JPH025088Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of a unit injector that integrates a fuel pressurizing mechanism and an injection mechanism in a fuel injection device.

As is well known, in a unit injector, the fuel pressurization mechanism and injection mechanism are integrated, so there is no high-pressure pipe that adversely affects fuel injection characteristics.
Therefore, the performance is better than that of other types of fuel injection devices, and a conventional example thereof is shown in FIG.

In FIG. 1, an injector body 1 and a case 2 are airtightly fixed via an O-ring 3.
A plunger barrel 4 and an injection mechanism section 5 are arranged within the injector main body 1 and case 2. The plunger barrel 4 has a plunger insertion hole 12 into which a plunger 11 is slidably inserted, and a tappet 13 is engaged with the upper end of the plunger 11, and a periodic external operating force is applied to the tappet 13. When applied, the plunger 11 reciprocates up and down in conjunction with the return force of the tapepet spring 14. As a result, a fuel reservoir chamber 16 surrounded by the injector body 1, the case 2, and the plunger barrel 4
Fuel is drawn into the pressurizing chamber 19 through the fuel inlet 20 formed in the plunger barrel 4, is pressurized, becomes high-pressure oil, and is sent under pressure to the injection mechanism section 5. In the injection mechanism section 5, a needle 24 is inserted into a nozzle body 22 and is seated on a valve seat 25 of the nozzle body 22, and is connected to a fuel reservoir 26 in front of the valve seat 25 from the pressurizing chamber 19 via a high pressure path 27. When high-pressure oil is sent to the engine, the needle 24 is pushed open against the needle spring 31 by the pressure, and the oil is injected into the engine cylinder (not shown) from a plurality of nozzle holes 23 formed at the tip of the nozzle body 22. It is something that will be done.

The plunger barrel 4 has its upper part inserted into a barrel insertion hole 6 formed in the injector body 1, and is held between the injector body 1 and the injection mechanism section 5, and has a convex step formed in the plunger barrel 4. The upper surface of the portion 8 is in close contact with the periphery of the lower opening end of the barrel insertion hole 6 to form a barrel attachment portion 9. Furthermore, in order to prevent circumferential rotation of the plunger barrel 4, it is necessary to limit the relative positional relationship in the circumferential direction with the injector main body 1, and for this purpose, a positioning device 33 is provided.

However, in the prior art, the positioning device 33 is located above the barreled part 9, so even though the fuel reservoir chamber 16 is sealed by the O-ring 3 and the barreled part 9, There was a risk that the fuel in the fuel reservoir chamber 16 would leak to the outside via the positioning device 33. Moreover, a positioning screw 33a is used in this positioning device 33 in consideration of reliability during installation. Since it is configured to engage with the positioning groove 33c, the positioning screw 33
This caused further increase in fuel leakage through the gap between the screw hole 33a and the screw hole 33b.

In addition, a leak return hole 21 is formed in the plunger barrel 4, which communicates approximately the center of the plunger insertion hole 12 with the fuel reservoir chamber 16, and a pressurization chamber 19 is formed in the plunger barrel 4.
A part of the pressurized fuel is introduced into the gap between the plunger 11 and the plunger insertion hole 12 and used for lubrication,
The fuel is configured to be returned to the fuel reservoir chamber 16 via the leak return hole 21. However, since the positioning device 33 is provided above the shank part 9 as described above, and the shank part 9 is located relatively below, the leak return hole 21 does not extend beyond the shank part 9. The plunger insertion hole 12 is drilled diagonally so as to open approximately in the center, and the machining for drilling the leak return hole 21 is troublesome, and together with the use of the positioning screw 33a in the positioning device 33, the manufacturing cost is high. It is.

Therefore, in this invention, a recessed step is formed in front of the lower opening end of the injector main body, and the lower surface of this recessed step and the upper surface of the convex step of the plunger barrel are brought into close contact to form a barrel mounting section. It is an object of the present invention to provide a unit injector which secures the sealing performance of a fuel reservoir chamber by locating a positioning device and a leak return hole below the attaching part and which can be manufactured at low cost.

Examples of this invention will be described below with reference to the drawings.

An embodiment of this invention is shown in FIG. 2, in which an injector body 1 and a case 2 are screwed together at their lower and upper parts and fixed via an O-ring 3. A plunger barrel 4 and an injection mechanism section 5, which will be described below, are arranged inside the case 2.

The plunger barrel 4 is
The upper part of the injector body 1 is inserted into a barrel insertion hole 6 formed in the injector body 1, and is held between the injector body 1 and the injection mechanism part 5 to fix the vertical position. A recessed step 7 is formed in front of the lower opening end of the barrel insertion hole 6 of the injector body 1, and the lower surface of this recessed step 7 and the upper surface of the convex step 8 formed on the plunger barrel 4 are in contact with the injector main body 1. A body attachment part 9 is formed by being brought into close contact with the mechanism part 5 by pressure.

Below this barrel attachment part 9 (injection mechanism part side) is a positioning device 10 that limits the relative positional relationship in the circumferential direction between the injector main body 1 and the plunger barrel 4.
The positioning device 10 is composed of a positioning groove 10a and a positioning pin 10b. The positioning groove 11a opens on the upper surface of the stepped portion 8 at the periphery of the stepped portion 8 of the plunger barrel 4, and is formed parallel to the axial direction of the plunger 11, which will be described below. On the other hand, the positioning pin 10b is inserted into a pin insertion hole 10c formed in the radial direction slightly before the lower opening end of the injector body 1, and its insertion tip engages with the positioning groove 10a to prevent rotation of the plunger barrel 4. are doing. Therefore, when attaching the plunger barrel 4 to the injector body 1, the positioning pin 10b is inserted into the pin insertion hole 10c of the injector body 1 in advance, and then the plunger barrel 4 is inserted into the barrel insertion hole 6 and inserted into the positioning groove 10a. The positioning pin 10b can be engaged, and positioning work can be performed easily and reliably.

The plunger 11 is slidably inserted into a plunger insertion hole 12 formed in the plunger barrel 4, and has a lead 11a and a vertical groove 11b formed at its lower end, and its upper end is engaged with a tappet 13. There is. A tappet spring 14 is provided between the tappet 13 and the injector body 1.
When a periodic external operating force is applied to the tappet 14, the plunger 11 reciprocates up and down within the plunger insertion hole 12 together with the return force of the tappet spring 14. Further, in this plunger 11, a control pinion 15 disposed in a space surrounded by the injector body 1 and the plunger barrel 4 is engaged so as to limit the relative positional relationship in the circumferential direction. By operating a control rack (not shown) engaged with the plunger 11.
is rotated to adjust its effective stroke.

The fuel reservoir chamber 16 is a space surrounded by the injector body 1, the case 2, and the plunger barrel 4.
As described above, since the positioning device 10 is located below the trunk attachment part 9, the upper part of the fuel reservoir chamber 16 is
It is sealed by the ring 3 and the body attachment part 9. This fuel reservoir chamber 16 is located in the injector main body 1
It is connected to fuel supply and discharge ports 18a and 18b through a fuel supply and discharge passage 17 formed in the fuel supply and discharge passage 17, and is surrounded by the plunger barrel 4, the plunger 11, and a spring case 28 of the injection mechanism section 5, which will be described below. The pressure chamber 19 communicates with the plunger barrel 4 through a fuel inlet 20 formed therein, and further communicates with the plunger insertion hole 12 through a leak return hole 21 formed in the plunger barrel 4 as well. This leak return hole 21 allows a portion of the fuel pressurized in the pressurizing chamber 19 to be transferred between the plunger 11 and the plunger insertion hole 12.
It is used for lubrication and returned to the fuel reservoir chamber 16 by being guided into the gap between the plunger barrel 4 and the plunger barrel 4. It is located below the barrel attachment part 9 and is formed straight in the radial direction of the plunger barrel 4. This is possible because the barrel attachment portion 9 is constructed so that the lower surface of the concave step 7 of the barrel insertion hole 6 and the upper surface of the convex step 8 of the plunger barrel 4 are in close contact with each other, as described above. The process for drilling the leak return hole 21 becomes easier.

The injection mechanism section 5 has a nozzle body 22 that is locked to the tip of the case 2, and this nozzle body 22 has the following features:
A plurality of nozzle holes 33 are formed at the tip, and
Valve seat 25 on which the needle 24 is seated slightly in front of the tip
is formed, and an oil reservoir 26 is further formed in front of this valve seat 25, and this oil reservoir 26 and the pressurizing chamber 1
9 are communicated with each other via a high pressure path 27. A spring case 28 screwed onto the case 2 is disposed between the nozzle body 22 and the plunger barrel 4.
and a stopper 29 are interposed. The spring case 28 houses a needle spring 31 that presses the needle 24 in the valve closing direction in a spring chamber 30 within the spring case 28, and also has an overflow hole that communicates the spring chamber 30 with the fuel reservoir chamber 16. 32 is formed, and the stopper 29 regulates the position of the needle 24 when the valve is opened.

In the above configuration, when a periodic external operating force is applied to the tappet 13, the plunger 11 reciprocates up and down in the plunger insertion hole 12 together with the return force of the tappet spring 14, and the fuel is removed in the upward stroke. Fuel is sucked into the pressurizing chamber 19 from the reservoir chamber 16 via the fuel inlet 20, and when the fuel inlet 20 is closed during the downward stroke, the sucked fuel is pressurized and becomes high-pressure oil, which flows through the high-pressure path 27. The oil is sent to the oil sump 26. For this reason, the pressure inside the oil reservoir 26 increases, and the needle 24 moves to the needle spring 3.
1 and the fuel is injected from the nozzle hole 23. Then, when the fuel inlet 20 again comes into communication with the pressurizing chamber 19 via the vertical hole 11b, the pressure in the pressurizing chamber 19 drops rapidly, and as a result, the pressure in the oil reservoir 26 also drops, and the needle 24 is again seated on the valve seat 25 by the needle spring 31, and the injection ends.

At this time, the upper part of the fuel reservoir chamber 16 is sealed by the O-ring 3 and the attached part 9, so there is no risk of fuel leaking to the outside. Incidentally, fuel in the fuel reservoir chamber 16 is supplied from a feed pump (not shown) via a fuel supply/discharge path 17, and excess fuel is returned to a fuel tank (not shown) via the fuel supply/discharge path 17 as well.

As described above, according to this invention, in the unit injector, a recessed step is formed in front of the lower opening end of the barrel insertion hole of the injector main body,
The bottom surface of this concave step and the top surface of the convex step of the plunger barrel are brought into close contact to form a barrel mounting section, and the positioning device is positioned below this barrel mounting section, so that the positioning device can be used to connect the fuel reservoir to the fuel storage chamber via the positioning device. The barreled portion can prevent fuel from leaking to the outside, thereby ensuring complete sealing of the fuel reservoir. In addition, since the leak return hole is also located below the barrel part, the leak return hole can be formed in the radial direction of the plunger barrel, and a positioning pin can be used as the positioning device, which reduces manufacturing costs. can be made inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conventional unit injector, and FIG. 2 is a sectional view showing a unit injector of this invention. 1...Injector body, 2...Case, 3...
... O-ring, 4 ... Plunger barrel, 5 ... Injection mechanism section, 6 ... Barrel insertion hole, 7 ... Concave step,
8... Convex step part, 9... Trunked part, 10... Positioning device, 10a... Positioning groove, 10b... Positioning pin, 11... Plunger, 12... Plunger insertion hole, 21... Leak return hole .

Claims (1)

[Scope of utility model registration request] The injector body and the case are airtightly fixed, and a plunger barrel and an injection mechanism are arranged inside the injector body and the case, and the upper part of the plunger barrel is inserted into a barrel insertion hole formed in the injector body. In a unit injector which is sandwiched between the injector main body and the injection mechanism section, and has a space between the injector main body, the case and the plunger barrel as a fuel storage chamber, the lower part of the barrel insertion hole of the injector main body A recessed step is formed in front of the opening end,
The lower surface of this concave step and the upper surface of the convex step formed on the plunger barrel are brought into close contact to form a shank part, and below the shank part, a peripheral edge of the convex step of the plunger barrel is formed. A positioning groove that is open on the upper surface of the convex step and formed parallel to the axial direction of the plunger, and a positioning pin that engages with the positioning groove and is inserted in the radial direction in the concave step of the injector body. and a leak return hole that communicates with the fuel reservoir chamber a plunger insertion hole formed in the plunger barrel in the radial direction and into which the plunger is slidably inserted. Injector.