JP2015117600A - Flow rate measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flow rate measurement device capable of shortening measurement time when measuring a flow rate of a fuel injected from a fuel injection valve, while switching measurement conditions.SOLUTION: A flow rate measurement device 100 includes: a high pressure pump 11; a common rail 12; a measurement unit 20 for measuring an injection amount from an injector 40; and a control unit 30 for controlling the high pressure pump 11 and the injector 40 on the basis of a plurality of measurement conditions including valve opening time TQ different from each other. The control unit 30 calculates an amount of change ΔI of a command value with respect to the high pressure pump 11 for generating flow amount change corresponding to a predicted amount of change ΔQ of an injection amount of the injector 40 at the time of measurement condition switch in a discharge amount of the high pressure pump 11. Also, at the time of measurement condition switch, a command value I' after correction which is corrected by the amount of change ΔI is imparted to the high pressure pump 11.

Description

  The present invention relates to a flow rate measuring device that measures the flow rate of fuel injected from a fuel injection valve.

  2. Description of the Related Art Conventionally, an injection amount measuring device that measures an injection amount of fuel injected from an injector is known (see Patent Document 1). In the injection amount measuring device of Patent Document 1, fuel is injected from an injector into a sealed container filled with fuel, the fuel is discharged from the sealed container by the pressure increased by the injection, and the flow rate of the discharged fuel is determined. measure. This makes it possible to measure the amount of fuel injected into the sealed container.

Japanese Patent No. 2880619

  In the injection amount measuring device, there are cases where a plurality of measurement conditions including the injection pressure of the injector and the valve opening time are set for one injector, and the injection amount of the injector is measured while continuously switching the measurement conditions. Since each measurement condition differs in either the injection pressure of the injector or the valve opening time, the target injection amount is different.

  By the way, there is an injection amount measuring device that employs a common rail fuel injection system. In such an injection amount measuring device, since fuel is supplied from the common rail to the injector, the injection pressure of the injector is equal to the pressure in the common rail. For this reason, it is necessary to control the discharge amount of the supply pump that supplies fuel to the common rail so that the pressure in the common rail is stabilized at the target pressure value. As a control method, PID feedback control using a deviation between a current pressure value detected by a common rail pressure sensor and a target pressure value is conventionally performed.

  In the injection amount measuring apparatus as described above, when continuously switching the measurement conditions, it is necessary to wait for the measurement until the pressure in the common rail is stabilized at the target pressure value after switching the measurement conditions. For example, there are cases where the measurement conditions with different injector injection pressures and different valve opening times are continuously switched, but in this case as well, the pressure in the common rail fluctuates immediately after switching the measurement conditions, so that it is stable. It is necessary to wait until the measurement. However, in the conventional PID feedback control, since the current pressure value in the common rail is detected and the corresponding control is performed, it takes a long time to stabilize the fluctuating pressure. The effect extends to the time efficiency of the measurement.

  The present invention has been created in view of such points, and the object thereof is to shorten the measurement time when measuring the flow rate of the fuel injected from the fuel injection valve while switching the measurement conditions. It is to provide a flow measuring device.

  A flow rate measuring device of the present invention is a flow rate measuring device that measures the flow rate of fuel injected from a fuel injection valve, a fuel pump that adjusts the flow rate of fuel discharged according to a given command value, and a fuel pump A pressure accumulating container for accumulating and holding the fuel discharged from the fuel and supplying the fuel to the fuel injection valve; a flow rate measuring means for measuring the flow rate of the fuel injected from the fuel injection valve; Storage means for storing a plurality of measurement conditions in which injection pressures are equal to each other and valve opening times are different from each other, and fuel for controlling the valve opening time of the fuel injection valve based on the measurement conditions An injection valve control means, a calculation means for calculating a command value for the fuel pump, and a pump control means for controlling the fuel pump are provided.

  The calculation means is a command change amount of a command value for the fuel pump for causing a flow rate change in the fuel discharged from the fuel pump, and a predicted change that is a predicted value of the change amount of the injection amount when the measurement condition is switched. A command change amount for causing a flow rate change equal to the amount is calculated. When the measurement condition is switched, the pump control unit gives the corrected command value corrected by the command change amount corresponding to the switching to the fuel pump.

  In the flow rate measuring device of the present invention, the injection amount of the fuel injection valve is changed by switching the measurement conditions. The predicted change amount of the injection amount is obtained as a predicted value of the change amount of the injection amount when the measurement condition is switched based on a plurality of measurement conditions stored in the storage unit. The command change amount is a change amount of the command value for controlling the fuel pump so that the discharge amount of the fuel pump changes by the same amount as the predicted change amount of the injection amount of the fuel injection valve when the measurement condition is switched. Desired.

  Here, in order to stabilize the pressure in the pressure accumulator vessel, it is necessary that the discharge amount from the pressure accumulator vessel is equal to the supply amount to the pressure accumulator vessel. The discharge amount from the pressure accumulator vessel is equal to the injection amount of the fuel injection valve, and the supply amount to the pressure accumulator vessel is equal to the discharge amount of the fuel pump. The measurement of the flow rate of the fuel injected from the fuel injection valve is based on the premise that the pressure in the pressure accumulating vessel is stable.

  In the flow rate measurement device of the present invention, when the measurement condition is switched, the pump control means gives the corrected command value corrected by the calculated change amount to the fuel pump, so that the fuel injection valve immediately after the change of the measurement condition is performed. The injection amount and the discharge amount of the fuel pump are kept equal as before the switching. For this reason, the pressure fluctuation in the pressure accumulator vessel due to switching of the measurement conditions is reduced.

  Therefore, the waiting time until the pressure in the pressure accumulator is stabilized after switching the measurement conditions is shortened, and the measurement time when measuring the flow rate of the fuel injected from the fuel injection valve while switching the measurement conditions can be shortened. It becomes possible.

1 is a schematic configuration diagram showing a flow rate measuring device according to a first embodiment of the present invention. It is explanatory drawing for demonstrating the flow of the fuel in the flow volume measuring apparatus by 1st Embodiment of this invention. It is this invention with the flowchart which shows the flow of the injection quantity measurement in the flow measuring device by 1st Embodiment of this invention. It is a time chart for demonstrating the injection quantity measurement in the flow measuring device by 1st Embodiment of this invention. It is a figure which shows the common rail pressure at the time of measurement condition switching by the flow measuring device by 1st Embodiment of this invention, and a comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the flow rate measuring device of the present embodiment can be applied to a common rail fuel injection system for a diesel engine, for example.

(First embodiment)
The configuration of the flow rate measuring device according to the present embodiment will be described with reference to FIGS. 1 and 2. The flow rate measuring device 100 can measure the injection amount of fuel injected from the injector 40 to be measured. As shown in FIG. 1, the flow rate measuring device 100 includes a supply unit 10 that supplies fuel to the injector 40, a measurement unit 20 that measures the injection amount of fuel injected from the injector 40, and a control unit 30 that controls them. It is composed of

  First, the injector 40 will be described. The injector 40 is a fuel injection valve that injects supplied fuel from a nozzle hole at the tip, and performs injection by opening and closing the nozzle hole with a built-in valve body. The injector 40 is electrically connected to the control unit 30 and is driven to open and close by a drive pulse TWV from the control unit 30. The valve opening time of the injector 40 is controlled by the length of the drive pulse TWV output from the control unit 30, thereby controlling the injection amount of the injector 40.

  Moreover, the injector 40 of this embodiment injects fuel from a nozzle hole, and leaks fuel from a leak flow path. Here, the injection amount for one injection of the injector 40 is Qinj, and the leak amount for each injection is Qleak (see FIG. 2). At this time, Qinj + Qleak is called OUT flow rate. The leak amount Qleak is extremely small compared to the injection amount Qinj, and the change amount of the OUT flow rate corresponds to the change amount of the injection amount Qinj.

  The supply unit 10 includes a high pressure pump 11 as a fuel pump, a common rail 12 as a pressure accumulating container, and a CR pressure sensor 13, and supplies fuel that has been increased to a predetermined pressure to the injector 40.

  The high pressure pump 11 pumps fuel from a tank (not shown) that accumulates fuel, pressurizes the fuel, and supplies the pressurized fuel to the common rail 12. Specifically, the high-pressure pump 11 measures the fuel supplied to the pressurizing chamber, a plunger that reciprocates through a motor, a rotary shaft that is driven by the motor, a pressurizing chamber that pressurizes the fuel by reciprocating the plunger. It comprises a metering unit, a discharge unit for discharging fuel from the pressurizing chamber, and the like.

  The metering unit of the high-pressure pump 11 is electrically connected to the control unit 30, and the lift amount of the metering valve is controlled by the current applied to the control unit 30. When the amount of lift of the metering valve changes, the flow path area from the metering unit to the pressurizing chamber changes, and the discharge amount of the high-pressure pump 11 changes. As a result, the pressure in the common rail 12 changes. That is, the pressure in the common rail 12 is adjusted by controlling the current applied to the high-pressure pump 11.

  The applied voltage to the high pressure pump 11 is switched. For this reason, below, the average value of the current that flows when a voltage is applied to the high-pressure pump 11 is treated as the command value I to the high-pressure pump 11.

  An encoder (not shown) is provided on the rotary shaft of the high-pressure pump 1. The encoder generates an NE signal composed of one reference pulse signal and several tens of rotation pulse signals every time the rotating shaft makes one rotation, and outputs these signals to the control unit 30. The control unit 30 generates an injection reference signal based on the NE signal. In the present embodiment, the reset timing of the CR pressure sensor 13 and the measurement pressure sensor 22, which will be described below, the opening timing of the discharge electromagnetic valve 23, the injection timing of the injector 40, and the like are set based on the NE signal and the injection reference signal. The

  The high-pressure pump 11 repeatedly discharges fuel at an interval (for example, several ms) shorter than the injection interval (for example, several tens of ms) of the injector 40. Here, the amount of fuel discharged by the high-pressure pump 11 for each injection of the injector 40 (per injection interval) is Qp (see FIG. 2).

  The common rail 12 temporarily stores the fuel pressurized by the high pressure pump 11. The fuel stored in the common rail 12 is discharged from the common rail 12 along with the injection of the injector 40 and supplied to the injector 40. Here, for each injection of the injector 40 (per injection interval), the amount of fuel discharged from the common rail 12 is Qi (see FIG. 2).

  The pressure in the common rail 12 (hereinafter referred to as CR pressure) is equal to the injection pressure of the injector 40. A CR pressure sensor 13 is attached to the common rail 12, and the CR pressure sensor 13 outputs a signal corresponding to the CR pressure to the control unit 30.

  The measuring unit 20 as a measuring means includes a pressure vessel 21, a measurement pressure sensor 22, a discharge electromagnetic valve 23, a regulator 24, a filter 25, a measurement flow meter 26, and a leak flow meter 27, and the injector 40 is a pressure vessel. The injection amount of the fuel injected into 21 is measured.

  The pressure vessel 21 has a liquid-tight predetermined volume, and temporarily stores the fuel injected from the injector 40 installed in the pressure vessel 21. The pressure vessel 21 is filled with fuel before measuring the injection amount of the injector 40.

  The measurement pressure sensor 22 is provided in the pressure vessel 21, detects the pressure in the pressure vessel 21, and outputs a signal corresponding to the pressure to the control unit 30.

  The discharge electromagnetic valve 23 is provided between the pressure vessel 21 and the regulator 24 and is opened and closed by a command signal from the control unit 30. When the discharge electromagnetic valve 23 is controlled to open, the fuel in the pressure vessel 21 is supplied to the regulator 24. When the supplied fuel pressure exceeds the set pressure, the regulator 24 keeps the pressure in the pressure vessel 21 at the set pressure of the regulator 24 by discharging the fuel corresponding to the pressure exceeding the set pressure.

  The filter 25 is installed on the downstream side of the regulator 24 and removes foreign matters and the like in the passing fuel. The measurement flow meter 26 is installed on the downstream side of the filter 25, detects the flow rate of fuel passing through the measurement flow meter 26 body, and outputs a signal corresponding to the detected fuel flow rate to the control unit 30.

  The leak flow meter 27 is provided in the leak flow path of the injector 40. The leak flow meter 27 detects the flow rate of leaked fuel leaking from the injector 40 together with the injection of the injector 40, and outputs a signal corresponding to the detected flow rate of fuel to the control unit 30.

  The control unit 30 is configured by a microcomputer centering on a CPU, ROM, RAM, flash memory, and the like. The control unit 30 is electrically connected to the high-pressure pump 11, the CR pressure sensor 13, the injector 40, the measurement pressure sensor 22, the discharge electromagnetic valve 23, the measurement flow meter 26, and the leak flow meter 27. The control unit 30 corresponds to “storage means”, “fuel injection valve control means”, “calculation means”, and “pump control means” in the claims.

  The control unit 30 can obtain the injection amount Qinj of the injector 40 by converting the fuel flow rate detected by the measurement flow meter 26. Similarly, the leak flow rate Qleak of the injector 40 can be obtained by converting the fuel flow rate detected by the leak flow meter 27. Further, the OUT flow rate of the injector 40 can be obtained based on Qinj and Qleak.

  Further, the control unit 30 can control the high pressure pump 11 so that the CR pressure becomes the set target pressure. For example, PID feedback control can be performed using a deviation between the CR pressure detected by the CR pressure sensor 13 and the set target pressure.

  In addition, when measuring the injection amount of the injector 40, the control unit 30 can control the high-pressure pump 11 and the injector 40 so that measurements based on a plurality of measurement conditions are sequentially performed. The injection amount measurement of the injector 40 will be described later.

  In the present embodiment, the measurement conditions for measuring the injection amount of the injector 40 are the target pressure (CR target pressure) Pc of the common rail 12, the valve opening time (INJ valve opening time) TQ of the injector 40, and the target injection amount. Qtrg is included. The CR target pressure Pc corresponds to the target injection pressure of the injector 40. The valve opening time TQ of the injector 40 corresponds to the pulse width of the drive pulse TWV described above. The target injection amount Qtrg is a standard injection amount for each injection determined based on the CR target pressure Pc and the INJ valve opening time TQ, and is a value within a certain range including an allowable error.

(Advance preparation)
In this embodiment, before the injection amount measurement of the injector 40 is started, the flow rate characteristic of the high-pressure pump 11 as the first flow rate characteristic and the second flow rate characteristic are measured using the injector 40 and the flow rate measuring device 100 to be measured. The flow rate characteristics of the injector 40 are actually measured.

The flow rate characteristic of the high-pressure pump 11 is a relationship between the average value (mA) of the applied current as the command value I to the high-pressure pump 11 and the OUT flow rate (mm ³ / st) of the injector 40. 1). In the formula (1), A is a coefficient, and B is a constant.
I = A × OUT flow rate + B (1)

The flow rate characteristic of the injector 40 is a relationship between the OUT flow rate (mm ³ / st) of the injector 40 and the INJ valve opening time TQ (μs), and is expressed by the following equation (2). In Equation (2), C is a coefficient, and D is a constant.
OUT flow rate = C × TQ + D (2)

In the expressions (1) and (2), the CR pressure is constant.
The control unit 30 calculates the equations (1) and (2) for the CR target pressure Pc included in each measurement condition, and stores the coefficient A and the coefficient C included in each equation.

(Measurement of injection amount of injector 40)
Hereinafter, the injection amount measurement of the injector 40 by the flow measuring device 100 will be described with reference to FIGS. 3 and 4. The process shown in the flowchart of FIG. 3 is started after the injector 40 to be measured is installed in the pressure vessel 21. The time chart of FIG. 4 shows signals before and after switching from the nth measurement condition to the (n + 1) th measurement condition.

  In the following, a case will be described in which measurement is continuously performed based on measurement conditions in which the CR target pressure Pc is equal and the INJ valve opening time TQ and the target injection amount Qtrg are different. Each measurement condition includes information regarding the order of measurement.

  First, in step S1, the control unit 30 reads the condition file including a plurality of measurement conditions, thereby setting the conditions of the supply unit 10, the measurement unit 20, and the injector 40, respectively.

For example, the conditions of the supply unit 10 include the rotation speed of the high-pressure pump 11, the CR target pressure Pc (measurement condition), the PID coefficient for PID feedback control of the high-pressure pump 11, the flow rate characteristic (coefficient A) of the high-pressure pump 11, And the flow characteristic (coefficient C) of the injector 40 is included. In the present embodiment, the rotation speed of the high-pressure pump 11 is set to a rotation speed that generates the injection reference signal every tens of milliseconds, for example.
The conditions of the measurement unit 20 include the reset timing of the measurement pressure sensor 22, the valve opening timing of the discharge electromagnetic valve 23, and the cumulative number N of injections for each measurement condition.
The conditions of the injector 40 include an INJ valve opening time TQ (measurement condition), a target injection amount Qtrg (measurement condition), and an injection timing.

  In S <b> 2, driving of the high-pressure pump 11, injection of the injector 40, and opening / closing of the discharge electromagnetic valve 23 of the measuring unit 20 are started.

  In S3, the control part 30 starts control of the injector 40 and the high pressure pump 11 so that the measurement conditions (INJ valve opening time TQ and CR target pressure Pc) which should be implemented from now on are satisfied.

Specifically, the control unit 30 outputs a drive pulse TWV corresponding to the valve opening time TQ to the injector 40.
When the measurement condition to be performed from now is the first measurement condition among the plurality of measurement conditions, the control unit 30 performs PID feedback calculation on the high-pressure pump 11 until the CR pressure reaches the CR target pressure Pc. Command value I is given. The case where the measurement conditions to be implemented from now on are the second and subsequent measurement conditions among the plurality of measurement conditions (in the case of S3 after the second time) will be described later.

  In S4, the control unit 30 determines whether or not the CR pressure is stable at the CR target pressure Pc. For example, when the CR pressure is within a range of “CR target pressure Pc ± allowable error” for a certain time, it is determined that the pressure is stable. The control unit 30 repeats this determination until it is determined that the CR pressure is stabilized at the CR target pressure Pc. When it is determined that it is stable, the process proceeds to S5.

  In S5, the control part 30 starts taking in the output data of the measurement part 20 as a measured value after generation | occurrence | production of the injection reference signal after transfering to S5, and measures the injection amount Qinj of the injector 40. In S5, the injection amount Qinj is measured for the injection of the injector 40 that is equal to or greater than the set number of injections N for one measurement condition.

  Each operation during measurement of the nth measurement condition will be described with reference to FIG. In FIG. 4, the number of NE signals is reduced from the actual number for the sake of simplicity.

  As shown in FIG. 4, the control unit 30 outputs a reset signal several ms before the injection reference signal, and outputs the INJ drive signal TWV simultaneously with the injection reference signal. The control unit 30 resets the measurement pressure sensor 22 and the CR pressure sensor 13 by the reset signal. The injector 40 injects fuel by the INJ drive signal TWV.

  The CR pressure temporarily decreases due to the fuel injection of the injector 40. The control unit 30 takes in the pressure value of the CR pressure sensor 22 immediately before the injection of the injector. The controller 30 performs PID feedback control on the high-pressure pump 11 so that the CR pressure is stabilized at the CR target pressure Pc even during measurement. In the PID feedback control, when the reset signal is generated, the command value I to the high pressure pump 11 can be updated based on the pressure value of the CR pressure sensor 22 taken immediately before. In this control, the CR pressure is stabilized by keeping the discharge amount Qp of the high-pressure pump 11 equal to the OUT flow rate of the injector 40.

  Further, the pressure in the pressure vessel 21 rises due to the fuel injection of the injector 40. The control unit 30 takes in the pressure value of the measurement pressure sensor 22 when the pressure in the pressure vessel 21 rises. Thereafter, when the discharge electromagnetic valve 23 is opened, the regulator 24 discharges the fuel corresponding to the pressure increased by the injection of the injector 40. The valve opening time of the discharge electromagnetic valve 23 is set to a time that can sufficiently discharge the fuel corresponding to the pressure increased by the injection of the injector 40. The measurement flow meter 26 measures the flow rate of the fuel discharged from the pressure vessel 21 by opening the discharge electromagnetic valve 23. The leak flow meter 27 measures the flow rate of the fuel leaked from the injector 40.

  The control unit 30 calculates the injection amount Qinj and the leak amount Qleak of the injector 40 based on the data for N times input from the measured pressure sensor 22, the measured flow meter 26, and the leak flow meter 27.

  In S6, the control unit 30 compares the measured injection amount Qinj with the target injection amount Qtrg, and determines pass / fail of the injector 40 as the measurement target based on the pass / fail standard.

  In S7, the control unit 30 determines whether there is a measurement condition to be performed next. If there is a measurement condition to be performed next, the process proceeds to S8, and if not, a series of measurement is terminated.

In S8, the correction value ΔI of the command value for the high-pressure pump 11 is calculated based on the current measurement condition and the measurement condition to be executed next.
Hereinafter, a method of calculating the correction value ΔI when the current measurement condition is the nth measurement condition and there is an n + 1th measurement condition to be performed next will be described. The CR target pressure Pc is the same value between the nth measurement condition and the (n + 1) th measurement condition, but the INJ valve opening time TQ and the target injection amount Qtrg are the nth measurement condition and the n + 1th measurement condition. It is assumed that the value is smaller than that.

First, the control unit 30 obtains a predicted change amount ΔQ when the measurement condition is switched from the current nth measurement condition to the next n + 1 measurement condition. The predicted change amount ΔQ is a change amount (mm ³ / st) of the OUT flow rate of the injector 40 that is predicted to change after the measurement conditions are switched, and is obtained based on a plurality of measurement conditions read in S1.

The predicted change amount ΔQ is obtained by the following equation (3) based on the INJ valve opening time TQ and the flow rate characteristic (coefficient C) of the injector 40. In Expression (3), the INJ valve opening time TQ (μs) of the nth measurement condition is represented as TQ (n + 1), and the INJ valve opening time TQ (μs) of the n + 1 measurement condition is represented as TQ (n + 1). Yes.
ΔQ = C × (TQ (n + 1) −TQ (n)) (3)

  According to Expression (3), the amount of change (decrease) in the OUT flow rate of the injector 40 due to switching of the measurement conditions is predicted.

Next, the control unit 30 is a change amount of a command value for the high pressure pump 11 for causing a change in the flow rate of the fuel discharged from the high pressure pump 11, and causes a change in the flow rate that is equal to the calculated predicted change amount ΔQ. The command value change amount (command change amount) is calculated. This command change amount is the correction value ΔI (mA). The correction value ΔI is obtained by the following equation (4) based on the flow rate characteristic (coefficient A) of the high-pressure pump 11.
ΔI = A × ΔQ (4)
By the above calculation, the control unit 30 can obtain the correction value ΔI.

  After S8, the process returns to S3 again, and the control unit 30 switches the measurement condition from the nth measurement condition to the (n + 1) th measurement condition. That is, the control of the injector 40 and the high pressure pump 11 is started so that the (n + 1) th measurement condition is satisfied. Here, the nth measurement condition and the (n + 1) th measurement condition have the same CR target pressure Pc and different INJ valve opening time TQ. Therefore, the control unit 30 outputs the INJ drive signal TWV having a different pulse width in order to switch the INJ valve opening time TQ.

Further, the control unit 30 provides the corrected command value I ′ corrected by the correction value ΔI to the high-pressure pump 11 simultaneously with the switching of the INJ valve opening time TQ (see FIG. 4). The corrected command value I ′ (mA) is obtained by adding the correction value ΔI to the current command value I and is obtained by the following equation (5).
I ′ = I + ΔI (5)

  Thereafter, the control unit 30 performs PID feedback control of the high-pressure pump 11 until the (n + 1) th measurement condition is satisfied. That is, the control unit 30 uses the corrected command value I ′ for the first command value as the command value for the high-pressure pump 11 after the switching of the measurement conditions, and the command value for the second and subsequent commands is the command value by PID feedback control. Is used.

  The steps after S4 are the same as those described above. That is, after determining that the CR pressure is stabilized at the CR target pressure Pc in S4, the control unit 30 performs measurement under the (n + 1) th measurement condition in S5.

(effect)
Here, advantages of the present embodiment will be clarified using a comparative example. Although the injection amount measuring device of the comparative example has the same physical configuration as the flow rate measuring device 100 of the present embodiment, control over the high-pressure pump 11 when the measurement conditions in the injection amount measurement of the injector 40 described above are switched. It is different from this embodiment. In FIG. 5, the CR pressure change before and after the switching of the measurement condition in the comparative example is indicated by a broken line, and the CR pressure change before and after the change of the measurement condition in the present embodiment is indicated by a solid line.

  In order to stabilize the CR pressure, it is necessary that the discharge amount Qi from the common rail 12 and the supply amount to the common rail 12 be equal. The discharge amount Qi from the common rail 12 is equal to the OUT flow rate of the injector 40, and the supply amount to the common rail 12 is equal to the discharge amount Qp of the high-pressure pump 11. During the measurement of the injection amount of the injector 40, the pressure of the common rail 12 is stabilized by keeping the discharge amount Qp of the high-pressure pump 11 equal to the OUT flow rate of the injector 40.

  The injection amount measuring device of the comparative example performs only PID feedback control without giving the corrected command value I ′ to the high-pressure pump 11 when the measurement conditions are switched. As described above, the PID feedback control is control using a deviation between the current pressure value detected by the CR pressure sensor 13 and the CR target pressure Pc, and the pressure value of the CR pressure sensor 22 is determined by the injection of the injector 40. Captured immediately before. For this reason, the command value I immediately after the measurement condition switching corresponds to the pressure value detected immediately before the injection of the injector 40 whose injection time TQ has been switched. After the measurement conditions are switched, the CR pressure changes, and after the change is detected, the command value I is updated corresponding to the change.

  Therefore, in the comparative example, immediately after the measurement conditions are switched, the OUT flow rate of the injector 40 changes, while the discharge amount Qp of the high-pressure pump 11 remains unchanged. For this reason, immediately after the measurement conditions are switched, the OUT flow rate of the injector 40 and the discharge amount Qp of the high-pressure pump 11 are different. Therefore, in the comparative example, as shown in FIG. 5, the CR pressure fluctuates greatly immediately after the measurement conditions are switched. In addition, it takes time to stabilize the greatly fluctuating pressure again.

  On the other hand, in this embodiment, the corrected command value I ′ is given to the high-pressure pump 11 simultaneously with the switching of the measurement conditions. The corrected command value I ′ is a command value corrected by a correction value ΔI obtained based on a plurality of measurement conditions obtained before the start of measurement, and a predicted change in the OUT flow rate of the injector 40 when the measurement conditions are switched. The discharge amount Qp of the high-pressure pump 11 is changed by the same amount as the amount ΔQ. Therefore, the discharge amount Qp of the high-pressure pump 11 given the corrected command value I ′ changes in the same manner as the OUT flow rate of the injector 40 whose measurement conditions have been switched.

  Therefore, in the present embodiment, the OUT flow rate of the injector 40 and the discharge amount Qp of the high-pressure pump 11 are kept equal even immediately after the measurement conditions are switched. Therefore, in this embodiment, as shown in FIG. 5, the fluctuation of the CR pressure immediately after switching of the measurement conditions is reduced. For this reason, the CR pressure after switching the measurement conditions can be quickly stabilized, and the overall measurement time when continuously switching the measurement conditions can be shortened.

  In the present embodiment, since the coefficients A and C for obtaining the correction value ΔI are obtained by actual measurement using the injector 40 to be measured, the discharge amount Qp of the high-pressure pump 11 is set to a more actual value of the injector 40. It is possible to change the flow rate equally with the change of the OUT flow rate.

  Further, in this embodiment, after giving a corrected command value I ′ to the high-pressure pump 11, a command value by PID feedback control is given. By using such a combination of command values, the CR pressure after switching measurement conditions can be stabilized efficiently.

(Second Embodiment)
The injection amount measuring device according to the second embodiment has the same physical configuration as the flow rate measuring device 100 of the first embodiment, but differs in the way of obtaining the correction value ΔI in S8 described above. Specifically, in the second embodiment, the correction value ΔI is calculated using the target injection amount Qtrg and the performance curve of the high-pressure pump 11. The performance curve of the high-pressure pump 11 is expressed, for example, as a graph when the horizontal axis is the pump discharge amount (mm ³ / st) and the vertical axis is the command value (mA) to the high-pressure pump 11. is there.

A method for calculating the correction value ΔI in the second embodiment will be described below.
First, the control unit 30 obtains a predicted change amount ΔQ (mm ³ / st) when the condition is switched from the nth measurement condition to the (n + 1) th measurement condition. The predicted change amount ΔQ is obtained by the following expression based on the target injection amount Qtrg (n) under the nth measurement condition and the target injection amount Qtrg (n + 1) under the n + 1th measurement condition.
ΔQ = Qtrg (n + 1) −Qtrg (n) (6)

Next, based on the performance curve of the high-pressure pump 11, the control unit 30 changes the command value I (mA) for causing a pump flow rate change (mm ³ / st) equal to the predicted change amount ΔQ. Is calculated as a correction value ΔI.
Thus, the correction value ΔI is obtained.

  In the second embodiment, since a performance curve that is a representative characteristic of the high-pressure pump 11 is used, there is an advantage that the preliminary preparation performed in the first embodiment is not required. Also in the second embodiment, as in the first embodiment, the CR pressure after switching the measurement conditions can be quickly stabilized, and the overall measurement time for a plurality of measurement conditions can be shortened.

(Other embodiments)
(A) In another embodiment, the timing for giving the corrected command value I ′ to the high-pressure pump 11 may not be the same as the switching of the INJ valve opening time TQ. In other words, “when the measurement condition is switched” described in the claims is a timing including the time at which the INJ valve opening time TQ is switched simultaneously and thereafter. For example, the control of the injector 40 and the high-pressure pump 11 is started so that the measurement condition after switching is satisfied by switching the measurement condition, but the corrected command value I is used as the first command value for the high-pressure pump 11 of the control. 'May be used. As a result, the method is more effective than the conventional method of performing only PID feedback control.

(A) In other embodiments, the plurality of measurement conditions may include measurement conditions with different CR target pressures Pc in addition to measurement conditions with equal CR target pressures Pc. In this case, the corrected command value I ′ may be given in switching between measurement conditions with the same CR target pressure Pc.

(C) Although the OUT flow rate including Qinj and Qleak is used for the calculation of the correction value ΔI in the first embodiment, the present invention is not limited to this. For example, in other embodiments, only Qinj that does not include Qleak may be used as the OUT flow rate. Thereby, the injection quantity of the injector which is not provided with a leak flow path can also be measured.

(D) In the above-described embodiments, the case where the high-pressure pump 11 whose current is controlled by the metering unit is described. However, the present invention is not limited to this, and the metering unit is controlled by other methods. A high-pressure pump may be used. Also in this case, the command change amount and the corrected command value in the present invention can be obtained according to the control method of the metering unit.

(E) In each of the above-described embodiments, the case where the flow rate measuring device 100 measures the injection amount of the injector 40 has been described. However, the present invention is not limited to this, and can be applied to various other flow rate measurements. is there.

  As mentioned above, this invention is not limited to such embodiment, In the range which does not deviate from the meaning of invention, it can implement with a various form.

10 ... Supply part 11 ... High pressure pump (fuel pump)
12 ... Common rail (accumulation vessel)
20 ... Measuring unit (measuring means)
30 ... Control unit (storage means, injection valve control means, calculation means, pump control means)
40 ... Injector (fuel injection valve)
100: Injection amount measuring device

Claims (4)

A flow rate measuring device (100) for measuring a flow rate of fuel injected from a fuel injection valve (40),
A fuel pump (11) in which the flow rate of fuel to be discharged is adjusted in accordance with a given command value (I);
An accumulator (12) for accumulating and holding the fuel discharged from the fuel pump and supplying the fuel to the fuel injection valve;
Measuring means (20) for measuring the flow rate of the fuel injected from the fuel injection valve;
Storage means (30) for storing a plurality of measurement conditions including an injection pressure and a valve opening time of the fuel injection valve, wherein the injection pressure is equal to each other and the valve opening time is different from each other;
Fuel injection valve control means (30) for controlling the valve opening time of the fuel injection valve based on the measurement condition;
A command change amount of a command value for the fuel pump for causing a change in flow rate in the fuel discharged from the fuel pump, and a predicted change amount that is a predicted value of the change amount of the injection amount when the measurement condition is switched Calculation means (30) for calculating a command change amount (ΔI) for causing a flow rate change equal to (ΔQ);
A pump control means (30) for providing the fuel pump with a corrected command value (I ′) corrected by the command change amount corresponding to the switching when the measurement condition is switched;
A flow rate measuring device comprising: The storage means has a first flow rate characteristic indicating a relationship between a command value for the fuel pump and an injection amount of the fuel injection valve, and a second flow rate indicating a relationship between a valve opening time of the fuel injection valve and an injection amount. I remember the characteristics further,
The flow rate measuring apparatus according to claim 1, wherein the calculation unit calculates the command change amount based on the first flow rate characteristic and the second flow rate characteristic. The measurement condition includes a target injection amount corresponding to a combination of an injection pressure and a valve opening time of the fuel injection valve,
The storage means further stores a fuel pump performance curve indicating a relationship between a command value for the fuel pump and a discharge amount of the fuel pump,
The injection amount measuring apparatus according to claim 1, wherein the calculating means calculates the command change amount based on the target injection amount and the fuel pump performance curve.   The pump control means provides the corrected command value as the first command value for the fuel pump and the command value by PID feedback control as the second and subsequent command values when the measurement condition is switched. The flow rate measuring device according to any one of claims 1 to 3.

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