JP2568415B2 - Distribution type fuel injection pump - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a distribution type fuel injection pump.

[Conventional technology and its problems]

2. Description of the Related Art As a fuel injection pump for a diesel engine, a type in which fuel is pressurized and distributed to each cylinder of an engine by a rotating and reciprocating plunger is known.

In this type of fuel injection pump,
In order to maintain and improve fuel efficiency and output, it is required to increase the pressure of the fuel and to shorten the injection for a short period of time. Enlarging the diameter of the plunger and enlarging the cross section of the plunger chamber is one of the measures to respond to the demand for the high pressure. However, this alone cannot cope with short-term injection.

Therefore, regarding this type of pump, in Japanese Utility Model Laid-Open No. 54-155016 and Japanese Utility Model Laid-open No. 60-162268, a shallow cut-off slit extended at the outer peripheral end of the cut-off port of the plunger is formed to control the control sleep. A method (rapid spilling) of discharging fuel at a high speed from the moment the edge is reached has been proposed.

This method increases the spill speed by increasing the slit width to improve fuel exhaustion.However, the flow of fuel from the plunger chamber to the cutoff slit through the blind hole is taken into account. Not done. For this reason, when the plunger diameter is increased, the injection amount is increased, and the oil feed rate is increased, the pressure loss up to the cutoff slit is large, and the absolute flow rate is small with a shallow slit. There was a problem that accurate high-pressure and short-term injection could not be achieved.

[Means for solving the problem]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and has as its object to reduce loss of energy given to fuel in a plunger chamber, to smoothly and quickly spill, and to provide high pressure. -To provide a distributed fuel injection pump capable of short-term injection.

In order to achieve this object, the present invention has a plunger that rotates and reciprocates, the plunger has a plurality of inlet slits on the outer periphery of an upper end, and has a blind hole at the center communicating with the pressurizing chamber. An outlet slit communicating with the outlet port of the barrel is branched in the middle of the control passage, and a control passage opened and closed by a control sleeve on the outer periphery is branched at the tip, wherein the control passage is inclined at an obtuse angle to the axis of the blind hole. And a control slit having a width dimension larger than the diameter of the oblique port and a depth dimension approximating the diameter of the oblique port.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a distribution type fuel injection pump according to the present invention, FIG. 2 shows an enlarged view of a main part, and FIGS.
The figure shows the conventional plunger structure in the right half and the plunger structure of the present invention in the left half with respect to the page.

In FIG. 1, 1 is a housing and 2 is a housing 1.
Is a hydraulic head fixed to an end of the hydraulic head. 3 is a drive shaft, 4 is a cam disk rotated by the drive shaft 3, and 5 is a plunger. The plunger is integrally connected to the cam disk 4, and the cam disk 4 is brought into rolling contact with the roller 6a of the roller assembly 6, The motor is reciprocated a plurality of times per rotation according to the number of cylinders of the engine.

Reference numeral 7 denotes a barrel, which is inserted into the hydraulic head 2 and fixed by a fixing plug 9.
The plunger 5 is slidably inserted into the center hole 7a of
The pressurizing chamber 8 is formed by the lower surface of the fixing plug 9 and the center hole 7a.

The barrel 7 is provided with one inlet port 7b. The inlet port 7b is communicated with a suction passage 2a formed in the hydraulic head 2, and is connected to the hydraulic head 2.
It is opened and closed by a magnet valve 10 attached to the.

In the plunger 5, inlet slits 5 a for the number of cylinders are formed on the outer periphery of the upper end portion, and a blind hole 5 b which is opened in the pressurizing chamber 8 is formed at the center. A single outlet slit 5c opening in the outer peripheral surface of the plunger 5 is formed in the middle of the blind hole 5b in the axial direction, and an outlet port 7c corresponding to the number of cylinders is formed in the barrel 7 at a position corresponding to the outlet slit 5c. Each outlet port 7c reaches the delivery valve assembly 11 via a respective discharge passage 2b formed in the hydraulic head 2.

A control passage 5d communicating with the outer periphery of the plunger 5, that is, the pump chamber 12, is formed at the tip of the blind hole 5b. The control passage 5d is opened and closed by a control sleeve 13 slidably fitted on the outer periphery of the plunger 5, and the control sleeve 13 is engaged with a ball pin 14a of a governor lever assembly 14 as is well known. The change in the position of the control sleeve 13 increases or decreases the fuel injection amount (effective stroke).

The feature of the present invention lies in the structure of the blind hole 5b including the control passage 5d. The control passage 5d includes a control slit 50 opened on the outer periphery of the plunger and an oblique port 51 communicating therewith.

More specifically, first, the control slit 50 is formed at the same position as the conventional control slit 500 as shown in FIG. 3, but as shown in the left half of FIG. large and depth H ₁ is dimensioned such that approximate the diameter of the slant port 51. This deep and so about twice that depth h ₁ of the conventional control slits 500 shown in the right half of Figure 3. Further, the control slit 50 does not have a shallow groove 501 unlike the conventional control slit 500, and has a uniform depth as a whole.

And in the conventional one, the tip 520 of the blind hole 5b reaches at least the end wall of the control slit 500, and the right-angled control port 510 reaches the control slit 500 from there. The tip 52 of the hole 5b is one of the control slits 50
Stop at a position between the pair of end walls 53, 54, and extend from this position to the bottom 55 of the control slit 50 and the end wall 53 on the rear side in the axial direction. An oblique port 51 is bored at (eg, 120 degrees). The oblique port 51 has at least two, preferably four
Individually formed.

Incidentally, apertures passing through the upper end i.e. pressure chamber 8 of the blind hole 5b is conventionally as shown in FIG. 4 right, depth h _2, the diameter d
But was only very shallow chamfer 560 of are formed, the present invention is in this region, for example the depth H ₂ is about three times or more the depth h _2, about 1.5 diameter D of the diameter d The entrance portion 56 is formed to have a large wrapper shape, such as twice or more.

If necessary, the passage connecting the outlet slit 5c and the blind hole 5b may be a slanted port.

[Operation of the embodiment]

 The operation and operation of the embodiment will be described.

The plunger 5 is rotated by the drive shaft 3,
It is reciprocated by the cam disk 4. In the descending stroke of the plunger 5, when the inlet port 7b of the barrel 7 and the inlet slit 5a of the plunger 5 communicate with each other, the fuel in the pump chamber 12 is sucked into the plunger.
As the pressure rises, the pressure in the pressurizing chamber 8 is increased.

In the injection stroke, the plunger 5 is rotated together with the cam disk 4, and the injection is started when the inlet slit 5a closes the inlet port 7b of the barrel 7, and almost simultaneously with the plunger 5 into the outlet port 7c of the barrel 7.
The outlet slit 5c of the fuel tank matches the high-pressure fuel and is sent to the discharge passage 2b of the hydraulic head 2 under pressure. The delivery valve spring overcomes the residual pressure in the injection pipe, and the delivery valve opens to open the injection pipe. And then injected into the injector and injected into the combustion chamber of the engine.

And the plunger 5 reaches the end of the rising stroke,
When the control passage 5d meets the control edge 13a of the control sleeve 13, the fuel in the plunger is returned to the pump chamber 12, and the pressure is reduced, whereby the delivery valve 11 is closed, and the pressure feeding ends. Here, in order to improve the fuel injection cutoff, the fuel flow during the flow from the pressurizing chamber 8 through the control passage 5d must be good.

Although the fuel is given a strong injection energy in the pressurizing chamber 8, there is a very large difference between the cross-sectional area of the pressurizing chamber 8 and the cross-sectional area of the blind hole 5b. Conventionally, fuel is rapidly throttled at the entrance of the blind hole 5b as shown by the streamline on the right side of FIG. 4, where a large pressure loss occurs first. Further, the fuel flowing through the blind hole 5b
As shown by the streamline on the right side of FIG. 3, the control port 510 is bent sharply at a right angle to the axis of the blind hole, and a portion of the control port 510 collides with the tip of the blind hole and returns. Lost. In addition, control port 510 has control slit 500
The control slit 500 has a shallow cut structure, the streamline is highly bent when the control edge 13a of the control sleeve 13 is viewed, and the rate of increase in the opening volume is small. For this reason, the flow resistance of the fuel is large as a whole, and the spill characteristics when the injection amount and the oil feed rate increase are poor.

In the present invention, the entrance 56 of the blind hole 5b is largely open in a trumpet shape with respect to the pressurizing chamber 8. Therefore, the fuel is not abruptly throttled, but flows into the blind hole 5b as a smooth streamline as shown on the left side of FIG. 4, and the pressure loss is small. Further, a passage connecting the blind hole 5b and the control slit 50 is an oblique port 51 inclined at an obtuse angle with respect to the blind hole axis. For this reason, the change in the flow direction of the fuel flowing through the blind hole 5b at high speed is small, and there is almost no fuel flow colliding and reflected at the tip of the blind hole. Therefore, the flow becomes a smooth streamline as indicated by the arrow on the left side of FIG.

The tip of the inclined port 51 communicates with an end wall 53 including a bottom wall 55 of the control slit 50, and the width of the control slit 50 is an inclined port.
The diameter is larger than the diameter of the oblique port 51, and the depth is close to the diameter of the oblique port 51. Therefore, the fuel that has passed through the inclined port 51 is not sharply bent, and
From the moment of encountering the 13 control edge 13a, it flows out smoothly and following the rapid increase of the opening volume.

〔The invention's effect〕

According to the present invention described above, the plunger has a plunger that rotates and reciprocates, the plunger has a plurality of inlet slits on the outer periphery of an upper end, and has a blind hole passing through the pressurizing chamber at the center. An outlet slit communicating with the outlet port of the barrel is branched in the middle, and the control passage that is opened and closed by the outer peripheral control sleeve is branched at the tip, and the control passage is inclined at an obtuse angle to the axis of the blind hole 5b. Since the port 51 is provided with a control slit having a width dimension larger than the diameter of the oblique port and a depth dimension approximating the diameter of the oblique port, a fuel flow through the blind hole 5b at a high speed is provided. The change in the flow direction is small, the flow becomes a smooth streamline, reaches the control slit 50 having a large cross-sectional area, and from the moment when it meets the control edge 13a of the control sleeve 13, the flow is smoothly changed. It is possible to spill following a rapid increase in the opening volume, and therefore the injection energy provided in the pressurizing chamber 8 is effectively utilized, and a large amount of fuel can be smoothly and quickly spilled per unit time. This makes it possible to meet the demands for high-pressure, short-term injection, thereby achieving an excellent effect.

[Brief description of the drawings]

FIG. 1 is a partially cutaway side view showing one embodiment of a distribution type fuel injection pump according to the present invention, FIG. 2 is an enlarged view of the same main part, and FIG. 3 is a fuel passage in a control passage of the present invention and a conventional control passage. FIG. 4 is a cross-sectional view showing half of the flow of fuel at the blind hole inlet according to the present invention and the conventional art. 5… Plunger, 5a …… Inlet slit, 5b ……
Blind hole, 5c …… Outlet slit, 5d …… Control passage,
7 ... Barrel, 7c ... Outlet port, 8 ... Pressurizing chamber, 13 ... Control sleeve, 50 ... Control slit, 51 ... Slanted port

Claims (1)

(57) [Claims] A plunger that rotates and reciprocates;
The plunger has a plurality of inlet slits on the outer periphery of the upper end, a blind hole in the center communicating with the pressurizing chamber, and an outlet slit communicating with the outlet port of the barrel is branched in the middle of the blind hole. A control passage, which is opened and closed by a control sleeve, wherein the control passage has a slanted port inclined at an obtuse angle with respect to the axis of the blind hole, and a width dimension larger than the diameter of the slanted port. And a control slit having a depth dimension approximating the diameter of the oblique port.