JP2008121563A - Fuel supply device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the fuel economy performance of an engine by suppressing electric power consumption in an electric low pressure fuel pump supplying fuel to an engine-driven high pressure fuel pump. <P>SOLUTION: The low pressure fuel pump is controlled based on a delivery quantity preset for start during the start of the engine. After the start, an engine operation state is discriminated between a steady operation state and a transient operation state. In the steady state operation, a delivery quantity of the low pressure fuel pump is set smaller than that during the start, and in the transient operation, the delivery quantity is set larger than that in the steady state if the operation state is in acceleration, and the delivery quantity is set smaller than that in the steady state if the operation state is in deceleration. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel supply device for an internal combustion engine that includes an engine-driven high-pressure fuel pump and an electric low-pressure fuel pump that supplies fuel to the high-pressure fuel pump.

In Patent Document 1, the fuel discharged from the electric low pressure fuel pump is regulated to a predetermined low pressure value by a low pressure regulator, and the fuel regulated to the predetermined low pressure value is used as the engine driven high pressure fuel pump. A fuel supply device for an internal combustion engine that adjusts the fuel discharged from the high pressure fuel pump to a predetermined high pressure value by a high pressure regulator and supplies the fuel adjusted to the predetermined high pressure value to a fuel injection valve Is disclosed.
Japanese Laid-Open Patent Publication No. 9-236060

By the way, conventionally, the discharge amount of the electric low-pressure fuel pump is controlled to be constant, and excess fuel is returned from the low-pressure regulator into the fuel tank, whereby the pressure of the fuel supplied to the high-pressure fuel pump is reduced to a predetermined low-pressure value. The pressure was adjusted.
For this reason, when the fuel consumption (fuel injection amount) of the engine is small, the amount of fuel returned from the low pressure regulator to the fuel tank increases. This is a fuel that is excessively discharged by the low-pressure fuel pump of this type, and this has been a factor that reduces the fuel efficiency of the engine.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to suppress power consumption in an electric low-pressure fuel pump that supplies fuel to an engine-driven high-pressure fuel pump and improve fuel efficiency performance of the engine. .

Therefore, the invention described in claim 1 is characterized in that the discharge amount of the electric low-pressure fuel pump that supplies fuel to the engine-driven high-pressure fuel pump is changed in accordance with the operating conditions of the internal combustion engine.
According to the above invention, the discharge amount of the electric low-pressure fuel pump is changed in response to the difference in the required minimum discharge amount depending on the operating conditions of the internal combustion engine.
Therefore, since the discharge amount of the electric low-pressure fuel pump becomes excessive with respect to the operating conditions at that time, it is possible to prevent the low-pressure fuel pump from consuming electric power wastefully and improve the fuel efficiency performance of the engine. it can.

The invention according to claim 2 is characterized in that the discharge amount of the low-pressure fuel pump is changed according to whether or not the internal combustion engine is started.
According to the above-described invention, when starting the internal combustion engine (for example, during the cranking and for a predetermined time after cranking), the fuel pressure in the pipe is quickly increased to the steady-state pressure. Needs to be discharged from the low-pressure fuel pump, the discharge amount of the low-pressure fuel pump is set to be larger than after the start.

Therefore, it is possible to reduce the power consumption of the low-pressure fuel pump after the start while ensuring the necessary discharge amount at the start of the internal combustion engine.
The invention according to claim 3 is characterized in that the discharge amount of the low-pressure fuel pump is changed according to whether the internal combustion engine is in a transient operation state or a steady operation state.
According to the above invention, the discharge amount required for the low-pressure fuel pump differs between when the engine is in steady operation and changes at a constant fuel consumption, and when the fuel consumption greatly fluctuates due to transient operation. The discharge amount is changed depending on whether the operation is in the transient operation state or the steady operation state.

Therefore, the amount of fuel supplied to the high-pressure fuel pump during transition is insufficient, preventing the fuel supply pressure / supply amount for the engine from becoming insufficient, and reducing the power consumption of the low-pressure fuel pump during steady operation. Thus, the fuel efficiency of the engine can be improved.
The invention according to claim 4 is characterized in that the discharge amount of the low-pressure fuel pump is changed according to whether the transient operation state of the internal combustion engine is the acceleration operation state or the deceleration operation state.

According to the above invention, the amount of discharge required during acceleration increases at the time of acceleration when the fuel consumption (fuel injection amount) increases and when the fuel consumption (fuel injection amount) decreases and decreases. The transient operation state is further discriminated between acceleration operation and deceleration operation, and the discharge amount of the low-pressure fuel pump is changed according to the discrimination result.
Therefore, it is possible to improve the fuel efficiency by reducing the discharge amount to the minimum necessary amount during deceleration while avoiding the shortage of the discharge amount during acceleration.

Embodiments of the present invention will be described below.
FIG. 1 is a system configuration diagram of a fuel supply device for an internal combustion engine according to an embodiment.
In FIG. 1, a fuel tank 12 for storing fuel to be supplied to a vehicle internal combustion engine 11 is provided, and the fuel in the fuel tank 12 passes through an electric low-pressure fuel pump 13 and an engine-driven high-pressure fuel pump 14. Then, the pressure is fed to the fuel injection valve 15.

The fuel injection valve 15 opens and drives the valve body with electromagnetic force generated by an electromagnetic coil, and injects fuel directly into each combustion chamber of the internal combustion engine 11, for example.
The low pressure fuel pump 13 pumps the fuel sucked from the fuel tank 12 to the high pressure fuel pump 14 via the low pressure fuel pipe 16.
A return pipe 17 for returning the fuel into the fuel tank 12 from the middle of the low-pressure fuel pipe 16 is provided, and a low-pressure regulator 18 for adjusting the fuel pressure in the low-pressure fuel pipe 16 is provided in the middle of the return pipe 17. Provided.

The low pressure regulator 18 opens when the pressure in the low pressure fuel pipe 16 exceeds a predetermined low pressure value, and returns the fuel into the fuel tank 12 via the return pipe 17 so that the fuel pressure in the low pressure fuel pipe 16 is predetermined. Do not exceed the low pressure value.
The high-pressure fuel pump 14 includes a high-pressure pump control solenoid 21, a pilot valve 22, a suction valve 23, a pump chamber 24, and a discharge valve 25.

The suction valve 23 is a one-way valve that controls the supply of the low-pressure fuel sent through the low-pressure fuel pipe 16 into the pump chamber 24, and the high pressure in the pump chamber 24 acts in the valve closing direction so that the pump The fuel pressurized in the chamber 24 is prevented from flowing out to the low pressure fuel pipe 16 side.
The intake valve 23 is forcibly opened by a pilot valve 22 driven by a high-pressure pump control solenoid 21.

In the non-energized state of the solenoid 21, the pilot valve 22 is pushed out by the spring 21a, so that the suction valve 23 is held in the open state. The suction valve 23 is held in the closed state by being pulled toward the solenoid 21 against the urging force.
A plunger 24a is fitted into the pump chamber 24 so as to be reciprocally movable, and the plunger 24a is reciprocated by a pump driving cam provided on the cam shaft of the engine 11.

Here, if the solenoid 21 is energized and the intake valve 23 is kept closed during a predetermined period when the plunger 24a is raised, the fuel in the pump chamber 24 is boosted, and the pump chamber 24 When the internal pressure exceeds a predetermined value, the discharge valve 25, which is a one-way valve, is opened to discharge high-pressure fuel.
The discharge valve 25 is connected to a fuel gallery pipe 32 via a high-pressure fuel pipe 31, and the fuel pressurized to a high pressure by the high-pressure fuel pump 14 is distributed to each fuel injection valve 15 connected to the fuel gallery pipe 32. Supplied.

A relief pipe 33 is provided for connecting the fuel gallery pipe 32 and the low-pressure fuel pipe 16. The relief pipe 33 opens when the fuel pressure in the fuel gallery pipe 32 becomes an abnormally high pressure. A relief valve 34 which is a one-way valve is provided.
A fuel pressure sensor 41 for detecting the fuel pressure in the fuel gallery pipe 32 is provided, and the control unit 51 controls the energization timing of the solenoid 21 so that the fuel pressure detected by the fuel pressure sensor 41 becomes the target fuel pressure. To do.

  The control unit 51 includes a microcomputer, and in addition to the fuel pressure sensor 41, an air flow meter 42 for detecting the intake air amount of the engine 11, a crank angle sensor 43 for detecting the crank angle of the engine 11, and the engine 11 A detection signal from a throttle opening sensor 44 that detects the opening of a throttle valve that adjusts the intake air amount is input, and an ON / OFF signal of a starter switch 45 is input.

Then, the control unit 51 determines the target high fuel pressure on the high pressure side from the engine load detected based on the detection signals of the various sensors, and the fuel pressure detected by the fuel pressure sensor 41 becomes the target high fuel pressure. In addition, the energization timing of the solenoid 21 is feedback-controlled.
Further, the control unit 51 performs feedforward control on the discharge amount of the low-pressure fuel pump 13 as shown in the flowchart of FIG.

In the flowchart of FIG. 2, in step S101, it is determined whether or not a predetermined time has elapsed since the starter switch 45 was switched from on to off.
When a predetermined time has elapsed since the starter switch 45 was switched from on to off, that is, after the start of the engine 11, the routine proceeds to step S102, where the target discharge amount of the low-pressure fuel pump 13 is set. Set a preset value for after starting.

When the energization of the low-pressure fuel pump 13 is duty-controlled and the discharge amount is controlled by the duty (on-duty), for example, 50% is set as the duty corresponding to the target discharge amount after starting.
On the other hand, if the predetermined time has not elapsed since the starter switch 45 is switched from on to off, that is, the starter switch 45 is in an on state or a predetermined time after the starter switch 45 is switched from on to off. When the engine 11 is within, the process proceeds to step S103, where a value preset for starting (> target discharge after start) is set as the target discharge of the low-pressure fuel pump 13.

When the energization of the low-pressure fuel pump 13 is duty-controlled and the discharge amount is controlled by the duty (on duty), for example, 100% is set as the duty corresponding to the target discharge amount at the start.
In step S104, energization of the low-pressure fuel pump 13 is controlled based on the set duty, and the discharge amount of the low-pressure fuel pump 13 is adjusted.

That is, in the low-pressure fuel pump 13, the discharge amount after the start is reduced compared to the time when the engine 11 is started. By setting the maximum discharge amount at the start, the fuel pressure can be quickly increased, while the maximum discharge is After start-up where no amount is required, by reducing the discharge amount, power consumption in the low-pressure fuel pump 13 can be suppressed, and fuel consumption can be improved.
The start time is not limited to the on state of the starter switch 45 or within a predetermined time after the starter switch 45 is switched from on to off. For example, after the starter switch 45 is turned off, the engine temperature is The time until the predetermined temperature is reached can be determined as the start time.

The flowchart of FIG. 3 shows a second embodiment of discharge amount control of the low-pressure fuel pump 13.
In step S201, it is determined whether or not the engine 11 is in a steady operation state by determining whether or not the absolute value of the change amount per unit time of the intake air amount or the throttle opening is equal to or less than a predetermined value. .
It should be noted that the transient operation can be determined from changes in the intake negative pressure, the accelerator opening, the fuel injection amount, etc., instead of the intake air amount and the throttle opening.

If it is determined that the engine 11 is in the steady operation state, the process proceeds to step S202, and a value preset for the steady operation state is set as the target discharge amount of the low-pressure fuel pump 13.
When the energization of the low-pressure fuel pump 13 is duty controlled and the discharge amount is controlled by the duty (on duty), for example, 50% is set as the duty corresponding to the target discharge amount for the steady operation state.

Further, the target discharge amount (duty) for the steady operation state can be variably set based on the engine load / engine speed.
On the other hand, if it is determined in step S201 that the absolute value of the amount of change in intake air amount or throttle opening per unit time exceeds a predetermined value and the engine 11 is in a transient operation state, the process proceeds to step S203.

In step S203, it is determined whether the intake air amount obtained by subtracting the previous value from the latest value or the amount of change in the throttle opening per unit time exceeds the predetermined value, whereby the transient operation is accelerated operation. It is determined whether or not the vehicle is decelerating.
When it is determined that the engine 11 is in the acceleration operation state, the process proceeds to step S204, where the target discharge amount of the low-pressure fuel pump 13 is a value preset for the acceleration operation state (> target discharge for the steady operation state). Amount).

When the energization of the low-pressure fuel pump 13 is duty controlled and the discharge amount is controlled by the duty (on duty), the duty corresponding to the target discharge amount for the acceleration operation state is larger than that for the steady operation. (For example, 100%) is set.
Note that the target discharge amount (duty) for the acceleration operation state can be variably set based on the engine load and the engine rotation speed. In this case, the target discharge amount (duty) corresponding to each operation condition is also possible. Is set to a larger value than in the steady state.

When accelerating, the fuel consumption (fuel injection amount) of the engine 11 increases and changes, so that the fuel pressure may become unstable. Therefore, the discharge amount of the low-pressure fuel pump 13 is increased compared to the steady state.
On the other hand, if it is determined in step S203 that the engine 11 is in the deceleration operation state, the process proceeds to step S205, where the target discharge amount of the low-pressure fuel pump 13 is set to a value preset for the deceleration operation state (<for steady operation state). Target discharge amount).

When the energization of the low-pressure fuel pump 13 is duty-controlled and the discharge amount is controlled by the duty (on-duty), the duty corresponding to the target discharge amount for the deceleration operation state is smaller than that for steady operation (For example, 30 to 40%) is set.
Note that the target discharge amount (duty) for the deceleration operation state can be variably set based on the engine load / engine speed, but in this case also, the target discharge amount (duty) corresponding to each operation condition Is set to a value smaller than that in the steady state.

In step S206, energization of the low-pressure fuel pump 13 is controlled based on the set duty to adjust the discharge amount of the low-pressure fuel pump 13.
At the time of deceleration, the fuel consumption (fuel injection amount) of the engine 11 decreases and changes. Therefore, even if the discharge amount of the low-pressure fuel pump 13 is reduced, the fuel pressure can be secured. 13 is reduced.

Therefore, while ensuring the required discharge amount at the time of acceleration when a large discharge amount is required, the discharge amount is reduced during steady operation relative to acceleration, and further, the discharge amount is reduced during deceleration operation than during steady operation. The power consumption in 13 can be suppressed, and fuel consumption can be improved.
For simplicity, distinguish between steady operation and transient operation, and increase the discharge amount during transient operation compared to during steady operation, while reducing the discharge amount during steady operation while ensuring the necessary discharge amount during acceleration. Thus, power consumption in the low-pressure fuel pump 13 can be suppressed.

The flowchart of FIG. 4 shows a third embodiment of discharge amount control of the low-pressure fuel pump 13.
In step S301, it is determined whether or not a predetermined time has elapsed since the starter switch 45 was switched from on to off.
If the predetermined time has not elapsed since the starter switch 45 is switched from on to off, that is, the starter switch 45 is in an on state or a predetermined time after the starter switch 45 is switched from on to off. When the engine 11 is within, the process proceeds to step S302, where the target discharge amount of the low-pressure fuel pump 13 is set to a value preset for starting.

When the energization of the low-pressure fuel pump 13 is duty-controlled and the discharge amount is controlled by the duty (on duty), for example, 100% is set as the duty corresponding to the target discharge amount at the start.
On the other hand, when the predetermined time has elapsed since the starter switch 45 was switched from on to off, that is, after the engine 11 is started, the process proceeds to step S303.

In step S303, it is determined whether or not the engine 11 is in a steady operation state by determining whether or not the absolute value of the change amount per unit time of the intake air amount or the throttle opening is equal to or less than a predetermined value. .
If it is determined that the engine 11 is in the steady operation state, the process proceeds to step S304, and a value preset in the steady operation state (<target discharge amount at start-up) is set as the target discharge amount of the low-pressure fuel pump 13. To do.

When the energization of the low-pressure fuel pump 13 is duty controlled and the discharge amount is controlled by the duty (on duty), for example, 50% is set as the duty corresponding to the target discharge amount for the steady operation state.
Further, the target discharge amount (duty) for the steady operation state can be variably set based on the engine load / engine speed.

On the other hand, if it is determined in step S303 that the absolute value of the amount of change in the intake air amount or the throttle opening per unit time exceeds a predetermined value and the engine 11 is in a transient operation state, the process proceeds to step S305.
In step S305, the transient operation is accelerated by determining whether or not the intake air amount obtained by subtracting the previous value from the latest value or the amount of change per unit time of the throttle opening exceeds the predetermined value. It is determined whether or not the vehicle is decelerating.

When it is determined that the engine 11 is in the acceleration operation state, the process proceeds to step S306, where the target discharge amount of the low-pressure fuel pump 13 is set to a value preset for the acceleration operation state (> target discharge amount in a steady state). Set.
When the energization of the low-pressure fuel pump 13 is duty controlled and the discharge amount is controlled by the duty (on duty), the duty corresponding to the target discharge amount for the acceleration operation state is larger than that for the steady operation. (For example, 100%) is set.

Note that the target discharge amount (duty) for the acceleration operation state can be variably set based on the engine load and the engine rotation speed. In this case, the target discharge amount (duty) corresponding to each operation condition is also possible. Is set to a larger value than in the steady state.
When accelerating, the fuel consumption (fuel injection amount) of the engine 11 increases and changes, so that the fuel pressure may become unstable. Therefore, the discharge amount of the low-pressure fuel pump 13 is increased compared to the steady state.

On the other hand, if it is determined in step S305 that the engine 11 is in the deceleration operation state, the process proceeds to step S307, where the target discharge amount of the low-pressure fuel pump 13 is set in advance for the deceleration operation state (<the target in the steady state) (Discharge rate) is set.
When the energization of the low-pressure fuel pump 13 is duty-controlled and the discharge amount is controlled by the duty (on-duty), the duty corresponding to the target discharge amount for the deceleration operation state is smaller than that for steady operation (For example, 30 to 40%) is set.

Note that the target discharge amount (duty) for the deceleration operation state can be variably set based on the engine load / engine speed, but in this case also, the target discharge amount (duty) corresponding to each operation condition Is set to a value smaller than that in the steady state.
In step S308, energization of the low-pressure fuel pump 13 is controlled based on the set duty, and the discharge amount of the low-pressure fuel pump 13 is adjusted.

According to the third embodiment, at the time of start-up and acceleration, the discharge amount of the low-pressure fuel pump 13 can be increased to secure the discharge amount necessary for increasing the fuel pressure or necessary for maintaining the fuel pressure. Since the discharge amount is reduced and the discharge amount is reduced during the deceleration operation as compared with the steady operation, the power consumption in the low-pressure fuel pump 13 can be suppressed, and the fuel consumption can be improved.
Next, in the system that detects the fuel pressure in the low-pressure fuel pipe 16 and feedback-controls the discharge amount of the low-pressure fuel pump 13 so that the detected value approaches the target low fuel pressure, An embodiment will be described in which after the start-up, the discharge amount of the low-pressure fuel pump 13 is changed according to the steady state / transition (acceleration / deceleration) to suppress the power consumption in the low-pressure fuel pump 13.

FIG. 5 shows a system that feedback-controls the discharge amount of the low-pressure fuel pump 13 so that the fuel pressure in the low-pressure fuel pipe 16 becomes the target low fuel pressure.
5, the return pipe 17 and the low-pressure regulator 18 are eliminated from the system shown in FIG. 1, and a low-pressure fuel pressure sensor 48 for detecting the fuel pressure in the low-pressure fuel pipe 16 is provided instead.

In the system shown in FIG. 5, the discharge amount of the low-pressure fuel pump 13 is controlled as shown in the flowchart of FIG.
In the flowchart of FIG. 6 showing the fourth embodiment of the discharge amount control, in step S401, it is determined whether or not a predetermined time has elapsed since the starter switch 45 was switched from on to off.

When a predetermined time has elapsed since the starter switch 45 was switched from on to off, that is, after the start of the engine 11, the routine proceeds to step S402, where the target value of the fuel pressure in the low pressure fuel pipe 16 is reached. As the target low fuel pressure, a value (for example, 200 kPa) set in advance for after starting is set.
On the other hand, if the predetermined time has not elapsed since the starter switch 45 is switched from on to off, that is, the starter switch 45 is in an on state or a predetermined time after the starter switch 45 is switched from on to off. When the engine 11 is within, the process proceeds to step S403, where the target low fuel pressure is set to a preset value for starting.

Here, the target low fuel pressure for starting is set higher than the target low fuel pressure for starting, for example, the target low fuel pressure for starting is set to 350 kPa.
In step S404, the duty control duty of the low-pressure fuel pump 13 is calculated based on the deviation between the set target low fuel pressure and the actual fuel pressure detected by the low-pressure fuel pressure sensor 48, and the low-pressure fuel is calculated based on the duty. By controlling the discharge amount of the pump 13, the actual fuel pressure detected by the low-pressure fuel pressure sensor 48 approaches the target low fuel pressure.

Here, the target low fuel pressure after the start is lower than at the start, and the discharge amount of the low-pressure fuel pump 13 is suppressed after the start, and the power consumption in the low-pressure fuel pump 13 is suppressed.
On the other hand, since the discharge amount is increased by setting the target low fuel pressure higher at the start than after the start, the fuel pressure can be raised at an early stage.
The flowchart in FIG. 7 shows a fifth embodiment of the discharge amount control applied to the system that feedback-controls the discharge amount of the low-pressure fuel pump 13.

In step S501, it is determined whether the engine 11 is in a steady operation state by determining whether the absolute value of the amount of change in the intake air amount and the throttle opening per unit time is equal to or less than a predetermined value. .
If it is determined that the engine 11 is in the steady operation state, the process proceeds to step S502, and a value (for example, 200 kPa) set in advance for the steady operation state is set as the target low fuel pressure.

The target low fuel pressure for the steady operation state can be variably set based on the engine load and the engine speed.
On the other hand, when it is determined in step S501 that the absolute value of the amount of change in the intake air amount or the throttle opening per unit time exceeds a predetermined value and the engine 11 is in a transient operation state, the process proceeds to step S503.

In step S503, transient operation is accelerated by determining whether the amount of intake air obtained by subtracting the previous value from the latest value or the amount of change in throttle opening per unit time exceeds the predetermined value. It is determined whether or not the vehicle is decelerating.
When it is determined that the engine 11 is in the acceleration operation state, the process proceeds to step S504, and a value preset for the acceleration operation state that is higher than the target low fuel pressure for the steady operation state is set as the target low fuel pressure. To do.

The target low fuel pressure for the acceleration operation state is set to a value higher than the target low fuel pressure for the steady operation state. For example, the target low fuel pressure for the acceleration operation state is set to 350 kPa.
Note that the target low fuel pressure for the acceleration operation state can be variably set based on the engine load and the engine speed, but in this case, the target low fuel pressure corresponding to each operation condition is higher than that in the steady state. Set to a large value.

At the time of acceleration, the fuel pressure (fuel injection amount) of the engine 11 increases and changes, so that the fuel pressure may become unstable. Therefore, by increasing the target low fuel pressure compared to the steady state, the low pressure fuel The discharge amount of the pump 13 is increased.
On the other hand, if it is determined in step S503 that the engine 11 is in the decelerating operation state, the process proceeds to step S505, where a value preset for the decelerating operation state is set as the target low fuel pressure.

The target low fuel pressure for the deceleration operation state is set to a value lower than the target low fuel pressure for the steady operation state. For example, the target low fuel pressure for the deceleration operation state is set to less than 200 kPa.
The target low fuel pressure for the deceleration operation state can be variably set based on the engine load / engine speed, but in this case, the target low fuel pressure corresponding to each operation condition is higher than that in the steady state. Set to a smaller value.

In step S506, the duty control duty of the low-pressure fuel pump 13 is calculated based on the deviation between the set target low fuel pressure and the actual fuel pressure detected by the low-pressure fuel pressure sensor 48, and the low-pressure fuel is calculated based on the duty. By controlling the discharge amount of the pump 13, the actual fuel pressure detected by the low-pressure fuel pressure sensor 48 approaches the target low fuel pressure.
At the time of deceleration, the fuel consumption (fuel injection amount) of the engine 11 decreases and changes. Therefore, even if the discharge amount of the low-pressure fuel pump 13 is reduced, the fuel pressure can be ensured. To reduce the discharge amount of the low-pressure fuel pump 13.

Therefore, while ensuring the required discharge amount at the time of acceleration where a large discharge amount is required, the discharge amount is reduced during steady operation with respect to acceleration, and further, the discharge amount is reduced during deceleration operation compared to during steady operation. The power consumption in 13 can be suppressed, and fuel consumption can be improved.
In addition, simply distinguishing between steady operation and transient operation, the target low fuel pressure during transient operation is increased compared to during steady operation to increase the discharge amount, while ensuring the necessary discharge amount during acceleration, It is possible to reduce power consumption in the low-pressure fuel pump 13 by reducing the discharge amount during steady operation.

The flowchart of FIG. 8 shows a sixth embodiment of the discharge amount control applied to the system that feedback-controls the discharge amount of the low-pressure fuel pump 13.
In step S601, it is determined whether or not a predetermined time has elapsed since the starter switch 45 was switched from on to off.
If the predetermined time has not elapsed since the starter switch 45 is switched from on to off, that is, the starter switch 45 is in an on state or a predetermined time after the starter switch 45 is switched from on to off. When the engine 11 is within, the process proceeds to step S602, where the target low fuel pressure is set to a preset value (350 kPa) for starting.

On the other hand, when the predetermined time has elapsed since the starter switch 45 was switched from on to off, that is, after the engine 11 is started, the process proceeds to step S603.
In step S603, it is determined whether or not the absolute value of the change amount per unit time of the intake air amount and the throttle opening is equal to or less than a predetermined value, thereby determining whether or not the engine 11 is in a steady operation state. .

If it is determined that the engine 11 is in the steady operation state, the process proceeds to step S604, and a value preset for the steady operation state is set as the target low fuel pressure.
The target low fuel pressure for the steady operation state is set to a value lower than that at the start, for example, 200 kPa.
The target low fuel pressure for the steady operation state can be variably set based on the engine load and the engine speed.

On the other hand, if it is determined in step S603 that the absolute value of the amount of change in the intake air amount or the throttle opening per unit time exceeds a predetermined value and the engine 11 is in a transient operation state, the process proceeds to step S605.
In step S605, transient operation is accelerated by determining whether the amount of intake air obtained by subtracting the previous value from the latest value or the amount of change per unit time of the throttle opening exceeds the predetermined value. It is determined whether or not the vehicle is decelerating.

When it is determined that the engine 11 is in the acceleration operation state, the process proceeds to step S606, and a value preset for the acceleration operation state is set as the target low fuel pressure.
The target low fuel pressure for the acceleration operation state is set to a value higher than the target low fuel pressure for steady state, for example, 350 kPa.
Note that the target low fuel pressure for the acceleration operation state can be variably set based on the engine load and the engine speed, but in this case, the target low fuel pressure corresponding to each operation condition is higher than that in the steady state. Set to a large value.

At the time of acceleration, the fuel consumption of the engine 11 (fuel injection amount) increases and changes, so that the fuel pressure may become unstable. Therefore, the low-pressure fuel pump can be increased by increasing the target low fuel pressure compared to the steady state. 13 is increased.
On the other hand, if it is determined in step S605 that the engine 11 is in the decelerating operation state, the process proceeds to step S607, where a value preset for the decelerating operation state is set as the target low fuel pressure.

The target low fuel pressure for the deceleration operation state is set to a value lower than the target low fuel pressure for steady state (for example, 200 kPa).
The target low fuel pressure for the deceleration operation state can be variably set based on the engine load / engine speed, but in this case, the target low fuel pressure corresponding to each operation condition is higher than that in the steady state. Set to a smaller value.

In step S608, an energization control duty of the low-pressure fuel pump 13 is calculated based on a deviation between the set target low fuel pressure and the actual fuel pressure detected by the low-pressure fuel pressure sensor 48, and the low-pressure fuel pump 13 is calculated based on the duty. Is controlled so that the actual fuel pressure detected by the low-pressure fuel pressure sensor 48 approaches the target low fuel pressure.
According to the sixth embodiment, at the time of start-up and acceleration, the discharge amount of the low-pressure fuel pump 13 can be increased by increasing the target low fuel pressure, and the discharge amount necessary for increasing the fuel pressure or maintaining the fuel pressure can be secured. On the other hand, the target low fuel pressure is lowered to reduce the discharge amount during steady operation after start-up, and further, the target low fuel pressure is lowered to reduce the discharge amount more than during steady operation during deceleration operation. Electricity consumption can be suppressed and fuel consumption can be improved.

Here, technical ideas other than the claims that can be grasped from the above embodiment will be described together with effects.
(A) In the fuel supply device for an internal combustion engine according to claim 2,
A fuel supply device for an internal combustion engine, wherein a start time of a starter switch and a predetermined time after the starter switch is switched from on to off are determined as a start time of the internal combustion engine.

According to the above invention, it is considered that the engine has been started until a predetermined time has elapsed since the starter switch was switched from on to off, and the low-pressure fuel pump discharges before and after the predetermined time has elapsed. The amount is changed.
Therefore, it is possible to maintain the fuel pressure by securing a relatively large discharge amount under the condition that the fuel pressure immediately after the complete explosion of the engine tends to become unstable.
(B) In the fuel supply device for an internal combustion engine according to any one of claims 1 to 4,
A fuel supply apparatus for an internal combustion engine, wherein a discharge amount of the low-pressure fuel pump is changed by changing a control signal of the low-pressure fuel pump to a value set in advance for each operating condition.

According to the above invention, the low-pressure fuel pump is preliminarily determined depending on whether it is at the start or after the start, in a steady operation state, in a transient operation state, in an acceleration operation state, or in a deceleration operation state. The low-pressure fuel pump is controlled by a control signal corresponding to the operating condition at that time.
Therefore, it is possible to easily control the discharge amount to be appropriate for each operating condition, to suppress the power consumption in the low-pressure fuel pump, and to improve the fuel efficiency performance of the engine.
(C) In the fuel supply device for an internal combustion engine according to any one of claims 1 to 4,
A fuel pressure sensor that detects a fuel pressure in a low-pressure fuel pressure system downstream of the low-pressure fuel pump, and feedback-controls the control signal of the low-pressure fuel pump so that the fuel pressure detected by the fuel pressure sensor approaches a target value; ,
A fuel supply apparatus for an internal combustion engine, wherein the discharge amount of the low-pressure fuel pump is changed by changing the target value in accordance with operating conditions.

According to the above invention, the target fuel pressure is changed depending on whether it is at the start or after the start, in a steady operation state or in a transient operation state, in an acceleration operation state or in a deceleration operation state, etc. Then, by controlling the low-pressure fuel pump so that the actual fuel pressure approaches the target fuel pressure, the discharge amount of the low-pressure fuel pump is changed according to the operating conditions.
Therefore, in a system that feedback-controls the discharge amount of the low-pressure fuel pump based on the target fuel pressure, it is possible to suppress power consumption in the low-pressure fuel pump and improve the fuel efficiency performance of the engine.

The system block diagram of the fuel supply apparatus in embodiment which performs feedforward control of the discharge amount of a low pressure fuel pump. The flowchart which shows 1st Embodiment of discharge amount control of a low pressure fuel pump. The flowchart which shows 2nd Embodiment of the discharge amount control of a low pressure fuel pump. The flowchart which shows 3rd Embodiment of the discharge amount control of a low pressure fuel pump. The system block diagram of the fuel supply apparatus in embodiment which performs feedback control of the pressure of a low fuel pressure system. The flowchart which shows 4th Embodiment of discharge amount control of a low pressure fuel pump. The flowchart which shows 5th Embodiment of the discharge amount control of a low pressure fuel pump. The flowchart which shows 6th Embodiment of discharge amount control of a low pressure fuel pump.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Internal combustion engine, 12 ... Fuel tank, 13 ... Low pressure fuel pump, 14 ... High pressure fuel pump, 15 ... Fuel injection valve, 16 ... Low pressure fuel piping, 17 ... Return piping, 18 ... Low pressure pressure regulator, 21 ... High pressure pump control Solenoid, 22 ... pilot valve, 23 ... intake valve, 24 ... pump chamber, 25 ... discharge valve, 31 ... high pressure fuel piping, 32 ... fuel gallery pipe, 33 ... relief piping, 34 ... relief valve, 41 ... fuel pressure sensor, 42 ... Air flow meter, 43 ... Crank angle sensor, 44 ... Throttle opening sensor, 45 ... Starter switch, 51 ... Control unit

Claims (4)

An internal combustion engine fuel supply apparatus comprising: an engine-driven high pressure fuel pump; and an electric low pressure fuel pump that supplies fuel to the high pressure fuel pump, wherein the fuel discharged from the high pressure fuel pump is supplied to the internal combustion engine. ,
A fuel supply device for an internal combustion engine, wherein a discharge amount of the low-pressure fuel pump is changed according to an operating condition of the internal combustion engine. 2. The fuel supply device for an internal combustion engine according to claim 1, wherein a discharge amount of the low-pressure fuel pump is changed according to whether or not the internal combustion engine is started. The fuel supply device for an internal combustion engine according to claim 1, wherein the discharge amount of the low-pressure fuel pump is changed according to whether the internal combustion engine is in a transient operation state or a steady operation state. 4. The fuel supply device for an internal combustion engine according to claim 3, wherein the discharge amount of the low-pressure fuel pump is changed according to whether the transient operation state of the internal combustion engine is an acceleration operation state or a deceleration operation state.

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