JPS62271956A - Fuel injection pump - Google Patents

Abstract

PURPOSE:To prevent a valve element in a solenoid valve from catching foreign matter and to sufficiently cope with cavitations or the like, by disposing a fuel filter composed of a net-like filter and porous plates which are stacked one upon another, downstream of a solenoid valve. CONSTITUTION:During suction stroke of a plunger 12 pressurized fuel in a fuel sump 2 is sucked into a fuel pressurizing chamber 11 from a suction port 50. Then, during compression stroke the pressure of fuel increases, and when the pressure exceeds the valve opening pressure of a fuel injection nozzle, fuel injection is initiated. After a predetermined time elapses, when a solenoid valve 35 is opened, an automatic valve 40 is opened so that high pressure fuel overflows from an overflow passage 21, and therefore, the fuel injection is terminated. During suction stroke, fuel pressure in the fuel sump 2 lifts up an automatic valve element 41 through the intermediary of a second overflow passage 21b, and when fuel counterflows, foreign matter is removed by a fuel filter assembly 26 which is formed of a net-like filter disposed between two porous plates so that high pressure and high speed fuel passing the net-like filter after flowing through one of the porous plates may prevent the filter assembly from being broken due to cavitations or the like.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention (Field of Industrial Application) The present invention opens an overflow passage by pilot operation, and drains the pressurized fuel in the fuel pressurization chamber from this overflow passage. This invention relates to a fuel injection pump that is equipped with an electromagnetic valve that causes fuel to overflow into a reservoir, and that terminates each fuel injection by the overflow of fuel.

[Conventional technology]

Conventionally, in fuel injection pumps that supply fuel to diesel engines and the like, it has been common to adjust the amount of fuel injected using an overflow metering method because the timing of fuel injection does not change.

In this overflow metering method, a solenoid valve is installed in the overflow passage that communicates the fuel pressurization chamber and the fuel reservoir, and during the fuel pressurization stroke, the solenoid valve allows the pressurized fuel in the fuel pressurization chamber to flow through the overflow passage. This method causes the fuel to overflow through the fuel tank, thereby terminating each fuel injection. The solenoid valve changes the overflow timing of the pressurized fuel and adjusts the fuel injection amount.

[Problem that the invention seeks to solve]

However, in a fuel injection pump with this structure, during the fuel suction stroke of the fuel pressurizing chamber, the valve element constituting the solenoid valve opens due to the fuel pressure in the fuel reservoir, causing a backflow of fuel in the overflow passage. In this case, there is a problem in that the fuel in the fuel reservoir is introduced into the overflow passage, and foreign matter in the fuel gets caught in the valve body.

It is also possible to install a mesh fuel filter in the overflow passage in order to prevent such foreign matter from entering.
This fuel filter is made of 1 set of thin wires arranged in a net shape to enable the removal of foreign matter.Furthermore, since fuel passes through the overflow passage at high pressure and high flow rate, the fuel filter may be damaged due to cavitation or erosion. There was a problem with it being put away.

The present invention has been made in view of the above problems.
The fuel injection pump is equipped with a fuel filter that protects the solenoid valve by preventing foreign matter from entering when fuel flows backwards in the overflow passage, and is also fully capable of dealing with cavitation and erosion caused by the passage of high-pressure, high-flow fuel. is intended to provide.

[Means for solving problems]

In order to solve the above problems, the present invention has the following configuration. That is, the present invention includes an overflow passage that communicates a fuel pressurizing chamber and a fuel reservoir, and an electromagnetic valve that communicates and shuts off the overflow passage. In a fuel injection pump that controls fuel injection by controlling fuel injection by overflowing pressurized fuel in a fuel pressurizing chamber into a fuel reservoir via an overflow passage, a - A fuel filter is installed. This fuel filter is formed by laminating a rope-shaped filter made of braided wire and a perforated plate with a large number of holes in the fuel overflow direction, with the perforated plate located on the most upstream side. .

[Effect]

The present invention having the above configuration operates as follows.

In other words, since a fuel filter is installed on the downstream side of the solenoid valve in the overflow passage, even if fuel backflow occurs in the overflow passage, foreign objects are removed from the fuel in the fuel pool and the fuel filter flows into the overflow passage. Inflow. This prevents the problem of foreign matter getting caught in the valve body of the solenoid valve.

Further, the fuel filter is formed by laminating a mesh filter and a perforated plate, and the perforated plate is located on the most upstream side. Therefore,
The pressurized, high-flow rate pressurized fuel that overflows from the fuel pressurization chamber through the overflow passage is not directly discharged to the mesh filter, but passes through the wire filter via the perforated plate, preventing damage due to cavitation, etc. be done.

〔Example〕

Next, the present invention will be explained in detail using FIGS. 1 to 3. FIG. 1 is a sectional view of a main part showing the configuration of the present invention.

In FIG. 1, a fuel injection pump P1 is a distribution type pump, and a plunger 12 is slidably inserted into a bore of a cylinder 1 of a plunger pump 10. This plunger 12 is fixed to the cam plate 5. The cam plate 5 is driven by a drive shaft (not shown) via a coupling (not shown). Cam plate 5
has four face cams and rotates on a fixed roller 7. The plunger 12 performs both rotational movement and reciprocating movement in accordance with the cam lift of the face cam.

The fuel pressurizing chamber 11 of the plunger pump 10 is formed by the bore of the cylinder 1 and the end surface 12a of the plunger 12. The cylinder 1 includes a suction boat 50 that communicates with the fuel pressurization chamber 11 via the suction group 12b of the plunger 12 during the suction stroke of the plunger i12, and a fuel pressurization chamber 11
An overflow boat 20 is provided at one end of which is open and allows the pressurized fuel in the fuel pressurization chamber 11 to overflow.

On the other end side of the overflow boat 20, there is an overflow passage 21 that communicates with the fuel reservoir 2 inside the fuel injection pump P1, and a side hot flow passage 22 that also communicates with the fuel reservoir 2 and is opened and closed by a solenoid valve 30. It is provided.

The overflow passage 21 includes a first overflow passage 21a formed within the cylindrical housing 25, and a second overflow passage 21b communicating with the first overflow passage 21a via the annular groove 24. Ru. Furthermore, the first overflow passage 21a and the side hot flow passage 22
are in communication via a communication passage 23, and this communication passage 2
3, an automatic valve 41 is provided. This automatic valve 40 includes a valve body 41 having a throttle 41a, and a valve body 41 having a throttle 41a.
a coil spring 42 that urges the flow toward the first overflow passage 21
It consists of The automatic valve 40 divides the first overflow passage 21a side and the side hot flow passage 22 side into two by the valve body 41, and when the side hot flow passage 22 is closed by the solenoid valve 30, the coil spring 42 It is energized to keep the first overflow passage 21a closed. In addition, the solenoid valve 30
When activated and the side hot flow passage 22 opens, the communication passage 23
As the fuel pressure inside decreases, the valve body 41 opens, opening the first overflow passage 21a. Thereby, the first overflow passage 21a and the second overflow passage 21b are communicated with each other.

Here, the first overflow passage 21a inside the cylindrical housing 25 which is inside the overflow passage 21 and is on the downstream side of the automatic valve 40
A fuel filter 26 is fixedly attached to the connecting portion between the annular groove 24 and the annular groove 24 .

Next, this fuel filter 26 will be explained using FIGS. 2 to 6. 2 and 3 are diagrams showing the structure of the fuel filter 26, with FIG. 2 being an enlarged sectional view and FIG. 3 being an exploded perspective view.

In FIGS. 2 and 3, the fuel filter 26 is composed of a cylindrical filter section 27 and annular end plates 29a and 29b that fix and hold the upper and lower openings of the filter section 27.

Furthermore, the filter section 27 is composed of a mesh filter 28 shown in FIG. 4 and a perforated plate 29 shown in FIG. The mesh filter 28 is a belt-shaped filter made up of four sets of filaments made of a highly corrosion-resistant metal such as stainless steel, and removes foreign matter from the fuel passing through it. Perforated plate 2
Reference numeral 9 is a thin plate-like metal having excellent corrosion resistance, such as stainless steel, with a large number of holes 29a formed therein. The filter section 27 is constructed by inserting a mesh filter 28 between two perforated plates 29, overlapping them, rolling them into a roll as shown in FIG. 6, and then fixing them by welding or the like.

That is, the filter section 27 is configured so that the mesh filter 28 and the perforated plate 29 are stacked in the direction of fuel flow at the connection between the first overflow passage 21a and the annular groove 24 in the cylindrical housing 25. The perforated plate 29 is located at the most upstream side within the overflow passage 21.

Next, the operation of this embodiment will be explained using FIG. During the suction stroke in which the plunger 12 moves to the left in the drawing, pre-pressurized fuel in the fuel reservoir 2 is sucked into the fuel pressurizing chamber 11 via the suction port 50 and the suction group 3. In the first half of the compression stroke when the plunger 12 moves to the right in the drawing, the solenoid valve 35 causes the side hot flow passage 22 to
is closed, and the coil spring 42 of the automatic valve 40 is closed.
The valve body 41 is urged downward in the figure, and the first overflow passage 21a is kept closed by the valve body 41. Therefore, as the plunger 12 moves to the right in the drawing, the fuel pressure in the fuel pressurizing chamber 11 increases, and when it exceeds the opening pressure of the injection nozzle (not shown), fuel starts to be injected into the engine fuel chamber. . After this fuel injection is started, a drive current is started to be supplied to the electromagnetic valve 35 from a fuel injection amount control circuit (not shown) at an appropriate time, and the electromagnetic valve 35 is opened to open the side hot flow passage 22. When this side hot flow passage 22 is opened, the pressurized fuel in the communication passage 23 begins to overflow into the low pressure side fuel reservoir 20 via the overflow passage 22, and the fuel pressure in the communication passage 23 decreases. The valve body 41 moves upward in the figure, and the first overflow passage 22a opens. By opening the first overflow passage 22a, the pressurized fuel in the fuel pressurizing chamber 11 is transferred to the overflow port 22a.
, the first ck/flow passage 22a, the fuel filter 26, and the second overflow passage 22b overflow into the low-pressure side fuel reservoir 20, and the fuel pressure in the fuel pressurizing chamber 11 decreases, causing the valve opening pressure of the injection nozzle to decrease. If it becomes smaller than , fuel will no longer be injected from the injection nozzle. In other words, this overflow ends each fuel injection.

Here, a fuel filter 26 is installed on the downstream side of the automatic valve 40 in the overflow passage 21. Therefore, during the fuel intake stroke, the valve body 41 is moved by the fuel pressure in the fuel reservoir 2 against the elastic force of the coil spring 42, and the first overflow passage 2 is moved.
Even if 1a is opened and a backflow of fuel occurs in the overflow passage 21, the fuel flowing from the fuel reservoir 2 has foreign matter removed by the fuel filter 26 and then flows therein. This prevents foreign matter from getting caught in the valve body 41 of the automatic valve 40.

In addition, the mesh filter 28 and the perforated plate 29 that constitute the fuel filter 26 are made of a metal with excellent corrosion resistance, and are mounted in a stacked manner in the direction of fuel overflow. It is located on the upstream side. Therefore, even if the pressurized fuel overflows at high pressure and high flow rate in the overflow passage 21, the pressurized fuel will not be directly discharged to the mesh filter 28 and will not pass through the perforated plate 2.
Pass through 9. As a result, the mesh filter 28 will not be damaged by cavitation or the like, and since the filter section 27 is constructed by laminating a large number of layers, it has excellent corrosion resistance.

〔Effect of the invention〕

As explained above, in the present invention, the fuel filter is installed downstream of the electromagnetic valve that communicates and shuts off the overflow passage.

As a result, even if a backflow of fuel occurs in the overflow passage, the fuel in the fuel reservoir will flow in after foreign matter is removed by the fuel filter. Therefore, foreign matter is prevented from getting caught in the valve body of the solenoid valve.

Further, this fuel filter is formed by laminating a mesh filter and a perforated plate in the direction of fuel overflow, and
The perforated plate is located at the most upstream side. Therefore, the high-pressure, high-flow pressurized fuel overflowing from the fuel pressurization chamber through the overflow passage is not directly discharged to the mesh filter, but instead enters the mesh filter through the perforated plate, resulting in damage due to cavitation, erosion, etc. is prevented.

Furthermore, by laminating a large number of mesh filters and porous plates, corrosion resistance can be further improved.

[Brief explanation of drawings]

Figures 1 to 6 relate to embodiments of the present invention.
2 is an enlarged sectional view of the fuel filter of FIG. 1, FIG. 3 is an exploded perspective view of the fuel filter of FIG. 1, and FIG. 4 is a sectional view of the fuel filter of FIG. 3. Fig. 5 is a front view showing a perforated plate forming the filter part of Fig. 3, and Fig. 6 is for explaining the processing method of the filter part of Fig. 3. FIG. 11... Fuel pressurization chamber, 20... Overflow port, 21...
...Overflow passage, 21a...First overflow passage, 21b...
・Second overflow passage, 22... Side hot flow passage, 26... Fuel filter, 28... Wire mesh filter, 29... Perforated plate, 35... Solenoid valve, 40... Automatic type valve. X~2 Figure 1 Figure 3 Figure 5 Series n4 customer 7411. - Figure 4 Figure 6

Claims (1)

[Claims] An overflow passage that communicates between the fuel pressurization chamber and the fuel reservoir, and an electromagnetic valve that communicates and shuts off the overflow passage, the electromagnetic valve communicates the overflow passage during the fuel pressurization stroke. , in a fuel injection pump that controls fuel injection by overflowing pressurized fuel in the fuel pressurizing chamber into the fuel reservoir via the overflow passage, the fuel injection pump includes a fuel injection pump in the overflow passage and downstream of the electromagnetic valve; is equipped with a fuel filter, which is formed by stacking a mesh filter made of braided wire and a perforated plate with many holes in the direction of fuel overflow. A fuel injection pump characterized in that a perforated plate is located.