JP2009057885A - Fuel pressure control device and fuel pressure control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel pressure control device capable of sufficiently exhibiting its original pressure bearing performance by obtaining a correct value of a rail pressure maximum value at controlling fuel pressure (rail pressure) in an accumulator. <P>SOLUTION: In the fuel pressure control device for controlling the rail pressure which is the fuel pressure in a common rail (accumulator), a plurality of sampling values of the rail pressure detected by a fuel pressure sensor (detection means) are acquired, a maximum value of the plurality of obtained sampling values is calculated and the calculated maximum value is used as a detection value as actual rail pressure. Feedback control is conducted so that the maximum value used as the detection value becomes closer to target fuel pressure Ptrg. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel pressure control device that controls fuel pressure in a pressure accumulating chamber, and a fuel pressure control system including the device.

Conventionally, a pressure accumulating chamber that stores fuel used for combustion of an internal combustion engine in a high pressure state, a fuel pump that pressurizes fuel into the pressure accumulating chamber, a fuel injection valve that injects fuel stored in the pressure accumulating chamber, and a pressure accumulating chamber There is known a fuel injection device provided with detection means for detecting the fuel pressure (hereinafter referred to as rail pressure). The operation of the fuel pump is feedback controlled so that the rail pressure detected by the detection means approaches the target value (see Patent Document 1).
Japanese Patent Laid-Open No. 5-106495

  Here, when viewed microscopically, the rail pressure fluctuates due to the following various factors. That is, when the fuel is pressurized and supplied to the pressure accumulating chamber by the fuel pump, the pressurized supply becomes a factor in increasing the rail pressure. Further, when fuel is being injected by the fuel injection valve, the injection becomes a factor in lowering the rail pressure. In addition, fuel leaks that occur at the sliding portions of the fuel pump and the fuel injection valve cause the rail pressure to drop.

  10 (a) and 10 (b) show changes in the intake and supply modes of fuel by the fuel pump, FIG. 10 (c) shows the injection timing by the fuel injection valve, and FIG. 10 (d) shows the actual timing. It represents the change in rail pressure. And since this leak amount increases with time due to a change with time of the sliding portion or the like, the fluctuation of the rail pressure changes from a solid line to a dotted line in FIG.

  Thus, since the rail pressure fluctuates when viewed microscopically, the detected value may be the maximum value or the minimum value of the rail pressure fluctuation depending on the timing at which the rail pressure is detected. And since it is necessary to control the rail pressure so that it does not exceed the pressure resistance of various parts, it is conceivable to control the rail pressure with a margin so that it does not exceed the pressure resistance. The injection pressure cannot be increased sufficiently, and the pressure resistance capability originally provided cannot be fully utilized. Therefore, it is desirable to control the rail pressure using a value detected at a timing predicted to be maximum (for example, a timing indicated by a symbol S in FIG. 10).

  However, in reality, the timing at which the rail pressure becomes maximum varies depending on various factors exemplified below, and it is difficult to accurately predict the rail pressure.

  (Example 1) The injection timing varies depending on the operating state of the internal combustion engine. For example, the injection start timing is generally advanced as the engine speed increases. Since the injection is a cause of the rail pressure drop as described above, if the injection timing changes, the rail pressure fluctuation state also changes and the timing at which the rail pressure becomes maximum also changes.

  (Example 2) In FIG. 10, since injection by the fuel injection valve is started while pressure is supplied by the fuel pump, a high injection pressure can be obtained. I can say that. However, in order to prevent loads of various auxiliary machines (for example, a fuel pump, an air conditioner compressor and an alternator, etc.) driven by the output shaft of the internal combustion engine from being concentrated on the output shaft at the same timing, for example, FIG. As shown, it may be desirable in terms of load distribution to the output shaft to drive the fuel pump so that pressurized supply is started after injection. As described above, since the pressurized supply is a factor for increasing the rail pressure, if the timing of the pressurized supply changes, the fluctuation state of the rail pressure also changes, and the timing at which the rail pressure becomes maximum also changes.

  (Example 3) In FIG.10 and FIG.11, with respect to one pressurization supply by the plunger of a fuel pump, injection by a fuel injection valve is performed once. Therefore, the rising fluctuation period of the rail pressure due to pressurization and the falling fluctuation period of the rail pressure due to injection are the same period. However, depending on the number of revolutions of the fuel pump, for example, as shown in FIG. 12, the injection is performed four times for three pressurization supplies. Then, since the rail pressure increase fluctuation cycle due to the pressurization supply and the decrease fluctuation cycle due to the injection are different, the rail pressure fluctuates in a different manner for each pressurization supply. That is, the timing at which the rail pressure becomes maximum changes for each pressurizing supply.

  If the timing at which the rail pressure becomes maximum changes due to various factors described above, and the rail pressure fluctuation state changes with time due to fuel leakage as described above, it is possible to accurately predict the timing at which the rail pressure becomes maximum. It becomes extremely difficult.

  The present invention has been made in order to solve the above-mentioned problems, and its purpose is to acquire an accurate value of the maximum rail pressure value and control the fuel pressure (rail pressure) in the pressure accumulating chamber. An object of the present invention is to provide a fuel pressure control device and a fuel pressure control system that can sufficiently exhibit pressure resistance.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

  According to the first aspect of the present invention, a pressure accumulating chamber that stores fuel used for combustion of the internal combustion engine in a high pressure state, a fuel pump that pressurizes and supplies the fuel to the pressure accumulating chamber, and a fuel that injects fuel stored in the pressure accumulating chamber. A fuel pressure control device that is applied to a fuel injection device that includes an injection valve and a detection unit that detects a fuel pressure in the pressure accumulation chamber, and that controls a fuel pressure in the pressure accumulation chamber. Obtaining means for obtaining the value, calculating means for calculating the maximum value of the plurality of sampling values obtained by the obtaining means, and control for controlling the fuel pressure in the pressure accumulating chamber according to the maximum value calculated by the calculating means And means.

  According to this, a plurality of sampling values which are detected values of the fuel pressure (rail pressure) in the pressure accumulating chamber are acquired, and the maximum value of the acquired sampling values is calculated. Therefore, the maximum value calculated in this way is detected at the timing predicted to be the maximum even when the timing at which the rail pressure reaches the maximum changes as in (Example 1) to (Example 3) described above. It is an accurate value compared to a single value. Therefore, according to the present invention in which the rail pressure is controlled according to the maximum value, which is a value with increased accuracy, the inherent pressure resistance capability can be sufficiently exhibited, and the fuel injection can be sufficiently increased in pressure. it can.

  The invention according to claim 2 is characterized in that the acquisition means acquires the sampling value detected by the detection means during a preset sampling period. Therefore, it is possible to improve the detection accuracy of the maximum value by setting the sampling period in a period including the timing at which the rail pressure is predicted to be maximum. In addition, if the sampling value is acquired only for the sampling period, the fuel pressure control device, such as the process of converting the sampling value from analog to digital, the process of calculating the maximum value, etc., compared to the case of acquiring the sampling value constantly Can reduce the processing load.

  Incidentally, as an example of setting the sampling period, it may be set to a range including the pressurization supply start timing by the fuel pump or a range including the injection start timing by the fuel injection valve. And it is suitable to set the said sampling period T1 for every pressurization supply start timing which arrives, or for every injection start timing which arrives so that the code | symbol T1 in FIG. 10 may illustrate.

  According to a third aspect of the present invention, in the case where the pressurization supply start timing by the fuel pump and the injection start timing by the fuel injection valve are not synchronized, the calculation means performs the first period including the injection start timing. Calculating a maximum value of the acquired sampling values, calculating an intra-group maximum value which is a maximum value among the plurality of maximum values acquired in a group period including a plurality of the first periods, and the control means Controls the fuel pressure in the pressure accumulating chamber according to the maximum value in the group.

  According to a fourth aspect of the present invention, the control means executes control of the fuel pressure in the pressure accumulating chamber according to the maximum value during a high load operation in which an output required for the internal combustion engine is a predetermined value or more. It is characterized by. Therefore, the rail pressure is controlled according to the maximum value, which is a value with increased accuracy, at the time of high load operation where the rail pressure may exceed the pressure resistance, so that the above-mentioned pressure resistance capability can be fully exhibited. An effect is exhibited suitably. Also, if the control according to the maximum value is not executed at times other than during high load operation, the process of converting the sampling value from analog to digital compared to the case where the control according to the maximum value is always executed, The processing load of the fuel pressure control device, such as processing for calculating the maximum value, can be reduced.

  According to a fifth aspect of the present invention, the control means executes control of the fuel pressure in the pressure accumulating chamber according to the maximum value during low speed operation where the rotational speed of the fuel pump is a predetermined value or less. To do. By the way, when the fuel pump is driven by the output shaft of the internal combustion engine, the rotational speed of the fuel pump is also low during the low speed operation of the internal combustion engine. Then, the amount of lubricating oil supplied to the sliding portion of the fuel pump is reduced, so that the fuel pump is easily seized. Therefore, if the control of the fuel pressure in the pressure accumulating chamber according to the maximum value during low-speed operation is performed as in the present invention, it is possible to accurately suppress the load of the fuel pump from exceeding an appropriate value, so that the above-described seizure prevention is prevented. Can be achieved.

  In the invention according to claim 6, the calculation means divides a plurality of sampling values into groups, calculates an average value of the sampling values for each group, and acquires the maximum value of the plurality of average values by the acquisition means. The maximum value of a plurality of sampling values. According to this, even if the sampling value is an abnormal value due to noise or the like, the abnormal sampling value is processed as an average value with other normal sampling values. For example, if the sampling values acquired within the sampling period are divided into three groups g1, g2, and g3 as shown by reference numerals g1, g2, and g3 in FIG. It is possible to reduce the influence of the abnormal sampling value on.

  As a specific means for controlling the rail pressure according to the maximum value, in the invention according to claim 7, the control means feedback-controls the operation of the fuel pump so that the maximum value becomes a target value. Features.

  According to this, if the feedback control is performed so that the maximum value does not exceed the pressure resistance, it is possible to accurately control the rail pressure to a value close to the pressure resistance. Can be sufficiently achieved.

  Further, as a specific means for controlling the rail pressure in accordance with the maximum value, in the invention according to claim 8, the control means controls the fuel pump so as to prevent the maximum value from exceeding a preset breakdown voltage. It is characterized by controlling the operation of. More specifically, during normal times, feedback control of the operation of the fuel pump is performed so that a sampling value other than the maximum value becomes the target value. When the maximum value exceeds a preset pressure resistance, the target value is forcibly reduced. And controlling the operation of the fuel pump.

  According to this, since it is possible to accurately control the rail pressure to a value close to the withstand pressure, the inherent withstand pressure capability can be sufficiently exhibited, and the fuel injection can be sufficiently increased in pressure.

  According to a ninth aspect of the present invention, the fuel pressure control device, the pressure accumulation chamber, a fuel pump that pressurizes and supplies fuel to the pressure accumulation chamber, a fuel injection valve that injects the fuel stored in the pressure accumulation chamber, and the pressure accumulation chamber A fuel pressure control system comprising: at least one detection means for detecting fuel pressure. According to this internal combustion engine control system, the various effects described above can be exhibited in the same manner.

  Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent configurations are denoted by the same reference numerals in the drawings.

(First embodiment)
The fuel pressure control device according to the present embodiment is applied to a fuel injection device that injects fuel to a diesel engine (internal combustion engine). First, the configuration of the fuel injection control device and the like will be described with reference to FIG.

  As shown in the figure, the fuel in the fuel tank 2 that stores the fuel is pumped up by the fuel pump 10 and supplied to the common rail 30 (pressure accumulating chamber) via the supply passage 21. Here, the fuel pump 10 includes a low-pressure pump 11 that pumps fuel in the fuel tank 2, a metering control valve 12 that communicates and blocks the low-pressure pump 11 and its downstream side, and a low-pressure pump via the metering control valve 12. 11 is provided with a high-pressure pump 15 for supplying the fuel sent from 11 to the outside. Here, the high pressure pump 15 corresponds to the first passage 13 and the second passage 14 which are fuel passages branched into two on the downstream side of the metering control valve 12, and the first high pressure pump 15 sucks the fuel in these passages. A plunger portion 18 provided with a plunger 16 and a second plunger 17 is provided. The hollow portion 19 inside the plunger portion 18 is provided with a rotating body 20 connected to the output shaft of the diesel engine. The first plunger 16 and the second plunger 17 are alternately displaced from the top dead center toward the bottom dead center by the rotation of the rotating body 20, so that the fuel in the first passage 13 and the second passage 14 is transferred. It is alternately sucked into the high-pressure pump 15.

  That is, as shown in FIG. 2A, when the second plunger 17 is displaced to the bottom dead center, the fuel in the second passage 14 is sucked with the displacement of the second plunger 17. On the other hand, at this time, since the first plunger 16 is displaced toward the top dead center, the fuel is pressurized and supplied to the outside through the first passage 13. As shown in FIG. 2B, when the first plunger 16 is displaced to the bottom dead center, the fuel is sucked through the first passage 13. On the other hand, at this time, since the second plunger 17 is displaced toward the top dead center, the fuel is pressurized and supplied to the outside through the second passage 14.

  As shown in FIG. 1, the first passage 13 and the second passage 14 join downstream and are connected to the supply passage 21. In addition, check valves 22 and 23 are provided on the upstream side of the first passage 13 and the second passage 14, respectively. As a result, the backflow of fuel when the first plunger 16 and the second plunger 17 are displaced is avoided.

  The fuel supplied by the fuel pump 10 is determined by the amount of fuel sucked into the fuel pump 10 (more precisely, the amount of fuel sucked into the high-pressure pump 15). That is, fuel is drawn into the high-pressure pump 15 by opening the metering control valve 12 when the first plunger 16 or the second plunger 17 is displaced toward the bottom dead center. The intake amount is determined by the valve closing timing of the metering control valve 12. In other words, the amount of fuel supplied to the outside from the fuel pump 10 is determined by the closing timing of the metering control valve 12. Incidentally, the low-pressure pump 11 as well as the high-pressure pump 15 are driven by the output shaft of the diesel engine.

  The fuel supplied from the high pressure pump 15 to the common rail 30 is supplied to the fuel injection valve 40 of each cylinder (here, four cylinders are illustrated) via the high pressure fuel passage 32. The fuel injection valve 40 includes a nozzle needle 44 and an electromagnetic solenoid 58 that open and close an injection hole for injecting fuel.

  When energization to the electromagnetic solenoid 58 is turned on, the electromagnetic force generated by the electromagnetic solenoid 58 operates so that the nozzle needle 44 opens the nozzle hole, and fuel is injected. On the other hand, when the energization to the electromagnetic solenoid 58 is turned off, the nozzle needle 44 is operated to close the injection hole by the elastic force of a spring (not shown), and the fuel injection is stopped. The fuel leaking from the fuel injection valve 40 is returned to the fuel tank 2 via the low pressure fuel passage 34.

  As shown in FIG. 1, the common rail 30 is provided with a pressure reducing valve 36 that communicates and blocks the inside of the common rail 30 and the low pressure fuel passage 34. Further, the common rail 30 is provided with a fuel pressure sensor 38 (detection means) for detecting the fuel pressure inside the common rail 30.

  The detection values of various sensors such as the detection value of the fuel pressure sensor 38 and the detection value of the accelerator sensor 64 that detects the depression amount (accelerator operation amount) of the accelerator pedal 62 are taken into the electronic control unit 60. The electronic control device 60 is configured to include a central processing unit and an appropriate memory, and operates various actuators such as a metering control valve 12, a pressure reducing valve 36, and an electromagnetic solenoid 58 based on detection values of various sensors. To do.

  Next, the operation control (rail pressure control) of the metering control valve 12 by the electronic control device 60 (fuel pressure control device) will be described in detail with reference to FIG. FIG. 3 is a functional block diagram relating to injection control and rail pressure control. In the figure, solid-line blocks indicate the inside of the electronic control device 60, and broken-line blocks indicate the outside of the electronic control device 60.

  The injection amount command value calculation unit M1 is injected per combustion cycle via the fuel injection valve 40 based on the depression amount (accelerator operation amount) of the accelerator pedal 62 by the user and the rotational speed of the output shaft of the diesel engine. The command value (command injection amount) of the fuel amount to be calculated is calculated. The command injection amount calculated here is converted into the energization time of the fuel injection valve 40 (specifically, the electromagnetic solenoid 58) in the energization time calculation unit M2. Then, according to the energization time calculated here, the fuel injection valve 40 is energized by the drive circuit M3.

  On the other hand, the target pressure calculation unit M4 sets a target value (target fuel pressure Ptrg) of the fuel pressure (rail pressure) in the common rail 30 based on the command injection amount and the rotational speed. Incidentally, the target fuel pressure Ptrg is low at the time of idling, and becomes high as it shifts to medium-high speed rotation. Then, PID control is performed so that the detected value of the fuel pressure in the common rail 30 follows the target value Ptrg. Specifically, the operation amount calculated by the PID control is calculated as the duty ratio Duty of the metering control valve 12 of the fuel pump 10.

  The drive circuit M5 sets the control current i based on the duty ratio Duty and the battery voltage, and the control current i from the drive circuit M5 is output to the metering control valve 12, so that the operation amount calculated by the PID control. In response to this, the metering control valve 12 operates. That is, feedback control is performed so that the rail pressure approaches the target fuel pressure Ptrg.

  Next, the rail pressure control processing procedure by the microcomputer included in the electronic control unit 60 will be described with reference to the flowcharts of FIGS. This process is repeatedly executed by the microcomputer at a predetermined cycle (for example, 10 ms), for example. 4 and 5 are executed separately, they may be executed at different predetermined cycles.

  In the series of processing shown in FIG. 4, first, in step S100, the target value Ptrg of the rail pressure is calculated based on the command injection amount Q and the rotational speed NE. Next, in step S200, a deviation ΔP between the detected value Pact detected by the fuel pressure sensor 38 and the target value Ptrg is calculated. Note that the detected value Pact is a value determined by the processing of FIG. 5, and the determination procedure will be described in detail later.

  Next, in step S300, an operation amount w of the metering control valve 12 calculated by PID control is calculated for the deviation ΔP. Next, in step S400, the manipulated variable w is converted to a duty ratio Duty corresponding to the current value applied to the metering control valve 12. Next, in step S500, a signal of the duty ratio Duty as an energization command value applied to the metering control valve 12 is output to the drive circuit M5, and the series of processing shown in FIG. 4 ends. The drive circuit M5 applies a control current i set based on the signal of the duty ratio Duty and the battery voltage to the metering control valve 12.

  The series of processes shown in FIG. 5 is a process for determining the detection value Pact used in step S200. In this process, a plurality of sampling values detected by the fuel pressure sensor 38 are acquired during a preset sampling period. Then, the maximum value of the plurality of acquired sampling values is calculated, and the calculated maximum value is determined as the detection value Pact.

  More specifically, first, in step S110, it is determined whether or not the current crank angle is within a preset sampling range. That is, in this embodiment, the sampling period is specified by the crank angle (sampling range).

  Here, the sampling range will be described in detail with reference to FIGS.

  6 is a time chart showing a part of FIG. 10, and FIGS. 6 (a) and 10 (c) show the injection timing of the first to fourth cylinders by the fuel injection valve 40. FIG. 6B and 10D show actual changes in rail pressure. FIG. 6C shows a crank angle pulse signal representing the rotation angle of the output shaft. FIG. 10A shows the transition of the fuel intake and supply mode by the first plunger 16, and FIG. 10B shows the transition of the fuel suction and supply mode by the second plunger 17, respectively.

  A symbol T1 in the figure indicates a sampling range according to the present embodiment. As shown in FIG. 10, the sampling range T1 is a predetermined range (for example, about 130 ° C.) around the crank angle when the pressure supply by the first and second plungers 16 and 17 is started. The crank angle is set. 6 and 10 indicate the sampling values detected by the fuel pressure sensor 38. In this embodiment, a plurality of sampling values are included in the sampling range T1 as shown in FIG. Is getting.

  If it is determined in step S110 shown in FIG. 5 that the current crank angle is within a preset sampling range (S110: YES), the process proceeds to step S120, where the sampling value S detected by the fuel pressure sensor 38 is detected. Is stored and stored in P (i). Next, in step S130, the previous value P (i-1) of the acquired sampling value is compared with the current value P (i), and the larger value is stored and stored in the maximum value Pmax.

  Next, in step S140, it is determined whether the current crank angle exceeds the sampling range and is the end angle. If it is determined that the end angle is reached (S140: YES), the process proceeds to step S150, and the maximum value Pmax calculated in step S130 is stored and stored in the detected value Pact as the actual rail pressure. If it is determined in step S140 that the angle is not the end angle (S140: NO), and if it is determined in step S110 that the current crank angle is not within the sampling range (S110: NO), the processing in FIG. Exit.

  According to the process of FIG. 5 described above, the sampling value S detected by the fuel pressure sensor 38 is acquired during the period in which the crank angle is in the sampling range. When the crank angle exceeds the sampling range, the acquisition of the sampling value S is terminated, and the maximum value Pmax of the plurality of sampling values S acquired during the sampling range period is determined as the detection value Pact as the actual rail pressure.

  Incidentally, when one of the first and second plungers 16 and 17 starts to be displaced from the top dead center toward the bottom dead center, the discharge amount by the fuel pump 10 is calculated. As a result, the intake amount is determined by the operation mode of the metering control valve 12 when the plungers 16 and 17 are displaced toward the bottom dead center. Further, in the example shown in FIG. 10, the fuel is injected through the fuel injection valve 40 corresponding to the first cylinder or the third cylinder corresponding to the time when the fuel is supplied from the first plunger 16 to the common rail 30. Further, the fuel is injected through the fuel injection valve 40 corresponding to the fourth cylinder or the second cylinder corresponding to the time when the fuel is supplied from the second plunger 17 to the common rail 30. As described above, in the example illustrated in FIG. 10, the fuel supply timing to the common rail 30 by the fuel pump 10 and the fuel injection timing via the fuel injection valve 40 correspond one-to-one.

  By the way, in the example shown in FIG. 10, the injection start timing by the fuel injection valve 40 is controlled in the vicinity of TDC (Top Dead Center). And since the said fuel injection start timing comes in the midst of pressurizing and supplying with the fuel pump 10, the high injection pressure can be obtained and it can be said that it is a desirable state at this point. On the other hand, in the example shown in FIG. 11, the pressure supply by the fuel pump 10 is started after the fuel injection start timing in order to distribute the load to the output shaft as described above. In other words, the fuel injection start timing comes before the start of pressurized supply.

  When the pressurization supply start timing of the fuel pump 10 is set as shown in FIG. 10, the sampling range T1 according to the present embodiment is centered on the crank angle at the start of pressurization supply as described above. The crank angle is set within a predetermined range (for example, about 130 ° C.). On the other hand, when the pressurization supply start timing is set as shown in FIG. 11, the timing at which the rail pressure becomes maximum is predicted in advance, and a predetermined range before and after the predicted timing (for example, about 130 ° C.). It is desirable to set a sampling range for the crank angle of A).

  As described above, according to the present embodiment, a plurality of sampling values S detected by the fuel pressure sensor 38 are acquired in a preset sampling period T1 (S120). Then, the maximum value Pmax of the plurality of acquired sampling values S is calculated (S130), and the calculated maximum value Pmax is used as the detected value Pact as the actual rail pressure (S150). Then, the metering control valve 12 is feedback-controlled so that the detected value Pact approaches the target fuel pressure Ptrg.

  Therefore, the maximum value Pmax calculated in this way is more accurate than the single value detected at the timing when it is predicted to be the maximum even when the timing at which the rail pressure reaches the maximum changes due to various factors. Value. Therefore, since the rail pressure is feedback-controlled based on the maximum value Pmax (detected value Pact), which is a value with increased accuracy in this way, the inherent pressure resistance capability can be sufficiently exhibited. That is, when the rail pressure is controlled with a margin so as not to exceed the breakdown voltage, the margin can be reduced. In other words, the target fuel pressure Ptrg used in the feedback control can be made closer to the pressure resistance. As described above, it is possible to sufficiently increase the pressure of fuel injection. Further, according to the present embodiment, the sampling value S is acquired only when the crank angle is within the preset sampling range T1. Therefore, compared with the case where the sampling value S is always acquired, the processing load of the electronic control unit 60 such as processing for converting the sampling value S from analog to digital and processing for calculating the maximum value Pmax can be reduced.

(Second Embodiment)
In the present embodiment, measures are taken when the sampling value S becomes an abnormal value due to noise or the like (see FIG. 7). That is, a plurality of sampling values S are grouped and an average value Pave of the sampling values S is calculated for each group, a maximum value Pmax is selected from the plurality of average values Pave, and the selected maximum value Pmax is used as an actual rail pressure. Is determined as a detected value Pact.

  Note that reference numerals g1, g2, and g3 in FIG. 7 indicate groups divided as described above. As shown in FIG. 7, a plurality of sampling values S to be grouped are included in one sampling range T1. An existing value. In other words, a plurality of sampling values S existing in one sampling range T1 are grouped into a plurality as described above. More specifically, referring to FIG. 8, first, in step S110, it is determined whether or not the current crank angle is within a preset sampling range T1. If it is determined that the current crank angle is within the sampling range (S110: YES), the process proceeds to step S120, where the sampling value S detected by the fuel pressure sensor 38 is acquired, stored in P (i), and stored. Let Next, in step S121, an average value Pave (i) of n sampling values S is calculated. Next, in step S131, the previous average value Pave (i-1) and the current average value Pave (i) are compared, and the larger value is stored and stored in the maximum value Pmax.

  Next, if it is determined in step S140 that the current crank angle exceeds the sampling range and is the end angle (S140: YES), the process proceeds to step S150, and the maximum value Pmax calculated in step S131 is determined. Is stored and stored in the detected value Pact as the actual rail pressure. If it is determined in step S140 that the angle is not the end angle (S140: NO), and if it is determined in step S110 that the current crank angle is not within the sampling range (S110: NO), the processing in FIG. Exit.

  As described above, according to this embodiment, even if the sampling value S is abnormal due to noise or the like, the abnormal sampling value S is smoothed as an average value Pave (i) with other normal sampling values S. Therefore, the influence of the abnormal sampling value S on the calculated maximum value Pmax can be reduced.

(Third embodiment)
In the first embodiment, the metering control valve 12 is feedback-controlled so that the maximum value Pmax (detected value Pact) approaches the target fuel pressure Ptrg. On the other hand, in the present embodiment, when the detected value Pact does not exceed the pressure resistance Plim, the sampling value S is used as it is as the detected value Pact as the actual rail pressure, and the sampling value S (detected value Pact) becomes the target fuel pressure Ptrg. The metering control valve 12 is feedback-controlled so as to approach. At the time of detecting an overpressure where the maximum value Pmax is equal to or higher than the pressure resistance Plim, the target fuel pressure Ptrg is forcibly decreased.

  More specifically, using FIG. 9, first, in steps S110 to S140, the maximum value Pmax is calculated by the same processing as in FIG. Next, if it is determined that the current crank angle exceeds the sampling range and is the end angle (S140: YES), the process proceeds to step S141, and the calculated maximum value Pmax is equal to or greater than the withstand pressure Plim stored in advance. It is determined whether or not. If it is determined that the maximum value Pmax ≧ pressure resistance Plim (S141: YES), the target fuel pressure Ptrg is forcibly decreased in subsequent steps S142 and S143.

  That is, the amount to be forcibly reduced (a reduction value) is calculated in step S142. Specifically, the difference between the maximum value Pmax and the withstand voltage Plim is calculated as a reduction value. In the subsequent step S143, the reduction integrated value α is forcibly decreased from the previous target fuel pressure Ptrg to calculate the current target fuel pressure Ptrg. In addition, the said reduction | decrease integrated value (alpha) is an integrated value of the reduction | decrease value calculated in step S142. That is, when it is determined in step S141 that the maximum value Pmax ≧ breakdown pressure Plim continues, the reduction value calculated in step S142 is added to the reduction integral value α.

  As described above, also in the present embodiment, the maximum value Pmax is an accurate value as compared with one value detected at the timing predicted to be the maximum. Therefore, using the maximum value Pmax, which is an increased accuracy as described above, as the actual rail pressure, the target fuel pressure Ptrg is forcibly decreased when the actual rail pressure (maximum value Pmax) exceeds the pressure resistance Plim. Therefore, the inherent pressure resistance capability can be fully exerted, and the pressure of fuel injection can be sufficiently increased.

(Fourth embodiment)
In the example shown in FIGS. 10 and 11, the number of times of fuel pressurization and supply by the fuel pump 10 performed per combustion cycle (four times) is the same as the number of times of fuel injection by the fuel injection valve 40 (four times). It is. Therefore, the pressurization supply start timing by the fuel pump 10 and the injection start timing by the fuel injection valve 40 are synchronized. And in each said embodiment, it applies to the fuel-injection apparatus set so that fuel pressurization supply and fuel injection might synchronize in this way.

  On the other hand, as shown in FIG. 12, the fuel injection device to which the present embodiment is applied, the number of times of fuel pressure supply by the fuel pump 10 executed per combustion cycle is the number of fuel injections by the fuel injection valve 40. Unlike the number of times, since the pressure supply is three times for four injections, the pressure supply start timing by the fuel pump 10 and the injection start timing by the fuel injection valve 40 are not synchronized.

  In applying such an asynchronous fuel injection device, in this embodiment, as shown in FIG. 12, a plurality of sampling ranges T1 (first period) are grouped into one group period T2. Then, the maximum value Pmax is calculated for each sampling range T1, the in-group maximum value PmaxG, which is the maximum value among the plurality of maximum values Pmax acquired in the group period T2, is calculated, and the in-group maximum value PmaxG is calculated. The detection value Pact as the actual rail pressure is determined.

  The sampling range T1 according to the present embodiment is set to a crank angle within a predetermined range (for example, about 130 ° C.) around the crank angle at the start of fuel injection. The group period T2 is set to one combustion cycle (for example, 720 ° C.).

  As described above, according to the present embodiment, it is possible to cope with an asynchronous fuel injection device in which the rail pressure varies with one combustion cycle as one cycle. That is, since the maximum value of the rail pressure during one combustion cycle is calculated as the maximum value PmaxG within the group, the maximum value PmaxG within the group is an accurate value compared to one value detected at the timing when the maximum value is predicted to be maximum. It becomes. Therefore, since the rail pressure is feedback-controlled based on the maximum value PmaxG (detected value Pact) in the group, which is a value with increased accuracy in this way, the inherent pressure resistance capability can be fully exhibited, and the fuel injection can be sufficiently increased in pressure. Can be aimed at.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be implemented as follows, for example. Further, the characteristic structures of the respective embodiments may be arbitrarily combined.

  As a modified example of the fourth embodiment, the sampling range T1 in which the in-group maximum value PmaxG appears is predicted in advance among the plurality of sampling ranges T1 in the group period T2, and the sampling value is limited to the predicted sampling range T1. S may be acquired. According to this, the processing load of the electronic control unit 60 can be reduced. Alternatively, once the intra-group maximum value PmaxG is calculated, the sampling value S may be acquired only in the sampling range T1 where the intra-group maximum value PmaxG appears.

  Similarly, as a modification of the second embodiment, a sampling range in which the maximum value Pmax appears from a plurality of average values Pave is predicted in advance, and the sampling value S is acquired only in the predicted sampling range to obtain the average value. Pave may be calculated, and the average value Pave may be determined as the detected value Pact as the actual rail pressure. According to this, the processing load of the electronic control unit 60 can be reduced. Alternatively, once the maximum value Pmax is selected from the plurality of average values Pave, the sampling value S may be acquired only in the sampling range in which the maximum value Pmax appears.

  -Only during high-load operation where the output required for the diesel engine is greater than or equal to a predetermined value, the process of FIG. 5 is executed to calculate the maximum value Pmax, and the maximum value Pmax is used as the detected value Pact as the actual rail pressure. You may do it. According to this, since the rail pressure is controlled in accordance with the maximum value Pmax, which is a value with increased accuracy, at the time of high load operation where the rail pressure may exceed the pressure resistance Plim, the inherent pressure resistance capability is sufficient. The above-mentioned effect that it can be exhibited in a suitable manner is preferably exhibited. In addition, the processing load on the electronic control device 60 can be reduced as compared with the case where the processing of FIG. 5 is always executed.

  When the low-speed operation in which the rotational speed of the high-pressure pump 15 included in the fuel pump 10 is equal to or less than a predetermined value, the maximum value Pmax is calculated by executing the processing of FIG. 5, and the detected value Pact using the maximum value Pmax as the actual rail pressure You may make it use as. According to this, at the time of low speed operation where the fuel pump is likely to be seized, the above-described effects such as the high pressure of the fuel injection can be suitably exerted, and the seizure of the high pressure pump 15 can be prevented.

  In each of the above embodiments, the sampling period T1 and the group period T2 are specified by the crank angle, but may be specified by time. For example, when setting the sampling period T1, the time range of a predetermined range (for example, about 100 ms) may be set around the time point when the pressure supply by the plungers 16 and 17 is started.

  In each of the above embodiments, the sampling value S is acquired at a processing cycle (for example, 10 ms) by the microcomputer, but the sampling value S is acquired at every predetermined angle (for example, 18 ° C. A, 9 ° C. A or 6 ° C. A). You may make it do.

The figure which shows the structure of the fuel-pressure control apparatus which concerns on 1st Embodiment, and a fuel-injection apparatus. Sectional drawing explaining operation | movement of the fuel pump of FIG. The functional block diagram of the fuel pressure control by the fuel pressure control apparatus of FIG. The flowchart which shows the process sequence which concerns on the fuel pressure control of FIG. The flowchart which shows the process sequence for determining the detection value Pact used by the process of FIG. The time chart which shows the one aspect | mode which acquires a sampling value. The time chart which shows the one aspect | mode which acquires a sampling value in 2nd Embodiment. The flowchart which shows the process sequence for determining detection value Pact in 2nd Embodiment. The flowchart which shows the process sequence which concerns on fuel pressure control in 3rd Embodiment. The time chart which shows the one aspect | mode of a rail pressure change. The time chart which shows the one aspect | mode of a rail pressure change, when performing the pressurization supply start by a fuel pump after fuel injection start. The time chart which shows the one aspect | mode of a rail pressure change in the case of applying an asynchronous fuel-injection apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Fuel pump, 30 ... Common rail (accumulation chamber), 38 ... Fuel pressure sensor (detection means), 40 ... Fuel injection valve, 60 ... Electronic control device (fuel pressure control device), Pmax ... Maximum value of sampling value, Ptrg ... Target Fuel pressure, S ... sampling value, S120 ... acquisition means, S130 ... calculation means, S150, S100 to S500 ... control means.

Claims (9)

An accumulator that stores fuel used for combustion of the internal combustion engine in a high-pressure state; a fuel pump that pressurizes fuel into the accumulator; a fuel injection valve that injects fuel stored in the accumulator; and A fuel pressure control device that is applied to a fuel injection device that includes a detecting means for detecting fuel pressure and controls the fuel pressure in the pressure accumulating chamber;
Obtaining means for obtaining a plurality of sampling values detected by the detecting means;
Calculating means for calculating a maximum value of a plurality of sampling values acquired by the acquiring means;
Control means for controlling the fuel pressure in the pressure accumulating chamber according to the maximum value calculated by the calculating means;
A fuel pressure control device comprising:   The fuel pressure control apparatus according to claim 1, wherein the acquisition unit acquires the sampling value detected by the detection unit during a preset sampling period. In the case where the pressure supply start timing by the fuel pump and the injection start timing by the fuel injection valve are not synchronized,
The calculation means calculates a maximum value of the sampling values acquired in a first period including the injection start timing, and among the plurality of maximum values acquired in a group period including a plurality of the first periods. Calculate the maximum value in the group that is the maximum value,
The fuel pressure control device according to claim 2, wherein the control means controls the fuel pressure in the pressure accumulating chamber according to the maximum value in the group.   The control means executes control of fuel pressure in the pressure accumulating chamber according to the maximum value during high load operation in which an output required for the internal combustion engine is equal to or greater than a predetermined value. 4. The fuel pressure control device according to any one of 3.   5. The control unit according to claim 1, wherein the control unit executes control of the fuel pressure in the pressure accumulating chamber according to the maximum value during low speed operation in which a rotation speed of the fuel pump is a predetermined value or less. The fuel pressure control apparatus as described in any one.   The calculation unit groups a plurality of sampling values, calculates an average value of the sampling values for each group, and calculates a maximum value of the plurality of average values as a maximum value of the plurality of sampling values acquired by the acquisition unit. The fuel pressure control apparatus according to any one of claims 1 to 5, wherein   The fuel pressure control device according to any one of claims 1 to 6, wherein the control means feedback-controls the operation of the fuel pump so that the maximum value becomes a target value.   The fuel pressure control device according to any one of claims 1 to 6, wherein the control means controls the operation of the fuel pump so as to prevent the maximum value from exceeding a preset withstand pressure. . The fuel pressure control device according to any one of claims 1 to 8,
At least one of a pressure accumulation chamber, a fuel pump that pressurizes and supplies fuel to the pressure accumulation chamber, a fuel injection valve that injects fuel stored in the pressure accumulation chamber, and a detection unit that detects fuel pressure in the pressure accumulation chamber;
A fuel pressure control system comprising:

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