WO2010029791A1

WO2010029791A1 - Fuel leakage diagnostic device and fuel leakage diagnosis method

Info

Publication number: WO2010029791A1
Application number: PCT/JP2009/058470
Authority: WO
Inventors: 博隆金子
Original assignee: ボッシュ株式会社
Priority date: 2008-09-11
Filing date: 2009-04-30
Publication date: 2010-03-18
Also published as: JPWO2010029791A1

Abstract

Provided are a fuel leakage diagnostic device and a fuel leakage diagnosis method with which it is easy to diagnose whether there is leakage of highly compressed fuel from a leak-proof pressurized storage-type fuel delivery device. The fuel leakage diagnostic device diagnoses whether there is fuel leakage from a leak-proof pressurized storage-type fuel delivery device equipped with a high‑pressure fuel system, which comprises a high‑pressure pump for pumping a highly compressed fuel, a common rail where the highly compressed fuel pumped from the high‑pressure pump is stored, and fuel injection valves for injecting the highly compressed fuel stored in the common rail into the cylinders of an internal combustion engine. The fuel leakage diagnostic device is equipped with a pressure detection unit that reads the pressure of the high‑pressure fuel system and stores the pressure reading, a retention control unit that retains the fuel inside the high‑pressure fuel system while the internal combustion engine is stopped, and a fuel leakage determination unit that determines whether there is fuel leakage by checking changes in the pressure in the high‑pressure fuel system after retention of the fuel in the high‑pressure fuel system has been started.

Description

Fuel leakage diagnosis device and fuel leakage diagnosis method

The present invention relates to a fuel leak diagnostic device and a fuel leak diagnostic method, and more particularly to a fuel leak diagnostic device and a fuel leak diagnostic method for diagnosing a fuel leak from a high pressure fuel system in a leakless accumulator fuel supply device.

Conventionally, as an internal combustion engine fuel supply device, an accumulator fuel supply device configured to inject high pressure fuel pumped by a high pressure pump and accumulated in a common rail into each cylinder of the internal combustion engine by a fuel injection valve has been used. Has been.
As a fuel injection valve used in such an accumulator fuel supply device, a nozzle needle that opens and closes an injection hole, a back pressure chamber in which high pressure fuel is supplied and a back pressure is applied to the nozzle needle by the pressure, and a back pressure chamber There is known a fuel injection valve provided with a back pressure relief mechanism for releasing the high pressure fuel. In this fuel injection valve, part of the high-pressure fuel from the common rail is supplied to the back pressure chamber, and the nozzle needle is released by allowing the high-pressure fuel in the back pressure chamber to escape to the return passage by a back pressure relief mechanism having an on-off valve or the like. The injection hole is opened by lifting, and high-pressure fuel is injected from the injection hole into the cylinder of the internal combustion engine.

So far, many fuel injection valves that employ electromagnetic solenoids have been used as means for controlling the opening and closing of the back pressure relief mechanism. In the case of an electromagnetic solenoid type fuel injection valve, in addition to the high-pressure fuel that is released by the back pressure relief mechanism, leaked fuel that leaks from the sliding part such as the nozzle needle and valve piston to the low-pressure part is returned to the return passage. ing. The high-pressure fuel in the back-pressure chamber is discharged only when it is released by the back-pressure relief mechanism, whereas this leaked fuel leaks when high-pressure fuel is present in the fuel injection valve. It has become.

On the other hand, in recent years, a piezo injector using a piezo actuator has begun to be used as a back pressure relief mechanism. In the case of a piezo injector, it is easy to adopt a structure in which there is no leaked fuel leaking to the low-pressure part other than the high-pressure fuel released by the back pressure relief mechanism, and it becomes possible to configure as a leakless pressure accumulator fuel supply device (for example, , See Patent Document 1). Adoption of a leakless structure is also being considered for electromagnetic solenoid fuel injection valves.

Such a leakless pressure accumulating fuel supply device eliminates the need to supply the leak to the fuel injection valve, thereby reducing the capacity of the high pressure pump and reducing the size of the high pressure pump. Further, in a vehicle or the like in which idling stop control is performed, high-pressure fuel does not leak at the time of idling stop, the pressure in the common rail is maintained, and the startability of the internal combustion engine after idling stop is improved. Furthermore, the fact that the pressure in the common rail is unlikely to decrease means that the pressure amplitude in the region where the high-pressure fuel flows is suppressed, and the durability of the components is improved.

JP 2007-510849 A

However, in such a leakless pressure-accumulation fuel supply system, if high-pressure fuel leaks due to endurance deterioration such as wear or connection failure of each component, the capacity of the miniaturized high-pressure pump is insufficient, and the common rail target It becomes difficult to ensure the pressure (hereinafter referred to as “target rail pressure”) and the required injection amount to the internal combustion engine. In addition, when high pressure fuel leaks, it takes time to increase the pressure of the common rail (hereinafter referred to as “rail pressure”) when the internal combustion engine is restarted after idling is stopped. Decreases. Furthermore, if high-pressure fuel leaks in an unexpected part, not only may the part be damaged by erosion or the like, but also the number of high-pressure fuel pressure amplitudes will increase due to a drop in rail pressure during idling stop control. There is also a risk of lowering durability. Therefore, in the leakless pressure accumulator fuel supply device, it is necessary to accurately grasp the presence or absence of leakage of high-pressure fuel.

Therefore, the inventors of the present invention diligently tried to solve such a problem by observing the pressure change in the high pressure fuel system while holding the fuel in the high pressure fuel system during the stop period of the internal combustion engine. The present invention has been completed. That is, an object of the present invention is to provide a fuel leakage diagnosis device and a fuel leakage diagnosis method that can easily diagnose the presence or absence of leakage of high-pressure fuel in a leakless accumulator fuel supply device.

According to the present invention, a high-pressure pump that pumps high-pressure fuel, a common rail that stores high-pressure fuel pumped from the high-pressure pump, a fuel injection valve that injects high-pressure fuel stored in the common rail into a cylinder of the internal combustion engine, The fuel injection valve includes a nozzle needle that opens and closes an injection hole, a back pressure chamber that is supplied with high pressure fuel and applies a back pressure to the nozzle needle by the pressure of the high pressure fuel, and a back pressure chamber. Leakless pressure accumulation fuel supply that has a back pressure relief mechanism that lifts the nozzle needle by allowing high pressure fuel to escape and opens the injection hole, and has no leak passage for fuel other than high pressure fuel in the back pressure chamber In the fuel leakage diagnosis apparatus for diagnosing the presence or absence of fuel leakage from the high pressure fuel system in the apparatus, a pressure detection unit for detecting and storing the pressure in the high pressure fuel system, and an internal combustion engine During the stop period, a fuel leakage control is performed by observing the pressure control in the high-pressure fuel system after the start of holding the fuel in the high-pressure fuel system and the holding control unit for holding the fuel in the high-pressure fuel system. A fuel leakage diagnosis device comprising a fuel leakage determination unit for determining the presence or absence of the fuel leakage is provided, and the above-described problem is solved.

Further, in configuring the fuel leakage diagnosis device of the present invention, the fuel leakage determination unit compares the pressure in the high pressure fuel system after a predetermined time has elapsed after starting to hold the fuel in the high pressure fuel system with a predetermined threshold value. Thus, it is preferable to determine the presence or absence of fuel leakage.

Further, in configuring the fuel leakage diagnosis device of the present invention, the fuel leakage determination unit determines the pressure drop amount or the pressure drop rate in the high pressure fuel system after the fuel starts to be held in the high pressure fuel system as a predetermined reference value. It is preferable to determine the presence or absence of fuel leakage by comparing with.

Further, in configuring the fuel leakage diagnosis device of the present invention, it is preferable that the stop period of the internal combustion engine is during idling stop control of the internal combustion engine.

Further, when configuring the fuel leakage diagnosis device of the present invention, when the temperature of the coolant used for cooling the internal combustion engine or the temperature of the high pressure fuel in the high pressure fuel system has decreased by a predetermined value or more from the temperature when the internal combustion engine is stopped. It is preferable to provide a diagnosis stop instruction unit for stopping the determination in the fuel leak determination unit.

Another aspect of the present invention is a high-pressure pump that pumps high-pressure fuel, a common rail that stores high-pressure fuel pumped from the high-pressure pump, and a fuel that injects high-pressure fuel stored in the common rail into a cylinder of an internal combustion engine. A fuel injection valve including a nozzle needle that opens and closes an injection hole, a back pressure chamber that is supplied with high pressure fuel and applies a back pressure to the nozzle needle by the pressure of the high pressure fuel, and Leakless, which has a back pressure relief mechanism that lifts the nozzle needle by allowing the high pressure fuel in the back pressure chamber to escape and opens the injection hole, and does not have a fuel leak passage other than the high pressure fuel in the back pressure chamber In a fuel leakage diagnosis method for diagnosing the presence or absence of fuel leakage from a high-pressure fuel system in an accumulator fuel supply system, the high-pressure fuel system is maintained while holding fuel in the high-pressure fuel system. By looking at the force variation is a fuel leakage diagnosis method characterized by determining the presence or absence of fuel leakage.

According to the fuel leakage diagnostic device and the fuel leakage diagnostic method of the present invention, during the stop period of the internal combustion engine, based on the pressure change in the high-pressure fuel system that should be essentially less likely to be reduced if it is a leakless accumulator fuel supply device, The presence or absence of fuel leakage in the high-pressure fuel system can be easily diagnosed. Therefore, durability deterioration such as wear and connection failure of each component can be found early and repaired and replaced, so that the fuel injection state, the startability of the internal combustion engine, and the durability of the accumulator fuel supply device of each component The improvement of the property is achieved.

Further, in the fuel leakage diagnosis apparatus of the present invention, the fuel leakage determination unit compares the pressure in the high-pressure fuel system with a threshold value to determine the presence or absence of fuel leakage. It is possible to reliably determine the presence or absence of fuel leakage that has occurred in the apparatus.

In the fuel leakage diagnosis apparatus of the present invention, the fuel leakage determination unit compares the pressure decrease amount or the pressure decrease ratio in the high pressure fuel system with a predetermined reference value to determine whether or not there is a fuel leak, The presence or absence of leakage can be reliably determined, and the degree of fuel leakage can be diagnosed.

Further, in the fuel leakage diagnosis device of the present invention, the stop period of the internal combustion engine is at the time of idling stop control of the internal combustion engine, so that the vehicle equipped with the internal combustion engine is in operation and the high pressure fuel system is The presence or absence of fuel leakage can be diagnosed using the time when the control for holding the high-pressure fuel is performed. Therefore, waste of the battery or the like can be suppressed and time required for diagnosis can be saved.

Further, the fuel leakage diagnosis device of the present invention includes a diagnosis stop instruction unit that stops the determination of the fuel leak determination unit when the temperature of the coolant or the temperature of the high-pressure fuel has decreased by a predetermined value or more since the stop of the internal combustion engine. It is avoided that it is determined that the fuel leaks when the pressure is reduced due to the contraction of the high-pressure fuel in the high-pressure fuel system due to the temperature change.

It is a figure for demonstrating the structural example of the pressure accumulation type fuel supply apparatus provided with the fuel leak diagnostic apparatus (control apparatus) of the 1st Embodiment of this invention. It is sectional drawing for demonstrating the structure of a piezo injector. It is a block diagram for demonstrating the structural example of the fuel leak diagnostic apparatus concerning 1st Embodiment. It is a chart figure which shows the rotation speed change and rail pressure change of an internal combustion engine at the time of idling stop control. It is a flow for demonstrating an example of the fuel leak diagnostic method concerning 1st Embodiment. It is a chart for demonstrating another fuel leak diagnostic method. It is a chart for demonstrating another fuel leak diagnostic method. It is a block diagram for demonstrating the structural example of the fuel leak diagnostic apparatus concerning 2nd Embodiment. It is a flow for demonstrating an example of the fuel leak diagnostic method concerning 2nd Embodiment.

Hereinafter, embodiments of the fuel leakage diagnosis apparatus and the fuel leakage diagnosis method of the present invention will be specifically described with reference to the drawings as appropriate. However, this embodiment shows one aspect of the present invention, and does not limit the present invention, and can be arbitrarily changed within the scope of the present invention. In addition, in each figure, about the thing which has attached | subjected the same code | symbol, the same member is shown and description is abbreviate | omitted suitably.

[First Embodiment]
1. Leakless Accumulated Fuel Supply Device (1) Basic Configuration FIG. 1 shows a leakless accumulator fuel supply device (hereinafter simply referred to as a fuel leak diagnostic device (control device) 100) according to a first embodiment of the present invention. FIG. 5 is a schematic diagram showing a configuration example of “accumulated fuel supply device”.
The accumulator fuel supply device 50 includes a fuel tank 1, a low pressure pump 2, a fuel filter 3, a high pressure pump 5, a common rail 10, a piezo injector 13 as a fuel injection valve, and the like as main elements. Each component is connected by a fuel pipe. Fuel supply passages 18a to 18d through which low-pressure fuel flows from the fuel tank 1 to the pressurizing chamber 5a of the high-pressure pump 5 are indicated by solid lines, and from the pressurizing chamber 5a to the common rail A high-pressure fuel passage 37 through which high-pressure fuel up to 10 flows and a high-pressure fuel passage 39 through which high-pressure fuel from the common rail 10 to each piezo injector 13 flows are shown by bold lines. In addition, the high-pressure pump 5, the pressure control valve 12, and the fuel return passages 30a to 30c from the piezo injector 13 to the fuel tank 1 are indicated by broken lines. The arrows in the figure indicate the traveling direction of the fuel in each passage.
Here, the high-pressure fuel system 40 is constituted by the common rail 10 and the piezo injector 13 downstream of the fuel discharge valve 9 of the high-pressure pump 5 and the high-

pressure fuel passages

37 and 39 connecting them.

In the accumulator fuel supply device 50, the fuel in the fuel tank 1 is sent to the high pressure pump 5 by the low pressure pump 2. At this time, the flow rate of the fuel sent to the pressurizing chamber 5a is adjusted by the flow rate control valve 8 comprising an electromagnetic proportional control valve in accordance with the operating state of the internal combustion engine and the target rail pressure. Further, the overflow valve 14 is connected to the fuel supply passage 18b so that the excess fuel is returned to the fuel tank 1 so that the pressure in the fuel supply passage 18b upstream of the flow control valve 8 is maintained at a predetermined value. .

The fuel supplied with its flow rate adjusted by the flow control valve 8 flows into the pressurizing chamber 5a via the fuel intake valve 6 when a negative pressure is generated in the pressurizing chamber 5a as the plunger 7 descends. Thereafter, when the plunger 7 is raised by the cam 15 and the fuel in the pressurizing chamber 5 a is pressurized, the fuel discharge valve 9 is opened, and high-pressure fuel is pumped toward the common rail 10.

In the common rail 10, the high-pressure fuel pumped from the high-pressure pump 5 is accumulated. A pressure sensor 21 is attached to the common rail 10, and feedback control of the pressure control valve 12 and the flow rate control valve 8 by the control device 100 is performed so that the rail pressure becomes the target rail pressure. As a result, the common rail 10 is in a state where high-pressure fuel having a target rail pressure is supplied to the plurality of piezo injectors 13.

The piezo injector 13 is provided with a back pressure relief mechanism 60 for opening and closing the injection hole. In the piezo injector 13, the energization control to the piezo actuator 51 of the back pressure relief mechanism 60 by the control device 100 is performed in a state where the high pressure fuel is supplied from the common rail 10, and the injection hole is opened and closed, so that various High pressure fuel is injected into a cylinder of an internal combustion engine (not shown) in an injection pattern.

(2) Fuel injection valve (piezo injector)
FIG. 2 shows a configuration example of the piezo injector 13 including a back pressure relief mechanism 60 including a piezo actuator 51 as an example of a fuel injection valve. The piezo injector 13 is configured such that fuel is injected by letting the high-pressure fuel in the back pressure chamber 91 loaded on the rear end side of the nozzle needle 83 escape by the back pressure relief mechanism 60. It is.

In the piezo injector 13 shown in FIG. 2, when high-pressure fuel is introduced from the high-pressure passage 61b of the injector housing 61 in a state where the piezo stack 51A is not extended, the nozzle needle 83 passes through the first hole 75a of the orifice plate 75. The high pressure fuel is guided from the periphery of the nozzle to the injection hole 79b side. The high-pressure fuel is also supplied to the back pressure chamber 91 via the first throttle hole 75b and is also guided to the axial hole 71a of the valve plate 71 via the second throttle hole 75c. At this time, since the reduced diameter portion 71b of the axial hole 71a is closed by the valve member 73, the high-pressure fuel is further guided from the periphery of the nozzle needle 83 to the injection hole 79b side through the third throttle hole 75d. .
In this state, the sum of the force that presses the nozzle needle 83 toward the injection hole 79b and the urging force of the needle spring 89 is greater than the force that presses the nozzle needle 83 toward the side opposite to the injection hole 79b. The injection hole 79b is closed.

On the other hand, when the piezo actuator 51 is energized to extend the piezo stack 51A, the displacement of the piezo stack 51A is transmitted to the displacement amplification piston 65, and further amplified in the displacement amplification chamber 66 and transmitted to the valve piston 67. When the valve member 73 is pressed by the valve piston 67, the valve member 73 is separated from the reduced diameter portion 71 b of the axial hole 71 a of the valve plate 71 and the reduced diameter portion 71 b is opened, while the third of the orifice plate 75 is opened. The throttle hole 75d is closed. Then, since the back pressure applied to the rear end portion of the nozzle needle 83 in the back pressure chamber 91 is released to the displacement amplification chamber 66 side, the force that presses the nozzle needle 83 to the side opposite to the injection hole 79b is the needle. The biasing force of the spring 89 is exceeded, the nozzle needle 83 is lifted from the valve seat, and the injection hole 79b is opened.
The fuel used for back pressure control of the nozzle needle 83 and released to the displacement amplification chamber 66 side is flowed to the fuel recirculation passage 30c via the fuel escape passage 61c and returned to the fuel tank.

The piezo injector 13 configured as described above has a configuration in which the high pressure fuel does not leak to the low pressure side in addition to the high pressure fuel in the back pressure chamber 91 being released by the escape control of the piezo actuator 51. Therefore, in a state where the piezo stack 51A is not extended and the reduced diameter portion 71b of the valve plate 71 is closed by the valve member 73, the leak fuel from the piezo injector 13 does not exist or becomes extremely small. In other words, if the piezo stack 51A is not extended and the pressure control valve 12 connected to the common rail 10 is closed, a state in which the rail pressure is difficult to decrease is formed. Therefore, even when the high-pressure pump 5 is downsized, the target rail pressure and the required injection amount are ensured, and the startability at the time of restarting the internal combustion engine in the idling stop control is prevented.

In the present embodiment, the piezo injector 13 is used as a fuel injection valve. However, there is no portion where the high pressure fuel leaks to the low pressure side other than the high pressure fuel in the back pressure chamber 91 is released by the back pressure control. Any electromagnetic solenoid injector may be used.

2. Control device (Fuel leak diagnosis device)
(1) Overall Configuration FIG. 3 is a functional block diagram showing a part related to fuel leakage diagnosis in the configuration of the control device 100 shown in FIG.
The control device 100 is configured around a microcomputer having a known configuration, and includes a pressure detection unit 101, an idling stop determination unit 102, an engine switch detection unit 103, a diagnosis execution switch detection unit 104, and a diagnosis start. A determination unit 105, a rail pressure / injection control unit (holding control unit) 106, and a fuel leakage determination unit 107 are provided. Specifically, each of these units is realized by executing a program by a microcomputer.

(2) Pressure Detection Unit The pressure detection unit 101 reads the sensor value (rail pressure) Prail of the pressure sensor 21 provided on the common rail 10 and stores it in a RAM (Random Access Memory) (not shown). The read rail pressure Prail is also output to the rail pressure / injection control unit 106 and the fuel leakage determination unit 107.

(3) Idling stop determination unit The idling stop determination unit 102 is based on information such as the rotational speed Ne of the internal combustion engine, the accelerator pedal operation amount Acc, the brake pedal operation amount Brk, the clutch position C, and the gear position G. Whether to perform idling stop control is determined. When it is determined that the idling stop control unit 102 performs the idling stop control, a signal Is indicating that the idling stop control is performed is output to the diagnosis start determination unit 105, and the rail pressure / injection control unit An internal combustion engine stop signal Es is output to 106.

(4) Engine switch detection unit The engine switch detection unit 103 detects ON / OFF of the ignition switch of the internal combustion engine. When the engine switch detection unit 103 detects that the ignition switch has been turned off, a signal Se indicating that the internal combustion engine is to be stopped when the ignition switch is turned off is sent to the diagnosis start determination unit 105. In addition to the output, a stop signal Es for the internal combustion engine is output to the rail pressure / injection control unit 106.

(5) Diagnosis execution switch detection unit The diagnosis execution switch detection unit 104 detects ON / OFF of the diagnosis execution switch. For example, when a fuel leakage diagnosis is performed at a vehicle dealer or the like, a diagnosis execution switch is turned ON, and when the diagnosis execution switch detection unit 104 detects that the diagnosis execution switch is turned ON, a diagnosis start determination unit 105 On the other hand, a signal De indicating that the internal combustion engine is stopped as a result of the diagnosis is output, and a stop signal Es for the internal combustion engine is output to the rail pressure / injection control unit 106.

(6) Diagnosis start determination unit The diagnosis start determination unit 105 determines whether or not the accumulator fuel supply apparatus 50 is in a state of executing a fuel leakage diagnosis. There may be one or more conditions regarding whether or not to perform the fuel leakage diagnosis. In the present embodiment, any one of the three conditions that the idling stop control of the internal combustion engine is executed, the ignition switch of the internal combustion engine is turned off, and the diagnosis execution switch is turned on. When is established, it is determined that the fuel leakage diagnosis is executed. The diagnosis start determination unit 105 outputs a signal Ds for executing a fuel leakage diagnosis to the rail pressure / injection control unit 106 and the fuel leakage determination unit 107 when these conditions are satisfied.

(7) Rail pressure / injection control unit (holding control unit)
The rail pressure / injection control unit 106 performs control of the rail pressure Prail and fuel injection control. In the normal operation mode of the internal combustion engine, the rail pressure / injection control unit 106 is based on the rail pressure Prail output from the pressure detection unit 101. 8 and feedback control of the pressure control valve 12 and energization control of the piezo injector 13 are performed.

Further, the rail pressure / injection control unit 106 functions as a holding control unit for the rail pressure Prail at the time of fuel leakage diagnosis. The rail pressure control unit 106 as a holding control unit holds the fuel in the high-pressure fuel system 40 when the diagnosis start determination unit 105 determines that the accumulator fuel supply device is in a state of executing the fuel leakage diagnosis. Take control. When control for holding fuel in the high-pressure fuel system 40 is started, the rail pressure / injection control unit 106 outputs a holding start signal Pk to the fuel leakage determination unit 107.

The control for holding the fuel in the high-pressure fuel system 40 is performed by closing the pressure control valve 12 connected to the piezo injector 13 and the common rail 10 together with the supply of the high-pressure fuel from the high-pressure pump 5 being stopped. The high pressure fuel system 40 is closed. At the time of idling stop control, since the fuel is originally held in the high-pressure fuel system 40 and the high-pressure fuel system 40 is closed in the same state, this control is used as it is.

Specifically, when the stop instruction signal Es for the internal combustion engine is output and the fuel injection to the internal combustion engine is stopped, the fuel pumping from the high pressure pump 5 is stopped and the fuel discharge valve 9 becomes a check valve. The inside of the high-pressure fuel passage 37 downstream of the pressurizing chamber 5a is blocked so that it cannot flow backward. Further, the pressure control valve 12 connected to the common rail 10 is fully closed, so that the high-pressure fuel is blocked from recirculating from the common rail 10 to the fuel tank 1. Further, in each piezo injector 13, the piezo stack 51 </ b> A is not expanded and the pressure in the back pressure chamber 91 is secured, so that the nozzle needle 83 is pressed toward the injection hole 79 b and the injection hole 79 b is closed. Is done. As a result, the high-pressure fuel system 40 is closed with the fuel held therein.

The fuel held in the high-pressure fuel system 40 may be held as it is with the pressure existing in the high-pressure fuel system 40 when the internal combustion engine is stopped, or held in a state adjusted to a predetermined pressure. Also good. In order to adjust the high-pressure fuel to a predetermined pressure, for example, after the rail pressure is once increased before the internal combustion engine is stopped, the pressure control valve 12 is used based on the rail pressure Prail after the internal combustion engine is stopped. This can be done by adjusting the pressure.

Furthermore, in the rail pressure / injection control unit 106 of the control device 100 of the present embodiment, when the rail pressure Prail falls below a predetermined value (second threshold value P3) when a fuel leakage diagnosis described later is performed, When the internal combustion engine is restarted, fuel injection is not performed until the rail pressure Prail reaches a predetermined value (second threshold value P3). Then, after the high pressure pump 5 is driven in the cranking state and the rail pressure Prail reaches a predetermined value (second threshold value P3), fuel injection into the internal combustion engine is permitted and the internal combustion engine is started. By not permitting the start of fuel injection to the internal combustion engine until the rail pressure Prail becomes equal to or higher than a predetermined value, abnormal operation of the internal combustion engine, damage to the internal combustion engine due to abnormal operation, and the like are prevented.

(8) Fuel leakage determination unit The fuel leakage determination unit 107 detects the fuel leakage from the high pressure fuel system 40 based on the pressure change in the high pressure fuel system 40 after the fuel starts to be held in the high pressure fuel system 40. Determine presence or absence. The fuel leak determination unit 107 of the control device 100 of the present embodiment reads the pressure detection unit 101 after a predetermined time tm has elapsed after the internal combustion engine has completely stopped after starting to hold the fuel in the high pressure fuel system 40. Whether or not there is a fuel leak from the high-pressure fuel system 40 is determined by determining whether or not the rail pressure Prail to be reduced has decreased to a predetermined first threshold value P2 or less.

Further, the fuel leak determination unit 107 of the control device 100 of the present embodiment is a case where the rail pressure Prail after a predetermined time tm has elapsed after the internal combustion engine has stopped has not decreased to the first threshold value P2 or less. On the other hand, if it is equal to or lower than the second threshold value P3 set to a value higher than the first threshold value P2, it is determined that there is a possibility that fuel leakage from the high-pressure fuel system 40 may start to proceed.
Although not shown in the figure, based on the determination result in the fuel leakage determination unit 107, if there is a fuel leak from the high-pressure fuel system 40 or there is a risk of it, the control device 100 informs the driver or the like. A warning is displayed to inform the user.

The predetermined time tm may be a predetermined time set in advance. In the case of idling stop control, the rail pressure Prail is detected and compared with the first threshold P2 when the internal combustion engine is restarted. You can also. The first threshold value P2 may be a value set in advance, but is set individually based on the rail pressure P1 detected at the time when control for holding fuel in the high-pressure fuel system 40 is started. May be.

3. FIG. 4 shows a temporal change in the rotational speed Ne of the internal combustion engine and a temporal change in the rail pressure Prail in the case where the idling stop control is executed. In FIG. 4, the solid line A indicates the rotational speed Ne of the internal combustion engine, and the solid line B (B 1), the broken line B 2, the dotted line B 3, and the alternate long and short dash line B 4 indicate the rail pressure Prail detected by the pressure sensor 21. Further, P1 is a necessary pressure in idle operation, P2 is a first threshold value (fuel leakage determination value), and P3 is a second threshold value (fuel injection permission pressure).
For example, when the idling stop determination unit 102 instructs execution of idling stop control at an arbitrary time t1, an internal combustion engine stop signal Es is output, and the rotational speed Ne of the internal combustion engine begins to decrease, at time t2. The internal combustion engine stops completely. At the time t1, at the same time, the rail pressure / injection control unit 106 closes the high-pressure fuel system 40 and controls to hold the fuel in the high-pressure fuel system 40. At this time, if there is no fuel leakage from the high-pressure fuel system 40, the rail pressure Prail remains unchanged at the rail pressure (P1 in FIG. 4) at the time t1, and is kept constant as shown by the solid line B1. Usually, since a very small amount of leaked fuel exists, the rail pressure Prail gradually decreases as shown by a broken line B2. If there is no fuel leakage from the high-pressure fuel system 40 or there is only a very small amount of leaked fuel, the amount of decrease in the rail pressure Prail is small, and the internal combustion engine is restarted at time t4 when the idling stop control is released. When starting, since the rail pressure Prail exceeds the second threshold value (fuel injection permission pressure) P3, the rail pressure Prail quickly rises to the necessary pressure P1 in the idling operation and immediately enters the internal combustion engine. Fuel injection is performed and the internal combustion engine is started.

However, when a fuel leak has occurred in the high-pressure fuel system 40, the rail pressure Prail significantly decreases after the stop point t1 of the internal combustion engine as indicated by the dotted line B3. Therefore, when the internal combustion engine is restarted at the time t4 when the idling stop control is released, the time t7 is required for the rail pressure Prail to reach the second threshold value P3 at which fuel injection to the internal combustion engine is permitted. It takes time until. Therefore, the start of the internal combustion engine is delayed, and it takes time until the rail pressure Prail reaches the necessary pressure P1 in the idle operation (t8).

Further, although the fuel leakage from the high-pressure fuel system 40 does not occur remarkably, when a slight fuel leakage occurs, after the stop time t1 of the internal combustion engine as shown by a one-dot chain line B4, Rail pressure Prail gradually decreases. Even in this case, it takes a little time for the rail pressure Prail to reach the second threshold value P3 at which fuel injection to the internal combustion engine is permitted from the time t4 when the idling stop control is released to the time t5. Therefore, the start of the internal combustion engine is delayed, and it takes time until the rail pressure Prail reaches the necessary pressure P1 in the idling operation (t6).

In order to detect such fuel leakage from the high-pressure fuel system 40, the fuel leakage determination unit 107 of the control device 100 of the present embodiment performs t3 after a predetermined time tm has elapsed from the state t2 in which the internal combustion engine is completely stopped. At this point, it is determined whether or not the rail pressure Prail has decreased to the first threshold value P2 or the second threshold value P3 or less, thereby performing a fuel leakage diagnosis of the high-pressure fuel system 40. When there is no fuel leakage from the high-pressure fuel system 40 (B1), or when there is only a very small amount of leaked fuel (B2), the rail pressure Prail at the time point t3 is less than or equal to the first threshold value P2. Of course, it does not fall below the second threshold value P3.

On the other hand, when a significant fuel leak has occurred from the high-pressure fuel system 40 (B3), the rail pressure Prail at time t3 has decreased to the first threshold value P2 or less, and the occurrence of fuel leak has occurred. Detected. Furthermore, even when the rail pressure Prail has not decreased to the first threshold value P2 or less, when the rail pressure Prail at the time t3 has decreased to the second threshold value P3 or less (B4), It is detected as a slight fuel leak.

4). Fuel Leak Diagnosis Method Next, a fuel leak diagnosis method for the high-pressure fuel system 40 performed by the control device 100 of the present embodiment will be described based on the flow of FIG.
In this fuel leakage diagnosis, first, in step S10, any one of the conditions that the idling stop control is executed, the ignition switch is turned off, and the diagnosis execution switch is turned on is met. Whether or not is determined. This determination is repeated until either condition is met.

If it is determined in step S10 that any of the conditions is met, the rail pressure Prail1 is detected in step S11, and then the internal combustion engine is stopped in step S12. Next, after the timer is operated in step S13, in step S14, control for holding the fuel in the high-pressure fuel system 40 is performed. Specifically, the injection from the fuel injection valve 13 is stopped, and the pressure control valve 12 connected to the common rail 10 is fully closed.

Next, in step S15, it is repeatedly determined whether or not the timer has passed the predetermined time tm until the timer has passed the predetermined time tm. When the timer elapses the predetermined time tm, after detecting the rail pressure Prail2 in step S16, it is determined whether or not the rail pressure Prail2 is equal to or lower than the first threshold value P2 in step S17. When the rail pressure Prail2 is equal to or lower than the first threshold value P2, a significant fuel leak has occurred. Therefore, in step S18, a fuel leak ERROR signal is output and, for example, a warning display indicating the occurrence of fuel leak is displayed. After completing this routine.

On the other hand, if the rail pressure Prail2 exceeds the first threshold value P2 in step S17, no significant fuel leakage has occurred, so that it is next determined in step S19 whether minor fuel leakage has occurred. move on. In step S19, it is determined whether or not the rail pressure Prail2 is equal to or lower than the second threshold value P3. When the rail pressure Prail2 is less than or equal to the second threshold value P3, it is estimated that a slight fuel leak has occurred. Therefore, in step S20, a fuel leak ALERT signal is output and, for example, a fuel leak may occur. This routine is terminated after displaying a warning indicating that there is. On the other hand, if the rail pressure Prail2 exceeds the second threshold value P3, there is no possibility of slight fuel leakage, so an OK signal is output in step S21 and the routine is terminated.

According to the fuel leakage diagnosis method as described above, the presence or absence of fuel leakage from the high-pressure fuel system 40 is diagnosed based on the pressure change of the high-pressure fuel system 40 during the stop period of the internal combustion engine. The self-diagnosis of the presence or absence of leakage of the high-pressure fuel in the high-pressure fuel system 40 is performed without performing a diagnostic operation, and the fuel leakage from the high-pressure fuel system 40 is detected at an early stage.

Since the control device 100 holds the fuel in the high-pressure fuel system 40 and detects a pressure change in the high-pressure fuel system 40, the controller 100 is configured to be able to diagnose the fuel leakage from the high-pressure fuel system 40. The fuel leak can be diagnosed using the high-pressure fuel supplied to the high-pressure fuel system 40, and the fuel leak diagnosis can be easily performed.

Further, if the stop period of the internal combustion engine for diagnosing fuel leakage is during idling stop control of the internal combustion engine, the fuel is held in the high-pressure fuel system 40 during operation of the vehicle on which the internal combustion engine is mounted. The fuel leakage of the high-pressure fuel system 40 can be diagnosed using the time when the control is performed. Therefore, waste of the battery or the like can be suppressed and time required for diagnosis can be saved.

5). Another Example of Fuel Leak Diagnosis Method (1) Another Fuel Leak Diagnosis Method 1
Another method for determining the presence or absence of fuel leakage includes, for example, comparing the pressure drop amount or the pressure drop rate until a predetermined time elapses after the fuel is held in the high-pressure fuel system with a predetermined reference value. It is done.
In this method, for example, as shown in FIG. 6, the rail pressure Prail3 is read when control for holding fuel in the high pressure fuel system is started, and after a predetermined time tm has elapsed based on the rail pressure Prail3. An allowable reference pressure drop amount D0 or a reference pressure drop rate R0 is set. After the elapse of the predetermined time tm, the rail pressure Prail4 is read, and the pressure drop amount D or the pressure drop rate R from the rail pressure Prail1 at the start of the holding control is calculated. Then, the pressure drop amount D or the pressure drop rate R is compared with the reference pressure drop amount D0 or the reference pressure drop rate R0, and the presence or absence of fuel leakage is determined.

燃料 By performing the fuel leakage diagnosis in this way, the fuel leakage diagnosis is accurately performed even if the rail pressure at the time of starting the fuel leakage diagnosis varies. These reference pressure drop amount D0 or reference pressure drop rate R0 may also be set in advance, or based on the rail pressure detected at the time when control for holding fuel in the high-pressure fuel system is started. May be set. Further, although not shown in the drawing, the (first) reference pressure drop D0 or the first pressure drop amount D0 or the occurrence of a light fuel leak as well as a noticeable fuel leak can be detected as in the fuel leak diagnosis shown in FIG. In addition to the (first) reference pressure decrease rate R0, the second reference pressure decrease amount or the second reference value that is smaller than the first reference pressure decrease amount D0 or the first reference pressure decrease rate R0. The reference pressure drop rate may be set.

(2) Another fuel leak diagnosis method 2
Further, as another method for determining the presence or absence of fuel leakage, for example, comparing the pressure decrease pattern in the high-pressure fuel system after starting to hold the fuel in the high-pressure fuel system with a predetermined reference pattern. It is done.
In this method, for example, as shown in FIG. 7, the rail pressure Prail5 is read when the control for holding the fuel in the high pressure fuel system is started, and the reference pattern X of the rail pressure drop is based on the rail pressure Prail5. Is set. Then, the rail pressure Prail is continuously read, and the rail pressure decrease pattern B (B1, B2, B3) is compared with the reference pattern X, and the method of decreasing the rail pressure is the method of decreasing the reference pattern X. Whether or not there is a fuel leak is determined by whether or not it is faster.

By performing the fuel leak diagnosis in this way, the rail pressure drop pattern corresponding to the rail pressure at the start of the fuel leak diagnosis and the degree of fuel leak is detected, and the degree of fuel leak from the high-pressure fuel system is accurately grasped. Is done. However, this reference pattern may also be a preset pattern, or may be set individually based on the rail pressure detected at the time when control for holding fuel in the high-pressure fuel system is started. Also good. Further, although not shown, in addition to the fuel leak diagnosis shown in FIG. 4, in addition to the remarkable fuel leak, the occurrence of a light fuel leak can be detected in addition to the (first) reference pattern X. The second reference pattern may be set in which the rail pressure lowers more slowly than the first reference pattern X.

(3) Another fuel leakage diagnosis method 3
Further, as another method for diagnosing fuel leakage, for example, when idling stop control is executed or when a diagnosis start switch is turned on, the internal combustion engine is stopped after a predetermined time has elapsed since the internal combustion engine stopped. When restarting, the time until the rail pressure is returned to a predetermined value and the energization amount to the pressure control valve are compared with a predetermined (first) threshold value.
Although this method is not shown, for example, the return value of the rail pressure that is returned when the internal combustion engine is restarted is set in advance, and the time until the rail pressure rises to the return value after the restart of the internal combustion engine, pressure control, etc. The amount of current supplied to the valve is compared with a (first) threshold value to determine the presence or absence of fuel leakage. For example, when a pressure control valve that is fully opened in a non-energized state is used, the greater the amount of fuel leakage, the greater the amount of power supplied to the pressure control valve until the rail pressure rises to the return value. In addition, as the amount of fuel leakage increases, the time until the rail pressure rises to the return value becomes longer.

Since the fuel leakage diagnosis can be made by performing the fuel leakage diagnosis in this way, the configuration of the fuel leakage determination unit can be diversified. In addition to the first threshold value, in addition to the first threshold value, the value of the energization amount is set higher than the first threshold value so that not only the remarkable fuel leakage but also the occurrence of minor fuel leakage can be detected as in the fuel leakage diagnosis shown in FIG. Also, a second threshold value that is smaller may be set.

[Second Embodiment]
The second embodiment of the present invention is a fuel leak diagnosis device (control device) 130 provided in a leakless pressure-accumulation fuel supply device similar to that described in the first embodiment. While having the same configuration as the control device 100 of the first embodiment, it is erroneously determined that a fuel leak has occurred due to a decrease in the pressure in the high-pressure fuel system 40 due to the contraction of the high-pressure fuel caused by a temperature change. It is configured not to be.

1. Control device (Fuel leak diagnosis device)
(1) Overall Configuration FIG. 8 is a functional block diagram showing a part related to fuel leakage diagnosis in the configuration of the control device 130 of the present embodiment.
The control device 130 is configured around a microcomputer having a known configuration, and includes a pressure detection unit 101, an idling stop determination unit 102, an engine switch detection unit 103, a diagnosis execution switch detection unit 104, and a diagnosis start. A determination unit 105, a rail pressure / injection control unit (holding control unit) 106, a fuel leakage determination unit 107, and a diagnosis stop instruction unit 108 are provided. Specifically, each of these units is realized by executing a program by a microcomputer.

Among these, the pressure detection unit 101, the idling stop determination unit 102, the engine switch detection unit 103, the diagnosis execution switch detection unit 104, the diagnosis start determination unit 105, the rail pressure / injection control unit 106, and the fuel leakage determination unit 107 are the first one. It has the same function as each part of the control apparatus 100 of the embodiment. However, the diagnosis start determination unit 105 outputs not only the rail pressure / injection control unit 106 and the fuel leakage determination unit 107 but also the diagnosis stop instruction unit when the diagnosis start condition is satisfied. Also output to 108.

(2) Diagnosis stop instruction unit The diagnosis stop instruction unit 108 is configured so that the temperature Tw of the coolant used for cooling the internal combustion engine and the temperature Tf of the high pressure fuel in the high pressure fuel system 40 are equal to or greater than a predetermined value from the start of execution of the fuel leak diagnosis. When the voltage drops, a fuel leak judgment stop signal S is output to the fuel leak judgment unit 107.

Specifically, the diagnosis stop instruction unit 108 of the fuel leak diagnosis apparatus 130 according to the present embodiment is stored in a RAM (not shown) when the signal Ds for starting the fuel leak diagnosis is output from the diagnosis start determination unit 105. The coolant temperature Tw and the temperature Tf of the high-pressure fuel in the high-pressure fuel system 40 are read, and the values at that time are set as reference values Tw0 and Tf0, respectively. Thereafter, the diagnosis stop instruction unit 108 continuously reads the coolant temperature Tw and the high-pressure fuel temperature Tf in the high-pressure fuel system 40 and obtains deviations ΔTw and ΔTf from the reference values Tw0 and Tf0. When the deviations ΔTw and ΔTf become equal to or greater than the predetermined values ΔTw0 and ΔTf0, a fuel leak determination stop signal S is output to the fuel leak determination unit 107. The coolant temperature Tw and the high-pressure fuel temperature Tf can be detected by a temperature sensor or the like provided in a region where the coolant or the high-pressure fuel flows.

The predetermined values ΔTw0 and ΔTf0 to be compared with the respective deviations ΔTw and ΔTf are set to values that can be estimated that the fuel density changes and the fuel contracts. For example, ΔTw0 = 20 ° C. and ΔTf0 = 20 ° C. Can do. Further, the predetermined values ΔTw0 and ΔTf0 may not be fixed values, and may be variables set according to the reference values Tw0 and Tf0 at the start of diagnosis, for example.

The diagnosis stop instructing unit 108 is configured such that the temperature of the high-pressure fuel in the high-pressure fuel system 40 decreases with the lapse of time after the internal combustion engine stops, and the fuel density changes, so that the fuel contracts and the high-pressure fuel system 40 It is provided to prevent a fuel leak from being determined to have occurred from the high-pressure fuel system 40 even when no fuel leak has occurred when the pressure drops. Therefore, information other than the coolant temperature Tw and the high-pressure fuel temperature Tf can be used as a determination criterion if it can be estimated that the temperature of the high-pressure fuel 40 system decreases.

2. Fuel Leak Diagnosis Method Next, a fuel leak diagnosis method for the high-pressure fuel system 40 performed by the control device 130 of the present embodiment will be described based on the flow of FIG.
In this fuel leakage diagnosis, in the same manner as each step described in the first embodiment, in step S10, the idling stop control is executed, the ignition switch is turned off, and the diagnosis execution switch is turned on. When it is determined that any one of the conditions is met, the rail pressure Prail1 is detected in step S11, and then the internal combustion engine is stopped in step S12.

Next, in this embodiment, the timer is operated in step S13, and the temperature Tw of the coolant at that time and the temperature Tf of the high-pressure fuel in the high-pressure fuel system 40 are read in step S31, and each of the values read in step S31 is read in step S32. The temperatures Tw and Tf are set to the reference values Tw0 and Tf0, respectively.

Next, similarly to the steps described in the first embodiment, in step S14, control for holding the fuel in the high-pressure fuel system 40 is performed, and in step S15, the timer elapses a predetermined time tm. Until then, it is repeatedly determined whether or not the timer has passed the predetermined time tm.

At this time, in this embodiment, if the timer has not elapsed the predetermined time tm and it is determined No in step S15, the process proceeds to step S33, and the coolant temperature Tw and the high-pressure fuel temperature Tf at that time are read. . Next, after calculating the deviation ΔTw (= Tw0−Tw) between the coolant temperature Tw and its reference value Tw0 and the deviation ΔTf (= Tf0−Tf) between the high-pressure fuel temperature Tf and its reference value Tf0 in step S34. In step S35, it is determined whether or not at least one of the deviations ΔTw and ΔTf is equal to or greater than the predetermined values ΔTw0 and ΔTf0.

If the deviations ΔTw and ΔTf are both less than the predetermined values ΔTw0 and ΔTf0, the process returns to step S15 and the diagnosis is continued. On the other hand, when at least one of the deviations ΔTw and ΔTf is equal to or greater than the predetermined values ΔTw0 and ΔTf0, the pressure in the high-pressure fuel system 40 is reduced due to the contraction of the fuel, and no fuel leakage occurs. Nevertheless, since it may be determined that a fuel leak has occurred, the fuel leak diagnosis is stopped and this routine is terminated.

When the timer has passed the predetermined time tm in step S15, the subsequent steps S16 to S21 are performed in the same manner as the steps described in the first embodiment, and whether the fuel leakage ERROR signal is output in step S18. Alternatively, the routine ends when the fuel leakage ALERT signal is output in step S20 or the OK signal is output in step S21.

According to the fuel leakage diagnosis method as described above, the fuel contracts due to a decrease in the temperature of the high-pressure fuel, and the pressure in the high-pressure fuel system 40 is decreased, so that there is a risk of erroneous diagnosis in the fuel leakage diagnosis. Disappear. Therefore, the reliability of the diagnosis result of the fuel leak diagnosis is improved.
The control for detecting the coolant temperature after the diagnosis is started and the temperature in the high-pressure fuel system and stopping the fuel leakage diagnosis when the temperature is lowered by a predetermined value or more from the start of the diagnosis is the fuel described in the first embodiment. The present invention can also be applied when performing another method 1 to 3 of leak diagnosis.

Claims

A high-pressure pump that pumps high-pressure fuel; a common rail that stores the high-pressure fuel pumped from the high-pressure pump; and a fuel injection valve that injects the high-pressure fuel stored in the common rail into a cylinder of an internal combustion engine. The fuel injection valve includes a nozzle needle that opens and closes an injection hole, a back pressure chamber that is supplied with the high pressure fuel and applies a back pressure to the nozzle needle by the pressure of the high pressure fuel, and the back pressure chamber. And a back pressure relief mechanism that lifts the nozzle needle to open the injection hole by letting out the high pressure fuel in the pressure chamber, and does not have a fuel leak passage other than the high pressure fuel in the back pressure chamber. In the fuel leakage diagnostic apparatus for diagnosing the presence or absence of fuel leakage from the high-pressure fuel system in the structure of the leakless pressure accumulating fuel supply device,
A pressure detector for detecting and storing the pressure in the high-pressure fuel system;
A holding control unit for holding the fuel in the high-pressure fuel system during a stop period of the internal combustion engine;
A fuel leakage determination unit that determines the presence or absence of the fuel leakage by looking at the pressure change in the high pressure fuel system after the fuel starts to be held in the high pressure fuel system;
A fuel leakage diagnosis device comprising:
The fuel leakage determination unit determines the presence or absence of the fuel leakage by comparing a pressure in the high pressure fuel system after a predetermined time has elapsed after starting to hold the fuel in the high pressure fuel system with a predetermined threshold. The fuel leakage diagnosis apparatus according to claim 1.
The fuel leakage determination unit compares the pressure drop amount or the pressure drop rate in the high pressure fuel system after the fuel is held in the high pressure fuel system with a predetermined reference value to determine whether the fuel leak has occurred. The fuel leakage diagnosis apparatus according to claim 1, wherein:
4. The fuel leakage diagnosis apparatus according to claim 1, wherein the stop period of the internal combustion engine is an idling stop control of the internal combustion engine.
When the temperature of the coolant used for cooling the internal combustion engine or the temperature of the high-pressure fuel in the high-pressure fuel system has decreased by a predetermined value or more from the temperature at the time of stop of the internal combustion engine, the determination in the fuel leak determination unit is stopped. The fuel leakage diagnosis apparatus according to any one of claims 1 to 4, further comprising: a diagnosis stop instruction unit that performs the operation.
A high-pressure pump that pumps high-pressure fuel; a common rail that stores the high-pressure fuel pumped from the high-pressure pump; and a fuel injection valve that injects the high-pressure fuel stored in the common rail into a cylinder of an internal combustion engine. The fuel injection valve includes a nozzle needle that opens and closes an injection hole, a back pressure chamber that is supplied with the high pressure fuel and applies a back pressure to the nozzle needle by the pressure of the high pressure fuel, and the back pressure chamber. And a back pressure relief mechanism that lifts the nozzle needle to open the injection hole by letting out the high pressure fuel in the pressure chamber, and does not have a fuel leak passage other than the high pressure fuel in the back pressure chamber. In the fuel leakage diagnosis method for diagnosing the presence or absence of fuel leakage from the high-pressure fuel system in the structure of the leakless accumulator fuel supply system having the structure,
A fuel leak diagnosis method, wherein the presence or absence of the fuel leak is determined by observing a pressure change of the high pressure fuel system while holding the fuel in the high pressure fuel system.