JPH0333913B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of controlling fuel supply to an internal combustion engine equipped with an electronically controlled fuel injection device, and more particularly to a method of increasing the amount of fuel supplied after a fuel supply cutoff (hereinafter referred to as fuel cut) is completed.

In general, in a fuel supply control method that is equipped with an electronically controlled fuel injection device and controls the amount of fuel supplied according to the operating state of the engine, fuel cut is performed during deceleration to improve fuel efficiency and exhaust gas characteristics, while the fuel cut ends. Later on, the amount of fuel supplied will be increased to improve driving performance. As such a control method, there is a method in which the fuel injection time is increased by a predetermined period after the fuel cut (Utility Model Application Publication No. 53-33721, ``Electronically Controlled Fuel Injection Device''), or a method in which the fuel injection time is increased by a predetermined period after the fuel cut, or a method in which the fuel injection period is A method has been proposed in which the amount of fuel is increased (Japanese Unexamined Patent Publication No. 56-47631 ``Method for controlling fuel supply device'').

However, in each of the above control methods, the engine operating state and/or the intermittent state of the power transmission device (hereinafter referred to as return conditions) at the time of returning from the fuel cut state to the fuel supply operating state may take on various aspects. Regardless of the recovery conditions, the amount of fuel supplied to the engine is always increased after the fuel cut is completed, without considering the recovery conditions under which the recovery was performed, so depending on the recovery conditions, the amount of fuel supplied after the fuel cut may be excessive. This may lead to inconveniences such as deterioration of fuel efficiency, exhaust gas characteristics, and engine operating performance.

On the other hand, no matter what the recovery conditions are, if the increase in the amount is not corrected after the fuel cut is completed, if the engine speed is low after the fuel cut, or if the clutch device that is part of the power transmission device Engine stall may occur when the gear system is cut off.

The present invention has been made in view of the above-mentioned circumstances, and includes an electronically controlled fuel injection device that injects fuel in synchronization with a crank angle signal that is sequentially output at each predetermined crank angle position of the engine immediately after the end of fuel supply cutoff. In a fuel supply control method for an internal combustion engine that controls an increase in the amount of fuel supplied by calculating the increase in fuel amount after the end of the supply cutoff, the power driven by the engine when the engine returns from the fuel supply cutoff state to the fuel supply operation state. Depending on the intermittent state of the transmission device, engine rotation speed thresholds for determining whether or not an increase in fuel is required after the end of the fuel supply cutoff are set to first and second predetermined values, respectively, and the power is increased at the end of the fuel supply cutoff. When the transmission device is in a disconnected state, the fuel increase is executed when the engine speed at the time of termination is lower than the first predetermined value, while the power transmission device is in a connected state at the end of the fuel supply cutoff. If the engine speed at the time of termination is lower than the second predetermined value and the power transmission device becomes disconnected within a predetermined period from the time of termination, the fuel amount is increased. To provide a fuel supply control method for an internal combustion engine, which makes it possible to avoid an engine stall in the case of clutch off or neutral at a low engine speed after the end of fuel cut, and also makes it possible to improve various characteristics of the engine. be.

Hereinafter, the method of the present invention will be explained with reference to the drawings.

FIG. 1 is an overall configuration diagram of a fuel supply control device for an internal combustion engine to which the method of the present invention is applied. Reference numeral 1 indicates, for example, a four-cylinder internal combustion engine, and an intake pipe 2 is connected to the engine 1. A throttle valve 3 is provided in the middle of the intake pipe 2. A throttle valve opening sensor 4 is connected to the throttle valve 3 to convert the valve opening of the throttle valve 3 into an electrical signal and send it to an electronic control unit (hereinafter referred to as "ECU") 5.

A fuel injection valve 6 is provided in the intake pipe 2 between the engine 1 and the throttle valve 3. This fuel injection valve 6 is provided for each cylinder slightly upstream of an intake valve (not shown) in the intake pipe 2, and each injection valve 6 is connected to a fuel pump (not shown) and is connected to an ECU.
The fuel injection valve opening time is controlled by a signal from the ECU 5.

On the other hand, an absolute pressure sensor 8 is provided immediately downstream of the throttle valve 3 via a pipe 7, and an absolute pressure signal converted into an electrical signal by the absolute pressure sensor 8 is sent to the ECU 5. Further, an intake air temperature sensor 9 is installed downstream thereof, and this air intake air temperature sensor 9 also converts the air intake air temperature into an electrical signal and sends it to the ECU 5.

The engine body 1 is provided with an engine water temperature sensor 10, which is made of a thermistor or the like, is inserted into the circumferential wall of the engine cylinder filled with cooling water, and supplies its detected water temperature signal to the ECU 5.

An engine rotation speed sensor (hereinafter referred to as "Ne sensor") 11 and a cylinder discrimination sensor 12 are installed around the camshaft or crankshaft (not shown) of the engine, and the former 11 receives a TDC signal, that is, 180 degrees of the engine crankshaft. The latter 12 outputs one pulse each at a predetermined crank angle position of a specific cylinder at a predetermined crank angle position for each rotation, and these pulses are sent to the ECU 5.

A three-way catalyst 14 is disposed in the exhaust pipe 13 of the engine 1 to purify HC, CO, and NOx components in the exhaust gas. On the upstream side of this three-way catalyst 14,
An O ₂ sensor 15 is inserted into the exhaust pipe 13 , and this sensor 15 detects the oxygen concentration in the exhaust gas and supplies the detected value signal to the ECU 5 .

Further, a sensor 16 for detecting atmospheric pressure and an engine starter switch 17 are connected to the ECU 5, and the ECU 5 is supplied with a detected value signal from the sensor 16 and a starter switch ON/OFF state signal.

Furthermore, a clutch switch 20 is connected to the ECU 5 for detecting an on/off state of a power transmission device 19 that is driven by the internal combustion engine 1 and transmits power to the drive wheels 18 . This clutch switch 20 is a clutch pedal 2 that performs an on/off operation of a clutch device 22 that forms a part of a power transmission device 19.
The clutch device 22 is mechanically or electrically interlocked with the clutch device 22, and is configured to detect the discontinuous state of the clutch device 22 and supply the result to the ECU 5 as an electrical signal (discontinuous state display parameter signal). The clutch switch 20 may be configured to detect the neutral state of the gear device, or both may be used in combination.

The ECU 5 determines the engine operating state such as the fuel cut operating range based on the various engine operating state display parameter signals and intermittent state display parameter signals described above, and also determines the fuel injection valve according to the following formula according to the engine operating state. 6. Calculate the fuel injection time T _OUT .

T _OUT = Ti×K ₁ + K ₂ ………(1) Here, Ti indicates the basic fuel injection time, and this basic fuel injection time Ti is calculated according to the intake pipe absolute pressure P _BA and the engine speed Ne. . The coefficients K ₁ and K ₂ are determined by the various sensors mentioned above, namely, the throttle valve opening sensor 4, the intake pipe absolute pressure sensor 8, the intake air temperature sensor 9, the engine water temperature sensor 10, the Ne sensor 11,
Engine parameter signals from the cylinder discrimination sensor 12, O ₂ sensor 15, atmospheric pressure sensor 16, and starter switch 17, as well as the clutch switch 20
It is a correction coefficient calculated according to the intermittent state display parameter signal from It is calculated based on a predetermined calculation formula.

The ECU 5 supplies the fuel injection valve 6 with a drive signal to open the fuel injection valve 6 based on the fuel injection time T _OUT determined as described above.

FIG. 2 is a diagram showing the circuit configuration inside the ECU 5 shown in FIG. 1. The engine rotation speed signal from the Ne sensor 11 shown in FIG. (hereinafter referred to as "CPU") 503 and Me
It is also supplied to counter 502. Me counter 5
02 counts the time interval from when the previous predetermined position signal was input from the Ne sensor 11 to when the current predetermined position signal was input, and the counted value Me is proportional to the reciprocal of the engine rotation speed Ne. Me counter 50
2 transmits this count value Me via the data bus 510.
Supplied to CPU 503.

The respective output signals from various sensors such as the throttle valve opening sensor 4, intake pipe absolute pressure _PBA sensor 8, engine water temperature sensor 10, and clutch switch 20 shown in FIG. 2 are corrected to predetermined voltage levels by a level correction circuit 504. After that, multiplexer 50
5 is sequentially supplied to an A/D converter 506. The A/D converter 506 sequentially converts the output signals from the aforementioned sensors and switches into digital signals and supplies the digital signals to the CPU 503 via the data bus 510.

The CPU 503 also uses a read-on memory (hereinafter referred to as "ROM") via a data bus 510.
507, random access memory (RAM) 50
8 and the drive circuit 509, and the RAM
508 temporarily stores the calculation results of the CPU 503 and the intermittent state of the clutch device 22;
The ROM 507 stores a control program executed by the CPU 503, a basic injection time Ti map of the fuel injection valve 6, a predetermined fuel cut determination value, a table of a fuel increase coefficient after fuel cut, etc., which will be described later. In accordance with the control program stored in the ROM 507, the CPU 503 controls the fuel injection time of the fuel injection valve 6 according to the aforementioned various engine parameter signals and intermittent state display parameter signals.
Calculate T _OUT and send these calculated values to data bus 5.
10 to the drive circuit 509. The drive circuit 509 supplies a control signal to the fuel injection valve 6 to open the fuel injection valve 6 according to the calculated value.

FIG. 3 shows a second method applicable to the method of the present invention.
This is a flowchart of a fuel cut determination subroutine executed by the ECU 5 shown in the figure.

First, the flag N _SMFLG is set to 0 (step 1). The value of this flag N _SMFLG (0 or 1) is
As will be described later, this is the condition for determining whether the return from the fuel cut state to the fuel supply operation state has been made under predetermined return conditions, that is, the condition for determining the post-fuel cut increase coefficient K _AFC . Next, it is determined whether the clutch switch 20 (FIGS. 1 and 2) is off (step 2), and the answer is affirmative (Yes), that is, the clutch device 22 (first
) is determined to be in the cutoff state, then the engine speed Ne is set to the first predetermined speed N _SK
It is determined whether the rotation is lower than (first predetermined value) (step 3). This first predetermined rotation speed N _SK
is used as a criterion for determining whether or not a predetermined return condition is satisfied.If the clutch is off at the time of return and the engine speed Ne is lower than this speed _NSK , the fuel is removed after the fuel cut is completed. The rotational speed is set to, for example, 1500 rpm, at which there is a risk of engine stalling if the increase correction is not performed. The answer to step 3 is negative (No)
If so, move to the basic control loop (step 4),
On the other hand, if it is affirmative (Yes), the flag N _SMFLG is set to 1 (step 5), and when the determination is made, the clutch is off and the engine speed Ne is the first predetermined speed _NSK.
It indicates that the rotation was lower than that, and then moves to the basic control loop (step 4). In this basic control loop, the above-mentioned correction coefficients K ₁ and K ₂ are calculated according to the detected values of various engine operating parameters, and then the fuel injection time T _OUT is calculated and each fuel injection valve 6
Activate.

On the other hand, if the answer to the determination in step 2 is negative (No), that is, if it is determined that the clutch device 22 is in the connected state, it is determined whether the throttle valve opening θth is less than or equal to the predetermined throttle valve opening _θFC . Determine (step 6). This predetermined opening degree θ _FC is set to a throttle valve opening degree when the engine is operated at a deceleration, such as an opening degree such that the throttle valve 3 (FIG. 1) is almost fully closed. If the answer to the determination in step 6 is negative (No), it is sent to the basic control loop (step 4), and if it is affirmative (Yes), the engine coolant temperature T _W is higher than the predetermined water temperature T _WFC , for example, 20°C. It is determined whether or not (step 7). The reason for this determination is that the lower the engine temperature, the more likely engine stall will occur when the clutch is _off after the fuel cut. This is because it is preferable to set it.

If the answer to step 7 is negative (No),
Next, it is determined whether the engine rotation speed Ne is higher than the second predetermined rotation speed N _FCL when the engine water temperature T _W is low (step 8), and the answer is negative (No). If so, move to the basic control loop (step 4). On the other hand, if the answer to step 7 is affirmative (Yes), then the engine speed is
Ne is engine water temperature T _W is other than low temperature (>20℃)
It is determined whether the rotational speed is higher than the second predetermined rotational speed N _FCH (step 9). The second predetermined rotation speeds N _FCL and N _FCH are the lower limit values of the engine rotation speeds at which the engine operating performance is not impaired by performing a fuel cut when the engine water temperature T _W is low or other than low temperature. set in the vicinity (eg 2000rpm and 80rpm). In addition, a second predetermined rotation speed in a state other than a low temperature state
N _FCH is used as a criterion for determining whether _or not a predetermined return condition is met.
If Ne is lower than the second predetermined rotation speed _N
800rpm). If the answer to step 9 is negative (No), a flag N _SMFLG is set to 1 (step 10), indicating that the clutch was on and the engine speed Ne was lower than the predetermined value N _FCH at the time of this determination. and moves to the basic control loop (step 4).

If the answer to step 8 or step 9 is affirmative (Yes), a fuel cut operation is performed (step 11). That is, at the time of determination, the clutch device 22 is in the connected state, the throttle valve opening θth is less than or equal to the predetermined opening θ _FC , and the engine rotation speed Ne is higher than the second predetermined rotation speeds N _FCL and N _FCH . In this case, it is determined that the fuel cut condition is satisfied.

FIG. 4 is a flowchart of a subroutine for calculating the post-fuel cut fuel increase coefficient K _AFC for carrying out the method of the present invention.

First, as mentioned above, in the fuel cut determination subroutine, it is determined whether or not the fuel cut is activated (step 1), and if the answer is affirmative (Yes), the ECU 5 is activated after the previous fuel cut is completed.
(Figures 1 and 2)
The number of pulses N _AFC of the TDC signal is set to 0 (step 2), the fuel injection time T _OUT is set to 0 (step 3), and each fuel injection valve 6 (Figs. 1 and 2) is made inactive. (Step 4).

On the other hand, if it is determined in step 1 that the fuel cut condition is not satisfied, that is, it is negative (No), it is determined whether or not the fuel cut condition was satisfied in the previous determination (step 5), and the answer is affirmative (Yes). ) In other words, if it is determined that the fuel cut has ended between the previous time and the current time, it is determined whether the flag N _SMFLG is 1, that is, whether the return was performed under the predetermined return conditions described above. Determine (step 6). If this answer is affirmative (Yes), flag N _MFLG is set to 1 (step 7), whereas if it is negative (No), flag N MFLG is set to 1 (step 7).
Set N _MFLG to 0 (step 8).

If the determination result in step 5 is negative (No), that is, it is determined that the fuel cut has already been completed before the previous determination, and in step 7
After completing step 8, it is determined whether the flag _NMFLG is 0 (step 9). If this answer is negative (No), that is, if it is determined that the return has been made under the predetermined return conditions, then next, the crank angle signal supplied after the end of the fuel cut,
It is determined whether the number of pulses N _AFC of the TDC signal is a predetermined number, for example 8 (step 10). If the answer is affirmative (Yes), the fuel increase coefficient K _AFC is set to 1 (step 11), and the subroutine ends without increasing the fuel amount. On the other hand, if the answer is negative (No), that is, if it is determined that the pulse number N _AFC is between 0 and 7, it is determined whether the clutch switch 20 (Figs. 1 and 2) is off. (Step 12).

If the answer to the determination in step 12 is negative (No), that is, if it is determined that the clutch device 22 (Fig. 1) is in a cutoff state where power transmission is impossible, then the fuel increase coefficient K after fuel cut is determined from _{the AFC} table after the end of fuel cut. The coefficient value K _AFC corresponding to the number of pulses N _AFC of the TDC signal input to is read out (step 13). This table shows the engine speed when the clutch device 22 is shut off after the fuel cut.
This is to set a fuel increase coefficient K _AFC that is applied to avoid engine stall due to a sudden decrease in Ne, and an example thereof is shown in FIG. In Figure 5, the number of pulses N _AFC (=0,
1, 2, ..., 7), the coefficient value K _AFC0 or
K _AFC7 is determined, and the coefficient K _AFC has _{a maximum value K AFC0 (} =
2.00), and gradually decreases as the pulse number N _AFC increases, and when the pulse number N _AFC reaches 7, it reaches the minimum value K _AFC7 (=1.20). next,
Add 1 to the number of pulses N _AFC stored in the ECU 5 (step 14) to count the number of times the subroutine has been executed.

If the answer to the determination in step 9 is affirmative (Yes), that is, it is determined that the restoration was not performed under the predetermined restoration conditions, and the answer to step 12 is negative (No).
That is, if it is determined that the clutch device is in the connected state, the increase coefficient K _AFC is set to 1 (step 15), 1 is added to the number of pulses N _AFC (step 14), and the number of times the subroutine has been executed is calculated. count.

In the above embodiment, in the subroutine for calculating the coefficient K _AFC , the intermittent state of the clutch device is determined from the end of the fuel cut until the predetermined number of pulses N _AFC is input, but when the clutch is disengaged, a phenomenon occurs in which the engine speed Ne suddenly decreases. Therefore, instead of this, it may be configured to detect the magnitude of the fluctuation in the engine rotational speed Ne during the relevant time and perform the increase correction when the fluctuation exceeds a predetermined fluctuation.

As explained above, according to the present invention, depending on the intermittent state of the power transmission device driven by the engine when the engine returns from the fuel supply cutoff state to the fuel supply operation state, the fuel supply after the fuel supply cutoff ends is determined. The engine speed thresholds for determining whether or not an increase is necessary are set to first and second predetermined values, respectively, and if the power transmission device is in a disconnected state at the end of the fuel supply cutoff, the The fuel increase is performed when the engine speed is lower than the first predetermined value, while when the power transmission device is in the connected state at the end of the fuel supply cutoff, the engine speed at the end is set to the second predetermined value. Since the fuel amount is increased when the power transmission device becomes disconnected when the power transmission device is lower than a predetermined value and within a predetermined period from the end of the fuel supply cutoff state, the engine stall due to clutch-off etc. after the end of the fuel supply cutoff state is prevented. It is possible to provide a fuel supply control method for an internal combustion engine that can avoid this and improve the fuel efficiency, exhaust gas characteristics, and driving performance of the engine.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram illustrating a fuel supply control device for an internal combustion engine to which the method of the present invention is applied, FIG. 2 is a block circuit diagram illustrating the circuit configuration of the electronic control unit of FIG. 1, and FIG. is a flowchart of the fuel cut determination subroutine of the present invention, FIG. 4 is a flowchart of the subroutine for calculating the fuel increase coefficient K _AFC after fuel cut according to the present invention, and FIG. 5 is the flowchart of the fuel cutoff determination subroutine of the present invention.
7 is a graph showing an example of table settings for K _AFC . DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 5... Electronic control unit (ECU), 6... Fuel injection valve, 11... Engine speed sensor, 19... Power transmission system, 20... Clutch switch, 22... Clutch device.

Claims (1)

[Claims] 1 Equipped with an electronically controlled fuel injection device, fuel is supplied by calculating the fuel increase after the fuel supply cutoff ends in synchronization with a crank angle signal that is sequentially output at each predetermined crank angle position of the engine immediately after the fuel supply cutoff ends. In a fuel supply control method for an internal combustion engine that increases the amount of fuel, the amount of fuel is increased after the fuel supply cutoff ends, depending on the intermittent state of the power transmission device driven by the engine when the engine returns from the fuel supply cutoff state to the fuel supply operation state. engine rotation speed thresholds for determining whether or not an increase in fuel is necessary are set to first and second predetermined values, respectively, and when the power transmission device is in a disconnected state at the end of the fuel supply cutoff, the end of the fuel supply cutoff is set. The fuel increase is executed when the engine speed at the time is lower than the first predetermined value, while when the power transmission device is in the connected state at the end of the fuel supply cutoff, the engine speed at the end is lower than the first predetermined value. A fuel supply control method for an internal combustion engine, characterized in that the fuel amount is increased when the power transmission device becomes disconnected when the power transmission device is lower than a second predetermined value and within a predetermined period from the end of the fuel transmission.