JP2000320374A - Fuel injection control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize improvement in fuel economy via proper-frequency fuel cuts, and stable convergence of engine speed via engine stall avoidance, in vehicles having a lockup clutch adapted to mechanically directly couple the input and output sides of the power train arranged in a connected relation to the engine output shaft. SOLUTION: In a decelerating operation, lockup clutch control data ATROCK are referred to, before a fuel-cut engine speed NFC and a fuel-recovery engine speed NFRE are set according to the lockup clutch status, or disengagement, slip control and engagement (steps S102 through S109). If an engine speed NE becomes not less than NFC while no fuel cut is put in execution, a fuel cut flag FLGFC is set (S112) to stop fuel injection, or if NE<=NERE during the fuel cut, the fuel cut flag FLGFC is cleared (S114) to restart the fuel injection, so that the fuel economy is improved while preventing engine stalling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for an engine that cuts fuel during deceleration operation. More specifically, the present invention relates to an input side and an output side of a speed change drive system connected to an output shaft of an engine. The present invention relates to a fuel injection control device for an engine that performs a fuel cut in accordance with a control state of a lockup clutch that can be directly connected mechanically.

[0002]

2. Description of the Related Art Conventionally, in a fuel injection control system for a vehicle such as an automobile, the engine speed has increased to a predetermined speed (fuel cut speed) or more during deceleration operation for the purpose of improving fuel efficiency and purifying exhaust gas. At this time, a fuel cut is performed to stop the fuel supply to the engine. When the engine speed becomes equal to or lower than the lower limit of the hysteresis width (fuel recovery speed), the fuel cut is canceled.

At the time of this fuel cut, it is necessary to consider the prevention of engine stall due to a decrease in the engine speed. For example, Japanese Patent Laid-Open No. 4-365942 discloses
When the deceleration of the vehicle is equal to or greater than a predetermined value, according to engagement / disengagement of a lockup clutch capable of directly connecting the input side and the output side of the torque converter connected to the output shaft of the engine,
There has been disclosed a technique for preventing an engine stall by increasing the fuel recovery rotational speed or increasing the amount of auxiliary air that bypasses a throttle valve of an intake system.

[0004]

However, in a vehicle provided with a lock-up clutch capable of mechanically directly connecting the input side and the output side of a speed change drive system connected to the output shaft of the engine, the vehicle is connected to the lock-up clutch. -Since the descent speed of the engine speed due to the fuel cut differs depending on the control state of slip / release, the engine speed accompanying the expansion of the fuel cut area and the fuel cut can be obtained with the uniquely set fuel cut speed and fuel recovery speed. It is difficult to achieve both stable convergence and

The present invention has been made in view of the above circumstances, and is directed to a vehicle having a lock-up clutch capable of mechanically directly connecting an input side and an output side of a speed change drive system connected to an output shaft of an engine. It is another object of the present invention to provide a fuel injection control device for an engine capable of achieving a reduction in fuel consumption by an appropriate frequency of fuel cut and a stable convergence of the engine rotation by avoiding an engine stall.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, when the engine speed is equal to or higher than the fuel cut speed during the deceleration operation, the fuel supply to the engine is performed by the fuel cut. After the fuel cut is executed, the fuel cut is canceled when the engine speed drops below the fuel recovery speed after the fuel cut is executed.The fuel cut speed is connected to the output shaft of the engine. And a fuel cut rotational speed setting means for variably setting the input side and the output side of the variable speed drive system to be mechanically directly connected in accordance with the control state of a lock-up clutch.

According to a second aspect of the present invention, in the first aspect of the invention, there is provided a fuel recovery rotation speed setting means for variably setting the fuel recovery rotation speed in accordance with a control state of the lock-up clutch. Features.

That is, according to the first aspect of the present invention, during deceleration operation, the lock-up clutch, which is capable of mechanically directly connecting the input side and the output side of the speed change drive system connected to the output shaft of the engine, is controlled. The fuel cut speed is variably set accordingly, and when the engine speed exceeds the fuel cut speed, the fuel supply to the engine is stopped by the fuel cut.

In this case, according to the second aspect of the invention, in addition to the fuel cut rotation speed, the fuel recovery rotation speed is variably set according to the control state of the lock-up clutch, and the fuel recovery rotation speed according to the control state of the lock-up clutch is controlled. Release the fuel cut at the rotation speed.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show a first embodiment of the present invention.
1 is a flowchart of a deceleration fuel cut determination routine, FIG. 2 is a flowchart of a fuel injection amount setting routine, FIG. 3 is a schematic configuration diagram of an engine system, and FIG. 4 is a circuit configuration diagram of an electronic control system.

In FIG. 3, reference numeral 1 denotes an engine,
In this embodiment, a horizontally opposed four-cylinder gasoline engine is shown. Cylinder heads 2 are provided in both left and right banks of a cylinder block 1a of the engine 1, respectively, and each cylinder head 2 is formed with an intake port 2a and an exhaust port 2b.

As an intake system of the engine 1, an intake manifold 3 communicates with each intake port 2a, and a throttle valve interlocked with an accelerator pedal through an air chamber 4 in which intake passages of respective cylinders are connected to the intake manifold 3. The throttle chamber 5 in which 5a is interposed communicates. An air cleaner 7 is mounted on the upstream side of the throttle chamber 5 via an intake pipe 6, and a chamber 8 communicates with a middle of an air intake passage connected to the air cleaner 7.

A bypass passage 9 for bypassing the throttle valve 5a is connected to the intake pipe 6, and the amount of bypass air flowing through the bypass passage 9 is adjusted to the bypass passage 9 by the valve opening during idling. Speed control valve (IS
C valve) 10 is interposed.

Further, an injector 11 is disposed immediately upstream of the intake port 2a of each cylinder of the intake manifold 3. The engine 1 of this embodiment is a SOHC four-valve engine having two intake valves 12 and two exhaust valves 13 for each cylinder.
A two-way injection type injector is adopted, and the injector 11 is disposed so that each injection direction is directed to the valve head of each intake valve 12, and a discharge electrode portion is provided between the two intake valves 12 for each cylinder. Spark plug 1 exposed to combustion chamber 14
5 are provided. The ignition plug 15 is connected to an igniter 17 via an ignition coil 16 provided for each cylinder.
Is connected.

The injector 11 is connected to the fuel supply passage 1.
The fuel tank 19 is in communication with the fuel tank 19 via the fuel tank 8. The fuel tank 19 is provided with an in-tank type fuel pump 20. The fuel from the fuel pump 20 is pressure-fed to the injector 11 and the pressure regulator 22 through the fuel filter 21 interposed in the fuel supply path 18, and is returned from the pressure regulator 22 to the fuel tank 19 to be supplied to the injector 11. The pressure is adjusted to a predetermined pressure.

On the other hand, as an exhaust system of the engine 1, an exhaust pipe 29 is communicated with a collection portion of an exhaust manifold 28 which communicates with each exhaust port 2 b of the cylinder head 2, and a catalytic converter 30 is interposed in the exhaust pipe 29. To the muffler 31.

Next, the arrangement of sensors for detecting the operating state of the engine will be described. Immediately downstream of the air cleaner 7 of the intake pipe 6, a thermal intake air amount sensor 32 using a hot wire or a hot film is interposed.
Throttle valve 5a provided in throttle chamber 5
A throttle sensor 33 having a built-in throttle opening sensor 33a and an idle switch 33b that is turned on when the throttle valve 5a is fully closed is provided in series.

The cylinder block 1a of the engine 1
A knock sensor 35 is attached to the cooling water passage 36. A cooling water temperature sensor 37 faces a cooling water passage 36 communicating the left and right banks of the cylinder block 1a. An O2 sensor 39 is provided on the exhaust pipe 29 upstream of the catalytic converter 30.

The crankshaft 40 of the engine 1
A crank angle sensor 42 is provided on the outer periphery of a crank rotor 41 which is axially mounted on the cam shaft 43. A cylinder discriminating sensor 45 is provided opposite to a cam rotor 44 connected to a cam shaft 43 which makes a half turn with respect to the crank shaft 40. ing.

The crank pulse output from the crank angle sensor 42 and the cylinder discrimination pulse output from the cylinder discrimination sensor 45 are processed by an engine control electronic control unit 49 (ECU 49) shown in FIG. That is, based on the input interval time of the crank pulse, the engine speed N
E is calculated, and the combustion stroke order of each cylinder (for example, #
(1 cylinder → # 3 cylinder → # 2 cylinder → # 4 cylinder) and a value obtained by counting the cylinder discrimination pulse from the cylinder discrimination sensor 45 by a counter, based on the pattern of the combustion stroke cylinder, the fuel injection target cylinder, and the ignition target. The cylinder of the cylinder is determined.

The engine control ECU 49 calculates control amounts for actuators such as the injector 11, the ignition plug 15, and the ISC valve 10, and outputs control signals, that is, fuel injection control including air-fuel ratio control, and ignition timing control. The CPU 50, the ROM 51, the RAM 52, the backup RAM 53, and the serial interface (S
CI) 54, a counter / timer group 55, and an I / O interface 56 are mainly composed of a microcomputer connected to each other via a bus line, and a constant voltage circuit 57 for supplying a stabilized power to each unit. A peripheral circuit such as a drive circuit 58 and an A / D converter 59 connected to the interface 56 is built in.

The counter / timer group 55 generates various counters such as a free-run counter, a counter for counting the input of a cylinder discrimination sensor signal (cylinder discrimination pulse), a fuel injection timer, an ignition timer, and a periodic interrupt. Various timers such as a timer for periodic interrupts, a timer for measuring the input interval of the crank angle sensor signal (crank pulse), a timer for measuring the elapsed time after starting the engine, and a watchdog timer for monitoring system abnormalities. Are collectively referred to for convenience, and various other software counters and timers are used.

The constant voltage circuit 57 is connected to the battery 61 via a first relay contact of a power supply relay 60 having two circuit relay contacts. The power supply relay 60 has one end of a relay coil grounded, Is connected to the drive circuit 58. A power supply line for supplying power from the battery 61 to each actuator is connected to the second relay contact of the power supply relay 60.

Further, one end of an ignition switch 62 is connected to the battery 61, and the other end of the ignition switch 62 is connected to an input port of the I / O interface 56. Further, the battery 61 includes
The fuel pump 20 is connected through a relay contact of the fuel pump relay 63.
One end of the relay coil is connected to the battery 61, and the other end of the relay coil is connected to the drive circuit 58.

The constant voltage circuit 57 is directly connected to the battery 61. When the ON of the ignition switch 62 is detected and the contact of the power supply relay 60 is closed,
While power is supplied to each unit in the ECU 49, backup power is always supplied to the backup RAM 53 regardless of whether the ignition switch 62 is ON or OFF.

The input port of the I / O interface 56 includes an idle switch 33b and a knock sensor 3
5, a crank angle sensor 42, a cylinder discriminating sensor 45, a vehicle speed sensor 46 for detecting a vehicle speed, and a starter switch 47 for detecting an engine start state are connected, and further via an A / D converter 59. The intake air amount sensor 32, the throttle opening sensor 33a, the cooling water temperature sensor 37, and the O2 sensor 39 are connected, and the battery voltage VB is inputted and monitored.

The output ports of the I / O interface 56 include an ISC valve 10, an injector 11, and
The relay coils of the power supply relay 60 and the fuel pump relay 63 are connected via the drive circuit 58, and the igniter 17 is connected.

On the other hand, reference numeral 70 denotes an electronic control unit 70 (TCU 70) for controlling the transmission, and an electronic control unit 70 for controlling the engine.
Like the CU 49, the microcomputer is mainly configured by a microcomputer, and is connected to the engine control ECU 49 via the SCI 54 so that data can be exchanged with each other.

In this embodiment, as a speed change drive system connected to the output shaft of the engine 1, a torque converter 76 having a lock-up clutch 75 for engaging an impeller and a turbine is provided. An automatic transmission 80 provided with a clutch mechanism unit including various hydraulic clutches and various hydraulic brakes for performing gear shifting and a main transmission mechanism unit including a planetary gear and the like is connected in series. The automatic transmission 80 is provided with a hydraulic control unit 85 in which various control valves for controlling line pressure and pilot pressure to each mechanism unit are integrally formed.

The TCU 70 includes signals from the throttle opening sensor 33a, the coolant temperature sensor 37, and the vehicle speed sensor 46, which are shared with the ECU 49, a turbine speed signal, an ATF oil temperature signal, a brake signal, and the select mechanism unit 8.
A signal or the like indicating the operating position (shift range position) of the lock-up clutch 7 is input through the hydraulic control unit 85.
5 is controlled, and the shift control of the automatic transmission 80 is performed.

The control for the lock-up clutch 75 is performed by, for example, determining the engagement, slip, and release characteristics of the lock-up clutch 75 from the throttle opening and the vehicle speed for each shift range position and traveling pattern. This is performed by controlling the clutch operating oil pressure via a control valve (not shown) provided.

In the engine control ECU 49, a ROM
51 according to the control program stored in the I / O
The detection signal from the sensors and switches, which is input via the interface 56, and the battery voltage, etc.
0, and receives the gear position of the transmission, control data of the lock-up clutch 75, and the like from the transmission control TCU 70 via the SCI 54, and receives these data, various data stored in the RAM 52, and the backup RAM 53. Learning value data stored in
A fuel injection amount, an ignition timing, a duty ratio of a control signal for the ISC valve 10 and the like are calculated based on fixed data and the like stored in the OM 51, and fuel injection control including air-fuel ratio control, ignition timing control, idle speed control And so on.

In the above-described engine control, during deceleration operation, when the engine speed rises above a predetermined fuel cut speed, fuel cut is executed to stop fuel supply to the engine, thereby reducing fuel consumption. The fuel cut is canceled when the engine speed falls below a speed (fuel recovery speed) having a predetermined hysteresis width with respect to the fuel cut speed after the fuel cut is executed.

In this case, if the fuel cut is determined by comparing the engine speed with the fuel cut speed uniquely set, depending on the control state of the lock-up clutch 75 of the speed change drive system, the engine stall due to the fuel cut is performed. May occur. For this reason, the ECU 49 variably sets the fuel cut rotation speed and the fuel recovery rotation speed according to the control state of the lock-up clutch 75, thereby simultaneously avoiding engine stall and reducing fuel consumption due to the effect of the fuel cut. I do.

That is, the ECU 49 has the functions of the fuel cut speed setting means and the fuel recovery speed setting means according to the present invention. Specifically, the functions of each means are realized by the routine shown in FIG.

The processing executed by the ECU 49 relating to the fuel injection control of the present invention will be described below with reference to FIGS.
This will be described with reference to the flowchart of FIG.

FIG. 1 shows a deceleration fuel cut determination routine for determining whether a fuel cut condition is satisfied at the time of deceleration operation. First, in step S101, it is determined whether the current operation state is a deceleration state. Find out. Whether the driving state is in the deceleration state is, for example, a condition that the deceleration obtained from the vehicle speed change is equal to or higher than a set value, or in a driving region where the vehicle speed is equal to or higher than the set vehicle speed and the throttle opening is equal to or lower than the set opening. If the current operating state is not the decelerating state, the process jumps to step S114 and the fuel cut flag FLG is determined.
Clear FC to 0 (FLGFC ← 0) and exit the routine.

The fuel cut flag FLGFC is FLGF
C = 1 indicates execution of fuel cut, and FLGFC = 0 indicates non-execution of fuel cut, which is referred to in a fuel injection amount setting routine described later. As will be described later, in the fuel injection amount setting routine, the fuel cut coefficient KFC, which is one of the correction terms when setting the fuel injection pulse width Ti that determines the fuel injection amount, according to the value of the fuel cut flag FLGFC, KFC = 0 corresponding to the cut execution or KFC = 1.0 corresponding to no fuel cut is set. Note that the operation states other than the deceleration state are not the gist, so details are omitted,
The fuel cut flag FLGFC is also set to 1 by another fuel cut determination routine even when the engine speed is higher than the permissible speed, for example.

On the other hand, in step S101,
If it is determined that the vehicle is decelerating, step S101
Then, the process goes to step S102 to check the control state of the lock-up clutch 75 with reference to the contents of the lock-up clutch control data ATROCK received from the TCU 70. This lock-up clutch control data ATRO
CK is a control status transmitted from the TCU 70 to the ECU 49 regarding the control state of the lock-up clutch 75. OFF indicates the clutch disengaged state, ON indicates the clutch engaged state, and indicates the slip control state if neither ON nor OFF. It indicates that there is.

If ATROCK = OFF and the lock-up clutch 75 is in the disengaged state, the process proceeds from step S102 to step S103, where the fuel cut speed for judging the fuel cut is compared with the engine speed. The first fuel cut set value NF is added to NFC.
After setting C1 (NFC ← NFC1), step S
At 104, the first fuel recovery set value NFRE1 is added to the fuel recovery rotation speed NFRE for determining the fuel cut release (fuel recovery) in comparison with the engine rotation speed.
Is set (NFRE ← NFRE1), and step S11 is performed.
The process proceeds to the processing after 0. The first fuel recovery set value N
FRE1 provides a predetermined hysteresis width for canceling the fuel cut with respect to the first fuel cut set value NFC1, and NFC1> NFRE1.

In step S102, ATRO
If CK ≠ OFF, the process proceeds to step S105, where A
It is checked whether TROCK = ON, that is, whether the lock-up clutch 75 is in the engaged state. Then, the lock-up clutch control data ATROCK is not OFF but ON.
If not, that is, if the lock-up clutch 75 is in the slip control state, the process proceeds from step S105 to step S106 to set the second fuel cut setting value NFC2 to the fuel cut rotation speed NFC (NFC ← NF
C2), in step S107, the fuel recovery rotational speed NFRE is set to a second fuel recovery set value NFRE2 having a predetermined hysteresis width with respect to the second fuel cut set value NFC2 (NFRE ← NFRE2; NF).
RE2 <NFC2), and proceed to the processing after step S110.

In step S105, ATRO
If CK = ON, that is, if the lock-up clutch 75 is in the engaged state, the process proceeds from step S105 to step S1.
In step S109, the third fuel cut setting value NFC3 is set to the fuel cut rotation speed NFC (NFC ← NFC3), and in step S109, the fuel recovery rotation speed NFRE is set.
In addition, a third fuel recovery set value NFR in which a predetermined hysteresis width is provided with respect to the third fuel cut set value NFC3.
Set E3 (NFRE ← NFRE3; NFRE3 <N
FC3), and proceed to the processing after step S110.

Here, the first, second, and third fuel cut setting values NFC used for variably setting the fuel cut rotation speed NFC according to the control state of the lock-up clutch 75.
1, NFC2 and NFC3 will be described.

When the lockup 75 is in the released state and the load on the engine is small, the first fuel cut set value NFC1 is compared with the probability that an engine stall will occur due to a rapid decrease in the engine speed due to the fuel cut. Therefore, the engine speed of the fuel cut, which can effectively achieve both the improvement of the fuel economy by the fuel cut and the avoidance of the engine stall, is obtained in advance by simulation or experiment.

Similarly, the second and third fuel cut set values N
FC2 and NFC3 improve the fuel efficiency and improve the engine speed by taking into account the speed at which the engine speed falls due to the fuel cut when the lock-up clutch 75 is in the slip control state or the engaged state and the engine is under a load from the transmission. The engine speed of the fuel cut at which the stall avoidance can be effectively achieved is obtained in advance by simulation or experiment.

In this case, although the relationship between the first, second, and third fuel cut speeds NFC2 and NFC3 is strictly different depending on the engine characteristics and the control characteristics of the lock-up clutch 75, generally, the clutch slip In the control state or the engagement state, the decrease in the engine speed due to the fuel cut is slower than in the clutch disengagement state, and the resistance to the engine stall is high. Therefore, the second and third fuel cut values NFC1 are lower than the first fuel cut set value NFC1. Can be set to a low rotation speed.

In this embodiment, for example, NFC1 = 1500
rpm, NFC2 = 1400 rpm, NFC3 = 147
5 rpm, in order to cope with engine stall, the fuel cut rotation speed in the lock-up clutch disengaged state is made the highest, and then the fuel cut rotation speed in the lock-up clutch engagement state and the lock-up clutch slip control state. Set. In addition, each set value NFC1, NFC2,
Expected a hysteresis width of 300 rpm for NFC3, NFRE1 = 1200 rpm, NFRE2 = 110
At 0 rpm and NFRE3 = 1175 rpm, the fuel cut rotation speed and the fuel recovery rotation speed in the lock-up clutch slip control state are minimized to enlarge the fuel cut region. This is because in the lock-up slip control state, the response delay when shifting from the slip state to the engaged state or the released state is small, and the lock-up clutch 75
This is because it is possible to quickly change the control state and deal with engine stall.

In this case, the hysteresis width between the fuel cut rotation speed NFC and the fuel recovery rotation speed NFRE may be changed according to the lock-up clutch control state. The cut area can be set more precisely. On the other hand, for simplicity, it is also possible to set the fuel recovery rotation speed NFRE to a fixed value set in advance.

Next, in the processing after step S110,
In step S110, it is checked whether or not the fuel is currently being cut by referring to the value of the fuel cut flag FLGFC. If FLGFC = 0 and the fuel cut is not currently being executed, the process proceeds to step S111 to check whether the current engine speed NE is equal to or higher than the fuel cut speed NFC. When NE <NFC, the routine exits the routine. When NE ≧ NFC, the routine proceeds to step S112, where the fuel cut flag FLGFC is set to 1 (FLGFC ← 1), and the routine exits.

In step S110, FLGF
If C = 1 and the fuel is currently being cut, the process proceeds from step S111 to step S113 to check whether or not the engine speed NE has dropped below the fuel recovery speed NFRE. If NE> NFRE, the routine exits from step S113 to continue fuel cut, and if NE ≦ NFRE, step S113 to step S113 is performed to cancel the fuel cut.
Proceeding to 114, the fuel cut flag FLGFC is cleared to 0 (FLGCC ← 0), and the routine exits.

The fuel cut flag FLGFC is referred to in the fuel injection amount setting routine shown in FIG.
In this fuel injection amount setting routine, first, at step S2
In step 01, a basic fuel injection pulse width Tp that determines the basic fuel injection amount is calculated from the engine speed NE and the intake air amount Q based on the output signal from the intake air amount sensor 32 (T
p ← K × Q / NE; K is an injector characteristic correction constant).

Next, the routine proceeds to step S202, where the value of the fuel cut flag FLGFC is referred to.
In step 03, the fuel cut coefficient KFC is set to 1.0 corresponding to non-execution of fuel cut (KFC ← 1.0), and step S
In step S204, when FLGFC = 1, that is, when the fuel cut is instructed, the fuel cut coefficient KFC is set to 0 corresponding to the fuel cut execution (KFC ← 0), and the flow proceeds to step S205.

In step S205, the basic fuel injection pulse width Tp is multiplied or added by various correction terms to calculate the fuel injection pulse width Ti that determines the final fuel injection amount to be supplied to the engine, and the routine exits.

As the correction multiplication term for the basic fuel injection pulse width Tp, for example, various correction coefficients COEF relating to cooling water temperature correction, acceleration / deceleration correction, full-open increase correction, post-idle increase correction and the like based on the output of the O2 sensor 39 are used. Air-fuel ratio feedback correction coefficient α relating to fuel-ratio correction, intake air amount measurement system such as intake air amount sensor 32, and injector 11
There are an air-fuel ratio learning correction coefficient KBLRC for correcting variations in fuel supply systems during production and deterioration over time, and a fuel cut coefficient KFC for fuel cut.The correction addition term depends on the battery voltage. There is a voltage correction pulse width Ts for correcting the ineffective injection time of the injector 11 that changes due to the change. Then, the fuel injection pulse width Ti is calculated from these correction terms (Ti ← Tp × COEF × α).
× KBLRC × KFC + Ts).

The above-described fuel injection pulse width Ti is set in the injection timer of the cylinder to be fuel-injected, and is output to the injector 11 of the corresponding cylinder at a predetermined timing. as a result,
When the fuel cut coefficient KFC is KFC = 1.0, a drive pulse signal having a normal fuel injection pulse width Ti is output to the injector 11 of the corresponding cylinder to drive the injector 11, and the fuel injection pulse width Ti Is injected in a quantity corresponding to. On the other hand, when the fuel cut coefficient KFC is KFC = 0, the fuel injection pulse width Ti becomes T
When i = Ts, the driving of the injector 11 is substantially stopped, and the fuel supply to the engine 1 is stopped by the fuel cut.

As a result, during deceleration operation, appropriate fuel cut can be performed in accordance with the control state of the lock-up clutch 75, fuel consumption is reduced by appropriate frequency of fuel cut, and engine rotation is stabilized by avoiding engine stall. Convergence can be achieved.

FIGS. 5 and 6 relate to the second embodiment of the present invention. FIG. 5 is a flowchart of a lockup determination routine, and FIG. 6 is an explanatory diagram of a lockup clutch control area map.

The second embodiment differs from the first embodiment in that the control state of the lock-up clutch 75 is controlled by the engine control ECU without relying on information from the transmission control TCU 70.
49 itself.

That is, the ECU 49 executes the lock-up determination routine shown in FIG.
The control state of 5 is determined to set the fuel cut rotation speed NFC and the fuel recovery rotation speed NFRE,
In the lock-up determination routine, the contents of the lock-up control data ATROCK are determined by referring to the lock-up clutch control area map based on the throttle opening TVO and the vehicle speed VSP in step S301, and the routine exits.

The lock-up clutch control area map is
As shown in FIG. 6, the output shaft speed NO of the automatic transmission 80
The open area, slip control area, and engagement area of the lock-up clutch 75 are divided based on the vehicle speed VSP that substitutes the UT and the throttle opening TVO, and the contents of the lock-up control data ATROCK are OFF and S, respectively.
LIP and ON are stored.

In the deceleration fuel cut determination routine described in the first embodiment, the ECU 49 sets the fuel cut rotation speed NFC and the fuel recovery rotation speed NFRE using the results of the lockup determination routine described above.

In the second embodiment, the ECU 49 determines the control state of the lock-up clutch 75 and sets the fuel cut rotation speed NFC and the fuel recovery rotation speed NFRE without waiting for the lock-up control data from the TCU 70. , Faster processing than in the first embodiment is possible,
Controllability can be improved.

[0063]

As described above, according to the first aspect of the present invention, during deceleration operation, the input side and the output side of the speed change drive system connected to the output shaft of the engine can be mechanically directly connected. The fuel cut-off speed is variably set according to the lock-up clutch control state, and when the engine speed exceeds the fuel cut-off speed, the fuel supply to the engine is stopped by the fuel cut. It is possible to realize a reduction in fuel consumption by fuel cut and a stable convergence of the engine rotation by avoiding the engine stall.

According to the second aspect of the present invention, in addition to the fuel cut rotation speed, the fuel recovery rotation speed is variably set according to the control state of the lockup clutch, and the fuel recovery speed according to the control state of the lockup clutch is controlled. Since the fuel cut is released at the recovery rotation speed, optimization and expansion of the fuel cut region can be promoted while preventing engine stall.

[Brief description of the drawings]

FIG. 1 is a flowchart of a deceleration fuel cut determination routine according to a first embodiment of the present invention;

FIG. 2 is a flowchart of a fuel injection amount setting routine;

FIG. 3 is a schematic diagram of an engine system according to the first embodiment;

FIG. 4 is a circuit configuration diagram of an electronic control system according to the first embodiment;

FIG. 5 is a flowchart of a lockup determination routine according to a second embodiment of the present invention.

FIG. 6 is an explanatory diagram of a lock-up clutch control area map according to the first embodiment;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine 49 ... ECU (Fuel cut speed setting means, fuel recovery speed setting means) 75 ... Lock-up clutch NE ... Engine speed NFC ... Fuel cut speed NFRE ... Fuel recovery speed

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3D041 AA22 AA25 AA71 AB01 AC09 AC15 AD02 AD04 AD18 AD51 AE08 AE14 3G093 AA05 BA05 BA19 CB07 DA01 DA06 DB05 DB10 DB21 EA05 FA10 FA11 FB02 FB06 3G301 HA01 HA08 HA02 LA04 LB03 MA24 NA08 NC04 ND01 ND21 NE16 NE18 NE20 NE26 PA11Z PE01Z PF02Z PF06Z

Claims (2)

[Claims] 1. During deceleration operation, when the engine speed is equal to or higher than the fuel cut speed, the fuel supply to the engine is stopped by the fuel cut, and after the fuel cut is executed, the engine speed is lower than the fuel recovery speed. In the fuel injection control device for an engine which releases the fuel cut when the fuel cut speed is reduced, the input side and the output side of the speed change drive system connected to the output shaft of the engine can be mechanically directly connected to the fuel cut rotational speed. A fuel injection control device for an engine, comprising: a fuel cut-off speed setting means variably set in accordance with a control state of a lock-up clutch. 2. The fuel injection control device for an engine according to claim 1, further comprising fuel recovery rotation speed setting means for variably setting the fuel recovery rotation speed in accordance with a control state of the lock-up clutch. .