KR100305362B1 - Distributive Fuel Injection Pump - Google Patents

Abstract

In the distribution shaft 5 of the distribution type fuel injection pump, several slide holes 5x extending in the radial direction are formed. The plunger 10 is accommodated in these slide holes so that the slide can slide. When the dispensing shaft rotates, the plunger reciprocates to pump fuel intermittently. A diamond-like carbon film is formed on the outer circumference of the slide portion 10a of the plunger. When the diameter of the slide portion of the plunger is D and the length is L, the ratio D / L is large and is 0.6 to 1.0.

Description

Dispensing Fuel Injection Pump

The present invention relates to a distribution type fuel injection pump using an inner cam, and more particularly to an improvement of a fuel pressure plunger used for this pump.

As disclosed in European Patents 0692622A2 and 0675280A1, in a fuel distribution pump using an inner cam, the drive shaft and the distribution shaft are connected to each other in the housing. A plurality of slide holes extending in the radial direction are formed at an end portion on the drive shaft side of the distribution shaft, and these slide holes are accommodated so that the plunger can slide. The cam ring is arrange | positioned so that the edge part of this distribution shaft may be enclosed. By the action of the cam formed on the inner surface of the cam ring when the dispensing shaft rotates, the pair of plungers reciprocate in the radial direction of the dispensing shaft, whereby fuel is intermittently pumped to the injection nozzle.

In the pump of the above configuration, the shorter the length (L), the larger the inclination of the plunger when sliding, and the larger the diameter (D), the larger the rotary motion moment applied to the inclined plunger, and as a result, Contact pressures increase locally at the edge of the plunger, resulting in adhesion due to overheating or wear. In order to prevent adhesion and abrasion due to such overheating, it is necessary to make the ratio D / L of the diameter D and the length L of the plunger sufficiently small.

However, in order to make D / L small enough, the plunger disposed in the cam ring must be made long. Moreover, the diameter D of the plunger must be made small. When the diameter D is made small, the reciprocating stroke of the plunger must be lengthened in order to secure the required fuel feeding amount.

As described above, as the plunger becomes longer and the stroke of the plunger becomes longer, the cam ring surrounding the plunger becomes a larger diameter, thereby inevitably increasing the size of the pump.

An object of the present invention can smoothly reciprocate the plunger even when the plunger has a small ratio D / L of the diameter D and the length L, and at the same time, minimize the wear of the plunger, Furthermore, it is providing the distribution type fuel injection pump which can aim at miniaturization.

The gist of the present invention is to form a diamond-like carbon film on the slide portion of the plunger. Diamond-like carbon film has a low frictional resistance and excellent wear resistance, so that even if the contact pressure between the outer circumference of the slide portion of the plunger and the inner circumference of the slide hole of the distribution shaft is high, the plunger can be smoothly slid. The wear of the part can be minimized. The ratio D / L of the diameter D and the length L of the plunger is preferably 0.6 to 1.0, more preferably 0.7 to 1.0. In this way, the injection pump can be made compact and a sufficient injection amount can be injected at high pressure.

1 is a longitudinal sectional view of a dispensed fuel injection pump of the present invention;

FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1. FIG.

3 is an enlarged front view of the plunger.

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

* Explanation of the symbols for the main parts of the drawings

1 housing 2 drive shaft

3: internal space 4: water feed pump

5: distribution shaft 6: support cylinder

5a: Main fuel passage 5b: Leakage hole

5c: distribution hole 5x: slide hole

2a: cylinder part 5m: flange part

5n: protrusion 7: control sleeve

8: Actuator for injection quantity control 9: delivery valve

10: plunger 11: shoe

EMBODIMENT OF THE INVENTION Hereinafter, one Embodiment of this invention is described with reference to drawings. First, the outline | summary of a distribution type fuel injection pump is demonstrated, referring FIG. As shown in FIG. 1, the distribution type fuel injection pump is provided with the housing 1. As shown in FIG. The drive shaft 2 which receives rotation torque from an engine penetrates through the left end part of this figure of the housing 1, and the right end part of the drive shaft 2 faces the internal space 3 of the housing 1. The feed water pump 4 is housed in the housing 1, and the feed water pump 4 is driven by the rotation of the drive shaft 2 to supply fuel to the internal space 3 at the pressure of water pressure. .

In the housing 1, the left end of the distribution shaft 5 which is coaxial with the drive shaft 2 is connected to the right end of the drive shaft 2. The support cylinder 6 is penetrated and fixed to the right end of the housing 1, and the right end of the distribution shaft 5 is inserted in the support cylinder 6 so as to rotate. At the right end of the distribution shaft 5, a main fuel passage 5a extending in the axial direction is formed. Further, on the outer circumferential surface of the distribution shaft 5, suction and leakage combined holes 5b leading to the middle portion of the main fuel passage 5a and distribution holes 5c leading to the right end of the main fuel passage 5a are provided. It is open.

At the left end of the distribution shaft 5, a plurality of cross sections extending in the radial direction from the left end of the main fuel passage 5a are formed with circular slide holes 5x. The right end of the drive shaft 2 is a tubular portion 2a (illustrated in FIG. 2 only) surrounding the left end of the distribution shaft 5, and the tubular portion 2a is formed with a plurality of slits extending in the axial direction. The support hole 5y is partitioned by the ring-shaped flange portion 5m (illustrated in FIG. 1 only) and the like of the distribution shaft 5. This support hole 5y leads to the radially outer end of the slide hole 5x and opens to the outer circumferential surface of the drive shaft 2.

Further, projections 5n protruding radially and outwardly from the distribution shaft 5 are fitted into the inner end portion (left end in FIG. 1) of the slit formed in the cylindrical portion 2a of the drive shaft 2. Both of them are connected.

In the housing 1, a control sleeve 7 is attached to the outer periphery of the intermediate portion of the distribution shaft 5. The above-described suction and spill hole (5b) is blocked by the control sleeve (7), and obliquely extending holes (not shown) formed in the control sleeve (7) in accordance with the rotation of the distribution shaft (5). It communicates with the internal space 3 of the housing 1 via, or it is interrupted from this internal space 3. This control sleeve 7 can be adjusted in the axial direction by the injection amount control actuator 8.

A plurality of discharge valves 9 (illustrate only one) are attached to the right end of the housing 1. These discharge valves 9 are configured to selectively communicate one by one to the distribution holes 5c in accordance with the rotation of the distribution shaft 5.

The plunger 10 is accommodated in each slide hole 5x so that it can slide. A shoe 11 is accommodated in each of the support holes 5y so as to slide in the radial direction. The shoe 11 is supported so that the cylindrical roller 12 can rotate.

In the housing 1, a cam ring 15 is arranged to form the same axis as the distribution shaft 5 so as to surround the left end of the distribution shaft 5 and the cylinder portion 2a of the drive shaft 2. As shown in FIG. 2, the cam surface 16 is formed in the inner peripheral surface of this cam ring 15. As shown in FIG. The roller 12 is in contact with the cam surface 16. The cam surface 16 is provided with the projection part 16a in the radial direction and the inward direction, and the retreat part 16b.

Furthermore, this cam ring 15 is rotated around the axis of the dispensing shaft 5 by the injector control actuator 17 so as to adjust its angular position.

In the distribution type fuel injection pump having the above configuration, when the drive shaft 2 rotates, the distribution shaft 5 also rotates after the drive shaft 2 rotates. With the centrifugal force by the rotation of this distribution shaft 5, the plunger 10, the shoe 11, and the roller 12 apply force to the radial direction and the outward direction of the distribution shaft 5, and the plunger 10 and The shoe 11 abuts, and the roller 12 and the cam face 16 of the cam ring 15 abut.

In response to the rotation of the distribution shaft 5, the contact position of the roller 12 moves from the protrusion 16a of the cam surface 16 to the retracted portion 16b (the plunger 10 has the distribution shaft 5). In the radially outward direction), the hole 5b of the distribution shaft 5 communicates with the internal space via the inclined hole of the control sleeve 7, and thus the internal space of the housing 1. The fuel in (3) is sucked into the main fuel passage 5a via the hole 5b.

In the process of moving the contact position of the roller 12 from the receding part 16b of the cam surface 16 to the protrusion 16a, by the cam action of this cam surface 16, the roller 12 and the shoe 11 are carried out. The plunger 10 is pushed in the radial direction and the inward direction of the distribution shaft 5 to move. At the beginning of this process, the pot 5b of the distribution shaft 5 is closed by the control sleeve 7. As a result, the fuel in the main fuel passage 5a becomes high pressure and is transferred to the discharge valve 9 selected by the dispensing port 5c, and from the discharge valve 9 to the injection nozzle mounted to the engine. And the fuel is injected into the engine. Furthermore, at the end of this process, since the hole 5b of the distribution shaft 5 communicates with the inclined hole of the control sleeve 7, the high pressure furnace in the main fuel passage 5a interposes the hole 5b. Leaks into the internal space 3, 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. The plunger 10 is made of high-speed tool steel such as SKH51, and includes a cylindrical slide portion 10a, projections 10b at both ends thereof, and the like. When the diameter of the slide part 10a is called D and the length is called L, the ratio D / L is 0.6-1.0, More preferably, it is 0.7-1.0. In this embodiment, the diameter D is 9.5 mm, the length L is 12 mm, and the ratio D / L is 0.79.

The ratio D / L is larger than the conventional example. That is, compared with the conventional example, the diameter D is large and the length L is small. In particular, the length L is smaller than the conventional one.

Since the length L of the plunger 10 can be shortened, the diameter of the cam ring 15 surrounding this plunger 10 can be made small, and also the pump can be made small in radial direction. In addition, as the diameter D is increased, the stroke of the plunger 10 for obtaining the required fuel pressure can be shortened. From this point of view, the diameter of the cam ring 15 can be further reduced. The pump can be made smaller in the radial direction.

The plunger 10 is accommodated in the slide hole 5x of the distribution shaft 5 in a very narrow gap in order to eliminate the leakage of the high pressure fuel, and almost no oil film is formed therebetween. Moreover, since the reciprocating motion is performed at high speed, the sliding condition is severe. Therefore, when the ratio (D / L) of the plunger 10 is large as described above, under such a severe sliding condition, a very high contact pressure is applied to the edge portion of the slide portion 10a of the plunger 10 and the plunger While the slide of (10) is not smooth, overheating and abrasion occur at this contact portion.

However, in this embodiment, since a DLC film (a carbon film such as diamond, an amorphous hard carbon film) is formed on the outer circumferential surface of the slide portion 10a of the plunger 10, such overheating adhesion and wear can be prevented. have. This is because the DLC film (DLC film) is carbon, which does not cause welding, has a low coefficient of friction, and can withstand high surface pressure. In this embodiment, the DLC film contains nitrogen and silicon in order to further improve the adhesiveness to the base material and the sliding characteristics (low μ). Here, nitrogen is 15 at% or less and diatom is 10 to 35 at%. It is preferable to make film thickness into 1 micrometer or more, and to set it as 5 micrometers or more from a viewpoint of intensity | strength.

As described above, tests of overheating adhesion and abrasion of the plunger 10 of the DLC film were carried out together with ultra-precision plunger and Ni-P plating with PTFE sprayed plunger. The test results are as follows.

Plunger Speed: 4m / sec

Fuel: Diesel (low sulfur)

Temperature: room temperature

Clearance: 2 μm (between the slide hole and the plunger)

Pump RPM: 2250rpm

Test time: 1000 hours

The test results are as shown in FIG. In Fig. 4, the ordinate denotes a surface state, and A denotes a state in which none of heating adhesion, abrasion, or peeling (more, peeling may occur only in the case of the plating or coating) occurs, and B Indicates wear, some peeling occurs, C means overheating, large wear, peeling occurs. That is, in the case of ultra-precision completion, overheating and large abrasion occur when the ratio D / L is 0.55 or more, and in the case of PTFE dispersed Ni-P plating, the wear and partial peeling occur at the ratio D / L of 0.6 to 0.7. Overheat adhesion, large abrasion, and peeling occur at 0.7 or higher. On the other hand, in the DLC film, even if the ratio D / L was 1.0, none of the overheated adhesion, large abrasion, and peeling occurred.

According to the above test results, in this embodiment, in order to maximize the advantages of the DLC coating, the ratio D / L of the plunger 10 is set to 0.6 or more in which wear and overheat adhesion occur in other surface treatments and platings. More preferably, it was 0.7 or more. Moreover, the ratio D / L of the plunger 10 was made 1.0 or less from the structural limit of the distribution type fuel injection pump.

Furthermore, the DLC film may be formed on the protruding portion 10b of the plunger 10.

Claims (3)

(a) the housing (1), (b) a drive shaft 2 penetrating the housing and having one end facing the inner space of the housing; (c) a distribution shaft (5) connected coaxially with one end of said drive shaft in a housing. The distribution shaft includes a main fuel passage 5a extending in succession in the axial direction, and a distribution shaft 5 having a plurality of slide holes 5x formed at the end of the drive shaft side and extending from the fuel passage in the radial direction of the distribution shaft. , (d) a plurality of discharge valves (9) mounted to the housing. The discharge valve includes a plurality of discharge valves 9 which are selectively communicated with the main fuel passage sequentially as the distribution shaft rotates, (e) a plurality of fuel pressurizing plungers 10 accommodated to slide into the sliding holes of the distribution shaft, (f) A cam ring (15) disposed so as to surround the distribution shaft. The cam ring has a cam surface 16 on its inner circumference, and is rotated along the rotation of the distribution shaft by the cam action of the cam surface. In the distribution type fuel injection pump having a configuration for reciprocating the plunger in the radial direction of the distribution shaft, The bar plunger 10 includes a cylindrical slide portion 10a which is slidably joined to the inner circumference of the slide hole 5x. A diamond-like carbon film is formed on the outer circumferential surface of the slide portion. A distribution type fuel injection pump, wherein the same carbon coating contains nitrogen and silicon. 2. The fuel distribution pump according to claim 1, wherein the ratio D / L is 0.6 to 10 when the diameter of the slide portion 10a is D and the length is L. 3. The dispense type fuel injection pump according to claim 2, wherein the ratio D / L is 0.7 to 1.0.

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