JP2007247541A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect abnormal output at an early stage even if the abnormal output occurs either in a high output side or a low output side in relation to a rail pressure sensor 7 for a fuel injection device 1. <P>SOLUTION: Since command injection quantity during idling can be estimated to be calculated as roughly fixed value, a microcomputer determines that abnormal output of the rail pressure sensor 7 occurs when a current value of the command injection quantity during idling is calculated as a value clearly different from values calculated in a past. Consequently, abnormal output can be detected at the early stage during idling operation even if abnormal output of the rail pressure sensor 7 occurs either in the high output side or in the low output side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel injection device that injects and supplies fuel to an engine.

  2. Description of the Related Art Conventionally, a fuel injection device has been provided with an operation state amount detection means (hereinafter referred to as a sensor) that detects an operation state amount (for example, fuel pressure accumulated in a common rail, engine speed, etc.) indicating an engine operation state. In addition, a command value of the injection amount by the injector (referred to as a command injection amount) is calculated according to the detected value of the operating state amount, and the injector is controlled based on the calculated command injection amount. For this reason, if the sensor cannot accurately detect the operation state quantity, the fuel injection device cannot appropriately calculate the command injection quantity, and various problems occur.

  For example, if an output abnormality occurs in a rail pressure sensor that detects rail pressure and is one of the sensors, and the rail pressure is detected higher than the true value (that is, if an output abnormality occurs on the high output side) The actual injection amount is smaller than the command injection amount. For this reason, the engine stall or engine output is reduced due to the shortage of the actual injection amount, or the PM accumulation amount is estimated to be larger than the true value, and excessive DPF regeneration processing (for example, excessive post injection) is performed. To do. On the contrary, when the rail pressure is detected lower than the true value, the actual injection amount becomes larger than the command injection amount. For this reason, smoke increases due to an excess of the actual injection amount.

Therefore, various techniques for detecting an output abnormality of the rail pressure sensor at an early stage are considered. For example, the output of the rail pressure sensor to the low output side is determined by determining whether or not the detected value of the rail pressure is within a predetermined range when the engine is started after a lapse of a predetermined time after the engine is stopped. A method for detecting an abnormality is known (see, for example, Patent Document 1). However, according to this technique, an output abnormality to the high output side cannot be detected.
JP 2003-222045 A

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is related to a rail pressure sensor, and an output is output early even if an output abnormality occurs on either the high output side or the low output side. An object of the present invention is to provide a fuel injection device capable of detecting an abnormality.

[Means of Claim 1]
According to a first aspect of the present invention, there is provided an injector for injecting and supplying fuel to an engine, accumulating fuel in a high pressure state, detecting a pressure of fuel accumulated in the common rail, and a common rail distributing to the plurality of injectors. A rail pressure sensor, and a control unit that calculates a command value of an injection amount by the injector according to a detection value by the rail pressure sensor and controls the injector based on the command value of the injection amount.

  Then, if the command value of the injection amount when the engine is idling is defined as the idling command injection amount, the control means can calculate the past value of the idling command injection amount when the engine is idling. Then, the current value of the idling command injection amount is compared, and based on the result of this comparison, it is determined whether or not an abnormality has occurred in the rail pressure sensor.

  In the present invention, when determining whether or not an abnormality has occurred in the rail pressure sensor, attention is paid to a command value (for example, a command value of the injection amount: a command injection amount) calculated to control fuel injection by the injector. To do. Here, the current value of the command injection amount is also calculated to be a substantially constant value in an engine state that repeatedly appears and is considered to exhibit a substantially constant amount of operation state, such as idle operation. It can be predicted.

  Therefore, when the current value of the idling command injection amount is calculated to be a value that is clearly different from the past value, some variation has occurred in the detected value of the operating state quantity that is the basis for calculating the idling command injection amount. Can be judged.

  Then, according to this means, when it is determined that some variation has occurred in the detected value of the operating state quantity as a result of the comparison between the past value and the current value with respect to the command injection quantity at the time of idling, the output is output to the rail pressure sensor. Judge that an abnormality has occurred. For this reason, even if the output abnormality of the rail pressure sensor occurs on either the high output side or the low output side, the output abnormality can be detected at an early stage during idle operation.

  BEST MODE FOR CARRYING OUT THE INVENTION The fuel injection device according to the best mode includes an injector that injects and supplies fuel to an engine, a common rail that accumulates fuel in a high pressure state, and that distributes the fuel to a plurality of injectors, and a rail that detects the pressure of fuel accumulated in the common rail A pressure sensor; and a control unit that calculates a command value of an injection amount by the injector according to a detection value by the rail pressure sensor and controls the injector based on the command value of the injection amount.

  Then, if the command value of the injection amount when the engine is idling is defined as the idling command injection amount, the control means can calculate the past value of the idling command injection amount when the engine is idling. Then, the current value of the idling command injection amount is compared, and based on the result of this comparison, it is determined whether or not an abnormality has occurred in the rail pressure sensor.

[Configuration of Example 1]
The configuration of the fuel injection device 1 according to the first embodiment will be described with reference to FIG.
The fuel injection device 1 injects and supplies fuel to a direct injection type engine 2 such as a diesel engine, for example.

  As shown in FIG. 1, the fuel injection device 1 includes a fuel supply pump 4 that sucks fuel from a fuel tank 3, discharges the sucked fuel at a high pressure, and an injector that injects fuel into a cylinder of the engine 2. 5 and the common rail 6 that accumulates the fuel that has been increased in pressure by the fuel supply pump 4 in a high-pressure state, distributes the accumulated fuel to each injector 5, and the pressure (rail pressure) of the fuel that is accumulated in the common rail 6. A rail pressure sensor 7 and an electronic control unit (ECU) 8 that controls driving of the fuel supply pump 4, the injector 5, and the like are provided.

  The fuel supply pump 4 is rotationally driven by the engine 2 and sucks and discharges fuel from the fuel tank 3, and is driven by the engine 2 to increase the pressure of the fuel discharged from the low-pressure pump. A high-pressure pump (not shown) that discharges to the common rail 6, and a metering valve 9 that is interposed between the low-pressure pump and the high-pressure pump and adjusts the flow rate of fuel discharged to the common rail 6 (referred to as pump discharge amount). .

  Here, the metering valve 9 adjusts the pump discharge amount by varying the opening degree according to a command from the ECU 8. At this time, the ECU 8 gives a command to the metering valve 9 with respect to the rail pressure so that the value detected by the rail pressure sensor 7 substantially matches the command value.

  The injector 5 communicates with the inside of the common rail 6 and has an injection nozzle 10 that injects fuel into the cylinder and an electromagnetic spill valve 11 that drives a valve body (not shown) of the injection nozzle 10. Here, the valve body of the injection nozzle 10 is driven by the balance fluctuation of the force acting in the axial direction to open the injection hole (not shown).

  That is, the urging force based on the pressure of the fuel distributed from the common rail 6 acts on the valve body in each of the valve closing direction and the valve opening direction. When the fuel that exerts pressure on the valve body in the valve closing direction is released to the fuel tank 3 by the operation of the electromagnetic spill valve 11, the urging force acting in the valve closing direction is weakened, and the valve body opens the nozzle hole. .

  The electromagnetic spill valve 11 has a solenoid coil (not shown) that is energized in response to a command from the ECU 8. When this solenoid coil is energized, the fuel that exerts pressure on the valve body in the valve closing direction is released. . The ECU 8 calculates the energization start timing and energization period command values for the solenoid coil. At this time, the ECU 8 calculates a command value (command injection amount) of the injection amount by the injector 5 according to various detection values such as rail pressure, and based on this command injection amount, determines the command value of the energization start timing and the energization period. calculate.

  The common rail 6 functions as a pressure accumulation container that accumulates fuel in a high-pressure state and a distribution container that distributes the accumulated fuel to each injector 5. A relief valve 12 is mounted at one end of the common rail 6 to open the fuel in the common rail 6 to the fuel tank 3 when the command value of the rail pressure decreases.

  Further, a rail pressure sensor 7 is attached to the other end of the common rail 6. Here, the rail pressure is one of the operation state quantities indicating the operation state of the engine 2, and the rail pressure sensor 7 is one of the operation state quantity detecting means (sensor) for detecting the operation state quantity.

  The ECU 8 captures various detection values, calculates various command values, and outputs a control signal based on the calculated command values. The ECU 8 receives a control signal from the microcomputer. A drive circuit (not shown) for supplying power to various actuators such as a solenoid coil of the electromagnetic spill valve 11 is configured.

  The microcomputer is a microcomputer having a well-known structure that includes a CPU that performs control processing and arithmetic processing, a storage device such as a ROM and RAM that stores various control programs and data, an input device, an output device, and the like. Then, the microcomputer takes in detection values from the rail pressure sensor 7 and other various sensors, and calculates a command value such as a command injection amount based on the taken-in detection values.

  The various sensors other than the rail pressure sensor 7 include an accelerator opening sensor 16 that detects the accelerator opening, an engine speed sensor 17 that detects the engine speed, a water temperature sensor 18 that detects the cooling water temperature of the engine 2, A fuel temperature sensor 19 for detecting the temperature of the fuel. That is, the accelerator opening, the engine speed, the cooling water temperature of the engine 2 and the fuel temperature are operating state quantities, and the accelerator opening sensor 16, the engine speed sensor 17, the water temperature sensor 18 and the fuel temperature sensor 19 are operated. It is a sensor that detects a state quantity.

  Then, if the command injection amount when the engine 2 is idling is defined as the idling command injection amount, the microcomputer can calculate the past value of the idling command injection amount when the engine 2 is idling, A comparison is made with the current value of the idling command injection amount, and based on the result of this comparison, it is determined whether or not an abnormality has occurred in the rail pressure sensor 7 among the various sensors.

  That is, according to the fuel injection device 1 of the present embodiment, when determining whether or not an abnormality has occurred in the rail pressure sensor 7, attention is paid to the idling command injection amount. Here, the command injection amount is also calculated to be a substantially constant value in an operation state in which the engine 2 appears repeatedly and the operation state amount is considered to exhibit a substantially constant value, such as idle operation. It can be predicted.

  If the current value of the idle command injection amount is calculated to be clearly different from the past value, the microcomputer determines that the idle state command injection amount is the basis of calculation of the idle command injection amount. It is determined that some variation has occurred in the detected value of the rail pressure. That is, the microcomputer determines that an output abnormality has occurred in the rail pressure sensor 7 when the current value is calculated to be clearly different from the past value for the command injection amount during idling.

[Control Method of Example 1]
A control method by the fuel injection device 1 according to the first embodiment will be described with reference to a flowchart shown in FIG.
First, in step S1, it is determined whether or not the engine 2 is idling. In step S1, for example, it is determined that the engine 2 is idling when the engine speed is equal to or lower than a predetermined value and the vehicle speed is zero. If it is determined that the engine 2 is idling (YES), the process proceeds to step S2, and if it is determined that the engine 2 is not idling (NO), this control process is terminated.

  In step S2, the current value of the idling command injection amount is stored. Here, various modes can be considered for the current value of the stored command injection amount during idling. For example, the moving average value of the latest idling command injection amount may be the current value of the idling command injection amount (referred to as aspect 1), and all the idling command injection amounts calculated after the start of the current idling operation. May be used as the current value of the idling command injection amount (referred to as aspect 2), and the maximum value of all the idling command injection amounts calculated after the start of the current idling operation is used as the idling command injection amount. It is good also as a present value (it is set as aspect 3).

  In step S3, it is determined whether the pump discharge amount is within a predetermined range. In step S3, the determination is made using, for example, a command value for the pump discharge amount. The command value for the pump discharge amount is calculated to control the opening of the metering valve 9.

  Next, in step S4, whether or not the difference ΔQi between the current value and the past value in the command injection amount during idling is within a predetermined range, that is, the difference ΔQi is smaller than the upper limit value α and the lower limit value − It is judged whether it is larger than β.

  Here, the upper limit value α is a predetermined threshold value indicating a positive number, and the lower limit value −β is a predetermined threshold value indicating a negative number. The upper limit value α and the lower limit value −β are set by adding an output absorption value due to a vehicle load such as an air conditioner or an alternator to an allowable value for the difference ΔQi. In other words, the upper limit value α and the lower limit value −β are set in consideration of the vehicle load so that the output abnormality of the sensor is not affected by the output absorption of the vehicle load.

  Here, various modes of the difference ΔQi are conceivable depending on the mode of the current value of the idling command injection amount stored in step S2. For example, in the case of aspect 1, the difference between the moving average value of the latest idle command injection amount at the time of the current control process and the moving average value of the latest idle command injection amount at the time of the previous control process is also set as the difference ΔQi. Good. Further, in the case of aspect 2, the difference between the average value of all the idle command injection amounts calculated after the start of the current idle operation and the average value of all the idle command injection amounts calculated in the previous idle operation. May be the difference ΔQi. Further, in the case of the aspect 3, the difference between the maximum value of all the idling command injection amounts calculated after the start of the present idling operation and the maximum value of all the idling command injection amounts calculated in the previous idling operation. May be the difference ΔQi.

  If it is determined in step S4 that the difference ΔQi is smaller than the upper limit value α and larger than the lower limit value −β (YES), this control process is terminated, and the difference ΔQi is equal to or larger than the upper limit value α or the lower limit value −. If it is determined that it is equal to or less than β (NO), the process proceeds to step S5, and an abnormal measure such as turning on a diagnostic lamp is performed.

[Operation of Example 1]
The operation of the fuel injection device 1 according to the first embodiment will be described by exemplifying a case where an output abnormality has occurred in the rail pressure sensor 7 as shown in FIG.

  For example, when the output of the rail pressure sensor 7 with respect to the true value of the rail pressure fluctuates to the high output side, the actual injection amount at idling becomes smaller than the command injection amount at idling, so the engine output decreases. For this reason, the microcomputer largely calculates the idling command injection amount in order to compensate for the decrease in the engine output. Therefore, the difference ΔQi becomes larger than before the output of the rail pressure sensor 7 changes to the high output side. As a result, when the difference ΔQi is greater than or equal to the upper limit value α, it is determined that an output abnormality has occurred in the rail pressure sensor 7.

  Further, when the output of the rail pressure sensor 7 with respect to the true value of the rail pressure fluctuates to the low output side, the actual injection amount at idling becomes larger than the command injection amount at idling, so the engine output increases. Therefore, the microcomputer calculates the idling command injection amount to be small in order to suppress the increase in engine output. Therefore, the difference ΔQi is smaller than before the output of the rail pressure sensor 7 changes to the low output side. As a result, when the difference ΔQi becomes equal to or lower than the lower limit value −β, it is determined that an output abnormality has occurred in the rail pressure sensor 7.

[Effect of Example 1]
According to the fuel injection device 1 of the first embodiment, the microcomputer compares the past value of the idling command injection amount with the current value of the idling command injection amount when the engine 2 is idling. Based on the comparison result, it is determined whether or not an output abnormality has occurred in the rail pressure sensor 7.
It can be predicted that the idling command injection amount is calculated to be a substantially constant value. Therefore, the fuel injection device 1 detects the operating state amount detection value that is a basis for calculating the idle command injection amount when the current value is calculated to be clearly different from the past value with respect to the command injection amount at idle. It is judged that some fluctuation has occurred. When the fuel injection device 1 determines that some variation has occurred in the detected value of the operating state quantity, the fuel injection device 1 determines that an output abnormality has occurred in the rail pressure sensor 7. For this reason, even if the output abnormality of the rail pressure sensor 7 occurs on either the high output side or the low output side, the output abnormality of the rail pressure sensor 7 can be detected at an early stage during idle operation.

It is explanatory drawing which shows the structure of a fuel-injection apparatus. It is a flowchart which shows the control processing by a fuel-injection apparatus. It is a correlation diagram of the true value of rail pressure, and the output of a rail pressure sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel injection apparatus 2 Engine 5 Injector 6 Common rail 7 Rail pressure sensor 8 Electronic control unit, ECU (control means)

Claims (1)

An injector that injects fuel into the engine;
A common rail for accumulating fuel in a high-pressure state and distributing the fuel to a plurality of the injectors;
A rail pressure sensor for detecting the pressure of the fuel accumulated in the common rail;
In a fuel injection device comprising: a control means for calculating a command value of an injection amount by the injector according to a detection value by the rail pressure sensor and controlling the injector based on the command value of the injection amount;
When the command value of the injection amount when the engine is idling is defined as an idle command injection amount,
The control means includes
When the engine is idling, the past value of the idling command injection amount is compared with the current value of the idling command injection amount,
A fuel injection device that determines whether or not an abnormality has occurred in the rail pressure sensor based on a result of the comparison.

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