JPH0640925Y2 - Fuel injector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a fuel injection device used in an internal combustion engine such as a diesel engine, and more particularly to a unit type fuel injection device.

[Prior Art] A conventional fuel injection device of this type is disclosed in, for example, Japanese Patent Laid-Open No. 59
The one described in Japanese Patent Publication No. -194073 is known.

The fuel injection device described in this publication includes a fuel pressurizing section for pressurizing fuel and an electromagnetic valve section for controlling the timing of pressurization of fuel by the fuel pressurizing section. The valve part is incorporated in the main body of the device.

The fuel pressurizing unit includes a fuel pressurizing chamber into which fuel is introduced and a pump plunger that pressurizes the fuel in the fuel pressurizing chamber. The fuel pressurizing unit reciprocates by following the rotation of the cam portion of the cam shaft. By moving the fuel, the fuel is pressurized. The pressurized fuel is injected into the combustion chamber of the engine from an injection nozzle incorporated in the apparatus body.

On the other hand, the solenoid valve portion is provided with a fuel supply return chamber connected to the fuel pump, a valve accommodating hole that is connected to the fuel supply return chamber, and has a valve seat formed at an intersection with the fuel supply return chamber. A valve body that is slidably installed in the valve housing hole and has a head that seats on the valve seat is formed at one end located in the fuel supply return chamber, and this valve body is seated against the biasing force of the valve spring. A solenoid that moves in the direction of the valve, and communicates with the fuel pressurizing chamber between the inner peripheral surface of the valve housing hole and the outer peripheral surface of the valve body, and returns the fuel by seating the valve body on the valve seat. Shut off against the room,
A lift from the valve seat of the valve element forms a fuel reservoir chamber that communicates with the fuel supply return chamber, and the head of the valve element abuts against the fuel supply return chamber to regulate the maximum lift amount of the valve element. A stopper portion is formed.

In the fuel injection device including the fuel pressurizing unit and the electromagnetic valve unit configured as described above, when the valve body is seated on the valve seat during fuel pressurization by the pump plunger, the fuel supply return chamber and the fuel reservoir chamber are shut off from each other. As a result, the fuel supply return chamber and the fuel pressurizing chamber are shut off. As a result, the fuel in the fuel pressurizing chamber is pressurized to a high pressure, and the fuel is injected into the combustion chamber of the engine from the fuel injection nozzle provided in the apparatus body. Further, when the valve body is lifted from the valve seat until it hits the stopper portion at the same pressurization, the fuel pressurizing chamber and the fuel supply return chamber communicate with each other through the fuel reservoir chamber, and the pressurized fuel supplies the fuel. Backflow into the return room. As a result, the pressure in the fuel pressurizing chamber decreases, and the fuel injection ends.

[Problems to be Solved by the Invention] In the above-described conventional fuel injection device, there is a problem that the injection of fuel is insufficient. That is, when the valve body is lifted from the valve seat in order to finish the fuel injection, the pressure in the fuel pressurizing chamber instantly propagates into the fuel supply return chamber, and the pressure between the facing surfaces of the valve body and the stopper portion is increased. Raise. The increased pressure causes the valve body to move in the seating direction,
The valve body is seated again or the valve opening area between the valve seat and the valve body is made extremely narrow. Therefore, the pressure in the fuel pressurizing chamber does not drop, and in an extreme case, the pressure in the fuel pressurizing chamber rises again. Of course, the valve body eventually lifts up to the stopper portion, and the fuel injection is terminated by this, but the valve body moves in the seating direction at the time of the above lift (hereinafter referred to as reverse movement). ) Is performed at least once, and when it is large, 2-3 times. Therefore, it takes time to decrease the pressure in the fuel pressurizing chamber by the amount of the reverse movement, which causes a problem of worsening the fuel injection failure.

The present invention has been made in order to solve the above problems, and can prevent the valve body from moving backward when the valve body is lifted, and thus can improve the fuel injection shortage. The purpose is to provide.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention is designed so that the fuel supply return chamber surrounds a stopper portion and has an inner peripheral surface which is slidable on a head portion of a valve body facing the stopper portion. An annular wall portion is provided which liquid-tightly partitions the stopper portion and at least the tip portion of the head portion from the fuel supply return chamber by movably fitting.

[Operation] When the valve body is lifted from the valve seat to end the fuel injection, the pressure in the fuel pressurizing chamber instantly propagates into the fuel supply return chamber through the fuel reservoir chamber, and the pressure in the fuel supply return chamber is increased. Raise. However, since the stopper portion and the tip portion of the head portion are liquid-tightly partitioned from the fuel supply return chamber by the annular wall portion, the pressure between the facing surfaces of the stopper portion and the head portion may increase. Absent. Therefore, the valve body instantaneously hits the stopper portion without moving in the reverse direction and maintains the maximum lift. As a result, the pressure in the fuel pressurizing chamber is rapidly decreased, and the fuel injection failure is improved.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 and FIG. 2 show an embodiment of the present invention, in which reference numeral 1 is an apparatus main body. The device main body 1 includes a main body 2. The main body 2 is composed of a vertical portion 2a extending vertically in FIG. 2 and a side portion 2b protruding laterally from an intermediate portion of the vertical portion 2a. Vertical part
A fuel pressurizing unit 3 for pressurizing the fuel is provided at 2a, and the fuel pressurized by the fuel pressurizing unit 3 is injected to a lower portion of the fuel pressurizing unit 3 into a combustion chamber (not shown) of the engine. A fuel injection unit 4 is provided for this purpose. On the other hand, the side part 2b
Is provided with an electromagnetic valve unit 5 for controlling the fuel injection start timing and the fuel injection end timing by the fuel pressurizing unit 3.

First, the fuel pressurizing section 3 will be described. In the vertical section 2a, a large-diameter cylinder hole 31 extending downward from the upper end surface thereof and a large-diameter cylinder hole 31 and an axis line from the bottom surface of the large-diameter cylinder hole 31 are provided. Small diameter cylinder hole 32 that matches and extends downward
And a fuel pressurizing chamber 33 into which fuel is introduced are connected.

A follow-up member 34 is slidably provided in the large-diameter cylinder hole 31. The follow-up member 34 is biased upward by a plunger spring 35 provided between the upper portion and the upper end surface of the vertical portion 2a, and is pressed and brought into contact with the cam portion of a cam shaft (not shown). It is designed to move up and down following the rotation of the shaft. A stopper shaft 36 that penetrates a vertically extending locking groove 21 formed in the vertical portion 2a is fixed to the outer peripheral surface of the follower member 34, and the stopper shaft 36 is an upper side surface of the locking groove 21. By hitting against, the movable range of the follow-up member 34 to the upper side is restricted.

On the other hand, a pump plunger 37 is slidably provided in the small diameter cylinder hole 32. This pump plunger 37
The upper end portion is attached to the lower end portion of the follow-up member 34 so as not to move in the vertical direction, whereby the follow-up member 34 is vertically moved integrally. The fuel in the fuel pressurizing chamber 33 is pressurized during the downward movement (forward movement), and the fuel is sucked into the fuel pressurizing chamber 33 during the upward movement (backward movement).
Further, in the central portion of the small diameter cylinder hole 32, the fuel in the fuel pressurizing chamber 33 and the pump plunger
A leak stopper groove 32a is formed to prevent leakage to the outside through the gap with the outer peripheral surface of 37.

Next, the fuel injection unit 4 will be described. A holding cylinder 41 is screwed to the lower end of the vertical portion 2a with its axis aligned with the axis of the small diameter cylinder hole 32. Inside the holding cylinder 41, a spacer 42 and a spring holder 43 are sequentially inserted downward from the vertical portion 2a side. These spacers 42
The spring holder 43 is fixed to the vertical portion 2a together with the holding cylinder 41 by tightening the holding cylinder 41. In addition, a nozzle holder 44 whose axis is aligned with the lower end of the holding cylinder 41 is screwed. Inside the nozzle holder 44, a spacer 45 and an injection nozzle 46 are sequentially inserted downward from the holding cylinder 41 side. The spacer 45 and the injection nozzle 46 are fixed to the holding cylinder 41 together with the nozzle holder 44 by tightening the nozzle holder 44, and in turn fixed to the vertical portion 2a.

In the fuel injection unit 4 having the above structure, when the fuel in the fuel pressurizing chamber 33 is pressurized by the pump plunger 37, the pressurized fuel is provided in the passage 22 and the spacer 42 formed in the vertical portion 2a. It is introduced into the injection nozzle 46 through a check valve 47 having a well-known structure, and a passage 48 formed across the spacer 42, the spring holder 43, the spacer 45 and the injection nozzle 46.
Then, the fuel introduced into the injection nozzle 46 is
The needle valve 46a of 46 is lifted against the biasing force of the nozzle spring 49, and is ejected from an injection hole (not shown) formed at the tip of the injection nozzle 46.

Next, the electromagnetic valve portion 5 will be described. In the side portion 2b, the large diameter hole portion 23, the small diameter hole portion 24, and the medium diameter hole portion 25 have their axes aligned with each other in order from the upper end surface to the lower end surface. Are connected in series.

The lower end of the solenoid valve 51 is inserted into the large diameter hole 23.
The solenoid valve 51 includes a valve housing 511 and a lid 512 screwed and fixed to an upper end portion of the valve housing 511. The valve housing 511 is fixed such that the lower end surface thereof abuts the bottom surface of the large diameter hole portion 23 via the spacer 52, and the central portion thereof penetrates from the upper end surface to the lower end surface and has a large diameter hole. A valve insertion hole 513 whose axis is aligned with the portion 23 is formed. A taper hole-shaped valve seat 513a is formed at the lower end opening of the valve insertion hole 513, and an annular groove 513b is formed slightly above the valve seat 513a.

A valve element 514 is slidably inserted in the valve insertion hole 513. The valve body 514 includes a shaft portion 514a slidably inserted in the valve insertion hole 513, and a head portion 514b formed below the shaft portion 514a with its axis aligned with the shaft portion 514a and seated on the valve seat 513a. The valve insertion hole 51 is provided between the shaft portion 514a and the head portion 514b.
An annular recess 514c that faces the annular groove 513b formed in 3 is formed. A fuel storage chamber 515 is formed by the annular groove 513a and the annular recess 514c.

It should be noted that the central portion of the valve insertion hole 513 prevents the fuel in the fuel storage chamber 515 from leaking to the armature chamber 520 through the space between the inner peripheral surface of the valve insertion hole 513 and the outer peripheral surface of the valve body 514. An annular groove 513c for forming is formed.

In addition, at the upper end of the shaft portion 514a of the valve body 514, the screw shaft portion 514d
Are formed. This screw shaft 514d has a nut 516
Are screwed together, and the nut 516 fixes the armature 517 to the screw shaft portion 514d. On the lower end surface of the lid 512 facing the armature 517, the solenoid 51
8 are arranged. When this solenoid 518 is energized,
The magnetic force pulls the armature 517 upwards against the biasing force of the valve spring 519. The valve body moves as the armature 517 moves, the head 514b is seated on the valve seat 513a, and the solenoid valve 51 is closed. On the other hand, when the energization of the solenoid 518 is stopped, the head 514b is lifted downward from the valve seat 513b by the urging force of the valve spring 519, and the solenoid valve
51 is designed to open. The solenoid 518
The energization start timing and the energization time are controlled by a control unit such as a microcomputer (not shown) according to the operating conditions such as the engine speed and load.

A stopper member 53 is screwed and fixed to the medium diameter hole portion 25. By inserting and fixing the stopper member 53 in the medium diameter hole portion 25, a space defined by the upper end surface of the stopper member 53, the valve housing 511 and the valve body 514 is formed in the small diameter hole portion 24. . The space is used as the fuel supply return chamber 54. The fuel supply return chamber 54 is connected to the fuel reservoir chamber 515 via the valve seat 513a. Therefore, the fuel supply return chamber 54 and the fuel sump chamber 515
When the valve body 514 is seated on the valve seat 513a, it is shut off and the valve body 5
When 14 is lifted from the valve seat 513a, it will be in communication. Further, the stopper member 53 is for restricting the maximum lift amount of the valve body 514, and a protrusion having a slightly smaller diameter than the head 514b ( Stopper portion) 53a is formed. The maximum lift amount of the valve body 514 is regulated by the head portion 514b hitting the upper end surface of the protruding portion 53a.

Further, by the stopper member 53 and the upper bottom surface of the medium diameter hole portion 25,
A ring-shaped spacer 55 and a tubular member (annular wall portion) 56, which are sequentially arranged upward from the stopper member 53, are sandwiched and fixed. The spacer 55 and the tubular member 56 are formed to have a diameter slightly larger than that of the protruding portion 53a, and are arranged so as to surround the protruding portion 53a. Moreover, the upper end of the tubular member 56 is located inside the small diameter hole 24 (the fuel supply return chamber 54
The lower end portion (tip portion) of the head portion 514b is slidably and liquid-tightly fitted to the inner peripheral surface of the upper end portion thereof. As a result, inside the tubular member 56 and the spacer 55, the stopper member 53 and the head portion 514b are partitioned,
Internal space 57 that is liquid-tightly shut off from the fuel supply return chamber 54
Are formed. This internal space 57 is a stopper member 53.
It is connected to a fuel tank (not shown) through a drain hole 53b formed inside.

In order to enable control of the fuel injection start timing and fuel injection end timing by the solenoid valve portion 5 configured as described above, the fuel passage is formed as follows.

That is, the fuel inlet 12 having the filter 11 is formed on the peripheral wall of the holding cylinder 41. Fuel is pumped into the fuel inlet 12 from a fuel tank by a fuel pump (not shown). Further, the fuel inlet 12 is communicated with the annular groove 32a through the passage 13 formed across the spring holder 43, the spacer 42 and the vertical portion 2a, and from there, further through the passage 14 to the fuel supply return chamber 54. It is in communication. The fuel supply return chamber 54 includes the passage 15 and the spacer.
It communicates with the fuel outlet 16 through an annular recess 42a formed in 42, and the fuel outlet 16 is connected to the fuel tank. Therefore, the fuel should have a certain pressure (usually 5-6 Kg /
It is constantly circulated through the fuel supply return chamber 54 with a cm ² ).

The fuel reservoir chamber 515 is communicated with the fuel pressurizing chamber 33 via the passage 17 formed across the valve housing 511, the spacer 52 and the main body 2. Therefore,
When the solenoid valve 51 is open and the pump plunger 37 is moving upward,
Fuel flows from the fuel supply return chamber 54 into the fuel pressurizing chamber 33 through the fuel reservoir chamber 515 and the passage 17, and when the solenoid valve 51 is opened and the pump plunger 37 is moved downward,
The fuel in 33 will flow back into the fuel supply return chamber 54. Further, when the solenoid valve 51 is closed and the pump plunger 37 is moved downward, the fuel supply return chamber 54 and the fuel storage chamber 515 are shut off, and the fuel supply return chamber 54 and the fuel pressurizing chamber 33 are shut off. . As a result, the fuel in the fuel pressurizing chamber 33 is pressurized to a high pressure and injected from the fuel injection unit 4.

In the fuel injection device having the above configuration, the pump plunger 37
When moving upward, the solenoid 518 is de-energized and the solenoid valve 51 is opened. Therefore, the fuel in the fuel supply return chamber 54 is introduced into the fuel pressurizing chamber 33 via the fuel reservoir chamber 515 and the passage 17.

When the pump plunger 37 turns downward, the fuel in the fuel pressurizing chamber 33 is pressurized, but the solenoid valve 51 maintains the open state in the initial stage of the downward movement of the pump plunger 37. Therefore, the fuel in the fuel pressurizing chamber 33 flows back to the fuel supply return chamber 54. Therefore, although the fuel is slightly pressurized, it does not reach the pressure for lifting the needle valve 46a against the nozzle spring 49 and is not injected from the injection nozzle 46.

When the pump plunger 37 is moving downward, the control unit determines the fuel injection start timing from the operating state of the engine, and when the solenoid 518 is energized based on the determination, the head 514b causes the valve seat 5 to move.
Seated on 13a, the solenoid valve 51 is closed. Then, the fuel supply return chamber 54 and the fuel storage chamber 515 are disconnected from each other,
As a result, the fuel supply return chamber 54 and the fuel pressurizing chamber 33 are shut off from each other. As a result, the fuel in the fuel pressurizing chamber 37 is pressurized. Then, the pressurized and high-pressure fuel is pressure-fed to the injection nozzle 46 through the passage 22, the check valve 47 and the passage 48,
It is ejected from the ejection hole of the ejection nozzle 46.

When the control unit determines that the fuel injection should be ended, the energization of the solenoid 518 is stopped based on the determination. Then, the valve body 514 is lifted by the urging force of the valve spring 519 until it abuts against the protruding portion 53a, and the solenoid valve 51 is opened. As a result, the fuel pressurizing chamber 33 is connected to the fuel supply return chamber 54 through the passage 17, the fuel reservoir chamber 515 and the valve seat 513b.
Communicate with. Therefore, the pressure in the fuel pressurizing chamber 33 decreases, and the fuel injection ends.

Here, in the above fuel injection device, the lower portion of the head portion 514b and the protruding portion 55a that abut each other are present in the internal space 57, and the internal space 57 is liquid-tightly shut off from the fuel supply return chamber 54. Therefore, the pressure in the fuel pressurizing chamber 33 becomes
It does not propagate between the 4b and the protrusion 53a. Therefore, the valve element 514 does not move backward during its lift, but instantaneously hits the protruding portion 53a and maintains the fully open state. Therefore, the fuel injection can be completed within an extremely short time after the power supply to the solenoid 518 is stopped, and so-called fuel shortage can be improved.

Next, another embodiment of the present invention will be described with reference to FIGS. The same parts as those in the above embodiment are designated by the same reference numerals and the description thereof will be omitted.

The main difference between the fuel injection device of this embodiment and the above embodiment is the electromagnetic valve portion 5A and the fuel injection control passage.

That is, in this embodiment, the side portion 2b also serves as the valve housing, and the valve body 514 is slidably inserted into the side portion 2b sequentially from the upper end surface to the lower end surface thereof. And two mounting holes 522, 523 whose axes coincide with the valve insertion hole 521 are formed. A valve seat 521a is formed at the intersection of the valve insertion hole 521 and the bottom surface of the mounting hole 522.
Further, the valve insertion hole 521 has an annular groove 513 in the above embodiment.
a is not formed, and in this case, the fuel reservoir chamber 524 is formed by the annular recess 514c formed in the valve body 514. An annular groove 521b for preventing fuel leakage is formed in the center of the valve insertion hole 521.

On the other hand, stopper members 525 are mounted in the mounting holes 522 and 523. The stopper member 525 includes a holding portion 526 and an abutting portion 52.
The holding portion 526 is loosely inserted into the mounting hole 523 and is fixed to the bottom surface of the mounting hole 523 with a bolt (not shown). On the other hand, the contact portion 527
Has its lower end screwed and fixed to a screw hole 526a formed in the center of the upper surface of the holding portion 526, and its upper end is fitted into the mounting hole 522. By fitting the upper end of the contact portion 527 into the mounting hole 522, the fuel supply return chamber 58 is formed at the end of the mounting hole 522 on the valve insertion hole 521 side.

Further, the head 514b of the valve body 514 abuts on the center of the upper surface of the abutting portion 527, and the abutting surface (stopper portion) 527a is surrounded so that the upper surface of the abutting portion 527 has an annular protrusion. A portion (annular wall portion) 527b is formed. The head portion 514b of the valve body 514 is slidably and liquid-tightly fitted to the inner peripheral surface of the annular protruding portion 527b. Head 514b
Are fitted to each other, an inner space 59 that is liquid-tightly partitioned from the fuel supply return chamber 58 by the inner peripheral surface, the abutting surface 527a, and the head 514b is formed inside the annular protrusion 527b. ing. This internal space 59 is the contact portion 527.
Also, it is connected to a fuel tank (not shown) through a drain hole 60 formed across the holding portion 526.

Further, although it is a passage for control, a joint 18 connected to a fuel pump (not shown) is fixed to the vertical portion 2a, and fuel is pumped to the fuel supply return chamber 58 via this joint 18. Thus, a passage 19 that connects the joint 18 and the fuel supply return chamber 58 is formed in the main body 2. However, in this embodiment, the fuel supply return chamber 58 is not connected to the fuel tank. Therefore, the pressure inside the fuel supply return chamber 58 is substantially equal to the discharge pressure of the fuel pump, and the pressure is set to ⁵ to 6 kg / cm ² as in the above embodiment. In addition, one end of the main body 2 and the spring holder 43 is open to the internal space of the spring holder 43, and the other end is a small diameter cylinder hole.
A return passage 20 that opens to the side surface of the side portion 2b is formed via the annular groove 32a of 32 and the annular groove 521b of the valve insertion hole 521, and the fuel drain is returned to the fuel tank via the return passage 20. It is like this.

In this embodiment, the nozzle holder 44 has the vertical portion 2a.
The spring holder 43, the spacer 45 and the injection nozzle 46 are fixed to the vertical portion 2a by the nozzle holder 44. Further, in FIGS. 4 and 5, reference numeral 6 is a sensor for detecting the lift amount of the needle valve 46a, and the detected value is input to a control unit (not shown).

The operation of the fuel injection device configured as described above is performed by the valve body 514.
When the pump plunger 37 moves downward while the valve is open, it is the same as the above-mentioned embodiment except that the fuel in the fuel pressurizing chamber 33 flows back to the fuel pump side, and therefore its explanation is omitted.

In the above embodiment, the head portion 514b of the valve body 514 is liquid-tightly fitted to the tubular member 53 or the annular projecting portion 527b which is the annular wall portion. Due to the dynamic fit, a slight gap is required, and a gap due to manufacturing error or the like is allowed. Even if such a gap exists, the pressure hardly propagates into the internal spaces 57, 59 from the gap.

[Advantage of the Invention] As described above, according to the fuel injection device of the present invention, the fuel supply return chamber surrounds the stopper portion, and the head portion of the valve body is slidably fitted to the inner peripheral surface. As a result, the stopper and the at least tip of the head are provided with an annular wall that liquid-tightly partitions the fuel supply return chamber.
The high pressure generated in the fuel pressurizing chamber does not act between the valve body and the stopper portion. Therefore, it is possible to prevent the reverse movement of the valve body moving toward the valve seat side when the valve body is lifted. Therefore, it is possible to finish the fuel injection within a very short time after opening the solenoid valve,
It is possible to obtain the effect that it is possible to improve the fuel injection failure.

[Brief description of drawings]

FIGS. 1 and 2 show an embodiment of the present invention. FIG. 1 is an enlarged sectional view of a main part, FIG. 2 is a vertical sectional front view,
3 to 5 show another embodiment of the present invention,
FIG. 3 is an enlarged cross-sectional view of the main part, FIG. 4 is a vertical sectional front view, and FIG.
The figure is a vertical side view. 1 ... Device body, 3 ... Fuel pressurizing section, 5, 5A ... Solenoid valve section, 33 ... Fuel pressurizing chamber, 37 ... Pump plunger, 51 ...
... Solenoid valve, 53a ... Projection (stopper), 54,58 ... Fuel supply return chamber, 56 ... Cylindrical member (annular wall), 57,59 ...
… Internal space, 513,521 …… Valve housing hole, 513a, 521a …… Valve seat, 514 …… Valve body, 514b …… Head, 515,524 …… Fuel storage chamber, 527a …… Abutting surface (stopper part), 527b… …
Annular protrusion (annular wall).

Claims (1)

[Scope of utility model registration request] 1. A fuel pressurizing chamber having a fuel pressurizing chamber into which fuel is introduced, a pump plunger for pressurizing fuel in the fuel pressurizing chamber, a fuel supply returning chamber to which fuel is supplied, and a fuel supplying return chamber. And a valve accommodating hole having a valve seat formed at an intersection with the fuel supply return chamber, and a valve accommodating hole slidably provided in the valve accommodating hole and located at one end located in the fuel supply return chamber. A valve seat provided with a head for seating on a seat, and communicating with the fuel pressurizing chamber between the inner peripheral surface of the valve housing hole and the outer peripheral surface of the valve body; A fuel reservoir chamber is formed, which is shut off from the fuel supply return chamber by being seated on the valve seat, and communicated with the fuel supply return chamber by a lift of the valve body from the valve seat, and the valve is provided in the fuel supply return chamber. Provided with a stopper part where the head of the body hits at the time of its maximum lift In the fuel injection device including the electromagnetic valve portion, the fuel supply return chamber is slidably fitted to a head portion surrounding the stopper portion and having an inner peripheral surface facing the stopper portion. A fuel injection device, comprising: an annular wall portion that liquid-tightly separates the stopper portion and at least a tip portion of the head portion from the fuel supply return chamber.