JP2014066203A - Fuel supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel supply system for supplying fuel to a common rail type engine, in which automatic bleeding can be well performed when starting the engine after running out of fuel, and the starting of the engine be well performed.SOLUTION: The fuel supply system includes a feed pump 9 to be driven by a common rail type engine E for supplying fuel from a fuel tank T to the engine E. A fuel filter 8 is provided upstream from the feed pump 9, and a bleeding circuit 18 for removing air is communicated with the middle of a fuel flowing passage 17 which causes the fuel to flow from the fuel filter 8 to the feed pump 9.

Description

  The present invention relates to a fuel supply system employed in, for example, a vehicle construction machine such as a backhoe or a traveling agricultural machine such as a tractor.

In a vehicle equipped with a diesel engine, when the engine is stalled after the remaining fuel in the fuel tank runs out and the engine is refueled, the air in the fuel supply path between the fuel tank and the engine is started. Otherwise, the engine will not start because the fuel will not flow to the engine.
If the manual pump is used to remove air from the fuel supply passage after the fuel has run out, it takes time and labor.

Therefore, there is a fuel supply system described in Patent Document 1 as a fuel supply system provided with an air vent circuit for automatically venting air in the fuel supply path when the engine is started after the fuel has run out.
The fuel supply system of Patent Document 1 includes a feed pump driven by a fuel injection pump of an engine, and a fuel filter provided in the middle of a fuel supply line from the feed pump to the fuel injection pump. One end of an air vent circuit is connected to the filter, and the other end of the air vent circuit is communicated with the air chamber of the fuel tank. The feed pump is connected to the fuel tank by a fuel supply pipe.

In this Patent Document 1, after running out of fuel, when fuel is replenished and the cell motor is rotated and cranked, the feed pump is driven, and the fuel is sucked from the fuel tank by the feed pump, and is sucked and pumped. It is described that air is discharged from the air vent circuit by the fuel to be discharged.
Moreover, there exists a fuel supply system of patent document 2 as a fuel supply system provided with the air bleeding circuit.

  In the fuel supply system of Patent Document 2, a fuel filter is provided in the middle of a fuel supply line between a fuel tank and a feed pump, and one end of an air bleeding circuit is connected to the fuel filter. The end side communicates with the air chamber of the fuel tank.

Japanese Utility Model Publication No.7-10055 Japanese Utility Model Publication No. 3-46218

In the fuel supply system described in Patent Document 1, the air vent circuit is always open, so that the pressure is released from the air vent circuit, and the fuel supply pressure for sending fuel from the feed pump to the engine. Decreases.
On the other hand, in a fuel supply system that supplies fuel to a common rail engine, a high fuel supply pressure is required. However, in the fuel supply system described in Patent Document 1, a fuel pump from a feed pump to a fuel injection pump is required. Since the fuel supply line is long and the fuel filter becomes a resistance, the pressure to send the fuel to the engine is not sufficient as it is. Therefore, it is necessary to provide a cock in the air vent circuit, and to close the cock in order to increase the fuel supply pressure after the air has escaped. Therefore, in this case, when releasing air, the cock must be opened, and when the air is exhausted, the cock must be closed, which causes a problem that the opening / closing operation of the cock is troublesome.

In addition, the fuel supply system described in Patent Document 2 is configured such that a fuel filter is disposed on the upstream side of the feed pump and air is vented from the fuel filter. However, the fuel supply system supplies fuel to the common rail engine. As a result of testing, it was found that if the air was vented from the fuel filter, the air could not escape well, and therefore the engine would not start easily and the cell motor had to be rotated for a long time.

  Accordingly, in view of the above-described problems, the present invention provides a fuel supply system that can automatically and satisfactorily perform air bleeding when starting an engine after running out of fuel, and can perform engine starting satisfactorily. Is an issue.

The technical means taken by the present invention to solve the technical problems are characterized by the following points.
The invention according to claim 1 includes a feed pump that is driven by a common rail engine and supplies the fuel in the fuel tank to the engine. A fuel filter is provided on the upstream side of the feed pump. An air vent circuit for allowing air to escape is communicated in the middle of the fuel flow passage through which the fuel flows.

The invention according to claim 2 is characterized in that the fuel filter is arranged at a position higher than the feed pump.
The invention according to claim 3 is characterized in that the opening area of the fuel flow passage is formed on the downstream side of the communicating portion of the air bleeding circuit.
The invention according to claim 4 is characterized in that a fuel feed pump comprising an electromagnetic pump that is driven by turning on an ignition key switch and sends fuel in the fuel tank to the feed pump is provided upstream of the fuel filter.

  The invention according to claim 5 is characterized in that a fuel cooler is provided upstream of the fuel filter, and a recirculation valve that closes at a predetermined temperature or higher and opens at a temperature lower than the predetermined temperature is provided in parallel with the fuel cooler. To do.

The present invention has the following effects.
According to the first aspect of the present invention, the fuel filter is disposed on the upstream side of the feed pump, and the air vent circuit is communicated in the middle of the fuel flow path through which the fuel flows from the fuel filter to the feed pump. When the engine is started after being cut, the fuel supply passage for supplying the fuel from the fuel tank to the engine can be automatically vented, so that the fuel can be circulated well to the feed pump. By arranging the fuel filter on the upstream side of the feed pump, the fuel supply line from the feed pump to the engine is shortened, so that the fuel supply pressure can be secured without closing the air venting circuit. The engine can be started well.

By connecting the air vent circuit in the middle of the fuel flow passage for flowing the fuel from the fuel filter to the feed pump as described above, the fuel supply passage for supplying fuel from the fuel tank to the engine can be well vented. Confirmed by testing.
According to the invention of claim 2, by disposing the fuel filter at a position higher than the feed pump, the fuel sent to the fuel filter is smoothly sent to the feed pump by natural fall.

According to the third aspect of the present invention, the inflow of air into the engine can be reduced by expanding the opening area of the fuel flow passage on the downstream side of the communicating portion of the air bleeding circuit and reducing the fuel flow velocity. Further, it is possible to prevent the engine stall or the engine rotation drop caused by the air biting after the engine is started.
According to the fourth aspect of the present invention, the fuel can be sent while automatically bleeding the air to the feed pump by turning on the ignition key switch. Therefore, before the ignition key switch is set to the engine start position, the feed pump Fuel can be sent and the engine can be started well.

  According to the fifth aspect of the present invention, it is possible to prevent the fuel cooler from being overcooled, thereby preventing the fuel filter from being clogged due to fuel wax precipitation.

It is a systematic diagram of a fuel supply system. It is detail drawing of the principal part.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The fuel supply system of the engine E shown in FIG. 1 shows a fuel supply system of a diesel engine E (common rail engine) equipped with a common rail fuel injection system CRS. For example, a vehicle system construction machine such as a backhoe, a tractor, etc. Adopted for traveling farm machines.
The common rail fuel injection system CRS includes a fuel pump 1 (supply pump) that generates high-pressure fuel from the fuel that is mechanically driven by the crankshaft of the engine E and is sent to the engine E. A rail 2 (accumulation chamber) that stores fuel that has been pressurized by the pump 1 is provided, and the high-pressure fuel stored in the rail 2 is timed from the injector 3 to each cylinder of the engine E under ECU control. It is a system that injects well.

  A fuel supply passage 4 for supplying fuel from the fuel tank T to the engine E is provided with a fuel segmenter 5, a check valve 6 (referred to as a first check valve), a fuel cooler 7, a fuel filter 8, from the upstream side. A feed pump 9 is provided in order, a fuel feed pump 10 is provided in parallel with the first check valve 6, and a recirculation valve 11 (this is referred to as a first recirculation valve) in parallel with the fuel cooler 7. Is provided.

The fuel segmenter 5 separates and stores moisture from the passing fuel and has a filter function.
The first check valve 6 is provided so as to prevent fuel backflow from the engine E side to the fuel tank T side.
The fuel feed pump 10 is composed of an electromagnetic pump, and is energized by turning on an ignition key switch 12 (from an off position where the ignition key is inserted / removed to an on position where the ignition system of the engine E is energized). And the fuel in the fuel tank T is sent to the engine E side.

In the fuel feed pump 10, the ignition key switch 12 is set to the engine start position where the starter is energized (while the cell motor is turned and cranked), and the engine E is in the operating state (the ignition key switch 12). Is in the ON position and the engine E is continuously rotating).
The fuel cooler 7 cools the passing fuel.

The first recirculation valve 11 allows fuel to flow to the engine E side without passing through the fuel cooler 7 at a low temperature (cold region).
That is, the diesel fuel contains paraffin having a relatively high melting point, and if the fuel is cooled too much by the fuel cooler 7, wax (paraffin crystals) precipitates, and this wax clogs the fuel filter 8. Causing the engine E to stop. Therefore, when the temperature is low and the fuel temperature is lower than the predetermined temperature, the first recirculation valve 11 is opened, so that the fuel is not passed through the fuel cooler 7 (through the first recirculation valve 11), and the fuel is moved to the engine E side. Shed. This prevents overcooling of the fuel and prevents wax precipitation.

Further, when the fuel temperature is equal to or higher than a predetermined temperature (high temperature or the like), the first recirculation valve 11 is closed so that the fuel is cooled by the fuel cooler 7 and flows to the engine E side.
The first recirculation valve 11 may be configured to open and close by manual operation. However, in order to prevent forgetting to switch, the first recirculation valve 11 opens at a temperature lower than a predetermined temperature and closes at a temperature higher than a predetermined temperature. It is good to comprise by the on-off valve (For example, the on-off valve which opens and closes a valve body by expansion / contraction of the temperature-sensitive actuator made to advance / retreat a piston by a thermo element).

The fuel filter 8 is located on the upstream side of the feed pump 9 in the fuel supply direction A, removes particles mixed in the passing fuel, and flows the fuel to the feed pump 9 (engine E side). It is arranged at a position higher than the pump 9.
The feed pump 9 is a pump that is mechanically driven by the crankshaft of the engine E, and sucks the fuel in the fuel tank T and sends it to the engine E (supply pump 1).

The feed pump 9 is attached and fixed to the crankcase of the engine E or incorporated in the crankcase.
The fuel supply system of the engine E is provided with a fuel return path 13 for returning surplus fuel from the supply pump 1 of the common rail fuel injection system CRS and surplus fuel from the injector 3 to the fuel tank T. A check valve 14 (this is referred to as a second check valve) is provided in the fuel return path 13 so as to prevent a back flow from the fuel tank T side to the engine E side.

Further, a fuel circulation passage 15 is branched from the upstream side of the second check valve 14 of the fuel return passage 13. A branch end of the fuel circulation channel 15 is connected to the fuel supply channel 4 on the upstream side of the fuel segmenter 5. The fuel circulation channel 15 is provided with a circulation valve 16 (this is referred to as a second circulation valve).
The second recirculation valve 16 is constituted by a temperature-sensing automatic on-off valve, and opens when the temperature of the fuel flowing through the fuel supply path 4 is lower than a predetermined temperature, and surplus fuel in the supply pump 1 and the injector 3 A part of the surplus fuel is caused to flow into the fuel supply path 4 and is closed when the temperature of the fuel flowing through the fuel supply path 4 is higher than a predetermined temperature, thereby preventing the temperature of the fuel flowing through the fuel supply path 4 from rising. .

In the fuel supply system of the engine E, one end side is communicated (connected) in the middle of the fuel flow path 17 from the fuel filter 8 to the feed pump 9, and an air vent circuit 18 for releasing the air in the fuel supply path 4 is provided. Is provided.
The other end side of the air vent circuit 18 communicates with the air chamber 19 of the fuel tank T. In the present embodiment, the other end side of the air vent circuit 18 is connected to the fuel return path 13 on the downstream side of the second check valve 14.

The air vent circuit 18 is provided with a check valve 20 (referred to as a third check valve) so as to prevent the backflow of air from the fuel tank T side to the engine E side.
As shown in FIG. 2, an intermediate block 21 is provided between the fuel filter 8 and the feed pump 9. The intermediate block 21 is provided at a position higher than the feed pump 9 (the fuel inlet side port 9a of the feed pump 9).

The intermediate block 21 may be provided at a position substantially the same height as the fuel outlet side port 8 a of the fuel filter 8 or a position lower than the fuel outlet side port 8 a of the fuel filter 8.
The fuel flow path 17 from the fuel filter 8 to the feed pump 9 includes a first flow path 22 between the fuel filter 8 and the intermediate block 21, a second flow path 23 formed in the intermediate block 21, and an intermediate block. 21 and a third flow path 24 between the feed pump 9.

The upstream side of the first flow path 22 communicates with the fuel outlet side port 8 a of the fuel filter 8, and the downstream side communicates with the upstream side port 23 a of the second flow path 23. The upstream side of the third flow path 24 communicates with the downstream port 23 b of the second flow path 23, and the downstream side of the third flow path 24 communicates with the fuel inlet side port 9 a of the feed pump 9.
The first flow path 22 is located at the same height level as the intermediate block 21 (second flow path 23), and the third flow path 24 is inclined so as to move downward toward the feed pump 9.

The opening area of the second flow path 23 is expanded in the middle of the fuel supply direction A as it goes downstream in the fuel supply direction A, and the opening area of the upstream port 23a of the second flow path 23 is The opening area of the downstream port 23b of the two flow paths 23 is formed large.
The opening area of the first flow path 22 (the inner diameter of a fuel supply pipe such as a hose or metal pipe constituting the first flow path 22) is an opening area corresponding to the opening area of the upstream port 23a of the second flow path 23. The opening area of the third flow path 24 (the inner diameter of the fuel supply pipe such as a hose and metal pipe constituting the third flow path 24) is the opening area corresponding to the opening area of the downstream port 23b of the second flow path 23. Has been.

In the present embodiment, the inner diameter of the fuel supply pipe constituting the first flow path 22 is φ8 mm, whereas the inner diameter of the fuel supply pipe constituting the third flow path 24 is φ11 mm. Note that the present invention is not limited to this.
In the intermediate block 21, a communication path 25 that constitutes a part of the air vent circuit 18 is formed by branching upward from the middle part of the second flow path 23. One end of the main flow path 26 of the air bleeding circuit 18 communicates with an end port on the branch end side of the communication path 25.

The other end of the main flow path 26 of the air vent circuit 18 is connected to the fuel return path 13, and the third check valve 20 is provided in the main flow path 26.
In the present embodiment, the opening area of the air vent circuit 18 (the communication path 25 and the main flow path 26) is formed to be substantially the same as the opening area of the second flow path 23.
In the fuel supply system having the above-described configuration, when the engine E is started by refueling after the remaining amount of fuel in the fuel tank T runs out and the engine stalls, the ignition key switch 12 is turned on. The fuel feed pump 10 is energized to drive the fuel feed pump 10. When the fuel feed pump 10 is driven, the fuel in the fuel tank T is sucked by the fuel feed pump 10 and sent to the feed pump 9. With this sent fuel, the air in the fuel supply path 4 is discharged through the air vent circuit 18 and the air in the fuel supply path 4 is automatically vented. Therefore, the fuel can be sent to the feed pump 9 before the ignition key switch 12 is set to the engine start position, and the engine E can be started well.

  By the way, if the air is vented from the fuel filter 8 in order to vent the air, the air does not escape well. Therefore, the engine E is difficult to start and the cell motor must be rotated for a long time. By venting air from the middle of the fuel flow passage 17 through which fuel flows to the feed pump 9, air is discharged well. This is evident as a result of testing.

Further, since the fuel filter 8 is located at a position higher than the feed pump 9, the fuel that has circulated to the communicating portion of the air bleeding circuit 18 easily flows to the feed pump 9 at a low position.
The feed pump 9 is driven by cranking with the ignition key switch 12 set to the engine start position, and pumps the fuel that has flowed to the feed pump 9 to the supply pump 1. 9, the fuel supply line from the feed pump 9 to the supply pump 1 is short, so that the fuel supply pressure can be secured without closing the air vent circuit 18, and the engine E can be started well.

After the engine E is started, the fuel in the fuel tank T is sucked by the feed pump 9 and pumped to the supply pump 1, and the fuel feed pump 10 is driven, but contributes much to the fuel supply. Instead, the fuel flows through both the first check valve 6 and the fuel feed pump 10 to the fuel cooler 7 side.
On the other hand, when the opening area of the fuel flow path from the fuel filter 8 to the feed pump 9 is uniformly formed from one end to the other end, a part of the air flows to the feed pump 9 together with the flow of fuel. However, in this embodiment, the opening area of the fuel flow passage 17 is set on the downstream side of the communication portion of the air vent circuit 18. By expanding and lowering the flow rate of fuel, it is possible to reduce the entry of air into the engine E, and it is possible to prevent the engine stall or the engine rotation drop caused by the air biting after the engine E starts.

In addition to the fact that the opening area of the fuel flow passage 17 is expanded on the downstream side of the communicating portion of the air vent circuit 18, the fuel filter 8 is positioned higher than the feed pump 9, so that the air The amount of fuel flowing to the feed pump 9 can be reduced.
Further, the third check valve 20 can prevent the reverse flow of air suction through the air vent circuit 18 when the fuel is flowing through the fuel supply path 4 (fuel flow path 17).

  When starting the engine E, the ignition key switch 12 may be set to the on position, and then the engine start position may be set with a slight time lag. May be.

7 Fuel cooler 8 Fuel filter 9 Feed pump 10 Fuel feed pump 11 Circulation valve 12 Ignition key switch 17 Fuel flow passage 18 Air vent circuit 19 Air chamber E Engine T Fuel tank

Claims (5)

  A feed pump (9) that is driven by a common rail engine (E) and supplies fuel in the fuel tank (T) to the engine (E) is provided. A fuel filter (8) is provided upstream of the feed pump (9). A fuel supply system characterized in that an air vent circuit (18) for allowing air to escape is communicated in the middle of a fuel flow passage (17) through which fuel flows from the fuel filter (8) to the feed pump (9). .   The fuel supply system according to claim 1, characterized in that the fuel filter (8) is arranged at a higher position than the feed pump (9).   The fuel supply system according to claim 1 or 2, wherein an opening area of the fuel flow passage (17) is formed on the downstream side of the communicating portion of the air bleeding circuit (18).   Provided on the upstream side of the fuel filter (8) is a fuel feed pump (10) comprising an electromagnetic pump that is driven by turning on the ignition key switch (12) and sends the fuel in the fuel tank (T) to the feed pump (9) side. The fuel supply system according to any one of claims 1 to 3, wherein the fuel supply system is provided.   A fuel cooler (7) is provided upstream of the fuel filter (8), and a recirculation valve (11) that closes at a predetermined temperature or higher and opens at a temperature lower than the predetermined temperature is provided in parallel with the fuel cooler (7). The fuel supply system according to any one of claims 1 to 4.

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