JP2009275665A - Fuel supply device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To favorably avoid a problem such as the clogging or corrosion of a fuel supplying system without obstructing the smooth distribution of fuel, concerning a fuel supply device of an internal combustion engine. <P>SOLUTION: The fuel supply device includes a fuel tank 12 which receives the oil supply of fuel including at least biotechnology fuel. The device further includes a main return passage 20 for returning the fuel which is not jetted by a fuel injection valve 18 to the fuel tank 12, and a sub return passage 28 branching off a middle part of the main return passage 20 and reaching the fuel tank 12. The device even further includes a switch valve 39 which can switch an inflow destination of the return furl returning from the fuel injection valve 18 to the fuel tank 12 between the main return passage 20 and the sub return passage 28, and a filter 32 provided in the sub return passage 28 and collecting products generated by the oxidation degradation of the fuel. When it is determined that fuel supply is influenced by the deterioration of the oxidation of the fuel, the switch valve 30 is controlled to change the inflow destination of the return fuel to the sub return passage 28. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel supply device for an internal combustion engine, and more particularly to a fuel supply device for an internal combustion engine that is suitable for use in an internal combustion engine that uses biofuel.

  Conventionally, for example, Patent Document 1 discloses a fuel injection device for an internal combustion engine capable of supplying biofuel. This conventional fuel injection device includes a normal fuel tank and a biofuel tank. Return fuel from the fuel injection device is returned to the normal fuel tank. As a result, the return fuel containing biofuel is returned to the normal fuel tank, so that the concentration of biofuel in the fuel supplied from the normal fuel tank to the fuel injection device is not replenished. It will gradually increase.

  In the above conventional technique, the supply flow rate of biofuel is controlled based on the fuel temperature, fuel viscosity, and the like after the biofuel is mixed. This avoids excessive mixing of biofuel at the fuel inlet of the fuel injection device, and avoids that the mixing ratio of biofuel becomes excessive and obstructs lubrication of the plunger sliding portion of the fuel injection device. Yes.

JP-A-2005-291104 JP 2003-3925 A JP 2006-207499 A Japanese Patent No. 4007437 JP 2007-186574 A

  When the biofuel is oxidized and deteriorated over time, a polymer having a large molecular weight and a high viscosity is produced, and acid and water are produced. If the product (acid, water, polymer) accompanying the oxidative deterioration is generated, there is a concern that problems such as corrosion and clogging may occur in the fuel supply system such as the fuel pump and the fuel injection valve. In order to deal with such problems, the conventional technique, that is, the method of controlling the supply flow rate of biofuel, is insufficient as a countermeasure since the supply of biofuel containing the polymer is continued. It is thought that.

  The present invention has been made to solve the above-described problems, and is a fuel for an internal combustion engine that can satisfactorily avoid problems such as clogging and corrosion of the fuel supply system without hindering the smooth flow of the fuel. An object is to provide a supply device.

A first invention is a fuel supply device for an internal combustion engine,
A fuel tank that receives fuel supply including at least biofuel; and
A fuel injection valve for injecting fuel into the internal combustion engine;
A fuel pump for supplying fuel in the fuel tank to the fuel injection valve;
A main return passage for returning fuel not injected by the fuel injection valve to the fuel tank;
A sub return path that branches from the middle of the main return path and reaches the fuel tank;
A switching means capable of switching a destination of return fuel returning from the fuel injection valve to the fuel tank between the main return passage and the sub return passage;
A collecting means provided in the sub-return passage for collecting a product generated by oxidative degradation of biofuel;
An oxidative deterioration influence determining means for determining whether or not the fuel is affected by the oxidative deterioration of the fuel;
A flow path control means for controlling the switching means so that the return destination of the return fuel becomes the sub return path when the oxidation deterioration influence determination means determines that the state is affected by the oxidation deterioration; ,
It is characterized by providing.

The second invention is the first invention, wherein
The collection means includes a filter for collecting the product substance,
The fuel supply device includes:
A return pump for urging discharge of the return fuel to the fuel tank in the auxiliary return passage closer to the fuel tank than the filter;
A pump driving means for operating the return pump when it is determined by the oxidation deterioration influence determining means that the state is affected by the oxidation deterioration;
Is further provided.

The third invention is the first invention, wherein
The collection means includes a water tank in which water is stored and receives supply of the return fuel,
The secondary return passage includes a water tank downstream passage having one end disposed in the upper layer of the water tank and the other end disposed in the fuel tank,
The fuel supply device includes:
A return pump for urging the water tank downstream passage to discharge the return fuel to the fuel tank;
A pump driving means for operating the return pump when it is determined by the oxidation deterioration influence determining means that the state is affected by the oxidation deterioration;
Is further provided.

Moreover, 4th invention is set in 3rd invention,
The water tank downstream passage further includes a filter for collecting the product substance.

According to a fifth invention, in any one of the second to fourth inventions,
The fuel supply device includes:
A flow rate adjusting passage connected to the main return passage and the fuel pump on the upstream side of the collecting means;
When the oxidative deterioration influence determining means determines that the degree of oxidative deterioration of the fuel is high, the discharge amount of the fuel pump is larger than the amount required for executing fuel injection by the fuel injection valve. A fuel pump control means for controlling the fuel pump;
Is further provided.

Further, a sixth invention is any one of the second to fourth inventions,
The switching means is further configured to be able to select a flow path form in which the main return passage and the sub return passage on the fuel tank side communicate with each other than the switching means.
The flow path control means communicates the main return passage and the sub return passage closer to the fuel tank than the switching means when the oxidation deterioration degree of the fuel is determined to be high by the oxidation deterioration influence determination means. Controlling the switching means to
The pump driving unit operates the return pump when the oxidation deterioration influence determination unit determines that the degree of oxidation deterioration of the fuel is high.

  According to the first invention, when it is determined that the fuel cell is affected by the oxidative deterioration of the fuel, the auxiliary return passage provided with the collecting means is selected as the return fuel inflow destination. As a result, it is possible to return the return fuel to the fuel tank after removing the product accompanying the oxidative degradation of the biofuel by the collecting means. For this reason, it is possible to prevent the fuel containing such a product from being supplied to a fuel supply system such as a fuel pump or a fuel injection valve, and it is preferable that problems such as clogging and corrosion occur in the fuel supply system. Can be avoided. Further, according to the present invention, only when it is determined that the fuel cell is affected by the oxidative deterioration of the fuel, the sub return path provided with the collecting means is selected. If it is not, the smooth distribution of the fuel can be prevented from being hindered by the presence of the collecting means for collecting the product.

  According to the second invention, even when the pressure loss in the auxiliary return passage increases due to the product generated being collected in the filter by the return pump provided in the auxiliary return passage together with the filter, Smooth discharge of the return fuel to the fuel tank can be realized. In addition, according to the present invention, the return pump is driven only when it is determined that the fuel cell is affected by the oxidative deterioration of the fuel, so that unnecessary energy consumption is avoided for the operation of the return pump. can do.

  According to the third aspect of the invention, the product (acid, water, polymer) generated by oxidative degradation in the process of passing through the fuel supply system is collected in the water tank and efficiently removed from the fuel. can do. Moreover, according to this invention, the return fuel after the said production | generation substance was removed in the water tank can be discharged | emitted smoothly to a fuel tank.

  According to 4th invention, the said production | generation substance (light polymer etc.) which could not be removed in the water tank can be collected and removed with a filter.

  According to the fifth aspect of the present invention, since the degree of oxidative degradation of the fuel is extremely high, it is not possible to sufficiently remove it once through the sub return passage, and a part of the oxidative degradation product flows into the fuel tank. However, it is possible to sufficiently remove the oxidative degradation product from the inside of the fuel tank by repeatedly collecting such product material by the collection means.

  According to the sixth aspect of the present invention, since the degree of oxidation deterioration of the fuel is extremely high, it cannot be sufficiently removed by passing through the sub-return passage once, and a part of the oxidation deterioration generation material flows into the fuel tank. However, it is possible to sufficiently remove the oxidative degradation product from the inside of the fuel tank by repeatedly collecting such product material by the collection means. Further, according to the present invention, compared with the fifth invention, the fuel can be circulated between the fuel tank and the collecting means without going through the fuel pump, so that it is included in the fuel in the fuel tank. The product substance in the fuel tank can be more reliably removed while preventing the product substance to be supplied to the fuel supply system more reliably.

Embodiment 1 FIG.
[System Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. As shown in FIG. 1, the system of this embodiment includes a diesel engine 10 mounted on an automobile. Further, the system of the present embodiment includes a fuel tank 12 for storing the fuel of the diesel engine 10.

  The fuel tank 12 is supplied with 100% biofuel such as rapeseed methyl ester (Rapeseed Methyl Esther) or a mixed fuel in which such biofuel and light oil are mixed at a predetermined ratio. .

  The fuel in the fuel tank 12 is pressurized to a predetermined fuel pressure by the fuel pump 14, stored in the common rail 16, and supplied from the common rail 16 to the fuel injection valve 18 of each cylinder. A main return passage 20 communicating with the fuel tank 12 is connected to the fuel injection valve 18. With such a configuration, fuel that has not been used for injection out of the fuel supplied from the common rail 16 to the fuel injection valve 18 returns to the fuel tank 12 through the main return passage 20.

  The fuel pump 14 is provided with a regulating valve (not shown) for adjusting the discharge pressure of the fuel pump 14, and a fuel passage 22 communicating with the main return passage 20 is connected. With such a configuration, the fuel supplied to the fuel pump 14 when the discharge pressure of the fuel pump 14 reaches a preset upper limit pressure due to the fuel having a flow rate higher than the predetermined value being supplied to the fuel pump 14. A part of the fuel gas flows back to the fuel tank 12 through the fuel passage 22 and the main return passage 20.

  Furthermore, the common rail 16 is provided with a pressure reducing valve 24 configured to open when the fuel pressure in the common rail 16 reaches a preset upper limit pressure, and communicates with the main return passage 20. A fuel passage 26 is connected. With such a configuration, the fuel pressure in the common rail 16 is adjusted to a predetermined pressure.

  Further, the system shown in FIG. 1 includes a sub return passage 28 that branches from the middle of the main return passage 20 and reaches the fuel tank 12. At the branch point between the main return passage 20 and the auxiliary return passage 28, the return fuel inflow destination returning from the fuel injection valve 18 side to the fuel tank 12 can be switched between the main return passage 20 and the auxiliary return passage 28. A switching valve 30 is installed.

  In the middle of the secondary return passage 28, a filter 32 for collecting a product (polymerized product or the like) generated by oxidative degradation of the biofuel is installed. Further, a return pump 34 for urging discharge of return fuel to the fuel tank 12 is installed in the auxiliary return passage 28 closer to the fuel tank 12 than the filter 32.

  A bioconcentration sensor 38 for detecting a biofuel concentration (RME concentration) B in the fuel flowing through the fuel passage 36 connecting the fuel tank 12 and the fuel pump 14 is incorporated. Furthermore, a fuel temperature sensor 40 for detecting the temperature T of the return fuel flowing through the main return passage 20 closer to the fuel injection valve 18 than the switching valve 30 is incorporated.

  Further, the system shown in FIG. 1 includes an ECU (Electronic Control Unit) 42. The ECU 42 includes various sensors for controlling the diesel engine 10 in addition to the bio-concentration sensor 38, the fuel temperature sensor 40, the fuel pump 14, the fuel injection valve 18, the switching valve 30, and the return pump 34 described above. The actuator is electrically connected.

[Control of Embodiment 1]
By the way, biofuel has many components which have an unsaturated bond, and tends to cause oxidative degradation with time. For example, RME, which is a biodiesel fuel used in the present embodiment, is mainly composed of oleic acid methyl ester, but the component has an unsaturated bond. For this reason, it undergoes oxidation to cause polymerization and the like, and a gum-like substance (product substance) having a large molecular weight and high viscosity is produced. As a result, the generated gum-like substance accumulates on the fuel pump 14, the fuel injection valve 18, etc., and the fuel flow path is clogged.

  In addition, the oxidative degradation of biofuel tends to progress as the fuel temperature increases. In particular, the fuel in the fuel tank 12 is heated to a high temperature in the course of being supplied to the fuel injection valve 18. The process in which the fuel heated in this way is once returned to the fuel tank 12 through the return passage (corresponding to the main return passage 20 in this embodiment) and then supplied to the fuel injection valve again. As a result, polymerization proceeds and a gum-like substance is easily generated.

  Therefore, in this embodiment, when it is determined that the fuel is oxidatively deteriorated based on the fuel temperature and the biofuel concentration, the path through which the return fuel passes is directly passed through the main return path 20. The path returning from the fuel tank 12 to the path returning to the fuel tank 12 through the auxiliary return path 28 is switched.

FIG. 2 is a flowchart of a routine executed by the ECU 42 in the first embodiment to realize the above function.
In the routine shown in FIG. 2, first, it is determined whether or not the biofuel concentration B is higher than a predetermined determination threshold value B _L (eg, 10%) (step 100). The higher the biofuel concentration in the fuel, the easier it is to produce a gum-like polymer with oxidative degradation. That is, in this step 100, it is determined whether or not the currently used fuel is a fuel containing biofuel having a predetermined concentration or higher (a fuel in which oxidation deterioration over a certain level is a concern).

  When the determination in step 100 is not established, that is, when it can be determined that the influence of oxidative degradation is not a problem level because the current fuel used is non-biofuel or low biofuel concentration, the filter 32 is used. The switching valve 30 is controlled so that a return path that does not pass through (that is, a path through which return fuel passes through the main return path 20 and returns to the fuel tank 12) is selected (step 102). In this case, the return pump 34 is turned off.

On the other hand, if the determination in step 100 is true, that is, if it is determined that the currently used fuel is a fuel containing a concentration of biofuel that is likely to be affected by oxidation degradation, then return fuel is used. It is determined whether or not the temperature T is higher than a predetermined determination threshold value T _L (for example, 80 ° C.) (step 104). The determination threshold value _TL is a value set in advance as a threshold value for determining whether or not the return fuel temperature has reached a temperature at which the influence of oxidation deterioration is a concern.

  If the determination in step 104 is not established, that is, if it can be determined that there is no concern about the effect of oxidative deterioration of the fuel, the return fuel returns to the fuel tank 12 through the main return passage 20 as it is. Is selected so that the return pump 34 is turned off (step 102).

  On the other hand, if the determination in step 104 is satisfied, that is, if it can be determined that the situation is concerned about the influence of fuel oxidative deterioration, the return fuel returns to the fuel tank 12 through the auxiliary return passage 28. The switching valve 30 is controlled so that the route is selected (step 106). In this case, the return pump 34 is turned on.

According to the routine shown in FIG. 2 described above, the filter 32 is provided as a return fuel flow path when the biofuel concentration B and the return fuel temperature T exceed the respective determination threshold values B _L and T _L. The sub return path 28 is selected and the return pump 34 is driven. As a result, the product (polymerized material) generated by the alteration such as polymerization in the process of passing through the fuel supply system can be collected by the filter 32 and removed from the fuel. For this reason, it is possible to prevent such a product from returning to the fuel tank 12. Thereby, it can prevent that the said production | generation substance is supplied to fuel supply systems, such as the fuel pump 14 and the fuel injection valve 18, and it can avoid that clogging arises in a fuel supply system.

  Further, according to the above routine, the configuration is such that the sub return passage 28 provided with the filter 32 is selected only when it is determined that the situation is affected by the oxidation deterioration of the fuel. If it is not, the smooth flow of the fuel can be prevented from being hindered by the presence of the filter 32 in which the product substance is collected.

Further, for example, if the auxiliary return passage 28 is used until there is no concern about the oxidative deterioration of the fuel, such as when using 100% light oil, excess energy for operating the return pump 34 is consumed. Become. On the other hand, according to the above routine, when the biofuel concentration B and the return fuel temperature T exceed the respective determination thresholds B _L and T _L , that is, it is recognized that there is a concern about the influence of oxidation degradation. Only when this is done, the sub return path 28 is selected as the return fuel flow path, and the return pump 34 is driven. For this reason, it is possible to avoid unnecessary energy consumption regarding the operation of the return pump 34.

  By the way, in the first embodiment described above, the return pump 34 for urging the discharge of the return fuel to the fuel tank 12 is provided on the downstream side of the filter 32. By providing such a return pump 34, the pressure loss when the return fuel passes through the filter 32, and further the pressure loss that further increases as the product substance is collected in the filter 32. Correspondingly, smooth discharge of the return fuel to the fuel tank 12 can be realized, which is preferable. However, since the return fuel flowing from the fuel injection valve 18 side is pushed by the pressure of the fuel pump 14, the return pump 34 is used to collect the product in the auxiliary return passage 28. It does not necessarily have to be provided.

In the first embodiment described above, the switching valve 30 corresponds to the “switching means” in the first invention, and the filter 32 corresponds to the “collecting means” in the first invention. Further, when the ECU 42 executes the processes of steps 100 and 104, the “oxidation deterioration influence determining means” in the first invention performs the process of step 106 when the determinations of steps 100 and 104 are established. By executing this, the “flow path control means” in the first aspect of the present invention is realized.
In addition, the “pump drive means” according to the second aspect of the present invention is implemented by the ECU 42 executing the process of step 106 when the determinations of steps 100 and 104 are established.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS.
[System Configuration of Embodiment 2]
FIG. 3 is a diagram for explaining a system configuration according to the second embodiment of the present invention. In FIG. 3, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted or simplified. Although the fuel temperature sensor 40 is not shown in FIG. 3, the fuel temperature sensor 40 may be provided as in the first embodiment.

  The configuration shown in FIG. 3 is characterized by the configuration of the auxiliary return passage 50 that branches from the main return passage 20 and reaches the fuel tank 12. That is, in the middle of the sub-return passage 50 of the present embodiment, a water tank 52 for collecting and removing product substances (acid, water, polymer) generated by oxidative degradation of the fuel is disposed. Water is stored in the water tank 52. The water tank 52 is made of an acid resistant material.

  The auxiliary return passage 50 includes two first auxiliary return passages 54 and a second auxiliary return passage 56 that are arranged via a water tank 52. More specifically, one end of the first sub return passage 54 is connected to the switching valve 30, and the other end is installed so as to be located in the lower layer (water layer) in the water tank 52. One end of the other second sub return passage 56 is disposed so as to be located in the upper layer (oil layer) of the water tank 52, and the other end is disposed in the fuel tank 12.

  A filter 58 is provided at the one end (the outlet of the water tank 52) of the second sub-return passage 56 to collect and remove light polymer or floating matter present in the upper layer (oil layer). A hygroscopic agent 60 for removing water mixed in the fuel in the passage 56 is installed in the middle of the second sub return passage 56. Further, a return pump 34 is installed in the second auxiliary return passage 56 closer to the fuel tank 12 than the moisture absorbent 60.

  As shown in FIG. 3, a level gauge 62 for detecting the water surface position in the water tank 52 is attached to the side surface of the water tank 52. Further, on the upper surface of the water tank 52, a water addition plug 64 used when adding water to the water tank 52 is provided. Further, on the side surface close to the bottom surface of the water tank 52, a drain plug 66 used for discharging water in the water tank 52 is provided.

FIG. 4 is a diagram for explaining the function of the water tank 52 provided in the system shown in FIG. 3.
FAME (fatty acid methyl ester), which is a biofuel mainly used in the diesel engine 10, has a highly reactive unsaturated bond, and the unsaturated bond is oxidized to generate an acid such as a fatty acid. Furthermore, the produced acid reacts with a metal in the fuel or a metal contained in the fuel path to produce a metal salt, and at that time, water is also produced.

  The acid and water generated as described above cause corrosion of the fuel path, and the metal salt tends to clog the fuel pump 14, the fuel injection valve 18, and the like. In addition, as described above, peroxides in which a part of the unsaturated bond is oxidized may be polymerized to form a polymer having a large molecular weight. Since the boiling point is high, the fuel pump 14 and the fuel injection valve 18 are clogged.

  As described above, the system of the present embodiment includes the water tank 52 for collecting and removing the oxidative degradation product (acid, water, polymer) in the fuel as described above. As shown in FIG. 4, when the return fuel is introduced into the water tank 52 in which water is stored, the fuel component itself floats without being mixed with water and is separated into an upper layer (oil layer).

  On the other hand, among the oxidative degradation products in the fuel, the acid remains in the lower layer (water layer) because it is easily dissolved in water. Further, water also remains in the lower layer (water layer). Furthermore, since the specific gravity of the polymer is large, it is basically precipitated in the lower layer (aqueous layer). Thus, according to the water tank 52 of the present embodiment, it is possible to satisfactorily separate the fuel and the oxidation degradation product from the return fuel containing the oxidation degradation product.

[Control of Embodiment 2]
Also in the present embodiment having the above-described configuration, when there is a concern about the effect of oxidative deterioration of the fuel, the path through which the return fuel passes through the main return path 20 and returns from the path to the fuel tank 12 as a sub return path. The path is switched back to the fuel tank 12 through 50.

FIG. 5 is a flowchart of a routine executed by the ECU 42 in the second embodiment to realize the above function.
In the routine shown in FIG. 5, first, it is determined whether or not the biofuel concentration B is higher than a predetermined determination threshold value B _L (for example, 5%) (step 200). The determination threshold value B _L is a threshold value of the biofuel concentration B that can tolerate oxidative degradation.

  If the determination in step 200 is not established, that is, if it can be determined that the biofuel concentration B of the currently used fuel is at a level that allows oxidative degradation, the return fuel passes through the main return passage 20 as it is. Then, the switching valve 30 is controlled so that the path returning to the fuel tank 12 is selected (step 202). In this case, the return pump 34 is turned off.

  On the other hand, if the determination in step 200 is true, that is, if it is determined that the currently used fuel is a fuel containing a concentration of biofuel that is likely to be affected by oxidative degradation, the return fuel is a secondary fuel. The switching valve 30 is controlled so that the path returning to the fuel tank 12 after being introduced into the water tank 52 through the return passage 50 is selected (step 204). In this case, the return pump 34 is turned on. In this routine as well, as in the routine shown in FIG. 2 above, based on the biofuel concentration B and the return fuel temperature T, it is determined whether or not the currently used fuel is a fuel that is likely to be affected by oxidation degradation. You may make it judge.

  Next, counting of the time during which the switching valve 30 is controlled so that return fuel is introduced into the auxiliary return passage 50 (switching valve operating time) is started (step 206).

  Thereafter, when the operation of the diesel engine 10 is stopped, the switching valve 30 is controlled so that the return fuel returns to the fuel tank 12 through the main return passage 20 without passing through the auxiliary return passage 50. At the same time, the return pump 34 is turned off (step 208).

  Then, the counting of the switching valve operating time is ended (step 210). Note that the counted switching valve operating time is stored, and is accumulated during the next operation of the diesel engine 10 until it is reset at the time of fuel refueling thereafter.

  According to the routine shown in FIG. 5 described above, the water tank 52 and the filter 58 serve as the return fuel flow path when it is determined based on the biofuel concentration B that the fuel is oxidatively deteriorated. Is selected and the return pump 34 is driven.

  As a result, product substances (acid, water, polymer) generated by oxidative degradation during the passage of the fuel through the fuel supply system can be collected in the water tank 52 and efficiently removed from the fuel. In addition, a light polymer that cannot be completely removed in the water tank 52 can be collected by the filter 58 and removed.

  For this reason, it is possible to prevent the generated material accompanying the oxidative degradation of the fuel as described above from returning to the fuel tank 12. Thereby, it can prevent that the said production | generation material is supplied to fuel injection systems, such as the fuel pump 14 and the fuel injection valve 18, and can avoid that corrosion and clogging arise in a fuel injection system.

  Further, according to the above routine, only when it is recognized that the influence of oxidation deterioration is a concern, the sub return path 50 is selected as the return fuel distribution path and the return pump 34 is driven. Become. For this reason, it is possible to avoid unnecessary energy consumption regarding the operation of the return pump 34.

  Further, according to the above routine, the time when the return fuel is introduced into the auxiliary return passage 50 during the operation of the diesel engine 10 is counted as the switching valve operating time. As the switching valve operating time increases, the amount of acid collected in the water tank 52 increases, so that the acid concentration in the water tank 52 increases and the level of the water surface gradually increases. Become.

  Therefore, based on whether the switching valve operating time has reached a predetermined threshold value, it is determined whether the acid concentration in the water has reached an allowable limit, and the acid concentration in the water has such an allowable limit. When reaching the above, a warning may be issued to prompt the vehicle user to replace the water. Similarly, based on the output of the level gauge 62, when the water surface level reaches an allowable limit, a warning for prompting draining may be issued.

In the second embodiment described above, the water tank 52 and the filter 58 correspond to the “collecting means” in the first invention.
The second auxiliary return passage 56 corresponds to the “water tank downstream passage” in the third aspect of the present invention. Further, the “pump drive means” in the third aspect of the present invention is realized by the ECU 42 executing the process of step 204 when the determination of step 200 is established.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG.
The system of the present embodiment can be realized by causing the ECU 42 to execute a routine shown in FIG. 6 to be described later instead of the routine shown in FIG. 2 or FIG. 5 using the hardware configuration shown in FIG. 1 or FIG. It can be done.

[Control of Embodiment 3]
By the way, when the biofuel concentration B and the return fuel temperature T of the currently used fuel are extremely high (that is, when the degree of oxidative deterioration of the fuel is extremely high), the auxiliary return passage 28 (or 50) is passed once. It may not be possible to fully collect and remove the product produced by oxidative degradation. Therefore, in this embodiment, when the degree of oxidative deterioration of the fuel is extremely high, in addition to the control of the first or second embodiment described above, the discharge amount of the fuel pump 14 is used for the fuel injection by the fuel injection valve 18. Increased more than needed.

  In the following embodiment, an example of control combining the control of the first embodiment (see FIG. 2) and the control of the fuel pump 14 of the present embodiment will be described. The control of the second embodiment described above (see FIG. 5) and the control of the fuel pump 14 of the present embodiment may be combined.

  FIG. 6 is a flowchart of a routine executed by the ECU 42 in the third embodiment in order to realize the above function. In FIG. 6, the same steps as those shown in FIG. 2 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

In the routine shown in FIG. 6, in step 106, the switching valve 30 is controlled and the return pump 34 is turned on so that the return fuel returns to the fuel tank 12 through the auxiliary return passage 28. Subsequently, it is then determined whether or not the degree of oxidative deterioration of the fuel is extremely high (step 300). More specifically, for example, the second determination in which the current biofuel concentration B and the return fuel temperature T are set to values larger than the determination thresholds B _L and T _L used in Steps 100 and 104, respectively. It can be determined that the degree of oxidative degradation is extremely high when both of the second determination threshold values are exceeded.

  If it is determined in step 300 that the degree of oxidative deterioration of the fuel is extremely high, the discharge amount of the fuel pump 14 is increased more than the amount required for the fuel injection by the fuel injection valve 18. The fuel pump 14 is controlled (step 302).

  According to the routine shown in FIG. 6 described above, when it is determined that the degree of oxidative deterioration of the fuel is extremely high, the discharge amount of the fuel pump 14 is increased as described above, so that the fuel pump 14 is supplied to the fuel pump 14. Excess fuel in the fuel is returned to the fuel tank 12 via the fuel passage 22, the main return passage 20, and the sub return passage 28. As a result, a fuel circulation path is formed in which a part of the fuel in the fuel tank 12 is introduced into the filter 32 provided in the auxiliary return passage 28 without going through the fuel injection valve 18 and then returns to the fuel tank 12 again. Will be.

  As a result, the degree of oxidative degradation of the fuel is so high that even if it passes through the sub-return passage 28 once and cannot be removed sufficiently, even if a part of the oxidative degradation product flows into the fuel tank 12, By repeatedly collecting such product substances by the filter 32, it becomes possible to sufficiently remove the oxidation degradation product from the fuel tank 12. Further, according to such a method, it is possible to remove the generated substance in the fuel tank 12 during operation of the diesel engine 10.

  By the way, in Embodiment 3 mentioned above, when the oxidation deterioration degree of a fuel is very high, the discharge amount of the fuel pump 14 is raised. However, the method for sufficiently removing the oxidation degradation product from the fuel tank 12 when the oxidation degradation product flows into the fuel tank 12 because the degree of oxidation degradation of the fuel is extremely high is limited to this. For example, the following method may be used.

  That is, the switching valve provided at the branch point between the main return passage 20 and the auxiliary return passage 28 (or 50) is added to the function of the switching valve 30, and the main return passage 20 closer to the fuel tank 12 than the switching valve. The flow path configuration (third flow path configuration) communicating with the auxiliary return passage 28 (or 50) is configured as a three-way valve having a selectable function. Then, for example, while the diesel engine 10 is stopped after it is determined that the degree of oxidative deterioration of the fuel is extremely high, the return valve 34 is controlled after the switching valve is controlled so that the third flow path configuration is selected. To drive.

  According to such a method, a part of the fuel in the fuel tank 12 does not go through the fuel pump 14 in addition to the fuel injection valve 18, but the filter 32 (or the water tank 52 and the filter provided in the auxiliary return passage 28) 58), a fuel circulation path to return to the fuel tank 12 is formed.

  As a result, as in the case where the control of the third embodiment described above is executed, the degree of oxidative deterioration of the fuel is extremely high. Even when a part of the fuel tank 12 flows into the fuel tank 12, it is possible to sufficiently remove the oxidative degradation product from the fuel tank 12 by repeatedly collecting such product substances by the filter 32. .

  Furthermore, according to such a method, fuel can be circulated between the fuel tank 12 and the filter 32 without using the fuel pump 14 as compared with the method of the third embodiment described above. The product substance contained in the fuel in the fuel tank 12 can be more reliably removed while preventing the product substance contained in the fuel from being supplied to the fuel supply system.

  In the third embodiment described above, the fuel passage 22 corresponds to the “flow rate adjusting passage” in the fifth aspect of the invention. Further, the “fuel pump control means” according to the fifth aspect of the present invention is realized by the ECU 42 executing the processing of steps 300 and 302 described above.

By the way, in the above-described first to third embodiments, whether the biofuel concentration B or the return fuel temperature T is affected by the oxidative deterioration of the fuel by comparing with the predetermined determination thresholds B _L and T _L. It is determined whether or not. More specifically, by determining whether or not the biofuel concentration B is higher than the determination threshold value _BL, it is determined whether or not the fuel is likely to be oxidized and deteriorated. Further, by determining whether or not the return fuel temperature T is higher than the determination threshold value _TL, it is determined whether or not it is in a state where oxidation deterioration is likely to occur (it can be estimated that oxidation deterioration has occurred). Yes. However, the determination method according to the present invention is not limited to this, and a viscosity sensor that detects the viscosity of the fuel is provided, and it is determined whether or not oxidation deterioration actually progresses from the viscosity of the fuel. Or by detecting the presence or absence of oxidative degradation from the output of a property sensor that detects other fuel properties other than the viscosity sensor to determine whether or not the fuel is affected by the oxidative degradation of the fuel. Also good.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure for demonstrating the system configuration | structure of Embodiment 2 of this invention. It is a figure for demonstrating the function of the water tank with which the system shown in FIG. 3 is provided. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Diesel engine 12 Fuel tank 14 Fuel pump 16 Common rail 18 Injector 20 Main return passages 22, 26, 36 Fuel passage 24 Pressure reducing valve 26 Fuel passages 28, 50 Sub return passage 30 Switching valve 32, 58 Filter 34 Return pump 36 Fuel passage 38 Bio concentration sensor 40 Fuel temperature sensor 42 ECU (Electronic Control Unit)
52 Water tank 54 First sub return passage 56 Second sub return passage 60 Hygroscopic agent 62 Level gauge 64 Water adding plug 66 Drain plug

Claims (6)

A fuel tank that receives fuel supply including at least biofuel; and
A fuel injection valve for injecting fuel into the internal combustion engine;
A fuel pump for supplying fuel in the fuel tank to the fuel injection valve;
A main return passage for returning fuel not injected by the fuel injection valve to the fuel tank;
A sub return path that branches from the middle of the main return path and reaches the fuel tank;
A switching means capable of switching a destination of return fuel returning from the fuel injection valve to the fuel tank between the main return passage and the sub return passage;
A collecting means provided in the sub-return passage for collecting a product generated by oxidative degradation of biofuel;
An oxidative deterioration influence determining means for determining whether or not the fuel is affected by the oxidative deterioration of the fuel;
A flow path control means for controlling the switching means so that the return destination of the return fuel becomes the sub return path when the oxidation deterioration influence determination means determines that the state is affected by the oxidation deterioration; ,
A fuel supply device for an internal combustion engine, comprising: The collection means includes a filter for collecting the product substance,
The fuel supply device includes:
A return pump for urging discharge of the return fuel to the fuel tank in the auxiliary return passage closer to the fuel tank than the filter;
A pump driving means for operating the return pump when it is determined by the oxidation deterioration influence determining means that the state is affected by the oxidation deterioration;
The fuel supply device for an internal combustion engine according to claim 1, further comprising: The collection means includes a water tank in which water is stored and receives supply of the return fuel,
The secondary return passage includes a water tank downstream passage having one end disposed in the upper layer of the water tank and the other end disposed in the fuel tank,
The fuel supply device includes:
A return pump for urging the water tank downstream passage to discharge the return fuel to the fuel tank;
A pump driving means for operating the return pump when it is determined by the oxidation deterioration influence determining means that the state is affected by the oxidation deterioration;
The fuel supply device for an internal combustion engine according to claim 1, further comprising:   The fuel supply device for an internal combustion engine according to claim 3, further comprising a filter for collecting the generated substance in the water tank downstream passage. The fuel supply device includes:
A flow rate adjusting passage connected to the main return passage and the fuel pump on the upstream side of the collecting means;
When the oxidative deterioration influence determining means determines that the degree of oxidative deterioration of the fuel is high, the discharge amount of the fuel pump is larger than the amount required for executing fuel injection by the fuel injection valve. A fuel pump control means for controlling the fuel pump;
The fuel supply device for an internal combustion engine according to claim 2, further comprising: The switching means is further configured to be able to select a flow path form in which the main return passage and the sub return passage on the fuel tank side communicate with each other than the switching means.
The flow path control means communicates the main return passage and the sub return passage closer to the fuel tank than the switching means when the oxidation deterioration degree of the fuel is determined to be high by the oxidation deterioration influence determination means. Controlling the switching means to
3. The fuel supply apparatus for an internal combustion engine according to claim 2, wherein the pump drive means operates the return pump when the oxidation deterioration influence determination means determines that the degree of oxidation deterioration of the fuel is high.

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