Accumulation type fuel injection control device

Abstract

To detect that flow limiters have been closed.SOLUTION: An accumulation type fuel injection control device 1 comprises: injectors 10; a common rail 5; a high pressure pump 3; a flow rate control valve 30 for adjusting a fuel pumping amount of the high pressure pump 3; flow limiters 50 that are each closed when a flow rate of fuel supplied to the injector 10 from the common rail 5 becomes excessive; a rail pressure sensor 15 for detecting a fuel pressure in the common rail; and an electronic control unit 9. The electronic control unit 9 comprises: a rail pressure control part 900 for controlling a rail pressure with the flow rate control valve 30; a fuel injection control part 902 for executing fuel injection of the injector 10; an instruction part 906 for performing fuel injection by a controlled amount corresponding to a predetermined inspection point; and a determination part 910 for determining whether or not the flow limiters 50 have been closed on the basis of energizing waveforms of the flow rate control valve 30 when the fuel injection is performed by the controlled amount corresponding to the inspection point.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an accumulator type fuel injection control device equipped with a flow limiter that prevents an excessive amount of fuel from flowing from a common rail that stores high-pressure fuel to an injector corresponding to each cylinder of an engine. [Background technology]

[0002] Conventionally, an accumulator type fuel injection control device equipped with a flow limiter that prevents excessive fuel from flowing from a common rail to an injector is known. Also, a diesel engine equipped with an accumulator type fuel injection control device equipped with a flow limiter is known. Such diesel engines are sometimes used in, for example, generators, ships, locomotives that run on tracks, etc.

[0003] The flow limiter shown in Patent Document 1 is provided between a common rail and an injector, and comprises a casing, a valve body that is slidable inside the casing and has an internal communicating passage through which fuel can pass, and a compression coil spring that presses the valve body in a direction away from a valve seat formed in the casing.

[0004] During operation of the accumulator type fuel injection control device, if some malfunction occurs and excessive fuel flows from the common rail to the injectors, the valve of the flow limiter moves and seats on the valve seat, stopping the supply of fuel from the common rail to the injectors. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2004-027966 A Summary of the Invention [Problem to be solved by the invention]

[0006] The flow limiter is mechanically operated by the balance between the fuel pressure on the upstream and downstream sides of the flow limiter and the biasing force of the compression coil spring that presses the valve body. Therefore, when the flow limiter is activated (valve closed), the electronic control unit (ECU) cannot recognize the activation. As a result, there is a possibility that the malfunction will be detected late.

[0007] The present invention has been made in light of the above-mentioned problems, and has an object to provide an accumulator type fuel injection control device in which an electronic control unit can detect the closure of a flow limiter. [Means for solving the problem]

[0008] According to the present invention, in an accumulator type fuel injection control device (1) including an injector (10) for injecting fuel into a combustion chamber of an engine, a common rail (5) for supplying the fuel to the injector (10), a high-pressure pump (3) for pumping the fuel to the common rail (5), a flow control valve (30) for regulating the amount of fuel pumped by the high-pressure pump (3), a flow limiter (50) for closing and stopping the supply when the flow rate of the fuel supplied from the common rail (5) to the injector (10) becomes excessive, a rail pressure sensor (15) for detecting rail pressure, which is the pressure of the fuel in the common rail, and an electronic control unit (9), the electronic control unit (9) There is provided an accumulator type fuel injection control device (1) comprising: a rail pressure control unit (900) that controls the flow control valve (30) so that the rail pressure becomes a target rail pressure; a fuel injection control unit (902) that executes fuel injection from the injector (10) by energizing the injector (10); an instruction unit (906) that performs fuel injection with a control amount corresponding to a predetermined inspection point for determining whether the flow limiter (50) is closed; and a determination unit (910) that determines whether the flow limiter (50) is closed or not based on an energization waveform of the flow control valve (30) when fuel injection is performed with the control amount corresponding to the inspection point, wherein the control amount corresponding to the inspection point includes the rail pressure and a fuel injection amount. Effect of the Invention

[0009] According to the accumulator type fuel injection control device of the present invention, the electronic control unit can detect the closure of the flow limiter without adding any new parts. [Brief description of the drawings]

[0010] [Figure 1] 1 shows the overall configuration of an accumulator type fuel injection control device 1 according to an embodiment of the present invention. [Diagram 2] 1 is a cross-sectional view of a flow limiter 50 according to an embodiment of the present invention. [Diagram 3] 1 is a cross-sectional view of a flow control valve 30 according to an embodiment of the present invention. [Figure 4] 4 shows a waveform of current flow through a coil of the flow control valve 30 according to the first embodiment of the present invention. [Diagram 5] FIG. 2 is a block diagram showing a configuration of a portion of an electronic control unit 9 that is related to the implementation of the present invention. [Figure 6] 4 is a subroutine flowchart according to the first embodiment of the present invention. [Figure 7] 6 is a diagram showing a waveform of current flow through a coil of a flow control valve 30 according to a second embodiment of the present invention. [Figure 8] 10 is a subroutine flowchart according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, a first embodiment of the present invention will be described with reference to the drawings as appropriate. The members, arrangements, etc. described below do not limit the present invention, and can be modified in various ways within the scope of the present invention. In addition, in each drawing, the same reference numerals indicate the same elements, and the description is omitted as appropriate. In each drawing, the illustration of detailed parts is simplified or omitted as appropriate. Also, duplicated descriptions are simplified or omitted as appropriate.

[0012] 1 shows the overall configuration of a fuel injection control device according to the present invention. The fuel injection control device according to the present invention is an accumulator-type fuel injection control device 1. The accumulator-type fuel injection control device 1 is a device for injecting fuel into a cylinder of an engine (not shown).

[0013] The embodiment of the present invention described below is an example in which the accumulator type fuel injection control device 1 is used in a diesel engine, and the equipment in which the diesel engine is mounted is a generator, a ship, a locomotive running on a railroad, etc. Diesel engines mounted in such equipment are characterized in that they are often operated for a relatively long period of time at a specific rotation speed. However, the present invention can also be implemented in cases in which the equipment in which the diesel engine in which the accumulator type fuel injection control device 1 is used is mounted is a vehicle such as a passenger car or truck.

[0014] The accumulator type fuel injection control device 1 includes, as main elements, a fuel tank 2, a low-pressure pump 11, a fuel filter 12, a high-pressure pump 3, a common rail 5, an injector 10, and an electronic control unit 9 (ECU (Electronic Control Unit)).

[0015] The low-pressure pump 11 and high-pressure pump 3 are connected by a low-pressure fuel passage 21, and the high-pressure pump 3 and common rail 5 are connected by high-pressure fuel passages 23 and 25, respectively. In addition, the high-pressure pump 3, common rail 5 and injector 10 are connected by return passages 27, 28 and 29, respectively, for returning surplus fuel not injected from the injector 10 to the fuel tank 2.

[0016] The low-pressure pump 11 pumps up and pumps the fuel in the fuel tank 2, and supplies the fuel to the high-pressure pump 3 via a low-pressure fuel passage 21. The low-pressure pump 11 is an in-tank electric pump provided in the fuel tank 2, and is operated by current supplied from a battery. However, the low-pressure pump 11 may be provided outside the fuel tank 2, or may be provided integrally with the high-pressure pump 3.

[0017] The high-pressure pump 3 pressurizes the fuel introduced by the low-pressure pump 11 and pumps the fuel through a high-pressure fuel passage 23 to the common rail 5 .

[0018] A fuel inlet of the high-pressure pump 3 is provided with a flow control valve 30 for adjusting the discharge amount of the high-pressure pump 3. The flow control valve 30 is located upstream of a pressurizing chamber formed in the high-pressure pump 3, into which fuel is introduced and pressurized by the reciprocating motion of a plunger, and adjusts the amount of fuel flowing into the pressurizing chamber. The flow control valve 30 uses an electromagnetic proportional control valve in which the stroke amount of a valve member for opening and closing the fuel passage is variable depending on the value of a supplied current, and the area of ​​the fuel passage can be adjusted.

[0019] The flow control valve 30 can be of a normally open type, in which the area of ​​the fuel passage is maximized when de-energized, or of a normally closed type, in which the area of ​​the fuel passage is minimized when de-energized. In this embodiment, the flow control valve 30 is of a normally open type, but the present invention can be implemented even if the flow control valve 30 is of a normally closed type.

[0020] The common rail 5 accumulates high pressure fuel pressurized by the high pressure pump 3, and supplies the fuel to each injector 10 connected via a high pressure fuel passage 25. A rail pressure sensor 15, a pressure control valve 13, and a flow limiter 50 are attached to the common rail 5.

[0021] The rail pressure sensor 15 detects the pressure of the fuel in the common rail 5 (hereinafter also referred to as “rail pressure”). A sensor signal of the rail pressure sensor 15 is sent to the electronic control unit 9.

[0022] The pressure control valve 13 is used to adjust the rail pressure by adjusting the flow rate of high-pressure fuel returning from the common rail 5 to the fuel tank 2. For example, an electromagnetic proportional control valve is used as the pressure control valve 13, in which the stroke amount of a valve member for opening and closing the fuel passage is variable depending on the value of a supplied current, and the area of ​​the fuel passage is adjustable. Also, instead of the pressure control valve 13, a mechanical safety valve that opens when a predetermined pressure is reached may be used.

[0023] The flow limiter 50 is attached to the common rail 5 and connected to the common rail 5 side end of the high-pressure fuel passage 25 that connects the common rail 5 and the injectors 10. That is, the fuel in the common rail 5 passes through the flow limiter 50 and the high-pressure fuel passage 25 in this order before being sent to the injectors 10.

[0024] The flow limiters 50 are provided on the paths along which fuel is supplied from the common rail 5 to each injector 10. In other words, the fuel supplied from the common rail 5 to each injector 10 passes through the flow limiter 50 corresponding to each injector 10 before reaching the injector 10.

[0025] The injector 10 has a conventionally known configuration and includes a nozzle body with an injection hole, and a nozzle needle that opens and closes the injection hole by moving back and forth. In the injector 10, the injection hole is closed by applying back pressure to the rear end side of the nozzle needle, and the injection hole is opened by releasing the applied back pressure. As the back pressure control means of the injector 10, for example, an electromagnetic solenoid type actuator is used. In the injector 10, the back pressure fuel used for injection control is returned to the fuel tank 2 via a return passage 29.

[0026] The electronic control unit 9 has a microcomputer of known configuration as a core, memory elements such as RAM and ROM, and includes a drive circuit for driving the injector 10 and an energization circuit for energizing the flow control valve 30 and the pressure control valve 13. The electronic control unit 9 also receives detection signals from a rail pressure sensor 15, as well as various detection signals such as engine speed, accelerator opening, vehicle speed (vehicle speed), and fuel temperature for engine operation control and fuel injection control. The electronic control unit 9 also includes various control units according to the embodiment of the present invention. The electronic control unit 9 also determines whether the flow limiter 50 is closed. Details will be described later.

[0027] Next, a description will be given of the structure of the flow limiter 50. Fig. 2 is a cross-sectional view of the flow limiter 50 according to this embodiment. The flow limiter 50 according to this embodiment is a conventional one.

[0028] The flow limiter 50 is provided upstream of the injector 10, and stops the flow of fuel when the fuel flowing into the flow limiter 50 from the common rail 5 exceeds a predetermined flow rate. During normal operation of the accumulator type fuel injection control device 1, the fuel in the common rail 5 flows into the flow limiter 50 from an inlet 52 and flows out from an outlet 53.

[0029] The flow limiter 50 includes a casing 51. A valve body 55, a valve seat 56, a compression coil spring 57, and a stopper 59 are provided in an internal space 54 of the casing 51.

[0030] The stopper 59 is press-fitted into the casing 51, and includes a communication passage 58 that communicates between the inlet 52 and the space 54. The communication passage 58 is formed with a pressure damping orifice 61 that narrows the passage area.

[0031] The compression coil spring 57 is disposed between the downstream end of the space 54 and the valve body 55, and presses the valve body 55 towards the stopper 59.

[0032] The valve body 55 is slidably disposed within the casing 51 with a tip portion 63 facing the outlet port 53. The valve body 55 includes a hollow portion 60 which is a hole drilled in the axial direction from the rear end portion 62 side to the vicinity of the tip portion 63, and a communication hole 65 which radially communicates the hollow portion 60 with the space 54 near the tip portion 63.

[0033] During normal operation of the accumulator type fuel injection control device 1, when fuel flows in from the common rail 5 through the inlet 52, the fuel passes through the communicating passage 58 and enters the space 54, moves the valve body 55 toward the valve seat 56 against the pressing force of the compression coil spring 57, passes through the hollow portion 60 and the communicating hole 65 formed in the valve body 55, passes through the space 54, and flows out of the outlet 53 and into the injector 10.

[0034] When there is no fuel or very little fuel flowing into the inlet 52 from the common rail, the rear end 62 of the valve body 55 comes into contact with the stopper 59 due to the pressing force of the compression coil spring 57 .

[0035] On the other hand, there are cases where an excessive amount of fuel flows from the common rail 5 to the injector 10. In this case, since the amount of fuel injected from the injector 10 may be excessive, the flow limiter 50 functions as a safety device. Specifically, when the amount of fuel injected from the injector 10 is excessive, the fuel pressure downstream of the flow limiter 50 decreases, and the stroke amount of the valve body 55 increases due to the pressure of the fuel from the common rail 5. Then, the tip portion 63 of the valve body 55 sits on the valve seat 56, and the supply of fuel from the common rail 5 to the injector 10 is stopped.

[0036] The flow limiter 50 shown in Fig. 2 is a so-called plunger type. Meanwhile, a flow limiter 50 called a ball type, in which a valve body 55 seated on a valve seat 56 is ball-shaped, is also known. In the ball type flow limiter 50, the flow passage downstream of the valve seat 56 is stepped, and a compression coil spring 57 is disposed on the stepped portion to press the ball-shaped valve body 55 toward a stopper 59. When an excessive amount of fuel flows from the common rail 5 to the injector 10, the ball-shaped valve body 55 seats on the valve seat 56 to block the flow of fuel. Even when a ball type flow limiter 50 is used, the present invention can be implemented.

[0037] The flow limiter 50 is mechanically operated, i.e., closed, by the balance between the fuel pressures upstream and downstream of the flow limiter 50 and the biasing force of the compression coil spring 57. Therefore, when the flow limiter 50 is closed, i.e., when the tip 63 of the valve body 55 seats on the valve seat 56 and the flow of fuel inside the flow limiter 50 is cut off, the electronic control unit 9 (ECU) cannot recognize this operation. The present invention detects the closure of the flow limiter 50 based on the control amount of the flow control valve 30, which controls the amount of fuel pumped out by the high-pressure pump 3.

[0038] Next, the structure of the flow control valve 30 will be described. Fig. 3 is a cross-sectional view of the flow control valve 30 according to this embodiment. The flow control valve 30 according to this embodiment is a conventional one. As described above, the flow control valve 30 according to this embodiment is a normally open type in which the area of ​​the fuel passage is maximized when not energized.

[0039] The flow rate control valve 30 includes a cylindrical member 32, a piston 31, a spring seat 36, a coil spring 33, and a piston pressing shaft 35. The cylindrical member 32 is provided in the circumferential direction and has an inlet 32a through which fuel flows in from the fuel inlet side of the high-pressure pump 3, and an outlet 32b provided in the axial direction and through which fuel flows out to the pressurization chamber side of the high-pressure pump 3.

[0040] The piston 31 is slidably provided inside the cylindrical member 32, and has a hollow portion 31a that opens to the outlet 32b side of the cylindrical member 32. The spring seat 36 is a disk-shaped member having a stepped hole in the center, and is press-fitted into the end of the cylindrical member 32 on the outlet 32b side.

[0041] A coil spring 33 is provided between the spring seat 36 and the piston 31, and the piston 31 is pressed by the coil spring 33 in the opposite direction to the outlet 32b.

[0042] A slot 34 that communicates with the hollow portion 31a of the piston 31 is formed on the outer peripheral surface of the piston 31. As the piston 31 slides as described below, the slot 34 faces the inlet 32a, so that the fuel flowing in from the inlet 32a flows into the hollow portion 31a of the piston 31 through the slot 34.

[0043] The fuel that has flowed into the hollow portion 31 a of the piston 31 passes through the inside of the cylindrical member 32 , flows out from the outlet 32 ​​b , and enters the pressurizing chamber of the high-pressure pump 3 .

[0044] One end of the piston 31, which is opposite to the outlet 32b, is in contact with one end of a piston pressing shaft 35 which constitutes a part of an armature assembly (not shown). This piston pressing shaft 35 is driven to press the piston 31 toward the outlet 32b against the pressing force of the coil spring 33 by electromagnetic force generated by energizing a coil (not shown), thereby changing the position of the piston 31. The amount of change in the position of the piston 31 is proportional to the amount of current energized to the coil (not shown), and the rate of communication between the slot 34 and the inlet 32a is adjusted according to the amount of displacement, thereby adjusting the flow rate of fuel from the inlet 32a to the hollow portion 31a of the piston 31.

[0045] When the coil (not shown) is not energized, the electromagnetic force acting on the piston pressing shaft 35 disappears, and the piston 31 is moved to the opposite side of the outlet 32b by the pressing force of the coil spring 33. In this state, the communication between the slot 34 and the inlet 32a is maximized, and the amount of fuel sucked into the pressurizing chamber of the high-pressure pump 3 is also maximized (see FIG. 3(a)).

[0046] Meanwhile, when the above-mentioned coil (not shown) starts to be energized, and as the current value increases, the piston 31 is pressed toward the outlet 32b against the pressing force of the coil spring 33. This causes the communication rate between the slot 34 and the inlet 32a to gradually decrease, and then the communication between the slot 34 and the inlet 32a is completely cut off, and fuel stops flowing into the pressurizing chamber of the high-pressure pump 3 (see FIG. 3(b)).

[0047] Fig. 4 shows the current waveform of the coil of the flow control valve 30. In Fig. 4, the horizontal axis represents the current value flowing through the coil, and the vertical axis represents the flow rate per unit time of the fuel passing through the slot 34. As described above, the flow control valve 30 has a characteristic that as the current value flowing through the coil increases, the amount of fuel passing through the slot 34, in other words, the amount of fuel sent to the pressurizing chamber of the high-pressure pump 3, decreases. Details will be described later.

[0048] 5 is a block diagram showing the configuration of a portion related to the implementation of the present invention in the electronic control unit 9. The electronic control unit 9 includes a rail pressure control unit 900, a fuel injection control unit 902, a memory unit 904, an instruction unit 906, a current value acquisition unit 908, and a determination unit 910.

[0049] The rail pressure control unit 900 performs feedback control of the rail pressure so that the rail pressure becomes a target rail pressure according to the operating state of the engine and the device on which the engine is mounted. The rail pressure control unit 900 performs feedback control of the rail pressure by controlling the flow control valve 30 and the pressure control valve 13 described above. The rail pressure control unit 900 grasps the operating state of the engine and the device on which the engine is mounted from various sensor values ​​and the like received by the electronic control unit 9, and determines the target rail pressure. The target rail pressure in each operating state is stored in advance in a storage unit 904 described later. The rail pressure control unit 900 is also used in the conventional accumulator type fuel injection control device 1, and this is used for the valve closing judgment of the flow limiter 50 of the present invention.

[0050] The fuel injection control unit 902 determines the fuel injection amount according to the operating state of the engine and the device on which the engine is mounted, and controls the fuel injection of the injector 10 by energizing the actuator for controlling the back pressure of the injector 10. The fuel injection control unit 902 grasps the operating state of the engine and the device on which the engine is mounted from various sensor values ​​and the like received by the electronic control unit 9, and determines the target injection amount. The target injection amount in each operating state is stored in advance in a storage unit 904 described later. The fuel injection control unit 902 determines the energization time for the actuator so that the fuel injection amount becomes the target injection amount based on the rail pressure received by the electronic control unit 9 from the rail pressure sensor 15, and executes the energization. The relationship between the energization time and the fuel injection amount for each rail pressure is stored in advance as a map in the storage unit 904 described later, so the fuel injection control unit 902 determines the energization time based on the map. The fuel injection control unit 902 is also used in the conventional accumulator type fuel injection control device 1, and the valve closing judgment of the flow limiter 50 of the present invention is diverted from this.

[0051] The storage unit 904 stores target values, such as rail pressure, fuel injection amount, and fuel injection timing, which are determined based on various sensor values, in an appropriate format such as a map. These are set during the development stage of the accumulator type fuel injection control device 1. The storage unit 904 also stores the current conduction characteristics of the flow control valve 30 described above, and information required for determining whether the flow limiter 50, which will be described later, is closed.

[0052] After detecting the start of the engine in which the accumulator fuel injection control device 1 is mounted, the instruction unit 906 controls each element constituting the accumulator fuel injection control device 1 so as to perform fuel injection with a control amount corresponding to a predetermined inspection point for determining whether the flow limiter 50 is closed. The control amount includes the rail pressure, the fuel injection amount, and the fuel injection timing.

[0053] The inspection point for determining whether the flow limiter 50 is closed (hereinafter, also simply referred to as the "inspection point") described above can be appropriately determined depending on the manner in which the engine equipped with the accumulator fuel injection control device 1 is used. As described above, the engine in this embodiment is mounted on equipment such as a generator, a ship, or a locomotive that runs on a railroad track. Such equipment is often operated at a specific rotation speed for a relatively long period of time, and therefore, for each equipment, for example, the specific rotation speed at which the equipment is operated for a long period of time can be set as the inspection point. Alternatively, the rated rotation speed of the engine equipped with the accumulator fuel injection control device 1 can be set as the inspection point.

[0054] The engine speed to be used as the inspection point is determined in advance through testing and is stored in the storage unit 904. Furthermore, the control amounts such as the rail pressure, fuel injection amount, and fuel injection timing corresponding to the inspection point are also determined in advance through testing and are stored in the storage unit 904. The instruction unit 906 reads out this information from the storage unit 904 and controls each element constituting the accumulator type fuel injection control device 1.

[0055] More specifically, the instruction unit 906 issues an instruction to the rail pressure control unit 900 so that the rail pressure in the common rail 5 becomes the rail pressure corresponding to the inspection point stored in the memory unit 904. The rail pressure control unit 900 controls the flow control valve 30 based on the output value of the rail pressure sensor 15 so that the rail pressure in the common rail 5 becomes the rail pressure corresponding to the inspection point. At this time, the rail pressure control unit 900 closes the pressure control valve 13 based on an instruction from the instruction unit 906, so that no fuel flows out from the pressure control valve 13. In other words, the rail pressure is feedback controlled only by the flow control valve 30.

[0056] Furthermore, the instruction unit 906 issues an instruction to the fuel injection control unit 902 so that fuel injection is performed at a fuel injection amount and injection timing corresponding to the inspection point. Based on the instruction from the instruction unit 906, the fuel injection control unit 902 controls the injector 10 so that fuel injection is performed at a fuel injection amount and injection timing corresponding to the inspection point.

[0057] The current value acquisition unit 908 acquires the value of the current flowing through the coil of the flow control valve 30 in a state in which fuel injection is performed with the control amount corresponding to the inspection point described above. The value of the current flowing through the coil of the flow control valve 30 is monitored by the rail pressure control unit 900, and the current value acquisition unit 908 uses the monitored value.

[0058] The judgment unit 910 judges whether the flow limiter 50 is closed, i.e., whether there is a point where the supply of fuel from the common rail 5 to the injector 10 is cut off, when fuel injection is performed with the control amount corresponding to the inspection point described above.

[0059] The determination by the determination unit 910 as to whether the flow limiter 50 is closed or not will be described with reference to Fig. 4. The diagram shown in Fig. 4 is stored in the memory unit 904 of the electronic control unit 9. y1 in Fig. 4 is the value of current flowing through the coil of the flow control valve 30 corresponding to the inspection point when the accumulator type fuel injection control device 1 is operating normally. The current value y1 is acquired when the pressure control valve 13 is closed.

[0060] When fuel injection is performed with a control amount corresponding to the inspection point in response to an instruction from the instruction unit 906 after the engine has started, the determination unit 910 compares a current value z1 flowing through the coil of the flow control valve 30 acquired by the current value acquisition unit 908 with a current value y1 previously stored in the storage unit 904. When the value of z1 is a value greater than the value of y1 by a predetermined amount or more, the determination unit 910 determines that one of the flow limiters 50 is closed.

[0061] This determination is based on the following reasons. When the flow limiter 50 corresponding to a certain cylinder of the engine closes, the fuel supply from the common rail 5 to the injector 10 is cut off, and fuel injection to that cylinder is no longer performed. This reduces the overall fuel injection amount. At this time, since the pressure control valve 13 is closed, the rail pressure control unit 900 reduces the amount of fuel pumped by the high-pressure pump 3 in order to suppress an increase in rail pressure.

[0062] The reduction in the amount of fuel pumped from the high-pressure pump 3 is brought about by the rail pressure control unit 900 increasing the value of the current flowing through the coil of the flow control valve 30. Therefore, the determination unit 910 detects the closure of the flow limiter 50 based on the increase in the value of the current flowing through the coil of the flow control valve 30 notified by the current value acquisition unit 908.

[0063] Explaining with reference to Fig. 4, as described above, y1 is the value of the current flowing through the coil of the flow control valve 30 corresponding to the inspection point when the accumulator type fuel injection control device 1 is operating normally. Also, the flow rate of the fuel passing through the flow control valve 30 at this time, i.e., the fuel pumping amount of the high-pressure pump 3, is a1.

[0064] On the other hand, when the flow limiter 50 is closed, the overall fuel injection amount is reduced, and the fuel pumping amount of the high-pressure pump 3 becomes b1, which is smaller than a1, due to feedback control of the rail pressure. This reduction in the pumping amount is brought about by the value of the current flowing through the coil of the flow control valve 30 becoming z1, which is larger than y1. The determination unit 910 sets a value obtained by adding a predetermined amount to y1 as a threshold value Th1, and determines that the flow limiter 50 is closed when the current value z1 is larger than the threshold value Th1.

[0065] Here, the threshold value Th1 can be determined in advance by testing. For example, the variation in the current value y1 flowing through the coil of the flow control valve 30 at the inspection point when the accumulator fuel injection control device 1 is normal can be grasped, and the value obtained by adding the variation to the current value y1 can be set as the judgment threshold value Th1. In other words, when z1 is larger than the possible range of the current value y1 flowing through the coil of the flow control valve 30, including the variation, the judgment unit 910 judges that the flow limiter 50 is closed.

[0066] Furthermore, when the judgment unit 910 judges that the flow limiter 50 is closed, it notifies the driver or the operator of the equipment in which the engine is mounted of the occurrence of a malfunction by, for example, turning on a warning lamp.

[0067] Next, the valve closing determination of the flow limiter 50, which is executed by the electronic control unit 9, will be described with reference to the subroutine flowchart shown in FIG.

[0068] When an ignition switch (not shown) is turned on to start processing by the electronic control unit 9, first, in step S102, the instruction unit 906 determines whether or not the engine in which the accumulator type fuel injection control device 1 is mounted has been started. If the instruction unit 906 detects that the engine has been started (if YES), the process proceeds to step S104. On the other hand, if the instruction unit 906 does not detect that the engine has been started (if NO), the process returns to the main routine (not shown).

[0069] In step S104, the rail pressure control unit 900 closes the pressure control valve 13 based on an instruction from the instruction unit 906. As a result, the rail pressure is feedback-controlled by the flow rate control valve 30 alone.

[0070] In the next step S106, the instruction unit 906 issues an instruction to the rail pressure control unit 900 and the fuel injection control unit 902 to inject fuel with a control amount corresponding to the inspection point for determining whether the flow limiter 50 is closed. In response to this instruction, the rail pressure control unit 900 controls the flow control valve 30 of the high-pressure pump 3 so that the rail pressure becomes the rail pressure corresponding to the inspection point. Thereafter, the fuel injection control unit 902 injects fuel with a fuel injection amount and fuel injection timing corresponding to the inspection point. As described above, the control amounts such as the rail pressure, fuel injection amount, and fuel injection timing corresponding to the inspection point are determined in advance by testing and stored in the storage unit 904. The rail pressure control unit 900 and the fuel injection control unit 902 read out this data from the storage unit 904 and control each element constituting the accumulator type fuel injection control device 1.

[0071] In the next step S108, the current value acquisition unit 908 acquires a current value z1 flowing through the coil of the flow control valve 30. The current value z1 flowing through the coil of the flow control valve 30 is monitored by the rail pressure control unit 900, and the current value acquisition unit 908 acquires the current value z1 by using the monitored value. The current value acquisition unit 908 notifies the determination unit 910 of the acquired current value z1.

[0072] In the next step S110, the determination unit 910 determines whether or not the current value z1 of the current flowing through the coil of the flow control valve 30 exceeds a predetermined threshold value Th1.

[0073] If the current value z1 of the current flowing through the coil of the flow control valve 30 exceeds the predetermined threshold value Th1 (YES), the process proceeds to step S112, where the determination unit 910 recognizes that the flow limiter 50 is closed, that is, that the supply of fuel from the common rail 5 to the injector 10 has been stopped in at least one cylinder. On the other hand, if the current value z1 of the current current flowing through the coil of the flow control valve 30 is equal to or less than the predetermined threshold value Th1 (NO), the determination unit 910 determines that the flow limiter 50 is not closed, the process ends, and the process returns to the main routine, not shown.

[0074] In step S114 following step S112, the determination unit 910 notifies the driver or the operator of the equipment in which the engine is mounted of the occurrence of a malfunction by turning on a warning lamp or the like.

[0075] In the above embodiment, an example has been described in which the flow limiter 50 is attached to the common rail 5, but the flow limiter 50 does not necessarily have to be attached directly to the common rail 5. For example, the flow limiter 50 may be provided midway through the high-pressure fuel passage 25 that connects the common rail 5 and the injector 10, or may be attached to the fuel inlet of the injector 10. The present invention can be implemented even if the flow limiter 50 is attached in any of these ways.

[0076] Next, a second embodiment of the present invention will be described. The above-mentioned first embodiment is an example of a case where a normally open type flow control valve 30 in which the area of ​​the fuel passage is maximum when de-energized is used. The second embodiment is an example of a case where a normally closed type flow control valve 30 in which the area of ​​the fuel passage is minimum when de-energized is used. Note that in the description of the second embodiment, the differences from the first embodiment will be mainly described, and the description of the same parts as the first embodiment will be omitted as appropriate.

[0077] Fig. 7 shows the current waveform of the coil of the normally closed type flow control valve 30. In Fig. 7, the horizontal axis represents the current value flowing through the coil, and the vertical axis represents the flow rate per unit time of the fuel passing through the slot 34. The normally closed type flow control valve 30 has the characteristic that the amount of fuel passing through the slot 34, in other words, the amount of fuel sent to the pressurizing chamber of the high-pressure pump 3, increases as the current value flowing through the coil increases.

[0078] Hereinafter, the valve closure judgment of the flow limiter 50 executed by the judgment unit 910 in the second embodiment will be described with reference to Fig. 7. The diagram shown in Fig. 7 is stored in the storage unit 904 of the electronic control unit 9. y2 in Fig. 7 is the value of current flowing through the coil of the flow control valve 30 corresponding to the inspection point when the accumulator type fuel injection control device 1 is operating normally. The current value y2 is acquired when the pressure control valve 13 is closed.

[0079] After the engine has started, when fuel injection is performed with a control amount corresponding to the inspection point in response to an instruction from the instruction unit 906, the determination unit 910 compares a current value z2 flowing through the coil of the flow control valve 30, acquired by the current value acquisition unit 908, with a current value y2 previously stored in the storage unit 904. When the value of z2 is smaller than the value of y2 by a predetermined amount or more, it is determined that one of the flow limiters 50 is closed.

[0080] This determination is based on the following reasons. When the flow limiter 50 corresponding to a certain cylinder of the engine closes, the fuel supply from the common rail 5 to the injector 10 is cut off, and fuel injection to that cylinder is no longer performed. This reduces the overall fuel injection amount. At this time, since the pressure control valve 13 is closed, the rail pressure control unit 900 reduces the amount of fuel pumped by the high-pressure pump 3 in order to suppress an increase in rail pressure.

[0081] The reduction in the amount of fuel pumped from the high-pressure pump 3 is brought about by the rail pressure control unit 900 reducing the value of the current flowing through the coil of the flow control valve 30. Therefore, the determination unit 910 detects the closure of the flow limiter 50 based on the reduction in the value of the current flowing through the coil of the flow control valve 30 notified by the current value acquisition unit 908.

[0082] Explaining with reference to Fig. 7, as described above, y2 is the value of the current flowing through the coil of the flow control valve 30 corresponding to the inspection point when the accumulator type fuel injection control device 1 is operating normally. Also, the flow rate of the fuel passing through the flow control valve 30 at this time, i.e., the fuel pumping amount of the high-pressure pump 3, is a2.

[0083] On the other hand, when the flow limiter 50 is closed, the overall fuel injection amount is reduced, and the fuel pumping amount of the high-pressure pump 3 becomes b2, which is smaller than a2, due to feedback control of the rail pressure. This reduction in the pumping amount is brought about by the value of the current flowing through the coil of the flow control valve 30 becoming z2, which is smaller than y2. The determination unit 910 sets a value obtained by subtracting a predetermined amount from y2 as a threshold value Th2, and determines that the flow limiter 50 is closed when the current value z2 is smaller than the threshold value Th2.

[0084] Here, the threshold value Th2 can be determined in advance by testing. For example, the variation in the current value y2 flowing through the coil of the flow control valve 30 at the inspection point when the accumulator fuel injection control device 1 is normal can be grasped, and the value obtained by subtracting the variation from the current value y2 can be set as the judgment threshold value Th2. In other words, when z2 is smaller than the possible range of the current value y2 flowing through the coil of the flow control valve 30, including the variation, the judgment unit 910 judges that the flow limiter 50 is closed.

[0085] Furthermore, when the judgment unit 910 judges that the flow limiter 50 is closed, it notifies the driver or the operator of the equipment in which the engine is mounted of the occurrence of a malfunction by, for example, turning on a warning lamp.

[0086] Next, the valve closing determination of the flow limiter 50 according to the second embodiment, which is executed by the electronic control unit 9, will be described with reference to the subroutine flowchart shown in FIG.

[0087] Steps S102 to S106 are similar to those in the first embodiment, and therefore the description thereof will be omitted.

[0088] In the next step S108a, the current value acquisition unit 908 acquires a current value z2 flowing through the coil of the flow control valve 30. The current value z2 flowing through the coil of the flow control valve 30 is monitored by the rail pressure control unit 900, and the current value acquisition unit 908 acquires the current value z2 by using the monitored value. The current value acquisition unit 908 notifies the determination unit 910 of the acquired current value z2.

[0089] In the next step S110a, the determination unit 910 determines whether or not the current value z2 of the current flowing through the coil of the flow rate control valve 30 is smaller than a predetermined threshold value Th2.

[0090] If the current value z2 of the current flowing through the coil of the flow control valve 30 is smaller than the predetermined threshold value Th2 (if YES), the process proceeds to step S112a, where the determination unit 910 recognizes that the flow limiter 50 is closed, i.e., that the supply of fuel from the common rail 5 to the injector 10 has been stopped in at least one cylinder. On the other hand, if the current value z2 of the current current flowing through the coil of the flow control valve 30 is equal to or greater than the predetermined threshold value Th2 (if NO), the determination unit 910 determines that the flow limiter 50 is not closed, the process ends, and the process returns to the main routine, not shown.

[0091] In step S114 following step S112a, the determination unit 910 notifies the driver or the operator of the equipment in which the engine is mounted of the occurrence of a malfunction by turning on a warning lamp or the like.

[0092] In the second embodiment, as in the first embodiment, the present invention can be implemented not only when the flow limiter 50 is attached to the common rail 5, but also when the flow limiter 50 is provided midway through the high-pressure fuel passage 25 connecting the common rail 5 and the injector 10, or when the flow limiter 50 is attached to the fuel inlet of the injector 10.

[0093] As described above, according to the present invention, it is possible to detect the closure of the flow limiter 50 without adding any new parts, thereby making it possible to quickly detect the occurrence of a failure.

[0094] Furthermore, since diesel engines installed in equipment such as generators, ships, and locomotives that run on tracks are often used at a specific rotation speed, the fault detection based on the control amount corresponding to the specific engine rotation speed according to the present invention is effective. However, the present invention can also be implemented when the equipment in which the diesel engine is installed is a vehicle such as a passenger car or truck.

[0095] In the above embodiment, the flow limiter 50 is judged to be closed when the engine is started, but a similar diagnosis can be performed at other timings. [Explanation of symbols]

[0096] 1: Accumulator type fuel injection control device, 3: High pressure pump, 5: Common rail, 9: Electronic control unit, 10: Injector, 15: Rail pressure sensor, 30: Flow control valve, 50: Flow limiter, 900: Rail pressure control unit, 902: Fuel injection control unit, 904: Memory unit, 906: Instruction unit, 908: Current value acquisition unit, 910: Determination unit

Claims

1. An injector (10) for injecting fuel into a combustion chamber of an engine; a common rail (5) for supplying the fuel to the injector (10); a high-pressure pump (3) for pumping the fuel to the common rail (5); a flow control valve (30) for adjusting the amount of fuel pumped by the high-pressure pump (3); a flow limiter (50) that closes and stops the supply of fuel when the flow rate of the fuel supplied from the common rail (5) to the injector (10) becomes excessive; a rail pressure sensor (15) for detecting a rail pressure, which is the pressure of fuel in the common rail; An electronic control unit (9); In an accumulator type fuel injection control device (1), The electronic control unit (9) a rail pressure control unit (900) that controls the flow control valve (30) so that the rail pressure becomes a target rail pressure; a fuel injection control unit (902) that performs fuel injection from the injector (10) by energizing the injector (10); an instruction unit (906) for injecting fuel at a control amount corresponding to a predetermined inspection point for determining whether the flow limiter (50) is closed; a determination unit (910) that determines whether or not the flow limiter (50) is closed based on an energization waveform of the flow control valve (30) when fuel injection is performed with a control amount corresponding to the inspection point, The control variables corresponding to the inspection points include a rail pressure and a fuel injection amount. Accumulator type fuel injection control device (1).

2. 2. The accumulator type fuel injection control device (1) according to claim 1, wherein the flow control valve (30) is an electromagnetic proportional control valve capable of adjusting an area of ​​a fuel passage by a supplied current value.

3. 3. The accumulator type fuel injection control device (1) according to claim 2, wherein the determination unit (910) determines that the flow limiter (50) is closed when a current value supplied to the flow control valve (30) falls outside a predetermined range when fuel injection is performed with a control amount corresponding to the inspection point.

4. 4. The accumulator type fuel injection control device (1) according to claim 3, wherein the predetermined range is a range of possible values ​​of the current supplied to the flow control valve (30) when the engine is operated at the test point.

5. 5. The accumulator type fuel injection control device (1) according to claim 4, wherein, when the flow control valve (30) is of a normally open type in which an area of ​​the fuel passage is maximum when not energized, the determination unit (910) determines that the flow limiter (50) is closed when a current value supplied to the flow control valve (30) when fuel injection is performed with a control amount corresponding to the inspection point is larger than the predetermined range.

6. 5. The accumulator type fuel injection control device (1) according to claim 4, wherein, when the flow control valve (30) is of a normally closed type in which an area of ​​the fuel passage is minimum when not energized, the determination unit (910) determines that the flow limiter (50) is closed when a current value supplied to the flow control valve (30) when fuel injection is performed with a control amount corresponding to the inspection point is smaller than the predetermined range.

7. The accumulator type fuel injection control device (1) according to any one of claims 1 to 6, wherein the determination unit (910) executes a determination as to whether or not the flow limiter (50) is closed when the engine is started.

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