JP4621951B2 - COMMON RAIL TYPE FUEL INJECTION DEVICE AND METHOD FOR COMPENSATION OF PRESSURE CHARACTERISTICS OF HIGH PRESSURE PUMP - Google Patents

Description

  The present invention relates to a common rail fuel injection device having a function of measuring and learning an actual fuel discharge amount in order to perform characteristic compensation for a high pressure pump that pumps fuel to a common rail that accumulates high pressure fuel, and The present invention relates to a method for compensating a pumping characteristic.

The common rail fuel injection system is used for the purpose of preventing the drop of rail pressure (pressure of fuel accumulated in the common rail) due to fuel injection and for increasing the rail pressure in response to changes in operating conditions. Rail pressure is controlled by controlling the amount. Among the high-pressure pumps, there is an intake metering type in which the amount of fuel discharged is controlled by metering the flow rate of fuel sucked into the pressurizing chamber of the high-pressure pump with a suction metering valve.
In the above-described type of common rail fuel injection device, the opening amount of the intake metering valve is adjusted by a control command given by the control device, thereby controlling the discharge amount of the high-pressure pump and controlling the rail pressure. Therefore, it is required that the discharge amount of the high-pressure pump with respect to the metering valve control value (driving current value for obtaining the opening of the predetermined suction metering valve) given to the suction metering valve has a predetermined pump characteristic. Is done.

However, due to various factors such as manufacturing variations of intake metering valves, variations due to deterioration, or changes due to temperature characteristics such as fuel viscosity and coil suction force, the metering valve control value is actually controlled by the high pressure pump. There is a possibility that the discharge amount (actual discharge amount) discharged varies. Thus, techniques for learning and correcting variations in the actual discharge amount of the high-pressure pump have been proposed.
For example, Patent Document 1 discloses a current direction between an actual applied current-discharge amount characteristic of a suction metering valve and a preset central characteristic at the time of warm idling and forced idling up prior to common rail pressure control. The amount of misalignment is calculated and the rotational speed direction is corrected. The tilt amount of the applied current-discharge amount characteristic line is calculated based on the discharge amount corresponding to the corrected misalignment amount, and the tilt direction is corrected. Technology is disclosed.

Further, in Patent Document 2, when the learning condition is satisfied, the pressure reducing valve control is performed so as to gradually increase the metering valve control value to gradually increase the opening of the suction metering valve and to keep the common rail pressure constant. The value is feedback controlled, the metering valve control value when the amount of change in the pressure reducing valve control value is equal to or less than the predetermined value is set as the “maximum discharge control value”, and the high-pressure pump in the supply pump starts suction. `` Suction start control value '' is obtained, pump characteristics are obtained from both control values, and the metering valve control value is calculated based on the suction metering valve opening calculated according to the vehicle operating state and the learning-corrected pump characteristics. The required technology is disclosed.
JP 2004-293540 A Japanese Patent Laid-Open No. 2005-139928

However, in the technique of Patent Document 1, it is possible to learn pump characteristics for a region where the engine speed is high as in forced idle up, but in a region where the discharge amount is large over the entire region where the engine speed is used. There is no compensation.
In the technique of Patent Document 2, learning / compensation can be performed from a region with a small discharge amount to a region with a large discharge amount. However, the compensation is performed on the condition of steady operation in which the target pressure of the common rail does not change. There is a problem that the frequency is reduced.

  The present invention has been made in view of the above circumstances, and its object is to provide a common rail fuel injection device capable of performing high-frequency learning over the entire pump discharge amount, and the pumping characteristics of the high-pressure pump. It is to provide a compensation method.

According to the common rail fuel injection device of the first aspect, when the deceleration command for the engine is generated, the control device reduces the high pressure fuel when the engine speed decreases to a predetermined measurement target value in the process of depressurizing the common rail. When a control command for supplying a predetermined amount is given to the high-pressure pump, the pressure change detecting means detects the rail pressure change of the common rail at that time by the pressure sensor, and the discharge amount calculating means is the rail detected by the pressure change detecting means. based on the pressure change, to calculate a discharge amount of the high pressure fuel that by the high-pressure pump. A plurality of coordinate points for acquiring data used for compensation in advance in the two-dimensional coordinates of the IQ characteristic, which is a characteristic of the applied current value to the suction metering valve and the discharge amount of the high-pressure pump based on the current value, are obtained in advance. set advance, and select one of the engine speed corresponding to their coordinate point as measured, you calculate the forward Tsugi吐 volume for different engine speed selected.
In other words, when the deceleration command is issued, the common rail is depressurized and the engine speed decreases, so that the speed for acquiring data for compensating the pumping characteristics in the process has a relatively high degree of freedom. It is possible to select, and selection at a low rotational speed is also easy. When a desired engine speed is reached, a control command is given to the high-pressure pump to discharge a predetermined amount of high-pressure fuel, and if a change in the rail pressure of the common rail is detected, the high-pressure pump is controlled based on the change in the rail pressure. that by calculating the discharge amount of the high pressure fuel, it is possible to compensate for the pumping characteristics of the high-pressure pump.

According to common rail fuel injection apparatus according to claim 2, wherein the correction value calculating means compares the I-Q characteristic is defined by the discharge amount calculating means ejection out amount and the high-pressure pump has been calculated by the specification Since the correction value of the fuel discharge amount by the high-pressure pump is calculated, the correction value can be acquired over a wide rotational speed range.

According to the common rail fuel injection device of the third aspect , the characteristic compensation means compensates the characteristic of the fuel discharge amount by the high-pressure pump for the control command based on the correction value calculated by the correction value calculation means. It is possible to perform learning for compensating the pumping characteristics over a wide rotational speed range.

According to the common rail fuel injection device of claim 4 , the pressure change detection means is based on the fuel discharge timing by the high-pressure pump, and when the pressure-feeding state of the fuel by the high-pressure pump is stabilized after the control command is output. Thereafter, the measurement timing of rail pressure change is set. In other words, the high-pressure pump is provided with a metering valve for adjusting the discharge amount, but for the metering valve, there is a time delay between when the control command is given and when the valve open state is stabilized. At the same time, there is a time delay between the intake and discharge of fuel in the high-pressure pump. Therefore, if the measurement timing of the rail pressure change is set in consideration of the time delay, the measurement can be accurately performed in a stable state.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. First, the configuration of the common rail fuel injection device will be described with reference to FIGS. 4 and 5. 4 is a system that injects fuel into a four-cylinder engine (for example, a diesel engine: not shown), and includes a common rail 1, an injector 2, a supply pump 3, a control device (pressure change detecting means, Discharge amount calculation means, correction value calculation means, characteristic compensation means) 4 and the like. This control device 4 is composed of an ECU (Engine Control Unit) and an EDU (Drive Unit: Electronic Drive Unit). FIG. 4 shows an example in which the ECU and EDU are mounted in one control device 4. However, the ECU and the EDU may be separately mounted.

The common rail 1 is a pressure accumulating container for accumulating high-pressure fuel supplied to the injector 2, and has a high pressure via a pump pipe (high-pressure fuel flow path) 6 so that rail pressure corresponding to fuel injection pressure is continuously accumulated. A plurality of injector pipes 7 that supply high-pressure fuel to each injector 2 are connected to the discharge port of the supply pump 3 that discharges fuel.
A pressure limiter 10 is attached to a relief pipe 9 that returns fuel from the common rail 1 to the fuel tank 8. The pressure limiter 10 is a safety valve, and is opened when the fuel pressure in the common rail 1 exceeds the limit set value, thereby suppressing the fuel pressure in the common rail 1 to be equal to or less than the limit set value.

  The common rail 1 is provided with a pressure reducing valve 11 that adjusts the opening degree of a discharge passage (passage that connects the common rail 1 and the relief pipe 9) that overflows the fuel accumulated in the common rail 1. The pressure reducing valve 11 rapidly reduces the rail pressure via the relief pipe 9, and the control device 4 adjusts the opening degree of the pressure reducing valve 11 so that the rail pressure is adjusted to a pressure corresponding to the vehicle running state. Reduction control can be performed quickly. The pressure reducing valve 11 includes a valve that changes the opening degree of the discharge passage and a solenoid that adjusts the valve opening degree (opening area) of the valve by a pressure reducing valve control value (pressure reducing valve driving current value) given from the control device 4. A normally open type valve that is a variable opening area type valve and whose valve opening is fully closed when energization of the solenoid is stopped is used.

  The injector 2 is mounted for each cylinder of the engine and supplies fuel to each cylinder. The injector 2 is connected to the downstream ends of a plurality of injector pipes 7 branched from the common rail 1 and is accumulated in the common rail 1. A fuel injection nozzle that supplies fuel to each cylinder and a solenoid valve that performs lift control of a needle housed in the fuel injection nozzle are mounted. The leaked fuel from the injector 2 is also returned to the fuel tank 8 through the relief pipe 9.

Next, the structure of the supply pump 3 will be described with reference to FIG. The supply pump 3 includes a feed pump 12 (disclosed in a state where the pump is expanded by 90 ° in the drawing), a regulator valve 13, a suction metering valve 14, a high-pressure pump 15, and the like. The feed pump 12 is a low-pressure supply pump that sucks fuel from the fuel tank 8 through the fuel filter 8 a and sends the fuel to the high-pressure pump 15, and is composed of a trochoid pump that is rotationally driven by the camshaft 16. When the feed pump 12 is driven, the fuel sucked from the fuel inlet 17 is supplied to the high-pressure pump 15 via the suction metering valve 14. The camshaft 16 is a pump drive shaft and is driven to rotate by an engine crankshaft.
The regulator valve 13 is disposed in a fuel flow path 19 that communicates the discharge side and the supply side of the feed pump 12, and opens when the discharge pressure of the feed pump 12 rises to a predetermined pressure. The pressure is adjusted so as not to exceed a predetermined pressure.

  The intake metering valve 14 is disposed in a supply passage 21 that guides fuel from the feed pump 12 to the high-pressure pump 15, and adjusts the intake amount of fuel sucked into the pressurizing chamber 22 (plunger chamber) of the high-pressure pump 15. Change and adjust rail pressure. The intake metering valve 14 includes a valve 23 that changes the opening degree of the supply passage 21 that guides fuel from the feed pump 12 to the high-pressure pump 15, and a metering valve control value that is given from the control device 4 (operating state in the control device 4). A variable opening area having a linear solenoid 24 for adjusting the valve opening (opening area) of the valve 23 based on an intake metering valve driving current value for obtaining the opening. For example, when the energization of the linear solenoid 24 is stopped, the valve opening degree is configured as a normally closed type.

  The high pressure pump 15 is a plunger pump that compresses the fuel supplied from the intake metering valve 14 to a high pressure and supplies the compressed fuel to the common rail 1. A plunger 25 (a, b) that is reciprocated by the camshaft 16, and this plunger 25 Are provided with a suction valve 26 for supplying fuel to the pressurizing chamber 22 whose volume is changed by the reciprocating motion of the gas, and a discharge valve 27 for discharging the fuel compressed in the pressurizing chamber 22 toward the common rail 1.

  The plunger 25 is pressed against a cam ring 29 mounted around the eccentric cam 28 of the camshaft 16 by a spring 30. When the camshaft 16 rotates, the two plungers 25a and 25b reciprocate along with the eccentric operation of the cam ring 29. To do. When the plunger 25 descends and the pressure in the pressurizing chamber 22 decreases, the discharge valve 27 closes, and the intake valve 26 opens and the fuel metered by the suction metering valve 14 is in the pressurizing chamber 22. To be supplied. Conversely, when the plunger 25 rises and the pressure in the pressurizing chamber 22 rises, the intake valve 26 closes. When the pressure pressurized in the pressurizing chamber 22 reaches a predetermined pressure, the discharge valve 27 is opened, and the high-pressure fuel pressurized in the pressurizing chamber 22 is supplied to the common rail 1 via the pump pipe 6. .

  The ECU mounted on the control device 4 is a computer unit having a CPU for performing control processing and arithmetic processing, a storage device for storing various programs and data (ROM, standby RAM or EEPROM, memory such as RAM), and the like. Based on the signals of the sensors (engine parameters: signals corresponding to the driving state of the vehicle, the operating state of the engine, etc.), various types (injection timing of the injector 2, opening control of the pressure reducing valve 11, (Opening control, etc.) is performed. An example of a specific calculation is as follows. For each fuel injection, the ECU determines each cylinder based on a program stored in the ROM and a sensor signal (vehicle operating state) read into the RAM. The target injection amount, the injection mode, the valve opening timing of the injector 2, and the like are determined.

The EDU mounted on the control device 4 is a drive circuit that gives a valve opening control value to the solenoid valve of the injector 2 based on an injector valve opening signal given from the ECU. The fuel is injected into the cylinder and the fuel injection is stopped when the valve opening current is turned off.
In addition to the rail pressure sensor (pressure sensor) 31 that detects the rail pressure, the ECU of the control device 4 detects an accelerator position, an accelerator sensor 32 that detects the accelerator opening, and an engine speed as means for detecting the driving state of the vehicle. An engine speed sensor 33, a water temperature sensor 34 for detecting the coolant temperature of the engine, an intake air temperature sensor 35 for detecting the intake air temperature taken into the engine, and other sensors 36 are connected.

  Next, the operation of this embodiment will be described with reference to FIGS. FIG. 3 is a timing chart showing an operation (two injection and one pressure feed) when the rail pressure is controlled to be constant when the engine is four cylinders and the supply pump 3 is a two-plunger type. As shown in FIGS. 3A and 3B, for the four cylinders (# 1 to 4), the injector 2 sequentially performs injection in the order of # 1, 3, 4, and 2. Then, the cam position of the supply pump 3 is displaced so that the pressure is alternately fed by the two plungers 25a and 25b (see FIG. 3C).

  As shown in FIG. 3D, the rail pressure of the common rail 1 is feedback controlled (proportional integral control) so that the actual pressure matches the target value (see (e) and (f)). Is lower than the latter, fuel is supplied in the pumping cycle of the supply pump 3, and when the former exceeds the latter, the fuel supply is stopped (see (g)).

  FIG. 2 is a flowchart showing the contents of the discharge amount learning process by the control device 4, and FIG. 1 is a timing chart showing changes in parameters in the learning process. When the control device 4 determines that the learning condition for the discharge amount is satisfied when the accelerator opening becomes “0 (OFF)” (step S1: YES, see FIG. 1A), the discharge condition of the supply pump 3 is determined. Is set (step S2). For example, in the two-dimensional coordinates of the IQ characteristic in FIG. 7, a plurality of coordinate points for acquiring data used for compensation are set in advance in a grid shape (lattice point shape), and the engine corresponding to these coordinate points is set. One of the rotational speeds NE is selected as a measurement target.

  Next, the control device 4 calculates the timing for A / D conversion of the output value of the rail pressure sensor 31 in order to measure the rail pressure of the common rail 1 under the discharge conditions set in step S2 (step S3). In this case, the position at which the discharge of the fuel by the supply pump 3 ends and the time delay from the time of fuel intake through the intake metering valve 14 to the discharge are also considered.

  As shown in FIG. 1B, the engine speed decreases monotonously when the accelerator is turned off. In this process, when the rotational speed reaches a predetermined value and the discharge condition is satisfied (step S4: YES, see FIG. 1B), the control device 4 is detected by the rail pressure sensor 31 at that time. The rail pressure is A / D converted and read (step S5). Then, when a predetermined metering valve control value (drive current command) is given to the suction metering valve 14 and fuel is discharged to the supply pump 3 (step S6), the rail pressure is converted to A / D at that time. It is confirmed whether various conditions are actually satisfied (step S7), and if the conditions are satisfied (YES), A / D conversion is executed (step S8, see FIG. 1C).

Subsequently, the pressure increase amount of the common rail 1 is calculated from the difference between the rail pressures before and after the fuel discharge A / D converted in steps S5 and S8 (step S9), and the actual fuel discharge by the supply pump 3 based on the pressure increase amount. The amount is calculated (step S10). Then, the magnitude of variation between the discharge amount obtained this time and the discharge amount obtained for the same engine speed in the past is calculated, and the average of them is obtained (step S11).
Then, it is determined whether or not the correction is possible depending on whether or not the variation in the discharge amount is within a certain value (step S12), and when it is determined that the variation is within the certain value (YES), the predetermined value obtained in step S10 is obtained. The correction amount of the discharge amount is calculated by comparing the actual discharge amount when a predetermined discharge command (current command) is given at the engine speed and the reference characteristic defined as the specification of the supply pump 3. (Step S13).

Moreover, in step S13, it differs according to each plunger 25a, 25b based on whether the plunger 25 of the supply pump 3 which pumped when discharging the fuel in step S6 is (a, b). The correction amount may be calculated in consideration of the pumping characteristics. Alternatively, a region may be divided and set for the IQ characteristic diagram shown in FIG. 7, weighting may be performed according to the region, and the correction amount may be calculated in consideration of the weight according to the region to which the measurement result belongs. good.
If the actual discharge amount is sequentially obtained for a plurality of predetermined measurement target points (I-Q coordinate points) by repeatedly executing the above processing, the actual discharge amount of the supply pump 3 can be measured over a wide range. Can be learned and compensated.

As described above, according to the present embodiment, when the deceleration command for the engine is generated, the control device 4 assigns the high-pressure fuel when the engine speed decreases to the predetermined measurement target value in the process of depressurizing the common rail 1. A control command for supplying only a fixed amount is given to the supply pump 3, and the rail pressure change of the common rail 1 at that time is detected by the rail pressure sensor 31.
That is, when a deceleration command is issued during driving of the vehicle, the common rail 1 is depressurized and the engine speed decreases, so that the speed can be selected with a relatively high degree of freedom in the process, and the low speed Selection in the region is also easy. Further, the engine deceleration command is issued at a high frequency during operation of the vehicle. When the desired engine speed is reached and the supply pump 3 discharges a predetermined amount of high-pressure fuel to detect a rail pressure change, the pumping characteristics of the supply pump 3 are compensated based on the change amount. Can do.

Further, since the supply pump 3 includes the intake metering valve 14 that adjusts the opening of the supply path for sending fuel to the high-pressure pump 15 and adjusts the discharge amount, the supply pump 3 is provided in the supply pump 3 configured by the intake metering type. The invention can be applied.
Further, since the control device 4 calculates the actual discharge amount of the high-pressure fuel from the supply pump 3 based on the detected rail pressure change, the actual discharge amount can be used for characteristic compensation, and the calculated actual Since the discharge amount and the reference characteristic of the supply pump 3 are compared and the correction value of the fuel discharge amount by the supply pump 3 is calculated, the correction value can be acquired over a wide rotation speed range. Furthermore, since the control device 4 compensates the fuel discharge amount characteristic (pumping characteristic) by the supply pump 3 with respect to the control command based on the calculated correction value, the control apparatus 4 compensates the pumping characteristic over a wide rotational speed range. Can be learned at a high frequency.

(Second embodiment)
FIG. 6 shows a second embodiment of the present invention. The second embodiment shows details for optimally setting the timing when the rail pressure is A / D converted after the supply pump 3 discharges the fuel in FIG. 2: step S8 of the first embodiment. In the case of the supply pump 3 adopting the suction metering method, the high pressure pump 15 discharges the fuel to the common rail 1 side after sucking the fuel via the suction metering valve 14, and the result is reflected in the actual rail pressure. There is a time delay before Further, due to the response characteristics of the intake metering valve 14 as an electromagnetic valve, there is also a time delay from when the pump control value (current command) is given until the valve opening is stabilized.

For example, as shown in FIG. 6D, when a predetermined pump control value is given at time A, the opening of the intake metering valve 14 is stabilized before time C (see FIG. 6E). . Further, considering the time delay between the suction and discharge, the timing at which the fuel sucked in with the valve opening being stabilized is reflected in the rail pressure is time E (see FIG. 6E).
That is, when a predetermined pump control value is given at time A, the discharge amount of the supply pump 3 is calculated first at time D, the A / D conversion timing before discharge, and the A / D conversion timing after discharge. The time point E may be set, and by setting the measurement range so that A / D conversion is performed after the time point D, the rail pressure can be measured with high accuracy.

  Note that the learning correction of the present invention is performed at the time of transition after the accelerator is turned off, so that the engine speed changes with time, but in order to obtain a discharge amount characteristic when stable suction is performed. In consideration of the opening stabilization time of the intake metering valve 14, the pump control value may be output at an earlier timing, and the engine speed and both engine speeds at the timing when the fuel is sucked and discharged are determined. Correction may be performed according to the difference.

  As described above, according to the second embodiment, the control device 4 is based on the fuel discharge timing by the supply pump 3 and after the time when the fuel pumping state by the supply pump 3 is stabilized after the control command is output. Since the measurement timing of the rail pressure change is set, the rail pressure can be measured accurately in a stable state.

The present invention is not limited to the embodiments described above and shown in the drawings, and the following modifications or expansions are possible.
Although an example using a variable opening area type valve as the intake metering valve 14 and the pressure reducing valve 11 has been shown, the opening degree may be adjusted by varying the opening time.
A normally open type intake metering valve may be used.
High pressure pump is not limited to the second plunger type, it may be one comprising first plunger, or three or more plungers.

The timing chart of the pumping characteristic learning process according to the first embodiment of the present invention. Flow chart showing processing contents by control device Timing chart showing the operation of controlling the rail pressure to be constant when performing 2-injection 1-pressure feeding to a 4-cylinder engine Diagram showing configuration of common rail fuel injection system Diagram showing the structure of the supply pump FIG. 3 equivalent view showing a second embodiment of the present invention. Supply pump IQ characteristics

Explanation of symbols

  In the drawing, 1 is a common rail, 2 is an injector, 3 is a supply pump, 4 is a control device (pressure change detection means, discharge amount calculation means, correction value calculation means, characteristic compensation means), 14 is an intake metering valve, and 15 is A high pressure pump, 22 is a pressurizing chamber, and 31 is a rail pressure sensor (pressure sensor).

Claims (8)

A common rail for accumulating high-pressure fuel, an injector for injecting the high-pressure fuel stored in the common rail into the engine, a pressure sensor for detecting the pressure of the high-pressure fuel stored in the common rail, and an application for suctioning and pressurizing the fuel A high-pressure pump including a pressure chamber, configured to discharge the high-pressure fuel pressurized in the pressurizing chamber to the common rail, and to adjust a discharge amount of the high-pressure fuel, and a control device for controlling the discharge amount A common rail fuel injection device comprising:
The high-pressure pump is rotationally driven by the crankshaft of the engine,
An intake metering valve that adjusts an opening of a supply path that sends fuel to the high-pressure pump and adjusts a discharge amount of the high-pressure pump;
The control device discharges a predetermined amount of high-pressure fuel by the high-pressure pump when the engine speed decreases to a predetermined measurement target value in the process of depressurizing the common rail by generating a deceleration command for the engine. Giving a control command to the high-pressure pump,
At that time, pressure change detecting means for detecting a rail pressure change of the common rail according to a sensor value detected by the pressure sensor,
Based on the rail pressure change detected by the pressure change detecting means, and a discharge amount calculating means for calculating the discharge amount of by that high pressure fuel in the high pressure pump,
And the applied current value to the suction control valve, the characteristics in which I-Q characteristic of the two-dimensional coordinates of the discharge amount of the high-pressure pump based thereon, was given a certain discharge command at a predetermined rotational speed of the engine In advance, a plurality of coordinate points for acquiring data used for compensation of the pumping characteristic indicating the actual discharge amount of the high-pressure pump is set in advance,
The discharge amount calculating means, a common rail, characterized in that said plurality of engine speed corresponding to the coordinate points for different engine speed is selected as the measurement object, and sequentially calculates the discharge rate of the high-pressure pump Fuel injector. Wherein a discharge amount discharged amount calculated by the calculation means, said are determined by the specifications of the high-pressure pump by comparing the I-Q characteristic, the correction value to calculate the correction value of the fuel discharge amount of the high-pressure pump The common rail fuel injection device according to claim 1, further comprising a calculation means.   The common rail fuel injection according to claim 2, further comprising characteristic compensation means for compensating characteristics of the fuel discharge amount by the high-pressure pump with respect to the control command based on the correction value calculated by the correction value calculation means. apparatus.   The pressure change detecting means is configured to change the rail pressure of the common rail from the time when the control command is output to the time when the fuel pumping state by the high pressure pump is stabilized based on the fuel discharge timing by the high pressure pump. The common rail fuel injection device according to any one of claims 1 to 3, wherein the measurement timing is set. A common rail for accumulating high-pressure fuel, an injector for injecting high-pressure fuel stored in the common rail into the engine, and a pressurizing chamber for sucking and pressurizing the fuel, the high-pressure fuel pressurized in the pressurizing chamber being A common rail type fuel injection apparatus comprising: a high pressure pump configured to discharge to the common rail and adjust a discharge amount of the high pressure fuel; and a control device for controlling the discharge amount. Compensating a pumping characteristic indicating an actual discharge amount of the high-pressure pump when a discharge command is given,
The high-pressure pump is rotationally driven by the crankshaft of the engine, and is applied to a pump equipped with an intake metering valve that adjusts the opening of a supply passage that sends fuel to the high-pressure pump and adjusts the discharge amount of the high-pressure pump. And
And the applied current value to the suction control valve, in the characteristics in which I-Q characteristic of the two-dimensional coordinates of the discharge amount of the high-pressure pump based thereon, a plurality of coordinate points for acquiring data to be used for compensation Set in advance, select any of the engine speeds corresponding to those coordinate points as the measurement target,
When a deceleration command for the engine is generated, a control command for discharging a predetermined amount of high-pressure fuel from the high-pressure pump is provided when the engine speed decreases to a predetermined measurement value in the process of depressurizing the common rail. To detect the rail pressure change of the common rail,
Wherein based on the rail pressure changes, the that by the high-pressure pump calculates the discharge amount of the high pressure fuel, by calculating the discharge rate of the sequential pre Symbol pressure fuel with a different engine speed and the selected, the Compensating a characteristic of a fuel discharge amount by the high-pressure pump with respect to a control command, a method for compensating a pumping characteristic of a high-pressure pump. And calculated discharge amount, by comparing the I-Q characteristic is defined by the specifications of the high-pressure pump, claim and calculates the correction value of the fuel discharge amount of the high-pressure pump 5 The method for compensating the pumping characteristics of the high-pressure pump described.   7. The method for compensating a pumping characteristic of a high-pressure pump according to claim 6, wherein the characteristic compensation of the fuel discharge amount with respect to the control command is performed based on the calculated correction value.   Based on the fuel discharge timing by the high-pressure pump, the measurement timing of the change in rail pressure of the common rail is set from the time when the control command is output to the time when the fuel pumping state by the high-pressure pump is stabilized. The method for compensating a pumping characteristic of a high-pressure pump according to any one of claims 5 to 7.

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