JPH0223712B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a fuel injection pump for an internal combustion engine.

In recent years, high-pressure injection has been required in fuel injection pumps for diesel engines due to the need to reduce fuel consumption, improve smoke emissions, and avoid using inferior fuel. Conventional jerk-type pumps, in which the delivery valve holder is screwed into an aluminum housing, cannot fully satisfy this requirement. Pumps with screw-in Veri valve holders tend to be used frequently. However, even with such pumps, as the injection pressure increases, insufficient strength of various parts becomes a problem.
As a countermeasure to this, the barrel and element holder are integrated to increase the strength of the barrel, and by closing the assembly hole on the lower end of the pump housing, the rigidity of the housing and the center bearing mounting part are increased, and the deflection of the camshaft is reduced. Therefore, development of fuel injection pumps with enhanced functionality without increasing the size of the fuel injection pump is underway.

The recently put into practical use fuel injection pumps as described above have a drawback that the assembly workability is very poor because they are of a completely sealed type in which the assembly hole in the lower end face of the housing is closed.

This will be explained with reference to FIG. The major features of the conventional structure are the following three points.

(1) The Atsupah spring seat e is indirectly locked to the pump housing j by a snap spring d or a pin to restrict upward movement. Such an unstable locking method has the disadvantage that the upper spring seat e may come off during driving.

(2) One piece of lower spring seat h, spring f, atsupa spring seat e, pinion g, plunger b, plunger barrel a, etc.
This method requires assembly into the bore of the pump housing j at one point, and the assembly work is poor.

(3) Keeping plunger b locked in lower spring seat h and standing upright, carefully move plunger barrel a downward so that the head of plunger b can be inserted into the sliding hole, and then move the plunger barrel a downward into the pump housing. Assemble from the upper assembly hole. This method of assembly is done in the back of the pump housing.
Since the plunger barrel is assembled by aiming at the plunger head in a place that is difficult to visually confirm, workability is poor, and the lower end of the plunger barrel often damages the plunger head, causing seizure of the plunger.

An object of the present invention is to provide a fuel injection pump that can greatly improve the assembling workability and reliability, and is characterized by an opening on the upper end surface. In a fuel injection pump having a pump housing with a bore formed therein, the female threaded portion is provided at the head of the plunger and screws into a jig for assembling the plunger into the pump housing with the plunger assembled in the plunger barrel; Atsupa spring seat that is directly latched to the barrel and has a cutout to avoid interference with the rack; a rack or pinion that has one tooth with a different thickness than the other teeth;
The pinion or rack is provided with a recess formed therein that engages with the single tooth.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a sectional view showing one embodiment of the fuel injection pump according to the present invention.

In the figure, there is a female thread on the head of plunger b.
b′ is provided.

The plunger barrel a, the plunger b, the upper spring seat e, the plunger spring f, the pinion g, the lower spring seat h, and the jig k are made into a small assembly, that is, a subassembly, and this is called A.

The final assembly method is to assemble the camshaft m and tappet i to the pump housing j, and then attach the rack c. In this state, attach the subassembly A to the assembly hole above the pump housing j, that is, the bore z that opens to the upper end surface of the pump housing j.
Assemble more.

At this time, the female threaded portion b' is used to attach a jig k that restricts the plunger from moving downward due to its own weight. After subassembly A is assembled, jig k is removed.

The shape of Atsupa spring seat e is shown in A, B, and C of FIG. In either case, a fitting surface q is provided for fitting to the plunger barrel a, or a shoulder portion p is provided for contact with the stepped portion of the plunger barrel a, and a shoulder portion p is provided to contact the stepped portion of the plunger barrel a. A notch r is provided. A is the simplest shape, and B is a shape obtained by dividing A. Furthermore, C is a combination of part 1' in B, which is made by integrally manufacturing part 1 and plunger barrel a, and part 2 in B.

That is, the upper spring seat e is directly latched to the plunger barrel a by fitting or abutting.

Regarding the rack c and pinion g, if a conventional involute gear is used, there is a possibility that the normal assembly positions of the pinion teeth and rack teeth may be shifted from each other because of the completely sealed housing. (Since there is no inspection window, it is not possible to confirm whether it is assembled in the correct position.)

Therefore, as shown in Fig. 4a and b, the thickness of one rack tooth a or pinion tooth t (on the reference pitch circle) of the remaining rack teeth or pinion teeth depends on the assembly position. have different tooth thicknesses (on the reference pitch circle), and a recessed portion is formed in the mating pinion or rack to engage with the teeth s and t having different tooth thicknesses. In this way, assembly can be performed only in the correct position, and incorrect assembly can be prevented.

The above case has the following effects.

Since subassembly A is assembled inside the pump housing using jig k via the female threaded part of the plunger head, assembly work efficiency is significantly improved compared to conventional ones, and damage to the plunger during assembly is avoided. Accidents such as this can be prevented.

The Atsupa Spring Seat is directly locked to the plunger barrel by fitting or contacting the shoulder, so unlike conventional locking structures that use a snap spring, etc., it is prevented from coming off during operation. Ru.

In addition, the tooth thickness of one tooth in the rack or pinion is made different from the tooth thickness of the other teeth, and the pinion or rack that meshes with the same rack or pinion is
Since one recessed portion is formed which engages with the two teeth, incorrect assembly is prevented.

[Brief explanation of drawings]

Figure 1 is a sectional view showing a conventional fuel injection pump.
Fig. 2 is a cross-sectional view showing a fuel injection pump according to an embodiment of the present invention, Fig. 3 A, B, and C are cross-sectional views showing the shape of the Atsupa spring seat, and Fig. 4 a shows a single tooth. FIG. 4b is an explanatory diagram showing a rack having a tooth thickness different from that of the remaining teeth, and FIG. 4b is an explanatory diagram showing a pinion having one tooth having a tooth thickness different from the remaining teeth. a... Plunger barrel, b... Plunger,
b'...Female thread part, c...Rack, e...Atsupa spring seat, g...Pinion, p...Shoulder part,
q...Mating surface, r...Notch, s...Rack tooth, t...Pinion tooth, z...Bore of pump housing.

Claims (1)

[Claims] 1. In a fuel injection pump having a pump housing j having a bore z opening at the upper end surface, a method is provided at the head of a plunger b to assemble the plunger b into the pump housing j with the plunger b assembled into the plunger barrel a. A female screw part b' into which the tool k is screwed, an atsuppa spring seat e formed with a notch r that is directly engaged with the plunger barrel a and avoids interference with the rack c, and one tooth is connected to another tooth. A fuel injection pump characterized in that it is equipped with a rack (c) or a pinion (g) formed to have a tooth thickness different from that of the tooth, and a pinion (g) or a rack (c) formed with one recessed portion that meshes with the one tooth.