JP2590497B2 - Fuel cut control method for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cut control method for an internal combustion engine that cuts fuel when a shift lever of an automatic transmission is shifted from a stop range to a travel range.

(Prior art)

Conventionally, a basic fuel injection time is determined by an engine load (intake pressure or intake air amount) and an engine rotation speed, and the basic fuel injection time is corrected by using various correction coefficients such as an intake air temperature and an engine cooling water temperature. 2. Description of the Related Art There is known a fuel injection method in which a time is determined, and a fuel injection valve is opened at a predetermined crank angle for a time corresponding to the fuel injection time to inject fuel.

Further, there is known a fuel cut device for cutting fuel supplied to an engine when an engine speed exceeds a predetermined speed for the purpose of preventing catalyst heating of an exhaust system of an internal combustion engine, reducing fuel consumption, and the like. ing.

The fuel cut in this case is, for example, when the throttle sensor detects the fully closed position of the throttle valve, and stops the fuel injection from the fuel injection valve when the engine speed is equal to or higher than a predetermined value (fuel during deceleration). In order to prevent overrun of the engine, fuel injection from the fuel injection valve is stopped when the engine speed exceeds a predetermined speed (high-speed fuel cut).

By the way, in the case of a vehicle with an automatic transmission, when a stopped vehicle is started, if a general driver is used, the shift lever is shifted from a stop range such as N (neutral) or P (parking) to D (drive), (Second), L
Normally, the driver depresses the accelerator pedal after performing a travel range shift operation such as (low) or R (reverse).

However, if the driver or a beginner is not accustomed to riding an automobile with an automatic transmission, the driver may depress the accelerator pedal at the time of starting and make an error such as shifting the shift lever from the stop range to the travel range in the high speed rotation state from the stop range. In this case, however, there is a problem that a relatively large output torque of the engine is transmitted to the automatic transmission and the gears of the vehicle drive system are damaged.

For this reason, the applicant has detected that the shift lever of the automatic transmission has been shifted from the stop range to the travel range, and upon this detection, the fuel cut rotational speed of the fuel cut during acceleration is changed to the fuel cut during normal operation. It has been proposed to set the rotation speed lower than the rotation speed (Japanese Patent Application No. 61-1048).
No. 63).

As a result, the engine speed at the time of the shift is rapidly reduced,
Excessive torque is prevented from being transmitted to the drive system of the vehicle.

By the way, when returning to the normal fuel cut speed after the setting of the low fuel cut speed, the fuel cut speed is gradually increased at every predetermined speed. Even if the engine speed is increased again, sudden start does not occur and the speed can be increased smoothly without increasing beyond the number.

It is also possible to determine the fuel cut time as a predetermined value in advance and set the fuel cut rotational speed to a low value only during the fixed time. Japanese Patent Application Laid-Open Nos. 60-4433 and 61-255231 relate to such fuel cut control.
There is a technique described in Japanese Unexamined Patent Application Publication No. HEI 9-86.

[Problems to be solved by the invention]

However, despite the fact that the decreasing rate (slope) of the engine speed after the fuel cut is almost constant, the same fuel is always maintained after the shift operation from the stop range to the travel range regardless of the engine speed. It has been cut time. For this reason, if the fuel cut time is set to be too short, it is not possible to prevent excessive torque transmission to the drive system. If the fuel cut time is set to be long, excessive torque transmission can be reliably prevented. However, even during normal acceleration, acceleration cannot be performed as required, resulting in sluggishness and impaired drivability.

In consideration of the above facts, the present invention sets an optimal fuel cut time at the time of shifting from the stop range to the traveling range, can prevent excessive torque transmission to the drive system due to the shift at the time of high engine speed, and at the time of normal acceleration. It is an object of the present invention to provide a fuel cut control method for an internal combustion engine which does not impair the drivability of the engine.

[Means for solving the problem]

The fuel cut control method for an internal combustion engine according to the present invention is a fuel cut control method for detecting an engine speed and performing a fuel cut when a fuel cut condition equal to or higher than a predetermined engine speed is satisfied. When the shift operation is performed from the stop range to the travel range, the fuel cut speed is set to a predetermined speed lower than the predetermined engine speed, and the fuel cut time is set based on the engine speed at the time of the shift operation. It is characterized in that fuel cut conditions are determined based on the predetermined low rotational speed for a predetermined fuel cut time.

[Action]

When the shift lever of the automatic transmission is shifted from the stop range to the travel range, the engine speed is detected.

In the present invention, based on the detected engine speed,
For example, the fuel cut time is set longer as the engine speed is higher and shorter as the engine speed is lower. As a result, the fuel cut time at the engine speed at the start of the fuel cut becomes an optimal value with no excess or deficiency, so that excessive torque transmission to the drive system can be prevented and the fuel cut time is too long. It is possible to prevent rattling during acceleration and does not impair drivability.

〔Example〕

Hereinafter, an internal combustion engine according to the present embodiment will be described in detail with reference to the drawings. The internal combustion engine is an engine of an automatic transmission specification mounted on a vehicle. FIG. 1 shows an outline of the engine. An intake air temperature sensor 14 for detecting an intake air temperature is provided near an air cleaner 10.
A throttle valve 12 whose opening is controlled by an accelerator pedal is further disposed downstream of the throttle valve. Further, a throttle opening sensor 16 for detecting the opening of the throttle valve 12 is attached to the throttle valve 12.

An air flow meter 13 is disposed between the air cleaner 10 and the throttle valve 12. The air flow meter 13 includes a compensation plate 13B rotatably disposed in a damping chamber 13A and a measuring plate 13C fixed to the compensation plate 13B. Is detected by a potentiometer 13D. The intake air amount is calculated based on the detection value of the potentiometer 13D.

A surge tank 18 is arranged downstream of the throttle valve 12, and the surge tank 18 is connected to a combustion chamber formed in the engine body via an intake manifold 20. A fuel injection valve 22 is attached to each intake cylinder 20 so as to protrude into the intake manifold 20 for each cylinder. The fuel injection valve 22 is controlled by the control device 52 to inject a predetermined amount of fuel calculated based on an intake air amount, an engine speed, and the like. Further, the controller 52 performs fuel cut control for stopping fuel injection when the throttle valve 12 is fully closed and the engine speed is equal to or higher than a predetermined value.

The combustion chamber formed in the engine body is connected to a catalyst device 25 filled with a three-way catalyst via an exhaust manifold 24. The exhaust manifold 24 is provided with an O ₂ sensor 26 that detects the concentration of residual oxygen in the exhaust gas and outputs a signal inverted at a stoichiometric air-fuel ratio. Further, a water temperature sensor 28 for detecting the temperature of the engine cooling water is attached to the engine block of the engine main body so as to penetrate the engine block and protrude into the water jacket. The engine block repeats a reciprocating motion by the combustion of the air-fuel mixture in the combustion chamber, and is converted into a rotary motion by a crankshaft, and then is subjected to an automatic transmission.
The navel driving force is transmitted. A range detection sensor 29 for detecting a D (drive) range and an N (neutral) range is attached to the automatic transmission 27. The timing of switching from the N range to the D range is detected based on the output signal of the range detection sensor.

A spark plug 46 is attached to each cylinder so as to penetrate the cylinder head of the engine body and protrude into the combustion chamber. The spark plug 46 is connected to a control circuit 52 via a distributor 48 and an igniter 50. ing. In the distributor 48, a rotation angle sensor 54 composed of a signal rotor fixed to the distributor shaft and a pickup fixed to the distributor housing is mounted. This rotation angle sensor 54
Outputs, to the control circuit 52, an engine speed signal composed of a pulse train generated every 30 CA, for example.

The control circuit 52 is configured to include a microcomputer. That is, as shown in FIG. 2, the control circuit 52 controls the RAM 56, ROM 58, MPU 60,
It includes an input / output port 62, an input port 64, output ports 68 and 70, and a bus 72 such as a data bus or control bus connecting these. An input / output port 62 includes an analog-to-digital (A / D) converter 74 and a multiplexer 7.
6 is connected. The multiplexer 76 has a potentiometer 13D and a buffer 77 via a buffer 75, respectively.
Via vehicle speed sensor 79, via buffer 78 water temperature sensor
28, the throttle opening sensor 16 is connected via a buffer 80, and the intake air temperature sensor 14 is connected via a buffer 82.

The MPU 60 controls the A / D converter 74 and the multiplexer 76 through the input / output port 62, and sequentially outputs the output of the water temperature sensor 28, the output of the intake air temperature sensor 14, and the output of the throttle opening sensor 16 to the A / D converter.
The converted data is stored in the RAM 56. The O ₂ sensor 26 is connected to the input port 64 via a comparator 84 and a buffer 86. The input port 64 is connected to the range detection sensor 29 via a buffer 87. Further, the rotation angle sensor 54 is connected to the input port 64 via a waveform shaping circuit 88.

The output port 68 is connected to an igniter via a drive circuit 92.
The output port 70 is connected to the fuel injection valve 22 via a drive circuit 94 having a down counter. Reference numeral 96 is a clock, and 98 is a timer. Above the ROM 58 (Matsupu basic control amount) Matsupu programs and the basic fuel injection time of the control routines described in Matsupu and less for obtaining a fuel Katsuhito time T _F based on the engine rotational speed NE shown in FIG. 3, etc. Is stored in advance. Fuel Katsuhito time T _F of Matsupu shown in Figure 3 is greater in proportion to the engine speed NE.

Basic fuel injection quantity, potentiometer 13D, is calculated based on the output value of the rotation angle sensor 54 (engine speed), successively corrected based on the output value of the intake air temperature sensor 14, O ₂ sensor 26 and water temperature sensor 28 It is supposed to be.

Further, the basic ignition timing is calculated based on the output values of the potentiometer 13D and the rotation angle sensor 54 in the same manner as the calculation of the basic injection amount, and the correction is sequentially performed based on the output value of the water temperature sensor 28. .

The operation of this embodiment will be described below with reference to the flowcharts of FIGS. The basic ignition timing calculation routine, the fuel injection routine, and the execution routine thereof are omitted because they are the same as the control of the conventional electronically controlled internal combustion engine.
The fuel cut routine at the time of shift switching, which is a feature of the present invention, will be described.

First, the fuel cut main routine of FIG. 4 will be described.

First, at step 100, the engine speed NE is read, and the routine proceeds to step 102. In step 102, the detected engine speed NE and the fuel Katsuhito rotational speed N _FC is compared. The fuel cut speed N _H corresponds to the higher engine speed N _H (7000 rpm) determined in the range shift fuel cut routine of FIG. Where NE
If it is determined that ≧ N _FC, the process proceeds to step 104, by executing the fuel Katsuhito, the process proceeds to the next routine. This fuel cut is continued until it is determined in step 102 that NE < _NH . That is, when it is determined that NE <N _FC at step 102, step 15 of whether (Figure 5 flag F is excisional described later migrate to step 106
4 or step 170) is determined. If a negative determination is made in step 106, the process proceeds to step 108. If the fuel cut is being executed, this is stopped, and then the process proceeds to the next routine. If the determination in step 106 is affirmative, that is, if the flag F is set, the process proceeds to step 104 regardless of the determination in step 102, and the fuel cut is executed.

Next, the range shift fuel cut routine will be described with reference to FIG.

First, in step 150, it is determined whether or not the current vehicle speed is equal to or less than X km / h. Xkm / h is preferably about 10 km / h. If the vehicle speed is higher than Xkm / h, even if there is a switch from the stop range to the travel range (shifting to the N range during normal traveling is not preferable,
It is possible to return to the range. ), Since the transmission of torque to the drive system is made smoothly, the fuel and proceeds to step 152 Katsuhito rotational speed N _FC high rotational speed N _H (7000rp
m), and then resets the flag F (0) in step 154 and proceeds to the next routine. If it is determined in step 150 that the vehicle speed is less than X km / h, the vehicle shifts from the stop range to the travel range. Since there is a possibility that excessive torque transmission may occur at the time of switching, the flow shifts to step 156 to confirm the current shift position. In step 156, it is determined whether the shift position is in the D range or not.
If it is not the D range, it is determined that the shift has not been switched, and the routine proceeds to step 152. If it is determined in step 156 that the camera is in the D range, the
The process proceeds to 158, and it is determined whether or not it is the moment when the range is switched from the previous N range. Here, if a positive determination is made reads the fuel Katsuhito time T _F based on the current engine speed from Matsupu (see FIG. 3) previously stored in the ROM58 and proceeds to step 160.

The next step in the 162 fuel Katsuhito rotational speed N _FC low rotational speed N _L (1500rpm), the process proceeds to the next routine.

Here, if a negative determination is made in step 158, the routine proceeds to step 166, where the previously set fuel cut speed N _FC (N _H or N _L ) is compared with the current engine speed NE, and NE <N _In the case of _FC , there is no need for a fuel cut, so the flow proceeds to step 152. Further, it is determined that in the case of NE ≧ N _FC is required fuel Katsuhito, the routine proceeds to step 168, shifted from the point read from the Matsupu fuel Katsuhito time T _F has elapsed from the N range to the D range and whether it is determined the, if you are passed returning fuel Katsuhito rotational speed shifts to step 152 to a normal high rotational speed N _F.
Further, when the fuel Katsuhito time T _F has not passed, the fuel Katsuhito rotational speed has been set as being maintained, then after excisional (1) The flag F at step 170, the process proceeds to the next routine. That is, if the routine proceeds to the fuel cut main routine after passing through this step 170, even if it is determined that NE < _{NH in} step 102 of FIG.
An affirmative determination is made in step 106, and the fuel cut is executed.

Fuel Katsuhito time T _F is longer becomes a value in proportion to the engine speed, reducing the engine speed to a substantially constant rotational speed at the same time and end of the fuel Katsuhito time T _F which was also set at any rotational speed be able to. Therefore, the fuel cut time is short when shifting from the N range to the D range in a state where the engine speed is relatively low, so that there is no backlash during acceleration after shifting to the D range. In addition, when shifting from the N range to the D range in a state where the engine speed is relatively high, a long fuel cut time is used, so that excessive transmission of torque to the drive system can be reliably prevented.

As described above, in this embodiment, the fuel cut time is set according to the engine speed at the start of the fuel cut.
It is possible to realize both prevention of deterioration of drivability and prevention of excessive torque transmission to the drive system.

In this embodiment, the range shift fuel cut control is executed in combination with the fuel cut control at the time of high engine rotation. However, the range shift fuel cut control may be controlled independently.

Further, in this embodiment, the internal combustion engine that calculates the fuel injection time based on the intake air amount and the engine rotation speed has been described. However, the internal combustion engine that controls the fuel injection amount and the ignition timing according to the intake pipe pressure and the engine rotation speed is described. Can also be applied.

〔The invention's effect〕

As described above, the fuel cut control method for an internal combustion engine according to the present invention sets an optimal fuel cut time at the time of shifting from the stop range to the travel range, and transmits excessive torque to the drive system due to the shift at the time of high engine speed. , And has an excellent effect of not impairing drivability during normal acceleration.

[Brief description of the drawings]

1 is a schematic block diagram of an engine according to the present embodiment, FIG. 2 is a control block diagram, FIG. 3 is a map for obtaining a fuel cut time from an engine speed, and FIG. 4 shows a fuel cut main routine. FIG. 5 is a flow chart showing a fuel cut routine at the time of shift switching. 16: throttle opening sensor, 22: fuel injection valve, 27: automatic transmission, 29: range detection sensor, 52: control device, 54: rotation angle sensor.

Claims (1)

(57) [Claims] An automatic transmission shifts from a stop range to a travel range by detecting an engine speed and performing fuel cut when a fuel cut condition equal to or higher than a predetermined engine speed is satisfied. When operated, the fuel cut speed is set to a predetermined speed lower than the predetermined engine speed, and the fuel cut time is determined based on the engine speed at the time of the shift operation, and the determined fuel cut time is set. Determining a fuel cut condition based on the low predetermined rotation speed during the period.