JP2007198133A - Fuel supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel supply device capable of improving cold startability of a diesel engine. <P>SOLUTION: The fuel supply device which supplies fuel to a diesel engine E, comprises a fuel tank 1 for storing fuel, a pump 2 for pressurizing and supplying the fuel flowing from the fuel tank 1 to the diesel engine E, a fuel filter 3 arranged in a fuel flow passage 5 from the fuel tank 1 to the pump 2, a pump filter 4 provided to a flow inlet to the pump 2 in the fuel flow passage 5 and a heater 10 for a pump filter for heating the pump filter 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel supply device that supplies fuel to a diesel engine, and more particularly to a fuel supply device that facilitates starting of a diesel engine in a low temperature environment.

  Diesel engine fuel oil contains about 18% normal paraffin, and heavier normal paraffin crystallizes in low temperature environments such as winter and cold regions, and wax (solid paraffin) is produced. It may precipitate. The precipitated wax may block a fuel filter or the like installed in a fuel supply device that supplies fuel to the engine, obstructing fuel supply to the engine, and hindering normal operation of the engine. Therefore, conventionally, a countermeasure has been taken such as adding an additive for suppressing the crystal size of the precipitated wax.

  As an index of low-temperature fluidity by light oil wax, it is standardized by the light oil plugging point test method (CFPP) defined in JIS-K2288. This CFPP standard value correlates with the crystal size of the precipitated wax, and is determined so that the diesel engine can be operated without any problem.

  On the other hand, various measures on the vehicle side have been proposed (see, for example, Patent Documents 1 and 2). In the fuel supply device described in Patent Document 1, when there is a possibility of wax precipitation due to a low fuel temperature, surplus fuel from a pump for pressurizing fuel and an injection nozzle of an engine to which fuel is supplied from the pump Is provided on the upstream side of the fuel filter. Thereby, immediately after the engine is started, fuel that has passed through the pump and the injection nozzle and has reached a high temperature is supplied to the upstream side of the fuel filter, so that the fuel filter can be prevented from being blocked by wax.

  Further, the cold region countermeasures of the diesel engine described in Patent Document 2 are based on the fact that in the diesel engine equipped with the common rail fuel injection system, the fuel in the common rail is caused by the tubular shape of the conventional common rail. In view of freezing, in order to solve this, a fuel heater for heating the fuel in the common rail is provided to prevent freezing and improve the low-temperature startability of the engine.

Japanese Utility Model Publication No. 58-136662 JP-A-8-338339

  In recent years, in order to satisfy exhaust gas regulations, diesel vehicles have been developed with ultra-high pressure fuel injection systems such as the above-described common rail fuel injection system that can be atomized by injecting fuel at high pressure to achieve a state close to complete combustion. Has been adopted. Along with this, the pump for pressurizing the fuel needs to be highly accurate compared to the conventional pump, and the pump filter installed at the fuel inlet to the pump has a smaller opening than the conventional one. Yes.

  Also, due to the increased number of parts in the engine room due to higher performance of the engine and for the cooling of the fuel temperature in summer, it has been conventionally arranged in the engine room ER as shown in FIG. 4 (a). An increasing number of vehicles have a fuel filter 3 (a filter disposed between the fuel tank 1 and the pump 2) out of the engine room ER as shown in FIG. 4B. In the figure, reference numeral 5 indicates a fuel flow path from the fuel tank 1 to the pump 2, reference numeral 6 indicates a return line for returning surplus fuel from the injection nozzles of the pump 2 and the engine 4 to the fuel tank, and reference E Indicates a diesel engine.

  Here, as shown in FIG. 4B, the line length L from the fuel filter 3 to the pump filter becomes longer and the opening is small as the fuel filter 3 is arranged outside the engine room ER. Concerned with the use of the pump filter, the wax deposited on the fuel between the fuel filter and the pump filter clogs the pump filter when starting the diesel engine in a low-temperature environment, and the required fuel flow rate cannot be secured. Is done.

  Due to such changes on the vehicle side, it may be difficult to satisfy the low temperature startability of the diesel engine only with the CFPP standard. In order to solve the above-mentioned problems by reforming the fuel, it is conceivable to further refine the crystal size of the precipitated wax, but further refinement may be difficult with the current additives. In addition, it is conceivable to reduce the content of heavy normal paraffin by reducing the light oil, but according to this, the yield of light oil is reduced, resulting in poor economic efficiency. Therefore, measures on the vehicle side are indispensable.

  In view of the circumstances described above, an object of the present invention is to provide a fuel supply device that can improve the low-temperature startability of a diesel engine.

  The above object is achieved by the fuel supply device according to the present invention described in (1) and (2) below.

  (1) A fuel supply device that supplies fuel to a diesel engine, a fuel tank that stores fuel, a pump that pressurizes fuel flowing from the fuel tank and supplies the fuel to the diesel engine, and the fuel tank from the fuel tank A pump filter heater for heating the pump filter, comprising: a fuel filter disposed in a fuel flow path to the pump; and a pump filter provided at an inlet of the fuel flow path to the pump. A fuel supply device provided.

  (2) A fuel supply device for supplying fuel to a diesel engine, a fuel tank for storing fuel, a pump for pressurizing and supplying fuel flowing from the fuel tank to the diesel engine, and A fuel filter disposed in a fuel flow path to the pump, and a pump filter provided at an inlet of the fuel flow path to the pump, the pump filter being closed, and thereby in the pump A fuel supply apparatus comprising a bypass circuit that bypasses the pump filter and allows fuel to flow into the pump when negative pressure occurs.

  According to the fuel supply device having the above configuration (1), when wax precipitated on the fuel between the fuel filter and the pump filter is trapped by the pump filter in a low temperature environment, the pump filter heater causes the wax to be removed. And the pump filter can be prevented from being blocked, and the required fuel flow rate can be ensured.

  Further, according to the fuel supply device having the configuration of (2) above, when the wax deposited on the fuel between the fuel filter and the pump filter is captured by the pump filter in a low temperature environment, the pump filter is thereby blocked. In addition, it is possible to sense the negative pressure generated in the pump and flow the fuel into the pump via a bypass to ensure a necessary fuel flow rate.

  As described above, according to the present invention, the low-temperature startability of the diesel engine can be improved. In the future, it is possible to cope with further increase in the pressure of the fuel injection system and further narrowing of the opening of the pump filter, preventing excessive negative pressure in the pump when the pump filter is closed and damaging the pump. Can be protected from. Further, since the fuel flow rate can be secured, the fuel control such as the fuel injection amount can be accurately performed and the optimum combustion state can be maintained, which contributes to the suppression of harmful components in the exhaust gas.

  Hereinafter, a preferred embodiment of a fuel supply apparatus according to the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic diagram showing a schematic configuration of a first embodiment of a fuel supply apparatus according to the present invention.

  As shown in FIG. 1, the fuel supply device of this embodiment is a fuel supply device that supplies fuel to a diesel engine E, and pressurizes a fuel tank 1 that stores fuel and a fuel that flows from the fuel tank 1. Pump 2 supplied to diesel engine E, fuel filter 3 disposed in fuel flow path 5 from fuel tank 1 to pump 2, and pump filter provided at the inlet of fuel flow path 5 to pump 2 4 is provided. In the figure, a thick solid line arrow indicates the flow of fuel, and a thin solid line arrow indicates a signal path of a pump filter heater control system, which will be described later.

  The precipitated wax that causes the pump filter 4 to be clogged in a low temperature environment is a wax that is precipitated mainly in a portion of the fuel flow path 5 between the fuel filter 3 and the pump filter 4. This is because in recent diesel vehicles as described above, the fuel filter 3 is disposed outside the engine room, and the portion between the fuel filter 3 and the pump filter 4 is exposed to the outside air and has a temperature higher than that of the fuel in the fuel tank 1. This is because the crystal size of the precipitated wax in this portion tends to increase. However, the amount of wax precipitated in the portion is small in quantity, and therefore, in this embodiment, the pump filter 4 is prevented from being blocked by being heated and dissolved when the engine is started.

  The pump filter 4 has a substantially cylindrical shape with a bottom, and its peripheral wall is a mesh with a small mesh. The opening is generally about 150 μm. The fuel flows into the inside of the pump filter 4 through the fuel flow path 5, and flows from the inside to the outside of the peripheral wall. Therefore, the precipitated wax is trapped inside the pump filter 4. In the present embodiment, a pump filter heater 10 for heating and dissolving the wax trapped inside the pump filter 4 is incorporated inside the pump filter 4.

  Various methods are conceivable for controlling the pump filter heater 10. As an example, the temperature of the fuel immediately before the pump filter 4 in the fuel flow path 5 is measured by a temperature sensor 11 such as a thermocouple or a platinum resistor, and the fuel temperature exceeds a predetermined threshold (for example, 0 The control unit 12 supplies power to the heater 10 when the temperature is lower than the temperature. The heater 10 and the temperature sensor 11 may be integrated. As another example, if the pump filter 4 is blocked and the fuel does not sufficiently flow into the pump 2, a negative pressure is generated in the pump 2, and this negative pressure is a pressure sensor 13 disposed in the pump 2. When the negative pressure exceeds a predetermined threshold value (for example, falls below −30 to −50 kPa), the control unit 12 supplies power to the heater 10. The electric power supplied to the heater 10 is suitably about 10 to 50 W at the current automobile power supply voltage of 12 V. However, if the amount of heat generated by the heater 10 is large, it can contribute to improvement of engine startability.

  The power supply to the pump filter heater 10 is suitably about 5 to 10 minutes after the engine E is started. After that, fuel that hardly contains precipitated wax flows through the fuel filter 3, and there is no possibility that the pump filter 4 is blocked.

  According to the fuel supply device of the present embodiment, when the wax deposited on the fuel between the fuel filter 3 and the pump filter 4 is trapped by the pump filter 4 in a low temperature environment, the pump filter heater 10 The necessary fuel flow rate can be ensured by dissolving the wax and preventing the pump filter 4 from being clogged.

(Second Embodiment)
FIG. 2 is a schematic diagram showing a schematic configuration of a second embodiment of the fuel supply apparatus according to the present invention, and FIG. 3 is a schematic diagram showing a schematic configuration of a modification of the fuel supply apparatus shown in FIG. In addition, the same code | symbol is attached | subjected to the part which is common in the fuel supply apparatus of 1st Embodiment mentioned above, and description is abbreviate | omitted or simplified.

  As shown in FIG. 2, the fuel supply device of the present embodiment is a fuel supply device that supplies fuel to a diesel engine E, and pressurizes fuel tank 1 that stores fuel and fuel that flows from the fuel tank 1. Pump 2 supplied to diesel engine E, fuel filter 3 disposed in fuel flow path 5 from fuel tank 1 to pump 2, and pump filter provided at the inlet of fuel flow path 5 to pump 2 4 is provided. In the fuel supply device of the present embodiment, when the pump filter 4 is closed and the fuel does not sufficiently flow into the pump 2 and a negative pressure is generated in the pump 2, the fuel is bypassed by the pump filter 4 and fuel is supplied. A bypass 14 is provided to flow into the pump 2. In the figure, a thick solid line arrow indicates a fuel flow, and a thin solid line arrow indicates a signal path of a control system for switching the fuel flow path to the detour 14.

  The bypass 14 branches from the fuel flow path 5 via an electromagnetic valve 15 disposed on the upstream side of the pump filter 4 in the fuel flow path 5 and is directly connected to the pump 2. The switching of the fuel flow path to the detour 14 is performed as follows, for example. When the pressure sensor 13 detects a pressure drop in the pump 2 that occurs when the pump filter 4 is closed (at about -90 kPa when fully closed), the pressure reaches a predetermined value (for example, about -30 to 50 kPa). The controller 16 drives the electromagnetic valve 15 to open toward the bypass 14.

  According to the fuel supply device of the present embodiment, when the wax deposited on the fuel between the fuel filter 3 and the pump filter 4 is captured by the pump filter 4 in a low temperature environment, the pump filter 4 is thereby blocked. The negative pressure generated in the pump 2 can be sensed and the fuel can be flowed into the pump 2 via the bypass 14 to ensure the required fuel flow rate.

  As shown in FIG. 3, a valve 17 that operates mechanically using a spring or a bimetal may be used instead of the electromagnetic valve 15. In the fuel supply apparatus shown in FIG. 3, the bypass 14 branches directly from the upstream side of the pump filter 4 in the fuel flow path 5 and is connected to the pump 2 via the valve 17. When a spring is used for the valve 17, the spring is deformed due to the pressure difference between the pressure in the pump 2 and the pressure in the bypass 14, and the valve opens and closes, and opens when a negative pressure is generated in the pump 2. To do. Further, when a bimetal is used for the valve 17, the bimetal is deformed as the temperature of the fuel changes, so that the valve opens and closes and opens at a low temperature.

  In addition, when the detour 14 is provided, the entry of foreign matter into the pump 2 is not considered, but the use of the detour 14 dissolves the wax trapped in the pump filter by the engine heat after the diesel engine is started. In addition, since a fuel filter (mesh size of about 5 to 20 μm) is disposed on the upstream side of the pump filter 4, there is no particular problem.

  As described above, according to the present invention, the low-temperature startability of the diesel engine can be improved. In the future, the pressure of the fuel injection system will increase and the opening of the pump filter will become even finer. This will prevent excessive negative pressure in the pump that occurs when the pump filter is closed and prevent damage to the pump. I can protect it. Further, since the fuel flow rate can be secured, the fuel control such as the fuel injection amount can be accurately performed and the optimum combustion state can be maintained, which contributes to the suppression of harmful components in the exhaust gas.

It is a mimetic diagram showing a schematic structure of a 1st embodiment of a fuel supply device concerning the present invention. It is a schematic diagram which shows schematic structure of 2nd Embodiment of the fuel supply apparatus which concerns on this invention. It is a schematic diagram which shows schematic structure of the modification of the fuel supply apparatus shown in FIG. (A) And (b) is a schematic diagram which shows schematic structure of a diesel vehicle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel tank 2 Pump 3 Fuel filter 4 Pump filter 5 Fuel flow path 10 Pump filter heater 14 Detour E diesel engine

Claims (2)

A fuel supply device for supplying fuel to a diesel engine,
A fuel tank for storing fuel;
A pump that pressurizes fuel flowing from the fuel tank and supplies the pressurized fuel to the diesel engine;
A fuel filter disposed in a fuel flow path from the fuel tank to the pump;
A pump filter provided at an inlet of the fuel flow path to the pump;
With
A fuel supply apparatus comprising a pump filter heater for heating the pump filter. A fuel supply device for supplying fuel to a diesel engine,
A fuel tank for storing fuel;
A pump that pressurizes fuel flowing from the fuel tank and supplies the pressurized fuel to the diesel engine;
A fuel filter disposed in a fuel flow path from the fuel tank to the pump;
A pump filter provided at an inlet of the fuel flow path to the pump;
With
A fuel supply device comprising a bypass circuit that bypasses the pump filter and allows fuel to flow into the pump when the pump filter is closed and thereby a negative pressure is generated in the pump. .

Images