JPH1137006A - Fuel supplying system structure of cylinder fuel injection engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide compatibility of the decrease in the capacity of a low- pressure pump and the improvement of the volumetric efficiency of a high- pressure pump. SOLUTION: A filter 31, a feed pump (a low-pressure pump) 32, a high- pressure pump 33, a common rail 34 communicating with and connected to injectors 14 of respective cylinders, and a highpressure regulator 35 are interposed in order from the upstream in a fuel passage 29 for supplying fuel from a fuel tank 30 to the injectors 14 of respective cylinders. A fuel bypass passage 29d for bypassing the upstream and the downstream of the feed pump (the low-pressure pump) 32 for feeding fuel from the fuel tank 30 to the high-pressure pump 33 is provided, and a check valve 37 for stopping the back flow of fuel to the upstream of the feed pump 32 and for allowing only the fuel flow to the high-pressure pump 33 side is arranged on this fuel bypass passage 29d.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-cylinder fuel injection engine for supplying fuel from a fuel tank to a high-pressure pump by a low-pressure pump, further boosting the fuel by the high-pressure pump, and supplying high-pressure fuel to an injector. More specifically, the present invention relates to a fuel supply system structure of a cylinder fuel injection engine that can achieve both a reduction in capacity of a low-pressure pump and an improvement in volumetric efficiency of a high-pressure pump.

[0002]

2. Description of the Related Art Conventionally, fuel efficiency and engine output have been improved.
Further, there is known an in-cylinder fuel injection engine in which fuel is directly injected into a cylinder (combustion chamber) to ignite and burn the injected fuel by a spark plug for the purpose of improving exhaust emission.

In this in-cylinder fuel injection engine, JP-A-2-169834 and JP-A-8-17
As disclosed in Japanese Patent No. 7699, etc., in order to directly inject fuel into the cylinder against the in-cylinder pressure, it is necessary to maintain the fuel pressure supplied to the injector at a high pressure. The low-pressure pump (feed pump) feeds the high-pressure pump, and the high-pressure pump further increases the pressure of the fuel to supply the high-pressure fuel to the injector.

That is, since the high-pressure pump has insufficient self-priming ability, an electric low-pressure pump is disposed upstream of the high-pressure pump, and the low-pressure pump supplies fuel from the fuel tank to the high-pressure pump. I have.

[0005]

However, a low-pressure pump and a high-pressure pump are arranged in series in a fuel passage from the fuel tank to the injector, and all the fuel supply to the high-pressure pump is covered by the low-pressure pump. The pump is
It is necessary to adopt a pump having a discharge flow capacity equal to or greater than the maximum discharge flow rate of the high-pressure pump, which causes an increase in current consumption by the low-pressure pump. Therefore, the low-pressure pump generally has a capacity slightly larger than the maximum discharge flow rate of the high-pressure pump.

For this reason, in a region where the fuel discharge flow rate of the high-pressure pump is small, such as in a low engine speed region, there is no problem because the low-pressure pump sufficiently supplies fuel to the high-pressure pump. In a region where the fuel discharge flow rate is large, the fuel flow path resistance increases due to the supply of fuel to the high-pressure pump via the low-pressure pump, and the fuel suction resistance of the high-pressure pump increases accordingly. There is a disadvantage that the efficiency is reduced.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a fuel supply system structure of a cylinder fuel injection engine capable of achieving both a reduction in capacity of a low-pressure pump and an improvement in volumetric efficiency of a high-pressure pump. And

[0008]

According to a first aspect of the present invention, a fuel is supplied from a fuel tank to a high pressure pump by a low pressure pump, and the fuel is further pressurized by the high pressure pump. In a fuel supply system structure of an in-cylinder fuel injection engine that supplies high-pressure fuel to an injector that injects fuel into a cylinder, a fuel bypass passage that bypasses the upstream and downstream of the low-pressure pump is provided, and the low-pressure pump is provided in the fuel bypass passage. A check valve that prevents fuel from flowing back upstream and allows only fuel to flow to the high-pressure pump.

According to a second aspect of the present invention, high-pressure fuel is supplied from a fuel tank to a high-pressure pump by a low-pressure pump, and the high-pressure pump further pressurizes the fuel to supply the high-pressure fuel to an injector for injecting the fuel into a cylinder. In the fuel supply system structure of the in-cylinder fuel injection engine, there is provided a fuel bypass passage communicating the low-pressure fuel passage from the low-pressure pump to the high-pressure pump with the fuel tank, and the fuel bypass passage is provided with a backflow of fuel to the fuel tank. A non-return valve for preventing fuel flow only to the high-pressure pump side is provided.

In other words, according to the first aspect of the present invention, in a region where the self-priming capability of the high-pressure pump is insufficient and the fuel discharge flow rate of the high-pressure pump is small, such as in a low engine speed region, the amount of fuel delivered by the low-pressure pump is reduced. Backflow to the upstream side of the low-pressure pump through the fuel bypass passage is prevented by a check valve disposed in the fuel bypass passage, and a sufficient amount of fuel is supplied from the low-pressure pump to the high-pressure pump. Can draw in fuel without resistance and operate with good volumetric efficiency. In a region where the fuel discharge flow rate of the high-pressure pump is large, such as a high engine speed region, the fuel suction capacity of the high-pressure pump itself increases. It is possible to directly suck the fuel from the upstream of the low pressure pump via the. Therefore, even in a region where the fuel discharge flow rate of the high-pressure pump is large, such as a high engine speed region, the fuel suction resistance of the high-pressure pump does not increase,
In addition, a sufficient fuel flow to the high-pressure pump is ensured, and the volume efficiency of the high-pressure pump can be improved while using a small-capacity low-pressure pump.

According to the second aspect of the invention, in a region where the self-priming capability of the high-pressure pump is insufficient and the fuel discharge flow rate of the high-pressure pump is small, such as in a low engine speed region, the fuel bypass of the fuel delivered by the low-pressure pump is reduced. Backflow to the fuel tank through the passage is prevented by a check valve disposed in the fuel bypass passage, and a sufficient amount of fuel is supplied from the low-pressure pump to the high-pressure pump. And operates under good volumetric efficiency. In a region where the fuel discharge flow rate of the high-pressure pump is large, such as a high engine speed region, the fuel suction capacity of the high-pressure pump itself increases. , Fuel can be directly sucked from the fuel tank. Therefore, it is possible to further reduce the fuel suction resistance of the high-pressure pump in a region where the fuel discharge flow rate of the high-pressure pump is large, such as a high engine speed region, and to secure a sufficient fuel flow rate to the high-pressure pump. It is possible to further improve the volumetric efficiency of the high-pressure pump while employing a low-pressure pump with a capacity.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a first embodiment of the present invention.

First, a schematic configuration of the in-cylinder fuel injection engine will be described with reference to FIG. In FIG.
Is a horizontally opposed 4-cycle 4-cylinder direct injection gasoline engine (hereinafter simply referred to as "engine") for vehicles such as automobiles as an example of an in-cylinder fuel injection engine. Cylinder heads 2 are provided in both left and right banks of a cylinder block 1a of the engine 1, respectively. An intake port 2a and an exhaust port 2b are formed in each cylinder head 2 corresponding to each cylinder.

In the intake system of the engine 1, an intake manifold 3 communicates with each intake port 2a, and a throttle chamber 5 communicates with the intake manifold 3 via an air chamber 4 in which intake passages of respective cylinders gather. An air cleaner 7 is attached to the upstream side of the throttle chamber 5 via an intake pipe 6, and the air cleaner 7 is connected to the air intake chamber 8.

The throttle chamber 5 is provided with a throttle valve 5a linked to an accelerator pedal 9. The accelerator pedal 9 representing the required load
In order to detect the depression amount (accelerator opening) of the accelerator pedal, an accelerator opening sensor 10 composed of a potentiometer or the like is attached to the support portion of the accelerator pedal 9.

The intake pipe 6 has a throttle valve 5
a bypass passage 11 is connected to the bypass passage 11 and an idle speed control valve (an idle speed control valve) that controls the idle speed by adjusting the amount of bypass air flowing through the bypass passage 11 according to the valve opening during idling. An ISC valve 12 is interposed.

Further, the cylinder head 2 has an injector 14 for directly injecting fuel into the combustion chamber 13 (inside the cylinder).
Are provided for each cylinder. An ignition plug 15 for exposing the discharge electrode at the tip to the combustion chamber 13 is attached to each cylinder of the cylinder head 2, and the ignition plug 15 is connected to the ignition plug 15 via an ignition coil 16 provided for each cylinder. The igniter 17 is connected.

A cooling water temperature sensor 19 faces a cooling water passage 18 which connects the left and right banks of the cylinder block 1a.

On the other hand, as an exhaust system of the engine 1, an exhaust pipe 21 is communicated with a collection portion of an exhaust manifold 20 which communicates with each exhaust port 2b of the cylinder head 2, and a catalytic converter 22 is interposed in the exhaust pipe 21. And is communicated with the muffler 23.

Further, a crank rotor 24 having a projection for detecting a crank angle at a predetermined crank angle on the outer periphery is axially mounted on a crankshaft 1b of the engine 1, and a crank angle sensor 25 is provided opposite to the crank rotor 24. ing. Further, a cam rotor 27 having a cylinder discriminating projection formed on the outer periphery thereof is connected to a camshaft 26 which makes a half rotation with respect to the crankshaft 1b, and a cylinder discriminating sensor 28 is provided opposite to the cam rotor 27.

Next, the structure of the fuel supply system of the engine 1 according to the present invention will be described with reference to FIGS. Reference numeral 29 in FIGS. 1 and 2 denotes a fuel passage for supplying fuel from the fuel tank 30 to each of the injectors 14. The fuel passage 29 is provided as an example of a fuel filter 31 and a low-pressure pump in this fuel passage 29 in order from the upstream side. A tank-type electric feed pump 32, a high-pressure pump 33 for increasing the pressure of fuel from the feed pump 32 to a predetermined high pressure, and a common rail 3 connected to each of the injectors 14.
And a high-pressure regulator 3 including a high-pressure mechanical pressure regulator for adjusting the fuel pressure to the injector 14 to a predetermined high pressure (for example, 7 MPa).
5 are interposed.

In the present embodiment, the high-pressure pump 33 is operated by transmitting power from the crankshaft 1b of the engine 1 via a power transmission mechanism such as a pulley or a belt, and operates from an engine-driven plunger pump or the like. That is, a fuel discharge capacity sufficient to cover the maximum fuel injection amount of the engine 1 is adopted.

An upstream side of the high-pressure pump 33 in the fuel passage 29 constitutes a low-pressure fuel passage 29a for feeding fuel from the fuel tank 30 by the feed pump 32. A low-pressure fuel passage 29a is provided between the high-pressure pump 33 and the high-pressure regulator 35. A high-pressure fuel passage 29b is provided, which pressurizes fuel from the fuel passage 29a and supplies high-pressure fuel to each of the injectors 14.

The low pressure fuel passage 29a downstream of the feed pump 32 and the fuel tank 30 are connected to a fuel return passage 29c.
The fuel pressure in the low-pressure fuel passage 29a is communicated to the fuel return passage 29c through a predetermined pressure (for example, 0.
A low-pressure regulator 36 such as a diaphragm pressure regulator for adjusting the pressure to 2 MPa is interposed.

Further, the downstream side of the high-pressure regulator 35
It is connected to a fuel return passage 29c between the low-pressure fuel passage 29a downstream of the feed pump 32 and the low-pressure regulator 36, and returns excess fuel from the high-pressure regulator 35 to the low-pressure fuel passage 24a. On the other hand, a small capacity feed pump 32 can be adopted.

On the other hand, a fuel bypass passage 29d for bypassing the upstream and downstream of the feed pump 32 is connected to the low-pressure fuel passage 29a, and the reverse flow of fuel to the upstream side of the feed pump 32 is connected to the fuel bypass passage 29d. And a check valve 37 is provided to allow only the fuel flow to the high-pressure pump 33 side.

A vapor processing valve 38 comprising an electromagnetic switching valve is connected to a purge passage 29e which communicates a high pressure fuel passage 29b between the common rail 34 and the high pressure regulator 35 and a fuel return passage 29c downstream of the low pressure regulator 36.
Are arranged.

The common rail 34 is provided with a fuel pressure sensor 39 for detecting the fuel pressure in the high-pressure fuel passage 29b.

On the other hand, calculation of control amounts for the injector 14, the ignition plug 15, and the ISC valve 12 and output of control signals, that is, fuel injection control, ignition timing control, idle speed control, operation control of the feed pump 32, Engine control such as opening and closing control of the vapor processing valve 38 is performed by an electronic control unit (ECU) 40 shown in FIG.

The ECU 40 is mainly composed of a microcomputer, and has a built-in peripheral circuit such as a drive circuit and an A / D converter.

The ECU 40 is connected to a battery 42 via a first relay contact of a power supply relay 41 having two circuit relay contacts. The relay coil of the power supply relay 41 is connected to the battery 42 by an ignition switch 43.
Through the ignition switch 43
Is turned on and the contact of the power supply relay 41 is closed.
The power is turned on to 40.

Further, the feed pump 32 is connected to the battery 42 via a relay contact of a feed pump relay 44. A power supply line for supplying power from the battery 42 to each actuator is connected to a second relay contact of the power supply relay 41.

The input ports of the ECU 40 include the accelerator opening sensor 10, the coolant temperature sensor 19, the crank angle sensor 25, the cylinder discriminating sensor 28, and the fuel pressure sensor 3.
9, and various sensors and switches such as a starter switch 45 for detecting an engine start state are connected. The output port of the ECU 40 is connected to the ISC
The valve 12, the injector 14, the igniter 17, the vapor processing valve 38, and the relay coil of the feed pump relay 44 are connected.

The ECU 40 processes input detection signals from sensors and switches in accordance with the stored control program, and based on various data based on these detection signals, the fuel injection amount, ignition timing, ISC valve 12 And the engine control such as fuel injection control, ignition timing control, idle speed control, operation control of the feed pump 32, open / close control of the vapor processing valve 38, and the like.

Next, the operation of the present embodiment will be described.

First, the ignition switch 43 is turned on.
Then, when power is supplied to the ECU 40, the system is initialized, and the drive signal from the ECU 40 opens the vapor processing valve 38, and the high-pressure fuel between the common rail 34 and the high-pressure regulator 35 through the purge passage 29e. The passage 29b communicates with the fuel return passage 29c downstream of the low-pressure regulator 36, and the feed pump relay 44 is turned on to energize the feed pump 32, so that the operation of the feed pump 32 is started.

Thus, the fuel in the fuel tank 30 is
It is delivered by a feed pump 32 via a filter 31 interposed in the low-pressure fuel passage 29a. Then, the fuel delivered by the feed pump 32 is regulated by the low-pressure regulator 36 and supplied to the high-pressure pump 33, and excess fuel is returned from the low-pressure regulator 36 to the fuel tank 30 via the fuel return passage 29c.

At this time, the engine 1 has not been started, and the high-pressure pump 33 has been stopped. However, the high-pressure pump 33 includes an engine-driven plunger pump as described above, Each of the discharge ports is provided with a check valve (not shown), so that fuel flows into the high-pressure fuel passage 29b via the high-pressure pump 33 by the check valve. Further, the high-pressure fuel passage 29b between the common rail 34 and the high-pressure regulator 35 is communicated with the fuel return passage 29c downstream of the low-pressure regulator 36 via the purge passage 29e by opening the vapor processing valve 38. Thus, the fuel is returned from the high-pressure fuel passage 29b to the fuel tank 30 via the purge passage 29e and the fuel return passage 29c.

Therefore, even if vapor is generated in the fuel passage 29, the vapor is discharged to the fuel tank 30. As a result, the fuel injection controllability due to the vapor is prevented from being deteriorated before the engine 1 is started.

When the starter switch 45 is turned on and the engine 1 is started, the ECU 40 calculates the engine speed based on the input interval time of the crank angle signal for each input of the crank angle signal from the crank angle sensor 25. Further, a cylinder such as a fuel injection target cylinder and an ignition target cylinder is determined based on a cylinder determination signal input from the cylinder determination sensor 28. Based on the engine speed and the engine operating state detected by the sensors, the ECU 40 determines various parameters such as a fuel injection pulse width that determines a fuel injection amount, an ignition timing, and a duty ratio of a drive signal for the ISC valve 12. The control amount is calculated, and at a predetermined timing, a drive signal based on the fuel injection pulse width is output to the injector 14 of the fuel injection target cylinder, and an ignition signal is output to the igniter 17 at a predetermined ignition timing to output the ignition signal of the target cylinder. The ignition plug 15 is ignited and a drive signal based on the duty ratio is output to the ISC valve 12 to perform engine control such as fuel injection control, ignition timing control, and idle speed control.

The ECU 40 closes the vapor processing valve 38 in synchronization with the starter switch 45 being turned on. Thereafter, the ECU 40 connects the common rail 34 and the high-pressure regulator 35 through the purge passage 29e. The communication between the high-pressure fuel passage 29b and the fuel return passage 29c downstream of the low-pressure regulator 36 is cut off.

When the engine 1 is started, the high-pressure pump 33 is driven, the fuel delivered from the feed pump 32 is pressurized by the high-pressure pump 33, and the high-pressure regulator 35 is closed by closing the vapor processing valve 38. The fuel pressure can be adjusted, and a predetermined high-pressure fuel adjusted by the high-pressure regulator 35 is supplied to the injector 14 of each cylinder via the common rail 34.

That is, after the engine 1 is started, the fuel pressure in the high-pressure fuel passage 29b is maintained at a predetermined high pressure by the high-pressure regulator 35, so that the amount of fuel injected into the combustion chamber 13 (in the cylinder) is reduced. It is possible to accurately measure by the valve opening time of the injector 14 based on the fuel injection pulse width drive signal output from the ECU 40.

After the engine starts, when the engine is running at a low speed, the driving speed of the high-pressure pump 33 is low.
Although the self-priming capability of the high-pressure pump 33 becomes insufficient, the low-speed rotation of the high-pressure pump 33 reduces the fuel discharge flow rate of the high-pressure pump 33 and the feed pump 32
The backflow of the fuel delivered by the above to the upstream side of the feed pump 32 through the fuel bypass passage 29d is prevented by the check valve 37 disposed in the fuel bypass passage 29d, and the fuel is transferred from the feed pump 32 to the high-pressure pump 33. A sufficient amount of fuel is supplied. Thus, when the engine is running at a low speed, the high-pressure pump 33 can suck the fuel with a low suction resistance, as in the conventional case, and operates with good volumetric efficiency.

At this time, since the required fuel injection amount is small, a sufficient amount of high-pressure fuel can be stably supplied to the injector 14 of each cylinder even if the fuel discharge flow rate by the high-pressure pump 33 is small.

On the other hand, as the driving speed of the high-pressure pump 33 increases with the engine speed, the fuel suction capacity of the high-pressure pump 33 increases and the fuel discharge flow rate of the high-pressure pump 33 increases.

In a region where the fuel discharge flow rate of the high-pressure pump 33 is large, such as in a high engine speed region, the ability of the high-pressure pump 33 itself to inhale fuel increases.
3 is a feed pump 3 via a fuel bypass passage 29d.
The fuel can be directly sucked from the upstream of the fuel cell 2. Also, a check valve 37 provided in the fuel bypass passage 29d is provided.
Prevents the fuel from flowing backward to the upstream side of the feed pump 32 and allows only the fuel flow to the high pressure pump 33 side.
Is opened, and the high-pressure pump 33 can self-prime through the fuel bypass passage 29d.

As a result, when the engine is running at high speed, in a region where the fuel discharge flow rate of the high pressure pump 33 is large due to the high speed rotation of the high pressure pump 33, the fuel is supplied from the feed pump 32 and the fuel bypass passage is formed by the self-priming action of the high pressure pump 33. By directly sucking fuel from the upstream of the feed pump 32 to the high-pressure pump 33 via the feed pump 32d, the feed pump 32
As a result, a sufficient amount of fuel can be secured on the suction side of the high-pressure pump 33, and the fuel suction resistance of the high-pressure pump 33 can be reduced.

Accordingly, even in a region where the fuel discharge flow rate of the high-pressure pump 33 is large due to the high-speed rotation of the high-pressure pump 33, such as an engine high-speed region, the fuel suction resistance of the high-pressure pump 33 does not increase and the high-pressure pump 33 Since a sufficient fuel flow rate is ensured, the small capacity feed pump 32
It is possible to improve the volumetric efficiency of the high-pressure pump 33 while employing the small-capacity feed pump 32.

In addition, even when the required fuel injection amount is large in response to the high engine speed and high load, a sufficient amount of stable high-pressure fuel can be supplied to the injector 14 of each cylinder. Control accuracy can be improved.

Next, a second embodiment of the present invention will be described with reference to FIGS.

The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

Hereinafter, the structure of the fuel supply system of this embodiment will be described.

In the first embodiment, an out-tank type electric feed pump is used as the low-pressure pump. On the other hand, in the present embodiment, an in-tank type electric feed pump provided in the fuel tank 30 is used. The pump 50 is employed. The in-tank type electric feed pump 50 is a well-known turbine type electric pump, and has a filter 51 mounted on a suction port.

The feed pump 5 is connected to the battery 42 via a relay contact of the feed pump relay 44.
0 is connected.

A low-pressure fuel passage 52a from the feed pump 50 to the high-pressure pump 33 communicates with the fuel tank 30 via a fuel bypass passage 52d.
A check valve 53 is disposed in the fuel bypass passage 52d to prevent backflow of fuel to the fuel tank 30 and allow only fuel flow to the high-pressure pump 33 side.

In the fuel tank 30, the open end of the fuel bypass passage 52d extends toward the bottom, and a filter 54 is mounted on the open end. The filter may be provided in the fuel bypass passage 52d upstream of the check valve 53 without mounting the filter 54 at the open end of the fuel bypass passage 52d.

The upstream side of the low pressure regulator 36 in the fuel return passage 29c is connected to the low pressure fuel passage 52a.
The rest of the configuration is the same as in the first embodiment.

Next, the operation of the present embodiment will be described.

When the ignition switch 43 is turned on,
When power is supplied to the ECU 40, the system is initialized, the purge processing valve 38 is opened by a drive signal from the ECU 40, the feed pump relay 44 is turned on, and the feed pump 50 is energized. The operation of 50 is started.

Then, by the operation of the feed pump 50, the fuel in the fuel tank 30 is sent out via the filter 51 and the low-pressure fuel passage 52a. Then, the fuel delivered by the feed pump 50 is regulated by the low pressure regulator 36 and supplied to the high pressure pump 33,
As in the first embodiment, the check valve (not shown) provided at the suction port and the discharge port of the high-pressure pump 33 allows the fuel to flow into the high-pressure fuel passage 29b via the high-pressure pump 33, Excess fuel is returned from the regulator 36 to the fuel tank 30 via the fuel return passage 29c.

Further, the high-pressure fuel passage 29b between the common rail 34 and the high-pressure regulator 35 through the purge passage 29e by opening the vapor processing valve 38,
The fuel is returned from the high-pressure fuel passage 29b to the fuel tank 30 via the purge passage 29e and the fuel return passage 29c due to the communication with the fuel return passage 29c downstream of the low-pressure regulator 36. Is generated, the vapor is discharged to the fuel tank 30 to prepare for the start of the engine 1.

When the starter switch 45 is turned on and the engine 1 is started, the ECU 40 synchronizes with the starter switch 45 to turn on the vapor processing valve 3.
8 is operated to close the valve, and thereafter, through the purge passage 29e,
The communication between the high-pressure fuel passage 29b between the common rail 34 and the high-pressure regulator 35 and the fuel return passage 29c downstream of the low-pressure regulator 36 is cut off.

When the engine 1 is started, the high-pressure pump 33 is driven, the fuel supplied from the feed pump 50 is pressurized by the high-pressure pump 33, and the high-pressure regulator 35 is closed by closing the vapor processing valve 38. The fuel pressure can be adjusted, and a predetermined high-pressure fuel adjusted by the high-pressure regulator 35 is supplied to the injector 14 of each cylinder via the common rail 34.

After the engine starts, when the engine is running at a low speed, the driving speed of the high-pressure pump 33 is low.
Although the self-priming capacity of the high-pressure pump 33 becomes insufficient, the low-speed rotation of the high-pressure pump 33 reduces the fuel discharge flow rate of the high-pressure pump 33 and the feed pump 50.
Backflow of the fuel delivered by the fuel tank 30 to the fuel tank 30 via the fuel bypass passage 52d is caused by the fuel bypass passage 5d.
A sufficient amount of fuel is supplied from the feed pump 50 to the high-pressure pump 33, which is prevented by the check valve 53 arranged in 2d.

Therefore, when the engine is running at a low speed, the high-pressure pump 33 can suck the fuel with a small suction resistance as in the first embodiment, and operates with good volumetric efficiency.

On the other hand, as the driving speed of the high-pressure pump 33 increases with an increase in the engine speed, the fuel suction capacity of the high-pressure pump 33 increases and the fuel discharge flow rate of the high-pressure pump 33 increases.

In a region where the fuel discharge flow rate of the high-pressure pump 33 is large, such as in a high engine speed region, the ability of the high-pressure pump 33 itself to inhale fuel is increased.
3 can suck the fuel directly from the fuel tank 30 via the fuel bypass passage 52d.

The check valve 53 disposed in the fuel bypass passage 52d prevents the fuel from flowing back to the fuel tank 30 and allows only the fuel flow to the high pressure pump 33 side. Check valve 53
Is opened, and the high-pressure pump 33 can self-prime through the fuel bypass passage 52d.

As a result, when the engine is running at high speed, in a region where the fuel discharge flow rate of the high pressure pump 33 is high due to the high speed rotation of the high pressure pump 33, the filter 54 and the filter 54 By directly sucking the fuel from the fuel tank 30 to the high-pressure pump 33 through the fuel bypass passage 52d, the direct current resistance of the fuel by the feed pump 50 is reduced, and a sufficient amount of fuel is secured on the suction side of the high-pressure pump 33. It is possible to do. Further, since the fuel bypass passage 52 is directly connected to the fuel tank 30, the fuel suction resistance of the high-pressure pump 33 can be further reduced.

Therefore, even in a region where the fuel discharge flow rate of the high-pressure pump 33 is large due to the high-speed rotation of the high-pressure pump 33, such as an engine high-speed region, the fuel suction resistance of the high-pressure pump 33 is further reduced and the high-pressure pump 33 Since a sufficient fuel flow rate is ensured, it is possible to employ a small-capacity feed pump 50, and it is possible to further improve the volumetric efficiency of the high-pressure pump 33 while employing the small-capacity feed pump 50. .

In addition, even when the required fuel injection amount is large in response to the high engine speed and high load, a sufficient amount of stable high-pressure fuel can be reliably supplied to the injector 14 of each cylinder. Control accuracy can be further improved.

The present invention is not limited to the above embodiments. For example, the fuel bypass passage 29d according to the first embodiment employing the out-tank type feed pump 32 can be used.
May be directly connected to the fuel tank 30, as in the second embodiment, without being connected to the fuel passage upstream of the feed pump 32. In this case, as in the second embodiment, the opening end of the fuel bypass passage 29d extends in the fuel tank 30 toward the bottom. Then, a filter is mounted on the opening end, or a filter is interposed upstream of the check valve 37 in the fuel bypass passage 29d.

[0074]

As described above, according to the first aspect of the present invention, a fuel bypass passage is provided for bypassing the upstream and downstream of a low pressure pump for supplying fuel from a fuel tank to a high pressure pump. A check valve that prevents the backflow of fuel to the upstream side of the low-pressure pump and allows only the fuel flow to the high-pressure pump side is provided in the bypass passage. In a region where the fuel discharge flow rate of the high-pressure pump is low and the fuel delivered by the low-pressure pump is backflowed to the upstream side of the low-pressure pump via the fuel bypass passage, a check valve disposed in the fuel bypass passage And a sufficient amount of fuel is supplied from the low pressure pump to the high pressure pump. Therefore, in an area where the fuel discharge flow rate by the high-pressure pump is small, such as an engine low-speed area,
As in the conventional case, the high-pressure pump can suck the fuel with a small suction resistance, and can operate with good volumetric efficiency.

In a region where the fuel discharge flow rate of the high-pressure pump is large, such as in a high engine speed region, the high-pressure pump itself has an increased fuel suction capacity. The stop valve is opened, and the high-pressure pump can take in the fuel directly from the upstream of the low-pressure pump via the fuel bypass passage by the self-priming action together with the fuel supply from the low-pressure pump. This reduces the DC resistance of the fuel from the low-pressure pump in areas where the fuel discharge flow rate of the high-pressure pump is large, such as in the engine high-speed range, and in this case, a sufficient amount of fuel is secured on the suction side of the high-pressure pump. The fuel suction resistance of the high-pressure pump can be reduced.

Accordingly, even in a region where the fuel discharge flow rate of the high-pressure pump is large, such as an engine high-speed range, the fuel suction resistance of the high-pressure pump does not increase and a sufficient fuel flow rate to the high-pressure pump is ensured. Therefore, it is possible to use a small-capacity low-pressure pump, and to improve the volumetric efficiency of the high-pressure pump while employing a small-capacity low-pressure pump.

Further, even when the required fuel injection amount is large in response to the high engine speed and high load, a sufficient amount of stable high-pressure fuel can be supplied to the injector, and the fuel injection control accuracy can be improved. Has an effect.

According to the second aspect of the present invention, a fuel bypass passage is provided for communicating the fuel tank with a low-pressure fuel passage from a low-pressure pump for supplying fuel from the fuel tank to the high-pressure pump and a high-pressure fuel pump. The self-priming capability of the high-pressure pump is insufficient in the bypass passage, because a check valve that prevents backflow of fuel to the fuel tank and allows only fuel flow to the high-pressure pump is installed. In a region where the fuel discharge flow rate of the high-pressure pump is small, the back-flow of the fuel delivered by the low-pressure pump to the fuel tank via the fuel bypass passage is prevented by the check valve disposed in the fuel bypass passage. A sufficient amount of fuel is supplied from the pump to the high pressure pump. Therefore, for example, in the low engine speed range,
In the region where the fuel discharge flow rate of the high-pressure pump is small, the high-pressure pump can suck the fuel with a small suction resistance and can operate with good volumetric efficiency, similarly to the first aspect of the invention. .

Further, in a region where the fuel discharge flow rate of the high-pressure pump is large, such as in a high engine speed region, the high-pressure pump itself increases the fuel suction capacity. The stop valve is opened, and the high-pressure pump can suck the fuel directly from the fuel tank via the fuel bypass passage by the self-priming action together with the fuel supply from the low-pressure pump. This reduces the DC resistance of the fuel from the low-pressure pump in areas where the fuel discharge flow rate of the high-pressure pump is large, such as in the engine high-speed range, and in this case, a sufficient amount of fuel is secured on the suction side of the high-pressure pump. can do. Also, since the fuel bypass passage is directly connected to the fuel tank,
As compared with the first aspect, the fuel suction resistance of the high-pressure pump can be further reduced.

Therefore, even in a region where the fuel discharge flow rate of the high-pressure pump is large, such as a high engine speed range, the fuel suction resistance of the high-pressure pump is further reduced, and a sufficient fuel flow rate to the high-pressure pump is ensured. It is possible to use a small-capacity low-pressure pump, and it is possible to further improve the volumetric efficiency of the high-pressure pump while employing a small-capacity low-pressure pump.

Further, even when the required fuel injection amount is large in response to the high engine speed and high load, a sufficient amount of stable high-pressure fuel can be reliably supplied to the injector, and the fuel injection control accuracy is further improved. Has the effect that can.

[Brief description of the drawings]

FIG. 1 is an overall schematic view of an in-cylinder fuel injection engine according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a fuel supply system according to the first embodiment;

FIG. 3 is an overall schematic view of an in-cylinder fuel injection engine according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a fuel supply system according to the first embodiment;

[Explanation of symbols]

 1 In-cylinder fuel injection engine 14 Injector 29a, 52a Low pressure fuel passage 29d, 52d Fuel bypass passage 30 Fuel tank 32, 50 Feed pump (low pressure pump) 33 High pressure pump 37, 53 Check valve

Claims (2)

[Claims] An in-cylinder fuel injection engine that supplies fuel from a fuel tank to a high-pressure pump by a low-pressure pump, further pressurizes the fuel by the high-pressure pump, and supplies high-pressure fuel to an injector that injects fuel into the cylinder. In the fuel supply system structure, a fuel bypass passage is provided for bypassing the upstream and downstream of the low-pressure pump, and the fuel bypass passage prevents backflow of fuel to the upstream side of the low-pressure pump and only the fuel flow to the high-pressure pump side. A fuel supply system structure for a cylinder fuel injection engine, characterized in that a check valve is provided to allow the fuel injection. 2. An in-cylinder fuel injection engine for supplying fuel from a fuel tank to a high-pressure pump by a low-pressure pump, further increasing the fuel pressure by the high-pressure pump, and supplying high-pressure fuel to an injector for injecting fuel into the cylinder. In the fuel supply system structure, a fuel bypass passage is provided for communicating a fuel tank with a low-pressure fuel passage from the low-pressure pump to the high-pressure pump, and the fuel bypass passage is prevented from flowing back to the fuel tank to the high-pressure pump side. A fuel supply system structure for a cylinder fuel injection engine, wherein a check valve that allows only the fuel flow is provided.