JP2016180372A - Fuel pressure control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel pressure control device which calculates a valve opening motion point at which a pressure regulator is valve-opened without causing chattering, and can control the pressure of fuel at high accuracy by correction based on the valve opening motion point.SOLUTION: In two motion ranges sandwiching a motion point at which a pressure regulator 19 is valve-opened, characteristic formulae of a voltage supplied to a motor 10 and a current flowing in the motor 10 at the application of the voltage to the motor are calculated on the basis of a detection result of a motion detection part, and calculates a common solution of the two characteristic formulae as a valve opening motion point being the motion point at which the pressure regulator 19 is valve-opened.SELECTED DRAWING: Figure 8

Description

  The present invention relates to an engine fuel pressure control apparatus that sucks fuel in a fuel tank of a vehicle with a low-pressure pump and supplies the fuel to a high-pressure pump through a fuel passage and directly injects the fuel into the cylinder by increasing the pressure with the high-pressure pump.

  An in-cylinder injection engine that directly injects fuel into a cylinder has a shorter time from fuel injection to combustion than an intake port injection engine that injects fuel into an intake port. Therefore, it is difficult to ensure a sufficient time for atomizing the liquid fuel injected into the cylinder. Therefore, in a cylinder injection engine, it is common to atomize fuel immediately after injection by increasing the pressure of the fuel and injecting it into the cylinder. As such an in-cylinder injection engine, there is known an engine in which fuel sucked from a fuel tank by an electric low-pressure pump is supplied to a high-pressure pump, discharged from the high-pressure pump, and pumped to a fuel injection valve.

  In the cylinder injection engine having such a configuration, when the pressure of the fuel discharged from the low-pressure pump is reduced, the fuel is boiled under reduced pressure due to the pressure drop when the high-pressure pump sucks the fuel, and vapor (bubbles) is contained in the fuel. May occur. When vapor is generated in the fuel, the fuel discharge efficiency of the high-pressure pump decreases, the fuel pressure (fuel pressure) discharged from the high-pressure pump cannot be set as the target fuel pressure, or the high-pressure pump is damaged by pressure waves caused by cavitation. There is a risk of doing so.

  As a method of suppressing the generation of this vapor, based on the vapor pressure characteristics according to the temperature of the fuel, a low pressure pump is used to lower the fuel pressure when the temperature is low while increasing the fuel pressure when the temperature is high. It is conceivable to vary the pressure of the discharged fuel. The pump characteristics may vary due to individual differences and changes over time, but feedback control using a fuel pressure sensor that detects the fuel pressure is generally used to control the fuel pressure with high accuracy in consideration of this variation. Is. However, mounting of a fuel pressure sensor causes new problems such as securing a mounting space and increasing manufacturing costs.

  On the other hand, the following Patent Document 1 describes a fuel pressure control device including a pressure regulator. The pressure regulator opens when the pressure of the fuel supplied from the low pressure pump to the high pressure pump exceeds a predetermined pressure, and operates to return a part of the fuel to the fuel tank. The fuel pressure control device controls the pressure of the fuel supplied from the low pressure pump to the high pressure pump so as to gradually increase from a low value, thereby opening the operating point of the low pressure pump when the pressure regulator opens. Calculate the valve operating point. This valve opening operating point changes due to variations in pump characteristics. By correcting the control of the low-pressure pump based on the calculated valve opening operating point, it becomes possible to control the fuel pressure in consideration of the variation in the characteristics of the low-pressure pump.

JP 2010-255501 A

  Here, the pressure of the fuel supplied from the low pressure pump to the high pressure pump varies with the pulsation of the high pressure pump. Therefore, when the low pressure pump is actually driven in the vicinity of the valve opening operation point to calculate the valve opening operation point as in the fuel pressure control device described in Patent Document 1, chattering occurs in the pressure regulator and noise is generated. There has been a problem that the pressure regulator is generated or the pressure regulator is damaged.

  The present invention has been made in view of such problems, and its purpose is to calculate a valve opening operating point that is an operating point at which the pressure regulator opens without causing chattering, and to open the valve opening operating point. It is an object of the present invention to provide a fuel pressure control device capable of controlling the fuel pressure with high accuracy by correction based on the above.

  In order to solve the above problems, a fuel pressure control device according to the present invention sucks fuel from a fuel tank (11) of a vehicle (100) by a low-pressure pump (13) and uses a high-pressure pump ( 16) A fuel pressure control device (FC) of the engine (200) that supplies the pressure by the high-pressure pump and directly injects the fuel into the cylinder, and opens when the pressure of the fuel flowing through the fuel passage exceeds a predetermined pressure. And a pressure regulator (19) for discharging the fuel from the fuel passage, the pressure and flow rate of the fuel that the low pressure pump needs to supply to the high pressure pump, and the voltage supplied to the motor (10) of the low pressure pump A storage unit (42) for storing a reference characteristic comprising a relationship with the current or the rotational speed of the motor, and a voltage and a voltage based on the reference characteristic stored in the storage unit. An operating point comprising a combination of a controller (40) for supplying current to the motor, a voltage to be supplied to the motor, and a current flowing to the motor or the number of rotations of the motor when the voltage is supplied to the motor. An operating point detecting unit (43) for detecting the motor, based on the detection result of the operating point detecting unit in two operating ranges sandwiching the operating point at which the pressure regulator is expected to open. A valve opening that is the operating point at which the pressure regulator opens, by calculating characteristic equations of the voltage supplied to the motor and the current flowing through the motor when the voltage is supplied to the motor or the rotational speed of the motor. As an operating point, a common solution of the two characteristic equations is calculated, a correction value is calculated based on a comparison between the valve opening operating point and the reference characteristic, and the correction value is used. With obtaining the correction characteristic by correcting the reference characteristic, and controls the low-pressure pump to supply the voltage and current to the motor based on the corrected characteristics.

  According to the present invention, two characteristic equations are derived in two operating ranges sandwiching the operating point where the pressure regulator is expected to open, and the valve opening operating point that is the operating point at which the pressure regulator opens is Calculate the common solution of two characteristic equations. Accordingly, when calculating the valve opening operating point, it is not necessary to actually drive the motor of the low-pressure pump at an operating point near the valve opening operating point, so that chattering of the pressure regulator can be prevented.

  In the present invention, a correction value is calculated based on the comparison between the valve opening operating point calculated in this way and the reference characteristic, and the correction characteristic is obtained by correcting the reference characteristic using the correction value. Based on this correction characteristic, the voltage and current are supplied to the motor to control the low-pressure pump. Therefore, it is possible to control the low-pressure pump with high accuracy by correcting the motor characteristics in consideration of variations based on individual differences of the low-pressure pumps and controlling the low-pressure pump based on the correction characteristics. .

  According to the present invention, the valve opening operating point, which is the operating point at which the pressure regulator opens, is calculated without causing chattering, and the fuel pressure is controlled with high accuracy by correction based on the valve opening operating point. It is possible to provide a fuel pressure control device capable of performing the above.

It is explanatory drawing which shows the vehicle carrying the fuel pressure control apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows the structure of ECU periphery of FIG. It is a flowchart which shows the process which ECU of FIG. 1 performs. It is the map which the memory | storage part of FIG. 2 has memorize | stored. It is explanatory drawing which made the graph which the memory | storage part of FIG. It is a flowchart which shows the process which ECU of FIG. 1 performs. It is a flowchart which shows the process which ECU of FIG. 1 performs. It is explanatory drawing which shows each operating point. It is a flowchart which shows the process which ECU of FIG. 1 performs.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same constituent elements in the drawings will be denoted by the same reference numerals as much as possible, and redundant description will be omitted.

  First, the outline of the fuel pressure control apparatus FC according to the present invention will be described with reference to FIGS. 1 and 2. The fuel pressure control device FC is a device that is mounted on the vehicle 100 and controls the pressure of fuel supplied to the engine 200 of the vehicle 100. The engine 200 has a plurality of cylinders (not shown), and is an in-cylinder injection type internal combustion engine that directly injects gasoline as fuel into each cylinder. The engine 200 generates the driving force (torque) of the vehicle 100 by burning the fuel supplied from the fuel tank 11.

  The fuel tank 11 is a container that stores fuel therein. A sub tank 12 is provided in the fuel tank 11. When the remaining amount of fuel in the fuel tank 11 is small, the sub-tank 12 takes in the fuel by the jet pump 21 and stores it intensively. On the other hand, when the fuel level in the fuel tank 11 is higher than the upper opening of the sub tank 12, the fuel in the fuel tank 11 flows into the sub tank 12 from the upper opening of the sub tank 12, and the sub tank 12 is filled with fuel. It is.

  In the sub tank 12, a low pressure pump 13 for sucking and discharging fuel is provided. A suction filter 14 is attached to the suction port of the low-pressure pump 13. The low pressure pump 13 has a motor 10. The motor 10 is driven to rotate by receiving electric power, whereby the fuel in the sub tank 12 is sucked into the low pressure pump 13 through the suction filter 14. The fuel discharged from the low-pressure pump 13 flows through the fuel passage 15 and is supplied to the high-pressure pump 16 and is also supplied to the jet pump 21 through the fixed return pipe 17.

  The fuel passage 15 is provided with a fuel filter 18 that filters the fuel discharged from the low-pressure pump 13. A return pipe 20 that branches from the fuel passage 15 is provided in a portion of the fuel passage 15 downstream of the fuel filter 18. Further, a temperature sensor 23 for detecting a fuel temperature Tf is provided in a portion of the fuel passage 15 downstream of the return pipe 20. The temperature sensor 23 outputs a signal corresponding to the detected temperature Tf.

  A pressure regulator 19 is connected to the return pipe 20. The pressure regulator 19 opens when the fuel pressure in the fuel passage 15 (the pressure of the fuel discharged from the low-pressure pump 13 and equivalent to the fuel pressure in the return pipe 20) exceeds a predetermined fuel pressure (for example, 650 kPa). . Accordingly, when the fuel pressure in the fuel passage 15 becomes equal to or higher than the predetermined fuel pressure, the pressure regulator 19 is opened, and the fuel in the fuel passage 15 is returned into the fuel tank 11 through the return pipe 20. Thus, the fuel pressure in the fuel passage 15 is controlled so as not to exceed a predetermined fuel pressure.

  A jet pump 21 is provided below the sub tank 12. A fixed return pipe 17 extending from the low pressure pump 13 is connected to the introduction port of the jet pump 21. An orifice 22 that determines the flow rate of fuel supplied to the jet pump 21 is provided in the middle of the fixed return pipe 17. The fuel supplied from the fixed return pipe 17 is ejected to the introduction port of the jet pump 21, thereby generating a negative pressure (pump action) in the jet pump 21. Due to this negative pressure, the fuel in the fuel tank 11 is sucked into the jet pump 21 and flows into the sub tank 12. Note that the return pipe 20 may be connected to the fixed return pipe 17 or the jet pump 21.

  A high pressure pump 16 is connected to the downstream end of the fuel passage 15. The high-pressure pump 16 is a piston pump that repeatedly sucks and discharges fuel by reciprocating a piston (not shown) in a pump chamber (not shown). The piston is driven as the cam shaft (not shown) of the engine 200 rotates.

  A delivery pipe 34 is connected to the downstream side of the high-pressure pump 16. The delivery pipe 34 is provided with a plurality of injectors 35. Each injector 35 is provided so as to protrude inside each of the plurality of cylinders of engine 200. As a result, the fuel whose pressure has been increased by the high-pressure pump 16 is sent to the delivery pipe 34 and directly injected from the injector 35 into each cylinder. The delivery pipe 34 is provided with a high-pressure side fuel pressure sensor 36 that detects a fuel pressure (pressure of fuel discharged from the high-pressure pump 16).

  The vehicle 100 is equipped with an air flow meter 37 and a crank angle sensor 38. The air flow meter 37 detects the flow rate of the air that the engine 200 sucks in the intake process, and outputs a signal corresponding to the detected value. The crank angle sensor 38 outputs a pulse signal at every predetermined crank angle in synchronization with the rotation of a crankshaft (not shown) of the engine 200.

  The engine control circuit (hereinafter referred to as “ECU”) 39 is an electronic device mainly composed of a microcomputer. The ECU 39 is electrically connected to various sensors such as the temperature sensor 23, the high-pressure side fuel pressure sensor 36, the air flow meter 37, and the crank angle sensor 38, and receives signals output from the various sensors. The ECU 39 is electrically connected to the controller 40 and the high-pressure pump 16 that drive the low-pressure pump 13 and controls them by outputting a control signal.

  FIG. 2 schematically shows functions of the ECU 39. The ECU 39 includes a storage unit 42, an operating point detection unit 43, a calculation unit 44, and a correction unit 45. The ECU 39 is configured to receive signals output from the current sensor 46 and the rotation speed sensor 47 that the controller 40 has. The current sensor 46 outputs a signal corresponding to the current supplied to the motor 10. The rotation speed sensor 47 outputs a signal corresponding to the rotation speed of the motor 10.

  The storage unit 42 is configured by a nonvolatile memory that can store various programs and data. For example, as shown in FIGS. 4 and 5 to be described later, the storage unit 42 has a required discharge amount Qfp [L / h] that is a flow rate of fuel that the low pressure pump 13 needs to discharge and a low pressure that is a pressure of fuel. The reference characteristic of the motor 10 that is composed of the relationship between the side target fuel pressure Pftg [kPa] and the voltage V [V] applied to the motor 10 is stored as a map. The ECU 39 executes various programs stored in the storage unit 42 to determine the amount of fuel injected by the injector 35, the ignition timing of the injected fuel, and the like, and controls the engine 200. At that time, the ECU 39 feedback-controls the high-pressure pump 16 so that the fuel pressure detected by the high-pressure side fuel pressure sensor 36 matches the high-pressure side target fuel pressure.

  As will be described later, the operating point detection unit 43 is a part that detects an operating point that is a combination of a voltage supplied to the motor 10 of the low-pressure pump 13 and a current supplied to the motor 10 together with the voltage. The operating point detector 43 detects the operating point based on a signal received from the current sensor 46 of the controller 40.

  The calculation unit 44 is a part that calculates various values necessary for control of the engine 200 based on data stored in the storage unit 42 and signals received by the ECU 39. For example, the calculation unit 44 calculates the crank angle and the rotational speed Ne of the engine 200 based on a signal received from the crank angle sensor 38.

  The correction unit 45 is a part that corrects the program and data stored in the storage unit 42. Specifically, the correction unit 45 corrects the reference characteristics of the motor 10 stored in the storage unit 42 as will be described later.

  Next, the process executed by the ECU 39 when controlling the low pressure pump 13 in the fuel pressure control device FC configured as described above will be described with reference to FIGS. 4 to 9. In the following, for the sake of simplicity, a detailed description will be given assuming that the processing performed by each part such as the operating point detection unit 43 of the ECU 39 is performed by the ECU 39 as a whole.

  The ECU 39 repeatedly executes the low-pressure pump control routine shown in FIG. 3 at a predetermined cycle while receiving power.

  First, in step S101 shown in FIG. 3, the ECU 39 calculates the low pressure side target fuel pressure Pftg based on the rotational speed Ne of the engine 200 and the fuel temperature Tf. The low-pressure side target fuel pressure Pftg is a target value of the pressure of fuel discharged from the low-pressure pump 13 (fuel pressure in the fuel passage 15).

  The ECU 39 calculates the low pressure side target fuel pressure Pftg based on a map or a mathematical expression. In the map or the like, the low-pressure side target fuel pressure Pftg is a fuel pressure necessary for suppressing the vapor (the minimum fuel pressure that can prevent the fuel from depressurizing and boiling due to the pressure drop when the high-pressure pump 16 sucks the fuel, or a slightly higher fuel pressure). Is set to The temperature Tf of the fuel is detected by the temperature sensor 23 as described above, but instead may be estimated based on at least one of the engine coolant temperature, the oil temperature, and the like.

  Next, in step S102, the ECU 39 calculates a required fuel injection amount Qeng, which is a fuel injection amount required by the engine 200. The ECU 39 calculates the required fuel injection amount Qeng by multiplying the amount of fuel injected by the injector 35 per one rotation of the engine 200 by the rotational speed Ne of the engine 200. When the vehicle 100 is traveling and “fuel cut” is being performed in which the supply of fuel to the engine 200 is stopped, the required fuel injection amount Qeng is zero.

  Next, in step S103, the ECU 39 calculates a fixed return flow rate Qrt that is a flow rate of fuel flowing through the fixed return pipe 17. The ECU 39 calculates the fixed return flow rate Qrt based on a map or a mathematical formula corresponding to the low pressure side target fuel pressure Pftg.

  Next, in step S104, the ECU 39 calculates a required discharge amount Qfp, which is a fuel discharge amount required for the low-pressure pump 13. The required discharge amount Qfp is the sum of the required fuel injection amount Qeng and the fixed return flow rate Qrt. When the fuel cut described above is executed, the required fuel injection amount Qeng is zero, so the required discharge amount Qfp is the same value as the fixed return flow rate Qrt.

  Next, the ECU 39 calculates the base drive voltage Vbase in step S105. The base drive voltage Vbase is a voltage that needs to be supplied to the motor 10 in order to cause the low-pressure pump 13 to discharge fuel at the low-pressure side target fuel pressure Pftg and the required discharge amount Qfp. The ECU 39 calculates the base drive voltage Vbase based on the maps shown in FIGS. 4 and 5 stored in the storage unit 42. FIG. 5 is a graph of FIG.

  Here, the maps shown in FIGS. 4 and 5 are reference characteristics that do not take into account variations due to individual differences or changes with time of the motor 10 of the low-pressure pump 13. Therefore, the actual characteristics of the motor 10 of the low-pressure pump 13 may be different from those of the maps shown in FIGS. For this reason, if the low-pressure pump 13 is driven based on the map, the accuracy of controlling the fuel pressure may be reduced.

  Therefore, in the fuel pressure control device FC, in the subsequent steps S106 and S107, learning is performed to correct the maps shown in FIGS. 4 and 5 so as to correspond to the actual characteristics of the motor 10, and the corrected map The low pressure pump 13 is driven based on the above. Hereinafter, this learning will be described.

  In step S106, the ECU 39 calculates a learning value VIrn. Details of the process executed by the ECU 39 in step S106 are shown in FIG.

  The ECU 39 determines whether or not a fuel cut flag is established in step S201 shown in FIG. That is, it is determined whether or not the vehicle 100 is traveling and is in a state of executing “fuel cut” in which the supply of fuel to the engine 200 is stopped. When it is determined that the fuel cut flag is not established (S201: NO), the ECU 39 ends the process. On the other hand, when it is determined that the fuel cut flag is established (S201: YES), the ECU 39 proceeds to the process of step S202.

  Next, in step S202, the ECU 39 detects a valve opening operating point that is an operating point of the motor 10 when the pressure regulator 19 opens. Details of the process executed by the ECU 39 in step S202 are shown in FIG.

  The ECU 39 sets the operating point 1 on the low pressure side in step S301 shown in FIG. Specifically, as shown in FIG. 8, in the operating range where the voltage V applied to the motor 10 is lower than the operating range A including the operating point at which the pressure regulator 19 is expected to open, the operating point 1 is set.

  Next, in step S302, the ECU 39 applies the voltage V1 corresponding to the operating point 1 to the motor 10 and detects the current value I1 supplied to the motor 10 at that time by the current sensor 46. The ECU 39 stores the voltage V1 and the current value I1.

  Next, the ECU 39 sets the operating point 2 on the low pressure side in step S303. This operating point 2 is also set in the operating range where the voltage V applied to the motor 10 is lower than the operating range A.

  Next, in step S304, the ECU 39 applies the voltage V2 corresponding to the operating point 2 to the motor 10 and detects the current value I2 supplied to the motor 10 at that time by the current sensor 46. The ECU 39 stores the voltage V2 and the current value I2.

  Next, in step S305, the ECU 39 calculates the characteristic formula (1) based on the voltages V1, V2 and the current values I1, I2. That is, the ECU 39 calculates the characteristic equation (1) that is a straight line passing through the operating point 1 (V1, I1) and the operating point 2 (V2, I2).

  Next, the ECU 39 sets the operating point 3 on the high pressure side in step S306. Specifically, as shown in FIG. 8, in the operating range where the voltage V applied to the motor 10 is higher than the operating range A including the operating point at which the pressure regulator 19 is expected to open, the operating point 3 Set.

  Next, in step S307, the ECU 39 applies the voltage V3 corresponding to the operating point 3 to the motor 10 and detects the current value I3 supplied to the motor 10 at that time by the current sensor 46. The ECU 39 stores the voltage V3 and the current value I3.

  Next, the ECU 39 sets the operating point 4 on the high pressure side in step S308. This operating point 4 is also set in the operating range where the voltage V applied to the motor 10 is higher than the operating range A.

  Next, in step S309, the ECU 39 applies the voltage V4 corresponding to the operating point 4 to the motor 10 and detects the current value I4 supplied to the motor 10 at that time by the current sensor 46. The ECU 39 stores the voltage V4 and the current value I4.

  Next, in step S310, the ECU 39 calculates the characteristic formula (2) based on the voltages V3 and V4 and the current values I3 and I4. That is, the ECU 39 calculates a characteristic equation (2) that is a straight line passing through the operating point 3 (V3, I3) and the operating point 4 (V4, I4).

  Next, in step S311, the ECU 39 calculates an operating point that is a common solution of the characteristic equation (1) and the characteristic equation (2). That is, the solution of simultaneous equations consisting of the characteristic equation (1) and the characteristic equation (2) is calculated, and the intersection of the respective straight lines becomes the valve opening operating point (Vp, Ip).

  Returning to FIG. 6, the description will be continued. After completing the calculation of the valve opening operating point in step S202, the ECU 39 calculates a correction value in the next step S203. Details of the process executed by the ECU 39 in step S203 are shown in FIG.

  In step S401 shown in FIG. 9, the ECU 39 calculates a valve opening pressure P0 that is a fuel pressure when the pressure regulator 19 opens, and a flow rate Q0 of the fuel passing through the orifice 22 at the valve opening pressure P0. The value of the valve opening pressure P0 can be calculated based on the mechanical characteristics of the pressure regulator 19. Further, the value of the flow rate Q0 can be calculated based on the low pressure side target fuel pressure Pftg.

  Next, in step S402, the ECU 39 calculates a reference voltage V0 corresponding to the valve opening pressure P0 and the flow rate Q0. Specifically, the ECU 39 needs to supply the motor 10 with the valve opening pressure P0 and the flow rate Q0 based on the maps shown in FIGS. 4 and 5 (maps corresponding to the reference characteristics of the motor 10). A reference voltage V0, which is a certain voltage, is calculated.

  Next, in step S403, the ECU 39 calculates a correction value from the voltage Vp at the valve opening operating point detected in step S202 and the reference voltage V0 calculated in step S402. That is, the deviation between the voltage Vp and the reference voltage V0 indicates the degree of variation in the characteristics generated in the motor 10 due to individual differences or changes with time, and a correction value corresponding to this deviation is calculated.

  Returning to FIG. 6, the description will be continued. The ECU 39, which has finished calculating the correction value in step S203, determines whether or not learning has been performed in the previous cycle in the next step S204. If it is determined that learning has not been performed in the previous cycle (step S204: YES), the ECU 39 proceeds to the process of step S205.

  Next, in step S205, the ECU 39 sets the correction value calculated in step S203 as the learning value VIrn.

  On the other hand, if it is determined in step S204 that learning has been performed in the previous cycle (step S204: NO), the ECU 39 proceeds to the process of step S206.

  Next, in step S206, the ECU 39 sets the average value of the previous learning value and the correction value calculated in step S203 as a new learning value VIrn. By adopting the average value, even when the correction value suddenly increases due to disturbance or the like, the influence can be mitigated.

  Returning to FIG. 3, the description will be continued. After completing the calculation of the learning value in step S106, the ECU 39 calculates the drive voltage Vfp supplied when driving the low-pressure pump 13 in the next step S107. This drive voltage Vfp is the sum of the base drive voltage Vbase calculated in step S104 and the learning value VIrn calculated in step S106. This drive voltage Vfp is a correction characteristic of the motor 10 corrected in consideration of individual differences and variations due to changes over time, and the maps shown in FIGS. 4 and 5 are rewritten based on this.

  Next, ECU39 transmits a control signal to the controller 40 based on the characteristic of the motor 10 obtained by correction | amendment by step S108. As a result, it is possible to perform control according to the actual characteristics of the motor 10, and it is possible to control the fuel pressure with high accuracy by eliminating the influence of variations in characteristics due to individual differences or changes with time of the motor 10. .

  As described above, according to the fuel pressure control device FC, the characteristic equations (1) and (2) are calculated in two operating ranges sandwiching the operating point at which the pressure regulator 19 is expected to open, and the pressure regulator 19 is opened. The common solution of the characteristic formulas (1) and (2) is calculated as the valve opening operating point that is the valve operating point. Therefore, when calculating the valve opening operating point, it is not necessary to actually drive the motor 10 of the low-pressure pump 13 at an operating point near the valve opening operating point, so that chattering of the pressure regulator 19 can be prevented. .

  The fuel pressure control device FC further calculates a correction value based on the comparison between the valve opening operating point thus calculated and the reference characteristic, and corrects the reference characteristic using the correction value to obtain the correction characteristic. Based on the correction characteristic, the voltage and current are supplied to the motor to control the low pressure pump 13. Accordingly, the motor characteristics are corrected in consideration of variations due to individual differences of the motor 10 and the control of the motor 10 based on the correction characteristics allows the pressure of the fuel discharged from the low-pressure pump 13 to be highly accurate. It becomes possible to control.

  The fuel pressure control device FC detects an operating point that is a combination of a voltage supplied to the motor 10 of the low-pressure pump 13 and a current supplied to the motor 10 together with the voltage. However, the present invention is not limited to this. It is not something. That is, the rotation speed of the motor 10 is adopted instead of the current supplied to the motor 10, and the combination of the voltage supplied to the motor 10 of the low-pressure pump 13 and the rotation speed of the motor 10 when the voltage is supplied to the motor 10. You may comprise so that the operating point which consists of may be detected.

  Further, in the fuel pressure control device FC, the operating point is not detected in the operating range A including the operating point at which the pressure regulator 19 is expected to open. As a result, it is possible to calculate the valve opening operating point without opening the pressure regulator 19.

  In addition, the fuel pressure control device FC detects the operating point while the vehicle 100 is running and the fuel cut that stops the fuel supply to the engine 200 is being executed. Thereby, since the required fuel injection amount Qeng of the engine 200 becomes zero and the operating point is detected when the motor 10 is stably driven, the detection accuracy can be improved.

  Further, the fuel pressure control device FC may detect the operating point when the change per unit time in the amount of fuel supplied to the engine 200 is a predetermined value or less. For example, this corresponds to the case where the vehicle 100 is idling or the case where a cruise control traveling is performed while the vehicle speed is controlled to be within a predetermined range. Even in such a case, since the operating point is detected when the motor 10 is stably driven, the detection accuracy can be improved.

  Further, the fuel pressure control device FC may detect the operating point when the vehicle 100 is stopped and the supply of fuel to the engine 200 is stopped. For example, the case where the vehicle 100 is in a so-called idle stop corresponds to this. Even in such a case, since the operating point is detected when the motor 10 is stably driven, the detection accuracy can be improved.

  The fuel pressure control device FC stores the correction value in the storage unit 42 that is a non-volatile memory, and after the operation of the vehicle 100 that has stored the correction value is stopped, At the start, the correction characteristic may be used to correct the reference characteristic to obtain the correction characteristic. As a result, the driving of the vehicle 100 is stopped, and the motor 10 can be appropriately controlled from the initial stage of driving using the correction value calculated in the previous driving in the next driving.

  The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. In other words, those specific examples that have been appropriately modified by those skilled in the art are also included in the scope of the present invention as long as they have the characteristics of the present invention. For example, the elements included in each of the specific examples described above and their arrangement, materials, conditions, shapes, sizes, and the like are not limited to those illustrated, but can be changed as appropriate. Moreover, each element with which each embodiment mentioned above is provided can be combined as long as technically possible, and the combination of these is also included in the scope of the present invention as long as it includes the features of the present invention.

10: motor 11: fuel tank 13: low pressure pump 15: fuel passage 16: high pressure pump 19: pressure regulator 39: engine control circuit 40: controller FC: fuel pressure control device 42: storage unit 43: operating point detection unit

Claims (6)

The fuel in the fuel tank (11) of the vehicle (100) is sucked by the low pressure pump (13) and supplied to the high pressure pump (16) through the fuel passage (15), and the pressure is increased by the high pressure pump to enter the cylinder. A fuel pressure control device (FC) for a direct injection engine (200),
A pressure regulator (19) that opens when the pressure of the fuel flowing through the fuel passage exceeds a predetermined pressure, and discharges the fuel from the fuel passage;
A reference characteristic consisting of the relationship between the pressure and flow rate of the fuel that the low-pressure pump needs to supply to the high-pressure pump and the voltage and current supplied to the motor (10) of the low-pressure pump or the rotational speed of the motor is stored. A storage unit (42);
A controller (40) for supplying voltage and current to the motor based on the reference characteristics stored in the storage unit;
An operating point detector (43) for detecting an operating point comprising a combination of a voltage supplied to the motor and a current flowing through the motor or the rotation speed of the motor when the voltage is supplied to the motor; Prepared,
Based on the detection result of the operating point detector, the voltage supplied to the motor and the voltage supplied to the motor in two operating ranges sandwiching the operating point where the pressure regulator is expected to open And calculating a characteristic equation for the current flowing through the motor or the rotational speed of the motor,
As a valve opening operating point that is the operating point at which the pressure regulator opens, a common solution of the two characteristic equations is calculated,
A correction value is calculated based on the comparison between the valve opening operating point and the reference characteristic, and the correction characteristic is obtained by correcting the reference characteristic using the correction value, and the voltage and current are calculated based on the correction characteristic. Is supplied to the motor to control the low-pressure pump.   2. The operation point detection unit according to claim 1, wherein the operation point detection unit does not detect the operation point in a predetermined operation range including the operation point at which the pressure regulator is expected to open. Fuel pressure control device.   3. The operating point detection unit according to claim 1, wherein the operating point detection unit detects the operating point when the vehicle is running and fuel supply to the engine is stopped. Fuel pressure control device.   3. The operation point detection unit according to claim 1, wherein the operation point detection unit detects the operation point when a change per unit time in a fuel supply amount to the engine is a predetermined value or less. 4. Fuel pressure control device.   3. The operating point detection unit according to claim 1, wherein the operating point detection unit detects the operating point when the vehicle is stopped and the supply of fuel to the engine is stopped. 4. Fuel pressure control device.   The correction value is stored in a non-volatile memory, and after the operation of the vehicle for which the correction value has been stored is stopped, the reference value is used using the correction value at the start of the next driving of the vehicle. 6. The fuel pressure control apparatus according to claim 1, wherein the correction characteristic is obtained by correcting the characteristic.

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