JPH0415395B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a nozzle-pump-shaped diesel engine fuel injection mechanism called a unit injector, and particularly to a unit injector for accurately determining the fuel injection start timing. METHODS AND APPARATUS.

(Conventional example) In a unit injector, fuel injection into the cylinder starts when the tip of the plunger closes the fuel hole in the barrel, but in the past, the dimensions of parts such as the plunger and barrel Variations in the injection start timing were prevented by strict control and by minimizing errors in the axial position of each part (stacking error) that occur during the assembly of the unit injector.

However, in that case, when assembling the unit injector, adjustment is required based on the operator's sense of touch, and assembly requires skill. Moreover, it is difficult to make the injection start timing sufficiently accurate.

(Objective of the Invention) An object of the present invention is to enable accurate and easy adjustment of the injection start timing of a unit injector.

(Structure of the Invention) The first invention provides an axial width of the spacer 44 supported on the plunger pressure receiving end in a state where the end of the plunger 43 on the injection nozzle 4 side and the end of the barrel 59 are aligned when assembling the unit injector alone. is adjusted so that the distance H1 between the pressure receiving surface of the spacer 44 and the end of the injector body on the side opposite to the injection nozzle is constant, and then when the unit injector is installed on the engine, it is screwed onto the rocker arm 53 so that the pressure end is connected to the spacer 44.
By adjusting the protrusion amount of the adjustment screw 55 that protrudes to the side, the spacer 44 can be attached to the pressure end of the adjustment screw 55.
This is a method for adjusting the injection start timing of a unit injector in which the setting position in the axial direction of the plunger end 60 on the side of the injection nozzle 4 is determined while the pressure receiving surface of the plunger is pressed by the elasticity of the plunger spring 58.

The second invention is used by applying it to the end face 47 of the injector body opposite to the injection nozzle 4 of the unit injector, and has an L-shaped cross section, and has an end face 41 that contacts the end face 47 of the injector body and a stepped portion 42 that contacts the spacer 44. A first adjustment fitting 40 for selecting a spacer 44 having a constant distance H1 and sandwiched between the stepped portion 42 and the pressure receiving end of the plunger from among a large number of spacer groups having different axial widths.
It has an L-shaped cross section, and the distance between one end surface 50 and the other end surface 49 that correspond to the injector body end surface 47 is a constant distance H2, and the distance H2 is equal to the distance H1 of the first adjustment fitting 40 on the injection nozzle 4 side. A second adjustment fitting 4 for setting the distance to be the sum of the distance L between the barrel end 61 and the injection nozzle 4 side end 62 of the fuel hole 52
8, a spacer 44 selected from a large number of spacer groups having different axial widths by the first adjustment fitting 40 and supported by the pressure receiving end of the plunger 43, and an adjustment screw 55 screwed into the rocker arm 53. , After removing the first adjusting fitting 40 from the spacer 44, attaching the second adjusting fitting 48 with the stepped portion 57 in contact with the pressure receiving surface 45 of the spacer 44,
The end surface 49 of the second adjusting fitting 48 is connected to the adjusting screw 5.
5, press until the end surface 50 of the second adjustment fitting 48 touches the end surface 47 of the injector body, and then remove the adjustment screw 55 from the rocker arm 53 to the spacer 44 side.
The amount of protrusion of the pressurizing end can be adjusted, and during operation, the first and second adjustment fittings 40,
48 and directly connect the pressurizing end of the adjusting screw 55 to the spacer 4 by the elasticity of the plunger spring 58.
This is an injection start timing adjusting device for a unit injector, characterized in that it is configured so as to correspond to No. 4.

(Embodiment) First, an example of a unit injector will be explained.
In FIG. 1, which shows the fractured side surface, the cylindrical body 2 (injector body) of the unit injector is shown.
is attached to the cylinder head 3 in an inclined position with respect to the center line O--O of the cylinder head 3 (only a portion of which is shown) via a cylindrical cap 1 that is concentrically screwed together.
Inside the holes 1a and 2a of the cap 1 and body 2 are an injection nozzle 4 whose tip projects into the combustion chamber in the cylinder head 3, an annular nozzle stopper plate 5, a cylindrical spring cage 6, and an annular check valve seat 7. , and the cylindrical barrel 8 are fitted concentrically,
Rotation is prevented by knock pins 9 and 10. A plunger 12 is fitted into the barrel 8 so as to be slidable and rotatable. A cylindrical tappet 13 is supported at the upper end of the plunger 12. The bolt 14 is loosely secured to the body 2 via a flange 14b, and an eccentric pin 14 integrated with the bolt 14
A is engaged with an elongated hole 15 in the axial direction provided in the tappet 13 to prevent relative rotation of the tappet 13 with respect to the body 2. A driving lever 16 is connected at right angles to the upper end of the plunger 12 at its lower end. The driving lever 16 has an arc-shaped notch 17 (Fig. 2) provided in the tappet 13.
The upper end is connected to a governor mechanism (not shown). Arc-shaped recess 18 of tapepet 13 in FIG.
A disc-shaped spacer 20 is supported inside, and the spacer 20 is in contact with the upper end of the plunger 12.
A cylindrical spring seat 21 is fitted into the body 2, and an integral spring seat 22 is provided on the tapepet 13. A plunger spring 23 is compressed between both seats 21 and 22.

A pump chamber 24 is formed in the barrel 3, and the pump chamber 24 includes an opening in the check valve seat 7, a disk-shaped check valve 25 provided in the spring cage 6, and a passage 26 in the cage 6 and nozzle stopper plate 5. , 27 to the injection nozzle 4. 28 is a needle valve, and the needle valve 28 normally closes the injection nozzle 4 by the elasticity of a spring 30.

The barrel 3 has a fuel hole 3 that can communicate with the pump chamber 24.
1 (radial hole), and the fuel hole 31 communicates with an annular groove 32 provided in the body 2. Plunger 12
has a lead 33 on the outer periphery that is inclined with respect to its center line.
(groove), and the lead 33 communicates with the pump chamber 24 via a passage within the plunger 12. Third
In the figure, the body 2 has, for example, radial holes 34 at three equally spaced locations, and the radial holes 34 communicate with the annular groove 32. Each radial hole 34 has the same shape and the same size, one of which communicates with a fuel supply passage 36 in the cylinder head 3 via an annular groove 35 of the body 2, and the other one communicates with the fuel supply passage 36 in the cylinder head 3. It communicates with a discharge passage 37 in 3. A throttle valve 38 is provided at the entrance of the passage 37.

Next, the operation of the unit injector will be explained.
In the state shown in FIG. 1, fuel is introduced into the pump chamber 24 from the supply passage in the cylinder head through the fuel hole 31 and the like. In this state, the plunger 1 is inserted through the spacer 20 by a rocker arm (not shown).
2, the plunger 12 moves into the pump chamber 24.
It begins to descend while pressurizing the fuel inside. At the beginning of the descent of the plunger, the fuel in the pump chamber 24 leaks to the outside through the fuel hole 31, but when the lower end of the plunger 12 matches the lower end of the fuel hole 31, that is, the plunger 12 completely closes the fuel hole 31. At this point, the fuel in the pump chamber 24 is discharged from the check valve 2.
5. The high-pressure fuel that begins to be fed to the injection nozzle 4 through the passages 26 and 27 and reaches the nozzle 4 immediately opens the needle valve 28 and is injected into the combustion chamber. Plunger 12 further descends and lead 3
3 communicates with the fuel hole 31, the fuel in the pump chamber 24 begins to leak to the outside via the lead 33 and the fuel hole 31, and fuel injection into the combustion chamber ends. When the aforementioned governor mechanism rotates the plunger 12 via the driving lever 16, the timing at which the reed 33 communicates with the fuel hole 31, that is, the timing at which fuel injection ends changes, thereby changing the fuel injection per stroke of the plunger 12. amount is changed. Note that even if the plunger 12 rotates, the fuel injection start timing does not change.

Excess fuel and air leaking from the pump chamber 24 to the outside through the fuel hole 31 in FIG.

Next, the injection start timing adjusting method and adjusting device according to the present invention will be explained. In other words, in a unit injector, in order to make the fuel injection start timing constant, the axial position of the plunger relative to the barrel, especially the side facing the pump chamber (injection nozzle side)
It is necessary to accurately determine the axial position of the plunger end. FIGS. 4 and 5 show a state in which the injection start timing is being adjusted. The unit injector schematically shown in these two figures has a slightly different structure in detail from that shown in FIGS. Please infer that this is not intended only for unit injectors. In FIGS. 4 and 5, for convenience of explanation, the unit injector is shown vertically.

First, FIG. 4 shows a state in which the unit injector itself is being assembled, and at this stage, the plunger spring has not yet been attached. At this stage, the first adjustment is performed. That is, 40 in FIG. 4 is a first adjustment fitting having an L-shaped cross section according to the present invention, and the distance between the end surface 41 of the fitting 40 and the step portion 42 is H ₁ (constant). Now, with the injection nozzle side plunger end 60 (lower end in the figure) and barrel end 61 aligned, that is, with the top clearance set to 0, the pressure receiving end (upper end in the figure) of the plunger 43 has a thickness (in the axial direction). Apply a large number of disc-shaped spacers with different widths one after another, and use the metal fitting 40 so that the amount of protrusion of the pressure receiving surface 45 from the end of the injector body on the side opposite to the injection nozzle (upper end in the figure) is exactly _H1 . Select the spacer 44. That is, in the optimal spacer 44, when the stepped portion 42 of the metal fitting 40 is brought into contact with the pressure receiving surface 45 of the spacer 44, the metal fitting 4
The end face 41 of 0 just hits the end face 47 of the injector body 46.

Next, FIG. 5 shows the state in which the unit injector is mounted on the engine. In this state, the second
Make the following adjustments. That is, 48 in FIG. 5 is a second adjustment fitting having an L-shaped cross section according to the present invention, and the distance between both end surfaces 49 and 50 of the fitting 48 is H ₂ (constant).
This H ₂ is set so that H ₂ =H ₁ +L. Here, L is the distance between the barrel end 61 on the injection nozzle side and the injection nozzle side end 62 of the fuel hole 52, and in reality, the distance L is set to, for example, about 5 mm, and the error is kept within, for example, 1%. It is set as. On the other hand, a screw hole 70 is provided in the rocker arm 53 which is pivotally supported on the cylinder head via a case (not shown).
and an adjustment screw 55 screwed into this screw hole 70.
A pressurizing end 56 of the spacer 44 protrudes toward the spacer 44 side.
Now connect the end 57 of the metal fitting 48 to the pressure receiving surface 4 of the spacer 44.
5, and then attach the pressure end 56 of the screw 55 to the metal fitting 48.
The end surface 50 of the metal fitting 48 is in contact with the end surface 49 of the metal fitting 48.
Adjust the amount of protrusion of the pressure end 56 by turning the screw 55 until it touches the end surface 47 of the injector body 46, that is, until the distance between the end surface 47 and the pressure end 56 becomes _H2 , and then tighten the adjustment screw 55 with the lock nut 54. Fix it. When the metal fitting 48 is removed in this state, the elasticity of the plunger spring 58 causes the spacer 44 to
The pressure-receiving surface 45 of the screw 55 contacts the pressure-applying end 56 of the screw 55 . At that time, as is clear from the above-mentioned relational expressions of H ₁ , H ₂ and L, the plunger end 60 on the injection nozzle side
corresponds exactly to the injection nozzle side end 62 of the fuel hole 52. As described above, fuel injection begins when the plunger end 60 and the end 62 of the fuel hole 52 coincide. In fact, at the cam position shown in FIG. 5, that is, at the top dead center of the plunger 43 when the metal fitting 48 is removed, the screw is screwed to such an extent that, for example, the plunger end 60 coincides with the end of the fuel hole 52 on the side opposite to the injection nozzle. The axial position of the plunger end 60 can be readjusted by turning 55 a predetermined number of times. Of course, both metal fittings 40 and 48 are removed during operation.

As mentioned above, the present invention is applicable not only to the unit injector of the type shown in FIGS. 1 to 3, but also to all nozzle-pump-shaped unit injectors. Furthermore, it is not always necessary to once align the plunger end 60 on the injection nozzle side with the injection nozzle side end 62 of the fuel hole 52; it is sufficient that the relative position of the plunger end 60 in the axial direction with respect to the barrel 59 is constant.

(Effects of the Invention) As explained above, according to the present invention, the axial position of the pressure receiving surface of the spacer is accurately adjusted while the plunger end on the injection nozzle side and the barrel end are aligned, and the pressure receiving surface of the spacer is further provided on the rocker arm. The axial position of the pressure end of the adjustment screw is also adjusted accurately, so when the pressure receiving surface of the spacer is in contact with the pressure end of the adjustment screw, the axial position of the plunger end on the injection nozzle side is accurate. Determined by For adjusting spacers and screws,
Since metal fittings are used for each, adjustment becomes easier. The structure of the metal fittings is also extremely simple.

As shown in FIG. 3, if the radial hole 34 of the injector body 2 has the same shape and the same size, the structure of the body 2 is simplified, and the radial hole 34 and the passage 36,
Polymerization of 37 is also facilitated.

[Brief explanation of drawings]

Fig. 1 is a cutaway side view showing an example of a unit injector, Fig. 2 is a view taken in the direction of - arrow in Fig. 1, and Fig.
The figure is a schematic cross-sectional view of FIG. 1, and FIGS. 4 and 5 are schematic views showing a state in which the injection start timing is being adjusted. 43... Plunger, 44... Spacer, 46... Injector body, 53... Locker arm, 55...
Adjustment screw, 59...barrel.

Claims (1)

[Claims] 1. When assembling the unit injector alone, the axial width of the spacer 44 supported on the pressure receiving end of the plunger is adjusted with the end of the plunger 43 on the side of the injection nozzle 4 and the end of the barrel 59 aligned. Spacer 44
The distance H1 between the pressure-receiving surface of
By adjusting the amount of protrusion of the adjusting screw 55 which is screwed into the screw 3 and whose pressurizing end protrudes toward the spacer 44 side, the pressure-receiving surface of the spacer 44 is pressed against the pressurizing end of the adjusting screw 55 by the elasticity of the plunger spring 58. In this state, the plunger end 60 on the injection nozzle 4 side
A method for adjusting the injection start timing of a unit injector so that the setting position in the axial direction is determined. 2 It is used by applying it to the end face 47 of the injector body on the side opposite to the injection nozzle 4 of the unit injector, and has an L-shaped cross section, and the end face 4 of the injector body
The interval between the end face 41 corresponding to the spacer 7 and the stepped portion 42 corresponding to the spacer 44 is a constant distance H1, and the stepped portion 4
2 and the plunger pressure receiving end from among a large number of spacer groups having different axial widths; and one end surface having an L-shaped cross section and corresponding to the injector body end surface 47 50 and the other end surface 49 is a constant distance H2, and the distance H2 is the distance H1 of the first adjustment fitting 40, the barrel end 61 on the injection nozzle 4 side, and the injection nozzle 4 side end 62 of the fuel hole 52. the second adjustment fitting 4 for setting the distance to the distance L between
8, a spacer 44 selected from a large number of spacer groups having different axial widths by the first adjustment fitting 40 and supported by the pressure receiving end of the plunger 43, and an adjustment screw 55 screwed into the rocker arm 53. , After removing the first adjusting fitting 40 from the spacer 44, attaching the second adjusting fitting 48 with the stepped portion 57 in contact with the pressure receiving surface 45 of the spacer 44,
The end surface 49 of the second adjusting fitting 48 is connected to the adjusting screw 5.
5, press until the end surface 50 of the second adjustment fitting 48 touches the end surface 47 of the injector body, and then remove the adjustment screw 55 from the rocker arm 53 to the spacer 44 side.
The amount of protrusion of the pressurizing end can be adjusted, and during operation, the first and second adjustment fittings 40,
48 and directly connect the pressurizing end of the adjusting screw 55 to the spacer 4 by the elasticity of the plunger spring 58.
4. An injection start timing adjustment device for a unit injector, characterized in that the injection start timing is adjusted so as to be applied to the unit injector.