JPS6339791B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a fuel injection pump, which allows the start of fuel injection to be changed.

In general, in the case of diesel engines, the fuel injection system is cited as a factor that greatly affects the performance. The structure of a conventional fuel injection pump used in this fuel injection system is, as shown in FIG. The plunger 4 compresses the fuel supplied from the fuel supply hole 6 provided in the plunger barrel 5 and injects the fuel into the cylinder of the diesel engine via the discharge valve 7. Pressure feeding continues until communication is established. The beginning and end of injection of such a fuel injection pump will be explained with reference to FIG. 2, which shows the main parts extracted and enlarged. A diagonal notch groove 4a is formed in the upper part of the plunger 4, and communicates with the upper surface of the plunger 4 through a vertical groove. Therefore, when the plunger 4 reaches the bottom dead center, fuel is supplied from the oil supply hole 6, the plunger 4 rises, and the fuel discharge starts from the moment the oil supply hole 6 and the oil drain hole 8 are closed. This is the beginning of injection. Then, the plunger 4 further rises, and the notch groove 4a of the plunger 4
When it communicates with the oil drain hole 8, the fuel is returned to the suction side and injection ends. This moment marks the end of the injection. On the other hand, the discharge amount, that is, the injection amount can be adjusted by the stroke from when the plunger 4 closes the oil supply and drain holes 6 and 8 until the notch groove 4a communicates with the oil drain hole 8, and this can be adjusted as shown in FIG. Then, adjust using the pinion 10 and rack 9 on the outer periphery of the plunger 4. Therefore, in such a fuel injection pump, the start of fuel injection is always constant, and the start of injection cannot be adjusted depending on the rotation speed or load of the diesel engine.
For this reason, it has been considered to form a cutout groove on the upper surface of the plunger, but in this case as well, if the injection amount is the same, that is, the stroke of the plunger is the same, the start of fuel injection will be constant.
As a result, it has not been possible to set the optimum injection start according to the operating conditions, especially when the range of normal rotational speeds and load ranges are wide, such as in diesel engines for automobiles. There is still much room for improvement, especially in low-temperature startability and engine performance.

The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide a fuel injection pump in which the pre-stroke of the plunger can be changed and the start of injection can be changed. In order to achieve this object, the present invention has a structure in which a plurality of oil supply and drainage holes are bored in the plunger barrel into which the plunger is fitted so that the prestroke of the plunger can be changed, and the oil supply and drainage holes are provided in the plunger. A sleeve is provided on the outer periphery of the plunger barrel to communicate one of the oil supply and drainage holes with the oil supply chamber, and this sleeve is moved to connect one of the oil supply and drainage holes to the oil supply and drainage hole that communicates with the oil supply chamber. A sleeve switching mechanism is provided to change the pre-stroke of the plunger and the start of injection by switching the oil hole, and the position where the notch groove and the oil supply/drain hole communicate with each other is changed by rotating the plunger. It is characterized by being equipped with an injection amount adjustment mechanism that changes the effective stroke of the lever plunger.

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

FIGS. 3 and 4 show an embodiment of the fuel injection pump of the present invention, with FIG. 3 being an overall sectional view and FIG. 4 being an enlarged perspective view showing an extracted main part.

In the drawings, parts that are the same as those in the prior art are designated by the same reference numerals.

The plunger barrel 5 into which the plunger 4 is precisely and slidably fitted is provided with a plurality of oil supply and drainage holes 11 and 12, two in the figure. Performs oil supply and oil drainage independently. A sleeve 13 is precisely and rotatably fitted around the outer periphery of the plunger barrel 5.
This sleeve 13 is provided with a hole that communicates with only one of the oil supply/drainage holes 11 or 12 and communicates the plunger chamber 14 and the oil supply chamber 15.
The holes are arranged so as not to be in a straight line, as shown in FIG. 5a. Two oil supply and drainage holes 11 bored in the plunger barrel 5,
12 is shifted by a distance j in the sliding direction of the plunger 4, that is, in the vertical direction, as shown in FIG. The plunger 4 is formed with cutout grooves corresponding to the number of oil supply and drainage holes, and in the figure, two cutout grooves are formed.
Two cutout grooves 4a, 4b are shown. on the other hand,
A pinion is provided on the outer periphery of the sleeve 13 as a rotating mechanism for the sleeve 13 for selecting and switching between the oil supply and drain holes 11 and 12. This pinion meshes with a rack 16, and by moving this rack 16, the sleeve 13 is rotated. However, only one of the oil supply and drainage holes 11 or 12 can be communicated with the oil supply chamber 15.

Next, control of the start of injection in such a fuel injection pump will be explained.

First, as shown in Fig. 5a and b, the sleeve 1
3 by moving the rack 16 to close the oil supply/drain hole 11 (the hatching is in the closed state in the figure) and open the oil supply/drain hole 12. In this case, the injection start is determined by the oil supply and discharge hole 12, but since the oil supply and discharge hole 12 is located a distance j above the oil supply and discharge hole 11, the prestroke of the plunger 4 is large. The start of injection will be relatively delayed. On the contrary, the sixth
As shown in Figures a and b, when the sleeve 13 is moved so as to open the oil supply/drain hole 11 and close the oil supply/drain hole 12, the pre-stroke is smaller by distance j than in the above case, so the oil supply/drainage is performed quickly. The oil hole 11 is closed by the plunger 4 to begin injection, and the beginning of the injection is relatively advanced. At this time, plunger 4
The effective strokes of are shown by h and i in the drawing, respectively.If the effective stroke h is set equal to i, only the start of injection can be changed while keeping the injection amount constant. Therefore, only the start of injection can be changed, and there is no extreme change in engine performance. However, in general, for a diesel engine, its output, fuel consumption rate, and fuel injection timing (start of fuel injection) are different.If the injection timing is delayed from the normal setting value, the output may decrease or the fuel consumption rate may increase. It is known that if it goes in the opposite direction, it tends to lead to an increase in output and a decrease in fuel consumption.

Therefore, as the difference in pre-stroke, that is, the difference j in the height direction between the oil supply and drainage holes 11 and 12 increases, the change in the injection timing becomes large. When switching to the oil hole 12, there is a risk that the injection timing will be delayed, resulting in a significant drop in performance, and in the case of an automobile diesel engine, drivability will be impaired. Therefore, it is necessary to increase the amount of fuel injected to at least avoid a decrease in output performance. Therefore, as shown in FIG.
The injection amount is increased by changing the shape of b as shown by the broken line a or the dashed-dotted line b to lengthen the effective stroke and set it to k in the figure. The relationship between the plunger rotation angle and the plunger oil delivery stroke at this time is shown in the seventh figure, corresponding to each changed notch groove.
It is a diagram. In the figure, the solid line represents the state before the notch groove was changed. As is clear from the figure, only the injection amount can be changed even at the same rack 9 position, and the problem of drivability is solved. Incidentally, by appropriately setting the shape of the notch groove 4a or 4b, it is possible to simultaneously change the fuel injection timing and the injection amount in a certain relationship, but in the fuel injection pump according to the present invention, the injection amount It is equipped with an injection amount adjustment mechanism that can change only the injection amount independently of the timing.
That is, when the plunger 4 is rotated by moving the rack 9 meshed with the pinion 10, the position where the oil supply/discharge hole 11 or 12 communicates with the notch groove 4a or 4b becomes the diagonal notch groove 4a or 4b. along the plunger 4 in the vertical direction. Therefore, the oil supply and drainage hole 11 is located on the upper surface of the plunger 4.
Alternatively, the effective stroke of the plunger 4 during the time when the oil supply/drainage hole 11 or 12 is opened with the cutout groove 4a or 4b after the oil supply/drainage hole 11 or 12 is closed can be changed, and the injection amount can be changed. Therefore, the injection timing and injection amount can be finely adjusted separately, and optimum drivability can be obtained.

In this way, the rack 16 can be operated manually to change the start of injection, or it can be connected to a conventionally used mechanical governor.
Furthermore, it is possible to use hydraulic pressure or electricity. For example, as a device that uses hydraulic pressure, the operating force of the power piston of the servo part of a fluid governor that has been put into practical use recently is connected so as to act on the rack 16 that rotates the sleeve 13, so that the operation of the fluid governor is controlled. The start of injection can also be controlled at the same time. Furthermore, as an electrically operated device, the operating force of an actuator of an electric governor (sometimes called an electronic governor), which has been researched and developed recently, is connected so as to act on the rack 16 that rotates the sleeve 13. Things can be considered. still,
In addition to exercising with each type of governor,
A new independent control section may be provided.

One possible application of such a fuel injection pump is, for example, when it is used for the purpose of improving low-temperature startability. In this case, the sleeve 13 is moved to advance the fuel injection timing at the time of startup to facilitate startup, and the sleeve 13 is returned to its original position once warm-up is complete. In this case as well, the injection timing can be automatically switched by controlling the sleeve 13 using signals detected from outside air temperature, engine cooling water temperature, oil temperature, etc.

In addition, the engine rotation speed, not only when starting,
Engine load (fuel injection control easy position),
EGR amount, supercharged engine supply air temperature and pressure,
By detecting various operating conditions such as exhaust temperature and controlling fuel injection timing, the engine can be kept in an optimal state.

In addition, in the embodiment described above, two oil supply and drainage holes are provided and corresponding notch grooves are provided in the plunger, but the number is not limited to two, and two or more oil supply and drainage holes are provided. In addition to providing an oil drain hole, a cutout groove corresponding to the oil supply and drain hole is also provided on the plunger, and by switching the sleeve according to the number of oil supply and drain holes, the injection start can be changed according to the number of oil supply and drain holes. be able to. In this case, the sleeve switching mechanism may be one that rotates the sleeve or a mechanism that moves it up and down.

Moreover, the method of changing the prestroke is not limited to the above embodiment, but as shown in FIGS. 8a and 8b,
A switching mechanism for the oil supply and drainage hole is provided without changing the position of the oil supply and drainage hole in the height direction, and the head 4c of the plunger 4 is
It is also possible to provide a level difference corresponding to each oil supply/drainage hole 11, 12, and in this case as well, the pre-stroke changes relatively as in the above-mentioned embodiment.

Furthermore, the one shown in FIG. 9 is one in which the pre-stroke is changed by changing the diameters of a plurality of oil supply and drain holes 11 and 12 (although the drawing shows the case of two). . In this case, in order to close the large-diameter oil supply/drainage hole 11, an additional stroke S in the figure is required. Therefore, the prestroke increases by this amount S, and the start of injection is delayed. In this case as well, the same effects as in the above embodiment can be obtained.

As described above in detail with the embodiments, according to the present invention, it is possible to change the start of fuel injection in stages corresponding to the number of switchable oil supply and drain holes, and
Separately from this, the injection amount can be changed by rotating a plunger having a diagonal cutout groove. As a result,
By changing the injection start and injection amount according to various operating conditions of the engine, optimal operating conditions can be ensured, which not only improves output performance but also improves startability and further purifies exhaust gas.

[Brief explanation of the drawing]

1 and 2 show a conventional fuel injection pump, FIG. 1 is an overall sectional view, FIG. 2 is an enlarged perspective view of the main part, and FIGS. 3 and 4 are of a fuel injection pump of the present invention. 3 is an overall sectional view, FIG. 4 is an enlarged perspective view of the main parts, FIGS. 5 and 6 are explanatory diagrams of the operating state, and FIG. 7 is a plunger rotation angle and plunger oil supply. Graphs showing the relationship with the stroke, FIGS. 8 and 9, are explanatory diagrams of other embodiments of the present invention. In the drawing, 1 is a pump body, 2 is a cam, 3 is a roller, 4 is a plunger, 4a, 4b are notched grooves,
4c is the head, 5 is the plunger barrel, 7 is the discharge valve, 9 is the rack, 10 is the pinion, 11 and 12 are the oil supply and drain holes, 13 is the sleeve, 14 is the plunger chamber, 15 is the oil supply chamber, 16 is the rack, a, b are lines indicating the shape of the notch groove of the plunger, h, i, k
is the stroke of the plunger, and j and s are the distances.

Claims (1)

[Claims] 1 A plurality of oil supply and drainage holes are bored in the plunger barrel into which the plunger is fitted so that the pre-stroke of the plunger can be changed, and a plurality of diagonal notched grooves are provided in the plunger corresponding to the oil supply and drainage holes. A sleeve is provided on the outer periphery of the plunger barrel that communicates one of the oil supply and drainage holes with the oil supply chamber, and the sleeve is moved to switch the oil supply and drainage hole that communicates with the oil supply chamber to control the prestroke of the plunger. The injection amount adjustment method includes a sleeve switching mechanism that changes the start of injection, and changes the effective stroke of the plunger by changing the position where the notch groove and the oil supply/drainage hole communicate with each other by rotating the plunger. A fuel injection pump characterized by being equipped with a mechanism.