JPH0960565A - Fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable fuel to be injected even when injection starvation of fuel is quick and fuel supplying pressure is low, and also to miniaturize a device. SOLUTION: A pressure control chamber 65 is provided on the opposite nozzle hole side of a control piston 22 to be reciprocated together with a needle valve. An annular clearance 64 is formed between a fuel passage 62 communicated with a high-pressure fuel passage and the pressure control chamber 65 by the outer peripheral wall of the control piston 22 and the inner peripheral wall of an injector body 13. Since fuel is easily allowed to flow in the annular clearance 64 in the high rotation of the engine in which common rail pressure Pc becomes high pressure, quick fuel injection starvation can be realized by facilitating inflow of fuel to the pressure control chamber 65. Moreover, since pressure of the pressure control chamber 65 is to be easily decreased when the common rail pressure Pc is low, fuel can be injected also in the low pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine (hereinafter referred to as "internal combustion engine").
"Internal combustion engine" is referred to as an engine).

[0002]

2. Description of the Related Art Conventionally, JP-A-3-43658, JP-A-3-965, and JP-A-1-257753 are known.
As disclosed in Japanese Unexamined Patent Publication No. JP-A-2003-264, there is known a fuel injection device which adjusts the pressure of a pressure control chamber provided on the side opposite to the injection hole of a needle valve by an electromagnetic valve to control the fuel injection timing and the fuel injection amount. . An example of such a fuel injection device is shown in FIGS. The fuel injection device shown in FIG. 10 and FIG. 11 is a pressure-accumulation fuel injection device that supplies high-pressure fuel, which is pressure-accumulated by a pressure accumulation pipe (hereinafter, “accumulation pipe” is referred to as a common rail) not shown, to the injector.

As shown in FIG. 10, the injector 100
A needle valve 101, a pressure pin 102 and a control piston 103 are housed therein so as to be capable of reciprocating,
The pressure pin 102 is attached to the spring 104 as shown in FIG.
Is urged below. A pressure control chamber 110 is provided on the side opposite to the injection hole of the control piston 103. The high-pressure fuel supplied from the common rail is supplied to the pressure control chamber 110 from the fuel passage 112 through the fuel filter 111 and also to the fuel pool 105 provided on the outer periphery of the needle valve 101. As shown in FIG. 11, a fuel supply throttle hole 113 is provided between the high pressure fuel passage 112 and the pressure control chamber 110, and an opening / closing control is performed by a solenoid valve 120 on the fuel outflow side of the pressure control chamber 110. A fuel outflow throttle hole 114 is provided. Fuel outflow throttle hole 114
Is smaller than the flow resistance of the fuel supply throttle hole 113.

When the electromagnetic coil 123 is de-energized, the valve member 121 of the electromagnetic valve 120 is urged downward in FIG. 10 by the urging force of the spring 122 to close the fuel outflow throttle hole 114. When the solenoid valve 120 is closed, the force that the needle valve 101 receives from the biasing force of the spring 104 and the fuel pressure of the pressure control chamber 110 in the valve closing direction of the needle valve 101 is
Since the force is larger than the force received from the fuel reservoir 105 in the valve opening direction of the needle valve 101, fuel is not injected from the injector 100.

When the electromagnetic coil 123 is energized, the magnetic force generated in the electromagnetic coil 123 causes the valve member 121 to move to the position shown in FIG.
Is lifted above and the pressure control chamber 110 and the low pressure side communicate with each other. When the solenoid valve 120 opens and the high-pressure fuel in the pressure control chamber 110 flows out from the fuel outflow throttle hole 114, the pressure in the pressure control chamber 110 decreases. When the fuel pressure in the pressure control chamber 110 becomes equal to or lower than a predetermined pressure, the needle valve 101 lifts upward in FIG. 10, and fuel is injected from the injector 100.

[0006]

Problems to be Solved by the Invention FIGS.
In the injector 100 as shown, from the common rail
Fuel supply pressure supplied to the injector 100 (hereinafter,
Fuel supply pressure supplied from the common rail to the injector
Force is called common rail pressure) P_CWas reduced
Common rail pressure P_CAnd in the pressure control chamber 110
Pressure P_VThe biasing force of the spring 104 is relative to
Fuel injection from the injector 100
To enable this, the common rail pressure P_CTo drop
Therefore, control room pressure ratio P_V/ P_C(Hereafter, P_V/ P_CTo
kps) is required to be small. That is, Como
Rail pressure P_COf the pressure in the pressure control chamber 110
Power P _VNeeds to be further reduced. For example,
Set load of ring 104 is 60N, control piston 103
The outer diameter of the needle valve 101 is 5 mm, and the maximum outer diameter of the needle valve 101 is 4 mm.
If the seat diameter of the idle valve 101 is 2.25 mm,
Of the control chamber pressure ratio kps that can be injected from the injector 100
The conditions are shown in FIG. As can be seen from FIG.
Pressure P_CControl chamber pressure ratio kps
Should gradually decrease.

As shown in FIGS. 10 and 11, in the case where throttle holes are provided on the fuel inflow side and the fuel outflow side of the pressure control chamber, the flow rate coefficient of the fuel inflow throttle hole 113 is C ₁ , the flow passage area is A _1. , The flow coefficient of the fuel outlet throttle hole 114 is C ₂ , and the flow passage area is A ₂ , the control chamber pressure ratio kps is expressed by the following equation (1).
It is represented by _{kps = (C 1 × A 1} ) 2 / ((C 1 × A 1) 2 + (C 2 × A 2) 2) ··· (1) that is, the fuel inflow throttle hole 113 and the fuel outflow throttle hole 1
If the shape of 14 is determined, the control chamber pressure ratio kps is constant regardless of the common rail pressure P _C. Here, in order to reduce the control chamber pressure ratio kps and enable injection even when the common rail pressure P _C is low, A ₁ should be made smaller than in equation (1), or
It is necessary to increase A ₂ . When A ₂ is increased, that is, the seat area of the valve member 121 is increased, the valve member 12
Since the hydraulic pressure that the valve 1 receives from the pressure control chamber 110 in the valve opening direction increases, it is necessary to increase the biasing force of the spring 122 that biases the valve member 121 in the valve closing direction. Along with this, the electromagnetic coil 12 that attracts the valve member 121 in the valve opening direction
Since 3 needs to be increased, there is a problem that the size of the solenoid valve itself is increased. On the other hand, when A ₁ is reduced, the flow resistance of the fuel supply throttle hole 113 increases, so that the high pressure fuel flows from the high pressure fuel passage 112 to the pressure control chamber 110.
It becomes difficult to flow into. When it becomes difficult for high-pressure fuel to flow into the pressure control chamber 110, the following problems occur.

As one of the demands on the fuel injection device, it is required to quickly cut off the fuel injection for improving the emission. To quickly cut off fuel injection,
Of course, it means that fuel injection is completed within a short time, but when considering the effect on the engine, crank angle is important rather than time, and injection may be completed from the maximum injection state within a small rotation angle range. Desired. Further, in order to inject a predetermined amount of fuel within a predetermined crank rotation angle from the start of injection to the end of injection, it is necessary to end the injection in a shorter time at higher engine speeds, so The higher the engine speed, the higher the common rail pressure. Therefore, it can be said that it is necessary to finish the injection from the maximum injection state in a shorter time as the common rail pressure becomes higher. Here, in order to quickly cut off the fuel injection, it is necessary to increase the valve closing speed of the needle valve 101. To this end, it is necessary to block the fuel outflow throttle hole 114 with the solenoid valve 120 and then quickly supply a large amount of high-pressure fuel from the fuel supply throttle hole 113 to the pressure control chamber 110. In order to supply a large amount of high-pressure fuel to the pressure control chamber 110 from the fuel supply throttle hole 113, the fuel supply throttle hole 11
Since it is preferable that the flow passage area A ₁ of 3 is large, if the flow passage area A ₁ is small, there is a problem that the fuel injection cutoff becomes worse.

The present invention has been made in order to solve such a problem. The fuel can be injected quickly even when the fuel supply pressure is low, and the fuel can be miniaturized. An object is to provide an injection device.

[0010]

[Means for Solving the Problems]

(Solution) A fuel injection device according to claim 1 of the present invention for achieving the above object, supplies high-pressure fuel to an injector provided for each cylinder of an engine, and injects each injector from an injection nozzle of the injector. A fuel injection device for injecting fuel into a combustion chamber, comprising: a high pressure fuel passage capable of supplying high pressure fuel to an injection hole of an injection nozzle; a valve member connecting and disconnecting the injection hole; and a valve member opposite to the injection hole side. A pressure control chamber for urging the valve member in the injection hole blocking direction by the fuel pressure supplied from the high pressure fuel passage and an electromagnetic valve for connecting and disconnecting the low pressure fuel passage, and the pressure control chamber and the low pressure A first throttle hole for limiting the amount of fuel flowing out from the pressure control chamber to the low pressure fuel passage is provided between the fuel passage and the first passage, and the first throttle hole with respect to the differential pressure between the high pressure fuel passage side and the pressure control chamber side is provided. The pressure of the throttle hole A flow rate limiting mechanism is provided in the fuel supply path from the high pressure fuel passage to the pressure control chamber, in which the ratio of the differential pressure between the control chamber side and the low pressure fuel passage side becomes smaller as the fuel pressure in the high pressure fuel passage decreases. A fuel injection device characterized by the above.

The fuel injection device according to claim 2 of the present invention is
2. The fuel injection device according to claim 1, wherein the flow rate limiting mechanism is an annular gap formed by an outer peripheral wall of the valve member and an inner peripheral wall of a cylinder that supports the valve member so as to reciprocate. . The fuel injection device according to claim 3 of the present invention is the fuel injection device according to claim 2, wherein an annular groove is formed in an outer peripheral wall of the valve member or an inner peripheral wall of the cylinder between the high-pressure fuel passage and the annular gap. Is provided.

A fuel injection device according to a fourth aspect of the present invention is
The fuel injection device according to claim 2 or 3, wherein the valve member is formed in a hollow shape in the axial formation range of the annular gap. A fuel injection device according to a fifth aspect of the present invention is the fuel injection device according to the second, third or fourth aspect, wherein the high pressure fuel passage and the pressure control chamber communicate with each other in addition to the annular gap as the flow rate limiting mechanism. It is characterized in that at least one throttle passage is provided.

The fuel injection device according to claim 6 of the present invention is
The fuel injection device according to claim 5, wherein the throttle passage has at least one of a second throttle hole and a throttle groove passage. The fuel injection device according to claim 7 of the present invention is the fuel injection device according to claim 6, wherein the second throttle hole is provided inside the valve member, and the throttle groove passage is an outer peripheral wall of the valve member. Is provided substantially along the axial direction.

A fuel injection device according to claim 8 of the present invention comprises:
The fuel injection device according to claim 4, wherein a hollow portion provided in the valve member communicates with the pressure control chamber, and the high pressure fuel passage communicates with the hollow portion in addition to the annular gap as the flow rate limiting mechanism. A feature is that a second throttle hole is provided. The fuel injection device according to claim 9 of the present invention is the fuel injection device according to any one of claims 1 to 8, wherein:
The high-pressure fuel accumulated in the accumulator pipe is supplied to the injector.

(Operation and Effect of the Invention) According to the fuel injection device of the first or second aspect of the present invention, the amount of fuel flowing from the pressure control chamber to the low pressure fuel passage is controlled between the pressure control chamber and the low pressure fuel passage. A first restricting hole for limiting is provided, and the ratio of the differential pressure between the pressure control chamber side of the first restricting hole and the low pressure fuel passage side to the differential pressure between the high pressure fuel passage side and the pressure control chamber side is A flow rate limiting mechanism that becomes smaller as the fuel pressure decreases is provided in the fuel supply path from the high-pressure fuel passage to the pressure control chamber.

For this reason, as the fuel pressure in the high-pressure fuel passage increases, the fuel easily flows in the flow rate limiting mechanism, so that the pressure in the pressure control chamber rises quickly when the solenoid valve is closed. Then, since the descending speed of the valve member increases, the injection of fuel is quickly cut off, so that harmful substances discharged into the exhaust gas can be reduced. Further, as the fuel pressure in the high pressure fuel passage decreases, the flow passage resistance of the flow rate limiting mechanism increases, so that the fuel pressure is increased even when the fuel pressure in the high pressure fuel passage is low without increasing the flow passage area of the first throttle hole. The fuel pressure in the pressure control chamber decreases to such an extent that the fuel can be injected.

According to the third aspect of the fuel injection device of the present invention, by providing the annular groove in the outer peripheral wall of the valve member or the inner peripheral wall of the cylinder between the high pressure fuel passage and the annular gap,
Since the fuel is uniformly guided in the annular groove and the pressure distribution in the circumferential direction of the annular gap becomes uniform, the eccentricity of the valve member with respect to the cylinder can be prevented. According to the fuel injection device of claim 4 of the present invention, in addition to the configuration of claim 2 or 3, the valve member is formed hollow in the axial formation range of the annular gap, so that the annular gap of the valve member Since the rigidity decreases and the annular gap expands due to the fuel pressure, the flow resistance of the annular gap tends to decrease as the fuel pressure increases. As a result, when the fuel pressure in the high-pressure fuel passage is higher, the fuel quickly flows into the pressure control chamber when the solenoid valve is closed from the open state, so that the fuel injection is quickly stopped.

Further, by changing the diameter or axial length of the space formed in the valve member, the flow path characteristics of the annular gap can be easily adjusted without changing the shape of other members, so that the design is free. The degree improves. Claims 5 to 5 of the present invention
According to the fuel injection device of any one of claims 8 to 8, the high-pressure fuel passage and the pressure control chamber are provided by providing at least one throttle passage that connects the high-pressure fuel passage and the pressure control chamber in addition to the annular gap as the flow rate limiting mechanism. The degree of freedom in design for adjusting the flow path characteristics during the interval is improved.

According to the fuel injection device of the ninth aspect of the present invention, the fuel injection timing and the fuel injection can be controlled with high accuracy by supplying the high-pressure fuel accumulated in the accumulator pipe to the injector.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) A pressure accumulating fuel injection device according to a first embodiment of the present invention is shown in FIGS. The injector 1 of the fuel injection device shown in FIG. 2 is supplied with high-pressure fuel accumulated in a common rail (not shown) through a fuel pipe (not shown).

In the nozzle body 11 of the injection nozzle 10 provided at the lower end of the injector 1, a needle valve 20 for opening and closing the injection hole 11a is reciprocally housed. The nozzle body 11 and the injector body 13 are connected by a retaining nut 14 with the distance piece 12 interposed therebetween. A pressure pin 21 and a control piston 22 that contacts or connects with the pressure pin 21 on the side opposite to the injection hole are provided on the side opposite to the injection hole of the needle valve 20. The pressure pin 21 is inserted into a spring 23, and the spring 23 urges the pressure pin 21 downward in FIG. A pressure control chamber 65 is provided on the side opposite to the injection hole of the control piston 22.

The needle valve 20, the pressure pin 21 and the control piston 22 constitute a valve member for connecting and disconnecting the injection hole 11a and a high pressure fuel passage 61 described later. Further, the nozzle body 11 and the injector body 13 include a needle valve 20, a pressure pin 21, and a control piston 22.
A cylinder that supports the valve member composed of is reciprocally movable.

The high-pressure fuel introduced from the fuel filter 60 into the high-pressure fuel passage 61 is supplied to the fuel pool 24 and the pressure control chamber 65 which are formed in an annular shape around the needle valve 20. The pressure of the high-pressure fuel in the fuel pool 24 biases the needle valve 20 in the lift direction, that is, the opening direction of the injector 1, and the pressure of the high-pressure fuel in the pressure control chamber 65 causes the control piston 22 to move downward in FIG. Energize in the valve closing direction.

The fuel passage 67 is a low pressure fuel passage for collecting leak fuel from the sliding clearance between the control piston 22 and the needle valve 20, and the low pressure fuel passage 32a.
Is in communication with. The solenoid valve 30 is a solenoid two-way valve that connects and disconnects the pressure control chamber 65 and the low-pressure fuel passage 32a. The flat valve seat 31 and the cylinder 32 are connected to the injector body 13 by a retaining nut 33, and the core 34 of the solenoid valve 30 is crimped to the end of the retaining nut 33. A fuel outflow throttle hole 66 as a first throttle hole capable of communicating the pressure control chamber 65 and the low pressure fuel passage 32a is formed in the flat plate valve seat 31. The electromagnetic coil 35 is the core 3
It is wound inside 4 and is supplied with power from the connector 40. Excess fuel in the injector 1 is discharged through the low-pressure fuel passages 32a and 33a, the fuel passage 34a formed in the core 34, and the fuel passage 41a formed in the screw nut 41.

The valve member 36 is supported by the inner wall of the cylinder 32 so as to be capable of reciprocating, and a spherical member 37 is slidably supported at the tip of the valve member 36. The valve member 36 is biased by a spring 39 in a direction to close the fuel outflow throttle hole 66. An armature 38 is fixed to the electromagnetic coil 35 side of the valve member 36. When the electromagnetic coil 35 is energized, the magnetic force generated in the electromagnetic coil 35 causes the valve member 3 to move.
6 is lifted together with the armature 38 against the biasing force of the spring 39, and the spherical member 37 is separated from the flat plate valve seat 31. Then, the pressure control chamber 65 and the low pressure fuel passage 32a communicate with each other through the fuel outflow throttle hole 66.

The fuel passage 62 communicates with the high pressure fuel passage 61, and as shown in FIG. 1, an annular groove 22a is formed in the outer peripheral wall of the control piston 22 facing the fuel passage 62. An annular passage 63 is formed by the annular groove 22a. A predetermined sliding clearance is formed between the outer peripheral wall of the control piston 22 and the inner peripheral wall of the injector body 13, and the annular clearance 63 is formed by this sliding clearance.
An annular gap 64 is formed on the side of the pressure control chamber 65.
Since the seal length due to the sliding clearance is shorter on the pressure control chamber side of the annular passage 63 than on the needle valve side, the high-pressure fuel introduced from the fuel passage 62 into the annular passage 63 passes through the annular passage 63 and the annular gap 64. It is easily introduced into the pressure control chamber 65. Further, by forming the annular passage 63 on the outer wall of the control piston 22, the high-pressure fuel supplied from the fuel passage 62 is uniformly introduced to the outer periphery of the control piston 22, and the control piston 2 with respect to the injector body 13.
2 is prevented from being eccentric.

Next, the operation of the injector 1 will be described. (1) When the energization of the electromagnetic coil 35 is off, the valve member 36 is urged by the flat valve seat 31 by the urging force of the spring 39, and the fuel outflow throttle hole 66 is closed. Therefore, the pressure P _V of the pressure control chamber 65 is equal to the common rail pressure Pc. The force that the needle valve 20 receives upward in FIG. 2 from the pressure in the fuel pool 24 is the sum of the urging force of the spring 23 and the force that the control piston 22 receives downward in FIG. 2 from the pressure in the pressure control chamber 65. Since it is also small, the needle valve 20 closes the injection hole 11a.

(2) When the electromagnetic coil 35 is energized, the armature 38 is attracted upward in FIG. 2 by the magnetic force generated between the armature 38 and the core 34, and the spherical member 37 is lifted together with the valve member 36. Along with this, the fuel outflow throttle hole 66 communicates with the low pressure fuel passage 32a, so that the high pressure fuel in the pressure control chamber 65 flows out from the fuel outflow throttle hole 66 to the low pressure fuel passage 32a. As the high pressure fuel flows out from the pressure control chamber 65 through the fuel outflow throttle hole 66 to the low pressure side, the high pressure fuel flows into the pressure control chamber 65 from the fuel passage 62 through the annular gap 64.

When the solenoid valve 30 is opened, the fuel flow rate Q _Or flowing out through the fuel outflow throttle hole 66 and the annular clearance 64
The fuel flow rate Q _CL flowing from the fuel passage 62 into the pressure control chamber 65 via the is generally expressed by the following equations (2) and (3). Q _or = C ₂ × A ₂ × SQRT ( ₂ × ΔP _or / ρ) (2) C ₂ : Flow coefficient of fuel outflow throttle hole, A ₂ : Flow area of fuel outflow throttle hole ΔP _or : Differential pressure between P _V and low pressure fuel passage (drain pressure ≈ 0) ρ: Fuel density Q _CL = (π × D _P × h ³ × ΔP _CL ) / (12 × μ × L) ... (3 ) D _P : Control piston diameter, h: Annular gap distance μ: Fuel viscosity coefficient, L: Annular gap axial length ΔP _CL : P _C −P _V Q _or is proportional to the square root of the differential pressure ΔP _or , Q _CL is the differential pressure ΔP _CL
Is proportional to When the solenoid valve 30 is opened and the fuel outflow throttle hole 66 and the low pressure fuel passage 32a communicate with each other, Q _or and Q _CL
Is equal to. Further, Q _or and Q _CL increase as the common rail pressure P _C increases. In the first embodiment, P
_{At C} = 150 MPa, ΔP _or : ΔP _CL = 1: 1, Δ
It is set so that P _or / ΔP _CL = 1 and at this time, kps = 0.5. Common rail pressure P _C is 15
If it becomes smaller than 0 MPa and Q _or and Q _CL become 1/4, ΔP _or and ΔP _CL are 1 respectively from equations (2) and (3).
Since it is / 16 and 1/4, the ratio is ΔP _or : ΔP _CL =
1: 4, ΔP _or / ΔP _CL = 1/4. At this time kp
s = 0.2 and P _C = 23.4 MPa. In this way, if the common rail pressure P _C decreases, ΔP _or / ΔP
_{When CL} and the control chamber pressure ratio kps decrease and the common rail pressure P _C increases, ΔP _or / ΔP _CL and the control chamber pressure ratio kps increase.

Kps = 0.5 at P _C = 150 MPa
Common rail pressure P when designed to
The change in the control chamber pressure ratio kps with the level of _C shown in FIG. In FIG. 3, the elastic deformation of the injector body 13 and the control piston 22 due to the high pressure fuel is not taken into consideration. Actually, when the common rail pressure P _C is high, the annular gap interval h is widened by elastic deformation, and when the common rail pressure P _C is lowered, the annular gap interval h is smaller than that under high pressure, so the fuel outlet throttle hole 66 is higher than that under high pressure. The flow path resistance of the annular gap 64 with respect to is increased. For this reason, when the common rail pressure P _C decreases, the pressure in the pressure control chamber 65 is more likely to decrease than when the common rail pressure P _C is high. Further, when the common rail pressure P _C decreases, the annular gap distance h becomes smaller than that at the time of high pressure, so that even if the flow rate in the annular gap 64 becomes 1/4, the differential pressure ΔP _CL of the annular gap 64 does not decrease to 1/4. Therefore, kps becomes smaller than 0.2.

In the first embodiment, an annular gap 64 is provided between the high pressure fuel passage 61 and the pressure control chamber 65, and the pressure control chamber 6
5 and the low pressure fuel passage 32a are provided with the fuel outflow throttle hole 66, the annular gap 64 and the fuel outflow throttle hole 66 are provided.
The control chamber pressure ratio kps decreases as the common rail pressure P _C decreases as shown in FIG. With such a configuration, the common rail pressure P _C, which requires particularly rapid fuel injection cutoff
When the engine is at a high rotation speed where the pressure becomes high, the fuel flows more easily in the pressure control chamber formed in the annular gap than in the fuel inlet side formed in the throttle hole, so that the fuel can easily flow into the pressure control chamber 65. By doing so, it is possible to realize quick fuel injection cutoff.

Further, in the first embodiment, the fuel outflow throttle hole 66
Without increasing the flow passage area, the control chamber pressure ratio kps becomes smaller when the common rail pressure P _C is low than when the common rail pressure P _C is low because of the difference in the flow passage characteristics of the annular gap 64 and the fuel outflow throttle hole 66. The pressure in the chamber 65 is likely to decrease, and fuel can be injected even when the common rail pressure P _C is low. Therefore, the size of the solenoid valve does not increase, and the device can be downsized.

(Second Embodiment) A second embodiment of the present invention is shown in FIG.
Shown in Components substantially the same as those in the first embodiment are denoted by the same reference numerals. An annular groove 70a is formed in the outer peripheral wall of the control piston 70 facing the fuel passage 62, and the annular groove 70a forms an annular passage 63. Further, from the end surface of the control piston 70 on the pressure control chamber 65 side to the annular groove 7
A cylindrical concave portion 70b is formed up to the vicinity of 0a, and a cylindrical hollow portion 71 is formed by this concave portion 70b.

When the pressure control chamber 65 communicates with the low pressure side through the fuel outflow throttle hole 66 when the solenoid valve 30 is energized,
From the fuel passage 62 through the annular gap 64, the pressure control chamber 65
High-pressure fuel flows into. At this time, the rigidity of the control piston 70 is lowered because the hollow portion 71 is formed in the control piston 70, so that the pressure of the high-pressure fuel flowing from the fuel passage 62 increases the degree of elastic deformation of the control piston 70. Therefore, when the high-pressure fuel flows into the annular gap 64 from the fuel passage 62, the annular gap distance becomes larger than that in the first embodiment, and the fuel easily flows into the pressure control chamber 65 from the fuel passage 62. In this case, the fuel injection in is quickly performed.

The relationship between the common rail pressure P _C and the control chamber pressure ratio kps in the second embodiment having such a configuration is shown by the dotted line in FIG. The solid line is the characteristic curve of the first embodiment shown for comparison. In the second embodiment, P _C = 150MP
Since the axial length of the annular gap 64 is made longer than that in the first embodiment so that kps = 0.5 at a, the dotted line is located below the solid line in FIG. Since the characteristic of the dotted line shown in FIG. 5 can be easily adjusted by changing the diameter or depth of the hollow portion 71 formed in the control piston 70 without changing the shape of other members,
The degree of freedom in design is improved.

(Third Embodiment) A third embodiment of the present invention is shown in FIG.
Shown in Components substantially the same as those in the first embodiment are denoted by the same reference numerals. An annular groove 72a is formed in the outer peripheral wall of the control piston 72 facing the fuel passage 62, and the annular groove 72a forms an annular passage 63. In addition, from the end surface of the control piston 72 on the pressure control chamber 65 side to the annular groove 7
A cylindrical concave portion 72b is formed up to the vicinity of 2a, and a cylindrical hollow portion 73 is formed by this concave portion 72b. Further, a fuel supply throttle hole 74 as a second throttle hole that radially penetrates the control piston 72 is formed at the position of the annular groove 72a so as to connect the annular passage 63 and the hollow portion 73 to each other. As a result, when the fuel flows from the pressure control chamber 65 to the low pressure side through the fuel outflow throttle hole 66 when the solenoid valve 30 is energized, not only the annular gap 64 but also the fuel passage 62 through the fuel supply throttle hole 74. High-pressure fuel is supplied to the pressure control chamber 65.

In the third embodiment, the high pressure fuel passage 6
By providing the fuel supply throttle hole 74 in addition to the annular gap 64 as a path for supplying fuel from 2 to the pressure control chamber 65, the characteristics shown in FIG. 7 can be obtained. In FIG. 7, the solid line shows the case where the elastic deformation generated by the hollow portion formed in the control piston 72 is small, and the dotted line shows the case where the elastic deformation effect is large. Both of these are P
_This is the case where the design is such that kps = 0.5 at _C = 150 MPa.

In the third embodiment, the fuel is supplied to the pressure control chamber 65 from the fuel supply throttle hole 74 in addition to the annular gap 64. Therefore, the relationship between the common rail pressure P _C and the control chamber pressure ratio kps is the annular gap and the throttle. It has characteristics that match the characteristics of the holes. That is, as the common rail pressure P _C increases, the control chamber pressure ratio kps also increases. Further, the intersection of the characteristic curve and the kps axis is located at kps> 0 regardless of the effect of elastic deformation. The value of the intersection of this characteristic curve and the kps axis can be expressed by the above-mentioned formula (1) as long as the annular clearance is small and the influence of elastic deformation is negligible.

The third embodiment has a more complicated structure than the first and second embodiments, but the common rail pressure P _C
It is possible to increase the degree of freedom in designing the relationship between the control chamber pressure ratio kps and the control chamber pressure ratio kps. (Fourth Embodiment) FIG. 8 shows a fourth embodiment of the present invention. Second
Components that are substantially the same as those in the embodiment are denoted by the same reference numerals.

In the fourth embodiment, the fuel supply throttle hole provided in the control piston in the third embodiment is replaced by a second throttle hole that directly connects the high pressure fuel passage 61 and the pressure control chamber 65 to the injector body 13. The fuel supply throttle hole 75 is provided. In the fourth embodiment, in addition to the annular gap 64, the fuel supply throttle hole 75 that communicates the high pressure fuel passage 61 and the pressure control chamber 65 is provided, so that the common rail pressure P _C and the control chamber pressure are the same as in the third embodiment. The characteristic curve representing the characteristic with the ratio kps intersects with the kps axis in the range of kps> 0.

(Fifth Embodiment) FIG. 9 shows a fifth embodiment of the present invention.
Shown in Components substantially the same as those in the first embodiment are denoted by the same reference numerals. An annular groove 80a is formed in the outer peripheral wall of the control piston 80 facing the fuel passage 62, and the annular groove 63a is formed by the annular groove 80a. A cylindrical recess 80b is formed from the end surface of the control piston 80 on the pressure control chamber 65 side to the vicinity of the annular groove 80a.
0b forms a cylindrical hollow portion 81. A groove is formed on the outer peripheral wall of the control piston 80 in the axial direction from the annular groove 80a toward the pressure control chamber 65, and a throttle groove passage 82 is formed by this groove. The throttle groove passage 82 communicates the annular passage 63 with the pressure control chamber 65.

In the fifth embodiment, the control piston 80 is used instead of the fuel supply throttle hole formed in the third and fourth embodiments.
Since the throttle groove passage 82 is provided on the outer peripheral wall of the, the characteristic curves are kps axis and kp as in the third and fourth embodiments.
It intersects at the position of s> 0. In the fifth embodiment, a groove is formed in the outer wall of the control piston 80, and the throttle groove passage 82 is formed by this groove. However, in the present invention, a groove is formed in the injector body that is a cylinder to form the throttle groove passage. Is also possible.

In the above-described embodiment of the present invention, the pressure-accumulation type fuel injection device for supplying the high pressure fuel accumulated by the common rail to the injector has been described. In the present invention, the fuel is supplied from the fuel injection pump to the injector without passing through the common rail. It is also possible to apply the configuration of the present invention to the fuel injection device. Further, in this embodiment, the annular groove is provided on the outer wall of the control piston to form the annular passage, but in the present invention, the annular groove may be provided on the inner wall of the injector body to form the annular passage.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main part of a fuel injection device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an injector of the fuel injection device according to the first embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a relationship between a common rail pressure P _C and a control chamber pressure ratio kps in the first embodiment.

FIG. 4 is a sectional view showing a main part of a fuel injection device according to a second embodiment of the present invention.

FIG. 5 is a characteristic diagram showing the relationship between the common rail pressure P _C and the control chamber pressure ratio kps in the second embodiment.

FIG. 6 is a sectional view showing a main part of a fuel injection device according to a third embodiment of the present invention.

FIG. 7 is a characteristic diagram showing the relationship between the common rail pressure P _C and the control chamber pressure ratio kps in the third embodiment.

FIG. 8 is a sectional view showing a main part of a fuel injection device according to a fourth embodiment of the present invention.

9A is a sectional view showing a main part of a fuel injection device according to a fifth embodiment of the present invention, and FIG. 9B is a sectional view of a control piston including the throttle groove passage of FIG. 9A.

FIG. 10 is a cross-sectional view showing a conventional injector.

FIG. 11 is a sectional view showing a main part of an injector according to a conventional example.

FIG. 12: Common rail pressure P _C and control room pressure ratio kps
It is a characteristic view which shows the injection possible area | region in the relationship with.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 injector 10 injection nozzle 11a injection hole 11 nozzle body 13 injector body 20 needle valve (valve member) 21 pressure piston (valve member) 22 control piston (valve member) 30 electromagnetic valve 35 electromagnetic coil 61 high pressure fuel passage 62 fuel passage (high pressure) Fuel passage) 63 Annular passage 64 Annular gap 65 Pressure control chamber 66 Fuel outflow throttle hole (first throttle hole) 71 Hollow part 74, 75 Fuel supply throttle hole (second throttle hole) 82 Throttling groove passage

Claims (9)

[Claims] 1. A fuel injection device for supplying high-pressure fuel to an injector provided for each cylinder of an internal combustion engine, and injecting fuel from an injection nozzle of the injector into a combustion chamber of each cylinder. A valve member for connecting and disconnecting the high pressure fuel passage capable of supplying high pressure fuel to the hole and the injection hole; and a valve member provided on the side opposite to the injection hole of the valve member for supplying fuel pressure from the high pressure fuel passage to the valve member. A pressure control chamber for urging in the injection hole blocking direction and a solenoid valve for connecting and disconnecting the low pressure fuel passage are provided, and the pressure control chamber and the low pressure fuel passage flow out from the pressure control chamber to the low pressure fuel passage. A first throttle hole for limiting the amount of fuel is provided, and a difference between the pressure control chamber side and the low pressure fuel passage side of the first throttle hole with respect to a pressure difference between the high pressure fuel passage side and the pressure control chamber side. The pressure ratio of the high pressure fuel passage is A fuel injection device, wherein a flow rate limiting mechanism that becomes smaller as the fuel pressure decreases is provided in a fuel supply path from the high-pressure fuel passage to the pressure control chamber. 2. The flow rate limiting mechanism is an annular gap formed by an outer peripheral wall of the valve member and an inner peripheral wall of a cylinder that supports the valve member so that the valve member can reciprocate. Fuel injection device. 3. The fuel injection device according to claim 2, wherein an annular groove is provided on an outer peripheral wall of the valve member or an inner peripheral wall of the cylinder between the high-pressure fuel passage and the annular gap. 4. The fuel injection device according to claim 2, wherein the valve member is formed in a hollow shape in the axial formation range of the annular gap. 5. The fuel according to claim 2, 3 or 4, wherein as the flow rate limiting mechanism, at least one throttle passage that connects the high pressure fuel passage and the pressure control chamber is provided in addition to the annular gap. Injection device. 6. The fuel injection device according to claim 5, wherein the throttle passage has at least one of a second throttle hole and a throttle groove passage. 7. The second throttle hole is provided inside the valve member, and the throttle groove passage is provided on an outer peripheral wall of the valve member substantially along the axial direction. Fuel injector. 8. A second throttle hole communicating with a hollow portion provided in the valve member and communicating with the pressure control chamber, and communicating the high pressure fuel passage with the hollow portion in addition to the annular gap as the flow rate limiting mechanism. The fuel injection device according to claim 4, further comprising: 9. The high pressure fuel accumulated in a pressure accumulator pipe is supplied to the injector.
9. The fuel injection device according to claim 8.