device of FIG. FIG. 3 is an operation flow diagram showing the procedure of the fuel supply control method of the present invention, FIG. 4 is a diagram showing the method of calculating the engine rotation speed Ne, and FIG. 5 is a diagram showing the deceleration determination timing by the fuel supply control method of the present invention. FIG. Explanation of symbols of main parts 2... Carburetor 3... Throttle valve 4... Intake pipe 11... Slow boat

Claims (2)

[Claims] (1) There is a fuel supply control method that cuts off the fuel supply to the engine or reduces the amount of fuel supplied when the engine speed is equal to or higher than a reference value during engine deceleration. detect,
The current detected value Ne_n of the detected engine rotational speed is averaged according to a predetermined functional relationship using the detected values of the engine rotational speed detected up to the previous time to calculate an averaged value N_A_V_E_n, and the current detected value Ne_n and the averaged value N_A_V_E are calculated.
A fuel supply control method, comprising: calculating a difference ΔN_E from _n, and setting the reference value high when the difference ΔN_E exceeds a predetermined value ΔN_E_T_H. (2) When calculating the averaged value N_A_V_E_n, the current detected value Ne_n of the engine rotation speed and the previous detected value Ne
The amount of change ΔNe in engine speed according to _n_−_1
2. The fuel supply control method according to claim 1, wherein when the amount of change ΔNe is greater than a predetermined value ΔNe_0, the degree of averaging is made smaller than when it is less than the predetermined value ΔNe_0.