JP3316155B2 - Plunger for fuel pressurization of distributed fuel injection pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel pressurizing plunger used in an internal cam type distribution type fuel injection pump.

[0002]

2. Description of the Related Art An internal cam type distribution type fuel injection pump is
The drive shaft and the distribution shaft are connected coaxially in the housing. A plurality of slide holes extending in the radial direction are formed at an end of the distribution shaft on the drive shaft side, and a plunger is accommodated in these slide holes so as to be slidable in the radial direction. A cam ring is arranged so as to surround the end of the distribution shaft. When the pair of plungers move radially and inward with the rotation of the distribution shaft by the cam action of the cam ring, the fuel is pressurized. The pressure is fed to the injection nozzle.

[0003]

In the pump having the above structure, when the diameter of the plunger is D and the length is L, the ratio D / L must be sufficiently reduced. This is because the shorter the length L, the greater the inclination of the plunger during sliding, and the greater the diameter D, the greater the rotational moment applied to the plunger in the inclined state. This is because the contact pressure is increased, causing seizure and wear.

However, in order to reduce D / L sufficiently, the plunger disposed in the cam ring must be lengthened. Further, the diameter D of the plunger must be reduced. If the diameter D is reduced, the reciprocating stroke of the plunger must be lengthened in order to secure a required amount of fuel to be pumped. As described above, the length of the plunger becomes longer and the stroke of the plunger becomes longer. As a result, the diameter of the cam ring surrounding the plunger increases, and the pump becomes larger.

[0005]

Means for Solving the Problems The invention of claim 1 is:
(A) a housing, (b) a drive shaft that penetrates the housing and one end of which faces the internal space of the housing, and (c) is coaxially connected to the drive shaft in the housing and extends along the axial direction. A distribution shaft having a main fuel passage, a plurality of slide holes formed on the drive shaft side and extending in a radial direction from the main fuel passage, and (d) mounted on the housing, and the main fuel is supplied with rotation of the distribution shaft. A plurality of delivery valves sequentially and selectively communicated with the passage, (e) a plurality of fuel pressurizing plungers accommodated in the slide holes of the distribution shaft so as to be slidable in the radial direction, and (f) surrounding the distribution shaft. It has a cam surface on the inner periphery, and the cam action of the cam surface causes the plunger to have a diameter with the rotation of the distribution shaft. And the cam ring for reciprocating in direction,
In the plunger of the distribution type fuel injection pump provided with, an amorphous hard carbon coating is formed on at least an outer peripheral surface of a cylindrical slide portion which is in sliding contact with an inner circumference of the slide hole, and the amorphous hard carbon coating is formed. Contains nitrogen and silicon, and when the diameter of the slide portion is D and the length is L,
D / L is 0.6 to 1.0.

[0006]

An embodiment of the present invention will be described below with reference to the drawings. First, an outline of the distribution type fuel injection pump will be described with reference to FIGS. As shown in FIG. 1, the distribution type fuel injection pump has a housing 1. A drive shaft 2 that receives rotational torque from the engine is penetrated through the left end of the housing 1 in the drawing, and the right end of the drive shaft 2 faces the internal space 3 of the housing 1. A feed pump 4 is accommodated in the housing 1, and the feed pump 4 is driven by rotation of a drive shaft 2 and supplies fuel to the internal space 3 at a pressure of several atmospheres.

In the housing 1, a left end of a distribution shaft 5 coaxial with the drive shaft 2 is connected to a right end of the drive shaft 2. A support cylinder 6 is fixedly penetrated to the right end of the housing 1.
The right end of the distribution shaft 5 is rotatably supported. The distribution shaft 5 has an axially extending main fuel passage 5a.
have. Further, on the outer peripheral surface of the distribution shaft 5, a suction and spill port 5b connected to the middle part of the main fuel passage 5a and a distribution port 5c connected to the right end of the main fuel passage 5a are opened.

The left end of the distribution shaft 5 has a large diameter. The left end has a plurality of slide holes 5x having a circular cross section extending radially from the left end of the main fuel passage 5a. A support hole 5y having a rectangular section is formed so as to be continuous with the radially outer end and open to the outer peripheral surface of the distribution shaft 5.

In the housing 1, a control sleeve 7 is mounted on the outer periphery of the distribution shaft 5 in the middle. The suction and spill port 5b is closed by a control sleeve 7, and the housing 1 is formed through an obliquely extending hole (not shown) formed in the control sleeve 7 as the distribution shaft 5 rotates. It communicates with the internal space 3 or is cut off from the internal space 3. The position of the control sleeve 7 is adjusted in the axial direction by an injection amount control actuator 8.

At the right end of the housing 1, a plurality of delivery valves 9 (only one is shown) are attached. The delivery valves 9 selectively communicate with the distribution ports 5c one by one in accordance with the rotation of the distribution shaft 5.

A plunger 10 is inserted into the slide hole 5x.
Are slidably accommodated. The shoe 11 is accommodated in the support hole 5y so as to be slidable in the radial direction. A cylindrical roller 12 is rotatably supported by the shoe 11.

In the housing 1, a distribution shaft 5 is provided.
A cam ring 15 coaxial with the distribution shaft 5 is disposed so as to surround the left end of the camshaft. As best shown in FIG. 2, the cam ring 15 has a cam surface 1 on its inner peripheral surface.
6 are formed. The cam surface 16 has the roller 12
Are in contact with each other. The cam surface 16 has a radially and inwardly projecting portion 16a and a retreating portion 16b. The cam ring 15 is adjusted to rotate about the axis of the distribution shaft 5 by an injection timing control actuator 17.

In the above-described distribution type fuel injection pump, when the drive shaft 2 rotates, the distribution shaft 5 also rotates following the rotation of the drive shaft 2. The centrifugal force generated by the rotation of the distribution shaft 5 causes the plunger 10, shoe 11, roller 12
Are urged radially and outwardly, so that the outer end of the plunger 10 is in contact with the shoe 11, and the roller 12 is in contact with the cam surface 16 of the cam ring 15.

In the process in which the contact position of the roller 12 shifts from the protruding portion 16a of the cam surface 16 to the retreating portion 16b with the rotation of the distributing shaft 5 (in the process of moving the plunger 10 in the radially outward direction), the distributing is performed. The suction and spill port 5b of the shaft 5 is released from the shielded state of the control sleeve 7, so that the fuel in the internal space 3 of the housing 1 is removed.
It is sucked into the main fuel passage 5a and the slide hole 5x through the port 5b.

In the process in which the contact position of the roller 12 shifts from the retreating portion 16b of the cam surface 16 to the projecting portion 16a, the cam action of the cam surface 16 causes the roller 12 and the shoe 11 to move.
The plunger 10 is pressed and moved in the radial and inward directions via the. At the beginning of this process, suction of the distribution shaft 5,
The spill port 5b is shielded by the control sleeve 7, so that the high-pressure fuel in the slide hole 5x is
Via the main fuel passage 5a, it is pressure-fed to the delivery valve 9 selected by the distribution port 5c, and is further pressure-fed from this delivery valve 9 to the injection nozzle mounted on the engine, and fuel injection to the engine is performed. Be executed. In addition,
In the latter half of this process, the suction and spill port 5b of the distribution shaft 5 comes out of the shielding state of the control sleeve 7, so that the high-pressure fuel in the main fuel passage 5a flows into the internal space 3 via the suction and spill port 5b. The fuel is spilled and the fuel injection ends.

Next, the plunger 10 of the distribution type fuel injection pump, which is a feature of the present invention, will be described with reference to FIG. This plunger 10 is SKH51
Made of high-speed tool steel such as
a and the projections 10b at both ends thereof. When the diameter of the slide portion 10a is D and the length is L, the ratio D / L is 0.6 to 1.0. In this embodiment,
The diameter D is 9.5 mm, the length L is 12 mm, and D / L
Is 0.79.

The above D / L is much larger than that of the conventional example. That is, the diameter D is larger and the length L
Is small. In particular, the length L is small. Since the length L of the plunger 10 can be reduced, the diameter of the cam ring 15 surrounding the plunger 10 can be reduced, and the pump can be reduced in size in the radial direction. In addition, by increasing the diameter D, the plunger 1 for obtaining a required fuel pumping amount is provided.
Since the stroke of zero can be shortened, the diameter of the cam ring 15 can be reduced from this point, and the pump can be reduced in size in the radial direction.

The plunger 10 is accommodated in the slide hole 5x of the distribution shaft 5 with a very small clearance in order to eliminate the leakage of high-pressure fuel, and an oil film is hardly formed between the two. And because it reciprocates at high speed,
The sliding conditions are severe. Therefore, when the D / L of the plunger 10 is increased as described above, under such severe sliding conditions, an extremely high contact pressure is applied to the edge portion of the slide portion 10a of the plunger 10, and seizure and abrasion occur here. Will occur.

However, in the present embodiment, the plunger 10
Since the DLC film (diamond-like carbon film, amorphous hard carbon film) is formed on the outer peripheral surface of the slide portion 10a, such seizure and wear can be prevented. This is because the DLC film does not cause welding because it is carbon, has a low friction coefficient, and can withstand a high surface pressure. In the present embodiment, the DLC film contains nitrogen and silicon in order to further improve the adhesion to the base material and the sliding characteristics (low μ). Where nitrogen is 15 at
%, And silicon is 10 to 35 at%. The thickness of the film is preferably 1 μm or more, and more preferably 5 μm or more from the viewpoint of strength.

The plunger 10 of the above DLC coating
Test of seizure and abrasion of super-finished plunger, P
This was performed together with a plunger of TFE-dispersed Ni-P plating. The test conditions are as follows. Plunger speed: 4 m / sec Fuel: light oil (low sulfur) Temperature: room temperature Clearance: 2 μm (between slide hole and plunger) Pump rotation speed: 2250 rpm Test time: 1000 hours

The test results are as shown in FIG. FIG.
, The vertical axis indicates the surface state, A means a state in which none of seizure, abrasion, and peeling (the peeling may occur only in the case of the plating and coating), and B means Wear, partially peeled, C
Means a state where seizure, large abrasion and peeling have occurred. That is, in the case of super-finishing, when D / L is 0.55 or more, seizure and large wear occur, and the PTFE dispersion N
In the case of i-P plating, D / L is 0.6-0.7 and wear,
Partial peeling occurs, seizure occurs at 0.7 or more, large wear,
Peeling has occurred. On the other hand, in the DLC coating, even when the D / L became 1.0, none of seizure, large abrasion, and peeling occurred.

Based on the above test results, in the present embodiment, the D / L of the plunger 10 is changed to a value such as abrasion or seizure due to other surface treatments, plating, etc., in order to maximize the advantages of the DLC coating. That's more than 6. In addition, the D / L of the plunger 10 was set to 1.0 or less from the structural limit of the distribution type fuel injection pump.

The DLC film may be formed on the projection 10b of the plunger 10.

[0024]

As described above, according to the first aspect of the present invention, the outer peripheral surface of the slide portion of the plunger is formed with nitrogen and silicon.
Since the amorphous hard carbon film containing silicon is formed and the D / L of the plunger is set to 0.6 to 1.0, downsizing of the pump can be ensured.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a distribution type fuel injection pump according to the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is an enlarged front view of a plunger.

FIG. 4 is a view showing a sliding test result of a plunger.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 2 Drive shaft 3 Housing internal space 5 Distribution shaft 5a Main fuel passage 5x Slide hole 9 Delivery valve 10 Plunger 10a Slide part 15 Cam ring 16 Cam surface

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-54150 (JP, A) JP-A 62-193173 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02M 41/14

Claims (1)

(57) [Claims] (A) a housing; (b) a drive shaft that penetrates through the housing and has one end facing the internal space of the housing; A distribution shaft having a main fuel passage extending along the direction, and a plurality of slide holes formed on the drive shaft side and extending in a radial direction from the main fuel passage; and (d) rotating the distribution shaft mounted on the housing. (E) a plurality of fuel pressurizing plungers housed in the slide holes of the distribution shaft so as to be slidable in the radial direction; It is disposed so as to surround the distribution shaft, and has a cam surface on the inner periphery. And a cam ring for reciprocating the plunger in the radial direction. The plunger of the distribution type fuel injection pump, comprising: an amorphous hard carbon film on at least an outer peripheral surface of a cylindrical slide portion slidingly contacting an inner periphery of the slide hole. To form
This amorphous hard carbon film contains nitrogen and silicon .
When the diameter of the slide portion is D and the length is L, D /
A plunger for pressurizing a fuel of a distribution type fuel injection pump, wherein L is 0.6 to 1.0 .