JPS6140458A - Injection amount detecting device in fuel injection type internal combustion engine - Google Patents

Abstract

PURPOSE:To enhance the accuracy of detection of fuel injection amount, by providing a capacitance type displacement sensor for detecting the displacement of the relative position of a control sleeve and a deviation computing means for computing the deviation between the displacement and a reference displacement. CONSTITUTION:A capacitance type displacement sensor 63 detects the displacement of relative position of a control sleeve in a fuel injection pump. A memory means 67 stores therein the displacement of the control sleeve in a reference condition. A deviation computing means 68 computes the deviation between the reference displacement and a displacement in an arbitrary operating condition. The memory means and the deviation computing means 68 constitute a compensating circuit. With this arrangement it is possible to greatly enhance the detection accuracy of fuel injection amount.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel injection amount detection device for a fuel injection type internal combustion engine.

(Prior art) In fuel-injected internal combustion engines such as diesel engines,
Similar to reciprocating spark ignition engines, electronically controlled fuel injection amount control devices have been proposed that have high control accuracy, excellent reliability, and are inexpensive.6 For example, fuel injection amount detection in conventional fuel injection internal combustion engines. There is a device as seen in Japanese Patent Publication No. 55-31307, which detects the actual injection amount or detects the injection amount by detecting the position of the fuel injection amount control member (actuator). directly controls the fuel injection amount.

(Problem to be solved by the invention, α) However, unlike reciprocating spark ignition engines, it is extremely difficult to develop an inexpensive, highly reliable system that can stably detect information regarding engine load, especially fuel injection amount, over a long period of time. Have difficulty. Therefore 8! Despite the fact that there is a means to accurately and stably control the fuel injection timing or the amount of part of the exhaust gas recirculated into the intake air using a computer that performs table look-ups based on engine rotational speed and load, the load factors, i.e. Currently, the control accuracy as a whole is unsatisfactory due to poor detection accuracy of the fuel injection amount.

For example, the above-mentioned fuel injection amount detection device has poor control accuracy due to deviations in control due to variations in size and shape of mechanical fuel injection amount control system components and wear over time.

The present invention calculates a reference displacement amount using a reference state as an initial condition,
To provide a fuel injection amount detection device that can absorb measurement errors due to mechanical variations and wear over time inherent in the detection device itself by correcting the detected displacement amount in any state using this reference displacement amount. It is.

(Means for Solving the Problems) The present invention provides a fuel injection type internal combustion engine 8 which calculates the fuel injection amount by detecting the position of the control sleeve of the distribution type fuel injection pump. Based on Seki's fuel injection amount detection device, this device includes a capacitive displacement sensor that converts the displacement of the relative position of the control sleeve into a change in capacitance between the electrodes and detects the amount of displacement in the reference state. a storage means for storing the
A deviation calculation means is provided for calculating the deviation between the reference displacement amount and the displacement amount in an arbitrary state.

(Sakuten) In this way, even if a displacement that includes measurement errors due to mechanical variations or changes over time is detected, this detected displacement can be corrected using the reference state as the initial condition, thereby eliminating it. Therefore, detection accuracy can be improved.

(Example) FIG. 2 is a schematic diagram of the first embodiment of the present invention.

In the figure, 1 is the air cleaner, 2 is the intake pipe, 3 is the main combustion chamber, and 4 is the air cleaner.
5 is a vortex chamber, 5 is a glow plug, 6 is an injection valve, and 7 is an injection pump. 8 is an exhaust pipe, 9 is a throttle valve that controls the amount of intake air, 10 is a Guya 7 ram that controls the throttle valve 9, 1
1 is an exhaust gas recirculation control (EGR) valve that controls the flow rate of exhaust gas recirculated from the exhaust pipe 8 to the intake air g2, and 12.13 is a solenoid valve. 14 is a vacuum pump constituting a negative pressure source; 15 is a constant pressure valve that produces a constant negative pressure from the negative pressure supplied from the pump 14; and 16 is a battery.

17 is a glow relay that controls the energization to the glow plug 5; 18 is a servo circuit that controls the fuel injection amount control member of the injection pump 7; and 19 is a glow lamp that indicates the state of energization to the glow plug 5. .

20 is an accelerator sensor that outputs an accelerator opening signal IS1 corresponding to the amount of depression of the accelerator pedal, and 21 is a reference pulse I for each specific crank angle (for example, 120 degrees).
a crank angle sensor 22 that outputs S2 and also outputs a unit pulse IS3 for every unit angle (for example, 1 degree);
23 is a neutral switch that detects that the transmission is in neutral and outputs a neutral signal ISA, and 23 is a vehicle speed signal IS that corresponds to the vehicle speed via the rotation speed of the output shaft of the transmission.
Vehicle speed sensor outputs 5, 24 is 8! Seki cooling water temperature (
8! This is a temperature sensor that outputs a temperature signal IS6 corresponding to the temperature of the sensor. Reference numeral 63 denotes a capacitive displacement sensor that detects the amount of displacement of the control sleeve in accordance with the engine load by a change in capacitance, and its configuration will be described later.

26 detects the temperature and pressure of the atmosphere and outputs an atmospheric density signal IS.
This is an atmospheric density sensor that outputs 8. The battery voltage signal IS9, the starter signal l5IO output when the starter switch is closed, the glow signal S11 output when the glow switch (glow relay) is closed, the fuel temperature signal l512, the fuel specific gravity signal l513, etc. are controlled by the control device 27.
is input as a control signal.

The control device 27 includes a central processing unit 28, a read-on memory (ROM) 29. Random access memory (RAM) 3
It is composed of a microcomputer equipped with 0 and input/output interface 7 ace 31, etc.
Based on IS 1 and 3, the luck at that time ['! ``Various signals O81 to O8 to optimally control the engine according to love?
Outputs 0SIO.

By the way, O81 is the throttle valve opening signal, O62 is the EGR control signal, OS3 is the fuel cutoff control signal, O34 is the fuel injection amount control signal, ○S5 is the injection timing control signal, OS6 is the glow control signal, and O87 is the glow lamp control. The signal 03IO is an enable signal (described later). The servo circuit 18 outputs the servo signal S1 by the fuel injection amount control signal OS4.
is output to control the control sleeve position, the amount of displacement of the control sleeve position at this time is detected by a displacement sensor 63 that detects a change in capacitance, and the detection signal IS7 is inputted to the control device 27 to Feedback control is performed to output the fuel injection amount signal O84 to the servo circuit 18 again so as to reduce the difference between the detection signal IS7 and the target fuel injection amount signal.

Further, as shown in FIG. 3, the fuel injection pump 7 uses a distribution type in this embodiment, and fuel is supplied from the inlet 32 of the pump body P to a feed pump driven by engine-driven drive shafts 71 and 33. 34. The fuel discharged from the feed pump 34 is regulated by a pressure regulating valve 35 to a pressure corresponding to the engine rotation speed, and then supplied to a pump chamber 36 inside the pump housing.

The fuel in the pump chamber 36 lubricates each sliding part and is simultaneously fed into the plunger barrel 38 through the suction boat 37. The plunger 39 is connected to the drive shaft 33
It is fixed to a camdigosph 40 which is rotationally driven by the engine, and is rotationally driven in synchronization with the engine. 41 is the drive shaft 33 and cam disc 40
This is a joint that connects the axially slidable parts.

The cam disc 40 has the same number of 7-eighth cams 42 as the number of cylinders in the engine, and each time the 7-eighth cam 42 passes over a roller 44 held by a roller ring 43, the cam disc 40 moves by a predetermined cam lift. It reciprocates together with the plunger 39. Therefore, the plunger 39
reciprocates in the axial direction while rotating, and as a result of this reciprocating movement, the fuel sucked from the suction boat 37 passes through the distribution boat 45 and the delivery valve 46 to the injection valve 6 in a state where it is pressurized to a predetermined pressure or higher. As the plunger 39 rotates, fuel is distributed and supplied to each cylinder in a predetermined order.

Here, the fuel injection amount is determined according to the position of the control sleeve 48 as a fuel injection amount control member that covers the cut-off port 47 formed in the blanker 39.

In other words, when the opening of the cut-off boat 47 passes the right end of the pump roll sleeve 48 due to the movement of the three plungers to the right in the figure, the fuel that was being pumped from the rush pump chamber 49 to the distribution boat 45 is returned to the pump 136 via the cut-off port 47, thus ending the pumping. Therefore, when the control sleeve 48 is moved relative to the plunger 39 to the right in the drawing, the injection timing is delayed and the fuel injection amount is increased, and when the control sleeve 48 is moved relative to the left in the drawing, the injection starts. The end time becomes earlier and the fuel injection amount decreases.

Further, the position of the control sleeve 48 that controls the injection amount as described above is controlled by the servo controller 50. That is, the slider 5 is attached to the output shaft 51 of the servo motor 50.
2 is screwed into the slider 52, and the tip of a link lever 54 is pivotally connected to this slider 52 via a pin 55. Link lever 5
4 is rotatably supported around a pin 55,
By engaging the pivot 56 protruding from the base end of the lever 54 with the control sleeve 48, the control sleeve 48 is displaced in the left-right direction in the figure as the link lever 54 swings about the pin 55. is configured to do so.

Therefore, the servo signal S1 output from the servo circuit 18
When the servo motor 50 rotates forward and backward in accordance with
4, the control sleeve 48 moves in the left-right direction. For this reason, there is no direct correspondence between the opening of the accelerator pedal and the fuel injection amount (position of the control sleeve), and the accelerator pedal is simply the driver's intention to "accelerate,""decelerate," or "maintain the status quo." It is only a means of transmitting the information to the control device 27. For convenience of explanation, the axis of the feed pump 34 and the axis of the timer piston 57 are shown rotated by 90 degrees in the figure.

Next, the capacitive displacement sensor used for fuel injection JIti detection will be explained. The displacement sensor is composed of a sensor body and a sensor circuit. Of these, the sensor body detects the displacement of the control sleeve 48. That is, in FIG. 3, the electrode 62 attached to the barrel 38 via the insulator 61 and the control sleeve 48 (
When a pair of electrodes (the other electrode) is formed and a voltage is applied between the electrodes, a sensor main body 63 is formed in which the substance between the electrodes (fuel in this case) is used as a dielectric.

fjfJ1 Figure (A) is a circuit configuration diagram of a sensor circuit for this sensor body, and Figure 1 (CB) is a correction circuit that corrects the output of this sensor circuit in a specific reference state. That is, the sensor body 63 is actually a variable capacitor, and the sensor body 63 and the fixed capacitor 64 are connected in series, and an AC power source 65 is connected to both ends thereof. *In addition, a detector 66 is connected to the connection point between the sensor body 63 and the capacitor 64, which converts the voltage at this connection point from alternating current to direct current.

First, the mathematical treatment of the sensor circuit constructed in this way will be described.
” (for example, in an idle state), the distance between the electrodes is D, the effective area of the electrode is S, and the displacement of the control sleeve 48 (displacement from the reference state to the right in FIG. 3) is χ (O≦χ<D)
, the capacitance C2 of the sensor body 63 is given by the following equation, where the dielectric constant of the fuel as a dielectric is ε.

C2=g-8/(D-χ) (1) If Eo is the voltage of the AC power supply 65, then the sensor body 6
The voltage E generated across 3 is given by the following equation.

E=Eo-C1/[C1+εS/(D-χ)]...(
2) That is, this is the output signal IS7 of the sensor body 63. Note that C1 is the capacitance of the capacitor 64.

In equation (2), if C1 is sufficiently smaller than εS/(D-χ), then C1 can be ignored in favor of εS/(D-χ), so equation (2) can be written as Can be approximated.

E=EoC1(D-χ)/εS (3) The AC voltage signal obtained in this way is converted to a DC voltage signal, but in this case, the output Vx of the detector 66 is proportional to E, so the proportionality constant K Using , equation (3) is given by the following equation.

V x=K EoC1(D-χ)/εS ・(4
) What we learn from this equation is that E (or Vx) is
Since it is a function of S and ε, E also changes according to changes in these parameters. In other words, the distance between the electrodes in the reference state! D. Since E is greatly affected by variations in the effective area S of the electrodes and changes over time, accurate detection cannot be expected. In particular, the distance between the electrodes is the distance from the control sleeve, which is a movable part, so the accuracy cannot be expected. difficult to maintain. Furthermore, the dielectric constant ε of the fuel changes depending on the temperature and also changes depending on the type of fuel, and changes in ε also affect the detection accuracy. Therefore, if such a change occurs, the detection signal will change greatly and this change will cause a measurement error, so accurate displacement detection cannot be expected.

Therefore, in order to eliminate such measurement errors, the present invention is configured to correct the detection signal using a reference state as an initial condition. In other words, the detector output ■× is the reference operating condition! ! ! A correction circuit is constructed from a storage means 67 that stores the amount of displacement of the control sleeve position in the idle state (for example, in an idle state), and a deviation calculation means 68 that calculates the amount of deviation between this reference displacement amount and the amount of displacement in an arbitrary operating state. Configure. Specifically, the storage means 67 may be constituted by a sample-and-hold circuit that measures the input signal at a series of predetermined points in time. That is, the storage means 67 inputs an enable signal O810 (outputted from the control device 27) which becomes an enable state when the standard operating state (for example, an idle state) is reached, and when the osio becomes an enabled state, it outputs the detector output. This measurement value is stored and held until the next measurement is taken. Further, the deviation calculation means 68 may be constructed from a differential amplifier.

Note that since the reference displacement amount stored in the storage means 67 is a value that does not need to be rewritten very frequently, the control device 27 may limit the timing at which the enable signal 03IO becomes enabled. For example, it is possible to limit the time when the engine is idling for the first time after starting the engine, and then prevent it from being rewritten until the engine is stopped.

The sensor circuit and correction circuit configured in this manner are provided in the servo circuit 18 in this embodiment, but the storage means 6
7. The function of the deviation calculation means 68 is controlled by the control device 'J! It is also possible to configure it with 27 storage and calculation functions. To explain this case with reference to the circuit diagram of FIG. 5, the control command value calculation means 70 performs control to provide an optimal target fuel injection amount according to a predetermined calculation procedure or table value lookup according to the operating conditions at that time. Calculate the target value of the command value. The control means 71 is based on the target value of this control command value!
- Output OS 4 to the servo circuit 18.

On the other hand, the amount of displacement of the control sleeve 48 detected by the sensor circuit 69 via the sensor body 63 is stored in the storage means 72. It is corrected by the deviation calculation means 73. Feedback correction means for correcting the target value of the control command value using the deviation between the detected displacement amount obtained in this way and the target value as a correction amount is composed of a subtracter 74 and an adder 75. That is, the subtracter 74 subtracts the detected displacement amount from the target value of the control command value to obtain a deviation, and the adder 75 adds this deviation to the target value of the control command value as a feedback correction amount. In addition, FIG. 4 is a schematic configuration diagram of the fuel injection amount control device in this case,
Components that are the same as those in FIG. 2 are given the same reference numerals, and their explanations will be omitted. 7 Displacement detection will be described first for milk production using the above configuration.

When the displacement amount of the control sleeve position in the standard operating state (idle state) is quantitatively determined, the detector output Vxo (=Vx(χ=0)) in the reference operating state is given by the following equation.

Vxo= K EoCI D/E S...
(5) Therefore, the output of the deviation calculation means 68 is Vxo
Since it is the difference between

Vxo-Vx=KEoC1χ/εs ・Equation (e) (
6) does not include the distance between electrodes under standard operating conditions. This means that measurement errors due to variations in the control sleeve position in the standard operating state or changes over time are not caused. Therefore, even if the position of the hunt roll sleeve changes and becomes sharp under the standard operating condition, it has no effect on the detection accuracy.

Next, we will discuss the fuel injection amount control device that uses this displacement detection to detect the fuel injection amount. In the conventional device, the optimum injection amount signal S1 obtained by arithmetic processing based on various inputs and signals is sent to the servo motor 50. Since the input is used to control the control sleeve position, and the control sleeve position is converted to the output signal of the potentiometer 5 meter for feedback control, mechanical variations due to the shape of the cut-off port of each pump and changes over time are avoided. There is a possibility that the correlation between the output value of the sagging meter (position of the control sleeve) and the fuel injection amount may be distorted due to such factors. For this reason, there is a large possibility that the same injection amount will not necessarily be obtained for the same command value, leading to a lack of output or the occurrence of smoke. This has caused problems such as the correlation between the noise and other factors being disrupted, resulting in variations in emission values and noise.

In contrast, in the present invention, the target fuel injection amount is determined in advance from the operating conditions, stored in the calculation unit and used as the target value, and the detected amount of the control sleeve position is corrected by the detected amount in a specific reference state. By doing so, the actual fuel injection amount is accurately known, this is compared with the target value, and the control sleeve position is feedback-controlled via the servo motor in order to reduce the deviation. This makes it possible to optimally control the fuel injection amount with good stability, regardless of manufacturing errors or changes over time in each part.

Furthermore, in conventional devices, which had a limit in detection accuracy and could not be expected to improve detection accuracy, the detection accuracy of the position detection means was a bottleneck in fuel injection amount control. Increasing the detection accuracy of the injection amount improves the overall control accuracy, making it possible to perform more stable feedback control of the fuel injection amount using a computer.

FIG. 6 is a longitudinal sectional view of a fuel injection pump according to a third embodiment of the present invention, and FIG. 7 is a sensor circuit diagram of a capacitive displacement sensor. Note that the same parts as in FIG. 1(A) and FIG. 3 are designated by the same reference numerals, and the explanation thereof will be omitted.

The feature of this embodiment is that it is applied to a differential capacitance displacement sensor. In the differential type displacement sensor, the control sleeve 48 is used as a movable electrode, and a pair of fixed electrodes 82 and 85 are provided in the direction of displacement of the control sleeve 48 with the sleeve 48 sandwiched therebetween. That is,
One fixed electrode 82 is fixed to the barrel 38 via an insulator 81, and the other fixed electrode 85 is fixed to a support member 84 which is also an insulator. When a voltage is applied between the fixed electrodes, a series-connected variable capacitor 83.86 is formed using the substance (fuel) between the control sleeve 48 and the fixed electrode 82.85 as a dielectric, and this becomes the sensor body. Note that the control sleeve 48 is grounded.

FIG. 7 shows a sensor circuit using such a sensor body, in which the potential difference between fixed electrodes connected to an AC power source 65 is amplified by a differential amplifier 87, and this output voltage is converted from AC to DC by a detector 66. be done.

In addition, in the figure, the potential difference is determined at the stage of AC voltage, but as shown in Figure 8, the potential difference of each fixed electrode is
The position EasEb is detected as a DC voltage
A similar result can be obtained by calculating the difference Vx (=Vxa-Vxb) between VXaw and Vxb after converting to IL=Vxb. In addition, in the third embodiment <txt," in the figure), the correction circuit for correcting the detector output is not shown because it is the same as the correction circuit in the first embodiment (see ff11 (B)), but the correction circuit It is also possible to provide the storage and calculation functions of the control device 27 as in the second embodiment (see FIG. 5), as in the second embodiment (see FIG. 5).

Regarding the mathematical treatment of the sensor circuit of the differential displacement sensor, the inter-electrode distance between the control sleeve 48 and the fixed electrodes 82 and 85 at the control sleeve position in a reference operating state (for example, an idle state! are respectively D a and D b (however, D=Da+, Db
), the variable capacitor 83.86 is the displacement of the control sleeve 48 in the right direction in FIG.
The power saving capacities Ca and Cb are respectively given by the following equations.

Ca”t ・S/(Da−χ) −(7)c
b=ε·S/(Db×χ) (8) Here, S is the effective area of the electrode, and ε is the dielectric constant of the fuel.

If the voltage of the AC voltage 65 is EO, then the fixed electrode 82.8
The potentials E a and E b generated at 5 are given by the following equations, respectively.

Ea=EoCb/(Ca+Cb)” (9)
E b= E oCa/ (Ca 〇 b)
-(10) That is, these are the output signals l67a and l5Tb of the sensor body.

The output Ea-Eb of the differential amplifier 87 that amplifies the potential difference between these potentials Ea and Eb is given by the following equation.

Ea-Eb=Eo(Cb-Ca)/(Ca+Cb)=E
o[(Da-Db) 2χ]/D (11) The output Vx of the detector 66 is proportional to Ea Eb, and is given by the following equation with K as its proportionality constant.

Vx=K(Ea-Eb)=KEo[(Da Db)-2χ]/D ・(12
) Therefore, equation (12) does not include the effective area S of the electrode and the dielectric constant ε of the fuel, and is not affected by variations in S, changes over time, changes due to the temperature of the fuel, and changes due to the type of fuel.

Freedom from measurement errors associated with S and ε is a feature of differential displacement sensors, but if the detector output Vx is further signal-processed by the correction circuit of the present invention (see Figure 1 (B)). , fj In the same manner as described in the S1 example, V xo = K E o (D a D b)/D
−(13) to output Vxo of the correction circuit using
Vx ultimately becomes as shown in the following equation.

Vxo−Vx=2KEoχ/D (14)
What can be seen from this equation (14) is that D n r D b can be removed.In other words, in this example, as in the first example, variations in the control sleeve position in the standard operating state and changes over time Here, D is the distance between the fixed electrodes, so even if there is variation, the change over time is extremely small and can be ignored.For this reason, overall, it causes measurement errors. The only difference is the variation in the distance between the fixed electrodes, making it possible to detect displacement with extremely high precision.

Therefore, when this displacement detection is used to detect the fuel injection amount, it is possible to improve the overall control accuracy of the fuel injection amount control as in the first embodiment, and also to avoid differences in fuel temperature changes and fuel types. Regardless of these factors, control accuracy can be maintained well.

(Effects of the Invention) The present invention provides a capacitive displacement sensor with a storage means for storing the amount of displacement detected in a specific reference operating state, and a deviation between the reference displacement 1 and the amount of displacement in any operating state. Since a deviation calculating means is provided to calculate the amount of displacement detected in any operating state, the amount of displacement detected in any operating state can be corrected using the reference operating state as the initial condition. Freed from errors, detection accuracy can be greatly improved.

[Brief explanation of drawings]

t51 Figure (A) is a circuit diagram of the sensor circuit according to the first embodiment of the present invention, Figure 1 (B) is a circuit diagram of the correction circuit, Figure 2 is a schematic diagram of the same, and Figure 3 is the fuel It is a longitudinal cross-sectional view of an injection pump. Figure M4 is a schematic diagram H11 of the 12th embodiment of the present invention, and FIG. 5 is a circuit configuration diagram of the control device in Figure M4. FIG. 6 is a vertical sectional view of an injection pump according to a third embodiment of the present invention;
FIG. 7 is a circuit diagram of the sensor circuit. FIG. 8 is a circuit diagram of a sensor circuit according to a fourth embodiment of the present invention. 6...Fuel injection valve, 7...Injection pump, 18...
Servo circuit, 20... Accelerator sensor, 21... Crank angle sensor, 38... Plunger barrel, 46...
...Delivery valve, 48...Controls'J-
7'(?l[)50... Servo motor, 61.81.
...Insulator, 62°82.85...Electrode, 63...
Sensor body, 64...Fixed capacitor, 65...AC power supply, 66.66A, 66B...Detector, 67.7
2... Storage means, 68.73... Deviation calculation means, 6
9...Sensor circuit, 7o...Control command value calculation means,
71... Control means, 74... Exclusion W, device, 75...
Adder, 83.86... Variable capacitor, 84...
Supporting member, 87... Differential amplifier. Patent applicant Nissan Motor Co., Ltd. Figure 1 (A) Figure 8 66B

Claims (3)

[Claims] 1. In a fuel injection amount detection device for a fuel injection internal combustion engine that calculates the fuel injection amount by detecting the position of the control sleeve of a distribution type fuel injection pump, the displacement of the relative position of the control sleeve is calculated by measuring the capacitance between the electrodes. A capacitive displacement sensor that converts the displacement into a change and detects it, a storage means that stores the amount of displacement in a reference state, and a deviation calculation means that calculates the deviation between the reference amount of displacement and the amount of displacement in an arbitrary state. A fuel injection amount detection device for a fuel injection type internal combustion engine, characterized in that it is provided with: 2. The capacitive displacement sensor includes a sensor body that changes the capacitance between the electrodes according to a displacement in the relative position between the pair of electrodes, a capacitor connected in series with the sensor body, and a capacitor connected to both ends of these. Claim 1, comprising: an AC power source, and a detector that converts the voltage at the connection point between the sensor body and the capacitor from AC to DC.
A fuel injection amount detection device for a fuel injection type internal combustion engine as described in 2. 3. The capacitive displacement sensor has a sensor body including a pair of fixed electrodes and a movable electrode that is located between the fixed electrodes and changes the capacitance between the electrodes according to displacement of the relative position with respect to the fixed electrodes. and an AC power supply connected between the fixed electrodes, and a differential amplifier that amplifies the potential difference between the fixed electrodes.
2. The fuel injection amount detection device for a fuel injection internal combustion engine according to claim 1, further comprising a detector that converts the output voltage of the differential amplifier from alternating current to direct current.