JP2001355495A - Fuel injection control device or on-vehicle internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control device for an on-vehicle internal combustion engine capable of controlling a starting timing of fuel cutting at the timing when a vehicle vibration can be exactly inhibited. SOLUTION: After an acceleration operation release (time t0), an engine load ratio in which an engine torque becomes '0' based on an engine rotation speed, an ignition timing, a cooling water temperature and the like is determined. Whereas, an actual engine load ratio K is determined by a suctioned air pressure based on a signal from a suctioned air pressure sensor. Both load ratios are compared and the timing when both load ratios are coincident is determined as a timing (time t1) at which the engine torque becomes '0' or a value near '0'. When a predetermined delay time c is passed from this timing, a fuel cutting is started. The delay time is set to a period (time t2 - time t4) for which the engine torque is firstly increased in the case where an engine rotation speed is higher than a predetermined value. Whereas, the delay time is set to a period (time t6 - time t8) for which the engine torque is secondly increased in the case where the engine rotation speed is lower than the predetermined value.

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 a vehicle-mounted internal combustion engine, and more particularly to a device for controlling a start timing of a fuel cut of the engine according to an operation state of a vehicle.

[0002]

2. Description of the Related Art Generally, a vehicle-mounted internal combustion engine performs a so-called fuel cut by temporarily stopping fuel supply by a fuel injection valve when its output is not required, for example, when the vehicle is decelerating or going down a slope. It has been known. A fuel injection control device that controls the execution of such a fuel cut usually sets a predetermined delay time, that is, a so-called fuel cut delay time, from when a fuel cut start condition is satisfied to when a fuel cut is executed. I have to.

On the other hand, there is also known a fuel cut delay time which is variable in accordance with, for example, a gear position of a transmission, an engine speed, an engine water temperature, a vehicle speed, and the like. Conventionally, for example, a device described in Japanese Patent Application Laid-Open No. H11-270390 has been proposed as a fuel injection control device in which the delay time is made variable in accordance with the gear position of the transmission.

In the device described in the above publication, the current gear position of the transmission is determined based on the engine speed and the vehicle speed, and the fuel cut delay time is changed according to the determined gear position. Incidentally, the delay time is set to be shorter as the shift speed increases. Then, after the driver depresses the accelerator pedal and the idle switch is turned on, the fuel cut is executed when a delay time set according to the determined gear position has elapsed. You.

[0005]

Normally, when the accelerator pedal is released, the engine torque gradually decreases. When the torque decreases to near "0", the engine torque repeatedly increases and decreases. Converges to Then, the vehicle vibration is caused by the fluctuation of the engine torque. In addition, it has been confirmed by the inventor that such a manner of changing the engine torque varies depending on an engine load factor or the like when the accelerator pedal is depressed.

For this reason, if the fuel cut is simply performed in accordance with the delay time set based on the above-mentioned shift speed, the fluctuation of the engine torque may increase depending on the timing at which the fuel cut is performed. When this is synchronized with the resonance cycle of the vehicle, the vehicle vibration increases with the execution of the fuel cut. That is, execution of the fuel cut causes deterioration of drivability.

The present invention has been made in view of the above circumstances, and has as its object to control the fuel injection of a vehicle-mounted internal combustion engine capable of controlling the start timing of a fuel cut at a time when vehicle vibration can be accurately suppressed. It is to provide a device.

[0008]

The means for achieving the above object and the effects thereof will be described below. The invention according to claim 1 detects an operating state of an internal combustion engine mounted on a vehicle, and controls a fuel cut start timing of the engine after releasing an accelerator operation in accordance with the detected operating state. In the fuel injection control device, the engine torque of the engine is “0” after the accelerator operation is released.
Alternatively, the gist of the present invention is to provide a fuel cut control means for monitoring a timing near the fuel cut and controlling the fuel cut start timing based on a delay time from the timing when the engine torque is "0" or a timing near the engine torque.

[0009] According to the above configuration, the delay time can be set as a time corresponding to the resonance cycle of the vehicle, and the fuel cut can be started at a time when the vehicle vibration can be accurately suppressed.

According to a second aspect of the present invention, in the fuel injection control device for an on-vehicle internal combustion engine according to the first aspect, the fuel cut control means sets the engine torque of the engine to “0” when the accelerator operation is released. Or obtaining an engine load factor near the engine load factor and comparing the obtained engine load factor with an actually detected engine load factor to monitor the timing when the engine torque becomes “0” or near the same. And

According to the above configuration, the value of the engine torque can be estimated by using the engine load factor. By comparing the determined engine load factor with the actually detected engine load factor, the engine torque can be estimated. It becomes possible to know the time when the torque becomes “0” or its vicinity.

According to a third aspect of the present invention, in the fuel injection control device for an on-vehicle internal combustion engine according to the second aspect, the fuel cut control means controls the rotational speed and the ignition timing of the engine when the accelerator operation is released. The gist of the present invention is to obtain an engine load factor at which the engine torque is “0” or close to the engine torque based on the engine torque.

According to the above configuration, the engine load factor at which the engine torque is at or near "0" can be obtained from the engine speed NE and the ignition timing. According to a fourth aspect of the present invention, in the fuel injection control device for an in-vehicle internal combustion engine according to the second aspect, the fuel cut control means determines a rotational speed, an ignition timing, and an engine resistance of the engine when the accelerator operation is released. The gist of the present invention is to obtain an engine load factor at which the engine torque is “0” or close to the engine torque based on the engine torque.

According to the above configuration, the engine load factor can be obtained as a more accurate value. The engine resistance can be determined based on the engine cooling water temperature or the operating state of auxiliary equipment such as an air conditioner, which has a correlation with the driving resistance of the internal combustion engine.

According to a fifth aspect of the present invention, in the fuel injection control device for an in-vehicle internal combustion engine according to any one of the first to fourth aspects, the fuel cut control means sets the delay time to a shift speed of a transmission. The point is to set the time as being asynchronous with respect to the resonance cycle of the vehicle determined according to the following.

According to the above configuration, the fuel cut is not started during the period when the engine torque shows a tendency to decrease, that is, during the period synchronized with the resonance cycle of the vehicle. For this reason, the torque fluctuation does not further increase due to the decrease in the engine torque due to the fuel cut, and the increase in the vehicle vibration can be accurately suppressed.

According to a sixth aspect of the present invention, in the fuel injection control apparatus for an on-vehicle internal combustion engine according to any one of the first to fourth aspects, the fuel cut control means may be arranged so that the engine torque is equal to or close to "0" The gist of the present invention is to set the delay time so that the fuel cut is started at a time when the engine torque tends to increase after this time.

According to the above configuration, the increase in the engine torque is offset by the decrease in the engine torque due to the fuel cut, and the fluctuation in the engine torque is suppressed. Therefore, it is possible to accurately suppress the increase in the vehicle vibration. become able to.

The invention described in claim 7 is the fifth or sixth invention.
In the fuel injection control device for an in-vehicle internal combustion engine described in the above, the gist of the invention is that the fuel cut control means variably sets the delay time according to the rotation speed of the engine at the time of releasing the accelerator operation.

According to the above configuration, the manner of change of the engine torque after the accelerator operation is released differs depending on the engine speed at the time of releasing the operation. Therefore, the delay time is variably set in accordance with the engine speed. The start timing of the fuel cut can be controlled at a time at which the vehicle vibration can be accurately suppressed in accordance with such a change in the engine torque.

According to an eighth aspect of the present invention, in the fuel injection control device for an on-vehicle internal combustion engine according to the seventh aspect, the fuel cut control means determines that the engine torque is equal to or less than "0". The delay time is set corresponding to a period in which the engine torque first increases and a period in which the engine torque increases second according to a high or low value of the engine speed from a certain reference. That is the gist.

Here, after the accelerator operation is released, the engine torque gradually decreases, and when it decreases to around "0", it converges to a certain negative value while repeatedly increasing and decreasing. At this time, if the engine speed at the time of canceling the accelerator operation is low, the time until the convergence of the engine torque tends to be longer after the engine torque becomes “0” or near the time. For this reason, if the same delay time is set to start the fuel cut regardless of the magnitude of the engine speed, the fuel cut at the start of the fuel cut is smaller when the engine speed is lower than when the engine speed is higher. Since the difference between this torque value and the torque value at the time of convergence is large, the vehicle vibration at the start of the fuel cut becomes large.

In this respect, according to the above configuration, the delay time is set in accordance with the engine speed, which is higher or lower than a certain reference, so that the vehicle vibration at the start of the fuel cut can be suppressed. Further, by setting the delay time so that the fuel cut is started during a period in which the engine torque tends to increase, the amplitude of the torque can be reduced, and the vehicle vibration can be suitably reduced. .

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a fuel injection control apparatus for a vehicle-mounted internal combustion engine according to the present invention will be described below with reference to FIGS.

As shown in FIG. 1, a fuel injection valve 1 for injecting fuel into a combustion chamber 11 of an internal combustion engine 10 is provided.
2 and an ignition plug 13 for igniting a mixture of the injected fuel and the intake air. An intake passage 16 and an exhaust passage 17 are connected to the combustion chamber 11, respectively. A surge tank 18 is provided in the middle of the intake passage 16.

Further, the fuel injection control such as the fuel cut is controlled by the electronic control unit (ECU) 20 based on the engine operating state and the like. Various sensors and switches for detecting the engine operating state are connected to the ECU 20, and these detection signals are appropriately taken in.

That is, the ECU 20 includes an intake pressure sensor 21 for detecting the magnitude of the pressure in the surge tank 18, a rotational speed sensor 22 for detecting the rotational speed of the internal combustion engine 10,
An idle switch 23 for detecting whether or not an accelerator pedal (not shown) is depressed; a shift position sensor 24 for detecting a shift position of a shift lever of a transmission (not shown), that is, a shift speed of the transmission; and a water temperature sensor 25 for detecting an engine coolant temperature. Are respectively input. ECU 20
Executes the fuel injection control based on the detection results of these sensors and the switches 21 to 25.

In this fuel injection control, the fuel cut is performed as follows. That is, during normal running of the vehicle,
For example, when the ECU 20 determines that a predetermined fuel cut execution condition such as an accelerator pedal depressing operation release is satisfied, a delay time according to the driving state of the vehicle is set. Then, the fuel cut is started based on the elapse of the set delay time. Then E
When the CU 20 determines that the predetermined release condition is satisfied, the fuel injection by the fuel injection valve 12 is restarted.

Next, a specific processing procedure of this fuel cut will be described in detail with reference to a flowchart shown in FIG. It should be noted that a series of processes shown in the figure are repeatedly performed at predetermined time intervals.

In this series of processing, first, in step S10
, The ECU 20 determines whether or not the engine speed NE is higher than a predetermined value a1 based on a signal from the speed sensor 22. The predetermined value a1 is for determining whether or not there is a risk that the internal combustion engine 10 will stall due to the execution of the fuel cut. And the engine speed NE
Is higher than the predetermined value a1, and if it is determined that the stall of the internal combustion engine 10 does not occur even if the fuel cut is performed, the process proceeds to step S12, and if the engine speed NE is equal to or less than the predetermined value a1, The process moves to step S14.

In step S12, the ECU 20 determines whether or not the accelerator pedal is fully closed. The fully closed state of the accelerator pedal refers to a state in which the driver of the vehicle depresses the accelerator pedal, that is, a state in which the accelerator operation is released. In a state in which the accelerator pedal is released, the idle switch 23 is turned on. Is determined based on the following. And the same step S1
In step 2, if the accelerator pedal is fully closed, the process proceeds to step S18, while if the accelerator pedal is depressed, the process proceeds to step S14.

If the determination in step S10 or step S12 is "NO" and the process proceeds to step S14, the ECU 20 sets the fuel cut execution flag X to "OF".
F ". The fuel cut execution flag X is set to “ON” once the fuel cut is started, and thereafter, when the condition of the subsequent step S10 or step S12 is not satisfied (step S10, step S12:
"NO") is a flag set to "OFF". Thereafter, the processing shifts to step S16, where the counter CN
T1 is reset to "0", and the process is once ended.

In step S18, the ECU 20 determines whether the flag X is "ON". If the flag X is "ON", the process proceeds to step S32 to execute the fuel cut, and the process is terminated once. On the other hand, if the fuel cut execution flag X is “OF
If “F”, the process moves to step S20.

In step S20, the ECU 20
Is based on a map (not shown) of the engine rotational speed NE and the ignition timing of the ignition plug 13 when the engine torque of the internal combustion engine 10 becomes "0", that is, when the output shaft of the internal combustion engine 10 is driven by a vehicle such as a transmission. The engine load factor b is determined when the system is driven to rotate. Further, the ECU 20 determines a delay time c for executing the fuel cut based on a map (not shown) of the transmission gear position and the engine speed NE.
Set.

Here, the engine load factor is the engine speed N
This is a value indicating the ratio of the current intake air amount to the maximum value of the intake air amount corresponding to E. When the intake air amount becomes equal to this maximum value, the engine load factor becomes 100%. In addition,
The engine load factor b is set to be larger as the engine speed NE is smaller and the ignition timing is more advanced. The intake air amount is obtained based on detection signals from the intake pressure sensor 21 and the rotation speed sensor 22, for example.

On the other hand, the delay time c is set so as to become shorter as the shift speed becomes higher. this is,
This is because the resonance cycle of the vehicle becomes smaller as the shift speed becomes higher. The delay time c is set to a relatively short period when the engine speed NE is equal to or higher than the predetermined value a2, and is set to a relatively long period when the engine speed NE is lower than the predetermined value a2. . This is the engine rotational speed NE when the accelerator pedal is released.
Is smaller, the convergence time of the engine torque after the time when the engine torque becomes “0” or nearer becomes longer,
If the same delay time c is set and fuel cut is started regardless of the magnitude of the engine speed NE, the engine speed N
When E is small, the difference between the torque value at the start of fuel cut and the torque value at the time of convergence is large as compared with the case where the rotational speed NE is high, and the vehicle vibration at the start of fuel cut may be large. Because there is.

When the engine load factor b and the delay time c are determined in this way, the ECU 20 proceeds to step S
Move to 22. In step S22, the ECU 20
Corrects the load factor b obtained by the processing in step S20 according to the engine resistance of the internal combustion engine 10. This correction is made based on the engine cooling water temperature and the operating state of an air conditioner or alternator (not shown). That is, the lower the engine cooling water temperature, the greater the friction in the driving portion of the internal combustion engine 10, so that the value of the engine load factor b is corrected so as to increase. Further, even when the air conditioner or the alternator is operated, the engine torque of the internal combustion engine 10 is reduced even if the intake air amount is the same due to the operation of these auxiliary devices, so that the value of the engine load factor b obtained above is increased. Is corrected to Thereby, the engine load factor b
Can be obtained as an accurate value corresponding to the engine resistance. After correcting the engine load factor b in this way, the ECU 20 shifts the processing to step S24.

In step S24, the ECU 20 determines whether or not the actual value of the engine load factor K is equal to or less than the value of the engine load factor b obtained above. In the present embodiment, by comparing the obtained engine load factor b with the engine load factor K, the timing at which the engine torque becomes “0” or near it is monitored. If the value of the engine load factor K is equal to or less than the determined engine load factor b in step S24, the process proceeds to step S26, and the value of the counter CNT1 is incremented by "1". This counter CNT1 corresponds to the elapsed time from when the engine torque becomes “0”. On the other hand, if the value of the engine load factor K is larger than the engine load factor b, the process is temporarily terminated.

In step S26, the counter CNT1
Is incremented, the process proceeds to step S28, and the ECU 20 determines whether or not the value of the counter CNT1 is greater than the value of the delay time c set as described above, that is, the engine torque is set to “0”. Then, it is determined whether or not the set delay time has elapsed. And
If the value of the counter CNT1 is larger than the value of the delay time c, the process proceeds to step S30. If the value of the counter CNT1 is equal to or less than the value of the delay time c, the process is temporarily ended.

After setting the fuel cut execution flag X to "ON" in step S30, the ECU 20 proceeds to step S32 to execute fuel cut. Thus, the start timing of the fuel cut is controlled.

Next, with reference to the timing chart of FIG. 2, description will be given of each change mode of the idle switch 23, the engine torque, the delay time c, and the start timing of the fuel cut after the depression operation of the accelerator pedal is released.

As shown in FIGS. 2A and 2B, when the driver depresses the accelerator pedal during normal running of the vehicle, the idle switch 23 is changed from the "OFF" state to the "ON" state. And the engine torque gradually decreases (at times t0 to t).
1). Thereafter, when the engine torque decreases to near "0" (time t1), the engine torque converges to a certain negative value while repeatedly increasing and decreasing with the resonance period of the vehicle determined according to the gear position of the transmission.

In the present embodiment, measurement of the delay time (counting of the counter CNT1) is started at a time (time t1) when the engine torque decreases to "0" or less. Therefore, the delay time c can be set as a time corresponding to the resonance cycle of the vehicle, and the fuel cut can be started at a time when the vehicle vibration can be accurately suppressed.

The delay time c is equal to a predetermined value a of the engine speed NE when the accelerator pedal is released.
2, the period in which the engine torque first tends to increase (the period from time t2 to time t4) and the period in which the engine torque tends to increase for the second time (from time t6 to time t8). Are set in correspondence with each other. Therefore, the vehicle vibration at the start of the fuel cut can be suppressed.

Further, by setting the delay time c so that the fuel cut is started during a period in which the engine torque shows a tendency to increase, as shown by a solid line after time t3 in FIG. An increase in the engine torque is offset by a decrease in the engine torque due to the fuel cut. Therefore,
The vibration of the engine torque can be suppressed to be small, and the vibration of the vehicle can be suitably reduced.

As described in detail above, according to the fuel injection control device for a vehicle-mounted internal combustion engine according to this embodiment, the following excellent effects can be obtained. (1) The delay time c can be set as a time corresponding to the resonance cycle of the vehicle, and the fuel cut can be started at a time when vehicle vibration can be accurately suppressed.

(2) By comparing the actual engine load factor K with the engine load factor b at which the engine torque is "0" or near it, it is possible to know the timing at which the engine torque becomes "0" or near. become able to.

(3) From the engine speed NE and the ignition timing, the engine load factor b at which the engine torque is "0" or near it can be obtained. (4) To correct the engine load factor b obtained based on the engine speed NE and the ignition timing based on the engine resistance,
The engine load factor b can be obtained as a more accurate value.

(5) Since the delay time c is set to a time that is asynchronous with respect to the resonance cycle of the vehicle determined according to the gear position of the transmission, a period during which the engine torque tends to decrease, that is, the vehicle speed, The fuel cut is not started during the period (time t1 to t5, t1 to t9 in FIG. 2) synchronized with the resonance cycle. Therefore, the torque fluctuation does not increase further due to the decrease in the engine torque caused by the fuel cut, and the increase in the vehicle vibration can be accurately suppressed.

(6) By setting the delay time c so that the fuel cut is started at a time when the engine torque tends to increase (time t2 to t4, t6 to t8 in FIG. 2),
The increase in the engine torque is offset by the decrease in the engine torque due to the fuel cut, and the fluctuation in the engine torque is suppressed. Therefore, the increase in the vehicle vibration can be accurately suppressed.

(7) Since the delay time c is variably set according to the engine speed NE when the accelerator pedal is depressed, the vehicle vibration can be accurately suppressed in accordance with the change in the engine torque. The start timing of the fuel cut can be controlled.

(8) When the engine speed NE is less than the predetermined value a2, the delay time c is set so that the fuel cut is started at the time when the engine torque tends to increase for the second time (time t6 to t8 in FIG. 2). Is set, the vehicle vibration at the start of the fuel cut can be further reduced.

In the above embodiment, for example, the configuration can be appropriately changed as follows. In the above embodiment, the delay time c is variably set in two stages according to the high and low values of the engine speed NE from the predetermined value a2. However, the delay time c may be set in three or more stages in accordance with the engine speed NE. May be variably set.

In the above embodiment, the engine load factor K is corrected based on the engine resistance. However, this correction may be omitted. In the above embodiment, the engine load factor b at which the engine torque becomes “0” and the actually detected engine load factor K are compared to monitor the timing at which the engine torque becomes “0” or near the engine torque. However, the timing at which the engine torque is “0” or near the engine torque may be monitored by directly detecting the engine torque.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a fuel injection control device for a vehicle-mounted internal combustion engine according to the present invention.

FIG. 2 is a timing chart showing changes in an idle switch, an engine torque, a delay time, and a fuel cut start timing after an accelerator operation is released.

FIG. 3 is a flowchart showing control of a fuel cut start timing.

[Explanation of symbols]

10 internal combustion engine, 11 combustion chamber, 12 fuel injection valve, 1
3: spark plug, 16: intake passage, 17: exhaust passage, 1
8 ... Surge tank, 20 ... Electronic control unit (ECU), 2
DESCRIPTION OF SYMBOLS 1 ... Intake pressure sensor, 22 ... Rotation speed sensor, 23 ... Idle switch, 24 ... Shift position sensor, 25 ...
Water temperature sensor.

Claims (8)

[Claims] A fuel injection control for an on-board internal combustion engine for detecting an operating state of an internal combustion engine mounted on a vehicle and controlling a fuel cut start timing of the engine after releasing an accelerator operation in accordance with the detected operating state. In the apparatus, after the accelerator operation is released, monitoring the timing when the engine torque of the engine becomes “0” or near the same, and monitoring the fuel cut by the delay time from the timing when the engine torque becomes “0” or near the same. A fuel injection control device for a vehicle-mounted internal combustion engine, comprising a fuel cut control means for controlling a start timing. 2. The fuel cut control means obtains an engine load factor at which the engine torque of the engine becomes "0" or near the engine torque when the accelerator operation is released, and the detected engine load factor is actually detected. 2. The fuel injection control device for a vehicle-mounted internal combustion engine according to claim 1, wherein a time when the engine torque becomes "0" or near the engine torque is monitored by comparing with an engine load factor. 3. The fuel cut control means obtains an engine load factor at which the engine torque becomes “0” or near the same based on a rotation speed and an ignition timing of the engine at the time of releasing the accelerator operation. A fuel injection control device for a vehicle-mounted internal combustion engine. 4. The fuel cut control means calculates an engine load factor at which the engine torque becomes "0" or near the same based on a rotational speed, an ignition timing, and an engine resistance of the engine at the time of releasing the accelerator operation. Item 3. A fuel injection control device for a vehicle-mounted internal combustion engine according to Item 2. 5. The fuel cut control means sets the delay time as a time that is asynchronous with respect to a resonance cycle of a vehicle determined according to a shift speed of a transmission.
A fuel injection control device for an in-vehicle internal combustion engine according to any one of the above. 6. The fuel cut control means controls the delay time so that the fuel cut is started at a time when the engine torque tends to increase after the time when the engine torque is at or near "0". The fuel injection control device for a vehicle-mounted internal combustion engine according to any one of claims 1 to 4, wherein the fuel injection control device is set. 7. The fuel injection control apparatus for a vehicle-mounted internal combustion engine according to claim 5, wherein said fuel cut control means variably sets said delay time in accordance with a rotation speed of said engine when said accelerator operation is released. 8. The fuel cut control means increases the engine torque first according to whether the engine speed is high or low from a certain reference after the time when the engine torque is at or near "0". 8. The fuel injection control device for a vehicle-mounted internal combustion engine according to claim 7, wherein the delay time is set corresponding to each of a period in which the engine torque tends to increase and a period in which the engine torque increases second time.