JP4600371B2 - Fuel injection control device - Google Patents

Description

  The present invention is, for example, a fuel pump driven by power generated by an engine output, which is employed in a common rail fuel injection control system of a diesel engine, and the like, and fuel that is pumped by driving the fuel pump is injected and supplied to the engine. The present invention relates to a fuel injection control apparatus that performs feedback control of a fuel injection pressure of a fuel injection valve based on a deviation (pressure deviation) between a target value and a measured value for a fuel supply system including the fuel injection valve.

  As this type of fuel injection control device, for example, there is a device described in Patent Document 1. This device is installed in a common rail fuel injection control system of a diesel engine, and the fuel injection pressure of a fuel injection valve that directly injects and supplies fuel (direct injection) into the engine cylinder is expressed as the pressure in the common rail (rail Pressure), and feedback control is performed so as to match (or approach) the target value. Note that PID control is employed for feedback control of the fuel injection pressure. Hereinafter, the feedback control of the fuel injection pressure will be described with reference to FIGS. 11 and 12. FIG. 11 is a flowchart showing the processing procedure of this control.

  As shown in FIG. 11, in this series of processes, first, in step S21, the target rail pressure PP and the actual rail pressure NP are read, and in the subsequent step S22, the pressure deviation DP (= NP− PP) is calculated. In further subsequent steps S231 to S233, the engine operating state and the pressure deviation DP are determined, and in subsequent steps S241 to S244, PID constants are obtained based on the different gains G1 to G4 corresponding to the determination results. , Have to set. As a result, the gain G1 in the idling operation state and the gain G2 in the non-idling operation state when the pressure deviation DP is larger than the threshold value DPTH21 (DP> DPTH21) and the pressure deviation DP is smaller than the threshold value DPTH22 (DP < In the case of DPTH22), the gain G3 is used, and in the case where the pressure deviation DP is not more than the threshold value DPTH21 and not less than the threshold value DPTH22 (DPTH21 ≧ DP ≧ DPTH22), the gain G4 is used.

  In this apparatus, the PID constant is thus obtained, and a correction amount is obtained by proportional operation (P control), integration operation (I control), and differential operation (D control). FIG. 12 shows the relationship between each gain and the correction amount. As shown in FIG. 12, in the non-idle operation state, when the pressure deviation DP is large, larger gains G2 and G3 are used, and when the pressure deviation DP is small, a smaller gain G4 is used. In the idle operation state, a smaller gain G1 is used.

In this device, the correction amount thus obtained is added to the target rail pressure PP to correct the target rail pressure PP, and the pressure control valve is driven to adjust the actual rail pressure NP to the corrected target rail pressure PP. A control current signal (duty ratio) for control is calculated.
Japanese Patent Laid-Open No. 11-236847

  As described above, in the apparatus described in Patent Document 1, by setting the threshold values DPTH21 and DPTH22 in appropriate locations in advance, a more preferable gain is selected according to the magnitude of the pressure deviation DP, and the gain is selected based on the rail pressure. It can be used for feedback control. That is, for example, during steady operation (when the measured value of the rail pressure is close to the target value), highly stable control is performed with a small gain value (a gain with a small correction amount per unit change amount of the pressure deviation DP). In addition, when the target rail pressure value is changed (transient period), a high response to a change in the target rail pressure value due to a large gain value (a gain with a large correction amount per unit change amount of the pressure deviation DP). It is possible to perform control to follow with the characteristics.

  However, in this apparatus, although the response in the transition period is certainly improved, the gain is optimized only for the pressure deviation DP, and there is still room for improvement.

  For example, when the threshold values DPTH21 and DPTH22 are set with emphasis on stability, it has been confirmed by the inventor that the response to changes in the target value is poor. For example, FIG. 13 is a time chart schematically showing a manner of following the target value when the target rail pressure value is changed (transition period) in both cases of high-speed engine operation and low-speed engine operation. . In FIG. 13, a characteristic line L51 indicates a pressure characteristic during high-speed engine operation, and a characteristic line L52 indicates a pressure characteristic during low-speed engine operation.

  As shown in FIG. 13, in this case, when the target rail pressure is changed at timing t50, the responsiveness to the change in the target value is better during engine high speed operation than during engine low speed operation. . For this reason, it is considered that such a device may have a problem that sufficient responsiveness can be obtained during high-speed engine operation, but sufficient responsiveness cannot be obtained during low-speed engine operation.

  The present invention has been made in view of such circumstances, and it is possible to perform fuel injection control in a more favorable manner depending on the situation, for example, to increase the responsiveness to changes in the target value during low-speed engine operation. The main object is to provide a fuel injection control device.

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

The invention according to claim 1 is directed to a fuel supply system including a fuel pump driven by power generated by an engine output and a fuel injection valve that injects fuel supplied by driving the fuel pump into the engine. In the fuel injection control device that feedback-controls the fuel injection pressure of the fuel injection valve based on a pressure deviation that is a deviation between the target value and the measured value, a parameter relating to the pulsation level of the fuel injection pressure together with the pressure deviation In addition, gain setting means for variably setting a gain related to feedback control of the fuel injection pressure is included, and the gain setting means sets a threshold value for selecting one from a plurality of different gains. It is variable based on a parameter relating to the pressure pulsation level .

  The inventor has stated that the above-described decrease in responsiveness during low-speed operation of the engine is caused by pulsation (pressure pulsation) of rail pressure (fuel injection pressure), and by extension, fuel that sends fuel to the rail. The present invention was invented by finding that it correlates with the actual pumping amount of the pump. Specifically, the pulsation level (amplitude) of the fuel injection pressure corresponds to a limit that cannot be adjusted any more in terms of control, that is, a minimum pressure deviation (minimum pressure range) that can be feedback controlled. Therefore, during steady operation, it is desirable to feedback-control the fuel injection pressure with a small gain (correction amount per unit time) that can be stably kept within this differential pressure range. The inventor has pointed out that the pressure pulsation level of the fuel pump driven by the engine power depends on the engine speed (NE), that is, the pulsation level increases as the engine speed increases. Pay attention. Specifically, in the fuel pump, a small amount of fuel flows out (see FIG. 3) at the sliding portion of the plunger (specifically, the gap with the housing). This fuel outflow amount affects the fuel injection pressure. In particular, in a fuel pump driven by power from the engine output, when the engine speed increases, the gap becomes substantially narrow due to the fluid characteristics of the fuel flowing through the gap between the plunger operating at high speed and the fixed housing. As a result, the amount of fuel outflow decreases, thereby increasing the actual pumping amount of the pump and increasing the pressure pulsation level. The inventor has come up with such a principle (mechanism) and, as described above, in addition to the pressure deviation, the parameter related to the pulsation level of the fuel injection pressure including the engine rotation speed is also taken into account for feedback control of the fuel injection pressure. A configuration for variably setting such a gain, that is, a configuration including gain setting means has been invented. With such a configuration, the fuel injection control can be performed in a more preferable manner by changing the gain according to the situation.

In addition, as the gain setting mode (change mode) by the gain setting means, the modes described in claims 1 , 2, and 3 are effective.

In this invention according to claim 1, before Symbol gain setting means, the plurality of different gains the threshold for selecting one (e.g., a plurality of gain set in accordance with the pressure deviation level) fuel injection It is configured to be variable based on a parameter relating to the pressure pulsation level.

In the invention described in claim 2, 3, the pre-Symbol gain setting means, the plurality of different gains regions (e.g. steady operation regions in accordance with the parameters of the pulsation level of the fuel injection pressure and the pressure difference, plus (Three regions, a side change region and a minus side change region) are provided, and the threshold value for selecting one region from a plurality of different regions is not constant with respect to the parameter relating to the pulsation level of the fuel injection pressure The gain related to the feedback control of the fuel injection pressure is set based on the gain setting map set in (1).

  With these configurations, it is possible to accurately change the gain according to the situation. For example, when the differential pressure range (pulsation level) for which feedback control is possible (adjustable) is small (for example, during low-speed engine operation), the gain used for feedback control is changed to a larger value when the pressure deviation is smaller. Therefore, even when the target value of the fuel injection pressure is changed, the responsiveness to the change of the target value is basically improved without impairing the stable control during steady operation (maintaining high controllability). Will be able to.

In addition, it is effective to use the parameters described in claims 4 to 8 as a parameter related to the pulsation level of the fuel injection pressure. For example, as in the invention according to claim 4,
-The rotational speed of the engine.
Or as claimed in claim 5,
-Discharge amount of the fuel pump (for example, measured value of discharge amount (actual discharge amount) or required discharge amount).
Or as claimed in claim 6,
The target value of the fuel injection pressure (target fuel injection pressure).
Or as claimed in claim 7,
A parameter relating to the viscosity of the fuel pumped by the fuel pump.
Etc. are effective. These parameters correlate well with the pulsation level of the fuel injection pressure (eg rail pressure). First, as described above, as the rotational speed of the engine increases, the amount of fuel outflow (leakage) at the sliding portion of the plunger decreases and the pulsation level of the fuel injection pressure increases. Further, when the discharge amount of the fuel pump (control based on the target value) increases, the fuel pumping amount per pumping by the fuel pump increases, and as a result, the volume (volume) fluctuation of the pressurizing chamber in one suction stroke increases. As a result, the pulsation level increases. Further, when the fuel injection pressure (control based on the target value) increases, the fuel to be pumped becomes hard (more dense) and the pulsation level increases. Further, when the viscosity of the pumped fuel is increased, the fuel is less likely to leak at the sliding portion of the plunger, and the pulsation level is increased by reducing the amount of fuel flowing out.

  In particular, in the apparatus according to claim 7, it is effective to use the temperature of the fuel as the parameter relating to the viscosity of the fuel pumped by the fuel pump as in the invention according to claim 8. . Generally, the higher the temperature of the fuel (particularly liquid fuel), the lower the viscosity (viscosity) of the fuel.

  According to a ninth aspect of the present invention, in the apparatus according to any one of the first to eighth aspects, the fuel pumping amount of the fuel pump is metered on the fuel suction side of the pump. .

  If the fuel pump adjusts the fuel pumping amount on the fuel discharge side, the pulsation level of the fuel injection pressure is adjusted (decreased or increased) at the time of metering, that is, at the time of fuel discharge (fuel pumping). ) Is possible. Therefore, in this case, the necessity for the configuration according to any one of claims 1 to 8 is low. On the other hand, when the fuel pump performs the metering of the fuel pumping amount on the fuel suction side (before the fuel pumping by the pump plunger) as in the above configuration, as described above, There is a high possibility that a pulsation level will occur during fuel pumping. For this reason, in such a configuration, the invention described in any one of claims 1 to 8 is particularly important.

  According to a tenth aspect of the present invention, in the apparatus according to any one of the first to ninth aspects, the fuel injection pressure of the fuel injection valve is a pressure in a common rail in a common rail fuel injection control system of a diesel engine. The feedback control of the fuel injection pressure is PID control, and the gain setting means sets a PID constant as the gain.

  Considering the practicality of the invention described in any one of claims 1 to 9 at present, these are the fuels in the common rail fuel injection control system of the diesel engine as in the device described in the above-mentioned Patent Document 1. It is particularly useful when used for PID control (feedback control) of injection pressure (rail pressure). Of the PID constants, the P constant (proportional gain) and the I constant (integration time) are particularly important for improving the response.

  Hereinafter, an embodiment embodying a fuel injection control device according to the present invention will be described with reference to the drawings. In addition, the apparatus of this embodiment is mounted in the common rail type fuel injection control system (high pressure injection fuel supply system) which made the control object the reciprocating type diesel engine as a car engine, for example. That is, this device, like the device described in Patent Document 1, injects high-pressure fuel (for example, light oil having an injection pressure of “1400 atm”) directly into the combustion chamber in the cylinder of a diesel engine (internal combustion engine). This is a so-called fuel injection control device for a diesel engine, which is used for feedback control (PID control) of the fuel injection pressure with respect to a target value when supplying (direct injection supply).

  First, an outline of a common rail fuel injection control system according to the present embodiment will be described with reference to FIG. Note that a multi-cylinder (for example, four-cylinder) engine for automobiles is assumed as the engine of the present embodiment.

  As shown in FIG. 1, in this system, the ECU (electronic control unit) 30 takes in sensor outputs (detection results) from various sensors and drives the fuel supply device based on the sensor outputs. Configured to control. The ECU 30 controls the drive of the fuel supply device, for example, to control the output (rotation speed and torque) of a diesel engine, and feedback control the fuel injection pressure (rail pressure) to the engine to a target value (target fuel pressure). is doing.

  Here, various devices constituting the fuel supply device are arranged in order of the fuel tank 10, the fuel filter 12, the fuel temperature sensor 13, and the fuel pump 14 from the upstream side of the fuel. That is, the fuel in the fuel tank 10 is pumped up by the fuel pump 14, and is pressurized and supplied (pressure fed) to the common rail 16 through the fuel filter 12 and the fuel temperature sensor 13. The common rail 16 stores the fuel pumped from the fuel pump 14 in a high-pressure state and supplies the fuel to the injectors (fuel injection valves) 20 of the respective cylinders through the high-pressure fuel passage 18 provided for each cylinder. The common rail 16 is provided with a fuel pressure sensor 22 for detecting the fuel pressure (rail pressure) in the common rail 16 so that the rail pressure can be detected and managed. In this system, the fuel pumped by driving the fuel pump 14 is directly supplied to each cylinder (inside the cylinder) of the engine by each injector 20 (direct injection supply).

  In addition to the above sensors, the vehicle (not shown) is further provided with various sensors for vehicle control. For example, the crankshaft 24 is provided with a crank angle sensor 26 that outputs a crank angle signal at every predetermined crank angle (for example, in a cycle of 30 ° CA) in order to detect the rotation angle position, rotation speed, and the like of the crankshaft 24. It has been. The accelerator pedal 28 is provided with an accelerator sensor 28 for outputting an electric signal corresponding to the state (displacement amount) of the pedal so as to detect the operation amount (accelerator opening degree) of the accelerator pedal by the driver. .

  Next, a detailed configuration of the fuel pump 14 will be described with reference to FIG.

  As shown in FIG. 2, the fuel pump 14 is basically configured to pressurize and discharge the fuel pumped up from the fuel tank 10 by the feed pump 40 with the high-pressure pump 50. . At this time, the amount of fuel pumped to the high-pressure pump 50 is adjusted by a suction adjustment valve 60 (SCV: Suction Control Valve) provided on the fuel suction side of the pump 14 (particularly before fuel pumping by the high-pressure pump 50). It has come to be measured.

  Here, the feed pump 40 has an outer rotor on the outer side and an inner rotor on the inner side, and the space created by each of the rotors is increased / decreased according to the rotation of each rotor, and fuel is sucked and discharged according to the increase / decrease. This is a so-called trochoid pump. The pump 40 is driven by a drive shaft 41 and functions as a low-pressure supply pump that sucks the fuel in the fuel tank 10 from the inlet 42 and sends the fuel to the high-pressure pump 50. The drive shaft 41 is interlocked with the crankshaft 24 (FIG. 1), and is driven by power from the engine output. That is, the drive shaft 41 is rotationally driven as the crankshaft 24 rotates, and rotates at a ratio such as “1/1” or “½” with respect to one rotation of the crankshaft 24, for example.

  The fuel sucked up by the feed pump 40 passes through the fuel filter 42a and is sent to the intake adjustment valve 60. At this time, the discharge pressure (fuel pressure) of the feed pump 40 is limited (adjusted) to a predetermined pressure or less by the regulator valve 43. The regulator valve 43 communicates the discharge side and the supply side of the feed pump 40 when the discharge pressure of the feed pump 40 exceeds a predetermined pressure.

  The intake adjustment valve 60 is configured to include a linear solenoid type electromagnetic valve, and adjusts the amount of fuel sucked into the high-pressure pump 50. By controlling the energization time for the intake adjustment valve 60 by the ECU 30 (FIG. 1), the amount of fuel drawn from the feed pump 40 to the high-pressure pump 50 through the fuel passage 44 can be adjusted. That is, the fuel sent by the feed pump 40 is adjusted to a required discharge amount (fuel pressure feed amount) by the suction adjusting valve 60 and enters the high-pressure pump 50 through the suction valve 53 (suction valve).

  The high-pressure pump 50 is a plunger pump that pressurizes the fuel metered by the suction adjustment valve 60 and discharges the fuel to the outside. The high-pressure pump 50 is mainly configured to include a plunger 51 that is driven to reciprocate by a drive shaft 41, and a pressurizing chamber 52a formed between the inner wall 52b of the housing 52 and the top surface of the plunger 51. The volume (volume) of the pressurizing chamber 52a (plunger chamber) changes as the plunger 51 reciprocates in the axial direction.

  The plunger 51 is pressed against a ring cam 56 mounted around an eccentric cam 55 (eccentric cam) by a spring 57. Although not shown, in detail, a cylindrical shaft hole for assembling the drive shaft 41 is formed at the center of the rectangular ring-shaped ring cam 56. A cylindrical eccentric cam 55 corresponding to the shape of the shaft hole is attached to the drive shaft 41 so as to be eccentric. Then, the ring cam 56 is assembled on the eccentric cam 55 of the drive shaft 41 in such a manner that the drive shaft 41 passes through the shaft hole of the eccentric cam 55, so that the drive shaft 41 and the ring cam 56 are connected to the eccentric cam 55. It is connected through. In the high-pressure pump 50, when the drive shaft 41 rotates, the eccentric cam 55 rotates eccentrically, and the ring cam 56 displaces following the eccentric cam 55, thereby pushing (or pulling) the plunger 51 in the axial direction. In this way, the two plungers 51 reciprocate between the pumping top dead center and the pumping bottom dead center.

  As described above, on the suction side of the high-pressure pump 50, the suction valve 53 that connects or blocks the pressurizing chamber 52a and the feed pump 40 side is disposed. On the other hand, a discharge valve 54 is also provided on the discharge side of the high-pressure pump 50 to communicate or block the pressurizing chamber 52a and the common rail 16 side. That is, when the pressure in the pressurizing chamber 52a is lowered by the lowering of the plunger 51, the discharge valve 54 is closed and the suction valve 53 is opened. As a result, fuel is supplied from the feed pump 40 into the pressurizing chamber 52 a via the suction adjustment valve 60. Conversely, when the pressure in the pressurizing chamber 52a rises due to the rise of the plunger 51, the suction valve 53 is now closed. When the pressure in the pressurizing chamber 52a reaches a predetermined pressure, the discharge valve 54 is opened, and the high-pressure fuel pressurized in the pressurizing chamber 52a is supplied toward the common rail 16.

  By the way, in such a fuel pump 14, for example, a pulsation (pressure pulsation) is generated in the rail pressure (fuel injection pressure) calculated from the sensor output of the fuel pressure sensor 22, and the pulsation level (amplitude) corresponds to each situation. It will be a thing. Hereinafter, differences in pressure pulsation levels in various situations will be described with reference to FIGS. 3 and 4. 3 is an enlarged schematic diagram showing a sliding portion of the plunger 51 in the fuel pump 14, and FIG. 4 is a time chart showing rail pressure pulsation levels δP1 and δP2 in the vicinity of the maximum pressure P0. In FIG. 4, (a) shows the pressure pulsation level during engine low speed operation, and (b) shows the pressure pulsation level during engine high speed operation.

  First, as shown in FIG. 3, in the fuel pump 14, a slight amount of fuel outflow LK occurs in the sliding portion of the plunger 51, specifically, in the gap between the outer peripheral wall of the plunger 51 and the inner wall 52 b of the housing 52. The amount of fuel outflow affects the rail pressure. In particular, in a pump driven by power generated by engine output, such as the fuel pump 14 used in the above system, when the engine speed increases, the fuel that flows through the gap between the plunger 51 that operates at high speed and the fixed housing 52 Due to the fluid characteristics, the gap becomes substantially narrow, so that the amount of fuel flowing out decreases, thereby increasing the actual pumping amount of the fuel pump 14 and increasing the pressure pulsation level.

  Specifically, the pulsation of the rail pressure in the vicinity of the maximum pressure P0 reached by the rise of the plunger 51 is as shown in FIGS. 4 (a) and 4 (b) at the time of engine low speed operation and engine high speed operation, respectively. Become. That is, the pressure pulsation level (amplitude) δP1 (differential pressure range P0 to P1) during low-speed engine operation is smaller than the pressure pulsation level (amplitude) δP2 (differential pressure range P0 to P2) during engine high-speed operation.

  Thus, as the engine speed NE increases, the amount of fuel outflow (leakage) at the sliding portion of the plunger 51 decreases and the pulsation level of the rail pressure increases. Further, not only the engine speed NE but also the required discharge amount QFIN (corresponding to the target value of the discharge amount) for the fuel pump 14, the target value of the rail pressure (target rail pressure PP), and the fuel temperature THF are similarly determined. It correlates well with the pulsation level of rail pressure. For example, if the required discharge amount QFIN and thus the discharge amount of the fuel pump 14 (control based on the required value (target value)) increases, the fuel pumping amount per pumping by the fuel pump 14 increases, and thus in one intake stroke. As the volume fluctuation (volume fluctuation) of the pressurizing chamber 52a increases, the pulsation level increases. Further, when the target rail pressure PP, that is, the fuel injection pressure (control based on the target value) is increased, the pumped fuel becomes harder (is denser) and the pulsation level is increased. Further, when the fuel temperature THF is lowered, the viscosity of the fuel is increased, and as a result, the fuel is less likely to leak at the sliding portion of the plunger, and the pulsation level is increased by reducing the amount of fuel flowing out.

  In the fuel injection control device of this embodiment, a threshold value DPTH (one of control parameters) for selecting one from a plurality of different gains is variably set based on these parameters. At this time, the ECU 30 is the part that performs the control mainly as the electronic control unit. The ECU 30 includes a well-known microcomputer (not shown), and operates various actuators such as the injector 20 in a desired manner based on detection values of various sensors that detect engine operating conditions and user requests. As a result, various controls related to the engine are performed. The microcomputer mounted on the ECU 30 basically includes a CPU (basic processing device) that performs various calculations, and a RAM (main memory that temporarily stores data and calculation results during the calculation) ( Random access memory (ROM), ROM (read only storage device) as program memory, EEPROM (electrically rewritable non-volatile memory) as data storage memory, and the like are used. The ROM stores various programs and control maps related to engine control including fuel injection control, and the data storage memory (EEPROM) stores various control data including engine design data. Are stored in advance.

  FIG. 5 is a block diagram showing various functions related to feedback control (PID control) of the fuel injection pressure mounted on the ECU 30. Note that these various functions variably set the threshold value DPTH based on the parameters correlated with the pressure pulsation level listed above, and based on the gain corresponding to the threshold value DPTH, the PID constant (proportional gain, integration time, (Derivative time) is set.

  As shown in FIG. 5, the ECU 30 calculates (variably sets) the threshold value DPTH using three maps M1 to M3. Specifically, the fuel temperature / pressure pre-correction threshold BDPTH is calculated based on the engine speed NE and the required discharge amount QFIN, for example, referring to the map M1. The required discharge amount QFIN corresponds to the required fuel injection amount, and is calculated and set based on the driver's request (for example, the operation amount of the accelerator pedal). FIG. 6 shows an example of the map M1 used for calculating the threshold value BDPTH.

  As shown in FIG. 6, in this map M1, if each value of the engine speed NE (unit: “rpm”) and the required discharge amount QFIN (unit: “cc / min”) is determined, the corresponding threshold value is determined. BDPTH is uniquely determined. As a result, the threshold value BDPTH, and thus the threshold value DPTH, is set to a larger value as the engine speed NE increases and as the required discharge amount QFIN increases.

  Further, referring to another map M2, for example, based on the fuel temperature THF calculated from the sensor output of the fuel temperature sensor 13 (FIG. 1), a correction value KTHF (correction value based on the fuel temperature) for the threshold BDPTH is calculated. To do. Then, the correction unit 31 multiplies the correction value KTHF by the previous threshold value BDPTH (correction calculation), thereby performing correction by the fuel temperature THF as a calculation process of the threshold value DPTH. FIG. 7 shows an example of a map M2 used for calculating the correction value KTHF.

  As shown in FIG. 7, in this map M2, if the value of the fuel temperature THF (the unit is “deg C”) is determined, the corresponding correction value KTHF is uniquely determined. As a result, the correction value KTHF, and thus the threshold value DPTH, is set to a smaller value as the fuel temperature THF increases. Incidentally, the correction value KTHF is variably set with the same tendency as the kinematic viscosity (absolute viscosity divided by density, unit “m ^ 2 / s”).

  Further, a correction value KPP (a correction value based on the target rail pressure) is calculated based on the target rail pressure PP while referring to still another map M3. Then, the correction unit 32 multiplies the correction value KPP with the previous threshold value corrected with the correction value KTHF (correction calculation), thereby further correcting the target rail pressure PP as a calculation process of the threshold value DPTH. I am doing so. The target rail pressure PP is calculated and set based on, for example, the engine speed NE, the target fuel injection amount, and the like. FIG. 8 shows an example of a map M3 used for calculating the correction value KPP.

  As shown in FIG. 8, in this map M3, if the value of the target rail pressure PP (unit: “MPa”) is determined, the corresponding correction value KPP is uniquely determined. As a result, the correction value KPP, and thus the threshold value DPTH, is set to a larger value as the target rail pressure PP increases. Incidentally, the correction value KPP is variably set with the same tendency as the Young's modulus of the fuel.

  Thus, the ECU 30 uses the above three maps M1 to M3 to set the threshold DPTH for selecting one from a plurality of different gains based on the parameters correlated with the pressure pulsation level listed above. Variable setting is made. Based on the threshold value DPTH, the gain setting unit 33 (gain setting means) sets a gain corresponding to the engine rotational speed NE and the pressure deviation DP (deviation between the target rail pressure PP and the actual rail pressure NP). In addition to selection, the PID constant is acquired and set based on this gain. At this time, the gain setting unit 33 has one of three types of POS gain (positive and positive change gain), NOM gain (normal and steady operation gain), and NEG gain (negative and negative change gain). Select the gain. Further, the pressure deviation DP is subjected to a predetermined calculation (here, subtraction) by the pressure deviation calculation unit 34, whereby a difference (DP =) between the target rail pressure PP and the actual rail pressure NP (detected value by the fuel pressure sensor 22). NP-PP).

  Next, with reference to FIG. 9, the fuel injection control executed by the above system will be described in detail particularly regarding the fuel injection pressure feedback control (PID control). FIG. 9 is a flowchart showing a processing procedure of processing relating to gain setting of the feedback control. The series of processes shown in FIG. 9 are basically performed at predetermined crank angles or sequentially at predetermined time intervals by executing a program stored in the ROM by the ECU 30. The values of various parameters used in the process of FIG. 9 are stored as needed in a storage device such as a RAM or EEPROM mounted in the ECU 30 and updated as needed.

  As shown in FIG. 9, in this series of processing, first, in step S11, parameters correlated with the pressure pulsation level listed above, that is, engine speed NE, required discharge amount QFIN, fuel temperature THF, target rail, and so on. The pressure PP and the actual rail pressure NP are acquired. In step S12, the pressure deviation DP (= NP-PP) and the threshold value DPTH are calculated as described above. In further subsequent steps S13 to S14, the magnitude of the pressure deviation DP is determined, and in subsequent steps S151 to S153, PID is based on different gains (POS gain, NOM gain, NEG gain) according to the determination results. I try to get a constant. The POS gain, NOM gain, and NEG gain are in accordance with the gains G3, G4, and G2 illustrated in FIG. That is, as a result, when the pressure deviation DP is equal to or larger than the positive number “DPTH” of the threshold value DPTH (DP ≧ DPTH), the POS gain (large gain on the positive side) is smaller than the negative value “−DPTH” of the threshold value DPTH. (DP ≦ −DPTH), the NEG gain (large gain on the negative side) is smaller than “DPTH” and larger than “−DPTH” (DPTH> DP> −DPTH). A NOM gain (a stable gain smaller than the above two gains) is used.

  FIG. 10 is a graph showing a selection mode of the gain. Specifically, this graph corresponds to a map (gain setting map) used for setting the gain in the gain setting unit 33 (FIG. 5). Here, for comparison, threshold values L21 and L22 (for example, threshold values DPTH21 and DPTH22 illustrated in FIG. 12 above) set to be constant with respect to the engine rotational speed NE are also indicated by broken lines in the drawing.

  As shown in FIG. 10, in this map, there are three different gain regions (steady operation region A, plus side change region B, minus side change region C) according to the pressure deviation DP and the engine speed NE. Threshold values L11 and L12 (“DPTH” and “−DPTH”) for selecting one area from the three different areas A to C are set in a manner that is not constant with respect to the engine speed NE. Has been. Specifically, during engine low speed operation, the smaller the engine speed NE, the smaller the pressure deviation DP, and the larger the gain from the NOM gain (area A) as the stable gain (POS gain (area B) if negative deviation, negative). Is used, the use gain is changed to NEG gain (area C). In this device (ECU 30), the gain is variably set using such a map. Then, for example, a correction amount corresponding to the use gain is acquired using a map similar to the map illustrated in FIG. That is, if the gain is set using such a map, even when the target rail pressure PP is changed, the target value of the target value is basically maintained without impairing the stable control during steady operation (while maintaining high controllability). Responsiveness to changes can be improved.

  That is, in this apparatus, after obtaining the correction amount in this way, this is added to the target rail pressure PP to correct the target rail pressure PP, and the actual rail pressure NP is adjusted to the corrected target rail pressure PP. A control current signal (duty ratio) for controlling the drive of the pressure control valve (suction adjustment valve 60) is calculated. Incidentally, the control to the negative side of the rail pressure (decompression control) is performed by, for example, idle driving of the injector 20 (injecting only air without injecting fuel) or an appropriate decompression valve (not shown) (for example, an on / off control type). This is done by opening and closing the solenoid valve.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  (1) For a fuel supply system including a fuel pump 14 driven by power generated by an engine output, the fuel injection pressure (rail pressure) of the injector 20 is set to a target value (target rail pressure PP) and a measured value. Feedback control is performed based on a pressure deviation DP which is a deviation from (actual rail pressure NP). As such a fuel injection control device (ECU 30), in addition to the pressure deviation DP, the engine rotational speed NE, the required discharge amount QFIN, the fuel temperature THF, and the target rail pressure PP are taken into account, and the gain relating to the feedback control of the rail pressure is increased. A variable setting program (gain setting means, FIG. 9) is provided. As a result, the fuel injection control can be performed in a more preferable manner by changing the gain according to the situation.

  (2) The threshold DPTH for selecting one from a plurality of different gains (POS gain, NOM gain, NEG gain), the engine speed NE, the required discharge amount QFIN, the fuel temperature THF, and the target rail pressure PP It was made variable based on. As a result, the gain can be accurately varied according to the situation.

  (3) A plurality of different gain regions (three regions of a steady operation region A, a plus side change region B, and a minus side change region C) are provided according to the pressure deviation DP and the engine speed NE, and each of these three different regions is provided. Based on a gain setting map (FIG. 10) in which a threshold value DPTH for selecting one area from the two areas A to C is set in a manner that is not constant with respect to the engine speed NE, The gain was variably set. Specifically, during engine low speed operation, the use gain is changed from a NOM gain as a stable gain to a larger gain with a smaller pressure deviation DP as the engine rotational speed NE is smaller. As a result, even when the target rail pressure PP is changed, the responsiveness to changes in the target value can be basically improved without impairing the stable control during steady operation (while maintaining high controllability). become able to.

  (4) Two thresholds (threshold L11 for changing from region A to region B or vice versa) for selecting three gain regions (steady operation region A, plus side change region B, minus side change region C) The threshold L12 for changing from the region A to the region C or vice versa is set so as to be line symmetric (only the sign is reversed) with the reference (here, “0”) of the pressure deviation DP as the symmetry axis. By doing this, it becomes possible to set the two threshold values L11 and L12 (“DPTH” and “−DPTH”) by calculating one threshold value DPTH, and it is easy to calculate the threshold value (reducing the processing load). )become.

  (5) The fuel pumping amount of the fuel pump 14 is adjusted on the fuel suction side of the pump 14. Depending on the application, it may be more convenient to perform metering on the fuel suction side of the pump 14. Even in such a case, with the above configuration, the fuel injection control can be performed in a more preferable manner by changing the gain according to the situation.

  (6) The feedback control of the pressure (rail pressure) in the common rail 16 in the common rail fuel injection control system of the diesel engine is performed as PID control, and a PID constant is set as a gain. This makes it possible to accurately control the fuel injection pressure.

  The present invention is not limited to the description of the above embodiment, and may be implemented as follows, for example.

  The gain may be variably set in consideration of the engine operation mode (for example, idling operation state) and the like in the same manner as the device described in the above-mentioned Patent Document 1.

  It is not an essential condition that the fuel pumping amount of the fuel pump 14 is metered on the fuel suction side of the pump 14. For example, the fuel pump 14 is metered on the fuel discharge side. May be performed.

  In the above embodiment, the value of the fuel temperature THF is used (considered) when correcting (variably setting) the threshold value DPTH. However, the present invention is not limited to this, and it relates to the viscosity of the fuel pumped by the fuel pump 14. If it is a parameter, the effect equivalent to the effect of said (1) will be acquired also when another parameter is used.

  Although the two threshold values L11 and L12 for selecting the gain region are set to be line symmetric with respect to the reference of the pressure deviation DP as a symmetry axis, the present invention is not limited to this, and each is calculated and set to be asymmetric. May be.

  In the gain setting map shown in FIG. 10, three types of gains are used properly in three areas. However, the effects of (2) and (3) can be achieved even if two areas are used or four areas or more. The equivalent effect can be obtained.

  In the above embodiment, the fuel temperature THF and the target rail pressure PP are used with respect to the reference threshold value (fuel temperature / pressure correction threshold value BDPTH) calculated based on the engine operating state (engine rotational speed NE and required discharge amount QFIN). Correction was made. However, the present invention is not limited to this, and an optimum gain may be set using, for example, a map showing the relationship between each of these parameters and the gain. Alternatively, maps may be provided separately, and the gains may be selected by selectively using (considering) only necessary parameters by switching them according to circumstances. Furthermore, parameters that are not necessary depending on the application may be omitted. In short, if the gain is variably set based on the rail pressure feedback control based on at least one of these parameters, the effect equivalent to the effect (1) can be obtained.

  In the above embodiment, various kinds of software (programs) are used, but similar functions may be realized by hardware such as a dedicated circuit.

  In the above embodiment, the case where the present invention is applied to a common rail system of a diesel engine is mentioned as an example. However, for example, a spark ignition type gasoline engine (particularly a direct injection engine) or the like is basically basically the same. Can be applied.

The block diagram which shows the outline of the common rail type fuel-injection control system to which this apparatus was applied about one Embodiment of the fuel-injection control apparatus which concerns on this invention. The block diagram which shows the detailed structure of a fuel pump. The schematic diagram which expands and shows the sliding part of the plunger in a fuel pump. Regarding the pulsation level of the rail pressure in the vicinity of the maximum pressure, (a) is a time chart showing the pressure pulsation level during engine low speed operation, and (b) is a time chart showing the pressure pulsation level during engine high speed operation. The block diagram which shows the various functions which concern on the feedback control (PID control) of the fuel injection pressure mounted in the said fuel-injection control apparatus. A map used to set the gain. A map used to set the gain. A map used to set the gain. The flowchart which shows the process sequence of the process which concerns on the setting of a gain. The graph which shows the selection mode of a gain. The flowchart which shows the process sequence of the process which concerns on the feedback control of the fuel injection pressure by the apparatus about an example of the conventional fuel injection control apparatus. The graph which shows the relationship between each gain and correction amount used with the conventional apparatus. The time chart which shows schematically the tracking aspect to the target value when the target rail pressure value is changed (transitional period) in the case of both the engine high-speed operation and the engine low-speed operation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Fuel tank, 13 ... Fuel temperature sensor, 14 ... Fuel pump, 16 ... Common rail, 20 ... Injector, 22 ... Fuel pressure sensor, 30 ... ECU (electronic control unit), 50 ... High pressure pump, 51 ... Plunger, 60 ... Suction tuning valve.

Claims (10)

The fuel injection pressure of the fuel injection valve is targeted for a fuel supply system comprising a fuel pump driven by power generated by the engine and a fuel injection valve that injects fuel supplied by driving the fuel pump to the engine. In the fuel injection control device that performs feedback control based on the pressure deviation that is the deviation between the target value and the measured value,
A gain setting means for variably setting a gain related to feedback control of the fuel injection pressure in consideration of a parameter related to a pulsation level of the fuel injection pressure together with the pressure deviation ,
The gain setting means makes a threshold for selecting one from a plurality of different gains variable based on a parameter relating to a pulsation level of the fuel injection pressure. . The gain setting means is provided with a plurality of different gain regions according to the pressure deviation and a parameter relating to the pulsation level of the fuel injection pressure, and a threshold value for selecting one region from the different regions 2. The gain according to the feedback control of the fuel injection pressure is variably set based on a gain setting map set in a manner that is not constant with respect to the parameter related to the pulsation level of the fuel injection pressure. Fuel injection control device.   The fuel injection pressure of the fuel injection valve is targeted for a fuel supply system comprising a fuel pump driven by power generated by the engine and a fuel injection valve that injects fuel supplied by driving the fuel pump to the engine. In the fuel injection control device that performs feedback control based on a pressure deviation that is a deviation between the target value and the measured value,
  A gain setting means for variably setting a gain related to feedback control of the fuel injection pressure in consideration of a parameter related to a pulsation level of the fuel injection pressure together with the pressure deviation,
  The gain setting means is provided with a plurality of different gain regions according to the pressure deviation and a parameter relating to the pulsation level of the fuel injection pressure, and a threshold value for selecting one region from the different regions Is configured to variably set a gain related to feedback control of the fuel injection pressure based on a gain setting map set in a manner that is not constant with respect to the parameter related to the pulsation level of the fuel injection pressure. Fuel injection control device.   The fuel injection control apparatus according to any one of claims 1 to 3, wherein one of the parameters related to a pulsation level of the fuel injection pressure is a rotation speed of the engine.   The fuel injection control device according to any one of claims 1 to 4, wherein one of the parameters related to a pulsation level of the fuel injection pressure is a discharge amount of the fuel pump.   The fuel injection control device according to any one of claims 1 to 5, wherein one of the parameters related to the pulsation level of the fuel injection pressure is a target value of the fuel injection pressure.   The fuel injection control device according to any one of claims 1 to 6, wherein one of the parameters related to a pulsation level of the fuel injection pressure is a parameter related to a viscosity of fuel pumped by the fuel pump.   The fuel injection control device according to claim 7, wherein one of the parameters related to the viscosity of the fuel is a temperature of the fuel.   The fuel injection control device according to any one of claims 1 to 8, wherein a fuel pumping amount of the fuel pump is adjusted on a fuel suction side of the pump.   The fuel injection pressure of the fuel injection valve is a pressure in a common rail in a common rail fuel injection control system of a diesel engine, the feedback control of the fuel injection pressure is PID control, and the gain setting means sets a PID constant to the gain. The fuel injection control device according to any one of claims 1 to 9, which is set as follows.

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