JP3527214B2 - Fuel injection valve - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a fuel injection valve used in a common rail system of a diesel engine.

[0002]

2. Description of the Related Art Conventionally, as a fuel injection system for a diesel engine, a common rail system for accumulating high pressure fuel in a common rail common to each cylinder is known. The fuel injection valve used in the common rail system is, for example,
It has a needle for opening and closing the injection hole, a control chamber for applying back pressure to the needle, and a control valve for increasing or decreasing the pressure in the control chamber. The control chamber communicates with a control valve communicating with the low pressure section and a high pressure fuel passage communicating with the common rail through orifices. When the control valve is driven to open, the pressure in the control chamber decreases and the needle lifts.

As an actuator for driving a control valve, an electrostrictive actuator excellent in responsiveness has recently attracted attention. Further, in order to efficiently transmit the displacement generated by the electrostrictive actuator to the control valve, the displacement of the large-diameter piston directly driven by the electrostrictive actuator is enlarged via hydraulic pressure and abuts on the valve body of the control valve. A fuel injection valve configured to transmit to a small diameter piston has been proposed (for example, US Pat. No. 5,779,149).

[0004]

The above-mentioned conventional technique has an advantage that a large area needle can be driven by opening and closing a small area control valve with a small driving force. However, in this configuration, the driving speed of the needle is
The following problem arises because it is defined by the inflow / outflow velocity of fuel into the control chamber by the orifice. That is, when the injection amount is large, it is preferable to increase the driving speed of the needle, but if the orifice diameter is set in accordance with this, the driving speed of the needle also increases during minute injection, and the controllability of minute injection deteriorates. On the other hand, if the orifice diameter is adjusted to the minute injection, the needle driving speed becomes slow and the injection rate cannot be increased sufficiently.

In view of this, the present invention aims to realize a combustion injection valve which can achieve both high speed driving of the needle at the time of large injection amount and low speed driving of the needle at the time of minute injection, and which is excellent in injection amount controllability. To aim.

[0006]

According to a first aspect of the present invention, there is provided a fuel injection valve comprising: a control chamber that applies a pressure in a valve closing direction to a needle that opens and closes an injection hole; and a space between the control chamber and the low-pressure fuel passage. A control valve that opens and closes to increase or decrease the pressure in the control chamber, and an actuator that drives the control valve to open and lower the pressure in the control chamber to lift the needle are provided. A needle chamber communicating with the high-pressure fuel passage is provided around the upper half of the needle, and a cylindrical needle guide member disposed at the upper end of the needle chamber allows the upper end of the needle to be oil-tight and slidable. And the space surrounded by the needle guide member and the upper end of the needle is used as the control chamber, and the needle is slidably provided on the needle body and the outer periphery of the upper end, and the outer peripheral surface is the needle guide. A stopper member, which is composed of a control area conversion ring that abuts the inner peripheral surface of the member, and which opposes the control area conversion ring at a predetermined interval.

According to the above construction, when the needle is lifted, the needle body and the control area conversion ring are lifted together up to the intermediate lift amount corresponding to the predetermined interval, and thereafter, only the needle body is lifted. To lift.
The lift speed increases as the control area decreases, so that after the intermediate lift amount, the lift speed is higher than before. Therefore, by changing the control area in two steps,
High speed drive of the needle at the time of large injection amount with a large lift amount,
The controllability can be greatly improved by achieving both low speed driving of the needle at the time of minute injection with a small lift amount.

According to a second aspect of the present invention, there is provided a displacement magnifying chamber for increasing / decreasing the pressure according to the displacement of the actuator, and a piston member for lowering the pressure increasing pressure of the displacement magnifying chamber to open the valve body of the control valve. It is preferable to provide since the displacement of the actuator can be effectively enlarged and the lift amount of the control valve can be increased.

According to a third aspect of the present invention, the enlarged diameter portion provided at the upper end of the needle body is projected above the control area conversion ring 12 and brought into contact with the upper surface of the control area conversion ring 12.
As a result, the contact between the needle body and the control area conversion ring can be maintained, and the displacement of the relative position can be reduced.

According to another aspect of the fuel injection valve of the present invention, the needle for opening and closing the injection hole, the displacement magnifying chamber for increasing and decreasing the pressure according to the displacement of the actuator, and the displacement for accommodating the pressure in the displacement magnifying chamber to displace the needle. And a piston member for lifting. Further, the piston member is composed of a piston body and a displacement magnifying power conversion ring slidably provided on an outer periphery of an upper end portion of the piston body, and the piston member is opposed to the displacement magnifying power ring at a predetermined interval in the lift direction. Parts are provided.

In this structure, when the needle is lifted, the piston body and the displacement magnifying ratio ring are lifted together up to an intermediate lift amount corresponding to the predetermined interval. After that, only the piston body is lifted. The lift speed becomes faster as the pressure receiving area of the piston member is smaller, that is, as the displacement enlargement ratio is larger. Therefore, after the intermediate lift amount, the lift speed is higher than before. Therefore, by changing the control area in two steps, high-speed drive of the needle at the time of large injection amount with a large lift amount and low-speed drive of the needle at the time of minute injection with a small lift amount are both achieved, and the controllability is increased. Can be improved.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment to which the present invention is applied will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a fuel injection valve of the present invention, which is preferably used for a common rail injection system of a diesel engine, for example. The fuel injection valve is provided with a second body B2 constituting a control valve 3 in contact with a lower end surface of a first body B1 accommodating the electrostrictive actuator 51, and below the second body B2 via a third body B3. Is provided with a fourth body B4 for housing.

A high-pressure fuel inlet 101 communicating with a common rail (not shown) is opened at the side wall of the first body B1, and the first to first
A high-pressure fuel passage 102 extends in the vertical direction in the third bodies B1 to B3 and is connected to a needle volume 4 as a needle chamber formed in the fourth body B4. The low-pressure fuel passage 104 formed in the first body B1 communicates with a fuel tank (not shown) via the low-pressure fuel outlet 103 on the side wall of the first body B1. The first to fourth bodies B1 to B4 are
The retainer 5 is externally fixed to the outer circumference by being oil-tightly fixed to each other.

A large-diameter piston 52 is slidably arranged in the first body B1 in contact with the lower end surface of the electrostrictive actuator 51. The large-diameter piston 52 is biased upward by a disc spring 531 arranged in the displacement magnifying chamber 53 below and expands / contracts in accordance with an applied voltage.
Displaces together with 1. First body B1 and second body B2
The displacement magnifying chamber 53 formed in the abutting portion of the above converts the displacement of the electrostrictive actuator 51 into a hydraulic pressure and transmits it to the small diameter piston 54 as a piston member sliding in the second body B2. The displacement is enlarged according to the pressure receiving area ratio of the large and small pistons 52 and 54. A low-pressure discharge annular groove 522 for discharging the fuel leaking from the displacement enlargement chamber 53 to the low-pressure fuel passage 104 via the low-pressure discharge passage 523 is formed on the outer periphery of the large-diameter piston 52. An O-ring 521 is provided.

Here, the displacement magnifying chamber 53 has a check valve 7
1 and the intermediate pressure passage 72, it communicates with the intermediate pressure chamber 7 provided at the lower end of the second body B2. Intermediate pressure chamber 7
Communicates with the needle volume 4 through the clearance around the intermediate pressure inlet pin 73, and with the low pressure fuel passage 104 through the clearance around the intermediate pressure outlet pin 74.
A predetermined intermediate pressure is controlled by appropriately setting the clearance around the intermediate pressure inlet pin 73 and the intermediate pressure outlet pin 74. When the oil pressure in the displacement magnifying chamber 53 decreases due to a leak or the like, the check valve 71 opens, and the displacement magnifying chamber 53 is replenished with fuel and maintained at a predetermined intermediate pressure.

The control valve 3 has a valve chamber 31 formed at the lower end of the second body B2, and a substantially spherical valve body 32 arranged in the valve chamber 31 and driven by a small diameter piston 54. There is. A low pressure port 33 opened and closed by the valve element 32 is opened at the center of the top surface of the valve chamber 31, and the low pressure port 33 communicates with an out volume 541 formed around the lower end of the piston 54. When the tip portion of the small-diameter piston 54 penetrates the low pressure port 33 and comes into contact with the valve body 32, and the valve body 32 opens the low pressure port 33, the hydraulic pressure in the valve chamber 31 passes through the out volume 541 and the out passage 542 to generate low pressure fuel. It is adapted to be discharged to the passage 104.

The valve chamber 31 is in constant communication with the control chamber 2 formed at the upper end of the fourth body B4 by the out-orifice 22 provided through the third body B3 and the out-orifice passage 21 continuing from the out-orifice 22. is doing. The out-orifice 22 opens at the outer periphery of the bottom surface of the valve chamber 31, and the control chamber 2
Is formed in the needle volume 4 provided in the fourth body B4, and exerts downward (valve closing direction) hydraulic pressure on the needle 1. An upper half portion of the needle 1 is located inside the needle volume 4, and a lower half portion is slidably inserted into a sliding hole 41 continuous with the needle volume 4. A plurality of injection holes 42 are opened at the tip of the sliding hole 41.

The upper end of the needle 1 is oil-tightly and slidably inserted into a cylindrical needle guide member 6 arranged at the upper end of the needle volume 4. A self-aligning ring 61 is sandwiched between the upper surface of the needle guide member 6 and the lower surface of the third body B3, and is arranged between the spring retainer 62 fixed to the outer periphery of the intermediate portion of the needle 1 and the lower surface of the needle guide member 6. The first spring 63 biases the needle guide member 6 upward, and simultaneously biases the needle 1 downward. The self-aligning ring 61 has a planar upper surface abutting on the lower surface of the third body B3, and a conical surface on the bottom side surface abuts on the upper surface of the needle guide member 6. Therefore, the deviation of the vertical degree between the needle 1 and the lower surface of the third body B3 is caused by the horizontal movement of the self-aligning ring 61,
It is absorbed by the movement of the needle guide member 6 in the rotation direction. In addition, the biasing force of the first spring 63 provides an oil-tight seal between the self-aligning ring 61, the needle guide member 6, and the third body B3.

The needle 1 comprises a needle body 11 and a control area conversion ring 12 slidably provided on the outer circumference of the upper end portion thereof. The outer peripheral surface of the control area conversion ring 12 slidably contacts the inner peripheral surface of the needle guide member 6. In the needle body 11, the enlarged diameter portion 13 at the upper end projects above the control area conversion ring 12, and the control area conversion ring 1
2 is in contact with the upper surface. A second spring 64 is disposed between the lower surface of the control area conversion ring 12 and the spring retainer 62 to bias the control area conversion ring 12 in a concession.

Here, although it is not always necessary to provide the second spring 64, there is an advantage that the control area conversion ring 12 is brought into close contact with the needle body 11 to reduce the loss at the start of the lift. Further, a flange portion projecting inward may be provided on the lower end edge of the needle guide member 6 to serve as a stopper portion that restricts the downward movement of the control area conversion ring 12.

The self-aligning ring 61 also serves as a stopper portion for restricting the upward movement of the control area conversion ring 12, and the lower surface of the self-aligning ring 61 serves as a stopper surface 65, which serves as the control area conversion ring 12. And the upper surface of the substrate 1 at a predetermined distance L. Therefore, the needle 1 lifts together with the needle body 11 and the control area conversion ring 12 up to the intermediate lift amount corresponding to the predetermined interval L, but when the control area conversion ring 12 abuts the stopper surface 65, thereafter Only the needle body 11 lifts. Thus, the lift speed of the needle 1 can be made variable by changing the control area in two steps. This will be described later.

Here, by the space surrounded by the needle 1, the needle guide member 6 and the self-aligning ring 61,
A control room 2 is formed. An in-orifice 24 is opened on the top surface of the control chamber 2, and communicates with the high-pressure fuel passage 102 via an in-orifice passage 23 continuous with the in-orifice 24. These in-orifice 24 and in-orifice passage 23
Is provided on the third body B3. The hydraulic pressure in the control chamber 2 increases and decreases as the control valve 3 opens and closes. When the hydraulic pressure in the control chamber 2 decreases and the needle 1 lifts, the needle volume 4 and the injection hole 42 communicate with each other through a gap around the needle 1. Then, high-pressure fuel is injected.

Next, the operation of the fuel injection valve 1 having the above structure will be described. FIG. 2B shows an electrostrictive actuator 51.
2 shows the relationship between the pressure change in the control chamber 2 and the lift amount of the needle body 11 and the control area conversion ring 12 when the actuator is driven, and a to c in FIG. 2A are a to c in FIG. The state of each part at point c is shown. In the initial state where the electrostrictive actuator 51 is not energized, the valve body 32 of the control valve 3 closes the low pressure port 33, so that the valve chamber 3 is closed.
1 and the control chamber 2 are maintained at the feed pressure by the high pressure fuel supplied from the high pressure fuel passage 102. At this time, the oil pressure of the control chamber 2 and the spring force of the spring 63 act downward on the needle 1, and the injection hole 11 is closed by overcoming the oil pressure of the needle volume 4 acting upward.

From this initial state, the electrostrictive actuator 5
When a predetermined drive voltage is applied to 1 (time 1 in FIG. 2B), the electrostrictive actuator 51 extends and the large-diameter piston 52 is displaced downward. Along with this, the pressure in the displacement magnifying chamber 53 rises, the small diameter piston 54 and the valve element 32 descend, the low pressure port 33 is opened, and the valve chamber 31 communicates with the out volume 541 reaching the low pressure fuel passage 104. . As a result, the pressure in the control chamber 2 decreases, and the needle 1
When the force acting downwards on the needle 1 becomes smaller than the force acting upwards on the needle 1, the needle body 11 starts to lift together with the control area conversion ring 12 (time 2 in FIG. 2B).

Due to the lift of the needle 1, the pressure in the control chamber 2 rises again, and when the lift speed of the needle 1 reaches a certain constant speed, the fuel flowing in and out of the control chamber 2 is balanced, and the pressure in the control chamber 2 increases. Is maintained at a constant pressure lower than the feed pressure (time 3 to 4 in FIG. 2B). During this time,
Like a in (A), the needle body 11 and the control area conversion ring 12 slide integrally, and the lift speed of the needle 1 becomes relatively low.

When the lift amount of the needle 1 reaches an intermediate lift amount corresponding to the distance L between the stopper surface 65 and the control area conversion ring 12 in the initial state, the control area conversion ring 12 is moved as shown by b in FIG. 2 (A). Comes into contact with the stopper surface 65 and the lift stops (time 4 in FIG. 2B). This is because the area of the control area conversion ring 12 that receives the oil pressure of the needle volume 4 decreases and the force that acts upward on the needle 1 decreases, so that even if the oil pressure in the control chamber 2 decreases, the needle 1 It is not displaced for a while and is held at the intermediate lift amount (time 4 to 5 in FIG. 2B).

When the pressure in the control chamber 2 drops to a certain pressure, the needle 1 lifts again (time 5 in FIG. 2B), but the displacement of the control area conversion ring 12 causes the stopper surface 6 to move.
Since it is regulated by 5, only the needle body 11 is lifted. That is, since the area that receives the hydraulic pressure is small, the lift speed of the needle 1 is higher than when the hydraulic pressure is applied to a large area including the control area conversion ring 12, as indicated by c in FIG. At this time, the pressure in the control chamber 2 is maintained at a constant pressure lower than that in the state of a in FIG. When the needle 1 main body 11 comes into contact with the top surface of the control chamber 2, the lift stops and the pressure in the control chamber 2 drops again (time 6 in FIG. 2B).

In this way, by changing the control area in two steps, when the lift of the needle 1 is small (during minute injection), the control area is increased (needle body 11).
The control area conversion ring 12) and the lift speed of the needle 1 can be reduced. On the other hand, when the lift of the needle 1 is large (when the injection amount is large), the control area can be reduced (only the needle body 11) and the lift speed of the needle 1 can be increased. Therefore, in-orifice 2
4. Even if the diameter of the out-orifice 22 is constant and the inflow / outflow speed of the fuel in the control chamber 2 is constant, it is possible to achieve both low speed driving at the time of minute injection and high speed driving at the time of large injection amount.

FIG. 3 shows a second embodiment of the present invention. In the present embodiment, the control valve 3 is not provided, and the fuel pressure of the system in which the needle 1 is directly driven by the hydraulic pressure of the displacement magnifying chamber 53 is used. In the valve, a configuration for varying the needle drive speed according to the injection amount is shown. In FIG. 3, members having the same functions as those of the respective constituent members of the fuel injection valve of FIG. 1 are designated by the same reference numerals, and the differences from the first embodiment will be mainly described below. . In the present embodiment, the fuel injection valve includes a second body B2 housing the balance piston 8 and a small diameter piston 54 below the first body B1 housing the electrostrictive actuator 51 and the large diameter piston 52.
A third body B3 for accommodating the needle, a fourth body B4 in which a spring chamber 65 is formed, and a fifth body B55 for accommodating the needle 1.

The needle 1 is slidably accommodated in the fifth body B5, and the upper end of the needle 1 is at the fourth body B5.
4 extends into the spring chamber 65. Spring chamber 6
5, a spring 63 is provided between the spring retainer 62 fixed to the upper end of the needle 1 and the top surface of the spring chamber 65, which communicates with the low pressure fuel passage 104, and urges the needle 1 downward. Further, the tip (lower end) of the small-diameter piston main body 54 housed in the third body B3 extends into the spring chamber 65, and the spring retainer 6 at the upper end of the needle 1 is held.
It is in contact with 2. A fuel reservoir 43 communicating with the high-pressure fuel passage 102 is formed around the middle portion of the needle 1.

Above the small diameter piston 54, the second body B
The balance piston 8 is slidably arranged in
The small-diameter tip of the balance piston 8 is in contact with the upper surface of the small-diameter piston 54. A space above the balance piston 8 serves as a balance pressure chamber 81 that communicates with the high-pressure fuel passage 102 via the balance pressure introduction passage 82, and downward oil pressure is applied to the small diameter piston 54 and the needle 1 via the balance piston 8. It is working. here,
The diameter of the balance piston 8 may be the same as or slightly larger than the diameter of the sliding portion of the needle 1 so as to be almost balanced with the upward hydraulic pressure acting on the needle 1 when the valve is opened.

Below the balance piston 8, an intermediate pressure chamber 7 is formed at the abutting portion of the second and third bodies B2, B3. The fuel flows into the intermediate pressure chamber 7 from the balance pressure chamber 81 through the clearance around the balance piston 8, and the fuel flows out to the low pressure fuel passage 104 through the clearance around the intermediate pressure outlet pin 74. By setting the clearance around the balance piston 8 and the intermediate pressure outlet pin 74 appropriately, a predetermined intermediate pressure is maintained.

In the present embodiment, the small diameter piston 54 is
The piston main body 54a for driving the needle 1 and the displacement magnifying power conversion ring 54b slidably provided on the outer circumference of the large diameter portion 54c at the upper end thereof. The space below the displacement magnification conversion ring 54b is a second displacement magnifying chamber 56,
The displacement magnifying chamber communication passage 55 formed in the second and third bodies B2 and B3 communicates with the displacement magnifying chamber 53 at the lower end of the first body B1. Therefore, the second displacement magnifying chamber 56 includes the check valve 71 and the displacement magnifying chamber 5 from the intermediate pressure chamber 7.
Fuel whose pressure is controlled to a predetermined intermediate pressure is introduced via 3 to apply upward hydraulic pressure to the small diameter piston 54. The flange 5 that abuts the lower surface of the large-diameter portion 54c of the piston body 54a is provided at the lower end edge of the displacement magnification conversion ring 54b.
4d is provided, and a disc spring 561 provided in the second displacement magnifying chamber 56 urges the displacement magnifying power conversion ring 54b upward.

The small diameter piston 54 has a second displacement magnifying chamber 56.
The pressure rises and the needle 1 is lifted. Here, the upper surface of the displacement magnifying power conversion ring 54b and the lower surface of the second body B2 serving as the stopper surface 83 are separated by a predetermined distance L.
Are opposed to each other, and thus, up to a predetermined distance L,
The piston body 54a of the small-diameter piston 54 and the displacement magnifying power conversion ring 54b lift together, but when the displacement magnifying power conversion ring 54b contacts the stopper surface 83, only the piston body 54a thereafter lifts. As described above, in the present embodiment, the lift speed of the needle 1 is made variable by changing the displacement magnification rate by the small diameter piston main body 54 in two steps.

FIG. 4B shows the relationship between the pressure change in the second displacement magnifying chamber 56 and the lift amount of the piston body 54a and the displacement magnifying power conversion ring 54b when the electrostrictive actuator 51 is driven. Parts (a) to (c) of FIG. 4B show the states of the respective parts at points a to c. In the initial state where the electrostrictive actuator 51 is not energized, the displacement magnifying chamber 53 and the second displacement magnifying chamber 56 are kept at a predetermined intermediate pressure, and the intermediate pressure chamber 7 and the balance pressure chamber 81 acting downward on the needle 1 are held. Oil pressure and spring 6
The spring force of 3 exceeds the hydraulic pressure of the second displacement magnifying chamber 56 and the fuel sump 43 that act upward on the needle 1,
The injection hole 11 is closed.

From this initial state, the electrostrictive actuator 5
When a predetermined drive voltage is applied to No. 1 (time 1 in FIG. 4 (B)), the electrostrictive actuator 51 expands and the large-diameter piston 52 displaces downward, and along with this, the displacement magnifying chamber 53 and the second displacement. The pressure in the expansion chamber 56 rises. When the pressure in the second displacement magnifying chamber 56 reaches a predetermined pressure, the force acting downward on the needle 1 becomes less than the force acting upward, and the small diameter piston 54 starts to lift. (Time 2 in FIG. 4B). At this time, as shown in a of FIG. 4A, the piston main body 54a and the displacement magnifying power conversion ring 54b lift together, so that the lift speeds of the small diameter piston 54 and the needle 1 become relatively low. The pressure in the second displacement magnifying chamber 56 is maintained at a constant pressure.

When the displacement magnification conversion ring 54b comes into contact with the stopper surface 83 as shown in FIG. 4 (b), the lift of the small diameter piston 54 and the needle 1 is stopped (FIG. 4).
(B) time 3). This is because the area of the small-diameter piston 54 that receives the oil pressure in the displacement magnifying chamber 56 decreases, and the force that acts upward on the small-diameter piston 54 decreases. 54 does not displace, and the needle 1 is held with an intermediate lift amount corresponding to the distance L between the displacement magnification conversion ring 54b and the stopper surface 83.

When the hydraulic pressure in the displacement magnifying chamber 56 rises sufficiently,
Although the small-diameter piston 54 and the needle 1 start to lift again, the displacement of the displacement magnifying power conversion ring 54b is restricted by the stopper surface 83 as shown in c of FIG. 4A, so that only the piston body 54a is lifted. become. That is, since the area of the displacement magnifying chamber 56 which receives the hydraulic pressure becomes small, the lift speed of the small diameter piston 54 and the needle 1 becomes faster than when the hydraulic pressure is applied to a large area including the displacement magnifying rate conversion ring 54b. At this time, the pressure in the second displacement magnifying chamber 56 is maintained at a constant pressure higher than that in the state of a in FIG.

When the balance piston 8 above the piston body 54a comes into contact with the top surface of the balance pressure chamber 81, the lift of the small diameter piston 54 and the needle 1 is stopped, and the hydraulic pressure in the displacement enlargement chamber 56 rises again. Thus, in the present embodiment, when the lift of the needle 1, that is, the small diameter piston 54 is small (during minute injection), the piston main body 54
a and the displacement enlargement ratio conversion ring 54b have large areas,
The displacement expansion rate is reduced by receiving the hydraulic pressure of the displacement expansion chamber 56,
The moving speed of the needle 1 can be reduced. On the other hand, when the lift of the needle 1, that is, the small-diameter piston 54 is large (at the time of large injection amount), the displacement enlargement ratio is increased by receiving the hydraulic pressure of the displacement enlargement chamber 56 in a small area of only the piston main body 54a. The moving speed of the needle 1 can be increased. Thus, by changing the displacement enlargement ratio of the small-diameter piston 54 in two steps, the needle 1 at the time of minute injection
It is possible to achieve both low speed driving and high speed driving of the needle 1 at the time of a large injection amount.

[Brief description of drawings]

FIG. 1 is an overall sectional view of a fuel injection valve according to a first embodiment of the present invention.

FIG. 2A is a sectional view of a main part of a fuel injection valve for explaining the operation of the first embodiment, and FIG. 2A is a control chamber pressure and control area conversion in the configuration of the first embodiment. It is a figure which shows the relationship of the lift amount of a ring and a needle main body.

FIG. 3 is an overall sectional view of a fuel injection valve according to a second embodiment of the present invention.

FIG. 4A is a sectional view of a main part of a fuel injection valve for explaining the operation of the second embodiment, and FIG. 4A is a displacement magnifying chamber pressure and displacement magnification in the configuration of the second embodiment. It is a figure which shows the relationship of the lift amount of a rate conversion ring and a piston main body.

[Explanation of symbols]

B1-B5 body 1 needle 11 Needle body 12 Control area conversion ring 13 Expanded part 2 control room 21 Out orifice passage 22 Out orifice 23 In-orifice passage 24 in orifice 3 control valve 31 valve chamber 32 valve 33 Low pressure port 4 Needle volume (needle chamber) 41 Sliding hole 42 injection holes 43 Fuel pool 51 Electrostrictive Actuator 52 Large piston 53 Displacement magnifying chamber 54 Small diameter piston (piston member) 54a Piston body 54b Displacement magnification conversion ring 54c Large diameter part 54d flange 55 Displacement magnifying chamber communication passage 56 Second displacement magnifying chamber 6 Needle guide member 61 Self-aligning ring 62 Spring holder 63, 64 spring 7 Intermediate pressure chamber 8 balance pistons 81 Balance pressure chamber 101 High pressure fuel inlet 102 high-pressure fuel passage 103 Low pressure fuel outlet 104 low-pressure fuel passage (low-pressure passage)

Front page continued (72) Inventor Kenji Oshima 14 Iwatani, Shimohakaku-cho, Nishio-shi, Aichi Japan Auto Parts Research Institute, Inc. (72) Inventor Masaaki Kato 1-1, Showa-cho, Kariya, Aichi Stock Company Denso ( 72) Inventor Yoshimasa Watanabe 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (56) Reference Japanese Patent Laid-Open No. 11-82221 (JP, A) US Patent 5779149 (US, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02M 47/00 F02M 47/02 F02M 61/10

Claims (4)

(57) [Claims] 1. A control chamber that applies a pressure in a valve closing direction to a needle that opens and closes an injection hole, and a control valve that opens and closes between the control chamber and a low-pressure fuel passage to increase or decrease the pressure in the control chamber.
In a fuel injection valve comprising an actuator that lifts the needle by lowering the pressure in the control chamber by driving the control valve to open, a needle chamber communicating with a high-pressure fuel passage is provided around the upper half of the needle. An upper end of the needle is oil-tightly and slidably inserted into a cylindrical needle guide member provided at the upper end of the needle chamber, and is surrounded by the needle guide member and the upper end of the needle. With the space as the control chamber, the needle is constituted by a needle body and a control area conversion ring slidably provided on the outer periphery of the upper end portion thereof and the outer peripheral surface of which abuts the inner peripheral surface of the needle guide member, Further, a stopper portion is provided above the control area conversion ring at a predetermined interval so as to be opposed to the control area conversion ring, and the stopper portion corresponding to the predetermined interval is provided when the needle is lifted. Until the lift amount is a lift the needle body and the control area conversion ring integrally, the fuel injection valve, characterized in that since it was to only the needle body is lifted. 2. A displacement magnifying chamber for increasing / decreasing a pressure according to a displacement of the actuator, and a piston member for lowering to open the valve body of the control valve as the pressure in the displacement magnifying chamber increases. The fuel injection valve described. 3. The fuel injection valve according to claim 1 or 2, wherein the upper end of the needle body is a diameter-expanded portion that protrudes from the upper surface of the control area conversion ring and increases in diameter stepwise. 4. A needle which opens and closes an injection hole, a displacement magnifying chamber which increases and decreases the pressure according to the displacement of an actuator, and a piston member which displaces as the pressure of the displacement magnifying chamber increases to lift the needle. In the fuel injection valve, the piston member is composed of a piston body and a displacement magnifying power conversion ring slidably provided on an outer periphery of an upper end portion thereof, and a predetermined space is provided in a lift direction of the displacement magnifying power ring. When the needle is lifted, the piston body and the displacement magnifying ring are integrally lifted up to an intermediate lift amount corresponding to the predetermined interval when the needle is lifted, and thereafter only the piston body is lifted. The fuel injection valve is characterized in that