JP2795138B2 - Fuel supply device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply apparatus suitable for use in a direct injection type internal combustion engine, and more particularly to a fuel supply apparatus for an internal combustion engine capable of performing fuel injection at a relatively high fuel pressure. About.

[0002]

2. Description of the Related Art A diesel engine is widely known as a so-called direct injection type internal combustion engine or a direct injection type internal combustion engine (direct injection type internal combustion engine) in which fuel is injected in a cylinder. However, in recent years, an in-cylinder injection type engine has also been proposed for a spark ignition type engine (generally, a gasoline engine is used, and is hereinafter referred to as a gasoline engine).

[0003] In such a direct injection internal combustion engine, in order to improve the performance of the engine and reduce the exhaust gas, there is a tendency that the fuel injection pressure is increased to atomize the fuel spray and shorten the fuel injection period. Further, in an engine having a supercharging mechanism, a high fuel injection pressure corresponding to the supercharging pressure is required at the time of supercharging. Therefore, the fuel supply device in the in-cylinder injection type internal combustion engine is configured to obtain such a sufficiently high fuel injection pressure (for example, about several tens of atmospheres).

For example, FIGS. 4 and 5 schematically show a configuration of a fuel supply device for an internal combustion engine that has been conventionally proposed as a device capable of obtaining such a high fuel injection pressure. 4 and 5, reference numeral 1 denotes a fuel injection valve;
Denotes a fuel tank, and 3 denotes a fuel passage provided between the fuel injection valve 1 and the fuel tank 2, and a fuel supply path for supplying fuel to the fuel injection valve 1 (hereinafter abbreviated as a supply path). 3A,
A fuel return path (hereinafter abbreviated as a return path) 3B returning from the fuel injection valve 1 to the fuel tank 2. 4
Reference numeral 5 denotes a low-pressure fuel pump provided upstream of the fuel passage 3 on the side of the fuel tank 2, and reference numeral 5 denotes a high-pressure fuel pump provided between the low-pressure fuel pump and the fuel injection valve 1. Reference numerals 6 and 7 denote a fuel filter provided at the inlet of the fuel passage, 8 denotes a check valve, 9 denotes a low pressure control valve as low pressure control means, and 10 denotes a high pressure control valve as high pressure control means. 21 is a cylinder, 22 is a piston, 22A is a piston rod, 2
3 is a crankshaft, 24 is a combustion chamber, 25 is a cylinder head, 26 is an intake passage, 27 is a spark plug, and 28 is an exhaust passage.

[0005] In such a fuel supply device, the fuel pressurized to some extent by the low-pressure fuel pump 4 is supplied to the high-pressure fuel pump 5.
Further, the pressure of the fuel is increased to a predetermined pressure. At this time, the discharge pressure from the low-pressure fuel pump 4 is stabilized to a predetermined range by the low-pressure control valve 9, and the discharge pressure from the high-pressure fuel pump 4 is further stabilized to a predetermined range by the high-pressure control valve 10.

As such a technique, for example, Japanese Unexamined Patent Publication No. Sho 62
No. 2,370,57.

[0007]

By the way, it is conceivable to employ either an engine driven pump or an electric pump as the fuel pumps 4 and 5 as described above.
When an electric pump is used for the high-pressure pump, the pump efficiency is reduced and the cost is increased. Therefore, it is generally considered that an engine-driven fuel pump is used for the high-pressure fuel pump 5. On the other hand, when the electric pump is used for the low-pressure pump, the above-described disadvantages in terms of pump efficiency and cost are reduced, and the advantage of the electric pump that a stable discharge pressure can be obtained is utilized. It is conceivable to employ an electric type.

However, since the discharge pressure of the engine-driven pump depends on the engine speed, if the high-pressure fuel pump is of an engine-driven type, the discharge flow rate of the high-pressure fuel pump will be reduced when the engine is running at low speed. However, when the engine speed is high, the volumetric efficiency of the high-pressure fuel pump increases, and the pump discharge flow rate may become excessive. On the other hand, in the low-pressure fuel pump employing the electric pump, the discharge flow rate does not depend on the rotation speed of the engine, so that it is usually slightly larger than the maximum fuel injection amount so that the maximum fuel injection amount can be satisfied. The pump discharge flow rate (that is, the maximum fuel injection amount + α) is set.

Therefore, when the engine is running at high speed, the discharge flow rate of the high-pressure fuel pump becomes larger than the discharge flow rate of the low-pressure fuel pump, and the fuel pressure at the inlet of the high-pressure fuel pump decreases. Cavitation occurs in this portion. There is a possibility that. Such cavitation is not preferable for fuel injection, but is not preferable because it may damage the pump, the fuel passage, and the injection valve.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has an internal combustion engine capable of suppressing a decrease in fuel pressure at an inlet of a high-pressure fuel pump so as to prevent cavitation at this portion. It is an object to provide a fuel supply device for a vehicle.

[0011]

According to a first aspect of the present invention, a fuel supply device for an internal combustion engine is provided between a fuel injection valve provided in an internal combustion engine and a fuel tank. A fuel supply path for supplying fuel to the fuel injection valve from the fuel supply path, a fuel return path for returning the surplus of fuel supplied to the fuel injection valve to the fuel tank again, and a low-pressure fuel pump provided in the fuel supply path A high-pressure fuel pump provided downstream of the low-pressure fuel pump in the fuel supply path, and a fuel pressure discharged from the high-pressure fuel pump disposed in the fuel return path and set to a first set pressure. High-pressure control means for regulating pressure, and a fuel return path disposed between the high-pressure control means and the high-pressure control means disposed downstream of the high-pressure control means, the fuel return path being lower than the first set pressure; Low-pressure control means for adjusting the pressure to a second set pressure; A fuel return path portion between the flop and the high-pressure fuel pump is characterized in that it includes an auxiliary passage connecting the fuel return passage portions between the said pressure control means and said low-pressure control means.

According to a second aspect of the present invention, there is provided a fuel supply device for an internal combustion engine according to the first aspect, wherein the high pressure control means is bypassed from a fuel return path upstream of the high pressure control means. A switching valve for providing fuel to the fuel return path on the upstream side of the low pressure control means, and selectively opening one of the auxiliary path and the bypass path; and the switching valve. And on-off valve control means for controlling the pressure.

According to a third aspect of the present invention, in the fuel supply device for an internal combustion engine according to the second aspect, when the operation of the high-pressure fuel pump is not sufficient, the opening / closing valve control means may be provided on the side of the bypass passage. It is characterized in that it is controlled to open. According to a fourth aspect of the present invention, in the fuel supply system for an internal combustion engine according to the second aspect, the on-off valve control means opens the bypass passage for a predetermined period immediately after the start of the engine. After the lapse of the predetermined period, the auxiliary passage is controlled to be opened.

According to a fifth aspect of the present invention, there is provided a fuel supply device for an internal combustion engine according to any one of the first to fourth aspects, wherein the fuel supply path portion on the upstream side of the high-pressure fuel pump and the downstream portion are provided. A high-pressure fuel pump section bypass passage is provided for connecting the fuel supply path section to the fuel supply passage section, and a check valve for passing fuel only from the upstream side to the downstream side of the fuel passage is provided in the high-pressure fuel pump section bypass passage. It is characterized by being provided.

[0015]

In the fuel supply apparatus for an internal combustion engine according to the first aspect of the present invention, the high-pressure fuel pump receives the fuel discharged from the low-pressure fuel pump, pressurizes the fuel to a high pressure, and moves the fuel to the fuel injection valve side. Pump. At this time, the pressure of the fuel pumped from the high-pressure fuel pump is adjusted to the first set pressure by the high-pressure control means. Thus, the fuel injection valve performs the fuel injection at the first set pressure.

When the discharge flow rate of the high-pressure fuel pump exceeds the discharge flow rate of the low-pressure fuel pump, the fuel pressure on the inlet side of the high-pressure fuel pump tends to decrease. The surplus fuel is supplied from the downstream side of the high-pressure control means to the inlet side of the high-pressure fuel pump through the auxiliary passage, and a decrease in fuel pressure at the inlet side of the high-pressure fuel pump is suppressed.

At this time, the fuel on the downstream side of the high pressure control means is regulated to a second set pressure lower than the first set pressure by the low pressure control means on the further downstream side. The side fuel pressure is maintained at this second set pressure.
Of course, the low pressure control means not only when the discharge flow rate of the high pressure fuel pump exceeds the discharge flow rate of the low pressure fuel pump,
Always adjust the fuel pressure on the inlet side of the high pressure fuel pump.

According to a second aspect of the present invention, there is provided a fuel supply device for an internal combustion engine according to the first aspect of the present invention, wherein the high pressure control means is bypassed from a fuel return path upstream of the high pressure control means. A switching valve for providing fuel to the fuel return path on the upstream side of the low pressure control means, and selectively opening one of the auxiliary path and the bypass path; and the switching valve. And on-off valve control means for controlling the pressure.

In the fuel supply device for an internal combustion engine according to the second aspect of the present invention, when the auxiliary passage is opened by the switching valve, the high pressure can be attained similarly to the configuration of the first aspect. The fuel pressure on the inlet side of the fuel pump is maintained at the second predetermined pressure, and a decrease in the fuel pressure is suppressed. On the other hand, when the bypass passage is opened by the switching valve, the fuel in the fuel passage portion on the upstream side of the high-pressure control means does not pass through the high-pressure control means but flows from the bypass passage to the downstream side of the high-pressure control means. For example, even if the discharge flow rate of the high-pressure fuel pump does not sufficiently occur, the fuel near the fuel injection valve downstream of the high-pressure fuel pump flows out downstream.
Therefore, for example, if vapor is contained in the fuel near the fuel injection valve, the vapor flows out downstream with the fuel and is removed from the vicinity of the fuel injection valve.

In the fuel supply device for an internal combustion engine according to the third aspect of the present invention, when the operation of the high-pressure fuel pump is not sufficient, the opening / closing valve control means opens the bypass passage side. The fuel near the fuel injection valve downstream of the high pressure fuel pump flows downstream. Therefore, as described above, for example, if vapor is contained in the fuel near the fuel injection valve, the vapor flows downstream with the fuel and is removed from the vicinity of the fuel injection valve.

Further, in the fuel supply device for an internal combustion engine according to the present invention, the on-off valve control means opens the bypass passage for a predetermined period immediately after the start of the engine. When the operation of the high-pressure fuel pump is not sufficient, the vapor contained in the fuel near the fuel injection valve flows out to the downstream side together with the fuel near the fuel injection valve downstream of the high-pressure fuel pump through the bypass passage. As a result, it is quickly removed from the vicinity of the fuel injection valve.

The auxiliary passage is opened after the lapse of the predetermined period, so that the engine is operated during the operation of the engine except immediately after the start of the engine. The fuel pressure on the inlet side of the high-pressure fuel pump is always kept at a predetermined pressure, and a decrease in the fuel pressure is suppressed. In the fuel supply device for an internal combustion engine according to the present invention, when the fuel in the fuel tank is pressurized by the low-pressure fuel pump in a region where the output of the high-pressure fuel pump is low, the fuel passes through the fuel supply passage. hand,
After being sent to the upstream part of the high-pressure fuel pump, it flows into the high-pressure fuel pump part bypass passage. Since the check valve provided in the high-pressure fuel pump section bypass passage allows fuel to pass only from the upstream side to the downstream side of the fuel supply path,
The fuel pressurized by the low-pressure fuel pump is supplied to the fuel injection valve without being obstructed and bypassing the high-pressure fuel pump through the high-pressure fuel pump unit bypass passage. Thus, fuel is injected from the fuel injection valve at a pressure corresponding to the output pressure of the low-pressure fuel pump.

When the output of the high-pressure fuel pump increases, the fuel pressurized by the low-pressure fuel pump and sent to the high-pressure fuel pump is further pressurized by the high-pressure fuel pump, and the fuel is injected from the fuel injection valve. Fuel is injected at a high pressure corresponding to the output pressure of the high-pressure fuel pump. At this time, the pressure on the downstream side of the high-pressure fuel pump becomes significantly higher than that on the upstream side, and the fuel may flow backward on the upstream side to the downstream side through the high-pressure fuel pump section bypass passage. The high-pressure fuel pump has a high output pressure.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIGS. 1 and 2 show a fuel supply system for an internal combustion engine as a first embodiment of the present invention, and FIG. FIG. 2 is a graph showing the characteristics of the output (discharge flow rate) of the fuel pump, and FIG. 3 is a schematic diagram showing a fuel supply device for an internal combustion engine as a second embodiment of the present invention. .

First, the first embodiment will be described. This fuel supply device for an internal combustion engine is provided in a gasoline four-stroke engine as an internal combustion engine, in particular, a direct injection gasoline engine that injects fuel directly into a cylinder. As shown in FIG. 1, a fuel passage 3 communicating between the fuel injection valve 1 and the fuel tank 2 is provided with a low-pressure fuel pump 4 and a high-pressure fuel pump 5. The fuel passage 3
Are a fuel supply path (hereinafter, abbreviated as a supply path) 3A for supplying fuel from the fuel tank 2 to the fuel injection valve 1, and a fuel return path (hereinafter, return) returning from the fuel injection valve 1 to the fuel tank 2. 3B).

The relationship between the main parts of the fuel supply device for an internal combustion engine and the engine is the same as that shown in FIG. The low-pressure fuel pump 4 is connected to the feed passage 3A of the fuel passage 3.
A feed pump provided in the fuel tank 2 at an upstream portion of the fuel tank 2, wherein an electric pump is used. In operation, the fuel in the fuel tank 2 is filtered downstream of the feed passage 3 A while being filtered by the fuel filter 6. It is designed to be driven to the side.
The pressurization of the fuel by the low-pressure fuel pump 4 at this time is performed from an atmospheric pressure state to several atmospheric pressures. The low-pressure fuel pump 4 is started when the engine is started, and is stopped when the engine is stopped. Of course, the low-pressure fuel pump 4 can generate a predetermined discharge pressure without depending on the rotation speed of the engine. Has become.

The high-pressure fuel pump 5 pressurizes the fuel discharged from the low-pressure fuel pump 4 to about several tens of atmospheres. The check valve 8 and the fuel filter 7 are interposed, the discharge pressure from the low-pressure fuel pump 4 is maintained by the check valve 8, and the fuel is further filtered by the fuel filter 7. The high-pressure fuel pump 5 uses an engine-driven pump (hereinafter, referred to as an engine-driven pump) such as a reciprocating compression pump which is more advantageous than the electric pump as the high-pressure pump in terms of pump efficiency and cost. Of course, it operates directly in conjunction with the operation of the engine, and generates a discharge pressure according to the rotation speed of the engine.

FIG. 2 shows an example of the output characteristics (discharge flow rate) of the fuel pumps 4 and 5 under the condition that the discharge pressure is kept constant. The flow characteristics are shown, and a straight line C shows the discharge flow characteristics of the low-pressure fuel pump 4. In each case of the straight lines A and B, the setting of the lift cam amount required for driving the high-pressure fuel pump 5 is different. In the case of B, the lift cam amount and the pump output are larger than in the case of A. I have. The actual discharge pressure of the fuel pumps 4 and 5 is determined by such discharge flow characteristics and the flow resistance of the low-pressure control valve 9 as low-pressure control means and the high-pressure control valve 10 as high-pressure control means described later.
In this case, the discharge flow rate characteristic cannot be read as it is as the discharge pressure characteristic, but the discharge pressure characteristic substantially corresponds to the discharge flow rate characteristic. Therefore, also from FIG. 2, the electric low-pressure fuel pump 4 has a predetermined discharge pressure (discharge flow rate) without depending on the rotation speed of the engine.
It can be seen that the engine-driven high-pressure fuel pump 5 generates a discharge pressure (discharge flow rate) in proportion to the rotation speed of the engine.

The low-pressure fuel pump 4 described above
In addition, in the high-pressure fuel pump 5, a discharge flow rate higher than the fuel injection amount must be obtained so that a desired fuel injection amount can always be realized. Of course, these fuel pumps 4,5
It is sufficient to use a high-output fuel pump so that a sufficient discharge flow rate can always be obtained. However, the unnecessary high-output fuel pumps 4 and 5 are useless in all aspects. I want to adopt 4,5.

From such a viewpoint, the capabilities of the fuel pumps 4 and 5 are set, but the low-pressure fuel pump 4 which can always obtain a constant discharge amount only needs to satisfy the maximum fuel injection amount. , Is set to a pump discharge flow rate that is slightly larger than the maximum fuel injection amount (that is, the maximum fuel injection amount + α). On the other hand, in the high-pressure fuel pump 5 in which the discharge flow rate changes in accordance with the rotation speed of the engine, the discharge flow rate is greatly reduced when the engine is rotating at a low speed. When the engine is running at a low speed, its capacity is set so that the discharge flow rate of the high-pressure fuel pump is substantially equal to the fuel injection amount.

The feed path 3A of the fuel passage 3 and the return path 3
B, that is, a portion of the feed passage 3A downstream of the fuel filter 7 upstream of the high-pressure fuel pump 5 and the return passage 3B.
A low-pressure control valve (low-pressure regulator) 9 for adjusting the discharge pressure from the low-pressure fuel pump 4 to a set pressure (for example, 3 atm) is provided between the low-pressure fuel pump 4 and the most downstream portion. In this fuel supply device, a portion of the feed passage 3A downstream of the fuel filter 7 upstream of the high-pressure fuel pump 5 and a portion of the return passage 3B downstream of the low-pressure control valve 9 are located between Auxiliary passage 3
The low pressure control valve 9 is provided at the most downstream portion of the return path 3B, and communicates with the supply path 3A via the auxiliary path 31. The auxiliary passage 31 will be described later in detail.

The low-pressure control valve 9 is closed until the discharge pressure from the low-pressure fuel pump 4 exceeds a set pressure (for example, 3 atm). Is directly returned to the fuel tank 2 to stabilize the pressure of the fuel supplied to the high-pressure fuel pump 5 near the set pressure. Of course, the low-pressure fuel pump 4 is set so that its discharge pressure is equal to or higher than the set pressure so that the above-mentioned set pressure is obtained.

Further, a portion immediately downstream of the fuel injection valve 1, that is,
A high-pressure control valve (high-pressure regulator) 10 for adjusting the discharge pressure from the high-pressure fuel pump 5 to a set pressure (for example, 50 atm) is provided at the most upstream portion of the return path 3B of the fuel passage 3. The high-pressure control valve 10 is closed until the discharge pressure from the high-pressure fuel pump 5 exceeds a set pressure (for example, 50 atm). The fuel is returned to the fuel tank 2 and the fuel pressure in the fuel injection valve 1 is stabilized at a predetermined pressure.

The above-mentioned auxiliary passage 31 connects the fuel passage portion between the high pressure control valve 10 and the low pressure control valve 9 in the return passage 3B and the fuel passage portion on the inlet side of the high pressure fuel pump 5 in the feed passage 3A. , So that they can communicate with each other. The auxiliary passage 31 allows the fuel on the downstream side of the high-pressure control valve 10 to be supplied to the inlet side of the high-pressure fuel pump 5, and reduces the fuel pressure at the inlet of the high-pressure fuel pump 5 to the fuel pressure on the downstream side of the high-pressure control valve 10. It is provided to hold in.

Further, the fuel supply device is provided with a high-pressure fuel pump 5 so that the fuel passing through the supply passage 3A of the fuel passage 3 can be supplied to the fuel injection valve 1 by bypassing the high-pressure fuel pump 5.
A high-pressure fuel pump unit bypass passage (hereinafter, referred to as a first bypass passage) that connects the upstream portion and the downstream portion of the fuel cell is provided. Also, in the first bypass passage 11,
A check valve 12 that allows fuel to pass only from the upstream side to the downstream side of the feed path 3A is provided. This check valve 12 is provided when the high-pressure fuel pump 5
If the fuel pressure is lower on the downstream side than on the upstream side,
When the bypass passage 11 is opened and the high-pressure fuel pump 5 operates sufficiently and the fuel pressure is higher on the downstream side than on the upstream side of the high-pressure fuel pump 5, the first bypass passage 11 is closed. I have.

Further, the fuel supply device is provided with a high-pressure control valve 1 such that the fuel in the fuel injection valve 1 can be discharged to the fuel tank 2 by bypassing the high-pressure control valve 10.
A bypass passage (hereinafter, referred to as a second bypass passage) 32 that connects the upstream portion and the downstream portion of the “0” portion is provided. The second bypass passage 32 is for discharging vapor (bubbles) contained near the fuel injection valve 1 in the fuel passage 3 at an early stage of engine start.

One end of the second bypass passage 32 (the portion connected to the downstream portion of the high-pressure control valve 10) is provided near one end of the above-described auxiliary passage 31, and one end of the auxiliary passage 31 and the second bypass An electromagnetic three-way valve 33 as a switching valve is provided between one end of the passage 32 and the return path 3B.
The electromagnetic three-way valve 33 allows only one of the auxiliary passage 31 and the second bypass passage 32 to communicate with the return passage 3B. The second bypass passage 32 is sometimes opened, and the auxiliary passage 31 is closed when the power is cut off. Then, when the ignition key switch 16 is operated to the starter position, the ignition key switch 16 is started in conjunction with
By opening the bypass passage 32, the fuel injection valve 1
Stop when the vapor contained in the vicinity of is completely discharged,
The second bypass passage 32 is closed, and the auxiliary passage 31 is formed.

If the vapor discharge operation is continued for a certain period of time by opening the second bypass passage 32, the discharge of the vapor near the fuel injection valve 1 is almost completed, but the discharge of the vapor is completed. The time until can be estimated based on, for example, experiments. In this embodiment, based on the vapor discharge completion time that can be predicted in advance,
The end of the vapor discharge operation, that is, the power supply to the electromagnetic three-way valve 33 is stopped, and the auxiliary passage 31 is switched to the open state.

For this purpose, an on-off valve control means 30 for controlling the opening and closing of the electromagnetic three-way valve 33 is provided. And a mechanism that stops the electromagnetic three-way valve 33 when the set time elapses. Further, for example, when the power supplied to the electromagnetic three-way valve 33 is electronically controlled by a controller, this controller can be used as the on-off valve control means 30. That is, the controller supplies power to the electromagnetic three-way valve 33 based on a starter-on signal from the ignition key switch 16 through the controller, starts an attached timer, and receives a signal indicating that a set time has elapsed from the timer. The supply of power to the three-way valve 33 may be stopped.

It is generally assumed that a short period of time (within a few seconds) after the engine is started is sufficient for the above-described vapor discharging operation time, that is, the opening time of the electromagnetic three-way valve 33. Since the fuel supply device for an internal combustion engine as the first embodiment of the present invention is configured as described above, the ignition key switch 16 is set to the starter-on position,
When the engine is started, the low-pressure fuel pump 4 and the high-pressure fuel pump 5 operate together with the engine start (that is, cranking). Also, the electromagnetic three-way valve 33 receives the electric power when the engine is started, and
To release.

As shown by the straight line C in FIG. 2, the low-pressure fuel pump 4 is brought into an output pressure state of a predetermined pressure (several atmospheric pressure) immediately after the start, but immediately after the start of the engine, the rotation of the engine does not increase. The high-pressure fuel pump 5 does not generate a sufficient discharge pressure as indicated by a straight line-in FIG. Therefore, immediately after the start of the engine, the high-pressure fuel pump 5 becomes rather resistant to the flow of the fuel flow in the fuel passage 3 due to the discharge pressure from the low-pressure fuel pump 4. Since fuel is supplied to the fuel injection valve 1 through the first bypass passage 11 provided in parallel with the fuel injection valve 5, the fuel is injected from the fuel injection valve 1 at a fuel pressure about the pressure adjusted by the low-pressure control valve 9. Can be performed.

That is, the check valve 12 is provided in the first bypass passage 11, and the check valve 12 is provided when the fuel pressure is lower on the downstream side than on the upstream side of the high-pressure fuel pump 5.
Since the first bypass passage 11 is opened, if the high-pressure fuel pump 5 does not generate a sufficient discharge pressure, the fuel is supplied to the fuel injection valve 1 at a pressure on the order of the adjustment level of the low-pressure control valve 9.

Generally, immediately after the start of the engine, the amount of fuel required for combustion is small, so that the pulse width of the fuel injection is short, and the pulse timing of the fuel injection is the same as in the conventional multipoint injection (MPI). This is performed only during the intake stroke, so that even if the fuel pressure is about the adjustment pressure level of the low-pressure control valve 9, if the fuel pressure is stable, the rotation of the engine can be smoothly increased. . As a result, as the engine speed increases, the discharge flow rate of the high-pressure fuel pump 5 increases as shown by the straight lines A and B in FIG. 2, and the discharge pressure of the high-pressure fuel pump 5 also increases smoothly.

When the high-pressure fuel pump 5 starts operating to some extent, the fuel pressure becomes higher on the downstream side than on the upstream side of the high-pressure fuel pump 5, and the check valve 12 closes the first bypass passage 11. As a result, the discharge pressure of the high-pressure fuel pump 5 is increased without any loss, so that the fuel pressure on the downstream side of the high-pressure fuel pump 5 is increased.

As a result, the discharge pressure of the high-pressure fuel pump 5 rises to a sufficient level, and fuel can be injected from the fuel injection valve 1 at a high fuel pressure, which is approximately equal to the adjustment pressure of the high-pressure control valve 10. In this way, for example, in an in-cylinder injection type internal combustion engine, it is required to shorten the fuel injection period (that is, the pulse width of the fuel injection) while smoothly increasing the engine rotation speed immediately after the engine start. Also, a high fuel injection pressure required according to the supercharging pressure at the time of supercharging can be obtained.

On the other hand, for example, in an internal combustion engine for an automobile,
After the engine stops, the temperature rise in the engine room caused by the stop of the engine cooling system and the pressure control valves 9 and 1
In the fuel passage 3, vapor (bubbles) is generated in the fuel passage 3 due to the fuel leak in the fuel injection valve 1 or 0, and the fuel supply is started with the vapor contained in the fuel passage 3 when the engine is started next time. In particular, the vapor present near the fuel injection valve 1 causes a delay or variation in the rise of the fuel pressure to be injected, or causes idle injection from the fuel injection valve 1, making it difficult to control the fuel injection.

The vapor existing near the fuel injection valve 1 flows through the return passage 3B of the fuel passage 3 when the fuel starts flowing through the fuel passage 3 by starting the fuel supply device. The high pressure control valve 10 provided in the return path 3B closes if the fuel pressure is not high, and shuts off the flow of fuel. Therefore, in the present apparatus, the second bypass passage 32 is provided in parallel with the high-pressure control valve 10, and the electromagnetic solenoid 3 opens and closes the second bypass passage 32.
Since the direction valve 33 opens the second bypass passage 32 for a predetermined period after the engine is started, fuel flows through the second bypass passage 32 to the downstream side of the return passage 3B while bypassing the high-pressure control valve 10.

With this fuel flow, the vapor contained in the fuel passage 3 near the fuel injection valve 1 is discharged to the outside of the fuel passage 3. As described above, even when the second bypass passage 32 is open, the low-pressure control valve 9 downstream of the second bypass passage 32 maintains the fuel pressure at the set pressure, so that the fuel is discharged while the vapor is being discharged. A sufficient fuel injection pressure from the injection valve 1 is ensured when the engine is started.

Accordingly, a certain level of fuel injection pressure can be obtained without causing delays and variations in the rise of fuel pressure caused by the vapor immediately after the start of the engine and phenomena such as idle injection. Therefore, it is possible to smoothly increase the engine rotation speed while maintaining good engine combustion, so that the practicality of, for example, an in-cylinder injection type engine can be greatly improved.

The solenoid three-way valve 33 closes the second bypass passage 32 after a predetermined period (relatively short time) elapses after the engine is started and the vapor is sufficiently discharged. Thereafter, the fuel pressure can be increased to a pressure controlled by the high-pressure control valve 10. The electromagnetic three-way valve 33 closes the second bypass passage 32,
Since the auxiliary passage 31 is opened, even when the discharge flow rate of the high-pressure fuel pump becomes larger than the discharge flow rate of the low-pressure fuel pump at the time of high-speed rotation of the engine, the fuel pressure at the inlet of the high-pressure fuel pump 5 is reduced. The decrease is suppressed, and the occurrence of cavitation at the inlet of the high-pressure fuel pump 5 is avoided.

That is, the discharge flow rate of the high-pressure fuel pump 5 is
Since the discharge flow rate of the low-pressure fuel pump 4 is constant while the rotational speed of the engine increases, the discharge flow rate of the high-pressure fuel pump 5 is reduced when the engine rotates at a high speed. May be exceeded. In such a case, the fuel pressure at the inlet of the high-pressure fuel pump 5 is supposed to decrease, but in this device, the fuel downstream of the high-pressure control valve 10 is supplied to the inlet of the high-pressure fuel pump 5 through the auxiliary passage 31. , The fuel pressure at the inlet of the high-pressure fuel pump 5 does not decrease. In particular, when the discharge flow rate of the high-pressure fuel pump 5 increases as described above, the downstream side of the high-pressure fuel pump 5 exceeds the set pressure, so that the fuel overflows to the downstream side by the high-pressure control valve 10, The portion of the auxiliary passage 31 is in a sufficient fuel pressure state. Further, since the low-pressure control valve 9 is located downstream of the auxiliary passage 31, the fuel pressure in the portion of the auxiliary passage 31 is controlled to the set pressure by the low-pressure control valve 9.

Therefore, the occurrence of cavitation at the inlet of the high-pressure fuel pump 5 is reliably avoided, the fuel pressure at the inlet of the high-pressure fuel pump 5 is always stabilized, and an extremely good fuel supply can be realized. Thus, damage to the fuel passage, the injection valve, and the like can be reliably avoided. As shown by a two-dot chain line in FIG. 1, a fuel pressure sensor 18 for detecting the fuel pressure for the fuel injection valve 1 is provided immediately downstream of the fuel injection valve 1, and the detection information of the fuel pressure sensor 18 is provided. It is also conceivable to detect a failure in the fuel supply system on the basis of the above and warn the driver of this, or feed it back to the fuel supply control. In this case, for example, if the fuel pressure detected by the fuel pressure sensor 18 becomes lower than the set pressure range, the fuel leaks due to, for example, damage to the fuel injection valve 1, the seal portion of the pump system, piping, or the like. It can be inferred. When the fuel pressure detected by the fuel pressure sensor 18 becomes higher than the set pressure range, it can be estimated that the valves and the like on the return path 3B such as the high-pressure control valve 10 and the electromagnetic three-way valve 33 are locked.

Next, a description will be given of a second embodiment. As shown in FIG.
In this embodiment, an accumulator 19 and a check valve 20 are added to the embodiment. That is, the accumulator 19 is provided in the fuel passage 3 in the portion of the fuel injection valve 1, and the check valve 20 is attached to the high-pressure fuel pump 5. This check valve 20 may be provided in series with the high-pressure fuel pump 5 at an inlet portion upstream of the high-pressure fuel pump 5 as shown in the drawing, or provided in series with the high-pressure fuel pump 5 at an outlet portion downstream of the high-pressure fuel pump 5. You may.

The accumulator 19 and the check valve 20 are used to maintain a constant internal pressure even when the temperature of the engine decreases from a high temperature to a normal temperature after the engine is stopped. This is to prevent vapor (bubbles) from entering the fuel passage 3 at the fuel injection valve 1 from the outside even if fuel leaks when the engine is cold.

With such a configuration, in the fuel supply system for an internal combustion engine according to the second embodiment, the low-pressure fuel pump 4 is activated at the same time as the engine is started, and the predetermined pressure (several atmospheric pressures) is immediately activated. ), The high-pressure fuel pump 5 is hardly operated, the check valve 12 is opened and the fuel is supplied through the first bypass passage 11, and the low-pressure control valve is supplied from the fuel injection valve 1. Fuel injection is performed at a fuel pressure of about the pressure adjusted in step 9.

Although the fuel pressure is about the same as the adjustment pressure level of the low-pressure control valve 9, the fuel pressure is stable, so that the rotation of the engine can be smoothly increased. Also increases smoothly. When the high-pressure fuel pump 5 starts operating to some extent, the check valve 12 closes the first bypass passage 11, and the discharge pressure of the high-pressure fuel pump 5 is adjusted without any loss of the high-pressure control valve 10. Since the fuel pressure is increased above the pressure, the same effect as in the first and second embodiments can be obtained.

In general, after the engine is stopped, the fuel pressure decreases due to a rise in the temperature in the engine room and a fuel leak in the pressure control valves 9 and 10 and the fuel injection valve 1, but the fuel pressure is sufficiently accumulated in the accumulator 19. The leaked fuel replenishes the leaked amount, so that a decrease in fuel pressure is suppressed. At this time, the fuel in the portion of the fuel injection valve 1 is prevented from leaking by the check valve 20 on the upstream side, and is prevented by the high-pressure control valve 10 on the downstream side. Of course, when the engine is stopped, the electromagnetic three-way valve 33 controls the second bypass passage 3.
2 is closed to prevent leakage here as well.

As a result, it becomes difficult for the vapor to enter the fuel passage 3 in the portion of the fuel injection valve 1 after the engine is stopped.
In addition, when vapor is generated in the vicinity of the fuel injection valve 1 by such an action, in the present device, the second bypass passage 32 in parallel with the high-pressure control valve 10 is opened for a predetermined period after the engine is started. Therefore, through the second bypass passage 32, the fuel flows downstream of the return passage 3 B while bypassing the high-pressure control valve 10, and together with the fuel flow, the vapor contained in the fuel passage 3 near the fuel injection valve 1. Is discharged outside the fuel passage 3.

In this configuration, since vapor is unlikely to be generated from the beginning, even if vapor is generated, it is slight, and the vapor is discharged very quickly after the engine is started. Therefore, the opening time of the second bypass passage 32 can be set extremely short, and the closing of the second bypass passage 32 makes it possible to quickly increase the fuel pressure. As described above, in the present embodiment, the fuel pressure can be increased more quickly than in the case of the above-described first embodiment, and the practicality of, for example, an in-cylinder injection engine can be greatly improved.

In the second embodiment, the fuel pressure sensor 18 may be provided to detect a failure as in the case of the first embodiment.

[0061]

As described above in detail, according to the fuel supply system for an internal combustion engine according to the first aspect of the present invention, the fuel supply device is provided between a fuel injection valve provided in the internal combustion engine and a fuel tank.
A fuel supply path for supplying fuel from the fuel tank to the fuel injection valve, a fuel return path for returning the surplus of fuel supplied to the fuel injection valve to the fuel tank again, and a fuel supply path provided in the fuel supply path. A low-pressure fuel pump, a high-pressure fuel pump provided downstream of the low-pressure fuel pump in the fuel supply path, and a fuel pressure discharged from the high-pressure fuel pump disposed in the fuel return path. A high-pressure control means for adjusting the pressure to a set pressure; and a high-pressure control means disposed downstream of the high-pressure control means in the fuel return path.
Low pressure control means for adjusting the pressure to a second set pressure lower than the set pressure, a fuel return path portion between the low pressure fuel pump and the high pressure fuel pump, and a low pressure control means between the high pressure control means and the low pressure control means. With a configuration in which the fuel return path portion and the auxiliary passage connecting the fuel return path portion are provided, even if the discharge flow rate of the high-pressure fuel pump becomes larger than the discharge flow rate of the low-pressure fuel pump, the fuel pressure at the inlet of the high-pressure fuel pump becomes a predetermined pressure The pressure is stably maintained, and the occurrence of cavitation at the inlet of the high-pressure fuel pump is prevented. In addition, the fuel injection can be performed well, the performance of the engine can be improved, and damage to the pump, the fuel passage, and the injection valve can be avoided.

According to the fuel supply device for an internal combustion engine of the present invention described in claim 2, in the structure of claim 1,
A bypass passage is provided for guiding fuel from a fuel return path portion on the upstream side of the high pressure control means to the fuel return path portion on the upstream side of the low pressure control means, bypassing the high pressure control means. By providing a switching valve that selectively opens one of the bypass passages and an on-off valve control unit that controls the switching valve, it is possible to prevent the occurrence of cavitation at the inlet of the high-pressure fuel pump. The same effect as that of the device described in Item 1 can be obtained, and the discharge of the vapor contained in the fuel can be promoted. In this respect, the fuel injection can be appropriately performed, and the performance of the engine is improved. be able to.

According to a third aspect of the present invention, there is provided a fuel supply system for an internal combustion engine according to the second aspect, wherein
When the operation of the high-pressure fuel pump is not sufficient, the on-off valve control means controls the opening of the bypass passage so that the discharge of the vapor in the fuel is prevented even in a situation where the discharge of the vapor in the fuel is difficult. As a result, the fuel injection can be performed properly, and the performance of the engine can be improved.

Further, according to the fuel supply device for an internal combustion engine of the present invention described in claim 4, in the structure of claim 2,
At the start of the engine, the opening / closing valve control means controls to open the bypass passage for a predetermined period immediately after the start of the engine and to open the auxiliary passage after the predetermined period has elapsed. It is possible to promptly discharge the vapor in the fuel and shift to a steady operation state of the engine while maintaining a good fuel injection state. In this steady operation state, it is possible to prevent the occurrence of cavitation at the inlet of the high-pressure fuel pump. Thus, fuel injection can be performed satisfactorily immediately after the start of the engine, the performance of the engine can be improved, and damage to the pump, the fuel passage, and the injection valve can be avoided.

According to a fifth aspect of the present invention, in the fuel supply device for an internal combustion engine according to the first aspect of the present invention, a portion of the fuel supply passage upstream of the high-pressure fuel pump is provided. A high-pressure fuel pump section bypass passage connecting the fuel passage section and the downstream fuel supply path section, and a non-return valve for allowing fuel to pass through the high-pressure fuel pump section bypass passage only from the upstream side to the downstream side of the fuel passage. With the configuration in which the valve is provided, even when the operation of the high-pressure fuel pump is not sufficient, the fuel can be injected at a stable fuel pressure by using the discharge pressure of the low-pressure fuel pump. Can be reliably discharged. Thereby, the performance of the engine can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a fuel supply device for an internal combustion engine as a first embodiment of the present invention.

FIG. 2 is a graph showing output characteristics of a fuel pump of a fuel supply device for an internal combustion engine as a first embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing a fuel supply device for an internal combustion engine as a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing a conventional fuel supply device for an internal combustion engine.

FIG. 5 is a configuration diagram schematically showing a conventional fuel supply device for an internal combustion engine in relation to a main engine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fuel injection valve 2 Fuel tank 3 Fuel passage 3A Fuel supply path (supply path) 3B Fuel return path (return path) 4 Low pressure fuel pump 5 High pressure fuel pump 6 Fuel filter 7 Fuel filter 8 Check valve 9 Low pressure control means Low pressure control valve (low pressure regulator) as high pressure 10 High pressure control valve (high pressure regulator) as high pressure control means 11 First bypass passage (High pressure fuel pump section bypass passage) 12 Check valve 16 Ignition key switch 18 Fuel pressure sensor 19 Accumulator 20 Reverse Stop valve 30 On-off valve control means 31 Auxiliary passage 32 Second bypass passage 33 Electromagnetic three-way valve

──────────────────────────────────────────────────続 き Continued on the front page (72) Nobuaki Murakami, Inventor 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Hideyuki Oda 5-33-8, Shiba, Minato-ku, Tokyo (56) References JP-A-62-237057 (JP, A) JP-A-7-11993 (JP, A) JP-A-2-153253 (JP, A) Jpn. 122146 (JP, U) Japanese Utility Model Hei 5-1854 (JP, U) Japanese Utility Model Hei 4-84761 (JP, U) Japanese Utility Model Hei 5-47430 (JP, U) (58) Fields surveyed (Int. ⁶ , DB name) F02M 37/00

Claims (5)

(57) [Claims] 1. A fuel supply passage provided between a fuel injection valve provided in an internal combustion engine and a fuel tank, for supplying fuel from the fuel tank to the fuel injection valve, and supplied to the fuel injection valve. A fuel return path for returning excess fuel to the fuel tank again, a low-pressure fuel pump provided in the fuel supply path, and a high-pressure fuel pump provided downstream of the low-pressure fuel pump in the fuel supply path. A high-pressure control means disposed in the fuel return path for adjusting the fuel pressure discharged from the high-pressure fuel pump to a first set pressure; and a high-pressure control means disposed in the fuel return path downstream of the high-pressure control means. Low pressure control means for regulating a fuel return path between the disposition position and the high pressure control means to a second set pressure lower than the first set pressure; and the low pressure fuel pump and the high pressure fuel pump. The high pressure control means and the low pressure Characterized in that it includes an auxiliary passage connecting the fuel return passage portions between the control means, a fuel supply system for an internal combustion engine. A bypass passage for bypassing the high pressure control means from the fuel return path portion upstream of the high pressure control means and guiding fuel to the fuel return path portion upstream of the low pressure control means; 2. The switching valve according to claim 1, further comprising: a switching valve that selectively opens one of the auxiliary passage and the bypass passage; and an on-off valve control unit that controls the switching valve. Fuel supply device for internal combustion engines. 3. The fuel supply device for an internal combustion engine according to claim 2, wherein the on-off valve control means controls the opening of the bypass passage when the operation of the high-pressure fuel pump is not sufficient. . 4. The on-off valve control means performs control such that the bypass passage is opened for a predetermined period immediately after the start of the engine, and the auxiliary passage is opened after the predetermined period elapses. The fuel supply device for an internal combustion engine according to claim 2, wherein 5. A high-pressure fuel pump section bypass passage connecting an upstream fuel supply path section and a downstream fuel supply path section of the high-pressure fuel pump is provided. The fuel supply device for an internal combustion engine according to any one of claims 1 to 4, further comprising a check valve for passing fuel only from an upstream side to a downstream side of the fuel passage.