JP2016056699A - Fuel injection system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To resolve pressure abnormality in a fuel pipe while suppressing the emission of gas fuel into the atmosphere when the pressure abnormality occurs in the fuel pipe.SOLUTION: A fuel injection system for an internal combustion engine includes a first injection valve 21 for injecting gas fuel in a predetermined pressure range, a control part 80 for controlling the fuel injection of the first injection valve 21, a pressure regulating valve 60 for reducing the pressure of the gas fuel from the first injection valve 21 down to a first pressure in the predetermined pressure range, a gas pressure sensor 48 for detecting the pressure of the gas fuel after regulated, and a relief valve 69 to be opened when the pressure of the gas fuel after regulated by the pressure regulating valve 60 becomes a second pressure in the predetermined pressure range, higher than the first pressure, for releasing the gas fuel from a fuel passage 41 to the outside. The control part 80 sets a third pressure higher than the first pressure and lower than the second pressure, as an abnormality determination reference value, and when a detected gas pressure exceeds the abnormality determination reference value, determines that the pressure of the gas fuel is abnormal and performs a pressure reduction with the fuel injection of the first injection valve 21.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a fuel injection system for an internal combustion engine, and more particularly to a fuel injection system applied to a fuel injection system for an in-vehicle internal combustion engine that uses gas fuel.

  Conventionally, an internal combustion engine that combusts a gas fuel such as compressed natural gas (CNG) has been put into practical use, and the internal combustion engine is provided with a fuel supply device that supplies gas fuel to a fuel injection valve. ing.

  For example, Patent Document 1 discloses a primary regulator that decompresses gas fuel from a fuel tank filled with gas fuel to a first predetermined pressure in a primary decompression chamber, and gas fuel decompressed by the primary regulator. A secondary regulator that further reduces the pressure to a second predetermined pressure in the secondary decompression chamber; a shut-off valve that is provided upstream of the primary regulator (that is, on the gas tank side) and shuts off the flow of gas fuel to each regulator; A fuel supply apparatus comprising: a safety device that detects a pressure abnormality in a fuel pipe and avoids the pressure abnormality in an abnormal state in which an outlet side pressure of the primary decompression chamber is higher than a first predetermined pressure. Proposed.

  In the fuel supply device of Patent Document 1, the safety device is configured such that the outlet side pressure of the primary decompression chamber is reduced by a safety valve provided in the gas passage between the primary regulator and the secondary regulator and the first pressure detection means. An abnormality determining means for determining that there is an abnormality in the fuel supply device when it is detected that a predetermined pressure has been exceeded.

JP-A-8-93569

  In the safety device of Patent Document 1, when a pressure abnormality is detected by the pressure detection means, the safety valve is opened to dissipate the gas fuel to the atmosphere, thereby reducing the pressure of the fuel pipe. However, dissipating gas fuel to the atmosphere leads to inconveniences such as a reduction in fuel consumption and the generation of a strange odor.

  The present invention has been made in view of the above, and when a fuel pipe pressure abnormality occurs, the fuel injection system for an internal combustion engine can eliminate the pressure abnormality of the fuel pipe while suppressing the atmospheric emission of the gas fuel. The main purpose is to provide

  The present invention provides a first injection means (21) that enables injection of gas fuel supplied from a gas tank (42) for storing gas fuel in a high pressure state through a fuel passage (41) in a range of a predetermined pressure; An injection control means (80) for controlling the injection of the gas fuel by the injection means; and a first pressure within a range of the predetermined pressure, the pressure of the gas fuel provided in the fuel passage and supplied to the first injection means. Pressure adjusting means (60) for adjusting the pressure to a reduced pressure, pressure detecting means (48) for detecting the pressure of the gas fuel after the pressure adjustment by the pressure adjusting means, the first injection means and the pressure adjusting means in the fuel passage And is opened when the pressure of the gas fuel after the pressure adjustment by the pressure adjusting means becomes a second pressure within the predetermined pressure range and larger than the first pressure. The fuel The relief gas (69) for releasing the gas fuel on the road to the outside and the third pressure that is larger than the first pressure and smaller than the second pressure as an abnormality determination reference value, the detected gas pressure by the pressure detecting means is When the abnormality determination reference value is exceeded, an abnormality determination means (80) for determining that the pressure of the gas fuel is abnormal, and when the abnormality determination means determines that there is an abnormality, the first injection means And a decompression means (80) for performing decompression by fuel injection.

  According to the present invention, in a high pressure state where the detected gas pressure exceeds the abnormality determination reference value, abnormality determination can be performed before the pressure of the gas fuel reaches the second pressure (relief pressure). In addition, when the high pressure is abnormal, the pressure of the gas fuel can be reduced by injecting the gas fuel by the first injection means. Therefore, the pressure of the gas fuel can be suppressed while suppressing the atmospheric emission of the gas fuel, and the fuel pipe can be protected from rupture.

The block diagram which shows the outline of the fuel-injection system of an engine. The figure which shows schematic structure of a 1st injection valve. The figure which shows schematic structure of a regulator. The block diagram of the electric power supply system of an engine fuel injection system. Explanatory drawing of the example of a setting of gas pressure. The flowchart which shows the procedure of an abnormality diagnosis process.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. The present embodiment is applied to a so-called bi-fuel type on-vehicle multi-cylinder engine (multi-cylinder internal combustion engine) that uses compressed natural gas (CNG) as a gas fuel and gasoline as a liquid fuel as combustion fuel. It is supposed to be embodied as a fuel injection system. An overall schematic diagram of this system is shown in FIG.

  An engine 10 shown in FIG. 1 is an inline three-cylinder spark ignition engine, and an intake system 11 and an exhaust system 12 are connected to an intake port and an exhaust port, respectively. The intake system 11 has an intake manifold 13 and an intake pipe 14. The intake manifold 13 has a plurality of (for the number of cylinders of the engine 10) branch pipe portions 13a connected to the intake port of the engine 10, and a collective portion 13b connected to the intake pipe 14 on the upstream side. ing. The intake pipe 14 is provided with a throttle valve 15 as air amount adjusting means. The throttle valve 15 is configured as an electronically controlled throttle valve whose opening degree is adjusted by a throttle actuator 15a such as a DC motor. The opening degree of the throttle valve 15 (throttle opening degree) is a throttle opening degree built in the throttle actuator 15a. It is detected by the degree sensor 15b.

  Further, the exhaust system 12 has an exhaust manifold 16 and an exhaust pipe 17. The exhaust manifold 16 has a plurality of (for the number of cylinders of the engine 10) branch pipe portions 16a connected to the exhaust port of the engine 10 and a collecting portion 16b connected to the exhaust pipe 17 on the downstream side. ing. The exhaust pipe 17 is provided with an exhaust sensor 18 for detecting exhaust components and a catalyst 19 for purifying exhaust. Specifically, an air-fuel ratio sensor that detects the air-fuel ratio from the oxygen concentration in the exhaust is provided as the exhaust sensor 18.

  A spark plug 20 is provided in each cylinder of the engine 10. A high voltage is applied to the ignition plug 20 at a desired ignition timing through an ignition device 20a including an ignition coil. By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 20, and the fuel introduced into the cylinder (combustion chamber) is ignited and used for combustion.

  Further, the present system is a fuel injection means for injecting and supplying fuel to the engine 10, a first injection valve 21 for injecting gas fuel (CNG fuel), and a second injection valve 22 for injecting liquid fuel (gasoline). And have. Each of these injection valves 21 and 22 injects fuel into the branch pipe portion 13a of the intake manifold 13 in the intake system 11, and gas fuel is supplied to the intake port of each cylinder by the injection of the first injection valve 21. The liquid fuel is supplied to the intake port of each cylinder by the injection of the second injection valve 22.

  Each of the injection valves 21 and 22 is an open / close type control valve in which the valve body is lifted from the closed position to the open position by electrically driving the electromagnetic drive unit. Each valve is driven to open by a valve opening drive signal. These injection valves 21 and 22 are opened by energization and closed by energization interruption. An amount of fuel (gas fuel, liquid fuel) corresponding to the energization time is injected from each of the injection valves 21 and 22. In this embodiment, the injection pipe 23 is connected to the tip of the first injection valve 21, and the gas fuel injected from the first injection valve 21 is branched through the injection pipe 23. 13a is injected. In addition, as a driving method of the fuel injection valve, a large current (boosted current) for improving the valve opening response is supplied for a short time at the beginning of the valve opening, and thereafter the valve opening maintaining current for maintaining the valve opening state is intermittently applied. In this embodiment, in order to simplify the configuration, the first injection valve 21 is opened by flowing a constant current during the energization period.

  Here, the configuration of the first injection valve 21 for gas injection will be described with reference to FIG. In FIG. 2, (a) shows a non-injection state, and (b) shows an injection state. The first injection valve 21 has a so-called self-seal (self-sealing) structure in which the closing sealability is enhanced by the pressure of the gas fuel supplied to itself.

  A valve body 32 is slidably accommodated in the cylindrical body 31, and the valve body 32 is biased in the valve closing direction by a spring 33 in the body 31. In FIG. 2A, the nozzle hole 34 provided at the tip of the injection valve is closed by the tip of the valve body 32. In the body 31, a first fuel chamber 35 is provided on the rear end side (upstream side) of the valve body 32, and a second fuel chamber 36 is provided on the front end side (downstream side) of the valve body 32. Yes. The valve body 32 is provided with a small-diameter portion 32a on the tip side of the sliding portion, and a second fuel chamber 36 is provided around the small-diameter portion 32a. The first fuel chamber 35 and the second fuel chamber 36 are in communication with each other via a fuel passage 37 provided in the valve body 32. The inlet side of the fuel passage 37 communicates with the first fuel chamber 35, and the outlet side thereof It leads to the second fuel chamber 36. The valve body 32 is displaced to the valve opening position in response to energization to the electromagnetic drive unit 38 composed of a solenoid or the like.

  In the first injection valve 21 configured as described above, gas fuel is supplied from a regulator 43 described later to the first fuel chamber 35, and the gas fuel is also introduced into the second fuel chamber 36 via the fuel passage 37. As shown in FIG. 2B, when the valve body 32 is displaced to the valve opening position against the biasing force of the spring 33 as the electromagnetic drive unit 38 is energized, the nozzle hole 34 is opened, and the gas is discharged. Fuel is injected.

  In the first injection valve 21, the valve body 32 is provided with a small-diameter portion 32 a on the distal end side thereof, so that the pressure receiving area on the first fuel chamber 35 side and the pressure receiving side on the second fuel chamber 36 side in the valve-closed state. The area is “pressure receiving area on the first fuel chamber 35 side> pressure receiving area on the second fuel chamber 36 side” (see FIG. 2A). Therefore, in the valve closing state shown in FIG. 2A, the pressure of the gas fuel supplied from the regulator 43 side (corresponding to the injection pressure) is in the direction in which the valve body 32 is closed (valve closing direction). It comes to act more greatly. 2B, the injection pressure also acts on the end face (the lower end face in the figure) of the small-diameter portion 32a, so that the fuel pressure in the valve closing direction acting on the valve body 32 and the valve opening direction are also applied. The fuel pressure is almost the same.

  Next, returning to the description of FIG. 1, the configuration of the gas fuel supply unit 40 that supplies the gas fuel to the first injection valve 21 and the liquid fuel supply unit 70 that supplies the liquid fuel to the second injection valve 22. Will be described.

  In the gas fuel supply unit 40, a gas tank 42 is connected to the first injection valve 21 via a gas pipe 41, and the pressure of the gas fuel supplied to the first injection valve 21 is in the middle of the gas pipe 41. There is provided a regulator 43 having a pressure adjusting function for adjusting the pressure under pressure. In the following description, the upstream side of the regulator 43 of the gas pipe 41 is referred to as a high-pressure pipe part 41a that forms a high-pressure side passage, and the downstream side is referred to as a low-pressure pipe part 41b that forms a low-pressure side passage.

  The regulator 43 (a pressure adjusting valve 60, which will be described in detail later) adjusts the pressure of gas fuel in a high pressure state (for example, a maximum of 20 MPa) stored in the gas tank 42 to a predetermined pressure. The fuel is supplied to the first injection valve 21 through the gas pipe 41.

  The pressure adjustment range by the regulator 43 is set to a part of the pressure range in which the first injection valve 21 can operate. For example, when the pressure range in which the first injection valve 21 can be operated is 1.0 MPa or less, the regulator 43 controls the pressure of the gas fuel so as to be in a predetermined pressure range (for example, 0.2 to 0.35 MPa). Adjust the vacuum.

  A gas fuel passage formed by the gas pipe 41 and the like has a tank main stop valve 44 (tank outlet valve) disposed near the fuel outlet of the gas tank 42 and a downstream side of the tank main stop valve 44. In addition, a shutoff valve 45 disposed near the fuel inlet of the regulator 43 is provided. These valves 44 and 45 allow and block the flow of gas fuel in the gas pipe 41. Both the tank main stop valve 44 and the shut-off valve 45 are electromagnetic on-off valves and are normally closed types that shut off the flow of gas fuel when not energized and allow the gas fuel to flow when energized.

  In the gas pipe 41, a gas pressure sensor 46 for detecting the fuel pressure and a temperature sensor 47 for detecting the fuel temperature are provided in the high pressure pipe portion 41a. A gas pressure sensor 48 that detects the pressure of the gas fuel and a temperature sensor 49 that detects the temperature of the gas fuel are provided in the low-pressure pipe portion 41b.

  Here, the configuration of the regulator 43 will be described with reference to FIG. The regulator 43 constitutes a mechanical pressure adjusting device that adjusts the fuel pressure in the low-pressure pipe portion 41b with respect to a mechanically determined set pressure.

  In FIG. 3, the regulator 43 has a high-pressure passage 51 connected to the high-pressure piping portion 41a (that is, the gas tank 42 side) and a low-pressure passage 52 connected to the low-pressure piping portion 41b (that is, the first injection valve 21 side). In the high-pressure passage 51, a shut-off valve 45 and a gas pressure sensor 46 are provided. The gas pressure sensor 46 detects the pressure of the gas fuel upstream from the shutoff valve 45. Reference numeral 53 is a filter for removing foreign matter.

  The configuration of the shut-off valve 45 is substantially the same as the configuration of the first injection valve 21, and has a self-seal (self-sealing) structure. To briefly explain the configuration, the shut-off valve 45 has a valve body 55 biased in the valve closing direction by a spring 54, and resists the biasing force of the spring 54 by energizing the electromagnetic drive unit 56. Thus, the valve body 55 is displaced from the valve closing position to the valve opening position. A first fuel chamber 57 is provided on the rear end side (upstream side) of the valve body 55, and a second fuel chamber 58 is provided on the distal end side (downstream side where the small diameter portion is provided) of the valve body 55. Yes. Both the fuel chambers 57 and 58 are communicated with each other through a fuel passage 59 provided in the valve body 55. In this case, high-pressure gas fuel is supplied to both the fuel chambers 57 and 58 from the gas tank 42, and in the closed state of the shutoff valve 45, a closing force is applied to the valve body 55 by the fuel pressure on the gas tank 42 side. . When the valve element 55 is displaced to the valve open position against the biasing force of the spring 54 with the energization of the electromagnetic drive unit 56 (as shown), high-pressure gas fuel flows downstream.

  In the regulator 43, a pressure adjustment valve 60 is provided on the downstream side of the shutoff valve 45. As a configuration of the pressure regulating valve 60, a valve body chamber 61 is provided in the high pressure passage 51, and a valve body 62 is accommodated in the valve body chamber 61. The valve body 62 is an opening / closing member that opens and closes the valve seat portion 63 that is an inlet portion of the low pressure passage 52. If the valve body 62 is in the open position, the valve seat portion 63 is opened and the high pressure passage 51, the low pressure passage 52, Is communicated. If the valve body 62 is in the closed position, the valve seat 63 is closed and the communication between the high pressure passage 51 and the low pressure passage 52 is blocked.

  The valve body 62 is opened and closed according to the fuel pressure (corresponding to the injection pressure) in the low pressure passage 52 and the force in the valve opening direction generated by the valve body actuating portion 65. The valve element actuating portion 65 is a space that is open to the atmosphere, and has an air opening portion 67 in which an adjustment spring 66 is provided, and a diaphragm as a partition member that partitions the air release portion 67 and the low-pressure passage 52. 68. The diaphragm 68 is provided integrally with the valve body 62. Fuel pressure in the low pressure passage 52 acts on the diaphragm 68 as a force in the valve closing direction, and an urging force of the adjustment spring 66 and atmospheric pressure act as a force in the valve opening direction.

  In such a configuration, if “force in the valve closing direction> force in the valve opening direction” is satisfied, the valve body 62 is held in the valve closing position. On the other hand, when the fuel pressure in the low pressure passage 52 decreases due to fuel injection or the like of the first injection valve 21 and becomes “force in the valve closing direction <force in the valve opening direction”, the valve element 62 opens with the displacement of the diaphragm 68. To be spoken. At this time, the opening position (valve lift amount) of the valve body 62 is determined according to the difference between the force in the valve closing direction and the force in the valve opening direction, and the opening area of the valve seat 63 is changed according to the opening position. As a result, the amount of fuel flowing from the high pressure passage 51 into the low pressure passage 52 is adjusted.

  A branch valve 52a branched from the low pressure passage 52 is provided with a relief valve 69 that vents gas when the fuel pressure in the low pressure passage 52 becomes abnormally high.

  In the present embodiment, in the regulator 43, the pressure adjusting means is configured by the pressure adjusting valve 60 including components such as the valve body 62 and the valve body operating unit 65. In the configuration of FIG. 3, the regulator 43 is provided with the cutoff valve 45, the gas pressure sensor 46, and the pressure adjustment valve 60, but this may be changed, for example, the cutoff valve 45, the gas pressure sensor 46, and the like. Can be provided in the high-pressure piping 41 a as a separate body from the regulator 43.

  Returning to the description of FIG. 1, in the liquid fuel supply unit 70, a fuel tank 72 is connected to the second injection valve 22 via a fuel pipe 71. The fuel pipe 71 is provided with a fuel pump 73 that feeds the liquid fuel in the fuel tank 72 to the second injection valve 22.

  The control unit 80 includes a CPU 81, a ROM 82, a RAM 83, a backup RAM 84, an interface 85, and a bidirectional bus 86. The CPU 81, ROM 82, RAM 83, backup RAM 84, and interface 85 are connected to each other by a bidirectional bus 86.

  The CPU 81 executes a routine (program) for controlling the operation of each unit in this system. The ROM 82 stores in advance various data such as a routine executed by the CPU 81, maps (including tables, relational expressions, and the like), parameters, and the like referred to when the routine is executed. The RAM 83 temporarily stores data as necessary when the CPU 81 executes a routine. The backup RAM 84 appropriately stores data under the control of the CPU 81 in a state where the power is turned on, and retains the stored data even after the power is shut off.

  The interface 85 includes sensors (crank angle sensor, air flow meter, cooling water temperature sensor) provided in the present system, including the throttle opening sensor 15b, the exhaust sensor 18, the gas pressure sensors 46, 48, and the temperature sensors 47, 49 described above. , Vehicle speed sensors, etc.), and outputs (detection signals) from these sensors to the CPU 81.

  The interface 85 is electrically connected to driving units such as the throttle actuator 15a, the ignition device 20a, the injection valves 21 and 22, the tank main stop valve 44, the shutoff valve 45, and the like, and drives these driving units. Therefore, the drive signal sent from the CPU 81 is output toward the drive unit. That is, the control unit 80 acquires the operating state of the engine 10 based on the output signals of the above-described sensors, and performs the above-described driving unit control based on this operating state.

  Various electric loads such as the first injection valve 21, the second injection valve 22, the tank main stop valve 44, and the shutoff valve 45 described above are configured to operate upon receiving power supply from the vehicle-mounted battery. FIG. 4 shows the configuration of the power supply system. In FIG. 4, the ignition device 20 a as an electric load, the injection valves 21 and 22, the tank main stop valve 44, the shut-off valve 45, and the starter 91 are connected to a battery 93 as a power supply unit via a power supply line 92. These electric loads are driven by power supplied from the battery 93. The starter 91 is a starting device for applying initial rotation when the engine 10 is started. In FIG. 4, an alternator 95 is connected to a battery 93 via a power supply line 92. The alternator 95 of the present embodiment is assumed to have a function of adjusting the power generation amount based on the detection result of the operating state of the engine 10. In the present embodiment, it is assumed that a booster circuit for boosting the voltage of the battery 93 is not provided in order to simplify the configuration.

  A control signal is input from the control unit 80 to the ignition device 20a, the tank main stop valve 44, and the shutoff valve 45, and the ignition device 20a applies a high voltage according to the control signal from the control unit 80. Outputs and produces sparks in the spark plug. Further, the tank main stop valve 44 and the shutoff valve 45 are switched from the closed state to the open state in response to a control signal from the control unit 80. In addition, the control unit 80 includes information indicating that starter driving (cranking) is being performed when the engine is started by driving the starter 91, and the elapsed time from the start of driving the starter 91 (cranking start). Information indicating the start completion of the engine 10 is input as start information.

  Further, the control unit 80 determines that the gas fuel has a high-pressure abnormality when a detected value of pressure by the gas pressure sensor 48 (hereinafter referred to as a detected gas pressure) exceeds a predetermined abnormality determination reference value. .

  When the pressure of the gas fuel exceeds the pressure resistance of the low pressure pipe portion 41b in the gas pipe 41, the low pressure pipe portion 41b of the gas pipe 41 may be damaged or deformed. Therefore, the relief valve 69 is opened when the pressure of the gas fuel reaches a relief pressure that is a predetermined pressure lower than the pressure resistance of the low-pressure pipe portion 41b so that the pressure of the gas fuel does not exceed the pressure resistance of the low-pressure pipe portion 41b. I have to. When the relief valve 69 is opened, the gas fuel is diffused into the atmosphere, thereby suppressing an increase in the pressure of the gas fuel in the low pressure pipe portion 41b.

  From the viewpoint of protecting the low-pressure pipe portion 41b, the relief pressure is preferably as low as possible as compared to the pressure pressure of the gas pipe 41. However, if the relief pressure is low, the amount of gas fuel that is diffused into the atmosphere increases, so there are problems with emission reduction and off-flavors. There is a concern of growing.

  Further, when the relief pressure is low, the difference between the pressure after the pressure reduction adjustment by the regulator 43 and the relief pressure becomes small. In this case, there is a possibility that the abnormality determination cannot be performed correctly by opening the relief valve 69 before the abnormality of the gas fuel is detected.

  Note that it is assumed that the difference between the pressure after the pressure reduction adjustment by the regulator 43 and the relief pressure is increased by increasing the pressure resistance of the low-pressure pipe portion 41b. In this case, however, the manufacturing cost of the fuel injection system is increased. To increase.

  Therefore, in the present embodiment, while suppressing an increase in manufacturing cost in the fuel system, the damage of the gas pipe 41 is suppressed, and when the pressure of the gas fuel increases, the pressure of the gas fuel is suppressed while suppressing the atmospheric emission of the gas fuel. It will be possible to properly carry out the abnormality determination.

  That is, as shown in the example of FIG. 5, in the present embodiment, the first injection valve 21 can operate with the relief pressure, the gas fuel pressure after the pressure reduction adjustment by the regulator 43, and the abnormality determination reference value of the gas fuel pressure. Within the proper pressure range.

  For example, when the pressure range D1 in which the first injection valve 21 can be operated is set, the pressure D2 of the gas fuel after the pressure reduction adjustment by the regulator 43 is set to the low pressure side in the pressure range D1. The relief pressure D3 is set to be on the high pressure side in the pressure range D1. Then, an abnormality determination reference value D4 is provided between the pressure D2 after the pressure reduction adjustment and the relief pressure D3. For example, when the pressure range D1 of the first injection valve 21 is set to 0 to 1.0 MPa, the pressure D2 after the decompression adjustment is set to a value in the range of 0.3 to 0.4 MPa, and the relief pressure D3 is set to 0.6 to 0.00. The value in the range of 8 MPa and the abnormality determination reference value D4 are set to values in the range of 0.4 to 0.6 MPa.

  At this time, the relief pressure D3 is preferably higher than a predetermined pressure D2 after the pressure reduction adjustment by the regulator 43, and is preferably, for example, not more than twice the pressure D2. In this case, a predetermined pressure difference is provided between the relief pressure D3 and the abnormality determination reference value D4, and there is also a predetermined pressure difference between the pressure D2 after pressure reduction adjustment by the regulator 43 and the abnormality determination reference value D4. Provided. As a result, it is possible to carry out the abnormality determination before the relief valve 69 is opened while ensuring that the first injection valve 21 is operable.

  It should be noted that abnormal pressure regulation of the regulator 43 and abnormal gas pressure sensor 48 are assumed as causes for the detected gas pressure to be equal to or higher than the abnormality determination reference value D4. The pressure regulation abnormality of the regulator 43 occurs due to a closed failure or the like in which foreign matter is caught in the pressure regulating valve 60. When a pressure regulation abnormality occurs in the regulator 43, the gas pressure cannot be adjusted by the regulator 43. Further, when the low-pressure pipe portion 41b and the high-pressure pipe portion 41a are brought into communication due to an abnormal pressure regulation of the regulator 43, the gas pressure rapidly rises. Therefore, even if the shutoff valve 45 is shut off, the detected gas pressure is temporarily relieved. The pressure D3 may be exceeded.

  Therefore, when the pressure regulation abnormality of the regulator 43 occurs, the control unit 80 reduces the gas pressure by performing fuel injection by the first injection valve 21. In this case, since the fuel injection by the first injection valve 21 can be performed before the gas pressure reaches the relief pressure D3, the gas pressure in the low-pressure pipe portion 41b can be reduced while suppressing the gas fuel from being released into the atmosphere.

  When the detected gas pressure exceeds or is likely to exceed the relief pressure D3, the control unit 80 determines whether the first fuel injection is stopped regardless of whether the fuel injection is stopped or the liquid fuel is being injected by the second injection valve 22. The fuel injection by the injection valve 21 is forcibly performed to reduce the gas pressure. Thereby, regardless of the operating state of the engine 10, when the gas fuel has a high pressure, the pressure of the gas fuel can be lowered while suppressing the atmospheric emission of the gas fuel.

  Further, when the gas fuel becomes high pressure due to abnormal pressure regulation, it is assumed that the gas pressure continues to rise even if the gas fuel is discharged using the first injection valve 21. In this case, when the gas pressure reaches the relief pressure D3, the relief valve 69 is opened. That is, in the case of the present embodiment, the relief valve 69 is opened only when the increase in gas pressure is not suppressed even if the pressure reducing process by the first injection valve 21 is performed. Can reduce atmospheric emissions.

  In the present embodiment, the relief pressure D3 is set within the pressure range D1 of the first injection valve 21. Therefore, the pressure reduction by the first injection valve 21 can be continued even after the gas pressure reaches the relief pressure D3. In this case, the state in which the gas pressure is high enough to exceed the relief pressure D3 can be eliminated at an early stage, the period during which the relief valve 69 is in the open state can be shortened, and the atmospheric emission of gas fuel can be reduced. Can be reduced.

  On the other hand, when the gas fuel becomes high pressure due to an abnormality in the gas pressure sensor 48, the gas pressure can be adjusted using the regulator 43. Therefore, in this case, the control unit 80 invalidates the detection value of the gas pressure by the gas pressure sensor 48 and regards the predetermined value as the current gas pressure, and continues the pressure adjustment by the regulator 43. As a result, the gas pressure is reduced.

  Next, processing of the fuel injection system for the internal combustion engine according to the present embodiment will be described with reference to the flowchart of FIG.

  In FIG. 6, it is determined whether or not the pressure of the gas fuel detected by the gas pressure sensor 48 is larger than the abnormality determination reference value D4 (S11).

  If the pressure of the gas fuel is larger than the abnormality determination reference value D4, it is determined whether or not the gas pressure sensor 48 is abnormal (S12). This process is performed when there is no predetermined correlation between the amount of fuel injected from the first injection means (required injection amount determined from the engine operating conditions) and the amount of change in the detected gas pressure on the pressure reduction side, that is, feedback in feedback control. When the control amount does not converge, it is determined that the gas pressure sensor 48 is abnormal.

  When the gas pressure sensor 48 cannot correctly detect the pressure of the gas fuel, feedback control using the feedback control amount calculated based on the erroneously detected gas pressure is performed. In this case, since the deviation of the detected value of the gas pressure cannot be absorbed by the feedback control, the feedback control amount does not converge. On the other hand, when the gas pressure sensor 48 correctly detects the gas pressure, the change in the gas pressure is absorbed by the feedback control according to the detection result of the gas pressure. Then, abnormality determination of the gas pressure sensor 48 is performed.

  If it is determined in S12 that the gas pressure sensor 48 is abnormal, the abnormality determination flag of the gas pressure sensor 48 is turned on (S13). Then, a predetermined value is output as a detected value of the gas pressure (S14). For example, a value determined based on the set gas pressure of the vehicle is output.

  If it is determined in S12 that the gas pressure sensor 48 is normal, the pressure regulation abnormality flag is set to ON (S15) because the pressure regulation by the regulator 43 is abnormal. In this case, the alternator 95 is instructed to generate power in order to charge the battery 93 (S16). Thereby, even under a situation where the gas pressure is high, a sufficient battery voltage can be secured, and the first injection valve 21 can be easily opened.

  Next, it is determined whether or not the detected gas pressure is greater than or equal to the relief pressure D3 (S17). If it is determined that the detected gas pressure is greater than or equal to the relief pressure D3, an instruction signal for closing the shutoff valve 45 is output so that the supply of gas fuel from the gas tank 42 is shut off (S18). . Then, the first injection valve 21 is opened to reduce the gas pressure in the low pressure passage 52 of the regulator 43 (S19).

  If it is determined in S17 that the detected gas pressure is lower than the relief pressure D3, it is determined whether or not the state in which the detected gas exceeds the abnormality determination reference value D4 continues for a predetermined time or more (S20).

  If a positive determination is made in S20, an instruction signal for closing the shutoff valve 45 is output (S21). Then, the first injection valve 21 is opened to reduce the gas pressure in the low pressure passage 52 of the regulator 43 (S22).

  If a negative determination is made in S20, it is determined whether there is a possibility that the detected gas pressure exceeds the relief pressure D3 because the speed at which the detected gas pressure increases is faster than a predetermined value (S23). If the determination is affirmative, the process proceeds to S21, and the supply of gas fuel from the gas tank 42 is shut off (S21). Then, the first injection valve 21 is opened to reduce the gas pressure in the low pressure passage 52 (S22).

  If a negative determination is made in S23, that is, if the detected gas pressure is less than the relief pressure D3 and there is no possibility that the detected gas pressure will exceed the relief pressure D3, the processing is terminated as it is not an abnormal state. Further, when it is determined in S11 that the detected gas pressure is smaller than the abnormality determination reference value D4, when various flags are on, these flags are turned off (S24), and an instruction signal for opening the shut-off valve 45 is opened. Is output (S25).

  According to the above, the following excellent effects are exhibited.

  The pressure of the gas fuel after the pressure reduction adjustment by the regulator 43 is set within a predetermined pressure range in which the fuel injection by the first injection valve 21 is possible, and the second pressure that is the pressure at which the relief valve 69 is opened is Similarly, the value was within a predetermined pressure range and larger than the first pressure. Furthermore, the third pressure that is larger than the first pressure and smaller than the second pressure is set as the abnormality determination reference value by the gas pressure sensor 46. When the pressure detection result (detected gas pressure) exceeds the determination reference value, the pressure reduction by the fuel injection of the first injection valve 21 is performed. In this case, in a high pressure state where the detected gas pressure exceeds the abnormality determination reference value, abnormality determination can be performed before the pressure of the gas fuel reaches the second pressure (relief pressure). In addition, when the high pressure is abnormal, the pressure of the gas fuel can be reduced by injecting the gas fuel by the first injection valve 21. Therefore, the pressure of the gas fuel can be suppressed while suppressing the atmospheric emission of the gas fuel, and the gas pipe 41 can be protected from rupture.

  For example, when a malfunction occurs in the pressure adjustment function of the regulator 43, the gas pressure rapidly increases, and thus the detected gas pressure may exceed the second pressure or exceed the second pressure. In view of this, when the detected gas pressure exceeds or may exceed the second pressure, pressure reduction by injection of gaseous fuel is performed. Thereby, the pressure of the 1st injection means can be lowered, suppressing outside discharge of gas fuel.

  When the detected gas pressure exceeds the abnormality determination reference value, if there is a predetermined correlation between the required injection amount determined from the operating conditions of the engine 10 and the change width on the reduced pressure side of the detected gas pressure, the pressure adjustment by the regulator 43 Judged to be abnormal. In this case, the cause of the fuel pressure exceeding the abnormality determination reference value can be specified. Further, when the detected gas pressure exceeds the abnormality determination reference value due to the pressure regulation abnormality by the regulator 43, the external release of the gas fuel when the regulator 43 is abnormal can be suppressed by reducing the pressure by the injection of the gas fuel. it can.

  When the detected gas pressure exceeds the abnormality determination reference value, if there is no predetermined correlation between the required injection amount determined from the operating conditions of the engine 10 and the change width on the reduced pressure side of the detected gas pressure, the gas pressure sensor 46 It can be determined that there is an abnormality. Note that, when the fuel detection pressure exceeds the abnormality determination reference value due to the abnormality of the gas pressure sensor 46, the pressure of the gas fuel can be lowered using the pressure adjusting function by the regulator 43, and therefore the first injection valve 21. No pressure reduction due to fuel injection was performed. In this case, the detected gas pressure can be suppressed without performing pressure reduction by fuel injection of the first injection valve 21.

  A power generation instruction signal for instructing the power generation of the alternator 95 that supplies power to the regulator 43 is output when it is determined that the regulator 43 has a pressure regulation abnormality. Thereby, the power supply voltage for opening the 1st injection valve 21 can be ensured also in the condition where gas pressure is high.

  -Since the pressure reduction by the fuel injection of the first injection valve 21 can be performed in the opened state of the relief valve 69, the period during which the relief valve 69 is in the opened state can be shortened. Reduce atmospheric emissions.

  In a bi-fuel type internal combustion engine that uses gas fuel and liquid fuel, when the detected gas pressure exceeds the abnormality determination reference value when supplying fuel with liquid fuel, the gas fuel generated by the first injection valve 21 The pressure was reduced by spraying. In the gas fuel injection stopped state (while liquid fuel is being supplied), the gas pressure can be reduced using the fuel injection by the first injection valve 21, so that the unburned gas can be released into the atmosphere in the liquid fuel supply state. While suppressing, an increase in the fuel pressure of the gas fuel can be suppressed.

  The first injection valve 21 is configured to open when a constant current is applied during the energization period, and the configuration can be simplified, but a configuration in which a large current is applied at the beginning of the valve opening. Compared to the above, it can be said that it is disadvantageous in terms of the valve opening operation under the situation where the fuel pressure is high. However, since the voltage applied to the first injection valve 21 is increased by power generation by the alternator 95 under the situation where the fuel pressure is high, the fuel injection in the high fuel pressure state is performed while using a simple configuration as the fuel injection valve. Can be suitably implemented.

  The present invention is not limited to the description of the above embodiment, and may be implemented as follows. In the following description, the same components as those described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  When the fuel injection by the first injection valve 21 is forcibly performed in order to lower the pressure of the low-pressure pipe portion 41b, the injection amount of the gas fuel at the fuel injection timing by the next first injection valve 21 is reduced. You may be made to do. In this case, an increase in pressure of the gas fuel can be suppressed without reducing fuel consumption.

  When the fuel injection by the first injection valve 21 is forcibly performed in order to reduce the pressure of the low-pressure pipe portion 41b, normal fuel injection is performed at the fuel injection timing by the next first injection valve 21. May be. In the case of gas fuel, since the influence of excessive supply of gas fuel to the engine 10 is small, such processing may be performed.

  -In the above, the pressure reduction process implemented by S19, S22 may be implemented with respect to all the cylinders in a multi-cylinder engine, and may be implemented with respect to some cylinders among several cylinders. In addition, when the cylinder that performs the decompression process can be selected, the number of cylinders that perform the decompression process may be selected according to the detected gas pressure. For example, when the detected gas pressure is equal to or higher than the relief pressure D3, the decompression process is performed on all the cylinders. On the other hand, when the detected gas pressure is not less than the abnormality determination reference value D4 and less than the relief pressure D3, a decompression process is performed on some cylinders. At this time, the number of cylinders that perform the decompression process may be adjusted according to the magnitude of the detected gas pressure. In other words, the higher the detected gas pressure, the greater the number of cylinders on which the decompression process is performed.

  In the above, the same decompression process is performed in S19 and S22, but each decompression process in S19 and S22 may be different. For example, in the case of S19, since the output of the gas pressure sensor 48 is higher than the relief pressure D3, the amount of gas fuel injected by the first injection valve 21 is increased compared to the process of S22. Alternatively, the decompression process may be performed on all cylinders in S19, whereas the decompression process may be performed on some cylinders in S22.

  DESCRIPTION OF SYMBOLS 21 ... 1st injection valve, 41 ... Gas piping, 42 ... Gas tank, 48 ... Gas pressure sensor, 60 ... Pressure adjustment valve, 69 ... Relief valve, 80 ... Control part.

Claims (8)

First injection means (21) that enables injection of gas fuel supplied from a gas tank (42) for storing gas fuel in a high pressure state through a fuel passage (41) within a predetermined pressure range;
Injection control means (80) for controlling injection of the gas fuel by the first injection means;
Pressure adjusting means (60) provided in the fuel passage for reducing the pressure of the gas fuel supplied to the first injection means to a first pressure within a range of the predetermined pressure;
Pressure detecting means (48) for detecting the pressure of the gas fuel after pressure adjustment by the pressure adjusting means;
The fuel passage is provided between the first injection means and the pressure adjustment means in the fuel passage, and the pressure of the gas fuel after the pressure adjustment by the pressure adjustment means is within the predetermined pressure range and the first pressure A relief valve (69) that opens when the second pressure is greater than the pressure and discharges gas fuel in the fuel passage to the outside;
The third pressure smaller than the first pressure and smaller than the second pressure is set as an abnormality determination reference value, and when the detected gas pressure by the pressure detection unit exceeds the abnormality determination reference value, the pressure of the gas fuel is increased. An abnormality determination means (80) for determining an abnormality;
A fuel injection system for an internal combustion engine, comprising: a pressure reducing means (80) that performs pressure reduction by fuel injection of the first injection means when the abnormality determining means determines that there is an abnormality.   The pressure reducing means performs pressure reduction by fuel injection of the first injection means when the detected gas pressure exceeds the second pressure or when it is determined that there is a risk of exceeding the second pressure. A fuel injection system for an internal combustion engine according to claim 1. When the detected gas pressure exceeds the abnormality determination reference value, the abnormality determination unit has a predetermined correlation between the amount of fuel injected from the first injection unit and the change width on the pressure reduction side of the detected gas pressure. It is determined that the pressure adjustment by the pressure adjusting means is abnormal,
3. The fuel injection of the internal combustion engine according to claim 1, wherein the pressure reducing means performs pressure reduction by the fuel injection when the detected gas pressure exceeds the abnormality determination reference value due to a pressure regulation abnormality of the pressure adjusting means. system. When the detected gas pressure exceeds the abnormality determination reference value, the abnormality determination unit has a predetermined correlation between the amount of fuel injected from the first injection unit and a change width on the pressure reduction side of the detected gas pressure. It is determined that the pressure detecting means is abnormal,
When the detected gas pressure exceeds the abnormality determination reference value, the pressure reducing means performs pressure reduction by fuel injection of the first injection means when the abnormality determining means determines that the pressure detecting means is abnormal. The fuel injection system for an internal combustion engine according to any one of claims 1 to 3. A power supply means (95) for adjusting a power generation amount based on an operating state of the internal combustion engine and supplying power to the pressure adjustment means;
5. A unit according to claim 1, further comprising: a power generation instruction signal that instructs the power supply unit to generate power when the abnormality determination unit determines that there is an abnormality. A fuel injection system for an internal combustion engine.   6. The fuel injection system for an internal combustion engine according to claim 1, wherein the decompression unit performs decompression by fuel injection of the first injection unit in a state where the relief valve is open.   The fuel injection system for an internal combustion engine according to any one of claims 1 to 6, wherein the second pressure is higher than the first pressure and lower than twice the first pressure. In addition to the first injection means, the present invention is applied to a fuel injection system including a second injection means (22) for injecting liquid fuel, and gas fuel injection by the first injection means and liquid fuel injection by the second injection means. A fuel injection control device for an internal combustion engine that is implemented by switching between
The pressure reducing means performs pressure reduction by the gas fuel injection when the detected gas pressure exceeds the abnormality determination reference value while the liquid fuel is being injected by the second injection means. A fuel injection system for an internal combustion engine according to any one of claims 1 to 7.

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