JP2015063935A - Fuel supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize the temperature of fuel supplied to a diesel engine, according to a property of the fuel.SOLUTION: In a fuel supply device 10 for supplying fuel to a diesel engine, a valve 16 is disposed between a jet nozzle 15 and a fuel cooler 18 on a return pipe line P for returning excessive fuel from the jet nozzle 15 to a fuel tank 11. Furthermore, a bypass pipe line P3 for connecting a valve 16 and a fuel filter 12, and a temperature sensor 17 for measuring the temperature of the fuel flowing in the return pipe line P2 are disposed. The valve 16 switches a channel of the excessive fuel flowing from the jet nozzle 15 through the return pipe line P2 when fuel temperature measured by the temperature sensor 17 is within a range of a setting temperature of 60°C-80°C, returns the fuel to the fuel filter 12 through the fuel cooler 18 when the fuel temperature is the setting temperature or more, and returns the fuel to the fuel filter 12 through the bypass pipe line P3 when the fuel temperature is the setting temperature or less.

Description

  The present invention relates to a fuel supply device that supplies fuel to a diesel engine.

  Diesel vehicle fuel supply systems have advanced to a high degree, realizing low fuel consumption and clean exhaust gas through precise control. In such precise control, the soundness of the fuel used is an important matter. 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 such as adding an additive for suppressing the crystal size of the precipitated wax has been taken.

  As an index of low-temperature fluidity by light oil wax, it is standardized by a light oil-clogging point test method (CFPP: Cold Filter Plugging Point) defined in JIS-K2288. This CFPP standard value correlates with the crystal size and is determined so that the diesel engine can be operated without any problem. On the other hand, various countermeasures in the fuel supply apparatus have been proposed.

  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. As a result, 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 upstream of the fuel filter, so that the fuel filter can be prevented from being blocked by wax.

  In Patent Document 2, it is proposed to install a fuel cooler in order to prevent the fuel temperature from becoming excessively high when the fuel is recirculated. According to this document, a return line for returning surplus fuel from the engine to the fuel tank, a fuel cooler provided in the return line, and one side connected to the engine side of the return line from the fuel cooler The other side is provided at a bypass line connected to the fuel tank side of the return line from the fuel cooler, and at a branch position of the return line and the bypass line, depending on the temperature of the fuel There has been proposed an engine fuel cooling device having a first switching valve that switches whether the surplus fuel is supplied to the fuel cooler side or the bypass pipe side.

  Thereby, for example, when the temperature of the fuel becomes relatively high, the first switching valve is switched to the fuel cooler side, and surplus fuel from the engine is guided to the fuel cooler to cool the fuel. On the other hand, when the temperature of the fuel becomes relatively low, it is possible to switch the first switching valve to the bypass line side so that the surplus fuel from the engine is returned to the fuel tank without passing through the fuel cooler. Therefore, it is possible to prevent the occurrence of supercooling when the fuel is at a low temperature, and it is possible to prevent the precipitation of the wax contained in the fuel oil and the occurrence of insufficient fuel supply to the engine due to the supercooling.

  In Patent Document 3, a fuel tank for storing fuel, a supply path for supplying fuel from the fuel tank to the engine, a return path for returning fuel from the engine to the fuel tank, and cooling air from the engine cooling fan are disclosed. Has proposed a fuel supply device including a fuel cooler for cooling the fuel flowing through the reflux path. As a result, surplus fuel that is supplied to the engine from the fuel tank via the supply path and is not used for combustion in the engine flows into the fuel cooler when returned to the fuel tank via the return path, and enters the engine. It is cooled using the provided cooling fan.

  Further, in Patent Document 4, a supply line that supplies fuel from a fuel tank to a fuel injection device of an engine, and a return line that cools surplus fuel from the fuel injection device by a fuel cooler and returns the fuel to the fuel tank. Depending on the temperature of the fuel that passes through the junction, and a bypass path that causes the fuel flowing through the return pipe to flow around the fuel cooler by bypassing the fuel cooler to the downstream junction from the upstream branch of the fuel cooler There has been proposed a fuel supply device for an internal combustion engine provided with a flow path switching means for communicating either the return pipe line or the bypass path with the fuel tank.

  According to this, since the return pipe and the bypass are switched according to the temperature of the fuel passing through the junction, that is, the actual fuel temperature returning to the fuel tank, the fuel temperature in the fuel tank can be controlled more accurately. it can.

Japanese Utility Model Publication No. 58-136662 JP 2004-162538 A JP 2003-278617 A JP 2012-122416 A

In recent years, from the viewpoint of reducing CO ₂ emissions, there is a social demand for the use of biodiesel fuel (BDF), which is a so-called carbon neutral, in which CO ₂ emissions generated by combustion are not counted. BDF contains a fatty acid methyl ester obtained by subjecting a raw oil or fat to chemical treatment such as methyl esterification to remove glycerin from the raw oil or fat.

  However, impurities remain in the fatty acid methyl ester, and triglyceride is known as one of them. The properties of triglycerides depend on the properties of fatty acids. For example, triglycerides composed of stearic acid, which is a saturated fatty acid, are known to have a high melting point of 72 ° C to 75 ° C. Since the operation method described above is not conscious of BDF, it has been possible to prevent wax precipitation by recirculating the conventional fuel. However, in the use of BDF, triglyceride that precipitates more easily than the wax in the conventional method is used as the fuel. There is a concern of clogging with filters.

  Although the above description relates to an example of biodiesel fuel, there is a growing need to make the temperature of fuel supplied to a diesel engine suitable for the nature of the fuel in general.

  The present invention provides a fuel supply device capable of optimizing the temperature of fuel supplied to a diesel engine according to the nature of the fuel.

  The fuel supply device of the present invention is a fuel supply device that supplies fuel to a diesel engine, a fuel tank that stores fuel, a fuel injection unit that injects fuel into a combustion chamber of the diesel engine, and the fuel tank; A fuel supply pipe connected to the fuel injection section to supply fuel from the fuel tank to the fuel injection section, and a fuel disposed on the supply pipe to remove impurities in the fuel supplied from the fuel tank A filter is connected to at least the fuel injection section and the fuel filter, and a return pipe that returns excess fuel from the fuel injection section to the fuel filter is disposed on the return pipe and flows through the return pipe. A fuel cooler that cools the fuel and returns it to the fuel filter, and a flow path switch disposed at a position between the fuel injection unit and the fuel cooler on the return pipe And a bypass pipe that connects the flow path switching unit and the fuel filter, and a temperature sensor that measures the temperature of the fuel flowing through the return pipe, and the flow path switching unit is controlled by the temperature sensor. When the measured fuel temperature is in the range of the set temperature of 60 ° C. to 80 ° C., the flow path of the surplus fuel flowing from the fuel injection section through the return pipe is switched. Then, the fuel is returned to the fuel filter, and when the temperature is equal to or lower than the set temperature, the fuel is returned to the fuel filter via the bypass pipe.

  As an embodiment of the fuel supply device of the present invention, for example, a fuel sensor is further provided that receives the supply of fuel from the flow path switching unit and determines the concentration of biodiesel fuel in the fuel.

  As one embodiment of the fuel supply device of the present invention, for example, when the concentration of biodiesel fuel determined by the fuel sensor is equal to or lower than a predetermined value, the flow path switching unit sets the set temperature range from 60 ° C. to 80 ° C. Set in the range of ℃ to lower temperature.

  The fuel supply device of the present invention is a fuel supply device that supplies fuel to a diesel engine, a fuel tank that stores fuel, a fuel injection unit that injects fuel into a combustion chamber of the diesel engine, and the fuel tank; A fuel supply pipe connected to the fuel injection section to supply fuel from the fuel tank to the fuel injection section, and a fuel disposed on the supply pipe to remove impurities in the fuel supplied from the fuel tank A filter is connected to at least the fuel injection section and the fuel filter, and a return pipe that returns excess fuel from the fuel injection section to the fuel filter is disposed on the return pipe and flows through the return pipe. A fuel cooler that cools the fuel and returns it to the fuel filter, and a flow path switch disposed at a position between the fuel injection unit and the fuel cooler on the return pipe A bypass pipe that connects the flow path switching unit and the fuel filter, a temperature sensor that measures the temperature of the fuel that flows through the return pipe, and fuel supplied from the flow path switching unit. A fuel sensor for determining the concentration of biodiesel fuel in the fuel flow sensor, and the flow path switching unit passes through the return pipe from the fuel injection unit according to the biodiesel fuel concentration determined by the fuel sensor. The set temperature range for switching the flow path of the surplus fuel flowing is changed.

  As one embodiment of the fuel supply device of the present invention, for example, the flow path switching unit raises the set temperature range when the concentration is equal to or higher than a predetermined value, compared to when the concentration is equal to or lower than the predetermined value.

  As one embodiment of the fuel supply apparatus of the present invention, for example, the flow path switching unit sets the range of the set temperature to 60 ° C. to 80 ° C. when the concentration is equal to or higher than a predetermined value.

  According to the present invention, it becomes possible to optimize the temperature of the fuel supplied to the diesel engine according to the properties of the fuel such as biodiesel fuel, improve the performance of the fuel supply device and the diesel engine, and improve the performance over a long period of time. The performance can be stably maintained.

The block diagram which shows the fuel supply apparatus of one Embodiment of this invention. The block diagram which shows the conventional fuel supply apparatus.

  Before describing the embodiments of the present invention, the premise of the present invention will be described.

  In the fuel supply device of a diesel vehicle that performs precise control, the soundness of the fuel used is an important matter. In order to maintain the soundness of the fuel, it is necessary to prevent the thermal deterioration of the fuel and the dissolution and mixing of the fuel filter blockage. The thermal deterioration of the fuel occurs when the fuel temperature rises due to the return fuel from the fuel pump, common rail, and injection nozzle receiving radiant heat from these devices. As countermeasures against thermal deterioration of the fuel, it is conceivable to provide a fuel cooler for cooling the fuel between the fuel pump, the common rail, the injection nozzle and the fuel tank in the conventional apparatus configuration (see Patent Documents 2 and 3). However, when the fuel cooler is simply installed, the fuel is exposed to a low temperature in a low-temperature environment where the wax is precipitated in the fuel, which may further promote the precipitation of wax crystals and cause the fuel filter to be clogged. .

  Filter clogging caused by the precipitation of wax crystals generated by supercooling of the fuel cooler is a trouble that occurs in a low temperature environment. Therefore, as a countermeasure, there is a system in which a bypass line is provided in the return fuel pipe as shown by a dotted line in FIG. 2 and when the return fuel is at a low temperature, the fuel is returned to the fuel tank without using a fuel cooler (Patent Document). 4). This system is intended to prevent a situation in which the fuel is excessively cooled and the wax crystals deposited in the fuel cannot be dissolved. Therefore, for example, in Patent Document 4, the flow path through which the fuel recirculates is switched using a recirculation temperature of 60 ° C. as a kind of threshold temperature. That is, in order to prevent excessive cooling when the fuel temperature is 60 ° C. or lower, the fuel returns to the fuel tank without passing through the fuel cooler, and from the viewpoint of preventing thermal degradation when the fuel temperature is 60 ° C. or higher, Go through the fuel cooler and return to the fuel tank.

  In the conventional fuel, the problem is prevented by setting the reflux condition at the above-described temperature. However, when biodiesel fuel, which has been studied as a light oil alternative fuel for diesel engines in recent years, is used, there is a concern that trouble may occur in the above-described apparatus.

  Biodiesel fuel is a fuel that is being investigated as an alternative to light oil because of increased environmental awareness, such as the prevention of global warming and the establishment of a recycling-oriented society. Biodiesel fuel is produced according to the following steps (1) to (3).

(1) Methanol and catalyst are added to vegetable oils such as rapeseed oil and palm oil, and animal oils to cause transesterification, which is then neutralized by adding acid, and then separated into fatty acid methyl esters and glycerin. .
(2) The separated fatty acid methyl ester is washed with water to remove the catalyst.
(3) Methanol is removed by further distillation.

  Although there is a step of removing impurities in the step of purifying the fatty acid methyl ester, the fats and oils used as raw materials, particularly triglycerides, remain as unreacted substances. Oils and fats such as triglycerides have a very high melting point (for example, tristearin has a melting point of 72 to 75 ° C.), and conventional reflux temperatures do not lead to dissolution of biodiesel fuel impurities (triglycerides) deposited on the fuel filter, There is a concern that the material deposited at the time when the fuel temperature becomes high will dissolve at once and cause troubles in the injection system. As described above, the temperature of the fuel is an important matter for using the latest diesel engine for a long period of time, but has not been sufficiently managed.

  Based on the above-mentioned concerns, the inventor has conducted extensive studies and has provided a new fuel supply device.

  FIG. 1 is a block diagram showing a fuel supply device 10 according to an embodiment of the present invention. The fuel supply device 10 includes a fuel tank 11, a fuel filter 12, a fuel pump 13, a common rail 14, an injection nozzle 15, a valve 16, a temperature sensor 17, a fuel cooler 18, and a fuel sensor 19. . As will be described later, each element is connected via a supply line P1, a return line P2, a bypass line P3, and a fuel discrimination sub line P4.

  The fuel supply device 10 is a device that supplies fuel to the engine, but the device of this embodiment supplies diesel fuel to a so-called diesel engine. The diesel fuel here also includes the biodiesel fuel described above. Biodiesel fuel includes those in which biodiesel fuel of a predetermined concentration or more is blended with general diesel fuel. In the present embodiment, diesel fuel or biodiesel fuel is stored in the fuel tank 11. The configuration, type, etc. of the fuel tank 11 are not particularly limited.

  The fuel filter 12 connected to the fuel tank 11 via the supply pipe line P1 is a filter that removes impurities (impurities) contained in the fuel. In general, when the diesel fuel is exposed to an environment below the wax deposition temperature, the filter is clogged with the wax deposited in the fuel tank 11 or the fuel filter 12, and a problem that the engine does not start occurs. Since the wax is dissolved by the radiant heat of the engine when the engine is started, the engine can be started by adding a low-temperature fluidity improver to the diesel fuel in advance to refine the wax crystals and ensuring the fuel fluidity. Countermeasures are implemented.

  The fuel pump 13 connected to the fuel filter 12 via the supply line P1 is a device that raises the pressure of the fuel and raises the injection pressure, and serves as a pressurizer for injecting the fuel at a high pressure. Bear. In order to comply with the recent exhaust gas regulations related to strict particulate matter (PM), it is necessary to suppress incomplete combustion when burning fuel. By making the fuel injection pressure high, the fuel after injection is made fine, and the fuel particles become smaller, so there is no unburned residue in the center, suppressing incomplete combustion and generating particulate matter Can be suppressed.

The common rail 14 connected to the fuel pump 13 via the supply line P1 is a system that stores the fuel whose pressure has been increased by the fuel pump 13 and uniformly supplies the fuel to the injection nozzle 15 described later. Electronic control finely controls injection conditions such as fuel injection pressure, injection timing, and injection period (injection amount) to achieve ideal combustion and suppress the generation of NO _x (nitrogen oxide).

  An injection nozzle 15 as a fuel injection unit connected to the common rail 14 via the supply line P1 is a device for injecting high-pressure fuel into a combustion chamber in a diesel engine (not shown) as indicated by an arrow A. is there.

  The valve 16 as a flow path switching unit is connected to each of the fuel pump 13, the common rail 14, and the injection nozzle 15 via a return pipe P2. Further, the valve 16 is disposed at a position between each of the fuel pump 13, the common rail 14, and the injection nozzle 15 on the return pipe P2 and a fuel cooler 18 described later. That is, not all of the fuel supplied from the fuel tank 11 is supplied to the combustion chamber in the diesel engine, and surplus fuel is generated. Therefore, surplus fuel that has not been consumed in each of the fuel pump 13, the common rail 14, and the injection nozzle 15 is returned to the valve 16 via the return pipe P2. The valve 16 is also directly connected to the fuel filter 12 via the bypass line P3, and is also connected to a fuel sensor 19 described later via the fuel discrimination sub line P4. Therefore, although the valve 16 functions as a three-way switching valve, various types such as a solenoid valve, a shape memory alloy, and a bimetal can be used, and the type thereof is not particularly limited.

  In this embodiment, surplus fuel is returned from the fuel pump 13, common rail 14, and injection nozzle 15, but it is not necessary to return surplus fuel from all these elements, and at least surplus fuel generated in the injection nozzle 15. Is returned to the valve 16 via the return line P2.

  The temperature sensor 17 is provided in the return line P2, and returns the temperature from the fuel pump 13, the common rail 14, and the injection nozzle 15, and measures the temperature of the fuel flowing through the return line P2. The temperature sensor 17 may be configured integrally with the valve 16 because of its structure, and the type of the temperature sensor 17 is not particularly limited, and the temperature sensor 17 can be disposed at an arbitrary position in the return pipe P2.

  The fuel cooler 18 connected to the valve 16 via the return line P2 is a device that cools fuel returning from the fuel pump 13, the common rail 14, and the injection nozzle 15 through the return line P2. The fuel cooler 18 is configured by an air-cooled heat exchanger having a cooling fan or the like, but the type is not particularly limited. The fuel cooled by the fuel cooler 18 joins the bypass pipe P3 via the return pipe P2, and is sent to the fuel filter 12 again.

  The fuel sensor 19 is connected to the valve 16 via the fuel discrimination sub pipe P4. The valve 16 is opened at a predetermined timing, and the return pipe P2 and the fuel discrimination sub pipe P4 are connected. At this timing, the fuel returning from the fuel pump 13, the common rail 14, and the injection nozzle 15 through the return pipe P2 is supplied to the fuel sensor 19 via the valve 16 and the fuel discrimination sub pipe P4. The fuel sensor 19 determines whether or not the concentration of biodiesel fuel in the fuel is equal to or higher than a predetermined value.

  In the illustrated example, the fuel sensor 19 is arranged on the fuel discrimination sub-pipe P4. However, like the temperature sensor 17, the fuel sensor 19 is arranged at an arbitrary position on the return pipe P2, and the concentration of the biodiesel fuel is adjusted. The arrangement position of the fuel sensor 19 is not particularly limited. In the illustrated example, the fuel that has passed through the fuel sensor 19 is returned to the return line P2 again via the fuel discrimination sub-line P4, but it is not always necessary to return to the return line P2.

  Further, as a method for determining the concentration of biodiesel fuel by the fuel sensor 19, a method using the light transmittance of the mixed fuel with respect to light within a specific wavelength range (see, for example, Japanese Patent Application Laid-Open No. 2009-281733), or a method using an ultrasonic sensor ( For example, various technologies such as “concentration measurement of biodiesel blended light oil using an ultrasonic sensor” and the automotive engineering society academic lecture preprint No. 138-10) can be used. The type of is not particularly limited.

  The fuel sensor 19 transmits to the valve 16 a signal regarding whether or not the concentration of the biodiesel fuel in the fuel is equal to or higher than a predetermined value (see dotted arrow line B). When the concentration of the biodiesel fuel is equal to or higher than a predetermined value (for example, 5% by mass), as described above, many components having a high melting point such as 72 ° C. to 75 ° C. are contained like triglyceride.

  And when the density | concentration of biodiesel fuel is more than predetermined value, the valve | bulb 16 is higher than the conventional switching temperature, for example, 60 to 80 degreeC, Preferably it is 70 to 80 degreeC, More preferably, it is 75 to 80 degreeC. The flow path switching operation is performed within the set temperature range. That is, when the temperature of the surplus fuel that has recirculated through the return line P2 is below this temperature range (temperature is measured by the temperature sensor 17), the valve 16 connects the return line P2 and the bypass line P3. The fuel is returned to the fuel filter 12 by performing the channel switching / setting operation. On the other hand, when the temperature of the fuel is equal to or higher than this temperature range, the valve 16 returns the fuel to the fuel cooler 18 by performing a switching / setting operation of the flow path that maintains the connection to the fuel cooler 18 on the return pipe P2. . This fuel is further returned to the fuel filter 12.

  If the surplus fuel that has passed through the return line P2 and the bypass line P3 is returned to the fuel tank 11, the fuel temperature is lowered between the fuel tank 11 and the fuel filter 12, and the wax in the fuel is deposited. There is a concern that 12 is clogged. In this embodiment, since the fuel once heated is directly returned to the fuel filter 12, such a concern is unlikely to occur. Further, even if the fuel is cooled through the fuel cooler 18, the temperature is higher than that of the fuel stored in the fuel tank 11, so that the temperature in the fuel tank 11 is prevented from rising and the fuel is prevented from deteriorating. For this purpose, the fuel is directly returned from the fuel cooler 18 to the fuel filter 12 instead of the fuel tank 11.

  On the other hand, when the concentration of the biodiesel fuel is equal to or lower than a predetermined value, the temperature of the switching operation of the valve 16 does not need to be as high as 60 ° C. to 80 ° C. Pull down. As a result, it is possible to prevent the fuel from being heated wastefully. In addition, when it is previously determined whether or not the fuel to be used is biodiesel fuel, the set temperature range may be manually switched.

  That is, in the present embodiment, the valve 16 is a set temperature range for switching the flow path of surplus fuel flowing from the injection nozzle 15 or the like through the return pipe P2 according to the concentration of biodiesel fuel determined by the fuel sensor 19. To change. And when this density | concentration is more than predetermined value, the valve | bulb 16 raises the range of preset temperature compared with the case where it is below predetermined value.

  In this embodiment, when the concentration is equal to or higher than a predetermined value, the set temperature range is set to 60 ° C. to 80 ° C., and when the concentration is equal to or lower than the predetermined value, the set temperature range is set to 40 ° C. to 50 ° C. The However, as the set temperature range, the optimum type of biodiesel fuel can be selected according to the concentration in the fuel.

  A biodiesel fuel containing a fatty acid alkyl ester can be used for the fuel supply device 10 of the present embodiment. Of course, usable biodiesel fuel is not particularly limited.

  Fatty acid alkyl esters are produced using animal oils and vegetable oils and the like as raw materials. For example, the fatty acid alkyl ester used in the present embodiment can be obtained from animal fats and vegetable fats and oils whose main component is triglyceride by various reactions and purifications. However, fatty acid alkyl esters derived from animal fats such as beef tallow, lard, and fish oil tend to have a large amount of unsaturated fatty acids, particularly polyunsaturated fatty acids having 2 or more unsaturated bonds. There are a lot of impurities. For this reason, it is preferable that the fatty acid alkyl ester to be used is made from vegetable oils and fats made from various plants such as coconut, palm palm, olive, sunflower, rapeseed, and soybean.

  In addition, with regard to fatty acid alkyl esters made from waste edible oil used for industrial and edible purposes, as a result of recent research, reaction methods and purification methods have been scrutinized. Since it is produced, it can be used.

  For the reaction method and purification method, there are a general alkali catalyst method using an alkali metal, an acid catalyst method using an acid catalyst such as an organic acid, a lipase method using a lipase enzyme, and the like. Is not particularly limited from the viewpoint of the reaction method and the purification method.

  The alkyl group of the fatty acid alkyl ester is various alkyl groups including isomers such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group.

  Table 1 shows representative examples of fatty acid alkyl esters to which the alkyl group is bonded. However, the type of fatty acid alkyl ester used is not limited to the following representative examples.

  As described above, according to the present invention, it is possible to optimize the temperature of the fuel supplied to the diesel engine according to the properties of the fuel, such as biodiesel fuel, and to improve the performance of the fuel supply device and the diesel engine. In addition, the performance can be stably maintained over a long period of time. And since the soundness maintenance of fuel becomes more reliable, more precise control operation for fuel supply becomes possible, and the usefulness of the diesel engine will also increase.

 In particular, when the fuel temperature is low, precipitates such as impurities can be dissolved in addition to wax crystals and light oil additives, maintaining the soundness of the fuel, and when the fuel temperature is high, by cooling the fuel with a cooler It is possible to prevent thermal deterioration of the fuel. Further, such a mechanism of the present invention is an effective measure even when a cracked light oil having poor oxidation stability is used as a light oil base material.

  The present invention is intended to be variously modified and applied by those skilled in the art based on the description in the specification and well-known techniques without departing from the spirit and scope of the present invention. Included in the scope for protection. Moreover, you may combine each component in the said embodiment arbitrarily in the range which does not deviate from the meaning of invention.

  According to the fuel supply device of the present invention, the temperature of the fuel supplied to the diesel engine can be optimized according to the properties of the fuel such as biodiesel fuel, and the performance of the fuel supply device and the diesel engine is improved. At the same time, the performance can be stably maintained over a long period of time. Therefore, the usefulness of a diesel engine increases and the possibility of application to various industrial fields increases.

DESCRIPTION OF SYMBOLS 10 Fuel supply apparatus 11 Fuel tank 12 Fuel filter 13 Fuel pump 14 Common rail 15 Injection nozzle (fuel injection part)
16 Valve (flow path switching part)
17 Temperature sensor 18 Fuel cooler 19 Fuel sensor P1 Supply line P2 Return line P3 Bypass line P4 Fuel discrimination sub line

Claims (6)

A fuel supply device for supplying fuel to a diesel engine,
A fuel tank for storing fuel;
A fuel injection section for injecting fuel into the combustion chamber of the diesel engine;
A supply line for connecting the fuel tank and the fuel injection unit and supplying fuel from the fuel tank to the fuel injection unit;
A fuel filter that is disposed on the supply pipe and removes impurities in the fuel supplied from the fuel tank;
A return pipe that connects at least the fuel injection section and the fuel filter, and returns surplus fuel from the fuel injection section to the fuel filter;
A fuel cooler disposed on the return line and cooling the fuel flowing through the return line and returning it to the fuel filter;
A flow path switching unit disposed at a position between the fuel injection unit and the fuel cooler on the return pipe;
A bypass pipe connecting the flow path switching unit and the fuel filter;
A temperature sensor for measuring the temperature of the fuel flowing through the return pipe,
The flow path switching unit switches the flow path of surplus fuel flowing from the fuel injection unit through the return pipe line within a set temperature range of 60 ° C. to 80 ° C. measured by the temperature sensor,
When the temperature is equal to or higher than the set temperature, the fuel is returned to the fuel filter through the fuel cooler,
A fuel supply device that returns fuel to the fuel filter via the bypass line when the temperature is equal to or lower than the set temperature. The fuel supply device according to claim 1,
A fuel supply apparatus, further comprising a fuel sensor that receives supply of fuel from the flow path switching unit and determines a concentration of biodiesel fuel in the fuel. The fuel supply device according to claim 2,
When the concentration of the biodiesel fuel determined by the fuel sensor is equal to or lower than a predetermined value, the flow path switching unit sets the set temperature range from 60 ° C. to 80 ° C. to a lower temperature range. apparatus. A fuel supply device for supplying fuel to a diesel engine,
A fuel tank for storing fuel;
A fuel injection section for injecting fuel into the combustion chamber of the diesel engine;
A supply line for connecting the fuel tank and the fuel injection unit and supplying fuel from the fuel tank to the fuel injection unit;
A fuel filter that is disposed on the supply pipe and removes impurities in the fuel supplied from the fuel tank;
A return pipe that connects at least the fuel injection section and the fuel filter, and returns surplus fuel from the fuel injection section to the fuel filter;
A fuel cooler disposed on the return line and cooling the fuel flowing through the return line and returning it to the fuel filter;
A flow path switching unit disposed at a position between the fuel injection unit and the fuel cooler on the return pipe;
A bypass pipe connecting the flow path switching unit and the fuel filter;
A temperature sensor for measuring the temperature of the fuel flowing through the return line;
A fuel sensor that receives the supply of fuel from the flow path switching unit and determines the concentration of biodiesel fuel in the fuel, and
The flow path switching unit changes a set temperature range for switching a flow path of surplus fuel flowing from the fuel injection unit through the return pipe according to the concentration of biodiesel fuel determined by the fuel sensor. Fuel supply device. The fuel supply device according to claim 4,
The flow path switching unit is a fuel supply device that raises the range of the set temperature when the concentration is equal to or higher than a predetermined value as compared to when the concentration is equal to or lower than a predetermined value. The fuel supply device according to claim 5,
The flow path switching unit is a fuel supply device that sets a range of the set temperature to 60 ° C. to 80 ° C. when the concentration is equal to or higher than a predetermined value.

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