JP2022054669A - Fuel injection system and control method for fuel injection system - Google Patents

Abstract

To provide a fuel injection device capable of preventing clogging of fuel during fuel injection before start of an internal combustion engine even when biofuel or inferior fuel is used.SOLUTION: A fuel injection system 1 includes: an injection device 3 having a nozzle 21a for injecting fuel to a combustion chamber of an internal combustion engine; a fuel tank 5 for supplying fuel to the injection device 3; an openable/closable recirculation flow passage 7 for recirculating fuel from a middle part of a fuel passage leading from the fuel tank 5 to the nozzle 21a to the fuel tank 5; and a control section 11 adjusting opening/closing of the recirculation flow passage 7. The fuel injection system further includes a fuel property acquisition section 13 acquiring information related to fuel properties. The control section 11 specifies properties of the fuel from the information acquired by the fuel property acquisition section 13 and adjusts an opening of the recirculation flow passage 7 in accordance with the specified properties of the fuel to control fuel injection pressure to pressure preventing clogging of the nozzle 21a.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a fuel injection system and a control method for the fuel injection system.

Internal combustion engines are driven using different types of fuels depending on the heat cycle. For example, diesel engines may use biodiesel fuel as well as fossil fuel diesel fuel, and fuels with different properties have the same heat cycle. May be used. In addition, the content of substances that affect the environment or interfere with normal combustion when released into the atmosphere after combustion is regulated, but the upper limit of the regulated value differs depending on the country or region, so the same type of fuel However, the properties may differ depending on the country or region. Inferior fuels refined without observing regulations have various properties. If such fuels having different properties are used under the same combustion conditions, the internal combustion engine may be damaged, and therefore the operating conditions may be changed according to the properties.

For example, in Patent Document 1, the fuel injection amount is controlled by estimating the properties of the fuel from the pressure in the combustion chamber during combustion. In Patent Document 2, the ignition timing is controlled by estimating the properties of the fuel from the amount of fine particles generated at the start of the spark-ignition internal combustion engine.

Japanese Unexamined Patent Publication No. 2004-346911 Japanese Unexamined Patent Publication No. 2004-132254

Biofuels and inferior fuels have the property of blocking the nozzle of the injection device depending on the combustion conditions. However, since the control of Patent Documents 1 and 2 estimates the fuel property from the combustion state after the start of the internal combustion engine, if a fuel having a property of blocking the nozzle of the injection device is used, the property is already estimated at the time of estimating the property. There was a risk of obstruction.

The present disclosure has been made in view of the above problems, and an object of the present invention is to provide a fuel injection system capable of preventing fuel clogging at the time of fuel injection even when biofuel or inferior fuel is used before starting the internal combustion engine.

One aspect of the present disclosure for achieving the above object is an injection device including a nozzle for injecting fuel into a combustion chamber of an internal combustion engine, a fuel tank for supplying fuel to the injection device, and the nozzle from the fuel tank. It is a fuel injection system provided with an openable / closable recirculation path for recirculating fuel from the middle of the fuel flow path leading to the fuel to the fuel tank and a control unit for adjusting the opening / closing of the recirculation path, and provides information on the properties of the fuel. A fuel property acquisition unit is provided, and the control unit identifies the fuel property from the information acquired by the fuel property acquisition unit, adjusts the opening degree of the recirculation path according to the specified fuel property, and adjusts the fuel. It is characterized in that the injection pressure is controlled to a pressure at which the nozzle is not clogged.

Another aspect of the present disclosure is an injection device including a nozzle for injecting fuel into the combustion chamber of the internal combustion engine, a fuel tank for supplying fuel to the injection device, and a flow path of fuel from the fuel tank to the nozzle. It is a control method of a fuel injection system provided with an openable and closable recirculation path for recirculating fuel to the fuel tank from the middle, and is acquired in a fuel property acquisition step of acquiring information related to fuel properties and a fuel property acquisition process. Pressure adjustment that controls the fuel injection pressure to a pressure that does not clog the nozzle by adjusting the opening degree of the recirculation path according to the specific step of specifying the fuel properties from the information provided and the properties of the fuel specified in the specific step. It is characterized by carrying out the process.

According to the present disclosure, it is possible to provide a fuel injection system capable of preventing fuel clogging at the time of fuel injection before starting the internal combustion engine even when biofuel or inferior fuel is used.

It is a figure which shows the schematic structure of the fuel injection system which concerns on embodiment of this disclosure. It is a flow chart which shows the procedure of control of the fuel injection system of FIG. It is a flow chart which shows the operation procedure of the fuel injection system of FIG. 1 while an internal combustion engine is driving.

Hereinafter, embodiments suitable for the present disclosure will be described in detail with reference to the drawings.

First, a schematic configuration of the fuel injection system 1 according to the embodiment of the present disclosure will be described with reference to FIG. FIG. 1 illustrates a system in which fuel is injected into the combustion chamber of a diesel engine, which is an internal combustion engine, as the fuel injection system 1. The fuel injection system 1 shown in FIG. 1 includes an injection device 3, a fuel tank 5, a return path 7, a fuel property acquisition unit 13, and a control unit 11.

The injection device 3 is a device including a nozzle 21a for injecting fuel into the combustion chamber of an internal combustion engine, and includes a supply pump 25, a common rail 23, and an injector 21.

The supply pump 25 is a pump that pumps fuel from the fuel tank 5 and sends it to the common rail 23, and is connected to the fuel tank 5 at the fuel supply path 9a. If the supply pump 25 can pump up the amount of fuel required for combustion of the internal combustion engine, a known piston type pump or internal cam type pump may be used.

The common rail 23 is a pressure accumulator chamber that temporarily holds the fuel supplied from the supply pump 25 at a predetermined target pressure and sends it to the injector 21, and is connected to the supply pump 25 by the fuel supply path 9b to provide fuel. Is supplied. Since the common rail 23 is a pressure accumulator chamber, it includes a pressure sensor 23a for detecting the internal pressure and a pressure adjusting valve 23b for adjusting the pressure.

The injector 21 is a device that injects fuel sent from the common rail 23 into the combustion chamber of an internal combustion engine for a predetermined injection time with a predetermined injection amount and injection pressure at a predetermined time, depending on the number of internal combustion engines. The number is provided. The injector 21 is connected to the common rail 23 at the fuel supply path 9c, and fuel is supplied. A nozzle 21a for injecting fuel is provided at the lower end of the injector 21, and the injection amount and injection time are adjusted by adjusting the opening and closing of the nozzle 21a with a solenoid valve or the like (not shown). Further, each injector 21 is provided with a check valve 27 that allows fuel to escape when the internal pressure exceeds the target pressure.

The fuel tank 5 is a tank that stores fuel and supplies it to the injection device 3. The fuel tank 5 can store a sufficient amount of fuel necessary for combustion of the internal combustion engine, and a known tank can be used as long as the components in the fuel do not corrode.

The recirculation path 7 is a flow path for recirculating fuel to the fuel tank 5 from the middle of the fuel flow path from the fuel tank 5 to the nozzle 21a. When the pressure in the common rail 23 or the injector 21 exceeds a predetermined target pressure, the return path 7 returns the fuel inside these to the fuel tank 5 to reduce the pressure to the target pressure. Specifically, the recirculation path 7 in FIG. 1 has a recirculation path 7a for recirculating fuel from the common rail 23 and a recirculation path 7b for recirculating fuel from the injector 21. That is, the common rail 23 is connected to the return path 7a, and the injector 21 is connected to the return path 7b. The return paths 7a and 7b merge in the middle to form the return path 7c, and the end of the return path 7c is connected to the fuel tank 5. The common rail 23 is provided with a pressure adjusting valve 23b as an openable / closable rail relief valve for adjusting the flow rate of fuel returning to the return passage 7a at a connection portion with the return passage 7a. In this configuration, the pressure of the common rail 23 can be adjusted by adjusting the valve opening degree of the pressure adjusting valve 23b to adjust the flow rate of the fuel returning to the return path 7a. The injector 21 is provided with a check valve 27 as an openable / closable injector relief valve for adjusting the flow rate of fuel recirculated to the recirculation path 7b at a connection portion with the recirculation path 7b. In this configuration, the pressure of the injector 21 can be adjusted by adjusting the valve opening degree of the check valve 27 to adjust the flow rate of the fuel returning to the return passage 7b. As the valve opening degree increases, the flow rate of fuel returned from the common rail 23 and the injector 21 to the fuel tank 5 via the return path 7 increases, so that the pressure of the common rail 23 and the injector 21 decreases. On the contrary, the smaller the valve opening degree, the smaller the flow rate of the fuel returned from the common rail 23 or the injector 21 to the fuel tank 5 via the return path 7, so that the pressure of the common rail 23 or the injector 21 increases.

The return path 7 also has a return path 7d for returning fuel from the supply pump 25 to the fuel tank 5.

The fuel property acquisition unit 13 is a device that acquires information related to the properties of the fuel stored in the fuel tank 5. Here, the property of the fuel means the physical property of the fuel, which is an index indicating the ease of clogging of the nozzle 21a, and specifically, the viscosity or the density of the fuel. This is because as the viscosity of the fuel increases, the viscous resistance increases, so that the injector 21 is likely to be clogged. This is because the higher the density of the fuel, the easier it is to wax and solidify in a low temperature environment, so that the nozzle 21a is easily clogged.

The fuel property acquisition unit 13 may be a device for directly acquiring the viscosity or density or an device for indirectly acquiring the viscosity or density as long as the information related to the fuel property can be acquired. Examples of the device for directly acquiring the viscosity and the density include a viscometer 13a for measuring the viscosity of the fuel in the tank 5 and a densitometer 13b for measuring the density, which are provided in the fuel tank 5 as shown in FIG. If the viscometer 13a and the density meter 13b are not corroded by fuel and can detect the viscosity and density with desired accuracy, a known sensor can be used.

Since the viscometer 13a and the density meter 13b are devices for detecting the cause of clogging the nozzle 21a, it is originally preferable to install the viscometer 13a and the density meter 13b at a position as close as possible to the nozzle 21a such as the injector 21 and the common rail 23. However, the injector 21 and the common rail 23 have a higher pressure than the inside of the fuel tank in order to set the fuel injection pressure to the target pressure, and the pressure pulsation is large due to repeated injection and stopping of the fuel. The densitometer 13b is unlikely to withstand this environment. Therefore, it is preferable to provide the viscometer 13a and the density meter 13b in the fuel tank 5.

Examples of the device for indirectly acquiring the viscosity and the density include a device for acquiring the position of the injection device 3 such as the GPS signal receiver 13c. GPS is an abbreviation for Global Positioning System. The reason why the viscosity and density can be indirectly acquired by the device that acquires the position is that the country or region where the inferior fuel or biofuel is used is determined to some extent, so it corresponds to the position coordinates received by the GPS signal receiver 13c. This is because if the country or region where the fuel is used is known, the properties of the fuel can also be identified. Specifically, for inferior fuels, there are countries and regions where the fuel refining method, the content rate of substances that cause an increase in viscosity and density, and the regulations related to them are loose. Biofuels include countries and regions with large-scale biofuel generators.

Since it is the position information that can be acquired by the GPS signal receiver 13c, in order to specify the fuel properties from the position information, the relationship between the position information and the fuel properties such as the viscosity and density of the fuel at that position Information indicating that is required separately. Information indicating the relationship between the position of the injection device 3 and the properties of the fuel used is referred to as fuel property position mapping 10 in the following description. The fuel property position mapping 10 is stored in advance by the control unit 11.

If there is at least one viscometer 13a, a density meter 13b, and a GPS signal receiver 13c, information on the properties of the fuel can be acquired. However, by providing two or more, redundancy may be increased when one of them fails.

The control unit 11 is a computer that controls the drive of the injection device 3, and in particular, is a computer that adjusts the opening and closing of the return path 7. The control unit 11 is electrically connected to the supply pump 25, the pressure adjusting valve 23b, the check valve 27, the solenoid of the injector 21, and the like, and transmits a signal for driving them. The control unit 11 is also electrically connected to the pressure sensor 23a, the viscometer 13a, the densitometer 13b, and the GPS signal receiver 13c, and a signal indicating the information acquired by these is input.

When the internal combustion engine is driven by the accelerator of the internal combustion engine being stepped on, the control unit 11 has a fuel injection amount, a fuel injection time, a fuel injection pressure, and a fuel injection timing based on the accelerator opening and the rotation speed of the internal combustion engine. To control. Therefore, the control unit 11 has a fuel injection amount map 11a, a fuel injection time map 11b, a fuel injection pressure map 11c, and fuel, which are information for determining the fuel injection amount, the fuel injection time, the fuel injection pressure, and the fuel injection timing. It has an injection timing map 11d.

The fuel injection amount map 11a is information showing the relationship between the accelerator opening degree, the rotation speed, and the fuel injection amount of the internal combustion engine, and specifically, is a function having these three variables as variables. The fuel injection time map 11b is a map showing the relationship between the fuel injection pressure, the fuel injection time, and the fuel injection amount, and is specifically a function having these three variables as variables. The fuel injection pressure map 11c is a map showing the relationship between the rotation speed of the internal combustion engine, the fuel injection amount, and the fuel injection pressure, and is specifically a function having these three variables as variables. The fuel injection timing map 11d is a map showing the relationship between the rotation speed of the internal combustion engine, the fuel injection amount, and the fuel injection timing, that is, the timing of injecting fuel, and specifically, it is a function having these three as variables.

When the accelerator of the internal combustion engine is stepped on, the control unit 11 acquires the accelerator opening degree from an accelerator opening degree sensor (not shown), and further acquires the rotation speed of the internal combustion engine by an engine rotation sensor or the like (not shown). Next, the acquired accelerator opening degree and rotation speed are substituted into the function of the fuel injection amount map 11a to obtain the fuel injection amount. Further, the acquired rotation speed and the obtained fuel injection amount are substituted into the function of the fuel injection pressure map 11c to obtain the fuel injection pressure. Further, the obtained fuel injection amount and fuel injection pressure are substituted into the function of the fuel injection time map 11b to obtain the fuel injection time. Further, the rotation speed and the fuel injection amount are substituted into the fuel injection timing map 11d to obtain the fuel injection timing. Finally, the control unit 11 controls the supply pump 25, the pressure adjusting valve 23b, and the injector 21 so as to inject fuel at the obtained fuel injection amount, fuel injection pressure, fuel injection time, and fuel injection timing.

However, the control unit 11 of the present embodiment identifies the fuel property from the information acquired by the fuel property acquisition unit 13, adjusts the opening degree of the recirculation path 7 according to the specified fuel property, and adjusts the fuel injection pressure. The pressure is controlled so that the nozzle 21a is not clogged. This control can be performed before the internal combustion engine is started, as long as the fuel property acquisition unit 13 can acquire information related to the fuel properties. For example, when new fuel is charged into the fuel tank 5 by refueling, the properties of the fuel in the tank change, so that refueling can be set as the control timing. When refueling is used as the control timing, the remaining amount of fuel may be obtained from the fuel gauge, and when the remaining amount of fuel increases, it may be determined that the fuel has been refueled. However, the properties of the fuel also change due to changes in the temperature inside the fuel tank 5 due to the external environment or deterioration due to changes in the fuel over time. Therefore, when a certain amount of time has passed since the previous control, for example, the operation of turning on the power by the ignition key immediately before the start of the internal combustion engine may be set as the control timing.

In this way, by adjusting the opening degree of the recirculation path 7 according to the properties of the fuel and controlling the fuel injection pressure to a pressure at which the nozzle 21a is not clogged, even when inferior fuel or biofuel is used, the fuel injection time is performed. Fuel clogging can be prevented before the internal combustion engine is started.

As a specific control, the control unit 11 controls the opening and closing of the return path 7 so that the fuel injection pressure becomes equal to or less than a predetermined upper limit injection pressure according to the properties of the fuel. The upper limit injection pressure is the upper limit of the fuel injection pressure at which the nozzle 21a is not clogged due to the properties of the corresponding fuel.

Generally, the larger the fuel injection pressure, the easier it is for the nozzle 21a to become clogged. Therefore, by setting the upper limit of the fuel injection pressure to the upper limit injection pressure, the pressure in the injection device 3, specifically, the pressure in the common rail 23 and the injector 21 does not exceed the injection pressure at which clogging may occur. You can surely prevent clogging.

However, if the fuel injection pressure to be set when the fuel is not inferior is a value exceeding the upper limit, and if the fuel is inferior fuel and the fuel injection pressure is simply suppressed to the upper limit or less, the internal combustion engine can be injected once. There is a possibility that the fuel supplied to the combustion chamber will be reduced and the combustion will be insufficient.

Therefore, it is preferable that the control unit 11 lengthens the fuel injection time as the fuel injection pressure decreases. When the fuel injection pressure is lowered in this way, if the fuel injection timing is lengthened, the reduction in the injection amount per unit time can be compensated for by extending the injection time by lowering the injection pressure.

Specifically, the control unit 11 injects fuel with a target injection amount predetermined according to the accelerator opening and the number of revolutions of the internal combustion engine, that is, the injection amount obtained by the fuel injection amount map 11a. And the fuel injection time should be adjusted. By adjusting the fuel injection pressure and fuel injection time without changing the target injection amount in this way, the injection time is extended according to the amount of decrease in the injection amount per unit time by lowering the injection pressure, and the target injection amount is extended. To maintain. Therefore, it is more advantageous in that the internal combustion engine can be driven according to the operation of the driver of the internal combustion engine such as the accelerator opening while preventing the fuel from being clogged.

When the fuel property acquisition unit 13 is a viscometer 13a or a densitometer 13b, the control unit 11 increases the opening degree of the recirculation path 7 as the viscosity or density of the fuel acquired by the viscometer 13a or the densitometer 13b increases. Control to reduce the pressure may be performed.

By actually measuring the viscosity or density of the fuel in this way and lowering the fuel injection pressure as these become larger, the physical properties directly linked to clogging are measured, so the injection pressure always drops when it is necessary to lower the fuel injection pressure. If it is not necessary to reduce the injection pressure, the injection pressure will not decrease.

When the fuel property acquisition unit 13 is the GPS signal receiver 13c, the control unit 11 identifies the fuel property from the position coordinates of the injection device 3 acquired by the GPS signal receiver 13c. Further, the opening degree of the return path 7 is adjusted according to the properties of the specified fuel, and the fuel injection pressure is controlled to a pressure at which the nozzle 21a is not clogged.

By specifying the fuel properties based on the position information of the injection device 3 in this way, if there is a device that acquires the position of the injection device 3 such as GPS without directly acquiring the fuel properties, the fuel properties can be obtained. The fuel injection pressure can be controlled accordingly.

Specific examples of the control in which the control unit 11 sets the upper limit of the fuel injection amount and the control in which the fuel injection timing is lengthened when the fuel injection pressure is lowered include the following means.

First, as shown in FIG. 1, a plurality of sets of the fuel injection time map 11b, the fuel injection pressure map 11c, and the fuel injection timing map 11d are stored in advance in the control unit 11 according to the properties of the fuel expected to be used. The plurality of fuel injection time maps 11b, fuel injection pressure map 11c, and fuel injection timing map 11d are functions so that the fuel injection pressure does not exceed the upper limit according to the properties of the fuel, and the fuel injection pressure is low. Is set so that the fuel injection time is long. Furthermore, it is a function that determines the fuel injection pressure and fuel injection time without changing the target injection amount.

Next, when the properties of the fuel in the fuel tank 5 change due to fuel being refueled to the fuel tank 5, the control unit 11 acquires information related to the fuel properties from the fuel property acquisition unit 13 and obtains information on the fuel properties of the fuel. Identify the properties. Further, the fuel injection time map 11b, the fuel injection pressure map 11c, and the fuel injection timing map 11d corresponding to the specified fuel properties are selected. After that, fuel injection control may be performed using the selected fuel injection time map 11b, fuel injection pressure map 11c, and fuel injection timing map 11d as long as the fuel properties do not change due to refueling of new fuel or the like. ..

In this way, the control unit 11 selects a set of fuel injection time map 11b, fuel injection pressure map 11c, and fuel injection timing map 11d corresponding to the properties of the fuel, and the fuel injection time, fuel injection pressure, and fuel injection pressure. The fuel injection timing may be determined.

In this configuration, the fuel injection pressure, fuel injection amount, fuel injection timing, and fuel injection time are determined in advance according to the fuel properties and the rotation speed of the internal combustion engine. Therefore, when the injection conditions are determined according to the fuel properties, these are used. It is not necessary for the control unit 11 to calculate the condition of. The fuel injection amount map 11a is a map for obtaining the fuel injection amount, but since the fuel injection amount does not change depending on the fuel properties, it is not necessary to prepare a plurality of fuel injection amount maps 11a according to the fuel properties. Therefore, the control unit 11 determines the fuel injection amount from one fuel injection amount map 11a regardless of the fuel properties. The control unit 11 applies the determined fuel injection amount and the rotation speed of the internal combustion engine to a set of fuel injection time map 11b, fuel injection pressure map 11c, and fuel injection timing map 11d selected according to the properties of the fuel to fuel the fuel. Obtain the injection time, fuel injection pressure, and fuel injection timing.

When the internal combustion engine is driven after the upper limit of the fuel injection amount is set according to the fuel properties in this way, the control unit 11 controls the injection device 3 to control the recirculation path 7 according to the fuel properties. The opening degree is adjusted to control the fuel injection pressure to a pressure at which the nozzle 21a is not clogged.

Specifically, it is preferable that the control unit 11 adjusts the opening degree of the return path 7 by adjusting the valve opening degree of the pressure adjusting valve 23b of the common rail 23. This is because the common rail 23 is a pressure accumulator chamber, so that a pressure sensor 23a is provided, and the pressure sensor 23a can be diverted to pressure control.

The control unit 11 may adjust the opening degree of the return path 7 by adjusting the valve opening degree of the check valve 27 of each injector 21. This configuration is advantageous in that clogging can be prevented for each individual injector 21. The above is a description of the schematic configuration of the fuel injection system 1 according to the embodiment of the present disclosure.

Next, the control method of the fuel injection system 1 according to the embodiment of the present disclosure will be described with reference to FIGS. 2 and 3. First, a pressure adjusting method before starting the internal combustion engine will be described with reference to FIG.

When the properties of the fuel in the tank change due to fuel being refueled to the fuel tank 5, the control unit 11 acquires information related to the fuel properties using the fuel property acquisition unit 13 (S1, in FIG. 2). Fuel property acquisition process). Specifically, when the fuel property acquisition unit 13 is a viscometer 13a or a densitometer 13b, the density and viscosity of the fuel in the fuel tank 5 are measured. When the fuel property acquisition unit 13 is the GPS signal receiver 13c, the position coordinates of the injection device 3 are acquired.

Next, the control unit 11 specifies the fuel properties from the information related to the fuel properties acquired in S1 (S2 in FIG. 2, the specific step). When the fuel property acquisition unit 13 is a viscometer 13a or a density meter 13b, the viscosity and density acquired in S1 are used as the fuel properties. When the fuel property acquisition unit 13 is the GPS signal receiver 13c, the position coordinates acquired in S1 are applied to the fuel property position mapping 10, and the fuel properties such as the viscosity and density of the fuel corresponding to the position are specified.

Next, the control unit 11 adjusts the opening degree of the recirculation path 7 according to the properties of the fuel specified in S2 to control the fuel injection pressure to a pressure at which the nozzle 21a is not clogged (S3 in FIG. 2, pressure adjusting step). Specifically, a set of fuel injection time map 11b, fuel injection pressure map 11c, and fuel injection timing map 11d corresponding to the properties of the fuel specified in S2 are selected. The above is the description of the pressure adjustment method before starting the internal combustion engine. The control of S1 to S3 is a feedforward control in which the upper limit of the pressure is determined before the start of the internal combustion engine and the injection device 3 is controlled so as not to exceed the upper limit. On the other hand, an example of feedback control in which the pressure of the injection device 3 being driven after the start of the internal combustion engine is detected and the pressure is controlled based on the detected value will also be briefly described with reference to FIG.

First, the control unit 11 detects the accelerator opening degree and the rotation speed of the internal combustion engine (S11 in FIG. 3). The control unit 11 applies the detected accelerator opening degree and rotation speed to the fuel injection amount map 11a to obtain the fuel injection amount. Further, the fuel injection time, the fuel injection pressure, and the fuel injection timing are determined from the obtained fuel injection amount, the fuel injection time map 11b, the fuel injection pressure map 11c, and the fuel injection timing map 11d selected in advance (FIG. 3). S12). Next, the control unit 11 controls the common rail 23 and the injector 21 so as to inject fuel into the combustion chamber at the fuel injection amount, the fuel injection time, the fuel injection pressure, and the fuel injection timing determined in S12 (S13 in FIG. 3). ..

Next, the control unit 11 detects the pressure of the common rail 23 or the pressure in the injector 21 by using a pressure sensor 23a or a pressure sensor (not shown) provided in the injector 21 (S14 in FIG. 3). Next, the control unit 11 refers to the fuel injection pressure map 11c and the like, determines whether or not the pressure detected in S14 exceeds a predetermined upper limit value according to the fuel properties, and if it exceeds the upper limit value, causes S16. If the upper limit is not exceeded, the process proceeds to S17 (S15 in FIG. 3).

When it is determined in S15 that the pressure exceeds the upper limit value, the control unit 11 opens the pressure adjusting valve 23b or the check valve 27 to reduce the pressure to the upper limit or less and return (S16 in FIG. 3). If the pressure adjusting valve 23b or the check valve 27 has already been opened, the valve opening degree is increased and the valve returns. If the pressure does not exceed the upper limit in S15, the pressure adjustment valve 23b and the check valve 27 are not opened, and if they are already open, they are closed or the opening is lowered to return (S17 in FIG. 3). .. The above is an explanation of an example of feedback control in which the pressure of the injection device 3 being driven after the start of the internal combustion engine is detected and the pressure is controlled based on the detected value.

As described above, the fuel injection system 1 of the present embodiment identifies the fuel properties from the information acquired by the fuel property acquisition unit 13, and adjusts the opening degree of the recirculation path 7 according to the specified fuel properties to adjust the fuel injection pressure. Is controlled to a pressure at which the nozzle 21a is not clogged. Therefore, even when biofuel or inferior fuel is used, it is possible to prevent fuel clogging at the time of fuel injection before starting the internal combustion engine.

Although the present disclosure has been described above based on the embodiments, the present disclosure is not limited to the embodiments. It is natural for a person skilled in the art to come up with various modifications and improvements within the scope of the technical idea of the present disclosure, and these are also naturally included in the present disclosure.

For example, in the above-described embodiment, the viscosity and density of the fuel are mentioned as the properties of the fuel, but the properties of the fuel are not limited to the viscosity and the density as long as the physical properties of the fuel are indicators of the ease of clogging of the nozzle 21a. For example, a physical characteristic value indicating the degree of waxing of the fuel may be used as the property of the fuel.

1: Fuel injection system 3: Injection device 5: Fuel tank 7, 7a, 7b, 7c, 7d: Circulation path 9a, 9b, 9c: Fuel supply path 10: Fuel property position mapping 11: Control unit 11a: Fuel injection amount map 11b: Fuel injection time map 11c: Fuel injection pressure map 11d: Fuel injection timing map 13: Fuel property acquisition unit 13a: Viscometer 13b: Density meter 13c: GPS signal receiver 21: Injector 21a: Nozzle 23: Common rail 23a: Pressure Sensor 23b: Pressure adjustment valve 25: Supply pump 27: Check valve

Claims (10)

An injection device provided with a nozzle for injecting fuel into the combustion chamber of the internal combustion engine, a fuel tank for supplying fuel to the injection device, and fuel being supplied to the fuel tank from the middle of the fuel flow path from the fuel tank to the nozzle. A fuel injection system including a recirculating recirculation path that can be opened and closed and a control unit that adjusts the opening and closing of the recirculation path.
Equipped with a fuel property acquisition unit that acquires information related to fuel properties,
The control unit
The fuel property is specified from the information acquired by the fuel property acquisition unit, and the opening degree of the recirculation path is adjusted according to the specified fuel property to control the fuel injection pressure to a pressure at which the nozzle is not clogged. Featuring fuel injection system. The control unit
The fuel injection system according to claim 1, wherein the opening / closing of the recirculation path is controlled so that the fuel injection pressure becomes equal to or lower than a predetermined upper limit injection pressure according to the properties of the fuel. The control unit
The fuel injection system according to claim 1 or 2, wherein the fuel injection time is lengthened as the fuel injection pressure decreases. The control unit
The fuel injection system according to claim 3, wherein the fuel injection pressure and the fuel injection time are adjusted so that the fuel is injected at a predetermined target injection amount according to the accelerator opening degree and the rotation speed of the internal combustion engine. The fuel property acquisition unit is a device that acquires the viscosity or density of the fuel as the property of the fuel.
Any of claims 1 to 4, wherein the control unit controls to increase the opening degree of the recirculation path and reduce the fuel injection pressure as the viscosity or density of the fuel acquired by the fuel property acquisition unit increases. The fuel injection system according to item 1. The fuel property acquisition unit is a device that acquires the position coordinates of the injection device.
The control unit
The fuel property position mapping indicating the relationship between the position of the injection device and the property of the fuel used is stored in advance.
The fuel injection system according to any one of claims 1 to 5, which specifies the properties of the fuel used from the position coordinates of the injection device acquired by the fuel property acquisition unit. The control unit
A fuel injection time map showing the relationship between fuel injection pressure, fuel injection time, and fuel injection amount,
A fuel injection pressure map showing the relationship between the rotation speed of the internal combustion engine, the fuel injection amount, and the fuel injection pressure,
A fuel injection timing map showing the relationship between the rotation speed of the internal combustion engine, the fuel injection amount, and the fuel injection timing,
Multiple sets are stored in advance according to the properties of the fuel.
Further, a fuel injection amount map showing the relationship between the accelerator opening, the rotation speed, and the fuel injection amount of the internal combustion engine is stored in advance.
The fuel injection amount is determined from the fuel injection amount map regardless of the fuel properties, and a set of the fuel injection time map, the fuel injection pressure map, and the fuel injection timing map are selected according to the fuel properties. The fuel injection system according to any one of claims 1 to 6, wherein the fuel injection time, the fuel injection pressure, and the fuel injection timing are determined. The injection device is
Injectors provided with the nozzles and provided in the number corresponding to the number of combustion chambers,
It is provided with a common rail which is a pressure accumulator chamber connected to the injector and the fuel tank to hold the fuel supplied from the fuel tank at a predetermined pressure and send it to the injector.
The common rail is connected to the recirculation path, and an openable / closable rail relief valve for adjusting the flow rate of fuel recirculated to the recirculation path is provided at the connection portion with the recirculation path.
The control unit
A request for controlling the fuel injection pressure by adjusting the pressure in the common rail by adjusting the opening degree of the rail relief valve according to the properties of the specified fuel and adjusting the flow rate of the fuel returned to the return path. Item 6. The fuel injection system according to any one of Items 1 to 7. The injection device is
The nozzle is provided, and a plurality of injectors of the number corresponding to the number of the combustion chambers are provided.
The injector is connected to the recirculation path, and an openable / closable injector relief valve for adjusting the flow rate of fuel recirculated to the recirculation path is provided at the connection portion with the recirculation path.
The control unit
A request for controlling the fuel injection pressure by adjusting the pressure in the injector by adjusting the opening degree of the injector relief valve according to the specified fuel properties and adjusting the flow rate of the fuel returned to the return path. Item 6. The fuel injection system according to any one of Items 1 to 7. An injection device provided with a nozzle for injecting fuel into the combustion chamber of the internal combustion engine, a fuel tank for supplying fuel to the injection device, and fuel being supplied to the fuel tank from the middle of the fuel flow path from the fuel tank to the nozzle. It is a control method of a fuel injection system having an openable and closable return path for recirculation.
The fuel property acquisition process for acquiring information related to fuel properties, and
A specific process for identifying fuel properties from the information acquired in the fuel property acquisition process, and
A pressure adjusting step of adjusting the opening degree of the return path according to the properties of the fuel specified in the specific step to control the fuel injection pressure to a pressure at which the nozzle is not clogged.
A method of controlling a fuel injection system, characterized in that.

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