JP2003184611A - Fuel supply device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel supply device for an engine, constituted by a return- less fuel supply system, allowing sure fuel cut even in case of sudden deceleration and the drop of a fuel pressure down to a fuel pressure corresponding to a fuel injection reset speed by the time that fuel injection is reset. <P>SOLUTION: An ECU sets a target fuel pressure Po in accordance with a throttle opening TVO and an engine speed Ne and controls a fuel pump so that an actual fuel pressure P becomes a target fuel pressure Po, and it performs fuel cut when the throttle opening is smaller than a first preset value TVO1 and drops the target fuel pressure Po down to a preset value corresponding to a reset speed value Ner when the throttle opening is lowered to a second preset value TVO2 before lowered to the first preset value TVO1. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine fuel supply system, and more particularly to the technical field of pressure control of fuel supplied to a fuel injection valve.

[0002]

2. Description of the Related Art As a fuel supply device for supplying fuel to a fuel injection valve of an engine, for example, a fuel pipe for returning excess fuel out of fuel supplied from a fuel tank to a fuel injection valve by a fuel pump to the fuel tank. Those who have are known. Further, by supplying only the amount of fuel corresponding to the fuel injection amount from the fuel pump to the fuel injection valve, a return pipe for the excess fuel from the fuel injection valve to the fuel tank is unnecessary, so-called returnless fuel supply. A system is known.

In an automobile engine, the fuel injection valve is closed to inject fuel when the engine speed is equal to or higher than a predetermined speed during deceleration for the purpose of improving fuel efficiency and emission. A fuel cut may be performed in which the fuel injection is restarted and fuel injection is restarted when the engine speed decreases and reaches the return speed.

When the fuel cut at the time of deceleration is performed by the engine adopting the returnless fuel supply system, even if the fuel discharge operation from the fuel pump is stopped at the same time as the fuel cut, the valve in the pump is closed. Since the fuel injection is stopped, the fuel pressure between the fuel pump and the fuel injection valve is maintained after the fuel cut, and as a result, the engine speed is decreasing. However, there is a problem that the fuel injection amount becomes overrich by using the fuel pressure at the time of high rotation, the engine operating state becomes unstable, and the emission deteriorates.

As a means for solving the above-mentioned problem at the time of fuel cut in a fuel supply device adopting this returnless fuel supply system, for example, as described in Japanese Patent Laid-Open No. 9-158803, when a fuel cut condition is satisfied. While reducing the fuel supply capacity of the fuel pump,
There is a system in which the fuel cut itself is performed after a lapse of a predetermined time. According to this, the fuel cut is performed after the fuel supply capacity of the fuel pump is reduced. Will be reduced to the fuel pressure of.

[0006]

However, in the case of the fuel supply device described in the above publication, the fuel injection by the fuel injection valve is actually stopped after a predetermined time has elapsed from when the fuel cut condition was established. That is, the fuel cut is delayed from the originally required timing, so that the fuel is unnecessarily injected during the delayed time.

In addition, even if the engine speed rapidly drops to the return speed from the fuel cut within the above-mentioned predetermined time due to sudden deceleration due to braking after the fuel cut condition is satisfied, for example, The cut is not performed, fuel is wastefully injected, and the opportunity for improving fuel efficiency is lost.

In addition, even when the fuel cut is performed in the fuel cut region, when the engine speed decreases to the return speed at a speed faster than the fuel pressure decrease speed due to the decrease in the supply capacity of the fuel pump, the fuel pressure Is reduced from the return speed to the required value, that is, the fuel injection is restarted with the fuel pressure higher than the required fuel pressure, and as a result, the fuel injection is performed at the fuel pressure equal to the required fuel pressure. Compared to the time when the fuel injection was over rich,
The engine operating condition becomes unstable, and the emission becomes worse.

Therefore, according to the present invention, in the fuel supply device constituted by the above-mentioned returnless fuel supply system, the fuel cut can be surely executed even when the rapid deceleration occurs, and the fuel pressure is restored to the fuel injection return. It is an object of the present invention to provide an engine fuel supply device capable of reducing the fuel pressure to a fuel pressure corresponding to the fuel injection return rotational speed by time.

[0010]

In order to solve the above problems, the present invention is characterized by having the following configuration.

First, in the invention according to claim 1 of the present application, a fuel supply pipe is provided between the fuel pump and the fuel injection valve,
A fuel supply device for an engine including a fuel supply system in which a recovery pipe for returning excess fuel from a fuel injection valve to a fuel tank is not provided, and fuel pressure detection means for detecting an actual fuel pressure in the fuel supply pipe, Engine load related value detection means for detecting a value related to engine load, engine rotation related value detection means for detecting a value related to engine rotation, and target fuel pressure based on the engine rotation related value and the engine load related value Target fuel pressure setting means for setting, fuel pressure control means for controlling the fuel pump so that the actual fuel pressure detected by the fuel pressure detecting means becomes the target fuel pressure set by the target fuel pressure setting means, and engine load When the engine load-related value becomes smaller than the first predetermined value, fuel injection from the fuel injection valve is stopped, and the state Fuel cut means for restarting fuel injection when the engine rotation-related value decreases to a predetermined return rotation value; and the first predetermined value before the engine load-related value decreases to the first predetermined value. Target fuel pressure lowering means is provided for reducing the target fuel pressure to a predetermined value corresponding to the return rotation value when the target fuel pressure is reduced to a large second predetermined value.

According to the present invention, when the engine load starts to decrease and the engine load related value becomes smaller than the second predetermined value, the target fuel pressure set by the target fuel pressure setting means is set by the target fuel pressure lowering means. When the engine load is reduced toward a predetermined value corresponding to the return rotation value, and the engine load is further reduced so that the engine load-related value becomes smaller than the first predetermined value, the fuel injection from the fuel injection valve is stopped. It

In this case, the actual fuel pressure detected by the fuel pressure detecting means is controlled to be substantially the same value as the target fuel pressure by the fuel pressure control means for controlling the fuel pump so as to reach the target fuel pressure. When the related value reaches the first predetermined value, that is, when the fuel cut condition is satisfied, the fuel pressure is already in a reduced state, so that it is possible to wait for the fuel pressure to decrease after the fuel cut condition is satisfied. As soon as the fuel cut condition is satisfied, the fuel cut can be surely performed. Of course, the fuel cut can also improve the fuel consumption and the emission.

Further, since the fuel pressure is reduced to a predetermined value corresponding to the return rotation value before the fuel is cut, even if the fuel cut is suddenly ended in a short time and the fuel injection is restarted, Problems such as unstable engine operating conditions and deterioration of emissions due to overrich fuel are suppressed.

The invention according to claim 2 of the present application is
In the invention according to claim 1, when the engine rotation related value is larger than the predetermined value, the target fuel pressure lowering means does not decrease the target fuel pressure even if the engine load related value decreases to the second predetermined value. Characterize.

By the way, in the engine in which the target fuel pressure is set on the basis of the engine rotation related value and the engine load related value, and the target fuel pressure is set to a larger value as the engine rotation speed becomes higher, for example, the return rotation of fuel cut. When the number is set to a predetermined low value, the difference from the return rotational speed increases as the engine rotational speed increases (when entering the fuel cut region) when the fuel cut condition is satisfied. That is, the higher the engine speed at the start of fuel cut, the greater the difference between the fuel pressure at that time and the fuel pressure corresponding to the return speed, and the fuel pressure when the engine load becomes the second predetermined value. The fuel pressure sharply decreases toward the fuel pressure corresponding to the return rotation value. For example, from the time when the engine load reaches the second predetermined value to the time when the engine load decreases to the first predetermined value. Even if the engine load is increased due to re-depression, the fuel pressure has already dropped significantly and the acceleration performance may be impaired. Therefore, when the engine rotation related value is larger than the predetermined value, the target fuel pressure is not decreased even if the engine load related value is decreased to the second predetermined value, in order to avoid this adverse effect.

Next, the invention according to claim 3 of the present application is, in the invention according to claim 1 or claim 2, provided with an injection amount setting means for setting a fuel injection amount according to an engine operating state. Second fuel cut means for stopping the fuel injection from the fuel injection valve when the fuel injection quantity set by the injection quantity setting means becomes smaller than the minimum injection quantity that can be injected by the fuel injection valve. Is provided.

According to the present invention, since the fuel is not injected more than the fuel injection amount set according to the engine operating state, deterioration of emission due to overrich is prevented. In addition, it is possible to prevent the feeling of deceleration from being deteriorated due to the injection of more fuel than the required fuel.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

As shown in FIG. 1, an engine 1 according to this embodiment includes an intake valve 12, an exhaust valve 13, an ignition plug 14, a fuel injection valve 15 provided in a combustion chamber defined by a piston 11. , An air cleaner 1 provided in the intake pipe 16
7, an air flow meter 18, a throttle valve 19 and a throttle opening sensor 20, an oxygen sensor 22 and a catalyst device 23 provided in the exhaust pipe 21, a water temperature sensor 24 and an engine rotation sensor 25 provided in the engine 1 main body. The engine control unit (ECU) 40 has an intake air amount detected by the air flow meter 18, a throttle opening detected by the throttle opening sensor 20, an engine water temperature detected by the water temperature sensor 24,
Engine speed detected by the engine speed sensor 25,
Based on the amount of oxygen in the exhaust gas detected by the oxygen sensor 22 and the like, the fuel injection valve 15 and the like are controlled so that an optimal operating condition for the current situation is realized.

Further, the fuel supply system of the engine 1 raises the pressure of the fuel supplied to the fuel tank 26, the low-pressure fuel pump 27 of variable discharge amount immersed in the tank 26, and the fuel injection valve 15. The high-pressure fuel pump 28, a low-pressure discharge line 29 that connects the high-pressure fuel pump 28 and the low-pressure fuel pump 27, a return line 30 that returns the excess fuel from the high-pressure fuel pump 28 to the fuel tank 26, and the low-pressure line. The discharge line 29 and the return line 30 are connected to the pressure regulating valve 31.
High pressure fuel pump 2 and pressure regulating line 32 connected via
Fuel from the relief valve provided in the fuel injection valve 15 only when the pressure in the high-pressure discharge line 33 from 8 to the fuel injection valve 15 and the high-pressure fuel pump 28 abnormally rises due to a failure or the like. Return line 34 as a safety device for returning the fuel to the high pressure fuel pump 28, and the high pressure discharge line 3
And a fuel pressure sensor 35 for detecting the fuel pressure in the fuel cell 3, and is constructed in a returnless fuel supply system. That is, the high pressure side return line 34 is
The fuel is not returned to the fuel tank 26. Further, the fuel pressure does not decrease except for the injection of fuel from the fuel injection valve 15 and the leakage from the seal portion of the injection valve 15 and the high-pressure fuel pump 28.

Here, the high-pressure fuel pump 28 is provided with a relief valve therein, and the high-pressure fuel pump 28 discharges to the high-pressure discharge line 33 by controlling the opening / closing of the relief valve with, for example, an electromagnetic solenoid. The amount of fuel to be supplied is controlled, and thereby the pressure of the fuel in the high pressure discharge line 33 is controlled. The fuel other than the fuel discharged to the high-pressure discharge line 33 is circulated in the high-pressure fuel pump 28 and returned to its inlet side.

The ECU 40 also receives a signal from the fuel pressure sensor 35 and outputs a control signal to the high pressure fuel pump 28.

Next, the contents of control by the ECU 40 will be described. That is, the ECU 40 uses the maps shown in FIGS. 5 and 6 based on the engine speed Ne detected by the engine speed sensor 25 and the throttle opening TVO detected by the throttle opening sensor 20 to determine the target fuel pressure. Po is set, and the high-pressure fuel pump 28 is controlled so that the actual fuel pressure P detected by the fuel pressure sensor 35 becomes the target fuel pressure Po.

Further, as shown in the time chart of FIG. 3, the ECU 40 controls the fuel injection valve 15 when the throttle opening TVO indicating the engine load state decreases and becomes smaller than the first predetermined value TVO1. Fuel injection is stopped, and the engine speed Ne reaches the predetermined return speed value Ner.
Fuel injection is restarted when the temperature decreases to a second predetermined value TVO2, which is larger than the first predetermined value TVO1 before the throttle opening TVO decreases to the first predetermined value TVO1. From then on, the target fuel pressure Po is reduced toward a predetermined value X (see FIG. 5) corresponding to the return rotation value Ner.

In that case, the ECU 40 determines that the fuel pressure sensor 3
Since the high pressure fuel pump 28 is controlled so that the actual fuel pressure P detected at 5 becomes the target fuel pressure Po, when the throttle opening TVO becomes the first predetermined value TVO1, that is, the fuel cut condition is satisfied. When the fuel cut condition is satisfied, the actual fuel pressure P has already dropped to approximately the predetermined value X, so that the actual fuel pressure P can be reliably established at the same time as the fuel cut condition is satisfied without waiting for the actual fuel pressure P to decrease after the fuel cut condition is satisfied. Fuel cut can be performed, and, of course, improvement of fuel efficiency and emission by fuel cut can also be achieved.

Further, since the actual fuel pressure P is decreased toward the fuel pressure X corresponding to the fuel injection return rotational speed Ner before the fuel is cut, the fuel cut is rapidly ended in a short time and the fuel injection is restarted. Even if it is done, the problem that the engine operating state becomes unstable and the emission deteriorates due to the overrich fuel is suppressed.

In the time chart of FIG. 3, the actual fuel pressure P is the target fuel pressure P even after the fuel cut at the time t3.
It is slightly higher than o because the fuel injection at the fuel injection valve 15 is stopped at the time t3 and the high pressure fuel pump 28
This is due to the fact that the fuel is retained in the high pressure discharge line 33 due to the stop of the fuel discharge from. It should be noted that this time chart is an example, and the actual fuel pressure P is reduced to a value substantially equal to the target fuel pressure Po by increasing the gradient of decrease in the fuel pressure at the portion indicated by arrow D in the fuel pressure map A of FIG. 5, for example. It is possible to

Further, the ECU 40 controls the fuel injection amount by controlling the injection pulse width corresponding to the opening time of the fuel injection valve 15. According to this control, when the fuel pressure has the same value, the fuel injection amount increases as the injection pulse width increases, and when the injection pulse width has the same value, the fuel injection amount increases as the fuel pressure increases. To do.

Hereinafter, this control will be described in more detail with reference to the flowchart of FIG. 2 and the time chart of FIG.

First, in step S1, the current operating state of the vehicle, specifically, the engine speed Ne as an engine speed related value is detected by the engine speed sensor 25, and at the same time,
Throttle opening TVO as a load-related value is detected by throttle opening sensor 20, and these detected values are input.

Next, at step S2, the engine speed Ne and the throttle opening T are calculated from the map A shown in FIG.
The value corresponding to VO is read and this value is set as the target fuel pressure Po.

The data set in the map A shown in FIG. 5 and the map B to be described later is 100 rpm of the engine speed.
The data is divided every 0 rotations, and the data to which the detected value belongs may be used as it is, or the value calculated by interpolation including the data adjacent to the detected value may be used. Further, these data may be set by further dividing the number of revolutions.

Next, in step S3, the current pressure P of the fuel in the high pressure discharge line 33 is detected by the fuel pressure sensor 35 and input.

Next, at step S4, it is judged if the operating condition of the vehicle is in the fuel cut region or not depending on whether the throttle opening TVO detected at step S1 becomes smaller than a predetermined value TV01.

Here, the target fuel pressure Po is the map A in FIG.
As shown in, the engine speed indicated by the chain line A is 2000
The line of rotation is set as a boundary and the tendency is different. Here, a region where the rotation speed is lower than this rotation speed is set as a low rotation speed region, and a region where the rotation speed is higher than this rotation speed is set as a high rotation speed region.

In this case, when in the high rotation range,
The target fuel pressure Po is set so as to increase substantially proportionally as the engine speed Ne increases, and the fuel pressure gradient in the load direction is prevented from occurring as indicated by arrow C, so that re-acceleration and This prevents the fuel pressure from going up and down due to shift change and deteriorating the combustibility.

On the other hand, in the low rotation speed region, as the throttle opening TVO becomes smaller as indicated by arrow D,
The target fuel pressure Po is also gradually decreased in the order of “5 → 5 → 5 → 4 → 3” so that the fuel pressure value is set to a fuel pressure value close to the idle operation region. Further, the area indicated by reference numeral a is shown in FIG.
Shows the overlap with the map B for deceleration fuel cut, and the numerical values described in the map A show values when not decelerating, and the map B shows values during fuel cut during decelerating.

That is, in the low rotation speed region, when the throttle opening TVO starts to decrease, there is a high possibility that it will be necessary to perform fuel cut during deceleration after that, so prior to execution of fuel cut, the target fuel pressure Po is set. Is reduced to a state in which the actual fuel pressure P is sufficiently reduced when the fuel cut is performed. Thus, the fuel cut can be surely performed at the same time as the fuel cut condition is satisfied without waiting for the fuel pressure to decrease after the fuel cut condition is satisfied.

Next, when it is determined in step S4 that the fuel cut area is not in the fuel cut region, the process proceeds to step S5, the fuel cut delay timer is reset and a predetermined value is set to the timer value, and in step S14, in step S3. Fuel injection is executed under the set fuel pressure condition. Then, after step S15, the feedback control of the fuel pressure at the time of executing the fuel injection is shown. That is, step S15
Then, it is determined whether or not the actual fuel pressure P is larger than the target fuel pressure Po, and when it is larger, the amount of fuel discharged from the high-pressure fuel pump 28 is larger than the amount of fuel injected from the fuel injection valve 15. , In step S16, the high pressure fuel pump 28
The amount of fuel discharged from the high-pressure fuel pump 28 is decreased by increasing the relief amount in the inside, and when the amount is small, the amount of fuel discharged from the high-pressure fuel pump 28 is smaller than the amount of fuel injected from the fuel injection valve 15. Because it is small, step S1
In step 7, the relief amount in the high-pressure fuel pump 28 is reduced to increase the amount of fuel discharged from the high-pressure fuel pump 28, thereby maintaining the actual fuel pressure P at substantially the target fuel pressure Po.

On the other hand, when it is determined in step S4 that the fuel cut region is in the fuel cut region, the process proceeds to step S6, the countdown of the fuel cut delay timer is started, and the timer value T is set to (T-1).

Next, in step S7, the engine speed N is calculated from the map B for the deceleration fuel cut region shown in FIG.
The value corresponding to e and the throttle opening TVO is read, and this value is reset as the target fuel pressure Po. Here, since the fuel is not injected during the fuel cut, it is possible to reduce the fuel pressure to zero, but if the fuel pressure is reduced to zero, there will be a delay in raising the fuel pressure to the required value again. is there. Therefore, in the map B of this embodiment, the target fuel pressure Po is set to a minimum value that can be immediately raised to the required fuel pressure when returning from the fuel cut.

Next, in step S8, it is determined whether or not the injection pulse width is larger than a predetermined value, that is, the target fuel pressure Po set in the fuel pressure map B and the minimum injection pulse width that can be mechanically achieved. It is determined whether or not the minimum injection amount of the fuel injection valve determined from is larger than the injection amount calculated from the engine operating state.
Even if the delay timer does not become 0 at 0, the fuel injection is stopped, that is, the fuel cut is executed, and step S
At 11, the relief valve of the high-pressure fuel pump 28 is fully opened to prevent the fuel from being discharged, and the discharge amount of fuel from the high-pressure fuel pump 28 to the high-pressure discharge line 33 is set to zero.

According to this, since the fuel is not injected more than the fuel injection amount set according to the engine operating state, deterioration of emission due to overrich is prevented. In addition, it is possible to prevent the feeling of deceleration from being deteriorated due to the injection of more fuel than the required fuel.

On the other hand, in step S8, the injection pulse width is
If it is determined that the value is larger than the predetermined value, step S9.
Then, it is determined whether or not the engine speed is greater than a predetermined value Ne1 (2000 rotations in this embodiment), and when it is not large, that is, in the low rotation range, even if the delay timer does not become 0, Step S1 described above
0, the process of step S11 is performed.

Here, the change of the target fuel pressure Po, the actual fuel pressure P, etc. when the fuel is cut based on the flow chart of FIG. 2 in the low rotation speed region will be described with reference to the time chart of FIG. explain. In this time chart, the engine speed Ne is equal to or lower than the predetermined speed Ne1,
An example is shown under the condition that the ejection pulse width is equal to or larger than a predetermined value.

First, at time t1, the throttle opening TVO starts to decrease due to the driver's accelerator operation or the like.
When the value decreases to the predetermined value TVO2 at 2, the target fuel pressure Po starts to decrease from time t2 as indicated by the arrow A in the map A, and the actual fuel pressure P decreases to follow this. Then, when the throttle opening TVO further decreases to a predetermined value TVO1 at time t3, it is determined in the fuel cut region determination in step S4 that the fuel cut condition is satisfied, and the injection pulse width is equal to or more than the predetermined value. Since the engine speed Ne is less than or equal to the predetermined speed Ne1, even if the delay timer is not 0, immediately at this time t3,
In step S10, the fuel injection is stopped.

Then, the engine speed Ne decreases due to this fuel cut, and at time t4 the engine return speed N
er is reached, the fuel injection is restarted, but the actual fuel pressure P at this time is the return rotational speed Ner by the time t3.
Since the fuel pressure is almost reduced to the required fuel pressure X, the problem that the engine operating condition becomes unstable and the emission deteriorates due to overrich fuel is suppressed when returning from the fuel cut. It

Next, the control when it is determined in step S9 that the engine speed is higher than the predetermined value Ne1, that is, in the high speed region, will be described. First, in step S12, it is determined whether or not the fuel cut delay timer has timed out. If not, in step S13, it is determined whether the actual fuel pressure P is greater than the fuel cut execution determination fuel pressure Px. . Then, when the actual fuel pressure P is higher, it is not the timing of fuel cut yet, so in step S14, fuel injection is executed,
When it is smaller, it is determined that the fuel cut timing has been reached, and the processing at the time of fuel cut in steps S10 and S11 described above is performed.

Here, the fuel cut execution determination fuel pressure Px
Is set to a value slightly higher than the target fuel pressure Po by adding a predetermined value α to the target fuel pressure Po at this time. In addition,
The predetermined value α is, for example, a value of about 0.3 MPa.

On the other hand, when it is determined in step S12 that the fuel cut delay timer has timed out, even if the actual fuel pressure P is not sufficiently reduced, in step S10 the fuel injection is forcibly stopped. To achieve the effects of fuel cuts such as improving fuel efficiency.

Here, changes in the target fuel pressure Po, the actual fuel pressure P, etc. when the fuel is cut based on the flow chart of FIG. 2 in this high rotation speed region will be described with reference to the time chart of FIG. explain. It should be noted that this time chart shows that the injection pulse width is equal to or larger than a predetermined value and the engine speed N
An example is shown under the condition that the actual fuel pressure P is reduced to the fuel cut execution determination fuel pressure Px before e is equal to or greater than the predetermined rotation speed Ne1 and the timer is not counted up.

First, at time t1, the throttle opening TVO starts to decrease due to the driver's accelerator operation or the like.
Even if the engine speed Ne is reduced to a predetermined value TVO2, the target fuel pressure P is different from that when the engine speed Ne is in the low speed region.
At time t3, the throttle opening TV is not decreased.
Only when it is determined that O has decreased to the predetermined value TVO1 and is in the fuel cut region, the target fuel pressure Po is reduced at once by the map B for fuel cut during deceleration.

However, the actual fuel pressure P is the target fuel pressure P
Since it does not immediately respond to a change in o, the fuel cut is performed after the actual fuel pressure P has dropped to the fuel cut execution determination fuel pressure Px. In this case, the actual fuel pressure P decreases to the fuel cut execution determination fuel pressure Px at time t3 ', and the fuel injection is stopped.

Then, the engine speed Ne decreases due to this fuel cut, and at time t4 the engine return speed N
The fuel injection is restarted when er is reached, but the actual fuel pressure P at this time is the return rotational speed Ne by the time t3 '.
Since the fuel pressure has almost dropped from r to the required fuel pressure X,
When returning from fuel cut, problems such as unstable engine operating conditions and deterioration of emissions due to overrich fuel are suppressed.

Now, the reason why the target fuel pressure Po is not reduced even when the throttle opening TVO is reduced to the predetermined value TVO1 in the high rotation speed region will be described. For example,
Like the engine of this embodiment, the engine speed Ne
In an engine in which the target fuel pressure Po is set to a larger value as the fuel consumption is increased, for example, if the fuel cut return rotational speed Ner is set to a predetermined low value,
The higher the engine speed Ne when the fuel cut condition is satisfied (when entering the fuel cut region), the greater the difference from the return speed Ner. That is, as the engine speed Ne at the time of fuel cut is higher, the difference between the actual fuel pressure P and the fuel pressure X corresponding to the return rotation value Ner at that time is larger, so the actual fuel pressure P is the second throttle opening TVO. From the fuel pressure when the predetermined value TVO2 of
The fuel pressure X rapidly decreases toward the fuel pressure X corresponding to er. In this case, for example, when the accelerator pedal is stepped on again and the engine load increases from the time when it reaches the second predetermined value TVO2 to the time when it decreases to the first predetermined value TVO1, the fuel cut condition is not satisfied. Even in such a case, the actual fuel pressure P has already dropped significantly and there is a risk that the acceleration performance will be hindered. Therefore, when the engine speed Ne is higher than the predetermined speed Ne1, in order to avoid this adverse effect, the target fuel pressure Po is not decreased even if the throttle opening TVO is decreased to the second predetermined value TVO2. .

By the way, while the fuel cut is being executed in steps S10 and S11, even if the engine speed Ne is increased and the target fuel pressure Po is increased by going down a slope, for example, the engine speed is lowered again and the engine speed is lowered. And the target fuel pressure P
Since it is considered that o decreases, the fuel pressure boosting control is not performed in order to prevent deterioration of emission and the like.

In the above embodiment, when the engine speed Ne is in the high speed range, the actual fuel pressure P after the fuel cut condition is satisfied is the fuel cut execution determination fuel pressure P.
Although the actual fuel cut is performed when x is reached, the fuel cut may be performed when the throttle opening is reduced to the predetermined value TVO2.

Further, in the above embodiment, the boundary value between the high speed region and the low speed region of the engine speed is 2000 revolutions, but the boundary value is not limited to this value, and the necessary conditions can be appropriately set. It may be set accordingly.

[0060]

As described above, according to the present invention, in the fuel supply device constituted by the returnless fuel supply system, the engine load decreases and the engine load related value becomes smaller than the first predetermined value. Fuel cut means for stopping the fuel injection from the fuel injection valve when the engine load is low, and restarting the fuel injection when the engine rotation related value drops to a predetermined return rotation value, and the engine load is the first predetermined value. Target fuel pressure lowering means for lowering the target fuel pressure to a predetermined value corresponding to the return rotation value from the time when the target fuel pressure is decreased to the second predetermined value which is larger than the first predetermined value before being decreased to the value. By providing the fuel, fuel cut can be surely performed even in the case of sudden deceleration, and the fuel pressure can be surely reduced to the fuel pressure corresponding to the fuel injection return speed by the time of fuel injection return. It is possible.

[Brief description of drawings]

FIG. 1 is a control system diagram of an engine according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a specific example of fuel injection control.

FIG. 3 is a time chart showing a specific example of fuel pressure control when the engine speed is in a low speed range.

FIG. 4 is a time chart showing a specific example of fuel pressure control when in the same high speed region.

FIG. 5 is a map used when setting a target fuel pressure during normal times.

FIG. 6 is a map used when setting a target fuel pressure at the time of deceleration fuel cut.

[Explanation of symbols]

1 Engine 15 Fuel Injection Valve 20 Throttle Valve Opening Sensor (Engine Load Related Value Detecting Means) 25 Engine Rotation Sensor (Engine Rotation Related Value Detecting Means) 28 High Pressure Fuel Pump (Fuel Pump) 29 Low Pressure Discharge Line 30 Return Line 31 Pressure Regulator 32 pressure control line 33 high pressure discharge line (fuel supply pipe) 34 return line 35 fuel pressure sensor (fuel pressure detection means) 40 ECU (target fuel pressure setting means, fuel pressure control means, fuel cut means, target fuel pressure reduction means, second fuel cut means)

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiromi Yoshioka             3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda             Within the corporation (72) Inventor Noboru Nakamura             3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda             Within the corporation F term (reference) 3G066 AA02 AB02 BA23 CB15 CE13                       DA02 DA06 DB07 DB17 DC09                       DC11 DC14 DC18 DC24                 3G301 HA01 HA04 JA03 JA21 JA28                       KA16 KA17 KA27 LB06 LB07                       LC06 MA24 MA25 NE06 NE19                       PA01Z PA11Z PB08A PD02Z                       PE01Z PE08Z

Claims (3)

[Claims] 1. A fuel for an engine having a fuel supply system in which a fuel supply pipe is provided between the fuel pump and the fuel injection valve, and a recovery pipe for returning excess fuel from the fuel injection valve to the fuel tank is not provided. A fuel supply pressure detecting means for detecting an actual fuel pressure in the fuel supply pipe, an engine load related value detecting means for detecting a value related to an engine load, and an engine rotation detecting a value for an engine rotation. Related value detection means, target fuel pressure setting means for setting a target fuel pressure based on the engine rotation related value and engine load related value, and the actual fuel pressure detected by the fuel pressure detection means is set by the target fuel pressure setting means. And a fuel pressure control means for controlling the fuel pump so that the target fuel pressure is controlled so that the engine load decreases and the engine load related value is smaller than the first predetermined value. Fuel cut means for stopping fuel injection from the fuel injection valve when the temperature becomes low, and restarting fuel injection when the engine rotation related value drops to a predetermined return rotation value in that state, and engine load related Since the target fuel pressure has decreased to the second predetermined value that is larger than the first predetermined value before the value has decreased to the first predetermined value, the target fuel pressure is changed to the predetermined value corresponding to the return rotation value. And a target fuel pressure lowering means for lowering the target fuel pressure. 2. When the engine rotation related value is larger than a predetermined value, the target fuel pressure lowering means does not lower the target fuel pressure even if the engine load related value is reduced to the second predetermined value. Item 2. The engine fuel supply device according to item 1. 3. An injection amount setting means for setting a fuel injection amount according to an engine operating state is provided, and the fuel injection amount set by the injection amount setting means is a minimum value that a fuel injection valve can inject. The fuel supply device for an engine according to claim 1 or 2, further comprising: second fuel cut means for stopping injection of fuel from the fuel injection valve when the injection amount becomes smaller than the injection amount. .