JP2014169662A - Fuel supply control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly diagnose abnormality such as clogging of a filter provided to a fuel supply system for supplying gas fuel to an internal combustion engine.SOLUTION: A fuel supply system comprises: a gas tank 42 for storing gas fuel in a high-pressure state; a first injection valve 21 for injecting the gas fuel; a pressure control valve 60 for adjusting injection pressure to be decreased; a shut-off valve 45 provided in a high-pressure passage 51 and having a blocking function for blocking distribution of the gas fuel; and a filter 54 for removing foreign matters provided in a low-pressure passage 52. A control part 80 switches the shut-off valve 45 into a valve-opening state when fuel is injected by the first injection valve 21 while the shut-off valve 45 is closed, and then, diagnoses abnormality such as clogging of the second filter 54 on the basis of fuel pressure detected by a low-pressure sensor 47 when fuel pressure in the high-pressure passage 51 nearer a downstream side than the shut-off valve 45 becomes not less than a predetermined value.

Description

  The present invention relates to a fuel supply control device for an internal combustion engine, and more particularly to a fuel supply control device applied to a fuel supply system for an on-vehicle internal combustion engine that uses gaseous fuel.

  2. Description of the Related Art Conventionally, internal combustion engines that are driven by burning gaseous fuel such as compressed natural gas (CNG) have been put into practical use. In such an internal combustion engine, the fuel supply system for supplying the gaseous fuel to the fuel injection valve has a gas tank for storing the gaseous fuel in a high pressure state, and is provided in the middle of the fuel pipe connecting the gas tank and the fuel injection valve. A configuration is known that includes a pressure adjustment valve that adjusts the pressure of the gaseous fuel supplied from the pressure regulator, and a shutoff valve that is provided upstream of the pressure adjustment valve and blocks the flow of the gaseous fuel to the pressure adjustment valve. . In addition, a filter for removing impurities mixed in the gaseous fuel is provided in the middle of the fuel pipe (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2000-282956

  When the filter arranged in the middle of the fuel pipe is clogged, the fuel supply to the downstream side of the filter is restricted, and the amount of fuel supplied into the cylinder of the engine may be insufficient. Conceivable. Continuing the operation of the internal combustion engine in spite of the occurrence of the clogging abnormality in the filter may cause inconveniences such as a lean misfire occurring in a high load region of the engine.

  The present invention has been made to solve the above-described problem, and is a fuel for an internal combustion engine that can properly diagnose the presence or absence of a clogging abnormality in a filter provided in a fuel supply system that supplies gaseous fuel to the internal combustion engine. The main object is to provide a supply control device.

  The present invention employs the following means in order to solve the above problems.

  The present invention includes a fuel tank (42) for storing gaseous fuel in a high pressure state, fuel injection means (21) for injecting the gaseous fuel supplied from the fuel tank through a fuel passage (41), and the fuel passage. A pressure adjusting means (60, 65) for reducing the pressure of the gaseous fuel supplied to the fuel injection means, and a high pressure passage portion (41a) between the fuel tank and the pressure adjusting means in the fuel passage. 51) and a shutoff valve (45) having a shutoff function for shutting off the flow of the gaseous fuel, and a low pressure passage portion (41b, 52) between the pressure adjusting means and the fuel injection means in the fuel passage. And a filter (54) for removing foreign matter provided in the internal combustion engine (10).

  According to the first aspect of the present invention, low pressure detection means (47) for detecting a fuel pressure downstream of the filter in the low pressure passage portion, and fuel injection by the fuel injection means in a state where the shutoff valve is closed. And when the shut-off valve is opened, the valve-opening means switches the shut-off valve to the open state, and then the downstream side of the shut-off valve in the high-pressure passage portion. A pressure determination means for determining whether or not the fuel pressure on the side has become a predetermined value or more, and based on the fuel pressure detected by the low pressure detection means when the pressure determination means determines that the fuel pressure has been determined to be the predetermined value or more, An abnormality diagnosing means for performing an abnormality diagnosis for a filter clogging abnormality.

  If clogging occurs in the filter disposed downstream of the pressure adjusting means in the fuel passage of the gaseous fuel, the change in the fuel pressure in the fuel passage after the shut-off valve is switched from the closed state to the opened state The aspect is different from that in the normal state. Specifically, the fuel pressure (high-pressure side gas pressure) in the fuel passage upstream of the decompression adjusting means and downstream of the shut-off valve shows the same change mode as normal, whereas the filter However, the fuel pressure (low pressure side gas pressure) in the fuel passage on the downstream side becomes slower than normal when the pressure rises. Paying attention to such events, in this configuration, after switching the shut-off valve from the closed state to the open state, the filter is clogged abnormally based on the low pressure side gas pressure when the high pressure side gas pressure recovers to a predetermined level or higher. Carry out an abnormal diagnosis. Thereby, the presence or absence of clogging abnormality can be appropriately diagnosed about the filter provided in the gaseous fuel supply system.

1 is an overall schematic configuration diagram of an engine fuel supply control system. FIG. The figure which shows schematic structure of a regulator. The time chart which shows pressure transition at the time of normal. The time chart which shows the pressure transition at the time of clogging abnormality of the 2nd filter 54. FIG. The flowchart which shows the process sequence of a filter abnormality diagnosis process. The figure explaining the filter abnormality diagnosis process of other embodiment.

  Hereinafter, the present embodiment 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) that is gaseous fuel and gasoline that is liquid fuel as combustion fuel. It is embodied as a fuel supply system. An overall schematic diagram of this system is shown in FIG.

  An engine 10 shown in FIG. 1 is a multi-cylinder (for example, in-line three-cylinder) spark ignition engine, and an intake pipe 11 is connected to an intake port via an intake manifold 12, and an exhaust manifold is connected to an exhaust port. An exhaust pipe 14 is connected via 13. The intake pipe 11 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 detected by a throttle opening degree sensor 15b built in the throttle actuator 15a.

  The exhaust pipe 14 is provided with exhaust sensors 18a and 18b that detect exhaust components and a catalyst 19 that purifies the exhaust. As the exhaust sensors 18 a and 18 b, oxygen sensors that output detection signals corresponding to the oxygen concentration in the exhaust are provided on the upstream side and the downstream side of the catalyst 19, respectively.

  An intake valve 25 and an exhaust valve 26 as engine valves for adjusting the amount of air introduced into the cylinder are respectively provided at the intake port and the exhaust port of the engine 10. When the intake valve 25 is opened, a mixture of air and fuel is introduced into the cylinder, and when the exhaust valve 26 is opened, the exhaust gas after combustion is discharged into the exhaust passage.

  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 is ignited and used for combustion.

  In this system, as fuel injection means for injecting and supplying fuel to each cylinder of the engine 10, a first injection valve 21 that injects gaseous fuel (CNG fuel) and a second injection that injects liquid fuel (gasoline). A valve 22 is provided. These injection valves 21 and 22 respectively inject fuel into the intake manifold 12.

  Each of the injection valves 21 and 22 is an open / close type control valve in which a valve body is shifted from a closed position to an open position by electrically driving an electromagnetic drive unit. These injection valves 21 and 22 are each driven to open by an on / off type valve opening drive signal, and an amount of fuel (gaseous fuel, liquid fuel) corresponding to the energization time to the electromagnetic drive unit is supplied to each of the injection valves 21 and 22. Is injected from.

  Next, the gaseous fuel supply part 40 which supplies gaseous fuel with respect to the 1st injection valve 21 is demonstrated. In the gaseous fuel supply unit 40, a gas tank 42 is connected to the first injection valve 21 via a gas pipe 41. In the middle of the gas pipe 41, a regulator 43 having a pressure adjustment function for adjusting the pressure of the gaseous fuel supplied to the first injection valve 21 is provided. The regulator 43 uses a predetermined set pressure (for example, 0.3 to 0.4 MPa, hereinafter referred to as a regulator), which is a high pressure state (for example, a maximum of 20 MPa) of gaseous fuel stored in the gas tank 42. The pressure is adjusted so as to become the set pressure Prg.). The gaseous fuel after the decompression 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.

  The fuel passage formed by the gas pipe 41 and the like further includes a tank main stop valve 44 disposed in the vicinity of the fuel outlet of the gas tank 42 and a fuel inlet of the regulator 43 that is downstream of the tank main stop valve 44. A shut-off valve 45 disposed in the vicinity is provided. These valves 44 and 45 allow and block the flow of gaseous fuel in the gas pipe 41. Both the tank main stop valve 44 and the shutoff valve 45 are electromagnetic on-off valves, and are normally closed types that shut off the flow of gaseous fuel when not energized and allow the flow of gaseous fuel when energized.

  In the present system, the regulator 43 is integrally provided with a high pressure sensor 46 as a pressure sensor for detecting the fuel pressure before pressure reduction adjustment (the fuel pressure of the high pressure piping portion 41a). In addition, the low pressure pipe portion 41b is provided with a low pressure sensor 47 as a pressure sensor for detecting the fuel pressure. In the present system, the liquid fuel supply unit 70 that supplies the liquid fuel to the second injection valve 22 includes a fuel tank 72 that stores the liquid fuel, and the fuel tank 72 is connected to the second fuel via the fuel pipe 71. Connected to the injection valve 22. 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.

  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 so that the pressure value (regulator set pressure) in a predetermined range mechanically determined.

  In FIG. 2, 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). The high-pressure passage 51 is provided with a shut-off valve 45 and a high-pressure sensor 46. The high pressure sensor 46 detects the pressure of the gaseous fuel in the high pressure passage 51 on the downstream side of the shutoff valve 45. Further, in the high-pressure passage 51, a first filter 53 for removing foreign matter is disposed upstream of the shut-off valve 45.

  In the regulator 43, a pressure adjustment valve 60 is provided on the downstream side of the shutoff valve 45. The pressure regulating valve 60 includes a valve body chamber 61 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 a 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 and the low pressure passage 52 are communicated. If the valve body 62 is in the closed position, the valve seat portion 63 is closed and the high pressure passage is opened. Communication between 51 and the low-pressure passage 52 is blocked.

  The valve body 62 is opened and closed according to the balance between 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. Specifically, the valve body actuating portion 65 includes an opening portion 67 having a space communicating with the intake pipe 11 of the engine 10, an adjustment spring 66 provided in a space portion of the opening portion 67, an opening portion 67, and a low pressure passage. And a diaphragm 68 as a partition member for partitioning 52. The diaphragm 68 is provided integrally with the valve body 62. On the diaphragm 68, the fuel pressure in the low pressure passage 52 acts as a force in the valve closing direction, and the biasing force of the adjustment spring 66 and the pressure in the intake pipe 11 (intake pipe pressure) act as the force in the valve opening direction. .

  In such a configuration, if “force in the valve closing direction> force in the valve opening direction”, the valve body 62 is held in the valve closing position. On the other hand, when the fuel injection by the first injection valve 21 is performed and the fuel pressure in the low-pressure passage 52 is reduced to “the force in the valve closing direction <the force in the valve opening direction”, the valve body 62 accompanies the displacement of the diaphragm 68. Is displaced in the valve opening direction. At this time, the valve opening position (valve element shift 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 determined according to the valve opening position. Is changed. By changing the opening area, the amount of fuel flowing from the high pressure passage 51 into the low pressure passage 52 is adjusted, and the fuel pressure in the low pressure passage 52 is held at the regulator set pressure. The regulator set pressure indicates a value corresponding to the intake pipe pressure, and the higher the intake pipe pressure is on the positive side (the higher the engine load is), the higher the displacement of the valve body 62 in the valve opening direction.

  In the low pressure passage 52, a second filter 54 for removing foreign substances is disposed downstream of the pressure regulating valve 60, and a low pressure sensor 47 for detecting the pressure of the gaseous fuel further downstream of the second filter 54, A temperature sensor 48 for detecting the temperature of the gaseous fuel is provided. Note that paper filters are used as the first filter 53 and the second filter 54. In addition, 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. The relief valve 69 is mechanically driven, and opens when the fuel pressure in the low pressure passage 52 becomes higher than a predetermined relief pressure P. A pressure adjusting means is constituted by a pressure adjusting valve 60 composed of components such as the valve body 62 and the valve body operating portion 65.

  The control unit 80 includes a CPU, a ROM, a RAM, a backup RAM, and the like, and executes various control programs stored in the ROM, thereby performing various controls of the engine 10 according to each engine operating state. . Specifically, the control unit 80 is electrically connected to the various sensors described above and other sensors (crank angle sensor 81, intake pipe pressure sensor 82, cooling water temperature sensor 83, vehicle speed sensor, etc.) provided in the system. The outputs (detection signals) from these sensors are input. The control unit 80 is electrically connected to driving units such as the ignition device 20a and the injection valves 21 and 22, and controls the driving of each driving unit by outputting a driving signal to each driving unit. To do.

  A drive signal is input from the control unit 80 to the drive units such as the ignition device 20a and the injection valves 21 and 22, and each drive unit is driven according to the input drive signal. Specifically, the ignition device 20a outputs a high voltage in response to an ignition signal from the control unit 80, and causes an ignition spark in the ignition plug. The first injection valve 21 injects an amount of gaseous fuel according to the injection signal from the control unit 80 into the intake port, and the second injection valve 22 outputs an amount of liquid fuel according to the injection signal from the control unit 80. Inject into the intake port.

  The control unit 80 selectively switches the fuel to be used according to the engine operating state, the fuel remaining amount in the tank, an input signal from a fuel selection switch (not shown), and the like. Specifically, when the remaining amount of gaseous fuel in the gas tank 42 falls below a predetermined value or when the use of liquid fuel is selected by the fuel selection switch, the liquid fuel is used preferentially, and the fuel tank When the remaining amount of liquid fuel in 72 falls below a predetermined value or when the use of gaseous fuel is selected by the fuel selection switch, the gaseous fuel is preferentially used.

  Incidentally, impurities such as water and oil components are usually mixed in the gas fuel filled in the gas tank 42. Further, in the pressure regulating valve 60, liquefaction occurs due to the pressure reducing action when passing through the valve seat 63, so that a highly viscous foreign matter containing an oil component is precipitated, and the precipitate flows through the gas pipe 41. is there. Such foreign matter is removed by the second filter 54 before being supplied to the first injection valve 21, but the foreign matter may cause clogging in the second filter 54. Further, when clogging occurs in the second filter 54, the passage of gaseous fuel is inhibited by the second filter 54, resulting in a shortage of the amount of fuel supplied from the first injection valve 21 into the cylinder, for example, high engine load. There is a risk that lean misfire may occur or the output may be reduced. Therefore, in the present embodiment, an abnormality diagnosis is performed to determine whether or not a clogging abnormality has occurred in the second filter 54.

  Hereinafter, the filter abnormality diagnosis process of this embodiment will be described in detail. In this system, when a clogging abnormality occurs in the second filter 54, the shutoff valve 45 is switched in the order of open state → closed state → open state during the period in which fuel injection is performed by the first injection valve 21. The control section 80 detects the fuel pressure (high-pressure side detection value) detected by the high-pressure sensor 46 and the low-pressure sensor 47. The filter abnormality diagnosis is performed based on the measured fuel pressure (low-pressure side detection value).

  A specific aspect of the filter abnormality diagnosis process of the present embodiment will be described using the time charts of FIGS. First, the case where the gaseous fuel supply part 40 is normal is demonstrated using FIG. In FIG. 3, the fuel pressure (high pressure side gas pressure Pt) downstream of the shutoff valve 45 in the high pressure passage 51 and the fuel pressure (low pressure side gas pressure) downstream of the second filter 54 in the low pressure passage 52 are shown as pressure transitions. Pf) and the intake pipe pressure Pin. In FIGS. 3 and 4, it is assumed that the gaseous fuel is being injected by the first injection valve 21.

  In a state where the engine 10 is operated using gaseous fuel, normally, an open command is output to the shutoff valve 45 to keep the shutoff valve 45 open. Thereby, the flow of the gaseous fuel from the high pressure passage 51 to the low pressure passage 52 is allowed, and the injection pressure is held at the regulator set pressure Prg during the period when the fuel injection by the first injection valve 21 is performed (˜t11). . At this time, the high-pressure side gas pressure Pt becomes a value (for example, ˜20 MPa) corresponding to the remaining amount of gaseous fuel in the gas tank 42, and the low-pressure side gas pressure Pf becomes the regulator set pressure Prg.

  When the shutoff valve 45 is switched to the closed state during the period in which the fuel injection by the first injection valve 21 is performed with the shutoff valve 45 opened (t11), the gaseous fuel is generated by the fuel injection by the first injection valve 21. As it is consumed, gaseous fuel is supplied from the high pressure passage 51 to the low pressure passage 52. Thereby, the high-pressure side gas pressure Pt gradually decreases. The low-pressure side gas pressure Pf is held at the regulator set pressure Prg by supplying gaseous fuel from the high-pressure passage 51 for a while from the timing t11. When the high-pressure side gas pressure Pt falls below the regulator set pressure Prg (t12), the low-pressure side gas pressure Pf gradually decreases in the same change manner as the high-pressure side gas pressure Pt.

  At a timing t13 when a predetermined closing time ta has elapsed since the closing command to the shut-off valve 45 is issued, an open command for opening the shut-off valve 45 is output, and the shut-off valve 45 is switched to the open state. Thereby, the flow of the gaseous fuel from the upstream side to the downstream side of the shutoff valve 45 is allowed, and the high-pressure side gas pressure Pt and the low-pressure side gas pressure Pf turn up. At this time, the low-pressure side gas pressure Pf rises to the regulator set pressure Prg (t14), and is then held at the regulator set pressure Prg. The high-pressure side gas pressure Pt shows the same behavior as the low-pressure side gas pressure Pf until the regulator set pressure Prg is reached (t14). However, after reaching the regulator set pressure Prg, the pressure rises further, It returns to the value corresponding to the remaining amount of gaseous fuel, that is, the fuel pressure P1 before the shutoff valve 45 is switched to the closed state (t15).

  On the other hand, when a clogging abnormality occurs in the second filter 54, as shown in FIG. 4, the high pressure side gas pressure Pt has the same mode of pressure change as in the normal state, whereas the low pressure side gas pressure Pf. Is different from the normal mode of pressure change. Specifically, when a close command is output to the shutoff valve 45 during the period of fuel injection by the first injection valve 21, the second filter 54 is clogged for a while from the output timing t 21. The low pressure side gas pressure Pf is maintained at the fuel pressure (in FIG. 4, slightly on the low pressure side than the normal regulator set pressure Prg). However, after the high-pressure side gas pressure Pt has decreased to the low-pressure side gas pressure Pf, the fuel supply to the downstream side of the second filter 54 is restricted due to the clogging of the second filter 54. As a result, the low-pressure side gas pressure Pf decreases at a pressure reduction rate greater than the high-pressure side gas pressure Pt. Therefore, at the timing t23 when the opening command for the shutoff valve 45 is output, the low-pressure side gas pressure Pf is lower than the high-pressure side gas pressure Pt.

  After t23 when the shut-off valve 45 is opened in response to an open command for the shut-off valve 45, the fuel supply to the downstream side of the second filter 54 is restricted due to clogging of the second filter 54, so the pressure rise is increased on the high-pressure side. It becomes slower than the gas pressure Pt. Further, when the pressure difference between the high-pressure side gas pressure Pt and the low-pressure side gas pressure Pf is compared before and after the shut-off valve 45 is opened at time t23, the time difference after time t23 when the shut-off valve 45 is switched to the open state is compared. The pressure difference appears more conspicuously.

  Paying attention to the above points, the control unit 80 switches to a state in which the shutoff valve 45 is opened when fuel injection is performed by the first injection valve 21 with the shutoff valve 45 closed, and the valve is opened. After switching to the state, the second filter 54 is clogged abnormally based on the fuel pressure (detected value of the low-pressure side gas pressure Pf) detected by the low-pressure sensor 47 when the high-pressure side gas pressure Pt becomes a predetermined value or more. An abnormal diagnosis of the

  Further, the pressure adjustment valve 60 of the present embodiment variably adjusts the injection pressure according to the intake pipe pressure of the engine 10, and the injection pressure (low pressure side gas pressure Pf) increases as the intake pipe pressure increases to the positive side. Become the side. Therefore, the low pressure side gas pressure Pf when the shutoff valve 45 is opened / closed during the fuel injection period of the first injection valve 21 is the same in the pressure change mode, but the intake pipe pressure is positive. The larger it is, the higher the pressure shifts. Considering this point, in this embodiment, after switching the shut-off valve 45 to the open state, the low pressure side gas pressure Pf (low pressure side) detected by the low pressure sensor 47 when the high pressure side gas pressure Pt becomes equal to or higher than a predetermined value. Based on the difference ΔPa1 (corresponding to the first relative pressure) between the detected value) and the intake pipe pressure Pin detected by the intake pipe pressure sensor 82, the clogging abnormality of the second filter 54 is diagnosed.

  More specifically, as shown in FIG. 4, after the shut-off valve 45 in the closed state is switched to the opened state, the low pressure is reached at the time when the high-pressure side gas pressure Pt becomes equal to or higher than a predetermined value (high pressure determination value K1 or higher). The low pressure side gas pressure Pf detected by the sensor 47 and the intake pipe pressure Pin detected by the intake pipe pressure sensor 82 at the same time are acquired, and a difference ΔPa1 (= Pf−Pin) between them is obtained. Further, the difference ΔPa1 is compared with the determination value. Regarding the determination value, in this embodiment, the difference ΔPb1 between the low-pressure side gas pressure Pf detected by the low-pressure sensor 47 before the pressure drop caused by the closing of the shut-off valve 45 in the low-pressure passage 52 and the intake pipe pressure Pin at that time ( (Corresponding to the second relative pressure) is used (see FIGS. 3 and 4). Then, the first relative pressure ΔPa1 and the second relative pressure ΔPb1 are compared, and the clogging abnormality diagnosis of the second filter 54 is performed based on the comparison result. At this time, if the fuel pressure P1 before switching the shut-off valve 45 to the closed state or a value slightly lower than that is set to the high pressure determination value K1, the second filter 54 is normal. The first relative pressure ΔPa1 and the second relative pressure ΔPb1 are substantially equal (see FIG. 3). On the other hand, when the clogging of the second filter 54 is abnormal, the first relative pressure ΔPa1 is smaller than the second relative pressure ΔPb1.

  Next, the processing procedure of the filter abnormality diagnosis processing of this embodiment will be described using the flowchart of FIG. This process is executed at predetermined intervals by the CPU of the control unit 80.

  In FIG. 5, in step S100, it is determined whether or not a predetermined diagnosis condition for executing abnormality diagnosis of the second filter 54 is satisfied. The diagnostic conditions include that a predetermined time has elapsed since the engine was started, that gaseous fuel has been selected as the fuel to be used, that the engine 10 is in a steady operation state, and that the shut-off valve 45 and the tank main stop valve 44 are This includes normality, that the first injection valve 21 is normal, and that the high pressure sensor 46 and the low pressure sensor 47 are normal. Whether the shutoff valve 45, the tank main stop valve 44, the first injection valve 21, the high pressure sensor 46, and the low pressure sensor 47 are normal is determined by inputting the result of an abnormality diagnosis by another routine (not shown). .

  If the predetermined diagnosis condition is satisfied, the process proceeds to step S101, and it is determined whether or not it is after the output of the close command for closing the shutoff valve 45. If it is before the output of the closing command, a negative determination is made in step S101, the process proceeds to step S102, and a closing time ta for keeping the shutoff valve 45 in the closed state is set (time setting means). In this embodiment, the closing time ta is set according to the engine operating state, and the closing time ta is set to a shorter time as the engine load is higher or the engine speed is higher.

  The reason why the closing time ta is variably set according to the engine operating state in each case is as follows. That is, the fuel injection amount injected from the first injection valve 21 is different every time, and the larger the engine 10 is at a higher load or higher rotation, the larger the fuel injection amount from the first injection valve 21 is set. . Therefore, when the shutoff valve 45 is switched from the open state to the closed state during the period of fuel injection by the first injection valve 21, the change mode of the injection pressure after the switching varies depending on the engine operating state. Specifically, the rate of decrease in the injection pressure increases as the engine 10 has a higher load or higher rotation. Further, the greater the rate of decrease in the injection pressure, the greater the amount of decrease in the injection pressure during a predetermined time after the shutoff valve 45 is closed. Therefore, there is a possibility that the amount of fuel supplied into the cylinder is insufficient and the engine stalls. Therefore, in the present embodiment, the closing time ta is variably set according to the engine operating state every time. In the present embodiment, the relationship between the engine load, the engine rotation speed, and the closing time ta is determined in advance as a map, and the control unit 80 displays the closing time ta corresponding to each engine load and engine rotation speed in the same map. The closing time ta is set by reading from.

  In the subsequent step S103, the high pressure determination value K1 is set as the pressure determination value for determining the determination timing of the clogging abnormality of the second filter 54. Here, the high-pressure side gas pressure Pt detected by the high-pressure sensor 46 is acquired at the timing immediately before the closing command is output to the shutoff valve 45, and the acquired sensor detection value P1 or a value near the pressure side lower than P1 is determined as a high pressure. Set to the value K1. In step S104, a close command for closing the shut-off valve 45 is output (valve closing means).

  In step S105, the second relative pressure ΔPb1 is calculated. Here, the pressure change of the low-pressure side gas pressure Pf after the output of the close command to the shut-off valve 45 is monitored, and the timing when the low-pressure side gas pressure Pf detected by the low-pressure sensor 47 becomes smaller than a predetermined value with respect to the previous value. Is detected. Then, by using the low-pressure side gas pressure Pf detected by the low-pressure sensor 47 and the intake pipe pressure Pin detected by the intake pipe pressure sensor 82 immediately before the timing, the second value is obtained by subtracting the intake pipe pressure Pin from the low-pressure side gas pressure Pf. The relative pressure ΔPb1 is calculated. The low-pressure side gas pressure Pf and the intake pipe pressure Pin used for calculating the second relative pressure ΔPb1 are not limited to those described above. For example, the low-pressure side gas pressure Pf detected by the low-pressure sensor 47 at the output timing of the shut-off valve 45 close command The intake pipe pressure Pin at that time may be used. Alternatively, the low-pressure side gas pressure Pf detected by the low-pressure sensor 47 before the shut-off valve 45 closing command output timing and the intake pipe pressure Pin at that time may be used.

  In step S106, it is determined whether or not the closing time ta has elapsed from the output timing of the closing command of the shutoff valve 45. Then, the process proceeds to step S107 on condition that the closing time ta has elapsed, and an opening command for opening the shutoff valve 45 is output (valve opening means).

  After outputting the shut-off valve 45 closing command, an affirmative determination is made in step S101, and the process proceeds to step S108. In step S108, it is determined whether or not it is after the output of an opening command for the shut-off valve 45. If the determination is affirmative, the process proceeds to step S109. In step S109, it is determined whether or not the high-pressure side gas pressure Pt detected by the high-pressure sensor 46 is equal to or higher than the high-pressure determination value K1 (pressure determination means). If Pt ≧ K1, the process proceeds to step S110.

  In step S110, a first relative pressure ΔPa1 is calculated. Here, the low pressure side gas pressure Pf detected by the low pressure sensor 47 at the time when Pt = K1 and the intake pipe pressure Pin at that time are acquired, and a value obtained by subtracting the intake pipe pressure Pin from the low pressure side gas pressure Pf is the first value. The relative pressure is ΔPa1. In subsequent step S111, the second relative pressure ΔPb1 calculated in step S105 is acquired, and it is determined whether or not ΔPb1 is equal to or greater than a predetermined value. If ΔPb1 ≧ predetermined value, the process proceeds to step S112, and the first relative pressure ΔPa1 and the second relative pressure ΔPb1 are compared. When the difference between the first relative pressure ΔPa1 and the second relative pressure ΔPb1 is less than the predetermined value K2, the process proceeds to step S113, and the second filter 54 is determined to be normal.

  On the other hand, when the second relative pressure ΔPb1 is less than a predetermined value, or when the second relative pressure ΔPb1 is greater than or equal to a predetermined value and the first relative pressure ΔPa1 is smaller than the second relative pressure ΔPb1 by a predetermined value K2 or more. The process proceeds to step S114, where it is determined that there is a clogging abnormality in the second filter 54 (abnormality diagnosis means). When it is determined that there is an abnormality in the clogging of the second filter 54, the fact is notified to the driver by a lamp display or a message display. Further, instead of the notification, or together with the notification, the output of the engine 10 may be limited, or the fuel used may be switched to liquid fuel.

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

  After the shut-off valve 45 is switched from the closed state to the open state, the second filter 54 has an opening based on the low pressure side gas pressure Pf detected by the low pressure sensor 47 when the high pressure side gas pressure Pt recovers to a predetermined level or higher. An abnormality diagnosis for clogging abnormality is performed. Thereby, the presence or absence of clogging abnormality can be appropriately diagnosed about the 2nd filter 54 provided in the gaseous fuel supply system.

  After switching the shut-off valve 45 from the closed state to the open state, the determination as to whether or not the high-pressure gas pressure Pt has recovered to a predetermined level or more is made based on the actual value detected by the high-pressure sensor 46. The determination can be performed with high accuracy, and consequently, the clogging abnormality diagnosis can be performed with high accuracy.

  In an engine operating state using gaseous fuel, the low-pressure side gas pressure Pf (injection pressure) changes according to the engine operating state. Specifically, as the engine load is higher or the engine rotational speed is higher, the intake pipe pressure increases to the positive side, and as a result of the valve body 62 of the pressure regulating valve 60 shifting to the valve opening side, the low pressure side gas pressure Pf is On the high pressure side. In view of this point, the above configuration is configured to diagnose the presence or absence of clogging abnormality of the second filter 54 based on the difference ΔPa1 between the low pressure side gas pressure Pf and the intake pipe pressure Pin. Judgment can be avoided.

  Further, when an abnormality diagnosis is performed based on the difference ΔPa1 between the low pressure side gas pressure Pf and the intake pipe pressure Pin, a pressure drop caused by closing the shutoff valve 45 in the low pressure passage 52 is used as a determination value to be compared with the difference ΔPa1. A difference ΔPb1 between the low pressure side gas pressure Pf detected by the low pressure sensor 47 and the intake pipe pressure Pin detected by the intake pipe pressure sensor 82 before the occurrence is used. The relationship between the regulator set pressure Prg and the intake pipe pressure Pin before switching the shut-off valve 45 to the closed state may be different depending on the engine operating state, changes over time, etc., but according to the above configuration, A determination value can be set, and diagnostic accuracy can be improved.

  The rate of decrease in the fuel pressure during the period in which the shutoff valve 45 is kept closed varies depending on the engine operating state, and the fuel injection amount increases as the engine 10 is heavily loaded or rotated at a higher speed. The rate of decrease in (injection pressure) increases. In addition, as the rate of decrease in the injection pressure increases, the amount of decrease in the injection pressure during a predetermined time after the shutoff valve 45 is closed increases, and as a result, there is a risk of engine stall due to misfire. In that respect, in the above-described configuration, the closing time ta is variably set according to the engine operating state every time, so that it is possible to prevent the engine from being stalled during the abnormality diagnosis of the second filter 54.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be implemented as follows, for example.

  In the above embodiment, the abnormality diagnosis is performed based on the comparison result between the first relative pressure ΔPa1 and the second relative pressure ΔPb1, but based on the comparison result between the first relative pressure ΔPa1 and a predetermined determination value K3. An abnormality diagnosis may be performed. In this case, when the first relative pressure ΔPa1 is larger than the determination value K3, it is determined to be normal. On the other hand, when the first relative pressure ΔPa1 is equal to or lower than the determination value K3, the second filter 54 is clogged abnormally. Judge that there is.

  In the above embodiment, the fuel pressure P1 before switching the shut-off valve 45 to the closed state or the vicinity value on the low pressure side is set to the high pressure determination value K1, but the fuel pressure on the low pressure side is further set to the high pressure determination value K1. May be set. For example, the regulator set pressure Prg may be set to the high pressure determination value K1, or the fuel pressure lower than the regulator set pressure Prg may be set to the high pressure determination value K1. In the latter case, when the second filter 54 is normal, the first relative pressure ΔPa1 is smaller than the second relative pressure ΔPb1 by α1, whereas when the second filter 54 is clogged abnormally, the first relative pressure ΔPa1. Becomes a value smaller than α1 with respect to the second relative pressure ΔPb1.

  In the above embodiment, when the high pressure side gas pressure Pt detected by the high pressure sensor 46 is equal to or higher than the determination value, the pressure determination means for determining whether or not the high pressure side gas pressure Pt is equal to or higher than a predetermined value. Although it is determined that the pressure Pt has become equal to or higher than the predetermined value, it is determined whether or not a predetermined time has elapsed since the opening command of the shut-off valve 45 is output instead of the configuration in which the high-pressure side gas pressure Pt is directly detected. And it is good also as a structure which determines with the high pressure side gas pressure Pt becoming more than predetermined when predetermined time passes.

  In the above embodiment, the low pressure side gas pressure Pf and the intake pipe pressure detected by the low pressure sensor 47 when the high pressure side gas pressure Pt becomes equal to or higher than the predetermined value after the shut-off valve 45 is switched to the open state. A difference ΔPa1 between both of the intake pipe pressures Pin detected by the sensor 82 is obtained, and the clogging abnormality of the second filter 54 is diagnosed based on a comparison result between the difference ΔPa1 and the determination value. On the other hand, in the present embodiment, the low pressure side gas pressure Pf detected by the low pressure sensor 47 when the high pressure side gas pressure Pt becomes equal to or higher than the predetermined value after the shutoff valve 45 in the closed state is switched to the open state. The second filter 54 is diagnosed as being clogged abnormally based on the comparison result with the determination value K4. When the second filter 54 is clogged, the low-pressure side gas pressure Pf is changed when the shutoff valve 45 is switched from the open state to the closed state to the open state in the period of fuel injection by the first injection valve 21. Shows a change mode different from that in the normal state, and in particular, the difference from the normal state appears remarkably after switching from the closed state to the open state (see FIG. 4). Therefore, according to the low pressure side gas pressure Pf after the shutoff valve 45 is switched from the closed state to the open state, it is possible to specify that the clogging abnormality of the second filter 54 has occurred.

  Specifically, after switching the shut-off valve 45 in the closed state to the open state (t23 in FIG. 4), the low pressure detected by the low pressure sensor 47 at the time when the high pressure side gas pressure Pt becomes equal to or higher than the high pressure determination value K1. The side gas pressure Pf is acquired. Then, the acquired low-pressure side gas pressure Pf is compared with the determination value K4, and when the low-pressure side gas pressure Pf is smaller than the determination value K4, it is determined that the second filter 54 is clogged abnormally. The determination value K4 may be set to a value on the low pressure side by a regulator set pressure Prg or a predetermined slight value.

  After the shut-off valve 45 in the closed state is switched to the open state, the high pressure side gas pressure Pt detected by the high pressure sensor 46 becomes equal to or higher than the predetermined value, and the low pressure sensor 47 at the same time. A difference ΔPtf from the detected low-pressure side gas pressure Pf may be obtained, and abnormality diagnosis may be performed by comparing the difference ΔPtf with the determination value. FIG. 6 shows a normal state in which the clogging of the second filter 54 does not occur during the period from when the shut-off valve 45 in the closed state is switched to the open state until the high-pressure side gas pressure Pt reaches the regulator set pressure Prg. As shown by the broken line, the low pressure side gas pressure Pf and the high pressure side gas pressure Pt show the same pressure value (t33 to t34). On the other hand, when the clogging of the second filter 54 is abnormal, the low-pressure side gas pressure Pf is lower than the high-pressure side gas pressure Pt as shown by the solid line in FIG. Therefore, when the low-pressure side gas pressure Pf is lower than the high-pressure side gas pressure Pt by the predetermined value K5 or more during the period t33 to t34, it can be determined that the second filter 54 is clogged abnormally. The predetermined value K5 may be variably set according to the intake pipe pressure in consideration of the difference in the injection pressure (regulator set pressure Prg) according to the intake pipe pressure of the engine 10. In this case, the predetermined value K5 may be decreased as the intake pipe pressure increases toward the positive side.

  When the abnormality diagnosis is performed by comparing the difference ΔPtf with the determination value, the difference ΔPa2 after the high-pressure side gas pressure Pt has recovered to the fuel pressure before switching the shut-off valve 45 in the valve opening state to the valve closing state (FIG. 6) may be used. In this case, as a determination value to be compared with the difference ΔPa2, the low pressure side gas pressure Pf detected by the low pressure sensor 47 and the high pressure detected by the high pressure sensor 46 before the pressure drop accompanying the closing of the shutoff valve 45 occurs in the high pressure passage 51. A difference ΔPb2 (= Pt−Pf) between the side gas pressures Pt may be used. At this time, ΔPa2 and ΔPb2 are substantially equal when the second filter 54 is normal, whereas ΔPa2 is larger than ΔPb2 when the second filter 54 is clogged abnormally.

  In the above embodiment, the configuration of the regulator 43 is a mechanical pressure adjusting device. However, an electromagnetic pressure adjusting device that variably adjusts the fuel pressure in the low pressure pipe portion 41b by energization control may be used. In the case of a system including the electromagnetic regulator 43, when the clogging abnormality diagnosis of the second filter 54 is performed, the regulator 43 is energized to shift the pressure adjustment valve to a predetermined open position. Alternatively, as the regulator 43, a mechanical pressure adjustment mechanism that adjusts the fuel pressure in the low-pressure pipe portion 41b so as to have a predetermined set pressure that is mechanically determined according to a pressure change downstream of the regulator 43. Alternatively, a pressure adjustment device including an electromagnetic pressure adjustment mechanism that variably adjusts the fuel pressure in the low-pressure pipe portion 41b by energization control may be used.

  In the above embodiment, the regulator 43 having one pressure regulating valve 60 arranged in the fuel passage from the gas tank 42 to the first injection valve 21 is used, but a plurality of pressure regulating valves 60 are arranged in the fuel passage. The present invention may be applied to a system including the regulator 43.

  In the above embodiment, a case has been described in which the present invention is embodied in a bi-fuel engine that uses gaseous fuel (CNG fuel) and liquid fuel (gasoline fuel) as combustion fuel. The present invention may be embodied in a gas engine that uses only fuel. Alternatively, the present invention may be embodied in an engine that uses a combination of gaseous fuel and liquid fuel.

  In the above embodiment, the gaseous fuel is CNG fuel, but other gaseous fuels in a gaseous state can be used in the standard state, for example, a fuel mainly composed of methane, ethane, propane, butane, hydrogen, dimethyl ether, etc. It is good also as a structure to use. Further, liquid fuel is not limited to gasoline fuel. For example, you may apply this invention to the system which mounts the supply system of gaseous fuel with respect to the diesel engine which uses light oil as a fuel for combustion.

  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), 41b ... Low pressure piping part (low pressure passage part) 42 ... Gas tank, 45 ... Shut-off valve, 46 ... High pressure sensor (high pressure detection means), 47 ... Low pressure sensor (low pressure detection means), 51 ... High pressure passage (high pressure passage portion), 52 ... Low pressure passage (low pressure passage portion), 54 ... second filter, 60 ... pressure adjusting valve (pressure adjusting means), 65 ... valve element operating part (pressure adjusting means), 80 ... control part (valve opening means, abnormality diagnosis means, valve closing means), 82 ... intake air Pipe pressure sensor (intake pressure detection means).

Claims (5)

A fuel tank (42) for storing gaseous fuel in a high pressure state, fuel injection means (21) for injecting the gaseous fuel supplied from the fuel tank through a fuel passage (41), and provided in the fuel passage, Pressure adjusting means (60, 65) for reducing the pressure of the gaseous fuel supplied to the fuel injection means, and a high pressure passage portion (41a, 51) between the fuel tank and the pressure adjusting means in the fuel passage. And a shutoff valve (45) having a shutoff function for shutting off the flow of the gaseous fuel, and a low pressure passage portion (41b, 52) between the pressure adjusting means and the fuel injection means in the fuel passage. Applied to a fuel supply system of an internal combustion engine (10) comprising a filter (54) for removing foreign matter.
Low pressure detection means (47) for detecting fuel pressure downstream of the filter in the low pressure passage portion;
A valve opening means for switching to a state in which the shut-off valve is opened when fuel injection is performed by the fuel injection means in a state in which the shut-off valve is closed;
Pressure determining means for determining whether or not the fuel pressure downstream of the shut-off valve in the high-pressure passage portion has become a predetermined value or more after switching the shut-off valve to the open state by the valve-opening means;
An abnormality diagnosing unit for performing an abnormality diagnosis on the clogging abnormality of the filter based on the fuel pressure detected by the low pressure detecting unit when it is determined by the pressure determining unit that the predetermined value is exceeded;
A fuel supply control apparatus for an internal combustion engine, comprising: The pressure adjusting means adjusts the injection pressure, which is the pressure of the fuel supplied to the fuel injection means, in accordance with the intake pipe pressure of the internal combustion engine.
An intake pressure detecting means (82) for detecting the intake pipe pressure;
The abnormality diagnosing means is a difference between both the fuel pressure detected by the low pressure detecting means and the intake pipe pressure detected by the intake pressure detecting means when it is determined by the pressure determining means that the predetermined value is exceeded. The fuel supply control device for an internal combustion engine according to claim 1, wherein the abnormality diagnosis is performed based on one relative pressure. The difference between the fuel pressure detected by the low pressure detecting means and the intake pipe pressure detected by the intake pressure detecting means before the pressure drop due to the closing of the shutoff valve in the low pressure passage portion is defined as a second relative pressure. Comprising means for calculating,
The fuel supply control device for an internal combustion engine according to claim 2, wherein the abnormality diagnosis unit performs the abnormality diagnosis based on a comparison result between the first relative pressure and the second relative pressure. High pressure detecting means (46) for detecting fuel pressure downstream of the shutoff valve in the high pressure passage portion;
The abnormality diagnosis unit is configured to detect the abnormality based on a difference between a fuel pressure detected by the low pressure detection unit and a fuel pressure detected by the high pressure detection unit when the pressure determination unit determines that the predetermined value is exceeded. The fuel supply control device for an internal combustion engine according to claim 1, wherein diagnosis is performed. A valve closing means for switching to a state in which the shut-off valve is closed when fuel injection is performed by the fuel injection means in a state in which the shut-off valve is opened;
The abnormality diagnosing means is configured so that, in an operating state of the internal combustion engine using the gaseous fuel, the valve opening means performs the valve opening means after the predetermined closing time has elapsed since the valve closing means switches the shutoff valve to the valve closed state. The shut-off valve is switched to an open state, and then the abnormality diagnosis is performed when it is determined by the pressure determination means that the predetermined value has been reached,
The fuel supply control device for an internal combustion engine according to any one of claims 1 to 4, wherein the predetermined closing time is variably set according to an operating state of the internal combustion engine.

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