JPH0523607B2 - - Google Patents

Description

[Detailed Description of the Invention] Purpose of the Invention [Field of Industrial Application] The present invention relates to a fuel injection amount measuring device, and more specifically, a fuel injection amount measuring device that can measure the fuel injection amount under conditions consistent with actual fuel injection. Regarding.

[Prior Art] When fuel is supplied by fuel injection, for example in a diesel engine or a gasoline engine equipped with an electronically controlled fuel injection device, it is necessary to precisely control the amount of fuel injected. , a fuel injection amount measurement device that accurately measures the fuel injection amount is required for development, design, inspection, etc. Therefore, various fuel injection amount measuring devices have been known in the past, and for example, the following three types have been used.

(1) Connect a cylinder with a piston biased in the fully closed direction by a spring to the injection side of the fuel injection valve, detect the amount of displacement d of the piston due to the amount of injected fuel, and calculate the difference between this amount of displacement d and that of the cylinder. The fuel injection amount is measured from the product (S×d) with the cross-sectional area S. Hereinafter, this will be referred to as a piston type fuel injection amount measuring device.

(2) Fuel is injected into a sealed container (volume V ₀ ) filled with fuel at a pressure equivalent to the pressure in the combustion chamber where fuel injection is actually performed (this is called back pressure), and the inside of the container is From the change in pressure P, the volume Vb of the injected fuel is determined by dVb/dt = (V ₀ /E) x (dP/dt) (E is the bulk modulus of fuel [Kg/dt).
cm ² ]). This is called a pressure-type fuel injection amount measuring device.

(3) The amount of fuel injected within a certain period of time is integrated and detected, and this is divided by the number of injections to determine the amount of fuel per fuel injection. This is called an accumulation type fuel injection amount measuring device.

[Problems to be Solved by the Invention] However, these various fuel injection amount measuring devices have the following problems, which can be said to have advantages and disadvantages, and further improvements have been desired.

(1-a) Like a piston type fuel injection amount measuring device,
In the case where the amount of displacement d is determined and the amount of injected fuel is determined from the cross-sectional area S of the cylinder, the cross-sectional area must be made small in order to improve the measurement resolution. However, if the amount of fuel is small, for example 0.1 mm ³
If you try to accurately determine the amount of fuel at a certain level, it becomes extremely difficult to increase the maximum measured fuel amount. Therefore, the range of fuel amount that can be injected by the fuel injection device (for example, 0 to 100 mm ³ /stroke)
Over the years, there has been a problem that it has not been possible to measure this accurately.

(1-b) Furthermore, when a piston is used, the inertia of the piston causes an overshoot in the measurement, and the fuel injection amount cannot be accurately measured until this becomes stable. Therefore, there was a problem in that the measurement responsiveness was low and the method could not be used to measure the fuel injection amount in situations where the internal combustion engine was operated at high speeds.

(1-c) Since the piston is biased by a spring,
It has been extremely difficult to keep the pressure (back pressure) in the cylinder where fuel injection is performed constant or to freely set it as one of the fuel injection conditions. Therefore, there was a problem in that it was not possible to conduct experiments and measurements in accordance with actual fuel injection conditions.

(1-d) Furthermore, when a piston is used, there is a problem that the piston has sliding resistance, making it difficult to accurately measure the amount of fuel injected. When attempting to reduce sliding resistance, sealing performance is generally sacrificed, which increases the amount of fuel leakage and becomes a factor that deteriorates the measurement accuracy of the fuel injection amount.

(2) On the other hand, the pressure-type fuel injection amount measuring device determines the amount of injected fuel from pressure changes within the container, so there is a problem that measurement accuracy deteriorates when air bubbles are mixed in. This is because pressure waves generated by fuel injection are reflected by air bubbles within the container, and these reflected waves appear as measurement errors.

(3) Furthermore, since the accumulated fuel injection amount measuring device calculates the amount of fuel injection per injection from the amount of fuel accumulated within a certain period of time, it is difficult to measure the dynamic characteristics of the fuel injection system, such as the internal combustion engine. There was a problem in that it was not possible to measure fluctuations in the amount of injected fuel, etc., which greatly affected vibrations (such as roughness). In addition, with this method, in order to improve measurement accuracy, it is necessary to increase the number of times the injected fuel is accumulated (the number of strokes). In this case, there was a problem in that it took a long time to measure and even adjust the amount of injected fuel. As a result, this has also been a factor in reducing the productivity of the fuel injection device.

As explained above, conventional fuel injection amount measuring devices have not been able to satisfy all three requirements: high measurement accuracy, wide measurement range, and high measurement responsiveness. These problems are the same in various other fuel injection amount measuring devices. As a result, it was considered that the performance of the fuel injection system could not be quantitatively understood during inspection, measurement, and adjustment. SUMMARY OF THE INVENTION The present invention has been made with the object of solving the above-mentioned problems and providing a fuel injection amount measuring device that can suitably measure the amount of fuel injection.

Structure of the Invention [Means for Solving the Problems] In order to achieve the above object, the present invention has the following structure as a means for solving the problems. That is, a part of the wall surface of the fuel injection chamber connected to the injection side of the fuel injection valve is constituted by a diaphragm, and a back pressure chamber maintained at a predetermined pressure that urges the diaphragm toward the fuel injection chamber side is provided. , further comprising: a fuel volume detecting section provided with a displacement amount detecting means for detecting a displacement amount of the diaphragm; when fuel injection into the fuel injection chamber is performed;
a fuel injection amount calculation means that calculates a fuel injection amount based on the detected displacement amount of the diaphragm; a discharge valve connected to the fuel injection chamber; and a discharge valve that discharges fuel from the fuel injection chamber by opening the discharge valve. a fuel discharge section having a discharge chamber that closes the discharge valve when injecting fuel into the fuel injection chamber, and opens the discharge valve according to the calculated fuel injection amount after the fuel injection ends; and fuel discharge control means for discharging the injected amount of fuel from the fuel injection chamber to the discharge chamber, and further controlling the pressure of the discharge chamber to a constant pressure lower than the pressurized pressure of the back pressure chamber. This is the configuration of a fuel injection amount measuring device including: differential pressure holding means for holding pressure;

Here, the fuel volume detection section converts the amount of injected fuel into a displacement amount of a diaphragm and detects the amount, and includes a fuel injection chamber, a back pressure chamber, and a diaphragm that separates the two chambers. The volume of the fuel injection chamber, the diameter of the diaphragm, etc. may be determined according to the upper limit of the measurement of the amount of fuel to be injected.

The displacement amount detection means detects the amount of displacement of the diaphragm, and directly detects the amount of displacement of the diaphragm (usually the amount of displacement at the center position) using various sensors,
For example, it may be configured to detect using a mechanical sensor such as a differential transformer or a potentiometer, or an optical sensor, or a diaphragm formed of a metal thin film may be used to detect changes in capacitance between electrodes. It may also be configured to detect electrically or magnetically based on changes in mutual inductance between the sensor and the coil. The latter method has the advantage that it is a non-contact type, and that the displacement of the entire diaphragm is reflected, making it possible to increase measurement accuracy.

The discharge valve may have any configuration as long as it discharges the fuel in the fuel injection chamber into the discharge chamber. For example, the discharge valve may be connected to the discharge chamber and discharge the fuel into the discharge chamber, or A delivery pipe connected to the fuel injection chamber may be provided in the discharge chamber, and two or more discharge valves may be attached to this delivery pipe. Further, the opening areas of these two or more discharge valves may be all the same, or may be all different.

The differential pressure maintaining means may be any means as long as it maintains a constant pressure difference between the back pressure chamber and the discharge chamber. It may be connected by piping via a valve, or it may be configured such that the pressures in the back pressure chamber and the discharge chamber are detected respectively and a solenoid valve or the like is controlled to maintain a constant pressure difference between the two chambers.

The fuel injection amount calculating means is a means for calculating the amount of injected fuel from the amount of displacement of the diaphragm, and the amount of displacement of the diaphragm with respect to a change in the volume of fuel injected into the fuel injection chamber is determined in advance experimentally or theoretically. , it can be configured to perform calculations with reference to this. If there is a linear (first-order) relationship or other relatively clear relationship, such as a quadratic relationship, between the displacement amount of the diaphragm and the amount of injected fuel, the fuel injection amount calculation means can be realized by a discrete circuit configuration. You can also. On the other hand, if the relationship between the two is complicated, the fuel injection amount calculation means may be constructed as a logical calculation circuit, and the fuel injection amount may be determined using a map or the like.

The fuel discharge control means is a means for discharging the fuel injected into the fuel injection chamber, and closes the discharge valve at the time of fuel injection, but after the end of fuel injection, the fuel injection amount calculation means This control means opens a discharge valve provided in a fuel injection chamber in accordance with the fuel injection amount. Therefore, like the fuel injection amount calculation means, it can be constructed as a discrete circuit or a logical operation circuit, and there is no problem in constructing both of them in one piece.

[Function] The fuel injection amount measuring device of the present invention having the above-mentioned configuration measures the amount of fuel injected into the fuel injection chamber of the fuel volume detection section based on the displacement of a diaphragm provided to separate the fuel injection chamber and the back pressure chamber. Detect by tilting. The back pressure chamber of the fuel volume detection section is pressurized to a predetermined pressure, and urges the diaphragm toward the fuel injection chamber. Furthermore, the pressure in the back pressure chamber and the pressure in the discharge chamber where fuel is discharged are maintained at a constant differential pressure by differential pressure maintaining means.

Therefore, in the fuel injection amount measuring device of the present invention, the displacement amount of the diaphragm according to the fuel injection amount is detected by the displacement amount detection means, and the fuel injection amount is calculated based on the displacement amount by the fuel injection amount calculation means. At the same time, the fuel discharge control means controls the opening of the discharge valve in accordance with the calculated fuel injection amount after the end of fuel injection.

In other words, a constant differential pressure is maintained between the pressure in the back pressure chamber and the pressure in the discharge chamber. Furthermore, the pressure in the back pressure chamber and the pressure in the fuel injection chamber match. From this, the pressure in the fuel injection chamber and the pressure in the discharge chamber are also maintained at a constant differential pressure. Under the condition of this constant pressure difference, the injected amount of fuel is discharged from the fuel injection chamber to the discharge chamber by opening the discharge valve after fuel injection is completed. The pressure in the fuel injection chamber and the pressure in the discharge chamber are factors that affect the discharge amount, but the differential pressure between the two chambers is constant. As a result, the influence of the pressure in both chambers on the discharge amount remains unchanged throughout each fuel discharge during measurement.

Therefore, the amount of fuel injected into the fuel injection chamber is accurately discharged into the discharge chamber each time after the end of fuel injection without fluctuation due to pressure changes. As a result, the volume of the fuel injection chamber is restored to the same volume each time before fuel injection, the diaphragm returns to its normal position, and variations in the position of the diaphragm are eliminated.

Since the diaphragm returns to its normal position each time before fuel injection, the influence of factors that cause errors, such as the hysteresis characteristics of active means such as the diaphragm and diaphragm displacement detection means, is eliminated, resulting in highly accurate measurements. .

In addition, since the fuel injection amount is measured from the amount of displacement of the diaphragm in the fuel volume detection section as described above, there are problems caused by using a conventional piston, problems in measuring based on pressure changes, and problems with constant pressure change. The problem of determining an average value from the amount of fuel accumulated over time is eliminated.

[Examples] In order to further clarify the configuration of the present invention described above, preferred embodiments of the present invention will be described next. FIG. 1 is a schematic diagram of a fuel injection amount measuring device as an embodiment of the present invention.

As shown in the figure, the fuel injection amount measurement device of the present embodiment includes a fuel volume detection section 1, a fuel discharge section 3 from which injected fuel is discharged, a measurement control section 5 that performs measurement control of the fuel injection amount, and a fuel injection amount measurement device. It is mainly composed of a valve drive unit 14 that opens and closes the discharge valves 7, 8, 9, and 10 of the discharge section 3 and the drain discharge valve 12. Here, the measurement control section 5 serves as a fuel injection amount calculation means and also as a valve drive unit 1.
4, it also acts as a fuel emission control means. The fuel injection pump VE used for measuring the fuel injection amount in the example is a distribution type pump for a 4-cylinder diesel engine, and is installed in a measuring punch, replacing the diesel engine as a driving source in actual use. A motor 15 is coupled to the drive shaft 17. The drive shaft 17 has 3
Different types of rotors 18a, 19a, 20a are fixed, and electromagnetic pickup coils 18b,
Along with 19b and 20b, each rotation speed sensor 18,
A cylinder discrimination sensor 19 and a TDC detection sensor 20 are formed.

The distribution type fuel injection pump VE sucks up fuel from the fuel tank 22 using an internal feed pump (not shown) and sends it into a well-known pressurizing pump chamber. Fuel pressurized by a plunger (not shown) is fed under pressure to a fuel injection valve 24 through one of the delivery valves 23 provided for four cylinders. In FIG. 1, only one system of delivery valve 23 and fuel injection valve 24 is shown. Incidentally, the overflowed fuel is transferred to the fuel tank 2 through the overflow pipe 26.
Returned to 2.

The injection side of the fuel injection valve 24 is connected to a fuel injection side port 30 of the fuel volume detection section 1 . The fuel volume detection unit 1 has a configuration in which a fuel injection chamber 36 and a back pressure chamber 37 are arranged approximately symmetrically around a diaphragm chamber 33 having a diaphragm 31 via propagation passages 34 and 35.

The fuel injection chamber 36 has a discharge port 38 on the opposite side of the fuel injection side port 30, and a part of the side wall forms a partition wall 39 made of a stainless steel thin film. On the other hand, the back pressure chamber 37 also includes two ports 40 and 41, and a portion of its side wall forms a similar partition wall 43. These partition walls 39 and 43 are connected to the fuel injection chamber 36 and the back pressure chamber 3.
7 from the propagation passages 34 and 35, respectively. The propagation passages 34 and 35 and the diaphragm chamber 33 are filled with a liquid having high insulation properties and a predetermined dielectric constant, silicone oil in this case, and is pumped into the fuel injection chamber 36 from the fuel injection valve 24. The displacement of the partition wall 39 due to the fuel, that is, the change in the volume of the fuel injection chamber 36 is transmitted to the diaphragm 31 via the silicone oil in the propagation passage 34, causing the diaphragm 31 to be displaced. The displacement of the diaphragm 31 is transmitted to the other partition wall 43 via the silicone oil in the propagation passage 35, displacing the partition wall 43 and changing the volume of the back pressure chamber 37. Here, a port 40 provided in the back pressure chamber 37 communicates with a constant pressure pipe 45, and the back pressure chamber 37 is filled with constant pressure nitrogen gas (N ₂ ). Therefore, even if the partition wall 43 is pushed due to the displacement of the diaphragm 31, the pressure in the back pressure chamber 37 remains constant during measurement due to the low bulk modulus of the gas (N ₂ ) and the sufficient dead volume of the back pressure chamber 37. The increase is negligible (about 1/100 of the back pressure). The pressure of nitrogen gas can be set arbitrarily between 10 and 60 kg/cm ² as one of the conditions for measuring the fuel injection amount, but in consideration of the case where excessive pressure is applied by mistake, the pressure in the back pressure chamber 37 is Another port 41 is equipped with a safety valve 47 with an operating pressure of 100 kg/cm ² .

As is clear from the enlarged view shown in FIG. 2, the diaphragm chamber 33 has a diaphragm 31 made of a thin metal film on the order of 100 μm thick in the center, and two independent walls on the inner walls on both sides facing the diaphragm 31. The two electrodes 51 and 52 are connected to the diaphragm 31.
It is formed concentrically by vapor deposition. Since the silicone oil filling the diaphragm chamber 33 has high insulation and a constant dielectric constant, a capacitance exists between the metal thin film diaphragm 31 and each electrode 51, 52 depending on the distance between them. A transmission section 55 connected to the diaphragm 31 and the electrodes 51 and 52 detects this capacitance. The method for detecting the capacitance will be described later.

The fuel that is sent into the fuel injection chamber 36 by fuel injection and presses the partition wall 39 to change the volume of the fuel injection chamber 36 is discharged from the discharge port 38 via the discharge pipe 56 after the measurement of the amount of fuel, which will be described later, is completed. The internal pressure is discharged to a discharge container 57 whose internal pressure is maintained at a constant pressure difference with the back pressure chamber 37. This constant pressure difference is applied to a connecting pipe 58 that connects the constant pressure pipe 45 and the discharge container 57.
This is realized by a constant differential pressure reducing valve 59 which is provided in the middle and acts as differential pressure holding means. The fuel injection chamber 36 is connected to the delivery pipe 6 in the container via the discharge pipe 56.
Since the delivery pipe 60 is provided with four discharge valves 7, 8, 9, and 10, by opening these discharge valves 7, 8, 9, and 10, the fuel can be discharged. Discharge takes place. The discharge valves 7, 8, 9, and 10 have different opening areas. The discharged fuel is stored at the bottom of the discharge container 57, but when the stored amount exceeds a predetermined amount, the overflow switch 62 operates and detects this, and the valve drive unit 14 opens the drain valve 12. The fuel is then discharged to the reservoir tank 64 via the drain passage 63. In addition, the discharge container 57
A pressure gauge 65 and a safety valve 66 are provided to detect the pressure inside the container, and a manual valve 68 is provided in the drain passage 63.

The fuel pumped by the fuel injection pump VE is
As explained above, the fuel is sent into the fuel injection chamber 36 of the fuel volume detection section 1, the volume of the fuel injection chamber 36 is changed once, and then the discharge valves 7, 8, 9, 10 of the fuel discharge section are opened. Accordingly, the discharge container 5
7, the detection of the volume change of the fuel injection chamber 36, which is performed in synchronization with the operation of the fuel injection pump VE, and the above-mentioned valve opening control of the discharge valves 7, 8, 9, 10, etc. are performed by measurement control. This is performed by the unit 5 and the drive unit 14 driven by the unit.

The measurement control unit 5 includes the rotation speed sensor 18 described above,
Signals from the cylinder discrimination sensor 19, TDC sensor 20, and transmission section 55 are input to the drive unit 14.
The discharge valves 7, 8, 9, and 10 are controlled to open at predetermined timing via the fuel injection pump VE.
The fuel injection amount is measured almost in real time, and the measurement results are displayed on a CRT display 70. Furthermore, the measurement control unit 5 further outputs the measurement results and the like to another control device, such as a host computer. Next, the internal configuration of the measurement control section 5 and the valve drive unit 14 will be explained with reference to FIG. 3, together with the circuit configuration of the transmission section 55.

The transmission section 55 includes an oscillator Os and two operational amplifiers OP.
1, OP2, divider Dv, compensation amplifier Ag, V/I
It consists of a converter Cv and three precision resistors R1, R2, R3 with the same resistance value. The ground side terminal of the oscillator Os is connected to the diaphragm 31 of the diaphragm chamber 33, and the other end is connected to two other precision resistors R via a precision resistor R1.
2, connected to R3 and operational amplifier OP1.
The other ends of precision resistors R2 and R3 are connected to diaphragm 3.
1 and are connected to electrodes 51 and 52 facing each other. As mentioned above, the diaphragm 31 and the electrode 5
Since there is a capacitance between capacitors 1 and 52 according to the distance d between them, these are shown as variable capacitance capacitors C1 and C2 in FIG.

Further, one input terminal of the operational amplifier OP2 is connected to the precision resistor R2 and the electrode 51, and the other is connected to the precision resistor R3 and the electrode 52. As a result, the output voltages of the operational amplifiers OP1, OP2 are determined based on the currents I1, I2 flowing from the oscillator Os into the circuit formed by the precision resistors R1, R2, R3 and the variable capacitance capacitors C1, C2. That is, the output voltage V1 of the operational amplifier OP1 is expressed as V1=K1×(I1+I2) with K1 as a proportional coefficient, while the output voltage V2 of the operational amplifier OP2 is expressed as K2.
Assuming that is a constant of proportionality, V2=K2×(I1−I2). Therefore, the outputs of both operational amplifiers OP1 and OP2 are input to the divider Dv to perform division V2/V1, and the output is compensated by the compensation amplifier Ag (I1
−I2)/(I1+I2) can be _obtained . Since the currents I1 and I2 correspond to the capacitances C1 and C2 formed between the diaphragm 31 and the electrodes 51 and 52, respectively, the output voltage _V0 is proportional to (C1-C2)/(C1+C2). That means you are doing it. This output voltage V ₀ is the V/I converter Cv
The V/I converter Cv converts the output voltage _V0 into a 4-20mA current signal in order to improve noise resistance in transmission. It is.

The measurement control unit 5 includes a well-known CPU 71 and ROM 7.
2. It is configured as a logical operation circuit centered around the RAM 73. The CPU 71 is connected to the ROM by the bus 75.
72, RAM 73, and each port for data input/output. The input ports for inputting data include a pulse input port 77;
The analog input port 78 is an external output port 80 as an output port for outputting data.
The discharge valve control output port 81 also inputs and outputs the CRT display 70.
There are also a keyboard panel 83 and a terminal input/output port 84 for transferring data. CPU71
executes data calculations, data input/output via each port, etc. according to a program stored in the ROM 72 in advance. The pulse input port 77 is connected to the rotation speed sensor 18, cylinder discrimination sensor 19, and TDC sensor 20, respectively.
Cylinder discrimination signal D indicating the rotational speed N of the fuel injection pump VE and which cylinder is at the fuel injection timing
Alternatively, it is possible to read the timing TDC, etc. at which the piston of the cylinder in which fuel injection is performed reaches top dead center. On the other hand, the analog input port 78 is
It is connected to an I/V converter 85 that converts a 4-20mA current signal sent from the transmission section 55 into a voltage signal, and the CPU 71 converts a signal (C1-C2)/(C1+C2) according to the displacement of the diaphragm 31. is input through this analog input port 78.

The external output port 80 is connected to a printer (not shown),
It is connected to a monitor TV, warning light, host computer, etc., and outputs a print signal Prnt, video signal Vd, rotational speed signal Sn, fuel injection amount signal Sτ, warning signal Swn, etc. according to the commands of the CPU 71. Served. Further, the discharge valve control output port 81 is connected to the four ports in the valve drive unit 14.
The CPU 71 is connected to three drive circuits 87, 88, 89, and 90, and the CPU 71 is connected to the discharge valve control output port 81.
By outputting a control signal through the controller, the opening of the discharge valves 7, 8, 9, and 10 connected to the drive circuits 87, 88, 89, and 90, respectively, can be controlled.

The valve drive unit 14 has a built-in 2-input NAND gate 92 and a drive circuit 94 for driving the drain valve 12.
One input of the input NAND gate 92 is connected to the overflow switch 62, and the other input is connected to the manually operated switch 96. Therefore, the amount of fuel in the discharge container 3 increases and the overflow switch 62 is activated.
When the drain valve 12 is turned on or the manual operation switch 96 is turned on, the drain valve 12 is opened.

Next, the measurement of the fuel injection amount by the measurement control section 5 will be explained using the flowchart of FIG. 4. The measurement control unit 5 starts processing from step 100 when the power is turned on. First, in step 100, so-called initialization processing such as clearing the internal registers of the CPU 71 is performed, and in the following step 110,
Processing such as setting the zero point reading timing and fuel injection discharge timing for zero point calibration in the measurement of the fuel injection amount is performed as follows.

When the motor 15 is started and measurement starts,
The measurement control circuit 5 opens and closes the discharge valves 7, 8, 9, and 10 at appropriate timings (default values) while transmitting the diaphragm 3 input from the transmission section 55.
The displacement amount of 1 is displayed on the CRT display 70. Changes in the amount of displacement of the diaphragm 31 are shown on the CRT display 7 with the crank angle of 0 to 720° as the horizontal axis.
Based on the amount of displacement of the diaphragm 31 displayed on the CRT display 70, the measurer uses the crank angle just before the start of fuel injection as the zero point reading timing, and then reads the zero point at an appropriate point after the end of fuel injection. Each crank angle is set as the fuel discharge timing using the keyboard panel 83. When the above settings are completed, the process proceeds to step 120 to measure the fuel injection amount.
Proceed to the following.

In step 120, it is determined whether the crank angle has reached the zero point reading timing. The crank angle is based on the timing TDC of the top dead center inputted from the TDC sensor 20 via the pulse input port 77, and the rotational speed signal N inputted from the rotational speed sensor 18 (outputted every 30° CA). It can be detected using

When it is detected that the crank angle has reached the zero point reading timing set in step 110,
The determination at step 120 is ``YES'', and the process proceeds to step 130, where the zero point is read.
This is the diaphragm 31 immediately before fuel injection.
The displacement amount is used as the zero point for measuring the fuel injection amount, and this is done to eliminate measurement errors due to various drifts in the measurement system. Of course, if there are no various drifts in the measurement system, the diaphragm 31 will always completely return to its original state before injection, so the zero point reading process can be omitted.

In the following step 140, the diaphragm 31
The amount of displacement is measured, and this is repeated until the subsequent step 150 determines whether or not the fuel discharge timing has arrived at ``YES''.
That is, changes in the amount of displacement of the diaphragm 31 are successively measured from the end of fuel injection until just before fuel is discharged.

The amount of displacement of the diaphragm 31 is read through the analog input port 78, but the signal input from the transmission section 55 is based on the capacitance C formed between the diaphragm 31 and the electrodes 51 and 52, as described above.
1, C2 is proportional to (C1-C2)/(C1+C2). These capacitances C1 and C2 are determined by the area of the electrodes 51 and 52 being A, the dielectric constant of the silicone oil sealed in the diaphragm chamber 33 being ε, and the average value of the distance between the diaphragm 31 and the electrodes 51 and 52.
do, and the amount of displacement of the diaphragm 31 due to the amount of injected fuel is Δd, then C1=ε×A/(do−Δd)…(1) C2=ε×A/(do+Δd)…(2). Therefore, from equations (1) and (2), we obtain Δd/do=(C1−C2)/(C1+C2) (3). Since the distance d ₀ is a constant, from equation (3), the transmission section 5
It can be seen that the output signal No. 5 corresponds to the displacement amount Δd of the diaphragm 31.

When the determination at step 150 is ``YES'', that is, when it is determined that the crank angle has reached the fuel discharge timing, the process proceeds to step 160, where the fuel injection amount τ is calculated and the fuel injection amount τ is calculated. A process for determining the control amounts of the valves 7, 8, 9, and 10 is performed. In this embodiment, it has been experimentally confirmed in advance that there is a proportional relationship between the displacement amount Δd of the diaphragm 31 and the fuel injection amount τ, as shown in FIG. The fuel injection amount τ can be easily determined as ×Δd (K3 is a coefficient). Furthermore, the control amount of the discharge valves 7, 8, 9, and 10 calculated in step 160 means that among the discharge valves 7, 8, 9, and 10, the opening time of the discharge valve 7 can be varied; Since the opening times of the valves 8, 9, and 10 are fixed, the number of discharge valves that should be opened and the opening of the discharge valve 7 are determined in order to directly discharge the amount of fuel injected into the fuel injection chamber 36. It's time. The calculation of the number of discharge valves and the opening time of the discharge valves 7 will be described later.

In the following step 170, a valve opening control signal for each of the discharge valves 7, 8, 9, and 10 is outputted via the discharge valve control output port 81 in accordance with the control amount determined in step 160. This control signal is sent to the valve drive unit 14, and its drive circuits 87, 88, 89,
90 as a drive signal for the discharge valves 7, 8, 9, and 10 and output to each valve. As a result, the discharge valves 7, 8, 9, and 10 are opened appropriately, and the fuel injection chamber 3
The fuel in 6 is discharged exactly in the injected amount. The purpose of accurately controlling the fuel discharge amount in this way is to accurately measure the fuel injection amount for repeated fuel injections.
In particular, this prevents the occurrence of a phenomenon in which bubbles are generated in the fuel in the fuel injection chamber 36 and degrade measurement accuracy when the discharge valves 7, 8, 9, and 10 are opened for too long. On the other hand, it also prevents the discharge valves 7, 8, 9, and 10 from being opened for insufficient time, thereby preventing excess fuel from being stored in the fuel injection chamber and resulting in poor displacement of the diaphragm.

In step 180 following step 170, it is determined whether or not to end the measurement of the fuel injection amount. If the measurement is not completed, the process returns to step 120 and repeats steps 120 to 180 described above.
However, when the measurement is completed, for example, a key operation to end the measurement is performed from the keyboard panel 83 of the measurement control unit 5, the process exits to "END" to end the measurement and ends this control routine.

Next, the number of discharge valves calculated in step 160 and the opening time of the discharge valves 7 will be explained with reference to the timing chart shown in FIG. The pressure difference between the discharge pipe 56 and the interior of the discharge container 57 is maintained at a constant pressure. This is due to the following reasons.
That is, the constant difference pressure reducing valve 59 connects the back pressure chamber 37 and the discharge container 5.
7 is adjusted to a constant differential pressure. Further, the back pressure chamber 37 and the fuel injection chamber 36 are at the same pressure via the diaphragm 31 and the partition walls 39 and 43. Therefore, there is a constant pressure difference between the fuel injection chamber 36 and the inside of the discharge container 57, and there is also a constant pressure difference between the discharge pipe 56 directly connected to the fuel injection chamber 36 and the inside of the discharge container 57. Therefore, the discharge valve 7,
Since the opening area of each of the valves 8, 9, and 10 is fixed, the discharge amount is uniquely determined only by the opening time of each discharge valve. Here, the discharge valve 7 has a variable opening time to change the discharge amount, and the other discharge valves 8, 9, and 10 have fixed opening times to keep the discharge amount constant.
Therefore, the opening time of the discharge valve 7 and the other discharge valves 8,
By controlling the opening and closing of 9 and 10, an arbitrary discharge amount can be obtained. This discharge amount is calculated as shown below. If the opening time of the discharge valve 7 is T, the opening area is A1, the flow coefficient is α, and the discharge amount is Q1, then ΔT=Q1/(α×A1)...(4) is obtained. Furthermore, since the opening times of the discharge valves 8, 9, and 10 are controlled to be constant, their discharge amounts are constant, and are Q2, Q3, and Q4, respectively. Here, as shown in FIG. 6, the amount of fuel τ1 injected into the fuel injection chamber 36 at one time is small, and the amount is fixed at a constant volume a.
When it is smaller, the discharge valves 7, 8, 9, and 10 are not opened, and fuel is injected into the fuel injection chamber 36 and measurement continues until the integrated fuel injection amount τ becomes larger than the volume a.

After that, when the accumulated fuel injection amount τ becomes larger than the volume a, the time T calculated by equation (4)
Only in case 1, the discharge valve 7 is opened and the fuel amount Q1 is discharged. Further, when the fuel injection amount τ2 per injection is large, for example, when the volume is larger than the volume b and smaller than the volume c, the discharge valves 7 and 8 are opened. The discharge amount at this time is the sum of the discharge amount Q1 by the discharge valve 7 and the constant discharge amount Q2 by the discharge valve 8. The discharge amount Q1 is determined by Q1=τ-Q2, and the opening time of the discharge valve 7 is the time T2 determined by substituting Q1=τ-Q2 into equation (4). Similarly, fuel injection amount τ3
When the volume is larger than the volume c and smaller than the volume d, the discharge valves 7, 8, and 9 are opened. The discharge amount at this time is the sum of Q1, Q2, and Q3, and the discharge amount Q1 is
Q1=τ-(Q2+Q3), and the opening time of the discharge valve 7 is the time T3 obtained by substituting Q1=τ-(Q2+Q3) into equation (4). Further, when the fuel injection amount τ4 is larger than the volume d and smaller than the volume e, the discharge valves 7, 8, 9, and 10 are opened. The discharge amount at this time is the sum of Q1, Q2, Q3, and Q4, and the discharge valve Q1 is determined by Q1 = τ - (Q2 + Q3 + Q4), and the opening time of the discharge valve 7 is determined by substituting it into equation (4). This is the time T4. Here, the volume e is the upper limit that can be discharged at one time, and is also the maximum measurement limit of the fuel injection amount measuring device in this embodiment. As described above, the discharge valve to be opened and the opening time T of the discharge valve 7 are determined according to the fuel injection amount τ, which is the control amount of the discharge valves 7, 8, 9, and 10.

The configuration of the fuel injection amount measuring device as an example and the processing performed by the measurement control unit 5 have been described in detail above.According to this example, fuel is injected into the fuel injection chamber 36, and the fuel injection amount is determined by the diaphragm 31.
Since the amount of displacement is detected as the amount of displacement, it is possible to measure the fuel injection amount with high accuracy (for example, within ±0.1 mm ³ ) over a wide measurement range (for example, 0 to 100 mm ³ /stroke). Moreover, the fuel injection amount is measured immediately after the fuel injection is completed, and immediately after the measurement, the discharge valves 7, 8, 9, and 10 are controlled using the constant pressure difference between the fuel injection chamber 36 and the discharge chamber 57, and the fuel injection amount is The fuel according to the amount is accurately delivered from the fuel injection chamber 36 to the discharge chamber 57
The volume of the fuel injection chamber 36 is restored to the volume before fuel injection. In this way, fuel injection chamber 3
The volume of 6 is restored to the same volume each time before fuel injection,
Since the diaphragm 31 returns to its normal position, highly accurate measurement is possible without the influence of hysteresis characteristics of the diaphragm 31, the measurement control section 5, etc. of the diaphragm 31, for example.

In addition, it is possible to continuously measure the fuel injection amount accurately in this way, and the fuel injection amount of the fuel injection pump VE can be accurately measured even in situations where the diesel engine is being driven at high rotational speeds. can be measured. As a result, it is possible to easily measure variations in fuel injection amount that are related to engine roughness, and it is also possible to easily measure
It has also become possible to complete VE adjustments in an extremely short time.

Furthermore, since the pressure in the back pressure chamber 37 can be easily changed, the fuel injection amount can be measured under various conditions of the pressure in the fuel injection chamber 36, and the fuel injection amount can be measured under conditions closer to those of the actual machine. be able to.

In this embodiment, the injected fuel does not directly press the measuring diaphragm 31, but displaces the diaphragm 31 via the partition wall 39 and the silicone oil in the propagation passage 34. Therefore, the dielectric constant ε of the medium that determines the capacitance formed between the diaphragm 31 and the electrodes 51 and 52 is always kept constant, improving measurement accuracy. Furthermore, even if excessive pressure is accidentally generated inside the fuel injection chamber 36, the partition wall 39 will not deform beyond a certain level, so even in such a case, the measuring diaphragm 31
There have been no cases of damage caused by excessive pressure, and measurement accuracy has not deteriorated. Furthermore, in this embodiment, since the amount of displacement of the diaphragm 31 is sequentially measured, data regarding the fuel injection process can also be obtained, and various characteristics of the fuel injection pump VE can be grasped even more accurately.

In the above embodiment, the measurement control section 5 corresponds to the fuel injection amount calculation means, and the steps in the processing are
120 to 160 correspond to processing as a fuel injection amount calculation means. The measurement control section 5 and the valve drive unit 14 correspond to the fuel discharge control means, and steps 160 and 170 correspond to the processing as the fuel discharge control means. The space inside the discharge container 57 corresponds to the discharge chamber. The transmission section 55 corresponds to displacement amount detection means. Connection piping 58 and constant differential pressure reducing valve 5
9 corresponds to the differential pressure holding means.

Although one embodiment of the present invention has been described above,
The present invention is not limited to this embodiment in any way, and can be used in a wide range of industries such as in-line fuel injection as well as measurement of the fuel injection amount of a fuel injection device in a gasoline engine. Of course, the present invention can be implemented in various other forms without departing from the scope.

Effects of the Invention As detailed above, the fuel injection amount measuring device of the present invention has an extremely excellent effect of being able to satisfy all three requirements of high measurement accuracy, wide measurement range, and high measurement responsiveness. . In particular, as described in the operation section, since the pressure in the discharge chamber is kept a constant pressure lower than that in the fuel injection chamber by the differential pressure holding means, the injected amount of fuel can be accurately discharged into the discharge chamber. This has the effect that the volume of the fuel injection chamber is restored to the same volume each time before fuel injection, the diaphragm returns to its normal position, and highly accurate measurement becomes possible. Therefore, if this is used to inspect, measure, and adjust the fuel injection pump, it will not only be possible to quantitatively and accurately grasp the performance of the fuel injection system, but also contribute to improving the performance of the fuel injection pump. This has the effect of shortening adjustment time and significantly improving productivity.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a fuel injection amount measuring device as an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of a diaphragm chamber 33 in the embodiment, and FIG. 3 is a block diagram showing an electrical system in the embodiment. 4 is a flowchart showing the fuel injection amount measurement control routine performed by the measurement control unit 5, FIG. 5 is a graph showing the relationship between the displacement amount Δd of the diaphragm and the fuel injection amount τ, and FIG. This is a timing chart showing the relationship between the amount τ and the discharge valve. 1...Fuel volume detection section, 3...Fuel discharge section, 5
...Measurement control section, 7, 8, 9, 10...Discharge valve,
12...Drain valve, 14...Valve drive unit, 24...Fuel injection valve, 31...Diaphragm, 33...Diaphragm chamber, 34, 35
...Propagation passage, 36... Fuel injection chamber, 37... Back pressure chamber, 39, 43... Partition wall, 51, 52... Electrode, 55... Transmission section, 57... Discharge container, 58...
...Connection piping, 59... Constant differential pressure reducing valve, 70...
CRT display, 71...CPU, 83...Keyboard panel, Ag...Compensation amplifier, Op1,
Op2... operational amplifier, Os... oscillator, VE...
fuel injection pump.

Claims (1)

[Claims] 1. A part of the wall surface of the fuel injection chamber connected to the injection side of the fuel injection valve is constituted by a diaphragm, and
a fuel volume detection section provided with a back pressure chamber maintained at a predetermined pressure that urges the diaphragm toward the fuel injection chamber, and further provided with displacement amount detection means for detecting the amount of displacement of the diaphragm; When fuel injection was carried out,
a fuel injection amount calculation means that calculates a fuel injection amount based on the detected displacement amount of the diaphragm; a discharge valve connected to the fuel injection chamber; and a discharge valve that discharges fuel from the fuel injection chamber by opening the discharge valve. a fuel discharge section having a discharge chamber that closes the discharge valve when injecting fuel into the fuel injection chamber, and opens the discharge valve according to the calculated fuel injection amount after the fuel injection ends; and fuel discharge control means for discharging the injected amount of fuel from the fuel injection chamber to the discharge chamber, and further controlling the pressure of the discharge chamber to a constant pressure lower than the pressurized pressure of the back pressure chamber. A fuel injection amount measuring device comprising: differential pressure holding means for holding pressure;