JP2008175085A - Pressure limiter of fuel injection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid the problem of receiving damage such as a scratch on a surface of a ball valve, by avoiding the problem of the ball valve colliding against a valve body in a state of the ball valve being eccentric toward a valve opening when a pressure limiter is closed. <P>SOLUTION: By providing a recess 48 for guiding the ball valve 24 to a central part of a lower end face of a needle 44, when the ball valve 24 is moving toward the valve closing direction after the pressure limiter 8 is opened, the position of the ball valve 24 is restricted by the recess 48, and the position of the ball valve 24 is fixed at the central part of the needle 44. Thereby, the position of the ball valve 24 when the ball valve 24 collides against the valve body 22 is aligned with the center of a valve opening 35, and an eccentric collision of the ball valve 24 is avoided. As a result, an impact applied to the ball valve 24 is made small, the problem of the occurrence of damage such as a scratch on a surface of the ball valve 24 is avoided, and high sealability is maintained even in a usage over a long period of time. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pressure limiter that is provided in a fuel injection device that injects pressure-accumulated fuel and opens when the pressure of the pressure-accumulated fuel rises above a preset valve opening pressure to limit the upper pressure limit of the pressure-accumulated fuel.

(Conventional technology)
2. Description of the Related Art Conventionally, there is known a common rail type fuel injection device that accumulates high pressure fuel pressurized by a high pressure pump in a common rail and injects fuel accumulated in a pressure accumulation chamber in the common rail from an injector. The common rail is equipped with a pressure limiter that opens when the fuel pressure in the pressure accumulation chamber rises above the valve opening pressure and limits the upper pressure limit of the pressure accumulation fuel.
Conventionally, a pressure limiter using a ball valve is known (see, for example, Patent Document 1).

A pressure limiter using a ball valve includes a valve body having a valve opening communicating with a pressure accumulating chamber, a spherical ball valve capable of closing the valve opening, and a piston having a needle inserted into a sliding hole of the valve body. The spring is configured to apply a biasing force to the piston and press the ball valve against the valve opening by the needle.
When the fuel pressure in the accumulator rises above the valve opening pressure and the valve opening force applied from the accumulator chamber to the ball valve exceeds the valve closing force applied to the ball valve by the spring, the valve valve opens due to the valve opening force. The fuel in the pressure accumulating chamber is discharged to the low pressure side through the valve opening.
When the valve opening opens and the pressure in the pressure accumulating chamber drops below the valve opening pressure, and the valve opening force applied from the pressure accumulating chamber to the ball valve is less than the valve closing force applied to the ball valve by the spring, the valve closing force causes the ball valve to Sit in the opening and close the valve opening.

(Problems of conventional technology)
In order to make the exhaust gas cleaner, high pressure injection of the injector is being promoted. With the high pressure injection of the injector, the fuel pressure of the common rail is increased, and the valve opening pressure of the pressure limiter is also increased. That is, the closing force of the ball valve (specifically, the biasing force of the spring) is strengthened.
For this reason, the valve closing force applied to the ball valve when the pressure limiter closes tends to increase with the high pressure injection of the injector.

Here, during the opening of the pressure limiter, the ball valve receives the pressure of the fuel ejected from the valve opening. For this reason, the ball valve may deviate from the axial center of the sliding hole during valve opening.
If the ball valve is displaced from the axial center of the sliding hole while the ball valve is open, and if it is pushed in the valve closing direction by the needle, the ball valve moving center does not coincide with the center of the valve opening. Collides with the valve body in an eccentric state with respect to the valve opening. For this reason, the collision force between the ball valve and the valve body is increased, and the surface of the ball valve may be damaged such as a scratch.
As described above, particularly in recent years, the valve closing force tends to be increased along with the high pressure injection, and therefore the possibility that the surface of the ball valve is damaged is increasing.

In addition, if damage such as scratches occurs on the surface of the ball valve, there is a concern that the sealing performance may be lowered when the ball valve is seated on the valve opening, and the valve opening pressure is lowered and the pressure is reduced via the pressure limiter during normal operation. It is expected that the amount of leakage returning to the side will increase.
Japanese Patent Laid-Open No. 4-72454

  The present invention has been made in view of the above problems, and its object is to avoid the problem of the ball valve colliding with the valve body in a state where the ball valve is eccentric to the valve opening when the ball valve is closed. An object of the present invention is to provide a pressure limiter for a fuel injection device capable of avoiding problems such as scratches.

[Means of claim 1]
The pressure limiter of the fuel injection device adopting the means of claim 1 includes a recess for guiding the ball valve at the tip of the needle that presses the ball valve in the direction in which the valve opening is closed.
Thereby, after the pressure limiter is opened, when the fuel pressure in the pressure accumulating chamber is lowered and the ball valve is pushed and moved in the valve closing direction by the needle, the position of the ball valve at the tip of the needle is moved by the recess at the tip of the needle. Confirmed. For this reason, the position of the ball valve when the ball valve collides with the valve body can be matched with the center of the valve opening.
The ball valve collides with the valve body in the state where it is aligned with the center of the valve opening (sitting on the valve opening), so there is no malfunction such as the ball valve eccentrically colliding with the valve opening, and the surface of the ball valve is scratched. This avoids problems that cause damage.
Thus, even if the pressure limiter opens and closes, damage such as scratches does not occur on the surface of the ball valve, so that fuel leakage does not occur even when used for a long time, and a highly reliable pressure limiter can be provided. it can.

[Means of claim 2]
In the pressure limiter of the fuel injection device adopting the means of claim 2, the bottom of the recess is provided on a plane perpendicular to the axial direction of the needle.
By providing the bottom of the concave portion on a flat surface, the load direction applied to the ball valve can be made to coincide with the axial direction (movement direction) of the needle even when the ball valve is pushed by the needle when the valve is closed. Thereby, when the ball valve is seated on the valve opening, it is possible to avoid a problem that an uneven load (a load inclined with respect to the moving direction of the needle) occurs in the ball valve. That is, it is possible to avoid a problem that an unbalanced collision force is generated when the ball valve is seated on the valve opening due to an unbalanced load on the ball valve.
In this way, since it is possible to avoid the problem that a biased collision force occurs when the ball valve is seated on the valve opening, it is possible to reduce the possibility of damage such as scratches on the surface of the ball valve. Even if it is used for this, fuel leakage does not occur, and a highly reliable pressure limiter can be provided.

[Means of claim 3]
In the pressure limiter of the fuel injection device adopting the means of claim 3, an annular side surface (hereinafter referred to as a concave inner annular surface) inside the concave portion is provided on a curved surface having a curvature larger than the surface curvature of the ball valve.
When the ball valve is seated on the valve opening in contact with the concave inner annular surface, a collision force is also generated at the contact portion between the ball valve and the concave inner annular surface, but the concave inner annular surface has a curvature larger than the surface curvature of the ball valve. By providing it on a large curved surface, it is possible to reduce the collision surface pressure of the contact portion between the ball valve and the concave inner ring surface, and to reduce the concentration of the collision force between the ball valve and the concave inner ring surface.
In this way, the collision surface pressure between the ball valve and the concave inner ring surface can be lowered, so that the possibility of damage such as scratches occurring on the surface of the ball valve can be further reduced and used for a long time. However, there is no fuel leakage, and a highly reliable pressure limiter can be provided.

The pressure limiter of the fuel injection device in the best mode includes a valve body, a ball valve, a piston including a needle, and a spring.
The valve body includes a valve opening communicating with the pressure accumulation chamber of the common rail, and a sliding hole extending in the axial direction on the low pressure side of the valve opening.
The ball valve has a spherical shape that can close the valve opening by sitting on the valve opening.
The needle is inserted into the sliding hole of the valve body and supported so as to be movable in the axial direction.
The piston receives a biasing force from the spring and applies a biasing force in the valve closing direction to the needle. Thereby, the ball valve is pressed in the valve closing direction by the needle, and the ball valve is pressed in the direction of closing the valve opening.
The spring is, for example, a compression coil spring, and biases the piston with a restoring force to give a biasing force in the valve closing direction to the needle and the ball valve.
The tip of the needle, that is, the contact portion of the needle with the ball valve, is provided with a recess for guiding the ball valve while the ball valve is seated. By this recess, when the pressure limiter is opened and then closed, the position where the ball valve collides with the valve body can be made coincident with the center of the valve opening.

  A pressure limiter of a fuel injection device to which the present invention is applied will be described with reference to FIGS. In the first embodiment, the schematic configuration of the “common rail fuel injection device” will be described first with reference to FIGS. 2 and 3, and then the “pressure limiter” to which the present invention is applied will be described with reference to FIG. To do.

[Description of common rail fuel injection system]
The common rail fuel injection device shown in FIG. 2 is a system that injects fuel into each cylinder of an engine (for example, a diesel engine: not shown), and includes a common rail 1, an injector 2, a supply pump 3, a control device 4, and the like. . FIG. 2 shows an example in which an ECU (engine control unit) and an EDU (drive unit) constituting the control device 4 are built in one case, but the ECU and the EDU may be provided independently.

  The common rail 1 is a pressure accumulating container that accumulates high-pressure fuel supplied to the injector 2 in a pressure accumulating chamber provided therein, and the high-pressure fuel is connected via a high-pressure pump pipe 6 so that a common rail pressure corresponding to the fuel injection pressure is accumulated. And a plurality of injector pipes 7 for supplying high-pressure fuel to each injector 2.

As shown in FIG. 3, a pressure limiter 8 is attached to one end of the common rail 1. The pressure limiter 8 opens when the common rail pressure exceeds a preset valve opening pressure, thereby returning the fuel in the common rail 1 to the fuel tank 10 via the relief pipe 9 and opening the common rail pressure. The details of the pressure limiter 8 will be described later.
A common rail pressure sensor 11 for detecting the common rail pressure accumulated inside is attached to the other end of the common rail 1. The common rail pressure sensor 11 is connected to the control device 4 so that the common rail pressure can be measured by the control device 4.
2 and 3 show an example in which the pressure limiter 8 and the common rail pressure sensor 11 are provided on the common rail 1, but in addition to the pressure limiter 8 and the common rail pressure sensor 11, the valve is opened by an instruction from the control device 4, A pressure reducing valve for rapidly reducing the common rail pressure may be provided. This pressure reducing valve may be provided integrally with the pressure limiter 8.

  The injector 2 is mounted in each cylinder of the engine and supplies fuel into each cylinder. The injector 2 is connected to the downstream ends of a plurality of injector pipes 7 branched from the common rail 1 and accumulated in the common rail 1. A fuel injection nozzle that injects high-pressure fuel into each cylinder and an electromagnetic valve that performs lift control of a needle housed in the fuel injection nozzle are mounted. The leaked fuel from the injector 2 is also returned to the fuel tank 10 via the relief pipe 9. The injector 1 may be another type of fuel injection valve such as a piezo injector controlled by a piezo actuator.

  The supply pump 3 is a fuel pump that sucks the fuel in the fuel tank 10 through a fuel filter 13 provided in the middle of the fuel suction pipe 12 and supplies the sucked fuel to the common rail 1 by high-pressure feeding. Inside, a low-pressure pump (feed pump) that sucks the fuel in the fuel tank 10 into the supply pump 3 and a high-pressure pump that pressurizes the low-pressure fuel sucked up by the low-pressure pump and pumps it to the common rail 1 are incorporated. The low pressure pump and the high pressure pump are driven by a common camshaft 14 that receives rotational power from the engine.

  Further, the supply pump 3 is equipped with an SCV (fuel metering valve) 15 for adjusting the opening of the fuel flow path in a fuel flow path for sending fuel from the low pressure pump to the high pressure pump. The SCV 15 is a valve that adjusts the amount of fuel sucked into the high-pressure pump by changing the amount of fuel pumped to the common rail 1 by being controlled by a pump drive signal given from the control device 4. The common rail pressure is adjusted by adjusting the amount of fuel discharged to the common rail 1 by pressure. That is, the control device 4 controls the SCV 15 to control the common rail pressure to a pressure corresponding to the vehicle running state.

The ECU of the control device 4 includes a CPU and a storage device (memory such as ROM, RAM, SRAM, EEPROM, etc.). The program stored in the ROM and the signals of the sensors read into the RAM (vehicle vehicle) Various calculation processes are performed based on the operation state.
An example of a specific calculation is as follows. For each fuel injection, the control device 4 is based on a program stored in the ROM and a sensor signal (vehicle driving state) read into the RAM. It is provided to determine the target injection amount for each cylinder, the injection mode, the valve opening and closing timing of the injector 2, and the opening (energization current value) of the SCV 15.
In addition to the common rail pressure sensor 11 that detects the common rail pressure, the ECU includes an accelerator sensor that detects the accelerator opening, a rotation speed sensor that detects the engine speed, and an engine as means for detecting the driving state of the vehicle. Sensors such as a water temperature sensor for detecting the cooling water temperature are connected.

  The EDU of the control device 4 includes an injector drive circuit and an SCV drive circuit. The injector drive circuit is a drive circuit that applies a valve opening drive current to the electromagnetic valve of the injector 2 based on an injector valve opening signal given from the ECU. By supplying the valve opening drive current to the electromagnetic valve, high pressure fuel is introduced into the cylinder. Fuel injection is stopped by stopping the valve-opening drive current supplied by injection. The SCV drive circuit gives a pump drive signal (drive current) to the solenoid valve of the SCV 15 based on a control signal (PWM signal) given from the ECU.

[Description of Pressure Limiter 8]
As described above, the pressure limiter 8 is connected to one end of the common rail 1 and opens when the pressure of the accumulated fuel in the common rail 1 (common rail pressure) rises above a preset valve opening pressure. This is a safety valve that limits the upper limit of fuel pressure. In the following description, for the sake of explanation, the upper side of FIG. 1 will be described as the upper side, and the lower side of FIG. 1 will be the lower side. However, the upper and lower sides are for explaining the embodiment and relate to the mounting direction of the pressure limiter 8. It is not a thing.

  The pressure limiter 8 includes a housing 21 fastened to the common rail 1, a valve body 22 coupled to the lower portion of the housing 21, a hollow screw 23 fastened and fixed to the upper portion of the housing 21, and a ball valve disposed in the valve body 22. 24, a piston 25 in which a part (a needle 44 described later) is inserted and arranged in the valve body 22, a spring 26 mounted in the housing 21, and the like.

The housing 21 has a substantially cylindrical shape with a through hole penetrating in the axial direction (vertical direction) inside, and a male screw 27 to be screwed into the common rail 1 is formed on the lower outer periphery, and the upper outer periphery is formed on the upper outer periphery. Is formed with a hexagonal portion 28 with which a fastening tool (such as a spanner) engages.
An enlarged diameter hole 31 into which the large diameter portion 22a of the valve body 22 is fitted is formed at the lower end of the housing 21, and the housing with a part of the valve body 22 assembled to the inside of the enlarged diameter hole 31. The valve body 22 is assembled to the housing 21 by caulking the lower end of the inner 21.
Inside the housing 21, a spring chamber 32 in which the spring 26 is arranged also serving as a sliding portion of the piston 25 is formed on the lower side, and a female screw hole 33 into which the hollow screw 23 is screwed is formed on the upper side. . Between the spring chamber 32 and the female screw hole 33, there is provided a reduced diameter portion 34 forming a spring seat on which an upper end of the spring 26 is seated via a shim 47 described later.

  The valve body 22 has a two-stage cylindrical shape that is attached to the lower end of the housing 21, and has a large-diameter portion 22 a that is inserted into the enlarged-diameter hole 31 of the housing 21 and a small-diameter portion that is inserted into the spring chamber 32. 22b. When the housing 21 is firmly fastened to the common rail 1, the upper and lower surfaces of the large-diameter portion 22a are strongly sandwiched between the common rail 1 and the housing 21 and sealed in a liquid-tight manner.

At the center of the valve body 22, a fuel passage that connects the pressure accumulation chamber in the common rail 1 and the spring chamber 32 is formed. A valve opening 35 that can be closed by a ball valve 24 pressed from the low pressure side (spring chamber 32 side, upper side) is formed in the middle of the fuel passage. The valve opening 35 is an annular valve seat having a diameter continuously increased toward the low pressure side, and this valve seat may be a conical surface extending at a constant angle or provided on a curved surface (R surface). There may be.
The fuel passage below the valve opening 35 opens into the pressure accumulating chamber in the common rail 1 when the pressure limiter 8 is connected to the common rail 1. The fuel passage below the valve opening 35 has a common rail pressure. Is applied.
On the other hand, a circular-shaped slide hole 36 extending upward from the valve opening 35 is formed in the fuel passage on the low pressure side of the valve opening 35, and a later-described needle 44 is provided on the inner peripheral surface of the slide hole 36. It is slidably supported in the axial direction.

The hollow screw 23 is fastened to a female screw hole 33 formed in the housing 21 to close the upper opening of the housing 21 and has a substantially bolt shape. A male screw 37 that is screwed into a female screw hole 33 formed in the housing 21 is formed on the lower outer periphery of the hollow screw 23. A hexagonal portion 38 with which a fastening tool (such as a spanner) is engaged is formed on the top of the hollow screw 23. A pipe connector (not shown) coupled to the relief pipe 9 described above is attached to the upper and lower intermediate parts of the hollow screw 23. A flange 39 having an enlarged diameter is provided at the lower end of the hexagonal portion 38, and the pipe connector is fastened to the upper end surface of the housing 21 and the flange by strongly fastening the hollow screw 23 to the housing 21 with the pipe connector attached. It is strongly sandwiched between the lower surface of 39 and sealed in a liquid-tight manner. In addition, the codes | symbols 41 and 42 shown in FIG. 1 are the seal washers which improve a sealing performance.
Inside the hollow screw 23 is formed a fuel hole 43 that allows the inside of the housing 21 and the inside of the pipe connector to communicate with each other. The fuel discharged into the spring chamber 32 when the pressure limiter 8 is opened is relief pipe 9. It comes to lead to.

  The ball valve 24 is a valve body having a spherical shape, and is provided with a diameter that forms a gap through which fuel can flow between the ball valve 24 and the inner peripheral surface of the sliding hole 36. The ball valve 24 is disposed at the back of the sliding hole 36 of the valve body 22 and is supported so as to be movable in the vertical direction inside the sliding hole 36. Then, when the ball valve 24 is seated on the valve opening 35, the valve opening 35 is closed, and the communication between the pressure accumulation chamber in the common rail 1 and the spring chamber 32 is blocked.

  The piston 25 is inserted into the sliding hole 36 of the valve body 22 and is supported by the inner peripheral wall surface of the sliding hole 36 so as to be slidable in the vertical direction. And a spring guide 45 having a thin cylindrical shape that is slidably supported in the vertical direction by an inner peripheral wall surface thereof, and a spring guide 46 having a cylindrical shape that is inserted inside the spring 26.

A cutout portion 44 a extending from the lower end of the needle 44 to the upper middle is formed on the outer peripheral surface of the needle 44. The notch 44 a communicates with the spring chamber 32 when the needle 44 is lifted together with the ball valve 24 and the lift amount of the needle 44 reaches a predetermined value, and the fuel overflowing from the valve opening 35 is supplied to the spring chamber 32. It is a guide. The notch 44a is obtained by processing a part of the outer peripheral surface of the needle 44 having a cylindrical shape into a flat surface, and is provided in a plurality (for example, two places) at symmetrical positions around the axis. In FIG. 1, the upper end portion of the notch 44 a is provided perpendicular to the axial direction, but it may be provided so as to be inclined so as to suppress the pressure at which high-pressure fuel escapes to the spring chamber 32 when the valve is opened.
The spring seat 45 has an upper surface on which the lower end of the spring 26 is seated, and the needle 44 presses the ball valve 24 downward (in a direction in which the ball valve 24 closes the valve opening 35) under the urging force of the spring 26.

  The spring 26 is a compression coil spring that is inserted into the spring chamber 32 in a compressed state. The upper end of the spring 26 is seated on a step formed by the reduced diameter portion 34 of the housing 21 via a ring-shaped shim 47, and the lower end is a piston 25. It sits on the spring seat 45 formed in the above. With this configuration, the piston 25 is pressed downward by the restoring force of the spring 26, and the ball valve 24 is pressed against the valve opening 35 by the lower end of the needle 44. The valve opening pressure of the pressure limiter 8 is set by the valve diameter of the valve opening 35 and the ball valve 24 and the compression load of the spring 26. The compression load of the spring 26 is a shim in addition to the compression load of the spring 26 itself. A thickness in the axial direction of 47 is also set.

Next, the operation of the pressure limiter 8 will be described.
The fuel pressure (common rail pressure) in the pressure accumulating chamber in the common rail 1 rises above the valve opening pressure of the pressure limiter 8 due to some unexpected factor, and the valve opening force applied to the ball valve 24 from the pressure accumulating chamber is When the valve closing force applied to the valve 24 is exceeded, the ball valve 24 is separated from the valve opening 35 by the valve opening force, and the piston 25 rises together with the ball valve 24. Then, when the upper end of the notch 44a formed in the needle 44 reaches the spring chamber 32 and the notch 44a and the spring chamber 32 communicate with each other, the fuel in the pressure accumulating chamber becomes the valve opening 35 → the ball valve 24 and the sliding hole 36. Gap → cutout portion 44a → the inner space of the housing 21 → the fuel hole 43 of the hollow screw 23 is led to the relief pipe 9, and the relief pipe 9 is returned to the fuel tank 10.

  The valve opening 35 is opened, and the fuel in the common rail 1 is discharged through the pressure limiter 8, whereby the common rail pressure is lowered. When the common rail pressure falls below the valve opening pressure and the valve opening force applied from the pressure accumulation chamber to the ball valve 24 is less than the valve closing force applied to the ball valve 24 by the spring 26, the piston 25 moves down together with the ball valve 24. When the upper end of the notch 44 a formed in the needle 44 enters the sliding hole 36, the communication between the notch 44 a and the spring chamber 32 is interrupted, and then the ball valve 24 is seated on the valve opening 35, thereby The overflow of high pressure fuel by the limiter 8 is completely blocked.

(Characteristic 1 in Example 1)
Here, since the ball valve 24 receives the pressure of the fuel ejected from the valve opening 35 toward the low pressure side during the valve opening of the pressure limiter 8, the ball valve 24 moves from the axial center of the sliding hole 36 during the valve opening. There is a possibility of deviation.
If the ball valve 24 is pushed in the valve closing direction by the needle 44 while the ball valve 24 is displaced from the axial center of the sliding hole 36 during the valve opening, the ball valve 24 does not coincide with the center of the valve opening 35 and the ball valve 24 The valve body 22 collides with the valve opening 35 in an eccentric state. For this reason, there is a possibility that the ball valve 24 and the valve body 22 will have a large collision force, such as the ball valve 24 colliding with the low-pressure corner of the valve opening 35, and the surface of the ball valve 24 may be damaged. is there.

  In order to avoid the problem, in the first embodiment, in the state where the ball valve 24 is seated at the tip of the needle 44, that is, the contact portion of the needle 44 with the ball valve 24 as shown in FIG. A recess 48 in which a part of the ball valve 24 (the upper side in the figure) fits is provided. The recess 48 guides the ball valve 24, and the ball valve 24 is not coupled to the recess 48. Specifically, a recess 48 into which a part of the ball valve 24 can enter is provided at the center of the lower end surface of the needle 44.

  Thus, by providing the concave portion 48 for guiding the ball valve 24 at the center of the lower end surface of the needle 44, after the pressure limiter 8 is opened, the common rail pressure is lowered and the ball valve 24 is pushed against the needle 44. When the ball valve 24 is directed toward the valve closing direction, the ball valve 24 is guided by the recess 48 and the position of the ball valve 24 is regulated by the recess 48, so that the position of the ball valve 24 can be determined at the center of the needle 44. For this reason, the position of the ball valve 24 when the ball valve 24 collides with the valve body 22 can be matched with the center of the valve opening 35.

Since the ball valve 24 collides with the valve body 22 (seats on the valve opening 35) in a state where the ball valve 24 coincides with the center of the valve opening 35, the impact when the ball valve 24 collides with the valve body 22 can be suppressed. Even if the valve closing force is increased along with the injection, it is possible to avoid the problem that damage such as scratches occurs on the surface of the ball valve 24.
Thus, even if the pressure limiter 8 is opened and closed, damage such as scratches does not occur on the surface of the ball valve 24, so that the sealing performance between the ball valve 24 and the valve opening 35 can be ensured even when used for a long time. The pressure limiter 8 with high reliability can be provided.

(Characteristic 2 in Example 1)
The recess 48 formed in the lower end surface of the needle 44 is a recess opened downward, and the bottom 48 a of the recess 48 is provided on a plane perpendicular to the axial direction of the needle 44.
The plane of the bottom 48a of the recess 48 has a circular shape when the needle 44 is viewed from the axial direction, and the diameter of the bottom 48a of the recess 48 having the circular plane is obtained by subtracting the diameter of the needle 44 from the diameter of the sliding hole 36. The diameter difference is the same as or slightly larger than the diameter difference. As a specific example, when the sliding clearance between the sliding hole 36 and the needle 44 is 7 μm to 10 μm, the diameter of the bottom 48 a is 20 μm to 25 μm.

Thus, by providing the bottom 48a of the recess 48 on a flat surface, the load direction applied to the ball valve 24 in the state in which the ball valve 24 is pushed by the needle 44 and moves in the valve closing direction when the valve is closed is the axis of the needle 44. It is possible to match the direction (movement direction). As a result, when the ball valve 24 is seated on the valve opening 35, it is possible to avoid a problem that a biased load is applied to the ball valve 24, and the ball valve 24 is seated on the valve opening 35 due to the biased load generated on the ball valve 24. It is possible to avoid the problem that a biased collision force is generated when
As described above, since it is possible to avoid a problem that a biased collision force is generated when the ball valve 24 is seated on the valve opening 35, it is possible to further reduce the possibility of damage such as scratches on the surface of the ball valve 24. The pressure limiter 8 can be provided with high reliability without causing fuel leakage even when used for a long time.

(Feature 3 in Example 1)
The concave portion 48 formed in the lower end surface of the needle 44 is a shallow recess having a substantially round hole shape, and an annular inner peripheral surface forming a depth in the concave portion 48, that is, the concave inner annular surface 48 b is the surface of the ball valve 24. It is provided on an inwardly curved surface (R surface) having a curvature larger than the curvature.
For example, when the ball valve 24 is seated on the valve opening 35 in contact with the concave inner annular surface 48b, a collision force is generated at the contact portion between the ball valve 24 and the concave inner annular surface 48b. By providing 48b on the inwardly curved surface having a curvature larger than the surface curvature of the ball valve 24, the contact pressure between the ball valve 24 and the concave inner annular surface 48b can be reduced, and the ball valve 24 and the concave inner annular surface 48b can be reduced. The concentration of the collision force at the abutting portion can be reduced.
In this way, the collision surface pressure between the ball valve 24 and the concave inner annular surface 48b can be reduced, so that the possibility of damage such as scratches occurring on the surface of the ball valve 24 can be further reduced, and for a long time. Even if it is used, no fuel leakage occurs, and the pressure limiter 8 with high reliability can be provided.

[Modification]
In the above embodiment, the bottom 48a of the recess 48 is provided on a plane. However, the bottom 48a is provided on a curved surface (R surface) having a curvature much larger than the surface curvature of the ball valve 24 or a very wide angle conical surface close to the plane. Alternatively, other shapes may be provided.
In the above embodiment, the concave inner annular surface 48b is provided on the curved surface (R surface). However, the concave inner annular surface 48b may be provided in other shapes such as a very wide angle conical surface.
In the above-described embodiment, the depth of the concave portion 48 is provided shallow, and the ball valve 24 is provided to be easily rotated when the valve is opened. However, in order to improve the guide performance of the ball valve 24 by the concave portion 48, the concave portion 48 is provided deeply. Also good.
Further, the present invention may be applied to the pressure limiter 8 integrated with the pressure reducing valve.

It is sectional drawing and a principal part enlarged view of a pressure limiter. It is the schematic of a common rail type fuel injection device. It is a side view of a common rail.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Common rail 8 Pressure limiter 22 Valve body 24 Ball valve 35 Valve opening 36 Sliding hole 44 Needle 48 Recess 48a Recess bottom 48b Recess inner annular surface (annular side surface inside recess)

Claims (3)

A valve opening communicating with a pressure accumulating chamber for accumulating pressurized fuel, and a valve body having a sliding hole on the low pressure side of the valve opening;
A spherical ball valve capable of closing the valve opening;
A needle inserted into the sliding hole and pressing the ball valve in a direction in which the valve opening is closed;
A recess provided at the tip of the needle, for guiding the ball valve;
A pressure limiter for a fuel injection device. In the pressure limiter of the fuel injection device according to claim 1,
The pressure limiter of a fuel injection device, wherein the bottom of the recess is provided on a plane perpendicular to the axial direction of the needle. In the pressure limiter of the fuel injection device according to claim 1 or 2,
A pressure limiter for a fuel injection device, wherein an annular side surface inside the recess is provided on a curved surface having a curvature larger than a surface curvature of the ball valve.

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