JP2020067022A - Fuel injection system - Google Patents

Abstract

To provide a fuel injection system which can suppress the clogging of a fuel filter resulting from the waxing of fuel without arranging a heater for heating the fuel.SOLUTION: In a fuel injection system, a fuel injection valve 20 comprises a second opening/closing valve 52 as a pressure adjusting valve which can adjust fuel pressure in a control chamber without moving a needle valve 31 by making the control chamber and a fuel discharge passage communicate with each other, or blocking the communication. In the fuel injection system, there are arranged return piping 65, 65a for connecting the fuel discharge passage and an upstream side of a fuel filter 66 being a downstream side of a fuel tank 61 in a low-pressure fuel passage. The fuel injection system also comprises a supply control unit for supplying fuel in the control chamber to the fuel filter 66 through the return piping without moving the needle valve 31 from a valve-closing position by making the control chamber and the fuel discharge passage communicate with each other by the pressure adjusting valve when the needle valve 31 is in the valve-closing position.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel injection system.

  Diesel engine fuel injection systems use light oil as fuel. Light oil is waxed in a low temperature environment, and the waxed fuel is filtered by a fuel filter arranged in the fuel supply path. On the other hand, when the amount of wax deposited on the fuel filter increases, the fuel filter may be clogged. When the fuel filter is clogged, there is a concern that the amount of fuel supplied to the engine will be insufficient and the output of the engine will be reduced. To solve these problems, it has been proposed to provide a fuel heater on the fuel filter and heat the fuel passing through the fuel filter with the fuel heater (see, for example, Patent Document 1).

JP, 2014-51920, A

  When a heater is provided in the fuel filter to heat the fuel, there is a concern that the heater consumes a large amount of power to dissolve the waxed fuel, or a new heater system needs to be provided.

  The present invention has been made in view of the above problems, and provides a fuel injection system capable of suppressing clogging of a fuel filter due to wax formation of fuel without providing a heater for heating the fuel. That is one purpose.

  In order to solve the above problems, the following means are adopted.

  The present invention relates to a fuel filter (66) disposed in a low pressure fuel passage (63) connecting a fuel tank (61) and a high pressure pump (62), and a fuel supplied from the high pressure pump in a high pressure state. And a fuel injection valve (20) for directly injecting high-pressure fuel in the pressure accumulation pipe into a cylinder of an internal combustion engine (70). Is a control chamber (36, 46) to which the high pressure fuel is supplied from the pressure accumulating pipe, and an injection hole (34) by moving to a valve opening position and a valve closing position according to the fuel pressure inside the control chamber. ) Is opened and closed by a needle valve (31), a fuel discharge passage (58) for discharging the fuel in the control chamber to the outside of the fuel injection valve, and the control chamber and the fuel discharge passage are connected and cut off. , The need A pressure adjusting valve (52) capable of adjusting the fuel pressure inside the control chamber without moving the valve, the fuel discharging passage and the low pressure fuel passage being located downstream of the fuel tank. A return pipe (65, 65a) is provided that connects the upstream side portion of the fuel filter, and the pressure control valve controls the control chamber and the fuel discharge passage when the needle valve is in the closed position. A supply control unit that supplies the fuel in the control chamber to the fuel filter through the return pipe without moving the needle valve from the closed position by communicating with the fuel filter.

  The fuel contained in the control chamber of the fuel injection valve is pressurized by a high pressure pump and has a high temperature. Further, the direct injection type fuel injection valve is arranged in the cylinder, and the fuel in the control chamber of the fuel injection valve is heated to a high temperature by the combustion heat of the internal combustion engine. Focusing on these points, the fuel filter is configured to be heated by supplying the fuel in the control chamber of the fuel injection valve to the fuel filter. With this configuration, the fuel filter can be heated by the high-temperature fuel supplied from the fuel injection valve, and the fuel deposits adhering to the fuel filter can be dissolved or the generation of fuel deposits can be suppressed. can do. Further, even if a heater for heating the fuel filter is not provided, it is possible to suppress the clogging of the fuel filter due to the wax formation of the fuel.

The figure which shows the schematic structure of a fuel injection system. The figure which shows an example of the injection rate pattern of a fuel injection valve. The figure showing the fuel injection valve at the time of valve closing. The figure explaining operation | movement of the fuel injection valve of a high speed valve opening mode. The figure explaining operation | movement of a fuel injection valve at the time of shifting to a high speed valve closing mode from a high speed valve opening mode. The figure explaining operation | movement of the fuel injection valve in high-speed valve closing mode. The figure explaining operation | movement of the fuel injection valve of low speed valve opening mode. The figure explaining operation | movement of a fuel injection valve at the time of shifting to a low speed valve closing mode from a low speed valve opening mode. The figure explaining operation | movement of the fuel injection valve in low speed valve-closing mode. The figure which shows the pressure reduction operation by a 2nd on-off valve. The figure which shows the operation | movement of a fuel injection valve and the flow of fuel at the time of filter temperature rising control. The flowchart which shows the process sequence of filter temperature rising control. The flowchart which shows the process sequence of the process which sets the number of cylinders which recirculates fuel, and a cylinder number in the temperature rise possible period. The time chart which shows operation | movement of filter temperature rising control compared with normal control. The schematic diagram which shows the state of a 1st on-off valve, a 2nd on-off valve, and a driven valve at the time of high-speed fall. The time chart which shows operation | movement of a low speed valve opening mode and a high speed valve closing mode. The time chart which shows operation | movement at the time of switching from a low speed valve opening mode and a high speed valve closing mode to a low speed valve closing mode. 7 is a time chart showing the operation of the fuel injection valve when opening the second opening / closing valve before fuel injection. 7 is a time chart when the filter temperature raising control is performed by overlapping the fuel injection period.

  Hereinafter, embodiments will be described with reference to the drawings. In the following respective embodiments, the same or equivalent portions are denoted by the same reference numerals in the drawings, and the description of the portions having the same reference numeral is cited.

  The present embodiment is embodied in a fuel injection system applied to a vehicle-mounted multi-cylinder diesel engine which is an internal combustion engine. In this fuel injection system, an electronic control unit (hereinafter, referred to as "ECU") is the center for controlling the fuel injection of the engine. As shown in FIG. 1, the fuel injection system 10 includes a fuel tank 61, a high pressure pump 62, a common rail 11, a fuel injection valve 20, and an ECU 90.

  In FIG. 1, the fuel tank 61 is provided with a fuel temperature sensor 71 for detecting the temperature of fuel (light oil) in the fuel tank 61 and a fuel property sensor 72 for detecting fuel properties (density and kinematic viscosity). . The fuel tank 61 is connected to a high pressure pump 62 via a low pressure fuel pipe 63. The high-pressure pump 62 is a mechanical pump that repeatedly sucks and discharges fuel as the plunger reciprocates in synchronization with the rotation of the output shaft (crank shaft) of the engine 70. In the present embodiment, the high-pressure pump 62 is a one-injection, one-pressure feed type in which the fuel is fed by the high-pressure pump 62 once for each combustion fuel injection of the engine 70. The fuel introduced into the high-pressure pump 62 from the fuel tank 61 is made high in pressure by driving the high-pressure pump 62, and the high-pressure fuel is discharged from the high-pressure pump 62.

  In the low-pressure fuel pipe 63, a fuel filter 66 that filters fuel is arranged downstream of the fuel tank 61 and upstream of the high-pressure pump 62. The fuel filter 66 removes foreign matter contained in the fuel. The common rail 11 is connected to the downstream side of the high-pressure pump 62 via a fuel pipe 64. Inside the common rail 11, the high-pressure fuel pumped from the high-pressure pump 62 is held in a high-pressure state. In this system, the common rail 11 is not provided with a pressure reducing valve that lowers the fuel pressure (rail pressure) in the common rail.

  A fuel injection valve 20 is connected to the common rail 11 via a high pressure pipe 12. The fuel injection valve 20 is a direct injection type that directly injects fuel into the combustion chamber of the engine 70, and is attached to each of a plurality of cylinders (four cylinders in this embodiment). Note that, in FIG. 1, only the fuel injection valve 20 of one cylinder is shown, and the description of the fuel injection valve 20 is omitted for the remaining cylinders.

  The ECU 90 is a microcomputer including a CPU, ROM, RAM, drive circuit, input / output interface, and the like. In addition to the detection signals of the fuel temperature sensor 71 and the fuel property sensor 72 described above, the ECU 90 receives detection signals from various sensors such as a crank angle sensor that detects the rotation speed of the engine 70 and an accelerator sensor that detects the accelerator operation amount. Input sequentially. The ECU 90 determines an optimum fuel injection amount and injection timing based on engine operation information such as engine rotation speed and accelerator operation amount, and outputs an injection control signal corresponding to the determined fuel injection amount to the fuel injection valve 20. Thus, in each cylinder, fuel injection from the fuel injection valve 20 into the combustion chamber of the engine 70 is controlled. The ECU 90 also controls the drive of the high-pressure pump 62 based on the engine operating state each time. The ECU 90 functions as an “injection control unit” and a “drive control unit”.

  Next, the configuration of the fuel injection valve 20 will be described in detail. The fuel injection valve 20 includes first to fourth main body portions 21 to 24, and the first to fourth main body portions 21 to 24 form an injection valve main body. The first to fourth main body portions 21 to 24 are arranged in this order in the axial direction of the fuel injection valve 20, and the fuel supplied from the common rail 11 to the first main body portion 21 is provided in the fourth main body portion 24. It injects from the injection hole 34. In the following description, the axial direction of the fuel injection valve 20 will be referred to as “vertical direction”, the first body portion 21 side of the fuel injection valve 20 will be referred to as “upward”, and the fourth body portion 24 side will be referred to as “downward”. .

  The first main body portion 21 is provided with a first high pressure passage 13 and a low pressure chamber 57. The first high-pressure passage 13 is formed across the first main body portion 21, the second main body portion 22, and the third main body portion 23, and penetrates the first to third main body portions 21 to 23. The end of the first high-pressure passage 13 on the side opposite to the second main body 22 side is connected to the high-pressure pipe 12. As a result, the high-pressure fuel from the common rail 11 is supplied to the first high-pressure passage 13 via the high-pressure pipe 12. A fuel temperature sensor 73 that detects the temperature of the fuel in the first high pressure passage 13 is attached to the first high pressure passage 13. The detection signal of the fuel temperature sensor 73 is input to the ECU 90.

  The low-pressure chamber 57 is formed in the boundary portion with the second main body portion 22 in the first main body portion 21 by denting the surface facing the second main body portion 22 upward. The high-pressure fuel in the first high-pressure passage 13 passes through the second main body portion 22, the third main body portion 23, and the fourth main body portion 24, and the low-pressure chamber 57 stores the fuel whose pressure has been reduced. The low pressure chamber 57 is connected to the return pipe 65 via the low pressure passage 58, and is further connected to the fuel tank 61. As a result, a part of the high pressure fuel supplied to the fuel injection valve 20 is returned from the low pressure chamber 57 to the fuel tank 61 through the return pipe 65. Inside the low pressure chamber 57, an on-off valve 50 that controls the injection state of fuel from the fuel injection valve 20 is provided. The low pressure passage corresponds to the “fuel discharge passage”.

  The second main body 22 is provided with a second high pressure passage 14, an intermediate chamber 26, a first passage 25, and a second passage 27. The second high-pressure passage 14 is a branch passage that branches from the first high-pressure passage 13, and is a fuel passage to which the high-pressure fuel from the common rail 11 is supplied. The second high pressure passage 14 is provided with a pressure increasing orifice 14a. The pressure rising orifice 14a limits the flow rate of the fuel flowing through the second high pressure passage 14. In the second high pressure passage 14, an annular chamber 14b is formed at the end opposite to the first high pressure passage 13. The annular chamber 14b is a fuel passage portion formed in an annular shape in the boundary portion with the third main body portion 23 in the second main body portion 22. The high pressure fuel from the first high pressure passage 13 is introduced into the annular chamber 14b through the second high pressure passage 14.

  The intermediate chamber 26 is a cylindrical chamber and is formed at the boundary between the second main body 22 and the third main body 23. The first passage 25 extends in the axial direction (vertical direction) of the fuel injection valve 20 inside the second main body portion 22 and penetrates the second main body portion 22. The first passage 25 has one end communicating with the low pressure chamber 57 and the other end communicating with the intermediate chamber 26. As a result, the intermediate chamber 26 communicates with the low pressure chamber 57 via the first passage 25.

  The second passage 27 is formed inside the second main body portion 22 and extends in the same direction (vertical direction) as the first passage 25. The second passage 27 penetrates through the second main body 22, one end of which communicates with the low pressure chamber 57, and the other end of which communicates with the first control chamber 46 of the third main body 23. There is. A decompression orifice 27 a is provided in the second passage 27 at a position close to the first main body portion 21. The flow rate of the fuel flowing through the second passage 27 is limited by the pressure reducing orifice 27a.

  The third main body portion 23 is provided with a first control chamber 46 and a connection passage 47. The first control chamber 46 is a chamber formed inside the injection valve body by denting the surface facing the second body portion 22 downward, and is connected to the annular chamber 14b. The high pressure fuel from the first high pressure passage 13 is supplied to the first control chamber 46 via the second high pressure passage 14.

  A driven valve 41 that is displaceable in the axial direction (vertical direction) of the fuel injection valve 20 is arranged inside the first control chamber 46. The driven valve 41 has a cylindrical shape, and has a third passage 42 formed in the center thereof so as to penetrate therethrough in the axial direction. The opening of the third passage 42 on the side of the second main body 22 is open to the intermediate chamber 26, and the opening on the side of the fourth main body 24 is open to the inside of the first control chamber 46. A pressure reducing orifice 42a is provided in the third passage 42, and the flow rate of the fuel flowing through the third passage 42 is limited by the pressure reducing orifice 42a.

  The driven valve 41 is provided with a spring 45 that biases the driven valve 41 in the direction toward the second main body 22 (upward). The driven valve 41 is in contact with the lower surface of the second main body portion 22 by the upward force due to the fuel pressure inside the first control chamber 46 and the biasing force of the spring 45. In this abutting state, the driven valve 41 blocks communication between the annular chamber 14b and the first control chamber 46, while the intermediate chamber 26 communicates with the first control chamber 46 via the third passage 42. Become. In this state, the fuel in the first control chamber 46 can flow into the low pressure chamber 57 via the third passage 42, the intermediate chamber 26 and the first passage 25.

  In the state where the driven valve 41 is in contact with the lower surface of the second main body portion 22, the fuel pressure inside the first control chamber 46 decreases and the upward force due to the fuel pressure inside the first control chamber 46 and When the urging force of the spring 45 falls below the downward force due to the fuel pressure inside the annular chamber 14b and the intermediate chamber 26, the driven valve 41 is displaced in the direction away from the lower surface of the second main body portion 22. As a result, the intermediate chamber 26 communicates with the first control chamber 46 without passing through the third passage 42, and the annular chamber 14b communicates with the first control chamber 46.

  The second passage 27 directly connects the low pressure chamber 57 and the first control chamber 46. That is, the first control chamber 46 communicates with the low pressure chamber 57 via the second passage 27 regardless of the position (lifted state) of the driven valve 41. Further, a connection passage 47 extending from the first control chamber 46 to the fourth body portion 24 is formed in the third body portion 23. The connection passage 47 is provided with an orifice 47a, and the orifice 47a limits the flow rate of the fuel flowing through the connection passage 47.

  The fourth body 24 is provided with a cylinder 35, a needle valve 31, a high pressure chamber 33, and a second control chamber 36. A plurality of injection holes 34 for injecting fuel toward the outside are formed at the tip of the cylinder 35. The needle valve 31 is housed inside the cylinder 35 so as to be vertically reciprocable. A spring 32 that biases the needle valve 31 downward is attached to the upper surface of the needle valve 31.

  The high pressure chamber 33 is provided in the middle of a passage that connects the first high pressure passage 13 and the injection hole 34. The tip of the needle valve 31 is arranged inside the high-pressure chamber 33. The second control chamber 36 is provided inside the cylinder 35 on the opposite side of the injection hole 34 (above the needle valve 31). The second control chamber 36 communicates with the first control chamber 46 via a connection passage 47. As a result, the high pressure fuel from the first high pressure passage 13 is supplied to the second control chamber 36 via the first control chamber 46 and the connection passage 47. The fuel pressure inside the second control chamber 36 and the urging force of the spring 32 attached to the needle valve 31 act on the needle valve 31, so that the needle valve 31 closes the injection hole 34 (downward). It is displaced and the fuel injection valve 20 is closed.

  When the fuel pressure inside the high pressure chamber 33 becomes larger than the total force of the fuel pressure inside the second control chamber 36 and the urging force of the spring 32, the needle valve 31 opens the injection hole 34 (upward direction). ), The fuel injection valve 20 is opened. By opening the fuel injection valve 20, the high pressure fuel in the high pressure chamber 33 is injected from the injection hole 34.

  Next, the structure of the on-off valve 50 will be described. Inside the low pressure chamber 57, a first opening / closing valve 51 and a second opening / closing valve 52 are provided as the opening / closing valve 50. The first opening / closing valve 51 is an electromagnetic valve that switches communication and disconnection between the low pressure chamber 57 and the first passage 25. The second opening / closing valve 52 is an electromagnetic valve that switches communication and disconnection between the low pressure chamber 57 and the second passage 27. The ECU 90 energizes and drives the first solenoid 53 and the second solenoid 54 independently of each other, so that the first opening / closing valve 51 connects and disconnects the first passage 25 and the low pressure chamber 57, and the second opening / closing valve 52. The communication between the second passage 27 and the low-pressure chamber 57 and the interruption thereof are controlled independently of each other.

  Specifically, when the first solenoid 53 is not energized, the first opening / closing valve 51 is in contact with the second body portion 22 by the urging force of the first spring 55. In this contact state, the first open / close valve 51 blocks the communication between the low pressure chamber 57 and the first passage 25 (valve closed state). When the first solenoid 53 is energized while the first opening / closing valve 51 is closed, the first opening / closing valve 51 moves upward against the urging force of the first spring 55 and is separated from the second main body portion 22. To do. In this state, the low pressure chamber 57 and the first passage 25 are in communication with each other (valve open state), and the inflow of fuel from the first passage 25 into the low pressure chamber 57 is allowed.

  Further, when the second solenoid 54 is not energized, the second opening / closing valve 52 is in contact with the second body portion 22 by the urging force of the second spring 56. In this contact state, the second on-off valve 52 blocks the communication between the low pressure chamber 57 and the second passage 27 (valve closed state). Further, when the second solenoid 54 is energized in the closed state of the second opening / closing valve 52, the second opening / closing valve 52 moves upward against the biasing force of the second spring 56 and is separated from the second main body portion 22. To do. In this state, the low pressure chamber 57 and the second passage 27 are in communication with each other (valve open state), and the fuel is allowed to flow from the second passage 27 into the low pressure chamber 57.

  In the fuel injection valve 20, the needle valve 31 is moved to the valve opening position and valve closing position by switching the valve opening and closing of the first opening / closing valve 51. As a result, the injection operation in which fuel is injected from the injection hole 34 and the injection stop operation in which fuel injection is stopped are switched. In addition, by controlling the opening / closing of the first opening / closing valve 51 and switching the opening / closing of the second opening / closing valve 52, the moving speed when the needle valve 31 moves to the opening position and the closing position is controlled. To do. That is, in the fuel injection valve 20, the opening / closing of the first opening / closing valve 51 and the second opening / closing valve 52 is independently controlled, so that the slope of the fuel injection rate, more specifically, the rising speed of the injection rate and The falling speed is controlled respectively.

  FIG. 2 shows an example of the injection rate pattern of the fuel injection valve 20. In any of the injection rate patterns, the first opening / closing valve 51 is opened at the start of fuel injection by the fuel injection valve 20, and the first opening / closing valve 51 is closed at the end of fuel injection. The second opening / closing valve 52 is controlled to open and close according to the rising speed and the falling speed of the injection rate.

  Specifically, in the high-speed valve opening mode in which the rising speed of the injection rate at the start of fuel injection is made steep, the second opening / closing valve 52 is opened (see FIGS. 2A and 2C), and the injection rate is increased. In the low speed valve opening mode in which the rising speed is slowed, the second opening / closing valve 52 is closed (see FIGS. 2B and 2D). Further, in the high-speed valve closing mode in which the falling rate of the injection rate at the end of fuel injection is made steep, the second opening / closing valve 52 is closed (see FIGS. 2A and 2B), and the injection rate rises. In the low speed valve closing mode in which the lowering speed is slow, the second opening / closing valve 52 is opened (see FIGS. 2C and 2D). Further, the rising speed and the falling speed of the injection rate may be changed midway. According to the fuel injection valve 20, for example, as shown in FIG. 2E, it is possible to realize an injection rate pattern in which the high speed valve closing mode is changed to the low speed valve closing mode.

  The relationship between the open / closed states of the first opening / closing valve 51 and the second opening / closing valve 52 and the operation of the fuel injection valve 20 will be described with reference to FIGS. Before the start of injection, the first solenoid 53 and the second solenoid 54 are de-energized so that the first on-off valve 51 and the second on-off valve 52 are both closed as shown in FIG. The communication between the high pressure chamber 33 and the injection hole 34 is blocked.

  The case of the injection pattern in the high speed valve opening mode and the high speed valve closing mode (see FIG. 2A) will be described with reference to FIGS. Before the start of injection, when the first on-off valve 51 and the second on-off valve 52 are closed, high-pressure fuel is introduced from the first high-pressure passage 13 to the second to fourth main body portions 22 to 24. The formed fuel storage portion (annular chamber 14b, intermediate chamber 26, first control chamber 46, second control chamber 36, high pressure chamber 33) and fuel passage (first passage 25, second passage 27, third passage 42, The connection passage 47) is maintained at a high pressure state equivalent to the fuel pressure in the first high pressure passage 13 (see FIG. 3).

  When both the first opening / closing valve 51 and the second opening / closing valve 52 are opened by energizing the first solenoid 53 and the second solenoid 54 in a state where the first opening / closing valve 51 and the second opening / closing valve 52 are closed, as shown in FIG. As shown in, the first control chamber 46 is communicated with the low pressure chamber 57 via the first passage 25, the third passage 42, and the second passage 27. As a result, the fuel inside the first control chamber 46 and the second control chamber 36 passes through two routes, a route passing through the first passage 25 and the third passage 42 and a route passing through the second passage 27. Flow into the low pressure chamber 57. Therefore, the fuel pressure inside the first control chamber 46 and the second control chamber 36 decreases at high speed, and the needle valve 31 is displaced at high speed in the valve opening direction (upward direction). As a result, fuel is injected from the injection hole 34. In this case, the injection rate rises at a high speed as shown in FIG.

  A differential pressure is generated before and after the decompression orifice 42a, and the sum of the upward force due to the fuel pressure inside the first control chamber 46 and the biasing force of the spring 45 is the inside of the intermediate chamber 26 and the annular chamber 14b. It is higher than the downward force due to fuel pressure. Therefore, the driven valve 41 is maintained in contact with the second main body portion 22 when both the first opening / closing valve 51 and the second opening / closing valve 52 are open (see FIG. 4).

  When the first opening / closing valve 51 is closed after the injection rate reaches the maximum, the fuel in the first control chamber 46 flows into the intermediate chamber 26 via the third passage 42, so that the inside of the intermediate chamber 26 is The fuel pressure rises (see FIG. 5). Further, by closing the second opening / closing valve 52, the communication between the low pressure chamber 57 and the first control chamber 46 is cut off. In this case, the downward force due to the fuel pressure inside the intermediate chamber 26 and the annular chamber 14b becomes larger than the total of the upward force due to the fuel pressure inside the first control chamber 46 and the biasing force of the spring 45. As a result, the driven valve 41 moves downward (see FIG. 6). This downward movement of the driven valve 41 causes the high-pressure fuel in the first high-pressure passage 13 to flow into the first control chamber 46.

  At this time, since both the first opening / closing valve 51 and the second opening / closing valve 52 are closed, the fuel pressure inside the first control chamber 46 rises at a high speed. When fuel flows from the first control chamber 46 into the second control chamber 36 through the connection passage 47 and the fuel pressure inside the second control chamber 36 becomes higher than a predetermined pressure, the needle valve 31 starts to descend and closes. The operation shifts (see FIG. 6). In this case, as shown in FIG. 2A, the injection rate falls at a high speed. After that, the injection hole 34 is closed by the needle valve 31, so that the fuel injection by the fuel injection valve 20 is stopped.

  Next, the case of the injection pattern in the low speed valve opening mode and the high speed valve closing mode (see FIG. 2B) will be described. Before the start of injection, in the state where the first opening / closing valve 51 and the second opening / closing valve 52 are closed (see FIG. 3), the second opening / closing valve 52 is maintained in the closed state as shown in FIG. When the on-off valve 51 is opened, the fuel inside the first control chamber 46 flows into the intermediate chamber 26 via the third passage 42 and the first passage 25. At this time, a differential pressure is generated before and after the decompression orifice 42a, and the sum of the upward force due to the fuel pressure inside the first control chamber 46 and the urging force of the spring 45 is the intermediate chamber 26 and the annular chamber 14b. It is higher than the downward force due to the internal fuel pressure. Therefore, the driven valve 41 is kept in contact with the second main body portion 22.

  In the state where the second opening / closing valve 52 is closed, the flow of fuel through the second passage 27 is not permitted, so the fuel pressure inside the first control chamber 46 decreases at a low speed, and the needle valve 31 moves at a low speed. Displaces in the valve opening direction. In this case, as shown in FIG. 2B, the injection rate rises at a low speed. That is, the rate of increase (inclination) of the injection rate when the first opening / closing valve 51 is open and the second opening / closing valve 52 is closed is the injection rate when both the first opening / closing valve 51 and the second opening / closing valve 52 are open. Is smaller than the rising speed (slope) of. After the injection rate reaches the maximum, the operation is the same as the operation at the time of high-speed fall shown in FIG.

  Next, the case of the injection pattern in the high speed valve opening mode and the low speed valve closing mode (see FIG. 2C) will be described. First, the operation at high speed startup is similar to the operation at high speed startup shown in FIG. After the injection rate reaches the maximum, as shown in FIG. 8, when the second opening / closing valve 52 is maintained in the open state and the first opening / closing valve 51 is closed, the fuel in the first control chamber 46 is transferred to the third passage. It flows into the intermediate chamber 26 via 42, and the fuel pressure inside the intermediate chamber 26 rises. Further, since the second opening / closing valve 52 is in the open state, the fuel inside the first control chamber 46 flows into the low pressure chamber 57 via the second passage 27. The fuel pressure inside the intermediate chamber 26 rises, and the downward force due to the fuel pressure inside the intermediate chamber 26 and the annular chamber 14b increases the upward force due to the fuel pressure inside the first control chamber 46 and the spring 45. When it becomes larger than the total of the urging forces, the driven valve 41 moves downward (see FIG. 9). This downward movement of the driven valve 41 causes the high-pressure fuel in the first high-pressure passage 13 to flow into the first control chamber 46.

  At this time, since the second opening / closing valve 52 is maintained in the open state, the fuel pressure inside the first control chamber 46 rises at a low speed. When the fuel flows from the first control chamber 46 into the second control chamber 36 through the connection passage 47 and the fuel pressure inside the second control chamber 36 becomes higher than a predetermined pressure, the needle valve 31 starts to descend and closes. The operation shifts (see FIG. 9). In this case, as shown in FIG. 2C, the injection rate falls at a low speed. That is, the decreasing rate (gradient) of the injection rate in the state where the first opening / closing valve 51 is closed and the second opening / closing valve 52 is open is the injection rate in the state where both the first opening / closing valve 51 and the second opening / closing valve 52 are closed. Is smaller than the decreasing speed (slope) of. After that, the injection hole 34 is closed by the needle valve 31, so that the fuel is not injected from the injection hole 34.

  FIG. 10 is a diagram showing a pressure reducing operation for reducing the fuel pressure in the common rail 11 by the second opening / closing valve 52 without injecting fuel from the fuel injection valve 20.

  As described above, when both the first opening / closing valve 51 and the second opening / closing valve 52 are closed, the fuel pressure inside the second control chamber 36, the first control chamber 46, and the intermediate chamber 26 is equal to that in the first high pressure passage 13. The fuel pressure is equal to the internal fuel pressure, and the driven valve 41 is in contact with the second main body portion 22 (see FIG. 3). In the pressure reducing operation, the second opening / closing valve 52 is opened from this state. As a result, as shown in FIG. 10, the fuel in the first control chamber 46 is discharged to the low pressure chamber 57 via the second passage 27, and the driven valve 41 is lowered as the pressure inside the first control chamber 46 decreases. Move in the direction.

  Here, in the fuel injection valve 20, in the state where the first opening / closing valve 51 is closed and the second opening / closing valve 52 is opened, the flow rate of the fuel through the pressure increasing orifice 14a is equal to the flow rate of the fuel through the pressure reducing orifice 27a. Is set larger than. Therefore, in the state where the first opening / closing valve 51 is closed and the second opening / closing valve 52 is opened, the amount of fuel discharged from the inside of the first control chamber 46 through the second passage 27 is larger than that of the second high pressure passage. The amount of fuel flowing from 14 into the first control chamber 46 increases. Therefore, in the state where the first opening / closing valve 51 is closed and the second opening / closing valve 52 is opened, the needle valve 31 blocks the high pressure chamber 33 from the injection hole 34, that is, fuel is not injected from the injection hole 34. The state is maintained.

  Further, fuel flows from the common rail 11 into the first control chamber 46 via the first high pressure passage 13 and the second high pressure passage 14, and the inflow fuel is discharged from the first control chamber 46 to the low pressure chamber 57, and fuel is injected. By returning to the upstream side (low pressure side) of the system, the fuel pressure inside the common rail 11 decreases. That is, the fuel pressure in the common rail 11 is reduced in a state where fuel is not injected from the fuel injection valve 20. Therefore, the fuel injection valve 20 has a function as a pressure reducing valve that reduces the fuel pressure in the common rail 11.

  In the fuel injection valve 20, when the first passage 25 and the low pressure chamber 57 communicate with each other by the first opening / closing valve 51, the driven valve 41 blocks communication between the annular chamber 14b and the first control chamber 46. As described above, the flow passage area of the decompression orifice 42a, the opening area of the intermediate chamber 26 on the side of the third main body portion 23 (first control chamber 46), the side of the third main body portion 23 (first control chamber 46) of the annular chamber 14b. The opening area and the biasing force of the spring 45 are set. That is, when the first passage 25 and the low pressure chamber 57 are communicated with each other by the first opening / closing valve 51, the driven valve 41 communicates the first control chamber 46 and the intermediate chamber 26 with each other through the third passage 42. This is achieved by limiting the flow rate of fuel by the pressure reducing orifice 42a, the exposed area of the driven valve 41 to the intermediate chamber 26, the exposed area of the driven valve 41 to the first high pressure passage 13, and the biasing force of the spring 45. Has been done.

  By the way, in a low temperature environment such as when the engine 70 is cold started, when the temperature of the fuel (light oil) becomes lower than the cloud point, the fuel becomes wax, and solids are precipitated or separated in the fuel. The waxed fuel is captured by the fuel filter 66 when passing through the fuel filter 66, and adheres to the fuel filter 66. If the amount of waxed fuel deposited on the fuel filter 66 increases, the fuel filter 66 may become clogged. In this case, it is feared that a sufficient amount of fuel cannot be supplied to the engine 70 and the output of the engine 70 is reduced.

  In view of such inconvenience, in the present system, attention is paid to the fact that the temperature of the fuel that has flowed from the fuel tank 61 into the fuel injection valve 20 via the high-pressure pump 62 and the common rail 11 is high, and this high-temperature fuel is used as a fuel filter. The fuel filter 66 is heated by supplying it to the upstream side of 66.

  Specifically, the fuel injection system 10 is provided with a recirculation mechanism 69 that recirculates the fuel inside the fuel injection valve 20 to a low pressure side in order to raise the temperature of the filter by the high temperature fuel inside the fuel injection valve 20. There is. The reflux mechanism 69, as shown in FIG. 1, includes a branch pipe 65 a and a reflux valve 67. The branch pipe 65a is a fuel pipe branched from the return pipe 65, and an end portion on the side opposite to the connection portion with the return pipe 65 is provided in the middle of the low-pressure fuel pipe 63 connecting the fuel tank 61 and the fuel filter 66. It is connected.

  The reflux valve 67 is provided in the branch pipe 65a. The return valve 67 is a solenoid valve whose opening is controlled based on a drive signal from the ECU 90, and changes the flow passage area of the branch pipe 65a according to the opening. When the return valve 67 is closed, the fuel flow into the branch pipe 65a is blocked, and the fuel inside the low pressure chamber 57 is returned to the fuel tank 61 through the return pipe 65. Further, in the state where the reflux valve 67 is opened, the fuel is allowed to flow into the branch pipe 65a, and the high temperature fuel inside the low pressure chamber 57 is introduced into the low pressure fuel pipe 63 through the branch pipe 65a. .

  FIG. 11 shows the operation of the fuel injection valve 20 and the flow of fuel when the control for raising the temperature of the fuel filter 66 by the recirculation of the high temperature fuel (filter temperature raising control) is performed. In FIG. 11, an arrow A indicates the flow of high temperature fuel that is recirculated to the low pressure side. As shown in FIG. 11, in the filter temperature raising control, the second on-off valve 52 is opened and the recirculation valve 67 is opened while the fuel is not injected from the injection hole 34 by closing the first on-off valve 51. Open the valve. As a result, the high-temperature fuel inside the first control chamber 46 flows into the low-pressure chamber 57 through the second passage 27, is further discharged into the low-pressure fuel pipe 63 through the return pipe 65 and the branch pipe 65a, and is discharged to the fuel filter 66. Supplied.

  Next, the processing procedure of the filter temperature raising control will be described with reference to the flowchart of FIG. This process is executed by the microcomputer of the ECU 90 at predetermined intervals in the situation where the fuel flow to the fuel filter 66 is stopped by the filter temperature raising control.

  12, in step S101, the state of the fuel stored in the fuel tank 61 is acquired. Here, as the state of the fuel, the fuel property (fuel density and kinematic viscosity) detected by the fuel property sensor 72 and the fuel temperature detected by the fuel temperature sensor 71 (hereinafter referred to as “pre-filter temperature Tb”) are acquired. .

  In a succeeding step S102, it is determined whether or not the fuel waxing condition is satisfied. Here, it is determined whether or not the pre-filter temperature Tb is equal to or lower than the wax formation determination value Tw. Regarding waxing determination value Tw In the present embodiment, the waxing determination is made according to the fuel property detected by the fuel property sensor 72 in consideration of the fact that the temperature at which the fuel is waxed (that is, the cloud point CP) varies depending on the fuel property. The value Tw is variably set. Specifically, the cloud point CP is estimated based on the fuel property detected by the fuel property sensor 72, and the waxing determination value Tw is set according to the estimated cloud point CP. At this time, the higher the cloud point CP, the larger the waxing determination value Tw is set.

  Regarding the estimation of the cloud point CP, in the present embodiment, the correspondence between the kinematic viscosity of the fuel and the cloud point CP of the fuel is previously stored in the ROM of the ECU 90, and the stored correspondence and the fuel property are stored. The cloud point CP of the fuel is estimated using the kinematic viscosity detected by the sensor 72. At this time, the higher the kinematic viscosity of the fuel, the higher the value of the cloud point CP is set. The waxing determination value Tw may be variable according to the cloud point CP, and the waxing determination value Tw may be a predetermined constant value. Further, instead of changing the waxing determination value Tw according to the cloud point CP, the waxing determination value Tw may be changed according to the area where the vehicle is used.

  The pre-filter temperature Tb is higher than the waxing determination value Tw, and if the waxing condition is not satisfied, a negative determination is made in step S102, and this routine is ended as it is. In this case, the fuel is not recirculated by the filter temperature raising control. On the other hand, when the pre-filter temperature Tb is equal to or lower than the waxing determination value Tw and the waxing condition is satisfied, the process proceeds to step S103, and the fuel temperature detected by the fuel temperature sensor 73 (hereinafter, “high-pressure post-temperature Th”). To get. In step S104, the engine rotation speed and the engine load are acquired, and the injection conditions (injection timing and injection period) of the fuel injection valve 20 are acquired.

  In the present system, the fuel temperature sensor 73 is provided in the first high pressure passage 13, but it is sufficient that the fuel temperature downstream of the high pressure pump 62 can be detected. Therefore, for example, the temperature detected by the sensor that detects the fuel temperature in the common rail 11 may be used as the high-pressure post-temperature Th.

  In the following step S105, the temperature raising flow rate Qu and the filter raising temperature target rail pressure PtB are set. The temperature raising flow rate Qu is a fuel flow rate that is supplied from the low pressure chamber 57 of the fuel injection valve 20 to the low pressure fuel pipe 63 through the branch pipe 65a, and dissolves the deposit (wax) accumulated on the fuel filter 66 and the fuel. This is the fuel flow rate necessary to suppress the precipitation of wax. Here, the temperature raising flow Qu is set based on the pre-filter temperature Tb and the high-pressure post-temperature Th. Specifically, the larger the difference between the pre-filter temperature Tb and the cloud point CP of the fuel, the larger the temperature raising flow rate Qc is set. Further, the higher the post-high pressure temperature Th is, the smaller the temperature raising flow rate Qu is set.

  Note that instead of the configuration in which the temperature increase flow rate Qc is set by the difference between the pre-filter temperature Tb and the fuel cloud point CP, the temperature increase flow rate Qc is determined by the difference between the pre-filter temperature Tb and a predetermined determination value. It may be configured to be set.

  The target rail pressure PtB is set to a higher pressure side than the target rail pressure PtA in the case of the normal control in which the filter temperature raising control is not performed in anticipation of the rail pressure decreasing due to the return of fuel to the fuel filter 66. Here, the target rail pressure PtB for filter temperature increase is calculated based on the injection amount command value Ki of the fuel injection valve 20 and the temperature increase flow rate Qc. The larger the injection amount command value Ki or the larger the temperature raising flow rate Qc, the higher the target rail pressure PtB is set.

  In step S106, based on the acquired injection condition, the period during which the second on-off valve 52 can be opened for the temperature rise of the filter within one combustion cycle of the engine 70 (hereinafter, also referred to as "temperature rise possible period Tf"). Set). In order to minimize the influence of the fuel injection valve 20 on the fuel injection, in the present embodiment, a period in which fuel is injected from the fuel injection valve 20 of each cylinder (fuel injection period T # n, where n is a cylinder number). ), That is, in a period in which the fuel injection valve 20 of any cylinder is not injecting fuel, the temperature increase possible period Tf is set.

  Specifically, from the end of the fuel injection period T # n of a certain cylinder (after the needle valve 31 is in the closed position) to the start of the fuel injection period T # n of the next combustion cylinder. Of the cylinder, that is, the period between the fuel injection period T # n and the fuel injection period T # n of each cylinder, the temperature increase possible period Tf is set (see FIG. 14). The end timing of the temperature-rising possible period Tf is set to a predetermined time B1 (for example, 20 to 30 ° C. A) before the injection start timing of the next combustion cylinder. As a result, it is possible to secure a period in which the rail pressure reduced by the recirculation of fuel for raising the temperature of the filter is set to the target pressure before the start of the next injection. In the case of a four-cylinder engine, a total of four temperature rise possible periods Tf are set within one combustion cycle (720 ° C.A).

  In this embodiment, the predetermined time B1 is variably set according to the engine rotation speed detected by the crank angle sensor. Specifically, the higher the engine speed is, the longer the predetermined time B1 is set. When the time until the start of fuel injection in the next combustion cylinder is not sufficiently secured, the driven valve 41 is separated from the second main body portion 22 in the first control chamber 46, that is, inside the control chambers 46 and 36. The next fuel injection will be performed when the fuel pressure is not sufficiently high. In this case, there is a concern that the injection start delay and the injection amount may become insufficient, resulting in an insufficient output of the engine 70. Considering this point, the predetermined time B1 is set according to the engine rotation speed, and thereby the rail pressure is made sufficiently high by the start of the next injection.

  In the following step S107, the number of cylinders and the cylinder number for opening the second opening / closing valve 52 are set during the temperature increase possible period Tf. The amount of fuel required to suppress and eliminate the clogging of the fuel filter 66 due to the waxed fuel differs depending on the pre-filter temperature Tb. Specifically, the lower the pre-filter temperature Tb, the more fuel is required to suppress and eliminate the clogging of the fuel filter 66. Further, the larger the number of cylinders that recirculate the fuel by opening the second opening / closing valve 52, the more the high temperature fuel inside the fuel injection valve 20 can recirculate to the fuel filter 66.

  In consideration of these points, in the present embodiment, the number N of cylinders in which the fuel is recirculated in the temperature increase possible period Tf is set according to the temperature increase flow rate Qu. Specifically, the larger the flow rate Qu for temperature increase, the larger the number of cylinders in which the fuel is recirculated is set. This sufficiently suppresses and eliminates clogging of the fuel filter 66, and unnecessarily opens the second opening / closing valve 52 when the fuel is not so low in temperature and the flow rate for temperature increase Qu is small, thereby deteriorating fuel efficiency. It's suppressed.

  In addition, when the second opening / closing valve 52 is opened for some of the cylinders where the temperature raising flow rate Qu is relatively small, and if there is a deactivated cylinder that suspends combustion of the engine 70, that deactivated cylinder is selected. , The second opening / closing valve 52 is preferentially selected as the cylinder to be opened in the temperature increase possible period Tf. By giving priority to the recirculation of fuel in the idle cylinder, it is possible to minimize the influence on the fuel injection.

  FIG. 13 is a flowchart showing a processing procedure of processing for setting the number N of cylinders and the cylinder number in which the fuel is recirculated in the possible temperature rise period Tf. In FIG. 13, in step S201, the number of cylinders N is set based on the temperature increase flow rate Qu. In a succeeding step S202, it is determined whether or not the number of cylinders N is smaller than the number of cylinders Ntotal included in the engine 70 (four in the present embodiment). If the number of cylinders N is equal to Ntotal, the process proceeds to step S203, and a drive cylinder that drives the second opening / closing valve 52 to recirculate the fuel in the temperature-rising period Tf is selected from the cylinders that perform combustion (combustion cylinders). To do.

  On the other hand, if the number N of cylinders is less than Ntotal, the process proceeds to step S204, and it is determined whether or not there are idle cylinders. If there are no deactivated cylinders, the process proceeds to step S203, and if there are deactivated cylinders, the process proceeds to step S204. In step S204, the deactivated cylinder is selected as the driving cylinder with priority. At this time, if the number N of cylinders is larger than the number of idle cylinders, the shortage is compensated by the combustion cylinders. Then, this process ends.

  Returning to the description of FIG. 12, in step S108, the temperature raising execution period Tc is set as a period during which the fuel inside the fuel injection valve 20 is actually recirculated in at least a part of the temperature raising possible period Tf. Here, the temperature raising execution period Tc is set based on the temperature raising flow rate Qc. Specifically, the higher the temperature raising flow rate Qu, the longer the temperature raising execution period Tc is set. By variably setting the temperature raising execution period Tc together with the number of cylinders N for opening the second opening / closing valve 52, it is possible to finely adjust the amount of fuel recirculated to the fuel filter 66 side.

  In the following step S109, the first on-off valve 51 is closed, the second on-off valve 52 is opened, and the return valve 67 is opened during the set temperature raising execution period Tc. As a result, the high temperature fuel inside the fuel injection valve 20 is supplied to the fuel filter 66. In this embodiment, the recirculation valve 67 is left open during the period when the waxing condition is satisfied. However, the reflux valve 67 may be opened / closed each time the second opening / closing valve 52 is opened / closed to raise the temperature of the filter. Further, the command value of the fuel pressure feed amount of the high pressure pump 62 is calculated so that the actual rail pressure of the common rail 11 becomes the target rail pressure PtB for raising the filter, and the high pressure pump 62 is driven based on the calculated command value. Control.

  After starting the recirculation of the fuel by the filter temperature raising control, the pre-filter temperature Tb is acquired in step S110, and it is determined in step S111 whether or not the waxing condition is canceled by using the acquired pre-filter temperature Tb. judge. When the pre-filter temperature Tb is equal to or lower than the waxing determination value Tw, the process returns to step S107, and the processes of steps S107 to S111 are executed again. At this time, the fuel may be recirculated to the fuel injection valve 20 of the same cylinder as the cylinder set last time, or the number of cylinders to be recirculated fuel may be set to the previous time based on the acquired pre-filter temperature Tb. The fuel recirculation may be performed by increasing or decreasing it.

  When it is determined in step S111 that the waxing condition is eliminated, the process proceeds to step S112, the recirculation valve 67 is closed, the recirculation of fuel to the fuel filter 66 by the filter temperature raising control is stopped, and this routine is ended. .

  FIG. 14 is a time chart showing a specific mode of the filter temperature raising control in comparison with the normal control in which the filter temperature raising control is not executed. In FIG. 14, (a) is a cam lift amount, (b) is a drive signal for the high pressure pump 62, (c) is a fuel pressure feed amount (pump discharge amount) of the high pressure pump 62, and (d) is an injection rate of the fuel injection valve 20. , (E) shows the amount of fuel recirculated from the fuel injection valve 20 to the fuel filter 66, and (f) shows the transition of the actual rail pressure. In addition, solid lines in (b), (c), (e), and (f) of FIG. 14 indicate the time when the filter temperature raising control is performed, and the alternate long and short dash line indicates the time when the normal control is performed.

  As shown in FIG. 14, the fuel recirculation by the filter temperature raising control is performed during a period in which the normal fuel injection by the fuel injection valve 20 is not affected. Specifically, the temperature increase possible period Tf is set within the period between fuel injection in each cylinder, and the temperature increase flow rate Qc is satisfied within the set temperature increase possible period Tf. The temperature raising execution period Tc is set. The temperature rise possible period Tf is after the injection end timing of each cylinder (that is, the timing when the needle valve 31 is shifted to the closed position), and before the timing before the injection start timing of the next combustion cylinder by time B1. Is set to.

  For example, when the current combustion cylinder is the first cylinder # 1, the period from the injection end timing DA of the first cylinder # 1 to the injection start timing DB of the next combustion cylinder (the third cylinder # 3 in FIG. 14). Of these, the period before the injection end timing DA and the time B1 before the injection start timing DB is set as the temperature increase possible period Tf of the first cylinder # 1. The temperature raising execution period Tc is set within the set temperature raising possible period Tf, and the second on-off valve 52 of the fuel injection valve 20 attached to the first cylinder # 1 is opened during the set temperature raising execution period Tc. By doing so, the fuel is discharged from the fuel injection valve 20 of the first cylinder # 1.

  At the time of normal control, as shown in FIG. 14F, the fuel pressure feed amount of the high-pressure pump 62 is controlled so that the actual rail pressure follows the target rail pressure PtA. On the other hand, during the execution of the filter temperature raising control, as the fuel is recirculated from the fuel injection valve 20 to the fuel filter 66, the fuel pressure feed amount of the high pressure pump 62 for increasing the temperature of the filter is increased to increase the rail pressure. Boost. At this time, the target rail pressure PtB is set to a high pressure side as the recirculation amount of fuel increases. The filter temperature raising control may be stopped when the required amount of fuel recirculation is large and the peak rail pressure exceeds a predetermined pressure (for example, a withstand pressure allowable value).

  Next, a specific mode of the filter temperature raising control according to the injection rate pattern will be described with reference to the time charts of FIGS. 15 and 16. FIG. 15 is a time chart (see FIG. 2B) showing the operation in the low speed valve opening mode and the high speed valve closing mode, and FIG. 16 shows the low speed valve opening mode and the high speed valve closing mode to the low speed valve closing mode. 3 is a time chart (see FIG. 2E) showing the operation at the time of switching. 15 and 16 show the operation of one cylinder (for example, the fuel injection valve of the first cylinder # 1) of all the cylinders. 15 and 16, it is assumed that the pre-filter temperature Tb is equal to or lower than the waxing determination value Tw immediately after the engine is started and the filter temperature raising control is performed for the combustion cylinder.

  In FIG. 15, at time t11, the first opening / closing valve 51 and the second opening / closing valve 52 are both closed, the lift amount of the driven valve 41 is 0, and the control chamber (first control chamber 46 and second control chamber 36). The fuel pressure inside the intermediate chamber 26 is high pressure P1, and the lift amount and injection rate of the needle valve 31 are zero.

  When the first on-off valve 51 is opened at time t12 based on the fuel injection start command, the fuel pressure inside the intermediate chamber 26 and the control chambers 46, 36 decreases. At this time, since the pressure reducing orifice 42a is provided in the third passage 42, the fuel pressure inside the intermediate chamber 26 drops faster than the fuel pressure inside the control chambers 46 and 36. Further, at time t13, when the fuel pressure inside the second control chamber 36 becomes lower than the predetermined pressure, the needle valve 31 starts to be displaced in the valve opening direction, and the fuel injection from the injection hole 34 is started. At this time, the fuel in the first control chamber 46 is discharged to the low pressure chamber 57 via the first passage 25, while the second opening / closing valve 52 is closed, so that the low pressure chamber 57 is discharged from the second passage 27. Not discharged to. Therefore, the fuel pressure inside the second control chamber 36 decreases at a slow speed. As a result, the needle valve 31 is displaced in the valve opening direction at a low speed, and the injection rate rises at a low speed.

  When the first opening / closing valve 51 is closed at time t14 based on the fuel injection end command, the fuel pressure inside the intermediate chamber 26 rises due to the supply of the high-pressure fuel from the first high-pressure passage 13. Further, when the difference in fuel pressure between the control chambers 46, 36 and the intermediate chamber 26 becomes small at time 15, the driven valve 41 is displaced in the direction away from the position (contact position) where the driven valve 41 contacts the second main body portion 22. As a result, the high pressure fuel from the first high pressure passage 13 flows into the first control chamber 46.

  After that, when the fuel pressure inside the second control chamber 36 becomes equal to or higher than the predetermined pressure, the needle valve 31 moves in the valve closing direction (time t16). At this time, both the first opening / closing valve 51 and the second opening / closing valve 52 are closed, and the fuel pressure inside the control chambers 46, 36 rises at high speed. Therefore, the needle valve 31 moves at a high speed in the valve closing direction, and the injection rate falls at a high speed. After that, at time t17, the lift amount of the needle valve 31 becomes 0, and the fuel is not injected from the injection hole 34.

  At the time t18 after a predetermined time B2 has elapsed from the time t17 when the needle valve 31 is displaced to the closed position and the waxing condition is currently satisfied, the second on-off valve 51 remains closed at the time t18. 52 is opened. In this case, without moving the needle valve 31 from the closed position (that is, the injection hole 34 is closed by the needle valve 31), the first control chamber 46 to the low pressure chamber 57 via the second passage 27. Fuel is discharged. As a result, the fuel pressure inside the control chambers 46, 36 and the intermediate chamber 26 decreases to the fuel pressure P2 that is lower than the high pressure P1 and higher than the intermediate pressure P3. At this time, the driven valve 41 remains separated from the second main body portion 22. Then, the second on-off valve 52 is closed at time t19 when the temperature raising execution period Tc has elapsed from time t18. In the cylinder for which the filter temperature raising control is performed, the fuel injection valve 20 performs the operation shown in FIG. 15 so that the fuel is injected from the fuel injection valve 20 and the fuel in the fuel injection valve 20 after the fuel injection is completed. Will be done.

  In the high speed valve closing mode, if the second opening / closing valve 52 is opened before the fuel pressure inside the control chambers 46, 36 becomes sufficiently high, the moving speed of the needle valve 31 in the valve closing direction becomes slow. (That is, switching to the low speed valve closing mode), the injection rate changes. Therefore, in the high-pressure valve closing mode, the second opening / closing valve 52 for heating the filter is opened after the predetermined time B2 has elapsed from the closing timing (time t17) of the needle valve 31.

  The recirculation valve 67 is opened during the period when the wax formation condition is satisfied, and the high temperature fuel discharged from the low pressure chamber 57 through the low pressure passage 58 is supplied to the fuel filter 66 through the return pipe 65 and the branch pipe 65a. To be done. The supply of the high-temperature fuel raises the temperature of the fuel filter 66, suppresses the precipitation of the solid content of the fuel, and melts the waxed fuel.

  Next, the operation at the time of switching from the low speed valve opening mode and the high speed valve closing mode to the low speed valve closing mode will be described with reference to FIG. In FIG. 16, at time t21, both the first opening / closing valve 51 and the second opening / closing valve 52 are closed, the lift amount of the driven valve 41 is 0, and the control chamber (the first control chamber 46 and the second control chamber 36). The fuel pressure inside the intermediate chamber 26 is high pressure P1, and the lift amount and injection rate of the needle valve 31 are zero. When the first on-off valve 51 is opened at time t22 based on the fuel injection start command, the fuel pressure inside the second control chamber 36 decreases at a slow speed. As a result, the needle valve 31 is displaced in the valve opening direction at a low speed, and the injection rate rises at a low speed.

  After that, when the first opening / closing valve 51 is closed at time t23, the fuel pressure inside the intermediate chamber 26 rises due to the supply of the high-pressure fuel from the first high-pressure passage 13. When the difference in fuel pressure between the control chambers 46, 36 and the intermediate chamber 26 becomes smaller, the driven valve 41 is displaced in the direction away from the second main body portion 22. As a result, the high pressure fuel from the first high pressure passage 13 flows into the first control chamber 46. After that, when the fuel pressure inside the second control chamber 36 becomes equal to or higher than the predetermined pressure, the needle valve 31 moves in the valve closing direction (time t24). At this time, both the first opening / closing valve 51 and the second opening / closing valve 52 are closed, and the fuel pressure inside the control chambers 46, 36 rises at high speed. As a result, the needle valve 31 moves at a high speed in the valve closing direction, and the injection rate falls at a high speed.

  The second opening / closing valve 52 is opened at time t25, which is on the way from the start of the movement of the needle valve 31 in the valve closing direction to the closing of the injection hole 34. As a result, the fuel inside the first control chamber 46 is discharged into the low pressure chamber 57 through the second passage 27, and the fuel pressure inside the control chambers 46 and 36 is maintained at a predetermined pressure. Therefore, the moving speed of the needle valve 31 in the valve closing direction switches from high speed to low speed, and the injection rate falls at low speed. After that, at time t26, the lift amount of the needle valve 31 becomes 0, and fuel is not injected from the injection hole 34. Further, the second on-off valve 52 is closed at time t27 when the temperature raising execution period Tc has elapsed from time t26.

  In FIG. 16, the waxing condition is satisfied, and the second opening / closing valve 52 is left open at time t26 when the lift amount of the needle valve 31 becomes 0 in order to perform the filter temperature increase control after the fuel injection is completed. Keep it. As a result, the fuel is discharged from the first control chamber 46 to the low-pressure chamber 57 without injecting the fuel from the injection hole 34, and the fuel pressure inside the control chambers 46, 36 and the intermediate chamber 26 decreases. Further, the high temperature fuel in the low pressure chamber 57 is discharged from the low pressure passage 58 and supplied to the upstream side of the fuel filter 66 through the return pipe 65 and the branch pipe 65a.

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

  A recirculation mechanism 69 that recirculates the fuel inside the fuel injection valve 20 to the low-pressure fuel pipe 63 is provided, and the high-temperature fuel in the first control chamber 46 of the fuel injection valve 20 is supplied to the upstream side of the fuel filter 66 by the recirculation mechanism 69. By doing so, the temperature of the fuel filter 66 is raised. According to this configuration, the fuel filter 66 can be heated by the high-temperature fuel supplied from the fuel injection valve 20, the fuel deposits adhering to the fuel filter 66 can be dissolved, and the generation of fuel deposits can be suppressed. You can Further, without providing a heater for heating the fuel filter 66, it is possible to suppress the clogging of the fuel filter 66 due to the deposition of fuel.

  The fuel injection valve 20 can change the injection rate by including the first opening / closing valve 51 and the second opening / closing valve 52. In the fuel injection valve 20 having such a configuration, the first on-off valve 51 is closed and the second on-off valve 52 is opened to keep the needle valve 31 in the closed position (that is, the injection hole). The fuel pressure inside the control chambers 46 and 36 can be reduced without injecting fuel from 34), and the function as a pressure reducing valve for reducing the fuel pressure in the common rail 11 is achieved. In the present embodiment, by utilizing such a function, the high temperature fuel in the control chambers 46 and 36 is supplied to the upstream side of the fuel filter 66, so that a heater or a complicated mechanism for preventing the fuel filter 66 from clogging is provided. Since it does not need to be provided, it is possible to reduce the system cost.

  On the condition that the waxing condition is satisfied, the filter temperature raising control is performed to raise the temperature of the fuel filter 66 by closing the first opening / closing valve 51 and opening the second opening / closing valve 52. It was configured. With such a configuration, the filter temperature raising control can be performed only when the temperature of the fuel filter 66 needs to be raised. As a result, it is possible to suppress the deterioration of fuel efficiency due to the recirculation of the fuel in the fuel injection valve 20 as much as possible.

  The temperature increasing flow rate Qu is set based on the pre-filter temperature Tb, and the second opening / closing valve 52 is driven so that the fuel amount corresponding to the set temperature increasing flow rate Qu is supplied to the fuel filter 66. . Since the temperature raising flow rate Qu differs depending on the pre-filter temperature Tb, this configuration can supply the amount of fuel required to suppress the clogging of the fuel filter 66.

  When the filter temperature raising control is performed, the number of cylinders that drive the second opening / closing valve 52 is variably set according to the temperature raising flow rate Qu. According to this configuration, the amount of fuel recirculated to the fuel filter 66 can be adjusted by a simple method of changing the number of cylinders that drive the second opening / closing valve 52, and the complexity of the system can be suppressed. .

  When there is a deactivated cylinder, the deactivated cylinder is preferentially used to perform the filter temperature raising control. As a result, the filter temperature raising control using the combustion cylinder can be suppressed as much as possible, and the influence on the normal fuel injection for torque generation can be minimized.

  The fuel injection amount of the high-pressure pump 62 is variably controlled based on the injection amount command value of the fuel injection valve 20 and the flow rate Qu for temperature increase. Since the fuel pressure feed amount of the high-pressure pump 62 is increased according to the temperature increase flow rate Qu, it is possible to prevent the actual rail pressure from becoming lower than the target rail pressure during normal fuel injection.

  It is conceivable that during the recirculation of the fuel from the fuel injection valve 20 to the fuel filter 66, the rail pressure decreases and thus the fuel injection valve 20 cannot inject the fuel commensurate with the command injection amount. In this respect, according to the present embodiment, the second on-off valve 52 is opened and the high temperature fuel is filtered by the fuel filter 66 during a period in which fuel injection is not performed in all the fuel injection valves 20 in one combustion cycle of the engine 70. It was configured to be refluxed. With this configuration, it is possible to sufficiently suppress the clogging of the fuel filter 66 while not affecting the normal fuel injection by the fuel injection valve 20.

  The second on-off valve 52, which was opened to raise the temperature of the filter, is closed after the injection of the current combustion cylinder is completed and before the injection start timing of the next combustion cylinder by a predetermined time B1. Therefore, the rail pressure lowered by the recirculation of fuel for raising the temperature of the filter can be raised to the target rail pressure by the start of the next injection.

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

  In the above-described embodiment, the fuel is circulated to the fuel filter 66 by opening the second opening / closing valve 52 during the period after the fuel injection from the fuel injection valve 20 is performed. The configuration may be such that the fuel is recirculated to the fuel filter 66 by opening the second opening / closing valve 52 during the period before execution. Specifically, in FIG. 14, when the current combustion cylinder is the first cylinder # 1, the next combustion cylinder (the third cylinder # 3 in FIG. 14) is changed from the injection end timing DA of the first cylinder # 1. Of the period up to the injection start timing DB, the period before the injection start timing DB by the time B1 from the injection end timing DA is set as the temperature increase possible period Tf of the third cylinder # 3, and the set temperature increase is possible. In the period Tf, by opening the second opening / closing valve 52 of the fuel injection valve 20 attached to the third cylinder # 3, the fuel is discharged from the fuel injection valve 20 of the third cylinder # 3.

  FIG. 17 is a time chart showing the operation of the fuel injection valve 20 (for example, the fuel injection valve of the third cylinder # 3) when the second opening / closing valve 52 is opened in the period before fuel injection. Note that FIG. 17 shows the operation in the low speed valve opening mode and the high speed valve closing mode.

  Both the first on-off valve 51 and the second on-off valve 52 are closed, the lift amount of the driven valve 41 is 0, the fuel pressure inside the control chamber and the intermediate chamber 26 is high pressure P1, the lift amount of the needle valve 31 and the injection. In the state where the ratio is 0, by opening the second opening / closing valve 52, the needle valve 31 is kept in the closed position, and the first control chamber 46 passes through the second passage 27 to the low pressure chamber 57. Fuel is discharged. As a result, the fuel pressure inside the control chambers 46, 36 and the intermediate chamber 26 is reduced to a fuel pressure that is lower than the high pressure P1 and higher than the intermediate pressure P3. Then, at time t30, the second opening / closing valve 52 is closed. As a result, the fuel pressure inside the control chambers 46, 36 and the intermediate chamber 26 returns to the high pressure P1. After that, at time t31 after a lapse of time B1 from time t30, the first opening / closing valve 51 is opened in response to the fuel injection start command, and at time t32, the first opening / closing valve 51 is closed by the fuel injection valve end command. Speak. In the low speed valve opening mode and the high speed valve closing mode, the second opening / closing valve 52 is maintained in the closed state.

  In the above-described embodiment, the filter temperature raising control is performed by setting the temperature raising possible period Tf in a period in which the fuel injection valve 20 of any cylinder is not injecting fuel, but during the fuel injection in one cylinder, The high temperature fuel may be recirculated to the fuel filter 66 by closing the first opening / closing valve 51 and opening the second opening / closing valve 52 of the fuel injection valve 20 of another cylinder. FIG. 18 shows a time chart in the case where the filter temperature raising control is carried out by overlapping the fuel injection period. In FIG. 18, the second opening / closing valve 52 of another cylinder (here, the fourth cylinder # 4) is opened so as to overlap with the period Tx in which the fuel injection is performed in the first cylinder # 1. As a result, in the period Ty, the high temperature fuel inside the fuel injection valve 20 attached to the fourth cylinder # 4 is supplied to the fuel filter 66.

  If the filter temperature rise control is performed during fuel injection, the rail pressure will drop during fuel injection.Therefore, basically filter temperature rise control during fuel injection is prohibited, and the fuel pressure is controlled at extremely low temperatures. Only when it is necessary to raise the temperature of the filter 66 at an early stage, the configuration may be implemented in combination with the filter temperature raising control during the fuel injection stop period. Further, when the filter temperature raising control is performed during fuel injection, the amount of rail pressure drop is limited so that the fuel is recirculated to the fuel filter 66 while suppressing disadvantages such as smoke deterioration and torque reduction. Good to do.

  The configuration may be such that it is determined whether or not a failure has occurred in at least one of the fuel injection valve 20 and the drive circuit, and if it is determined that there is a failure, execution of the filter temperature raising control is restricted. In this case, when it is determined that there is a failure in some of the cylinders, the execution of the filter temperature raising control is prohibited for the cylinders that are determined to have a failure, and the flow rate Qu for raising the temperature of the fuel injection valve 20 of the normal cylinder is Qu. The amount is increased. Further, in the system in which the heater for heating the fuel filter 66 is provided, instead of the filter temperature raising control using the fuel injection valve 20, the fuel filter 66 is heated by the heater to suppress clogging of the fuel filter 66. You may do it.

  A heater for heating the fuel filter 66 may be provided, and the filter temperature raising control by the recirculation of the fuel from the fuel injection valve 20 and the heating control of the fuel filter 66 by the heater may be used together. In this case, the filter temperature raising control by the recirculation of the fuel from the fuel injection valve 20 is preferentially executed, and the heating control is also used when the temperature of the fuel filter 66 cannot be sufficiently raised only by the recirculation of the fuel. The clogging of the fuel filter 66 is suppressed.

  In the above-described embodiment, the number of cylinders N is variable according to the temperature raising flow rate Qu. However, regardless of the temperature raising flow rate Qu, the fuel injection valve 20 of all cylinders is used and the fuel filter 66 has a high temperature. The fuel may be supplied. In this case, for example, the opening degree of the recirculation valve 67 is changed or the opening period of the second opening / closing valve 52 is changed according to the flow rate Qu for temperature increase (that is, the temperature increase execution period Tc is changed). It may be configured.

  The waxing condition includes that the pre-filter temperature Tb is equal to or lower than the waxing determination value Tw, and the filter temperature raising control is performed under the condition that the pre-filter temperature Tb is equal to or lower than the waxing determination value Tw. . Instead of this, the amount of foreign matter deposited on the fuel filter 66 may be detected, and the filter temperature raising control may be performed when the detected amount of deposit is equal to or greater than a predetermined value. Specifically, for example, the differential pressure before and after the fuel filter 66 is detected, and when the differential pressure is equal to or higher than a predetermined value, the filter temperature raising control is performed.

  In the above-described embodiment, the filter temperature raising control is performed on the condition that the waxing condition is satisfied. However, it is determined whether or not the engine is being started, and if the engine is being started, the filter is constantly raised. The temperature may be controlled.

  In the above-described embodiment, the case of applying the configuration in which the injection rate is variably controlled by controlling the opening / closing of the second opening / closing valve 52 has been described, but the needle is formed by connecting and disconnecting the control chamber and the fuel discharge passage. A configuration is provided in which an on-off valve dedicated to filter temperature raising is provided as a pressure adjusting valve capable of adjusting the fuel pressure inside the control chamber without moving the valve 31, and the filter temperature raising control is performed by controlling the drive of this on-off valve. May be

  The configuration of the fuel injection valve 20 is not limited to the configuration shown in FIG. For example, in the fuel injection valve 20 of FIG. 1, when the driven valve 41 blocks the first high pressure passage 13 and the first control chamber 46, the second passage 27 is formed inside the driven valve 41 and the third passage 27 is formed. It may be configured to communicate with the first control chamber 46 via a passage different from the passage 42. Alternatively, when the second passage 27 is in communication with the intermediate chamber 26 and the driven valve 41 blocks the first high pressure passage 13 and the first control chamber 46, the second passage 27 connects the intermediate chamber 26 and the third passage 42. It may be configured to communicate with the first control chamber 46 via the.

  Further, in the fuel injection valve 20 of FIG. 1, two or more opening / closing valves are provided as the second opening / closing valve 52 for adjusting the moving speed of the needle valve 31, and opening / closing of these two or more opening / closing valves are individually controlled. Thus, the moving speed of the needle valve 31 may be adjusted with higher accuracy. In this case, the flow rate of fuel through the pressure increasing orifice 14a is set to be larger than the total of the flow rates of fuel through the pressure reducing orifices provided in the fuel passages of the two or more on-off valves.

  -Each component described above is a conceptual one, and is not limited to the above embodiment. For example, the functions of one constituent element may be distributed to a plurality of constituent elements, or the functions of a plurality of constituent elements may be realized by one constituent element.

  10 ... Fuel injection system, 11 ... Common rail (accumulation pipe), 13 ... 1st high pressure passage, 20 ... Fuel injection valve, 25 ... 1st passage, 26 ... Intermediate chamber, 27 ... 2nd passage, 31 ... Needle valve, 34 ... injection hole, 36 ... second control chamber, 41 ... driven valve, 46 ... first control chamber, 51 ... first opening / closing valve, 52 ... second opening / closing valve (pressure adjusting valve), 57 ... low pressure chamber, 58 ... low pressure Passage, 65 ... Return pipe (return pipe), 65a ... Branch pipe (return pipe), 63 ... Low-pressure fuel passage, 66 ... Fuel filter, 67 ... Reflux valve, 69 ... Reflux mechanism, 70 ... Engine (internal combustion engine), 90 ... ECU (supply control unit, injection control unit, condition determination unit, flow rate setting unit, cylinder number setting unit, pumping amount calculation unit, drive control unit).

Claims (9)

A fuel filter (66) arranged in a low-pressure fuel passage (63) connecting the fuel tank (61) and the high-pressure pump (62) and filtering fuel, and a pressure accumulation pipe for storing the fuel supplied from the high-pressure pump in a high-pressure state A fuel injection system comprising: (11) and a fuel injection valve (20) for directly injecting high-pressure fuel in the accumulator pipe into a cylinder of an internal combustion engine (70),
The fuel injection valve,
A control chamber (36, 46) to which the high pressure fuel is supplied from the pressure accumulating pipe;
A needle valve (31) for opening and closing the injection hole (34) by moving to a valve opening position and a valve closing position according to the fuel pressure inside the control chamber;
A fuel discharge passage (58) for discharging the fuel in the control chamber to the outside of the fuel injection valve;
A pressure adjustment valve (52) capable of adjusting the fuel pressure inside the control chamber without moving the needle valve by connecting and disconnecting the control chamber and the fuel discharge passage,
Equipped with
A return pipe (65, 65a) that connects the fuel discharge passage and a portion of the low-pressure fuel passage that is downstream of the fuel tank and upstream of the fuel filter is provided,
By connecting the control chamber and the fuel discharge passage with the pressure regulating valve when the needle valve is in the closed position, the needle valve is not moved from the closed position to the inside of the control chamber. A fuel injection system comprising: a supply control unit that supplies fuel to the fuel filter through the return pipe. The fuel injection valve,
The needle valve is disposed in a first passage (25) that connects the control chamber and the fuel discharge passage, and connects and disconnects the control chamber and the fuel discharge passage to open and close the needle valve. A first opening / closing valve (51) for moving to a position,
The needle valve is connected by connecting the control chamber and the fuel discharge passage and in a second passage (27) different from the first passage, and connecting and disconnecting the control chamber and the fuel discharge passage. A second on-off valve (52) capable of adjusting the fuel pressure inside the control chamber without moving,
Equipped with
The pressure regulating valve is the second opening / closing valve,
An injection control unit that variably controls the injection rate of the fuel injection valve by controlling opening / closing of the first opening / closing valve and the second opening / closing valve,
The supply control unit interrupts the communication between the control chamber and the fuel discharge passage via the first passage by the first opening / closing valve, so that when the needle valve is in the closed position, The fuel according to claim 1, wherein the fuel in the control chamber is supplied to the fuel filter through the return pipe by connecting the control chamber and the fuel discharge passage through the second passage with two opening / closing valves. Injection system. Based on the fuel temperature on the upstream side of the high-pressure pump, a condition determination unit for determining whether or not a predetermined deposition condition for producing a deposit of the fuel is established,
The fuel according to claim 1 or 2, wherein the supply control unit supplies the fuel in the control chamber to the fuel filter when the condition determination unit determines that the predetermined deposition condition is satisfied. Injection system. A flow rate setting unit that sets the flow rate of the fuel in the control chamber supplied to the fuel filter based on the fuel temperature on the upstream side of the high-pressure pump,
The fuel injection system according to claim 1, wherein the supply control unit supplies the fuel in the control chamber to the fuel filter based on the fuel flow rate set by the flow rate setting unit. The internal combustion engine comprises a plurality of the cylinders, the fuel injection valve is provided for each cylinder,
Further comprising a cylinder number setting unit for setting the number of cylinders for supplying the fuel in the control chamber to the fuel filter based on the fuel flow rate set by the flow rate setting unit,
The supply control unit supplies the fuel in the control chamber to the fuel filter by controlling the pressure adjustment valves in the fuel injection valves in the number corresponding to the number of cylinders set by the cylinder number setting unit. Item 4. The fuel injection system according to Item 4. Further comprising a deactivated cylinder determination unit that determines whether or not there is a deactivated cylinder that deactivates combustion,
The supply control unit, when the deactivated cylinder determination unit determines that there is the deactivated cylinder, preferentially selects the deactivated cylinder as a cylinder that supplies the fuel in the control chamber to the fuel filter, and deactivates the deactivated cylinder. The fuel injection system according to claim 5, wherein the fuel in the control chamber is supplied to the fuel filter by controlling the pressure adjustment valve of the fuel injection valve provided in a cylinder. A pressure feed amount calculation unit that calculates the fuel pressure feed amount of the high-pressure pump based on the injection amount command value of the fuel injection valve and the fuel flow rate set by the flow rate setting unit;
A drive control unit for controlling the drive of the high-pressure pump based on the fuel pressure feed amount calculated by the pressure feed amount calculation unit;
The fuel injection system according to claim 4, further comprising: The internal combustion engine comprises a plurality of the cylinders, the fuel injection valve is provided for each cylinder,
The supply control unit supplies the fuel in the control chamber to the fuel filter during a period in which none of the plurality of fuel injection valves is injecting fuel from the injection hole. The fuel injection system according to the paragraph.   The supply control unit, after starting the supply of the fuel in the control chamber to the fuel filter, a predetermined time before the injection start timing of the next combustion cylinder, the control chamber and the fuel discharge passage by the pressure adjustment valve. 9. The fuel injection system according to claim 8, wherein the communication is cut off.

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