JP6314860B2 - Fuel filter clogging detection device - Google Patents

Description

  The present invention relates to a clogging detection device that detects clogging of a fuel filter disposed in a fuel path from a fuel tank to a high-pressure pump.

  Conventionally, in an engine fuel supply system, a fuel filter is disposed in a fuel path from a fuel tank to a high-pressure pump. The fuel filter is used to remove foreign matters contained in the fuel, but if the fuel filter is continuously used in a state where the fuel filter is clogged (clogged), the flow rate of the fuel passing through the fuel filter or the fuel path is reduced. The engine power shortage is caused by the air inside. Moreover, since the differential pressure across the fuel filter increases, the filter element may be damaged. For this reason, it is necessary to detect clogging of the fuel filter. For example, the prior art according to Patent Document 1 includes a pressure sensor that detects a fuel pressure, and discloses a method for determining that the fuel filter is clogged when the detected pressure of the pressure sensor exceeds a set pressure. ing.

JP 2013-68195 A

However, in the above prior art, the pressure sensor is disposed only on the side where the pressure largely fluctuates between the inlet side and the outlet side of the fuel filter. For example, in a configuration in which a fuel filter is disposed on the downstream side of the feed pump, in other words, in a configuration in which fuel sent from the feed pump passes through the fuel filter and is supplied to the high-pressure pump, the inlet side is closer to the inlet side than the outlet side of the fuel filter. Since the pressure fluctuation is large, the pressure sensor is arranged only on the inlet side of the fuel filter. However, even if the pressure fluctuation on the outlet side is smaller than that on the inlet side of the fuel filter, the fuel pressure on the outlet side does not change. For this reason, even if only the pressure on the inlet side of the fuel filter is detected and compared with the set pressure, it is difficult to accurately detect clogging of the fuel filter.
The present invention has been made to solve the above-described problems, and an object of the present invention is to accurately detect clogging of a fuel filter based on a detection value of a pressure sensor arranged upstream of the fuel filter. An object of the present invention is to provide a clogging detection device for a fuel filter.

  The present invention is arranged in a high-pressure pump that pressurizes and discharges sucked fuel, a feed pump that sends fuel pumped up from the fuel tank to the high-pressure pump, and a fuel path from the fuel tank to the high-pressure pump. The fuel filter is applied to an engine fuel supply system comprising a fuel filter for filtering fuel and a pressure regulating valve for adjusting a fuel pressure in a fuel path from the fuel filter to the high-pressure pump to a constant pressure. A clogging detecting device for detecting clogging of the fuel, wherein the pressure sensor detects a fuel pressure upstream of the fuel filter (hereinafter referred to as pre-filter pressure), and is detected in an initial state of the fuel filter. Adjustment pressure initial value calculation means for calculating an adjustment pressure initial value of the pressure regulating valve from a pre-filter pressure and an initial pressure loss value of the fuel filter; and the engine A clogging amount estimating means for estimating a clogging amount of the fuel filter from a difference between the pre-filter pressure detected at a stop or under a stable operation state and the adjusted pressure initial value, and the clogging amount estimating means Clogging determination means for comparing the amount of clogging with a threshold value to determine whether or not the fuel filter is clogged.

According to the above configuration, the fuel pressure in the fuel path from the fuel filter to the high pressure pump is adjusted to a constant pressure by the pressure regulating valve. However, since the initial variation of the adjustment pressure of the pressure regulating valve is large with respect to the allowable pressure loss of the fuel filter, it is important to grasp the initial value of the adjustment pressure. In the present invention, the adjustment pressure initial value of the pressure regulating valve is calculated from the pre-filter pressure detected in the initial state of the fuel filter and the initial pressure loss value of the fuel filter. The initial pressure loss value of the fuel filter can be set as a constant from the filter specification, for example.
By calculating the adjustment pressure initial value of the pressure regulating valve, it is possible to eliminate the influence due to the initial variation of the regulation pressure, so that the fuel pressure downstream of the fuel filter can be maintained at a constant pressure by the pressure regulating valve. As a result, the clogging amount of the fuel filter is estimated from the difference between the pre-filter pressure detected by the pressure sensor and the adjusted pressure initial value of the pressure regulating valve (pre-filter pressure−adjusted pressure initial value), and the fuel is calculated based on the clogged amount. Presence of filter clogging can be accurately determined.

1 is a configuration diagram of an accumulator fuel supply system according to Embodiment 1. FIG. 3 is a flowchart illustrating a processing procedure of an ECU that detects clogging of a fuel filter according to a first embodiment. 2 is a characteristic diagram of a pressure regulating valve according to Embodiment 1. FIG. 3 is a graph showing the relationship between the differential pressure across the fuel filter and the clogging amount according to the first embodiment.

  The mode for carrying out the present invention will be described in detail with reference to the following examples.

[Example 1]
Example 1 describes a fuel filter clogging detection device in an engine fuel supply system.
As shown in FIG. 1, the fuel supply system includes a high-pressure pump 3 that increases the pressure of low-pressure fuel sent from the feed pump 1 and discharges it to the common rail 2.
An injector 5 is connected to the common rail 2 via a high-pressure pipe 4, and high-pressure fuel accumulated in the common rail 2 is supplied to the injector 5. The injector 5 is attached to each cylinder of an engine (for example, a diesel engine), and the injection timing, the injection amount, and the like of the fuel injected into the combustion chamber of the engine are electronically controlled by the ECU 6. Of the fuel supplied from the common rail 2 to the injector 5, surplus fuel that is not injected from the injector 5 is returned to the fuel tank 7.

The feed pump 1 is, for example, an electric pump, and pumps fuel from the fuel tank 7 and sends it to the high-pressure pump 3.
The high pressure pump 3 includes a cam shaft 8 that is driven by an engine and rotates, and a plunger 10 that is driven by a cam 9 provided on the cam shaft 8 to reciprocate between a top dead center and a bottom dead center in a cylinder. Have A pressurizing chamber 11 whose volume changes in accordance with the movement of the plunger 10 is formed on one end side (the opposite cam side) of the cylinder, and the other end side of the cylinder communicates with the cam chamber 12. In the pressurizing chamber 11, a suction valve 13 is disposed on the inlet side where the fuel flows in, and a discharge valve 14 is disposed on the outlet side where the fuel flows out.
A fuel filter 15 that filters the fuel discharged from the feed pump 1 and removes foreign matters is disposed on the downstream side of the feed pump 1.
A pressure sensor 16 that detects a fuel pressure upstream of the fuel filter 15 (hereinafter referred to as pre-filter pressure) is disposed in the fuel path from the feed pump 1 to the fuel filter 15.

On the downstream side of the fuel filter 15, the fuel path is branched in two directions, one fuel path is connected to the pressurizing chamber 11 via the suction valve 13, and the other fuel path is the cam chamber of the high-pressure pump 3. 12 is connected.
An intake metering valve 17 for metering the flow rate of fuel sent to the pressurizing chamber 11 is disposed in one fuel path. The intake metering valve 17 is, for example, an electromagnetic proportional valve whose valve opening is controlled by the ECU 6. A pressure regulating valve 18 that adjusts the fuel pressure downstream of the fuel filter 15 to a constant pressure is connected to the other fuel path. The fuel flowing into the cam chamber 12 through the other fuel path is used as lubricating oil for the tappet mechanism that transmits the rotational motion of the cam 9 to the plunger 10. The fuel flowing out from the pressure regulating valve 18 and the fuel overflowing from the cam chamber 12 are returned to the fuel tank 7 together with the surplus fuel not injected from the injector 5 described above.

When the plunger 10 is driven by the cam 9 and moves from the top dead center to the bottom dead center in the high pressure pump 3 described above, the pressure in the pressurizing chamber 11 decreases and the suction valve 13 opens. Thus, the fuel metered by the suction metering valve 17 flows into the pressurizing chamber 11.
When the plunger 10 reaches the bottom dead center and moves in the cylinder from the bottom dead center to the top dead center, the fuel in the pressurizing chamber 11 is pressurized and the fuel pressure rises. When the fuel pressure rises above the valve opening pressure of the discharge valve 14, the discharge valve 14 is opened, so that the high pressure fuel flows out from the pressurizing chamber 11 and is pumped to the common rail 2.
The ECU 6 executes a clogging detection process for detecting clogging of the fuel filter 15 based on detection information (pre-filter pressure) of the pressure sensor 16.

Hereinafter, the specific procedure of the clogging detection process of the fuel filter 15 by the ECU 6 will be described based on the flowchart shown in FIG. Steps S1 to S9 described below correspond to S1 to S9 given for each process in the flowchart shown in FIG.
Step S1 (filter state determining means of the present invention): It is determined whether or not the fuel filter 15 is in the initial state. The initial state of the fuel filter 15 includes a state where the fuel filter 15 is not used (for example, a state at the time of factory shipment) and a state close to unused. Specifically, the initial state of the fuel filter 15 is determined based on the operating time of the engine or the travel distance of the vehicle accumulated from the state in which the fuel filter 15 is not used. If the determination result in step S1 is YES, that is, if it is determined that the fuel filter 15 is in the initial state, the process proceeds to the next step S2, and if the determination result is NO, the process jumps to step S4.

Step S2: The pre-filter pressure is detected in the initial state of the fuel filter 15, and the detected value is stored in the memory of the ECU 6. The processing in step S2 is performed by operating the feed pump 1 (electric pump) with the engine stopped.
Step S3 (adjusted pressure initial value calculating means of the present invention): The adjusted pressure initial value of the pressure regulating valve 18 is calculated from the pre-filter pressure detected in step S2 and the initial pressure loss value of the fuel filter 15 and stored in the memory. As shown in FIG. 3, the adjustment pressure of the pressure regulating valve 18 has an initial variation of several tens of kPa (median value ± 50 to 100 kPa) and is larger than the allowable pressure loss of the fuel filter 15 (max 50 kPa). It is important to know the initial value of pressure. The initial pressure loss value of the fuel filter 15 can be set as a constant from the filter specification.

  Step S4... The fuel WAX concern condition is determined. The conditions for concern about the WAX conversion of the fuel include the temperature of the fuel flowing into the fuel filter 15 or the engine cooling water temperature or the outside air temperature correlated with the fuel temperature. If these temperatures are below a certain value, the fuel is waxed. Concerned. When the temperature of the fuel flowing into the fuel filter 15 is low, the fuel becomes wax and the viscosity becomes high, so that it may be difficult to normally pass through the fuel filter 15. In this case, since it is not clogging due to the accumulation of foreign matters on the fuel filter 15, if the determination result in step S4 is YES, that is, if the condition for fearing the waxing of the fuel is satisfied, the subsequent processing is performed. Do not exit. If the determination result is NO, the process proceeds to the next step S5.

Step S5 (clogging amount estimation means of the present invention): The clogging amount is estimated from the differential pressure across the fuel filter 15. As shown in FIG. 4, as the differential pressure across the fuel filter 15 increases, the amount of clogging of foreign matter accumulated on the fuel filter 15 increases. Therefore, the amount of clogging of the fuel filter 15 is estimated from the differential pressure across the fuel filter 15. it can. Specifically, the amount of clogging of the fuel filter 15 is estimated from the difference between the pre-filter pressure detected under a stable operating state such as when the engine is stopped or idling, and the adjusted pressure initial value calculated in step S3. To do.
Step S6 (clogging determining means of the present invention): It is determined whether or not the clogging amount estimated in step S5 is larger than a threshold value (the differential pressure allowable value shown in FIG. 4). If the determination result is YES, that is, if the clogging amount is larger than the threshold value, the process proceeds to the next step S7, and if the determination result is NO, the process is terminated without performing the subsequent processing.

Step S7 (clogging determining means of the present invention): It is determined whether or not the state where it is determined in step S6 that the amount of clogging is larger than the threshold value has continued a plurality of times. If the determination result is YES, that is, if the state where the amount of clogging is determined to be greater than the threshold value continues for a plurality of times, the process proceeds to the next step S8, and if the determination result is NO, the process is terminated without performing the subsequent processing. To do.
Step S8 (clogging determining means of the present invention): It is determined that the fuel filter 15 is clogged. In this case, it can be determined that the clogging is not due to waxing of the fuel but due to the accumulation of foreign matter on the fuel filter 15.
Step S9: A warning is displayed on the meter in the driver's seat that the fuel filter 15 is clogged, and the driver is prompted to replace the fuel filter 15.

[Effects of Example 1]
In the fuel supply system of the first embodiment, the fuel pressure downstream of the fuel filter 15 is maintained at a constant pressure by the pressure regulating valve 18, so that the fuel pressure (filter pre-pressure) detected by the pressure sensor 16 and the pressure regulating valve 18 The differential pressure across the fuel filter 15 can be obtained from the adjusted pressure. However, since the adjustment pressure of the pressure regulating valve 18 has a large initial variation with respect to the allowable pressure loss of the fuel filter 15, it is important to grasp the initial value of the adjustment pressure. On the other hand, in the first embodiment, the initial adjustment pressure value of the pressure regulating valve 18 is calculated from the pre-filter pressure detected in the initial state of the fuel filter 15 and the initial pressure loss value of the fuel filter 15. The influence by can be eliminated.

  As a result, the clogging amount of the fuel filter 15 is estimated from the difference between the pre-filter pressure detected by the pressure sensor 16 and the initial adjustment pressure value of the pressure regulating valve 18 (pre-filter pressure-adjustment pressure initial value). Thus, it is possible to accurately determine whether or not the fuel filter 15 is clogged. Further, since the fuel pressure downstream of the fuel filter 15 can be maintained at a constant pressure by the pressure regulating valve 18, the pressure sensor 16 for detecting the fuel pressure downstream of the fuel filter 15 is unnecessary, and the front and rear of the fuel filter 15 are not required. The cost can be reduced when compared with a configuration in which the pressure sensor 16 is installed.

[Modification]
In the first embodiment, the electric feed pump 1 is illustrated, but for example, a mechanical trochoid pump driven by the cam shaft 8 of the high-pressure pump 3 may be employed.

1 Feed Pump 3 High Pressure Pump 6 ECU (Fuel Filter Clogging Detection Device)
7 Fuel tank 15 Fuel filter 16 Pressure sensor 18 Pressure regulating valve S1 Filter state determination means S3 Adjusted pressure initial value calculation means S5 Clogging amount estimation means S7 Clogging determination means

Claims (7)

A high-pressure pump (3) for pressurizing and discharging the inhaled fuel;
A feed pump (1) for sending the fuel pumped from the fuel tank (7) to the high-pressure pump (3);
A fuel filter (15) arranged in a fuel path from the fuel tank (7) to the high-pressure pump (3) to filter fuel;
The fuel filter is applied to an engine fuel supply system including a pressure regulating valve (18) for adjusting a fuel pressure in a fuel path from the fuel filter (15) to the high pressure pump (3) to a constant pressure. A clogging detection device (6) for detecting clogging of (15),
A pressure sensor (16) for detecting fuel pressure upstream of the fuel filter (15) (hereinafter referred to as pre-filter pressure);
Adjusted pressure initial value calculating means for calculating the adjusted pressure initial value of the pressure regulating valve (18) from the pre-filter pressure detected in the initial state of the fuel filter (15) and the initial pressure loss value of the fuel filter (15). (S3),
A clogging amount estimating means (S5) for estimating a clogging amount of the fuel filter (15) from a difference between the pre-filter pressure detected when the engine is stopped or under a stable operating condition and the adjusted pressure initial value;
Clogging judgment means (S6, S7, S8) for judging whether or not the fuel filter (15) is clogged by comparing the clogging quantity estimated by the clogging quantity estimation means (S5) with a threshold value. A clogging detection device for a fuel filter (15). In the clogging detection device (6) of the fuel filter (15) according to claim 1,
It has filter state determination means (S1) for determining whether or not the fuel filter (15) is in the initial state, and it is determined by the filter state determination means (S1) that the fuel filter (15) is not in the initial state. In this case, the clogging detection device for the fuel filter (15), wherein the adjustment pressure initial value calculation means (S3) is executed. In the clogging detection device (6) of the fuel filter (15) according to claim 2,
The filter state determining means (S1) determines an initial state of the fuel filter (15) based on an operating time of the engine or a travel distance of the vehicle accumulated from an unused state of the fuel filter (15). The clogging detection apparatus of the fuel filter (15) characterized by the above-mentioned. In the clogging detection device (6) of the fuel filter (15) according to any one of claims 1 to 3,
The feed pump (1) is an electric pump,
The clogging amount estimation means (S5) estimates the clogging amount of the fuel filter (15) in a state where the feed pump (1) is operated when the engine is stopped. Clogging detection device. In the clogging detection device (6) of the fuel filter (15) according to any one of claims 1 to 3,
The clogging amount estimation means (S5) estimates the clogging amount of the fuel filter (15) when the engine is idling, and the clogging detection device for the fuel filter (15) is characterized in that: In the clogging detection device (6) of the fuel filter (15) according to any one of claims 1 to 5,
The clogging determination means (S7) determines that the fuel filter (15) is clogged when a state where it is determined that the clogging amount of the fuel filter (15) is larger than the threshold value continues a plurality of times. The clogging detection apparatus of the fuel filter (15) characterized by the above-mentioned. In the clogging detection device (6) of the fuel filter (15) according to any one of claims 1 to 6,
The clogging determination means (S6, S7, S8) is configured to detect the temperature of the fuel flowing through the fuel path from the fuel tank (7) to the fuel filter (15), or the coolant temperature or the external temperature correlated with the fuel temperature. A clogging detection device for a fuel filter (15), wherein whether or not the fuel filter (15) is clogged is determined when an air temperature is higher than a predetermined value.

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