JP2007016687A - Accumulator fuel injection control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an accumulator fuel injection control device for preventing the fluctuation of actual pressure in an accumulator to keep it as approximate target pressure, while avoiding the shortage of a discharge amount due to a fuel supply pump. <P>SOLUTION: The accumulator fuel injection control device comprises a target pressure setting means for setting target pressure P<SB>0</SB>of fuel in the accumulator 1, and a viscosity detecting means for detecting the viscosity of the fuel. When in the conditions that the discharge amount of the fuel from the fuel supply pump 3 to the accumulator is kept constant and the supply amount of the fuel from the accumulator to a fuel injection valve 2 is kept constant, the current target pressure set by the target pressure setting means is corrected to be lower depending on the detected viscosity of the fuel so as to keep the actual pressure of the fuel in the accumulator almost stable as constant target pressure. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pressure accumulation type fuel injection control device mainly used for a diesel engine.

  Conventionally, as a fuel injection device for a diesel engine, a pressure accumulating container (common rail) for accumulating high pressure fuel, an injector (fuel injection valve) for supplying high pressure fuel in the common rail into each cylinder of the engine, and pressurization 2. Description of the Related Art An accumulator fuel injection apparatus is known that includes an intake metering type fuel supply pump (supply pump) that pressurizes fuel that is sucked into a room to increase the pressure and pump it to a common rail.

  In this accumulator fuel injection device, an intake metering valve that adjusts the amount of fuel delivered to the common rail in order to adjust the fuel pressure in the common rail (common rail pressure) corresponding to the fuel injection pressure to the target fuel pressure. Is built into the supply pump. Under this configuration, for example, when accelerating, the suction metering valve adjusts the opening degree of the fuel supply passage through which fuel is introduced from the fuel tank into the pressurized chamber, and changes the pump discharge amount discharged from the supply pump to change the common rail pressure. Is configured to boost the voltage. In addition, a pressure reducing valve for reducing the common rail pressure from a high pressure to a low pressure is installed at the end of the common rail. Under this configuration, for example, at the time of deceleration, the pressure reducing valve is configured to open (open) a fuel discharge path for discharging fuel from the common rail to the low pressure side (fuel tank) of the fuel system to reduce the common rail pressure. .

  Thus, the common rail pressure is adjusted by the pump discharge amount discharged from the supply pump, and this pump discharge amount is determined by the injection amount from the injector and the seal portions of each part, for example, the seal portion of the injector, the seal of the supply pump. And the amount of fuel leak from the seal portion of the pressure reducing valve, etc. In this case, as shown in FIG. 7, in the normal common rail pressure control state in which the metering valve of the supply pump is not fully opened and the pump discharge amount has not reached the limit (upper limit), the common rail pressure can be controlled by the metering valve. State. That is, the common rail pressure is within a range where the target pressure can be adjusted, and there is no problem in following the pressure. However, when the metering valve is fully open and the common rail pressure is controlled when the pump discharge is at the limit, the target common rail pressure increases, the fuel temperature increases, or the fuel properties When the situation becomes smaller, the amount of fuel leakage increases as shown in FIG. 2A, the discharge amount from the supply pump cannot supplement the required discharge amount, and cannot follow the common rail pressure.

  That is, as shown in FIG. 2A, when the supply pump is operated at the maximum discharge amount with the metering valve fully opened, the required discharge amount is predetermined depending on the target (target) common rail pressure, injection amount, and leak amount. Even if the value is determined, the discharge amount of the supply pump may be smaller than the required discharge amount due to the increase in the leak amount due to the change in the fuel property due to the increase in fuel temperature. That is, the discharge amount of the supply pump is insufficient and the target common rail pressure is not reached.

  FIG. 3A is a graph showing fluctuations in actual common rail pressure (actual pressure) due to changes in fuel temperature. That is, when the fuel temperature rises, the discharge amount becomes insufficient, and the actual common rail pressure becomes lower than the target common rail pressure, making it impossible to follow the target common rail pressure. As described above, the actual temperature decreases from the target pressure, so that the fuel temperature decreases. When the fuel temperature decreases, the amount of leak decreases, the supply pump discharge amount meets the required discharge amount, and the actual pressure increases this time. As described above, the actual pressure fluctuates in a wave shape as indicated by a broken line in FIG. 3A with respect to a constant target pressure of the common rail.

Such fluctuations in the actual pressure of the common rail make it difficult to control the injection amount of the injector, and there is a problem that accurate injection amount control is difficult.
In addition, the target pressure of the common rail is set so that the most efficient combustion is performed, and if the actual pressure of the common rail becomes lower than the target pressure, it will increase smoke and reduce output and fuel consumption. Cause inconvenience.

In Patent Document 1, the amount of pressure drop of the used fuel from when the discharge of the supply pump is stopped until a predetermined condition is satisfied is measured, and the fuel properties (viscosity of the used fuel) are measured from the measured pressure drop amount. , Estimating the fuel leak amount due to factors including variations in machine differences in the injection system and changes over time, and thereby using the injection system control correction amount corresponding to the fuel leak amount to control the injection system (for example, pump discharge amount control, An accumulator type fuel injection device used for correction of (common rail pressure control) is shown.
However, in the method according to Patent Document 1, it is necessary to calculate the correction amount from the predicted pressure drop amount and the actual pressure drop amount, and the control must be repeatedly performed frequently, and the control is complicated.

JP 2003-239794 A

  The present invention has been made in view of the above problems, and its purpose is that the amount of fuel discharged from the supply pump to the common rail is in a constant pressure feed state (maximum discharge), and the amount of fuel supplied from the common rail to the injector or the like is quantified. Even in the discharge state, the shortage of the pumping amount by the supply pump can be solved, thereby preventing the fluctuation of the actual pressure of the common rail pressure and maintaining it almost at the target pressure, and the injection amount control by the injector can be easily and accurately performed. It is possible to provide an accumulator fuel injection control device that can perform efficient combustion and improve output and fuel consumption.

The present invention provides the accumulator fuel injection control device according to each of the claims as means for solving the above-mentioned problems.
The accumulator fuel injection control device according to claim 1 includes target pressure setting means for setting a target pressure of fuel in the accumulator vessel, and steady pressure feed detecting means for detecting a quantitative pumping state to the accumulator vessel by the fuel supply pump. , Steady discharge detection means for detecting a constant discharge state from the pressure accumulator to the fuel low pressure side, and limit pumping area detection for detecting whether the pumping capacity of the fuel supply pump is in the limit area where the maximum capacity is exhibited And a pressure swell detection means for detecting whether or not a pressure swell fluctuation width value, which is a width value of the periodic pressure swell fluctuation of the pressure accumulator vessel, is greater than or equal to a predetermined value, and the target pressure setting means includes The undulation exceeding the predetermined value by the pressure swell detecting means under the condition of detecting all of the above-described detection of the constant-pressure feeding state, the above-described detection of the constant-quantity discharge state, and the detection of being in the limit region In state If this is detected, the target pressure of the fuel in the pressure accumulating vessel is corrected to be lower than the current target pressure, so that the pressure in the accumulating vessel is stabilized and the injection amount can be easily controlled. At the same time, the engine can maintain a good combustion state, and the output and fuel consumption can be improved.

The pressure accumulation type fuel injection control device according to claim 2 further includes pressure detection means for directly detecting the fuel pressure in the pressure accumulation container, and the pressure swell detection means is in a pressure swell state based on a value detected by the pressure detection means. In this way, the pressure swell state may be directly detected.
According to a third aspect of the present invention, there is provided the pressure accumulation type fuel injection control device further comprising fuel temperature detection means for detecting the temperature of the fuel circulating through the pressure accumulation type fuel injection control device, wherein the pressure swell detection means is based on a value detected by the fuel temperature detection means. Thus, the viscosity index of the circulating fuel is detected, and the pressure swell state is detected based on the corresponding value of the viscosity index and the pressure swell fluctuation range stored in advance. Alternatively, the pressure swell state may be detected indirectly.

In the pressure accumulation type fuel injection control device according to claim 4, when the detected value of the viscosity index is high (the viscosity is high), the target pressure of the fuel in the pressure accumulation container is corrected below the current target pressure. Thus, the pressure swell state can be reduced.
The pressure-accumulation fuel injection control device according to claim 5 further comprises viscosity detection means comprising a viscosity sensor for detecting the viscosity of the fuel circulating through the pressure-accumulation fuel injection control device, and the pressure swell detection means stores the viscosity stored in advance. Based on the corresponding value between the output value from the sensor and the pressure swell fluctuation range value, the pressure swell state is detected. Thus, from the output value from the viscosity sensor, the pressure in the accumulator vessel is also detected. A pressure swell state can be detected.

The pressure-accumulation fuel injection control device according to claim 6 determines whether the viscosity detection value detected by the viscosity detection means is higher or lower than a predetermined threshold value, and when the fuel is low viscosity, The current target pressure is corrected downward by the target pressure setting means, so that the discharge amount of the fuel supply pump can secure the required discharge amount (required pumping amount), and the actual pressure of the fuel will fluctuate. Therefore, it is possible to maintain the substantially target pressure.
The pressure-accumulation fuel injection control device according to claim 7 further includes fuel temperature detection means for detecting the temperature of the fuel, and is corrected to a target pressure determined based on the detected viscosity detection value and the fuel temperature. Thus, the difference in viscosity due to temperature can be taken into account, and the target pressure can be set more accurately.

  Hereinafter, an accumulator fuel injection control apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram showing the overall configuration of an accumulator fuel injection control apparatus according to an embodiment of the present invention. The accumulator fuel injection control device is connected to an accumulator vessel (common rail) 1 that forms an accumulator chamber for accumulating high-pressure fuel corresponding to the fuel injection pressure, and is connected to the accumulator vessel 1 respectively. A plurality of injectors (fuel injection valves) 2 for injecting fuel into the cylinder, a supply pump (fuel supply pump) 3 driven to rotate by the engine, and a control for electronically controlling the plurality of injectors 2 and the supply pump 3 And an electronic control unit (ECU) 10 as a unit. In FIG. 1, only the injector 2 corresponding to one cylinder is shown, and the injectors corresponding to the other cylinders are omitted.

  A high pressure corresponding to the fuel injection pressure needs to be continuously stored in the pressure accumulating vessel 1, and for this purpose, the pressure accumulating fuel is supplied from the supply pump 3 to the pressure accumulating vessel 1 through the high-pressure channel 11. Yes. The injector 2 of each cylinder is connected to the downstream end of a plurality of high-pressure channels 12 (only one is shown in FIG. 1) branched from the pressure accumulating vessel 1, and a fuel injection nozzle that injects fuel into each cylinder of the engine, The electromagnetic fuel injection valve has an electromagnetic actuator that drives the nozzle needle accommodated in the fuel injection nozzle in the valve opening direction, and a biasing means such as a spring that biases the nozzle needle in the valve closing direction. The fuel injection from these injectors 2 to each cylinder is performed by energizing and stopping energization (ON / OFF) of the injection control electromagnetic valve 4 as an electromagnetic actuator that controls the back pressure of the nozzle needle of the fuel injection nozzle. Be controlled. That is, while the injection control electromagnetic valve 4 of the injector 2 of each cylinder is open, the high-pressure fuel accumulated in the pressure accumulator 1 is injected and supplied to each cylinder of the engine.

  The supply pump 3 includes a known feed pump (not shown) that pumps low-pressure fuel from the fuel tank 5 and a plunger that is driven by the pump drive shaft by rotating the pump drive shaft in accordance with the rotation of the crankshaft of the engine. (Not shown) and a pressurizing chamber (not shown) for pressurizing fuel by the reciprocating motion of the plunger. The supply pump 3 pressurizes low-pressure fuel sucked from the fuel tank 5 through the filter 6 to high pressure by a feed pump (low-pressure supply pump), and pumps the low-pressure fuel to the pressure accumulating vessel 1 through the high-pressure channel 11. It is. In the fuel flow path from the feed pump of the supply pump 3 to the pressurizing chamber, the amount of fuel discharged from the supply pump 3 to the pressure accumulating container 1 is adjusted by adjusting the degree of opening (opening) of the fuel flow path. A metering valve 7 as an electromagnetic actuator for changing the pump discharge amount) is attached.

  The metering valve 7 is an intake metering valve that adjusts the amount of fuel sucked into the pressurizing chamber of the supply pump 3 by electronic control by a pump drive signal from the ECU 10 and changes the pump discharge amount. Thus, the common rail pressure corresponding to the fuel injection pressure injected from each injector 2 to each cylinder of the engine is controlled. The metering valve 7 operates on the side where the pump discharge amount increases (the valve opening increases) as the pump drive signal from the ECU 10, that is, the drive current supplied from the ECU 10 increases. It is desirable to control the drive current to the metering valve 7 by duty control. By using duty control that changes the valve opening degree of the metering valve 7 by adjusting the ON / OFF ratio (duty ratio) of the pump drive signal per unit time, high-precision digital control becomes possible.

  Both the leaked fuel from the injector 2 and the leaked fuel from the supply pump 3 return to the fuel tank 5 through the low-pressure channels 13 and 14. In addition, a pressure limiter (not shown) is disposed in the middle of the high-pressure channel 11 and functions as a pressure safety valve that prevents the common rail pressure from becoming abnormally high. In other words, when the common rail pressure exceeds the limit set pressure, the pressure limiter opens the valve against the urging force of the spring and allows the fuel to escape into the low pressure flow path, so that the fuel pressure falls below the limit set pressure. suppress.

  The ECU 10 is configured to include functions such as a CPU that performs control processing and arithmetic processing, a storage device (EEPROM, RAM) that stores various programs and data, an input circuit, an output circuit, a power supply circuit, and a pump drive circuit. A microcomputer having the structure is provided. And the sensor signal from various sensors is comprised so that it may input into a microcomputer, after A / D-converting with an A / D converter.

  The ECU 10 includes an injection amount / injection timing control means, and is configured to perform injection amount control / injection timing control of the injector 2 of each cylinder. It includes an optimal injection timing (injection start timing) according to the engine operating conditions, an injection amount / injection timing calculating means for calculating a target injection amount (injection period), and an injection according to the engine operating conditions and the target injection amount. An injection pulse width calculating means for calculating an injector injection pulse for an injection pulse time (injection pulse width) for calculating a pulse, and an injection control solenoid valve 4 of the injector 2 of each cylinder via an injector drive circuit (not shown). It is comprised from the injector drive means which applies an injector injection pulse.

  That is, the ECU 10 detects engine operation information such as the engine rotation speed (engine rotation speed) detected by the rotation speed sensor 21 and the access opening detected by the access opening sensor 22, and further detected by the cooling water temperature sensor 23. The target injection amount is calculated in consideration of the correction of the engine coolant temperature and the fuel temperature detected by the fuel temperature sensor 24, and according to the injection pulse width calculated from the common rail pressure and the target injection amount detected by the common rail pressure sensor 25. Thus, an injector injection pulse is applied to the injection control solenoid valve 4 of the injector 2 of each cylinder. As a result, the engine is operated.

Further, in the present embodiment, the ECU 10 detects the state of quantitative pumping from the supply pump 3 to the pressure accumulating vessel 1 from the detection value detected by the flow sensor 27 provided from the supply pump 3 to the high pressure flow path 11 of the pressure accumulating vessel 1. From the detected value detected by the steady pressure feed detecting means and the flow rate sensor 28 provided in the high pressure flow path 12 from the pressure accumulator 1 to the injector 2, the fixed discharge state from the pressure accumulator 1 to the injector 2 (fuel low pressure side) is determined. A steady discharge detecting means for detecting, a limit pumping area detecting means for fully opening the metering valve 7 and detecting whether or not the pumping capacity of the supply pump 3 is in a limit area where the maximum capacity is exhibited; based on a detection value from the pressure sensor 25 provided in the container 1, periodic pressure undulation is the width value W of the variable pressure undulation fluctuation width value W is a predetermined value W ₀ than the pressure accumulator 1 The pressure swell detecting means for detecting whether or not the fuel is discharged, and the metering valve 7 is fully opened so that the fuel discharge amount from the supply pump 3 to the pressure accumulating vessel 1 is in a constant pressure feeding state (maximum discharge) and the pressure accumulating vessel 1 is injected Target pressure setting means for setting the common rail pressure when the fuel supply amount to 2 is in the fixed discharge state as a target pressure, and according to the detected viscosity value of the fuel detected by the viscosity detecting means 26, Alternatively, when the pressure swell fluctuation value W is determined to be greater than or equal to the predetermined value W ₀ by the pressure swell detection means, the current target pressure of the common rail pressure set by the target pressure setting means is corrected downward, and the fuel used The target pressure of the common rail pressure can be changed according to the properties (viscosity).
The pressure swell detection means detects the viscosity index of the circulating fuel based on the detection value by the fuel temperature detection means which is the fuel temperature sensor 24 instead of directly detecting by the pressure sensor 25 of the pressure accumulating vessel 1 described above. In addition, an indirect detection method may be employed in which the pressure swell state is detected based on the correspondence value between the viscosity index and the pressure swell fluctuation value W stored in advance.

That is, when the metering valve 7 is fully opened and the fuel discharge amount from the supply pump 3 to the pressure accumulating vessel 1 is in a constant pressure feeding state, and the fuel supply amount from the pressure accumulating vessel 1 to the injector 2 is in a constant amount discharging state, FIG. As shown in a), the fuel suction amount Q ₁ of the supply pump 3 is constant, whereas the discharge amount (pressure feed amount) Q ₂ of the supply pump 3 increases as the fuel temperature rises. It tends to decrease in proportion to an increase in the leak amount L. If the viscosity is large fuel discharge amount Q ₂ of the supply pump 3 is also increased fuel temperature as shown by the broken line, constant need discharge amount to be determined by the target pressure of the common rail pressure (necessary pumping quantity) Q _o Although it is possible to ensure, when the viscosity of the fuel is small, the discharge amount Q ₂ is that the discharge amount Q ₂ and fuel temperature as shown by the solid line is increased can not be secured the necessary discharge amount Q _o insufficient Get up.

Thus the fuel temperature increases, the discharge amount Q ₂ of the supply pump 3 can not be secured the necessary discharge amount Q _o insufficient, the actual pressure P in the common rail pressure accumulator container 1 as shown in FIG. 3 (a) ₁ will be lowered below a certain target pressure P _o as shown by a broken line. As the actual pressure P ₁ decreases, the injection amount of the injector 2 also deviates from the compatible state, and sufficient combustion in the cylinder cannot be ensured, so that the fuel temperature also decreases. When the fuel temperature decreases, the fuel leak amount L decreases, the discharge amount Q ₂ of the supply pump 3 satisfies the required discharge amount Q _o, and the actual pressure P _{1 of the} pressure accumulating vessel 1 begins to increase. In this way, the actual pressure P ₁ of the common rail pressure will be varied in a wave shape at below the target pressure P _o. Such fluctuation of the actual pressure P ₁ makes it difficult to accurately control the injection amount of the injector 2.

Therefore, in the present embodiment, in order to prevent such fluctuation of the actual common rail pressure P ₁ , as described above, the steady-state pumping detecting means for detecting the constant-pumping state of the supply pump 3 and the fixed amount from the pressure accumulating vessel 1 are used. steady ejection detection means for detecting the discharge state, the pressure undulation detection means limit pumping region detection unit, the pressure undulation fluctuation width value W of the accumulator vessel 1 detects whether a predetermined value W ₀ or more for detecting the limit range of the supply pump 3 Viscosity detecting means 26 for detecting the viscosity of the fuel, target pressure setting means for setting the target pressure of the common rail pressure of the pressure accumulating vessel 1, and the target pressure can be corrected according to the viscosity of the fuel or the fluctuation of the pressure swell. It is a thing.
That is, as a situation that does not satisfy the discharge amount Q ₂ must discharge amount Q _o of the supply pump 3 does not occur, when the viscosity of the fuel detected by the viscosity detector 26 is lower than the predetermined threshold value, the fuel If the pressure undulation detecting means detects that the pressure undulation fluctuation range value W is equal to or greater than the predetermined value W ₀ , the pressure fluctuation is too large, as shown in FIG. lowering the pressure P _o required discharge amount is corrected downward by the target pressure modifying means Q _o required discharge amount after the change of the lower Q _'o.

Thus, by setting the target pressure P _o to the corrected target pressure P ′ _o corrected downward, the discharge amount Q ₂ of the supply pump 3 satisfies the required discharge amount Q ′ _o after the change even if the fuel temperature rises. be able to. Therefore, the fluctuation of the actual pressure P ₁ resulting from the insufficient pumping amount is eliminated, and the substantially constant actual pressure P ₁ that is substantially the same as the fixed target pressure P ′ _o is maintained as shown in FIG. 3B. . Thus, in order to stabilize in the state where the actual pressure P ₁ is lowered, the fuel temperature T is also stabilized at a lower level.

  A viscosity sensor may be used as the viscosity detection means 26, but by comparing the pressure drop amount of the fuel in the pressure accumulating container per unit time when the internal combustion engine is stopped with an index value indicating the viscosity of the fuel. You may make it detect. That is, both the fuel entry into the pressure accumulator 1 and the fuel out of the pressure accumulator 1 are stopped. For example, the internal combustion engine is stopped and remains in the pressure accumulator immediately after the engine is stopped. The degree of pressure drop in the fuel high pressure state to be detected is detected as pressure drop amount / value per predetermined time. This detected value can be used as an index value indicating the viscosity of the fuel. Specifically, the corresponding value of the pressure drop / value per predetermined time and the index value indicating the viscosity of the fuel is stored in advance or derived by calculation.

  FIG. 4 is a flowchart showing a procedure for correcting the target pressure of the common rail pressure according to the first embodiment of the present invention. First, in step S1, it is detected whether or not the amount of fuel discharged from the supply pump 3 to the pressure accumulating container 1 is in a constant pressure feed state by the steady pressure feed detection means. When it is in the constant pressure feed state, the process proceeds to step S2, and it is detected by the steady discharge detection means whether or not the fuel supply amount from the pressure accumulator 1 to the injector 2 is in the constant discharge state. When it is in the constant discharge state, the process proceeds to step S3, and it is detected whether or not the pumping capacity of the supply pump 3 is in the limit area where the maximum capacity is exhibited by the limit pumping area detecting means. When the pumping capacity of the supply pump 3 is in the limit region, the process proceeds to step S4.

In this manner, the fuel discharge amount from the supply pump 3 to the pressure accumulator 1 is in a constant pressure feed state, the fuel supply amount from the pressure accumulator vessel 1 to the injector 2 is in a constant discharge state, and the pumping capacity of the supply pump 3 is further increased. Under the condition that the maximum capacity is exhibited, the pressure swell detector detects whether the periodic pressure swell fluctuation value W in the pressure accumulator 1 is equal to or greater than a predetermined value W ₀ (step S4). ). If it is detected that the swell state is equal to or greater than the predetermined value W ₀ , the process proceeds to step S5, and the current target pressure P ₀ set by the target pressure setting means is corrected downward. In addition, when each is set to No in steps S1 to S4, the process returns to the start. In this way, it is possible to prevent fluctuations in the actual pressure of the common rail pressure of the pressure accumulating vessel 1.

FIG. 5 is a flowchart showing a procedure for correcting the target pressure of the common rail pressure according to the second embodiment of the present invention. This flowchart is executed when the engine is started and when fuel supply is detected. First, in step S11, the viscosity of the fuel is detected by the viscosity detector 26. Next, in step S12, it is determined whether the fuel is high-viscosity or low-viscosity depending on whether the detected viscosity detection value is larger or smaller than a predetermined threshold value. When the fuel is determined to be a high viscosity, the process proceeds to step S13, sets the target pressure (pressure limit) P _o of the common rail pressure to normal. That is, even the fuel temperature rises, the discharge amount Q ₂ of the supply pump 3 is less than the required discharge amount Q _o is determined not, leave the target pressure P _o set by the target pressure setting means deep. When the fuel is determined to be a low viscosity in step S12, the process proceeds to step S14, the target pressure (pressure limit) of the common rail pressure P _o Correct downward by the target pressure setting means, corrected target pressure P _'o To.
As described above, by setting the usable pressure in advance according to the fuel property (viscosity), it is possible to prevent fluctuations in the actual pressure (actual pressure) of the common rail pressure of the pressure accumulating vessel 1.
In this case, the establishment of steps S1 to S4 in the first embodiment of FIG. 4 is a prerequisite.

FIG. 6 is a flowchart showing a procedure for setting a target pressure of the common rail pressure according to the third embodiment of the present invention. First, in step S21, the viscosity of the fuel is detected by the viscosity detecting means 26. Next, the target pressure (pressure upper limit value) of the common rail pressure is calculated from the viscosity detection value detected in step S22. In this case, the usable pressure due to the fuel properties (viscosity) is tabulated and stored in the ECU 10, and the pressure upper limit value is drawn from this table. In this case, when the upper pressure limit drawn from the target pressure P _o and the table set by the target pressure setting means as in the second embodiment is different from the pressure upper limit target pressure P _o in the target pressure setting means The pressure upper limit value directly drawn from the table may be set as the target pressure without following such a procedure.

FIG. 7 is a flowchart showing a procedure for setting the target pressure of the common rail pressure according to the fourth embodiment of the present invention. First, when the engine is started and when fuel supply is detected, the fuel viscosity is detected in step S31, and the detected viscosity detection value is stored. Next, the temperature of the fuel shown in step S32 is periodically detected during normal operation. In step S33, a target pressure (pressure upper limit value) of the common rail pressure is calculated from the detected viscosity detection value and the fuel temperature. Even in this case, as in the third embodiment, the usable pressure based on the fuel property (viscosity) and the fuel temperature is tabulated and stored in the ECU 10, and the pressure upper limit value is derived from this table. Even in this case, if the target pressure P _o set by the target pressure setting means and the pressure upper limit value drawn from the table are different, the target pressure P _o is corrected to match the pressure upper limit value by the target pressure setting means. However, the pressure upper limit value directly drawn from the table may be set as the target pressure without following such a procedure.

  As described above, in the conventional accumulator fuel injection device, the amount of leak varies greatly depending on the properties (viscosity) of the fuel used, and the fuel with low viscosity is used when the characteristics are adjusted for normal fuel. In some cases, the discharge amount of the supply pump may be insufficient due to the influence of the leakage amount. In the present invention, the shortage of the discharge amount is predicted in advance based on the fuel property (viscosity), so that the target pressure of the common rail pressure is set. By lowering, it is possible to prevent the discharge amount from being insufficient. Thereby, the actual pressure of the common rail pressure is balanced, and a stable pressure state can be secured.

It is a conceptual diagram which shows the whole structure of the pressure accumulation type fuel-injection control apparatus of embodiment of this invention. It is a figure explaining the difference of the effect of prior art (a) and this invention (b). It is a figure explaining the difference of the effect of prior art (a) and this invention (b). It is a flowchart which shows the correction procedure of the target pressure of a common rail pressure which is 1st Example of this invention. It is a flowchart which shows the correction procedure of the target pressure of a common rail pressure which is 2nd Example of this invention. It is a flowchart which shows the setting procedure of the target pressure of a common rail pressure which is 3rd Example of this invention. It is a flowchart which shows the setting procedure of the target pressure of a common rail pressure which is 4th Example of this invention. It is a figure explaining the problem of a prior art.

Explanation of symbols

1 Pressure storage container (common rail)
2 Injector (fuel injection valve)
3 Supply pump (fuel supply pump)
4 Electromagnetic valve for injection control 5 Fuel tank 7 Metering valve 10 Electronic control unit (ECU)
11,12 High pressure flow path 13,14 Low pressure flow path

Claims (7)

A fuel supply pump that pressurizes and pumps inhaled fuel; and
An accumulator container for accumulating high-pressure fuel pumped from the fuel supply pump;
A fuel injection valve for injecting high-pressure fuel from the pressure accumulator into the engine;
Target pressure setting means for setting a target pressure of fuel in the pressure accumulating vessel;
An accumulator fuel injection control device comprising:
A steady-state pumping detecting means for detecting a constant pumping state to the pressure accumulating container by the fuel supply pump;
Steady discharge detection means for detecting a fixed discharge state from the pressure accumulator to the fuel low pressure side;
Limit pumping area detecting means for detecting whether the pumping capacity of the fuel supply pump is in a limit area where the maximum capacity is exhibited;
Pressure swell detection means for detecting whether or not the pressure swell fluctuation width value, which is the width value of the periodic pressure swell fluctuation of the accumulator vessel, is a predetermined value or more,
The target pressure setting means detects the pressure swell under conditions for detecting all of the detection of the above-described quantitative pumping state, the above-described detection of the constant discharge state, and the detection of being in the limit region. An accumulator fuel injection control device that corrects the target pressure of the fuel in the accumulator container to be lower than the current target pressure when it is detected that the swell state is a predetermined value or more by the means. Pressure detecting means for directly detecting the fuel pressure in the pressure accumulating vessel,
2. The accumulator fuel injection control device according to claim 1, wherein the pressure swell detection means detects a pressure swell state based on a detection value by the pressure detection means. A fuel temperature detecting means for detecting the temperature of the fuel circulating in the pressure accumulation type fuel injection control device;
The pressure swell detection means detects the viscosity index of the circulating fuel based on the detection value by the fuel temperature detection means, and prestores the correspondence value between the viscosity index and the pressure swell fluctuation value, The pressure accumulation type fuel injection control device according to claim 1, wherein a pressure swell state is detected.   4. The accumulator fuel injection control according to claim 3, wherein when the detected value of the viscosity index is high (viscosity is high), the target pressure of the fuel in the accumulator vessel is corrected below the current target pressure. apparatus. Viscosity detection means comprising a viscosity sensor for detecting the viscosity of the fuel circulating through the accumulator fuel injection control device,
2. The pressure swell detection means detects a pressure swell state based on a pre-stored value corresponding to the output value from the viscosity sensor and the pressure swell fluctuation range value. 2. The accumulator fuel injection control device according to 1.   Whether the viscosity detection value detected by the viscosity detection means is higher or lower than a predetermined threshold value is determined. If the fuel is low viscosity, the target pressure setting means sets the current target pressure. The pressure-accumulation fuel injection control device according to claim 5, wherein the pressure-accumulation fuel injection control device is corrected downward.   A fuel temperature detecting means for detecting the temperature of the fuel, and the target pressure determined based on the viscosity detection value detected by the viscosity detecting means and the fuel temperature detected by the fuel temperature detecting means; The pressure accumulation type fuel injection control device according to claim 5 or 6, wherein the pressure accumulation type fuel injection control device is corrected by a target pressure setting means.

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