JP2845005B2 - Fuel pump control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a fuel pump for pumping fuel to, for example, an automobile engine.

[0002]

2. Description of the Related Art In the fuel system of a gasoline engine,
A fuel tank storing fuel and a carburetor or a fuel injection valve for supplying fuel to the engine are connected by a fuel supply passage, and a fuel pump is interposed in the passage. Then, the fuel in the fuel tank is sucked and discharged by the fuel pump and is pressure-fed to a fuel injection valve or the like.

Conventionally, a general fuel pump is always driven in a constant state so as to cope with a fuel injection amount when the engine is under a high load, and an amount of fuel corresponding to the fuel injection amount is constantly discharged. That is, in FIG.
As shown by 1, a fixed amount of fuel is discharged from the fuel pump regardless of the magnitude of the engine load.

However, the amount of fuel actually required by the engine is proportional to the magnitude of the engine load. Therefore, in a low load operation state or the like, the same amount of fuel as in a high load state is discharged from the fuel pump even though the required amount of fuel in the engine is extremely small. The excessively discharged fuel is returned to the fuel tank through the return pipe, but the return fuel is heated by the heat from the engine, and the temperature of the returned fuel is increased. Cause.

Therefore, various techniques for reducing the amount of return fuel have been considered. For example, Japanese Patent Laying-Open No. 58-48767 discloses a technique for detecting a load state of an engine and variably controlling the magnitude of a voltage applied to an electric motor of a fuel pump according to the load state. . According to this technique, the discharge amount of the fuel pump can be continuously increased or decreased in accordance with the load state so as to match the required fuel amount.

As shown by a characteristic line L2 in FIG. 5, a plurality (4 in FIG.
A technique has been proposed in which the amount of discharged fuel is set so that a larger amount of fuel than the required amount of fuel is discharged from the fuel pump.

[0007]

However, in the former technique, the following problem occurs when the engine load increases rapidly. That is, in this technique, the magnitude of the voltage applied to the electric motor is controlled in accordance with the magnitude of the engine load, so that the responsiveness of the fuel pump itself is sufficiently high. However, a fuel pipe or a delivery pipe is interposed between the fuel pump and the fuel injection valve or the carburetor.
The effect of these volumes causes a delay in the response of the fuel supply. At this time, since only the required amount of fuel corresponding to the engine load is discharged from the fuel pump, if the response delay occurs as described above, the fuel pressure temporarily decreases,
The amount of fuel supplied to the engine decreases and the air-fuel ratio becomes lean.

Further, in the latter technique, as described above, a larger amount of fuel is discharged than the required amount of fuel, so that excess fuel supply is increased as compared with the former technique. The present invention has been made in view of the above-described circumstances, and has as its object the purpose of a fuel pump that can reduce the amount of return fuel and can prevent a decrease in fuel pressure even when the load suddenly increases. It is to provide a control device.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is used for a fuel pump for sucking and discharging fuel from a fuel tank and supplying the fuel to an internal combustion engine. A fuel pump control device for continuously increasing or decreasing the amount of fuel discharged from the fuel pump, comprising: a rotation speed detection means for detecting a rotation speed of the internal combustion engine; and a rotation speed detected by the rotation speed detection means. A discharge fuel amount calculating means for calculating a discharge fuel amount of the fuel pump necessary at the time of full load of the internal combustion engine, and a fuel having substantially the same amount as the discharge fuel amount calculated by the discharge fuel amount calculation means. Control means for controlling the driving of the fuel pump to discharge the fuel.

[0010]

When the internal combustion engine is operating, the rotation speed of the internal combustion engine is detected by the rotation speed detecting means. The discharge fuel amount calculation means calculates a discharge fuel amount of the fuel pump required at the full load of the internal combustion engine at the rotation speed detected by the rotation speed detection means. Then, the control means controls the drive of the fuel pump, and causes the fuel pump to discharge substantially the same amount of fuel as the discharge fuel amount calculated by the discharge fuel amount calculation means.
That is, under a constant load condition of full load, a discharge fuel amount according to the rotation speed of the internal combustion engine is set, and the discharge fuel amount of the fuel pump is variably controlled according to the rotation speed. Therefore, it is possible to cope with an increase in fuel supply when the load suddenly increases while minimizing the fuel return amount.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will now be described with reference to FIGS.
This will be described with reference to FIG. As shown in FIG. 1, a cylinder block 2 of an automobile engine 1 as an internal combustion engine includes:
A plurality of cylinders 3 are arranged side by side in a direction perpendicular to the paper surface. A piston 4 is accommodated in each cylinder 3 so as to be vertically movable. Each piston 4 is connected to a crankshaft (not shown) via a connecting rod 5. A combustion chamber 6 is formed above the piston 4, and an intake passage 7 and an exhaust passage 8 communicate with each combustion chamber 6.
The communicating portion between the combustion chamber 6 and the intake passage 7 is an intake port 9, and the communicating portion between the combustion chamber 6 and the exhaust passage 8 is an exhaust port 10. The cylinder head 11 of the engine 1 has an intake valve 12 and an exhaust valve 1 for each cylinder 3.
3 are provided to open and close the intake port 9 and the exhaust port 10.

In the intake passage 7, a surge tank 14 and an air cleaner 15 are arranged in this order from the intake port 9 to the upstream side, and the air filtered by the air cleaner 15 flows through the intake passage 7, as indicated by the arrow. The gas passes through the surge tank 14 and the like and is sucked into each of the combustion chambers 6. The surge tank 14 is for smoothing the pulsation of the intake air. A throttle valve 25 is provided in the intake passage 7 upstream of the surge tank 14. The throttle valve 25 opens and closes in conjunction with the depression operation of the accelerator pedal, and the amount of intake air introduced into the combustion chamber 6 is adjusted by the opening and closing operation.

A fuel injection valve 16 for injecting fuel toward the intake port 9 is provided for each cylinder 3 in the intake passage 7 near each intake port 9. The fuel in the fuel tank 17 is supplied to each fuel injection valve 16 by the fuel pipe 1.
9 and the delivery pipe 20. In the middle of the fuel pipe 19, a fuel pump 21 and a fuel filter 22
And is interposed. The fuel pump 21 is an electric motor 21
The fuel in the fuel tank 17 is sucked and discharged by the driving of the electric motor 21a.

The fuel discharged from the fuel pump 21 is pumped to a delivery pipe 20 through a fuel filter 22 and a fuel pipe 19. The pumped fuel is distributed to each fuel injection valve 16 by a delivery pipe 20. The amount of fuel discharged from the fuel pump 21 changes according to the magnitude of the control voltage Vp applied to the electric motor 21a. In the present embodiment, the discharge fuel amount is increased as the control voltage Vp increases, and the discharge fuel amount is set to be maximum when the control voltage Vp is 12V.

A return pipe 23 branches from the delivery pipe 20 and is connected to the fuel tank 17. In the middle of the return pipe 23, a pressure regulator 24
Is interposed. The pressure regulator 24 adjusts the pressure of the fuel (hereinafter simply referred to as fuel pressure) to be pumped to each fuel injection valve 16 by a fixed pressure higher than the pressure of the intake air in the intake pipe (intake port 9). To return the surplus fuel (return fuel) to the fuel tank 17 through the return pipe 23.

The mixture of fuel injected from each fuel injection valve 16 and outside air introduced into the intake passage 7 is:
When the intake valve 12 is opened, it is introduced into each combustion chamber 6 through the intake port 9. In order to ignite the air-fuel mixture introduced into the combustion chamber 6, an ignition plug (not shown) is attached to the cylinder head 11 for each cylinder 3. Then, the air-fuel mixture introduced into each combustion chamber 6 is exploded and burned by the ignition of the spark plug, and the driving force of the engine 1 is obtained via the piston 4, the connecting rod 5, the crankshaft and the like. When the exhaust valve 13 is opened, the combustion gas generated in the combustion chamber 6 is discharged to the exhaust port 10.
Is discharged to the outside through the exhaust passage 8.

In this embodiment, an electronic control unit (hereinafter referred to as "ECU") 26 for controlling the driving of the fuel pump 21 to adjust the amount of discharged fuel is provided. This ECU 26 constitutes a discharge fuel amount calculation means and a control means. The input side of the ECU 26 is electrically connected to a rotation speed sensor 27 as rotation speed detecting means for detecting the engine speed NE. Also, the ECU 26
The electric motor 21a of the fuel pump 21 is electrically connected to the output side of the fuel pump 21 via a fuel pump controller 28. Then, the ECU 26 outputs a command signal based on the detection signal from the rotation speed sensor 27. Based on this command signal, the fuel pump controller 28 outputs a signal for driving the fuel pump 21. as a result,
The magnitude of the control voltage Vp applied to the electric motor 21a of the fuel pump 21 is adjusted, and the discharge fuel amount of the fuel pump 21 is continuously controlled to increase or decrease.

Further, in this embodiment, a constant-speed traveling device (auto-drive) for keeping the traveling speed of the automobile constant is provided. The constant-speed traveling device includes an actuator 30 and an auto-drive controller (not shown).
And The actuator 30 is connected to the throttle valve 25 via a cable 29, and the opening of the throttle valve 25 is adjusted by driving the actuator 30. The auto-drive controller detects the traveling speed of the vehicle, and when in the auto-drive mode, controls the actuator 30 so that the actual traveling speed becomes the target traveling speed.

Next, the operation and effect of the embodiment constructed as described above will be described. The flowchart of FIG. 2 shows a routine for controlling the driving of the fuel pump 21 among the processes executed by the ECU 26.

When shifting to this routine, the ECU 26 first determines in step 101 whether the fuel pump control execution condition is satisfied. The execution conditions in this determination are satisfied, for example, when a predetermined time has elapsed after the engine is started or when the cooling water temperature of the engine 1 is equal to or lower than the predetermined temperature. If this execution condition is not satisfied, the ECU 26 proceeds to step 1
At 02, the control voltage Vp applied to the electric motor 21a of the fuel pump 21 is set to a constant value (12 V). Then, in step 103, the ECU 26 outputs a command signal for driving the fuel pump 21 with the control voltage Vp to the fuel pump controller 28, and ends this routine. Then, the control voltage Vp to the fuel pump 21 is adjusted by the fuel pump controller 28, and as a result, the fuel of the maximum discharge fuel amount is discharged from the fuel pump 21.

If the fuel pump control execution condition is satisfied in step 101, the ECU 26 executes step 1
At 04, the current engine speed NE and the fuel injection amount TAU by the speed sensor 27 are fetched. This fuel injection amount TAU is calculated based on the intake air amount or the like in another routine process.

Subsequently, the ECU 26 proceeds to step 105 and determines whether or not the auto drive operation is being performed. During the normal operation in which the auto-drive operation is not performed, the ECU 26 prepares for a sudden increase in the load.
In step 106, a required fuel amount QFMAX when the engine is fully loaded according to the engine speed NE is calculated. This QFMAX is calculated using the following equation.

QFMAX = TAUMAX · Q1 · (P1 / 2.55) ^1/2 · (N / 2) · NE · 10 ^-6 where TAUMAX is the fuel injection amount when the engine is fully loaded, and Q1 is the fuel injection valve. Flow rate of fuel injected from 16;
P1 is the fuel pressure, N is the number of cylinders, and the required fuel amount QFMAX when the engine is fully loaded is shown by a characteristic line A1 in FIG.

Next, at step 107, the ECU 26 adds the return fuel amount α for normal operation to the required fuel amount QFMAX at step 106, and sets the addition result (= QFMAX + α) as the set discharge fuel amount QFB. .
This set discharge fuel amount QFB is shown by a characteristic line A2 in FIG.

Then, in step 108, the ECU 26 calculates a control voltage Vp applied to the electric motor 21a of the fuel pump 21, which is necessary for setting the amount of fuel discharged from the fuel pump 21 to the set amount of discharged fuel QFB. . This calculation is performed using, for example, a map in which the control voltage Vp for the set discharge fuel amount QFB is defined in advance. The calculated control voltage Vp is a value lower than the control voltage (= 12 V) required to obtain the maximum discharge fuel amount. In this way, when the control execution condition of the fuel pump 21 is satisfied and the control voltage Vp when the auto drive operation is not being executed is calculated, the ECU 26 performs the process of step 103 and ends this routine. Then, the fuel of the set discharge fuel amount QFB, which is larger by the return fuel amount α than the required fuel amount QFMAX at the time of full engine load corresponding to the engine speed NE at that time, is discharged from the fuel pump 21.

If it is determined in step 105 that the auto-drive operation is being performed, the ECU 26 determines that the vehicle is in an operating state in which a sudden load change is unlikely to occur, and the process proceeds to step 109. The required fuel amount QF according to the number NE and the fuel injection amount TAU is calculated. This required fuel amount QF is a value lower than the required fuel amount QFMAX at the time of full engine load,
It is calculated using the following equation.

QF = TAU · Q1 · (P1 / 2.55) ^1/2 · (N / 2) · NE · 10 ⁻⁶ Here, TAU is a fuel injection amount, and Q1, P1, and N are the aforementioned values. Same as in the formula. The required fuel amount QF is indicated by a characteristic line A3 in FIG.

Next, at step 110, the ECU 26 adds the return fuel amount β for the auto-drive operation to the required fuel amount QF at step 109, and calculates the addition result (= QF + β) as the set discharge fuel amount QFB. I do. This set discharge fuel amount QFB is shown by a characteristic line A4 in FIG. After calculating the set discharge fuel amount QFB, the ECU 26 calculates the control voltage Vp in step 108. This control voltage Vp has a lower value than the control voltage Vp when the engine is fully loaded. As described above, the fuel pump 21
When the control voltage Vp when the control execution condition is satisfied and the auto-drive operation is being executed is calculated, the ECU 2
6 performs the processing of step 103 and terminates this routine. Then, the fuel pump 21 discharges a smaller amount of fuel than the set discharge fuel amount QFB during normal operation described above.

The reason why the set discharge fuel amount is set lower during the execution of the auto-drive operation than during the normal operation is as follows. During the auto-drive operation using the constant-speed traveling device, the actual traveling speed of the automobile becomes constant after reaching the target vehicle speed, and it is difficult for a sudden engine load fluctuation to occur. Therefore, during the auto-drive operation, even if the control voltage Vp to the fuel pump 21 is lower than during the normal operation, a problem such as a decrease in the fuel pressure does not occur.

In step 107, the required fuel amount QFM
AX is added to return fuel amount α to set discharge fuel amount QF
The reason why the value B is set or the return fuel amount β is added to the required fuel amount QF in step 110 to obtain the set discharge fuel amount QFB is as follows. If the return fuel amounts α and β are not added, the amount of fuel corresponding to the required fuel amounts QFMAX and QF will be discharged at full load, and the actual return fuel will be lost. Then, the pressure regulator 24 cannot control the fuel pressure. Therefore, a certain amount of return fuel is required, and as described above, the set discharge fuel amount QF
B includes the return fuel amounts α and β.

As described above, in this embodiment, the rotation speed sensor 2
7, the engine speed NE is detected, and the required fuel amount QF when the engine is fully loaded at the engine speed NE.
MAX is calculated (step 106), and the required fuel amount Q
The drive of the fuel pump 21 is controlled so as to discharge the same amount of fuel as FMAX (the set discharge fuel amount QFB in step 107) (steps 108 and 103).
That is, in the present embodiment, during normal operation except for the auto-drive operation, in order to cope with a sudden increase in the engine load, the discharge fuel amount according to the engine speed NE is set under a constant load condition of full load. Then, the amount of fuel discharged from the fuel pump 21 is variably controlled according to the engine speed NE.

For this reason, in the prior art in which the applied voltage is variably controlled in accordance with the load state of the engine, the engine load suddenly increases at timing t1 and the pressure in the intake pipe decreases as shown by the broken line in FIG. When the fuel pipe 1
9 and the volume of the delivery pipe 20, the fuel pressure in the delivery pipe 20 rises with a delay and the total fuel pressure temporarily drops, whereas in the present embodiment, the amount based on the amount required at full load is used. Since the fuel is always discharged, this fuel discharge causes the fuel pipe 19 as described above.
And the response delay caused by the volume of the delivery pipe 20 can be absorbed. Therefore, in this embodiment, as shown by the solid line in FIG. 3, the fuel pressure in the delivery pipe 20 can be instantaneously increased, and the total fuel pressure can be maintained at a predetermined pressure.
Therefore, it is possible to prevent the fuel supply amount to each of the fuel injection valves 16 from being reduced due to the decrease in the fuel pressure, and to prevent unnecessary leaning of the air-fuel ratio.

The total fuel pressure in FIG. 3 is adjusted by the pressure regulator 24 so that the fuel pressure adjusted by the pressure regulator 24, that is, the fuel pressure acting on the fuel injection valve 16 becomes higher than the pressure in the intake pipe by a constant pressure. Fuel pressure.

Further, in this embodiment, the fuel pump 21 is not required to discharge the required fuel amount at the full load for each engine speed NE, instead of discharging the required fuel amount from the fuel pump 21 at the full engine load over the entire speed range. A discharge fuel amount (required fuel amount QFMAX) is calculated, and a predetermined fuel amount α is added to the required fuel amount QFMAX to obtain a set discharge fuel amount QFB. For this reason, not only the prior art in which a constant amount of fuel (the characteristic line L1 in FIG. 5) required at the time of full load of the engine is always discharged from the fuel pump, a plurality of discharged fuels according to the magnitude of the engine load. In this embodiment, the fuel is returned from the return pipe 23 to the fuel tank 17 in the present embodiment, as compared with the prior art in which the fuel amount is set and the fuel pump discharges a larger amount of fuel (the characteristic line L2 in FIG. 5) than the required fuel amount. The amount of returned fuel can be reduced.

Further, in this embodiment, the fuel pump 2 is used during the auto drive operation in which the engine load does not fluctuate greatly.
The control voltage Vp applied to the first electric motor 21a was lower than the control voltage Vp other than during the auto-drive operation. For this reason, the amount of return fuel can be further reduced during the auto-drive operation. Therefore, the amount of fuel evaporated in the fuel tank 17 due to the return fuel can be reduced.

The present invention is not limited to the configuration of the above embodiment, and may be arbitrarily changed without departing from the spirit of the present invention, for example, as follows. (1) In the above embodiment, the required fuel amount Q at the time of full load of the engine
The formula was used to calculate FMAX, but instead of this,
A map that defines the relationship between the engine speed NE and the required fuel amount QFMAX may be used. (2) In the above embodiment, the equation was used to calculate the required fuel amount QF, but instead, a map defining the relationship between the engine speed NE, the fuel injection amount TAU, and the required fuel amount QF may be used. Good. (3) The present invention is applicable to a fuel pump 21 of a type incorporated in the fuel tank 17 and a fuel pump 21 of a type installed separately from the fuel tank 17.

[0037]

As described above in detail, according to the present invention, the number of revolutions of the internal combustion engine is detected, and the required amount of fuel discharged from the fuel pump when the internal combustion engine is fully loaded at the number of revolutions is calculated. Since approximately the same amount of fuel as the discharged fuel is discharged from the fuel pump, the return fuel amount can be reduced, and even if the load increases rapidly, the fuel pressure can be prevented from lowering. It has an excellent effect.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a control device of a fuel pump according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an operation of one embodiment.

FIG. 3 is a graph showing a relationship among a pressure in an intake pipe, a fuel pressure in a delivery pipe, and a total fuel pressure in one embodiment.

FIG. 4 is a diagram showing a relationship between an engine speed and a set discharge fuel amount in one embodiment.

FIG. 5 is a graph showing a relationship between an engine load and a discharged fuel amount according to a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine as an internal combustion engine, 17 ... Fuel tank, 2
DESCRIPTION OF SYMBOLS 1 ... Fuel pump, 26 ... ECU which comprises discharge fuel amount calculation means and control means, 27 ... Rotation speed sensor as rotation speed detection means, NE ... Engine rotation speed, QFB ... Set discharge fuel amount, QFMAX ... Engine full load Required fuel amount at the time

Claims (1)

(57) [Claims] 1. A fuel pump for injecting and discharging fuel in a fuel tank and supplying the fuel to an internal combustion engine so as to continuously increase or decrease the amount of fuel discharged from the fuel pump in accordance with the operating state of the internal combustion engine. A control device for a fuel pump, comprising: a rotation speed detection unit configured to detect a rotation speed of the internal combustion engine; and a rotation speed detected by the rotation speed detection unit.
A discharge fuel amount calculation means for calculating a discharge fuel amount of the fuel pump required at a full load of the internal combustion engine; and a fuel pump which discharges substantially the same amount of fuel as the discharge fuel amount calculated by the discharge fuel amount calculation means. Control means for controlling the driving of the fuel pump.