JPH11270390A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict the generation of shock at any speed by shortening the delay time as harder to be influenced by the fluctuation of the engine torque so as to bring the timing of fuel cut forward. SOLUTION: When the accelerating operation is interrupted, fuel injection time TINJ is lowered with lowering of the volume efficiency EV, and engine torque TQ is lowered. In the case where speed of a manual transmission(M/T) is held at three stages, fuel cut is started at the time when the delay time TQ3 is passed, and the fuel injection time Tinj is quickly reduced by ΔTinj3 . As a result, a fluctuation by ΔTQ3 is generated in the engine torque TQ, and a fluctuation by ΔG3 (a shock to a driver) is generated in the forward and backward acceleration G of a vehicle. At this stage, delay time TDR1 , TDR3 , TDR5 , are set shorter as higher the speed is set (a fifth speed side) so that the fluctuation quantity ΔG1 , ΔG3 , ΔG5 of the forward and backward acceleration G becomes equal to each other.

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 internal combustion engine, and more particularly, to a setting of a delay time of a fuel cut executed when the vehicle is decelerated.

[0002]

2. Description of the Related Art In general, this type of fuel injection system executes a fuel cut for interrupting fuel injection to an engine in order to reduce wasteful fuel consumption when the vehicle is decelerated. The conditions for executing the fuel cut include that the throttle valve of the engine is fully closed, that the engine speed is equal to or higher than a predetermined value, and that the delay time has elapsed. For example,
As shown in FIG. 6, when the accelerator pedal is depressed when the vehicle is decelerated (idle switch is turned on), if the engine speed is equal to or higher than a predetermined value at the time when the delay time TDR has elapsed, the fuel cut ( F / cut).

As shown in FIG. 6, the delay time TDR used at this time is such that the volume efficiency Ev (the amount of intake air per intake stroke) decreases due to the throttle being fully closed,
Accordingly, the fuel injection time TINJ set based on the intake air amount is set to decrease to a predetermined ΔTINJ. After the elapse of TDR, the fuel cut is executed,
The fuel injection time TINJ sharply decreases to 0 with ΔTINJ. Therefore, the engine torque TQ fluctuates by ΔTQ, and the longitudinal acceleration G of the vehicle fluctuates by ΔG (that is, a shock felt by the driver).

In order to reduce the fluctuation amount ΔG of the longitudinal acceleration G, the delay time TDR may be extended to reduce the reduction amount ΔTINJ of the fuel injection time TINJ. Is shortened, and sufficient fuel economy cannot be achieved. Therefore, conventionally, it is assumed that the first speed is selected in which the fluctuation of the engine torque TQ most affects the longitudinal acceleration G (that is, the shock felt by the driver is large). The delay time TDR is set so that the variation ΔTQ of the engine torque TQ is suppressed to such an extent that the driver does not feel uncomfortable.

[0005]

However, as is well known, the frequency of fuel cuts during normal driving is extremely high, so that there is a considerable difference in the total fuel consumption reduction depending on the control quality. Will happen. Therefore, there has been a demand for a fuel injection control device that can further reduce fuel consumption.

It is an object of the present invention to provide a fuel injection control device for an internal combustion engine that can further reduce fuel consumption while suppressing shock during fuel cut.

[0007]

In order to achieve the above object, according to the present invention, the current gear position of the transmission is determined by a gear position determining means, and the delay time is set by a delay time setting means according to the gear position. Is set, and when the fuel cut condition is satisfied and the delay time has elapsed, the fuel cut execution means executes the fuel cut processing. Since the shock caused by the fluctuation of the engine torque at the time of the fuel cut varies depending on the shift speed, the shift time less affected by the fluctuation of the engine torque shortens the delay time so that the execution timing of the fuel cut is advanced. It is possible to substantially extend the fuel cut time while suppressing the shock even at the shift speed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a fuel injection device for an internal combustion engine embodying the present invention will be described below. In FIG. 1, reference numeral 1 denotes an automobile engine, for example, an in-line four-cylinder gasoline engine. In this embodiment, the engine is combined with a five-speed manual transmission (hereinafter, referred to as M / T). An intake pipe 2 having an air cleaner 5, a throttle valve 6, an ISC valve 7, and the like is connected to an intake port 2 of the engine 1 via an intake manifold 4 in which a fuel injection valve 3 is attached to each cylinder. . A three-way catalyst 11 and an exhaust pipe 12 having a muffler (not shown) are connected to the exhaust port 9 via an exhaust manifold 10.

In FIG. 1, reference numeral 13 denotes an ignition plug driven by an ignition unit 14 to ignite an air-fuel mixture in a combustion chamber 15, reference numeral 16 denotes a water temperature sensor for detecting a cooling water temperature, and reference numeral 17 denotes a water temperature sensor.
With the rotation of the crankshaft, the crank angle synchronization signal θ
This is a crank angle sensor that outputs CR. Reference numeral 18 denotes a throttle position sensor for detecting the opening of the throttle valve 6, reference numeral 19 denotes an idle switch for detecting the fully closed state of the throttle valve 6, reference numeral 20 denotes an air flow sensor for detecting the amount of intake air, and reference numeral 21 denotes a large switch. Atmospheric pressure sensor for detecting atmospheric pressure, 22 is an intake air temperature sensor for detecting intake air temperature, 23
Is an O ₂ sensor for detecting the oxygen concentration in the exhaust gas.

An input / output device (not shown) and a storage device (ROM, RA,
M, a nonvolatile RAM, etc.), a central processing unit (CPU), an ECU (electronic control unit) 3 including a timer counter, etc.
1 is provided, and performs overall control of the air-fuel ratio control device including the engine 1. The input side of the ECU 31 is connected to the various sensors described above, and is connected to a vehicle speed sensor 32 that outputs a pulse-shaped vehicle speed signal Vpu in accordance with the rotation of the driving wheels of the vehicle. Input detection information. On the other hand, the above-described fuel injection valve 3, the ignition unit 14, and the like are connected to the output side.
The fuel injection valve 3, the ignition unit 14, and the like are driven based on the fuel injection time and the ignition timing calculated from the detection information of various sensors. The engine speed Ne
Is calculated from the time interval of generation of the crank angle synchronization signal θCR output by the crank angle sensor 17, and the vehicle speed Vs is calculated from the time interval of generation of the vehicle speed signal Vpu output by the vehicle speed sensor 32.

Next, a description will be given of a control process of the fuel injection device configured as described above, particularly when the ECU 31 executes a fuel cut operation. The ECU 31 executes the delay time setting routine shown in FIGS. 2 and 3 at a predetermined control interval (for example, 25 ms). First, in step S2, the ECU 31 inputs the crank angle synchronizing signal θCR from the crank angle sensor 17 and the vehicle speed signal Vpu from the vehicle speed sensor 32. In step S4, the ECU 31 calculates the engine speed Ne and the vehicle speed Vs from the detected information. And the ratio Ne
/ Vs. Next, in step S6, the ratio Ne /
It is determined whether or not Vs corresponds to the first gear ratio of the M / T.

That is, since a constant relationship is always established between the engine speed Ne and the vehicle speed Vs according to the gear stage of M / T, the current M is determined based on the ratio Ne / Vs.
It can be estimated to which gear stage / T has been switched. Therefore, the ratio Ne / Vs obtained from the gear ratios of the first to fifth gears is stored in advance in the ROM as a determination value having a predetermined area in consideration of a sensor detection error and the like. Calculated ratio Ne / Vs
Is in the first speed determination region.

If the determination in step S6 is Yes (Yes), the ECU 31 increments the shift determination counter Cs by one in step S8, and proceeds to step S10.
Then, it is determined whether or not the shift determination counter Cs is equal to or greater than the determination value Csx. If the determination is No (No), this routine ends. If the determination in step S10 is Yes, that is, if the state switched to the first speed has continued for a predetermined time, the ECU 31 sets the confirmation counter DCA to a preset first speed delay time TDR1 in step S12,
In step S14, the shift confirmation flag Fa is set, and this routine ends.

Similar to the processing for the first gear in steps S6 to S14, the processing for the second gear is performed in steps S16 to S24 in step S2.
The processing for the third speed is performed in steps 6 to S34, the processing for the fourth speed is performed in steps S36 to S44, and the processing for the fifth speed is performed in steps S46 to S54. Then, in step S16, step S26, step S36, and step S46,
Based on the ratio Ne / Vs of the engine speed Ne and the vehicle speed Vs, it is determined whether or not the current speed is in the second to fifth speeds. S22, step S32, step S4
2. In step S52, the determination counter DCA is set to a preset delay time TDR2 to TDR5 for each gear. The lengths of these delay times TDR1 to TDR5 will be described later in detail, but are set shorter for higher gears (5th gear).

On the other hand, if the determination of any of the processes in step S6, step S16, step S26, step S36, and step S46 is No, that is, the ratio Ne / V
If s is not within the determination range of any of the first to fifth speeds and it is estimated that a shift operation is being performed, the ECU 31 proceeds to step S56.
Move to In step S56, the shift determination counter Cs is reset. In step S58, the undetermined counter DCB is set to the same first-speed delay time TDR1 as in the case of the first speed, and in step S60, the shift determination flag Fa is cleared. Then, this routine ends.

When a shift operation is performed after any of the gear positions is determined, the ratio Ne / Vs shifts from the determination region before the shift to the determination region after the shift.
At this time, the ratio Ne / Vs always passes outside the determination region. Therefore, in this case, the ECU 31 resets the shift determination counter Cs in step S56, increments the shift determination counter Cs again from 0 for the shift speed after the shift, and performs the determination determination process for the new shift speed.

On the other hand, the ECU 31 executes a fuel cut control routine shown in FIG.
0 ms). First, the ECU 31 proceeds to step S72.
Then, it is determined whether or not the idle switch 19 is turned on. If the determination is No, that is, if it is estimated that the driver has depressed the accelerator pedal and the fuel cut should not be performed in the operating region, This routine is terminated. If the determination in step S72 is Yes, that is, when the accelerator pedal depression operation is interrupted,
In step S74, the value of the confirmed counter DCA is decremented by 1, and in step S76, the value of the undetermined counter DCA is also decreased.
Decrement B by one.

Then, in a step S78, it is determined whether or not the shift confirmation flag Fa is set.
In the case of es, in step S80, the fixed counter DC
It is determined whether or not A is 0, and in the case of No, this routine ends. If the determination in step S80 is Yes,
That is, after the accelerator operation is interrupted, the decision counter D
Delay time TDR1 of the current gear set to CA
If it is estimated that TDR5 has elapsed, the ECU 31 proceeds to step S82, where the current engine rotation speed Ne is determined.
Is greater than or equal to a predetermined determination value Nex. If the determination is Yes, a fuel cut process is executed in step S84, and this routine ends. Although not described in detail, in step S84, a process of inhibiting the injection amount control of the fuel injection valve 3, which is performed in another routine, is performed.

If the determination in step S78 is No, the ECU 31 determines in step S86 whether the undetermined counter DCB is 0. If the determination is Yes, that is, since the accelerator operation is interrupted, When it is estimated that the first-speed delay time TDR1 set in the confirmation counter DCB has elapsed, the ECU 31 performs the processing from step S82 onward in the same manner as described above.

As described above, in this fuel cut control routine, the delay times TDR1 to TD corresponding to the current gear position are set.
After the elapse of R5, the fuel cut process is started in step S84, and during the shift operation, the fuel cut process is started after the elapse of the longest delay time TDR1. When the accelerator operation is restarted and the determination in step S72 becomes Yes, the ECU 31 does not proceed to step S84, and the fuel cut process is stopped.

In the present embodiment, as the gear position determining means, the E at the time of executing the processing of step S2 and step S4.
The CU 31 functions as the delay time setting means and executes the processing of steps S6 to S60.
The EC when the CU 31 functions and executes the processing of steps S72 to S84 as the fuel cut execution means.
U31 functions.

Next, the relationship between the execution state of the fuel cut performed by the above processing and the shift speed will be described in detail with reference to the time chart of FIG. In this figure, the case where three types of delay times TDR1, TDR3, and TDR5 are set is compared. For example, a description will be given assuming that the current gear stage is held at the third speed and the delay time TDR3 is set. When the accelerator operation is interrupted (idle switch 19 is turned on), the fuel injection time T INJ also decreases with a decrease in volumetric efficiency Ev (the amount of intake air per intake stroke), and accordingly the engine torque TQ gradually decreases. When the delay time TDR3 has elapsed (Y at step S80 in FIG. 4)
At the point of time es), the fuel cut is started, and the fuel injection time TINJ rapidly decreases to 0 with the decrease amount ΔTINJ3. As a result, a variation of ΔTQ3 occurs in the engine torque TQ, and a variation of ΔG3 occurs in the longitudinal acceleration G of the vehicle (that is, a shock felt by the driver).

The above is the case of the third speed, but the same phenomenon occurs at the first speed and the fifth speed. Here, as shown in FIG. 5, the delay times TDR1 to TDR5 are set shorter for higher gears (the fifth speed side), so that the higher the gears, the earlier the fuel cut execution timing is, and the fluctuations in the fuel injection time TINJ. , And the engine torque TQ greatly fluctuates. However, the longitudinal acceleration G is less affected by the fluctuation of the engine torque TQ as the gear is higher (specifically, the influence varies in accordance with the gear ratio). The variation amounts ΔG1 to ΔG5 of the longitudinal acceleration G become substantially equal. In other words, taking into account the gear ratios of the respective gears, the fluctuation amounts ΔG1 to ΔG5 of the longitudinal acceleration G are set to be equal to each other and to a size that does not cause the driver to feel uncomfortable. , The lengths of the delay times TDR1 to TDR5 are set.

The reason why the longest delay time TDR1 is applied when the gear position is not determined, such as during a gear shift operation, is as follows. During the original gear shifting operation, the gear is in the neutral position (neutral) or the clutch is disconnected, so there is no danger of shock due to fuel cut. As described above, when the gear position is switched to the lower gear side and the determination of the second speed has not been made yet, the fuel cut is started earlier by the delay time TDR5 in spite of the actual second speed, and a shock is generated. It can be expected to occur. In this case, assuming that the shift confirmation flag Fa has not been set in step S78 in FIG. 4, the longest delay time TDR1 is applied in step S86, thereby preventing the occurrence of a shock.

As described above, in this embodiment, the delay time TDR1 to TDR5 is set shorter for a higher gear which is less affected by the fluctuation of the engine torque TQ, so that the execution timing of the fuel cut is advanced. Therefore, it is possible to achieve a further reduction in fuel consumption by suppressing the shock at the time of fuel cut to the extent that the driver does not feel discomfort at any of the gears, and extending the substantial fuel cut time. .

Although the description of the embodiment has been completed above, the embodiments of the present invention are not limited to this embodiment. For example,
In the above embodiment, a fuel injection control device for an internal combustion engine combining an M / T as a transmission has been embodied. However, a similar effect can be obtained even when combined with an automatic transmission (A / T) or a continuously variable transmission (CVT). The effect can be obtained. In this case, information on the current gear position may be input to the ECU 31 from a control unit that controls the A / T or CVT, and the delay time may be set based on the information.

[0027]

As described above, according to the fuel injection control apparatus for an internal combustion engine of the present invention, the delay time of the fuel cut is set according to the gear position of the transmission. For gears that are difficult to receive, the delay time is shortened so that the execution timing of the fuel cut is advanced, and the shock is suppressed at any gear,
By extending the substantial fuel cut time, further reduction in fuel consumption can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a fuel injection control device for an internal combustion engine according to an embodiment.

FIG. 2 is a flowchart showing a delay time setting routine executed by an ECU.

FIG. 3 is a flowchart illustrating a delay time setting routine executed by an ECU.

FIG. 4 is a flowchart illustrating a fuel cut control routine executed by an ECU.

FIG. 5 is a time chart showing a relationship between a fuel cut execution status and a shift speed.

FIG. 6 is a time chart showing a state of execution of a fuel cut in a conventional technique.

[Explanation of symbols]

Reference Signs List 1 engine (internal combustion engine) 31 ECU (gear ratio determining means, delay time setting means, fuel cut executing means)

Claims (1)

[Claims] 1. A shift speed determining means for determining a current shift speed of a transmission combined with an internal combustion engine, and a delay time for fuel cut is set according to the shift speed determined by the shift speed determining means. A delay time setting means for performing a fuel cut process for interrupting fuel injection to the internal combustion engine after a delay time set by the delay time setting means when a preset fuel cut condition is satisfied. A fuel injection control device for an internal combustion engine, comprising: a fuel cut execution unit.