JP2014114791A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform driving of cut-off valve and electric loads properly in a structure including the cut-off valve for cutting off a circulation of gaseous fuel and the electric loads other than the valve.SOLUTION: In a fuel passage made of a gas pipe 41 and the like, a pressure regulating valve 60 is provided which regulates a pressure of gaseous fuel supplied to a first injection valve 21 to reduce the pressure, and a tank main stop valve 44 and a cut-off valve 45 are provided. Electric power is supplied to the cut-off valve 45 and electric loads other than the valve, such as a starter, from a battery. A control unit 80 determines that a regulator upstream pressure is more than or equal to a predetermined value. In addition, under a condition determined that the cut-off valve 45 is closed and the regulator upstream pressure is more than or equal to the predetermined value, the control unit 80 controls driving of the cut-off valve 45 so that timing of open driving of the cut-off valve 45 does not overlap with a driving period of the electric load or a predetermined period including start timing of the driving within the same driving period.

Description

  The present invention relates to a fuel injection control device for an internal combustion engine.

  Conventionally, an internal combustion engine in which gas fuel such as compressed natural gas (CNG) is burned has been put into practical use. In such an internal combustion engine, a fuel supply system configured to supply gas fuel to the fuel injection valve is provided in the middle of a gas tank that stores the gas fuel in a high pressure state and a fuel pipe that connects the gas tank and the fuel injection valve. A pressure adjustment valve that adjusts the pressure of the gas fuel supplied from the pressure regulator, and a shut-off valve that is provided upstream of the pressure adjustment valve (that is, on the gas tank side) and blocks the flow of the gas fuel to the pressure adjustment valve Is known (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 11-294222

  By the way, as a configuration of the shut-off valve, an electromagnetic drive type and a so-called self-seal (self-sealing) structure is proposed in which the sealing performance is enhanced by the pressure of the gas fuel supplied to the shut-off valve. . In this case, when the shutoff valve is opened from the closed state so that the gas fuel can flow in the fuel passage, if the pressure of the gas fuel on the gas tank side is high, a large amount of electric power is required to drive the shutoff valve. Can be considered. For this reason, when the opening drive of the shut-off valve and the driving of an electric load other than the shut-off valve are performed in duplicate, there is a concern that the drive may be hindered in any of the shut-off valve and other electric loads.

  The present invention provides a fuel injection control device for an internal combustion engine that can appropriately drive the shut-off valve and the electric load in a configuration including a shut-off valve that shuts off the flow of gas fuel and the other electric load. The main purpose is to do.

  Hereinafter, means for solving the above-described problems and the effects thereof will be described.

  The present invention is provided in a gas tank (42) for storing gas fuel in a high pressure state, fuel injection means (21) for injecting gas fuel supplied from the gas tank through a fuel passage (41), and the fuel passage, A pressure adjusting valve (60) for adjusting the pressure of the gas fuel supplied to the fuel injection means, and an upstream side of the pressure adjusting valve in the fuel passage, and the gas fuel from the gas tank in a closed state The pressure in the closing direction is applied by the pressure, the flow of the gas fuel is shut off by the closing, and the shut-off valve (45) that is driven by the power supply from the power supply unit (93) to be in an open state, The present invention is applied to a fuel injection system including an electric load (44, 91) other than the shut-off valve driven by power supply. The pressure determining means for determining that the fuel pressure in the high pressure passage (41a, 51) between the gas tank and the pressure regulating valve is equal to or higher than a predetermined value, and the shutoff valve are closed. In addition, under the situation where the pressure determination means determines that the fuel pressure in the high pressure passage portion is equal to or higher than a predetermined value, the timing of the opening drive that opens the shutoff valve from the closed state is the driving timing of the electric load, or Shut-off valve control means for controlling the drive of the shut-off valve so as not to overlap with a predetermined time within the same drive timing and including the start timing of the drive.

  When the fuel pressure in the high pressure passage between the gas tank and the pressure regulating valve is in a high pressure state, it is difficult to open the shut-off valve, and the driving power required for the opening operation increases. That is, the shutoff valve is provided with a force in the closing direction by the pressure of the gas fuel from the gas tank in the closed state, and shuts off the flow of the gas fuel by the closure, and the high pressure passage portion is in a high pressure state. Then, a relatively large drive power is required to shift to the open state. For this reason, when the shut-off valve is driven to open at the same time as another electric load is driven, there is a concern that the power for opening the shut-off valve is insufficient.

  In this regard, according to the above configuration, when the fuel pressure in the high pressure passage portion is in a high pressure state, the timing for opening the shut-off valve does not overlap with the driving timing of another electric load or a predetermined timing within the driving timing. In this way, the drive of the shut-off valve is controlled. Therefore, even when the fuel pressure in the high-pressure passage is in a high pressure state and it is difficult to open the shut-off valve, the drive power required to open the shut-off valve can be secured, and the shut-off valve can be opened properly. Can be implemented. As a result, in a configuration including a shut-off valve that shuts off the flow of gas fuel and an electrical load other than that, the shut-off valve and the electrical load can be appropriately driven.

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 figure which shows the structure of the electric power supply system with respect to each electric load. The flowchart which shows the engine starting process by gas fuel. The flowchart which shows the valve opening permission determination process of a cutoff valve. The time chart for demonstrating the mode of the engine start by gas fuel. The flowchart which shows an injection switching control process. The time chart for demonstrating the switching operation | movement from gas fuel to liquid fuel.

  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.

  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. The regulator 43 (a pressure adjusting valve 60, which will be described in more detail later) is configured to use gas fuel in a high pressure state (for example, a maximum of 20 MPa) stored in the gas tank 42 with a predetermined set pressure (for example, an injection pressure of the first injection valve 21). The gas fuel after the pressure reduction adjustment is supplied to the first injection valve 21 through the gas pipe 41. In the gas pipe 41, the upstream side of the regulator 43 is a high-pressure pipe portion 41a that forms a high-pressure side passage, and the downstream side is a low-pressure pipe portion 41b that forms a low-pressure side passage.

  Further, a gas fuel passage formed by the gas pipe 41 and the like further includes a tank main stop valve 44 (tank outlet valve) disposed in the vicinity of the fuel outlet of the gas tank 42 and a downstream side of the tank main stop valve 44. And a shutoff valve 45 disposed in the vicinity of the fuel inlet of the regulator 43. The valves 44, 45 allow and shut off the flow of gas fuel in the gas pipe 41. Yes. Both the tank main stop valve 44 and the shut-off valve 45 are electromagnetic on-off valves, and are normally closed so that the flow of gas fuel is cut off when not energized and the flow of gas fuel is allowed when energized.

  In the gas piping 41, a pressure sensor 46 for detecting the fuel pressure and a temperature sensor 47 for detecting the fuel temperature are provided in the high pressure piping portion 41a, and a pressure sensor 48 for detecting the fuel pressure in the low pressure piping portion 41b. A temperature sensor 49 for detecting the fuel temperature is provided.

  The shut-off valve 45 and the pressure sensor 46 can be provided integrally with the regulator 43. In this embodiment, a configuration in which the shut-off valve 45 and the pressure sensor 46 are provided integrally with the regulator 43 is adopted. (Details will be described later in FIG. 3).

  Here, a specific 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 pressure sensor 46 are provided. The pressure sensor 46 detects the pressure of the gas fuel upstream of 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. The configuration will be briefly described. The shut-off valve 45 has a valve body 55 biased in the valve closing direction by a spring 54, and the valve body 55 is closed against the biasing force of the spring 54 by energizing the electromagnetic drive unit 56. The valve is displaced from the 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 shutoff valve 45, the pressure sensor 46, and the pressure adjustment valve 60 are integrally provided in the regulator 43, but this may be changed, for example, the shutoff valve 45 and the pressure sensor 46 are connected to the regulator. It is also possible to provide it in the high-pressure piping part 41 a as a separate body from 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, etc.) provided in the present system, including the throttle opening sensor 15b, the exhaust sensor 18, the pressure sensors 46, 48, and the temperature sensors 47, 49 described above. A vehicle speed sensor or the like), 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 an operation state based on the output signals of the above-described sensors, and performs the above-described drive unit control based on the operation state.

  Various electric loads such as the tank main stop valve 44 and the shut-off valve 45 described above are configured to operate upon receiving power supply from the vehicle-mounted battery, and the configuration of the power supply system is shown in FIG. 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.

  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.

  By the way, when the fuel pressure in the high-pressure passage (the high-pressure pipe 41a and the high-pressure passage 51) between the gas tank 42 and the pressure regulating valve 60 is in a high pressure state, the opening operation of the shut-off valve 45 is caused accordingly. It becomes difficult to increase the driving power required for the valve opening operation. That is, the shutoff valve 45 is provided with a force in the closing direction by the pressure of the gas fuel from the gas tank 42 in the closed state, and shuts off the flow of the gas fuel by the closure. It is necessary to generate a driving force that overcomes the fuel pressure on the side. Therefore, when the high-pressure passage portion is in a high-pressure state, a relatively large drive power is required to shift to the open state. Therefore, when the shut-off valve 45 is driven to open at the same time as another electric load, the electric power for driving the shut-off valve 45 to open is concerned.

  Therefore, in the present embodiment, the control unit 80 determines that the fuel pressure in the high-pressure passage is in a high-pressure state, and under that high-pressure state, the start timing of the valve-opening drive of the shut-off valve 45 is other electrical load. The drive of the shutoff valve 45 is controlled so as not to overlap with the drive time or a predetermined time within the drive time (pressure determination means, shutoff valve control means). As a result, even when the fuel pressure in the high pressure passage portion is in a high pressure state and the valve opening operation of the shut-off valve 45 is difficult, the drive power required to open the shut-off valve 45 is ensured. The valve opening drive of 45 can be appropriately performed. In the following description, the fuel pressure in the high-pressure passage is also referred to as “regulator upstream pressure” for convenience.

  FIG. 5 is a flowchart showing a procedure of engine start processing using gas fuel, and this processing is repeatedly performed by the CPU 81 of the control unit 80 at a predetermined cycle.

  In FIG. 5, in step S <b> 11, it is determined whether or not there is a request for engine start with gas fuel. For example, when the remaining amount of the liquid fuel is small, the start by the gas fuel instead of the liquid fuel is selected as the engine start, and a corresponding start request is generated. If there is no start request, the process is terminated as it is, and if there is a start request, the process proceeds to the subsequent step S12.

  In step S12, it is determined whether the regulator upstream pressure is equal to or greater than a predetermined determination value K1. The regulator upstream pressure is calculated from the detection value of the pressure sensor 46. The determination value K1 is a threshold value for determining whether the regulator upstream pressure is high enough to affect the valve opening operation of the shutoff valve 45, and is, for example, 10 MPa. If the regulator upstream pressure is less than the determination value K1, the process proceeds to step S13, and engine start (cranking) by the starter 91 is started. Further, subsequently, in step S14, an opening command for opening the shut-off valve 45 is output, in step S15, an opening command for opening the tank main stop valve 44 is output, and in step S16, the first injection valve 21 is output. Allow gas fuel injection by. Thereafter, this process is terminated.

  On the other hand, if the regulator upstream pressure is equal to or higher than the determination value K1, the process proceeds to step S17, and engine start (cranking) by the starter 91 is started. In the subsequent step S18, the injection of gas fuel by the first injection valve 21 is permitted. Thereafter, in step S19, a permission determination is made as to whether or not the shutoff valve 45 may be opened. This permission determination is performed according to the procedure shown in FIG.

  In FIG. 6, in steps S31 to S35, success or failure of the valve opening permission condition is determined. Specifically, in step S31, it is determined whether the engine start has been completed. The determination of whether or not the start is complete may be performed, for example, depending on whether or not the engine speed has increased to a predetermined value (start completion determination value, for example, 700 rpm).

  In step S32, it is determined whether a predetermined time has elapsed from the start of cranking. In step S33, it is determined whether the engine speed (cranking speed) by cranking is stable.

  In step S34, it is determined whether or not the battery voltage is equal to or higher than a predetermined determination value K2. This determination value K2 is a threshold value for determining whether or not power supply for normally driving both the starter 91 and the shutoff valve 45 is possible even in a state where the regulator upstream pressure ≧ K1, in other words, For example, it is a threshold value for determining that the battery voltage has not dropped excessively.

  In step S35, it is determined whether or not the injection pressure that is the fuel pressure on the downstream side of the regulator is equal to or less than a predetermined determination value K3. The injection pressure is calculated from the detection value of the pressure sensor 48. The determination value K3 is a threshold value for determining that the injection pressure has decreased to a level at which the fuel injection by the first injection valve 21 is hindered. In other words, the injection pressure is excessively decreased. It is a threshold value for determining whether or not. The determination value K3 is, for example, a set pressure −α in the regulator.

  And if any of step S31-S35 is YES, it will progress to step S36 and will open | release the shut-off valve 45. Further, if all of Steps S31 to S35 are NO, the present process is terminated without permitting the opening of the shutoff valve 45.

  Returning to the description of FIG. 5, in step S <b> 20, it is determined whether or not opening of the shut-off valve 45 is permitted based on the determination result in step S <b> 19 (the process of FIG. 6). If the valve opening is not permitted, the process is terminated as it is. That is, the shut-off valve 45 is not opened and is kept closed. If the valve opening is permitted, the process proceeds to step S21. In step S21, an opening command for opening the shutoff valve 45 is output.

  Thereafter, in step S22, it is determined whether or not a predetermined time (for example, several seconds) has elapsed since the output of the opening command for the shutoff valve 45. Then, if the predetermined time has not elapsed since the opening command, the present process is terminated, and if the predetermined time has elapsed, the process proceeds to step S23. In step S23, an opening command for opening the tank main stop valve 44 is output, and then this process is terminated.

  FIG. 7 is a time chart for explaining how the engine is started with gas fuel. Note that the tank main stop valve 44 and the shutoff valve 45 are in a closed state before the timing t1 before the engine is started.

  Now, at the timing t1, the request | requirement of starting using gas fuel arises. In this example, it is assumed that the regulator upstream pressure is equal to or higher than the determination value K1 at the timing t1. Further, it is assumed that the battery voltage is smaller than the determination value K2 and the injection pressure is larger than the determination value K3. In this case, cranking by the starter 91 is started in response to the start request, but the tank main stop valve 44 and the shutoff valve 45 are maintained in the closed state. At timing t1, the battery voltage temporarily decreases as the starter is driven. After timing t1, the engine speed increases due to cranking.

  Thereafter, at the timing t2, the fuel injection of the first injection valve 21 is started while the tank main stop valve 44 and the shutoff valve 45 are closed, and the engine is started with gas fuel. Along with this, the injection pressure (regulator downstream pressure) decreases.

  Thereafter, at timing t3, the engine start has been completed, a predetermined time has elapsed since the start of cranking, or the engine rotation speed (cranking rotation speed) due to cranking is stable. Accordingly, the shut-off valve 45 is opened. Here, the shutoff valve 45 is opened based on the fact that a predetermined time has passed since the cranking start. Furthermore, the tank main stop valve 44 is opened at a timing t4 delayed from the opening of the shutoff valve 45. At timing t5, completion of engine start is determined based on an increase in engine rotation speed due to combustion of gas fuel, and cranking by the starter 91 is completed. Thereafter, the engine speed increases with acceleration and the like, and the battery voltage increases due to the increase in the amount of power generated by the generator.

  By the way, if the regulator upstream pressure is smaller than the judgment value K1 at the time when the start request is generated (timing t1), the starter drive, the open drive of the shut-off valve 45, and the open drive of the tank main stop valve 44 are overlapped. These are allowed to be performed, and both of these are performed at timing t1.

  If the battery voltage is equal to or higher than the determination value K2 or the injection pressure is equal to or lower than the determination value K3 at the time when the start request is generated (timing t1), the starter drive and the opening drive of the shut-off valve 45 are performed at the timing t1. The tank main stop valve 44 is opened at a timing delayed from the opening of the shut-off valve 45.

  Even when a request for switching from liquid fuel to gas fuel is generated, it is determined whether the regulator upstream pressure is equal to or higher than the determination value K1, as in FIG. When the regulator upstream pressure is equal to or greater than K1, after the gas fuel injection by the first injection valve 21 is permitted, each of the electric valves is operated in the order of the valve opening drive of the shutoff valve 45 and the valve main drive valve 44. The load may be driven (steps S18 to S23 in FIG. 5).

  Next, the injection switching control in the case of stopping the injection of gas fuel by the first injection valve 21 (including the case of switching from gas fuel to liquid fuel) will be described. FIG. 8 is a flowchart showing the procedure of the injection switching control process, and this process is repeatedly performed by the CPU 81 of the control unit 80 at a predetermined cycle.

  In FIG. 8, in step S41, it is determined whether or not a request for switching from gas fuel to liquid fuel is generated. Then, if a switching request is not generated, the present process is terminated as it is, and if a switching request is generated, the process proceeds to the subsequent step S42. In step S42, it is determined whether the regulator upstream pressure is greater than or equal to a predetermined determination value K4. This determination value K4 is a threshold value for determining whether or not the regulator upstream pressure is high enough to affect the valve opening operation of the shutoff valve 45. For example, the determination value K4 is a determination value K1 (see FIG. 5). It is good that it is 10 MPa similarly to step S12).

  If the regulator upstream pressure is less than the determination value K4, the process proceeds to step S43, and a close command for closing the tank main stop valve 44 is output. In step S44, a close command for closing the shutoff valve 45 is output, and in step S45, fuel injection of the first injection valve 21 is stopped.

  On the other hand, if the regulator upstream pressure is equal to or higher than the determination value K4, the process proceeds to step S46, and a close command for closing the tank main stop valve 44 is output. In subsequent step S47, it is determined whether or not a predetermined time (for example, several seconds) has elapsed from the output of the close command of the tank main stop valve 44. If the predetermined time has elapsed from the close command, the process proceeds to step S48. In step S48, an opening command for closing the shutoff valve 45 is output. In subsequent step S49, it is determined whether or not a predetermined time (for example, several seconds) has elapsed from the output of the shutoff valve 45 closing command. If the predetermined time has passed from the closing command, the process proceeds to step S50. In step S50, the injection of gas fuel by the first injection valve 21 is stopped.

  FIG. 9 is a time chart for explaining the switching operation from the gas fuel to the liquid fuel. Prior to timing t11, fuel injection with gas fuel is performed, and the tank main stop valve 44 and the shutoff valve 45 are in the open state.

  In FIG. 9, at timing t11, a request for switching from gas fuel to liquid fuel occurs. In this example, it is assumed that the regulator upstream pressure is equal to or higher than the determination value K4 at the timing t11. In this case, in response to the switching request, power supply to the tank main stop valve 44 is first stopped and the tank main stop valve 44 is closed. Thereafter, at timing t12, the energization of the shutoff valve 45 is stopped and the shutoff valve 45 is closed. Further thereafter, at timing t13, the injection of gas fuel by the first injection valve 21 is stopped.

  In short, when the regulator upstream pressure is high (when K1 or more), a series of injections in the order of closing the tank main stop valve 44, closing the shutoff valve 45, and stopping injection of the first injection valve 21. Stop control is implemented. However, when the regulator upstream pressure is not high (less than K1), the series of injection stop control is not performed.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  When the regulator upstream pressure (the fuel pressure in the high-pressure passage between the gas tank 42 and the pressure regulating valve 60) is in a high pressure state, the timing for opening the shut-off valve 45 depends on other factors such as the tank main stop valve 44 and the starter 91. The drive of the shut-off valve 45 is controlled so as not to overlap with the driving timing of the electric load or a predetermined timing within the driving timing (for example, the initial cranking period). Therefore, even when the upstream pressure of the regulator is high and it is difficult to open the shut-off valve 45, the drive power required to open the shut-off valve 45 can be secured, and the shut-off valve 45 is appropriately opened. it can. For example, when the engine is started or when switching from the engine operating state using liquid fuel to the engine operating state using gas fuel, the shut-off valve 45 can be appropriately driven to open. As a result, in the configuration including the shutoff valve 45 and other electrical loads, the shutoff valve 45 and the electrical load can be appropriately driven.

  When the injection pressure (supply gas pressure) is in a low pressure state, priority should be given to increasing the injection pressure. In such a case, the shutoff valve 45 can be opened regardless of overlap with the drive of the starter 91. Valve drive was implemented. As a result, when the injection pressure is in a low pressure state, the injection pressure can be quickly increased, and the engine 10 can be appropriately operated with gas fuel.

  When the battery voltage is sufficiently high, there is a margin in power supply to each electric load, and even if the regulator upstream pressure is high and the shutoff valve 45 is difficult to open, the power to the shutoff valve 45 is high. Supply and power supply to the starter 91 (other electric load) can be performed simultaneously. Therefore, when the battery voltage is sufficiently high, the injection pressure can be increased quickly, and the engine 10 can be properly operated with gas fuel.

  When the engine is started by the starter 91, electric power is required to drive the starter 91. In particular, at the beginning of driving the starter 91, the driving power becomes large. Therefore, if the regulator upstream pressure is high and the shutoff valve 45 is difficult to open, there is a concern that the shutoff valve 45 cannot be properly opened. In this regard, since the drive of the shutoff valve 45 is controlled so that the valve opening start timing of the shutoff valve 45 does not overlap the start timing of the starter 91 or the initial start timing (starting cranking period) by the starter 91, the shutoff valve 45 is controlled. The proper valve opening operation can be realized.

  The valve opening start timing of the shut-off valve 45 is not overlapped with the drive timing for opening the tank main stop valve 44, and the shut-off valve 45 is driven to open before the tank main stop valve 44 is opened. Thus, the drive of the shut-off valve 45 is controlled. That is, each valve is opened in order from the downstream side in the gas pipe 41. Thereby, the valve opening drive of these shut-off valve 45 and the tank main stop valve 44 can each be implemented appropriately. In this case, when the tank main stop valve 44 is opened first, the regulator upstream pressure rises before the shut-off valve 45 is opened. However, by opening the tank main stop valve 44 later, the shut-off valve 45 is opened. It is possible to suppress an increase in the upstream pressure of the regulator before the valve is opened, which is convenient for driving the shutoff valve 45 to open.

  When the shut-off valve 45 is closed when the engine is started, the injection of gas fuel by the first injection valve 21 is allowed before the opening drive thereof, so that the shut-off valve 45 is in a closed state. However, the engine can be started with gas fuel. When the regulator upstream pressure is high, high-pressure gas fuel flows out downstream of the regulator 43 due to fuel leakage at the shutoff valve 45 or the pressure regulating valve 60, and at least fuel injection by the first injection valve 21 is performed. It is considered that the injection pressure is increased as much as possible. Therefore, even when the shut-off valve 45 is closed, the gas fuel can be injected by the first injection valve 21.

  When switching from gas fuel to liquid fuel (in other words, when stopping the injection of gas fuel by the first injection valve 21), each valve is sequentially shut off from the upstream side in the gas pipe 41. . That is, the driving is stopped in the order of the tank main stop valve 44 → the shut-off valve 45 → the first injection valve 21. Thereby, it is possible to prevent the fuel pressure in the gas pipe 41 from becoming higher than that during the injection of the gas fuel after the injection of the gas fuel is stopped. Therefore, the opening operation of the shutoff valve 45 can be facilitated at the start of the next injection of gas fuel. This effect can be similarly expected for the first injection valve 21.

  In spite of a request for switching from gas fuel to liquid fuel, the injection of the gas fuel is not stopped immediately, and the injection of the gas fuel is stopped after the tank main stop valve 44 and the shutoff valve 45 are closed. In the configuration, there is a concern that the driver may feel uncomfortable. In this respect, in the above configuration, the control (corresponding to “a series of injection stop control”) in which the injection of the gas fuel is stopped after the tank main stop valve 44 and the shutoff valve 45 are closed is a high regulator upstream pressure. Only done in certain cases. In this case, the control in which the injection of gas fuel is stopped after the tank main stop valve 44 and the shutoff valve 45 are closed is performed only in a situation where the shutoff valve 45 is difficult to close, and the driver feels uncomfortable. Can be minimized.

(Other embodiments)
You may change the said embodiment as follows, for example.

  In the above embodiment, for example, when the upstream pressure of the regulator is equal to or higher than the determination value K1 at the time of starting the engine, after the start of the cranking, the shut-off valve 45 is moved first and the tank main stop valve 44 is opened in order. Although it is configured to be driven, it is possible to change this and configure the shut-off valve 45 and the tank main stop valve 44 to be opened simultaneously after cranking is started. In addition, the fuel injection by the first injection valve 21 is permitted prior to the opening of the shut-off valve 45, but this is changed so that the fuel injection by the first injection valve 21 is performed simultaneously with the opening of the shut-off valve 45. It is good also as a structure to permit.

  In the above embodiment, when the injection pressure is less than or equal to the predetermined value, or when the battery voltage is greater than or equal to the predetermined value, the shutoff valve 45 is set according to the drive request regardless of the overlap of drive with other electric loads. Although it is configured to open (see FIG. 6), instead of or in addition to this, when the engine water temperature is equal to or higher than a predetermined value (when the engine warm-up is completed) A configuration may be adopted in which the shut-off valve 45 is driven to open in response to a drive request regardless of the overlap of driving.

  In the shut-off valve 45, oil (oil content in gas fuel) enters the sliding portion of the valve body 55. When the engine water temperature is low, the oil becomes highly viscous, so the shut-off valve 45 is opened. It seems to be in a difficult state. On the other hand, since the viscosity of the oil decreases when the engine water temperature is high, the shutoff valve 45 is relatively easy to open. Therefore, when the engine water temperature is equal to or higher than the predetermined value as described above, the shut-off valve 45 may be driven to open in response to a drive request regardless of the drive overlap with other electric loads. Note that the driving load is relatively small even when the starter is started in a state where the engine water temperature is high. Therefore, from the viewpoint of power consumption on the starter side, it can be said that it is desirable to drive the shut-off valve 45 in response to the drive request regardless of the starter drive overlap when the engine water temperature is equal to or higher than the predetermined value. .

  In order to stop the injection of gas fuel by the first injection valve 21, the gas pipe 41 starts from the upstream side (tank main) on condition that the outside air temperature is a predetermined value (for example, 10 ° C. or 0 ° C.) or less. Each valve may be blocked in the order of stop valve 44 → shutoff valve 45 → first injection valve 21).

  As each injection valve 21, 22, an opening adjustment type injection valve whose valve opening (opening opening area) is adjusted continuously or in multiple stages by electrically driving an electromagnetic drive unit (not shown). In this case, the valve opening is adjusted by a duty signal input from the control unit 80. At this time, the fuel flow rate per unit time is adjusted according to the valve opening degree of each injection valve 21, 22, and the fuel (gas fuel, liquid fuel) whose flow rate is adjusted is supplied to the intake port of each cylinder.

  In the above embodiment, the injection valves 21 and 22 are provided for each cylinder of the multi-cylinder engine. However, the injection valves 21 and 22 may be provided in common for a plurality of cylinders. . For example, a configuration in which gas fuel or liquid fuel is injected into a collection portion of the intake system 11 may be employed.

  In the above embodiment, the present invention is embodied in a bi-fuel engine that uses gas fuel (CNG) and liquid fuel (gasoline) as combustion fuel. However, this is changed to a gas that uses only gas fuel. It is also possible to embody the present invention with an engine.

  In the above embodiment, the CNG fuel is used as the gas fuel, but other gas fuels that are gas in the standard state can be used, for example, methane, ethane, propane, butane, hydrogen, DME, etc. as the main component. A configuration using fuel may also be used. Further, the liquid fuel is not limited to gasoline fuel, and for example, light oil or the like may be used.

  DESCRIPTION OF SYMBOLS 10 ... Engine (internal combustion engine), 21 ... 1st injection valve (fuel injection means), 41 ... Gas piping (fuel passage), 41a ... High pressure piping part (high pressure passage part), 42 ... Gas tank, 44 ... Tank main stop valve (Electric load), 45 ... shut-off valve, 51 ... high-pressure passage (high-pressure passage section), 80 ... control section (fuel injection control device, pressure determination means, shut-off valve control means), 91 ... starter (electric load), 93 ... In-vehicle battery (power supply unit).

Claims (8)

A gas tank (42) for storing gaseous fuel in a high pressure state;
Fuel injection means (21) for injecting gas fuel supplied from the gas tank through the fuel passage (41);
A pressure adjusting valve (60) provided in the fuel passage for reducing the pressure of the gas fuel supplied to the fuel injection means;
In the fuel passage, provided upstream of the pressure regulating valve, a force in the closing direction is applied by the pressure of the gas fuel from the gas tank in the closed state, the flow of the gas fuel is shut off by the closing, and a power supply unit ( 93) a shut-off valve (45) which is driven by the power supply from 93 to be opened;
An electric load (44, 91) other than the shut-off valve, driven by power supply from the power supply unit;
A fuel injection control device for an internal combustion engine applied to a fuel injection system comprising:
Pressure determining means for determining that the fuel pressure in the high pressure passage (41a, 51) between the gas tank and the pressure regulating valve is equal to or greater than a predetermined value;
In a situation where the shutoff valve is closed and the pressure judgment means determines that the fuel pressure in the high pressure passage is equal to or higher than a predetermined value, the timing of the opening drive to open the shutoff valve from the closed state is Shut-off valve control means for controlling the drive of the shut-off valve so as not to overlap with the drive timing of the electric load, or within a predetermined timing including the start timing of the drive within the drive timing;
A fuel injection control device for an internal combustion engine, comprising: An injection pressure determination means for determining that an injection pressure, which is a pressure of gas fuel supplied to the fuel injection means, is equal to or less than a predetermined value;
When the injection pressure determining means determines that the injection pressure is less than or equal to a predetermined value, the shut-off valve control means sets the shut-off valve in response to a drive request regardless of overlapping driving with the electric load. The fuel injection control device for an internal combustion engine according to claim 1, wherein the fuel injection control device is driven to open. Voltage determining means for determining whether or not the output voltage of the power supply unit is equal to or higher than a predetermined value;
The shut-off valve control means opens the shut-off valve in response to a drive request when the output voltage is judged to be equal to or higher than a predetermined value by the voltage judgment means, regardless of overlapping driving with the electric load. 3. The fuel injection control device for an internal combustion engine according to claim 1, wherein the fuel injection control device is driven. The electric load is applied to a fuel injection system including a starter (91) for applying an initial rotation for start to the internal combustion engine,
The shut-off valve control means controls the driving of the shut-off valve so that the timing for opening the shut-off valve does not overlap with the drive timing of the starter or the initial start timing by the starter. 4. The fuel injection control device for an internal combustion engine according to claim 3. The electric load is applied to a fuel injection system provided with a tank outlet valve (44) provided in the vicinity of a fuel outlet of the gas tank and having a shut-off function for blocking the flow of gas fuel,
The shut-off valve control means drives the shut-off valve so that the shut-off valve opening drive timing does not overlap with the drive timing for opening the tank outlet valve and prior to the tank outlet valve open drive. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 4, wherein the drive of the shut-off valve is controlled as described above.   An injection request for starting injection of gas fuel by the fuel injection means in a situation where the shut-off valve is closed and the pressure determination means determines that the fuel pressure in the high pressure passage portion is equal to or higher than a predetermined value The fuel injection control device for an internal combustion engine according to any one of claims 1 to 5, further comprising means for permitting the injection of the gas fuel before the timing of opening the shut-off valve in the event of occurrence of . The electric load is applied to a fuel injection system provided with a tank outlet valve (44) provided in the vicinity of a fuel outlet of the gas tank and having a shut-off function for blocking the flow of gas fuel,
In the state where both the shutoff valve and the tank outlet valve are open, when a stop request is made to stop the injection of gas fuel by the fuel injection means, the tank outlet valve is moved first after the shutoff valve. 7. An injection stop control means for carrying out a series of injection stop controls that close these in turn and then stop the injection of gas fuel by the fuel injection means. A fuel injection control device for an internal combustion engine as described.   The injection stop control unit performs the series of injection stop control when the pressure determination unit determines that the fuel pressure in the high pressure passage is equal to or higher than a predetermined value, and the pressure determination unit performs the series of injection stop control. The fuel injection control device for an internal combustion engine according to claim 7, wherein the series of injection stop control is not performed when it is determined that the fuel pressure of the part is less than a predetermined value.

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