JPH0442521Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field] The present invention relates to a jerk type fuel injection pump.

[Conventional technology]

Figure 2 shows the main structure of a conventional jerk-type fuel injection pump. In the figure, 1 is the pump housing, 2 is the plunger, 3 is the barrel, 4 is the delivery valve seat, 5 is the delivery valve, 51 is the delivery suction/return collar, 52 is the delivery valve guide, 6 is the delivery valve spring, and 7 is the delivery valve holder. , 8 is a stopper, and 9 is an injection pipe (not shown). Numerals 31 and 32 are oil supply and drain holes, respectively, and 21 is a lead portion of the plunger.

Next, the operation of the conventional example will be explained.

When fuel is supplied from the oil supply hole 31 to the plunger chamber 33, the oil supply and discharge holes 31 and 32 pushed up from the plunger 2 by a cam (not shown) are closed, and the pressure inside the plunger chamber 33 increases, causing the oil to The fuel pushes up the delivery valve 5 against the force of the spring 6 and is discharged into the delivery valve chamber 71, and then is sent into the injection pipe 9 and is injected from the fuel injection valve (not shown). When the plunger 2 further rises, the lead portion 21 communicates with the oil drain hole 32, and oil is discharged into the oil supply chamber 101. Despite the rise of the plunger 2, fuel discharge ends and the delivery valve 5
falls and closes, and eventually the injection from the fuel injection valve also ends.

However, in high-speed, high-output engines, the pressure inside this injection pipe is high, and therefore, injection from the fuel injection valve may continue even after the delivery valve 5 is closed.
Additionally, the fuel injection valve may open again after it has been closed. This is called secondary injection, and it causes smoke exhaust and deterioration of fuel efficiency. To prevent this, a suction collar 51 is provided on the delivery valve 5 to provide a suction action at the end of discharge.

However, when injecting at very high pressure, a large amount of suction is required, and as a result, the suction speed (negative discharge speed) that occurs at the end of discharge becomes excessive, and negative pressure (cavity) is generated immediately after the end of injection. This causes capitation erosion within the injection system. As a result, the durability of the fuel injection valve and injection pipe is significantly reduced, and engine performance is also significantly reduced.

Therefore, what was proposed as another conventional example is the third one.
As shown in the figure, this is a delivery valve 5 that can control the suction and return speed. In the figure, 53 is a small projection formed at the bottom of the delivery valve, and this diameter is smaller than the diameter of the delivery valve suction-back collar 51 (usually 1/2 or less), while the delivery valve seat 4 has a throttle hole 41. A protrusion 53 is inserted into the throttle hole 41. When the delivery valve 5 descends, the protrusion 53 enters the throttle hole 41 and the delivery valve lower chamber is inserted. 42
Since the cross-sectional area of the outlet from the plunger chamber 33 to the plunger chamber 33 is reduced to limit the amount of outflow, the descending speed of the delivery valve 5 gradually slows down, making it possible to prevent both cavitation and secondary injection as described above.

Next, the communication holes 61 and 62 will be explained.

The communication holes 61, 62 open above the oil supply/drainage hole of the plunger chamber 33, and communicate the plunger chamber with the delivery valve lower chamber. Without these communication holes 61 and 62, even at the beginning of discharge, the plunger chamber 33 would be connected to the delivery valve lower chamber 42.
Delivery valve 5
initially rises slowly, but as soon as the protrusion 53 comes out from the throttle hole 41 upward, the rising speed becomes rapid, and the lift of the delivery valve 5 becomes excessive, which can cause damage to the stopper 8 and the delivery valve spring 6. arise. Therefore, the communication holes 61 and 62 are provided to prevent the list at the start of discharge from the delivery valve 5 from becoming excessively large.
However, the drawback of these communication holes 61 and 62 is that their workability is very poor. In order to open the communication holes 61 and 67, it is necessary to set an electric discharge machining jig in the plunger chamber 33, and to bring electrical contacts into contact with the points of the communication holes 61 and 62, so that the barrel 3 is melted by electric heat generation. , special and expensive equipment such as an electrical discharge machine is required, and it takes a great deal of time to set up the jig. Furthermore, if the plunger diameter is 20 mm or more (mainly for large ships), there is room to insert a jig, but if the plunger diameter is less than 20 mm (mainly for automobiles and industrial machinery), it is extremely difficult to insert a jig. Therefore, it is impossible to process a plunger of 10 mm or less with the current technology level.

[Problem that the invention attempts to solve]

The purpose of the present invention is to eliminate the drawbacks of the conventional device,
Even when the plunger diameter is small, there is no need to use special and expensive equipment such as an electric discharge machine, and the connecting hole between the plunger chamber and the lower chamber of the delivery valve can be easily drilled using a commonly used drilling machine. Our goal is to provide high performance and inexpensive fuel injection pumps.

[Means for solving problems]

The fuel injection pump of the present invention is a fuel injection pump in which the plunger barrel is provided with a communication hole that communicates the delivery valve lower chamber and the plunger chamber.
An opening 61 of the communication hole to the plunger chamber and a drill guide waste hole 63 provided on an extension of the opening 61 for drilling the opening are provided so as to open above and below the fuel supply oil drain hole 31, respectively,
Furthermore, the setting position of the drill guide waste hole 63 is shifted in the circumferential direction of the plunger barrel with respect to the fuel supply/drainage hole 31 to achieve the above object.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, the plunger chamber side communication hole 61 communicates with the delivery valve lower chamber communication hole 62 via the barrel side communication hole 64. Plunger chamber side communication hole 6
1 is bored at an angle slightly inclined from perpendicular to the plunger sliding hole 34 of the barrel 3. The extended line is shown as a dotted line, and a drill guide hole 63 is installed on this line. This drill guide waste hole 63 is a drill guide hole provided for drilling the communicating hole opening 61 on the plunger chamber side.

In addition, the plunger chamber side opening 61 of the communication hole is opened at a position above the oil supply and drainage hole 31 of the plunger chamber 33, and the waste guide hole 63 for the drill is opened at an appropriate position below the oil supply and drainage hole 31. If a suitable position is selected, it is possible to avoid any influence on the oil supply and drainage action of the plunger even if the waste hole 63 is not provided with a blind plug. The rest of the structure is the same as the conventional example shown in FIG. 3, and the same members as in FIG. 3 are designated by the same reference numerals.

It goes without saying that the connecting hole other than the opening on the plunger side can be easily drilled using a drilling machine.

[Effect of idea]

As mentioned above, the fuel injection pump of the present invention has a delivery valve with a protrusion and a communication hole that communicates the delivery valve chamber with the plunger chamber, and the opening of the communication hole on the plunger chamber side is connected to the plunger of the barrel by sliding. The plunger diameter is small because it is installed at an angle slightly tilted from perpendicular to the hole, and a drill guide hole is installed on the extension line of the hole and below the oil supply and drain hole of the plunger chamber. Even if an expensive electrical discharge machine or the like cannot be used, the opening 61 on the plunger chamber side of the communication hole between the plunger chamber and the lower chamber of the delivery valve can be easily machined using a commonly used general-purpose drilling machine. Also, there is no need to plug the drill guide disposal hole. Therefore, cavitation occurs within the fuel injection system to prevent secondary injection in high-speed, high-load engines.
A fuel injection pump that prevents the occurrence of erosion, a decrease in the durability of the fuel injection valve and the injection pipe, and a decrease in engine performance can be manufactured at a low cost.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of a fuel injection pump according to the present invention, FIG. 2 is a sectional view of a main part of a first conventional example, and FIG. 3 is a sectional view of a main part of a second conventional example. 3...Barrel, 5...Delivery valve, 31...
...Fuel supply and drain hole, 33...Plunger chamber, 42...
...Delivery valve lower chamber, 53...Protrusion, 61...
...Opening portion of the communication hole on the plunger chamber side, 63...Discarded hole for drill guide, 64...Communication hole.

Claims (1)

[Scope of utility model registration request] In a fuel injection pump in which a communication hole for communicating a delivery valve lower chamber and a plunger chamber is provided in a plunger barrel, an opening 61 of the communication hole to the plunger chamber and an extension line of the opening 61 for drilling the opening are provided. Drill guide waste holes 63 are provided so as to open above and below the fuel supply and oil drain hole 31, respectively, and the drill guide waste holes 6
3 is shifted in the circumferential direction of the plunger barrel with respect to the fuel supply/drainage hole 31.