JPH05157014A - Bubble discharge device for diesel engine - Google Patents

Abstract

PURPOSE:To provide a bubble discharge device to separate/remove bubbles in fuel in the downstream of a fuel filter in a fuel supply system of a diesel engine. CONSTITUTION:A bubble discharge device 1 is provided with a bubble separating film 15 arranged in a fuel supply passage between a fuel filter 3 and a fuel injection pump 4 so as to capture bubbles in fuel, an upper chamber 12 formed above the bubble separating film, a return passage 16 having a venturi part 20 inside and a communicating passage 19 to communicate the upper chamber 12 and the return passage 16 with each other. The bubbles captured by means of the bubble separating film 15 rise, and are sucked out into the return passage 16 due to a negative pressure generated in the venturi part 20, and are returned to a fuel tank 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bubble discharging device used in a fuel supply system of a diesel engine.

[0002]

2. Description of the Related Art Generally, a fuel supply system of a diesel engine is provided with a fuel filter and a fuel injection pump in that order from a fuel tank to a fuel injection nozzle, while another fuel injection nozzle and a fuel injection pump are provided. The surplus fuel is directly returned to the fuel tank through the return passage.

By the way, in this way, the fuel flowing through the fuel supply system may contain a large amount of bubbles (air), and if this bubble flows into the fuel injection pump as it is, the injection characteristics of the fuel injection amount and the like change. Then, it may cause a malfunction of the engine.

In order to deal with such a problem, in Japanese Utility Model Laid-Open No. 63-164558, the upper portion of the fuel filter is integrated so that a part of the return passage passes through, and the return passage is provided from the upper portion of the fuel filter. There is disclosed an automatic air bleeding fuel piping device adapted to discharge air.

[0005]

By the way, in a fuel supply system having a so-called distribution type fuel injection pump in which fuel is distributed from the fuel injection pump to each fuel injection nozzle, in order to increase the pressure in the pump. In some cases, a fuel feed pump may be built in the fuel injection pump, or a fuel feed pump may be provided between the fuel filter and the fuel injection pump. In the case where a feed pump is arranged, the fuel supply passage on the downstream side of the filter has a negative pressure due to the suction of the feed pump, and air bubbles are likely to be generated in the fuel.

In such a case, even if air is removed from the upper part of the fuel filter by the above device, it is not effective against bubbles generated thereafter, and the bubbles flow into the fuel injection pump as they are. In addition, since the pressure inside the fuel filter becomes lower than the pressure inside the return passage due to the suction of the pump, it is difficult to discharge bubbles.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a device capable of removing bubbles from the supplied fuel in a diesel engine even when the fuel supply becomes negative due to a fuel feed pump or the like. And

[0008]

To achieve the above object, according to the present invention, a fuel filter and a fuel injection pump are sequentially arranged in a fuel supply system from a fuel tank to a fuel injection nozzle, and fuel injection is performed. A device for removing bubbles from the fuel supplied by a diesel engine, which is designed to return excess fuel from a nozzle or a fuel injection pump to a fuel tank, and captures bubbles in the fuel provided between a fuel filter and a fuel injection pump. Bubble separation membrane, a space formed above the bubble separation membrane, a return passage having a venturi portion therein for passing the surplus fuel, and a communication passage communicating the space and the venturi portion. There is provided a bubble discharging device having:

[0009]

The bubbles trapped by the bubble separation membrane are sucked out from the space formed above by the negative pressure generated in the venturi portion, flow into the return passage, and are returned to the fuel tank.

[0010]

Embodiments of the present invention will be described with reference to the drawings.
1 showing a schematic structure of a fuel supply system equipped with a bubble discharging device according to the present invention, 1 is a bubble discharging device, 2 is a fuel tank, 3 is a fuel filter, and 4 is a fuel feed pump (not shown). Fuel injection pumps 5 indicate fuel injection nozzles, respectively.

Regarding the fuel supply path to the fuel injection nozzle 5, first, the fuel sucked up from the fuel tank 2 via the in-tank filter 6 and the suction pipe 7 is supplied to the fuel supply path 8
After passing through the fuel filter 3 and the bubble discharging device 1 according to the present invention, it is supplied to the fuel injection pump 4 and is pumped to each fuel injection nozzle 5 (only one is shown in the figure). It will be.

Further, the surplus fuel in the nozzle and the surplus fuel in the fuel injection pump which are not injected from the fuel injection nozzle 5 in this way pass through the return passage 9 as shown by the arrow in the figure, and are discharged to the bubble discharging device 1. After passing through, it will be finally returned to the fuel tank 2. The fuel passage shown by the chain double-dashed line in the figure shows the structure of a conventional fuel supply system in which the present device 1 is not mounted.

Next, the structure and operation of the above-described bubble discharging device 1 will be described with reference to FIG.

Referring to FIG. 2 showing a cross section of the apparatus, the apparatus is composed of an upper casing 10 and a lower casing 11.
Inside the upper casing 10 and the lower casing 11, an upper chamber (space) 12 and a lower chamber 13 which form a reservoir of the fuel supplied from the fuel filter 3 are formed, and a fuel inlet pipe is provided between these chambers. In order to capture the bubbles in the fuel supplied to the inside of the device via 14, a net-shaped bubble separation membrane 15 having a myriad of holes on its entire surface is sandwiched.

As is apparent from FIG. 1, the fuel inlet pipe 14 is connected to the fuel supply passage 8 from the fuel filter 3 to guide the fuel into the apparatus. Similarly, the fuel outlet pipe 15 is provided below the lower casing 11. Is inserted and fixed, is connected to the fuel injection pump 4 via the fuel supply passage 8, and the fuel that has passed through the bubble separation membrane 15 is guided to the fuel injection pump 4.

The upper wall 10a of the upper chamber 12 formed in the upper casing 10 is sloped like a pent roof as shown in the drawing, and further above it, a part of the return passage 9 (FIG. 1). And a return passage 16 through which excess fuel is passed through so as to cross the casing,
This passage has a return inlet pipe 1 inserted and fixed at both ends.
7 and the outlet pipe 18 are connected to the return passage 9 shown in FIG.

The above-mentioned upper chamber 12 and return passage 1
6 is a communication passage 1 that extends upward at approximately the center of the upper wall 10a.
9, the communication passage 19 is the return passage 1
It intersects with 6 almost perpendicularly. A venturi 20 and an orifice 21 are provided inside the return passage 16 and the communication passage 19 in the vicinity of the connecting portion to reduce the passage cross-sectional area.

The operation of the bubble discharging device 1 constructed as above will be described. In FIG. 2, solid arrows show the flow of fuel in the apparatus, and dotted arrows show the flow direction of air, that is, bubbles, contained in the fuel.

First, the bubble-blended fuel flowing from the fuel filter 3 flows into the upper chamber 12 through the fuel inlet pipe 14, but at that time, relatively large bubbles remain as they are in the upper wall 10a of the upper chamber 12. It will move upward as it is along the gradient of.

On the other hand, relatively small bubbles ride on the fuel flow and descend in the upper chamber 12,
These will be separated from the fuel by the bubble separation membrane 15, and a large number of small bubbles will gather on the separation membrane, gradually becoming large bubbles and moving upward.

That is, according to the present invention, only the fuel from which bubbles have been removed by the bubble separation action of the bubble separation membrane 15 provided in the bubble discharge device 1 passes through the lower chamber 13 and the fuel outlet pipe 15 and injects fuel. It will be supplied to the pump 4.

On the other hand, as described above, the communication passage 19 that opens to the return passage 16 is provided above the upper chamber 12, and further inside the return passage 16 in the vicinity of this communication passage opening, more specifically, than the opening. A venturi portion 20 having a small passage cross-sectional area is provided slightly upstream, so that the flow velocity of the return fuel from the fuel injection pump 4 and the like is increased when passing through the venturi portion 20, and Negative pressure is generated on the downstream side of.

As a result, the air accumulated in the upper wall 10a of the upper chamber 12 through the communication passage 19 is sucked out to the return passage 16 side by this negative pressure, and the return fuel entrapped in bubbles thereafter. The fuel is discharged from the return outlet pipe 18 to the fuel tank 2 through the return passage 8 (FIG. 1). In this embodiment, the orifice 21 is provided in the communication passage 19, but this is not the case.
It is provided in order to prevent excessive fuel outflow from the upper chamber 12 side for the purpose of adjusting the flow rate of bubbles and fuel passing through 9, and its size is adjusted according to the required fuel supply amount and the capacity of the device. It is something.

As described above, according to the present embodiment, the bubble discharging device having an extremely simple structure as shown in the figure is provided in the conventional fuel supply system, so that the fuel filter 3 can be installed without any significant change in layout. It becomes possible to eliminate air bubbles in the fuel.

By the way, in the above-mentioned embodiment, the bubble discharging device 1 is provided between the fuel filter 3 and the fuel injection pump 4, but the device itself is incorporated in the fuel filter 3 and the fuel injection pump 4 itself. Is also possible. Figure 3
Is a device in which the device is integrated with the fuel outlet side of the fuel filter 30, and is intended to make the entire fuel supply system compact.

According to this embodiment, as shown in the figure, the upper casing 31 constituting the above-mentioned bubble discharging device is integrated with the diaphragm cover 33 of the manual pump 32 provided in the fuel filter 30, while the lower casing is formed. 34 is integrated with the filter cap 35, and like the previous embodiment,
A return passage 16 'having a venturi portion is provided in the upper casing 31, and a bubble separation membrane 15' is provided below the return passage 16 '.

Regarding the other constituent elements, 36 is a filter element, 37 is a filter case, and 38 is a diaphragm. The solid arrow indicates the fuel flow direction, and the dotted arrow indicates the bubble flow direction. Since it is the same as the previous embodiment, its explanation is omitted here.

FIG. 4 shows an embodiment in which the bubble discharging device is conversely integrated with the fuel inlet portion of the fuel injection pump, and like the embodiment of FIG. 3, the overall supply system is made compact. However, the structure is such that, as shown in the figure, the upper casing 41 of the device is attached to the inlet of the fuel injection pump 40, and the lower casing 42 is integrated with the pump body 43. The separation membrane 15 ″ is arranged (the operation is similar to that of the previous embodiment, and therefore omitted).

In common with each of the above-mentioned embodiments, the upper wall of the upper chamber is provided with a slope toward the communicating portion with the return passage. ), It is provided with the intention that the air bubbles are surely discharged to the return passage.

Further, according to the present invention, since the fuel filter is always provided on the upstream side of the bubble separation membrane in common with each of the embodiments, the fuel is cleaned by the filter and therefore the bubble separation membrane. Even if the filter is provided, clogging due to impurities is unlikely to occur, and since the downstream side of the filter has a negative pressure due to the suction action of the feed pump, the bubbles are relatively large and can be easily removed by the separation membrane.

[0031]

As described above, according to the present invention, the air in the fuel supplied from the fuel filter can be separated from the fuel by the bubble separation membrane provided in the bubble discharging device. The generated air (bubbles) flows into the return passage from the upper part of the space formed above due to the negative pressure generated in the venturi portion, and is returned to the fuel tank, so that the bubbled fuel flows into the fuel injection pump. Can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a fuel supply system of a diesel engine incorporating a bubble discharging device according to a first embodiment of the present invention.

2 is a vertical cross-sectional view of the bubble discharging device of FIG.

FIG. 3 is a filter cross-sectional view showing a second embodiment of the present invention, in which a bubble discharging device and a fuel filter are integrated.

FIG. 4 is a view showing a third embodiment of the present invention and showing a partial cross section of a pump in which a bubble discharging device and a fuel injection pump are integrated.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Bubble discharge device 2 ... Fuel tank 3 ... Fuel filter 4 ... Fuel injection pump 5 ... Fuel injection nozzle 9, 16 ... Return passage 12 ... Upper chamber (space) 15, 15 ', 15 "... Bubble separation membrane 19 ... Connection Passage 20 ... Venturi section

Claims (1)

[Claims] 1. A diesel engine in which a fuel filter and a fuel injection pump are sequentially arranged in a fuel supply system from a fuel tank to a fuel injection nozzle, and excess fuel from the fuel injection nozzle or the fuel injection pump is returned to the fuel tank. A device for removing bubbles from fuel supplied to an engine, comprising a bubble separation membrane provided between a fuel filter and a fuel injection pump to capture bubbles in the fuel, and a space formed above the bubble separation membrane. A bubble discharging device having a return passage having a venturi portion therein for passing the surplus fuel, and a communication passage communicating the space and the venturi portion.