JPH07259696A - Delivery valve of fuel injection pump - Google Patents

Abstract

PURPOSE:To provide a delivery valve having its structure for suppressing cavitation which is generated in a fuel passage part, at the time of & return operation of fuel, after fuel injection operation is completed, in the delivery valve of the injection pump of a fuel injection type internal combustion engine. CONSTITUTION:A delivery valve is formed by bending both routes of Angleich cut 11 which 16 provided on the sucking return color 7 of a valve main body 5 and the flat surface notch part 12 for a fuel passage which is provided on a guide part 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a delivery valve for a fuel injection pump of a fuel injection type internal combustion engine, which carries out the pumping of the fuel from the start to the end of the pumping of the pump, the backflow prevention and the sucking back.

[0002]

2. Description of the Related Art In a fuel injection pump mechanism for a fuel injection type internal combustion engine, when the injection of the fuel to the injection nozzle side is completed, the injection nozzle side communicates with the plunger chamber.
In the next fuel pressure feeding, the time delay between the pump pressure feeding start and the nozzle injection operation becomes large. Further, if the residual pressure in the passage toward the injection nozzle side is high after the fuel injection, the sharpness of the fuel injection from the nozzle deteriorates, causing post-leakage. Therefore, it is necessary to cut off the communication between the passage to the injection nozzle and the plunger chamber after the pressure feeding of the fuel is completed.

The delivery valve is provided to perform this function, and when the fuel injection is completed, the pressure in the passage to the injection nozzle is rapidly lowered to a predetermined pressure to ensure the operation of the fuel injection nozzle. It has a sucking back action for improving the disconnection of the injection, and an action for blocking the space between the plunger chamber and the passage to the injection nozzle in order to maintain the pressure in the passage to the injection nozzle until the next injection is performed. As shown in FIG. 4, the delivery valve (1) is provided between the plunger chamber (2) of the pump element and the passage (3) to the injection nozzle.

FIG. 5 shows a conventional example of this delivery valve. As shown in FIG. 5, the delivery valve includes a valve seat (4) (shown in cross section) and a valve body (5) that fits on the inner surface of the valve seat (4) and slides on the inner surface. The valve body (5) has a cylindrical structure having a predetermined diameter D. A peripheral groove (6) having a predetermined width along the circumferential direction at a predetermined distance from the end face in the axial direction at one end thereof.
Are formed. The portion having the diameter D from the end face to the peripheral groove (6) is the suck-back collar (7). The portion of diameter D on the side opposite to the suction back collar (7) across the circumferential groove (6) is the guide portion (8), and the guide portion (8) slides on the inner surface of the valve seat (4). To do. Valve body (5)
The other end of the is a throttle (valve piston) (9) having a diameter d ₁ smaller than D, and this throttle (9) faces the guide part (8) toward the conical surface (16).
The via, greater than smaller d ₁ than _{D d 2 (D> d 2} >
It is connected to a cylindrical portion having a diameter of d ₁ ). The cylindrical portion having the diameter of d ₂ is further connected to the guide portion (8) via the conical surface (17). When the delivery valve (1) is closed, that is, when the valve body (5) is at the lowest point, the throttle (9) and the conical surface (16) connected to the throttle (9) make the valve seat (4) corresponding to that position. ) Is fitted to the seat surface (18) of the above () to block the inflow of fuel from the plunger chamber (2) side. A dashpot chamber (10) is formed by a cylindrical portion having a diameter of d ₂ , a conical surface (17) continuous with the cylindrical portion, and the inner surface of the valve seat (4) corresponding to this portion.

Notch planes (11) and (12) having a predetermined width are formed on the cylindrical surfaces of the sucking back collar (7) and the guide portion (8) along the cylinder axis, respectively, and the circumferential groove ( It is formed continuously across both parts across the 6). The notch plane (12) and the circumferential groove (6) of the guide portion serve as a fuel passage when the valve body (5) is lifted to the injection nozzle side. Notch planes (1) formed in the suck back collar (7)
1) is Angreich cut (hereinafter, suck back color (7)
The notch plane formed in the above is referred to as an Angleich cut (11)), and this function will be described later in the description of the operation.

FIG. 6 shows a cross section of a dashpot valve which is an example of the above delivery valve (1). As shown in Fig. 6, the valve spring (1
3) is inserted, and the valve body (5) is always biased toward the plunger chamber (2). With this structure, the dead volume can be reduced and a high injection pressure can be obtained. The delivery valve having such a configuration operates as follows.

First, the plunger rises to start the fuel pressure stroke, and when the fuel pressure overcomes the pressure of the valve spring (13), the valve body (5) is pushed up. When the valve body (5) continues to rise, and the lower end surface of the throttle (9) begins to enter the area of the seat surface (14) of the valve seat (4), that is, when the valve starts to open, fuel is injected into the dashpot chamber. It flows into (10). At the same time, the fuel passes through the notch plane (12) for the fuel passage provided in the guide portion (8) of the valve body (5), the circumferential groove (6) and the Angleich cut (11), and the injection nozzle side. Spill to. While the valve body (5) rises, the dashpot chamber (10) is proportional to the increment Δl of its rising distance, Δl · π (D ² −d ₁ ² ).
/ 4 minutes increase in volume, but this dashpot chamber (1
If the pressure before the volume increase of 0) is zero (atmospheric pressure),
As the volume increases, the pressure in the dashpot chamber (10) becomes negative and a cavity (bubble) is generated. The generation of the cavity is remarkable in the low speed range (when the pump rotation speed is small) as shown in FIG.

The throttle (9) is attached to the seat surface (1
When seated in 4), close the valve to prevent backflow of fuel to the plunger chamber (2) side. The Angreich cut (11) is provided for the following reason.

In low speed operation, negative pressure is generated on the injection nozzle side, and fluctuations in residual pressure in the passage (3) to the injection nozzle side make the injection amount unstable each time. Therefore, the Angreich cut (11) is provided in the suck back collar (7) to reduce the suck back efficiency.

[0010]

By the way, the above-mentioned conventional delivery valve has the following problems.

During fuel pressure feeding, the valve body (5) rises,
When the volume of the dashpot chamber (10) increases and the pressure in this portion drops, the dashpot chamber (10) becomes a negative pressure, and as described above, many bubbles are generated in the chamber. These bubbles are not only in the dashpot chamber (10) but also in the guide part (8) of the valve body (5) and the Angleich cut (11).
Widely distributed in the department. This state is shown in FIG.

Under these conditions, the upper end of the valve body (5), which has flowed back through the Angleich cut (11), during the period from the start of rising of the valve body (5) to the release of the fitting of the throttle (9). The fuel on the side flows back to the notch plane (12) of the guide portion through the circumferential groove (6) in a short-circuited manner, but further rushes into the dashpot chamber (10) and then the dashpot chamber (1
Relieve the negative pressure in 0). This backflow of fuel is instantaneously performed, and the negative pressure in the dashpot chamber (10) is instantaneously eliminated. At the same time, since a large number of the bubbles are instantly collapsed, cavitation corrosion is caused in the notch plane (12) and the Angleich cut (11) of the guide portion where the bubbles are present. This state is shown in FIG.

When this cavitation corrosion progresses over time and becomes large, the set value of the desired fuel injection amount is gradually increased, and a large amount of black smoke is emitted when the engine is accelerated. FIG. 9 shows that cavitation corrosion in this delivery valve affects the injection amount characteristic.
In FIG. 9, the curve shown by the solid line shows the case where there is no cavitation corrosion, and the curve shown by the broken line shows the case that there is cavitation corrosion. As can be seen from FIG.
It is understood that in the presence of cavitation corrosion, the injection amount is higher than that in the case where there is no cavitation corrosion even if the pump rotation speed is the same. In light of the social demand for pollution prevention, which has been sought after by wealth in recent years, there is an urgent need to solve this problem.

The present invention has been made to solve the above problems, and in the delivery valve of the injection pump of the fuel injection type internal combustion engine, the volume of the dashpot chamber increases when the fuel is pumped at the time of starting the fuel injection. It is an object of the present invention to suppress the phenomenon that cavitation occurs in the valve body due to the generation of negative pressure due to the above, and thereby prevent cavitation corrosion from occurring.

[0015]

A delivery valve for a fuel injection pump according to the present invention includes a small-diameter throttle and a large-diameter guide portion provided above the throttle and adjacent to each other via a circumferential groove in a valve seat. The valve body equipped with a suck-back collar is lifted according to the start of pressure-feeding of fuel,
In addition, it is fitted so as to be seated on the seat surface in accordance with the end of the pressure feeding of the fuel, and in the dashpot chamber formed between the seat surface and the guide portion, the suction collar is formed from the upper end of the valve body. In a dashpot type delivery valve in which a passage, a circumferential groove, and a passage formed in a guide portion are communicated in series, the passage formed in the suck-back collar and the passage formed in the guide portion are arranged in the circumferential direction of the circumferential groove. It is characterized in that it is provided at a position away from each other, whereby the above object is achieved.

The invention according to claim 2 is characterized in that the passage formed in the sucking back collar and the passage formed in the guide portion are cut planes, and the planes of the planes are different from each other. Therefore, the above object is achieved.

The invention according to claim 3 is characterized in that, among the passages, at least the passage formed in the suction collar is a through hole in the vertical direction, whereby the above object is achieved.

[0018]

In the delivery valve of the present invention, the passage formed in the sucking back collar portion of the valve body and the passage formed in the guide portion thereof are provided at positions distant from each other in the circumferential direction. The pressure of the fuel on the upper end side of the valve body that occurs until the gap disappears from the passage formed in the suction back collar to the passage formed in the guide part through the circumferential groove, The rapid pressure drop that has occurred between the nearest passages is not caused, and the occurrence of cavitation corrosion due to the collapse of a large number of bubbles that occur at such locations is prevented or suppressed.

[0019]

EXAMPLES Examples of the present invention will be described below. The present invention is not limited to the embodiments.

FIG. 1 shows a delivery valve of an embodiment according to the present invention. The same numbers are assigned to the parts common to the conventional example. The structure of the delivery valve of the present embodiment is almost the same as that of the conventional example described above, and therefore only the characteristic parts of the delivery valve of the present embodiment, which are different from the conventional example, will be described below.

In the conventional delivery valve, since the machining is simple, the Angreich cut (11) and the notch plane (12) of the guide portion (fuel passage of the guide portion) are sandwiched by the circumferential groove (6). In the delivery valve of this embodiment, as shown in FIG. 1, the Angreich cut (11) and the notch plane (12) of the guide portion are formed so that the paths of the respective passages are straight. ) And the circumferential groove (6)
It is provided so that the path of each passage is bent with the passage in between. By providing the Angleich cut (11) and the notch plane (12) of the guide part in this way, the angle is cut from the start of fuel pressure feeding to the removal of the fitting of the throttle (9) of the valve body (5). The reverse flow of fuel from the cutout (11) to the notch plane (12) of the guide part does not occur instantaneously due to the excessive pressure difference as in the conventional case, and the negative pressure of air bubbles is concentrated. Backflow of fuel to large areas is also prevented.

Therefore, during the period from the start of the pressure feeding of the fuel until the engagement of the throttle (9) is removed, the dashpot chamber (10), the notch plane (12) of the guide portion, and the Angleich cut (11) are set at the beginning of the pressure feeding. Since it is possible to allow the fuel to flow into the circumferential groove (6) where the air bubbles are scattered rather than at the place where a large number of generated air bubbles (cavities) are distributed, the occurrence of cavitation corrosion is prevented or suppressed. The effect is particularly remarkable in the low speed range. The inventor confirmed this.

As a means for suppressing the sudden inflow of fuel from the suck-back collar (7) side to the notch plane (12) of the guide part, a fuel passage provided in the suck-back collar (7) is used as a guide part. As shown in FIG. 2, instead of the Angleich cut (11) that is directly connected to the notch plane (12), a through hole (15) with a small diameter is used, and its path is cut in the guide part. The cut plane (12) may be formed at a position different from the path. The through holes are easy to form, and it is easy to take measures to prevent cavitation corrosion.

Further, as shown in FIG. 3, the cutout plane (12) of the guide portion may be a plurality of two to four, and they may be provided with the cylindrical surface of the guide portion (8) sandwiched therebetween. However, also at this time, it is important to provide the fuel passage (through hole (15)) provided in the suck-back collar (7) at a position different from the path of the notch plane (12) of the guide portion.

[0025]

According to the present invention, in the delivery valve of the injection pump provided in the fuel injection type internal combustion engine, it is possible to suppress the cavitation generated on the valve surface at the time of sucking back the fuel after the fuel is injected. It is possible to prevent the delivery valve from being corroded. Therefore, the durability and reliability of the delivery valve are remarkably improved, and the amount of black smoke in the exhaust gas emitted during engine acceleration is significantly suppressed.

According to the second aspect of the present invention, the negative pressure in the dashpot chamber can be eliminated without generating air bubble concentration points in the circumferential groove, and cavitation corrosion is caused over the entire operating range. It can be prevented.

Further, according to the invention of claim 3, since the fuel passage provided in the sucking-back collar portion is a through hole, it is easy to manufacture and (preliminarily specified by an experiment or the like).
Since it can be selectively and easily provided at a position corresponding to the peripheral groove portion where there are few air bubbles, the occurrence of cavitation corrosion can be easily suppressed.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing another embodiment of the present invention.

FIG. 3 is a diagram showing another embodiment of the present invention.

FIG. 4 is a view showing an installation position of a delivery valve in an injection device of an injection type internal combustion engine.

FIG. 5 is a diagram showing a conventional example of a delivery valve.

FIG. 6 is a view showing a dashpot type delivery valve.

FIG. 7 is a diagram showing a state of bubbles generated in a delivery valve when the dashpot chamber has a negative pressure during fuel pressure feeding.

FIG. 8 is a diagram showing the presence of cavitation corrosion in a delivery valve.

FIG. 9 is a diagram showing an influence of cavitation corrosion in a delivery valve on an injection amount characteristic. [Brief description of drawings] 1 Delivery valve 2 Plunger chamber 3 Passage to injection nozzle 4 Valve seat 5 Valve body 6 Circumferential groove 7 Suck back collar 8 Guide part 9 Throttle 10 Dashpot chamber 11 Angleich cut 12 Notch of guide part Flat surface 13 Valve spring 14 Seat surface 15 Through hole 16, 17 Conical surface 18 Seat surface

Claims (3)

[Claims] 1. A valve main body having a small-diameter throttle, a large-diameter guide portion and a suction-back collar provided adjacent to each other above the throttle via a circumferential groove in a valve seat. Lifted according to the start, and
It is fitted so that it will be seated on the seat surface in response to the completion of fuel pumping, and in the dashpot chamber formed between this seat surface and the guide portion, there is a passage formed in the suction collar from the upper end of the valve body. In a dashpot type delivery valve in which the circumferential groove and the passage formed in the guide portion are communicated in series, a position in which the passage formed in the suck-back collar and the passage formed in the guide portion are separated from each other in the circumferential direction of the circumferential groove. A delivery valve for a fuel injection pump, characterized in that 2. The fuel injection according to claim 1, wherein the passage formed in the sucking back collar and the passage formed in the guide portion are cut planes, and the planes of the planes are different from each other. Pump delivery valve. 3. The delivery valve for a fuel injection pump according to claim 1, wherein at least the passage formed in the suction collar of the passage is a vertical through hole.