JP4211727B2 - Fuel injection valve - Google Patents

Description

  The present invention relates to a fuel injection valve.

  2. Description of the Related Art Conventionally, for example, in a fuel injection valve that injects fuel into a cylinder of a diesel engine, there is one that includes two needles and performs variable injection injection that changes the injection hole area according to the needle lift (see Patent Document 1). .

In the technique disclosed in Patent Document 1, two needles arranged in an inner and outer double, a conical valve seat shared by these needles, and a valve seat are formed on each needle (first needle, second needle). And the first nozzle hole and the second nozzle hole corresponding to each other), and the nozzle hole area is made variable by opening and closing the first nozzle hole and the second nozzle hole according to the needle lift. More specifically, there is one control chamber for applying pressure in the valve closing (sitting) direction to these needles, and the needles are controlled to open and close by the pressure receiving area. In order to suppress fuel leakage between the needles, the inner needle is slidably disposed on the inner periphery of the outer needle. The volume surrounded by the so-called abutment between each needle and the valve seat is relatively small.
WO03 / 069511

  In the prior art disclosed in Patent Document 1, since the volume surrounded by the contact portions of the needles and the valve seat is formed to be relatively small, the second needle is also applied to the second needle almost simultaneously with the opening of the first needle. There is a possibility that the receiving pressure for lifting the two needles may be instantaneously applied. In some cases, if the second needle opens without time delay at the same time as the opening of the first needle, it is aimed to inject from the first nozzle hole and the second nozzle hole with a time difference. This makes it impossible to perform variable injection injection as intended.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a needle having a double-arranged needle and an injection hole that is opened and closed corresponding to each needle. An object of the present invention is to provide a fuel injection valve that can be opened with a predetermined time difference between the needle and the second needle.

  In order to achieve the above object, the present invention comprises the following technical means.

That is, in the first and second aspects of the invention, the inner needle and the outer needle, which are doubly arranged inside and outside, and the inner needle and the outer needle are accommodated so as to reciprocate, and the inner needle and the outer needle are separated and seated. And a nozzle body having a nozzle hole formed in the valve seat, the inner needle is reciprocally accommodated on the inner periphery of the outer needle, and both needles are located on the valve seat side with respect to the valve seat. In a fuel injection valve that receives high-pressure fuel pressure from the end and separates independently, the end on the valve seat side is provided between the inner periphery of the outer needle and the outer periphery of the inner needle, and opens the outer needle. After the valve, a volume is formed that delays the increase in fuel pressure when high pressure fuel flows in and lifts the inner needle ,
The inner needle has a large-diameter shaft portion slidable on the inner periphery, and the volume portion extends toward the valve seat side of the large-diameter shaft portion and has a radial step with respect to the large-diameter shaft portion. Of the outer diameter (d) at a portion having a radial step with respect to the outer diameter (D) of the large-diameter shaft portion at the outer diameter of the inner needle. The outer diameter ratio (d / D) is set in the range of 0.67 to 0.93,
The valve seat has a substantially conical inner valve seat corresponding to the inner needle and a substantially conical outer valve seat corresponding to the outer needle. The inner valve seat and the outer valve seat are seats of the inner valve seat. The angle difference (θb−θa) between the seat angle (θb) of the outer valve seat and the seat angle (θa) of the inner valve seat is 30 ° to 80 °. It is characterized by being set to a range .

  According to this, the fuel injection in which the inner needle is accommodated in the inner periphery of the outer needle so as to be able to reciprocate, and both needles receive high pressure fuel pressure from the valve seat side end to the valve seat and are separated independently. In the valve, the end on the valve seat side is provided between the inner periphery of the outer needle and the outer periphery of the inner needle, and when the high pressure fuel flows after the outer needle opens, the inner needle is lifted. Since a volume portion that delays the increase in fuel pressure is formed, it is between the inner circumference of the outer needle and the inner circumference of the inner needle as compared with the volume surrounded by the contact portion of each needle and the valve seat. It is possible to make the volume relatively large. Therefore, since the volume can be formed relatively large, a predetermined time difference can be provided between the valve opening timing of the outer needle and the valve opening timing of the inner needle.

In the invention described in claim 1, the inner side needle has a slidable large diameter portion in a circumferential within said volume portion is extended toward the valve seat side of the large diameter portion, the large It is characterized in Tei Rukoto formed to be the fuel filled between the inner periphery having a radially stepped with respect to diameter shaft portion.

  As a result, the volume portion extends toward the valve seat side of the large-diameter shaft portion of the inner needle that can slide on the inner periphery of the outer needle, and has a radial step with respect to the large-diameter shaft portion. Since the fuel is formed between the inner periphery of the outer needle and the inner periphery of the outer needle, the inner periphery of the outer needle and the inner needle of the inner needle are compared with the volume surrounded by the contact portion of each needle and the valve seat. The volume can be made relatively large according to the size of the radial step formed by the radial step.

In the first aspect of the present invention, the valve seat has a substantially conical inner valve seat corresponding to the inner needle, and a substantially conical outer valve seat corresponding to the outer needle. The outer valve seat is formed by changing the seat angle of the inner valve seat and the seat angle of the outer valve seat.

  According to this, as a method of enlarging the volume surrounded by the so-called abutting portions of each needle and the valve seat, the valve seat corresponds to the substantially conical inner valve seat corresponding to the inner needle and the outer needle. The inner valve seat and the outer valve seat are formed by changing the seat angle of the inner valve seat and the seat angle of the outer valve seat. Therefore, the volume can be increased by changing the shape of the valve seat side that forms the volume, compared to the substantially conical valve seat shared by the needles of the prior art.

  Note that the seat angle is an angle between tapered surfaces formed on a conical surface when the valve seat is formed in a conical shape, for example, an opening degree of the valve seat surface.

In the invention according to claim 2 , the valve seat has an inner seal portion where the inner needle is separated and seated, and an outer seal portion where the outer needle is separated and seated. The valve seat part between the inner seal part and the outer seal part is characterized by being formed in a concave shape in a direction away from the inner needle and the outer needle.

According to this, in the valve seat, when the valve seat shape between the valve seat side corresponding to the inner needle and the valve seat side corresponding to the outer needle is formed in a shape other than a substantially conical shape, Of these, the valve seat portion between the inner seal portion and the outer seal portion is preferably formed in a concave shape in the direction away from the inner needle and the outer needle. Thereby, it is possible to effectively expand the volume.
Moreover, in invention of Claim 3, it has the specific nozzle hole always connected to a volume part among the said nozzle holes, It is characterized by the above-mentioned.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments in which a fuel injection valve of the present invention is embodied will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a partial cross-sectional view showing a main part of a valve portion related to the fuel injection valve of the present embodiment. FIG. 2 is a schematic cross-sectional view showing an example of the fuel injection valve of the present embodiment. FIG. 3 is a graph showing the relationship between the pressure applied to the volume portion surrounded by the contact portions of the needles and the valve seat in FIG. 1 and the valve opening timing of the needles.

  A fuel injection valve 1 shown in FIG. 2 is inserted and mounted in a cylinder head of an engine (not shown), and is configured to inject directly into each cylinder of the engine. Specifically, the fuel injection valve 1 has a substantially cylindrical shape, receives fuel from a fuel introduction portion (not shown) (in the direction of the arrow indicating fuel inflow in the figure), and injects fuel from the tip via an internal fuel passage. The fuel injection valve 1 includes a valve portion that blocks and allows fuel injection, and an electromagnetic drive portion that drives the valve portion. The fuel that flows into the fuel passage from the fuel introduction portion is supplied to the cylinder of the engine from the valve portion. Supply to the jet.

  Note that high-pressure fuel supplied from a fuel injection pump (not shown) through a fuel pipe to a common rail (not shown) is accumulated at a constant high pressure in the common rail, and passes through the fuel pipe to the fuel injection valve 1 disposed in each cylinder. It is introduced into the fuel introduction part. Of the introduced fuel, surplus fuel is returned to a fuel tank (not shown) via a fuel outlet (not shown) (in the direction of the arrow indicating fuel return in the figure). A fuel injection pump (not shown) is provided to adjust the fuel discharge pressure in accordance with the engine speed, load, intake fuel pressure, intake air amount, cooling water temperature, and the like.

  As shown in FIG. 1, the fuel injection valve 1 includes a nozzle body 11, a first needle 50 and a second needle 60 that are accommodated in the nozzle body 11 so as to be reciprocally movable, and an electromagnetic valve 90. . The nozzle body 11, the first needle 50, and the second needle 60 constitute a valve portion that blocks and allows fuel injection. The electromagnetic valve 90 constitutes an electromagnetic drive unit that drives the valve unit by hydraulic pressure. More specifically, the nozzle body 11, the first needle 50, and the second needle 60 constitute a valve body (hereinafter referred to as a nozzle body) 10 that performs fuel flow and shut-off. The nozzle body 10 is coupled to the valve housing 20 having the fuel introduction portion by a fastening member such as a retaining nut 19.

  As shown in FIG. 1, the nozzle body 11 is a bottomed, generally hollow cylindrical body, and includes a guide hole 11 a that accommodates the first needle 50 and the second needle 60 in a reciprocating manner therein, and a valve seat 12. (Specifically, the first valve seat 12b and the second valve seat 12a), the nozzle holes 30 and 40, and the volume portion 80 are formed. The guide hole 11a extends in the axial direction inside the nozzle body 11, and accommodates the first needle 50 and the second needle 60 so as to be movable in the axial direction. The guide hole 11a has one end connected to a back pressure chamber 70 as a pressure control chamber, and the other end connected to the valve seat 12 (specifically, the first valve seat 12b).

  As shown in FIGS. 1 and 2, the second valve seat 12a as the inner valve seat and the first valve seat 12b as the outer valve seat are formed in a substantially conical surface, and each of the valve seats 12b and 12a. A first injection hole 30 and a second injection hole 40 are formed on the downstream side of the fuel flow. Specifically, the first valve seat 12b has a substantially truncated cone surface, one end on the large diameter side is continuous with the guide hole 11a, and the other end on the small diameter side is connected to the second valve seat 12a. The first valve seat 12b has a substantially conical surface, and the first valve seat 12b is partitioned by the second lower end surface 65 of the second needle 60 and the first valve seat 12a on the second nozzle hole 40 side. Has a sack portion. The sac portion is a sack hole formed in a bag shape with a small space volume on the tip side of the nozzle body. Here, the sac portion constitutes a sac chamber having a bag-like predetermined space volume.

  An abutting portion (hereinafter referred to as a first abutting portion) 51 of the first needle 50 is disposed on the first valve seat 12b so as to be abutted and separated. A second contact portion 61 of the second needle 60 is disposed on the second valve seat 12a so as to be able to contact and separate. The contact portions 51 and 61 are theoretically circular.

Here, the contact portions 51 and 61, the first valve seat 12b and the second valve seat 12a corresponding to the contact portions 51 and 61, the contact portions 51 and 61 are the first valve seat 12b and the second valve seat 12b, respectively. The first seal portion S1 and the second seal portion S2 that are substantially circular and block and allow the flow of fuel are configured by contacting and separating from the two valve seats 12a. Further, the volume portion 80 of the first valve seat 12b and the second valve seat 12a is formed between the first needle 50 (specifically, the first contact portion 51) and the second needle 60 (specifically, the second contact portion 61). It is surrounded by the space and the valve seat 12 and has a predetermined space volume. In addition, what added the volume of the level | step-difference volume part 86 mentioned later here to the volume of the volume part 80 WHEREIN: The fuel pressure at the time of a high pressure fuel flowing in after the valve opening of the 1st needle 50 lifts an inner needle The volume part which delays the raise of is comprised.

  As shown in FIGS. 1 and 2, the nozzle holes 30 and 40 are formed as passages that communicate between the inside and the outside of the nozzle body 11. Here, the nozzle hole (hereinafter referred to as the first nozzle hole) 30 is disposed on the downstream side of the first valve seat 12b, that is, the first seal portion S1, and is blocked and allowed by the first seal portion S1. Constitutes a first fuel injection means for injecting fuel. An injection hole (hereinafter referred to as a second injection hole) 40 is disposed downstream of the second valve seat 12a, that is, the second seal portion S2, and injects fuel that is blocked and allowed by the second seal portion S2. A second fuel injection means is configured.

  As shown in FIG. 2, the oil sump chamber 14 is formed in an annular recess in the middle portion of the inner wall that forms the guide hole 11 a. Fuel supply passages 23 and 13 for supplying fuel are connected to the oil reservoir chamber 14. The oil sump chamber 14 divides the guide hole 11a into an upper part of the guide hole and a lower part of the guide hole in the axial direction.

  The first needle 50 is formed in a substantially cylindrical shape, and is loosely fitted in the guide hole 11a through a predetermined gap. A first upper end surface 53 that receives the hydraulic pressure in the back pressure chamber 70 is formed on the side opposite to the nozzle hole of the first needle 50, and on the nozzle hole side of the first needle 50, facing the first valve seat 12b, A substantially conical first lower end surface 55 is formed. The first lower end surface 55 is disposed on the inner peripheral side with respect to the first contact portion 51. When the first contact portion 51 is seated and separated from the first valve seat 12b, the first needle 50 is closed and opened, so that the fuel from the first injection hole 30 is blocked and allowed. Here, with respect to the first valve seat 12b and the second valve seat 12a, the first needle 50 and the second needle 60 apply high pressure fuel pressure from the end portions on the first valve seat 12b and the second valve seat 12a side. It is configured to receive pressure and be separated independently.

  In the present embodiment, a first pressure receiving surface 54 formed in the shape of a truncated cone is provided in the middle of the first needle 50 in the axial direction, as shown in FIG. Is provided. Note that the first lower end surface 55 is not limited to the configuration having the first lower end surface 55 and the first pressure receiving surface 54 on the inner and outer sides with respect to the first contact portion 51, and the first lower end surface 55 is on the inner peripheral side with respect to the first contact portion 51. A first lower end surface inner peripheral portion formed in a truncated cone surface shape, and a first lower end surface outer peripheral portion formed in a conical shape disposed on the outer peripheral side with respect to the first contact portion 51; You may make it comprise.

  A first spring 59 as an urging means is disposed between the first upper end surface 53 and the back pressure chamber 70, and the first spring 59 is first in the seating direction for seating on the first valve seat 12b. The upper end surface 53 is configured to be biased. By adjusting the pressure in the back pressure chamber 70, the first needle 50 is reciprocated in the axial direction. A fuel passage 15 is formed between the outer periphery of the first needle 50 and the inner periphery of the guide hole 11a of the nozzle body 11 facing the outer periphery (see FIG. 2). The fuel passage 15 constitutes a fuel path that guides the high-pressure fuel supplied through the oil reservoir chamber 14 to the first injection hole 30 side and the second injection hole 40 side.

  The second needle 60 is formed in a substantially cylindrical shape, and is accommodated in the first needle 50 so as to be reciprocally movable. Specifically, the second needle 60 is accommodated in the inner periphery 52 of the first needle 50 so as to be reciprocally movable. As shown in FIG. A small-diameter shaft portion 60a having an outer diameter d smaller than an outer diameter D representing the size of the outer periphery of the shaft portion 60b.

  A second upper end face 63 that receives the hydraulic pressure in the back pressure chamber 70 is formed on the side opposite to the injection hole of the second needle 60 (see FIG. 2), and a second valve seat is provided on the injection hole side of the second needle 60. A second lower end surface 65 is formed opposite to 12a. The second lower end surface 65 is disposed on the inner peripheral side with respect to the second contact portion 61. A second pressure receiving surface 64 formed in a truncated cone shape is provided on the large diameter shaft portion 60b on the outer peripheral side with respect to the second contact portion 61. When the second abutment portion 61 is seated and separated from the second valve seat 12a, the second needle 60 is closed and opened, and accordingly, the fuel from the second injection hole 40 is shut off and allowed.

  Between the second upper end surface 63 and the back pressure chamber 70, a second spring 69 is disposed as an urging means, and the second spring 69 is second in the seating direction in which the second valve seat 22 is seated. The upper end surface 63 is configured to be biased. By adjusting the pressure in the back pressure chamber 70, the second needle 60 is reciprocated in the axial direction.

  In the present embodiment, the small-diameter shaft portion 60a is arranged to face the inner circumference 52 with a predetermined step in the radial direction. Thereby, the step volume part 86 is formed. The step volume portion 86 constitutes a volume portion 80, and the space volume of the step volume portion 86 contributes to the expansion of the space volume of the volume portion 80. The size of the predetermined step is indicated by (D−d) / 2. When a preferable range of the predetermined step is expressed by an outer diameter ratio (hereinafter referred to as a two-stage diameter ratio) d / D, the d / D two-stage diameter ratio range is 0.67 to 0.93. Is preferred. When the two-stage diameter ratio d / D is smaller than 0.67, the space volume of the volume portion 80, that is, the waste volume in which the fuel is accumulated, becomes too large, so that the second needle 60 after being seated on the second valve seat 12a. There is a risk that the so-called back of fuel (spray) from one nozzle hole 30 may exceed the allowable value. When the two-stage diameter ratio d / D is larger than 0.93, the waste volume of the volume portion 80 is too small, so that the second needle 60 is opened before the required target valve opening timing of the second needle 60. The problem arises.

  In addition, in this embodiment, as shown in FIG. 1, it is comprised so that an angle difference may arise between the seat angle (theta) a of the 2nd valve seat 12a, and the seat angle (theta) b of the 1st valve seat 12b (this example). Then, θa <θb). Thereby, it is possible to make the space volume of the volume part 80 large compared with the space volume of the volume part 980 of the comparative example (refer FIG. 5) to which a prior art is applied. Here, the seat angles θa and θb are the angles between the tapered surfaces formed on the conical surface when the valve seats 12a and 12b are formed in a conical shape, for example, the opening degree of the valve seat surface.

  Furthermore, the angle difference between the seat angle θb and the seat angle θa is preferably in the range of 30 ° to 80 °. When the angle difference is smaller than 30 °, the waste volume of the volume portion 80 is small, which causes a problem that the second needle 60 opens before the required target valve opening timing of the second needle 60. When the angle difference is larger than 80 °, the waste volume of the volume portion 80 is increased, so that the fuel (spray) from the first nozzle hole 30 after seating on the second valve seat 12a of the second needle 60 is so-called after. Anyone may exceed the tolerance. Further, if the angle difference is greater than 80 °, the opening area with respect to the lift of the second needle becomes a low gradient, so that the pressure loss of the fuel flow (hereinafter referred to as pressure loss) increases in the second seal portion S2. There is a possibility that the problem that the spray of fuel injected from the two nozzle holes 40 is not atomized occurs.

  A fuel supply passage 23 and a return passage 29 are connected to the back pressure chamber 70. A first inlet throttle 71 is provided at the inlet, and a first outlet throttle 72 is provided at the outlet. The fuel supply passage 23 is branched halfway in order to supply high-pressure fuel to the back pressure chamber 70 and the oil sump chamber 24. The return passage 29 is connected to a return fuel path for returning surplus fuel in the back pressure chamber 70 to the fuel tank. An electromagnetic valve 90 is provided on the downstream side of the return fuel path to switch communication between the return path 29 and the low pressure path on the fuel tank side. By adjusting the area ratio of the flow path cross-sectional area of the first inlet throttle 71 and the first outlet throttle 72 by the electromagnetic valve 90, the balance between the inflow amount and the outflow amount of the high-pressure fuel into the back pressure chamber 70 can be adjusted. Accordingly, the fuel pressure increase / decrease speed in the back pressure chamber 70 is adjusted.

  Here, the back pressure chamber 70 constitutes a common pressure control chamber that applies a seating direction pressure to the first upper end surface 53 of the first needle 50 and the first upper end surface 63 of the second needle 60.

  The electromagnetic valve 90 includes a control valve 91, and a solenoid 92 and a third spring 93 are provided above the control valve 91. When the drive current is not supplied to the solenoid 92, the control valve 91 is seated on a valve seat (not shown) by the urging force of the third spring 93 and the return passage 29 is blocked. When the drive current is supplied, the control valve 91 is separated from the valve seat by the exciting suction force generated in the solenoid 92 and opens the return passage 29. The drive current is supplied to the solenoid 92 at a timing determined according to the operating state of the engine by an engine control unit (ECU) (not shown).

  Here, the conditions for opening and closing the first needle 50 and the second needle 60 will be described. Since the first needle 50 and the second needle 60 are basically the same in configuration, only the first needle 50 will be described here. The pressure Pu of the back pressure chamber 70 and the urging force Fs of the first spring 59 act on the first upper end surface 53 in the seating direction of the first valve seat 12b. On the other hand, the pressure of high-pressure fuel (hereinafter referred to as common rail pressure) Pd supplied from the common rail acts on the first pressure receiving surface 54 or the first lower end surface 55 in response to opening and closing of the valve. Specifically, under the valve opening conditions, the first needle 50 is closed, that is, the contact portion 51 is seated on the first valve seat 12b and the first seal portion S1 is sealed, so the common rail pressure Pd Acts on the first pressure receiving surface 54. Under the valve closing condition, since the first needle 50 is opened, the common rail pressure Pd acts on the first pressure receiving surface 54 and the first lower end surface 55.

  The pressure receiving areas of the first upper end surface 53, the first pressure receiving surface 54, and the first lower end surface 55 are A53, A54, and A55, respectively. The outer diameter of the first needle 51 (specifically, the first upper end surface 53 and the first pressure receiving surface 54) is D50, and the diameter of the contact portion 51 (hereinafter referred to as the seal diameter) is D50s. From the above balance condition, the valve opening condition is A54 × Pd> A53 × Pu + Fs, and the valve closing condition is (A54 + A55) × Pd> A53 × Pu + Fs. Therefore, the valve opening pressure and valve closing pressure of the first needle 50 vary depending on the pressure receiving area A53, the seal diameter D50s, that is, the pressure receiving area A54, the biasing force Fs due to the spring size of the first spring 59, and the like.

  For the second needle 60, the pressure receiving areas of the second upper end surface 63, the second pressure receiving surface 64, and the second lower end surface 65 are A63, A64, and A65, respectively, and the outer diameter of the second needle 60 is D60, The seal diameter D60s of the contact portion 61 is set. Since the opening condition is A64 × Pd> A63 × Pu + Fs and the closing condition is (A64 + A65) × Pd> A63 × Pu + Fs, the valve opening pressure and the valve closing pressure of the second needle 60 are It changes depending on the urging force Fs due to the area A63, the seat diameter D60s, that is, the pressure receiving area A64, the spring size of the second spring 69 and the like.

  In the above description, the pressure receiving area does not indicate the actual surface area of each surface, but a shaft for receiving the acting force of the pressure Pu and the common rail pressure Pd so that the needles 50 and 60 move in the axial direction. Direction projected area. For example, the valve opening pressure can also be adjusted by adjusting the area ratio between the pressure receiving area A63 of the second upper end surface 63 of the second needle 60 and the pressure receiving area A64 of the second pressure receiving surface 64, and the first needle 50, the second needle 60 can be opened independently, and the first needle 50 and the second needle 60 can be opened almost simultaneously. In the following description of the valve opening pressures of the first needle 50 and the second needle 60, the valve opening pressures are different, and the valve opening pressure of the first needle 50 is slightly smaller or substantially the same as the valve opening pressure of the second needle 60. Suppose that

  The operation of the fuel injection valve 10 having the above-described configuration will be described below. FIG. 1 shows when fuel injection is stopped. In FIG. 3, the horizontal axis indicates the elapsed time T until the second needle 60 opens after the first needle 50 opens, and the vertical axis indicates the fuel pressure P in the volume portion 80. It is.

(When injection stops)
The relatively high-pressure fuel accumulated in the common rail is supplied to the back pressure chamber 70 and the fuel passage 15 through the fuel supply passage 23 as shown in FIG. At this time, since the drive current is not supplied to the solenoid 92, the control valve 91 is seated on the valve seat by the urging force of the third spring 93 to block the return passage 29. Since the supplied fuel remains in the back pressure chamber 70, the fuel pressures in the first and second pressure control chambers 70, 80 and the fuel passage 15 are substantially equal. Since the urging force for pressing the first needle 50 against the first valve seat 12b is larger than the urging force for lifting, the contact portion 51 is seated on the first valve seat 12b, The fuel is not injected from the first injection hole 30. Further, since the urging force for pressing the second needle 60 against the second valve seat 12a is larger than the urging force for lifting, the contact portion 61 is seated on the second valve seat 12a and the fuel passage 15 The fuel inside is not injected from the second injection hole 40.

  At this time, since the first seal portion S1 and the second seal S2 are sealed, fuel of low pressure (equivalent to atmospheric pressure or pressure in the combustion chamber) is accumulated in the volume portion 80.

(Operation to the opening of the first nozzle hole)
When a drive current is supplied to the control valve 91 to the solenoid 92, the control valve 91 is lifted by the magnetic attractive force generated by the solenoid 92, and the return passage 23 is opened. When the return passage 23 is opened, the fuel pressure in the back pressure chamber 70 decreases. The pressure decreases at a predetermined lowering speed according to the area ratio of the first inlet throttle 71 and the first outlet throttle 72. When the fuel pressure in the back pressure chamber 70 decreases to the valve opening pressure of the first needle 50, the first needle 50 is lifted, the first contact portion 51 is separated from the first valve seat 12b, and the first needle 50 Is opened. When the first needle 50 is opened, the fuel in the fuel passage 15 flows into the first injection hole 30 and the fuel is injected from the first injection hole 30.

  Since the valve opening pressure of the second needle 60 is higher than the valve opening pressure of the first needle 50, the second contact portion 61 is seated on the second valve seat 12a and the second seal portion S2 is sealed. . As a result, the valve opening of the second needle 60 is maintained, and the fuel does not flow out from the second nozzle hole 40. At this time, since the fuel is injected only from the first injection hole 30, the injection rate as the fuel injection characteristic is in a relatively low state.

(Operation to the opening of the first nozzle hole and the second nozzle hole)
In the opening process of the first nozzle hole 30 described above, when the first contact portion 51 is separated from the first valve seat 12b, the seal state of the first seal portion S1 is released, and the high pressure (common rail pressure) from the fuel passage 15 is released. ) Pd fuel flows into the volume 80. At this time, since the fuel in the volume 80 is low-pressure fuel, it takes time to reach the high-pressure Pd state from the low-pressure state even if the fuel at the common rail pressure Pd flows in instantaneously. The time to reach is determined by the inflow amount ΔQ of the high-pressure Pd fuel. When the volume of the volume 80 is V and the fuel deposition elastic modulus is E, (high pressure Pd−low pressure) = ΔQ × E / V Become.

  Here, when the valve opening pressure P2o of the second needle 60 is used instead of the high pressure Pd, it is expressed by the following relational expression: P2o−low pressure = ΔP (see FIG. 3) = ΔQ × E / V. Since the common rail pressure Pd and the second valve opening pressure P2o are extremely large compared to the low pressure, the low pressure in the relational expression is almost zero. In the present embodiment, the volume of the volume 80 is increased by the step volume 86, and even if high-pressure Pd fuel flows into the volume 80 as shown by the solid line in FIG. The elapsed time until the pressure ΔP corresponding to the pressure is reached (hereinafter referred to as the actual valve opening time of the second needle 60) is formed relatively large. As shown in FIG. 3, the actual valve opening time of the second needle 60 can be extended to the required target valve opening time ΔTa of the second needle 60. As a result, a predetermined time difference is given to the valve opening timing of the first needle 50 and the second needle 60, so that the variable injection hole injection of the first injection hole 30 and the second injection hole 40 becomes possible.

  Here, a comparative example (see FIG. 5) to which the conventional technique is applied will be described. In the comparative example, as shown in FIG. 5, the volume portion 80 is formed to have a small volume. Therefore, the actual opening of the second needle 960 (opening time ΔTp in the drawing) may be advanced by the time ΔTo compared to the target valve opening timing ΔTa. As a result, in the comparative example, although the first injection hole 30 and the second injection hole 40 are aimed at variable injection injection, the first needle 50 is opened as shown by the two-dot chain line in FIG. At the same time, the pressure received by the high-pressure fuel in the fuel passage 15 is instantaneously applied to the second needle 960 and the valve is opened with almost no time delay.

(Operation to stop injection)
When a predetermined valve opening time corresponding to the operating state of the engine has elapsed, the supply of drive current to the solenoid 92 is stopped. When the supply of the drive current is stopped, the magnetic attractive force of the solenoid 92 is lost, and the control valve 91 blocks the return passage 29. Then, since the fuel outflow from the first outlet throttle 72 to the downstream is stopped, the pressure in the back pressure chamber 70 starts to rise again. When the pressure in the back pressure chamber 70 rises to the valve closing pressure of the first needle 50, the first needle 50 closes. When the pressure in the back pressure chamber 70 rises to the valve closing pressure of the second needle 60, the second needle 60 closes. As a result, fuel injection from the first nozzle hole 30 and the second nozzle hole 40 is stopped.

  Next, the operation and effect of the present embodiment will be described. (1) In the present embodiment, the second needle 60 is accommodated in the inner periphery of the first needle 50 so as to be capable of reciprocating, so that the valve seats 12a and 12b can be moved. In the fuel injection valve in which both needles 50 and 60 receive high pressure fuel pressure from the valve seat side end and are separated independently, the inner periphery of the first needle 50 and the second needle are provided at the valve seat end. A volume portion 80 (in detail, a step volume 86 is provided between the outer circumference of the 60 and delays the rise in fuel pressure when the high pressure fuel flows in after the first needle 50 is opened and the second needle 60 is lifted). A volume 80) is formed. Thereby, compared with the volume of the volume part 980 enclosed between the contact parts 951 and 961 of each needle 960 and 50 of conventional examples, such as a comparative example to which a prior art is applied, and the valve seat 912, the 1st needle 50's. It is possible to form a relatively large volume between the inner periphery and the inner periphery of the second needle 60. Therefore, since the volume can be made relatively large, a predetermined time difference ΔTa can be given to the valve opening timing of the first needle 50 and the valve opening timing of the second needle 60.

  (2) In the present embodiment, the volume portion 80 is extended toward the valve seat side of the large-diameter shaft portion 60b of the second needle 60, which can slide on the inner periphery of the first needle 50, The large-diameter shaft portion 60b is formed so as to be filled with fuel between the inner periphery of the first needle 50 with a radial step. Therefore, in comparison with the volume of the volume portion 980 surrounded by the valve seat 912 between the contact portions 951 and 961 of the needles 960 and 50 of the conventional example such as the comparative example to which the conventional technology is applied, The volume can be made relatively large according to the size of the step volume portion 86 formed by the circumference and the radial step of the second needle 60.

  (3) In order to optimize the volume 80, particularly the step volume 86, the two-stage diameter ratio d / D of the small diameter shaft 60a and the large diameter shaft 60b in the second needle is 0.67 to It is preferably in the range of 0.93. When the two-stage diameter ratio d / D is smaller than 0.67, the space volume of the volume portion 80, that is, the waste volume in which the fuel is accumulated, becomes too large, so that the second needle 60 after being seated on the second valve seat 12a. There is a risk that the so-called back of fuel (spray) from one nozzle hole 30 may exceed the allowable value. When the two-stage diameter ratio d / D is larger than 0.93, the waste volume of the volume portion 80 is too small, so that the second needle 60 is opened before the required target valve opening timing of the second needle 60. The problem arises.

  (4) In this embodiment, the valve seat is composed of a substantially conical first valve seat 12b corresponding to the first needle and a substantially conical second valve seat 12a corresponding to the second needle 60. The second valve seat 12a and the first valve seat 12b are configured to be formed by changing the seat angle θa of the second valve seat 12a and the seat angle θb of the first valve seat 12b. Therefore, the volume can be increased by changing the shape of the valve seats 12a and 12b forming the volume of the volume portion 80 as compared with the substantially conical valve seat 912 shared by the conventional needles such as the comparative example. I can plan.

  (5) In more detail, an angle difference is generated between the seat angle θa of the second valve seat 12a and the seat angle θb of the first valve seat 12b, and the angle between the seat angle θb and the seat angle θa. The difference is preferably in the range of 30 ° to 80 °. When the angle difference is smaller than 30 °, the waste volume of the volume portion 80 is small, which causes a problem that the second needle 60 opens before the required target valve opening timing of the second needle 60. When the angle difference is larger than 80 °, the waste volume of the volume portion 80 is increased, so that the fuel (spray) from the first nozzle hole 30 after seating on the second valve seat 12a of the second needle 60 is so-called after. Anyone may exceed the tolerance.

  (6) As a method of enlarging the volume surrounded by the so-called abutting portions of each needle and the valve seat, the inner periphery of the first needle 50 is provided at the end of the second needle 60 on the valve seat 12a side. The seat angle θa of the second valve seat 12a and the seat angle θb of the first valve seat 12b are not limited to those having the small diameter shaft portion 60a so as to provide a predetermined radial direction step (specifically, the step volume portion 86) with respect to 52. It may be configured such that an angle difference is generated between the two. In any method, since the volume of the volume portion 80 can be formed relatively large, the valve opening timing of the first needle 50 and the valve opening timing of the second needle 60 have a predetermined time difference ΔTa. Can be made.

  (7) As a method of enlarging the volume surrounded by the so-called contact portions of each needle and the valve seat, the inner periphery of the first needle 50 is provided at the end of the second needle 60 on the valve seat 12a side. 52 between the seat angle θa of the second valve seat 12a and the seat angle θb of the first valve seat 12b, and a feature having a small-diameter shaft portion 60a so as to provide a predetermined radial step (specifically, a step volume portion 86). It is preferable to have a feature that causes an angle difference. Thereby, in order to give the predetermined time difference ΔTa between the valve opening timing of the first needle 50 and the valve opening timing of the second needle 60, the volume of the volume portion 80 is effectively made relatively large and the volume is required. The size can be adapted to the target time difference ΔTa.

(Second Embodiment)
A second embodiment will be described with reference to FIG. In the following description, the same or equivalent components as those in the first embodiment are denoted by the same reference numerals, and description thereof will not be repeated. FIG. 4 is a partial cross-sectional view showing the main part of the valve part according to this embodiment.

  In the second embodiment, as shown in FIG. 4, the second needle 160 is pivotally supported by the first needle 150 and the nozzle body portion 113.

  As shown in FIG. 4, the second needle 60 includes a large-diameter shaft portion 160b that can slide on the inner periphery 152 of the first needle 150, and a small-diameter shaft portion that has a smaller outer diameter than the large-diameter shaft portion 160b. 160a. The small diameter shaft portion 160a is accommodated in the nozzle body portion 113 disposed on the tip end portion 111b side of the nozzle body 111 so as to be movable in the axial direction. The first needle 150 is accommodated in a guide hole (not shown) of the nozzle body 111 so as to be reciprocally movable. The first contact portion 151 of the first needle 150 is seated on and separated from the first valve seat 112. The first abutting portion 151 has a first abutting upper portion 151b that is separated and seated on the fuel upstream side of the valve seat 112 across the first injection hole 30; It has the 1st contact lower side part 151a to seat. Here, the first contact portion 151 (specifically, the first contact upper portion 151b and the first contact lower portion 151a) and the first valve seat 112 are sealed with the first injection hole 30 interposed therebetween. 1 seal part S1 is comprised.

  As shown in FIG. 4, the nozzle body 113 is formed as a separate member on the tip 111b side of the nozzle body 111, and is joined and fixed by press-fitting or welding. The nozzle body 113 may be integrally formed with the nozzle body 111. The guide hole 113a of the nozzle body portion 113 is provided with a second valve seat 113s in which the second contact portion 161 of the second needle 160 (specifically, the small diameter shaft portion 160a) is separated and seated.

  In the present embodiment, as shown in FIG. 4, the small-diameter shaft portion 160 a is disposed so as to provide a predetermined radial step (specifically, a step volume portion 186) with respect to the inner periphery 152. As shown in FIG. 4, the volume portion 180 includes a first lower end surface 155 of the first needle 150, an upper end surface of the nozzle body portion 111b, and the first needle 150 and the nozzle body portion 111b. A space volume surrounded by two needles 160 is formed.

  In the present embodiment described above, the volume portion 180 is disposed in the first lower end surface 155 of the first needle 150, the upper end surface of the nozzle body portion 111b, and inside the first needle 150 and the nozzle body portion 111b. Since it is formed by the space volume surrounded by the second needle 160, it can be formed relatively larger than the volume part 980 of the prior art such as a comparative example. Therefore, since the volume of the volume part 180 can be formed relatively large, a predetermined time difference ΔTa can be provided between the valve opening timing of the first needle 150 and the valve opening timing of the second needle 160.

  Furthermore, in this embodiment, the outer diameter of the second needle 160 (specifically, the second upper end surface 153, the first pressure receiving surface 164) (hereinafter referred to as the outer diameter of the large-diameter shaft portion) is db, the outer diameter of the small-diameter shaft portion. When the diameter (hereinafter referred to as the small-diameter shaft outer diameter) is da, the large-diameter shaft outer diameter db and the small-diameter shaft outer diameter da are different in size (db> da in this embodiment). Yes. Thereby, the volume of the step volume part 986 can be expanded effectively.

  The large-diameter shaft outer diameter db and the small-diameter shaft outer diameter da may be approximately the same size. Even with such a configuration, the volume of the volume portion 180 can be made relatively large compared to the volume portion 980 of the prior art such as the comparative example.

  In the present embodiment, the second valve seat 113s of the contact portion 161 of the second needle 160 is disposed in the nozzle body portion 113. Since the first needle 150 and the first valve seat 112 have the first seal portion S that seals with the first injection hole 30 in between, the first needle 150 and the second needle as shown by the arrows in FIG. Even if there is fuel leaking from the sliding portion between 160, fuel leakage can be effectively suppressed by the fuel leakage from the first injection hole 30.

  In the first embodiment described above, instead of the configuration in which an angle difference occurs between the seat angle θa of the second valve seat 12a and the seat angle θb of the first valve seat 12b, the first of the valve seats 12a and 12b The valve seat part between 1 seal part S1 and 2nd seal part S2 may be comprised so that it may form in a concave shape toward the direction away from the 1st needle 50 and the 2nd needle 60. FIG. Even with such a configuration, it is possible to effectively expand the volume of the volume portion 80.

  In the first and second embodiments described above, the valve opening timing of the first needle 150 and the valve opening of the second needle 160 are simply increased by increasing the volume of the volumes 80 and 180 as compared with the prior art. A predetermined time difference ΔTa can be given to the time.

  Instead of expanding the volume of the volume portion 80, the second needle is supported in the first needle so as to be movable in the axial direction, and the second needle is engaged with the first needle by the occurrence of a predetermined lift of the first needle. It is also conceivable to use a configuration that is stopped. In this configuration, when the first needle is lifted for a predetermined lift h or more, for example, it is possible to mechanically pull up the second needle and set the valve opening time difference between the first needle and the second needle. However, in order to form a structure in which the second needle can be locked in the first needle, it is necessary to press-fit a sleeve serving as a locking member into the first needle and perform welding or the like. After the press-fitting, there is a problem that it is difficult to accurately adjust the predetermined lift h because a joining step for welding or the like is required and there is a joining step for joining two members such as welding.

It is a fragmentary sectional view which shows the principal part of the valve part concerning the fuel injection valve of the 1st Embodiment of this invention. It is typical sectional drawing which shows one Example of the fuel injection valve of the 1st Embodiment of this invention. It is a graph which shows the relationship between the pressure added to the volume part enclosed between the contact parts of each needle in FIG. 1, and a valve seat, and the valve opening time of a needle. It is a fragmentary sectional view which shows the principal part of the valve part concerning 2nd Embodiment. It is a fragmentary sectional view which shows the principal part of the valve part of a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel injection valve 10 Nozzle body 11 Nozzle body 12 Valve seat 12a 2nd valve seat (inner valve seat)
12b First valve seat (outer valve seat)
19 Retaining nut 20 Valve housing 30 First nozzle hole 40 Second nozzle hole 50 First needle (outer needle)
51 1st contact part 53 1st upper end surface 54 1st pressure receiving surface 55 1st lower end surface 59 1st spring 60 2nd needle (inner needle)
60a small diameter shaft portion 60b large diameter shaft portion 61 second contact portion 63 second upper end surface 64 second pressure receiving surface 65 second lower end surface 69 second spring 70 back pressure chamber (pressure control chamber)
71 First inlet throttle 72 First outlet throttle S1 First seal part (outer seal part)
S2 Second seal part (inner seal part)
80 Volume part 86 Step volume part (part of volume part)
θa (the second valve seat) seat angle θb (the first valve seat) seat angle

Claims (3)

An inner needle and an outer needle that are arranged in duplicate inside and outside;
The inner needle and the outer needle are slidably accommodated, and the inner needle, a valve seat from which the outer needle is separated and seated, and a nozzle body having a nozzle hole formed in the valve seat,
Fuel in which the inner needle is accommodated in the inner periphery of the outer needle so as to be reciprocally movable, and both the needles receive high-pressure fuel pressure from the end on the valve seat side and separate independently from the valve seat. In the injection valve,
The end on the valve seat side is provided between the inner circumference of the outer needle and the outer circumference of the inner needle, and high pressure fuel flows after the outer needle is opened to lift the inner needle. A volume that delays the rise in fuel pressure at the time is formed ,
The inner needle has a large-diameter shaft portion slidable on the inner periphery,
The volume portion extends toward the valve seat side of the large-diameter shaft portion, has a radial step with respect to the large-diameter shaft portion, and is filled with fuel between the inner periphery. The outer diameter ratio (d / D) of the outer diameter (d) at the portion having the radial step with respect to the outer diameter (D) of the large-diameter shaft portion in the outer diameter of the inner needle is 0. It is set in the range of 67 to 0.93,
The valve seat has a substantially conical inner valve seat corresponding to the inner needle and a substantially conical outer valve seat corresponding to the outer needle,
The inner valve seat and the outer valve seat are formed by changing the seat angle of the inner valve seat and the seat angle of the outer valve seat, and the seat angle (θb) of the outer valve seat and the seat of the inner valve seat 2. The fuel injection valve according to claim 1, wherein an angle difference (θb−θa) of the angle (θa) is set in a range of 30 ° to 80 ° . The valve seat has an inner seal portion where the inner needle is separated and seated, and an outer seal portion where the outer needle is separated and seated,
The valve seat portion between the inner seal portion and the outer seal portion of the valve seat is formed in a concave shape in a direction away from the inner needle and the outer needle. The fuel injection valve according to 1. 3. The fuel injection valve according to claim 1 , wherein, among the nozzle holes, a specific nozzle hole that always communicates with the volume portion is provided.

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