JP2012087633A - Fuel pressure sensor diagnostic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel pressure sensor diagnostic device capable of determining an abnormality of a fuel pressure sensor.SOLUTION: The fuel pressure sensor diagnostic device includes: a metering control unit 3 which controls metering of a supply pump 103 so that the fuel pressure to be detected by the fuel pressure sensor 106 becomes a fuel pressure indicator value; and an abnormality determination unit 4 which determines abnormality of the fuel pressure sensor 106 when correlation between a present fuel pressure indicator value and the fuel supplied amount to a fuel rail 104 by the metering control is separated by a threshold value or more from correlation between a past fuel pressure indicator value and the fuel supplied amount to the fuel rail 104 by the metering control.

Description

  The present invention relates to a fuel pressure sensor diagnostic apparatus capable of determining an abnormality of a fuel pressure sensor.

  In diesel engines and high-pressure direct-injection gasoline engines, in-cylinder direct injection is performed using a common rail system. As shown in FIG. 7, the common rail system 101 stores the fuel supplied from the supply pump 103 connected to the outlet of the supply pump 103 and the supply pump 103 that supplies the fuel sucked up from the fuel tank 102 in a meterable manner. A fuel rail 104 (also referred to as a pressure accumulation chamber or a common rail), an injector 105 that injects fuel from the fuel rail 104 into the engine, and a fuel pressure sensor 106 that detects a fuel pressure (also referred to as rail pressure) in the fuel rail 104 , A fuel pressure adjustment valve 107 for extracting fuel from the fuel rail 104 for fuel pressure adjustment, a recovery line 108 for returning the fuel returned from each part of the supply pump 103, the injector 105, and the fuel pressure adjustment valve 107 to the fuel tank 102; By electronically controlling the fuel injection timing, fuel injection amount, Fee electronic control circuit for controlling the pressure (ECM; Engine Control Module, ECU; Electronical Control Unit etc., hereinafter referred to as ECM) and a 109.

  When fuel is injected into the engine from the injector 105, the fuel pressure in the fuel rail 104 is accumulated at a suitable high pressure that can be injected against the engine internal pressure because the pressure in the engine is high due to the compression stroke. The The fuel pressure suitable for injection varies depending on the engine condition in consideration of noise performance and exhaust gas performance. Therefore, the fuel pressure instruction value is set in several engine parameters, for example, a fuel pressure instruction value map referred to by engine speed and fuel injection amount. On the other hand, in the supply pump 103, fuel is pumped and supplied to the fuel rail 104 by equal amounts repeatedly, and the amount supplied in one operation can be adjusted by electronic control. This is called metering. The ECM 109 performs metering control of the supply pump 103 so that the fuel pressure detected by the fuel pressure sensor 106 becomes the fuel pressure instruction value.

  Thus, the supply pump 103 supplies fuel to the fuel rail 104 to increase the fuel pressure in the fuel rail 104, and the fuel pressure in the fuel rail 104 is decreased by the fuel consumption by the injector 105. Further, when the fuel pressure detected by the fuel pressure sensor 106 exceeds the fuel pressure indication value, the fuel pressure adjusting valve 107 extracts the fuel in the fuel rail 104 and returns it to the fuel tank 102 from the recovery line 108, thereby returning the fuel pressure inside the fuel rail 104. The fuel pressure can be reduced to the fuel pressure indication value.

  The fuel injection amount instruction value for instructing the fuel injection amount from the injector 105 is determined by referring to a map based on engine parameters such as the engine speed and the accelerator opening, and this is a conventionally known technique related to engine control. Therefore, detailed explanation is omitted. The ECM 109 controls the drive amount of the injector 105 according to the fuel pressure and the fuel injection amount instruction value so that the fuel is injected from the injector 105 according to the fuel injection amount instruction value. The drive amount of the injector 105 varies depending on the actuator structure of the injector 105, but is controlled by the drive time (energization time), the applied voltage value, the applied current value, and the like. In the following, the driving amount is represented by energization time.

JP 2007-40113 A Japanese Patent No. 4466509

  It is difficult to measure the amount of fuel that is actually injected into the engine during engine operation. Therefore, conventionally, the characteristic of FIG. 8 is made into a map, and control is performed by using this map so that the fuel injection amount actually injected becomes the fuel injection amount instruction value. That is, if this map is referred to by the fuel injection amount instruction value and the fuel pressure, the required injector energization time can be obtained.

  The characteristic of FIG. 8 is that when the fuel pressure is constant, the fuel injection amount increases when the energization time is lengthened, and when the energization time is constant, the fuel injection amount increases when the fuel pressure is increased. ing. Since such a characteristic map is used, there is a possibility that the conventional common rail system 101 may attempt to improve the engine torque by modifying the fuel pressure sensor 106. Specifically, a resistance element, an amplifier, or the like is added between the fuel pressure sensor 106 and the ECM 109 so that a signal corresponding to a fuel pressure lower than the actual fuel pressure enters the ECM 109. Is misrecognized.

  As shown in FIG. 9, it is assumed that the ECM 109 recognizes a fuel pressure (one-dot chain line) lower than the actual fuel pressure (solid line) by the modification. When the injector 105 is driven by obtaining the energization time according to the fuel pressure recognized by the ECM 109 as the fuel pressure indication value, the actual fuel pressure is high, so the actual fuel injection amount is recognized by the ECM 109. (= Fuel injection amount instruction value).

  However, such a modification deteriorates exhaust gas performance and shortens the life of the engine. For example, if there is an injection amount restriction value (broken line) that represents a range of fuel injection amount that is desirable from the viewpoint of exhaust gas performance and life, the ECM 109 actually does control even if it intends to perform control within the range of the injection amount restriction value. Is controlled outside the range of the injection amount restriction value. The fuel injection control by the ECM 109 is performed by setting a map of the fuel injection amount in advance so that not only the exhaust gas performance, the fuel consumption and the output torque performance but also the environmental reliability such as engine reliability and noise are optimized. Therefore, when the actual fuel injection amount increases, various performances deteriorate and reliability cannot be maintained.

  Although it is not easy to remodel the ECM 109 to increase the fuel injection amount instruction value or to remodel the injector 105 to increase the actual fuel injection amount with respect to the fuel injection amount instruction value, it is not easy. Since the remodeling of 106 is relatively easy, it is likely to be the target of the remodeling.

  Not only the modification of the fuel pressure sensor 106, but if the reading of the fuel pressure sensor 106 becomes inaccurate such as higher or lower than the actual due to the failure of the fuel pressure sensor 106, the fuel injection amount cannot be controlled correctly, which is a problem. .

  In response to this problem, the technique of Patent Document 1 determines the abnormality of the fuel pressure sensor by detecting the increase in the fuel injection amount from the increase in the output torque, but in order to detect the output torque, It is necessary to mount a relatively expensive sensor such as an oxygen concentration sensor, which increases the cost of the vehicle.

  The technology of Patent Document 2 adds an electric circuit for abnormality determination to the fuel pressure sensor. However, the addition of such an electric circuit and the addition of an interface on the ECM side corresponding to the addition of such an electric circuit are required, which increases the cost of the vehicle. And is difficult to apply to existing vehicles.

  Accordingly, an object of the present invention is to provide a fuel pressure sensor diagnostic apparatus that solves the above-described problems and can determine whether or not a fuel pressure sensor is abnormal.

  In order to achieve the above object, the present invention provides a supply pump that supplies fuel in a meterable manner, a fuel rail that stores fuel supplied from the supply pump, and an injector that injects fuel from the fuel rail into an engine. And a fuel pressure sensor diagnostic device applied to a common rail system including a fuel pressure sensor for detecting a fuel pressure in the fuel rail, wherein fuel is injected from the injector according to a fuel injection amount instruction value. An injector controller that controls the drive amount of the injector according to the pressure and the fuel injection amount instruction value; and an adjustment controller that performs metering control of the supply pump so that the fuel pressure detected by the fuel pressure sensor becomes the fuel pressure instruction value. The relationship between the amount control unit, the current fuel pressure indication value, and the amount of fuel supplied to the fuel rail by metering control is the past fuel pressure. When it deviates more than a threshold value from the relationship between the amount of fuel supplied to the fuel rail by the pointer value and the metering control, in which a malfunction determination unit that determines an abnormality of the fuel pressure sensor.

  A fuel supply amount determination unit that determines a fuel supply amount based on an instruction value given to the supply pump by the metering control unit for metering control may be provided.

  Based on the fuel injection amount instruction value and the fuel pressure detected by the fuel pressure sensor, an operation condition determination unit that determines the engine operation condition, and a record of storing the relationship between the fuel pressure instruction value and the fuel supply amount for each engine operation condition A learning unit, and the abnormality determination unit is configured to store a fuel relationship between a fuel pressure instruction value and a fuel supply amount under a certain engine operating condition in the past in the same engine operating condition stored in the actual learning unit. The deviation of the fuel supply amount may be obtained in light of the relationship between the pressure instruction value and the fuel supply amount.

  The present invention exhibits the following excellent effects.

  (1) The abnormality of the fuel pressure sensor can be determined.

It is a block diagram of the fuel pressure sensor diagnostic apparatus which shows one Embodiment of this invention. It is a figure explaining the fuel pressure adjustment of the fuel rail by the metering control of a supply pump. It is a figure explaining the supply pump of an area metering system. It is a figure explaining the supply pump of an angle metering system. It is a flowchart which shows the procedure of the results learning in the fuel pressure sensor diagnostic apparatus of this invention. It is a flowchart which shows the procedure of abnormality determination in the fuel pressure sensor diagnostic apparatus of this invention. It is a block diagram of a common rail system. It is the characteristic figure which showed the fuel injection quantity with respect to the energization time of an injector by making fuel pressure into a parameter. It is an energization time versus fuel injection amount characteristic diagram for explaining that the fuel injection amount increases due to the modification of the fuel pressure sensor.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, the fuel pressure sensor diagnostic apparatus 1 according to the present invention is applied to the common rail system 101 described in FIG.

  The fuel pressure sensor diagnostic device 1 includes an injector control unit 2 that controls the drive amount of the injector 105 according to the fuel pressure and the fuel injection amount instruction value so that the fuel is injected from the injector 105 according to the fuel injection amount instruction value, and the fuel pressure. A metering control unit 3 that performs metering control of the supply pump 103 so that the fuel pressure detected by the sensor 106 becomes the fuel pressure command value, and the fuel supply amount to the fuel rail 104 by the current fuel pressure command value and metering control When the relationship between the fuel pressure sensor 106 and the fuel supply amount to the fuel rail 104 by metering control is more than a threshold, the abnormality determination unit 4 determines that the fuel pressure sensor 106 is abnormal. It is provided.

  The fuel pressure sensor diagnostic apparatus 1 includes a fuel supply amount determination unit 5 that determines a fuel supply amount based on an instruction value that the metering control unit 3 gives to the supply pump 103 for metering control.

  The fuel pressure sensor diagnostic apparatus 1 includes an operation condition determination unit 6 that determines an engine operation condition based on a fuel injection amount instruction value and a fuel pressure detected by the fuel pressure sensor 106, a fuel pressure instruction value and a fuel for each engine operation condition. A performance learning unit 7 that stores the relationship with the supply amount is provided. The abnormality determination unit 4 stores the relationship between the fuel pressure instruction value and the fuel supply amount under a certain current engine operating condition, and the fuel pressure instruction value and fuel supply under the same previous engine operating condition stored in the result learning unit 7. The difference in fuel supply will be determined in light of the quantity relationship.

  The injector control unit 2 and the metering control unit 3 are conventionally used. The control of the injector control unit 2 follows a map in which the characteristics shown in FIG. 8 are set. The control of the metering control unit 3 will be described later with reference to FIGS. The abnormality determination unit 4, the fuel supply amount determination unit 5, the operating condition determination unit 6, and the performance learning unit 7 constitute the characteristic portions of the present invention, and their detailed operations will be described later with reference to FIGS.

  The injector control unit 2, the metering control unit 3, the abnormality determination unit 4, the fuel supply amount determination unit 5, the operating condition determination unit 6, and the result learning unit 7 are realized by software executed by the ECM 109.

  Here, the fuel pressure adjustment of the fuel rail 104 by the metering control of the supply pump 103 will be described in detail with reference to FIG.

  The supply pump 103 mainly includes a feed pump 121, a metering valve 122, and a pressure feeding mechanism 123. The fuel from the fuel tank 102 passes through the fuel filter and is taken into the supply pump 103 via the pipe. The fuel filtered again by the goose filter 124 in the supply pump 103 flows into the inlet of the feed pump 121. The feed pump 121 is always operated, and continuously feeds fuel from the inlet to the outlet by rotating the eccentric impeller 125. A metering valve 122 is provided at the outlet of the feed pump 121.

  The metering valve 122 is a member that meteres the fuel that passes in a certain time. Therefore, only the metered amount of the fuel delivered from the feed pump 121 passes through the metering valve 122 and is supplied to the pressure feeding mechanism 123. The excess amount flows to the overflow portion 126 and is collected in the fuel tank 102.

  The pressure feeding mechanism 123 stores the fuel supplied from the metering valve 122 in the cylinder 127, the plunger 128 strokes in the cylinder 127, pushes out the fuel in the cylinder 127, and discharges the pushed-out fuel from the discharge valve 129. .

  The metering valve 122 includes a metering valve that performs metering by narrowing the opening area of the fuel outlet and a metering valve 122 that performs metering by changing the time during which the fuel outlet is open (crank angle period).

  The metering valve 131 shown in FIG. 3A includes a cylindrical stator 132 and a cylindrical valve 134 that moves in the stator 132 by the electromagnetic force of the coil 133. One end of the valve 134 is a fuel inlet. The valve 134 and the stator 132 are respectively provided with a valve port 135 and a stator port 136 that penetrate the cylindrical wall in the radial direction. The stator port 136 is a fuel outlet.

  When duty control is performed on the energized pulse current for the coil 133, the displacement of the valve 134 proportional to the average current is obtained. The relative positions of the valve port 135 and the stator port 136 in the axial direction change due to the displacement of the valve 134. As shown in FIG. 3B, a portion where the valve port 135 and the stator port 136 overlap (shown in white) is a communication portion between the fuel inlet and the fuel outlet. In a state where the valve port 135 and the stator port 136 do not overlap at all, the fuel inlet and the fuel outlet are blocked (fully closed). In a state where the valve port 135 and the stator port 136 are exactly overlapped, the fuel inlet and the fuel outlet communicate with each other with the largest flow path cross-sectional area (fully open). In a state where the valve port 135 and the stator port 136 partially overlap each other, the valve port 135 and the stator port 136 are intermediate between fully closed and fully opened.

  As shown in FIG. 3C, a valve opening degree proportional to the duty ratio of the energized pulse current is obtained. Accordingly, as shown in FIG. 3D, when the map is set so that the duty ratio changes with respect to the fuel pressure instruction value and the fuel pressure is to be increased, the duty ratio is increased and the fuel rail 104 is moved. When it is desired to increase the amount of fuel supplied and reduce the fuel pressure, it is possible to reduce the duty ratio and reduce the amount of fuel supplied to the fuel rail 104.

  The metering valve 141 shown in FIG. 4A is provided such that the valve 143 having the fuel inlet moves relative to the casing 142 having the fuel outlet so that the two positions in the axial direction can be taken. When a current flows through the coil 144, the valve 143 moves to one position, so that the fuel outlet and the fuel inlet communicate with each other inside the valve 143. When the current in the coil 144 disappears, the valve 143 At 145, the other position is returned to shut off the fuel outlet and the fuel inlet.

  As shown in FIG. 4B, a crank angle sensor 147 made of an electromagnetic pickup is provided facing a gear-shaped angle pulser 146 attached to the crankshaft.

  As shown in FIG. 4C, the angle pulse from the crank angle sensor 147 and a valve opening / closing signal for designating a crank angle period (referred to as an open period) in which the valve 143 is to be opened are logically ORed. 144 is energized. As shown in FIG. 4D, when the map is set so that the open period changes with respect to the fuel pressure indication value and the fuel pressure is to be increased, the open period is lengthened and the fuel to the fuel rail 104 is increased. When it is desired to increase the supply amount and decrease the fuel pressure, it is possible to perform control such that the open period is shortened and the fuel supply amount to the fuel rail 104 is decreased.

  Next, the operation of the fuel pressure sensor diagnostic device 1 according to the present invention will be described.

  The fuel pressure sensor diagnostic apparatus 1 is configured to learn the relationship between the fuel pressure instruction value and the fuel supply amount periodically or every event. Defaults are set at the time of factory shipment, and calculation and learning are repeated while the user uses them. In the following, calculation and learning are performed for each operation (for example, for each key-on), and the determination during the previous operation and the determination during the current operation among the repetitions will be described.

  As shown in FIG. 5, during the previous operation, in step S1, the fuel pressure instruction value to be given to the fuel pressure in the fuel rail 104 is obtained by referring to the fuel pressure map. An example of the fuel pressure map is shown in the figure. That is, the map of the fuel pressure instruction value is referred to by the engine speed and the fuel injection amount. The fuel pressure indication value is larger when the value of the fuel pressure map is larger.

  When the fuel pressure instruction value is given, the metering control unit 3 performs metering control of the supply pump 103 according to the method of FIG. 3 or FIG. At this time, the metering control instruction value given to the supply pump 103 is the duty ratio or the open period. The amount of fuel supplied from the supply pump 103 to the fuel rail 104 within an appropriate unit time can be substantially determined from the metering control instruction value.

  However, it is necessary to consider several engine parameters as factors for determining the fuel supply amount in addition to the metering control instruction value. The supply pump 103 has an internal leak, and the internally leaked fuel returns to the recovery line 108 (see FIG. 7). Since the internal leak depends on the fuel temperature, even if the same metering control instruction value is given to the supply pump 103, the actual fuel supply amount varies depending on the fuel temperature. Further, since the fuel density (specific gravity) decreases when the fuel temperature is high, the fuel supply amount (weight) is small with respect to the same metering (duty ratio, valve opening period). Therefore, if the fuel temperature in the supply pump 103 is measured, for example, at the measurement position T in FIG. 2, the fuel temperature is an element for determining the fuel supply amount. Further, the fuel temperature increases as the engine speed increases. Therefore, the engine speed is an element for determining the fuel supply amount. Further, when the atmospheric temperature becomes high, the fuel temperature rises in the piping from the fuel tank 102 to the supply pump 103, so that the atmospheric temperature is also an element for determining the fuel supply amount.

  Therefore, in step S2, the fuel supply amount determination unit 5 adds engine parameters such as engine speed, fuel temperature, and atmospheric temperature to the metering control instruction value that the metering control unit 3 gives to the supply pump 103. To determine the fuel supply amount. With respect to these engine parameters, it is preferable that correction amounts for the metering control instruction values are set in the maps, and the fuel supply amount is corrected by referring to these maps with the engine parameters.

  On the other hand, in step S3, the operating condition determination unit 6 determines engine operating conditions. This is because the relationship between the fuel pressure instruction value and the fuel supply amount is different when the engine operating conditions are different. The fuel pressure of the fuel rail 104 increases with the fuel supply from the supply pump 103 and decreases with the fuel injection of the injector 105. Therefore, the fuel injection amount (= fuel injection amount instruction value) in the injector 105 becomes the engine operating condition. Further, the fuel consumption in the injector 105 includes consumption due to back leak in addition to fuel injection into the engine. The back leaked fuel returns to the recovery line 108 (see FIG. 7). The amount of back leak depends on the fuel pressure and the fuel temperature. Therefore, the engine operating condition is determined mainly by using the fuel injection amount instruction value and the fuel pressure as factors, and adding some engine parameters to this. Engine parameters that are factors for determining engine operating conditions include engine speed, fuel temperature, atmospheric temperature, and the like. Using these elements, a plurality of discrete engine operating conditions are set in advance so that the relationship between the fuel pressure command value and the fuel supply amount is the same under the same engine operating conditions. The fuel pressure used here is the fuel pressure detected by the fuel pressure sensor 106.

In step S4, the result learning unit 7 stores the relationship between the fuel pressure instruction value and the fuel supply amount for each engine operating condition. For example, when the engine rotation speed is 700 rpm and the fuel injection amount instruction value is 0.001 cm ³ / rotation, the fuel pressure instruction value is 30 MPa, and the fuel supply amount corresponds to a duty ratio of 10% of the metering control instruction value. Suppose it was a quantity. The relationship between the fuel pressure instruction value and the fuel supply amount is stored in the learning map corresponding to the engine operating conditions of the time. An example of a learning map is shown in the figure. Since the calculation result of the fuel supply amount is inconsistent with the default line set at the time of shipment from the factory with respect to the engine operating condition, a new line is learned so that a line parallel to the default line includes the calculation result.

  This learned line represents how much fuel can be sent from the supply pump 103 under certain engine operating conditions to maintain the fuel pressure on the fuel rail 104. However, there is no significant difference from the factory default line, and the figure is exaggerated. The default line ignores individual differences of vehicles, and is set uniformly for each lot based on experimental data from representative vehicles. The line learned after shipment is based on the characteristics of the individual. Each time the engine operating condition changes, the learned line is stored in the learning map of the engine operating condition.

As shown in FIG. 6, during the current operation, the fuel pressure instruction value, the fuel supply amount, and the engine operating condition are determined in steps S11, S12, and S13, as in the previous operation. In step S14, abnormality determination unit 4 calculates the relationship between the fuel pressure instruction value and the fuel supply amount under a certain engine operating condition. For example, when the engine speed is 1000 rpm and the fuel injection amount instruction value is 0.01 cm ³ / rotation, the fuel pressure instruction value is 100 MPa, and the fuel supply amount corresponds to the duty ratio of 20% of the metering control instruction value. Suppose that the supply amount. In this case, the relationship between the fuel pressure instruction value and the fuel supply amount is compared in a learning map of engine operating conditions equivalent to this.

  In step S15, the abnormality determination unit 4 stores the relationship between the fuel pressure instruction value and the fuel supply amount under a certain engine operating condition at the past in the same engine operating condition stored in the past learning unit 7. The deviation of the fuel supply amount is obtained in light of the relationship between the indicated value and the fuel supply amount. When the deviation is equal to or greater than the threshold value, it is determined that the fuel pressure sensor 106 is abnormal. For the determination of abnormality, the driver is immediately warned or the fact that abnormality has occurred in the fuel pressure sensor 106 is stored in the ECM 109 so that it can be read out at the time of diagnosis at the inspection / repair shop. Good. Note that the abnormality determined here is not a failure such as a simple disconnection or short circuit, but also includes a case where the fuel pressure sensor 106 is modified by the driver, so it is stored in the ECM 109 without warning the driver. You can just do it. Once the abnormality of the fuel pressure sensor 106 is determined, learning is not performed.

  An example of the comparison in the learning map is shown in the figure. The learning map stores a learning line under the engine operating condition learned from the calculation result at the previous operation. From this learning line, it can be seen that the calculation result at the time of the current driving is greatly deviated. In order to quantitatively determine the magnitude of the deviation, the distance between the learning line learned during the previous operation and the calculation result during the current operation (preferably, the distance between the fuel supply amounts at the same fuel pressure indication value) is defined as the deviation. Define and set a threshold in advance.

  If the same engine operating conditions and the same fuel pressure indication value are the same during the previous operation and the current operation, the fuel supply amount should be the same. Thus, it can be determined that there is a cause for the difference in the relationship between the fuel pressure command value and the fuel supply amount to be greater than or equal to the threshold value. Here, if the fuel pressure sensor 106 is modified between the previous operation and the current operation, and a signal corresponding to a fuel pressure lower than the actual fuel pressure enters the ECM 109, As a result of the metering control, the actual fuel pressure becomes higher than the fuel pressure instruction value. Therefore, the actual fuel injection amount in the injector 105 is larger than the fuel injection amount recognized by the ECM 109 (= fuel injection amount instruction value). For this reason, the fuel consumption of the fuel rail 104 increases, and in order to maintain the fuel pressure at the same fuel pressure indication value, the fuel supply amount must be increased. As a result, it is necessary to increase the metering control instruction value given to the supply pump 103.

  In the fuel pressure sensor diagnostic device 1 of the present invention, the fuel supply amount is determined from the metering control instruction value (for example, duty ratio), and the fuel supply amount for making the same fuel pressure is the previous time (for example, yesterday's operation). ) To this time (for example, during today's operation), the fuel pressure detected by the fuel pressure sensor 106 has suddenly decreased, that is, the fuel pressure sensor 106 has an abnormal reading. It is determined that this has occurred.

  As described above, in the fuel pressure sensor diagnostic device 1 of the present invention, the relationship between the current fuel pressure command value and the fuel supply amount to the fuel rail 104 by metering control is based on the past fuel pressure command value and metering control. Since the fuel pressure sensor 106 is determined to be abnormal when it deviates by more than a threshold value from the relationship with the amount of fuel supplied to the fuel rail 104, the fuel pressure sensor 106 can be diagnosed.

  Further, the fuel pressure sensor diagnostic device 1 of the present invention does not require any special member (expensive sensor or new circuit), and even if a member is added, it is sufficient to add an inexpensive fuel temperature sensor. The vehicle cost is not increased.

DESCRIPTION OF SYMBOLS 1 Fuel pressure sensor diagnostic apparatus 2 Injector control part 3 Metering control part 4 Abnormality determination part 5 Fuel supply amount determination part 6 Operating condition determination part 7 Performance learning part

Claims (3)

A supply pump that supplies fuel in a meterable manner;
A fuel rail for storing fuel supplied from the supply pump;
An injector for injecting fuel in the fuel rail into the engine;
A fuel pressure sensor diagnostic device applied to a common rail system including a fuel pressure sensor for detecting a fuel pressure in the fuel rail,
An injector control unit that controls a drive amount of the injector according to a fuel pressure and a fuel injection amount instruction value so that fuel is injected from the injector according to a fuel injection amount instruction value;
A metering control unit for metering the supply pump so that the fuel pressure detected by the fuel pressure sensor becomes a fuel pressure instruction value;
The relationship between the current fuel pressure indication value and the fuel supply amount to the fuel rail by metering control deviates by more than a threshold value from the relationship between the past fuel pressure indication value and the fuel supply amount to the fuel rail by metering control. A fuel pressure sensor diagnostic device comprising: an abnormality determination unit that determines that the fuel pressure sensor is abnormal when   2. The fuel pressure sensor diagnostic device according to claim 1, further comprising a fuel supply amount determination unit that determines a fuel supply amount based on an instruction value given to the supply pump by the metering control unit for metering control. . An operating condition determining unit that determines an engine operating condition based on a fuel injection amount instruction value and a fuel pressure detected by the fuel pressure sensor;
A performance learning unit for storing a relationship between a fuel pressure instruction value and a fuel supply amount for each engine operating condition;
The abnormality determination unit is configured to store a relationship between a fuel pressure instruction value and a fuel supply amount under a certain current engine operating condition, and a fuel pressure instruction value and a fuel supply under the same engine operating condition stored in the past learning unit. 3. The fuel pressure sensor diagnostic apparatus according to claim 1, wherein the difference in fuel supply amount is obtained in light of the relationship between the amounts.