JP2010216382A - Abnormality determination device for fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abnormality determination device for a fuel injection device correctly determining abnormality of the fuel injection device and determining a cause of the abnormality of the fuel injection device. <P>SOLUTION: This device includes a reference pressure change setting means presetting a first order differential value of change of fuel pressure caused by fuel injection as a reference value, and an abnormality determination means determining abnormality of the fuel injection means based on slippage quantity of the first order differential value of change of fuel pressure detected by the fuel pressure detection means from a threshold which is the reference value set by the reference pressure change set means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an abnormality determination device that determines an abnormality of a fuel injection device that injects fuel into an internal combustion engine using a common rail.

  Conventionally, in a fuel injection amount control device applied to a diesel engine, a common rail system for supplying high-pressure fuel to a common rail (accumulation chamber) is known. In this common rail type diesel engine, a fuel injection device connected to the common rail by the pressure of fuel stored in the common rail (hereinafter also referred to as a “fuel injection valve (injector)”) enters the combustion chamber (cylinder) of the engine. Direct fuel injection.

  In addition, the fuel injection valve can inject fuel from the fuel injection valve in a short injection time by improving the response. The combination of this fuel responsive fuel injection valve and the common rail that can store high-pressure fuel enables fuel to be injected vigorously, and the fuel characteristics of the engine are reduced by injecting fine fuel into the combustion chamber of the engine. It has been improved. Thus, by improving the combustion characteristics of the engine, the exhaust gas of the engine is cleaned.

Further, in a diesel engine, the output characteristics of the engine change depending on the amount of fuel injected. Therefore, in the fuel injection amount control device of the common rail system, it is necessary to appropriately control the injection amount of fuel injected from the fuel injection valve. .
In general, the control of the fuel injection amount in the common rail fuel injection amount control device is performed by an electronic control unit (Electronic Control Unit).

  In such a fuel injection amount control device, the pressure of the fuel stored in the common rail is high, and the fuel injection valve may repeatedly open and close in a short time. There is a case where fuel is not normally injected due to wear of the portion. In such a situation, Patent Document 1 discloses a technique for detecting an abnormality of a fuel injection valve.

Japanese Patent Laid-Open No. 10-299557

  According to the technique disclosed in Patent Document 1, the fuel pressure in the common rail before the fuel injection valve injects fuel into the combustion chamber of the engine and after the fuel injection from the fuel injection amount instructed to the fuel injection valve. The difference (ideal value) is estimated, and a failure of the fuel injection valve is determined from the difference between the estimated fuel pressure difference and the actually measured fuel pressure difference.

  However, in the technique disclosed in Patent Document 1, failure of the fuel injection valve is determined based only on the fuel pressure difference before and after the injection, and consideration is given to how the fuel pressure changes. Absent. However, since the way of changing the fuel pressure at the time of injection should be different depending on the presence or absence and content of the failure, as long as it is based only on the difference in fuel pressure as in Patent Document 1, it cannot be determined correctly. There's a problem. Further, since there is a difference between the instructed fuel injection amount and the actually injected fuel injection amount, there is a problem that the accuracy of determining the failure of the fuel injection valve is lacking.

  The present invention has been made on the basis of the above problem recognition, and in a fuel injection device abnormality determination device in a common rail fuel injection amount control device, it is possible to correctly determine abnormality of the fuel injection device, and An object of the present invention is to provide an abnormality determination device for a fuel injection device that can determine (failure diagnosis) what causes the abnormality occurring in the fuel injection device.

In order to solve the above-described problem, the abnormality determination device for a fuel injection device according to the invention described in claim 1 (for example, the ECU 2 in the embodiment) is a fuel accumulating unit (for example, the common rail in the embodiment) that stores high-pressure fuel. 13), fuel injection means (for example, fuel injection valve 6-1 to fuel injection valve 6-4 in the embodiment) for injecting the fuel stored in the fuel pressure storage means into the combustion chamber of the internal combustion engine, and the fuel Fuel pressure detection means (for example, fuel pressure sensor 37-1 to fuel pressure sensor 37-4 in the embodiment) provided between the pressure accumulating means and the fuel injection means, and detects the pressure of the fuel injected into the combustion chamber. ), And a difference in determining abnormality of the fuel injection means based on the fuel pressure detected by the fuel pressure detection means (for example, fuel pressure P in the embodiment). In the determination device, a reference pressure change setting means (for example, a reference pressure in the embodiment) that presets a first-order differential value of a change in fuel pressure caused by fuel injection as a reference value (for example, the reference pressure gradient Ps in the embodiment). The differential value of the change in the fuel pressure detected by the fuel pressure detecting means (for example, the actual fuel pressure gradient in the embodiment) using the reference value set by the change setting unit 201) and the reference pressure change setting means as a threshold value And an abnormality determination unit (for example, an abnormality determination unit 203 in the embodiment) that determines an abnormality of the fuel injection unit based on a deviation amount from Pa).
Thus, a specific value representing the change in fuel pressure is set in advance as a reference value by first-order differentiation of the change in fuel pressure caused by fuel injection, and this reference value is set as a threshold value. Further, the fuel pressure change detected by the fuel pressure detecting means is first-order differentiated to obtain a specific value representing the change in the fuel pressure. Then, based on the amount of deviation between the set reference value and the change value of the fuel pressure detected by the fuel pressure detection means, the abnormality of the fuel injection means is determined.

According to a second aspect of the present invention, the reference pressure change setting means includes a first reference value (for example, a lower limit reference in the embodiment) which is a small value obtained by reducing a predetermined value with respect to the set reference value. Value Psmin) and a second reference value that is a large value obtained by increasing a predetermined value with respect to the set reference value (for example, the upper limit reference value Psmax in the embodiment), and the abnormality The determination unit is configured such that when the first derivative of the change in fuel pressure detected by the fuel pressure detection unit is outside the range between the first reference value and the second reference value, the fuel injection unit It is characterized by determining that it is abnormal.
Thus, a value in a predetermined range is set as a threshold value with respect to the reference value set by the reference pressure change setting means.

According to the first aspect of the present invention, the specific value representing the change in the fuel pressure is set in advance as the reference value by first-order differentiation of the change in the fuel pressure caused by the fuel injection, and this reference value is set as the threshold value. . Further, the fuel pressure change detected by the fuel pressure detecting means is first-order differentiated to obtain a specific value representing the change in the fuel pressure. Then, in order to determine abnormality of the fuel injection means based on the amount of deviation between the set reference value and the value of change in the fuel pressure detected by the fuel pressure detection means, the fuel injection means is added without adding a special sensor. Abnormality (failure diagnosis) can be determined.
In addition, it is possible to clarify the criterion for determining the abnormality of the fuel injection means, and to determine the abnormality of the fuel injection means based on whether or not the change in the fuel pressure detected by the fuel pressure detection means exceeds the threshold value.
As a result, it is possible to correctly determine abnormality of the fuel injection means.

According to the second aspect of the present invention, since a value in a predetermined range is set as a threshold value with respect to the reference value set by the reference pressure change setting means, the change in the fuel pressure detected by the fuel pressure detection means is detected. When the value exceeds the threshold, it can be determined in which direction the threshold is exceeded.
As a result, it is possible to determine what causes the abnormality of the fuel injection means.

1 is a block diagram showing a schematic configuration of a fuel injection amount control device according to an embodiment of the present invention. It is the figure which showed the example of the cross-section of the fuel injection valve in this embodiment. It is the graph which showed the example of the relationship between the control signal of a fuel injection valve in this embodiment, fuel pressure, and an injection rate. It is a graph explaining the method of abnormality determination in the abnormality determination apparatus of the fuel injection valve of this embodiment. It is the flowchart which showed the process sequence of the abnormality determination in the abnormality determination apparatus of the fuel injection valve of this embodiment. It is the block diagram which showed the processing block of the abnormality determination in the abnormality determination apparatus of the fuel injection valve of this embodiment.

  A fuel injection amount control device 10 including an abnormality determination device for a fuel injection device according to an embodiment of the present invention will be described with reference to FIG. The fuel injection amount control device 10 is applied to a diesel engine (hereinafter referred to as “engine 1”) mounted on a vehicle (not shown), and controls the pressure of fuel supplied to the combustion chamber of the engine 1.

The fuel tank 11 stores the fuel supplied to the engine 1. In the fuel tank 11, a low pressure pump P1 is provided.
The low-pressure pump P1 is provided with a motor P1-M connected to an ECU (Electronic Control Unit) 2. The low pressure pump P1 is an electric pump whose motor P1-M is controlled by the ECU 2 and is always operated during operation of the engine 1. The fuel in the fuel tank 11 is reduced to a predetermined pressure (for example, 0.5 MPa (megapascal)). Increase pressure and discharge.
A filter 17 is provided on the suction side of the low-pressure pump P1, and a fuel supply path 12 is connected on the discharge side. The connected fuel supply path 12 has a filter 18 having a heater for controlling the temperature of the fuel by the control from the ECU 2, and an electromagnetic flow rate control for controlling the flow rate of the fuel supplied from the low-pressure pump P 1 by the control from the ECU 2. A valve 21 is provided sequentially.

A fuel return path 16 that returns fuel to the fuel tank 11 is branched and connected to the fuel supply path 12 between the filter 18 and the electromagnetic flow control valve 21. A pressure control valve 22 that controls the pressure of the fuel supply path 12 is interposed in the fuel return path 16. The pressure control valve 22 is opened when the pressure in the fuel supply passage 12 exceeds the predetermined pressure, and returns the fuel into the fuel tank 11 through the fuel return passage 16.
In the fuel supply path 12 between the filter 18 and the electromagnetic flow control valve 21, a fuel temperature sensor 35 is provided between the connection portion of the fuel return path 16 and the electromagnetic flow control valve 21. The fuel temperature sensor 35 detects the temperature of the fuel discharged from the low pressure pump P1, and outputs a detection signal SgTemp indicating the detected temperature to the ECU 2.

  A high pressure pump P2 is connected to the downstream side of the electromagnetic flow control valve 21, and a common rail 13 is connected to the discharge side of the high pressure pump P2 via a high pressure pipe 13a. The high pressure pump P2 further increases the pressure of the fuel supplied from the low pressure pump P1 and supplies it to the common rail 13. The pressure of the fuel discharged by the high-pressure pump P2 is controlled by the flow control of the electromagnetic flow control valve 21.

A high-pressure pipe 13d is connected to the return path side of the common rail 13, and a fuel return path 16 is connected to the high-pressure pipe 13d. The high pressure pipe 13d is provided with an electromagnetic pressure control valve 23, and the fuel return path 14 is connected from the electromagnetic pressure control valve 23 to the fuel return path 16.
The electromagnetic pressure control valve 23 has a function that operates mechanically and a function that operates electrically by control from the connected ECU 2. In the mechanical operation, the valve is opened when the fuel pressure Prail exceeds a predetermined set pressure Prail_max (for example, 200 MPa (megapascal)) by the operation of the high-pressure pump P2. Thereby, the fuel in the common rail 13 is returned into the fuel tank 11, and the fuel pressure Prail is reduced to a predetermined set pressure Prail_max. In the electrical operation, the valve is opened according to a pressure reduction instruction from the ECU 2 that is output as necessary, so that the fuel accumulated in the common rail 13 can be discharged and the pressure can be reduced.

Further, the common rail 13 balances the amount of fuel pressurized and supplied by the high-pressure pump P2 with the amount discharged and depressurized by the electromagnetic pressure control valve 23 or the like, so that the internal space is in a high-pressure state (for example, , 200 MPa (megapascal)).
The common rail 13 has a high-pressure pipe 13b for supplying fuel to four fuel injection valves 6-1 to 6-4 (hereinafter collectively referred to as “fuel injection valves 6”) that inject fuel into the engine 1. -1 to 13b-4 are connected.
The fuel injection valve 6 is opened by a control signal from the ECU 2 and injects fuel supplied from the common rail 13 into the combustion chamber of the engine 1.

Near the connection points of the high-pressure pipes 13b-1 to 13b-4 to the common rail 13, orifices 13c-1 to 13c-4 (hereinafter, collectively referred to as “orifice 13c”) are provided. The orifice 13c is a common rail that is generated by pressure fluctuation of fuel pressure in the high-pressure pipes 13b-1 to 13b-4 (hereinafter collectively referred to as "high-pressure pipe 13b") generated by fuel injection from the fuel injection valve 6. The effect of 13 pressure fluctuations can be reduced.
Further, fuel pressure sensors 37-1 to 37-4 (hereinafter, collectively referred to as “fuel pressure sensor 37”) are attached to the downstream side of the orifice 13c. The fuel pressure sensor 37 detects the fuel pressure on the downstream side of the orifice 13c. The fuel pressure sensor 37 outputs a detection signal SgP indicating the detected pressure to the ECU 2.

The fuel return path 15 indicates a fuel return path from each fuel injection valve 6, and a fuel supply path between the low pressure pump P 1 and the filter 18 via a check valve 24 and a pressure control valve 25 connected in parallel. 12 is connected.
A check valve 24 and a pressure control valve 25 provided in the middle of the fuel return path 15 adjust the pressure of the discharged oil from the fuel injection valve 6 to be constant. The pressure control valve 25 also has a function of pressurizing the fuel return path 15 from the fuel supply path 12 to the fuel injection valve 6 by the low-pressure pump P1 connected to the fuel supply path 12 when the operation of the engine 1 is started.

The ECU 2 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), an EEPROM (Electrically Erasable Programmable ROM), and an I / O (Input / Output) interface (all not shown). It consists of a microcomputer.
The ECU 2 controls the fuel injection timing at the fuel injection valve 6 from the crank angle information SgDeg of the engine 1 detected by the crank angle sensor 33 provided in the engine 1. Further, the ECU 2 determines the operating state of the engine 1 in accordance with detection signals such as the detection signal SgTemp from the fuel temperature sensor 35 and the detection signal SgP from the fuel pressure sensor 37, and the electromagnetic flow control valve 21, electromagnetic pressure The pressure of the common rail 13 is controlled by controlling the control valve 23 and the low pressure pump P1, and the fuel injection amount control is executed by opening and closing the fuel injection valve 6.

In the ECU 2, based on the detected fuel pressure, the fuel pressure Prail which is the fuel pressure in the common rail 13 and the fuel pressure fluctuation caused by the fuel injection by the fuel injection valve 6 are led.
In addition, although the fuel pressure sensor 37 illustrated the form provided independently in each high-pressure piping 13b-1 to 13b-4, and decided that each fuel pressure sensor 37 detected fuel pressure independently, at least high pressure The fuel pressure sensor 37 provided at any one of the pipes 13b-1 to 13b-4 can detect the fuel pressure of the common rail 13 and the high-pressure pipes 13b-1 to 13b-4. At that time, the ECU 2 performs processing for deriving the fuel pressure of the common rail 13 and the other high-pressure pipe 13b from the detection signal detected by one fuel pressure sensor 37.

With the above-described configuration, in the fuel injection amount control device 10, the operating state of the high-pressure pump P <b> 2 controlled by the electromagnetic flow control valve 21, the open / close state of the electromagnetic pressure control valve 23, and the open / close state of the fuel injection valve 6. Thus, the fuel pressure Prail of the common rail 13 is controlled within a range having a predetermined set value Prail_max as an upper limit.
In addition, the connection by the continuous line shown by FIG. 1 shows piping of fuel system, and the connection by a dashed-dotted line shall show the connection by the control line by an electrical signal. In addition, although the low pressure pump P1 is provided in the fuel tank 11, the low pressure pump P1 may be disposed outside the fuel tank 11.

  Next, the fuel injection operation in the fuel injection amount control device 10 of the present embodiment will be described. FIG. 2 is a diagram illustrating an example of a cross-sectional structure of the fuel injection valve 6 that injects the fuel supplied from the common rail 13 into the combustion chamber of the engine 1 in the present embodiment. In FIG. 2, the fuel injection by the fuel injection valve 6 is performed by applying an applied voltage to the piezo actuator 601 based on a control signal from the ECU 2, and expanding and contracting the piezo actuator 601 in accordance with the applied voltage. By controlling the applied voltage, the amount of fuel injected from the fuel injection valve 6 to the engine 1 is controlled.

  A piezo actuator 601 is disposed at the upper part of the fuel injection valve 6, and a piston 602 is attached to the lower end of the piezo actuator 601. The lower end of the piston 602 protrudes to the control chamber 612 through the opening 611 communicating with the low pressure passage 625 connected to the fuel return passage 15. A hemispherical control valve 603 having a flat lower portion is attached to the tip of the piston 602 that penetrates the opening 611. In addition, a communication passage 622 branched from the high-pressure passage 621 connected to the common rail 13 communicates with the bottom surface of the control chamber 612. The upper spherical surface of the control valve 603 blocks the fuel path from the control chamber 612 to the low-pressure passage 625 by closing the opening 611 when the piston 602 moves upward due to the piezo actuator 601 contracting. Further, the lower flat portion of the control valve 603 blocks the communication passage 622 when the piston 602 moves in the downward direction due to the extension of the piezo actuator 601, whereby the fuel path from the high pressure passage 621 to the control chamber 612. Shut off.

  On the other hand, a cylindrical vertical hole 614 is provided in the lower portion of the fuel injection valve 6, and a rod-shaped needle 604 is disposed in the vertical hole 614. In the vicinity of the center of the needle 604, a large-diameter portion 604b having a diameter larger than that of the other portion is provided, and a space below the large-diameter portion 604b in the vertical hole portion 614 serves as a fuel reservoir 615. . The high-pressure fuel from the common rail 13 is always supplied to the fuel reservoir 615 through the high-pressure passage 621.

  Further, the tip 604 a of the needle 604 has a conical shape, and when the needle 604 is lowered, the tip 604 a enters a recess 616 formed on the bottom surface of the fuel reservoir 615. The recess 616 has an opening 617 having a diameter smaller than the maximum diameter of the tip 604 a of the needle 604. The recess 616 is formed with an injection hole 618 for injecting the fuel accumulated in the fuel reservoir 615 into the combustion chamber of the engine 1.

  Further, a back pressure chamber 613 that communicates with the high pressure passage 621 through the communication passage 623 and communicates with the control chamber 612 through the communication passage 624 is formed in the upper portion of the needle 604. The ceiling of the back pressure chamber 613 restricts the upward movement of the needle 604.

  In the fuel injection valve 6 configured as described above, when the piezo actuator 601 is contracted, the piston 602 moves upward, and the lower flat portion of the control valve 603 is separated from the bottom surface of the control chamber 612 and the control chamber 612. The communication passage 622 is connected, and the upper spherical surface of the control valve 603 blocks the opening 611 so that the control chamber 612 and the low pressure passage 625 are blocked. Thereby, the high pressure fuel from the common rail 13 is supplied to the back pressure chamber 613 sequentially through the high pressure passage 621, the communication passage 622, the control chamber 612, and the communication passage 624, and the fuel supplied to the back pressure chamber 613 is supplied to the low pressure passage. Since it does not leak to 625, the pressure in the back pressure chamber 613 increases. The pressure applied to the back pressure chamber 613 acts as a force for pushing the needle 604 downward. When the pressure value is equal to or higher than a predetermined value, the needle 604 comes into contact with the recess 616 to close the opening 617, and the pressure is reduced. As the size further increases, the tip 604a of the needle is further pushed into the opening 617, whereby fuel injection from the injection hole 618 is stopped (see FIG. 2A).

  When the piezo actuator 601 extends from the above state, the piston 602 moves downward, and the upper spherical surface of the control valve 603 is separated from the opening 611, the control chamber 612 and the low pressure passage 625 are connected, and the back The fuel accumulated in the pressure chamber 613 leaks to the low pressure passage 625 side, so that the pressure in the back pressure chamber 613 decreases. Then, the needle 604 is held at a position where the pressure of the back pressure chamber 613 and the pressure of the fuel reservoir 615 are balanced, and is away from the recess 616. As a result, the fuel accumulated in the fuel reservoir 615 flows out to the concave portion 616 side through the gap formed between the opening 617 of the concave portion 616 and the tip 604a of the conical needle. A corresponding amount of fuel is injected from the injection hole 618 (see FIG. 2B).

  As the amount of fuel leaking into the low pressure passage 625 increases as the piezo actuator 601 extends, the pressure in the back pressure chamber 613 further decreases, the balance position where the needle 604 is held moves upward, and the tip of the needle The amount that 604a is pushed into the opening 617 is reduced, and the gap between the opening 617 and the tip 604a of the needle is increased. Along with this, the amount of fuel injected from the injection hole 618 also increases. In this way, by controlling the expansion and contraction of the piezo actuator 601, the amount of fuel injected by the fuel injection valve 6 can be controlled.

  When the piezo actuator 601 further extends and the lower flat portion of the control valve 603 comes into contact with the bottom surface of the control chamber 612, the control chamber 612 and the communication passage 622 are shut off, and the high-pressure fuel from the common rail 13 is high pressure. The fuel that has been supplied to the back pressure chamber 613 is eliminated by a path that sequentially passes through the passage 621, the communication passage 622, the control chamber 612, and the communication passage 624. As a result, the pressure balance between the pressure in the back pressure chamber 613 and the pressure in the fuel reservoir 615 cannot be maintained, and the upper portion of the needle 604 eventually comes into contact with the ceiling of the back pressure chamber 613, and the needle 604 moves further upward. Cannot move in the direction. This state is a state where the size of the gap, that is, the fuel injection amount becomes the maximum value.

  Next, control of the fuel injection amount in the fuel injection amount control device 10 of the present embodiment will be described. FIG. 3 is a graph showing the relationship between the injection control signal Ti input to the fuel injection valve 6 in this embodiment, the fuel pressure P of the high-pressure pipe 13b, and the injection rate dQ / dt of the fuel injected from the injection hole 618. . The fuel injection by the fuel injection valve 6 is performed by applying an applied voltage corresponding to the injection control signal Ti from the ECU 2 to the piezo actuator 601, but in the description of FIG. 3, the waveform of the injection control signal Ti is It represents the magnitude (voltage level) of the applied voltage applied to the piezo actuator 601. The waveform of the fuel pressure P represents the fuel pressure in the high-pressure pipe 13b detected by the fuel pressure sensor 37.

In FIG. 3, when the application of the applied voltage to the piezo actuator 601 is started (timing t1), the fuel injection valve 6 starts fuel injection. As a result, the fuel pressure P starts to decrease with a predetermined delay time (timing t2).
Thereafter, when the application of the applied voltage to the piezo actuator 601 is stopped, the fuel injection valve 6 stops the fuel injection and the fuel pressure P rises with a predetermined delay time (timing t3).

  Except for the change in the fuel pressure P caused by factors other than the fuel injection, the waveform showing only the fuel injection is the waveform of the fuel injection rate dQ / dt. The waveform of the fuel injection rate dQ / dt represents the amount of fuel injected by the fuel injection valve 6. That is, in the waveform of the fuel injection rate dQ / dt, the area (integrated value) in the section from the timing t2 to the timing t3 corresponds to the fuel injection amount by the fuel injection valve 6.

  Thus, the fuel injection amount of the fuel injection valve 6 can be controlled by controlling the applied voltage applied to the piezoelectric actuator 601 by the ECU 2.

  Next, an abnormality determination method in the abnormality determination apparatus of the present embodiment will be described. FIG. 4 is a graph illustrating an abnormality determination method in the abnormality determination device for the fuel injection valve 6 according to the present embodiment. A waveform A1 in FIG. 4 represents the fuel injection rate dQ / dt when the fuel injection valve 6 is operating normally, and a waveform B1 represents the fuel pressure P at that time. The waveform A2 represents the fuel injection rate dQ / dt when the operation of the fuel injection valve 6 is abnormal, and the waveform B2 represents the fuel pressure P at that time. The area surrounded by the waveform A1 and the waveform A2 and the horizontal axis corresponds to the fuel injection amount.

  In FIG. 4, it is assumed that the fuel injection amount by the waveform A1 and the fuel injection amount by the waveform A2 are the same fuel injection amount. That is, the waveform A1 obtains the desired fuel injection amount in the period from the timing t2 to the timing t3-1, while the waveform A2 requires the time from the timing t2 to the timing t3-2 and has the same desired fuel injection amount. Have gained. Here, if there is no restriction on the injection time associated with the operation of the engine 1, the fuel injection amount by the waveform A1 and the fuel injection amount by the waveform A2 are made the same by increasing the fuel injection time in this way. However, in the actual operation of the engine 1, there is a restriction on the injection time, and therefore it may be impossible to ensure the same fuel injection amount only by the control for increasing the injection time. .

Therefore, the fuel injection valve 6 with the fuel pressure P having the waveform A2 has a long time taken to obtain the same fuel injection amount, and therefore has poor combustion characteristics in the engine 1 and must be determined to be abnormal.
In this situation, since the fuel injection amount is the same, it is not possible to determine abnormality based only on the fuel injection amount.

  Therefore, in the abnormality determination device for the fuel injection valve 6 of the present embodiment, the slope of the change in the fuel pressure P is obtained by first-order differentiation of the value of the fuel pressure P, and the abnormality of the fuel injection valve 6 is determined based on the inclination. judge. For example, in FIG. 4, an initial slope c1 of the waveform B1 when the fuel injector 6 is operating normally is obtained in advance, and this slope c1 and the fuel pressure P actually detected by the fuel pressure sensor 37 are obtained. The initial slope c2 of the waveform B2 obtained from the above is compared, and when the slope c2 is a value equal to or smaller than the slope c1, it is determined that the fuel injection valve 6 is abnormal.

  In the above description, it has been described that the abnormality is determined based only on the magnitude relationship between the normal inclination c1 and the actually detected inclination c2. However, the case where the inclination c2 is outside the predetermined inclination range is described. You may make it determine with it being abnormal.

  The cause of the abnormality of the fuel injection valve 6 when the inclination c2 is equal to or less than the inclination c1 is the fuel in the fuel injection valve 6 that is generated due to deterioration (wear) of the sliding portion in the fuel injection valve 6. Leaks. For example, when the large-diameter portion 604b of the needle 604 is worn (the large-diameter portion 604b is constantly moving up and down by injecting fuel, friction occurs with the vertical hole portion 614 and wears). When the fuel is injected, the amount of fuel in the fuel reservoir 615 leaks out from the gap between the large diameter portion 604b and the vertical hole portion 614 to the back pressure chamber 613 side. As a result, the fuel pressure in the fuel reservoir 615 decreases, and the amount of fuel injected from the injection hole 618 decreases.

  The cause of the abnormality of the fuel injection valve 6 when the inclination c2 is equal to or greater than the inclination c1 is an increase in the amount of fuel injection generated due to external deterioration (wear) of the fuel injection valve 6. For example, if the injection hole 618 for injecting fuel into the combustion chamber of the engine 1 expands, the fuel injection amount increases even when the same control is performed. As a result, the fuel pressure in the high-pressure pipe 13b is rapidly reduced.

  Next, the abnormality determination process in the abnormality determination device of this embodiment will be described. FIG. 5 is a flowchart showing a processing procedure of abnormality determination in the abnormality determination device for the fuel injection valve 6 of the present embodiment. The injection control signal Ti that instructs the fuel injection valve 6 to inject fuel is output at a predetermined timing, and is requested by applying an applied voltage corresponding to the injection control signal Ti to the piezo actuator 601. The description will be made assuming that the fuel injection amount is predetermined.

  First, when requesting fuel injection from the fuel injection valve 6, the ECU 2 calculates the fuel pressure from the requested fuel injection amount based on, for example, the following equation (1) in step S10.

  In the above equation (1), Q is the fuel injection amount, C is the flow coefficient, A is the opening area of the fuel injection valve 6, P is the fuel pressure value, ρ is the fuel density, and T is the opening time of the fuel injection valve 6. Show. Expression (1) is obtained by the following equation. The opening area A of the fuel injection valve 6 controlled by the injection control signal Ti (the size of the gap between the opening 617 in FIG. 2 and the tip 604a of the needle) and the opening time T (opening in FIG. 2) This shows that the fuel is injected in an amount corresponding to the time during which there is a gap between the portion 617 and the tip 604a of the needle. Therefore, the ECU 2 can obtain the fuel pressure from the requested fuel injection amount Q and the injection control signal Ti at that time. In the present invention, the detailed calculation method of the fuel pressure P is not defined.

  The calculated fuel pressure is first-order differentiated to calculate a fuel pressure gradient (reference pressure gradient Ps). Then, a lower limit reference value Psmin obtained by subtracting a predetermined value from the calculated reference pressure gradient Ps and an upper limit reference value Psmax obtained by adding a predetermined value to the reference pressure gradient Ps are determined.

This step S10 is performed only at the initial stage when the engine 1 is mounted on a vehicle not shown, and the requested fuel injection amount is the same as the fuel injection amount actually injected by the fuel injection valve 6 in response to the request. The injection control signal Ti is corrected so that In the present invention, the method for correcting the injection control signal Ti is not defined.
The fuel injection amount actually injected by the fuel injection valve 6 is calculated from the fuel pressure of the high-pressure pipe 13b detected by the fuel pressure sensor 37, for example, based on the above equation (1).
Thereafter, the processes after step S20 are repeated according to the operation of the engine 1.
Step S10 is also performed when the reference pressure gradient Ps is calculated again.

  In step S <b> 20, the ECU 2 reads the fuel pressure in the high-pressure pipe 13 b detected by the fuel pressure sensor 37. In step S30, the read fuel pressure is first-order differentiated to calculate a fuel pressure gradient (actual fuel pressure gradient Pa).

  Subsequently, in step S40, the ECU 2 checks whether or not the calculated actual fuel pressure gradient Pa exceeds the lower limit reference value Psmin. If the actual fuel pressure gradient Pa exceeds the lower limit reference value Psmin, the ECU 2 performs step. Proceed to S50. If the actual fuel pressure gradient Pa does not exceed the lower limit reference value Psmin in step S40, the process proceeds to step S41.

  If the actual fuel pressure gradient Pa does not exceed the lower limit reference value Psmin in step S40, the ECU 2 warns in step S41 that the actual fuel pressure gradient Pa of the fuel injection valve 6 does not exceed the lower limit reference value Psmin. For example, the content indicating that there is a leak in the fuel injection valve 6 is displayed on a display unit (not shown), and the process is completed.

  On the other hand, if the actual fuel pressure gradient Pa exceeds the lower limit reference value Psmin in step S40, the ECU 2 checks in step S50 whether or not the calculated actual fuel pressure gradient Pa is less than the upper limit reference value Psmax. If the actual fuel pressure gradient Pa is less than the upper reference value Psmax, the process proceeds to step S60. If the actual fuel pressure gradient Pa is not less than the upper reference value Psmax in step S50, the process proceeds to step S51.

  In step S50, if the actual fuel pressure gradient Pa is not less than the upper limit reference value Psmax, the ECU 2 warns in step S51 that the actual fuel pressure gradient Pa of the fuel injection valve 6 is not less than the upper limit reference value Psmax. When the injection hole 618 of the injection valve 6 is widened, the content indicating that fuel exceeding the requested injection amount is injected is displayed on a display unit (not shown), and the process is completed.

  On the other hand, if the actual fuel pressure gradient Pa is less than the upper reference value Psmax in step S50, the ECU 2 determines that the actual fuel pressure gradient Pa of the fuel injector 6 is less than the lower reference value Psmin and the upper reference value Psmax in step S60. The range (normal range) is displayed on a display unit (not shown), and the process is completed.

  Next, an abnormality determination processing block in the abnormality determination device of the present embodiment will be described. FIG. 6 is a block diagram illustrating processing blocks in the ECU 2 that is an abnormality determination device that performs abnormality determination of the fuel injection valve 6 in the fuel injection amount control device 10.

  In FIG. 6, the processing block in the ECU 2 that determines the abnormality of the fuel injection valve 6 includes a reference pressure change setting unit 201, a fuel pressure calculation unit 202, an abnormality determination unit 203, and a display control unit 204.

  The reference pressure change setting unit 201 calculates the fuel pressure that changes as the fuel injection valve 6 injects fuel based on the fuel injection amount instructed by the fuel injection amount control device 10 of the present embodiment, and then calculates the fuel pressure. The fuel pressure is first-order differentiated to calculate a fuel pressure gradient (reference pressure gradient Ps), which is stored in a storage unit (not shown). Then, a lower limit reference value Psmin obtained by subtracting a predetermined value and an upper limit reference value Psmax obtained by adding a predetermined value are determined from a reference pressure gradient Ps stored in a storage unit (not shown) to determine abnormality. The data is output to the unit 203.

  The reference pressure gradient Ps is stored only in the initial stage when the engine 1 is mounted on a vehicle (not shown), but a new reference pressure gradient Ps can be stored according to the subsequent operation of the engine 1. .

  Based on the detection signal SgP from the fuel pressure sensor 37, the fuel pressure calculation unit 202 calculates the fuel pressure of the high pressure pipe 13b, that is, the current actual fuel pressure (fuel pressure P), and calculates the calculated fuel of the high pressure pipe 13b. The actual fuel pressure value of the pressure is output to the abnormality determination unit 203.

  The abnormality determination unit 203 performs first-order differentiation on the actual fuel pressure input from the fuel pressure calculation unit 202 to calculate a fuel pressure gradient (actual fuel pressure gradient Pa). Then, the calculated actual fuel pressure gradient Pa is compared with the lower limit reference value Psmin and the upper limit reference value Psmax input from the reference pressure change setting unit 201, and the comparison result is output to the display control unit 204.

The display control unit 204 outputs a display control signal for display on a display unit (not shown) based on the comparison result with the reference value input from the abnormality determination unit 203. Thus, a display corresponding to the display control signal input from the display control unit 204 is displayed on a display unit (not shown), and the abnormality determination result of the fuel injection valve 6 is presented, for example, to a vehicle inspector (not shown). .
In the present invention, the method for presenting the abnormality determination result is not specified.

As described above, according to the present embodiment, the abnormality of the fuel injection valve 6 can be detected based on the slope of the actual fuel pressure that changes when the fuel is injected by the fuel injection valve 6. Further, based on the inclination of the actual fuel pressure and the inclination of the reference of the fuel pressure, it is determined what causes the abnormality of the fuel injection valve 6, that is, what causes the abnormality of the fuel injection valve 6. (Failure diagnosis).
As a result, it is not necessary to check the output characteristics of the engine when the engine 1 is operated, the pressure fluctuation in the combustion chamber of the engine 1, etc., and other than the fuel supply system (high pressure pump P2, common rail 13, fuel injection valve 6). The abnormality of the fuel injection valve 6 can be correctly determined without being affected by the disturbance factor.

  The reference pressure gradient Ps calculated in the present embodiment has been described as being calculated from the value of the requested fuel injection amount. For example, the requested fuel injection amount and the reference pressure gradient Ps are associated with a storage unit (not shown). It is also possible to adopt a configuration in which abnormality determination of the fuel injection valve 6 is performed using a reference pressure gradient Ps stored in a storage unit (not shown).

  Further, the calculation and storage of the reference pressure gradient Ps has been described based on the fact that it is performed only at the initial stage when the engine 1 is mounted on a vehicle (not shown). Is stored in a storage unit (not shown), a new reference pressure gradient Ps is calculated from the stored previous actual fuel pressure value (normal value), and the calculated new fuel pressure is calculated. The reference pressure gradient Ps may be stored.

  In addition, for example, the actual fuel pressure at the time when it was determined to be normal last time is periodically stored in a storage unit (not shown), and then stored when a vehicle (not shown) equipped with the engine 1 is serviced. By reading out the actual fuel pressure, the fuel injection valve 6 can be used for grasping the progress of the abnormality.

In the present embodiment, the method of calculating the fuel pressure gradient (reference pressure gradient Ps) by first-order differentiation using the fuel pressure calculated from the requested fuel injection amount value has been described. A reference waveform (for example, waveform B1 in FIG. 4) of a change in fuel pressure that changes according to the fuel injection amount may be stored. Then, the stored reference waveform is compared with the actual injection waveform (for example, the waveform B2 in FIG. 4) showing the change in fuel pressure when the fuel injection valve 6 actually injects the fuel. Judge abnormalities.
Also, for example, the time from when the fuel injection is requested until the fuel pressure reaches the lowest value (peak value) is stored, and the time until the stored peak value and the actual fuel injection are obtained. The abnormality of the fuel injection valve 6 can also be determined by comparing with the time to the peak value.
With such a configuration, the obtained abnormality determination result can be used for adjusting the output timing of the injection control signal Ti that instructs the fuel injection valve 6 according to the operation of the engine 1. That is, if the fuel pressure peak value obtained by actual fuel injection is the same as the peak value calculated from the requested variable injection, and the time from the fuel injection request to the peak value is different, the fuel injection Although the valve 6 is normal, there is a possibility that the timing for requesting the fuel injection is shifted, so that it can be used for adjusting the timing of the fuel injection request.

In the present embodiment, the number of fuel injection valves 6 is four and the number of common rails 13 is one. However, the number of fuel injection valves 6 is not limited to four and one, but depends on the configuration of the engine 1. The quantity can be set arbitrarily.
Although the engine 1 has been described as a diesel engine, the fuel injection amount control device 10 can be applied to a gasoline engine.

  The invention can be applied to various industrial internal combustion engines including an internal combustion engine for a ship propulsion device such as an outboard motor.

2 ECU (abnormality determination device)
13 Common rail (fuel accumulator)
6,6-1,6-2,6-3,6-4 Fuel injection valve (fuel injection means)
37, 37-1, 37-2, 37-3, 37-4 Fuel pressure sensor (fuel pressure detecting means)
201 Reference pressure change setting unit (reference pressure change setting means)
203 Abnormality determination unit (abnormality determination means)
P Fuel pressure Ps Reference pressure gradient (reference value)
Pa Actual fuel pressure gradient (change in fuel pressure)
Psmin lower limit reference value (first reference value)
Psmax upper reference value (second reference value)

Claims (2)

A fuel pressure storage means for storing high-pressure fuel; a fuel injection means for injecting fuel stored in the fuel pressure storage means into a combustion chamber of an internal combustion engine; and the fuel pressure storage means and the fuel injection means. A fuel pressure detecting means for detecting the pressure of the fuel injected into the combustion chamber, and an abnormality determination device for determining an abnormality of the fuel injection means based on the fuel pressure detected by the fuel pressure detecting means,
Reference pressure change setting means for presetting, as a reference value, a first derivative of a change in fuel pressure caused by fuel injection;
An abnormality in which abnormality of the fuel injection unit is determined based on a deviation amount from a primary differential value of a change in fuel pressure detected by the fuel pressure detection unit with a reference value set by the reference pressure change setting unit as a threshold value A determination means;
An abnormality determination device comprising: The reference pressure change setting means includes
A first reference value which is a small value obtained by reducing a predetermined value with respect to the set reference value;
A second reference value which is a large value obtained by increasing a predetermined value with respect to the set reference value;
Set
The abnormality determining means includes
When the primary differential value of the change in the fuel pressure detected by the fuel pressure detection means is outside the range between the first reference value and the second reference value, the fuel injection means is abnormal. judge,
The abnormality determination device according to claim 1.

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