JP2015010509A - Fuel injection system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the abnormal injection of a hydraulically-actuated fuel injection valve.SOLUTION: A fuel injection system for an internal combustion engine includes the hydraulically-actuated fuel injection valve for injecting fuel to be supplied into the internal combustion engine. The fuel injection system has means for acquiring a fuel pressure value and a hydraulic fluid pressure value. The fuel pressure value is a value for the pressure of the fuel to be supplied into the fuel injection valve or a value having correlation with the pressure of the fuel. Similarly, the hydraulic fluid pressure value is a value for the pressure of hydraulic fluid to be supplied into a pressure control chamber or a value having correlation with the pressure of the hydraulic fluid. The fuel injection system according to the present invention reduces the pressure of the fuel to be supplied to the fuel injection valve when a difference between a first reference value set according to the hydraulic fluid pressure value and the fuel pressure value is smaller than a first threshold value.

Description

  The present invention relates to a fuel injection device for an internal combustion engine. More specifically, the present invention relates to a fuel injection device including a hydraulically operated fuel injection valve.

  For example, Patent Document 1 discloses an injector that is a fuel injection valve for injecting gaseous fuel. This injector has a needle valve that opens and closes an injection hole by moving up and down. The needle valve is urged in the valve closing direction by the pressure in the control chamber and the spring. In addition, this injector has a solenoid valve in the upper part of the control chamber. When the solenoid valve is not energized, the control chamber and the hydraulic oil return path are disconnected, and when energized, the control chamber and the return path are in communication. The hydraulic oil in the control chamber is increased or decreased by switching between the shut-off and the communication state, thereby increasing or decreasing the pressure in the control chamber. As the pressure in the control chamber increases or decreases, the urging force applied to the needle valve increases or decreases, and the needle valve is opened or closed.

JP 2009-281298 A JP 2010-174736 A JP 2005-248743 A JP 2007-332879 A JP 2003-148274 A

  In the case of the two-fluid fuel injection valve as in Patent Document 1, the control chamber pressure and the spring load due to the hydraulic oil act as the valve closing force of the needle valve, and the pressure of the fuel gas and the pressure of the sack portion (valve closing) In-cylinder pressure) acts as a valve opening force of the needle valve. Here, the hydraulic oil and the fuel are supplied separately. For this reason, the balance between the hydraulic oil pressure and the fuel gas pressure may be biased. When the fuel gas pressure rises above the set pressure, the fuel opens the needle valve due to the closing force applied to the needle valve. The valve force may be larger. In such a case, an abnormal injection of gaseous fuel may occur.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel injection device for an internal combustion engine which is improved to suppress abnormal injection by a hydraulically operated fuel injection valve for injecting fuel.

  The present invention is a fuel injection device for an internal combustion engine that achieves the above object, and includes a hydraulically operated fuel injection valve that injects fuel supplied to the internal combustion engine. The fuel injection valve is connected to a fuel supply path that supplies fuel to the fuel injection valve. In addition, a hydraulic oil supply path for supplying hydraulic oil to the pressure control chamber is connected to the pressure control chamber that controls the pressure that biases the needle valve that opens and closes the nozzle hole of the fuel injection valve in the valve closing direction. A shut-off valve that opens and closes the fuel supply path is installed in the fuel supply path. The fuel injection device has means for acquiring a fuel pressure value and a hydraulic oil pressure value. Here, the fuel pressure value is a value of the pressure of the fuel supplied to the fuel injection valve or a value correlated with the pressure of the fuel. Similarly, the hydraulic oil pressure value is a value of the hydraulic oil pressure supplied to the pressure control chamber or a value having a correlation with the hydraulic oil pressure. The fuel injection device of the present invention is supplied to the fuel injection valve when the difference between the first reference value set according to the hydraulic oil pressure value and the fuel pressure value is smaller than the first threshold value. Pressure reducing means for reducing the pressure of the fuel.

  The first reference value in the present invention is a value that is appropriately set according to the hydraulic oil pressure value. Further, the first reference value or the first threshold value may be corrected according to a pressure increase capability value that correlates with a capability of increasing or decreasing the pressure of the hydraulic fluid by the means for increasing or decreasing the hydraulic fluid pressure. Further, the first reference value or the first threshold value may be further corrected in accordance with a pressure in the fuel tank or a tank pressure value and a fuel pressure value, which are values correlated therewith.

  The fuel injection valve of the present invention is connected to the fuel supply passage, and has a pressure relief passage for allowing the fuel in the fuel supply passage to flow out of the fuel supply passage, and a pressure relief valve for opening and closing the pressure relief passage. May be. In this case, the pressure relief valve may be opened when the difference between the second reference value and the fuel pressure value is smaller than the second threshold value. Here, the second reference value is a value set according to the hydraulic oil pressure value. When the first reference value and the second reference value are used in this way, the second reference value is set to a value larger than the first reference value, or the second threshold value is smaller than the first threshold value. Set to a value.

  In the above invention, the first threshold value or the second threshold value is the balance between the force in the valve closing direction applied to the needle valve and the force in the valve opening direction in addition to the pressure in the pressure control chamber, and the first reference value and the hydraulic oil pressure. It is a value set as appropriate based on the relationship with the value. Therefore, for example, the first threshold value may be zero. In this case, in other words, the fuel injection device of the present invention closes the shutoff valve when the fuel pressure value exceeds the first reference value.

  Further, the pressure reducing means can reduce the fuel pressure by closing the shutoff valve. In the case of the above-described configuration including the pressure relief passage and the pressure relief valve, the pressure reducing means may reduce the fuel pressure by opening the pressure relief valve.

  According to the present invention, when the difference between the first reference value set according to the hydraulic pressure value and the fuel pressure value becomes smaller than the first threshold value, the fuel pressure is reduced. As a result, the occurrence of abnormal injection due to an increase in fuel pressure can be suppressed. The first reference value to be compared with the fuel pressure value is set according to the operating oil pressure. Accordingly, it is determined whether or not abnormal injection can occur in relation to not only the fuel pressure value but also the hydraulic oil pressure and the fuel pressure. Therefore, since a state in which abnormal injection can occur is predicted with higher accuracy, control for reducing the fuel pressure can be performed only when necessary.

It is a schematic diagram for demonstrating the whole structure of the system of Embodiment 1 of this invention. It is a schematic diagram for demonstrating the injector in Embodiment 1 of this invention. It is a timing chart for demonstrating the control in Embodiment 1 of this invention. It is a timing chart for demonstrating the control in Embodiment 1 of this invention. It is a flowchart for demonstrating the control routine which a control apparatus performs in Embodiment 1 of this invention. It is a flowchart for demonstrating the control routine which a control apparatus performs in Embodiment 2 of this invention. It is a figure for demonstrating the base value of the 1st upper limit value in Embodiment 3 of this invention, the 1st upper limit value, and the 2nd upper limit value. It is a figure for demonstrating the relationship between the pressure | voltage rise capability and offset value in Embodiment 3 of this invention. It is a figure for demonstrating the relationship between the differential pressure | voltage of the pressure of a fuel tank and the pressure of a fuel, and a correction coefficient in Embodiment 3 of this invention. It is a flowchart for demonstrating the control routine which a control apparatus performs in Embodiment 3 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is simplified or omitted.

Embodiment 1 FIG.
[Overall Configuration of System of Embodiment 1]
FIG. 1 is a diagram for explaining the overall configuration of the system according to the first embodiment of the present invention. The system of FIG. 1 has an internal combustion engine 2. The internal combustion engine 2 can use hydrogen as a fuel, and can be preferably used as a power source of a vehicle, for example. The internal combustion engine 2 is provided with a plurality of cylinders. An intake passage 4 communicates with the intake port of each cylinder of the internal combustion engine 2. An exhaust passage 6 communicates with the exhaust port of each cylinder of the internal combustion engine 2.

  Each cylinder of the internal combustion engine 2 is provided with an injector 10 for injecting hydrogen as fuel into the cylinder. The injector 10 is a hydraulically operated electronically controlled fuel injection valve. The injector 10 for each cylinder has a fuel passage 12. A fuel supply port (not shown) for receiving fuel supply from the outside is provided at the end of the fuel passage 12, and is connected to a common fuel delivery pipe 14 at the fuel supply port of the fuel passage 12.

  A fuel pressure sensor 16 is installed in the fuel delivery pipe 14. The fuel pressure sensor 16 can detect the pressure of the fuel in the fuel delivery pipe 14 (hereinafter also referred to as “fuel pressure”). A fuel line 18 is connected to the fuel delivery pipe 14. The fuel line 18 branches into branch passages 20, 22, 24 on the upstream side. The upstream end of the branch passage 20 is connected to the high-pressure hydrogen fuel tank 26, and the upstream end of the branch passage 22 is connected to the high-pressure hydrogen fuel tank 28. The branch passages 20 and 22 are respectively provided with main stop valves 30 and 32 for opening and closing the branch passages 20 and 22. The branch passage 24 is connected to a fuel filling port 34.

  A tank pressure sensor 36 for detecting the pressure of the hydrogen fuel from the high-pressure hydrogen fuel tank 26 or 28 is installed in the vicinity of the branch point to the branch passages 20 and 22 of the fuel line 18. A pressure reducing mechanism 38 is installed downstream from the branch point of the fuel line 18. The decompression mechanism 38 is a device that decompresses the fuel compressed to a high pressure stepwise to a target value. A shutoff valve 40 for opening and closing the fuel line 18 is installed on the downstream side of the pressure reducing mechanism 38 of the fuel line 18.

  Further, a pressure release line 42 (pressure release passage) is connected to the fuel delivery pipe 14. The pressure release line 42 is provided with a pressure release valve 44 for opening and closing the pressure release line 42. By opening the pressure relief valve 44, the fuel in the fuel delivery pipe 14 can be led out from the fuel delivery pipe 14 to the pressure relief line 42 side.

  In addition, the injector 10 of each cylinder has a hydraulic oil passage 50. A hydraulic oil supply port (not shown) for receiving the supply of hydraulic oil from the outside is provided at the end of the hydraulic oil passage 50, and the hydraulic oil passage 50 is connected to the hydraulic oil delivery pipe at the hydraulic oil supply port. 52.

  A hydraulic pressure sensor 54 is installed in the hydraulic oil delivery pipe 52. The hydraulic pressure sensor 54 can detect the pressure of hydraulic fluid introduced into the hydraulic fluid delivery pipe 52 (hereinafter also referred to as “hydraulic pressure”). A hydraulic oil line 56 is connected to the hydraulic oil delivery pipe 52, and the hydraulic oil line 56 is connected to a hydraulic oil pump 58. The upstream side of the hydraulic oil pump 58 is connected to a hydraulic oil supply unit (not shown). As the hydraulic oil, for example, light oil, gasoline, engine oil or the like is used. The hydraulic oil is introduced into the hydraulic oil line 56 from the hydraulic oil supply unit by the hydraulic oil pump 58, and the hydraulic oil is supplied to the injector 10 through the hydraulic oil delivery pipe 52 and the hydraulic oil passage 50.

  The system in FIG. 1 includes an ECU 60. The ECU 60 is a control device that controls the operation of the internal combustion engine. The ECU 60 captures and processes signals from various sensors including the fuel pressure sensor 16, the hydraulic pressure sensor 54, and the tank pressure sensor 36. Various sensors are attached to the internal combustion engine 2 and various parts of the vehicle. The ECU 60 processes the signals of the acquired sensors and operates the actuators according to a predetermined control program. The actuators operated by the ECU 60 include the solenoid valve of the injector 10, the main stop valves 30, 32, the shutoff valve 40, the pressure relief valve 44, and the like. There are many actuators and sensors connected to the ECU 60 other than those shown in the figure, but the description thereof is omitted in this specification.

[Configuration of Injector of Embodiment 1]
FIG. 2 is a diagram for explaining the injector 10 according to the first embodiment. FIG. 2 shows an enlarged part of the injector 10. The fuel passage 12 of the injector 10 extends inside the body of the injector 10 and is connected to a nozzle chamber 72 formed between the needle valve 70 and the body. The needle valve 70 is built in the body of the injector 10 so as to be movable in the axial direction. The nozzle hole formed at the tip of the body is opened and closed by the axial movement of the needle valve 70, and gaseous fuel is injected from the nozzle hole while the nozzle hole is open.

  The end of the needle valve 70 opposite to the nozzle hole is in contact with the command piston 74. The command piston 74 is disposed in the body so as to be movable in the axial direction. A spring 76 that urges the needle valve 70 toward the valve closing side is provided in the vicinity of the end of the command piston 74 that is in contact with the needle valve 70.

  The end of the command piston 74 opposite to the needle valve 70 constitutes the wall surface of the control chamber 78 (pressure control chamber). A hydraulic oil passage 50 communicates with the control chamber 78, and hydraulic oil is supplied from the hydraulic oil passage 50 into the control chamber 78. With this configuration, the pressure of the hydraulic oil in the control chamber 78 acts on the command piston 74.

  In addition, a return passage 80 communicates with the control chamber 78. A solenoid valve 88 is installed between the control chamber 78 and the return passage 80. The valve 88 of the electromagnetic valve is biased in the valve closing direction by a spring 90. The solenoid valve blocks between the control chamber 78 and the return passage 80 by the biasing force of the spring 90 when not energized. On the other hand, when energized, the solenoid valve brings the control chamber 78 and the return passage 80 into communication with each other by the valve 88 being sucked in the valve opening direction.

[Operation of Injector of Embodiment 1]
The fuel injection by the injector 10 configured as described above is basically controlled by increasing or decreasing the pressure in the control chamber 78 by switching between energization and non-energization of the solenoid valve. By the way, the main forces acting on the needle valve 70 of the injector 10 are (1) pressure in the control chamber 78, (2) urging force by the spring 76, (3) pressure in the nozzle chamber 72, and (4) sack pressure (or valve closing). Time is in-cylinder pressure). Of these, the above (1) and (2) act as a valve closing force that urges the needle valve 70 toward the valve closing side, and (3) and (4) urge the needle valve 70 in the valve opening direction. Acts as a valve opening force.

  The pressure in the control chamber 78 of (1) varies depending on the hydraulic pressure and switching between deenergization and energization of the solenoid valve. That is, since the return passage 80 is closed when the solenoid valve is not energized, the pressure in the control chamber 78 in (1) becomes a high pressure state corresponding to the oil pressure. On the other hand, when the solenoid valve is energized, the hydraulic oil flows into the return passage 80, so that the control chamber pressure in (1) is low. The pressure in the nozzle chamber 72 (3) and the pressure in the sac chamber (4) both vary depending on the fuel pressure.

  Therefore, in order to ensure that the valve closing force is greater than the valve opening force when the solenoid valve is not energized and the valve opening force is greater than the valve closing force when the solenoid valve is energized, it is necessary to The balance is required to be maintained within an appropriate range.

[Control of this embodiment]
Therefore, in the first embodiment, the ECU 60 executes the following control for adjusting the differential pressure between the hydraulic pressure and the fuel pressure. 3 and 4 are timing charts for explaining the control in Embodiment 1 of the present invention. FIG. 3 shows an example when the hydraulic pressure is high, and FIG. 4 shows an example when the hydraulic pressure is low. 3 and 4, the broken line of the hydraulic pressure is a value obtained by subtracting a certain differential pressure required for the hydraulic pressure and the fuel pressure from the actual hydraulic pressure. That is, the broken line of the hydraulic pressure indicates the first upper limit value that is the upper limit value that allows the fuel pressure to rise.

  For example, in the example shown in FIG. 3, at time t1, the solenoid valve is energized and fuel injection is started. Although the hydraulic pressure and the fuel pressure are temporarily decreased by the start of fuel injection, the hydraulic pressure and the fuel pressure are gradually increased toward the respective target values by feedback control. Thereafter, fuel injection is stopped at time t2. The fuel pressure is kept high until the time t3 when the fuel injection is started next after the fuel injection is stopped at the time t2. In the example of FIG. 3, the fuel pressure is kept lower than the first reference value, and a necessary differential pressure is ensured between the hydraulic pressure and the fuel pressure. Accordingly, the shutoff valve 40 is maintained in the open state.

  On the other hand, in the example shown in FIG. 4, when fuel injection is started at time t4, similarly, after the oil pressure and the fuel pressure are temporarily reduced, the fuel pressure is increased by feedback control. On the other hand, the hydraulic pressure once rises and then decreases again. In the example of FIG. 4, after the fuel injection valve is closed at time t5, the fuel pressure exceeds the first upper limit value at time t6. As described above, when the fuel pressure exceeds the first upper limit value, it is determined that a necessary differential pressure is not secured between the fuel pressure and the hydraulic pressure. Accordingly, at the same time t6 when such a state is reached, the shutoff valve 40 is closed. The fuel supply from the fuel line 18 is stopped by closing the shutoff valve 40. Thereafter, the fuel injection from the injector 10 is performed again at time t7 while the shutoff valve 40 is maintained in the closed state. As a result, the fuel pressure starts to decrease and is returned to a state smaller than the first upper limit value.

  In the control of the present embodiment, the first upper limit value that is the upper limit value of the fuel pressure is set according to the hydraulic pressure. The relationship between the first upper limit value and the hydraulic pressure is stored in advance in the ECU 60 as a map. The relationship between the first upper limit value and the hydraulic pressure is set as appropriate based on the differential pressure between the hydraulic pressure and the fuel pressure, which is necessary to ensure a correct balance between the valve closing force and the valve opening force. The required differential pressure varies depending on the configuration of the injector 10, and can be obtained by experiments, simulations, or the like.

  Further, in the present embodiment, when the fuel pressure exceeds the first upper limit value, the shutoff valve 40 is closed and the hydraulic pressure increase control for increasing the hydraulic pressure by the hydraulic oil pump 58 is executed. As a result, the differential pressure between the hydraulic pressure and the fuel pressure can be increased early.

[Specific Control of this Embodiment]
FIG. 5 is a flowchart for illustrating a control routine executed by ECU 60 in the first embodiment of the present invention. The routine of FIG. 5 is a routine that is repeatedly executed at regular intervals during the operation of the internal combustion engine 2. In the routine of FIG. 5, first, in step S102, the hydraulic pressure epcr is detected. The ECU 60 takes in the output of the hydraulic pressure sensor 54 and detects the hydraulic pressure epcr corresponding thereto.

  Next, in step S104, the fuel pressure epr is detected. Here, the output of the fuel pressure sensor 16 is taken into the ECU 60, and the fuel pressure epr is detected accordingly. Next, in step S106, a first upper limit value mx1 is set. The first upper limit value mx1 is obtained according to a map or the like that defines the relationship between the hydraulic pressure epcr and the first upper limit value mx1 stored in advance in the ECU 60 in accordance with the hydraulic pressure epcr detected in step S102.

  Next, in step S108, it is determined whether or not the fuel pressure epr detected in step S106 is greater than the first upper limit value mx1 set in step S104. In step S108, when it is not recognized that the fuel pressure epr is larger than the first upper limit value mx1, the process proceeds to step S110, the cutoff valve 40 is maintained at the current opening degree, and the control of the fuel pressure at the normal time is maintained.

  On the other hand, if it is determined in step S108 that the fuel pressure epr is greater than the first upper limit value mx1, then in step S112, the shutoff valve 40 is closed. The shut-off valve 40 is closed by a control signal from the ECU 60. As a result, the fuel supply to the fuel delivery pipe 14 is temporarily stopped, and the fuel pressure is reduced by the next fuel injection. Next, hydraulic pressure increase control is executed in step S114. The hydraulic pressure is increased by operating the hydraulic oil pump 58 according to a control signal from the ECU 60. Thereafter, the current process is temporarily terminated.

  As described above, according to the present embodiment, when the fuel pressure becomes larger than the first reference value set in accordance with the oil pressure, the control for decreasing the fuel pressure and increasing the oil pressure is performed. Thereby, when the differential pressure between the fuel pressure and the hydraulic pressure becomes smaller than the allowable range, the balance between the valve opening force and the valve closing force of the injector 10 can be returned to the correct state. Therefore, abnormal injection of the injector 10 can be suppressed.

  Also, for example, if the upper limit value for the fuel pressure is a fixed value and the shutoff valve is closed when the fuel pressure exceeds the upper limit value (fixed value), there is a sufficient differential pressure between the hydraulic pressure and the fuel pressure. Even in this state, the shut-off valve may be closed. On the other hand, in the present embodiment, the upper limit value for the fuel pressure is set according to the oil pressure. Accordingly, the shutoff valve 40 can be prevented from closing until the fuel pressure is sufficiently smaller than the hydraulic pressure, and deterioration of the shutoff valve 40 due to an increase in the number of opening / closing operations can be suppressed.

  In the present embodiment, the example has been described in which the differential pressure required for the hydraulic pressure and the fuel pressure is a fixed value, and the value obtained by subtracting the fixed value from the hydraulic pressure is the first upper limit value. However, in the present invention, the necessary differential pressure between the hydraulic pressure and the fuel pressure is not limited to a constant value in the entire pressure range. Therefore, in the present invention, the first upper limit value may be set as appropriate according to the oil pressure, and for example, a value obtained by multiplying the oil pressure by a certain coefficient may be used as the first upper limit value. The same applies to the following embodiments.

  In the present invention, the case where the shutoff valve 40 is closed when the fuel pressure exceeds the first upper limit value set according to the hydraulic pressure has been described. However, the present invention is not limited to this, and the shutoff valve 40 may be closed when the difference between the fuel pressure and the first upper limit value exceeds the first threshold value. In other words, the embodiment is an example in which the first threshold value is set to 0, and the value obtained by reducing the required differential pressure from the hydraulic pressure is used as the first reference value. However, for example, the first reference value set according to the oil pressure is calculated according to the detected oil pressure, in addition to the detected value of the oil pressure, the average value, the smoothed value, and the estimated value of the detected oil pressure. A value related to the hydraulic pressure may be set as the first reference value. In this case, the first threshold value is set according to the differential pressure required for the hydraulic pressure and the fuel pressure, and when the differential pressure between the first reference value and the fuel pressure exceeds the first threshold value, the cutoff valve What is necessary is just to control so that 40 may be closed. In this case, the first threshold value may be a value set according to the hydraulic pressure or the fuel pressure. The same applies to the following embodiments.

  In the present embodiment, the case where the first reference value corresponding to the hydraulic pressure is set to be higher than the fuel pressure if the injector 10 is normal has been described. However, the present invention is not limited to this. For example, the fuel pressure may be set to a balance smaller than the hydraulic pressure by increasing the biasing force of the spring 76 of the injector 10. As described above, even in the case of an injector that is used in a balance where the fuel pressure is higher than the hydraulic pressure even during normal operation, the control according to the present invention is the difference between the first reference value set according to the hydraulic pressure and the fuel pressure. Whether or not the control for reducing the fuel pressure is to be performed may be determined based on whether or not “1 reference value−fuel pressure” is smaller than the first threshold value. Also, this determination can be made in the same manner based on, for example, the ratio between the first reference value and the fuel pressure. For example, when “fuel pressure / first reference value”, which is the ratio of the fuel pressure to the first reference value, is smaller than the first threshold value, control for reducing the fuel pressure may be performed. The same applies to the following embodiments.

  In the present embodiment, the case where the fuel pressure is reduced by the control for closing the shutoff valve 40 when the difference between the fuel pressure and the hydraulic pressure becomes small has been described. However, the present invention is not limited to this. For example, the fuel pressure may be reduced by closing the main stop valve 30 or 32, or the fuel pressure may be reduced by opening the pressure relief valve 44. It is good also as what makes it. The same applies to the following embodiments.

  Moreover, in this Embodiment, the case where acquisition of fuel pressure and hydraulic pressure, control of the electromagnetic valve of the injector 10, the cutoff valve 40, etc. was performed by ECU60 was demonstrated. However, the present invention is not limited to this. In the present invention, it may be executed by a control device provided separately from the ECU 60, such as acquisition of fuel pressure and hydraulic pressure, valve closing control of the shut-off valve 40 or the like for lowering the fuel pressure, etc. Alternatively, a microcomputer may be installed in the injector 10, and fuel pressure and hydraulic pressure acquisition, valve opening control, and the like may be executed by the microcomputer. The same applies to the following embodiments.

  In the present invention, the connection destination of the press line 42 is not particularly limited. The depressurization line 42 may be connected to a safely installed discharge line so that the fuel can be safely discharged to the outside. Alternatively, a low-pressure tank may be separately installed, and the depressurization line 42 may be connected to the tank so that the fuel is discharged to the tank. In this case, the fuel may be supplied from the tank to the intake system, or may be discharged to the exhaust system and used for post-processing. The same applies to the following embodiments.

  Further, in the present embodiment, when the difference between the fuel pressure and the hydraulic pressure becomes small, the control for increasing the hydraulic pressure is performed together with the control for decreasing the fuel pressure by closing the shutoff valve 40. However, the present invention is not limited to this, and only control for reducing the fuel pressure may be performed. The same applies to the following embodiments.

  In the present embodiment, the pressure in the fuel delivery pipe 14 determined based on the output of the fuel pressure sensor 16 is defined as “fuel pressure”, and the pressure in the hydraulic oil delivery pipe 52 determined based on the output of the hydraulic sensor 54. The case where is used as “hydraulic pressure” has been described. However, the present invention is not limited to this, and the pressure of the fuel supplied to the injector 10 or a value correlated therewith may be detected or estimated by other means and used. Similarly, the pressure of hydraulic oil supplied to the control chamber 78 of the injector 10 or a value correlated therewith may be detected or estimated by other means and used. The same applies to the following embodiments.

  In the present embodiment, the case where hydrogen is used as the fuel has been described. However, the fuel injection device of the present invention is not limited to the case where hydrogen is used as the fuel, and can be preferably used particularly as a fuel injection device for gaseous fuel.

  In the present embodiment, the fuel passage composed of the fuel line 18, the fuel delivery pipe 14, and the fuel passage 12 corresponds to a “fuel supply passage” in the present invention. Further, the hydraulic oil passage constituted by the hydraulic oil line 56, the hydraulic oil delivery pipe 52, and the hydraulic oil passage 50 corresponds to the “hydraulic oil passage” in the present invention. Further, the shutoff valve 40 or the main stop valve 30 or 32 in the present embodiment corresponds to a “shutoff valve” in the present invention.

  Further, in the routine of FIG. 5 of the present embodiment, the process of step S102 is executed, thereby realizing the “means for obtaining the hydraulic oil pressure value” in the present invention, and the process of step S104 is executed. Thus, the “means for obtaining the fuel pressure value” is realized, and the “pressure reducing means” is realized by executing the processing of step S112.

Embodiment 2. FIG.
The system of the second embodiment has the same configuration as the system of the first embodiment. In the system of the second embodiment, in addition to the control of the first embodiment, a second upper limit value that is larger than the first upper limit value is set, and when the fuel pressure exceeds the second upper limit value, the pressure relief valve 44 is opened. Control. Here, the second upper limit value is a value obtained by reducing the hydraulic pressure by a certain amount. The difference between the hydraulic pressure and the second upper limit value is set smaller than the difference between the hydraulic pressure and the first upper limit value. That is, the second upper limit value is set larger than the first upper limit value and close to the hydraulic pressure.

  The relationship between the second upper limit value and the hydraulic pressure is stored in advance in the ECU 60 as a map. Such a relationship between the second upper limit value and the hydraulic pressure is appropriately set based on a differential pressure between the minimum hydraulic pressure and the fuel pressure in order to ensure a correct balance between the valve closing force and the valve opening force. The Such a differential pressure varies depending on the configuration of the injector 10, and can be obtained by experiments, simulations, or the like.

  FIG. 6 is a diagram for illustrating a control routine executed by ECU 60 in the second embodiment of the present invention. The routine of FIG. 6 is a routine that is executed in place of the routine of FIG. 5 and is the same as the routine of FIG. 5 except that the process of steps S202 to S206 is performed after the process of step S114 of the routine of FIG. Is.

  In the routine of FIG. 6, when the hydraulic pressure increase control in step S114 is executed, next, in step S202, the second upper limit value mx2 is calculated. The second upper limit value mx2 is calculated according to a map stored in advance in the ECU 60.

  Next, in step S204, it is determined whether or not the fuel pressure epr detected in step S104 is greater than the second upper limit value mx2. If it is not determined in step S204 that the fuel pressure epr is greater than the second upper limit value mx2, the current process ends as it is.

  On the other hand, if it is determined in step S204 that the fuel pressure epr is greater than the second upper limit value mx2, then the pressure relief valve 44 is opened in step S206. As a result, the fuel is discharged from the fuel delivery pipe 14 to the depressurization line 42, and the fuel pressure starts to decrease. Thereafter, the current process ends.

  As described above, in the present embodiment, when the second upper limit value larger than the first upper limit value is provided and the fuel pressure rises to the second upper limit value, the pressure is increased along with the closing of the shutoff valve 40. The valve-release valve 44 is opened. As a result, for example, even when the pressure reducing mechanism 38 and the shutoff valve 40 fail at the same time, such as when the shutoff valve 40 cannot be closed alone, the occurrence of abnormal injection can be suppressed.

  In the present embodiment, as in the case of setting the first upper limit value, the differential pressure between the minimum required oil pressure and fuel pressure is a fixed value, and the value obtained by subtracting this fixed value from the oil pressure is the second upper limit value. An example of values has been described. However, in the present invention, the minimum required differential pressure is not limited to a constant value in the entire pressure range. Therefore, the second upper limit value may be set as appropriate according to the oil pressure, and for example, a value obtained by multiplying the oil pressure by a certain coefficient may be used as the second upper limit value. The same applies to the following embodiments.

  In the present invention, the case where the pressure relief valve 44 is opened when the fuel pressure exceeds the second upper limit value set in accordance with the hydraulic pressure has been described. However, the present invention is not limited to this, and the pressure relief valve 44 may be opened when the difference between the fuel pressure and the second upper limit value exceeds the second threshold value. That is, this embodiment is an example in which the second threshold value is set to 0, and a value obtained by reducing the minimum required differential pressure from the hydraulic pressure is used as the second reference value. However, for example, the second reference value is a value that does not include the minimum necessary differential pressure, for example, the detected oil pressure in addition to the detected value of the oil pressure, the average value or the smoothed value of the detected oil pressure, and the estimated value. It is good also as a value calculated according to. In this case, the second threshold value is set according to the minimum required differential pressure between the hydraulic pressure and the fuel pressure, and when the differential pressure between the second reference value and the fuel pressure exceeds the second threshold value, What is necessary is just to control so that the pressure relief valve 44 may be opened. In this case, the second threshold value may be a value set according to the hydraulic pressure or the fuel pressure. Further, according to the present invention, the first reference value and the second reference value may be set to the same value as long as the second threshold value is set to a minimum necessary differential pressure and set to a value smaller than the first threshold value. Good. The same applies to the following embodiments.

  In the present embodiment, the case has been described in which the hydraulic pressure and the first and second reference values are set higher than the fuel pressure if the injector 10 is normal. However, the present invention is not limited to this. For example, the fuel pressure may be set to a balance smaller than the hydraulic pressure by increasing the biasing force of the spring 76 of the injector 10. As described above, even in the case of an injector that is used in a balance in which the fuel pressure is higher than the hydraulic pressure even during normal operation, the control according to the present invention is the difference between the second reference value set according to the hydraulic pressure and the fuel pressure. Whether or not the control for reducing the fuel pressure is to be performed may be determined based on whether or not “2 reference value−fuel pressure” is smaller than the second threshold value. This determination can be made in the same manner based on, for example, the ratio between the second reference value and the fuel pressure. For example, when “fuel pressure / second reference value”, which is the ratio of the fuel pressure to the second reference value, is smaller than the second threshold value, control for reducing the fuel pressure may be performed. The same applies to the following embodiments.

Embodiment 3 FIG.
The system of the third embodiment has the same configuration as the system of the first embodiment. In the third embodiment, in addition to the control of the second embodiment, the first upper limit value is set to a value corrected according to the pressure increase capability and the pressure difference between the pressure of the high-pressure hydrogen fuel tank 26 or 28 and the fuel pressure. Control to set.

[Calculation of first upper limit value]
FIG. 7 is a diagram for describing the base value of the first upper limit value, the first upper limit value, and the second upper limit value in the third embodiment of the present invention. It is a figure for demonstrating the 1st, 2nd upper limit set in Embodiment 3 of this invention. In FIG. 7, the horizontal axis represents the hydraulic pressure, and the vertical axis represents the fuel pressure. In FIG. 7, (a) represents a base value, (b) represents a first upper limit value, and (c) represents a second upper limit value.

In the third embodiment, first, as shown in FIG. 7A, the fuel pressure base value is set according to the hydraulic pressure. The fuel pressure base value is set according to the map according to the oil pressure, and is, for example, the same value as the first reference value in the first embodiment. In the present embodiment, the base value is set to the pressure capacity and the differential pressure between the pressure of the high-pressure hydrogen fuel tank 26 or 28 (hereinafter also referred to as “tank pressure”) and the fuel pressure (hereinafter also referred to as “fuel differential pressure”). The value corrected accordingly is set as the first upper limit value. Specifically, as described below, an offset value ofs corresponding to the boosting capability and a correction coefficient k corresponding to the fuel differential pressure are set, and a value obtained by correcting the base value mxb by the following equation (1) is: The first upper limit value mx1 is used.
First upper limit value mx1 = base value mxb−offset value ofs × correction coefficient k (1)

[About offset value]
For example, even if the fuel pressure does not increase, if the hydraulic pressure can be increased while the minimum required differential pressure between the fuel pressure and the hydraulic pressure is secured, the minimum required difference between the fuel pressure and the hydraulic pressure. The pressure can be maintained. On the other hand, when the pressure increase capability of the hydraulic pressure by the hydraulic oil pump 58 is low and the increase in fuel pressure is faster than the increase in hydraulic pressure, the differential pressure between the fuel pressure and the hydraulic pressure is smaller than the minimum required differential pressure at an early stage. Is expected.

  Therefore, in the present embodiment, a value corrected by an offset value corresponding to the boosting capability of the hydraulic oil pump 58 is used as the first upper limit value. FIG. 8 is a diagram for explaining the relationship between the boosting capability of the hydraulic pump 58 and the offset value. In the present embodiment, the offset value is a value that is subtracted from the base value set according to the hydraulic pressure. As shown in FIG. 8, the offset value decreases as the boosting capability increases. Since the offset value is a value that is subtracted from the set base value, the first upper limit value set for the fuel pressure is corrected so as to be lower as the boosting capability is lower. . Further, the lower the boosting capacity of the hydraulic oil pump 58, the larger the difference between the second upper limit value and the first upper limit value, and a large margin is secured.

  In actual control, a boosting capability value that is a value correlated with the boosting capability, such as a rate of change in hydraulic pressure per unit, is used as a value indicating the boosting capability of the hydraulic oil pump. The specific relationship between the boosting capacity value and the offset value is determined by considering the necessary differential pressure between the hydraulic pressure and the fuel pressure, and the necessary margin between the first upper limit value and the second upper limit value. Or obtained by simulation or the like. A map that defines the set relationship is stored in the ECU 60 in advance.

[About correction factors]
Further, even when the fuel pressure is increasing, the degree of increase in the fuel pressure is reduced as the tank pressure is approached, and the increase in fuel pressure is expected to stop when the tank pressure is reached. . That is, the smaller the fuel differential pressure, the smaller the subsequent increase in fuel pressure is expected. Therefore, even if the fuel pressure is high, if the fuel differential pressure is small, the differential pressure between the hydraulic pressure and the fuel pressure is secured even if the timing to start the control to lower the fuel pressure or the hydraulic pressure increase control is delayed. It is thought that the state can be maintained.

  Therefore, in the present embodiment, an offset value, which is a correction value for the base value of the first upper limit value, is corrected and used according to the differential pressure between the tank pressure and the fuel pressure. FIG. 9 is a diagram for explaining the relationship between the fuel differential pressure and the correction coefficient for the offset value in the present embodiment.

  As shown in FIG. 9, the correction coefficient is set so as to increase as the fuel differential pressure increases. The correction coefficient is used by multiplying the offset value. Accordingly, the offset value is corrected so as to increase as the fuel differential pressure increases. Accordingly, the first upper limit value is a value corrected so as to be smaller as the fuel differential pressure is larger when the same hydraulic pressure and the same boosting capacity are compared. That is, the higher the fuel differential pressure, the faster the fuel pressure rises. Therefore, the shutoff valve 40 is closed early and control is performed to increase the hydraulic pressure. Further, the larger the fuel differential pressure, the larger the margin between the first upper limit value and the second upper limit value, thereby reliably preventing abnormal injection.

  The specific relationship between the fuel differential pressure and the correction coefficient k as shown in FIG. 9 is obtained in advance in the injector 10 based on data from experiments, simulations, and the like. This relationship is determined as a map or the like and stored in the ECU 60, for example.

  FIG. 10 is a flowchart for illustrating a control routine in the third embodiment of the present invention. The routine shown in FIG. 10 is executed in place of the routine shown in FIG. 6. The routine shown in FIG. 6 has the processes shown in steps S302 to S312 in place of the process in step S106 after the process in step S104 of the routine shown in FIG. Is the same.

  After the hydraulic pressure epcr is detected in the routine of FIG. 10, the base value mxb is calculated in step S302. The base value mxb is, for example, the first upper limit value in the first embodiment, and is calculated according to a map stored in advance in the ECU 60 according to the hydraulic pressure epcr.

  Next, in step S304, the boosting capacity value of the hydraulic oil pump 58 is detected. The pressure increase capability value of the hydraulic pump is calculated according to an arithmetic expression or the like stored in advance in the ECU 60. Next, in step S306, an offset value ofs is calculated according to the boosting capability value. The relationship between the boosting capability value and the offset value ofs is determined in advance in the ECU 60 as a map. In the process of step S306, the offset value ofs corresponding to the boost capability value calculated in step S304 is calculated according to this map.

  Next, in step S308, the tank pressure epgb is detected. Here, the output of the tank pressure sensor 36 is taken into the ECU 60, and the tank pressure epgb is detected based on this.

  Next, in step S310, a correction coefficient k for the offset value ofs is calculated. The ECU 60 stores in advance a relationship between the correction coefficient k and the tank pressure epgb as a map. Here, the correction coefficient k corresponding to the tank pressure epgb detected in step S308 is calculated according to the map.

  Next, in step S312, the first upper limit value mx1 is calculated. The first upper limit value mx1 is calculated according to the above equation (1) using the base value mxb, the offset value ofs, and the correction coefficient k calculated in steps S302, S306, and S310.

  Next, the determination process of step S106 is executed. However, here, the first upper limit value mx1 calculated in step S312 is used. After step S106, the processing of steps S106 to S114 and S202 to S206 proceeds in the same manner as the routine of FIG. 6, and the current processing ends.

  As described above, according to the present embodiment, the first upper limit value is a value obtained by correcting the base value set according to the hydraulic pressure according to the boosting capacity value. As a result of this correction, the first upper limit value is set to be smaller when the boosting capability is lower than when the oil pressure is the same. As a result, as the hydraulic oil pressure increases later, the shutoff valve 40 and the hydraulic pressure increase control are started at a stage where the fuel pressure is lower. Therefore, even when the pressure increase capability of the hydraulic pressure is low, it is possible to suppress the differential pressure between the fuel pressure and the hydraulic pressure from becoming smaller than the allowable range.

  Further, the lower the boosting capacity of the hydraulic oil pump 58, the larger the margin between the first upper limit value mx1 and the second upper limit value mx2. Accordingly, even when the hydraulic pressure boosting capability is low, a large margin can be secured until the fuel pressure reaches the second upper limit value mx2, and the hydraulic pressure is increased before the fuel pressure reaches the second upper limit value mx2. The second upper limit value mx2 set as the upper limit value can be increased. Therefore, it is possible to prevent the fuel from being discharged from the pressure relief line 42 to the outside by opening the pressure relief valve 44.

  In the present embodiment, the case has been described in which the first upper limit value mx1 is set to a larger value as the fuel differential pressure is smaller and the fuel increase rate is expected to be smaller. Thereby, it is possible to avoid closing the shutoff valve 40 until it is unnecessary. The margin between the first upper limit value mx1 and the second upper limit value mx2 is set so as to increase as the fuel differential pressure increases. Thus, since the margin is determined according to the rate of increase in the fuel pressure, unnecessary fuel discharge due to the unnecessary opening of the pressure relief valve 44 can be suppressed.

  As described in the first and second embodiments, also in the present embodiment, the shutoff valve 40 is closed or the pressure relief valve 44 is based on whether or not the fuel pressure exceeds the first and second upper limit values. The case where the valve is opened has been described. However, the present invention is not limited to this, and when the difference between the fuel pressure and the first or second upper limit value exceeds the first or second threshold value, the shutoff valve 40 is closed or the pressure relief valve 44 is closed. It is good also as a structure which opens a valve. That is, this embodiment is an example in which the first and second threshold values = 0 are set, and the value obtained by reducing the required differential pressure from the hydraulic pressure is used as the first and second reference values. However, for example, as a value according to the oil pressure, for example, a detected value of the oil pressure, or an average value thereof, an estimated value of the oil pressure, and other values related to the oil pressure calculated according to the detected oil pressure are first, The second reference value may be used.

  Further, in the present embodiment, the case where the first reference value is changed according to the pressure increasing capability of the hydraulic oil pump 58 has been described. However, the present invention is not limited to this. In the present invention, for example, when the difference between the fuel pressure and the first reference value is smaller than the first threshold value, the shutoff valve 40 is controlled to be closed, and according to the boosting capability of the hydraulic oil pump 58. The first threshold value may be corrected. In this case, the first threshold value may be set to be smaller as the boosting capability of the hydraulic oil pump 58 is larger. Even in this case, when the pressure increasing capability of the hydraulic oil pump 58 is low, it is possible to start the control for reducing the fuel pressure when the differential pressure between the hydraulic pressure and the fuel pressure is large.

  Similarly, in the present embodiment, the case where the first reference value is changed according to the fuel differential pressure has been described. However, the present invention is not limited to this. In the present invention, for example, when the difference between the fuel pressure and the first reference value is smaller than the first threshold value, the shutoff valve is controlled to be closed, and the first threshold value is corrected according to the fuel differential pressure. It is good also as what to do. In this case, the relationship between the fuel differential pressure and the first threshold value may be set so that the first threshold value increases as the fuel differential pressure increases. Even in this case, as the differential pressure between the fuel pressure and the tank pressure is larger, the control for reducing the fuel pressure can be started when the differential pressure between the hydraulic pressure and the fuel pressure is larger.

  In the present embodiment, a correction value corresponding to the pressure increase capability of the hydraulic oil pump 58 and the fuel differential pressure is set with respect to the first reference value or the first threshold value, thereby the first reference value or the first threshold value. The case where the threshold value is corrected has been described. However, the present invention is not limited to this, and the first reference value or the first threshold value may be directly set according to the oil pressure, the boosting capacity value, and the fuel differential pressure.

  In the present embodiment, the case where the first reference value or the first threshold value is set according to the fuel differential pressure has been described. However, the present invention is not limited to the above in consideration of the fuel differential pressure, and even if the first reference value or the first threshold is set according to the hydraulic pressure and the boosting capacity value. Good.

  In the present embodiment, the hydraulic oil pump 58 corresponds to the “increasing / decreasing means” of the present invention. However, in the present invention, the increase / decrease means is not limited to the hydraulic oil pump 58, and may have other configurations as long as the hydraulic pressure of the hydraulic oil flowing through the hydraulic oil supply path can be increased or decreased. .

  Further, in the above embodiment, when the number of each element, number, quantity, range, etc. is mentioned, it is mentioned unless otherwise specified or clearly specified in principle. The invention is not limited to the numbers. The structures, steps, and the like described in this embodiment are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

  In the present embodiment, by executing the process of step S304, the “means for obtaining as a boosting capability value” of the present invention is realized, and by executing the process of step S312, the “correcting means” is realized. Realize.

2 Internal combustion engine 4 Intake passage 6 Exhaust passage 10 Injector 12 Fuel passage 14 Fuel delivery pipe 16 Fuel pressure sensor 18 Fuel line 20, 22, 24 Branch passage 26, 28 High-pressure hydrogen fuel tank 30, 32 Main stop valve 34 Filling port 36 Tank Pressure sensor 38 Pressure reducing mechanism 40 Shut-off valve 42 Pressure release line 44 Pressure release valve 50 Hydraulic oil passage 52 Hydraulic oil delivery pipe 54 Hydraulic sensor 56 Hydraulic oil line 58 Hydraulic oil pump 60 ECU
70 Needle valve 72 Nozzle chamber 74 Command piston 76 Spring 78 Control chamber 80 Return passage 88 Valve 90 Spring

Claims (6)

A hydraulically operated fuel injection valve that injects fuel supplied to the internal combustion engine;
A fuel supply path for supplying fuel to the fuel injection valve;
A shut-off valve installed in the fuel supply path to open and close the fuel supply path;
A hydraulic oil supply path connected to a pressure control chamber for controlling a pressure for energizing a needle valve for opening and closing the nozzle hole of the fuel injection valve in a valve closing direction, and for supplying hydraulic oil to the pressure control chamber;
Means for obtaining, as a fuel pressure value, a fuel pressure supplied to the fuel injection valve or a value correlated with the fuel pressure;
Means for obtaining, as a hydraulic oil pressure value, a hydraulic oil pressure supplied to the pressure control chamber or a value correlated with the hydraulic oil pressure;
When the difference between the fuel pressure value and the first reference value set according to the hydraulic oil pressure value is smaller than a first threshold value, the pressure of the fuel supplied to the fuel injection valve is reduced. Pressure reducing means for causing,
A fuel injection device for an internal combustion engine, comprising:   2. The fuel injection device for an internal combustion engine according to claim 1, wherein the pressure reducing unit reduces the pressure of the fuel by closing the shutoff valve. A pressure relief passage that is connected to the fuel supply passage and allows the fuel in the fuel supply passage to flow out of the fuel supply passage;
A pressure relief valve for opening and closing the pressure relief passage;
Means for opening the pressure relief valve when a difference between the fuel pressure value and a second reference value, which is a value set according to the hydraulic oil pressure value, is smaller than a second threshold value; ,
The fuel injection device for an internal combustion engine according to claim 2, further comprising: A depressurization passage connected to the fuel supply passage and allowing the fuel in the fuel supply passage to flow out of the fuel supply passage;
A pressure relief valve for opening and closing the pressure relief passage,
2. The fuel injection device for an internal combustion engine according to claim 1, wherein the pressure reducing means reduces the fuel pressure by opening the pressure relief valve. 3. Increase / decrease means for increasing / decreasing the pressure of the hydraulic oil flowing through the hydraulic oil supply path;
Means for obtaining, as the boosting capacity value, a value that correlates to the ability of the hydraulic oil to boost the hydraulic oil;
Correction means for correcting the first reference value or the first threshold according to the boosting capability value;
The fuel injection device for an internal combustion engine according to any one of claims 1 to 4, further comprising: Means for obtaining a pressure value in a fuel tank connected to the fuel supply path or a correlation value correlated with a pressure in the fuel tank as a tank pressure value;
6. The fuel injection for an internal combustion engine according to claim 5, wherein the correction means further corrects the first reference value or the first threshold value according to the tank pressure value and the fuel pressure value. apparatus.

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