JP6498000B2 - Pressure sensor failure diagnosis method and common rail fuel injection control device - Google Patents

Description

  The present invention relates to a failure diagnosis of a pressure sensor that detects a rail pressure in a common rail fuel injection control device, and more particularly to a device that improves diagnosis speed and reliability.

In the so-called common rail fuel injection control device, the pressure sensor is indispensable for detecting the actual rail pressure required in the rail pressure control, and its failure has a great influence on the rail pressure control. Various diagnostic methods and devices have been proposed and put into practical use.
For example, the detection signal of the pressure sensor is obtained in a state where it is determined that the fuel pressure of the common rail has decreased to atmospheric pressure, the fuel pressure corresponding to the detection signal is calculated, and the calculated fuel pressure and atmospheric pressure are calculated. A method called a so-called offset test for determining that the pressure sensor has failed when the difference between the two is greater than or equal to a predetermined value has been proposed (see, for example, Patent Document 1).

JP 2007-242332 A (page 3-6, FIG. 1 to FIG. 2)

  However, since the execution timing of the offset test described above is limited when the vehicle operation starts or when the vehicle operation is stopped, the occurrence of a pressure sensor failure during vehicle travel is detected without delay as much as possible. However, there is a problem that it is not quick and responsive.

  The present invention has been made in view of the above circumstances, and provides a pressure sensor failure diagnosis method and a common rail fuel injection device capable of diagnosing the presence or absence of a pressure sensor failure with as little delay as possible. It is.

In order to achieve the object of the present invention, a pressure sensor failure diagnosis method according to the present invention comprises:
The fuel in the fuel tank is pressurized and pumped to the common rail by a high pressure pump, and high pressure fuel can be injected into the internal combustion engine via a fuel injection valve connected to the common rail. A pressure sensor failure diagnosis method in a common rail fuel injection control device configured to be controllable based on a detection signal of a pressure sensor for detecting pressure,
Measure the fuel injection time of each of the fuel injection valves, and diagnose that the pressure sensor is faulty or abnormal when all of the measured fuel injection times are outside the predetermined standard injection time range It is comprised so that it may do.
In order to achieve the above object of the present invention, a common rail fuel injection control device according to the present invention includes:
The fuel in the fuel tank is pressurized and pumped to the common rail by a high pressure pump, and high pressure fuel can be injected into the internal combustion engine via an injector connected to the common rail, and the pressure of the common rail is controlled by the electronic control unit. A common rail fuel injection control device configured to be controllable based on a detection signal of a pressure sensor that detects a pressure of a common rail,
The electronic control unit is
The fuel injection time of each of the fuel injection valves is measured, it is determined whether all of the measured fuel injection times are outside a predetermined standard injection time range, and all of the fuel injection times are determined to be a predetermined standard. When it is determined that it is out of the injection time range, the pressure sensor is configured to be diagnosed as malfunctioning or abnormal.

According to the present invention, since the presence or absence of a pressure sensor failure can be diagnosed using the fuel injection time of the fuel injection valve, the execution of the diagnosis is limited to a specific timing or a specific operating condition unlike the conventional case. Therefore, it is possible to know the occurrence of a failure as much as possible, and as a result, it is possible to respond quickly and contribute to ensuring the reliability and safety of the operation of the apparatus.
Also, unlike conventional systems, the output level of the pressure sensor does not fundamentally affect the stability and certainty of failure diagnosis, providing a more accurate and stable failure diagnosis than in the past. be able to.

It is a block diagram which shows the structural example of the common rail type fuel-injection control apparatus to which the pressure sensor failure diagnostic method in embodiment of this invention is applied. It is a subroutine flowchart which shows the procedure of the pressure sensor fault diagnosis process performed in the common rail type fuel-injection control apparatus in embodiment of this invention. FIG. 3A is a schematic diagram for explaining the relative relationship between the energization of the fuel injection valve and the displacement of the nozzle needle, and FIG. 3A is a schematic diagram schematically showing the change waveform of the energization current of the fuel injection valve. ) Is a schematic view schematically showing the displacement of the nozzle needle of the fuel injection valve.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3.
The members and arrangements described below do not limit the present invention and can be variously modified within the scope of the gist of the present invention.
First, a configuration example of a common rail fuel injection control device to which a pressure sensor failure diagnosis method according to an embodiment of the present invention is applied will be described with reference to FIG.
The common rail fuel injection control device includes a high pressure pump device 50 that pumps high pressure fuel, a common rail 1 that stores the high pressure fuel pumped by the high pressure pump device 50, and high pressure fuel supplied from the common rail 1 to the engine 3. A plurality of fuel injection valves 2-1 to 2-n that inject and supply to the cylinders, and an electronic control unit (indicated as “ECU” in FIG. 1) 4 for executing fuel injection control processing, rail pressure control processing described later, and the like Is the main component.
Such a configuration itself is the same as the basic configuration of this type of fuel injection control apparatus that has been well known.

The high-pressure pump device 50 has a known and well-known configuration in which the supply pump 5, the metering valve 6, and the high-pressure pump 7 are configured as main components.
In this configuration, the fuel in the fuel tank 9 is pumped up by the supply pump 5 and supplied to the high-pressure pump 7 through the metering valve 6. As the metering valve 6, an electromagnetic proportional control valve is used, and the amount of energization is controlled by the electronic control unit 4, so that the flow rate of fuel supplied to the high-pressure pump 7, in other words, the discharge of the high-pressure pump 7. The amount is to be adjusted.

A return valve 8 is provided between the output side of the supply pump 5 and the fuel tank 9 so that surplus fuel on the output side of the supply pump 5 can be returned to the fuel tank 9. .
The supply pump 5 may be provided separately from the high-pressure pump device 50 on the upstream side of the high-pressure pump device 50 or may be provided in the fuel tank 9.
The fuel injection valves 2-1 to 2-n are provided for each cylinder of the engine 3, and are supplied with high-pressure fuel from the common rail 1, and perform fuel injection by injection control by the electronic control unit 4. Yes.

The common rail 1 of the present invention is provided with a pressure control valve 12 by an electromagnetic proportional control valve in a return passage (not shown) for returning surplus high-pressure fuel to the tank 9, and controls the rail pressure together with the metering valve 6. To be used.
In the embodiment of the present invention, appropriate rail pressure control can be realized by appropriately changing the operation states of the metering valve 6 and the pressure control valve 12 in accordance with the operation state of the engine 3. It has become.

The electronic control unit 4 has, for example, a microcomputer (not shown) having a known and well-known configuration, a storage element (not shown) such as a RAM and a ROM, and a fuel injection valve 2- A drive circuit (not shown) for driving 1 to 2-n and an energization circuit (not shown) for energizing the metering valve 6 and the pressure control valve 12 are configured as main components. It has become a thing.
In addition to the detection signal of the pressure sensor 11 that detects the pressure of the common rail 1 being input to the electronic control unit 4, various detection signals such as the engine speed, the accelerator opening degree, and the fuel temperature are received from the engine 3. It is input for use in operation control and fuel injection control.
Such a configuration itself is the same as the basic configuration of this type of common rail fuel injection control device that has been conventionally known.

Next, the procedure of the pressure sensor failure diagnosis process executed by the electronic control unit 4 in the embodiment of the present invention will be described with reference to FIG.
When the processing by the electronic control unit 4 is started, it is determined whether or not the fuel injection system is operating stably (see step S102 in FIG. 2).
That is, it is determined whether or not the fuel injection control operation is in a stable state. It is preferable to determine which operating state is stable based on the test results and simulation results in consideration of the specific specifications of the common rail fuel injection control device and the specific specifications of the vehicle.

For example, so-called PID control is normally used in rail pressure control in a common rail fuel injection control device. Whether or not the control state of the PID control is stable is determined whether or not the fuel injection control operation is stable. One of the indicators can be considered. That is, specifically, whether or not the change amount of the rail pressure per unit time in the PID control is within a predetermined range, and when the change amount of the rail pressure is within the predetermined range, It is assumed to be in a stable state.
It should be noted that it is preferable to make a comprehensive determination using a plurality of determination indexes rather than relying on one determination index for determining whether the fuel injection control operation is stable.
For example, it is also preferable to consider the determination conditions such as whether the target injection amount or the target rail pressure is an abnormal instruction value, or whether the change amount does not exceed a predetermined change amount.

  Therefore, if it is determined in step S102 that the fuel injection control operation is stable (in the case of YES), the process proceeds to step S104 described below, while the fuel injection control operation is not stable. If it is determined (NO), a series of processes are terminated and the process returns to the main routine (not shown) because it is not in a state suitable for executing the subsequent processes.

In step S104 and step S106, the fuel injection times of the fuel injection valves 2-1 to 2-n are sequentially measured.
That is, the fuel injection times of the fuel injection valves 2-1 to 2-n are respectively measured in accordance with a predetermined measurement order (see step S104 in FIG. 2), and every fuel injection valve 2- It is determined whether or not the fuel injection times 1 to 2-n have been measured (see step S106 in FIG. 2). If it is determined that all fuel injection times have not yet been measured (in the case of NO), the next measurement order is performed. When it is determined that the fuel injection time of all the fuel injection valves 2-1 to 2-n has been measured while the process of step S104 is executed for the corresponding fuel injection valves 2-1 to 2-n (YES) In the case), the process proceeds to step S108 described below.

In step S108, it is determined whether or not any of the fuel injection times measured for each of the fuel injection valves 2-1 to 2-n is outside a predetermined standard injection time range.
Here, the fuel injection time is a time during which fuel is injected by the fuel injection valves 2-1 to 2-n. As a specific method for defining the fuel injection time, the fuel injection start time and the fuel Depending on how to grasp the end point of injection, it is possible to adopt two types of regulations as described below. In the pressure sensor failure diagnosis method according to the embodiment of the present invention, which of the two fuel injection times is taken is arbitrary, and is not limited to either one.

One of the specific ways of specifying the fuel injection time is to specify the time from the start of energization to the solenoid valves of the fuel injection valves 2-1 to 2-n to the closing of the nozzle (sitting of the nozzle needle). It is way.
Here, the timing of the start of energization is grasped in the fuel injection control process that is executed in the electronic control unit 4 as in the conventional case, and does not need to be acquired again in step S108, but is acquired in the fuel injection control process. It is enough to divert.

  In addition, the timing at which the nozzles are closed, that is, the acquisition of when the nozzle needles (not shown) of the fuel injection valves 2-1 to 2-n are seated on the valve seat (not shown) has been well known in the past. It is possible to use a specific method, and it is not necessary to be limited to a specific method. It is arbitrarily selected in consideration of the specific specification of the vehicle, the specific specification of the common rail fuel injection control device, etc. It should be.

  As a conventionally well-known method of knowing the valve closing timing, for example, there is a method of detecting the displacement of the nozzle needle with a piezoelectric element and acquiring the valve closing time (valve closing timing) (for example, a special feature). Table 2013-542373 gazette). In addition, if it supplements about the acquisition method of the valve closing timing using the displacement of this nozzle needle, this method will assist the seating and separation of the nozzle needle on the valve seat, so that the end of the nozzle needle seated on the valve seat A change in pressure in a control chamber formed so that inflow and outflow of high-pressure fuel can be controlled in the vicinity of the end portion on the opposite side of the portion is detected by a piezoelectric element. That is, at the stage where the nozzle needle immediately before closing the valve is descending toward the valve seat, the fuel is discharged from the nozzle, so that the pressure in the control chamber is almost constant. After that, when the nozzle needle is seated on the valve seat and closed, fuel is no longer injected from the nozzle, so that the pressure in the control chamber rises and is displaced in the axial direction of the nozzle needle according to the change in pressure in the control chamber. The timing at which the nozzle needle is seated on the valve seat and closed is detected as the valve closing timing by detecting the difference in the pressing force on the piezoelectric element by the columnar member provided as possible. Yes.

Next, the second method of defining the fuel injection time is a method of defining the time from nozzle opening to valve closing.
Here, the valve opening timing can be grasped as described below.
FIG. 3 schematically shows an energization current waveform when energization is performed for fuel injection by the fuel injection valves 2-1 to 2-n (see FIG. 3A), and at that time FIGS. 3A and 3B schematically show the displacement of the nozzle needle (see FIG. 3B), and the timing for opening the nozzle will be described below with reference to FIG.
First, the nozzle needle normally has electrical characteristics of the individual fuel injection valves 2-1 to 2-n from the time of starting energization of the fuel injection valves 2-1 to 2-n (see FIG. 3A). Ascending starts at a time delayed by a certain time T determined by, and this delay time T can be grasped in advance by a test or simulation.
Generally, since the nozzle opening timing coincides with the fuel injection start timing, the valve opening timing is acquired in advance as described above, stored in an appropriate storage area of the electronic control unit 4, and used for calculating the fuel injection time. be able to.

The standard injection time range is a time range in which the fuel injection time can be determined to be a normal value in consideration of variations in characteristics of the fuel injection valves 2-1 to 2-n, deterioration, and the like.
The appropriate range of the standard injection time range varies depending on the fuel injection amount and the rail pressure. In other words, there is a certain relative relationship between the standard injection time range, the fuel injection amount, and the rail pressure, and the specific values are specific specifications of the vehicle and specific specifications of the common rail fuel injection control device. It is preferable to determine based on test results and simulation results in consideration of specifications.

  In the embodiment of the present invention, the upper limit value of the standard injection time range is defined as the standard maximum injection time for convenience, and the lower limit value of the standard injection time range is defined as the standard minimum injection time for convenience. The standard injection time range is determined by reading appropriate values as the standard maximum injection time and the standard minimum injection time from the preset standard injection time readout map each time when executing step S108. .

  That is, the standard injection time read-out map is an appropriate standard minimum injection time and standard maximum injection selected based on test results, simulation results, etc., for various combinations of target fuel injection amounts and target rail pressures. The time is configured to be readable by inputting the target fuel injection amount and the target rail pressure, and is stored and held in an appropriate storage area of the electronic control unit 4 so that it can be used in the execution of the process of step S108. It is.

The target fuel injection amount and the target rail pressure are calculated and calculated in the fuel injection control process that is separately executed in the electronic control unit 4 as in the prior art. Therefore, in step S108, it is not necessary to calculate and calculate again, and the values calculated in the fuel injection control process may be used for reading the standard minimum injection time and the standard maximum injection time according to the above map. is there.
Also, instead of the standard injection time readout map as described above, an arithmetic expression for calculating the standard minimum injection time and the standard maximum injection time according to the target fuel injection amount and the target rail pressure is set and used. Even so, it is preferable.

  Therefore, in step S108, the fuel injection time of each of the fuel injection valves 2-1 to 2-n is outside the standard injection time range, that is, exceeds the standard minimum injection time, and If it is determined that the pressure is not within the range below the standard maximum injection time (in the case of YES), it is diagnosed that the pressure sensor 11 is faulty (or abnormal) (see step S110 in FIG. 2), and a series of processing ends. Then, the process returns to the main routine (not shown).

  As described above, when the fuel injection times of all the fuel injection valves 2-1 to 2-n are out of the standard injection time range, the reason why the pressure sensor 11 can be diagnosed as a failure or abnormality is usually It is rare that the fuel injection time of all of the fuel injection valves 2-1 to 2-n is out of the standard injection time range almost at the same time, or an abnormal operation state, rather than a pressure sensor. As a result of failure or an abnormal state 11, an inappropriate rail pressure is detected, and a target injection amount is calculated based on the inappropriate detected rail pressure, and fuel injection control is executed based on the calculated result. As a result, it is considered that it is reasonable to infer that the fuel injection time of all the fuel injection valves 2-1 to 2-n exceeds the original range.

  In the main routine (not shown), when the pressure sensor 11 is diagnosed as malfunctioning or abnormal, alarm processing such as lighting of the display element or ringing of the ringing element is executed as in the prior art, step S110. On the basis of the diagnosis result, a predetermined alarm process is executed.

On the other hand, if it is determined in step S108 that the fuel injection times of the fuel injection valves 2-1 to 2-n are not outside the standard injection time range (in the case of NO), in other words, For example, when the fuel injection time of any of the fuel injection valves is within the standard injection time range, or when the fuel injection times of all the fuel injection valves are within the standard injection time range, the pressure sensor 11 is normal. (See step S112 in FIG. 2), a series of processing is terminated, and the process once returns to the main routine (not shown).
It can be considered that a fuel injection valve whose fuel injection time is outside the standard injection time range is highly likely to be in a malfunction or abnormal state.
In this way, for those that are determined to be abnormal based on the diagnostic results of the individual fuel injection valves, alarm processing is performed by turning on the warning lamp or ringing the ringing element while limiting the torque by reducing the injection amount. It is also possible to perform.

  The present invention can be applied to a common rail fuel injection control device in which a quick and highly accurate failure diagnosis of a pressure sensor is desired.

DESCRIPTION OF SYMBOLS 1 ... Common rail 2-1-2-n ... Fuel injection valve 4 ... Electronic control unit 11 ... Pressure sensor 12 ... Pressure control valve

Claims (8)

The fuel in the fuel tank is pressurized and pumped to the common rail by a high pressure pump, and high pressure fuel can be injected into the internal combustion engine via a fuel injection valve connected to the common rail. A pressure sensor failure diagnosis method in a common rail fuel injection control device configured to be controllable based on a detection signal of a pressure sensor for detecting pressure,
Measure the fuel injection time of each of the fuel injection valves, and diagnose that the pressure sensor is faulty or abnormal when all of the measured fuel injection times are outside the predetermined standard injection time range If the measured fuel injection time is outside the predetermined standard injection time range, the fuel injection valve measured outside the standard injection time range has failed or is abnormal. A pressure sensor failure diagnosis method, characterized by diagnosing the presence.   2. The pressure sensor failure diagnosis method according to claim 1, wherein the fuel injection time is a time from a start of energization to the fuel injection valve to a closing of a nozzle of the fuel injection valve.   The pressure sensor failure diagnosis method according to claim 1, wherein the fuel injection time is a time from opening to closing of a nozzle of the fuel injection valve.   The pressure sensor failure diagnosis method according to claim 2, wherein the standard injection time range is determined based on a relative relationship between a target injection amount and a target rail pressure. The fuel in the fuel tank is pressurized and pumped to the common rail by the high-pressure pump, and the high-pressure fuel can be injected into the internal combustion engine via the fuel injection valve connected to the common rail, and the pressure of the common rail is controlled by the electronic control unit. A common rail fuel injection control device configured to be controllable based on a detection signal of a pressure sensor that detects the pressure of the common rail,
The electronic control unit is
The fuel injection time of each of the fuel injection valves is measured, it is determined whether all of the measured fuel injection times are outside a predetermined standard injection time range, and all of the fuel injection times are determined to be a predetermined standard. When it is determined that it is outside the injection time range, the pressure sensor is diagnosed as malfunctioning or abnormal, and it is determined that a part of the fuel injection time is outside the predetermined standard injection time range. In this case, the common rail fuel injection control device is configured to diagnose that the fuel injection valve whose fuel injection time outside the standard injection time range is measured is faulty or abnormal .   The said electronic control unit is comprised so that the time from the energization start to the said fuel injection valve to the valve closing of the nozzle of the said fuel injection valve may be measured as said fuel injection time. The common rail fuel injection control device described.   6. The common rail fuel injection control according to claim 5, wherein the electronic control unit is configured to measure a time from the opening to the closing of the nozzle of the fuel injection valve as the fuel injection time. apparatus. The electronic control unit is
8. The common rail fuel injection control device according to claim 6, wherein the standard injection time range is set based on a relative relationship between a target injection amount and a target rail pressure. .

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