JPH09209868A - Fuel supply device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve control precision concerning a fuel supply device of an internal combustion engine favourable as a device to highly precisely control fuel quantity to supply be supplied to the internal combustion engine. SOLUTION: A fuel injection valve 10 to inject fuel is provided in the inside of an internal combustion engine. An accumulator 12 is communicated to the fuel injection valve 10. A pump chamber 50 of a plunger pump 49 is communicated to the accumulater 12. The pump chamber 50 and a fuel supply chamber 30 are communicated to each other through communicating holes 54a, 54b. An outward opening valve 52 to open to the side of the pump chamber 50 in accordance with differential pressure of the pump chamber 50 and the fuel supply chamber 30 is provided. A sensor needle 22 to put the fuel supply chamber 30 and an accumulator 40 in a communicated state in the case when fuel pressure reserved in the accumulator 12 is low in comparison with target pressure and an opening part 28a are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply system for an internal combustion engine, and more particularly to a fuel supply system for an internal combustion engine suitable as a system for controlling the amount of fuel supplied to the internal combustion engine with high accuracy.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Laid-Open No. 4-31167.
As disclosed in No. 0, there is known a fuel injection device in which a fuel injection valve for injecting fuel into an internal combustion engine is connected to a pressure accumulation chamber for accumulating fuel at a predetermined pressure. According to such a device, the amount of fuel injected from the fuel injection valve and the valve opening time of the fuel injection valve can be accurately matched.
Therefore, according to the above conventional device, the amount of fuel supplied to the internal combustion engine can be controlled with high accuracy.

The above-mentioned conventional device is provided with a plunger pump for pressure-feeding fuel to the pressure accumulating chamber, and an electromagnetic spill valve that opens according to the fuel pressure stored in the pressure accumulating chamber.
The plunger pump pumps the fuel at a discharge pressure sufficiently larger than the fuel pressure stored in the pressure accumulating chamber. Further, the electromagnetic spill valve is arranged in a bypass passage that connects the discharge port of the plunger pump and the fuel tank. When the electromagnetic spill valve is open, the fuel discharged from the plunger pump flows into the fuel tank through the bypass passage. In this case, the fuel pressure in the accumulator is not increased. on the other hand,
When the electromagnetic spill valve is closed, the fuel discharged from the plunger pump flows into the pressure accumulating chamber without being bypassed by the fuel tank. In this case, the fuel pressure in the accumulator is increased.

In the above conventional device, the electromagnetic spill valve is controlled so that the pressure in the pressure accumulating chamber becomes a predetermined target pressure. That is, the electromagnetic spill valve is controlled so that the flow rate of the fuel supplied from the plunger pump to the pressure accumulating chamber becomes a flow rate according to the deviation between the fuel pressure in the pressure accumulating chamber and the target pressure. When the electromagnetic spill valve is controlled in this manner, the fuel pressure in the pressure accumulating chamber is always controlled near the target pressure, and highly accurate fuel injection amount control is realized.

[0005]

However, in the above-mentioned conventional device, the plunger pump always pumps fuel with a constant discharge capacity regardless of the fuel pressure in the accumulator. In this case, the plunger pump consumes energy required for returning the fuel to the fuel tank in addition to the energy required for increasing the fuel pressure in the pressure accumulating chamber to the target pressure.
In this respect, the above-mentioned conventional device has a problem that sufficient energy saving is not achieved due to the constant discharge capacity of the plunger pump.

The present invention has been made in view of the above points, and controls the amount of fuel flowing into the pump chamber of the plunger pump to an amount corresponding to the fuel pressure in the pressure accumulating chamber, thereby achieving the above object. It is an object of the present invention to provide a fuel supply device for an internal combustion engine that solves

[0007]

The above object is achieved by the present invention.
A fuel injection valve for injecting fuel into the internal combustion engine, a pressure accumulator chamber for supplying fuel of a predetermined pressure to the fuel injection valve, and a plunger pump for pressure-feeding fuel to the pressure accumulator chamber. In a fuel supply device for an internal combustion engine, comprising: a fuel supply chamber that communicates with a pump chamber of the plunger pump; and an outer valve that opens to the pump chamber side according to a pressure difference between the pump chamber and the fuel supply chamber. And a fuel pressure responsive valve that brings the fuel supply chamber and a fuel supply source into conduction when the fuel pressure stored in the pressure storage chamber is lower than a predetermined pressure. To be done.

In the present invention, the fuel injection valve is communicated with the pressure accumulating chamber. The fuel pressure in the accumulator is reduced by injecting fuel from the fuel injection valve. A plunger pump communicates with the pressure accumulating chamber. The fuel pressure in the accumulator is increased by the fuel being pumped from the plunger pump. A fuel supply chamber communicates with the pump chamber of the plunger pump. The electrical connection between the pump chamber and the fuel supply chamber is controlled by an external valve.

When the plunger of the plunger pump is displaced in the direction of expanding the volume of the pump chamber, the internal pressure of the pump chamber is reduced, so that the outer valve is opened. At this time, if the fuel exists in the fuel supply chamber, the fuel flows from the fuel supply chamber into the pump chamber. When the plunger of the plunger pump is displaced in the direction of reducing the volume of the pump chamber, the internal pressure of the pump chamber is increased, so that the outer valve is closed. At this time, if fuel is present in the pump chamber, the fuel is pumped toward the pressure accumulating chamber.

A fuel supply source communicates with the fuel supply chamber via a fuel pressure responsive valve. When the fuel pressure in the accumulator is lower than the predetermined pressure, the fuel pressure responsive valve opens and fuel is supplied from the fuel supply source to the fuel supply chamber. The fuel supplied to the fuel supply chamber is then supplied to the pressure accumulating chamber by the plunger pump. As a result, the fuel pressure in the accumulator is increased.
On the other hand, when the fuel pressure in the pressure accumulating chamber is not lower than the predetermined pressure, the fuel pressure responsive valve is closed, so that the fuel is not supplied from the fuel supply source to the fuel supplying chamber. In this case, fuel is not unnecessarily pumped from the plunger pump.

[0011]

1 is a system configuration diagram of a fuel supply system for an internal combustion engine according to an embodiment of the present invention. The fuel supply system of this embodiment includes a fuel injection valve 10.
Although the fuel supply device includes a plurality of fuel injection valves 10 corresponding to a plurality of cylinders included in the internal combustion engine, only one fuel injection valve 10 is shown in FIG. 1 for simplicity. The fuel injection valve 10 is an electromagnetic valve that operates according to a drive signal supplied from the outside, and is arranged so that its tip is exposed to the combustion chamber of the internal combustion engine.

A pressure accumulating chamber 12 is communicated with the fuel injection valve 10. The pressure accumulating chamber 12 is a space having a volume V ₀ , and the inside thereof is filled with fuel. In the combustion chamber of an internal combustion engine,
When the fuel injection valve 10 is opened, fuel is injected in an amount according to the pressure of fuel stored in the pressure accumulating chamber 12 (hereinafter referred to as fuel pressure) and the opening time of the fuel injection valve 10.

A discharge amount adjusting mechanism 14 is connected to the pressure accumulating chamber 12. The discharge amount adjusting mechanism 14 includes a fuel pressure introducing member 16. The fuel pressure introducing member 16 is a tubular member having a through hole 16 a whose one end communicates with the pressure accumulating chamber 12. The fuel pressure introducing member 16 is sandwiched between the cap 18 and the upper housing 20.

The upper housing 20 has a through hole 20a at the center thereof. The through hole 20 a communicates with the through hole 16 a of the fuel pressure introducing member 16. Also, the through hole 2
One end of the sensor needle 22 is slidably and slidably inserted into the inside of 0a. The sensor needle 22 is
The upper housing 20 has a through hole 20a, a shaft portion 22a having substantially the same diameter, a disk portion 22b formed in the middle of the shaft portion 22a, and a needle portion 22c formed at the lower end portion of the shaft portion 22a.

A washer 24 is fitted to the shaft portion 22a of the sensor needle 22 so as to engage with the disc portion 22b. A spring 26 is arranged around the shaft portion 22a of the sensor needle 22. One end of the spring 26 abuts the washer 24, and
The other end is in contact with the lower inner housing 28.
The sensor needle 22 is biased upward in FIG. 1 by the biasing force of the spring 26.

The lower inner housing 28 is a tubular member having an opening 28a on the upper side in FIG. Inside the lower inner housing 28, a fuel supply chamber 30 communicating with the opening 28 a is formed. Opening 28a
Has one end tapered so that it can be fitted with the needle portion 22c of the sensor needle 22.

A lower outer housing 32 is disposed outside the lower inner housing 28. Further, the lower outer housing 32 is fitted into a fitting portion 34 a included in the pump housing 34. The position of the lower inner housing 28 is fixed by thus fitting the lower outer housing 32 into the pump housing 34.

The upper housing 20 described above is connected to the lower outer housing 32 via a connecting member 36. The connecting portion 36 is provided when the sensor needle 22 is located at the displacement end on the upper housing 20 side, that is, when the disc portion 22b of the sensor needle 22 is located at the upper housing 2.
0 is in contact with the needle portion 22c of the sensor needle 22 and the through hole 28a of the lower inner housing 28.
The upper housing 20 and the lower outer housing 32 are connected so that a predetermined space is formed between the upper housing 20 and the lower outer housing 32.

A through hole 36a is formed in the side surface of the connecting member 36. One end of a tubular member 38 is fitted in the through hole 36a. The other end of the tubular member 38 is connected to the fuel feed pump 42 via the accumulator 40. The fuel feed pump 42 is a pump that pumps the fuel stored in the fuel tank 44 toward the accumulator 40. In this embodiment, the fuel feed pump 42 pumps the fuel so that the accumulator pressure of about 300 kPa is maintained.

A through hole 34a is formed in the pump housing 34 at a position corresponding to the lower portion of the fuel supply chamber 30. A plunger 46 is inserted in the through hole 34a so as to be liquid-tight and slidable. Also, the through hole 34a
An annular groove 34b is formed in the periphery of the so as to surround the plunger 46. The annular groove 34b communicates with the reservoir tank 48 via a communication passage formed in the pump housing 34. The fuel leaking around the plunger 46 is captured by the annular groove 34b and guided to the reservoir tank 48.

Of the space defined by the through hole 34a of the pump housing 34, the plunger 46 in FIG.
The space formed in the upper part of the above constitutes a pump chamber 50 of the plunger pump 49. The pump chamber 50 communicates with the pressure accumulating chamber 12 via the check valve 51. The check valve 51 is a one-way valve that allows only a fluid flow from the pump chamber 50 to the pressure accumulating chamber 12.

Further, the pump chamber 50 communicates with the fuel supply chamber 30 via the outer opening valve 52. The outer opening valve 52 includes an outer opening valve seat 54 and a valve body 56. The outer opening valve seat 54 is formed with communication holes 54 a and 54 b that communicate the fuel supply chamber 30 and the pump chamber 50. Valve body 56
Is a spring 58 disposed inside the fuel supply chamber 30.
Is urged in a direction to close the communication holes 54a and 54b. The outer open valve 52 is provided in the pump chamber 50 and the fuel supply chamber 3.
When a pressure difference that can resist the urging force of the spring 58 is generated between the valve body 56 and the valve 0, the valve body 56 is displaced toward the pump chamber 50 side to open the valve.

The plunger 46 is provided in the pump housing 34.
The shaft portion 46a that slides inside the through hole 34a and the stepped portion 46b that is formed on the lower end side of the shaft portion 46a in FIG. The plunger 46 is slidable by a plunger locking member 60 that is locked by the stepped portion 46b.
It is fixed to.

The sliding member 62 is a tubular member having a closed end on the lower end side and an open end on the upper end side in FIG. The sliding member 62 is slidably held by a sliding portion holding member 64 arranged below the pump housing 34.
Further, inside the sliding member 62, a spring 66 is provided, one end of which abuts on the pump housing 34 and the other end of which abuts on the latch member 60. The spring 66 is
As the plunger 46 is displaced downward in FIG. 1,
The latch member 60 and the sliding member 62 are urged.

The fuel supply system according to this embodiment has a sliding member 62.
A cam 68 that comes into contact with and rotates. The cam 68 is a member that rotates using the output torque of the internal combustion engine as a drive source, and is connected to the crankshaft. The cam 68 has two cam peaks 68a, which are 180 degrees out of phase with each other.
68b is formed. Therefore, the sliding member 62 causes the pump housing 3 to rotate every time the internal combustion engine rotates 180 ° CA.
It is pressed to the 4 side.

When the sliding member 62 is pushed toward the pump housing side 34 by the cam 68, the plunger 46 is displaced toward the top dead center. When the lift amount of the cam 68 exceeds the maximum value, the plunger 46 then moves to the spring 66.
It is pressed downward in FIG. 1, that is, toward the bottom dead center by the urging force generated by. Therefore, when there is no external force that hinders the sliding of the plunger 46, the plunger 46 reciprocates once between the top dead center and the bottom dead center every 180 ° CA of rotation of the internal combustion engine.

In the fuel supply system of this embodiment, the spring constant of the spring 26 for urging the sensor needle 22 is
The target pressure Pt of the pressure accumulating chamber 12 (12 MPa in this embodiment)
) And the cross-sectional area S of the shaft portion 22a of the sensor needle 22 is set to be substantially equal to the urging force generated by the spring 26. Therefore, the accumulator 1
When the fuel pressure P of 2 is lower than the target pressure Pt,
The force for pressing the sensor needle 22 upward in FIG. 1 is larger than the force for pressing the sensor needle 22 downward in FIG. In this case, the sensor needle 22 is separated from the opening 28a of the lower inner housing 28, and the opening 28a
Becomes conductive. When the opening 28a is in the conductive state,
The fuel fed from the fuel feed pump 42 is introduced into the fuel supply chamber 30. Therefore, in this case, a pressure of about 300 kPa is maintained inside the fuel supply chamber 30.

By the way, in the process in which the plunger 46 moves from the bottom dead center to the top dead center, the internal pressure of the pump chamber 50 is increased. Therefore, in this process, even if the internal pressure of the fuel supply chamber 30 is high, the valve body 56 of the outer opening valve 52 is not opened. On the other hand, in the process in which the plunger 46 moves from the top dead center to the bottom dead center, the internal pressure of the pump chamber 50 becomes negative. Therefore, in this process, when the internal pressure of the fuel supply chamber 30 is high, the valve body 56 of the outer opening valve 52 is opened.

When the valve body 56 of the outer valve 52 is opened with the opening 28a kept open, the communication holes 54a,
The fuel flows into the pump chamber 50 from the fuel supply chamber 30 through 54b, and the same amount of fuel as the inflow amount passes through the opening 28a from the accumulator 40 side to the fuel supply chamber 3.
Flows into zero. The fuel flowing into the pump chamber 50 as described above is pressure-fed toward the pressure accumulating chamber 12 in the process in which the plunger 46 is displaced from the bottom dead center toward the top dead center. As a result, the fuel pressure P in the pressure accumulating chamber 12 is increased toward the target pressure Pt.

In the present embodiment, as described above, the pump chamber 50 is provided from the accumulator 40 side via the fuel supply chamber 30.
When the fuel flows into the chamber, the flow resistance of the fuel is
6 so as not to interfere with the sliding of the communication holes 54a, 5
4b and the opening 28a have a sufficiently large area. Therefore, when the opening 28a is opened, that is, when the fuel pressure P in the pressure accumulating chamber 12 is lower than the target pressure Pt, the plunger 46 is fully closed between the top dead center and the bottom dead center. Is displaced to. At this time, the plunger pump 4
9 discharges fuel to the accumulator 12 with its own maximum discharge capacity.

When the fuel is discharged from the plunger pump 49 toward the pressure accumulating chamber 12 as described above, the fuel pressure P in the pressure accumulating chamber 12 is increased to the target pressure Pt or more. When the fuel pressure P is increased above the target pressure Pt, the force pressing the sensor needle 22 downward in FIG. 1 becomes larger than the force pressing the sensor needle 22 upward in FIG. In this case, the sensor needle 22 is attached to the lower inner housing 2
8 is seated in the opening 28a, and the opening 28a is in a blocked state.

When the opening 28a is closed, the inflow of fuel from the accumulator 40 side to the fuel supply chamber 30 is prohibited thereafter. As described above, the accumulator 40 maintains a pressure of about 300 kPa. Therefore, immediately after the opening 28a is blocked, the fuel supply chamber 3
There is also a fuel pressure of about 300 kPa inside 0. Therefore, in the process in which the plunger 46 is displaced from the top dead center toward the bottom dead center immediately after the opening 28a is blocked, the outer opening valve 5 is opened.
The second valve element 56 is opened.

After the valve body 56 of the outer opening valve 52 is opened as described above, in the course of the displacement of the plunger 46 toward the bottom dead center, the internal pressure of the pump chamber 50 and the fuel supply chamber 30 becomes a negative pressure, and the fuel Flows into the pump chamber 50. The negative pressure in the pump chamber 50 increases as the displacement of the plunger 46 progresses. Therefore, when the spring force of the spring 66 is small, a situation may occur in which the spring force of the spring 46 and the negative pressure are balanced before the plunger 46 reaches the bottom dead center. Under such a condition, the plunger 46 cannot be fully displaced to the bottom dead center even if the valve body 56 of the outer valve 52 is open. In this case, the amount of fuel discharged from the plunger pump 49 when the plunger 46 is subsequently displaced toward the top dead center is smaller than the maximum discharge capacity of the plunger pump 49.

If the opening 28a is still in the closed state after the fuel is slightly discharged from the plunger pump 49 as described above, the internal pressure of the fuel supply chamber 30 is maintained at a negative pressure. In this case, the lift amount of the cam 68 exceeds the maximum value,
Even if the urging force toward the bottom dead center acts on the plunger 46,
The valve body 56 of the outer opening valve 52 no longer opens, and the plunger 46 is maintained near the top dead center. Therefore, thereafter, fuel is not discharged from the plunger pump 49 toward the pressure accumulating chamber 12 until the opening 28a is brought into the conductive state.

In this embodiment, the fuel pressure P in the accumulator chamber 12
Is depressurized each time fuel is injected from each of a plurality of fuel injection valves (hereinafter, the number is n) provided in the internal combustion engine. Assuming that TAUmax is the maximum value of the fuel injected from each fuel injection valve once, the internal combustion engine will generate 720 ° C.
The maximum amount of fuel consumed during A rotation is n · TAUma
It can be represented by x.

On the other hand, the maximum fuel discharge capacity of the plunger pump 49 is designed so that the fuel discharge amount of n · TAU / 4 or more can be obtained by the plunger 46 reciprocating once. Therefore, according to the fuel supply system of the present embodiment, the fuel pressure in the pressure accumulating chamber 12 can be maintained near the target pressure Pt even when the motion state of the internal combustion engine is maintained near the maximum load state. When the motion state of the internal combustion engine is a medium / light load state, the fuel pressure P in the pressure accumulating chamber 12 is maintained near the target pressure Pt without discharging fuel from the plunger pump 49 every 180 ° CA. You can

In the fuel supply system of this embodiment, when the fuel pressure P in the pressure accumulating chamber 12 is equal to or higher than the target pressure Pt, the fuel does not flow into the pump chamber 50, so that the plunger 46 is in the idle state. When the spring force of the spring 66 is small, the discharge of fuel from the plunger pump 49 is suppressed by maintaining the plunger 46 near the top dead center. Thus, if the plunger 46 is maintained near the top dead center, the energy required for the rotation of the cam 68 can be suppressed to an extremely small energy. Therefore,
According to the fuel supply device of the present embodiment, when the fuel pressure P in the pressure accumulating chamber 12 is accurately controlled to the target pressure Pt, the energy required to drive the plunger pump 49 can be minimized.

FIG. 2 shows a system configuration diagram of a fuel supply system for an internal combustion engine which is a second embodiment of the present invention. In FIG. 2, the same parts as those shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In the fuel supply device of this embodiment, the spool valve 70 and the lower inner housing 7 are provided as constituent elements of the discharge amount adjusting mechanism 14.
2 is provided. The spool valve 70 has its upper end inserted in the through hole 20a of the upper housing 20 and its lower end inserted in the through hole 72a of the lower inner housing 72 in a liquid-tight and slidable manner. The spool valve 70 includes a through hole 20a of the upper housing 20 and a through hole 72a of the lower inner housing 72, a shaft portion 70a having substantially the same diameter, and a disc portion 70b formed in the middle of the shaft portion 70a.

The lower inner housing 72 is provided with an opening 72a on the upper side in FIG.
It is a cylindrical member provided with 2c. Fuel introduction holes 72b, 7
2c indicates that when the spool valve 70 is located at the upper displacement end in FIG. 1, the fuel introduction holes 72b, 72c and the opening 20 are completely connected to each other, and the spool valve 70 is at the upper displacement end in FIG. The fuel introduction holes 72b, 72c are designed to be gradually closed by the spool valve 70 as it is displaced downward from the position.

According to the above construction, as the fuel pressure P in the pressure accumulating chamber 12 is lower than the target pressure Pt, the fuel introduction hole 7
2b and 72c largely open inside the opening 72a.
Further, as the fuel pressure P in the pressure accumulating chamber 12 approaches the target pressure Pt, the opening areas of the fuel introduction holes 72b, 72c and the opening 72a are reduced. Therefore, according to the fuel supply device of the present embodiment, the lower the fuel pressure P in the pressure accumulating chamber 12 is compared with the target pressure Pt, the more the fuel flows from the accumulator 40 side into the pump chamber 50 when the fuel flows. Resistance is suppressed small. Further, as the fuel pressure P in the pressure accumulating chamber 12 approaches the target pressure Pt, the flow resistance when the fuel flows into the pump chamber 50 from the accumulator 40 side is significantly changed.

The plunger pump 49 changes the lift amount of the cam 68 from the minimum value to the maximum value of the fuel sucked into the pump chamber 50 while the lift amount of the cam 68 is displaced from the maximum value to the minimum value. In the process, it discharges toward the accumulator 12. Therefore, the fuel discharge capacity of the plunger pump 49 is determined by the amount of fuel sucked into the pump chamber 50 in the process in which the lift amount of the cam 68 is displaced from the maximum value to the minimum value.

In the structure of this embodiment, the amount of fuel sucked into the pump chamber 50 in the process in which the lift amount of the cam 68 is displaced from the maximum value to the minimum value is from the accumulator 40 side to the pump chamber 50. The smaller the flow resistance when the fuel flows, the larger the amount, and the larger the flow resistance, the smaller the amount. Therefore, in the present embodiment, the fuel discharge capacity of the plunger pump 49 increases as the fuel pressure P of the pressure accumulating chamber 12 is lower than the target pressure Pt, while
The fuel pressure P in the pressure accumulating chamber 12 decreases as it approaches the target pressure Pt.

The fuel discharge capacity of the plunger pump 49 is
When the fuel pressure P changes according to the deviation between the target pressure Pt and the fuel pressure P as described above, the fuel pressure P can be more accurately compared to the target pressure Pt as compared with the case where the discharge capacity of the plunger pump 49 is always constant.
Can be controlled to. Therefore, according to the fuel supply system of the present embodiment, the fuel injection amount can be controlled with higher accuracy than the fuel supply system of the first embodiment described above.

In the fuel supply system of this embodiment,
The fuel discharge capacity of the plunger pump 49 is changed by restricting the displacement amount of the plunger 46 from the top dead center toward the bottom dead center. When the amount of displacement of the plunger 46 toward the bottom dead center is suppressed, the energy required to displace the plunger 46 to the top dead center can be suppressed. Therefore, according to the fuel supply system of this embodiment,
In accurately controlling the fuel pressure P in the pressure accumulating chamber 12 to the target pressure Pt, the energy required to drive the plunger pump 49 can be saved to the minimum.

By the way, in the above-mentioned embodiment, the spool valve 70 whose lower end portion is formed in the shape of a plane circle is used. However, by setting the shape of the lower end portion of the spool valve 70 to a predetermined curved surface shape, the pressure accumulation It is possible to further improve the controllability of the fuel pressure P in the chamber 12. Hereinafter, the conditions to be imposed on the spool valve 70 in order to obtain a high degree of controllability regarding the fuel pressure P will be described.

That is, when the fuel pressure P in the pressure accumulating chamber 12 is decreased by ΔP, the pressure accumulating chamber 1 is made up to compensate for the pressure decrease.
The amount of fuel ΔQ to be supplied to 2 can be expressed by the following equation. However, in the following equation, V ₀ and K represent the volume and bulk elastic modulus of the pressure accumulating chamber 12, respectively.

ΔQ = ΔP · V ₀ / K (1) On the other hand, the effective opening area of the fuel introduction holes 72b and 72c is S,
The pressure difference acting on both ends of the fuel introduction holes 72b, 72c is Δ
p, the fuel density is ρ, and the representative value of the time required for the plunger 50 to displace from the top dead center to the bottom dead center is T, the fuel supply chamber 3 passes through the fuel introduction holes 72b and 72c.
The amount Δq of the fuel sucked into 0 can be expressed by the following equation using the adaptation coefficient α.

Δq = α · S · T · √ (2 · Δp / ρ) (2) ΔQ calculated by the above formula (1) and Δq calculated by the above formula (2) are When the amount of fuel supplied from the plunger pump 49 to the pressure accumulating chamber 12 is equal to the amount of fuel required to set the fuel pressure P of the pressure accumulating chamber 12 to the target pressure Pt, the amount becomes equal. Therefore, the above equations (1) and (2)
If the parameters in the equation can be controlled so that ΔQ = Δq holds, the fuel pressure P in the pressure accumulating chamber 12 can be controlled to the target pressure Pt with extremely high accuracy.

In the above equation (1), both V ₀ and K are constants. Further, in the above formula (2), both α and ρ are constants. Therefore, if T and Δp are approximated by a constant in the equation (2), the condition of ΔQ = Δq can be rewritten as the following equation using the constant β.

S = β · ΔP (3) That is, in the fuel supply system of this embodiment, the fuel pressure P = Pt−ΔP acting on the upper end of the spool valve 70.
With respect to the effective opening area S of the fuel introduction holes 72b, 72c
By setting the shape of the lower end of the spool valve 70 and the spring constant of the spring 26 so that the area becomes S = β · ΔP, the fuel pressure P in the pressure accumulating chamber 12 is controlled to the target pressure Pt with extremely high accuracy. It becomes possible to do.

In the first embodiment shown in FIG. 1, the sensor needle 22 is the fuel pressure responsive valve according to claim 1, and in the second embodiment shown in FIG. 2, the needle valve 70 is the same. In the fuel pressure responsive valve according to claim 1, and in the first and second embodiments shown in FIGS. 1 and 2, the fuel feed pump 42 and the accumulator 40 serve as the fuel supply source according to claim 1. , Respectively.

[0052]

As described above, according to the first aspect of the invention, the fuel can be pumped to the plunger pump only when the fuel pressure in the accumulator is lower than the predetermined target pressure. Therefore, according to the fuel supply device for an internal combustion engine of the present invention, it is possible to accurately control the fuel pressure in the accumulator to the target pressure while achieving sufficient energy saving for driving the plunger pump.

[Brief description of drawings]

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

FIG. 2 is a system configuration diagram of a fuel supply device for an internal combustion engine that is a second embodiment of the present invention.

[Explanation of symbols]

 10 Fuel Injection Valve 12 Accumulation Chamber 14 Discharge Adjustment Mechanism 22 Sensor Needle 28, 72 Lower Inner Housing 28a Opening 30 Fuel Supply Chamber 40 Accumulator 42 Fuel Feed Pump 49 Plunger Pump 50 Pump Chamber 52 Outer Valve 70 Needle Valve

Claims (1)

[Claims] 1. A fuel injection valve for injecting fuel into an internal combustion engine, a pressure accumulator chamber for supplying fuel of a predetermined pressure to the fuel injection valve, and a plunger pump for pressure-feeding fuel to the pressure accumulator chamber. A fuel supply device for an internal combustion engine, comprising: a fuel supply chamber that communicates with a pump chamber of the plunger pump; and an outer valve that opens to the pump chamber side in accordance with a pressure difference between the pump chamber and the fuel supply chamber. A fuel pressure responsive valve that brings the fuel supply chamber and the fuel supply source into a conductive state when the fuel pressure stored in the pressure storage chamber is lower than a predetermined pressure. Fuel supply device.