JPH0553213B2 - - Google Patents

Description

[Detailed Description of the Invention] Object 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.

[Conventional technology]

When fuel is supplied by fuel injection, for example in diesel engines or gasoline engines with electronically controlled fuel injection, the amount of fuel injected must be precisely controlled, so it is necessary to accurately measure the amount of fuel injected. A fuel injection amount measuring device 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), and the fuel is injected into the sealed container (volume Vo). The volume Vb of the injected fuel is calculated from the change in the pressure P inside the tank as follows: dVb/dt = (Vo/E) x (dP/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.

[Problem that the invention seeks to solve]

However, these various fuel injection amount measurement devices have the following problems, which can be described as having advantages and disadvantages.
Further improvements were desired.

(1-a) Like a piston type fuel injection amount measuring device,
In the case where the displacement amount d is determined and the fuel injection amount is determined from the cylinder cross-sectional area S, 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 one tries to accurately determine the amount of fuel at a certain level, it becomes extremely difficult to increase the maximum amount of fuel to be measured. Therefore, the range of fuel amount that can be injected by the fuel injection device (for example, 0 to 150 [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 is a problem in that the measurement response is low and the fuel injection amount cannot be measured in situations where the internal combustion engine is operated at high rotational speeds.

(1-c) Furthermore, when a piston is used, there is a problem in 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 fuel injection amount from pressure changes in 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 fuel injection amount, which have a large effect on vibration roughness (vibration roughness, etc.). In addition, with this method, in order to improve measurement accuracy, it is necessary to increase the number of times the fuel injection amount is accumulated (stroke number). In this case, there was a problem in that it took a long time to measure and even adjust the fuel injection amount.
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 response. These problems are the same in various other fuel injection amount measuring devices. As a result,
During inspection, measurement, and adjustment, it was considered that the performance of the fuel injection system could not be quantitatively understood. SUMMARY OF THE INVENTION The present invention has been made with the object of solving the above 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] The present invention, which was made to solve the above problems, comprises: a fuel injection chamber that communicates with the injection side of a fuel injection valve and into which fuel is injected; a discharge means for discharging fuel inside the injection chamber to the outside in response to the fuel injection; a back pressure chamber facing the fuel injection chamber and maintained at a predetermined pressure; a buffer member having a communication hole disposed at a predetermined position facing the pressure chamber; and a buffer member interposed between the fuel injection chamber and the back pressure chamber to isolate the two chambers, and to prevent the injected fuel from flowing through the buffer member. a diaphragm that is displaced according to the volume; a displacement detection means that is disposed inside the back pressure chamber and detects the displaced position of the diaphragm without contacting the diaphragm; The gist of the present invention is a fuel injection amount measuring device comprising: fuel injection amount detection means for detecting the fuel injection amount of the fuel injection valve based on the amount of displacement of the diaphragm.

[Effect]

In the present invention configured as described above, the amount of fuel injected into the fuel injection chamber by the fuel injection valve is detected based on the amount of displacement of the diaphragm interposed between the fuel injection chamber and the back pressure chamber. That is, when fuel injection is performed, the accompanying dynamic impact force is reduced by the buffer member, and the volume of the fuel injection chamber gradually increases in accordance with the amount of fuel injection. On the other hand, since the back pressure chamber is maintained at a predetermined pressure, the diaphragm is displaced in accordance with the increase in the volume of the fuel injection chamber without causing a pressure change inside the fuel injection chamber. Therefore, the fuel injection amount detection means detects the fuel injection amount of the fuel injection valve based on the displacement amount of the diaphragm.

As described above, in the present invention, since the impact force such as pressure waves generated with fuel injection is reduced by the buffer member, the volume of the fuel injection chamber is gradually increased in accordance with the fuel injection amount. Therefore, the fuel injection amount can be detected with high accuracy.

Further, in the present invention, a change in the volume of the fuel injection chamber is detected based on the amount of displacement of the diaphragm. A diaphragm has extremely low inertia compared to a piston or the like. Moreover, since the displacement amount detection means detects the displacement amount without contacting the diaphragm, the movement of the diaphragm is not inhibited. Therefore, the diaphragm is instantaneously displaced depending on the fuel injection amount. Therefore, in the present invention, the responsiveness of fuel injection amount measurement is improved.

Furthermore, in the present invention, since the discharge means discharges fuel according to the fuel inside the fuel injection chamber and the fuel injection amount, the fuel injection amount per injection can be accurately and continuously measured many times. Ru.

Here, as the material constituting the buffer member, various materials such as a plate material having apertures and a porous material can be used.

In addition, the displacement amount detection means is provided with a first detection section disposed at a position where the detection result changes according to the displacement of the diaphragm, and a first detection section that has the same configuration as the first detection section and is responsive to at least the displacement of the diaphragm. Depending on the situation, it may also be configured with a second detection section disposed at a position where the detection result does not change. By configuring the displacement amount detection means in this way, even if an error occurs in the output of the first detection section due to temperature change, the error can be corrected by comparing it with the output of the second detection section. be able to. Therefore, measurement accuracy is further improved.

〔Example〕

Next, preferred embodiments of the present invention will be described in detail based on the drawings. FIG. 2 shows a system configuration of a fuel injection amount measuring device according to an embodiment of the present invention. As shown in the figure, the fuel injection amount measuring device 1 mainly includes a detection section 2 that measures the fuel injection amount, and a measurement control section 3 that performs measurement control of the fuel injection amount. The fuel injection pump 4 used for measuring the fuel injection amount is a fuel injection pump for a diesel engine, and is fixed on a bench for measurement, and a motor 5 is connected to the drive shaft 6 instead of the diesel engine as the drive source in actual use. Connected. In addition, the rotating shaft of the motor 5 has
An angle sensor 7 is provided that detects the rotational speed, cylinder discrimination signal, top dead signal, etc. and outputs the detected information to the measurement control section 3.

The fuel injection pump 4 sucks fuel from the fuel tank 8 , pressurizes it, and pumps it to the fuel injection valve 9 attached to the detection section 2 . Note that in FIG. 2, only one system of the plurality of fuel injection valves is illustrated. The detection unit 2 outputs an injection amount signal corresponding to the amount of fuel injected from the fuel injection valve 9 to the meter control unit 3. On the other hand, in response to a drive signal from the instrumentation control section 3, the detection section 2 discharges the fuel injected into its interior, and the discharged fuel flows into the fuel tank 8.

Next, the configuration of the detection section 2 will be explained based on FIG. 1. The detection unit 2 includes, inside the main body 10, a fuel injection chamber 11 in which the fuel injection valve 9 is disposed, and a back pressure chamber 12 provided opposite to the fuel injection chamber 11. The fuel injection chamber 11 and the back pressure chamber 12 are connected to a desk plate 13 and a bellows 1 as a diaphragm.
4. The desk plate 13 is made of iron, and the bellows 14 is made of iron or plastic. Furthermore, the bellows 14 generates a pressing force (approximately 200 KPa) from the back pressure chamber 12 toward the fuel injection chamber 11 due to the elasticity of its bellows structure. The pressing force is the back pressure chamber 12 at the time of fuel injection.
Acts as back pressure. Moreover, the fuel injection chamber 11
A buffer member 15 is provided inside and near the desk plate 13 facing the desk plate 13 . The buffer member 15 is made of a porous material such as sintered metal or ceramics, and has communication holes.

Further, the fuel injection chamber 11 has a first communication portion 16
is connected to a discharge valve 17 as a discharge means via a discharge means, and to a safety valve 19 via a second communication passage 18. The discharge valve 17 is a solenoid valve that opens when excited by the measurement control section 3 and discharges the fuel inside the fuel injection chamber 11 to the outside. Furthermore, the safety valve 19 operates when the pressure inside the fuel injection chamber 11 exceeds an arbitrarily determined operating pressure.
The pressure inside the fuel injection chamber 11 is released to the outside to prevent an excessive pressure rise inside the fuel injection chamber 11.

On the other hand, inside the back pressure chamber 12, a non-contact displacement sensor 20 that detects the displacement amount of the desk plate 13 due to the contraction of the bellows 14 according to the fuel injection amount is fixed by a casing (not shown). There is. The displacement sensor 20 as a measuring stage is
This is a high-frequency vibration type displacement meter that includes a detection coil, and when a metal body (in this embodiment, the desk plate 13) approaches the detection coil, the inductance and loss of the detection coil change due to electromagnetic induction. The displacement amount sensor 20 outputs the detected result as an injection amount signal to the measurement control section 3 described above.

Then, the measurement control unit 3 detects the fuel injection amount of the fuel injection valve 9 based on the injection amount signal from the displacement amount sensor 20. That is, the measurement control section 3 corresponds to fuel injection amount detection means.

Next, the operation when measuring the fuel injection amount will be explained. Both the discharge valve 17 and the safety valve 19 are in a closed state, and fuel is injected from the fuel injection valve 9 into the fuel injection chamber 11 whose back pressure chamber is maintained at a predetermined pressure. The dynamic impact force generated inside the fuel injection chamber 11 due to the fuel injection is reduced by the buffer member 15. Therefore, when fuel injection is performed, the pressure increase inside the fuel injection chamber 11 is quickly alleviated, and the volume increases in accordance with the injected fuel. Due to the increase in volume,
A pressing force is applied to the desk plate 13 in the direction of the back pressure chamber 12 . Therefore, the bellows 14 contracts and the desk plate 13 is displaced to a position corresponding to the increase in volume. The displacement amount at this time is detected by the displacement amount sensor 20. Displacement sensor 2
The injection amount signal and fuel injection amount output by
It has been previously confirmed through experiments that there is a linear relationship as shown in the figure. Therefore, the measurement control unit 3 measures the fuel injection amount based on the above relationship from the detected injection amount signal. After that, the measurement control section 3
The discharge valve 17 is opened by the drive signal outputted by the
An amount of fuel corresponding to the measured fuel injection amount is discharged from the fuel injection chamber 11 to the outside. As a result, the volume of the fuel injection chamber 11 is reduced to the initial volume at the start of the measurement. Therefore, the displaced desk plate 13 returns to its initial position by the urging force of the bellows 14.

Next, an example of the measurement control described above will be explained with reference to the timing chart of FIG. 4. First, at time T1 before fuel is injected, a reference injection amount signal Vo is detected. Next, fuel injection is performed from time T2 to time T3, and the injection amount signal increases. An injection amount signal V1 corresponding to this fuel injection is detected at time T4. Here, the actual injection amount signal S, which is the difference between the injection amount signal V1 and the reference injection amount signal V0, corresponds to the actual fuel injection amount. The discharge valve 17 is opened for a period of time τ from time T5 after the fuel injection amount is measured in this manner. Then, as shown in FIG. 5, a predetermined amount of fuel is discharged according to the pressure difference between the inlet side and the outlet side of the discharge valve 17. The measurement control section 3 is
The valve opening time τ is determined so that the discharge amount corresponds to the measured fuel injection amount. Thereafter, fuel injection, measurement, and discharge are repeatedly performed. Note that the fuel may be discharged for each fuel injection as described above, or for example, the accumulated fuel may be discharged for every predetermined number of fuel injections.

According to the above configuration, since the fuel injection amount is measured based on the amount of displacement of the desk plate 13 due to contraction of the bellows 14, the amount of fuel injection is 0.1 to 200 [mm ³ /stroke]
It is possible to perform measurements over a wide measurement range of 60 to 80 [Hz] while ensuring high responsiveness.

Moreover, since the fuel injection amount can be measured in the relatively small volume fuel injection chamber 11 due to the effect of the buffer member 15, the detection unit 2 can be downsized.

Furthermore, since the responsiveness is high, the fuel injection amount can be measured for each cycle.

Furthermore, measurement with high accuracy (for example, within ±0.1 [mm ³ ]) is possible. This is because when measuring the fuel injection amount, the actual injection amount signal S, which is the difference between the reference injection amount signal V0 and the injection amount signal V1, is used.
This is because errors in the initial positions of the bellows 14 and the bellows 14 are canceled out.

Although only one detector 2 has been described in this embodiment, since a plurality of detectors having the same configuration as the previously described detectors are provided, fuel injection amounts for multiple cylinders can be measured at the same time.

As described above, the behavior of a fuel injection pump in an over-operating state can be quantitatively measured. As a result, it becomes possible to easily measure fluctuations in fuel injection amount that are related to engine roughness. Therefore, the efficiency of adjusting the fuel injection pump is improved.

In addition, in this example, the measurement of the fuel injection amount of the fuel injection pump of a diesel engine was explained.
For example, it can also be used to measure the amount of fuel injected from a fuel injection valve of a gasoline engine.

In this embodiment, the buffer member 15 is made of a porous material, and the back pressure is maintained by the elastic force of the bellows 14. However, as shown in FIG. 6, for example, a plate 24 having a throttle hole 24a may be used as the buffer member 23, and
2 may be connected to a constant pressure chamber 22 equipped with a relief valve or a constant difference pressure reducing valve through a third communication passage 21, and filled with constant pressure nitrogen gas (N ₂ ) to generate a back pressure chamber. . This configuration provides the following effects in addition to the effects of the embodiments already described. In other words, by keeping the back pressure constant,
Alternatively, the back pressure can be freely set as one of the measurement conditions.

Further, for example, as shown in FIG. 7, the displacement sensor 20 is disposed at a position where its output changes according to the displacement of the desk plate 13, and the correction sensor 25 having the same configuration is installed in accordance with the displacement of the desk plate 13. It may also be provided at a sufficiently distant position so that the output does not change. If configured like this,
For example, even if the environmental temperature changes over a wide range, it is possible to perform accurate measurements by correcting errors caused by the temperature changes. That is, as shown in FIG. 8, the displacement sensor 2 changes as the temperature changes.
When the output voltage of 0 (indicated by a solid line) changes, the output voltage (indicated by a broken line) of the correction sensor 25 also changes in accordance with the temperature. Therefore, if the fuel injection amount is measured based on the differential fluctuation force voltage (indicated by a dashed line) which is the difference between the output voltages of the displacement amount sensor 20 and the correction sensor 25, the error caused by the temperature change can be offset.

Although several embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way, and may be implemented in various forms without departing from the gist of the present invention. Of course.

Effects of the Invention As detailed above, in the fuel injection amount measuring device of the present invention, the impact force such as pressure waves generated due to fuel injection is reduced by the buffer member.
The fuel injection amount can be detected with high precision.

Further, in the present invention, a change in the volume of the fuel injection chamber is detected based on the amount of displacement of the diaphragm. Since the inertia of the diaphragm is extremely small and the amount of displacement thereof is detected without contact, the diaphragm is instantly displaced in accordance with the amount of fuel injected. Therefore, in the present invention, the responsiveness of fuel injection amount measurement can be improved.

Further, in the present invention, since the discharge means discharges fuel according to the fuel inside the fuel injection chamber and the fuel injection amount, it is possible to accurately and continuously measure the fuel injection amount per injection many times. I can do it.

In addition, the displacement amount detection means is provided with a first detection section disposed at a position where the detection result changes according to the displacement of the diaphragm, and a first detection section that has the same configuration as the first detection section and is responsive to at least the displacement of the diaphragm. If the second detection section is arranged at a position where the detection result does not change, it is possible to correct errors in the output of the detection section due to temperature changes or the like. Therefore, measurement accuracy can be further improved.

[Brief explanation of the drawing]

Fig. 1 is a partial sectional view of a detector according to an embodiment of the present invention, Fig. 2 is a system configuration diagram of an embodiment of the present invention, and Fig. 3 similarly shows the relationship between the injection amount signal and the fuel injection amount. Graph, FIG. 4 is a timing chart showing the operation thereof, FIG. 5 is a graph showing the relationship between the discharge amount of the discharge valve and the valve opening time, and FIG. 6 is a modification of the embodiment of the present invention. FIG. 7 is a partial sectional view showing another embodiment of the present invention, and FIG. 8 is a graph showing the relationship between the output voltage and temperature. 1...Fuel injection amount measuring device, 2...Detection unit, 9
... Fuel injection valve, 11 ... Fuel injection chamber, 12 ...
Back pressure chamber, 13... Disc plate, 14... Bellows, 15... Buffer member, 17... Release valve, 2
0...Displacement sensor.

Claims (1)

[Scope of Claims] 1. A fuel injection chamber that communicates with the injection side of the fuel injection valve and into which fuel is injected; and a discharge means that discharges the fuel inside the fuel injection chamber to the outside in response to the fuel injection. a back pressure chamber facing the fuel injection chamber and maintained at a predetermined pressure; and a buffer member having a communication hole disposed inside the fuel injection chamber at a predetermined position facing the back pressure chamber. a diaphragm interposed between the fuel injection chamber and the back pressure chamber to isolate the two chambers and displaced according to the volume of the injected fuel; and a diaphragm disposed inside the back pressure chamber. , displacement amount detection means for detecting the displaced position of the diaphragm without contact with the diaphragm; and detecting the fuel injection amount of the fuel injection valve based on the displacement amount of the diaphragm detected by the displacement amount detection means. A fuel injection amount measuring device comprising: a fuel injection amount detection means; 2. The fuel injection amount measuring device according to claim 1, wherein the buffer member is made of a porous material. 3. The fuel injection amount measuring device according to claim 1, wherein the buffer member has a plate shape having a throttle hole passing through it. 4. A first detecting section disposed at a position where the displacement amount detecting means changes the detection result according to the displacement of the diaphragm, and a first detecting section having the same configuration as the first detecting section, and at least a displacement of the diaphragm. 2. The fuel injection amount measuring device according to claim 1, comprising a second detection section disposed at a position where the detection result does not change depending on the condition.