JP5804639B2 - Fuel leak detection method and common rail fuel injection control device - Google Patents

Description

  The present invention relates to a method for detecting fuel leakage in a common rail fuel injection control apparatus, and more particularly to a method for improving reliability and the like.

As a conventional method of this type, for example, a method of determining a failure of a high-pressure pump or the like when the detected value of the pressure sensor that detects the pressure of the common rail does not exceed a predetermined value during a predetermined time from the start of the engine Have been proposed and put to practical use (see, for example, Patent Document 1).
As another conventional method, for example, there is a method in which a failure occurs when the actual rail pressure detected by the pressure sensor is lower than the command rail pressure and the command discharge amount of the high pressure pump becomes maximum. .

JP 2006-29098 A (page 4-7, FIGS. 1 to 5)

However, the above-described conventional method has a problem in that it cannot detect an abnormality or failure in a subsequent use state because it detects an abnormality or failure in a predetermined time when the engine is started.
In the latter conventional method, the change in rail pressure when a fuel leak occurs in the high pressure circuit and the change in rail pressure when a low pressure system failure such as filter clogging occurs are substantially the same. There is a problem that it is not possible to distinguish between the fuel leakage and low-pressure system troubles such as filter clogging.

  The present invention has been made in view of the above circumstances, and provides a fuel leak detection method and a common rail fuel injection control device that can detect a failure by distinguishing between a fuel leak in a high pressure circuit and a fault in a low pressure system. is there.

In order to achieve the above object of the present invention, a fuel leak detection method according to the present invention comprises:
Fuel in the fuel tank is pressurized and pumped to a common rail by a high-pressure pump, enabling high-pressure fuel injection to the engine via a fuel injection valve connected to the common rail, and a metering valve upstream of the high-pressure pump And a fuel leakage detection method in a common rail fuel injection control device, wherein the metering valve is driven and controlled by an electronic control unit so that the rail pressure of the common rail can be controlled.
When the actual rail pressure is lower than the command rail pressure and the command discharge amount to the high pressure pump is at the maximum discharge amount, and the command discharge amount to the high pressure pump is reduced, the actual rail pressure is reduced. When a drop occurs, it is configured to determine that the fuel leaks from the high-pressure circuit.
In order to achieve the above object of the present invention, a common rail fuel injection control device according to the present invention includes:
Fuel in the fuel tank is pressurized and pumped to a common rail by a high-pressure pump, enabling high-pressure fuel injection to the engine via a fuel injection valve connected to the common rail, and a metering valve upstream of the high-pressure pump However, a pressure control valve is provided on the downstream side of the high-pressure pump, and the common rail is configured to control the rail pressure of the common rail by driving and controlling the metering valve and the pressure control valve by an electronic control unit. Fuel injection control device,
The electronic control unit is
It is determined whether or not the actual rail pressure is lower than the indicated rail pressure and the indicated discharge amount for the high pressure pump is maintained at the maximum discharge amount, the actual rail pressure is lower than the indicated rail pressure, and the When it is determined that the command discharge amount for the high-pressure pump is maintained at the maximum discharge amount, the command discharge amount for the high-pressure pump is reduced, and it is determined that the actual rail pressure has decreased. In such a case, it is determined that the fuel leakage from the high-pressure circuit has occurred.

  According to the present invention, it is possible to determine the fuel leakage of the high-pressure circuit of the common rail fuel injection control device and the failure of the low-pressure system by a simple method, so that it is possible to take an appropriate measure and further improve the device. There is an effect that safety and reliability can be improved.

It is a block diagram which shows the structural example of the common rail type | mold fuel-injection control apparatus in embodiment of this invention. It is a subroutine flowchart which shows the procedure of the fuel leak detection process performed by the electronic control unit which comprises the common rail type | mold fuel-injection control apparatus shown by FIG. Relation between current flow of normal open type metering valve and discharge amount of high pressure pump when fuel leakage of high pressure circuit occurs, and current flow of metering valve and high pressure pump when low pressure system malfunction occurs It is a general | schematic characteristic diagram which shows the relationship with the discharge amount. Relationship between current flow of normal close type metering valve and discharge amount of high-pressure pump when fuel leakage of high-pressure circuit occurs, and current flow of metering valve and high-pressure pump when malfunction of low-pressure system occurs It is a general | schematic characteristic diagram which shows the relationship with the discharge amount.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 4.
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, the common rail fuel injection control device shown in FIG. 1 will be described.
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 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 are configured as main components. .
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.

FIG. 2 shows a subroutine flowchart showing the procedure of the fuel leak detection process executed by the electronic control unit 4. Hereinafter, the fuel leak detection process in the embodiment of the present invention will be described with reference to FIG. explain.
The fuel leak detection process shown in FIG. 2 is performed as one of the subroutine processes while the electronic control unit 4 executes various controls such as the conventional rail pressure control as outlined above. It is supposed to be executed.

Thus, when the processing by the electronic control unit 4 is started, the actual rail pressure (actual pressure) of the common rail 1 detected by the pressure sensor 11 is determined based on the accelerator opening, the engine speed, and the like. It is determined whether or not it is lower than the command rail pressure (command pressure) calculated in the rail pressure control process by (see step S102 in FIG. 2).
When it is determined in step S102 that the actual pressure is lower than the command pressure (in the case of YES), the process proceeds to the process of step S104 described below, while the actual pressure is determined not to be lower than the command pressure. In this case (in the case of NO), a series of processing is terminated because it is not a failure state, and the process returns to the main routine once.

In step S104, it is determined whether the pump command discharge amount for the high pressure pump 7 calculated in the rail pressure control process of the electronic control unit 4 has reached the maximum discharge amount of the high pressure pump 7, and the pump command discharge amount is determined. When it is determined that the maximum discharge amount of the high-pressure pump 7 has not been reached (in the case of NO), a series of processing is terminated and it is temporarily returned to the main routine because it is not a failure state.
On the other hand, if it is determined in step S104 that the pump instruction discharge amount has reached the maximum discharge amount of the high-pressure pump 7 (in the case of YES), whether or not the state has been maintained beyond the reference time Ts. Is determined (see step S106 in FIG. 2). In step S106, “T” is an elapsed time after the pump instruction discharge amount reaches the maximum discharge amount of the high-pressure pump 7. For example, in the electronic control unit 4, a well-known time-programming program It is timed by execution.

Therefore, in step S106, when it is determined that the state in which the maximum discharge amount of the high-pressure pump 7 has reached the reference time Ts has not been maintained (in the case of NO), a series of processing is determined as not being a failure state. Is terminated and the process returns once to the main routine.
On the other hand, if it is determined in step S106 that the state in which the maximum discharge amount of the high-pressure pump 7 has reached has been maintained beyond the reference time Ts (in the case of YES), the pump instruction discharge amount is reduced. (See step S108 in FIG. 2).
Specifically, if the metering valve 6 is configured to be in a so-called normal open state in which the valve is open when no current is supplied, in that case, the current supply is increased. As a result, the pump command discharge amount is reduced.
When the metering valve 6 has a so-called “normally closed” configuration, the energization current is reduced to reduce the pump command discharge amount.

  Next, it is determined whether or not a decrease in the actual rail pressure detected by the pressure sensor 11 has occurred due to the reduction in the pump command discharge amount (see step S110 in FIG. 2), and it is determined that a decrease in the actual rail pressure has occurred. If this is the case (in the case of YES), it is determined that an error state (failure state) in which high-pressure circuit fuel leakage has occurred (see step S112 in FIG. 2) and the engine has been stopped (step in FIG. 2). S114), a series of processing is completed, and the process once returns to a main routine (not shown).

  On the other hand, if it is determined in step S110 that the actual rail pressure has not decreased (in the case of NO), an error state is caused due to a defective part or the like in the low-pressure system (see step S116 in FIG. 2). A warning process is executed (see step S118 in FIG. 2), a series of processes are terminated, and the process once returns to a main routine (not shown).

Here, as described above, by determining whether or not the actual rail pressure has decreased after the pump command discharge amount has been lowered, it is possible to determine whether the high pressure circuit has failed or the low pressure system has failed. This will be described with reference to FIG.
First, in FIG. 3, the horizontal axis represents the energization current I of the metering valve 6, and the vertical axis represents the discharge amount Q of the high-pressure pump 7. It is assumed that the metering valve 6 is a so-called normally open valve.
The above-mentioned failure determination is possible because the inventors of the present invention have conducted intensive tests and studies, and as a result, a failure in the high-pressure circuit, that is, some failure (for example, fuel leakage) has occurred from the discharge side to the downstream side of the high-pressure pump 7. In the case where there is a failure in the low pressure system, that is, the upstream side of the input side of the high pressure pump 7 (for example, filter clogging, filter waxing, air mixing, etc.), the energizing current I of the metering valve 6 is changed. This is based on the finding that the change in the pump discharge amount is different.

  That is, in the case of a failure of the high-pressure circuit, the discharge amount (required discharge amount) required for the high-pressure pump 7 is the sum of the fuel consumption in the fuel injection valves 2-1 to 2-n and the fuel leakage. However, the required discharge amount exceeds the maximum discharge amount Qa of the high-pressure pump 7. Therefore, even if the energization current I of the metering valve 6 is lowered and the discharge amount of the high pressure pump 7 is set to the maximum discharge amount Qa, the fuel amount discharged to the high pressure circuit by the high pressure pump 7 is insufficient with respect to the required discharge amount. The actual rail pressure does not reach the indicated rail pressure.

  For this reason, when there is some failure in the high-pressure circuit, more specifically, as a most typical example, when the fuel leakage occurs, the discharge amount of the high-pressure pump 7 with respect to the change in the energization current I of the metering valve 6 The change is that the discharge amount becomes the maximum discharge amount Qa of the high-pressure pump 7 until the energization current I is zero to a certain current value, and when the current value increases beyond a certain current value, the discharge amount becomes zero as the current value increases. (Refer to the solid characteristic line in FIG. 3).

On the other hand, if any failure occurs in the low-pressure system, the high-pressure pump 7 that requires a discharge amount of the fuel consumed by the fuel injection valves 2-1 to 2-n has a fuel suitable for it. Therefore, even if the energizing current I of the metering valve 6 is decreased, the discharge amount of the high-pressure pump 7 is insufficient and does not reach the maximum discharge amount Qa.
For this reason, when some failure occurs in the low-pressure system, the change in the discharge amount of the high-pressure pump 7 with respect to the change in the energization current I of the metering valve 6 is as follows. When the value Qb is smaller than the maximum discharge amount Qa of the high-pressure pump 7 (see the characteristic line of the two-dot chain line and the characteristic line of the solid line in FIG. 3) and the current value increases beyond a certain current value, As in the case of a failure, the discharge amount decreases toward zero as the current value increases (see the solid characteristic line in FIG. 3).

  Due to the difference in the change characteristics, for example, when the high pressure circuit is out of order, the energization current I of the metering valve 6 is shown in FIG. When the value of the characteristic line discharge amount constant region (for example, I1 in FIG. 3) is changed to a value (for example, I2 in FIG. 3) in the region where the discharge amount decreases as the energization current I increases, the discharge amount is reduced. Since it decreases, the actual rail pressure will decrease. Therefore, when it is determined in the process of step S110 that the actual rail pressure has decreased (in the case of YES), it can be determined that fuel leakage, which is a typical failure state of the high-pressure circuit, has occurred ( (See step S112 in FIG. 2).

On the other hand, in the case of a fault in the low pressure system, the discharge amount is constant even if the energization current I of the metering valve 6 is changed from I1 to I2 in the processing of step S108, as in the above-described example of the high voltage circuit. (See the characteristic line of the two-dot chain line in FIG. 3), the actual rail pressure does not decrease, and it is not determined that the actual rail pressure has decreased in the process of step S110. This can be determined (see step S116 in FIG. 2).
It should be noted that the reduction amount of the pump command discharge amount in step S108, in other words, the increase amount of the energization current I of the metering valve 6 is the individual amount to which the common rail fuel injection control device in the embodiment of the present invention is applied. It is preferable to set based on the results of tests and simulations taking vehicle conditions and the like into consideration.

When the metering valve 6 has a so-called “normally closed” configuration, the relationship between the energizing current I of the metering valve 6 and the discharge amount Q of the high-pressure pump 7 described in FIG. 3 is shown in FIG. As shown.
In FIG. 4, the horizontal axis represents the energization current I of the metering valve 6, and the vertical axis represents the discharge amount Q of the high-pressure pump 7.
Similarly to FIG. 3, the solid characteristic line represents the relationship between the energizing current I of the metering valve 6 and the discharge amount of the high-pressure pump 7 when the high-pressure circuit has failed, and the two-dot chain line characteristic line is As in FIG. 3, the relationship between the energizing current I of the metering valve 6 and the discharge amount of the high-pressure pump 7 when the low-pressure system fails is shown.
As shown in FIG. 3, basically, as described with reference to FIG. 3, when the energizing current I of the metering valve 6 is lowered from I1 to I2 in order to lower the pump command discharge amount in the process of step S108, In the case of a circuit failure, the discharge amount of the high-pressure pump 7 decreases (see the characteristic line in FIG. 4), but in the case of a low-pressure system failure, the discharge amount of the high-pressure pump 7 does not change. Can understand.

  In the above-described embodiment of the present invention, the example in which the fuel leakage detection process is performed in the configuration in which the rail pressure of the common rail 1 is controlled only by the metering valve 6 has been described, but the configuration of the common rail fuel injection control device As an example, an electromagnetic pressure control valve is provided in a return passage (not shown) for returning surplus high-pressure fuel from the common rail 1 to the tank 9 and is used to control the rail pressure together with the metering valve 6. It may be.

  It is suitable for a common rail type fuel injection control device with a simple configuration, in which it is desired to discriminate between a fuel leak in a high-pressure circuit and a failure in a low-pressure system.

DESCRIPTION OF SYMBOLS 1 ... Common rail 2-1-2-n ... Fuel injection valve 3 ... Engine 4 ... Electronic control unit 6 ... Metering valve 7 ... High pressure pump

Claims (4)

Fuel in the fuel tank is pressurized and pumped to a common rail by a high-pressure pump, enabling high-pressure fuel injection to the engine via a fuel injection valve connected to the common rail, and a metering valve upstream of the high-pressure pump And a fuel leakage detection method in a common rail fuel injection control device, wherein the metering valve is driven and controlled by an electronic control unit so that the rail pressure of the common rail can be controlled.
When the actual rail pressure is lower than the command rail pressure and the command discharge amount to the high pressure pump is at the maximum discharge amount, and the command discharge amount to the high pressure pump is reduced, the actual rail pressure is reduced. A fuel leak detection method comprising: determining that a fuel leak has occurred in a high-voltage circuit when a drop occurs.   2. The fuel leak detection method according to claim 1, wherein when the instruction discharge amount to the high pressure pump is reduced, if the actual rail pressure does not decrease, it is determined that the low pressure system is faulty. Fuel in the fuel tank is pressurized and pumped to a common rail by a high-pressure pump, enabling high-pressure fuel injection to the engine via a fuel injection valve connected to the common rail, and a metering valve upstream of the high-pressure pump A common rail fuel injection control device configured such that the metering valve is driven and controlled by an electronic control unit to control the rail pressure of the common rail,
The electronic control unit is
It is determined whether or not the actual rail pressure is lower than the indicated rail pressure and the indicated discharge amount for the high pressure pump is maintained at the maximum discharge amount, the actual rail pressure is lower than the indicated rail pressure, and the When it is determined that the command discharge amount for the high-pressure pump is maintained at the maximum discharge amount, the command discharge amount for the high-pressure pump is reduced, and it is determined that the actual rail pressure has decreased. The common rail fuel injection control device is configured to determine that the fuel leaks in the high-pressure circuit. The electronic control unit is
4. The common rail according to claim 3, wherein when the command discharge amount to the high pressure pump is reduced, if the actual rail pressure does not decrease, it is determined that the low pressure system has failed. Fuel injection control device.

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