JPH0523610B2 - - 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 accurately measure the fuel injection amount under conditions consistent with actual fuel injection. Concerning a measuring device.

[Prior Art] When fuel is supplied by fuel injection, for example in a diesel engine or a gasoline engine using an electronically controlled fuel injection device, the amount of fuel injected must be precisely controlled. , 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 Vo) filled with fuel at a pressure equivalent to the pressure in the combustion chamber, etc. where fuel injection is actually performed (this is called back pressure). From the change in pressure P, the volume Vb of the injected fuel is determined by dVb/dt = (Vo/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. Note that E is a constant representing the bulk modulus.

(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, since the pressure-type fuel injection amount measuring device determines the amount of injected fuel from pressure changes within the container, there is a problem in 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 detection unit provided with a displacement amount detection means for detecting the displacement amount of the diaphragm; and a peak value at an initial stage of fluctuation of the detected displacement amount of the diaphragm when fuel injection is performed into the fuel injection chamber. a peak detection unit that detects the displacement amount of the diaphragm, and a fuel injection amount is calculated from the peak value of the displacement amount detected by the peak detection unit based on the correspondence between the peak value of the displacement amount of the diaphragm and the actual fuel injection amount. a fuel injection amount calculation means that calculates the fuel injection amount; a fuel discharge section having a discharge valve connected to the fuel injection chamber and a discharge chamber that discharges fuel from the fuel injection chamber when the discharge valve opens; and the fuel injection chamber. When injecting fuel into the fuel injection chamber, the discharge valve is closed, and after the fuel injection is completed, an amount of fuel corresponding to the injected amount is transferred from the fuel injection chamber to the discharge chamber by opening the discharge valve. This is the configuration of a fuel injection amount measuring device comprising: a fuel discharge control means for discharging fuel; and a fuel injection amount measuring device.

[Operation] In the present invention configured as described above, fuel is injected into the fuel injection chamber from the fuel injection valve. At this time, since the discharge valve is closed, the fuel injected into the fuel injection chamber presses the diaphragm toward the back pressure chamber. Then, the diaphragm is displaced toward the back pressure chamber depending on the amount of injected fuel, but even if the diaphragm is displaced, the back pressure chamber is maintained at a predetermined pressure, so the pressure in the fuel injection chamber does not change. For this reason,
The displacement amount of the diaphragm is determined only by the fuel injection amount. That is, since other factors, that is, changes in pressure, do not affect the amount of displacement of the diaphragm, the correspondence between the amount of displacement of the diaphragm and the amount of fuel injection is stable, and the amount of displacement does not fluctuate due to pressure changes.

Also, when fuel is injected into the fuel injection chamber,
The volume of the fuel injection chamber increases rapidly within a short period of time. Therefore, the amount of displacement of the diaphragm repeats overshoot and undershoot, which gradually decrease over a certain period of time. The natural frequency of the damped vibration of the diaphragm, or the ratio of the diaphragm displacement amount to the convergence value of the peak value, that is, the correspondence relationship between the peak value and the actual fuel injection amount, is determined by various factors of the measurement system of the fuel volume detection section. It has been theoretically and experimentally confirmed that this is determined by, for example, the shape and structure of the fuel injection chamber, the type of fuel, etc.

Therefore, in the present invention, the peak value at the initial stage of variation of the diaphragm displacement amount is detected by the peak detection section. Then, by the fuel injection amount calculation means,
Based on the correspondence between the peak value of the diaphragm displacement amount and the actual fuel injection amount, the fuel injection amount is calculated from the detected peak value of the displacement amount.

In this way, based on the stable correspondence between the displacement of the diaphragm and the amount of fuel injection, which is achieved by maintaining the back pressure chamber at a predetermined pressure, fuel injection is performed from the peak value at the beginning of the fluctuation of the displacement of the diaphragm. Since the fuel injection amount is calculated, the fuel injection amount can be calculated in a short time and with high accuracy without waiting for the detected diaphragm displacement amount to attenuate due to overshoot, undershoot, etc. As a result, the fuel injection amount can be measured with high accuracy even in the high rotation range where short-time calculations are required.

Further, after measuring the fuel injection amount, the fuel discharge control means promptly discharges fuel in an amount corresponding to the injected fuel amount from the fuel injection chamber to the discharge chamber. That is, since fuel is not discharged regardless of the injection amount, the volume of the fuel injection chamber is restored to the same amount to some extent every time before fuel injection, and the range of variation in the return position of the diaphragm is reduced.

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. In addition, the back pressure chamber is maintained at a predetermined pressure, but this may be achieved by a configuration such as installing a highly responsive regulator, constant differential pressure reducing valve, etc. in the pressure system on the back pressure chamber side. The pressure in the back pressure chamber may be set by , and kept apparently constant by a low bulk modulus of a gas portion having a predetermined volume.

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 peak detection section and the fuel injection amount calculation means may be configured as a discrete circuit including a peak hold circuit or a logic operation circuit.

The fuel discharge control means is a means for discharging the fuel injected into the fuel injection chamber to the discharge chamber, and after determining the fuel injection amount by the fuel injection amount calculation means, controls the amount of fuel corresponding to the injected fuel amount. This is a means for discharging fuel from the fuel injection chamber. 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.

Incidentally, it is needless to say that the fuel discharge does not need to be performed every time fuel injection is performed, and may be performed every predetermined number of fuel injections.

[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 measuring device of the present embodiment includes a fuel volume detection section 1, a discharge container 3 that discharges injected fuel, a measurement control section 5 that performs measurement control of the fuel injection amount, and a discharge container 3. discharge valves 7, 8,
It is mainly composed of a valve drive unit 14 that opens and closes the drain discharge valve 12 and the drain discharge valve 12. Here, the measurement control section 5 functions as a fuel injection amount calculation means and, together with the valve drive unit 14, also functions as a fuel discharge control means. Fuel injection pump VE used for measuring fuel injection amount in the example
is a distribution type pump for a four-cylinder diesel engine, which is installed on a bench for measurement, and has a motor 15 coupled to its drive shaft 17 in place of the diesel engine as a driving source in actual use. Three types of rotors 18a, 19a, 20a are fixed to the drive shaft 17,
Electromagnetic pick-up coils 18b, 19b provided opposite to rotors 18a, 19a, 20a,
Together with 20b, they form a rotation speed sensor 18, a cylinder discrimination sensor 19, and a TDC detection sensor 20, respectively.

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, one of the two ports 40 and 41 provided in the back pressure chamber 37 communicates with the constant pressure chamber 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 is kept constant due to the low bulk modulus of the gas (N ₂ ) and the sufficient dead volume including the constant pressure chamber 45. The pressure of nitrogen gas is 10 to 60 kg/1 as one of the conditions for measuring the amount of fuel injection.
It can be set arbitrarily between ^cm2 , but in consideration of the case where excessive pressure is accidentally applied, the other port 41 of the back pressure chamber 37 is equipped with a safety valve 47 with an operating pressure of 100 kg/ ^cm2. ing.

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 insulating properties 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. diaphragm 31
and the transmission section 55 connected to the electrodes 51 and 52,
This capacity is detected. 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 58 after the measurement of the amount of fuel, which will be described later, is completed. Discharge container 3 whose internal pressure is kept constant (atmospheric pressure)
is discharged. The fuel injection chamber 36 is a discharge pipe 58
The delivery pipe 60 has four discharge valves 7,
Since discharge valves 8, 9, and 10 are provided, fuel is discharged by opening these discharge valves 7, 8, 9, and 10. The discharged fuel is transferred to the discharge container 3.
However, when the stored amount exceeds a predetermined amount, the overflow switch 62 operates to detect this, and the valve drive unit 14 opens the drain valve 12 and the fuel flows through the drain passage 63. It is discharged into the reservoir tank 64. The discharge container 3 is provided with a pressure gauge 65 and a safety valve 66 for detecting the pressure inside the container, and the drain passage 63 is provided with a manual valve 68.

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 unit 1, the volume of the fuel injection chamber 36 is changed once, and then the discharge valves 7, 8, 9, 10 of the discharge container 3 are opened. Accordingly, the discharge container 3
However, detection of volumetric changes in the fuel injection chamber 36, which is performed in synchronization with the operation of the fuel injection pump VE, and control to open the above-mentioned discharge valves 7, 8, 9, and 10, etc., are performed by the measurement control unit 5. This is performed by the drive unit 14.

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.

Furthermore, 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, if the outputs of both operational amplifiers OP1 and OP2 are input to the divider Dv and the division V2/V1 is performed, 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 Vo is proportional to (C1-C2)/(C1+C2). This means that This output voltage Vo is output to the measurement control section 5 via the V/I converter Cv. still,
The V/I converter Cv has an output voltage Vo of 4-
This converts it into a 20mA current signal.

The measurement control unit 5 includes a well-known CPU 71 and a 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 output signal of the I/V converter 85 is also input to a peak hold section 86 as a peak detection section, and the peak hold section 86 receives the volume signal V constantly sent from the I/V converter 85. peak value
Configured to hold Vp. This results in
The CPU 71 via the analog input port 78
A signal corresponding to the displacement of the diaphragm 31 (C1-
You can input the peak value of C2)/(C1+C2) at any time. The peak value Vp of the signal held in the peak hold section 86 according to the displacement of the diaphragm 31 is held until the peak hold section 86 is reset by the CUP 71.

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 and the timing chart of FIG. 5. The measurement control unit 5 starts processing from step 100 when the power is turned on. First, in step 100, CPU71
Performs so-called initialization processing such as clearing internal registers, etc. In the following step 110, the zero point reading timing θ1 for zero point calibration in the measurement of the fuel injection amount and the reading timing θ of the volume signal peak value Vp are determined.
2. Reading timing θ3 of steady volume signal Vm, fuel discharge timing θ4, θ5, comparison constant k between volume signal V and fuel amount F in fuel injection chamber 36, initial number of fuel injections IN, and number of fuel injections N (N> IN) etc. setting processing is performed as follows.

When the motor 15 is started and measurement starts,
The fuel injection valve 24 is lifted and fuel is injected. Next, the measurement control circuit 5 controls the discharge valves 7, 8, 9, 10 at an appropriate timing (default value).
While opening and closing the valve, a volume signal V based on the capacitance of the diaphragm 31 inputted from the transmission section 55
is displayed on the CRT display 70. Since the change in the volume signal V based on the capacitance of the diaphragm 31 is displayed on the CRT display 70 with the horizontal axis representing the crank angle of 0 to 720 degrees, the measurer can:
Each timing θ1, θ2, θ3, θ is determined based on the volume signal V displayed on the CRT display 70.
4 and θ5 are each set using the keyboard panel 83.

Here, the volume signal V in the timing chart of FIG.
The above timings θ1, θ2, θ3, θ4, and θ5 will be explained using a graph showing an example.

Zero point reading timing θ1 refers to the crank angle at which the volume signal V is read when the volume signal V has decreased to the level before starting measurement, and the discharge valves 7, 8, 9, and 10 operate to inject fuel. Since the diaphragm 31 returns to its initial position when the fuel that has entered the chamber 36 is discharged into the discharge container 3, at this time,
This means that the volume signal V has returned to the level before the start of measurement.

Although the reading timing θ2 of the volume signal peak value Vp is described later, the peak value of the volume signal V for each injection held in the peak hold section 86 immediately after fuel is injected into the fuel injection chamber 36 is read. It refers to the crank angle at the time.

The reading timing θ3 of the steady volume signal Vm is
This refers to the crank angle at which the volume signal V is read at an arbitrary time when the volume signal V has settled down to a certain level after the fuel is injected into the fuel injection chamber 36.

The fuel discharge timing θ4 is the crank angle at which the discharge valves 7, 8, 9, and 10 are opened to discharge the fuel in the fuel injection chamber 36 into the discharge container 3 after reading the steady volume signal Vm. Say something.

The fuel discharge timing θ5 means that the discharge valves 7, 8, 9, 10 are activated after the volume signal peak value Vp is read.
The valve is opened and the fuel in the fuel injection chamber 36 is discharged from the container 3.
Refers to the crank angle when discharging to.

Furthermore, in step 110, a proportionality constant k is determined that relates the volume signal V to the fuel amount F in the fuel injection chamber 36.
, the initial number of fuel injections IN and the number of fuel injections N (N
>IN) and other settings are also performed using the keyboard panel 83.

After completing each of the above settings, the process proceeds to step 120 and subsequent steps to measure the fuel injection amount.

In step 120, a variable n indicating the number of injections is returned to zero. Since this variable n represents the number of fuel injections, it is set to zero here. next,
The process proceeds to step 130, where a variable n indicating the number of injections is incremented. After completing the processing of steps 120 to 130, the processing proceeds to step 140, where it is determined whether the crank angle .theta. has reached the reading timing .theta.1 of the zero point volume signal Vo. The crank angle θ is based on the timing TDC of 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). ) can be used for detection. Crank angle θ at zero point reading timing
If the crank angle θ has not reached 1, a weight is applied until the crank angle θ reaches the crank angle θ1.
Only when the crank angle θ reaches the crank angle θ1 does the process proceed to the next step 150.

In step 150, the zero point volume signal Vo is read. This is done in order to use the amount of displacement of the diaphragm 31 immediately before fuel injection as the zero point for fuel injection measurement, and to eliminate measurement errors due to various drifts in the measurement system. After reading the volume signal Vo at this zero point, the process proceeds to step
Proceed to 160. In step 160, a proportionality constant k relating the volume signal V and the amount of fuel in the fuel injection chamber 36 is determined.
is used to calculate the amount of fuel Fo (=k×Vo) in the fuel injection chamber 36 based on the volume signal Vo at the zero point.
Here, the amount of displacement of the diaphragm 31 is the volume signal V
The fact that this volume signal V and the fuel amount F in the fuel injection chamber 36 are in a proportional relationship will be explained below.

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 each electrode 51 and 52 being A, and the area of the diaphragm chamber 33.
The dielectric constant of the silicone oil sealed in the diaphragm 31 and the electrodes 51 and 52 is the average value of the distance between
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 do is a constant, it can be seen from equation (3) that the volume signal V, which is the output signal of the transmission section 55, corresponds to the displacement amount Δd of the diaphragm 31.

Furthermore, in this embodiment, there is a difference between the displacement amount Δd of the diaphragm 31 and the fuel amount F in the fuel injection chamber 36.
As shown in Figure 6, the existence of a proportional relationship has been experimentally confirmed, so F=k1×
Since the amount of displacement Δd of the diaphragm 31 corresponds to the volume signal V, as a result, the fuel amount F is expressed as F=k×V.

In step 170 following step 160, it is determined whether the crank angle .theta. has reached the reading timing .theta.2 of the volume signal peak value Vp after fuel injection. If the crank angle θ has not reached the crank angle θ2, a weight is applied until the crank angle θ2 is reached, and the process proceeds to the next step 180 only when the crank angle θ reaches the crank angle θ2. At step 180, the CPU 71 calculates the volume peak value Vp held in the peak hold section 86.
is read. Here, regarding the fact that the peak value Vp of the volume signal V can be read from the peak hold section 86 at the timing of the crank angle θ2,
This will be explained in detail using a graph representing the volume signal V in the timing chart of FIG.

As shown in the graph of the volume signal V in the timing chart of FIG. The diaphragm 31 vibrates in a damped manner over a certain period of time at a frequency specific to the diaphragm 31 . This vibration reaches its maximum amplitude immediately after fuel injection, gradually attenuates as time passes, and settles down to a constant level at crank angle θ3. On the other hand, the peak hold section 86 is
Since only the peak value Vp is held in the volume signal V constantly sent from the transmission section 55 (indicated by a dashed line), the CPU 71 calculates the volume held in the peak hold section 86 at the crank angle θ2. By reading the signal V, the volumetric signal peak value Vp in fuel injection can be read. Note that the period of vibration of the volumetric signal V is a vibration period unique to the measurement system and is not dependent on the fuel injection amount.

Following step 180 in which the volume signal peak value Vp described above is read, step 190 determines the maximum fuel amount Fp (=k× Vp)
Calculate and proceed to the next process. At step 200,
The relative difference between the fuel amount Fo at the zero point and the maximum fuel amount Fp (Fp - Fo) determines the relative difference maximum fuel amount from the zero point.
Fpn (=Fp−Fo) will be calculated. This maximum relative difference fuel amount Fpn will be used in a later step.

In step 210, it is determined whether the number of fuel injections n is equal to or greater than a predetermined initial number of injections IN. If it is determined that the number of fuel injections n is less than or equal to the initial number of injections IN, the process proceeds to step 220. The following series of processes from steps 220 to 290 are processes that are repeatedly executed when the number of fuel injections n is less than or equal to the initial number of injections IN, and the relative difference maximum fuel amount
Relative fuel amount representing Fpn and actual fuel injection amount
This process is performed to obtain the constant L that relates Fn (hereinafter, steps 220 to 290
This process is called constant L setting process). Here, this constant L setting process will be explained.

First, in step 220, it is determined whether the crank angle .theta. has reached the crank angle .theta.3 at which the volume signal V after fuel injection has settled down to a certain level.
If the crank angle θ has not reached θ3, a weight is applied until the crank angle θ reaches θ3, and only when the crank angle θ reaches θ3 does the process proceed to the next step 230. In step 230,
A steady volume signal Vm, which is the volume signal V at the crank angle θ3, is read. This steady volume signal Vm is
As mentioned above, this value represents the value when the volume signal V has settled down to a constant level after fuel injection. In step 240, the fuel amount Fm (=k×Vm) is calculated based on this steady volume signal Vm, and in the next step 250, the relative difference fuel amount Fn (=Fm - Fo) representing the actual fuel injection amount is calculated. calculate. step
In step 260, the relative difference fuel amount Fn thus calculated and the relative difference maximum fuel amount Fpn calculated in step 200 are used to calculate the difference between the relative difference maximum fuel amount Fpn and the relative difference fuel amount Fn in the n-th fuel injection. ratio Ln
(=Fpn/Fn) is calculated. When this process is completed, the process proceeds to step 270, where the average value of the ratio Ln (=Fpn/Fn) from the first to the Nth fuel injection is calculated, and the thus calculated value is the constant L.
(= _o 〓 ⁱ⁼¹ Li/n). Here, the processing of steps 260 to 270 will be explained in detail.

The vibration of the diaphragm 31 during fuel injection is
This is an inherent vibration in this measurement system, and there is a difference between the relative difference fuel amount Fn, which represents the actual fuel injection amount, and the relative difference maximum fuel amount ^Fpn . (β×tp+φ)
Theoretically and experimentally, it is found that sinφ=β/√ ² + ² = 1/M α, β are constants specific to the measurement system, and tp is a minimum value greater than or equal to zero that satisfies sin(β×tp+φ)=−1. is in demand. Therefore, it can be expressed as Fpn/Fn=Ln (Ln is a constant). This ratio Ln is unique to the measurement system regardless of the fuel injection amount, but considering measurement errors, etc., calculate the ratio Ln for each injection and calculate the average value L (= _o 〓 ⁱ⁼¹ Li / n) (step)
270).

Steps following steps 260 and 270 above
At 280, the relative fuel difference amount Fn representing the actual fuel injection amount is outputted to be displayed on the CRT display 70.

In step 290, it is determined whether the crank angle .theta. has reached the crank angle .theta.4, which indicates the fuel discharge timing after reading the steady volume signal Vm. If the crank angle θ has not reached θ4, a wait is applied until the crank angle θ4 is reached, and the process moves to the next step only when the crank angle θ4 is reached. The constant L setting process in steps 220 to 290 is repeated the number of initial injections IN, and the average value L of the ratio Ln for the IN fuel injections is calculated.

On the other hand, in step 210, the number of fuel injections n
When it is determined that the number of injections exceeds the initial injection number IN,
The process involves executing steps 350 to 370.

In step 350, the relative difference fuel amount is calculated from the maximum relative difference fuel amount Fpn found in step 200 using the constant L found in the constant L setting process.
Processing to calculate Fn (=Fpn/L) is performed.
In order to display the relative fuel difference amount Fn indicating the actual fuel injection amount thus determined on the CRT display 70, in step 360, the relative fuel difference amount Fn is output. Next, in step 370, the volume signal peak value is
It is determined whether or not the crank angle θ has reached the crank angle θ5, which is the fuel discharge timing after reading Vp, and a weight is applied until the crank angle θ reaches θ5. Only then will it move on to the next process.

After completing the constant L setting process in steps 220 to 290 or the series of processes in steps 350 to 370 described above, the process proceeds to step 300.
At crank angle θ4 or θ5, fuel injection chamber 3
Discharges the amount of fuel according to the injected fuel amount Fn in 6,
Proceed to step 310. In step 310, the peak value Vp of the volume signal V held in the peak hold section 86 is reset. Peak hold section 86
When it is reset, it again works to maintain the peak value of the volume signal V sent from the transmission section 55. After completing step 310,
In step 320, it is determined whether the number of fuel injections n is equal to or greater than a predetermined number of injections N. If the number of fuel injections n is equal to or less than the preset number of injections N, the process returns to step 130. The measurement process is repeated again, and when it is determined that the number of fuel injections n is equal to or greater than the set number of injections N, the process exits to END and the main control routine ends.

The configuration of the fuel injection amount measuring device and the processing performed by the measurement control unit 5 as an embodiment have been described above in detail.According to this embodiment, fuel injection is performed while maintaining the back pressure chamber 37 at a predetermined pressure. Since the fuel injection amount is detected as the amount of displacement of the diaphragm 31, it can be accurately measured (for example, within ±0.1 mm ^{3 ) over a wide measurement range (for example, 0 to 100 mm 3 /} stroke).
Fuel injection amount can be measured. Moreover, in this embodiment, after the constant L setting processing in steps 220 to 290, the amount of injected fuel is determined based on the volume signal peak value Vp, as shown in the timing chart of FIG. As a result, there is no need to wait until the volume signal V settles down to a certain level (crank angle θ3) in consideration of hunting of the volume signal V due to fuel injection, and the injection pump is rotated at high speed (3000 rpm).
Even with the above method, the fuel injection amount can be measured accurately. Furthermore, the fuel injection amount measurement device of this embodiment can measure the fuel injection amount immediately after fuel injection is completed, and can measure the fuel injection amount even in situations where the diesel engine is being driven at a high rotation speed.
The fuel injection amount of the fuel injection pump VE can be measured with good response. As a result, it is not only possible to easily measure variations in fuel injection amount that are related to engine roughness, but also to complete adjustment of the fuel injection pump VE in an extremely short time. In addition, 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 the actual machine. There is also an effect that it can be done.

Although the present embodiment is configured to hold the volume signal peak value Vp using the peak hold section 86, it is of course possible to configure the volume signal peak value Vp to be read by a program executed by the CPU 71. It is about.

In the above embodiment, the measurement control section 5 particularly corresponds to the fuel injection amount calculation means, and among its processing, steps 150, 160, 180 to 200, and 350 correspond to the processing as the fuel injection amount calculation means. The measurement control section 5 and the valve drive unit 14 correspond to the fuel discharge control means, and among these processes, steps 370 and 300 correspond to the processes as the fuel discharge control means. The discharge container 3 corresponds to a fuel discharge part, and the space inside the discharge container 3 corresponds to a discharge chamber. The transmission section 55 corresponds to displacement amount detection means. The peak hold section 86 corresponds to a peak detection section.

Effects of the Invention As detailed above, the fuel injection amount measuring device of the present invention can satisfy high measurement accuracy, wide measurement range, and high measurement responsiveness. In particular, it is equipped with a peak detection section, and the fuel injection amount calculation means calculates the fuel injection amount from the peak value at the beginning of the fluctuation of the diaphragm displacement amount, so it can be calculated in a short time without waiting for the detected diaphragm displacement amount to decay. This makes it possible to measure the fuel injection amount with high precision up to the high rotation range where calculations are required in a short time. As a result, by using the fuel injection amount measuring device of the present invention for inspection, measurement, and adjustment of fuel injection pumps, it is possible to not only quantitatively and accurately grasp the performance of the fuel injection system, but also improve the performance of the fuel injection pump. In addition, the adjustment time can be shortened and productivity can be significantly improved.

[Brief explanation of the drawing]

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 processing of the fuel injection amount measuring device according to the embodiment of the present invention, FIG. 5 is a timing chart showing the timing of measurement in the embodiment, and FIG. A graph showing the relationship with the fuel injection amount F in the fuel injection chamber 36 is shown. 1...Fuel volume detection section, 3...Discharge container, 5...
...Measurement control unit, 7, 8, 9, 10...Discharge valve, 1
2...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, 70...CRT display,
71...CPU, 83...Keyboard panel, 8
6...Peak hold section, 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; a peak detection unit that detects a peak value at an initial stage of variation in the detected displacement amount of the diaphragm when fuel injection is performed; and a correspondence relationship between the peak value of the displacement amount of the diaphragm and the actual fuel injection amount. a fuel injection amount calculation unit that calculates a fuel injection amount from the peak value of the displacement amount detected by the peak detection unit; a discharge valve connected to the fuel injection chamber; and a valve opening of the discharge valve. a fuel discharge part having a discharge chamber for discharging fuel from the fuel injection chamber; the discharge valve is closed when fuel is injected into the fuel injection chamber; and after the fuel injection is completed, the amount of fuel injected is A fuel injection amount measuring device comprising: fuel discharge control means for discharging a corresponding amount of fuel from the fuel injection chamber to the discharge chamber by opening the discharge valve.